The horizontal spray dryer is one of the popular drying equipment in the industry at present, with a wide range of applications. It can be said that it is a dryer for processing solutions, suspensions, or mud like materials. The drying effect of horizontal spray dryer is also very good and efficient. Its product is in the form of powder with uniform particles, and no need to add crushing process. At present, the market share of horizontal spray dryer in chemical industry, light industry and food industry is very high. The spray drying equipment can change the operating conditions in a large range to control the quality indicators of the product, such as particle size distribution, moisture content, biological activity, solubility, color, aroma, taste, etc. It has the characteristics of fast heat transfer, rapid water evaporation, short drying time, good product quality, crisp texture, good solubility, can improve the dissolution rate of some preparations, and is suitable for heat sensitivity. In addition, spray drying can also be used to prepare microcapsules. The spray drying equipment uses compressed air or water vapor to atomize the material liquid. Through mechanical action, the material to be dried is dispersed into very fine particles like fog, (increasing the evaporation area of water, accelerating the drying process) contacts with hot air, removes most of the water in an instant, so that the solid matter in the material is dried into powder. The horizontal spray dryer has a fast drying speed, and the surface area of the liquid material is greatly increased after atomization. In the hot air flow, 95% -98% of the water can be evaporated instantly, and the drying time is only a few seconds. It is especially suitable for drying heat sensitive materials. The horizontal spray dryer has good uniformity, fluidity and solubility, high product purity and good quality. The production process is simplified, the operation control is convenient, and there is no need for crushing and screening after drying, reducing production processes and improving product purity.
In order to meet market needs and improve product solubility, blending, and packaging performance. Some spray drying equipment adds granulation equipment, but it will increase the heat denaturation of products and the loss of aromatic substances. spray drying equipment effectively solves the integration problem of drying tower, separation chamber and cooling chamber. In the falling rate drying stage of spray drying, the temperature of powder increases with the decrease of water content. Taking dairy products as an example, when the temperature of the dry air at the bottom of the drying tower is 90-100 ℃, the temperature of the powder is around 60 ℃. To prevent thermal denaturation, it is hoped to cool down quickly at the end of drying. For this reason, MD horizontal spray dryer is equipped with a flow cooling chamber at the lower part of the drying tower. This system has micro powder separated by cyclone, which is transported to the flow cooling chamber at the lower part of the separation chamber with air, and cooled to about 30 ℃ with the powder separated by gravity in the separation chamber, and then discharged. The result has a good control effect on thermal denaturation.
Spray drying equipment has fast drying speed and good product performance
After spray, the feed liquid is atomized into dispersed particles, and the surface area is greatly increased. After contacting with hot air, the drying process can be completed in a very short time. Under normal circumstances, 95% to 98% of water can be evaporated within 1-3 seconds at 100-150 ℃. Due to the instantaneous completion of the drying process, the particles of the finished product can basically maintain a spherical shape similar to the liquid droplets, thus having good dispersibility, excellent washability, and high solubility.
1、 Advantages of horizontal spray dryer:
1. Due to the large surface area/volume ratio of the droplet group, the horizontal spray dryer requires a short time to dry materials (usually 15-30 seconds, sometimes only a few seconds). The horizontal spray dryer does not need strict filtering equipment, and if there is no fibrous liquid in the feed liquid, the feed liquid channel will not be blocked basically. It can adapt to high viscosity liquid (compared with pressure spray drying). Due to the easy adjustment of the speed of the atomizer, it is relatively easy to air produce product particle size, and the particle size distribution is also narrow.
2. The horizontal spray dryer has large production capacity and high product quality. The amount of spray per hour can reach several hundred tons, which is one of the larger capacity of the dryer. Although the inlet temperature of the drying medium can reach several hundred degrees Celsius, the material temperature does not exceed the wet bulb temperature of the air during most of the whole drying process. Therefore, spray drying is particularly suitable for drying heat sensitive materials (such as food, drugs, biological products and dyes).
3. The horizontal spray dryer is easy to adjust, and the operating conditions can be changed in a large range to control product quality indicators, such as particle size distribution, moisture content, biological activity, solubility, color, aroma, taste, etc. When adjusting the processing capacity, it is not necessary to change the working state of the atomizer, and the same product can be obtained for the feed rate.
4. The horizontal spray dryer simplifies the process flow. The operation process of evaporation, crystallization, filtration and crushing can be completed in one step by spray drying. Due to the fact that the mist generated by the centrifugal atomizer is basically on the same horizontal plane, the droplets move along the radial and tangential composite directions, with almost no axial initial velocity, so the diameter of the dryer is relatively large. The diameter and length are relatively small, allowing for maximum utilization of the space in the drying room.
2、 Disadvantages of horizontal spray dryer:
1. When the inlet temperature of drying medium is lower than 150 ℃, the volumetric heat transfer coefficient of the dryer of horizontal spray dryer is low, and the volume of the equipment used is large. In addition, the heat utilization rate of low-temperature operation is low, and the consumption of drying medium is large, so the power consumption is also high. The machining accuracy of the dispersed disc is required to be high, and it should have good dynamic balance performance. If the balance state is poor, the spindle and bearings are easily damaged;
2. For the production of fine powder products, separation equipment is required to avoid product loss and environmental pollution. The stack density of the product is lower in the horizontal spray dryer.
3. The contact mode between fog droplets and gas is basically in a parallel flow form, and the dispersion plate cannot be placed vertically;
