· -. o· H t·. , , ~ ... - __ .., ___ ,__..__~_..--~- .... ....:...--··---~ ·--~~- ._;L ________..___.....:, __ _.. ___ ~~--~;~.-..'.:;~ i I I ~~ I t.J~ I l ·-······- .. __: --·.. .. .. --·------... ·-----•~"'-'""",..,w.... · ..... _..__ e_e ......... --... __ _.....-· .... w-·.oo.·· . ..,, ......,..., • ..,.._,,_. _ •..._ .... ·.~··-..re=-·'*'e.;.,;..;io;i·"""'•-.o" ... ffillllll;ji·fi-=•·llll=tO.w.._.._ ~ --- ~ ! 1 L.J I! \ r~ 216 Treatment and Reuse I L,; TO C£NRIIATOII TIIAIISMISIIOII fi I 1t ! ~ t STUNt j t $ ,·' .-AT£11 , SU,L'I' I ..... SYSTEM ' QUAliTY t, • CONTROL IOILlll ' SUCK SYSl[NI ! CII!CULATINC WATtll ~ COIIDEN~AT[ c II[TUIIN fU[l STORAGE AHO TR .. N\PORT • SOLID WAST[ sYSTlM ~c OIS,OSAL i ~[J Figure 1. Fossil fueled power plant features 5. Fuel Storage and Transport System. where the fossil fuel is transferred from the incom­ 1 ing transport system to a point of storage prior to use in the boiler, and then transported to the .f boiler i tse!f. ' 6. Air Quality Control System. where the control of ~,articulate and sulfur oxide poilutants (AQCS) is effected. 7. Solid Waste Disp_osal System. where solids generated in plant operations are treated and t i stored or processed for reuse or resale. j I l ~ l FACTORS AFFECTING WATER/W ASTEW ATER MANAGEMENT AT FOSSIL­ ~ I! FUELED POWER PLANfS I u I ~' As previously noted, the features of water and wastewater management plans vary among plants. The primary factors influencing these variations are: ~L 1. Generic Fuel Type. The use of gas, oil, lignite or coal will affect the number of water use operations and wastewater sources in the plant. The lignite and coal fired plants will have sig­ nificantly greater management requirements than either gas or oil fired plants. r 2. Specific Fuel Quality. Once a fuel type is selected, significant variations in the fuel ~L characteristics still remain. For example, depending on the coal source, the ash, moisture and 1 sulfur content will vary drastically and cause significantly different water use requirements and wastewater sources, quantity and quality. Similarly with fuel oil, the fuel number (i.e. 2-5), source and ~ansportlstorage methods will influence water use and wastewater genera­ ~L tion. (Attention is brought to the process of fuel washing, for example, which is required for I fuel oil contmninated with salt water added in the transportation qperation). 3. Heat Dissipation System. Depending on the type system in usc or planned, variations in f L chemical addition, tlow volume. etc. results. Variations among sy!:items will be reflected in the potential opportunities for water management 4. Location. The location l~lctor will cause variations in water availability and quality, water I quality stand.1rds, meteorology, air quality control systems required, etc. which, in turn, effect I' t..J water mallagcment considerations and opportuni tics. l I I~ . .J IL ------~-· _.,.,__..,_....,....to .. '• ........ '""'~ .-.