Refractory for coke oven

The coke oven is the basic equipment of the coking plant. It is a kind of thermal equipment with complex structure and continuous production. It is mainly composed of combustor, carbonization chamber, regenerator chamber, furnace top, ramp, small flue, etc. It is used to heat coal to 950~1100℃ in isolation from the air, and obtain coke and other by-products through dry distillation.

At present, the life of a coke oven is generally 25~30 years, and the refractory materials used are mainly silicon brick, clay brick and high aluminum brick. The environmental conditions of each part of the coke oven and the requirements for refractories are as follows.

(1) Partition wall between carbonization chamber and combustion chamber

The partition wall serves to transfer heat and insulate the furnace gas and support the load. The coking temperature of coke is generally 950~1050℃. In order to ensure coking, the surface temperature of one side of the coking chamber of the coke oven partition should be heated to 1100~1250℃, while the surface temperature of the rear wall after coke is released and cold coal is added drops sharply to about 700℃, while the temperature on one side of the combustion chamber fluctuates between 1200~1450℃. The partition wall on one side of the carbonization chamber is worn by pushing; Since the coal distillation and coking process is carried out under the condition of isolating air, it is required that the air tightness of the partition wall should be good, the air permeability should be tight at high temperature, and no shrinkage deformation should occur. The products should be of regular shape and accurate size, so as to ensure that the masonry joints are small and will not cause cracking. In the coking chamber, water is discharged in the process of coking, and the combustion products of the combustion chamber gas contain a small amount of water. At the same time, due to the chemical erosion of the salt in coal, the decomposition of gas and the deposition of carbon, the structure and performance of the partition may be damaged and the strength decreases.

Based on the above characteristics, almost all coke ovens in the world are made of silicon brick for the partition refractory of carbonization chamber and combustion chamber. Compared with other refractory materials, the volume change and thermal conductivity change less in the range of 700~1450℃, its high temperature strength, load softening temperature and refractory-similar (1620~1660℃), wear resistance, not easy hydration. With the needs of large scale coke oven and intensive production, silicon carbide refractory with high thermal conductivity, volume stability and high temperature strength can also be used. But the price is expensive, in oxidizing atmosphere easy oxidation damage, so it is seldom used at present. The silicon brick with high density and high thermal conductivity mixed with metal oxide (CU2O, TiO2) can reduce the thickness of partition wall, strengthen the heat transfer, improve the productivity of coke oven, and improve the service life of furnace.

(2) Refractory for other parts

The bottom of the coking chamber not only bears the weight of coal or coke, but also suffers from friction during coke pushing process, which is easy to wear and destroy. The top of the carbonization chamber is subjected to dynamic and static loads of the upper covering layer and the coal feeder. Therefore, should choose a high temperature strength, wear - resistant refractory. Usually, because its working conditions and requirements are similar to other parts of the carbonization chamber, it still uses silicon brick.

The furnace head at both ends of the carbonization chamber, due to the sudden change of temperature when the furnace door opens, drops from 1000℃ to below 500℃, exceeding the temperature limit of stable volume of silicon brick, so the furnace head should choose high aluminum products with good thermal shock resistance and high softening temperature under load. At present, high quality high aluminum brick, silica wire brick or andalusite brick are mainly used for masonry.

Ramp: The ramp connects the combustion chamber and the regenerator chamber, which requires the material to resist thermal stress and the brick structure to be stable. Clay brick is used in small coke oven, while silicon brick is generally used in large coke oven.

Regenerator: the side wall has large temperature difference between hot and cold alternately. High quality clay brick is adopted. Some in order to maintain integrity, also use silicon brick, the outside with clay brick protection. Regenerator latticed brick, usually made of clay.