scholarly journals Bed structure and its impact on liquid distribution in a trickle bed reactor

2021 ◽  
Author(s):  
Akarsha Srivastava ◽  
Krishna Nigam ◽  
Shantanu Roy
Keyword(s):  
Gas Flow ◽  
Flow Characteristics ◽  
Two Phase ◽  
Liquid Distribution ◽  
Trickle Bed Reactor ◽  
Catalytic Sites ◽  
Void Structure ◽  
Liquid Distributor ◽  
Trickle Bed ◽  
Catalyst Pellets

The work reported in this investigation involves the determination of the hydrodynamic properties of the Trickle Bed Reactor which has been loaded in various ways to mark the effect of the loading methodologies employed to pack the catalyst pellets. The bed structure of a packed three-phase reactor is critical to study as it provides the essential contact between the phases and provides the catalytic sites where the reaction takes place. Depending on the structural properties of the bed such as local void structure, liquid distribution, two-phase pressure drop, and holdup of fluids gets affected. The study aims to envelop the catalyst bed characteristics such as the local void structure, the length of the catalyst bed, flow characteristics such as liquid and gas flow rate, and liquid distributor at the top of the catalyst bed to gauge and quantify their effect on the hydrodynamics of a trickle bed reactor.

scholarly journals Liquid distribution and its effect on local mass transfer in a packed column of Pall rings

2021 ◽  
Author(s):  
Yongjia Zhu
Keyword(s):  
Mass Transfer ◽  
Gas Flow ◽  
Transfer Coefficients ◽  
Liquid Distribution ◽  
Fully Developed Flow ◽  
Flow Rates ◽  
Local Mass ◽  
Local Mass Transfer ◽  
Liquid Distributor ◽  
Wall Flow

The spatial variations of liquid distribution and local mass transfer coefficient in a 0.30-m column of 25.4-m Pall rings were investigated. The data of liquid distribution was collected with a 39-cell liquid collector and a wall-flow tube from a doubled-wall section in the column at the packing-support level. The local mass transfer coefficients were measured via the electrochemical technique by individual cathodic nickel-coated Pall rings placed at various spatial positions. Both measurements were conducted at various fluid flow rates with three liquid distributor designs at different bed heights. Liquid distribution and local mass transfer coefficients observed were far from uniform in the column. The wall flow developed along the packed bed until a fully developed flow pattern was reached. With more uniform initial liquid distribution, the less packing height needed to reach the fully developed flow pattern along with higher the mass transfer efficiency in the column. Ladder-type liquid distributor (LLD) showed less angular effect in measurements. Increasing the liquid flow rate slightly improved the uniformity of liquid distribution and enhanced the mass transfer. No influence of gas flow rate on liquid distribution and mass transfer coefficient was found at the range of gas flow rates used. These gas flow rates were much lower than the loading point. Liquid maldistribution factor and mass transfer maldistribution factor decreased with increases in the uniformity of the initial liquid distribution. These values were 0.21(0.48). 0.16(0.26) and 0.14(0.22) for single-point liquid distributor (SPLD), cross-type liquid distributor (CLD) and LLD, respectively. By comparison, a good agreement was observed on the relation of liquid maldistribution factor and mass transfer maldistribution factor.

scholarly journals Liquid distribution and its effect on local mass transfer in a packed column of Pall rings

2021 ◽  
Author(s):  
Yongjia Zhu
Keyword(s):  
Mass Transfer ◽  
Gas Flow ◽  
Transfer Coefficients ◽  
Liquid Distribution ◽  
Fully Developed Flow ◽  
Flow Rates ◽  
Local Mass ◽  
Local Mass Transfer ◽  
Liquid Distributor ◽  
Wall Flow

The spatial variations of liquid distribution and local mass transfer coefficient in a 0.30-m column of 25.4-m Pall rings were investigated. The data of liquid distribution was collected with a 39-cell liquid collector and a wall-flow tube from a doubled-wall section in the column at the packing-support level. The local mass transfer coefficients were measured via the electrochemical technique by individual cathodic nickel-coated Pall rings placed at various spatial positions. Both measurements were conducted at various fluid flow rates with three liquid distributor designs at different bed heights. Liquid distribution and local mass transfer coefficients observed were far from uniform in the column. The wall flow developed along the packed bed until a fully developed flow pattern was reached. With more uniform initial liquid distribution, the less packing height needed to reach the fully developed flow pattern along with higher the mass transfer efficiency in the column. Ladder-type liquid distributor (LLD) showed less angular effect in measurements. Increasing the liquid flow rate slightly improved the uniformity of liquid distribution and enhanced the mass transfer. No influence of gas flow rate on liquid distribution and mass transfer coefficient was found at the range of gas flow rates used. These gas flow rates were much lower than the loading point. Liquid maldistribution factor and mass transfer maldistribution factor decreased with increases in the uniformity of the initial liquid distribution. These values were 0.21(0.48). 0.16(0.26) and 0.14(0.22) for single-point liquid distributor (SPLD), cross-type liquid distributor (CLD) and LLD, respectively. By comparison, a good agreement was observed on the relation of liquid maldistribution factor and mass transfer maldistribution factor.

