Calculation method of excess air ratio for blast furnace gas fired boiler

As the influence of nitrogen content in fuel gas is not considered in the conventional calculation method (1) of the excess air ratio in the flue gas, the calculation method is not appropriate in the calculation of thermal efficiency for the blast furnace gas fired boiler. In this paper, the calculation formula (18) of the excess air ratio in the flue gas for the blast furnace gas fired boiler was derived. Taking the performance tests of blast furnace gas fired boiler and natural gas fired boiler as examples, the excess air ratio in the flue gas was calculated according to (1) and (18) respectively. The results show that for the blast furnace gas fired boiler, the calculation result of (1) is significantly lower than that of (18). The disparity in the corresponding calculation results of thermal efficiency is obvious. Therefore, (1) is unsuitable for the performance test of blast furnace gas fired boiler. For natural gas fired boiler, the calculation results of (1) and (18) are almost the same.