- Time:Jul 20, 2023
一. Customize exclusive refractory materials according to working conditions
Taking the dry process cement kiln as an example, it has the technological characteristics of high kiln temperature, slow kiln speed, severe alkali erosion, complex structure and high energy saving requirements. It is not suitable for expensive refractory materials, but must match the working conditions. According to different working conditions and environments, different types of refractory materials need to be selected.
(1) The clinker sintering temperature of the firing zone is 1300°C~1450°C, and the flame temperature is as high as 1800°C~2000°C. Under such high temperature, any refractory brick will be quickly decomposed and destroyed. In order to resist the high temperature, a layer of kiln skin needs to be attached to protect the lining brick. In particular, it should be pointed out that magnesia-iron spinel bricks have high temperature resistance and high strength, are easy to hang on the kiln skin, and also solve the environmental pollution problem of magnesia-chrome bricks used in cement kilns. They are the most widely used products in cement firing zones.
(2) There are many options for the upper and lower transition zones, such as magnesia-aluminum spinel bricks, silicon molybdenum bricks, silicon molybdenum wear-resistant bricks, composite structure silicon molybdenum bricks, etc. Among them, the aluminum-silicon series refractory materials developed in recent years - silicon molybdenum bricks, especially the silicon molybdenum bricks with andalusite, have excellent thermal shock resistance and significantly improved product wear resistance, and have achieved good results in the transition zone.
Zhenjin Company's Mengdian cement 4.8*70m cement kiln has brick matching schemes in different temperature zones, and the silicon molybdenum bricks can be used for up to 3 years.
(3) The selection of refractory materials for seat belts is mainly based on capital and life. For example, high-strength alkali-resistant bricks can be used safely for 1-2 years, anti-stripping high-alumina bricks for 2-3 years, and ZJAS-1650 silica bricks for 3-5 years. the
（4）The lining of the cooling zone is one of the weakest links in the large-scale kiln lining. Because the temperature is as high as 1400°C and the temperature fluctuates greatly, the wear of the clinker and the erosion of the air flow are very serious here. This requires that the brick lining has a small thermal conductivity, good wear resistance and thermal shock resistance; alkaline bricks with excellent thermal shock resistance can use silica molybdenum bricks, magnesia aluminum spinel bricks, etc.
（5）Due to the extrusion of refractory materials by mechanical force at the kiln mouth, refractory materials with better thermal shock resistance, corundum or steel fiber reinforced corundum castables or kiln mouth castables can be used.
二、pay attention to the quality of refractory material construction
The service life and replacement cycle of refractory materials have a lot to do with the performance and construction quality of refractory materials, and their use effect has a greater relationship with the quality of construction. There is a saying in the industry that "three points for materials, seven points for construction". Therefore, the construction of refractory materials must strictly follow the construction specifications, and control every link and every detail. the
(1) Preparation before refractory masonry
Before masonry construction, first clarify the construction tasks; secondly, do a good job of "three checks", that is, check personnel, check materials, and check the site; then make preparations, eliminate hidden dangers, reduce problems, and make a plan to deal with possible accidents.
① Carefully analyze the drawings, clarify the construction tasks, understand the design intent, and clarify the design requirements and key points of each part.
②Coordinate well with the leaders of the designer, supplier, and construction party, specify the responsibilities to the individual, and ensure the best construction quality.
③ Check the refractory materials, construction machinery and auxiliary facilities and tools entering the site to confirm whether their varieties, specifications, quantity and quality meet the construction requirements, and whether the personnel and organizations participating in the construction meet the predetermined requirements.
④ Check the construction site carefully, check whether the inside of the kiln is cleaned, whether there is any deformation of the simplified body, whether the welds and connections are smooth, and whether the brick retaining ring is perpendicular to the kiln axis. It is required to achieve sufficient lighting, smooth transportation, complete tools, mechanical and electrical equipment, and complete personnel. In case of mechanical and electrical equipment and other failures, they can be eliminated in time.
⑤ According to the construction tasks and the actual situation on the site, prepare the progress plan and cross-operation plan of the masonry project, make good construction technology, material and work preparations, and formulate a plan in case of failure to ensure that the kiln lining construction is carried out harmoniously and orderly and achieves the best quality.
