The requirements for non-ferrous metal smelting for refractory materials are relatively complex. It must not only have sufficient high temperature resistance, but also have a certain high temperature strength. The selection of refractory materials has strict requirements. At the same time, the smelting of various non-ferrous metals has its own characteristics, and it is necessary to selectively select refractory materials.
At present, the refractories used in the non-ferrous metal smelting industry in China are roughly divided into two categories: acidic refractories and alkaline refractories. Slightly acidic refractories are mainly trivalent oxides (Al₂O₃-SiO₂ series), mainly including high alumina bricks, mullite bricks, zirconium corundum bricks, etc.; while alkaline refractories are mainly divalent oxides (MgO -Al₂O₃, MgO-Cr₂O₃ series), including magnesia-chrome bricks, magnesia-alumina bricks, magnesia-alumina spinel bricks, etc.
1. Design and application practice of refractory materials in lead metallurgy industry
1) Furnace Bottom Design
After years of practical production experience, for lead smelting, the metallurgical furnaces used include dozens of metallurgical furnaces that process various lead materials, but the refractory lining of metallurgical furnaces mainly uses magnesia-chrome bricks, high-alumina bricks, high-alumina Quality refractory ramming material, etc.
(1) The permanent layer area at the bottom of the furnace
In the design of the furnace lining, each position in the furnace body is different, and the selection of refractory materials also changes accordingly. Taking the fixed horizontal metallurgical furnace body as an example, the furnace bottom generally uses magnesia-chrome bricks, high-alumina bricks, aluminum-chromium spinel, high-alumina ramming materials, magnesia ramming materials, etc., and some use high-strength ramming materials. The anti-seepage ramming material is also composed of Al₂O₃-SiO₂ series, and the content of Al₂O₃ is >75%. The specific gravity of liquid lead is 10.6g/cm³, and the permeability is extremely strong. Therefore, the refractory material at the bottom of the furnace should not only have the function of heat dissipation, but also have a high ability to prevent seepage of lead.
At present, the widely used practice is to first lay high-alumina bricks on the steel plate of the furnace bottom. A layer of refractory material with resistance to lead penetration should be provided on the upper part of the cushion. Currently, magnesium ramming material or high-strength anti-seepage ramming material (high alumina) are used, both of which can act as a barrier. The ratio of magnesia ramming material is: magnesia: magnesium powder = 7:3, with brine, magnesia particle size: 0.2~0.5mm70%, 1.5~3.0mm 30%; the composition of high-strength anti-seepage ramming material It is: high-aluminum aggregates and bone powder of various particle sizes are configured. After baking at high temperature, the aggregates of various particle sizes are expanded and tightly combined to achieve the ideal anti-seepage lead purpose.
It must be noted that after the magnesium and magnesium-chromium ramming materials are rammed, they need to be baked at a low temperature. After baking out the free water, the expansion joints should be filled with fine magnesium powder to ensure the strength and compactness of the ramming layer. sex. The thickness of the ramming material is recommended to be 150~300mm, which is convenient for one-time completion of ramming, and can complete the baking more uniformly, forming an overall layer with better anti-seepage effect.
(2) furnace bottom working layer area
For the selection of refractory materials for the safety layer and working layer of the bottom of the furnace, magnesia-chrome bricks are widely used. Among them, the safety layer can be directly bonded magnesia-chrome bricks, and the working layer is semi-rebonded magnesia-chrome bricks. With the fluctuation of the lead liquid level, the temperature of the bottom of the furnace fluctuates obviously, so the semi-rebonded magnesia-chrome bricks with good thermal shock resistance should be selected. brick. The safety layer and working layer of the furnace bottom are also made of high-alumina bricks. Generally, this furnace type will have a bottom lead layer with a height of ~400mm, so the furnace bottom will not be eroded by slag, and the content of Al₂O₃ can be selected. Not less than 75% High alumina bricks are used as lining bricks for the safety layer and working layer at the bottom of the furnace.
2) The working area in the furnace
The selection of refractory materials in the working area (furnace wall, furnace top) in the furnace is divided into two areas, one is the refractory bricks in the molten pool area (especially the slag line area), and the other is the refractory bricks in the meteorological area.
(1) The molten pool area in the furnace
The refractory bricks in the molten pool area (especially the slag line area) will be eroded and washed by the molten slag. The composition of the lead smelting slag is relatively complex, and the high-alumina refractory material will participate in the slag-forming reaction, so high-alumina refractory bricks are selected. It is not suitable, and magnesia-chromium refractory bricks should be used. At the same time, considering the slag erosion resistance and erosion resistance of refractory bricks, magnesia-chrome bricks with electrofusion and recombination should be selected.
The bricks of this material are superior to semi-recombined magnesia-chrome bricks in slag corrosion resistance. The increase of Cr₂O₃ content can improve the slag corrosion resistance of bricks, so try to choose magnesia-chromium refractory bricks with higher Cr₂O₃ content.
(2) Meteorological area in the furnace
The refractory bricks in the meteorological zone will not be eroded by slag, but only by the splash erosion of a small amount of slag and the erosion of dusty smoke. Therefore, magnesia-chromium refractory bricks with lower Cr₂O₃ can be selected. The magnesia-chrome bricks used in the lead smelting reduction furnace of a domestic factory used direct-bonded magnesia-chrome bricks with high Cr₂O₃ in the early stage of production, and the surface of the magnesia-chrome bricks in the meteorological area was free of metal and slag. The bricks are broken into two sections and the structure is loose. According to the analysis results, it is judged that Fe³﹢ and Fe²﹢ in the refractory bricks are reduced to elemental Fe in a large amount, which leads to the loose structure of the brick body.
Therefore, in the maintenance, the fused recombined magnesia-chrome brick with lower Cr₂O₃ was used (Cr₂O₃ content is 12%). The main reason for this improvement is that the apparent porosity of the fused magnesia-chrome brick is low, and the content of Fe³﹢ and Fe²﹢ in the refractory brick is reduced, so that it is more suitable for the strong reducing atmosphere in the meteorological area and prolongs the service life. After switching to this type of electrofusion combined with magnesia-chrome bricks, the use time has been greatly extended and good results have been achieved.
2. Conclusion
There are many types of furnaces used in the domestic lead smelting industry, and cooling devices are also used in various metallurgical furnaces, which have a good effect on prolonging the service life of metallurgical furnaces. However, from the perspective of the use process, for lead smelting, which has a high degree of superheat, complex raw materials, and lead matte easily corrodes the smelting process of the cooling device, the operation of slag hanging by the cooling device still has certain safety hazards, so the cooling device is lined with internal linings. Having refractory materials is still indispensable. The correct use of refractory materials and cooling devices complement each other and can play a role in mutual protection.
On the basis of the characteristics of the smelting process, the characteristics of smelting materials, and the correct selection and use of refractory materials, to ensure the normal operation of the metallurgical furnace, ensure a reasonable furnace life, and make the enterprise obtain economic benefits, it is also necessary to have a correct and reasonable refractory material design. , including structural design, expansion calculation, and heating and baking of masonry all affect the normal use of refractory materials.
Therefore, on the basis of the existing development, it is necessary to further study and improve refractory materials in terms of erosion resistance, slag corrosion resistance, stress analysis, baking system, etc., which requires refractory material suppliers, design units and The joint efforts of many users can make the refractory material achieve better application effect.
