Dew and Bubble Points of Simulated Natural Gases MARIO H. GONZALEZ and ANTHONY 1. LEE Institute of Gas Technology, Chicago, 111. 60616
Experimental dew and bubble points and densities of the saturated phase envelopes for 10 simulated natural gas samples are presented. The effect of helium on the phase behavior of natural gases is also illustrated.
THIS
s t u d y was undertaken t o obtain d a t a on t h e physical properties of natural gases a t cryogenic conditions. T h e gases tested are multicomponent mixtures representing one lean a n d one rich natural gas. T o provide a means of isolating the efTect of the various components on the physical properties of natural gas, each natural gas was investigated as a series of compositions. A mixture of nitrogen, m e t h a n e , ethane, a n d propane was prepared initially in t h e same ratio as in the natural gas, from which a complete set of test results was obtained. B u t a n e was t h e n added, a n d its effect on the properties of natural gas was studied. T h e pentanes were t h e n added a n d so on, u p t o heptane. I n this way, the properties of the mixtures were studied. APPARATUS T h e a p p a r a t u s used for this work is a modified version of a phase equilibria cell described before ( I , 2 ) . A schematic flow diagram is presented in Figure 1. T h e equilibrium cell is presented in Figure 2. As shown in Figure 1, sample fluid is stored in a 3-liter reservoir ( B ) a n d compressed b y t w o 250-cc. Jerguson gages (C, D).Mercury lines run from t h e b o t t o m of t h e gages t o a high-pressure mercury injection p u m p ( G ) a n d a 3-liter mercury reservior ( E ) . T o avoid stratification, multicomponent samples are mixed by a recirculation p u m p
by a copper coil, through which a regulated a m o u n t of liquid nitrogen flows, and by a heating element regulated by a Bailey temperature controller. T h e thermostatic fluid is stirred with a squirrel-cage fan driven by a n electric motor. T h e arrangement permits control of t h e t e m p e r a t u r e to within i 0 . 0 5 ' F . of t h e set point. T h e temperature of t h e bath, assumed t o be t h e same a s t h a t of the sample in t h e glass cell a t equilibrium, is measured b y a calibrated copper-constantan thermocouple. T h e thermocouple was calibrated against a p l a t i n u m resist a n c e thermometer a t 50°F. intervals over t h e range of +100" t o -320' F . T h e p l a t i n u m resistance thermometer used is a Rosemount engineering temperature s t a n d a r d with calibration traceable t o NBS. T h e e.m.f. produced by the thermocouple is balanced with a Leeds a n d K o r t h r u p K-2 potentiometer with a reference cold junction kept a t 32°F. T h e s t a t e of balance is shown by a Leeds a n d S o r t h r u p T y p e E deflection galvanometer. T e m p e r a t u r e s can be accurately read t o within =0.04' F. Dew a n d bubble points are determined visually in a borosilicate glass cell. T h e fluid inside the cell is agitated by raising a n d lowering a n enclosed steel ball with a U magnet. Densities of t h e dew and bubble point fluids are calculated from the calibrated volume of t h e glass cell a n d t h e a m o u n t
(F)(8).
-STIRRER D R I V E N B Y ELECTRIC M O T O R
T h e pressure measurements are obtained from a 2000p.s.i. Heise gage (H)t o within + 2 p.s.i. a n d from a 5000p.s.i. dead-weight tester (K)t o within =0.1 p.s.i. T h e Heise gage was used t o obtain approximate values of t h e experimental pressure, a n d the dead-weight tester was used to determine t h e exact value of this pressure. T h e measurements were made through the mercury separator ( J ) with a sensitivity exceeding t h e i O . l p.s.i. sensitivity of t h e dead-weight tester. A correction was made for t h e hydrostatic head of t h e oil in t h e 2-foot line from t h e separator t o t h e dead-weight tester. Thermostatic conditions for t h e observations are achieved by placing t h e phase cell ( & I inside a 2.5-gallon Dewar flask containing a fluid-usually isopentane or propanekept a t a constant temperature. T e m p e r a t u r e is controlled Figure 1 . Schematic of dew and bubble point apparatus A Vocuum pump B Somple fluid reservoir C Jerguson g o g e D. Jerguson g a g e E . Mercury reservoir F . Magnetic p u m p G. Mercury injection p u m p
H. 1.
J. K.
Heise g o g e Seporotor Deod-weight tester
VENT TC ATMOSPHERE
VAPORIZING
GRADUATED G L A S S CELL COPPER TUR BINE TUBE
M
*-~-
_.
