Improvements in or relating to the manufacture of paper pulp from straw or other fibrous material

摘要

Paper pulp is manufactured from straw or the like by cooking with caustic potash, the resulting black liquor being concentrated and treated with sulphuric, nitric or phosphoric acid, or mixtures thereof, to yield corresponding potassium salts, which may be used as fertilizer, either as formed in solution or after evaporation to dryness. Alternatively, the black liquor may be evaporated and calcined, the calcined ash being treated with the acid. Other fertilizer constituents may be added to the black liquor. As shown in the flow dia gram, chopped straw from the hopper 1 and caustic potash solution from tank 3 are fed to digester 2. After digestion the mixture is blown into dump tank 4 from which steam is condensed at 5, black liquor is drained off at 6 to storage tank 7 and drained pulp is dumped into stock tanks 8 and thence to pulp washers 9. Wash water, pre-heated by condenser 5, after pulp washing passes to de-foaming tank 11 and may be re-circulated. Strong black liquor from tank 7, which may be used to make up the lye in tank 3, passes to evaporators 13, is mixed with appropriate acids from tanks 14 and passes to de-gassing trays 15 and reaction tanks 16, fitted with stirrers. In tanks 16 chalk or whiting may be added. The liquor is stored in tank 19 and passes to a film drier 20, mill 21 and is bagged at 22. Specification 702,025, [Group VIII], is referred to.ALSO: Paper pulp is manufactured from straw or the like by cooking with caustic potash, the resulting black liquor being concentrated and treated with sulphuric, nitric or phosphoric acid, or mixtures thereof, to yield corresponding potassium salts, which may be used as fertiliser, either as formed in solution or after evaporation to dryness. Alternatively, the black liquor may be evaporated and calcined, the calcined ash being treated with the acid. Other fertilizer constituents may be added to the black liquor. As shown in the flow diagram, chopped straw from the hopper 1 and caustic potash solution from tank 3 are fed to digester 2. After digestion the mixture is blow into dump tank 4 from which steam is condensed at 5, black liquor is drained off at 6 to storage tank 7 and drained pulp is dumped into stock tanks 8 and thence to pulp washers 9. Wash water, pre-heated by condenser 5, after pulp washing passes to de-foaming tank 11 and may be recirculated. Strong black liquor from tank 7, which may be used to make-up the lye in tank 3, passes to evaporators 13, is mixed with appropriate acids from tanks 14 and passes to degassing trays 15 and reaction tanks 16, fitted with stirrers. In tank 16 chalk or whiting may be added. The liquor is stored in tank 19 and passes to a film drier 20, mill 21 and is bagged at 22. Specification 702,025 [Group VIII] is referred to.