The service life of the rotary kiln lining depends largely on the quality of the bricks and the quality of the masonry, but also on the composition of the raw materials, the nature of the fuel, the regulation of the flame and the stability of the thermal system of the kiln. Because the kiln lining rotates with the rotary kiln at high temperature, it is in a state of vibration for a long time, and it also has to bear the wear and impact of the charge, which not only requires the kiln lining bricks to have high strength and thermal shock stability at high temperature, but also puts forward higher requirements for the construction quality of the rotary kiln. This article introduces the construction essentials and quality control of rotary kiln furnace, as well as the construction of expansion joints, brick retaining rings and lock bricks.
Ensure quality, ensure safety, and minimize masonry time.
There are two commonly used masonry methods in rotary kilns: wet masonry and dry masonry. The following is a brief introduction to the construction essentials of the two construction methods.
For spall-resistant high-alumina bricks, silica bricks, silica red bricks, etc., wet masonry is generally used. In the process of wet masonry, the following matters must be paid attention to:
1) Refractory bricks require that the masonry joints are full of grout, and the width of the brick joints should meet the design requirements of the drawings.
2) After each refractory brick is placed, it should be beaten with a wooden hammer or rubber hammer in order to squeeze out the excess fire mud, and the brick joint and the shell should be completely tightly attached, and the fire bricks should be in contact with each other and firmly combined. When beating refractory bricks, it should be prevented from inappropriate knocking or crushing to damage the refractory bricks or damage the fire clay that begins to solidify.
3) Before the clay of the brick joint is not completely hardened, the excess clay should be scraped off, if there are some places that need to be filled with clay, the scraper should be used to plug the new clay, that is, the masonry joint.
4) The ash joint should be horizontal and vertical, the arc surface should be flat, and the joint should be tight, and the size of the masonry should be consistent with that of each equipment.
5) The straight wall should be built with staggered joints, and the vault and kiln should be built with straight joints in the direction of the circumferential ring belt. Masonry should strive for a straight brick joint, smooth arc surface. The geometry of the masonry should meet the requirements of the drawings to ensure quality.
6) In the process from construction to production, the masonry should be prevented from being damp and frozen, and it should also be prevented from prematurely appearing too high temperature, so that the refractory mud can not reach the due strength.
Dry masonry is generally suitable for magnesia brick systems, such as straight magnesia bricks, magnesia-aluminum spinel bricks and mafic spinel bricks.
The requirements of the arch ring refractory bricks built by dry masonry are similar to those of wet masonry, and finally they should be wedged with a steel plate with a thickness of 2mm. The steel plate should be flat, without concave and convex, thorny, and rusty, and the head should be ground out with a grinding wheel to grind out a wedge angle of less than 60 in order to wedge in. A brick joint can only be wedged into one steel plate, and it is forbidden for a brick joint to be wedged into two steel plates. The steel plate should not be wedged into the brick joints of the lock joint bricks, and should be separated by 1 2 brick joints.
First of all, before the masonry lining, the convex degree of the weld in the kiln cylinder should be carefully checked whether it meets the welding technical requirements of the kiln cylinder, and the weld beyond the specified limit should be polished with a portable grinding wheel. Before masonry, the rotary kiln should be thoroughly cleaned, kept clean and dry, so that there is no ash, no rust, no oil and no water traces, and the metal rust must be removed with a wire brush. Ensure that there is a good combination between the refractory brick and the kiln cylinder.
Secondly, the refractory bricks of the rotary kiln must be laid out before masonry, and the masonry must be checked and inspected in stages based on the precise positioning line. The axial reference line of the rotary kiln is about 1 along the circumferenceThe 5m chord is long, and the axial direction should be parallel to the axis of the rotary kiln. The circumferential reference line of the rotary kiln is every 10m, and the circumferential control line is placed every 1m. The planes formed by the closed hoop lines should be parallel to each other and perpendicular to the axis of the rotary kiln. These positioning lines will be the standard for routine inspection during the masonry process. Multiple inspections, and timely adjustment and correction, will effectively prevent the accumulation of large deviations in the masonry process. The pay-off of the axis of the rotary kiln should be carried out by professional surveyors, and the pay-off should be measured using approved measuring instruments.
