618
Ind. Eng. Chem. Process Des. Dev., Vol. 18, No. 4, 1979
A plot of log (Ai/Ao)vs. i yields a straight line with slope
The value of kd can be determined by comparing the slope of the curves when different cycles Bc are used. Nomenclature A = number of moles of solid in the reactor A. = initial value of A A , = value of A following the ith pulse B = defined as (1 - n).k-Wo/q c = concentration of reactive gas at the outlet of the reactor co = concentration of reactive gas at the inlet to the reactor c, = actual concentration of reactive gas in the reactor E, = dimensionless error on the value of the rate constant, d u z /avg(k) i = index for the ith pulse j = index for the jth product K, = relative response factor of the jth component k = reaction rate constant k d = rate constant for the decomposition reaction k, = lower bound on k k , = upper bound on k M = a bivalent metal m = number of values of k , averaged No = Avogadro number N , = number of active sites per unit area (assumed constant) n = order of reaction PI, = number of moles of the product j produced in the ith pulse q = flow rate of carrier gas R, = specific rate of conversion, defined by eq 38 r, = rate of reaction as measured in the ith pulse r = rate of formation of the jth product in the ith pulse = area of a peak when a pulse of magnitude Wo is injected and no reaction takes place sa = specific surface area S, = area of peak of unreacted reactive gas (ith pulse) S, = area of peak of the jth product from the ith pulse ST= area of peak of reactive gas of magnitude W, t = time ti = injection time of the ith V = specific molar volume of the reactive gas go= number of moles of gas injected in each pulse
&
W , = number of moles of reactive gas that will react stoichiometrically with W , Wi = number of moles of gas that leave the reactor unreacted in the ith pulse W , = number of moles (or grams) of solid placed in the reactor and available for reaction X = defined by eq 34 Greek Letters 0 = stoichiometric coefficient y = defined by eq A4 6 = a constant which assumes the value 1when there is a pulse in the reactor and 0 when there is not e = a small dimensionless constant C#J. = A J A o fraction of solid left unreacted after ith pulse u* = standard deviation 0, = cycle period Literature Cited Armstrong, V., Himms, G. W., Chem. Ind., 543 (June 10, 1939). Attar, A,, "The Fundamental Chemistry and Modelllng of the Reactions of Sulfur in Coal Pyrolysis", paper presented at the AIChE Meetlng, Houston, Texas, March 1977. Attar, A., Fuel, 57,201 (1978). Bertrand, M. F., British Patent 462 934 (1937). Bragg, L., Claringbull, G. F., "Crystal Structures of Minerals", p 127, Corneil University Press, Ithaca, N.Y., 1965 Furusawa, Y., Suzuki, M.,Smith, J. M., Catal. Rev., 13,44 (1976). Glund, W., Keiler, K., Klempt, W.. Bertehorn, R., Ber. Ges. Kohlentech., 3,211 (1930). Greenwood, N. N., "Ionic Crystals, Lattice Defects and Nonstoichiornetry", . .p 40, Butterworths, London, 1970. Levenspiel, O., "Chemical Reaction Engineering", p 338 Wiley, New York, N.Y., 1962. Parks,-G. D., "Mellons Modern Inorganic Chemistry", p 390, Longmans, London, 1961. Pell, M., Graff, R . ,A,, Squires, A. M., pp 151-157 in "Sulfur and SO, Developments", Chem. Eng. Prog. Tech. Manual", 1971. Powell, A. R. Ind. f n g . Chem., 13,33 (1921). Ruth, L. A., Squires, A. M., Graff, R. A,, "Desulfurization of Fuels with Calcined Dolomite", presented at the 161st National Meeting of the Amerlcan Chemical Society, Los Angeles, Calif. March 1971. Ruth, L. A., Squires, A. M., Graff, R. A,, Environ. Sci. Techno/., 6, 1009 (1972). Squires, A. M., Int. J . Sulfur Chem. Part E , 7(1), 65 (1972). Stinnes, G. M., British Patent 371 117 (1930). Szekely, J., Evans, J. W., Sohn, H. Y., "Gas-Solid Reactions", Chapters 2-4, Academic Press, New York, N.Y., 1976. Thiessen, G., "Forms of Sulfur in Coal", Chapter 12, p 475 in "chemistry of Coal Utilization", H. H. Lowry, Ed., Wiley, New York, N.Y., 1945. West, J. R., Chem. Eng. Prog., 44(4), 298 (1948).