(2) Precautions for refractory masonry
①Basic requirements for bricklaying: the brick lining should be close to the kiln body, that is, the "four corners" of the cold end of the bricks are required (bricks: the big head and the kiln body are fully adhered to without seams), the bricks are tight, the brick joints are straight, the circles are accurate, the bricks are locked firmly, and they are not in place. To ensure reliable concentricity between the brick circle and the cylinder, the kiln lining structure is stable, so that the pressure of the cylinder on the brick circle and the stress inside the brick lining are evenly distributed on each brick in the entire lining to prevent stress concentration.
② Lock the brick lining so that the brick locking belt does not become the weakest link in the kiln lining.
③Reduce the amount of steel plate to avoid extrusion of the adjacent brick due to volume expansion of the steel plate after oxidation, resulting in cracking and peeling of the brick.
(3) Brick joints and treatment
① Properly leave appropriate brick joints for alkali-resistant bricks, and try not to use any joint material in the joints to absorb the compressive stress in the brick lining.
②The thermal expansion of high-alumina brick lining and alkali-resistant brick lining is much smaller than that of alkaline brick lining, resulting in smaller expansion stress, so there is no need to deliberately leave brick joints; the mud in the brick joints must be full.
(4) Do not use steel hammer
Refractory bricks are brittle materials that cannot withstand the impact of rigid tools. Flexible tools such as wooden hammers, rubber hammers or hard plastic hammers must be used to operate, otherwise, they will be damaged during operation and cracks will appear, or even breakage.
(5) Brick linings for immovable equipment are built using the "Ding Masonry Method"
"Ding laying method" is a laying method in which the length of the brick is the direction of the thickness of the lining, that is, the brick joint is perpendicular to the hot surface. Even if the brick lining is corroded, it will not fall off, which can improve the service life of the brick lining.
(6) Construction method
① The arch method is used to lay bricks, and the arch method is generally used on large kilns with a diameter of more than 4m.
② Bricklaying by top support method
For small and medium-sized kilns with a diameter of less than 4m, the top support method is mainly used to lay bricks.
When laying bricks in a kiln with a diameter of more than 3.6m, two kiln supports are required, which is called the cross-shaped top support method.
For kilns with a diameter of less than 3.6 meters, only one kiln support is required, which is called the in-line top support method.
三、Adhere to scientific and reasonable daily operation and maintenance
(1) Heating of the kiln: After the kiln lining is built, it must be properly baked. The temperature should not rise too fast during baking, so as not to cause excessive thermal stress and cause the brick lining to crack and peel off. The kiln lining baking must be carried out continuously until it is completed, and it is necessary to achieve "slow heating, no turning back".
(2) Adhesion and protection of the kiln skin: The key to the service life of the brick lining is the stability of the kiln skin with firing. In order to form the first layer of kiln skin, it is necessary to control the fineness and uniformity of the clinker grains, reasonable ingredients, and make it firmly bonded to the refractory bricks. As the newly bonded clinker builds up, the kiln skin thickens until the kiln skin becomes so thick that the clinker can no longer bond to each other. The quality of the first layer of kiln skin is crucial to prolonging the life of the kiln lining.
(3) Reduce the number of kiln shutdowns and increase the operating rate of the precalciner kiln: In order to increase the operating rate of the precalciner kiln and reduce the number of kiln shutdowns, frequent unplanned start and stop of the kiln should be avoided. Frequent kiln shutdown will lead to rapid cooling and excessive shrinkage of lining bricks, resulting in severe destructive stress, which in turn will lead to cracking and damage of bricks and distortion of kiln lining, reducing the service life.
(4) Stabilize the thermal system of the kiln: when the kiln is in operation, if the thermal system is unstable, it will cause the kiln lining to be hot and cold, and the kiln skin will collapse for a long time, and it is very easy to crack and peel off the refractory bricks, and the bricks are fried, and the service life is greatly shortened. the
In general, in order to prolong the service life of cement kiln refractories, it is necessary to control the scheme design, product quality, on-site construction, technical services, product upgrades and other aspects, and to solve the systematic needs of cement enterprises with personalized, intensive and rapid response overall service solutions.
After more than 30 years of technical precipitation and experience accumulation, Zhengzhou Zhenjin Refractory Co., Ltd. provides full-life cycle management and system maintenance to effectively guarantee the use effect of refractory products, promote the longevity and synchronization of refractory use, improve the safe operation rate of kilns, create value for customers, and achieve win-win cooperation with customers.
