DE1751714A1 - Method and device for generating cold - Google Patents

Description

Method and device for generating cold

The invention relates to a method and a device for Generation of cold by fractional condensation of a gas mixture containing components with different boiling points at increased pressure, at least one of the liquid fractions in the decompression and evaporation vapor produced by at least one low-boiling fraction, subsequent evaporation and heating by heat exchange with media to be cooled and recompression of the gas mixture thus obtained.

Such processes are primarily used in liquefaction used by natural gas. The cold is thereby through circulation of a gas mixture, which from the contained in the natural gas

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Components consists, produced. Both an open and a closed cycle can be used, ie the natural gas to be liquefied and the cycle gas can be liquefied together or separately. If, however, a gas to be liquefied, the another material composition comprising as serving as a refrigerant medium gas mixture, then it should result in a closed circuit. An example of this is the liquefaction of air with the help of a hydrocarbon mixture as a Kälternediuin.

These mixed gas circuits have recently found a very broad field of application because of the comparison to the classic type of refrigeration by connecting several separate refrigeration circuits with different ones in series Refrigerants only a single refrigeration circuit and, accordingly, only a single compressor, mostly one Turbo compressor, is necessary.

These advantages are offset by two disadvantages: First the energy requirement is higher than with the mentioned prior art refrigeration processes and secondly it has been found in the investigations on which the invention is based that it is not possible with known means the relaxed liquid as evenly as it is with

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mixed gas circuits is necessary on the inlet cross-section of the heat exchanger to be cooled.

The invention has set itself the task of addressing these disadvantages z "u overcome, i.e. on the one hand the energy requirement for the Reduce cold generation through mixed gas circuits and on the other hand for a better distribution of the relaxed To provide liquid in the heat exchanger to be cooled.

Experience has shown that this object is achieved in that at least one of the liquid fractions in an ejector, in which at the same time the relaxation and evaporation of the at least one lower-boiling fraction produced steam is compressed and intimately mixed with the relaxed liquid, is relaxed to evaporator pressure and that the Intimate mixture of liquid and vapor leaving the ejector to which heat exchange is supplied with the media to be cooled.

As shown in FIG. 1, an ejector consists of in a manner known per se from a nozzle a, through which the under Medium under pressure, the so-called propulsion jet, emerges and is arranged equiaxially with an enveloping jet Tube b, the middle section of which is called the mixing space c and its ■ conically widening end section d is called the diffuser

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will. The propulsion jet that relaxes as it emerges from the nozzle sucks in gas from the environment through the annular gap between nozzle and pipe and mixes with it. The sucked in Gas is thereby after. Principle of impulse transmission condensed.

Up to now, ejectors have been used in refrigeration technology to to be reduced even further, so that even lower temperatures can be reached, as is crucial, for example, in helium refrigeration systems through which a cold bath of helium boiling under vacuum is to be provided. It serves as a propulsion jet Helium in a supercritical state, which is initially brought to a subcritical intermediate pressure by an ejector relaxed and then separated in a separator into the liquid and the gaseous phase. The liquid will now further relaxed to the evaporator pressure in a throttle valve. The steam leaving the evaporator is in the ejector on the Intermediate pressure compressed; the gas escaping from the separator is fed to the refrigeration cycle compressor. In this way the losses that occur with the usual irreversible throttle expansion from the condenser to the evaporator pressure, be reduced. The invention differs from this in that several in the course of the fractional condensation a gas mixture separated fractions in ejectors from

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The condenser is immediately released to the evaporator pressure that the mixture of steam leaving the ejector and liquid without the interposition of a separator is fed directly to the heat exchange and that the to compressing vapor not from the liquid supplied to the ejector under consideration, but from the evaporation of a ■ low-boiling liquid originates from.

