Environmental retrofits at WPS

A series of emission control projects have been completed at our coal-fueled power plants. These projects help us to meet stricter state and federal air quality regulatory requirements.

Nitrogen oxide retrofit project (NOx)

To better control the combustion process and reduce NOx emissions, we installed low NOx burners and "Separated Over-Fire Air" or SOFA. The equipment was installed during regular scheduled maintenance outages at each of the seven units. The Public Service Commission of Wisconsin and the Wisconsin Department of Natural Resources approved the construction of the NOx reduction projects.

The new equipment was installed to better control the combustion process. The equipment will reduce NOx emissions by 40 to 50 percent overall. NOx emissions and their downwind impacts are regulated under multiple State and Federal air quality regulatory programs.

Annual Nitrogen Oxide Emissions

Mercury reduction projects

We installed new equipment to handle and inject dry sorbent materials into the power plant's exhaust gas. The sorbents are made of powdered activated carbon. The carbon sorbent is specially sized and chemically-treated to capture mercury, acting like a mercury-absorbing sponge. It is injected into the exhaust gases before reaching existing particulate matter control equipment. That allows mercury to be separated from the exhaust before the gases reach the chimney.

The used carbon sorbent is collected and co-mingled with the fly ash. The ash is tested to determine if it can be reused or put in a landfill. The mercury is physically and chemically bound to the carbon sorbent. That prevents it from re-emitting to the air or water. Expected mercury reduction is in the 60 to 85 percent range using the activated carbon injection system.

These projects enable WPS to meet compliance targets according to Wisconsin Mercury Rule (NR446) and the federal Mercury and Air Toxics Standard (MATS).

Annual Mercury Emissions

Columbia Energy Center sulfur dioxide emission reduction project

WPS owns 31% of the Columbia Energy Center which is located near Portage, Wisconsin. The plant has recently installed a dry flue gas desulfurization system. The system reduces the plant's sulfur dioxide (SO2) emissions. It became operational in 2014. WPS shares ownership of the plant with Wisconsin Power and Light and Madison Gas and Electric.


WEC Energy Group