What is a carbon dioxide compressor?

What is a carbon dioxide compressor?

Carbon dioxide compressor is a kind of mechanical equipment specially used to increase the pressure of carbon dioxide (CO). To put it simply, its working principle is to compress gaseous carbon dioxide by motor or other power source, and raise it from the initial low-pressure state to the required high-pressure state. Because of the special physical properties of carbon dioxide (low critical point and easy liquefaction), this kind of compressor needs special consideration in design and use.

Core special requirements include:

Critical point and liquefaction: the critical temperature of carbon dioxide is about 31°c, and the critical pressure is about 7.38 mpa. This means that at ambient temperature (usually below 31°c), as long as the pressure is high enough, carbon dioxide will liquefy. In the process of compression, if the temperature is not properly controlled, liquid may appear in the cylinder in advance, which may lead to liquid impact of the compressor (damage to the valve and cylinder). Therefore, the compression process often requires precise temperature control or multistage compression interstage cooling.

Phase change control: some processes need gas, while others need liquid. The compressor must ensure that the medium maintains the correct phase state at the specified stage.

Strong corrosiveness (when water is contained): Dry carbon dioxide has weak corrosiveness to steel. However, once mixed with water (which is difficult to avoid completely in the process of capture), carbonic acid will be formed, which will cause strong corrosion to ordinary carbon steel equipment. Therefore, it is often necessary to use stainless steel or corrosion-resistant coating for compressor flow parts.

Lubrication problem: carbon dioxide has a strong dissolving effect on some lubricating oils, which easily leads to thinning of lubricating oils and loss of lubrication effect. Therefore, many high-pressure carbon dioxide compressors use oil-free lubrication or special synthetic lubricating oil.

Supercritical state: In some modern applications (such as supercritical extraction), it is necessary to compress carbon dioxide to supercritical state (temperature and pressure all exceed the critical point). At this time, carbon dioxide has the density similar to liquid and the diffusivity similar to gas, which puts forward extremely high requirements for the design and control of compressor.

To sum up, the carbon dioxide compressor is a vital equipment in the fields of food, chemical industry, energy and environmental protection. It can tame this special gas and make it serve human beings in gas, liquid and even supercritical state.