Preparation of phosphate porous thermal insulation castable from aluminum silicate industrial waste

One of the ways to improve the efficiency of thermal equipment is to use thermal insulation materials on the equipment lining. Conventional thermal insulation materials are mainly small-sized and single-piece refractory bricks (clay ultra-light bricks and foamed corundum bricks). The production process of these shaped products consumes a lot of energy, and it is difficult to prepare large-sized products. Porous heat-resistant castable can make up for the shortcomings of shaped products. Technical personnel of relevant research units in Russia developed a production process of porous heat-resistant castable. In this process, in order to make the castable porous and hardened, the porous castable with average bulk density of 0.4 ~ 1.10 gcm-3 and maximum service temperature of 1600℃ was prepared by using aluminum powder and phosphate binder to react and release heat.

The aggregates used in the test process include finely ground bauxite clinker, post-high alumina catalyst used in petrochemical industry (with specific surface area of 3800 ~ 4600 cm2g-1 and Al2O3 content of 70%~75%), and some waste materials of dispersed aluminum silicate materials (dust collected during clay clinker production with Al2O3 content not less than 32%). These industrial dust wastes are dispersive, do not need fine grinding, and have high activity for orthophosphoric acid because of their composition characteristics.

Phosphate binder for refractory castables was prepared from fine powder of clay clinker production waste. The method was to dissolve the fine powder in 60% phosphoric acid, and then separate unreacted components by decantation. According to this method, the aluminum-silicon phosphate liquid phosphate binder with an average volume density of 1.46 ~ 1.48 GCM-3 can be obtained, and its properties can remain unchanged for 6 months. The fire resistance of the composite bonding material made of developed bonding agent and high alumina catalyst waste exceeds 1700℃.

A heat-resistant aerated phosphate castable with average bulk density of 0.5 ~ 0.7 GCM-3 and compressive strength of 1.3~3.0 MPa was prepared by using the developed binder, finely ground clay clinker powder and clay clinker aggregate with particle size less than 1 mm. The application temperature of this heat-resistant porous castable is between 1400℃ and 1500℃. If corundum aggregate is used instead of clay clinker aggregate, the service temperature of castable can reach 1500~1600℃.