METHOD AND PLANT FOR CONVERTING GAS INTO HYDRATE

Abstract: A method for converting a hydrate-forming gas (2) into a hydrate (5), as the gas (2) combines with a hydrate-forming liquid (3) which is supplied to the gas (2) in finely dispersed shape at hydrate generating pressure and temperature conditions. A subsequent storing and/or transportation of said gas (2) in the shape of gaseous hydrate (5) may also be included. The converting process takes place in at least one chamber (1), as the following process steps are undertaken. Said gas (2) is supplied to the chamber (1) at a hydrate-forming pressure, preferably equal to the working pressure of said gas and at a random temperature, preferably equal to the working temperature of said gas. A temperature controlling medium (11), preferably having a high heat capacity, is guided into the gas-filled portion of said chamber (1) at a temperature below the hydrate generating temperature of said gas (2), and the temperature controlling medium (11) is guided out of the chamber (1), after having passed through the chamber (1) in direct contact with said gas (2) and said hydrate-forming, finely dispersed liquid (3), the medium hereby bringing out at least a substantial part of the latent heat liberated during the generation of said hydrate (5).

Description: METHOD AND PLANT FOR CONVERTING GAS INTO HYDRATE, The present invention relates to a method for storing gas by generating hydrate. The invention also relates to a method for subsequent extraction of gas from the generated hydrate. Further the invention relates to a plant for storing and for extracting of gas. The hydrate is generated in at least one chamber; as hydrate-forming gas is brought together with a finely distributed hydrate-generating liquid in the chamber at such temperature and pressure conditions that the hydrate will be formed. Later on an extraction of gas from said hydrate may be obtained by heating the hydrate. Storing of gas is an efficient method both of adapting deliveries to variations in the market and to obtain a more efficient transportation of gas in pipes. Storage also secures against failure in gas supplies and is in this con¬ nection of the greatest importance when stores are located close to the consumers or close to the market. Conventionally gas is stored in underground reservoirs such as emptied oil and gas reservoirs or in subterranean water magazines. Then a prerequisite is that extraordinary geological structures exist at the location where the store is to be placed. Storing of gas in subterranean salt strata has also been attempted, but then the salt deposits have to be present at the site where the gas is to be stored. It has to be mentioned that conventional storing of natural gas substantially has been obtained either by cryo¬ genic cooling treatment to liquefy the gas (LNG=Liquefied Natural Gas) or by heavy compression of the gas (CNG=Com- pressed Natural Gas) . These methods are used both for stor¬ age and transportation, however both represent very expensiv storage methods which involve many risks. The above men¬ tioned conditions have made it possible to arrange high capacity gas storage close to the consumer only in a few special cases. It is also previously known to convert gas, e.g. natura gas, into hydrate by cooling the gas together with water until hydrate(s) is/are formed. Such storage of gas in the shape of hydrate is previously known, in particular for transportation purposes. In this connection reference is made to Norwegian printed application No. 149,976, Norwegian patent application No. 90.0395, US patent No.3,888,434 and PCT application No. NO91/00104 of 8th June 1991. Hydrates can store large amounts of gas. In optimal conditions 1 m 3 of water may absorb approx. 180 3 natural gas, thus representing a considerable storage capacity. However, the storage capacity will vary according to the gas in question. The most important advantages obtained by storing gas i hydrate are the moderate requirements for pressure and tem¬ perature. The requirements for storing hydrate may be obtai ned by relatively simple means and at low costs, as neither the pressure need be extraordinarily high nor the temperatur extremely low. Further comments on this are given below. A this point it is only to be mentioned that even if the princ iple is previously known, it has so far not been used commer cially according to our knowledge. The reason for this is probably that many of the previously proposed solutions were intended to use the principle for transporting gas. And hy¬ drates have proved in practice to be difficult to transport. . The object of the present invention is to provide a method and means for storing gas, especially, but not exclus ively, natural gas, in a place which can be chosen without many limitations as to choice of location, and without large investments for the control of pressure and temperature. A further, important, object of the present invention i to produce a method for generating hydrate where the gas to be included in the hydrate and/or the liquid to be included in the hydrate, is not required to be cooled before the gas and/or the liquid is introduced into the generating chamber. Further objects of the present invention are: to provide a method for temporary storage of gas near the consumer in reasonably priced, roughly hewn chambers in rock without special requirements regarding