PRESSURE DROP IN FIXED BED REACTORS: EFFECT OF CATALYST SHAPE AND SIZE

1994 ◽  
Author(s):  
E. A. Foumeny ◽  
Amol Kulkarni ◽  
S. Roshani ◽  
A. Vatani
Keyword(s):  
Pressure Drop ◽  
Fixed Bed ◽  
Fixed Bed Reactors ◽  
Shape And Size

scholarly journals DEM--CFD modeling and simulations of hydrodynamic characteristics and flow resistance coefficient in fixed-bed reactors

2021 ◽  
Author(s):  
Yaping Li ◽  
Le Xie ◽  
Yonghua Zhou ◽  
Chongwen Jiang ◽  
Hong Zhong
Keyword(s):  
Pressure Drop ◽  
Flow Resistance ◽  
Fixed Bed ◽  
Resistance Coefficient ◽  
Spherical Particles ◽  
Hydrodynamic Characteristics ◽  
Model Parameters ◽  
Large Set ◽  
Fixed Bed Reactors ◽  
Fixed Beds

The ability to predict void fraction, pressure drop, and flow resistance coefficient in fixed-bed reactors is significant to their optimal design. In this study, the discrete element method (DEM) is combined with computational fluid dynamics (CFD) to simulate the hydrodynamic characteristics of fixed-beds. A realistic random packing structure for fixed-beds with spherical particles was generated via the DEM method and then meshed using Ansys ICEM software for the CFD simulation. A grid independency study was performed to select appropriate grid model parameters. A large set of numerical experiments was conducted to investigate the hydrodynamic characteristics with respect to different inlet velocities and particle sizes, and the simulated pressure drop data were used to calculate the flow resistance coefficient. The output flow resistance coefficients agreed well with those calculated by the classical models in laminar and turbulent flow regimes, thereby indicating the accuracy and advantage of the proposed DEM–CFD approach.

scholarly journals Impact of Shape and Size of Catalysts on the Physical Properties and Pressure Drop in Fixed Bed Catalytic Systems

2020 ◽  
Vol 9 (6) ◽  
pp. 1103-1109
Keyword(s):  
Pressure Drop ◽  
Surface Area ◽  
Pore Volume ◽  
Fixed Bed ◽  
Catalyst Design ◽  
Fixed Bed Reactor ◽  
Bet Surface Area ◽  
Different Shapes ◽  
The Impact ◽  
Shape And Size

Catalyst shape and size selection is an important aspect of the industrial catalyst design. Shapes of different sizes were made using alumina and characterized using standard methods used in the industry. Tableting machine, extruder and granulating equipment were used for forming different catalytic shapes. The samples were characterized by BET surface area, pore volume (N2 adsorption and water pick-up) and the sphericity & voidage calculations were performed for different alumina shapes. The physical strength and bulk density of the shapes were analyzed using ASTM methods. Spheres exhibited highest pore volume as the forming process exert minimum external force to the material. BET Surface area of all the samples were found comparable. The impact of different shapes and sizes on the pressure drop across the bed was studied for different gas flow rates using a fixed bed reactor set-up. Sphericity & voidage were calculated for different shapes and sizes and a modified Ergun equation was used for theoretical evaluation of the pressure drop. The experimental & theoretical results were compared and the relative error was noted. The study showed how the theoretical and experimental values differ as non-ideality in the flow across the packed bed increases. For special shapes like trilobe extrusions, impro

Conversion Enhancement of Fixed-Bed Reactors Using Two-Dimensional Hollow Cylindrical Catalyst Pellet

2013 ◽  
Vol 11 (1) ◽  
pp. 159-168 ◽  
Author(s):  
Mohammad Asif
Keyword(s):  
Pressure Drop ◽  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Two Dimensional ◽  
Concentration Gradients ◽  
Fixed Bed Reactors ◽  
Catalyst Pellet ◽  
Conversion Level ◽  
Catalyst Pellets ◽  
Rigorous Model

Abstract The key challenge in the operation of any industrial fixed-bed heterogeneous reactor is to enhance the conversion level while keeping the pressure-drop low. Towards this end, the use of finite hollow cylindrical catalyst pellets instead of spherical ones is proposed here. The absence of the pellet core helps to lower the effect of the internal mass transport resistance besides providing a greater surface area. Another equally important advantage is a lower pressure-drop due to the higher bed void fraction associated with hollow pellets. A rigorous model of the heterogeneous fixed-bed reactor containing finite hollow cylindrical catalyst pellet is presented here accounting for the concentration gradients both in the axial as well as the radial directions, thus, resulting in a two-dimensional partial differential equation for the solid catalytic phase.

