Ind. Eng. Chem. Process Des. Dev. 1980, 79, 289-294
a firm should or should not enter into the manufacture of an existing chemical. To use the procedure, two pieces of information are required: (1) the demand curve for the product; (2) estimates of the annual cost of manufacture. Using the above information, eq 4a and 4b are solved simultaneously and a search over process unit sizes can be performed to find the size that maximizes profit under each market assumption (Cournot's Implicit Collusion). In this manner, a range of process unit sizes along with estimates of market share, price, output, and profits can be determined for the firms. Tables similar to Tables VI1 and VI11 can also be prepared which can serve the process designer as quick, qualitative guides for the characterization of firms' behavior on any specific chemical market that the firm may be considering entering. By means of this procedure, more information is available for the dec:ision-making process without the usual assumptions to estimate market shares and production. Furthermore, the rule-of-thumb procedures so common in setting price are not needed. We cannot conclude from our studies which of the two assumptions, Implicit Collusion or Cournot's, describes better the market behavior of the oligopolistic firms in the chemical process industries. The only way to test the validity of the two assumptions would be to compare their predictions with actual performance for a particular duopoly. To do this, the total cost equation must be derivable from the process technical information and enough price
28s
history must be available to estimate a demand curve at the time of decision. The equilibrium price and industry output plus each firm's market share could then be compared with the actual situation. Of course, such a comparison assumes that the firms behave in an optimal fashion either by analysis or by experience. Acknowledgment The authors would like to acknowledge the financial support provided by the Latin American Scholarship Program of the American Universities (LASPAU), the Chemical Engineering Department of the University of Delaware, and the Universidad Catijlica Madre y Maestra, Santiago, Dominican Republic. The authors are also most grateful for many helpful discussions with Professor Eric Brucker, Dean, College of Business and Economics of the University of Delaware. Literature Cited Bogaert, R., M.ChE. Thesis, University of Delaware, Newark, DE, 1979. Cohen, K. J.; Cyert, R. M. "Theory of the Firm: Resource Allocation in a Market Economy", Prentice-Hall: Englewocd Cliffs, NJ, 1965; p 138. Leftwich, R. H. "The Price System and Resource Allocation", 5th ed.; The Dryden Press: Hinsdaie, IL, 1973; p 9. Miller, R. L. "Intermediate Microeconomics", M&aw-Hill: New York, NY, 1978; p 293. Von Neumann, J.; Magenstern, 0. "Theory of Games and Economic Behavior", Princeton University Press: Princeton, NJ, 1953; Chapter 1. Wei, J.; Russell, T. W. F.; Swartzhnder, M. W. "The Structure of the Chemical Processing Industries", McGraw-Hill: New York, NY, 1979; p 52.
Received f o r reuiew June 26, 1979 Accepted November 26, 1979
Prediction of the Composition of Petroleum Fractions Mohiammad R. Riazi and Thomas E. Dauberl' Department of Chemical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802
Based on the composition of defined hydrocarbon mixtures, an accurate, generalized method is proposed to predict t h e firactional composition of paraffins, naphthenes, and aromatics contained in both light and heavy petroleum fractions. Viscosity, specific gravity, and refractive index of the desired fraction are used as input parameters.
