Supercritical Making Nanoparticle System (PGSS)
Nanoparticles with Supercritical Fluids, Co2 extraction system
The development of ultrafine particles, especially nano-sized particles, has become a hot field in the current high-tech, and has been widely used in materials, chemicals, light industry, metallurgy, electronics, biomedicine and other fields. There are various methods for preparing ultrafine particles. Supercritical fluid deposition technology is a new technology under investigation. In the case of supercritical conditions, lowering the pressure can result in supersaturation and a high saturation rate can be achieved, and solid solutes can be crystallized from the supercritical solution. Since this process is carried out in a quasi-homogeneous medium, the crystallization process can be controlled more accurately. It can be seen that solid deposition from supercritical solutions is a promising new technology that produces fine particles with a small average particle size and can control the size distribution.
Several different supercritical fluid deposition technologies have been proposed, such as SAS, GAS, SESS, SEDS, PGSS, etc., and the specific process is specified according to user requirements.
The following is a description of a continuously operating gas antisolvent crystallization process (GAS) experimental setup. When performing GAS operation, the CO2 pump is used to send CO2 to the top of the crystallizer, and the pressure of the crystallizer is controlled by a back pressure valve. CO2 is cooled to a temperature below 0 °C before entering the pump to prevent cavitation. The crystallizer is installed in an air bath whose temperature is regulated by a temperature controller, a heater and a circulation fan. After the separator is installed in the crystallizer, the temperature is controlled by the water bath cycle. When the system is stable, the solution is pumped from the reservoir through the nozzle into the crystallizer using a high pressure pump. The sub-millimeter droplets ejected from the nozzle are dispersed in a continuous medium composed of an anti-solvent gas, and solute particles are precipitated due to the expansion and evaporation of the droplets. A glass cylinder and a metal filter plate are provided in the crystallizer for collecting particles. After the fluid mixture leaves the crystallizer, it is depressurized in the separator. After collecting enough particles, the solution supply is stopped, and CO2 is continuously introduced, and the residual solvent on the particles is removed by CO2 in the crystallizer.
A supercritical fluid (generally understood as a gas) dissolves into a liquid solution to form a saturated solution, and a saturated solution in which a supercritical fluid is dissolved rapidly passes through a nozzle and is decompressed in a short time to form fine particles, which is a PGSS technique.
PGSS is divided into two categories based on the mechanism of formation of solid particles through nozzles (corresponding to different liquid types): one is because of the degree of subcooling—that is, the PGSS process in which a large number of solid particles are formed by melt crystallization (PGSS with super-Cooling, PGSS). -C); one type is a PGSS process with a spray drying mechanism (PGSS withspray-Drying, PGSS-D).
Therefore, the former corresponds to a molten lipid or a polymer substance saturated with a supercritical fluid; the latter corresponds to a water or an organic solution saturated with a supercritical fluid or a compressed gas.
In terms of mechanism, the PGSS-C process is because the swollen saturated solution of the supercritical fluid quickly passes through the nozzle, and the lipid or polymer substance reaches a supercooled state at the nozzle, especially at the nozzle outlet, so that the molten solute forms a large number of crystal nuclei in an instant. And the nucleation of the nucleus is completed in a short time, and finally a large number of uniform particles are formed; the PGSS-D process is a saturated solution of supercritical fluid or compressed gas (the swelling degree to the general aqueous solution is not high, but the organic solution is added, swelling The degree can also be very high) quickly passing through the nozzle, generating a process of atomization, and using a heated carrier (such as nitrogen or air) to rapidly evaporate the liquid in the atomized droplets, causing the atomization system to form a supersaturated state to produce crystals, forming a large amount of solids. particle.
Other methods developed based on PGSS technology include: CAN-BD (Carbon dioxide Nebulization with aBubble-Dryer), SAA (Supercritical-Assisted Atomization), DELOS (Depressurization of An Expanded Liquid Organic Solution), etc. The basic principles are the same as PGSS. However, the operation method is different, and it is not repeated here.
The use of PGSS technology can avoid the use of solvents or a small amount of organic solvents, and the consumption of supercritical fluid is greatly reduced compared to RESS (CO2 consumption in PGSS is about 103 times smaller than RESS technology).
The process of PGSS is simple and has a wider range of uses. A variety of substances (droplets, solid materials, liquid solutions, suspensions, etc.) can be treated with PGSS.
However, the influencing factors of the PGSS process are complex, with supercritical conditions, multi-phase changes, high-speed turbulence and nozzle microstructure.
The process rules of the experimental research and the parameters of the model study are still not very clear, and the factors affecting the particle morphology are many and mutually restrained, and the influence laws of different systems are different.
Design pressure: 40MPa
Design temperature: 120 ° C
The volume of the kettle body: 1000mL The volume of the kettle body is designed according to user requirements or process requirements.
The above technical parameters are the parameters of the produced equipment, for reference, detailed information on design, production and corresponding requirements, please consult.