ETRIC – Effective Thermal Reclaiming Integrated with Capture (Flexible Funding 2023)

Dr Abby Samson, formerly University of Sheffield, was awarded funding in the UKCCSRC’s Flexible Funding 2023 call to look at “ETRIC – Effective Thermal Reclaiming Integrated with Capture”.  Marcin Pokora, University of Sheffield, provides an insight into the project.

Why effective solvent reclaiming is needed

Carbon capture using amine-based solvents is now a mature and widely deployed technology. However, it is increasingly clear that CO₂ capture without effective solvent management is not sustainable at scale. During operation, amine solvents degrade through thermal, oxidative, and chemical pathways, producing a complex mixture of by-products. If these degradation products are allowed to accumulate, they reduce capture efficiency and create operational challenges, including corrosion, foaming, increased solvent losses, and rising maintenance costs.

Thermal reclaiming is the primary strategy used to remove degradation products and maintain solvent quality in industrial capture plants. Yet, despite its importance, reclaimer operation remains poorly understood and only weakly optimised, particularly under conditions representative of long-term commercial operation. In some cases, reclaiming itself may unintentionally recycle certain degradation products, allowing them to persist in the solvent inventory.

This research addresses a central challenge for large-scale CO₂ capture: how to operate thermal reclaimers in a way that maintains solvent quality indefinitely, while minimising solvent loss, energy use, and degradation product carryover.

Project overview

The aim of this project is to improve the understanding and operation of thermal reclaiming systems for amine solvents, with a particular focus on monoethanolamine (MEA). The research combines experimental reclaiming studies with process modelling to identify optimal operating conditions, and to determine which degradation products are effectively removed and which are likely to persist.

Specifically, the project seeks to:

1. Identify operational limits that prevent excessive degradation and volatile carryover during reclaiming
2. Quantify trade-offs between maximising solvent recovery and minimising impurity recycling
3. Develop a predictive model for continuous two-stage thermal reclaiming that can support long-term solvent management strategies in commercial plants

Experimental reclaiming capability

A lab-scale thermal reclaimer was designed and constructed using glassware to allow controlled experimental investigation. Early designs, based on conventional distillation setups, suffered from significant heat losses and poor efficiency. Through several iterations, the system was progressively improved with:

• Modified flask shapes
• Enhanced heating using upgraded heating mantles and tapes
• A pump-fed solvent delivery system to improve control and repeatability
• Attached a Coriolis flow meter at the end of the apparatus for real time density measurements

The evolution of the experimental setup is shown in Figure 1.

The final configuration was used to conduct batch thermal reclaiming experiments on industrially degraded end-of-life MEA solvent. Visual changes in solvent appearance before and after reclaiming are shown in Figure 2.

Reclaiming process definition

The batch reclaiming process was structured into three distinct stages:

• Filling and concentration stage: Degraded solvent (with water and caustic added where required) is heated until a characteristic temperature is reached. This temperature marks the onset of excessive degradation and increased volatile carryover.
• MEA recovery stage: The inflow of degraded solvent is stopped and only water is added. As MEA is recovered, the system temperature drops and stabilises, indicating the completion of solvent recovery. At this stage, a balance must be struck between solvent recovery, the risk of recycling volatile degradation products and usage of excessive amounts of water.
• Final concentration stage: Excess water is removed to minimise the volume of the waste stream while maintaining residue flowability. Care is required to avoid unwanted evaporation of non-target components.

While clear visual differences between degraded and reclaimed solvents were observed, further chemical analysis is required to quantify reclaiming effectiveness at this stage.

In-line density monitoring during reclaiming

To explore real-time monitoring of solvent behaviour during reclaiming, a liquid density meter was integrated directly into the reclaiming setup. This enabled continuous measurement of liquid density during operation, providing a non-intrusive proxy for changes in solvent composition as reclaiming progressed.

