RESEARCH OF THERMOPHYSICAL PROPERTIRES OF COAL
FOR IMPROVEMENT OF QUALITY OF YEKIBASTUZ BASIN COAL FIRING
Department of Standardization
and Certification, Eurasian National University, Astana 010008 Kazakhstan,
A. Rakhisheva
Introduction
Coal is the main energy required
for needs of national economy in the Republic of Kazakhstan. Hydroelectric power
stations are mainly situated in the East of country. There are no nuclear power
stations in the republic and now their construction is very problematical in many
countries after Fukusima (Japan) NPP accident. Thus importance of
thermoelectric power stations as the main heat and energy supply rose again
lately in main cities. In this case, obviously, role of coal as the main heat
carrying agent rises and demands increase to its quality.
Main qualities of
coal are characterized by their such thermal properties as calorific value, heat
of formation, heat capacitance, thermal conductivity and temperature
conductivity. It ought to be remarked, that article, devoted to thermal
conductivity and temperature conductivity and to calorific value of Yekibastuz
basin “Severny” different section and different courses coal is essential and timely.
It should be noted, that coal of Yekibastuz is the main fuel not only
for thermal electric power stations of Kazakhstan, but also for South of Russia
and South China [1].
Goal: Next goal is set in article work on the basis of above-stated:
research of Yekibastuz basin “Severny” section different courses coal
thermophysical properties (thermal conductivity and temperature conductivity
and calorific value) by experimental and computational methods.
Scientific novelty.
- Thermal conductivity of
“Severny” section 16 place coal was researched by 
- calorimetric method for the first time;
- Density of “Severny” section
16 place coal was researched by pycnometric method;
- Temperature conductivity of
“Severny” section 16 place coal was calculated;
- 16 place coal firing
enthalpy was experimentally and analytically defined [1-3].
It ought to be specially remarked, if some Kazakhstan`s coal
(Shubarkol, Maikube, Karazhyra coal) have facts on thermal capacity, then thermal
conductivity and temperature conductivity on the example of “Severny” section
coal is being researched in republic for the first time.
Thermal resistance
for each specimen (Ð0) is computed by
formula:
, m2 K/W.
(1)
Thermal conductivity of the
researched material is defined by formula:
, W/ (ñm K). (2)
Experimental results on
thermal conductivity of coal specimens are processed in 298 – 423K interval and
approximated in kind of 
equation, Wt/ (MK) (the table 1).
Table 1. Thermal conductivity 
of temperatures 298,15-426 Ê
|
¹
places |
|
|||||
|
298,15 |
323 |
348 |
373 |
398 |
423 |
|
|
6.8 |
1,0730 |
0,7825 |
0,5820 |
0,4815 |
0,4810 |
0,4805 |
|
5.9 |
0,7480 |
0,6127 |
0,3623 |
0,4829 |
0,4887 |
0,5145 |
|
8.6 |
1,4361 |
0,9728 |
0,7096 |
0,6463 |
0,5831 |
0,6198 |
|
2.3 |
0,9133 |
0,8672 |
0,7872 |
0,8049 |
0,7888 |
0,7926 |
|
4.4 |
0,4675 |
0,2114 |
0,1554 |
0,0995 |
0,2435 |
0,3875 |
|
9.0 |
1,5237 |
1,0522 |
0,7807 |
0,7092 |
0,6377 |
0,7662 |
|
1.0 |
1,3433 |
1,0391 |
0,8348 |
0,7306 |
0,7263 |
0,7220 |
|
6.0 |
1,1418 |
0,8313 |
0,6208 |
0,6103 |
0,5998 |
0,5893 |
|
7.1 |
1,6192 |
1,2169 |
0,9146 |
0,8124 |
0,8102 |
0,9079 |
|
2.8 |
1,4092 |
1,2069 |
1,1047 |
1,0024 |
1,0002 |
0,9979 |
|
4.0 |
0,9618 |
0,7523 |
0,5428 |
0,5332 |
0,5238 |
0,6142 |
|
1.8 |
1,8314 |
1,0641 |
0,6934 |
0,5296 |
0,5624 |
0,6951 |
|
1.0 |
1,2466 |
0,8643 |
0,6821 |
0,4998 |
0,2176 |
0,6353 |
|
5.2 |
2,3459 |
1,7464 |
1,3469 |
1,1475 |
1,0480 |
1,0485 |
Equations of
temperature dependence of coal thermal conductivity in 298,15 – 423K interval are
set out on computer by least squares method, which are listed in table. Further
their densities were defined for thermal conductivity calculation of coal.
It is seen from calculations, that values of thermal
conductivity of most of researched coal is sharply descend from 298,15 K to 423
K. High values of correlation ratios
show certainty of received equations.
Table 2. Equations of
temperature dependence of coal thermal conductivity 
|
¹¹
places |
coefficients of equalization |
Temperatur-es interval, Ê |
Coefficient of correlation,
R |
||
|
à |
â |
ñ.105 |
|||
|
6.8 |
-6,587 |
1,198.10-2 |
3,632 |
298,15-423 |
0,90 |
|
5.9 |
-3,395 |
6,630.10-3 |
1,886 |
298,15-423 |
0,88 |
|
8.6 |
-9,569 |
1,747.10-3 |
5,161 |
298,15-423 |
0,91 |
|
2.3 |
-7,049.10-2 |
1,355.10-3 |
0,518 |
298,15-423 |
0,77 |
|
4.4 |
-9,425 |
1,776.10-2 |
4,083 |
298,15-423 |
0,83 |
|
9.0 |
-11,476 |
2,114.10-2 |
5,958 |
298,15-423 |
0,83 |
|
1.0 |
-6,282 |
1,183. 10-2 |
3,690 |
298,15-423 |
0,96 |
|
6.0 |
-8,401 |
1,558. 10-2 |
4,432 |
298,15-423 |
0,94 |
|
7.1 |
-8,401 |
1,591. 10-2 |
4,479 |
298,15-423 |
0,83 |
|
2.8 |
-3,748 |
7,910. 10-3 |
2,553 |
298,15-423 |
0,72 |
|
4.0 |
-6,101 |
1,162. 10-2 |
3,254 |
298,15-423 |
0,86 |
|
1.8 |
-16,303 |
2,931. 10-2 |
8,342 |
298,15-423 |
0,91 |
|
1.0 |
-9,133 |
1,671. 10-2 |
4,860 |
298,15-423 |
0,88 |
|
5.2 |
-11,119 |
2,002. 10-2 |
6,369 |
298,15-423 |
0,86 |
One of the main thermo
chemical characteristics of coal is their calorific value, which is expressed by heat quantity,
extracted during full combustion of unit of their weight.
