(616f) Volumetrically Heated Electrified Chemical Reactor Systems with Characterization As Artificial Electromagnetic Media

Heavy industry is one of the most challenging sectors of the economy to decarbonize due in part to the dominant role of fossil fuels as an energy source for producing high grade heat. To this end, the electrification of thermochemical processes with clean electricity has great potential as both an immediate and long-term solution towards the scalable decarbonization of chemical production. In this talk, I will discuss new paradigms in thermochemical reactor design in which the reactors are volumetrically heated using high frequency magnetic induction. We focus on induction over other heating methods due to its scalability in power and volume. A principal focus is to treat the chemical reactor as an artificial electromagnetic medium that can be tailored and co-designed with the power electronics to enhance heating efficiency and specify the heating profile in a manner that optimizes reaction engineering properties.

I will first discuss metamaterial reactors in which a volumetric open-cell lattice baffle is designed and inductively heated using a helical magnetic coil. The baffle simultaneously serves as a heating susceptor and support for catalyst impregnation. The baffle layout and power electronics are co-designed to ensure the heating profile is volumetric and heating efficiencies are maximized. We first consider a 1.5” diameter reactor containing a volumetric silicon carbide-based foam baffle, which can be modeled as a uniform effective homogeneous medium and which can be heated by megahertz power electronics with over 90% efficiency. We show the reactor can be configured to perform the reverse water gas shift (RWGS) reaction at 600 C and that the reactor operates in ideal plug flow conditions with radially uniform heating profiles. We further show in a scale up analysis that the energy efficiency of the system naturally increases with reactor size and that total system efficiency is only limited by AC-DC power conversion. Finally, we show how the baffle architecture can be tailored to accommodate arbitrary volumetric heating profiles in a manner that further enhances chemical conversion and reduces reactor size.

I will then discuss a new class of resonant metamaterial reactors in which the reactor is a volumetric magnetic resonator. The structure of the reactor is that of a sheet of metal rolled in to a “Swiss roll” geometry. Our resonant metamaterial reactor has multiple features. First, when inductively heated at resonance, the coupling efficiency of the induction system is near unity and is nearly independently of reactor and coil geometry. Second, an individual Swiss roll structure does not get heated at off-resonant frequencies, meaning that Swiss roll structures specified to resonate at different frequencies can be independently addressed and heated via frequency multiplexing. Third, Swiss roll structures get uniformly heated and have exceptionally high surface area, eliminating heating and heat transfer bottlenecks in thermochemical reactions. We design and demonstrate a Swiss roll reactor that performs the RWGS reaction with high (95%+) heating efficiencies and uniform volumetric heating profiles.

Finally, we show that our concepts in the co-design of reactors and power electronics can extend to new reactor modalities outside of fixed bed systems. As an example, we show that molten salt reactors can be heated to very high temperatures (~1000 C) through the direct inductive heating of the salts themselves. In this effort, large signal AC impedance spectroscopy is used to characterize the electromagnetic properties of molten salts, and these properties are used to co-design the power electronics frequency and reactor form factor to enable volumetric heating with coupling efficiencies of over 90%. These reactors can be utilized for methane pyrolysis, and we show that highly efficient magnetic induction is sustained when the reactor is operated as a bubbling bed.