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Journal articlePan Z, Trusler JPM, Jin Z, et al., 2025,
Interfacial property determination from dynamic pendant-drop characterizations
, Nature Protocols, Vol: 20, Pages: 363-386, ISSN: 1750-2799The properties of the interface between materials have practical implications in various fields, encompassing capillary action, foam and emulsion stability, adhesion properties of materials and mass and heat transfer processes. Studying the dynamics of interfaces is also fundamental for understanding intermolecular interactions, change of molecular conformations and molecular aggregations. Pendant-drop tensiometry and its extension, the oscillating drop method, are simple, versatile methods used to measure surface tension, interfacial tension and interfacial rheological properties. These methods can, however, generate unreliable results because of inadequate material preparation, an incorrect calibration method, inappropriate selection of data for analysis, neglect of optical influences or operating the system outside the linear viscoelastic regime. In addition, many studies fail to report accurate uncertainties. This protocol addresses all these critical points and provides detailed descriptions of some operation tips relating to purifying methods for different kinds of material, the time frame for analyzing measurement data, the correction method for optical effects, implementation of the oscillating method with a common programmable pump and remedies for some common problems encountered during the measurement. Examples of interfacial tension measurements for two- and three-phase systems, as well as interfacial dilational modulus measurements for N2 and surfactant solutions, are provided to illustrate procedural details and results. A single measurement takes minutes to hours to complete, while the entire protocol, including the leak test, cleaning, repeated measurements and data analysis, may take several days.
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Journal articleBrotto JDO, Danaci D, Fennell PS, et al., 2025,
Enhancing low-carbon iron and steel production with torrefied biomass
, BIOMASS & BIOENERGY, Vol: 193, ISSN: 0961-9534- Cite
- Citations: 1
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Journal articleAzzan H, Gmyrek K, Danaci D, et al., 2025,
Effective macropore diffusivity of carbon dioxide on binderless pellets of Y-type zeolites
, Adsorption, Vol: 31, ISSN: 0929-5607The adsorption kinetics of carbon dioxide (CO2) in three cationic forms of binderless pellets of Y-types zeolites (H-Y, Na-Y, and TMA exchanged Na-Y) are studied using the zero-length column (ZLC) technique. The measurements were carried out at 288.15 K, 298.15 K and 308.15 K using different flowrates and an initial CO2 partial pressure of 0.10 bar – conditions representative of post-combustion CO2 capture applications. The mass transport within the adsorbent pellets was described using a 1-D Fickian diffusion model accounting for intra- and inter-crystalline mass transport. For the latter, the parallel pore model formulation was used to explicitly account for the adsorbent’s macropore size distribution in estimating the volume-averaged diffusivity of the gas. Experiments carried out using different carrier gases, namely helium and nitrogen, were used (i) to determine that these systems are macropore diffusion limited and (ii) to simplify the parameter estimation to a single parameter - the macropore tortuosity. The latter (τ = 1.3 − 2.5) was in good agreement with independent measurements using MIP (τ ≈ 1.7). The associated diffusion coefficient, Demac, was found to vary due to differences in the materials’ macropore size distributions and overall porosity. Upon combining the parallel pore model formulation with the temperature dependencies for the pore diffusivities derived from molecular theories of gases, we predict Demac ∝ Tb with b = [0.78 − 0.88] depending on the macropore size distribution. Notably, for the range of temperature tested in this study, Demac varies approximately linearly with temperature (b ≈ 1)– in contrast to the commonly reported correlation of b = 1.75, which may be more appropriate for systems where molecular diffusion dominates and Knudsen diffusion is negligible. The binderless pellets of Y-type zeolites studied exhibit generally higher values for the effective macropore diffus
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Journal articleKaerger J, Valiullin R, Brandani S, et al., 2025,
Diffusion in nanoporous materials with special consideration of the measurement of determining parameters (IUPAC Technical Report)
, Pure and Applied Chemistry, Vol: 97, Pages: 1-89, ISSN: 0033-4545The random motion (the diffusion) of guest molecules in nanoporous host materials is key to their manifold technological applications and, simultaneously, a ubiquitous phenomenon in nature quite in general. Based on a specification of the different conditions under which molecular diffusion in nanoporous materials may occur and of the thus resulting relevant parameters, a survey of the various ways of the measurement of the determining parameters is given. Starting with a condensed introduction to the respective measuring principles, the survey notably includes a summary of the various parameters accessible by each individual technique, jointly with an overview of their strengths and weaknesses as well as of the respective ranges of observation. The presentation is complemented by basic relations of diffusion theory and molecular modeling in nanoporous materials, illustrating their significance for enhancing the informative value of each measuring technique and the added value attainable by their combination. By providing guidelines for the measurement and reporting of diffusion properties of chemical compounds in nanopores, the document aims to contribute to the clarification and standardization of the presentation, nomenclature, and methodology associated with the documentation of diffusion phenomena in nanoporous materials serving for catalytic, mass separation, and other relevant purposes.
