Troubleshooting And Equipment Advantages Of Spray Drying Equipment

The Spray Dryer is one of the most popular Drying Equipment in the industry, with a wide range of applications. It can be said to be a Dryer for processing solutions, suspensions or slurry-like materials. The drying effect of the spray dryer is also very good and the efficiency is high. The product is a powder with uniform particles, and there is no need to increase the pulverization process. At present, the market share of spray dryers in the chemical, light industry and food industries is very high.

At present, with the improvement of living standards, quality and quality requirements have begun to increase. If you want to develop for a long time, you need to discuss the advantages and disadvantages of spray dryer technology from the details, and answer the questions in essence.

1. Advantages of spray dryer:

1. Due to the large surface area/volume ratio of the spray dryer, the drying time of the material is very short (usually 15-30 seconds, sometimes only a few seconds). The spray dryer does not require strict filtering equipment, and the material liquid, such as non-fibrous liquid, basically does not block the material liquid channel. It can be adapted to higher viscosity materials (compared with pressure spray drying). Because the rotation speed of the atomizer is easy to adjust, it is easier to empty the product particle size, and the particle size distribution is also narrow.

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

3. The spray dryer is easy to adjust, and the operating conditions can be changed in a large range to control the quality indicators of the product, such as particle size distribution, moisture content, biological activity, solubility, color, fragrance, taste, etc. When adjusting the processing capacity, there is no need to change the working state of the atomizer, and the same product can be obtained for the feed rate.

4. The spray dryer simplifies the process flow. The evaporation, crystallization, filtration, pulverization and other operations can be completed in one step by spray drying. Because the mist groups produced by the centrifugal atomizer are basically on the same horizontal plane, the mist droplets move in the combined radial and tangential directions, and there is almost no axial initial velocity, so the diameter of the dryer is relatively large. The diameter and length are relatively small, and the space of the drying chamber can be used to the maximum.

2. Disadvantages of spray dryer:

1. When the inlet temperature of the drying medium is lower than 150 degrees Celsius, the volumetric heat transfer coefficient of the spray dryer dryer is relatively low, and the volume of the equipment used is relatively large. In addition, the heat utilization rate of low temperature operation is low, and the drying medium consumption is large, therefore, the power consumption is also large. The processing accuracy of the dispersing disc is required to be high, and it must have good dynamic balance performance. If the balance is not good, the spindle and the bearing are easily damaged;

2. For the production of fine powder products, separation equipment is required to avoid product loss and environmental pollution. The bulk density of the product spray dryer is lower.

3. The contact mode of mist and gas basically belongs to the parallel flow mode, and the dispersion disc cannot be placed vertically;

In order to meet market needs, improve product solubility, blending and packaging performance. Some Spray Drying Equipment increases the granulation equipment, but it will increase the thermal denaturation of the product and the loss of aromatic substances. The spray drying equipment effectively solves the integration problem of the drying tower, the separation chamber and the cooling chamber. In the reduced-rate drying stage of spray drying, the temperature of the powder rises as the moisture decreases. Taking dairy products as an example, when the temperature of the drying air in the lower part of the drying tower is 90-100°C, the temperature of the powder is about 60°C. In order to prevent thermal denaturation, it is desirable to cool down quickly at the end of drying. In this regard, the MD spray dryer is equipped with a flow cooling chamber at the lower part of the drying tower. This system has cyclone-separated fine powder, which is transported by air to the flow cooling chamber at the lower part of the separation chamber, together with the powder separated by gravity in the separation chamber. Cool to about 30°C and then discharge. As a result, it has a good control effect on thermal denaturation.

Spray drying equipment has fast drying speed and good product performance

After the material liquid is sprayed, it is atomized into dispersed particles, the surface area is greatly increased, and the drying process can be completed in a very short time after contact with hot air. Under normal circumstances, 95%~98% of water can be evaporated within 1~3s at 100~150℃. Since the drying process is completed in an instant, the particles of the finished product can basically maintain a spherical shape similar to the droplets, so that it has good dispersibility, excellent brewability and high solubility.

