DE1501749A1 - Method of transporting gas - Google Patents

Description

DH.ING. F. WUKSTHOFF ffolAftjHKN β I VV ! f HW

GDPL. ING. G. PULS sJhÖÖ

DH.ETPECHMANN « ^l " ° » β» Οβ 01

PATENTANWAI / TE ^ o

la-31 588

Description of the patent application

SHELL INTERNATIONAL RESEARCH MAATSCHAPPIJ N.V. 3o, Carel van Bylandtlaan, The Hague, The Netherlands

concerning
Method of transporting gas.

The invention relates to the use of refrigerants in the liquefaction and re-evaporation of oases, preferably from methane or natural gas, especially during transport or peak balancing.

To reduce the cooling and liquefaction costs of gas at To reduce gas transport in the liquefied state, a method is already known in which

a) liquefies the gas by cooling at a production site and placed in a tank in a liquid state,

b) the filled tank is transported to a place of use will,

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c) at the place of use, the liquefied gas is evaporated again by heat exchange with a refrigerant,

d) the refrigerant cooled according to c) is placed in a tank,

e) the tank filled according to d) is transported to the place of production,

f) at the place of production the gas according to a) through heat exchange with the refrigerant delivered according to e) is cooled.

In this known method, the cold is used tob place of use to place of production bit help transfer a · refrigerant. In this context it should be noted that the place of production is the place at which the gas is liquefied for shipping, and that the place of use is the place at which the liquefied gas is converted into the gaseous state for consumption on arrival.

As already mentioned, the coolant can also be used for the storage of gas, for example natural gas or methane, for peak storage. In tents where there is little demand for natural gas or nethane, this can be liquefied by exchanging heat with the cold refrigerant. The liquefied methane or natural gas can then be stored in suitable, thermally insulated tanks, and at times

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In high demand for natural gas or methane, the liquefied methane or natural gas can be vaporized by exchanging heat with the "warmed up" refrigerant, with the refrigerant being cooled. The cooled coolant becomes then temporarily in suitable, thermally insulated tanks stored until a period of low demand for natural gas or methane occurs again. Then the cooled coolant is again used to liquefy a certain amount Methane or natural gas is used, which is then temporarily stored until there is demand for natural gas or methane increases again.

Of course, it is desirable that the refrigerant absorb a large amount of cold per Vd.-unit can, so that only a small tank space is required for storage or transport of the refrigerant. To this The purpose of the coolant is to have a relatively high specific heat and a relatively high specific heat, among other things Have weight.

According to the invention, for use in the above-mentioned transport method for peak compensation, a Proposed cold carrier, which is characterized by a carrier liquid that occurs during heat exchange not solidified and has a boiling point above, at or slightly below room temperature, and a

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Contains substance that is subject to a phase change during heat exchange.

In a suitable embodiment of the invention the substance is chosen so that it completely or partially melts or melts during the heat exchange solidified. In addition, the substance has a boiling point above, at or slightly below room temperature.

The liquid substance, which may be dispersed in the carrier liquid, solidifies on cooling, so that their heat of fusion is added to the specific heat of the refrigerant. Accordingly, the more the liquid substance solidifies, the greater the cooling effect.

During the solidification of the liquid substance, the temperature of the coolant remains constant. Included heat is transferred from the refrigerant to the liquefied gas that is to be evaporated again, without simultaneous Drop in temperature of the secondary refrigerant. This is beneficial in terms of a high heat transfer rate

Of course, these advantages also result, when the cold refrigerant is heated by bringing it into heat exchange with the gas to be liquefied.

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A good effect is achieved if water is used as the substance in the coolant. Water has one high heat of fusion and a high specific weight.

An even better effect is achieved if water, which contains an agent for lowering the freezing puddle, is used as the substance in the coolant. Through this the temperature range in which the substance remains liquid is increased. This is favorable in terms of the increase the specific heat of the secondary refrigerant, since the

specific heat of the liquid substance is higher than the specific heat of the solid substance.

Suitable means of lowering the freezing point are ammonia, hydrochloric acid, alcohol, a mixture of alcohols, glycol or a mixture of glycols.

The coolant can be converted into a stable emulsion in a manner known per se. In the Solidification of the disperse substance particles then forms a suspension. An emulsion that is easy to use or suspension is also obtained if, for example, with the help of a liquid jet or with mechanical aids is stirred.

