Eskişehir – Alpu ve Tekirdağ – Çerkezköy kömür havzalarının gaz içeriği ve bileşiminin değerlendirilmesi
An assessment of gas content and composition of Eskişehir - Alpu and Tekirdağ - Çerkezköy coal basins
Yazar: ANIL SOYLU
Danışman: DOÇ. DR. ABDULLAH FİŞNE
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Maden Mühendisliği Ana Bilim Dalı / Maden İşletme Bilim Dalı
Derece: Yüksek Lisans, 2018
Konu: Maden Mühendisliği ve Madencilik = Mining Engineering and Mining

Özet:
Kömürün gaz içeriği, kömürleşme süreci sırasında varlık gösteren fiziksel ve kimyasal
faktörler sonucunda oluşmakta, depolanmakta ve taşınmaktadır. Alpu/Eskişehir ve
Çerkezköy/Tekirdağ kömür havzalarından alınan numuneler üzerinde yapılan
deneylerin sonuçları yorumlanarak hazırlanmış bu çalışmada, kömür yatağı metanının
jeolojik, iş güvenliği ve gaz üretimi açısından özellikleri değerlendirilmiştir. Bu
çalışmada öncelikle kömürün oluşum süreci ve kömürün gaz içeriğinin oluşum süreci,
dünyada yapılmış diğer çalışmalarda elde edilen bulgular toplanarak açıklanmış ve
yapılacak deney ve yorumlarda kullanılacak kısımlar özellikle irdelenmiştir. Kömür
numuneleri yüzeyden yapılan sondajlardan alınmış ve yüzeye çıkar çıkmaz
desorpsiyon kanisterlerine yerleştirilmiştir. Bu numuneler üzerine yayılan gaz tayini,
artık gaz tayini, gaz bileşim analizi ve kısa analiz gibi deneyler yapılmıştır. Sonrasında
bu deney sonuçları birbirileri ile ilişkilendirilmiş ve bu ilişkilendirmelere göre
havzalarda gerçekleşmiş olan kömürleşme süreci, farklı gaz bileşiklerinin hangi şartlar
altında oluşmuş olabileceği, bu sürecin hidrojeolojik aktivitelerle bağlantısı, ortaya
çıkan tablonun muhtemel kömür madenciliği sürecinde olabilecek iş güvenliği yönleri
ve kömür yatağı metanı üretimi gibi diğer açılardan değerlendirilmiştir. Bu
değerlendirmelere göre gaz bileşimi verilerinin dağılımının saçılımlı ya da
kümelenmiş hallerinin, havzada farklı damarlar arasında gaz geçişi olduğu ve
çatlaklar, hidrojeolojik durum vb. altyapısını hazırlayan faktörler olduğu görülmüştür.
Bu sebepler ve gaz oluşumunun son dönemlerinde etkin faktörlere göre, kömürün gaz
içeriğinin belirli bir bileşik ile doğru ya da ters orantıya sahip olabileceği ortaya
konulmuştur. Çalışmaların yapıldığı havzalarda gaz içeriklerinin azot ile negatif, etan
ile pozitif ilişkili olarak değiştiği görülmüştür. Bunlarla beraber azot ve karbon
monoksit gazlarının hangi şartlar altında oluşmuş olabileceği açıklanmıştır. Kömürün
ve yan kayaçların gaz içeriğinin bir çok farklı gaz molekülünden oluştuğu anlaşılmış
ve buradan hareketle yeraltı madenlerinde, galerilere gönderilmesi gereken hava
miktarının bu bileşiklerin hepsinin sınır değerleri gözetilerek belirlenmesi gerektiği
sonucu ortaya çıkmıştır. Kömürün gaz içeriğindeki bu bileşikler, aynı zamanda
kömürün kendiliğinden yanmasını izleme amaçlı kullanılan yangın oranlarını
hesaplarken kullanıldığı için, kömürün gaz içeriği bu oranları saptırmaktadır. Bu
çalışmada kömürün gaz içeriğinin yangın oranlarına etkisini gidermek için
denklemlerde iyileştirmeler yapılmış ve elde edilen denklemler açıklanmıştır.

Abstract:
Coal seam gases, particularly methane, have significance in energy industry. One
aspect of this is the health and safety concerns of mining operations performed in order
to produce coal. Gas content of the seams may cause methane explosions that is
generally resulted numbers of fatalities in an only one accident if not investigated and
necessary precautions are taken properly. Furthermore, gas and dust outbursts during
mining activities is directly related to gas content of the strata, its origin and generation
process. Also, fire ratios utilized to monitor gob area of longwall mining is produced
by several calculations performed on various gas composition values. On the other
hand, if it is technically and economically feasible, this gas content can be utilized to
produce natural gas that can be used to assist mining activities as energy supply or it
can be sold to the energy market. Today, both coal and natural gas dominate energy
industry in Turkey and in the World. And, it is hard to change these energy sources in
the following decades. Another affect of coalbed methane is environmental results that
even if this methane isn't produced or doesn't cause any mining accident, allowing it
to escape atmosphere means increasing effect of greenhouse gases that methane is far
more effective in causing global warming than carbon dioxide. These issues are
covered in this thesis and basically, gas content and composition of coal seams and
adjacent rock formations are studied.
