Water Plant Evaluation

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Steam Generation Systems, Inc.1108 Lavaca St., Suite 110-309 • Austin, Texas 78701 USA • 832-725-7662 • www.SteamGenerationSystems.com

FINAL REPORT

for

PROPOSAL No. SGS-0106-00-002

Survey of Water Treatment Plant for Cogeneration

Facility

Prepared by:

Alex C. McDonald, Ph.D.

March, 2006






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Table of Contents

OBJECTIVES .............................................................................................................................................................. 3

SCOPE OF WORK ..................................................................................................................................................... 4

1.0 EXECUTIVE SUMMARY................................................................................................................................ 5

1.1 EXISTING WATER PLANT.................................................................................................................................. 5 1.2 NEW WATER PLANT......................................................................................................................................... 6 1.3 STAND-ALONE FACILITY.................................................................................................................................. 7

2.0 EXISTING WATER PLANT ............................................................................................................................ 8

2.0.1 Description of Existing Systems .......... .......... ........... .......... ........... .......... ........... .......... ........... .......... ..... 8 2.1 RAW WATER .................................................................................................................................................... 9

2.1.1 Chlorinators ............................................................................................................................................ 9 2.1.2 Polymer/Coagulant ................................................................................................................................. 9 2.1.3 Caustic ................................................................................................................................................... 10 2.1.4 Chemical Mix Tank ............................................................................................................................... 10 2.1.5 Clarifiers ............................................................................................................................................... 11

2.2 INTERMEDIATE QUALITY (IQ) WATER ........................................................................................................... 13 2.2.1 Cation Exchange Units .......................................................................................................................... 14 2.2.2 Anion Exchange Units ........................................................................................................................... 15

2.3 HIGH QUALITY (HQ) WATER .................................................................................................................. 17 2.3.1 Mixed-Beds ............................................................................................................................................ 17 2.3.2 Condensate Return ................................................................................................................................ 18

2.4 WASTE WATER NEUTRALIZATION AND BRINE SOAK WATER ........................................................................ 18 2.5 OPERATING COSTS AND MANPOWER REQUIREMENTS.................................................................................... 19

2.6 EQUIPMENT CAPACITIES ................................................................................................................................ 19

3.0 NEW WATER PLANT.................................................................................................................................... 21

3.1 CLARIFICATION / FILTRATION.......................................................................................................................... 21 3.2 FILTER WELL /CLEAR WELL............................................................................................................................. 21 3.3 INTERMEDIATE QUALITY (IQ) WATER ........................................................................................................... 22

3.3.1 Cation Exchange ................................................................................................................................... 22 3.3.2 Anion Exchange .................................................................................................................................... 24

3.4 HIGH QUALITY (HQ) WATER ......................................................................................................................... 24 3.5 OPERATING COST AND MANPOWER REQUIREMENTS ..................................................................................... 25 3.6 EQUIPMENT CAPACITY................................................................................................................................... 25

4.0 STAND-ALONE FACILITY .......................................................................................................................... 27

4.1 CASE A: NO STEAM EXPORT.......................................................................................................................... 27 4.2 CASE B: STEAM EXPORT FACILITY ................................................................................................................ 27 4.3 OPERATING COST AND MANPOWER REQUIREMENTS ..................................................................................... 28 4.4 EQUIPMENT CAPACITIES ................................................................................................................................ 28






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OBJECTIVES

To survey existing water plant systems at the Facility which provides all water required for the CG

Cogeneration Plant. This survey will include MECHANICALS AND DESIGN of the units, plant

OPERATING characteristics and load patterns and the CHEMICAL TREATMENT AND

CONTROL programs. As part of survey, an evaluation of potential new water treatment systems

within the water plant, and their impact on plant operating costs will be performed.

The objective of this work is to identify/characterize key factors of the water plant treatment

systems to achieve the following:

• Evaluate the existing water plant systems.

⇒ Estimate operating costs and manpower required for efficient operation by

CG as a dedicated, stand-alone facility.

⇒ Recommend options for the existing water plant systems and the impact on

operating cost, manpower requirements and quality of product water on CG

as a dedicated, stand-alone facility.

⇒ Prepare a diagram of existing piping routing, location, size for make-up

water and out fall.

• Recommend the design of mechanical systems, capacities and operationalfactors of a new water plant systems sized to meet the requirements of CG as a

dedicated, stand alone facility.

⇒ Prepare a process diagram showing flow/capacity of all primary

components and a general equipment list for the new water plant systems.

⇒ Estimate operating costs and manpower required for efficient operation of

the new water plant systems.

⇒ Prepare a diagram of piping routing, location, size for make-up water and

out fall.






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SCOPE OF WORK

The proposed study will focus on design/capacity and operation of the water plant systems.Potential for cost savings from water use and re-use systems will be investigated.

The study will focus on four types of contributing factors:

1. Mechanical and Design

2. Operational

3. Chemical Treatment and Control.

4. Produced water quality specification.

These factors are not independent variables and must be addressed collectively. The work to be

performed to investigate these primary factors is outlined below.

1. Mechanical and Design

• Review manufacturer’s guidelines and design parameters for waterside

systems including flow rates, pressure, production rates, chemistry

control (blowdown, variable service), factors influencing produced water

quality.

• Evaluate the current condition of the raw water plant and boiler systems.

This will be performed by review of historical records, including records

of internal inspections, outage reports.

2. Operation

• Assess planned operation procedures and service duty requirements.

Emphasis will be placed on the impact of these procedures on water

treatment costs and manpower requirements.

• Audit historical chemistry records, maintenance records (failure

patterns), treatment requirements and correlate these to water system

operation.

