Lead smelting raw materials are mainly lead sulfide concentrate and a small amount of lump ore. There are two methods of lead smelting: pyrometallurgy and hydrometallurgy. At present, pyrometallurgy is mainly used in the world, and hydrometallurgy is still in the experimental research stage. Pyrometallurgy basically adopts sintering roasting-blast furnace smelting process, accounting for 85-90% of total lead production. Secondly, reactive smelting method, whose equipment can be chamber furnace, short kiln, electric furnace or vortex furnace; Precipitation smelting is rarely used. Lead is mainly refined by pyrometallurgy, followed by electrolytic refining, but electrolytic refining is not widely used in China due to customary reasons.
The raw materials for zinc smelting are mainly zinc sulfide concentrate and a small amount of zinc oxide products. In recent 20 years, zinc hydrometallurgy has developed rapidly. At present, 70-80% of the total zinc production is produced by wet process. Crude zinc obtained by pyrometallurgy is refined by distillation or directly used. Electrolytic zinc obtained by hydrometallurgy is of high quality and does not need refining.
The refractory lead-zinc sulfide mixed concentrate is generally smelted in a closed blast furnace to produce lead and zinc at the same time.
For the lead-zinc oxide mixed ore which is extremely difficult to separate, China has formed a unique treatment method after long-term research, that is, the raw ore of the lead-zinc oxide mixed ore or its enriched products are sintered or pelletized, and then melted in a blast furnace to obtain the slag of crude lead and lead-zinc, and the slag is further fumed in a fuming furnace to obtain zinc oxide products, and electrolytic zinc is obtained by hydrometallurgy. In addition, zinc oxide products can also be obtained by direct fuming in rotary kiln.
Second, the influence of concentrate impurities on lead and zinc smelting:
1. Impurities in lead concentrate:
Copper: Copper-bearing sulfide exists in the concentrate. At the sintering and roasting temperature, copper oxide reacts, which is reduced to metallic copper in the smelting process, and enters crude lead, such as crude lead with high copper content (> 2%). It is necessary to make matte and recover copper, otherwise it is difficult to separate lead from slag during smelting, which will easily block the siphon, cause difficulties in treatment, and affect the health of workers and lead volatilization loss. When the copper content in lead products is high, it is easy to harden lead. Therefore, the copper content in lead concentrate is required to be
Zinc: exists in lead concentrate in the state of zinc sulfide, and becomes ZnO when roasting. There is no chemical change in the smelting process, and most of them enter the slag, which increases the viscosity of the slag and narrows the specific gravity difference between lead liquid and slag, making it difficult to separate them and affecting the recovery rate of lead. Part of ZnO may condense on the furnace wall, which makes the operation difficult. When the zinc content in raw materials is high, it will cause high iron slag and increase the loss of lead in slag. Zinc can easily harden lead metal and cannot be pressed into thin sheets.
Arsenic: It exists in the form of arsenopyrite and realgar (As2S3) in the concentrate. In the process of smelting, a part of it is reduced to As2O3 and volatilized into flue gas, which causes extremely harmful air pollution. Part of arsenic enters into lead bullion and slag. When the arsenic content in crude lead is high, it is necessary to remove arsenic by alkali refining. Na2so 4 contained in scum is easily soluble in water, which pollutes water sources and causes human and animal poisoning. Arsenic is easy to alloy with lead and harden it, so the arsenic content in lead concentrate should not exceed 0.6%.
Magnesium oxide (MgO): The melting point is 2800℃, which increases the melting point of slag, easily reduces the solubility of iron oxide in slag and makes slag sticky. Generally, when the MgO content reaches 3.5%, faults often occur, so it is hoped that the MgO content of lead concentrate will not be greater than 2%.
Alumina (Al2O3): The melting point is 2050℃, which increases the melting point and viscosity of slag. Especially, zinc spinel (ZnO Al2O3) formed by combining with ZnO is insoluble in blast furnace, which significantly improves the melting point and viscosity of slag. Therefore, it is required that Al2O3 in the concentrate should not exceed 4%.
