Publications
307 results found
Adjiman C, Atkinson A, Azad A, et al., 2009, A Review of Progress in the UK Supergen Fuel Cell Programme, 11th International Symposium on Solid Oxide Fuel Cells (SOFC), Publisher: ELECTROCHEMICAL SOC INC, Pages: 35-42, ISSN: 1938-5862
Lymperiadis A, Adjiman CS, Jackson G, et al., 2008, A generalisation of the SAFT-gamma group contribution method for groups comprising multiple spherical segments, FLUID PHASE EQUILIBRIA, Vol: 274, Pages: 85-104, ISSN: 0378-3812
A new group contribution (GC) approach based on the statistical associating fluid theory (SAFT-gamma) has recently been proposed [A. Lymperiadis, C. S. Adjiman, A. Galindo, G. Jackson, J. Chem. Phys. 127 (2007) 234903]. In this continuum equation of state CC approach, the molecules are formed from fused heteronuclear spherical segments each of which represents a distinct chemical functional group. The different segments are characterised by size and attractive energy (well-depth and range) parameters, and a shape-factor parameter which describes the contribution that each segment makes to the overall molecular properties. In addition a number of bonding sites are included on a given segment to deal with association interactions where appropriate; the association between sites introduces two additional energy and range parameters. Our heteronuclear molecular models are thus fundamentally different from the homonuclear models employed with other GC versions of SAFT in which the GC concept is introduced to obtain average molecular parameters. In the Current work, we generalise the SAFY-gamma equation of state to treat chemical groups which are represented by more than a single spherical segment. This allows for a good description of the properties of large functional groups such as carboxyl and carbonyl groups. The original parameter table for the CH(3), CH(2), CH(3)CH, ACH (where AC denotes an aromatic carbon), ACCH(2), CH(2)=, CH= and OH groups is now extended to include the C=O, COCH, and NH(2) groups by examining the vapour-liquid equilibria (VLE) of pure 2-ketones, carboxylic acids, and primary amines. It is demonstrated that the proposed theory provides an excellent description of the vapour-liquid equilibria for all of the chemical families considered, and that the new group parameters can be used in a predictive fashion to model the phase behaviour of larger compounds not included in the estimation database. One of the principal advantages of the SAFT-gamma for
Schreckenberg JMA, Adjiman CS, Galindo A, et al., 2008, Modelling the fluid phase behaviour in aqueous surfactant and water + oil + surfactant solutions and the effects of added salts, AIChE Annual Meeting, Conference Proceedings
Surfactants are widely used due to their amphiphilic properties and their solubility in water and many organic solvents. The phase behaviour of surfactant mixtures is therefore of great interest, both from the scientific and industrial perspective. Transferable molecular models of the alykylpolyoxyethylene (C 1E j) non-ionic surfactants are developed within the Wertheim TPT1 formalism for use with the statistical association fluid theory for potentials of variable range (SAFT-VR). Short-range attractive interaction sites allow the explicit treatment of water and surfactant hydrogen bonding. The fluid phase equilibria of binary aqueous surfactant solutions are examined with a particular emphasis on the regions of liquid immiscibility known as closed-loop regions. Additional association sites for the surfactant are used to better describe the experimental closed-loop; the physical significance of these extra sites can be explained in terms of the micellar aggregation of the surfactants where only the hydrophilic head groups are exposed to water so that the solubility of the surfactant is effectively one of a fully hydrophilic chain with sites all along its length. The fluid phase equilibria of ternary water + hydrocarbon (oil) + C iE j solutions are examined to represent the liquid two and three phase regions. Transferable molecular interaction parameters are determined which give an excellent description of the phase behaviour of these systems. The interaction parameters provide a predictive platform for surfactant mixtures of various molecular weights and permit to examine global behaviour. The pressure dependence of the liquid phase behaviour in these systems is also studied. The closed-loop is observed to diminish with increasing pressures. At low pressures and with increasing temperature the three phase region in water + oil + C iE
