Thermal insulations from rice husk ash, an agricultural waste

Rice husk ash, an agricultural waste material, is available in large quantitaties in the rice paddy growing countries of the world at little or no cost. This ash is highly porous, mostly silica and possesses refractory and thermal insulation properties. It is therefore an attractive starting raw material for the manufacture of low to moderate cost thermal insulations for dryers, ovens, kilns and furnaces, including those employed in the ceramic industry. This paper deals with manufacture, properties and usage of a spectrum of low to high temperature thermal insulations and insulating refractories that can be made from rice husk ash, namely: (i) Calcium ferrite bonded porous silica refractory: (ii) Sodium silicate bonded porous silica refractory; (iii) Fired and chemically bonded forsterite insulating refractory; (iv) Hydraulic setting calcium silicate/silica thermal insulation.