极深条件下的高效长壁采煤外文文献翻译、中英文翻译

英文原文High performance longwall extraction in large depthH.C.WKnissel & H. MischoTechnical University of Clausthal, Institute for Mining, Clausthal-Zellerfeld, GermanyABSTRACT: Stagnation of coal prices to a low level on the international coal trading markets reduces profits and pressured the German hardcoal companies to reduce the mining costs by increasing of the face output and at the same time by reducing the numbers of working points. This concentration could be achieved by the insertion of high performance longwall operations.The success of longwall operations is.dependent upon key points like Geology, equipment and the mine layout. This paper discusses the definition of high performance longwall extraction in large depths and introduces the standard parameters of the equipment and the typical coefficients of these longwall operations as well.Keywords: high performance; longwall; large depth1 INTRODUCTIONThe economic conditions for the German hardcoal mining industry have changed significantly in recent years. The German hardcoal industry had until the early 1990s a secure selling market. The ,Jahrhundertvertrag” guaranteed the purchase of German hardcoal by heavy industry and steel and energy providers. In the last few years the development of the European Union and a sweeping liberalization of the energy markets lead to heavy European and international rivalry. This increasing competition, caused by the import of inexpensive hardcoal from overseas, pressured the German hardcoal industry to react. It was necessary to concentrate the extraction on the most profitable collieries and to excavate only the most suitable parts of the deposits. Until recently it was required to mine the entire deposit. Although the number the mining operations decreased from 147 in 1990 to 64 in 1997 a 56 % decrease, the coal output decreased by only 32 % to 47 mu, tons. This concentration will continue. Additionally, a reduction of the costs of production and an increase in productivity required thedevelopment of new and innovative techniques and face equipment. The goal of these developments is to compensate for the competitive disadvantage due to the great depth of the German hardcoal deposits with the most modern technology and mining methods.Hard coal mining in Germany is based on a century-old tradition. Figure 1 shows the German hardcoal basins.Even 500 years ago only the out-crop of the coal seams was mined. Since the mid-i 9th century, the Industrial Revolution and the resulting need for energy promoted the recovery of the deposits and the extraction in ever-increasing depths. Since 1920 the average mining depth has increased from 330 m to 648 m in 1959 and lies today at 1,006 m (1997). Some longwaU operations have reached depths of around 1,450 m.Figure 1: German hardcoal basinsFigure 2: Sinking of the seam-bearing strata in the Ruhr-area in the northern directionAn additional problem is the increasing coverage of the remaining hardcoal deposits. Figure 2 shows the sinking of the seam-bearing strata in the Ruhr-area in the northern direction.The new working areas and hardcoal mines, which open up the deposits in great depth, are attached without exception to the existing old coal mines. The main problem is to improve these existing mines, originally designed for much smaller working point capacity, to handle high performance longwall operations and to transport the entire conveyance discharge through the old mine to the coal preparation plant.2 HIGH PERFORMANCE LONGWALL OPERATIONSIn Germany the term “high performance longwall operation” is not clearly defined. Usually we describe it as the longwall which extract a net amount of over 16,000 t high quality coal per day. That means 30,000 t run-of-mine coal per day. These operations can be roughly described by the following simple guidelines (1). Net production (effective delivery):Over 16,000 t high quality coal from great depths 1,000m Gross Production (total delivery):Up to 1.6 times the net production, 30,000 t run-of-mine coal/d Face length:Up to 480 m (600 m are planned) Power consumption:Up to 4,500 kW at the longwall Working length:Several kilometers Area increment of face advance:Over 16 m2/min up to 25 m2/min Supporting Performance:At least 1.2 times the area increment of face advance, up to 30 m2/min Productivity in the longwall:Over 200 t v.F.IMS (European record: 452 t v.F./MS in Ensdorf Colliery) Goaf treatment:Roof-fall exploitation Development design:With parallel headings and inclinesIn order to integrate the high performance longwall operations in the existing collieries, it was necessary to carry out adaptation measures. The first measure was to optimize the development design and orientation of the new working areas and attached mines.2.1 Demands on the mine layoutThe great depth, in which the German hardcoal deposits lie, has a large influence on the mine layout. Each roadway must, therefore, be lined with extensive and expensive sliding roadway arch supports regardless if it is a main transport drift or only a short-term parallel gate. The construction costs reach up to DM 15,000 ($US 9,000 ) per meter roadway. Attempts to replace the sliding roadway arch supports with bolted supports or to develop the roadway in a rectangular rather than arch profile, did not achieve all desired results to stabilize the roadway or reduce the development costs.The mine layout connected to the high performance longwall must fulfill the following requirements:- Suitable infrastructure for the efficient transport of material to the longwall Short traveling time for the workers for a long effective working time Fast transport of workers with passenger lifts and belt riding Transport of large cross-sections, for example transport of complete shield units Efficient material transport, maximal 3 h from storage depot over the surface to the longwall- Suitable