Professor Mathieu Lucquiaud, University of Sheffield, was awarded funding in the UKCCSRC’s Flexible Funding 2022 call to look at “SMART – Solvent Management At Reduced Throughput & prototype demonstration”. Mike Ownsworth, University of Sheffield, provides an insight into the project.
Track-1 of the UK Carbon Capture, Usage and Storage Programme is made up of the initial two CCUS clusters: HyNet and the East Coast Cluster. Both clusters include amine post-combustion capture (PCC). PCC uses an amine solvent to capture CO2 out of the combustion products, which is heated to release the captured CO2 and then compressed for permanent storage. Impurities in the flue gas stream are also absorbed and can cause the solvent to break down when it is heated, or simply cannot be removed from the circulating solvent as fast as they are collected, eventually requiring complete replacement of the solvent inventory.
The first two examples of large-scale PCC – Boundary Dam 3 (Canada) and Petra Nova (USA) – have had reports of high solvent management costs and associated problems, and Petra Nova has only recently restarted operations. To avoid similar problems in UK, the Environment Agency ‘Guidance: Post-combustion carbon dioxide capture: best available techniques (BAT)’ recommends realistic pilot (or full scale) tests using fully representative (or actual) flue gases over a period of at least 12 months.
Very long tests of 8,000 hours or longer, as recommended by the guidance, are prohibitively expensive if pilot plants large enough to give realistic absorber performance and energy requirements are used. The SMART project is developing a pilot test unit focused only on solvent management and emissions control. This can be much smaller, perhaps as low as 10-80 kg CO2/day, roughly 1% of the flue gas of the larger pilot. In addition, novel small-scale reclaimers and water and acid washes are being included, to allow a range of solvent management techniques to be tested.
The SMART unit concept is aimed at a low cost and size including solvent reclaiming, and environmental emissions controls also having representative thermal and composition conditions for the solvent being tested. The unit is too small to assess operational energy requirements accurately, yet it can be expected to give useful indications of ‘showstoppers’. Principally, verifying that a build-up of unwanted degradation products and heat stable salts can be avoided, and that emissions to atmosphere from the long-term solvent inventory can be controlled to acceptable levels
A model of a first stage reclaimer was produced by Lucas Joel and presented to the GHGT-17 conference in 2024. Graphs of the model output are shown in Figure 1.
Figure 1: Reclaimer temperature as a function of moles of non-volatile impurity in the blowdown. (Joel, 2024)
A standalone reclaimer has been constructed in a laboratory at the University of Sheffield and is being used to validate the models which were presented.
Figure 2: Standalone reclaimer constructed at the University of Sheffield (behind splash guards)
The standalone reclaimer was initially operated on fresh MEA solvent, but has recently moved on to using aged solvent from the Translational Energy Research Centre. Alongside the standalone reclaimer, a test unit including Absorber, Desorber Reboiler and integral Reclaimer is being constructed.
The size of the SMART test unit fits between bench-top laboratory units, easily made in glassware and tubing, and larger pilot plants, that can be fully fabricated in stainless steel with flanged joints and having fully automated controls. As such, the assembly poses some interesting trade-offs. A choice made early in the design of the SMART unit was to use screwed joints to allow flexibility in the arranging and positioning of the various components. The joints on the components are larger than would usually have threaded connections. That has led to difficulties getting a perfect seal. In the end, many of the joints have been redesigned as flanges or seal welded, losing the intended flexibility in any case.
The SMART prototype is being constructed in a laboratory at the University of Sheffield (figure 3). It will initially address reclaiming of MEA from degraded MEA carbon capture solvent. In the laboratory, a simulated flue gas will be produced from air, added CO2 and traces of single contaminant gases.
Figure 3: SMART Lab Unit under construction at University of Sheffield
The test rig can be used in a continuous mode of operation to allow investigation of solvent desorption and reclaiming at various temperatures and pressures. The effects of the single trace contaminants, the effects of blowdown from the desorber to the reclaimer and the continuous operation of that reclaimer will also be investigated. Progress on the construction and commissioning of the test unit was made to the PCCC8 conference in 2025 by Mike Ownsworth.
After the SMART unit has been assembled and operated in a lab environment, it will initially be relocated to an industrial location to be attached to a slipstream from a real flue gas. The exact contaminants present in the real flue gas will depend heavily on the upstream industrial process. It is expected that there might be significant NOx, SOx, CO and particulates which could contain metals or other trace organic material. Each industrial flue gas will have a different amount of residual oxygen. All these things will affect the degradation rate and therefore the extent of reclaiming which is desirable and practical.
