US3264862A

US3264862A - Process and device for analyzing binary fluid mixtures

Info

Publication number: US3264862A
Application number: US311423A
Authority: US
Inventors: Herman R Felton; James W Williams
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1963-09-25
Filing date: 1963-09-25
Publication date: 1966-08-09
Anticipated expiration: 1983-08-09

Description

9, 1966 H. R. FELTON ETAL PROCESS AND DEVICE FOR ANALYZING BINARY FLUID MIXTURES Filed Sept. 25, 1963 Y INVENTORS HERMAN R. FELTON JAMES W. WILLIAMS BY WKWW ATTORNEY United States Patent 3,264,862 PRQCESS AND DEVICE FOR ANALYZING BENARY FLUID MIXTURES Herman R. Felton, Wilmington, Del., and James W. Williams, Perms Grove, Ni, assignors to E. 1. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed Sept. 25, 1963, Ser. No. 311,423 Claims. (Cl. '7325) This invention relates to a process for analyzing binary fluid mixtures to determine their composition and to a form of analyzer device which is particularly adapted for use in such process.

Binary fluid mixtures are well known and are widely used as propellents of other materials such as insecticides, fungicides, deodorants, hair-treating compositions, foodstuffs, paints, and the like, from pressurized containers to form aerosols, sprays, and foams. Also, binary fluid mixtures are well known and used as refrigerants, dielectrics, as reactants in some chemical processes, and for other purposes. Usually such binary fluid mixtures are produced by mixing the two components or ingredients in the desired proportions, preferably in a continuous process. Also, some chemical processes are known which produce binary fluid mixtures, the proportions of the components of which can be varied, but in which it is desired to produce mixtures in which the components are in particular proportions.

It is usually desired to frequently analyze such binary fluid mixtures to determine their composition, that is, the proportions of the components therein. A number of devices are known which can be used to determine the composition of binary fluid mixtures. These include mass spectrometers, vapor phase chromatographic units, infrared spectrometers, and the like. Such devices and the processes of using them have certain characteristics which render them undesirable for many applications, such as being expensive; non-transportable; batchwise in operation, requiring that a sample of the binary fluid mixture be withdrawn from a stream thereof, transported and placed in the device for analysis; and slow in operation, requiring a time lapse from sample withdrawal to final analysis of from several minutes to an hour or more.

It is an object of this invention to provide a novel analyzer for determining the composition of binary fluid mixtures, particularly one which is inexpensive and readily transportable. Another object is to provide an analyzer of the foregoing character with which it is possible to rapidly determine the composition of a binary mixture with a high degree of accuracy, and particularly one which can be continuously operated. A further object is to provide a novel process for analyzing binary vaporizable fluid mixtures to deter-mine their composition economically and rapidly. A still further object is to provide such a process which may be operated batchwise, intermittently, periodically, or continuously as desired. Other objects are to advance the art. Still other objects will appear hereinafter.

The foregoing and other objects may be accomplished in accord with this invention which comprises a novel process for analyzing binary vaporizable fluid mixtures having a normal boiling point below 250 C. and a novel analyzer which is particularly adapted for use in such process, both as defined and described in detail hereinafter.

The process of this invention comprises:

(A) Flowing the binary fluid mixture at a predetermined initial pressure of from about 1 atmosphere to about 2000 p.s.i.-g. and at a predetermined initial temperature "ice of up to about 250 C. through a restricted orifice having a diameter of from 0.001 to 0.025 inch,

(B) Expanding the mixture flowing from the orifice in an unheated expansion chamber while maintaining said chamber at a predetermined pressure which is less than the vapor pressure of the mixture at the operating temperature of said chamber and at least /2 atmosphere below the pressure back of the orifice,

(C) Measuring the temperature of the expanded binary fluid mixture flowing from said orifice, and

(*D) Comparing the measured temperature with the temperatures of a series of similarly expanded binary fluid mixtures of the same components but of known varying composition.

The analyzer of this invention comprises:

(A) A supply chamber for the binary fluid mixture to be analyzed,

(B) An expansion chamber,

(C) A tube having an internal diameter of from 0.001

to 0.125 inch connecting the supply chamber to the expansion chamber,

( D) An orifice having a diameter of from 0.001 to 0.025 inch at the expansion chamber end of said tube, and

(E) Temperature sensing means in said expansion chamber positioned in front of said orifice and spaced therefrom by & to inch, including (a) means extending outside of said expansion chamber for indicating the temperature of the temperature sensing means,

said supply chamber and said expansion chamber having a diameter at least twice the diameter of said tube, and said expansion chamber having a volume of at least 1.5 ml.