Especially in the case of a mixed gas cycle, the Use of ejectors as relaxation organs in particular advantageous because here due to the fact that to be compacted Steam from a lower temperature Evaporation is available, the irreversible expansion in the throttle valve not only partially, but completely can be replaced by the reversibility approaching relaxation in the ejector. It does two things at the same time achieved: Once in the expansion device itself, such an intimate mixing of liquid and vapor is achieved, that the liquid droplets are evenly distributed over the heat exchanger cross-section and from the gas flow into the Zones of higher temperature are entrained, so that complete evaporation of even higher-boiling liquid components is guaranteed. This is especially true for mixed gas circuits especially important because here every heat exchanger has to bridge relatively large temperature differences, while '

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the temperature difference available for heat exchange in a certain cross-sectional plane is small and because the liquid to be evaporated contains components with different boiling points and the parts that are more difficult to evaporate in the case of uneven distribution, remain at the points of the heat exchanger that are less heavily flushed by the gas flow.

Second, the device used for expansion simultaneously increases the energy requirement for the cycle compressor reduced by increasing the suction pressure. While in the usual mixed gas circuits with throttle expansion the evaporator pressure of that working at the lowest temperature Heat exchangers up to the heat exchanger working at the highest temperature because of the flow resistance gradually decreases, the evaporator pressure according to the invention can be increased or increased in the direction mentioned be held at the same level; in unfavorable cases, at least the pressure loss due to the flow resistance is reduced reduced.

The invention does not involve any additional outlay in terms of equipment, since throttle valves and ejectors differ with regard to each other the manufacturing costs hardly differ.

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Zv; eck: Nä3i £; it is evident that the evaporative pressure is so; in each case that who are available for work when despoking ir.i ejector Energy is sufficient to uin aie while relaxing and vaporizing the .at least one lower-boiling fraction arose Steam aience to compress the evaporator jerk.

One embodiment of the invention consists in that: 3 the amount of liquid to be expanded per unit of time in an ejector and the amount of steam to be compressed in this ejector, ir; Measured lr.i \ ^J , are of the same order of magnitude. In the liquefaction of natural gas, it is advantageous in a further embodiment of the invention to select the gas quantities conducted in the refrigeration cycle to be approximately three to five times as large as the gas quantity to be liquefied by the generated cold.

In order to prevent the mixture of liquid and vapor leaving the ejector from separating, it must be ensured that that there are no parts acting as separators between the ejector and the heat exchanger. In further development the invention this is achieved in that the mixture formed in the ejector of liquid and vapor over the as Diffuser of the ejector formed inlet nozzle of the heat exchanger is introduced into this.

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According to a particularly preferred embodiment of the invention is liquefied by the generated cold, under Pressurized gas in an ejector is expanded into a separator and then stored, which is caused by the action of heat created on the stored liquid. Steam is compressed in this ejector and that in the separator leaving gas is in a separate flow path in the Heat exchange with the media to be cooled.

The method according to the invention can still be thereby Make it more advantageous that the liquid fractions prior to decompression by heat exchange with the already relaxed Liquid become supercooled.

The device for performing the method according to the invention is characterized in that an ejector such is connected to the cold end of a heat exchanger that the inlet port of the heat exchanger at the same time represents the diffuser of the ejector.

In addition to natural gas components, there are also other refrigerant mixtures, e.g. mixtures of olefins or of olefins and paraffins suitable as cooling media. As a further example of a refrigerant that can be used in a mixed gas cycle, let us consider

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a mixture of halogenated paraffins, such as those under the Trade names "Freon" have become known, tait ethylene and Methane listed.

The method and apparatus according to the invention will now be discussed using the schematic representations in FIGS. 2-4, for example explained. In Fig. 2, the scissors sketch is one with reproduced closed refrigeration cycle working process; this procedure is preferably used when the natural gas pressure is between about 20 and 60 at. In Fig. J5 the schematic diagram of a method is shown, that works with an open cooling circuit and is therefore also suitable for liquefying natural gas at lower pressure is. Fig. 4 shows the connection between ejector · and ■; ärr; .aus exchanger.

