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翻译部分
英文原文
High Productivity —A Question of Shearer Loader Cutting Sequences
K. Nienhaus, A. K. Bayer & H. Haut, Aachen University of Technology, GER
1 Abstract
Recently, the focus in underground longwall coal mining has been on increasing the installed motor power of shearer loaders and armoured face conveyors (AFC), more sophisticated support control systems and longer face length, in order to reduce costs and achieve higher productivity. These efforts have resulted in higher output and previously unseen face advance rates. The trend towards “bigger and better” equipment and layout schemes, however, is rapidly nearing the limitations of technical and economical feasibility. To realise further productivity increases, organisational changes of longwall mining procedures looks like the only reasonable answer. The benefits of opti-mised shearer loader cutting sequences, leading to better performance, are discussed in this paper.
2 Introductions
Traditionally, in underground longwall mining operations, shearer loaders produce coal using either one of the following cutting sequences: uni-directional or bi-directional cycles. Besides these pre-dominant methods, alternative mining cycles have also been developed and successfully applied in underground hard coal mines all over the world. The half-web cutting cycle as e.g. utilized in RAG Coal International’s Twentymile Mine in Colorado, USA, and the “Opti-Cycle” of Matla’s South African shortwall operation must be mentioned in this context. Other mines have also tested similar but modified cutting cycles resulting in improved output, e.g. improvements in terms of productiv-ity increases of up to 40 % are thought possible。
Whereas the mentioned mines are applying the alternative cutting methods according to their spe-cific conditions, –e.g. seam height or equipment used, –this paper looks systematically at the differ-ent methods from a generalised point of view. A detailed description of the mining cycle for each cutting technique, including the illustration of productive and non-productive cycle times, will be followed by a brief presentation of the performed production capacity calculation and a summary of the technical restrictions of each system. Standardised equipment classes for different seam heights are defined, after the most suitable and most productive mining equipment for each class are se-lected. Besides the technical parameters of the shearer loader and the AFC, the length of the long-wall face and the specific cutting energy of the coal are the main variables for each height class in the model. As a result of the capacity calculations, the different shearer cutting methods can be graphically compared in a standardised way showing the productivity of each method. Due to the general char-acter of the model, potential optimisations (resulting from changes in the cutting cycle and the benefits in terms of higher productivity of the mining operation) can be derived.
3 State-of-the-art of shearer loader cutting sequences
The question “Why are different cutting sequences applied in longwall mining?” has to be an-swered, before discussing the significant characteristics in terms of operational procedures. The major constraints and reasons for or against a special cutting method are the seam height and hard-ness of the coal, the geotechnical parameters of the coal seam and the geological setting of the mine influencing the caving properties as well as the subsidence and especially the length of the longwall face. For each mining environment the application of either sequence results in different production rates and consequently advance rates of the face. The coal flow onto the AFC is another point that varies like the loads on the shearer loader, especially the ranging arms and the stresses and the wear on the picks. A thorough analysis is necessary to choose the best-suited mining cycle; therefore, general solutions do not guarantee optimal efficiency and productivity.
A categorization of shearer loader cutting sequences is realised by four major parameters . Firstly, one can separate between mining methods, which mine coal in two directions – meaning from the head to the tailgate and on the return run as well – or in one direction only. Secondly, the way the mining sequence deals with the situation at the face ends, to advance face line after extract-ing the equivalent of a cutting web, is a characteristic parameter for each separate method. The nec-essary travel distance while sumping varies between the sequences, as does the time needed to per-form this task, too. Another aspect defining the sequences is the proportion of the web cutting coal per run. Whereas traditionally the full web was used, the introduction of modern AFC and roof sup-port automation control systems allows for efficient operations using half web methods. The forth parameter identifying state of the art shearer loader cutting sequences is the opening created per run. Other than the partial or half-opening method like those used in Matla’s “Opti-Cycle”, the cutting height is equal to the complete seam height including partings and soft hanging or footwall material.
Bi-directional cutting sequence
The bi-directional cutting sequence, depicted in Figure 1a, is characterised by two sumping opera-tions at the face ends in a complete cycle, which is accomplished during both the forward and return trip. The whole longwall face advances each complete cycle at the equivalent of two web distances by the completion of each cycle. The leading drum of the shearer cuts the upper part of the seam while the rear drum cuts the bottom coal and cleans the floor coal. The main disadvantages of this cutting method are thought to be the unproductive time resulting from the face end activities and the complex operation. Therefore, the trend in recent years was to increase face length to reduce the relative impact of sumping in favour of longer production time.
