Sector Review of Coalbed Methane Development and
Utilization and Its Potential for CDM Projects
China Coal Information Institute (CCII)
1. China coalbed methane(CBM) reserve
CBM is a non-conventional natural gas accompanying coal, with its reserve
equivalent to conventional natural gas. CBM is a clean energy. Developing and
utilizing CBM can not only increase energy supply but also improve coal mine safety
and reduce greenhouse gas emission.
China is one of the major coal producers in the world, and it is also one of the
countries possessing the richest coal resources. Its coal reserve, including the proven
reserve and the future reserve, is around 5 trillion metric tons，ranking the top in the
world. Meanwhile, China also possesses rich CBM resources, with its CBM resources
between 300-2000m in depth 30-35 trillion m3. Since these CBM resources are
distributed in different coal-bearing basins featuring different coal-forming periods
and different types of reserve bed, there are wide differences in their reserve depths,
exploration degrees, etc., which brings about some difficulties for successful CBM
recovery. According to the statistics, the gassy mines and gas burst mines account for
48% of the key state-owned coal mines in China.
2. Current situation of China CBM recovery technologies
The CBM recovery technologies in China fall into two categories, underground
drainage and surface development. As the main technologies to develop coal mine gas
at the present time and in the near future, the underground drainage technologies have
been applied in a great number of coal mining areas. The surface development
technologies mainly include surface standard well technologies and surface gob well
technologies.
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The underground CMM（Coal Mine Methane） drainage in China started up early, and
currently the drainage technologies have been fully mature, basically taking a leading
role in the world, with a complete system of underground drainage technologies,
which is suitable for the CMM drainage under various geological conditions. The
common underground drainage technologies include current coal seam drainage,
adjacent coal seam drainage, gob area drainage and comprehensive drainage.
For the adjacent coal seam drainage, the drilling site is deployed in the auxiliary air
return way of the working face, and the drainage hole is drilled in the cracked zone
formed by the working face and arrives at the adjacent coal seam. The adjacent coal
seam pressure-release CMM drainage technology is now most extensively applied in
China. When the gas liberation from the adjacent coal seam is greater than 30m3/min,
the drainage rate using this technology could be as high as above 85%.
There are two ways for CBM surface recovery, CBM drainage in virgin coal seams,
and CMM drainage in mining areas. Since 1990, CBM surface recovery technologies
have been tested and spread in China, and great progress has been made so far, but a
breakthrough remains to be made in large-scale CBM commercial development.
In recent years, with China putting stress on coal mine safety, the input in CMM
drainage systems has been increased, and the CMM drainage amount has increased
rapidly. In 2003, the CMM drainage amount in China reached 1.521billion m3.
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Drainage Amount（Mm )
1600
1500
1400
1300
1200
1100
1000
900
800
700
600
500
400
300
200
100
0
1521
1146
980
434
458
1990
1991
534
564
600
630
530
1992
1993
1994
1995
1996
729
742
789
1997
1998
1999
858
2000
2001
2002
2003
Figure 1 The CMM drainage amounts in China during 1990-2003
3. Current status of CMM development and utilization in China
China began utilizing CMM at the end of 1970. Until now, over 100 CMM utilization
projects have been completed, all of which are located in the coal mining areas, and
most of them are designed to supply the household fuel gas for the purpose of
improving the living standard of the citizens in the coal mining areas. In recent years,
with increasing awareness of environmental protection, China has liberalized the
natural gas price, and CMM has been given more recognition as an energy resource.
Therefore, a great number of CMM projects have been developed for power
generation, industrial fuel gas production, etc.
3.1 CMM power generation
CMM power generation is a way to use CMM with multiple benefits. It converts
CMM into electric power, which not only makes the transportation convenient but
also effectively reduces the greenhouse gas emission.
In recent years, CMM power generation has developed very rapidly in China. The gas
combustion power generators in CMM power plants can be divided into two types,
gas combustion turbines and gas combustion engines. Gas combustion engines are of
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small size, portability, high heat efficiency (as high as 40%) and high adaptability to
CMM concentration change, among other advantages, suitable for small-scale power
plants. Gas combustion turbines are featured of high intensity power with 50MW or
100MW per unit, but their power generation efficiencies are usually around 30%,
which are suitable for large-scale CMM power plants.