A binary fluid mixture, as employed in this invention, will be understood to be a mixture which, except for trace amounts of impurities, consists of only two components, either or both of which is a gas, a vapor, or a liquid at norm-a1 room temperatures (about 25 C.) and atmospheric pressure. The binary fluid mixture, and each component thereof, should have a normal boiling point has a normal boiling point below room temperature and has a vapor pressure above atmospheric pressure at room temperature. [Many fluids and binary fluid mixtures, which normally are gases, may be readily liquefied at room temperature by subjecting them to pressures equal to or above their vapor pressures at that temperature, and frequently are maintained and handled as liquids under those conditions, and this invention is particularly useful for the analysis of such binary liquid mixtures.

It is well known that gases cool when expanded rapidly and that liquid mixtures also cool when evaporated without the application of heat, evaporation resulting in expansion. When a binary fluid mixture is expanded through a restricted orifice into an expansion chamber in accord with the process of this invention, the temperature of the expanded mixture is lower than its temperature before the expansion. It has been found that, When the temperature of the mixture entering the analyzer and the different pressures in the supply chamber and the expansion chamber are maintained substantially constant, the temperature of the expanded mixture is characteristic of the compositon of the mixture and varies regularly with variation in that composition. Thus, it has been found possible to determine the composition of a binary fluid mixture of known ingredients, but of unknown composition, by determining the temperature of the expanded mixture under predetermined conditions, and comparing that temperature with the temperatures produced by a series of binary mixtures of the same ingredients in differing known proportions under the same conditions. Therefore, by the use of the process and the analyzer of this invention, a binary vaporizable fluid mixture can be analyzed and its composition quickly determined in a simple and easy manner. The accuracy of the analysis will depend primarily upon the sensitivity and accuracy of the temperature sensing means. By the use of an electronic temperature sensing means, it is usually possible to obtain analyses which are accurate within 2%, which is sufficient for most practical purposes and commercial operations.

The invention may best be understood from the following detailed description, taken with the accompanying drawings in which:

FIG. 1 is a view in vertical cross-section of a preferred form of analyzer for the practice of this invention;

FIG. 2 is a diagrammatic view of a second form of analyzer which is suitable for the practice of the invention; and

FIG. 3 is a diagrammatic view of a third form of analyzer which is suitable for the practice of the invention.

Referring more particularly to FIG. 1, the analyzer comprises a supply chamber 10, adapted to contain a supply of the binary fluid mixture to be analyzed, which supply chamber is provided with an inlet 12 for feeding the binary fluid mixture to the supply chamber 10, and a tube 14 of restricted diameter provided with an orifice 16. A screen or other filtering means 18, positioned across the inner end of the inlet 12, is optional and is provided when necessary to remove solid particles entrained in the binary fluid mixture and to prevent such particles from clogging tube 14 or orifice 16. An expansion chamber 20 is secured to the end of the supply chamber and encloses tube 14. Expansion chamber is closed at the top and is provided with an outlet 22 which, optionally may contain a trap 24. The expansion chamber 20 also contains a temperature sensing means 26 which is positioned in front of the orifice 16 and includes a means 28 extending outside of the expansion chamber for indicating the temperature of the temperature sensing means 26. Usually, the chamber 20 will also contain a screen 30 surrounding the temperature sensing means 26 to prevent the impingement of liquid material on the temperature sensing means, but said screen may be omitted if desired or if unnecessary.

In operation, a charge of the binary fluid mixture to be analyzed will be introduced through inlet 12 into supply chamber 10 at a predetermined initial temperature and a predetermined initial pressure, usually those of the source of the mixture. The expansion chamber 20 will be unheated and uncooled (other than by the expanded binary fluid mixture) and will be maintained under a pressure of at least /2 atmosphere below the pressure back of the orifice and below the vapor pressure of the binary fluid mixture at the operating temperature of the chamber. The binary fluid mixture flows through tube 14 and orifice 16 and, on leaving the orifice 16, expands (including partial or complete evaporation if any of the components of the mixture is a liquid), whereby the temperature of the mixture is lowered. The cooled, expanded binary fluid mixture immediately impinges upon and cools the temperature sensing means 26, the change in the temperature of which is indicated by means 28. The binary fluid mixture then flows through expansion chamber 20, trap 24 and outlet 22. The flow of the binary fluid mixture through tube 14 and orifice 16 is continued until an equilibrium temperature is reached at the temperature sensing means 26, that is, until the temperature indicating means 28 shows no further change in the temperature of the temperature sensing means.

