Yingfeng Machinery－More Than 30 Years Experience In Clay Brick Making Machine ,Tunnel Kiln, Rotary Tunnel Kiln.
Reasons and solutions of affecting bricks quality
1, Malformed adobe, appears large cracks. In more serious cases, the whole adobe will split.
Reasons: the plasticity index of pug is too low, almost no plasticity.
Solution: to increase the plasticity index of raw materials, such as clay, coal slime or clay agent, etc.
For raw materials of low plasticity index, it can also be improved after aging, watering, stirring, rolling, extruding and other methods.
2, The body of adobe is not smooth, the obvious particles, more sand pits, and horns or flutes are missing.
Reasons: The shatter of raw materials does not meet the requirements of making bricks because there is much large particles.
Solutions: Install fine grinding equipment, as required for crushing the raw materials to make particles 3 mm or less.
Some kiln owners are not willing to spend money in equipping the machinery of raw material pre-treatment, such as roller crusher,double shaftmixers. Some kilns are only equipped with a pair of rollers, some only with mixers, some even neither of them. How can we get good bricks if there are bricks, tile, stone and other debris in the mud raw materials? Even if it is hard to send someone to pick them out clean. The fundamental way to solve the problem is equipped with auxiliary equipment.
3, The quality of adobe is unstable, sometimes good and sometimes poor.
Reasons: uneven mixing of raw materials
Solutions: Increase the mixer and feeder
Some brick factories are not equipped with rollers and mixers, even without the feeders, all by artificially feeding into the brick machine with shovel, which inevitably occurs two major drawbacks.①, raw material soil cannot be stirred and mixed well. The plasticity of raw soil is not exactly the same, and sometimes the disparity is very great, the Yellow River sludge is like that.②, the inside fuels such as coal, coal gangue, slime and others cannot be stirred evenly. The two heterogeneous, will inevitably lead to the instability of adobes’ quality.
4, malformed adobe and mud column, will spread immediately after cutting.
Reasons: Failure of the vacuum chamber
Solutions: a, improve the maintenance, service, repair technology of brick machine to ensure the normal function of brick machines’ properties. b, make the necessary technical transformation
b, Another reason for resulting in failure of the vacuum chamber, is the sand-based raw material, so the closed mud layer of the upper auger is too thin, easy to be drawn through, causing the vacuum failure, so the adobe could not be molded. The best way to solve this problem is to change the ratio of raw materials, to increase the plasticity index of raw materials. The other way is to cut the front end of the superiors auger to 2-10 centimeters according to the material properties of soil (must be conducted under the guidance of skilled technical personnel, don’t do it by yourself).
5, Many brick cracks on adobes or broke into two sections, more wastes after sintering.
Reasons: There are too many viscous ingredients in raw materials, so the plasticity index is too high.
Solutions: change the ratio of raw materials, reduce the plasticity index. The plasticity index of clay can be up to 25, can be properly incorporated into the coal ash, slag, fly ash or waste of brick powder to make it thin.
6, Soft adobe, easy to form, or crack after cutting.
Reason: the improper control of moisture in the mud.
Solution: soft adobe, easy to be deformed, showing that the water of sludge is too much, should reduce water. If the mud column quickly occurs crack or split of mud column after molding, which is caused by too little water in mud, it can be solved by increasing appropriate water.
7. Brick production capacity not stable
Reason: Not equip with box feeder
Solution : Some brick factory owners in order to save money, they refuse to use box feeder but some labors to feed soil manually .Therefore, soil feeding amount is not stable,sometimes more than what the extruder need, some times, less what extruder need, thus greatly influencing production capacity.
All in all, there are all kinds of raw materials to make bricks, in addition to the different climate, some abnormal situations inevitably occur in the production and it is really hard to avoid. If there are problems, knowing the following two points will be easy. One isto havea team with a strong sense of responsibility and a technical team ofprofessional mechanics. Two is to timely communicate high and difficult technical problems with industry colleagues.
1. Select mature technical solutions to ensure that the production line reaches the standard and reaches the production capacity.
