Abstract: A multi-fuel boiler is provided in which coal is burned in combination with oil or gas in such manner that the particulate emission from the coal, normally relatively high, is reduced to a level comparable to oil. In one example, coal of a quality that would normally burn with a Bacharach smoke spot test number of 6 can be burned with a test number below 2.This is accomplished by utilization of a horizontal oil or gas flame directed across the flue gas exit of the combustion chamber in opposition to the flow of coil combustion gases to change the normal flow pattern of the combustion gases. This creates turbulence, which provides additional combustion time at combustion temperatures in the presence of excess air.