Numerical Simulation Of New Type Of Coke Oven Heating System

The working condition of coke oven heating system is very complex.In the process of high temperature coking,it is not only costy but also difficult to have an intuitive understanding of its working condition by using traditional experimental method.Therefore,it is of practical significance to study it by means of numerical simulation.Through numerical simulation of the coke oven heating system,we can analyze heat transfer conditions with extreme high temperature that are difficult to observe by experimental equiptments,and reflect the influence of various operating parameters on the coking process at a lower cost,so as to obtain the optimal method of the coking process-which is of great significance to the production,energy saving,emission reduction and other aspects involved in coking industry.Based on designed structure of JNX-70-2 coke oven,heat transfer model of combustion chamber and carbonization chamber of staged-heating jet compound coke oven and heat transfer model of cellular regenerative chamber are built respectively by CFD software and reasonable simplification.The reliability of two models are verified by comparing measured data from the factory with calculated results of designed models.By analyzing working conditions of heat and mass transfer in heating system of coke oven,we obtained main conclusions are as follows:For staged heating combustion chamber,the flame center is located in the middle and upper part of upflow near gas inlet of the middle of combustion chamber;in carbonization chamber,the temperature of coal material near the wall of combustion chamber is relatively low,which is about 100 K lower than that of other parts of carbonization chamber at end of coking process;during the whole coking process,concentration of NOx at outlet of combustion chamber is found to be increased with the time;the increase of air excess coefficient in combustion chamber will reduce gas phase temperature and improve the homogeneity phenomenon of over high local temperature;at the same time,the increase of air excess coefficient will also increase concentration of NOx at outlet and then decrease,and the best air excess coefficient is 1.35;for every 5%increase of COG concentration in the mixed gas,the temperature of gas phase in the combustion chamber will be increased with 100 K;also,with increase of COG concentration,the heat flux of the wall of carbonization chamber and combustion chamber increases and the coking time shortens;staged combustion technology can obviously reduce the concentration of NOx in exhaust gas of combustion chamber and improve the homogeneity of temperature distribution of gas phase,but under the same gas and air inlet conditions,the staged combustion technology has no significant effect on shortening the coking time.Compared with the traditional single-stage heating combustion chamber,the average NOx concentration at the outlet of combustion chamber can be reduced by 15.6%and 26.2%respectively by adopting two-stage heating and three-stage heating technology.As for cellular regenerative chamber,and taking blast furnace gas regenerative chamber as an example,it is found that the gas flow in the top space of chamber has strong eddy current motion during the heating period,which strengthens the heat transfer between gas and the lattice brick;the periodic changing temperature of gas and solid in different height of coke oven lattice brick is obtained;it is also found that the increase of the thermal conductivity of the lattice brick will reduce the temperature of the gas at the outlet of the chamber,while the temperature eficiency of the chamber and the maximum temperature drop of the gas at the outlet during the cooling period have a linear relationship with the thermal conductivity of the lattice brick;the increase of the density and specific heat capacity of the lattice brick will slightly reduce the average temperature efficiency of the regenerative chamber and improve the stability of the outlet gas temperature during the cooling period;every 50 K increase of the temperature of the exhaust gas inlet temperature during the heating period will increase the outlet gas temperature during the cooling period by about 25 K,resulting in the decrease of the average temperature efficiency and the increase in the maximum temperature drop of outlet gas during the cooling period;the optimal distribution coefficient of waste gas flow is about 0.94,when the excess air coefficient is 1.35.