-<; -rr-~•;~ ... - , _....._...._. _____________ ___ __________________________ _ ...... ~~.....,_ I ~· ; RL~( n~rer and Wastewaier Management 217 \ ! s. Market/Plant Betterment Factors. Economic, metallurgical, and plant water chemistry I• rt .: affect the plan as well as the potential for marketing process wastes. For example, when the op­ ! portunity exists to market flyash, dry collection systems are used in the plant in favor of wet systems. The problems of wet sludge transport and ponding are thus obviated. ~ rLJ WATER/WASTES MANAGEMENT GAS AND OIL FIRED PLANTS (Figure 2) Gas and oil fired power plants result in fewer water use locations and significantly fewer wastewater sources than coal fired plants and are thus briefly addressed in the following. Features Common to Gas and Oil Fired Plants The major water use .IGCation at such plants is the cooling system, whereas low volume waste sources L'"tat occur in a semi-continuous mode or batch nature include: -Boiler blowdown --~- .water treat.rn~nt wastes -Cooling system cieanout w~~ -Boiler cleaning wastes Features Unique to Oil Fired Plants Depending on fuel quality characteristics, the following unique wastes management systems may be required: -Particulate removal -S~ scrubbing -Fuel washing These operations require a water supply and result in polluted streams. Also, as required under 10-CFR 110 and 112, Spill Prevention, Control and Countermeasure (SPCC) plans are required to insure that oily waste discharges to the receiving water body are prevented. · MAJOR \VATER USE LOCATIONS AND WASTEWATER CONSIDERATIONS AT COAL FIRED PLANTS The key water use locations and associated wastewater considerations at a ••typical" 600 MWe coal fired power plant include the following (Figures 3, 4, 5): ! . Boiler Makeup. A 350 gpm design capability is typically provided for the boiler makeup water system although actual water use is considerably less. Because a high, purity makeup water is required, treatment utilizing sedimentation, filtration and demineralization is pro­ • \'idcd. 'These operations result in the production of sludges, backwash and regenerant wastes, respectively, which require treatment and disposal. 2. Bottom Ash Hopper Sealing and Cooling. In this operation, 200 to 600 gpm of water is trpically used to cool the metal walls of the bottom ash hopper and maintain a water seal be­ tween the boiler and ash hopper walls to prevent gas escape. In many older, existing plants, this water is discharged without any re-use, whereas, in fact, it is quite suitable as supply to other plant systems such as ash sluicing or Air Quality Control System (AQCS) makeup. The drscharge stream is typically at a temperature of about 150 +oF, contains a high settleable solids load and may be acid to neutral in pH. 3. &uom Ash Sluicing. This operation is highly variable in water demand depending on: ·Cool type and ash content · · -Ash accumulation rate -Frt-quency of sluicing ·Duration of sluicing operation ... .,., ........ ,, ....- 1 •l i __......... ..........._.-~·---- .. ··- ___.____. .. ~ -~ .. ~ ._... ___• .J..- I ,! .J I M t l · Treatment and Reuse I ' . ._j 218 l • Pt. I, l GAS OR Oll:_FIRJ_D PLANT WASTES lJ Ij • COOLING TOWER SLOWDOWN I • • LOW VOLUME WASTE SOURCES n,· A BOILER SLOWDOWN ~ ~ -~ I , LJ WATER TREATMENT WASTES ! COOLING TOWER BASIN CLEANOUT WASTES .. BOtl.ER CLEANING WASTES I • DOMESTIC WASTES " nLJ UNIQUE OIL·FIRED PLANT WASTES ~ 0 • PRECiPITATOR/SCRUBBER WASTES (DEPENDENT ON FUEL QUALITY) l PARTICULATE WASTES S02 WASTES • FUEL HANDLING WASTES ~Di SALT WATER REMOVAL • SPILL PREVENTION, CONTROL & COUNTERMEASURE (SPCC) PLAN (10 CFR 110 & 112) r,) FUEL STORAGE AREA WASTES il r·:..J FUEL HANDliNG AREA WASTES ~ fl ~ lJ Figure 2. Water and wastewater. management areas at gas and oil fired power plants • PROCESS WATER BOILER MAKEUP ASH COOLING AND SEALING BOTTOM ASH SLUICING FLY ASH SLUICING S02 SC~UBBER SYSTEM ,. II • COOLING WATER ~w CONDENSER COOLING (1 cfs/MW) AUXILIARY (SEALS, BEARINGS, PUMPS: 0.01-0.1 cfs/MWe) i:f I i l~ • POTABLE/PLANT SERVICE WATER I WASHDCWN I L SINKS I l fiRE PROTECTION HVAC J l0 1 u !. i } !' l I Figure 3. Major water usc locations a·.t coal fired power plant i i t .l.J Ii i t 1. I b I _.. .... --..~- ~~-:_,..,.., ...,..~~ ..... ____,....., ...... _.-.-' " ..- .- l, S # ~~ I ¥9t46!i ,Qj@ Q$ Q J»UUJI'(Aqll FC ..... iCNI ___ IU1 {,, i __ _.......,....,..,__ .. ·- .. - In~ _.LJ ___ -._..:....-_..... _____....... -...... ~--·-·· --- _.....:~-------~---~·- ··---~--· .. -··-· ..... --·-~~ ;, I ~ ' '. 219 L.J Water and Wastewater Management I':e l ~ . : I • BOILER MAKEUP l_J lI 350 GPM DESIGN CAPABILITY (TYPICAL) SEDIMENT ATION/FI L TRATioN/OEMINERALIZATION PI (PRODUCES WATER TREATMENT WASTES) -~j~.~ i ' Lj \ • BOTTOM ASH COOLING & SEALING I TYPICALLY 200-600 gpm r::;::J I -~.ij ( 1 150° F+ \ HIGH SETTLEABLE SOLIDS { pH : 2-7 (RE-USE IN S0 AND PARTICULATE REMOVAL SYSTEMS) 2 • BOn'OM ASH SLUICING WATER VOLUME IS FUNCTION OF: COAL TYPE AND ASH CONTENT ASH ACCUMULATION RATE/FREQUENCY OF SLUICE NUMBER OF SLUICES/DAY l· NEED TO PRODUCE A 3-8% SLURRY POND WASTES (HIGH SUSPENDED SOLIDS) l RECYCLE TO ASH/S02/PARTICULATE SYSTEMS (LOW QUALITY WATER USES) "TYPICALLY" ONCE PER SHIFT; 45-90 MINUTE DURATION \ t I Figure.;_ Process water considerations (600 MWe) \' l l \,, • F~ Y ASH SLUICING l i l PRECIPITATION PREFERRED t WET PARTICULATE SCRUBBEn iCa IN ASH+ S02 + H20 RESULTS IN SCALING I PLUGGING \' PROBLEMS) I I IF MARKET POTENTIAL (DRY PRECIPITATOR} I W::T SLUICING (PRODUCE 5-10% SLURRY) l • S02 SCRUBBER SYSTEM LIME SLURRY FEED (OR POWDERED LIMESTONE SLURRY FEED. PACKED BED) 5-10% CaS04 SLUDGE PRODUCED THICKENING TO' 40% SOLIDS POND SLUDGE (LINERS) POTENTIAL "CHANNELING'' PROBLEMS IN PACKED TOWEPS (PRODUCES VARIABLE pH) . Figure 5. Process water considerations (600 MWe} l ~ -----'!::.~--..-.....-- I I _.. --.---- ·--·-- --------~-~- ~ L J 1.. ~ r I ! I . Treatment and Reuse Il L:J 220 l' ,RI1 Typically, the sluicing operation is de•igned to produce a 5 to 8 percent ash slurry. Obviously, i· I t \ water demand in the opemtion is reduced as the solids content" is i ncrc.ast~d. although pumping · l LJ constraints must be considered before a slurry solids content is fixed. Ash sluicing wasteS are normally ponded on-site and pond supernatant can be re-used within the plant. ~ 4. Fly Ash Sluicing. In order to meet source standards for air quality tlue gas partic- ~ ; { co~ntrol, ' ' ; ulate (i.e. flyash) removal is required. Current engineering practice incorporates the use of ~ ~-.J l ! ' electrostatic precipitators in this context although wet scrubbers have betm used in the past. ! Wet scrubbers have inherent maintenance problems associated with scale formation caused by r n ~ (, ~ 1 .1 the precipitation of CaS04 due to the complexing of calcium (present in the flyash) and flue u 1- 1 i i J..~ ~.s s gas S02 in the presence of water. Unless the precipitated flyash has a market, precipitator par­ . l ticulate accumulations are sluiced wi.th water (in a 5 to 10 percent slurry) to on-site ponds .