scholarly journals Computation of Two-Phase Flows in Low-NOx Combustor Premix Ducts Utilizing Fuel Film Evaporation

1997 ◽  
Author(s):  
Heiko Rosskamp ◽  
Michael Willmann ◽  
Sigmar Wittig
Keyword(s):  
Gas Turbines ◽  
Gas Flow ◽  
Turbulence Modeling ◽  
Coke Formation ◽  
Flow Characteristics ◽  
Computer Code ◽  
Two Phase ◽  
Boundary Layer Equations ◽  
Film Evaporation ◽  
Wall Film

For aircraft gas turbines as well as for industrial gas turbines current and future developments aim at the implementation of lean premixed-prevaporized (LPP) combustor techniques. For the development and optimization of these combustors powerful CFD-codes are required. A new code developed at the Institut für Thermische Strömungsmaschinen (ITS), University of Karlsruhe, provides detailed information on the gas flow as well as on the propagation and evaporation characteristics of liquid wall films inside combustors. The flow characteristics of the gas phase are predicted using a Finite-Volume 3D-Navier-Stokes code with k-ε turbulence modeling. To calculate the evaporation characteristics of a propagating wall film, a two-dimensional wall film model based on the boundary layer equations is proposed. The present paper comprises a comparison between calculations and experiments for the verification of the code and a detailed study on the evaporation characteristics of fuel films. The results obtained allow judgement to be made on the risk of coke formation on the prefilming surface and suggest that in some operating points a LPP combustor can be operated utilizing solely film evaporation. In addition, the computer code developed also accounts for many familiar types of shear driven film flows such as internal prefilming air blast atomizer flows for example.

RADIAL LIQUID DISTRIBUTION IN A TRICKLE BED REACTOR

1987 ◽  
Vol 60 (1-6) ◽  
pp. 243-252 ◽  
Author(s):  
M. BORDA ◽  
J.F. GABITTO ◽  
N.O. LEMCOFF
Keyword(s):  
Liquid Distribution ◽  
Trickle Bed Reactor ◽  
Trickle Bed

Visualization Study on Two-Phase Flow Behaviors in the Gas-Liquid-Solid Microreactor for Hydrogenation of Nitrobenzene

2016 ◽  
Author(s):  
Hao Feng ◽  
Xun Zhu ◽  
Rong Chen ◽  
Qiang Liao
Keyword(s):  
Flow Rate ◽  
Liquid Flow ◽  
Gas Flow ◽  
Two Phase Flow ◽  
Flow Direction ◽  
Flow Characteristics ◽  
Phase Flow ◽  
Microchannel Reactor ◽  
Two Phase ◽  
Modified Surface

In this study, visualization study on the gas-liquid two phase flow characteristics in a gas-liquid-solid microchannel reactor was carried out. Palladium nanocatalyst was coated onto the polydopamine functionalized surface of the microchannel through eletroless deposition. The materials characterization results indicated that palladium nanocatalyst were well dispersed on the modified surface. The effects of both the gas and liquid flow rates as well as inlet nitrobenzene concentration on the two-phase flow characteristics were studied. The experimental results revealed that owing to the chemical reaction inside the microreactor, the gas slug length gradually decreased along the flow direction. For a given inlet nitrobenzene concentration, increasing the liquid flow rate or decreasing the gas flow rate would make the variation of the gas slug length more obvious. High inlet nitrobenzene concentration would intensify both the nitrobenzene transfer efficiency and gas reactants consumption, and thereby the flow pattern in the microchannel was transferred from Taylor flow into bubble flow. Besides, the effect of both flow rate and original nitrobenzene concentration on the variation of nitrobenzene conversion and the desired product aniline yield were also discussed.

scholarly journals Liquid Distribution in Trickle-Bed Reactor

2000 ◽  
Vol 55 (4) ◽  
pp. 407-415 ◽  
Author(s):  
C. Marcandelli ◽  
A. S. Lamine ◽  
J. R. Bernard ◽  
G. Wild
Keyword(s):  
Liquid Distribution ◽  
Trickle Bed Reactor ◽  
Trickle Bed

scholarly journals Flow Study and Wetting Efficiency of a Perforated-Plate Tray Distributor in a Trickle Bed Reactor

2010 ◽  
Vol 8 (1) ◽  
Author(s):  
Damian Enrique Ramajo ◽  
Santiago Marquez Damian ◽  
Marcela Raviculé ◽  
Maria M. Monsalvo ◽  
Mario Storti ◽  
...  
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Perforated Plate ◽  
Operating Conditions ◽  
Liquid Volume ◽  
Liquid Distribution ◽  
Trickle Bed Reactor ◽  
Ceramic Ball ◽  
Trickle Bed

