T. Liu, C. Wang, Y. Wei, Y. Zhao, Y. ShangLaser Inst. Shandong Academy of Science, China

D. Huo, Z Wang

Yanong NingIntelligent Sensor Systems Ltd. UK

Presentation: S&A IOP and OFS-20, Edinburgh 16.10.2009

HAZARD MONITORING IN MINES USING FIBER OPTIC

SENSORS

22

OUTLINE

nnBackground Background -- Mine HazardsMine HazardsnnFOS based Intelligent Mine Safety Monitoring SystemsFOS based Intelligent Mine Safety Monitoring SystemsnnRoof condition and water burst monitoringRoof condition and water burst monitoringnnEarly fire detectionEarly fire detectionnnPower safety monitoringPower safety monitoringnnSpontaneous fire early warningSpontaneous fire early warning

nnMethane gas monitoringMethane gas monitoringnnField trials: coal mines, tailings dam landslide Field trials: coal mines, tailings dam landslide nnSummarySummary

33

CHINESE COAL MINE INDUSTRYnnCoal provides majority of the energy (>70%); Coal provides majority of the energy (>70%); nnAnnual Production: ~3 billion tons,Annual Production: ~3 billion tons,nn ~ 1/3 of world coal production;~ 1/3 of world coal production;

nnNumber of coal mines: ~15,000Number of coal mines: ~15,000nn -- State and local government own ~3,000, State and local government own ~3,000,

the rests are small mines;the rests are small mines;nnUsed to be >70,000 mines Used to be >70,000 mines nnKey Issue: Key Issue: SAFETYSAFETY

44

COAL MINE SAFETYn2001-2005: nNumber of coal mine accidents:18,516nNumber of death: 31,064 (AVE: 17 per day !)nIn recent years, both the government and the mine operators invested heavily on safety technologies, the fatality rate dropped, but total number still very high.

nFATALITIES DUE TO EXPLOSION: nState owned mine groups have world class safety standard;n However, in small mines casualty rate over 100 times higher.

55

MAJOR COAL MINE HAZARDS

2006 Jan-Oct: FatalitiesGASOUTBURST

ROOF

WATER

TRANSPORT

FIRE

BLASTERS

346

415

75

987

1615

Roof collapse, rock & coal outburst

Methane explosion

Flooding

66

n To develop a comprehensive mine disaster management system based on fiber optic sensor network, nCapable of mining hazard early warning and control.

MOTIVATION

77

n Various mining hazards are inter-linked, they do not happen alone;n Detectable symptoms exist prior to disasters happen.

PRINCIPLE

88

ROOF COLLAPSE, ROCK BURST

n Large area of roof sudden collapses,n thousands of tons of rock and coal burst outn casualties and struct damages.

99

MINE ROOF DEFORMATION

nRoof monitoring: roof displacement, seismic, not compulsory:n Resistance strain gauges, suffer drifts, often off line…

1010

Rock Strain, Roof Displacement Sensors

n FBG roof displacementsensor,n d transferred to FBG strain.

n FBG rock strain sensor array on steel bar

FBG array

1111

Sensors for Water Burst Detection

n FBG Pressure sensor with built-in temperature sensor;n For mineral mine safety application, where major hazards are water flooding, tailing dam, and roof fall.

1212

Multi-Parameter FBG Sensor Sys.

n FBG-based T, P, water level, ε, d sensor multiplexing n system, nWDM & Spatial multiplexing, up to 100 fiber channels,n Address >1,000 sensors per system;n Mine safety certified (MA); n with internet access and TXT message auto-warning.

1313

nCantilever based accelerometer: nAcceleration results in mass displacement,

then FBG strain variation.

MICRO-SEISMIC SENSOR

1414

Micro-Seismic Sensor Interrogation1. Saw-tooth laser current sweep to locate FBG reflect. Spectrum

2. SCM PID control to lock the DFB LD to -3dB point in the FBGspectrum.

1515

Micro-Seismic Sensor Interrogation

nFBG edge to give acceleration signal;nPID LD current lock to track FBG slow drift.

1616

Micro-Seismic Sensor Character.n Sensitivity: 0.1mg;n Range: 0-10g.n BW: 3-400 HznAuto-drift compensation

1717

COAL MINE FIREn2008.09 Hegang Spontaneous coal fire causing 19 people died;

n2007.02 Henan Province, 17 died in a power cable joint overheat caused fire.

1818

FBG Interrogator

Optical fiber cable

On-line high voltage switchgear temperature monitoring

Internet server

Fiber connection

Mining Power Station Condition Monitoring

FBG Temperature sensor

1919

narmoured cable for underground mined-out area;nalong power cable.

