The objective of this project is to demonstrate the feasibility of using the Rotary Combustor (RC) to replace conventional pulverized coal burners as a means of reducing plant emissions on utility and industrial boilers. The RC consists of a slowly revolving, perforated drum in which a shallow bed of coal ash and limestone is held in suspension by substoichiometric air. Granular coal and limestone are introduced into the drum where coal is partially burned and limestone is calcined. The resultant fuel gas is then blown through a firetube where secondary air is added and nitrogen is fixed by disassociating the NOX precursors before the gas is allowed into the combustion chamber. Combustion is then completed in a conventional flame. The RC is installed on the burner wall of the coal boiler to replace the existing burners and milling equipment, thus eliminating the power consumption of the mills and raising overall plant efficiency. Limestone is fed in with the coal to capture the sulfur in the rotary gasifier section, which is very effective as the temperature window is controlled. Thus, sulfur capture of over 90% is achievable. The RC incorporates a firetube which stages combustion, thereby reducing NOy to significantly lower levels than other burners, that is, below 100 parts per million by volume. Therefore, the RC addresses both SOx and NOX reduction in the same burner. The Phase II objective is to complete the detailed design of a 6.8 mBTU/hour unit, then manufacture and test the RC on a commercial manufacturer's package boiler test rig. A test schedule has been drawn up in cooperation with the Pittsburgh Energy Technology Center in which it is intended to test the unit on both medium and high sulfur coal while simultaneously measuring both SOx and NOy, as well as the combustion performance indicator CO. A series of parametric tests will be carried out with professional emission monitoring. The RC will also be demonstrated to utilities, coal companies, and other interested parties. Anticipated Results /Potential Commercial Applications as described by the awardee:The demonstration of the RC by firing into a package boiler with simultaneous low emissions of SOx and NOX should be a convincing demonstration of the burner. The successful development of the RC should offer utilities and industrial boiler users the opportunity of refiring existing coalfired steam boilers with burners that should comply with Phase II of the Clear Air Act Amendment of 1990, while realizing a power gain. Both capital and running costs of the RC will be substantially less than current fuel gas desulfurization and DeNOx control of approximately $100Aiw.
