1. The requirements of the pharmaceutical industry for spray dryers
1.1 Atomization device
The atomization device of the spray dryer generally has centrifugal type, pressure type and air flow type. The transmission shaft of the centrifugal disc of the centrifugal atomizer is located inside and outside the drying room, so it is difficult to prevent the fine particles from the shaft seal from falling off; the feed liquid of the pressure atomization system must be pumped through a high-pressure pump. During operation, the friction between the piston and the cylinder and the sealing of the connecting rod will affect the cleanliness of the liquid. In contrast, air-flow atomization is more suitable for drying in the pharmaceutical industry because the air used for atomization and the feed liquid can be cleaned and filtered before entering the tower to filter out the particles (including bacteria) entrained in them.
1.2 Filtration of feed liquid and compressed air for atomization
The feed liquid before spraying should be filtered through a 0.3 microporous membrane before being introduced into the spray tower, and the oil and water carried by the compressed air for atomization should be removed before being filtered through a microporous membrane.
1.3 hot air
The hot air comes from the atmosphere, and the amount of dust particles entrained is large, and the flow rate is large. After heating, the temperature is required to reach above 140°C, and the heater will peel off the particles during operation. For this reason, the hot air filtration system should be considered in accordance with the temperature requirements of the hot air, and an air filter that can withstand high temperature and long-term high-efficiency operation should be developed.
1.4 Delivery of dry products
Clean air should be used around the outlet of the dry product to prevent dust or debris from the surrounding environment from mixing into the dry product.
2. Pharmaceutical Industry Expectations of Spray Dryers
From the working principle of the spray dryer, it can be seen that the process of the spray dryer is similar to that of the airflow dryer. After the air is initially filtered, it is heated by a heater. The shell channel is generated by the hot air distributor to generate uniform airflow into the drying chamber. The material is filtered through the centrifugal atomizing disc or pressure nozzle to produce dispersed and fine material mist. The material mist contacts with the swirling hot air, the water evaporates rapidly, and the material is dried in a very short time. This equipment is suitable for drying liquid materials with good fluidity such as solutions, emulsions, suspensions, and pastes.
Drying equipment involves various processes such as material transportation, heat transfer, fluid movement, and even crushing, and has high requirements for equipment or machinery processing and manufacturing. Over the years, the processing methods and processing equipment of domestic drying equipment have been relatively traditionally hand-made, and both the function and appearance of the equipment are affected to a certain extent. Not only that, the size of the parts cannot be guaranteed to have good interchangeability due to manual single-piece manufacturing, which brings a lot of inconvenience to the maintenance of drying equipment and the exchange of wearing parts.
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