GRDA permits coal-to-gas conversion, new gas unit at Chouteau

The Oklahoma Department of Environmental Quality on July 1 went out for comment on an air permit application by the Grand River Dam Authority to add new air emissions controls at its coal-fired Chouteau plant and to build new gas-fired capacity at the site.

GRDA is seeking this construction permit to accomplish several goals, said the department in a July 1 supporting document. Under the federal Mercury and Air Toxics Standards (MATS), the authority proposes to add powdered activated carbon injection to Unit 2 to control mercury and to convert the existing electrostatic precipitator (ESP) to a pulse jet fabric filter to capture mercury and other metallic hazardous air pollutants (HAPs). As part of this upgrade of Unit 2, system controls will be updated with safety improvements recommended by the manufacturer.

GRDA will also construct a natural gas-fired combined cycle combustion turbine (CCCT) called Unit 3. If economically feasible, Unit 1 will be converted from coal-fired to natural gas-fired. Finally, control system logic for the auxiliary boilers will be upgraded.

Notable is that the plant recently underwent a name change, from the GRDA Coal Fired Complex to the Grand River Energy Center.

Unit 1, to be converted to gas, has 490 MW of capacity

The Chouteau plant currently consists of two coal-fired, Foster Wheeler opposed-wall boilers, designated as Units 1 and 2.

  • Unit 1, which has a rated capacity of 490 MW, was built in 1978 and is designed to burn sub-bituminous (Wyoming) coal. Current air quality control equipment on Unit 1 consists of an electrostatic precipitator (ESP).
  • Unit 2, which has a rated capacity of 520 MW, was built in 1982 and is designed to burn sub-bituminous (Wyoming) coal, or a blend of Wyoming and Oklahoma bituminous coal.

An alternative operating scenario for Units 1 and 2 authorized under a prior permit consists of operating on refined coal, using additives S-Sorb and Mer-Sorb in a process known as Chem-Mod.

Existing flue gas desulfurization (FGD) air quality control equipment on Unit 2 consists of a spray dryer absorber (SDA) followed by an electrostatic precipitator (ESP). The igniters in these units are gas-fired.

Two auxiliary oil-fired boilers were originally installed for start-up of the main units, but are no longer needed for this purpose. They are operated occasionally to assure that they are still in good condition. They may be used for supplying steam to plant auxiliary equipment and for plant heating as necessary.

PAC system on the surviving Unit 2 will capture mercury

The planned powdered activated carbon (PAC) injection system at Unit 2 will inject sorbent upstream of both the SDA and the pulse jet fabric filter (PJFF) system to remove mercury and mercury compounds that are released from the coal into the flue gas during the combustion process. PAC particles adsorb mercury, are then collected in the fabric filter system, and are removed with the fly ash waste.

The new burners to be installed in the conversion of Unit 1 from coal to gas will give the unit a capacity of 5,400 MMBTUH. To prevent condensation of liquid hydrocarbons that might otherwise form due to pressure drop from the gas delivery line, an approximately 12 MMBTUH gas heater will be installed.

The CCCT Unit 3, using the Mitsubishi Heavy Industries Model M501J, will include a combustion turbine generator (CTG), a duct-fired heat recovery steam generator (HRSG), and a steam turbine generator (STG). Unit 3 will have a total heat input of 4,160.9 MMBTUH with an output of 495 MW (net).

Unit 3 will fire only pipeline grade natural gas, the department noted. A new linear mechanical draft cooling tower (LMDCT), a new inlet air chiller, a new fuel gas heater, a new diesel emergency generator, and a new auxiliary boiler will also be installed to support the CCCT. Natural gas will be delivered to the site via a new pipeline. The CTG will be designed to operate only in a combined cycle mode. Selective catalytic reduction (SCR) for NOx control is included in the project design.

About Barry Cassell 20414 Articles
Barry Cassell is Chief Analyst for GenerationHub covering coal and emission controls issues, projects and policy. He has covered the coal and power generation industry for more than 24 years, beginning in November 2011 at GenerationHub and prior to that as editor of SNL Energy’s Coal Report. He was formerly with Coal Outlook for 15 years as the publication’s editor and contributing writer, and prior to that he was editor of Coal & Synfuels Technology and associate editor of The Energy Report. He has a bachelor’s degree from Central Michigan University.