Liquid CO2: What is it and why is it useful?
Carbon dioxide, or CO2, is a gas that we breathe out every day. It is also a gas that is found in the atmosphere, where it acts as a greenhouse gas and contributes to global warming. But did you know that CO2 can also exist as a liquid under certain conditions? And that liquid CO2 has many applications in various industries and sectors? In this article, we will explore what liquid CO2 is, how it is produced, and what it can be used for.
What is liquid CO2?
Liquid CO2, or LCO2, is the liquid state of carbon dioxide. It is formed when CO2 gas is compressed and cooled to high pressure and low temperature. Under normal atmospheric pressure, CO2 gas cannot become liquid. It can only become solid, which is what we call dry ice. To make LCO2, we need to compress CO2 gas to above 5.1 atm (5.2 bar; 75 psi), and cool it to below 31.1 °C (88.0 °F) (the critical point) and above −56.6 °C (−69.9 °F) (the triple point).
LCO2 is a colorless and odorless liquid that has a density of 1101 kg/m3 when it is at full saturation at −37 °C (−35 °F). It has a very low solubility in water, ranging from 0.02 to 0.10 % at temperatures from −29 °C (−20 °F) to 22.6 °C (72.7 °F) and pressures from 15 to 60 atm.
How is liquid CO2 produced?
Liquid CO2 can be produced from various sources of CO2 gas, such as natural gas wells, coal-fired power plants, fermentation processes, or industrial processes. The CO2 gas is first purified and dried to remove any impurities and moisture. Then, it is compressed and cooled using compressors and heat exchangers. The compressed and cooled CO2 gas then enters a storage tank or a vaporizer, where it becomes liquid CO2.
Liquid CO2 can also be captured from the atmosphere using direct air capture (DAC) technology, which uses chemical reactions to extract CO2 from the air. The captured CO2 gas is then compressed and liquefied using similar methods as above. DAC technology is still in development and has the potential to reduce the concentration of CO2 in the atmosphere and mitigate climate change.
What are the uses of liquid CO2?
Liquid CO2 has many uses in different industries and sectors, such as:
●Food and beverage: Liquid CO2 can be used to refrigerate and freeze food and beverages, as well as to preserve them from bacterial and fungal growth. Liquid CO2 can also be used to carbonate drinks, such as soda, beer, wine, and sparkling water, by injecting it into the liquid under pressure. Liquid CO2 can also enhance the flavor and texture of drinks by making them more acidic and refreshing.
●Fire protection: Liquid CO2 can be used as a fire extinguisher because of its anti-flammable properties. The liquid CO2 is stored under pressure in a cylinder and released as a gas when needed. The gas works by displacing the oxygen that fuels the combustion and by cooling the burning surface to prevent further damage. Liquid CO2 is effective for extinguishing electrical fires and flammable liquids, such as oil, gasoline, and solvents.
●Oil recovery: Liquid CO2 can be used to enhance oil recovery from oil wells by injecting it into the reservoir under high pressure. The liquid CO2 mixes with the oil and reduces its viscosity, making it easier to flow out of the well. The liquid CO2 also expands the oil volume and pushes it towards the production well. This method can increase the oil recovery rate by up to 20 %.
●Baking: Liquid CO2 can be used as a leavening agent for baking bread by creating air pockets in the dough. Liquid CO2 is produced by yeast or baking soda when they react with sugar or acid in the dough. The liquid CO2 expands when heated in the oven, making the bread rise and become light and fluffy.
●Carbon capture and storage: Liquid CO2 can be used as a way of storing carbon dioxide that would otherwise be emitted into the atmosphere and contribute to global warming. Liquid CO2 can be transported by pipelines or ships to underground or subsea storage sites, where it can be injected into porous rocks or saline aquifers that can trap it permanently or for long periods of time. This method can reduce the carbon footprint of various industries and sectors that produce large amounts of CO2 emissions, such as power generation, cement production, or steel making.
These are some of the common uses of liquid CO2, but there are many more applications that involve this versatile liquid. For example, liquid CO2 can also be used for welding, water treatment, plastics production, and greenhouse cultivation.
Conclusion
Liquid CO2 is a liquid state of carbon dioxide that is formed under high pressure and low temperature. It has many advantages and uses in various industries and sectors, such as food and beverage, fire protection, oil recovery, baking, and carbon capture and storage. Liquid CO2 is a valuable and useful substance that can improve the quality of life and the environment.
