Design Optimization Of Electrochemical Hydrogen Pump Coupled With Dual Membrane Separation For CO₂ Formic Acid Production

Hydrogenation is an important way to realize CO₂resource utilization.CO₂electrochemical hydrogenation has attracted much attention due to its mild reaction conditions and easy control.The existing computational fluid dynamics（CFD）model of the electrochemical hydrogen pump reactor has low computational efficiency and is difficult to be used in process design,which restricts the development of the CO₂electrochemical hydrogenation process.As a new and efficient two-way enrichment and separation unit,the dual membrane separator also urgently needs to be embedded in process simulation software.In view of the above problems,the thesis takes the process of CO₂electrochemical hydrogenation to formic acid as an example.Firstly,the mathematical model of the electrochemical hydrogen pump reactor is established,then the reactor and the dual membrane separator are modularized in HYSYS.The formic acid production process with electrochemical hydrogen pump coupled with dual membrane separator is designed using medium and high hydrogen-carbon ratio（H₂to CO₂molar ratio）tail gas as raw material,which provides a theoretical basis for the CO₂formic acid production process.In order to solve the problem that the existing mathematical models of electrochemical hydrogen pump reactors and dual membrane separator cannot be used for process design,the thesis establishes a reactor mathematical model that is kinetic coupling mass transfer and realizes the modularization of the reactor and the dual membrane separator.Firstly,a cathode hydrogenation kinetic model was established according to the linear Butler-Volmer equation,and the model parameters were optimized through the combination of GA and LM algorithms.According to the gas transmission law in the fuel cell,a plug flow model of the reactor is established and combined with the cathode kinetic model.The error between the simulated and the experimental result is only 4.72%,indicating the accuracy of the reactor model.Subsequently,the modularization of the electrochemical hydrogen pump reactor and the dual membrane separator are realized in HYSYS,which provided a process simulation tool for the design of the formic acid production process by the electrochemical hydrogenation of CO₂.It has not been reported in the literature.Aiming at the tail gas of medium hydrogen to carbon ratio（take the tail gas of hydrogen production from coal as an example）,an electrochemical hydrogen pump coupled with dual membrane separator for formic acid production process is proposed.The dual membrane separator is used for bidirectional enrichment and simultaneous recovery of H₂and CO₂in the hydrogen production tail gas and the electrochemical hydrogen pump can achieve CO₂electrochemical hydrogenation in atmospheric pressure with high efficiency,which strengthens the coupling of separation and hydrogenation reaction and realizes the high-efficiency resource utilization of H₂and CO₂in the tail gas with medium CO₂concentration.Compared with the process of producing formic acid with an electrochemical hydrogen pump coupled with a single membrane separator,the CO₂separation factor has increased by 37.40%,and the unit mass cost of formic acid has been reduced by 2.31%.Further compared with the K-L process（methyl formate hydrolysis route）of industrial formic acid production,the unit quality cost of formic acid has been reduced by 3.31%,and CO₂emissions can be reduced by 33442t per year,which has significant economic and environmental and social benefits.Aiming at the tail gas with high hydrogen-to-carbon ratio（taking the hydrogen production tail gas from natural gas as an example）,an electrochemical hydrogen pump coupled with a dual membrane separator for formic acid production process is designed,and the second stage CO₂membrane separator is used to achieve high-efficiency resources of low-concentration CO₂hydrogen-containing tail gas.The NSGA-II algorithm is used to optimize the CO₂conversion and selectivity with multi-objective.Compared with the process of producing formic acid with an electrochemical hydrogen pump coupled with single membrane separator.the CO₂separation factor has increased by 84.97%,and the unit mass cost of formic acid has been reduced by 8.35%;the unit mass cost of formic acid is equivalent to that of the KL process,and the annual CO₂emission reduction is 10837t.Under the condition of low-concentration CO₂and hydrogen-containing tail gas,the formic acid production process with electrochemical hydrogen pump coupled with dual membrane separator has significant social and environmental benefits.