US2754666A - Method and apparatus for liquefying gases - Google Patents

Description

Filed Oct. 29, 1952 A INVENTOR 05022! /w I BY M QRNEY I tid/.ula

United States Patent O METHOD AND APPARATUS FOR LIQUEFYING GASES Robert Spitzer, New York, N. Y., assignor to M. H. Treadwell Co., Inc., New York, N. Y., a corporation of New York Application October 29, 1952, Serial No. 317,454

7 Claims. (Cl. 62-122) This invention relates to the liquefaction of gases and more particularly to the liquefaction of chlorine. While the invention is described hereinafter chiefly in connection with the liquefaction of chlorine, it will be understood it is not limited thereto and includes the liquefaction of other gases. In the specitication and claims, all pressures are absolute.

Chlorine gas is produced in electrolytic cells at a pressure about or just below atmospheric pressure, usually a pressure of from 1/2 to 11/2 inches of water below atmospheric pressure. Heretofore this chlorine gas has been liquefied by compressing the dried gas to a pressure of from 20 pounds per square inch to 165 pounds per square inch and cooling to a temperature of from 55 F. to 70 F., respectively. Various types of compressors have been used, such, for example, as sulfuric acid lubricated piston compressors, carbon ring compressors, sulfuric acid ring compressors and diaphragm compressors. However, due to the corrosive nature of the gases handled, the operation of these compressors invariably presents diiculties and their mechanical eiciencies are relatively low.

It is among the objects of this invention to provide a process for liquefying chlorine and other gases, which process does not involve the use of a compressor for compressing the gas and which process, except for the valves employed to control flow, does not require for its practice mechanism having moving parts which come into contact with the gas or the liqueed gas.

Another object of this invention is to provide a process for liquefying gases, including chlorine, which process is ecient in practice and economical to carry out.

Still another object of this invention is to provide an arrangement of apparatus for practicing the process of this invention which arrangement is compact, simple, eficient in operation and relatively inexpensive to maintain.

Other objects and advantages of this invention will be apparent from the following detailed description thereof.

In accordance with this invention a stream of chlorine gas at or below atmospheric pressure is mixed with a stream of chlorine vapor. under superatmospheric pressure and produced by vaporizing liquid chlorine. There is thus produced a stream of chlorine gas under pressure. This stream is cooled to condense at least that portion of the chlorine gas which corresponds in amount to the amount of chlorine vapor admixed with the incoming chlorine gas stream. A portion of the chlorine liquid thus produced is vaporized to produce the stream of chlorine vapor u nder pressure employed to compress the chlorine gas. The remainder of the chlorine liquid may be withdrawn as product.

When liquefymg a chlorine gas containing incondensables, such as air, carbon dioxide and hydrogen, and it isV desired to eifect substantially complete condensation of the chlorine, a two stage condensation procedure should preferably be employed.

A one stagecondensation procedure, such as that hereinabove described, may be used to effect substantially ICC complete condensation of pure chlorine or partial condensation of chlorine when liquefying a chlorine gas containing incondensables. In the use of a two stage condensation procedure, the uncondensed chlorine gas from the lrst condensation stage is passed through a second stage where the residual chlorine gas is condensed. Desirably, the second stage of the condensation or liquefaction is carried out by passing a portion of the liquid chlorine under pressure from the irst stage through a heat interchanger where the liquid is cooled by chlorine gas flowing in heat exchange relationship therewith. The thus cooled chlorine liquid under pressure is then expanded creating refrigeration which is employed to effect the condensation of the chlorine in the second stage. The expanded chlorine gas is employed to pre-cool the chlorine liquid in the aforesaid heat interchanger. In this way condensation of the chlorine is effected most efliciently.

The accompanying drawing shows for purposes of exempliiication a preferred layout of equipment for practicing the process of this invention. It will be understood this invention is not limited to the arrangement of equipment shown in the drawing.

In the drawing 10 indicates a vapor injector of any well known type which may be a single or multistage injector. This injector communicates through a line 11 with a source of chlorine gas which may be at atmospheric pressure or slightly below atmospheric pressure. For example, line 11 may communicate with a collector main receiving chlorine from electrolytic chlorine generating cells. A line 12 connects vapor injector 10 with a vaporizer 13. A valve 14 desirably operated by a pressure controller 15 of any conventional type and which is responsive to the pressure in the feed line 11 controls the supply of chlorine vapor under a predetermined pressure to the vapor injector 10. The stream of chlorine vapor under pressure flowing through injector 10 effects flow of chlorine gas through line 11 into the vapor injector. The chlorine vapor thus supplied by the vaporizer 13 desirably is at a pressure within the range of from to 1000 pounds, preferably at about 1000 pounds, per square inch.