Calorific value of
coal may be more exactly defined by experimental method with a help of special calorimeter.
Standardized calorimeters are used for this purpose. Method, standardized in CIS
countries is used for this purpose, based on combustion of fuel hinge in
special calorimetric bomb with hermetically closed tap in atmosphere pressed to
25-30 at of oxygen with following definition of distilled water quantity in
water calorimeter. All terms of experiment and also demands to place were
strictly kept for increase of analysis exactness, where the calorimeter was set
up.
Practical importance. Separate specimens of coal with various compounds of their components were
chosen for definition of coal calorific value. Coal from courses ¹ 8,6 (content
of carbon 57,48%), ¹ 6.0 (ñ=44,63%) and 4
(40,56%) was selected for experiments. Coal calorific value
was defined by GOST 147-54. Matter of method is in combustion of fuel hinge
in calorimetric bomb in the medium of pressed oxygen and quantitative
evaluation of segregated heat at that. On the basis of calorimetric metering it
is found out6 that calorific value of selected coal has the following values:
-21225 (¹8.6) kJ/kg -13623 kJ/kg (¹6.0) and 9443 kJ/kg (¹4.0). The received
results indicate, that absolute values of calorific value descend symbatically
owing to decline of the carbon mass content in composition of coal.
Equation is
received by least squares method, which indicates dependence of calorific value
of coal from percentage content of carbon in coal:
(%,Ñ),kJ/kg
(3)
Thermal firing of
the coal of rest courses are calculated on the basis of received equation.
It have defined
from the received results, that satisfied convergency of experimental and
computing datum on calorific value of
coal of courses (8.6), (6.0) and (4.0) and indicated certainty of equation
reached by us and correctness of values of heat of combustion of coal from
other courses, calculated on the basis of noted equation [4-5].
Scientific results. It is found out, that coal of courses (6.8),
(5.9), (8.6), (9.0), (7.1) and 1,0 (second) have much more calorific values.
It is been
researched for coal of 16 courses of Yekibastuz basin “Severny” section by
experimental and computational methods for the first time:
1. By calorimetric method at 298,15 – 423K interval of thermal
conductivity of coal and took out equations of their temperature dependence.
2. Densities of 16 courses coal was defined by pycnometric method. Research indicated, that coal from
(M.P,2.3) course has maximal density, where the content of carbon is minimal
(16,38%) and ash content is maximal (74,05%).
3. Thermal conductivity of coal was computed with use of experimentally
defined experience datum on thermal capacities, thermal conductivities and
densities.
4. Calorific values of coal were defined by experimental and computing
methods. Equation of calorific value dependence from carbon content in composition
of coal is taken out [4-5].
Recommended: Continue research works for solution of coal extraction question of
recommended courses of Yekibastuz basin.
Research of thermodynamic
and thermophysical properties of coal has important meaning for physical
chemistry of solid fuel for formation of fundamental base of datum by
thermophysical characteristics on level of modern inquiries and data banks. Received results
present practical interest at projecting of chemical procedures of hydrocarbons
processing and present practical interest for physical and chemical simulation of directed transformation of coal of Kazakhstan [5].
Literature
1. Kassenov B.K., Yermaganbet B.T.,
Bekenova N.Å., Rakhisheva A.D. Chemical
and X-ray phase analysis of coal of various courses of Yekibastuz region
“Severny” section. Materials of International SPC “Science and its role in
modern world”, “Bolashak” Karagandy
University, 2011. P. 148-152
2. Kassenov B.K., Yermaganbet
B.T., Bekenova N.Å., Rakhisheva A.D.
Research of thermal capacity and calorific value of coal of various courses of
Yekibastuz region “Severny” section. Materials of International SPC “Science
and its role in modern world”,
“Bolashak” Karagandy University, 2011. P. 152-154
3. Kassenov B.K., Yermaganbet
B.T., Rakhisheva A.D., Bekenova N.Å. Thermodynamic and
thermophysical characteristics of coal of Yekibastuz region “Severny” section. Reporter
of KarSU after Å.À.Buketov. Chemical series, 2011. ¹2.- P. 10-15
4. Kassenov B.K., Yermaganbet
B.T., Bekenova N.Å., Rakhisheva A.D. Thermophysical
properties of coal of various courses of Yekibastuz region “Severny” section.
Materials of International SPC “Heterogenic processes in enrichment and metallurgy”,
dedicated to 75 years of Honoree of RK, corresponding member of NAS RK Zh.N.Abishev.
Karagandy, Chemical and Metallurgical Institute. 2011.P.115-116
5. Rakhisheva À.D. Master’s
dissertation on theme: “Thermal conductivity, temperature conductivity and calorific
value of coal of various courses of Yekibastuz region “Severny” section” Astana,
Kazakh University of Technology and Business. 2011. P.1-59