US3656657A

US3656657A - Apparatus for dispensing fluid mixtures in uniform proportions from pressure containers

Info

Publication number: US3656657A
Application number: US833945A
Authority: US
Inventors: Burton F B Smith; John M Siegmund
Original assignee: Allied Chemical Corp
Current assignee: Allied Corp
Priority date: 1969-06-17
Filing date: 1969-06-17
Publication date: 1972-04-18
Anticipated expiration: 1989-04-18
Also published as: DE2028463A1; FR2050005A5

Abstract

An improvement in apparatus for dispensing mixtures of fluids having different vapor pressures, held under pressure in liquid and gas phases, in uniform proportions, from a pressurized container comprising the conventional elements of a pressure container, a perforated dip-tube extending within the pressure container through the vapor and liquid spaces of the container when charged and terminating in a closed free end in proximity to a wall of the pressure container, and means to provide controlled fluid flow from within the pressure container. The improvement comprises providing a bottom orifice in the dip-tube, substantially at the end of the dip-tube which terminates in the liquid space of the container when charged with fluid, and at least one upper orifice smaller in diameter than the bottom orifice located in the dip-tube at points corresponding to the levels at which from about 10-90 percent volume of the full charge of liquid is present in the pressure container. The apparatus is particularly suited for removing non-azeotropic refrigerant mixtures from pressurized containers in which such mixtures are stored and dispensed.

Description

United States Patent Smith et al.

[151 3,656,657 [451 Apr. 18, 1972 APPARATUS FOR DISPENSING FLUID MIXTURES IN UNIFORM PROPORTIONS FROM PRESSURE CONTAINERS lnventors: Burton F. B. Smith, Madison; Jo M.

Siegmund, Morris Plains, both of NJ.

Allied Chemical Corporation, New York, NY.

[73] Assignee:

June 17, 1969 US. Cl ..222/4, ZZZ/402.18, 222/464 Int. Cl .,....B65d 83/14 Field of Search ..222/464, 564, 4, 402.18, 394

References Cited UNITED STATES PATENTS FOREIGN PATENTS OR APPLICATIONS 1,280,428 11/1961 France Primary Examiner-Robert B. Reeves Assistant Examiner-Francis J. Bartuska Attorney-Jay P. Friedenson [5 7] ABSTRACT An improvement in apparatus for dispensing mixtures of fluids having different vapor pressures, held under pressure in liquid and gas phases, in uniform proportions, from a pressurized container comprising the conventional elements of a pressure container, a perforated dip-tube extending within the pressure container through the vapor and liquid spaces of the container when charged and terminating in a closed free end in proximity to a wall of the pressure container, and means to provide controlled fluid flow fromwithin the pressure container. The improvement comprises providing a bottom orifice in the diptube, substantially at the end of the dip-tube which terminates in the liquid space of the container when charged with fluid, and at least one upper orifice smaller in diameter than the bottom orifice located in the dip-tube at points corresponding to the levels at which from about 10-90 percent volume of the full charge of liquid is present in the pressure container. The apparatus is particularly suited for removing non-azeotropic refrigerant mixtures from pressurized containers in which such mixtures are stored and dispensed.

16 Claims, 3 Drawing Figures PATENTEDAPR 18 1972 3,656, 657

SHEET 1 OF 3 INVENTORS BURTON F. B. SMITH BY JOHN M. ,suzemuuo A Hop/var MENTED m 1 81-972 SHEET 2 [IF 3 JNVENTORS BURTON F. B. SMITH 1;

JOHN M SIEGMUND ATTORNEY PATENTEDAPRIBIQIE. 3,656,657

sum 3 BF 3 (D 5 3 u. [I m LU 3 D.

