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  • Conference paper
    Klink S, Wedler C, Trusler J, Richter Met al., 2023,

    Fueling the future: Density, viscosity, and speed of sound measurements of Oxymethylethers at temperatures from (298 to 423) K and pressures from (0.1 to 100) MPa

    , 22nd European Conference on Thermophysical Properties
  • Journal article
    Zhang Z, Wong JJ, Scott SA, Fennell PSet al., 2023,

    Spouted fluidised bed reactor for kinetic measurements of the reduction of Fe2O3 in a CO/CO2 atmosphere part II: An extended random pore model for solid-state diffusion

    , CHEMICAL ENGINEERING RESEARCH & DESIGN, Vol: 194, Pages: 597-609, ISSN: 0263-8762
  • Journal article
    Demirdesen D, Wedler C, Low RE, Trusler JPMet al., 2023,

    Speed of sound in gaseous 1,1-difluoroethene (R1132a) at temperatures between 193 K and 383 K at pressures up to 3 MPa

    , International Journal of Thermophysics, Vol: 44, Pages: 1-15, ISSN: 0195-928X

    The speed of sound in gaseous 1,1-difluoroethene (refrigerant R1132a) was measured at temperatures between 193 K and 383 K at pressures up to the lesser of approximately 85 % of the vapour pressure and 3 MPa. The measurements were carried out using a bespoke cylindrical acoustic resonator. The acoustic path length of the resonator was calibrated as a function of temperature by measuring resonance frequencies of the cavity filled with nitrogen gas. The measurements on nitrogen also served to validate the measurement system. The expanded relative uncertainty of the speed of sound in 1,1-difluoroethene at 95% probability was estimated to be 0.021 %. Comparing the results with a preliminary equation of state for 1,1-difluoroethene shows deviations within ± 0.3 %.
  • Journal article
    O'Dwyer E, Kerrigan E, Falugi P, Zagorowska M, Shah Net al., 2023,

    Data-driven predictive control with improved performance using segmented trajectories

    , IEEE Transactions on Control Systems Technology, Vol: 31, Pages: 1355-1365, ISSN: 1063-6536

    A class of data-driven control methods has recently emerged based on Willems' fundamental lemma. Such methods can ease the modelling burden in control design but can be sensitive to disturbances acting on the system under control. In this paper, we extend these methods to incorporate segmented prediction trajectories. The proposed segmentation enables longer prediction horizons to be used in the presence of unmeasured disturbance. Furthermore, a computation time reduction can be achieved through segmentation by exploiting the problem structure, with computation time scaling linearly with increasing horizon length. The performance characteristics are illustrated in a set-point tracking case study in which the segmented formulation enables more consistent performance over a wide range of prediction horizons. The computation time for the segmented formulation is approximately half that of an unsegmented formulation for a horizon of 100 samples. The method is then applied to a building energy management problem, using a detailed simulation environment, in which we seek to minimise the discomfort and energy of a 6-room apartment. With the segmented formulation, a 72% reduction in discomfort and 5% financial cost reduction is achieved, compared to an unsegmented formulation using a one-day-ahead prediction horizon.
  • Journal article
    Pan Z, Trusler JPM, 2023,

    Experimental and modelling study of the interfacial tension of (n-decane plus carbon dioxide plus water) in the three phase region

