DE1170435B - Process for the liquefaction of a gas to be stored in the liquid state under low pressure - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Class: F 25 j

German KI .: 17g-l

Number: 1170 435

File number: A 345571 a / 17 g

Filing date: May 4, 1960

Opening day: May 21, 1964

The invention relates to a method for liquefying an in the liquid state under low Pressure of the gas to be stored, at which the gas, which is under a relatively high pressure, passes through Heat exchange with at least one liquefied gas precooled by subsequent heat exchange cooled further with an auxiliary amount of the gas that was relaxed to perform work and then up its storage pressure is relaxed.

It is well known that the transport of a gas from the place of extraction or production to the place of use through pipes or in bottles is at an elevated level Pressure arduous and costly, as the distance to be covered is usually quite large is. An economical method of transport is to liquefy the gas at its place of extraction and it in the liquid state in trolleys or ships with heat-insulating containers to be transported and finally returned to the gaseous state upon arrival at the destination convict.

It is known to be rather difficult to liquefy gas, such as methane and even hydrogen and Helium, to be liquefied by adding one or more auxiliary cold-generating fluids right from the start used according to the so-called cascade method and then finally a cooling by expanding a fraction of the gas to be liquefied while performing external work causes. The gas is therefore cooled under a relatively high pressure by exchanging heat with at least a cold-producing liquid, relaxes an auxiliary amount of this gas with external work and cools the gas again under increased pressure by exchanging heat with the expanded auxiliary quantity from, whereupon the gas is relaxed to its storage or storage pressure and the obtained Liquid is collected or recovered.

The invention relates to an improvement of the method described, which enables an increased Cold production through relaxation with external work and a final, increased cooling of the pressurized gas to achieve such that the amount of gas after the expansion maintains the gaseous state at the bearing pressure remains low.

The improvement also enables the gas to be liquefied with a relatively low cost Amount of energy and a steady course of operation.

The method of the invention is characterized in that at least part of the auxiliary amount of the Process for liquefying a liquid under low pressure to be stored gas

Applicant:

L'AIR LIQUIDE, Societe Anonyme pour l'Etude et! 'Exploitation des procedos Georges Claude, Paris

Representative:

Dr. H.-H. Willrath, patent attorney, Wiesbaden, Hildastr. 18th

Named as inventor:

Raymond Brunand, Paris,

Jacques Grunberg, Quebec (Canada)

Claimed priority:

France of May 15, 1959 (794 788)

Gas after an expansion to a lying between the initial and the storage pressure of the gas Value in the heat exchange with the gas to be liquefied or the auxiliary quantity heated and afterwards the work-performing relaxation is directed.

A particularly advantageous application of the method consists in the liquefaction of methane or gases rich in methane, such as natural gas. In this case, the methane, which is under relatively high pressure, is exchanged with heat liquefied a cryogenic liquid; the liquid methane is produced by heat exchange with the Aid amount that was relaxed while performing external work before relieving the pressure on the camp hypothermic; the gaseous auxiliary amount is evaporated and then with heat exchange with the liquid methane is heated under high pressure before entering the expansion machine. Of the The energy requirement is relatively low in relation to the amount of liquefied methane.

The gas to be liquefied, in particular natural gas, generally contains impurities which are not very volatile, such as C ₂ and C ₃ hydrocarbons (ethane, ethylene, propane, propylene). These tend to be condensed in the expansion machine and damage it or at least impair the operation of the machine.

409 590/108

3 4

According to a particular embodiment of the It is available at 21 ° C under a pressure of

