The crude bismuth and zinc in addition to silver-rich silver refining slag output by the de-segregation of bismuth, prior to recovering the silver, the slag must be Ag-Zn eluted off the zinc, both the recovery of zinc, and for recovery of silver Good pretreatment.

Dezincification can be carried out by distillation or acid leaching. The composition of the molten slag produced after the precipitation of the silver-rich slag is shown in Table 2, and the phase analysis of bismuth, zinc and silver is shown in Table 1. From Table 1, mainly metallic bismuth, bismuth condition exists, the zinc is present mainly in the state of zinc oxide, silver metal to silver state exists.

Distillation

From the phase analysis, it is known that 83% or more of the zinc in the slag is present in the ZnO state. Therefore, it is necessary to incorporate a reducing agent into the slag during distillation to evaporate zinc as zinc vapor. In order to lower the temperature of the distillation, vacuum distillation is employed.

Table 1 Phase analysis of molten slag (%)

First, the process.

As shown in Figure 1.

Figure 1 Flow chart of vacuum distillation of molten slag

Second, the main technical conditions.

Distillation temperature: 750 deg.] C, distillation time; 3-4 hours, reduction of coal consumption of 3 times the theoretical amount, the degree of vacuum: 1999.83 - 2664.40 Pa.

The composition and volatilization rate of the vacuum distillation product are shown in Table 2.

Table 2 Vacuum distillation product composition (%)

Third, the main equipment.

One jaw crusher and one vacuum furnace.

Fourth, the product uses.

The condensed zinc is returned to the bismuth refining plus zinc and silver; the distillation residue and the high silver enamel are used as the silver extraction raw material.

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