mids professional manual

User's Manual

MiDS Professional 9.1

ITT Water & Wastewater

Copyright © 2001 ITT Water & Wastewater

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REGARDLESS OF WHETHER ANY REMEDY SET FORTH HEREIN FAILS IN ITS ESSENTIAL PURPOSE, IN NO EVENT WILL WATER & WASTEWATER BE LIABLE TO YOU FOR ANY SPECIAL, CONSEQUENTIAL, INDIRECT OR SIMILAR DAMAGES, INCLUDING ANY LOST PROFITS OR LOST DATA ARISING OUT OF THE USE OF INABILITY TO USE THE SOFTWARE OR ANY DATA SUPPLIED THEREWITH, EVEN IF WATER & WASTEWATER OR ANYONE ELSE HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES, OR FOR ANY CLAIM BY ANY OTHER PARTY.

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User's Manual MiDS Professional 9.1 Contents • i

Contents

MiDS 9.1 - Introduction 5 MiDS 9.1 - Mixing Design System......................................................................................5

Getting Started 6 System Requirements ..........................................................................................................6 Program contents .................................................................................................................6 Program installation.............................................................................................................6

Installing MiDS 9.1 ...............................................................................................6

General Instructions 8 Start MiDS 9.1 .....................................................................................................................8 Workflow.............................................................................................................................9 Help .....................................................................................................................................9

Search Products 10 Overview product search ...................................................................................................10

Search mixers ......................................................................................................10 Search jet aerators ...............................................................................................11

Selection archive................................................................................................................11 Predefined applications .......................................................................................11 Mixing duties.......................................................................................................12 Solver parameters ................................................................................................12

Tank Selection ...................................................................................................................12 Circular................................................................................................................13 Rectangular..........................................................................................................13 Racetrack.............................................................................................................13 Closed ditch.........................................................................................................14

Selection Criteria ...............................................................................................................15 Mixer selection criteria........................................................................................15 Jet aerator selection criteria .................................................................................17

Search Result Screen 20 Overview of search results.................................................................................................20 Mixer search result screen .................................................................................................20

Result List ...........................................................................................................21 Single Model Search (SMS)................................................................................22 Change Selection Criteria....................................................................................22 Mixer data ...........................................................................................................22 Mixer Positioning ................................................................................................23 Dimensional drawings .........................................................................................24 Guidebar calculations ..........................................................................................25 LCC – Life Cycle Cost Analysis .........................................................................26 View Solver Parameters ......................................................................................30

Jet aerator search result screen...........................................................................................31 Result List ...........................................................................................................31 Change Selection Criteria....................................................................................32

ii • Contents User's Manual MiDS Professional 9.1

Jet aerator data .................................................................................................... 33 View Solver Parameters ..................................................................................... 33

Printouts 35 Printouts overview ............................................................................................................ 35

Project Management 38 Project management overview.......................................................................................... 38 Create new project ............................................................................................................ 38 Save projects ..................................................................................................................... 38 Open stored project ........................................................................................................... 39

Settings 40 Overview settings ............................................................................................................. 40 Setup ................................................................................................................................. 40 Address ............................................................................................................................. 41 User Profiles ..................................................................................................................... 41 Application settings .......................................................................................................... 42

Browse Products 43 Overview browse .............................................................................................................. 43

Browse mixers .................................................................................................... 43 Browse jet aerators ............................................................................................. 43

Applications in MiDS 45 Overview applications ...................................................................................................... 45 Wastewater Treatment – General Information.................................................................. 45

Biological Treatment .......................................................................................... 45 MAST................................................................................................................. 46 Sludge Handling ................................................................................................. 46 Chemical Treatment ........................................................................................... 47

Wastewater Treatment – Biological Treatment ................................................................ 47 General Information – Biological treatment ....................................................... 47 Input Parameters – Biological treatment ............................................................ 48 Mode of operation .............................................................................................. 48 Average bulk flow velocity ................................................................................ 48 Size for inflow mixing........................................................................................ 50 Bottom diffusers input ........................................................................................ 50

Wastewater treatment – MAST......................................................................................... 51 General Information – MAST ............................................................................ 51 Input Parameters – MAST.................................................................................. 51 MAST calculations ............................................................................................. 53 Jet aerator positioning......................................................................................... 55

Wastewater Treatment – Sludge Handling ....................................................................... 56 General Information – Sludge handling.............................................................. 56 Input Parameters – Sludge handling ................................................................... 57

Wastewater Treatment – Chemical Treatment.................................................................. 58 General Information – Chemical Treatment ....................................................... 58 Input Parameters – Chemical Treatment ............................................................ 59 Inflow to mix ...................................................................................................... 59

Industry – General Information......................................................................................... 59 Drilling mud ....................................................................................................... 59 Pulp and paper .................................................................................................... 60 Spray paint sludge .............................................................................................. 61

Industry – Drilling Mud.................................................................................................... 62 General Information – Drilling mud................................................................... 62

User's Manual MiDS Professional 9.1 Contents • iii

Flygt mixers in Oil and Gas.................................................................................62 Input Parameters – Drilling mud .........................................................................62 Material Recommendations.................................................................................63

Industry – Pulp and Paper..................................................................................................63 General Information – Pulp and paper.................................................................63 Flygt mixers in Pulp and Paper............................................................................63 Input Parameters – Pulp and paper ......................................................................63

Industry – Spray Paint Sludge ...........................................................................................65 General Information – Spray paint sludge...........................................................65 Input Parameters – Spray paint sludge ................................................................65

Agri-/Aquaculture – General Information .........................................................................65 Agriculture...........................................................................................................65 Aquaculture .........................................................................................................66

Agri-/Aquaculture – Manure .............................................................................................67 General Information – Manure ............................................................................67 Input Parameters – Manure..................................................................................67

Agri-/Aquaculture – Fish Ensilage ....................................................................................68 General Information – Fish ensilage....................................................................68 Input Parameters – Fish ensilage .........................................................................68 Material Recommendations.................................................................................68

Mixing Duties in MiDS 69 Mixing duties overview .....................................................................................................69 Blending.............................................................................................................................69

General information – Blending ..........................................................................69 Input parameters – Blending................................................................................70

Suspension .........................................................................................................................70 General information – Suspension ......................................................................71 Input parameters – Suspension ............................................................................71

Circulation .........................................................................................................................72 General information – Circulation.......................................................................72 Input parameters – Circulation ............................................................................72

Glossary of Terms 73

User's Manual MiDS Professional 9.1 MiDS 9.1 - Introduction • 5

MiDS 9.1 - Introduction

MiDS 9.1 - Mixing Design System MiDS 9.1 is a design tool intended for all professionals in the mixing system design and mixer application field.

The program features mixer selection modules and a number of mixer system tools. Outline dimensional drawings and product data sheets can be viewed and printed.

The program can be described as a PC-based product catalog designed to support product selection.

MiDS 9.1 was developed by ITT Water & Wastewater, Market and Sales systems.

Design: Magnus Nilsson

Programming: Tomas Sjögren (Pepto)

Manual/On-Line help: John Arvidsson

Manual edition 3, Sundbypark, Sweden 2008-10-22

6 • Getting Started User's Manual MiDS Professional 9.1

Getting Started

System Requirements The minimum software and hardware requirements are:

• Windows 98 SE, Windows NT4 SP6a, Windows 2000 SP2, Windows XP (updated, i.e. not first basic version).Windows 95, Windows NT4 SP4.

• Internet Explorer 5.0.

• Adobe Acrobat Reader 5.0

• CD-ROM drive, 2x speed.

• 486 66 MHz (Pentium recommended).

• 32 MB RAM.

• 30 MB free disk space for a Client installation, or 30 - 150 MB for a Laptop installation without CD-ROM, depending on the database contents.

Program contents The CD contains:

• SETUP.EXE. MiDS 9.1 installation program.

• MiDS 9.1. Executable program.

• MiDS 9.1 Manual. The manual is in Adobe Acrobat PDF format.

• MiDS 9.1 Help. The manual is in Windows Help format.

Program installation MiDS 9.1 must be installed using the installation program SETUP.EXE and requires 30 -150 MB of free disk space.

Installing MiDS 9.1 1. Start Windows.

2. Insert the MiDS 9.1 CD in the CD-ROM drive.

3. Start Setup.exe.

4. Follow the instructions in the program.

A Program Group and a number of Program Icons are created during installation:

• MiDS 9.1. Main program, starts MiDS 9.1

User's Manual MiDS Professional 9.1 Getting Started • 7

• Uninstall MiDS 9.1. MiDS 9.1 can be uninstalled under the “Add/Remove Programs” in the Control Panel.

8 • General Instructions User's Manual MiDS Professional 9.1

General Instructions

Start MiDS 9.1 Clicking the icon created at installation starts MiDS 9.1.

Start MiDS 9.1

Enter user name and password in the login window.

Login window

User's Manual MiDS Professional 9.1 General Instructions • 9

Workflow There are two alternative methods to select a product in MiDS 9.1:

• Search. The user specifies the mixing/aeration application or mixing duty and the program selects a number of products that fulfill the specified requirements (see “Search Products”).

• Browse. The user selects a mixer or jet aerator in the database, and product performance and data can be displayed (see “Browse Products”).

Help To help the user to fully understand and utilize all features in the program and guide the user through the workflow, MiDS 9.1 provides an extensive help facility.

MiDS Help uses a Windows–Help that includes descriptions of how to use the program features. The help also includes an index and a function to search for words in the help text.

In MiDS, pressing the function key [F1] or clicking on the right mouse button on the function or window where help is required activates the online help function. Help can also be started from the Help – drop-down bar at in the top of the screen.

MiDS 9.1 Help contents

10 • Search Products User's Manual MiDS Professional 9.1

Search Products

Overview product search To search for a suitable solution for a given mixing or aeration application or mixing duty using MiDS, one has to go through three steps in the search window:

1. Select an application or mixing duty in the selection archive and fill in all the process parameters.

2. Select the tank geometry and fill in the tank dimensions.

3. Set the selection criteria to define limitations of the product selection. Since the selection criteria are different for mixers and for jet aerators, the selection criteria are not possible to set until an application is selected.

When everything is defined, press Search to initiate the calculations.

A more detailed explanation of the three parts will follow.

Mixer search window

Search mixers From the given data (and reasonable assumptions) on duty, tank geometry and liquid rheology, required thrust is calculated and one or more mixers producing a thrust higher than or equal to the required thrust will be selected.

MiDS will select mixers according to the most demanding of the following mixing requirements:

1. 3.

2.

User's Manual MiDS Professional 9.1 Search Products • 11

• Obtain a certain average bulkflow velocity

• Overcome the yield stress

• Create enough shear stress to resuspend particles

• Mixing time

The most critical of the above demands limits the search and will be shown in the search result window.

Search jet aerators For aeration both required thrust and required SOR are calculated and used for selecting JAs. Required thrust is calculated in the same way as for mixers. Required SOR is calculated from one of three possible levels i) given SOR, ii) given AOR, or iii) biological load calculations. Jet aerators are selected based on fulfilling both the thrust and the SOR requirements.

Selection archive The mixing may be specified on three different levels:

1. Predefined applications

2. Mixing duties

3. Solver parameters

Clicking in the selection archive field in MiDS makes the selection.

