Refractories for kiln production of carbon materials

The production of carbon materials mainly uses primary and secondary roasting furnaces and graphitization treatment furnaces, collectively known as carbon material roasting furnaces. Solid carbon raw materials, binder and impregnation agents are usually used in the production of carbon materials. Solid carbonaceous raw materials include petroleum coke, asphalt coke, metallurgical coke, anthracite and graphite, etc. Binding agent and impregnation agent include coal tar, coal tar, anthracene oil and synthetic resin, etc.

The first process of carbon production is to calcine the carbon raw materials, that is, the carbon raw materials under the condition of isolated air for high temperature heat treatment (1250~1500℃), in order to remove the water and volatile materials, improve the density of raw materials, mechanical strength and oxidation resistance, improve the electrical conductivity of raw materials.

Carbonaceous raw materials calcined, all kinds of carbon material production, the corresponding use of a variety of different kiln. At present, the calcining furnaces used at home and abroad mainly include pot calcining furnaces, rotary kiln and rotary bed calcining furnaces, electric calcining furnaces and coke ovens.

(1) pot calcining furnace. Due to the different heating methods and fuel used, it can be divided into the following types of furnace. Compared with the downstream calcining furnace, the countercurrent calcining furnace has more burning channels, lengthened calcining zone and increased the calcining time of raw materials in the tank, so as to make full use of the volatiles escaping during calcining and achieve the purpose of high yield.

The maximum temperature of the burner is 1300~1380℃, and the temperature of the burner reaches 1500℃. When loading and discharging carbon material, the tank wall receives mechanical friction and impact. When calcining the masonry of the calcining tank and fire path, the masonry is scoured and penetrated by gas and eroded by low-melting salt slag. Flame insulation heating in pot furnace. This part requires refractories with good thermal conductivity, high softening temperature under load, good mechanical strength and other properties, mostly choose silicon brick to masonry. In the combustion of the gas nozzle by the role of high temperature, should choose high aluminum brick masonry.

(2) electric calcining furnace. The electric calcining furnace has the advantages of simple and compact structure, high degree of automation, easy operation, high calcining temperature, part of the calcined materials have the property of half graphitization, especially suitable for the calcining of anthracite. According to the different power supply modes of electric calcining furnace, it can be divided into single-phase electric calcining furnace and three-phase electric calcining furnace.

The function of the carbon products roasting furnace is to heat all kinds of carbon products formed under high pressure indirectly under the condition of isolated air according to the specified roasting temperature, so as to improve the mechanical strength, electrical conductivity and high temperature resistance of the carbon products.

At present, the kiln used in roasting process in our country include: inverted flame kiln, tunnel kiln, electric roasting furnace and ring roasting furnace, among which the roasting furnace with cover is the most.

Common carbon roasting furnace is continuous and multi-chamber, which is divided into closed type and open type. Closed roasting furnace is divided into two types of furnace type with and without fire well. Each furnace chamber of multi-chamber roasting furnace is generally arranged in two rows side by side, and divided into several specifications according to the number of rooms.

The selection of refractory materials for carbon roaster mainly considers the following factors:

(1) Temperature factor. The masonry of the electrode box heating wall, fire well box and combustion nozzle on the upper part of the closed roasting furnace is subjected to the medium-high temperature action of about 1400℃ and the influence of the temperature change during each roasting cycle.

(2) bear the quality of masonry and products. Therefore, the choice of mechanical strength is higher, the load softening temperature is higher, the thermal shock resistance is better material, the material can be satisfied with high quality clay brick. The furnace cover shall be made of heat-insulating refractory material.

Synthesizing the use conditions of the above carbon calcining furnace, carbon products calcining furnace, graphitization furnace, the refractory materials of masonry carbon kiln to Al₂O₃- SIO ₂ system materials as the main body. Such as silicon brick, clay brick, high aluminum brick varieties. In order to strengthen production, high density silicon brick, magnesium brick and carbonized brick are studied. In some parts, such as coke oven door, because of long-term temperature changes in the environment, the requirements of thermal shock resistance of higher materials, such as high quality clay brick, andalusite brick.