A specific embodiment of the form of analyzer shown in FIG. 1 was used in the examples presented hereinafter, in which the chamber 10 and the inlet 12 were formed of inch I.D. copper tubing, the chamber 10 being 1 inch long and having a volume of 1 ml., and the tube 14 was a hypodermic needle 1 inch long having a bore of 0.005 inch I.'D., the open end of the needle forming the orifice 16. The chamber 20 was 4 inches high and had an internal diameter of inch and a volume of 2 ml. The temperature sensing means 26 was a commercial thermistor positioned /8 inch from the orifice 16 and was connected to a Wheatstone bridge circuit commonly employed for thermistor type temperature measurements, and a micr-oammeter 28 which shows the imbalance of the Wheatstone bridge due to changes in the temperature of the thermistor. The Wheatstone bridge and meter read and show the current in microamperes. The current readings can be converted to temperature readings, if desired, but this usually is unnecessary as the current readings are equally useful as a measure of the change in the temperature of the thermistor, and it is more convenient to use the current reading for thus purpose. The means 28 may also be a potentiometer-recorder used to indicate the bridge output and thereby give a permanent recording of the thermistor temperatures.

While a thermistor is the preferred form of temperature sensing means 26, other forms may be used, particularly thermocouples and other like electronic temperature sensing devices which detect and measure rather small changes in temperature and are rapid acting, particularly those which are accurate to il C. Thermometers, such as mercury and toluene filled types, can be used but usually are less desirable because they are slow acting and are not sufliciently sensitive for most cases, i.e. do not show sufiiciently small temperature changes. The temperature indicating means 28 will be of any conventional form and type that is adapted to indicate and/or record the temperature of the temperature sensing means in front of the orifice. In the case of thermometers, means 28 will be the upper portion of the thermometer containing the required temperature markrngs.

The temperature sensing means 26 must be spaced from the orifice 16 a sufiicient distance to not obstruct the orifice and to permit the binary fluid mixture to expand on leaving the orifice, but sufiiciently close to the orifice so, that the expanded binary fluid mixture will immediately impinge on the temperature sensing means while said expanded mixture i at the lowered temperature caused by the expansion. Since the expansion of the binary fluid mixture upon leaving the orifice is substantially instantaneous (flashing), the temperature sensing means usually will be spaced from the orifice by X32 to about inch, preferably about 4: inch.

Usually, it is also desirable to surround the sides of the temperature sensing means 26 by a screen 30. Some binary fluid mixtures, upon expansion, tend to cool sufficiently to cause partial liquefaction thereof. Other binary fluid mixtures,' which are normally liquid, expand insufliciently to cause complete vaporization. The temperature measured by the temperature sensing means should be of gaseous material, since any liquid material impinging on the temperature sensing means would cause further cooling by evaporation tending to produce erratic and inaccurate results. Screen 30 prevents liquid droplets from contacting the temperature sensing means and ensures that the temperature of only gaseous material is measured. Thus, screen 30 greatly improves the accuracy ofthe analyzer. If it is known that no liquid occurs in the expanded binary fluid mixture, screen 30 may be omitted.

The orifice 16 should have a diameter of from 0.001 to about 0.025 inch, preferably from about 0.004 to about 0.02 inch, so as to cause a detectable temperature change in fluids expanded there-through. It may be of any available shape, but usually a circular orifice is most convenient.

The orifice 16 is at the end of tube 14 which should have an internal diameter at least equal to that of the orifice and up to 0.125 inch inch). Thus, if the internal diameter of the tube 14 is equal to the desired diameter of the orifice, the orifice will be the open end of the tube 14. If the internal diameter of the tube 14 is greater than the desired diameter of the orifice, the orifice may be formed by pinching the end of the tube 14 or by drilling a hole of the desired diameter in the closed olt end of the tube 14. The tube 14 is provided to prevent selective flashing of the components of the binary fluid mixture. For this purpose, the tube 14 should be at least about 1 inch in length. The maximum length of the tube 14 will be limited by practical considerations such as convenience, economics, and the like.

The supply chamber should have an internal diameter of at least about twice the internal diameter of the tube 14. In the specific form shown in FIG. 1 and specifically described hereinbcfore, the analyzer is designed for the analysis of discrete samples of binary fluid mixtures. For such purpose, the supply chamber normally should be of a size to hold at least a sufficient quantity of the binary fluid mixture to cause the temperature of the temperature sensing means 26 to reach an equilibrium temperature and to permit that temperature to be observed and/ or recorded. A volume of about 1 ml. was found to be sufficient when the temperature sensing means was a thermistor temperature measuring means as in the preferred embodiment described hereinbefore. When slower acting and less sensitive temperature sensing means are employed, the volume of binary fluid mixture required to reach the equilibrium temperature will be larger, requiring a supply chamber of larger capacity. For practical and economic reasons, the supply chamber 10 usually will not have a capacity of more than about 10 ml.

