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CO2 extraction vessel design: working modes, 4 requirements

CO2 Extraction Vessel Design

The supercritical CO2 extraction vessel is one of the keys to the development of supercritical fluid extraction technology. It needs to solve the mechanical, heat exchange, fluid transportation, and safety guarantees caused by the high pressure (generally 8-35Mpa or higher) during the CO2 extraction process. It should have the characteristics of safety, easy operation, strong versatility, and continuous operation under the premise of meeting the production purpose.

CO2 extraction vessels
CO2 extraction vessels

Basics of CO2 extraction vessels

According to the regulations on pressure vessels, supercritical CO2 extraction vessels are high-pressure equipment, and different CO2 extraction vessels need to be selected for different forms of materials.

Dia-To-Height Ratio (or Aspect Ratio)

An important parameter of the CO2 extraction vessel structure is the theDia-To-Height Ratio (or Aspect Ratio):

  • For solid materials, the dia-to-height ratio is about 1:4~1:5.
  • For liquid materials, the dia-to-height ratio is about 1:10.

Read More: CO2 Extraction Vessels: 4 Basics, 6 Special Requirements, 7 Important Parts

Additional CO2 Extraction Vessel Design Points

Due to the high pressure of the CO2 extraction vessel, the research and use of high-strength special steel can reduce the wall thickness of the CO2 extraction vessel, saving materials and costs.
The CO2 extraction vessel separation kettle can be set with one or more stages of separation according to the separation purpose and can be combined with rectification, adsorption, and other processes to achieve the purpose of extraction, separation, and purification.

CO2 Extraction Vessel for 3 scale types CO2 extraction machines

types 1#: Tabletop CO2 Extractor/Desktop CO2 Extractor

Tabletop CO2 extractor(Desktop CO2 Extractor) for laboratory, its volume is generally less than 200mL, simple structure, no CO2 circulation equipment, pressure capacity up to 35Mpa, suitable for laboratory exploratory work. In recent years, an extractor with an extractor volume of about 2mL has been developed, which can be used directly with analytical instruments and is mainly used as a supercritical CO2 fluid extractor for preparing analytical samples.

types 2#: Small CO2 extraction machine for laboratory

The volume of the CO2 extraction container of the small CO2 extraction machine is generally 500~5000mL, and the pressure-bearing capacity can reach 70Mpa. It has good matching, CO2 can be recycled, and is suitable for process research and small batch sample production.

types 3#: Industrial CO2 extraction machine

The volume of the CO2 extraction container of industrialized supercritical CO2 extraction equipment is generally 10L to several cubic meters.

The CO2 extraction container between 10L and 20L can be configured flexibly, can be used for small-scale industrial CO2 extraction production, and can also be used as medium-sized test equipment in the laboratory to conduct scale-up experiments on the CO2 extraction process to verify the experimental conclusions.

Read More: Supercritical CO2 Extraction Machine: What is it? Three Types. 4 Tips for CO2 Extraction

Two working modes of the CO2 extraction vessel for CO2 extrator

  1. Single CO2 extraction container: When the object of supercritical CO2 fluid extraction is a solid material, the batch operation is adopted. If a single CO2 extraction container is used, it takes more than one hour to raise the temperature, boost the pressure and cool down, and several hours to cycle.
  2. Multiple CO2 extraction containers: In order to improve production efficiency, a semi-continuous operation mode in which two or more extraction kettles are connected in parallel can be used, that is, when one extraction kettle is working, the other can be unloaded and loaded. Open the structure to save auxiliary operation time, and stabilize the composition of the extraction flow, so as to achieve the purpose of improving product quality.

Choice of CO2 separation method

For the material to be extracted, the key lies in the characteristics of difficult separation and collection, so it is necessary to choose a suitable separation method.

Generally, in order to improve the separation efficiency and yield, a separation method combining two separation tanks and a fractionation column can be used so that the extract can be effectively separated.

Four Design Requirements for CO2 Extraction Vessels

CO2 Extraction Vessel Design
CO2 Extraction Vessel Design

The pressure vessel should be designed according to the original data and process requirements provided by the design task, that is, the process design conditions should be met first.

The design conditions are usually represented by design condition diagrams, which mainly include sketches, design requirements, takeover tables, etc. The sketch schematically shows the container body, the shape of the main internal parts, the main structural dimensions, the location of the connection, the form of the support, and other content that needs to be expressed.

Design requirements mainly include the following:

  • Working medium: medium scientific name or molecular formula, main components, relative density, and hazard, etc.
  • Pressure and temperature: working pressure, working temperature, ambient temperature, etc.
  • Operation mode and requirements: indicate continuous operation or intermittent operation, and whether the pressure and temperature of the CO2 extraction process are stable; if there are fluctuations in pressure and temperature, the frequency and range of change should be indicated; for containers that are frequently opened and stopped Just indicate the number of driving and parking times per year;
  • Others: The volume, material, corrosion rate, design life of the CO2 extraction container, whether it is equipped with safety accessories, whether it is insulated, etc. should also be indicated.

Read More: Supercritical carbon dioxide