Tunnel kilns have been widely used as burning equipment of domestic wall material enterprises in recent years, and their operating conditions are showing uneven trends. Some enterprises have higher kiln capacity, some have lower kiln capacity, the quality of the kiln is good bad, and the energy consumption varies somewhat. Here is a brief explanation and analysis of some daily operations and common problems in firing.
1 Capacity and quality
1.1 Production capacity: At the beginning of the design and construction of the kiln, the annual production capacity was estimated. The output is based on the cross-sectional size of the industrial furnace, the level of the slab layer, the type of product, the roasting performance of the raw material and its The status of the relevant equipment and facilities is comprehensively obtained. The speed of the fireworks during the firing of the brick stack in the kiln is called the roasting speed, and the speed of the roasting speed largely determines the output of the kiln. The fire speed at the bottom of the brick stack during roasting determines the speed of the roasting speed, especially the fire speed of the bottom fire on both sides can reflect the speed of the roasting speed. This is because the lower sides of the brick stack are affected by many aspects. When roasting, it always burns last. After the fire temperature is formed, it first cools down and becomes the weakest link in the stack.
The speed of the bottom fire is the result of a comprehensive factor. It involves the design and construction of the kiln, the stacking condition of the billet, the mixing of the internal combustion, and the operation of the roasting personnel. The related links can be operated in a reasonable, standardized and orderly manner.
1.2 Quality of brick products
High-quality brick products mainly show that the appearance color is consistent, the difference is big, there is no crack, the specifications are consistent, and the compressive strength meets the standards. When the bricks are roasted, the temperature they are subjected to will have a certain difference. When the temperature difference is too large, the color of the product will have a large difference. Generally, a temperature difference of 10 ℃ ~ 30 ℃ will cause a big difference in the color of the product. influences. The bricks on the upper and lower parts of the brick stack, the bricks on the inside and the edges are affected by the difference in the placement of the wind pressure, the length of the roasting time, and the effects of flue gas erosion. This will also lead to The product color varies.
When new ingredients are added to the raw material, the color of the product may change. This is because the chemical composition contained in each raw material mixed fuel is different. The series of physical and chemical reactions that occur after drying and roasting make the product The colors are different.
The stacking form and structure of the stack have a great influence on the roasting. In order to make the fire distribution more uniform and take into account a certain fire speed, we must adhere to the principle of stacking stacking of "side density is medium and thin, top density is low". . The hot air flow shows a tendency to float upward when running in the kiln, but it is moved obliquely upward by the pre-tropical wind pressure, so that the upper part of the stack will be heated first and then burned, while the middle of the stack The lower part is in a state of slow heating and little heat. Therefore, the dense and thin code method on the stack is used to change the airflow stratification of the billet stack, which significantly improves the fire speed and the temperature difference between the upper and lower brick stacks.
The internal combustion blending condition can also affect the kiln's production capacity and product quality. It requires proper calorific value, uniform stirring, and selects ignition point neutral fuels. Those fuels that are flammable at low temperatures and burn at high temperatures should be used less . Fuels that contain calcium cause too many corrosive substances in the flue gas can be used to avoid the flue gas harming products and fans.
2 Operation of roasting personnel
2.1 Preliminary preparations: roasting personnel must understand the conditions of the kiln and drying room before running without ignition. For the wind, air gate, flue, kiln wall, kiln roof, fire eye, track, sand sealing groove, sand pipe, Fully familiar with and master waste heat extraction, heating and dehumidification systems.
Secondly, the operator should understand the length of the kiln and plan a reasonable firing curve. Under normal circumstances, the pre-heating zone should be longer to create a reasonable heating time for the brick, ensuring sufficient heating time and a loose preheating environment. . The length of the roasting belt should be appropriate. If it is too long, it will easily produce overfire bricks, if it is too short, it will cause underfire and the fire will slow down. The length of the heat preservation belt depends on the fire condition of the roasting belt and the appearance of the product after leaving the kiln. Cooling with a length of 2 to 3 kiln cars will do.
Kiln workers also need to understand the basic properties of brick raw materials such as drying sensitivity, dehydration rate, and roasting temperature. It is necessary to take into account the coordination of drying and firing.
