Crystallization of MgSO₄ 7H₂O

Plant for the crystallization of MgSO4 7H2O

Magnesium sulfate appears as a soluble component in various industrial streams. Typically, MgSO₄ is not found as a pure substance in solution, but rather as a mixture with other components.

Consequently, crystallization plants for MgSO₄ are usually designed as cooling crystallization plants. This process crystallizes magnesium sulfate as heptahydrate, namely MgSO₄ 7H₂O.

In the cooling crystallization of MgSO₄ 7H₂O (also known as Epsom salt due to its bitter taste), the vacuum cooling crystallization variant in multiple stages has become particularly established.

Especially, the cooling crystallization in horizontal crystallizers with air stirring offers the opportunity to produce grain sizes that allow for separation by simple centrifugation through gentle handling of the crystal.

The crystallization of MgSO₄ 7H₂O can theoretically also be achieved in plants with direct surface cooling. However, due to the need for circulation organs and the tendency of directly cooled surfaces to build up incrustations, this has proven to be economical only for smaller throughput quantities.

The production of MgSO₄ H₂O is also possible, but is used less frequently. Here, all typical evaporation crystallization plants can be used:

Evaporation crystallization plant with mechanical vapor recompression
Evaporation crystallization plant with thermal vapor recompression
Multi-effect evaporation crystallization plant with fresh steam heating

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Frequently Asked Questions

Is it also possible to crystallize anhydrous MgSO₄?

Indeed, the production of MgSO₄ is possible, but due to the high transformation temperature, it is not common in crystallization plants.

What materials are used in evaporation plants for MgSO₄ solution and crystallization plants for MgSO₄ and its hydrates?

Although the MgSO₄ component itself is not corrosive and allows the use of simple stainless steels, other chloride or acidic components of the solution may necessitate higher-grade materials.

What components are typically contained in MgSO₄ solutions?

Usual components include Na ions and Cl ions, as well as acids like H₂SO₄.