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Journal articleBukar I, Bell R, Muggeridge AH, et al., 2025,
Carbon Dioxide Migration Along Faults at the Illinois Basin-Decatur Project Revealed Using Time Shift Analysis of Seismic Monitoring Data
, GEOPHYSICAL RESEARCH LETTERS, Vol: 52, ISSN: 0094-8276- Cite
- Citations: 5
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Journal articleSkinner S, Shah N, Fan L, 2025,
Comparison of steam and dry reforming adsorption kinetics in solid oxide fuel cells
, Fuel -
Journal articleRovelli A, Kurotori T, Brodie J, et al., 2025,
Porosity-limited transport during two-phase surfactant/polymer floods in a layered sandstone
, Energy and Fuels, Vol: 39, Pages: 2471-2481, ISSN: 0887-0624Surfactant/polymer flooding presents itself as an attractive technique for the full utilization of current reservoirs given its potential to yield high oil recoveries. Despite this appeal, discrepancies between laboratory and field results exist and limit their industrial implementation. Within the scale-up process, corefloods serve as a key tool for the evaluation of the recovery potential; however, due to complexities in the fluid system itself, these are commonly performed on homogeneous core samples. To further understand this, we conduct a surfactant/polymer flood as a tertiary recovery method within a Nugget sandstone core. A notable feature of the chosen core is its stratified nature, with layers of high and low porosity characterized via X-ray CT. Via the use of direct imaging, coupled with a step tracer test, preferential flow paths and slow-to-ingress regions of the core are identified, information that is then coupled with the surfactant/polymer flood results to better understand the mechanisms at play. To better understand the influence of the structured heterogeneity present within the core, the results are compared to an analogous experiment within a homogeneous sandstone core. We note the inability of an oil bank to form and the comparatively larger variability of the recoveries between different porosity layers within the core. Lastly, we highlight how, despite a high overall recovery of 80%, inefficiencies in the displacement process are still present and only observable due to the direct imaging methodology implemented, ultimately showcasing its value in this context.
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Journal articleSaleh MA, Ryan MP, Trusler JPM, et al., 2025,
The interfacial processes controlling carbon dioxide mineralisation in magnesium and calcium silicates
, Fuel, Vol: 380, ISSN: 0016-2361Nanometre to micrometre scale interfacial processes control CO2 mineralisation in silicate rocks targeted for carbon sequestration. Understanding the chemical mechanisms prompted by the addition of CO2 into aqueous-rock systems is necessary to design and manage industrial scale mineralisation operations. This work presents a synthesis of the past two decades of research on chemical processes taking place at the solid mineral interface, and how they drive or inhibit ex-situ or in-situ mineralisation. Studies cited in this review focus on samples representative of mafic or ultramafic rocks, their constituent mineral phases, and the calcium silicate wollastonite. Key findings include 1) Mechanical passivation is not caused solely by silica formation, a variety of chemical species can inhibit reactions by forming pervasive layers, including the target carbonate phase. 2) The functionality of engineered carrier solutions primarily derives from sodium bicarbonate which provide a pH buffering effect, excess CO32– ions, and limit mass transport resistance from Si-rich passivating compounds. 3) Non-uniform mineralisation is exhibited in whole rocks and can be attributed to the inherent pore characteristics and heterogeneous distribution of grain sizes that produce micro-environments of preferential carbonation in natural mafic rock samples. 4) Thin water films facilitate a coupled dissolution-re-precipitation mechanism in water-bearing supercritical (CO2-rich) environments. 5) Mineralisation in both aqueous and supercritical CO2 systems generates product layers of comparable morphology, consisting of interstratified carbonate-silica growths. Yet, experiments involving a wet supercritical CO2 phase tend to generate carbonates at lower temperature conditions indicating enhanced reactivity or a more porous passivating layer.
