In this paper, the thermodynamic properties of the PbO-ZnO-FeO-Fe2O3-SiO2-CaO six-component slag system were studied by using the molecular-ion coexistence theory, and the influence of slag composition changes on the activity of each structural unit was analyzed. The results show that the calculated value of the activity model is in good agreement with the measured value of the experiment, and the activity of each structural unit is greatly affected by the composition of the slag, but less affected by the temperature. High temperature is conducive to the decomposition of lead silicate and the formation of calcium-containing compounds, but the activity of ZnO will decrease. When the mass fraction of PbO increases, the main reaction is to combine with PbO·SiO2 to form 2PbO·SiO2. Increasing the mass fraction of ZnO and CaO is beneficial to the decomposition of lead silicate and an increase in PbO activity. When the iron-silicon ratio increases, it will promote the decomposition of lead silicate and the formation of ZnO·Fe2O3, so the activity of PbO will increase and the activity of ZnO will decrease. When the calcium-silicon ratio is low, the binary combination product of CaO and SiO2 is mainly CaO·SiO2, and when the calcium-silicon ratio rises above 0.5, the activities of 2CaO·SiO2 and 3CaO·2SiO2 will increase rapidly.

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In this paper, a large bottom-blown lead smelting furnace is studied by numerical simulation, the flow characteristics of different planes, monitoring points and molten pool regions are analysed, and a formula is established to predict the velocity distribution of molten pool in the bottom-blown furnace. The results show that the flow between two adjacent oxygen lances will influence each other and effectively reduce the existence of a low-velocity region. The high-velocity region at the liquid surface is mainly distributed above the bubble molten pool reaction region (BMRR), and the velocity is transmitted to the upper/lower sides. The wall shear stress is mainly distributed at the bottom and on the walls on both sides of the BMRR. The pre-stabilisation time of a bottom-blown furnace is 2 s, and the unstable state existing in the local region will not have a great influence on the overall flow field in the furnace. The distribution of the bubble plume and the high-velocity region overlaps under the free liquid surface, and their boundaries are basically consistent. The fitting effect of the velocity cumulative percentage curve and each point is very good.