They were doing fluidized bed combustion of Iowa coal mixed with Iowa limestone at ISU’s power plant to try to control the sulfur, mercury and ash. They might be still doing that, but it wasn’t very economical, and they ended up with huge piles of calcium carbonate/sulfate that leached the sulfur into the ground and couldn’t be mixed into concrete as they had hoped.
I mined the coal and put it in the FBC. When Iowa had a 5 pound SO2 limit, we could make Iowa coal work by washing in hydrocyclones. The washer took out the pyritic sulfur and lowered the ash from 18 to about 7 percent, raising BTUs to 10500, comperable to an Illinois Number 2 coal. The Iowa State and later, Iowa, put in their FBC, suddenly the washer didn’t call the tune; BTUs did, and higher heat coals from West KY came up river by barge and were trucked to Ames and Iowa City. That was the end of the wash plant and the little mines that fed it.