Because the unit is small, long-term (>8000hr) representative trials will be possible without incurring excessive costs. The small number of previous long-term tests carried out on real flue gases have shown accelerating degradation effects after a period of operation. Following optimisation to confirm operating parameters such as draw off to the reclaimer and reclaiming temperature, the SMART unit can be operated for a long duration to establish whether continuous reclaiming can avoid the onset of the accelerating degradation. The long duration operation can also demonstrate the feasibility at this scale of the of the year-long pilot trial as recommended in the BAT guidance.
Read more on Mathieu’s Flexible Funding 2022 project page (including the GHGT-17 paper and the PCCC8 presentation).
Professor Chenggong Sun, from the University of Birmingham, was awarded funding in the UKCCSRC’s Flexible Funding 2022 call to look at “CO2 Utilisation for Accelerated Carbonation Curing towards Net-Zero Circular Concrete Industry”.
Funded by the UKCCSRC through its flexible funding programme, researchers at the University of Birmingham have successfully developed and validated CO2 carrier technology as a credible and potentially transformative alternative to compressed CO2 systems for enhanced carbonation curing in low and zero-carbon concrete production.
The innovative technology overcomes major technical and operational limitations of compressed CO2 systems by functioning through dispersed “CO2 capsules” embedded during the concrete mixing phase. These carriers release CO2 in situ and uniformly across the entire concrete bulk at a regulated rate determined by carrier material properties, maximizing carbonation efficiency while reducing costs and improving operability for cast-in-place applications.
Critical to success is the precise matching of CO2 release rates with carbonation kinetics, which ensures efficient CO2 utilization while maintaining concrete structural integrity. The CO2 sequestration capacity scales directly with carrier material properties, enabling predictable performance optimization. Additionally, diverse substrate selection possibilities open pathways for advanced material development to further enhance the technology’s potential.
The research findings provide a solid foundation for continued development and eventual commercialization. As the construction industry intensifies its focus on decarbonization, CO2 carrier technology represents a significant step forward in making sustainable concrete production more accessible, cost-effective, and operationally viable across diverse construction applications.
Read more on Chenggong’s Flexible Funding 2022 project page.
Dr Muir Freer and Dr Clair Gough, Tyndall Centre for Climate Change Research at the University of Manchester, were awarded funding in the UKCCSRC’s Flexible Funding 2022 call to look at the “Integrating Dispersed Cement Production into the UK’s CCS Network”.
Delivering on Net Zero targets requires innovative solutions, particularly for sectors with high emissions, such as cement production. While the UK’s Carbon Capture and Storage (CCS) clusters are pivotal, integrating dispersed cement production facilities into this network would enable the sector to make significant emissions reductions through CCS deployment. In this research, we explore the potential pathways for incorporating these dispersed sources into the UK’s CCS infrastructure.
Cement Production and CCS
This flexibly-funded research project focused on the integration of dispersed CO2 sources, such as cement and lime facilities, into the UK’s CCS network. Using the Carbon Navigation System Model (CNS) [1] the research explored CO2 routing decisions and the implications of alternative transportation modes to connect these dispersed facilities to the UK CCS clusters.
Industrial clusters group multiple industrial facilities to share CO2 capture, transport and storage infrastructure. These clusters, typically located along the coast, provide access to low-carbon transport options, such as shipping and rail, to offshore geological storage sites via CO2 pipeline. While new clusters are emerging, the research focuses on access to the UK’s Track 1 Hynet and East Coast clusters (targeting deployment in the mid 2020s) and Track 2 Scottish and Viking clusters (targeting deployment by 2030) supported by the Government’s Cluster Sequencing Process.
Cement production contributes approximately 7% [2] of the world’s total emissions; alongside measures for demand reduction and material substitution, the sector presents unique challenges to abating emissions from its calcination, fuel combustion and manufacturing processes. While the use of alternative fuels, material substitution and process optimisation can contribute to emissions savings, bringing cement production towards net zero will require CCS technologies. The industry estimates that to achieve net zero, CCS will contribute about 60% of the sector’s emission reductions by 2050 [3]. However, most cement and lime facilities are located outside of the existing CCS clusters. In order to deploy CCS, these facilities will require a mix of CO2 transportation modes, including pipelines and non-pipeline transportation (NPT) such as heavy goods vehicles (HGVs), rail and shipping. NPT is necessary for emitters without pipeline access to connect to offshore geological storage sites via CCS clusters.