Selection archive (all possible selections are not shown)

Predefined applications To make the product selection process more effective and standardized, the most common applications have been predefined. They are divided into three main groups (wastewater treatment, industry and agri-/aquaculture).

All available applications are described in detail in a special chapter.


Mixing duties When mixers are to be defined for applications that are new or are not among the predefined applications, the mixing duties should be used to define the mixing. The mixing duties do not describe the actual application, but rather the liquid characteristics and mixing requirements.

There are three possible mixing duties to make calculations with MiDS 9.1:

• Blending

• Suspension

• Circulation

Almost all applications suitable for submersible mixers can be defined with these three mixing duties.

All available mixing duties are described in detail in a special chapter.

Solver parameters The solver parameters are the fundamental parameters that MiDS calculates the various applications from and uses internally for the mixer selection calculations. The experienced MiDS user may specify a case via the solver parameters or, when there are good reasons, change the parameters calculated by MiDS for a given application.

MiDS Solver parameters

Tank Selection The tank geometry for a given application is defined by clicking on the tank in the selection field. There are four different geometric tank shapes:

1. Circular

2. Rectangular


3. Racetrack

4. Closed Ditch

Tank selection

Circular It is possible to define four different types of cylindrical tanks in MiDS.

1. Standard circular tank

2. Circular conical tank

3. Circular annular tank

4. Circular annular-conical tank

Circular tank definition window

Rectangular In the case of a tank with a sloping bottom or walls, the mean value should be given. If the geometry deviates a lot from the standard rectangular tank, please consult a Water & Wastewater Application Engineer.

When defining rectangular tanks, beware of aspect ratios greater than 20 in cases of long, narrow tanks or shallow tanks. At present, MiDS will not allow you to proceed with the selection calculations. The solution is to divide a high aspect ratio tank into more manageable subsections and add the required thrust.

Racetrack Length - For racetrack tank applications, the input for the length is the length of the middle wall (midfeather wall). MiDS will calculate the mean total length (for one circulation).

Width - The input for the width is the width of one lane.

Friction Losses - The friction losses to the tank walls and bottom are calculated by MiDS for the given geometry. MiDS uses a default value for the roughness. The total friction is presented as a dimensionless coefficient (which can be changed by the user in the solver parameters).


Point (bend) Losses - The point losses are caused by sudden changes in flow direction due to turns or obstructions in the flow path. In racetrack applications, point losses always occur at the bends. The point loss input for MiDS is a dimensionless coefficient, which depends on the shape of the tank (circular bends, rectangular bends or large bands), and the presence and shape of guide vanes.

The total loss coefficient is the sum of aeration losses, point losses and friction losses.

Racetrack definition window

Closed ditch Length - For multiple channels or serpentine tank applications, the input for the length is the sum of the lengths of the individual channels in the tank. It has to be calculated by the user. In tanks where the liquid circulates longer than 200 m (660 ft), several (serial) mixer locations should be used (the mixers located at different bridges). This is to prevent separation (stratification) of the liquid and to avoid scum build-up.

Width - For serpentine tank applications, the input for the width is the width of the individual channels.

Friction Losses - The friction losses are input as a dimensionless coefficient. These losses are due to the surface roughness of the tank walls and the dividers between each of the channels.

Point Losses - The point losses are caused by sudden changes in flow direction due to turns or obstructions in the flow path. In serpentine tank applications, point losses occur at the bends just like in racetracks. The point loss input for MiDS is a dimensionless coefficient.

The total loss coefficient is the sum of aeration losses, point losses and friction losses. The point and friction losses are presented in the closed ditch window and the aeration loss in the solver parameters.


Closed ditch tank window

Selection Criteria MiDS selects products that are within a given set of selection criteria. To suit the given application, it is possible to change the selection criteria within fixed limits. Mixer and jet aeration selections use (partly) different selection criteria, hence it’s not possible to specify selection criteria until an application is selected.

Mixer selection criteria For mixers, the selection criteria in MiDS 9.1 are: Thrust margin, maximum liquid temperatures, liquid pH, mixer types, number of mixers, phases, approval, frequency, propeller type/material, propeller diameter, jetring, minimum submergence and vortex suppressor; see descriptions in the following sections.


Mixer selection criteria window

Note: There could also be other customer specific demands, for example: propeller tip speed or energy dissipation rate.

Thrust margin When the program does a search, the required thrust to fulfil the mixing requirement is first calculated. Thereafter, suitable mixers that produce enough thrust to match the required thrust are included in the search. The thrust margin limits how much more produced thrust selected mixer(s) can have compared to the required thrust.

If the produced thrust exactly matches the required thrust, it is equivalent to a 0% thrust margin. If the produced thrust is twice the required thrust, it is equivalent to a 100% thrust margin.

Max liquid temperature The upper temperature limit for the liquid surrounding the mixers is 40 °C or 115 °F. Warm liquid versions are available for all of the Flygt compact mixers (4600 – series). The warm liquid versions of the 4600 series can operate at temperatures up to 90 °C (or 195 °F). When using a cooling jacket, 40 °C (115 °F) should be entered even if the liquid temperature is higher (please note that the mixer cannot be used in higher temperatures than 90 °C, 195 °F, from a material point of view). Flygt “banana blade” mixers 4410 and 4430 are not available in warm liquid versions.

Liquid pH Value The pH range for the standard coated cast iron and carbon steel machines is 5.5 to 11.4. The stainless steel models will be able to operate reliably outside of this range, however, ITT Water & Wastewater Applications Engineering should be contacted if your application calls for this. Note that while the pH value is a useful guide, it can be inconclusive. The chemical makeup of your process liquid has a significant influence over how it reacts with the iron, steels, polymers and elastomers making up the mixer.

Number of mixers The minimum and maximum number of mixers to be used in the search can be set here.

Phases All Flygt mixers are available in a 3 phase version. A few mixer models are also available in a 1 phase version.

Approval Almost all Flygt mixers are available with explosion proof approval (Eex).

Propeller type/material This setting gives you three options:

• Standard – which will search for standard Stainless Steel propellers for the 4600-series and Fiberglass reinforced polyurethane propellers for the 4410 and 4430.

• High Chrome – which will search for High Chrome propellers available for the 4600-series.


• 2-bladed SS – on special order, there are two bladed propellers in stainless steel available for the 4630 to 4660, to be used in extremely clogging environments.

Propeller diameter The propeller diameter of Flygt mixers ranges from 0.21 m (8 1/2 in.) on the 4610 to a maximum of 2.5m (98 3/8 in.) on the 4410 and 4430, the banana blade machines. Selection in the program is also limited by the geometry given for the tank.

Jetring All Flygt compact mixers (4600-series) are available with jet rings. Applications that may not require jet rings might be manure treatment, primary municipal sludge, digesters and small tanks. For sludge applications with concentrations higher than 10 %, paper pulp concentrations higher than 4 % or similar viscous fluid applications, consult with ITT Water & Wastewater Application Engineering about using a prolonged jetring.

Recommended submergence Each Flygt mixer model has a minimum recommended submergence. If the mixer operates closer to the surface than the minimum submergence, a vortex can form, causing vibration that may damage the seals and bearings of the mixer. When MiDS 9.1 selects a mixer, machines that would be operating below their minimum submergence are automatically eliminated. This elimination process can be overridden if the NO option is selected.

Vortex suppressor plate As an option for the compact mixers, a vortex suppressor plate can be installed on the mixer. This will reduce the required minimum submergence to about 1/3. Selecting YES together with YES on “Select for min. Submergence”, this reduced submergence will be used as a limit.

Jet aerator selection criteria For jet aerators, the selection criteria in MiDS 9.1 are: Thrust margin, SOR margin, motor power margin, maximum liquid temperature (only max 40 ºC available), ejector type, installation, number of aerators, phases (only 3-phases available), approval (only standard available), frequency; see descriptions in the following sections.


Jet aerator selection criteria window

Thrust margin When the program does a search, the required thrust to fulfill the mixing requirement is first calculated. Thereafter, suitable JAs that produce enough thrust may be selected. If the produced thrust exactly matches the required thrust, it is equivalent to a 0 % thrust margin. If the produced thrust is twice the required thrust, it is equivalent to a 100 % thrust margin.

SOR margin Required SOR may be i) given, ii) calculated from given AOR, or iii) calculated from biological load data. Produced SOR is calculated with regard to the diffuser submergence depth. If the produced SOR exactly matches the required SOR, it is equivalent to a 0 % SOR margin. If the produced SOR is twice the required, it is equivalent to a 100 % SOR margin.

Power uptake percentage (% of maximum power) Power uptake is calculated and related to maximum allowed power uptake, and the percentage of maximum power is used as a selection criterion with 0-100 % as default range vales.

Maximum liquid temperature The jet aerators are only available for maximum 40 ºC / 104 ºF. For clarity the liquid temperature is included as a selection criterion anyway.

Ejector type Two different ejector types are available, the smaller 4812 and the larger 4817.


Installation The jet aerators are possible to install as self standing S installation, or as guided P installation.

Number of aerators The minimum and maximum number of jet aerators to be used in the search can be set here.

Phases The jet aerators are only available in a 3 phase power version. For clarity the phases are included as a selection criterion anyway.

Approval The jet aerators are only available in standard version (not Eex). For clarity the approval is included as a selection criterion anyway.

Frequency The jet aerators are available for both 50 and 60 Hz power frequency.

20 • Search Result Screen User's Manual MiDS Professional 9.1

Search Result Screen

Overview of search results Based on the specifications made in the search window, application, tank, selection criteria and background data, MiDS calculates requirements to fulfill the specified duties in terms of required thrust and SOR. The search result windows have the same basic layout independent of applications, but the details and available functionality are, of course, a bit different.

Mixer search result screen The mixer search result screen looks as below. Based on the required thrust a number of mixer selections that all fulfill the mixing requirements are listed. One solution is presented per mixer model if possible within the set selection criteria. As default, the most energy efficient solution for each mixer is presented. The results from the search are presented in a list in the search result window.

Mixer search result window

The result window also includes data on which the selection is made. The data includes the tank specifications, the application or mixing duty and the selection criteria. The most limiting of the four mixing requirements is also given below the list (selection is based on). From this window, the user has a number of alternative actions to choose from to aid the mixer selection further.

• Result list

• Single mode search

• Change selection criteria

User's Manual MiDS Professional 9.1 Search Result Screen • 21

• Mixer data

• Positioning recommendations

• View dimensional drawings

• Guide bar calculations

• Life Cycle cost analysis

• View solver parameters

• Project report printout (see below chapter)

A mouse click on a row highlights a mixer selection and gives access to all the above alternatives.

It is possible to export the data from the selection list to a .txt file by marking the selections to be exported and pressing Ctlr+F10. This opens an export window where the file to be exported should be specified.

Result List The result from a search is presented in a list in the search result window. The list columns include:

1. Number of mixers in the selection

2. Mixer sales code

3. Propeller code

4. Jetring

5. Angle of propeller (degrees)

6. Diameter of propeller (m/ft)

7. Speed of propeller (rpm)

8. Total power uptake for all mixers (kW)

9. Requested thrust (N)

10. Thrust margin (%)

11. Maximum rated power (per mixer) P1 (kW)

12. Actual power (per mixer) P1 (kW)

13. Actual power in relation to maximum power (%)

14. Rated output power (kW/hp)

Column heads of the mixer search results window

The selections are sorted by total power uptake by default. The list may, however, be sorted by any of the above properties by clicking the column head. Click twice (NOT double-click) to change between ascending and descending.