Received f o r review October 31, 1977 Accepted March 31, 1979
Prediction of Phase Equilibria in Sour Natural Gas Systems Using the Soave-Redlich-Kwong Equation of State Katherine A. Evelein and R. Gordon Moore' Deparlment of Chemical Engineering, The University of Calgary, Calgary, Canada T2N 1N4
A modified Soave-Redlich-Kwong equation of state, which utilizes empirical binary interaction parameters in the mixing rules for the a and b coefficients, has been used to correlate complex phase behavior for mixtures of hydrocarbons and nonhydrocarbons. The correlation has been shown in a previous article to predict complex phase behavior associated with the systems hydrogen sulfide-water and carbon dioxide-water. This paper presents an extension of the previous study to predict complex phase behavior such as azeotropism and three phase equilibria for light hydrocarbon systems containing the nonhydrocarbons nitrogen, carbon dioxide, and hydrogen sulfide. Interaction parameters are presented for all the binaries considered.
Introduction Natural gases containing substantial quantities of the acid gases hydrogen sulfide and carbon dioxide are the norm rather than the exception for Canadian gas fields. 0019-7882/79/1118-0618$01.00/0
Equilibrium coefficient correlations presently available to the plant designer have often been found to be inadequate for prediction of the phase behavior of fluids containing more than 2 or 3 mol YO hydrogen sulfide. I n this work 0 1979
American Chemical Society
Ind. Eng. Chem. Process Des. Dev., Vol. 18, No. 4, 1979
Table I. Sources of Binary Data Used to Fit Interaction Parameters
R2Tci2
a ( T ) = 0.42747 -[I + mi(1 -
Pci
conditions binary
temp, K
data source
H2S-CO,
Sobochinski and Kurata
H2S-N,
Robinson and Besserer
4137
344
17 237
278 283
12 411 1575-2790
324
2758
273 278 222 311 172 171.4 29 8 283
11663 6895
m, = 0.480 + 1.574~0, - 0.176~0, (4) The mixing rules employed were u = EE (1 - ~ , , ) x , x , ( u ~ ~ , ) ~ ~ (5)
(1959) 11972)
I
Reameret al. (1951a) Robinson and Kalra
H,S-CH, H2S-C2H,
Gilliland and Scheeline
C0,-N, CO ,-CH, C0,-C ,H6 CO,-C,H, N2-CH, N,-CH,
Zenner and Dana (1963) Robinson e t al. (1959) Hamam and Lu (1954) Reamer e t a1 (1951b) Cines e t al. (1953) Chang and Lu (1967) Schindler e t al. (1966) Price and Kobayashi
CH,-C,H,
2
3
8
Reamer e t al. (1950) Matschke and Thodos
344 333
all 4137 4482 a11 13 790 5516
(1 - C , , ) X J , ( ~+, b,)/2
(6)
N
C [biE- yic)2 + (xiE E=
5860 4137
(1962)
a correlation of phase equilibrium based on Soave’s (1972) modification of the Redlich-Kwong equation of state will be presented. It can be applied with confidence to fluids with large concentrations of carbon dioxide, hydrogen sulfide, and nitrogen. Attention will be given to mixtures of nitrogen, carbon dioxide, hydrogen sulfide, methane, ethane, and propane; the method can be extended to mixtures containing heavier hydrocarbons or other acid gases such as sulfur dioxide. The E q u a t i o n of S t a t e Soave’s equation has been shown by West and Erbar (1973) to yield accurate predictions of hydrocarbon phase behavior. Robinson et al. (1976) utilized a binary interaction parameter in the “a” coefficient of the equation in developing a correlation for the water content of sour natural gases. Evelein et al. (1976) introduced a second interaction parameter into the “b” coefficient of the equation in order to describe the phase behavior of the hydrogen sulfide-water and carbon dioxidewater binaries. The correlation utilizing two interaction parameters is demonstrated in the present work to reproduce the phase behavior of ordinary paraffin mixtures and also to predict “complex” phase behavior, such as azeotropism and three phase equilibrium, that occur in acid gas mixtures. The Redlich-Kwong equation of state is
where, for any pure component i bi = 0.08664 RT,i/P,i
1 1
where k,, and C,, are empirical binary interaction parameters. A two-parameter search routine was used to determine k,, and C,, which minimized the function
(1959)
CH4-C3H8
CC
b=
(1940)
N7,-C3H8
1
and
(1974)