Challenges of Integrating Dispersed Emitters
Integrating dispersed cement facilities into the CCS network presents several challenges:
- Distance from Clusters: Many cement facilities are located far from existing CCS clusters, complicating CO2 transport logistics.
- Infrastructure Costs: Building new pipelines or upgrading existing infrastructure can be expensive and time-consuming.
- Regulatory Hurdles: Navigating the regulatory landscape and obtaining necessary permits for new infrastructure takes time.
- Flexible Transport Solutions: Dispersed sites require a variety of transport solutions, such as a combination of pipelines, rail and shipping, depending on location and infrastructure availability.
Importance of Inland Clusters
An inland cluster serves as an extension hub connecting dispersed carbon-emitting facilities to the Track-1 and 2 CCS networks. Developing inland clusters could serve as hubs that connect high carbon-emitting facilities to the main CCS network. The performance of transporting CO2 from dispersed sites via non-pipeline methods is highly sensitive to external factors, such as fuel price increases or transportation decarbonisation. Our study highlights the role of specific inland ’feeder’ pipelines, such as the proposed Derbyshire pipeline connecting the inland Peak Cluster to the North-West cluster, with the potential to significantly reduce both the operating costs and carbon emissions of integration.
Figure: Distribution and capture potential of cement and lime facilities in the UK relative to proposed CCS infrastructure.
Integrating the cement industry to CCS clusters
This research has identified the following measures through which to address challenges and leverage opportunities in integrating dispersed cement production into the CCS network:
- Formation of Inland Clusters: Inland clusters can enhance the carbon and fiscal efficacy of CCS integration and reduce sensitivity to transportation price volatility.
- High-Capacity Feed-In CO2 Pipelines: Linking rail terminals and shipping ports to the main trunk CO2 pipelines can improve the integration performance of dispersed emitters and alleviate logistical challenges.
- Low-Carbon Transportation: Improve the use of low-carbon transportation methods, such as rail and shipping, and the use of decarbonised transport fuels for existing and future CCS projects.
- Data and Knowledge Sharing: Develop a transparent, interactive database for facility operators to explore non-pipeline transportation options for CO2.
- Cross cluster thinking: Address the diverse infrastructural constraints of clusters across the UK to enhance network resilience.
[1] Freer, M., Gough, C., Welfle, A., Lea-Langton, A., 2022. Putting Bioenergy With Carbon Capture and Storage in a Spatial Context: What Should Go Where? Frontiers in Climate 4.
[2] https://www.iea.org/reports/technology-roadmap-low-carbon-transition-in-the-cement-industry
[3] https://cement.mineralproducts.org/MPACement/media/Cement/Publications/2020/MPA-UKC-Roadmap-to-Beyond-Net-Zero_Oct20.pdf
Read more on Muir’s Flexible Funding 2022 project page.
Dr Stavros Michailos, University of Hull, was awarded funding in the UKCCSRC’s Flexible Funding 2022 call to look at “Co-DAC: Low-energy Direct Air Capture potential when combined with a Post Combustion Capture plant”.
Direct Air Capture (DAC) has emerged as an important engineering tool to combat climate change as it can indirectly capture CO2 emissions from different sectors that are hard-to-abate. As with any new technology, improving costs is a key challenge for DAC and a significant contributor to these costs is the energy penalty to capture CO2 from an initial concentration of ~420ppm.
To tackle this, we have developed a novel design that integrates an MEA DAC absorber with a conventional post-combustion capture (PCC) plant, co-DAC, as depicted in Figure 1. Two configurations have been proposed as follows:
a) the air absorber and the flue gas (FG) absorber are placed in series and the whole amount of the lean flow goes to the air absorber to capture air CO2 and then is sent to the top of the FG absorber; three cases have been tested in which the semi-rich solvent loading at the exit of the air absorber is either 0.3, 0.25 or 0.20 molCO2/molMEA;
b) because it is expected that at high semi-rich loadings the FG absorber is not efficiently utilised, a split stream of the cold lean (0.12 molCO2/molMEA) is sent to the top of the FG absorber (with the flowrate adjusted to get a loading of 0.3 molCO2/molMEA at the bottom of the top FG absorber bed to avoid irreversibilities when mixing with the incoming semi-rich) while the rest of the lean solvent enters the air absorber and captures CO2 until the loading reaches 0.3 molCO2/molMEA and then enters at the top of the second bed of the FG absorber.
