Performance Of Trickle-bed Reactor Research Articles

Study of Hydrodynamics and Residence Time Distribution in a Trickle Bed Reactor

This study focuses on investigating the hydrodynamics using computational fluid dynamics (CFD) simulation and residence time distribution (RTD) within a trickle bed reactor (TBR). CFD simulation was performed on a packed column filled with structured packing of glass beads, while the experiments for RTD studies were conducted in a TBR filled with random packing of Raschig rings. The geometry of TBR and size of packing during CFD simulation was kept close to that of the experimental setup. CFD simulation results were obtained which predicted the flow of fluid through the TBR at different vertical planes along the column. The fluctuations of liquid velocity at various positions inside the reactor were predicted by the CFD model. RTD studies were performed for both pulse input and step input using a non-reactive tracer such as sodium hydroxide. The flowrate of water was varied from 0.6 LPH to 6 LPH for pulse input, while for step input the ratio of water to tracer flowrates was kept at 1:1, 1:2 and 2:1. This study allows us to understand how hydrodynamics and residence time distribution may have an effect on the performance of TBR.

Optimizing Power-to-Gas Technology for Efficient Renewable Energy Storage and Integration in Germany: a Review

This study explores the integration of renewable energy sources into the German power grid, with a specific focus on the application of Power-to-Gas (PtG) technology as a solution for energy storage and optimization. Amidst the growing penetration of renewables, characterized by their intermittent nature, the challenge of maintaining a stable and reliable energy supply becomes paramount. This research delves into the use of Polymer Electrolyte Membrane (PEM) electrolysis for hydrogen storage and biological methanation within the PtG process chain, aiming to enhance the efficiency of methane production and the operational performance of trickle-bed reactors. By developing an economically viable approach for PtG technology and suggesting future business models, this work contributes to the identification of the most suitable electrolysis technology for sector coupling and grid integration. The findings indicate that PtG not only offers a promising pathway for the sustainable integration of renewable energies but also underlines the need for novel, application-oriented storage solutions and the optimization of system components for better market penetration and efficiency. This research underscores the pivotal role of PtG technology in bridging the gap between renewable energy production and the existing energy infrastructure, paving the way for a more sustainable and resilient energy system in Germany.

Sunshine-to-fuel: Demonstration of coupled photovoltaic-driven biomethanation operation, process, and techno-economical evaluation

The accelerating green transition envisions large shares of renewable intermittent power supplies, which challenges the balancing of the grid. A promising approach to long-term storage is the power-to-X technology of biomethanation. This study developed an operating model for ex situ biomethanation in a trickle bed reactor (TBR) based on daily photovoltaic (PV) solar generation profiles from the California Flats solar cell park and demonstrated long-term discontinuous biomethanation of raw biogas. The TBR was operated discontinuously for 29 days, where biomethane admissible for natural gas grid injection could be achieved within a ramp-up time of < 16 min after an adaptation period of 6 days with a purity of < 2 % hydrogen and > 97.5 % biomethane. The shutdown periods demonstrated a continuous digestion of accumulated acids and biomass. Therefore, shutting off the hydrogen addition could synergistically be employed as a clean-in-place procedure, where ∼60 % of the accumulated volatile fatty acids were converted during 12 h of standby. The TBR performance was subsequently used to evaluate the economic feasibility of integrating biomethanation to convert and store solar PV energy. The levelized cost of production of grid-quality biomethane by a small commercial biomethanation system, subject to solar PV energy (28 MWhe d−1), was found to be 147.84 $ (MWhCH4 HHV)−1 in a 2030 scenario.

Combining a robust thermophilic methanogen and packing material with high liquid hold-up to optimize biological methanation in trickle-bed reactors

The hydrogen gas-to-liquid mass transfer is the limiting factor in biological methanation. In trickle-bed reactors, mass transfer can be increased by high flow velocities in the liquid phase, by adding a packing material with high liquid hold-up or by using methanogenic archaea with a high methane productivity.This study developed a polyphasic approach to address all methods at once. Various methanogenic strains and packings were investigated from a microbial and hydrodynamic perspective. Analyzing the ability to produce high-quality methane and to form biofilms, pure cultures of Methanothermobacter performed better than those of the genus Methanothermococcus. Liquid and static hold-up of a packing material and its capability to facilitate attachment was not attributable to a single property. Consequently, it is recommended to carefully match organism and packing for optimized performance of trickle-bed reactors. The ideal combination for the ORBIT-system was identified as Methanothermobacter thermoautotrophicus IM5 and DuraTop®.

