The closed circulation centrifugal spray dryer system is rarely used in the domestic pharmaceutical industry. Its characteristics: the heat carrier forms a closed circulation loop in this system, which is conducive to saving the heat carrier, recovering organic solvents, and preventing toxic substances from polluting the atmosphere. The materials commonly used in the pharmaceutical and chemical industry are often materials containing organic solvents, or materials that are easily oxidized, flammable, explosive, and some may even be toxic. When using a closed cycle system, most of the heat carriers are inert gases (such as nitrogen, carbon dioxide, etc.). The exhaust gas discharged from the drying tower is removed of fine particles by cyclone and wet dust collectors, and then enters the condenser. The function of the condenser is to condense the solvents (or moisture) in the exhaust gas, and the condensation temperature must be below the dew point of the highest allowable concentration of the solvent to ensure the condensation effect. After dehumidification, the exhaust gas is pressurized by a fan and enters an indirect heater before being turned into hot air, which is repeatedly reused.
Working principle of closed cycle centrifugal spray dryer
The closed cycle spray drying system works in a closed environment. The drying medium is inert gas, usually N2, which is suitable for drying materials containing toxic gas or materials prone to oxidation during the drying process.
After being heated by a heater, nitrogen enters the drying tower, and the liquid material is transported to the centrifugal nozzle by a screw pump. The liquid is atomized into droplets by a high-speed rotating centrifugal atomizer, and the heat and mass exchange process is completed in the drying tower. The dried powdered material is discharged from the bottom of the tower. The evaporated organic solvent gas, under the action of a fan, removes the dust trapped in the gas through a cyclone separator and a spray tower. The saturated organic solvent gas is condensed into liquid by the condenser and discharged from the condenser. The non condensable gas medium is continuously heated and reused as a drying carrier in the system. The conventional conventional centrifugal spray drying achieves the purpose of moisture removal through continuous air supply and exhaust, which is also an obvious difference between explosion-proof closed centrifugal spray drying equipment and conventional centrifugal spray drying equipment;
Among them, the drying medium in the drying system is N2, and the internal operation is positive pressure, maintaining a certain positive pressure value. If the internal pressure drops, the pressure transmitter will automatically control the N2 inlet to ensure system pressure balance. Due to the use of inert gases such as N2 as circulating gas, it has a protective effect on dry materials. The circulating gas undergoes processes of moisture loading and removal, and the medium can be reused.
Application of closed circulation centrifugal spray dryer
(1) There is a risk of combustion or explosion when solvents in solids come into contact with air;
(2) After drying, there is an odor or toxic components emitted, which pollutes the environment;
(3) During the drying process, solids are prone to oxidation when they come into contact with oxygen;
(4) Prevent bacterial contamination during drying;
(5) The moisture in the material is divided into organic solvents and needs to be recovered;