532
Znd. Eng. Chem. Res. 1991,30, 532-536
Components. Chem. Eng. Sci. 1979,34,951. Gomez-Nieto,M. A. High Pressure Vapor Liquid Equilibrium: The Propane-Ethanol-Acetone System. Ph.D. Dissertation, Northwestern University, Evanston, IL, 1977. Gordon, A. R.; Hines, W. G. (1946) In Vapor-Liquid Equilibrium Data Collection; Gmehling, J., Onken, U., Eds.; DECHEMA: Frankfurt, Germany, 1977; Vol. 1/2a, pp 323-325. Griswold, J.; Wong, S. Y. Phase Equilibria with Acetone-Methanol-Water System from 100°C into the Critical Region. Chem. Eng. Prog. Symp. Ser. 1952, 48 (3), 18. Gupte, P. A.; Daubert, T. E. Extension of UNIFAC to High Presswe Vapor-Liauid Equilibrium Using Vidal Mixing Rules. Fluid Phhse Eqiilib. 1986,28, 155-170 Hall, D. J.; Mash, C. J.; Pemberton, R. C. NPL Rep. Chem. 95, January 1979. Heidemarh, R. A.; Prausnitz, J. M. A Van der Waals-type Equation of State for Fluids with Associating Molecules. Proc. Natl. Acad. Sci. 1976, 73, 1773. Ikonomou, G. D.; Donohue, M. D. Extension of the Associating Perturbed Chain Theory to Mixtures with more than One Associating Component. Fluid Phase Equilib. 1988,39, 129. Jackson, G.; Chapman, W.G.; Gubbins, K. E. Phase Equilibria of Associating Fluids: Spherical Molecules with Multiple Bonding Sites. Mol. Phys. 1988,65, 1. Kay, W. B.; Donaham, W. E. Liquid-Vapor Equilibria in the is0 Butanol-n Butanol, Methanol-n Butanol and Diethyl Ether-n Butanol Systems. Chem. Eng. Sci. 1965,4, 1. Lee, R. J.; Chao, K. C. Local Composition Embedded Equation of State for Strongly Nonideal Fluid Mixturee. Znd.Eng. Chem. Res. 1989,28,1251-1261. Marinichev, A. N.; Suearev, M. P. (1965) In Vapor-Liquid Equilibrium Data Collection; Gmehling, J., Onken, U., Eds.; DECHEMA: Frankfurt, Germany, 1977; Vol. 1/2a, pp 79-81,629. Polak, J.; Murakami, S.; Benson, G. C.; Pflug, H. D. (1970) In Vapor-Liquid Equilibrium Data Collection; Gmehling, J., Onken, U., Ma.; DECHEMA: Frankfurt, Germany, 1982; Vol. 1/2c, p 488.
