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.

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 CO 2 reduction by H 2 , 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 CO 2 conversion. (ii) CO 2 conversion at constant SEI follows a nonmonotonic trend with H 2 excess. CO 2 conversion increases with H 2 excess up to H 2 :CO 2 = 3:1 upon shifting the chemical equilibrium. At larger H 2 :CO 2 , both gas cooling, promoted by the high H 2 content, and hindered CO 2 collisions in a highly diluted stream hamper CO 2 conversion. (iii) SEI enhances CO 2 conversion, but the effect decreases with increasing SEI due to equilibrium limitations. A stoichiometric H 2 :CO 2 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.