1.550
e. F. PRUTTON AND R.L. SAVA4GE [ C O N T R I B U T I O N FROM THO DEPARTMENT O F CHEMICAL EXGINEERING, C A S E SCHOOL OF
Vol. (i7 APPLIEDSCIENCE]
The Solubility of Carbon Dioxide in Calcium Chloride-Water Solutions at 75, 100, 120' and High Pressures' 13s C. F. PRUTTON AND R. L. SAVAGE^ Introduction pheric pressure. Sanders used a static system to The chemical reaction of hydrochloric acid on measure the solubility of carbon dioxide in water calcium carbonate, which takes plact during the a t several temperatures and a t pressures up to 100 acid treatment of oil wells, results in the fornia- atm. The results are of only qualitative value tion of carbon dioxide and calcium chloride solu- since two sets of values vary by as much as 10%. tions. I n certain areas, as in California and the The results obtained by Wiebe and Gaddyginclude Gulf Coast, where high bottom hole pressures are a pressure range up to 700 atm. for the solubility encountered, the liberation of carbon dioxide gas of carbon dioxide in water a t 50, 75, and 100'. bubbles by the reaction has been q ~ e s t i o n e d . ~The values for the solubility of carbon dioxide in It has been claimed that the high pressures would water a t 100' were used to verify the results reprevent this reaction or, if the reaction did take ported by Wiebe and Gaddy, who used a flow place, that the carbon dioxide would remain system. completely dissolved in the calcium chloride soluApparatus tion and, therefore, would be unavailable for A modification of the apparatus used by Frolich agitation and dispersal of drilling mud sheaths or and co-workers1° was used to determine the soh-' other insoluble particles. Thermodynamic calculations reported by bility of carbon dioxide in calcium chloride soluChamberlain and Boyer4 and by Stone and tions. The 300-ml. capacity copper-plated reKefley6 indicate that a carbon dioxide pressure of action vessel, A (Fig. l),was supported in a heater approximately lo3 atmospheres would be neces- which could be rocked through 60' to provide sary to prevent the reaction of hydrochloric acid agitation of the equilibrium solution. High preson calcium carbonate. If it is assumed that the sure tubing connected the top of the autoclave to reaction will take place a t pressures of less than an exhaust valve, F, and to the two high pressure lo8 atmospheres, then a measurement of the solu- gages. A high pressure needle valve, B, a t the bility of carbon dioxide in calcium chloride solu- bottom of the autoclave controlled the flow of tions under such pressures as may be encountered saturated solution into the glass trap where the in oil wells would indicate whether or not the gas was evolved to be measured in a buret over carbon dioxide gas would be evolved from the mercury, and the remaining solution was collected spent acid solution. The results of the present to be weighed. Measurements of the actual temperatures of investigation indicate that the carbon dioxide the solutions were made with a portable type gas would be evolved. Previous investigations of the solubility of potentiometer using a calibrated copper-concarbon dioxide in calcium chloride solutions have stantan thermocouple placed in the pyrometer been carried out in this Laboratory but without well inside the vessel. The heating of the equicovering fully a range of concentrations, pressures librium vessel was controlled by a Leeds and and temperatures.6 The solubilities of carbon Northrup recorder coupled with a Lindbergh condioxide in water and water solutions of salts or troller. By maintaining a definite wall temperaother solutes have been reported but in only a few ture, it was possiblc to control the equilibrium cases were these determined under pressure. conditions to within oiie degree above the desired h.IacKcnzic7 determined the solubility of carbon value. Some samples were withdrawn when the dioxide in solutions of calcium chloride a t ntmos- solution was two degrees above the equilibrium temperature, but the error could be tolerated ( I ) This paper is part oi a thesis presented by K. I,. Savage i n since there is such a small cffect on solubility due partial fulfillment of t h e reiiuiremenls f o r the degree of hiaster of to temperature charige between 75 and 120". Science i n Cheniical I!ngincerinp; a t Case School of Applied Science. A 20,000-lb. per sq. inch Bourdon type gage, G, Original manuscript received April 29, 1943. (2) Present address. Bottelle Mcrnori:il institiite. Coliimbiis, itidicatc(1 tlic approxiinate pressure in the system Ohio. while n Crosby dead-weight pressure balance, I, (3) J . K. Kcnnelly, "I.imestoiic-l.a(len Clay Drilling \1iid as incasuretl the exact pressure wlicn a saniple of Acidizing Acid," C d i j o r n i u Oii IVci?d, 36, K O ,1 7 , 9-11 ( I O Z L ' j . saturated solution was removed from the auto(4) I,, C. Chamberlain, Jr., a n d K. F. Iioyer, I d . Eng. C h c n t . , 31, 400-406 (1'339). clave. This Crosby pressure balance could be ( 5 ) J. B. Stone and I) C . Kcfley, The Oil W'ecbly, Tov. 11, p. 38 used to measure pressures up t o 25,000 Ib. per sq. (1940). ( 6 ) From thesis presented for the degree o f Bachclor of Chemical Engineering, Case School of Applled Science, 1940 by B. N. Schrauf, C. 17. Prutton a n d M. I.. Riehl, "Solubility of Carhou Dioxide i n C'nlrium Chloride Solutions" I'rogresn Report, unpiih;isheri, 1!1I1) ( 7 ) AlxcKenzic. . I i i i r P i l y r i b (Z! I,450 (1877)
(81 \l'. Sander, 2 . Ohysiii. Chcnz., 78, 513-549 (1012). (9) R . Wiebe and V . I,, Gaddy, 'Tlirs J O U R N A L , 61, 318-318 ( 1 039). (1111 Per I; I'rolich, E,J . 'I'aiicli, J J. Hog;m and A . S . Peer, r n d . F w C C k r u . , 1 3 , 518 ( 1 9 3 1 ) .