3. Chemical Treatment • Audit historical records of type and amounts of chemicals fed.

• Correlate chemical feed procedures with unit operation and manpower

requirements.

• Assess the effectiveness of the current chemical feed procedures.






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1.0 EXECUTIVE SUMMARY

The existing water plant is an extensive system which is deeply integrated into the facilities. The

integration of the water plant into both these facilities makes estimation of separate design

requirements difficult.

Based on the information provided, it has not been possible to complete all of the objectives

established in the original proposal. Operating costs and manpower required for the existing, and

the “new” water plant as a stand-alone facility have not been estimated. Accurate piping routing

and locations relative to equipment is also not provided due to the lack of an existing site plan. In

addition, while estimated capacities of primary components are included, detailed information on

the specific flows required for plant facilities is incomplete. These objectives will be addressed

when the design requirements and information are made available.

The plant has undergone a number of expansions and operating changes over the years.

Demineralization capacity has been increased to meet growing water requirements and the

system has been modified to meet plant discharge requirements. The neutralization of regenerant

wastes has developed into a primary function, often over riding demineralizer efficiency as the

operating focus. The entire system has extensive computer-controls, automation and interlock

capabilities, but the efficiencies that these systems can provide are not being fully realized.

Manpower utilization is relatively low for such a complex system, considering that regenerant

wastes are batch neutralized and the number of anion brine soaks necessary to remove organic

fouling.

Based on the information obtained, operational and mechanical improvements are recommended.

The goal of these recommendations is to increase the existing water plant throughput, improve

efficiency and improve water quality. These recommendations are also made with a view toward

limiting capital expenditures and improving operating costs where possible. The focus of our

recommendations and conclusions are divided into three scenarios; 1) operation of the existing

water plant, 2) requirements of the upgraded “new” water plant and 3) requirements of a stand-

alone water plant to meet the sole needs of the CG power generation facility.

1.1 Existing Water Plant.

The capacities and efficiency of the existing water plant can be improved by making

modifications to operations:

• Increase filter well capacity to permit increased flow and base loading of

clarifiers.

• Replace anion resin with macroreticular resin.






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• Consider using small anion vessels as organic traps.

• Consider using weak acid resin in some of the cation vessels.

• Optimize clarifier operation for throughput increase.

• Optimize clarifier operation to improve color and organic removal.

• Optimize demineralizer regeneration procedures to improve throughput.

• Optimize demineralizer regeneration procedures to improve waste generation

and neutralization.

• Relocate cationic polymer feed to the raw water pump sump.

• Replace existing cationic polymer with a chlorine resistant product.

These recommendations are not expected to substantially impact man power requirements for the

water plant. Marginal savings in operational costs are possible from reduced regeneration

frequencies. However, the modifications are expected to improve the throughput capacity of the

equipment and the quality and consistency of the produced water. This will have a tangible,

beneficial impact on operation and maintenance of downstream equipment.

1.2 New Water Plant

With modifications in service and operation of the existing water plant, only minor additions in

primary equipment will be necessary to meet the needs of the completed CG power generation

facility and the existing export needs. Recommendations to achieve this include:

• Replace the three (3) small anion units with three (3) larger units with capacity

of 650 ft3 of resin.

• Add a fifth (5) cation unit equivalent in capacity to the existing units.

• Add a third (3) mixed bed unit equivalent in capacity to the existing units.

• Institute the operational modifications recommended above for the existing

water plant.

The existing clarification and filter systems are sufficient for operation and no additional capacity

is required. These recommendations will not substantially change the man power requirements

for the “new” water plant when compared to the existing water plant. The impact on the cost per

gallon produced by the plant is difficult to estimate because of two conflicting effects. Firstly the

gross capacity and flows through the plant will increase due to the demands of the CG facility

and result in a decrease of some fixed costs per gallon produced. However, the increase in High

Quality (HQ) water required for export steam, combined with the low level of condensate return






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will increase costs. A detailed cost model can be calculated once the accurate water/steam flows

to the completed CG power generation facility and the existing plant are provided.

1.3 Stand-Alone Facility

As a stand-alone water plant with no export steam, the CG power generation facility requires

only small quantities of HQ make-up water. Raw surface water, without clarification or

filtration, would be adequate for cooling tower make-up. Under these conditions, most of the

current treatment system as well as the expansion would be unnecessary. As steam export

increases, the capabilities of the current system with improvements become increasingly more

necessary.






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2.0 EXISTING WATER PLANT

2.0.1 Description of Existing Systems

Raw surface water enters the facility at

Junction Box B, where any excess water

overflows into the ditch system of the

complex. Raw water for clarification/water

treatment and other process applications

flows via gravity in three 36” conduits from

Junction Box B to Junction Box C where it

is then conveyed via a concrete conduit to

various plant locations including the water

treatment plant.

Raw water is pumped and chlorinated from

sump 108C to five (5) circular upflow clarifiers. The plant has undergone a number of

expansions and operating changes over the years. These changes include modifications to the

clarifiers; including (1) the discontinuation of lime-softening, and (2) discontinuation of

magnesium oxide feed for silica removal. Most of the equipment associated with these two

processes remains on plant site. A cationic polymer, used for solids coagulation and settling in

the upflow clarifiers, is fed ahead of the small chemical mix vessel. Additional trim chlorination,controlled by chlorine “residual”, is used for organic removal. Twenty (20) % caustic is fed after

chlorinating to control the water pH and for general corrosion reduction.

