Reasons for green clay bricks to collapse easily

1. Determine the process according to the raw materials
The one-time burning process of the tunnel kiln has the advantages of saving space, reducing manpower, high degree of automation, and saving investment. However, whether the one-time burning process can be used depends on the performance of the raw materials. The raw materials suitable for the one-step burning process include coal gangue, shale and raw materials with a high content of coal gangue and shale. For soft raw materials with high content of fly ash, clay and laterite, soft shale and large drying shrinkage, and low critical moisture, use the one-time burning process with caution. Even if one-time burning is used, the drying time should be prolonged and reduced. The heating rate of the green body. Strictly control the height of the pallet truck, and generally should be controlled below 12 floors. For those manufacturers who plan to build a production line of a fired tunnel kiln, the raw materials should be tested and analyzed, and the opinions of experts should be listened to to prevent such problems from continuing to occur.

2. Raw material processing
In addition to higher raw material performance requirements, the one-time burning process also requires raw material processing, and the raw material particle gradation is more reasonable. For coal gangue or hard shale, although it is suitable to use the one-time burning process, if the raw material processing fineness is unreasonable. If the aging effect is not good, the forming of the bricks cannot be guaranteed. Strength of wet billet and drying effect. When the green body enters the drying kiln and heats up, it becomes soft and its strength decreases. The bottom body cannot withstand the pressure of the upper body and collapses. Therefore, the fineness of raw materials must meet: ∠0.5mm accounted for more than 55%, 05.mm-1mm accounted for 20%-25%, and 1mm-2mm accounted for less than 20%. The lower the plasticity index of the raw material, the higher the proportion of fines should be.

Raw material aging is the key to ensuring the quality of brick molding. For coal gangue, shale, especially industrial waste slag, the raw materials for brick making, which are mixed with multiple raw materials, raw material aging is an indispensable process because of low plasticity and low plasticity. When there is no aging process for mostly granular raw materials, it takes only a few minutes from the time the raw materials are crushed and mixed with water to enter the brick machine to discharge the blanks. The added moisture is only on the surface of the raw material particles, and does not penetrate the inside of the particles. The quality of the formed body cannot be guaranteed. Only when the raw materials are mixed with water to the molding moisture content and sent to the aging warehouse, after more than 3 days of aging, and then crushed by a pair of rollers or wheel mills, can the quality of the molded body be ensured. The raw material should not add water as much as possible in the upper part of the extruder, because the water added by the upper level stirring does not have enough time to penetrate into the raw material. This surface water is rubbed with the brick screw auger under the action of strong extrusion pressure. The formation of a water film between the laminar flow of mud will cause delamination and cracks in the green body during the drying process, which not only affects the drying quality of the green body, but also reduces the strength of the green body, leading to the collapse of the green body. What must be explained here is that the aging raw materials must be mixed with water and then sent to a closed and moisturizing aging silo for aging. The moisture content of the raw materials entering the aging silo is basically equal to the moisture content required for molding, not like some brick factories. It\'s just that the powdered and fine dry materials are piled up to say that they are aging, in fact, the dry materials that are not stirred with water have almost no aging effect.

3. Using semi-hard plastic molding
The use of the one-time sintering process requires high strength of the molded body. Therefore, a semi-rigid plastic molding machine with high extrusion pressure should be used to ensure that the green body has high strength and dry quality. The output of semi-rigid plastic molding machine is relatively low, the extrusion pressure is relatively high (generally, the extrusion pressure is 40kg/cm2), and the molding water content of the green body is about 13%-15%. The diameter of the mud tank is more than 500 mm. The semi-rigid plastic molding machine mentioned here is not the 50-50-35 two-stage vacuum extruder produced by most machinery manufacturers at present. It is a high-output extruder, and a single machine can meet the annual output of 60 million to 70 million sintering. Brick production line, this kind of brick machine has good comprehensive performance, high pressure and high output, and the water content of the green body is about 14%~17%, which is suitable for manual drying wheel kiln roasting or tunnel kiln double-stacking process. If you must choose this type of brick machine in the one-time code burning process, you must inform the machinery manufacturer to customize it. When manufacturing, reduce the spindle speed of the brick machine and increase the extrusion pressure to meet the one-time code burning process.