the surrounding rock, - to provide a method for storing gas by which it is not necessary to have any previous cooling or pressurising of th gas to be stored. to provide a method for storing and subsequent extrac¬ tion of gas by using naturally or artificially available col or hot water sources such as coolig water from gasworks or the like. to provide a means for storing and subsequent extractio of gas where all energy exchange takes place by recirculatin a cooling/heating medium through a heat pump or exchanger which are part of the means. to provide a means for storing and subsequent extractio of gas where special jets are used for introducing the hyd¬ rate-forming liquid into the gas, while other jets, with greater transport capacity are used for a medium for cooling or heating the gas/hydrate during storing/extraction. to provide a stationary means suitable for both produc¬ tion of hydrates, storage of hydrates and extraction of gas from the stored hydrate. to provide a mobile hydrate cannon which can generate hydrates for storage/transport. Yet another intention and speciality of the invention will be disclosed in the detailed description given below of a means which makes use of the present invention. In order to present a clearer understanding of the present invention reference is made to the detailed represe tation of embodiments given below with reference to the accompagnying drawings, where: Fig. 1 illustrates the principles for a means for genera ing/storing/dissociating gas where the gas is fir converted to hydrate, fig. 2 shows a diagram which gives pressure/temperature ratios at the point of convertion from gas/liquid mixture to hydrate, for natural gas and water, an fig. 3 outlines how a series of caverns blasted from rock can be adapted and arranged for constructing a complete means according to the present invention, fig. 4 shows a means for generating hydrates for subse- quent transport or storage, and fig. 5 shows a mobile "hydrate cannon", also according to the present invention. The same reference numbers are used in all the drawings for components with the same function, where this is exped- ient. The main principle will first be explained with refer¬ ence to fig. 1 and fig. 2, as gas 2 is assumed stored, bound to hydrate 5 in a chamber 1. The chamber 1 is a pressure chamber which is constructed to withstand the hydrate storing pressure concerned. For natural gas the storing pressure at the temperatures concerned lie under 80 barg (barg = bar gauge) . The temperature ought to lie between 0°C and the equilibrium curve for hydrate as shown in fig. 2, i.e. below ca. 15°C at the pressure concerned. The pressure should preferably be about 30-50 barg and the temperature about 0- 12°C for natural gas. The pressure/temperature region con¬ cerned is hatched in fig. 2 and does not make great demands on the chamber, with regard to either pressure or tempera¬ ture. When the store is constructed in rock, the storage temperatur will be equal to the natural temperature of the rock. This means that in the Nordic countries there will be no special requirement for heat insulation or for cooling the store while the hydrate is in storage. Only if the store is located in warmer climates might cooling be necessary. Cooling is therefor normally limited to the period when gas is being filled into the store. Correspondingly, there will be a need for supplying heat during the removal of gas from the store. This will be described in more detail below. It is, however, also important that the temperature in the stor does not sink below the freezing point for water, as this could lead to blockage of intake and discharge pipes. Storage in chambers blasted from rock can also be advan tageous as rock caves are capable of maintaining the neces- sary hydrostatic pressure under the conversion of gas to hydrate without any extra investments for equipment. The process for forming hydrates will now be looked at. Forming of hydrates occurs when the chamber 1 is filled with gas 2 through a pipe 10 which is lead in at the top of the chamber. The chamber 1 communicates directly with the gas which participates in the actual process. Neither pumps nor valves are required to bring the gas into or out of the chamber 1. This can be controlled exclusively by the level of pressure in the chamber 1. The same pipe 10 is used during subsequent discharge of gas from the chamber. Concerning the level of pressure with natural gas the following is noted: During the forming of hydrate it can be advatageous to have a gas pressure between about 30 and 50 barg. In the pipe there is usually a gas pressure of betwee 50 and 80 barg. And in fewer cases the gas pressure in the pipe can be as low as 16 barg or as high as 180 barg. It ca therefore be necessary to adjust the gas pressure somewhat, both when lead from pipe to store and after discharge from store and subsequent return to pipe. It is, however, here only a question of very simple adjustments, e.g. with a throttle control. Correspondingly it can be expedient to undertake a drying of the gas during return to the pipe after discharge from the store. Said drying is however usual after all form of underground storage and will not be gone into any further here. Besides a cold hydrate-forming liquid 3 with a tempera¬ ture of ca. 2° C is introduced into the chamber 1, and is spread and finely dispersed with the help