Patent Application
20160024922
The present disclosure relates to a method and device for ensuring working conditions, and more particularly to a method and device for ensuring working conditions along a longwall face in an underground mine.
A known problem in longwall mining of coal seams is gas emission of methane gas. That methane gas emission results from both natural outflow and generation during the coal winning process. Capillary bound methane gas is released from the coal as the extraction machine cuts along the coal seam. That released methane gas bears the risk of methane gas explosions.
Generally, ventilation of the mine allows maintaining gas concentrations at an acceptable level. For example, ventilation provides air from an air inlet side, guides the same along the longwall, and releases the same at an outlet side, thereby taking with it any released methane gas.
Nevertheless safety regulations require measuring the methane gas concentration constantly in underground mining. If a measured methane gas concentration reaches a critical value, the entire longwall mine including, for example, extraction machine, shield supports and haulage systems is stopped until the methane gas concentration undercuts a statutory level. Those stops and even more the following boot-up procedure of the longwall mine are responsible for a majority of operation stops and failures in winning processes having increased methane gas emissions as it is typically the case in longwall mining of thin coal seams.
For a longwall mine, DE 10 2007 014 662 A1 discloses a gas measurement arrangement with a plurality of gas sensors. In case a calculated extraction rate of the extraction machine does not correlate with a measured gas concentration, a warning signal is provided.
The present disclosure is directed, at least in part, to improving or overcoming one or more aspects of prior systems.
According to a first aspect of the present disclosure, a longwall installation unit configured to form a longwall installation assembly together with a plurality of longwall installation units of the same kind to extend along the longwall face in a longwall mine having a compressor device is disclosed. The longwall installation unit may comprise a dilution gas nozzle installed in the longwall installation unit and configured to be fluidly connected to the compressor device.
According to another aspect of the present disclosure, a method for ensuring working conditions along a longwall face in an underground mine comprises providing a mine ventilation, and in addition to the mine ventilation, providing a dilution gas to the longwall face from at least one of a plurality of dilution gas supply units arranged at spatially separated positions along the longwall face.
Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings.
The following is a detailed description of exemplary embodiments of the present disclosure. The exemplary embodiments described therein and illustrated in the drawings are intended to teach the principles of the present disclosure, enabling those of ordinary skill in the art to implement and use the present disclosure in many different environments and for many different applications. Therefore, the exemplary embodiments are not intended to be, and should not be considered as, a limiting description of the scope of patent protection. Rather, the scope of patent protection shall be defined by the appended claims.
The present disclosure is based in part on the realization that conventional ventilation systems in longwall mining may be not sufficient to dilute released methane gas, and direct the same away from the longwall face. For example, if mining thin coal seams, small cross section areas limit ventilation flows as working conditions for man and machine decrease if ventilation is increased. This may in particular be the case if local methane gas concentrations are temporarily and locally increased.
Longwall installation units as disclosed herein may be capable to specifically provide dilution gas to desired regions of the longwall face, thereby specifically diluting measured methane gas concentration peaks and ensuring acceptable working conditions for man and machine.
An exemplary longwall mine 1 is shown in
In operation, extraction machine 10 cuts along longwall face 2 in a reciprocating manner to extract coal 3. For example, extraction machine 10 may be a shearer or a plow. Material mined by extraction machine 10 drops onto face conveyor 4 that transports the extracted pieces of rock and minerals to a main roadway 12 (also referred to as drift). There, the extracted pieces are passed to a pass-over conveyor or roadway conveyor 14. The transported pieces may be crushed and further transported via, for example, a belt conveyor.
Face conveyor 4 is arranged along longwall face 2 and comprises a plurality of face conveyor segments 5. Neighboring face conveyor segments 5 are connected to one another, for example, so as to resist separation when a tensile force is applied and so as to restrict relative angular movement. For example, face conveyor segments 5 are arranged in a row between two stations, which respectively accommodate sprockets and use the sprockets to redirect a conveyor chain of face conveyor 4.
To maintain longwall face 2 accessible, a shield support assembly 17 is arranged along longwall face 2. Shield support assembly 17 comprises a plurality of shield supports 16 arranged along longwall face 2. At each shield support 16, a moving device (not shown) is supported, which can consist of in each case one pushing or walking bar, which can be loaded hydraulically in both directions in order to push face conveyor 4 optionally and section by section in the work direction (arrow A) or pull up individual shield supports 16 in the work direction. Longwall face 2 is further kept open by shield caps forming an upper unit of each shield support 16. Surrounding rock can only break in and form the so-called old workings after advancing of shield supports 16.