2. Impurities in zinc concentrate:
Copper: It often exists in the concentrate in the sulfide state of copper. Cuprous oxide in different forms is mainly formed during roasting, and the residual copper sulfide is easy to form matte, which reduces the melting point of the charge. In zinc hydrometallurgy, Cu++ in solution corrodes pipes and valves, and in vertical tank distillation, a small amount often enters crude zinc, which affects the quality of commercial zinc. Therefore, the content of copper in zinc concentrate is required to be no more than 2%.
Lead: When the content of lead sulfide in zinc concentrate is high, fusible lead and sulfur are formed, which first promotes agglomeration, and even melts roasted materials, which hinders desulfurization. Lead oxide is easy to form low melting point crystals with many metal oxides, and it begins to melt at 800℃, which leads to the agglomeration of burden in fluidized bed furnace and flue. In lead hydrometallurgy, it is converted into lead sulfate, and sulfuric acid is consumed during roasting. Lead is consumed in lead hydrometallurgy. Condensation becomes impurities in zinc ingots, which affects the quality of commercial zinc. Lead sulfate in roasted ore is reduced to lead sulfide in distillation tank, which can form matte with other metal sulfides, causing corrosion of tank wall. Therefore, the lead content in zinc concentrate is required to be no more than 3%.
Iron: When iron exists in zinc concentrate in the form of marmatite, zinc ferrite is formed during roasting. In the process of zinc hydrometallurgy, dilute acid leaching can not dissolve zinc ferrite, which affects the leaching rate of zinc and increases the treatment cost of leaching residue. Free FeS in the concentrate is transformed into Fe2O3 during roasting, and enters the solution in the form of FeSO4 during sulfuric acid leaching, and floc Fe(OH)3 is generated during oxidation neutralization, which affects the clarification speed of thickener. When SiO2 _ 2 exists in the ore, it is easy to form silicate with FeO to corrode the tank wall; When crude zinc enters the distillation column, the iron content in crude zinc directly affects the service life of the distillation column. Therefore, it is expected that the iron content in zinc concentrate should not exceed 16% and that in zinc hydrometallurgy should not exceed 10%.
Arsenic: The concentrate contains arsenic, which enters the flue gas during boiling roasting and causes V2O5 poisoning during sulfuric acid production. Most arsenic in roasted ore is removed during leaching, but the solution with high arsenic content consumes a lot of FeSO4 _ 4 (iron content is 20 times as high as arsenic content) and takes away more iron slag and zinc. As can discharge on the cathode, resulting in plate burning (cathode reverse melting).
Silica: Concentrate often contains free silica and various bonded silicates, which react with zinc oxide at high temperature to form zinc silicate. During wet leaching, silicic acid enters the solution in the form of colloid, which makes the product concentrated and the filtration process extremely difficult. At the high temperature of distillation, SiO _ 2 forms silicate with Cao and FeO, which corrodes the tank wall and hinders distillation. It is required that the silica content in the concentrate should not exceed 7%.
Fluorine: Fluorine in the flue gas of boiling roasting is easy to corrode the tiles in the acid-making system and damage the equipment. When the fluorine content in the electrolyte is high, the cathode zinc is not easy to peel off. It is required that F in zinc concentrate should not be greater than 0.2%.
Third, comprehensive recovery of associated components in lead-zinc smelting:
1. Comprehensive recovery in lead smelting;
Sulfur: It is recovered from the flue gas of sintering machine and used to produce sulfuric acid.
Copper: It is recovered in the form of matte in blast furnace smelting or in the form of copper-bearing dross in pyrometallurgical refining.
Thallium: Recovered from sintering flue gas.
Gold, silver, platinum group metals, selenium, tellurium and bismuth: recovered from electrolytic refining anode mud or pyrometallurgical refining scum.
