Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
  • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
  • F17C11/00—Use of gas-solvents or gas-sorbents in vessels
  • F17C11/007—Use of gas-solvents or gas-sorbents in vessels for hydrocarbon gases, such as methane or natural gas, propane, butane or mixtures thereof [LPG]

Definitions

• the present invention relates to a sorption store for storing gaseous substances, which comprises a closed container, a feed device comprising an inlet in the container wall and an inlet shut-off element and has an outlet having an outlet shut-off element in the container wall.
• the invention further relates to a method of filling a sorption store with a gas where the sorption store comprises a closed vessel which is at least partly filled with an adsorption medium and has an inlet and an outlet which can each be closed by means of a shut-off element.
• Sorption stores are increasingly being used nowadays in addition to pressurized gas tanks.
• Sorption stores generally comprise an adsorption medium having a large internal surface area on which the gas is adsorbed and thereby stored.
• heat is liberated as a result of the adsorption and has to be removed from the store.
• heat has to be supplied for the process of desorption when taking gas from the store. Heat management is therefore of great importance in the design of sorption stores.
• the patent application US 2008/0168776 A1 describes a sorption store for hydrogen which comprises an external container which is thermally insulated from the surroundings and in the interior of which a plurality of pressure containers comprising an adsorption medium are arranged. The intermediate spaces between the pressure containers are filled with a cooling liquid in order to be able to remove the heat evolved during adsorption.
• the patent application WO 2005/044454 A2 describes an apparatus for storing gaseous hydrocarbons, which comprises a container filled with an adsorption medium. An external circuit for the gas to be stored and in which the gas stream is cooled in order to remove heat evolved in the adsorption is provided.
• a disadvantage of known sorption stores is that filling with gas proceeds only slowly. Especially in the case of mobile applications, for example in motor vehicles, this disadvantage is particularly serious. It is an object of the invention to provide a method of storing gaseous substances which allows fast charging of gas and improved taking-off of gas.
• the apparatus should have a simple construction and require little electric energy during operation.
• a further object is to provide a method of quickly and efficiently charging the store and removing gas from the store. This object is achieved by the subject matter of the invention as described in claim 1 . Further advantageous embodiments of the invention may be found in the dependent claims. Further subjects of the invention are indicated in claim 1 1 and the claims dependent on this.
• the method of the invention is carried out using a sorption store which comprises a closed container having an inlet and an outlet which can each be closed by means of a shut-off element.
• the container is at least partly filled with an adsorption medium.
• the method of the invention comprises the following steps:
• Sorption stores as are known from the prior art are, for charging, usually connected to a pressure line from which the gas to be stored flows at constant pressure into the store until a predetermined final pressure in the store has been reached.
• gas is stored both by adsorption on the adsorption medium and also in the voids between and in individual particles of the adsorption medium or in regions of the container which are not filled with adsorption medium.
• the voids are firstly filled with gas.
• the pressure in the store follows, with virtually no lag time, the pressure of the gas flowing into the container. To minimize the total time required for the charging operation, this first step should be carried out as quickly as possible, by the gas being introduced at the pressure which is prescribed as final pressure at the end of the charging operation.
• step (b) part of the gas is adsorbed, resulting in the temperature of the adsorption material and thus also that of the surrounding gas rising. Due to the rapid opening of the outlet shut-off element with the inlet shut-off element continuing to be open in step (c), a gas flow is generated in the vessel and this flows over the adsorption medium and ensures transport of the heat evolved as a result of the adsorption from the container. In addition, the gas flow increases the thermal conductivity of the adsorption medium, which likewise contributes to more rapid removal of the heat.
• the outlet shut-off element is closed.
• the adsorption rate can be derived from the adsorption kinetics; for the purposes of the present invention, the term adsorption kinetics refers to the course of adsorption of the gas on the adsorption medium over time under isothermal and isobaric conditions. Methods of determining the adsorption kinetics are known to those skilled in the art, for example by means of pressure jump experiments or adsorption balances (e.g. in "Zhao, Li and Lin, Industrial & Engineering Chemistry Research, 48(22), 2009, pages 10015-10020").
• the course of the adsorption kinetics can frequently be approximated by an exponentially decaying function which at the beginning displays a sharp rise and then becomes ever flatter as it converges toward a final value.
• An example of such an approximation is the function a-(1 -e "bt ), where a and b are positive constants.
• the adsorption kinetics can also be approximated by other functions, for example a concave function, a function which is constant in sections, a function which is linear in sections or a linear function which joins the initial value and the final value. Approximation functions can be determined for the adsorption rate in this way.
