Study On Suitable Thermal Parameters Of Sinter Annular Cooler Based On Criterion Of Enthalpy Exergy

The recovery of waste heat resources in the sintering process is one of the key tasks of modern steel complexes since the 11th Five-Year Plan in China.It has been incorporated in China’s "Iron and Steel Industry Adjustment and Upgrade Plan(2016-2020)".There are 2 technical paths of sintering waste heat recovery in China during the "13th Five-Year Plan"period and even longer.The first one is the implementation of technology change on vertical tank waste heat recovery,and the other one is the excavation of waste heat recovery technology based on annular cooler model.Among them,the dredging of waste heat recovery technology based on the model of annular cooler is of more practical significance.Since the 1990 s,the first annular cooler waste heat recovery project was put into use with great progress in Ma’anshan iron and steel plant.Domestic and foreign scholars and technicians have done a lot of work around the problem of air leakage of the annular cooler.At the same time,people also ignored a fact.The design and operation of the annular cooler were mainly based on the cooling of sinter rather than the recovery of waste heat.Did the structural type,structural parameters and operating parameters of the existing annular cooler match the recovery of the sinter waste heat?Based on the above,this study took the technology of waste heat recovery of annular cooler as the engineering background.The main line was the relationship between 3 kinds of variables in thermal process.The research content was the gas-solid heat transfer in annular cooler.The numerical calculation was taken as the research method.The study on the thermodynamic behavior in the annular cooler was carried out to determine the appropriate structure and operating parameters and provided theoretical guidance for the actual production conditions adjustment.The main research contents,conclusions and innovations are shown as below.(1)The numerical calculation model of heat transfer between the sinter and the heat carrier in annluar cooler was improved.The secondary development of UDF was carried out on the platform of COMSOL software.For the first time,the speed of the annular cooling trolley was compiled into the model.The viscous force term and inertial force term coefficient were embedded to describe the resistance characteristics of the sinter layer.And the heat transfer coefficient between gas and solid was also embedded.A 3-dimensional numerical model of steady-state gas-solid heat transfer in sinter annnular cooler was established.(2)The enthalpy exerg of outlet heat carrier was put forward as the evaluation index of waste heat recovery.The enthalpy exerg is composed with temperature exergy and pressure exergy.The temperature exergy represents the positive effect of generating capacity quantitatively.The pressure exergy represents the negative effect of generating capacity quantitatively.Therefore,the enthalpy exerg is the quantitative description of the "net power generation" of a ton sinter.(3)The major factors affecting the enthalpy exergy of outlet heat carrier are the height of.the material layer,the length of the waste heat recovery section,the particle diameter of sinter and cooling gas inlet flow.With the increase of cooling gas flow import and length of the waste heat recovery section,the enthalpy exergy of outlet heat carrier gradually rises,and begins to decline after reaching the peak point.With the improvement of cooling gas inlet temperature,the enthalpy exergy grows linearly.With the increase of particle diameter,the enthalpy exergy falls.(4)A 405 m2 annular cooler with an annual output of 3.7 million tons sinter was taken as an example.The proper structure and operating parameters were determined as follows.The cooling gas flow rate of per ton sinter is 1212 Nm3 and the height of the sinter bed is 1.12 m,which is reduced by 37.85%and 25%respectively compared with the current working conditions.And the length of the waste heat recovery section is 81.2 m,which is 40.89%longer than the length currently set.The enthalpy exergy of outlet heat carrier increases 7.0%after optimization.According to the present generation level of 13～15 kW·h of per ton sinter,the total annual power generation can be increased by 336.7 to 388.85 million kW·h.