Abstract: A method for incinerating excess sludge from biological waste water treatment plants, in particular sludges arising from the manufacture of paper or paper pulp, preferably using the magnesium fusion process. Before incineration, the excess sludge is neutralized with the same base as used in the paper pulp process and the dust entrained by the combustion gas is precipitated to recover the base.

Abstract: A process and plant for drying and then separating moist salts, such as magnesium sulfite, in which the moist magnesium sulfite is heated to a temperature greater than or equal to about 200.degree. C. in a dryer and the passed through a solid materials lock into a separating plant. The dryer is heated by a circulating stream of exhaust vapors which is heated in a heat exchanger by exhaust gas generated in the separating plant so that the water of crystallization of the magnesium sulfite as well as residual humidity is eliminated during the drying process. Vapor-free acid anhydride, usually sulphur dioxide, is prepared in the separating plant from the dehydrated salt and a metal oxide, e.g., MgO, is recovered or otherwise used. The acid anhydride may be liquified and has a large degree of purity.

Abstract: A multi-stage, especially a two-stage mixing of two media of different viscosity, and a respective mixing nozzle provided therefor. The first medium of higher viscosity is divided into two or more partial streams. The first partial stream is passed through an injector, in which the second medium of lower viscosity is mixed in, in particular tangentially. In an adjoining mixing chamber, the second partial stream of the first medium is admixed into the flowing mixture of the first partial stream and the second medium of lower viscosity and envelops the same, preferably in an opposite or counter-twist to the flowing twist of the first mixture of the first partial stream and second medium. This is especially suitable for bleaching of cellulose with oxygen.

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.

Abstract: Methods and apparatus pertaining to reduction of sodium sulfate to sodium sulfide include the feeding of sodium sulfate into a combustion chamber in which the sodium sulfate is exposed to a reducing atmosphere while at the same time being exposed also to a temperature above the melting point of sodium sulfide. Thus, a liquid accumulates at the bottom of the combustion chamber and this liquid will of course contain a considerable amount of sodium sulfide reduced from the sodium sulfate.