636
Ind. Eng. Chem. PIOcess Des. Dev. 1983, 22, 636-639
VoiattMy of Wyoming Coal Liquids at High Temperatures and Pressures Shuen-Cheng Hwang,+ Grant M. WHoon,t and Conrtantlne Tsonopoulos' Exxon Research and Engineering Company, Florham Park, New Jersey 07932, and Wiffec Research Company, Incorporated, Provo, Utah 84601
The volatility of Wyoming coal liquids has been experimentally determined at 700-850 O F and 1950 psia with a flow apparatus to minimlze thermal decomposition effects at high temperatures. Measurements were made on two liquids produced wlth the Exxon Donor Solvent process from Wyomlng coal, in mlxtwes with H, and methane. VLE data measured in this work were analyzed with a modified Chao-Seader correlation and a modified Rediich-Kwong equation of state. Both VLE correlations are shown to be equivalent in the prediction of the volatility of coal liqu'kb-when a new vapor pressure method is used. Comparison of the ME data on Wyoming coal liquids with those on Illinois coal liquids previously published (wnson et al., 1981) indicates that the coal source apparently has little effect on the volatility of coal IiquMs, provided the liquids have a similar boiling-point distrlbution.
Introduction
The volatility of liquids produced with the EDS (Exxon Donor Solvent) coal liquefaction process from Illinois coal has been reported by Wilson et al. (1981), while the density, viscosity, and surface tension of liquids produced from Illinois and Wyoming coals have been reported by Hwang et al. (1982). Here we will discuss the volatility of liquids produced with the EDS process from Wyoming coal-an extension of our 1981 paper. The EDS Process is being developed by Exxon Research and Engineering Company as a unique cooperative undertaking involving government and industry. Funding and guidance are provided by the following eight Sponsors: U.S.Department of Energy, Exxon Company, U.S.A., Electric Power Research Institute, Japan Coal Liquefaction Development Company, Phillips Coal Company, Anaconda Minerals Company, Ruhrkohle AG, and ENI. An overview of the development is given in a recent publication (Vick and Epperly, 1982). Experimental Procedure and Results
A detailed description of the experimental work was presented in our previous paper (Wilson et al., 1981). As noted there, the accuracy of measured K values (vaporliquid composition ratios) should generally be better than 5%. Measured pressures are accurate to f1%, and measured temperatures are accurate to f l O F . Two Wyoming subbituminous coal liquids produced with the EDS process were studied. These two Wyoming coal liquids are very similar to the Illinois Coal Liquids I and I1 studied in our previous paper (Wilson et al., 1981); that is, they are 400-750 OF cuts. The boiling-point distribution, specific gravities at 60/60 OF, and molecular weights for the two Wyoming coal liquids, as well as those for the three Illinois coal liquids examined in 1981, are summarized in Table I. The VLE (vapor-liquid equilibrium) measurements on the two Wyoming coal liquids with H2and methane are summarized in Table II. The Hzlevel in the charge varied between 0.5 and 1.2 w t %, while the methane/Hz weight ratio was kept at 1.23. Also included in Table I1 are two data points for Illinois Coal Liquid I1 Exxon Research and Engineering Co. Research Co.
1Wiltec
0196-4305/03/1122-0636$01.50/0
Table I. Boiling-Point Distribution, Specific Gravity, and Molecular Weight of Coal Liquids Wyoming coal liquids WA-5
WA-6
Illinois coal liquids
I
I1
111
boiling-point distribution, "F wt % distilled
1 10 30 50 70 90 99 specific gravity (60/60 O F ) molecular weight
350 390 430 478 545 695 805 0.970
350 390 432 488 563 658 735 0.987
167
169
390 404 416 460a 534 658 830 0.972 168
360 392 426 475 528 628 730 0.965
370 404 470 580 722 916 1050 1.055
169
214
a The value was incorrectly reported as 504 "F by Wilson Determined by freezing point depression et al. (1981). of benzene; estimated accuracy is t 3%.
