US2984989A - Vaporizing apparatus - Google Patents

Description

May 23, 1961 v. c. GARBARINI VAPORIZING APPARATUS 2 Sheets-Sheet 1 Filed Sept. 2, 1958 V/cfar C. Garb an'ni l/VVEA/TOR y 23, 1953 v. c. GARBARIN] 2,984,989

VAPORIZING APPARATUS Filed Sept. 2, 1958 2 Sheets-Sheet 2 FIG-2 Vicfor C Garbarini IIVVEA/ 70R l mafi wwd TTOR/VEY United States Parent VAPORIZING APPARATUS Victor C. Garbarini, Fords, N.J., assignor to Esso Research and Engineering Company, a corporation of Delaware Filed Sept. 2, 1958, Ser. No. 758,303

Claims. (Cl. 6252) This invention relates to apparatus for vaporizing liquid mixtures at ambient temperatures. It relates particularly to apparatus for vaporizing light hydrocarbon liquids such as liquified gas mixtures of which representative samples are desired to be taken for analytical purposes.

Present methods of analysis for light hydrocarbons (C C by mass spectrometry and gas-liquid or gassolid chromatography require gaseous samples. A simple way of effecting vaporization of a liquid sample is to allow it to throttle through a needle valve into an evacuated receiving container with the sample material that actually passes the valve flashing completely from the liquid to the vapor state.

A potential disadvantage of this simple vaporization technique is that there will be cooling of the sample material passing the valve. Some heavy ends so cooled will tend to be left behind in the valve and connecting piping as liquids. The working sample finally collected after the valve has been shut may not, therefore, be truly representative of the main body of hydrocarbon liquid from which it was drawn.

This disadvantage might, in theory, be overcome by applying heat to the valve. Heating of a throttle valve using conventional means, however, is both inconvenient and unreliable, and also creates a potential hazard when highly inflammable or thermally unstable fluids are being handled. Accordingly, vaporizing valves have been constructed with extended external surfaces intended to act as means for gathering heat from the atmosphere and transferring it to fluid flowing through the valve to obtain a substantially isothermal expansion of this fluid. A fabricator of such valves is the Manufacturers Engineering and Equipment Company of Hatboro, Pa., whose products bear the trade name MEECO. The MEECO vaporizing valve comprises a long needle in a body or casing formed or fitted externally with a plurality of heat absorbing fins.

Another potential disadvantage of the simple vaporization technique even when a MEECO valve is used, however, is that of accumulation of liquid in the receiving chamber downstream of the needle valve as the pressure builds up in this chamber. Once the valve is opened, there will, of course, be an increase in pressure in the initially evacuated receiving chamber. As the pressure therein rises the pressure drop across the needle valve may decrease significantly, and liquid materials arriving at the inlet to the valve be only partially flashed to vapor in their passage through the valve with some liquid carrying over to the receiving chamber.

Likewise, as pressure builds up in the receiving chamber with fluid flowing thereinto, some sample constituents initially vaporized may be condensed again; that is, there may be reliquefaction. When the needle valve is fully shut ofl, therefore, the material in the receiving chamber may comprise a vapor above a liquid, and this vapor, the actual substance for subjection to analysis, will be significantly different in composition from the parent body of hydrocarbon liquid.

Patented May 23, 1 b

ice

According to this invention the foregoing potential disadvantages of the throttle valve vaporization apparatus and process are substantially eliminated by employing a valve adapted to give substantially isothermal expansion of fluid passing therethrough, and limiting back pressure on this valve to prevent pressure downstream of the valve, that is, in the sample receiving chamber, from building up to a level that would permit any constituent of the material being sampled to exist as a liquid.

It is a principal object of this invention to provide a method and means for obtaining vapor samples from gases which have been liquefied under pressure.

It is a particular object of this invention to provide a method and means according to the aforesaid principal object wherein and whereby a step of vaporizing liquid samples shall be performed substantially isothermally and said vapor samples be gathered only up to a certain limiting and predetermined pressure.

It is another particular object of this invention to provide a method and means according to the aforestated principal object wherein and whereby said vapor samples may be obtained for routine analytical use quantitatively, rapidly, and with minimum liquid sample requirements.

These and other objects may be perceived and a fuller understanding of this invention obtained by referring to the following description and claims taken in conjunction with the accompanying drawings in which:

Fig. 1 represents a layout of an apparatus embodiment of this invention which is particularly adapted for the vaporizing of comparatively small liquid samples on an intermittent basis as in laboratory use.