Invention, this disadvantage is avoided by 41.8 kg / cm ² . The introduced through the line 1 that the relaxation under the performance of external work and conducted through the heat exchangers 2 and 6 is carried out on a gas, which is freed of its gas in the latter successively in countercurrent little volatile impurities and 5 by liquid propane, which is through the lines 3, which flows through a closed circuit and 7 enters the exchanger and leaves it in the gas and the task of a cold-generating supplementary state through the lines 4 and 8, takes over in the liquid. The purified, relaxed course of the gas under pressures of about 4.5 kg / cm ² is then used to cool the cooling or 1 kg / cm ² evaporation of the impure gas, which was previously heated in this way At about -32 ° C exchange with one or more other cold-cooled methane is then liquefied in exchanger 10 with generating liquids, with the help of methane gas, which enters at 11 under low pressure through indirect heat exchange with this and at 12 exits, an auxiliary cooling, whereupon the pure gas is heated, subjected again to treatment. Then it successively gets compressed and returns to the circulation. i ₅ through lines 13 and 17 into the heat outlet. The methane to be liquefied is often under exchanger 14 and 18, where it is in countercurrent with a variable pressure and with a liquefied ethylene, which through the lines 15 variable content of stronger volatile impurities and 19 in and out through the lines 16 and 20 (nitrogen) and less volatile impurities, liquefied, while the latter is available under pressure from cleaning agents (hydrocarbons). It evaporates about 4.5 kg / cm ² and 1 kg / cm ^{2, respectively.} It is therefore necessary that the refrigeration production of the liquefied natural gas is then divided into two partial flows of these changes. The first substream is the more important and while being adjusted. This is achieved according to a method of operation of the invention that flows successively through the lines 21 and 26 in that the heat exchangers 22 and 27, which are in methane to a precisely defined level, at about 25 countercurrent in the course of evaporation of two -100 ° C lying temperature level are flowed through by pure methane fractions, of which heat exchange with the cold-generating one is liquid and liquefies and cools approximately under a liquid and is then pressure of 6 kg / cm ² and the other already ßend from -100 ° C is partially evaporated to a temperature in the vicinity and is under a pressure from the storage temperature under low pressure to _3o about 1 kg / cm ² . This first partial flow, which is caused by the expansion of a methane, flows out through the line 30 as a liquid further cooled to a fraction of approximately −150 ° C. with external work. The second substream that cools down. To fix easily the Kälteproduk- only a few percent of the total amount represents tion as a function of demand by the amount likewise cooled to below -150 ° C, and the fraction obtained by the expansion machine _35, although in exchanger 32 by heat exchange im flowing, controlled. Countercurrent with methane vapor under low pressure,

In addition, it is also possible in accordance with a different embodiment and then again with the first partial flow seduction form of the invention that agrees with the outside. The liquid methane is then expanded to about 1 kg / cm ² by the work expanded methane up to a temperature valve 35 and to be cooled to a level which is even lower than the 40 led the separator 36. The vapors that are in the temperature at which it forms from the relaxation process of the relaxation are emitted through the machine. This is done in that pipe 37 is discharged and combined with the vapors, a fraction of liquid methane is added to the methane which comes from the storage container and which evaporates on contact with the former. together through line 33 to the heat ex-

The preferred cryogenic liquids 45 are supplied to exchanger 32. The liquid that is now a for cooling down the methane are: Propane or a temperature of about -160 ° C Propylene and then ethane or ethylene. At their, finally, through the line 38 in the storage container point or at the same time, however, other ter 39. This storage container has, for example Using cryogenic fluids, like- an inner metallic liner made of for example ammonia, fluorinated hydrocarbons 50 surrounded by a layer of heat-insulating material or carbonic anhydride. is so that the losses of liquid methane that

In the following, evaporation will not occur on the basis of a small amount bordering example and with reference to the remain limited.

Drawing of a plant for the liquefaction of nature- The relaxation with external work performance

gas described according to the invention. The plant 55 follows a pure methane fraction, which is used in particular for the liquefaction of large amounts of natural gas described in the following closed cycle, namely more than 10,000 m ³ per passes through.

Day, measured under normal conditions. The pure, under low pressure and

The natural gas to be liquefied has the following unheated methane, the origin of which is indicated below

Approximate average composition on: 60 is given, is by the compressor 43 on

brought a pressure of about 30 kg / cm ² . There-

Methane after 88.2% flows through it through lines 44 and 48

StirVstnff η so / one after the other the heat exchangers 45 and 49, in

OL1CK.MU11 U, O / 0, -. _r ., .., «r \ n * ~ * · * ~ t

where it down to about - Co-Konlenwasserstoffe is cooled _{65 with liq} ig _em propane 30 ° C in counter-current, and this in

(Ethylene, athan) 9.5%. Pressures of around 4.5 kg / cm * or 1 kg / cm ²

C ₃ hydrocarbons evaporate. It then flows through line 52 into the

(Propylene, propane) 1.5% exchanger 53 in countercurrent to cold gas

shaped methane under low pressure, which cools it down to - 80 ° C. It is then passed through line 56 into exchanger 57, where it is liquefied by means of ethylene entering through line 58 and exiting through line 59 and boiling under approximately atmospheric pressure. It is then supercooled in exchanger 61 to approximately -130 ° C., in heat exchange to one part with a liquid methane stream, which is expanded to 6 kg / cm ² through valve 63, and the other part with gaseous, under pressure of about 1 kg / cm ² standing methane entering through line 29 and exiting through line 54.

