Improve the service life of refractories for cement kiln
Time:
2021-09-15
With the rapid development and improvement of China's large-scale precalciner cement kiln related technology and supporting equipment,
With the rapid development and improvement of China's large-scale precalciner cement kiln related technology and supporting equipment, the overall technical level of China's cement industry has approached or reached the international leading level, but the overall service life of domestic refractory materials is still certain compared with foreign technology. The gap, in addition to the refractory production enterprise product research and development level, but also with the overall construction level of refractory materials, and people's emphasis on construction quality has a greater relationship.
Through long-term visits to domestic cement production enterprises, the author found that most cement companies have the following restrictions on the service life of refractory materials: First, the production tasks are heavy, the maintenance time is tight, and some cement enterprises support the refractory materials. The importance of construction is not high, there are irrational refractory materials, repeated kiln maintenance; second, the overall technical level of domestic refractory construction team is uneven, except for some large cement groups have relatively stable maintenance team In addition, most small and medium-sized cement enterprises rely on the external construction team to repair or replace refractory materials, thus restricting the overall construction quality of refractory materials to varying degrees. Third, because most cement companies implement the separation of refractory supply and construction. Some construction teams have little knowledge of the performance and construction requirements of refractory materials, and the level of specialization is low. It is difficult to guarantee the construction performance and service life of refractory materials. At the same time, the technical solutions and construction specifications for refractory construction in the domestic cement industry are looser than those in the power and petrochemical industries, and the details of the overall construction quality are not adequately captured. In addition, some construction techniques with better application techniques are difficult to implement in the current environment. Take expansion joint construction as an example:
First, in the construction design, generally combined with the high temperature performance of the refractory material, a zigzag expansion joint is left in one meter, and one meter is cast at a distance of one meter in the construction, and the expansion joint is made of ceramic fiber cotton having a certain thickness. This construction method can guarantee the construction quality of the refractory castable expansion joint, but the construction progress is relatively slow. Second, due to the slow construction schedule and long construction period of the above construction methods, some construction teams use wooden plywood to maintain expansion joints. The expansion gap reserved by the wooden plywood is used, and the plywood leaves a gap after the high temperature is burned out. If the refractory material cannot completely offset the expansion gap, the refractory material will crack under long-term operation, and it is easy to accidentally occur from the crack.
The author believes that the use of ceramic fiber cotton as a reserved expansion gap filler can effectively ensure the construction quality. On the one hand, ceramic fiber cotton has good thermal insulation performance; on the other hand, ceramic fiber cotton can reserve the filling gap filler. effect. The service life and service life of refractory materials have a great relationship with the performance and construction quality of refractory materials, especially refractory castables. Because it is a semi-finished material, its use effect has a greater relationship with the quality of construction. Said the "three-point material, seven-point construction". Therefore, the construction of refractory materials must strictly follow the construction specifications, control every link, every detail. Taking refractory castables as an example, the following details should be strictly controlled during construction:
1. Add water. Generally, the refractory castables will provide a construction specification after leaving the factory, and the amount of water added to the castable during construction is clearly defined. In the actual construction, it is necessary to control the amount of water added during the mixing process (preferably not to exceed the upper limit of the recommended value) to ensure that the castable has sufficient fluidity, but does not allow the castable to flow. If the water supply is not required for the convenience of construction, the overall performance of the castable will be greatly reduced, which is the change of the strength of the castable with the amount of water added.
2. Stirring time. The mixing time of castables is closely related to the amount of water added during construction. Generally, the mixing time is required to be controlled at 3~5min, and the speed of the mixer is preferably above 19 rev/min. Under the premise of the same amount of water added, the longer the stirring time, the better the fluidity of the castable.
3. Welding and thermal expansion treatment of the anchor. The welding of the anchor should first ensure that the arrangement is reasonable and the direction of the force meets the requirements. At the same time, the stainless steel welding rod used for welding should be carried out in accordance with the specifications. The weld should be smooth and full, and the thermal expansion of the anchor should be done well. deal with.
Should pay attention to the construction: 1 template selection and support. Whether the construction formwork adopts the wood formwork or the steel mold, the strength requirements shall be met; the support process shall be carried out strictly according to the drawing size, and the drum mold, the rising mold and the running mode shall not appear in the vibrating process. 2 maintenance of castables. The mold curing time and mold release curing time of castables should meet the requirements of the specification. Generally, at the ambient temperature of 5 °C ~ 35 °C, the mold curing time is not less than 24 hours, and the mold release curing time is not less than 24 hours. Ensure the early strength of the castable. 3 baking of castables. The castable must be baked before use. The baking should meet the baking system to ensure that the free water and crystal water in the castable can be fully discharged, so as to avoid the phenomenon of “peeling and bursting” in the early stage of feeding or use. The normal use of castables. For some special parts, it is best to carry out separate baking before the whole baking. For some key parts (such as the front kiln mouth, kiln hood, heat section of the cooler, etc.), bamboo chopsticks can be used to reserve the vent hole. The construction of refractory bricks should pay attention to the correct matching of the fire mud, the saturation of the mud and the control of the gray joints; the refractory brick masonry in the rotary kiln should pay attention to the arrangement and arrangement of the locking bricks, and the jointing and position of the locking bricks.
In short, in the masonry process of refractory materials, it must be strictly controlled from every detail and every link. Only in this way can the construction quality be guaranteed and the service life of refractory materials can be guaranteed. Here, it is necessary to mention the "Tongda Refractory System", which is a service chain that integrates refractory design, research and development, product manufacturing, and engineering construction to ensure the integrity of the entire system.
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