Study On Numerical Simulation Of Smelting Process And Gas-solid Flow In Imperial Smelting Furnace

The Imperial Smelting Furnace (ISF), as a kind of importantequipment of lead and zinc smelting, was still found to have someproblems, such as furnace accretion, short cleaning cycle, short life of therefractory which restrict its application greatly. In this paper, based on thenumerical simulation method, the smelting process and multi-phase flowin the furnace were studied systematically in order to optimizing theparameters of structure and operation.Firstly, the thermodynamics and kinetics mechanism of combustionreaction of coke and the reduction reaction of lead oxide and zinc oxidewere studied. Main reactions in the furnace were confirmed. Moreover, the one-dimensional mathematic model of smelting process in the furnacewas developed, by analyzing the heat and mass transfer as well asreaction rates for gas phase, particle phase and inter-phase.Based on Euler solution of differential equations, the program wasdeveloped with VB language, to simulate the smelting process in ImperialSmelting Furnace and to carry out one-dimensional numericalcomputation of temperature and mass flux in the furnace. Thecomputational results of temperature and concentration of the gas abovebed were close to the tests, which proved the validity of model.According to the temperature and flux distribution along the furnaceheight, the computational region was divided into five different zones: material heating zone, lead oxide reduction zone, zinc oxide reductionzone, coke gasification zone and coke combustion zone, for theoreticalanalysis of the operational process.With the mathematic model, further research into the operationparameters in this furnace was carded out. The results showed that, if thevolume of primary air is increased 5.9％, the maximum temperature ofgas and solid would increase 10.5％and 14％, the location of themaximum temperature and reduction zone would move upward 0.42m and 0.8m, respectively. If the temperature of primary air is increased6.8％, the maximum temperature of gas and solid would increase 7.2％and 10％respectively, the location of reduction zone could move upward0.5m. If the coke is increased 2.9％, the maximum temperature of gas andsolid would decrease 3.4％and 6.1％respectively, and the location ofreduction zone would move downward 0.4m.The three-dimensional numerical simulation of cold gas-solid flowin the furnace was developed through two-fluid model based on Fluent6.2.Further numerical simulations on parameters of structure and operation inthe furnace were carried out. The results indicated that, for this researchobject, the increase of the primary air velocity would enlarge the raceway, but excessive primary air might result in the penetration phenomenon.The optimal velocity of primary air was about 265 m/s. Increasing theinserting depth of primary air nozzle could enlarge the middle-gasvelocity at the lower part of the furnace. Decreasing the inclination angleof primary air nozzle would increase the middle-gas velocity at the lowerpart of the furnace. But, when the inclination angle was too small, it waseasy to produce the penetration phenomenon. Increasing this angle woulddiminish the raceway. The results showed that more appropriateinclination angle was between 10°and 20°.