The vaporizer 13 may be of any well known type, such, for example, as an evaporator arranged to receive steam under pressure from a line 16, which steam passes in indirect heat exchange relation with liquid chlorine supplied to the vaporizer by means of a line 17 communicating with an injector 18, which in turn communicates through a line 19 with the vaporizer 13. As customary, the vaporizer 13 may be provided with a trap 20 equipped with a flow control valve 21 controlling flow of condensate from the vaporizer 13 and a purge line 22 for purging the vaporizer when desired.

In the embodiment shown in the drawing ilow of liquid chlorine to the vaporizer is accomplished by providing feed line 12 leading from the vaporizer with a branch 23, ow through which is controlled by a tloat valve 24. This valve is responsive to the level of liquid within the vaporizer and is designed to maintain a body of liquid chlorine within the vaporizer at all times. In operation chlorine vapor under a desired predetermined pressure within the range of 100 to 1000 pounds per square inch is recirculated through line 23, injector 18, line 19 and the upper portion of the vaporizer 13. This stream of chlorine vapor under pressure effects flow of iiquid chlorine through line 17 into the vaporizer where the liquid chlorine is heated by steam or other heating medium sup- `plied to the vaporizer 13 thus generating the chlorine in a stream of chlorine gas leaving the vapor injector under a pressure of from 50 to 250 pounds per square inch, preferably about 150 pounds per square inch. It will be' understood that instead of supplying the liquid chlorine to the vaporizer 13 by means of an injector 18, a pump or other suitable feed means may be employed to supply the liquid chlorine to the vaporizer 13.

From the injector 10 to the chlorine gas stream under pressure of from 50 to 250 pounds per square inch flows through line into the first stage condenser 26. This condenser may be of any well known indirect heat exchange type, cooled, for example, by water, air or other cooling medium supplied through inlet 27. The cooling iediurn ows in indirect heat exchange relation with the mixture of chlorine gas passing through condenser 26 and exits through the outlet 28. Cooling of the cornpressed chlorine gas results in condensation of a portion of the gas; the amount of chlorine thus condensed should at least equal and preferably exceed the amount of chlorine supplied to the vaporizer 13. The condensate, as well as incondensables which may be present ows from condenser 26 into a tank 29. The base of this tank communicates with line 17 leading to the injector 18 here inabove described and also with a line 30 through which a portion of the condensate from tank Z9 is supplied to a refrigerant economizer 31.

Economizer 31 is an indirect heat exchanger for flow of liquid chlorine under pressure entering this economizer through line 345 and exciting through line 32. This liquid flows in indirect heat exchange relation with chlorine gas entering through line 33 and exiting through line 34 which communicates with the injector 10. Thus, injector 10 serves to compress chlorine gas flowing thereto from both lines 34 and 11 in the embodiment of the invention shown in the drawing.

Overow condensate from tank 29, as well as uncondensed chlorine gas and incondensables flow from tank 29 through a line 35 into a second stage condenser 36. This mixture ilows in indirect heat exchange relation with chlorine gas produced by expansion of the chlorine liquid flowing from line 32 through iloat controlled expansion valve 37 which maintains a desired level of chlorine liquid in the second stage condenser. Flashing of the liquid to vapor produces refrigeration which is imparted to the mixture flowing through the second stage condenser 36. From the second stage condenser 36 the gas ows through iine 33 which communicates with the economizer 31.

The condensate thus produced in condenser 36 and any incondensables which may be present leave this condenser through a line 39 which communicates with a pair of product receiving tanks 40 and 41. Two tanks are provided so that one may be charged while the other is discharged. These tanks are provided with a suitable vent i2 through which incondensables may be vented. A back pressure control valve 43 actuated by controller 44 is provided to maintain the system under a desired superatmospheric pressure. Tanks 40 and 41 are provided with suitable valve controlled draw-ott lines 45 which communicate with a header 46.

The following example of liquefying chlorine in accordance with the process of this invention in the layout of equipment shown in the accompanying drawing is given for purposes of illustration only. It will be understood the invention is not limited to this example.