Introduction In prediction of physical and thermodynamic properties of petroleum fractions it is important to determine the proportion of paraffinic, naphthenic, and aromatic hydrocarbons present in the fraction (Huang and Daubert, 1974; Riazi, 1979). Since the composition of petroleum fractions is not usually experimentally determined, development of a reliable method to estimate molecular type analysis is quite necessary. Many methods have been developed to predict the percentage of paraffins, naphthenes, and aromatics in an olefin-free petroleum fraction. The most common procedures are the n-d-llf method and the refractivity-intercept-density method The n-d-M method of Van Nes and Van Westen (1951) for estimating the percentage carbon as aromatic, naphthenic, or paraffinic structure from measured values of density, refractive index, sulfur content, and molecular weight is a set of empirical equations at 20 or 70 "C. 0196-4305/80/1119-0289$01.00/0
The refractivity-intercept-density method of Kurtz et al. (1958) is a triangular graphical relation between percentage carbon as aromatic, naphthenic, or paraffinic; refractivity intercept ( R J ;and density. This method requires that the aromatic percentage must be known. A number of other procedures have been discussed in various sources (Boelhower et al., 1954; Kurtz et al., 1958, 1936,1937; Van Nes and Van Westen, 1951; Waterman et al., 1958). However, all of the existing methods are useful only for high-boiling virgin fractions and are accurate only for data on which the method is based. The main purpose of this work was to develop a general method to predict mole fraction of paraffinic, naphthenic, or aromatic compounds for light and heavy fractions which is not based on the composition of a certain group of petroleum fractions. Development If the mole fraction of paraffins, naphthenes, and aromatics for an olefin-free petroleum fraction are defined as 0 1980 American
Chemical Society
290
Ind. Eng. Chem. Process Des. Dev., Vol. 19, No. 2, 1980
Table I. Values of Characterization Factors in Figure 1 value range hydrocarbon type
M
Ri
VGC
K
I
Daraffin Aapht hene aromatic
331-535 2 4 8-4 29 180-395
1.048-1.05 1.03-1.046 1.07-1 . l o 5
0.74-0.75 0.89-0.94 0.95-1.13
13.1-13.5 10.5-13.2 9.5-12.53
0.267-0.27 3 0.278-0.308 0.29 8-0.362
xp,x,, and x, respectively, three expressions for prediction of these three unknowns can be developed. This requires a set of three independent equations relating xp, x, and x, to each other and some other known parameters. The first equation is the obvious molar balance. xp x, x, = 1 (1)
I
I
I
I
I
I
I Ob
1
A 1
I oa
I
1
I
I
I
I
o a4
0 76
KI
I
I
o
2a
I
I
I
I
12
I I
I
I
I
13
(3)
S - 0.24 - 0.022 log (V, - 35.5) (4) 0.755 in which Vl and V, are Saybolt universal viscosities at 100 and 210 OF, respectively. Equations 3 and 4 give approximately the same value for VGC of a given hydrocarbon. Since in the above equations viscosity is defined as Saybolt universal (SSV viscosity, therefore they cannot be used for light hydrocarbons (approximately M 180). Figure 1 and Table I show a comparison between Ri and VGC with two other characterization factors: Watson K and a factor I proposed by Huang (1977). Parameter I is a function of only refractive index. (5)
From Figure 1 it is obvious that R i and VGC separate paraffins, naphthenes, and aromatics better than either of the other two parameters. Also, Ri and VGC vary over a small range when compared with K and I. This indicates that a single value for Ri, for instance, can characterize Ri values for all paraffins. Data on viscosity, refractive index, and density of heavy hydrocarbons were taken from API Research Project 42 (1962). For heavy ( M > 200) hydrocarbons, average values of Ri and VGC for each homologous hydrocarbon group were estimated. Values of 1.0482,
