The Recovery And Utilization Of The Flue Gas Afterheat Under The Restriction Of Industrial Process

China is a big country in the metallurgical industry.The energy saving potential of industrial production processes such as coking and steelmaking on the steel industry chain is huge.Recycling such waste heat from flue gas is an important way to achieve energy saving in the metallurgical industry process.The recovery and utilization of the flue gas waste heat generated by the coking and steelmaking process is restricted by the production process.It is of great significance to explore the principles,methods,processes and conditions of industrial flue gas waste heat recovery and utilization including coking and steelmaking under the process limitation.In this paper,the waste heat recovery methods and processes of metallurgical coke oven red coke,raw coal gas and steel-making electric furnace flue gas are studied under the corresponding production process limitations.The main research work and results are as follows:1.Based on the production process of metallurgical coke oven and electric furnace steelmaking,the characteristics,production process and process of coke oven red coke,coke oven waste gas and steelmaking electric furnace flue gas waste heat were studied and combed the corresponding constraints of waste heat recovery.Combined with the applicable conditions of the traditional thermal energy power cycle,studied how to design and construct the corresponding waste heat recovery cycle under process constraints.For example,the temperature and flow rate of raw gas is unstable and contains coal tar.If the temperature is lower than 450 ° C,condensation will occur,causing coking and carbon deposition on the inner wall of the riser.In view of this characteristic,the engineering scheme design of using the saturated water vapor Rankine cycle higher than 450 ? as the first-level cycle and requiring the parallel flow adjustment of multiple risers in order to obtain stable water vapor and consistent parameters the main points.2.The process of coke oven waste heat recovery was designed and studied: 1)In view of the characteristics of residual heat of high temperature exhaust gas in the red coke dry quenching process,a reheated reexpansion carbon dioxide transcritical organic Rankine cycle was proposed.2)The effects of cycle parameters on net output power and recovery efficiency of waste heat were studied,and the method of determining the optimal operating parameters for compound cycle was obtained.3)Based on this compound cycle,the coke oven waste heat recovery process was designed,and the net output power and waste heat recovery efficiency of the combined cycle were calculated under the optimal working conditions.It was found that the Rankine cycle was 17.85% higher than that of the traditional water Rankine cycle,34.51%.3.The process of waste heat recovery of coke oven gas was studied and designed: 1)Coke oven waste gas waste heat utilization temperature is limited and the poor capability of saturated steam circulation in the process restriction,a saturated steam organic Rankine cycle was proposed.2)The effect of cycle parameters on the efficiency of electricity generation was studied,and the method of determining the optimal working parameters of composite circulation was obtained.3)Based on this compound cycle,The waste heat recovery process of coke oven gas was designed,and the technological constraint index of the wall temperature of coke oven riser was studied.The heat transfer process was studied,and the law of the influence of water flow on the temperature of the rising wall and the outlet temperature of the crude gas was given.It provided quantitative indicators for avoiding the occurrence of coking and coking phenomena in the riser.4)Based on this process,the process parameters were optimized with the optimization of power generation efficiency.The results show that the efficiency of the new process is higher than that of the traditional saturated steam cycle by 34.72%.4.The process of flue gas waste heat recovery in steelmaking electric furnace has been designed and studied: 1)Aiming at the characteristics of flue gas waste heat in steel-making electric furnaces,nitrogen Brayton trans critical organic Rankine cycle has been put forward;2)The effect of cyclic parameters on net output power has been studied,and it has been found that the increase of primary cyclic pressure and the decrease of final expansion pressure increase the net output power.It also led to the increase of exhaust gas temperature and obtained the method of determining the optimal working conditions of composite cycle.3)based on this compound cycle,the process of recovering the waste heat from the steelmaking electric furnace flue gas was designed,and the maximum net output power and waste heat recovery efficiency were 22.52% higher than that of the traditional process,22.31%.