Longwall mine 1 is equipped with a plurality of dilution gas supply units 20 connected via control connection line 22 (indicated by a dashed dotted line in
Each dilution gas supply unit 20 comprises a dilution gas nozzle 30. A dilution gas valve 28 may be fluidly interconnected between dilution gas source 27 and dilution gas nozzle 30. Each dilution gas valve may be associated with dilution gas supply unit 20 or may be installed within dilution gas line 26. As exemplarily shown in
Dilution gas valve 28 is, for example, a shut-off valve configured to either allow or block flow of dilution gas from dilution gas line 26 to dilution gas nozzle 30. Alternatively, dilution gas valve 28 may be a control valve configured to control the amount of said dilution gas flow there through.
Control unit 24 provides signals causing dilution gas valve 28 to adopt its state via control connection line 22. Control unit 24 may be a single microprocessor or plural microprocessors that may includes means for controlling, among others, an operation of the various components of longwall mine 1. Control unit 24 may include all the components required to run an application such as, for example, a memory, a secondary storage device, and a processor such as a central processing unit or any other means known in the art for controlling longwall mine 1 and its various components. Various other known circuits may be associated with control unit 24, including power supply circuitry, signal-conditioning circuitry, communication circuitry, and other appropriate circuitry. Control unit 24 may analyze and compare received and stored data, and, based on instructions and data stored in memory or input by a user, determine whether action is required. For example, control unit 24 may compare received values with target values or preset threshold values and trends stored in memory, and based on the results of the comparison, control unit 24 may transmit signals to one or more components to alter the operation status thereof.
Control unit 24 may include any memory device known in the art for storing data relating to operation of longwall mine 1 and its components. The data may be stored in the form of one or more maps that describe and/or relate, for example, valve opening timing. Each of the maps may be in the form of tables, graphs, and/or equations, and include a compilation of data collected from lab and/or field operation of longwall mine 1. The maps may be generated by performing instrumented tests on the operation of longwall mine 1 under various operating conditions while varying parameters associated therewith. Control unit 24 may reference these maps and control operation of one component in response to the desired operation of another component.
As used herein, the term “connected” used in connection with the control unit refers to the presence of a control connection line and the ability of the control unit to control operation of a connected component, and/or receive control signals or measured values from a connected component.
Dilution gas source 27 may be arranged at any place of the underground mine and/or the surface and may be connected to control unit 24. Usually, dilution gas source 27 is substantially free of methane gas. To provide a dilution gas to dilution gas line 26 with a pressure above ambient pressure, dilution gas source 27 may be, for example, a compressor device. Dilution gas source 27 may provide air drawn from the surface and/or well-ventilated regions of the underground mine such as roadway 12.
In the shown configuration of
The present disclosure is not limited to embodiments, in which solely shield supports 16 are equipped with dilution gas nozzles 30. Generally, any longwall installation unit, such as face conveyor segments 5 or shield supports 16, configured to form a longwall installation assembly, such as face conveyor 4 or shield support assembly 17, together with a plurality of longwall installation units 5, 16 of the same kind to extend along longwall face 2 in a longwall mine 1 may comprise dilution gas nozzle 30. Dilution gas nozzle 30 may be installed in longwall installation unit 5, 16 and configured to be fluidly connected to compressor device 27. It is noted that dilution gas supply related features described in connection with shield support 16 or face conveyor segment 5 may be also applicable to other longwall installation units. Face conveyor segment 5 and shield support 16 are only exemplary embodiments of longwall installation units.
In some embodiments, each longwall installation unit 5, 16 may comprise one or more respective dilution gas nozzles 30, in other embodiments every second to every fifteenth longwall installation unit 5, 16 may comprise one or more dilution gas nozzles 30. In other words, of the plurality of longwall installation units 5, 16, at least a sub-group of the plurality longwall installation units 5, 16 may have a dilution gas nozzle 30.
Although shown in
Referring again to
As each methane gas sensor 32 is connected via control connection line 22 to control unit 24, signals indicating a methane gas concentration at a respective methane gas sensor 32 can be provided to control unit 24 in form of signals. For example, methane gas sensors 32 may be arranged along longwall face 2 such that neighboring methane gas sensors 32 are spaced from one another within a range from 5 m to 50 m, such as within a range from 10 m to 30 m.
