Computational and experimental study on conversion of biogas into valuable fuels and useful chemicals using non-thermal plasma



Xu, C
(2019) Computational and experimental study on conversion of biogas into valuable fuels and useful chemicals using non-thermal plasma. Doctor of Philosophy thesis, University of Liverpool.

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Abstract

This project has studied reforming of biogas into fuels and valued chemicals using non-thermal plasma through experiments and simulations. CH4, CO2 and H2 are used as the inlet gas. All simulation results have been validated by the experimental results. Different reactions which are relevant to reforming of biogas, including pure CO2 splitting, hydrogenation of CO2, dry reforming of CH4 and steam reforming of CH4, have been investigated and the mechanisms of them have been clearly defined by the simulations. The overall aim of this project is to investigate the effects of the different operating conditions, including discharge power, residence time, compositions of inlet gas, etc., on conversion of biogas and reaction pathways for the desired products in a dielectric barrier discharge (DBD) reactor. The major challenge to simulate DBD plasma-assisted reactions is the power description. Apart from the existing researches, the project raises a novel method to describe the DBD plasma power using the technique of advanced signal process. All simulations in this project are performed in a Fortran 90 language environment using the ZDPlaskin. Vibrational excitations of CO2 play significant roles in CO2 splitting and their contributions to decompose CO2 are enhanced with an increasing discharge power. In terms of hydrogenation of CO2, a higher H2/CO2 ratio has a positive effect on conversion of CO2. The mechanism to generate CH4 is difficult to be defined by the common method based on sensitivity analysis due to the slow generation of CH4, so a reverse educing method is used to summarise the pathways of the hydrogeneration process. Besides, C2H2 and C2H6 are the major gas-products observed in dry reforming methane. According to the simulations, 60.3% of CH3 radicals are consumed by recombination to produce C2H6, while more than 99% of CH2 radicals are consumed by oxidisation reactions to generate aldehydes. This project also investigates the steam reforming of methane in a high/low steam environment. By doping deuterium, in form of D2O, into the DBD reactor, a compound-specific isotope analysis (CISA) is performed to identify the contributions of methane and steam to produce hydrogen gas and trace the radicals released from steam to define a clearer and more accurate mechanism.

Item Type: Thesis (Doctor of Philosophy)
Divisions: Fac of Science & Engineering > School of Electrical Engineering, Electronics and Computer Science
Depositing User: Symplectic Admin
Date Deposited: 22 Aug 2019 10:11
Last Modified: 03 Mar 2021 10:23
DOI: 10.17638/03044413
Supervisors:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3044413