Export the result list It is possible to export all the data from the list for selected mixers or all mixers in the list, and open it in Microsoft EXCEL or WORD.


• Mark the mixers to export in the list. Holding down the Ctrl-key while clicking on the rows can mark several mixers.

• Press Ctrl + F10.

• A Save dialog will open. Give the file a name and save it in a location where you can find it.

• Open the program where you want to import it. Select Open from the file menu and change the file format to .txt or “all file formats”.

Single Model Search (SMS) Single Model Selection (SMS) mode can be used to find alternative solutions for the same mixer model with, e.g. jetring, without jetring, a different blade angle or propeller diameter, etc. Mark a mixer solution row in the list with a mouse

click and use the - - icon.

To exit the SMS mode click the All - - icon. This returns MiDS to the previous search result window.

Change Selection Criteria The selection criteria used during the search are displayed under the result list.

Use the Sel. Criteria - -button to change the criteria. By confirming a change, the program will make a new search according to the new criteria, and present it in the result list. The changed selection criteria will be saved with the case.

Mixer selection criteria

Mixer data By double-clicking a row/mixer selection, a product data window is presented.

Alternatively, the - - icon may be used. The user may get an overview of all vital information regarding the product data and the mixer selection in the product data window.


Product data – Mixer selection

Product data – Product data

Mixer Positioning If SECAD 4.02 or higher version is installed SECAD will be used for positioning and drawing generation, see further help in SECAD on this.

Clicking the - - icon, opens a window for selection of mixer model, after which SECAD is launched.


Window for specifying mixer model for positioning in SECAD.

Mixer selection and tank geometry is exported into SECAD. SECAD 4.02 handles up to 4 mixers. SECAD version 4.03 handles up to 10 mixer and all tank shapes except racetracks. Note that in the drawing of mixer only up to two are located in the drawing automatically, remaining mixers are located outside of the tank. Note that mixers can be relocated by dragging and dropping using the mouse pointer.

If SECAD is not installed MiDS built in positioning module is used. MiDS internal positioning only handles rectangular and circular tanks with one or two mixers. For other geometries or for solutions with more than two mixers the icon will be grayed out and the functionality will not be available. For positining advices see chapter further down.

Mixer positioning window, the MiDS built in module

Dimensional drawings

MiDS 9.1 includes dimensional drawings in pdf-format. By clicking the - - icon, the dimensional drawing window opens.


Dimensional drawings window

Double clicking a line in the drawings field opens the drawing in Acrobat.

Guidebar calculations MiDS 9.1 includes a function for guidebar calculations, which is activated by

clicking the icon. The guidebar calculations check that stress and deflection are within limits when the selected mixer is installed on a specified guidebar system. The mixer is specified from the result window and the guidebar may be specified or default values may be used. The drop-down curtain allows a selection of standard Flygt guidebar systems:

1. Single guidebar system

2. Tripod guidebar system

3. Tripod guidebar system with upper support

4. Double guidebar system

Note: All of these are not available for all mixer models.

Guidebar calculations window


A click on the Calculate - - button gives the results: Maximum tension, maximum deflection and first natural frequency (only for 4410 and 4430). The results also include a statement indicating whether or not the tensions and deflection are within the limits.

LCC – Life Cycle Cost Analysis Life Cycle Cost (LCC) analysis is a management tool that can help companies minimize waste and maximize energy efficiency for many types of systems, including mixing systems. Life cycle cost analysis is used when, e.g., comparing life cycle costs for different solutions. Future energy costs and miscellaneous annual costs are calculated into a capitalized present day value based on the selected interest rate. The calculation is based on the summation of the cost elements that make up the LCC.

LCC = (Cic + Cin + Ce + Co + Cm + Cs + Cd + Cenv)

C = cost element

ic = initial cost, purchase price (mixer, guidebar, auxiliary services)

in = installation and commissioning cost (including training)

e = energy costs (predicted cost for system operation, including mixers, controls, and any auxiliary services)

o = operation cost (labor cost of normal system supervision)

m = maintenance and repair cost (routine and predicted repairs)

s = down time cost (loss of production)

d = decommissioning/disposal cost (including restoration of the local environment and disposal of auxiliary services).

env = environmental cost (contamination from mixed liquid and auxiliary equipment)

Mixer solutions selected in the search results window can be compared.

1. Select mixers by searching.

2. Mark one or several selections in the results list and click the icon. (Holding down the Ctrl-key while clicking on the rows can mark several mixers.) A window for economy analysis appears. The marked mixer selections are ”transferred” into the analysis window.

3. Enter values for interest rate, energy rate, years of operation and annual operation time.


LCC-Analysis window

For each mixer selection in the LCC analysis:

1. Select the LCC - - button, this opens the initial investment tab.

2. Enter the cost of the mixers, controls, accessories, etc in the appropriate text boxes. This will encompass Cic (Total Equipment Cost). The pump cost should be per pump while the balance of the items should be total cost. Costs that are not applicable should be left as ”0.00”.

3. Continue with installation cost and commissioning cost (including any training), to make up Cin.

4. Enter any decommissioning cost.

5. Select the Annual Costs tab.


LCC – Initial investment and decommissioning costs window

1. The annual mixer energy cost is calculated and displayed.

2. Enter any other annual energy cost for the auxiliary equipment. This will be added to, and displayed as the total energy cost.

3. The next two text boxes are for the mixer operating cost and any additional operating costs.

4. They give the Total Cost of Operation.


LCC – Annual/capitalized costs window

5. The next two boxes are for the mixer maintenance cost and any other maintenance costs.

6. These two boxes are added together and displayed as total cost of maintenance.

7. Next are inputs for down time cost and environmental cost. These are added to the three above totals to give the total annual cost.

8. Select OK to view the bar graphs in the LCC Window.

The LCC-Analysis has a special help window that includes help regarding the elements of the LCC.


LCC Help window

View Solver Parameters

From the search results window click on the - - icon to open a window where all the solver parameters used for the calculations are presented. Note that in this window, the solver parameters cannot be changed, only reviewed.

MiDS Solver parameters for a given application


Jet aerator search result screen The jet aerator search result screen looks as below. Based on the required thrust and SOR a number of jet aerator selections that all fulfill both the requirements are listed. As default, the list is sorted on descending SAE (standard aeration efficiency).

Jet aerator search result window

The result window includes the data on which the selection is made. This indata includes tank specification, application, and selection criteria. Since products are search for both required thrust and SOR the most limiting is given in the “selection is based on:” line. This is not always the same for all products and thus it is only given when a result row is selected. The possible actions from this window are:

• Result list

• Change selection criteria

• Jet aerator data

• View solver parameters (only solver parameters for the mixing duty)

• Project report printout (see below)

A click on a row highlights a product selection, calculates the “Selection is based on”, and enables the above alternatives.

It is possible to export the data from the selection list to a .txt file by marking the selections to be exported and pressing Ctlr+F10. This opens an export window where the file to be exported should be specified.

Result List The result from a search is presented in a list in the search result window. The list columns include:

1. No (Number of jet aerators in the selection)

2. JA denomination

3. Installation (S or P)

4. Ejector type (4812 or 4817)


5. Required SOR (kg/h; lb/h)

6. AOR/SOR ratio (= 0 if calculation level is given SOR)

7. SOR margin (%)

8. Req. F (Requested thrust, N)

9. F-marg. (Thrust margin, %)

10. Tot P1 (Total power uptake for all jet aerators, kW)

11. Max P1 (Maximum rated power input (per unit), kW)

12. Actual power uptake in relation to maximum power (%)

13. Rated P2 (Rated output power, kW/hp)

14. SAE (Standard aeration efficiency, kg O2/kW; lb O2/hph)

The selections are sorted by SAE by default. The list may, however, be sorted by any of the above properties by clicking the column head. Click twice (NOT double-click) to change between ascending and descending.

Export the result list It is possible to export all the data from the list for selected JAs in the list as a txt file, and open it in Microsoft EXCEL or WORD.

• Mark the mixers to export in the list. Holding down the Ctrl-key while clicking on the rows can mark several mixers.

• Press Ctrl + F10.

• A Save dialog will open. Give the file a name and save it in a location where you can find it.

• Open the program where you want to import it. Select Open from the file menu and change the file format to .txt or “all file formats”.

Change Selection Criteria The selection criteria used during the search are displayed under the result list.

Use the Sel. Criteria - -button to change the criteria. By confirming a change, the program will sort the result list according to the new criteria, and present it in the result list. The changed selection criteria will be saved with the case.

Jet aerator selection criteria

See above chapter “Jet aerator selection criteria” for more specifics about the selection criteria.


Jet aerator data By double-clicking a row, a product data window is presented. Alternatively, the

- - icon may be used. The user may get an overview of the product data.

Product data – Jet aerator

View Solver Parameters

From the search results window click on the - - icon to open a window where all the solver parameters used for the calculations are presented. Note that in this window, the solver parameters cannot be changed, only reviewed. For MAST onlu the solver parameters used for the required thrust calculations are presented here.


MiDS Solver parameters for a given application

User's Manual MiDS Professional 9.1 Printouts • 35

Printouts

Printouts overview From several different windows, printouts can be made of various parts of the mixer selection process. Several of these parts can also be summarized by

clicking the icon, from the search result window, which opens the print report window.

Print report window

The print report window gives possibilities you may want to include in the report:

• Mixer selection (default)

• LCC Analysis

• Guidebar calculations

If LCC analysis and/or Guidebar calculations are selected, the program will first start these functions so you can make your input and confirm them (if you have not already made these analyses for the selected mixer). Clicking OK opens the print preview window.

36 • Printouts User's Manual MiDS Professional 9.1

Mixer selection print preview window

User's Manual MiDS Professional 9.1 Printouts • 37

Jet aerator selection print preview window

From the print preview window, the printout may be printed on a printer (it

will send it to your default printer) or exported to a pdf file .

Positioning recommendations and dimensional drawing may be printed from there respective functions.

38 • Project Management User's Manual MiDS Professional 9.1

Project Management

Project management overview MiDS 9.1 includes a database that manages projects and cases. The database is organized in such a way that a project may contain several cases (e.g., different processes, tanks or alternative conditions).

The search window includes functions to:

• Create new projects

• Save projects

• Open stored projects

Create new project The icon creates a new project. A new mixer search window is opened and new unsaved projects are numbered from 1.

Save projects To save a project click the icon, this opens the save case window.

User's Manual MiDS Professional 9.1 Project Management • 39

Save case window

The project name and case names are obligatory fields. For a new project, enter the project and case names. To save cases in an existing project, use the drop down curtain and find the project name in the list.

The other fields (proposal number, customer, contact, selection by and comments) may be used to better specify the project on the printed report.

The mixer search window is stored, including tank geometry and application specifications.

Open stored project The icon opens the project management window. All projects stored in the database are listed here and can be opened. The main functions of this window are described in the figure below. By double-clicking a project name, the second level is reached, and this is where all cases stored under the project are found.