I I4
I
N
I
I
0 2b
I
11
lpl I L
I
108
El
i
I
I
10
1
I O
N A
9
I
A 0 92
I
I
I
1 1
I
I
A
I
0 30
I 0 32
1
I
I
0 34
1 0 36
Figure 1. Comparison of different characterization factors (see Table I).
1.038, and 1.081 were obtained for the average Ri of paraffins, naphthenes, aromatics, while values of 0.744,0.915, and 1.04 were obtained for the average VGC of paraffins, naphthenes, and aromatics, respectively. By using Kay’s mixing rule, Ri and VGC of an olefin-free petroleum fraction can be obtained by the following equations Ri = 1 . 0 4 8 2 ~+~1 . 0 3 8 + ~ ~1 . 0 8 1 ~ ~ (6) VGC = 0 . 7 4 4 ~+~0 . 9 1 5 ~+ ~1 . 0 4 ~ ~
VGC =
I = - n2 - 1 n2 + 2
I
- 1 VGC
The VGC is defined by Hill and Coats (1928) as 1 0 s - 1.0752 log (VI - 38) VGC = 10 - log (V, - 38)
I
104
I02
+ +
Thus, two more equations are needed. In development of these equations, it is necessary that properties of petroleum fraction be related to the properties of each homologous hydrocarbon group by a mixing rule, the simplest of which is Kay’s rule. Therefore, at least two parameters are needed to develop the two equations. In order to predict the composition of petroleum fractions with reasonable accuracy, fractions are divided into two molecular weight ranges-viscous fractions (200 < M < 500) and light fractions ( M < 200). It should be noted that these molecular weight range values are approximate values. 1. Viscous Fractions. Among different characterization factors proposed in the literature, refractivity intercept (Ri) and viscosity gravity constant (VGC) were chosen for development of the two equations to use with eq 1. In selection of these two parameters, it was attempted to choose a parameter which can best separate different homologous hydrocarbon groups. Refractivity intercept (Kurtz and Ward, 1936, 1937) is defined by d Ri=n- 2
L
c 3 2 N I
I
R,
(7)
A regression of 33 defined hydrocarbon mixtures changes the constants in these equations less than 2%. Various compositions of these ternary systems were used-n-octadecane(P)-2-butyl-l-hexahydrindan(N)-2(ar), 6-dimethyl-3-octyltetralin(A); n-octadecane(P)-1-a-decalylpentadecane(N)-2(ar),6-dimethyl-3-octyltetralin(A); and n-octadecane(P)-9(-as-perhydroindacenylheptadecane(N)-11-a-naphthyl-10-heneicosene(A)-whereP, N, and A refer to paraffin, naphthene, and aromatic, respectively. After regression, eq 6 and 7 become Ri = 1 . 0 4 8 6 + ~ ~1 . 0 2 2 + ~ ~1 . 1 1 ~ ~ (8) VGC = 0 . 7 4 2 6 ~+~0 . 9 + ~ ~1 . 1 1 2 ~ ~
(9)
Ri and VGC equations together with eq 1 can then be solved simultaneously to obtain equations for xp, x,, and x, which can then be used to predict the composition of viscous fractions ( M > 200) if Ri and VGC are known. The final results after simultaneous solution of eq 1, 8, and 9 may be summarized as follows xP = - 9.00 + 12.53Ri - 4.228VGC (10)
+ 2.973VGC
(11)
+ 7.37Ri + 1.255VGC
(12)
X,
= 18.66 - 19.90Ri
X,
= - 8.66
2. Light Fractions. As mentioned earlier for light petroleum fractions the VGC cannot be calculated as defined by eq 3 and 4. It was attempted to define a new
Ind. Eng. Chem. Process Des. Dev., Vol. 19, No. 2, 1980
291
Table 11. Data o n t h e Composition of Light Petroleum Fractions' composition no. 1
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42
M
Tb
d
n
S
102 131 144 120 142 162 227 214 126 129 162 127 157 171 153 127 133 130 127 162 132 161 130 126 166 161 137 130 166 137 133 127 133 165 154 165 157 160 137 133 130 170