100 pounds of chlorine gas per hour at atmospheric pressure and a temperature of 80 F. and approximately 2 pounds incondensables chiey air, hydrogen and carbon dioxide are supplied to the vapor injector 10 through line 11. 49.5 pounds of chlorine gas per hour at a ternperature of 70 F. are also supplied to this vapor injector through line 44, this gas having been employed to effect condensation in the second stage condenser 36, as hereinafter more fully described. The resultant mixture is compressed to a pressure of 150 pounds per square inch by 895 pounds of saturated chlorine vapor per hour supplied to the vapor injector 10 from the vaporizer 13 under a pressure of 1000 pounds per square inch. 1044.5 pounds of chlorine vapor and 2 pounds incondensables are thus supplied to the first stage condenser 26 where this mixture is cooled by water which enters at a temperature of about 70 F. Approximately 75% of the incoming chlorine, as well as all of the chlorine (895 pounds per hour) supplied to the vaporizer 13, is condensed in the first stage condenser.

The liquid chlorinecon'densate, as well as uncondensed vapor, enter the tank 29 which is under the system pressure of approximately 150 pounds per square inch. 895 pounds of liquid chlorine per hour are withdrawn from this tank and passed through line 17 into the injector 18, feed of this liquid chlorine being effected by the chlorine vapor circulated through the line 23, Valve 24 and injector 13. 49.5 pounds per hour of liquid chlorine at a temperature of F. iiows from the tank 29 through line 30 into the economizer 31 where it is cooled to a temperature of 25 F. by 49.5 pounds of chlorine gas per hour entering at a temperature of 30 F. and leaving economizer 31 at a temperature of 70 F. This chlorine gas flows from the economizer 31 through line 34 into the injector 10. The cooled liquid chlorine at a temperature of 25 F. and a pressure of 150 pounds per square inch tlows through the expansion valve 37 and is flashed into vapor at substantially atmospheric pressure. The resultant vapor tiows through the second stage condenser 36 in indirect heat exchange relation with the liquid chlorine, uncondensed chlorine and inerts passing through this condenser. This liquid mixture is thus cooled to a temperature of -25 F. at which temperature and under a pressure of pounds per square inch it enters the storage tank 4.0 or 41; 99.2 pounds of liquid chlorine per hour are thus fed into a storage tank.

If it is desired to liquefy 75 or less of the chlorine under the above noted conditions of chlorine concentration and temperature of cooling medium supplied to the first stage condenser, this can be effected employing only the rst stage of condensation. In this event the second stage condenser and associated economizer need not be employed, and, hence, may be omitted in installations designed to liquefy 75 or less of the chlorine under the above noted conditions. Thus, in those cases where 25% or more of the chlorine generated can be used in the gaseous phase and it is desired to liquefy 75% or less of the chlorine containing about 2% by volume of incondensables, the installation embodying this invention may involve only a single stage of condensation.

While the invention has been described above in connection with the liquefaction of chlorine it is not limited thereto. It may be employed in the liquefaction of other gases, such, for example, as ammonia (NH3), stibine (SbHs), arsenic pentauoride (AsFs), arsine (AsHs), carbon tetratluoride (CF4), carbon dioxide (CO2), carbon oxysuliide (COS), chlorine monouoride (CIF), chlorine triuoride (ClFa) cyanogen (CzNz), fiuorine (F2), chlorotriuorogermane (GeFaCl), germanium monohydride (GeH), hydrogen bromide (HBr), hydrogen chloride (HCl), hydrogen uoride (HF), hydrogen iodide (HI), phosphine (HSF), hydrogen sulfide HzS), hydrogen telluride (HzTe), nitrous oxide (N20), nitrogen dioxide (NO2), nitrosyl chloride (NOCl), phosphorus triuoride (PFg), phosphorus oxyfluoride (POP3), radon (Rn), trifluoro silicane (SiHFa), silicon tetrafluoride (SiFi), silane (Sil-i4), disilicane (SizHs), trisilicylamine ((SiH3)3N), sulfur tetrafluoride (SP4), sulfur dioxide (SO2), sulfuryl iiuoride (SOzFz), telluriam hexafluoride (TeFs), stannane (SnHi) uranium hexafluoride (UF6), and other liqueiiable gases.

