Numerical Simulation Of Flow Field And Temperature Field In CDQ Furnace

Because of the advantages of both energy saving and environmental protection,CDQ(Coke Dry Quenching)has been widely used in iron and steel enterprises in China.CDQ furnace is the core equipment of the process,where circulating gas cools the red hot coke.The coke quenching process is on the lack of systematic research,and actual production is based on experience and practice.At the same time,research on the heat transfer and gas flow,and relationship between the law and processing parameters are not too much,making the operating parameters not being well optimized.Therefore,it's a key issue based on the actual CDQ equipment,and it's urgent to establish mathematical model of CDQ furnace,to study the gas flow and heat transfer process and optimize the operating parameters of CDQ furnace.In this study,an actual CDQ furnace with processing capacity of 140t/h was applied as the basis for research.According to the engineering structure diagram,the size of the geometric model was determined.Basing on the geometric model and the characteristics of heat transfer law,a three dimensional model including physical model and mathematical model was established by CFD software,ANSYS Fluent 16.1.A mixing method of structured and unstructured grid approach was used to discrete computational domain.Fluid domain was separated into two parts by using dual cell approach and non-equilibrium thermal model was used in porous media.Standard k-? model was used to describe the gas flow in the furnace,and with the help of UDF to code volumetric convective heat transfer coefficient.Effect of four factors including the temperature of gas inlet,recirculating gas volume,coke inlet temperature and coke particle size influence the coke quenching process were discussed in this study.These four factors were also conducted by orthogonal experiment in order to find out how important of the factors on heat absorption ratio.Finally,the optimal parameters combination of dry quenching furnace was obtained.The main achievements of this study are listed as follows:(1)The flow and temperature distribution in 3D CDQ furnace are obtained.Velocity close to the gas outlet of CDQ furnace is higher than in the center.Circulating gas enters into the annular airway through ramps,finally export to gas outlet along the circumferential direction of annular airway.Velocity is associated with the position,close to the inner wall is greater than the outside,and much higher near the gas outlet.(2)Coke temperature gradually decreases from top to bottom,the temperature of cooling gas rises gradually from bottom to top too,and coke temperature is always higher than gas temperature at the same height in cooling chamber.In the pre-chamber,both of their temperature are equal and remain unchanged.Under standard operating condition,the coke temperature decreased linearly from bottom to top,make the best use of the cooling chamber.(3)The study on four major parameters of CDQ furnace shows that a reduction of 10K make coke outlet temperature decreased by 19?20K,when gas inlet temperature decreases from 410K to 390K with fixed circulation gas volume,but which has little influence on the temperature gradient in the cooling chamber;Circulating gas volume increased from 140000m3/h to 180000m3/h,both gas and coke outlet temperature are significantly reduced,the heat exchange place move to the upper part of the cooling chamber,utilization of the cooling chamber is low and the quality of coke decreased;When coke inlet temperature increases from 1173K to 1273K,every 50K increase can make the coke outlet temperature increase with 9?10K and gas outlet temperature increase with 51-55K,i.e.,higher coke inlet temper has a greater influence on gas outlet temperature;When the particle diameter increases from 0.04m to 0.06m,every 0.01m increase can make the gas outlet temperature raise with 9?11K,i.e.,smaller particles size is better for the recovery of coke heat.(4)Using orthogonal experiment method,the important of four parameters(gas inlet temperature,circulating gas volume,coke inlet temperature and coke particle diameter)on sensible heat absorption ratio is discussed.The results show that the sequence of the effects on sensible heat absorption ratio from large to small is circulating gas volume,coke inlet temperature,gas inlet temperature,coke particle diameter;Gas inlet temperature is adjusted to 390K,and the circulating gas volume is adjusted to 155000m3/h,which are the optimum combination of parameters.