Cooling pathways for deep Australian longwall coal mines of the future

Cooling of coal mines in the Bowen Basin, characterized by steep geothermal gradient, is presently achieved mostly through rental surface bulk air cooling in summer months. This paper argues that future mines will be required to focus their cooling resources more intensively to manage a challenging thermal environment where virgin coal temperatures over 50 °C at a depth of 500 m are expected. Currently, mine cooling systems are employed to maintain the wet bulb temperatures(WBT) to below 27 °C at which point the risks of heat stroke or other heat related issues are manageable. The capacities of these systems are in the range of 6–10 MW refrigeration power. The relationship between high working temperature environment and injury frequency rates is well established. Therefore, provision of appropriate cooling strategies and understanding their optimum performance and suitability are important to Australian coal mines of the future. This paper evaluates the underground temperature profiles of deep, gassy coal mines with propensity for spontaneous combustion and proposes the long term cooling pathways to effectively manage the thermal hazards. Thermodynamic modeling is performed on a longwall face and includes air leakage effects from goaf streams at various locations along the longwall face. The strategy summarizes the application of underground bulk air cooling, chilled water sprays on the shearer and the resulting temperature profiles. Considering the new mining projects planned for the Bowen Basin region, a review of implementable cooling strategies such as mid-gate mobile bulk air coolers(BACs), spot coolers, underground bulk air cooling and the use of chilled water to enhance the positional efficiency of cooling plants,are discussed in this paper. Finally, the comparison of ‘rental' versus ‘ownership' of cooling plants is analysed as part of long-term cooling strategies.     

Techno-economic feasibility assessment of a diesel exhaust heat recovery system to preheat mine intake air in remote cold climate regions

Underground mines in Arctic and Subarctic regions require the preheating of mine intake air during winter. The cold fresh air of those remote areas can be as severe as -40 ℃ and commonly needs to be heated to around +3 ℃. This extensive amount of heating is usually provided by employing large-size air heaters,fueled by diesel, propane, natural gas, or heavy oil, leading to high energy costs and large carbon footprints. At the same time, the thermal energy content of a diesel generator sets(gen-sets) exhaust is known to be one-third of the total heating value of its combusted fuel. Exhaust heat recovery from diesel gen-sets is a growing technology that seeks to mitigate the energy costs by capturing and redirecting this commonly rejected exhaust heat to other applications such as space heating or pre-heating of the mine intake air. The present study investigated the possibility of employing a simple system based on off-theshelf heat exchanger technology, which can recover the waste heat from the exhaust of the power generation units(diesel gen-sets) in an off-grid, cold, remote mine in Canada for heating of the mine intake air. Data from a real mine was used for the analysis along with environmental data of three different location-scenarios with distinct climates. After developing a thermodynamic model, the heat savings were calculated, and an economic feasibility evaluation was performed. The proposed system was found highly viable with annual savings of up to C$6.7 million and capable enough to provide an average of around 75% of the heating demand for mine intake air, leading to a payback period of about eleven months or less for all scenarios. Deployment of seasonal thermal energy storage has also been recommended to mitigate the mismatch between supply and demand, mainly in summertime, possibly allowing the system to eliminate fuel costs for intake air heating.     

Principles and technology for stepwise utilization of resources for mitigating deep mine heat hazards

As is well known, deep mines are hot. As mining depth increases, the temperature of the surrounding rock also increases. This seriously affects mine safety and production and has restricted the exploitation of deep coal resources. Therefore, reducing the working face temperature to improve working conditions by controlling these heat hazards is an urgent problem. Considering problems in cooling deep mines both domestically and abroad along with the actual conditions of the Zhangshuanglou coal mine, we propose a HEMS technology that uses heat resources from deep mines in a stepwise manner. HEMS means a high temperature exchange machinery system. Mine inrush-water is used as a source of cooling. Twice the energy is extracted from the mine inrush water. Heat is used for building heating in the winter and cold water is used for cooling buildings in the summer. This opens a new technology for stepwise utilization of heat energy in deep mines. Energy conservation and reduced pollution, an improved environment and sustainable economic development are realized by this technique. The economic and social effects are obvious and illustrate a good prospect for the application and extension of the method.     

Progress of heat-hazard treatment in deep mines

Based on the urgency of thermal hazard control in deep coal mines, we studied the status of deep thermal damage and cooling technology both at home and abroad, summarized the causes of deep thermal hazard, analysed and compared the control technologies for deep thermal hazards. The results show that the causes of deep thermal damage can be attributed to three aspects, i.e., climate, geological and mining factors, of which the geological factors are deemed the major reasons for thermal hazards. As well, we compared a number of cooling technologies of domestic and overseas provenance, such as central air conditioning cooling technology, ice cooling technology and water cooling technology, with one other cooling technology, i.e., the HEMS cooling technology, which has a large and important effect with its unique "pure air" cooling technology, realizes the utilizing of heat resources from underground to the ground. This technology makes use of heat obtained underground; thus the technology can promote low-carbon environmental economic development in coal mines, in order to achieve lowcarbon coal production in China.     

