Optimization of production process parameters of rice husk silica (RHS) refractories

The parameters necessary to aid the industrial production of rice husk silica refractory using PEG 8000 as binder and slaked lime as dopant (mineralizer) have been studied. The optimal value of the dopant - Ca(OH)(2) was determined to be around 1.4%. Percentages beyond 2.6% result in the formation of pseudo-wollastonite, with decreased mechanical properties of the refractory. The investigations here have shown that an optimum prefiring temperature should be chosen from the range 1250 to 1350 degrees C, since the highest modulus of rupture (MOR) necessary for handling the produced refractories occurs within this range, and is consequent upon the tridymitization of the refractory body within this temperature range. The compaction pressure range that is optimal for good sintered density, apparent porosity and MOR falls between 90 and 110 MPa. However, pressure necessary for green powder compaction is dependent on the type of binder used, as each binder has its own young modulus, which affects its crushing resistance.