| 摘要 |
<p>PURPOSE:To enable partial combustion in a catalyst layer for combustion and reduce the amount of NOx by carrying out the self-circulation of combustion gas to be mixed with primary fuel and increasing a temperature of the resultant mixed gas to a level suitable for catalytic combustion. CONSTITUTION:Vapor phase combustion by secondary fuel is first carried out, the self-circulation of a combustion gas at a high temperature is performed to be mixed with air 15, and a temperature of the resultant mixed gas 17 is increased to a level required for catalytic combustion. Since a mixed gas flow passage 41 is provided with an air inlet port 12 at a portion thereof, to which air is fed, and which is formed into a throttled shape, a negative pressure is caused at this portion, and combustion exhaust gas 16 in a furnace flows thereinto from an opening of a furnace wall 32 through an exhaust gas circulation passage 11, thus the circulation of exhaust gas is achieved. When a load level at the furnace becomes higher and a temperature of the mixed gas 17 reaches a level (300 deg.C or above for a propane and 450 deg.C or above for a methane) suitable for catalytic combustion, a feed valve 28 for primary fuel is opened by a signal from a temperature setter 22, whereby the air and the combustion exhaust gas flow to a catalyst layer 9 for combustion as the mixed gas for primary fuel.</p> |
