College of Agriculture, Engineering
and Science (CAES)

Dr Paul Zvawanda who is passionate about mentoring and imparting knowledge to upcoming engineers.

PhD Study Holds Promise for Natural Gas Purification

Given the significant technical and logistical requirements to make the complex operation of natural gas processing efficient and economically viable, the need to optimise natural gas transportation and purification processes motivated Dr Paul Zvawanda’s research to provide technical data on the performance of the natural gas purification process.

This work involved the measurement and thermodynamic modelling of high-pressure vapour-liquid equilibria data for mixtures of key components present in the natural gas streams, such as methane, propane, carbon dioxide, water, methanol and triethylene glycol.

Working at UKZN’s Thermodynamics Research Unit (TRU), a national leader in separation technology, specifically high- and low-pressure phase equilibrium measurements and modelling, Zvawanda worked under the supervision of Professor Prathieka Naidoo, and Drs Wayne Nelson and Kuveneshan Moodley.

‘Natural gas processing involves removing impurities from gas streams since some of them may lead to blockages in pipelines due to hydrate formation, and then enhance corrosion and lessen the calorific value of the gas,’ said Zvawanda.

These impurities are usually eliminated using various solvents depending on the process, for example methanol and triethylene glycol, and Zvawanda focused on the measurement and thermodynamic modelling of phase equilibria data for seven chemical mixtures of relevance to the natural gas industry to close gaps in the available data.

Using a new horizontal variable volume view cell apparatus in the TRU that allows for analytic and synthetic methods of phase equilibria measurement, he generated a hundred new data points over a temperature range of 10 to 50 degrees Celsius and pressure of up to 18 megapascals. The chemical composition ranges investigated and conditions are typical of those found in gas pipelines and gas dehydration plants.

Supported by the South African Research Chair (SARChI) in Fluorine Processing and Separation Technology held by Professor Deresh Ramjugernath, his work aligned with the TRU’s research on optimising natural gas transportation and purification processes. Natural gas processing in South Africa is an attractive option that is being assessed by the Department of Mineral Resources and Energy. The Unit’s recent studies have expanded into process development and optimisation through process simulation and control.

Zvawanda’s work resulted in the publication of results in the Journal of Chemical and Engineering Data and selection for the Editors’ Choice® for the American Chemical Society publishing house, which has more than 65 journal categories that publish 50 000 articles annually, demonstrating its broad impact. Some of his recommendations have also been carried into a master’s project in the TRU, which Zvawanda is mentoring.

‘This data contributes to the information required for the process design, control and monitoring of methanol and/or triethylene glycol in gas conditioning systems,’ said Zvawanda.

His data will also help refine thermodynamic models to predicate phase behaviour in multicomponent systems in applications such as gas hydrate inhibition, gas dehydration, subsea gas processing, carbon capture, and storage.

Zvawanda explained that experimental data play a conclusive role in validating theoretical methods and correcting parameters in correlations. These new measurements contributed to a databank for the thermophysical properties of polar solvents in hydrocarbons at high pressures, which is vital for knowledge generation and in the design of separation processes.

His PhD research was not without its challenges; Zvawanda had to switch to an alternative synthetic method of measurements when his analytic one did not work, and his first sapphire equilibrium cell broke, necessitating the use of a backup. However, he highlighted the importance of perseverance and determination.

Growing up in Zimbabwe, Zvawanda was always interested in the engineering profession for its applicability to everyday life, and the serious fuel shortages in that country in the early 2000s prompted him to investigate chemical engineering for its potential to alleviate fuel poverty through understanding the processes and equipment involved in oil and gas refining and investigating alternative fuels.

After completing a BTech (honours) degree in fuels and energy engineering at Chinhoyi University of Technology and a master’s at Gubkin Russian State University of Oil and Gas in Russia, he chose to pursue his PhD at UKZN because of its well-resourced personnel and laboratories that support research.

Zvawanda hopes to apply his talents in a major oil and gas multinational company to gain industrial exposure and see theories in action. He also hopes to continue research, working on projects of industrial and academic importance, especially relating to energy transition and the creation of a circular economy for sustainable development.

He is passionate about mentoring and imparting knowledge to upcoming engineers and seeks to add value in both the academic and industrial arenas, and ultimately to use his technical expertise and knowledge to be a “technoprenuer” in the fuels and energy industry.

Zvawanda credited Naidoo, Nelson and Moodley for their guidance and support, and thanked Ramjugernath for the resources to purchase material and construct the apparatus used. He expressed appreciation to Professor Dominique Richon for his assistance and expertise in the development of the equipment.

Zvawanda thanked Miss Sivanna Naicker, Mr Ayanda Khanyile and all the technical staff in Chemical Engineering for their help, support, teaching and guidance, and his colleagues Mr Paul Ngcobo, Mr Phakamile Ndlovu, Mr Edward Marondedze, Dr Mojgan Ebrahiminejadhasanabadi and Dr Marcin Durski for their inspiration and support. He said his family, particularly his wife Ms Palocia Magorimbo, his son Nyashadzashe and his parents Mr and Mrs C. Zvawanda provided indispensable support and motivation.

Zvawanda acknowledged the National Research Foundation and the SARChI for their financial support that made his study possible.

Words: Christine Cuenod

Photograph: Sandile Ndlovu