H2S-C,H,
(TRi)0,5)]2(3)
and
pressure, kPa
289
(2)
T h e correlation for a ( T ) proposed by Soave (1972) was used, where, for any pure component i
1=1
(7) N Initial estimates of the interaction parameters for each binary pair were obtained by matching the vapor and liquid compositions a t a single condition (Table I). This condition was normally the maximum temperature and pressure for which data were given. The fitting procedure involved selecting a number of values of k, and determining for each k,,the value of C which resulted in the minimum value of E. The k , ana C,, values which provided the best fit for the one condition were then further refined. This involved perturbing the interaction parameters to provide the best overall graphical match of the experimental data. Initial attempts to use a statistical two parameter search routine for all of the data were not successful due to the highly nonideal phase behavior exhibited by many of the systems considered in this study. Interaction parameters for the binary systems are presented in Table 11. It would appear for systems not involving carbon dioxide that a trend exists between the value of the interaction parameter and the molecular structure. These trends were not utilized in this study. It was also noted that the accuracy of the fit over the complete data range could have been further improved by utilizing temperature-dependent interaction parameters. This procedure was not pursued as it was not considered to be desirable from a computational viewpoint. B i n a r y Phase Behavior The incorporation of two binary interaction parameters in a phase behavior simulator based on the SRK equation of state generally increases the accuracy over that which can be obtained with no interaction parameters. Table I11 presents a comparison between values predicted using the modified SRK simulator and the experimental data of Reamer et al. (1951b) for the carbon dioxide-propane binary at 278 K (40 O F ) . Also included are values predicted assuming the interaction parameters are zero (no interaction parameters). When no interaction parameters are used, the largest difference between the experimental and calculated compositions is approximately 0.08 mole
Table 11. Binary Interaction Parameters kij
component H,S H2S 0.00 CO, N, CH4 C2H6
C3%
kij
CO,
N,
CH4
C,H6
0.07 0.00
-0.03 -0.13 0.00
0.03 0.20 0.11 0.00
0.08 0.00 0.03 0.05 0.00
619
C,H,
H,S
CO,
N2
0.24 0.16 -0.06 0.08 0.05 0.00
0.00
-0.04 0.00
-0.10 -0.10 0.00
CH4
-0.07 0.12 0.12 0.00
‘ZHS
0.00 0.19 0.00 0.05 0.00
0.25 0.03 -0.11 0.06 0.07 0.00
Ind. Eng. Chem. Process Des. Dev., Vol. 18, No. 4, 1979
620
Table 111. Effect of Interaction Parameters on t h e Phase Boundaries for the Carbon Dioxide-Propane Binary a t 278 K mole fraction propane vapor phase
liquid phase
without interaction
pressure, kPa
exptl
689 1034 1379 1724 2068 2413 2758 3103 3447
0.7944 0.5324 0.3964 0.3136 0.2659 0.2124 0.1691 0.1312 0.0898
with interaction
exptl
0.7999 0.5339 0.3971 0.3123 0.2545 0.2105 0.1743 0.1410 0.1047
0.9753 0.9116 0.8398 0.7598 0.6684 0.5639 0.4468 0.3286 0.2044
0.8214 0.5199 0.3873 0.3018 0.2420 0.2076 0.1802
without interaction
with interaction
0.9675 0.8895 0.81 51 0.7306 0.6393 0.5877 0.5242
0.9735 0.9073 0.8382 0.7648 0.6853 0.5969 0.4954 0.3760 0.2375
Table IV. Effect of Interaction Parameters o n the Bubble Point Curve for the Carbon Dioxide-Hydrogen Sulfide Binary
H,S vapor phase mole fraction
bubble point pressure, kPa
9653
temp, K
ZH,S
exptl
with interaction
293.2 294.3 299.8 305.4 310.9 316.5 322.1 327.6 333.2 338.7
0.100 0.156 0.356 0.505 0.626 0.720 0.800 0.860 0.914 0.959
5516 5516 5516 5516 5516 5516 5516 5516 5516 5516
5416 5358 5253 5218 5185 5181 5164 5214 5255 5336
without interaction
exptl
with interaction
without interaction
5521 5508 5521 5547 5551 5557 5516 5518 5480 5463
0.075 0.112 0.245 0.352 0.440 0.522 0.604 0.695 0.790 0.891
0.073 0.112 0.246 0.352 0.453 0.548 0.646 0.735 0.828 0.915
0.081 0.123 0.263 0.366 0.458 0.544 0.635 0.720 0.813 0.905
I
9 653
8 2 7 ~
I
8214
DATA CF REAMER ET AL
4
.