Kazantsev AV, Karamertzanis PG, Adjiman CS, et al., 2008, Computational prediction of effects of pressure on organic crystal structure, AIChE Annual Meeting, Conference Proceedings
Adjiman CS, Clarke AJ, Cooper G, et al., 2008, A rational approach to solvent choice in the development of homogeneous catalytic reaction systems, AIChE Annual Meeting, Conference Proceedings
The choice of solvent or solvent mixture in which to carry out a reaction is usually made in the early stages of process development. This decision can have a huge effect on process performance, by affecting reaction rates and selectivity, by placing demands on downstream purification units and by contributing to the environmental impact of the process. In this work, we present a systematic approach to solvent selection, which greatly widens the options considered during process design, and can lead to significant improvements in reaction performance. The approach was first developed for model single-step reaction and is extended here to more complex reaction schemes. It involves (i) a targeted set of experiments to quantify reaction kinetics and solvent influences on rate (ii) a computer-aided solvent design step in which potentially better solvents are identified, and (iii) synthetic verification of the results. The approach is presented through application to the ring-closing metathesis (RCM) of a diene catalyzed by the 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene ruthenium complex (Grubbs II catalyst. The Grubbs II catalyst is in many ways promising for RCM in an industrial context, but the amount of catalyst that is typically used to achieve good productivity makes its adoption expensive. It is difficult to postulate what solvent properties best promote the reaction, as the conversion is the result of complex balance between the rates of catalyst activation, the metathesis reaction itself, and catalyst deactivation. We demonstrate how the proposed methodology has led to the discovery of better solvents for this reaction, in which complete conversion is achieved quickly with 10 times less catalyst than is required for the usual solvent, dichloromethane. Through this approach, we have also been able to gain a better understanding of the kinetics of the key reactions, providing essential information for process design and scale-up.
Giner B, Sheldon T, Pollock M, et al., 2008, An approach for developing intermolecular models for use within Saft-Vr from quantum mechanical calculations and experimental data, AIChE Annual Meeting, Conference Proceedings
Kazantsev AV, Karamertzanis PG, Adjiman CS, et al., 2008, A computationally efficient algorithm for accurate local energy minimization of crystal structures containing flexible molecules, AIChE Annual Meeting, Conference Proceedings
Pereira FE, Keskes E, Adjiman CS, et al., 2008, A physical absorption process for the capture of CO2 from CO2-rich natural gas streams using hydrocarbon solvents, with post-capture CO2 re-compression, AIChE 100 - 2008 AIChE Annual Meeting, Conference Proceedings
The increasing importance of natural gas as a source of energy poses difficult gas separation design challenges, as the high flow-rate streams recovered from gas fields are at high pressures (typically about 10MPa) and can contain a high proportion of CO2 (up to 70%). Conventional separation techniques are usually restricted to low CO2 content or low pressure feeds, and consequently there is a pressing need for an alternative process that is appropriate for such a scenario. In addition, increasingly stringent regulation of CO2 emissions has rendered release of CO2 to the atmosphere more difficult. There is growing pressure for the captured CO2 to be re-compressed before it may be re-injected and re-used on site, or transported for further use elsewhere. This step is energy intensive, and could potentially change the economic outlook of the separation process, and consequently the entire natural gas production operation. A process for the separation of gaseous CO2/CH4 has been developed, capable of economically treating natural gas feeds at the high pressures and CO2 concentrations mentioned. The process has been modelled for a system comprising methane, CO2 and alkane solvent. The separation process model includes absorption and desorption units, as well as heat exchangers and a CO2 re-compression stage. An advanced equation of state, SAFT-VR, has been employed in this study. This facilitates accurate representation of the complex thermodynamic and fluid-phase equilibrium behaviour of high pressure/temperature CO2-hydrocarbon mixtures. The work has been carried out using the modelling-optimisation software gPROMS. The process is optimised by considering an economic objective over a 15-year lifetime. In addition to finding the best equipment sizes and operating conditions, the alkane chain length of the physical solvent is also treated as an optimisation variable, to achieve the most cost effective absorption for differing CO2 content. Several case studies are examin
