Production Process of Clay Sintered Brick
Production process of clay sintered brick
Sintered bricks: All bricks used for building load-bearing and non-load-bearing walls made of clay, shale, coal gangue or fly ash as raw materials, which are formed by molding and high-temperature roasting, are called sintered bricks.
According to different raw materials, it is divided into sintered clay brick, sintered fly ash brick, sintered shale brick and so on. Sintered ordinary bricks for sintered bricks with a solid or void ratio of less than 25% are called sintered ordinary bricks.
The production and use of ordinary clay bricks has been more than 3,000 years old in China. Today, ordinary clay bricks still dominate the wall materials used in construction projects. Although ordinary clay bricks have many shortcomings, ordinary clay bricks are still the main wall for a long time in the future, especially in rural areas, due to low price, simple process, mature design and construction technology and people's inertia. One of the body materials.
The main raw material of ordinary clay bricks is silty or sandy clay. The main chemical components are SiO2, Al2O3 and Fe2O3 and crystal water. Due to different geological conditions, a small amount of alkali metal and alkaline earth metal oxide may be contained. The production process of clay bricks mainly includes earth borrowing, sludge making, billeting, drying, and roasting.
In addition to clay, shale, coal gangue, fly ash, etc. can be used as raw materials because their chemical composition is similar to clay. However, because they are less malleable than clay, it is often necessary to add a certain amount of clay to make the bricks meet the plasticity requirements of the blank. In addition, the coal gangue and fly ash in the brick are flammable industrial wastes, containing unburned carbon, and are burned in the body as the brick is fired, thereby saving a large amount of external coal for roasting. This type of brick is also called internal combustion brick or semi-internal combustion brick. The content of impurities in the raw material also has a large influence on the baking temperature of the clay brick and the color of the finished product.
Roasting is a key part of the brick making process. Generally, the calcination temperature is controlled between 900 and 1100 ° C, and the brick is burned to partially melt and sintered. If the baking temperature is too high or the time is too long, it is easy to generate overfire bricks. The characteristics of over-fire bricks are color depth, brittleness, and large deformation. If the baking temperature is too low or the time is insufficient, the underfire brick is easily generated. The characteristics of under-fired bricks are light color, knocking and dumb, low strength, high water absorption and poor durability.
When the brick kiln is roasting, it is an oxidizing atmosphere, and the brick is red due to the formation of ferric oxide (Fe2O3), which is called red brick.
After firing in an oxidizing atmosphere, and then smoldering in a reducing atmosphere, red Fe2O3 is reduced to blue-gray ferrous oxide (FeO), which is called blue brick. The green brick is generally denser than the red brick, alkali resistant and durable, but due to the high price, the production application is less. In addition, in the production, industrial waste such as coal slag and fly ash with high carbon content can be incorporated into the soil of the blank to make internal combustion bricks. When the brick is baked to a certain temperature, the carbon in the waste is also burned in the dry body, so that a large amount of fuel and 5% to 10% of the clay raw material can be saved. The internal combustion bricks burn evenly, the apparent density is small, the thermal conductivity is low, and the strength can be increased by about 20%.