Notes from Site Visit at TECO Energy’s Polk Power Station on October 8, 2009 

EPA conducted a site visit at TECO Energy’s Polk Power Station (Polk) located in South 

Mulberry, FL on Thursday, October 8, 2009 to learn about the operations at the plant, 

specifically the integrated gasification combined cycle (IGCC) unit. Table 1, located at the end 

of this memorandum, identifies the site visit participants. The presentation that the Polk 

personnel gave during the site visit is provided as Attachment 1 to this memorandum. 

This memorandum describes the information collected during the site visit and the pre-site visit 

phone call, which was held on October 2, 2009. 

Plant Overview 

TECO personnel provided an overview of operations for Tampa Electric Generation, as shown in 

Attachment 1. This memorandum focuses on operations at the Polk Power Station. Attachment 2 

contains an overall water balance diagram for the plant. 

 Polk currently operates five electric generating units at the power plant, with a 

gross generating capacity of 920 MW. The table below contains some general 

information for the five generating units. 

Unit 

Installation 

Date 

Gross Capacity 

(MW) Unit Type Fuel Type 

1 1996 320 

(250 MW net) 

Integrated Gasification 

Combined Cycle (IGCC) – 

base load 

Syngas generated from 

coal and petroleum 

coke/distillate oil 

2 2000 150 Simple cycle combustion 

turbine 

Natural gas/distillate oil 

3 2002 150 Simple cycle combustion 

turbine 

Natural gas/distillate oil 

4 2007 150 Simple cycle combustion 

turbine 

Natural gas 

5 2007 150 Simple cycle combustion 

turbine 

Natural gas 

 The Polk plant comprises over 4,000 acres (of which 750 acres comprises the 

cooling pond) and currently employs 80 people. 

 Cooling water for the plant is supplied by a 750-acre unlined cooling pond. 

Cooling water recirculates from the process to the pond. Due to evaporation, well 

water is used to makeup water to the cooling pond. Periodically, water from the 

cooling water is discharged to the Little Payne Creek, due to dissolved solids that 

build up in the pond or due to extreme rainfall events. The cooling pond also 

receives treated water from the slag runoff retention basin, the oily water 

collection and treatment system, and the storm water collection system. 

 The Polk site was previously mined for phosphate. 
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Unit 1 IGCC Operations 

 The gasification technology used at Polk was originally developed by Texaco and 

is now owned by GE. 

 The current plant configuration consists of a single train, with one gasifier 

supplying one combustion turbine. 

 Saturated steam created in the gasifier is pumped to the Heat Recovery Steam 

Generation (HRSG) unit and used to power a steam turbine. 

 Syngas from the gasifier is processed and cleaned before being used to power the 

combustion turbine. Diluent nitrogen is combusted with the syngas to reduce NOx 

formation. 

 The plant uses 2,200 tons per day of fuel. Current fuel is a blend of 30% coal and 

70% petroleum coke. The station has experimented with use of several fuel blends 

comprised of various coals and petroleum coke, and has also included various 

biomass blends as well. Low rank fuels, which can be used in slurry fed gasifiers, 

lower the overall efficiency of the unit. 

 Coal is received via covered truck, bottom dumped onto a conveyor, and stored in 

one of two 5,000-ton silos. The plant can hold approximately 5 days of fuel on 

site. Approximately 95 trucks per day are received at full capacity. 

 The plant stores slag generated in the gasifier in an outdoor lined pile. The slag is 

either marketed offsite (in the cement industry or used as a fuel component at 

Tampa Electric’s Big Bend Station) or it is fed with the coal to the slurry 

preparation rod mill. Polk has also periodically transferred slag to an off-site 

landfill for disposal. 

 Runoff from the slag pile is collected in two runoff basins, which are designed to 

hold the volume for a 100-year 24-hour storm event. The runoff is sampled 2 

times per year. Leachate from the runoff basins is held in a leachate pond, prior to 

filtration and discharge to the cooling pond. The slag pile bottom liner is 60 ml 

and top liner is 80 ml. Leachate from the slag storage area is sampled and 

analyzed on a semi-annual basis. The most recent sample was collected in May, 

2010. The laboratory report for this sampling event, which lists all pollutants 

analyzed as well as the test results, is included as Attachment 3. 

 

 Coal and petroleum coke is fed to the rod mill to be ground and mixed with water 

and recycled char (slag) from the IGCC process to create a slurry. The slurry is 

then pumped to the gasifier where it is mixed with oxygen from the air separation 

plant to create a syngas. 

 The gasification process operates between 2,300F and 2,700F. This process 

creates syngas, slag, and flyash. 
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 The constituents in syngas vary depending on the fuel blend. Currently, the 

syngas is about 30% hydrogen, 45% carbon monoxide, 15% carbon dioxide, 3% 

nitrogen, and about 1% sulfur. 