196 28 2 321 260 32 2 404 547 535 297 306 39 7 298 385 417 385 29 7 31 5 30 4 29 5 39 2 303 40 5 312 30 0 406 397 329 307 40 5 329 31 6 297 317 40 3 37 2 40 3 38 5 39 2 329 318 307 41 7
0.7322 0.77 33 0.8008 0.7358 0.7586 0.8045 0.8578 0.8433 0.7517 0.7701 0.799 0.769 0.801 0.810 0.786 0.7637 0.762 0.759 0.752 0.788 0.759 0.792 0.763 0.763 0.808 0.806 0.782 0.775 0.805 0.778 0.7740 0.77 0.767 0.786 0.779 0.797 0.7915 0.793 0.7756 0.7711 0.7671 0.799
1.4074 1.4335 1.4436 1.4188 1.4260 1.4444 1.4776 1.4694 1.428 1.434 1.4463 1.433 1.447 1.45 1.444 1.4301 1.435 1.4325 1.427 1.449 1.424 1.45 1.4345 1.4343 1.4485 1.45 1.437 1.4352 1.448 1.437 1.4354 1.4328 1.4365 1.443 1.4398 1.4457 1.444 1.4442 1.4382 1.4356 1.4378 1.4464
0.7365 0.7774 0.8046 0.7395 0.7624 0.8083 0.8616 0.847 5 0.7555 0.7740 0.803 0.7725 0.805 0.816 0.7899 0.7675 0.7658 0.7628 0.7558 0.792 0.7628 0.796 0.7668 0.7668 0.8121 0.8101 0.786 0.7789 0.809 0.7819 0.7779 0.77 39 0.7709 0.7899 0.7829 0.8 0.7955 0.797 0.7795 0.775 0.771 0.8025
v210
XP
Xn
Xa
0.364 0.444 0.525 0.414 0.503 0.739 1.239 1.179 0.464 0.520 0.7 1 0.555 0.75 0.83 0.78 0.535 0.51 0.47 0.458 0.700 0.52 0.74 0.508 0.50 0.79 0.76 0.60 0.55 0.74 0.557 0.530 0.516 0.515 0.753 0.665 (1.43) (1.27) (1.33) (0.92) (0.87) (0.83) (1.55)
0.362 0.397 0.186 0.619 0.593 0.309 0.298 0.388 0.605 0.490 0.375 0.420 0.300 0.260 0.538 0.500 0.665 0.650 0.655 0.580 0.510 0.563 0.656 0.637 0.285 0.295 0.390 0.420 0.365 0.455 0.475 0.510 0.600 0.590 0.600 0.420 0.435 0.425 0.460 0.490 0.500 0.420
0.582 0.396 0.698 0.306 0.308 0.643 0.456 0.415 0.135 0.31 5 0.440 0.390 0.495 0.525 0.181 0.270 0.170 0.170 0.170 0.225 0.395 0.187 0.171 0.174 0.505 0.495 0.415 0.400 0.455 0.350 0.320 0.310 0.150 0.200 0.190 0.405 0.385 0.395 0.320 0.295 0.290 0.410
0.056 0.205 0.106 0.076 0.099 0.048 0.233 0.172 0.260 0.195 0.185 0.190 0.205 0.215 0.281 0.230 0.165 0.180 0.175 0.195 0.095 0.250 0.173 0.189 0.210 0.210 0.195 0.180 0.180 0.195 0.205 0.180 0.250 0.210 0.210 0.175 0.180 0.180 0.220 0.215 0.210 0.170
M = molecular weight; Tb = 50% normal boiling point, F; d = liquid density a t 20 ' C and 1 a t m , g/cm3;n = refractive index at 20 " C and 1 a t m ; v z l O= kinematic viscosity at 210 ' F, cSt. Values in t h e parentheses are kinematic viscosities at 100 O F , cSt. xprx,, x, = inole fraction of paraffin, naphthene, and aromatic. References: no. 1-8: Lenoir and Hipkin ( 1 9 7 3 ) ; no. 9-42: private communication (1977). Values of n for no. 9-42 are calculated using the method suggested in this work (eq 24).
characterization factor for light hydrocarbons to be used instead of VGC and then to develop a series of equations similar to eq 10, 11, ,and 1 2 for prediction of the composition of light petroleum fractions. Specific gravities of light paraffinic and naphthenic hydrocarbons are plotted against the natural logarithm of their kinematic viscosities at 100 O F in Figure 2. An almost linear relationship exists between S and In uloO for paraffins and naphthenes, each with the same slope. The following equations represent the lines for paraffins: S = 0.0332 In vloO + 0.7336 (13) for naphthenes: S = 0.0332 In vloo
+ 0.7853
(14)
These equations can reproduce data within an average deviation of less than 2 % . The new characterization factor for light hydrocarbons may be defined as a function of S and In ulW. V G F = a bS + c In ulW (15) where V G F = viscosity gravity function, new characterization parameter, S == specific gravity a t 60160 O F , vloO = kinematic viscosity at 100 OF,cSt, and a, b, c = numerical
+
constants. Arbitrary values of 0.74 and 0.92 have been chosen for the average V G F of paraffins and naphthenes, respectively. Thus by substituting eq 13 and 14 into eq 15 the constants a, b, and c can be determined and eq 15 becomes