Comparison of jet loop and trickle-bed reactor performance in large-scale exploitation of glucose reductive aminolysis

Commercial scale jet-loop and trickle bed reactor simulations have been performed for the reductive aminolysis of glucose with dimethylamine (DMA) in combination with an experimental assessment in a (large) lab-scale fed-batch and trickle bed reactor. Based on the intrinsic kinetics of the sequence of homogeneous and heterogeneously catalyzed reaction steps in the reductive aminolysis reaction network, coupled with a different flow pattern and catalyst-to-liquid ratio, significant differences in the yield of N,N,N’,N’-tetramethylethylenediamine (TMEDA) and N,N-dimethylaminoethanol (DMAE) can be expected for both reactor types. Yet, TMEDA is obtained in the highest yields irrespective of the reactor type. In the jet-loop reactor, which is operated overall as a batch reactor, an optimized TMEDA yield up to 57 % is simulated, while a non-negligible yield of DMAE, up to 12 %, is also achieved. The optimized operating conditions are such that they correspond to the high DMA to glucose ratio used during lab-scale fed-batch experimentations, also explaining why the jet-loop product spectrum is almost identical to the latter. This is ensured by the efficient heat-exchange in the jet-loop reactor, which is, in contrast, one of the main bottlenecks for exploitation of the reductive aminolysis in a trickle bed reactor. The second challenge to address in the trickle bed reactor is the limited extent of hydrogen transfer from gas to liquid, which can only be partially overcome by increasing the feed flow rates. While isothermal operation indicates TMEDA yields of about 60 %, non-isothermally simulated TMEDA yields only amount to 40 %. The latter yield loss was also validated experimentally in the trickle bed reactor and confirmed that avoiding degradation reactions remains challenging as it is critical in the reductive aminolysis of glucose.

Eulerian simulations of liquid distribution generated by chimney and bubble cap distributors

• Measurements on flow through single units of industrial gas-liquid distributors. • Liquid flow morphology analyzed using dual-tip voidage probes. • Development of Eulerian CFD model with weighted drag formulation and validation. • Performance analysis of chimney and bubble cap distributor configurations. • Effect of addition of liquid dispersion plates on liquid distribution. Gas–liquid distributors form an integral part of an industrial packed bed reactor, esp. trickle bed reactors used for hydrodesulphurization of liquid fuels. Among several process parameters that influence performance of trickle bed reactors, gas–liquid distributors are of foremost importance. In the present work, we have developed a computational model based on Eulerian two-fluid approach to simulate the gas–liquid flow in widely–varying flow regimes encountered in a distributor unit. The predictions are validated using the liquid distribution measured using high-speed imaging, morphology of gas–liquid flow measured using in–house developed voidage probes, and pressure drop measurements. Owing to the difference in the inherent nature of flow through the standard chimney and standard bubble cap distributors, the liquid discharge pattern, uniformity and symmetry of flow streams, and pressure drop across the distributor were found to be significantly different from each other. Further, the addition of liquid dispersion plates to the outlet of the main distributor unit not only resulted in improved liquid discharge pattern and wider coverage span, but also in a highly dispersed stream. Lastly, the application of the above study and the presented methodology was demonstrated for predicting the gas–liquid distribution through industrial trays, using standard bubble cap and chimney trays.

Analyzing the impact of implementing different approaches of the approximation of the catalyst effectiveness factor on the prediction of the performance of trickle bed reactors

Abstract A steady-state diffusion model comprising of diffusion and reaction in a catalyst pellet was used to study and understand the effect of the approximation of the catalyst effectiveness factor in the modeling of trickle bed reactors. The hydrogenation of alpha-methylstyrene was chosen as the case study reaction from literature for liquid-limited reaction conditions. The effectiveness factor values in this study were sensitive to reactor scale equations during the prediction of reactor performance. The approximation of accounting for the overall catalyst effectiveness factor in the reactor scale model equations from different models and solving the reactor scale model equations by different modeling approaches was assessed. It was observed that evaluating the overall effectiveness factor from pellet scale model equations and integrating the parameter in the reactor scale axial dispersion model at every local axial collocation point to simulate the reactor performance showed better agreement to the experimental data. This approach evaluates the effectiveness factor locally with the variation of the reactant concentration at different axial points across the reactor rather than using one value for the entire reactor. The approach of using a single effectiveness factor for the whole bed and using the effectiveness factor approximated as a fitted polynomial to the reactant concentrations did not properly predict the reactor performance.