DATA OF REAME'I €TAL
6895
6895
-
5516
; 4137 Y Y)
2758
1379
0
L
I
c
c2
03
04
LlOLE
05
06
07
08
09
0
02
01
04
03
fraction propane. This difference is reduced to 0.03 mole fraction when interaction parameters are used. Table IV presents bubble point pressures and vapor compositions as calculated for various temperatures and liquid compositions for the carbon dioxide-hydrogen sulfide binary. The experimental data are the 5516 kPa isobar presented by Sobochinski and Kurata (1959). The difference between the experimental and calculated bubble point pressure is less than 1% when interaction parameters are used and greater than 6% for no interaction parameters. It is interesting to note that the vapor compositions are more accurate a t low pressures when no interaction parameters are used. This is due to the fact that the interaction parameters for this binary were chosen to provide a match of the bubble point pressure. Figures 1 to 5 present comparisons of predicted and experimental phase boundaries for a number of binary systems. Figure 1 provides a comparison between the experimental data of Reamer et al. (1950) and the calculated values for the methane-propane system at 311 K (100 O F ) . The accuracy of the prediction is seen to de-
06
07
08
09
IO
MOLE FRACTION C3H8
FRACTION C H q
Figure 1. Pressure-composition diagram for the methaneepropane binary at 311 K.
05
Figure 2. Pressure-composition diagram for the carbon dioxidepropane binary at 311 K. ".,
I
I $
1
I
DATA OF REAMER ET AL DATA OF KOHN AND KURATA
0
I
/-\*
4
Y
8274
E 5516
2758
0
0
1
1
01
02
I MOLE
03 FRACTION
04
1 05
1 06
cn4
Figure 3. Pressure-composition diagram for the hydrogen sulfide-methane binary at 311 K.
generate as the critical pressure is approached. No attempt was made to continue the calculations into the critical
Ind. Eng. Chem. Process Des. Dev., Vol. 18, I
DATA OF ROBINSON AND BESSERER
.
t7237r f
1i
;,
I I
i
i 4
1
1 01
02
03
04 MOLE
05 06 FRACTION N2
37
06
09
IO
Figure 4. Pressure-composition diagram for the hydrogen sulfide-nitrogen binary at 278 K. 4826
1
I
No. 4, 1979 621
Table V. Calculated Bubble and Dew Point Pressures for the Propane-Hydrogen Sulfide Binary a t 2758 kPa
-
exptl bubble or dew point pressure equal t o 2758 kPa bubble point ZC,H
0.10 0.1610 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90
dew point
__
pressure, temp, K kPa temp, K
pressure, kPa
2760 2757 2761 2774 2777 2770 2759 2730 2711 2747
2787 2752 2768 2741 2715 2699 2720 2748 2777 2791
310.3 310.3 310.6 311.7 313.4 315.8 319.3 323.7 329.5 337.5
310.7 310.3 311.0 313.6 317.5 321.9 326.9 331.9 337.0 341.2
Table VI. Calculated Bubble and Dew Point Pressures for the Propane-Hydrogen Sulfide Binary at 4137 kPa exptl bubble or dew point pressure equal to 4137 kPa bubble point
0
01
32
C3
04
MOLE
05 06 F R 4 C T ON N p
07
OB
09
10
Figure 5. Pressure-composition diagrams for the nitrogen-methane binary at 126, 156, and 172 K.
region due to the excessive time required for convergence a t these conditions. Figure 2 gives the carbon dioxide-propane pressurecomposition diagram a t 311 K (100 O F ) . Excellent agreement is noted over the range of compositions studied. The 311 K isotherm pressure-composition diagram for the methane-hydrogen sulfide binary is shown in Figure 3. The experimental data are taken from Reamer et al. (1951a) and Kohn and Kurata (1958). Very good overall agreement is again observed. Figure 4 presents the pressure-composition diagram a t 278 K (40 O F ) for the hydrogen sulfide-nitrogen binary as reported by Robinson and Besserer (1972). The predicted composition of the hydrogen sulfide rich phase shows excellent agreement with the experimental data. A departure from the experimental composition of the nitrogen rich phase is observed for increasing pressures. Pressure-composition diagrams for the nitrogenmethane binary are given in Figure 5. The experimental data a t 126 K (-233 O F ) , 156 K (-180 O F ) , and 172 K (-150 O F ) were reported by Cines et al. (1953). Good overall agreement is observed a t the three temperatures studied. Additional data are available for the nitrogen-methane system (Stryjek et al., 1974a); however, these data were not utilized in this work. Three binary systems which display positive azeotropes were considered in this study. The binary systems considered were ethane -hydrogen sulfide, ethane-carbon dioxide, and propane-hydrogen sulfide. Because the compositions of the liquid and vapor phases are similar throughout the two-phase region, dew point pressure and bubble point pressure calculations were used in preference
ZC-H.
