| 摘要 |
PURPOSE:To reduce a response delay by calculating the concentration of residual O2 contained in a waste gas from a ratio of the flow rate of a supplied fuel to the flow rate of air in quantities to be controlled in the air-fuel ratio control to protect the boiler from abnormal combustion. CONSTITUTION:In order to obtain the concentration of residual O2 contained in a waste gas from the flow rate of a fuel and the flow rate of air with respect to a furnace combustion state, the base concentration of residual O2 in the waste gas is impaled from the fuel flow rate to a function generator 51. Further, in a function generator 52, an air flow rate in conformity with the fuel flow rate is calculated. A difference between the calculated air flow rate and an actual air flow rate 12 is obtained by a subtractor 55, and the difference is added to the O2 base concentration made by the function generator 51 by an adder 56. In monitoring the furnace combustion state, an alarm (ANN1) is output by the comparison of the same with a function generator 53 of the set value of residual O2 in the waste gas, in which combustion becomes unstable. Further, the plant is tripped by the comparison of the same with a function generator 54 of the set value residual O2 in the waste gas, in which there is a possibility of burner misfiring. By these procedures, it becomes possible to prevent the danger of abnormal combustion of the boiler from occurring. |
