Notes from Site Visit at Kansas City Power & Light ’s Iatan Generation Station

on April 28 , 20 1 0

E PA conducted a site visit at Kansas City Power & Light’s Iatan Generation Station (Iatan) located in Weston, MO on April 28, 2010 to learn about the operations at the plant, specifically the FGD system and the FGD wastewater treatment system. The presentation given by plant personnel is included as Attachment 1 to these notes. The FGD system and FGD wastewater treatment system process flow diagrams are included as Attachment 2 and 3 to these notes

, respectively

.

These notes describe the information collected during the site visit. Table 1, at the end of these notes, identifies the site visit participants.

Plant Overview

**•** Iatan operates two electric generating units. Units 1 and 2 burn both Powder River Basin (PRB) coal. Units 1 and 2 have gross generating capacities of 755 and 920 MW, respectively and net gene rating capacit ies of 705 and 850, respectively. The table below contains some general information on the current operation of each steam electric generating unit.

Unit Installation
Date Net Capacity

(MW) Particulate
Control NOx Control SO 2 Control

1 19 80 705 Baghouse SCR Wet FGD
2 2010 850 Baghouse SCR Wet FGD

**•** Iatan receives its coal via t rain . The plant burns approximately 11,000 tons of coal per day. Iatan stores 70 to 75 days worth of coal on site for Unit 1 and approximately 30 days worth of coal for Unit 2. The coal pile runoff is collected in a holding pond and then discharged to the Missouri River.

**•** Iatan operates dry fly ash handling systems on Units 1 and 2. Each unit is equipped with a baghouse (fabric filter) to collect the fly ash . Unit 1 was initially built with an electrostatic precipitator, but it was replaced with a new fabric filter.

**•** Iata n also operates a flue gas mercury control system on each unit . The plant injects powdered activated carbon (PAC) into the flue gas upstream of the baghouses. Therefore, the PAC material, with adhered mercury, and fly ash are collected in the baghouses.

**•** The dry fly ash and PAC material is pneumatically conveyed from the baghouse hoppers to the fly ash silo for each unit . The plant has the capability to unload the fly ash wet or dry. For wet unloading, the fly ash is conditioned with either
service wate r or the FGD brine from the treatment system for dust control. This fly ash material is transferred to the onsite landfill for disposal. The plant can also unload the fly ash dry for beneficial reuse

.Page 2

**•** Iatan operates dry bottom ash handling on both units. Unit 1 was initially installed with a wet bottom ash handling system, where bottom ash was sluiced to an ash pond, but the unit was recently retrofitted with a mechanical drag system.
Unit 2 operates a similar mechanical drag system.

**•** The mechanical drag system s remove the wet pyrites, bottom ash, and economizer ash from the trough directly underneath the boiler furnace. The ash is continuously removed and conveyed to a bottom ash bunker.

**•** Th e bottom ash is dewatered in the bunker

, loaded into trucks

, and reused off site or trucked to the onsite landfill for disposal. According to the plant, some of the bottom ash is marketed for use in cement manufacturing. The water collected in
the bunker i s returned to the bottom ash system.

**•** Overflow drains from the mechanical drag system are directed to an overflow tank and ultimately sent to the Unit 2 cooling tower or clarifiers.

**•** Iatan operates a once through cooling water system for Unit 1 and a recir culating cooling tower system for Unit 2.

Flue G as Desulfurization System

**•** Units 1 and 2 both have a wet FGD system to control the sulfur dioxide emissions from the plant

. Both systems are limestone forced oxidation systems, with a spray tower design. A process flow diagram for the FGD system is included in
Attachment 2.

**•** Iatan operates a common limestone preparation system for both units. The plant
uses ball mills and reclaim water, described later in the notes, to generate the limestone slurry used in the FGD system. The slurry , which is approximately 30 percent solids, is pumped through a hydrocylone to classify the slurry. The solids that are too large are returned to the ball mills and the remaining solids are transferred to the limestone storage tank. The limestone slurry is then pumped to the reaction tank of the FGD system.