The effluent from the clarifiers is gravity fed to a series of nine (9) mixed media filters for

removal of remaining solids. Filtered water is collected in an underground storage facility or

filter well. Clarified and filtered water from the filter well is pumped to a demineralizer system

consisting of four (4) cation and six (6) anion units to provide Intermediate Quality (IQ) water.

IQ water from the demineralizers provides boiler feed water and also feed water to two (2)

mixed-bed polishers. The two mixed-bed polishers provide high quality (HQ) demineralized

water for process usage.

Sulfuric acid and caustic are used to regenerate exhausted cation and anion exchangers;

respectively. Regeneration is performed in a counter-flow manner. Caustic and brine are also

used in an alkaline brine wash (soak) to improve organic removal from the anion resins. Waste

effluent from the ion exchange regeneration process is collected and neutralized in five

neutralization tanks before transfer to on site bio-ponds.






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2.1 Raw Water

Two (2) raw water pumps with design capacities of 5,000 and 12,000 gpm respectively, take

suction from the 108C sump, which is supplied with water from the canal and gravity flow

conduits from Junction Box C. It

was reported that the manufacture of

the pumps and some of the

replacement parts have been

discontinued. At the pumps’ rated

capacities, either pump can supply

enough water to handle current

demands of the water treatment plant,

which is approximately 3000 gallons

per minute.

2.1.1 Chlorinators

Two (2) Fischer & Porter 500 lb/day chlorinators are used to

educt chlorine gas into the influent raw water at two different

locations to facilitate the removal of organics and color.

Normal demand is 400-700 lbs/day of chlorine to achieve a

recorded free chlorine residual of ≈ 0.5 ppm.

2.1.2 Polymer/Coagulant

Polymer is pumped from a storage tank into a water carry-line and fed into the raw water feed

line prior to the small chemical mix vessel, which distributes water to the five clarifiers. The

optimum Polymer feed dosage is determined by jar tests. Polymer dosage feed rates normally

range from 10-25 ppm.






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• Cationic polymers perform better underconditions where adequate mixing

energy is provided. The present

polymer feed location does not provide

adequate time or the mixing energy

needed for the cationic polymer to

effectively charge neutralize the

incoming raw water turbidity.

Additional mixing energy could be

achieved by feeding diluted polymer

directly into the raw water sump at

108C. The polymer and particles of turbidity would then be transported and

mixed through the pump impellers. This would provide better polymer/solids

contact and a more consistent clarification process.

• Since high chlorinating rates are required for color and organic removal in the raw

SBA water, a chlorine-resistant polymer is required.

2.1.3 Caustic

Twenty percent caustic is fed to the raw SBA water for

pH control in order to mitigate mild steel corrosion.

The caustic is fed in the raw water line after

chlorinating and before the polymer feed location.

2.1.4 Chemical Mix Tank

The mix tank receives raw water that has been treated

with chlorine, caustic, and polymer. The chemical mix

tank is very small at only around 700 gallons in

capacity. Residence time is less than 15 seconds at

normal raw water flow rates of 3000 gpm. The mix

tank is equipped with internal baffles to aid mixing of

the coagulant for particle charge neutralization. It

receives raw water containing the polymer coagulant,

chlorine, and caustic.






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• The current mix vessel does not provide sufficient residence time or mixing

energy to ensure optimum coagulation. (See notes on polymer/coagulant feed).

2.1.5 Clarifiers

Five (5) Permutit precipitators have been modified

into up-flow sludge blanket clarifiers. The operating

capacity is shown as ~ 4,000 gallons per minute. Each

clarifier receives influent from the chemical mix tank,

which currently provides less than adequate mixing

energy for the initial coagulation.

Each clarifier

has dimensions of thirty-nine feet (39’) in diameter and

twenty-two feet (22’) in height, therefore a surface area of

1,194 ft2 (square feet). Unless solids loading is very high

or mechanical restrictions exist, satisfactory clarification

can be achieved at flow rates of one (1) to one and a half

(1.5) gallons per minute per square foot of surface area

(gpm / ft2). At a nominal flow of 1.0 gpm / ft

2each

clarifier has a capacity of 1,194 gallons per minute (gpm)

for a total operating capacity of 5,970 gpm. At this flowrate the clarified water has a rise rate of only eight feet (8’)

per hour which is equivalent to 1.6 inches per minute. At

a surface loading of 1.5 gpm / ft2 each clarifier is capable

of 1,791 gpm or a total plant water clarification capacity of

8,955 gpm with a rise rate of 12 feet / hour equivalent to

2.4 inches per minute.

Although the floc settling rate for this clarification system

is not known, polymeric coagulant/solids floc may have

settling rates less than 2 inches / minute. In those circumstances where floc settling rates are less

than that required for good clarification at the desired flow rates, many options are available to

improve floc-settling rates.

• Consider the addition of other coagulants such as Ferric Sulfate or Alum. Alum Floc

has a settling rate of about 2 in./min (a surface loading of 1.25 gpm/ft2) with Ferric

Floc having a higher settling rate.

• Evaluate high molecular weight polymeric flocculants.






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• Test polymers with different charge densities and molecular weights.

• Evaluate the use of clay additives.

• Investigate the installation of settling tubes.

• Continuous recycle of clarifier blowdown sludge to the raw water sump to increase

solids contact and minimize solids bridging due to long sludge residence times.

• Optimize the upflow clarifier operating parameters such as agitator speeds, sludge

density, blanket levels, and consistent hydraulic loading.

Given the current clarification capacity of approximately 6,000 gpm at 1 gpm/ft2

and the

numerous options available to ensure or enhance this capacity, the addition of the clarifier/filter

(Trident or similar systems) is not considered necessary. This is of particular importance since

the proposed units operate much differently from the existing system and may introduceunnecessary complexity to the production of clarified and filtered water. Batch processes with

numerous operating steps and moving beds are less reliable in producing adequate and consistent

quality water than the current clarifiers.