According to the scheme of FIG. 2, the pressurized Natural gas supplied through line 1, cooled and liquefied in the heat exchangers 2, 3 * '^ and 5 and in the ejector 6 relaxed to about 1.2 ata. In the separator 7, liquid and gas are separated from one another. The liquid spills over the control valve <., in the storage tank 9 The vapor generated on the stored liquid is under a ::. Pressure of about 1.02 ata and can therefore only be below

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Utilization of its cold content can be returned by the system, e.g. if it is so is compressed to such an extent that the pressure drop in the heat exchanger and the other parts of the system is overcome. Urn this cold gas blower To relieve or save, the steam is sucked in from the tank 9 via line 10 by the ejector 6, to 1.2 ata compressed, returned through line 11 and released as fuel gas.

The cycle gas consists of nitrogen, methane, etnane, Propane and butane. It is in the compressor 12 to 30 - 35 at compressed and cooled in the water cooler 13. The main ones condensing Ci. - as well as part of the C, - and CV -

k 3 c;

Hydrocarbons are separated in the separator 14, supercooled in the heat exchanger 2 and expanded to 1.6 ata in the ejector 15, evaporated in the heat exchanger 2 and sucked in again by the circuit compressor 12 at a pressure of 1.5 ata. The steam leaving the separator 14 is cooled in the arm exchanger 2 to such an extent that predominantly Cp and C ^ hydrocarbons condense , 6 ata relaxed and your heat exchanger again ';) supplied to be evaporated in countercurrent to the gas and liquid flows to be cooled

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the heat exchanger 3 through line 1ö with a pressure of 1.55 ata, v.'ird. fed to the ejector 15 and compressed in this to 1jU ata, so that the pressure drop in the heat exchanger 3 is compensated. The gas v 'withdrawn from the separator is partially condensed while cooling in the heat exchanger. The predominantly liquefied components ethane and methane are collected in separator 19, ^{subcooled, T} heat exchanger 4, expanded to 1.4 ata in ejector 20 and evaporated under this pressure in heat exchanger 4. üie leave the heat exchanger 4 under a pressure of 1.35 ata, reach the ejector via line 21 and are compressed in this to 1.0 ata. The gas coming from the separator 19, now mainly consisting of methane and nitrogen, is finally cooled and liquefied in the heat exchangers 4 and 5, expanded to 1.2 ata in the throttle valve 22 and returned through the heat exchanger 5. The pressure drop in the heat exchanger 5 is approximately 0.5 ata, so that the steam reaches the ejector 20 via line 23 at a pressure of 1.15 ata and is compressed by this to 1, -i ata. In this case, the amount of circulating gas is three times as large as the amount of natural gas to be liquefied.

In the method according to FIG. 3, this is done by conduction incoming, under a pressure of 35 at standing natural gas and

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the cycle gas compressed to 3 at in the compressor 31 and cooled in the water cooler 32 together through line 33 the heat exchanger 3 ^ supplied. There they liquefy predominantly the heavy hydrocarbons are collected in the separator 35 and supercooled in the heat exchanger 36 and relaxed in the ejector 37 to 1.6 ata. The resulting steam passes through line 38 under a pressure of 1.55 ata in the heat exchanger 3 ^ and is from the circuit compressor 31 sucked under a pressure of 1.5 ata. Of the The steam leaving the separator 35 is continued in the heat exchanger 36 with condensation of predominantly ethane and propane cooled down. The liquid phase is separated in the separator 39, supercooled in the heat exchanger 4o and in the ejector 41 to 1.6 ata relaxed. The steam leaving the heat exchanger 40 through line 42 is at a pressure of 1.55 ata and is compressed in the ejector 37 to 1.6 ata. The steam withdrawn from the separator 39 continues in the heat exchanger 4o cooled down. Mainly ethane and methane are liquefied, collected in separator 43 and supercooled in heat exchanger ^ 4 and relaxed in the throttle valve 45 to 1.4 ata. The liquid evaporates in the heat exchanger 44 giving off its evaporation cold and the resulting steam arrives via line 46 with it a pressure of 1.35 ata in the ejector 41, where it is compressed to 1.6 ata.

