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Optimisation production through process engineering

- Wits University

Researchers say there are still large gaps in our understanding of the associated utility systems in batch chemical processes.

Professor Thokozani Majozi holds the DST-NRF Chair in Sustainable Process Engineering at Wits.

“Our main research area is sustainable process engineering, within which we are addressing two broad areas - batch chemical processes and continuous processes,” explains Majozi, who’s PhD from the University of Manchester’s Institute of Science and Technology focused on the optimisation of multipurpose batch chemical processes.

More than 50% of South African chemical processes fall within the batch processing type. Ironically, none of the engineering undergraduate programmes in the country focus on this category of chemical processes.

In addition to handling time effectively, which is fundamental in the design and synthesis of batch plants, Majozi realised that there are still large gaps in our understanding of the associated utility systems in batch chemical processes.

These include water and energy.

“In general, batch processes use and generate smaller amounts of water and wastewater, respectively,” he explains.

“However, the nature of industries in which they are generally encountered, like pharmaceuticals and agrochemicals, suggest that they have higher toxic levels in comparison to their continuous counterparts. Consequently, there is a need to develop dedicated techniques to optimise water use.”

On continuous processes, Majozi’s group has been focusing on debottlenecking utility systems, with emphasis on steam system networks and cooling water systems.

“Our approach is to look at the cooling tower and heat exchanger network as one unit because they work together and cannot be improved in isolation.”

“If you look at them together, all the evidence suggests you will ultimately get a better system,” he says. “We are also looking at power stations because one of the key units of operation is the cooling tower. 

After you have produced superheated steam to run your turbines, the steam is condensed back into water that is then recycled back into the boiler and supplemented by the makeup stream.”

The condensation step is extremely important for the efficiency of the system and the design of the cooling tower is fundamental. Majozi and his team are also exploring the overall efficiency of power generation facilities, including renewable energy options.

His team also focuses on Clean Coal Technology and how to optimise complex power generation systems to achieve maximum efficiencies. On the batch processes side, Majozi is addressing industry production efficiencies.

“The challenge is to help industry use their available capital optimally to meet their production targets for a range of products with different equipment requirements. This requires careful scheduling to meet the prescribed targets within prescribed time horizons,” he concludes.