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Optimising an underground mine cooling water operation
Anastasiou, J. 2025. Optimising an underground mine cooling water operation. Unpublished masters thesis. Stellenbosch: Stellenbosch Univeristy [online]. Available: https://scholar.sun.ac.za/items/5ab1f703-165f-429d-a952-33d87a3c65ef
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867613892901863424 |
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| access_status_str | Open Access |
| author | Jordan, Anastasiou |
| author2 | Louw, Tobi |
| author_browse | Jordan, Anastasiou Louw, Tobi |
| author_facet | Louw, Tobi Jordan, Anastasiou |
| author_sort | Jordan, Anastasiou |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Anastasiou, J. 2025. Optimising an underground mine cooling water operation. Unpublished masters thesis. Stellenbosch: Stellenbosch Univeristy [online]. Available: https://scholar.sun.ac.za/items/5ab1f703-165f-429d-a952-33d87a3c65ef |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/132044 |
| institution | Stellenbosch University (South Africa) |
| last_indexed | 2026-06-10T12:43:21.794Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/132044 Optimising an underground mine cooling water operation Jordan, Anastasiou Louw, Tobi Shipman, William Stellenbosch University. Faculty of Engineering. Dept. of Chemical Engineering. Cooling systems Mine ventilation Refrigeration and refrigerating machinery Engineering systems -- Computer simulation UCTD Anastasiou, J. 2025. Optimising an underground mine cooling water operation. Unpublished masters thesis. Stellenbosch: Stellenbosch Univeristy [online]. Available: https://scholar.sun.ac.za/items/5ab1f703-165f-429d-a952-33d87a3c65ef Thesis (MEng)--Stellenbosch University, 2025. ENGLISH ABSTRACT: Deep-level mines such as the Mponeng gold mine in Carletonville require energy intensive cooling processes to keep the environment for mine workers and machinery workable at a somewhat 5 km underground, where temperatures reach up to 65 °C. This cooling circuit in particular consists of storage dams, cooling towers and five refrigeration plants which account for a large percentage of the plant’s energy usage. Mintek was contracted to provide control to the circuit, initially limited to only two valves, and due to the lack of accurate models and parameters describing the system, they could not implement fridge plant scheduling according to Eskom’s time-of-day tariffs. It is estimated that scheduling fridge plant operation based on the downstream underground needs as well as the price of electricity could save up to R16 million per year in energy costs. To realise the possible economic benefits, the circuit is first modelled from first principle mass and energy balances, and the model parameters estimated based on recorded plant data using regression in MATLAB. To validate that the model parameters provide the best possible predictive accuracy, an identifiability analysis is carried out, making use of the profile likelihood method. Parameters are assessed for structural and practical identifiability, indicating the quality of the data and the model. Disturbances to the process are modelled stochastically, with an auto-regressive function. To demonstrate the possible financial savings, a model predictive controller (MPC) and optimiser are implemented in simulation. This includes setting up individual MPCs on each of the units as a base layer of control, and then applying an optimiser as a top layer. The optimiser is responsible for determining the on and off statuses of the fridge plants while ensuring that the chill dam, the battery for cold water inventory, does not run dry and that the underground demand is always met. This allows for financial comparisons to be made between the case where the optimiser is switched off and no scheduling of fridge plant operation occurs, and when it is switched on and scheduling is occurring. The investigation found an overall average annual savings of about R21 million for the optimised case. This amounts to an annual cost savings of 17.83% when compared with the non-optimised case. A 70.45% energy savings was also achieved during peak-cost hours. AFRIKAANSE OPSOMMING: Myne wat diep ondergronds strek soos die Mponeng goudmyn in Carletonville, vereis energie-intensiewe verkoelingsprosesse om die omstandighede 5km onder die grond vir mynwerkers en masjinerie werkbaar te hou, waar temperature tot 65 °C kan styg. Hierdie verkoelingstelsel bestaan grootliks uit opgaardamme, verkoeltorings en vyf verkoelingsaanlegte en maak ‘n groot persentasie van die aanleg se energieverbruik uit. Mintek was gekontrakteer om beheer op die kring toe te pas, maar het aanvanklik slegs twee kleppe op die stelsel beheer, en weens die gebrek aan akkurate modelle en parameters wat die stelsel beskryf, kon hulle nie die skeduleering van die verkoelingsaanleg volgens Eskom se tyd-van-dag-tariewe implementeer nie. Daar word beraam dat die suksessvolle skedulering van die verkoelingsaanleg, gebaseer op die stroomaf ondergrondse behoeftes, die bedryf R16 mijoen per jaar aan elektrisiteits koste kan bespaar. Om die moontlike ekonomiese voordele te verwesenlik, word die sisteem eers gemodelleer vanaf eerste beginsel massa en energie balanse, en die modelparameters word beraam op grond van aangetekende aanlegdata deur regressie in MATLAB te gebruik. Om te bevestig dat die modelparameters die beste moontlike voorspelbare akkuraatheid verskaf, word 'n identifiseerbaarheidsanalise uitgevoer, wat van die profielwaarskynlikheidsmetode gebruik maak. Parameters word geassesseer vir strukturele en praktiese identifiseerbaarheid, wat die kwaliteit van die data en die model aandui. Versteurings aan die proses word stogasties gemodelleer, met 'n outoregressiewe funksie. Om die moontlike finansiële besparings te demonstreer, word 'n model voorspellende beheerder (MPC) en optimeerder in simulasie geïmplementeer. Dit sluit in die opstel van individuele MPC's op elk van die eenhede as 'n basislaag van beheer, en dan die toepassing van 'n optimeerder as 'n boonste laag. Die optimeerder is verantwoordelik vir die bepaling van die aan- en af-statusse van die verkoelingsaanlegte, terwyl verseker word dat die verkoeldam, die stoorplek vir kouewatervoorraad, nie droogloop nie en dat daar altyd aan die ondergrondse vraag voldoen word. Dit maak voorsiening vir finansiële vergelykings wat getref kan word tussen die geval waar die optimeerder afgeskakel is en geen skedulering van verkoelingsaanlegte se werking plaasvind nie, en wanneer dit aangeskakel word en skedulering plaasvind. Die ondersoek het 'n algehele gemiddelde jaarlikse besparing van sowat R21 miljoen vir die geoptimaliseerde geval gevind. Dit kom neer op 'n jaarlikse kostebesparing van 17.83% in vergelyking met die nie-geoptimaliseerde geval. 'n Energiebesparing van 70.45% is ook tydens spitskoste-ure behaal. Masters 2025-05-20T14:25:40Z 2025-05-20T14:25:40Z 2025-03 Thesis https://scholar.sun.ac.za/handle/10019.1/132044 Stellenbosch University 127 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Cooling systems Mine ventilation Refrigeration and refrigerating machinery Engineering systems -- Computer simulation UCTD Jordan, Anastasiou Optimising an underground mine cooling water operation |
| title | Optimising an underground mine cooling water operation |
| title_full | Optimising an underground mine cooling water operation |
| title_fullStr | Optimising an underground mine cooling water operation |
| title_full_unstemmed | Optimising an underground mine cooling water operation |
| title_short | Optimising an underground mine cooling water operation |
| title_sort | optimising an underground mine cooling water operation |
| topic | Cooling systems Mine ventilation Refrigeration and refrigerating machinery Engineering systems -- Computer simulation UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/132044 |
| work_keys_str_mv | AT jordananastasiou optimisinganundergroundminecoolingwateroperation |