Spray drying is one of the most popular drying equipment in the industry, which has a wide range of applications. It can be said to be a dryer for processing solution, suspension or slurry like materials. The drying effect of spray drying is also very good and the efficiency is high. The product is powder with uniform particles and does not need to add grinding process. Now, spray drying has a very high market share in the chemical industry, light industry and food industry.

1、 Advantages of spray drying:

1. Spray drying due to the large surface area / volume ratio of droplet group, the time required for material drying is very short (generally 15-30 seconds, sometimes only a few seconds). No strict equipment is required for spray drying. If there is no fibrous liquid in the feed liquid, the feed liquid channel will not be blocked. Be able to get used to high viscosity liquid (compared with pressure spray drying). Because the rotating speed of the atomizer is easy to adjust, it is easy to empty the product particle size, and the particle size distribution is narrow.

2. Spray drying has large capacity and high quality. The amount of spray per hour can reach hundreds of tons, which is one of the larger capacity of the dryer. Although the inlet temperature of the drying medium can reach hundreds of degrees Celsius, the material temperature does not exceed the wet bulb temperature of the air during most of the drying process. Therefore, spray drying is particularly suitable for the drying of heat sensitive materials (such as food, drugs, biological products and dyes).

3. Spray drying is convenient for conditioning. It can change the operating conditions in a large range to control the product quality indicators, such as particle size distribution, moisture content, biological activity, solubility, color, aroma, taste, etc. When conditioning the processing capacity, it is not necessary to change the operating state of the atomizer, and the same product can be obtained for the feed rate.

4. Spray drying simplifies the process flow. It can complete the transpiration, crystallization, crushing and other operation processes in one step with spray drying operation. Because the fog group generated by the centrifugal atomizer is basically on the same horizontal plane, the fog drops move along the radial and tangential composition directions, and there is almost no axial initial velocity, so the diameter of the dryer is relatively large.

2、 Spray drying defects:

1. When the inlet temperature of the drying medium is lower than 150 ℃, the volumetric heat transfer coefficient of the spray dryer is low, and the volume of the equipment used is relatively large. In addition, the low-temperature operation has low heat utilization rate and large consumption of drying medium. Therefore, the power consumption is also large. The processing accuracy of the dispersion disc is required to be high, and it should have good dynamic balance performance. If the balance state is not safe, the main shaft and bearing are easy to be damaged;

2. For the production of fine powder products, separate equipment is required to prevent product loss and environmental pollution. The bulk density of the product is lower in spray drying.