SOLUBILITY OF CARBON DIOXIDE IN CALCIUM CHLORIDE SOLUTIONS
Sept., 1945
EXHAUST
-
SOLUTION THERMOCOUPLE7 CONTROLLER THERYWOUPLE
"p!?H
HEAT
HlQH PRE EPUlLl~RlUYVESSEL
1551
carbon dioxide was pumped as a liquid from an inverted cylinder of.gas into the autoclave a t room temperature. A coil of copper tubing immersed in a n ice-water-bath served as a feed line froin the inverted carbon dioxide cylinder to the high pressure liquid proportioning pump, and high pressure tubing connected the pump to the sampling valve, B, a t the bottom of the autoclave. An initial pressure of 3900 to 5500 lb. per sq. inch at room temperature yielded a pressure in excess of 10,000 Ib. per sq. inch a t equilibrium temperature. Before the first sample was withdrawn from the equilibrium vessel, the system was held a t the desired temperature for several hours, and a small amount of solution was run out, in case equilibrium had not been established in the short section of tubing between the autoclave and valve. This assured the presence of the saturated solution a t the valve seat; failure to do so resulted in erratic values for the solubility.
e
f
CONDENSER
QA8 BURETTE
1
0.0250
I '
LE
E
Fig. 1 .-Diagram of gas solubility apparatus.
inch, pressure readings being duplicated to t l lb. per sq. inch a t ten thousand. The manufacturer guaranteed for the gage a calibrated accuracy of *0.25% but not better than * 1 lb. The 20 and 30% calcium chloride stock solutions were made from the required amount of CaC12-2H20 (Bakers c. P.) and some of the 20% solution was diluted to make a 10% stock solution. As determined on a Westphal balance, the density of the solutions indicated that the exact concentrations were 10.1, 20.2, and 30.2% calcium chloride. The carbon dioxide was a commercial gas for medicinal purposes (Ohio Chemical Company) and the solid calcium carbonate was small crystals of Iceland Spar (General Chemical Company).
Procedure The method for determining the solubility of carbon dioxide in a calcium chloride solution consisted of allowing the carbon dioxide to come to equilibrium with the solution in the autoclave a t the desired temperature, drawing off a sample of the solution, measuring the gas evolved a t atmospheric pressure, and weighing the sample of solution from which the gas had been evolved. After the vessel was thoroughly rinsed, the calcium chloride solution was drawn into the autoclave through the sampling valve, B, and the aspirator suction on the exhaust valve, F, was continued to remove any gases which would leave the solution a t room temperature. In order to build up the desired pressure in the system, the
0
200 400 600 Total pressure in atmospheres. Fig. 2.--Solubility of COSin calcium chloridewater solutions at 75
'.
Immediately before sampling, the valve was again opened slightly, and the pressure in the system was restored by turning the capstan of the pressure balance. With the glass trap, C, connected to the high pressure valve, B, the sample of solution was collected to be weighed after the gas expanded into the buret system, D, E. During the three to six minutes required to collect the sample, the pressure in the system was maintained by turning the capstan. on the pressure balance to force oil into the trap, H, to replace the volume of solution removed. The final measurement of the volume of carbon dioxide evolved was taken thirty to forty-five minutes later a t the temperature of the water jacket on the buret system. In order to obtain a series of solubility deter
ininations a t one equilibrium temperature, the pressure in the system was lowered after a sample had been taketi, whereupon the solution \vas again agitated until it was in equilibrium with the gas plixse. Duplicate samples could be collected by iorciiig iiiore oil into the trap to maintain the pressure. Assurance that equilibrium had been attained was afforded by the concordant values from several samples collected when the system had come to equilibrium from a lower prvssurc..
II
200 Tirtal prcy.urc
410 iii
l;llfl
atnloajihcrci
1"ig. :J. -Solubility of CO? i n calciiiln cl11i~ri~lc 17-at1.r 51~111 t i o i i q a t 1WJ'.
For the measurement of the carbon dioxide evolved a t atmospheric pressure, the volume of the liquid collected was subtracted froin the gas buret reading. This resultant volume of carbon dioxide, corrected for the vapor pressure of the solution and reduced to standard conditions, was used to calculate the mole fraction of carbon dioxide in the solution. The temperature of the sample tube, c', was assumed to be that of the huret, and since there is an appreciable solubility o f carbon dioxide in water at room temperature atid atmospheric pressure, a correction was calculated from the Bunsen absorption coefficient ( = 0.759 a t 25')11 multiplied by the factor [(mm. Hg - P ~ , o ) / 7 6 0 d ~ , oP ] .H ~ and O were the vapor pressure and density of water at the temperature of the buret and mm. Hg was the barometric reading. A similar correction for the calcium chloride solutions was calculated from the values reported by MacKenzie7 for the solubility of carbon dioxide in calcium chloride solutions at atmospheric pressure and room temperature. I t was necessary to extrapolate his data t.o obtain a value for the solubility of carbon dioxide in 30c/b calcium chloride solutions. T4e same factor (rnm.Hg - P,,1,.)/760 tlSoin. ~ 0 x 1 rll)
