China's Refractories

Abstract: In order to reduce the thermal energy loss of high temperature kilns and furnaces and lower the surface temperature of the kiln body, magnesia insulation materials were prepared using self-made magnesia porous aggregates (using high purity magnesia powder as starting material and potassium oleate as the foaming agent), middle grade magnesia powder, calcium aluminate cement, and SiO2 micropowder as starting materials, introducing walnut shell powder impregnated with silica sol (short for Sws) as a pore-forming agent. The effects of the Sws addition (0, 10%, 15%, and 20%, by mass) and the sintering temperature (1 300, 1 350, 1 400, and 1 480 ℃) on the properties of magnesia insulation materials were studied. The results show that (1) for the specimens fired at 1 480 ℃, when the Sws addition is 10%, the cold compressive strength is 22 MPa; when the Sws addition is 20%, the thermal conductivity is 0.368 W·m-1·K-1 (350 ℃); (2) nano-silica in the silica sol reacts with MgO in the matrix to form forsterite, which encapsulates the pores volatilized from the walnut shell powder and forms closed pores.

Key words: foaming method, ignition loss method, walnut shell powder impregnated with silica sol, magnesia porous aggregates, magnesia insulation materials