Final Notes from Site Visit at American Electric Power’s Cardinal Steam Electric Plant on February 2 , 2 010

EPA conducted a site visit at American Electric Power’s Cardinal Steam Electric Plant (Cardinal) located in Brilliant

, OH on Tuesday

, February 2 , 2010 to learn about the operations at the plant

, including the operation of the flue gas desulfurization ( FGD ) wastewater treatment system

. Table 1 identifies the site visit participants. The presentation Cardinal gave during the site visit is included as A ttach ment 1

.

Plant Overview

**•** Cardinal operates three coal

- fired electric generating units

. American Ele ctric Power ( AEP ) owns U nit 1 and operates th e facility. Buckeye Power owns U nits 2 and 3

. The table below contains some general information on the current operation of each steam electric generating unit.

Unit Installation Date Gross Net Capacity

(MW) Pa rticulate Control NOx Control SO 2 Control 1 1967 600 ESP (Electrostatic precipitator) (cold

side) SCR (2001) Wet FGD (March 2008)

2 1967 600 ESP (cold

- side) SCR (2001) Wet FGD (December 2007) 3 1977 630 ESP (hot

- side) SC R (2001) Wet FGD (Planned for 201 2 )

**•** Cardinal burns 4.5 million tons of coal annually. Units 1 and 2 burn only bitumino us coal . Unit 3 burns 80% low sulfur coal and 20% P owder R iver B asin ( PRB ) coal

. After Cardinal completes the FGD scrubber on U nit 3 , the plant plans

on switching co als to burn a coal with a higher sulfur c on tent ( or whatever coal is cheapest )

. The FGD systems on U nit 1 and 2 were originally designed for a coal with 7.5 lbs sulfur dioxide ( SO 2 ) per mmbtu. However, starting in 2001 during NO x season , the sulfur in the coal was reduced to 2.5 lbs SO 2 per mmbtu to reduce sulfur trioxide ( SO 3 ) formation.

**•** Cardinal receives c oal for U nits 1 and 2 via truck ; whereas, coal for U nit 3 is received via barge. The plant stores a pproximately 30

- 60 day s’ supply of coal on site.

**•** Units 1 and 2 use the following air pollution control technologies in the following order: low NOx burners, SCR system, ESP, and FGD absorber. Unit 3 operates the same order of air pollution control technologies ; however, the FGD absorber has not yet been installed.

**•** Cardinal does not regenerate the SCR catalysts on site.**•** Cardinal operates an on

- site landfill that receives a portion of the FGD gypsum (the majority of the gypsum is used in wallboard manufacturing) . The landfill has a l eachate collection system. The leachate collected from the system has an internal outfall (O utfall 602) and is ultimately discharged via final O utfall 019. Cardinal is required to monitor at internal O utfall 602 for flow, dissolved solids, fluoride, boron, mercury, and s elenium.

Flue Gas Desulfurization System

**•** U nits 1 and 2 both hav e wet FGD systems

. Cardinal is in the process of adding a n FGD system to U nit 3

. The FGD system for U nit 3 will be designed similarly to Units 1 and 2; h owever, Cardinal is n ot installing a stack for Unit 3

. Instead the flue gas will be inserted into the center of the cooling tower. This will lead to better dispersion and additional droplet removal within the cooling tower

. Placement of the stack in the cooling tower, where it will be cle ar of the cooling tower plume impingement and the unsafe conditions created when it freezes on the stack shell, is less expensive th a n building a free

- standing stack. Cardinal states that a stack can cost up to 30 million dollars to install. Alt hough this technology is commonly used in Europe, Cardinal is the first US plant to build

one

.

**•** Units 1 and 2 both have 95% SO 2 removal capability using high sulfur coal (7.5 lb S/mmbtu). Additionally, b oth units have a trona injection system for SO 3 miti gation

.