Figure 1. Process configurations for the proposed Co-DAC system
Simulations have showcased that the specific reboiler duty (SRD) can drop to 3.5 GJ/tCO2, a figure that is well within the range of reported energy penalty for conventional FG capture. The main reason for this energy reduction is that, with co-DAC, the rich loading entering the desorber is high enough, >0.45 molCO2/molMEA, compared to a standalone DAC, ~0.30 molCO2/molMEA. The importance of achieving a high rich loading for efficient operation has been showcased by the authors in a recent paper and we have also presented the results of the co-DAC assessment in the GHGT-16 conference.
It can be seen in Figure 2, that if solvent from an air absorber can be fed to an FG absorber, its rich loading can be increased and the overall SRD for combined DAC and PCC will remain low, as long as the lean loading is above (just above, for maximum effect) the desorber inflexion value.
Figure 2. The air absorber solvent flowrate, the average SRD for all CO2 captured, the total reboiler duty, the fossil CO2 capture, L/G ratio and rich loading as a function of the net negative CO2
After the proof-of-concept modelling studies, we have proceeded with designing the DAC absorber lab set-up. Figure 3 is the 3D schematic of the co-DAC process, with an integrated bypass for the DAC side so that the PCC unit can still run without the DAC unit if needed.
Figure 3. The 3D schematic of the lab scale Co-DAC process
The lab DAC absorption column will have a large diameter compared to PCC, as a large quantity of air will be required to pass through the column for the solvent to have a meaningful change in loading. The absorption column will have a diameter of 300 mm, and BX structured packing from Sulzer with the option to upgrade this packing to a hybrid one that specialises in ultra-low liquid fluxes. The DAC column will have a maximum height of 1.5 m, due to height constraints within the laboratory, including space for the liquid distributor and gas disengagement. However, there is potential for multiple columns to be used if more packing height is required. Sulzer have advised that the BX packing can take a maximum gas velocity of 3 m/s. The main equipment of the DAC has been delivered, see Figure 4, and will be assembled following a HAZOP study.
Figure 4. The DAC and the water wash columns (A) and the Sulzer BX packing (B)
Further, modelling of the DAC absorber as once through configuration has been carried out. Figure 5 shows that for a liquid flowrate between 10-12 kg/h, a capture efficiency of ~50% and a change in the loading of ~0.1 molCO2/molMEA can be achieved. The latter is suitable for a co-DAC configuration as higher differential can lead to inefficient mass transfer in the FG absorber.
Figure 5. The CO2 Capture rate (A) and the (B) loading differential as a function of liquid flowrate for a column height of 1 m
A preliminary TEA has been carried out based on the Sherman FEED study and revealed that co-DAC capture costs are in the range of 116-614 $/tCO2, showcasing the potential of the proposed co-DAC system for cost-effective net-negative capture.
Further modelling will be done to accurately model the DAC system. For example, a greater range of L/G ratio will be tested, through changing the gas flowrates and a wider range of liquid flowrates. Special effort should also be made to find a solution to reach a target concentration of solvent at the outlet for a target absolute loading differential, through changing the inlet concentration of MEA for different flowrates. This could be done either through inclusion of air saturator before the absorption column, or by adding water to the lean stream.
For each case investigated, the process conditions for the wash water column will be investigated to minimise emissions whilst minimising the water footprint of the DAC unit. Finally, a comprehensive techno-economic assessment of the co-DAC system will be carried out.
Overall, the study proposed a novel solution of reducing the energy costs of DAC, and future research will focus on examining the performance of the DAC absorber, including mass transfer measurements and associated fluid flow rates, and reaction rates based on realistic system scenarios. Finally, a detailed discussion about the benefits and challenges of the DAC system can be found here.
Lucas Joel (University of Sheffield), Stavros Michailos (University of Hull), Mathieu Lucquiaud (University of Sheffield), Jon Gibbins (University of Sheffield)
Read more on Stavros’s Flexible Funding 2022 project page.
Dr Tohid N.Borhani, University of Wolverhampton, was awarded funding in the UKCCSRC’s Flexible Funding 2022 call to look at the “Modelling and Simulation and Economic Evaluation of CO2 Capture Using Downflow Gas Contactor (DGC) Process”.