INVENTORS BURTON F. B. SMITH BY JOHN M.SIEGMUND ATTORNEY There is a recognized need in the art for apparatus capable of storing a mixture of fluids having different vapor'pressures under pressure in liquid and gas phases and dispensing the.

same in uniform or substantially uniform proportions. Due to the different vapor pressures of the components of such fluid mixtures which are maintained under pressure and which do not form constant boiling azeotropes, the vapor and liquid phases of the mixtures donot possess the same composition. if such mixtures are simplywithdrawn from the container in which they are stored,fractionation takes place with accompanying changes in composition. Composition change of the mixture can amount to as much as 3 or more percent, and even composition changes of aslittle as 1 percent or below cannot betolerated in certain circumstances.

The art has addressed itself to this problem and there have been devised various designs of. apparatus for the purpose of enabling the withdrawal of such mixtures from pressurized containers in uniform proportions. Many of the known designs are based on'the use of a perforated dip-tube which extends into the liquid and vapor spaces of the container when charged with fluid. When fluid flow from the apparatus is per-v tion with said opening. which dip-tube is closed at its free end and extends within the pressure container substantially to the opposite wall thereof. and means to provide controlled fluid flow from within the pressure container.

The modification which constitutes the invention herein consists of critically arranging the size and location of the orifices in the dip-tube. The invention thus consists of providing a bottom orifice in the dip-tube substantially at the end thereof which terminates inthe liquid space of the container when charged with fluid, and providing at least one upper orifice each of which is smaller in diameter than the bottom orifice located in the dip-tube at points corresponding to the levels at which from about 10-90 percent volume of the full charge of liquid is present in the pressure container.

it has been found that when such criticalities are observed, the proportions of. the components in the mixtures removed from the container may be readily controlled so as to be uniform 'or substantially uniform. Uniformity within a l percent composition change is easily obtained with uniformity well within a 0.25 percent composition change being readily obtainable. On the other hand, when devices such as mitted, liquid enters the orifice or orifices in-the dip-tube below the liquidsurface while vapor enters the orifice or orifices exposed by the drop of the liquid level. in this manner the vapor rich in the lower boiling component entering the diptube mixes with the liquid in the tube, thereby enriching the liquid and tending to maintain uniform composition. Examples of such prior art-devices are described in U.S. Pat. No. 1,938,036 and U.S. Pat. No. 2,183,639.

For-one reason or another, the prior art devices have not been wholly satisfactory. For example, it is pointed out in U.S.

' Pat. No. 2,183,639 that in previously known devices in which the dip-tube is provided with a single opening of thebottom, liquid only is removed with the result that the residual liquid becomes progressively richer in the component having the higher vapor pressure'and thus the composition of the mixture removed changes; it is further explained that when such a-dip tube is provided with a plurality of openings of which one is in the vapor phase at least during a portion of the discharge, a slow rate of discharge results causing the discharge of only gas thereby 'also resulting in a change in composition in the fluid removed. These types of devices are exemplified by U.S. Pat. No. 1,938,036. The I attempted solution to these prior art problems according to U.S. Pat. No. 2,183,639 was to provide a dip-tube with an inner and outer chamber formed by a tube described in U.S. Pat. No. 1,938,036 are employed, although the tendency of the composition to change, as would occur with non-perforated dip-tube equipment, may be retarded, no real controlover the composition of the mixture withdrawn from the container is available and the composition of the mixtures withdrawn from such equipment changes progressively;

in one embodiment of the invention, the opening in the pressure container is in the top of the container and the perforateddip-tube extends downwardly into the container and terminates in the liquid space of the container when charged.

in another embodiment of the invention, the opening in the pressure container is in the bottom of the container and the perforated dip-tube extends upwardly into the container and terminates in the vapor space of the container when charged.

enclosed in a concentric jacket member. The disadvantages of I extra weight, complexity of construction and increased cost of such a device are apparent. indeed subsequent attempts to design more satisfactory devices of this type have resulted in more complex and cumbersome equipment.

It is a major object of this invention to provide a novel apparatus for the storing of fluid mixtures having components with different vapor pressures, which is capable of dispensing such fluid mixtures in uniform or substantially uniform .proportions, which apparatus is simple in construction and operatron.

