Browsing by Author "van der Merwe, Arno"

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    Developing zero-waste baselines to identify compressed air system inefficiencies in deep-level mines.
    (Stellenbosch : Stellenbosch University, 2023-02) van der Merwe, Arno; Schutte, Cornelius Stephanus Lodewyk ; Gous, Andries Gustav Stephanus; Stellenbosch University. Faculty of Engineering. Dept. of Industrial Engineering.
    ENGLISH ABSTRACT: As one of the main exporting industries of South Africa, the gold mining industry has seen a decrease in gold exports in past years. A weakening economy and rolling blackouts prompt Eskom to increase it’s tariff to battle the lack of supply and ever-increasing demand. As the price of electricity increases, the operating costs of mines increase, due to the high reliance on electricity by the mines. The largest electricity consumer on deep-level mines are the compressors and compressed air system. Not only is compressed air the largest consumer of electricity, it was determined to be a very ineffective and inefficient system due to numerous losses and improper use of the resources. Between 30 and 40 % of savings can be realized if the compressed air system inefficiencies are repaired. This highlights the need to identify, localise and quantify the inefficiencies in the compressed air system, with the goal to reduce the overall operating costs of the compressed air system. The compressed air system consists of the supply side, which are the compressors, the distribution network, which is the network of pipes, valves and meters, and lastly, the demand side, which is all the equipment which consumes the compressed air to function. Some unavoidable losses found in the compressed air network are friction losses, however, these losses only reduce pressure and not mass flow. The phenomenon auto compression can also increase pressures in lower levels, due to the weight of the air. Optimal operation of a system can be described as the best achievable performance of the system in question. Optimal performance can be compared to a system performing with zero waste. Zerowaste on the other hand, is a concept and paradigm which challenges operation design to limit and minimise wastages in any given system, either by recycling or optimizing the system. With these concepts in mind, the zero-waste baseline concept was derived as a comparative performance indicator of any given system. Using the zero-waste baseline, a method was developed to identify, localise and quantify compressed air system inefficiencies, by comparing the actual performance of the system with the developed zero-waste baselines. These baselines are developed based on the demand side equipment and the time of use of the specified equipment. With the principle of mass conservation, the difference between actual performance and the zerowaste baseline can be calculated and is then defined as the wastages and inefficiencies in the compressed air system. The zero-waste baseline method was tested on a deep-level gold mine. The major consuming equipment were determined to be refuge bays, pneumatic drills, pneumatic cylinders and pneumatic loaders. It was found that this mine wasted 229 MWh every day, which is equal to R300 622 per day. After physical audits of the major underground levels, the error of the waste calculation was calculated to be 4 %. Therefore, this method can be implemented to determine where the largest wastages are and assist in fixing these wastages