Fire Prediction and Locationnn 66--10 km range10 km range

nRaman DTS nT Monitor and fire warning nlocation system

T vs L

2020

Spontaneous Coal Mine Fire Detection

n Underground spontaneous coal fire can occur as soon as 14 days after production production;n Early detection can be made by monitoring CO (@1567nm), CH4 (@1665nm) and C2H4

(@)1630nm; O2 (@762nm);

nRatio of CO/O2, C2H4/C2H6 are useful indicators;n Require ppm sensitivity

and accuracy;

C2H4/C2H6 vs coal T

2121

Multi-Gas Trace Detection System

n Multiple reflection to enhance the detection sensitivity;n 2nd harmonic detection and PLIA to reduce noise;n ~ 1 ppm sensitivity for CO, sub-ppm for C2H4, C2H6;

laser

Gas cell

10 kHz

PD

2222

Multiple Gas Trace Detection System

LD1

LD2

LD3

SwitchSwitch

Gas cell probe

AD, 1f/2fPC

LD…

nOne gas cell addressed by a bank of laser diodes, which emits atn absorption band of the gases to be monitored.

2323

Multi-Gas Detection System

y = 0.0033x - 0.0043

R2 = 0.9988

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0 20 40 60 80 100 120

C2H2 Concentration (ppm)

V_2f

o/V_

fo

(au)

2nd harmonic signal

-1.8

-1.6

-1.4

-1.2

-1

-0.8

-0.6

0 50 100 150 200 250 300

Sample points

V_2fo (v)

100ppm

80ppm

30ppm

0

Modulation frequency signal

-1.5

-1.4

-1.3

-1.2

-1.1

-1

-0.9

0 50 100 150 200 250 300

Sample points

Signal（

V） 100ppm

80ppm

30ppm

0

n C2H2 concentration vs V2f/V1f.

Illustration how the harmonic detection system work.

2424

GASSY MINE DISTRIBUTION,CHINA

nnOver 50% underground coal mines in the world are gassy;Over 50% underground coal mines in the world are gassy;

2525

n2001.11, Shanxi Datong, nExplosion, 54 people died;n Operation to suppress poisonous gases emitted.

METHANE EXPLOSION

n2006.11 Jiangxi explosion,7 people died.

n2001, Shanxi, explosion99 people died

2626

From Geo-Physics Vol. 19, p 856

Seismic Event 17:17

Gas outburst in ~40 minutes

Seismic Trigger Methane Gas Burst

2727

FO Methane Gas Sensor

n Ambient Gas Sensor

n Pipeline gas sensor

nSensor consists of pairs of fiber collimators as gas cell;nFixing Support and anti-vibration mechanism;nDust and moisture filters

2828

FO Methane Detection Principle

1665nm DFB LD

nLaser sweep with internal referencing to achieve field stability.

2929

y = 1.0025x + 0.0526

0

2

4

6

8

10

12

0 2 4 6 8 10 12

标准气体浓度（％）

测量浓度（％）

FOS Methane Monitor

n Unique benefits: n Long calibration cycle;n Immune to gas cross talk;n Robust to humidity and ambient Tn Intrinsically safe

3030

Coal Bed Methane UtilizationMonitoring - Latest Field Trial

n(Huainan Coal Mine methane power generation plant 2009.09）

0

0.2

0.4

0.6

0.8

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49

data points（once/half hours in two days）

concentration（

%）

fiber gas sensor(MS-GXM-01) Traditional sensor1 Traditional on-line sensor

3131

Coal Mine Methane Utilization Monitoring

(Methane extraction power generation plant, Fuxin, Liaoning, 07. 2008

3232

Intelligent Mine Safety Platform

nnAll fiber optic multiAll fiber optic multi--parameter sensor parameter sensor network, comprising 3 subnetwork, comprising 3 sub--systems;systems;nn Multiplexed FBGMultiplexed FBG sensor array (sensor array (d, P, d, P, T, T, εε, a, flow, AE, a, flow, AE))nn Laser absorptionLaser absorption based gas sensor based gas sensor array (array (Ch4, CO, CCh4, CO, C22HH44, CO, CO22, O, O22))nn DTSDTSnnData fusion systemData fusion system

3333

瓦斯检测

温度检测

应力检测

矿震检测

USB

RS232

RS232

RS232

PC

Switch

Switch

Switch

Switch

光缆

巷道

采煤面A

掘进面B

温度A1

温度A2

温度B1

温度B2

瓦斯A1

瓦斯A2

瓦斯B1

瓦斯B2

应力A1

应力A2

应力B1

应力B2

数据库

Internet

客户端

煤矿井下

报警

客户端 客户端

CH4

Optical detection Units

T, P

d

micro-seismic

fiber cable

Ground Monitor Centre Underground

FIELD TRIALS: LINGZI COAL MINE, SHANDONG

Coal production

D/B alarm

3434

Field Trial: LINGZI COAL MINE, SHANDONG

Temperature

Seismic

Strain

Methane

The first trial in 2007

3535

FIELD INSTALLATION

Fire-Proof CableConnection

Strain sensor array

Illustration of Fiber Optic Sensor Installation in the Mine.