It will be noted this invention provides a method of liquefying liqueliable gases which eliminates the necessity of using compressors for compressing the gas and which is eicient in operation and economical to carry out. It will be further noted the arrangement of apparatus for practicing this invention is compact, simple to operate, ecient in operation, and, hence, involves relatively small maintenance expenses.

Since certain changes may be made in carrying out the above described embodiments of the invention without departing from its scope, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense. Thus, while in the embodiment hereinabove described the chlorine gas which effects cooling in the second stage is expanded to atmospheric pressure, it could be expanded to below this pressure. This would involve providing the line 34 leading to the injector with a second injector to maintain subatmospheric pressure conditions within line 34, economizer 31, line 33 and the portion of condenser 36 through which the expanded gas flows. Also instead of supplying the gas to be liqueled at sub or atmospheric pressure it may be supplied at relatively low superatmospheric pressures.

Furthermore, the parts may be suitably insulated and arranged for most ecient heat exchange and optimum utilization of available heat and refrigeration. Thus, for example, the liquid chlorine flowing through line 19 may be passed in heat exchange relation with the chlorine gas stream ilowing through line 25 to precool the chlorine gas entering the condenser 26 and warm the chlorine liquid entering the vaporizer 13.

What is claimed is:

1. A method of liquefying chlorine gas containing incondensables from the group consisting of air, carbon dioxide and hydrogen and at approximately atmospheric pressure, which method comprises step 1, vaporizing liquid chlorine obtained from step 4 to produce a stream of chlorine vapor under pressure; step 2, passing said stream of chlorine vapor under pressure through an injector communicating with the chlorine gas to be liquefied and with chlorine gas coming from step 6 and thus producing a stream of chlorine gas under pressure containing said incondensables; step 3, cooling the stream from step 2 to condense the major portion but not all of the chlorine gas; step 4, dividing the liquid chlorine from step 3 into three streams, one of which is employed in step 1 of the process; step 5, cooling another of the streams of liquid chlorine from step 4 containing chlorine gas not condensed in step 3 and said incondensables to eect condensation of the residual chlorine gas, withdrawing the chlorine condensate thus produced from the process as product and venting the incondensables from the process; and step 6, expanding the third stream of liquid chlorine from step 4 to produce refrigeration which is employed to efect the cooling in step 5 and passing the chlorine gas thus produced to step 2 of the process.

2. A method of liquefying a liqueable gas under approximately atmospheric pressure which method comprises step 1, vaporizing a portion of the liquefied gas obtained from step 4 to produce a vapor stream under pressure; step 2, passing said vapor stream under pressure through an injector communicating with the gas to be liqueed and with the gas coming from step 6 and thus producing a stream of gas under pressure; step 3, cooling said stream from step 2 to condense an amount thereof at least equal to the amount of gas vapor produced in step 1, but not all of said stream; step 4, dividing the condensate from step 3 into three streams one of which is utilized in step 1 of the process; step 5, cooling the second stream of condensate from step 4 along with uncondensed constituents from step 3 to condense uncondensed constituents and withdrawing from the process the condensate produced in step 5 as the liqueed gas product; and step 6, expanding the third stream of condensate from step 4 to produce refrigeration which is employed to effect the cooling in step 5 and passing the gas produced by expanding said third stream of condensate to step 2 of the process.

3. A method of liquefying chlorine which comprises step 1, vaporizing liquid chlorine obtained from step 4 to produce a stream of chlorine vapor under pressure; step 2, passing said stream of chlorine vapor under pressure through an injector communicating with chlorine gas to be liquefied and with chlorine gas coming from step 6 and thus producing a stream of chlorine gas under pressure; step 3, cooling the stream from step 2 to condense the major portion but not all of the chlorine gas; step 4, dividing the liquid chlorine from step 3 into three streams, one of which is employed in step 1 of the process; step 5, cooling another of the streams of liquid chlorine from step 4 along with chlorine gas not condensed in step 3 to elfect condensation of said chlorine gas; and step 6, expanding the third stream of condensate from step 4 to produce refrigeration which is employed to eiTect the cooling in step 5 and passing the chlorine gas thus produced to step 2 of the process.

4. The method defined in claim 3, in which the chlorine vapor generated in step 1 is at a pressure of from 100 to 1000 pounds per square inch, the mixed stream produced in step 2 is at a pressure of about 150 pounds per square inch and the chlorine liquid in step 6 is expanded from a pressure of about pounds per square inch to atmospheric pressure.

