Process for the preparation of anhydrous sodium sulfate

Details Process for the preparation of anhydrous sodium sulfate Process for the preparation of anhydrous sodium sulfate

1996-11-27

1999-02-16

Nguyen, Ngoc-Yen

Chemistry: physical processes

Physical processes

Crystallization

23298, 23302R, 423551, 423553, C01D 500

Patent

active

058715517

ABSTRACT:
A process for the preparation of anhydrous sodium from a thenardite ore containing sodium sulfate comprising the steps of: crushing the thenardite ore; lixiviating the crushed ore in a first lixiviation step with water or with an exhausted solution from a succeeding step, at a temperature between about 28.degree. C. and 40.degree. C., obtaining a suspension comprising a sodium sulfate saturated solution, sludges and insoluble material, settling the sludges and insoluble material from the saturated solution to separate a clarified solution; crystallizing the clarified saturated solution in a first crystallization step at a temperature between 32.degree. C. and 20.degree. C., maintaining the height of the solution not exceeding about 15 centimeters, to obtain a Glauber salt with large crystals of sodium sulfate and ten molecules of water. When the clarified saturated solution is crystallized, an exhausted solution is produced which is drained and recycled back to the first lixiviation step. Melting the crystals, free from solution, at a temperature about 60.degree. C. to dissolve the sodium sulfate crystals in their own crystallization water, to obtain a suspension comprising a sodium sulfate saturated solution with a density of 1.335 g/cc and crystals of anhydrous sodium sulfate in a proportion of about 17% by weight of the Glauber salt; and settling the crystals of anhydrous sodium sulfate. The clarified saturated solution of the previous step is recycled in a second crystallization step to separate the anhydrous sodium sulfate and finally a drying step is carried out to obtain anhydrous sodium sulfate crystals.

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