At the present time, main CMM power projects in China include the 120MW CMM
power project in Jincheng Coal Mining Group, gas comprehensive utilization project
in Huainan Coal Mining Group, 20MW CMM power project in Songzao Coal and
Power Company, and CMM power project in Shuicheng, Guizhou.
Since gas combustion engines have higher heat efficiencies, all these projects use
domestic or foreign gas combustion engines in order to improve power generation
efficiencies and comprehensive utilization efficiencies of underground drained gas.
3.2 CMM for civil use
Currently, China CMM is mainly for civil use，accounting for above 70% of the total
CMM utilization. The average methane concentration in the underground drainage gas
is 30-50%, and the gas could be sent directly to the households, cafeterias, hospitals,
schools, etc. in the mining areas. Since there are a small number of households in the
mining areas, the large-scale civil use must be based on cities.
At the present time, the main CMM projects for civil use in China include: CMM
supply by Fushun Mining Area to Shenyang City, CMM supply as fuel gas to
Yangquan City, CMM supply by Fuxin Mining Area to Fuxin City, and CMM supply
by Tiefa Coal Mining Group to Diaobingshan City.
3.3 CMM Industrial Utilization
CMM industrial utilization mainly includes industrial fuel and chemical production.
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Although CMM utilization focuses on producing carbon black and formaldehyde in
past years with low economic effectives, now it moves to be as industrial fuel
replacement of industrial coal gas, natural gas, liquefied petroleum gas or coal.
Currently the CMM utilization projects are undergoing includes Tiefa CMM provided
to ceramics plant in Faku project and Yangquan CMM used for alumina roasting
project.
4. Potential Emission Reduction from CMM Utilization Projects in China
The coal output was up to 1.956 billion ton and the gas drained from underground was
only 1.8 billion m3 in 2004 in China. It is predicted that the coal output will be over
2.1 billion ton in 2005. CMM will be more than 17 billion m3 (pure CH4) released
from coal mining processes every year which equivalent to 183 million ton CO2. In
which the gas from ventilation air accounts for 91% (see figure 2) with low than 1%
concentration, emitted into atmosphere directly, which is relatively difficult to use.
CMM
3%
no-used
rcoveried CMM
6%
Consumption
91%
VAM
Figure 2 CMM Sources Type in 2004 in China
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Another characteristic of CMM in China is low utilization ratio for the gas from coal
mines which accounts for nearly 65% of the total extraction. This should be attributed
to the fact that methane recovery and capture is just ensuring work safety
underground as an auxiliary to coal mining. Thus methane recovery ratio is only about
23% in the coal mines where have installed methane recovery system underground.
Based on the experiences of coal mines, in case of making full use of recovered
methane and facilitating methane recovery by encouraging its utilization, the recovery
ratio could be up to over 50% under the condition of current technologies and
equipment in China. Additionally, in the past two years, Chinese government pays
more attention to coal mine safety, strengthens work safety inspection and
management step by step, established the guideline of “Draining Gas Before Mining,
Monitoring and Controlling, Coal Production depended on Ventilation”,which will
result in more methane recovery systems to be established and existing systems to be
retrofitted.
It is expected that methane output from underground will be over the point of 3 billion
m3 soon in several years. The emissions reduction of CO2 will be up to 23.5 million
ton from methane destroyed only calculated on the utilization ratio of 60%.
Additionally, the ventilation air methane utilization projects are developing by coal
mining areas and research institutes. Currently the methane released from ventilation
air is morn than 15 billion m3 each year in the country. Considerable emissions
reduction will be achieved if this part of resource can be used appropriately.
As estimated, by 2010, the utilization ratio by large and medium coal mines will be
80% of total CMM extracted, i.e. 1.6 billion m3. If half of it could be developed as
CDM project, the total emission reduction potential will be 4.8 million ton of CO2e.
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