• the gas stream flowing in the container or from the container is measured by means of a flow sensor and the flow rate of the gas in the container is set as a predetermined multiple of the adsorption rate over time.
• the multiple is preferably from 1 .5 to 100, particularly preferably from 3 to 40. At excessively small values of the multiple, there is a risk of the heat not being able to be removed sufficiently. At very high values, an unnecessarily large quantity of energy has to be expended in order to ensure the high flow without an adequate gain in respect of heat removal being able to be achieved.
• the temperature of the gas stream is measured at at least one point in the interior of the container and the flow rate of the gas in the container is if necessary adjusted so that a predetermined maximum temperature is not exceeded.
• the temperature is particularly preferably measured in at least one channel- shaped subchamber.
• the adjustment of the flow rate is preferably carried out by varying the degree of opening of the outlet shut-off element.
• the shut-off elements are particularly preferably configured as regulating valves, in particular the outlet shut-off element.
• the inflowing gas is cooled before being fed in, in particular with a constant temperature.
• the gas exiting from the outlet is recirculated in a circulation circuit to the inlet.
• the gas is advantageously compressed and cooled; appropriate apparatuses such as compressors, pumps and heat exchangers are known to those skilled in the art.
• the adsorption medium preferably comprises zeolite, activated carbon or metal organic frameworks.
• the porosity of the adsorption medium is preferably at least 0.2.
• the porosity is defined as the ratio of void volume to total volume of any subvolume in the container. At a low porosity, the pressure drop on flowing through the adsorption medium increases, which has an adverse effect on the charging time.
• the adsorption medium is present as a bed of pellets and the ratio of permeability of the pellets to the smallest pellet diameter is at least 10 "14 m 2 /m.
• the rate at which the gas penetrates into the pellets during charging depends on the speed at which the pressure in the interior of the pellets approaches the pressure on the outside of the pellets. The time required for this pressure equalization and thus also the loading time of the pellets increases with decreasing permeability and with increasing diameter of the pellets. This can have a limiting effect on the total process of charging and discharging.
• the container has at least two parallel, channel-shaped subchambers which are each at least partly filled with the adsorption medium and whose channel walls are cooled in its interior.
• the at least one separation element or a plurality of separation elements, in particular all separation elements present, preferably have a double wall so that a heat transfer medium can flow through them. Preference is also given to all channel walls of the channel-shaped subchambers being double walls to allow a heat transfer medium to flow through them.
• a section of the interior wall of the container forms a channel wall of a channel-shaped subchamber or a plurality of channel-shaped subchambers.
• the container wall is preferably a double wall.
• the entire container wall including the end faces is configured so as to allow a heat transfer medium to flow through it, in particular configured as a double wall.
• each channel- shaped subchamber it has been found to be advantageous for the spacing of the channel walls in each channel- shaped subchamber to be from 2 cm to 8 cm.
• spacing refers to the shortest distance between two points on opposite walls viewed in cross section perpendicular to the axis of the channel.
• the spacing corresponds to the diameter
• in the case of an annular cross section it corresponds to the width of the annulus
• in the case of a rectangular cross section it corresponds to the shorter of the distances between the parallel sides.
• the range mentioned has been found to be a good compromise between heat transfer and fill volume of the adsorption medium.
• heat transfer between adsorption medium and wall deteriorates, and in the case of smaller spacings the fill volume of the adsorption medium at given external dimensions of the container decreases.
• the weight of the sorption store and its production costs increase, which is disadvantageous, in particular in the case of mobile applications.
• subchambers differ by not more than 40%, particularly preferably by not more than 20%. Such a configuration aids uniform removal of heat during charging and introduction of heat during emptying of the container.
• subchambers are selected so that, during charging of the container with gas, the flow velocities in the channel-shaped subchambers differ by not more than 20% per channel pair. Particular preference is given to the flow velocities in all channel-shaped subchambers differing by not more than 20%.
• the flow effect is of primary importance.
• the minimum flow velocity limits the maximum charging of the container in a given time or limits the duration of charging at a given fill amount of gas.
• the inflowing gas is conveyed through a perforated inflow tube or through a plurality of perforated inflow tubes into the adsorption medium. This results in a more uniform gas flow and a more homogeneous temperature distribution in the adsorption medium.
• the container of the sorption store is preferably cylindrical and the at least one separation element is arranged essentially coaxially to the axis of the cylinder.
