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.     

Heat stress management in underground mines

Heat management must be maintained within the mine working environment to minimize stress on equipment and personnel. The issue is a growing concern as mines continue to expand in size, depth and infrastructure. Heat management is a concern as it relates to both heat sensitive equipment and more importantly the health and safety of the workers found within the mine. Proper application of engineering protocols and work practice controls will have a direct impact on the health and safety of workers and increased productivity. Using continuous monitoring stations placed in strategic locations throughout the mine to capture the environmental conditions, various strategies can be used in the planning and prevention of potential hazard exposure. Economic analysis is used to select the most feasible strategy for heat stress control. This paper presents a step by step methodology that may be considered by ventilation specialists to effectively implement a heat management control system. A case study based on a detailed heat management assessment conducted for a potash mine in Saskatchewan, Canada is presented.     

Geological factors controlling deep geothermal anomalies in the Qianjiaying Mine,China

Here, the geological factors controlling deep geothermal anomalies in mines were studied based on the geotemperature, lithologic thermal conductivity, and related geological data collected from the Qianjiaying Mine, China. A simulation of the change in magma waste heat, conducted using the ANSYS Workbench, revealed the distribution characteristics of geothermal anomalies in this mine and the corresponding geological control factors. The results revealed the following points. (1) First-degree heat hazard level (temperature = 31–37 ℃) occurred in the central and southwestern parts of the mine at an ~600-m depth, while second-degree heat hazard level (temperature ≥ 37 ℃) occurred at an ~800-m depth. The geotemperature and geothermal gradient in the southwestern part of the mine were anomalously high. (2) The geotemperatures measured in the mine generally reflected a standard increase with depth, while the geothermal gradient remained unchanged with depth. The geothermal gradient and its average value in the study area were 0.70–4.23 and 2.12 °C·hm⁻¹, respectively. (3) A combination of stratum characteristics, geological structure, and groundwater characteristics led to geothermal anomalies in mines; additionally, the waste heat from magma had no significant effect on the geothermal field.     

Closed-loop bulk air conditioning:A renewable energy-based system for deep mines in arctic regions

With depletion of shallow deposits, the number of underground mines expected to reach more than 3 km depth during their lifetime is growing. Although surface cooling plants are mostly effective in mine airconditioning, usually secondary cooling units are needed below 2 km depth. This need emerges due to the elevated thermal impacts caused by auto-compression of mine air as well as heat emissions from strata and mine machinery. As a result, in cold climates, like Canada, ultra-deep mines need their secondary underground cooling plants running year-round while the intake air must be heated to protect the sensitive machinery and liners from freezing during the winter season. To cool mine air, horizontal bulk-airconditioners with direct spray cooling systems are commonly used due to their high performance.Conventionally, sprayed water in bulk-air-coolers are mechanically circulated and refrigerated in coupled refrigeration plants. This set up can be transformed to a natural cooling/heating process by resurfacing the warm underground bulk-air-cooler spray water for mine air heating on the surface and re-sinking the chilled water for cooling in the underground bulk air coolers. This could significantly cut-down the fossil-fuel consumption in burners for mine air pre-conditioning and refrigeration cost when applicable.This paper presents an anonymous real-life example to study the feasibility of the proposed idea for an ultra-deep Canadian mine.     

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.     

合肥滨湖新区地源热泵技术的应用研究

地埋管地源热泵技术是一种利用自然浅层岩体储冷蓄热特性,实现对建筑物供暖和制冷的低碳技术.本文根据该技术在合肥滨湖新区某工程的实际应用,对工程的岩土和水文地质勘察报告资料进行了分析,同时进行了空调全年动态负荷的计算,在技术特点、经济效益、能源结构、环境影响等方面与常规空调进行了对比研究,得出了地埋管地源热泵技术在合肥滨湖新区应用中节能减排的计算数据,指出在类似地质条件的合肥滨湖新区,该项技术具有的广阔的应用前景.     

