EPA readies haze limits for the coal-fired Sundt Unit 4 in Arizona

The U.S. Environmental Protection Agency plans to publish in the Feb. 18 Federal Register a proposed Federal Implementation Plan (FIP) that will impose new air emissions requirements for a unit at the coal-fired Sundt plant in Arizona.

This proposed FIP addresses the requirements of the Regional Haze Rule (RHR) and interstate visibility transport for the disapproved portions of Arizona’s Regional Haze (RH) State Implementation Plan (SIP) as described in a final rule published on July 30, 2013. The final rule on Arizona’s RH SIP partially approved and partially disapproved the state’s plan to implement the regional haze program for the first planning period.

The Feb. 18 proposed rule addresses the RHR’s requirements for Best Available Retrofit Technology (BART), Reasonable Progress Goals (RPGs) and Long-term Strategy (LTS) as well as the interstate visibility transport requirements for pollutants that affect visibility in Arizona’s 12 Class I areas as well as areas in nearby states.

The BART sources addressed in this proposed FIP are Tucson Electric Power‘s (TEP) Sundt Generating Station Unit 4, Lhoist Nelson Lime Plant Kilns 1 and 2, ASARCO Inc. Hayden Smelter, and Freeport-McMoran Inc. Miami Smelter. The sources with proposed controls for reasonable progress are the Phoenix Cement Clarkdale Plant and the CalPortland Cement Rillito Plant.

Public hearings in Arizona on the proposed FIP are planned for Feb. 25 and 26.

EPA is proposing to find that Sundt Unit 4 is eligible for and subject to BART. EPA is proposing BART emissions limits on Sundt Unit 4 for NOx, SO2 and PM10 based on the corresponding control technologies.

  • For NOx, the agency is proposing an emission limit of 0.36 lb/MMBtu consistent with the use of selective non-catalytic reduction (SNCR).
  • For SO2, it proposes an emission limit of 0.23 lb/MMBtu consistent with the use of dry sorbent injection (DSI).
  • For PM10, the federal agency is proposing a filterable PM10 emission limit of 0.03 lb/MMBtu based on the use of the existing fabric filter baghouse.
  • Finally, it is also proposing a switch to natural gas as a better-than-BART alternative.

Sundt is an electric utility power plant located in Tucson, Arizona, operated by Tucson Electric Power. The plant consists of four steam electric boilers and three stationary combustion turbines for a total net generating capacity of about 500 MW. Sundt Unit 4 is a steam electric boiler that was manufactured in 1964 and placed into operation in about 1967. Unit 4 is a dry bottom wall-fired boiler with a maximum gross capacity of 130 MW when firing coal.

Originally designed to fire natural gas and fuel oil, Sundt Unit 4 was converted to also be able to fire coal in the early 1980s as a result of an order issued by the U.S. Department of Energy. The unit now fires both coal and natural gas. As part of the coal conversion, the unit was equipped with a fabric filter for particulate matter control. Unit 4 was upgraded in 1999 with low-NOx burners (LNB) and overfire air (OFA) designed to meet Phase II Acid Rain Program requirements. It has no SO2 emissions controls, but has a limit on coal sulfur content.

TEP has indicated that the capacity of Sundt Unit 4 while firing coal is reduced compared to its capacity using natural gas. As reported to the Energy Information Administration (EIA), Unit 4 has a 173 MW nameplate capacity while firing natural gas. However, the maximum gross capacity at which the unit could operate for a sustained period of time while burning coal is about 130 MW. This is due primarily to the fact that the amount of coal that can be introduced to the boiler is limited by the size of the boiler. Excess coal injection causes the flame to impinge on the back wall of the boiler which damages the boiler tubes, EPA noted.

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.