Supercritical Drying Machine & Equipment & Chamber & Aerogel
Supercritical dry extraction technology is the latest discipline emerging in modern industrial separation, and it is an advanced separation process that is emerging internationally.
The so-called supercritical fluid refers to the fluid whose thermodynamic state is above the critical point (PC, TC). The critical point is the state where the gas interface has just disappeared. The supercritical fluid has very unique physical and chemical properties, and its density is close to that. The liquid has a viscosity close to that of a gas, and has a large diffusion coefficient, a small viscosity, and a large dielectric constant, so that the separation effect is good and it is a good solvent.
Supercritical drying extraction means high pressure, at a suitable temperature, the solvent is contacted with the extract in the drying kettle, the solute is diffused into the solvent, and the operating conditions are changed in the separator to precipitate the dissolved material for separation purposes.
The object to be dried is placed in the environment of supercritical fluid, the gas/liquid interface of the medium disappears, there is no liquid phase surface tension, the drying process is mild, and the damage of the material structure by the drying stress is largely avoided;Due to the high diffusion coefficient of supercritical fluids, the drying speed is faster and the microporosity is higher;
The drying and solvent removal processes are carried out under high pressure, and the desolvation process has a bactericidal effect;
The drying temperature is above room temperature, so it is especially suitable for drying with heat sensitive and variability materials;
It can effectively dissolve and extract large relative molecular mass and high boiling point difficult to volatile substances;
The organic solvent can be effectively removed from the solid material by changing the operating conditions;
CO2 precision injection and precision venting can be realized to ensure that the frame structure of the material to be dried is not damaged;
The supercritical device has the following characteristics due to the selection of CO2 medium as a supercritical dry extractant:
1, A wide range of operations, easy to adjust.
2, The selectivity is good, by controlling the pressure and temperature, the desired components are extracted in a targeted manner.
3, The operating temperature is low, dry extraction near room temperature conditions, which is especially suitable for heat sensitive components, the possibility of oxygen oxidation and light reaction is excluded during the extraction process, and the extract can maintain its natural flavor.
4, FRom dry extraction to separation in one step, the extracted CO2 does not remain on the extract.
5, CO2 is non-toxic, tasteless, non-combustible, cheap and easy to obtain, and can be recycled.
6, Dry extraction speed is fast.
Supercritical dry extraction technology has developed rapidly in the world, and has been industrialized in the fields of hops, spices, Chinese herbal medicine, oil, petrochemicals, food and health care.
In the supercritical state, there is no more interface between the gas and the liquid, but a uniform fluid between the gas and the liquid. This fluid is gradually discharged from the gel due to the absence of gas - At the liquid interface, there is no capillary force, so it does not cause shrinkage and structural damage of the gel until all the fluid is discharged from the gel, and finally a gas-filled material having a nanopore structure is obtained.
Supercritical drying of aerogels using co2
Due to the surface tension of the solvent inside the gel skeleton, the collapse of the skeleton is caused under ordinary drying conditions.
Supercritical drying is designed to achieve the critical point of the solvent during the drying process by pressure and temperature control, and complete the liquid phase to supercritical fluid transition.
During the process, the solvent has no obvious surface tension, and the transition of the wet gel to the aerogel is completed while maintaining the skeleton structure.
The apparatus used for supercritical drying is an autoclave, and the airtightness of the autoclave is required to be high.
Generally, the supercritical drying process requires a relatively long experimental cycle, a low yield, and a high cost for preparing a more demanding product.