In this work, a computational fluid dynamics analysis (CFD) employing the Eulerian two-fluid model was carried out with the aim to understand the distribution process and to determine the wetting efficiency of the primary tray distributor (perforated plate) of a trickle bed reactor (TBR) under several operating conditions. The overall inlet geometry was considered, and the small holes of the perforated plate were modeled by sinks (drains) and sources, employing CFD and experimental models to obtain the hole discharge flow coefficients. The influence of the ceramic-ball bed above the catalyst bed was considered by a suitable correlation to estimate liquid distribution inside it.Results showed that because of the scarce liquid sloshing above the tray, little difference on liquid flow rate through the tray holes was found. Due to the really low inlet mass flow rate of gas, it has negligible influence on liquid behavior, which drops through holes slowly without spraying. Thus, the ceramic-ball bed above the catalyst bed is exclusively wetted in a small area under the tray holes. Although the ceramic-ball bed improves liquid distribution, which guarantees a minimum liquid volume fraction at all places, significant differences on the liquid mass flow rate across the top of the catalyst bed were found. Additional causes of low efficiency in TBR like the well-known fouling vulnerability of perforated-plate trays and unevenness were analyzed. For the first, two simple modifications were proposed to improve tray performance: reducing the amount of gas chimneys to only one and adding additional drip points and replacing the tray holes by short risers in order to avoid plugging.

Investigating the Effect of Pipe Inclination on Two-Phase Gas-Liquid Flows Using Advanced Instrumentation

2011 ◽  
Author(s):  
Abolore Abdulahi ◽  
Lokman A. Abdulkareem ◽  
Safa Sharaf ◽  
Mukhtar Abdulkadir ◽  
Valente Hernandez Perez ◽  
...  
Keyword(s):  
Time Series ◽  
Void Fraction ◽  
Flow Rate ◽  
Gas Flow ◽  
Oil And Gas ◽  
Silicone Oil ◽  
Flow Characteristics ◽  
Superficial Velocity ◽  
Wire Mesh ◽  
Two Phase

Pipes that make up oil and gas wells are not vertical but could be inclined at any angle between the vertical and the horizontal which is a significant technology of modern drilling. Hence, this study has been undertaken to look at the effect of inclination on flow characteristics especially at 10 degrees from both horizontal and vertical. Air/silicone oil flows in a 67 mm slightly deviated pipe have been investigated using advanced instrumentation: Wire Mesh Sensor Tomography (WMS) and Electrical Capacitance Tomography (ECT). They provide time and cross-sectionally resolved data on void fraction. Both the ECT probes and WMS were mounted on the inclined pipes upstream just at the point where flows were fully developed. By keeping the liquid flow rate constant at 10 litres/min (or liquid superficial velocity of 0.052m/s), gas flow rate was varied from 10 litres/min to 1000 litres/min (or gas superficial velocity from 0.05m/s to 4.7m/s). Then other values of liquid superficial velocity were considered. Visual observations were considered. Time series and void fraction were then measured for WMS while time series and liquid holdup were measured for ECT. The raw data were processed and then interpreted for proper analysis. From an analysis of the output from the tomography equipment, flow patterns were identified using both the reconstructed images as well as the characteristic signatures of Probability Density Function (PDF) plots of the time series of cross-sectionally averaged void fraction as suggested by some authors. Bubbly, slug and churn flows were observed for 10° from vertical pipe while bubbly, plug as well as slug flow when the pipe was inclined at 10° from horizontal. Examples of the PDFs are well illustrated which compares the use of ECT with WMS. In addition, statistical data such as Power Spectral Density (PSD), dominant frequency, mean void fraction as well as the structure velocities from cross correlation of the two planes of ECT have been identified.

Visualization Study of Gas-Liquid Two-Phase Flow in a Hydrophobic Pipe

2007 ◽  
Author(s):  
Takayoshi Kikuchi ◽  
Tatsuya Hazuku ◽  
Yutaka Fukuhara ◽  
Tomoji Takamasa ◽  
Takashi Hibiki
Keyword(s):  
Flow Regime ◽  
Void Fraction ◽  
Gas Flow ◽  
Two Phase Flow ◽  
Flow Characteristics ◽  
Phase Flow ◽  
Two Phase ◽  
Experimental Conditions ◽  
Churn Flow ◽  
Effect Of Surface

To evaluate the effect of pipe wall surface wettability on flow characteristics in a vertical upward gas-liquid two-phase flow, a visualization study was performed using an acrylic pipe and a hydrophobic pipe. Such basic flow characteristics as flow patterns, pressure drop and void fraction were investigated in these pipes. In the hydrophobic pipe, an inverted-churn flow regime was observed in a region where the churn flow regime was observed in the acrylic pipe, while a droplet flow regime was observed in the region where an annular flow regime was observed in the acrylic pipe. At a high gas flow rate, the average void fraction in the hydrophobic pipe was higher than in the acrylic pipe. The effect of surface wall wettability on frictional pressure loss was confirmed to be insignificant under the present experimental conditions.

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