US2941376A - Devices for the controlled dispensation of a liquefied gas from a pressure container - Google Patents

Description

June 21, 1960 w. MESSERLI 2,941,376

DEVICES FOR THE CONTROLLED DISPENSATION OF A LIQUEFIED GAS FROM A PRESSURE CONTAINER Filed Oct. 15, 195? DEVICES FOR THE CONTROLLED DISPENSATION OF A LIQUEFIED GAS FROM A PRESSURE CON- TAINER Walter Messerli, Wettingen, Switzerland (3 Quartierstrasse, Wettingen, Aargau, swltzerland) Filed Oct. 15, 1957, Ser. No. 690,278 Claims priority, application Switzerland Oct. 17, 1956 1 Claim. (CI. 62-55) The present invention relates to a device for the con- 5 trolled dispensation of a liquefied gas from a pressure container. The problem of such a controlled dispensation arises for example in the operation of rectification columns for the fractionated distillation of nitrogen and oxygen from liquid air.

It is the main object of the invention to provide a device of the kind referred to which is stable in operation even for small outputs and which requires little attention, once adjusted to a certain performance.

It is another object of the invention to provide a device of the kind referred to which is insensitive to the presence of carbon dioxide in the-liquefied air to be fractionated and which dispenses with the purification of the latter from carbon dioxide.

With these and other objects in view I provide a device for the controlled dispensation of a liquefied gas, comprising in combination: a pressure container in operation partly filled with the liquefied gas, and an obturator member controlling the discharge of liquefied gas from the said pressure container and subject to the opposing controlling forces of the gas pressure prevailing in the said pressure container above the liquid level therein and the alegbraic sum of the said gas pressure acting on the surface of the said liquid and of a column of liquefied gas under the said surface, in the sense of the said obturator member being opened upon the said column attaining a predetermined head and then allowing the dispensation of liquefied gas from the said pressure container.

These and other features and objects of my invention will be clear from the following description of some embodiments thereof given by way of example with reference to the accompanying drawing in which:

Fig. l is a diagram of a first embodiment,

Fig. 2 shows a modification of a detail of Fig. 1,

Fig. 3 is a diagram of a second embodiment.

According to Fig. l the pressure container 1 contains in its interior a rectification column 2 indicated symbolically by sieve bottoms of the conventional kind. Liquid air is supplied through a pipe 3 to this container in which prevails for example a pressure of 7 atmospheres gauge. Through the pipe 4 a liquefied gas containing mainly oxygen is withdrawn from the container. Through pipe 5 liquefied gas containing mainly nitrogen is discharged from the container 1. These liquefied gases are passed to further rectification devies (not shown) for a sharper separation of oxygen from nitrogen. It has now been found in practice that it is very diflicult to withdraw from the pipes 4 and 5 accurately the quantities of liquid required for keeping the operation going. Particularly in smaller plants for the fractionated distillation of e.g. 5 to 30 litres per hour often so instable conditions occur that an operative is constantly occupied with regulating control valves inserted in the pipes 4 and 5.

Numerous tests have proved that this instability is obviated if one succeeds in keeping the liquid level constant in the container 1, and in removing at any time the liquid enriched in oxygen, which accumulates in the lower position, in small batches from the container, as soon as the level adjusted to is slightly surpassed. For this purpose a differential valve 6 1s provide which has a diaphragm 7. The upper chamber 8 bounded at the bottom by said diaphragm 7 is in communication with the container 1 through a pipe 9, namely above the liquid level 10 desired. The lower chamber 11 bounded on top by the said membrane 7 is in communication through a tube 12 with the said to an overflow tube 13 provided in the container 1.

To the membrane 7 the upper end of a valve stem 14- is attached which carries at its lower end a valve head 15 co-operating with a valve seat 16. With the valve 6 open, the liquid can pass from the pipe 4 between the components 15 and 16 into a pipe 17 wherein for ex ample a pressure of 0.5 atmospheres gauge prevails.

It is to be remarked that the upper part of the valve 6,-

namely the chambers 8 and 11, as well as the upper part;

of the tube 12 are not heat-insulated and are accordingly at a room temperature of e.g. 10 C., while the pipes 4 and 17 as well as the lower part of the tube 12 are heatinsulated and have a very low temperature, for example of less than l'80 C.

The device described operates as follows:

The excess of the liquid accumulating on the bottom of the pressure container 1 flows through the overflow tube 13 into the pipe 4, and hence into the tube 12 of the differential valve 6. Here some of the liquefied gas evaporates, and in the tube 12 for example-a level 18, and the pipe 4 a level 19 establishes itself.

