WO2015002556A2 - A method and system for detecting and reducing methane hazard in vicinity of a longwall - Google Patents

A method and system for detecting and reducing methane hazard in vicinity of a longwall Download PDF

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Publication number
WO2015002556A2
WO2015002556A2 PCT/PL2014/000123 PL2014000123W WO2015002556A2 WO 2015002556 A2 WO2015002556 A2 WO 2015002556A2 PL 2014000123 W PL2014000123 W PL 2014000123W WO 2015002556 A2 WO2015002556 A2 WO 2015002556A2
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Prior art keywords
longwall
shearer
methane
stress
concentration
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PCT/PL2014/000123
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French (fr)
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WO2015002556A3 (en
Inventor
Zbigniew ISAKOW
Kazimierz SICIŃSKI
Adam GOŁĄBEK
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Instytut Technik Innowacy Jnych Emag
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Application filed by Instytut Technik Innowacy Jnych Emag filed Critical Instytut Technik Innowacy Jnych Emag
Priority to RU2015101764/03A priority Critical patent/RU2594917C1/en
Priority to CN201480002448.5A priority patent/CN105765407B/en
Priority to UAA201501088A priority patent/UA117660C2/en
Publication of WO2015002556A2 publication Critical patent/WO2015002556A2/en
Publication of WO2015002556A3 publication Critical patent/WO2015002556A3/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
    • G01V1/001—Acoustic presence detection
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
    • E21F17/00—Methods or devices for use in mines or tunnels, not covered elsewhere
    • E21F17/18—Special adaptations of signalling or alarm devices
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/0004—Gaseous mixtures, e.g. polluted air
    • G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
    • G01N33/0062—General constructional details of gas analysers, e.g. portable test equipment concerning the measuring method or the display, e.g. intermittent measurement or digital display
    • G01N33/0063—General constructional details of gas analysers, e.g. portable test equipment concerning the measuring method or the display, e.g. intermittent measurement or digital display using a threshold to release an alarm or displaying means
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B21/00—Alarms responsive to a single specified undesired or abnormal condition and not otherwise provided for
    • G08B21/02—Alarms for ensuring the safety of persons
    • G08B21/10—Alarms for ensuring the safety of persons responsive to calamitous events, e.g. tornados or earthquakes
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B21/00—Alarms responsive to a single specified undesired or abnormal condition and not otherwise provided for
    • G08B21/02—Alarms for ensuring the safety of persons
    • G08B21/12—Alarms for ensuring the safety of persons responsive to undesired emission of substances, e.g. pollution alarms
    • G08B21/16—Combustible gas alarms
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/0004—Gaseous mixtures, e.g. polluted air
    • G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
    • G01N33/0027—General constructional details of gas analysers, e.g. portable test equipment concerning the detector
    • G01N33/0036—General constructional details of gas analysers, e.g. portable test equipment concerning the detector specially adapted to detect a particular component
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V2210/00—Details of seismic processing or analysis
    • G01V2210/10—Aspects of acoustic signal generation or detection
    • G01V2210/12—Signal generation
    • G01V2210/123—Passive source, e.g. microseismics

Definitions

  • the present invention relates to a method and system for detecting and reducing methane hazard in vicinity of a longwall in a coal mine, or in vicinity of several longwalls in the area of coal mining, in conditions of methane and rock burst hazards.
  • Canadian patent application CA2263216 discloses a system for continuous measurement and detection of methane in the mine atmosphere during mining of the body if coal with the shearer mining head.
  • Two methane sensors located on opposite sides of the arm of the mining head within 30 inches from the head are basic measuring elements of the system. Additionally the measuring system is equipped with an air flow sensor, oxygen sensor and carbon monoxide detector, which are connected by wires to the microprocessor controller for recording, detection, monitoring and / or analysis of the information about the mine atmosphere. This information is then displayed on a screen by the shearer operator or in the dispatch room on the mine surface.
  • An advantage of the invention is the measurement of methane in immediate vicinity of the mining head of the shearer.
