September 1952
INDUSTRIAL AND ENGINEERING CHEMISTRY NOMENCLATURE
A , B, C, D = constants d = density, grams per ml. p = vapor pressure, mm. or pounds per square inch absolute po = vapor pressure of pure components at boiling point of solution P = total still ressure Pa = isothermarvapor pressure of azeotrope Pr = isothermal vapor pressure of reference substance R = ideal gas constant T = absolute temperature z = mole fraction in liquid phase y = mole fraction in vapor phase z, = multiplication factor & = molar volume of pure liquid at solution boiling point 6% = second virial coeflicient of vapor y o = activity coefficient yi = activity coefficient, corrected
Subscripts 1 refers to more volatile component, %propanol 2 refers t o less volatile component, water LITERATURE CITED
(1) Bachman, K. C., and Simons, E. L., IND. ENG.CHEM.,44, 202 (1952). (2)Benedict, M.,Johnson, C. A,, Solomon, E., and Rubin, L. C., Trans. Am. Inst. Chem.. Engrs., 41, 371 (1945).
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(3) Brunel, R. F., Crenshaw, J. L., and Tobin, E., J. Am. Chem. SOC.,43, 561 (1921). (4) Brunjes, A. S.,and Bogart, M. J. P., IND. ENG.CHEM..35, 255 (1 943). (5) Carlson, H. C., and Colburn, A. P., Zbid., 34, 581 (1942). (6) Gilmont, R.,private communication. (7) Horsley, L. H., Anal. Chem., 19,603 (1947). (8)Langdon, W.M., and Keyes, D. B., IND.ENG.CHEX.,34, 938 (1942). (9) Lange, N. A., “Handbook of Chemistry,” 6th ed.. pp. 1443, 1452, Sanduaky, Ohio, Handbook Publishers, Inc., 1946. (10) Lebo, R. B., J . Am. Chem. Soc., 43, 1005 (1921). (11) Lecat, M., 2. anorg. u. aZZgem. Chem., 186, 119 (1930). (12) Licht, W., Jr., and Denzler, C. G., Chem.. Eng. Progress, 44, 627 (1948). (13) Nutting, H. S.,and Horsley, L. H., Anal. Chem., 19,602 (1947) (14) Othmer, D. F., IND.ENQ.CHEM.,32, 841 (1940). (15) Othmer, D. F.,and Morley, F. R., Zbid., 38, 751 (1946). (16) Othmer, D. F.,and Silvis, S. J., private communication, (17) Othmer, D. F.,and Ten Eyck, E. H., Jr., IND.ENG.CHEM.,41, 2897 (1949). (18) Parks, G. S.,and Barton, B., J . Am. Chem. SOC., 50,24 (1928). (19) Redlich, O.,and Kister, A. T., IND.ENQ. CHEM.,40, 345 (1948). (20) Scheibel, E. G.,Zbid., 41, 1076 (1949). Zbid., 34,701 (1942). (21) Schumaker, J. E., and Hunt, H., (22) Skolnik, H., Ibid., 43, 172 (1951). (23) Wilson, A., thesis, Rutgers University, 1951. (24)Young, S.,and Fortley, F. C., #J. Chem. SOC.,1902, 728. RECEIVED for review December 20, 1851. ACCEPTEDMarch 26, 1952. Detailed operating instructions for the high pressure still are available upon request from Edward L. Simons.
Phase Behavior in the Hydrogen Sulfide-Water System F. T. SELLECK, L. T. CARMICHAEL, AND B. H. SAGE California Znstitute of Technology, Pasadena 4 , Calif.
B
O T H hydrogen sulfide and water are encountered in many petroleum reservoirs. A knowledge of the phase behavior of mixtures of these two components forms a part of the background of information requisite for an understanding of effective means of producing petroleum. The early investigations of the hydrogen sulfide-water system were directed primarily to a study of hydrates and t o the development of generalizations of phase behavior for binaty systems. D e Forcrand and coworkers (8, 3, 6) studied the hydrogen sulfide-water system in some detail, placing primary emphasis on the properties of the hydrates. Villard reviewed the history and made studies of this and other systems forming hydrates (22). Scheffer studied this system in some detail, determined the three-phase pressures with accuracy (16),and followed this experimental investigation with an overall review (17)at states involving solid phases. At a much later date Scheffer and Korvezee established with some certainty the composition of the hydrate (9)and confirmed the earlier finding of de Forcrand (4)t h a t the hydrate contains 6 molecules of water per per molecule of hydrogen sulfide. The higher values obtained earlier (9,6) appear to have resulted from the occlusion of water in the hydrate. Only limited data concerning the solubility of hydrogen sulfide in water have been obtained ( 7 ) . The quadruple point was well established (15-17) by Scheffer. Schreinemakers ($0)discussed the significance of the quadruple point and the triple point curves in this system, and Wright and Maass (8.4) determined the pressures and temperatures for equilibrium of the hydrate, the aqueous liquid, and the gas phase at temperatures near the freezing point of water.
