Carbon Capture Process Research Articles

A Carbon Capture and Utilization Process for the Production of Solid Carbon Materials from Atmospheric CO2 - Part 2: Carbon Characterization.

This article is the second part of a study reporting the results of a novel carbon capture and utilization (CCU) process, which converts atmospheric CO2 into solid carbon materials. The CCU process combines direct air capture (DAC) with catalytic methanation, which is then followed by methane pyrolysis in a reactor filled with liquid tin. While Part 1 discussed the performance of the overall process and individual process steps regarding conversions and yields, Part 2 characterizes the solid carbon products obtained under various synthesis conditions. The effects of the pyrolysis temperature and the composition of the gas mixture from the methanation step on the solid carbon product are analyzed. Carbon powder is synthesized from methane with either H2 or CO2 as most important impurity. Carbon samples are characterized using SEM, TEM, Raman spectroscopy, XPS and XRD analysis. Very thin, disordered carbon flakes, soot aggregates and large carbon onions are identified as the main solid products of the process. Their formation mechanisms in the liquid metal-filled pyrolysis reactor are discussed.

A Carbon Capture and Utilization Process for the Production of Solid Carbon Materials from Atmospheric CO2 - Part 1: Process Performance.

The successful operation of a process that converts atmospheric CO2 into solid carbon products is presented as an alternative to fossil based solid carbon production. In a first step, CO2 is removed from the atmosphere by a direct air capture (DAC) unit. The gas is then mixed with hydrogen and enters a methanation unit. Depending on the operation conditions, gas mixtures consisting of mainly methane with either H2 or CO2 as side-component are obtained. After precipitating the water formed during the methanation step, the remaining gas mixture is fed into a bubble column reactor filled with liquid tin. During the rise of the gas bubbles, methane is thermally split up into hydrogen and solid carbon. The latter is continuously removed from the liquid metal surface as a fine powder by pneumatic conveying. This article is the first of two articles, focusing on the performance of the methanation and methane pyrolysis steps. The experimental results are complemented by thermodynamic analyses and reaction modelling. A detailed analysis of the solid carbon product of the process is presented in the second part.

Landfill-gas-to-biomethane via a new carbon capture and utilization technology: One-pot sodium chloride batch mineralization

A new landfill-gas-to-biomethane route adopts a new carbon capture and utilization process via sodium chloride (NaCl) mineralization. The new process exports chlorine (Cl2), dense carbon dioxide (CO2), hydrogen (H2) and sodium carbonate (Na2CO3). Process absorbs CO2 from landfill-gas with aqueous NaOH/Na2CO3 in batch multi-purpose columns that execute several processing steps in one-pot; namely: CO2 absorption; sodium bicarbonate (NaHCO3) precipitation; NaHCO3 filtration driven by pressurized CO2; NaHCO3 breakage to Na2CO3 via hot CO2 injection; Na2CO3 cooling via cold CO2 injection; and solid Na2CO3 disposal through column lateral doors. The one-pot columns avoid investment with several steady-state complex equipment like bubble-columns, centrifuges, filters, solid dryers, heaters, mud pumps and solid transporters. The depleted solvent from the one-pot columns is regenerated via steady-state, high current-density, brine electrolysis wherein solvent continually feeds cathodes, while brine continually feeds anodes as sodium source. Sodium reaches the cathode through selective Flemion F9010 ion-exchange membrane. CO2 is partially mineralized to Na2CO3 and partially exported as supercritical CO2. Process output-ratios per captured CO2 are: 1.159kgNa2CO3/kg, 0.7754kgCl2/kg, 0.4299kgCH4/kg, 0.0219kgGREEN−H2/kg and 0.51875kgCO2/kg, while the input-ratios are 1.2782kgNaCl/kg, 0.197kgH2O/kg and 1.7495kWh/kg. The new landfill-gas-to-biomethane (480,000Nm3/d landfill-gas) was evaluated environmentally and techno-economically reaching 48.6MMUSD investment, 112MMUSD/y revenues and 418.34MMUSD net value (30 years).