The coolant can also contain a solid that adsorb or adsorb the liquid substance

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can absorb. Silica gel can be used for this. A heterogeneous coolant of this type can in itself be converted into a stable suspension in a known manner.

Various liquids are suitable for use as the carrier liquid for the refrigerant. A suitable liquid is, for example, isopentane. A liquid can also be selected as the carrier liquid which already contains an agent for lowering the freezing point. In this context the eutectic mixtures of 88 # isopentane and 12 # n-pentane or of 85% isopentane and 15 # isohexane may be mentioned, which appear suitable because of their low melting point.

It was found that the coolant can still be pumped if the dispersed substance particles do not contain more than $ o% liquid, based on the

m
Total volume of the secondary refrigerant.

The gas can be at a pressure of 1 atm. liquefied and transported in a tank. In many cases but it is advisable to use a higher pressure.

During the liquefaction of the gas, the coolant is heated to room temperature, for example. Possibly the heated coolant can be used at the place of production, e.g. in the chemical industry. The -

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however, warmed coolant can also be filled into a tank and transported to the place of use. In general such a transport is carried out under a pressure of 1 atm. made, the application of a higher pressure is but also possible.

In many cases, the cooled coolant can be transported from the place of use to the place of production in the same tank in which the liquefied gas was transported in the opposite direction. This measure has the advantage that the tank stays cold all the time. As a result of the high specific heat and in general high specific weight of the refrigerant according to the invention is usually the tank that is used for transport of the liquefied gas was used, coarse enough for the transport of the cold refrigerant in the opposite one Direction.

According to another, very useful embodiment the invention, a coolant is used with a substance that one or more during the heat exchange Is subject to transitions between the solid, the liquid or the vapor state.

In this way, the heat capacity of the coolant is increased by the heat of evaporation or the heat of condensation

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the substance increased significantly. In this context it should be noted that the heat of vaporization and the The heat of condensation of a substance is always greater than the heat of fusion and the heat of solidification. This heat output can also be harnessed by keeping the temperature of the secondary refrigerant sufficient during cooling is greatly degraded. The substance passes from the vapor phase via the liquid phase into the solid phase. If necessary, cooling can be carried out for so long that the carrier liquid of the refrigerant also partially solidifies.

During the transition of the substance from a phase

in the other, the temperature of the secondary refrigerant remains

nn

constant. Thereupon the heat is converted from the refrigerant to the liquefied one Gas will be transferred that is to be evaporated again, or it will take the heat from the gas that is to be liquefied should be transferred to the secondary refrigerant without a simultaneous drop in or rise in the temperature of the secondary refrigerant. This This fact is favorable in terms of a high rate of heat transfer. The temperature at which the Substance passing from one phase to the other depends of course primarily on the substance selbeg & b. aside from that a further substance can be added to the substance to lower the temperature of the phase transition. As a result, greater procedural freedom is achieved.

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In a suitable embodiment, carbon dioxide is used as the substance. The heat of sublimation of carbon dioxide is about 135 cal / g and is thus considerably higher than the heat of fusion of water, which is about Is 8o cal / g. Therefore, with a certain amount of weight of a refrigerant, its carrier liquid contains solid carbon dioxide particles as a substance, a considerably larger amount of gas can be liquefied than with the same amount of weight of a refrigerant, its Carrier liquid contains ice particles as a substance. The ratio of the amount of payload, i.e. the amount of liquefied methane or liquefied natural gas, the amount of refrigerant is therefore cheaper.

This ratio is even more favorable if the carrier liquid of the refrigerant is ammonia as the substance contains. Be pure the sublimation of solid ammonia about * k> o cal / g consumed.

Methane is suitable as an additive to the substance.

Since carbon dioxide is cheap, there may be economic justification for doing this during the liquefaction of the Carbon dioxide gas evaporating into the atmosphere blow off. In this case, each time at the place of use a new amount of carbon dioxide can be used.

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But you can also bind the evaporating carbon dioxide in such a way that it can easily be restored later can be set freely. ' It can then be in a variety of ways Way to be used. The bound carbon dioxide can be stored or transported to the place of use, and, after its release, can be used again as a substance in the coolant. The carbon dioxide can e.g. be bound in the form of bicarbonates or ammonium carbonates. These can be easily decomposed by moderate heat will.

