Modern Technology Coal Natural Gas Diesel Heavy Oil Fire Clay Brick Tunnel Kiln

Technical Parameters:

Elimination of product defects of sintered brick in tunnel kiln:

No matter how good the kiln is, the sintered bricks will have various defects if they are not handled properly.

1. Cracks: In the process of firing bricks and tiles in the kiln, cracks or net-like cracks are prone to occur. There is also a kind of fine cracks called hair-like cracks. Fracture and net-like cracks are not dry, the strength of the green body is low, the preheating temperature is too rapid, the temperature inside and outside the body is very different, and the evaporation rate of water inside and outside the body is very different, which inevitably damages the structure of the green body. Commonly known as "burst."

Solution: Extend the preheating time and raise the gate appropriately, especially if the gate cannot be raised too high, to avoid excessively high temperature in the kiln at the entrance of the car. In addition, the residual moisture of the bricks entering the kiln should be controlled within 6%. The appearance of fractures and reticular cracks is extremely important. Hair-like cracks are caused by too rapid cooling during baking, which mainly prolongs the holding time.

2. Mute sound: The main reason is that the wet billet is preheated too quickly, and the temperature rises quickly without sufficient drying, forming internal cracks. The dried bricks are stored in a humid atmosphere or are subjected to the adverse effects of the smoke from the pre-heating zone in the kiln to regain moisture. The moisture contained in the bricks that have passed the winter is subject to the alternating effect of freezing and thawing, and the temperature of the burned products is too fast and cold, etc., which are the reasons for the mute sintered bricks. Only by eliminating abnormal operations can the above-mentioned defects be eliminated.

 3. Black leg bricks: Kang leg bricks are piled up by unburned coal and slag, forming a surface with wavy blue and black markings, commonly known as "black leg bricks". For fuel ash content, choose a higher Kang leg code method , Properly raise the gate (close to the burning zone) and strengthen the bottom fire. For example, when adding coal, it should be added frequently to make the fuel fully burned. It is also possible to increase the internal combustion of the bricks and reduce the black-legged bricks.

4. Embossing: The so-called embossing is the embossing of blue or cyan on the overlap of bricks and bricks (on the strip surface). With the promotion of internal combustion bricks, embossing is more and more common, and bricks and bricks overlap. Because of the lack of oxygen absorbed by internal fuel combustion, it is in a reducing atmosphere, where the iron oxide in the clay is reduced to FeO or Fe3O4, so the embossing is blue or cyan.

And because these low-valent iron oxides have a strong combustion-supporting effect on clay, when calcining, the amount of liquid phase at the imprint is higher than other parts, causing the part to shrink and deform after baking. The flowers appear concave pits.

The main solution to eliminate or reduce the embossing phenomenon: choose an appropriate code or change the shape of the blank. Minimize the overlapping area of the noodles and the top surface as much as possible, extend the firing cycle appropriately, make the fuel burn as completely as possible, and ensure a sufficient oxidizing atmosphere.

 5. "Bread bricks": Because the bricks heat up too fast, the surface of the bricks becomes vitrified sharply, and the surface of the bricks becomes solid and compact, but the reactions that generate gas in the bricks have not yet ended, and the generated gas cannot escape through the high-viscosity melt. It causes significant expansion of the interior of the green body, deforming the brick and becoming a "bread brick".

At this time, it is necessary to appropriately reduce the amount of fuel blended, control the burning speed, and grasp the appropriate excess air coefficient, which can effectively prevent the production of "bread bricks". Of course, the hollow rate of bricks can be increased, which is also a reliable way to avoid the production of "bread bricks".

6. "Lime burst" exists in the sintered bricks. The lime particles are digested and expanded under the action of water vapor and carbon dioxide in the atmosphere, causing the surface of the brick to peel off. This phenomenon is called "lime burst". Crumb stone containing limestone is prone to "lime burst".

Sieving and fine crushing are effective to remove stone particles with a material diameter of 1mm or more. With sufficient high temperature, sufficient holding time, and reducing atmosphere, the stone particles in the brick can be sintered without being harmful.