Optimizing energy consumption in post-combustion CO2 capture at an NGCC power plant: A simulation-based approach

Abstract Approach
This study aims to optimize the energy consumption in post-combustion carbon capture processes at a Natural Gas Combined Cycle (NGCC) power plant to address the challenges associated with steam extraction from NGCC power plants and explore non-condensable energy requirements by leveraging heat integration and alternative solvent compositions. The research used simulations with commercially available software and literature-derived data to address the challenges of high energy consumption in such processes. Emphasis is placed on optimizing the solvent composition and implementing advanced heat optimization strategies to reduce the energy consumption. Four scenarios with different solvent compositions were investigated using monoethanolamine (MEA) and aqueous piperazine (PZ). The results show that the process parameter optimization and heat optimization strategies can result in

Non-Isothermal Thermogravimetric Analysis of Carbonation Reaction for Enhanced CO2 Capture

An in-depth investigation into CaO-based carbonation reaction kinetics for CO2 sorption is being conducted using simultaneous thermal analysis (STA), with the application of advanced thermogravimetric and differential scanning calorimetry techniques. Utilizing advanced thermal analysis system for real-time monitoring of simultaneous measurements of mass changes and thermal effects are conducted, ensuring precision and versatility in data acquisition. The study explores the intricacies of the non-isothermal carbonation process across a wide range of temperatures, shedding light on the temperature-dependent trends in reaction rates. Innovative statistical methods, combining regression techniques and Arrhenius equation, are employed to determine energy and reaction kinetics. The sensitivity of carbonation process to varying pressure conditions is meticulously examined in the study, providing pivotal discernment for optimization of reaction parameters across diverse applications. The integration of STA with statistical modeling alongside systematic analysis of temperature-dependent trends and pressure-order relationships not only enhances the understanding of CO2 capture efficiency but also improves the robustness and accuracy of the findings. Furthermore, meticulous cross-validation with existing studies provides a critical evaluation of the experimental approach’s precision and limitations. This study enhances understanding of CaO carbonation kinetics, providing practical implications for carbon capture processes and contributing to sustainable industrial processes.

Techno-economic analysis and optimisation of Piperazine-based Post-combustion carbon capture and CO2 compression process for large-scale biomass-fired power plants through simulation

This study aims to investigate a cost-effective and energy-efficient amine-based post-combustion carbon capture (PCC) process for large-scale supercritical biomass-fired power plants (SC BFPP). Thus, we have quantified the energy and economic performance of the PCC process with different configurations and solvents. Three process configurations which included the standard configuration, the absorber intercooler (AIC) with the advanced flash stripper (AFS) and the AIC, AFS and side stream extraction (SSE) were simulated in Aspen Plus® V11 using 30 wt% and 40 wt% piperazine (PZ) as solvent. In addition to this, CO2 compression trains using the heat pump (HP) and supercritical CO2 cycle (s-CO2) were also simulated. Sensitivity analysis of the PCC process was carried out to investigate the impact of important parameters on the energy performance of the process. Furthermore, energy analysis shows that a minimum energy consumption of 2.78 GJ/tCO2 was achieved with the PCC process using 40 wt% PZ, a combination of the AIC, AFS and SSE for capture and s-CO2 for compression. This achieved a significant energy saving of 1.01 GJ/tCO2 compared with the standard PCC process using 30 wt% monoethanolamine that is used as the benchmark in this study. The economic analysis results showed that the minimum CO2 capture cost of 55.70 $/tCO2 was achieved using the AIC-AFS-SSE-sCO2 configuration and 40 wt% PZ as solvent. This represents a 19.5 % reduction in cost compared with the standard 40 wt% PZ process with a cost of 69.18 $/tCO2. The optimisation of the PZ-based PCC process was carried out to determine the optimal solvent concentration with the minimum carbon capture cost. It was found that the optimal PZ concentration for the PCC process based on standard and AFS configurations were 37.5 wt% and 32.5 wt%, respectively. The optimisation of the stripper pressure for the minimum carbon capture cost was conducted. As a result, compared with the standard PCC process using 40 wt% PZ, the energy consumption and CO2 capture cost of the optimised process at the suggested pressure of 7 bar were reduced by 41.6 % and 32.4 %, respectively.

