Closed cycle spray dryerIt is a closed circuit circulating spray drying process specially used for the suspended liquid made of ethanol, acetone, hexane, gas oil and other organic solvents, and the products with inert gas (or nitrogen) as the drying medium. The entire process is oxidation free, the medium is recyclable, and the inert gas (or nitrogen) can be recycled. The closed cycle system designed for organic solvent recovery has extremely high requirements for explosion-proof control, high system self-control performance, and strict GMP requirements. It is commonly used for spray drying of precision ceramics, pharmaceuticals, battery materials, hard alloy (Wc. Fe) powder.

The closed spray drying system is also called closed cycle spray drying system. Its feature is that the system forms a closed cycle loop, and the heat carrier can be recycled. For the drying of volatile organic solvents that are toxic or can cause harm to people and the environment after escaping, the organic solvents or products contained in the liquid are easily oxidized, flammable, and explosive materials. Generally, materials that require this process cannot come into contact with oxygen gas, so inert gases (such as nitrogen, carbon dioxide, etc.) are mostly used as heat carriers. The exhaust gas discharged from the dryer, after gas-solid separation, also needs to go through a condenser to recover solvents or remove moisture, and then enter the dryer for recycling after being heated by a heater. This type of dryer requires the addition of refrigeration equipment in the system, which incurs high operating costs and requires high airtightness of the equipment. The dryer is mainly operated at normal or slightly positive pressure to prevent air from entering the system.

The closed cycle spray drying equipment works in a closed environment. The drying medium is inert gas (or nitrogen), which is suitable for drying materials containing toxic gas or materials prone to oxidation during the drying process; The system uses inert gas as the circulating gas, which has a protective effect on dry materials. The circulating gas undergoes processes of moisture loading and dehumidification, and the medium can be reused; After being heated by the heater, nitrogen enters the drying tower, and the liquid material is transported to the centrifugal nozzle by the screw pump. The liquid is atomized into powder material by the high-speed circulating atomizer and discharged from the bottom of the tower. The evaporated organic solvent gas, under the negative pressure of the fan, condenses the powder dust trapped in the gas into liquid through the cyclone separator and spray tower dust removal. 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; The drying system operates under positive pressure internally, maintaining a certain positive pressure value. If the internal pressure drops, the pressure transmitter automatically controls the inflow to ensure system pressure balance.