Heat transfer study in corrugated wall bubbling fluidized bed reactor: Experiments and CFD simulations

Gasification technology must ideally be bestowed with the following traits: auto/allothermal process, non-diluted biosyngas abolishing downstream N2 separation or upstream O2 enrichment, thermal coupling via micro-segmentation between endothermic and exothermic steps to improve heat exchanges and enhance thermal efficiency, and high yield and heating value of biosyngas. These attributes represent the foremost challenges next-generation biomass steam gasifiers must cope with. With the endeavor of approaching such ideal configuration, Iliuta et al. proposed a reactor concept of allothermal cyclic multicompartment bubbling fluidized beds. Gas solid fluidized bed reactors would be used to obtain the enhanced heat and mass transport and conversion performances as compared to packed beds. Corrugated walls were installed in narrow gas-solid bubbling fluidized bed (CWBFB) enclosures to decrease minimum bubbling velocity, reduce bubble sizes, improve gas distribution, offer stable operation and minimize the particles carryover or loss. Thorough analyses of wall-to-bed heat transfer coefficient in flat- (FWBFB) and corrugated- (CWBFB) wall bubbling fluidized beds were performed for a variety of wall declinations and operating conditions covering a range of corrugation angles, inter-wall clearances (C), initial rest bed heights (Hi) and ratios of gas superficial velocity to minimum bubbling velocity, Ug/Umb (1-1.55). Fast response self-adhesive heat flux probes and thermocouples were employed to simultaneously measure the wall-to-bed heat flux, surface temperature and bed temperature. These instruments were used to measure the heat transfer coefficient (HTC) at different (18) axial and lateral locations. For a given set of parameters, significant increase in HTC was observed at lower gas flow rate in CWBFB as compared to FWBFB. It showed that CWBFB inventory required lesser Umb (gas flow rate) and offered more economical gas solid fluidization phenomena as compared to FWBFB. Full 3-D transient Euler-Euler CFD simulations employing kinetic theory of granular flow were also carried out which corroborated with experimental findings

Liquid spreading in trickle-bed reactors: Experiments and numerical simulations using Eulerian--Eulerian two-fluid approach

Liquid spreading in gas-liquid concurrent trickle-bed reactors is simulated using an Eulerian twofluid CFD approach. In order to propose a model that describes exhaustively all interaction forces acting on each fluid phase with an emphasis on dispersion mechanisms, a discussion of closure laws available in the literature is proposed. Liquid dispersion is recognized to result from two main mechanisms: capillary and mechanical (Attou and Ferschneider, 2000; Lappalainen et al., 2009- The proposed model is then implemented in two trickle-bed configurations matching with two experimental set ups: In the first configuration, simulations on a 2D axisymmetric geometry are considered and the model is validated upon a new set of experimental data. Overall pressure drop and liquid distribution obtained from $\gamma$-ray tomography are provided for different geometrical and operating conditions. In the second configuration, a 3D simulation is considered and the model is compared to experimental liquid flux patterns at the bed outlet. A sensitivity analysis of liquid spreading to bed geometrical characteristics (void-fraction and particles diameter) as well as to gas and liquid flow rates is proposed. The model is shown to achieve very good agreement with experimental data and to predict, accurately, tendencies of liquid spreading for various geometrical bed characteristics and/or phases flow-rates

High-Pressure Trickle-Bed Reactors: A Review

A Concise Review of Relevant Experimental Observations and Modeling of High-Pressure Trickle-Bed Reactors, based on Recent Studies, is Presented. the Following Topics Are Considered: Flow Regime Transitions, Pressure Drop, Liquid Holdup, Gas-Liquid Interfacial Area and Mass-Transfer Coefficient, Catalyst Wetting Efficiency, Catalyst Dilution with Inert Fines, and Evaluation of Trickle-Bed Models for Liquid-Limited and Gas-Limited Reactions. the Effects of High-Pressure Operation, Which is of Industrial Relevance, on the Physicochemical and Fluid Dynamic Parameters Are Discussed. Empirical and Theoretical Models Developed to Account for the Effect of High Pressure on the Various Parameters and Phenomena Pertinent to the Topics Discussed Are Briefly Described

Pore-network modeling of trickle bed reactors: Pressure drop analysis

A pore network model (PNM) has been developed to simulate gas–liquid trickle flows inside fixed beds of spherical particles. The geometry has been previously built from X-ray micro-tomography experiments, and the flow in the throats between pores is modeled as a pure viscous Poiseuille two-phase flow. The flow distribution between pores and throats is obtained by solving mass and momentum balance equations. As a first application of this simple but powerful meso-scale model, a focus is proposed on the ability of PNM to estimate pressure drop and liquid saturation in co-current gas–liquid flows. PNM results are compared to the classical 1D pressure drop models of Attou et al. (1999), Holub et al. (1992) and Larachi et al. (1991). Agreement and discrepancies are discussed, and, finally, it has been found that the actual PNM approach produces realistic pressure drops as far as inertial contributions to friction are negligible. Concerning liquid saturation, the PNM only estimates its value in the throats between pores. As a consequence, liquid saturations are overestimated, but they can be easily corrected by an ad hoc empirical model

Emulating the dynamic behavior of gas-liquid flows in porous media under marine swell conditions for floating platform applications

Talk: Regular Abstract: Boundaries for hydrocarbon exploitation are being increasingly stretched towards remoter and deeper spots around the Globe. This entails recourse to floating production systems as an alternative to conventional off-shore oil platforms such as Deep Draft Semi Sub, Extendable Draft Platform, and so forth. Floating platforms are commonly integrated with floating units such as Floating Storage and Offloading (FSO), Floating Production Unit (FPU), Floating Liquefied Natural Gas (FLNG) and Floating Production Storage and Offloading (FPSO) which are used to replace costly pipeline infrastructures and onshore refining-treating facilities. It is thus not a surprise that development and application of floating units, e.g., FPSO and FLNG in deep-water oilfields, are subject to vivid research by the petroleum industry. One of the challenges confronting well-designed units resides on how the efficiency and performance of offshore facilities correlate with the restless sways caused by marine swells and how these latter impact the hydrodynamic characteristics of the reactors that are embarked on-board. In this presentation, we will discuss our recent results on multiphase packed-bed reactors mounted on a six-degrees-of-freedom hexapod robot to emulate swell movements and to analyze the hydrodynamic alterations brought about by separate or combined degrees of freedom under yaw and pitch rotations, and jerky swell movements versus stationary (straight and inclined) bed configurations. A twin-plane capacitance Wire Mesh Sensor (WMS) installed on the moving packed beds is used to measure the dynamic features of local phase distribution patterns, local and averaged liquid saturations and velocities, and flow regime changes under various configurations, e.g., concurrent two-phase upflow, downflow and drainage mode. Deviations from well-known behavior of straight and stationary packed-bed two-phase flows will be highlighted, quantified and interpreted.Non UBCUnreviewedAuthor affiliation: LavalFacult