Industrial-scale 12-layered-bed vacuum pressure swing adsorption for fuel cell-grade H2 production from carbon-captured steam methane reforming syngas

Vacuum pressure swing adsorption (VPSA) is primarily used to produce high-purity H2 from CO2-rich syngas in steam methane reforming (SMR) plants. Since carbon capture is essential, the performance of current H2 VPSA processes is affected by feeding carbon-captured SMR syngas (CO2-lean SMR syngas). This study conducted the performance evaluation and optimization for a fuel cell-grade H2 production by an industrial-scale 12-layered-bed VPSA process with a 24-step cycle from CO2-lean SMR syngas. The multi-scale dynamic model for the VPSA process was validated with petrochemical industry data from a current SMR-VPSA plant. A sensitivity analysis using CO2-lean SMR syngas indicated the high loss of H2 during desorption steps, suggesting the need for optimization of the VPSA process. Owing to the complex interconnectivity of 12 beds via 24 steps, the framework of a dynamic model-based deep neural network (DNN) and DNN-based optimization was developed to design and optimize the VPSA process. Even without changing equipment or adsorbent configuration, the VPSA process achieved fuel cell-grade H2 production (>99.9999 % H2 and > 88 % recovery with < 0.2 ppm CO). The results indicate that CO2 capture rates, ranging from 90 to 99 %, can be independently determined under techno-economic and environmental conditions, as this capture range of CO2-lean SMR syngas gives a minor impact on the performance of VPSA process. The proposed three-step framework, which encompasses dynamic modeling, surrogate modeling, and multi-objective optimization, provides a systematic and feasible approach for designing and optimizing the VPSA process in an SMR plant integrated with a carbon capture process, to achieve a low-carbon economy.

A simulation-based techno-economic-safety-social-environmental decision-making framework for prioritizing plastic waste treatment processes

Chemical recycling technologies hold promising potential in converting mixed plastic waste into energy and chemicals. This study proposed a simulation-based quantitative life cycle sustainability assessment framework for the potential plastic waste valorization processes. Sustainability metrics including environment, economy, safety, society, and energy were quantified and comprehensively investigated. Based on the Bayesian best-worst weighting and vector-based ranking methods, the normalized and weighted life cycle sustainability scores were used to prioritize the best process. Gasification-based technology was found superior than incineration-based technology, especially in the economic, techno-energetic, and social aspects. However, incinerated-based process with direct CO2 emissions performed better in the environmental aspects compared with the process integrating with carbon capture and utilization unit. Additional environmental burdens were brought to the system when incorporating the carbon capture and methanol synthesis process. Increased system complexity might bring unexpected environmental burdens, and sometimes even outweighed the benefits. Various weights were assigned to the multi-criteria decision-making model, and the gasification-based process consistently ranked first across all scenarios.

An efficient carbon-neutral power and methanol polygeneration system based on biomass decarbonization and CO2 hydrogenation: Thermodynamic and economic analysis

This study presents a novel approach to enhance methanol synthesis (MS) efficiency through integration with an MEA-based decarbonized biomass direct-fired power plant (BFPP-CCS). The integration optimizes the utilization of chemical energy from feedstocks by combining exothermic MS reactions with diverse thermal energies, which effectively captures chemical energy through synergistic utilization from MS and various thermal inputs. Gradual methanol conversion maximizes both its chemical and fuel properties. Through such integration, the enhancement of waste heat and purge gas utilization in MS and BFPP carbon capture processes results in a 3.42 MW improvement in power generation and a 26.0 % reduction in associated energy penalties from CCS. Analysis of a 150 kton/yr MS facility and a 35 MW BFPP-CCS demonstrates 2.87 % increase in overall efficiency and reduction in CCS heat consumption by 1.03 GJ/tCO2. Moreover, this integrated approach yields a 33.1 M$ NPV increase and 3.4 years DPP decrease, achieving carbon-neutral power and liquid fuels production. Sensitivity analysis indicates the polygeneration system performs optimally around 250 °C and 60 bar, with a preference for 0.90 MS recycle ratio. Additionally, factors such as carbon recovery rate, electrolysis efficiency, and fixed carbon content in biomass are quantitatively revealed as crucial for maximizing carbon mitigation potential.

Modeling biomimetic absorbent compounds for capturing carbon dioxide

Carbon capture and storage is a critical component of negative emission technologies for achieving economy-wide carbon neutrality to mitigate climate change and limit global temperature increase. Removal of CO2 can be undertaken after the standard pollution controls. Yet, the separation of CO2 from flue gas via CO2 capture processes is challenging because a high volume of gas must be treated, the CO2 is dilute, the flue gas is at atmospheric pressure, trace impurities can degrade capture media, and the captured CO2 must be compressed. We present a computational study of a novel family of biomimetic materials for such carbon capture processes based on the Crassulacean Acid Metabolism. Phosphoenolpyruvate serves as a template for designing similar molecules for use as CO2 solvents with designed thermochemical properties.