• In addition, the stated plan would be to feed Alum as a coagulant to the new

clarifier/filters. It is recommended that consideration be given to feeding Alum to

the existing clarifiers and increase their rated capacity as opposed to the

installation of the proposed Trident or equivalent unit.

• The installation of the proposed Trident or equivalent unit would also impose the

requirement of additional backwash capacity. The filter well has limited capacityand the inventory of water is rapidly depleted whenever a current filter is

backwashed. Additional backwash water requirements from the filter well would

cause serious depletion of filtered water or cause operational problems if water

were unavailable.

• Another consideration, in evaluating future clarifier capacity requirements, is the

proposed use of clarified/filtered water from the filter well as cooling water make-

up. This adds approximately 700 gpm to the clarifier and filter water throughput

demand. Although the evaporative cooler make-up water should be clarified and

filtered, the main cooling water make-up to the surface condenser does not need to

be clarified and filtered. Raw water or ditch water, which is the current practice atthe CG facility, can be used as cooling water make-up. This will reduce the

required clarification and filter requirements by 700 gpm.

• The current filter well has a capacity of only 170,000 gallons. This reduces the

ability to operate the clarifiers at higher rates since filter well capacity is limited.

Increasing the backwash requirements for the Trident or comparable system and






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using filtered water for cooling tower makeup would further exacerbate this

situation.

• Current filter backwash requires 3,500 gpm for approximately 20 minutes, which

seriously depletes the available filter well water.

Doubling the storage capacity of the filter well

would improve operation of the plant. It

would provide additional filter backwash

water, permit better hydraulic load control of

the clarifiers (base loading) and better

response for short-term emergency

requirements for filtered water. However, it is

recognized that increase in the current under ground storage may not be feasible.

2.1.6 Filters

Nine (9) Permutit mixed media gravity fed

filters with a total design capacity of ~ 7500

gpm provide filtered water to a 170,000 gallon

underground concrete storage well. Five (5)pumps, with a total design capacity of 6350

gpm, take suction from the filter well and

provide filtered water to the demineralizer

system and other site users. Backwash for any

of the filters is restricted to one per shift due to

the backwash sump capacity and the pump out

rate.

• As stated earlier, operating flexibility of the water plant as well as clarifier flow

rates could be increased with additional filter well storage capacity. Filters could

be backwashed, more thoroughly or more frequently, without depleting the supply

of filtered water or inducing a hydraulic surge in the clarifiers. If the filter well

capacity were increased, clarifiers could be based loaded and a better water

reserve would be available for demineralization and backwash.

2.2 Intermediate Quality (IQ) Water






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2.2.1 Cation Exchange Units

There are currently four (4) cationic ionexchangers in service. Each unit is 11’ in

diameter and 11’ straight sides and containing

525 ft3 of strong acid resin. The resin depth is

5’ 6’’ in each unit. The units are regenerated

in reverse or counter-current flow using 4 lbs

of sulfuric acid per ft3 of resin. The service

flow rate is 900 gpm (1.7 gpm/ft3) with

theoretical exhaustion at about 1.3 MM gallons

of water or a designed once/day regeneration

schedule.

Operating under the present unit guidelines, four cation units can produce a maximum or 3600

gpm until one unit needs to be regenerated. With one unit in regeneration the other 3 units can

produce a nominal 2700 gpm of cation-exchanged water. Although the theoretical service

throughput is 1.3 MM gallons for each cation exchanger, most units are frequently regenerated

before reaching theoretical exhaustion or sodium breakthrough. With the current design of the

waste-water neutralization system combined with the plant’s efforts to minimize acid/base usage

costs, a cation exchange unit must be taken off-line and regenerated whenever an anion exchange

unit is being regenerated. Analogously, anion units will be taken off-line for early regeneration

whenever a cation unit must be regenerated. Therefore, the acid/base neutralization requirements

have a significant and negative impact on the demineralizer system operation. Coupled with thebrine “squeezing” process, the demineralizer system loses flexibility and cannot be operated

efficiently to provide demineralized water at the lowest cost and minimum water consumption.

The current net demand for cation exchange water is reported as 3300 gpm. This demand is met

with the current four units. Since cation regeneration is “tied-to” neutralization requirements for

anion regeneration, significant average service capacity is lost. Operating to theoretical capacity

or exhaustion is not possible on many occasions. To meet the capacity demands, all four cation

units are either in service or being regenerated. Essentially there is no standby cation exchange

unit because of the above mentioned neutralization requirements as well as other operating

practices.

If we assume that neutralization restraints are removed from the operating procedures and a

standby cation unit is present; there are still additional recommendations to increase the capacity

and/or service flow of all cation units:

• The lbs. of regenerant, sulfuric acid per cubic foot of resin, could be increased

from four (4) lbs. to six (6) or even eight (8) lbs. of sulfuric acid. Six (6) lbs. of






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acid would increase the kilograin capacity and throughput slightly more than 20%,

and 8 lbs. per cubic foot would increase capacity by almost 40%. Increased

regenerant also reduces sodium leakage. Lower sodium from the cation unit willalso reduce the silica leakage from the anion units. Without increasing the

quantity of resin or the number of vessels, the capacity could be increased by 40%

by increasing regenerant. Suggested service flow rates are 0.5 to 5.0 gpm/ft3. The

current service flow rate of 1.7 gpm/ft3

or 900 gals / min. could be increased by

40% to 1360 gpm per cation unit. This would take advantage of the increased

capacity from the increase in regenerant dosage/ft3. With one unit on stand by, the

current four cation units would have a nominal continuous capacity of 4,000 gpm

(3 units operating). To increase cation exchanger capacity to 5,000 gpm another

unit of comparable size would need to be installed.

