The requirements for refractory materials in lead smelting are complex. It is necessary to have sufficient high-temperature resistance, certain high-temperature mechanical strength, and good slag erosion resistance, slag and flue gas erosion resistance. Therefore, there are very strict requirements for the selection of refractory materials in the furnace. Therefore, magnesium chrome bricks are mainly selected in its high-temperature working area. The selection of refractory materials in the working area (furnace wall and furnace top) in the furnace cavity of lead smelting furnace is divided into two areas, one is the magnesium chromium brick in the molten pool area (especially the slag line area), and the other is the magnesium chromium brick in the meteorological area.
- Molten pool area in furnace
Refractory bricks in the molten pool area (especially in the slag line area) will be eroded and washed by slag. The composition of lead smelting slag is complex, and high alumina refractory materials will participate in slag forming reaction. Therefore, it is inappropriate to select high alumina refractory bricks, and magnesia chrome refractory bricks should be selected. At the same time, considering the slag corrosion resistance and erosion resistance of refractory bricks, magnesium chromium bricks recombined by electrofusion should be selected. The slag erosion resistance of the brick made of this material is better than that of semi reconstituted magnesia chrome brick. The increase of Cr2O3 content can improve the slag corrosion resistance of bricks. Therefore, magnesium chromium bricks with high Cr2O3 content shall be selected as far as possible.
- Meteorological area in furnace
Refractory bricks in meteorological area will not be eroded by molten slag, but only by a small amount of splashing erosion of melting edge and scouring of dusty flue gas. Therefore, magnesium chromium bricks with low Cr2O3 can be selected.
The magnesia chrome brick used in the lead smelting reduction furnace of a domestic factory uses the directly bonded magnesia chrome brick with high Cr2O3 content in the initial stage of production. There are phenomena such as no metal and slag wrapping on the surface of magnesia chrome brick in the meteorological area, brick breaking into two sections, loose structure and so on. According to the analysis results, it is judged that Fe3 + and Fe2 + in the refractory brick are reduced to elemental Fe in large quantities, resulting in loose brick structure. Therefore, the fused reconstituted magnesia chrome brick with low Cr2O3 content was used in maintenance (Cr2O3 content of S is 12%). The main reason for this improvement is that the apparent porosity of fused reconstituted magnesia chrome brick is low, and the content of Fe3 + and Fe2 + in refractory brick is reduced, so as to better adapt to the strong reducing atmosphere in meteorological area and prolong the service life. After using this type of electrofusion combined with magnesium lattice brick, the service time is greatly prolonged and good results are achieved.
On the basis of smelting process characteristics, smelting material characteristics and correct selection and use of refractory materials, in order to ensure the normal operation of metallurgical furnace, ensure reasonable furnace life and enable the enterprise to obtain economic benefits, there must also be correct and reasonable refractory material design, including structural design, expansion calculation and heating and baking of masonry, which affect the normal use of refractory materials. Therefore, on the basis of the existing development, it is necessary to further study and improve the erosion resistance, slag erosion resistance, stress analysis and baking system of refractories. It requires the joint efforts of refractories suppliers, design units and users to make refractories achieve better application results.