Investigation of spatially patterned catalytic reactors
The theme of this work is to enhance the performance of a primary reaction system by introducing dual-functionality into a packed-bed reactor via a spatial pattern. This paper focuses on a generic system in which the primary reaction is equilibrium-limited and an auxiliary reaction is incorporated to act as a drain-off mechanism alleviating the equilibrium constraint. It is found that patterns in which the two catalysts are spatially layered (and maintained at different temperatures) or well-mixed (and operated at a common temperature) can both offer significant improvements over an unpatterned reactor. Operating the well-mixed pattern at high temperature is generally superior to switching between high- and low-temperature layers in the segmented configuration. The exception to this rule occurs when the mixed bed is punished for being hot as either the equilibrium ceiling on the primary reaction drops sharply or a competitive reaction dominates at high temperature. The extent to which the layered pattern’s improvements are compromised by axial heat dispersion between zones is examined in terms of a backflow mixing cell model.
Integrated catalytic membrane reactors for decomposition of ammonia
A model is presented for the simulation of an integrated catalytic membrane reactor for the removal of toxic ammonia traces from coal gasification streams. Heat integration and equilibrium shifting are achieved by introducing integrated reaction network and various catalyst pattern strategies. Different configurations of spatially patterned catalytic beds (layers) have been investigated. Two important reactions were considered namely, the decomposition of ammonia as a primary reaction and methanation reactions as secondary reactions. An effective length criterion is used to evaluate the performance of the reactor. Optimal conditions were observed and explanations offered. The results show substantial improvement in the reactor performance in terms of high conversions, low temperatures and reduced mass of the catalyst used. The investigation, although is restricted to two catalyst layers, has uncovered some of the rich characteristics of this system.
Packed bed axial thermal conductivity
Abstract Packed bed axial thermal conductivity has been evaluated from steady state packed bed axial temperature profiles. Solid particles of different sizes, shapes and thermal conductivities have been used for measurements, which covered large interval of Reynolds numbers, Re ϵ 3 >. Empirical relation for estimation of Peclet number for axial heat transport, which includes effects of all significant heat transport mechanisms, has been obtained in the form