Reverse traveling microwave reactor – Modelling and design considerations

Farnaz Eghbal Sarabi,Jiawen Liu,Andrzej I Stankiewicz,Hakan Nigar

doi:10.1016/j.ces.2021.116862

Farnaz Eghbal Sarabi, Jiawen Liu + Show 2 more

Open Access

https://doi.org/10.1016/j.ces.2021.116862

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Abstract

Microwave heating presents a potentially green alternative for energy supply to chemical and catalytic reactors as it can be based on the electricity from renewable sources. The Reverse Traveling Microwave Reactor (RTMR) is a novel heterogeneous catalytic reactor concept, based on the coaxial waveguide structure. The reactor has two microwave ports on both ends, and microwave irradiation is periodically switched between those ports to minimize the temperature gradients along the catalyst bed. In the current paper, Comsol Multiphysics® simulation environment has been used to develop a 3D multiphysics model of the RTMR. Based on the model, operational characteristics of the reactor including electric field distribution and transient temperature profiles have been studied. Simulation results show that periodically reversed microwave irradiation improves the homogeneity of the temperature distribution inside the catalyst bed. The study provides new insights into the design and scale-up of microwave-assisted catalytic flow processes.

Highlights

Microwave chemistry applications have been investigated for more than three decades, due to the several advantages that microwave energy offers in terms of reaction speeding up, volumetric heating, and improving product yields and selectivity (Polaert et al, 2017; Oliver Kappe, 2008; Adnadjevicet al., 2017; Cherbanski, 2011)
Microwave irradiation was investigated as an alternative to traditional heating for temperature swing adsorption processes in Candice Ellison et al research
Regarding the energy and CO2 emissions perspective, Ahmadreza Amini et al showed that a 60–80 percent reduction in energy consumption could be achieved, and the ability for microwave heating could reduce CO2 emissions by 3–5 times (Amini et al, 2021)

Summary

Introduction

Microwave chemistry applications have been investigated for more than three decades, due to the several advantages that microwave energy offers in terms of reaction speeding up, volumetric heating, and improving product yields and selectivity (Polaert et al, 2017; Oliver Kappe, 2008; Adnadjevicet al., 2017; Cherbanski, 2011). Mono- and multi-mode microwave applicators, known as microwave cavities, are dominant types They generally suffer from non-uniform heating and hot spots formation, due to the existence of a standing microwave pattern (Stankiewicz et al, 2019). These cavities are strongly dependent on the supplied microwave frequency and sample size, mono-mode cavities. A novel microwave reactor concept is introduced based on the coaxial wave-guide structure This reactor has two microwave ports on both sides, and microwave irradiation is periodically switched between these two ports to provide a more uniform heating profile and minimize the temperature gradients along the load. The microwave incident direction is reversed in order to avoid temperature differences along the load

Reverse traveling microwave reactor design

Mathematical model of RTMR

Heating profile control

Microwave power switching frequency

Findings

Conclusion