of jets 4 which ar specially constructed to give finely dispersed drops of water. Special jets might be used for this purpose, e.g. jets with mechanically vibrating elements, most likely with vibrations in the ultra sound region, in order to achieve small, mist-like drops which fall slowly down through the ga 2 in the chamber 1 when they are formed. In this manner a very large contact surface between gas and the hydrate-for¬ ming liquid is obtained, at the same time as the large cont¬ act surface is maintained over a relatively long time span because the small, finely dispersed drops have a low falling speed through the gas, and the chamber is high. In addition to the jets 4 there are other jets 6 which introduce a temperature regulating medium 11. This medium 1 may be water and can if desired be introduced through the same pipe system as the hydrate-forming liquid 3 which also may be water. Concerning the hydrate-forming liquid, this can if desired be supplied with certain additives, such as, for example, surfactants and crystallization nuclei particles. Such additives are intended to affect the size of the drops and the rate of crystallization and are therefore primarily of interest as additives to the hydrate-forming liquid. The jets 6 which are specially equipped to attain a temperature regulation of the gas 2, have, however, a much greater transport capacity for liquid than the jets 4 and do not provide such a fine dispersement of the flow of liquid. It must be noted that the supply pipes for the tempera¬ ture regulating medium 11 to jets 6 and supply pipes for the hydrate-forming liquid 3 to the jets 4 can be completely separate and that the liquids can even be different. This i not however a requirement, since in a simple and preferred embodiment a common pipe system and the same liquid are used through both jets. The latter embodiment is preferred preci sely because of its simplicity both with regard to construc¬ tion and running. Therefore both liquids are most often referred to as water. A feature of the invention is that the cold water 3, 11 is sprayed right into the gas 2 which is taken directly and completely untreated from a supply system or a process sys¬ tem. The hydrate 5 resembles snow or ice and is formed in the chamber 1 when cold water 3 comes in contact with cold gas 2. The hydrate's specific gravity is a little lower tha that of water, and unused water collects at the bottom of th chamber 1. By forming hydrates according to the invention all cooling is limited to the cooling of the liquid 11 out¬ side the chamber 1, as absolutely all cooling of the gas 2 takes place by heat exchange between gas and cooled liquid inside the chamber 1. At the bottom of the chamber 1 is a collection well 7 for superfluous liquid which is not included in the produc¬ tion of hydrate 5, and this extra liquid 11 can be made to circulate through a heat exchanger 8 which is placed outside the chamber, and from there the liquid, again cooled to abou 2°C, is sent back through a recirculation loop to the jets 4 and/or 6. When hydrate 5 is formed, the pressure of gas 2 falls i the chamber 1 and because the pressure in the supply system 10 is maintained, more gas is added as the hydrate is formed As long as all the latent heat (about 80 cal/g liquid) is removed, the process will continue until the store is full, i.e. when there is gas over the hydrate 5. And the released latent heat will continually be removed as long as the sperfluous water 11 is circulated through the heat ex¬ changer 8 supplied with cooling water 9 from an external source. All the necessary transport of energy takes place by circulation of cold water through the chamber 1. The amount of cooling water 11 necessary is about ten times the amount of water 3 which in the same time span is required to be supplied through the jets 4 for forming hydrate. It is therefore essential that that there are separate cooling water jets 6 which can supply larger amount of water than th hydrate-forming jets 4. All the water which is supplied and does not take part in the forming of hydrate, will gradually be collected at the bottom of the chamber l by drain pipe 7 and be circulated through the heat exchanger 8 for renewed cooling. As external cooling medium 9 a natural source of cold water is preferrable or the heat exchanger can be con¬ nected to a refrigeration machine. The shape of the store is important, since great height as mentioned in fig. 1, increases the time of contact betwee the cooled water and gas, and thereby increases the formatio of hydrate. Conditions occurring when the chamber 1 is full of hydrate 5 in storage will now be observed. When hydrate 5 i formed, it will simply remain in the same place where it is formed until it is desired to be melted during the dissocia- tion. This is an important feature of the present invention because moving or transporting hydrates is associated with great difficulties. As storage time passes the hydrate will pack to a more compact mass under the influence of gravity, and then there will be room for the formation and storage of some more hydrate in the same chamber. The storage condition, i.e. hydrate form, is maintained and kept stable as long as the surrounding temperatures lie between 0°C and about 15°C and the pressure is as given in the curve in fig. 2. It is only necessary to maintian the pressure in relation to the equilibrium