  • Polish patent application PL388788 (A1 ) discloses a method and apparatus for automatic detection of the rock burst and methane outflow, where more physical phenomena have been correlated: increase in methane concentration, increase in the air pressure, and acoustic phenomena are identified simultaneously. Correlation of changes in these three parameters is a basis for estimation of methane and rocks outburst. This information is sent to the mine control room on the surface.
  • Proposed device consists of a measuring chamber, microprocessor measuring system, power supply and a display connected to the transmission control system, which is connected via a telephone line to the control room on the surface.
  • the measuring chamber is equipped with a methane concentration sensor, air pressure sensor and a microphone.
  • the aim of the invention is to provide a method and a system that increase efficiency of detection and minimize methane explosive conditions in the longwall area in the mine with methane and rock burst hazardous conditions, by taking into account the whole of associated seismic events that have an impact on methane hazard.
  • These are the phenomena identified in both dynamic and static terms, associated with the build-up of stress in the rock mass, which will allow for predicting occurrence of this phenomenon in monitored area taking appropriate pre-emptive action.
  • the regions of stress concentration are periodically localized on the longwall panel length by a passive velocity tomography using seismometers and low- frequency geophones. These data are compared to current seismoacoustic measurements localizing groups of crashes accompanying cracking of the rock mass in the longwall panel length, with measurements of methane concentration and the air flow in the working.
  • the places of stress concentration in front of the longwall are additionally localized with an active attenuation-damping tomography taking into account the shearer position relative to the working. Then, these variables are correlated in time and space, and after finding that the correlation coefficient exceeds predetermined critical value, preventive procedures to minimize methane hazard are initiated.
  • the places of stress concentration are determined with an attenuation-damping tomography by analysis of signals detected by the seismic recording system with low-frequency geophones deployed in advanced galleries. These signals are directly correlated with the shearer location at the longwall through the real-time measurements of energy of vibrations generated by its mining head in one mining cycle, and determined with the low-frequency geophones in the longwall workings. After each cutting cycle these results are compared to the values recorded in previous cycle, and the places of increased stress concentration are identified. The signals from the sensors are sent to the seismic recording system to enable scaling of the stress changes isoline.
  • the air flow is measured at the face end (inlet) and at the face end (outlet) of the longwall workings along with mobile measuring of the air flow directly at current location of the longwall shearer.
  • changes in amplitude of the correlation coefficient and rate of these changes are analyzed.
  • the exact localizations for procedures minimizing methane hazard are determined in the longwall.
  • these procedures comprise preventive drilling for methane removal.
  • a seismic recording system In the system for measuring methane concentration along the longwall, a seismic recording system, a methanometric system, an executive system and a warning module are connected to the microprocessor analytical system.
  • a seismoacoustic recording system with at least four geophones and the shearer location and operation control system with the shearer position detector are connected to the seismic recording system with at least four seismometers, at least four low-frequency geophones and at least two stress sensors.
  • the wall methanometers, the shearer mobile methanometer, two stationary air velocity sensors located at the face end (inlet) and at the face end (outlet) of the longwall workings, and the shearer mobile air speed sensor are connected to the methanometric system.
  • the connections between the analytical system, seismic recording system, methanometric system, executive system, warning module, and between the seismic recording system, seismoacoustic recording system and the shearer location and operation control system are realized with the Ethernet cables.
  • Fig. 1 - shows a block diagram of the measuring system
  • Fig. 2 - shows a diagram of stresses in the area in front of the longwall during the last mining cycle
  • Fig. 3 - shows a diagram of the measurement of methane concentration in the longwall working during the mining cycle
  • Fig. 4 - shows a diagram of the correlation function parameters analyzed in time.
  • the regions of stress N concentrations are periodically localized in the longwall panel length by the passive velocity tomography using four seismometers 8 and four low- frequency geophones 9. Received data are compared with current seismoacoustic measurements localizing groups of crashes M accompanying cracking of the rock mass at the longwall panel length working B, with measurements of methane concentration and air flow in the working.
