What soil is good for burning bricks?

Generally, clay is used to burn, and the specifications are mostly in the ninth five-year plan and the eighth five-year plan. Color is due to water cooling and natural cooling. The colors of iron oxide and ferrous oxide are red and cyan. However, many countries are actively promoting the production and use of coal ash bricks and sand bricks out of active and far-reaching consideration of land, environment and energy, which is related to the well-being of future generations, the resources of the earth, and the pollution and treatment of three wastes.

Therefore, the production and use of standard clay bricks and porous clay bricks are strictly restricted. Until it is completely unused, it is replaced by fly ash bricks, mountain sand bricks, construction waste bricks and so on.

Detailed description of brick burning process:

1, raw material preparation?

According to the local natural geological analysis, clay and shale are the main raw materials for brick burning. Clay can be obtained locally and then transported to the sintering plant for screening. Shale mainly comes from local mining, and then it is screened to meet the requirements of brick-making particles and transported to the sintering plant for use. Send technicians to bring clay and shale samples to the laboratory for testing, ask the experimenters to design the mixture ratio of sintered bricks, and then mix the sintered bricks according to the mixture ratio issued by the laboratory.

In the process of selecting raw materials, firstly, according to the particle size requirements of brick mixing ratio, large particles are screened out. The screened qualified particles are transported to the mixing station by conveyor belt, and mixed with water according to the laboratory mixture ratio. In the screening process, the screened large particles are transported by the loader to the crusher for crushing, and then the crushed small particles are transported by the loader to the screening machine for re-screening, so as to meet the granularity requirements of raw materials for brick burning.

In addition, in the process of raw material screening, the hardness of the materials used must be strictly controlled. If the hardness is too large and the structure is dense, it will affect the quality of the finished product and must be broken to weaken its own hardness and meet the requirements of brick making.

Step 2 spread

Generally, the process of sintering bricks is accompanied by two times of stirring, one is after the selection of raw materials and the other is before aging; The first time is the second stirring of aging molding materials.

The first mixing is to fully mix the raw materials prepared according to the laboratory mixture ratio, so that the mixture has certain plasticity. In the process of mixing, be sure to control the moisture. The domestic experience is about 20%, in which the moisture content of raw materials is 4% ~ 5%, and water is added by water pump during the mixing process 15% ~ 16%. The mixture after one-time stirring automatically and orderly falls into the aging bin, so that the moisture in the mixture fully makes Brownian motion, that is, the moisture fully penetrates into the mixture particles, thereby improving the moisture homogenization degree of the mixture and increasing its plasticity. Domestic experience shows that the aging process generally takes 7 days. The cured mixture is conveyed to the second mixer through the conveyor belt, and stirred for the second time, so that the mixture is fully uniform and becomes loose particles, and then conveyed to the red brick extrusion equipment with the conveyor belt for green body extrusion.

3. Extrusion molding

The mixture after secondary stirring enters a vacuum brick extruder through a conveyor belt for extrusion molding. In the process of extrusion, the pressure should be controlled at 3.8MPa, and the vacuum degree should not be greater than -0.08MPa. Then, it will be cut into standard solid bricks or hollow bricks by slitter, blank cutter and blank turning machine, and the blanks will be grouped and put on the kiln car.

dry

According to the weather conditions, natural drying or artificial drying is adopted on site. Because the highest temperature in the desert area of Niger reaches 60℃, it basically meets the temperature requirement of green body natural drying, and natural drying can be carried out on site under the conditions of weather and temperature. However, if the weather and temperature conditions cannot meet the requirements of natural drying, artificial drying will be adopted on site. Domestic experience shows that the general drying cycle is 24 ~ 32h. The moisture content of the dried green body is generally controlled at 3% ~ 6%, and the next process can only be carried out after the moisture content of the green body meets the requirements. If the water content of the green body is too high, cracks will occur at high temperature during roasting, and in severe cases, it will pile up.

In-situ natural drying is planned to adopt large-area and multi-level dispersion drying to ensure that the extruded blank is fully exposed to the sun and achieve the purpose of drying. Natural drying needs to extend the drying time to meet the drying requirements. In the process of natural drying, we should always pay attention to the change of weather. In case of cloudy, rainy and other bad weather, it is necessary to take preventive measures in advance to prevent the formed blank from being damaged by rain.

Manual drying generally requires the establishment of a drying chamber, and the size of the drying section depends on the production scale of red bricks. General domestic small section: length 55 ~ 65 m, width 1.2 ~ 2.2 m, height 0.75 ~ 1.0 m, code blank height 750 ㎜; Large section: length 55 ~ 65m, width 1.7 ~ 4.66m, height 1.7 ~ 2.4m, and blank height 2350mm. In-situ drying plans to use the waste heat generated after roasting, and the temperature is controlled at 120℃ ~ 150℃. Using axial fan to maintain indoor ventilation and uniform heating of the blank, to ensure that the residual heat is dispersed and uniformly attached to the blank, and to take the evaporated water out of the drying chamber to achieve the purpose of drying.

Step 5 bake

The dried green body is transported to the roasting kiln by car ferry, and then pushed into the heating place of the roasting kiln by hydraulic jacking for roasting and molding. Generally, the green body height of a roasting kiln is 1.580mm, which should not be too high. Too high will damage the bottom blank, and the height must be appropriate, so as to make full use of the space in the kiln for roasting and heat absorption.

Roasting kiln is divided into preheating zone, roasting zone and cooling zone. After passing through the preheating zone, the green body is slowly heated and dehydrated. When it slowly reaches the baking zone, the minerals in the green body undergo violent physical and chemical reactions to generate various silicate melts, which are firmly combined with unmelted minerals, and then recrystallized in the cooling zone to form hard sintered brick products.

In the roasting process, the temperature in the kiln must be well controlled when burning natural gas, and the temperature rise rate in the kiln should not be too fast after burning, so as to avoid the stress caused by the sudden change of the green body volume and the disadvantage that the gas generated in the reaction process is difficult to eliminate. After sintering, the green body expands and becomes brittle, which requires that the temperature of the baking belt should not be too high, otherwise the green body will easily soften and deform into bread bricks.

In addition, a cooling fan is arranged at the top of the roasting kiln to provide sufficient combustion-supporting air for natural gas combustion while cooling brick products. The cooling fan at the bottom of kiln can cool the working environment of kiln car and prolong the service life of kiln wheel. At the same time, the exhaust fan discharges the waste gas with low temperature and high water content out of the kiln. By manually controlling the exhaust air volume and intake air volume, the pressure curve in the kiln can be changed and the temperature control in the kiln can be changed. When the top car speed, intake air volume and exhaust air volume reach a balance, the natural gas fire will not move, and the roasting zone will burn good products.

6. Finished product pattern.

After roasting, the finished products are transported outside the kiln by handcart, and can be piled up manually by forklift on site to improve efficiency.

Building production efficiency, complete brick making. At the same time, in the process of finished product stacking, the finished brick stacks are numbered according to the factory order for the factory to use.