Notes from Site Visit at Allegh eny Energy’s Harrison Power Station on September 10, 2008

EPA conducted a site visit at Allegheny Energy’ s Harrison Power Station located in Harrison, WV on Wednesday, September 10, 2008 to learn about the operations at the plant, specifically the FGD wastewater treatment system. Tabl e 1, located at the e nd of this memorandum, identifies the site visit partic ipants. The presentati on that the Harrison pe rsonnel presented during the site visit is provided as an at tachment to the memorandum.

This memorandum describes the information collected during the site visit and the pre-site visit phone call, which was held on August 20, 2008.

Plant Overview

• Harrison operates three gene rating units at the power plant. Each unit generates

650 MW.

Unit Installation

Date Capacity (MW) Particulate

Control NOx Control SO 2 Control

1 December

1972 650 Cold-side

ESP SCR installed May 2002 Wet FGD installed January 1994

2 December

1973 650 Cold-side

ESP SCR installed May 2003 Wet FGD installed January 1994

3 December

1974 650 Cold-side

ESP SCR installed May 2003 Wet FGD installed January 1994

• All three units have cold-side ESPs, which achieve between 98 and 99 percent removal of the fly ash and other particulates.

• Harrison currently operates the SCRs duri ng the ozone season. However, Harrison may begin year-round operation next year.

• Harrison operates magnesium-enhanced lime inhibited oxidation FGD scrubbers

on all three units.

• Harrison burns eastern bituminous coal. Th e sulfur content of the coal, based on 2008 data from the coal supplier, is approximately 2.85 lbs S/BTU or 3.45% sulfur. The chlorine content of the coal, based on 2008 data from the coal supplier, is 0.05-0.1% (dry basis).

• Harrison is also beginning to burn PRB co al in addition to th e eastern bituminous coal. Currently, PRB accounts for approximate ly 7 percent of th e total burn for each unit. Harrison stated that the plant is using PRB because it is cheaper than eastern bituminous, even accounting for add itional transportation costs. However, the PRB coal contains approximately 9,000 BTU/lb, while the eastern bituminous coal contains approximately 12,000 BTU/lb.Page 2

• Harrison burns between 17,000 and 18,000 tons of coal per day and consumes 450,000 tons of lime per year.

• Harrison’s coal pile has its own settling pond which receives all coal runoff. The coal pile runoff pond drains to the wastewat er lagoons. During the site visit, EPA collected a sample from the coal pile runoff pond and measured the pH of the sample using a pH meter. The pH of th e coal pile runoff pond was measured as 2.95 S.U. EPA observed that the pond water had a slight yellow tint.

• Harrison operates a recirculating cooling water system with cooling towers. The cooling tower blowdown is either used as bottom ash sluice source water or

transferred to the wastewater treatment lagoons and discharged to the West Fork River. A process flow diagram for the handling of the plant’s wastewater is provided as an attachment to this memorandum.

• The level of the West Fork River is ma intained by an upstream dam. In addition,

two reservoirs are used to control the volume of the river.

• Harrison stated that 80 percent of the merc ury is removed from the flue gas by the combination of the SCR and FGD systems.

FGD System

• Harrison operates a wet magnesium-e nhanced lime inhibited oxidation FGD scrubber on each of the three generating units. All three FGD scrubbers began operating in January of 1994.

• Harrison’s lime supply naturally contains a small percentage of magnesium. The lime supplied to the plant typically c ontains 2.9 percent MgO and 90 percent CaO. Harrison stated that the ideal Mg O content is 2.5 to 2.7 percent. Although the magnesium is naturally present in th e lime acquired by Harrison, the plant can add additional magnesium if necessary. The FGD scrubber chemistry is enhanced by the addition of magnesium oxide.

• The lime manufacturer calcines limestone into lime prior to delivering the lime to Harrison. The additional processing is one reason why lime is more expensive than limestone on a per unit mass basis.

• The lime supplied to Harrison is first transported by barge and then by rail. Harrison receives 15-17 rail cars per day, 5 days a week. The lime is stored in two silos which each hold approximately 40,000 to 45,000 tons of lime (approximately a 30-35 day supply).