• Embodiments in which the longitudinal axis of the at least one separation element is inclined by a few degrees up to a maximum of 10 degrees relative to the axis of the cylinder are considered to be "essentially" coaxial. This configuration ensures that the channel cross sections vary only slightly along the axis of the cylinder, so that uniform flow over the length of the channel can be established.
• various cross-sectional areas for the cylindrical container are possible, for example circular, elliptical or rectangular. Irregularly shaped cross-sectional areas are also possible, e.g. when the container is to be fitted into a hollow space of a vehicle body. Circular and elliptical cross sections are particularly suitable for high pressures above about 100 bar.
• the invention further provides a sorption store for storing gaseous substances, which comprises a closed container, a feed device comprising an inlet in the container wall and an inlet shut-off element and an outlet having an outlet shut-off element in the container wall.
• the container has at least one separation element which is located in its interior and is configured so that the interior of the container is divided into at least two parallel, channel-shaped subchambers which are at least partly filled with an adsorption medium and whose channel walls are coolable.
• the contours of the interior wall of the container and the at least one separation element and optionally the plurality of separation elements is/are essentially conformal.
• conformal means that the contours have the same shape, for example all circular, all elliptical or all rectangular.
• the expression “essentially conformal” means that small deviations from the basic shape are still encompassed by “the same shape”. Examples are round corners in the case of a rectangular basic shape or deviations within manufacturing tolerances.
• Such a configuration allows optimal utilization of the interior space of the container with a view to a very large amount of adsorption medium combined with efficient heating management.
• the above-described preferred structural features such as the double-walled separation elements, spacings of the channel walls and/or the coaxial arrangement of the separation elements in a cylindrical container also represent preferred embodiments of the sorption store of the invention.
• the choice of the wall thickness of the container and of the separation elements depends on the maximum pressure to be expected in the container, the dimensions of the container, in particular its diameter, and the properties of the material used. In the case of an alloy steel container having an external diameter of 10 cm and a maximum pressure of 100 bar, the minimum wall thickness has, for example, been estimated at 2 mm (in accordance with
• the internal spacing of the double walls is selected so that a sufficiently large volume flow of the heat transfer medium can flow through them. It is preferably from 2 mm to 10 mm, particularly preferably from 3 mm to 6 mm.
• the at least one separation element is particularly preferably configured as a tube so that the interior space of the tube forms a first channel-shaped subchamber and the space between the outer wall of the tube and the interior wall of the container or optionally between the outer wall of the tube and a further separation element forms a second, annular subchamber.
• the contour of the tubular separation element viewed in cross section is conformal with the contour of the interior wall of the container; they are, for example, both circular or both elliptical.
• a plurality of separation elements are present and are all configured as tubes having various diameters and are arranged coaxially. Their contours viewed in cross section are likewise conformal with the contour of the interior wall of the container.
• the feed device comprises at least one inlet in the container wall and at least one inlet shut-off element.
• the feed device comprises components which distribute the gas flowing in through the at least one inlet over all subchambers in a directed manner, e.g. a deflection element or a distributor device.
• the feed device comprises a plurality of passages through the container wall through which the inflowing gas is directed to the channel-shaped subchambers.
• the inflowing amount of gas is particularly preferably distributed over the channel-shaped subchambers in such a way that the ratios of the individual amounts of gas to one another correspond to the ratios of the cross-sectional areas of the subchambers.
• the invention further provides a method of taking gas from a sorption store according to the invention, wherein a heat transfer medium whose temperature is greater than the temperature of the gas in the channel-shaped subchambers flows through the channel walls.
• the sorption store of the invention makes faster heat transport from the adsorption medium or into the adsorption medium possible. This significantly decreases the time required for charging of the store with a given amount of gas. As an alternative, the store can be charged with a larger amount of gas in a given time.
• the invention makes rapid and constant provision of gas possible.
• the channel walls are heated, for example in the case of the double-walled configuration using a heat transfer medium whose temperature is greater than the temperature of the gas in the channel- shaped subchambers is passed through the double wall.
• the sorption store of the invention is simple to construct and as a result of its compact construction is particularly suitable for mobile applications, for example in motor vehicles.
• the embodiment with double channel walls has the additional advantage that the heat transfer medium merely has to be changed or its temperature altered appropriately to change from cooling to heating. This embodiment is therefore suitable for mobile use both during filling and in the driving mode.