Projects (management) window

40 • Settings User's Manual MiDS Professional 9.1

Settings

Overview settings Settings are user-defined parameters that can be used to customize the program According to the user’s wishes. In MiDS 9.1, the settings are found in the setup menu. The settings include:

• Setting of default values

• Address

• User profiles

• Application settings

Setup The setup window is used to set default values of the following:

• General – including printout language

• Units – including units for length, velocity, flow, power, weight, force and viscosity.

• Economy – default values for the LCC calculations.

• Positioning – angle increments for automatic positioning (not exported to SECAD).

• Programs – include search path to the pdf-archive.

User's Manual MiDS Professional 9.1 Settings • 41

Setup window

Make the desired changes and click the OK button the changes will be implemented on all open cases. Press Save and the changes can be stored in a profile, existing or new. Read more about profiles in the chapter “User Profiles”

Address By setting the address in the address window of MiDS 9.1, it appears on all printouts.

Address window, with HQ address as example

User Profiles The user profiles in MiDS 9.1 allow a number of settings to be stored under one profile. There are two default profiles, one EU and US.

New profiles can be added by clicking Add. Clicking Edit can change existing profiles.

User profiles window

42 • Settings User's Manual MiDS Professional 9.1

The last profile used before the program is closed will be used the next time MiDS is started. The profile that currently is active can be seen in the bottom border (status bar) of the program.

Status bar

Application settings The application settings concern the air diffuser settings. By default, the Sanitaire diffusers are used. By clicking Add, the diffuser definition window opens and the user may specify another diffuser.

Diffuser settings window

Diffuser definition window

User's Manual MiDS Professional 9.1 Browse Products • 43

Browse Products

Overview browse The icon starts the Browser. With the browse function, product data are displayed, and by selecting a product and using the options the number of hits may be limited to more easily find a given product.

Browse mixers When a mixer is selected in the list, the following options are available:

• View product data

• View and print dimensional drawings

• Print product data

Browse mixers window

Browse jet aerators When a jet aerator is selected in the list, the following options are available:

• View product data

44 • Browse Products User's Manual MiDS Professional 9.1

• Print product data

Browse jet aerators window

The list gives performance with increasing depths for one product. Depth may be expressed as ejector submergence, which is measured from ejector outlet centreline to the surface, or as liquid depth, in which case the distance from bottom to ejector centreline has been subtracted. The printout of jet aerator data shows the same tables.

Jet aerator data printout

User's Manual MiDS Professional 9.1 Applications in MiDS • 45

Applications in MiDS

Overview applications In MiDS 9.1, the following pre-defined applications are available:

Wastewater treatment

• Biological treatment

• MATS (Mechanical Aeration Selection Tool)

• Sludge handling

• Chemical treatment

Industry

• Drilling mud

• Pulp and Paper

• Spray paint sludge

Agri-/Acuaculture

• Manure

• Fish ensilage

Wastewater Treatment – General Information Wastewater treatment is carried out in various steps that require mixing. These are Mechanical (not at the present stage in MiDS), Biological, Sludge and Chemical Treatment.

When selecting mixers, the economical aspects must always be made with respect to power consumption and investment cost; for example, using a mixer with or without the jetring.

Biological Treatment For help on biological treatment in MiDS see wastewater treatment – biological treatment.

The objective of biological treatment is to reduce the level of oxygen consuming organic pollutants (biological oxygen demand, BOD) in the wastewater. Modern plants also include the removal of nutrients (nitrogen, phosphorus). Microorganisms can reduce the quantities of organic pollutants in the treated

46 • Applications in MiDS User's Manual MiDS Professional 9.1

effluent in the processing system. Presently, the most common processes employed are activated sludge and biological filters. Mixers are typically employed in the activated sludge process in anoxic, anaerobic and aeration tanks.

Anoxic Tank – No aeration In the activated sludge process, an anoxic zone has no dissolved oxygen in the water for the microorganisms. Instead, the microorganisms consume the oxygen present in nitrites and nitrates. This process is called denitrification. The mixing requirements are usually to prevent sedimentation and to prevent separation, mix-up of all inflows, and to break any short-circuits between inlet and outlet.

Anaerobic Tank – No aeration In the anaerobic zone, the wastewater contains no dissolved oxygen. Nor is there any oxygen present as a nitrite or nitrate. This total absence of oxygen stimulates the growth of phosphorus consuming microorganisms. The mixing requirements are usually to prevent sedimentation and to prevent separation, mix-up of all inflows, and to break any short-circuits between inlet and outlet.

Anox/ox Tank – Aeration turned off Anox/ox tanks can be sized by specifying the aeration equipment, but to have it shut off.

Aerated Tank – Aeration The wastewater in the aerobic zone is heavily oxygenated, usually by means of bottom diffusers fed by compressed air. Horizontal flow mixers can play an important role by increasing the contact time between the air bubbles and the water. The microorganisms in the aerobic zone use the additional oxygen supply for both BOD removal and the conversion of ammonia to nitrates, a process called nitrification. As in the anoxic and anaerobic applications, in aerated tanks, mixers mix-up inflows, prevent short circuits, prevent separation and prevent sedimentation.

MAST For help on mechanical aeration selection in MiDS see wastewater treatment – mechanical aeration.

Mechanical aeration with jet aerators (JA) can be used as an alternative to bottom diffusers. The efficiency is normally not as good, but the mechanical aeration has a number of benefits:

• The equipment is simple and robust.

• Installation is simple, the self standing JA does not need any installation on the bottom, the tank does not even have to be emptied.

Sludge Handling For help on sludge handling in MiDS see wastewater treatment – sludge handling.

The microorganisms described under biological treatment convert the organic pollutants into carbon dioxide and more microorganisms (sludge). Most of the sludge is recirculated back into the wastewater treatment process, but excess sludge must be continuously removed and disposed of. Sludge handling refers to the treatment of excess sludge prior to its final disposal. The aim of sludge treatment is to create a product that can be used as fertilizer, or be safely deposited. Operations encountered in sludge treatment, which may require


mixing, are thickening, stabilization and digestion. Sludge treatment often also includes sludge holding tanks, which is a very common mixer application.

Thickening Sludge generated by the treatment process has a high water content. Removing water from the sludge reduces its volume, this reduces costs of further sludge treatment.

Stabilization Stabilization converts the sludge into a relatively inert and biologically stable material.

Digestion The purpose of sludge digestion is to produce a safe final product suitable for final disposal. Digestion stops further biological activity in the sludge and thus prevents unpleasant smells, emission of potentially dangerous gasses, etc.

Chemical Treatment For help on chemical treatment in MiDS see wastewater treatment – chemical treatment.

Chemical treatment of wastewater is used to remove pollutants that would otherwise not be broken down through biological processing. Chemicals, often in the form of metallic salts (e.g., Fe or Al), are added to the wastewater to exchange ions with the pollutants and bring about settling through precipitation and/or flocculation. Mixing is required in these processes to ensure a high level of contact between the added chemicals and the pollutants prior to flocculation and precipitation.

Wastewater Treatment – Biological Treatment

General Information – Biological treatment • These options are applicable for normal municipal wastewater with

concentration by weight less than 1 %, and an SVI index less than 50.

• The sizing recommendations given by MiDS always assume that sand and other heavy particles are removed from the liquid to be mixed.

• Mixers in aerated tanks should never be working right above or close to an aeration system that is in operation. Always keep a safety distance equal to approximately one depth between a mixer and aeration, if both systems are running at the same time.


Input Parameters – Biological treatment

Application > wastewater > biological treatment window

Mode of operation One of the three modes of operation is first selected:

• Anox or Anaerobe or Deox – No aeration: In these processes, no aeration equipment is installed in the tank.

• Anox/Ox – Aeration turned off: In this process, mixers and aeration alternate running. When the aeration is on the mixer is off, and vice versa (but never at the same time). When sizing for this process, MiDS take account the flow loss of the physical appearance of the aeration equipment.

• Aerobic – Aeration: Aeration and mixers working together in the tank.

NOTE: The mixers are never to be installed right above or too close to the operating aeration system. When sizing for this process, MiDS takes into account the flow loss of the aeration system and airflow.

Average bulk flow velocity General note on average bulk flow velocities Many wastewater treatment plant consultants use velocity measurements as a means of measuring the level of mixing intensity. In these instances, a job specification will often call for a manufacturer's guarantee on a minimum average bulk flow velocity for a given application.

Consult the job specifications for the velocity requirement. A typical value is approximately 0.30 m/s (1.0 ft/s). Make sure your units are consistent with the system of units you have selected MiDS to work with.


The specified bulk flow velocity strongly affects the required mixing capacity. The required thrust is a function of average bulk flow velocity squared. Preventing sedimentation can usually be satisfied by a 0.27 m/s (0.9 ft/s) average bulk flow velocity.

MiDS input Based on the presence of aeration, input on type of pretreatment and the location of the tank outlet, MiDS gives a recommendation of an average velocity.

Type of pretreatment A 10 mm screen removes coarse particles from the wastewater and a primary sedimentation removes the particles with high settling velocities. These pretreatment processes lower the required mixing capacity. In MiDS, select one of the following:

• No screening or screen > 10 mm (1/2 inch). This alternative requires the highest velocity.

• Screen <= 10 mm (1/2 inch), no primary sedimentation. With a 10 mm (1/2 inch) screen, coarse particles are removed and the required mixing capacity is reduced.

• Screen <= 10 mm (1/2 inch), primary sedimentation. With both screening and primary sedimentation

Outlet location in tank:

• Top – if the out let is an overflow, a higher velocity is needed to guarantee a well-mixed suspension.

• Bottom (=bottom draw off)

The average velocities recommended based on the above conditions are (m/s):

Example

Anoxic/Anaerobic Aerated

BDO + SCR + PSED 0.22 0.25 BDO + SCR 0.26 0.28 BDO 0.30 0.33 SCR + PSED 0.25 0.27

SCR 0.28 0.31 Else 0.32 0.35

BDO = Bottom draw off, SCR = 10 mm screening, PSED = primary sedimentation.

MiDS 9.1 has an option for accepting or rejecting the recommended bulk flow velocity. In the case of a rejection, the user may specify a required average bulk flow velocity.

Velocity Guarantee Using the velocity guarantee option, a safety margin of 28 % on the thrust is added, which equals 13 % on the average bulk flow velocity (when e.g., 0.3 m/s is selected MiDS calculates with 0.34 m/s). The major reasons for using the velocity guarantee are:

1. When an average bulk flow velocity is going to be verified by field measurements, there are numerous pitfalls. Different results might be obtained depending on the instrument used (propeller velocity meter measures in one direction, while other instruments might measure in several directions), measurement times and grids used. The velocity guarantee could be used as safety margin for these differences.


2. The safety margin compensates for extreme influences of very rough surfaces, positioning less than optimal, variances in mixer performance, unknown obstacles such as pipes, etc.

The customer sometimes asks for an average bulk flow velocity guarantee. Using the velocity guarantee option must be carefully considered when there is hard competition as larger or more mixers are selected. Using guarantees too frequently can also give an impression that Water & Wastewater isn't competent in selecting mixers or confident of the mixer performance (which is absolutely wrong!).

Size for inflow mixing Checking this box will result in a mixer sizing based on preventing sedimentation and on that mixing of the inflows shall be complete mixed-up within the mixed zone, homogenizing taking place during the process retention time. Not using this function will lower the mixing requirement to prevent separation and prevent sediments (off-bottom suspension).