5. The method dened in claim 3, in which in step 6 the third stream of liquid chlorine condensate is precooled by passage in indirect heat exchange relation with chlorine gas, the thus cooled condensate is expanded to produce chlorine gas, this chlorine gas is employed to eiect the cooling of step 5 by owing in indirect heat exchange relation with the material which is cooled in step 5 and this chlorine gas is thereafter employed to effect said precooling of the said third stream of liquid chlorine condensate and then passed to the injector in step 2 of the process.

6. The method dened in claim 3, in which a portion of the vapor produced in step 1 is passed through an injector communicating with the stream of chlorine liquid which is vaporized to produce the chlorine vapor employed in step 1 of the process and thus eects ow of said chlorine liquid into the vaporizer.

7. Apparatus for liquefying gases, in combination, a vaporizer, an injector, a line connecting said vaporizer with said injector for ow of vapors from said vaporizer to said injector, a iirst condenser, a second condenser, a heat interchanger, a line leading from said heat interchanger to said injector, a second line for supplying the gas to be liquefied to said injector, means leading from said first condenser to said vaporizer and including an injector for etfecting flow of condensate from said first condenser to said vaporizer by circulation of vapors generated in said vaporizer through said second-mentioned injector, and means connecting said rst condenser with said second condenser, said condensers and heat interchanger being constructed and arranged for iow of a portion of the liquid condensate produced in the rst condenser through the heat interchanger where it is cooled, then through an expansion valve into the second condenser where it is flashed into vapor, which is passed from the second condenser through the heat interchanger and thence to the first-mentioned injector.

References Cited in the file of this patent UNITED STATES PATENTS 1,014,120 Coleman Jan. 9, 1912 1,073,843 Blau Sept. 23, 1913 1,497,546 Claude .lune 10, 1924 1,913,268 Falkenberg June 13, 1933 1,945,367 Gobert Jan. 30, 1934 1,972,705 Crosthwait Sept. 4, 1934 2,014,701 Seligman Sept. 17, 1935 2,035,814 Kallam Mar. 31, 1936 2,166,191 Whitney July 18, 1939 2,174,302 Whitney Sept. 26, 1939 2,568,223 De Baufre Sept. 18, 1951 2,637,174 Austin May 5, 1953

Claims (1)

1. A METHOD OF LIQUEFYING CHLORINE GAS CONTAINING INCONDENSABLES FROM THE GROUP CONSISTING OF AIR, CARBON DIOXIDE AND HYDROGEN AND AT APPROXIMATELY ATMOSPHERIC PRESSURE, WHICH METHOD COMPRISES STET 1, VAPORIZING LIQUID CHLORINE OBTAINED FROM STEP 4 TO PRODUCE A STREAM OF CHLORINE VAPOR UNDER PRESSURE; STEP 2, PASSING SAID STREAM OF CHLORINE VAPOR UNDER PRESSURE THROUGH AN INIECTOR COMMUNICATING WITH THE CHLORINE GAS TO BE LIQUEFIED AND WITH CHLORINE GAS COMING FROM STEP 6 AND THUS PRODUCING A STREAM OF CHLORINE GAS UNDER PRESSURE CONTAINING SAID INCONDENSABLES; STEP 3, COOLING THE STREAM FROM STEP 2 TO CONDENSE THE MAJOR PORTION BUT NOT ALL OF THE CHLORINE GAS; STEP 4, DIVIDING THE LIQUID CHLORINE FROM STEP 3 INTO THREE STREAMS, ONE OF WHICH IS EMPLOYED IN STEP 1 OF THE PROCESS; STEP 5, COOLING ANOTHER OF THE STREAMS OF LIQUID CHLORINE FROM STEP 4 CONTAINING CHLORINE GAS NOT CONDENSED IN STEP 3 AND SAID INCONDENSABLES TO EFFECT CONDENSATION TO THE RESIDUAL CHLORINE GAS, WITHDRAWING THE CHLORINE CONDENSATE THUS PRODUCED FROM THE PROCESS AS PRODUCT AND VENTING THE INCONDENSABLES FROM THE PROCESS; AND STEP 6, EXPANDING THE THIRD STREAM OF LIQUID CHLORINE FROM STEP 4 TO PRODUCE REFRIGERATION WHICH IS EMPLOYED TO EFFECT THE COOLING IN STEP 5 AND PASSING THE CHLORINE GAS THUS PRODUCED TO STEP 2 OF THE PROCESS.

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