    , Fluid Phase Equilibria, Vol: 568, Pages: 1-11, ISSN: 0378-3812

    The interfacial tensions (IFTs) between hydrocarbon-, water- and CO2-rich phases are important in the processes of carbonated water injection for enhanced oil recovery and carbon geological storage. In this work, the IFTs between decane-rich and water-rich phases, in the presence of the third CO2-rich phase, were measured by the pendant drop method and modelled with the density gradient theory at temperatures from 298.15 K to 353.15 K and at pressures up to the critical point pressure of (CO2 + decane) (maximum 11 MPa at 353 K). The dynamic IFT decreased over time due to CO2 adsorption on the interface and mass transfer into the decane-rich drop until equilibrium was reached. As expected, the equilibrium IFTs were observed to decrease with increasing pressure. At low pressures, the equilibrium IFTs decreased with increasing temperature while, at high pressures, the reverse was observed. By comparing the IFTs of ternary (decane + CO2 + H2O) system with those of binary (decane + H2O) system, it was found that CO2 could reduce system IFT, for example by 15.2 mN/m at T = 333 K and p = 10 MPa. The extent of reduction depends on the solubility of CO2 in the liquid phases and the extent of adsorption at the interface. Furthermore, the equilibrium IFT was found to be linearly dependant on the CO2 concentration in the water-rich phase isothermally, and an empirical relation was developed with an average absolute deviation of 0.3 mN/m. Density gradient theory coupled with the volume translated CPA equation of state was found to provide an accurate description of the IFTs with an average absolute deviation of 0.8 mN/m, proving its capability of predicting IFTs of (alkane + CO2 + water) in the three-phase region. The density profile in the interfacial region is also demonstrated. There is an enrichment of CO2 molecules at the interface and the enrichment is more pronounced with increasing pressure or decreasing temperature.
  • Journal article
    Wedler C, Trusler JPM, 2023,

    Review of density and viscosity data of pure fatty acid methyl ester, ethyl ester and butyl ester

    , Fuel, Vol: 339, Pages: 1-13, ISSN: 0016-2361

    Biodiesel fuels consist of a mixture of different fatty acid esters. The thermophysical properties of the fatty acid esters are decisive for combustion and storage. Especially density and viscosity influence, e.g., energy density, spray quality and lubrication in a diesel engine. For some of the fatty acid esters, several studies on thermophysical properties can be found in the literature in a wide pressure and a reasonably wide temperature range. However, for several of the esters, data at high pressures as well as low and high temperatures are missing; for some of them, even data at atmospheric pressure are missing. To develop thermophysical property models, comprehensive sets of experimental density and viscosity data are required. Therefore, this work reviews the available experimental data on density and viscosity of fatty acid methyl, fatty acid ethyl and fatty acid butyl esters. Data gaps present in the literature are illuminated. 16 different esters are considered for each of the three ester families. The homologous series of saturated esters from hexanoate (C6:0) to octadecenoate (C18:0) as well as the unsaturated esters oleate (C18:1), linoleate (C18:2), and linolenate (C18:3) are included. In addition, an overview of generalised models for the description of density and viscosity at elevated pressure is given.
  • Conference paper
    Cooper J, Bird M, Acha S, Amrit P, Chachuat B, Shah N, Matar Oet al., 2023,

    The Carbon Footprint of a UK Chemical Engineering Department – The Case of Imperial College London

    , The 30th CIRP Life Cycle Engineering Conference, Publisher: Elsevier, Pages: 444-449, ISSN: 2212-8271

    As the UK strives towards net-zero it is important that all sectors, including Higher Education, take immediate measures to cut their greenhouse gas emissions. The greenhouse gases emitted by different Higher Education institutions are studied and are shown to be large. However, these studies are based on aggregated data, and it is therefore uncertain how effective institute-wide policies to cut emissions are at department level. Herein, we present a generic framework for university departments to calculate their carbon footprint considering Scope 1, 2 and 3 emissions. We estimate the carbon footprint of the Chemical Engineering Department at Imperial College London to be 7,620 and 8,330 tCO2eq in 2018/19 and 2019/20, respectively. Scope 3 emissions account for 54% of the Department's emissions with Scope 1 and 2 accounting for the remaining 46%. Scope 3 emissions are largely driven by purchased goods and travel, while Scope 1 emissions are predominantly from electricity usage.
  • Journal article
    Bikane K, Yu J, Shah SM, Long X, Paterson N, Pini R, Millan Met al., 2023,

    High pressure CO<sub>2</sub> gasification of Morupule coal: Kinetics and morphological development of chars