However, the chamber 10 and inlet 12 may take other forms such as a pipe or tube provided with conventional couplings for connecting the analyzer with other sources of the binary fluid mixtures such as a process stream, blending equipment, storage vessels, and the like, whereby the analyzer and the process can be operated continuously or intermittently as desired. If desired, the inlet 12 may be provided with a valve or other closure means for isolating the analyzer from the source of the binary fluid mixture and for preventing the charge of binary fluid mixture from escaping through the inlet.

The binary fluid mixture in supply chamber 10 will be at a predetermined initial temperature of from about 80 C. to about 250 C., and at a predetermined initial pressure of from about 1 atmosphere to about 2,000 p.s.i.g. (pounds per square inch gauge). The initial temperature and initial pressure of the binary fluid mixture will depend on the normal boiling point of the binary fluid mixture and the pressure at which the expanison chamber can be maintained conveniently. The expansion chamber must be maintained at a pressure below the vapor pressure of the binary fluid mixture at the temperature of operation and at least /2 atmosphere below the pressure back of the orifice, the /2 atmosphere pressure being required to allow for the pressure drop across the orifice and to cause the binary fluid mixture to flow through the orifice. Thus, the initial temperature and pressure of the binary fluid mixture and the pressure in the expansion chamber must be coordinated to provide the necessary pressure dilferential.

If the binary fluid mixture has a normal boiling point below room temperature, whereby it is normally gaseous, the initial temperature may be its normal boiling point or any higher temperature that is convenient and the initial pressure may be from about /2 atmosphere above the pressure of the expansion chamber to any convenient higher pressure. Such binary fluid mixture may be used in gaseous form. Where the binary fluid mixture is one which is readily liquefied at about room temperature, it usually will be most convenient to employ it in the form of a liquid at room temperature and at an initial pressure equal to its vapor pressure at that temperature or at a slightly higher pressure and to operate the expansion chamber at atmospheric pressure, the vapor pressure of the liquid normally being at least /2 atmosphere above normal atmospheric pressure. Binary fluid mixtures which are readily liquefied at about room temperature usually are those in which the components have normal boiling points of from about 40 C. to about 24 C.

If the binary fluid mixture has a normal boiling point of 25 C. or higher so that its vapor pressure at 25 C. is equal to or less than atmospheric pressure, the required pressure differential between the initial pressure and the pressure in the expansion chamber may be obtained (1) by employing an initial temperature above the normal boiling point of the binary mixture so that its vapor pressure is increased to the required extent, or (2) by reducing the pressure in the expansion chamber to the required extent, or (3) by both increasing the initial temperature to raise its vapor pressure and decreasing the pressure in the expansion chamber. Where the binary fiuid mixture has a normal boiling point above 50 C., it usually will be desirable to employ procedure (3), i.e. to increase the initial temperature and decrease the pressure in the expansion chamber. When the binary fluid mixture has a normal boiling point of 25 C. to 50 C., it will usually be desirable to use only (1) or (2), preferably (2), i.e., reducing the pressure in the expansion chamber. It is frequently desired to operate the expansion chamber at about atmospheric pressure (i.e. not under reduced pressure), in which case the initial pressure of the binary fluid mixture must be at least 1.5 atmospheres.

In most cases, the initial temperature and the initial pressure will be those of the source of the binary fluid mixture, such as those of a process stream, blending equipment, or storage vessel. Usually, the source of the binary fluid mixture will be a storage vessel or blending equipment, in which case, the binary fluid mixture will be at normal room temperature, i.e. about 25 C. When the binary fluid mixture is gaseous, it will usually be at a superatmospheric pressure of from about 15 to about p.s.i.g. When the binary fluid mixture is a liquefied gas, the pressure in the supply chamber 10 usually will be the vapor pressure of the mix-ture.

For normal commercial purposes requiring an accuracy of 11%, temperature sensing means and pressure sensing means are not required in supply chamber 10 or inlet 12. However, such means may be provided where it is desired to obtain more accurate analyses.

Expansion chamber 20 should be sufiiciently large to receive the expanding binary fluid mixture passing from the orifice 16 without causing backpressure. For such purpose, it should have a volume of at least about 1.5 ml., preferably at least about 2 ml., and a diameter at least twice the diameter of tube 14. The expansion chamber may be as large as desired, the maximum size being dictated by economic and like considerations.

