The Public Service Commission of Wisconsin on Nov. 12 approved Wisconsin Public Service Corp. (WPSC) to spend $17.3m to upgrade the coal dust collection systems at the Weston power plant in Marathon County, Wisc.
WPSC proposes to construct the facilities to enhance control of combustible dust in compliance with standards set by the Occupational Safety Health Administration (OSHA) and enhance environmental performance emission standards being promulgated by the U.S. Environmental Protection Agency (EPA). The $17.3m cost estimate includes Allowance for Funds Used During Construction (AFUDC).
Weston is located in the villages of Kronenwetter and Rothschild, along the Wisconsin River, about seven miles south of Wausau. It includes four coal-fired units, two natural gas/oil-fired combustion turbine generators, and auxiliary systems. Unit 1 (60 MW) began operating in 1954. Unit 2 (75 MW) began operating in 1960. Unit 3 (321 MW) began operating in 1981. Weston 4, the newest and largest unit at 525 MW, began operating in 2008. WPSC owns 70% (368 MW) of Weston 4, and Dairyland Power Cooperative owns the remaining 30% (157 MW).
Weston currently has a total of eight dry dust collectors (baghouses) used to control dust emissions from the material transfer and processing points in the coal handling system. Two of the three dust collectors used to support train unloading are located outdoors, while one is inside an existing structure. The remaining five dust collectors are located inside existing structures designed to support the plant fueling system.
Systems needed to control dusty Powder River Basin coal
The facility uses Powder River Basin (PRB) coal, which contains a large amount of fines in its delivered condition, and then breaks down further at each material transfer point due to its friable nature.
WPSC was approved to upgrade the existing on-site coal dust collection system at Weston with a new dry dust collection system that is designed to enhance control of the emissions of the fine particulate that is inherent with PRB coal.
The proposed dry dust collection equipment will be installed on-site at five locations and a dust transport system will interconnect all five locations. The project scope includes: replacing the crusher house dust collectors, dumper house dust collectors, and Weston 3 silo fill dust collectors; upgrading the junction house dust collector; and installing a new dust collector for the original coal reclaim dust collector.
In April 2013, the commission granted WPSC approval to install a new $275m multi-pollutant control system, known as ReAct, to Weston Unit 3. It involves three process stages: adsorption of SO2, NOx and mercury onto a moving bed of activated coke (AC) pellets as flue gas passes through it; regeneration of the AC pellets by thermal desorption of the pollutants; and byproduct recovery, including creation of sulfuric acid from the sulfur-rich gases coming out of the process. The ReAct project is to begin construction in September 2014 and be fully operational by 2016.
WPSC’s dust collector upgrade project will interface with the ReAct fines collection system, in that the crusher house dust collector will have a port that the ReAct facilities will be able to connect to. The crusher house dust collector will be designed to handle multiple sources of dust and can accept the AC fines from the ReAct storage silo outlet. The crusher house dust collector will be designed marginally larger to accept the ReAct source. It will be sized to treat 32,000 cubic feet per minute (cfm), with only 1,000 cfm coming from ReAct. The ReAct AC fines will still be cascaded in the Weston 3 coal silos as originally planned, but without the need for the dust collector and agglomerator originally proposed with the ReAct project.