• The lime is slaked into hydrated lime sl urry consisting of calcium hydroxide and magnesium hydroxide. Harrison uses a ball mill to slake the lime. Both the calcium hydroxide and magnesium hydroxi de reactions are exothermic and generate heat, which results in the lime slurry having a high temperature. The high temperature of the slurry helps to dissolve the magnesium in the slurry.Page 3

• Magnesium enhances the FGD scrubber chemistry in the following ways:

o MgSO 3 is roughly 200 times more soluble than CaSO 3 (three percent of the aqueous phase is dissolved MgSO 3 ). For this reason, more sulfur can remain bonded in solution before MgSO 3 is converted to CaSO 3 , which is precipitated out of solution.

o Magnesium chemistry maintains a hi gh alkalinity (1500-2000 ppm) and pH. Under these non-equilibrium conditions, SO 2 absorption is favorable

and the mass transfer resistance between the liquid and the gas is the rate limiting step. In forced oxidation, ther e is an additional resistance to mass transfer within the liquid phase because of the low solubility and alkalinity

of calcium sulfate.

o Magnesium sulfite is converted to magnesium bisulfite which captures twice as many sulfur dioxide molecules in solution as calcium sulfite.

• Harrison stated that the FGD scrubbers remove approximately 98 percent of the

SO 2 in the flue gas. The flue gas emmision SO 2 concentration is approximately 20

ppm.

• Harrison adds elemental sulfur to the F GD scrubbers to inhi bit the oxidation of

the calcium sulfite to calcium sulfate Adding emulsified sulfur to the FGD scrubbers forms the thiosulfate species (S 2 O 3 2- ), which is an oxygen scavenger and removes oxygen from the system befo re it oxidizes the calcium sulfite.

• Although the Harrison plant operates an inhibited oxidation FGD scrubber system, Harrison estimates that 15 percen t of the solids generated in the FGD

scrubber are calcium sulfate due to natu ral oxidation. Harrison stated that this calcium sulfate is not present as gypsum in the product. Rather, there are crystals of calcium sulfate dispersed between crystals of calcium sulfite.

• Harrison stated that elemental sulfur is typically only added to the FGD system during the ozone season, which is when the SCR system is operating. Harrison stated that when the SCR is operating it has caused issues with the oxidation of the calcium sulfite and, theref ore, the elemental sulfur is needed. Harrison stated that operating the SCR without the el emental sulfur addition allows gypsum crystals to form. Allowing a combinati on of calcium sulfite and gypsum crystals

to form would interfere with the soli ds separation proce ss for the scrubber

blowdown.

• Harrison stated that the chlorides cont ent within the scrubber is 4,000 to 5,000 ppm. The scrubbers’ maximum chloride s design capacity is 12,000 ppm. The

sulfite concentration in the scrubber is 4,000-6,000 ppm and the total dissolved solids concentration is 2.5-3.0 perc ent. The TDS is primarily MgSO 3 . TDS levels can cause operational problems if allowed to reach 4 percent. At these TDS levels, the density of th e scrubber slurry begins to increase, which negatively affects the settling rates in the thickener and reduces the centrif uge performance.Page 4

Harrison stated that the elevated TDS le vels do not affect the sulfur dioxide removals in the FGD system.

• Harrison stated that the pH in the sc rubber is typically between 6.3 and 6.4. The scrubbers are operated to maintain the desi red pH level. As pH drops, the plant adds more lime slurry to control pH levels.

• Harrison stated that the FGD scrubber system works better with a high sulfur coal.

Harrison stated that the sulfur content of the eastern bituminous coal ranges from 3 to 3.5 percent, and has been a pproximately 3.4 percent in 2008.

• Each of the FGD scrubbers has four sp ray levels; however, Harrison only operates three of the sprays levels at a time. Each spray level has its own recirculation pump. Each of the recirculation pumps r ecirculate the scrubber slurry at a flow rate of 125,000 gpm, for a total of 375,000 gp m of recirculation for each scrubber.

• The FGD scrubber blowdown flow rate to the thickeners is 3,500 – 4,000 gpm.

This stream flows from the scrubber th rough a pipe housing to the thickeners. Before the waste slurry is fed into th e thickeners it flows through a distribution box which adds make up water from West Fork River and a polymer which aids in solids settling. A process flow diagram for the handling of the FGD wastewater is provided as an attachment to the memorandum.

• Harrison has four thickeners which are not designated to a particular FGD scrubber (i.e., each thickener usually contains slurry from all three FGD scrubbers). However, Harrison has the abil ity to direct flow exclusively from any FGD scrubber to any of the thickeners.

• Each thickener has a volume of 4,329,000 ga llons. The average retention time for

each of the thickeners is 17 hours.

• The thickener overflow is recycled back to the FGD scrubbers. Because the FGD scrubber blowdown is commingled in th e thickeners, the FGD wastewater

returned to the FGD scrubbers is a combination of all the units.

• There are two underflow pumps on each thickener. The underflow, which is 30 to 40 percent solids, is sent to the centri fuges. Harrison has 15 centrifuges (three trains each with five centrifuges), but t ypically only four cent rifuges from each train are in operation at a ny given time (i.e., a total of 12 centrifuges operating at a time).