2.2 Fire control
During roasting, use a thermometer and visual observation to understand the degree of fire. The degree of fire is generally between 920 ℃ and 980 ℃. In order to reduce coking bricks raw bricks, the temperature should be well controlled, and the firing time can be appropriately extended, that is, "low temperature long firing". When the kiln temperature is too high, the bricks are already burned in the early and middle zone of the roasting zone. At this time, the roasting zone should be shorter, otherwise the bricks will be burned. When the temperature is insufficient, the firing zone should be extended when raising the fire temperature.
Visual temperature is still an important way to understand the fire. The relationship between color and temperature is:
Dark red (but red): 450 ℃ ～ 480 ℃
Dark red to purple red: 480 ℃ ～ 600 ℃
Purple to red: 600 ℃ ～ 700 ℃
Big red to cherry red: 700 ℃ ～ 800 ℃
Cherry red to yellow-red: 800 ℃ ～ 900 ℃
Yellowish red to orange yellow: 900 ℃ ～ 1000 ℃
Orange to light yellow: 1000 ℃ ～ 1100 ℃
Light yellow to bright yellow:> 1100 ℃
When looking at the fire, only the temperature of the upper brick, but also the temperature of the middle and bottom, the sides and the middle, and the temperature of the front, middle and back fire of the roasting zone. It is necessary to adjust the operation plan in time when the fire changes.
2.3 Foreign investment fuel
When the fire temperature is insufficient during roasting, it is necessary to increase the temperature by adding fuel. Commonly used is coal, which should be flammable at low temperature (400 ℃), long flame with a calorific value above 3200kj / kg, fine crushed coal with particle size less than 0.8cm, and moisture content less than 10%. When investing in coal externally, we must grasp the input position, input quantity, input frequency, and input time. At the same time, we must observe the effect of temperature increase after coal injection, whether it is fully burned, and whether there is carbon deposition.
3 Product defects
There are many types of defective products in production, and the reasons are different. The following is an analysis of common product defects.
3.1 coke brick
Also known as overfire bricks, most of them are caused by the products' high temperature and long holding time during firing. The kiln-burning workers need to find out and deal with it in time, and measures are in place. When the temperature is too high, the following measures can be taken: the high temperature is taken away by increasing the wind pressure to increase the suction force; the fire eye cover of the high temperature area is opened to allow cold wind to be sucked in the high temperature emerges outward; use the blower to blow in the middle fire eye The cold wind should be blown in the place the code is relatively thin, and the fan power is preferably between 1.5 kw and 2.2 kw; accelerate the pushing frequency of the blank car, and push the high-temperature kiln car into the cooling zone to cool down. However, the cooling cannot be compromised, the quality of the products cannot be affected, the damage to the industrial kiln and the drying system can be damaged.
3.2 Raw brick
The reason for the production of green bricks is exactly the opposite of coke bricks, that is, the baking temperature is low the holding time is too short. If the bricks of the whole kiln car are born, it means that the fire temperature is too short, and the fireworker has errors in operation. the incorporation of fuel itself is enough, which is the problem that needs to be solved in the process. If there are only raw bricks on both sides of the kiln car, it may be that the fire temperature is lacking, the middle of the billet stack is too dense the margin is too large. If there are only raw bricks in the lower 1 to 3 layers of the edge of the brick stack, and there are a lot of sand in the sand sealing groove, it means that the wind pressure in the kiln is too large the suction under the kiln is too small.
3.3 Crack
During the firing process of bricks and tiles in industrial furnaces, it is easy to produce cracks network cracks, and there is a fine crack called hair crack. Fractures and network cracks are the green body, the strength of the green body is low, the preheating temperature is too rapid, the temperature difference between the inside and outside of the body is very large, and the evaporation rate of water inside and outside the body is very different, which inevitably destroys the structure of the body , Commonly known as "burst". There are three reasons for cracks during firing: ① The pre-heating temperature is too rapid, and there should be a gradual and gradual heating process. ②When the temperature is too high, the billet is fully preheated, ③The temperature of the heat preservation belt is too fast, and the product is cooled rapidly high temperature to low temperature.