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Journal articleKucherenko S, Giamalakis D, Shah N, 2025,
Application of global sensitivity analysis for identification of probabilistic design spaces
, International Journal for Uncertainty Quantification, Vol: 15, Pages: 17-25, ISSN: 2152-5099The design space (DS) is defined as the combination of materials and process conditions that provides assurance of quality for a pharmaceutical product. A model-based approach to identify a probability-based DS requires costly simulations across the entire process parameter space (certain) and the uncertain model parameter space and material properties space. We demonstrate that application of global sensitivity analysis (GSA) can significantly reduce model complexity and reduce computational time for identifying and quantifying a probabilistic DS by screening out nonimportant uncertain parameters. The novelty of this approach is that the use of an indicator function, which takes only binary values as a model function, allows application of a straightforward GSA based on Sobol' sensitivity indices and avoids using more costly Monte Carlo filtering or GSA for constrained problems. We consider a chemical reaction example to illustrate how this formulation results in a model reduction and a significant decrease of model runs.
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Conference paperDarraj N, Manoorkar S, Spurin C, et al., 2025,
Pore-Scale Investigation of Heterogeneity Effects on Saturation and Trapping for Geological CO2 Storage in Dolomites
The effectiveness of subsurface CO<inf>2</inf> storage is intrinsically tied to our understanding of how geological heterogeneity-particularly at the pore scale-influences multiphase flow behaviour. This is especially true in carbonate formations, where the inherent complexity and spatial variability of pore structures can significantly alter fluid displacement dynamics, trapping efficiency, and overall storage performance. Unlike sandstone rocks, carbonates often exhibit a wide range of pore types, each contributing differently to connectivity and capillary forces. These small-scale variations in pore morphology and wettability can result in highly localized saturation patterns, which in turn govern the CO<inf>2</inf> pathways during injection and post-injection phases. In this study, 3D micro-CT imaging at a voxel size of 5.6 μm was employed to examine the Edwards Brown dolomite, capturing pore-scale heterogeneities that are typically unresolved in core-scale experiments. The imaging resolution enables direct observation of both the small features and larger macropore networks, offering a more complete representation of the carbonate pore system. The resulting pore-scale analysis reveals that spatial variations in porosity and capillary entry pressure lead to selective phase invasion and heterogeneous saturation distributions in both the wetting (brine) and non-wetting (decane was used as an analogue fluid) phases. These conditions generate discontinuous and tortuous flow pathways, which disrupt the assumption of uniform displacement typically embedded in upscaled reservoir models. This challenges conventional upscaling approaches that often homogenize heterogeneity, potentially overlooking the nuanced mechanisms that influence CO<inf>2</inf> immobilization. By quantifying these effects, the study provides a framework for refining predictive models that account for heterogeneity-driven flow modifications-offering more realist
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Journal articleRovelli A, Brodie J, Rashid B, et al., 2025,
Multimodality imaging of fluid saturation and chemical transport for two-phase surfactant/polymer floods in porous rocks
, Transport in Porous Media, Vol: 152, ISSN: 0169-3913Multicomponent, two-phase flow in porous media is a problem of practical relevance that remains difficult to study experimentally. Advanced methodologies are needed that enable the monitoring of both the saturation of each fluid phase within the pore space and the concentration of the chemical species within the fluids. We present an approach based on multimodality imaging and apply it to the case study of surfactant/polymer flooding in a sandstone for enhanced oil recovery. X-ray computed tomography and positron emission tomography (PET) are applied for the asynchronous acquisition of dynamic profiles of saturations (aqueous and oleic) and of the solute concentration within the surfactant/polymer slug, respectively. This complementary dataset enables precise investigation of the evolution of both the oil bank and the induced mixing at its rear arising from the surfactant/polymer flooding process. The dilution index, intensity of segregation and the spreading length are used to quantify the degree of mixing within the surfactant/polymer slug as a function of time from the spatial structure of the solute concentration field. Relative to the single-phase flow scenario, a threefold increase in dispersivity is observed. We demonstrate that mixing is systematically overestimated if only the PET dataset is used—highlighting the importance of implementing multimodality imaging. We also show that the advection–dispersion equation model, parameterised using the dispersivity derived from the experiments, provides reasonable estimates for the rate of both mixing and spreading.
