developing a minerals processing project - thomas w. hedrick p.e

8/11/2019 Developing a Minerals Processing Project - Thomas W. Hedrick P.E.

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Developing a Minerals Processing Project By: Thomas W. Hedrick, P.E.

This article aims to give a brief step-by-step insight into the process that must be undertaken in order todevelop a new cement or lime plant project. A project can only be as successful as its planning. Froma timeline point of view, the planning phase can last from 12 to 16 months until the decision is made togo forward with the project. Construction can start once firm engineering and equipment orders havebeen placed and end with the startup and commissioning of the project, generally, 33 to 48 monthslater.

The following tables 1a and 1b illustrate the process and list the activities:1. Management; generally by the Owner or developer2. Government Interaction; by a firm that processes government permits and social integration3. Engineering Activities; by a Consultant --from conceptualization to commissioning4. Construction Activities; plant and infrastructure are erected and production starts.


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Phase 1 - Conceptual Study

During this phase, the idea is created based on the needs of the Owner. The important determinationsfor the concept are as follows:

1. The Owner must appoint a single source of contact for the project with appropriate authority.2. The Engineering/Management Team must choose a qualified and experienced Consulting

Engineering Company.3. Raw Materials: measured reserves of an ample supply of good quality raw materials must be

proven.4. Market Analysis must be undertaken to determine the size of production plant desired.5. Permits must be considered along with any limitations that are likely. This will form the basis of

a preliminary impact statement.6. The most appropriate plant site must be determined based on cost and logistics.7. A Conceptual Analysis must be performed taking the following into consideration:

a. Plot Plan: plant layout at its physical location.b. Logistics; access to and from the facilityc. Infrastructure; utilities, natural gas, coal, process water, accessd. Block Flow Diagram; a graphical representation of the plant processe. CapEx; from references, the plants cost must be projected f. OpEx; from an analysis of the location, the plant operating costs must be projectedg. Risk Analysis; an outline of major risks and strategyh. Definition of Environmental Standards and all permitting requirementsi. Conceptual Schedule

The Conceptual Report will provide a first insight to the economic feasibility of the project.

Figure 1: Site selection, with an eye for ore geology, mining, logistics, technical feasibility, mining, plan etc.


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Phase 2 - Pre-Feasibility Study

At this point, there is definite Owner interest based on the results of the Phase 1 Study. This phaserefines the project as follows:

1. Raw Materials; probable reserves of raw materials are determined following extensive drillingand laboratory testing

2. Market Analysis; more definition is given to projected sales for the eventual production.3. Permits; the studies required for filing permits are started.4. Plant Site; the site location and layouts are finalized.5. Engineering analysis:

a. Plot Plan; define the materials handling and process flowb. Logistics; access to and from the facility is further refinedc. Equipment list specific to quarry and plant is developedd. Block Flow Diagram; the graphical plant process is refinede. CapEx; plants costs are developed from budgetary vendor informationf. OpEx; operating costs are developed from refined location and equipmentg. Economic Analysish. Risk Analysis; major risks are outlinedi. Strategy; the overall plant strategy is developed with a view to moving the project

forward j. The Project Schedule is refined based on the changes and developments of the pre-

feasibility study.

The pre-feasibility report indicates to the Owner that the project looks promising and has an attractivepayback. The quarry and plant sites are now known, chosen in an area conveniently located in relationto the raw materials source and with good access for logistics.

Figure 1 shows a site where the ore geology is promising, as well as a good location for transportation

and reasonable mining costs.

Phase 3 - Feasibility Study

The project continues to be attractive and it is time to firm things up. The Owner will choose a projectteam leader. The feasibility steps are as follows:

1. Raw Materials; drill cores are examined for proven raw materials reserves.2. Emissions Standards; process design is tailored to meet the emissions standards necessary for

the plant location and fuel sources.3. Preferred Equipment list; Owners have a preference for particular equipment that can be listed

for the upcoming firm equipment quotations.4. Market Analysis; a professional market study report is finalized.5. Construction Strategy; the extent of the Owners participation is discussed. This raises further

questions, such as: will the savings of an EPCM project prevail, or will the project pay forpassing the risk to a design build contractor? Should the equipment supply be Ownerpurchased, and the construction design build?