Dowell NM, Adjiman CS, Galindo A, et al., 2008, Modeling CO2 capture in amine solvents with an advanced association model: Process optimisation and a platform for solvent design, AIChE Annual Meeting, Conference Proceedings
Karamertzanis PG, Kazantsev AV, Issa N, et al., 2008, Modeling and prediction of the crystal structure of pharmaceutical Co-crystals, AIChE Annual Meeting, Conference Proceedings
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Luna-Ortiz E, Lawrence P, Pantelides CC, et al., 2008, Optimal flow assurance policies for hydrate prevention in deep-water gas production systems, AIChE Annual Meeting, Conference Proceedings
Lafitte T, Galindo A, Adjiman CS, et al., 2008, Accurate perturbation theory for chains of soft-core attractive segments of arbitrary softness, AIChE Annual Meeting, Conference Proceedings
Lymperiadis A, Adjiman CS, Galindo A, et al., 2008, Molecular based group contribution approaches for the prediction of the thermophysical properties of fluids, AIChE Annual Meeting, Conference Proceedings
Golbert J, Adjiman CS, Brandon NP, 2008, Microstructural Modeling of Solid Oxide Fuel Cell Anodes, INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, Vol: 47, Pages: 7693-7699, ISSN: 0888-5885
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- Citations: 73
Lo BP, Haslam AJ, Adjiman CS, 2008, An algorithm for the estimation of parameters in models with stochastic differential equations, CHEMICAL ENGINEERING SCIENCE, Vol: 63, Pages: 4820-4833, ISSN: 0009-2509
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- Citations: 6
Folic M, Adjiman CS, Pistikopoulos EN, 2008, Computer-aided solvent design for reactions: Maximizing product formation, INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, Vol: 47, Pages: 5190-5202, ISSN: 0888-5885
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- Citations: 43
Dunnett AJ, Adjiman CS, Shah N, 2008, A spatially explicit whole-system model of the lignocellulosic bioethanol supply chain: an assessment of decentralised processing potential, BIOTECHNOLOGY FOR BIOFUELS, Vol: 1
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- Citations: 112
Lymperiadis A, Adjiman CS, Galindo A, et al., 2008, A heteronuclear group contribution method for associating chain molecules (SAFT-γ), 18TH EUROPEAN SYMPOSIUM ON COMPUTER AIDED PROCESS ENGINEERING, Vol: 25, Pages: 871-876, ISSN: 1570-7946
Luna-Ortiz E, Lawrence P, Pantelides CC, et al., 2008, An integrated framework for model-based flow assurance in deep-water oil and gas production, 18th European Symposium on Computer Aided Process Engineering (ESCAPE-18), Publisher: ELSEVIER SCIENCE BV, Pages: 787-792, ISSN: 1570-7946
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- Citations: 2
Adjiman CS, Clarke AJ, Cooper G, et al., 2008, Solvents for ring-closing metathesis reactions, CHEMICAL COMMUNICATIONS, Pages: 2806-2808, ISSN: 1359-7345
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- Citations: 52
Rodriguez Perez J, Adjiman CS, Immanuel CD, 2008, State estimation for dynamic prediction of hydrate formation in oil and gas production systems, 18th European Symposium on Computer Aided Process Engineering (ESCAPE-18), Publisher: ELSEVIER SCIENCE BV, Pages: 507-512, ISSN: 1570-7946
Since oil and gas production is moving to deeper waters, subsea pipelines are being subjected to higher pressures and lower temperatures. Under such conditions, the formation of hydrates is promoted. Hydrates are solid, non-flowing compounds of gas and water whose formation can cause line blockages, with the consequent economical losses and safety risks. The increasing hydrate formation propensity suggests the necessity to predict the possibility of hydrate formation in on-line operation so as to take preventive control actions and thereby provide flow assurance. Although a detailed dynamic model will enable the prediction of the possibility of hydrate formation, model inaccuracies and process disturbances will make this prediction less accurate. The usage of key available measurements will enable to address these disadvantages. The aim of this paper is to develop a combined state and parameter estimator for this process, by combining a dynamic model with available measurements.
