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3 Key Knowledge: Small CO2 Extractor Sealing Structure

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The extraction vessel is a key component in the supercritical CO2 extraction equipment, and its operating pressure is high and the working environment is harsh.
The CO2 extraction process is mostly a semi-batch operation, and the extraction container needs to be switched on and off frequently for feeding and discharging, so its sealing structure generally adopts a quick-opening structure. The supercritical CO2 fluid has strong solubility and high permeability, and the damage to the sealing material of the extraction container is usually very serious, so its sealing material and structure must be adapted to the characteristics of supercritical CO2 fluid.

3 types of small CO2 extraction machine seal structure

The sealing structure of small CO2 extraction machines generally adopts three sealing structures: screw type, slider type, and clamp type.

Extraction container for small CO2 extraction machines
Extraction container for small CO2 extraction machines


  1. Threaded sealing structure: The threaded quick-opening high-pressure self-tightening sealing structure is simple in design and easy to operate, but the rubber O-ring has a serious swelling phenomenon, which makes it difficult to disassemble, and the threaded structure cannot play a fast-opening function well. Under high pressure, the thread structure is prone to seizure.
  2. Slider-type sealing structure: The slider-type quick-opening high-pressure self-tightening sealing structure is more complicated, and it is easy to realize mechanized operation, which is suitable for large-scale installations. high.
  3. Clamp-type sealing structure: Clamp-type quick-opening high-pressure self-tightening sealing structure switches quickly, and can use hydraulic mechanized opening and closing container cover, which is easy to operate and suitable for large-scale extraction devices, but the sealing ring also has serious swelling phenomenon, and it is difficult to disassemble, and large-scale clamps require large-scale forgings, and the processing volume is large.

2 methods to improve the sealing structure of the CO2 extraction machine

Improvement of sealing structure

Considering that the sealing structure of the extraction container should meet the requirements of safe and reliable operation and rapid switching, by analyzing the above three structures, the clamp-type quick-opening high-pressure self-tightening sealing structure can be used, and it has been improved. It is convenient, that the part of the sealing ring is designed in the top cover so that the sealing ring does not need to be installed or removed when the top cover is installed and removed, thus reducing the number of times of installation and removal of the sealing ring, and does not cause wear on the sealing ring, and can well ensure the sealing The structure is safe, efficient, convenient and fast.

Improvements in sealing materials

By analyzing the sealing materials of the three quick-opening high-pressure self-tightening sealing structures, it can be seen that under the action of the strong solubility and high permeability of supercritical CO2 fluid, the cheap and high-quality rubber materials cannot meet the requirements of the process. Experiments found that polytetrafluoroethylene has low swelling in supercritical CO2 fluid, and its strength can be improved to meet the high-pressure performance requirements of supercritical CO2 fluid extraction equipment.

5L Small CO2 Extraction Machine Extraction Container Structure and Features

CO2 extraction vessels
CO2 extraction vessels

The CO2 extraction vessel is the core component of the supercritical extraction device. It must be able to withstand high pressure, resist corrosion, have reliable sealing, and be safe and convenient to operate.

5L Small CO2 Extraction Machine Extraction Container Structure

The cylinder, top cover, and clamp of the CO2 extraction container are all forged as a whole, and the manufacturing material is stainless steel. The quick-opening structure of the extraction container adopts a clamp-type quick-opening high-pressure self-tightening sealing structure. The two-lobed clamps are connected and fixed on the cylinder by cylindrical pins. The lifting device of the top cover adopts a lifting ring.

4 characteristics

  1. The sealing material is a reinforced PTFE C-ring seal.
  2. The C-shaped sealing ring is designed on the top cover. When the extraction cover is opened, the sealing ring is taken out together with the top cover. wear and tear, and easy to operate.
  3. The top cover and the extraction container barrel are connected and fastened with a quick-opening two-lobed clamp. Due to the different forms of the force surface, the inner surface of the clamp in contact with the top cover and the flange shoulder of the cylinder is flat, while the common sealing surface of the clamp is a conical surface.
  4. The initial pre-tightening force of this structure is obtained by the assembly accuracy, which is different from the common clamp sealing structure, which is pre-tightened by the clamping amount of the clamp after the top cover is axially moved by the cooperation of the conical surface. The switch of the clamp is more flexible and convenient, and the work efficiency is greatly improved.

Read More:

  1. CO2 Extraction Pumps: Basics, Top 3 Requirements, 6 Applications, 8 Features
  2. CO2 Extraction Vessels: 4 Basics, 6 Special Requirements, 7 Important Parts, 4 Key Design Requirements