ENHANCING THE ENERGY AND ENVIRONMENTAL EFFICIENCY OF SURFACE HEAT EXCHANGERS OF SMOKE GASES OF WATER BOILER HOUSES

Background. In water-heating boiler houses, where natural gas is burned to produce heat in the form of hot water, it is necessary to reduce its consumption by reducing the temperature of the wasting flue gases from the boilers and, accordingly, increasing their efficiency. But nowadays, a more important problem is the problem of environmental protection, one of the directions of its solution is the reduction of emissions of nitrogen oxides with flue gases in gas boiler houses. Objective. The purpose of the paper is to improve the energy efficiency of moderate-centralized and centralized heating boiler houses by reducing the temperature of the exhaust flue gases and the beneficial use of heat in heat exchangers for own needs of the boiler houses or external consumers, and optimize the operating modes of the surface heat exchangers for humidification of blast air, used for reducing nitrogen oxide emissions. Methods. The analysis of the influence of surface utilizers of the temperature and moisture content of humidified air fed into the boiler furnaces on the energetic and environmental efficiency was made by using the numerical calculation method. Results. The dependences of the bypass coefficient, the specific amount of the heat removed from the heaters and its increment from the final flue gas cooling temperature, as well as the emissions of nitrogen oxides into the environment when humidifying blast air with temperatures of 50 and 60 °С, at various initial flue gas temperatures in the range of 140–190 °C were obtained. Conclusions. It is shown that, from the point of view of practical implementation in boiler houses, air humidification at the temperature of 50 °C is the main priority, while its moisture content is 85 g/kg d.a., and the flue gas at the inlet to the utilizer is 190 g/kg d.g. the optimum temperature of the gases leaving the air heater is 27–32 °C, the bypass coefficient is 0.26–0.33, the specific amount of the heat removed from the heaters compared to the non-humidified mode can be increased by 28%, and the emissions of nitrogen oxides with flue gases into the environment can be reduced by more than 3 times.