Carbon capture is recognised as one of the most effective technologies to reduce the environmental impact of human activities [1–4]. There are several processes that can be used in the post-combustion and pre-combustion conditions. Processes such as absorption, adsorption, membrane, cryogenic, etc. Between these processes, absorption using different solvents, especially using amine solvents, is the most mature process in the world [5]. This method consists of removing carbon from exhaust gas using solvent before processing or releasing to the atmosphere. The performance of this technology relies on the equipment/unit configuration and type, solvent types, and operating system of the process [6,7]. Therefore, by changing and modifying each of these parameters, we can change the performance of absorption-desorption systems.
One of the most promising parameters that can improve the performance of CO2 absorption process in aspect of cost and solvent utilisation is changing or modifying equipment/unit in the process. So far, different types of unit operations have been developed for CO2 absorption such as rotating packed bed (RPB), packed column, trayed column and Bubble column. Each of these unit operations has their own advantages and disadvantages. Thus, novel concept designs are currently developed to increase the overall performance of the system while minimising cost. One of them is the Downflow Gas Contactor (DGC) which can be a promising alternative for numerous applications. Indeed, DGC can be classified as a mass transfer device preliminary designed for contacting liquid and gas.
Figure 1: Batch DGC unit used in this study
In this study, we have examined the batch DGC to capture CO2 suing water and MEA solution (Figure 1). The result of experimental work was promising, and DGC can be considered as a high potential unit operation for carbon capture, and capture the CO2 by more than 90% carbon capture level (Table 1). Primary cost analysis showed that this unit can be cheaper than conventional packed column. By considering an industrial base case the size of DGC to do the same level of carbon capture is 0.89 m for diameter and 7 m length of column. If we need to use packed column to do the same job, we will need a column with 12.8 diameter and 18.4 m length. More research and work to convert batch DGC to steady state system is required. In addition, steady state stripper DGC should be designed.
Table 1: Carbon capture from mixture of N2 and CO2 using 5 wt% MEA solution
A model of the batch DGC system was developed to investigate the effectiveness of its CO2 absorption with no packing. The DGC is characterized by bubbly flow, and mass transfer is controlled by its hydrodynamics, which affects the holdup, bubble size and mass transfer coefficient. The interfacial area which is directly proportional to the mass transfer flux is in turn dependent on bubble diameter and gas fractional holdup. The model development consists of two parts: (1) first principle mathematical equations development, and (2) implementation in Aspen Custom Modeler (ACM) and validation (Figure 2). The two parts were carried out and here we report the key findings. Although, there are yet-to-be resolved numerical problems in the validation of the model for comparison with experiments, a useful conclusion can be drawn as follows.
We found that under the operating regimes and reactor dimensions of the DGC, the control of gas holdup and interfacial area is essential. The interfacial area was as high as 757.2 m2/m3 for 5 mm-size gas bubbles but it reduced with larger bubbles. Superficial velocity or volumetric gas flow rate directly influences the holdup. The findings were presented at a larger meeting with collaborators/partners. Thus, in theory, the DGC reactor operating in downward concurrent flow with no packing can be used to capture CO2. We propose that for more accurate inferences, more robust future investigation can consider the mapping of reactor’s physical and operating parameters to the gas holdup data to be acquired by experiments using laboratory or pilot sized reactor. These would provide an experimental basis for the creation of predictive and scale-up rules for the DGC reactor.
Figure 2: Model structure in this study
More experimental work is ongoing to find out the mass transfer coefficient and holdup parameters in the column. This study was a primary feasibility study to show that DGC can be used for carbon capture, and we are working on more research proposals to scale up this system in the future.
Read more on Tohid’s Flexible Funding 2022 project page.
Acknowledgments
We extend special appreciation to both Membracon UK Ltd [8] and WRK Ltd [9] as key collaborators within this project. WRK provided the patented DGC technology and Membracon as their UK delivery partner. They provided invaluable technical support, without which this research would not have been feasible.
References
[1] Akimoto K, Sano F, Oda J, Kanaboshi H, Nakano Y. Climate change mitigation measures for global net-zero emissions and the roles of CO2 capture and utilization and direct air capture. Energy and Climate Change 2021;2:100057. https://doi.org/https://doi.org/10.1016/j.egycc.2021.100057.
[2] Shu DY, Deutz S, Winter BA, Baumgärtner N, Leenders L, Bardow A. The role of carbon capture and storage to achieve net-zero energy systems: Trade-offs between economics and the environment. Renewable and Sustainable Energy Reviews 2023;178:113246. https://doi.org/https://doi.org/10.1016/j.rser.2023.113246.
[3] English JM, English KL. An overview of carbon capture and storage and its potential role in the energy transition. First Break 2022;40:35–40.