Design and analysis of negative CO2 emission methanol synthesis process incorporating green hydrogen and blue hydrogen

Methanol (MeOH) production by integration of green and blue hydrogen is evaluated herein. From 2018 to 2023, methanol demand increased by 3.6 % due to its use in various chemical industries as an eco-friendly fuel and as a method of transporting hydrogen and capturing renewable CO2. Moreover, due to the continual decrease in the cost of renewable energy, research into the use of green hydrogen from electrolysis is being conducted. Most of this research has focused on producing methanol from the green hydrogen obtained from proton-exchange membrane (PEM) electrolysis along with CO2 emissions from power plants. The present study examines processes based on oxyfuel combustion with oxygen obtained from either the PEM or an air separation unit (ASU) to produce methanol. By using oxyfuel combustion, the carbon capture process (which accounts for 30–50 % of the blue hydrogen cost) and pure (>98.75 %) 7.45 tCO2/tH2 can be obtained by separating H2O from the flue gas. By using the PEM, green hydrogen can capture 0.35 tCO2/tMeOH of external CO2. Furthermore, a carbon techno-economic analysis (CTEA) and a sensitivity analysis are conducted to evaluate the sustainability and feasibility of the proposed processes. As a result, the levelized cost of methanol (LCOM) is $373.91/tMeOH for the Blue process and $428.78/tMeOH for the Blue + Green process, each of which is below the current market price of $500/tMeOH. If the PEM price continues to decrease, and the carbon credit increases by €300/tCO2, after 2030, the Blue + Green process will become more lucrative than the Blue-only process. Thus, by considering the continuous decrease in renewable energy prices, the production of methanol via a hybrid Blue + Green process is suitable for a sustainable future.

Autoignition of methane and methane/hydrogen blends in CO2 bath gas

Combustion in large dilutions of carbon dioxide (CO2) has the potential to enable fossil fuel combustion with 100 % inherent carbon capture by simplifying the post-combustion carbon capture process into the facile separation of CO2 and water. Emerging technologies that employ CO2 as a bath gas, exemplified by the Allam-Fetvedt cycle, are gaining widespread international attention, evidenced by ongoing plant developments in both the United Kingdom and the United States. This study presents new ignition delay time datasets (IDTs) for the combustion of methane and methane/hydrogen blends at 20 and 40 bar. The chemical kinetics governing these distinct conditions are investigated by utilizing two distinct chemical kinetic mechanisms, namely UoS sCO2 2.0 and NUIGMech1.1. Ignition delay datasets of methane/hydrogen blends are presented alongside a detailed discussion of the effect CO2, in contrast to N2, on the combustion mechanism. The differences in kinetics of pure methane and pure hydrogen are also discussed with regards to key reactions and the radical pool. This study aims to elucidate the intricate interplay of factors shaping ignition dynamics in CO2– enriched environments.

Investigating different scenarios of integrating solar-assisted carbon capture with combined cycle power plant and water desalination system

In this work, an optimal algorithm-based integration of solar thermal energy with carbon capture and desalination processes were proposed. The stripper columns, identified as the most energy-consuming equipment, were designed with constant capacities to ensure practicality and applicability. Results show that, without affecting the power plant's efficiency, using a solvent tank as an energy storage system (scenario-2) increases total CO2 capture from 45 % to 98 % compared to a part-time solar power system (scenario-1). Utilizing two solvent tanks reduces waste energy from 87 % to 67 % (scenario-3), while achieving 100 % CO2 capture. Using three different stripper columns (scenario-4) lowers the levelized cost of energy by 20 %. Incorporating an additional multiple effect distillation system (scenario-5) reduces levelized cost of energy and energy loss by 26 % and 74 %, respectively. Approximately 28 % of the total solar energy collected (4.64 × 106 MWh) was used to capture 1.57 × 106 ton.year−1 of CO2. The remaining energy was used in desalination to produce 9.4 × 106 m³.year−1 of fresh water, increasing overall energy efficiency from 28 % to 81 %, and reducing waste energy to 0.88 × 106 MWh, just 26 % of previous scenarios' waste.

