AM & BM mullite clay bricks for dry quenching

AM & BM mullite clay bricks for dry quenching

Aiming at the damage of the CDQ oven body, synthesizing various problems existing in the current domestic CDQ production process, it is found that the main damaged part of the CDQ oven body is the corbel brick in the chute area. The damage mechanism of vulnerable parts is as follows.

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Refractories for dry quenching coke ovens

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Damage mechanism of refractory materials used in CDQ coke oven chute area

In view of the damage of the CDQ oven body, based on the various problems existing in the current domestic CDQ production process, it is found that the main damaged part of the CDQ oven body is the corbel brick in the chute area. The damage mechanism of vulnerable parts is as follows.

1 Structural reasons

Through theoretical calculation and analysis, Lu Yiguo et al. pointed out that the damage to the refractory material in the chute area is dominated by structural stress. The ramp corbel is affected by the pressure of the upper ring beam and the weight of the ring air duct, the friction force of the coke moving downward, the scouring force of the coke powder entrained by the upward circulating gas, and the internal force of the expansion and contraction of the material itself. When the furnace body heats up, the annular air duct and the ring beam expand outward along the diameter direction, while the corbel expands and changes toward the furnace core, forming a shear force; due to the temperature change of the coke and circulating gas, the diameter of the ring beam basically does not change under the action of no external force. Change, only the brick joints of the ring beam are pulled apart. The temperature of coke, circulating gas and refractory material continuously changes along the height of the chute, especially the temperature in the lower part of the chute area changes between 300 and 700 ℃, which will cause great thermal stress, resulting in cracking and peeling of the refractory material, etc. . When the corbel is cold-shrinked, the pressure of the upper masonry causes the brick at the head to be pulled off, and at the same time, the brick is cracked, eroded and damaged due to the influence of the temperature change of coke and circulating gas.

2 Causes of chemical attack

While being damaged by structural stress, the medium in the furnace has a chemical effect on the refractory material, which mainly includes the following aspects:

(1) The CO in the circulating gas undergoes a chemical reaction (2CO→CO₂+C) in the range of 300~600℃, and the separated free carbon has an erosive effect on the refractory material, which will cause the refractory brick masonry to crack or be completely damaged.

(2) Domestic mullite bricks and silicon carbide bricks generally contain Fe₂O₃, and the lining bricks have been eroded by CO, H₂ and other gases for a long time at high temperature, and are easily reacted with Fe₂O₃ in a strong reducing atmosphere. The reaction equation is:

3CO+Fe₂O₃→2Fe+3CO₂

H2+Fe₂O₃→3H₂O+2Fe。

The generated CO₂(g), H₂O(g) and the hot coke generate strong reducing gases CO and H₂ at high temperature, which further accelerates the generation of free carbon.

(3) Alkali attack. In Ukraine's research on CDQ lining bricks, it was found that the surface of coke is enriched with certain alkali metals, and a small amount of potassium sodium or potassium sodium salt vapor can be generated above 750 ℃, which will decompose the mullite crystal phase structure. Low-melting substances such as hexagonal potassium sodium nepheline that form a brittle structure cause the surface layer of the product to fall off in layers, and the wear is accelerated under the action of coke and airflow.

(4) Chemical erosion and damage caused by chemical interaction between various harmful media and furnace lining materials.

Physical and chemical indicators

Main physical and chemical performance index requirements of BM type bricks

Project	Index
Al₂0₃，%≥	55
Fe₂0₃，≤	1.3
Refractoriness，°C ≥	1770
Normal temperature compressive strength，MPa ≥	85
Bulk density，g/cm³≥	2.4
Apparent porosity，% ≤	19
Under load softening temperature(O. 2MPa, T₂)，°C ≥	1500
High temperature flexural strength，MPa 1100°C * 0. 5h ≥	20
Reburn line changes，% 1300°C * 2h	+0.1~-0.5
Normal temperature compressive strength，MPa ≥	85
Thermal shock stability(1100°Cwater-cooled)，times ≥	10
Abrasion resistance≤CC	12

Main physical and chemical indicators of AM bricks

Project	Index
Al₂0₃，%≥	55
Fe₂0₃，≤	1.3
Refractoriness，°C ≥	1770
Normal temperature compressive strength，MPa ≥	60
Bulk density，g/cm³≥	2.35
Apparent porosity，% ≤	120
Under load softening temperature(O. 2MPa, T₂)，°C ≥	1500
High temperature flexural strength，MPa 1100°C * 0. 5h ≥	15
Thermal shock stability(1100°Cwater-cooled)，times ≥	25
Reburn line changes，% 1300°C * 2h	+0.1~-0.5

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Clay bricks coking Refractory

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AM & BM mullite clay bricks for dry quenching

Main physical and chemical performance index requirements of BM type bricks

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