Under the premise of ensuring that the rotary kiln cylinder is clean and dry, and that there is no ash, no rust, no oil and no water traces, and the positioning line is accurate, the rotary kiln can be masonry. In the masonry process of the rotary kiln, the following matters should be noted:
1) Bricklaying should be sequentially laid from the exit end of the kiln to the entrance end, and be carried out in sections according to the length given in the drawings
2) At the beginning of masonry, lay a row of bricks along the kiln length baseline, and then take turns to build masonry on both sides of it until it is slightly larger than a semicircle;
3) When the axial staggered bricks, each 4 6 rows must be checked once whether the brick rows are smooth, whether the arc length of the masonry is equal, and the problems should be corrected in time
4) The brick lining must be close to the shell, the brick and the brick are tightly intertwined, the brick joint is straight, the intersection is accurate, the brick is locked, the position is good, and it does not sagging and emptying. In short, it is necessary to ensure that the brick lining and the kiln body are reliably concentric during the kiln operation, and the stress in the brick lining should be evenly distributed throughout the lining and on each brick lining;
5) When masonry, attention should be paid to the large and small heads of the bricks, and they should never be invertedThe bricks must be close to the cylinder, and the bricks must be close to each other
6) When the kiln lining masonry is built, it should be built in accordance with the design ratio, and there should be no "steps or climbing", and it should be adjusted with different types of bricks or mud or narrow strip steel plates in time. In case of unevenness of the cylinder, it can be leveled with thick cement, and it is not allowed to be lined with cardboard or other things;
7) When locking the mouth, the lock brick selection should be appropriate, the gap between all aspects of the lock brick should be consistent after pushing it from the side, and then wedge it with a steel plate, and the wedge brick steel plate should be used as little as possible, two to three pieces per ring. The lock brick can not be put together in two, and the wedge brick steel plate should not be hit on the two sides of the lock brick;
8) For the place where the processing bricks need to be used, the processing bricks should be processed as much as possible, and the size of the processed bricks shall not be less than 1 2 of the original bricks in the length and width direction, and the processing must be flat;
9) After the brick lining of the whole kiln is completed, the brick lining of the whole kiln should be checked and fastened as necessary.
Expansion joint width of refractory brick masonry of different materials.
For the alkaline bricks with large expansion coefficient used in the masonry of the rotary kiln, the longitudinal expansion space should be considered. Each ring (about 198mm in length) should be considered to be stuffed with 2mm thick cardboard in the length direction of each brick to allow room for expansion. Since the radial expansion can be compensated by the expansion of the brick joint and the rotary kiln cylinder, the expansion joint is no longer left.
2) Brick retaining ring in the rotary kiln.
There is generally a brick retaining ring in front of the kiln cylinder, and there may be one or two brick retaining rings in the rear according to the conditions. The spacing of the brick retaining ring is usually not less than 10m, and it is not within 4m of the centerline of the wheel belt and the large gear. Within the scope of the firing zone and the transition zone requiring the stable existence of the kiln skin, the brick retaining ring should not be set. The special retaining bricks are usually built in the lower part of the retaining ring, that is, the retaining ring points to the direction of the kiln head. If there is no special brick retaining ring brick, the retaining brick at the retaining ring can be cut on the spot, and the cut part is 8mm narrower than the thickness of the retaining ring and 5mm deeper than the depth of the retaining ring. In order to avoid possible cracking, the cut out part should have large rounded corners, and a thick cardboard of 3mm should be inserted between the brick and the retaining ring. In terms of reliability, the shorter two brick retaining rings are better than a higher brick retaining ring, and the former can be built with original bricks to improve the safety level. The material of the retaining brick is better than the refractory brick with higher strength and more stable performance.
The masonry quality of cement rotary kiln lining bricks determines the service life of refractory bricks to a large extent, so we must pay great attention to and strictly control the process of building a rotary kiln. High-quality masonry is an indispensable prerequisite to ensure the efficient and stable operation of the rotary kiln.