Oxygen-rich Top-blown Lead Smelting Process Optimization

Direct lead smelting process has many advantages, such as low energy consumption, good effect of environmental protection and low cost. A domestic company produces lead bullion by self-developed process of oxygen-enriched air top-blowing, However, the level of automation control did not meet the requirements, so the operating rate was not high, the fluctuations of dust rate is large, the direct recovery rate of lead is too low in the smelting process, thereby the lead production is affected and leading to the economic profit decreased.In this paper, according to the components of the company's lead sulfide concentrates and accessories as well as the specific components requirements for mixture and lead-rich slag which produced from top-blown smelting. Under the situation of normal self-heating smelting, SiO2/Fe and CaO/SiO2 in the slag is 0.75 0.85 and 0.3～0.5 respectively, and sulfur content in the mixture is about 16%. The program of burdening calculation is written by Vsiual Basic 6.0 computer language according to material balance and heat balance in the process of smelting. The ratio of concentrate and accessories and the corresponding consumption of oxygen-enriched air and pulverized coal could be calculated by the burdening program which could successful solve the problem of mixture composition fluctuations caused by volatile ingredient of raw material, thus making a useful preparation for top-blowing smelting.The process of lead smelting by oxygen-enriched air top-blowing is complex multi-phase and multi-component system. The thermodynamic model of multi-phase and multi-component chemical equilibrium is built by using equilibrium constant method based on S.R.Brinkley principle in this paper, and the ratios of the various activity coefficients involved in the model has been amended combined with actual data of production. The approximate solution with the model is solved by fsolve function in Matlab, and the molar amount of each component in various phases was obtained when the system of smelting process has reached equilibrium. The relationship between the amount of oxygen-enriched air and distribution rate of lead in slag phase, crude lead phase and dust, the effect of the amount of oxygen-enriched air on composition of crude lead, lead-rich slag and dust were investigated by changing the excess coefficient of oxygen-enriched air. The calculated results show that when the excess coefficient was 1.2, the direct recovery rate of lead was 36.64%; the rate of lead into the slag was 45.5%; the amount of lead into the dust is 17.85% of the total lead; sulfur content in crude lead was less than 0.1%. The results fit better with the actual situation.The control parameters and Molar quantity of each component in each phase could be predicted by the thermodynamic semi-empirical model in the process of lead smelting by oxygen-enriched air top-blowing accurately. Thus, this model has paved foundation for automatization control to the process of smelting. It also can optimize the smelting process.