temp,K
0.10 0.1315 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90
329.7 329.6 330.0 331.6 333.8 336.8 341.0 346.0 352.3 360.0
dew point
pressure, kPa temp,K 4173 4167 4174 4200 4209 4198 4181 4131 4094 4100
330.0 329.6 330.8 333.2 336.9 341.5 346.3 353.0 356.8 362.4
pressure, kPa 4205 4167 4202 41 56 4109 4084 4067 4209 4102 4130
to the flash routine. The algorithms used were those described by Evelein (1976). Pressure composition diagrams at 228 K (-49.4 O F ) , 255 K (-0.1 O F ) , and 283 K (50.3 O F ) are presented for the ethane-hydrogen sulfide binary in Figure 6. The experimental data are taken from Robinson and Kalra (1974) and Robinson et al. (1975). Excellent agreement is observed between the pressure and composition of the azeotropes a t the two lower pressures. A t the highest temperature, 283 K, the azeotropic pressure is too low by 103 kPa (15 psi) and the calculated range of the azeotropic composition differs from the experimental value by approximately 0.07 mole fraction. Figure 7 gives the pressure-composition diagram for the ethane-carbon dioxide binary a t 243 K (-22 O F ) and 222 K (-60 O F ) . The experimental data of Hamam and Lu (1974) and Fredenslund and Mollerup (1973) are predicted with errors in the calculated bubble point pressure of less than 2 70. Calculated vapor compositions differ from the experimental values by less than 0.01 mole fraction. Tables V and VI present comparisons of calculated dew point pressures for the propane-hydrogen sulfide binary a t experimental pressures of 2758 kPa and 4137 kPa, respectively. The calculated pressures reported in both tables differ by less than 2% from the experimental data of Kay and Rambosek (1953). Table V shows that at the experimental pressure of 2758 kPa (400 psia), the bubble and dew point pressures calculated a t the experimental azeotropic condition differ by 5.5 kPa (0.8 psi). For the experimental pressure of 4137 kPa as given in Table VI, the calculated bubble and dew point pressures are equal a t the experimental azeotropic temperature. The vapor composition calculated at this condition is 0.1206 mole fraction propane which is 0.0016 mole fraction greater than
622
Ind. Eng. Chem. Process Des. Dev., Vol. 18, No. 4, 1979 3447
I
1
I
T.243
K
1793
0
02
04 06 MOLE FRACTION CZH6
08
10
Figure 6. Pressure-composition diagrams for the hydrogen sulfide-ethane binary.
the calculated liquid composition. Estimation of the maximum two-phase temperature or cricondentherm was attempted for a nitrogen-ethane mixture containing 0.4982 mole fraction ethane. The calculations were carried out using a dew point pressure routine and are compared to the experimental data of Eakin et al. (1955). Figure 8 shows that the lower dew point pressure could be calculated to 266.7 K (20.3 OF) but that no lower dew point pressures could be calculated to 267.2 k (21.3 O F ) . Hence, the cricondentherm for this mixture is predicted to exist between these temperatures. This agrees well with the experimental value of 266.2 K. Attempts to calculate the upper dew point curve were less successful. The calculated upper dew point pressures are greater by 1034 kPa (150 psi) to 2068 kPa (300 psi) than the experimental values. Further data on the nitrogenethane system have been reported by Stryjek (1974b). These data were not utilized as the above calculations were performed prior to their release. Reamer et al. (1950) presented data concerning the maximum pressure and temperature states for the methane-propane binary. They reported a cricondentherm of 305 K (88.7 O F ) and a cricondenbar of 10053 kPa (1458 psia). Calculations to predict the cricondentherm and cricondenbar resulted in values of 307 K (92.3 O F ) and 11300 kPa, respectively. The binaries methane-hydrogen sulfide and nitrogenethane display three-phase liquid-liquid-vapor equilibria near the critical temperature of methane and nitrogen, respectively. Three-phase equilibria conditions have been reported by Kohn and Kurata (1958) for the methanehydrogen sulfide binary and by Yu et al. (1969) for the ethanenitrogen binary. Three-phase conditions calculated using the method of Evelein et al. (1976) are compared with the experimental values in Tables VI1 and VIII. Very
