US2930682A - Transportation of fluids - Google Patents

Description

March 29, 1960 E. w. HENDERSON 2,930,632

TRANSPORTATIQN OF FLUIDS Filed Oct. 24. 1955 GAS STRIPPER SOLUTION OF GAS & SOLVENT? GAS LEAN SOLVENT p e T (ABSORBER F/G 2 3 CO2 FEED "STRIPPER Q ACETYLENE STRIPPER TURBINE s H h 0-& H y

NO.l ACETYLENE INVENTOR STRIPPER E.w. HENDERSON HO By LEAN SOLVENT\ FIG. .3. MM

A ORNE TRANS? ORTATKGN F FLS Eulas W. Henderson, Bartlesvilie, Okla, assignor to Phillips Petroleum Company, a corporation of Delaware Application October 24, 1955, Serial No. 542,232

9 Claims. (Cl. 48-190) This invention relates to an improved method for transporting gases dissolved in a solvent, for example, by way of a pipe line. In one of its aspects, the invention relates to a method for forming a solution of a gas in a solvent by cooling at least one of said gases and said solvent to a temperature such that at a low pressure an admixture of them will result in substantially only a liquid phase. In another aspect, the invention relates to a method for transporting a gas which is dissolved in a carrier liquid under elevated pressure but which has been dissolved in said carrier liquid at a low pressure as described herein.

In the manufacture of olefinic gases which have a great variety of chemical uses, it is usually more economical to build one large centrally located plant to manufacture the olefin and distribute the product to the various points of use by pipeline. An example of such an arrangement is an ethylene plant in one place and users of the gaseous product located within a range of about 1 to 50 miles. As a by-product of the manufacture of ethylene, there is obtained acetylene.

The present invention is particularly applicable to the transportation of acetylene, but is not limited thereto. Prior to this invention there has not been a suitable means for transporting acetylene by pipeline over long distances. It is unsafe to compress gaseous acetylene above about 30 p.s.i.a., and at this low pressure the capacity of a pipe line is extremely low. Transcontinental natural gas pipe lines usually operate at about 800 p.s.i.g., so it can be seen that it would be very uneconomical to transport gas at 15 p.s.i.g. (3O p.s.i.a.). Two methods for the storage and handling of high pressure gaseous acetylene are known, but neither method is applicable to so-called long lines transportation. These methods are: (1) the use of explosion proof equipment, i.e., the equipment is built sufiiciently strong to withstand an explosion, and (2) the lines are filled with a great number of small tubes, or suitable packing, which will prevent the formation of an explosionwave. Injection of water to remove heat from gaseous acetylene in a transfer line has also been suggested. This also is disadvantageous when the long distances involved in pipe line transport are considered.

An object of the present invention is to provide a method of transporting a gas, say, acetylene, in a pipe line dissolved in a solvent and shipped at a high pressure. Another object of the invention is to provide a method for cyclically utilizing the solvent to ship additional quantities of gas. A further object is to recover cooling or refrigeration and energies involved in pressure reduction in the method of the invention as will appear hereinafter.

I have found that in the transportation of certain gases it is possible to transport more material in a given size line in solution than in the gas phase, where the operating pressure in the gas phase is limited by safety or other considerations. For example, the density of gaseous acetylene at 68 F. and 30 p.s.i.a. is about 2.04 grams/ liter, but one liter of dimethyl forrnamide (DMF) will dissolve about 41 grams of acetylene at 68 F. and 15 p.s.i.a. When it is noted that the solubility of acetylene I 2,930,682 Patented Mar. 29, 1960 in DMF increases appreciably with pressure, and that such solutions can be handled safely at high pressures, it is obvious that a given line will transport many times the amount of acetylene in solution than in the gas phase. I have also found that concentrated solutions of gases suitable for transport in pipe lines at high pressures can be formed without the use of high pressures in the gas phase by the sequence of steps of: (1) cooling the gas and solvent streams to a low temperature, while at a low pressure, (2) mixing these two streams and supplying sutficient cooling to cause the gas to go completely into solution at the operating pressure, (3) passing the solution thus formed through a pump to raise it to the transport pressure, and (4) passing the solution through a heat exchanger to recover a substantial amount of the low temperature refrigeration. The high transport pressure prevents the formation of a gas phase, when the temperature of the solution is raised.