Other objects of the invention will be apparent from the following description.

SUMMARY OF THE INVENTION We have found that the objects of the invention are accomplished by modifying, in a manner hereinafter described, previously known apparatus designed for the purpose of storing and dispensing a mixture of such fluids from pressurized containers. Such previously known apparatus is substantially as described in U.S. Pat. No. 1,938,036 and comprises the conventional components of a pressure container having an opening therethrough, a perforated dip-tube in communica- This approach is unusual in this art. No workable prior art device for a. similar purpose is known to the inventors in which the perforated dip-tube is inserted through the bottom of a pressurized container and terminates in the vapor space. The absence of prior art pertinent to this embodiment can perhaps be explained by the fact that onewould have predicted that,

with such an arrangement,'there could have been obtained liquid flow only through the orifice or orifices exposed to the liquid phase in the container'with no adequate compensating effect from a substantial vapor flow through the orifice or orifices exposed to the vapor phase within the container. Nonetheless, with the :critical sizing and location of the orifices in accordance withthe invention, as described above, it has been found that a sufficient pressure-drop .is obtained across the orifices-so as to result in a very satisfactory two- 'phase flow rate. The above described bottom entry embodiment has advantages over the previously described top-entry embodiment in that it can easily be adapted for use with auxil- .liary pumping to increase flow rates. This is particularly advantageous when large cylinders or tanks are used and large volumes of fluids can be transferred therefrom.

BRIEF DESCRIPTION OF THE DRAWINGS through the bottom of the container and terminates in the vapor space of the container when charged. 7

FIG. 3 is a graph showing the results of experiments con- 7 ducted with three different types of equipment. Curves A, B,

and C plot the weight percent SF of SF ICCI F, mixture in the discharge from the equipment, against the volumes of fluid remaining in the equipment after various discharge intervals.

DETAILED DESCRIPTION OF THE INVENTION AND OF THE PREFERRED EMBODIMENTS With reference to the drawings 1 is a container of any desired shape or size capable of containing fluid under pressure. Opening 2 is provided in container 1 which is in the top wall in the embodiment of FIG. 1 and in the bottom wall in the embodiment of FIG. 2. Perforated dip-tube 3 having a closed end 4 extends through opening 2 and extends within container 1 through vapor space 5 and liquid space 6 of the container when charged, and substantially to the opposite wall 7 of the container. Means to provide controlled flow of fluid from within container 1, such as a valve of conventional construction, is provided, but is not shown on the drawing. A connecting tube 8 may be attached to dip-tube 3 by means of flanges 9 and 10 in order to transfer fluid discharged from the container to a desired destination. i

A bottom orifice 11 is provided in dip-tube 3 substantially at the end thereof which terminates in liquid space 6 of container 1 when charged. The preferred size of bottom orifice 11 is such that the ratio of bottom orifice diameter 11 to the diptube internal diameter is from about 1:2 to 1:10, and still preferably from about I22 to 1:5.

Upper orifices 12 each of which is smaller in diameter than bottom orifice 11 are located in the dip-tube at points corresponding to the levels at which from about 10-90 percent volume of the full charge of liquid is present in the pressure container when charged. Preferably, upper orifices 12 are uniformly located alone in the tube in the range indicated. Preferably the size of the upper orifices is such that the ratio of the bottom orifice diameter to the diameter of each upperorifice is from about 1.121 to 5:1 and still preferably from about 15:1 and 3:1. The upper orifices may vary in size and shape as long as the surface area of each orifice is less than the surface area of bottom orifice 11. The number of upper orifices 12 is not absolutely critical to this invention. A satisfactory working device may be constructed with only one upper orifice. With only one upper orifice, the orifice should preferably be located on dip-tube 3 at a point corresponding to the level at which about 30-70 percent volume of full charge of liquid is present in container 1. Preferably from two to nine upper orifices should be provided which are distributed uniformly on the dip-tube as indicated. Still preferably, the number of upper orifices is from three to five. Ten or more upper orifices can be provided if desired, but without advantage. In the case of the embodiment of FIG. I, the bottom orifice is preferably located in the closed end 4 of dip-tube 3. In the case of the embodiment of FIG. 2, an upper orifice may be located in closed end 4 of dip-tube 3 provided this point otherwise satisfies the requirements discussed above. The optimum number, sizes, and locations of the bottom orifice and the upper orifices will vary within the indicated limits depending upon the specific mixture and the particular application contemplated, and can readily be ascertained by those skilled in the art by routine experimentation.

