Cooperative research on the combustion characteristics of cofired desulfurized Illinois coal and char with natural gas. Final technical report, September 1, 1991--August 31, 1992

摘要

The DTFF is extended to larger sample collecting capability and higher temperatures, resulting in the establishment of the Ash Characterization Facility and the High Temperature Drop Tube Furnace. The Ash Characterization Facility enables continuous coal injection and sampling under controlled conditions. Several hundred milligrams of char or ash can be collected in one-half hour. The High Temperature Drop Tube Furnace uses a plasma torch to preheat the gas to over 2000 K and inject it into a ceramic tube which enters a furnace designed for 1700C (1973 K) operation, so that temperatures and heating rates encountered by pulverized coal particles in the flames of large boilers or in the advanced slagging cyclone combustors can be simulated. An aerodynamic coal feeder works well in supplying coal continuously to the drop tube. A watercooled, Helium-quench sampling probe collects the solid samples. A scanning electron microscope is used to study the morphology of ash and char particles. A sulfur determinator, a gas chromatograph provide analytical means in the laboratory, and the Illinois State Geological Survey performs other necessary analyses of the samples. Tests on cofiring coal with I to 4% methane show that sulfur retention in ash was related to temperature and residence time. The addition of methane caused changes in gas temperature profile in the tube and also changes in chemical composition of the gases. The overall effect on sulfur retention is seen to be a result of several complex interacting factors. Further detailed studies are necessary to clarify the contribution of each factor and to provide clues to the mechanism of the process.