When the binary fluid mixtures to be analyzed are gaseous or are liquefied gases, expansion chamber 20 usually will be maintained at normal atmospheric pressure; the pressures in supply chamber 10 and the pressure drop through tube 14 and orifice 16 being suflicient to provide the necessary pressure diflerential to cause the binary fluid mixture to flow through tube 14 and orifice 16, expand, and cool. If the binary fluid mixture is a liquefied gas, the pressure drop across tube 14 and orifice 16 maintains suflicient pressure (the vapor pressure of the liquid) in supply chamber 10 so that the mixture does not vaporize until it issues from orifice 16 and the pressure in expansion chamber 20 will be below that vapor pressure by an amount at least equal to that pressure drop. When the binary fluid mixture to be analyzed is a liquid having a normal boiling point of about C. to about 50 C., the expansion chamber 20 usually will be maintained at a reduced (subatmospheric) pressure by the application of a vacuum to the expansion chamber, e.g. by way of outlet 22; the particular reduced pressure depending upon the volatility and boiling point of the binary liquid mixture, the temperature and pressure in supply chamber 10, and the pressure drop through tube 14 and orifice 16, and can be readily determined by those skilled in the art.

A trap 24 may be placed between expansion chamber 20 and outlet 22 to help prevent the diffusion of moist air into the expansion chamber and the freezing of the moisture in the expansion chamber when the temperature of the expanded binary fluid mixture is below the freezing point of water.

Usually, the outlet 22 is a simple vent of restricted diameter with respect to the diameter of expansion chamber 20. In the preferred embodiment hereinbefore described, it had an internal diameter of inch. When the binary fluid mixture is sufliciently valuable or if it is of such character that it is undesirable for the binary fluid mixture to be vented into the atmosphere, the outlet 22 will be connected to a suitable receiver or a recovery system for the binary fluid mixture. Also, when it is desired to operate expansion chamber 20 under reduced pressure, outlet 22 may be connected with a source of constant vacuum.

The various parts of the analyzer may be constructed of any material which will withstand the temperatures and pressures under which it is to be used and which is substantially inert to the binary fluid mixtures to be analyzed under those conditions. Suitable materials include brass, copper, steel, stainless steel, nickel, Monel, Inconel, aluminum, polytetrafluoroethylene, and the like. In the preferred embodiment hereinbefore described, tube 14 was made of chrome plated steel and the rest of the analyzer (other than the thermistor) was made of brass and copper.

When it is desired to analyze binary fluid mixtures of two particular substances in unknown proportions, the analyzer is first calibrated with a series of known binary fluid mixtures of those substances. More specifically, a series of several mixtures of the two substances in varying known proportions are passed through the analyzer at predetermined temperatures and pressures in supply chamber 10 and in expansion chamber 20 which temperatures and pressures are to be employed with the binary fluid mixtures to be analyzed. A calibration curve is prepared from the temperatures or temperature changes or current readings produced by those known mixtures. The binary fluid mixture to be analyzed is then passed through the analyzer under substantially the same temperature and pressure conditions as were used in the calibration, and the observed temperature or current reading is compared with those obtained with the known mixtures to determine its composition; i.e. the composition of the analyzed binary fluid mitxure is read off of the calibration curve as indicated by the observed reading.

Usually, the analyzer is used in connection with control of a process for producing the binary fluid mixture, e.g. blending, where variations in the composition of the mixture are in a rather limited range. In such cases, it is only necessary to calibrate the analyzer over a fairly narrow range bracketing the range of expected variations, i.e. to employ in the calibration a series of only a few mixtures of known composition in which the proportions are varied over a range which approximates the range of expected variations in the mixtures to be analyzed. Also, since the temperatures of the expanded binary fluid mixtures vary regularly with variations in the proportions of the components thereof, it is not necessary to employ in the calibrations a large number of known mixtures with small variations in proportions. Differences in the concentration of any component of the order of 4-6% between the adjacent members of the series of known mixtures are usually suflicient and normally are used.

Referring more particularly to FIG. 2 of the drawings, the analyzer comprises a supply vessel 210 for the binary fluid mixture to be analyzed, a tube 214 optionally provided with a valve 215, an orifice 216, an expansion chamber 220, and a temperature sensing and measuring means 226. The supply vessel 210, as shown, is a storage vessel for the binary fluid mixture. The expansion chamber 220, as shown, is a tubing or pipe, open at the right end to form the outlet. Also as shown, the temperature sensing means 226 positioned in the expansion chamber is a thermocouple connected to temperature indicating means (not shown). The

elements

210, 214, 216, 220 and 226 correspond generally to the

elements

10, 14, 16, 20 and 26, respectively, of FIG. 1, and the ranges of dimensions set forth with respect to

elements

10, 14, 16, 20 and 26 of FIG. 1 are similarly applicable to

elements

210, 214, 216, 220 and 226, respectively, of FIG. 2.

