Hydrodynamics of a three-phase fixed-bed reactor operating in the pulsing flow regime at an elevated pressure

Abstract Results are presented for a three-phase reactor operating at an elevated pressure in the pulsing flow regime. For the system air–water and pressures of 0.1– 0.9 MPa lines are determined that define the change of the hydrodynamic model from the gas continuous flow regime (GCF) to the pulsing flow regime (PF). Also, parameters are found that characterize the pulsing flow of fluids, namely the velocity of pulses travelling along the bed, the frequency of pulsations and their structure, i.e., the length of the pulses and that of the liquid-rich zone.

Hydrodynamics of a Pressurised Three-phase Fixed-Bed Reactor, Operating in the Pulsing Flow Regime

Kinetics of vinyl acetate biodegradation by Pseudomonas fluorescens PCM 2123

Abstract The microbial degradation of vinyl acetate (VA) by Pseudomonas fluorescens PCM 2123 strain was studied in both batch and continuous modes. The purpose of the experiments was to determine the kinetic model of the cell growth and biodegradation rate of vinyl acetate (VA), which was the sole carbon and energy source for tested microorganisms. The experiments, carried out in a batch reactor for several initial concentrations of growth substrate in the liquid phase ranging from 18.6 to 373 gsubstrate·m−3 (gs·m−3) made it possible to choose the kinetic model and to estimate its constants. The Haldane inhibitory model with the values of constants: μm = 0.1202 h−1, KS = 17.195 gs·m−3, Ki =…

The Application of CFD Methods for Modeling of a Three-Phase Fixed-Bed Reactor

The mathematical model of the three-phase fixed-bed reactor (TBR) consisting of the continuity equation, the momentum balances of each phase and mass balances of reaction mixture components were presented and discussed. These balances are the result of averaging by means of Euler’s procedure and form the basis of the Computational Fluid Dynamics (CFD). Although the CFD model is based on fundamental principles some empirical relations (closure lows) must be implemented into the momentum balance in order to ensure a proper description of the dynamics of very complex three-phase system. Therefore, the sensitivity of a multiphase CFD model with respect to relations defining drag forces between …

Air purification from a mixture VOCs in the pilot-scale trickle-bed bioreactor (TBB)

The efficiency of the air bio-purification from the mixture of two volatile organic compounds (styrene and p-xylene) was studied. The process was carried out in a pilot-scale trickle-bed bioreactor installation designed to purify ∼200 m 3 h -1 of the polluted air. The bioreactor operated at concurrent flow of gas and liquid (mineral salt solution) through packing (polypropylene Ralu rings) covered with a thin layer of microorganisms (bacterial consortium of Pseudomonas sp. E-022150 and Pseudomonas putida mt-2). The experiments, carried out for various values of a reactor load with pollutant, confirmed the great efficiency of the investigated process. At the tested bed load with pollution (i…

Influence of the porosity profile and sets of Ergun constants on the main hydrodynamic parameters in the trickle-bed reactors

Abstract The Eulerian multiphase code has been applied for the comparative simulation of the experimental results obtained for varying flow rates of both fluid phases and for systems of various physicochemical properties used in the laboratory trickle-bed reactor (TBR). Therefore six different radial porosity profiles and three sets of the Ergun constants used in the relations defining the interphase momentum exchange have been implemented into the CFD code. The mean relative error of the pressure drop and of the averaged holdup as well as the standard deviation determined with respect to the experiments have been used as the criterion for the validation of the theoretical model. These valu…

Hydrodynamics of a cocurrent downflow of gas and foaming liquid through the packed bed. Part II. Liquid holdup and gas pressure drop

Abstract In the present study the results of experiments have been presented whose aim was to determine the values of liquid holdup as well as gas pressure drop through the packing for systems foaming under the pulse flow regime. On the basis of 245 experimental points for the pulse flow regime the verification of the models describing the hydrodynamics of the system has been performed. Attention was focused on the models of Benkrid et al. (Chem. Eng. Sci. 52 (1997) 4021), Pina et al. (AIChE J. 47 (2001) 19) and Fourar et al. (Chem. Eng. Sci. 56 (2001) 5987). It has been concluded that none of the models analysed describes the hydrodynamics of the foaming systems with enough accuracy. Next,…

Parametric sensitivity of a CFD model concerning the hydrodynamics of trickle-bed reactor (TBR)

Abstract The aim of the present study was to investigate the sensitivity of a multiphase Eulerian CFD model with respect to relations defining drag forces between phases. The mean relative error as well as standard deviation of experimental and computed values of pressure gradient and average liquid holdup were used as validation criteria of the model. Comparative basis for simulations was our own data-base obtained in experiments carried out in a TBR operating at a co-current downward gas and liquid flow. Estimated errors showed that the classical equations of Attou et al. (1999) defining the friction factors Fjk approximate experimental values of hydrodynamic parameters with the best agre…

Hydrodynamics of the cocurrent downflow of a gas and a foaming liquid through a packed bed. Part I. Estimation of the transition boundary between the hydrodynamic regimes from the gas continuous flow to the pulsing flow

Abstract In the study the results of investigations are presented aimed at determining such values of the operating parameters for which the change of the hydrodynamic regime occurs from the gas continuous flow (GCF) to the pulsing flow (PF). Nitrogen, helium and argon were used as the gas phase while the liquid phase was formed by the aqueous solutions of the alcohols C 1 –C 4 of the concentrations which ensured the foaming of the system. Thus a wide range of physicochemical properties of the system was covered in the experiments. The present study, as well as Part II, contain a wealth of experimental data which characterise the PF through the packing for the foam-forming systems. It is de…

Analysis of the hydrodynamics of a periodically operated trickle-bed reactor—A shock wave velocity

Abstract The relationship describing the shock wave velocity was formulated for the trickle-bed reactor operating at periodically changed feeding the bed with liquid phase. The values of shock wave velocity calculated from derived equations were compared with experimental values obtained for both fast and slow mode of base–pulse periodic liquid feeding and using liquids differing in physicochemical properties. A good agreement between these two sets of values of shock wave velocity was obtained. It has to be emphasized that the relationship (Eq. (26) ) derived in this study enables to estimate the values of the shock wave velocity when only mean values of variables of a process are known.

Modelling wet-air oxidation of phenol in a trickle-bed reactor using active carbon as a catalyst

BACKGROUND Catalytic wet air oxidation (CWAO) of phenol in a trickle-bed reactor has been investigated (operating parameters: P=1.85 MPa, T=393, 413, 433 K, L=0.17–1.77 kg m−2 s−1 and G=0.2–0.62 kg m−2 s−1). Activated carbon was used as a catalyst. The experimental results have been simulated by Eulerian multifluid model (CFD) and for comparison by the plug flow model. RESULTS The experiments proved that active carbon can be applied as a catalyst in the phenol oxidation processes revealing a catalytic activity comparable with that of commonly used metal oxides. The highest conversion of phenol obtained in long-lasting experimental runs carried out at stable catalytic activity (PO2 = 0.31 MP…

Hydrodynamics of a co-current three-phase solid-bed reactor for foaming systems

The objective of the present study was to evaluate the parameters, which characterize the pulsing flow of the gas and liquid through a bed, namely the frequency of pulsation, the velocity of the pulses and the pulse structure, for foaming systems. The paper presents the results of experiments aimed at determining the effect of the foaming power and the surface tension of liquid phase on the values of the measured parameters.