Research On Reducing Exhaust Gas Temperature And Preventing Low-temperature Corrosion Of Utility Boiler

With the development of China's economy and the rasing prices of the coal, in response to nation's call of energy saving and emission reduction, many domestic power plants take the rectification measure to reduce exhaust gas temperature and recover.boiler waste heat. Research on reducing exhaust gas temperature are carried on from three aspects:operation and maintenance, equipment improvements and adding new equipments. And three new designed heat exchangers, heat pipe heat exchanger, low-pressure economizer and heat pipe applied in low-pressure economizer which are widely used in recent years, is calculated and analyzed. Furthermore, an analysis and comparison of methods to reduce exhaust gas temperature is conducted from four ways:benefits condition, low temperature corrosion condition, equipment systems condition, and negative effects condition. The result shows that methods to reduce exhaust gas temperature have their own advantages and disadvantages. According to the actual situation in power plants and the characteristics of each method, choice will be made in practice so that advantages can be played and disadvantages can be avoid.For the problem of low-temperature corrosion may arise while reducing exhaust gas temperature, formulas at home and abroad to calculate acid dew point and their influencing factors are analyzed in order to determine and control acid dew piont. We find that, the linear relationship between acid dew point calculated by the formulas and natural logarithm of sulfur content of fuel, and the value calculated by the A.G.Okkes formula is most close to the average value. A method of controling the acid dew point by coal blending which considerd putting the acid dew point calculated by A.G.Okkes formula into the stipulative conditions of coal blending model, is put forword. In order to use the model in a power plant, coal blending is optimized using genetic algorithm programmed with Matlab. The result shows that it can not only achieve the purpose of coal blending, but also control the acid dew point so that it can prevent the occurrence of low temperature corrosion. Thus, this is instructive for power plant to purchase coal and blended coal combustion.