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  • 1.
    Creaser, Derek
    et al.
    Luleå tekniska universitet.
    Andersson, Bengt
    Chalmers University of Technology, Department of Chemical Reaction Engineering.
    Hudgins, Robert
    Department of Chemical Engineering, University of Waterloo.
    Silveston, Peter
    Department of Chemical Engineering, University of Waterloo.
    Kinetic modelling of oxygen dependence in oxidative dehydrogenation of propane2000In: Canadian Journal of Chemical Engineering, ISSN 0008-4034, E-ISSN 1939-019X, Vol. 78, no 1, p. 182-193Article in journal (Refereed)
    Abstract [en]

    Several Mars-Van Krevelen-type redox kinetic models were developed for the catalytic oxidative dehydrogenation of propane and examined for their ability to predict high propene yields at low oxygen/propane feed ratios. The intent in this study was to use modelling as a means of extracting further mechanistic insight from experimental data rather than to identify the best model. Thus, a conventional redox model with a consecutive reaction mechanism and a single pathway for the production of carbon oxides predicts higher propene selectivity but only at the expense of low propane conversion. Experimental data indicated, however, that even at the same propane conversion, propene selectivity increased as the oxygen partial pressure was lowered. Models that successfully describe the data had an additional carbon oxide production path involving the reaction of propane with deeply oxidizing surface oxygen species. Kinetic models and experimental data examined do not fully resolve how these deeply oxidizing surface oxygen species are formed. However, they do reflect the accepted view that lattice oxygen selectively produces propene whereas more weakly bound surface adsorbed oxygen reacts to completely oxidize propane.

  • 2.
    Furlan, John M.
    et al.
    GIW Industries Inc., Department of Engineering and R&D.
    Visintainer, Robert J.
    GIW Industries, Department of Engineering and R&D.
    Sellgren, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Centrifugal pump performance when handling highly non-Newtonian clays and tailings slurries2016In: Canadian Journal of Chemical Engineering, ISSN 0008-4034, E-ISSN 1939-019X, Vol. 94, no 6, p. 1108-1115Article in journal (Refereed)
    Abstract [en]

    Recent loop testing performed at the GIW Hydraulic Lab (Furlan et al. 2013, 2014) has provided pump performance data for two highly non-Newtonian slurries of significantly different character: a high clay content slurry with minimal coarse solids; and a typical, low clay content, two component tailings slurry. The importance of air removal in the sump and pipe loop was demonstrated using a simple, yet novel de-aeration system. In addition to the measurement of performance losses, determination of the upper limit of "pumpability" for these slurries relative to their concentration and associated yield stress was investigated. However, once the slurry was de-aerated, no limits could be found, other than those dictated by suction side losses (NPSHA) or excessive pipeline friction gradients, indicating that the only true limit in practice is one of system economics, i.e. pump operating and capital cost. Experimentally measured pump head and efficiency were compared against corresponding predictions from two different models: the Walker and Goulas technique (Walker and Goulas, 1983), and the Graham et al. technique (Graham et al., 2009), with special focus given to the dependence of the losses on pump rotary speed.

  • 3.
    Nohlgren, Ingrid
    et al.
    Luleå tekniska universitet.
    Theliander, Hans
    Zhuang, Qianlin
    Dr. Jack McKenzie Limerick Pulp and Paper Research and Education Centre, University of New Brunswick.
    Heiningen, Adriaan R.P van
    Dr. Jack McKenzie Limerick Pulp and Paper Research and Education Centre, University of New Brunswick.
    Model study of the direct causticization reaction between sodium trititanate and sodium carbonate2000In: Canadian Journal of Chemical Engineering, ISSN 0008-4034, E-ISSN 1939-019X, Vol. 78, no 3, p. 529-539Article in journal (Refereed)
    Abstract [en]