Performance enhancement of biological methanation with trickle bed reactors by liquid flow modulation

AbstractExperiments were carried out to investigate the influence of liquid flow modulation of trickle bed reactors (TBR) on biological hydrogen methanation (BHM). The modulation promises to improve the gas‐liquid mass transfer and has already been demonstrated in trickle bed reactors of other fields of application. Therefore, the influence of four different circulation intervals with pauses from two to 1,440 min was investigated in TBR for BHM. The results showed that as pause intervals without sprinkling became longer, the methane content increased from 88.61 ± 1.58 vol‐% at a circulation interval of 2 min to up to 97.19 ± 0.46 vol‐% at a circulation interval of 1,440 min. The analysis of the process liquid indicated a stable biological process at any trial phase. This study demonstrated that the performance of TBR on BHM can be significantly improved by liquid flow modulation, thus significantly reducing operating costs.

Effect of capillary pressure force on local liquid distribution in a trickle bed

Accurate prediction of the local liquid volume fraction (εL) distribution, an important process parameter that governs the performance of Trickle Bed Reactors (TBRs), is still a challenge. In the present work, Eulerian multi-fluid simulations of local εL distribution were performed in a laboratory-scale pseudo-3D (rectangular) and cylindrical TBR and the predictions were compared with the Electrical Resistance Tomography (ERT) measurements of Singh et al. (2017). The effect of formulation of capillary pressure force (F‾C) was investigated and it was found that -PC∇εL definition of F‾C preserved the functional relation between the capillary pressure (PC) and εL, and that εL∇PC definition of F‾C reversed the same. Through the simulations performed for the pseudo-3D column, we showed that the alteration in the functional relation severely affects the ability of F‾C=εL∇PC definition to predict the effects of particle diameter, gas and liquid flow rates. It was elucidated that such an alteration underpredicts F‾C and could necessitate the inclusion of additional dispersion forces for particles with small diameters. F‾C implemented as -PC∇εL provided satisfactory predictions of the steady-state local εL distribution for the bed pre-wetted with the pseudo-Kan pre-wetting method. However, the PC model required an empirical correction ([(dP/dthr)(εS)0.6]-13.957) to predict the steady-state local εL distribution in the bed pre-wetted using the Levec method. While the modified F‾C predicted the time-averaged local εL distribution satisfactorily for different liquid flow rates and liquid distributor configurations, it was seen that further reduction in F‾C was required to predict the dynamic liquid spreading behavior under synthetically created pulsing flow conditions.

Performance of Trickle Bed Reactor and Active Carbon in the Liquid Phase Oxidation of Phenol

Application of trickle-bed reactor and active carbon catalyst to catalytic wet air oxidation of phenolic pollutants is explored over a wide range of operating conditions. The study focuses on the assessment of key engineering aspects such as reactor start-up, gas-liquid flow directions and effects of temperature, pressure, phenol feed concentration and liquid flow rate on activity and stability performance of unsupported active carbon. Moreover, for analyzing the potential integration of CWAO as a pre-treatment in biological wastewater remediation, intermediate distribution and biodegradability enhancement of treated effluents are obtained from HPLC analysis and respirometry assays, respectively. Finally, since slow carbon burn-off is occurring at CWAO conditions, some promising options for improvement of catalyst stability are pointed out on both molecular (iron coating of active carbon) and reactor (periodic reactor operation) scale.

TWO-PHASE PRESSURE DROP IN A TRICKLE BED REACTOR INVOLVING NEWTONIAN/NON-NEWTONIAN LIQUID PHASE

Pressure drop is an important parameter in the process design and performance of trickle bed reactors as it affects the energy requirements and hence the operating cost and sizing of the reactor. Various hydrodynamic factors that influence the two-phase pressure drop of a trickle bed reactor when Newtonian liquid phases are involved include gas flow rate, liquid flow rate, surface tension of the liquid phase, viscosity of the liquid phase, and bed characteristics such as porosity and sphericity of the packing material. For viscoinelastic fluid flow consistency index K and flow behavior index n are observed to affect the pressure drop significantly, whereas, for viscoelastic fluids, fluid elasticity leads to higher pressure drop. In the present study the effects of various parameters (involving bed characteristics and liquid-phase properties ranging from simple water-like Newtonian fluids to complex viscoelastic non-Newtonian fluids) on two-phase pressure drop are investigated. A wide range of correlations for two-phase pressure drop are available in the literature, however, none of the correlations seem to be applicable over a wide range of bed characteristics and fluid-phase properties as investigated in the present study. The experimental observations indicated that the pressure drop rises significantly when the flow regime changes from low to high interaction. Hence the data corresponding to low- and high-interaction regimes are treated separately to yield suitable correlations for Newtonian and non-Newtonian fluids. The correlations developed predicted the literature data for Newtonian liquid -phases to within±20%. The correlations are extended to predict two-phase pressure drop for viscoinelastic and viscoelastic liquid phases.