In the upper chamber 8 then prevails the pressure of 7 atmospheres gauge as in the container 1, while in the lower chamber 11 a pressure prevails of 7 atmospheres gauge plus the pressure of the liquid column of the head H. By the overflow of the liquid into the overflow tube 13 the head H increases, so that eventually the diaphragm 7 is deflected upwardly and it raises the valve head 15 from its seat 16, on which it is normally retained by a force proportional to the pressure difference in the pipes 4 and 17 and-to the free [cross section areaof the valve seat. Then the liquefied, strongly oxygen containing gas flows from the pipe 4 intothe pipe 17 and from there to the further rectification devices. Thereby the liquid level 18 drops, and accordingly also .the pressure in the chamber 11 below the membrane 7, which causes the valve 6 to close again. Since the cross section area of the pipe 4 and of the overflow tube amounts to a few square millimetres only, the quantities passing at any time into the pipe 17 when opening the valve 6 are very small. The valve plays accordingly very frequently which very effectively prevents any freezing of the valve head 15 to its seat 16. This is of importance when using liquid air in which there is still contained some carbon dioxide. This carbon dioxide has, as well known, the tendency of freezing fast on valves in which a pressure drop takes place, which leads to such great difliculties that one mostly purifies the air prior to liquefaction by means of expensive appliances containing potash lye or the like in order .to eliminate the carbon dioxide. In the device described no such difficulties arise even in the presence of carbon dioxide. This is of great importance since it is thereby made possible to dispense completely with the aforementioned purifying appliances, which are expensive in first costs and in operation.

The valve 6 operates fully automatically, and it has been found, that after a correct adjustment, once and for all, of a through-flow valve arranged in the pipe 5 no further servicing is required for maintaining stable operation.

In the modification of detail according to Fig. 2 on the valve stem .14, below the valve head 15, yet another valve head 21 is arranged which rests on the valve seat PatentedJune-21, 1960 pipe 4 which is connected V 3 22. By a pipe 20 the pipe 4 is in communication also with the space below the valve seat 22. Consequently a force proportional to the cross section area of the seat 22 and to the pressure difference in the pipes 4 and 17 acts from below on the stem 14, so that the diaphragm.

7 is .partly released from the downwardly directed force mentioned hereinbefore. This is of advantage at a very high pressure in the pipe 4 since the diaphragm 7 would otherwise have to be made very large.

In the embodiment according to Fig. 3 the obturator member 23 is designed as a slide valve having a slider member 24. The chambers 8 and 1 1 of the obturator member 23 are connected, as in the case of Fig. 1, to the container 1, of which the lower part only is illustrated. The membrance 7 is additionally biased by a spring, the pressure of, which may be adjustable if desired. When the slider member 24 .is raised, the lower chamber 26 of a second obturator member 27 is connected through the pipe 27', the opened obturator member 23 and the pipe 28 to. the container 1 above the liquid level 10. The diaphragm 29 of the valve 27 is deflected upwardly against the bias of a spring 30, and thereby the valve head 15 is liftedoif its seat 16, whereafter the liquid can flow oil from the pipe 4 into the pipe 17.

When the slide valve 23 closes again, the gas contained in the chamber 26 escapes through a restricted orifice 31 so that in this chamber consequently atmospheric pressure prevails.

ne may alternatively arrange the differential valve 6 otFig. 1 above the container 1 and connect its chambers 8 and 11 to the container 1 in such a manner that in the chamber 11 the pressure prevailing above the liquid level is effective and in the chamber 8 the difference of this pressure and of a column of liquefied gas, whereby the sameresult is attained as in the case of Fig. 1.

While I have described herein and illustrated in the accompanying drawing what may be considered typical and particularly useful embodiments of my said invention, I wish it to be understood that I do not limit myself to the particular details and dimensions described and illustrated, cEor obvious modifications will occur to a person skilled in the art.

What I claim as my invention and desire to secure by Letters Patent, is:

A device for the dispensation of a liquefied gas comprising: a pressure container in operation partially filled with a volume of liquefied gas; an obturator member having an upper chamber in communication with said pressure container above thelevelof said volume of liquefied gas contained therein and a lower chamber; an overflow tube extending into said container and said gas in communicative relationship with said lower chamber, said tube coacting with said container .to define a maximum volume of retention of said liquefied gas in said container and discharge means for receiving all of said liquefied gas in excess of said volume; diaphragm means operatively disposed in said obtu-rator intermediate said upper and said lower chambers in sealing relationship therewith; and valve means operatively associated with and responsive to saiddiaphragm means, said diaphragm means maintaining said valve means in closed position when said volume of said liquefied gas is less than said maximum volume and actuating said valve means into open position when said volume of said liquefied gas exc-eeds'saidmaximum volume to discharge said liquefied ga's in excess of said maximum volume from said tube through said valve means whereupon said diaphragm means returns said valve means to said closed position, said overflow tube comprising a first portion extending into said container and a second portion external of said container in communication with said lower chamber, and said second portion comprising a heat insulated pipe while said chambers are without heat insulation thereby providing a temperature differential therebetween to volatilize a portion of said liquefied gas and create additional pressure in the lower chamber to actuate said diaphragm when excess liquefied gas occurs in said overflow tube.

References Cited in the file of this patent UNITED STATES PATENTS 207,482 Blessing Aug. 27, 1878 1,851,422 Durando Mar. 29, 19.32 2,280,383 DeBaufre Apr. 21, 1942 2,541,409 Cornelius Feb. 13, 1951 2,788,080 Guarin Apr. 9, 1957

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