Development, validation, quantification and applications of refinery primary reference gas mixtures using various analytical techniques
| dc.contributor.author | Mphaphuli, Gumani Ethel | |
| dc.date.accessioned | 2024-02-06T09:11:25Z | |
| dc.date.available | 2024-02-06T09:11:25Z | |
| dc.date.issued | 2024 | |
| dc.description | A research report submitted in partial fulfilment of the requirements for the degree Master of Science to the Faculty of Science, School of Chemistry, University of the Witwatersrand, Johannesburg, 2023 | |
| dc.description.abstract | The carbon-intensive energy economy of South Africa has increasingly become an environmental issue contributing to climate change, with little study done on the refinery gases contribution to air pollution in the country. Refinery gas is a mixture of complex hydrocarbons and non-combustible gases recovered from refining and conversion processes in the fuel industry, with some intermediate products used as energy sources. The sale of these fuels often follows the guidelines of carbon trading schemes as stipulated by the environmental protection frameworks. Furthermore, refinery gas measurements are challenging because of plausible cross-interferences among target gases during preparation and value assignment. Thus, development of technical capabilities for reliable measurements and reference materials for refinery reference gas mixtures is crucial for measurement solution in the energy industry. This study focused on the development of complex multicomponent refinery gas mixtures with target gases of carbon dioxide (CO2), carbon monoxide (CO), oxygen (O2), nitrogen (N2), methane (CH4), ethane (C2H6), propane (C3H8) and 1,3-butadiene (C4H6) in helium (He) at two amount fractions ranges of 1 000 to 4 000 µmol.mol-1 (low range) and 1 to 22 %mol.mol-1 (high range) to shorten the traceability chain while developing technical skills and measurement equivalence. This was achieved through purity analysis of starting materials in accordance with International Organization for Standardization (ISO) 19229:2019 and gravimetric preparation in accordance with ISO 6142:2015. Verification of gas mixtures was done using gas chromatography with thermal conductivity detection for the quantification of components CO, CO2, O2 and N2 and flame ionisation detection for the quantification of components CH4, C2H6, C3H8, and C4H6 in accordance with ISO 6143:2001. Quantification of trace-level impurities during purity analysis was performed on a gas chromatography coupled with a flame ionisation detector, a pulse discharge helium ionisation detector, and a thermal conductivity detector. The final purities of the starting materials were successfully quantified at > 99.99 %mol.mol-1 for iv C2H6, C4H6, and C3H8 and > 99.999 %mol.mol-1 for CH4, CO, CO2, O2, N2 and He. Two ranges of refinery reference gas mixtures were prepared using static gravimetric method. The high range gas mixtures were prepared using a singlestep dilution method, while the low range gas mixtures used a multi-step dilution method that posed challenges related to the pressures, purities, and chemistries of the starting materials. Single-point calibration method was deployed for the verification of the matrixmatched refinery reference gas mixtures. The final percentage relative expanded uncertainty ranged from 0.313 to 3.281% for hydrocarbons (CH4, C2H6, C3H8, and C4H6) and 0.150 to 3.045% for CO, CO2, N2, and O2 at 95% confidence level (k = 2). The analytical method using gas chromatography coupled with various detectors developed in this study was successful in corroborating the gravimetric amount fractions and the verification amount fractions for the specified components of interest in the developed refinery reference gas mixtures accurately within a 1% difference. | |
| dc.description.librarian | TL (2024) | |
| dc.description.sponsorship | National Metrology Institute of South Africa (NMISA) | |
| dc.faculty | Faculty of Science | |
| dc.identifier.uri | https://hdl.handle.net/10539/37519 | |
| dc.language.iso | en | |
| dc.school | Chemistry | |
| dc.subject | Carbon-intensive energy | |
| dc.subject | Refinery gas | |
| dc.title | Development, validation, quantification and applications of refinery primary reference gas mixtures using various analytical techniques | |
| dc.type | Dissertation |