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Suspension melt crystallization the efficient purification alternative

Melt crystallization plant

Melt crystallization plants in the chemical industry.

Process description

Installation DB Acetonitrile 3

The typical configuration for a suspension based melt crystallization system is shown in the schematic. Crude product is cooled in scraped surface crystallizers. These may be exchanger type or vessel type crystallizers depending on the specific application. The crystallizer produces pure product crystals and thus concentrates the impurities in the remaining liquid mother liquor. The crystals are then separated from the impurity rich mother liquor producing a pure product stream and a reject stream. The reject contains the concentrated impurities but also valuable product which may be recovered depending on the specific application.

Each individual crystal is suspended in the mother liquor and is allowed to grow free flowing in the liquid. With billions of crystals per cubic meter the growth surface can reach 5,000 to 10,000 m² per m³ of volume. This massive growth surface allows near ideal growth rates that result in the characteristic pure crystals expected from the eutectic crystallization process.

Since all of the impurities are now in the mother liquor it is most important to remove all of this liquid from the outside of the crystals. The crystallizer suspension is pumped into a wash column where the pure crystals are separated and then washed to remove any remaining mother liquor. The efficient washing action provided in the wash column is unmatched by any other solid/liquid separation device. The pure product crystals are then melted and discharged from the system.

Suspension based crystallizers produce pure crystals. Wash columns can effectively remove all of the mother liquor and thereby produce ultra high purity product.

Industrial applications
Capacities ranging from 10 kg/h up to 50,000 kg/h product

How it works

Melt crystallization schema

Principles of melt crystallization

How it works

The typical configuration for a suspension based melt crystallization system is shown in the schematic. Crude product is cooled in scraped surface crystallizers. These may be exchanger type or vessel type crystallizers depending on the specific application. The crystallizer produces pure product crystals and thus concentrates the impurities in the remaining liquid mother liquor. The crystals are then separated from the impurity rich mother liquor producing a pure product stream and a reject stream. The reject contains the concentrated impurities but also valuable product which may be recovered depending on the specific application.

Each individual crystal is suspended in the mother liquor and is allowed to grow free flowing in the liquid. With billions of crystals per cubic meter the growth surface can reach 5,000 to 10,000 m² per m³ of volume. This massive growth surface allows near ideal growth rates that result in the characteristic pure crystals expected from the eutectic crystallization process.

Since all of the impurities are now in the mother liquor it is most important to remove all of this liquid from the outside of the crystals. The crystallizer suspension is pumped into a wash column where the pure crystals are separated and then washed to remove any remaining mother liquor. The efficient washing action provided in the wash column is unmatched by any other solid/liquid separation device. The pure product crystals are then melted and discharged from the system.
Suspension based crystallizers produce pure crystals. Wash columns can effectively remove all of the mother liquor and thereby produce ultra high purity product.

Service products

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