Density data were temperature-corrected to a reference temperature and compared against predictions from the reclaiming model. As shown in Figure 3, the measured density evolution closely follows the modelled steady-state behaviour, indicating that in-line density monitoring has strong potential as an operational diagnostic tool for reclaiming systems.

Figure 3. Comparison of measured liquid temperature and in-line density of reclaimed 35 wt.% MEA during thermal reclaiming with model-predicted steady-state temperature and calibrated solvent density. Density values are corrected to a reference temperature.

While further validation is required, these early results suggest that density measurements could be used to infer solvent condition and reclaiming progress in real time, reducing reliance on off-line sampling and analysis.

Analytical and modelling approaches

Several analytical methods are being developed and applied to characterise reclaiming performance:

• pH and Conductometric titration have been successfully used to quantify heat-stable salt content, amine concentrations and CO_2.
• Thermogravimetric analysis (TGA) has shown strong potential for determining amine concentration, with promising results currently awaiting publication.
• Gas chromatography (GC) is being explored to quantify specific degradation products, although analytical challenges remain.
• Coriolis Density flow meter has shown potential is monitoring the concentrations of reclaiming solvent in real time and showed matching results to modelling results.

In parallel, a process model for a continuous two-stage thermal reclaiming system has been developed. The objective of the model is to identify operating conditions under which degradation product formation and removal are balanced, allowing solvent quality to be maintained over long timeframes.

Good agreement has been achieved between a detailed MathCAD model and a simplified Excel-based implementation (Figure 4), enabling rapid exploration of operational trends. For example, the model shows that increasing water flow reduces system temperature, while higher non-volatile impurity concentrations increase it.

What we’ve found so far

Lab-scale thermal reclaiming can produce visually cleaner solvent from heavily degraded industrial MEA, but visual improvement alone is insufficient to assess true reclaiming effectiveness.

The reclaiming process involves unavoidable trade-offs between solvent recovery, impurity carryover, and waste stream minimisation.

Modelling results demonstrate that key operating parameters exert predictable and interpretable effects on system behaviour, supporting the feasibility of continuous two-stage reclaiming as a long-term solvent management strategy.

Dissemination and engagement

Over the past two years, this work has been presented at three UKCCSRC conferences and was awarded the Early Career Researcher poster prize at the UKCCSRC Spring 2024 Conference (Figure 5).

Figure 5. Winning the ECR poster prize. Picture taken from the UK Carbon Capture and Storage Research Centre

The research was also presented as an oral poster format at the 2024 GHGT-17 conference in Calgary, Canada, enabling direct engagement with researchers and industrial stakeholders working on solvent management and reclaiming (Figure 6). A conference paper entitled “An Experimental Investigation of Optimum Conditions for Continuous Two-Stage Reclaiming of MEA Solvent Inventories from Commercial Plants” accompanied this presentation.

Furthermore, this research was selected as an oral presentation at the 2025 PCCC-8 conference in Marseille, France (Figure 7).

Next steps

Several key areas remain to be addressed:

• Sub-atmospheric reclaiming operation, to assess its impact on efficiency and degradation behaviour
• Optimisation of caustic addition, including best practice for heat-stable salt neutralisation and minimising excess usage
• Experimental validation of the two-stage reclaiming model using real reclaiming data

Further dissemination is planned in multiple journal publications covering:

• Amine thermal reclaimer configurations and operation for post-combustion capture plants – insights from a generic open-access model
• Performance of two-stage reclaiming systems
• Optimum reclaiming conditions and degradation product carryover

Conclusion

This work highlights the complexity and critical importance of solvent reclaiming in amine-based CO₂ capture systems. The diversity of degradation products and their behaviour during reclaiming present both analytical and operational challenges, helping to explain the limited published literature in this area.

As CO₂ capture deployment accelerates and investment increases, robust well-understood solvent management strategies will be essential for ensuring long-term plant reliability and economic viability. This research contributes experimental capability, modelling tools, and practical insight towards that goal and provides a foundation for improving reclaiming practice in future commercial capture plants.

Read more on Abby’s Flexible Funding 2023 project page.