    , CHEMICAL ENGINEERING JOURNAL, Vol: 462, ISSN: 1385-8947
    • Cite
    • Citations: 12
  • Journal article
    Nguyen HGT, Toman B, van Zee RD, Prinz C, Thommes M, Ahmad R, Kiska D, Salinger J, Walton IM, Walton KS, Broom DP, Benham MJ, Ansari H, Pini R, Petit C, Adolphs J, Schreiber A, Shigeoka T, Konishi Y, Nakai K, Henninger M, Petrzik T, Kececi C, Martis V, Paschke T, Mangano E, Brandani Set al., 2023,

    Reference isotherms for water vapor sorption on nanoporous carbon: results of an interlaboratory study

    , Adsorption, Vol: 29, Pages: 113-124, ISSN: 0929-5607

    This paper reports the results of an international interlaboratory study sponsored by the Versailles Project on Advanced Materials and Standards (VAMAS) and led by the National Institute of Standards and Technology (NIST) on the measurement of water vapor sorption isotherms at 25 °C on a pelletized nanoporous carbon (BAM-P109, a certified reference material). Thirteen laboratories participated in the study and contributed nine pure water vapor isotherms and four relative humidity isotherms, using nitrogen as the carrier gas. From these data, reference isotherms, along with the 95% uncertainty interval (Uk=2), were determined and are reported in a tabular format.
  • Journal article
    Joewondo N, Garbin V, Pini R, 2023,

    Experimental evidence of the effect of solute concentration on the collective evolution of bubbles in a regular pore-network

    , CHEMICAL ENGINEERING RESEARCH & DESIGN, Vol: 192, Pages: 82-90, ISSN: 0263-8762
  • Journal article
    van de Berg D, Petsagkourakis P, Shah N, del Rio-Chanona EAet al., 2023,

    Data-driven coordination of subproblems in enterprise-wide optimization under organizational considerations

    , AIChE Journal, Vol: 69, Pages: 1-24, ISSN: 0001-1541

    While decomposition techniques in mathematical programming are usually designed for numerical efficiency, coordination problems within enterprise-wide optimization are often limited by organizational rather than numerical considerations. We propose a “data-driven” coordination framework which manages to recover the same optimum as the equivalent centralized formulation while allowing coordinating agents to retain autonomy, privacy, and flexibility over their own objectives, constraints, and variables. This approach updates the coordinated, or shared, variables based on derivative-free optimization (DFO) using only coordinated variables to agent-level optimal subproblem evaluation “data.” We compare the performance of our framework using different DFO solvers (CUATRO, Py-BOBYQA, DIRECT-L, GPyOpt) against conventional distributed optimization (ADMM) on three case studies: collaborative learning, facility location, and multiobjective blending. We show that in low-dimensional and nonconvex subproblems, the exploration-exploitation trade-offs of DFO solvers can be leveraged to converge faster and to a better solution than in distributed optimization.
  • Journal article
    Iruretagoyena D, Fennell P, Pini R, 2023,

    Adsorption of CO2 and N2 on bimetallic Mg-Al hydrotalcites and Z-13X zeolites under high pressure and moderate temperatures

    , CHEMICAL ENGINEERING JOURNAL ADVANCES, Vol: 13, ISSN: 2666-8211
  • Journal article
    Leonzio G, Mwabonje O, Fennell PS, Shah Net al., 2023,

    Corrigendum to “Environmental performance of different sorbents used for direct air capture” [Sustain. Prod. Consum. 32 (2022) 101–111]

    , Sustainable Production and Consumption, Vol: 36, Pages: 415-415, ISSN: 2352-5509
  • Journal article
    Anto-Darkwah E, Kurotori T, Pini R, Rabinovich Aet al., 2023,

    Estimating Three-Dimensional Permeability Distribution for Modeling Multirate Coreflooding Experiments

    , SUSTAINABILITY, Vol: 15
  • Journal article
    Krevor S, de Coninck H, Gasda SE, Ghaleigh NS, de Gooyert V, Hajibeygi H, Juanes R, Neufeld J, Roberts JJ, Swennenhuis Fet al., 2023,