Effect of hydrodynamic multiplicity on trickle bed reactor performance

AbstractMultiple hydrodynamic states in trickle bed reactors have been the subject of numerous hydrodynamic investigations. The extent of variation in the hydrodynamic parameters (like holdup and pressure drop) is large and this variation can be expected to have a significant impact on the conversion in a reaction system. This study presents reaction data for α‐methyl styrene hydrogenation in a trickle bed reactor over a range of conditions that include gas and liquid limitations. It is seen that liquid flow rate variation induced hysteresis has a large impact on the conversion. For gas‐limited reactions, the upper branch of the pressure drop hysteresis loop has a higher conversion than the lower branch at the same linear fluid velocities and catalyst weight, while for liquid‐limited reactions the lower branch has a higher conversion than the upper branch (the difference in productivity being up to 20%). These trends cannot be explained by differences in wetting efficiency. Instead, it is proposed that for this system the gas–liquid mass transfer rate is the limiting step in gas‐limited reactions, while the liquid–solid mass transfer rate is the limiting step in liquid‐limited reactions. © 2007 American Institute of Chemical Engineers AIChE J, 2008

Liquid flow texture analysis in trickle bed reactors using high-resolution gamma ray tomography

Abstract Trickle bed reactor performance and safety may suffer from radial and axial liquid maldistribution and thus from non-uniform utilization of the catalyst packing. Therefore, experimental analysis and fluid dynamic simulation of liquid–gas flow in trickle bed reactors is an important topic in chemical engineering. In the present study for the first time a truly high-resolution gamma ray tomography technique was applied to the quantitative analysis of the liquid flow texture in a laboratory cold flow trickle bed reactor of 90 mm diameter. The objective of this study was to present the comparative analysis of the liquid flow dynamics for two different initial liquid distributions and two different types of reactor configurations. Thus, the hydrodynamic behavior of a glass bead packing was compared to a porous Al2O3 catalyst particle packing using inlet flow from a commercial spray nozzle (uniform initial liquid distribution) and inlet flow from a central point source (strongly non-uniform initial liquid distribution), respectively. The column was operated in downflow mode at a gas flow rate of 180 L h−1 and at liquid flow rates of 15 and 25 L h−1.

Hydrogenation of Dicyclopentadiene intoendo-Tetrahydrodicyclopentadiene in Trickle-Bed Reactor: Experiments and Modeling

Hydrogenation of dicylcopentadiene (DCPD) into endo-tetrahydrodicylcopentadiene (endo-THDCPD), in the presence of a Pd/Al2O3 catalyst, was experimentally and theoretically studied in a quasi-adiabatic trickle-bed reactor (TBR) with a diameter of 24 mm and a length of 850 mm. Effects of several operation parameters, including the liquid hourly space velocity (LHSV) (5.86−14.65 h-1), hydrogen pressure (1.0−2.0 MPa), inlet liquid concentration (0.52−1.35 mol/L), and inlet temperature (319.15−379.15 K) on the TBR performance were investigated systematically in terms of DCPD conversions, THDCPD yields, global hydrogenation rates, and axial temperature profiles. A plug-flow model for TBR incorporating partial wetting, mass and enthalpy balance, and phase equilibia behavior was developed to simulate the experimental results, based on a phenomenological pellet-scale model suggested by Rajashekharam et al. in a previous publication [Chem. Eng. Sci. 1998, 53 (4), 787−805]. The comparisons of experimental and simulated results indicated that the developed model reliably predicted the performance and axial temperature profiles.

Hydrodynamic study of fixed beds with cocurrent upflow and downflow

The performance of trickle bed reactor was studied by comparing the two modes of operation: cocurrent upflow and downflow of gas and liquid. The three important hydrodynamic parameters, two-phase pressure drop, total liquid holdup and axial dispersion were studied and the results for both modes of operation were compared. It was found that the two-phase pressure drop and total liquid holdup are higher for the upflow mode of operation at lower gas and liquid velocities, but with increasing flow rates, the two parameters were comparable for upflow and downflow modes. The values of Peclet number were higher in downflow mode of operation for the entire range of flow rates studied indicating the presence of lower backmixing in the downflow mode of operation. A comparison of the experimental observation with the correlations available in literature is presented. Correlations for estimating total liquid holdup and Peclet number (based on regression analysis) have been proposed.