Each methane gas sensor 32 may have a minimum distance to a neighboring dilution gas nozzle 30. Said minimum distance may be set to ensure that a methane gas sensor does not directly come into contact with dilution gas at the moment in which the same is supplied by respective dilution gas supply unit 20 such that measurements of methane gas sensors 32 may be not falsified as those would not longer be representative for the respective region. A minimum distance as used herein refers to a combination of distances along each spatial axis, which at least ensures a reduction of the effect of a “short-circuit” between a dilution gas nozzle and a methane gas sensor. For example, a minimum distance in direction of longwall face 2 between neighboring methane gas sensor 32 and dilution gas nozzle 30 may be at least 1 m, and/or a distance between a methane gas sensor 32 and longwall face 2 in direction of working direction A may be greater than a distance between a neighboring dilution gas nozzle 30 and longwall face 2 in direction of working direction A.
A user input device 34 and a display device 36 are arranged, for example, in a displaceable manner, at an accessible location of longwall mine 1. User input device 34 and display device 36 are connected via respective connection lines 38, 40 to control unit 24.
Using user input device 34 and optionally display device 36, a miner can control operation of longwall mine 1 including, but not limited to, cutting depth, cutting speed, advancing speed, conveyor speed, and/or dilution gas supply. To enable user inputs, user input device 34 is configured to receive the same, for example, via a keyboard or a touch panel. Display device 36 is configured to visualize information received from control unit 24.
A ventilation system of the mine provides air through roadways 12 and along longwall face 2 as indicated by direction arrows V. The ventilation system may be set up such the mine ventilation can be adapted generally by control unit 24.
Shield support 16 comprises skids 42, hydraulic cylinders 44, a shield cap 46, and a gob shield 50 and is equipped with a dilution gas nozzle 30.
Shield support 16 has two mutually adjacent skids 42, which in underground mining are also referred to as floor skids, since they rest on the rock soil forming the floor of a face. On each floor skid 42, a multitelescopic strong hydraulic cylinder 44 (in underground mining also referred to as a hydraulic prop) is supported. The cylinder head of hydraulic cylinder 44 presses from below against a shield cap 46. Shield cap 46, which is in underground mining also referred to as a roof cap, presses against the rock which forms the ceiling of the face, the so-called roof.
The distance between floor skids 42 and shield cap 46 can be adjusted by retraction or extension of hydraulic cylinders 44. A link mechanism 48 ensures by means of a gob shield 50, as well as by means of a corner cylinder 52, that floor skids 42 and shield cap 46, in each state of extension of hydraulic cylinders 44, stand substantially plane-parallel to each other. Link mechanism 48 is exemplary configured as a lemniscate link mechanism. Link mechanism 48 has a front link 54 and a rear link 56, both being supported at a distance apart against two bolt receptacles 58 and 60 as well as against floor skid 42.
Bolt receptacles 58, 60 are respectively configured on a side plate 62 of gob shield 50, and shield cap 46 is connected to gob shield 50 in an articulated manner by a hinge bolt. Corner cylinder 52, which is attached by its one end to a supporting bracket on gob shield 50 and with its other end against shield cap 46, serves for the additional bracing of the articulated connection between gob shield 50 and shield cap 46 and can be hydraulically loaded or unloaded as desired. Additionally, a shield canopy 64 may be connected to shield cap 46 in an articulated manner.
As mentioned above, dilution gas nozzle 30 may be installed in shield support 16. In the configuration of
In the configuration shown in
Face conveyor segment 5 may further comprise a material transport strand 68 and a return travel strand 70. In the shown configuration, the material transport strand 68 is arranged above the return travel strand 70. Both strands 68, 70 are configured to guide an endless conveyor with transport carriers (not shown). In other embodiments, both strands 68, 70 may be arranged side by side.
In some embodiments, dilution gas nozzle 30′ may be mounted at or integrated into spill plate 66, for example, mounted at or integrated into a top section of spill plate 66.
As already described in connection with
In some embodiments, dilution gas nozzle 30, 30′ may comprise a mounting mechanism that is configured for retrofitting dilution gas nozzle 30, 30′ to shield support 16 and/or face conveyor segment 5. Existing shield supports and/or face conveyor segments can be equipped with dilution gas nozzle 30, 30′. It will be appreciated by those having skill in the art that exemplary disclosed shield support 16 is of a specific type as described above, however, any known shield support type may be equipped with dilution gas supply nozzle 30.
Dilution gas nozzle 30, 30′ may be installed at shield support 16 and/or face conveyor segment 5 in an adjustable manner facilitating adjustment of the direction in which a nozzle outlet of dilution gas nozzle 30 is directed. For example, dilution gas nozzle 30, 30′ may be pivotally installed at shield support 16 and/or face conveyor segment 5.