The liquid, pure methane leaving exchanger 61 through line 62 is then divided into three parts. A first part, which is expanded to 6 kg / cm ² in valve 63, is evaporated in exchanger 61, heated to approximately −100 ° C. and then fed through lines 64 and 65 to an expansion turbine 66. A second part is led through line 23 to an expansion valve 24, evaporates and heats up to -100 ° C. in exchanger 22 in countercurrent with natural gas in the course of liquefaction and then passes through lines 25 and 65 'to turbine 66. The two The first partial flows combine during the expansion to about 1 kg / cm ² in this turbine and cool down to -145 ° C. A third part of liquid methane is now added via the line 67 and the expansion valve 68, which partially evaporates and the temperature of the whole is reduced to -158 ° C. The three combined partial flows then reach the heat exchanger 27, in which they ensure increased subcooling of the liquid natural gas under pressure. They are heated to about -135 ⁰ C and pass through the conduit 29 back into the exchanger 61, then through line 54 to exchanger 53, where it at about - 40 ⁰ C are heated, and then return via line 55 back to compressor 43.

The liquid propane is fed to the plant at a pressure of approximately 12 kg / cm ² through line 70; it is expanded through the valves 71 and 72 to 4.5 kg / cm ² and through the valves 73 and 74 to about 1 kg / cm ² before it is pressurized by heat exchange with natural gas and with pure methane, as already described above , evaporated.

The liquid ethylene enters the plant through line 75 under a pressure of approximately 18 kg / cm ² . It is expanded through the valve 76 to 4.5 kg / cm ² and through the valves 77 and 78 to approximately 1 kg / cm ² before it evaporates in the manner already described.

The vaporized propane and ethylene are preferably recompressed and then the circuit with the help of a compressor and a pipe system, for the sake of clarity are not shown, fed back.

The plant described above enables liquefaction when processing larger quantities of natural gas of about 95% of the natural gas used. The loss of liquefied gas through evaporation in the course of the expansion of the fluid under pressure it is thus reduced to about 5%.

Claims (6)

Patent claims: 1. Process for liquefying a liquid to be stored under low pressure Gas, in which the gas is under a relatively high pressure by heat exchange precooled with at least one liquefied gas through subsequent heat exchange and then cooled further with an auxiliary amount of the gas that was relaxed to perform work is relaxed to its bearing pressure, characterized in that at least one part the auxiliary amount of the gas after an expansion (24, 63) to one between the initial and the storage pressure of the gas in the heat exchange with that to be liquefied Gas (22) or the auxiliary quantity (61) is heated and then fed to the work-performing expansion will. 2. The method according to claim 1, characterized in that when the to be liquefied is contaminated Gas with less volatile constituents, on the one hand, the contaminated gas and, on the other hand, the auxiliary quantity of the gas, which by these constituents is noticeably freed, it is cooled down that the relaxation (63) to an intermediate pressure and then the heating (61) and the relaxation with external Work (66) causes the auxiliary quantity and the contaminated gas anew by heat exchange (27) with the relaxed auxiliary amount, which is returned to the circuit (29), cooled will. 3. The method according to claim 1, characterized in that the gas to be liquefied is methane and is liquefied by successive heat exchange (2, 6, 14, 18) with cold-generating liquids and cooled to a temperature of about -100 ° C and then from - 100 ° C due to the amount of cold occurring during the expansion (66) of the auxiliary amount is further cooled to a temperature in the range of its storage temperature under low pressure (27). 4. The method according to claim 1, characterized in that the work-performing relaxed Auxiliary amount of a final cooling by adding (68) and evaporation of a liquid Gas partial flow is subjected. 5. The method according to claim 3, characterized in that the cold-generating liquids, which are used to cool the methane are propane or propylene and ethane or ethylene. 6. The method according to claim 3, characterized in that the cold-generating liquids evaporated under two different pressure levels with the pressurized methane and be heated. Considered publications:
U.S. Patent No. 2,456,386. 1 sheet of drawings 409 590/108 5.64 © Bundesdruckerei Berlin