商业综合体冷站用能分析与优化

商业综合体由于在内部空间结构、功能及人员行为方面的复杂性,其负荷特征、空调运行及室内环境等状况复杂,冷站设计及节能优化需要结合自身特点。首先,针对商业综合体分析其空调使用需求特征,通过室内热湿环境实测分析,发现室内环境较传统商业建筑波动较大,不同业态室内环境有显著差异。其次,通过冷站实际运行工况分析其能耗特征、供冷系统运行模式及问题,发现商业综合体冷负荷稳定、冷站运行时间长、冷机设计容量普遍存在过大的问题。最后,利用DeST软件对两类典型空间分布（环绕型、中庭型）的商业综合体建立模型,分析不同区域、不同时间段的负荷特征,并根据业态负荷或时间负荷特征对冷源设计方案进行优化设计和对比,发现按照业态负荷特征对体量大、业态布局分散且各业态负荷差异大的商业综合体进行冷源设计对冷站节能有利。     

A review of laser scanning for geological and geotechnical applications in underground mining

Laser scanning can provide timely assessments of mine sites despite adverse challenges in the operational environment. Although there are several published articles on laser scanning, there is a need to review them in the context of underground mining applications. To this end, a holistic review of laser scanning is presented including progress in 3D scanning systems, data capture/processing techniques and primary applications in underground mines. Laser scanning technology has advanced significantly in terms of mobility and mapping, but there are constraints in coherent and consistent data collection at certain mines due to feature deficiency, dynamics, and environmental influences such as dust and water. Studies suggest that laser scanning has matured over the years for change detection, clearance measurements and structure mapping applications. However, there is scope for improvements in lithology identification, surface parameter measurements, logistic tracking and autonomous navigation. Laser scanning has the potential to provide real-time solutions but the lack of infrastructure in underground mines for data transfer, geodetic networking and processing capacity remain limiting factors. Nevertheless, laser scanners are becoming an integral part of mine automation thanks to their affordability, accuracy and mobility, which should support their widespread usage in years to come.     

Deep mine cooling,a case for Northern Ontario:Part Ⅰ

Cooling energy needs,for mines in Northern Ontario,are mainly driven by the mining depth and its operation.Part I of this research focusses on the thermal energy loads in deep mines as a result of the virgin rock temperature,mining operations and climatic conditions.A breakdown of the various heat sources is outlined,for an underground mine producing 3500 tonnes per day of broken rock,taking into consideration the latent and sensible portions of that heat to properly assess the wet bulb global temperature.The resulting thermal loads indicate that cooling efforts would be needed both at surface and underground to maintain the temperature underground within the legal threshold.In winter the air might also have to be heated at surface and cooled underground,to ensure that icing does not occur in the inlet ventilation shaft-the main reason why cooling cannot be focussed solely at surface.     

生态住宅自然能源利用系统的研究

根据目前住宅能源的需求和特点．论述了发展生态住宅的迫切性,分别对太阳能集热器——水源热泵系统、太阳能地热能供暖供冷式空调系统、利用地下水的中央空凋机组系统、完全自然能源供热制冷系统等几个系统进行技术经济分析,表明太阳能、地热能作为可再生能源用于生态住宅和建筑中,具有明显的经济效益、节能效益和环境效益,有较高的推广价值．     

Evaluating the impact of auxiliary fan practices on localised subsurface ventilation

Mines are continually expanding in size and depth, leading to an increased reliance on localised subsurface ventilation systems. The use of underground auxiliary fans is a favoured method to increase and control airflow in working areas. However, the effectiveness of auxiliary fans in this regard is not clear. This paper evaluated the performance of these underground fan systems in four different South African deep-level gold mines. A total auxiliary fan system efficiency of 5% was found across six systems, with the average fan efficiency of 33 fans at 38%. The results showed that these fans deviate significantly from their design operating points. Therefore, there are significant shortcomings in current underground fan practices. Our detailed investigations led to the conclusion that the assemblage of underground auxiliary fan systems results in significant energy inefficiencies. Therefore, maintaining good underground fan practice such as optimal fan selection, ducting design and maintenance is crucial for the efficacy of a mine ventilation network.     

