DE1941330A1 - Process and device for the extraction of helium from hydrogen - Google Patents

Description

KNIFE GEIESHEIM GMBH MG 517 -

Password: hydrogen-helium extraction. · - ·

Inventor: O. Kaiser

Process and device for the extraction of helium from hydrogen

The invention "relates to a method and a device for Extraction of helium from hydrogen, with the Pail especially thought that the helium is in a large amount of hydrogen is located.

Several methods are known for producing helium from hydrogen. A simple process is to burn the hydrogen. This is uneconomical for the pallet ₁ that the helium is in a low concentration in the hydrogen, since the credit for the heat generation only accounts for about 40% of the value of the hydrogen. It is also known to remove the hydrogen at about 77 K by adsorption on activated carbon. Pure large amounts of hydrogen, however, result in huge adsorbers and too high a cooling requirement to cool them down to the low temperature. Separation by diffusion is also unfavorable, since the separation effect is poor and a very large wall surface is required. By using cryogenic temperatures, a strong concentration of the helium and the generation of helium-free hydrogen is possible. At such low temperatures, however, all higher-boiling impurities such as N «» Ar, CH., Are solid and must first be removed from the hydrogen through considerable effort, namely by freezing out according to the reverse principle or by adsorption.

The object of the invention is to provide a method for Extraction of helium from hydrogen to create which

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does not have the defects mentioned, especially with large amount of hydrogen and in the presence of nitrogen in the helium-containing hydrogen is advantageous.

A method has now been found for the extraction of helium from a raw gas consisting at least of hydrogen and helium, in which, according to the invention, the raw gas is washed under high pressure in a scrubbing column with liquid nitrogen where the hydrogen is at least for the most part, but the helium is only partially due to its lower solubility is dissolved and the undissolved helium content at the top of the column than with nitrogen and possibly other components contaminated gaseous concentrate is obtained, while the saturated scrubbing nitrogen is discharged at the bottom of the column will.

Because of the treatment of the helium-containing raw gas with nitrogen, the method is particularly advantageous when nitrogen is already present in the raw gas and the hydrogen produced in the process may contain nitrogen. The scrubbing nitrogen drawn off at the bottom of the column is saturated with raw gas. It is expediently relaxed, whereby the dissolved gas is outgassed together with the also dissolved helium content and discharged from the system. This outgassing can be done in a number of ways, which will be discussed below. The washing sticks regenerated in this way can can be used again as scrubbing liquid in the column.

The small amount of helium that leaves the separation system together with the hydrogen after degassing can be used to when a hydrogen-consuming chemical process is downstream, in which the helium is enriched and fed back to the separation system in a mixture with hydrogen will. Such a circuit circuit is for example possible in the synthesis of ammonia. '.

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Advantageous values for pressure and temperature for dissolving the hydrogen in liquid nitrogen are 118 bar and 88 K. This means that the high hydrogen content of 33 mol "p can be achieved in the bottom liquid.

An extension of the procedure is also complete Extraction of the helium from the hydrogen is possible. For this purpose, the column receives a feed under the raw gas Lower part in which the helium dissolved in the washing nitrogen is stripped out with helium-free hydrogen. The one for this The required stripping hydrogen is advantageously obtained when the scrubbing nitrogen is regenerated. Of course can be contained in the raw gas as well as in the scrubbing nitrogen and in the stripping hydrogen, which do not significantly affect the process *

The scrubbing nitrogen can be regenerated in various ways and depends largely on the requirements of the company. It may be possible to do without them entirely. If desired, can be made out the saturated scrubbing nitrogen hydrogen of high purity or under high pressure can be obtained by applying the pressure of the saturated scrubbing nitrogen is lowered in several stages, with the outgassing hydrogen in each case before the subsequent Pressure stage is separated in a separator. In order to obtain the stripping hydrogen, it is sufficient to do a one-off To relax. It is also possible to use the saturated scrubbing nitrogen under the high column pressure to cool to generate the required stripping hydrogen. The regenerated liquid scrubbing nitrogen is through brought a pump to the column pressure and again applied to the wash column.