Bottom diffusers input The MiDS default values for bottom diffusers input are values typical for the Sanitaire diffuser system (Number of Diffusers/Area, Diffuser Area Perpendicular to Flow, Distance: Bottom to Top of Diffuser and Airflow/Diffuser). Check the job specifications to determine what type of air diffuser system your application is using, plus its location and geometry.

The inputs required are:

• Type of diffuser (default is Sanitaire).

• Diffusers per aerated m2.

• Air flow per diffuser.

• Covered bottom area (the percentage of the total bottom area covered by diffuser grids).

• Number of aerated zones. If the distance between two grids is more than 2 m (7 ft), they should be considered as two aerated areas. If the distance is less than 2 m, the covered bottom area is considered as one single aerated area.

Losses due to aeration occur as the density difference between air and water creates a vertical spiral flow that to some extent acts as a hydraulic wall. The losses are thus influenced by flow from the diffusers, dimension of the diffusers, diffuser grid density and number of aerated zones. The cross section area of the diffusers causes additional point losses not related to the airflow.

The calculations in MiDS are valid for fine bubble diffusers (bubble raising velocity 0.8 ft/s, 0.23 m/s).

NOTE: Some input is in percentage of tank dimensions. This approach is used so the default values are dimensionless and independent of tank dimensions.


Wastewater treatment – MAST

General Information – MAST • This application is only valid for wastewater with a ds

concentration by weight < 1 %.

• The sizing recommendations given by MiDS always assume that sand and other heavy particles are removed from the liquid to be mixed.

• The jet aerators should not be positioned so that the air jet from one unit enters another unit.

Input Parameters – MAST

Application > wastewater > MAST window


Level of calculation One of the three levels of calculation first has to be selected (depending on what level is selected, different in-parameters are required and corresponding in-boxes are opened or greyed):

• SOR: An SOR (standard oxygen requirement) value is given. MiDS searches the data base for suitable JA units.

• AOR: An AOR (actual oxygen requirement) value is given. Using the alpha value, MiDS converts the AOR into an SOR and searches the product database.

• Load: Using the load of oxygen demanding substances (biological oxygen demand (BOD), and ammonia nitrogen) and flow, MiDS calculates an AOR and an SOR.

Load definition and levels Depending on the wwtp load different input values may be recommended. The load includes side streams (such as decantation water, …) and is defined in terms of food to mass (F/M) ratio and sludge retention time (SRT), see below table.

Load F/M – ratio

kg O2/kg MLSS day SRT (days)

Low 0.05 – 0.25 (0.30 – 0.50) 10-25 Average 0.25 – 0.50 (0.50 – 0.80) 3-4 High 0.70 – 1.30 (0.80 - ) 0.5-1.5

In brackets the volumetric F/M-ratio (kg O2 per m3-reactor volume).

Recommended values (BOD, TK-N, alpha, oxygen requirement, bulkflow velocity) Note that these recommendations are very general and they have to be carefully considered for each specific case.

Alpha and oxygen requirement are recommended depending on load, see below table.

Recommendations for BOD, TK-N, and bulkflow velocity are given according to the below table. Recommendations depend on if pre-sedimentation is used, and if the water is normal of high concentration. Normal concentration water is sufficient for most applications, the high concentration might be used for e.g., high loaded industrial wwtps. Pre-sedimentation = NO Pre-sedimentation = YES Normal

water High conc water

Normal water

High conc water

BOD (mg/l)

300 800 200 550

TK-N (mg/l)

40 300 35 250

Bulkflow velocity (m/s) (ft/s)

0.30 0.30 0.27 0.27

In general recommendation of these values should be used with care, and the assumptions should be clearly stated. If the user has another value this may be used instead.

Load alpha Oxygen requirement weight O2/ weight)

Low 0.80 1.80 Average 0.75 1.00 High 0.70 0.50


Beta, theta, DO (Dissolved oxygen), liquid temperature, site elevation These data are (together with alpha) used for the conversion of AOR to SOR. Normal values are recommended. These have to be carefully considered and changes to better fit actual conditions.

MAST calculations JAs are selected based on both oxygen supply and mixing demands, see below illustration.

Required SOR calculation Required SOR (standard oxygen requirement) is calculated according to the below equation:

Where,

• AOR is the actual oxygen requirement,

• Alpha (α, -) is KLa wasterwater / KLa clean water

• beta (β, -) is a saturation factor, and is used to correct for dissolves solids in wastewater.

• theta (θ, -), is a correction factor for the wastewater temperature.

• DOfield (mg/l) is working dissolved oxygen in wastewater

• T (ºC) is operating temperature of wastewater

• Pfield/Pmsl is the ratio of barometric pressure at site to pressure at mean sea level. This is calculated from site elevation above sea level. The ratio corrects for reduced oxygen solubility at higher altitudes.

• CsatT (mg/l) is surface DO saturation concentration at design temperature and standard pressure for the particular aeration equipment at the design submergence.

• Csat20 (mg/l) is surface DO saturation concentration at 20 ºC and standard conditions for the particular aeration equipment at the design submergence.

F required (N) for mixing

SOR required (kgO2/h) for aeration

No. of units required for mixing

No. of units required for aeration

Largest no. of units required

SOR=AOR

(α β(CsatT)Pfield - DOfield (θΤ−20) Pmsl

(Csat20)


Required AOR calculation AOR is calculated as:

AOR = Q * [Oxygen requirement * BOD + 4.6 * TK-N]

Where,

• Q is the flow,

• Oxygen requirement is recommended as a function of load, see above table,

• BOD (mg/l) is the biological oxygen demand (mg/l). BOD5 is generally considered,

• TK-N (mg/l) is total Kjelldahl nitrogen, and

• 4.6 is the oxygen requirement for nitrification.

The “4.6 * TK-N” – term is only used if the “nitrification” button = Yes. This equation assumes total BOD reduction and nitrification.

Note that this simplifies a more complete calculation by:

• Not accounting for effluent levels of BOD and TK-N

• Not accounting for possible credit O2 from denitrification

Required thrust Required thrust for mixing is calculated in basically the same way as for mixing applications, based on a required average bulk flow velocity of the flow. The required velocity is recommended according to the above table depending on whether pre-sedimentation is used or not.

JA performance and selection Oxygen transfer

Using an oxygen transfer rate of 5 % per m submergence, jet aerator oxygen transfer is calculated based on the submergence depth of the ejectors. The total oxygen transfer is matched against required SOR and required number of units for aeration calculated.

Thrust

The JA produced thrust is calculated from

F = nz*rho*Qw*uw

Where,

• nz is the number of ejectors,

• rho is the density (= 1000 kg/m3),

• Qw is the water flow per ejector(l/s), and

• uw is the flow velocity(m/s).

Due to the density differences, only water flow is considered (Qw). For the calculations of corresponding velocity (uw) for the water, however, water and air flow has to be considered.

uw = [Qw/nz + Qa/nz*(10/(10+D))]/adiff/1000

Where,


• Qa is the air flow (l/s) corrected for the pressure at the diffuser submergence (D),

• Adiff is the diffuser outlet area (m2), and

• 1000 converts from l/s to m3/s.

MAST result window

MAST selection result window

The columns of the MAST result window is by default sorted on descending SAE (standard aeration efficiency).

Jet aerator positioning The jet aerators should basically be positioned according to the same principles as mixers. One important difference is however, that no JA (or other equipment) should be installed in the air jet of the jet aerator. The length of the air jet is unfortunately very difficult to predict since it depends highly on local hydraulic conditions.

Below is a table of estimated air jet lengths. The data should be taken as very indicative only.


Ejector submergence (m) Denomination 1 2 3 4 5 6 750 Hz Air jet lenght (m) JA 112-S/P5-3085-460 1.6 2.0 2.3 JA 112-S/P5-3102-460 1.8 2.3 2.6 2.9 JA 117-S/P5-3127-437 4.4 5.4 6.2 6.9 7.6 JA 117-S/P5-3153-432 4.9 6.1 7.0 7.7 8.4 9.0 9.6JA 117-S/P5-3171-433 5.6 6.9 7.8 8.6 9.4 10.0 10.6JA 217-S/P5-3202-641 5.0 6.1 7.0 7.8 8.4 9.0 9.6JA 317-S/P5-3202-610 5.4 6.7 7.6 8.4 9.1 9.8 10.4JA 417-S/P5-3301-620 5.6 6.9 7.8 8.6 9.3 10.0 10.6 Ejector submergence (m / ft) 1/3.3 2/6.6 3/9.8 4/13.1 5/16.4 6/19.7 7/23.0

60 Hz Air jet lenght (ft) JA 112-S/P6-3085-460 5 7 8 9 JA 112-S/P6-3102-460 6 7 9 9 JA 117-S/P6-3127-437 15 18 21 23 26 JA 117-S/P6-3153-432 17 21 24 26 29 31 33JA 117-S/P6-3171-433 20 24 27 30 32 35 37JA 217-S/P6-3202-641 19 23 26 29 31 33 35JA 317-S/P6-3202-610 19 23 26 29 31 33 35JA 417-S/P6-3301-620 19 23 26 29 31 34 36

Wastewater Treatment – Sludge Handling

General Information – Sludge handling Basically, only municipal sludge from wastewater treatment is considered (other types of sludge can be compared to municipal sludge, and thus translated). The basic types of sludge are primary, secondary, final or chemically digested and mixed sludge.

Different applications of sludge handling in MiDS 9.1:

• Sludge storage / holding tanks

• Digesters

Sludge Types: Biological Sludge - Sludge from a secondary clarifier. Pre-settling or fine mesh screening is assumed to have taken place.

Biological Sludge nps (No Pre Settling) - Sludge from secondary clarifier. Biological Sludge without presettling or fine mesh screening. Contains more non-organic matters than the biological sludge.

Primary Sludge - Sludge from a primary clarifier. Can contain significant amounts of sand, rags and other debris. Mixer without a jetring is recommended. For low concentrations, higher mixing capacity is needed compared with


biological sludge (at the same concentration), but for higher concentrations, the biological sludge requires more mixing as the yield stress of the biological sludge increase more.

Lime Stabilized Sludge - Typically has a lower viscosity than biological sludge at the same solids concentrations.

Digested Sludge - Typically less viscous than biological sludge due to the digestion. This is true both during and after digestion.

Chemical Sludge - Comes from a settling tank after flocculation.

Mixed Sludge - Can be a combination of any of the types of sludge described above. When rugs etc are present, a mixer without a jetring is recommended.

NOTE: Polymers can affect the consistency of the sludge a lot. The viscosity and yield stress can increase as much as ten times!

Input Parameters – Sludge handling

Application > wastewater > sludge handling window

Input parameters in common for sludge storage and digesters - Type of sludge handling is selected:

• Sludge storage / holding tanks

• Digester

- Concentration by Weight. The percentage of solid particles (by weight) in a representative sample of the fluid. For example, a 1 kg sample of a fluid having a 5 % concentration of solids by weight would contain 0.05 kg of solid particles and 0.95 kg of liquid. At concentrations higher than 8 %, a rheological test is recommended.

Sludge storage / holding tanks - Type of sludge is selected from the drop down menu.