Fig. 2 represents a layout of an apparatus embodiment of this invention which is particularly adapted for the vaporizing of comparatively large liquid samples on a semi-continuous or continuous basis as in field or plant use.

Referring now to Fig. 1, l6 designates the needle member of a needle valve for liquified gas vaporization. This needle is enclosed in a long sleeve or valve body 12 in which the valve seat is formed. Surrounding valve body 12 is a plurality of fins 14 either formed integrally with the valve body, or, if formed separately, so attached thereto that heat may flow freely from the fins to the valve body. At the sample inlet end of the valve body and below the valve packing region there is a chamber region 16 wherein supply, vacuum, and dumping connections are made to the valve. Desirably this chamber will be as small as practicably possible. The packing and needle adjusting means of the illustrated valve may be considered conventional.

Fluid supply to the needle valve comes from a sample source such as a bomb cylinder 18 containing a body of gas 'liquified under pressure. This cylinder is provided with ashutoff valve 2! and may have a short nipple-like extension therebeyond to enter a quickly manipulable coupler 22 on supply line 24 to the needle valve. While line 24 is shown of appreciable length for purposes of illustration and description, in practice it will be kept as short as possible and coupler 22 may effectively be fitted directly to chamber 16.

Leading away from valve chamber 16 are dumping line 26 and vacuum line 28. Line 26 which is provided with a dumping valve 39 is the means for discharging unused portions of liquid samples after vaporizing operations have been concluded. Line 28 which is provided with vacuum shutofi valve 32 is used for the evacuation of valve chamber 16 and lines 24 and 26 before vaporizing operations are commenced; that is, before valve 20 is opened. Lines 26 and 28 like line 24 are shown of appreciable length for disclosure purposes, but also like line 24 will be kept as short as possible in practice and may simply comprise direct connections from valve chamber 16 to dumping and vacuum valves 30 and 32.

in the course of a vaporizing operation which will be described in detail presently, valve chamber 16 and lines 24, 26, and 23 to the extent that these lines exist must be maintained full of liquid material at all times. As a check on this condition a pipe or tubing section 34 of transparent or translucent plastic or glass is provided on the downstream side of dumping valve 30. The function of this tubing section is to allow observation of the rapid boil-off of unused liquid sample material after conclusion of a vaporizing run. This is indicated by a momentary fogging inside the tubing. Failure to obtain such boil-ofi will be information to an operator that insuflicient sample material was supplied or that the vaporizer was not used properly, and in any case that the preceding vaporizing run was invalid.

The outlet line 36 of the needle valve branches into two lines 38 and 40. Line 40 is provided with a compound pressure gauge 42, a vacuum-tight check valve 44, and a back pressure regulating valve 46, which is, in effect, a relief valve with an adjustable setting. The outlet end of regulating valve 46 is joined with that of sight tube 34 in a common vent line 48. In many appartus embodiments of this invention, regulating valve 46 may be eliminated as an individual piece of equipment with its function being obtained through spring loading within check valve 44.

Branch line 49 leading away from the outlet end of the needle valve is itself branched into two lines 50 and 52. Line 50 is provided with a vacuum shutoff valve 54. Theroutlet end of this valve is joined with that of valve 32 in a common vacuum line 56. Line 52, the other branch of line 49, may be provided with an antidumping valve 58 as shown closely adjacent a quick coupler 6! through which attachment to the line ismade of an evacuated bomb cylinder 62 for vaporized sample reception. This cylinder is provided with a shutoff valve 64. The function of anti-dumping valve 58 is to hold vapor pressure in the system substantially up to the point of receiving cylinder attachment, so that neither need wastage of vapor be tolerated nor re-evacuation of the system performed if a succession of pre-evacuated receiving cylinders 62 are to be filled. Valve 58 may be omitted in apparatus embodiments of this invention where the foregoing effects are not considered important or bothersome. Fine mesh screens or other filtering devices may be incorporated into the quick couplers 22 and 60 to prevent solid contaminants from entering the apparatus.