The expression at points corresponding to the levels at which about 10-90 percent volume (and 30-70 percent volume) of the full charge of liquid refers to the levels of liquid in the container which would be created by the indicated percentage volumes of liquid based on a full charge. This may readily be determined by fixing the position of the dip-tube, filling the container to the desired volume and observing the level at which the dip-tube is wet. It is deemed desirable to express the relationship in this way since the shape of the containers used may vary substantially and have different diameters at different reference points. For the purpose of this discussion, it will be assumed that a full charge of liquid occupies 100 percent of the volume of the container. Of course, in practice, the container is never completely charged with liquid. Usually a charge of up to about 90-95 percent by volume is madeleaving 5-l0 percent by volume vapor space to allow for expansion of the liquid.

Charge of fluid to the container may be accomplished in a conventional manner.

In operation, to withdraw fluids from the pressure container, the closure valve (notv shown in the drawing) of conventional construction, is opened, preferably completely for maximum flow, and either the vapor pressure of the mixture or mechanical pumping or a combination of both, may be used to discharge the mixture from the container. Liquid enters the orifices exposed to the liquid phase in the container while vapor enters those orifices exposed to the vapor phase in the container and also those orifices which become exposed to the vapor phase by the drop of the liquid level as the container is discharged. The vapor entering dip-tube 3 in this manner mixes with the liquid in the tube thereby enriching the liquid in the tube.

In an illustrative embodiment of the top-entry dip-tube embodiment of FIG. I, a 35 gallon cylindrical pressure container 36 inches long, having a diameter of 18 inches, is positioned laterally and is equipped with a 0.311 inch internal diameter perforated dip-tube. The dip-tube extends through the top wall of the container and tenninates within about 0.025 inch from the bottom wall of the container. The dip-tube is closed at the bottom but has an orifice in the bottom wall which is 0.100 inch in diameter. Four upper orifices, each 0.047 inch in diameter, are provided in the side wall of the dip-tube at points corresponding to the levels at which 20, 35, 50 and 70 percent of the full charge of liquid is present in the pressure container. This device is tested by charging the cylinder with about 345 lbs. (75 F.) of a mixture of 10 weight SF (b.p. 83 F./760mm.)/ weight CCl F (b.p. 2 l.6 F./760mm.). This corresponds to a charge which is about 90 volume percent of the theoretical full charge. Fluid is discharged from the cylinder and the weight percent of SF in the fluid being discharged is determined at various intervals. A curve is then drawn through these experimentally determined points. The resulting curve graphically shows the variation in SF, content of the fluid as the cylinder is discharged.

The above experiment is repeated with the same apparatus and same charge, except that in one case, a non-perforated dip-tube, with an open bottom, is used as a control and, in another case, a perforated dip-tube identical to the perforated dip-tube described above is employed excepting that the bottom orifice is eliminated to illustrate results obtainable with a previously known type of equipment. Curves are prepared as described above. FIG. 3 shows the three curves obtained by the aboveidentified experiments. Curve A represents the control experiment. Curve B represents the experiment using the prior art device. Curve C represents the experiment using a perforated dip-tube having a large bottom orifice in accordance with the invention. R is the reference line on the drawing showing the 10% SF, concentration.