S E TL-. . ;r
BALL
d , 2
Figure 2. Equilibrium cell, low-temperature bath assembly
T O G P S CHPROE
CYLINDER
--grr1 P---~
Table I. Quality of Material Used
Components Nitrogen Methane Ethane Propane n-Butane n-Pentane Hexane Heptane
Purity, Mole 99.99 99.95 99.97 99.90 99.91 99.98 99.0 99.0
Source Matheson Matheson Phillips 66 Phillips 66 Phillips 66 Phillips 66 Phillips 66 Phillips 66
Grade Prepurified Ultra-Pure Research Research Research Research Pure Pure
Phose cell o n d thermostat
172
JOURNAL OF CHEMICAL AND ENGINEERING D A T A
of gas displaced a t t h e t e m p e r a t u r e a n d pressure of t h e Jerguson gage. T h e quality of t h e material used is presented in T a b l e I. EXPERIMENTAL T h e mass spectrographic analysis of t h e gases studied in t h e dew a n d bubble point a p p a r a t u s is shown in Table 11. Figure 3 shows comparison of t h e envelopes of t h e 0 48
a,,
-260 -260
-240
-2m
-zM
-1w
-lW
-iY,
-120
-It0
TEMPERATURE,
.80
.60
-40
-20
0
+PO
0 $0
OF
E
:
Figure 3. Dew and bubble points for natural gas samples Nos. 1, 2 , 3, and 4
028
p 0
-
0 60
0 I5
0 IO
-HE FEGIOhS INDICATED CORRESPONO TO SAMRE N O , OPEN SYMBOLS SAWRATEO viiP0R CLOSED SYMBOLS SATURaTEO LIQUIO
0 55
0 50
0 05
_t(
0
0 45
TEMPERATURE *F
E 040
Figure 6. Saturated vapor-liquid densities for natural gas samples Nos. 7, 8, 9, and 10
Y >. 035
-
Y)
--
030 8000 25 7000 20
-_
600
,
5w
i
0 15 0 10
-
-
7
-
i
: _ _ -
-
~
0 05
0
TEMPERATURE..F
Figure 4. Saturated vapor-liquid densities for natural gas samples Nos. 1, 2, 3, and 4
-
2w--
1 280
-
,
260
240
220
2m ill0 TEMPERATURE
IM
-40
120
-00
OF
Figure 7. Two-phase envelopes for samples Nos. 1 and 5 I100 1000
900 6
0
0
1
L
+
-
-
1
A -
I800
* w.TOO Q 3
600
v,
E 500 &
400
300
200 100
0 -260
240
220
2 m
W
-60
-40
-120
-ka
gl
.60
TEMPERATURE, *F
Figure 5 . Dew and bubble points for natural gas samples Nos. 7 , 8, 9, and 10 VOL. 13, No. 2, APRIL 1968
-40
2
0 TEMPERATURE,
*F
Figure 8. Dew and bubble points for natural gas samples Nos. 4 and 6
173
Table 11. Analyses of Gas Samples
Sample No.; Mole L c Constituent N He CHI C.H,, C IH.: CIHi, C Hi, CeHIi C-Hi, Total
1
2
3.80 0.07 91.70 4.30 0.04
3.30 0.14 88.70 6.60 1.30
...
... ...
...
3 3.40 0.18 86.80 6.50 2.50 0.65
...
...
... ...
...
...
... -
99.91
100.04
100.03
7 1.50
9
4
5
6
3.40 0.17 86.20 6.40 2.40 0.46 0.09 0.87 0.01 100.00
3.30
3.10
...
...
...
...
...
91.00 5.60 0.12
81.40 11.10 1.80 0.26
95.90 2.60 0.01
95.00 2.60 0.78
94.50 2.60 0.81 0.52
...
...
100.02
2.30 ... 99.96
1.60
10 1.40
1.60
...
...
...
...
...
...
94.30 2.70 0.74 0.49 0.10 0.27
99.98
100.03
100.00
...
... ... ... ...
...
100.01
...
... ...
8
...
~
Table Ill. Experimental Dew and Bubble Points for Natural Gas Samples
Dew Points Press., p.s.i.a.
Temp., F.
14.0 55.1 98.1 151.3 158.8 159.8 165.0 211.6 299.6 455.5 635.5 738.0 747.0 751.2 769.7 763.8"
-200.0 -180.0 -160.0 -150.0 -147.5 -146.0 -145.0 -140.0 -130.0 -114.0 -104.3 -103.2 -103.8 -103.9 -104.7 -106.0
54.2 150.0 342.3 421.4 487.7 534.7 571.7 630.4 782.2 804.7 810.7 859.2 892.2 884.2 878.4 877.6 877.2 873.2 871.7 873.2 86'7.2 868.4 864.4 871.7 879.7 875.7 872.2 869.7 860.2 849.7 840.T
-120.0 -100.0 -80.0 -81.2 -78.3 -76.0 -75.0 -73.5 -73.4 -75.0 -75.0 -77.0 -80.0 -81.0 -81.7 -81.9 -81.9 -83.0 -85.0 -85.6 -80.0 -81.0 -82.0 -83.0 -83.0 -84.0 -85.0 -87.0 -89.0 -92.0 -93.9
Bubble Points Density, Press., g./cc. p.s.i.a. SAMPLE1 0.004 738.0 0.026 656.5 0.050 608.8 0.068 512.5 0.068 445.0 0.063 337.5 0.067 245.0 0.083 236.5 0.098 231.0 0.142 240.2 0.186 251.2 0.200 348.0
Dew Points
Temp., F.