    The solid state reaction between sodium trititanate and sodium carbonate, forming mainly sodium pentatitanate, was investigated. Experiments were carried out in a micro-differential reactor made of quartz glass at various temperatures between 800 and 880°C and in a pilot fluidized bed reactor operated in a semi-batch mode. In the former reactor, basic kinetic data was obtained by measuring the release of carbon dioxide. Different kinetic models were considered to describe the conversion, such as the Valensi-Carter model for diffusion controlled reaction rates and the phase-boundary model for first-order reaction kinetics. Furthermore, a model that included both diffusion in the solid material and the chemical kinetics was derived. This model described the experimental data obtained in the micro-differential reactor very well. However, for the fluidised bed experiments, these different kinetic models did not accurately describe the experimental data. Therefore, an improved model was developed, which also took into account the time taken for the reactants to achieve physical contact. This model gave good agreement with the experimental data.

  • 4.
    Sellgren, Anders
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Addie, Graeme
    V.P. Engineering, Research and Development, GIW Industries Inc., Grovetown, GA.
    Scott, Stephen
    Effect of sand-clay slurries on the performance of centrifugal pumps2000In: Canadian Journal of Chemical Engineering, ISSN 0008-4034, E-ISSN 1939-019X, Vol. 78, no 4, p. 764-769Article in journal (Refereed)
    Abstract [en]

    The addition of clay to sand slurries has been found to reduce the pipeline friction losses, thus lowering the pumping head and power consumption. Pump water heads and efficiencies are decreased by the presence of solid particles. Experimental results are presented for a centrifugal pump with an impeller diameter of 0.625 m for three narrowly graded sands with average particle sizes of 0.64, 1.27, and 2.2 mm. Reductions in head and efficiency of up to 30% were observed for sand slurries with volume concentrations of up to 35%. Head and efficiency were lowered by about one-third for sand-clay mixtures with sand to clay mass ratios between 4:1 and 6:1. Comparisons are made with design criteria and a mechanistic model approach based on a prediction of the relative motion of the solids and water in the volute region of the pump.

  • 5.
    Sellgren, Anders
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Visintainer, Robert J.
    GIW Industries Inc..
    Furlan, John M.
    GIW Industries Inc..
    Matousek, Václav
    Czech Technical University in Prague.
    Pump and pipeline performance when pumping slurries with different particle gradings2016In: Canadian Journal of Chemical Engineering, ISSN 0008-4034, E-ISSN 1939-019X, Vol. 94, no 6, p. 1025-1031Article in journal (Refereed)
    Abstract [en]

    A pipeline slurry friction loss model consisting of three regimes was initially proposed by Wilson then extended to four components consisting of fluid, pseudo-homogeneous, heterogeneous, and fully stratified regimes. The weighting technique using up to four regime-related components often works well for friction loss estimations based on simple input data and model parameters. This also holds for the Hydraulic Institute's pump performance derating procedure for settling slurries. The comparisons and discussion focus on coarse particle slurries and some cases where the modelling estimations for pipeline and pump performance were not particularly accurate

  • 6.
    Wilson, Kenneth
    et al.
    Consultant, Canada.
    Sellgren, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Developments in slurry flow modelling in a historical perspective2016In: Canadian Journal of Chemical Engineering, ISSN 0008-4034, E-ISSN 1939-019X, Vol. 94, no 6, p. 1019-1024Article in journal (Refereed)
    Abstract [en]

    Durand's slurry flow model attempted to find a single formula for sand-size particles and larger, but Babcock's data showed that a single formula could not apply. A subsequent group of models is based on Wilson's layered force-balance analysis of slurry flows applied to friction losses and deposition limit. Models based on variants of this analysis include those by Shook and others at the Saskatchewan Research Council (SRC). Early versions of Wilson's model relied on particle fall velocity to find friction losses, but the classical iterative method of finding fall velocity has now been replaced by a direct method. This is based on the shear Reynolds number of the particle, which can be expressed in terms of the better known Archimedes number. Thus, calculations of slurry friction and limit of deposition involve two principal parameters: the Archimedes number and the diameter ratio d/D.

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