Spray dryer in food industry processing
Spray drying refers to the process of dispersing the material liquid into mist droplets with an atomizer and drying in hot air at the same time to obtain a powdery or granular finished product. Since the spray drying of the material liquid is completed in an instant, it is necessary to maximize its dispersion, that is, increase the surface area per unit volume of the solution, thereby accelerating the heat and quality process (drying process). At present, in the industrial range of dyes, medicines, pesticides, aquatic products, forestry, metallurgy, food, ceramics, etc., hundreds of products are obtained by spray drying methods.
Advantages of spray drying technology:
1. Fast drying speed and short time. After the material liquid is atomized, the surface area increases to more than 10,000 times. For example, atomizing 1L of material liquid into a droplet with a diameter of 50um can increase its surface area to 120m2. It can instantly (0.01~0.04s) evaporate 95%~98% of water in the hot air stream, and the drying time is generally only 5~ 40s.
2. Good product quality. Spray drying uses a wide temperature range (80~300℃). Even if high-temperature hot air is used, since heat exchange is mainly used to evaporate material moisture, the outlet temperature will not be very high. The quality of the dried product is good, and protein denaturation and vitamins are not prone to occur. Defects such as loss and oxidation. Therefore, it is particularly suitable for heat-sensitive food processing that is easy to decompose and denature. At the same time, because the drying process is completed in hot air, the product can basically maintain hollow particles or loose agglomerates similar to mist droplets, and has good dispersibility, fluidity and melting properties.
3. Simple process and convenient control. The mass fraction of water in the feed liquid is usually 40% to 60%, and some special feed liquids have a mass fraction of water as high as 90%. It can also be dried directly to obtain powder or fine granular products without evaporation. The process of crystallization, separation, crushing and screening simplifies the production process. By changing the concentration of raw materials, hot air temperature, spray conditions, etc., products with different moisture and particle sizes can be obtained, which is easy to operate and easy to control. Because spray drying is carried out in a fully enclosed drying tower, the drying chamber has a certain negative pressure, which not only guarantees sanitary conditions but also avoids flying dust.
Disadvantages of spray drying technology:
①The equipment is more complex, covers a large area, and invests more at one time
②The energy consumption is large, the thermal efficiency is not high, and the power consumption is large;
③In the production of products with small particle size, the waste gas contains about 20% of the particles, and it is necessary to select an efficient separation device. The auxiliary device is more complicated and the cost is higher;
④The inner wall of the drying chamber is easy to adhere to product particles, the cavity is large, and the cleaning workload of the equipment is large.
