Spray Drying Process for High Specific Gravity Materials
In powder engineering, atomization and drying of solution, suspension or lotion is one of the technical means to quickly obtain products. Compared with oven, freeze drying and other means, spray drying has high production efficiency, low production cost and better product uniformity. Spray drying technology has been developed for 30 years, and it has been quite mature, widely used in food, medicine, chemical industry, ceramics, new materials and many other fields.
However, due to the diversity of materials, spray drying equipment is basically customized. For some special products, production equipment needs to repeatedly consider material characteristics to meet usage needs. For example, some products are heat sensitive and can only adopt lower inlet and outlet air temperatures; Some products are prone to oxidation and can only be produced in an inert environment; Some materials use organic solvents or hazardous solvents instead of water, which not only prevent exhaust emissions into the air, but also consider environmental protection, explosion, safety, and other risks; Some materials have a high specific gravity and are prone to precipitation in suspensions.
Today we will talk about the last one.
Products with a relatively large proportion are typically new materials, such as metal powders, anode materials, solid electrolytes, or functional ceramic materials used in the new energy industry. In the suspensions made of these materials, because of the large proportion, the spray drying tower is challenged.
In spray drying, atomization is the first step, and the upstream of atomization is liquid preparation and material liquid transportation. Leaving aside explosion prevention, the most important aspect of these two processes is how to prevent the precipitation of high density particles. Although some excipients may be added to the solvent to increase viscosity, precipitation cannot be ignored. Our approach is:
1. From liquid preparation to liquid inlet, a stirring blade needs to be installed on the liquid preparation tank;
When transporting materials and liquids, regardless of the flow rate, try to use pipelines with finer inner diameters. If you want to increase the flow rate, you can increase the speed/pressure of the inlet pump to achieve this;
3. The path of the liquid conveying pipe should be as short as possible, and if necessary, an oscillator can be installed on the conveying pipe;
The above methods can effectively reduce the sedimentation of the liquid during the preparation and transportation process. For nozzles, if a two fluid nozzle is used, a cleaning needle can be configured if necessary to automatically clear nozzle blockages; For pressure type nozzles, high pressure can effectively avoid the nozzle. The nozzle can be selected based on the material's fineness, but ceramic slurry has a high solid content and poor flowability, making pressure nozzles relatively suitable.
We know that the direction of the spray and the direction of the hot air have the design of downstream and countercurrent. For materials with large specific gravity, the countercurrent form is used when necessary, that is, the nozzle is installed at the bottom of the spray drying tower, and the hot air enters the tower from above. This design can significantly increase the droplet travel (first upward and then downward), improve drying efficiency, and avoid the rapid drop of droplets to the lower end due to the gravity and wind speed during downstream design, where the droplets/powder enter the cyclone separator before being completely dried.
If the solvent is an organic solvent or the product is sensitive to oxygen, a nitrogen environment is necessary. The source of nitrogen can be nitrogen cylinders, industrial nitrogen, or nitrogen generators. Considering the cost, environment, and safety of using nitrogen, a closed-loop design is the most suitable.
Jiangsu Shengman Group was established in 2011. We have extensive experience in equipment design and delivery for thermal sensitive, oxygen sensitive, and high specific weight material products. We have many installation cases in the new materials and ceramic industries, such as Terui Battery, Cologne New Energy, Tianneng, Wanhua Chemical, etc.
Our consistent service philosophy is to deeply understand customer needs, customize the most suitable equipment, and ensure high-quality manufacturing, delivery, and after-sales service. Therefore, we have established a drying testing center that can complete drying tests from research and development to the pilot stage, and have various analytical and testing instruments to work with users to understand product characteristics, optimize product formulas and process parameters, and provide customers with optimal solutions.