Abstract: There is disclosed a process and a plant for bleaching cellulosic materials by aid of ozone. A concentrated solution of ozone in an aqueous medium (strong water) is supplied under pressure to the materials suspended in an aqueous medium and is mixed therewith in a mixing device. The mixture is conducted through a reaction vessel, the bleached material is separated from the bleaching liquor, and possibly present residual ozone is destroyed. The plant includes an arrangement for preparing a pulp suspension, at least one bleaching tower to receive the mixture of pulp suspension and concentrated ozone solution, an arrangement for producing an ozonic gas, filtering means, pumps and ducts for connecting the plant parts. The arrangement for producing ozone is flow-connected with an absorption column for preparing the concentrated ozone solution and a mixing arrangement is provided for mixing the pulp suspension with the concentrated ozone solution.

Abstract: To produce an ozonic aqueous solution, optionally in addition to recovering a gas having an elevated ozone content, an aqueous solution is treated in an absorption vessel under pressure with an ozonic gas produced in an ozone generator by silent electrical discharge in air or oxygen the ozonic gas being compressed to a pressure of up to 10 bar before treating the solution therewith. An aqueous ozonic solution under pressure is decompressed into the ozonic gas prior to compressing the ozonic gas, wherein ozone is released into the ozonic gas thus forming a gas having an elevated ozone content (strong gas).

Abstract: Method and apparatus for delignifying chemical pulp by means of oxygen, in which an aqueous slurry of chemical pulp is formed, then mixed with a caustic agent, followed by contact with a delignifying fluid. Water is drained off the slurry without reduction of pressure and while maintaining temperature following which the resulting slurry is maintained under these temperature and pressure conditions for a discrete period of time. The thus-obtained treated slurry is then washed.