Multiple steady states and transitional regimes in a cylindrical fixed-bed catalytic reactor

2010 ◽  
Vol 44 (2) ◽  
pp. 119-125 ◽  
Author(s):  
S. A. Bostandzhiyan ◽  
K. G. Shkadinskii
Keyword(s):  
Fixed Bed ◽  
Steady States ◽  
Multiple Steady States ◽  
Catalytic Reactor

scholarly journals Multiple Steady States in the Photocatalytic Reactor for Colored Compounds Degradation

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 3804
Author(s):  
Jakub Szyman
Keyword(s):  
Limit Point ◽  
Light Absorption ◽  
Reaction Rate ◽  
Fixed Bed ◽  
Steady States ◽  
Multiple Steady States ◽  
Photocatalytic Reactor ◽  
Inlet Stream ◽  
Ideal Mixing ◽  
Photocatalytic Reactors

The paper reports the occurrence of multiple steady-state zones in most of the constructions of fixed-bed photocatalytic reactors. Such a phenomenon has not been ever observed in a field of photocatalytic reactors. The simulation has been provided for a common case in a photocatalysis—the degradation of colored compounds. The mathematical model of the photocatalytic reactor with immobilized bed has been stated by a simple ideal mixing model (analogous to the CSTR model). The solution has been continued by the two parameters—the Damköhler number and the absorption coefficient related to the inlet stream concentration. Some branches of steady states include the limit point. The performed two-parametric continuation of the limit point showed the cusp bifurcation point. Besides the numerical simulation, the physical explanation of the observed phenomenon has been provided; the multiple steady-states occurrence is controlled by light absorption–reaction rate junction. When the reaction rate is limited by the light absorption, we can say that a light barrier occurs. The dynamical simulations show that when the process is operated in a field of multiple steady states, the overall reactor efficiency is related to the reactor set-up mode.

scholarly journals Ammonia synthesis fundamentals for a model-based HAZOP study

2015 ◽  
Vol 8 (1) ◽  
pp. 5-10 ◽  
Author(s):  
Ján Janošovský ◽  
Juraj Labovský ◽  
Ľudovít Jelemenský
Keyword(s):  
Process Model ◽  
Ammonia Synthesis ◽  
Fixed Bed ◽  
Steady States ◽  
Hazard Identification ◽  
Fixed Bed Reactor ◽  
Multiple Steady States ◽  
Nonlinear Behaviour ◽  
Model Based ◽  
Operation Conditions

Abstract Hazard and operability (HAZOP) analysis is a highly disciplined process hazard analysis (PHA) technique based on the exploration of the effects of process variables deviations. Inconveniences of a conventional HAZOP study are its time-consuming character and high cost. The principal objective of this paper is to present a new methodology for hazard identification of a selected chemical production process. Model-based HAZOP study is a very robust tool for predicting a systems response to deviations from design or operation conditions. An approach based on the mathematical modelling of a process can help to identify sources of hazard that could be overlooked by conventional PHA techniques. A case study focused on the multiple steady states phenomenon in an ammonia synthesis reactor is presented. The process simulation was performed using the Aspen HYSYS v8.4 process modelling environment. Nonlinear behaviour of the investigated fixed-bed reactor system was confirmed by an accident in an industrial ammonia synthesis reactor. The analysed system exhibited the feed temperature and pressure dependence of various operation parameters. This fact indicates the presence of multiple steady states. From the safety analysis point of view, switching between steady states can lead to process hazards.

MULTIPLE STEADY STATES OF ADIABATIC FIXED-BED REACTORS

1993 ◽  
Vol 126 (1) ◽  
pp. 155-177 ◽  
Author(s):  
RICHARD C. DOUGHERTY ◽  
JOHN R. THYGESON ◽  
RAYMOND HU
Keyword(s):  
Fixed Bed ◽  
Steady States ◽  
Multiple Steady States ◽  
Fixed Bed Reactors

Dimethyldisulphide Hydrodesulphurization on NiCoMo / Al2O3 Catalyst

2017 ◽  
Vol 68 (7) ◽  
pp. 1496-1500
Author(s):  
Rami Doukeh ◽  
Mihaela Bombos ◽  
Ancuta Trifoi ◽  
Minodora Pasare ◽  
Ionut Banu ◽  
...  
Keyword(s):  
Good Accuracy ◽  
Fixed Bed ◽  
Continuous System ◽  
Space Velocity ◽  
Molar Ratio ◽  
Catalytic Reactor ◽  
Liquid Hourly Space Velocity ◽  
Hydrodesulfurization Process ◽  
Al2o3 Catalyst ◽  
Simplified Kinetic Model

Hydrodesulphurization of dimethyldisulphide was performed on Ni-Co-Mo /�-Al2O3 catalyst. The catalyst was characterized by determining the adsorption isotherms, the pore size distribution and the acid strength. Experiments were carried out on a laboratory echipament in continuous system using a fixed bed catalytic reactor at 50-100�C, pressure from 10 barr to 50 barr, the liquid hourly space velocity from 1h-1 to 4h-1 and the molar ratio H2 / dimethyldisulphide 60/1. A simplified kinetic model based on the Langmuir�Hinshelwood theory, for the dimethyldisulphide hydrodesulfurization process of dimethyldisulphide has been proposed. The results show the good accuracy of the model.

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