**•** The FGD systems are wet limestone forced oxidation jet bubbling reactors (JBR) designed by Bla c k and Veatch

. Service water and JBR slurry is used to cool the flue gas from 300°F to 126°F. Once cooled

, the flue gas enters the JBR and is bubbled into the JBR slurry

. In the slurry, air is injected to supply o xygen to form a sulfate product

. T he SO 2 reacts with limestone (CaCO 3 ) and o xygen to form gypsum (calcium sulfate), water, and carbon dioxide ( CO 2 )

. The pH in the absorber is maintained at approximately 4.8 S.U . Limestone is more easily dissolved at a lower pH, so with this low pH

, the plant does not have to grind the limestone as much as other plants. The vapor pressure of the slurry affects the SO 2 absorption in the liquid phase, forming a we ak acid. Subsequent neutralization, precipitation, and oxidation steps convert the weak acid to calcium sulfate.

**•** Cardinal receives l imestone at the plant via barge. Cardinal operates an on

- site ball mill to crush the limestone . The limestone slurry formed in this process is sent to a hydro cy clone

. Oversized material is returned to the ball miss grinding circuit via the hydrocyclone underflow . The correctly sized material (hydrocyclone overflow ) i s used to replenish the JBR slurry; it is approximately 30% solids by weight

.

**•** The blowdown rate from the JBR varies to maintain a 20 percent solids concentration in the JBR, which results in a chloride s concentration of around 4 ,000 to 5,000 ppm , depending on the chloride in the coal. T he syste m is designedto have a limit of 12,000 ppm of chlorides ; h owever, Cardinal has found that the FGD scrubber system operates best if the chloride s concentration does not g o above 4 ,000

- 5,000 ppm.

**•** Blowdown from the FGD scrubber is continuous and goes to the Hydroclone Feed Tanks

. Blowdown from the hydroclone fee d tanks is pumped to a set of primary hydrocyclones

.

**•** T h e underflow from the primary hydrocyclones is transferred to vacuum belt filters to dewater the gypsum. Cardinal wash e s the gypsum as it is applied to the vacuum belt filters to reduce the chlo rides in the gypsum. Filtrate from the vacuum belt filters is sent to the reclaim tank. Wastewater in the reclaim tank is either recycled back to the JBR or sent to the wastewater treatment system.

**•** T he dewatered g ypsum contains 95% solids and less than 10 ppm of chlorides. The gypsum must have less than 10% moisture for Cardinal to be able to sell it to wallboard manufacturers. Cardinal sells approximately 50% of the gypsum to Serpentine. All gypsum that is not sold is transported to an on

- site landfill.

**•** The overflow from the primary hydrocyclone s is transferred to the wastewater treatment system . This waste stream contains approximately two percent solids. Cardinal also blows down from the reclaim tank.

**•** Cardinal only has one set of primary hydrocyclone s per dewatering train

. Personnel state that the plant only needs primary hydrocyclone s because the hydrocyclone s are sized correctly to feed the vacuum filters

. FGD Wastewater Treatment System

**•** A process flow diagram for the FGD wastewater treatment s ystem at Cardinal is included as A ttach ment 2

.

**•** Cardinal began sending FGD waste water to the wastewater treatment plant in January 2008. According to plant personnel, i t took two to three weeks for the
treatment system to fill up with water

.

**•** The hydrocyclon e overflow and reclaim water are both transferred to the FGD wastewater treatment system. The plant has a sample point for the combination of the two streams before they enter the wastewater treatment system , but there is
not a sample point for the individ ual streams.

**•** The FGD w as tewater is first combined in two equili zation (EQ) tank s . The EQ tanks main purpose is to help the system maintain a steady flow rate. Mainly

, the EQ tanks contain hydrocyclone overflow and wastewater from the reclaim water tank. S umps from the wastewater treatment building are also transferred to the EQ tank. If the e ffluent from the FGD wastewater treatment system does not meet the specifications for discharge, the plant can pump the effluent back t o the EQ tank.**•** The wastewater f rom the two EQ tanks is combined and then split to enter either of two trains of the FGD wastewater treatment system , which operat e in parallel. The wastewater first enters the desaturation tank s

. Cardinal adds l ime to the desaturation tanks to maintain a pH of plus 9.0 S.U . Cardinal personnel state d that lime is not added to target any specific metals. In the desaturation tanks, the water is softened, reducing the potential for scaling downstream.

