A PROCESS FOR PREPARING OF WHITE RICE SHELL ASHES HAVING A SMALL DEGREE OF CARBON UTILIZED IN CONSTRUCTION MATERIAL

摘要

1508825 White husk ash REFRATECHNIK ALBERT GmbH 26 March 1975 [4 April 1974] 12802/75 Heading C1A White rice husk ash of low carbon content (< 2%) is prepared by heating husks to a separation temperature of 200-450‹C below the ignition point of the husks to remove volatile constituents, then heating the fixed carbon in the husks to a temperature of 450-700‹C, and then heat-treating the resulting husk-ash in a stream of oxidizing agent at 700‹-800‹C, greater than the crystallization temperature of the silica. In a preferred embodiment, the husks are brought to the separation temperature of 200-250‹C at a heating rate of 10-40‹C/min-1, starting at a feed temperature of below 100‹C, and are then heated at the same rate to an oxization temperature of 450-550‹C and the resultant husk ash is heat-treated at the same rate to 700-800‹C The preferred rate of heating is 25‹C/min-1. The reagent for the oxidizing step is preferably either combustion-supporting air of aircoefficient from 4À0-6À0, or water-vapour. A mineralizing agent such as alkali-metal halide, may be added to accelerate the separation of the fixed carbon in gaseous form, or to facilitate the crystallization of silica. The crystallization may be delayed in the oxidation step by the addition of HCl. The husks may be comminuted before heattreatment to increase the bulk weight.