The Study On Heat Transfer Calculation And Performance Evaluation In A Coking Furnace Riser

There is a lot of waste heat in coke oven waste gas,which is of great significance to energy saving and emission reduction in China.The coke oven riser heat exchanger is the main equipment to recover the waste gas waste heat,and the waste gas waste heat recovery in the jacket riser is a complex heat transfer process.However,there are many problems in the operation of the rising tube heat exchanger system,especially the calculation of the heat transfer coefficient of the rising tube heat exchanger adopts static calculation parameters,and the operating conditions of the system are dynamic,which inevitably leads to the inaccurate calculation results of the heat transfer coefficient.Therefore,it is practical to study the heat transfer coefficient and performance of riser heat exchanger under dynamic conditions for waste heat recovery of waste gas meaning and guiding value.Firstly,the convection and radiation heat transfer of waste gas flowing in the riser are studied.Based on the thermal equilibrium equation,the differential equation of heat transfer of waste gas flow in rising pipe is derived,considering the influence of inlet temperature,emissivity of inner wall surface,convection heat transfer coefficient and Stanton number on temperature change of inner wall of rising pipe and outlet temperature of waste gas.the variation curve of the temperature of the inner wall of the rising pipe along the axis direction and the average heat transfer coefficient of the waste gas are obtained.the average heat transfer coefficient of the waste gas in the jacketed rising pipe is 30?36 W/(m~2·k).The results show that the radiation heat transfer process is mainly affected by two parameters:the emissivity of the inner wall and the inlet temperature of the waste gas.The larger the emissivity of the inner wall surface,the greater the radiation heat transfer,and the greater the influence of the fluid velocity on the convection heat transfer.In a coking period,the coke oven should reasonably control the flow rate of the waste gas,which can avoid the condensation of tar in the inner wall of the rising pipe;when designing the rising pipe,increasing the emissivity of the inner wall can improve the heat transfer efficiency of the rising pipe.Secondly,the efficiency heat transfer unit number method is used to design the heat exchanger,and the design of the rising tube heat exchanger will be optimized by minimizing the energy loss of the heat exchanger.On the basis of these calculation parameters and the running period of waste gas,the optimal calculation model of the rising tube heat exchanger system is established,and finally the optimal design parameters of the rising tube heat exchanger system are obtained.Thirdly,the paper studies the heat transfer process of convection heat transfer in the riser heat exchanger system.By establishing the internal convection heat transfer model of water-vapor two-phase flow,the relationship of heat transfer loss rate of convection heat transfer with phase state change is constructed.The study of two-phase convection heat transfer during vaporization cooling has a good guiding effect on the structural design and operation parameters of waste gas waste heat recovery jacket.