The binary fluid mixture in supply vessel 210 normally is at room temperature and at the usual storage pressures, e.g. the vapor pressure of the mixture in the case of binary liquefied gas mixtures. The operation, calibration and use of the analyzer of FIG. 2 is similar to those described for FIG. 1 for binary fluid mixtures available under those conditions of temperature and pressure.

Referring particularly to FIG. 3, the analyzer comprises a tube 314, an orifice 316, an expansion chamber 320, an outlet 322, and a temperature sensing means 326. Tube 314 had an internal diameter of A; inch, corresponded to tube 14 of FIG. 1, and was adapted to be connected at its left end to available supplies of the binary fluid mixtures to be passed through the analyzer. The orifice 316 was formed, in one instance, by pinching off the end of tube 314 and, in a second instance, by drilling a small hole in the closed off end of tube 314. The end of tube 314, containing the orifice 316, was fitted into one arm of a T-tube of about A inch internal diameter which formed the expansion chamber 320. The temperature sensing means 326 comprised a thermocouple in the second arm of the T-tube which was otherwise sealed off to prevent the flow of fluid through that arm. The third arm was open to the atmosphere and formed outlet 322.

The dimensions of

elements

314, 316, 320, 322 and 326 may be varied as described with respect to

elements

14, 16, 20, 22 and 26, respectively, of FIG. 1. Also, such elements function similarly to the respective elements of FIG. 1. The embodiment of FIG. 3 may be operated, calibrated and used in the same manner as described with respect to FIG. 1. It was operated at room temperature and atmospheric pressure to analyze binary liquefied gas mixtures.

Although the process and analyzer of this invention may be used with any binary fluid mixture having a normal boiling point up to 250 C., i.e. which will vaporize when passed through the restricted orifice into an expansion chamber which is under a pressure below the vapor pressure of the mixture at the temperature of operation, it is particularly useful with binary fluid mixtures which are gases or liquids having normal boiling points below 50 C., including especially liquefied gases. Some examples of such mixtures are about 40 to about 70% by weight of monofluorotrichloromethane (B.P. 23.77 C.) and about 60 to about 30% by weight of dichlorodifluoromethane (B.P. 29.8 C.) used as aerosol propellents; mixtures of dichlorodifluoromethane and diehlorotetrafluoroethane (B.P. 355 C.) used as refrigerants and aerosol propellents; mixtures of monochlorodifluoromethane (B.P. 40.8 C.) and monochloropentafluoroethane (B.P. 38.7 C.) used as refrigerants; mixtures of about to about 26% by weight of isobutane (B.P. 10.2 C.) and about 85 to about 74% by weight of dichlorodifluoromethane; and mixtures of octafluorocyclobutane (B.P. -6.06 C.) with any of nitrous oxide (B.P. 89.5 C.), propane (B.P. 42.l7 C.), cyclopropane (B.P. 34.4 C.), hexafluoroethane (B.P. '78.1 C.) or monochloropentafluoroethane used as aerosol propellents for foodstuffs or gaseous dielectrics. Other mixtures, which can be analyzed with the present invention, will be apparent to those skilled in the art.

In order to more clearly illustrate this invention, preferred modes of practicing it, and the results obtained thereby, the following examples are given in which the parts and proportions are by weight except where specifically indicated otherwise.

Example 1 Seven binary fluid mixtures, in liquid form at 25 C., of trichlorofluoromethane and dichlorodifluoromethane of varying known composition were prepared and passed through the specifically described specific embodiment of the analyzer of FIG. 1 with the liquids under their own vapor pressure at 25 C. in chamber 10 and with the expansion chamber under atmospheric pressure, and the output of the thermistor used as means 26 was determined. From this data, a calibration curve was prepared. The data are given in the table below, together with the vapor pressures of the mixtures at C. in pounds per square inch absolute (p.s.i.a.) and in atmospheres (atm.).

* The rest of each mixture consisted of dichlorodifluoromethane.

Then another mixture, consisting of trichlorofluoromethane and 50% dichlorodifluoromethane was passed through the analyzer. The microamperes developed at means 26 were 32.4, which corresponds to 50% trichlorofluoromethane on the calibration curve. Analyses of several other known mixtures of these same compounds under the same conditions indicated that an accuracy of i0.5% was developed. The actual observed changes in the temperatures of the mixtures, caused by their expansion through the orifice, were of the order of 40 C.

In a similar manner, a calibration curve for liquefied mixtures of dichlorodifluoron'lethane and 1,2-dichlorotetrafluoroethane were prepared. Using the calibration curve thus obtained, other known liquefied mixtures of these two materials were analyzed and accuracies of il% were observed.