[4] Cormos A-M, Dinca C, Petrescu L, Chisalita DA, Szima S, Cormos C-C. Carbon capture and utilisation technologies applied to energy conversion systems and other energy-intensive industrial applications. Fuel 2018;211:883–90.
[5] N.Borhani T, Wang M. Role of solvents in CO2 capture processes: The review of selection and design methods. Renewable and Sustainable Energy Reviews 2019;114. https://doi.org/10.1016/j.rser.2019.109299.
[6] Aghel B, Janati S, Wongwises S, Shadloo MS. Review on CO2 capture by blended amine solutions. International Journal of Greenhouse Gas Control 2022;119:103715. https://doi.org/https://doi.org/10.1016/j.ijggc.2022.103715.
[7] Borhani TN, Wang M. Role of solvents in CO2 capture processes: the review of selection and design methods. Renewable and Sustainable Energy Reviews 2019.
[8] Membracon UK | Global Leader In Water Treatment Since 2002 n.d. https://www.membracon.co.uk/
[9] WRK Design and Services – Consulting Chemical Engineers n.d. http://wrkdesign.co.uk/
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.
Dr Nejat Rahmanian at the University of Bradford was awarded funding in the UKCCSRC’s Flexible Funding 2022 call to look at the “Evaluation of Biomass Wood Pellets for Power Generation Applications”.
In the ever-evolving landscape of renewable energy in the UK, biomass has surged as a major player, contributing 12.9% of the total energy production in 2021. With the nation’s ambitious net-zero emissions target for 2050, biomass energy is set to constitute 10% of the energy mix. Bioenergy with Carbon Capture and Storage (BECCS) will play a vital role in emissions reduction. Wood pellets are central to this transition, crucial for co-firing and co-generation, but their proper handling is essential for efficiency and safety in energy production. This integration reflects the UK’s commitment to sustainable, eco-friendly power generation.
Figure 1 – Bioenergy with Carbon Capture and Storage (BECCS). Source: earth.org
It is important to note that while the utilisation of wood pellets for biomass energy has gained momentum, there still exists a critical gap in understanding the many different aspects of the nature of these pellets. This includes their physical, mechanical and chemical properties, particularly when used in power generation applications. This project aimed to address these knowledge gaps by characterising biomass wood pellets used as a feedstock in UK power plants.
This project strives to shed light on the physical, mechanical and chemical properties of 12 biomass wood pellets samples used in the UK (Figure 2). Various properties were examined, including density, durability, moisture, particle size distribution and strength. The core goal was to establish a comprehensive understanding of how these properties interrelate and influence energy release and emissions, particularly the generation of CO2.
Figure 2 – 12 Biomass wood pellet samples
The pellet density was found to vary significantly among samples, with Sample G at 979.06 kg/m3 and Sample E at 1150.07 kg/m3. While there is no specific density standard, ENplus standards for pellet size were met. Density is influenced by factors such as wood type, moisture, particle size, binders and compression pressure used in manufacturing process. Bulk density also varies, with Sample J at 628.20 kg/m3 and Sample E at 589.90 kg/m3, falling mostly within the ENplus standard of 600-750 kg/m3. Wood type, moisture content and manufacturing processes impact bulk density. High bulk density is preferable for cost effective transportation and storage.
Mechanical durability, a key property, varied among samples. While meeting the ENplus standard of ≥ 98%, Sample G had the lowest mechanical durability at 98.73%, and sample E had the highest at 99.96%. Mechanical durability is vital for pellets to withstand transportation, storage and handling. Low durability can lead to issues such as reduced combustion efficiency and higher emissions, as well as an increased risk of fire explosions during handling. Moisture content analysis revealed that all samples fell into the M10 category with relative moisture less than 10%.
The particle size distribution for wood pellet samples A to L was generally uniform, with slight deviations in C and E, likely due to increased moisture and durability. The maximum force needed to break the pellets varied significantly, with Pellet K being the strongest at 0.835 kN, and Sample G the weakest at 0.451 kN. These variations are influenced by factors like density, durability and moisture. Additionally, thermal treatment can alter pellet properties, affecting strength, grindability, HHV and particle size.