V G F = - 1.816 + 3.4848 - 0.1156 In vloo
(16)
Equation 16 gives the value of V G F for any hydrocarbon or fraction for which its specific gravity and kinematic viscosity a t 100 O F are known. By following the same procedure a correlation relating V G F to specific gravity and kinematic viscosity at 210 O F can be derived
V G F = - 1.948 + 3.5358 - 0.1613 In vzl0
(17)
in which vzlo is kinematic viscosity at 210 O F in centistokes. Equations 16 and 17 which are similar to eq 3 and 4 give almost the same value for V G F of a hydrocarbon or petroleum fraction. Using eq 16 and 17, average values of V G F for light paraffins, naphthenes, and aromatics are 0.74, 0.92, and
292
Ind. Eng. Chem. Process Des. Dev., Vol. 19, No. 2, 1980
ln(kinematic
V I S C O I I ~ ~ )0 1
100' F
Figure 2. Viscosity-gravity relationship. Table 111. Data o n t h e Composition of Viscous Petroleum Fractions" composition
M 233 248 267 281 305 245 28 2 325 403 265 297 523 250 394 253 364
no. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
M
d
n
S
0.9082 0.9360 0.9568 0.9 67 1 0.9742 0.8497 0.8709 0.8845 0.9001 0.8319 0.8425 0.8750 0.8912 0.8664 0.877 0.907
1.5016 1.5212 1.5366 1.5452 1.5492 1.4719 1.4842 1.4919 1.5002 1.4637 1.4694 1.4865 1.4896 1.477 1.4838 1.5142
0.9119 0.9397 0.9605 0.9708 0.9779 0.8535 0.8746 0.8883 0.9046 0.8357 0.8463 0.8760 0.8939 0.87 0.88 0.936
Tb
569.6 620.0 652.4 688.4 724.4 582.2 648.8 717.2 798.2 614.6 675.8 937.0
-------
----
----
VI, 48.2 66.7 111.1 203.1 516.5 43.2 58.7 108.8 336.0 45.5 59.4 463.0 60.6 155.4 54.6 680.5
XD
Xn
Xa
0.341 0.304 0.309 0.318 0.329 0.584 0.565 0.584 0.590 0.700 0.694 0.784 0.105 0.720 0.580 0.102
0.459 0.430 0.370 0.340 0.322 0.318 0.307 0.289 0.280 0.227 0.224 0.133 0.639 0.250 0.340 0.455
0.190 0.226 0.321 0.342 0.349 0.097 0.128 0.128 0.130 0.073 0.081 0.083 0.256 0.030 0.080 0.443
molecular weight; Tb = normal boiling point, O F ; d = liquid density a t 20 " C and 1 atm, g/cm3;n = refractive index at 20 ' C and 1 atm; S = specific gravity at 6 0 / 6 0 F; V,, = Saybolt Universal Viscosity at 100 F, SSU. References: no. 1-11: Van Nesand Van Westen ( 1 9 5 1 ) ; no. 1 2 : Witco ( 1 9 7 3 ) ; no. 1 3 : P e n n z o i l ( l 9 7 5 ) ; no. 14-16: A.S.M.E. (1953). a
=
Table IV. Results of Prediction of t h e Composition of Light Petroleum Fractions abs dev," mole fraction no. of data source oils Lenoirand Hipkin industrial company total
molwt range
8
100-230
34
126-171
42
100-230
" Absolute deviation = Xpred N = number of data points.
Xn
XP
Rirange
VG F range
xprange
range
av
bias
max
av
bias
max
1.0411.051 1.0441.055
0.7871.06 0.8270.950
0.190.62 0.260.66
0.300.65 0.130.53
0.039
-0.023
-0.125
0.043
-0.003
0.093
0.033
-0.010
-0.095
0.04
0.019
0.114
1.0411.055
0.7870.95
0.190.66
0.130.65
0.034
-0.012
-0.125
0.041
0.015
0.114
-
Xn
x e x p ~max ; = maximum deviation; av = ( l / N ) z :Ideviationl; bias = ( l / N ) x d e v i a t i o n ;
1.12. Average values for Ri of paraffins, naphthenes, and aromatics are 1.046, 1.04, and 1.066, respectively. Therefore, Ri and VGF for a petroleum fraction can be estimated by Ri = 1 . 0 4 6 + ~ ~1 . 0 4 + ~ ~1 . 0 6 6 ~ ~ (18)
V G F = 0 . 7 4 ~+ ~0 . 9 2 ~+ ~1 . 1 2 ~ ~
(l9)
Physical properties of 45 light defined hydrocarbon mixtures were estimated using the composition of the mixture, properties of components from API Reseach Project 44 (1978), and Kay's mixing rule. After regression of eq 18 and 19 with the compositions of the 45 defined hydrocarbon mixtures and solution simultaneously with eq 1, the following expressions were derived for xP, x,, and x,.
