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DOE/FE’s Power Plant Water Management R&D Program Summary, July 2005 

## Department of Energy/Office of Fossil Energy’s Power Plant Water Management R&D Program

Thomas J. Feeley, III 1 , Lindsay Green 2 , James T. Murphy 2

, Jeffrey Hoffmann 1 , and Barbara A. Carney 1

1. U.S. Department of Energy, Na tional Energy Technology Laboratory

2. Science Applications International Corporation

INTRODUCTION

Coal-fired power plants utilize significant quant ities of both coal and water for generating electrical energy. For example, a 500 MW power plant bur ns approximately 250 tons per hour of coal while using over 12 million gallons per hour of water for cooling and other process requirements a . The United States Geological Survey (USGS) estimates that thermoelectric generation b accounts for approximately 136,000 million gallons per day (MGD) of freshwater withdrawals c , ranking only slightly behind agricultural irrigation as the largest source of freshwater withdrawals in the United States. 1 As U.S. population and associated economic development continues to expand, the demand for electricity will increase. The Energy Information Administratio n’s (EIA) latest forecast estimates U.S. coal-fired generating capacity will grow from approxima tely 305 GW in 2003 to 389 GW
in 2025. 2 As such, coal-fired power plants may increasingly compete for freshwater with other sectors such as domestic, commercial, agricultural, industrial, and in-stream use – particularly in regions of the country with limited freshwater supplie s. In addition, current and future water-related environmental regulat ions and requirements will also challenge the operation of existing power plants and the permitting of new thermoelectric generation projects.

In response to these challenges to natio nal energy sustainability and security, the Department of Energy/Office of Fossil Ener gy’s National Energy Technology Laboratory (DOE/NETL) has initiated an integrated re search and development (R&D) effort under its Innovations for Existing Plants (IEP) program directed at technol ogies and concepts to reduce the amount of freshwater used by pow er plants and to minimize any potential impacts of plant operations on water quality. This paper provides background information on the relationship between water and thermo electric power generati on and describes the R&D activities currently being sponsored by DOE/NETL’s IEP program to address current and future water-energy issues.

a Actual cooling water flow rate requirements for a pa rticular plant will vary depending on type of cooling water system and design parameters.

b Thermoelectric generation includes coal, oil, natural gas and nuclear power generation. Coal-based generation represents approximately 58% of total U.S. thermoelectric generation based on EIA AEO 2005
estimates.

c This includes both surface and ground water withdrawals.BACKGROUND

Water Use for Thermoelectric Power Generatio n

Therm o electric generation represents the larg est segm ent of U.S. electricity production and coal-based power plants alone generate more than half of the nation’s electricity supply. According to U S GS water use survey data, 346 billion gallons of freshwater per day (BGD) was used in the United States in 2000. Figure 1 presents the percentage of

tota l U.S. f r eshwater wit hdrawal by source category. Therm o ele c tric generation accounted for 39% (136 BGD) of all freshw ater withdrawals in the nation in 2000, second only to irrigation. E ach kW h of therm o electric gene ration requires approximately 25 gallons of water d , prim arily used for cooling purposes – a 500 M W power plant would use approxim a tely 300 m illion gallons of water per day. However, power plants also use water for operation of pollution control devices such as flue gas desulfurization (FG D ) technology as well as for as h handling, wastewater treatm ent, and wash water. W h en discussing water and therm o electric generation, it is im portant to distinguish between
water use and water consum pti on. Water use represents the to tal water withdrawal from a source and water consumption represents the amount of t h at withdr awal that is not
returned to the source. Alt hough therm o electric generation is the second largest user of water on a withdrawal basis, it was only re sponsible for about 3% of the total of 100
BGD freshwater consum ed in 1995 com p ared to 81% for irrigation as shown in Figure

2. 3

Fi gure 1 – U. S

. Freshw ater Wi thdr aw al ( 2 0 0 0 ) Fi gure 2 – U. S

. Freshw ater Co nsum pti o n (1 9 9 5 )

Fr es hw ater W i t hdr a w al b y S e c t o r

T her m oel e c t r i c
39% P ubl i c S upp l y
13%

A quac u l t u r e
1%

I ndus t r i a l

5% M i ni ng

1% Li v e s t oc k

1% I rri g a t i o n

40% Do m e s t i c

1% Fr es hw at er C ons um pt ion by S e c t or

C o mme r c ia l

1% Do m e s t i c

7%

I rri g a t i on

81% Li v

e s t o c k

3% T h erm o e l ec t r i c
3% Min i n g

1% I n dus t r i a l

3%

As discussed above, large quantities of c ooling water are required for therm o electric power plants to support the generation of elect ricity. Therm o electric generation relies on a fuel source (fossil or nuclear) to heat wate r to steam that is used to drive a tu rb inegenerator. Steam exhausted from the turbin e is condensed and recycled to the stea m

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y 2 0 05 d This num b er is a weighted a v era g e t h at captures t o tal therm o electric water with d r awal s an d gene rat i o n fo r bot h once

