Retrofit Of Low Temperature Economizer For 2×660MW Unit In The Third-stage Project Of Shangdu Power Plant

In order to solve the problem of high flue gas temperature,improve the efficiency of the unit,promote energy saving and emission reduction,the low temperature economizer is installed on the heating surface of the boiler rear end on 2×660MW units of the third-stage project in Shangdu power plant.Based on the design data and the actual situation of the site,this paper analyzes the feasibility of the low temperature economizer retrofit.Introduce the project overview and states,provide three kinds of retrofit ways,analyze the technical difficulties in the retrofit,and put forward relevant solutions.Calculate the investment cost and the project cost,and its economic benefits and environmental benefits were analyzed and evaluated by the equivalent enthalpy drop method.The results show that the project installs air heater and low temperature economizer system,the water will be mixed from 7# low pressure heater inlet and outlet to 80? to heat the secondary air,improve the temperature of air preheater inlet secondary air to 45?,the temperature of the primary air outlet is 45?.Because of the air preheater inlet temperature rises to 45?,the flue gas temperature is decreased from 160? to 95?,low temperature economizer from 7# low pressure heater inlet and water outlet mix to 70?,the backwater temperature from 6# low pressure heater outlet is 121.9?,the heating surfaces will be made by ND steel.Through calculation,the economic benefit and environmental protection of program 1 is the best.The program 1 can reduce the coal consumption of about 3.61 g/kW·h,annual save standard coal about 10483 tons;annual coal revenue 3.46 million yuan;annual save water volume of 433 thousand tons;annual save income 1.77 million yuan;the total annual income of 5.23 million yuan.The investment cost of each unit is 26.19 million yuan,two machines with a total cost of 52.39 million yuan.After installing the low temperature economizer,the discharge of pollutants of the unit is reduced and the environmental protection benefit is remarkable.Therefore,installing the low temperature economizer is feasible.