which were inadvertently omitted from our previous paper (Wilson et al., 1981). Analysis of Vapor-Liquid Equilibrium D a t a
Two correlations were used in the analysis of the VLE data. Detailed description of these two correlations is given by Wilson et al. (1981). The first one is a modified Chao-Seader method, while the second, referred to by the initials RKJZ, is the Joffe-Zudkevitch modification of the Redlich-Kwong equation. The binary interaction constants, Cij's, for the RKJZ correlation are given by Wilson et al. (1981). As in the 1981paper, the analysis of the VLE data with Chao-Seader and RKJZ was carried out with two correlations for the vapor pressure of coal liquid fractions: the MB (Maxwell-Bonnell) correlation and the new method proposed by Wilson et al. (1981). Volatility of Coal Liquids. The vaporization or volatility of coal liquids at reactor conditions is a key VLE calculation in a coal liquefaction process. It is important, therefore, that volatility be predicted reliably. The volatility of coal liquids has been expressed in terms of the overall weight fraction vaporized. Since H2 and methane have a much smaller molecular weight than the coal liquids, the overall weight fraction vaporized essentially 0 1983 American Chemical Society
Ind. Eng. Chem. Process Des. Dev., Vol. 22, No. 4, 1983 637
Table 11. VLE Measurements on H,-CH,-Coal Liquid Mixtures charge, wt %a
t,O F
a
P, psia
H,
CH4
CH4/H, ratio
wt K values
wt fraction
vaporized
H*
CH4
0.1243 0.1655 0.3419
44.85 22.58 12.05
28.57 15.02 8.68
700 775 850
1950 1950 1950
1.154 0.949 1.119
Wyoming Coal Liquid WA-5 1.421 1.23 1.169 1.23 1.377 1.23
700 775 850
1950 1950 1950
0.725 0.548 0.852
Wyoming Coal Liquid WA-6 0.893 1.23 0.674 1.23 1.049 1.23
0.0666 0.0653 0.2280
46.05 34.24 11.91
34.78 26.33 8.71
1.13 1.72
Illinois Coal Liquid I I b 1.60 1.42 2.45 1.42
0.213 0.302
30 .O 34.2
18.7 20.5
77 5 1950 775 1950 The balance is the coal liquid.
These data were inadvertently omitted from our previous paper (Wilson et al., 1981).
Table 111. Volatility of EDS Coal Liquidsa Wyoming coal liquids (6 points) method Modified Chao-Seader vapor pressure Maxwell-Bonnell new method RKJZ vapor pressure Maxwell-Bonnell {new method
{
a %
dev = 100
X I
0.4
-
total (24 points)
%avdev
%bias
%avdev
%bias
%avdev
%bias
25.4 7.6
+ 24.5 + 2.1
20.9 12.8
+1.60 -1.4
22.0 11.5
+18.4 -0.5
6.0 8.3
+4.9 -8.2
13.8 12.5
+0.1 -9.6
11.9 11.5
+ 1.3 -9.3
(calcd - exptl)/exptl; % av dev = ( l / N ) x i I(% dev)i I; N = no. of data points; % bias = ( l / N ) Z i ( %dev)i. I
I
ExperimmBl 0 WA-5 0 WA6 Pmdiclims ----C-S Wtm MuuOll.BOnndl
I
/
/
/
1
/
0 WA-5 0.4
- _ _Predictions --
-
N
N
B
0
$
0.3-
1
"
'
Exprlmental
0
n
$
Illinois coal liquids (18 points)
0 WA.6 RKJZ With Maxwell.Banmll
RKJZ With New Method
/
/ o
0.3 -
z
z
0 U
4
E
Y
0.2 -
~
c
0.2
-
0.1
-
I
0
z
P
$ 0.1
-
00 7M
800
0
TEMPERATURE, 'F
Figure 1. Analysis of vaporization data (P= 1950 psia) for Wyoming coal liquids with modified Chao-Seader.
Figure 2. Analysis of vaporization data ( P = 1950 psia) for Wyoming coal liquids with RKJZ.
