Spray Drying Machine

Spray drying machine in the lab, also known as small spray dryer, is a kind of laboratory instrument mainly for processing liquid materials. Generally, the whole laboratory spray dryer is compact in design and can be moved. The machine is self-contained and does not require auxiliary facilities.

Spray drying technology is a systematic method that is applied to the drying of materials. Through mechanical action, it disperses the materials to be dried into very fine mist-like particles, (increasing the area of water evaporation, accelerating the drying process) and hot air contact, removing most of the water in an instant, so that the solid material in the material is dried into a powder state.

The air enters the air distributor at the top of the drying tower through the filter and heater and then enters the drying chamber evenly in a spiral shape. The material liquid is sent from the material liquid tank to the centrifugal atomizer at the top of the drying tower by the filter and pump so that the liquid is sprayed into very small droplets. The end product is discharged from the bottom of the drying tower and the cyclone separator while the exhaust gas is discharged by the fan.

Spray dryer working in the following three methods.

a. The principle of the pressure spray drying method is to use a high-pressure pump to collect materials into 10-200 fog particles through an atomizer (spray gun) at a pressure of 70-200 atm to be in direct contact with hot air. Then heat exchange is carried out and drying is completed in a short time.
b. Basically, all pressure spray drying devices have a guide groove to make the liquid flow rotate. The purpose of the guide groove is to try to increase the turbulence of the solution during spraying.

The principle of the centrifugal spray drying method
a. Using a disc rotating at high speed in the horizontal direction to produce centrifugal force to the solution, so that it is thrown out at high speed to form a film, filament, or droplet.
b. Due to the effect of friction, obstruction, and tearing of air, the tangential acceleration is generated with the rotation of the disc, and the radial acceleration is generated by centrifugal force; maintain a combined speed of movement on the disc to form a spiral shape.
c. After the liquid is thrown from the disc along this spiral, they are dispersed into very small droplets, which move at an average speed along the tangential direction of the disc.
d. At the same time, the droplets are subject to the gravitational pull and fall.
e. Since the size of the particles sprayed is different, the flight distance of these drops is also different. Therefore, the particles fall at different distances to form a cylinder symmetrical to the center of the axis of rotation.

Requirements for obtaining uniform droplets in laboratory rotary dryer
a. Reduce the vibration when the disc rotates.
b. The amount of liquid entering the disc remains constant per unit of time.
c. The surface of the disc should be flat and smooth.
d. The circumferential rate of the disc should not be too small.

Principle of airflow spray drying
a. The wet material enters the spray dryer at the same time as the heated natural air through the conveyor and mixes them thoroughly.
b. Due to the large heat mass exchange area, the purpose of evaporation and drying could be achieved in a very short period.
c. The end product after drying is discharged from the cyclone separator, and a small part of the flying powder is recycled by the cyclone dust collector or cloth bag dust collector.

Small scale spray dryer components are composed of a drying tower, atomizer, cyclone separator, material receiving bottle, waste collection bottle, air compressor, fan, spray dryer body, and integrated control circuit.

Spray dryer technology can dry solution and emulsion into powder or granular products directly. Using this method, the processes of evaporation, concentration, crushing and others can be omitted, and the products obtained from the uniform distribution of particles.

Spray drying has the characteristics of fast heat transfer, rapid evaporation of water, and instant drying time. The finished product made by spray dryer has good quality and dissolution performance. Spray dryers can also improve the dissolution rate of certain formulations. Besides, the machines can also be used to prepare microcapsules.

For different physical properties or chemical properties of materials, as well as the size and solubility of the powder or particles that need to be obtained from the experiment, researchers may need different types of laboratory spray dryers to get the ideal experimental results.

The material with higher sugar content refers to fruit juice, Chinese herbal medicine or natural product extracts, etc.; the material with heat sensitivity refers to enzyme preparation live bacteria, or something like this.

Most of the materials containing polysaccharide disaccharides have a low melting point, which makes them melt when they are heated; and polysaccharide disaccharides easy to absorb moisture, so when using a spray dryer, it is easy to appear the phenomenon of the sticky wall, and it is not easy to get good dry powder or granule.

In addition, when the spray drying machine deals with enzyme preparation, live bacteria, and some polymer materials which are easily denatured under high temperature, it is very easy to cause their inactivation or denaturation. To solve this problem, you can lower the inlet air temperature and the outlet air temperature of the spray dryer.

There has always been a problem of difficult drying of organic solvent materials in spray drying for the laboratory because the general organic solvent contains flammable and explosive properties. The emergence of explosion-proof closed laboratory spray dryers makes it possible to circulate the material in a closed spray drying system. Even if the whole system is filled with inert gas (such as nitrogen or argon), the explosion-proof closed lab dryer can effectively avoid the contact between organic solvent gas and external oxygen, ensuring safe production.

In some experiments, researchers need to get some samples with large particles, such as the catalyst industry, which needs particles of about 100 microns to have a better catalytic effect. But the ordinary spray dryer can only get the particles below 30 microns. ANTITECK, as one of the spray drying equipment suppliers, offers spray dryers that can make granules of about 100 microns. The machine also enables the spray granulation of small powder particles and can obtain large particles of 100 microns or more.

Researchers can use laboratory spray dryers for the preparation of ordinary powders or the drying of materials directly. These spray drying machines are small in size, fast in speed, low in noise, and easy to operate. The dried powder has good sphericity and the particle size is normally distributed.

a. Check whether the instrument is operating properly or not.

b. To ensure the purity of the end product, the operator should check the inside of each part of the instrument before operating the machine. Check carefully that the instrument connections are in place to avoid damaging the instrument or affecting the results during the experiment.

c. Turn on the power switch of the instrument.

d. Turn on the aspirator switch to allow air to flow through the system. It is recommended to set the aspirator to operate at 100%.

e. Set the inlet temperature and then turn on the heating switch. For aqueous samples, the inlet temperature should be set in the range of 100℃ to 220℃ (usually 150℃).

f. When reaching the preset inlet temperature, the operator should turn on the air compressor and adjust the needle valve on the flow meter. Typically, the adjustment is made to a height of 4 cm (approximately 600 L/ H).

g. Prepare distilled water and turn on the peristaltic pump.
    a) Press the sample tube onto the mercury and begin optimizing for optimal conditions. The pump is typically set at 30%.
    b) If the outlet temperature is too high, the operator should lower the inlet temperature or increase the speed of the pump.
    c) If the sample is not completely dry (wall sticking occurs), the operator may increase the inlet temperature or decrease the pump speed. Note: The temperature limit for the outlet temperature is the actual temperature that the product can withstand.

h. If the sample solution tends to clog the nozzle, the operator can turn on the nozzle cleaning switch to set the cleaning frequency.

i. When the machine is ready, the operator can convert the input from steaming water to a sample solution.

j. After sample injection, switch to distilled water to clean the tubing and nozzle.
NOTE: This procedure must be performed strictly to ensure that no sample remains in the tubing (especially the nozzle).

k. When turning off the machine:
    a) turn off the inlet temperature heating switch first to keep the aspirator operating;
    b) Turn off the extractor until the outlet temperature drops below 70℃.

l. Remove the product.

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