HANOI UNIVERSITY OF MINING AND GEOLOGY --- NGUYEN VAN THINH RESEARCH ON METHANE DRAINAGE REGIME WHEN EXPLOITING TO DEEP IN UNDERGROUND COAL MINES IN QUANG NINH AREA Specializ: Mining
Trang 1HANOI UNIVERSITY OF MINING AND GEOLOGY
-
NGUYEN VAN THINH
RESEARCH ON METHANE DRAINAGE REGIME WHEN EXPLOITING
TO DEEP IN UNDERGROUND COAL MINES IN QUANG NINH AREA
Specializ: Mining Code: 9520603
SUMMARY OF TECHNICAL DOCTORAL THESIS
HANOI - 2019
Trang 2Ha Noi University of Mining and Geology
Reporter 2: Dr Nguyen Anh Tuan, Vietnam National coal and mineral
industries holding Corporation limited;
Reporter 3: Dr Dao Hong Quang, Vinacomin Institute of Mining Science anh Technology
The thesis will be defended before the school level of thesis jury
in Ha Noi University of Mining and Geology
Trang 3MỞ ĐẦU
1 Necessity of thesis
According to the Decision No 403 / QD-TTg dated March 14, 2016 of the Prime Minister on approving the adjustment of the development planning of Vietnam's coal industry to 2020, considering the prospects until 2030, at Article
1, Section II.2.b states "The volume of commercial coal produced in the industry in the planning stages: About 41 - 44 million tons in 2016; 47-50 million tons by 2020; 51 - 54 million tons in 2025 and 55-57 million tons in
2030 "
In order to meet the requirements for the output of pit coal mines, it is increasingly necessary to go deep, expand the scale as well as apply mechanization in mining and digging The increase in coal production leads to the amount of methane being released to the ovens and the furnace to prepare more and more Methane is a gas that can cause very dangerous explosions
In the history of pit coal mining in the world and in Vietnam, there have been many CH4 gas explosions that have killed dozens, even hundreds, of people and destroyed the facilities of coal mines Due to the dangerous nature of methane released in the pit of mines causing the risk of fire and explosion, the coal mining industry in the world as well as in Vietnam always put the issue of methane fire prevention and fighting on top, including the study of methane drainage and methane storage in coal seams is the source of the release of methane gas into mine kilns
In our country, the researches on gas storage and methane drainage have been carried out for many years but mainly focused on mines with high gas emission, not yet universal and have not been proposed newspaper when exploiting deep into each mineral deposit or underground coal mine to take measures to prevent gas accumulation exceeding the effective permissible limit
In order to assess the danger of methane for each coal mine or mining area, it is necessary to determine the methane release mode of the mine or
mining area Of particular importance is the study of determining the
containment of methane in coal seams and the degree of leaching of gases to quantify mine kilns in a quantitative way to apply the method of exploiting and using room facilities Suitable methane explosion protection and safety
guarantee and improve economic efficiency
Therefore, "Research on methane drainage regime when exploiting to deep in underground coal mine in Quang Ninh region" is urgent
2 Research aim of thesis
- Study on methane drainage regime in underground coal mines in Quang Ninh area when exploiting deeply
- Proposing suitable solutions for preventing and combating methane fire when exploiting in underground coal mines in Quang Ninh region
Trang 43 Research objective and scope
Object of the study: Gas emission and methane content in coal seams
affect the mining process down to underground coal mines in Quang Ninh
Scope of research: The topic is underground coal mines in Quang Ninh
The thesis uses a combination of the following research methods:
- Methods of surveying, synthesizing and inheriting documents;
- Methods of analysis, statistics and graph methods;
- Methods of linear interpolation and non-linearity
6 Scientific and practical meaning of thesis
6.1 Scientific meaning:
- Develop regression functions using the least squares method to forecast gas storage and methane release in underground coal mines in Quang Ninh region;
- Predict the process of methane release into mining areas on the basis of determining the level of methane drainage at the extraction level on her forecasting methane drainage for the next extraction level
6.2 Practical meaning: The research results contribute to the
determination and prediction of methane drainage and coal mining areas of coal mines in Quang Ninh in the deep exploitation areas to take appropriate measures to prevent methane explosion
7 New points of thesis
- Constructing regression function on the methane gas storage in coal seams in underground coal mines in Quang Ninh region with the form y = a.xb