 The slag and about 50% of the flyash generated collects in a water pool located at 

the bottom of the gasification unit. The wet slag and flyash moves through the 

slag crusher onto the slag drag conveyor where it is deposited onto a screen. The 

coarse material captured by the screen is collected and sold to the cement 

industry. Water and fines passing through the screen are considered “black 

water” which is pumped to the settler feed tank. 

 Remaining flyash and syngas flow through a convective syngas cooler to a water 

scrubber (referred to as the “syngas scrubbers”) for the removal of particulates 

and hydrochloric acid (HCl) from the syngas. The scrubber blowdown, also 

referred to as “black water,” is pumped to the settler feed tank at about 400 gpm. 

 Syngas is further cleaned in the carbonyl sulfide (COS) hydrolysis unit, which 

converts the COS to hydrogen sulfide (H2S). Following this unit, the gas is cooled 

through three small heat exchangers and sent to the acid gas removal system. 

 In the acid gas removal system, the syngas is scrubbed with methyl diethanol 

amine (MDEA), which captures the H2S in the syngas. The cleaned syngas is 

then heated, filtered with a 10-micron cartridge filter, and sent to the combustor. 

 The MDEA and H2S solution from the bottom of the scrubber is transferred to the 

MDEA stripper, which uses steam to release the H2S from the MDEA. The H2S 

and other noncondensibles gases are transferred to the sulfuric acid plant. The 

MDEA is collected, cooled, and reused in the scrubber. 

 The sulfuric acid plant produces about 200 tons per day of 93-98% acid. 

Unit 1 Wastewater Treatment 

 Diagrams of the wastewater flow and management associated with Unit 1 are 

included as Attachment 4. 

 Black water that collects in the settler feed tank is pumped to one of two gravity 

settlers, where a flocculant and coagulant are added. The overflow from the tanks 

is referred to as grey water and is stored in a conical tank. Most of the grey water 

is recycled to the syngas scrubbers, as shown in Attachment 2. Approximately 

100 gpm is transferred to the brine concentration system. 

 The underflow from the gravity settlers is recycled directly to the slurry 

preparation step. 

 Grey water transferred to the brine concentrator is sent through a vapor 

compression cycle to evaporate the majority of the water. The brine concentrate, 

which contains about 30,000-40,000 ppm chlorides, is transferred to a second 

evaporation step followed by a crystallizer to reclaim solid ammonium chloride 
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from the waste stream. The solids (16% moisture) are disposed off site. 

Approximately 15 tons of solids are produced each week. 

 In the past, Polk experienced exceedances of the NPDES permit limit on selenium 

in discharges from the cooling water pond. Several forms of selenium were 

measured (Se-4, Se-6, and selenocyante). The source of the selenium responsible 

for the permit exceedances was found to be the neutralized weak acid return from 

the sulfuric acid plant. Selenocyanate has also been measured at low levels in 

leachate from the slag pile. 

 Condensate from the brine concentrator is reused for pump seals and instrument 

tap flushes. It contains less than 100 ppm chlorides. 

Simple Cycle Unit Operations (Units 2 through 5) 

 Units 2 and 3 are fueled by oil and natural gas, while units 4 and 5 are fueled only 

by natural gas. 

 The air compressors are cleaned with a water/detergent solution every other year. 

The gas turbines are cleaned about every three years. 

 Miscellaneous wastewaters, including contaminated precipitation, pump and seal 

leakage, and maintenance are managed in the oily water system. 

 Water in the oily water system is treated through an API oil/water separator, 

followed by a dissolved air flotation (DAF) unit, equalization basin, and sand 

filter (NPDES outfall I-004). The plant does not adjust the pH in the equalization 

basin or at outfall I-004 as it is not required by their NPDES permit. The treated 

water, including filter backwash, is then discharged to the cooling pond. 
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 Table 1. Site Visit Attendees 

Name Organization (Representing) Telephone E-mail Kevin Young TECO Energy 813-228-4232 kayoung@tecoenergy.cStanley Kroh TECO Energy 813-228-4257 smkroh@tecoenergy.coPaul Carpinone TECO Energy 813-228-4858 plcarpinone@tecoenergMike Perkins TECO Energy 813-228-1111 mrperkins@tecoenergyTemi Linjewile TECO Energy 813-376-8823 tmlinjewile@tecoenergJames P. Moore, Jr. TECO Energy 813-228-1111 jpmoore@tecoenergy.cDonna Hill UWAG 205-257-5234 dbhill@southernco.com Ron Jordan EPA/Office of Water 202-566-1003 jordan.ronald@epa.gov Deb Bartram ERG (Contractor to EPA) 703-633-1669 deborah.bartram@erg.c