Masters Degrees (Chemical Engineering)

Permanent URI for this collection

https://scholar.sun.ac.za/handle/10019.1/782

Browse

Browsing Masters Degrees (Chemical Engineering) by Author "Amanful, Bright"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    Retrofitting a typical South African sugar mill to co-produce a range of alternative sweeteners: a stochastic techno-economic study
    (Stellenbosch : Stellenbosch University, 2023-03) Amanful, Bright; Görgens, Johann Ferdinand; Dogbe, Eunice Sefakor; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.
    ENGLISH ABSTRACT: An alternative to the current trend of maximizing sugar recovery in a three-stage sugar crystallization process, is the diversion of A-molasses into an annexed biorefinery to produce alternative sweeteners. This is aimed at improving the value chain of the South African sugar industry and has become necessary due to cost and market challenges that make maximum sugar recovery unprofitable. Among the many challenges are the rising cost of sugar production, decreasing demand for sugar, plummeting prices of sugar on the global sugar market and the implementation of sugar tax, which consequentially limits the industry's ability to operate profitably and sustainably. Isomaltulose, allulose, short chain fructooligosaccharides (scFOS), and thaumatin are alternative sweeteners known to have similar physical and organoleptic properties to sucrose. These are recognized as safe, have growth trajectories and market demands, and are widely utilized in the food, beverage, and pharmaceutical industries. Amolasses is considered a low-cost feedstock, suitable for the bioproduction of these high-value sweeteners, in support of the long-term objective to create a more diversified, cost-effective, and competitive industry. Single product and multiproduct scenarios for the bioproduction of the sweeteners were simulated in Aspen Plus® and techno-economic analysis was performed for each scenario. In the case of the single product scenarios, the available 25.43 tons/h of Amolasses from a typical South African sugar mill resulted in product throughputs representing 38%, 28%, 95%, and Two multiproduct scenarios were developed for the co-production of isomaltulose, allulose and scFOS in a single facility, using either six bioreactors or a single bioreactor. Such a facility could utilize all the available A-molasses to produce less than 15% of the global market for each of the three products, thereby substantially reducing the risk of market oversupply. Deterministic economic analysis resulted in an IRR of 50% and payback period of 3.01 years for the six-bioreactor scenario, while the single bioreactor scenario achieved an IRR of 60% and payback period of 2.80 years. Stochastic Monte Carlo analysis was applied to quantify the financial risks of these investments, considering historical price and CAPEX variabilities, demonstrating a mean IRR of 41% for the one-bioreactor scenario, and a 36% IRR for the six-bioreactor scenario. While the stochastically determined IRRs affirm the superficiality of the deterministically determined profitability, a 100% probability that the stochastic IRRs exceed 20% indicates a risk-averse portfolio. Moreover, the stochastic IRRs were higher than other products considered for sugarcane diversification, further demonstrating the benefits of combining products with attractive market prices in a single facility. By considering mixed product campaigns (MPC) and non-integer batch formulations, it was possible to schedule a single shared bioreactor system for the manufacture of all three products to exploit the economies-of-scale benefits compared to the use of six smaller bioreactors. For the MPC scheduling, batches of the various products were repeated in four time periods over the time horizon thereby allowing the overall product demand to be satisfied under a reduced make span objective.