represents only the volatility of the coal liquids. The experimental volatility of Wyoming coal liquids and comparisons with Chao-Seader and RKJZ predictions are shown in Figures 1 and 2. The corner in the isobars for both coal liquids is due to the variable H,level in the feed: 1.15 (700 OF), 0.95 (775 OF), and 1.12 wt % (850 O F ) for WA-5, and 0.73 (700 O F ) , 0.55 (775 O F ) , and 0.85 wt % (850 O F ) for WA-6. As shown in Figure 1, the Chao-Seader with the MB vapor pressure correlation overpredicts the experimental data, especially a t 850 OF. When the MB procedure is replaced by the new method, the predicted volatility is lower and is in better agreement with experimental data. The average deviation at 850 OF is reduced from 47% to 13%. Figure 2 shows the comparison of the experimental data with RKJZ predictions. RKJZ fits the experimental data
much better than Chao-Seader-when both use the MB correlation. When the MB procedure is replaced by the new method, the overall deviation increases slightly, but RKJZ now underpredicts the volatility of both Wyoming coal liquids. A summary of the predictions for the weight fraction vaporized or the volatility of EDS coal liquids is given in Table 111. For all 6 points on the Wyoming coal liquids, it is shown that, when the MB vapor pressure procedure is used, RKJZ is markedly superior to Chao-Seader: 6.0 vs. 25.4% average deviation in the predicted weight fraction vaporized. However, replacement of MB by the new vapor pressure method brings the deviations obtained with the two VLE correlations together: 8.3% with RKJZ vs. 7.6% with Chao-Seader. Comparison of all 24 points on both Illinois and Wyoming coal liquids indicates that RKJZ with either MB or the new vapor pressure procedure
638 Ind. Eng. Chem. Process Des. Dev., Vol. 22, No. 4, 1983 Table IV. K Values of H, in EDS Coal Liquids" Wyoming coal liquids (6 points) %avdev %bias
method modified Chao-Seader vapor pressure Maxwell-Bonnell new method RKJZ vapor pressure Maxwell-Bonnell new method See Table 111.
Illinois coal liquids (18points) %avdev %bias
total
(24points) %avdev
%bias
28.6 27.1
-28.6 -27.1
30.2 29.3
-30.2 -29.3
29.8 28.7
-29.8 -28.7
26.6 13.5
-26.6 -10.9
27.7 19.7
-25.7 -1 1.2
27.4 18.1
-25.9 -11.1
Table V. K Values of Methane in EDS Coal Liquids" Wyoming coal liquids (6 points) method modified Chao-Seader vapor pressure Maxwell-Bonnell new method RKJZ vapor pressure Maxwell-Bonnell new method
1
a
Illinois coal liquids (18points)
%avdev
%bias
%avdev
11.3 10.1
-10.0 -8.9
17.5 17.9
27.9 14.2
-27.9 -13.7
24.8 16.8
total
(24points)
%bias
%avdev
%bias
-8.7 -8.3
16.0 16.0
-9.0 -8.5
-24.5 -1 1.1
25.6 16.1
-25.4 -11.7
See Table 111. 1w 90
c
I
0 WA-5
OWA6
_-__ c.s
Predictions
-
Predictions
----C.S
RKJJWith New MerhDd
I
-RKJZ]
With New Method
7w
775
*F
76
80
'7 * R 1
84
Figure 3. K values of H2in Wyoming coal liquids at 1950 psia.
is generally equivalent to Chao-Seader with the new vapor pressure procedure, but is clearly superior to the ChaoSeader/MB combination. K Values of Lights in Coal Liquids. Experimental K values of H2and methane in Wyoming coal liquids are shown in Figures 3 and 4, along with the predictions with Chao-Seader and RKJZ, both using the new vapor pressure method. At 775 O F , the experimental K values of H2 and methane in WA-6 are probably in error since they are higher than those in WA-5 by a factor of 1.6. Both RKJZ and Chao-Seader generally underpredict the K values of H2and methane. A summary of the predictions of the K values of H2and methane in EDS coal liquids is given in Table IV and V, respectively. I t indicates that the results with RKJZ were significantly improved when the MB procedure was replaced by the new vapor pressure method. However, replacement of MB by
7.6
84
80
88
104 T
'
Figure 4. K values of methane in Wyoming coal liquids at 1950 psia.
the new method has no effect on the predictions of K values of light gases with Chao-Seader, which works better for methane than for H2. Effect of H2on Volatility of Coal Liquids. The effect of H2on the volatility of coal liquids is shown in Figure 5. Experimental data on weight fraction vaporized for Illinois Coal Liquids I and I1 and for Wyoming Coal Liquids WA-5 and WA-6 are plotted as a function of weight percent H2charged. As mentioned earlier, the boilingpoint ranges for these four coal liquids are very similar; roughly, they are 400-750 O F cuts. The curves are the calculated volatilities with Chao-Seader and RKJZ, both with the new vapor pressure method. This comparison suggests that the experimental result on Illinois Coal Liquid I1 at 850 O F with 0.855 wt % H2charged is most likely in error. Figure 5 also indicates that the coal source
Ind. Eng. Chem. Process Des. Dev. 1983, 22, 639-645
.