Prausnitz, J. M.; Lichtenthaler, R. N.; de Amvedo, E. G. Molecular Thermodynamics of Fluid-Phase Equilibria. In Fugacities in Liquid Mixtures: Excess Functions; Neal, R. Amudson, Ed.; Prentice-Hall: Englewood Cliffs, NJ, 1986. Reid, R. C.; Prausnitz, J. M.; Poling, B. E. The Properties of Gases and Liquids, 4th ed.; McGraw-Hill: New York, 1987. Sada, E.; Morisue, T. Isothermal Vapor-Liquid Equilibrium Data of IsoPropanol-Water System. J. Chem.Eng. Jpn. 1975, 8, 191. Schmidt, G. C. (1926) In Vapor-Liquid Equilibrium Data Collection; Gmehling, J., Onken, U., Eds.; DECHEMA Frankfurt, Germany, 1977; Vol. 1/2a, pp 116-122. Schwartzentruber, J.; Renon, H. Extension of UNIFAC to High Pressures and Temperatures by the Use of a Cubic Equation of State. Ind. Eng. Chem. Res. 1989,28,1049-1055. Soave, G. Equilibrium Constants from a Modified Redlich-Kwong Equation of State. Chem. Eng. Sci. 1972,27, 1197. Tamir, A.; Appelblat, A.; Wagner, M. Fluid Phase Equilib. 1981,6, 113. In Vapor-Liquid Equilibrium Data Collection; Gmehling, J., Onken, U., Eds.; DECHEMA: Frankfurt, Germany, 1982, Vol. 1/2c, p 77. Udovenko, V. V.; Frid, I. B. (1948) In Vapor-Liquid Equilibrium Data Collection; Gmehling, J., Onken, U., Eds.; DECHEMA: Frankfurt, Germany, 1977; Vol. 1/2a, pp 337-340. Vinichenko, I. G.; Susarev, M. P. (1966) In Vapor-Liquid Equilibrium Data Collection;Gmehling, J., Onken, U., Eds.;DECHEMA: Frankfurt, Germany, 1977, Vol. 1/2a, p 327. Whiting, W. B.; Prausnitz, J. M. Equations of State for Strongly Nonideal Fluid Mixtures: Application of Local Composition Toward Density-Dependent Mixing Rules. Fluid Phase Equilib. 1982, 9, 119. Wilson, G. M. Excess Free Energy of Mixing. J. Am. Chem. SOC. 1964, 86, 127. Receiued for reuiew March 19, 1990 Reuised manuscript receiued August 2, 1990 Accepted August 31, 1990
Solubility of Carbon Dioxide in Tar Sand Bitumen: Experimental Determination and Modeling Milind D. Deo,* Chia J. Wang, and Francis V. Hanson Department of Fuels Engineering, Uniuersity of Utah, Salt Lake City, Utah 84112
An understanding of the solubility of carbon dioxide (CO,)in tar sand bitumen is essential for the development of in situ processes in the recovery of bitumen from tar sand deposita. The solubility of COz in the Tar Sand Triangle (Utah), the PR Spring Rainhow I (Utah),and the Athabasca (Canada) tar sand bitumens was determined with the use of a high-pressure microbalance a t temperatures of 358.2 and 393.2K and pressures up to 6.2 MPa As expected, the solubilities increased with pressure a t a given temperature and decreased with increases in temperature. The’PengRobinson and the Schmidt-Wenzel equations of state were used to match the experimentally observed solubilities. Correlations for the interaction parameters between C02and the bitumen were developed for both equations of state, wherein the interaction parameter could be obtained by using specific gravity and the UOP K factor for the bitumen. The correlations were developed with the optimum interaction parameters obtained for each of the samples at each temperature.
Introduction Depleting petroleum reserves and increasing energy demands will eventually require better exploitation of unconventional petroleum reserves like oil shale and tar sands. Tar sands are a mixture of sand and bitumen. The organic constituent, bitumen, cannot be recovered by ordinary petroleum production methods due to its high viscosity and the lack of reservoir energy in most deposita. The world’s known tar sand reservoirs contain more than 2100 billion barrels of bitumen in place, with about 30 billion barrels of bitumen in place in the United States. The state of Utah has about 96% of the total United States tar sand resource (excluding the state of Alaska). This
represents a potentially significant domestic energy resource, compared with the crude oil reserves of the continental United States. Information regarding the Utah tar sand and oil deposita is available in reporta by the Utah Geological and Mineralogical Survey (Ritzma, 1979; Wood and Ritzma, 1972). Much research effort has been spent on oil recovery mechanisms and other aspects of the recovery process when C02is used aa a recovery agent (Holm and Josendal, 1974; Mungan, 1981). As a result of these studies, a number of ways in which C 0 2 becomes effective in removing oil from porous rock were recognized. These findings were summarized by Holm and Josendal, 1974:
088S-SS85/91/2630-0532$02.5~~~ 0 1991 American Chemical Society
Ind. Eng. Chem. Res., Vol. 30,No.3, 1991 533 1. COOdissolves in the crude, thus promoting swelling of the crude. 2. COOreduces the viscosity of the crude. 3. COzvaporizes and extracts portions of the crude into the COz-rich phase. The viscosity-reducing characteristic of COzmakes it an attractive recovery agent for heavy oils (Klins and Farouq Ali, 1982). There is little information in the literature concerning the potential of COOflooding for the recovery of hydrocarbon constituents from tar sand reservoirs. In order to assess this potential, it is necessary to obtain a better understanding of the influence of COz on properties of bitumen like density and viscosity. The interaction of COz with the bitumen, in terms of the solubility of COzand the swelling behavior, must also be determined. This work was intended to examine the solubility of COz in tar sand bitumen as an initial step in providing a better understanding of the influence of COOon the properties of bitumens at reservoir conditions.