02
04 06 MOLE FRACTION C2H6
08
IO
Figure 7. Pressure-composition diagrams for the carbon dioxide-ethane binary. Table VII. Three-phase Temperatures for Methane-Hydrogen Sulfide Binary temp, K pressure, kPa
exptl
calcd
3447 4137 4826
183
186 193 199
193
Table VIII. Three-phase Pressures for Nitrogen-Ethane Binary pressure, kPa temp, K
exptl
calcd
122.0 128.9
2603 3578
2648 3640
good agreement was obtained in both cases. Multicomponent Systems Vapor-liquid equilibria were calculated for the ternary systems methane-ethane-propane, nitrogen-methanecarbon dioxide, nitrogen-methane-ethane, and methane-hydrogen sulfide-carbon dioxide. Figures 9 and 10 provide comparisons between calculated composition and the experimental values reported by Price and Kobayashi (1959) for the methane-ethane-propane system a t 283 K (50 OF). Figure 9 shows that the predicted vapor compositions are in good agreement with the experimental values up to pressures of 5516 kPa (800 psia) and acceptable agreement a t pressures to 8274 kPa (1200 psia). As shown in Figure 10, predicted liquid phase compositions are in good agreement at pressures to 5516 kPa but exhibit significant deviations a t 8274 kPa. Experimental (Sarashina et al., 1972) and calculated equilibrium coefficients for the nitrogen-methane-carbon
Ind. Eng. Chem. Process Des. Dev., Vol. 18, No. 4, 1979 13 79C
12411
1 -
DATA
OF
EAKIN E T A L
0
'\'
b@$\ 100 % PROPANE
A
-A .
I I 032
.. .. .. .
9 653
a -
623
0274
1
6895
8274 kPa
a
6 8 9 5 LPa
5516 LPO
VI VI
Y L
a
4137
5516
tP0
100%ETHANE
1 0 0 % METHANE
Figure 10. Liquid phase compositions for the ternary methaneethane-propane at 283 K (data of Price and Kobayashi, 1959).
4137
--i
2 750
200
211
222
233
244
TEMPERATURE
255
266
277
I K)
Figure 8. Dew point pressure curve for a mixture of 0.4982 mole fraction ethane.
-
DATA OF SARASHINA : ET AL
i
i 01
I
-col !
01 02 03 MOLE F R 4 C T l O N METHANE IN V4POUR
Figure 11. Individual component K values for the nitrogenmethane-carbon dioxide ternary at 273 K and 8108 kPa. 00
I
loo x
METHANE
100 % ETHANE
Figure 9. Vapor phase compositions for the ternary methaneethane-propane at 283 K (data of Price and Kobayashi, 1959).
dioxide system a t 273 K (32 O F ) and 8108 kPa (1176 psia) are presented in Figure 11. The predicted K values for methane and carbon dioxide are in good agreement with the experimental values over the range of compositions studied. Nitrogen K values show good agreement a t low methane vapor fractions but the error increases as the concentration of methane in the vapor increases. The overall agreement is sufficient for most engineering calculations. The data of Robinson and Bailey (1957) for the ternary system methane-hydrogen sulfide-carbon dioxide a t 311 K (100 O F ) and 8273 kPa (1200 psia) are compared with the experimental values in Figure 12. The overall agreement is acceptable for most engineering calculations. Figure 13 presents equilibrium coefficients for nitrogen, methane, and ethane, respectively, in a ternary mixture
-
i
-
-
01
DATA W R081NSON A N D B A I L E Y
-I
624
Ind. Eng. Chem. Process Des. Dev., Vol. 18, No. 4, 1979 I
50
!
'
l
~
l
I
l
I
I
/
l
c
'.'
fL 2 05 '
O
01
F
. .- .
'
METHANE
DATA ff CHING AND LU
*
1379 kPa
+
2068kR 2725kk
a
.
0 5 1
,
ETHANE
.
3
~
C , = b coefficient interaction parameter k , = a coefficient interaction parameter P = pressure Pci = critical pressure of component i R = gas constant T = temperature Tci = critical temperature of component i xi = mole fraction of component i zi = mole fraction of component i in the mixture wi = acentric factor Superscripts E = experimental C = calculated
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Received for review December 5, 1977 Accepted March 31, 1979
The financial support of the National Research Council of Canada, the University of Calgary, and the Province of Alberta Graduate Scholarship is g r e a t l y appreciated.