- t h ro ug h a n d reci rc ul at i ng c o ol i n g sy st em s.generator or boiler. The steam condensation ty pically oc cu rs in a shell-and-tube h eat exchanger known as a condenser. T h e steam is condensed on the shell side by the flow of cooling water through tube bundles located w ithin the condenser. C ooling water m a s s flow rates of greater than 25 tim e s the stea m ma s s fl o w r a t e a r e necessary depending on
the allowab l e tem p erature rise of the cooling water – typically 15-2 5 oF. There are basically tw o types of cooling water syst em designs – once-through (open loop) or recirculating (closed loop). In once-through sy stem s the cooling water is withdrawn from a local water body su ch as a lak e , river, or ocean and the warm cooling water is subsequently discharged back to the sam e water body after passing through the condenser. As a result, plants equipped with once-through cooling water system s have relatively high water use, but low water consum ption. The m o st comm on type of recirculating system uses wet cooling towers to dissipate the h eat f r om the cooling water
to the a t m o sphere. In wet rec i rcu l ating sy s t e m s the warm cooling water is ty pically

pum p ed from the condenser to a cooling tower where the heat is diss ipated directly to

am bient air by evaporation of the water and he a ting the a i r. The cooling water is then recycled b a ck to the con d enser. In addition to cooling towers, cooling ponds or lakes can
also be used to accom p lish evaporation in recircu l ating syste m s.

Because of evaporative losses, a po rtion of the cooling water needs to be discharg ed fr om the system – known as blowdown

− to prevent the buildup of m i nerals and sedim e nt in
the water th at cou l d adv e rsely affect perfor m a nce. For a wet recirculating system , only

m a keup water needs to be withdrawn from the local water body to replace water lost through evaporation and blowdow n. As a result, plants equi pped with wet recirculating
system s have relatively low water use, but high water consumption, compared to oncethrough system s. Typica l wet recirculating c ooling water system flow rates for a 650 M W coal-fired plant are shown in Figure 3

. Figure 3 - Pr ocess Flow Schematic for We t Recirculating Cooling W a ter Sys t em

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y 2 0 05 Boiler

Feedw a ter Boiler

Stea m Evaporat ion

& Drift 5,03 5,0 00 lb/hr

6,50 0 gpm

650 M W

Generator Turbine

Cooling

To w e r 260, 00 0 gpm Condensate War m Water

20 o F Ri se Stea m Condenser Cool Wat e r 10,0 00 gpm

Mak e
- u p Wate r Blo w do wn

7,00 0 gpm 500 gpm4

DOE/FE’s Power Plant Water Management R&D Program Summary, July 2005 Wet cooling towers are available in two ba sic designs – mechanical draft and natural
draft. Mechanical draft towers utilize a fan to move ambien t air through the tower, while natural draft towers rely on the difference in air density between the warm air in the
tower and the cooler ambient air outside the tower to draw the air up through the tower. In both designs the warm cooli ng water is discharged into the tower for direct contact
with the ambient air.

A second type of recirculating cooling system is known as dry cooling. Dry recirculating cooling systems use either direct or indirect air-cooled steam condens ers. In a direct aircooled steam condenser the turbine exhaust steam flows through air condenser tubes that are cooled directly by conductive heat transfer using a high flow rate of ambient air that is blown by fans across the outside surface of the tubes. Therefore, cooling water is not used in the direct air-cooled system. In an indirect air-cooled st eam condenser system a
conventional water-cooled surface condenser is used to condense the steam, but an aircooled closed heat exchanger is used to c onductively transfer the heat from the water to the ambient air. As a result, there is no evapor ative loss of cooling water with an indirectair dry recirculating cooling system and both water use an d consumption are minimal. Due to relatively higher capital and opera ting costs and lower performance, dry recirculating cooling systems are not as pr evalent as the wet recirculating cooling
systems.

Of the 136 BGD of freshwater use by thermo electric generators in 2000, USGS estimated approximately 88% was used at plants w ith once-through cooling systems. Table 1 presents an estimate of average water use and consumption for once-through and recirculating systems based on year 2000 data from EIA’s Form 767 report. 4 Oncethrough systems have very high water use require ments, but since nearly all of the water is returned to the source body, consumptiv e losses are low on a percentage basis. Recirculating wet systems have lower water use requirements, but consumptive losses through direct evaporation can be relativel y high on a percentage basis. In 2001, approximately 31% of thermoelectric genera ting units were equipped with wet cooling towers, representing approximately 38 % of installed generating capacity.

Table 1 – Average Cooling System Water Use and Consumption

Average gal/kWh Type of Cooling Water System Water Use Water Consumption Once-through 37.7 0.1 Recirculating wet 1.2 1.1

It is difficult to estimate future freshwater use and consumption by thermoelectric generation due to changes in the type of generation, method of cooling, and source of water. Based on EIA projec tions of thermoelectric generation in 2025, DOE/NETL estimates that daily freshwat er withdrawals could decreas e to 113 BGD or increase to 138 BGD, and that daily freshwater consumpti on could remain at 3.3 BGD or increase to

8.7 BGD. 55

DOE/FE’s Power Plant Water Management R&D Program Summary, July 2005 Impact of Water Availability on Thermoelectric Power Generation

Freshwater availability is a critical limiting factor in economic development and sustainability and directly impacts elect ric-power supply. A 2003 study conducted by the Congressional General Accounting Office i ndicates that 36 states anticipate water shortages in the next ten years under normal water conditions, and 46 states expect water shortages under drought conditions. 6 Water supply and demand estimates by EPRI for the years 1995 and 2025 also indicate a high likelihood of local a nd regional water shortages
in the United States. 7 The area that is expected to face the most serious water constraints
is the arid southwestern United States

.