Experimental Section Procedure. Bitumen samples from two different Utah deposita (Tar Sand Triangle and PR Spring Rainbow I) and the Athabasca tar sands from Canada were used in this investigation. The bitumen-impregnated sandstone was reduced to 1-cm particles by conventional crushing and grinding techniques prior to extraction of the bitumen. Approximately 2000 g of the crushed tar sand were placed in a largescale Soxhlet extractor and refluxed with toluene until the extraction of the bitumen from the tar sand was completed, that is, until the refluxed solvent was colorless. The selection of toluene as a preferred solvent for bitumen extraction and the development of the extraction procedure was based on a series of experiments with bitumen-wet domestic tar sands. Tetrahydrofuran (THF) and toluene were determined to be superior to carbon tetrachloride, dichloromethane, benzene, and trichloromethane. The bitumen recoveries with THF and toluene were confirmed by pyrolysis in air at 773 K for 16 h. The sample tested did not contain connate water, and the pyrolysis temperature was below the carbonate decomposition temperature (>923 K by TGA). Pyrolysis of the vacuum-dried (393 K) residual sand from which the native bitumen had been extracted indicated negligible ( 0.8 (3)
or [In (14.7/PC) - 5.927 + 6.096/Tbr + 1.289 In Tbr 0.169Tb,S]/(15.251 - 15.688/Tbr - 13.472 In Tbr + 0.436Tb:) for Tbr 5 0.8 (4)
o =
For these correlations, T b and T,are in rankine and P, is in psia. If the Watson K factor of the oil is known, then T b can be calculated from
Tb = ( K x SG)3
(5)
The critical properties obtained by the use of eqs 1-4 are tabulated in Table I. It should be emphasized that these are the pseudocritical properties of the bitumen which has been represented as a single pseudocomponent. Other available correlations (Cavett, 1962; Riazi and Daubert, 1987) were used to examine the variation in critical properties. Though the critical properties did vary numerically for the different correlations used, the use of these properties did not alter the fundamental trends observed in solubility predictions with Kesler-Lee correlations. Hence, the results of these calculations are not reported here. At a certain temperature and a series of pressures, the optimum interaction parameter based on the sum of the root-mean-square (rms) deviation between the experimental and calculated solubilities was determined. Nonlinear regression was used for thia optimization. The criterion used for the optimization bas nP
rms = [C[(xical - ~ p ~ P ) ~ ] /Xn 100 ~ ] ~ / * (6) ill
For each of the bitumens, at each temperature, an optimum interaction parameter was calculated. The optimum interaction parameter obtained for each of the data sets for each of the equations of state and the respective rms deviations are tabulated in Table 111. This table also lists the interaction parameters used in the prediction calculations which were calculated by using the correlations developed in the following paragraphs. The optimum interaction parameter decreased with increasing temperature. Deo et al. (1989) observed a similar trend for heavy hydrocarbons with COzusing the P-R EOS and the S-W EOS. Interaction parameters for some of these systems are reproduced in Table IV. It has been suggested that the interaction parameter can be related to the temperature, specific gravity, and acentric
+ AZT, + A,(SG) + A ~ o
(7)
