1. Selection of refractory components for side-blown furnaces
From the working principle of the side-blown furnace, it can be known that the hearth and slag chamber of the side-blown furnace will be eroded and scoured by the melt, and the flue will be eroded by a small amount of slag splashing and dust-laden flue gas. Under normal furnace conditions, the temperature of these three areas is 1100~1300℃; but in the case of unstable furnace conditions, the temperature of these three areas can reach above 1400℃. In the actual production process, the side-blown furnace needs to be supplied with oxygen-enriched primary air and secondary air, and a strong oxidizing atmosphere is formed locally, so the side-blown furnace should choose refractory bricks that are not easily oxidized. The main components of slag are FeO, SiO2, CaO, Al2O3. High alumina refractories and silica refractories will participate in slag making, so they are not suitable for side blowing furnaces. Therefore, the refractory material for side-blown furnace needs to have the characteristics of high temperature resistance, strong thermal stability, high load deformation temperature, high compressive strength, oxidation resistance, and no participation in slagging. Combined with the characteristics of refractory materials, magnesia refractory materials should be selected for side-blown furnaces. The increase of Cr2O3 content in magnesia refractory can improve the slag corrosion resistance of the material. Therefore, magnesia-chromium refractories with higher Cr2O3 content are selected for the refractory bricks of the side-blown furnace hearth, slag chamber and flue.
Fused aluminum chrome sand
2. Selection of refractory combination form for side-blown furnace
According to the different bonding forms of magnesia-chromium refractories, it includes direct-bonding, semi-rebonding, fused-rebonding and other magnesia-chromium refractories. Among them, the direct-bonded magnesia-chromium refractory is made of high-purity sintered magnesia and chromite as raw materials, and the fused magnesia and chrome ore are directly sintered; the semi-rebonded magnesia-chromium refractory is made of fused magnesia-chrome sand. It is a kind of grain, which is made by adding part of chrome ore and magnesia or sintering synthetic magnesia-chromium material as fine powder, and sintering at high temperature; electro-melting combined with magnesia-chromium refractory material is made by electro-melting chrome ore and fused magnesia in an electric furnace. Fused magnesia-chromium sand is obtained, and then sintered at high temperature. See Table 1 for the comparison of properties of 3 types of magnesia-chromium refractory bricks.
Table 13 Comparison of properties of magnesia-chromium refractories
It can be seen from Table 1 that the performance of electrofusion recombined magnesia-chromium refractory is better, and the performance of semi-recombined magnesia-chromium refractory is second. Combined with the loss of refractory materials in the hearth, slag chamber and flue areas in the side-blown furnace, semi-recombination, electrofusion recombination, and direct-combination magnesia-chromium refractories are used in the hearth, slag chamber, and flue areas respectively.
3. Chemical composition and physical properties of refractory materials for side-blown furnaces
The chemical composition and physical properties of the above three types of magnesia-chromium refractories,
Table 23 Chemical composition and physical properties of magnesium-chromium refractories
The service life of refractory materials directly affects the production rate and production cost. It is necessary to select the appropriate type and combination of refractory materials according to the working environment in different regions. This is an effective means to improve the service life of refractory materials.