The apparatus embodiment of this invention illustrated in Fig. 1 having been described, its operation will now be considered. For this consideration assume that supply cylinder 18 and receiving cylinder 62 are in place on the apparatus as shown. Valve 20 of cylinder 18 will be closed, and valve 64 of cylinder 62 may be open al though it need not be if cylinder 62 has been evacuated prior to installation on the vaporizing apparatus. Assume also that the back pressure regulating valve 46 has been set to open at some pressure less than that which would allow any constituent of the fluid material in cylinder 18 to exist as a liquid. For liquefied petroleum gas mixtures C or lighter, the regulated back pressure could conveniently be 1 pound per square inch above atmospheric pressure. For less volatile fluids such as gasoline, the back pressure could be as low as /2 pound per square inch absolute provided that line 48 is connected to a region of reduced pressure such as the suction side of a vacuum pump.

Initially the needle member 10 of the needle valve assembly will be off its seat in valve body 12; that is, the needle valve will be open. Dumping valve will be closed; and anti-dumping valve 58 will be open. Vacuum shutoff valves 32 and 54 will be open also. Upon operation of whatever vacuum producing means of liquified gas.

is connected to line 56, valve chamber 16 and all lines of the apparatus except those beyond vacuum-tight check valve 44 and dumping valve 30 in the direction of vent line 48 will be evacuated. This includes receiving cylinder 62 if it has not been evacuated previously and its shutofi valve 64 is open. Compound gauge 42 will indicate the lowering of pressure in the system.

After a satisfactory condition of evacuation of the apparatus has been achieved, the needle member 10 is seated again in valve body 12; vacuum shutofi valves 32 and 54 are closed, and receiving cylinder valve 64 opened it it has been closed up to this time. Any rise of pressure in the system as shown on gauge 42 as valve 64 is opened indicates that not all of the gas or gas producing material originally in cylinder 62 has been removed. Assuming a satisfactory conditon of evacuation, however, supply cylinder valve 20 will be opened next to admit liquefied gas under pressure to valve chamber 16. Needle member 10 may then be backed off its seat in valve body 12 an appropriate amount to allow the flow of fluid through the needle valve assembly.

As liquefied gas to be vaporized flows down the long, narrow annular space between the needle member and the valve body, it will be dropping in pressure and tending to drop in temperature according to the usual throttling process in the course of flashing to a vapor. However, as soon as temperature of fluid in the throttle valve drops below the environmental temperature of the valve or atmospheric temperature, the difference in temperature across the valve body will cause a flow of heat therethrough toward the fluid.

Such flow of heat will be at a significant rate because of the large heat transfer area of valve body fins 14. This flow will tend to restrict the temperature drop taken by fluid flowing through the needle valve from supply cylinder 18, and will furnish heat of vaporization to that portion of the fluid flowing through the valve which might otherwise remain a liquid if the throttling process were adiabatic; Accordingly, fluid arriving at valve outlet line 36 will be completely vaporized, having not only been expanded to a reduced pressure level from its conditlon of liquefaction under pressure in supply cylinder 18, but also been substantially sustained in temperature durlng the expansion process.

From outlet line 36 vapor flows through line 38 toward check valve 44 and back pressure regulating valve 46, and through line 40 toward receiving cylinder 62. As operation of the apparatus is continued, pressure will rise in cylinder 62, and, check valve 44 having opened, against regulating valve 46. At some time a pressure level will be reached corresponding to the setting of valve 46, and upon opening of this valve there will be flow of vapor out the vent line 46 and no further pressure rise in cylinder 60.

After valve 46 has opened, needle member 10 may be seated in valve body 12 to end the flow of liquified gas, and anti-dumping valve 58 and receiving cylinder valve 64 be closed. Coupler 60 may be manipulated to release cylinder 62 for the latter to be removed from the apparatus; If another previously evacuated cylinder is to be filled with vapor it may be coupled to the apparatus in place of the one just removed; its shutoff valve 64 and the anti-dumping valve 58 opened, and needle member 10 backed off its seat to allow further flow and vaporization On the other hand, if no more vapor samples are to be taken at the time, shutofi valve 20 on supply cylinder 18 may be closed and dumping valve 30 opened to vent residual high pressure fluid from valve chamber 16 and lines connected thereto, observation of boiling off of the vented fluid being taken through sight tube 34. 7

It might appear that the foregoing process of taking vapor samples could be carried out simply by manipulating needle member 10 While gauge 42 was observed, and shutting off flow through the needle'valve upon achievement of a particular pressure. That is, it might appear that the function of pressure regulating Valve 44 to limit the pressure level in the system automatically could be replaced in practice with a manual function. Actually, the vaporization of a liquid sample with consequent build-upof pressure in the receiving cylinder for vaporizing equipment of laboratory size will be extremely rapid, and once the needle valve has been opened human agency cannot be relied upon to shut it at just the right time. Closing needle valve too late will allow over pressuring of the receiving cylinder, while closing it too early may result in collection of a vapor sample at sub-atmospheric pressure. Most apparatuses for the analysis of light hydrocarbons require vapor samples at some positive pressure. By having a back pressure regulating valve in the vaporizing system, not only is a convenience factor supplied but also and more important a considerable possibility for human error in operation of the equipment is removed.