The HHV of wood pellets represents the heat released during complete combustion. It fluctuates based on wood type, moisture content and the production process. Woods composition, including cellulose, lignin, protein and starch impacts HHV. Carbon and hydrogen content, being energy rich elements, also influence HHV. Sample K displayed the highest HHV at 22.37 MJ/kg, while Sample C had the lowest at 16.71 MJ/kg. Gas release analysis indicated that the amount of oxygen used significantly affected CO2 emissions. The specific burning conditions and wood type contributed to variations in carbon emissions.
In conclusion, this project has shed some light on the intricate world of wood pellets and their critical role in the sustainable biomass energy landscape of the UK. It was found that various properties influence their performance, from density and mechanical strength to heating values and CO2 emissions. These findings provide a comprehensive foundation for understanding the complexities of wood pellets and offer valuable insights for enhancing the efficiency and sustainability of biomass energy utilisation in the UK’s ever-evolving energy landscape. As the demand for sustainable sources continues to grow, a deeper understanding of wood pellets is pivotal in ensuring a greener, more eco-conscious future.
Read more on Nejat’s Flexible Funding 2022 project page.
Dr Amir Jahanbakhsh at Heriot-Watt University was awarded funding in the UKCCSRC’s Flexible Funding 2022 call to look at the “Rockit – the geochemistry of turning carbon to rock via geological CO2 storage in basalts”.
The focus of my project was on in-situ carbon mineralisation. Basalt, one of the most prevalent types of extrusive igneous rocks found on Earth’s surface, has erupted in massive quantities over geological periods due to volcanic activity. Basaltic rocks are notably abundant in divalent cations like Ca2+, Mg2+, and Fe2+, which exhibit high reactivity when exposed to CO2-rich fluids. Consequently, they hold significant potential for capturing and storing CO2 by facilitating the formation of stable carbonate minerals such as calcite (CaCO3), magnesite (MgCO3), and siderite (FeCO3). Usually, CO2 and water are injected together in basalt formations, inducing a rapid chemical reaction for storing CO2 in carbonized form.
Although basalts have shown promising potential for secure and permanent storage (removal) of CO2, there are still research questions around the geochemical reactions’ timescale, effective parameters and the whole process optimization. We performed a series of CO2–brine-basalt interaction experiments at high-pressure and high-temperature conditions resembling storage conditions. We investigated the effect of grain size, pressure, salinity and basalt rock type on the process of CO2 carbonation.
This work was a collaboration between the Research Centre for Carbon Solutions (RCCS) at Heriot-Watt University and the School of Geosciences at the University of Edinburgh. This was the second collaborative work between the two teams on projects addressing one of the unprecedented challenges of the century. As a result of this collaboration, we have been successful in harnessing our expertise across disciplines and organisations, exchanging and sharing knowledge, and integrating geochemistry with the engineering approach in order to investigate the uncertainties in the performance of basaltic rock for carbon storage purposes. This project helped me to build a close collaboration with research fellows at the University of Edinburgh and, hopefully, this is a good start for a long-term collaboration.
As a researcher who has been mainly focusing on modelling and application of numerical simulations to investigate scientific problems, this funding opportunity provided me to expand my experience into the experimental world. Understanding the challenges and limitations behind designing and collecting experimental data which potentially should be used for validation of any modelling or simulation work has been a great experience which has happened throughout this project.
I would like to thank all my funders – UKCCSRC, RCCS, and IDRIC – for supporting me throughout this project.
Read more on Amir’s Flexible Funding 2022 project page.
Dr Yongliang (Harry) Yan at Newcastle University was awarded funding in the UKCCSRC’s Flexible Funding 2022 call to look at the “Applying Machine Learning in Screening Perovskite-based Oxygen Carriers for Chemical Looping Applications”.
Chemical looping is a versatile and emerging platform for cost-effective CO2 separation, and sustainable chemical and energy conversion. Oxygen carriers (OCs) constitute the cornerstone of chemical looping processes. The traditional process of developing the desired perovskite-based OCs is based on trial-and-error synthesis and characterisation, which is costly and time-consuming. To overcome this shortcoming, we developed a ML approach that can learn and build a model to make predictions for future OCs in chemical looping applications illustrated in Figure 1.
Figure 1 – Workflow of developing a machine-learning model for oxygen carriers in the chemical-looping process
In this work, we applied artificial neural networks (ANNs) trained by the database of Materials Project to predict oxygen vacancy formation energies of perovskite oxides for chemical looping hydrogen production (CLHP). An analysis of ML model was conducted to identify the relationship between fundamental properties of the perovskite oxide and its oxygen vacancy formation energy. Based on their variance contribution, we found the heat of formation, volume and band gap are the strongest descriptors to predict the oxygen vacancy formation energies of perovskite oxides.