  • the places of stress N concentration in front of the longwall are localized additionally by the active attenuation-damping tomography taking into account the position of the shearer 13 in the longwall panel length working B.
  • the values of the above-mentioned parameters are compared. After finding causal correlation in time and space and if assumed critical value of correlation coefficient is exceeded, the preventive procedures are performed to minimize methane hazard by methane-removing drilling in the identified areas of the longwall and / or by performing additional ventilation.
  • the analytical system 5 correlates the information obtained from the seismic recording system 1 , seismoacoustic recording system 2 and methanometric system 3, and detects potential hazardous states which are signalized on the warning module 7.
  • the warning signals are generated in case of spatio-temporal coincidence of increase in stress concentration, methane concentration, and activity phenomena in the form of localized concentration of seismic and seismoacoustic activities accompanying cracking of the rock mass. After finding that thresholds of relative increments of stress and methane concentration are exceed, the thresholds of warnings and / or automatic switching-off of electrical equipment in the area of controlled longwall are lowered. Relative changes of recorded increments of parameters associated with measurement of methane concentration, stress N, airflow and seismoacoustic activity are continuously monitored. These changes are analyzed in spatio-temporal correlation taking into account the amplitude of changes of the correlation coefficient ⁇ and speed of these changes ⁇ / ⁇ .
  • the information is transmitted from the analytical system 5 to the methanometric system 3 in order to immediate automatic switching-off of the electrical equipment in vicinity of monitored longwall according to pre-configured control switch-off matrix in the executive system 6.
  • the places of stress N concentration are determined by the active attenuation- damping tomography by analyzing signals recorded by the seismic recording system 1 from the low-frequency geophones 9. This is done on the basis of correlating these signals with the shearer 13 position in the longwall and by real-time measuring of energy of vibrations generated by the mining head of the shearer 1 3 in each cutting cycle X and defined by low-frequency geophones 9 in the galleries A.
  • the strain sensors 10 are mounted and their signal is sent to the seismic recording system 1 .
  • the methanometric system 3 is equipped with the longwall methanometers 14 arranged along the longwall, the shearer mobile methanometer 15, the stationary air speed sensors 16 and the shearer mobile air speed sensor 17, which measures the air velocity along the longwall at current location of the shearer 13 in the workings.
  • Seismic recording system 1 equipped with seismometers 8, low-frequency geophones 9, and seismoacoustic recording system 2 equipped with geophones 1 1 , localizes the seismic phenomena throughout whole mine and precisely in front of controlled longwall.
  • seismoacoustic data Based on results of the passive velocity tomography, seismoacoustic data, and determined localizations of stress N concentration using the active attenuation-damping tomography, and taking into account local changes in methane concentration correlated with these parameters, the localizations in the monitored body of coal C, where the procedures minimizing methane hazard are carried out, preferably by preventive drilling removing the methane, are precisely determined.
  • the system according to the invention consists of cooperating and temporally correlated elements: the seismic recording system 1 , the seismoacoustic recording system 2, the methanometric system 3, and the position and operation control system 4 of the shearer in the longwall.
  • the seismic recording system 1 the methanometric system 3, the executive system 6, and the warning module 7 are connected to the analytical system 5.
  • the systems listed above and those on the surface of the mine D are connected by the Ethernet cables.
  • the seismic recording system 1 situated on the surface of the mine D with attached four seismometers 8, four low-frequency geophones 9 and two strain sensors 10, is connected to the seismoacoustic recording system 2 and to the position and operation control system 4 of the shearer.
  • the shearer position sensor 12 located on the longwall shearer 13 is connected to the position and operation control system 4. Further, to the methanometric system 3 are connected: the longwall methanometers 14, which are located along the longwall workings preferably every 15 m, the mobile shearer methanometer 15 built on the longwall shearer 13 in vicinity of the mining head, two stationary air speed sensors 16 located at the face end (inlet) and at the face end (outlet) of the longwall working B, and the mobile shearer air speed sensor 17 installed in the longwall shearer 13.