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Journal articleLi C, Shah N, Li Z, et al., 2024,
Modelling of wind and solar power output uncertainty in power systems based on historical data: A characterisation through deterministic parameters
, JOURNAL OF CLEANER PRODUCTION, Vol: 484, ISSN: 0959-6526 -
Journal articleIbrahim D, Giarola S, Panoutsou C, et al., 2024,
Modelling and optimisation of low-indirect land used change biomass supply chains
, Bioresource Technology Reports, Vol: 28, ISSN: 2589-014XBiofuels derived from biomass feedstocks produced following the implementation of measures that avoid indirect land used change (ILUC) have the potential of reducing dependency on fossil-based fuels without competing with food value chain. This work develops a model- and optimisation-based methodologies that address challenges related to the production of low-ILUC biomass feedstocks. Case studies investigated include planning of Iow-ILUC biomass feedstock production, biomethane production using low-ILUC biomass feedstocks, integrated production of first generation (1G) and second generation (2G) bioethanol using Miscanthus, and production of hydrotreated vegetable oil (HVO) using castor seeds. Analysis of results show that farmers interested in these models are recommended to sell low-ILUC biomass such as soybean, wheat and brassica above the breakeven price to avoid losses. The estimated selling price for the three crops are 362 €/t, 321 €/t and 381 €/t respectively. To meet the demand of 40,000 t/yr of 2G bioethanol in the UK, approximately 17,094 ha of underutilised land is required. Policy makers should consider options to support alternatives such as retrofitting, and inter-cropping to avoid or mitigate ILUC.
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Journal articleMuazu RI, Yaseneva P, Shah N, et al., 2024,
Life cycle sustainability assessment of bioderived advanced materials: A state-of-the-art Review
, Journal of Environmental Chemical Engineering, Vol: 12, ISSN: 2213-3437Bioderived advanced materials possess unique functional properties together with a potential to improve environmental sustainability. This study conducts a critical review of literature on life cycle sustainability assessment (LCSA) of biobased higher-value products with emphasis on bioderived advanced materials including nanocelluloses (cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs)), and carbon materials (lignin carbon fibre (LCF) and hard carbons (HCs)). The environmental impact of CNCs production from Kraft and dissolving pulp via sulfuric acid hydrolysis is significantly influenced by the end-of-life (EoL) management of sulfuric acid either via recycling or neutralisation with sodium hydroxide. This highlights trade-offs and the need for more sustainable EoL options. Likewise, the production of CNFs using Kraft, dissolving and sulfite pulp via 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidation followed by mechanical homogenisation or sonication indicates higher environmental impact compared with enzymatic hydrolysis. Sustainability of LCF is significantly influenced by the lignin recovery and fabrication technique, thus low-cost sustainable solvents and pathways for LCF production should be prioritised. Existing studies indicate the advantages of HCs production via hydrothermal carbonisation (HTC). However, the sustainability performance of HC is highly influenced by the carbon yield and electrochemical performance, therefore, a comprehensive optimisation of the operating variables is crucial for advancing the sustainability and development of bioderived HCs for energy applications. Significant methodological disparities were observed among the reviewed studies, leading to variations in assessment outcomes. Economic and environmental assessments are frequently presented as standalone results even for combined assessments, which further stresses the inherent heterogeneity across assessment tools.