Uni-directional cutting sequence
In contrast to the bi-directional method, the shearer loader cuts the coal in one single direction when in uni-directional mode. On the return trip, the floor coal is loaded and the floor itself cleaned. The shearer haulage speeds on the return trips are restricted only by the operators’ movement through the longwall face, or the haulage motors in a fully automated operation. The sumping procedure starts in near the head gate, as shown in Figure 1b. The low machine utilisation because of cutting just one web per cycle is the main disadvantage of the uni-directional cutting sequence. Besides the coal flow can be quite irregular depending on the position of the shearer in the cycle.
Half web cutting sequence
The main benefit of half web cutting sequences is the reduction of unproductive times in the mining cycle, which results in high machine utilisation. This is achieved by cutting only a half web in mid face with bi-directional gate sequences as shown in Figure 2a. The full web is mined at the face ends, with lower speeds allowing faster shearer operation in both directions in mid seam. Beside the realisation of higher haulage speeds, the coal flow on the AFC is more balanced for shearer loader trips in both directions.
Half-/partial-opening cutting sequence
The advantage of the half- or, more precisely, partial- opening cutting sequence is the fact that the face is extracted in two passes. Figure 2b shows that the upper and middle part of the seam is cut during the pass towards the tailgate. Whereas the last part of this trip for the equivalent of a ma-chine length the leading drum is raised to cut the roof to allow the roof support to be advanced. On the return trip the bottom coal is mined with the advantage of a free face and a smaller proportion of the leading drum cutting coal; consequently leading to less restrictions of the haulage speed due to the specific cutting energy of the material. The shearer sumps in mid seam near the head gate to the full web without invoking unproductive cycle time. Like for the trip the tailgate the leading drum has to be lowered a machine length ahead of the main gate.
4 Production capacity calculations
A theoretical comparison of the productivity between different mining methods in general, or in this case between different shearer loader cutting cycles, is always based on numerous assumptions and technical and geological restrictions. As a result, this production capacity calculation does not claim to offer exact results, although it does indicate productivity trends and certain parameters for each analysed method.
The model works with so-called height classes varying the seam thicknesses between 2m and 5m in steps of 50cm. Equipment is assigned to each class, having been selected by looking at the best-suited technical properties available on the market [4]. Apart from the defined equipment, it is assumed that the seam is flat and no undulations or geological faults occur. In the model, the ventilation and the roof support system represent no restrictions to the production. Since the aim of this model is to show ways to further increases in longwall productivity, the calculation is based on a fully automated system with no manual operators required at the face. The haulage speed of the shearer is therefore only restricted by the AFC capacity, the cutting motors and the haulage motors respectively.
The variable parameters in this comparison of the four cutting sequences are, (besides seam thick-ness) the specific cutting energy of the coal to be cut and the length of the longwall face. The former varying between 0.2 and 0.4kWh/m³, the latter between 100m and 400m in 50m intervals. The 100m shortwalls were deliberately selected, since they are coming more into focus for various reasons. Geotechnical aspects, like e.g. the caving ability of the hanging wall and faults, restrict long-wall panels in many places to maximum face lengths of 150m or less, like in South Africa and Great Britain. For this reason, a detailed analysis of the potential of such longwalls is deemed appropriate.
5 Conclusions
In recent years much effort has been put into the optimisation of longwall operations to increase productivity and efficiency. In many cases the emphasis of these improvements was mainly focused on the equipment, e.g. increased motor power or larger dimensions of AFC’s. The organisational aspect has sometimes been neglected or did not rank as high on the agenda as other topics. In this paper, it has been demonstrated that the selected mining method has a significant impact on the achievable productivity.
In a theoretical model four cutting sequences have been compared to each other while varying seam thickness, face length and coal properties in terms of specific cutting energy.
For each seam or height class a defined set of equipment was used with consistent restraints. Though each mine is unique, some general conclusions can be drawn analysing the capacity model. Under the restrictions of the model the half web cutting sequence offers the highest output of all analysed methods fol-lowed by the half-opening mode. Depending on the face length, the bi-directional cutting method has advantages compared to the uni-directional sequence in terms of higher productivity.
