Thermal Parameters Research And Thermodynamic Analysis Of Sinter Waste Heat Recovery System With A 2.6 Million T/a Vertical Tank

The vertical tank technology for sinter waste heat recovery,proposed by our research team with the intellectual property,is an efficient technology for waste heat recovery.Compared with the current indexes,its electricity generation capacity per ton of ore is expected to increase by double.The technology of sinter waste heat recovery with vertical tank has been incorporated into the Iron and Steel Industry Adjustment and Upgrading Plan of China(2016-2020).Structural and operational parameters of vertical tank determine the outlet parameters of heat carrier,and then determine the subsequent electricity generation capacity per ton of ore.The research on thermal parameters of vertical tank is limited to this research group.It focuses on numerical calculation and experimental research,lacks the principles and methods of determining thermal parameters,and the research condition is limited.Meanwhile,the thermodynamic analysis of sinter waste heat recovery system with vertical tank is still in blank.Based on this,firstly,the 3D local thermal non-equilibrium steady state model of vertical tank was established.Secondly,the appropriate criterion of vertical tank thermal parameters was determined,then the principle and method to determine the thermal parameters of vertical tank was compacted.Thirdly,the typical conditions may be encountered in the production process was predicted and the numerical study of gas-solid heat transfer in the vertical tank on the typical working condition was conducted.Finally,the thermodynamic analysis of sinter waste heat recovery system with vertical tank was carried out.The main conclusions and innovations are as follows.(1)The sinter velocity and the gas-solid volumetric heat transfer coefficient,resistance coefficient of sinter bed layer are embedded gas-solid heat transfer model based on the pattern of moving bed,and then the 3D local thermal non-equilibrium steady state model of vertical tank is established.The reliability of mathematical model is verified through the comparison of calculated results with the experimental results.The mean deviation between the calculated results of outlet sinter temperature and test results is 8.51%,the mean deviation between the calculated results of outlet cooling air temperature and test results is 5.95%.(2)The enthalpy exergy of outlet heat carrier is the appropriate criterion of vertical tank thermal parameters to represent the net electricity generation capacity of sinter waste heat recovery system with vertical tank.The principles to determine the vertical tank thermal parameters are as follows.Firstly,the basic temperature requirements of vertical tank process should be satisfied.Secondly,both the direct motion of sinter and the uniformity of airflow distribution should be considered.Finally,the enthalpy exergy of outlet heat carrier should be selected as evaluation index when optimizing the vertical tank thermal parameters.The methods to determine the vertical tank thermal parameters are as follows.First of all,thermal parameters satisfied the basic temperature requirements of vertical tank process should be obtained.And then the orthogonal test should be designed with the maximum enthalpy exergy of heat carrier as the objective function.According to the confinement range of thermal parameters,the thermal parameters are optimized and the suitable structural and operational parameters of vertical tank are determined.(3)The suitable thermal parameters for a 2.6 million t/a vertical tank are as follows.Under the condition of single vertical tank,the temperature of cooling air is 353K,the inner diameter and height of cooling section are 8.0m and 9.0m respectively,and the inlet flow rate of cooling air is 86kg/s.The outlet enthalpy exergy of cooling air in vertical tank is 20.31 MW and the average gas-solid water equivalent ratio of vertical tank is 1.18.Under the condition of double vertical tanks,the temperature of cooling air is 353K,the inner diameter and height of cooling section are 6.0m and 8.0m respectively,and the inlet flow rate of cooling air is 50kg/s.The enthalpy exergy of outlet heat carrier for two vertical tank is 20.54MW and the average gas-solid water equivalent ratio of vertical tank is 1.31.(4)The thermodynamic analysis of the waste heat recovery system in the pattern of sinter-vertical tank-boiler is conducted with the method of enthalpy analysis and exergy analysis.The results show that,the thermal efficiency of sinter subsystem,vertical tank subsystem,boiler subsystem and the whole system are 35.67%,86.36%,9.83%and 24.59%respectively,compared with the traditional sinter waste heat recovery system the thermal efficiency increased by 39.32%.And the exergy efficiency are 25.28%,71.57%,91.09%and 16.48%respectively,compared with the traditional sinter waste heat recovery system the exergy efficiency increased by 94.79%.