The following conclusions can readily be drawn from an examination of curves A, B and C. In the control experiment (curve A), as the cylinder is discharged, the proportion of SF, in the fluid being withdrawn progressively and rapidly decreases so that when the charge in the container is only 10 percent of the original volume, the composition change in SP is almost 2 weight percent. In the prior art experiment (curve B), as the cylinder is discharged, again the proportion of SF, in the fluid being withdrawn progressively decreases so that when the charge in the container is only 10 percent of the original volume, the composition change in SF, is a little over 1.5 percent weight percent. While in this case, the orifices in the dip-tube do tend to retard the downward trend of the falling SE concentration, it is apparent that the concentration of SF is not actually being controlled.

On the other hand, with the apparatus of the invention (curve C), there is no progressive downward trend of the SF, concentration. The SP concentration oscillates close to the desired 10 weight percent SE level as fluid is discharged from Even when only 10 percent of the original volume of the" charge in the cylinder remains, the SF concentration is only about 0.3 weight percent off the desired 10 weight percent level.

Apparatus in accordance with the bottom-entry embodiment of FIG. 2 is constructed with the same size pressure container and dip-tube with the same number and size orifices as described above for the top-entry embodiment and is charged with the same fluid mixture. In this embodiment, of course, the bottom orifice is in the side wall of the dip-tube at the same relative distance from the container wall as is the bottom orifice in the top-entry embodiment. It was found that the container discharges satisfactorily solely under the vapor pressure of the container charge, and that as in the top-entry embodiment, good control over the SP concentration in the discharged fluid is obtained. Again, instead of a progressive change in the concentration of SF component, good control is exercised over the SF concentration with the SF concentration oscillating close to the desired 10 weight percent level.

Experiments similar to those described above are performed with apparatus in accordance with the invention, excepting that an additional upper orifice is provided in the diptube at points outside the 10-90 volume percent of full charge. In such cases, inadequate control is exercised over the SF concentrations of the discharged fluid. Instead of an oscillating effect, above and below the desired 10 weight percent concentration of SF,,, the concentration of SF progressively decreases. In the bottom-entry dip-tube embodiment, an initial rise in the concentration of SE, is noted, but subsequently the concentration of SF, in the fluid discharge progressively decreases as in the top-entry dip-tube embodiment.

The novel apparatus of the invention is applicable to virtually any non-azeotropic mixture of fluids under pressure in liquid and gas phases, the components of which have different vapor pressures, regardless of the boiling points of the mixture components, and regardless of the number of components. lllustrative mixtures suitable for use in the apparatus of the invention include the following: N and octafluorocyclobutane; CO and CI-ICIF N 0 and CCl F SF and CCl F C H and n-C H CO and ethylene oxide, and a ternary mixture of SF,,, CClF and octafluorocyclobutane.

The temperature under which the mixture components is maintained has no effect on the operation of the apparatus of the invention.

It will be apparent that various modifications to the particular embodiments described and various different applications may be made without departing from the scope and spirit of this invention. For example, a plurality of dip-tubes can be provided to provide flexibility in flow rates; the dip-tubes can be bent in order to reach more inaccessible areas of the pressurized containers; the orifices can be of any desired shape; and the pressurized containers can be associated with aerosol type valves and used as aerosol dispensers. Other modifications and applications will readily occur to those of ordinary skill in the art.

We claim:

1. In an apparatus for storing and dispensing a mixture of fluids having difierent vapor pressures and under pressure in liquid and gas phases, comprising a pressure container having an opening therethrough, a perforated dip-tube in communication with said opening, which dip-tube is closed at its free end and extends within the pressure container substantially to the opposite wall thereof, and means to provide controlled fluid flow from within the pressure container; the improvement which consists of:

a. providing a bottom orifice in the dip-tube substantially at the end thereof which terminates in the liquid space of the container when charged with fluid, the ratio of the bottom orifice diameter to the dip-tube internal diameter being from about 1:2 to 1:10, and

b. at least one upper orifice, each of which is smaller in diameter than the bottom orifice, located in the dip-tube at points corresponding to the levels at which from about 10-90 percent volume of the full charge of liquid is present in the pressure container.