For the existing one-time sintering process, the brick factory that uses a two-stage vacuum extruder below 50-50-35 and the phenomenon of blank collapse can replace the lower-level 4-level motor with a 6-level motor and increase the motor pulley by 15%-20 %, or do not change the motor, only reduce the original motor pulley by 10%-15% to reduce the extrusion speed and increase the extrusion pressure, which can effectively improve the strength and appearance quality of the formed body, and ensure that the blank does not collapse during drying. kiln.

4. Drying kiln structure
The structure of the drying kiln is determined according to the properties of the raw materials and the pressure of the brick machine. The main factors that determine the length of the drying kiln are the drying sensitivity of the raw materials, the shrinkage rate, the critical moisture, and the forming moisture. Regardless of whether the top air supply or the combined top and side air supply are used, the air supply position has a great influence on the drying effect of the green body. The position where the hot air is sent depends on the critical moisture and drying sensitivity of the raw material. For raw materials with low critical moisture and high drying sensitivity, before the air supply position is unreliable, generally the first air supply point at the front end should be more than 15m away from the car inlet, otherwise dry cracks will occur. The total length of the drying kiln should be more than 70m for raw materials with high molding moisture and large shrinkage, otherwise it may cause excessive heating and excessive water vapor and collapse of the billet.

5. Code kiln car
The kiln car must ensure that the fuel is evenly distributed across the kiln section and the airflow must be evenly distributed across the kiln section. A few days ago, almost all brick factories use internal combustion bricks. The principle of the kiln car yard should be the tying method of medium-sparse side and dense bottom, so that it not only satisfies the concentration of heat in the middle of the kiln, the sparse bricks and the less heat, but also satisfies Because of the large gap in the middle, the moisture can easily flow out. However, it is difficult for many manufacturers to understand that solid bricks are easier to collapse than hollow bricks during the drying process. This is due to the fact that solid bricks use more raw materials, heavy weight, and more total water under the same volume. The tidal volume is large, and if the moisture is not exhausted, the billet will collapse. Therefore, the density of solid bricks should be sparser. The total density of solid bricks is controlled at (standard bricks) 240 blocks/m3—260 blocks/m3, and 90 porous bricks are controlled at 160 blocks m3-170 blocks/m3.

Parameters

1. Determine the process according to the raw materials
The one-time burning process of the tunnel kiln has the advantages of saving space, reducing manpower, high degree of automation, and saving investment. However, whether the one-time burning process can be used depends on the performance of the raw materials. The raw materials suitable for the one-step burning process include coal gangue, shale and raw materials with a high content of coal gangue and shale. For soft raw materials with high content of fly ash, clay and laterite, soft shale and large drying shrinkage, and low critical moisture, use the one-time burning process with caution. Even if one-time burning is used, the drying time should be prolonged and reduced. The heating rate of the green body. Strictly control the height of the pallet truck, and generally should be controlled below 12 floors. For those manufacturers who plan to build a production line of a fired tunnel kiln, the raw materials should be tested and analyzed, and the opinions of experts should be listened to to prevent such problems from continuing to occur.

2. Raw material processing
In addition to higher raw material performance requirements, the one-time burning process also requires raw material processing, and the raw material particle gradation is more reasonable. For coal gangue or hard shale, although it is suitable to use the one-time burning process, if the raw material processing fineness is unreasonable. If the aging effect is not good, the forming of the bricks cannot be guaranteed. Strength of wet billet and drying effect. When the green body enters the drying kiln and heats up, it becomes soft and its strength decreases. The bottom body cannot withstand the pressure of the upper body and collapses. Therefore, the fineness of raw materials must meet: ∠0.5mm accounted for more than 55%, 05.mm-1mm accounted for 20%-25%, and 1mm-2mm accounted for less than 20%. The lower the plasticity index of the raw material, the higher the proportion of fines should be.

