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AssigneeChempolis Oy
InventorsPasi Rousu, Paivi Rousu, Esa Rousu, Juha Anttila
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The invention relates to a process for treating bleaching liquors from pulping processes based on organic acids. The process is characterized in that inorganic acid such as nitric acid, phosphoric acid and/or sulphuric acid, is added into a bleaching liquor obtained from the bleaching or a stage closely associated with bleaching, whereby organic acids contained in the bleaching liquor are released into the bleaching liquor. The organic acids are then separated from the bleaching liquor and recycled to the cooking stage to be used as cooking chemicals. The nitrogen-, phosphor- and/or sulphur-containing product thereby produced, from which organic acids have been separated, is recovered to be used as a fertilizer or as raw material for a fertilizer.
A process for treating bleaching liquors from pulping processes based on organic acids, the process comprising cooking and bleaching of pulp, characterized by
A process according to any one of the preceding claims, characterized in that the bleaching liquor to which the inorganic acid is added in stage (a) is a bleaching filtrate.
A process according to any one of the preceding claims, characterized in that the amount of inorganic acid to be added in stage (a) is such that it allows a bleaching liquor pH within a range of 0 to 6, preferably 0 to 3, to be obtained.
A process according to any one of the preceding claims, characterized in that nitric acid is added in stage (a) to adjust the pH of the bleaching liquor to the range of 0 to 6, preferably 0 to 3.
A process according to any one of the preceding claims, characterized in that in stage (b) organic acids are separated by evaporation or extraction.
A process according to any one of the preceding claims, characterized in that the nitrogen-, phosphor- and/or sulphur-containing product obtained from stage (c) is converted into a solid form to be used as a fertilizer.
A process according to any one of the preceding claims, characterized in that the solvent or reagent used in the pulp production comprises formic acid, acetic acid or a mixture thereof.
A process according to any one of the preceding claims, characterized in that before stage (a) the bleaching liquor is concentrated by evaporation, preferably to a dry matter content of 10 to 75% and the evaporated water is used as process water.
A process according to any one of the preceding claims, characterized in that the raw material used for the pulp comprises herbaceous plants.
Dependencies are inferred from the claim text.