- Time:Oct 31, 2022
Rotary kiln is one of the most important equipment in cement production, the whole clinker calcination process is basically completed in rotary kiln, rotary kiln operation is directly related to the efficiency of cement plant. The main role of firebrick in rotary kiln is to protect the kiln cylinder from damage caused by high temperature gas and high temperature materials, ensure the normal operation of production, and also play the role of energy saving and consumption reduction. In cement production, the abnormal damage of refractories leads to frequent kiln shutdown accidents. The use of refractories has become a key link restricting the efficient operation of cement kilns. Under the comprehensive influence of thermal factors, chemical factors and mechanical stress, the refractory bricks of cement kiln are damaged in many ways. For many years, the refractory brick in rotary kiln is affected by the increase of kiln speed, the increase of kiln temperature, the change of technological conditions and the construction quality, and the mechanical factor is an important factor leading to the damage of refractory materials.
1. Classification of refractory bricks for cement kiln
The common refractory bricks in cement kilns can be divided into two categories, alkaline bricks and non-alkaline bricks. The basic bricks produced by ZHENJIN REFRACTORIES spinel bricks, which are used in the upper and lower transition zones and firing zones of rotary kilns. The non-alkaline bricks produced by ZHENJIN REFRACTORIES mainly include a series of silicon non-wear resistant bricks and anti-peeling high aluminum bricks, which are mainly used in decomposition belt, safety belt and cooling belt and other parts.
2. Mechanical factor damage mechanism and analysis of firebrick
In general, the mechanical damage of refractory brick includes the ellipticity of kiln cylinder, the dislocation of brick lining, the improper lock of refractory brick and the extrusion of brick retaining ring.
(1) Cylinder ellipticity
Cylinder ellipticity refers to the difference between the maximum radius and the minimum radius of the cylinder multiplied by 2 during the rotation of the rotary kiln. The influence on the ellipticity of the cylinder is mainly caused by the weight of the lining brick, the load of the kiln material and the weight of the cylinder itself, which is mainly manifested as the abnormal slip amount. Too low slip amount will cause the fluctuation of working conditions in the kiln and the collapse of the kiln skin, and the cylinder body will be locked and the lining degree of the kiln will be damaged. Excessive slip will cause excessive deformation of kiln cylinder and damage of refractory brick due to excessive mechanical stress.
Improvement measures: regular detection of pulley slip and cylinder ellipticity, real-time measurement of temperature difference between kiln cylinder and pulley during operation, pulley gap fan must ensure that there is enough cooling air, to prevent the temperature difference between the pulley belt and the cylinder is too large, if necessary, pulley gap adjustment, the fire bricks with abnormal ellipticity are wet.
(2) Dislocation of brick lining
Due to the loose masonry, the refractory brick of cement rotary kiln frequently opens and stops the kiln, and the deformation of the kiln cylinder body causes the relative movement between the kiln cylinder body and the cold side of the lining brick, resulting in the torsional and oblique dislocation of the lining brick and the explosion and Angle loss of the brick surface. The refractory brick of cement rotary kiln has a large area of torsional and oblique dislocation.
Improvement measures: In the construction process, the technical team of ZHENJIN REFRACTORIES requires strict masonry quality control and key supervision, strictly prohibit the use of refractory bricks with large defects, and the expansion joints of refractory brick lining must be reserved according to the design, and the width of expansion joints must not have negative tolerance. The lining of important parts and complex parts should be prelaid first, and the deformed area of the cylinder body should be properly levelled with fire mud before laying.
(3) the refractory brick lock is improper
Ribbon grooves will appear when the refractory brick lock is improper, which is generally shown in the axis direction of the kiln, showing a ribbon deep groove with a width of 2-4 bricks. The main reason is that the amount and location of lock bricks and steel plates are improper in the lock area. The lock brick is too tight, resulting in damage cracks inside the brick.
Improvement measures: In the process of masonry, the lock brick is properly elastic, and only one iron plate is inserted into each ring brick joint and it is driven evenly. The number of lock bricks in each ring shall not exceed 2, the cool-lock bricks shall not be built next to each other, and the vertical lock bricks shall not be located on a horizontal line.
(4) brick ring extrusion
Fire brick damage is easy to occur at the brick retaining ring, which can be divided into two categories: horizontal or inclined shear cracks in the upper corner of the brick retaining ring, especially in the brick lining at the mouth of the kiln; The fire brick at the brick retaining ring is pushed by too much brick lining, and the deformation of the cylinder at the brick retaining ring will further aggravate the damage process.
Improvement measures: The design team of ZHENJIN REFRACTORIES requires that appropriate number of brick retaining rings should be set, the position between brick retaining rings should not be too long, the brick retaining ring should not be welded in one part all year round, and the position of brick retaining ring should be moved during maintenance. At the same time, the precast corner-missing brick should be used in the brick retaining ring instead of cutting brick.
Mechanical stress damage is the key factor leading to the damage of refractory brick. The causes of damage can be analyzed according to the damage phenomenon of refractory brick, and then targeted improvement can be made. In addition, ZHENJIN REFRACTORIES can make a comprehensive analysis according to the damage of firebrick combined with the ovality of cement kiln cylinder, brick retaining ring and construction of firebrick. Reducing the damage of refractory brick caused by mechanical factors can prolong the service life of refractory brick, ensure the efficient and safe operation of cement kiln, and achieve the purpose of energy saving and cost saving.
