The Minnesota Pollution Control Agency is taking comment until March 4 on air permit changes sought by Heartland Corn Products, including for a new combined heat and power (CHP) installation at its natural fermentation fuel ethanol production plant located in Winthrop, Sibley County, Minnesota.
At the facility, corn is ground and mixed with water and enzymes, cooked, and then fermented in tanks. The resulting liquid is separated from the solids, and distilled to produce pure fuel‐grade ethanol. The pure ethanol is denatured with gasoline, and stored in tanks prior to shipping by truck or rail.
The major air permit amendment the company seeks will authorize the construction and operation of a CHP system as the primary source for on‐site steam and electricity. The existing boilers will remain as a backup source. The CHP will consist of a 55 MMBtu/hr combustion turbine (known as EQUI 164) with a 73 MMBtu/hr duct burner (EQUI 165), providing additional energy for the heat recovery steam generator (HRSG).
EQUI 164 has a peak load heat input of 46.1 MMBtu/hr (HHV). EQUI 165 is rated at 73 MMBtu/hr. Both EQUI 164 and EQUI 165 combined will be subject to a 42 ppm (15% O2) NOX limit or 2.3 lb/MWh useful output. Heartland will comply with the SO2 limit of 0.060 lb/MMbtu heat input by firing EQUI 164 and EQUI 165 with natural gas only.