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Journal articleHecht MH, Krevor S, Yen AS, et al., 2024,
Mineral alteration in water-saturated liquid CO<sub>2</sub> on early Mars
, NATURE GEOSCIENCE, Vol: 17, Pages: 1204-1208, ISSN: 1752-0894 -
Journal articleNedoma M, Azzan H, Yio M, et al., 2024,
The effect of adsorbent shaping on the equilibrium and kinetic CO<sub>2</sub> adsorption properties of ZIF-8
, MICROPOROUS AND MESOPOROUS MATERIALS, Vol: 380, ISSN: 1387-1811 -
Journal articleLi C, Shah N, Li Z, et al., 2024,
Decoupling framework for large-scale energy systems simultaneously addressing carbon emissions and energy flow relationships through sector units: a case study on uncertainty in China's carbon emission targets
, Computers and Chemical Engineering, Vol: 191, ISSN: 0098-1354The energy system requires meticulous planning to achieve low-carbon development goals cost-effectively. However, optimizing large-scale energy systems with high spatial-temporal resolution and a rich variety of technologies has always been a challenge due to limited computational resources. Therefore, this study proposes a soft-linkage framework to deconstruct large-scale energy system optimization models based on sectors while ensuring the total carbon emission limit and the electricity supply-demand balance. Using China's energy system as a case study, the impact of uncertainty on emission reduction targets is analyzed. A long-term emission target curve is only described by the total carbon budget and its temporal distribution. Results show that different carbon budget time series can lead to total transition cost variations of up to nearly 100 trillion yuan. Moreover, although a lower carbon budget would increase the total cumulative transition cost quadratically, excessively high carbon budgets raise national natural gas demand, threatening energy security.
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Journal articleYang H, Zhao M, Lv Y, et al., 2024,
Upgraded syngas through selective partial oxidation of tar using Ni-doped LaFeO3 with tuned oxidation potential
, CHEMICAL ENGINEERING JOURNAL, Vol: 500, ISSN: 1385-8947- Cite
- Citations: 2
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Journal articleWedler C, Ferre A, Azzan H, et al., 2024,
Binary adsorption equilibria of three CO2+CH4 mixtures on NIST reference zeolite Y (RM 8850) at temperatures from 298 to 353 K and pressures up to 3 MPa
, Journal of Chemical and Engineering Data, Vol: 69, Pages: 4216-4229, ISSN: 0021-9568Adsorption equilibria of CO2, CH4, and their mixtures were measured on binderless pellets of NIST reference zeolite NaY (RM 8850) using a static gravimetric setup. The unary adsorption isotherms are reported at temperatures from 298 to 393 K up to a pressure of 3 MPa and compare favorably with independent results on RM 8850 powder. The competitive adsorption measurements were performed at temperatures from 298 to 353 K and up to 3 MPa for three premixed gas mixtures with CO2 molar feed compositions of 0.25, 0.50, and 0.75. The results constitute the first competitive adsorption dataset reported for any of the NIST reference materials. RM 8850 shows a strong selectivity for CO2 adsorption toward CH4. The experimental unary and binary adsorption isotherms are accurately modeled using the simplified statistical isotherm model (SSI). Notably, the agreement with the model improves only slightly (and within experimental uncertainties) when the whole dataset is used for parameter fitting as opposed to only using the unary data.
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Journal articleNguyen T-T-G, Wedler C, Pohl S, et al., 2024,
Experimental speed-of-sound data and a fundamental equation of state for normal hydrogen optimized for flow measurements
, The Journal of Chemical Thermodynamics, Vol: 198, ISSN: 0021-9614Speed-of-sound measurements for normal hydrogen (n-hydrogen) in a temperature range between 273 K and 323 K were carried out using a cylindrical resonator at pressures from 1 MPa to 10 MPa and a dual-path pulse-echo system at pressures from 20 MPa to 100 MPa. The relative expanded uncertainties (k = 2) of the measurements range from 0.04 % to 0.08 %. Based on these measurements and data from the literature, a fundamental equation of state (EOS) was developed for the calculation of thermodynamic properties of n-hydrogen. It is expressed in terms of the Helmholtz energy with the independent variables temperature and density. Due to the fundamental nature of the Helmholtz energy, the equation can be used to calculate all thermodynamic properties from one mathematical expression. In contrast to typical EOS of this kind, the boundary conditions are somewhat more restricted. The relevant temperature and pressure ranges are limited to typical pipeline and storage conditions of gaseous hydrogen, including temperatures relevant for measurements with critical nozzles (140 K to 370 K with pressures up to 100 MPa). The computational speed for the implementation of the correlation in measurement sensors plays a superior role. Therefore, the equation is kept as short as possible, and exponents are of integer-kind. Most of the experimental data are still reproduced within their measurement uncertainties.
