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Kiln car is an important part of tunnel kiln, which constitutes the bottom system of the whole kiln. In tunnel kiln, the sealing quality of kiln bottom system seriously affects its working effect. When the air leakage is serious, the temperature difference in the kiln will increase, the roasting time will be prolonged, and the fuel consumption will increase.

When the kiln is working normally, it is difficult to estimate the role of the kiln car. However, if we do not pay enough attention to the problem of kiln car, it will cause undue loss of production. Due to air leakage, there is a large temperature difference in the pre-tropical zone, which extends the drying cycle of the product. Due to air leakage, the products under the billet can not be heated and cooled normally, and the phenomenon of raw burning will be very serious. Because the high temperature gas in the kiln leaks under the kiln car in the positive pressure belt, the kiln car bearing is easy to be burned out.

The working condition of metal parts and refractory lining of kiln car is very complicated. They are subject to the periodic action of high temperatures and are subjected to great mechanical stress. In rapid roasting, a kiln car has to complete a cycle every day and night, and the heating and cooling rate can often reach 100 ° C ~150 ° C per hour. In this case, the surface of the kiln car lining rises sharply to 1000 ° C or higher, resulting in a great temperature difference in the direction of the lining thickness, resulting in a great thermal stress.

The kiln car material is not only under the condition of volume stress, but also under the external force. When pushing, the metal frame and partial kiln car lining are subjected to huge forces. The local displacement caused by transverse thermal expansion or contraction makes the kiln car stressed. Due to the collapse accident of sand or burnt products or billets blocking the track, the kiln car is also in a complex stress situation, which can be explained by the above, the design and production of the car should not be paid attention to, and the best materials should be used under possible conditions.

Kiln car frame system should be very strong, not easy to deformation. Kiln car lining material should have sufficient refractoriness and small coefficient of thermal expansion. In addition, the lining should have a high compressive strength and should be subjected to thermal shock.

Usually, the frame of the tunnel kiln car is made of section steel, and the lower part is the axle and wheels. The frame is covered with insulation layer and refractory lining brick. There are inserts on both sides of the kiln car - sand sealing plates to prevent air leakage on both sides.

In order to strictly separate the air under the kiln and the kiln car, so that the hot gas in the kiln does not leak into the car, or the cold air under the kiln car is sucked into the kiln car, so the kiln car joint is constructed in this way: the upper lining brick of the kiln car is extended at one end, and the other end is indented. When the kiln car enters the kiln, the protruding part of one kiln car overlaps with the recessed part of the adjacent kiln car. Zigzag sealing between kiln car and kiln car increases airflow resistance and reduces air leakage.

The edge of both ends of the lining bricks on the kiln car should be laid flat like all lining bricks, so that the joint is accurate and tight, and the surface of the lining bricks is straight.

The role of kiln car lining bricks is to protect the kiln car from high temperature damage in the kiln. Therefore, it is required to use fire-resistant and heat-insulating materials for masonry, and it is required that the lining bricks have better air tightness.

The lining bricks of tunnel kiln car are made of refractory clay brick and heat-resistant concrete. From the brick specifications, there are special-shaped refractory clay bricks and standard refractory clay bricks.

In order to meet the use requirements and reduce the one-time investment, the lining bricks around the kiln car are made of special-shaped refractory clay bricks, the top layer is made of standard refractory clay bricks, and the middle layer is made of 2-3 ordinary clay bricks. The thickness of brick masonry is generally about 300㎜.

There are generally 2 expansion joints in the lining brick masonry, which are distributed in the vertical center of the kiln car, and the seam width is 10㎜. The ash joint of the brick masonry requires about 3㎜ to 5㎜.

The commonly used insulation materials for bedding are asbestos - clay or diatomaceous earth - cement.

Asbestos-clay composition (%) : soft fireclay (30-35)∶ asbestos 20∶ slag (40-45).

Diatomite - Cement composition (%) : diatomite (75) : 400# cement (25).

Asbestos clay material, soft fireclay and slag must be ground fine, the maximum particle size is not more than 3㎜.