Example 2 Three binary fluid mixtures of isobutane and dichlorodifluoroethane in liquid form at 25 C. were prepared and passed through the same analyzer and under the same conditions as in Example 1. The compositions of the mixtures, their vapor pressures, and the microampere readings obtained are indicated in the table below in the same manner as in Example 1:

Vapor Pressure at 25 C. Wt. Percent Isobutane Mlcroamperes P.s.i.a. Atm.

Vapor Pressure at 25 C.

Wt. percent Isobutane Microampcres P.s.i.a. Atm.

Analyses of other known mixtures of these two compounds in this composition range also indicated that accuracies of 11% were obtained.

Example 3 Gaseous mixtures of nitrous oxide and octafluorocyclobutane were prepared and passed through the analyzer of Example 1 at three ditterent pressures in chamber 10 and are included in the table below. The pressure in expansion chamber 20 in every case was one atmosphere. From the data thus obtained, calibration curves were prepared at each pressure.

Mieroamperes at Indicated Pressures in Chamber 10 Wt. percent N 0 tion, many variations can be made in the form, construction and size of the analyzer, and in the binary fluid mixtures, the procedures, and the conditions employed, Without departing from the spirit or scope of this invention.

From the foregoing description, it will be apparent that this invention provides a novel process for easily and rapidly analyzing binary fluid mixtures with a high degree of accuracy, and a novel form of analyzer which is particularly adapted for practicing such process and which is inexpensive and simple in construction and readily transportable. 'Both the process and the analyzer can be operated batchwise, intermittently or continuously, as desired. Thus, the process and the analyzer have many advantages over the prior art methods and equipment, whereby this invention constitutes a valuable advance in and contribution to the art.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An analyzer for binary vaporizable fluid mixtures of known components which comprises (A) a supply chamber for the binary fluid mixture to be analyzed,

(B) an expansion chamber,

(C) a tube having an internal diameter of from 0.001 to 0.125 inch connecting the supply chamber to the expansion chamber,

(D) an orifice having a diameter of from 0.001 to 0.025 inch at the expansion chamber end of said tube, and

(E) temperature sensing means in said expansion.

chamber positioned in front of said orifice and spaced therefrom by A to 4 inch, including (a) means extending outside of said expansion chamber for indicating the temperature of the temperature sensing means; said supply chamber and said expansion chamber having a diameter at least twice the diameter of said tube, and said expansion chamber having a volume of at least 1.5 ml.

2. An analyzer for binary vaporizable fluid mixtures of known components which comprises (A) a supply chamber for the binary fluid mixture to be analyzed,

(B) an expansion chamber,

(C) a tube having an internal diameter of from 0.001

to 0.125 inch and length of at least 1 inch connecting the supply chamber to the expansion chamber,

(B) an electronic temperature sensing means accurate to '-1 C. in said expansion chamber positioned in front of said orifice and spaced therefrom by to 4 inch, including (a) means extending outside of said expansion chamber for indicating the temperature of the temperature sensing means; said supply chamber and said expansion chamber having a diameter at least twice the diameter of said tube, and said expansion chamber having a volume of at least 1.5 ml.

3. An analyzer for binary vaporizable fluid mixtures of known components which comprises (A) a supply chamber for the binary fluid mixture to be analyzed,

(B) an expansion chamber,

(C) a tube having an internal diameter of from about 0.004 to 0.125 inch and -a length of at least 1 inch connecting the supply chamber to the expansion chamber,

(D) an orifice having a diameter of from about 0.004 to about 0.02 inch at the expansion chamber end of said tube, and

(B) an electronic temperature sensing means accurate to 11 C. in said expansion chamber positioned in front of said orifice and spaced therefrom by to inch, including (a) means extending outside of said expansion chamber for indicating the temperature of the temperature sensing means;

said supply chamber and said expansion chamber having a diameter at least twice the diameter of said tube, and said expansion chamber having a volume of at least 2 ml. 4. An analyzer for binary vaporizable fluid mixtures of known components which comprises (A) a supply chamber for the binary fluid mixture to be analyzed,

(B) an expansion chamber,

(C) a tube having an internal diameter of from 0.001

to 0.125 inch and a length of at least 1 inch connecting the supply chamber to the expansion chamber,

(D) an orifice having a diameter of from 0.001 to 0.025 inch at the expansion chamber end of said tube,

(E) an electronic temperature sensing means accurate to :1 C. in said expansion chamber positioned in front of said orifice and spaced therefrom by to inch, including (a) means extending outside of said expansion chamber for indicating the temperature of the the temperature sensing means,

(b) and a screen surrounding the side of the temperature sensing means to prevent the impingement of liquid droplets on the temperature sensing means;

