Method of treating materials in a fluidized bed reactor

Claim 1

WHAT WE CLAIM IS: 1 A method of treating a material which contains inorganic chemicals and organic chemicals which comprises the steps of 30 a) subjecting said material to combustion in a fluidized bed reactor and recovering flue gases which have entrained hot solid particles; b) introducing said flue gases from step a) into a dust separator to remove the hot solid particles entrained in the flue gases; c) introducing said hot solid particles from step b) into a prereactor and mixing 35 therewith said material to preheat and at least partially dry said material whereby a preheated material is obtained. d) introducing said preheated material from step c) together with said hot solid particles into said fluidized bed reactor, subjecting the preheated and dried material in the presence of said hot particles to combustion therein to obtain flue gases; 40 e) introducing the flue gases from step d) into said dust separator to separate hot solid particles which are recycled in step c). 2 A method as claimed in claim 1, in which gases are formed in step c), said gases are subjected to a dust separation step to remove solid particles and at least a portion of the gases are introduced into said fluidized bed reactor in step d) 45 3 A method as claimed in claim 1, in which thermal decomposition of the organic chemicals present in the material to be treated is achieved in step c). 4 A method as claimed in claim 19, wherein gasification of the organic chemicals present in the material to be treated is achieved in step c). 5 A method as claimed in any of claims 1 to 4, in which the material to be treated is 50 spent liquor from a pulping process which contains sodium compounds and the organic chemicals in said material to be treated are carbon-containing combustibles. 6 Amethod as claimed in any of claims 1 to 5, in which the inorganic chemicals in said material to be treated contain sodium and sulfur compounds. 7 A method as claimed in claim 4, in which the material to be treated is preheated and 55 at least partially dried in step c) byh contact with a portion of said hot solid particles obtained in step b) and the material is then brought into contact with another portion of said hot solid particles for the gasification of the organic components in said material. 8 A method as claimed in any of claims 1 to 7, in which chemical reactions in the material to be treated are brought about in step c) by contact with said hot solid particles 60 removed from the flue gases. 9 A method as claimed in claim 5, in which the material to be treated is the spent liquor from a sodium-hydroxide-based pulping process, the spent liquor is mixed in step c) with alumina hydrate, the hot solid particles removed from the fluidized bed reactor from step b) contain sodium aluminate and at least a portion of the sodium aluminatecontaining hot 65 a cl 1 561 237 solid particles removed from the flue gases coming from the fluidized bed reactor is added to the spent liquor in step c). A method as claimed in claim 9, in which a portion of said particles which is removed from the flue gases in step b) is dissolved in water, whereafter alumina hydrate is separated by precipitation from the produced solution, it is removed, it is added to said 5 material in step c) and the sodium containing chemicals are recovered. 11 A method as claimed in claim 9, in which a portion of said hot solid particles from step b) is dissolved in water, whereafter the produced solution is neutralized with carbon dioxide by contacting it with the flue gases in order to form alumina hydrate which is removed and sodium is recovered as sodium carbonate 10 12 A method as claimed in claim 1, in which alumina hydrate and at least a portion of the hot sodium aluminate-containing particles removed from the flue gases coming from the fluidized bed reactor in step b) are mixed with a spent liquor from a pulping process based on alkali and sulphur compounds and the sulphur content of said spent liquor is recovered as hydrogen sulfide which is removed before said spent liquor is introduced into said 15 fluidized bed reactor in step d). 13 A method as claimed in claim 12, in which the material to be treated is a spent liquor from a sulfite pulping process and hydrogen sulfide formed in step c) is converted by combustion into sulphur dioxide which is absorbed in a solution containing the sodium aluminate removed from the flue gases in step b) in order to form alumina hydrate 20 14 A method as claimed in claim 13, in which said alumina hydrate is removed from the solution, whereby a sodium sulfite digestion liquor is obtained. A method as claimed in claim 12, in which the material to be treated is a spent liquor from a sulfate pulping process and the hydrogen sulfide formed in step c) is absorbed in a solution which contains both sodium aluminate removed from the flue gases and 25 sodium hydroxide whereby alumina hydrate is formed. 16 A method as claimed in claim 14, in which said aluminate hydrate formed is removed from the solution and a sodium sulfate digestion liquor is obtained. 17 A method as claimed in claim 1, in which the material being treated in the fluidized bed reactor is peat and said hot particles are hot dust which is removed from the flue gases 30 and said hot dust is recycled in step c). 18 A method as claimed in any of claims 1 to 17 in which in step c) the material is in the form of a liquor and is at least partially dried by said preheating. 19 A method as claimed in any of claims 1 to 18 in which there are recovered in step e) at least one of gases, liquids or solids 35 A method as claimed in claim 1, in which the material being treated is sewage sludge. 21 A method substantially as herein described with reference to and as illustrated in the accompanying drawings. 22 A solid, liquid or gas whenever recovered by the method of claim 19 40 Potts, Kerr & Co, Chartered Patent Agents, 27 Sheet Street, Windsor, 45 Berkshire SL 4 i BY and 15, Hamilton Square, Birkenhead, Merseyside L 41 6 BR 50 Printed for Her Majesty's Stationery Office, by Croydon Printing Company Limited, Croydon Surrey, 1980. Published by The Patent Office, 25 Southampton Buildings, London, WC 2 A l AY,from which copies may be obtained.