EPA plans to approve air permitting related to new U.S. Capitol cogen

The U.S. Environmental Protection Agency is taking public comment on its proposed air permit for a coal-to-gas switch at a federal plant unit in Washington, D.C.

EPA proposes to approve a permit application submitted by the Architect of the Capitol for a Plantwide Applicability Limit (PAL) at the Capitol Power Plant (CPP) in Washington, D.C.

EPA is issuing a proposed permit that would grant conditional approval for establishing PALs to address emissions of particulate matter less than 10 micrometers (PM10), nitrogen dioxide (NO2), and greenhouse gases (GHGs). The proposed permit establishes PALs for PM10 at 42.8 tons per year (TPY), NOx (oxides of nitrogen, used to regulate emissions of NO2) at 248.1 TPY, and GHGs at 203,816 TPY carbon dioxide equivalent (CO2e). An Oct. 1 hearing on the proposed approval is planned.

A PAL is a flexible permit that reduces the permitting burden for facilities when changes are made and ensures that emissions will not increase above the significant emissions level. A facility may modify or add new emissions units without triggering the requirements for a major preconstruction permit, so long as they maintain emissions below the PAL. A PAL does not relieve a facility from complying with any other Federal or District regulation.

The CPP became operational in 1910 and was originally designed to provide heat and electricity to the U.S. Capitol. CPP eliminated electricity production in 1951, and the plant currently provides steam and chilled water to 23 facilities on Capitol Hill, including the House and Senate office buildings, the Supreme Court and the Library of Congress.

On March 28, the Architect of the Capitol submitted an application to EPA to construct and operate a cogeneration plant at the U.S. Capitol Power Plant. It asked EPA to establish plantwide applicability limits for those regulated New Source Review pollutants that would otherwise cause a significant increase in emissions due to the project. The pollutants included PM2.5, PM10, NO2, greenhouse gases (GHGs), and NOx as a precursor for ozone.

The cogeneration project will include two combustion turbines (CTs) rated at 7.5 MW each and two Heat Recovery Steam Generation (HRSG) units rated at approximately 71.9 MMBtu/hr each. The proposed cogeneration plant will use natural gas and ultra low sulfur diesel oil in the two combustion turbines in order to very efficiently generate both electricity and heat for steam. These combustion turbines are inherently more energy efficient and have lower emissions intensity than the current boilers at CPP. As such, the project has the potential to reduce the CPP’s current potential to emit of NOx by up to approximately 80%.

Electrical power generated from the CTs would be fed into the CPP’s electrical distribution system for consumption within the limits of the CPP facility for most of the year. The CPP electrical needs during the winter will be less than the cogeneration plant produces and the excess electricity will be fed to the other buildings within the architect’s portfolio. Each turbine set will use a HRSG for the production of steam. Maximum steam generation production will be 180,000 pounds per hour and will reduce the need to utilize existing boiler capacity at the facility. Most of the new facility will be housed in an existing structure at the East Plant.

CPP currently has seven boilers on site, ranging from 160 MMBtu/hr (Boilers 1–3) to 50 MMBtu/hr (Boiler 4-7). Boilers 1-2 are co-fired by coal and natural gas, and Boilers 3-7 are fired by natural gas and fuel oil.

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.