Spray drying is a method of applying systematic technology to material drying. What are the forms?

Spray drying is a method of applying systematic technology to material drying. After the thinner is atomized in the drying chamber, in contact with the hot air, the moisture rapidly vaporizes to obtain a dry product. This method can directly dry the solution and emulsion into powder or granular products, and can save the steps of evaporation and pulverization.

Through mechanical action, the material to be dried is dispersed into very fine mist-like particles (to increase the evaporation area of water and accelerate the drying process) and contact with hot air to remove most of the water in an instant to make the solid in the material The substance dries into a powder.

Mechanism of action

(1) Pressure spray drying method:

①Principle: Using a high-pressure pump, the material is passed through an atomizer (spray gun) at 70-200 atmospheres to polymerize into 10-200 atomized particles that directly contact the hot air for heat exchange, and drying is completed in a short time.

②Pressure spray atomization device: M-type and S-type, with guide grooves that make the liquid flow rotate, the axis of the M-type guide groove is perpendicular to the nozzle axis, and does not intersect with it; the axis of the S-type guide groove is at a certain angle to the horizontal. The purpose is to try to increase the turbulence of the solution when spraying.

(2) Centrifugal spray drying method:

①Principle: Centrifugal force is given to the solution by using a high-speed rotating disk in the horizontal direction, which will be thrown out at high speed to form a film, filament or droplet. Due to the friction, obstruction and tearing of the air, it will be generated with the rotation of the disk. The tangential acceleration and the radial acceleration generated by the centrifugal force result in moving on the disk at a combined speed, and its trajectory is a spiral. After the liquid is thrown from the disk along the spiral, it is dispersed into very small The droplets move along the tangential direction of the disc at an average speed, and at the same time the droplets fall due to the gravity of the earth, due to the different sizes of particles sprayed. Therefore, they fly at different distances, so the particles falling at different distances form a cylinder symmetrical about the center of the rotation axis.

②Requirements to obtain more uniform droplets: a. Reduce the vibration when the disc rotates b. The amount of liquid entering the disc remains constant per unit time c. The surface of the disc is flat and smooth d. The circumferential velocity of the disc should not be too small, rmin =60m/s, if the milk (100-160m/s) is less than 60m/s, the spray droplets are not uniform, and the spray distance seems to be mainly composed of a group of droplets and a group of fine droplets near the sinking plate, and varies with the speed Decrease.

③The structure of the centrifugal sprayer: requirements: the wetted periphery is long, can make the solution reach high speed, spray evenly, the structure is firm, light, simple, no dead corners, easy to disassemble and wash, and has high productivity.

(3) Airflow spray drying method:

①Principle: The wet material enters the Dryer through the conveyor and the heated natural air at the same time. The two are fully mixed. Due to the large heat and mass exchange area, the purpose of evaporation and drying can be achieved in a short time. The dried product is discharged from the cyclone separator, and a small part of the fly powder is recycled by the cyclone dust collector or the bag filter. Q type airflow dryer is a negative pressure operation, the material does not pass through the fan; QG type airflow drying is a positive pressure operation, and the material is crushed by the fan; FG type airflow dryer is a tail gas circulation type; JG type airflow drying is an enhanced airflow The dryer, which integrates flash drying and airflow drying, is a new type of Drying Equipment designed by our factory according to user requirements.

Structural parts

According to the movement direction between the hot air and the dry particles in the drying room, it is classified: co-current type, counter-current type, mixed-flow type. Co-current type is often used in cow milk. The parallel flow type can be dried at a higher inlet air temperature without affecting the quality of the product.

a. Horizontal parallel flow

b. Vertical descending parallel flow type

c. Vertical descending mixed flow type.

d. Vertical upward parallel flow