PURPOSE: To ensure an amount of gas, which is 25% of that required during maximum combustion load (called MCR) specified for safety, during starting, by a method wherein, based on measurements of O2 concentration in exhaust gas and gas in a wind box, a recirculating exhaust gas amount and an amount of the air supplied for combustion are regulated.
CONSTITUTION: The flow rate of recirculating gas and flame are held through regulation of the openings of dampers 23 and 32 on a feed line for the air for combustion. During such time, O2 concentration in a wind box of gas supplied to a starter burner 11a is measured by an O2 meter 31. When O2 concentration is reduced to below a set value, the air A required by circulating gas is fed through regulation of the opening of the damper 32 to ensure combustion of the starting burner. Simultaneously, with a damper 21 opened, a part of exhaust gas is exhausted outside a system, and meanwhile, O2 concentration in exhaust gas is measured in a recirculating line 24 by a difference O2 meter 33 (or 33a) attached to an outlet for recirculating gas to detect O2 concentration in exhaust gas which is exhausted to the outside, and further the measurements are utilized as a correction value for control of O2 concentration in gas in the wind box of the starting burner 11a.
ISHII KEIJI
ISODA KAETSU
SHIBATA MITSUHIRO
