Arizona Electric Power to eliminate coal at one Apache unit

The Arizona Department of Environmental Quality is taking comment until March 21 on a draft air permit allowing Arizona Electric Power Cooperative to back out coal at one of the units of its Apache power plant.

“This Significant Permit Revision No. 59195 to Operating Permit No. 55412 is to be issued to the Arizona Electric Power Cooperative (AEPCO) for its Apache Generating Station to authorize a change for Steam Unit 2 (ST2) from coal to combusting pipeline natural gas, and to authorize a change in air pollution control for Steam Unit 3 (ST3) to selective non-catalytic reduction (SNCR) and the use of low NOX burners,” said a permitting document. “Additionally, this revision sets specific emission limits for Steam Unit 1 (ST1) in stand alone operation and for ST1 and Gas Turbine 1 (GT1) in combined Cycle mode.”

By unit, the changes are:

  • Steam Unit 1 – This revision sets emission rates for SO2, PM10, and NOX. SO2 and PM10 emission rates are set at 0.00064 and 0.0075 lb/MMBtu respectively. These emission rates are effective upon issuance of this revision. Effective Dec. 5, 2017, this revision will set an emission rate for NOX in stand alone operation to be 0.056 lb/MMBtu, and an emission rate for NOX of 0.10 lb/MMBtu for operation in combined cycle mode with GT1. Additionally, effective December 5, 2017 a daily NOX limit of 1,205 lbs averaged over 30 calendar days has been set for operation in both stand-alone mode and combined cycle mode with GT1.
  • Steam Unit 2 – As part of this revision ST2 will be converted from coal to pipeline natural gas firing effective on Dec. 5, 2017. This revision does authorize AEPCO to use coal as a fuel in ST2 in the event of a natural gas disruption such as a pipeline freeze-up or break.
  • Steam Unit 3 – This revision will authorize the facility to install and operate SNCR and low NOX burners for the additional control of NOx emissions from ST3 effective Dec. 5, 2017. Also, the NOx emission limit will be revised from 0.07 lb/MMBtu to 0.23 lb/MMBtu, based on a 30 boiler operating day average.

Said the agency in a public notice: “The Significant Revision to AEPCO’s permit is intended as a component of the SIP revision in order to assist in satisfying the Arizona Regional Haze Best Available Retrofit Technology (BART) requirements. The Permit Revision changes AEPCO’s Steam Unit 2, which normally burns coal, to only burn natural gas. Additionally, on Steam Unit 3, which burns coal, AEPCO will install selective non-catalytic reduction (SNCR), low NOX burners and overfire air as additional air pollution control equipment.”

The Arizona DEQ will be holding a public hearing on this permitting on March 26 at the City of Benson Council Chambers.

The AEPCO website said the Apache Generating Station in Cochise, Ariz., has: 605 MW of combined gross capacity; two steam units that can burn coal or natural gas, which enhances flexibility to use the least-cost fuel; one natural gas-fired boiler; and four gas turbines. AEPCO said it offered this switch of one unit from coal to only burning gas as a regional haze compliance option, along with the new air controls for the remaining coal unit.

The U.S. Energy Information Administration database shows the Apache plant last year getting coal from Arch Coal‘s Black Thunder mine in Wyoming and the El Segundo mine in New Mexico of Peabody Energy.

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.