Page 11 - Advanced Mine Ventilation

x Contents

12.3 Dust Concentration Measurement by Light-Scattering Instruments 195
12.4 The Tapered Element Oscillating Microbalance Instrument
(A Personal Dust Monitor) 196
12.5 Respirable Dust Sampling Strategy 199
12.6 Threshold Limits for Various Dusts Prevailing in Mines 207
12.7 Diesel Particulate Monitor 209
References 209

Section Three Combustible Gas Control 211

13 Origin of Gases in Coal Mines 213
13.1 Introduction 213
13.2 Properties of Gases in the Mine Atmosphere 214
13.3 Characteristics of Coal 218
13.4 Characterization of Methane from Coal 219
13.5 Coalbed MethanedAn Energy Source 223
References 226

14 Reservoir Properties of Coal Seams 227
14.1 Gas Content of Coal 227
14.2 Coal Matrix Permeability 234
14.3 Diffusivity of Methane in Coal 238
14.4 Reservoir Pressure 242
Problems 244
References 245

15 Premining Degasification of Coal Seams 247
15.1 Coal Seam Reservoir Parameters 248
15.2 Premining Degasification 249
15.3 Application of In-Mine Horizontal Drilling 258
15.4 Application of Vertical Wells With Hydraulic Fracturing 259
15.5 Application of Horizontal Boreholes Drilled From Surface 261
15.6 Optimum Widths of Longwall Panels 262
15.7 Field Observations of Optimum Longwall Panel Width 265
Problems 265
References 266

16 Postmining Degasification of Coal Mines 267
16.1 The Gas Emission Space 268
16.2 European Gob Degasification Methods 271
16.3 US Gob Degasification Method 275
16.4 Gas Capture Ratios by Vertical Gob Wells 279
16.5 Gob Well Production Decline 280
Problem 281
References 281