Mathematical simulations of the performance of trickle bed and slurry reactors for methanol synthesis

Three- and two-phase reactor models were developed to simulate the performance of trickle bed and slurry reactors for methanol synthesis. The combination of orthogonal collocation and quasi-linearization was used to solve the trickle bed reactor model incorporating resistance to interparticle and intraparticle diffusion and resistance to mass transfer between gas and liquid phases. Model parameters were estimated independently from either published correlations or literature data. The model predicts significant resistance to intraparticle diffusion on the performance of trickle bed reactors. However, comparisons between pilot size trickle bed and slurry reactors illustrate the superior performance of trickle bed reactors over the slurry reactors for methanol synthesis even with diffusion limitations.

Multiphase Flow Packed-Bed Reactor Modeling: Combining CFD and Cell Network Model

The performance of a multiphase flow packed-bed reactor was evaluated by a mixing-cell network model in which the cell-scale flow field information was provided by multifluid CFD modeling. Such a sequentially combined modeling approach was able to show the heterogeneity of liquid species conversion in a trickle-bed reactor that has been confirmed by in situ magnetic resonance experiments.1 A conventional plug flow model (PFM) and axial dispersion model (ADM) showed either overpredicted or underpredicted conversion compared with the conversion computed from the CFD-Cell Network model. Preliminary case study has shown the ability of the CFD-Cell Network model in assessing the impact of flow distribution on the trickle-bed reactor performance, which is a great help to trickle-bed reactor design and diagnosis.

Unsteady-state operation of trickle-bed reactors

An experimental and theoretical study of forced unsteady-state operation of trickle-bed reactors in comparison to the steady-state operation is the subject of this paper. It is well known that changes in the control variables influence the regime and the performance of trickle-bed reactors. In this study as one example for a forced periodic operation of a trickle-bed reactor an unsteady-state technique was used in which the catalyst bed is contacted periodically with different liquid flow rates. The unsteady-state operation was considered as square-waves cycling liquid flow rate at the reactor inlet. The hydrogenation of alpha-methylstyrene to cumene: C 6 H 5 (CH 3 )=CH 2 ( L ) + H 2 ( G ) → C 6 H 5 CH(CH 3 ) 2 ( L ) over a Palladium-catalyst (0.7% Pd/ γ -Al 2 O 3 ) was selected as a model reaction. The experimental results of the alpha-methylstyrene hydrogenation in a laboratory-scale trickle-bed reactor showed, that the reactor performance can be significantly improved by feed liquid flow modulation. The simulation studies demonstrate that the liquid flow variation has a strong influence on the liquid hold-up oscillation and on the catalyst wetting efficiency. Consequently the time average alpha-methylstyrene conversion will be increased, because the mass transfer resistance between the phases (gas–liquid, gas–solid and liquid–solid) affect the overall reaction rate and consequently the conversion will be improved.

Effects of Induced Pulsing Flow on Trickle-Bed Reactor Performance

The benefits of trickle-bed reactor operation under the induced pulsing flow regime are investigated using experiments and modeling. Under these conditions, by cycling the liquid feed, trickling and pulsing flow regimes can be made to alternate during the cycle period under time-averaged conditions corresponding to the trickling flow regime. For the hydrogenation of phenylacetylene over Pt/γ-Al2O3 catalyst, experimental results obtained in a laboratory-scale reactor operating under mild gas-limiting conditions indicate better performance for steady flow, as opposed to induced pulsing flow. The model predictions compare well with the experimental data. Further, simulations of a trickle-bed reactor over a wide range of initial reactant concentrations and pressures predict up to 45% improvement in styrene selectivity for induced pulsing flow under liquid-limited conditions. The findings suggest that enhancements in reactor performance due to induced pulsing can be expected for liquid-limited systems, which g...

Multi-functional trickle bed reactor for butylacetate synthesis

Esterification—the reaction of acetic acid and butanol in a trickle bed reactor, packed with a strong acid ion-exchange resin, operating with partial evaporation of reaction mixture into inert gas (nitrogen) stream—was investigated in this study. The experiments were carried out under atmospheric pressure. Reaction temperature was maintained in the interval from 70 to 120 °C, i.e. above the boiling point of the azeotropic mixture containing part of unreacted alcohol and both reaction products, i.e. ester and water. Partial evaporation of the reaction mixture into the inert gas (nitrogen) stream passing through the catalyst bed and consequent separation of reaction products into vapour and liquid phases shifted the chemical equilibrium of the reaction. The paper propose two different techniques for increasing the performance of trickle bed reactor for mentioned esterification: simultaneous reaction and evaporation and periodic modulation of the feed rate.