Patent GB-638496-A (GB)
Title: Process for treating cellulosic raw material in order to obtain valuable products and by-products
IPC: D21C1/02
Filed: 1946-08-28
Abstract: Raw cellulosic materials such as wood, straw, or alfa, are subjected to a heat treatment with water at a temperature between 160 DEG  C. and about 210 DEG  C., the duration of the treatment being more than 2 hours at 160 DEG  C. and not more than 1 hour at 210 DEG  C., and the water being present in sufficient quantity continuously to immerse, sprinkle or wash the cellulosic material and to dissolve or disperse the solubilized organic compounds formed.  The treatment is carried out so as to obtain a cellulosic pulp and a solution containing sugars.  According to the extent of the treatment within the limits of temperature and duration defined, the cellulosic pulp obtained may be suitable for making cardboard or paper or may be a more profoundly disintegrated mass suitable as a food for cattle or for use in processes involving hydrolysis of the cellulose by acids or by fermentation.  The treatment with water is carried out in a digester.  Gases produced during the treatment may be absorbed by active carbon, or soda lime, which may be suspended in the digester out of contact with the water. The gases produced may be blown off during the treatment.  If desired, a very small proportion of alkali may be mixed with the water to absorb gases, e.g. 0.5 to 1.5 per cent by weight of the cellulosic material.  Such an addition also reduces or eliminates acidity which develops during the treatment.  In an example, poplar wood chips are heated with 2-4 times their weight of water, the temperature rising to 195 DEG  C. in 15 minutes and being maintained at that value for 17-30 minutes.  The material is then quickly cooled, crushed and washed.  It may be used for making paper sheets or cardboard.  The solution contains acids, sugars and other organic compounds.  In other examples, alfa is treated at 180 DEG  C. for 15-20 minutes or at 170 DEG  C. for 90 minutes.  If desired, the treatment with water may be carried out in two or more stages.  The pulp obtained may be further refined by treatment with caustic soda solution followed by bleaching with chloride of lime.  For obtaining a paste or disintegrated mass of fibres the treatment with water, e.g. at 180-200 DEG  C., is increased by 2-6 times that required for obtaining paper pulp. Such a mass when dried may be used as cattle food.  It may also readily be hydrolysed, e.g. with very dilute mineral acid.ALSO:A cellulosic pulp in a solution containing sugars, suitable, when dried, as cattle food, is obtained by subjecting raw cellulosic materials such as wood, straw, and alfa, to a heat treatment with water at a temperature between 160 DEG  C. and about 210 DEG  C., the duration being more than 2 hours at 160 DEG  C. and not more than 1 hour at 210 DEG  C., and the water being present in sufficient quantity continuously to immerse, sprinkle, or wash the cellulosic material and to dissolve or disperse the solubilized organic compounds formed.  Gases produced may be absorbed by active carbon, or soda lime, or they may be blown off during the treatment. Small additions of alkali may be mixed with the water to absorb gases e.g. 0.5-1.0 per cent by weight of the cellulosic material.  Such additions reduce acidity which develops during the treatment.  Poplar wood chips may be cooked at 192 DEG -200 DEG  C. for 34-120 minutes. Straw may be treated at 190 DEG -197 DEG  C. for 24-90 minutes, and alfa may be treated at 180 DEG  C. for 30-120 minutes.