Method of removing volatile constituents and carbon from rice hulls

摘要

A method of removing carbon from carbonaceous rice hull ash from which the volatile constituents have been removed comprises forming a bed of the ash, causing an oxygen-containing gas to flow upwardly therethrough at a rate controlled to maintain a temperature between 500 DEG and 800 DEG C. in the presence of oxygen-containing gas until the carbon is removed. The oxygen-containing gas may be air, and the preferred rate is between 55 and 174 lb./hour/square foot of bed. Initially the gas burner 32, Fig. 1, heats the space between the container 34 and the brickwork 12 to 500 DEG -800 DEG C., and the air supply enters through conduit 22, passes down the paths 14 into the central chamber 29 through passages 30. The rice hulls are introduced tangentially into the combustion chamber from conduit 42, and air is supplied at a rate sufficient to suspend the rice hulls and move them upward in a time just longer than necessary to consume the volatile parts of the hulls. The heat from the burner is then reduced. The hulls with the volatile constituents removed are deflected by the baffles 50 over the periphery of the cone 44 and fall down the inside wall of the cone, the majority of the gas escaping up the stack 52. The burnt hulls fall into a bed in container 34 which is supplied with oxygen-containing gas from conduit 66. A curing period of 20-30 minutes gives a product which is 90-98% amorphous silica. The ash-product in container 34 is removed through the rotary valve 36.