Many low rank coals (especially lignites) have only marginallyhigh sulfur contents, resulting in emissions of 2 to 3 pounds ofsulfur dioxide (SO2) per million Btu. This sulfur is present inabout equal amounts of pyritic, sulfatic, and organic sulfur.Therefore, physical cleaning methods are typically notapplicable. However, these coals have high oxygen contents, andmuch of this oxygen is present in carboxylic acid functionalitiesthat could provide sites for calcium ion exchange. Calcium couldbe incorporated into the coal structure, close to the sulfur,where it could efficiently trap sulfur during fluid bedcombustion. Thus, the calcium-exchanged material would becombustible as a compliance coal, eliminating the need formechanically intensive scrubbing or sorbent injection techniques.The ash content of the coal may be somewhat higher, but the totalplant solids would be less and solids handling would be simpler.In Phase I, the method of ion exchanging coal with calcium in asimulated stockpile will be investigated, as well as theperformance of the product in a small fluid bed combustor (FBC).Anticipated Results /Potential Commercial Applications as described by the awardee: Demonstration of the economicproduction of compliance FBC fuels from moderately high sulfurcoals should increase their marketablility. Capital and operatingcosts of FBCs would be lower, encouraging their usage. This wouldbe environmentally beneficial, since FBC nitrogen oxide emissionlevels are normally within EPA compliance limits. Phase II ofthis effort will integrate coal company and FBC vendorparticipation in pilot-scale testing of the SO2 control method.
