Lead ore smelting technology and process
Lead material
Most of the smelting sulfide lead concentrate feed, a small part of lead zinc oxide ore, which comprises the polyvalent metal can be recovered almost in the smelting process. Chinese lead sulfide concentrates often contain less valuable metals: lead, zinc, copper, arsenic, antimony, bismuth, cadmium, mercury, gold, silver, selenium, tellurium, indium, germanium, thallium. In the sintering process, more than 95% of the mercury enters the flue gas; 70% of the strontium, 30-40% of cadmium, selenium, tellurium, and a small part of arsenic, antimony, bismuth and other metals enter the soot; the rest remain in the agglomerate and return In the powder. In the blast furnace smelting process, almost all gold, silver and most of copper, arsenic, antimony, antimony, tin , selenium and tellurium enter the crude lead, more than 95% of the zinc and antimony, more than 50% of the indium enters the slag, 80~ 90% of cadmium enters the dust. In the preliminary refining process of the fire method, most of the copper, tin and indium in the crude lead enter the scum, and metals such as gold, silver and bismuth remain in the lead. In the lead electrorefining process, metals that are more positive than lead, such as gold, silver, copper, ruthenium, osmium, arsenic, selenium, tellurium, etc., remain in the anode mud, and metals that are more negatively charged than lead, such as iron and zinc, Nickel , cobalt and lead dissolve together and enter the electrolyte, but do not precipitate at the cathode.
Mercury can be recovered from the flue gas of the sintering machine, and the soot generally returns to the ingredients, and the cadmium and antimony are recovered after the cycle enrichment. Treatment of blast furnace dust can recover metals such as cadmium, zinc, indium and antimony.
When scum is smelted, it produces crude lead, matte (including arsenic matte), slag and soot. It can recover copper and lead from matte and slag, and recover indium and arsenic from soot. When processing coarse lead with higher tin content, high tin scum can be re-selected to obtain lead concentrate and tin concentrate, and lead and tin are separately recovered.
In China's low-grade lead-zinc oxide ore, some of the lead, zinc, cadmium, and antimony volatilized into the dust during the blast furnace chemical process, and some of it entered the crude lead, and most of it remained in the slag. The slag is volatilized by the smelting furnace, and lead, zinc, cadmium and bismuth enter the soot and are recovered from the soot.
Refining
The crude lead obtained after the primary smelting is further refined, and there are two kinds of fire method and wet method. At present, the fire method is the mainstay in the world, and the wet method lead is still in the experimental research stage. Foreign countries mainly rely on fire law, and China mainly focuses on electrolytic refining. The electrolysis method is characterized by better recovery of valuable metals such as gold, silver, and antimony, and the availability of pure lead. Fire refining is more flexible, and it can be organized according to the impurities in the crude lead and the market demand, and the investment is also saved.
Introduction to the main smelting process
Lead-up in Kivcet: The Soviet Union Institute of Nonferrous Metals Mining and Metallurgy began experimenting in 1967; in 1988, industrialized continuous production was realized. The process was jointly developed by the Moscow Institute of Nonferrous Metals of the former Soviet Union and Kazakhstan. Sami, Italy, purchased the patent and built a 80,000 tonne/year crude lead plant in VesmePort. The license and basic design fees are as high as $10 million, and the investment is huge. Leading method of the Leads method is strict in the preparation of materials. After the ingredients are added to the furnace, it is required to be sufficiently dried to less than 0.5% of water and the particle size is about 100 mesh. The final slag contains more than 3% lead, and there are still low-level pollution problems, and the production energy consumption is high.
QSL smelting lead: developed by the German Lurgi company, has been established in China, Germany, South Korea, the process of raw material preparation requirements are relatively loose, material moisture, particle size composition is not strictly limited. Since the oxidation and reduction are completed in the same device, the final slag contains 5%-10% lead, high oxygen consumption and high power consumption.
