Copper scum is the product of the first step of crude lead pyrometallurgical refining except impurity copper. The output is about 2% of the crude lead. The main components are Cu and Pb (usually containing 10-20% copper and 60-80% lead). In addition, it also contains valuable metals such as Sn, Ag, Bi, and As, which have extremely high recycle value.

At home and abroad, the soda iron filing method is generally used in a reverberatory furnace or a rotary furnace, and the products are crude lead, matte, slag and soot. The advantage is that the recovery rate of Pb and Cu is high, but the method has complicated process flow, various kinds of additives, troublesome ingredients, incomplete separation of Cu and Pb, and pollution of the environment by flue gas.

The vacuum distillation method for treating copper scum has the advantages of simple process flow, high production efficiency and environmental friendliness. The principle is using the large vapor pressure of lead and its oxides and sulfides, and under vacuum conditions, Under vacuum conditions, it promotes the volatilization of lead and its compounds, causing lead in copper scum and metals with lower boiling points to evaporate.

Copper and metals with higher boiling points are not volatile and remain in the form of matte to achieve the separation of copper and lead.

The copper scum is placed in a vacuum metallurgical furnace, and under the condition that the vacuum degree of 30 Pa, the distillation temperature is controlled at 1000-1200°C, and Pb and PbS in the copper scum are volatilized into the gas phase, the crude lead is obtained after condensation. The Cu and Cu2S in the copper scum are left in the distillation residue (copper) to realize the separation of copper and lead in the copper scum. The raw lead contains less than 2% copper, and the product matte contains less than 2% lead.