Numerical Simulation Of Combustion In Coke Oven Chamber During Regenerator Maintenance Based On FLUENT Softwate

The function of coke oven regenerator is to store and recover the heat generated from combustion chambers and preheat the air and blast furnace gas and coke-oven gas mixture(fuel gas).The checkered bricks in the regenerators can be blocked,melted and collapsed after a long-term operation,causing the abnormal heating and low temperure in the combustion chambers.There are few researches and reports on the influence of the wall opening condition of the regenerator on the combustion condition of the Chamber and the construction safety.Therefore,the regenerator maintenance is required to clear up the problematic bricks in hot conditions.In this paper,the numerical simulations are carried out assuming steady-state combustion using a combustion chamber of the JN-70-2 coke oven as a physical model with the Fluent software.Considering that the flow direction of gases in the rising passage and the descending passage of combustor is changed every 30 minutes,the opening of regenerator wall could be in the rising flow or in the descending flow.Above two working conditions were studied to investigate the effect of regenerator opening on the temperature field,pressure field,concentration field,excess air coefficient and gas flow trajectory,bansed on which the feasibility and optimum operating conditions of regenerator maintenance are given.When the opening of regenerator is in the descending flow,the simulation results shows that the inlet air flow capactiy decreases compared with the normal operating conditions and becomes smaller with the decreasing of outlet vacuum degree.The excess air coefficient is calculated to be less than 1.0 acoording to the flow capactity of fuel gas,indicating the combustion of fuel gas and air is insufficient.After opening the regenerator,the maximum temperature of combustion chamber decreases,which is reduced by 100 K compared with the normal operating conditions when the outlet pressure is-60 pa.The lower the outlet vacuum degree,the smaller the maximum temperature zone and the lower the maximum temperature.The air can flow into the regenerator from the opening,then flow out from the outlet,and the air flow capacity increases with the increasing of outlet vacuum degree.As mentioned above,the fuel gas is excessive due to the insufficient air,which not only waste energy but also can cause potential safety hazard by gas leak.Therefore,it is unsuitable for opening of regenerator in the descending flow and needed to seal the opening to avoid safety accident.When the opening of regenerator is in the rising flow,the simulation results shows that the inlet air flow capactiy increases compared with the normal operating conditions and becomes higher with the decreasing of outlet vacuum degree,resulting larger excess air coefficient.After opening the regenerator,the maximum temperature of combustion chamber decreases,which is reduced by 550 K compared with the normal operating conditions when the outlet pressure is-60 pa.The lower the outlet vacuum degree,the smaller the maximum temperature zone and the lower the maximum temperature.And the maximum temperature zone is located at the bottom of combustion chamber,even in the inlet of fuel gas.The air can flow into the regenerator from the opening,and flow out from the outlet,hence the air flow capacity entered into the combustion chamber can be calcauted by the difference between the two.It is shown that excessive cold air can be introduced into the combustion chamber,resulting in the shift of ignition point to the inlet of fuel gas and the decrease of temperature in combustion chamber,which will cause the security risk and affect the coke quality.It is poposed that the flow capacity of fuel gas should be increased by turning up the opening of valve by turning down the inlet of air or increasing the outlet acuum degree.