diagram for the stored gases concerned. Such an equilibrium diagram for natural gas is shown in fig. 2 and as can be seen the tem¬ peratures in question will mean the storage pressure can be kept under ca. 80 barg. Storage of gas does not therefore require other energy supplies than that which is required to maintain the desired and relatively low over-pressure, and perhaps the desired temperature if this is not the same as the surrounding tem- perature. In this connection it can be mentioned that a so-calle water curtain 12 can be used round storage chamber 1, to maintain the desired pressure conditions. The effect of suc a, per se, known water curtain 12, is to increase the ground water pressure and thereby the prevailing pressure in the rock chamber 1, beyond the natural ground water pressure. Finally the conditions during extraction of gas from th hydrate 5 will be considered. Discharge of gas from the chamber takes place when heat is applied to the hydrate 5 so that it melts. The process will naturally go more quickly under a somewhat reduced pressure combined with a heat supply. Thereby the gas is released automatically and is pressed out through the pipe 10, i.e. through the same pipe through which the gas was supplied when the storage process took place. Pumps and similar equipment for controlling the gas supply or the gas discharge are therefore not necessary since the pressure conditions in the chamber control these conditions. If the pressure in the external pipe nettwork i higher than the discharge pressure, however, this will re- quire a compression stage. Otherwise the only grounds for including pumps or valves in the supply pipe 10 are, there¬ fore, safety conditions, and maintenance and repaires to the plant. The necessary supply of heat is brought about by the supply of hot water. This is done most easily by using exactly the same circulation nettwork 7, 8, 6, which was use for cooling. Here, a special heat exchanger can be used, o the same heat exchanger 8 which was used for cooling. The only difference being that one must now add hot water 13 fro an external heat exchanger circuit. The amount of released gas and the rate at which the gas is released is decided and controlled by the amount of heat added. It is again remarke that all control of the energy exchange takes place only in the heat exchange system which lies outside the storage chamber 1. The amount of heat which has to be added in order to release gas corresponds to the amount of heat which was removed during the storing procedure. For natural gas this represents ca. 4% of the energy content in the gas. The energy for heating can preferrably be taken from external, natural heat reservoirs, or the plant can be planned so that the store is located near a power station which in any case discharges cooling water, such as a gasworks or the like. In order to increase the discharge speed it can be expedient to adjust the pressure in the store to a lower level, in some cases right down to atmospheric pressure. The means according to the present invention is special in that it is simple and requires very few control and steer ing systems. It is remarked that the gas which is to be stored is introduced into the storage rooms untreated and at the prevailing temperature conditions. A reduction in pres¬ sure can, however, be relevant if the pressure in the pipes is especially high. In this way large and expensive plants with necessary steering and control routines for cooling the gas to a suitable temperature are avoided. According to the present invention all cooling takes place inside the storage chamber 1 itself, and only by water 3 and 11 being circulate through the chamber and pervading the gass/hydrate. This gives an extremely simple and easily controlled transport of energy in the plant. Further, no, or very few, control or steering functions are necessary at the gass supply/gas discharge 10. This connection can quite simply be an open gas pipe which leads directly into the process or transport system concerned. An the chamber 1 can be blasted directly from the rock in the vicinity of the place of use. Special mention is made of th fact that crystalline rock with a suitable structure is roun in the vicinity of the user both in Norway and other coun¬ tries such as Switzerland, Spain, Sweden, Finland, and Aust¬ ria for example. In all these countries one would be quite free, with the help of the present invention, with regard to where a store could be located, and one could then place suc stores near the place of consumption, which would ensure a regular supply even under large and sudden changes in demand. In this connection it can be mentioned that several similar rock chambers can be placed near to each other as shown in fig. 3. And the running of such a plant can then vary depending on the differences in demand. If the differ¬ ences in demand are not too great, one chamber at a time can be completely filled with hydrates during the storage period and, in the same way, one chamber at a time can be taken int use when there is need for an extra supply of gas to the consumers. This can be described as all the chambers being connected in series. If the differences in consumption are very great, gas can however be discharged from two or more storage chambers at the same time, i.e. in parallel. By varying in this way between series and parallel running of several