When using tunnel kiln to burn bricks, various parameters used in production should be determined according to the basic properties of raw materials.
The firing output of the kiln is that the performance indicators of the fired product meet the requirements of the national standard, not just how much is fired, and the output of the kiln is how much. Some kiln-fired products are only 3mm~4mm on the surface, but the inside is not completely fired. Such products that do not meet the requirements of the national standard cannot be used as the basis for calculating the output of the tunnel kiln.
The length, width and height of the kiln are calculated according to the output of the kiln. When calculating the length, width and height of the kiln, the heating and cooling rates of the raw materials, the firing time of the raw materials, the highest firing temperature and the firing temperature range should be considered. And other factors.
The tunnel kiln should also have a complete working system, and various parameters of the working system must be calculated in detail, so as to ensure the normal operation of the tunnel kiln, so as to achieve the purpose of correct construction and correct use of the tunnel kiln, and to ensure that the tunnel kiln burns In the process of reaching the target and reaching the production.
2. Reasonable layout of the tunnel kiln system to make the firing stable.
According to the definition of tunnel kiln, tunnel kiln should be equipped with ventilation system, fuel combustion system, vehicle entry system, and sealing system. These subsystems constitute the working system of tunnel kiln. The close cooperation of each system can make the tunnel kiln work normally.
According to the requirements of the firing atmosphere in the kiln, the number and position of the fans used on the kiln are equipped, the air pressure of the fans is determined according to the shape of the fired products and the density of the kiln, and the ventilation volume of the fans is determined according to the output.
According to what kind of fuel is used, the method of fuel combustion system, what kind of combustion equipment to use, and the arrangement position and quantity of combustion equipment should make the temperature in the kiln as uniform as possible. The main contents included in the entry system are entry mode and entry time interval.
The sealing system includes the sealing between the kiln car and the kiln body, the sealing between the kiln door and the kiln body, the sealing between the pipeline and the kiln body, and the sealing between the kiln cars. It is isolated to form a good firing space inside the tunnel kiln, so that the semi-finished product can be fired into the finished product inside the kiln.
The division of the three zones in the firing process of the tunnel kiln should be carried out according to the basic properties of the raw materials, and should not be arbitrarily divided, so as to ensure the normal production and stable operation of the tunnel kiln.
3. Recognize the importance of kiln car and ensure the stable quality of fired products.
The kiln car is an indispensable equipment in the production process of the tunnel kiln, and it is also the key equipment related to the performance of the tunnel kiln and whether it can be used normally.
In order to make the kiln car play the role of key equipment, the first thing is to maintain a good seal between the kiln car and the tunnel kiln body, so as to completely isolate the inside of the kiln from the outside of the kiln, so that the cold air outside the kiln cannot enter at will In the kiln, the hot air in the kiln will not leak into the kiln, so that the firing process in the kiln can be carried out smoothly.
Secondly, the seal between the kiln cars should also be reliable, the reason is as mentioned above. Third, the operation of the kiln car should be stable, so as to avoid the occurrence of such phenomena as kiln collapse, uneven firing, and difficulty in entering the car. Fourth, the thermal insulation layer on the kiln car is very important. If the thermal insulation layer of the kiln car has a good thermal insulation effect, the temperature in the kiln will be consistent, the quality of the fired products will be uniform, and the color will be the same. If the thermal insulation effect of the kiln car is not good, Then, the temperature difference between the upper and lower sides of the kiln will be large, and the fired products will be cooked on the top and cooked on the bottom, or cooked on the top and under the coke. In short, the product quality is uneven and the color difference is large.
Some factories have been in operation for less than a year, and the kiln car often has problems and needs to be replaced, which not only increases production costs, but also changes the understanding of tunnel kilns, and feels that tunnel kilns are inferior to other kilns. In fact, the root cause is the insulation layer of the kiln car, and the seemingly simple insulation layer problem has not been properly handled.
Some kiln cars did not reduce the thickness and material of the thermal insulation layer, but the thermal insulation effect was still very poor. Why is the temperature under some tunnel kiln cars only 40℃~50℃, people can check it smoothly under the car, while the temperature under some cars is so high that people can't get into the car at all. In fact, the reason is very simple, it is caused by the gap in the insulation layer of the kiln car.
