Residential coal stoves emit various pollutants such as CO, NO_x, SO_x, and smoke. The emissions can be reduced by varying the burning conditions in the stove. This investigation studied the effect of various burning conditions on the emissions from a two-stage lump coal combustor burning Wyoming bituminous coal. The parameters that were varied include primary air mass flow rate, secondary air mass flow rate, secondary air temperature, secondary air inlet velocity, and secondary air swirl. Each parameter was varied independently to attempt to isolate its effect on emissions. In addition, radial and axial probe sampling was conducted in the combustor's secondary combustion zone to determine the CO concentrations. A chemical kinetic model of CO oxidation was formulated and compared to the measured CO concentrations. A wide range of emission factors can be achieved for the various pollutants by varying the burning conditions. The CO, NO_x, SO_x, and smoke emission factors range from 7.0 to 159, 0.67 to 3.1, 0.98 to 2.0, and 0.16 to 3.7 g/kg respectively. The emissions tests appear to be reasonably repeatable with emission factors and coal burning rates agreeing within 15% in most cases. The various tests indicate that increasing the primary zone equivalence ratio decreases the CO emission factor. The smoke emissions from the test combustor are quite low compared to those from typical commercial coal stoves. The amount of swirl has a large effect on mixing in the secondary combustion zone, and highly stratified flows are created by certain burning conditions. The CO oxidation model does not correlate well with the experimental results since possible CO formation from hydrocarbons, and stratified flow effects are not considered. / Master of Science

The emissions, efficiency, and combustion chamber conditions of the Rayburn Prince 76, a clean-burning, hand-fired coal heater developed by the British have been studied. It was desired to determine if the downdraft design of the Prince would lead to low emissions when operated on American coals. Temperature and species concentrations were measured in the unit's secondary combustion chamber. Temperatures and gas residence times in the secondary combustion chamber were found to range from 440 to 1040°C and 15 to 40 ms, respectively. Little soot and volatile oxidation probably occurred in the chamber, due to the relatively low temperatures and short residence times. The emissions and efficiency of the heater were determined for operation on two bituminous coals at both high and low firing rates. The CO, NO_x, SO_x, and smoke emission factors were found to range from 38 to 120 g/kg, 1.2 to 5.8 g/kg, 3.3 to 5.4 g/kg, and 2.3 to 16 g/kg, respectively. The smoke emission factors for the Prince were found to be up to six times lower than those found using identical coals in updraft stoves. The overall efficiency of the unit was determined to range from 54 to 60%. The sensible energy losses were found to represent the majority of the total energy losses. / M.S.