Prediction of air flow,methane, and coal dust dispersion in a room and pillar mining face

In underground coal mines, uncontrolled accumulation of methane and fine coal dust often leads to serious incidents such as explosion. Therefore, methane and dust dispersion in underground mines is closely monitored and strictly regulated. Accordingly, significant efforts have been devoted to study methane and dust dispersion in underground mines. In this study, methane emission and dust concentration are numerically investigated using a computational fluid dynamics(CFD) approach. Various possible scenarios of underground mine configurations are evaluated. The results indicate that the presence of continuous miner adversely affects the air flow and leads to increased methane and dust concentrations.Nevertheless, it is found that such negative effect can be minimized or even neutralized by operating the scrubber fan in suction mode. In addition, it was found that the combination of scrubber fan in suction mode and brattice results in the best performance in terms of methane and dust removal from the mining face.     

防止500 kV地下变电站出风井白雾的产生

500 kV静安地下变电站采用闭式喷淋冷却塔的循环冷却系统,当环境温度低或空气湿度较高的时候,冷却塔排出的热气容易在出风井附近产生白雾,对周围环境有一定的影响.分析白雾产生的机理：站内冷却系统主要为油浸主设备进行冷却,热量由冷却塔排出室外,在雨季、冬季的时候,当环境温度较低或湿度较高时,冷却塔排出的热、湿空气被外界冷空气冷却,冷凝成水珠,形成白雾。经分析,只要将冷却塔内加装吸热模块,将排除的空气再次加热,将温度提高,排出的湿、热空气与外界空气在焓湿图上的混合线正好与饱和湿度线相切,避开饱和区域,使排出的空气不产生白雾。运行情况表明：该方法不仅能够消除白雾,而且节能环保.     

Implementing a DIKW model on a deep mine cooling system

The South African mining industry has been experiencing increasing economic pressure. Deep mines also suffer from very hot workplaces, which leads to safety risks. These factors place stress on managers to reach their production targets while providing safe workplace conditions. The data information knowledge wisdom(DIKW) model, also known as the wisdom hierarchy, was implemented on a deep mine cooling system. This study aims to show that a simple model such as the DIKW model can assist managers in improving their deep mine cooling system's performance. The study found that the DIKW approach is a suitable approach for use on mine cooling systems to facilitate operational improvements.Applying the DIKW approach to a case study on a mine cooling system created substantial awareness and facilitated a cooling duty improvement of 55% which relates to an increase of 5.3 MW of refrigeration. The results of this study indicate that the DIKW approach may be a suitable approach to optimise management on deep mines using their existing infrastructure.     

燃气轮机进气采用喷雾蒸发冷却方式的温度分析

对燃气轮机的进气采用喷雾蒸发冷却的方式降温是一个绝热加湿冷却过程。对进气空气的温度进行分析计算,并通过计算的结果分析在我国新疆地区燃气轮机采用喷雾蒸发冷却方式冷却进气空气的优越性。     

Diesel generator exhaust heat recovery fully-coupled with intake air heating for off-grid mining operations: An experimental,numerical, and analytical evaluation

The customarily discarded exhaust from the fossil fuel-based power plants of the off-grid mines holds the thermal potential to fulfill the heating requirement of the underground operation. This present research fills in an important research gap by investigating the coupling effect between a diesel exhaust heat recovery and an intake air heating system employed in a remote mine. An integrative approach comprising analytical, numerical, and experimental assessment has been adapted. The novel analytical model developed here establishes the reliability of the proposed mine heating system by providing comparative analysis between a coupled and a decoupled system. The effect of working fluid variation has been examined by the numerical analysis and the possible improvement has been identified. Experimental investigations present a demonstration of the successful lab-scale implementation of the concept and validate the numerical and analytical models developed. Successful deployment of the fully coupled mine heating system proposed here will assist the mining industry on its journey towards energy-efficient, and sustainable mining practices through nearly 70% reduction in fossil fuel consumption for heating intentions.     

A comparative study of dust control practices in Chinese and Australian longwall coal mines

Mine dust is one of the main hazards in underground longwall mines worldwide.In order to solve the mine dust problem,a significant number of studies have been carried out regarding longwall mine dust control,both in China and Australia.This paper presents a comparative study of dust control practices in Chinese and Australian longwall mines,with particular references to statutory limits,dust monitoring methods and dust management practices,followed by a brief discussion on the research status of longwall mine dust control in both countries.The study shows that water infusion,face ventilation controls,water sprays,and deep and wet cutting in longwall shearer operations are commonly practiced in almost all underground longwall mines and that both Chinese and Australian longwall mine dust control practices have their own advantages and disadvantages.It is concluded that there is a need for further development and innovative design of more effective dust mitigation products or systems despite the development of various dust control technologies.Based on the examinations and discussions,the authors have made some recommendations for further research and development in dust control in longwall mines.It is hoped that this comparative study will provide beneficial guidance for scholars and engineers who are engaging in longwall mine dust control research and practice.     

