The Experts below are selected from a list of 6339 Experts worldwide ranked by ideXlab platform

Katharina Kohsehoinghaus - One of the best experts on this subject based on the ideXlab platform.

  • inhibiting and promoting effects of no on dimethyl ether and dimethoxymethane oxidation in a Plug Flow Reactor
    Combustion and Flame, 2021
    Co-Authors: Hao Zhang, Steffen Schmitt, Lena Ruwe, Katharina Kohsehoinghaus
    Abstract:

    Abstract The effects of NO addition (1000, 2000 ppm) on the low-temperature oxidation of dimethyl ether (DME) and dimethoxymethane (DMM), as particular cases of oxymethylene ethers (OMEn) with n = 0 and 1, have been investigated in a Plug-Flow Reactor at near-atmospheric pressure in a temperature range of 400–1000 K. An in-situ electron ionization molecular-beam mass spectrometer (EI-MBMS) was used to measure the reactants, intermediates, and products, with particular attention on nitrogenous species that were scarcely detected previously. Explorative modeling with published mechanisms was performed, indicating the necessity of further model development. Potential kinetic fuel/NO interactions are discussed based on the experimental observations. The results reveal an overall inhibiting effect of NO addition on DME reactivity in the low-temperature regime, but a pronounced promoting effect at higher temperatures. For DMM, a similar temperature-dependent effect of NO was observed, but only for high NO concentration (2000 ppm). NO addition significantly suppresses the formation of hydrocarbon intermediates for both DME and DMM, but remarkably promotes the formation of methyl formate and methanol for DME. Several nitrogenous species were detected upon NO addition. The interactions of NO + HO2 and NO + OH, together with the regeneration routes of NO, are thought to be influential for both DME and DMM oxidation, while the significance of the NO + RO2 (R, fuel radical) reaction depends on the reactivity of the respective RO2 radical of DME and DMM. These results contribute to the understanding of OMEn/NO interactions and serve as a basis for further model development by providing new and detailed speciation data for DME/NO and DMM/NO oxidation.

Costin Sorin Bildea - One of the best experts on this subject based on the ideXlab platform.

  • Steady-state behaviour of PFR-separation-recycle systems with simultaneous exothermic and endothermic, first-order reactions
    Computers & Chemical Engineering, 2009
    Co-Authors: Klaas Steur, Costin Sorin Bildea, Pietro Altimari, Alexandre C. Dimian
    Abstract:

    A systematic investigation of Plug-Flow Reactor (PFR)-separation-recycle systems where first-order exothermic and endothermic reactions are simultaneously performed is presented. The nonlinear behaviour is analyzed for two Flowsheet alternatives and four plantwide control structures. It is shown that the system can exhibit a complex nonlinear behaviour. For the parameter values used, regions of unfeasibility, two or three multiple steady states and branches of isolated solutions were found. The undesired nonlinear phenomena can be avoided by fixing the Reactor-inlet Flow rates of each reactant or, when this is impossible due to the Flowsheet structure, by providing sufficient cooling capacity.

  • coupling exothermic and endothermic reactions in Plug Flow Reactor separation recycle systems
    Industrial & Engineering Chemistry Research, 2008
    Co-Authors: Pietro Altimari, Costin Sorin Bildea
    Abstract:

    The nonlinear behavior of Plug-Flow Reactor−separation−recycle systems, where the endothermic first-order reaction A → R + Q and the exothermic second-order reaction B + Q → P simultaneously take place, is investigated. As the physical properties of the species involved vary, possible Flowsheets are identified and feasible control strategies are suggested. Bifurcation analysis of the Reactor−separation−recycle system is performed by choosing set-point variables as bifurcation parameters. Steady state multiplicity is invariably detected leading to complex behavior. Implications on plantwide control are thoroughly discussed and guidelines are provided which enable to select values of set-point variables in a way that guarantees safe operation.

Denis Dochain - One of the best experts on this subject based on the ideXlab platform.

  • Optimal LQ-Feedback Regulation of a Nonisothermal Plug Flow Reactor Model by Spectral Factorization
    IEEE Transactions on Automatic Control, 2007
    Co-Authors: Ilyasse Aksikas, Joseph J. Winkin, Denis Dochain
    Abstract:

    The linear-quadratic (LQ) optimal temperature and reactant concentration regulation problem is studied for a partial differential equation model of a nonisothermal Plug Flow tubular Reactor by using a nonlinear infinite dimensional Hilbert state space description. First the dynamical properties of the linearized model around a constant temperature equilibrium profile along the Reactor are studied: it is shown that it is exponentially stable and (approximately) reachable. Next the general concept of LQ-feedback is introduced. It turns out that any LQ-feedback is optimal from the input-output viewpoint and stabilizing. For the Plug Flow Reactor linearized model, a state LQ-feedback operator is computed via the solution of a matrix Riccati differential equation (MRDE) in the space variable. Thanks to the reachability property, the computed LQ-feedback is actually the optimal one. Then the latter is applied to the nonlinear model, and the resulting closed-loop system dynamical performances are analyzed. A criterion is given which guarantees that the constant temperature equilibrium profile is an asymptotically stable equilibrium of the closed-loop system. Moreover, under the same criterion, it is shown that the control law designed previously is optimal along the nonlinear closed-loop model with respect to some cost criterion. The results are illustrated by some numerical simulations.

  • Stability analysis of an infinite-dimensional linearized Plug Flow Reactor model
    2004 43rd IEEE Conference on Decision and Control (CDC) (IEEE Cat. No.04CH37601), 2004
    Co-Authors: H. Aksikas, Joseph J. Winkin, Denis Dochain
    Abstract:

    A stability analysis is performed for a linearized Plug Flow Reactor model. The dynamics of the linearized process are described by linear partial differential equations (PDE's) with spatial-dependent coefficients. The analysis is performed on an equivalent triangularized model, that is described by a triangular system of PDE's. Then the stability of the linearized model is established, by using the invariance of stability under system equivalence.