5. An analyzer for binary vaporizable fluid mixtures of known components which comprises (A) a supply chamber for the binary fluid mixture to be analyzed,

(B) an expansion chamber,

(C) a tube having an internal diameter of from about 0.004 to 0.125 inch and a length of at least 1 inch connecting the supply chamber to the expansion chamber,

(B) an electronic temperature sensing means accurate to :1" C. in said expansion chamber positioned in front of said orifice and spaced therefrom by about /8 inch, including (a) means extending outside of said expansion chamber for indicating the temperature of the temperature sensing means,

said supply chamber and said expansion chamber having a diameter at least twice the diameter of said tube, and said expansion chamber having a volume of at least 2 ml.

6. A process for analyzing a binary fluid mixture of known components having a normal boiling point below 50 C., which process comprises (A) flowing the binary fluid mixture at a predetermined initial pressure of from about 1 atmosphere to about p.s.i.g. and at a predetermined initial temperature of up to about 250 C. through a restricted orifice having a diameter of from 0.001 to 0.025 inch,

(D) comparing the measured temperature with the temperatures of a series of similarly expanded binary fluid mixtures of the same components but of known varying composition.

7. A process for analyzing a binary fluid mixture of known components having a normal boiling point below 50 C., which process comprises (A) flowing the binary fluid mixture at a predetermined initial pressure of from about 1 atmosphere to about 125 p.s.i.g. and at a predetermined initial temperature of up to about 250 C. through a restricted orifice having a diameter of from about 0.004 to about 0.02 inch,

(D) comparing the measured temperature with the temperatures of a series of similarly expanded binary fluid mixtures of the same components but of known varying composition which bracket the range of expected variations in the composition of the mixture to be analyzed.

8. A process for analyzing a binary fluid mixture of known components having a normal boiling point below room temperature, which process comprises (A) flowing the binary fluid mixture at a predetermined initial pressure of at least 1.5 atmospheres and at a predetermined initial temperature of from about room temperature to about 250 C. through a restricted orifice having a diameter of from about 0.004 to about 0.02 inch,

(B) expanding the mixture flowing from the orifice in an unheated expansion chamber while maintaining said chamber at about atmospheric pressure,

(C) measuring the temperature of the expanded tbinary fluid mixture flowing from said orifice, and

(D) comparing the measured temperature with the temperature of a, series of similarly expanded binary fluid mixtures of the same components but of known varying composition which bracket the range of expected variations in the composition of the mixture to be analyzed.

9. A process for analyzing a binary fluid mixture of known components having a normal boiling point below room temperature, which process comprises (A) flowing the binary fluid mixture at a predetermined initial pressure of at least 1.5 atmospheres and at about room temperature through a restricted orifice having a diameter of from about 0.004 to about 0.02 inch,

10. A process for analyzing a binary fluid mixture of known components having a normal boiling point of from about C. to about 24 C., which process comprises (A) flowing the binary fluid mixture in liquid form at about room temperature and at a pressure of at least 2 atmospheres and which is at least equal to the vapor pressure of the mixture at that temperature through a restricted orifice having a diameter of from about 0.004 to about 0.02 inch,

(D) comparing the measured temperature with the temperatures of a series of similarly expanded binary fluid mixtures of the same components but of known varying composition which :bracket the range of expected variations in the composition of the mixture to be analyzed.

OTHER REFERENCES Perkins, A.: College Physics, N.Y., Prentice Hall, 1948,

pages

214 and 215.

RICHARD C. QUEISSER, Primary Examiner.

DAVID B. DEIOMA, Assistant Examiner,

Claims

4. AN ANALYZER FOR BINARY VAPORIZABLE FLUID MIXTURES OF KNOWN COMPONENTS WHICH COMPRISES (A) A SUPPLY CHAMBER FOR THE BINARY FLUID MIXTURE TO BE ANALYZED, (B) AN EXPANSION CHAMBER, (C) A TUBE HAVING AN INTERNAL DIAMETER OF FROM 0.001 TO 0.125 INCH AND A LENGTH OF AT LEAST 1 INCH CONNECTING THE SUPPLY CHAMBER TO THE EXPANSION CHAMBER, (D) AN ORIFICE HAVING A DIAMETER OF FROM 0.001 TO 0.025 INCH AT THE EXPANSION CHAMBER END OF SAID TUBE, (E) AN ELECTRONIC TEMPERATURE SENSING MEANS ACCURATE TO $1* C. IN SAID EXPANSION CHAMBER POSITIONED IN FRONT OF SAID ORIFICE AND SPACED THEREFROM BY 1/32 TO 1/4 INCH, INCLUDING