infrastructure for product extraction: Sufficient dimensional analysis of the belt conveyor If possible, inclines to avoid vertical conveyance If necessary, storage bunkers for homogenization of the conveyance discharge- Adequate ventilation area Control of the climatic conditions, for example formation and mining product temperature, waste heat of the mining machinery Control of the gas emission- Adequate energy supply Electrical energy Compressed air and hydraulics Water for cooling water, consolidation and nozzle reception Cooling capacity and air conditioningSince the above-mentioned requirements were, in many cases, taken into consideration in the planning and development of new fields and connecting mines, they are capable of economical and trouble-free high performance longwall operations today.dust consolidation and nozzle reception Cooling capacity and air conditioningSince the above-mentioned requirements were, in many cases, taken into consideration in the planning and development of new fields and connecting mines, they are capable of economical and trouble-free high performance longwall operations today.2.2 Connection of the high performance longwall to the mining layoutThe layout of the fields and the connection of the longwall operations to the mining layout is intimately associated with the development of the mining layout itself. The following requirements should, therefore, be considered (1):- Development of the connecting mine and the working areas in the coal seam with inclines even in great depth Delivery with belt conveyors: no junctions from horizontal to vertical haulage No junctions from horizontal to vertical haulage in transport and carriage roads- Parallel headings should be directly connected with a main deliveiy or transport road if possible Linear product extraction from the longwall Faster material transport to the longwall, reduction of the transport time Short travelling time, extension of the effective working time Short ventilation circuitsUnder certain circumstances a homogenization of the conveyance discharge may be necessary. In particular for the continuous operation of the small belt conveyors in the old parts of the mines and a continuous preparation in particular, a homogenous conveyance discharge is necessary.2.3 Design of the longwallIn order to operate high performance longwalls under the difficult geologic and climatic conditions prevalent in depths greater than 1,000 meters, aspecial longwall design is needed. These longwalLs are generally cut as retreating faces to the main haulage road. This has the advantage of obtaining information about the seam, for example coal gas content, before starting the excavation.With gas rich longwalls, in particular, a preliminary degassing can be undertaken before the extraction begins. Due to the high overburden pressure at great depths, a significant expenditure is necessary to prepare and maintain the parallel extraction and transport roads. To limit this expenditure the parallel gates are abandoned after passage of the face. There are no coordination problems between the longwall operation and the drifting as well, and there is no additional material handling in the parallel mining heading with building and support material. An additional argument for retreating longwalls is the shortening of the conveyance distance and the constant optimization of the conveyance over the running time of the working panel.Until the early l990s face lengths of only up to 270 m were technically possible and allowed at great depths. Today the new high performance longwalls are designed as double longwall systems with two 350 m face lengths or as single longwalls with up to480 m face lengths. Greater face lengths are not practical at this time because the layout of the face conveyor reaches its limits. At present the length of the face conveyor and the resulting vibrations create significant problems for durability. The maximal possible power consumption of the face conveyor limits the loading rate and, therewith, the total length of the face conveyor length of the escape way exceeds the regulated length. Another significant problem is the air cooling.The maximal seam pitch in the longwall is generally reported to be 40 gon. Steeper deposit sections are not suitable for economically profitable recovery using standing high performance longwall techniques. A gently declining mining direction through the strike has proven to be useful in increasing the stability of the wall and avoiding the flaking of the seam through the tipped coal face.2.4 Safety RegulationsDue to the slow escape speeds in the longwall, a long face increases the duration of a possible escape over the acceptable and allowed limits. In order to confront this problem several measures were implemented. Care was taken when selecting and constructing the individualshield supports in order to attain comfortable and sufficiently wide gangway. In addition it became necessary to equip the face workers with the most modern filter self-rescuers. These filter self-rescuers guarantee lower inhalation resistance at significantly reduced temperatures of the breathable air (65C). The organization of the escape routes was also reorganized. Medical examinations show that regular short pauses regulated by specially-trained escape leaders strongly reduce the physical burden of the individual miner during the escape without significantly increasing the escape time. Moreover, it may be necessary to employ selected, physically fit miners at steep faces. When calculating the length of the escape ways, according to the German hardcoal mining regulations, only the speed traveled by foot is taken into account. Passenger lifts, which would increase the escape speed and would usually be used, are not included in the calculation (2).The introduction of high performance longwall operations and the planning