Evaporation crystallization process is a common operation unit in pharmaceutical and chemical processes, and it is widely used in the production process of almost all crystalline drugs. At present, the evaporative crystallization commonly used by enterprises mainly includes heat convection type and forced circulation type. The above two types of evaporative crystallization equipment are mostly forced external circulation evaporative crystallization.
The principle of this evaporator is to heat the material solution in the external heater under the action of the pump, and evaporate it in the evaporator. After so many cycles, when the solution concentration exceeds the solubility at this temperature, the solute precipitates and crystallizes. In this state The solution in which crystals have appeared continues to be heated repeatedly under the action of the pump. The circulation process of evaporation, until a large number of crystals appear, the solution becomes a very thick suspension of crystals and cannot be circulated. Because many varieties of drugs are heat-sensitive, and the hardness of the crystals is high, the solution is very viscous after reaching saturation. , the fluidity is greatly reduced. Therefore, the problems in the use of the above-mentioned currently commonly used evaporators are poor quality of pharmaceutical products, high evaporation temperature in the later stage, low effect of material and liquid utilization, increased energy consumption, and low product yield. , and the equipment is worn out due to the erosion of a large number of crystals, the service life is short, and the metal particles washed out pollute the drug, which increases the metal content of the drug and reduces the purity of the product.
There are many types of crystallization equipment. According to the method of obtaining supersaturated state of the solution, it can be divided into evaporation crystallization equipment and cooling crystallization equipment; according to the flow mode, it can be divided into mother liquor circulation crystallization equipment and magma (that is, a mixture of mother liquor and crystal) circulation crystallization equipment; according to operation The method can be divided into continuous crystallization equipment and batch crystallization equipment.
Commonly used crystallization equipment includes: crystallization tank, a tank-shaped container with a jacket on the wall or a coil inside the tank to heat or cool the solution in the tank. The crystallization tank can be used as evaporative crystallization equipment or cooling crystallization equipment. In order to increase the intensity of crystal production, a stirrer can be added in the tank.
The crystallization tank can be used for continuous operation or batch operation. The crystals obtained by intermittent operation are larger, but the crystals are easy to connect into crystal clusters, entrain mother liquor, and affect the purity of the product. This kind of crystallization equipment has a simple structure and low production intensity, and is suitable for the production of small batches of products (such as chemical reagents and biochemical reagents, etc.).