    Subsurface carbon dioxide and hydrogen storage for a sustainable energy future

    , NATURE REVIEWS EARTH & ENVIRONMENT, Vol: 4, Pages: 102-118
    • Cite
    • Citations: 254
  • Journal article
    Thaysen EM, Butler IB, Hassanpouryouzband A, Freitas D, Alvarez-Borges F, Krevor S, Heinemann N, Atwood R, Edlmann Ket al., 2023,

    Pore-scale imaging of hydrogen displacement and trapping in porous media

    , INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, Vol: 48, Pages: 3091-3106, ISSN: 0360-3199
    • Cite
    • Citations: 73
  • Journal article
    Chiquier S, Patrizio P, Bui M, Sunny N, Mac Dowell Net al., 2023,

    A comparative analysis of the efficiency, timing, and permanence of CO<sub>2</sub> removal pathways(Vol 15, pg 4389, 2022)

    , ENERGY & ENVIRONMENTAL SCIENCE, Vol: 16, Pages: 321-321, ISSN: 1754-5692
  • Journal article
    Andrews E, Muggeridge A, Jones A, Krevor Set al., 2023,

    Pore structure and wetting alteration combine to produce the low salinity effect on oil production

    , Fuel: the science and technology of fuel and energy, Vol: 332, Pages: 1-15, ISSN: 0016-2361

    Low salinity water flooding is a promising enhanced oil recovery technique that has been observed, in experiments over a range of scales, to increase oil production by up to 14% in some systems. However, there is still no way of reliably predicting which systems will respond favourably to the technique. This shortcoming is partly because of a relative lack of pore scale observations of low salinity water flooding. This has led to a poor understanding of how mechanisms on the scale of micrometres lead to changes in fluid distribution on the scale of centimetres to reservoir scales. In this work, we use X-ray micro-CT scanning to image unsteady state experiments of tertiary low salinity water flooding in Berea, Castlegate, and Bunter sandstone micro-cores. We observe fluid saturations and characterise the wetting state of samples using imagery of fluid–solid fractional wetting and pore occupancy analysis. In the Berea sample, we observed an additional oil recovery of 3 percentage points during low salinity water flooding, with large volumes of oil displaced from small pores but also re-trapping of mobilised oil in large pores. In the Bunter sandstone, we observed 4 percentage point additional recovery with significant displacement of oil from small pores and no significant retrapping of oil in large pores. However, in the Castlegate sample, we observed just 1 percentage point of additional recovery and relatively small volumes of oil mobilisation. We observe a significant wettability alteration towards more water-wet conditions in the Berea and Bunter sandstones, but no significant alteration in the Castlegate sample. We hypothesise that pore structure, specifically the topology of large pores impacted recovery. We find that poor connectivity of the largest pores in each sample is strongly correlated to additional recovery. This work is the first systematic comparison of the pore scale response to low salinity flooding across multiple sandstone samples. Moreover
  • Journal article
    Bazyleva A, Acree WE, Diky V, Hefter GT, Jacquemin J, Magalhaes MCF, Magee JW, Nordstrom DK, O'Connell JP, Olson JD, Polishuk I, Schmidt KAG, Shaw JM, Trusler JPM, Weir RDet al., 2023,

    Reference materials for phase equilibrium studies. 2. Solid-liquid equilibria (IUPAC Technical Report)

    , Pure and Applied Chemistry, Vol: 94, Pages: 1-23, ISSN: 0033-4545

    This article is the second of three projected IUPAC Technical Reports on reference materials for phase equilibrium studies. The goal of this project was to select reference systems with critically evaluated property values for the verification of instruments and techniques used in phase equilibrium studies of mixtures. This report proposes seven systems for solid–liquid equilibrium studies, covering the four most common categories of binary mixtures: aqueous systems with organic solutes, aqueous systems with inorganic solutes, non-aqueous systems, and systems with low solubility. For each system, the available literature sources, accepted data, smoothing equations, and estimated uncertainties are given.
  • Journal article
    Eckel A-ME, Liyanage R, Kurotori T, Pini Ret al., 2023,

    Spatial moment analysis of convective mixing in three-dimensional porous media using X-ray CT images

