In the process of coupling disaster prevention and control
of gas
and coal spontaneous combustion in goaf, there is a great contradiction
between the gas drainage and carbon dioxide inerting technology. The
key performance indexes are put forward to solve the coupling disaster,
such as the air quantity of the intake airway (A), the gas drainage
rate (B), the carbon dioxide injection rate (C), and the injection
depth (D). Using the numerical simulation method and the orthogonal
test of four factors and three levels, we establish the coupling disaster
model of the no. 7436 working face in the Kongzhuang coal mine. Using
a combination of the relative membership degree method and range analysis,
the optimal level of each factor is determined, which is A
II
B
III
C
II
D
II
. Furthermore, the distribution
law of the airflow field is obtained under the conditions of different
gas drainage rates and carbon dioxide injection rates. The results
show that the gas concentration decreases with an increase in gas
drainage in the upper corner, but it has little impact on the width
of the oxidation zone. The gas concentration can be reduced to 1%,
while the gas drainage rate is higher than 35 m
3
/min. With
an increase in gas injection rate, the carbon dioxide emission rate
increases in the upper corner, but the width of the oxidation zone
decreases. Also, the gas injection rate should be less than 800 m
3
/h. Moreover, with an increase in injection time in the upper
corner during the injection process, the carbon dioxide and gas concentrations
increase, and the maximum carbon dioxide concentration is 1.3%, and
the maximum gas concentration is 0.42%, which is consistent with the
results of numerical simulations.
The utilization of CO2 is extremely important
to solve
the environmental problems and coal spontaneous combustion in goaf.
There are three kinds of CO2 utilization in goaf: adsorption,
diffusion, and seepage. Since adsorption will consume CO2 in goaf, the optimization of CO2 injection amount is
very critical. A self-developed adsorption experimental device was
used to determine the CO2 adsorption capacity of three
different particle sizes of lignite coal samples at 30–60 °C
and 0.1–0.7 MPa. The factors affecting CO2 adsorption
by coal and its thermal effect were studied. In the coal and CO2 system, the CO2 adsorption characteristic curve
is not affected by temperature, but there are differences in that
with different particle sizes. The adsorption capacity increases with
the increase of pressure, while it decreases with the increase of
temperature and particle size. Under atmospheric pressure, the adsorption
capacity of coal is a logistic function relationship with temperature.
Furthermore, the average adsorption heat of CO2 on lignite
shows that the interaction force between CO2 molecules
has a stronger effect on CO2 adsorption than the effect
of heterogeneity and anisotropy on the coal surface. Finally, the
existing gas injection equation is improved theoretically with CO2 dissipation, which provides a new idea for the work of CO2 prevention and fire suppression in goaf.
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