Stability of multiple fans in mine ventilation networks

In large mines, single fan is usually not enough to ventilate all the working areas. Single mine-fan approach cannot be directly applied to multiple-fan networks because the present of multiple pressures and air quantities associated with each fan in the network. Accordingly, each fan in a multiple-fan system has its own mine characteristic curve, or a subsystem curve. Under some consideration, the conventional concept of a mine characteristic curve of a single-fan system can be directly extended to that of a particular fan within a multiple-fan system. In this paper the mutual effect of the fans on each other and their effect on the stability of the ventilation network were investigated by Hardy Cross algorithm combined with a switching-parameters technique. To show the validity and reliability of this algorithm, the stability of the ventilation system of Abu-Tartur Mine (one of the largest underground mine in Egypt) has been studied.     

Optimized model-based control of main mine ventilation air flows with minimized energy consumption

In early 2018, the Boliden Garpenberg operation implemented an optimized control strategy as an addition to the existing ventilation on demand system. The purpose of the strategy is to further minimize energy use for main and booster fans, whilst also fulfilling airflow setpoints without violating constraints such as min/max differential pressure over fans and interaction of air between areas in mines. Using air flow measurements and a dynamical model of the ventilation system, a mine-wide coordination control of fans can be carried out. The numerical model is data driven and derived from historical operational data or step changes experiments. This makes both initial deployment and lifetime model maintenance,as the mine evolves, a comparably easy operation. The control has been proven to operate in a stable manner over long periods without having to re-calibrate the model. Results prove a 40% decrease in energy use for the fans involved and a greater controllability of air flow. Moreover, a 15% decrease of the total air flow into the mine will give additional proportional heating savings during winter periods.All in all, the multivariable controller shows a correlation between production in the mine and the ventilation system performance superior to all of its predecessors.     

Application of HEMS cooling technology in deep mine heat hazard control

This paper mainly deals with the present situation, characteristics, and countermeasures of cooling in deep mines. Given existing problems in coal mines, a HEMS cooling technology is proposed and has been successfully applied in some mines. Be-cause of long-term exploitation, shallow buried coal seams have become exhausted and most coal mines have had to exploit deep buried coal seams. With the increase in mining depth, the temperature of the surrounding rock also increases, resulting in ever increasing risks of heat hazard during mining operations. At present, coal mines in China can be divided into three groups, i.e., normal temperature mines, middle-to-high temperature mines and high temperature mines, based on our investigation into high temperature coal mines in four provinces and on in-situ studies of several typical mines. The principle of HEMS is to extract cold energy from mine water inrush. Based on the characteristics of strata temperature field and on differences in the amounts of mine water inrush in the Xuzhou mining area, we proposed three models for controlling heat hazard in deep mines: 1) the Jiahe model with a moderate source of cold energy; 2) the Sanhejian model with a shortage of source of cold energy and a geothermal anomaly and 3) the Zhangshuanglou model with plenty of source of cold energy. The cooling process of HEMS applied in deep coal mine are as follows: 1) extract cold energy from mine water inrush to cool working faces; 2) use the heat extracted by HEMS to supply heat to buildings and bath water to replace the use of a boiler, a useful energy saving and environmental protection measure. HEMS has been applied in the Jiahe and Sanhejian coal mines in Xuzhou, which enabled the temperature and humidity at the working faces to be well controlled.     

Optimal use of mobile cooling units in a deep-level gold mine

The South African gold mining sector remains a significant contributor to the country's economy. Facing several challenges that hinder the realisation of South Africa's full mineral potential, the sector's sustainability and profitability can be enhanced through implementing operational improvement measures.Mobile cooling units(MCUs) were identified as a potential focus area for operational improvement.MCUs are used as tertiary or in-stope cooling in hot underground workings. In this paper, a method was presented to characterise the performance of existing MCUs based on three key performance indicators(KPIs), namely, the wet-bulb temperature ratio(WTR), efficiency and position. Optimisation strategies were then elected and implemented based on these KPIs. The implementation of this method in a South African gold mine attained a reduction in pumped water volumes, reduced operating costs through electricity cost savings and improvements in underground ventilation air temperatures.     

深井降温的技术经济分析

本文论述了典型深井降温空调系统的技术特点,提出了我国深井降温系统应用年计算费用法进行技术经济分析的方法.工程实例的技术经济比较表明,深井降温应用冰冷却系统比常规矿井空调系统具有更大的优越性.