Bismuth silver zinc slag is a scum formed by bismuth refining plus zinc and silver, using Zn as a collector to collect impurities such as Au, Ag, Cu, Pb. The lead-silver-zinc shell is a condensate that floats on the surface of lead liquid during the refining process of crude lead refining plus zinc and silver. It is an alloy of Zn with Au, Ag and Pb.

Lead, silver and zinc shells contain a large amount of Pb and a small amount of lead and zinc oxide and impurities such as Cu, As, Sb.

Silver zinc slag and silver zinc shell have high comprehensive utilization value.

The vacuum distillation method utilizes the difference in boiling point and vapor pressure between various elements in the silver-zinc slag/shell, and performs distillation under conditions of a certain temperature and vacuum.

The silver-zinc slag/shell is placed in a vacuum metallurgical furnace, and the distillation temperature is controlled at 900-950°C under a vacuum of 30 Pa or below it (the higher the temperature, the higher the volatility of Bi, Pb and Zn, but if the distillation temperature  more than 950 ° C, Ag also began to volatilize significantly).

The Zn and Bi or Pb in the silver zinc slag/shell volatilizes into the gas phase, and after condensation, a zinc bismuth alloy is obtained.

The Ag, Au, Cu, etc. in the silver zinc slag/shell are effectively enriched in the distillation residue to obtain the crude silver, which is beneficial to the next step of refining, thereby realizing Bi-Zn or Pb-Zn in the silver-zinc slag/shell and separation of Ag.