Disposal of waste liquors and recovery of inorganic chemicals therefrom

摘要

1,081,739. Disposal of waste liquors by evaporation. CONTAINER CORPORATION OF AMERICA. July 29, 1966, No. 34277/66. Heading BIB. Inorganic material is recovered from waste liquor containing organic and inorganic material, e.g. waste wood pulping liquor, by spraying the liquor, supplied from tank 17, through pneumatic device 3 into a vessel 1 which contains a bed 14 of solid particles maintained in a fluidized state by supplying oxygen-containing gas, e.g. air, into the lower part of the vessel through an orifice plate. The temperature of the bed is maintained above the combustion temperature of the organic material in the liquor but below the melting temperature of the inorganic components, usually at a temperature between 1000‹ and 1800‹F. Some evaporation of the liquor takes place in the freeboard space 24, where the temperature is less than 1000‹F., and the partially-concentrated liquor is deposited as a thin layer on the fluidized particles where the remainder of water is evaporated and the combustion of the organic material takes place. The solid particles of bed 14 preferably comprise the inorganic material derived from the process, but silica grains may also be used. Bed 14 is maintained at the desired height by discharging dry granular material through valve 6 to screenclassifier 7. Fine solids are recycled to the bed through conduit 38. If necessary, the coarse solids can be treated to separate a desired product, e.g. sodium sulphate, from inert material. The waste liquor is preferably concentrated to about 35% by weight solids, e.g. by multiple effect evaporation, before it is introduced into vessel 1. Exhaust gases and water-vapour flow from vessel 1 to cyclone 4, where entrained solid particles are separated and then recycled to bed 14 via screw 5. In order to remove fine solid particles, the exhaust gases are scrubbed with dilute liquor in system 8, before being discharged through conduit 29 to the atmosphere, either directly or through an SO 2 - removal tower. The scrubbing liquid collected in sump 35 is pumped through conduit 37 to tank 17 or to scrubbing system 8. The preconcentrated liquor is preferably introduced into vessel 1 partly as fine spray and partly as coarse spray; this may be achieved by an adjustable feed gun or by employing two feed guns. Atomizing devices 25 and 26 are provided to introduce water or weak liquor into the freeboard space 24 in order to maintain the temperature of this space at 350‹ - 600‹F. The fluidizing air is blown through preheater 2 before it is supplied through conduit 12 to the bed 14. If necessary, extraneous fuel in the form of natural gas, fuel oil or coke may be added to the fluidized bed. Examples are given which relate to the disposal of waste sodium sulphite (black) liquor and of magnesium bisulphite (red) liquor.