Particle size control for spray drying is a complex and delicate process that involves the synergy of multiple operating parameters. In the spray drying process, the thickness of the particles is not only affected by factors such as pressure, viscosity, nozzle pore size and inlet and outlet temperature, but also by other factors such as liquid flow, hot air velocity, raw material composition, etc.
First of all, pressure is an important factor affecting the particle size of droplets. In the spray drying process, increasing the pressure can increase the degree of atomization of the liquid, thereby reducing the droplet size. As the pressure increases, the droplets decrease. -0 of droplet size and pressure3 powers proportional. However, when the pressure is too high, it can lead to clogging or increased wear of the nozzle, which in turn affects the uniformity and stability of the droplets. Therefore, in practice, it is necessary to select the appropriate pressure value according to the characteristics of the raw material and the performance of the equipment.
Secondly, viscosity is also a key factor affecting the thickness of the particles. The particle size of the powder is 0 of the viscosity of the slurry17～0.2 power proportional. High-viscosity liquids are generally more difficult to atomize and produce larger droplets. In order to achieve the ideal particle size, this can be achieved by adjusting the viscosity of the slurry. For example, the viscosity can be reduced by adding a diluent or adjusting the ratio of the raw material to reduce the droplet size.
Nozzle aperture is also one of the key factors in determining the size of the droplets. Increasing the nozzle aperture results in an increase in droplet size, and vice versa. Therefore, when selecting a nozzle, it is necessary to select the appropriate nozzle aperture according to the characteristics of the raw material and the process requirements. At the same time, the shape and design of the nozzle will also have an impact on the uniformity and stability of the droplets, so it is necessary to pay attention to the selection and installation of the nozzle in actual operation.
The inlet and outlet temperature is one of the important factors affecting the physical and chemical properties of spray drying powder. A higher drying temperature can provide more heat and speed up water evaporation, which increases the drying rate and reduces the moisture content of the product. However, excessively high temperatures can also cause water to evaporate too quickly, allowing the microspheres to form more quickly without enough time to shrink, resulting in larger particle sizes. Therefore, in practice, it is necessary to select the appropriate inlet and outlet temperature according to the characteristics of raw materials and product requirements.
In addition to the above factors, liquid flow and hot air velocity also affect the particle size of spray drying. Increasing the flow rate of the liquid can increase the drying rate, but it may also lead to an increase in the droplet size. The hot air velocity will affect the movement trajectory and evaporation velocity of the fog droplets in the hot air, thereby affecting the uniformity and stability of the particles.
In addition, the composition and properties of the raw materials can also have a significant impact on the spray drying process. Certain components may cause increased adhesion between droplets, forming agglomerations that can affect particle uniformity. Therefore, when selecting raw materials and adjusting process parameters, it is necessary to comprehensively consider the influence of these factors on the spray drying process.
In summary, in order to obtain the ideal spray drying particle size and distribution, it is necessary to consider a variety of factors and conduct sufficient trials and studies. In practice, the spray drying process can be optimized by adjusting parameters such as pressure, viscosity, nozzle pore size, inlet and outlet temperature, etc. At the same time, it is also necessary to pay attention to the influence of equipment performance, raw material characteristics and other factors on the spray drying process. Through continuous exploration and practice, we can find the best combination of process parameters to achieve high-quality and efficient production of spray dried products.