Institut za rudarstvo i metalurgiju Bor

Preparing a coal layer for the gasification
are consists in making slope and vertical
wells to the surface terrain. To floor
of the coal layer through wells are pipes
set, and contact with middle tube through
which the drill and cementing. Well
through the coal layer is not pipes set. The
bottom of the well is about 0.5 m from the
floor of coal layer. Construction of well
system, wells schedule and their diameter
are determined specifically for each deposit
based on geological characteristics of
the deposit. The formation of the channel
between wells is applied with controlled
drilling with which through layer well a
horizontal well, to the floor of coal layer,
which connects the vertical wells. Fractures
of coal layer are performed using
high pressure air, hydraulic, or fire, to ensure
the passage of air through the pores in
coal. Coal layer is ignite inserting glowing
coke through a well and insufflation of air,
at low pressure or with brener.
During pyrolysis, coal is glowing and
frees resins, oils, lower hydrocarbons and
volatile. Gasification occurs when water
vapor, oxygen, carbon dioxide and hydrogen
react with hot coal.
Methane is a product of pyrolysis and
boost production of its lower temperatures
and higher pressures. The results indicate
that the increased pressure causes the penetration
the pyrolysis through coal layer and
so stimulates gasification process. Carbon
oxidation reactions dominate at lower temperatures
and lower pressures, which leads to
higher carbon dioxide content in the produced
gas and lower heating value. Such
conditions are typical of earlier, relatively
shallow UCG probe.
Basic principles that could be applied
to Aleksinac deposit of oil shale and coal
is that the coal gasification is carried out
with pure oxygen under pressure to 20 bar,
and that the heat obtained by this procedure
is used for reduced of oil shale partially
in floor of coal layer and for the
most part in overlie of oil shale.
The usual procedure for reduce oil
shale is to done gasification of coal or the
solid rest of the processing of reduced of
oil shale products and that gasification
products with its heat made reduced oil
shale in the higher part of the manhole
himself.
Nature is made to Aleksinac deposit
has just such an arrangement (the only
thing that would be favorable is that the
floor oil shale does not exceed the thickness
of coal layer).
The procedure would be as follows:
Gasification of coal layers are released
gasification products CO, H2, CH4 with a
temperature of 700° C and coal layer with
its thickness from 6 m down to thickness
of approximately 0.8 m (depending on the
ash content). As the result, there is a natural
crashing of overlie of oil shale, their
disintegration and prepare for reduce. Hot
products of gasification perform reduce of
overlie oil shale passing through the mass
of disintegrated oil shale. Floor oil shale is
heated with passage of heat.
In the Aleksinac deposits are proposed
gasification with pure oxygen (to obtain
the modified procedure of Linde-Frenkl).
It is proposed modifications to the previous
air cooling using heat obtained by
cooling gas from wells. Gasification with
pure oxygen rather than air, it is suggested
due to the much faster conducting the
process, greater utilization coefficient of
heat and gaseous products to obtain far
greater heat value.
Gasification of coal derived gas and
oxygen with the pressure that normally has
about 16.7 MJ/m 3 enriches the gaseous
products oil shale reduce and reaches a
value of about 20.9 MJ/m 3 . As such, it
belongs to medium caloric gas and can be
No 1, 2010. 54
MINING ENGINEERING