Investigation of Environmental and Operational Challenges of Adsorbents Synthesised from Industrial Grade Biomass Combustion Residues (Flexible Funding 2022)

Dr Salman Masoudi Soltani, Brunel University, was awarded funding in the UKCCSRC’s Flexible Funding 2022 call to look at the “Investigation of Environmental and Operational Challenges of Adsorbents Synthesised from Industrial Grade Biomass Combustion Residues”.

Bioenergy with Carbon capture and Storage (BEECS) is a net-negative technology that is recognised by many as a prominent tool in the uphill battle against climate change. However, combustion of biomass is associated with production of large quantities of problematic waste residue, Biomass Combustion Ash. In our previous works, we managed to extract and produce value-added products (CO2 adsorbents) from this industrial-grade residue. However, they were all in powder form.

This is common practice in material design in a laboratory setting but, for industrial reactors, scale-up is needed in terms of both the amounts of material and also in the size of the adsorbent particles. This stems from better heat transfer and lower pressure losses of mm-scale particles (pellets, beads, granules, discs, etc.) as well as issues of dusting and solid handling (someone who has ever spilt flour while baking can also feel this pain…).

So, we (Dr Salman Masoudi Soltani’s research group) stepped onto a journey of making our powder-form adsorbent into pellets, investigating different binder compositions and ratios as well as production pathways. Turns out, the order in which the material is activated and pelletised has a significant impact on the final properties and, depending on your material, careful consideration is needed to maximise the benefits of your particular adsorbent.

To start, let’s discuss the binder. I guess the name says it all. It is a particular chemical that collects and keeps together the small powder particles into a bigger shaped particle. There is a plethora of options to select here. We opted for polyvinyl alcohol (PVA) since it is a low-cost, readily available, non-toxic and biodegradable option. This polymer is also water soluble (so we avoid using toxic or hazardous solvents) as well as being potentially sourced from waste. This highlights the crucial principles of green chemistry and sustainability that we adopt in our lab.

On the other hand, since PVA is an organic binder, we noticed that it would decompose under high temperature conditions and the particles that were produced following the pathway of “pelletisation then activation” were not resilient enough to be deployed on an industrial scale. As such, we suggested this approach to be better suited for inorganic binders (such as clay).

However, when we looked into the alternative production pathway, i.e. “activation then pelletisation”, our PVA binder would work much better. Still, the numbers were shy of the requirement for industrial deployment but suited our laboratory applications. The next step would be to attain the desired industrial requirements for the strength and resilience of the pellets, but this would have to be done using industrial equipment as opposed to lab-scale units.

Mike Gorbounov (RA) at the IEEE NANO 2023.

These results have been presented and published as part of the IEEE 2023 International Conference on Nanotechnology in Korea (Jeju island is beautiful, by the way). Furthermore, a poster has been featured at the UKCCSRC Spring 2023 Conference at Cardiff University as well as at the Brunel University London Chemical Engineering bi-annual symposium.

Finally, right after this project, Mike Gorbounov (the research assistant (RA)) defended his PhD thesis (titled “Valorisation of Biomass Combustion Ash in Preparation and Application of Activated Carbon for CO2 Adsorption”) with minor corrections. Well done Dr Mike!

Read more on Salman’s Flexible Funding 2022 project page.