1、 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 armored face c
2、onveyors (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, ho
3、wever, is rapidly nearing the limitations of technical and economical feasibility. To realize further productivity increases, organizational changes of longwall mining procedures looks like the only reasonable answer. The benefits of opti-mised shearer sequences, leading to better performance, are d
4、iscussed 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 d
5、eveloped and successfully applied in underground hard coal mines all over the world. The half-web cutting cycle as e.g. utilized in RAG Coal Internationals Twenty mile Mine in Colorado, USA, and the “Opti-Cycle” of Matlas South African shortwall operation must be mentioned in this context. Other min
6、es have also tested similar but modified cutting cycles resulting in improved output, e.g. improvements in terms of productivity 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 he
7、ight or equipment used, this paper looks systematically at the differ-ent methods from a generalized point of view. A detailed description of the mining cycle for each cutting technique, including the illustrations of productivitve and non-productive cycle times, will be followed by a brief presenta
8、tion 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 suitalble and most productive mining equipment for each class are selected .Besides the technical pa
9、rameters 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 standa
10、rtdised way showing the productivity of each method. Due to the general character of the model potential optimizations (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
11、sequences The question “Why are different cutting sequences applied in longwall mining?” has to be answered , 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 hardne
12、ss 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 producti
13、on 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 ； therefo
14、re, general solutions do not guarantee optimal efficiency and productivity . A categorization of shearer loader cutting sequences is realized 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
15、 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 extracting the equivalent of a cutting web, is a characteristic parameter for each separate method. The necessary travel distance while sumping va
16、ries 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 so modern AFC and roof support automation control systems allows for
17、 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 Matlas “Opti-Cycle”, the cutting height is equal to the complete seam heigh
18、t including parting s and soft hanging or footwall material. Bi-directional cutting sequence The bi-directional cutting sequence, is characterized by two sumping operations at the face ends in a complete cycle, which is accomplished during both the forward and return trip. The whole longwall face ad
19、vances 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 u
20、nproductive 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,
21、 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 mo
22、tors in a fully automated operation. The sumping procedure starts in near the head gate .The low machine utilization 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 t
23、he 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 utilization. This is achieved by cutting only a half web in mid face with bi-directional gate sequences. The ful
24、l web is mined at the face ends, with lower speeds allowing faster shearer operation in both directions in mid seam. Beside the realization 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 advan
25、tage 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 machine length
26、 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 sp
27、ecific 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 theoretic
28、al 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 off
29、er exact results, although it does indicate productivity trends and certain parameters for each analyzed 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
30、best-suited technical properties available on the market. 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
31、 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 that AFC capacity ,the cutting motors and the haulage motors res
32、pectively. The variable parameters in this comparison of the four cutting sequences are ,the specific cutting energy of the coal to be cut and the length of the longwall face . The former varying between 0.2 and 0.4 3/kW m , the latter between 100m and 400m in 50m intervals. The 100m shortwalls were
33、 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.