6. Permits; applications for all permits are filed.7. Public Relations; the Public Relations consultant finalizes the assessment of social issues and a

program to be implemented.8. Plant Site; the site location is refined.


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9. Engineering analysis:a. Plot Plan; materials handling is developed and the plot plan revised accordingly.b. Logistics; all aspects of transportation and materials handling are valued.c. Equipment list; the equipment list is refined.d. Preliminary civil, structural, mechanical and electrical design is established.e. Detailed Geotechnical Studyf. Final Block Flow Diagramg. Equipment Bid Package(s) are issued, comprising:

i. Design Criteriaii. Equipment Specsiii. Process Flow diagramsiv. Electrical and Automation specificationsv. Terms and Conditions

h. Short list of construction companies. A Bill of Quantities is issued to obtain budgetaryoffers

i. CapEx; update based on firm pricing j. OpEx; update based on equipment electionk. Economic Analysisl. Risk Analysis; risk strategy is implemented in conjunction with each item in the CapExm. Strategy; the strategy is executed to move the project forwardn. The Project Schedule is established based on chosen strategies.

Figure 2: Full geological evaluation means detailed geological mapping based on core samples, and ultimatelydeveloping an economical mining plan


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Phase 4 - Project Authorization

The Owners board of directors agrees to proceed with the project. Financing for the project is securedbased on the Feasibility Study. The Owner firms up the land ownership, property leases and materialscontracts. Energy contracts for both fuel and power should be secured.

Permits generally go through public hearings and the work is cleared to start construction.

Figure 3: Plot Plan for new kiln line on existing site

Figure 3 is a new plant kiln line on an existing site. Logistics for construction (laydown areas) and futuretruck traffic flow must be coordinated with the local community for project success

The Owner provides materials samples for the process equipment bidders. The equipment bidder willhave done the laboratory testing and provide a confident performance guarantee that the processequipment will meet all the necessary emissions standards. Sample general conditions of purchase andperiod of warranty will be provided by the Owner.

During the Feasibility stage, equipment bidders should have been able to respond to an RFQ in 12weeks. The engineers technical bid evaluation period will depend on the number of bidders. Typicallythere is a period of clarification, checking and validation necessary before the vendors are short-listed.


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Figure 4: Block Flow diagram to visualize the new and existing

Figure 4, the Block Flow diagram helps to explain the new portions and how they interface with theexisting portions of this second production line facility.

Once the short-list of equipment vendors is received by the Owner, compliance with the bid, generalconditions, terms and guarantees can take quite a period to obtain agreement. To speed up theprocess, many vendors will provide a price to develop engineering, thus shortening the elapsed time.Proceeding with engineering is a time saving and cost saving move. These projects typically rangebetween 1/3 and 2/3rds of a billion dollars. Delaying the plant is most costly to the Owner.

Phase 5 Design Engineering

The general plant arrangement is agreed to by the preferred vendor and the plot plan is generallylocked from changes. (important for permit applications) The project manager will interview and selectthe individuals for construction positions.

The OEM (original equipment manufacturer) proceeds with engineering (even if the purchase contractis not completely finalized). Assume here, that the strategy for construction is that the OEM will developthe equipment arrangement drawings. These drawings will need to be sufficiently advanced before themajor structures can be engineered.

Typically, these plants are located for logistics purposes along a river, lake or RR, but present greatchallenges to the structural engineer for deep foundations. Piling can be both a substantial cost and asubstantial time. We recommend that the geotechnical investigation be started no later than thefeasibility stage. This way we know the type and capacity of piling typically available in the area. Werecommend that a piling bid (with conceptual sizes and locations) be let, contractor chosen and readyto mobilize as soon as the OEM can establish major structures loads and locations.