In any event, the demand for water for thermoelectric generation will increasingly compete with demands from other sectors of the economy such as agriculture, domestic, commercial, industrial, mining, and in-stream us e. EPRI projects the potential for future constraints on thermoelectric power in 2025 for Arizona, Utah, Texas, Louisiana, Georgia, Alabama, Florida, and all of the Pacific Coast states. Competition over water in the western United States, in cluding water needed for power plants, led to a 2003 Department of Interior initia tive to predict, prevent, and alleviate water-supply conflicts. 8

Other areas of the United States are also susceptible to freshw ater shortages as a result of drought conditions, growing populations, and increasing demand.

Concern about water supply expressed by state regulators, local decision-makers, and the general public is already impacting power projects across the United States. For example, Arizona recently re jected permitting for a proposed power plant because of
concerns about how much water it w ould withdraw from a local aquifer. 9 An existing Entergy plant located in New York is being required to install a closed-cycle cooling water system to prevent fish deaths resu lting from operation of its once-through cooling
water system. 10 Water availability has also been identified by several Southern States Energy Board member states as a key factor in the permitting process for new merchant power plants. 11 In early 2005, Governor Mike Rounds of Sout h Dakota called for a summit to discuss drought-induced low flows on the Missouri River and the impacts on irrigation, drinking-water sy stems, and power plants. 12 Also, residents of Washoe County, Nevada expressed opposition to a propos ed coal-fired power plant in light of concerns about how much water the plant would use. 13 Another coal-fir ed power plant to be built in Wisconsin on Lake Michigan ha s been under attack from environmental groups because of potential effects of the facility’s cooling-wa ter-intake structures on the Lake’s aquatic life. 14

Such events point towards a likely future of increased conflicts and competition for the water the power industry will ne ed to operate their thermoelectric generation capacity.
These conflicts will be national in scope, but regionally drive n. It is likely that power plants in the west will be confronted with i ssues related to water ri ghts, that is, who owns the water and the impacts of ch ronic and sporadic drought. In the east, current and future environmental requirements, such as the Clean Water Act’s intake structure regulation, could be the most significant impediment to securing sufficien t water, although local drought conditions can also impact water avai lability. Key environmental regulations that can potentially impact power plants are summarized below.6

DOE/FE’s Power Plant Water Management R&D Program Summary, July 2005

Environmental Regulations Affecting Thermoelectric Power Generation Water Use

The U.S. Environmental Protection Agency (EPA) has been charged with maintaining and improving the Nation's water resources for uses including but not limited to agricultural, industrial, nutritional, ecological, and recreational. To accomplish this goal, EPA has issued several regulations under th e Clean Water Act and the Safe Drinking Water Act that directly impact the discharge of pollutants from power plants to receiving
waters as well as the intake of water fo r cooling and other power plant needs. The following is a summary of regulations that affect power plant water use.

The Clean Water Act

The Clean Water Act (CWA) provides for the regulation of discharges to the Nation's surface waters. The CWA calls for a federal-state partnership in which the federal government sets the standards for pollution di scharge and states are responsible for the implementation and enforcement. Initial emphasis was placed on "point source" pollutant discharge, but 1987 amendments au thorized measures to address "non-point source" discharges, including st ormwater runoff from industri al facilities. Permits are
issued under the National Pollutant Discha rge Elimination System (NPDES), which designates the highest level of water polluti on or lowest acceptable standards for water discharges. With EPA approval, the states ma y implement standards more stringent than federal water quality st andards but they may not be less st ringent. Certain sections of the CWA are particularly applicable to water issues related to power generation and are
described below in more detail.

• CWA §303 Water Quality Standards and Implementation Plans - Section 303 of the CWA, the Total Maximum Daily Load (TMDL) program, requires states to develop lists of impaired waters—water bodies that do not meet water quality standards (WQS) that the states have se t, even after the installation of the minimum required levels of pollution c ontrol technology. States must then establish priority rankings for waters that do not meet the WQS and develop
TMDLs for these water bodies. A TMDL specifies the maximum amount of a pollutant that an impaired water body can receive and still meet WQS. While states are responsible for establishi ng the TMDL, the CWA requires EPA to approve or disapprove the impaired wa ter lists and TMDLs established by the states. After establishing a TMDL, states have 10 years to develop implementation plans for improving the quality of the affected waters.

• CWA §316(a) Water Thermal Discharge – Section 316(a) requi res the regulation of water thermal discharge from cooli ng water systems in order to protect shellfish, fish, and ot her aquatic wildlife.

• CWA §316(b) Cooling Water Intake Structures – Section 316(b) is arguably the most urgent water-related issue facing th ermoelectric power generation in the near term. This section requires that the location, design, construction and capacity of cooling water intake structures refl ect the best techno logy available for minimizing adverse environmental impact, such as impingement or entrainment of aquatic organisms due to the operati on of cooling water in take structures.7

DOE/FE’s Power Plant Water Management R&D Program Summary, July 2005 •

•

•

• Regulations to implement Section 316(b) are being issued in three phases that cover different facility categories. The Phase I rule was issued in December 2001 and effectively requires all new thermoelect ric power generation plants to install closed-cycle cooling systems due to st andards for water intake capacity and velocity. The Phase II rule, issued in Ju ly 2004, applies to existing thermoelectric power generation plants that withdraw more than 50 MGD of water and use at least 25 percent of the water withdraw n for cooling purposes only. Although the Phase II rule requires significant percenta ge reductions in both impingement and
entrainment losses from uncontrolled levels , it also provides flexible compliance alternatives so that conversions of open-cycle to closed-cycle cooling water systems are not mandated. Regulations for Phase III were proposed in November 2004 and will apply to other industrial s ources and new offshore and coastal oil and gas extraction facilities.