Lymperiadis A, Adjiman CS, Galindo A, et al., 2007, A group contribution method for associating chain molecules based on the statistical associating fluid theory (SAFT-γ), JOURNAL OF CHEMICAL PHYSICS, Vol: 127, ISSN: 0021-9606
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- Citations: 203
Dunnett A, Adjiman C, Shah N, 2007, Biomass to heat supply chains applications of process optimization, PROCESS SAFETY AND ENVIRONMENTAL PROTECTION, Vol: 85, Pages: 419-429, ISSN: 0957-5820
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- Citations: 65
Golbert J, Adjiman CS, Brandon NP, 2007, Micro-structural Modelling of SOFC Anodes, ECS Transactions, Vol: 7, Pages: 2041-2047
Folic M, Adjiman CS, Pistikopoulos EN, 2007, Design of solvents for optimal reaction rate constants, AICHE JOURNAL, Vol: 53, Pages: 1240-1256, ISSN: 0001-1541
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- Citations: 55
Hawkes AD, Aguiar P, Croxford B, et al., 2007, Solid oxide fuel cell micro combined heat and power system operating strategy: Options for provision of residential space and water heating, JOURNAL OF POWER SOURCES, Vol: 164, Pages: 260-271, ISSN: 0378-7753
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- Citations: 72
Pereira Lo B, Haslam AJ, Adjiman CS, 2006, Chapter 1 Parameter estimation for stochastic differential equations: algorithm and application to polymer melt rheology, Computer Aided Chemical Engineering, Vol: 21, Pages: 143-148, ISSN: 1570-7946
A parameter estimation algorithm for stochastic differential equation (SDE) systems is proposed. The problem is formulated using the maximum likelihood (MLE) objective function, and a modified Levenberg-Marquardt (LM) algorithm is developed for its solution. Stochastic sensitivity equations are derived and used in order to obtain reliable parameter estimates. Computational efficiency is addressed by varying the simulation size according to the proximity of the current iterate to the optimal solution, as indicated by the magnitude of the trust-region radius. To evaluate the confidence intervals of the parameters, a global uncertainty analysis is proposed, which is based on sampling and accounts for experimental uncertainty and model noise. The algorithm is applied to a stochastic model of polymer rheology. © 2006 Elsevier B.V. All rights reserved.
Keskes E, Adjiman CS, Galindo A, et al., 2006, A new physical absorption process for the capture of Co2 from Co2-rich natural gas streams, AIChE Annual Meeting, Conference Proceedings
The increasing importance of natural gas as a source of energy poses difficult gas separation design challenges, as the streams recovered from gas fields are at high pressures and can contain a high proportion of CO2. A new CO2/CH4 gas separation process is presented. Capture of CO2 from natural gas is carried out using an n-alkane solvent in a conventional physical absorption process. A methodology to find optimal process condition and solvent is developed using an advanced EOS, process modeling-optimization software, and detailed process cost estimation. Natural gas feeds containing ≤ 70% mole/mole of CO2 could be treated economically using this process. This is an abstract of a paper presented at the 2006 AIChE Annual Meeting (San Francisco, CA 11/12-17/2006).
Oulton RF, Adjiman CS, 2006, Global optimization and modeling techniques for planar multilayered dielectric structures, APPLIED OPTICS, Vol: 45, Pages: 5910-5922, ISSN: 1559-128X
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- Citations: 5
Hawkes AD, Aguiar P, Hernandez-Aramburo CA, et al., 2006, Techno-economic modelling of a solid oxide fuel cell stack for micro combined heat and power, Journal of Power Sources, Vol: 156, Pages: 321-333, ISSN: 0378-7753
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