The Process Of Waste Heat Recovery And Utilization And Resistance Characteristics For Sinter In Vertical Tank

The efficient recovery and utilization of waste heat resources is one of the main methods which reduces energy consumption of sintering process. At present, the main mode to recovery and utilization the waste heat resources in the sintering process is cooling by blasting and grade recovery, which has a certain degree of "inherent shortage", i.e. the air leakage rate of cooling system is as high as30%～50%, the rate of waste heat recovery is only10%-40%, which goes against sintering waste heat recovery.Based on this point, the method of vertical tank sintering waste heat recovery is proposed from the ideas of coke dry quenching (CDQ) technology. The basic process is as follow:the hot sinter goes into the tank from the top, and the hot sinter goes down to the cooling section with the continuous discharge of cold sinter. In the cooling section, the hot sinter is cooled by heat exchange with the circulatory gas, and finally, the cooled sinter discharges from the bottom. At the same time, the temperature of cooling air in the tank is increased after heat exchange, and the air discharged through the circular flue. The circulatory gas with high temperature enters the waste heat boiler to carry on heat exchange after going through a filter, and the circulatory gas with low temperature which exhausts from the boiler goes into secondary filter and separates more fine solids sinter. Then, the gas is sent into pre-heater by circulation fan, and after heat exchange, the gas goes into the tank again for recycling. Compared with the traditional cooling methods, the new method for waste heat recovery not only overcomes the low efficiency of waste heat resource recovery caused by air leakage, but also overcomes the problem of recovering only part of the waste heat, and nearly all the sensible heat can be recycled.The feasibility of the method that recovers the waste heat of sinter in vertical tank depends mainly on three aspects, i.e. the resistance characteristic of sinter material layer, the gas-solid heat transfer characteristic in sinter material layer, and the influence to the metallurgy performance of sinter by different cooling ways. Aiming at the problem of resistance characteristic of unit material layer, this paper analyzed the influence of apparent velocity, grain size, the distributing and so on to the resistance of material layer by the method of experiment. The influense of Critical Re*to the unit material layer pressure loss is discussed. At the same time, the influence of the edge effect, the sharp of the section to the unit material layer pressure loss is studyed assisting through numerical simulation by the FLUENT software. The experiment process mainly adopts cold sinter The results of the research show that:(1) The main factors that influence the character of tank gas-solid resistance:particles equivalent diameter, apparent velocity, grain temperature, edge effect and trapezoidal section. Among them, the unit material layer pressure loss of sinter reduces with the increase of sinter particle size and increases with the increase of empty tower velocity; the unit material layer pressure loss of the cold sinter is fitted by the equation:The Ergun equation is revised by introducing the equation of gas state when the temperature of sinter particles changes, the revised equation is:The influence of edge effect in the actual production process can not be neglected, and the proportion of section isn’t same through the passes flow and the passes; The pressure loss of trapezoidal section model reduces with the increase of base angle; Distributing a certain thickness of uniform particle sinter in the process between two times of falling sinter is helpful for distribution of sintering wind, the pressure of tank increases.(2) Critical Re*increases with the increase of the particle size, was fitted through relation curves of the tank and the sinter particles of equivalent diameter, the fitting equation is: (3) The related design parameters of heat recovery mode is:the range of apparent velocity is1～2m/s, and according to the revised Ergun equation, of resistance of unit material layer is in the range of1.1～2.5kPa in the actual production...