1. Blast furnace
Blast furnaces are widely used in the rough smelting process of copper, lead, lead-zinc, antimony and other metals.
The blast furnace is composed of furnace roof, furnace body, main bed (also called throat), hearth, tuyere device and so on.
Solid materials such as smelting charge (concentrate, sintered ore, etc.), coke, flux, and reverse material are added from the top of the furnace, and the high-pressure air blown into the tuyere device on the side of the lower part of the furnace will react with the materials going down during the process of melting, oxidizing, reducing, etc. to complete the smelting process. At present, most of them are closed furnace roofs, and the furnace body is a full water jacket. Refractory materials are only used in the throat and hearth. Because the slag is alkaline slag, the throat part is mainly made of magnesia bricks, magnesia-chrome bricks, and aluminum-chrome bricks;
2. Reverberatory furnace
The operating temperature of the reverberatory furnace head is generally 1400-1500°C, and the flue gas temperature is generally 1150-1200°C. From bottom to top, the bottom of the furnace is asbestos board, insulation brick layer, clay brick layer, magnesia-alumina brick or magnesia brick layer. The furnace wall is mostly made of magnesia-aluminum bricks or magnesia bricks, and some important parts are built with magnesia-chrome bricks to prolong the service life, and the outer walls are generally made of clay bricks. The roof of the furnace adopts a suspended roof, and the roof of a small reverberatory furnace adopts a brick arch, and the material of the arch is magnesia-alumina brick.
Most of the lead (copper) smelting factories in my country adopt the traditional sintering-blast furnace smelting process, because it has the following defects:
a. During the sintering process, sulfur combustion is not sufficient, and the ratio of returned materials is high;
b. The content of lead (copper) in blast furnace charge is low;
c. A large amount of smoke pollutes the environment.
Therefore, people have been working hard to explore new processes for smelting lead, the purpose of which is nothing more than two aspects:
1. Use the heat of reaction for smelting;
2. Replace the original multi-step method with a one-step process.
Foreign countries have successfully researched new lead smelting furnaces and new processes such as Isa furnace (Osmet furnace), Kaldor furnace, QSL method, Kifset method, Xiluo method, and oxygen-enriched lead smelting furnace.
3. Isa Furnace (Osmet Furnace)
The Aisa furnace body is a simple vertical cylindrical shape, and its technical core is the use of a submerged top-blown combustion lance. Based on many years of small-scale experimental research, the Aisa Smelter built a lead smelting Aisa furnace with a processing capacity of 5T/H in 1983.
Melting pool temperature 1170~1200°C Isa smelting process: the furnace body is a vertical cylinder with a refractory lining and the spray gun is inserted into the furnace from the center of the furnace top. The head of the spray gun is immersed in the slag layer of the molten pool. The air or oxygen-enriched air required for the smelting process is sent to the liquid layer below the slag surface through the spray gun to form a molten pool in a strongly agitated state. Melting produces slag and lead (copper).
Because the characteristic of the lead (copper) smelting process of the Isa furnace is that the material mixing time is very short, and the molten metal, slag, and acid gas are strongly stirred in the furnace, which also determines that its working environment is much harsher than the traditional lead (copper) smelting method:
a. The strong erosion of the refractory lining by molten lead (copper), slag and acid gas;
b. Chemical erosion and penetration of the refractory lining by guns;
c. Thermal stress damage.
Therefore, the refractory lining of the lead (copper) smelting furnace of Aisa furnace must have the following excellent performances in order to achieve the purpose of long life, high efficiency and low consumption of the kiln:
a. It has high compressive strength at room temperature and high temperature, and low porosity to resist the erosion of materials, molten metal and slag;
b. Made of high-quality and high-purity raw materials, there are very few low-melting substances in the product, which can effectively resist the deterioration and damage caused by the chemical reaction between the environment and the furnace lining and improve the permeability resistance;
c. It has high-quality thermal shock stability and is subject to thermal stress (slight stress damage caused by temperature changes).
4. Kaldor Furnace
The main factors of damage to the refractory materials used in the Kaldor furnace and the requirements for the refractory materials are the same as those of the Isa furnace (Osmet furnace).
The Kaldor furnace is also called oxygen oblique-blown converter. Because the furnace body is tilted and rotated, the contact between liquid metal and liquid slag is increased, and the reaction efficiency is improved. Due to the rotation of the furnace body, the furnace body is evenly heated and eroded, which is beneficial to prolong the life of the furnace.
