Abstract: A method for combusting slagging coal in a furnace comprising a firebox and at least one injection nozzle having a bore for a primary airstream and an annular passage for a secondary airstream, the nozzle communicating with the firebox, which method comprises (a) injecting a primary airstream containing a pulverized coal and injecting a secondary airstream through the injection nozzle into the flame zone of the furnace firebox, the combined primary and secondary airstream composing the total air for combustion and combusting the coal to yield a flame of combustion, and (b) injecting a sufficient amount of oxygen into the primary airstream such that an oxygen enriched primary airstream emanates from the injection nozzle and the oxygen concentration of the total air for combustion is about 22 to 27 volume percent, whereby the amount of slag deposition is reduced.

Abstract: A method is described for burning pulverized high ash coal in a furnace firebox and reducing ash fines which comprises(a) injecting a primary airstream containing a pulverized coal which is at least 7 wt % ash and a secondary airstream into the flame zone of a furnace firebox and combusting the coal to yield a flame of combustion, and(b) injecting a sufficient amount of oxygen into the flame zone via the secondary airstream such that the oxygen concentration of the combined primary and secondary airstreams is between 21 to about 28 vol %.In a preferred embodiment, the oxygen enrichment addition is proportioned between the primary and the secondary air streams.