Vysoka Skola Chemicko-technologicka

Vysoka, Skola Chemiko-technologicka

Zdenek Jerman

Jaroslav Kralicek

Stanislav Najmr

A process for producing a pure magnesium sulphite from crude crystalline magnesium sulphite. Into a full suspension or flow containing magnesium sulphite crystals at least one further water-containing and heat-supplying flow is led. The heat-supplying flow rapidly increases the temperature of the suspension to above 80.degree. C. in less than 10 seconds, preferably in less than 2 seconds. The solid water-insoluble fraction is then separated from the resulting flow, and the pure product is recrystallized from the solution. The solution may be recycled into the process either for further purification or for use as at least one heat-supplying flow.

Process for producing pure magnesium sulphite

Process of purification of magnesic raw material. Sulphur dioxide is allowed to react with an aqueous suspension of calcinated magnesite, crude or contaminated magnesium oxide, magnesium hydroxide, hydrated magnesium carbonates, or crude crystals of magnesium sulphite, and, after reaching a pH of 3 to 7.5 the reaction mixture is separated into a solid phase at least one fraction of which is rich in MgSO.sub.3.xH.sub.2 O, wherein x stands for 3 or 6, and at least one fraction containing concentrated impurities. The whole process is carried out at least once. A reaction mixture having a pH below 5 can be preferably transferred to pH 5.2 by the addition of an alkali, e.g. magnesium oxide or magnesium hydroxide, whereupon separation of at least two fractions of the solid phase is accomplished. The fractions obtained can be further purified by mixing in a hydrophilic liquid, and by a following separation. The fraction of crude magnesium sulphite crystals can be heated to a temperature over 60 degress C., preferably to 90 to 100 degrees C., whereupon the solution containing magnesium sulphite is separated from solid impurities, or the treated mixture is cooled to a temperature below 60 degrees C. and solid phases are separated into one or more fractions rich in MgSO.sub.3.xH.sub.2 O and to one or more fractions mainly containing impurities. Filtration, sedimentation, or centrifugation can be used for the separation.

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Usti n/L., Czechoslovakia

Zdenek Jerman