The volumetric and phase behavior of water has been investigated in detail and was summarized by Keenan and Keyes (8). These data have been employed in the present study and no reference to the basic investigations is made. Hydrogen sulfide has been studied less extensively. Murphy (11) determined the volumetric behavior and measured the vapor pressure of this compound, and West ($3) summarized its thermodynamic properties. Additional data concerning the volumetric behavior and vapor pressure recently became available ( 1 2 ) . The present study relates t o measurements of the three-phase pressures and temperatures which are associated with t h e quadruple point found by Scheffer (15) at a temperature of 85.1’ F. and a pressure of 325 pounds per square inch. The composition of the coexisting phases in a two-phase equilibrium involving an aqueous liquid and a gas phase for temperatures between 100’ and 340” F. was determined. The measurements were made at pressures as high as 5200 pounds per square inch. The composition of the hydrogen sulfide-rich liquid was also measured a t temperatures below the critical temperature of t h a t compound. METHODS AND APPARATUS
The equipment employed was similar t o t h a t utilized in an earlier study (19) of nitrogen dioxide, with the exception t h a t a somewhat smaller spherical pressure vessel, for brevity called a bomb, was used in the present investigation. The details of the construction of the bomb are shown in Figure 1. An unsupported-area seal was provided t o close the threaded joint. The design of the seal is depicted in an enlarged insert in this figure. Lead sealing rings were employed in the present investigation, al-
I N D U S T R I A L A N D E N (3 I N E E R I N G C H E M I S T R Y
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though it has been found t h a t carefully annealed gold rings may be used effectively for measurements at temperatures higher than the melting point of lead. N o difficulty was experienced with the lead seals from corrosion or mechanical failure a t temperatures u p t o 340" F. The bomb was constructed of Type 310 steel which contained 25 weight % chromium and 20 weight % nickel. This metal stock vias found t o be relatively resistant t o corrosion by mixtures of water and hydrogen sulfide. The interior surface of the bomb was plated with chromium to a thickness of 0.003 inch. LEAD FROM CONTACT
PRESSURE DIAPHRAGM
0.074 CAD. STAINLESS STEEL TUBING
\'1 iEAD
Vol. 44, No. 9
change in the additive correction for the diaphragm of approximately 1.10 pounds per square inch as a result of a change in temperature from 100" to 340' F. S o measurable influence of the effect of pressure upon the calibration of the diaphragm was noted. The isochoric vessel v a s not well suited t o measurements of bubble point pressures of this system. For this p u r p o s ~the apparatus shown schematically in Figure 3 was employed.
A displacement plunger, A , of conventional design ( 1 4 ) was used to introduce or withdraw working fluid from the verse], B. This vessel was immersed in an oil bath, C, which was maintained a t a constant temperature by means of a mercury-and-glaqs regulator used in conjunction with an electronic thyrotron control circuit. The sample of hydrogen sulfide and water was confined within a glass piston-cylinder combination, D. The piston and cylinder were constructed from a hypodermic syringe of relatively thin-walled glass and were carefully ground and lapped to give a substantially fluid-tight joint, E. The glass piston-cylinder combination was attached to the closure of the pressure vessel by means of a tapered spring-loaded joint, F . A valve, G, constructed of Carpenter 20 steel was used in introducing and withdrawing the samples from the piston-cylinder combination. It was found that, if the working liquid in H was relatively immiscible with the system under investigation, the transfer of material from the interior of the cylinder was less than 0.1% of the eamplc in a period of approximately one week. h polymerized tetrafluoromethane with a viscosity of approximately 150 centipoises a t 100" F. was employed as the confining liquid. This compound was found to be completely inert and relatively immiscible with either the hydrogen sulfide or water. Bgitation of the sample waP obtained by oscillation of the vessel, B.
p 4 - 4 0 THDS.
Figure 1. Details of Construction of Spherical Pressure Vessel The pressure within the bomb was determined with the aid of an aneroid-type diaphragm shown in Figure 2. It was found that the plane diaphragm used earlier (19) gave measurable variations of calibration with time. The aneroid type of diaphragm used in the present studies was prepared from Type 302 steel which was rolled in a direction parallel t o the plane of the diaphragm. It was machined t o a thickness of 0.010 inch as a part of the cup, A , shown in Figure 2. The convolutions were prepared by grinding the plane diaphragm t o the form illustrated in this figure. The dimensions are not critical, but those shown yielded a diaphragm with the sensitivity of approximately 0.2 pound per square inch per 0.001 inch movement of the center. As indicated in this figure, the diaphragm was supported on both sides and successfully withstood pressure differentials as great as 2000 pounds per square inch. A lead ring was employed a t B of Figure 2 to seal the bomb and t o retain the liquid used to back thc diaphragm, N o other changes were made in the constant volume equipment used earlier (19). The pressure within the system was determined by means of a pressure balance ( 1 4 )which was calibrated against the vapor pressure of carbon dioxide a t the ice point (1). The balance has changed in calibration by less than 0.04% during the past decade, and even with the added uncertainties of calibration introduced by the presence of the diaphragm it is believed that the pressures were known within 0.1% or 1 pound per square inch, whichever was larger. The diaphragm was calibrated as a function of temperature a t low pressures by the use of a mercury-in-glass manometer to determine thedifference in pressure required tomove the diaphragm enough to actuate a signal light. I t s behavior a t high pressures was ascertained by the use of a mercury-in-steel U-tube ( 1 4 ) t o determine, with the aid of a balance, the actual pressure within the bomb. These data indicate a systematic
SECTIOh
A-4'
" 1 2 CONCENTRIC, GROO'IES 0.004 x 0.050'
Figure 2. Assembly of Diaphragm Used for Pressure Measurements The temperature of the working section for both the steel spherical bomb and the glass piston-cylinder combination was determined by means of platinum-in-glass, strain-free resistance t,hermometers. These working instruments were compared with a similar device which has been calibrated by the National Bureau of Standards. Mueller-type bridges were employed for thc measurement of the resistance of the thermometer. The temperature of the spherical bomb was known within 0.03' F. of the international platinum scale while the temperature of the glass pistoncylinder combination was determined within 0.1 ' F. of that seal
