Quantitative Raman Spectroscopic Determination of the Composition, Pressure, and Density of CO2-CH4 Gas Mixtures
Table 5
Comparison of the results obtained from Raman spectroscopy and microthermometry.
No.
Raman resultsa
Microthermometry resultsb
Differencec
A (CH4)/A (CO2)
υCH4 (cm−1)
XRaman mol% CH4
PRaman (MPa)
ρRaman (g·cm−3)
Pcal1 (MPa)
ρcal1 (g·cm−3)
Tm (°C)
Th (°C)
XMicroth mol% CH4
ρMicroth (g·cm−3)
Pcal2 (MPa)
ΔX mol%
ΔP (MPa)
Δρ (g·cm−3)
S.1
31.821 ±0.765
2911.342 ±0.006
86.6 ±0.1
50.2 ±0.8
0.345 ±0.003
48.8
0.349
−79.5
−89.1
87.5 ±0.8
0.364 ±0.005
59.6 ±1.1
−0.9
−9.4
−0.019
S.2
24.901 ±0.053
2911.644 ±0.029
83.1 ±0.5
42.2 ±1.2
0.342 ±0.006
41.3
0.345
−75.3
−83.1
82.5 ±1.2
0.398 ±0.006
61.1 ±0.8
0.6
−18.9
−0.056
S.3
12.214 ±0.487
2913.341 ±0.023
70.8 ±1.5
22.4 ±0.8
0.284 ±0.013
20.7
0.301
−67.4
−44.6
70.7 ±0.8
0.286 ±0.001
20.9 ±0.1
0.1
1.5
−0.002
S.4
4.907 ±0.036
2911.464 ±0.008
49.3 ±1.3
46.8 ±0.9
0.569 ±0.012
43.2
0.582
−65.6
−59.8
49.0 ±1.3
0.631 ±0.010
62.8 ±0.3
0.3
−16.0
−0.062
S.5
3.573 ±0.024
2911.469 ±0.008
41.4 ±1.9
46.7 ±0.8
0.636 ±0.017
44.8
0.643
−64.8
−64.2
43.5 ±1.1
0.677 ±0.012
64.3 ±3.0
−2.1
−17.6
−0.041
S.6
1.495 ±0.0011
2911.811 ±0.004
22.8 ±2.1
38.6 ±0.7
0.766 ±0.017
37.3
0.772
−61.7
−24.8
20.9 ±1.0
0.795 ±0.011
39.9 ±1.4
1.9
−1.3
−0.029
aXRaman, PRaman, and ρRaman are determined from equations (1), (4), and (5) based on A (CH4)/A (CO2) and υCH4; Pcal1 is the pressure calculated from XRaman and ρRaman using the GERG-2008 EoS; ρcal1 is the density calculated from XRaman and PRaman using the GERG-2008 EoS. bXMicroth and ρMicroth are obtained from the VX diagram of Thiery et al. [18] based on Tm and Th; Pcal2 is the pressure calculated from XMicroth and ρMicroth using the GERG-2008 EoS. cΔX = XRaman − XMicroth. ΔP = PRaman − Pcal2. Δρ = ρRaman − ρMicroth. Note that all data are measured at room temperature (∼24°C), and the uncertainty is provided for 1σ.
