Lead metallurgy is the best carrier for producing silver: generally, the recovery rate of gold and silver from lead is above 95%, so the recovery of gold and silver is directly related to the production of lead. At present, about 80% of primary lead in the world is produced by the traditional sintering-blast furnace smelting process. The traditional method is mature, perfect and reliable, but the disadvantage is that the concentration of SO2 in sintering flue gas is low, and it is still difficult to recover sulfur. Blast furnace smelting needs expensive metallurgical coke. In order to solve the above problems, metallurgical workers have studied a new lead smelting process. Since 1980s, new lead smelting methods such as QSL method, flash smelting method, TBRC converter top blowing method, Kievsetan method and Elsa smelting method have appeared one after another. Among them, QSL process is a new direct lead smelting process developed by Lurgi Company of Germany in 1970s. Although Canada, South Korea and China have successively purchased this patent to build factories, the production effect is not satisfactory. Flash smelting method has not yet achieved industrial production; The TBRC method was invented by the Swedish company Politon, but the operation of this method is intermittent and the lining is seriously corroded. Kifset method was successfully studied by the Institute of Nonferrous Metals of the former Soviet Union, and now many manufacturers have realized industrial production. This is a new lead smelting process with advanced indexes and mature and reliable technology. However, the unit investment of this method is large, and only when it is used in large-scale production plants can its benefits be fully exerted.
Isa lead smelting technology is based on the Siro immersion lance inserted from above to inject oxygen into the melt. A vortex molten pool is generated, so that a strong oxidation reaction or reduction reaction occurs quickly. In the first stage, the high-lead slag produced by the smelting furnace is sent to the reduction furnace through the launder, and the flue gas produced by oxidation desulfurization is sent to the acid-making system after dust removal. In the second stage reduction furnace, the generated lead bullion and waste residue are continuously discharged from the discharge port and separated in the traditional forehearth, and the generated flue gas is discharged through the chimney after dust removal.
Esau smelting process. The process has advanced process flow, wide adaptability of raw materials, flexible production scale, advanced indicators and high SO2 flue gas concentration, which can solve the problem of flue gas pollution in the production process. At the same time, the smelting process is strengthened, with high recovery rate of gold and silver, good utilization of waste heat and low energy consumption. It not only meets the transformation requirements of lead and silver smelting in No.308 Plant, but also promotes the metallurgical production and technical progress of silver and lead in China. Therefore, it is recommended to introduce ISA process as the first scheme of crude lead smelting production process in this project.
Although there are still some difficulties in the traditional blast sintering-blast furnace flue gas acid production, in recent years, this method is still used in the reconstruction and expansion projects of large lead plants such as Zhuzhou Smelter, Shenyang Smelter and Jiyuan Smelter in China, because it has the advantages of rapid construction, commissioning and production.
There are two refining methods for crude lead: pyrometallurgy and electrolysis. Generally speaking, electrolytic separation of silver, gold, bismuth and antimony is effective, with high recovery rate of metals such as lead and silver, good working conditions and high degree of mechanization and automation. The disadvantage of electrolytic method is that the capital investment is higher than that of pyrometallurgical method. Pyrolysis needs to deal with a large number of intermediate products, which leads to high energy consumption and higher production cost than electrolysis. In view of the fact that the crude lead in this project contains more metals such as silver and bismuth.
The conventional method to treat lead anode mud is to obtain gold and silver by pyrometallurgy-electrolysis process, and to obtain refined bismuth by reducing and smelting slag. The process is simple, the technology is mature, and it is easy for workers to operate, but the recovery rate of valuable metals is not high. Antimony and lead volatilize into smoke and dust in the form of oxides, which is not only inconvenient for comprehensive recovery, but also causes secondary pollution.
Tungsten and Cobalt: A Method for Recovering Tungsten and Cobalt from Supercarbide at High Temperature
The method of recovering tungsten and cobalt by high temperature treatment: superhard carbide is formed by mixing tungsten, cobalt and carbon powder and sintering. Tungsten and cobalt powder can be recovered by high temperature treatment of cemented carbide developed by Nippon New Metal Company, with an annual output of 80 tons.
After heat treatment in inert gas at 1800 ~ 2300℃, the cobalt in cemented carbide is spongy and easy to be pulverized. At the heat treatment temperature, cobalt in superhard alloy is not in sponge state below 1800℃, while tungsten carbide in the alloy will decompose to form the third phase above 2300℃, which is not effective.
After heat treatment, the block debris is coarsely crushed to -850μm by jaw crusher or roller crusher, and then finely crushed into regenerated powder. Due to the coarse granulation process, the regenerated powder obtained by this method is easy to grow during sintering. After treatment, the cobalt content and carbon content in the alloy are almost unchanged, but the impurities of iron and silicon increase, which has no effect on the manufacture of cemented carbide. According to the crushing conditions, the particle size of regenerated powder can be slightly crushed to below 65438±0 μm m.
This method uses relatively easy procedures, does not destroy the original components of cemented carbide, and any cemented carbide can be regenerated into powder with a certain particle size without special equipment, so it is an economical recovery method. Compared with the previous method of refining and recovering with chemical reagents, it has great advantages.