  • the operating elements 18 switching off particular devices with electric drives installed in the underground part E of the mine in the region of the monitored longwall are connected to the executive system 6 comprised in the methanometric system 3.

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Abstract

A method of detecting and reducing methane hazard in the longwall area is characterized in that the regions of stress (N) concentration are periodically localized on the longwall panel length by a passive velocity tomography using seismometers (8) and low-frequency geophones (9). These data are compared with current seismoacoustic measurements localizing places (M) of groups of crashes accompanying cracking of the rock mass in the longwall panel length, with measurements of methane concentration and the air flow in the working. The places of stress (N) concentration in front of the longwall are additionally localized with an active attenuation-damping tomography taking into account a shearer (13) position relative to the working (B). Then, these variables are correlated in time and space, and after finding that the correlation coefficient exceeds predetermined critical value, preventive procedures to minimize methane hazard are initiated. In the measurement system the seismic recording system (1), methanometric system (3), executive system (6), and warning module (7) are connected to the microprocessor analytical system (5). The seismic recording system (1) with attached at least four seismometers (8), at least four low-frequency geophones (9) and at least two strain sensors (10), is connected to the seismoacoustic recording system (2) with at least four geophones (11), and to the position and operation control system (4) of the shearer (13) with a shearer position sensor (12).

Description

A Method and system for detecting and reducing methane hazard in vicinity of a longwall
The present invention relates to a method and system for detecting and reducing methane hazard in vicinity of a longwall in a coal mine, or in vicinity of several longwalls in the area of coal mining, in conditions of methane and rock burst hazards.
The state of the art
Various methods, devices and electronic systems for measurement of methane concentration in the air inside the mine, and the monitoring systems, including these for warning of increase in methane concentration above a safe level and for automatic shutdown of electrical equipment in hazardous area to minimize the risk of methane explosion and fire have been proposed. In all of them a sample of air is taken, methane concentration is measured, and the result of this measurement is sent to the mine methanometric system. The result can be transmitted via a local hub which performs a function of the energy switching off in the controlled area, and thereby preventing of sparking which could trigger methane explosion.
Similar solutions of methane hazard problem are proposed by Wasilewski S. in "The systems for control and monitoring of gas hazards in Polish coal mines" (Work Safety and Environmental Protection in Mining, No. 12, 2012), and in numerous patent documents, e.g. US5268683 (A), RU2268365 (C1 ), PL390972 (A1), CN101441803 (A), UA6161 (A), PL386488 (A1 ), PL151847 (B1 ).
Canadian patent application CA2263216 (A1 ) discloses a system for continuous measurement and detection of methane in the mine atmosphere during mining of the body if coal with the shearer mining head. Two methane sensors located on opposite sides of the arm of the mining head within 30 inches from the head are basic measuring elements of the system. Additionally the measuring system is equipped with an air flow sensor, oxygen sensor and carbon monoxide detector, which are connected by wires to the microprocessor controller for recording, detection, monitoring and / or analysis of the information about the mine atmosphere. This information is then displayed on a screen by the shearer operator or in the dispatch room on the mine surface. If methane concentration in the air exceeds acceptable value the power supply of the shearer is switched off and a separate ventilation with fresh air is turned on to decrease concentration of methane in affected area. When methane concentration falls below acceptable level, the electrical power is supplied to the shearer again. An advantage of the invention is the measurement of methane in immediate vicinity of the mining head of the shearer.
Kabiesz J. (ed.) in "Methods of the rock bursts risk assessment in the coal mine workings" (Central Mining Institute in Katowice, pp.165-320, 2010) as well as the patent documents US2014034388 (A1 ), US2014123748 (A1 ), PL152339 (B1 ), PL202149 (B1 ) disclose geophysical methods and systems for measuring and assessing seismic hazard, including a state of the rock burst hazards in the coal mines. Proposed solutions are focused on measuring the signals reflecting the stress and deformation state of the rock mass which may cause rock burst or increase the crump risk in workings or their surroundings as a result of disadvantageous geological and mining conditions.
