PURPOSE: To enable to suppress the rate of generation of NOx in a combustion furnace, by flowing recycling gas low oxygen concentration into the spaces directly above a traveling grate and in the upper part of a furnace body.
CONSTITUTION: Part of combustion gas exhausted from a combustion furnace 1 is blown into the space directly above a traveling grate 2 passing through a recycling gas passage 10A. The recycling gas is of low oxygen concentration, by which combustible gas of high concentration in a zone 8 and the gas of high oxygen concentration in a zone 9 can favorably be mixed with each other in a combustion furnace body 1. Generation of NOx is suppressed because NOx contained in the combustion gas of high concentration in the zone 8 is reduced by HCN, NH3, and HC in the presence of oxygen in the zone 9 of high oxygen concentration. Besides, part of combustion gas is blown into the upper part of a combustion furnace body 1 through a recycling gas passage 10B, so that mixing of air with combustible gas is promoted, and complete combustion can be taken place by the air of small quantity.
HONDA HIROKI
OOUCHI YOSHIMITSU
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