• Fig. 1 embodiment of a sorption store having a perforated inflow tube for carrying out the method of the invention
• Fig. 2 embodiment of a sorption store according to the invention
• Fig. 3 embodiment of a sorption store according to the invention having two channel-shaped subchambers and a plurality of perforated inflow tubes
• FIG. 4 cross sections of the embodiments of fig. 1 to 3
• FIG. 5 embodiment of a sorption store according to the invention having a circulation circuit Fig. 6 adsorption rate of the simulation example
• Figures 1 to 4 show schematic sections through sorption stores.
• the illustrated sorption stores have an essentially cylindrical container 10.
• Fig. 1 to 3 each depict longitudinal sections through the axis of the cylinder, and
• fig. 4 shows corresponding cross sections perpendicular to the axis of the cylinder.
• Fig. 1 shows a first preferred embodiment of a sorption store for carrying out the method of the invention.
• the container 10 has a circular cross section and has passages through the container wall for flow of gas at both end faces. At the upper end face, there is an inlet 21 which can be shut off by means of an inlet shut-off element 22. At the lower end face, there is an outlet 23 having an outlet shut-off element 24.
• the interior of the container 10 is completely filled with an adsorption medium 40. From the inlet-end passage in the container wall, an inflow tube 25 extends downward coaxially with the axis of the cylinder. The inflow tube is closed at the bottom and perforated over its circumference, with the diameter of the exit openings decreasing from the top downward.
• the container wall is configured as a double wall to allow a heat transfer medium to flow through it.
• Corresponding inflow and outflow connections for a heat transfer medium are provided, but not shown in the drawing.
• the broken-line arrows symbolize the gas flow within the container. Gas flowing in through the inlet 21 exits from the openings in the inflow tube 25 into the adsorption medium 40 and flows radially to the container wall and downward in the direction of the outlet 23. Part of the gas is adsorbed on the adsorption medium 40 and the remainder leaves the container 10 through the outlet 23.
• the perforated inflow tube 25 results in a more uniform flow and a more homogeneous temperature distribution.
• FIG. 2 A preferred embodiment of a sorption store according to the invention is depicted in fig. 2.
• the container 10 has a circular cross section and has passages through the container wall at both end faces. At the upper end face, there is an inlet 21 which can be shut off by means of an inlet shut-off element 22. At the lower end face, there is an outlet 23 having an outlet shut-off element 24.
• a separation element 15 In the interior of the container 10, there is a separation element 15 which is configured as a tube having a circular cross section and is arranged coaxially to the axis of the cylinder. The interior space of the tube forms a first channel-shaped subchamber 30. The space between the outer wall of the tube and the interior wall of the container forms a second, annular subchamber 31 .
• the separation element 15 has a spacing from both end faces.
• the two subchambers 30, 31 are completely filled with an adsorption medium 40.
• the subchambers 30, 31 are bounded by a covering plate which extends over the entire cross section of the container.
• a covering plate which extends over the entire cross section of the container.
• five openings through which gas can flow into the subchambers are present in the covering plate.
• the covering plate functions as flow equalizer which ensures uniform flow of gas into the subchambers 30, 31.
• the openings depicted are illustrative and can also have a different configuration. For example, annular or interrupted annular openings can be present in the annular outer region of the covering plate.
• the broken-line arrows symbolize the gas flow within the container.
• Inflowing gas firstly goes into the space which is not filled with adsorption medium between the upper passage through the container wall and the covering plate and becomes uniformly distributed there.
• the gas flows through the openings in the covering plate into the two subchambers 30, 31 where it adsorbs on the adsorption medium.
• the adsorption medium and the surrounding gas heat up as a result of the adsorption.
• the container wall and the separation element 15 are configured as double walls and a heat transfer medium flows through them to effect cooling, so that a radial temperature gradient is established between the middle of the channel-shaped subchambers and the peripheries thereof.
• the flow according to the invention through the container 10 during charging results in removal of the heat evolved in adsorption and thus lower maximum temperatures in the adsorption medium.
• Fig. 3 shows a further preferred embodiment of a sorption store according to the invention.
• the configuration of the store corresponds to that shown in fig. 2 with the modification that a perforated inflow tube 25 extends coaxially to the axis of the cylinder downward from the openings in the covering plate.
• the inflow tubes effect a more uniform flow of the contents of the container and a more homogeneous temperature distribution in the adsorption medium.
• Fig. 4 shows cross sections perpendicular to the axis of the cylinder.
• the upper drawing shows a cross section through the sorption store of fig. 1
• the lower drawing shows a cross section through a sorption store as per fig. 2 or 3.
