The Role of Direct Air Capture in Combating Climate Change

Innovative engineering technologies are essential to combat climate change. ToffeeX, in collaboration with a large energy organisation, is at the forefront of developing the next generation of engineering design tools, known as physics-driven design. Based on intelligently coupling physics simulations and advanced mathematical optimization, physics-driven design can provide a step-change in the performance of engineering components.

One key technology to mitigate and prevent the risks of climate change is direct air capture (DAC).

Direct air capture removes carbon dioxide (CO₂) directly from the atmosphere, in contrast to point source capture, which captures CO₂ emissions directly from industrial sources such as power plants and factories before they are released into the atmosphere. DAC involves using chemical reactions to capture CO₂ from the air, typically by-passing air through a filter that contains a chemical sorbent. The captured CO₂ can then be stored underground or used in various industrial processes, effectively reducing the amount of greenhouse gases in the atmosphere and helping to mitigate climate change.

Project Overview

ToffeeX and a multi-national energy organisation collaborated to design a contactor assembly utilizing porous metal-organic frameworks (MOFs) for the adsorption and desorption of CO2.

MOFs are materials made from metal ions connected by organic molecules, forming porous structures. These structures have a high surface area, allowing them to hold gases and other substances effectively. Due to their high surface area and porosity, selective adsorption capabilities and high energy efficiency, among other benefits, MOFs are a highly promising technology for the adsorption of CO₂ in carbon capture units.

The core of this development is the application of physics-driven design to create efficient and cost-effective contactors. We carried out design activities for both 3D-printed MOF contactors and MOF-coated metal contactors.

Project Overview

  • Modelling: Derivation of physics models for fully coupled fluid-thermal-adsorbate systems at both micro and macro scales, validated using experimental results for traditional packed-bed (MOF pellet) contactors.
  • Efficient Simulation: ToffeeX provides advanced computational tools to produce performance predictions at low computational costs, ensuring rapid design iteration, development and deployment.
  • Customizable Adsorption Isotherms: Based on correlating experimental data provided by the client, a range of novel isotherm models were generated and made available for user selection.
  • Design for Additive Manufacturing: Consideration of manufacturing constraints ensures that both metal contactors (for MOF coating) and 3D-printed MOF designs are manufacturable using additive techniques. In addition, extruded ‘2D’ designs were generated which could be manufactured using direct ink writing using MOFs.
  • In-depth Insights: High fidelity simulations provide key quantities such as total CO2 uptake, pressure drop, temperature at the contactor exit, as well as detailed data not measurable experimentally such as adsorbate at each point in the MOF, enabling model and design refinement.

Optimization

ToffeeX’s design balances pressure drop (reducing pump costs) and adsorption efficiency (reducing cycle time). Key features include:

  • High Surface Area: Promotes high CO2 uptake.
  • Controlled Pressure Drop and Volume: Optimization of total pressure drop and MOF volume for maximum performance.
  • Periodic Unit Compositions: Development of optimization tools for contactors composed of periodic units, standardizing and streamlining manufacturing.
  • Control of Plant-Level Costs: Balancing capital and operational costs for a full contactor unit.

Achievements and Future Steps

Several topology-optimized geometries were generated. Notably, a small contactor geometry has been successfully 3D-printed in metal and coated in MOF for experimental testing. This pillar-type 3D-printed MOF contactor, built from unit cells, marks a significant milestone in the project.

Conclusion

By harnessing advanced modelling, simulation, and optimization techniques, we are making significant strides in the field of carbon capture. This collaboration not only supports green initiatives but also paves the way for a sustainable future. Through continued innovation and partnership, we are committed to developing solutions that will help mitigate climate change and promote environmental stewardship.