• Conservation of IQ water should be investigated. Filtered water, instead of IQ

water, could be used for backwash, acid dilution, and rinsing for the cation

regeneration. This would represent a conservation of an average of 100 gpm IQ

water.

2.2.2 Anion Exchange Units

There are six (6) anion exchange units; three

(3) small and three (3) larger vessels. The

small units are 8’ in diameter with 9’ straight

sides and contain 221 ft3

of resin. The resindepth is 4’ 6”. The large units are 12’ in

diameter with 10’ straight sides and contain

650 ft3 of resin at a resin depth of 5’ 9”. These

units employ counter-current regeneration with

a total stated capacity of 3800 gpm. Current

operation normally requires that one small and

one large anion unit be in regeneration;

therefore, nominal anion exchanger capacity is 2500 gpm, with 500 gpm from the 2 small anion

exchangers and 2000 gpm from the 2 remaining large anion units. Under present operating

procedures there is no standby unit.

The anion units are regenerated using approximately 4.5 lbs/ft3 of caustic. Each anion unit is

also “brine squeezed” about once / month to remove organics. This process is fairly time

consuming and additional anion units will be required to compensate for the brine treatment,

unless additional solutions to organic contamination are investigated or implemented.

• As with cation exchange units the regenerant dosage for anion resins can be

increased to 6, 8 or even 12 lbs/ft3

of caustic. For many anion exchange resins,






16

the capacity increase is about 10% for each 2 lbs/ft3 of caustic, therefore

increasing regenerant from 4.5 lbs. to 12 lbs. per cubic foot would increase the

capacity by approximately 40% for each anion exchanger unit. Silica leakagewould normally also decrease. The recommended service flow rate is normally

between 1-3 gpm/ft3. If higher regenerant dosages were used, present service

flows could be increased and still be within the recommended range. An

increase of caustic regenerant to 10-12 lbs/ft3

would allow the service flow rate

to be increased in all the on-line, (5) large, units to 2.0 gpm/ft3. This would give

a service flow of 6,500 gpm with the sixth unit being in stand-by.

With two anion units normally in regeneration in the current operating system, service capacity

could also be increased by considering the following option:

• Replace the three small anion units, which contribute only 500 gpm, with threelarger units of sufficient size to give the desired capacity. At present the three

larger anion units can easily produce 3,000 gpm; therefore, another three units of

equal size could satisfy the 5,000 gpm water demand as well as have a standby

unit.

• Since organic contamination is a serious problem for strong base anion exchange

resins, macroreticular resins such as IRA-958, organic traps, and Alum or Ferric

coagulants in the clarification process should be investigated.

• Although IRA-402 is a gel resin with enhanced pore size, changing to a resin

with even large pore spacing such as IRA-458 should be considered. Converting

to IRA-958 or similar macroreticular resins would significantly reduce the rate of

organic fouling and may improve average service water capacity. The need for

brine squeezing could be greatly reduced which greatly simplifies the whole

demineralization process.

• Organic traps make use of macroreticular strong base anion exchange resins such

as IRA-958 operated in the chloride form strictly for organic removal. The

organics are absorbed on the resin but removed by regenerating with salt/caustic.

The best system requires separate anion vessels and regeneration procedures.

The organic trap is placed ahead of the strongly basic anion resin, but its

operation essentially minimizes organic fouling and the complex and timely

process of “brine squeezing” of exchange resins.

•

Organic concentration in the SBW raw water varies seasonally. Although TOCindicates the level of organic contamination, it does not predict which waters will

have more tendencies to foul anion exchange resins, because molecular weight

variation of organics is not detectable by TOC analysis. Determining the actual

organic fouling tendencies of water, through laboratory testing of various anion

exchange resins, would be extremely valuable in simulating plant operations.






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• Removal of organics in the clarification/filtration processes is usually an

excellent approach. Maximizing chlorination then dechlorinating ahead of the

demineralizer will usually greatly reduce organics.• The use of Alum or Ferric salts in the clarification process will assist in the

removal of organics to below troublesome levels.

The addition of the CG LP Co-Generation project as a “Stand-Alone" facility should only

increase the demand for Intermediate Quality (IQ) water by 200-300 gallons per minute. This

amount of water would normally easily compensate for steam venting, boiler blowdown and/or

sample lines for any large combined cycle heat recovery facility. Based solely on this “Stand-

Alone” concept, no water plant expansion would be necessary. The increase in IQ water demand

can easily be handled by the existing pre-treatment and demineralization system. Even if

clarified and filtered water is used for cooling tower make-up, the current water plant could

handle the extra 900 plus gpm.

2.3 HIGH QUALITY (HQ) WATER

2.3.1 Mixed-Beds

The two (2) mixed-bed polishing units currently in service are essentially the same size but are

referred to as the large and small units. Both are 10’ in diameter with 10’ straight sides. Each

mixed-bed contains about 230 ft3 of strong acid cation exchange resin and 155 ft3 of strong base

anion exchange resin. One is operated at 900 gpm and the other at 1,000 gpm with no apparentreason for the difference. The current requirement is only 600 gpm of HQ water for on site users.

At any given time, one polisher is either in regeneration or on standby while the other is in

operation. Each mixed-bed is capable of producing 18 MM gallons of high quality polished

water before regeneration; however, effluent conductivity must be below 0.5 micromhos with

silica below 0.1 ppm.