Another concentration of the head of the wash column accumulating helium concentrate can be achieved if a cooling coil is arranged there, in the one

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small amount of the withdrawn at the bottom of the column and previously cooled hydrogen-containing scrubbing nitrogen is relaxed.

In an advantageous embodiment of the invention, the saturated scrubbing nitrogen withdrawn from the column foot is used relaxed and put into a rectification column to perform work, conducts, from the base of which hydrogen-free nitrogen is withdrawn which is returned as washing liquid to the washing column. From the head of the reclamation column = - flow Hydrogen and nitrogen and possibly other components contained in the raw gas, practically in the composition of the raw gas, but without helium, or, if there is no stripping process is provided with reduced helium content. A . Part of this overhead product can be recompressed and used as stripping gas be used. The rectification column can, for example, be heated by raw gas entering the plant. To a To obtain hydrogen-free helium concentrate, it is sufficient if only a small part of the saturated scrubbing nitrogen is made anhydrous from the column foot and upside down the scrubbing column is abandoned, whereas another part remains afflicted with a hydrogen residue and with a Another pump is applied to the scrubbing column below the point of application of the hydrogen-free nitrogen

The advantage of the process with work-producing relaxation of the saturated scrubbing nitrogen is that the process can be designed in such a way that it works without an external source of heat or cold.

If, in order to save a pump, all of the scrubbing nitrogen is completely freed from hydrogen in a rectification column a strong sump heating is required. this is due to the fact that the temperature of the flowing liquid increases with decreasing hydrogen content, so the high for the process required amount of washing liquid must be heated. Another object of the invention is therefore

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to create a rectification process which can be carried out under the conditions mentioned.

It has now been found that a rectification process for removing a dissolved gas from a .Liquid, whose temperature increases sharply with falling gas content, in particular the removal of hydrogen from nitrogen, can be carried out if, according to the invention, the gas-free liquid obtained by indirect heat transfer to the The liquid running down in the rectification column cools.

A rectifying column is suitable for carrying out the process according to the invention, which consists of a column jacket with an upper and lower closure plate and several column bases, an outlet line for the bottom product on the lower closure plate and an outlet line for the top product on the upper closure plate. Furthermore, one or more heating coils can be arranged in the column foot. According to the invention, the column bottoms are designed as baffle plates, through which tubes are guided with the formation of annular gaps. The tubes are combined by an upper and a lower tube nest, the discharge line leading from the lower closure base into the lower tube nest and the upper tube nest having a discharge line for the cooled sump product. The rectification column according to the invention resembles a heat exchanger with straight vertical pipes and horizontal baffle plates.Each baffle plate has a low liquid bath and only allows liquid to pass downwards at the annular gaps to the tubes, so that trickle films form on the tubes. The steam is led upwards between the metal sheets and pipes; when the raw gas is washed, the amount of steam flowing upwards is extremely reduced. Columns provided with random packings or bubble-cap trays are therefore appropriate.

The wash column is preferably operated such that at its base, the saturated Waschetickstoff under a pressure of

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Karin be about 118 bar, a temperature of about 88 K and about 33 mole withdrawn io hydrogen.

As already stated at the beginning, the method according to the invention is not dependent on the raw gas, scrubbing liquid and stripping gas being in pure form, it can be in they may also contain admixtures, provided they do not interfere with the process. The nitrogen can even be omitted entirely, whereby its job for example of carbon monoxide, argon or Methane is taken over.

The accompanying drawings illustrate an embodiment ™ example of the invention.

It represent:.

Pig. 1 a scheme of the process according to the invention with complete helium separation and the process according to the invention Regeneration of the scrubbing nitrogen in a special rectification column.

P, ig. 2 shows a section from the rectification column.