Another benefit of the back pressure regulating valve is that it will allow fluid to flow through the system while temperature conditions in receiving cylinder 62 are becoming stable. The first vapor particles arriving in the cylinder will be at substantially atmospheric temperature but very low'pressure, and will be compressed with corresponding rise in temperature by succeeding vapor particles flowing into cylinder 62. At the moment that valve 46 opens, the vapor in the cylinder will be at the regulated pressure but ata temperature at least somewhat higher than atmospheric.

Continued flow of vapor through the needle valve and the back pressure regulating valve for a short while will allow heat to flow from the vapor in cylinder62 to the atmosphere through the cylinder wall, while external vapor pressure is maintained on the cylinder contents with a httle more material flowing in as these contents cool. When cooling has been substantially completed, cylinder 62 may be shut off and removed from the vaporizing apparatus according to procedures given already with confidence that the pressure and temperature of the vapor within it are stable.

A slight variation of the foregoing operating procedure for the apparatus of Fig. 1 will be to leave receiving cylinder valve 64 closed after the system has been pumped down, vacuum shutofl valves 32 and 54 closed, and the needle valve opened. Pressure will build up rapidly in the various open lines of the system until the predetermined limiting back pressure has been achieved, and valve 46 has opened to vent the total vapor flow out line 48 before any material has entered the receiving cylinder. This venting may be continued for any period necessary to allow the internal surface of the various lines and fittings of the system to become saturated with adsorbed hydrocarbon heavy ends. When valve 64 is finally opened, therefore, the fluid flowing from the supply to the receiving cylinder will not be altered in composition along the Way by adsorption of any components on intermediate pipe or valve surfaces.

Referring now to Fig. 2, what is shown is a vaporizing apparatus arrangement which will be particularly useful in the following circumstances: when vacuum is not available; when high pressure and/or large volume liquid samples are available as in plant or field use, and when semi-continuous or continuous vaporizing is required as in gathering a large number of individual vapor samples or generating a vapor stream for calibrating continuous flow type gas analyzers.

In Fig. 2 the high pressure liquid inlet line to the vaporizing apparatus is designated 66. This line may be provided with any suitable coupling means such as quick coupler 68 for attachment to the liquid sample source. Line 66 leads to a filter 70 which may be employed to arrest the flow of any foreign matter carried over from the liquid sample source. Downstream of the filter is a sample inlet shutoff valve 72. From this valve the inlet line proceeds to a crossto which are connected an inlet pressure gauge 74, the inlet fitting 76 of the vaporizing needle valve, and an excess liquid outlet or'high pressure blow-through line 78.

Pressure gauge 74 'is not compounded; and should be capable of indicating relatively high pressures, 400 pounds per square inch for example. The vaporizing valve for the apparatus of Fig. 2 may be just the same as that shown in Fig. 1 comprising a needle member 10, a valve body 12, and heat absorbing fins -14. Inlet connection 76 for the needle valve supplies fluid for flow therethrough in a direction in reverse of the vaporizing flow in the apparatus of Fig. 1.

In Fig. l the relatively high pressure liquid sample is supplied to the valve at the end adjacent the packing, and any liquid which may be left accidentally to vaporize in valve chamber 16 after the valve has been shut may seep out through the packing as gas to relieve any potentially dangerous condition of high pressure. In the apparatus of Fig. 2 such relief is provided by a safety valve 80 in the excess liquid outlet line 78. Valve 80 may be conveniently of the spring-loaded toggle type'susceptible to opening by external manipulation of the toggle mechanism or internal pressure of about 350 pounds per square inch. The outlet side of valve 80 is connected through a series of fittings to a vent line 82.

Connected to the chamber region of the needle valve assembly are a vapor product outlet line '86 and a vapor product pressure regulating valve inlet line 88. Vapor product pressure gauge 84 connected to line 88 need not be a compound gauge since it is contemplated that the low pressure side of the apparatus of Fig. 2 will always operate at a positive pressure. Product outlet line 86 leads to an outlet shutoff valve 90. Beyond this valve are appropriate coupling means such asquick coupler 92 whereby the vaporizing apparatus-may be connected to a desired vapor receiving device. Shown in place on the apparatus is a receiving cylinder 94 which is provided with shutoff valves 96 and 98, one at either end. With both of these valves open, vaporized material may be blown through cylinder 94 to purge it of air or any other prior contents. When purging is complete, valves 98 and 96 may be closed in the order stated for vapor sample collection.

