Supercritical CO2 fluid extraction has the characteristics of fast mass transfer rate, strong penetrating ability, high extraction efficiency, and low operating temperature, and has become one of the most effective methods to obtain high-quality products.
Composition of the supercritical CO2 extraction machine
The supercritical CO2 extraction machine is a device used for supercritical fluid extraction. The CO2 extractor is mainly composed of a freezing part, a pressurizing part, an extraction part, a separation part, and a recovery part, but according to the different production processes and fluid media, the composition of the CO2 extraction equipment is also different.
Extraction and separation
Its main CO2 extraction process consists of two parts: extraction and separation.
In the extraction equipment, at a specific temperature and pressure, the raw material (biomass) is brought into contact with the supercritical CO2 fluid, and when the dynamic balance of the material components between the gas and liquid is reached, the temperature and pressure are adjusted to separate the extraction product from the supercritical CO2 fluid and complete the whole process of supercritical extraction.
Design requirements for CO2 extraction equipment
However, the supercritical CO2 fluid extraction process requires high-pressure equipment, coupled with some special properties of supercritical CO2 fluid, there are many special requirements for process equipment that are different from general chemical separation processes, making supercritical CO2 fluid extraction whether it is a laboratory. The small CO2 extraction machine or industrial CO2 extraction machine has special structures that are different from general chemical equipment.
The design of supercritical CO2 extraction equipment should follow the principles of safety, reliability, continuous operation, and wide application to meet the needs of different product extraction processes. Therefore, the equipment design of supercritical CO2 extraction machines is the key to the development of supercritical CO2 fluid extraction technology. one. Since the process is at high pressure (generally 8~35MPa, sometimes higher), a large number of mechanical, heat exchange, and fluid transport problems need to be solved.
4 process technical requirements of supercritical CO2 extraction equipment
The supercritical CO2 extraction machine is a comprehensive embodiment of the modern CO2 extraction process, CO2 extraction pumps(CO2 high-pressure pump), engineering amplification, and CNC professional level.
CO2 extraction process
First of all, it is necessary to find out the best-operating conditions, the best yield, and a series of technical requirements to ensure product quality for a system (biomass). This is the main line running through an industrial CO2 extraction machine.
CO2 high-pressure pump
In addition to the CO2 extraction vessels(pressure vessels), the supercritical CO2 extraction equipment also involves an important piece of equipment, that is, the CO2 extraction pumps(CO2 high-pressure pump). Due to the low density and easy gasification of the fluid CO2 during the pressurization process, it is difficult to design and manufacture CO2 extraction pumps(CO2 high-pressure pumps). This problem has been well resolved in China.
Relatively speaking, supercritical CO2 extraction is high-tech, especially in terms of mass transfer, it lacks many physical parameters, which makes it difficult for engineering scale-up.
Industrial CO2 extraction equipment has high requirements for instrument control, because it is the implementation guarantee of high-pressure technology and product quality, and should have the functions of correct detection of pressure, temperature, flow, and liquid level under high pressure, remote display, and safety alarm. Using microcomputers to realize the automatic control of the whole process is the development direction of large-scale supercritical CO2 fluid extraction.
5 Challenges for Next-Generation CO2 Extraction Machines
In view of the high-pressure vessel(CO2 extraction vessels) for solid substance extraction, further progress is still needed on the following issues
New structure research
Supercritical fluid extraction equipment is a typical CO2 extraction vessel(CO2 high-pressure vessel) subjected to pulsating loads. The medium store’s huge energy. Once it fails, it will cause serious losses. However, the existing structure is difficult to realize the online monitoring of the safety state, so it is necessary to carry out research on the structure and design method of the CO2 extraction vessel(CO2 high-pressure vessel) with the advantages of explosion suppression and explosion prevention, simple manufacture, and easy to realize the online monitoring of the safety state.
Compatibility of supercritical fluids
The mechanical properties of CO2 extraction vessel(CO2 high-pressure vessel) materials in supercritical fluids are studied to avoid degradation or decomposition of the medium and prevent material corrosion. For example, pure CO2 does not have special corrosiveness, but after adding entertainers or solvents such as water and organic acids, there may be complex corrosion fatigue problems.
Rapid entry and exit of solid matter into and out of high-pressure vessels
Since the extraction time of supercritical fluid of solid substances usually takes several hours, unless a continuous feeding and discharging device with a compact structure and reliable performance are successfully researched, the rapid opening and closing lid sealing device can still be regarded as an effective measure to improve production efficiency. At present, there is still a need to carry out research on high-pressure quick-opening and closing sealing devices with excellent performance and corresponding safety interlocking devices.
Research on Sealing Element Materials
Supercritical fluids, such as supercritical CO fluids, have the strong penetrating ability and dissolving abilities. Common rubber sealing materials cannot meet the requirements of the process. One rubber ring can only be used once, and the swelling of the rubber ring will also affect the loading and unloading of the container. . The rubber rings produced by some foreign companies can be used multiple times, but our country has not solved the problem of multiple uses of rubber sealing materials, and the research work on this aspect should be carried out.
Anti-blocking of pipes and valves
Some extracts form a very viscous oil phase; some extracts contain insoluble solid substances; supercritical fluids such as CO2 have a phase transition, which may form a liquid phase or even dry ice, so appropriate pipelines should be studied, especially valves anti-blocking technology.