Problems that should be paid attention to in the construction of tunnel kiln
The performance of the tunnel kiln depends not only on the integrity of the design, but also closely related to the construction. The quality of each construction step affects the quality and performance of the tunnel kiln.
1. Construction materials must be guaranteed.
In the design process of the kiln, the material properties and usage requirements of various materials are considered, and the usage position and thickness of the materials are calculated. In order to ensure the construction quality, the use position and amount of materials shall not be arbitrarily changed during the construction process, nor the variety and quality grade of the materials used.
If it is to be replaced, the strength grade of the structural material must be higher than that of the original design material, and the thermal conductivity of the insulation material to be replaced must be lower than that of the original material.
2. Construction according to design requirements.
In the process of using the tunnel kiln, the technical requirements that should be met in the construction process, the construction difficulty and the solutions are fully considered. Many norms and standards are used in the design, including national standards and norms, provincial and ministerial-level standards and norms, local-level standards and norms, and industry standards and norms.
In the construction requirements, specific requirements are put forward for each part. These requirements are in line with the requirements of the construction specifications and standards. If you want to change them, you must refer to the corresponding items of the specifications and standards, and make changes according to the requirements of the specifications and standards. Change.
The materials used in construction are generally those published in national standards. If the specifications and models of the materials are to be changed, the original design materials should be replaced by materials with higher performance in accordance with the national standards.
Problems and lessons in tunnel kiln construction
As we all know, there are three principles to produce good fired bricks: raw materials are the foundation, kiln equipment is the key, and management is the foundation. If it is not designed, the materials used are inferior, and the construction is arbitrarily commissioned, the kiln will become the biggest obstacle to the sustainable development of the production enterprise. There are the following fatal problems in the reconstruction and new construction of tunnel kilns, which should be paid great attention by colleagues in the whole industry:
1. The furnace design is unreasonable
Some enterprises do not pay attention to the process design of sintering kilns. There are generally simple kiln structures, unscientific drying kiln structures, and unreasonable air duct design, so that various tunnel kilns of different lengths appear in front of us. In order to meet the owner's blind request to reduce the cost, many tunnel kilns are overweight and weak.
Whether the tunnel kiln design is reasonable and perfect directly restricts the quality of the kiln. Some investors pay too much attention to investment control and ignore the design and construction of the kiln, resulting in high coal consumption, high cost, high maintenance frequency, A vicious cycle of low reliability and difficult operation.
2. Most construction teams are unqualified, and the construction quality is worrying
It is one of the most prominent problems at present to arbitrarily entrust the construction of units without kiln construction qualifications. They lack necessary job training and qualification certification of construction personnel. The construction quality of most tunnel kilns cannot be guaranteed, the foundation is not strong, and the kiln The body is cracked, the drying effect of the bricks is not good, and the phenomenon of serious collapse and falling of the bricks occurs frequently during the drying process, and the product energy consumption is high and the quality is poor. Quality accidents and quality lawsuits are not uncommon.
Burning bricks requires coal or other fuels. How to maximize the thermal efficiency is the technical key of brick kiln design. The sintering temperature of brick is between 850 ° C and 1050 ° C. In order to save coal, the heat insulation effect of the kiln must be improved. The rotary tunnel kiln is stacked with refractory fiber cotton, which not only reduces the weight of the kiln body, reduces the thermal expansion and contraction stress of the kiln body, but also improves the thermal insulation performance of the kiln body. The kiln temperature is maintained for a long time, and the bricks consumed at one time increase in large area. The internal combustion heat energy can more effectively improve the kiln temperature and save fuel.
In ordinary tunnel kilns, in order to prevent high-temperature flue gas from flowing into the kiln car and burning out the wheels and bearings, it is also necessary to set up a gas source under the kiln car. In the whole heating system, the air supply pressure at the bottom and surface of the vehicle must be kept balanced, and the high temperature flue gas and cold air at the bottom of the vehicle must not rise to reduce the kiln temperature.
