Valorizing the Steel Industry Off-Gases: Proof of Concept and Plantwide Design of an Electrified and Catalyst-Free Reverse Water–Gas-Shift-Based Route to Methanol

Abstract

Conversion of steel industry off-gases to value-added chemicals enabled by renewable electricity can significantly reduce the environmental burden of the steelmaking process. Herein, we demonstrate that CO2 reduction by H2, both contained in steel mill off-gases, to form syngas via the reverse water–gas-shift reaction is effectively performed by nanosecond pulsed discharges at atmospheric pressure. The experimental results suggest the following: (i) An optimum interelectrode distance exists, maximizing CO2 conversion. (ii) CO2 conversion at constant SEI follows a nonmonotonic trend with H2 excess. CO2 conversion increases with H2 excess up to H2:CO2 = 3:1 upon shifting the chemical equilibrium. At larger H2:CO2, both gas cooling, promoted by the high H2 content, and hindered CO2 collisions in a highly diluted stream hamper CO2 conversion. (iii) SEI enhances CO2 conversion, but the effect decreases with increasing SEI due to equilibrium limitations. A stoichiometric H2:CO2 feed ratio in the plasma reactor is recommended for higher energy efficiency. Intensifying MeOH productivity via SEI elevation is not advised as a 2-fold SEI increase results only in 17% higher MeOH throughput.

On the Electrification of CO2-Based Methanol Synthesis via a Reverse Water–Gas Shift: A Comparative Techno-Economic Assessment of Thermo-Catalytic and Plasma-Assisted Routes

“…In the very first attempt toward electrification of the conventional CAMERE process, de la Fuente et al replaced the thermo-catalytic RWGS reactor with a microwave (MW) plasma-assisted one . The application of nonthermal MW plasma RWGS reactors demonstrated a trade-off between energy efficiency and CO 2 conversion, with the latter reaching 82% when the feedstock included only H 2 and CO 2 (H 2 /CO 2 molar ratio of 3). − MW plasma noncatalytic reactors are scalable and feature high energy efficiency and lower cooling demand when the plasma is ignited at subatmospheric pressure (<0.1 bar) since a nonthermal plasma is favored. , Recently, Delikonstantis et al demonstrated that the RWGS reaction can also be enabled at atmospheric pressure by a nonthermal plasma, employing a nanosecond pulsed plasma …”