Thus, according to the present invention, there has been provided a method for forming a solution of a gas, say, acetylene, which comprises cooling said gas and/or the solvent into which it is to be dissolved to a temperature at which upon admixture of the gas and solvent a homogeneous solution will be formed at a low or at an ordinary pressure.

Further according to the present invention, there has been provided a method for forming a solution of a gas such as acetylene in a solvent such as dimethyl formamide and then transporting the gas in the solution to a place of utilization, say, by a pipe line, which comprises cooling the said gas and/or the said solvent, as described, forming the said substantially homogeneous solution and then raising the pressure upon the said solution to a value at which the said solution will remain substantially entirely liquid at ordinary temperatures. The gas is then transported, in solution, to a place of utilization which may be several miles away from the place at which the liquid or homogeneous solution of the gas in a solvent was formed. The transporting in the pipe line will, of course, be substantially at ambient temperatures and at high pressures. Handling of a gas such as acetylene is quite safe at the said pressures as long as the acetylene is maintained completely in solution.

Still further according to the present invention, a method for transporting acetylene as a solute has been provided which comprises forming the homogeneous solu tion as before, raising the pressure thereon, transporting the solution to a place of utilization and at the place of utilization causing the pressure to be reduced and while so doing, causing the acetylene escaping from the solution to do useful work. The solvent from which the acetylene? has been substantially completely removed can be re turned by way of a parallel pipe line or other means to be reused to transport further quantities of acetylene.

From the additional description which follows, other aspects, objects, as well as features and advantages of the invention, are made apparent.

The attached figure and table illustrate the preferred embodiment of my invention as applied to the transportation of acetylene. The invention is equally applicable to the transportation of other gases in which the transport pressure in the vapor phase is limited. Specific operating. conditions for acetylene are shown, but it is obvious that these conditions can be varied over a wide range and still operate within the scope of the invention.

Any suitable solvent for acetylene may be used. Examples of suitable solvents are acetone, acetaldehyde, methyl formate, methyl acetate and DMF. A more complete list of suitable solvents is shown on page 31 of The Chemistry of Acetylene, by Nieuwland and Vogt.

The feed stream may be any suitable source of crude acetylene. In the example, it is a deoiled efiluent from nuances 3 a'Wulfi process acetylene plant. This particular feed contains an appreciable amount of methyl acetylene, and in the example, the methyl acetylene and acetylene are shipped together to the destination, where they can be separated by fractionation. It desired, the methyl acetylene may be removed, before shipment, so that the transported solution comprises essentially solvent and acetylene.

This invention is particularly applicable to the transportation of acetylene over distances in the range of 5-50 miles, but can be used to transport acetylene any desired distance. For distances of less than about 5 miles, it is often more economical to transport the total absorber Kettle 'product stream, than to transport an enriched stream as shown in the specific embodiment. If the distance is over about 5 or miles, it may be necessary to provide intermediate pump stations in the transport line. If it is desired to transport essentially pure acetylene, then all of the carbon dioxide stripper kettle product is passed to an acetylene stripper, and the solution formed from lean solvent. 7

The transport line can be operated at any desired pressure, but pressures higher than 700 or 800 p.s.i.g. are usually not economical. If the transport line is operated at fairly high pressure, say above 150 p.s.i.a, then it is usually desirable to install a power recovery turbine in the line immediately before the solution i introduced into an acetylene stripper, because this acetylene stripper operates at a fairly low pressure. The recovered power may be used to drive the solvent return pump, when the solvent is returned to the point of origin of acetylene.

