1. Working principle of spray dryer:
1. Principle of spray dryer:
The spray dryer uses an atomizer to disperse the raw material liquid into droplets, and uses hot gas (air, nitrogen or superheated steam) to dry the droplets to obtain the product through drying. The raw material liquid for spray drying can be a solution, emulsion, suspension or molten liquid or paste liquid. The dried product can be made into powder, granules, hollow balls or pills as needed. Liquid atomization atomizer disperses the liquid material into droplets and is a key part of spray drying.
2. Principle of pressure spray dryer:
Pressure atomizer: Use a high-pressure pump to obtain high pressure from the liquid. When high-pressure liquid passes through the nozzle, the pressure energy is converted into kinetic energy and dispersed in the form of droplets during high-speed injection.
3. Principle of air spray dryer:
Air flow atomizer: Compressed air or steam is ejected from the nozzle at extremely high speed (≥300 m/s). Friction caused by the difference in velocity between the gas and liquid phases breaks the liquid into droplets.
4. Principle of centrifugal spray dryer:
Using a rotary atomizer: the material liquid is thrown from the edge of the disc and atomized by centrifugal force (circumferential speed 90-160 rpm/ms) in the high-speed turntable.
2. Basic operating procedures of spray dryer:
1. Preparation before starting
Before starting the spray dryer, please prepare the items required for the experiment, clean the cooling water barrel and feed barrel, check the water inlet pump and the water inlet pipe under the water inlet barrel for leaks; clean and dry the water tank, powder collector and pipes if necessary of water. Then pour a certain amount of water into the cooling water tank, and pour the liquid to be spray-dried into the water tank.
Note: To ensure product quality, the equipment must be thoroughly cleaned before use and sterilized according to product requirements.
2. Start
Turn on the power of the spray dryer →→ Turn on Heating I and Heating II, and set the temperature setting of Heating I → → Start the cooling pump (and check whether the circulating water of the cooling pump flows back) → → Start during heating. When the I temperature reaches about 100°C, start the cooling pump. Fan →→ Turn on the atomizer (and check whether the atomizer is operating normally through sound detection) →→ When the heating I temperature reaches the set temperature, start the feeding pump to start feeding.
3. Shut down
Preparation work before the spray dryer: When the liquid addition is about to end, replace the empty powder collector, add clean water to the hopper, reduce the amount of water entering the atomizer, and keep the outlet temperature unchanged (this is very important, otherwise The moisture content of the powder left in the drying chamber will change); preliminary cleaning of the atomization plate and feed pipe, rinse with water for about ** minutes; then it can be closed.
Shutdown procedure: first turn off heating I, then turn off heating II→→then turn off the feed pump→→then turn off the atomizer→→wait for the temperature to drop to about 50℃, then turn off the induced draft fan→→turn on the machine and turn on and off the cooling pump→→ → Then turn off the power.
4. Equipment cleaning
After turning off the power of the equipment, open the door of the drying room, clean the walls and bottom of the drying room and the accumulated powder near the centrifugal atomizer, and then clean the equipment.
The cleaning work includes the parts that are in contact with the feed liquid: such as the feed barrel, feed pipe, feed liquid distribution plate, and atomization plate of the centrifugal atomizer; the parts that are in contact with the finished product, such as the drying chamber wall, exhaust pipe, Cyclone separators, etc. also need to be thoroughly cleaned, as well as air filters and centrifugal fans.
