A new method for prolonging the life of CRK-cement rotary kiln refractories

As a refractory material to protect the normal operation of the cement kiln, it is the top priority. How to improve the service life of cement kiln refractories to ensure the normal operation of cement kiln has always been an important research topic and focus of cement enterprises.

The measures to improve the refractory materials of rotary kiln are introduced from three different new angles of selection, installation and maintenance of refractory materials.
These measures are indispensable to prolong the life of cement kiln refractories, because only by comprehensively using multiple means can the purpose of prolonging the life be truly achieved.

1. Selection of refractory materials

For the selection of refractory materials, we must follow 3 major principles.

1. The refractory material must be able to meet the basic functions, but at the same time, the variety and quantity of refractory bricks should be minimized to facilitate control;

2. The life control of different parts of the refractory material in the rotary kiln should be consistent. For example, the service life of the kiln mouth castable, the upper and lower transition zones, and the firing zone are basically synchronized.

3. Control the overhaul cycle, ensure that one overhaul is performed every 1 year, and strive for 2 overhauls every 3 years. According to the temperature of different zones in the kiln, different varieties of refractory materials are selected.

The firing zone must use alkaline bricks. It mainly includes magnesia-chrome bricks, low-chromium and chromium-free, zirconium-containing or zirconium-free special magnesia bricks and dolomite bricks. There are many choices for the upper and lower transition zones, such as magnesia-alumina spinel bricks, silicon molybdenum bricks, silicon molybdenum bricks, etc., which have high thermal shock stability and have achieved good results in the transition zone. The selection of safety belt refractory materials is mainly based on the service life. Generally, high-strength alkali-resistant bricks can have a service life of 1-2 years, and anti-stripping high-alumina bricks have a service life of 2-3 years. The lining of the discharge opening is one of the weakest links in the kiln lining of large kilns. Silicon carbide bricks, silicon molybdenum bricks, silicon molybdenum bricks, spinel bricks, etc. can be used in kilns with small deformation, which have a lower temperature at the kiln mouth. Yes, high-alumina bricks with excellent thermal shock resistance can be used.

2. Installation of refractory materials

The service life of refractory material has a lot to do with its construction quality, especially refractory castable, because it is cast on site, its use effect is directly related to the quality of construction. In the construction and installation of refractory bricks, attention should be paid to the correct combination of fire mud, the saturation of mud, and the control of ash joints; the arrangement and arrangement of lock bricks should be paid attention to in the masonry of refractory bricks, and the insertion joints and positions of the lock brick panels should be controlled. In the construction of castables, special attention should be paid to the amount of water added during the mixing process, as long as the castables have sufficient vibrational fluidity, if excessive water is added, its overall performance will be affected.

In addition, the stirring time of the castable will also affect its effect. Generally, the stirring time required for the castable will be controlled at 3-5 min, and the speed of the mixer should preferably be above 19 rpm. Appropriate mixing time can maximize the construction performance and service performance of the castable.

Finally, the baking time of the castable should not be sloppy. It is necessary to ensure that the water in the castable can be completely discharged, so as to avoid bursting in the early stage of feeding or use, which will affect the normal use of the castable.

3. Maintenance of refractory materials

The cooling system of the kiln lining when the kiln is stopped will also have a great impact on the service life of the unreplaced refractory bricks. Therefore, when the kiln is stopped without changing bricks, it must be cooled slowly to ensure the safety of the kiln lining. The stability of the kiln skin on the brick lining in the firing zone and the transition zone on both sides is a decisive condition affecting the service life of the brick lining. Minimize the number of kiln shutdowns, because frequent unplanned startup and shutdown of the kiln will cause rapid cooling of the hot surface of the lining brick, excessive shrinkage, and serious damage stress in the brick, resulting in premature cracking and damage. When the kiln is running, if the thermal system is unstable, it will also cause the lining of the kiln to be hot and cold, and the kiln skin will collapse for a long time.