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Analysis of Damage Mechanism of Carbon Brick and Graphite Brick Applied on Blast Furnace
Dec 19, 2018

As the blast furnace smelting efficiency increases, the stress on the refractory lining is increased, and a comprehensive process is embodied in the blast furnace bottom and the hearth lining, and is composed of a combination of thermochemical erosion and thermomechanical erosion. Can be summarized as follows:

(1) Dissolution of carbon/graphite bricks in molten iron.

The carbon entering the solution dissolves the carbon/graphite bricks in the carbon-saturated molten iron.

(2) Metal penetration.

The penetration of molten iron will change the physical properties (indicators) of carbon/graphite bricks.

(3) Zinc and alkali metal deposition.

Cracks are caused by the formation of deposited compounds. When the blast furnace is shut down, the deposited ZnO reacts with the carbon brick to form 2ZnO·SiO2 or zinc aluminate to cause damage to the brick; and the potassium oxide deposit migrates to the temperature range of 900°C in the carbon/graphite brick to react with carbon. It is accompanied by an increase in volume, which leads to the destruction of carbon/graphite bricks; further deposition of potassium, such as the formation of potassium carbide compounds such as KC8, KC24 and KC60, causes the carbon/graphite bricks to peel off and decompose.

(4) The flow of molten product, which leads to an increase in mass transfer and heat transfer, and loss of carbon material on the carbon/graphite brick surface.

(5) The thermal stress caused by the pressure existing in the furnace, the crack formed by the unstable heat flow in the lining causes the carbon/graphite brick to peel off.

(6) The oxidation of carbon/graphite brick by water vapor causes carbon/graphite brick loss.

The mechanisms of these damages are not individual, but overlap and reinforce each other. In addition, local damage to the blast furnace carbonaceous lining is also an important mechanism. Therefore, in order to prevent the uneconomical damage due to the damage of individual components, the increase in production leads to high erosion of the lower portion of the blast furnace, and strong chemical attack such as slag and alkali vapor, so it is desirable to use mechanical, chemical and thermal erosion in various parts of the blast furnace. The damaged refractory material is in particular a carbon/graphite refractory material.

The blast furnace hearth is the most critical part, which is the decisive factor for the length of life of the left and right blast furnaces. The typical furnace erosion is shown in Figure 1. It shows that this kind of "foot-like" or "bowl shape" at the corner of the hearth The turbidity loss in the lower part of the furnace wall and the formation of the vulnerable layer of the furnace wall. The cause of the blast furnace ending the furnace prematurely. In order to extend the life of the blast furnace, it is necessary to control the occurrence of two kinds of turbidity.

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