采煤专业毕业设计外文文献翻译高效生产一个关于采煤机截割的次序的问题.docx

1、采煤专业毕业设计外文文献翻译高效生产 一个关于采煤机截割的次序的问题外文文献翻译英文原文High Productivity A Question of Shearer Loader Cutting Sequences1 AbstractRecently, 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 supp

2、ort 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

3、 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 I

4、ntroductionsTraditionally, 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 ap

5、plied in underground hard coal mines all over the world. The half-web cutting cycle as e.g. utilized in RAG Coal Internationals Twentymile Mine in Colorado, USA, and the “Opti-Cycle” of Matlas South African shortwall operation must be mentioned in this context. Other mines have also tested similar b

6、ut 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

7、 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

8、 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 a

9、nd 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 productivi

10、ty 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 sequencesThe question “Why are di

11、fferent 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

12、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

13、 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 guara

14、ntee 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 dire

15、ction 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 d

16、oes 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

17、 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 Matlas “Opti-Cycle”, the cutting height is equal to the complete seam height including partings and soft ha

18、nging or footwall material. Bi-directional cutting sequenceThe 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 eac

19、h 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 unproductiv

20、e 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 sequenceIn contrast to the bi-directional method, the shearer

21、 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 fu

22、lly 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 po

23、sition 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 sequence

24、s 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-op

25、ening cutting sequenceThe 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

26、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

27、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 c

28、apacity calculationsA 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 calc

29、ulation 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 bee

30、n 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 pro

31、duction. 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 motor

32、s 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/m, the latter between 100m a

33、nd 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.