The CapEx preliminary quantities can be used to approach contractors for the civil andmechanical/structural work budgetary pricing and general interest.


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The structural design will proceed on silos and storage bins. As OEM information is exchanged,structural design can proceed on major buildings (mill, preheater, cooler, etc).

Project utilities (phone, power, water, internet) are established.

Permit application is well along or complete. The public relations firm has established good communityrelations for the site.


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Phase 6 - Early Site work

The Owner will start the site activities by establishing the construction trailer, site fence and begin toprepare the site. Grading, parking, laydown, security is all established.

Figure 5: Site work must integrate construction roads, trailers and allow existing production to continue

The Owner s project team will develop the project strategy for: 1. Site Security2. Site Safety procedures and training3. Document controls4. Project schedule5. Monitoring the construction logistics.6. Establish the Owner s quality control team.

Hundreds of workers are involved with the construction of a typical plant. A construction gate, withsecurity is mandatory. Construction traffic should not be mixed with customer traffic in a brownfieldproject. (Figure 5) Parking, construction restroom areas, lighting and timekeeping issues should all bepart of the strategy. Separate strategy applies to vehicles allowed in the plant area.

Safety training is mandatory for all visitors, construction workers and employees. Initial site safetytraining, continuous safety programs and safety practice monitoring strategy is a must.

The equipment vendors will provide experts for assembly and operation of their craft. These technicalservices generally need room (and utilities) for a job-site trailer.


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The emphasis on document control cannot be overemphasized. There will be thousands of documentsissued and revised during the project. At the end, the Owner will want the latest, accurate, as-builtdrawings to work with over the useful life of the plant. This document organization belongs in-house andgenerally is performed with competent computer software.

Hand-in-hand with the documents and overview of the work is the project schedule. Two considerationsare key drivers of the project schedule. First, the cost of the interest on the capital expenditure and,secondly, the thought of the payback (per day) of an operating plant. The Owner should always askwhat is the cost of each day the plant could have been working, but instead was construction delayed.

An Owner should employ a competent scheduler and monitor all aspects of the work.

Figure 6: Preheater vessels arrive by barge, fully nearly fully assembled

The construction logistics is a strategy all to itself. Sourcing of the equipment will be world-wide (figure6) and it all comes together at the plant. There will be thousands of truckloads of equipment, manyrequiring covered storage during the process. The strategy may include storage area by process area(all raw mill equipment in one area, preheater in a second, etc). The strategy should include a lay-downarea where smaller assemblies are pre-assembled before moving to the congested plant area. (Figure7) This strategy probably includes software (much like a warehouse) so that all parts locations areknown.


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Figure 7: Staging and pre-assembly area of pre-heater tower cyclones

Two areas of quality are of concern to the Owner. First is the fabrication of the equipment. One strategymay include subcontracting to a competent group the fabrication oversight of major equipment. Drivingthis strategy may be the choices of OEM and brands of components. You are expecting a plant with 90to 95% availability. Is the equipment properly sourced and fabricated? No warranty will cover the lostproduction time while a casting is swapped out.

The second area of quality is the final assembly. Much of the plant is process in nature and the chutes,ducts, shells and components will be field aligned and welded. No contract type (design build or EPCM)escapes proper oversight from a professional team.

Many sites require deep foundations. During the feasibility stage, most Owners will obtain a preliminarygeotechnical report that recommends piling (or other solutions) that are typical for the area. Once theplant-site is firm, a more in-depth geotechnical report should be commissioned. With report in hand, thestructural engineers can create a piling bid package, with typical lengths and diameters. As early aspractical (after the major structures are located by the OEM) the selected piling contractor can begininstallation. This should occur as early in the schedule as possible. Drilled piling will have spoils torelocate, and piling installation needs to be complete to start the foundations.

Early site work planning sets the stage for successful construction work.