Linear regression was used to back out the coefficients in eq 7, using the optimum interaction parameters obtained and the physical properties of the bitumen. For the P-R EOS,the following correlation was obtained. 6 = 3.8453 - 1.42471: - 2.9594(SG) + 0.2724~ (8) The correlation for the S-W EOS is given by the following equation. 6 = 4.029 - 2.18861; - 2.7765(SG) - 0.34140 (9) The interaction parameter for the S-W EOS appears to be slightly more dependent on temperature, based on the correlations. The interaction parameters of heavy hydrocarbons also appear temperature dependent. Thus, a procedure has been developed for predicting the solubilities of COz in tar sand bitumen. The tar sand bitumen was represented as a single component, and the measured bulk properties of the bitumen were used. The trend in interaction parameters is similar to the one seen for a few heavy hydrocarbons. The above trend does not imply phenomenological similarity between the bitumen and pure heavy hydrocarbons, as the bitumen is a highly complex mixture of hydrocarbons. The parallel trend in the interaction parameters arises because of the single pseudocomponent representation of the bitumen, which resulta in critical properties similar to those estimated for heavy hydrocarbons. It is recognized that a one-component lumped representation is far too simplistic for substances as complex as tar sand bitumens and petroleum liquids. However, evaluation of more detailed modes of representation requires more data, both about the characteristics of the bitumen and about its interaction with substances such as COP The data collected in this work are adequately modeled by the approach used. Summary High-pressure TGA analysis was used to measure the solubility of COz in three different bitumen samples. Determining solubility was a first step toward characterization of the bitumen-C02interaction. An understanding of this interaction would permit the use of C02 in the in situ production of petroleum liquid from tar sands. Two temperatures and a series of pressures up to 6.2 MPa were used in these measurements. As expected, the solubilities decreased with temperature and increased with pressure. The solubility data were predicted by using the P-R EOS and the S-W EOS wherein the oil was modeled as a single pseudocomponent. A generalized correlation, based on temperature, bitumen specific gravity, and
Znd. Eng. Chem. Res. 1991,30,536-543
536
acentric factor, was established for the interaction parameter between COz and the bitumen component for both equations of state studied. The specific gravities and viscosities of the bitumen samples were determined experimentally, and the critical properties were estimated by established correlations. The trend in interaction parameters was similar to that observed for the interaction parameters of heavy hydrocarbons with COz. Acknowledgment We acknowledge the financial support provided by the Mobil Research and Development Corporation through a grant from the Mobil Foundation. Nomenclature K = Watson characterization factor n = number of points SG = specific gravity at 60 O F x = liquid-phase mole fraction y = vapor-phase mole fraction d = interaction parameter w = acentric factor Subsripts and Superscripts
b = boiling point
br = reduced boiling point c = critical; pressure or temperature cal = calculated, using the EOS exp = experimental 1 = for component i j = for component j i j = for the binary system of components i and j r = reduced; pressure or temperature Registry No. C02, 124-38-9. Literature Cited Bunger, J. W. Techniques of Analysis of Tar Sand Bitumen. Division of Petroleum Chemistry Preprints; American Chemical So-