More complex methods and measuring devices have also been described, taking into account identification and correlation of higher number of physical phenomena for assessment of methane hazard. Polish patent application PL388788 (A1 ) discloses a method and apparatus for automatic detection of the rock burst and methane outflow, where more physical phenomena have been correlated: increase in methane concentration, increase in the air pressure, and acoustic phenomena are identified simultaneously. Correlation of changes in these three parameters is a basis for estimation of methane and rocks outburst. This information is sent to the mine control room on the surface. Proposed device consists of a measuring chamber, microprocessor measuring system, power supply and a display connected to the transmission control system, which is connected via a telephone line to the control room on the surface. The measuring chamber is equipped with a methane concentration sensor, air pressure sensor and a microphone.
Causal correlation of geophysical phenomena and methane outbursts in the mine workings is known in mining. However, these processes are not fully recognized yet, therefore are not technically used for reduction of methane hazards. Trenczek S. & Wojtas P. (Scientific Papers of the Institute of Mining University of Technology, No. 1 17, Studies and Research No. 32/2006, p. 337) focused on identification of risks associated to methane outflows detected immediately after strong rock bursts. These solutions propose to link the seismoacoustic and seismic systems used in the longwall area with the methanometric system. Information about a strong seismic bump near the longwall shall be provided immediately, i.e. with a delay not exceeding 10 seconds, to the methanometric system, which switches off the electrical devices in the area of this longwall.
Discussion of the prior art
Known methods and systems for detection and reduction of methane risks that correlate physical phenomena, and in particular those that identify correlation of seismic phenomena and methane breakouts in mined longwall areas, do not provide satisfactory performance, especially in terms of precise localization of hazardous areas. This is essential for prompt and effective preventive action to minimize these risks. Disclosures in the prior art take into account causal connection of methane outbursts just after seismic events that results from current measurement of methane concentration and the air flow only after dynamic seismic or seismoacoustic phenomena that have been recorded by the mine seismic systems based on the seismometers and low-frequency geophones, and by the seismoacoustic systems using high-frequency geophones. Other known methods and systems for direct measurement of methane concentration in the mine atmosphere, e.g. a method described in Polish patent application PL388788 (A1 ), use for methane risk assessment a higher number of correlated physical phenomena such as measurement of 'methane concentration with the air pressure and the acoustic signal, but these known methods do not provide satisfactory performance. This is because they are used for the power turn- off after strong tremors, including the rock bursts. The hitherto known solutions do not allow for prediction of methane outflow prior to the rock burst, for example due to increased stresses in the rock mass that precede critical event.
The aim of the invention The aim of the invention is to provide a method and a system that increase efficiency of detection and minimize methane explosive conditions in the longwall area in the mine with methane and rock burst hazardous conditions, by taking into account the whole of associated seismic events that have an impact on methane hazard. These are the phenomena identified in both dynamic and static terms, associated with the build-up of stress in the rock mass, which will allow for predicting occurrence of this phenomenon in monitored area taking appropriate pre-emptive action.
Summary of the invention
According to invented method of detecting and reducing methane hazard in the longwall area, the regions of stress concentration are periodically localized on the longwall panel length by a passive velocity tomography using seismometers and low- frequency geophones. These data are compared to current seismoacoustic measurements localizing groups of crashes accompanying cracking of the rock mass in the longwall panel length, with measurements of methane concentration and the air flow in the working. The places of stress concentration in front of the longwall are additionally localized with an active attenuation-damping tomography taking into account the shearer position relative to the working. Then, these variables are correlated in time and space, and after finding that the correlation coefficient exceeds predetermined critical value, preventive procedures to minimize methane hazard are initiated.
The places of stress concentration are determined with an attenuation-damping tomography by analysis of signals detected by the seismic recording system with low-frequency geophones deployed in advanced galleries. These signals are directly correlated with the shearer location at the longwall through the real-time measurements of energy of vibrations generated by its mining head in one mining cycle, and determined with the low-frequency geophones in the longwall workings. After each cutting cycle these results are compared to the values recorded in previous cycle, and the places of increased stress concentration are identified. The signals from the sensors are sent to the seismic recording system to enable scaling of the stress changes isoline.
