Wisconsin Public Service permits cutting-edge ReACT system

Wisconsin Public Service Corp. (WPSC) is requesting a construction permit to install a multi-pollutant control technology commercially known as ReACT on the coal-fired Weston Unit 3.

The purpose of the ReACT system is to reduce SO2, NOx, mercury (Hg), and other air pollutant emissions from the unit, the company said in a 260-page air permit application filed Aug. 13 at the Wisconsin Department of Natural Resources. Construction and initial operation of this system is expected to be completed in mid to late 2016.

Regenerative Activated Coke Technology (ReACT) is an advanced multi-pollutant technology that uses activated coke (AC), said expert testimony filed Sept. 17 at the Wisconsin Public Service Commission by Wisconsin Public Service. ReACT technology has been successfully implemented on large coal-fired boilers in Japan, was tested last decade on the coal-fired Valmy power plant in Nevada, and is commercially available worldwide, wrote H. James Peters, employed by technology provider Hamon Corp. as Executive Vice President of Strategic Planning and Business Development.

The utility, a subsidiary of Integrys Energy Group (NYSE: TEG), filed its initial application with the PSC for approval of this project on May 7.

In the Aug. 13 air permit application, Wisconsin Public Service provides a lot of technical details, including diagrams, on the ReACT system. The ReACT system at Weston Unit 3 was selected because it meets the following overall objectives:

Reduce SO2, NOx and mercury emissions in order to comply with current, pending and future environmental regulations including the federal Cross-State Air Pollution Rule (CSAPR) (or a similar replacement regulation) and federal and state mercury rules.

  • Allow beneficial use of by‐products from emission control systems to the extent practicable.
  • Minimize increased emissions of any other regulated pollutants.
  • Provide long‐term equipment reliability, operability, and maintainability.
  • Ability to continuously operate and provide control during startup and shutdown periods.

There are four coal-fired units and two gas-fired combustion turbines at Weston. The coal units are Weston Unit 1 (57.2 MW), Unit 2 (79.8 MW), Unit 3 (323.9 MW) and Unit 4 (551 MW). The combustion turbines are Weston Unit 31 (19.5 MW) and Unit 32 (48.1 MW). Weston Unit 4 began operating in 2008 with state-of-the art emissions controls already installed and is co-owned with Dairyland Power, while WPSC owns all of Units 1-3.

ReACT mainly cuts SO2, with extra control of other emissions

ReACT is a regenerative activated coke (AC) technology that provides for control of SO2 with a coincident reduction of NOx, Hg, and other pollutants. The system also produces commercial grade sulfuric acid. The ReACT system will incorporate the following major components:

  • ReACT process adsorption equipment;
  • ReACT process thermal regeneration equipment;
  • AC and AC fines handling and storage equipment;
  • Reagent (ammonia) material handling and preparation facilities;
  • Sulfuric Acid Plant with pre and post treatment systems;
  • Sulfuric Acid bulk storage and offloading systems;
  • Nitrogen Generation System including cryogenic backup storage; and
  • New Induced Draft (ID) fans and associated ductwork.

All existing air pollution control technology serving Weston 3 will remain in service or available for service. The fabric filters were installed on Weston Unit 3 in 2000, as part of a separate air pollution control project, and will continue to be in service to support the ReACT system. Low NOx burners and a separated over fire air system were installed for NOx control in 2009. Boiler Combustion Optimization software was also added to the unit’s Distributed Control System to further improve NOx control. These systems will continue to be in service to support the ReACT system. A powdered activated carbon injection system (ACI) was installed on Weston Unit 3 in late 2009 for mercury emissions control. This system is expected to be available to provide operational flexibility to meet current and future emissions control requirements.

The utility noted in the air permit application that it is currently in the process of obtaining a permit to install dry sorbent injection (DSI) on Weston Unit 3. It is anticipated that DSI will begin operation in early 2013 and will operate until ReACT has been installed and is operational in the second half of 2016. Therefore, this project falls within the contemporaneous period for ReACT. DSI will cause increases in CO2e. However, since DSI will not be operated after ReACT is installed and operational, the emission decreases associated with ceasing DSI operation will also be within the contemporaneous period, the utility noted.

AC waste fines to be used as supplemental fuel

Wisconsin Public Service said that some of the coal-based waste AC fines will be burned in the plant in addition to the normal Powder River Basin (PRB) coal. “It is projected that under normal operating conditions, approximately 200 to 800 lb/hr of AC fines will be screened at the bottom of the regenerator depending on load and the AC circulation rate. In order to be conservative it is assumed that 1,600 lb/hr of AC fines will be screened to evaluate potential emission increases from firing this material. Note that emissions from firing AC fines will be offset by a decrease in coal combustion. AC is made from coal and has a higher heat content than the PRB coal fired at Weston. The heat content of AC fines were tested to be 10,178 Btu/lb, while the heat content of PRB coal in Weston 3 averaged 8,733 btu/lb over the baseline period (November 1, 2009 through October 31, 2011). WPSC suggests a 12‐month rolling throughput limit of 7,000 tons/yr of AC fines to ensure compliance with potential emissions from this new fuel.”

The utility said in its Wisconsin Public Service Commission testimony that the likely source of the AC, at least initially, is China.

Also, the utility is proposing to restrict future operation of the coal-fired Weston Unit 1 in order to obtain enough contemporaneous CO2e emission decreases for ReACT to cover the increases it has forecasted. The utility selected the two‐year baseline period of February 2009-January 2011 to measue Weston Unit 1 emissions. Using CO2 continuous emissions monitoring data, there are 342,286 tons of CO2 available to offset the possible increase from ReACT and 173,860 tons are needed to offset the possible significant increase.

WPSC requested that the Wisconsin DNR include a construction permit requirement (and revision to the Weston Title V permit) that would limit future CO2 emissions from Weston Unit 1 to 168,426 tons in any 12‐month rolling period after ReACT becomes operational. This will generate the 173,860 tons of CO2 decreases needed to absolutely ensure that CO2e increases from ReACT remain below the Prevention of Significant Deterioration (PSD) threshold.

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.