It is advisable to also add the ammonia, which passes into the gas phase when the gas is cooled and liquefied bind in such a way that it can easily be set free again. A suitable way that Binding ammonia consists in catching the released ammonia in water. The bound ammonia can be stored or trarfportiero to the place of use so that it when it is released, it can be reused as a substance in the coolant. Ammonia is valuable uid can E.g. in the vicinity of the place where the methane or natural gas is produced, further processed into fertilizers.

The vapor, which forms the substance in the refrigerant when cooled, should be collected at the place of use form a heterogeneous system with the carrier liquid.

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This is conveniently achieved by during the Heat exchange, in which the liquefied gas is evaporated again, initially the carrier liquid of the refrigerant cooled and then the vaporous substance is introduced into the carrier liquid and thereby into the liquid or solid phase, so that an emulsion or suspension is formed. The temperature the carrier liquid of the refrigerant is generally so low during the introduction of the vaporous substance, that the steam immediately condenses or solidifies. The vapor can e.g. narrow orifices and injected under pressure. If necessary, the steam can also beforehand through heat exchange be cooled with the evaporating natural gas or methane.

Numerous liquids can be used as carrier liquid for the coolant, for example isopentane. One can also choose a liquid which contains an agent for lowering the freezing point. The eutectic mixtures of 88 % isopentane and 12% n-pentane or of 5% isopentane and 15% isohexane are suitable because of their low melting points.

When the gas is liquefied, e.g. natural gas or methane, the temperature of the coolant rises

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e.g. to room temperature. If necessary, the heated coolant can be used immediately, e.g. in a chemical plant will. However, the components of the secondary refrigerant can also be fed into one or more tanks and thus to the To be transported to the place of use.

The cooled coolant can be taken from the place of use be transported to the place of production in the same tank in which the liquefied gas is transported from the place of production to the Place of use was transported. This has the advantage that the tank always remains cold. As a result of the high specific Heat of the refrigerant according to the invention is the tank that is used to transport the liquid gas became more than large enough to transport the secondary refrigerant in the opposite direction.

The method according to the invention is suitable for the transport or for peak compensation for natural gas, methane, xthane, propane, butane or other gases

When the coolant, which consists of the carrier liquid with the substance, is cooled, the sub « be evenly dispersed in the carrier liquid. When the coolant is produced long before it cools down and contains a liquid substance, the addition of a is to stabilize the dispersion Emulsifier necessary. This addition of an emulsifier can

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but be accompanied by the disadvantage that the viscosity of the coolant, especially at low temperatures, increases.

If the substance has a high vapor pressure or is in the gas phase, a "carrier liquid, which contains a sufficient amount of the dispersed substance, only under increased pressure and / or thoroughly Stirring form.

It is therefore proposed that the substance be dispersed in the carrier liquid at a specific moment and to produce them in a certain way, e.g. by exchanging the carrier liquid with the liquefied Gas is cooled and the substance is added to the cooled carrier liquid. In this way it is ensured that only a relatively short period of time between the formation of the dispersion and the phase change of the dispersed substance pass. As a result, too the risk that the dispersed liquid substance particles combine with one another is small, and consequently only a small amount of emulsifier is required, which affects the viscosity of the coolant has no adverse effect.

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If the substance is a liquid with a high vapor pressure, this vapor pressure is markedly lowered, when the liquid substance is brought into contact with the cooled carrier liquid, so that possible Disturbances caused by steam formation are reduced.

In a suitable embodiment of the last-mentioned method, the substance becomes the carrier liquid added at the moment in which the carrier liquid was cooled to a temperature equal to or is lower than the temperature at which the substance under the given conditions in the liquid State passes. If the substance is in vapor form, it will condense more easily when it has cooled down with the Carrier liquid is brought into contact.

In another suitable embodiment, the substance is added to the carrier liquid at the moment when the carrier liquid has reached a temperature has been cooled that is equal to or lower than the temperature at which the substance is below the given Conditions goes into the solid state. As a result, the particles formed are hardly in liquid Phase exist, so that even if a corrosive substance is used, the refrigerant formed does not Has corrosive properties. Consequently

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For example, the apparatus for heat exchange can be made of a material that meets low requirements in terms of chemical resistance. In this In this case, the use of emulsifiers is not necessary.

If necessary, the substance can be pre-cooled, before adding it to the cooled carrier liquid will. In this way, vapors can first be condensed or compressed and then the cooled carrier liquid can be added.