Simultaneously the air flow is measured at the face end (inlet) and at the face end (outlet) of the longwall workings along with mobile measuring of the air flow directly at current location of the longwall shearer. In the process of correlation of relative changes of registered variables, in particular increments of parameters associated with measurement of methane concentration, stress, air flow, or seismoacoustic activity, changes in amplitude of the correlation coefficient and rate of these changes are analyzed.
Then, based on results obtained from the passive velocity tomography, seismoacoustic observations, and the sites of stress concentration localized with the active attenuation-damping tomography, and taking into account local changes in methane concentration correlated with these parameters, the exact localizations for procedures minimizing methane hazard are determined in the longwall. Preferably these procedures comprise preventive drilling for methane removal. When correlation in time of analyzed parameters is found, in particular if critical thresholds are exceeded by relative increases of stress and methane concentration, the thresholds for warnings and / or for automatic switching-off of the electrical equipment in the area of controlled longwall are reduced.
In the system for measuring methane concentration along the longwall, a seismic recording system, a methanometric system, an executive system and a warning module are connected to the microprocessor analytical system. A seismoacoustic recording system with at least four geophones and the shearer location and operation control system with the shearer position detector are connected to the seismic recording system with at least four seismometers, at least four low-frequency geophones and at least two stress sensors. The wall methanometers, the shearer mobile methanometer, two stationary air velocity sensors located at the face end (inlet) and at the face end (outlet) of the longwall workings, and the shearer mobile air speed sensor are connected to the methanometric system. The connections between the analytical system, seismic recording system, methanometric system, executive system, warning module, and between the seismic recording system, seismoacoustic recording system and the shearer location and operation control system are realized with the Ethernet cables.
Exemplary embodiments of the invention are shown in the drawings where Fig. 1 - shows a block diagram of the measuring system, Fig. 2 - shows a diagram of stresses in the area in front of the longwall during the last mining cycle, Fig. 3 - shows a diagram of the measurement of methane concentration in the longwall working during the mining cycle, Fig. 4 - shows a diagram of the correlation function parameters analyzed in time.
Example I (method)
In the method of detecting and reducing methane hazard in vicinity of the longwall, the regions of stress N concentrations are periodically localized in the longwall panel length by the passive velocity tomography using four seismometers 8 and four low- frequency geophones 9. Received data are compared with current seismoacoustic measurements localizing groups of crashes M accompanying cracking of the rock mass at the longwall panel length working B, with measurements of methane concentration and air flow in the working. The places of stress N concentration in front of the longwall are localized additionally by the active attenuation-damping tomography taking into account the position of the shearer 13 in the longwall panel length working B. In the next step the values of the above-mentioned parameters are compared. After finding causal correlation in time and space and if assumed critical value of correlation coefficient is exceeded, the preventive procedures are performed to minimize methane hazard by methane-removing drilling in the identified areas of the longwall and / or by performing additional ventilation.
The analytical system 5 correlates the information obtained from the seismic recording system 1 , seismoacoustic recording system 2 and methanometric system 3, and detects potential hazardous states which are signalized on the warning module 7. The warning signals are generated in case of spatio-temporal coincidence of increase in stress concentration, methane concentration, and activity phenomena in the form of localized concentration of seismic and seismoacoustic activities accompanying cracking of the rock mass. After finding that thresholds of relative increments of stress and methane concentration are exceed, the thresholds of warnings and / or automatic switching-off of electrical equipment in the area of controlled longwall are lowered. Relative changes of recorded increments of parameters associated with measurement of methane concentration, stress N, airflow and seismoacoustic activity are continuously monitored. These changes are analyzed in spatio-temporal correlation taking into account the amplitude of changes of the correlation coefficient ΔΚ and speed of these changes ΔΚ/Δί.