T

CH4

3636

FIELD TRIALS: LINGZI COAL MINE, SHANDONG

nIllustration of water pressure measurement using fiber optic pressure sensors.

Optical fiber Pressure sensor

Water input

Wateroutput

3737

FIELD TRIALS: LINGZI COAL MINE, SHANDONG

nFiber Optic temperature sensors and methane sensors installed in underground coal mine.

Temperature sensorFiber opticMethane sensor

3838

FIELD TRIALS: LINGZI COAL MINE, SHANDONG

nUnderground temperature is recorded at approximately 22 degree C, accurate within +/-0.5 degree.

3939

FIELD TRIALS: LINGZI COAL MINE, SHANDONG

nRecord of methane gas concentration change with time (increase of concentration can be observed after blaster events which agrees with the conventional sensor data).

blasters

4040

Laiwu Iron Ore Mine Roof Monitoring

Displacement sensor

Fiber load cell

4141

nRecorded mining blaster signals by two FO seismic sensors located 170 m apart. The time delay is apparent which can be used for seismic source location.

25000

27000

29000

31000

33000

35000

37000

39000

0 500 1000 1500 2000

系列4

25000

27000

29000

31000

33000

35000

37000

39000

0 500 1000 1500 2000

系列3

FIELD TRIALS:Laiwu Iron Ore Mine

Fiber seismic sensormount plate

∆t

4242

FIELD TRIALS: Internet Access

n The FOS mining safety information system isfor on-line remote access via internet.

4343Internet access

4444

Tailings Dam Condition Monitoring

nMineral mine hazards mainly concerned nwith underground roof and ground tailingsndam safety monitoring.nFiber optic water level and displacement nSensor net work are developed.

Illustration of an ironore mine tailings dam monitoring system in Beijing, 06.2008.

4545

Field Trial: Methane Sensor UK Waste Process Power PlantnGlobal secure remote methane monitoring and Data Access

nOn-going field trail min the UK 09.2009.

4646

Field Trial: Methane Sensor UK Waste Process Power PlantnGlobal secure remote methane monitoring and Data Access

4747

0

10

20

30

40

50

60

70

80

90

100

00:00:00 04:48:00 09:36:00 14:24:00 19:12:00 00:00:00

Time

Met

hane

Con

cent

ratio

n (%

)

Field Trial: Methane Sensor UK Waste Process Power PlantnGlobal secure remote methane monitoring and Data Access

nOn-going field trail min the UK 09.2009.

4848

On Going Work – Comparative Study With PZT Seismic Sensor Network

Coal

Pro

duct

ion a

rea

nReal PZT Seismic recordingnAnd location.

nTo put OFS in the same nLocation as the PZT and compare

PZT Seismic event location

sensors

4949

Challenges and Opportunities n OFS can play a key role in enhancing even

revolutionizing coal mine and mineral mine safety;

n Fiber optic FBG sensors, DTS, laser spectroscopic

gas sensors, seismic sensors have been successfully

demonstrated to become a comprehensive mining

safety and hazard management info system …

n The diversified, on-line, multi-location information

provides a foundation for more accurate and timely

mining hazard early warning and control;

5050

Challenges and Opportunities n OFS intrinsically safe in explosive environment, is

irreplaceable for the development of modern

intrinsic safe and digital mining.

n OFS also play key role in environmental system

such as coal bed methane utilization...

n Many opportunities and challenges for OFS

application in the mines, e.g. sensitive fiber

microphone array for emergency rescue

communication; dust monitoring; cable and

sensor protection, etc.

5151

Acknowledgement

nThanks to our colleagues at Laser Inst,

Shandong Academy of Science and

Shandong Micro-Sensor Photonics Ltd;

nColleagues in coal and mineral mines for

supporting the trials.

nGrants from National, provincial and the

Shandong Academy of Science are

acknowledged

5252

ü Welcome your collaboration !ü Together, OFS can save lives and the planet !

Thank you for your attention !