Transfer Functions for Periodic Reactor Operation: Fundamental Methodology for Simple Reaction Networks

Abstract

Dedicated to Professor Rüdiger Lange on the occasion of his 65th birthday A method for frequency response analysis of chemical reactors with periodically modulated inlet concentration is presented and demonstrated for simple firstorder irreversible consecutive and parallel as well as reversible reactions applying an isothermal continuous stirred-tank reactor (CSTR). The frequency response of these reaction types is studied by simulations in time and frequency domain, the latter being based on Laplace transformation of the material balance. The results allow for clearly distinguish between the quasi and relaxed steady state as well as the full transient region with impact on designing reactors for dynamic operation. Furthermore, the relation between the dynamic response and the time constants of the system is discussed.

Frequency Response Analysis of the Unsteady-State CO/CO2 Methanation Reaction: An Experimental Study

“…The H2O magnitude decreases by 11 dB/decade over the whole range of cycle period durations, while the CH4 magnitude seems to exhibit different slopes, the average of 7 dB/decade being between those of H2O and Ar. The decreasing slopes for CH4 and H2O compared to Ar are expected from our theoretical considerations, 7 since both components are formed by reaction. Interestingly, the slopes of CH4 and H2O differ from each other, though both are formed simultaneously.…”

“…1,6 Moreover, the input fluctuations can appear stochastically over a wide frequency range, 1 which may result in a complex reactor behavior depending on the input frequencies. 7 Dynamic changes in the inlet composition, however, may also affect the thermal behavior of the methanation reactor, since the hydrogenation of CO and CO2 is highly exothermic.…”

Dynamic Methanation of CO2 – Effect of Concentration Forcing

“…The time delay between Ar and H 2 (~0.5 s) is caused by the reaction of H 2 to methane and H 2 adsorption on the surface. It can be assumed that in the quasi-steady state (see [19]) the carrier is saturated with water, so that the measured concentration directly corresponds to the produced amount of water. The time lag between H 2 O and Ar (~0.8 s) reveals that adsorbed carbonaceous species are hydrogenated with a higher reaction rate than water formation or that water is retarded due to adsorption effects.…”

Transient Flow Rate Ramps for Methanation of Carbon Dioxide in an Adiabatic Fixed‐Bed Recycle Reactor

“…Under isothermal conditions, the heat of reaction is not considered. Hence, the activator is not present in the system and the reactor exhibits a stable operation with damping behavior . The dynamic phenomena induced by DIFIs are the wrong‐way behavior, moving hot spots, and extinction waves.…”