| Flash smelting is one of the dominant technologies used in the copper pyrometallurgical production process.Enhancing the smelting process and improving the production capacity of the flash smelting furnace(FSF)are important goals for the development of copper smelting enterprises in China.The keys to achieving these goals are improving the heat transfer between the gas and particles,so that the particle heating process inside the furnace can be accelerated.Based on the numerical results of smelting process in the FSF,the Monte Carlo method was used to obtain further detailed information on radiative heat transfer.The weights of each heat transfer mode in the particle heating process were computed,and the direction to strengthen the gas-particle heat transfer was investigated.The main work and conclusions can be summarized as follows.(1)Taking an industrial flash smelting furnace as the prototype,numerical simulation was carried out to analyze the flow,heat transfer,and reactions between the gaseous and particle phases inside the FSF,and a computational model was established by using the Monte Carlo method to analyze the radiative heat transfer of particles.The reliabilities of these two models were both verified.(2)Numerical analysis was carried out to simulate the typical operating condition of copper flash smelting production.According to the numerical results,a ‘grid division and parameter equivalence method’ was proposed to analyze the particle dispersion and calculate the particle equivalent parameters in the reaction shaft.Then,the Monte Carlo method was applied to figure out the radiative heat of particles.The results showed that,in the heating ignition zone of reaction shaft(shaft height from 0.5m to 4m),the sources of radiative heat absorbed by particles were ranked in the order of proportion: side wall > top wall > particles.While for the particles inside the material cone at the height of 3～4m,the percentage of absorbed heat sources was arranged as side wall > particles > top wall.Moreover,in the heating ignition zone,the net radiative heat of particles inside the material cone increased first and then decreased along with the shaft height,while that of outer parts continued to decrease.(3)The influence of central natural gas was assessed by comparing the changes of particle radiative heat in the reaction shaft of FSF.The results indicated that the absorbed and the net radiative heat of the particles inside the material cone increased when the central natural gas was burned,while those of outer particles decreased.Meanwhile,the burning of central natural gas increased the uniformity of the net radiative heat along with the direction of circumferential variation.(4)To investigate the weights of different heat transfer modes in the particle heating process,both numerical simulation and the Monte Carlo analysis were carried out under different concentrate feed rates.The results showed that radiative heat transfer was the dominant heat transfer mode for particles in the heating process.Under the low concentrate feed rates,the influence of convective heat transfer on the particle heating process decreased first,then increased along with the shaft height.While under the high concentrate feed rates,the influence of radiative heat transfer increased constantly.Therefore,to enhance the heat transfer in the flash smelting furnace,it is suggested that the amount of central natural gas and central oxygen should be increased under the high concentrate feed rates,and the speed of process air could also be increased appropriately but within a reasonable oxygen coefficient range.Figures 58,Tables 12,References 79... |
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