• Biological Sludge - Sludge from secondary clarifier. Pre-settling or fine mesh screening is assumed to have taken place.

• Biological Sludge nps (No Pre Settling) - Sludge from secondary clarifier. Biological Sludge without pre-settling or fine mesh screening. Contains more non-organic matter than the biological sludge.


• Primary Sludge - Sludge from primary clarifier. Can contain significant amounts of sand, rags and other debris. Mixer without jetring is recommended. For low concentrations, higher mixing capacity is needed compared with biological sludge (at the same concentration), but for higher concentrations the biological sludge requires more mixing as the yield stress of the biological sludge increase more.

• Lime Stabilized Sludge - Typically has a lower viscosity than biological sludge at the same solids concentrations.

• Digested Sludge - Typically less viscous than biological sludge due to the digestion. This is true both during and after digestion.

• Chemical Sludge - Comes from a settling tank after flocculation.

• Mixed Sludge - Can be a combination of any of the types of sludge described above. When rugs etc are present, a mixer without a jetring is recommended.

- Required Mixing Time - The retention time can be calculated by dividing the total tank volume to be mixed by the inflow rate. The required mixing time will be equal to or less than the calculated retention time.

Digester Complete mix-up select YES/NO - A YES input will size the mixers for complete mix-up of the whole volume. A NO input will size the mixers for local mixing such as to only prevent sedimentation or only break surface scum, etc.

If the digester also contains primary sludge with large amounts of rugs etc., a mixer without a jetring should be considered.

NOTE: These two requirements cannot be met using only one mixer in a deep digester. It should be noted that gas production (methane) during the digestion process contributes to the mixing.

Wastewater Treatment – Chemical Treatment

General Information – Chemical Treatment In flash mixing, the requirement is to completely mix a chemical into the wastewater as quickly as possible. This type of mixing requires a high level of mixing intensity, hence a compact (stainless steel) mixer is preferred. Detention times can be less than one minute in flash mixing.


Input Parameters – Chemical Treatment

Application > wastewater > Chemical treatment/Flash mixing window

Inflow to mix Mixers are selected so that the flow created gives a mixing time that is equal to or shorter than the residence time (=Volume/throughflow).

Industry – General Information In the industry segment, there are numerous potential applications for Flygt submersible mixers. In MiDS 9.1 the following are available:

1. Drilling mud

2. Pulp and paper

3. Spray paint sludge

Drilling mud For help on drilling mud in MiDS see industry – drilling mud.

Drilling Mud is used in drilling operations on land and off shore. When drilling for oil and gas and when drilling underwater, the requirements on drilling mud are special, and therefore the mud has unusual properties.

The mud is supposed to lubricate the drill, to remove cuttings and transport them out of the hole, to prevent seawater from entering the hole, and to prevent blow-outs in the event of hitting a high-pressure pocket.

Applications for mud mixers are found in the production, in storage on land and on supply ships (where the mud is stored and eventually brought to drilling platforms), platforms and drilling ships.

For environmental reasons, today drilling mud is not only based on oil. Mud may also be based on water.

The desired properties are achieved by using typical additives:

• High specific gravity (SG), typically between 1.6 and 2.5 (in pounds per gallon roughly 13 PPG - 21 PPG), is achieved by adding, e.g., barite. In supply ships, a very high SG can be specified, although the pumps on the ship are known to not handle more than some lower value (say 1.8). The higher the SG, the fewer the mixers that will not overload.

• High yield stress (typically between 5 Pa and 60 Pa - or between 10 lb/100 ft2 and 125 lb/100 ft2) and high viscosity (some 300 cP to 1500 cP) are provided by adding bentonite, for example. This also adds thixotrophy to the mud. In principle this means that if the mud


is left to rest for some time, it will have an apparent yield stress somewhat higher than the nominal value. Intermittent duty mixers should therefore be sized for some extra yield stress.

• Other additives may be used to refine the thickness properties (yield stress and viscosity).

Pulp and paper For help on pulp and paper in MiDS see industry – pulp and paper.

The vast bulk of cellulose pulp is made from wood. Half is made from softwoods (long fibers) but an increasing part is now being produced from hardwoods (short fibers). Wastepaper also has become an important raw material for some new paper grades.

Paper pulp consists of mechanically and/or chemically treated fibers suspended in a slurry. Pulp is produced basically through two different processes, i.e. the mechanical or chemical pulping processes.

In the mechanical process, wood is defiberized mechanically which gives a pulp yield of some 90-99 % of the wood used. Mechanical pulp has good opacity, a special value for the printing paper grades.

In the chemical processes, i.e. the sulphite, and the kraft processes, wood is treated at elevated temperature with chemicals, which dissolve 50-60 % of the wood in the pulping liquid, resulting in a yield of some 40-50 % of the wood used. Chemical pulp can be bleached to high brightness levels and is generally stronger than mechanical pulp.

Paper is made of cellulose fibers bound to each other forming a paper sheet. Paper can also contain various fillers such as clay and chalk. By selecting raw materials, preparation methods of fibers and paper machinery, paper grades with different properties can be obtained.

Paper making is basically forming, de-watering, pressing and drying a sheet of fibers, utilizing the capacity of the fibers to create bindings.

Common applications for Flygt mixers in the pulp and paper industry are in pulp storage, in the machine chest and for the white water.

Biological treatment of wastewater in the pulp and paper industry is similar to municipal wastewater treatment. The same sizing can be applied provided the initial waste solids content is less than 1 % by weight. So, use the Wastewater Treatment application in MiDS. Effluent with inorganic contents such as chalk, lime etc can form hard sediment that needs extra mixing capacity to prevent sedimentation.

Pulp Storage Along the production line of pulp and paper, pulp (stock) or fiber suspensions need to be stored waiting for further processing. When stored, these suspensions must be kept in suspension to avoid sediment and hard crust build up. It is also very important that the consistency of pulp is evenly distributed in the storage volume to secure the pulp quality as well as to facilitate emptying with transfer pumps. The fiber suspension or pulp (stock) can be stored in towers, tanks or chests with different sizes and shapes. One common shape is a pulp storage tower but also rectangular or circular tanks and mid-feather chests are commonly used for storing fiber suspensions and pulp (stock). The pulp enters at one point, inlet, and is pumped out at the outlet with pulp transfer pumps. In a tower, the inlet is at the top and the outlet is at the bottom. Without complete mixing of the pulp, a high degree of consistency is not kept and sedimentation problems occur. Another problem is the buildup of hard crusts on the surface due to incomplete mixing and the fact that many pulp qualities are easily de-watered. The


sediments and crusts decrease the active storage volume affecting the retention time and sometimes make it impossible to empty the storage tank or tower. The concentration of pulp, when being stored, varies normally between 3-5 % by weight.

Machine Chest In the machine chest, placed just in front of the paper machine, the final concentration adjustment of the pulp/stock is made. Accurate control of the pulp/stock effluent consistency is the main objective in machine agitator design. The feed to the machine chest is generally well blended, but continuous mixing is needed to provide absolute minimum consistency variations in the feed to the fan pump or the paper machine head box. Mixing is also needed for preventing sedimentation and to brake in- and outlet flows. From the pulp storage tower, the pulp is transferred to a smaller mixing/blending chest where the first dilution and pH adjustment of the stock take place. The last chest in the stock preparation chain is the machine chest. The machine chest is a relatively small chest that can have different shapes, e.g. tower, rectangular, cylindrical. In the machine chest, the final concentration adjustments take place and the stock is ready to enter the paper machine. In most cases, the pulp/stock is diluted with white water from the short circulation. In most cases, the concentrations of the pulp/stock are between 2.5-3 % by weight when leaving the machine chest.

White Water The white water system collects water from the wire and press section of the paper machine. The water contains additives and fibers and is called white water. The white water is recycled to dilute the pulp coming from the machine chest. The different systems for reusing the white water are called the short and long circulation. The short circulation takes care of the water from the press section passing the wire pit and the mixing pump back to the paper machine. The long circulation takes care of the excess of white water coming from the short circulation. The excess of white water is stored in the so called white water chest and is mainly used for controlling the concentrations of pulp but is also cleaned internally to minimize the load on the effluent handling plant. Mixing is sometimes necessary in the white water chests and tanks due to the risk for sludge or slime build-up. In stagnant areas, fibers may collect and build up. Many white water chests do have less than optimum shapes and fillets making it impossible to use conventional non-submersible agitators. The concentration of solids and fibers in the white water is often low, below 0.5%, but the contents of the fillets can make mixing hard due to hard sediment buildup.

Spray paint sludge For help on spray paint sludge in MiDS see industry – spray paint sludge.

During large scale spray painting operations, it is unavoidable that a quantity of paint particles remains airborne. These particles often contain materials that are hazardous to humans as well as the environment. The wet filter method is used to capture and process the airborne paint particles and consists of a curtain of water through which the air contaminated with spray particles is passed. Particles captured by the water curtain are then flushed down into a sludge tank.

In order to avoid having the paint separate in the sludge tank and dry out on the surface or settle to the bottom of the tank, bentonite, a coagulant, is added to the water and has to be mixed well throughout the tank volume. To achieve optimum results, there has to be constant contact between the coagulant and the spray particles.

Obviously, Flygt mixers can be beneficial for this sort of application. The mixers generate a horizontal flow pattern in order to create immediate contact between the paint particles and the coagulant.


Paint Sludge after treatment is removed and the water is returned through the spray booth.

Industry – Drilling Mud

General Information – Drilling mud Drilling mud often has unusual properties. The specific gravity may be high as well as the yield stress and the viscosity. The mud may also have thixotrophical properties.

Flygt mixers in Oil and Gas For more information about the customer’s process and Flygt mixer application in the oil and gas industry, it is recommended to use the Flygt oil and gas binder.

Input Parameters – Drilling mud

Application > industry >drilling mud window

Type of application Select type of application from the drop down menu:

• Mud storage

• Mud preparation

• Active mud tanks

Specific gravity (SG) No default value.


Yield stress No default value.

Apparent viscosity No default value.

Material Recommendations HC propellers are recommended to obtain a reasonable power margin and to withstand abrasion from the bentonite. SS propellers are recommended when brine is expected in the tanks, which may often be the case on supply ships and platforms.

Industry – Pulp and Paper

General Information – Pulp and paper The applications in MiDS 9.1 for pulp and paper are: pulp storage, machine chest and white water.

Flygt mixers in Pulp and Paper For more information about the customer’s process and Flygt mixer application in the pulp and paper industry it is recommended to use the Flygt pulp and paper binder.

Input Parameters – Pulp and paper

Application > industry > pulp and paper window

Type of Application Select from the drop down menu one of the following:


1. Pulp Storage - When stored, the fiber must be kept in suspension to avoid sediment and hard crust build-up. The concentration of pulp, when being stored, varies normally between 3-5 % by weight.

2. Machine Chest - Accurate control of the pulp effluent consistency is the main objective in machine agitator design, continuous mixing is needed to provide absolute minimum consistency variations. In most cases, the concentrations of the pulp/stock are between 2.5-3% by weight when leaving the machine chest.

3. White Water - Mixing is sometimes necessary in the white water chests and tanks due to the risk for sludge or slime build-up. The concentration of solids and fibers in the white water is often low, below 0.5%, but the contents of the fillets can make mixing hard due to hard sediment build-up.