Line 88 leads to the inlet side of a vapor product back pressure regulating valve 100. This valve may be of the spring-loaded diaphragm type and need not be vacuum tight. Desirably valve 100 may be adjusted to open or relieve over a range of inlet pressures, and it is by means of such adjustment that the pressure of the vapor product of the apparatus of Fig. 2 available in line 86 is set. When valve 100 opens in the regular way, fluid flowing through it will leave by way of relief line 102 which is connected to vent line 82.

As a protective feature for the low pressure side of the apparatus, regulating valve 100 may be provided with an emergency relief line 104 which is connected to it in the region above the diaphragm. In case of any unexpected pressure build up on the downstream side of the vaporizing valve, the diaphragm of regulating valve 100 will rupture and the high pressure material escape safely through emergency line 104 and vent 82 with no dam-age to any low pressure parts other than the diaphragm which may be replaced easily.

Operation of the apparatus of Fig. 2 will be similar in principle to that of the apparatus of Fig. 1, although somewhat different in detail. With the needle valve closed and sample inlet shutoff valve 72 open, safety valve 8% may be lifted by hand to allow high pressure fluid to blow through to vent line 82 as a check that there is indeed liquid material under pressure available at the sample source. Valve 80 should then be closed, and, after opening valves 96, 96, and 98, the needle valve be opened to allow fluid to flow therethrough to be vaporized at substantially constant temperature and to purge the system of air and any other contaminants.

During the purging process, the vapor product pressure regulating valve 100 should be so adjusted that at least a slight positive pressure in line 88 will be required to open it. This is to insure that there will be appreciable vapor flow through product line 86 and receiving cylinder 94;

At the conclusion of purging, valve 93 on cylinder 94 will be closed. This will divert all vapor flow through valve 100 and cause an increase in the reading of product pressure gauge 84. The pressure regulating valve may then be adjusted in accordance with observations of gauge 84 to give the desired back pressure on the system which will be the limiting pressure of accumulation of vapor in receiving cylinder 94.

Although this invention has been described with a certain degree of particularity, it is to be understood that the present disclosure has been made only by way of example, and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of this invention as hereinafter claimed.

What is claimed is:

1. An apparatus for vaporizing gases which have been liquefied under pressure comprising a needle valve having a needle member and a body member characterized by inlet and outlet ends, supply means whereby gas liquefied under pressure is furnished to the inlet end of said valve body member for passage through said needle valve, fins affixed to said valve body member whereby heat flow through said valve body member from the environment of said needle valve to fluid passing through said valve is facilitated, receiving means at said outlet end of said valve body wherein vapors of gases liquefied under pressure and revaporized during passage through said needle valve are statically gathered, and pressure regulating means in gas line connection with said needle valve at said outlet end whereby pressure of vapor in said receiving means and the outlet end of said valve is prevented from rising above a predetermined value. 7

2. An apparatus according to claim 1 in which said pressure regulating means comprises a relief valve.

31A process for vaporizing gases which have been liquified .under pressure comprising passing said gases through a needle valve having a body member wherein a reduction in pressure of said gases is efiected; transferring heat to said gases through said body member of said valve during the passage of said gases therethrough at such rate to maintain these gases at substantially constant temperature; statically gathering vapors of said gases which have been revaporized during passage through said needle valve, and limiting to a predetermined value the pressure up to which said vapors may be gathered;

4. A process according to claim 3 in which said gases comprise hydrocarbons in the range of C to C 5. A process according to claim 3 in which said predetermined value of pressure is lower than the pressure at which any constituent of said gases can exist as a liquid at the gathering temperature.

References Cited in the file of this patent V UNITED STATES PATENTS 1,813,168 Kalischer July 7, 1931 1,878,798 Muffly Sept. 20, 1932 1,942,944 Smith Jan. 9, 1934 2,525,874 De Larzelere Oct. 17, 1950 2,670,609 Matteson Mar. 2, 1954 2,734,346 Dickieson Feb. 14, 1956 2,750,071 Ritchie June 12, 1956 2,780,899 Benson et al. Feb. 12, 1957

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