Raw material aging is the key to ensuring the quality of brick molding. For coal gangue, shale, especially industrial waste slag, the raw materials for brick making, which are mixed with multiple raw materials, raw material aging is an indispensable process because of low plasticity and low plasticity. When there is no aging process for mostly granular raw materials, it takes only a few minutes from the time the raw materials are crushed and mixed with water to enter the brick machine to discharge the blanks. The added moisture is only on the surface of the raw material particles, and does not penetrate the inside of the particles. The quality of the formed body cannot be guaranteed. Only when the raw materials are mixed with water to the molding moisture content and sent to the aging warehouse, after more than 3 days of aging, and then crushed by a pair of rollers or wheel mills, can the quality of the molded body be ensured. The raw material should not add water as much as possible in the upper part of the extruder, because the water added by the upper level stirring does not have enough time to penetrate into the raw material. This surface water is rubbed with the brick screw auger under the action of strong extrusion pressure. The formation of a water film between the laminar flow of mud will cause delamination and cracks in the green body during the drying process, which not only affects the drying quality of the green body, but also reduces the strength of the green body, leading to the collapse of the green body. What must be explained here is that the aging raw materials must be mixed with water and then sent to a closed and moisturizing aging silo for aging. The moisture content of the raw materials entering the aging silo is basically equal to the moisture content required for molding, not like some brick factories. It\\'s just that the powdered and fine dry materials are piled up to say that they are aging, in fact, the dry materials that are not stirred with water have almost no aging effect.

3. Using semi-hard plastic molding
The use of the one-time sintering process requires high strength of the molded body. Therefore, a semi-rigid plastic molding machine with high extrusion pressure should be used to ensure that the green body has high strength and dry quality. The output of semi-rigid plastic molding machine is relatively low, the extrusion pressure is relatively high (generally, the extrusion pressure is 40kg/cm2), and the molding water content of the green body is about 13%-15%. The diameter of the mud tank is more than 500 mm. The semi-rigid plastic molding machine mentioned here is not the 50-50-35 two-stage vacuum extruder produced by most machinery manufacturers at present. It is a high-output extruder, and a single machine can meet the annual output of 60 million to 70 million sintering. Brick production line, this kind of brick machine has good comprehensive performance, high pressure and high output, and the water content of the green body is about 14%~17%, which is suitable for manual drying wheel kiln roasting or tunnel kiln double-stacking process. If you must choose this type of brick machine in the one-time code burning process, you must inform the machinery manufacturer to customize it. When manufacturing, reduce the spindle speed of the brick machine and increase the extrusion pressure to meet the one-time code burning process.

For the existing one-time sintering process, the brick factory that uses a two-stage vacuum extruder below 50-50-35 and the phenomenon of blank collapse can replace the lower-level 4-level motor with a 6-level motor and increase the motor pulley by 15%-20 %, or do not change the motor, only reduce the original motor pulley by 10%-15% to reduce the extrusion speed and increase the extrusion pressure, which can effectively improve the strength and appearance quality of the formed body, and ensure that the blank does not collapse during drying. kiln.

4. Drying kiln structure
The structure of the drying kiln is determined according to the properties of the raw materials and the pressure of the brick machine. The main factors that determine the length of the drying kiln are the drying sensitivity of the raw materials, the shrinkage rate, the critical moisture, and the forming moisture. Regardless of whether the top air supply or the combined top and side air supply are used, the air supply position has a great influence on the drying effect of the green body. The position where the hot air is sent depends on the critical moisture and drying sensitivity of the raw material. For raw materials with low critical moisture and high drying sensitivity, before the air supply position is unreliable, generally the first air supply point at the front end should be more than 15m away from the car inlet, otherwise dry cracks will occur. The total length of the drying kiln should be more than 70m for raw materials with high molding moisture and large shrinkage, otherwise it may cause excessive heating and excessive water vapor and collapse of the billet.

5. Code kiln car
The kiln car must ensure that the fuel is evenly distributed across the kiln section and the airflow must be evenly distributed across the kiln section. A few days ago, almost all brick factories use internal combustion bricks. The principle of the kiln car yard should be the tying method of medium-sparse side and dense bottom, so that it not only satisfies the concentration of heat in the middle of the kiln, the sparse bricks and the less heat, but also satisfies Because of the large gap in the middle, the moisture can easily flow out. However, it is difficult for many manufacturers to understand that solid bricks are easier to collapse than hollow bricks during the drying process. This is due to the fact that solid bricks use more raw materials, heavy weight, and more total water under the same volume. The tidal volume is large, and if the moisture is not exhausted, the billet will collapse. Therefore, the density of solid bricks should be sparser. The total density of solid bricks is controlled at (standard bricks) 240 blocks/m3—260 blocks/m3, and 90 porous bricks are controlled at 160 blocks m3-170 blocks/m3.