COMPUTING DEVICE FOR UNBURNT PART IN ASH AT COAL-FIRED BOILER

摘要

PURPOSE:To improve efficiency in minimizing exhaust gas loss by a method wherein the amount of unburnt part in combustion ash is obtained by continuous computation in actual operation time and operation is carried out in reducing excess air as much as possible at all times. CONSTITUTION:Respective outputs of a computing element 6 for received heat amount of generated steam, a computing element 7 for fuel heat input, and a computing element 8 for boiler efficiency are fed into a computing element 9 for unburnt rate to obtain an unburnt rate. The output of the element 9, the changed amount of fuel 3, and an ash ratio 10 in fuel previously obtained are fed into a computing element 11 for the unburnt part in ash to obtain the unburnt part in combustion ash. The unburnt part in ash thus obtained becomes a bias 16 for setting a heat ratio suitably. The bias 16 is added to or subtracted from the valve of a setting device 17 for an air fuel ratio as the ratio of air to fuel in a bias from and fed into a device 20 for setting an air flow amount to keep the amount of the unburnt part in ash under a limited value. An excess air amount set by the device 20 is used to control the air flow amount 4.