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Bungener S.L.,Ecole Polytechnique Federale de Lausanne | Van Eetvelde G.,Ghent University | Descales B.,Ineos Technologies Inc. | Marechal F.,Ecole Polytechnique Federale de Lausanne
Chemical Engineering Transactions | Year: 2015

Steam is a key energy vector for industrial sites, used for process heating, direct injection and stripping, tracing and cogeneration of mechanical power. Steam networks transport steam from producers to consumers and across different pressure levels. The steam production equipments (boilers, cogeneration units and heat exchangers) should be dimensioned to always supply key consumers as well as to deal with extreme demand caused by exceptional events such as unit startups or extreme weather. An important issue to be dealt with is that of unexpected boiler shutdowns, which can take significant amounts of time to bring back online. In cases where demand surpasses the available production of steam, load shedding is necessary in order to keep the network operable. A penalty cost can be associated to load shedding. A well dimensioned steam network is one which is resilient to such events, being able to overcome extreme demand and unexpected boiler shutdowns at minimum cost. This paper proposes a methodology for evaluating the operability of a steam network when facing unexpected boiler shutdowns. A Monte-Carlo simulation is carried out on a multi-period steam network problem, randomly shutting down boilers according to their failure properties (probability of failure and duration of failure). The aim of this method is to evaluate how resilient a steam network is to boiler shutdowns. The Monte-Carlo simulation is applied to a steam network model built using a Mixed Integer Linear Programming (MILP) formulation, whose objective function is to minimise the operational costs of the steam network and therefore also to minimise the penalty costs associated to load shedding. A case study based on anonymised industrial data is used to demonstrate the method. Two investment propositions are evaluated and compared using the proposed method. Copyright © 2015, AIDIC Servizi S.r.l.,. Source

Blanton T.N.,Eastman Kodak Co. | Rajeswaran M.,Eastman Kodak Co. | Stephens P.W.,State University of New York at Stony Brook | Whitcomb D.R.,Imation | And 3 more authors.
Powder Diffraction | Year: 2011

High-resolution powder X-ray diffraction has been used to determine the crystal structure of silver behenate, [Ag(O2C(CH2)20CH3]2. Using CASTEP density functional plane wave pseudopotential techniques to obtain an optimized structural model, Rietveld refinement of the structure gives Rwp=8.66%. The unit cell is triclinic, space group P1, with cell dimensions of a=4.1769(2) Å , b=4.7218(2) Å , c=58.3385(1) Å , α=89.440(3)°, β=89.634(3)°, γ=75.854(1)°. The structure is characterized by an 8-membered ring dimer of Ag atoms and carboxyl groups with a fully extended all-trans configuration of the alkyl side chains. The dimers are joined by four-membered Ag-O rings creating a polymeric network, giving rise to one-dimensional chains along the b-axis. This structure is supported by EXAFS measurements of the local structure around the silver atoms and IR measurements. © 2011 International Centre for Diffraction Data. Source

Lin S.S.-Y.,Northwestern University | Lin S.S.-Y.,Ineos Technologies Inc. | Yang J.,Ford Motor Company | Kung H.H.,Northwestern University | Kung M.C.,Northwestern University
Topics in Catalysis | Year: 2013

Hydrogen storage properties of NaAlH4 can be improved by mixing it with Co/carbon catalysts. The importance of cobalt nanoparticles was established by varying the amount of active cobalt in the reaction vessel. This was achieved either by keeping the weight of NaAlH4 and carbon constant while varying the amount of Co/carbon catalyst used or by poisoning the cobalt active site with CO. Another approach to improve the hydrogen storage properties of complex metal hydride is through nano-confinement of the hydride in carbon pores. LiBH4-carbon composite formed via liquid phase infusion of LiBH4 into carbon was examined for reversibility in the hydriding/dehydriding cycles. The physical constraints imposed by the carbon nano-pores appeared to be effective in deterring the loss of cyclability due to sintering of the hydride. The loss in hydrogen storage appeared to be the result of LiBH4 reaction with impurities/reactive functional groups on the carbon. © 2013 Springer Science+Business Media New York. Source

Lesage F.,University of Lorraine | Nedelec D.,University of Lorraine | Descales B.,INEOS Manufacturing France | Stephens W.D.,Ineos Technologies Inc.
Computer Aided Chemical Engineering | Year: 2012

A CSTR dynamic model dedicated to gas-phase propylene polymerization was designed using Aspen Custom Modeler. It was then used to model a semi-batch lab-scale reactor in order to identify some kinetic parameters. A model of a full scale industrial reactor has also been developped and its results were successfully compared with actual plant data. © 2012 Elsevier B.V. Source

Hemelsoet K.,Ghent University | Qian Q.,University Utrecht | De Meyer T.,Ghent University | De Wispelaere K.,Ghent University | And 5 more authors.
Chemistry - A European Journal | Year: 2013

The optical absorption properties of (poly)aromatic hydrocarbons occluded in a nanoporous environment were investigated by theoretical and experimental methods. The carbonaceous species are an essential part of a working catalyst for the methanol-to-olefins (MTO) process. In situ UV/Vis microscopy measurements on methanol conversion over the acidic solid catalysts H-SAPO-34 and H-SSZ-13 revealed the growth of various broad absorption bands around 400, 480, and 580 nm. The cationic nature of the involved species was determined by interaction of ammonia with the methanol-treated samples. To determine which organic species contribute to the various bands, a systematic series of aromatics was analyzed by means of time-dependent density functional theory (TDDFT) calculations. Static gas-phase simulations revealed the influence of structurally different hydrocarbons on the absorption spectra, whereas the influence of the zeolitic framework was examined by using supramolecular models within a quantum mechanics/molecular mechanics framework. To fully understand the origin of the main absorption peaks, a molecular dynamics (MD) study on the organic species trapped in the inorganic host was essential. During such simulation the flexibility is fully taken into account and the effect on the UV/Vis spectra is determined by performing TDDFT calculations on various snapshots of the MD run. This procedure allows an energy absorption scale to be provided and the various absorption bands determined from in situ UV/Vis spectra to be assigned to structurally different species. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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