Zinc: Recovered from blast furnace slag by fuming.
Cadmium: Recovered in smoke and dust.
2. Comprehensive recovery in zinc smelting;
Sulfur: Recovered from the flue gas of boiling roasting.
Lead: Recovered from zinc oxide leaching residue.
Gold and silver: Recovered from leaching residue as concentrate by flotation.
Cadmium: Recovered from copper-cadmium slag.
Copper: Recovered from copper-cadmium slag.
Indium, gallium and germanium: recovered from indium-germanium slag.
Cobalt: Recovered as cobalt slag when cleaning liquid.
Thallium: Recovered from the smoke and dust in the process of fluoride and chlorine removal (multi-hearth furnace or rotary kiln).
Four, lead and zinc smelting product quality standards:
1. See table 1 for lead metal.
2. See Table 2 for zinc metal.
Lead and gold metal GB 496-64 table 1
Leading product number
Dai Hao
Chemical composition (%)
Use examples
Pb≮
Heterogeneity is not greater than
(Reacting to what others say or expressing anger or annoyance) Hmm.
copper
fool
tin
be like
bismuth (Bi)
Continuing education (UK)
zinc (Zn)
Magnesium+calcium+sodium
total
1
Pb— 1
99.994
0.0005
0.0005
0.0005
0.00 1
0.0005
0.003
0.0005
0.0005
0.003
0.006
Lead powder and its special use
2
Lead -2
99.990
0.0005
0.00 1
0.00 1
0.00 1
0.00 1
0.005
0.00 1
0.00 1
0.003
0.0 1
Lead plate calendered products, optical glass and lead.
three
Lead -3
99.980
0.00 1
0.00 1
0.004
0.002
0.002
0.006
0.002
0.002
0.003
0.02
Lead alloy grid and printed lead plate
four
Lead -4
99.950
0.00 15
0.00 1
0.005
0.002
0.002
0.03
0.003
0.003
Mg 0.005
Calcium+sodium 0.002
0.05
Acid-resistant lining and pipeline
five
Lead -5
99.900
0.002
0.002
Sb+Sn
0.0 1
0.005
0.06
0.005
0.005
0.0 mg1
Calcium+sodium 0.04
0.0 1
Solder, printed lead alloy, lead-clad cable, bearing alloy
six
Lead -6
99.500
0.002
0.004
Sb+Sn+As
0.25
0. 10
0.0 1
0.0 1
Mg 0.02
Calcium+sodium 0. 10
0.5
Lead alloy, quenching tank, waterway pipe joint
Zinc and gold metal GB 470-64 Table 2
zinc (Zn)
product
figure
Dai Hao
Chemical composition (%)
Use examples
Zinc≮
Heterogeneity is not greater than
lead
Continuing education (UK)
cadmium (Cd)
copper
be like
fool
tin
total
Te 1
Zn—0 1
99.995
0.003
0.00 1
0.00 1
0.000 1
0.005
Advanced alloys and special uses
1
Zn— 1
99.99
0.005
0.003
0.002
0.00 1
0.0 1
Die casting, electro-zinc plating, advanced zinc oxide, pharmaceutical chemical reagent.
2
Zinc -2
99.96
0.0 15
0.0 1
0.0 1
0.00 1
0.04
Electrode zinc plate, brass, die casting, zinc alloy
three
Zinc -3
99.90
0.05
0.02
0.02
0.002
0. 1
Zinc plate, hot-dip galvanizing, copper alloy
four
Zinc -4
99.50
0.3
0.03
0.07
0.002
0.005
0.0 1
0.002
0.5
Zinc plate, hot dip galvanizing, zinc oxide, zinc powder
five
Zinc -5
98.70
1.0
0.07
0.2
0.005
0.0 1
0.02
0.002
1.3
Zinc-containing copper alloy, common zinc oxide, common castings
Appendix III:
Calculation method of industrial grade index in mining area
According to the geological data obtained in the general survey and evaluation stage and the general technical and economic indicators of lead-zinc mines in China, the simple and easy "price method" can be used to calculate the industrial grade (referring to the average grade of mining areas).