Gas content of coal seam is generated through coalification process that takes up to
hundereds of million years to be completed. Deposited organic material mostly coming
from plants are become peat due to activities of microorganisms. Methane generation
is started during this process with several other gas compounds. After this stage, the
organic material becomes lignite. As coalification process continues gas content of the
material increases. Also, carbon content as it is more and more locked in cyclic
compounds and calorific value of coal increses. On the other hand, volatile
compounds, moisture and content of other elements decreases. Then, lignite turns into
bituminous ranked coals and finally, anthracite is formed. Methane generation is
occured in all of these stages. Formation of other gases is occured depending on
biologic activity, geologic factors, temperature and stress conditions. Some of formed
gas content can be deposited in coal seam and rest of the content migrates to other
formations and atmosphere. Because of this process, gas content with variety of
compounds and coal features possess clues concerning coalification of the very basin.
Gas composition of coal gas content is dominated by methane. Carbon dioxide and
nitrogen gases can also be found as dominating compounds. Beside of these, complex
hydrocarbons, hydrogen, helium, carbon monoxide and hydrogen sulfide can be found
in coal seams in trace amounts. Each of these gas compounds is formed in different
conditions. Such as at specific temperature intervals, different gas compounds are
generated. Stress may promote other chemical reactions to occur. And, available
element and compounds in burried organic material determines what sort of gas
molecules can be formed in strata. Gas composition and amount are crucial parts of
this thesis.
The gas content of coal is formed as a result of physical and chemical factors present
during the carbonization process and it is also stored and transported by this way. In
order to investigate gas content and compositions and also relationship between these
gases, two coal basins are selected. These coal basins are located in Alpu/Eskişehir
and Çerkezköy/Tekirdağ in Turkey. The coal seams in both basins show property of
lignite rank with high moisture and volatile content. In this study, the properties of
coal bed methane in terms of geological, occupational safety and gas production are
evaluated. First of all, the process of coal and coal content formation are explained due
to the studies which have been carried out on the world. In experimental studies, the
coal samples are taken from the surface drillings and they are placed into the
desorption canisters as soon as they reached the surface. The obtained samples are
analysed by different methods. Gas emission, residual gas measurement, gas
composition analysis and proximate analysis are realized to investigate the properties
of them.
The methods used during these works are firstly gas content measurement by direct
desorption measurement as gas content is determined in three parts. These parts are
desorbed gas, residual gas and lost gas before specimen is put into desorption canisters.
In this method, lost gas is estimated. Gas concentration determination is applied on
samples taken from desorbed gas. Then, the samples are introduced to a gas
chromatograph which is capable of measure almost whole compounds. Since desorbed
gas samples taken are contaminated with athmospheric air, normalization calculations
are utilized. Proximate analysis experiments are done in order to understand the most
basic properties of the coal basins.
According to the results, Çerkezköy basin is not gassy and Alpu basin coals gas content
is relatively higher. Many gas compunds are found in both fields that methane,
nitrogen, carbon dioxide, ethane and other hydrocarbons, hydrogen, helium and carbon
monoxide in Alpu Basin. Methane and nitrogen are the first and the second dominating
gases in both fields. Although Çerkezköy basins' gas composition is generally similar
and in order, results of Alpu samples are highly scattered with high standard deviation
caused by fracture and hydrogeologic mechanisms.
Gas content is firstly formed in coal seams and transported to close rock formations.
Secondary transport from host back to home might occur via these fractures and
groundwater. A secondary transport provides decreasing effect of gas content of coal
and this interactions' footprints can be found in gas composition of coal and adjacent
rock layers. Due to this, nitrogen ratio has a negative relation with gas content. On the
other hand, ethane is positively correlated with gas content of both basins.
Origin of formation of almost each gas compound, which can be found in coal, is
explained with examples in literature. Formation of less mentioned gas compounds
such as nitrogen and carbon monoxide are explained. Nitrogen gas and ethane are
found in basins showing biogenically generated gas signals. Carbon monoxide
represents strong relation with ethane which can occur starting around hundered
celcius degree with thermogenic gas formation process.
Since many gas compounds are present in the fields, there will be extra criteria for
each gases in order to determine air quantity that should be sent to underground. Also,
concentration of some of the gas compounds present in gas content of coal are used in
calculations of fire ratios which used to monitor oxidation reactions on coal surfaces.
Because of this, fire ratios can be highly misleading that this case is explained and
shown with curves of fire ratios with respect to methane readings. One step further is
improvements on fire ratio equations that based on eliminating coal gas content
sourced gases from readings and recalculating fire ratios.