The method shown works without an external source of cold or heat. The raw gas to be processed contains 1 mol $> helium, 84 mol # hydrogen and only 15 mol # nitrogen.

In line 1, the raw gas is fed to the low-temperature system at around 118 bar and 295 K. It cools down in the Heat exchangers 2, 3 and 4 and reaches the column 5 at about 87 K through the line 8. The upper part 6 of this column is a wash column and the lower part 7 is a stripping column. In the scrubbing column, the raw gas from line 8 and the Stripping steam from the stripping column 7 according to the invention with liquid Dissolved nitrogen except for a small helium-rich vapor residue that formed. The stripping column 7 prevents

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that the helium content, which is dissolved in the liquid from the washing column 6, out of the column 5 downwards escapes.

Pure washing nitrogen flows through the line 9 over the Packing of the washing column 6 downwards and is saturated with the hydrogen-rich steam flowing upwards. In the stripping column 7 reached, the scrubbing liquid can no longer absorb any additional amount of grass, sojdaß that with the line 10 fed helium-free stripping gas in the entire area of the stripping column 7 is retained as vapor. as Stripping gas is a gas that essentially corresponds to the composition of the raw gas, but it does not contain any helium. The packing of the stripping column 7 bring liquid and vapor to mass transfer, with helium from the liquid phase passes into the vapor phase and is conveyed upwards in the steam. Finally, the line 11 can be used to exit the column foot 12 transport away a saturated helium-free liquid, which practically all of it in the column 5 contains incoming hydrogen and nitrogen. The hydrogen concentration in this liquid is about 33 Hol $.

In the upper part of the random packing of the scrubbing column 6, a helium-rich gas cushion is formed, from which the helium concentrate is withdrawn by means of line 14. The helium concentrate contains the 9 entering wash nitrogen contains at least 1.5 mol $ ™ nitrogen via line in height of the feed point. A considerable part of this impurity can be condensed out with the small coil 13, so that the crude helium withdrawn through line 14 only contains about 0.8 mol of nitrogen. In the coil, just above the freezing temperature, an H ₂ -N ₂ wet vapor is boiling, which is produced from a small amount of the nitrogen liquid from line 11, which contains 33 mol of hydrogen. For this purpose, after precooling in the cooler 15, the fluid is expanded by the throttle valve 16 to about 1.5 bar.

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The large amount of scrubbing nitrogen that is transferred via line 9 to the Wash column 6 must be abandoned is by regeneration of the saturated scrubbing nitrogen from the column foot 12 recovered. First, the saturated washing nitrogen arrives through line 17 to expansion machine 18, where 'your pressure is lowered from 118 bar to about 10 bar, the temperature drops from about 88 to 72 K and a wet vapor is formed, the liquid of which only contains 2 mol of hydrogen. Without This hydrogen, which is still dissolved in the liquid, is expelled by the rectifying column 19 by a further reduction in pressure. During this rectification process, the liquid is constantly in the boiling state, so that its temperature decreases increasing hydrogen content. As a result the pure nitrogen liquid in the discharge line 20 has a temperature of 105 K.

For this warming of the large ones in the rectification process the amount of liquid trickling down and the heating power of the is sufficient to generate the necessary steam Heat exchanger 3, that is to say the nitrogen evaporator, does not come off alone. Therefore, the heat that is needed when Cooling of the pure liquid nitrogen is released, exploited according to the invention. For this purpose, the drain line 20 is withdrawn liquid nitrogen passed back above the bottom into the rectification column 19 and that into the lower one Tube nest 34, from which tubes 21 lead vertically upwards through the rectification column 19. The tubes 21 open into the upper tube nest 35, from which the cooled liquid scrubbing nitrogen via line 36 from the rectification column 19 is deducted. The tubes 21 pierce with training of annular gaps, the column trays, which are designed as baffle plates.