chambers which are part of the plant, extremely grea disparities in the level of consumption can be satisfied. When consumption sinks the chambers can again be filled with hydrates, while the supply of gas is greater than demand. As an example of the size of such a plant it can be sai that each chamber can have a length of 400-1000 i, a width o 15-20 m and a height of 40-60 m. Up to 20 such chambers can be included in one and the same plant. The present invention is relevant both to a method for performing such production of hydrate as well as storing and discharge of gas, and a plant where this can be undertaken. Fig. 4 shows an embodiment of the present invention where the hydrate 5 which is produced in the hydration cham¬ ber 1 does not necessarily remain in the chamber until the gas is to be used again, but where the hydrate 5 in the form of a loose, somewhat watery mass is taken out through an opening 14 near the bottom of the chamber 1. As represented in the figur the hydrate 5 can with advantage be driven out with the help of a transport screw 15 which is placed ob¬ liquely out through opening 14. When this transport screw 1 is in operation much of the water in the hydrate 5 runs back into the chamber 1, e.g. via the water discharge pipe 16 at the bottom of the transport screw 15, while the solids of th hydrate are driven out through the opening 14 of transport screw 15 to a suitable external store or a suitable transpor vehicle (not shown) . Otherwise the same reference numbers are used in fig. 4 as in the already shown fig. 1, except that there is shown; a pressure regulator 18 at the gas intake 10 for ensuring that the gas 2 in the chamber 1 is maintained at a hydrate-forming pressure P even if the gas's process pressure out in the plant should differ somewhat fro this; as well as a pump 19 for circulating the temperature regulating medium 11. In fig. 5 it is further shown how the generating chambe can be constructed as a mobile or even a portable hydrate cannon 20. The same reference numbers are used as earlier, and it will be understood that the hydrate 5 is produced continuously here inside the hydrate cannon 20 and is spraye continuously out of the same together with the superfluous cooling liquid 11 which enters via the jet 6. In this case hydrate 5 will not build up in the generating chamber 1, as hydrate 5 will immediately be carried out with the cooling medium 11 into a receiving system not shown which for exampl can filter the hydrate from the used cooling water 11 by means known per se. It must be underlined that the hydrate cannon 20 does not necessarily have to be held vertically, but can take any position desired. In fig. 5 the hydrate cannon is shown equipped with a tapered mouth 23. This is primarily in order to ensure that the pressure inside the hydrate cannon 20 will be sufficien¬ tly high for the hydrate to be formed, even if the pressure of the surroundings is lower than the desired hydrate-formin pressure P. In the figur a discharge apparatus is also shown, e.g. in the form of a passive or driven transport screw 25 at the opening. This, if required, is to ensure that hydrate 5 will not clog together at the discharge pipe 23 and make a barrier which cannot be bypassed. When such a "hydrate cannon" is used, the temperature regulating medium 11 only functions as a cooling medium. It is noted that the tapering 23 will not be necessary if the hydrate cannon 20 is used in a surrounding chamber 24 with regulated pressure. In this connection it can be mentioned that many detail of the plant can be important for its effective utilization. In just such a way, as large a number of the jets which handle the hydrate-forming liquid can with advantage be located near the roof of the chamber so that the whole cha¬ mber is continuously filled with finely dispersed liquid under the whole hydrate generating process. At the same tim the temperature regulating jets 6 give off so much cooled liquid that new, hot gas, which comes into the chamber, is quickly brought down to its hydrate-forming temperature at the prevailing pressure. It is remarked that a liquid such as water, has a very high coefficient of thermal surface conductance and therfore ensures a faster cooling of heated gas than what one could obtain with other and more compli¬ cated cooling principles. Rapid cooling is also obtained because of direct contakt between the cold water and the hot gas, and at the same time the spray effect of the cold water causes strong movement in the gas which both expedites the cooling and hydrate generation in a simple and very effectiv manner. It can be advantageous to allow the temperaure regulat¬ ing liquid 11 to be water with different additives, e.g. to adjust freezing point and/or crystallization capacity. Seawater can also be used. In a particular embodiment one can even use another liquid than water as the cooling medium, since the medium only circulates within the system without being used up. In the same way a suitable, freely chosen liquid can be used as the heating medium during the heating process. However, it is preferred that both the hydrate-forming liquid and the temperature regulating medium are the same liquid and flow through a common pipe system. However, it should be noted that even if the same pipe system is used the liquid and the medium do not have to be the same and neither do they have t be introduced