Flue gases from thermal power plants, primarily coal-fired ones, are the main air pollutants. How to economically and efficiently remove carbon dioxide (CO2) from flue gases? – that is the question.
The concentration of CO2 in the smoke emissions of heat engines is quite low, and its separation is very expensive. If it is possible to reduce the cost of extracting it, then this technology will also solve the challenge set by the XPRIZE Carbon Remova competition – to extract carbon dioxide directly from the atmosphere.
This is possible in the case when the modernized power plants will consume not fossil fuels, but biofuels. Carbon removed from the atmosphere by plants, when burned at thermal power plants, after being removed from flue gases, is buried and is not returned to the atmosphere.
The new most promising technology for removing CO2 requires the use of oxygen, which in many cases is not always cheap to produce. The cheapest way is to separate oxygen from the air in large cryogenic air separation plants (ASUs). In the costs of ASU, a significant part is accounted for by energy costs.
There is a good prospect of reducing the cost of oxygen production – by about three to four times. The fact is that the world has a free (waste) resource, amounting to hundreds of millions of tons. Its rational use can reduce the price of oxygen production and, accordingly, the price of flue gas purification from CO2. This resource exists in the form of the now untapped refrigeration resource of liquefied natural gas (LNG).
Taking into account the potential of Europe and Japan (432 million tons of LNG), the annual accumulation of CO2 from flue gases is about 2.1 gigatonnes. This represents 21% of the CO2 removal requirement, estimated at about 10 gigatonnes per year, to keep global temperature rise below 1.5 or 2°C.