The Safe Drinking Water Act – The Safe Drinking Water Act (SDWA) serves to protect
humans from contaminants in the Nation’s public drinking water supply. Amended in 1986 and 1997, the law requires many actions to protect drinking water and its sources. The SDWA requires EPA to set national drinking water standards and create a joint federal-state system to ensure compliance. While the provisions of the SDWA apply directly to public water systems in each state, the Act is relevant to thermoelectric power generation because waste streams may contai n detectable levels of elements or compounds that have established drinking wate r standards. Under the SDWA, regulations that would require additional limits on mercury, arsenic, and other trace metals could also affect how power plants di spose of coal by-products.

INNOVATIONS FOR EXISTING PLANTS PROGRAM

DOE/NETL’s IEP Program is a comprehensive R&D effort directed at the development of advanced technologies and knowledge produc ts that can enhance the environmental performance of the existing fleet of coal-fir ed power plants. In response to the growing recognition of the inter-dependence between freshwater availability and quality and electricity production, the IEP program was broadened in 2003 to include research directed at coal-fired power plan t related water management issues. 15 The overall goal of
this effort is to reduce the am ount of freshwater needed for power plant operations and to minimize potential impacts on water quality. The research encompasses laboratory and bench-scale activities through pilot- and full- scale demonstrations and is performed in partnership and collaborati on with industry, academia, t echnology developers, and other government organizations. The program is bu ilt around four specific areas of research:

Non-Traditional Sources of Pr ocess and Cooling Water Innovative Water Reuse and Recovery Advanced Cooling Technology Advanced Water Treatment and Detection Technology

The following is a brief summary of se veral recently completed and on-going R&D projects in these four res earch areas. Several water-re lated projects funded under the8

DOE/FE’s Power Plant Water Management R&D Program Summary, July 2005 University Coal Research and the Clean Coal Power Initiative programs are also
discussed.

Non-Traditional Sources of Process and Cooling Water

Research and analysis are being conducted to evaluate and develop cost-effective approaches to using non-traditional sources of water to supplement or replace freshwater for cooling and other power plant needs. Wate r quality requirements for cooling systems
can be less restrictive than many other applications such as drinking water supplies or agricultural applications, so opportunities exist for the ut ilization of lower-quality, nontraditional water sources. Examples incl ude surface and underground mine pool water 16

, geological carbon sequestration and coal-bed methane produc ed waters, and industrial and/or municipal wastewater.

Strategies for Cooling Electric Generating Fa cilities Utilizing Mine Water: Technical and Economic Feasibility

West Virginia University’s Water Research Institute conducted a study to evaluate the
technical and economic feasib ility of using water from abandoned underground coal mines in the northern West Virginia and southwestern Pennsylvania region to supply cooling water to power plants. 17 The amount of mine water available, the quality of the water, and the types of water treatment needed are all factors that were analyzed during this study. Non-traditional wate r sources such as coal mine discharges not only have the potential to reduce freshwater power plant c ooling requirements, they also can improve the efficiency of the cooling process due to the lower water temperatures associated with deep mine pools.

The study included identification of available mine water reserves in the region with sufficient capacity to support power plan t cooling water requirements under two scenarios. The first scenario was to pr ovide the makeup water requirements for a 600 MW plant equipped with a closed-loop recirc ulating cooling water system. The second scenario was to provide the entire coo ling water requirement for a 600 MW plant equipped with a closed-loop recirculating cooling water system utilizing a flooded underground mine as a heat si nk. If feasible, th e second scenario would eliminate the need for a wet cooling tower to dissipate the heat to the atmosphere.

The study identified eight poten tial sites under the fi rst scenario where underground mine water is available in sufficient quantity to support the 4,400 gallons per minute (gpm) makeup water requirements for a closed-loop 6 00 MW plant. Three of these sites were further evaluated for prelimin ary design and cost analysis of mine pool water collection, treatment, and delivery to a power plant. On e site was selected fo r each of three mine pool water chemistry categories based on “net al kalinity” as measured in mg/L equivalent
concentration of CaCO 3 − net acidic (<-50 mg/L), neutral (-50 to +50 mg/L), and net alkaline (>+50 mg/L). The net alkalinity of the mine pool water determines the water treatment requirements. The mine pool wate r treatment process includes pre- and postaeration, neutralization with hydrated-lime, and clarific ation. A water treatment option9

DOE/FE’s Power Plant Water Management R&D Program Summary, July 2005 using hydrogen peroxide for neutralization was also evaluated. The cost analysis concluded that depending on site conditions and water treatment requirements that utilization of mine pool water as a source of cooling water makeup can be cost competitive with freshwater makeup systems. Table 2 provides a summary of the capital and operating cost estimates for mine pool wa ter collection and treatment systems at the
three sites.

Table 2 – Cost Estimate for Mine Pool Water Collection and Treatment System

Cost Flaggy Meadows (net-acidic) Irwin (near-neutral) Uniontown (net-alkaline) Total Capital Cost, $ 5,740,000 3,770,000 3,464,000 Operating Cost, $/yr 1,367,000 363,000 433,000 Annualized Cost, $/1000 gallons 0.79 0.26 0.29

Based on fluid and heat flow modeling of th e second scenario, it was determined that interconnection of two adjoining mines would be necessary to provide sufficient heat transfer residence time to adequately cool th e recirculating water fl ow. As a result, the study identified only one potential site for a closed-loop recircul ating cooling water system utilizing a flooded underground mine as a heat sink. Furthermore, that site would be limited to the cooling water requireme nts of a 217 MW unit. This project was completed in January 2005.