塑料注射模具冷却系统的简易算法

提出冷却水道紊流界膜强制散热的简易算法；同时提出空气自然对流散热、辐射散热、注射机固定模板散热的计算公式，并以具体算例证实其所占的比例。     

Simulation and optimization approach for uncertainty-based short-term planning in open pit mines

Accuracy in predictions leads to better planning with a minimum of opportunity lost. In open pit mining,the complexity of operations, coupled with a highly uncertain and dynamic production environment,limit the accuracy of predictions and force a reactive planning approach to mitigate deviations from original plans. A simulation optimization framework/tool is presented in this paper to account for uncertainties in mining operations for robust short-term production planning and proactive decision making. This framework/tool uses a discrete event simulation model of mine operations, which interacts with a goalprogramming based mine operational optimization tool to develop an uncertainty based short-term schedule. Using scenario analysis, this framework allows the planner to make proactive decisions to achieve the mine's operational and long-term objectives. This paper details the development of simulation and optimization models and presents the implementation of the framework on an iron ore mine case study for verification through scenario analysis.     

Mine production index(MPI)-extension of OEE for bottleneck detection in mining

Although mining production depends on various equipments, significant amount of production loss can be attributed a specific equipment or fleet. Bottleneck is defined not only by production loss but also by our satisfaction from the equipment. The user satisfaction could be measured as machine effectiveness.Mining literatures on performance improvement and optimization of equipment operations assert importance of availability, utilization and production performance as key parameters. These three parameters are useful for evaluating effectiveness of equipment. Mine production index(MPI), which can represent the effect of these factors, has been applied for continuous operation in mining. MPI uses Fuzzy Delphi Analytical Hierarchy Process to determine importance of each three parameter for individual equipment. A case study in a Swedish open pit mine was done to evaluate the field application of MPI.The results reveal that crusher is the bottleneck equipment in studied mine. As a methodical approach,an algorithm which uses MPI and detects bottleneck in continuous mining operation has been proposed.     

Rockburst mechanism in soft coal seam within deep coal mines

A number of rockburst accidents occurring in soft coal seams have shown that the rockburst mechanism involved in soft coal seams is significantly different from that involved in hard coal seams. Therefore, the method used to evaluate rockburst in hard coal seams is not applicable to soft coal seams. This paper established an energy integral model for the rockburst-inducing area and a friction work calculation model for the plastic area. If the remaining energy after the coal seam is broken in the rockburstinducing area is greater than the friction work required for the coal to burst out, then a rockburst accident will occur. Mechanisms of ‘‘quaking without bursting" and ‘‘quaking and bursting" are clarified for soft coal seams and corresponding control measures are proposed as the optimization of roadway layouts and use of ‘‘three strong systems"(strong de-stressing, strong supporting, and strong monitoring).     

Physiological responses of people in working faces of deep underground mines

The research studied the influences of high temperature, high pressure, high humidity, noise and other harmful factors in mining conditions on the people health and safety, and investigated the impacts of confined environmental on human physiology factors, including temperature, humidity, noise, pressure, toxic and harmful gases in terms of environmental characteristics in underground mines and an artificial intelligence system for simulation of the environment in a confined space of deep mines. Our results show that the systolic pressure, diastolic pressure, mean pressure, heart rate, respiratory rate, typing test speed and memory level percentage are negatively correlated with temperature value, and positively correlated with humidity value; the human temperature and weight are positively correlated with temperature value, and negatively correlated with humidity value. This research lays the foundation for the study of interaction between the deep confined space environment and safety behavior.     

水泵汽蚀防护措施的研究现状

介绍了水泵汽蚀现象、危害及影响因素,对水泵汽蚀防护的各种措施进行了阐述.     

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.     

复合水体下急倾斜煤层开采的水害防治研究

淮南孔集煤矿山西组A1、A3煤层总厚6m,为第四系含水砂层下底板岩溶水上复合含水体威胁的急倾斜煤层。对于砂层水害防治,采用合理留设防水煤柱,沿用“小阶段、长走向、间歇开采”的方式方法;对于底板岩溶水患防治,采用“疏水降压、限压开采”的防治水方法;对于局部抽冒及流水钻孔涌砂造成地表抽冒漏斗及岩溶塌陷漏斗,采取了“按尺核产、严禁超限出煤”、“小流量、长历时、控砂疏水”的有力措施。实现了安全开采,取得了良好的效果。     

Investigation of the role of personal factors on work injury in underground mines using structural equation modeling