中文译文
高效生产 — 一个关于采煤机截割的次序的问题
1 摘要
目前, 地面下长壁采煤法致力于增加安装在采煤机和甲板输送机的电机功率, 以及更先进的支架控制系统和增加工作面长度,以达到减少费用和取得较高的生产效率的目的。这种努力已经造成较高的开支和先前未见过的设备费用增长速度。现在趋向于 "更大和更好" 的仪器和装备，然而这种趋势在技术上和费用上的可行性已经达到极限。为了要实现进一步促进生产力的增加，合理、有机地规范长臂采煤法的工序应该是解决提高生产效率问题的唯一的合理答案。在本文中论述了通过合理安排采煤机的截割次序以实现提高采煤工作效率。
2 简介
传统上，在地面下长壁采煤法操作方面，采煤机挖掘过程中，使用以下截割次序之一:反方向的或双方向的循环。除了这两种主要的方法，交替循环采煤也已经应用在地下的硬煤层开采中，它被成功地推广在全世界的挖掘过程中。就半边切断循环举例来说，在科罗拉多,美国在二十里煤矿利用，而且 Matla's 的南非短巷道操作的开采也在这被应用。 其他类似的采掘已经通过验证改进截割次序能提高开采产量,举例来说，它大约能够在产量上增加40%的。
然而提到应用在采煤上根据特殊情况而改变切割的方法,–用煤层高度和设备的使用来举例说明,论文系统地论述通过从不同的角度采取不同的方法。详细描述了采矿的每种切割方法, 包括能生产的和不能生产的循环,以下将会给出一个简短的关于采煤机生产能力的计算和每个系统在技术上的受到的约束的概要说明。根据煤层的厚度采用不同标准的设备和合适的装置 。此外采煤机和甲板输送机，工作面的长度和特定采煤机截割方式等技术参数在本模型中根据不同的煤层厚度而改变。
根据采煤的产量，不同采煤机截割的方法可以通过一个标准化方法绘制产量图来反映不同截割方法的优劣。 根据模型的特征,最优的结果 ( 通过改变截割方式而得到的不同的采煤产量)就能获得。
3 采煤截割次序的技术说明
"为什么长壁采煤法应用的不同切割次序?"这个问题是必须回答的,在以讨论操作工序的主要规则之前，切割方法主要受到煤层的厚度和煤层硬度等因素的限制，就像煤层的物理参数和矿的地质学条件影响煤的崩落能力一样，同样也会影响长壁采煤法工作面的煤层塌方。对于不同的地质条件，不同的截割次序都会得到不同的生产效率和不同质量的工作面。 煤送入甲板输送机之上正如采煤机截割，是采煤中的另外一个问题,尤其是在截齿上受到的屈服应力和疲劳应力。 一个对于选择最适合的截割次序的全面分析是必要的-适合采矿替换;因为，一般性的解答是不能保证最佳的效率和产量。
对于一个采煤机截割次序的分类是通过四个主要的参数来规定的.第一，能在采矿方法之间分开,向矿井的两个方向即从头到尾。第二，根据截割次序，在到达工作面尾部, 预先在选取一个等价的线切断网,是区分截割方法的一个独立的参数。必须有一定的距离空间以改变截割次序, 因为做这些需要一定的时间。 定义截割次序的另外一个方面是网状断煤的轨迹。 然而传统地完整的使用, 现代的甲板输送机和液压支架系统允许使用有效率的一半网方法操作。区分截割工艺的以前那些参数就可以把不同的截割方式区分。除了部份或半开口像被用在Matla的循环截割中的那些一样的方法,切断高度分别包括柔软悬吊装置和采煤机的高度，它和煤层厚度相等。
双方向的截割次序
在图1中被描述的双方向的截割次序, 是表示工作面二点之间的特点，在一个完全的截割操作周期中, 是在两者的向前和返回期间是完成的。整个长壁采煤法每个周期的完成等价于在网状截割轨迹的一个巡回。滚筒的前端面截割煤层的顶部而滚筒的后端面截割煤层的下部，同时起到清除落煤的作用。这个切割的方法主要的缺点主要表现在截割时间和操作比较复杂。 因此，趋势近几年来要增加工作面的长度以减少挖掘过程中的冲击载荷和延长截齿的寿命。
单方向的截割次序
与双方向的方法相反,在单向模型里截割采煤机截割是朝一个方向进行的。 在回返行程中，地板煤是被采煤机底板它本身清理。截割运动在往返时被在工作面限制了操作运动推进的速度。截割操作在工作面的开头部位,如图1 b所示。因为切割动作只能是一个方向循环而使截割的工作效率低，它是单向截割次序的主要缺点。此外煤流可能是相当不规则，它依赖于采煤机在截割周期中的位置。