Ind. Eng. Chem. Process Des. Dev., Vol. 19, No. 2, 1980
xP = - 23.94 X, X,
+ 24.21Ri - 1.092VGF
+ 0.627VGF
(21)
+ 15.22Ri + 0.465VGF
(22)
= 41.14 - 39.43Ri = - 16.2
(20)
The above equations can be used to predict the composition of an olefin-free petroleum fraction if Ri and VGF are known. Equations 20, 21, and 22 are similar to eq 10, 11,and 12 for composition prediction of viscous fractions. Since refractive indices of petroleum fractions are not always known, it is important to predict refractive index with a good degree of accuracy in order to estimate the refractivity intercept from eq 2. Huang (1977) correlated molecular weight to boiling point, refractive index and density as follows
M = 7.7776
X 10-67- 2.11971-2.089d b
(23)
where M = molecular weight, T b = normal boiling point, OR, d = density at 20 "C and 1 atm, g/cm3, and I = characterization factor defined in eq 5 . By rearranging eq 23 and 5, the following correlations for prediction of refractive index of petroleum fractions were derived.
M S 200: I = 3.583 x 10-3Tb1.0147(M/d)-0.4787(24a) 1%
=
(-)+ 21 1 1-I
where n = refractive index at 20 " C , Tb = 50% boiling point at 1 atm, O R , h4 = molecular weight, and d = liquid density at 20 "C and 1 atm, g/cm3. Equation 24 can predict refractive index of light ( M < 200) fractions within an average deviation of about 0.5% while for heavy fractions the error is abfout4-5%. For heavy fractions, a correlation similar to eq 24 can be derived by use of data available on refractive indices of heavy hydrocarbons in API Research Project 42 (1962). After regression of data, the following equation was derived
M 2 200: I = 1.4 X r,i =
10-3Tb1.0u(M/d)-0.3984
(-)+ 21 1 1-I
The equations can predict refractive indices of heavy petroleum fractions within an average deviation of 0.2%.
Evaluation of the I?roposed Correlations Tables I1 and I11 show experimental data on the composition of light and heavy petroleum fractions from various sources. All physical properties necessary to use the proposed correlations are also given. Equations 20, 21, and 22 were used to predict the composition of the light ( M < 200) fractions listed in Table 11. A summary of results is given in Table IV, and point-by-point evaluations are available. Average deviations of 0.03 and 0.04 mole fractions were obtained for xp and x,, respectively. Similar results for heavy fractions are shown in Table V using eq 10, 11,and 12 for prediction of the composition of the fractions listed in Table 111. Average deviations of 0.018 and 0.01 mole fractions for xp and x,, respectively, were obtained. The results are generally better than those of existing methods such as the n-d-M method. Table VI shows a comparison of the use of experimental vs. predicted compositions as input to enthalpy and viscosity prediction methods. As shown, predicted compo-
293
294
Ind. Eng. Chem. Process Des. Dev. 1980, 19, 294-300
Table VI. Comparison of t h e Use of Experimental vs. Predicted Compositions for Enthalpy and Viscosity Predictions
pro pert y liquid enthalpy vapor enthalpy viscosity at 100 " F (light) viscosity at 2 10 F (light) viscosity at 100 F (heavy) viscosity at 210 " F (heavy)
av deva
no. of fractions
exptl compn
pred compn
435 292 38
2.4 Btuilb 3.7 Btullb 2.9%
2.7 Btu/lb 3.5 Btullb 2.8%
38
5.7%
5.2%
10
8.1%
8.5%
10
3.5%
3.5%
a Absolute deviation = predicted property - experimental property. Deviation, % = [(predicted property - experimental property)/experimental property] x 100. av = (l/N) z 1 deviation 1 . iv'' = number of data points.