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Journal articleLeonzio G, Triantafyllou N, Shah N, 2024,
A sustainability analysis for a circular power-to-liquid process for diesel production
, Sustainable Production and Consumption, Vol: 51, Pages: 657-669, ISSN: 2352-5509The power-to-liquid process is a key emerging technology for fossil-free raw materials and energy systems. In this work, techno-economic, and environmental analyses are carried out for a Fischer-Tropsch process producing diesel and characterized by the recovery of carbon dioxide through direct air capture, as well as the recovery of water and heat. The main aim of this study is to verify with respective analyses the circularity of carbon dioxide, water and heat and to conduct a global sensitivity analysis to identify significant system process parameters for some key performance indicators, when changed simultaneously. Despite the proven circularity based on material and energy balances ensuring a power-to-liquid efficiency of about 44 %, results show that the water closed loop is not ensured from an environmental point of view. The water consumption impact category is, in fact, a positive value (0.58–0.74 m3depriv/kgdiesel), while the climate change impact category is a negative value (−1.22 to −0.28 kgCO2eq/kgdiesel). A heat closed loop is attained according to the pinch analysis. The diesel production cost is competitive with the market price (1.76 and 2.07 $/literdiesel respectively when solar and wind energy are used). Regarding the sensitivity analysis, it is found that only costs and efficiency depend on the geographic location of the plant, in contrast to other key performance indicators. Overall, an additional optimization of the process is hence required to ensure a closed water loop from an environmental point of view and reduce further the production cost.
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Journal articleSaleh MA, Shiel H, Ryan MP, et al., 2024,
Enhanced Olivine Reactivity in Wet Supercritical CO<sub>2</sub> for Engineered Mineral Carbon Sequestration
, ENERGY & FUELS, Vol: 38, Pages: 21028-21041, ISSN: 0887-0624 -
Journal articleNarciso CRH, Martinez CG, O'Connell B, et al., 2024,
Thermophysical behavior of carbonated aqueous solutions containing monoethanolamine and degradation products
, Journal of Chemical and Engineering Data, Vol: 69, Pages: 3435-3449, ISSN: 0021-9568The impact of the degradation of monoethanolamine (MEA) on the physicochemical properties of the solvent is experimentally characterized. Based on the identification of three main degradation products of MEA: oxazolidine-2-one (OZD), N-(2-hydroxyethyl)ethylenediamine (HEEDA), and 1-(2-hydroxyethyl)-2-imidazolidinone (HEIA), new measurements for the density, surface tension, and viscosity of partially carbonated solutions containing water, MEA and those products were conducted at different MEA/degradation product molar ratios. The experiments covered a temperature range from 298.15 to 353.15 K at atmospheric pressure. The more stable and impactful degradation product, HEIA, was analyzed separately to determine its vapor pressure, as well as the density and viscosity of aqueous solutions with HEIA mass fractions of 100, 75, 50, and 25% in the same temperature range. The reported data demonstrate the difference in the performance of aqueous MEA solutions containing degradation products as compared to a fresh solution. This aspect is crucial for understanding the impact and effectiveness of postcombustion CO2 capture using aqueous amine systems in an industrial setting.
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Journal articleAi L, Maitland GC, Hellgardt K, 2024,
Formation and phase equilibria of gas hydrates confined in hydrophobic nanoparticles
, Chemical Engineering Science, Vol: 298, ISSN: 0009-2509The promotion of gas hydrate formation is of fundamental importance to facilitate its great potential applications in, for example, gas separation, transportation and energy storage. The employment of Dry Water (DW), which is a powdery Pickering system composed of macro water droplets surrounded by stabilising hydrophobic nanoparticles, is considered an effective method for enhancing hydrate formation. The promotion mechanism underlying this observation, however, has yet to be well understood. In this work, the effect of DW on both formation kinetics and thermodynamic stability of gas hydrates was investigated using a micro differential scanning calorimetry (µDSC) in CH4 and CO2 hydrate systems, using two different hydrophobic nanoparticles. Distinctly shorter induction times and higher conversion ratios were observed for DW compared to bulk water. The DW system stabilised by more hydrophobic nanoparticles showed benefits in accelerating nucleation, while the other system, which consisted of smaller DW droplets, led to a superior enhancement of hydrate growth. Besides the effect on formation kinetics, it was also noted that DW influenced the µDSC hydrate dissociation peak characteristics, including melting points and melting peak shapes. This phenomenon suggested that the centre- and surface-droplet hydrates in DW may have different structures, due to the “hydrophobic effect” of the nanoparticles structuring the near-surface water, so exhibiting melting points corresponding to bulk hydrate or to a more structured surface hydrate (with raised melting point), respectively. To support this “hydrophobic effect” hypothesis, a series of hydrate and ice formation experiments were conducted in porous media having different hydrophobicity, the results of which demonstrated that hydrates adjoining confined hydrophobized surfaces, in other systems similar to DW, also displayed higher melting temperatures.