0.50
0,45
I
I
I
parison of the Chao-Seader and RKJZ predictions with experimental data on Wyoming coal liquids reported here has confirmed the conclusions reached for Illinois coal liquids (Wilson et al., 1981). In predicting the volatility of coal liquids, RKJZ with either MB or the new vapor pressure method is generally equivalent to Chao-Seader with the new method, but is clearly superior to the Chao-Seader/MB combination. In predicting the K values of light gases, replacement of MB by the new method improves the RKJZ prediction significantly but has no effect on Chao-Seader. More data are needed to better establish the temperature dependence of the H2and methane K values. The experimental data on both Illinois and Wyoming coal liquids indicate that the coal source apparently has little effect on the volatility of VLE behavior of coal liquids, provided the coal liquids have a similar boiling-point distribution.
I
ExwrimmUi (P = 1950 p i i d 775 860
- 700 OF
0.40
I
-
0
OF
+
'F
0 Ill. COIl
Liq. I
111. Coil Liq. Ii
Pndictloni
0.30
-
0.25
-
0.20
-
0.15
-
639
Acknowledgment James R. Freeman and Richard S. Owens of Wiltec Research carried out the experimental measurements. 00
0.25
0.50
075
100
125
150
175
WEIGHT % H2 CHARGED
Figure 5. Effect of H2on vaporization of coal liquids.
apparently has little effect on the volatility or VLE behavior of coal liquids, provided the liquids have a similar boiling-point distribution. Conclusions The study of the volatility of EDS coal liquids has been extended to liquids produced from Wyoming coal. Com-
Registry No. Hydrogen, 1333-74-0;methane, 74-82-8. Literature Cited Hwang, S. C.; Tsonopoulos, C.: Cunningham, J. R.; Wilson, G. M. I n d . Eng. Chem. PrOcessDes. D e v . 1982, 21, 127. Vlck, G. K.: Epperly, W. R. Science 1982, 217(4557), 311. Wilson. G. M.: Johnston, R. H.; Hwang, S. C.; Tsonopoulos, C. I n d . Eng. Chem. Process D e s . D e v . 1981, 20, 94.
Received for review October 18, 1982 Accepted March 24, 1983
Cyclohexane Dehydrogenation for Thermochemical Energy Conversion George 8. DeLancey, Suphan Kovenklioglu; Arthur B. Ritter,+ and James C. Schneidert Stevens Institute of TechnoicqY, Department of Chemistry and Chemical Engineering, Hoboken, New Jersey 07030
A study of cyclohexane dehydrogenation to benzene and hydrogen at atmospheric pressure and in the temperature range of 533-589 K was carried out with the objective of obtaining rate data to be used in the design and evaluation of a reactor system for energy collection and conversion in a thennochemical cycle. An internal recirculation reactor was employed. External gradients were observed at higher reaction rates. A reaction mechanism where the rate-determinlng step is the A-Q shllt of the adsorbed cyclohexene was found to be more suitable in correlating the rate data than a mechanism where the dissociative adsorption step is rate controlling. Side reactions which were found to be minor over the range of experimental conditions were attributable to impurities in the cyclohexane feedstock. No loss in catalyst activity was observed.
Introduction The economic and efficient storage of thermal energy is intimately linked to the solution of the critical international problem of diminishing availability of traditional energy ~~~s and the utilization of new ones, such s o h 'University of Medicine and Dent&,vin New Jersey, Newark, NJ.
* Lummus Company, Bloomfield, NJ.
0198-4305/83/1122-0639$0 1.50/0
and nuclear, for meeting the daily demands of industrial and domestic users. One attractive alternative is thermochemical storage systems (Mar and Bramlette, 1978). These systems are based upon the controlled utilization of highly energetic chemical reactions which are reversible over the temperature range of interest. The endothermic reaction is driven by the energy source, which defines the upper limit of the temperature range, and the thermal energy is recovered from the exothermic reaction at the energy sink, which defines the lower limit of the temper0 1983 American Chemical Society