These mixed-bed polishers can obviously handle more service flow and be regenerated more

frequently. Maximum service flow capacity for mixed bed polishers is usually based on pressure

drop considerations for the vessel, sodium leakage limitations of effluent water, and resin

durability factors rather than regeneration schedules. The two present mixed-beds contain

approximately 390 ft3

of combined cation and anion exchange resin. At a designed service flowrate of 2-5 gpm/ ft

3of resin, each mixed-bed can provide 780-1950 gpm of HQ water for a total

capacity of 1560-3900 gpm. Unless there is a back-pressure and/or unexpected sodium leakage

problem, the required HQ water expansion capacity of 3,807 gpm can be handled by the current

two mixed-bed units. A third mixed-bed of equal dimensions would be required to serve as a

stand-by unit.






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The addition of the CG LP Co-Generation project as a “Stand-Alone" facility should only

increase the demand for High Quality (HQ) water by 200-300 gallons per minute. This water

would be received from the IQ water demineralizers. This amount of HQ water would normallyeasily compensate for steam venting, boiler blowdown and/or sample lines for any large

combined cycle heat recovery facility. Based on this “Stand-Alone” concept no water plant

expansion would be necessary. The existing pre-treatment, demineralization, and mixed-bed

polishing system can easily handle the increase in HQ water demand. Even if clarified and

filtered water is used for cooling tower make-up, the current water plant could handle the extra

900 plus gpm.

2.3.2 Condensate Return

Current plant operation requires continuous condensate return of 800-1000 gpm to the PowerHouse and existing co-generation unit. This quantity of condensate return ensures the

availability of demineralizer intermediate quality water to boilers. An additional supply of ~125

gpm of condensate is to be available with the completion of the project. No condensate water

balance for current or future operations was available. Several boilers will be shuttered after the

completion of the co-generation facility, which is designed to export steam.

Based on the proposed expansion, most steam will now be produced using High Quality (HQ)

water, which is more costly to produce than the Intermediate Quality (IQ) water currently used to

produce steam and condensate. Greater economic loss occurs when condensate produced from

more costly make-up water is not returned for reuse.

The importance of quality condensate recovery cannot be overemphasized. Condensate return

also reduces the need for IQ water production. Any reduction in IQ water requirement cascades

beneficially throughout the water plant system resulting in decreased requirements for

clarification, filtration, and neutralization. This reduces operating cost and also impacts the

current capital expansion requirements.

2.4 Waste Water Neutralization and Brine Soak Water

There are five (5) fiberglass waste neutralization tanks each with a capacity of 30 M gallons. Thesystem is equipped with 2,000 gpm recirculating/transfer pumps for pH control, with the optional

addition of either sulfuric or caustic. Due to high TOC and TDS waters from the brine soak of

anion resins, the discharge of neutralized waste is monitored for pH and TOC prior to disposal to

on-site bio-oxidation ponds.

The process of wastewater disposal from demineralization has seemingly taken precedent over

the demineralization process. The demineralizers are operated inefficiently in deference to






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neutralization and cost reduction concepts in acid/base usage during neutralization. Significant

attention should be given to reestablishing a focus of priority to demineralization performance,

yet still achieve neutralization of wastewaters.

• The removal or replacement of the three small anion units and the use of acrylic

resins and/or organic traps could have tremendous potential in simplifying or even

reducing the cost of neutralization. Organic traps offer the opportunity to reduce

the frequency of brine soaks or squeezing thus greatly reducing the quantity of

high TDS wastewater.

• Increasing the frequency of brine soaks and expanding the neutralization process

with additional tanks, mixing capabilities and more complex controls should be

eliminated if at all possible. Minimizing the fouling of active anion exchangers

by preceding them with organic traps also offers the opportunity for operationalsimplicity and flexibility in all aspects of IQ water production.

2.5 Operating Costs and Manpower Requirements

The current water system is highly integrated with other plant facilities. Caustic, acid, and power

supply are shared by numerous CG operations and separate costs for the water system are

undocumented and unavailable. The water plant manpower is currently at two (2) operators/shift

with no direct supervision.

The annual budget would provide a detailed review of the itemized operating and capital project

cost projections for the year 2000. Previous records should indicate past cost allocations to thewater plant.

The designed plant expansion introduces significant additional equipment and complexity of

operations and it is anticipated that additional operators and/or manpower costs would be

necessary. A projected annual operating cost could be built from past known costs plus any costs

anticipated from the final expansion plans.

2.6 Equipment Capacities

The existing water plant as designed is capable of reliably generating a maximum of:

• 6,000 gpm clarified and filtered water

• > 3,000 gpm IQ water, limited by the current anion exchange capacity

• 2,600 gpm mixed bed






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The operational and service modifications required to achieve these capacities are discussed

above.






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3.0 NEW WATER PLANT

The following evaluation is based solely upon the new water plant design scenarios (Bechtel)

provided by SGS. Justification for the water/steam requirements for the installation was not

provided.

3.1 Clarification/ Filtration

Based on the objectives of the project and the design bases, the maximum clarification system

capacity required is 5,870 gpm. This clarification capacity was established for the “Ethylene

Startup” scenario.

Cooling tower make-up water of 702 gpm is included in the 5,780 gpm clarification requirement.

If raw water instead of clarified and filtered water is used as cooling tower make-up, the actual

clarifier capacity requirement decreases to 5,168 gpm. As discussed previously, the current five

clarifiers can produce over 6,000 gpm; therefore expansion of the clarification capacity by the

installation of the Trident or similar unit is not necessary. Without the Trident or similar units

the backwash water requirements reduce by 15-20 gpm and the maximum clarified water

requirements become 5,150 gpm.

