In the present monograph, various issues related to methane hazard in Polish hard coal mines are discussed. Chapter 1 contains a description of methane emission as a source of atmosphere pollution, while Chapter 5 presents the methods of methane capture and possible ways of its utilisation. In Chapters 2 and 4, the authors focus on a method for determining coalbed methane content and predicting it with the use of neural networks. Chapters 3 and 6 are devoted to presenting a new method of the classifi cation of methane hazard in hard coal mines and to describing adequate methods of monitoring and control. As an example, an evaluation of methane hazard in the area of longwall F-1 in seam 406/1, ventilated with a U system, is described in Chapter 7.
In Chapters 8, 9 and 10, methods of methane drainage implemented in the Polish mining industry are presented and the influence of mining and geological conditions on their efficiency is discussed. The effi ciency of particular drainage methods is discussed and compared, as well as methods of increasing it considering the low permeability of coal deposits in Poland.
The main reason for this monograph is to show how many technological problems need to be solve in order to conduct excavation in coal mines in condition of high methane hazard. The amount of methane emitted to the workings during mining is strictly defi ned by mining regulation, and it is of high importance for coal mines to forecast coalbed methane content before mining is started.
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Introduction 9
1. Emissions of methane from hard coal mines as a source of atmosphere pollution 13
1.1. Introduction 13
1.2. Methods of reducing methane emissions into the atmosphere 15
1.3. Emissions of methane from Polish hard coal mines into the atmosphere 18
1.4. Methods of methane drainage from the strata implemented in Polish mines 19
1.5. Effi ciency of methane drainage from coal seams under development 23
1.6. Conclusions 24
2. Determination of methane content in coal seams along with measurement uncertainty specifi cation 25
2.1. Introduction 25
2.2. A method of determining coalbed methane content 26
2.3. Gas loss during collecting coal samples for measurement 27
2.4. The procedure of determining coalbed methane content 29
2.5. Evaluation of measurement uncertainty 31
2.6. Analysis of measurement uncertainty of coalbed methane content 32
2.7. Conclusions 37
3. Proposed revisions of the categorisation of methane hazard in underground mines 38
3.1. Introduction 38
3.2. Determining coalbed methane content 39
3.3. Evaluation of methane hazard in mines extracting hard coal 40
3.4. Proposed revisions of the categorisation of methane hazard 43
3.4.1. Methane hazard in underground mining plants extracting hard coal and lignite 43
3.4.2. Methane hazard in underground mining plants extracting nonferrous metal ore and salt 46
3.5. Conclusions 46
4. Predicting the release of methane into the longwall workings in Polish coal mines using neural networks 48
4.1. Introduction 48
4.2. Artifi cial neural networks 50
4.3. Description and analysis of data used to predict the evolution of methane release 51
4.4. Determination of the neural network structure used to predict absolute methane-bearing capacity 54
4.5. Evaluation of the effectiveness of teaching neural network 57
4.6. Conclusions 59
5. Possibilities of capturing and utilising methane from hard coal mines 60
5.1. Introduction 60
5.2. Methane resources in hard coal deposits in Poland 60
5.3. The current system of supporting the utilisation of methane from hard coal mines 62
5.4. Utilising the captured methane 63
5.5. Conclusions 66
6. Monitoring and controlling methane hazard in excavations in hard coal mines 67
6.1. Introduction 67
6.2. Methane hazard control in other countries 68
6.2.1. The United States of America 68
6.2.2. Australia 69
6.2.3. Russia and Ukraine 71
6.3. Estimation of methane hazard resulting from binding legal regulations in Poland 72
6.3.1. Mining excavations with auxiliary ventilation 72
6.3.2. Longwalls with U and Y ventilation systems 76
6.3.3. Characteristics of Longwall B-11 in seam 348 76
6.4. System of continuous control over methane drainage system 84
6.5. Conclusions 86
7. Estimation of methane hazard in the area of U-ventilated longwall 87
7.1. Introduction 87
7.2. Development of guidelines for testing air parameters in order to assess methane hazard 88
7.3. Verifi cation of standards of sampling air from the goaf 91
7.4. Guidelines for the measurement and operational methanometric security of the longwalls mined in the presence of methane hazard 95
7.4.1. General principles for the control and prevention of methane hazard 95
7.4.2. Principles for the control of the amount of methane in air by using a mobile methanometer 96
7.4.3. Control of methane hazard by means of automated methane monitoring 97
7.4.4. Inspection and maintenance of the automated system of methane monitoring 99
7.4.5. Recording the measurements of the automated system of methane monitoring 100
7.5. Conclusions 100
8. Infl uence of mining and geological conditions on the effi ciency of coal mine methane drainage in Polish mines 102
8.1. Introduction 102
8.2. Methods for methane drainage in Polish coal mines 103
8.2.1. Methane drainage of longwalls with Y ventilation system 106
8.2.2. Methane drainage of longwalls from parallel tailgate roadways 107
8.2.3. Methane drainage of longwalls from cut off parallel tailgate road 107
8.2.4. Methane drainage of longwalls with an overlying drainage gallery 107
8.2.5. Methane drainage of longwall working to the rise 109
8.2.6. Other methods of methane drainage 109
8.3. Effi ciency of methane drainage conducted during mining by means of different methods 110
8.4. Conclusions 114
9. Possibilities of increasing the effi ciency of mine methane drainage in the conditions of low permeability of coal seams 116
9.1. Introduction 116
9.2. Gas fl ow in rock-mass 117
9.3. Pre-mining methane drainage 119
9.4. Methane drainage with increased permeability 120
9.5. Results of calculations of methane fl ow into methane drainage boreholes 121
9.6. Methane drainage effi ciency before mining 123
9.6.1. Methane drainage of a panel in Longwall B-1 in seam 406/1 125
9.6.2. Methane drainage of a panel in Longwall F-1 in seam 406/1 125
9.6.3. Pre-mining methane drainage of a panel in longwall G-4, seam 412łg+łd and 412łg 127
9.6.4. Methane drainage of a panel in longwall G-4, seam 412łg+łd and 412łg 128
9.7. Conclusions 128
10. Effi ciency of methane removal using different drainage systems in Polish hard coal mines 130
10.1. Introduction 130
10.2. Methane drainage systems in Polish coal mines 130
10.2.1. Methane drainage of a panel in Longwall G-6, seam 410 130
10.2.2. Methane drainage of a panel in Longwall Cw-2, seam 364/2 132
10.2.3. Methane drainage of a panel in Longwall B-13, seam 348 134
10.3. Methane drainage from overlying drainage gallery 136
10.3.1. Methane drainage of a panel in longwall XIII, seam 405/1 136
10.4. Methane drainage effi ciency in the developed coal seams 138
10.5. Conclusions 138
References 143