Abstract: Effluent containing organic impurities which are difficult to degrade is purified by oxidation in the aqueous phase at temperatures of 100.degree. to 310.degree. C. and under elevated pressure. This is effected by initially treating the effluent in a first stage with gases containing oxygen, but without the addition of catalysts, until the C.O.D. value has been reduced by 50 to 98%. The effluent which has received preliminary treatment in this way is subsequently treated, in a second stage, with an oxidizing agent stronger than oxygen, in the liquid phase and at the same, or at a higher, temperature, until the C.O.D. value has fallen to approximately 0 g/l.

Abstract: When explosive gases are introduced into a combustion chamber care must be taken that no pre-ignition occurs. To this end, the gas is spatially subdivided into discrete volume elements, for example by means of a bundle of tubes having an internal diameter which does not exceed twice the quenching distance of the explosive gases. Such a division ensures that the wall distances of the gas portions of one volume element are greater than their quenching distances.

Abstract: In the regeneration of aqueous waste sulfuric acid by distilling off water often foam is formed which severely interferes with the work-up of the acid. This formation of foam is suppressed by adding alkylsulfonic and/or alkylarylsulfonic acids.

Abstract: The invention provides a process for the regeneration of dilute sulfuric acid containing organic impurities and possibly also inorganic salt in several steps. In the first step, the dilute acid is concentrated by indirect heat exchange with the vapors of the second step, and in the second step it is concentrated by direct heat exchange with a countercurrent mixture of steam and acid vapors coming from a third step. In this third step, the acid discharged from the second step is mixed in direct heat exchange with superheated steam. The regenerated sulfuric acid is separated from this mixture and the remaining steam/vapor mixture is forwarded to the second step. In the case where the dilute acid contains organic substances, an oxidant is added in at least one of these process steps.

Abstract: The foam formation arising when aqueous waste sulfuric acid is concentrated can be suppressed by adding aromatic nitro compounds such as nitrobenzene to the acid.

Abstract: Gray cast iron can be protected against corrosion by the vapors of boiling concentrated sulfuric acid when a compound containing positive nitrogen, e.g., nitrogen oxide, is introduced into the gas space between the cast iron to be protected and the boiling sulfuric acid.

Abstract: A two step process for concentrating and desalting dilute sulfuric acid including, first indirectly countercurrently contacting and heating the dilute acid with steam from a second step, removing overhead water vapor and withdrawing concentrated acid, and second further concentrating the acid by directly countercurrently contacting and heating the acid with superheated steam, removing overhead steam and additional water vapor, which is used in the first heating step. Acid of a higher concentration is withdrawn and cooled to crystallize and remove salts and the more highly concentrated sulphuric acid recovered.