During the heating of the cold coolant in heat exchange with the gas to be liquefied, e.g. Natural gas or methane, the substance dispersed in the carrier liquid can be separated from the carrier liquid as soon as the substance is no longer in a solid state. That way, the substance can and the carrier liquid is stored in separate tanks and transported to the point of use. This is then of distributing if -the substance is corrosive, but the carrier liquid is not corrosive, because in this Only trap the tank in which the substance is stored or transported from chemically resistant material must be built while the tank for the carrier liquid can consist of a material with low resistance to chemicals.

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The requirements with regard to the boiling point of the substance in the carrier liquid of the refrigerant restricts the choice of this substance. Precautions must also be taken with corrosive substances because the dispersed particles of the substance come into contact with the tank walls, pipes and heat exchangers come.

As a result, in a suitable embodiment of the refrigerant according to the invention, at least some of the substance particles that undergo phase change during heat exchange in containers locked in.

When heat is exchanged between the refrigerant and the gas, a heat flow is created within the refrigerant between the carrier liquid and the substance particles · This heat flow also penetrates the walls that make up the Enclose substance particles. The substance particles undergo a phase change. The specific The heat of the coolant increases significantly due to the latent heat that is absorbed or developed in the process. During the Phase changes, the temperature of the carrier liquid does not change or changes only to a small extent, which in terms of rapid heat transfer is advantageous.

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Since the substance particles that absorb or release the latent heat are enclosed, the Do not allow substance to come into contact with tank walls, heat exchangers or other equipment. Even the evaporated substance remains enclosed, so that no substance losses occur through evaporation. This results in a high degree of independence both from the boiling point and from any corrosive properties of the substance of the particles. The degree of this independence can be controlled by the choice of mechanical properties and chemical properties Resistance of the material for the containers.

The speed of heat exchange between the gas to be liquefied or vaporized, and the coolant is partly determined by the speed of the heat exchange that takes place through the walls of the Container takes place. The size and shape of the containers can be adapted to the requirements in this regard will. Numerous embodiments are of course possible. For example, a large number of hollow objects must be stacked in such a way that good contact with the purapfärtgen carrier liquid is possible.

It can be advantageous to use not just one but two or more different substances,

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e.g. a mixture of water and ammonia on the one hand and toluene on the other hand, each from Yerschledener Absorb or dissipate latent heat temperature, so that the heat exchange with the gas at various constant or practically constant temperatures can be made. The different substances can be put together in be enclosed in one or more containers · However, one or more of these substances can also be included or their combinations can be included individually so that they are from each other and from the carrier liquid are separated. This can be of value, for example, when the substances physically or chemically interact with one another react.

Finally, at least two tanks can be used for the coolant, each of which is additional one of the substances mentioned for the carrier liquid contains. The contents of these tanks can then be separated from the heat exchange with the gas that is liquefied or is to be evaporated again, e.g. subjected to different temperatures. ,

The containers in which the substances are enclosed 1st (are) can be made from a highly conductive netall, e.g. aluminum. This causes a quick Heat transfer. The containers can also be made of plastic

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copy

e.g. made of high pressure polyethylene. This «material has the advantage that it is very chemically resistant.

The containers can also consist of two or more materials, e.g. of a large number of layers made of different materials, of a coated one. material or from a material that contains reinforcing elements of another material. This can then be important if the required density, strength and chemical resistance cannot be achieved with one material alone can be achieved, or only with the formation of wall thicknesses that are too strong for the desired heat exchange are. For example, a plastic can be used to obtain a tight wall with high chemical resistance while maintaining mechanical strength with Using a layer of sheet metal is increased. Often all that is sufficient for stiffening is a grid or a hound,

The substance may contain "a" in capsules Capsules allow a favorable ratio between them Thickness and strength of the wall. They can be evenly distributed in the tank space, they can also be tightly packed in tanks that are irregularly shaped or contain stiffening elements on the inside be suspended in the carrier liquid and introduced into the tank in suspended form

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COPY

During the heat exchange between the coolant

and the gas, the carrier liquid between the

included
Gas and the / substance particles circulate ^ and alternately enter into heat exchange with them. In this case, the carrier liquid can come into contact with the gas at different temperatures and, if more than one tank is used, it can also enter into heat exchange with the substance particles at different temperatures.

If the substance particles are enclosed in capsules, the capsules can during the heat exchange be suspended between the refrigerant and the gas in the carrier liquid. In this case, the cooled Coolant also from the place of use to the place of production in be transported in a tank in which the liquefied gas was previously transported to the place of use. this has the advantage that the tank always remains cold.

