Prioritisation of Environmental Improvement Projects in Deep-Level Mine Ventilation Systems

Mining, Metallurgy & Exploration https://doi.org/10.1007/s42461-023-00738-w Prioritisation of Environmental Improvement Projects in Deep‑Level Mine Ventilation Systems J. Swanepoel1 · J. C. Vosloo1 · J. H. van Laar1 · W. A. Pelser2 Received: 5 October 2022 / Accepted: 1 February 2023 © The Author(s) 2023 Abstract Deep-level underground mining costs in South Africa are continuously rising due to the increased depth at which gold is being mined, resulting in a rise in virgin rock temperature and an increase in cooling requirements. Therefore, mines must evaluate various ventilation and cooling optimisation projects required to be implemented throughout their life of mine (LOM). This study develops a method to identify and prioritise large capital expenditure (CAPEX) underground environmental improvement projects, to improve thermal comfort underground. The solution presents a ‘multi-criteria decision-making’ (MCDM) process, incorporating the ‘analytic hierarchy process’ (AHP) and the ‘technique for order performance by similarity to ideal solution’ (TOPSIS) into the method to provide for scientific decision-making. These projects are evaluated based on four criteria, namely project risk, the impact on the underground thermal comfort, cost, and implementation time. This study’s solution uses ventilation simulations to determine the impact of the projects on the underground environment. The identification and evaluation of an environmental improvement project to best suit the current economic climate, while improving underground conditions and decreasing the safety risk is an essential aspect of the solution developed in this study. The method was implemented on a mechanised deep-level underground mine and showed that surface refrigeration is the most suitable alternative, which was implemented at the case study mine as validation of the developed solution. The study proves that the MCDM method is an adequate solution to incorporate subjective criteria into the decision-making process, resulting in a scientific and structured approach to making significant and complex decisions. Keywords Multi-criteria decision-making method (MCDM) · Deep-level underground mining · Analytic hierarchy process (AHP) · Environmental improvement · Project prioritisation · Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) 1 Introduction 1.1 Background to Mining Project Selection Peaking at a production output of 1000 tonnes of gold mined in 1970 [1], South Africa was one of the top gold producers globally but has since battled to remain in the top 10 goldproducing countries. The rising cost of gold mining, which can be attributed to rising electricity prices, increased labour costs, the age of operations, and increasing mining depth, is * J. Swanepoel 1 Center for Research and Continued Engineering Development (CRCED) Pretoria, North-West University, Pretoria, South Africa 2 Department of Industrial Engineering, Stellenbosch University, Stellenbosch, South Africa considered one of the main reasons South Africa’s gold production is declining [2]. For sustainable gold mining, strategic capital spend is required to counter the drastic cost increases faced by the mining industry. A ‘flexible’ ventilation and cooling plan that introduces ventilation and cooling at different stages of mine exploration, that can absorb the changes and development in planning is often suggested; however, this is not the case at every mine [3]. Infrastructure deterioration and cost-cutting occur due to an increase in mining costs [4]. Many studies have been conducted on improving the ventilation system and selecting the most suitable solution for the respective operational mine [5–14]. Most of these studies focused on benefit–cost analysis to establish the most beneficial solution at the lowest cost. Determining the benefit of a ventilation project is a complex task due to the dynamics and integrated nature of a 13 Vol.:(0123456789) Mining, Metallurgy & Exploration deep-level underground mine. There is an increasing presence of modern simulation tools to assist in solving these dynamic and integrated ventilation systems [15, 16]. Ventilation and climate simulation models have been used countlessly in designing and predicting future ventilation systems [15–21]. Although the most effective methods are used to quantify the impact at the lowest cost, risk should be considered in the decision-making process, as safety is a main priority in the mining sector. Deciding which project should be implemented is crucial for maximising the economic benefit without compromising safety (both acute and chronic) [22, 23]. Several studies considered incorporating additional aspects, such as the risk factor that is difficult to quantify during the decision-making process, but were unable to do so as the decision is left open to bias [6, 9, 13, 14, 19, 20]. Multi-criteria decision-making (MCDM) methods have been used in many industries to assist decision-makers with multicriteria decision-making [24–29]. Mining-related studies are contemplated in more detail in the remainder of this section. MCDM methods assist in structuring a scientific decision-making process while achieving the most accurate results. MCDM methods can handle large amounts of data with different criteria during essential decision-making [30]. Yavuz [31] explained that MCDM problems consider only a single objective: choosing from a list of alternatives to identify which alternative is the best fit. In the mining sector, MCDM has been used many times during the decisionmaking process of mining method selection [22, 31–43]. Table 1  Summary of the research literature review 1.2 Literature on Recent Advances in MCDM and Ventilation Optimisation To better understand what has been done relating to MCDM methods in the mining industry and project evaluation of environmental improvement projects, the literature on underground mines was examined based on the following: A—Whether the study uses MCDM methods to solve a decision-making problem. B—Does the study evaluate projects’ impact on underground thermal conditions? C—Is environmental simulation software used to determine the project’s impact in the underground environment? Table 1 Summarises all the latest literature on MCDM TOPSIS methods and project evaluation in the underground mining industry. The literature study showed that only three studies touched on an aspect of underground ventilation in the MCDM process; Kluge’s [33] and Nourali’s [34] studies of underground mining method selection dedicated one criterion to how the mining method would impact the ventilation without detailed evaluation. Kursunoglu [35] used the MCDM method during a fan selection process. The impact of each fan on the methane build-up and air quantity Main author A Literature criteria B Acuña, Baiden, Gruting, Jacobs Ali, Amorocho, Asr, Javanshirgiv x TOPSIS Bascompta, Makay, Maré, Mathews, Nel, Samito, (...truncated)