Type of Pulp RMP Refiner Mechanical Pulp

TMP Thermo Mechanical Pulp

CTMP Chemical Thermal Mechanical Pulp

CP Chemical Pulp

RP Recovery Pulp, (waste paper pulp)

RMP, TMP, RP and CTMP are characterized by a high amount of short fibers and is the direct result of the beating process that mechanical pulps undergo. CP is characterized by long and flexible fibers, high network strength and a low friction factor.

In mechanical pulp, the fibers are shorter and are less entwined compared to CP. Higher mixing capacity is needed for RMP and TMP than CP.

Concentration by Weight The concentration of fibers in the pulp stock along a paper production line range from as low as 0.2 % to highs in the range of 25 to 30 %. The upper concentration limit for Flygt mixer pulp applications is approximately 5 % by weight. This is dependent on the pulp type and the degree of homogeneity required. In MiDS, the concentration and pulp type defines the required yield stress.

De-watering Capacity (Drainability / Drainage Resistance) To measure the beating degree and de-watering capacity, CSF - Canadian Standard Freeness or SR - Schopper-Riegler is used. In MiDS this value, together with pulp type, defines the required yield stress and apparent viscosity (MiDS also defines the required yield stress from concentration by weight and pulp type, and uses the highest value from these two evaluations to estimate the needed mixer capacity). If csf/SR is not entered, MiDS uses only concentration by weight and pulp type to estimate the required yield stress to prevent separation.

Inflow Check the job specifications for inflow rate. MiDS sets the mixing time from the inflow rate and tank volume, then estimates the required capacity for mixing time. This is often important in machine chests. If not entered, the only mixing requirement is to prevent separation (overcome the yield stress).


Industry – Spray Paint Sludge

General Information – Spray paint sludge In the wet filter method, in order to avoid having the paint separate in the sludge tank and dry out on the surface or settle to the bottom of the tank, bentonite, a coagulant, is added to the water and has to be mixed well throughout the tank volume. There has to be constant contact between the coagulant and the spray particles to achieve optimum results. Flygt mixers can be beneficial for this sort of application. The mixers generate a flow pattern in order to create immediate contact between the paint particles and the coagulant.

NOTE: The wet filter method can cause some problems with the mixer's seal when the unit is turned off and non de-glued particles remaining in the sludge adhere to the seal surfaces. To avoid this type of seal failure, continuous mixer operation or continuous seal flushing is recommended.

Input Parameters – Spray paint sludge

Application > industry >spray paint sludge window

Average velocity Enter the average velocity of the bulk flow (0.5 m/s default value).

Agri-/Aquaculture – General Information Mixing in agriculture is currently found in liquid manure treatment and storage. Aquaculture applications include the processing and storage of fish ensilage.

Agriculture For help on agriculture in MiDS see agri-/aquaculture – manure.

Environmental restrictions regarding nitrogen leakage into groundwater plus ammonia emissions into the atmosphere have resulted in a need for more comprehensive manure handling. This is particularly important in regions having intensive agriculture.

Manure treatment requires additives that are mixed into the manure slurry for stabilization, reduction of ammonia emissions and nitrogen leakage. Therefore,


mixing is an important part of the manure treatment process, often requiring homogenizing and the breaking up of the surface crust.

Aquaculture For help on agriculture in MiDS see agri-/aquaculture – fish ensilage.

Destratification and improved aeration of fish ponds and basins Stratification and water quality are important in aquaculture ponds and can affect production economics. Temperature and dissolved oxygen levels can vary throughout the pond affecting feeding behavior, crowding, and stress. Intensely stratified ponds may be supersaturated at the surface with anoxic or very low dissolved oxygen levels at the pond bottom.

Mixing circulating pond water can reduce oxygen stress and thermal stratification, and alleviate conditions of poor water quality. Artificial circulation can increase temperatures in thermally stratified ponds, uniformly distribute phytoplankton, and increase dissolved oxygen levels at the pond bottom.

Circulation does not add oxygen directly to the water, but redistributes oxygen and heat within the pond. This means more even distribution, better feeding, improved water quality and hence increased growth and production.

For large ponds or basins, the 4430 mixer with largest blade diameter is recommended.

Mixing of ensilage in storage tanks Fish offal (skin, bones, meat and waste fish) in fish slaughteries is usually transported to a tank where formic acid is added (HCOOH). The acid and the offal is mixed using a pump (F-pump) and transformed into a homogenized and less viscous liquid that can be stored in tanks for later disposal or usage. In these storage tanks, agitation is needed to prevent the liquid from sedimentation when it is further transported to a final disposal stage. The pH value in storage tanks is 3,8 or lower.

Note: Never use equipment of galv. steel when formic acid is present due to explosion risks.

Flow generation around net cages for fish grow-out Water quality around and in the net cages is important for production economics. Temperature and dissolved oxygen levels can vary over time and may be improved by generating a flow of water through the net cages. Another important duty is to avoid build-up of noxious substances in the area below the floating cages.

Artificial flow can be generated with mixers that are mounted on floating rafts or as fixed installations below the net cages. This will prevent sedimentation build up and sludge as well as enhance the aeration.


Agri-/Aquaculture – Manure

General Information – Manure MiDS 9.1 handles three different types of manure: poultry, dairy, and pig. The manure characteristics vary widely as do their required mixing capacities. For example, poultry manure contains heavy material, and requires more power per volume to be resuspended or homogenized than pig or dairy manure.

Manure viscosity can be significantly reduced when additives are used. At the same time, larger particles and straw form a reinforcing network within the manure and extra power is required to break up their composition.

In general, high consistency manure shows non-Newtonian properties and pseudoplastic behavior. In these cases, yield stress, a characteristic for this kind of liquid, becomes an important design parameter. Therefore, you should consult a Water & Wastewater Applications Engineer if your application has a weight concentration greater than 9 % dairy manure, 15 % pig manure or 20 % for poultry manure.

Input Parameters – Manure

Application > agri/aqua > manure treatment window

Type of application Select one of:

• Farming

• Industry

Type of manure • Dairy

• Pig

• Poultry

The order of increasing viscosity is: pig < dairy < poultry, while the order of increased yield stress depends on the concentration.

Concentration by weight Determines the yield stress and viscosity.


Agri-/Aquaculture – Fish Ensilage

General Information – Fish ensilage The waste when processing fish in aquaculture can be ground and mixed with chemicals to produce a mixture called an ensilage that later on can be used to produce food for pets or farm animals.

When storing the fish ensilage, it is important to mix the whole volume either intermittently or continuously to prevent it from being destroyed.

Input Parameters – Fish ensilage

Application > agri/aqua >fish ensilage storage window

Type of application Select from the drop down menu:

1. Cod.

2. Salmon or Mackerel.

Cod has a higher yield stress than Salmon and Mackerel.

Material Recommendations The entire mixer should be made of ASTM 316L stainless steel material due to the acidic environment.

User's Manual MiDS Professional 9.1 Mixing Duties in MiDS • 69

Mixing Duties in MiDS

Mixing duties overview MiDS 9.1 allows mixer selections based on three different mixing duties:

1. Blending

2. Suspension

3. Circulation

These mixing duties are meant to be used in cases where none of the pre-defined applications fit the given application.

Blending

General information – Blending The mixing duty blending is to be used when a given volume of liquid has to be mixed at a certain time to a given homogeneity. There are two types of blending

• Inflow blending – mixing so that fluid leaving the tank is mixed to a certain homogeneity.

• Batch blending – a certain maximum blending time and a certain minimum homogeneity.

70 • Mixing Duties in MiDS User's Manual MiDS Professional 9.1

Input parameters – Blending

Mixing duties > blending window

The input parameters are divided into blending properties, which differ depending on the type of blending (inflow or batch blending) and liquid properties.

Blending properties • Total inflow into the tank (only for inflow blending) – gives a

required homogenization time, which the mixer flow must exceed.

• Inlet area to the tank is an optional input parameter (only for inflow blending).

• Specified mixing time (only batch blending) – is a way to set the homogenization time directly.

• Homogeneity of blending – sets the degree of homogeneity, default is 95 %.

Liquid properties The liquids to be blended must be specified. Three of the five below must be given (the other two are calculated from the given three):

1. SG – liquid 1.

2. SG – liquid 2.

3. Concentration by weight – liquid 2.

4. Concentration by volume – liquid 2.

5. SG – mixture.

Suspension

User's Manual MiDS Professional 9.1 Mixing Duties in MiDS • 71

General information – Suspension The mixing duty suspension is to be used for applications where there is liquid containing solids to be kept in suspension, i.e. prevent sedimentation. Depending on the type of solids, the suspensions is:

• Inorganic or

• Organic

Only circular and rectangular tanks are allowed.

Input parameters – Suspension

Mixing duties > suspension window

Type of solids in suspension Select inorganic or organic liquid suspension.

Liquid properties • Yield stress

• Apparent viscosity

Three of the following:

1. SG – liquid.

2. SG – particle.

3. Concentration (by weight).

4. Concentration (by volume) (only for inorganic suspension).

5. SG – mixture.

Particle size and settling velocity

For inorganic solids, the particle size may be provided and a corresponding settling velocity calculated.

72 • Mixing Duties in MiDS User's Manual MiDS Professional 9.1

For inorganic solids, the settling velocity must be provided.

Homogeneity of suspension The required degree of homogeneity of the suspension must be set, 95 % is used as a default value.

Circulation

General information – Circulation To be used in cases where the average bulk flow velocity, heat, or mass transfer are specified.

Input parameters – Circulation

Mixing duties > circulation window

Required input parameters are:

• Average bulkflow velocity.

• Apparent viscosity.

• SG-mixture.

User's Manual MiDS Professional 9.1 Glossary of Terms • 73

Glossary of Terms

Aerobic Wastewater process conditions with a significant amount of free oxygen dissolved in the water.

Anaerobic Wastewater process conditions without oxygen dissolved in the water.

Anoxic Wastewater process conditions without free oxygen, with bound oxygen, normally in NO2 or NO3 compounds.

AOR Actual oxygen requirement (often expressed as kg O2/h, or lb O2/h)

Apparent viscosity The viscosity for a psuedoplastic liquid at a certain shear rate.

Batch (tanks) Tanks that are 1) filled, 2) liquid processed, 3) emptied, in contrast to through flow tanks.

Bingham plastic A liquid having non-Newtonian behavior with a yield stress and a linearly increasing viscosity with increasing shear rate.

Blending Mixing of two or more liquids

BOD Biological oxygen demand (often expressed in mg/l). Both BOD5 and BOD7 occurs. We recommend the translation factor: BOD7 = 1.15*BOD5.

Bottom draw off Outlet located at the bottom. For mixing requirement prevent sediments, less mixing capacity is needed compared to an overflow, weir, outlet.

74 • Glossary of Terms User's Manual MiDS Professional 9.1

Bulk flow In mixing applications, the overall flow pattern set up in a tank which is generated by one or more mixer jets. Water in a cylindrical tank may slowly turn, for example.

Bulk flow velocity Total flow in a tank (any section, through the center of rotation, times the integrated velocity give the bulk flow, when divided by 2 - forward and recirculated flow). The bulk flow determines the erosion, level of suspension, degree of homogeneity, etc. Maximizing the bulk flow is usually the main task with the positioning of the mixer.

