Technical sciences / 10. Mining engineering.

 

Doctor PhD − Mussin R.A.

Doctor PhD − Achmatnurov D.R.

Student - Kalibekova A.K.

Magister – Zakharov A.M.

 

Karaganda state technical university, Kazakhstan.

 

Thermodynamic substitution methane sorption volume

 

Thermodynamics  sorption processes full differential adsorption is defined as:

the amount of adsorbed methane on coal under a pressure p and temperature T kmol / kg.

The differential relation between isotherms, isobars and isotherms determined by M.M.Dubininu as:

 .

Studying sorption processes in the laboratory can create artificially closed thermodynamic system. The mining conditions at the coal seam degassing or in the process of gassing in mines system of coal-methane is thermodynamically open. Most general thermodynamic characteristic of such systems sorption processes if it is a change of the free energy F (J / mol) for changing the gas content of coal from a1 to a2 (a2> a1)

,

t = T / Tkr: Ta - the critical temperature of the gas. Pcr - critical gas pressure, Pa.

The differential change in the free energy (ôîðìóëà äåëüòà u) system is also called differential adsorption performance Hell, which is equal to the difference between the chemical potentials u gas in the transition from a free state to absorbed. Given that S entropy of the system is related to the chemical potential of the ratio:           

From Figure 1.14, you can define the differential adsorption entropy (kJ / mol).

⁄��-2*R,

The isosteric heat of adsorption on carbon methane Q (J / mol) is:

The work done by one mole of gas in the transition from a free to sorbed state, on the basis of 1.14 is as follows:

Energy balance of sorption process can be represented as

Ek - the kinetic energy of the molecules of gas, J / mol.

U0 - the residual energy of the gas molecules in the sorption amount. J / mole.

From 1.19 to 1.18, and considering expression of Ek

Where i=3 for monatomic gases, i=5 for diatomic, i = 6 for polyatomic gases.

Table 1.7 shows the values ​​of residual energy in the sorption of known volume and common gases and air at pressures from 0.1 to 10 MPa and the temperature ranges characteristic for a reservoir (K0 290-320. By analysis of the gases taken in which T <290K. gases are arranged in order of increasing temperature and reflux.

U0 values ​​vary between -20 (helium) to 9kDZh / mol. (ethylene). The general tendency to increase with increasing U traced reflux temperature but in a number of substances close to each other there are significant deviations.

The probability P of separation of molecules from the surface of the sorbent.

=,

E - activation energy. Eotr - the energy output of the molecule sorption capacity.

The larger the value at the data U T and p, the more dynamically unstable molecules in the sorption volume. Obviously, the amount kst = (p) -1 is a characteristic of their thermodynamic stability. From the data in Table 1.7. gases can be arranged in descending order of their thermodynamic stability or index kst.

In the case of using as control sredst effects of substances having a critical temperature higher reservoir temperatures to determine their position in the sequence (1.22) can be used by the formula:

,

 = pressure of the gas under normal conditions, Pa.

 

Gas

Têèï at 101kPa

i

a

0,1

1,0

5,0

10,0

helium

4,3

3

7892,70

Hydrogen

20,4

5

1132,37

Neon

27,3

3

1337,56

Nitrogen

77,4

5

206,67

Carbon monoxide

81,2

5

190,65

Air

81,2

6

207,86

Fluorine

85,0

5

259,48

Argon

87,5

3

205,96

Oxygen

90,2

5

202,46

Methane

111,6

6

123,55

Krypton

120,2

3

119,89

nitric oxide

121,4

5

198,56

Ozone

161,7

6

127,11

Ethylene

169,2

6

61,74

 

To intensify the gas release from the coal can actually be employed are water, hydrochloric acid and carbonic acid, air, nitrogen.

Rules that determine the choice of the means of control:

- The higher the residual energy of the molecules of a solute in the sorption volume, the less thermodynamic stability

- If there is a mixture of several gases, the advantage in the long gas sorption belongs to a large thermodynamic stability

For comparison, the binding energy of the carbon lattice with molecules of methane, hydrogen chloride and carbon dioxide by converting the Lennard-Jones.

Na-Avogadro's number, mole-1.

C is a constant despersionnogo attraction.

r- distance from the center of the molecule to the penny I sorbate carbon atom lattice

n - the number of summation over the lattice atoms.

 

 

 

 

REFERENCES

 

1 Kolmakow W.A. Metanovydelenie i bor'ba c nim w shachtahh (Methane emission and struggle against it in mines). Moscow: Nedra. 1981. 46-54. (in Russ.)

2 Ajruni A.T. Teorija i praktika bor'by c rudnichnymi gasami na bol'shikh glubinakh (Theory and practice of struggle against mine gas at great depths).  Moscow: Nedra, 1981. 332. (in Russ.)

3 Ajruni A.T. i dr. Pod redakziej G.D.Lidina. Gasoobil'noct' kamennougol'nykh shakht SSSR. Kompleksnoe osvoenie gasonosnykh ugol'nykh mectorozhdenij (Gassy coal mines of the USSR. Integrated development of gas-bearing coal deposits). Moscow: Nauka, 1990.  213. (in Russ.)