The bricks of the rotary tunnel kiln are directly stacked on the ground, without air supply under the vehicle, and the ground temperature is directly fully utilized. It is found that the aluminum silicate fiber blanket can still be calcined normally after 48 hours of coal and air shutdown in actual production, which is impossible for ordinary tunnel kilns. In the annular rotary tunnel kiln, when the firing temperature of bricks is reduced to room temperature, the heat released is enough to dry wet bricks of the same volume, so there is no need to build a hot air furnace, nor need to use the superheat roasting process to consume more coal to dry the heat.
In the heating system of the annular rotary tunnel kiln, dry air enters from the kiln tail and cools the sintered bricks through the cooling section to reduce the temperature of the sintered bricks at the outlet of the kiln tail to room temperature, that is, all the heat emitted by the sintered bricks is carried to the roasting section and drying section through the air entering the kiln for combustion support and drying. The energy saving of circular rotary tunnel kiln is its remarkable feature. Its reasonable process design, layout and simple logistics route also greatly reduce the energy consumption of the whole brick factory.
The circular rotary tunnel kiln fully adopts mechanized operation and automatic digital control system. The temperature in the kiln is directly displayed on the display screen of the control system. There is no need to hire high-paying fire-watching teachers, which fundamentally eliminates brick-making and greatly increases production.
Compared with the traditional tunnel kiln, the new energy-saving and environment-friendly mobile rotary tunnel kiln has great advantages. It can be predicted that the production mode of the new energy-saving and environment-friendly mobile rotary tunnel kiln will be widely used in the field of sintered bricks by comparing the Helu aluminum silicate fiber blanket.
Components and structure
A typical clay brick kiln consists of several main parts:
Chamber: This is where the bricks are stacked and fired. It is designed to withstand high temperatures and has proper ventilation to ensure even heating.
Fuel supply system: Depending on the type of kiln, it may use coal, gas, or other fuels. The fuel supply system controls the amount of fuel entering the kiln to maintain the desired temperature.
Ventilation system: Necessary for removing excess heat, gases, and ensuring proper air circulation during the firing process. This helps in achieving consistent quality bricks.
Types of clay brick kilns
There are different types of clay brick kilns, including:
Bull's trench kiln: This is a long, trench-like structure where bricks are placed on the sides and fired from one end. It is a relatively simple and low-cost kiln but may have less efficient heat utilization.
Fixed chimney kiln: It has a fixed chimney for exhaust gases. Bricks are stacked inside and fired. This type of kiln offers better control over the firing process compared to some other traditional kilns.
Tunnel kiln: A more advanced and industrialized kiln. Bricks are moved through a long tunnel on a conveyor belt while being fired at different temperatures in different zones. This provides a continuous production process and better quality control.
The firing process
The firing process in a clay brick kiln involves several stages:
Drying: Before firing, the bricks need to be dried to remove moisture. This is usually done in a separate drying chamber or by natural air drying.
Preheating: The bricks are gradually heated to a certain temperature to drive off remaining moisture and prepare them for the high-temperature firing stage.
Firing: The bricks are subjected to high temperatures, typically ranging from 800 to 1200 degrees Celsius, depending on the type of brick being produced. This causes chemical and physical changes in the clay, making the bricks hard and durable.
Cooling: After firing, the bricks need to be cooled slowly to avoid cracking. This can be done by natural cooling or by controlled ventilation.
Environmental impact
Clay brick kilns can have an environmental impact:
Air pollution: The burning of fuels in the kiln releases pollutants such as sulfur dioxide, nitrogen oxides, and particulate matter, which can contribute to air pollution.
Land use: The extraction of clay for brick production can lead to land degradation and loss of agricultural land.
Energy consumption: Kilns require a significant amount of energy for firing, which can contribute to greenhouse gas emissions if fossil fuels are used.
To address these issues, efforts are being made to develop more sustainable brick production methods, such as using alternative fuels, improving kiln efficiency, and recycling waste materials.
Name: Mr. Kai
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Address: Block 5, South Longhai Road and East Tongbai Road, Zhongyuan District, Zhengzhou City, Henan Province, China