Overfire air admission with varying momentum air streams

摘要

A tangentially-fired, pulverized coal burning furnace (10) having overfire air (OFA) introduced into the upper portion of the furnace. The fuel and air are introduced (36, 38) into the furnace at the burner level tangentially of an imaginary circle, so that the resultant fireball moves upwardly within the furnace with a rotational spin. The OFA is introduced (40, 42) tangentially of an imaginary circle, in the reverse rotational direction to that of the fireball, so that the exhaust gases flowing from the furnace to the rear gas pass (16) flows in a straight line, with little or no spin. The OFA is made up of a mixture of low pressure air and high pressure air of sufficient volume and pressure to nullify the spin of the fireball.