ciety: Washington, DC, 1977; p 716. Cavett. R. H. Phvsical Data for Distillation Calculations-VawrLiquid EquiliGria. Proceedings of the 27th APZ Meeting,-San Francisco; 1962; p 351. Deo, M. D.; Nutakki, R.; Orr, F. M., Jr. Schmidt-Wenzel and Peng-Robinson Equations of State for C02-Hydrocarbon Mixtures: Binary Interaction Parameters and Volume Translation Factors. SPE 18796. Proceedings of the SPE Califomia Regional Meeting, 1989; p 485. Holm, L. W.; Josendal, V. A. Mechanism of Oil Displacement by Carbon Dioxide. J. Pet. Technol. 1974,26, 1427. Hougen, 0. A,; Wataon, K. M.; Ragatz, R. A. In Chemical Process Principles, Part I. Material and Energy Balances, 2nd ed.; Wiley New York, 1959; p 406. IP Standards for Petroleum and Its Products, Part 1, Section 2, 35th ed.; The Institute of Petroleum: London, 1976; p 837. Kesler, M. G.; Lee, B. I. Improved Prediction of Enthalpy of Fractions. Hydrocarbon Process. 1976,55 (3,153. Klins, M. A.; Farouq Ali, S. M. Heavy Oil Production by Carbon Dioxide Injection. Can. J . Pet. Technol. 1982, Sept.-Oct., 64. Mulliken, C. A.; Sandler, S. I. The Prediction of COz Solubility and Swelling Factors for Enhanced Oil Recovery. Znd. Eng. Chem. Process Des. Deu. 1980, 19,709. Mungan, N. Carbon Dioxide Flooding-Fundament. Can. J. Pet. Technol. 1981, Jan-Feb, 87. Peng, D. Y.; Robinson D. B. A New Two Constant Equation of State. Znd. Eng. Chem. Fundam. 1976,15,59. Riazi, M. R.; Daubert, T. E. Characterization parameters for Petroleum Fractions. Znd. Eng. Chem. Res. 1987,26, 755. Ritzma, H. R. 'Oil Impregnated Rock Deposita of Utah". Utah Geological and Mineral Survey, 1979, Map 47. Schmidt, G.; Wenzel, H. A Modified van der Waals Equation of State. Chem. Eng. Sci. 1980,&5,1503-1512. Simon, R.; Graue, D. J. Generalized Correlations for Predicting Solubility, Swelling and Viscosity Behavior of C02-Crude Oil Systems. J. Pet. Technol. 1966,17,102. Syncrude Research. Syncrude Analytical Methods for Oil Sand and Bitumen Processing; AOSTRA: Edmonton, Alberta, Canada, 1979; p 46.
Wood, R. E.; Ritzma, H. R. 'Analysis of Oil Deposita in Utah". Utah Geological and Mineral Survey, Special Studies 39, 1972; p 19. Received for review April 2, 1990 Revised manuscript received July 30, 1990 Accepted September 4, 1990
On-Line Monitoring of Drop Size Distributions in Agitated Vessels. 1. Effects of Temperature and Impeller Speed Eleni
G.Chatzi,* Costas J. Boutris, and Costas Kiparissides
Chemical Engineering Department and Chemical Process Engineering Research Institute, Aristotle University of Thessaloniki, P.O. Box 1517, 540 06 University City, Greece
Transient drop size distributions in a batch stirred tank were measured by a laser diffraction technique. Ita short measuring time permitted on-line analysis with minimal possible instrumental, sampling, and dispersion errors. Comparison with the previously used photographic technique showed increased sensitivity in measuring the small diameter drops. In this study, the effecta of temperature and impeller speed were investigated for a system of 1%styrene in water stabilized with 0.1 g/L poly(viny1 alcohol) (PVA)as a suspending agent. The system assumed characteristic bimodal distributions within a very short time. Further stirring only reduced the drop sizes without substantially affecting the shape of their distribution. Increasing the agitation rate caused a shift of both peake to smaller diameters since higher turbulence intensity is more effective in breaking the drops. An increase in temperature resulted in a size reduction and narrowing of the large-size peak of the distribution. Finally, the minimum time required for the system to reach steady state a t different conditions was found to depend on the Weber number of the main flow. An increase of agitation rate or a decrease of interfacial tension caused a reduction of the minimum transition time, thus allowing the system to approach equilibrium much faster. Introduction Stirred tanks are widely used in the chemical induetry. The analysis of flow patterns and mixing mechanisms in
agitated vessels has been the subject of numerous theoretical and experimental investigations. It has been shown that flow and mixing conditions in stirred vessels strongly
0888-6886/91/2630-0636$02.60/0(0 1991 American Chemical Society