**•** The wastewater travels from each desaturation t anks to a primary clarifier (i.e., desaturation tank A flows into primary clarifier A ; and desaturation tank B flows into primary clarifier B). The sludge from each primary clarifier is pumped to the sludge holding tank s

.

**•** The overflow from each primary cl arifier is transferred to the coagulant mix tank s

. Cardinal adds f erric chloride and sulfuric acid to each of the coagulant mix tank s

. The s ulfuric acid is added to lower the pH to 8.0

- 8.3 S.U

. Cardinal determined that ferric chloride forms a precipit ate better at this pH set point

. Cardinal is also plan ning to add organosulfide to each mix tank by December 2010. Cardinal is adding organosulfide to specifically target mercury removal. The organosulfide storage tank has not been built yet.

**•** After the coa gulant mix tank s , the wastewater is transferred to the secondary clarifier s, where Cardinal adds anionic polymer. The secondary clarifiers are solids contact clarifiers. The sludge from each secondary clarifier is either recycled back to the desaturation t ank to act as seed crystals or sent to one of the sludge holding tanks.

**•** The sludge in each of the two sludge holding tanks is dewatered using one of four filter presses. The filtrate from the dewatering process is sent to the filtrate equalization tank and returned to the secondary clarifiers. Cardinal personnel
state d that the filtrate goes to the secondary clarifier rather than back to the EQ tank because the wastewater has already been processed so there is no need for it to go through the entire process all over again.

**•** The dewatered solids from the filter presses are trucked to the Carinal FAR1 Residual waste landfill

.

**•** The overflow from the secondary clarif i er s is transferred to the effluent storage tank s . Although Cardinal had planned to install gravity filters after the effluent tanks as shown in the process flow diagram for the wastewater treatment sys tem, they decided not to add these units. C ardinal personnel state that the floc is too fine for the gravity filters to funct ion efficiently. Furthermore, they stated that it would be impossible to add ultrafiltration or microfiltration at the end of the process because of scaling /plugging problems.

**•** Cardinal has lim its for the discharge of effluent from the FGD wastewater treatment system ( internal outfall 601 ) for pH and suspended solids. Additionally,
t he plant must monitor the following pollutants: flow, temperature, specific conductance, dissolved solids, alkalin ity, chlorides, fluorides, sulfate, arsenic,barium, boron, cadmium, chromium, copper, iron, lead, mercury, nickel, selenium, and zinc.

**•** There is a sample point for the effluent where the plant does compliance monitoring. Cardinal takes 24

- hour composite s amples at the location

. The flow rate of the effluent is around 645

- 700 gpm ; however, t h e effluent is not necessarily continuous over the entire day and depends largely on the amount of wastewater recirculating through the system. FGD w astewater still flow s through the sample point even when wastewater is being recirculated in the system

.

**•** Effluent from the FGD wastewater treatment system is discharged to the river at the same location where once

- through cooling water is discharged at final outfall 001

. Twen ty feet below the surface of the river there is a 20

- foot long header which disperses the release of the treated wastewater.Table 1 . Site Visit Attendees

Name Organization (Representing) Telephone E

- mail

Tom Hart AEPSC 614

- 716

- 3260 tomlhart@AEP.com
Deanna King AEPSC 614

- 716

- 1234 djking@aep.com

JR Holland AEP

– Cardinal 740

- 598

- 6806 JRholland@aep.com

Bernie Lombard AEP

- Cardinal 740

- 598

- 6514 BLombard@AEP.com

Tom Kaufmann AEP

– Cardinal 740

- 598

- 6511 Tdkaufmann@aep.com

Donna Hill Southern Company, UWAG 205

- 257

- 5234 dbhill@southernco.com

Josh Hall EPA 202

- 566

- 1002 hall.josh@epa.gov

TJ Finseth Eastern Research Group 703

- 633

- 1698 thomas.finseth@erg.com
Becky Schwantes Eastern Research Group 703

- 633

- 1715 becky.schwantes@erg.com