Monoliths as suitable catalysts for reverse‐flow combustors: Modeling and experimental validation

Abstract

The performance of a bench-scale monolithic reverse-flow reactor (RFR) for methane combustion has been experimentally studied in this work. The influence of the different operating parameters, such as total gas flow rate (2.5 Â 10(STP)), methane inlet concentration (1000-5500 ppm), and switching time (300-900 s) on the reactor performance (outlet conversion and stability), has been experimentally determined. The validation of a heterogeneous one-dimensional dynamic model for monolithic beds with the obtained experimental data allows the use of this model to simulate the behavior of industrial-scale reactors. In the second part of the work, a systematic comparison of particulate and monolithic RFRs is carried out through design curves. Reactor length for 99% outlet conversion and the corresponding pressure drop is determined for varying operating conditions (surface velocity and inlet methane concentration).

Evaluation of the use of ceramic foams as catalyst supports for reverse-flow combustors

“…Thus, the intricate pore network of the foam creates turbulence in the fluid that continually breaks the hydrodynamic boundary layer, resulting in higher mass and heat transfer coefficients than for honeycomb monolith supports, where the flow pattern is usually laminar. Foam supports share with honeycomb monoliths the low pressure drop and high bed porosity, which allow reactor operation at very high superficial velocities (high flow rates) [5,8].…”

A new method for controlling the ignition state of a regenerative combustor using a heat storage device

“…In addition, very low switching times reduce considerably the life of the switching valves. The selected switching time value, 120 s, is a good balance between these two situations [32,34]. The model, being one-dimensional, does not require feed flow rate as design parameter.…”

“…The description of the experimental procedure and validation has been published in previous works; different types of solid bed materials have been tested: random particles [35], honeycomb monoliths [32] and ceramic foams [34].…”

“…The model has been formulated applying the mass and energy conservation equations separately to the gas and solid phases, as shown in Table 1. This type of heterogeneous model predicts the dynamics of heat exchange between the gas and solid phases accurately, which is of key importance in regenerative beds [32].…”

“…The other physical and transport properties appearing in the equations are calculated using correlations from the literature; for further details refer to previous works in this field [32,[34][35].…”