API Research Project 44, Selected Values of Properties of Hydrocarbons and h a t e a Compounds' , Taoles of Physical and Thermodynamic Properties of Hydrocarbons. A and M Press, College Station, Texas (extant 1978). A S M.E. Research Cornminee on Lubrication, 'Viscosity and Density of Over 40 Luoricating Fluids of Known Composition at Pressures to 150,000 psia and Temperatures to 425 OF ', Report No. 1. 1953. Boelhower. C.. Waterman, H. 1.. J . Inst. Pel., 40. 116 (1954). Hili. J B.. Coats, H. B.. Ind. Eng. Chem.. 20, 641 (1928). huang. P. K.. Ph.D Thesis, Department of Chemical Engineering, The Pennsylvanla State University, University Park, Pa., 1977. hdang. P. K.. Daubert, T. E., Ind. Eng. Chern. Process Des. Dev , 13, 359 (1974). Kurtz. S.S IJr.. King. R. W., Stout. W. J.. Peterkin, M. E., Anal. Chern , 30, 1225 (1958). Kurtz. S. S , Jr., Ward, A. L.. J . Franklin Inst.. 222. 563 (1936). K d z , S. S., Jr.. Ward. A. L., J . Franklin Inst.. 224, 583. 697 (1937). Lenoir. ". M.. Hipkin. H. G., J . Chern. Eng. Data. 18, 195 (1973). Private communications, Witco Chem. Co., 1973. Private communications. Pennzoil Co., 1975. Private communications, Indbstrial Co., 1977. Riazi, M. R.. Ph.D. Thesis. Department of Chemical Engineering, The Pennsylvania State University, University Park, Pa.. 1979. Van Nes, K , Van Westen, H. A.. "Aspects of the Constbtion of Mineral Oils". Elsever PJOiiShing Co.. InC.. New Yorrc, 1951. Waterman. H I , Boehower. C , Cornelissen, J.. Correht;on Between physical Constants and Chemical StrLcture", Elsevier Publishing Co.. Inc.. New York, 1958.
Received f o r rerieu July 23, 19'79 . k e e p r e d December 7 , 1979
sitions do not materially affect the results. Literature Cited American Petroleum Institute (API) Research Project 42, "Properties of Hydrocarbons of High Molecular Weight", American Petroleum Institute (1962).
The Department of Refining of the American Petroleum Institute provided major financial support of this research.
Kinetics of Oxydesulfurization of Upper Freeport Coal D. Slagle, Y. T. Shah,' and J.
B. Josh1
Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 1526 1
The kinetics of the oxidation of pyritic sulfur, organic sulfur, and carbon for the Upper Freeport coal are investigated. Experiments were conducted in a semi-batch manner. The effects of batch time (0-2400 s),temperature (150-210 "C),partial pressure of oxygen (0.69-3.44 MPa), and total pressure (3.44-6.88 MPa) were studied. Two alternate mechanisms have been proposed for the oxidation of pyritic sulfur. In one mechanism the fine pyrite particles are assumed to be uniformly distributed in coal particles and the continuous reaction model was found to hoM where the rate of reaction is second order with respect to pyritic sulfur. In the other mechanism, the pyrite particles are assumed to exist free from coal and the shrinking core model was found to hold where the rate of reaction is controlled by diffusion through ash. Both the carbon oxidation and organic sulfur reactions are zero order with respect to carbon and organic sulfur, respectively. The activation energies for all three reactions agree closely with those reported in the literature.
Introduction The sulfur in coal occurs in three forms: pyritic, organic, or sulfate. Pyrites, classified as compounds with the formula FeS, (where the standard value of x is 2), accounts for the bulk of the sulfur in Eastern coals. Organic sulfur is a broad classification containing any sulfur which is chemically bound to the actual coal matrix. Organic sulfur is the dominant sulfur form in Western coals. Sulfates constitute less than a few percent of the total sulfur in most coals. The direct burning of coal causes the production of noxious sulfur oxides (S0,'s). Presently, control of sulfur oxide emissions is achieved mainly by either stack gas scrubbing or physical coal cleaning techniques. The former process is both expensive and energy intensive. The latter, although relatively inexpensive and simple to operate, is less effective. In fact, depending on the sulfur composition of the feed coal, a plant burning physically pre-cleaned coal 0196-4305/80/1119-0294$01.00/0
may also have to employ flue gas scrubbing in order to meet environmental standards (Trindade et al., 1974). A possible alternative to these processes is chemical coal cleaning, i.e., removal of the sulfur by means of a chemical reaction before burning the coal. There are presently six major chemical coal cleaning methods being developed (Oder et al., 1977). One of the promising processes is the oxydesulfurization process (Friedman and Warzinski, 1977; Friedman et al., 1977). In this process, the sulfur is removed by oxidizing coal in the presence of water. The process is operated at pressures between 1.6 and 10 MPa and temperatures between 150 and 220 "C. Normally air is used as the gas phase. The purpose of this paper is to report a kinetic study for the D.O.E. oxydesulfurization process. Kinetic rate expressions for the inorganic and organic sulfur removal reactions and carbon oxidation reaction for Upper Freeport coal are presented.
0 1980 American
Chemical Society