• Fig. 5 shows an embodiment of the sorption store of fig. 1 integrated into a circulation circuit 50.
• the outlet 23 is connected via the outlet shut-off element 24 to the suction side of a compressor 51 whose pressure side is in turn connected via a heat exchanger 52 to the inlet 21 of the container 10.
• Flow according to the invention through the sorption store is ensured by the circulation circuit. Only the amount of gas which is adsorbed on the adsorption material is fed in via the external circuit 21 .
• this embodiment has the advantage that no external gas network has to be used to maintain the flow.
• pellets have the same properties in respect of size, permeability, density, heat capacity, conductivity, enthalpy of adsorption and adsorption kinetics.
• a tube having a circular cross section is installed as separation element concentrically to the axis of the cylinder. It has a double wall and an internal diameter of 5 cm. Its wall thickness is a total of 1 cm, and the gap width between the walls of the double wall is 3 mm.
• the interior of the container is thus divided in a channel pair into two parallel, channel-shaped subchambers. The spacings of the channel walls are 5 cm in both subchambers. The spacing between the tube ends and the respective end-face interior surfaces of the container is 1 cm.
• the container wall is likewise a double wall having a wall thickness of a total of 1 cm, and the gap width between the walls of the double wall is 3 mm.
• the container has a fill volume of 19 liters and is filled with pellets of a metal framework (MOF) of the type 177 as adsorption medium.
• MOF type 177 comprises zinc clusters which are joined via 1 ,3,5-tris(4-carboxyphenyl)benzene as organic linker molecule.
• the specific surface area (Langmuir) of the MOF is in the range from 4000 to 5000 m 2 /g. Further information on this type may be found in US 7,652,132 B2.
• the pellets have a cylindrical shape with a length of 3 mm and a diameter of 3 mm. Their permeability is 3-10 "16 m 2 . The ratio of permeability to smallest pellet diameter is thus 10 "13 m 2 /m.
• the porosity of the bed is 0.47.
• the filling of the container with pure methane, which is fed in with a temperature of 27°C, is examined.
• the predetermined final pressure is 90 bar absolute.
• a heat transfer medium flows through the container wall and the respective separation elements in such a way that a constant wall temperature of 27°C is established . Under these conditions, the container can be filled with a maximum of 2 kg of methane.
• Fig. 6 shows the adsorption rate for methane for the adsorption medium simulated at a pressure of 90 bar and a temperature of 27°C. This curve is typical of preferred adsorption media such as MOFs, zeolites or activated carbon.
• the drawings in fig. 7 show the results of three scenarios.
• the gas is fed from the beginning at a constant pressure of 90 bar into the above- described container.
• the outlet shut-off element remains closed during the entire charging time and no flow through the container takes place.
• the temperature in the bed of pellet reaches its maximum of about 342 K after about 8 minutes.
• the same container configuration as in the comparative scenario is used as a basis.
• the outlet shut-off element is quickly opened after the first pressure rise, so that flow through the container is established.
• the flow rate is measured and regulated to five times the adsorption rate over the entire duration of charging.
• the adsorption medium is loaded significantly more quickly than in the comparative example.
• the temperature maximum in the bed is reached after about 7 minutes and is, at about 332 K, significantly lower than in the comparative example (lower graph in fig. 7).
• the scenario is altered from the first scenario according to the invention in that the flow is regulated to twenty times the adsorption rate.
• the simulation results demonstrate that the heat of adsorption is removed effectively by means of the mode of operation according to the invention, which leads to a reduced temperature maximum in the adsorption medium and more rapid loading with the gas to be stored.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Filling Or Discharging Of Gas Storage Vessels (AREA)
• Separation Of Gases By Adsorption (AREA)

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• 2013
  • 2013-10-08 CN CN201380051044.0A patent/CN104704282A/zh active Pending
  • 2013-10-08 EP EP13846003.5A patent/EP2906869A4/de not_active Withdrawn
  • 2013-10-08 BR BR112015005914A patent/BR112015005914A2/pt not_active IP Right Cessation
  • 2013-10-08 KR KR1020157009014A patent/KR20150067183A/ko not_active Withdrawn
  • 2013-10-08 WO PCT/IB2013/059194 patent/WO2014057416A1/en not_active Ceased
  • 2013-10-08 JP JP2015536259A patent/JP2015531465A/ja active Pending
  • 2013-10-09 AR ARP130103673A patent/AR092966A1/es unknown

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