Work injuries in mines are complex and generally characterized by several factors starting from personal to technical and technical to social characteristics. In this paper, investigation was made through the application of structural equation modeling to study the nature of relationships between the influencing/associating personal factors and work injury and their sequential relationships leading towards work injury occurrences in underground coal mines. Six variables namely, rebelliousness, negative affectivity, job boredom, job dissatisfaction and work injury were considered in this study. Instruments were developed to quantify them through a questionnaire survey. Underground mine workers were randomly selected for the survey. Responses from 300 participants were used for the analysis. The structural model of LISREL was used to estimate the interrelationships amongst the variables. The case study results show that negative affectivity and job boredom induce more job dissatisfaction to the workers whereas risk taking attitude of the individual is positively influenced by job dissatisfaction as well as by rebelliousness characteristics of the individual. Finally, risk taking and job dissatisfaction are having positive significant direct relationship with work injury. The findings of this study clearly reveal that rebelliousness, negative affectivity and job boredom are the three key personal factors influencing work related injuries in mines that need to be addressed properly through effective safety programs.     

Instability energy mechanism of super-large section crossing chambers in deep coal mines

The stress concentration and failure at chamber intersections in coal mine are intense, especially in deep-buried, super-large section conditions. In this paper, the plastic radius of super-large section chamber under unequal pressure was corrected on the basis of the size effect. Then, stress and failure evolution of intersections under different crossing angles and equivalent angular bisectors were revealed. Furthermore, 2 trajectory curves of failure and stress were analytically expressed, which divided the intersection into 5 influencing zones in the light of stress superposition degree. After determining instability trigger point and instability path, instability energy criterion of intersection can be obtained as K > 1, which means that the external energy is greater than the sum of energy consumed by surrounding rock instability and supporting structure failure. Taking coal-gangue separation system of Longgu Coal Mine as example, it was found that there was instability risk under original parameters. For long-term stability, an optimization design method was proposed by considering safety factor, and optimal support scheme was obtained. Field monitoring showed intersections deformations were relatively small with the maximum of 125 mm, which verified the rationality of theoretical analysis. This study provides guidance for the stability control of the intersections under the same or similar conditions.     

Characteristics of water inflow and chemical grouting treatment of a Liu Yuanzi Coal Mine shaft in the Ordos Basin

During shaft constructing, a borehole water inflow of 30 m3/h was encountered in Liu Yuanzi Coal Mine in the southwestern Ordos Basin, whose aquifer is mainly cretaceous. On the basis of regional hydrogeological conditions, a mercury intrusion method and scanning electron microscope were used in this study. We conclude that the loose, porous and easily collapsible clay particles of the cretaceous aquifer rock mass were the major geological cause for water hazards during the construction of the shaft. We propose an approach of chemical grouting from the working surface and in the end succeeded in blocking the water.     

基于差分进化算法的配电网智能换相策略

结合三相智能换相开关的换相过程, 提出一种以差分进化算法为核心、以混合固态开关为基础的配电网智能换相系统。以三相电流不平衡度和换相开关动作次数为目标, 采用差分进化算法对换相策略进行寻优, 通过初始化、变异、交叉与选择操作, 获得最优的换相策略, 提高了系统的实时性和准确性。通过将磁保持继电器与以绝缘栅双极型晶体管(insulated gate bipolar transistor, IGBT)为主体的固态开关相结合方式, 提出采用混合固态开关进行快速切换的方法, 使换相开关具有功耗低、通流能力强的特点, 提高了系统的可靠性。通过实际测试验证了算法和切换开关在快速切换与提高换相过程电能质量方面的可行性。     

Deformation and failure study of surrounding rocks of dynamic pressure roadways in deep mines

In order to understand the change rules of stress-displacement in surrounding rocks of dynamic pressure roadways in deep mines and to obtain a theoretical basis for analyses of roadway stability and designs of support,we established a coupling equation of adjacent rock strength,mining stress and supporting resistance on the basis of an elastic-plastic theory of mechanics.We obtained an analytical solution for stress and displacement distribution of elastic and plastic regions in surrounding rock of dynamic pressure roadway..Based on this theory,we have analyzed the changes in stress-displacement in elastic and plastic regions of surrounding rocks of dynamic pressure roadways in the Haizi Coal Mine.The results show that:1) radial and tangential stress change violently within the first 4 m from the inner surface of a roadway after excavation;radial stress increases while tangential stress decreases within a range of about 6 m from the inner surface of the roadway as a function of q3;2) radial and tangential stress increase with an increase in the mining pressure coefficient k;the increase in the rate of tangential stress is greater than that of radial stress;3) the radial displacement of the inner surface of roadways decreases with an increase in q3,provided that k remains unchanged.