2. Apparatus according to claim 1 in which the ratio of the bottom orifice diameter to the dip-tube internal diameter is from about 1:2 to 1:5.

3. Apparatus according to claim 2 in which the ratio of the bottom orifice diameter to the diameter of each upper orifice isfrom about 1.1:1 to 5:1.

4. Apparatus according to claim 3 in which there are from two to 10 upper orifices distributed uniformly on the dip-tube at points corresponding to the levels at which from about 10-90 percent volume of the full charge of liquid is present in the pressure container.

5. Apparatus according to claim 4 in which the number of upper orifices is from three to six.

6. Apparatus according to claim 3 in which the opening in the pressure container is in the top of the container and the perforated dip-tube extends downwardly into the container and terminates in the liquid space of the container when charged.

7. Apparatus according to claim 6 in which the bottom orifice is located in the closed end of the dip-tube terminating in the liquid space of the container when charged.

8. Apparatus according to claim 7 in which there are from two to 10 upper orifices distributed uniformly on the dip-tube at points corresponding to the levels at which from about 10-90 percent of full charge of liquid is present in the pressure container.

9. Apparatus according to claim 8 in which the number of upper orifices is from three to six.

' 10. Apparatus according to claim 8 in which the ratio of the bottom orifice diameter to the diameters of each of the upper orifices is from about 1.5:1 to 3: 1.

11. Apparatus according to claim 9 in which the bottom orifice is located in the closed end of the dip-tube.

12. Apparatus according to claim 11 in which the bottom orifice is in the form of an open constriction in the closed end of the dip-tube.

13. Apparatus according to claim 3 in which the opening in the pressure container is in the bottom of the container and the dip-tube extends upwardly into the container and terminates in the vapor space of the container when charged.

14. Apparatus according to claim 13 in which there are from two to 10 upper orifices distributed uniformly on the diptube at points corresponding to the levels at which from about 10-90 percent volume of full charge of liquid is present in the pressure container.

15. Apparatus according to claim 14 in which the ratio of the bottom orifice diameter to the diameters of each of the upper orifices is from about 1.521 to 3:1.

16. Apparatus according to claim 14 in which the number of upper orifices is from three to six.

Claims

1. In an apparatus for storing and dispensing a mixture of fluids having different vapor pressures and under pressure in liquid and gas phases, comprising a pressure container having an opening therethrough, a perforated dip-tube in communication with said opening, which dip-tube is closed at its free end and extends within the pressure container substantially to the opposite wall thereof, and means to provide controlled fluid flow from within the pressure container; the improvement which consists of: a. providing a bottom orifice in the dip-tube substantially at the end thereof which terminates in the liquid space of the container when charged with fluid, the ratio of the bottom orifice diameter to the dip-tube internal diameter being from about 1:2 to 1:10, and b. at least one upper orifice, each of which is smaller in diameter than the bottom orifice, located in the dip-tube at points corresponding to the levels at which from about 10-90 percent volume of the full charge of liquid is present in the pressure container.

3. Apparatus according to claim 2 in which the ratio of the bottom orifice diameter to the diameter of each upper orifice is from about 1.1:1 to 5:1.

10. Apparatus according to claim 8 in which the ratio of the bottom orifice diameter to the diameters of each of the upper orifices is from about 1.5:1 to 3:1.

14. Apparatus according to claim 13 in which there are from two to ten upper orifices distributed uniformly on the dip-tube at points corresponding to the levels at which from about 10-90 percent volume of full charge of liquid is present in the pressure container.

15. Apparatus according to claim 14 in which the ratio of the bottom orifice diameter to the diameters of each of the upper orifices is from about 1.5:1 to 3:1.