What are the factors of blast furnace bottom damage?

      The working conditions of the furnace bottom are extremely harsh and its durability is a decisive factor in the life of a generation of blast furnaces. The blast furnace bottom is under high temperature and high pressure conditions for a long time. According to the blast furnace bottom breakage condition after shutdown and production bottom temperature inspection shows that the bottom breakage can be divided into two stages: at the beginning of the furnace is the iron infiltration will be brick floating up and form a pan-shaped deep pit, the second stage is the formation of the fusion layer after chemical erosion.

      The cause of the furnace bottom breakage: First, the furnace bottom brick is subjected to liquid slag iron, gas pressure, gravity of the material column 10% ~ 20%, a total of up to (2 ~ 5) × 105Pa / c ㎡; Second, the brick masonry brick joints and cracks. When the iron penetrates into the crevice under high pressure, it cools slowly and solidifies at 1150°C. During the process of condensation, graphite carbon is precipitated, the volume expands, and the crevice is enlarged, so mutual cause and effect, the iron can penetrate very deep. Because the density of iron (7.1g/m³) is much higher than the density of blast furnace clay brick (2.2g/m³), the density of high alumina brick (2.3~3.7g/m³) and the density of carbon brick (1.6g/m³), the brick will float under the action of the hydrostatic pressure of iron.

      When the furnace bottom erosion to a certain depth, the erosion of the slag iron water gradually weakened, the brick lining under the pit in the long-term high temperature and pressure, part of the softening recrystallization, the formation of a layer of fusion layer, its thickness of about 700 ~ 1400mm, small blast furnace is much thinner. Fused layer is a dense organization, brick seam disappears, high capacity weight of the whole, compared with the lower brick not fused, brick is compressed, porosity significantly reduced, bulk density significantly increased, and iron infiltration after the brick thermal conductivity becomes better, enhanced heat dissipation capacity, so that the iron solidification isotherm shifted up (generally 1150 ℃). Because the fusion layer of brick and brick has been sintered into a whole, the pit bottom surface of the iron temperature is also lower, brick seam is no longer a weak link, so the fusion layer can resist iron infiltration. The main cause of damage to the furnace lining into the carbon in the ferrous water will be reduced to silicon dioxide in the brick, and absorbed by the iron.

      The broken bottom of the furnace is generally consistent at home and abroad. The bottom of the erosion line is flat bottom-shaped, erosion depth of 1.5 ~ 2.5m or so. Dangerous area from the bottom of the furnace to the perimeter wall, that is, the center line of the iron mouth below the perimeter wall of the furnace bottom the more down the more serious erosion, the more down the erosion line to the more outward expansion, the formation of garlic head shape, the furnace cylinder and the furnace bottom around the residual charcoal bricks often have a ring to the center of the furnace center line as the center of the sparse brittle layer, some residual brick in the hole, which is due to iron penetration in the brick and generate brittle layer, the inner part of the brittle layer by the iron Take away. In addition, some blast furnace integrated furnace bottom around the charcoal brick and the center of the high alumina brick bite masonry, and high alumina brick expansion rate than the charcoal brick, easy to make the charcoal brick by high alumina brick top up, the gap between the upper and lower layers of the charcoal brick widen, iron infiltration.

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