Because oxygen is used, smelting and blowing are carried out in the same furnace, so the smelting process is strengthened, the process is shortened, and the concentration of SO2 in the flue gas is increased.
Correct selection of the shape and size of the furnace chamber is very important for the smooth progress of the chemical reaction in the smelting process of the Kaldor furnace, the reduction of splashing, the reduction of furnace bottom erosion, and the convenience of manufacture and installation.
The blowing is carried out at a high temperature of about 1100-1300°C, so in order to ensure a certain furnace life, it is necessary to choose a reasonable furnace lining material and determine a strict masonry method.
In the design of the lining, refractory materials of different thicknesses and materials should be selected according to the working environment and main erosion of each part to achieve the most reasonable configuration and reduce costs; however, considering that the average erosion rate of the Kaldor furnace is relatively fast (the service life is 2-3 months), and for the standardization and convenience of on-site masonry management and the trend of international standardization, the design of the same thickness and material is adopted, and the brick type is reduced. If the buyer has other requirements, it can be designed according to the buyer’s requirements.
5. Oxygen bottom blowing furnace
1. QLS method
The QLS method completes the oxidation and reduction reactions in the same reactor, and the reaction process is actually divided into two steps. Whether the design configuration of the inner lining is reasonable or not is directly related to the life of the furnace; the design configuration of the inner lining includes two aspects: one is to determine a reasonable structure and size; the other is to correctly select refractory materials. The QLS method is only available in silver in my country. The thickness of the furnace lining is 350mm. The upper part of the molten pool is made of fused semi-rebonded magnesia-chrome bricks; the bottom of the molten pool is made of fused and rebonded magnesia-chrome bricks LDMGe-26.
2. Bottom-blown oxygen-enriched lead smelting furnace
Oxygen bottom-blown oxygen-enriched lead smelting furnace is a horizontal cylindrical reaction furnace. The upper part of the molten pool is made of directly bonded magnesia-chrome brick LZMGe-18; the bottom of the molten pool is made of fused semi-rebonded magnesia-chrome brick LDMGe-18. Or all use fused semi-rebonded magnesia-chrome bricks LDMGe-18. The total consumption is about 160 tons.
6. volatilization kiln
The volatilization kiln is a rotary kiln for processing leaching slag and recovering valuable metals such as Zn, Pb, In, Ge, etc.
The characteristic of the volatilization kiln is that the masonry of the kiln rotates with the kiln shell at high temperature, and is in a state of vibration for a long time. At the same time, it also bears the wear and impact of the furnace charge; the damage of the refractory material is mainly manifested as:
(1) Erosion of molten slag and metal.
(2) Mechanical wear.
(3) Due to high temperature, the temperature in the intermittent reaction zone in the kiln is as high as 1300-1500 °C.
Therefore, aluminum-chrome slag bricks or magnesium-aluminum-chrome bricks are mainly used in the intermittent reaction zone in the kiln to achieve the purpose of prolonging the service life of the kiln lining.
The characteristics of magnesia aluminum chrome bricks are:
One is to add large-grain pre-synthesized spinel materials during production, and use the expansion inconsistency of various minerals at high temperatures to cause micro-cracks inside, thereby improving the thermal shock stability of the product;
The second is that chromium ore contains Fe2O3, and Fe2O3 diffuses into MgO, which enhances the direct combination of periclase and magnesium aluminum spinel, promotes the combination between particles and the matrix, and improves the high temperature strength of the material;
The third is to add chromite, in which Cr2O3 forms continuous solid solution with Al2O3 and MgO, which improves the density and wear resistance of the material.
7. Tilting furnace
In order to process rough copper, Guiye introduced the patented technology of tilting furnace from MAERZ, Germany, including tilting furnace body, combustion system, ingot casting system, waste heat boiler, dust collection system and other auxiliary facilities.
The tilting furnace has the characteristics of reverberatory furnace feeding and slag removal, and the rotary anode furnace can change the furnace position according to different operation cycles. It has a high degree of mechanization and automation (hydraulic equipment is used for tilting, and a flexible and fast special feeding machine is used for feeding), high combustion efficiency, and low labor intensity for workers. Guiye’s 350-ton tilting furnace is currently the largest model, capable of processing materials containing 100,000 tons of copper per year. The refractory material used is fused rebonded magnesia-chrome brick or fused semi-rebonded magnesia-chrome brick, with a Cr2O3 content of 18 or more.