Oxygen-enriched top-blown immersion smelting method (ISA and Ausmelt lead smelting): a smelting method derived from the top-blown immersion spray gun technology developed by the Australian Federal Institute of Scientific and Industrial Research (CSIRO) in the early 1970s. Smelting category. In the late 1970s, Australia's MIM and CSiRO collaborated to develop smelting technology to directly smelt lead and obtain patent rights under the Isa smelting lead method. Inventors of the top-blown immersion spray gun in the early 1980s formed Ausmelt and developed it in the field of spray guns and some new applications. Both MIM and Ausmelt have obtained the right to transfer the technology. The technology uses two vertical furnaces of the same structure for oxidation and reduction smelting. At present, the production of oxidation zone of ISA method has become normal, and the SO2 flue gas produced by the oxidation furnace can be used for acid production, but the production stability of the reduction section is poor. At the same time, the process oxygen lance replacement is frequent, generally needs to be replaced once every 4-7 days, the operation rate is low, the gun changing mechanism is complicated, and the investment is large.
Caldo converter smelting lead: The technology developed by the Swedish company Politden is an application of oxygen metallurgy in the top-blown converter, and it is also a melting pool smelting category.
The lead-smelting process is carried out in two stages: oxygen-rich melting and oxidation, and reduction of molten material. The lead content of the slag can be determined according to the amount of reducing agent and the reduction time, and the lead content of the slag is also about 3%. However, the flue gas produced by oxidation and reduction has a large difference in sulfur dioxide content. In the oxidation section, the concentration of sulfur dioxide is as high as 16%, and the concentration of sulfur dioxide in the reduction section is less than 400 ppm. For the continuous production of the acid plant, the oxidation stage flue gas is first compressed and condensed to liquefy 50% of the sulfur dioxide, and the remaining sulfur in the flue gas is acid.
In fact, ISA and Kaldo are not one step of lead smelting. Only Kivcet and QSL are one-step lead smelting. The former is not to be oxidized and reduced by two furnaces, and it is not carried out in stages.
Blast furnace method lead smelting: The lead smelting production of this process has high energy consumption, low SO2 concentration, and can not achieve two-turn two-supply acid production, serious pollution and poor working conditions. According to different equipment, it is divided into sintering pot-blast furnace, sintering machine-blast furnace and closed blast furnace ISP. Sintering pan-blast furnace countries have clearly stated that they must be eliminated by the year 2000. At present, most of the companies currently producing mainly use the sintering machine-blast furnace process. ISP technology can be used for smelting with mixed lead-zinc ore raw materials, which has the advantages of wide range of raw materials and low process cost.
Oxygen Bottom Blowing Lead (SKS): In 1998, a number of units invested in the use of the Shuikou Mountain Bottom Blowing Lead Test Workshop to carry out the verification test of the oxygen bottom blowing smelting-blast furnace reduction lead smelting (ie SKS method). The multi-month test proves that the process is reliable and the indicators are feasible. The bottom-blow smelting process is used to replace the sintering and powder-reversing processes in the conventional lead-smelting process. Due to the high concentration of SO2 in the bottom blowing furnace, it is conducive to acid production, and the recovery rate of sulfur is as high as 95% to 96%. At the same time, SO2 and lead dust pollution are completely cured due to the elimination of sintering and powder breaking. The bottom blowing smelting process does not require additional fuel, is completely self-heating and can use some waste heat to generate electricity.
More importantly, about 50% of the lead in the bottom blowing process directly produces crude lead through the interaction reaction, and the high lead slag entering the blast furnace contains 40% to 45% lead, which is comparable to the lead in the agglomerate, so the blast furnace smelting material Compared with the sintering process, the ratio is reduced by about 50%. Therefore, the coke consumption is significantly reduced, so that the cost of lead smelting is lower than that of the conventional process, and the profit of sulfuric acid can achieve good economic benefits. The process raw material has strong adaptability, and can directly treat lead concentrates of various grades, and can also process various lead-containing materials and secondary materials, such as lead plates and used batteries.
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