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Technical Specifications of the Direct Air Capture of CO₂ Unit from Soletair Power made for German ZBT

Lappeenranta, Finland: The discovery of fire was a turning point in the evolution of human beings, but that has also acted as a “burning point” for the planet; that led to the burning of carbon. Unrestricted burning of natural resources, deforestation, and competitive industrialization – ran parallelly for decades. These set off such an alarming level of CO₂ in the atmosphere that, researchers say, can no longer be tackled even by planting trees. The effect of this can be seen with the increasingly changing weather phenomena – melting of glaciers, more frequent heatwaves, forest fires and droughts. It is terrifying to imagine what an even more dreary future might look like.

Scientists and policymakers agreed upon one solution: finding alternate ways to capture the atmospheric CO₂ partly and achieving a net negative emission. Some very promising technologies emerged that can reduce the amount of CO₂ released into the atmosphere such as CCS (Carbon Capture and Sequestration), BECCS (Bio-Energy with Carbon Capture and Storage) and DAC (Direct Air Capture).

Soletair Power is a Finnish startup utilizing DAC technology to remove CO₂ indoors enabling people with better work performance and at the same time building a greener future for the planet.

What is direct air capture of CO?

Direct Air Capture is a group of technologies that filters CO₂ from the air or other low concentration sources, e.g. building ventilation. The concentration of CO₂ may vary from 400 ppm in ambient air to 1000-2000 ppm in building ventilation exhausts.

Traditional CCS technologies focus primarily on capturing CO₂ from concentrated point sources such as flue gases, effluents from biogas plants and other industrial processes. The concentration of CO₂ is typically around 10-15% in flue gases and can be even higher in off-gases released from purifying or upgrading steps used in biological processes.

The significant difference in the concentration of CO₂ between ambient air and point sources differentiates the design of DAC and carbon capture units.

Technical Specifications of Soletair Power’s DAC unit delivered to ZBT

Operating for 12 hours a day, Soletair Power’s DAC unit can produce up to 21 kg/day of >98% pure CO₂, compressed to above 10 bar. The unit is housed in a 12 m × 2.4 m × 2.87 m container which is designed to limit the noise level to approximately 62 dB.

This unit uses weak base anion resin as the adsorbent for CO₂ capture. Engineers at Soletair Power have tested the lifespan of this resin using a rapid multi-cycle-per-day test rig to ensure its capture performance and service life.

A large volume of air needs to be moved inside to capture the required amount of CO₂. Using computational fluid dynamics (CFD), Soletair Power has designed a vessel that can hold the optimum amount of sorbent, maintain the required airflow rates, while limiting the pressure drop to allow the use of conventional fans. To ensure uniform distribution of air inside the vessel, the geometry inside is made highly symmetric allowing uniform velocity even at large airflows.

To produce high purity CO₂, the temperature-vacuum adsorption process is used. In the vacuum- swing step, the air inside the chamber is removed using vacuum pumps to achieve a vacuum level of below 100 mbar. In the temperature-swing step, the sorbents are heated below 90°C promoting the release of CO₂ and water. Heating is accomplished using warm water flowing through specially designed heat transfer elements inside the vessel.

Due to the low-temperature level of operation of the system, several sources of heating can be used. In this project, purely electric heating of water in a hot water silo is used. In other projects, there were heat pumps, and in some cases, district heating plus boosters can also be used.

The gas collected from the vessel is a mixture of CO₂ and water which is separated using various physical methods that lead to the condensation of water, leaving out dry CO₂ as the product. This CO₂ is collected using dry-vacuum pumps to eliminate oil contamination ensuring ease in downstream use of CO₂. The product gas is stored in buffer tanks operating at up to 10 bar, from where gas boosters are employed to compress CO₂ up to the pressure required by the customer.

Soletair Power’s DAC system comes fully instrumented to ensure stable and safe operation. The customer can gather operational data from relevant process instruments. The container is also equipped with indoor air and product gas quality monitors, control units and several smoke detectors. The unit can be integrated into the customer’s system by using industrially relevant communication protocols.

Data-driven and scalable

Starting from the development of sorbent, to the design of the vessel – all decisions are guided by extensive research and data gathered from experiments. The sorbent used at Soletair Power has been chosen after being subjected to long-duration cycles and underwent a battery of tests. Active collaboration with local universities and research institutes ensured a proper understanding of the properties and limitations of the sorbent.

Extensive use of computational fluid dynamics modeling further substantiates the performance of the sorbent. Soletair Power employs design-of-experiment principles to ensure the vessels have the lowest pressure drop given the technical boundaries of the project.

Soletair Power is uncompromising in terms of quality assurance. The parts such as the pumps, sensors, and process valves used in the deliveries are top brands and obtained from reliable suppliers. The components undergo several technical checkpoints before being put into use.

The DAC units at Soletair Power follow a modular design principle allowing customers to install multiple units and assemble them on site. Customers may choose to get a unit with a large production capacity, or they can also get a regular unit and get add-on units later to increase capacities of production.

About Soletair Power:

Soletair Power is a Finnish startup founded in 2016 that manufactures solutions for carbon capture directly from the ambient air. The captured carbon dioxide is stored as long-lived products such as hydrocarbons or synthetic fuel. Soletair Power is backed by technology giant Wärtsilä Corporation and secured more than a million euros as seed funding for playing a vital role towards a carbon-neutral future.


About Hydrogen and Fuel Cell Center ZBT:

ZBT is one of the leading research institutes in Europe for fuel cell and hydrogen technologies and a sought-after R&D partner in both European and national cutting-edge research as well as in industrial projects focusing on automotive applications and stationary power generation.



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