In case of temporary increase in the correlation coefficient of analyzed parameters and the rate of its increase being above assumed critical value, the information is transmitted from the analytical system 5 to the methanometric system 3 in order to immediate automatic switching-off of the electrical equipment in vicinity of monitored longwall according to pre-configured control switch-off matrix in the executive system 6. The places of stress N concentration are determined by the active attenuation- damping tomography by analyzing signals recorded by the seismic recording system 1 from the low-frequency geophones 9. This is done on the basis of correlating these signals with the shearer 13 position in the longwall and by real-time measuring of energy of vibrations generated by the mining head of the shearer 1 3 in each cutting cycle X and defined by low-frequency geophones 9 in the galleries A.
After each cutting cycle X, these results are compared to the data recorded in previous cutting cycle XM and the places of increased stress concentration are identified. To enable scaling of the baseline of stress changes in the longwall galleries A, the strain sensors 10 are mounted and their signal is sent to the seismic recording system 1 . The methanometric system 3 is equipped with the longwall methanometers 14 arranged along the longwall, the shearer mobile methanometer 15, the stationary air speed sensors 16 and the shearer mobile air speed sensor 17, which measures the air velocity along the longwall at current location of the shearer 13 in the workings.
Seismic recording system 1 equipped with seismometers 8, low-frequency geophones 9, and seismoacoustic recording system 2 equipped with geophones 1 1 , localizes the seismic phenomena throughout whole mine and precisely in front of controlled longwall. Based on results of the passive velocity tomography, seismoacoustic data, and determined localizations of stress N concentration using the active attenuation-damping tomography, and taking into account local changes in methane concentration correlated with these parameters, the localizations in the monitored body of coal C, where the procedures minimizing methane hazard are carried out, preferably by preventive drilling removing the methane, are precisely determined.
Example II (system)
The system according to the invention consists of cooperating and temporally correlated elements: the seismic recording system 1 , the seismoacoustic recording system 2, the methanometric system 3, and the position and operation control system 4 of the shearer in the longwall. In the arrangement according to the invention (Fig. 1) the seismic recording system 1 , the methanometric system 3, the executive system 6, and the warning module 7 are connected to the analytical system 5. The systems listed above and those on the surface of the mine D are connected by the Ethernet cables. The seismic recording system 1 situated on the surface of the mine D with attached four seismometers 8, four low-frequency geophones 9 and two strain sensors 10, is connected to the seismoacoustic recording system 2 and to the position and operation control system 4 of the shearer. Four geophones 11 are connected to the seismoacoustic recording system 2. The shearer position sensor 12 located on the longwall shearer 13 is connected to the position and operation control system 4. Further, to the methanometric system 3 are connected: the longwall methanometers 14, which are located along the longwall workings preferably every 15 m, the mobile shearer methanometer 15 built on the longwall shearer 13 in vicinity of the mining head, two stationary air speed sensors 16 located at the face end (inlet) and at the face end (outlet) of the longwall working B, and the mobile shearer air speed sensor 17 installed in the longwall shearer 13. The operating elements 18 switching off particular devices with electric drives installed in the underground part E of the mine in the region of the monitored longwall are connected to the executive system 6 comprised in the methanometric system 3.

Claims

Claims
1. A method of detecting and reducing methane hazard in vicinity of a longwall, comprising measurement and analysis of methane concentration and of parameters defining degree of risk of the rock burst in the longwall area, in which if critical value is exceeded by the measured values an alarm signal is triggered and the supply of electricity in hazardous area is automatically switched-off, characterized in that on the longwall panel length the areas of stress (N) concentrations are periodically localized by a passive velocity tomography with use of the seismometers (8) and the low-frequency geophones (9), these data are compared with current seismoacoustic measurements localizing places of cratches (M) groups accompanying cracking of the rock mass at the longwall panel length, with measurements of methane concentration and measurements of the air flow in the working, whereas the places of stress (N) concentration in front of the longwall are localized additionally by an active attenuation-damping tomography taking into account the shearer (13) position in the longwall working (B), then these parameters are correlated in time and space, and after finding that correlation coefficient exceeds predetermined critical value preventive procedures minimizing methane risk are performed.