from the same sources. It is also preferrable that the jets for adding hydrate-forming liquid 3 and temper ature regulating medium 11 are different and have a differen construction even if the media are the same. The plant must, of course, be supplied with the neces- sary pumps and valves for the system to operate satisfactor¬ ily, but these components are not described in detail or shown on the figures, since the location of such auxiliary equipment and the requirements made to it, must be calculate by experts in the field, depending on which liquids and gase are used and on the details of construction otherwise stipul ated for the chamber and its surroundings. It must be pointed out that the features which are mentioned above can all be used separately or be combined in a number of ways without coming outside the framework of the present invention. Thus the most important principle of the invention is that all cooling, or at least the greater part of the necess ary cooling, of the gas which is to be included in the hyd¬ rate is undertaken by direct cooling as the volume of gas is sprayed through with forceful jets of water which has a temperature lower than the temperature at which the hydrate is formed. This principle involves a series of important advantage such as rapid, effective, and inexpensive cooling, water is available as a possible transport medium for the hydrate produced, which can easily be collected by a filter as the cooling water flows through, and above all a simple method for extracting from the generating chamber all latent heat produced as the water and gas is changed to hydrate, is obtained. This last mentioned feature is very important, as in previous plants there have been stoppages in hydrate production after a short time precisely because the latent heat released has not been removed quickly enough. This cooling principle and heat transport principle will be just as useful for a chamber which is used exculusively for generating hydrate, but which is not intended to be used as a store for the ready made hydrate. With respect to the above it is pointed out, therefore, that the main principle according to the present invention can be used both in connection with purely producing hydrate in a generating chamber and, as a principle for temporary storage of gas as the hydrate is kept stationary in the chamber where it is formed and not removed from this chamber at all in the form of hydrate, but is again changed to gas, primarily as a consequence of heating. When this is said it will also be understood that a number of different solutions are available and the most important of these are outlined briefly below. For example the hydrate can be produced directly in large tanks which either are an integral part of, or placed in large transport vehicles such as ships or trucks. It is thereby possible to transport the hydrate in light tanks which do not need to withstand higher pressure than from a few bar up to 10 bar, even if, as in the case of several gases, it must be produced at relatively high pressure such as up to 50 bar g. This has, as already mentioned, great positive effects on expense as well as security during the transport phase. As a special solution one can also visualize that the generating chamber itself can be a small hydrate cannon wher the shape of the generating chamber together with the amount of gas and cooling liquid which passes through it gives a sufficiently increased pressure inside the cannon so that hydrate can be produced from all relevant gases, while the hydrate which is blown or washed out of the cannon can easily be separated from the cooling water and stored at low pres¬ sure. Of course, one can also visualize such a hydrate cannon operating inside a larger chamber which can be tightly closed and therefore maintain the necessary pressure for hydrate formation. In this case the hydrate cannon can simply be comprised of a cylindrical, cartridge-shaped hyd¬ rate cannon which is quite open without any narrowing of its open end, and with the necessary connections for gas, hyd¬ rate-forming liquid and cooling agent at its closed end. As an example it can be mentioned that when water is used both as hydrate-forming liquid and as cooling agent, about 10 times as much water is required for cooling as is required for hydrate-forming. As will be understood from the above the invention includes all four following methods of production: 1. The hydrate is generated in a chamber and remains there until the gas is needed again and is dissociated by heating the hydrate. 2. The hydrate is formed in the generating chamber and re¬ mains stationary in this chamber which, however, can be mobile. This means that the already generated hydrate can remain in the chamber which is transported to the place of consumption where the gas is released from the hydrate while the hydrate is still in the chamber where it was produced. 3. The gas is produced in a relatively small hydrate canno and is sprayed straight over into large storage tanks which can for example be perforated so that cooling water runs through. Then the hydrate can be transporte to the desired place in these transport tanks. 4. The hydrate can be produced in a chamber which operates exclusively as a generating chamber and be moved echan ically from the generating chamber to the desired trans port system for passage to the place of consumption.