- Establish a map of methane zoning according to the scope and depth of underground coal mines in Quang Ninh region
- Forecast of methane release for market ovens at underground coal mines
in Quang Ninh area, with actual measurement results by multiplying forecast results with coefficient k = 0,9316 and plus 0.0029
8 Scientific thesis
- The deeper the mining, the higher the gas storage and methane release;
- Same geological condition, methane drainage depends on coal seam
thickness and mining output;
Trang 5- For the system of mining and division of layers, the methane drainage in the upper layer is greater than the escape of methane in the lower layer
9 The thesis structure
The thesis consists of 4 chapters, Introduction sections and Conclusion conclusions, pages, including drawings and tables
Chapter 1 OVERVIEW OF METHODS TO STUDY METHANE DRAINAGE IN UNDERGROUND COAL MINES IN THE WORLD AND VIETNAM
1.1 GENERAL CHARACTERISTICS OF METHANE
Methane (CH4) is the simplest type of saturated carbonate of paraffin group Colorless gas, odorless, tasteless Its density in normal conditions is 0.716 kg / m3, which is several times lighter than air It is soluble in ethanol, ether, poorly dissolved in water (up to 3.5% under normal conditions) Although methane is a gas that does not affect respiration, significant concentrations in the air are dangerous because methane gas pushes oxygen (4.8% methane will push 1% oxygen) Methane is a potentially explosive gas When the volume content of methane is in the range of 5 - 15% and the minimum oxygen content of about 8% of the mixture is explosive, the explosive mixture is strongest when the methane content reaches 9.5% The explosion limit of methane is not fixed and depends on the pressure, temperature, combustion position and initial heating intensity Under reduced pressure, the explosion limit will shrink In the direction of increasing temperature - the explosion limit will expand and vice versa
1.2 OVERVIEW OF METHODS TO STUDY METHANE DRAINAGE IN UNDERGROUND COAL MINES IN THE WORLD
a Methods in Western European countries
In Western European countries, people often use the method of forecasting the methane escape into the oven by Shulza, Wintera and Stuffkena
Inside:
M- Released gas relative to the longwall (m3CH4/T-ng.đ)
Wtn- Do contains natural gas of coal seams (m3CH4/T)
Wlc- Gas reservoir of nearby reservoir (m3CH4/T)
mlc- Thickness of adjacent seams; (m)
mkt- Thickness of exploitation seam
n lc - Number of air discharges from adjacent reservoirs (above or below), this number depends on the distance from the adjacent seams to the existing seams
b Statistical method of the Soviet Union
The basis of this method is the system of statistic data in the past in terms
Trang 6of air discharge of the mining area or exploitation floor and other factors such
as extraction level and length of longwall The accuracy of the method depends
on the reliability of the statistics The methane emission of the new extraction level is calculated according to the formula:
Inside:
Mp - The level of methane emission of the extraction level m3/Tngđ
H – Depth of new cascade level (m) (m)
H0- Depth of methane-containing cliff wall (m)
L- The gas-rich level indicates the depth increase so that the relative air discharge increases by 1 m3CH4 / T-ng.đ; unit (m/m3CH4/T)
The value of the gas-rich level L is summarized from the statistics collected at the already and exploited levels The L value is determined by the following formula:
H1- Exploitation depth of shallow level (m)
H2- Depth of exploitation of deeper level (m)
Mp1- The methane drainage is shallow (m3CH4/T-ng.đ)
Mp2- The methane drainage is deep (m3CH4/T-ng.đ)
For mines with many statistics of H1, H2 and different Mp1 Mp2 values, the relationship between M- relative discharge and H- depth of exploitation can be shown
On the basis of the regular line M = f (H), we can predict the predicted
Mp gas discharge according to the depth value of the new exploitation level
In this method, the higher the number of Mpi and Hi statistics, the higher the forecast
The drawback of the method is that there is a need for many statistical figures over the years at different levels
c Method of forecasting the methane release from the extraction area of
experimental mine "Barbara", Poland
According to this method, the absolute solubility of methane released into the oven is calculated according to the following general formula:
Vkt: Escape methane gas from coal mining, m3/ph
- Llc : Length of longwall, m
- mkh : The thickness of the exploitation layer, m
- Yv : Volumetric weight of coal in the seams T/m3
- Wv : The content of methane in the coal seams m3/ Tkhối cháy
Trang 7- Vg: Methane gas escapes from the face of longwall
- Vtr: Methane gas escapes from above of the longwall
- Vdi: Methane gas escapes from the bottom of the longwall