    , Industrial and Engineering Chemistry Research, Vol: 62, Pages: 762-774, ISSN: 0888-5885

    Dissolution trapping is one of the primary mechanisms of carbon dioxide (CO2) storage in deep saline aquifers. The determination of the realized rates of CO2 dissolution requires an understanding of the mixing process that takes place following the emplacement of CO2 into the formation. Owing to the difficulty of reproducing the time-dependent convective process in porous media, experiments so far have largely focused on 2D systems (e.g., Hele-Shaw cells) and used analogue fluid pairs with properties that differ from the subsurface CO2/brine system. Here, we present a novel experimental approach to investigate the evolution of the convective mixing process in 3D porous media (homogeneous packings of glass beads) using X-ray computed tomography (CT). We explore a range of Rayleigh numbers (Ra = 3000–55000) and observe directly the mixing structures that arise upon dissolution. We compute from the images the temporal evolution of the spatial moments of the concentration distribution, including the cumulative dissolved mass, the location of the center of mass, and the standard deviation of the concentration field. The scalings of the spatial moments suggest an impact of hydrodynamic dispersion on the longitudinal mixing. We propose a simplified representation of the mixing process by analogy with the 1D advection–dispersion model. This enables the estimation of the bulk advective velocity and the effective longitudinal dispersion coefficient for each bead packing. These estimates suggest that the presence of the finger pattern and the counter-current flow structure enhance the longitudinal spreading of the solute by roughly 1 order of magnitude compared to unidirectional dispersion of a single-solute plume.
  • Conference paper
    Bird M, Acha S, Escriva EJS, Shah Net al., 2023,

    Data-driven Modelling of Supermarket Refrigeration Systems for Model Predictive Control Applications

    , Pages: 761-768

    With uncertainty in energy markets, and the effects of climate change looming, reducing energy use and operational cost of existing building systems is more important than ever. To this end, this paper presents a grey-box modelling approach to characterise the behaviour of chilled and frozen and coldrooms using basic system specifications and measured data. An overall energy balance is used to devise a discrete state space model for each cabinet, characterised by unknown empirical parameters relating to heat capacity and heat transfer properties. Historical system data from a UK supermarket are used in combination with a genetic algorithm optimisation to determine the optimal empirical parameters for 10 display cases and 10 coldrooms. The resulting cabinet temperature predictions have a good level of accuracy, achieving a root-mean squared error (RMSE) of 0.37°C to 0.98°C. Overall this data-driven approach is effective and efficient in modelling refrigeration systems, and can be easily generalised to any system where historical data is available. Finally, the use of the proposed approach in cost minimisation or demand response application is presented.
  • Book chapter
    Sarkis M, Fung J, Lee MH, Bernardi A, Shah N, Papathanasiou MMet al., 2023,

    Integrating environmental sustainability in next-generation biopharmaceutical supply chains

    , Computer Aided Chemical Engineering, Pages: 3405-3410

    Maximizing product availability to the public and minimizing costs are primary objectives in the biopharmaceutical sector. Nevertheless, awareness of the environmental sustainability of supply chain operations is becoming increasingly relevant in recent years. To assist decision-makers in balancing financial and environmental sustainability we present an optimization framework which determines candidate supply chain structures network designs and operational plans. Supply chain structures are assessed with respect to total cost and environmental score, with the latter integrating environmental impacts related to climate change, water usage and energy consumption. A Pareto set of candidate solutions is found which provides insights in complex trade-offs between impact categories and cost: centralized manufacturing is selected to lower unit production cost and better use water resources, whilst decentralized manufacturing improves energy usage. Emissions from CO<inf>2</inf> are lowered through cost minimization.
  • Journal article
    Delle Piane C, Ansari H, Li Z, Mata J, Rickard W, Pini R, Dewhurst DN, Sherwood Net al., 2023,

    Influence of Organic Matter Type on Porosity Development in Organic-Rich Shales: Combining Microscopy, Neutron Scattering and Physisorption Approaches