In the event the Ethylene start-up should occur during a coincidental shutdown of one clarifier,

the remaining four clarifiers could produce an adequate supply of water on a short-term basis tohandle start-up requirements of 5,150 gpm.

Other than optimizing the current clarification system through evaluation of

coagulants/flocculants, chemical feed locations, mixing, and other parameters pertinent to

clarifier performance, no additional clarifiers are required for the system expansion.

3.2 Filter well/Clear well

The current filter well capacity is approximately 170,000 gallons. Additional filter well capacity

of 170,000 gallons would allow for greater flexibility in filter backwashing and ensure watersupply to the demineralizer system. Additional filter well capacity would also allow an increase

in clarifier base loading and minimize hydraulic surges during clarification.

Since the current filter well is located as sub-surface storage it would be very difficult if not

impossible to increase the capacity of the current filter well. Ground space is not readily

available, and it may also be impractical to add any additional capacity as surface storage because






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gravity-flow filtration is currently used. Any surface storage would require pumps and control

systems in order to be used as additional filter well capacity.

Although additional filter well storage would increase the system flexibility, it appears there is no

easy or practical way to increase the filter well storage at the present water plant location.

3.3 Intermediate Quality (IQ) Water

3.3.1 Cation Exchange

The largest IQ water demand for the expansion project is 4,503 gpm which is required for the

“Ethylene Start-up” scenario. This is significantly higher than the “Peak Normal” requirement

which is 3,914 gpm.

The current cation exchange system consists of four (4) cation exchange units each with 525 ft3

of resin. Each unit is capable of handling over 1500 gpm without exceeding the pressure drop

constraint of 20 psi maximum. For each cation exchange unit to produce the required 1125 gpm

of quality water, would necessitate a change in the quantity of regenerant acid per cubic foot of

resin if the systems were to retain the same regeneration schedule. As noted earlier, increasing

acid regeneration from 4 lbs/ft3

to 8 lbs/ft3

of resin would provide a 40 % increase in capacity,

thus compensating for the additional throughput.

Different regeneration procedures would be required if the sulfuric regenerate were increasedabove the current dosage of 4 lbs./ft3. Increasing the service flow rate and the sulfuric acid

regeneration dosage would allow the unit regeneration frequencies to remain the same if based on

exhaustion or throughput.

Using both weak acid and strong acid cation resins in each cation exchanger is another approach

to increase the service capacity of the cation exchange system. Compared to strong acid resins,

weak cation resins have higher exchange capacities and regenerate to 100% capacity, but only

exchange those cations associated with alkalinity.

The filter well water contains about 20% of its anions as bicarbonate alkalinity. The weak-acid

cation resin would remove cations, equivalent to the available alkalinity, whereas, the strong-acidresin would remove those cations not associated with alkalinity. By replacing strong acid resin

with weak acid resins where sufficient alkalinity exists, the capacity of the system can be

dramatically increased even at the same acid regeneration dosage.

Although a few procedures may need to be changed, it is apparent the present four (4) cation

units could handle the expansion demands for 4,503 gpm of IQ water. An additional cation

exchange unit of similar capacity would need to be installed as a standby unit.






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3.3.2 Anion Exchange

In order to meet the maximum IQ water production rate of 4,503 gpm, changes in the anion unitsare required. The current system has six anion units, three small and three larger vessels. As

previously discussed the three small units represent only 750 gpm of IQ water capacity as

compared to 3,000 for the three larger units. It is recommended that these three small units

should be replaced with the appropriate number of large units. This would tremendously reduce

operational complexity and improve reliability of IQ water production.

With a total of five (5) large units, each containing 650 ft3

of anion exchange resin and

regenerated at larger caustic dosages, 4,503 gpm of IQ water could be produced with four units in

operation and one unit on standby.

The greatest factor in the reliability of anion exchange capacity is the control or prevention of organic fouling. Current acrylic resin technology and macroreticular resin structures both greatly

reduce the fouling tendency normally associated with anion resins. To minimize organic fouling,

these technologies can be used in the anion exchanger units, in organic traps ahead of the system,

or in both.

Organic traps are not designed to remove anions from the water, they serve to collect organics

and protect the anion exchange resins that follow. Organic fouling of IQ water anion exchange

resin does interfere with the exchange of anions; therefore, the resins must be cleaned regularly.

“Brine squeezing” of organic traps is conducted less frequently, since the collected organics do

not interfere with other functionality of the resin.

Although brine squeezing will still be required, the decreased frequency in favor of the organic

traps warrants consideration. Although the economics is not known, it appears that retaining the

three small anion units and adding several more large anion units while increasing the squeezing

frequency only exacerbates the operating difficulties and even perhaps the capital cost of the

water system.

Considering the complexity and difficulty associated with brine “squeezing”, the time involved,

and the large impact on water discharge characteristics, it appears that organic traps as well as

acrylic resins may provide the most reliable system for IQ water production.

3.4 High Quality (HQ) Water

The proposed largest demand for HQ water is 3,807 gpm corresponding to the “Steam

Emergency” scenario. High Quality water is currently produced using two mixed-bed units with

inlet water consisting of condensate and IQ water. The current production of HQ water is only

600-700 gpm; therefore, the increase in maximum demand to 3,807 gpm is substantial. This is






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also significantly higher than the “Peak Normal” requirement 2,698 gpm. Because the mixed bed

units always receive demineralized and condensate water as influent, the mixed-bed units

function as “polishers”. At their current service flow rate they are regenerated after 20-30 days of operation or after 18 MM gals of water have been processed.

