Numerical Simulation On Structure And Operation Optimization Of Kalugin Hot Blast Stove For Consumption Reduction And Energy Conservation

Compared with other types of hot blast stove,Kalugin top combustion hot blast stove（Kalugin hot stove for short）has the characteristics of large heat storage area,reasonable and symmetrical structure,uniform heat transfer,and high heat efficiency,etc.,so it has been recognized and widely used in the steel industry worldwide.The swirl combustion mode of the Kalugin hot stove makes the fuel gas and the combustion air fully mixed,the combustion is more complete,and the flue gas with higher temperature is generated.However,a large number of numerical simulation results reported in literature show that the high-temperature flue gas generated by combustion forms a rotating vortex ring in the combustion chamber of the Kalugin hot stove.It is the existence of this vortex ring that prevents a considerable part of high-temperature flue gas from directly flowing into the regenerator.If the vortex ring can be eliminated or moved up from the lower part of the combustion chamber,more high-temperature flue gas can directly flow into the regenerator to heat up the checker bricks without participating in the circulation flow in the vortex ring,thus further improving the thermal efficiency of the hot stove.Therefore,in order to fully explore the potential of improving energy efficiency of Kalugin hot stoves,the present research takes the Kalugin hot stove of a steel plant as the research object and proposes to install a"Union Jack"shaped flow diversion baffle wall at a certain height above the regenerator in the hot stove to control the vortex ring,and uses CFD numerical simulation method to optimize the structure and size of the baffle wall,so as to maximize the amount of the high-temperature flue gas directly flowing into the regenerator to heat up the checker bricks and improve the heat exchange efficiency between the flue gas and the checker bricks.In addition,on the basis of determining the best performed baffle wall structure and size,the present research also optimizes the operation of the hot stove by adjusting the preheating temperature of the combustion air,so as to reduce the fuel gas consumption while maintaining or increasing the hot blast temperature and to achieve the goal of energy conservation,emission reduction and fuel consumption reduction.In order to improve the efficiency of simulation calculation,a three-dimensional steady-state CFD model of the Kalugin hot stove installed with a"Union Jack"shaped flow diversion baffle wall and a two-dimensional transient CFD model for a single channel of checker bricks in the regenerator are established in this work,respectively.The former model is used to quickly predict average temperature and average mass flowrate of high-temperature flue gas flowing into different regions of the regenerator during the combustion period,which is used as the inlet boundary condition for the latter model.The latter model is used to rapidly simulate the transient heating（combustion period）and cooling（air supply period）process of the checker bricks.In this way,the two models are combined and implemented alternately,so that high efficiency numerical simulations on the Kalugin hot stove being investigated in the present work for multiple and continuous operation cycles（combustion period and air supply period）are realized.In addition,considering the nonuniform temperature distribution of the flue gas flowing into the checker bricks from the top of the regenerator,in this research the regenerator is divided into five temperature regions according to the temperature distribution characteristics on the top face of the regenerator,and numerical simulations are conducted on each region,respectively,by using the two-dimensional transient CFD model for a single channel of checker bricks,so as to predict the transient heat transfer between the gas（flue gas and cold air）and the checker bricks in different temperature regions of the regenerator during each operation cycle of the hot stove.Therefore,the variation of hot blast temperature at the outlet of hot stove with time can be predicted more accurately.The present numerical simulation results show that:（1）Compared with the conventional Kalugin hot stove（without installing flow diversion baffle wall）,the existence of the baffle wall restricts the vortex ring development in the combustion chamber and move it further up from the regenerator,increases the temperature of flue gas entering the regenerator,and thus improves the heat exchange efficiency between the flue gas and the checker bricks in the regenerator.When the installation height of the baffle wall h₁ is 0.3 m and the height of the baffle wall itself h₂ is 0.8 m,the maximum average temperature of the flue gas flowing into regenerator can reach1362℃,so it is considered that the baffle wall structure has the best flow diversion effect.（2）On the basis of the baffle wall structure with the best flow diversion effect,and maintaining the fuel gas and combustion air flowrates at 100000 Nm³/h and 65000Nm³/h,respectively,the hot stove operation is optimized through adjusting the preheating temperature of the combustion air.The simulation results show that with the increase of combustion air preheating temperature,the temperature of flue gas flowing into the regenerator during the combustion period increases,so the temperature of hot blast during air supply period also increases.When the preheating temperature of combustion air is above 230℃,the average temperature of flue gas flowing into the regenerator can reach 1368℃,so that the hot blast with temperature above 1200℃can be achieved during the air supply period.