  • optimal temperature control of a steady state exothermic Plug Flow Reactor
    Aiche Journal, 2002
    Co-Authors: Ilse Smets, Denis Dochain, Jan F Van Impe
    Abstract:

    Optimal heat exchanger temperature profiles of exothermic tubular Reactors were determined under the assumption of steady-state and Plug-Flow characteristics. The minimum principle of Pontryagin (optimal control theory) was applied in a straightforward analytical sense. To enable a trade-off between process performance and heat loss, a combined cost criterion was defined. In the first approach of specifying only, terminal costs, the optimal control input was of the bang-bang type that keeps the heat exchanger temperature constant at its maximum or minimum value. Afterwards, the terminal cost criterion was extended with an integral part that accounts for the global heat loss during the process. This integral cost part induced a control of the bang-singular-bang type. The desired performance call be met by selecting appropriate weights for terminal and integral costs.

Lena Ruwe - One of the best experts on this subject based on the ideXlab platform.

  • inhibiting and promoting effects of no on dimethyl ether and dimethoxymethane oxidation in a Plug Flow Reactor
    Combustion and Flame, 2021
    Co-Authors: Hao Zhang, Steffen Schmitt, Lena Ruwe, Katharina Kohsehoinghaus
    Abstract:

    Abstract The effects of NO addition (1000, 2000 ppm) on the low-temperature oxidation of dimethyl ether (DME) and dimethoxymethane (DMM), as particular cases of oxymethylene ethers (OMEn) with n = 0 and 1, have been investigated in a Plug-Flow Reactor at near-atmospheric pressure in a temperature range of 400–1000 K. An in-situ electron ionization molecular-beam mass spectrometer (EI-MBMS) was used to measure the reactants, intermediates, and products, with particular attention on nitrogenous species that were scarcely detected previously. Explorative modeling with published mechanisms was performed, indicating the necessity of further model development. Potential kinetic fuel/NO interactions are discussed based on the experimental observations. The results reveal an overall inhibiting effect of NO addition on DME reactivity in the low-temperature regime, but a pronounced promoting effect at higher temperatures. For DMM, a similar temperature-dependent effect of NO was observed, but only for high NO concentration (2000 ppm). NO addition significantly suppresses the formation of hydrocarbon intermediates for both DME and DMM, but remarkably promotes the formation of methyl formate and methanol for DME. Several nitrogenous species were detected upon NO addition. The interactions of NO + HO2 and NO + OH, together with the regeneration routes of NO, are thought to be influential for both DME and DMM oxidation, while the significance of the NO + RO2 (R, fuel radical) reaction depends on the reactivity of the respective RO2 radical of DME and DMM. These results contribute to the understanding of OMEn/NO interactions and serve as a basis for further model development by providing new and detailed speciation data for DME/NO and DMM/NO oxidation.

B L Korsunskii - One of the best experts on this subject based on the ideXlab platform.

  • steady states of a Plug Flow Reactor operating on a heterogeneous liquid liquid system
    Russian Journal of Physical Chemistry B, 2018
    Co-Authors: N G Samoilenko, E. N. Shatunova, V A Bostandzhiyan, B L Korsunskii
    Abstract:

    A Plug Flow Reactor operating on a heterogeneous liquid−liquid system in which an exothermic bimolecular reaction takes place is modeled. The effect of the main governing parameters (Peclet and Damkheler numbers and a dimensionless parameter P characterizing mass transfer between the liquid phases) on the thermal modes of the Reactor is examined. Depending on the values of these parameters, one or three steady states can be realized in the Reactor. It is established that, with increasing parameter P, the region of multiplicity of steady states expands and shift toward lower values of the Damkohler number. The phenomenon of hysteresis is observed in the region of multiplicity of steady states.

  • thermal modes of a Plug Flow Reactor with a liquid liquid heterogeneous system
    Russian Journal of Physical Chemistry B, 2017
    Co-Authors: N G Samoilenko, E. N. Shatunova, V A Bostandzhiyan, B L Korsunskii
    Abstract:

    The thermal modes of a Flow Plug Reactor with an exothermic chemical reaction are numerically simulated. A heterogeneous reaction system consisting of two immiscible liquids is studied: one of the liquids (dispersed phase) in the form of droplets is distributed in the other (dispersion phase). The characteristics of the thermal modes of the Reactor at various values of two governing parameters, the Damkohler number and the rate of extraction of the dissolved substance from the dispersed phase into the dispersion phase is examined. Two modes of chemical reaction in the Reactor are demonstrated to be possible: low-temperature and high-temperature. Critical criteria of thermal ignition are formulated. The dependence of the structure of the thermal wave on the governing parameters is investigated.

  • Consecutive reactions in a countercurrent Plug-Flow Reactor. Gas-liquid system
    Russian Journal of Physical Chemistry B, 2013
    Co-Authors: L. V. Kustova, N G Samoilenko, B L Korsunskii
    Abstract:

    A mathematical model of a bimolecular two-step consecutive exothermic reaction in the liquid phase of a gas-step consecutive exothermic reaction in the liquid phase of a gas-Flow Reactor is proposed. Spatial profiles of the heatings and relative concentrations of the reactants in both phases for the steady state of the system are presented. The behavior of the reaction intermediate product is examined. The kinetic characteristics of the reaction are demonstrated to substantially influence the behavior of the system in the Reactor.