半滚筒截割次序
半滚筒截割的主要优点是它减少采煤机在截割过程中的无效截割时间,造成高机器利用。如图 2 所显示的半滚筒截割次序处于工作面中间位置时，它与双方向截割次序具有一致性。完整的滚筒在截割结束时,藉由更快速地允许的较低速度在煤层的中间部位向两个方向操作。除了实现较高的牵引速度，在甲板输送机被的采煤机双向循环的煤流而平衡。
半开口切割次序
这种方法的优点更突出，它实际上是在二个方法中的提高和改进。如图2 b所示煤层的上端面和中间部分在向它的后端面时被截割。在回程底部的煤与自由的面和工作面的较小比例的来切断煤层来一起截割；结果其牵引速度由于受到材料的切割能特性而限制。滚筒截割在煤层的中间部位不会产生无效的截割时间。类似的回程后门工作面必须在进入主工作面之前减小机身长度。
4 生产力计算
不同的采矿方法之间的生产力在理论上的做一个大体的比较, 因为在这情况通过在不同的之间采煤机的截割周期,总是存在很多假定和技术上的以及地质学的限制为基础。因而，不能提供精确的结果,但是它为每个截割方法的分析确实提供了生产力的高低趋势和某些参数。
该模型实用于煤层厚度在2 m 和 5 m 之间以50cm为一个等级的被称之为厚煤层的煤矿类型,根据不同的等级选择不同的设备，可以在市场上选择最适合该等级开采的设备。除了规范仪器之外，它假设煤层是平坦的且没有波动和地质上的缺陷。在模型中，通风和顶层支持系统不对生产超出限制。 既然这一个模型的目标要实现进一步的增加生产力，该计算是基于在没有人工的操作干预的情况下一个完全自动化的系统操作的工作面。制约牵引速度的唯一因素是甲板输送机,切割电动机和牵引电动机相互独立。
通过比较四种截割次序的可变参数 (除了煤层厚度) 煤截割的能耗和长壁采煤法的工作面的长度被降低。前者在0.2 到0.4，后者在100 m 和 400 m 之间每间隔50 m，因为它们受到多方面的因素影响。 在地理方面, 像举例来说墙壁崩落能力和缺陷,它限制煤层最大工作面长度达到150 m, 像在南非和英国。 因为这一个原因,如此一项详细长壁采煤发的潜在可行性分析被认识合理的。
煤层厚度 采煤机 截割电机 滚筒
直径 SL
清理区 甲板输送机
宽 输送区 电动机
2.0m SL 300 2×480kW 1500mm 0.40 1332mm 0.67 3×800kW
2.5m SL 300 2×480kW 1600mm 0.60 1332mm 0.67 3×800kW
3.0m SL 300/
SL 500 2×480kW
2×750kW 1600mm 0.75 1332mm 0.67 3×800kW
3.5m SL 300 2×750kW 2000mm 0.75 1332mm 0.67 3×1000kW
4.0m SL 300 2×750kW 23mm 1.00 1532mm 0.87 3×1000kW
4.5m SL 300 2×750kW 200mm 1.00 1532mm 0.87 3×1000kW
5.0m SL 300 2×750kW 2700mm 1.00 1532mm 0.87 3×1000kW
5 总结
近几年来，很多工作都是致力于长壁采煤法的最优化以增加到生产力和效率的目的。在许多情况，他们过于强调把重心集中在设备,举例来说 增加甲板输送机的电动机功率和增大其尺寸。而某些积极的方面有时被在不同程度上被忽略，它们没有被提升到一个比较重要的日程。 在论文中，通过选择不同的截割次序的采矿方法在生产力上所取得的成功产生深远影响。
当煤层厚度、工作面长度、煤层的性质以及相关的截割能耗改变时 ,四中截割模式在一个理论上可以进行相互比较。对于每种煤层和其厚度等级的限制而选择响应的设备。虽然每种截割方式不同,但通过分析该模型可以得到一般性的结论。根据模型的约束条件，半滚筒截割的产量最高；在相同的工作面长度的情况下,双方向的截割方法比单方向的截割方法生产率高。