Then the predicted oxygen vacancy formation energies of perovskite oxides were used to evaluate the equilibrium conversions of gases for chemical looping reactions and identify suitable perovskites for CLHP. In this project, a shortlist of top five candidates has been selected by the ML models together with the human expertise, which could be synthesised and tested in the lab-scale reactor for CLHP with the further financial support.
Read more on Yongliang’s Flexible Funding 2022 project page.
Dr Katriona Edlmann at the University of Edinburgh was awarded funding in the UKCCSRC’s Flexible Funding 2022 call to look at the “Carbonation Negative Emission Technology – CarbNet”. This is her reflective journey from idea to innovation.
“If at first you don’t succeed…” the ethos of scientific research 😊 As developing a new method to test carbon sequestration in alkaline solutions presented a mix of excitement and challenges, it became the unofficial mantra of our CarbNet project.
Our mission was simple on paper but challenging in practice: develop a method to sequester carbon dioxide into alkaline solutions. Beginning this endeavour required designing a new experimental rig. Like any pioneering venture, we had our share of setbacks. From air stones getting clogged to exothermic reactions pushing our vessels’ temperature boundaries, each challenge was a lesson in resilience and adaptation. Each setback pushed us to refine our method and ensured experimental safety.
Before diving deep into the core experiments, addressing potential uncertainties was vital. One concern was water evaporation from our open cylinder system, especially given the high temperatures. This prompted another essential experiment to explore water evaporation potential to ensure precision in our core studies. It is an essential part of the process, ensuring we account for every variable prompted another essential experiment. With this settled, our post-Christmas experiments were set to commence.
Investigation into water evaporation
The New Year ushered in fresh energy into the laboratory and the arrival of two Environmental Geoscience students. Their dissertations centred around carbon capture, and their inquisitiveness and passion became an invaluable asset to CarbNet.
By April, it was time to celebrate as our students submitted their dissertations. The culmination of their hard work deserved a fitting celebration, sweetened with some spectacular Matcha cookies. Their contributions to CarbNet were invaluable.
The promising outcomes from our early experiments laid the foundation for our next endeavour: crafting a working prototype. Integrating a solar PV panel, marked an important intersection of renewable energy with carbon capture. The UKCCSRC’s support in reshuffling our funds was instrumental in this achievement and encapsulated our vision of merging renewable energy with carbon capture.
Outside the lab, we sought inspiration and knowledge. The UKCCSRC webinar, “Squaring the Circular Economy with CCS,”, was not just relevant but also filled gaps in our knowledge, especially regarding the intricate engineering aspects of capture technologies.
June brought our experiments to a close, with findings that exceeded our expectations, culminating in results that solidified our confidence in the project. The conclusive evidence showed the capability of sequestering captured CO2 as solid carbonates using NaOH and KOH alkali bases. Furthermore, the scope to optimise the process offers a tantalizing prospect for future innovations. The potential for tweaking the sequestration process to yield desired products is particularly exciting.
End results – solid carbonates
Our presentation to the project stakeholders at Cloburn Quarry was more than just an update – it merged our scientific findings with tangible industrial applications, a testament to the real-world impact of CarbNet. The synergy between our findings and potential applications in the Quarry cement works is promising. Collaborations like these pave the way for practical solutions to pressing environmental concerns.
As we wrap up this phase of CarbNet, the journey is far from over. From refining our prototype to exploring and fostering new collaborations with industry, our roadmap is extensive and exciting. With Co-I Ali Hassanpouryouzband’s new fellowship at the University of Edinburgh focusing on Net Zero technologies, the future looks bright and we are eager for what the future holds.
Looking back, the CarbNet journey has been a rollercoaster of challenges, solutions and successes. But every twist and turn enriched our understanding and brought us closer to our goal. Here’s to more breakthroughs and collaborations in our pursuit of a greener sustainable future. Onwards and upwards!
Read more on Katriona’s Flexible Funding 2022 project page.
The UK Carbon Capture and Storage Research Community (UKCCSRC) is supported by the Engineering and Physical Sciences Research Council (EPSRC) as part of the UK Research and Innovation (UKRI) Energy Programme.
The mission of the UKCCSRC is to ensure that carbon capture and storage (CCS) plays an effective role in helping the UK achieve net-zero greenhouse gas emissions by 2050.
Location
D03 Ella Armitage Building
University of Sheffield
40 Leavygreave Road
Sheffield
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