If desired, only one line may be used, rich solvent being pumped through the line for a period of time, say, 24 hours, and then lean solvent being returned through the line for a like period. This arrangement requires storage at both ends of the line for continuous operation of the units, but eliminates the need for a second line.

The attached figures illustrate the invention. Numerou's variations may be made in the described method, without departing from the scope of the invention.

In the attached drawings, Figure l shows in diagrammatic form the general idea of circulating in parallel pipe lines a solvent which when moving in one direction contains acetylene dissolved therein and transported thereby at a relatively high pressure and which when moving in the reverse direction consists substantially of solvent containing little or no acetylene. In Figure 2, there is shown a profile view of a segment of parallel pipe lines having interchange pump stations located therealong as will be further discussed below. Figure 3 is a diagrammatic illustration of a more complete embodiment of the invention in the sense that it contains, in addition to a showing of the pipeline, certain elements of apparatus which are employed to cause the gas acetylene in this specific example, to go into the solvent and at the other end of the system to be removed therefrom and utilized.

Referring to the table and to Figure 3, it will be noted that the composition of a feed containing acetylene and which is fed to the absorber is given in column 1 of the table. The same holds true for the various streams of Figure 3 which are numbered to correspond to the columns in the table. Briefly, the feed ll, containing acetylene enters near the bottom of the absorber 16, in which it is contacted with dimethyl formamide at about Plunder a pressure of about 44 pounds per square inch absolute. In the absorber, as shown in column 3 of the table, the dimethyl formamide picks up substantially all of the acetylene. However, some other gases including carbon dioxide are also dissolved in the dimethyl iorrnamide solvent. Bottoms from the absorber pass by way of stream 3 into carbon dioxide-stripper. Prior to entering the carbon dioxide stripper, the temperature of the streamis'raised to about 53 F. and the pressure is lowered to about 15 pounds per square inch absolute. The overhead of the carbon dioxide stripper is identified in column 4 of the table. It will be noted that substantially all of the carbon dioxide, which was originally in stream 3, passes overhead from the carbon dioxide stripper together with other gases through pipe 4. Bottoms from the carbon dioxide stripper containing acetylene and a considerably smaller proportion of methyl acetylene and, of course, dimethyl tormamide, are removed by way of stream 5 and passed at least in part by way of the pump into stream 6 which is maintained at a pressure of about 176 pounds per square inch absolute and is at a temperature of approximately F. This stream is a pipe line stream. A portion of stream 5 is passed by way of a heater to produce stream 8 at about 250 P. which is fed to acetylene stripper from which lean solvent is removed by way of stream Ill and passed, at least in part, to the top of the absorber upon passing through cooling means not shown. Overhead from the acetylene stripper, that is, stream 9, is passed through a cooler and cooled to 60 F., mixed with at least a portion of the bottoms from the CO stripper (stream 7), raised to a pressure of about 176 p.s.i.a., and passed as stream 11 into admixture with stream '6, the admixture now constituting pipe line solution 12 which is shipped any desired distance. Solution 12 at destination is at approximately 176 pounds per square inch absolute and at about 100 F., in this example, the pressure having been maintained by booster stations, not shown for simplicity, and is there passed through the pressure reduction turbine to do useful work. From the turbine, the exhaust is passed to acetylene stripper 13 in which at about 250 F. and 17 pounds per square inch absolute the acetylene is stripped from the solvent. Solvent is removed as bottoms from the acetylene stripper, cooled and pumped by way of recycle solvent line 14 and the pump back to absorber 16. As presently shown, the useful work performed by the solution expanding through the pressure reduction turbine, at least in part supplies by way of connection 15 the energy to drive the recycle solvent pump. This is a feature of the present invention.

Referring to Figure 2, it can be seen that at pump station A, material flowing down the mountain in one line will develop energy that can be recovered in an expansion engine and used to force liquid in the other parallel line up the mountain. Of course, it is still necessary to supply sufiicient outside energy to overcome the net friction loss in both pipes but this can be supplied in large central stations in easily accessible areas. My invention minimizes the need for compressor stations in mountain areas. Also it can be seen that if sufiicient energy is supplied to the pipe line at point B to lift the material over the mountain that high pressure pipe would be required. According to my invention, a plurality of interchangepump stations can be used and still use approximately the same weight pipe used in level country.

