GB1059282A - Production of cellulosic fibre pulp - Google Patents

Abstract

A cyclic process for the production of cellulose pulp from bamboo and for the fertilization of the bamboo comprises the steps of pulping bamboo with an aqueous solution of nitric acid, separating the insoluble material, containing cellulose pulp, from the spent liquor, neutralizing at least a part of the liquor and applying the neutralized liquor to growing bamboo plants. Bamboo from the plantation may be chipped and then digested with dilute nitric acid. The digested pulp is separated from the spent acid and washed first with water, then with aqueous ammonia or potassium hydroxide, and finally with water, and shives are removed. It is then bleached in a multistage process with chlorine, aqueous caustic soda and calcium "hypochlorite" obtained by treating lime with chlorine in water. The bleached pulp is washed with water, dewatered by pressing, dried and baled. Gases from the digester are washed with water for recovery of nitric acid. This water, the spent acid from the digester and part of the wash water from the first wash of the pulp after digestion are mixed and fortified with concentrated nitric acid for re-use. The rest of the water from the first wash is used to neutralize the spent liquor from the alkali treatment and subsequent water wash, and the resulting liquor is returned to the plantation for use as fertilizer. In modifications: the spent acid may be neutralized with potassium carbonate, lime, hydrated lime, magnesia or dolomite; bleaching may be carried out with hydrogen peroxide or chlorine dioxide; the effluent from the bleaching step may neutralized, treated to remove toxic substances, and go to the plantation; and a predigestion with aqueous potassium hydroxide may precede the acid treatment, and the spent liquors from this digestion may then be neutralized with spent acid and returned to the plantation. The pulps obtained can be used to make paper or cellulosic chemicals.ALSO:A cyclic process for the production of cellulose pulp from bamboo and for the fertilization of the bamboo comprises the steps of pulping bamboo with an aqueous solution of nitric acid, separating the insoluble material, containing cellulose pulp, from the spent liquor, neutralizing at least a part of the liquor and applying the neutralized liquor to growing bamboo plants. Bamboo from the plantation may be chipped and then digested with dilute nitric acid. The digested pulp is separated from the spent acid and washed first with water, then with aqueous ammonia or potassium hydroxide, and finally with water, and shives are removed. It is then bleached in a multistage process with chlorine, aqueous caustic soda and calcium "hypochlorite" obtained by treating lime with chlorine in water. The bleached pulp is washed with water, dewatered by pressing, dried and baled. Gases from the digester are washed with water for recovery of nitric acid. This water, the spent acid from the digester and part of the wash water from the first wash of the pulp after digestion are mixed and fortified with concentrated nitric acid for re-use. The rest of the water from the first wash is used to neutralize the spent liquor from the alkali treatment and subsequent water wash, and the resulting liquor is returned to the plantation for use as fertilizer. In modifications the spent acid may be neutralized with potassium carbonate, lime, hydrated lime, magnesia or dolomite; bleaching may be carried out with hydrogen peroxide or chlorine dioxide; the effluent from the bleaching step may be neutralized, treated to remove toxic substances, and go to the plantation; and a predigestion with aqueous potassium hydroxide may precede the acid treatment, and the spent liquors from this predigestion may then be neutralized with spent acid and returned to the plantation. The pulps obtained can be used to make paper or cellulosic chemicals.