Tobacco enrichment process for low-grade lead-zinc ore
Germanium is not independent for the exploitation of mineral resources, but associated to the non-ferrous metal mineral ore and coal mines, etc., can only be extracted at the same time the main metal recovered from associated metals germanium. Low-grade germanium oxide Guizhou Province is rich in lead zinc ore resources. The geological data indicate that the reserves of lead and zinc in the Guizhou mills are 2015.65 million tons, the reserves of base metals are 178 tons, the average grades of Zn are 4.26%, the Pbs are 2.36%, and the Ge 55g/t; the lead and zinc reserves of the cats and cats mines are 69,100 tons, and the average grade is Zn 8.16. %, Pbl.47 %; The lead and zinc reserves of Zhangkouyu Mine are 70.31 million tons, the grade of Zn is 1.5%~10.54%, and the Pb is 0.12%~1.84%. These mines exist in the form of oxides, which are difficult to beneficiated . At present, the industry uses oxidized ore to make a group, adding a flux (lead slag) to smelt in a blast furnace, and the slag is smelted by a furnace to produce a cerium-rich zinc-lead concentrate-smoke dust as a next step of the wet method. Processing raw materials for recovering valuable metals such as zinc, lead, antimony and silver . 
First, the smelting process
(1) Chemical composition of raw materials, fuels and products
The raw materials in the enrichment process of fire are mainly ore, and the flux is lead slag and a small amount of limestone . The blast furnace uses coke as a fuel and a reducing agent, and the pulverizing furnace uses pulverized coal as a fuel and a reducing agent. The main components of ore, lead slag and products are listed in the table below. The coke contains fixed carbon of 68% to 73%, ash of 12% to 25%, volatile matter of 2.5% to 4.0%, moisture of 2% to 8%, and calorific value of 25 100～27 200kJ/kg; raw coal contains fixed carbon 60%～68%, ash 15%～20%, volatile content 14%～25%, moisture<510%, calorific value 26 780～29 200kJ/kg.
The proportion of the blast furnace into the furnace is agglomerate: lead slag: coke = 4:1:0.9, wherein the agglomerate contains 7% of reduced coal. Under normal circumstances, the blast furnace slag rate is about 73%, the smelting furnace slag rate is about 89%, and the total slag rate is 63% to 67%.
(2) Principles of the smelting process
The process of enriching lead oxide zinc ore, including blast furnace ore, smelting and smelting furnace blowing, the reduction reaction in the process is generally a heterogeneous reaction and the process becomes complicated. The main reactions occur as follows:
Reaction (1) is a gasification reaction of carbon to provide a carbon monoxide reducing agent to the system. The reactions (2) to (4) are reversible reactions, which are carried out in the forward direction at a high temperature and are carried out in the reverse direction at a low temperature. The reaction (7) is the reaction of the iron in the blast furnace, and the reaction (8) is the reaction to eliminate and prevent the iron accumulation in the furnace. It is shown that when the ZnO content in the molten slag exceeds 3%, the iron in the blast furnace can be effectively prevented. The reduced products zinc, lead, lead oxide and cerium oxide have high vapor pressure or sublimation pressure at high temperature, and enter the flue gas in a gaseous state during the smelting and enrichment process. (3) Smelting process
A factory in Guizhou uses a blast furnace smelting process with a smelting and enriching process of a fuming furnace to treat low-grade lead-zinc ore. The essence of the smouldering process is that a mixture of air and pulverized coal is introduced into the molten slag for reduction blowing. At high temperatures, metals such as lead, zinc, antimony, and silver in the slag are volatilized in the form of metals, lead oxide, or cerium oxide, and are concentrated in soot to be recovered. The process is briefly described as follows:
After the ore is dried, it is blended with 7% of reduced coal to make agglomerate; the raw coal is dried, ball milled, pneumatically graded and transported to obtain pulverized coal for use in the flue gasifier. Each batch of material is added to the blast furnace in the order of coke, lead slag (flux) and agglomerate. The slag flows directly into the smelting furnace through the chute to blow the blast furnace, and the flue gas of the smelting furnace is cooled by the water-cooled tobacco lane and the surface cooler. Enter the bag filter to collect dust, that is, get the enriched product - smog.
The blast furnace is operated with a low column and the height of the column is 1.8 to 2.2 m. Therefore, it has the dual action of volatile metal and molten mineral at a high temperature of 1 200 ~ 1 280 °C, the volatilization rate of zinc and antimony is more than 0%, and the lead is more than 70%. The blast furnace flue gas enters the cooling system, and the molten slag directly flows into the flue gas furnace through the slag chute to be blown. The blast furnace 2 has a bed area of ​​414m. The normal batch materials are: 450kg of coke, 500kg of lead slag, 2 000kg of agglomerate; 40 to 45 times a day.
The grade of the main metal in the blast furnace slag is (%): Zn 4.3 to 4.5, Pb 0.82 to 0.84, and Ge 0.0037 to 0.004. When the condition of the blast furnace is not normal, especially when the furnace is filled with iron, the flow performance of the slag is very poor and cannot be blown into the smelting furnace. The slag is directly quenched with water, causing loss of valuable metals. In general, the blast furnace slag rate is about 73%.