Membrane-based carbon capture for waste-to-energy: Process performance, impact, and time-efficient optimization

The energy crisis and rising waste production results in the need for more waste-to-energy solutions. However, capturing fossil-based carbon from waste incineration is crucial. The power consumption and overall impact of the carbon capture process are essential for the identification of the most suitable solution. The aim of this paper is to promote a time-efficient optimization, optimize a membrane-based post-combustion carbon capture process, and quantify its impacts on a waste-to-energy plant for various system configurations with different levels of CO2 recovery and purity. The proposed robust evaluation of the system with non-linearities resulted in the utilization of genetic algorithms with subsequent verification. Quantifying power consumption allows the comparison of different carbon capture technologies. The results confirm the importance of process optimization, show the influence of individual parameters, and quantify the disproportionate drop in power consumption with decreasing target CO2 recovery. The power consumption can be as low as 1.14 GJ/tonne of CO2 for CO2 purity of 95 % and recovery of 50 % and 1.66 GJ/tonne of CO2 for CO2 purity of 95 % and recovery of 90 %. The results also suggest that carbon neutrality can be achieved without compromising the R1 efficiency classification of energy recovery.

Comparison of Water- and Amine-Based Carbon Capture Processes for Air and Oxyfuel Combustion Technologies

Comparison of Water- and Amine-Based Carbon Capture Processes for Air and Oxyfuel Combustion Technologies

Mixed matrix membrane-based transport membrane condenser for improving the waste heat recovery performance in carbon capture process

Applying a transport membrane condenser (TMC) based on the hydrophilic ceramic membrane to recover the waste heat from the hot stripped gas could effectively reduce the heat consumption of CO2 regeneration in the carbon capture process. However, the high cost of ceramic membrane hindered the development of this technology. So in this study, a novel mixed matrix membrane (MMM) was proposed to replace the conventional ceramic membrane. MMMs were prepared by mixing carbon nanotube (CNT) into polyvinylidene fluoride (PVDF) casting solution through non-solvent phase separation method, and then were adopted for the waste heat recovery from the stripped gas featured with the molar ratio of CO2 to H2O(g) of 1:1∼1:2. Furthermore, the heat transfer resistance between the stripped gas and bypassed CO2-rich solvent when adopting MMMs was also analyzed through computational fluid dynamics (CFD). Results indicated that the addition of CNT or hydroxylated CNT (CNT-OH) effectively enhanced the heat recovery performance of MMMs. Moreover, MMMs prepared by mixing CNT-OH and hydroxylated boron nitride (BN–OH) further boosted the heat flux, achieving a maximum value of 23.72 MJ/(m2·h), representing an increase of up to 8.41 % compared to the original PVDF membrane without adding any additives. At the experimental conditions in this study, the gas-side individual thermal resistance dominated the overall thermal resistance and consequently the heat transfer performance. With an increase in the stripped gas flow rate, the ratio of individual heat transfer resistance of membrane to the overall resistance increased. Notably, the installation of baffles on the gas side of TMC reduced the gas-side thermal resistance. In this study, the optimum thermal conductivity of the organic membrane increased with the waste heat recovery scale from stripped gas. In addition, when the thermal conductivity of membrane exceeded 4 W/(m·°C), the increase in thermal conductivity on the waste heat recovery was not significant. This study confirmed the application potential of MMMs in the waste heat recovery.

Waste heat recovery in carbon capture process using a novel amphipathic inorganic membrane

To reduce the CO2 regeneration heat requirement in the CO2 chemical absorption process, a novel amphipathic ceramic membrane-based transport membrane condenser was developed in this study to act as a heat transfer medium in the rich solvent-split mechanism for enhancing the waste heat recovery performance from the stripped gas (i.e., mainly the gas mixture of CO2 and water vapor). Both hydrophobic and hydrophilic segments coexisted on one membrane surface of amphipathic ceramic membrane, while the other surface was totally hydrophilic. The surface characterization and waste heat recovery performance of the flat sheet amphipathic membrane were investigated, and the original hydrophilic ceramic membrane was adopted as the control. Results showed that the water contact angle with 108.9 ± 4° was screened for the hydrophobic surface of the ceramic membrane to achieve the best waste heat recovery performance. Additionally, the waste heat recovery performance of amphipathic membrane firstly increased and then dropped with an increase in the area ratio of hydrophobic surface to the total membrane surface. The maximum waste heat recovery of 13.39 MJ/(m2·h) was achieved at a hydrophobic area ratio of 37.5 % without segmenting by the hydrophilic surface, which was 5.6 % higher than that of the original hydrophilic ceramic membrane. Furthermore, the maximum water recovery of amphipathic membrane was 8.24 % higher than the original hydrophilic ceramic membrane. When the total area of hydrophobic surface was fixed, dividing the hydrophobic surface into two equally sized hydrophobic segments spaced by the hydrophilic segments could further improve the waste heat recovery performance of amphipathic membrane. This study might provide a new insight on improving the waste heat recovery performance of ceramic membrane.