Although not shown in
In some embodiments, support 16 and/or face conveyor segment 5 may further comprise a dilution gas valve 28 (not shown in
In some embodiments, a dilution gas line 26 (not shown in
In the following, functionality of dilution gas supply units is described.
During the extraction process, longwall face 2 moves in direction of arrow A (also referred to as working direction and advancing direction) as well as particular components of longwall mine 1 such as shield supports 16, face conveyor 4, and extraction machine 10 work its way into the seam in direction of arrow A.
As coal 3 is extracted from longwall face 2 by extraction machine 10, capillary-bound methane gas may be released from coal 3. However, not only the extraction process itself generates methane gas, but methane gas is also released due to natural outflow.
To dilute methane gas along longwall face 2, mine ventilation (along arrows V in
Control unit 24 may further receive signals from methane gas sensors 32 measuring a methane gas concentration at a plurality of spatially separated regions along longwall face 2 around respective methane gas sensors 32. Control unit 24 may determine a methane gas concentration value for each region, and may determine at least one region for which the methane gas concentration value is greater than a preset threshold value. In addition to mine ventilation, dilution gas from at least one of the plurality of dilution gas nozzles 30 may be provided to those regions for which the methane gas concentration value is greater than the preset threshold value.
For example, methane gas sensor 32 measures a methane gas concentration that is greater than a preset threshold value and provides a respective signal to control unit 24. Control unit 24 than identifies at least one dilution gas supply unit 20 neighboring the respective methane gas sensor 32. Then, that/those dilution gas supply units 20 determined by control unit 24 is/are caused to provide dilution gas via dilution gas supply nozzle 30. To facilitate flow of dilution gas, control unit 24 may provide a control signal to the respective dilution gas valve(s) 28. In other words, each dilution gas supply unit 20 is associated with at least one methane gas sensor 32, and control unit 24 is configured to control dilution gas valve 28 of each dilution gas supply unit 20 based on a signal received from associated methane gas sensor 32. Association between methane gas sensor 32 and dilution gas valve 28 may be based on a minimum distance between both.
For example, the dilution gas may be ambient air drawn from the surface, and/or methane gas-free regions of the underground. In the activated state of dilution gas supply units 20, dilution gas source 27 may ensure presence of dilution gas in a pressurised state in dilution gas line 26, for example, in a pressure range between 5 bar and 6 bar.
Supply of dilution gas may be stopped if a methane gas concentration of the respective region, which is measured by a respective methane gas sensor 32, returns to a value that is lower than a preset safety concentration threshold value.
In some embodiments, in addition to mine ventilation along arrows V, dilution gas from at least one of the plurality of dilution gas supply units 20 may be provided before, to, and/or behind the cutting region relative to a moving direction of a cutting region around reciprocating extraction machine. For example, high methane gas concentrations generated during cutting may be reduced due to preliminary measures (dilution before cutting region), direct measures (dilution of cutting region), and subsequent measures (dilution behind cutting region). Note that, for providing dilution gas from dilution gas supply units 20 before, to, and/or behind the cutting region, no measurements of methane gas concentrations are necessary.
Alternatively or additionally, control unit 24 may react on measured methane gas concentrations in that a cutting speed of extraction machine 10, a cutting depth of extraction machine 10, and/or an advancing speed of shield supports 16, and/or a conveyor speed of face conveyor 4. For example, cutting speed, cutting depth, conveyor speed, and/or advancing speed may be reduced if a methane gas concentration value is greater than a preset threshold value.
In some embodiments, control unit 24 may be configured to control a mine ventilation (for example along arrows V in
As described above, control unit 24 may be further configured to control advancing of shield supports 16, which may facilitate control over the ventilation cross section, which may be defined by the longwall face 2, the roof, shield support 16 and floor. The per se known sequenced advancing of the shield supports 16 may be decelerated or stopped at or before regions where an increased methane gas concentration is measured, which may keep the ventilation cross section at that region as large as possible to vent off methane gas.
Alternatively or additionally, control unit 24 may be connected to face conveyor 4 to control operation thereof. Control of a speed of face conveyor 4 may have the effect that a faster transportation of extracted material on face conveyor 4 may reduce the amount of outflow of capillary-bound methane gas of already extracted material transported on face conveyor 4 adjacent to longwall face 2. Instead, capillary-bound methane gas of already extracted material may then outflow in a considerable amount after pass-over to roadway conveyor 14.
Additionally, dilution gas supply units 20 may be assisted by a water based deduster system (not shown). The water based deduster system may be connected to control unit 24, which may also control operation of the water based deduster system based on signals received from methane gas sensors 32. For example, a plurality of water nozzles may be provided at shield supports 16 along longwall face 2.