2. The method according to claim 1 , characterized in that the places of stress (N) concentration determined with the attenuation-damping tomography by analysis of signals detected by a seismic recording system (1 ) comprising the low- frequency geophones (9), are directly correlated with the position of the longwail shearer (13) in the longwail by the real-time measurements of energy of vibrations generated by its mining head in one mining cycle (X) and determined with the low-frequency geophones (9) in the longwail galleries (A), and after the end of each mining cycle (X,) these results are compared to the values recorded in previous cutting cycle (ΧΜ), and the places of increased stress (N) concentration are identified, wherein the signals from the stress sensors (10) are sent to the seismic recording system (1) to enable scaling of the stress changes isoline.
The method according to claim 1 or 2, characterized in that simultaneously the air flow is measured at the face end (inlet) and the face end (outlet) of the longwail working (B) along with mobile measuring of the air flow directly at the current location of the longwail shearer (13) in this working.
The method according to claim 1 or 2 or 3, characterized in that in the process of correlation of relative changes of registered variables, in particular increments of parameters associated with measurements of methane concentration, stress, air flow, and seismoacoustic activity, the amplitude of changes (ΔΚ) of correlation coefficient (K) changes in time and space, and rate of these changes (ΔΚ/Δί) are analyzed.
The method according to any of claims 1 to 4, characterized in that on the basis of results obtained from the passive velocity tomography, seismoacoustic observations, and determined sites of stress (N) concentration localized with the active attenuation-damping tomography, and taking into account local changes in methane concentration correlated with these parameters, the localizations for procedures minimizing methane hazard are determined in the longwall working (B), these procedures being preferably preventive drilling for methane removal.
6. The method according to any of claims 1 to 5, characterized in that, after finding correlation in time of analyzed parameters, in particular if critical thresholds are exceeded by relative increases of stress and methane concentration, the thresholds for warnings and / or for automatic switching-off of the electrical equipment in the area of controlled longwall are reduced.
7. A system for detecting and reducing methane hazard in vicinity of a longwall comprising a methanometric system equipped with the methanometers localized in the longwall working and on the longwall shearer, a hazard alarm, and a system switching-off electrically powered devices in the monitored area, characterized in that a seismic recording system (1 ), a methanometric system (3), an executive system (6), and a warning module (7) are connected to an analytical system (5), wherein the seismic recording system (1 ) with attached at least four seismometers (8), at least four low-frequency geophones (9) and at least two strain sensors (10), is connected to a seismoacoustic recording system (2) with at least four geophones (1 1), and to a position and operation control system (4) of the shearer (13) with a shearer position sensor (12).
8. The system according to claim 7, characterized in that the longwall methanometers (14), a mobile shearer methanometer (15) and two stationary air speed sensors (16) disposed at the face end (inlet) and the face end (outlet) of the longwall working (B), and a mobile shearer air speed sensor (17) are connected to the methanometric system (3).
9. The system according to claim 7 or 8, characterized in that the connections between the analytical system (5), the seismic recording system (1 ), the methanometric system (3), the executive system (6) and the warning module (7), and between the seismic recording system (1 ), the seismoacoustic recording system (2), and the shearer position and operation control system (4) are realized with the Ethern
PCT/PL2014/000123 2014-10-30 2014-10-31 A method and system for detecting and reducing methane hazard in vicinity of a longwall WO2015002556A2 (en)

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RU2015101764/03A RU2594917C1 (en) 2014-10-30 2014-10-31 Method and circuit for detecting and minimizing methane hazard in area of mining face
CN201480002448.5A CN105765407B (en) 2014-10-30 2014-10-31 For detecting and reducing the method and system of the methane harm near longwell
UAA201501088A UA117660C2 (en) 2014-10-30 2014-10-31 A method and system for detecting and reducing methane hazard in vicinity of a longwall

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