    , Neutron News, Vol: 34, Pages: 8-9, ISSN: 1044-8632
  • Book chapter
    Soh QY, O'Dwyer E, Acha S, Shah Net al., 2023,

    Modular stochastic optimization for optimal rainwater harvesting system design

    , Computer Aided Chemical Engineering, Pages: 697-702

    Rainwater Harvesting (RWH) systems can serve a dual functionality as a flood mitigation structure as well as providing local water availability. Optimisation-based design strategies must be transferrable enough to incorporate the influence of the local climate and case-specific catchment area characteristics into the design process, which can be a significant endeavour when required for every individual implementation. To increase the accessibility of optimisation methods in the appropriate sizing of RWH systems, this paper presents a modularised optimisation model, where tank components and dynamics are contained as individual blocks. These blocks can then be pieced together to produce a full system model, allowing optimisation models to be easily built for any combination and design of RWH system. This is implemented with a multi-tank RWH system, where an evaluation of the optimised system configuration showed a good balance between the dual objectives of providing improved flood mitigation and local water reuse, in comparison to an existing system derived through alternative sizing strategies.
  • Book chapter
    Triantafyllou N, Papaiakovou S, Bernardi A, Lakelin M, Shah N, Kokossis A, Papathanasiou MMet al., 2023,

    Machine learning-based decomposition for complex supply chains

    , Computer Aided Chemical Engineering, Pages: 1655-1660

    Personalised medicine products represent a novel category of therapeutics often characterised by bespoke manufacturing lines and dedicated distribution nodes. An example of such products is Chimeric Antigen Receptor (CAR) T-cells, whose manufacturing poses challenges to volumetric scale-up, leading to increased production and supply chain costs. From a modelling perspective, such networks lead to complex large-scale supply chain models that grow exponentially as the demand increases and more therapies are tracked simultaneously throughout the supply chain. In this work, we present a hybrid model that utilizes the potential of machine learning for strategic planning by forecasting optimal supply chain structures and Mixed Integer Linear Programming (MILP) for detailed scheduling. The proposed model is robust to uncertain demand patterns and can reduce the number of linear constraints and binary variables in the original MILP by more than 64.7%.
  • Book chapter
    Lyons B, Bernardi A, Shah N, Chachuat Bet al., 2023,

    Methane-to-X: an economic assessment of methane valorisation options to improve carbon circularity

    , Computer Aided Chemical Engineering, Pages: 2435-2440

    Methane side streams are produced in many different chemical processes and are normally combusted to provide process heat or to generate electricity. However, this practice is becoming less and less attractive as the industry strives towards net-zero targets and increasing the circularity of chemicals. Methane could instead be recovered and used as a valuable feedstock to produce other platform chemicals, such as H<inf>2</inf> or ethylene, which could be beneficial both for the economic performance and the carbon circularity of the system. In this work, seven different methane valorisation routes to produce additional chemicals are investigated. The considered routes include: i) five syngas-based routes combined with methanol synthesis and a methanol-to-olefins process; ii) plasma methane pyrolysis; and iii) oxidative coupling of methane. The results suggest that oxidative coupling of methane is the most profitable, with methane pyrolysis, tri-reforming and autothermal reforming also being more profitable in the base case. All routes have lower scope 1 and 2 emissions than the base case, however, dry-reforming and bi-reforming have the lowest emissions thanks to credited CO<inf>2</inf> feed streams.
  • Book chapter
    van de Berg D, Jimbo RXJ, Shah N, del Rio-Chanona EAet al., 2023,

    Tractable Data-driven Solutions to Hierarchical Planning-scheduling-control

    , Computer Aided Chemical Engineering, Pages: 649-654

    Using numerical optimization for the hierarchical integration of decision-making units is crucial to provide feasibility and optimality of all levels. However, realistically modelling hierarchical decision-making calls for multilevel formulations, which are numerically intractable and mathematically difficult. In this work, we show how to leverage two data-driven techniques – derivative-free optimization and optimality surrogates – to decrease the computational burden of multilevel problems. We reformulate a tri-level planning-scheduling-control problem into a single-level black-box problem wherein each evaluation calls a scheduling instance with embedded optimal control surrogates. We show that solving this integrated problem instead of the single-level instance leads to changes in the optimal production planning and scheduling sequence, and discuss trade-offs associated with both techniques.
  • Book chapter
    Triantafyllou N, Shah N, Papathanasiou MM, Kontoravdi Cet al., 2023,