Reduce wall sticking and coke powder, improve the quality of finished products

Severe wall sticking phenomenon

The main manifestation is that there are sticky wet powder everywhere in the drying chamber of the spray drying equipment. The reason is that the feed volume is too large to fully evaporate; the drying chamber is not heated enough before the spraying starts; when the spraying starts, the feed flow rate is adjusted too large; the added feed liquid is unstable. In response to the different causes of the above-mentioned problems, the following measures can be taken in sequence: appropriately reduce the feed volume; appropriately increase the inlet and outlet temperature of the hot air; when starting spraying, the flow rate should be small, gradually increase, and adjust until appropriate; check the pipeline Whether it is blocked, adjust the solid content of the material to ensure the fluidity of the material and liquid.

Spray dryers, centrifugal spray dryers and multi-nozzle spray dryers are three typical spray equipment. The spray direction of centrifugal spray and multi-nozzle spray is horizontal or vertical (axis direction). In the horizontal direction, in order to make the hot air and the liquid droplets contact well and improve the drying efficiency, let the hot air form a vortex, which is easy to cause adhesion, and the attached and deposited materials will cause thermal denaturation and cleaning difficulties. When the speed of the hot air is along the axis of the drying tower, the flow line of the hot air often deviates as a whole, and the hot air cannot mix well with the material and liquid, resulting in low efficiency and partial adhesion.

Product moisture content is too high

The exhaust air temperature is the main factor affecting the moisture content of the finished product, so the reason for the high moisture content of the product is generally that the exhaust air temperature is too low. The exhaust air temperature can be adjusted by the amount of feed. Therefore, the corresponding measure is to appropriately reduce the feed volume to increase the exhaust air temperature.

Low product purity and excessive impurities

The possible reasons for this situation are as follows: (1) The air filtration effect is not good; (2) The powder is mixed into the finished product; (3) The purity of the raw materials is not high; (4) The equipment is not cleaned thoroughly. The remedial measures that can be adopted are: check whether the filter material in the air filter is evenly laid and whether the filter has been used for too long, if it should be replaced immediately; check the coke powder at the hot air inlet to overcome the turbulence; the material liquid should be filtered before spraying ; Re-clean the equipment.

The powder of the product is too fine, the phenomenon of running powder is serious, and the product yield is low

Too fine particles of the product will affect its solubility and preparation performance. The reason is that the solid content is too low or the feed volume is too small. The remedy is to increase the solid content of the material liquid, increase the feed volume, and increase the inlet air temperature. Excessive powder loss will greatly affect the yield of the finished product. The general reason is the poor separation effect of the cyclone separator. If this happens, check whether the cyclone separator is deformed due to knocks or collisions; improve the air-tightness of the inlet and outlet of the cyclone separator, and check whether the inner wall and the discharge port are blocked by material accumulation. Of course, the separation efficiency is also related to the specific gravity and particle size of the powder. For some materials, a second-stage dust removal can be added as needed.

The rotating speed of the centrifugal nozzle of the spray drying equipment is too low, and the evaporation is too low

The main reason is that the parts of the centrifugal nozzle are out of order, so stop using the nozzle and check the internal parts of the nozzle. The reasons may be: the air volume of the entire system is reduced; the temperature of the hot air inlet is low; the equipment has air leakage and cold air enters the drying room. The remedial measures are: check whether the rotation speed of the centrifuge is normal; check whether the position of the centrifuge regulating valve is correct; check whether the air filter and air heater pipes are blocked; check whether the grid voltage is normal; check whether the electric heater is working normally; Whether the component connection is sealed.

There is noise or vibration when the centrifugal nozzle is running

Mainly due to the improper cleaning and maintenance of the nozzle, residual substances in the nozzle or the bending and deformation of the spindle may be caused by the poor dynamic balance of the centrifugal disk. Solution: Check if there is any remaining substance in the spray plate, if there is any, clean it in time; if the spindle is found to be abnormal, replace it. Re-adjust or replace the dynamic balance of the centrifugal plate.