Institut za rudarstvo i metalurgiju Bor

Practically, the “in-situ” exploitation
suffers the challenges to protect the
ground water on contamination by the
kerogene oil and other produced gases and
sediments. Promising so called “freezewall”
technology has been tested to isolate
the groundwater from subsurface area
where the “in-situ” process is carried out
until the postproduction and remediation
activities of land is complete. [7]
AIR POLLUTANTS IN THE
OIL SHALE COMBUSTION
The main air pollutants in the oil shale
combustion are nitrogen oxides, sulfur
dioxide, hydrogen chloride and solid particles.
The most harmful gas that is emitted
CO2. Air pollutant concentration in the
exhaust gases primarily depends on combustion
technology and combustion regime,
while the emission of solid particles
is determined by the efficiency of device
for catching the fly ash. Regarding to the
emission of air pollutant, oil shale is characterized
by low content of nitrogen in
organic matter (0.3%), high concentration
of organic sulfur (1.6 to 1.8% in a part that
is accepted as a fuel), high Ca /S ratio (8-
10) and an abundance of carbonate minerals
(16-19% mineral CO2 – in a part that is
accepted as a fuel).
NOx during fuel combustion can be
formed in the following ways: in the reaction
between the nitrogen and oxygen
from the air (thermal NOx), in the reaction
between hydrocarbon radicals and molecular
nitrogen (immediate or rapid NOx)
and nitrogen from fuels. The most important
parameter that affects the amount of
nitrogen oxides in the exhaust gases is
oxygen concentration (high air factor).
The main sulfur component in the oil
shale is calcium. Therefore, in order to
characterize the potential in the process of
sulfur capturing, the ratio Ca/S is used.
Because oil shale contains the alkaline
metals, a part of sulfur is linked with this
component, usually in a form of sulfate.
However, not all alkali metals present in
the fuel converted to sulfate, primarily one
part depends on the volatility of alkali
metals from mineral matter in the combustion
process. Emission of sulfur dioxide
and volume of conversion into vapor from
this part of combusted sulfur, during combustion
of oil shale, depends on many
factors.
Carbon dioxide is classified as a greenhouse
gas. It is formed in the reactions of
combustion the organic carbon and minerals
present in the fuel as carbonates. Full
conversion of organic carbon in CO2 is
possible only in complete combustion. Release
of carbon dioxide from the carbonate
mineral, is determined by the behavior of
fuel mineral in the combustion process.
Combustion technology that is used for fuel
burning does not affect significantly the
effects and quantity of CO2 formation from
organic. Certainly, the combustion technology
has a great impact on emission of CO2
mineral. Concentration of CO2 mineral,
formed by the carbonate compound, is determined
by the conditions of thermal decomposition
of minerals and also by direct
combustion of gaseous components present
in the exhaust gases and minerals that contain
CO2. [4]
EFFECT OF UNDERGROUND
GASIFICATION
Care about the environment is one of
the most important factors that have to be
taken into account when it is accessed to
the process of underground gasification
(UG) and if its impact on the environment
is barely noticeable and very low. The
main product of gasification is gas, although
some by-products remain under
the earth, or used by the conventional
processes or injected back into the layer.
At the same time there are still some significant
impacts that must be taken into
account, in particular, the underground
and above-ground impact. Basically, hydrological,
geological and hydrogeologi-
No 1,2010. 143
MINING ENGINEERING