Use of Produced Water in Recirculated Coo ling Systems at Power Generation Facilities

The Electric Power Research Institute (EPRI) evaluated the feasibili ty of using produced waters, a by-product of natural gas and oil extraction, to meet up to 10 percent of the approximately 20 MGD of make-up cooling water demand for the mechanical draft cooling towers at Public Service of Ne w Mexico’s 1,800 MW San Juan Generating Station (SJGS) located near Farmington, New Mexico. 18 Two major issues are associated with this use of produced water: 1) collection and transportation of the produced water to the plant and 2) treatment of the produced water to lower the total dissolved solids (TDS)
concentration.

Providing cost-effective collection and tran sportation of produced water from the wellhead or disposal facility to the power pl ant is a significant issue. There are over 18,000 oil and gas wells in the Sa n Juan Basin in New Mexic o, where SJGS is located, that generate more than 2 MGD of produced water. Most of the produced water in the region is collected in tanks at the wellhead and transported by truck to local saltwater disposal facilities. The SJGS evaluated a two-phased approach for transportation of produced water to the plant site (Figure 3). In the first phase, an 11-mile pipeline would be built to gather and conve y close-in production. Existi ng unused gas and oil pipelines would be converted to transport produ ced water in the second phase.Fi gure 3 – Pi p e l i n e Sys t em f o r T r ansp or ta ti on o f Pr od uc ed W a ter t o S a n Ju an Gene rati n g St ati o n

Water quality is an issue when using produ ced w a ter to supplem ent plant cooling water requirem e nts due to high TDS concentrations. Cooling water currently used at the SJGS
is withdraw n from the San Juan River and c ontains only 360 m g /L of TDS com p ared to produced water with a TDS concentrati on ranging from 5,440 to 60,000 m g /L. For

com p arison, sea water contains 26,000 m g /L. Therefore, the produced w a ter would have
to be treated prior to use at the p l ant in order to reduce TDS to an accep tab l e lev e l.

In addition to cooling tower m a ke-up, produced water was also evaluated for use as
bottom ash sluice water, fly ash wetting wa ter, and FGD absorber m a ke-up. It was
determ ined that FGD absorber m a ke-up w ould be the least co stly use f o r tre a ted produced water. The most econom ical treatm e nt m e thod identified was high efficiency

revers e os mosis with a brine concentrato r distillation unit that would process approxim a tely 1,100 gpm of produced water. Ba sed on this equipm ent arrangem ent, the cost for produced water treatm ent would incl ude an initial capital cost of $14.1 million and operating costs of $2.98 m illion per year that includ es approx imately 2 M W for auxiliary power. The total project capital cost including collecti on, transportation, and

treatm ent fa cilities is $4 3.1 m illion. Th is study was com p leted in April 2 005.

Innovative Water Reus e and Recovery

Research is curren tly un derway to d e velop advanced technologies to reuse power p l an t cooling water and associated waste heat and investigate m e thods to recover water from coal and power plant flue gas. Such advances have the po tential to r e duce f o ssil f u el power plant water withdraw al and consum ption.

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y 2 0 05Water Extraction from Coal-F ired Power Plant Flue Gas

The University of North Dakota’s Ener gy & Environm ental Research Center (UNDEE R C) is developing a technology to ex tract water vapor from c o al-fired power plant flue gases in order to reduce m a keup water requireme nts f o r

the plan t’s coo ling
water system. 19 The flue gas contains large am ount s of water vapor produced from the
coal com bus tion process. Coal contains in -situ water and the com bustion of the hydrogen
within the coal m a trix also releases additi onal w a ter. The amount of water potentially available for recovery from the f l ue gas is suf f i cient to sub s tantia lly redu ce the need f

o r plant m a keup water withdrawals.

This project has two objectives. The first obj ec tive is to de velop a cost-ef f e ctive liquid
desiccant-based dehum idification technology to recover a large fraction of the water present in the plant flue gas. The sec ond objective is to perform an engineering
evaluation to determ ine how su ch a techno log y can be integrated to recover w a ter,
im prove effi ciency, and reduce stack em i ssions of acid gases and carbon dioxide.

The liquid desicc ant-b a sed dehum idif ication s y stem utiliz es low-grad e heating a nd cooling sources available at the power plan t. A conceptual schem a tic of the proposed
prototype system is shown in Figure 4. The fl ue gas is cooled and then subjected to a liquid desiccant absorption proce ss that rem oves water f

r o m th e flue gas. By stripping off the absorbed water, the weak desiccant solution is regenerated back to the strong desiccant solution. The water vapor that is produced during the regeneration process is
condensed and m a de available for plant m a keup water.

Fi gure 4 - Co nceptu al Desi gn of Liquid Desiccant Process

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y 2 0 05To date, a desiccant selection and charac terization evaluation has been conducted by ranking the m e rits of potential desiccants ba sed on physical and chem ical data along with laboratory testing. One of the de siccants was selected for ini tial pilot-scale testing. Data
f r om the pilot-sca l e testing show that the perform a nce of t h e sy stem was better than predicted by chem ical process m odels. Based on pH and chem istry, extracted water quality is good and off-gas of und esirable species, such as SO 2 and NOx, from the
solution was m i ni m a l. Prospects for commercial developm ent of the process are

encourag ing

. This project will b e co mplete in Septem ber 2005.