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The gas leaving the separator 4 ^ is the largest Part made of methane. It is liquefied and supercooled in the heat exchanger 44, expanded to 1.2 ata in the ejector 4γ, in the separator 4ü separated from the gaseous components. The liquid becomes the liquid gas via a control valve 49 tank 50, in which it is loaded depending on the fill level of the Tanks with a pressure up to 2.5 ata is entered at the foot end. The gas cushion under the tank roof is under one Pressure of approx. 1.03 ata. The steam escaping from the tank is compressed to 1.2 ata in the ejector 47 and via a line 52 withdrawn from the system.

The method according to FIG. J5 is, as already mentioned, also for Liquefaction of natural gas under relatively low pressure is suitable. If the natural gas pressure is lower than the final pressure of the cycle compressor, so the natural gas is fed into an intermediate stage of the cycle compressor and together with the cycle gas is compressed to the desired final pressure.

Fig. 4 shows the connection of the ejector E to the heat exchanger V /. The reference symbols have the same meaning as in FIG. 1: The propulsion jet is in the nozzle a, in this If the pressurized liquid formed by fractional condensation is relaxed and in the mixing space c

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it mixes with the one sucked in through the mouth of the pipe b, from the warm end of the next lower one Temperature working heat exchanger coming steam. This is compressed according to the principle of impulse transmission. The resulting intimate mixture of liquid and steam enters the cold end of heat exchanger W through diffuser d. The diffuser d is at the same time the inlet pipe of the heat exchanger Vi; he is connected to the mixing room c via planes F.

8 claims
4 sheets of drawings

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^Bathroom original

Claims (1)

-15- LINDE AKTIENGESELLSCHAFT 17517U (H 451) H G8 / 0 52 Str / Kp July 15, 1968 Claims . Method of generating cold by fractional Condensation of a gas mixture containing components with different boiling points at elevated pressure, Relax at least one of the liquid fractions in the decompression and evaporation of at least vapor produced by a lower-boiling fraction, evaporation and heating by heat exchange with media to be cooled and compressing the material obtained in this way Gas mixture, characterized in that at least one of the liquid fractions in an ejector in which at the same time the during the expansion and evaporation of the at least one lower-boiling fraction, the vapor formed is compressed and is intimately mixed with the expanded liquid, expanded to evaporator pressure and that the ejector leaving intimate mixture of liquid and steam is supplied to the Vlärmeaustausch with the media to be cooled. ORIGINAL BATH 109852 / 0AA7 17517U LINDE AKTIENGESELLSCHAFT 2. The method according to claim 1, characterized in that the evaporator pressure is chosen so that the relaxation Sufficient energy available in the ejector to relax and evaporate the at least one lower-boiling fraction to compress the amount of steam produced to the evaporator pressure. 5. The method according to claim 1 or 2, characterized in that that the amount of liquid to be expanded per unit of time in an ejector and that to be compressed in this Amount of steam, measured in Nm, is of the same order of magnitude to get voted. 4. The method according to any one of claims 1 to 5, characterized in, that when natural gas is liquefied, the amount of gas carried in the refrigeration cycle is about three to five times is chosen as large as the amount of natural gas to be liquefied by the cold generated. 5. The method according to any one of claims 1 to 4, characterized in that that the mixture of liquid and vapor formed in the ejector via the formed as a diffuser of the ejector Inlet nozzle of a heat exchanger is introduced into this. 1098 5 2 / 0U7 -17- LINDE AKTIENGESELLSCHAFT 6. The method according to any one of claims 1 to 5 *, characterized in that that by the generated cold liquefied, pressurized gas in an ejector into a separator relaxed into it uuu uann stored that the vapor created by the action of heat on the stored liquid is compressed in this ejector and that the gas leaving the separator in a separate flow path exchanging heat with media to be cooled is heated. 7. The method according to any one of claims 1 to 6, characterized in that that the liquid fractions before decompression by heat exchange with the already relaxed liquid be hypothermic. o. Device for carrying out the method according to one of Claims 1 to "J, characterized in that an ejector (E) is connected to that at the cold end of a heat exchanger (W) in such a way that the inlet connection of the heat exchanger simultaneously serves as the diffuser (d) aes ejector (Fig. 4). ORIGINAL BATHROOM 109852/0447