**•** Both FGD systems have five spray levels, but the plant typically only operates
three or four of the spray levels at a time. The plant pumps the limestone/gypsum slurry in the reaction tank up to the various spray levels in the absorber which
flows counter

- current to the flue gas.

**•** The limestone reacts with the sulfur dioxide to generate calcium su lfite and the calcium sulfite is oxidized to calcium sulfate (i.e., gypsum) in the reaction tank.

**•** Iatan does not use any additives (e.g., organic acids) in the FGD system.Page 3

**•** The FGD system has a maximum chlorides level of 12,000 ppm. The system operates with a chlorides level of 4,000 to 5,000 ppm. The system operates at a
low chlorides concentration because of the low chlorine content in the PRB coal.

**•** The solids in the FGD system range from 16 to 18 percent solids. When the
solids concentration reache s 18 percent, the plant blows down from the system.
The FGD blowdown is transferred to a set of hydrocyclones which separate s the gypsum from the water.

**•** The underflow from the hydrocyclones is transferred to the filter feed tank. From
the filter feed ta nk, the gypsum is pumped to the vacuum rotary drum filters, which dewater the gypsum. Iatan does not have the capability to wash the

gypsum. The gypsum is dewatered to a moisture content of approximately 20 percent. The plant does not market the gypsum, so it is trucked to the onsite landfill. Iatan stated that they are still trying to market the gypsum, so they try to separate the gypsum from the fly ash in the landfill. The filtrate from the rotary
drum filters is transferred to the reclaim water tank.

**•** The overflow from the hydrocyclones is transferred to the reclaim water tank. The reclaim water tank also receives the filtrate from the rotary drum filters, mist eliminator wash, sump water from the limestone preparation, FGD absorbe r , and
bottom ash s torage areas, and cooling tower blowdown.

FGD Wastewater Treatment

**•** Diagrams of the FGD wastewater treatment system are included in Attachment 3

.

**•** Most of the water in the reclaim water tanks is reused in the FGD system. However, a bleed stream from the reclaim tank is transferred to the FGD wastewater treatment system.

**•** From the reclaim tanks, the wastewater is either directed to the ZLD wastewater storage tank or the ZLD backup holding tank. From the wastewater storage tank,
the wastewater enters the m etal removal clarifier. Iatan adds a coagulant and polyelectrolyte to the clarifier. The underflow from the clarifier is transferred to a
thickener. The thickener also receives the raw water clarifier underflow.

**•** The underflow from the thickener is mixed with a polymer and dewatered using a belt filter press. The solid waste is trucked to the onsite landfill for disposal. The
overflow from the thickener is transferred to the raw water clarifier

.

**•** The overflow from the metal removal clarifier is transferred to the evaporator feed tank where the plant adds sulfuric acid and an antiscalant. The plant lowers the pH from 5.5 to 5.2 S.U.

**•** From the evaporator feed tank, the wastewater is pumped through a heat exchanger, where the process distillate heats the FGD wastewater, and then to thePage 4

deaerators. The deaerators allow the noncondensibles such as carbon dioxide and

oxygen to vent to the atmosphere.

**•** Iatan operates two trains of the ev aporation process. At the time of the site visit,
Iatan was making process modifications on Train A to improve consistency in performance . After modifications were made to that system, the plant planned to
make similar modifications for Train B.

**•** The wast ewater from the deaerators is then fed to the sump of the falling

- film brine concentrator. Brine from the sump is pumped to the top of the brine
concentrator and enters the heat transfer tubes. Iatan also adds caustic, an antifoaming agent, and seeded cal cium sulfate to the brine as it is pumped to the top of the brine concentrator. While falling down the heat transfer tubes, part of the solution is vaporized and then compressed and introduced to the shell side of the brine concentrator (i.e., the outside of the tubes). The temperature difference between the compressed vapor and the brine solution causes the compressed vapor to transfer heat to the brine solution, which flashes to a vapor. As heat is transferred to the brine, the compressed vapor cools an d condenses as distilled

water.

