With the development of new dry cement production technology, the corresponding refractory materials have also made great progress. In addition to the breakthroughs in conventional refractory bricks, the performance of refractory castables has become more and more perfect, and is widely used in amorphous parts in kilns. As we all know, refractories castables are a kind of amorphous refractory materials without calcination. They are made of refractory aggregates, refractory powders and binders in a certain proportion. During construction, they have good fluidity after adding water and stirring, and then they are formed and cured to solidify and harden.
The use characteristics of castables are as follows: First, the masonry structure has few joints, strong integrity, good sealing, and can avoid the infiltration of clinker powder during application and operation; second, it is easy to anchor and convenient to construct, which is conducive to improving masonry efficiency and masonry quality; third, the raw materials are widely available, which is convenient for comprehensive utilization of resources, and the delivery time is short, which can reduce inventory and related costs accordingly. Based on these advantages, the application ratio of castables in cement burning systems has increased year by year. Taking the 5000t/d new dry kiln as an example, the ratio of refractories castables to refractory bricks has reached 1:1.
Measures to speed up the service life
Refractory castables are generally a kind of high-temperature resistant concrete, so it also conforms to the theory of concrete. For example, the amount of water added is the fundamental reason for controlling whether the castable can achieve the designed strength. However, driven by interests, some construction parties will add a lot of water to the casting material to speed up the construction progress during the construction of refractories castables, which leads to the service life of the kiln refractory lining after construction being much lower than the design requirements, and even serious problems have occurred after half a year of use, and it must be overhauled (while well-constructed refractory castables do not need overhaul for 3 to 5 years). We know that the investment in refractory materials accounts for a small proportion of the entire plant construction investment (about 2% to 4%), but its impact on the future operation of the entire system is very large. The loss of one day's shutdown due to a refractory lining accident can be as low as hundreds of thousands or even millions of yuan. Therefore, ensuring the high operating rate of the firing system can achieve high-quality, high-yield and low-consumption operation of the system.
The use of castables must be strictly implemented in accordance with regulations
(1) The amount of water added to the refractory castable must be strictly controlled in accordance with the instruction manual and must not exceed the limit. Under the premise of ensuring construction performance, it is better to add less water rather than more.
(2) The mixing time of the castable is not less than 5 minutes. A forced mixer should be used during operation. When mixing, it is better to dry mix first, then add 80% of the amount of water, and then slowly add the remaining water depending on the dryness and wetness until a suitable working consistency is obtained.
(3) The castable material poured into the mold frame should be immediately vibrated in layers with a vibrator. The height of each layer should not exceed 300mm, and the vibration interval should be 250mm. When vibrating, try to avoid touching the anchors, do not damage the insulation layer, do not vibrate or re-vibrate the same part for a long time, and slowly withdraw the vibrator after seeing the slurry on the surface of the castable to avoid segregation and voids in the castable layer.
(4) When pouring a large area, it should be constructed in blocks. The pouring area of each block should be about 1.5m². Expansion joints should be set according to the design and should not be omitted. The expansion joints should be set in the middle of the anchor interval.
