Crystallization of (NH₄)₂SO₄

Multi-effect ammonium sulfate crystallization plant

Ammonium sulfate is an important additive to fertilizers, among other applications. Crystallization plants for ammonium sulfate are usually carried out according to the principle of evaporation crystallization, as the solubility of (NH₄)₂SO₄ is only weakly dependent on temperature.

Similar to plants for the production of sodium chloride, the process of mechanical vapor recompression has increasingly established itself in the past. Especially due to the relatively low boiling point elevation of the solution and thus also low specific electrical energy consumption per ton of crystallized salt, the plants are often built as single-stage plants with vapor recompression. Here, the solubility of ammonium sulfate is exceeded by evaporating water, and the (NH₄)₂SO₄ solution thus becomes supersaturated. The reduction of supersaturation occurs through growth on existing crystals.

Of course, multi-stage crystallization plants for the production of ammonium sulfate are also possible, with the aim of minimizing the consumption of live steam as well as cooling water by realizing as many effects as possible.

Another method of crystallizing ammonium sulfate is the execution as a plant with thermal vapor recompression.

Due to the increasing requirements for very coarse (NH₄)₂SO₄ crystals, the design of the apparatuses, besides classical recirculation circuits, also relies on coarse crystallizers, such as DTB crystallizers or Oslo crystallizers.

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Frequently Asked Questions

Is it also possible to produce ammonium sulfate crystals through cooling crystallization?

In principle, cooling plants are also suitable for the crystallization of (NH₄)₂SO₄. These can be executed as direct cooling or vacuum cooling.

As a rule, this is not favored due to the need for coarse ammonium sulfate crystals and since the parameters necessary are not met in typical streams.

In which industrial sectors is ammonium sulfate produced?

Ammonium sulfate is found in all industrial applications where ammonia reacts with sulfuric acid. It is also a byproduct in the production of caprolactam.

From the undersaturated solution, the ammonium sulfate can then be crystallized according to the described methods.