    Combined Bayesian optimization and global sensitivity analysis for the optimization of simulation-based pharmaceutical processes

    , Computer Aided Chemical Engineering, Pages: 381-386

    We propose an efficient framework that employs Bayesian optimization and global sensitivity analysis for the optimization of detailed pharmaceutical flowsheets. Global sensitivity analysis based on quasi-random sampling is utilized to reduce the dimensionality of the problem by identifying critical process and economic parameters that contribute significantly to the variability of Key Performance Indicators (KPIs) such as batch size and OpEx. Then, Bayesian optimization is performed in the previously identified critical input space based on gaussian process surrogate models and a number of different acquisition functions to find the optimal critical operating conditions that minimize the aforementioned KPIs. We apply this framework to the manufacture of plasmid DNA (pDNA), which is a critical raw material for advanced therapeutics, leading to a surge in demand for pDNA for clinical or commercial use. Optimized manufacturing recipes identified with the proposed framework are projected to achieve an up to 170% increase in the batch size and a 34.7% decrease in the OpEx per batch.
  • Book chapter
    Leonzio G, Chachuat B, Shah N, 2023,

    Enviro-economic analysis of tandem and direct processes for ethylene electrosynthesis

    , Computer Aided Chemical Engineering, Pages: 2217-2222

    Ethylene is the most important organic chemical in terms of global demand and production capacity. Of the sustainable alternatives to conventional ethylene production based on steam cracking of natural gas and naphtha, both direct electrochemical reduction of CO<inf>2</inf> as well as a tandem process consisting of CO<inf>2</inf> electro-reduction to CO followed by CO electro-reduction to ethylene have attracted attention. This conference paper presents a comparison between the tandem and direct CO<inf>2</inf> electro-reduction processes both from an economic and environmental point of view, including a global sensitivity analysis of key process parameters on production cost and climate change impact. The results depict a clear trade-off between the economic and environmental performance of both electrochemical routes, although the tandem process remains more favorable at the current carbon price of the EU emission trading system (ETS).
  • Journal article
    Bian H, Ai L, Heng JYY, Maitland GC, Hellgardt Ket al., 2023,

    Effects of chemical potential differences on methane hydrate formation kinetics

    , Chemical Engineering Journal, Vol: 452, Pages: 1-11, ISSN: 1385-8947

    To underpin the increasing interest in practical applications of gas hydrates, for gas storage and separation for instance, the formation and growth of hydrates at liquid-gas interfaces are of fundamental importance. Although the thermodynamics of hydrate formation has been widely studied and is well understood, the kinetics of these processes is not well characterised. In this work, a high-pressure, low-temperature stirred reactor was used to conduct hydrate formation kinetic studies in a temperature range from 276.5 to 283.5 K and a pressure range from 5 to 10.5 MPa, with a special focus on 1) the impact of agitation conditions on the available water-gas interfacial surface area for mass transfer and growth rate during hydrate formation, and 2) the effect of the chemical potential driving force on the formation rate. Five hydrate growth regimes were identified, with varying degrees of gas mass transfer control across the gas-water interface depending on the extent to which hydrate layers built up at this interface, gas needed to move through solid hydrate layers, and the extent to which the gas was entrained within the water phase. The formation rate in the initial linear growth regime, before the onset of solid hydrate gas mass transfer effects, was found to depend in an essentially exponential manner on the chemical potential difference from the equilibrium state. Semi-empirical models related to Arrhenius-type kinetic models were used to correlate the data, the best of which reproduced the formation rates from the chemical potential differences to within ± 5 %. The approach has general applicability to help determine the balance between kinetic and thermodynamic factors in identifying the optimum pressure-temperature conditions for processes for gas storage, gas separation and other hydrate applications.

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