Title: Machine learning-based ethylene concentration estimation, real-time optimization and feedback control of an experimental electrochemical reactor

Abstract

With the increase in electricity supply from clean energy sources, electrochemical reduction of carbon dioxide (CO₂) has received increasing attention as an alternative source of carbon-based fuels. As CO₂ reduction is becoming a stronger alternative for the clean production of chemicals, the need to model, optimize and control the electrochemical reduction of the CO₂ process becomes inevitable. However, on one hand, a first-principles model to represent the electrochemical CO₂ reduction has not been fully developed yet because of the complexity of its reaction mechanism, which makes it challenging to define a precise state-space model for the control system. On the other hand, the unavailability of efficient concentration measurement sensors continues to challenge our ability to develop feedback control systems. Gas chromatography (GC) is the most common equipment for monitoring the gas product composition, but it requires a period of time to analyze the sample, which means that GC can provide only delayed measurements during the operation. Moreover, the electrochemical CO₂ reduction process is catalyzed by a fast-deactivating copper catalyst and undergoes a selectivity shift from the product-of-interest at the later stages of experiments, which can pose a challenge for conventional control methods. To this end, machine learning (ML) techniques providemore » a potential approach to overcome those difficulties due to their demonstrated ability to capture the dynamic behavior of a chemical process from data. Motivated by the above considerations, we propose a machine learning-based modeling methodology that integrates support vector regression and first-principles modeling to capture the dynamic behavior of an experimental electrochemical reactor; this model, together with limited gas chromatography measurements, is employed to predict the evolution of gas-phase ethylene concentration. The model prediction is directly used in a proportional-integral (PI) controller that manipulates the applied potential to regulate the gas-phase ethylene concentration at energy-optimal set-point values computed by a real-time process optimizer (RTO). Specifically, the RTO calculates the operation set-point by solving an optimization problem to maximize the economic benefit of the reactor. Finally, suitable compensation methods are introduced to further account for the experimental uncertainties and handle catalyst deactivation. The proposed modeling, optimization, and control approaches are the first demonstration of active control for a CO₂ electrolyzer and contribute to the automation and scale-up efforts for electrified manufacturing of fuels and chemicals starting from CO₂.« less

Authors:

Çıtmacı, Berkay ^[1]; Luo, Junwei ^[1]; Jang, Joon Baek ^[1]; Canuso, Vito ^[1]; Richard, Derek ^[1]; Ren, Yi Ming ^[1]; Morales-Guio, Carlos G. ^[1]; Christofides, Panagiotis D. ^[1]

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+ Show Author Affiliations

1. University of California, Los Angeles, CA (United States)

Publication Date:

Fri Jul 01 00:00:00 EDT 2022

Research Org.:

Univ. of California, Los Angeles, CA (United States)

Sponsoring Org.:

USDOE Office of Energy Efficiency and Renewable Energy (EERE)

OSTI Identifier:

1976960

Alternate Identifier(s):

OSTI ID: 1961079

Grant/Contract Number:  

EE0007613

Resource Type:

Accepted Manuscript

Journal Name:

Chemical Engineering Research and Design

Additional Journal Information:

Journal Volume: 185; Journal Issue: C; Journal ID: ISSN 0263-8762

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

42 ENGINEERING; electrochemical reactor; CO2 reduction; support vector regression; data-driven modeling; gas chromatography; real-time optimization; feedback control