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Journal articleStrunge T, Küng L, Sunny N, et al., 2024,
Finding least-cost net-zero CO2 strategies for the European cement industry using geospatial techno-economic modelling
, RSC Sustainability, Vol: 2, Pages: 3054-3076, ISSN: 2753-8125Cement production is responsible for approximately 7% of anthropogenic CO2-equivalent (CO2e) emissions, while characterised by low margins and the highest carbon intensity of any industry per unit of revenue. Hence, economically viable decarbonisation strategies must be found. The costs of many emission reduction strategies depend on geographical factors, such as plant location and proximity to feedstock or on synergies with other cement producers. The current literature lacks quantification of least-cost decarbonisation strategies of a country or region's total cement sector, while taking stock of these geospatial differences. Here, we quantify which intervention ensembles could lead to least-cost, full decarbonisation of the European cement industry, for multiple European regions. We show that least-cost strategies include the use of calcined clay cements coupled with carbon capture and storage (CCS) from existing cement plants and direct air capture with carbon storage (DACCS) in locations close to CO2 storage sites. We find that these strategies could cost €72–€75 per tonne of cement (tcement−1, up from €46–€51.5 tcement−1), which could be offset by future costs of cement production otherwise amounting to €105–€130 tcement−1 taking the cost of CO2e emission certificates into account. The analysis shows that for economically viable decarbonisation, collaborative and region-catered approaches become imperative, while supplementary cementitious materials including calcined clays have a key role.
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Journal articleEluwah C, Fennell PS, 2024,
Novel carbon-free innovation in centralised ammonia cracking for a sustainable hydrogen economy: the hybrid air-volt ammonia cracker (HAVAC) process
, Energy Advances, Vol: 3, Pages: 2627-2647, ISSN: 2753-1457The Hybrid Air-Volt Ammonia Cracker (HAVAC) represents a novel approach to centralised ammonia cracking for hydrogen production, enhancing both efficiency and scalability. This novel process integrates renewable electricity and autothermal operation to crack blue or green ammonia, achieving a high thermal efficiency of 94% to 95%. HAVAC demonstrates impressive ammonia conversion rates up to 99.4% and hydrogen yields between 84% and 99.5%, with hydrogen purity of 99.99% meeting ISO 14687:2019 standards.Key innovations include the process's flexibility to operate in three modes: 100% renewable electricity, 100% air autothermal, or a hybrid approach. This versatility optimizes energy use and adapts to varying conditions. The Gas Heated Cracker (GHC) within HAVAC efficiently reduces energy demands by utilizing waste heat.Modelled using the Aspen Plus Simulator and validated against experimental data, HAVAC's economic analysis indicates a levelized cost of hydrogen (LCOH) between $3.80/kg-H₂ and $6.00/kg-H₂. The process's environmental benefits include reduced greenhouse gas emissions and effective NOx waste management. Future research will focus on scaling up, reducing ammonia feed cost, optimizing catalysts, and enhancing waste management. HAVAC offers substantial promise for advancing hydrogen production and supporting a sustainable, carbon-free hydrogen economy. The technical and economic data generated by this analysis will assist decision-makers and researchers in advancing the pursuit of a carbon-free hydrogen economy.
