Choice of various crystallization equipment types
The evaporation crystallization process is a common operating unit in pharmaceutical and chemical processes, and is widely used in the production process of almost all crystalline drugs.
Evaporative crystallization commonly used in enterprises today mainly includes thermal convection type and forced circulation type. The above two types of evaporative crystallization equipment are mostly crystallization by forced external circulation evaporation.
The principle of the evaporator is that the material solution is heated by the pump under the action of the pump and evaporated in the evaporator. After such a plurality of cycles, after the solution concentration exceeds the solubility at the temperature, the solute precipitates crystal, in this state. The solution in which the crystal has appeared continues to be heated repeatedly by the action of the pump until a large amount of crystals appear, and the solution becomes a very thick suspension of the crystal which cannot be circulated.
Since many varieties of the drug are heat-sensitive and the hardness of the crystal is high, the solution is very viscous after reaching a saturated state, and the fluidity is greatly reduced. Therefore, it appears in the use of the above-mentioned commonly used evaporators. The problem is that the quality of the drug product is poor, the evaporation temperature is high in the later stage, the utilization effect of the liquid material is low, the energy consumption is increased, the final product yield is low, and the equipment is worn due to the erosion of a large number of crystals, and the service life is short, and the metal particles washed out The drug is contaminated, the metal content of the drug is increased, and the purity of the product is lowered.
There are many types of crystallization equipment. The method of obtaining supersaturation in solution can be divided into evaporation crystallization equipment and cooling crystallization equipment; according to the flow mode, the mother liquor circulation crystallization equipment and the crystal slurry (ie, the mixture of mother liquor and crystal) can be recycled; The method can be divided into continuous crystallization equipment and batch crystallization equipment.
Commonly used crystallization equipment includes: a crystallization tank, a trough-shaped container, a jacket or a coil inside the vessel for heating or cooling the solution in the tank.
The crystallization tank can be used as an evaporation crystallization apparatus or a cooling crystallization apparatus. In order to increase the strength of crystal production, a stirrer can be added to the tank.
The crystallization tank can be used for continuous operation or intermittent operation. The crystal obtained by the batch operation is large, but the crystals are easily connected into crystal clusters, entraining the mother liquor and affecting the purity of the product.
The crystallization device has a simple structure and low production strength, and is suitable for the production of small batch products (such as chemical reagents and biochemical reagents).