Dr C Sempuga

Qualifications

• B.Sc. Chemical Engineering (2006), University of the Witwatersrand, Johannesburg.
• Ph.D in Chemical Engineering (2011), University of the Witwatersrand, Johannesburg.

Currently teaching

Dr Sempuga is a senior researcher and head of the process synthesis research group at the Institute for the Development of Energy for African Sustainability (IDEAS) at UNISA since 2013. He currently supervising and co-supervising five master and two PhD students, and is also leading a Work Integrated Learning (WIL) program at IDEAS, which provide training to final year UNISA diplomat students as part of the requirements for them to complete their study program. The training involve teaching them theoretical concepts such mass and energy balance and the use of simulation tools such as Aspen and Matlab, at the level required for them to successfully conduct their practical work. The practical work consists of both laboratory work (gasification, Fischer Tropsch, Bio-reactors, Design and construction and running of pilot plants).

Dr Sempuga also leads a community engagement project in Lenasia (South of Johannesburg) which aims and providing access to clean and sustainable energy to impoverished communities using dry and wet wastes produced locally.

Fields of academic interests

Dr Sempuga's research work consisted of developing design methods and tools to synthesise chemical processes with the aim of reducing their energy consumption as well as minimising the waste production and more importantly minimising CO₂ emissions. A graphical approach in which the mass, energy and entropy (work) balances of a process or a number of processes can be assessed and compared with each other, on a single two-dimensional diagram, was developed. The graphical approach uses values of Enthalpy and Gibbs free energy to gain insight into the energy and work requirements of chemical processes of interest without the need of complex calculations. This enables the designer to set up targets and also provides assistance during the design process in order to achieve the targets. The graphical approach is used for both new and existing systems and try to find answers to questions such as, what is the optimal feed material to produce a specific product for a system; what is the minimum energy required, what technology can be used in order to achieve or get as close as possible to the optimum points for a system; where are the biggest losses of mass or energy in the system and how it can be improved, by looking at both the individual equipment as well as the system as a whole using fundamental principles.

Journal articles

• Muvhiiwa, R. F.; Sempuga, B.; Hildebrandt, D.; Van Der Walt, J. Study of the Effects of Temperature on Syngas Composition from Pyrolysis of Wood Pellets Using a Nitrogen Plasma Torch Reactor. J. Anal. Appl. Pyrolysis 2018.
• Sempuga, B. C.; Yao, Y. CO2 Hydrogenation from a Process Synthesis Perspective: Setting up Process Targets. J. CO2 Util.2017, 20, 34–42
• Hildebrandt, D.; Glasser, D.; Patel, B.; Sempuga, B. C.; Fox, J. A. J. A. Making Processes Work. Comput. Chem. Eng.2015, 81, 22–31
• Sempuga, B.C; Hausberger, B; Patel, B; Hildebrandt, D; Glasser, D. Classification of chemical processes: A graphical approach to process synthesis to improve reactive process work efficiency. Industrial & Engineering Chemistry Research, 2010, 49 (17), 8227 – 8237
• Sempuga, B.C; Hildebrandt, D; Patel, B; Glasser, D. Work to chemical processes: The relationship between Heat, Temperature, Pressure and process complexity. Industrial & Engineering Chemistry Research, 2011, 50(14), 8603 – 8619
• Sempuga, B.C; Hildebrandt, D; Patel, B; Glasser, D. Efficient Combustion: A process synthesis approach to improve the efficiency of coal fired power stations. Industrial & Engineering Chemistry Research, 2012, 51 (26), 9061 – 9077
• B.C. Sempuga, D. Hildebrandt, D. Glasser, M. Seedat, Designing a Waste to Energy Plant for Informal settlements, in: P.G. Eden, R. Mario; Siirola, D. John; Towler (Ed.), 8th Int. Conf. Found. Comput. Process Desing, Elsevier B.V., Cle Elum, Washington, 2014: pp. 609–614