Wear-resistant refractory castable for circulating fluidized bed boiler

Circulating fluidized bed boiler is a key project of national "7th five year plan" and "8th five year plan".The boiler has strong adaptability to coal quality and can be used for lean coal, coal gangue and coal cinder, etc. The coal powder cycle times are many, the combustion rate reaches 98%, the thermal efficiency is high, the desulfurization effect is good, the environmental pollution is small, it is an ideal steam supply, heating and power generation equipment. 

Because of the new boiler coal particle fluidization velocity is high, more than 5 m/s, local up to 21 meters/seconds, of the furnace lining refractories with strong under the high temperature erosion wear, combined with the impurities in pulverized coal and furnace lining materials of chemical reactions and frequent heat exchange, leading to the original of the refractory lining erosion, wear, peeling and collapsed, often have to stop the furnace maintenance (usually for 3 ~ 4 months), seriously affected the normal operation of the boiler and production.Therefore, it is of great significance to develop a new type of wear-resistant castable for circulating fluidized bed boiler to adapt to the popularization and application of the new type of boiler.

The circulating fluidized bed boiler is subjected to the strong collision, scour and wear of high concentration, high speed and turbulent flying ash particles, as well as the erosion of high temperature thermal stress and chemical substances, which seriously affects the service life of the boiler.Therefore, refractory manufacturers have been studying various kinds of lining refractories suitable for their harsh working conditions, especially lining refractories that meet the technical requirements of high strength, high abrasion resistance, high erosion resistance and good thermal shock stability.Circulating fluidized bed boiler lining with refractory material has gone through several stages: the first stage is shaped products refractory material;The second stage is clay binding castable;The third stage is high alumina refractory castable with phosphoric acid, polyphosphate, sodium silicate, pure calcium aluminate cement and other binder.Although the wear-resisting and refractory materials in the third stage have improved their service performance compared with the first two kinds, it is difficult to guarantee the construction performance due to the high content of CaO in the binder and many impurities in the high aluminum raw material, which leads to the high porosity, low strength and poor wear resistance of the material under high temperature.The fourth stage is on the basis of the above materials successfully developed by low cement, ultra-low cement and no cement combination of rigid jade series wear resistant castable (vibration castable and artesian castable).

Our company began to develop wear-resistant refractory castables, including vibration castables and self-flowing castables, for lining of CFB boilers in the mid 1990s.

Vibration castable is mainly low cement castable, low cement castable is a kind of castable developed on the basis of cement binding castable and clay binding castable, it is often called "high technology castable", "high density castable" and "high performance castable" and so on at home and abroad.In terms of ingredients, the low cement castable castable with cement and clay castable is similar, they are both composed of refractory aggregate, refractory powder and binder, the difference is in the matrix composed of refractory powder and binder, with super fine powder (granularity ﹤ 1 um) to replace part of cement or in combination with clay, then add a small amount of dispersant make superfine powder evenly spread between the aggregate particles, filling the gap in the sub-micron, so as to form a structure with uniform density.The key of low cement castable lies in the introduction of ultra-fine powder and dispersion technology, which greatly increases the compactness of castable, and greatly improves its main properties such as fire resistance, strength, abrasion resistance and thermal shock resistance.

Artesian castable is a new high-tech product developed on the basis of vibration castable based on the theory of solid fluid.The self-flowing castable has the following characteristics: the slurry has high thixotropy, and it can flow, degassing, spread flat and compact by itself without vibration equipment during construction, which saves labor and time and has high efficiency.And self flow castable mainly adopts composite superfine powder of coagulation, reduce the content of CaO, which overcomes the weakness of CaO dehydrated to form, the castable density increase, the thermal shock stability, strength, abrasion resistance and refractoriness and main performance have been improved greatly, reach or exceed the famous at home and abroad of circulating fluidized bed boiler design, proposed by the manufacturer's standard lining material.                           

Wear-resisting and fire-resistant self-flowing castable developed by our company has excellent performance, great strength, good thermal shock stability, small change of reburning line, erosion resistance, no cracking, no peeling, good volume stability.