Concrete construction operation of cement kiln lining

The construction of cement kiln lining is to turn the kiln lining scheme into reality. When the refractory lining of the cement rotary kiln system is constructed with fire clay, the design of the ash joint should be less than 2mm.

Circular joints should be used for arch and cylinder lining, and staggered joints should be used for straight wall and inclined plane. For kiln cylinder and cylinder cooler, the refractory lining must also ensure that the brick ring and the cylinder body are concentric, so it should ensure that the brick surface and the cylinder body are completely close, and the bricks should be in contact with each other and combine firmly. When building the brick lining of immovable equipment, the fire mud fullness shall reach more than 95%, and the surface brick seam shall be evenly sewn with original slurry, but the excess mud on the brick lining surface shall be scraped off in time. Use wooden or rubber hammers when laying bricks. Do not use iron hammers.

Before the construction of castables, the following inspection should be strictly carried out:

(1) Check the shape and cleanliness of the equipment to be poured.

(2) check the good condition of construction machinery and tools.

(3) Check the type, size, layout and welding quality of the anchors. The metal anchors must be compensated for expansion.

(4) Check the surrounding firebrick lining and insulation layer to prevent water loss of castable measures.

(5) Check the packing and delivery date of castables, and conduct pre-test to check whether they are invalid.

(6) Check the construction water, the quality of which must meet the standard of drinking water.

(7) the formwork for castable construction can be made of steel plate or hard board. The template should have sufficient strength, good rigidity, no distortion, no shift, no leakage. The steel mold should be coated with release agent, and the wood board should be painted with waterproof paint.

(8) The water quantity of castable shall be strictly controlled and shall not exceed the limit. Under the premise of ensuring construction performance, adding water should be less rather than more.

(9) Stirring time of castable shall not be less than 5min. The operation should use a forced mixer, dry mixing before mixing, and then add 80% of the total water to stir, and then depending on the degree of dry and wet, slowly add the remaining water to continue to stir, until the appropriate working consistency is obtained. Clean the mixer before mixing different castables.

(10) The castable must be used in whole bucket or bag. Stirred castable generally should be used up within 30 minutes. In the role of high temperature dry environment but also appropriate to shorten this time. The castables that have been initially coagulated or even agglomerated shall not be poured into the mold frame, nor shall they be mixed with water for reuse.

(11) The castable poured into the mold frame should be layered with vibrator immediately. The height of each layer should be no more than 900mm, and the vibration spacing should be about 250mm. When vibrating, the anchorage should be avoided as far as possible, the insulation layer should not be damaged, and the permanent vibration and revitalization should not be allowed in the same position. The vibrator should be slowly drawn out until the surface of the castable is slurry, to avoid segregation and cavity in the castable layer. After casting, the castable can no longer be subjected to pressure and shock before solidification.

(12) When large area is poured, it should be constructed in blocks, and the area of each pouring area should be about 1.5m³. Expansion joints should be left according to the design and should not be omitted. Expansion joints should be left in the middle of the anchorage interval.

(13) after the surface of the castable is dry, the exposed part in the air should be covered with plastic film or straw bag immediately. After the initial setting arrives, the water should be sprinkled regularly to maintain the surface moist. The maintenance time should be at least two days, and the water should be sprinkled frequently on the first day. After the final setting of the castable, the side die can be removed and the water sprinkling maintenance can continue.

The kiln lining shall not be put into use until it has passed the acceptance inspection after the completion of masonry. But it must be baked by a certain temperature system before use. When the kiln is stopped but the kiln lining is not changed, appropriate cooling system must be used to cool the kiln before it stops operation. In this way, the kiln lining can be ensured to be in a safe state for normal use. The heating system in baking and cooling system in cooling depend on the structure, material and brick type of kiln lining and masonry method.

In the kiln lining material, the alkaline brick itself has the largest linear expansion coefficient, the worst thermal shock resistance, and is used in the place with the highest temperature in the kiln. Therefore, the temperature gradient in the alkaline brick lining is the steepest, the temperature difference stress is the largest, so it is the most easy to produce cracking and spalling, and its service life is the shortest among all the refractory brick lining in the kiln. Appropriate heating system for baking and proper cooling system for cooling are the key points for kiln lining, especially alkaline brick lining.

For the composite lining including castable layer, the baking time should be up to 1 week. Baking inside the kiln barrel and lining of the preheating system can be done simultaneously. The design unit must provide the specific baking system in the kiln lining design.

Baking of kiln lining must be carried out continuously until finished without interruption. Therefore, on the eve of baking, the relevant equipment must be field test run, but also must ensure that there is no power failure in baking, in case of interruption due to accident, according to a certain cooling system to cool to normal temperature, and then bake again. If it is possible to resume baking in a short period of time, effective insulation measures can be taken, starting from the actual temperature drop.

In order to ensure that the brick surface temperature from normal temperature to 800℃ low temperature baking time to reach 8h, it is best to bake with fuel oil. If fuel supplies are difficult, combustible firewood can be used instead.

During the drying period, the kiln body should be rotated according to a certain system with the auxiliary transmission device, and the casting speed should be accelerated from intermittent slow rotation to continuous slow rotation, and finally reach the normal kiln speed. The temperature of all the brick surfaces in the firing zone should be uniform, so as to ensure the regularity of the center line of the kiln barrel and the normal ellipticity.