of overly long faces also creates new problems for explosion protection. The German hardcoal mining industry requires the erection of explosion water barriers with 200 1 water/rn2 roadway cross-section at 400 m intervals to extinguish the beginnings of methane gas explosions. These requirements are clearly exceeded by the introduced great face lengths with a distance of up to 120 m from the face end to the nearest barrier. Two different methods to meet the latent danger of a methane explosion were developed. The entrance of fresh air through the lower section of the shield column and the abandoned belt road is drastically reduced by consequent sealing of the gate end using Figure 3：GROUTING side packs and flue dust insertion piping for the prevention of air leakage in the abandoned workingsgrouting side packs and piping of flue dust against this grouting side pack. The goal is to reduce air leakage and to avoid the formation of an explosive gas mixture behind the shield column. Figure 3 shows the arrangement of the grouting side packs and flue dust in the abandoned workings.In order to limit the starting length of a methane explosion, a mobile explosion water barrier (Saar-Ex 2000) was developed. This system is based on the active Tremonia barriers which, sensor-controlled, produce and distribute a fine water mist throughout the roadway cross section before the explosion wave can continue. ThisSaar-Ex 2000 explosion water barrier reduces the distance fromthe face end to the first barrier to a constant 30 m.2.5 New developments of longwall techniquesThe desired high face output could not be achieved using the formerly applied face equipment. It was, therefore, necessary to modernize and, if need be, redevelop the individual components of the face equipment for the demands of a high performance longwall. (I)These demands to achieve a high face output are summarized as follows: High coal output of the longwall machine with a power consumption up to 500 kW per drum Application of point attack bits with a necessary high bit cutting depth of 8-10 cm even by lower drum rotational speeds; this is necessary for an effective reduction of the dust production Effective pie track flushing to avoid Hot-Spots and to consolidate the dust。 Large drum cutting depth, up to 1,000 mm Optimized drum loading capacity by the use of cowls and Globoid-drums High winning speed, speed over 13 mlmin needs a powerful wheel-rackatrack haulage system High technical availabilityThe shearer loaders SL from the company Eickhoff which fulfill the above-mentioned criteria, are most commonly used in German high performance longwall operations. It was then necessary to switch from the previously used I kVtechnology in the longwall, present in most mines, to a 3 or 5 kV power supply. Figure 4 shows a shearer loader SL.The armored flexible face conveyors in the longwall area were equipped to reach high chain speed and manage large loaded cross sections in order to handle the expected increase in tonnage.Much effort has been placed in the face support in order to continue the development of the longwall technique. The newly developed two-leg lemniscate powered face supports are used today without exception with the IFS (immediate forward support). The yield support resistances are suited for the high demands of great depths and amount up to 5,700 kN (yield load density of 600 kN/m2). An additional demand on the shield support was the necessity for high supporting performance of up to 30 m2/min in connection with short cycle times and quick roof support through the use of extensible canopies. The large cutting depth of the drum shearer requires a maximum advance distance for the shearer and the support of 1,200 mm. The operating range of this support should make heights of 1.80 to 4 m possible.In order to optimize the longwall face move, the transport dimensions and weight were limited to make complete transport under ground possible. Within the framework of the new developments in longwall techniques, the system width was increased from the customary spacing of 1.50 m to 1.75 m for the longwall conveyor as well as the shield support. This enlargement of the system width primarily serves the purpose of minimizing the number of possible trouble sources in the longwall.An analysis in the late-eighties and nineties showed that great expenditure was required to control the face-end zone and the belt entry. It was not possible to use the common face suport in the parallel mining roadways due to the lining of the mining parallel headings with TH-sliding roadway arches. Moreover, several meters between the parallel mining roadway and the first shield had to be built up conventionally using single legs and strike beams. Only after the development of the new face end shields and prop drawer shields for the parallel mining roadways was it possible to use high performance longwall technology to support the face end zone and the belt entry with modem powered supports (3).Figure 4: Shearer loader SL from EickhoffTo control the longwall face-end it was necessary to develop new power support systems as seen above. There was, however, no need for new side discharge technology. The direct side discharges used in the Ruhr area and the free side discharges with discharge pan used in the Saar area were able to handle even the great output of high performance longwalls.The DSK (Deutsche Steinkohle AG) has realized the above-mentioned concept in different high performance longwall operations. One of these operations is described below.3 HIGH PERFORMANCE LONGWALL EXTRACTION “LONG WALL 2000” AT THE ENSDORF COLLIERYThe Ensdorf colliery was one of the first to introduce high performance longwall operations to the German hardcoal mining industry in 1995 under the concept “Longwall 2000”. The goal of this trial was to install a longwall system that could guarantee the daily output of