Claims: C l a i m s 1. A method for convertion of a hydrate-forming gas (2) into hydrate (5) by exposing the gas (2) to a hydrate-formin liquid (3) which is added to the gas (2) in a finely dis- persed form at hydrate generating pressure and temperature conditions, possibly followed by storing and/or transporta¬ tion of the gas (2) as a gaseous hydrate (5) , said conver¬ tion taking place in at least one chamber (1) , c h a r a c t e r i z e d in that during the converting of the gas (2) into a hydrate (5) the following process steps are executed: the gas (2) is supplied to the chamber (1) at a hydrate generating pressure, preferably equal to the existing workin pressure of the gas and at a random temperature, preferably equal to the existing working temperature of the gas, a temperature regulating medium, preferably having a high heat capacity, is supplied into the gas-filled portion of said chamber (1) at a temperature below the hydrate-form¬ ing temperature of said gas (2) , and that - the temperature regulating medium; after being transpor ted through the chamber (1) in direct contact with the gas (2) and the hydrate-forming, finely dispersed liquid (3) ; is transported out of the chamber (1) taking with it at least a substantial part of the latent heat which is released durin the formation of the hydrate (5) ; during a possible storage of the generated hydrate the following process steps may al be executed: a cooling of the generated hydrate (5) as a controlled amount of the cooled temperature regulating medium, at a controlled temperature lower than the hydrate-forming tempe ature, is continued to be transported into the chamber (1) after the generation of said hydrate; and that during a possible reconvertion of gas (2) from the generated hydrate; - the temperature controlling medium (11) is supplied to the chamber (1) at a temperature above the hydrate-forming temperature. 2. Method according to claim 1, c h a r a c t e r i z e d in that the generated hydrate (5) is stored in the chamber (1) until the gas (2) is desired to be used, as the gas (2) is then dissociated at the desired speed from the hydrate (5) by introducing the temperature regulating medium (11) into the chamber (1) at a temperature which is greater than the hydrate-forming temperature (Th) and that the amount and/or the temperature of the medium (11) is regulated in accordance with the speed and the pressure with which it is desired the gas is to be released. 3. Method according to one of claims l or 2, c h a r a c t e r i z e d in that the temperature regulating medium (11) is introduced into the generating chamber (1) in the form of jet streams with a compact pattern of diverging, converging, crossing and/or parallel jet streams, and where preferrably at least some of the jet streams change direction and/or strength as a function of time. 4. Method according to one of claims 1 - 3, c h a r a c t e r i z e d in that the temperaure regulating medium (11) is introduced at such a high jet stream speed that the gas (2) is set into strong agitation inside the generating chamber (1) . 5. Method according to one of the claims 1 - 4, c h a r a c t e r i z e d in that the temperature regulating medium (11) as it is discharged from the generating chamber (1) is recirculated and underway is again regulated for temperature. 6. Method according to one of the claims 1 - 5, c h a r a c t e r i z e d in that the generated hydrate (5) is extracted continually or in batches from the generating chamber (1) and is transported to another place of use or storage. 7. Method according to one of claims 1 - 6, c h a r a c t e r i z e d in that the pressure (P) at which the gas (2) is supplied is in the region of 5-100 barg and preferrably in the region 10-50 barg. 8. Method for converting and subsequent storage of gas, according to one of the above claims, where storage is carr¬ ied out as the gas is converted so that it becomes part of a hydrate (5) when it is brought together with a hydrate-for¬ ming liquid (3) at temperature/pressure conditions which lea to hydrate forming, c h a r a c t e r i z e d in that the chamber(s) (l) in which the hydrate (5) is formed, is(are) supplied with gas (2), preferrably at the prevailing process temperature, and that - a temperature regulating medium (11) is introduced into the chamber(s) (1) through special jets (6) , in a cooled condition when more gas (2) is desired stored and/or when the hydrate (5) produced is desired coole so that it is retained in the hydrate form; and in a heated condition when extraction of gas (2) is desired from the hydrate (5) . 9. Method according to one of the claims 1 - 8, c h a r a c t e r i z e d in that cooling of gas and heating of hydrate respectively occurs substantially by direct cont¬ act between the gas or hydrate and the temperature regulatin medium (11) which is recirculated through a heat exchaner (8) installed outside the chamber(s) (1) and that preferrably th same heat exchanger (8) is used for cooling or heating the recirculated temperature regulating medium (11) both during the formation of hydrate (5) and during the extraction of ga (2) from the hydrate (5) . 