Use of Coal Drying to Reduce Water Cons u m ed in Pulverized Coal Power Plants

Lehigh University is conducting laboratory-scale testing to evaluate the perform a nc e and

econom ic fe asibility of using low-grade power plant waste heat to partially dry low -rank coals prior to com bustion in the boiler. 20 The project will b e com p leted in Decem b er 2005. W h ile bitum i nous coals have m i ni m a l m o is ture content (less than 10%), low-rank coals have significant m o isture content – subbitum i nous and lignite coals range from 15-
30% and 25-40% m o isture, respectively. In th is process heat from condenser return cooling water is extr acted upstream of the cooling tower to warm am bient air tha t is then used to dry the coal. Lowering th e tem p er ature of the return cooling water reduces evaporative loss in the tower, thus reducing overall water consum ption.

In addition, drying the coal prior to com busti on can im prove the plant heat rate, and in
return reduce overall air e m issions. Figure 5 shows a schematic of the plant layou t with the air heater and coal dryer. Variations of this approach are also b e in g evaluated that include using heat from com bustion flue gas to supplem ent the condenser return cooling water to dry the coal. Inf o rm ation from this project is being used to design a full-scale coal dry i ng system at Great River Energy’s 5 46 MW lignite-fired Coal Creek P o wer Station located near Underwood, North Dakota. The Coal Creek project is being funded
under DOE/NETL’s Clean Coal Power Initiative.

Fi gure 5 - Sc h emati c o f L e hi gh C oal Dr yi n g Pr ocess

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DOE/FE’s Power Plant Water Management R&D Program Summary, July 2005 An Innovative Fresh Water Production Proces s for Fossil Fired Power Plants Using Energy Stored in Main Condenser Cooling Water

The University of Florida is investigating an innovative diffusion-dr iven desalination process that would allow a power plant that us es saline water for cooling to become a net producer of freshwater. 21 Hot water from the condenser provides the thermal energy to drive the desalination process. Saline water cools and conde nses the low pressure steam and the warmed water then passes through a diff usion tower to produce humidified air. The humidified air then goes to a direct contact condenser where fresh water is condensed out. This process is more a dvantageous than conve ntional desalination technology in that it may be driven by low- temperature waste heat . Cool air, a byproduct of this process, can also be used to cool nearby buildings.

To date, a diffusion driven desalination faci lity has been designed that can produce 1.03 MGD of fresh water from the waste heat of a 100 MW plant. The only energy cost to use this process is the energy us ed to power the pumps and fans. An economic simulation of the system has been performed and shows th at production cost is competitive with the
costs associated with reverse osmosis or flas h-evaporation technologies. This project will be completed in 2005.

Advanced Cooling Technology

This component of the program is focused on research to deve lop technologies that improve performance and reduce costs associ ated with wet cooling, dry cooling, and hybrid cooling technologies. In addition, the research area covers innovative methods to control bio-fouling of cooling water intake structures as well as advances in intake
structure systems.

Development of Hybrid Cooling Water System

In conjunction with the produced water feasib ility study being conducted at the San Juan Generating Station, EPRI will al so conduct pilot-scale testing of a hybrid cooling technology. The Wet Surface Air Cooler (WSA C) is a closed-loop cooling system coupled with open-loop evaporative cooli ng. Warm water from the steam condenser flows through tubes that are externally dren ched with spray water. Heat is removed through the evaporative effect of the spray water. The tubes are always covered in water,
hence the name “wet surface”. The WSAC is capable of ope rating in a saturated mineral regime because of its spray cooling configurat ion. A high spray rate is used to ensure that the tubes are constantly flooded and help s the spray nozzles from becoming plugged. Co-current flow of air and spray water elim inates dry spots on the underside of the tubes where fouling often occurs. The tubes have no fins and are spaced far enough apart that solids or precipitates from the poor qualit y water are washed into the basin.

At SJGS this system will be used as auxiliary cooling for condenser cooling water. The spray water will be blowdown water from the existing cooling towers. The testing will
determine to what extent the WSAC can c oncentrate untreated c ooling tower blowdownbef o re ther m a l perf orm a nce is com p rom i sed. It will b e used as a pre-conc en tra ting device for the cooling tower blowdown that is typ i c a lly evapo r ated in a brine concentrator or evaporation pond at this zero di scharge facility. The p ilot test unit will be
skid m ounted and will consis t of three separate tube bun dles. Each bundle will be

construc ted of a diff erent m e tal to evaluate th e corrosion poten tia l of the degraded wa ter. The pilot un it will be in strum e nted to m onito r therm a l perf orm a nce, conductiv ity of the spray water, and corrosion.

Environmentally-Safe Contro l of Z e bra Mussel Fouling

Zebra m u ssels are sm all, fingernail-sized b i va lves that c a n live in r i ve rs and lakes in

enorm ous densities. Native to Europe, these mussels were f i rst discov ered in Lak e St. Clair, near Detroit, in 1988 and have since spread as far south as Louisiana and as far
west as Oklahom a. Figure 6 shows the distribu tion of zebra mussels in North Am erica.
Zebra m u ssels can attach to alm o st any hard s u rface and their co lonization on co oling
water intake struc t ur es can res t r i ct water in take and lead to significant plant outages.
There is a need for econom i cal and environm entally safe m e thods for zebra mussel
control where this invasive sp ecies has becom e problem atic. Researchers with the New York State Education Departm e nt are condu cting a three-year study to evaluate a particular strain of natu rally occu rrin g bacteria, P s eudomonas fluorescens, that has sho w n to be selectively lethal to zebra m u s s els but benign to non-target organism s. 22 Testing is being conducted on the service water treatm en t system for Rochester G a s and Electric Corporation’s Russell Station that withdr aws 4 to 5 MGD from Lake Ontario.