Second, the furnace is blown
The purpose of the smelting furnace is to further volatilize the valuable metals in the blast furnace slag. One blast furnace is equipped with two smelting furnaces. The area of ​​each two gasifiers is 1.2m 2 . The blast furnace and the smelting furnace are directly connected by a slag chute, that is, the blast furnace slag directly flows into the smelting furnace. The blowing process uses intermittent operation and two furnaces alternate. The smelting furnace uses pulverized coal as a fuel and a reducing agent to control the motor speed with a thyristor to adjust the amount of pulverized coal to control the furnace temperature and reduce the atmosphere. The working temperature of the smelting furnace is generally 1 100~1 150 °C, the feeding time of each furnace is 10-15 min, the slag discharging time is 5-10 min, and the reduction blowing time is 70-90 min. The thickness of the slag layer is about 0.8 to 0.9 m, the amount of slag per furnace is about 4 tons, and the number of furnaces per day is 9 to 10 furnaces. The slag rate of the smelting furnace is about 89%. The composition of the main metal in the waste slag is (%): Zn l.0 to 1.5, Pb 0.1 to 0.15, and Ge < 0.001.
Third, cooling and dust collection
The high temperature furnace gas (about 1 000 °C) of the blast furnace and the smelting furnace is cooled by the water-cooled tobacco lane, and the temperature is lowered to 300-400 °C. At the same time, zinc, lead, antimony monoxide and the like in the flue gas are simultaneously reoxidized into ZnO, PbO and GeO 2 powders during the cooling process. In order to make the flue gas suitable for bag dust collection, the flue gas cooled by the water-cooled flue gas enters the surface cooler and further cooled to 150-200 °C, and the flue gas temperature is less than 100 °C, and then enters the bag dust collecting system. The filter medium for bag dust collection is glass fiber. The dust collecting device has the advantages of simple structure, simple operation and high dust collecting efficiency, and generally reaches 95% to 98%. The exhaust gas is directly discharged into the atmosphere through the filter bag.
Fourth, vaporization cooling device
The blast furnace and its associated smoulder water jackets are all equipped with vaporized cooling water jackets. The vaporization cooling device is mainly composed of a cooling element, a steam drum, a rising pipe, a descending pipe, a sewage pipe, an upper header, a lower header, and the like. The vaporization cooling requires the use of soft water, and the sewage is discharged regularly according to the regulations, so that the salt content and alkalinity of the steam drum water meet the requirements. The vaporization cooling device has the following characteristics: it can generate steam for production and daily use, improve the heat utilization rate of the furnace; save a lot of industrial water and reduce energy consumption; the steam water system is simple in equipment and easy to operate and maintain.
Fifth, the main equipment
Blast furnace: It is a vertical structure with a small rectangular structure. The bottom of the furnace is made of refractory bricks and is tamed with refractory ramming material. The furnace body is a water jacket. The inner wall of the water jacket is welded by boiler steel plate, and the outer wall is welded by ordinary steel plate. The water jacket is provided with inlet and outlet pipes, sewage pipes, reinforcing ribs and regulating valves. The feeding door is arranged on both sides of the middle part of the furnace body, and the middle part of the furnace body is a slope water jacket. The upper part of the furnace is made of refractory bricks, and the exhaust port is rectangular, which is directly connected to the horizontal combustion chamber. The lower part of the furnace has a ring duct connected to the inlet of the furnace.
Cigarette furnace: It is a rectangular parallelepiped structure with a cast iron piece at the bottom; the furnace body is similar to a blast furnace and is also a water jacket. The inner wall of the water jacket is welded by steel plate, and the outer wall is welded by ordinary steel plate. The water jacket is provided with inlet and outlet pipes, sewage pipes, reinforcing ribs and regulating valves. The water jacket is divided into a tuyere water jacket, a slag injection water jacket, a slag water jacket, a slope water jacket, and a furnace top water jacket. There are also tuyere devices and brackets and so on.
Dust collection equipment: It adopts bag dust collector, which has simple structure and high dust collection efficiency.
Other equipment: drying kiln for drying of raw coal and ore; pelletizing machine for compacting ore; ball mill for producing pulverized coal; air supply and extraction equipment, such as air compressor, leaf fan, Roots blower , centrifugal fans; various types of pumps and other ancillary facilities.
Six main technical indicators
The method of enriching lead-zinc ore by the fuming method is simple, easy to operate, less equipment, small in area and easy to manage. The main metal recovery rate (%): Zn 70, Ge 72, Pb 85; energy consumption per ton of product: electricity consumption 1 600 ~ 1 800 kW · h, coke 2.2 ~ 2.6t, raw coal 1.6 ~ 1.8t; blast furnace The distribution rate of the fuming furnace is generally 75% to 80%.
Seven, related technical issues
The use of the fuming method for the treatment of low-grade lead-zinc ore is a prerequisite for normal production, ensuring that the blast furnace and the fumigrator have a higher rate of compounding to obtain better technical and economic indicators. The physicochemical properties of the molten slag have a great influence on the technical and economic indicators of the whole process. It is not only related to the volatilization rate and recovery rate of lead, zinc and antimony, but also related to the smooth progress of the entire smelting process. Improper batching, it is easy to cause a series of failures in the operation of the blast furnace, such as high melting point of slag, iron deposit in the furnace, wall slag, large slag viscosity, poor fluidity, etc., resulting in a lower rate of blast furnace and smelting furnace, thereby reducing the price of valuable metals. Recovery rate. Studies have shown that the slag composition of the smelting process is (%): CaO 12-16, SiO 2 18-22, FeO 25-30, Al 2 O 3 510, MgO 110. Within this composition range, the melting point and viscosity of the slag are low, and the slag flow performance is good, which is beneficial to improve the fitting rate of the blast furnace and the fuming furnace, thereby improving the technical and economic indicators of the whole process.
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