Comprehensive analysis of common fault handling and working principle of spray dryer

Spray dryers are used in a wide range of applications. According to the characteristics of the material, it can be used for hot air drying, centrifugal granulation and cold air granulation. Most products with different characteristics can be produced by this machine.

Since the drying process is completed in an instant, the finished product particles can substantially maintain the spherical shape of the droplets, and the product has good dispersibility, fluidity and solubility.

The production process is simplified and the operation control is convenient. Spray drying is usually used for solutions with a solid content of less than 60%. After drying, no further pulverization and screening are required, which reduces the production process and simplifies the production process. For the particle size, bulk density and moisture of the product, within a certain range, the operating conditions can be changed and adjusted, and the control and management are very convenient.

In order to prevent the material from being polluted and to extend the life of the equipment, all parts in contact with the material are made of stainless steel. After being sprayed, the liquid is atomized into dispersed particles, and the surface area is greatly increased. After contact with hot air, the drying process can be completed in a very short time. Under normal conditions, at 100 to 150 ° C, 95% to 98% of water can be evaporated within 1 to 3 seconds. Since the drying process is completed in an instant, the particles of the finished product can substantially maintain a spherical shape similar to that of the droplets, thereby having good dispersibility, excellent brewing property, and high solubility.

Possible failures and solutions for spray dryers in production:

The main problem of sticking wall is that there is sticky wet powder everywhere in the drying room. The reason is:

The feed amount is too large to evaporate sufficiently;

Insufficient heating in the drying chamber before the start of spraying;

When the spray is started, the discharge flow is adjusted too large;

The added feed liquid is unstable. In view of the different reasons for the above problems, the following measures can be taken in sequence: appropriately reduce the amount of feed; appropriately increase the inlet and outlet temperatures of the hot air; when starting the spray, the flow rate should be small, gradually increase, and adjust to the appropriate time; Whether it is blocked, adjust the solid content of the material to ensure the fluidity of the liquid.

The moisture content of the product is too high. The exhaust air temperature is the main factor affecting the moisture content of the finished product. Therefore, the reason why the moisture content of the product is too high 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 amount to increase the exhaust air temperature.

The reasons for the low purity of the product and the excessive impurities cause the following reasons:

Air filtration is not good;

The powder is mixed into the finished product;

The purity of raw materials is not high;

The equipment is not thoroughly cleaned. The remedies available are: check whether the filter material in the air filter is evenly laid, whether the filter is used for too long, if it should be replaced immediately; check the coke powder at the hot air inlet to overcome the eddy current; filter the liquid before spraying ;Re-clean the device.

The product powder is too fine, and the product particles are too fine, which will affect its solubility and brewing performance. The reason is that the solid content is too low or the feed amount is too small. The remedy is to increase the solid content of the feed liquid, increase the feed amount, and increase the inlet air temperature.

The phenomenon of running powder is serious, the product yield is low, and the loss of running powder is too much, which greatly affects the yield of the finished product. The general reason is that the separation effect of the cyclone separator is poor. If this happens, check whether the cyclone is deformed due to knocking or collision; improve the airtightness of the inlet and outlet of the cyclone, and check whether the inner wall and the discharge port are blocked. Of course, the separation efficiency is also related to the specific gravity of the powder and the size of the particle size. Some materials can be added to the second stage dust removal as needed.

The rotation speed of the centrifugal nozzle is too low, mainly because the centrifugal nozzle component is out of order, so stop using the nozzle and check the internal parts of the nozzle.

The reason for the low evaporation is probably:

The amount of air in the entire system is reduced;

The inlet temperature of hot air is low;

The equipment has air leakage and cold air enters the drying room. The remedy is:

Check if the speed of the centrifuge is normal;

Check if the position of the centrifuge control valve is correct;

Check if the air filter and air heater pipe are blocked;

Check if the grid voltage is normal;

Check if the electric heater is working properly;

Check that the components of the equipment are connected in a sealed manner.

The noise or vibration during the operation of the centrifugal nozzle is mainly caused by the residual material in the nozzle or the bending and deformation of the main shaft caused by improper cleaning and maintenance of the nozzle, or the centrifugal disc is not well balanced. Solution; check if there is any residual material in the spray disk, if it should be cleaned in time; if the spindle is abnormal, replace it; re-adjust or replace the dynamic balance of the centrifugal disk.

The spray dryer has become one of the most popular drying equipments due to its fast drying, good drying effect and low energy consumption. Many companies choose spray dryers for production and processing, and they have a higher market share due to their more applicable materials.

1 spray dryer dryer main tower inner wall adhere to wet powder:

Reason: The feed rate of the material is too fast, and the amount is too large, resulting in incomplete drying; it is not carried out according to the operation in the equipment operation manual, and the main tower of the equipment is not heated;

Solution: slow down the feeding speed and quantity, properly adjust the feed pump; increase the inlet and outlet temperature; observe whether the equipment has material blockage;

2 products have a lot of impurities:

Reason: The source of impurities is mainly that the drying medium contains impurities, the purity of the material liquid is not high, and impurities exist in the spray dryer.

Solution: Check the air filter, replace the filter that has been used for a long time, sample the material, filter the impurities, and thoroughly clean the equipment.

3 The phenomenon of running powder is serious, and the recovery rate of the product is very low:

Cause: There is a problem with the cyclone separator and the dust removal performance is low.

Solution: Check if there is a gap in the cyclone and whether the air tightness is intact. The secondary dust removal is appropriately increased according to the material characteristics.

4 product particles are too fine or too large particles:

Cause: The solid content of the feed liquid is too low, and the too low feed treatment amount will cause the product powder to be too fine. The reason why the particles are too large is that the wind pressure is too low, the heat is not enough, and the moisture content of the liquid is too high.

Solution: If the particles are too fine, it is necessary to increase the solid content of the liquid; appropriately increase the feed amount and increase the inlet air temperature to prevent incomplete drying; the solution of excessively large particles: properly adjust the wind pressure, and test the heating system Whether the heat demand is met and the moisture content of the material is controlled.

5 pulse bag filter dust removal effect is not good:

Reason: The problem is mainly on the bag or the pulse valve.

Solution: Observe whether the bag is suitable for the drying equipment. If necessary, replace the new bag with the cloth bag, check the grounding wire, and check whether the pulse valve is working normally.

6 spray dryer operation is very noisy:

Reason: The place where noise is generated is mainly the atomizing disk and the bearing.

Solution: Check if the atomizing disk is in equilibrium, check whether the bearing is working properly, repair or replace it when the gear tooth damage occurs, and check if the lubricating oil is properly added.

There are some problems in the operation of the spray drying equipment. These issues are more common and easy to handle. Maintaining scientific and rigorous operating habits is not only a guarantee for the normal operation of the equipment, but also a guarantee for improving work efficiency and saving costs.