Clogging Build-up of unwanted solids on a propeller, the hub or any hardware which results in a flow blockage.

Concentration by weight Concentration by weight is the percentage of solid particles in a representative sample of the fluid. For example, a 1 kg sample of a fluid having a 20 % concentration of solids by weight would contain 0.2 kg of solid particles and 0.8 kg of liquid.

Concentration by volume Concentration by volume is the percentage of solid particles (by volume) in a representative sample of the fluid. For example, a 1 liter sample of a fluid having a 20 % concentration of solids by volume would comprise 0.2 liter of solid particles and 0.8 liter of liquid.

Consistency Usually, concentration by weight or d.s., dry solid content.

Degree of homogeneity A homogenous suspension exists when the particle concentration and the particle size distribution are constant throughout the tank. The degree of homogeneity indicates the allowable difference in concentration and size distribution between different parts of a tank. For example, a degree of homogeneity of 95 % means that the solids concentration at the bottom of the tank is 5 % higher than at the top. Similarly, a degree of 75 % indicates the solids concentration at the bottom of the tank is 25 % higher than at the top.

Destratifying Breaking layers of liquid with different densities, caused by differences in temperature, etc.

Detention time Time for processing a given volume of liquid.

Dispersion Fine scale mixing or distribution of non miscible phases, e.g. solid/liquid, gas/liquid, liquid/liquid (emulsion).


Dynamic viscosity Kinematic viscosity of a liquid times its density. The dynamic viscosity is often denoted η (Greek eta) and has the unit Pa s or cP (centiPois), 1 cP = 10-3 Pa s.

Efficiency For hydraulic efficiencies: the ratio between mass flow times pressure produced and the power consumed. (I.e. useful output divided by power input.)

Ejector A specialized pump which uses a high velocity jet to entrain a secondary phase, e.g. water, gas or solids.

Emulsion A mixture of non-soluble liquids, e.g. water and oil often requiring intensive mixing

Engineering factor The engineering factor is a multiplier generally between 0.8 and 1.4 used to adjust for conditions not addressed by your previous inputs.

MiDS is designed from a basic knowledge of mixing, mixers, applications, etc. All assumptions, especially concerning applications, are based on accumulated knowledge. We are not able to consider local variables, competition, need for accuracy, etc. When a sales situation arises, the MiDS user is the one with the most accurate picture of the situation. He or she is best suited to include a factor, which will make the calculation more conservative or more attractive.

Examples:

-A sludge is very well screened - A lower factor can be used.

-It is not very important if some settling occurs, because the mixer is only used as a back-up device.

-Extra capacity is needed, as the mixer(s) cannot be positioned optimally.

-An industrial application is very important; lowest cost is not. Therefore, an engineering factor is justified.

-The competition is very tough. Settlings are not likely to disturb the process.

Adjustment to actual situation is advised.

Many reasons for adjustments can be foreseen. A tool such as MiDS will always be square, and it is an advantage to be able to master the program. The program should be a sales tool, and its user superior to competitors.

Benefits of an engineering factor:

- Better sizing in accordance with actual conditions.

- Better feeling of how the program works.

- Less predictable offers.

- More successful offers, and thus more sales.

- More responsibility by users.

The required thrust used to select mixers, F, is proportional to the engineering factor, EF, as F = EF * (appl. req. thrust).

Consult with an ITT Water & Wastewater Applications Engineer if your application requires you to employ an engineering factor other than 1.0.


For some applications the program shows recommendation for a factor deviating from 1.0. As it implies, we recommend using that factor.

Erosion The mechanism that leads to material wearing away from a surface. In mixer applications, this could be particles from a bottom layer of sediment.

Floating scum An unwanted layer which can build up on the surface in a wastewater or manure treatment process. This layer can be broken down by using chemicals, surface draw off, water spray, or by a mixer jet.

Flygt World leading in the field of submersible mixers and pumping equipment.

Froude number A dimensionless number based on the ratio between inertial and gravitational forces.

Guide bar system Vertical steel bars on which mixers are mounted. These facilitate vertical and angular adjustment of the machines.

Homogenizing Mixing of either a liquid-liquid or liquid-solid combination in order to diminish differences in concentration throughout its volume. (see Degree of Homogeneity)

Hydraulic radius The ratio of the cross sectional area of the tank to the perimeter in contact with the fluid. Used in MiDS to calculate the friction loss in racetracks.

Inflow Rate of the flow into a tank.

Jet The discharge stream of a mixer. This stream is characterized by a conic shape, increasing in diameter as the distance from the mixer propeller increases.

Jet ring A shaped ring around the mixer propeller forming a nozzle that improves its efficiency to create a concentrated jet.

Kinematic viscosity The dynamic viscosity of a liquid divided by its density. The kinematic viscosity is often denoted ν (Greek nu) and has the unit cSt (centiStoke), 1 cSt = 10-6 m2/s.


Laminar flow Liquid elements moving in layers along smooth paths without being mixed, characterized by the absence of random three dimensional disturbances.

Losses Caused by surface friction or flow obstructions, which dissipate the kinetic energy in flowing liquid. In mixing, tank walls and bends are sources of losses. For different types of losses in MiDS see tank selection.

Mixer A machine that mixes liquids (or solids, or gases). A submersible mixer is comprised of a propeller driven by a submersible electric motor.

Mixing requirements In most mixing applications the goal is to (more or less) homogenize the liquid, within a certain time, over the depth or along the length of a throughflow tank. To achieve the needed homogeneity some mixing requirements can be defined: Prevent short-circuits between inlets and outlet, mix-up the volume (blending, ...), prevent separation (suspend solids, break stratification, mix emulsions) and prevent sediment.

Mixing time Time for the mixer to mix a given volume of liquid to a certain degree of homogeneity.

Momentum One of the basic dynamic quantities: mass flow, momentum and dynamic energy.

NPSH Net Positive Suction Head, a parameter used to measure a propeller or an impeller's sensitivity to cavitation.

Off bottom mixing Defines degree of suspension: convention states that no particle stays longer than 1-2 seconds. There is, however, no demand on particle distribution throughout the remainder of the mixed volume.

Particle settling velocity The rate at which solid particles settle to the bottom of a tank. It is dependent on particle size, density, concentration and flocculation, the particles' tendency to clump together.

Plug flow A flow that moves as an intact unit, without axial mixing from inlet to outlet.

Power uptake A mixer's electrical power consumption.


Racetrack A long ditch with a center dividing wall forming an oval around which the process liquid circulates.

Rain water An important factor in wastewater treatment. Rain water as runoff contains pollutants from roads, parking lots, and other drainage areas.

Resuspend The action of lifting particles from a tank bottom after they have settled.

Retention basin A holding tank used to even out peak flows over time, usually employed to store stormwater.

Retention time Average time the process liquid stays in the tank, assuming no short circuiting takes place.

Reynolds number A dimensionless number used to indicate the relationship between dynamic forces and viscous forces within a moving liquid. Its magnitude can be used to predict whether a flow is laminar or turbulent.

SAE Standard aeration efficiency (expressed as kg O2/kWh, or lb O2/hph).

Sanitaire A US company which produces a line of fine bubble bottom diffusers for aeration in wastewater treatment plants. Default values in the aeration menus of the MiDS wastewater section give the typical Sanitaire geometries.

Scour A term describing the effect of erosion due to a mixer jet impinging on a surface comprised of settled solids.

Seal, mechanical For Flygt mixers, the mechanical seal is a face seal consisting of two rings which are pressed together, one static and one rotating, preventing leakage into the machine along the propeller shaft.

Serpentine A (closed) racetrack with several lanes.

SG Specific gravity.


Shaft power The power delivered from the mixer's motor to its propeller.

Shear Friction between layers of flowing fluid which cause a resistance to flow.

Shear rate The velocity gradient (dv/dy) between layers of flowing fluid.

Shield A researcher who made the, now classic, early basic investigations into particle erosion.

Short circuiting A condition caused by poor mixer placement resulting in the process fluid flowing directly from tank inlet to outlet without first mixing throughout the tank.

Slurry A mixture of solids and liquid, e.g. lime and water, wet concrete, bentonite, paper pulp, etc.

SOR Standard oxygen requirement (often expressed as kg O2/h, or lb O2/h)

Specific gravity SG, defined as the density of a liquid or solid divided by the density of water, i.e. water has a SG of 1.0. For example, a liquid with a density that is double the density of water would have a specific gravity of 2.0. Similarly, a liquid with a density half that of water has a specific gravity of 0.5.

Examples of specific gravities:

Water 1.0, Vegetable Oil 0.92, Kerosene 0.81, Gasoline 0.72, Blackstrap Molasses 1.5, Iron Ore (Magnetite) 8.6, Coal (Anthracite) 1.8, Wood fibers (Spruce) 0.56, Cement 2.6, Sand 2.6.

Specific gravities of liquids change only slightly within the temperature ranges found in most Flygt mixer applications.

SG Slurry

The specific gravity of a slurry is the specific gravity of a homogenous mixture of both the solid particles and their transport liquid.

STP Sewage Treatment Plant

Stratification Layering in a still volume of liquid caused by density differences, temperature differences, type of liquid, etc.


Submergence For Flygt mixers, the distance between the upper propeller tip with the machine in a horizontal orientation and the surface of the liquid in the tank.

Suspension A mixture of undissolved solids in a liquid.

Through flow The total volume of continuous flow passing through a tank over a given time period.

Thrust The axial reaction force that the flow through the mixer propeller produces.

Tracer An additive introduced to detect the characteristics and degree of mixing in a tank. In the pulp and paper industry, lithium is used for this purpose.

Turbulence Characterized by random, three-dimensional motion of fluid particles. Dynamic forces dominate in comparison to viscous forces.

Viscosity The resistance to the movement between one layer of fluid to an adjacent layer, or in other words the fluid resistance to flow. It is, therefore, a very significant parameter in mixer sizing. At concentration by volume higher than 20 % the viscosity of the mixture might increase, especially if the particles are small, less than 10-20 micrometer. Input for viscosity in MiDS is in centiPois which is denoted by cP (or cp). See also dynamic viscosity and kinematic viscosity.

Examples of liquids and their viscosities in centiPois (Note that temperature has a significant influence on the viscosity):

Example

Temperature (°C)

Viscosity

(cP) Water 20 1.4 Water 54 0.55 Vegetable Oil 16 37.0 Kerosene 16 2.2

Gasoline 16 0.4 Blackstrap Molasses 16 3900 Syrup 8 10000

If you are unsure of the viscosity of your fluid, Cameron Hydraulic Data, published by Ingersoll-Rand, is a good source of fluid property data for many liquids. In most cases with slurries, it is necessary to perform a rheology test on a representative sample.

Vortex A rotating flow pattern typically forming at the inlet to a mixer propeller. Vortex formation is highly dependent on mixer submergence and is to be avoided


because of its detrimental effect on efficiency and bearing life. A vortex protection shield may be used to allows for less submergence.

Vortex suppressor plate For Flygt mixers, a plate mounted over the inlet side of the mixer propeller, which both diminishes vortex formation and allows for less submergence. Sometimes also called "vortex protection shield".

WWTP Waste Water Treatment Plant

Yield stress The stress a liquid can withstand without deformation or flowing. A gel is an example of a liquid, which does not flow unless its yield stress is exceeded.

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