These mixed-bed polishers can obviously handle more service flow and be regenerated more

frequently. Maximum service flow capacity for mixed bed polishers is usually based on pressure

drop considerations for the vessel, sodium leakage limitations of effluent water, and resin

durability factors rather than regeneration schedules. The two present mixed-bed units are 10’ in

diameter with 10’ straight sides and contain approximately 390 ft3

of combined cation and anion

exchange resins about 5’ in depth. At a designed service flow rate of 2-5 gpm/ ft3

of resin, each

mixed-bed can provide 780-1950 gpm of HQ water for a total capacity of 1560-3900 gpm.

Unless there is a backpressure or unexpected effluent quality problem, the required HQ water

capacity of 3,807 gpm can be handled by the current two mixed-bed units. A third mixed-bed of equal dimensions would be required to serve as a stand-by unit.

3.5 Operating Cost and Manpower Requirements

Based on the evaluation of the water plant operated to these requirements, additional manpower

is not required compared to the existing water plant operations.

3.6 Equipment Capacity

The following flow requirements were used for a basis of primary equipment additions:

• 600 gpm unfiltered raw water to cooling tower make-up (continuous)

• 5,168 gpm clarified and filtered water (“Ethylene Startup” scenario)

• 4,503 gpm IQ water (“Ethylene Start-up” scenario).

• 3,807 gpm HQ (“Steam Emergency” scenario).

Based on the evaluation of the water plant operated to these requirements, the following primaryequipment additions are required:

• Replace the three small anion units with three larger units with capacity of 650 ft3

of resin). The total of six units of equal size would produce an estimated 5,000

gpm water with one unit in standby.






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• Addition of a fifth cation unit equivalent in capacity to the existing units. The

total of five units of equal size would produce an estimated 4,500 gpm water with

one unit in standby.

• Addition of a third mixed bed unit equivalent in capacity to the existing units.

Each mixed-bed contains about 230 ft3

of strong acid cation exchange resin and

155 ft3

of strong base anion exchange resin. Based upon a service flow rate of 2-5

gpm/ ft3 of resin, this would provide up to 3,900 gpm with one unit as a standby

unit.

• The existing clarification and filter systems are sufficient for operation and no

additional capacity is required.

It should be noted that the above capacities and equipment additions are based upon “short

duration events”. Normal peak operating conditions require significantly lower capacities asfollow:

• 5,190 gpm clarified and filtered water which includes 742 gpm to cooling tower

make-up and evaporative coolers.

• 3,914 gpm IQ water.

• 2,688 gpm HQ.

Using these normal peak operating capacities, the equipment additions are still required andrecommended in order to provide the specified “N+1” redundancy for clarifiers, cation/anion

exchangers and mixed-bed exchangers.

The operational and service modifications required to achieve these capacities are discussed

above.






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4.0 Stand-Alone Facility

Recommendations are provided for operation of the water plant to provide water only for the

HRSG Plant (CG LP Co-Generation Facility).

4.1 Case A: No Steam Export

As a stand-alone facility, with essentially 100% condensate recovery, only a small volume of HQ

make-up water is required. HQ water is only necessary to replace steam venting, continuous

water samples, and/or blowdown. Also, if raw water is used for cooling tower make-up, then

clarified/filtered water requirements are also fairly low. Essentially a Power Plant of almost any

capacity can be operated with water systems capable of producing peak <500 gpm of HQ Water.

To produce this quantity of HQ water for continuous operation, several options can be

considered:

• Well water or city water that has been clarified or filtered can be used as feed

water to a HQ water plant. The HQ facility would consist of filters, reverse

osmosis, followed by demineralization.

• If surface water were used as raw water, clarification and filtration would precede

reverse osmosis and demineralization.

• For start-up operations several hundred thousand gallons of HQ storage would be

required or alternatively a commercial mobile water service could be used.

4.2 Case B: Steam Export Facility

If all steam exported is returned as condensate, the water plant make-up system would be the

same as described above. Provisions for polishing the returned condensate would probably be

desirable depending on steam usage and operational requirements.

If condensate return were substantially less than exported steam, then water make-uprequirements would increase proportionately.

• Make-up water would require clarification and filtration, followed by

demineralization. Reverse osmosis would probably be eliminated from

consideration in those cases where make-up demands approach 700-800 gpm.





S G i S I

• Additional demineralization capacity would provide all high quality make-up

water after clarification and filtration.

4.3 Operating Cost and Manpower Requirements

Insufficient information is available to determine to the manpower required to operate the water

plant as a “stand alone” facility.

Based solely on day to day operating requirements, one (1) operator per shift, unsupervised

would meet normal water plant needs. As a stand alone facility integrated into a power

generation facility, dedicated chemistry, operations and maintenance personnel may not berequired. Many such facilities rely on the plants existing, or contracted operation and

maintenance personnel to perform these duties in the water plant. The direct manpower costs

including supervisors, maintenance and repair personnel, instrumentation & calibration

technicians, laboratory support, engineering & other support personnel, as well as management

costs are difficult to assess without the current annual budget.

The current annual budget would provide a detailed review of the itemized operating and capital

project cost projections for the year 2000. Previous records should indicate past manpower cost

allocations to the water plant.

4.4 Equipment Capacities

Insufficient information is available at this time to estimate equipment requirements for operation

of the water plant as a stand-alone facility producing water solely for power plant operation. In

the absence of steam export requirements, the produced water requirements are very low (< 500

gpm HQ peak). However, the CG units as designed produce steam for export and may be

difficult or impossible to operate as a contained, power generation system which is not integrated

into a secondary user.

Documents

Water Plant Evaluation