University of Iowa pursues air controls for two coal-fired boilers

The Iowa Department of Natural Resources (IDNR) will be taking comment until July 11 on a proposed Prevention of Significant Deterioration (PSD) air quality construction permit that would allow the University of Iowa (U of I) to add dry sorbent injection to two coal-fired boilers at its power plant located in Iowa City.

This project is the addition of dry sorbent injection systems to Boiler 10 and Boiler 11 and two new sorbent storage silos. The dry sorbent injection systems will allow the U of I to meet HCl emission limits in an upcoming federal regulation for industrial boilers. The U of I is also removing an electrostatic precipitator and adding a baghouse to Boiler 10.

The U of I operates and maintains a main Power Plant, three Chilled Water Plants and a Water Plant on the main campus, and satellite facilities at the UI Research Park (Oakdale Campus). The plants provide steam, water, high-quality water, chilled water, electricity, and sewer to the entire campus, including The University of Iowa Hospitals and Clinics. The UI Power Plant utilizes six boilers, four natural gas generators, and three steam turbine generators to generate steam and electricity that is distributed to other University of Iowa sites and facilities.

Boiler 10 and Boiler 11 are located at the main UI Power Plant.

  • Boiler 10 is permitted to burn bituminous coal, tire derived fuel, natural gas, and biomass. It utilizes low NOx burners (LNB) and flue gas recirculation (FGR) when firing natural gas. Boiler 10 was originally permitted in 1975. The permit was amended in 2001 to add an air heater and replace the economizer, in 2009 to increase the allowable PM10 emission limit, in 2012 to increase the allowable PM10 emission limit and add natural gas combustion, and in 2013 to allow for the combustion of biomass. 
  • Boiler 11, which is a circulating fluidized bed (CFB) boiler, is permitted to burn bituminous coal, up to 80% (by weight) oat hulls, and clean cellulosic biomass. In addition, it is allowed to burn natural gas during startup. The state of Iowa wrote its first permit for Boiler 11 in 1995. The permit was subsequently amended in 2003 to allow for the combustion of oat hulls, and in 2013 to allow for the combustion of biomass.

On Feb. 9, the department received an Air Construction Permit Application for Boiler 10 and Boiler 11. The facility requested the addition of dry sorbent injection systems to the boilers to control HCl emissions and the replacement of the electrostatic precipitator, which controls Boiler 10 emissions, with a baghouse. The facility also requested Air Construction Permits for two new dry sorbent storage silos. The dry sorbent injection systems are being added to meet the requirements of National Emissions Standards for Hazardous Air Pollutants (NESHAP) Subpart DDDDD (National Emission Standards for Major Sources: Industrial, Commercial, and Institutional Boilers and Process Heaters).

Effective Jan. 16, 2016, NESHAP Subpart DDDDD (also called the Boiler MACT) requires federal compliance with emission limits for carbon monoxide (CO), mercury (Hg), hydrogen chloride (HCl), and either particulate matter (PM) or total selected metals (TSM) as a surrogate for the wide range of remaining hazardous air pollutants (HAPs) from combustion processes. The University of Iowa has received an extension of the effective date to Sept. 30, 2016.

The facility will use hydrated lime and sodium bicarbonate as the sorbent. Feasibility tests were run in 2013 on both boilers to determine the sorbent injection system operating conditions necessary to meet the new Boiler MACT emission limits.

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.