"Price method" formula is as follows:
① Total cost per ton of ore: the sum of the cost of mining, beneficiation, ore transportation, enterprise management fee and concentrate sales fee per ton of ore;
Mining cost: that is, ore drawing cost, different development methods (adits and shafts), different mining methods and water discharge all affect mining cost. At present, the mining cost of small underground mines in China is about 12-23 yuan/ton, and that of large and medium-sized mines is 10-28 yuan/ton.
Mineral processing cost: Lead-zinc ore is generally flotation, and its mineral processing cost is affected by factors such as mud content of ore, mineral particle size, reagent consumption and tailings transportation distance. At present, the cost of flotation is generally 10- 16 yuan/ton.
Raw ore transportation cost: refers to the transportation cost of the mined ore from the pit mouth to the concentrator, which is affected by the transportation distance and transportation mode (electric locomotive, ropeway, etc.). ). At present, pit mining in China is generally 1- 1.5 yuan/ton.
Enterprise management fee: Enterprise management fee is influenced by enterprise scale and management level. At present, China's large and medium-sized enterprises 2-4 yuan/ton, small enterprises 3-5 yuan/ton.
Concentrate sales fee: all expenses (transportation fee, handling fee, management fee, etc. ) The delivery place for transporting the lead-zinc concentrate from the mine concentrator to the smelter is the concentrate sales fee. The transportation fee can be calculated according to the distance of highway, railway and waterway transportation and the freight rate stipulated by the relevant departments. However, when participating in the calculation of the above formula, the concentrate sales fee should be converted into the raw ore sales fee.
② Mining dilution rate: Due to different geological conditions, different mining methods and different management levels, the mining dilution rate is different. At present, the dilution rate of pit mining in China is generally 10-25%.
③ Mineral processing recovery rate: select indicators according to the test results of ore washability in specific mining areas.
④ Ton price of metal contained in concentrate: it is the current price stipulated by the state, and its pricing unit is tons of metal contained in concentrate.
Because in the formula, the concentrate sales fee needs to be converted into the raw ore sales fee, and the quantity of concentrate is difficult to determine when the grade has not been determined, so it is difficult to convert and distribute. In order to avoid this problem, the following formula can be used instead. In the following formula, the total cost of one ton of ore does not include the conversion fee allocated by the concentrate sales fee.
The concentrate price in the formula needs to be converted. If zinc concentrate contains 55% Zn, the price of metal content per ton is 10 10 yuan, and the price per ton of concentrate is 10 10 yuan× 55% = 555.5 yuan.
In the formula, the sales cost of concentrate is the sales cost per ton of concentrate, and the cost converted into raw ore is not shared.
In the geological evaluation of each specific mining area, the parameters of the specific mining area can be substituted into the above formula to find out the industrial grade of the mining area, thus evaluating the economic significance of the mining area.
According to the calculation of general technical and economic indicators of lead-zinc mine production in China and the actual production data of some mines, the industrial grade of mining areas is generally required, that is, sulfide ore Pb+Zn 4-5%, mixed ore Pb+Zn 6-8% and oxide ore Pb+Zn 8- 10%. The data can also be used as a reference for economic evaluation of the deposit and considering whether the mining area should be transferred to detailed investigation. And the mining area around the production mine, this data can be reduced appropriately. In the future, considering the continuous improvement of mine management and mining technology, the reference data of industrial grade in the above mining areas will inevitably decrease gradually.
There are other methods to calculate the industrial grade of mining areas besides the "price method", but most of them are more complicated than the above methods. Considering the limited information available in the exploration stage, it is not listed one by one. If necessary, you can consult the industrial design department.