On the dynamic behavior of the catalytic fixed-bed reactor in the region of multiple steady states—I. The influence of heat conduction in two phase models

1972 ◽  
Vol 27 (11) ◽  
pp. 1909-1915 ◽  
Author(s):  
G. Eigenberger
Keyword(s):  
Heat Conduction ◽  
Dynamic Behavior ◽  
Fixed Bed ◽  
Steady States ◽  
Fixed Bed Reactor ◽  
Multiple Steady States ◽  
Two Phase ◽  
Phase Models

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.

scholarly journals Dynamic Simulation of Adiabatic Catalytic Fixed-Bed Tubular Reactors: A Simple Approximate Modeling Approach

2014 ◽  
Vol 14 (1) ◽  
pp. 25
Author(s):  
Wiwut Tanthapanichakoon ◽  
Shinichi Koda ◽  
Burin Khemthong
Keyword(s):  
Dynamic Model ◽  
Dynamic Behavior ◽  
Dynamic Simulation ◽  
Flow Rate ◽  
Fixed Bed ◽  
Axial Dispersion ◽  
Fixed Bed Reactor ◽  
Inlet Temperature ◽  
Acetylene Hydrogenation ◽  
Tubular Reactors

Fixed-bed tubular reactors are used widely in chemical process industries, for example, selective hydrogenation of acetylene to ethylene in a naphtha cracking plant. A dynamic model is required when the effect of large fluctuations with time in influent stream (temperature, pressure, flow rate, and/or composition) on the reactor performance is to be investigated or automatically controlled. To predict approximate dynamic behavior of adiabatic selective acetylene hydrogenation reactors, we proposed a simple 1-dimensional model based on residence time distribution (RTD) effect to represent the cases of plug flow without/with axial dispersion. By modeling the nonideal flow regimes as a number of CSTRs (completely stirred tank reactors) in series to give not only equivalent RTD effect but also theoretically the same dynamic behavior in the case of isothermal first-order reactions, the obtained simple dynamic model consists of a set of nonlinear ODEs (ordinary differential equations), which can simultaneously be integrated using Excel VBA (Visual BASIC Applications) and 4th-order Runge-Kutta algorithm. The effects of reactor inlet temperature, axial dispersion, and flow rate deviation on the dynamic behavior of the system were investigated. In addition, comparison of the simulated effects of flow rate deviation was made between two industrial-size reactors.Keywords: Dynamic simulation, 1-D model, Adiabatic reactor, Acetylene hydrogenation, Fixed-bed reactor, Axial dispersion effect

Hydrodynamics of co-current two-phase flow in an inclined rotating tubular fixed bed reactor — Wetting intermittency via periodic catalyst immersion

2015 ◽  
Vol 128 ◽  
pp. 147-158 ◽  
Author(s):  
Hans-Ulrich Härting ◽  
André Bieberle ◽  
Rüdiger Lange ◽  
Faïçal Larachi ◽  
Markus Schubert
Keyword(s):  
Two Phase Flow ◽  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Phase Flow ◽  
Two Phase

Multiple steady states in two-phase reactors under boiling conditions

2003 ◽  
Vol 58 (11) ◽  
pp. 2203-2214 ◽  
Author(s):  
R. Waschler ◽  
S. Pushpavanam ◽  
A. Kienle
Keyword(s):  
Steady States ◽  
Multiple Steady States ◽  
Two Phase

Design of a Chemical Pulse Reactor

1979 ◽  
Vol 34 (12) ◽  
pp. 1446-1451
Author(s):  
B. Denzel ◽  
F. F. Seelig
Keyword(s):  
Numerical Technique ◽  
Substrate Inhibition ◽  
Fixed Bed ◽  
Tubular Reactor ◽  
Fixed Bed Reactor ◽  
Low Flow ◽  
State Equations ◽  
Reactor Outlet ◽  
Catalytic Reactors ◽  
Two Phase

Abstract The general reaction X + Y + M → P + M may - due to substrate inhibition at the catalytic site M - give rise to bistability phenomena in an isothermal tubular fixed bed reactor. The parametric conditions for bistability in the single pellet are studied by a numerical technique. Solution of the steady state equations for a two phase model of the tubular reactor shows that narrow zones with high conversion are possible, similar to ignition zones in nonisothermal catalytic reactors. By a cyclic operation with alternating periods of charging the catalyst phase with substrate and discharging it by chemical reaction, pulses of high product concentration can be generated at the reactor outlet. This is demonstrated by simulation of the system assuming low flow velocity as it is characteristic for reaction columns with liquid mobile phase.

Sign in / Sign up

Export Citation Format

Share Document