Figure 6 - Nor t h America Di stributi o n of Z e bra Mus s els

To date, res earch suggests that that this m e thod for zebra mussel control will pose less of
an environ m ental risk than th e cu rrent u s e of biocides like chlorine . However, if this

m e thod is to be widely adopted, it m u st also be cost com p etitive. Laboratory experiments to define key nutrients required to produce m o r e toxin per bacterial cell are underway.
This is a lo ng-term experim e nt and an accura te m easurement of this increase in cell toxicity will not be available until design of the entire chem ically-d efined culture m e dium and culturing protocol is finalized in 2005.

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E’s Po w e r Pl a n t Wat e r Ma n age me n t R& D Progr a m Su m m ary , J u l

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DOE/FE’s Power Plant Water Management R&D Program Summary, July 2005 Enhanced Performance Carbon Foam Heat Exchanger for Power Plant Cooling

Ceramic Composites, Inc. has partnered with SPX Corporation to develop high thermal conductivity foam to be used in an air-coo led steam condenser for power plants that could significantly decrease energy consum ption associated w ith conventional dry cooling systems. 23 In addition, the availability of a more efficient dry cooling technology would offer an alternative to power plants for minimizing adverse impacts such as organism intake, warm water discharge, and evaporative water loss associated with wet or wet-dry hybrid cooling t echnology. This project will be complete in July 2006.

Advanced Water Treatment and Detection Technology

Future controls on the emission of mercury a nd possibly other trace elements have raised concerns about the ultimate fate of these contaminants once they are removed from the flue gas. Preventing these “air pollutants” from being transferred to surface or ground
waters will be critical. In addition, ammonia from select ive catalytic reduction systems used to control nitrogen oxide emissions can appear in a power plant’s wastewater
streams such as ash sluice water. Research is needed for advanced technologies to detect and remove mercury, arsenic, selenium and other components from the aqueous streams of coal-based power plants should effluent standards be tightened in the future.

Fate of As, Se, and Hg in a Passive Integr ated System for Trea tment of Fossil Plant

Waste Water

Tennessee Valley Authority (TVA) and EPRI are conducting a three-year study of a passive treatment technology to remove trace le vels of arsenic, merc ury, and selenium, as well as ammonia and nitrate from fossil power plant wastewater. An extraction trench containing zero-valent iron for removal of trace contaminants is included in the study in order to evaluate an integrated passive tr eatment system for removal of these trace compounds. This project will be complete in 2006.

Demonstrating a Market-Based Approach to the Reclamation of Mined Lands in West Virginia

EPRI is demonstrating a market-based approach to abandoned mine land (AML) reclamation by creating marketable wate r quality and carbon emission credits. The project involves the re clamation of thirty acres of AML in West Virginia through (1) the installation of a passive system to treat acid mine drainage, (2) application of fly ash as a mine soil amendment, and (3) reforesta tion for the capture and sequestration of atmospheric carbon dioxide (CO 2 ). Water quality and CO 2 uptake will be measured and the costs and environmental benefits of the remedial treatments will be developed. Potential eco-credits include water quality cr edits due to decreased acid mine drainage and other benefits resulting fr om the soil amendment, as well as potential credits for CO 2 sequestration due to more than 36,000 seedlings to be planted at the site. This project will be completed in 2005.16

DOE/FE’s Power Plant Water Management R&D Program Summary, July 2005 Novel Anionic Clay Adsorbents for Boile r-Blow Down Waters Reclaim and Reuse

The University of Southern California is conducting a feasibility study of using novel anionic clay sorbents for treating and reusin g power plant boiler blowdown water that can
contain metals such as arsenic and selenium. 24 Currently, it is difficult to economically and effectively clean this waste stream as flow rates are high and the metals concentrations are at trace levels. The goal of this project is to develop an inexpensive clay-based adsorbent that can be used to treat the high-volume, low-concentration wastewater stream. This project will be complete in August 2005.

Specifically Designed Constructed Wetlands: A Novel Treatment Approach for Scrubber

Wastewater

Clemson University will evaluate pilot-scale constructed wetland treatment systems for treatment of trace elements in coal-fired pow er plant FGD wastewater. The overall goal of this project is to decrease arsenic, me rcury, and selenium concentrations in FGD wastewater to achieve applicable discharge limitations. Specific objectives are to: 1) measure trace element removal performance; 2) determine wetland treatment system biogeochemical reactions and rates; and 3) m easure changes in the bioavailability of the trace elements (e.g. toxicity of sediments in constructed wetl ands and toxic ity of outflow waters from the treatment system). The pilo t-scale constructed wetland treatment system consists of a 6,800 liter (L) upstream equaliz ation basin followed by three parallel
treatment trains. Each of the treatment tr ains includes four 378- L cells – two wetland cells planted with bulrush, a gravel mangane se oxidation cell, and a wetland cell planted
with cattails. Both simulated and actual F GD wastewater samples will be included in the evaluation. This project will be complete in August 2005.

SUMMARY

Freshwater resources and reliable and secure electrical energy are inextricably linked. Thermoelectric generation requires a sustaina ble, abundant, and predictable source of water and is second only to irrigation as th e largest user of freshwater in the United States. As the demand for electricity incr eases, so will the need for water for power generation. However, thermoelectric power plants will increasingly compete with demands for freshwater by the domestic, comm ercial, agricultural, industrial, and instream use sectors. In addition, current and future water-related environmental regulations and requirements will continue to challenge power plant operations. As such, there will be increasing pressure to retire existing plants and deny permits for new power plants due to water availab ility and quality issues.