PATENT APPLICATIONS

CiRlGINAL INSPECTED

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Claims (28)

Claims Process for transporting gas, preferably methane or natural gas, by cooling and liquefying of the gas, transport in liquid state in a tank, transfer of the liquid gas at the place of use into the gaseous state through heat exchange with a coolant, introducing the cooled Coolant in the tank, transferring the filled tank to the place where the gas is generated, where it is cooled again and liquefaction of the gas takes place by heat exchange with a refrigerant, characterized in that that a coolant is used, which consists of a carrier liquid whose boiling point is above, at or is slightly below room temperature and contains a substance in undissolved form, which during the Heat exchange undergoes one or more phase changes. 2. The method according to claim 1, characterized in that a substance is used which partially or completely melts or solidifies during the heat exchange and has a boiling point above, at or slightly below room temperature. 909848/0899 3. The method according to claim 1 and 2, characterized in that the substance Water used. 4. The method according to claim 3, characterized in that the water is a means for Freezing point depression, preferably ammonia, contains at least one alcohol or at least one glycol. 5 · Method according to claim 1 - k , characterized characterized in that the substance is dispersed in the carrier liquid, preferably in the form of a stable emulsion, and its droplets remain suspended during solidification by cooling. 6. The method according to claim 1-5 »characterized in that there is a refrigerant used, which additionally contains plague bodies to which the substance is absorbed or adsorbed, preferably silica gel. 7. The method according to claim 6, characterized in that there is a refrigerant used in the form of a stable suspension. - 3 909848/0899 8. The method according to claim 1, characterized in that g e k e η η, that one uses a substance which is a substance for lowering the temperature of the phase transition contains. 9. The method according to claim 1 and 8, characterized
characterized that one has carbon dioxide
used, 10. The method according to claim 1 and 8, characterized
characterized in that ammonia is used. 11. The method according to claim 9 _t, characterized in that the vaporous carbon dioxide is released into the atmosphere. 12. The method according to claim 9 »characterized in that the gaseous carbon dioxide binds in such a way that it can easily be set free again. 13. The method according to claim 14, characterized in that the bound carbon dioxide is used stored and / or transported to the place of use. 909848/0899 14. The method according to claim lo, characterized in that the ammonia in the vapor state in binds in such a way that it can easily be set free again, preferably dissolving in water. 15. The method according to claim 1Λ, characterized in that the bound ammonia stored or transported to the place of use. 16. The method according to any one of claims 1, 8-15, characterized in that the carrier liquid of the refrigerant is first cooled by heat exchange with the liquefied gas and then the Introduces substance in vapor form into the carrier liquid. 17. Process according to Claims 1 - 16, characterized in that isopentane is used as the carrier liquid, preferably a mixture of 88 % isopentane and 12% of n-pentane or a mixture of isopentane and 15% isohexane. 18. The method according to claim 1-17, characterized in that one uses a refrigerant whose Trägerfltissigkeit includes means for freezing points degradation. 909848/0899 BATHROOM ORIGINAL - 5 - "^" 15017A9 19. The method according to claim 1-18, characterized in that the cooled Coolant in the same tank from the place of use to the Place of production transported, inÄem the liquefied Gas transported from the place of production to the place of use became. 20. The method according to claim 1-19, characterized characterized in that the carrier liquid is initially liquefied by heat exchange with the Gas cools and then adds the substance. 21. The method according to claim 2o, characterized in that the substance at the moment the carrier liquid clogs, irj & em this carrier liquid has been cooled to a temperature which is equal to or lower than the temperature, in which the substance changes to the liquid state under the given conditions. 22. The method according to claim 2o, characterized in that the substance is added to the carrier liquid at the moment in which the carrier liquid has been cooled to a temperature which is equal to or lower than the temperature at which the substance under the given conditions in the solid state passes. 909848/0899 23. The method according to claim 2o - 22, characterized in that the substance is pre-cooled. 24. The method according to claim 1-23, characterized characterized in that the substance dispersed in the carrier liquid is removed from the carrier liquid separates as soon as it is no longer in a solid state. 25. The method according to claim 1-24, characterized characterized in that the substance is enclosed in containers, preferably in the form of capsules. 26. The method according to claim 25, characterized in that metal containers, preferably made of aluminum. 27. The method according to claim 25, characterized in that plastic containers, preferably made of high pressure polyethylene. 28. The method according to claim 25-27, characterized in that the carrier liquid circulated during the heat exchange between the gas and the enclosed substance. 909848/0899