Each baffle plate has a low liquid bath and only lets in liquid at the annular gaps to the pipes through the bottom so that trickle films form on the pipes. The steam is back and forth between the sheets and pipes led up.

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After further deep freezing in the regulating heat exchanger 22 and in the preheater 23, the pure liquid nitrogen is with it the pump 24 brought to the column pressure. By actuating the two valves 25, the amount of through the regulating heat exchanger 22 flowing high-tension scrubbing nitrogen stream regulated, so that the column 5 in the desired temperature range can be held. At the same time, the inlet temperature of the pump 24 is always at the low value of held about 74 K in order to achieve a small volume of liquid for the lowest possible pump work.

The steam emerging from the top of the rectification column 19 through line 26 has practically a raw gas composition but no helium. After heating, part of this gas is branched off with the compressor 27 to column pressure compressed, cooled in the heat exchangers 2, 3 and 4 and passed into the stripping column 7 as stripping gas 10. That Hp-Np product contains almost the entire amount of raw gas and leaves the low-temperature system with about 9 | 5 bar through a line

Connected to the system is an adsorption device 29 » which processes the crude helium from line 14 to pure helium at low temperature, which is withdrawn through line 30. This helium cleaner is only shown symbolically in the drawing, since its structure is not essential for the invention is. The adsorption device 29 is supplied with cold in the form of liquid nitrogen via line 31 and is there this back in line 32 as steam.

The cold balance of the entire system is controlled solely by the Relaxation machine 18 disputed. This creates significantly more energy from the system than through the pump 24 comes in.

In Pig. 2 shows a part of the rectifying column 19 according to the invention on an enlarged scale. The direction of flow dea pure washing nitrogen in the pipes is indicated by arrows 37, those of steam by an arrow 38 «

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Claims (18)

