Canada-based Vitalis ‒ an OEM providing CO2 (R744)-based technologies, including high-pressure CO2 biomass extraction and fine powder processing ‒ has found a 43% COP increase by integrating an R744 heat pump in CO2 extraction processes over an HFC unit.
The design of the R744 heat pump/glycol system used for CO2 extraction processes and its future potential optimization were presented by James Seabrook, President of Vitalis, at the ATMOsphere America Summit 2023, held June 12–13 in Washington, D.C. The event was organized by ATMOsphere, publisher of R744.com.
The two different CO2 technologies can be “confusing,” Seabrook said. “The extraction process uses high-pressure CO2, often with a working pressure of 5,000psi [345bar], as a solvent to remove a molecule of interest instead of using the toxic solvent hexane; one side is about evaporating and the other about condensing,” he added.
The extraction process uses a closed-loop system, starting with liquid CO2 in the receiver, which is pumped up to the extraction pressure and then heated or cooled to a particular molecule solvency temperature. “We then separate these molecules by vaporizing the CO2, collecting [the molecules] and recycling the CO2 by condensing it back into the receiver,” Seabrook explained, adding that is where the R744 system comes into play.
For the past seven years, Vitalis has offered CO2 extraction with an HFC condensing unit with no heat reclaim and a gas boiler providing hot water for industry clean-in-place (CIP) processing. Seabrook reports the baseline reference COP of the boiler and HFC unit is 1.05 at an ambient operating temperature of 30°C (86°F) in the Kelowna, British Columbia (Canada) area.
Seabrook highlighted two design cases that improve the COP and reduce carbon emissions for industrial extraction processing.
R744 and Glycol
In case one, the HFC condensing unit is replaced by an R744 heat pump that returns heat to a glycol system, heating the glycol to about 82°C (180°F). “This is what we are implementing now in our new equipment,” Seabrook noted, reporting a COP of 1.5, a 43% efficiency increase when operating in the same conditions.
“We had a higher COP and were able to drop the 52kW [14.8TR] compressor to a 35kW [10.0TR] one,” Seabrook said. In addition, the heat from the R744 unit reduced gas usage and resulted in an annual reduction of 35 metric tons of carbon emission. “We saved our customers a little bit of money while decarbonizing this machine,” he noted.
R744 and CO2
Seabrook divided the case two design into:
- Using the R744 heat pump to heat CO2, and
- Using the R744 heat pump to heat CO2 and provide hot water return (HWR).
The company projects the COP rises to 2.16 when using the R744 heat pump to heat CO2, increasing efficiency by 106% compared to the HFC/gas boiler while saving 35 metric tons of carbon emissions annually.
The COP increases to 3.1 when adding HWR and negates the need for a gas boiler for CIP processing. Without a gas boiler, carbon emissions are reduced by 59 metric tons annually. Heat recovery can supply hot water above 80°C (176°F).
“With additional hot water reclaim, we have a much higher return on investment,” Seabrook said. “We can perfectly balance our heat absorption and our heat rejection.”
“Case two is our future optimization [of extraction processes], but we have some technical challenges for implementing it,” Seabrook noted. “The problem is that our process fluid operates at 5,000psi,” with some applications requiring 10,000psi (689bar).
With existing heat exchanger technology, we are in a better position to do case one right now, he explained. “In the future, we plan to work on internally developing a high-pressure R744 heat exchanger, designing the equipment to optimize our system.”
With its North American headquarters in Kelowna, Vitalis was founded in 2016 and has customers on five continents. According to the company’s website, it was the “first ” to make large-scale supercritical CO2 extraction of natural ingredients accessible.
“Outside of the actual extraction machines, we also use CO2 in a variety of other ways, including refrigerant, thermal siphons, and cooling process fluids like alcohol,” Seabrook noted. The company’s heat pumps for industrial and commercial heating and cooling applications run in capacity sizes from 100 to 3,000kW (28.4 to 853TR).
“We can perfectly balance our heat absorption and our heat rejection.”James Seabrook, President of Vitalis