Density, g./cc.
Press., p.s.i.a.
Temp., F.
-110.0 -125.0 -130.0 -140.0 -150.0 -170.0 -200.0 -210.0 -220.0 -230.0 -240.0 -280.0
0.249 0.282 0.289 0.301 0.316 0.345 0.387 0.397 0.408 0.414 0.424 0.442
190.1 436.9 439.9 628.6 703.3 830.6 903.4 962.9 980.9 994.9 1006.1 1005.4 1008.0 1008.4 1007.4 1000.9 995.6 988.4 957.4 938.4 934.6 930.9"
-60.0
0.206
0.210 0.222 0.234 SAMPLE 2 0.008
0.018 0.050 0.067 0.111 0.121 0.129 0.145 0.194 0.206 0.177 0.208 0.246 0.253 0.255 0.260 0.140 0.205 0.223 0.226 0.216 0.220 0.228
801.9 732.9 733.9 582.1 442.9 303.1 303.1 241.4 270.9 450.9 689.9
-100.0 -110.0 -110.0 -130.0 -150.0 -180.0 -180.0 -210.0 -240.0 -270.0 -280.0
0.324 0.366 0.362 0.426 0.471 0.522 0.537 0.579 0.614 0.652 0.666
0.236
0.260 0.267 0.278 0.294 0.307 0.328 0.325 SAMPLE3
-100.0 45.4 -80.0 82.6 "Critical point.
174
0.002 0.005
875.9 726.4
-90.0 -110.0
0.223 0.272
-40.0 -40.0 -36.0 -36.1 -38.8 -42.0 -47.0 -49.0 -52.0 -55.0 -55.0 -56.0 -56.0 -60.0
-64.0 -68.0 -72.0 -76.0 -78.9 -81.1 -81.3
Bubble Points Density, Press., g./cc. p.s.i.a SAMPLE 3 0.010 0.022 0.033 0.051 0.058 0.070 0.088 0.106 0.114 0.122 0.132 0.124 0.129 0.128 0.138 0.147 0.155 0.159 0.175 0.182 0.187 0.191
507.3 510.3 315.4 269.6 282.4 276.4 368.9 473.8
Temp., F.
Density, g./cc.
-140.0 -140.0 -180.0 -200.0 -200.0 -220.0 -240.0 -260.0
0.325 0.318 0.366 0.386 0.383 0.404 0.421 0.439
-80.0 -90.0 -110.0 -110.0 -130.0 -150.0 -170.0 -200.0 -230.0
0.191 0.265 (3.315 0.298 0.343 0.371 0.397 0.428 0.455
-104.4 -110.0 -110.0 -120.0 -140.0 -160.0 -180.0 -200.0
0.209 0.235 0.235 0.258 0.302 0.329 0.348 0.348
SAMPLE 4 46.4 57.4 74.6 122.6 346.9 373.1 447.9 429.6 476.6 523.6 660.4 784.3 962.6 1076.4 1104.4 1042.3 999.4"
-70.0 -50.0 -20.0 0.0 +16.1 +18.0 +20.0 +21.4 +22.5 +24.0 +23.5 +20.0 +10.0
67.4 123.6 215.9 241.6 434.9 643.9 804.6 781.9 776.4 774.6"
-170.0 -150.0 -130.0 -130.0 -110.0 -100.0 -98.0 -99.0 -100.0 -101.0
0.0
-60.0 -67.0 -75.2
0.002 962.9 0.003 895.9 0.002 747.9 0.006 747.4 0.016 589.9 0.018 444.6 0.025 350.9 0.028 279.3 0.030 302.6 0.033 0.044 0.054 0.074 0.090 0.159 0.167 0.17 SAMPLE 5 0.006 760.1 0.009 721.6 0.016 747.4 0.023 644.9 0.043 475.9 0.074 337.6 0.141 233.6 0.147 152.4 0.154 0.161
( Continued)
JOURNAL OF CHEMICAL AND ENGINEERING DATA
Table Ill. Experimental Dew and Bubble Points for Natural Gas Samples (Contjnued)
Press., p.s.i.a. 45.4 61.4 69.6 112.6 190.4 244.6 277.4 333.4 378.4 419.6 521.9 609.4 649.9 732.9 816.9 816.6 1143.4
Dew Points Temp., Density, OF. g./cc.
-70.0 -50.0 -20.0 0.0 20.0 30.0 35.0 40.0 44.0 47.0 51.0
