Gas-Solid Heat Transfer Of Shaft Sinter Packed Bed-An Analytical Method

Gas-solid heat transfer is one of the key problems in the vertical cooling waste heat recovery process of sinter.Based on the experiment,numerical simulation,several operating parameters which influence the recovery performance of waste heat had been studied,such as sinter inlet temperature,gas-solid ratio.However the results were not universal,as these studies were mostly directed for a specific device.The existing heat transfer coefficient between sinter and air is not applicable to engineering,because most of them are area heat transfer coefficient,or the error is large.The uniform distribution of air flow is the prerequisite for the establishment of one-dimensional gas-solid heat transfer model,but there is a lack of general knowledge about the relationship between air flow distribution and pressure distribution inside the bed.Therefore in this paper,by using pressure lines and streamlines,the general law of the gas flow in the bulk bed of sinter and its relationship with the resistance loss are analyzed,which provides the theoretical basis for the establishment of the one-dimensional gas-solid heat transfer model.A one-dimensional heat transfer model for engineering equipment is established.Based on the vertical cooling waste heat recovery unit,volumetric heat transfer coefficient between sinter and air is given.The main factors influencing the heat transfer between sinter and air are studied by the analytical method.The distribution of sintered ore and air temperature along the height of material layer under different gas-solid ratio are studied,and the synergistic degree of sinter and air temperature field is given as the ratio of air to solid water.Based on the field synergy theory,the optimum gas-solid ratio is studied.Based on the studies above,the paper got the following conclusions:(1)The volumetric heat transfer coefficient empirical formula of vertical cooling of sinter were as follows,where 0.674?Pr?0.688,502.6?Rep?2056.2.Nu=162.6Rep0.541pr0.4(2)In the same section,if there is a pressure gradient,there must be segregation of the gas flow,but there is not necessarily a segregation of the gas flow.In the application of pressure distribution to analyze the distribution of air flow,special attention should be paid to analyze the distribution of porosity within the material layer.As for un-sintered sinter,the wall efficiency is negligible.(3)The temperature efficiency of the sinter and air increases as the number of heat transfer units increase,and the temperature efficiency of the air decreases as the gas to solid water equivalent ratio increases.The temperature efficiency of the sinter increases as the gas to solid water equivalent ratio increases.The heat transfer efficiency of sinter furnace is raised with the increasing number of heat transfer units.(4)The trend of gas-solid temperature in the height direction of the material layer is different under the condition of different gas-solid water equivalent ratio.When the air-water equivalent is more than the sinter water equivalent,the gas-solid heat exchange is mainly concentrated on the upper material layer;When the air-water equivalent is less than the sinter water equivalent,the gas-solid heat exchange is mainly concentrated on the lower material layer;when the gas-solid water equivalent is equal,gas-solid heat exchange occurs evenly across the height of each section.At this time,the synergistic effect of temperature field between sinter and air is the best,and the heat transfer performance is the best.