implementing electrolyte simulation in a water treatment … · 2014-10-14 · hysys, aspen plus...

Copyright [insert date set by system] by [CH2M HILL entity] • Company Confidential

Implementing Electrolyte Simulation in a Water Treatment Process Simulator

Given by Krystal Perez

OLI Simulation Conference 2014

October 22, 2014

Copyright 2014 by CH2M HILL

Project Overview

100 MW Coal Fired Power Plant, located in Midwest

Project Drivers

– Concern with ability of 200 gpm boiler feedwater treatment system

to meet design feed flows

– WTP is operationally intensive (many cleanings required)

– Scaling observed during commissioning, manganese and

phosphorus identified as issue

– Concerns for cycle up of contaminants. The waste streams from the

power plant are sent to the publicly owned treatment works (POTW),

which sends secondary treated wastewater as the supply for the

WTP for boiler feed water.

– Project needed complex water chemistry analyses as well as

ability to account for the recycles within the plant and with the

POTW (water source & wastewater discharge location)


Project Goals

Develop a plant water balance using a dynamic simulation

model to troubleshoot WTP from an equipment and

performance perspective.

Evaluate scenarios for new water sources or changing water

quality and their effects on WTP performance and ability to meet

wastewater discharge permit limits.

Evaluate scaling potential throughout the water balance at the

power plant.

Provide recommendations for changes to water source or

modifications to WTP operation.


Dynamic Modeling with SourceTM

SOURCETM is CH2M HILL’s proprietary dynamic water treatment plant

simulator that uses water quality as a measure of performance of

processes throughout the entire facility.

The water quality parameters that are modeled throughout the process

allow for analysis/optimization of new designs and existing facilities

Focus on physical/chemical treatment


Dynamic Modeling with SourceTM

Source™ model is built in the ExtendSIM® model platform

The ExtendSIM® platform is object-oriented and designed to run time-series calculations

CH2M HILL has taken the ExtendSIM® platform and created proprietary libraries of intelligent objects (i.e. blocks) designed to simulate a unit process. The blocks are arranged to simulate a particular system.

Blocks in this project model included cooling tower, clarifier, microfilter, RO cartridge filter, reverse osmosis, electrodeionization, and ion exchange blocks.

Some blocks were created new for this work (cooling tower, heat exchanger, EDI and IX)

The model is organized to appear like a process flow diagram (PFD), aiding in communication and understanding of the complete process


Why does CH2M HILL use SourceTM?

Need for customizable, dynamic simulator for water and wastewater treatment

Client was familiar with GoldSim, but requested that it not be used due to chemistry shortcomings

Source already had many of the necessary unit operation blocks customized for wastewater treatment

Source model designed to look like PFD

HYSYS, Aspen Plus would have required additional work to customize for wastewater process

Other software like BioWin, GPS-X, and WEST have chemical species limitations & cannot produce a system-wide mass balance


Pairing SourceTM with OLI Engine Developer Edition

SOURCE model benefits/limitations

– Ability to track performance dynamically over time

– PFD interface

– Ability to predict unit process treatment performance

– Calculate effects of recycle streams

– Can turn over a run time version of the model so the client would have a

tool (would require client to license OLI software)

– Limited application for water chemistry calculations as they apply to a power

plant or industrial waters

OLI Stream Analyzer model benefits/limitations

– Ability to calculate complex chemistry stabilities, balances, and mixtures

– Difficult to calculate iterative solutions, like with recycle streams, in a

treatment facility

– Difficult to perform calculations for many water quality scenarios quickly

Client need satisfied by pairing Source with OLI Engine Developer Ed


Source PFD – Upstream Processes

OLI Engine call


Source PFD – Downstream Processes


Simulation Scenarios

Operating Scenario Descriptions and Flows

Scenario Description

Cooling

Tower

Makeup

(gpm)

Boiler Feed

Water Supply

(gpm)

Total

(gpm)

1: Average cooling tower makeup rate

and design boiler feed water

400 290 690

2: Worst case wastewater generation

(Max Day cooling tower demand, and

design boiler feed water flow)

1,234 290 1,534


Chemistry/ Scaling Analysis

Historical Scaling Information:

– Iron and Manganese: High concentrations found in RO cartridge filter

scale

– Calcium phosphate: Found in heat exchanger scale

– Organics: Feedwater from POTW contains TOC, nitrogen,

phosphorous supporting biological growth

– Aluminum: Soluble aluminum possible contributor

– Silica: Typical foulant

– Cooling Water: Concentrating of constituents in cooling tower loop



Summary of Cooling Tower Loop Scaling Potential Analysis

Compounds Raw

Water

Cooling Tower

Blowdown

(20 deg C)

Cooling Tower HEX

Loop 4X

(39.7 deg C)

Ca3(PO4)2

(mg/L)

6 315 3,278

FePO4.2H2O

(mg/L)

303 4,766 658

Al(OH)3

(mg/L)

412 312 274

Calcium phosphate selected as indicator for a more detailed scaling evaluation



Summary of Scaling Potential Analysis Under Various Operating Conditions

Condition Temp, °C

PO4 Limit for (Ca3PO4)2

Scaling, mg/L

Raw WW 19.4 3.5

Raw WW to 35 °C 35 1.5

RO Concentrate (65% recovery) 20 3.5

RO Concentrate (65% recovery), pH 6.4 20 1.5 (FePO4 scale),

4.5 (Ca3(PO4)2 scale)

CT 1.5 X cycle, 25 °C 25 7.5

CT 1.5 X cycle, 35 °C 35 4.5

CT 2 X cycle, 25 °C 25 4.5

CT 2 X cycle, 35 °C 35 2.5

CT 3 X cycle, 25 °C 25 2.5

CT 3 X cycle, 35 °C 35 1.5

CT 4 X cycle, 25 °C 25 2.5

CT 4 X cycle, 35 °C 35 1.5

Table 3

Summary of Scaling Potential Analysis

Raw WW phosphate concentrations were ~66 mg/L as a result of the discharge

of potato processing wastewater from potato processing farms

Results used to develop treatment recommendations


Project Recommendations / Outcomes

Scaling control for water treatment system

– Bench/pilot testing to investigate phosphorous scaling can be

managed with pH reduction and dispersant

– Bench/pilot testing to optimize manganese removal

– Phosphorous removal with iron addition and clarification if scaling

can’t be controlled

Scaling control for cooling towers

– Manage scaling by providing equipment redundancy and downtime

for cleaning

– Phosphorous removal same as above

Team now has an analysis tool, which will be used to further

investigate cycle-up scenarios, variable raw water qualities, and

treatment improvements.


Latest Source + OLI Engine Development

Evaluating other applications to add efficiency and client value

by pairing Source & OLI Engine

Valuable where:

– “Cycle up” scenarios are of key interest

– Customizable unit operation blocks are desired

– Process must be analyzed over time

– Water balance is complex (with interconnectivity and recycle loops)

– There is a desire to have all flows and water qualities in a central

model

Currently developing linked Source/OLI Engine tool for

evaporation/crystallization applications


Latest Source + OLI Engine Development


Lessons Learned

Increasing the number of OLI “calls” will slow down modeling

OLI callable engine originally truncated the solids formed at 200

species; CH2M HILL teaming with OLI addressed this issue

User needs to consider what species are most important for the

chemistry analysis

– Ran OLI callable engine “speed tests”

– Each ion leads to many potential species in the chemistry solution space

– Time savings by reducing the number of raw water ions from 25 (solution

space of 590 species) down to 20 (solution space of 460 species) was 9

minute run time to 4.5 minute run time

Partner with OLI for development success

Worked together to identify and address software issues, both with

Source and the OLI Engine Developer Edition


Lessons Learned

When creating a new simulation, start simple and QC using OLI

Analyzer

Understand differences between OLI Analyzer and OLI Engine model,

such as:

– Stream densities (important for high strength solutions)

– Example: Displaced water

• Water Analysis reconcile object sets the total liquid volume to 1L

• Callable Engine calculates total volume including solids and water is

displaced when solids are formed

• This means that QC results between Analyzer and Callable Engine do not

match when solids are formed

Small differences in dilute flow composition, if not resolved at the

outset of the simulation, can lead to quite significant differences when

constituents are concentrated into residual sludges and/or brines

Simulations use large amounts of flow and water quality data – making

this process challenging but also very informational!

Discussion

Thank you!

Krystal Perez ([email protected])

implementing electrolyte simulation in a water treatment … · 2014-10-14 · hysys, aspen plus...

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