The primary objective of the present Phase 3 effort is to perform the final testing at a 20 MNBtu/hr commercial scale of an air cooled, slogging coal combustor for application to industrial steam boilers and power plants. The focus of the test effort will be on combustor durability, automatic control of the combustor`s operation, and optimum environmental control of emissions inside the combustor. In connection with the latter, the goal is to achieve 0.4 lb/MMBtu of SO{sub 2} emissions, 0.2 lb/MMBtu of NO{sub x} emissions, and 0.02 lb particulate/MMBtu. Meeting the particulate goal will require the use of a baghouse or electrostatic precipitator to augment the nominal 80% ash retention in the combustor. The NO{sub x} emission goal will require a modest improvement over reductions achieved to date in the combustor of 0.26 lb/MNBtu. To reach the SO{sub 2} emissions goal inside the combustor may require a combination of reduction inside the combustor and inside the boiler by injection of suitable sorbents. To date, SO{sub 2} levels as low as 0.6 lb/MNBtu, equal to 81% reduction in 2% sulfur coals, have been measured with boiler injection of sorbents.