267 results found
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
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
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
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
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.
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
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
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
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
Lymperiadis A, Adjiman CS, Galindo A, et al., 2008, A heteronuclear group contribution method for associating chain molecules (SAFT-gamma), 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
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-gamma), JOURNAL OF CHEMICAL PHYSICS, Vol: 127, ISSN: 0021-9606
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
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
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
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
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
Haslam AJ, von Solms N, Adjiman CS, et al., 2006, Predicting enhanced absorption of light gases in polyethylene using simplified PC-SAFT and SAFT-VR, FLUID PHASE EQUILIBRIA, Vol: 243, Pages: 74-91, ISSN: 0378-3812
Sheldon TJ, Folic M, Adjiman CS, 2006, Solvent design using a quantum mechanical continuum solvation model, INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, Vol: 45, Pages: 1128-1140, ISSN: 0888-5885
Lo BP, Haslam AJ, Adjiman CS, et al., 2006, Chapter 3 A method for the systematic estimation of parameters for a stochastic reptation model, Vol: 22, Pages: 69-83, ISSN: 1570-7946
A parameter estimation algorithm for the thermodynamically consistent reptation model (Öttinger, 1999; Fang et al., 2000), which is based on stochastic differential equations, is proposed. The problem is formulated using the maximum likelihood (MLE) objective function, and a modified Levenberg-Marquardt algorithm is developed for its solution. Stochastic sensitivity equations are derived and used in order to obtain reliable parameter estimates. The issue of computational efficiency is addressed by varying the number of ensembles used in the integration of model based on the proximity of the current iterate to the optimal solution, as quantified by the magnitude of the trust region radius. The algorithm is applied to data for a sample of LDPE, to estimate mesoscale polymer properties from measurements of shear viscosity. © 2006 Elsevier B.V. All rights reserved.
Sheldon TJ, Giner B, Adjiman CS, et al., 2006, Chapter 7 The derivation of size parameters for the SAFT-VR equation of state from quantum mechanical calculations, Vol: 22, Pages: 143-159, ISSN: 1570-7946
Keskes E, Adjiman CS, Galindo A, et al., 2006, Integrating Advanced Thermodynamics and Process and Solvent Design for Gas Separation, 16TH EUROPEAN SYMPOSIUM ON COMPUTER AIDED PROCESS ENGINEERING AND 9TH INTERNATIONAL SYMPOSIUM ON PROCESS SYSTEMS ENGINEERING, Vol: 21, Pages: 743-748, ISSN: 1570-7946
Folic M, Adjiman CS, Pistikopoulos EN, 2006, A computer-aided methodology with robust design criteria for selection of solvents for reactions, Joint Conference Event of the 9th Symposium on Process Systems Engineering (PSE 2006)/16th European Symposium on Computer Aided Process Engineering (ESCAPE-16), Publisher: ELSEVIER SCIENCE BV, Pages: 787-792, ISSN: 1570-7946
Blanco Gutierrez RF, Pantelides CC, Adjiman CS, 2006, Risk analysis and robust design under technological uncertainty, Joint Conference Event of the 9th Symposium on Process Systems Engineering (PSE 2006)/16th European Symposium on Computer Aided Process Engineering (ESCAPE-16), Publisher: ELSEVIER SCIENCE BV, Pages: 191-196, ISSN: 1570-7946
Technological innovation in process design often leads to increased technological risk arising from incomplete knowledge. We propose a systematic approach to manage this risk using mathematical models that are sufficiently detailed to quantify risk. Global sensitivity analysis is used to determine the complete probability distributions for the key performance indicators of the process, thereby allowing informed decisions to be taken regarding the acceptability of the risk inherent in a given design. It also produces global sensitivity indices which allow the identification of the critical uncertain parameters on which additional R&D needs to be focused if the risk is deemed to be unacceptably high. If the risk is acceptable, then scenario-based approximation is used to handle the residual uncertainty in the critical parameters. Issues regarding the robust and efficient solution of problems involving large numbers of scenarios based on nonlinear models with thousands of variables are considered. The methodology is demonstrated via a case study concerning the design of a catalytic tubular reactor.
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