It is also within the scope of the invention to use diiferent solvents at diiierent periods of time or a mixture of solvents. When the return line is not being used for solvent, water may be injected at the high points in that line to flow in a direction opposite to the flow of the solution and thus develop power to aid in moving it over mountains. I

It will be noted that according to this invention, only a portion of the absorption solvent, for example, dimethyi formamide, is used to do the actual transporting in the pipe line.

Althoughthe invention has been described in detail with respect to the transportation of acetylene, it is also applicable to the transportation of other gases, such as methylacetylene, ethylacetylene, vinylacetylene, diacetylene, or, for that matter, to any other gases, especially gases which for some reason are better or more economically transported as herein described. Thus, for example, other hydrocarbon gases, for example, low-boiling normally gaseous hydrocarbons, can be transported in,

say, a normally liquid hydrocarbon or other suitable solvent. Herein and in the claims acetylene is to be read generic to acetylenes.

sure reducing zone, said pressure reducing zone being adapted to supply the energy released in said pressure reducing zone as a source of power to a pumping zone,

Table Absorber CO, Low Acetylene Stripper Strip- Cold Pipe Absorber Over- Absorber Stripper Stripper Pipe line Temper- Stripper Overper Soluline Feed head Bottoms Over- Bottoms Solvent ature Feed head Kettle tion Soluhead Solvent tion Stream N0 1 2 3 4 5 6 7 8 9 10 11 12 Hydrogen 33. 557 33. 544 13 13 Nitrogen 3, 654 3. 646 8 8 Carbon Monoxide 5.351 5,340 11 11 Meth 899 16, 795 104 104 5 1. 162 1, 021 141 124 17 17 17 17 17 Methyl Acetylene.- 476 470 87 383 14 2 367 367 369 383 gropylene 222 18; 35 29 6 6 6 6 6 Dimethyl Formsmiden. 43. 003 43.003 1, 282 172 41, 549 41, 549 172 1, 452 Total mols/S Day 66, 267 61. 182 48, 088 1.169 46, 919 1, 401 188 45, 330 3, 781 41, 549 3, 969 7, 368 Total lbs/S Dny.. 799. 020 658, 444 3, 279. 795 32, 996 3, 246. 799 213, 912 Total GaL/S Day 450, 804 443,083 Total M sell/S Day. 25, 115 23, 118 443 Reasonable variation and modification are possible within the scope of the foregoing disclosure, drawings, and the appended claims to the invention, the essence of which is that there have been disclosed a method for forming a solution of a normally gaseous material in a liquid solvent by first cooling at least one of a liquid solvent and the gas to a temperature and at a low pressure, the temperature being such that upon admixture of the gas and liquid solvent there will exist substantially only one phase and that will be a liquid phase, and a method for transporting the gas as a solution in a liquid solvent which comprises compressing such a solution, if desired allowing it to come to ambient temperature, and shipping the compressed solution, as a solution, to a place of utilization, there recovering the gas from the solution and recycling the solvent for reuse, the energy of the pressure of the gas as it is recovered from the solvent being employed, if desired, to do work, especially, according to the invention, to drive a 'pump returning the solvent for reuse.

I claim:

1. A method for transporting an acetylene gas at a transport pressure of at least 150 p.s.i.a. wherein said gas is dissolved in a liquid solvent for acetylene which comprises cooling at least one of said liquid solvent and said gas to a low temperature; contacting said gas and said liquid solvent at said low temperature, and at a low safe pressure of the order of about 30 p.s.i.a., such that a mixture of them after said contacting will exist substantially only in a liquid phase; raising the pressure of said liquid phase to said transport pressure, thereby avoiding compressing said acetylene to said transport pressure as a gas; and transporting the liquid phase thus obtained at said transport pressure a substantial distance through a pipe line to a place of utilization.