**•** The distillate from the brine concentrator is collected and transferred to a distillate tank. Within this tank, some additional steam vapor is returned to the shell side of
the brine concentrator . The remaining distillate is used to heat the incoming FGD wastewater and is then sent to the clean ZLD sump.

**•** The concentrated brine slurry from the brine concentrator tubes falls into the sump and is recycled with the feed (i.e., FGD wastewater) back to the top of the
brine concentrator, while a small amount is continuously withdrawn from the sump and transferred to a set of hydrocyclones. To prevent scaling within the brine concentrator as a result of the gypsum present in the FGD wastewater, the
brine concentrator is seeded with calcium sulfate. The calcium salts preferentially precipitate onto the seed crystals instead of the tube surfa ces of the brine

concentrator. The hydrocyclones recover the calcium sulfate seed crystals in the underflow and recycle the seed to the reci rculation stream entering the top of the brine concentrator. The overflow from the hydrocyclones is the concentrate that is
transferred to the brine blowdown tank

.

**•** From the brine blowdown tank, the brine is transferred to the brine storage tank.
The plant uses the brine as a source for conditioning the fly ash prior to disposal
in the landfill.

**•** As described previously, the distillate from the brine concentrator is collected in
the clean ZLD sump . This sump water is then transferred to the raw water

c larifiers and reused in the plant.

**•** The evaporation system concentrates the brine by a factor of seven

.Page 5

**•** The evaporation system was designed for a TDS concentration of 15,000 ppm; however, at the time of the visit, the TDS concentration was 70,000 ppm, wh ich was causing issues with the evaporation system. The plant had been cycling the water in the FGD system to raise the chlorides level, but because the plant uses PRB coal, which generally has lower chlorides, the additional recirculation was causing a m uch higher build up of TDS.

**•** The system began operating in March 2009 and was not operating continuously at
the time of the visit.

Ash Pond

**•** Iatan has an ash pond that was used for handling the bottom ash sluice water and depositing fly ash that was not m arketed. However, since the conversion to the dry bottom ash system and the installation of the onsite landfill, the pond has not received any additional ash waste.

**•** The ash pond is not lined and is approximately 15 to 20 feet deep, based on the origina l construction. The pond consists of two cells operated in series. There is currently no discharge from the pond.

**•** Iatan is looking into dewatering the solids in the pond and marketing the material
for reuse.

Landfill

**•** Iatan operates an onsite landfill, which began operation in January 2009. The
landfill has four stages and the plant is currently filling Stage 1. The landfill has a two foot clay liner, 60 mm HDPE liner, and 12 inches of sand.

**•** The plant collects la ndfill leachate and runoff in a collection pond s . The leachate is used for dust suppression control on the landfill. The plant has an emergency discharge outfall from the collection pond.

**•** Iatan has eight groundwater monitoring wells around the la ndfill. All of the wells

are considered by the Missouri Department of Natural Resources ( MDNR ) to be downgradient of the landfill

.

**•** Iatan conducted two years of groundwater monitoring prior to putting any solids
in the landfill.Page 6

Table 1. Site Visit Attendees

Name Organization (Representing) Telephone E

- mail

Gary Brown KCPL 816

- 386

- 5225 gary.brown@kcpl.com

Paul Ling KCPL 816

- 556

- 2899 p aul.ling@kcpl.com

Tom Mackin KCPL 816

- 556

- 2957 tom.mackin@kcpl.com

Nick Voris KCPL 816

- 386

- 5225 nick.voris @kcpl.com

Donna Hill UWAG 205

- 257

- 5234 dbhill@southernco.com

Ron Jordan EPA/Office of Water 202

- 566

- 1003 jordan.ronald@epa.gov

Bill Swietlik EPA/Office of Water 202

- 566

- 1129 swietlik.william@epa.gov

Deb Bartram ERG (Contractor to EPA) 703

- 633

- 1669 deborah.bartram@erg.com

TJ Finseth ERG (Contractor to EPA) 703

- 633

- 1698 thomas.finseth@erg.com