Oxygen‐Stable Electrochemical CO2 Capture using Redox‐Active Heterocyclic Benzodithiophene Quinone

Electrochemical carbon capture offers a promising alternative to thermal amine technology, which serves as the traditional benchmark method for CO2 capture. Despite its technological maturity, the widespread deployment of thermal amine technologies is hindered by high energy consumption and sorbent degradation. In contrast, electrochemical methods, with their inherently isothermal operation, address these challenges, offering enhanced energy efficiency and robustness. Among emerging strategies, electrochemical carbon capture systems using redox‐active materials such as quinones stand out for their potential to capture CO2.However, their practical application is currently limited by their low stability in the presence of oxygen. We demonstrate that benzodithiophene quinone (BDT‐Q), a heterocyclic quinone, exhibits high stability in electrochemical carbon capture processes with oxygen‐containing feed gas. Conducted in a cyclic flow system with a simulated flue gas mixture containing 13% CO2 and 3.5% O2 for over 100 hours, the process demonstrates high oxygen stability with an electron utilization of 0.83 without significant degradation, indicating a promising approach for real world applications. Our study explores the potential of new heterocyclic quinone compounds in the context of carbon capture technologies.

Oxygen-Stable Electrochemical CO2Capture using Redox-Active Heterocyclic Benzodithiophene Quinone.

Electrochemical carbon capture offers a promising alternative to thermal amine technology, which serves as the traditional benchmark method for CO2capture. Despite its technological maturity, the widespread deployment of thermal amine technologies is hindered by high energy consumption and sorbent degradation. In contrast, electrochemical methods, with their inherently isothermal operation, address these challenges, offering enhanced energy efficiency and robustness. Among emerging strategies, electrochemical carbon capture systems using redox-active materials such as quinones stand out for their potential to capture CO2.However, their practical application is currently limited by their low stability in the presence of oxygen. We demonstrate that benzodithiophene quinone (BDT-Q), a heterocyclic quinone, exhibits high stability in electrochemical carbon capture processes with oxygen-containing feed gas. Conducted in a cyclic flow system with a simulated flue gas mixture containing 13% CO2and 3.5% O2for over 100 hours, the process demonstrates high oxygen stability with an electron utilization of 0.83 without significant degradation, indicating a promising approach for real world applications. Our study explores the potential of new heterocyclic quinone compounds in the context of carbon capture technologies.

Addressing small-scale temperature swing adsorption challenges using intensified fluidised bed technology for carbon capture process development

Polyethylenimine (PEI)-based adsorbents exhibit high CO2 capacities, making them potential candidates for mitigating unavoidable industrial CO2 emissions. However, desorption of CO2 from PEI, and from adsorbents in general, has received far less attention in the literature than adsorption. Whilst Temperature Swing Adsorption (TSA) is simple to conceptualise, it is difficult to implement in small-scale experiments in practice. Here we study the desorption characteristics of a commercial branched PEI adsorbent in a small-scale swirling fluidised bed reactor (TORBED) to improve the small-scale heat transfer rates. Our experimental results show that higher desorption temperatures, higher gas flow rates, and higher CO2 concentrations during adsorption can improve the desorption efficiency (defined as the amount of CO2 removed as a fraction of the initial amount adsorbed). In terms of kinetics, we found that the fractional order kinetic model provided the best fit to the PEI adsorbent, implying that this adsorbent involves multiple simultaneous molecular interactions, physisorption processes, and chemisorption processes, that cannot be described by simpler pseudo 1st or 2nd order models. Desorption rates in the TORBED in this study were 1 order of magnitude faster than fluidised beds, and 2–3 orders of magnitude faster than packed beds.