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CO2 Gas Recovery System: Principle, Flow Process, 4 Caution

The CO2 gas recovery system of the supercritical CO2 fluid extraction machine is an oil-free, reciprocating piston, single-acting small CO2 gas booster compressor; the cooling method is divided into air-cooled and water-cooled; Designed for higher users, the machine does not need to be lubricated with thin oil, and the moving seals in the cylinder are made of self-lubricating materials to ensure that the compressed air source will not be polluted twice, and can be used to compress or recover clean air, nitrogen, freon, Stable gaseous medium such as carbon dioxide gas. The CO2 gas booster compressor adopts automatic control mode, with a small leakage, low noise, no need for specialized personnel on duty, and can operate reliably for a long time.

CO2 Recovery System Pump
CO2 Recovery System Pump

The CO2 gas recovery system of the supercritical CO2 fluid extraction machine is a non-standard equipment, generally produced according to user requirements: the rated suction pressure of the machine is from micro-positive pressure to 4.0MPa or higher, the exhaust pressure can be up to 15.0MPa, and the exhaust volume The maximum can be 1500Nm3/h, and the installed power of a single machine can reach 55kw.
The CO2 gas booster compressor adopts the overall skid-mounted type, and all the components are connected before leaving the factory. The user only needs to connect the inlet and outlet pipes and turn on the power to enter the commissioning procedure.

Working principle

CO2 gas recovery system for CO2 extraction machines
CO2 gas recovery system for CO2 extraction machines

The CO2 booster compressor of the supercritical CO2 extraction machine is composed of the main engine, a motor, a base, a pipeline system, a cooling system, and a display control system.
The movement mechanism of the CO2 booster compressor is composed of a crankshaft, connecting rod, piston, and other parts. The crank connecting rod mechanism is driven by the motor through the belt to drive the crankshaft of the compressor to rotate, the crankshaft drives the connecting rod, and the connecting rod drives the piston to reciprocate. The linear movement causes the cylinder volume to change. The automatic air valve determines the cylinder’s suction and exhaust process, so as to achieve the purpose of increasing the gas pressure. The crankshaft rotates once to complete a working cycle, and the gas with lower pressure enters the cylinder through the suction port and is compressed into gas with higher pressure, and is discharged for use.

There is no liquid lubricant in the CO2 booster compressor. The piston ring and guide ring are made of high-quality PTFE with self-lubricating properties. All main parts have a certain anti-rust ability. Make sure the machine works reliably

Gas flow process

Under standard conditions:

  • The carbon dioxide gas is sucked into the first-stage cylinder of the CO2 booster compressor of the supercritical CO2 extraction machine through the filter. After the first-stage compression, it is discharged to the first-stage cooler for cooling and then sucked into the second-stage cylinder. The cooler is then discharged through the check valve (to the high-pressure air tank – user configuration) for use.
  • For example, the suction pressure of the CO2 booster compressor of the supercritical CO2 extraction machine is greater than or equal to 2.0Mpa, the primary start valve is closed, and the gas is only compressed by the second cylinder of the compressor and discharged to the gas storage tank.

In addition: the setting value of the pneumatic valve of the three-stage compression carbon dioxide compressor is:

  • Inlet valve (0.6~1.5Mpa), the first-level pneumatic valve is opened, and the other pneumatic valves are closed.
  • Intake value (1.5~2.8Mpa), the first and third stage pneumatic valves are closed, and the second stage pneumatic valve is opened.
  • When the air intake is greater than 2.8Mpa, the primary and secondary pneumatic valves are closed, and the third-level pneumatic valve is opened.

An unloading solenoid valve is also set on the exhaust pipeline, which empties the pipeline and the gas in the cylinder when the machine is stopped to prepare for the next light-load start (to prevent the motor from starting frequently, it should be more than 3 minutes to start again after stopping).

Control method

The CO2 booster compressor of the supercritical CO2 extraction machine is monitored by a pressure sensor, and the start and stop are controlled by two pressure transmitters. The specific control methods are:

Start: When the intake pressure exceeds the set value and the start conditions are met, press the start button and the main motor starts to start.
Stop: When the intake pressure is lower than the lower limit (0.5Mpa) and the exhaust pressure reaches the set value, the compressor will automatically stop.


  1. Recycling of dry ice volatilized gas from CO2 plant, recycling of CO2 from the factory,
  2. Industrial and pharmaceutical CO2 extraction processes using the properties of CO2 fluid
  3. Large-scale carbon dioxide compressor is mainly used in urea synthesis equipment


When an industrial two-stage wet co2 booster compressor designing and using, it should be noted that:

  • The critical temperature of carbon dioxide is high, and it can be liquefied at 31.3 ° C and 7.14 MPa. When used in winter, the interstage cooling temperature should not be too low;
  • It is beneficial to gas when carbon dioxide is below 60 MPa.
  • Due to the relatively high relative density of carbon dioxide gas, it is not appropriate to use an enormous average piston speed, otherwise, the gas valve resistance is high;
  • CO2 gas contains a small amount of water, which is highly corrosive, so the gas valve, coolers, and buffer tanks are required to be made of stainless steel.
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