Supercritical drying is a novel drying method developed utilizing the characteristics of supercritical fluids. Currently, commonly used drying techniques, such as ambient drying, oven drying, freeze-drying, and vacuum drying, often inevitably cause material agglomeration during the drying process. This results in coarsening of the basic particles of the dried material, a sharp decrease in specific surface area, a significant reduction in porosity, and uneven drying degrees in different parts of the material, which is particularly detrimental to the preparation of nanomaterials or high-specific-surface-area materials. In contrast, supercritical drying technology allows the drying medium to fully penetrate the interior of the object to be dried under critical pressure and temperature conditions, uniformly reaching a supercritical state throughout the object. It gently and thoroughly exchanges with solvent molecules, thereby smoothly and uniformly stripping them from the drying material without affecting the structure or porosity between the solid particles of the dried material or causing agglomeration of solid particles. The displaced solvent is slowly released by changing operational parameters from the supercritical state to the gaseous state, achieving a non-destructive drying effect on the material. 

Technical Features 

Supercritical drying is a complex process where mass and heat transfer occur simultaneously. The object to be dried is completely immersed in an environment of supercritical fluid, making the drying process gentle and greatly avoiding the destruction of material structure by drying stress. Due to the diffusivity of supercritical fluids, the drying speed is faster compared to traditional methods. Because of high permeability, materials treated with supercritical drying have more uniform drying degrees in all parts. Additionally, since the drying and desolvation processes are conducted under high pressure, the desolvation process also has a sterilizing effect. 

Technical Advantages  

Materials dried using supercritical fluid drying technology do not shrink or crack, largely maintaining the structure and state of the dried material, effectively preventing material agglomeration and coalescence. It can be performed at temperatures close to human body temperature, making it particularly suitable for drying heat-sensitive materials. It is suitable for drying solvents of high molecular weight, high boiling point, and difficult-to-volatilize substances, with high purity after drying. The entire process is simple to operate, and organic solvents can be easily removed from solid materials by changing operational conditions.

Application Areas 

In recent years, as a novel drying process, supercritical fluid drying technology has developed rapidly and has been applied in the industrial-scale production and preparation of various materials, such as the drying of antibiotics and other pharmaceutical products, the treatment of microbial cells in food and pharmaceutical raw materials, the preparation of medical materials, and catalyst preparation. Especially in the preparation of monolithic aerogels and nanopowders with high specific surface area, pore volume, low density, and low thermal conductivity, supercritical fluid drying technology has become one of the important technical means.