PRODUCTION OF CELLULOSE BY THE SODA-ANTHRAQUINONE PROCESS (SAP) WITH RECOVERY OF THE BOILING CHEMICALS

摘要

For the production of cellulose from wood and annual plants, a boiling process is proposed in which the boiling liquor contains free soda lye and sodium salts of the alkylbenzole sulphonic acids or aromatic and aliphatic carboxylic acids. Delignification is reinforced on the addition of anthraquinone or its derivatives to the boiling liquor. There is no need to restrict the quantities of the anthraquinone additive owing to its price since anthraquinone resists wet oxidation and can be recycled in the boiling process. The solubility and hence the effect of the anthraquinone is enhanced by the use of sulphonic acid salts. In order to recover the processing chemicals contained in the black liquor it is proposed that the dissolved lignin be precipitated with mineral or carboxylic acid, the hemi-celluloses be separated by ultra-filtration and the resins by extraction, where appropriate, and the remaining organic components except for the sulphonic and carboxylic acids salts be burned in the aqueous phase with air and/or oxygen. The chemical solution freed from the wood decomposition products may be returned to the liquor after caustification of the carbonates and, after the partial crystallisation of the aliphatic carboxylic acid salts, made available in the circuit for cellulose production. The sodium acetate isolated by crystallisation can be broken down into acetic acid and sodium hydroxide by diaphragm electrolysis. The soda lye is returned to the boiling process and the acetic acid treated separately.