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Journal articleWard A, Papathanasiou M, Pini R, 2024,
The impact of design and operational parameters on the optimal performance of direct air capture units using solid sorbents
, Adsorption, Vol: 30, Pages: 1829-1848, ISSN: 0929-5607Direct capture of CO2 from ambient air is technically feasible today, with com mercial units already in operation. A demonstrated technology for achievingdirect air capture (DAC) is chemical separation of CO2 in a steam-assistedtemperature-vacuum swing adsorption (S-TVSA) process. However, the poten tial to develop scalable solutions remains high, requiring a detailed understandingof the impact of both process design and operation on the performance of theDAC unit. Here, we address this knowledge gap by presenting a state-of-the-artprocess simulation tool for the purification of CO2 from ambient air by a 5-stepS-TVSA process. By considering the benchmark adsorbent APDES-NFC, we con duct multi-objective productivity/energy usage optimization of the DAC unit,subject to the requirement of producing a high purity CO2 product (≥95%).For the base case scenario, we find a maximum productivity of Prmax = 6.20kg/m3/day and a minimum specific equivalent work of WEQ,min = 1.66 MJ/kg.While in reasonable agreement with published data, our results indicate thatthe description of both competitive adsorption and adsorption kinetics are keyfactors in introducing uncertainty in process model predictions. We also demon strate that the application of formal optimization techniques, rather than designheuristics, is central to reliably assess the process performance limits. We identitythat system designs employing moderate CO2 sorption kinetics and contactorswith low length-to-radius ratios yield the best performance in terms of systemproductivity. Finally, we find that moderate-high ambient relative humidities (50-75%) offer significantly favourable performance, and that a wide range of feed temperatures (5-30oC) can be accommodated via process optimization withouta significant impact on performance.
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Journal articlevan de Berg D, Shah N, del Rio-Chanona EA, 2024,
Hierarchical planning-scheduling-control — Optimality surrogates and derivative-free optimization
, Computers and Chemical Engineering, Vol: 188, ISSN: 0098-1354Planning, scheduling, and control typically constitute separate decision-making units within chemical companies. Traditionally, their integration is modelled sequentially, but recent efforts prioritize lower-level feasibility and optimality, leading to large-scale, potentially multi-level, hierarchical formulations. Data-driven techniques, like optimality surrogates or derivative-free optimization, become essential in addressing ensuing tractability challenges. We demonstrate a step-by-step workflow to find a tractable solution to a tri-level formulation of a multi-site, multi-product planning-scheduling-control case study. We discuss solution tractability-accuracy trade-offs and scaling properties for both methods. Despite individual improvements over conventional heuristics, both approaches present drawbacks. Consequently, we synthesize our findings into a methodology combining their strengths. Our approach remains agnostic to the level-specific formulations when the linking variables are identified and retains the heuristic sequential solution as fallback option. We advance the field by leveraging parallelization, hyperparameter tuning, and a combination of off- and on-line computation, to find tractable solutions to more accurate multi-level formulations.
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Journal articleSmith A, Hampson G, Krevor S, 2024,
Global analysis of geological CO2 storage by pressure-limited injection sites
, International Journal of Greenhouse Gas Control, Vol: 137, ISSN: 1750-5836Limiting global warming to a 2 °C rise may require large-scale deployment of carbon capture and storage (CCS). Due to the key role CCS plays in integrated assessment models of climate change mitigation, it is important that fundamental physical constraints are accounted for. We produce a global estimate of CO2 storage resource that accounts for pressure-limits within basin-scale reservoir systems. We use a dynamic physics model of reservoir pressurisation that is sufficiently simple to be incorporated into energy systems models. Our estimates address regionally inconsistent methodologies and the general lack of consideration for pressure limitations in global storage resource estimates. We estimate a maximum pressure-limited resource base and explore scenarios with different injection patterns, and scenarios where the extent of CCS deployment is limited by the history of regional hydrocarbon exploration and the readiness of countries for deployment. The maximum pressure-limited global storage achievable after thirty years of injection is 3640GtCO2 (121GtCO2yr-1), increasing to 5630GtCO2 (70 GtCO2yr-1) at the end of the century. These represent an update to volumetric-based estimates that suggest in excess of 10,000Gt of storage resource available. When CCS deployment is limited to the top ten countries ranked by the GCCSI Storage Readiness Index, our maximum storage estimate decreases to 780GtCO2 (26GtCO2yr-1) at the mid-century and 1177GtCO2 (15GtCO2yr-1) at the end of the century. These latter results fall within the range of projected deployment by the IPCC and IEA and suggest that reservoir pressurisation will limit CCS deployment if development does not rapidly expand beyond the current implementation.
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Journal articleZhang Y, Jackson C, Krevor S, 2024,
The feasibility of reaching gigatonne scale CO<sub>2</sub> storage by mid-century
, NATURE COMMUNICATIONS, Vol: 15
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