- p - Mining speed of longwall, m/ngđ 1.3 OVERVIEW OF METHODS TO STUDY METHANE DRAINAGE UNDERGROUND COAL MINES IN VIETNAM
Research on methane drainage in Vietnam has been mentioned by a number of authors such as Tran Tu Ba and Le Van Thao
Currently, in Vietnam is using the method of rigorous mine "Barbara" of Poland to study the application of prediction of air discharge into a longwall suitable for the conditions of Vietnamese underground coal mines because:
Geological and technological factors of Polish and Vietnamese underground mines are not similar Especially if talking about geological-mining conditions, Poland's coal is energy coal (Bitumineous), while Vietnam coal is coal-anthracite (Anthracite) The coal seams of Poland are quite deep (thousands of meters) and most of them are curb The coal seams in Quang Ninh area are mostly steep ones, which are closer to the ground (currently, the deepest coal mine in Vietnam is Khe Cham II-IV coal mine is expected to reach -500 and will produce output in 2022) For that reason, it is necessary to calculate and control the actual measurement results to be able to propose adjustment coefficients to suit the geological conditions of underground mines
in Quang Ninh area
1.4 REVIEW CHAPTER 1
- Methane is a dangerous gas for coal mines exploited by pit method because this gas appears regularly in coal mines (especially mines of anthracite and anthracite coal as in Quang Ninh area) ) and when a methane explosion occurs, it often causes great loss of life and property and affects the mine production
- The demand for coal in the world as well as in Vietnam is increasing At the same time, the coal output exploited by pit method is increasing in proportion to the exploitation by opencast method Therefore, the issue of ensuring the safety of methane fire in underground coal mines needs to be put
on top
- There are two main methods to study the storage and escape of methane methane: Study on the storage and drainage of methane in the geological exploration and study of the storage and drainage of methane in the extraction process In Vietnam Study the storage and drainage of methane during geological exploration with little data, used to serve the initial mine design work; Study on the storage and drainage of methane in the mining process used
to classify mines
Trang 8Chapter 2 CHARACTERISTICS OF METHANE CONTENT OF COAL SEAMS IN
UNDERGROUND COAL MINES IN QUANG NINH
2.1 GENERAL CHARACTERRISTICS OF METHANE STORAGE IN COAL SEAMS
The concentration of methane is the amount of methane gas calculated according to the standard conditions in 1 ton of combustion coal block
The determinant of the level of methane containing coal deposits is the closest tectonic change Coal seams with conditions of methane accumulation are usually the reservoirs below the gas-permeable layer of soil The phenomenon of gas-permeable coal seam layers does not create two types of closed and open mineral forms The level of each reservoir of methane gas in the minerals depends on the existence of methane separation layers
The characteristic of closed type deposits is the coexistence of permeable coal seam layers both in the covering soil layers and in carbon lava layers alternating between coal seams Thus the layers of this separation, the shift of methane from the deeper layers slowed down As the depth of extraction increases, this type of mineral methane content increases and there is
gas-a difference in egas-ach cogas-al segas-ams
2.2 GEOLOGICAL CHARATERISTICS OF QUANG NINH COAL AREA Coal mines in Quang Ninh coal basin are affected by very strong bending and fracturing activities, highly degraded coal In Quang Ninh coal basin, there are over 84.5% of coal mines belong to group III, only a few belong to group II and mine group IV However, the grouping of mines is essentially an average value Each coal mine has its own geometric fields in each high homogeneous architectural block and has geometric anisotropic characteristics with different anisotropic coefficients
Within the coal basin, the sediments of the Hon Gai Formation have the largest distribution area, concentrating into two large bands near the longitudinal parallel between the area of Bao Dai and Pha Lai - Ke Bao
Quang Ninh coal basin sediments are uniformly classified by geologists as age (T3n - r) and named Hon Gai formation The physical composition is almost identical and the monotone repetition of the same rock layers in the section, it is difficult to divide the stratigraphic and the cross-sectional comparison only has relative meaning
2.3 RESULTS OF DETERMINATION OF METHANE STORAGE IN COAL SEAMS IN UNDERGROUND COAL MINES IN QUANG NINH
Table 1 Results of analysis of methane concentration in coal seams of
underground mines in Quang Ninh region