Abstract: A cellulose containing vegetable material is bleached by the steps of chlorinating said material, followed by ammonia treatment and post bleaching with washing stages between said steps. Waste waters resulting from the washing stages are purified by subjecting said waste waters to electrodialysis and recovering ammonium chloride from the purified waste waters. The recovered ammonium chloride is used to pre-treat the cellulose material prior to chlorination thereof and the purified waste waters are reused in the washing stages.

Abstract: It has been found that solvent residues can be removed from aqueous paper pulps by stripping with economic volumes of gases. This can be done in conventional contacting equipment without reducing pulp consistencies below the levels typical of commercial paper-making operations. The solvents stripped out are recoverable and do not constitute a source of pollution.

Abstract: A process is provided for delignifying and bleaching cellulose pulp, which comprises carrying out the delignification and bleaching with oxygen and alkali in the presence of sodium bicarbonate, while removing carbon dioxide from the gas phase as required to maintain a carbon dioxide partial pressure within the range from about 0.001 to about 3 bars, thereby improving the selectivity of the delignification and bleaching.

Abstract: Gaseous reaction apparatus wherein a portion of the supplied gas is discharged from the reaction vessel at a location below the upper level of a therein contained columnar mass of material wherein the gas is discharged into a receiving chamber extending along the outer periphery of the vessel and open to the lower portion of the vessel through an unrestricted opening being free from screens and filters, and such discharged portion of the gas, with or without cooling, is recirculated back into the upper inlet end of the vessel, thereby controlling the temperature in the vessel by removing or redistributing heat therein. Such apparatus is particularly useful in the gas phase treatment of fibrous material such as the bleaching or delignification of lignin-containing cellulose pulp.

Abstract: Cellulose pulp, in the form of an alkaline, dilute aqueous slurry, is continuously bleached and delignified by oxygen dissolved and intimately dispersed and subdivided into the slurry so that no agglomerated bubbles are formed. The alkaline, dilute slurry is prepared by adding not more than about 2/3 of an oxygenated, alkaline solution to the undiluted pulp entering the system, subjecting the resulting partially diluted alkaline pulp slurry to an elevated temperature and pressure, then further diluting said partially diluted alkaline pulp slurry with the remainder of oxygenated alkaline solution.