Technical And Economic Analysis On Coal-fired Industrial Boiler Exhaust Gas Temperature And Thermodynamic Optimization

Our country is accelerating energy-saving projects to improve energyefficiency and promote energy conservation. About85%of industrial boilers arecoal-fired boilers, its coal consumption accounted for23%of annual coal production.The actual average thermal efficiency of the coal-fired industrial boilers is onlyabout60%, the energy efficiency is low.Flue gas heat loss accounted for about70%of the total heat loss of boiler, reducing boiler flue gas temperature is the key toimprove the thermal efficiency of the boiler.Ways to reduce to reduce the flue gas temperature of coal-fired industrialboilers is adjusting the boiler operating system itself and add heating surface to coolthe flue gas deeply. The former includes the optimization of combustion adjustment,control excess air ratio, keeping the heating surface cleaning, heat transferenhancement of heat transfer and other means. The method of the flue gas depthcooling after another, have their own characteristics. This article is based on both acomposite phase change heat exchanger which's heat exchange tube's walltemperature is uniform,controllable and adjustable and a cast iron air preheaterwhich is resistant to corrosion and not ash fouling with internal thread structure andexternal ribs.Add the rear heating surface to study on reducing the flue gastemperature of the coal-fired industrial boilers.Select the representative products of a coal-fired industrial boilers, a hot waterboiler which type is SZL7.0-1.0/115/70,as the object of study. Study the structuraland thermodynamic parameters of the rear heating surface in the relationship withthe change of the flue gas temperature on the heat recovery system and the newboiler system with the rear heating surface.Do the techno-economic analysis to reducing the flue gas temperatureapplication of technical principles of economics, above the two cases.The economicevaluation index changes with the exhaust gas temperature are determinedand thecomprehensive analysis in two casesshows the optimal design of flue gastemperature which may provide reference for the design of waste heat recovery andthe standard of industrial boiler flue gas temperature.Thermodynamic optimization analysis to the rear heating surface is performedon the condition of the established optimum flue gas temperature designvalues.According to the principle of inevitable exergy loss, it was identified that thebest working fluid flow rate of the heat exchanger unit to provide guidance for theoptimization of the heating surface.Based on the principle of exergy analysis,theexergy efficiency of the thermal unit is determined.The exergy efficiency ofcomposite phase change heat exchanger is greater than the economizer.Merger the two heat exchanger units with composite phase change heat exchanger.Applicatepinch technology to study its reasonable collocation with cast iron air preheaterusing economic goals.And determined the optimal pinch point temperaturedifference of the rear heat transfer.Determined the optimumworking fluidsaturationtemperature in the heat pipe of the composite phase change heat exchangerunder the condition ofthe optimal pinch point temperature.