2. A method of transporting an acetylene in solution With a liquid solvent for acetylene a substantial distance in a pipeline to a place of utilization which comprises cooling at least one of said liquid solvent and said acetylene to a low temperature, contacting said acetylene and said liquid solvent at said low temperature, and at a safe pressure of the order of about 30 p.s.i.a., such that a mixture of them after said contacting will exist substantially only in a liquid phase, raising the pressure of said mixture to a pipeline transport pressure of at least 150 p.s.i.a and introducing said mixture of increased pressure into said pipeline, thereby having avoided compressing said acetylene to a high pressure as a gas, flowing said mixture at said transport pressure a substantial distance through said pipeline, passing said mixture through a presfurther reducing the pressure of said mixture at an elevated temperature to recover acetylene from said solvent at said place of utilization, and flowing lean solvent from said place through said pumping zone in a parallel pipeline to an acetylene source for receiving additional quantities of acetylene.

3. A method according to claim 2 wherein one of the liquids flowing downwardly in one pathway is employed to develop energy of pumping the other liquid flowing upwardly in an adjacent parallel pathway.

4. A method of transporting an acetylene in solution with a liquid solvent for acetylene a substantial distance in a pipeline from a place of origin to a place of utilization which comprises cooling at least one of the liquid solvent and said acetylene to a low temperature, contacting said acetylene and said liquid solvent at said low temperature, and at a low pressure, such that a mixture of them after said contacting will exist substantially only in a liquid phase, said phase being obtained without having compressed said acetylene to a high pressure as a gas, passing a first portion of said mixture through a first pumping zone to elevate the pressure of said mixture to the desired transport pressure and introducing said mixture into said pipeline, passing a second portion of said mixture, after raising the temperature of said mixture, to a stripping zone for recovering acetylene from said mixture, introducing said acetylene recovered from said stripping zone into said pipeline, thereby enriching said pipeline mixture with acetylene, flowing said enriched mixture a substantial distance through said pipeline, passing said mixture through a pressure reduction zone adapted to supply the kinetic energy released in said pressure reduction zone as a source of power to a second pumping zone, further releasing the pressure of said mixture at a temperature sufficiently elevated to recover acetylene from said solvent at said place of utilization, and flowing lean solvent recovered at said place through said second pumping zone to an acetylene source for receiving additional quantities of acetylene.

5. A method according to claim 4 for transporting an acetylene-solvent solution wherein the solvent is dimethyl formamide (DMF) and the acetylenes comprise acetylene and methylacetylene.

6. A method according to claim 5 wherein the solution is transported a distance of about 5-50 miles in a pipe line between the origin and place of utilization.

7. A method of transporting an acetylene in solution with a liquid solvent for acetylene a substantial distance in a pipeline from a place of origin to a place of utilization which comprises cooling at least one of the liquid solvent and an'acetylene to a low temperature, contacting said acetylene and said liquid solvent at a low temperature, and at a low pressure, in an absorption zone such that a mixture of them after said contacting will exist substantially only in the liquid phase, said phase being obtained without having compressed said acetylene to a high pressure as a gas, passing said mixture after heating to a first stripping zone to remove gaseous impurities from said mixture, removing said mixture substantially free of impurities from said stripping zone and passing said mixture to a first pumping zone to elevate the pressure of said mixture to the desired transport pressure and introducing said mixture into said pipeline, passing a second portion of said mixture removed from said stripping 'zone, after heating, to a second stripping zone from which lean solvent is removed as bottoms and returned to said absorption zone and an overhead stream rich in acetylene is removed from said second stripping zone, cooling and raising the pressure of said overhead acetylene stream and introducing said acetylene stream into said pipeline,

thereby enriching said pipeline mixture with acetylene,

flowing said enriched mixture a substantial distance through said pipeline, passing said solution through a pressure reduction zone adapted to supply the kinetic energy released in said pressure reduction zone as a source of power to a second pumping zone, further releasing the pressure of said mixture at a temperature sufiiciently elevated to recover acetylene from said solvent at said place of utilization, and cycling lean solvent recovered at said place of utilization through said second pumping zone to said place of origin through a second adjacent parallel pipeline for reuse in the method.

