The rotary kiln is called the heart of the cement clinker line. The quality of the refractory brick lining directly affects the operation of the rotary kiln. Therefore, the lining of the rotary kiln has always been the top priority of the quality control of the entire clinker line. . At a foreign construction site where the author participated, during the construction of the rotary kiln, the owner requires all refractory bricks to be wet-laid (the side of each brick must be smeared with fire mud). When locking, only 2 refractory bricks per ring are allowed 3mm steel plate. Bricks dropped on the first day of feeding (the rotary kiln was 4.8mx74m short, of which 3 spinel bricks dropped at the 36m position in the transition zone, and 7 magnesia bricks dropped at the 28.8m position in the firing zone). The company’s project department organizes production personnel to repair the missing bricks with spare bricks, and at the same time inspect the spinel bricks and magnesia bricks ring by ring, and inject iron plates according to the actual situation. After the second ignition, everything went smoothly. After 11 months, the refractory bricks were replaced for the first time. The analysis of the brick drop and brick repair is as follows:
According to 14.1.9 of the “GB50521-2014 Industrial Kiln Construction and Acceptance Specification”, the basic bricks are mainly used for dry masonry. According to our construction experience, both spinel bricks and magnesia bricks belong to alkaline bricks. This type of bricks are mainly dry-laid. Except for very few parts, refractory bricks need to be adjusted to avoid “climbing” phenomenon. A small amount of fire mud. If every refractory brick is smeared with fire mud, it will inevitably cause the brick gap to become larger, which greatly increases the risk of brick dropping. Another reason is that alkaline bricks are easy to absorb moisture. Drinking water is not suitable for mixing with fire mud. The melting point of water glass is about 1100°C, which is lower than the temperature of the burning zone. Fire mud mixed with water glass is in the production process. It is easy to be heated and melted to form a gap. Therefore, dry-laying of alkaline bricks is the experience gained through a lot of practice.
According to 14.1.15 of “GB50521-2014 Industrial Kiln Construction and Acceptance Specification”, it is stipulated that the steel plate lock used in each ring is generally no more than 3 pieces. However, considering the actual situation, this article still retains the original specification.” There should be no more than 4 locks in the lock area of each ring. When the refractory bricks are “locked”, the steel plate is used to squeeze the refractory bricks, reduce the gap between the refractory bricks, enhance the integrity of the refractory bricks, and ensure rotation in the rotary kiln In the case of refractory bricks, there is no “drawing” or falling. The number of steel plates driven depends on whether the ring refractory bricks are locked.
The key step of “locking” is to set up a jack and use hydraulic power to squeeze the refractory bricks to both sides. The pressure that different types of refractory bricks can withstand varies greatly. For example, magnesia bricks will be fractured when the pressure is increased to about 15MPa, and silica bricks can be pressurized to 35MPa. Because the fractured refractory bricks must be discarded, the pressure of the magnesia bricks must be controlled within 15 MPa when pressurized, which means that the ring magnesia bricks have gaps before the last brick is built. If the last brick to be built is slowly driven in with a wooden square and a sledgehammer, this gap will disappear to a large extent. In many cases, only one 3mm steel plate needs to be driven into this ring; but if the last brick Yes, this gap still exists, and this ring needs to be driven into 3 or more steel plates according to the actual situation.
In the actual construction process, the last few bricks of the lock are required to be carefully arranged to ensure that the last brick is driven into the arch as much as possible. However, during the adjustment process, it is unavoidable that the last brick is 5~7mm smaller than the left space. In this case, the conventional treatment is to put the last few locks of refractory bricks with fire mud, reduce the last space, and then slowly drive into the last brick, the fire mud in the adjacent brick joints is squeezed out, and finally hit Into the steel plate.
To sum up, because the strength of refractory bricks is different, there is a reasonable error in size, and there are different construction techniques. One-sided emphasis on less steel plate will only cause the loosening of the bricks, leaving the hidden danger of later falling bricks. The re-ignition until the overhaul lasted more than 11 months. Practice proved the feasibility of “alkaline brick dry-laying”, which brought convenience to the construction of foreign construction sites in the future and avoided similar problems again.