• Harrison’s centrifuges have variable-sp eed control, but the plant typically operates them at 2,000 rpm. The centrifuge spins and pushes the solids to the outside walls of the centrifuge. A rotating screw within the centrifuge rotates in the opposite direction of the centrifuge and pushes the soli ds back toward the inlet side of the centrifuge and out of the syst em. The water stays towards the inside of the screw and flows through holes located on the inner part of the screw to the opposite end of the centrifuge.Page 5

• The water leaving the centrifuge, referred to as centrate, is transferred to one of two centrate tanks and is then recy cled back to the FGD scrubbers.

• Harrison adds Nalco flocculant to the centrifuges as needed. They may take samples from the centrifuge to determine the appropriate amount of Nalco

flocculant to add.

• The solids recovered from the centrifuges contain approximately 45 to 50 percent water. Harrison combines the centrifuge d FGD cake with fly ash and hydrated lime in a pug mill. The pug mill typically operates continuously while the solid waste process is in operation (e.g., dewa tering centrifuges an d landfill activities).

• The product from the pug mill is a cementiti ous material which falls from the pug mill conveyor to surge bins. The material is loaded directly from the surge bins into trucks which transport the solid waste to a landfill. Each truckload hauls approximately 100 tons of waste. The mi xed material from the pug mill is solid enough to move/shape the wa ste with bulldozers.

• Harrison stated that in the winter months it may be necessary to add more lime to the pug mill than in summer months. The higher lime ratio results in higher reaction temperatures and faster curing. This makes the final product easier to transport by truck.

• Harrison stated that the solids handling system was designed to run 16 hours per day, 7 days per week. However, they have found that operating 24 hours per day, 5 days per week and performing maintena nce on the weekends resulted in less operational downtime.

• Harrison stated that they do not need to operate with a chlo ride purge stream because the chlorides are being purged from the system with the FGD solids that

are sent to the landfill. Because th e centrifuged FGD cake contains 45 to 50 percent water, a large amount of dissolved chlorides ar e present in the cake and are purged from the system.

SCR System

• Harrison stated that the SCR systems began in 2002 and 2003.

• Harrison stores urea on site and converts it to ammonia for injection into the SCR systems. Harrison decided to use urea instead of storing anhydrous ammonia because of safety concerns.

• Each SCR has four layers of catalyst. Harrison stated that three of the four layers are in operation.

• Harrison stated that they will be regenerating the catalyst for the first time next year. The catalyst will be shipped to SCR Tech in Ch arlotte, NC for regeneration.Page 6

Ash Handling and Wastewater Treatment

• Harrison operates a wet bottom ash hand ling system. The bottom ash sluice is transferred to hydrobins to dewater th e ash. Each unit has two hydrobins. The overflow from the hydrobins is sent to th e wastewater treatment lagoons. Harrison has been marketing some of the bottom ash as a blasting agent, known as “black beauty”. Additionally, the plant uses the bottom ash to line the on-site landfill or

sells some of the bottom ash to the state of West Virginia for use on roads for skid

control.

• The wastewater treatment lagoons also r eceive air preheater wastewater, floor drain wastewater, ion excha nge wastewater, coal pile runoff (after settling), and

other low-volume wastewaters.

• Harrison has two treatment lagoons, but only one lagoon operates at any given time. The lagoon effluent is discharged dire ctly into West Fork River. The last time Harrison switched lagoons was in October 2006.

• Harrison operates a dry fly ash handling syst em. Most of the dry fly ash is used to

create a cementitous material with the FGD by-product, which is then landfilled. In addition, some of the fly ash is land filled and some is sold to make cheap

cement used to fill in mine subsidence.

Landfill

• Harrison operates an on-site landfill for the disposal of the FGD solids material, as well as fly ash.

• Originally, the landfill only received fly ash. Since the installation of the FGD scrubber, Harrison has added a geosynthet ic lining; however, the original area where the fly ash was landfilled is still unlined.

• The runoff and leachate from the lined porti on of the landfill is collected in three water collection sedimentation ponds (A, B, and C).

• The unlined portion of the landf ill has an underdrain system that drains to a sump. This leachate collected in the sump is directed to Harrison’s wetlands treatment system by a system of ditches and underground collection pipes.

Wetlands Treatment System

• Harrison’s wetlands treatment system consis ts of 12 terraced cells and has been in operation for five years. There are two equalization basins. Terraced below the equalization cells are cells consisting of bull rush and cattail, for the removal of metals such as aluminum and iron, followed by peat moss cells for removal of trace metals, followed by limestone gravel cells for removal of manganese.Page 7

• In November 2006, through an agreement with the State, Harrison’s wetland treatment system began treating acid mine drainage from an on-site abandoned mine. The acid mine drainage is blended with the leachate prior to entering the wetlands treatment system. Harrison stat ed that selenium is present in both

wastestreams.

