The excess air coefficient of the industrial gas steam boiler increases(assuming the optimum excess air coefficient originally), the temperature in the furnace decreases, which reduces the radiation heat absorbed by the water wall and the flue gas temperature at the furnace outlet slightly decreases. Due to the increase of flue gas volume and increase of flue gas velocity, the increase of heat transfer coefficient is larger than that of heat transfer temperature difference. Therefore, heat absorption of superheater is increased. Due to the increase of exhaust gas temperature and flue gas volume, q2 increases, and the efficiency of industrial gas steam boiler decreases. When the fuel quantity is constant, the evaporation amount decreases, so the steam temperature increases. Generally speaking, for every 0.1 increase in excess air coefficient, the steam temperature increases by 8~1. O ��.
If the excess air coefficient of the furnace is already high, the excess air coefficient increases further and the steam temperature increases. If the excess air coefficient is too large, the furnace temperature and the flue gas temperature at the furnace outlet may be greatly reduced, and the superheater will decrease the steam temperature because of the decrease of heat transfer temperature difference, which will occur only under very bad combustion conditions.