10. Method according to one of the previous claims, c h a r a c t e r i z e d in that the temperature regulating medium and/or an extra, auxiliary medium (9,13) to cool/heat the circulating, temperature regulating medium (11) , is take from an available source of water with a suitable tem¬ perature. 11. Method according to one of the claims l - 10, c h a r a c t e r i z e d in that the temperature regulating medium (11) has the same, or substantially the same, composi¬ tion as the hydrate-forming liquid (3) and that the medium and the liquid are introduced at least in part through the same pipe system. 12. Method according to one of the claims 1 - 11, c h a r a c t e r i z e d in that the temperature regulating medium (11) and/or the hydrat-forming liquid (3) is comprised mainly of water, possibly with some additives. 13. Means for convertion of a hydrate-forming gas (2) to a hydrate (5) , by exposing the gas (2) to a hydrate-forming liquid (3) which is added to the gas (2) in a finely dispers¬ ed form, under hydrate generating pressure and temperature conditions, and with any subsequent storage and/or transport of the gas (2) in the form of a gas hydrate (5) , said conver¬ tion taking place in at least one chamber (1) , c h a r a c t e r i z e d in that the means includes at least one chamber (1) with inlet openings (4) for the hydrate- forming liquid (3) and at least one inlet opening (10) for the gas (2) , and that the means includes besides: at least one set of jets (6) for supply of a temperatur regulating medium (11) , and at least one outlet (7) for superfluous amounts of the temperature regulating medium (11) . 14. Means according to claim 13, c h a r a c t e r i z e d in that it also includes: - a pressure regulator (18) preferably located at the gas's (2) intake opening (10) to regulate the pressure (P) o the gas (2) so that it will remain inside the region of pressure in which hydrate can be formed. 15. Means according to claim 13 or 14, c h a r a c t e r i z e d in that it also includes a recir- culation means (16,17) for the superfluous amount of tempera ture regulating medium (11) , as well as a heat exchanger plant (8) for regulating the temperature of the medium (11) . 16. Means according to one of the claims 13 - 15, c h a r a c t e r i z e d in that the jets (6) for supplying the termperature regulating medium (11) are jet nozzles adapted for providing jet streams at high pressure, each individual stream having a small cross-section. 17. Means according to one of the claims 13 - 16, c h a r a c t e r i z e d in that at least one of the jets (6) for supplyingthe temperature regulating medium (11) is placed near the area where the gas (2) is introduced into th generating chamber (1) and preferrably so that the pattern o jet streams will be most compact in exactly this region. 18. Means accoding to one of claims 13 - 17, c h a r a c t e r i z e d in that it also includes a dis¬ charge opening (14) for generated hydrate (5) . 19. Means according to claim 18, c h a r a c t e r i z e d in that the discharge opening (14) for hydrate is provided with a transport device (15,25) for hydrate. 20. Means according to one of claims 13 - 19, c h a r a c t e r i z e d in that the generating chamber (1) is located on, or is an integral part of, a transport device particularly an ocean-going vessel. 21. Means according to one of the claims 13 - 20, c h a r a c t e r i z e d in that the chamber (1) is a relat ively small, mobile or even portable cylinder (20) which is closed at one of its ends (21) and open at its other end (22), said cylinder (20) is equipped with inlets (4,6,10) fo gas (2) , hydrate-forming liquid (3) and the temperature regulating medium (11) , which in this instance operates exclusively as a cooling medium, at its closed end; and preferrably is equipped with a discharge mouthpiece (23) at its open end. 22. Means according to one of the claims 13 - 21, c h a r a c t e r i z e d in that the gas inlet/gas outlet (10) communicates directly with gas pipes between the place of production and the consumer. 23. Means according to one of the claims 13 - 22, c h a r a c t e r i z e d in that the jets (4) for supply of the hydrate-forming liquid (3) are providedwith a mechanical, high frequency generator, e.g. in the form of an ultra sound source. 24. Means according to one of the claims 13 - 23, c h a r a c t e r i z e d in that the chamber (s) (l) is/are constructed in a geological formation, especially in the form of chamber(s) in rock.

Inventors: SKOVHOLT OTTO, TORP TORE ANDREAS, SKOVHOLT, OTTO, TORP, TORE, ANDREAS
Applicants: NORSKE STATS OLJESELSKAP, SKOVHOLT OTTO, TORP TORE ANDREAS, DEN NORSKE STATS OLJESELSKAP A.S
Application year: 1993
Main classification: F17C11
IPC codes: C10L9, F17C11