• Harrison stated that no chemicals are added to the wetland treatment system. However, part of the treatment system consists of manganese oxidizing beds, which contain limestone gravel.

• Harrison’s 2008 Constructed Wetlands Treatment System Report shows that the system met the NPDES permit limits for pH, aluminum, iron, manganese, hexavalent chromium, selenium, and TSS. In many cases, the influent to the treatment system was above the permit limits.Page 8Table 1. Site Visit AttendeesNameOrganization (Representing)TelephoneE-mailJoe Lapcevic Allegheny Energy (724)838-6099 jlapcevic@alleghenyenergy.comBill Cannon Allegheny Energy (724) 838-6018 wcannon@alleghenyenergy.comDan Berisko Allegheny Energy (304)584-2384 dberisk@alleghenyenergy.comMarce Tennant Allegheny Energy (304)584-2268 mtennan@alleghenyenergy.comDennis Napier Allegheny Energy (304)584-2263 dnapier@alleghenyenergy.comBrent Banks Allegheny Energy (304)584-2243 bbanks@alleghenyenergy.comBill Glessner Allegheny Energy (304) 584-2262 wglessn@alleghenyenergy.comJulie Ford Allegheny Energy (304) 584-2329 jford@alleghenyenergy.comDonna Hill Southern Company (205) 257-5234 dbhill@southernco.comRon Jordan EPA/Office of Water (202) 566-1003 jordan.ronald@epa.comJosh Hall EPA/Office of Water(202) 566-1002 hall.josh@epa.comDeborah Bartram ERG (Contractor to EPA) (703) 633-1669 deborah.bartram@erg.comTJ Finseth ERG (Contractor to EPA)(703) 994-7130 thomas.finseth@erg.comKurt Blohm ERG (Contractor to EPA)(703) 633-1675 kurtis.blohm@erg.comALLEGHENY ENERGYHARRISON POWER STATIOND W BERISKOFLUE GAS FLOW DIAGRAM - UNIT OPERATIONS12345678UNIT KEY:1 COAL P[ILE2 MILLS3 BOILER4 SCR5 AIR HEATER6 ESP7 ABSORBER8 STACKFLUEGASALLEGHENY ENERGYHARRISON POWER STATIOND W BERISKOFGD LIQUOR FLOW DIAGRAM - UNIT OPERATIONS78 91011121314151617TO STACKTOLANDFILLUNIT KEY:7 ABSORBER8 LIME LOADOUT9 DRY LIME SILO10 LIME SLAKER11 SLAKED LIME SILO12 THICKENER13 THICKENER OVERFLOW TANK14 THICKENER UNDERFLOW TANK15 CENTRIFUGES16 CENTRATE TANK17 PUGMILLSALLEGHENY ENERGYHARRISON POWER STATIOND W BERISKOMAJOR CHEMICAL REACTIONS IN MG-LIME SCRUBBERS1) SO2+ H2O↔H2SO3Sulfur dioxide absorption into solution.2) H2SO3+ Ca(OH)2→CaSO3↓+2 H2O Neutralization with calcium component oflime to form insoluble calcium sulfite.3) H2SO3+ Mg(OH)2→MgSO3 +2 H2O Neutralization with magnesium componentof lime to form soluble magnesium sulfite.4) H2SO3+ MgSO3→Mg(HSO3)2Critical neutralization reaction utilizingsoluble magnesium sulfite.5) Mg(HSO3)2+ Ca(OH)2→CaSO3↓+ MgSO3Neutralization reaction with calcium component of lime to forminsoluble calcium sulfite andto regenerate soluble magnesium sulfite for reuse. ( Magnesium catalytic effect. )7) SO3= + 1⁄2 O2→SO4= Oxidation of sulfite to sulfate.6) SO3= + H+↔HSO3 ̄Buffering equilibrium reaction of sulfiteand bisulfite resulting in enhancedalkalinity in scrubber liquor.ALLEGHENY ENERGYHARRISON POWER STATIOND W BERISKOSOLUBILITY VALUES FOR VARIOUS SCRUBBER SPECIESSOLID0.000MgOMagnesium OxideSOLID0.004CaSO3•2H2OCalcium SulfiteSOLID0.260CaSO4•2H2OCalcium SulfateLIQUOR74.5CaCl2•6H2OCalcium ChlorideSOLID0.001CaCO3Calcium CarbonateLIQUOR66.0MgSO3•6H2OMagnesium SulfiteLIQUOR71.0MgSO4•7H2OMagnesium SulfateLIQUOR116.MgCl2•6H2OMagnesium ChlorideSOLID0.010MgCO3Magnesium CarbonatePHASESOLUBILITY(In 100 partswater)SYMBOLNAMEDrawing F8950134