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Phase 7 - Heavy Construction

The Owner is thinking of the cost of money (interest payments) and the missed opportunity of salesfrom the plant. Owners want short schedules. Successful Construction time is a balance of completeengineering, and starting non-process related items early. (Figure 8)

Figure 8: Construction planning, coordination with structural steel and OEM logistics must be planned

The tightest schedule will depend on coordination of OEM certified arrangement drawings coordinatedwith the structural engineer. We have mentioned the major structures location (mills, kilns, coolers,preheater) for establishing any deep foundations. We would like to install the homo silo and clinker silo,

just to get out of the way of the pyro-process. Material handling, finished cement storage and coalhandling are all required parts that should be started as soon as practical.

The project schedule will likely be defined by the preheater building. It is the tallest structure and themost complicated. To accelerate it, structural work is generally done in 3 parts; the foundation,superstructure and floor system. Some countries will favor slip-forming the outside structure, others atotal steel structure. Because of the erection constraints, a hybrid partial concrete with the upper floorsin steel is also popular. An old rule of thumb is that once the pre-heater tower is constructed, and all the


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process ductwork is in place, there is 8 months of work to finish. This work is mechanical, electrical andrefractory installation. (See figure 9)

Figure 9: Preheater tower with major pyro-process cyclones and the kiln in place

With the pre-heater tower defining the schedule, the raw mill, finish mill, kiln and clinker cooler circuitsare all important, but generally not the critical path. Remember, the purpose of this article is to presentan overview so we are really just brushing over the construction schedule.

With our brush, we assume that the hundreds of workers install the thousands of truckloads of all theequipment constructed all the structure to support the process. We bring in the actual employees thatwill run the plant to parallel the last months of construction. We wave our pen and the hundreds ofinstruments are wired and communicate with the control center that commands the scores of electricalmotors. All these things are cold aligned, rotational direction confirmed and hot run without product. Thethousands of connections seem to work (good thing we started some of these systems early). Finally, itis time to turn on the process burners.


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Phase 8 Start-up and Commissioning

One of the first things we do is fill the material storages with the initial raw materials charge. The quarrytruck delivers the first of several loads of crusher run into the wear-lined feed hopper. We test ourgrizzly feeder and send large stone to the primary crusher. The secondary screens scalp out anythingwe missed, as we go about the business of making our first raw materials.

After secondary screening and homogenizing storage, we check the chemical materials propertiesthrough the cross-belt gamma ray nuclear analyzer. We know exactly what we stored and send into thepyro-processing line. And so it goes, ramping up the materials flow and testing the various parts of thenew plant. We have several weeks set aside to verify the capacities of each of the new pieces ofequipment. The factory representative has a duel role to train our plant operators, as well to verify thatthe equipment meets or exceeds the guaranteed performance.

Figure 10: Master Project Schedule (shown in summary format)

The process of starting up a plant (Figure 10) and certifying that it complies with the written guarantee(commissioning) takes 2 to 4 months and often depends on how consistent the raw materials actuallyare compared to what was predicted in the bid tender offer and materials testing performed by thesuppliers back at the beginning of the project bid stage.


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Figure 11: World's tallest pre-heater tower. Note the cyclones must be elevated over the top then lowered into place

In a few paragraphs, this article has described 2 to 4 years in the lives of the plant engineers, Ownersand their operators. If the consultancys work was done correctly, the plant that has been created willhave a good raw materials supply and, with technology updates, it will remain competitive producingcement or lime for the next 50 to 100 years.

Thomas W. Hedrick, P.E.Senior Project Consultant

PEC Consulting Group [email protected]. +1 (314) 824-3971

PEC Consulting Group LLC10123 Corporate Square Dr.

St. Louis, Missouri 63132www.peccg.comTel. +1 (314) 824-3900

Mr. Hedrick has over 35 years experience in minerals processing. Besides structural engineering, hespecializes in materials handling. Currently, he holds many patents and writes for several publications.

An edited version of this article has been submitted to World Cement Magazine for publication in the April 2013 issue.
mailto:[email protected]://www.peccg.com/http://www.peccg.com/mailto:[email protected]

developing a minerals processing project - thomas w. hedrick p.e

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