In some embodiments, dilution gas nozzle 30 may be integrated into a nozzle unit (not shown) of a shield support, which also comprises a water spray nozzle of the aforementioned water-based deduster system.
Based on a chronological sequence of measured methane gas concentrations in each region by a respective methane gas sensor 32, control unit 24 may be further configured to determine a temporal development of a methane gas concentration at each region. Thereby, control unit 24 may derive a methane gas concentration trend for each region. Control unit 24 may further determine at least one region for which the methane gas concentration trend is greater than a preset threshold trend, and, in addition to mine ventilation, control unit 24 may provide the dilution gas to those regions for which the methane gas concentration trend is greater than the preset threshold trend.
As described above, in some embodiments, dilution gas nozzle 30 may be mounted to or integrated into shield support 16 or face conveyor segment 5 in an adjustable manner such that a direction in which a nozzle outlet of dilution gas nozzle 30 is directed may be adjusted by control unit 24, for example, based on measured methane gas concentrations. For example, nozzle outlet of dilution gas nozzle 30 may be directed to the region where an increased methane gas concentration is measured. Providing dilution gas nozzles 30 in an adjustable manner may further facilitate decreasing overall quantity of dilution gas nozzles 30 along longwall face 2. The reason is that an adjustable dilution gas nozzle 30 may be capable to provide dilution gas to a greater region compared to a dilution gas nozzle 30, which is not adjustable.
In some embodiments, control unit 24 determines a methane gas concentration profile of longwall face 2 based on signals received from the methane gas sensors 32. Based on the determined methane gas concentration profile, a plurality of different operation scenarios of longwall mine 1 may be determined by control unit 24. Those operation scenarios may relate to at least one of variation of cutting speed, cutting depth, conveyor speed, dilution gas supply, ventilation, and advancing speed. For example, in the case one methane gas sensor 32 may measure an increasing methane gas concentration, a first operation scenario may include a reduced cutting speed, a second operation scenario may include a reduced cutting depth, a third operation scenario may include activation of at least one neighboring dilution gas supply unit 20, and a third operation scenario may be a combination of the first, second and third operation scenario. Those operation scenarios may be output from control unit 24 to display device 36. There, the different operation scenarios may be presented to a user. The user may choose one of the proposed operation scenarios via user input device 34. Based on the user chosen operation scenario, control unit 24 then may control longwall mine 1.
A plurality of preset dilution gas supply programs may be stored in control unit 24. Examples of dilution gas supply programs may be a dilution gas curtain, sequential spraying, and hot spot spraying. Dilution gas curtain may refer to a program, in which at least two neighboring dilution gas units 20 may be caused to supply dilution gas. Sequential spraying may refer to a program, in which at least two neighboring dilution gas units are activated sequentially, and hot spot spraying may refer to a program, in which at least one dilution gas unit is caused to supply dilution gas. For example, based on measured methane gas concentrations measured by methane gas sensors 32, control unit 24 may determine one of the plurality of preset dilution gas supply programs, and may control dilution gas supply units 20 based on the determined dilution gas supply program. Alternatively, control unit 24 may determine a dilution gas supply program in accordance with a user input.
Contrary to a conventional mine ventilation, dilution gas supply units 20 are specifically designed to allow providing dilution gas to methane gas concentration peak regions for diluting methane gas. Moreover, dilution gas supply units 20 and mine ventilation may work hand in hand by increasing the effects of each other. For example, diluted methane gas diluted by dilution gas supply units 20 may be vented away from longwall face 2 by mine ventilation (along arrows V in
Methane gas concentration peaks may move (flow) along longwall face 2 in direction of mine ventilation V (along arrow V in
Accordingly, methane gas concentration peaks are considerably reduced, which may increase operational hours of longwall mine 1 as well as productivity and safety while ensuring working conditions for man and machine as dilution gas is only supplied to specific predetermined regions.
According to another aspect, a dilution gas supply unit 20 is configured for use in a longwall mine 1 with a longwall face 2. Dilution gas supply unit 20 comprises a dilution gas line 26, a dilution gas valve 28 installed in dilution gas line 26, and a dilution gas nozzle 30 fluidly connected to dilution gas line 26, and configured to be installed at a position facing longwall face 2.
In some embodiments, the dilution gas nozzle 30 of dilution gas supply unit 20 is configured to provide dilution gas in an adjustable direction and/or amount.
Although the preferred embodiments of this invention have been described herein, improvements and modifications may be incorporated without departing from the scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 13159606.6 | Mar 2013 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2014/000649 | 3/11/2014 | WO | 00 |
