The Arizona Department of Environmental Quality (ADEQ) is taking public comment until March 12 on a draft air permit renewal for the coal-fired Cholla power plant of Arizona Public Service Co. (APS) in Navajo County.
Permit renewals like this are routine, though the ADEQ did mention in a technical support document that APS plans to replace one of the plant’s SO2 scrubbers.
“Cholla generating station currently utilizes fabric filters at Units 1, 3 and 4, and a mechanical dust collector and Venturi flooded disc scrubbers Unit 2 for control of particulate matter emissions,” the agency noted. “Cholla has proposed to replace the mechanical dust collector with a fabric filter on Unit 2. For sulfur dioxide emissions removal, Unit 1 utilizes a tray tower absorber with lime reagent. Unit 2 utilizes Venturi flooded disc scrubbers/absorbers with lime reagent. Units 3 and 4 use sulfur dioxide spray tower absorbers with lime reagent for the control of SO2. APS has proposed to replace the scrubber on Unit 2 with a new flue-gas desulfurization unit. All four units are retrofitted with low-NOx burners and over-fire air system to control NOx emissions.”
The four units at Cholla typically burn 3.5 million to 4 million tons of coal annually or about 70% of the total potential burn rate of approximately 5.6 million tons, the support document noted. Specs are given in the document for the coal that goes to the plant from the Lee Ranch and El Segundo strip mines, which are located near each other in New Mexico and are owned by Peabody Energy (NYSE:BTU).
Cholla can produce about 1,160 MW in total. Units 1, 2 and 3 are owned by APS and Unit 4 is owned by PacifiCorp, the ADEQ said. All four units are operated by APS. Unit 1 was completed in 1962, Units 2 and 3 were completed in 1978 and 1980, and Unit 4 was placed in commercial operation in 1981.
The PacifiCorp website noted that in 2008, PacifiCorp significantly upgraded Cholla Unit 4’s emissions control equipment by installing a state-of-the-art cloth filter bag house and high-efficiency SO2 scrubber.
APS is part of Pinnacle West Capital Corp. (NYSE:PNW).