Using cold to capture CO2 from industrial fumes. Founded in mid-2020 by two young entrepreneurs, Paul Taton and Hugo Lucas, startup Revcoo installed a two-tonne-per-day CO2 demonstrator at the Eiffage lime plant in the north last summer. “We are on our way to reaching TRL 7! » welcomes Hugo Lucas, co-founder of Revcoo.
Innovative cryogenic process
Their process belongs to the family of afterburning technologies – the plant purchasing this equipment does not need to change the process – by changing the temperature. Air Liquide already sells cryogenic CO2 capture equipment called Cryocap. “But our approach is completely different. Air Liquide liquefies all the smoke, which is not our case.”explains Mr. Lucas, who instead cites US company SES Innovations, bought by cryogenic equipment maker Chart Industries, as its main competitor. “Their technology and cost targets are similar to ours, but they have a different way of freezing CO2.”He says.
The Revcoo capture process requires four different modules. “We are making a vent point in the chimney to pass the smoke to our various units”, adds Hugo Lucas. First stage: preconditioning, in which the smoke is compressed to 10 bar, then fine particles are removed using a filter. “Then we dry the smoke: since our process is cryogenic, there should be no traces of water”— emphasizes the co-founder.
The pre-treated smoke, mainly composed of O2, N2 and CO2, then passes into a capture module designed to separate nitrogen. “Here we use classic membrane technology. We will certainly look to PSA technologies in the future.”, promotes Mr. Lucas. The third equipment (cryocooler) is intended only for nitrogen liquefaction. “Temperature levels around -196°C”he explains.
Capturing CO2 by Liquefying Nitrogen
This is where the ingenuity of the Revcoo process lies: this nitrogen, at a very low temperature, will be used to freeze the CO2 in a fourth module called the Revcoo desublimator. “But be careful: we don’t freeze 100% CO2, otherwise the cost of energy will be too high! » insists Hugo Lucas. “Only 30% of CO2 freezes. » The trick is to use the energy contained in that 30% solid CO2 to liquefy the remaining 70% CO2. “Frozen CO2 reaches around -140°C and CO2 liquefies around -50/-55°C”explains the businessman, specifying that “the smoke is at a pressure of about 5 bar due to the pressure differences that have occurred during the process.”
The CO2 is then recovered in gaseous form. “Energy released during the transition of CO2 from solid and liquid to gaseous phases is reintroduced into the loop”dot co-founder.
Simplified diagram describing the Revcoo process. © Revka
Revcoo uses only electrical energy, as opposed to the conventional post-combustion capture process (by chemical absorption with amines), which consumes heat from fossil fuels. “The cost of energy in our process depends, among other things, on the concentration of CO2 in the processed flue gases”says the specialist.
Thus, Hugo Lucas estimates that for smoke containing 20% CO2, their process requires 350 kWh of electricity, namely 1.26 gigajoules, to capture one tonne of CO2. An amount that rises to 550-600 kWh – about 2 gigajoules – if the smoke concentration drops to 10%. By comparison, the amine process (the most advanced) requires 2 to 3 gigajoules per ton of captured CO2. “Thanks to the French Energy Balance, we emit 59 kg of CO2 per tonne caught”he adds.
From an economic standpoint, Revcoo ensures that it is competitive with the most mature technologies on the market: “For smoke with a concentration of 20% and given that kWh is 8 cents, a ton of captured CO2 is 30 euros.”, counts Hugo Lucas. For the amine process, the cost of a collected, transported and stored ton is estimated to be between 50 and 150 euros per ton.
Revcoo aims to bring to market a product capable of capturing 20 tons of CO2 per day by processing 2,500 normal cubic meters (Nm3) per hour of smoke from 2023. “Before that, in 2022, we want to install a pilot of the same capacity in Eiffage”adds Mr. Lucas.