What is the difference between CO2 and compressed air?
Like regular air, carbon dioxide (CO2) is compressible. Although both qualify as gasses, most similarities end there. There are many differences between the two, though, so let’s take a look at what sets them apart.
Ease of compression of air compared to compression of CO2
CO2 is easier to compress compared to air. This means it produces less heat and, in this way, asks less of the equipment used for compression. This compression process also poses challenges.
One of them is the moisture that is being created. In the case of compressed air, this generally poses no major problem if we drain it. But the moisture generated during the compression of carbon dioxide creates carbonic acid. As a result, you must take precautions to prevent corrosion in the equipment. This includes using stainless steel or coated material for components that touch the condensate.
CO2 is a heavier molecule. It can generate higher levels of vibrations and, if compressed too much (i.e. at high pressure), it can liquefy. This could result in damage to the compressor.
How do you liquefy CO2?
CO2 compressor versus air compressor design
That brings us to the hardware.
From the outside, it would be difficult to tell an air compressor apart from a CO2 compressor. Inside, there are some differences:
- A CO2 compressor has more stainless steel to protect against corrosion.
- It's usually larger and more robust than an air compressor. This is so it can deal with higher stresses and vibrations.
- A CO2 compressor does not feature a direct inlet line. It needs to get the gas from a CO2 source. So, there is an inlet system where CO2 gets treated before reaching the compressor.
Compressed air is ambient air, compressed. It can release into the atmosphere (through leaks in the system) without harm.
But carbon dioxide is a harmful greenhouse gas, so you should avoid its release into the atmosphere. Compressed air is safe to breathe, but an accumulation of carbon dioxide in an enclosed space is a health hazard to anyone nearby.
To avoid releasing carbon dioxide, store it or re-use it in other applications.
Uses of compressed air versus uses of compressed carbon dioxide
Another major difference is air and CO2 use when compressed.
Generally, we compress air to use it to power a pneumatic tool, convey materials, operate a brake, etc.
Conversely, we compress carbon dioxide to move it or store it. Once compressed, CO2 can carbonate beverages and create inert atmospheres in specific processes. Or, it can become a feedstock for chemical reactions.
Careful handling of CO2 is critical for environmental protection. Earth Day 2022 — and the expanded Earth Month in April — bring to light efforts to remove CO2 from the atmosphere.
Some carbon dioxide producers have reused or captured CO2 (with CO2 compressors). Most others have been releasing it into the air. Because of environmental concerns, taxes, and increasingly stringent regulations, carbon-capturing has become popular as a sustainable and less expensive option. And there's a need for compressor installation wherever there's a need for CO2 capture.
To learn more, please visit: https://www.atlascopco.com/en-us/compressors/industry-solutions/carbon-capture-solutions
Article adapted from original WIKI post