.ίο- 1t4f330 KNIFE GRIESHEIM GKBH MG 517 Claims . Process for the extraction of helium from a raw gas consisting at least of hydrogen and helium, thereby characterized, .that the raw gas (8) washed under high pressure in a scrubbing column (6) with liquid nitrogen (9) where the hydrogen is at least for the most part, but the helium because of its lower solubility is only partially dissolved and the undissolved helium content at the top of the column than with nitrogen and possibly further components contaminated gaseous concentrate (H) is obtained, while the saturated Scrubbing nitrogen is discharged at the bottom of the column, 2. The method of claim 1, wherein all of the raw gas contained-helium is extracted, characterized in that 'that the proportion of helium dissolved in the saturated scrubbing nitrogen expelled in a stripping column (7) by helium-free stripping hydrogen (10) and together with the stripping hydrogen (10) and is passed with the raw gas into the foot of the scrubbing column (6), 3. The method according to claim 2, characterized in that only one column (5) 'is used, the upper part of which as Wash column (6) and its lower part serves as a stripping column (7), and at its foot (12) with hydrogen and optionally further components of saturated, helium-free nitrogen is drawn off in liquid form. 4-, method according to claim 1, characterized in that at least part of the hydrogen-saturated, helium-containing scrubbing nitrogena a hydrogen-consuming chemical process, in particular one - 11 - 109814/0916 Ammonia synthesis, is supplied, in which the helium is enriched, after which the enriched gas mixture is subjected to the extraction process again. 5. The method according to claim 2 or 3t, characterized in that that from the withdrawn liquid at the column foot (12), saturated with hydrogen and optionally with further Components containing helium-free nitrogen (17) the required helium-free stripping hydrogen is obtained, by releasing this liquid containing a lot of hydrogen at a lower pressure or at a high column pressure is cooled. 6. The method according to any one of claims 1 to 5, characterized in that that at least part of the scrubbing nitrogen from the column foot (12) is relaxed and nitrogen liquid is obtained which contains little or no hydrogen and by a pump (24) as a washing liquid is abandoned to the top of the column. 7. The method according to claim 6, characterized in that the relaxation of the washing nitrogen doing work he follows. 8. The method according to any one of claims 6 or 7, characterized in that that at least part of the saturated scrubbing nitrogen (11) from the column foot (12) into a the foot-heated rectification column (19) is depressurized, from the foot of which hydrogen-free scrubbing nitrogen is drawn off, and the top product of which consists of hydrogen, nitrogen and optionally other components. 9 · The method according to claim 8, wherein the entire in the raw gas contained helium is extracted, characterized in that part of the withdrawn from the rectifying column (19) Overhead products (26) recompressed (27) and flows back into the stripping column (7) as stripping gas (10). 1098U / 0916 - 12 - 10. The method according to any one of claims 8 or 9t thereby characterized in that only a small part of the saturated scrubbing nitrogen (11) from the column bottom (12) in the Rectification column (19) made completely free of hydrogen and pumped (24) to the top of the wash column (6), while another part releases its hydrogen except for a small amount in a separator, also to the, Pressure of the wash column (16) is pumped and below the feed point of the pure nitrogen (9) to the 'wash column (6) is abandoned. 11 «Method according to one of claims 1 to 10, in which hydrogen is produced at high pressure or high purity is to be, characterized in that the pressure of at least part of the saturated scrubbing nitrogen (11) is lowered in several stages from the column base (12), the outgassing hydrogen being separated off with a separator before the subsequent pressure stage. 12. The method according to any one of claims 1 to 11, characterized in that the saturated scrubbing nitrogen (11) the column foot (12) under a pressure of about 118 bar, a temperature of about 88 K and with about 33 mol i <> hydrogen leaves. 13. The method according to any one of claims T to 12, characterized characterized in that a small part of the scrubbing nitrogen (1!) from the column foot (12) is cooled and fed into a cooling coil (.13) is expanded in the head of the column (5, 6). 14. The method according to any one of claims 1 to 13, characterized characterized in that the washing of the raw gas and optionally the stripping of the washing liquid in with packing columns (5, 6, 7) provided with bubble trays. - 13 - 10 9 8 14/0916 15. Rectification process to remove a dissolved gas (hydrogen) from a liquid (nitrogen), the temperature of which increases sharply with falling gas content, in particular according to one of claims 8 to 11, thereby characterized in that the gas-free · liquid obtained (20) cooled by indirect heat transfer to the liquid running down in the rectification column (19) will. 16. Rectifying column for carrying out the method according to claim 15, consisting of a column jacket with an upper and lower closure plate as well as several column plates, a discharge line for the bottom product at the lower Closure base and a discharge line for the top product on the upper closure base, and optionally Feed and discharge lines for at least one heating coil arranged in the column foot, characterized in that the Column bottom (33) are designed as baffle plates through which tubes (21) form annular gaps . are guided and which are combined in an upper (35) and lower (34) pipe nest, the discharge line (20) leads from the lower closure base into the lower tube nest (34) and the upper tube nest (35) has a discharge line (36) for the cooled bottom product. 17. The method according to one or more of the preceding claims, in which the raw gas contains at least 15 mol $> nitrogen is under a pressure of about 118 bar and a temperature of about 295 K, and without an external heat or cold source, almost the entire amount of the Raw gas is obtained helium-free under a pressure of about 9 »5 bar, characterized in that saturated scrubbing nitrogen (17) from the column foot (12) is expanded to about 10 bar, the bottom of the rectification column (19) with raw gas (1) after Pre-cooling is heated, and that by - 14 1098U / 0916 a regulating heat exchanger (22) regulates the temperature of the pure washing nitrogen (9) after the pump (24) becomes while the temperature of the pure wash nitrogen is kept constant at about 74 K in front of the pump (24). 18. The method according to any one of claims 1 to 11 and 13 to 16, characterized in that the solution of the hydrogen carried out there only or predominantly with nitrogen is replaced by solution in carbon monoxide, argon or methane. August 12, 1969
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