Tertiary Nitrification Pilot Plants on Parisian Waste Water

1990 ◽  
Vol 22 (1-2) ◽  
pp. 347-352 ◽  
Author(s):  
C. Paffoni ◽  
B. Védry ◽  
M. Gousailles
Keyword(s):  
Waste Water ◽  
Metropolitan Area ◽  
Fixed Bed ◽  
Point Of View ◽  
Operating Conditions ◽  
Research Center ◽  
Daily Output ◽  
Practical Point ◽  
Fixed Bed Reactors

The Paris Metropolitan area, which contains over eight million inhabitants, has a daily output of about 3 M cu.meters of wastewater, the purification of which is achieved by SIAAP (Paris Metropolitan Area Sewage Service) in both Achères and Valenton plants. The carbon pollution is eliminated from over 2 M cu.m/day at Achères. In order to improve the quality of output water, its tertiary nitrification in fixed-bed reactors has been contemplated. The BIOFOR (Degremont) and BIOCARBONE (OTV) processes could be tested in semi-industrial pilot reactors at the CRITER research center of SIAAP. At a reference temperature of 13°C, the removed load is approximately 0.5 kg N NH4/m3.day. From a practical point of view, it may be asserted that in such operating conditions as should be at the Achères plant, one cubic meter of filter can handle the tertiary nitification of one cubic meter of purified water per hour at an effluent temperature of 13°C.

Role of filter media in an anaerobic fixed-bed reactor

1995 ◽  
Vol 31 (9) ◽  
pp. 137-144 ◽  
Author(s):  
T. Miyahara ◽  
M. Takano ◽  
T. Noike
Keyword(s):  
Anaerobic Bacteria ◽  
Fixed Bed ◽  
Methanogenic Bacteria ◽  
The Other ◽  
Fixed Bed Reactor ◽  
Filter Media ◽  
Fixed Bed Reactors ◽  
Attached Bacteria ◽  
The Relationship

The relationship between the filter media and the behaviour of anaerobic bacteria was studied using anaerobic fixed-bed reactors. At an HRT of 48 hours, the number of suspended acidogenic bacteria was higher than those attached to the filter media. On the other hand, the number of attached methanogenic bacteria was more than ten times as higher than that of suspended ones. The numbers of suspended and deposited acidogenic and methanogenic bacteria in the reactor operated at an HRT of 3 hours were almost the same as those in the reactor operated at an HRT of 48 hours. Accumulation of attached bacteria was promoted by decreasing the HRT of the reactor. The number of acidogenic bacteria in the reactor packed sparsely with the filter media was higher than that in the closely packed reactor. The number of methanogenic bacteria in the sparsely packed reactor was lower than that in the closely packed reactor.

Modeling of aerated upflow fixed bed reactors for nitrification

1999 ◽  
Vol 39 (4) ◽  
pp. 85-92 ◽  
Author(s):  
J. Behrendt
Keyword(s):  
Mathematical Model ◽  
Mass Transfer ◽  
Liquid Phase ◽  
Gas Phase ◽  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Bulk Liquid ◽  
Initial Value ◽  
Fixed Bed Reactors ◽  
Number Of Cells

A mathematical model for nitrification in an aerated fixed bed reactor has been developed. This model is based on material balances in the bulk liquid, gas phase and in the biofilm area. The fixed bed is divided into a number of cells according to the reduced remixing behaviour. A fixed bed cell consists of 4 compartments: the support, the gas phase, the bulk liquid phase and the stagnant volume containing the biofilm. In the stagnant volume the biological transmutation of the ammonia is located. The transport phenomena are modelled with mass transfer formulations so that the balances could be formulated as an initial value problem. The results of the simulation and experiments are compared.

scholarly journals Hydrodynamics of narrow-tube fixed bed reactors filled with Raschig rings

2020 ◽  
Vol 5 ◽  
pp. 100057 ◽  
Author(s):  
E.M. Moghaddam ◽  
E.A. Foumeny ◽  
A.I. Stankiewicz ◽  
J.T. Padding
Keyword(s):  
Fixed Bed ◽  
Narrow Tube ◽  
Fixed Bed Reactors
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