8. A method according to claim 7 wherein one of the liquids flowing downwardly in one of the pipelines is employed to develop energy for'pumping the other liquid flowing upwardly in an adjacent parallel pipeline.

9. A method of transporting an acetylene in solution with a liquid solvent for acetylene a substantial distance in a pipeline from a place of origin to a place of acetylene utilization which comprises cooling at least one of the liquid solvent and an acetylene to a low temperature, contacting said acetylene and said liquid solvent at a temperature of about 25 F. and a pressure of about 45 p.s.i.a. in an absorption zone such that a mixture of them after said contacting will exist substantially only in the liquid phase, said mixture being obtained without having compressed acetylene to a high pressure as a gas, heating and reducing the pressure of said mixture removed from said absorption zone, passing said mixture at a temperature of about 53 F. and a pressure of about p.s.i.a. to a first stripping zone to remove overhead gaseous impurities such as C0 and lighter gases from said mixture,

passing a first portion of said mixture removed as stripping zone bottoms to a first pumping zone to elevate the pressure of said mixture to a'transport pressure of about R, mixing said cooled acetylene with at least a portion of the bottoms from said first stripping zone, raising the pressure of said mixture to a pressure of about 176 p.s.i.a. and introducing said :mixture into said pipeline, thereby enriching said pipeline mixture with acetylene, flowing said enriched mixture at a temperature of about F. and a pressure of about 176 p.s.i.a. a substantial distance through said pipeline, passing said mixture through a pressure reduction zone wherein the pressure of said mixture is reduced to a pressure of about 17 p.s.i.a., said pressure reduction zone being adapted to supply the kinetic energy released in said pressure reduction zone as a source of power to a second pumping zone, releasing the pressure of said mixture at a temperature of about 250 F. to recover acetylene from said solvent at said place of acetylene utilization, and cycling lean solvent recovered at said place of utilization, after cooling, through said second pumping zone to said place of origin through a second adjacent parallel pipeline for reuse in the method.

References Cited in the file of this patent UNITED STATES PATENTS 541,462 Suckert June 25, 1895 847,727 Bruckener Mar. 19, 1907 1,938,991 Wulff Dec. 12, 1933 2,146,448 Scott Feb. 7, 1939 2,535,148 Martin et al Dec. 26, 1950

Claims (1)

1. A METHOD OF TRANSPORTING AN ACETYLENE GAS AT A TRANSPORT PRESSURE OF AT LEAST 150 P.S.I.A. WHEREIN SAID GAS IS DISSOLVED IN A LIQUID SOLVENT FOR ACETYLENE WHICH COMPRISES COOLING AT LEAST ONE OF SAID LIQUID SOLVENT AND SAID GAS TO A LOW TEMPERATURE, CONTACTING SAID GAS AND SAID LIQUID SOLVENT AT SAID LOW TEMPERATURE, AND AT A LOW SAFE PRESSURE OF THE ORDER OF ABOUT 30 P.S.I.A., SUCH THAT A MIXTURE OF THEM AFTER SAID CONTACTING WILL EXIST SUBSTANTIALLY ONLY IN A LIQUID PHASE, RAISING THE PRESSURE OF SAID LIQUID PHASE TO SAID TRANSPORT PRESSURE, THEREBY AVOIDING COMPRESSING SAID ACETYLENE TO SAID TRANSPORT PRESSURE AS A GAS, AND TRANSPORTING THE LIQUID PHASE THUS OBTAINED AT SAID TRANSPORT PRESSURE A SUBSTANTIAL DISTANCE THROUGH A PIPE LINE TO A PLACE OF UTILIZATION.

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