In response to this challenge to national en ergy sustainability and s ecurity, DOE’s Office of Fossil Energy/NETL is carrying out an R& D program focused on the development and application of advanced technologies and c oncept to better manage how power plant use and impact freshwater. Research is cu rrently underway to assess and develop nontraditional sources of cooling and process wa ter, advanced cooling water technologies, innovative water reuse and recovery technologies, and advanced wastewater treatment17

DOE/FE’s Power Plant Water Management R&D Program Summary, July 2005 and detection technologies. It is anticipated that this research will help to alleviate potential conflicts between growing demands for electricity and in creasing pressures on
the Nation’s freshwater resources. For mo re information on NETL’s power plant water R&D activities, please visit: http://www.netl.doe.gov/coal /E&WR/water/index.html

.

DISCLAIMER

Reference in this article to any specific comme rcial product or service is to facilitate understanding and does not imply endorseme nt by the U.S. Department of Energy.

REFERENCES

1 U.S. Geological Survey. Estimated Use of Water in the United States in 2000 ; USGS Circular 1268;
March 2004.

2 Energy Information Administration. Annual Energy Outlook 2005 , EIA Report No. DOE/EIA0383(2005); February 2005.

3 U.S. Geological Survey. Estimated Use of Water in the United States in 2000 ; USGS Circular 1268;
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4 SAIC. Water-Energy RD&D Scoping Study; Final Report to the U.S. De partment of Energy, NETL; September 2003.

5 U.S. Department of Energy, NETL; Estimated Freshwater Needed to Meet 2025 Electricity Demand Projections ; Draft Internal Report; March 2004.

6 United States Genera l Accounting Office. Freshwater Supply, States’Views of How Federal Agencies Could Help Them Meet the Challe nges of Expected Shortages ; GAO Report No. GAO-03-514; July 2003.

7 Electric Power Research Institute. A Survey of Water Use and Sustainability in the United States With a

Focus on Power Generation ; EPRI Report No. 1005474; November 2003.

8 U.S. Department of the Interior. Water 2025 – Preventing Crises and Conflict in the West ; May 2003.

9 Land Letter. Western Power Plants Come Under Scrutiny as Demand and Drought Besiege Supplies; March 4, 2004; http://www.e enews.net/Landletter.htm

10 Greenwire. State Orders N.Y.’s Indian Point to Take Steps to Protect Fish; November 13, 2003; http://www.eenews.ne t/Greenwire.htm

11 Clean Air Task Force. Wounded Waters – The Hidden Side of Power Plant Pollution ; February 2004.

12 Billingsgazette.com. South Dakota Governor Seeks Summit on Missouri River , February 2005.

13 Reno-Gazette Journal. Nevada Residents Wary of Sempra Water Rights Purchases , February 22, 2005.

14 Milwaukee Journal Sentinel. Wisconsin Energy Just Can’t Stay Out of the News with Their Intake

Structures , February 18, 2005.

15 Feeley, III, T.J. and Ramezan, M., Electric Utilities and Water: Emerging Issues and R&D Needs , Water Environment Federation, 9 th Annual Industrial Wastes Technical an d Regulatory Conference, San Antonio, TX , April 13-16, 2003

16 Veil, J.A., Kupar, J.M., Puder, M.G., and Feeley, III, T.J., Beneficial Use of Mine Pool Water for Power

Generation , Ground Water Protection Council Annual Forum, Niagara Falls, NY, September 13-17, 2003.

17 Strategies for Cooling Electric Generating Facilities Utilizing Mine Water: Technical and Economic Feasibility Project . Final Report to the U.S. Department of Energy under Cooperative Agreement No. DEPS26-03NT41719; West Virginia Water Research Institute – West Virginia Univeristy, September 30,

2004.

18 Use of Produced Water in Recirculating Cooling Systems at Power Generating Facilities . Semi-Annual Technical Progress Reports to the U.S. Department of Energy under Cooper ative Agreement No. DEFC26-03NT41906; Electric Power Resear ch Institute, August-December 2004.

19 Water Extraction from Coal-Fired Power Plant Flue Gas . Quarterly Progress Report to the U.S. Department of Energy under Cooperative Agreement No. DE-FC26-03NT41907; Energy & Environmental Research Center - University of North Dakota, September 2004.18

DOE/FE’s Power Plant Water Management R&D Program Summary, July 2005 20 Use of Coal Drying to Reduce Water Cons umed in Pulverized Coal Power Plants . Quarterly Report to the U.S. Department of Energy under Cooperative Ag reement No. DE-FC26-03NT41729; Energy Research Center - Lehigh University, October 2004.

21 Innovative Fresh Water Production Process for Fossil Fuel Plants . Annual Report to the U.S. Department of Energy under Cooperative Agreement No. DE-FG26-02NT41537; University of Florida, September 2004.

22 U.S. Department of Energy, NETL: Environmentally Safe Control of Zebra Mussel Fouling Fact Sheet ; September 2004.

23 SPX Cooling Technologies and Services and Ceramic Composites to Test Carbon Foam Heat Exchangers for Power Plant Cooling . SPX Corporation News Release. October 13, 2004.

24 Novel Anionic Clay Adsorbents for Boiler-Blow Down Waters Reclaim and Reuse. Proposal to the U.S. Department of Energy under Cooperative Agreement No. DE-PS26-04NT41898-11; University of Southern California, December 2003.