JP2005273717A - Adsorption type natural gas fuel storage system - Google Patents

Abstract

An adsorption-type natural gas fuel storage device in which the storage amount does not decrease even after repeated use is provided.
An adsorption-type natural gas fuel storage device having a natural gas storage tank provided with a natural gas supply port and a natural gas discharge port, wherein the natural gas storage tank has an adsorbent having a maximum pore diameter. The first tank 31 filled with sorbent, the second tank 32 filled with the adsorbent having the pore diameter next to the adsorbent filled in the first tank, and the pore diameter next to the adsorbent filled in the second tank. A third tank 33 filled with an adsorbent material and a fourth tank 34 filled with an adsorbent material having a minimum pore diameter, the first tank, the second tank, in order from the natural gas supply port and the natural gas discharge port side, The third tank and the fourth tank are connected in series via the gas passage.
[Selection] Figure 2

Description

  The present invention relates to an adsorption-type natural gas fuel tank, and more particularly to a fuel tank configuration that efficiently adsorbs and stores a plurality of gas components (2 or more carbon atoms) contained in natural gas.

  Natural gas is a mixed gas containing about 88% of methane, about 7% of ethane, about 2% of propane, about 3% of butane, etc. As a method of storing this natural gas at a high density, a method of cooling natural gas and storing it as liquefied natural gas (LNG), a method of compressing under high pressure and storing it as compressed natural gas (CNG), etc. are known. Yes.

  However, since the method of storing as LNG requires a large-scale cooling facility, there is a problem that the cost of the facility and the fuel cost required for cooling is high, and the use as a fuel tank is mounted on an automobile or the like. The system becomes complicated.

  On the other hand, the method of storing as CNG has a problem that the energy density of CNG is lower than that of LNG. For example, even if CNG is compressed at a pressure of about 20 MPa, the energy density is only 1/3 of LNG. Currently, the pressure in gas storage facilities installed in urban areas is 1 MPa or less, so the storage density is lower than that of LNG, and large-scale storage facilities are required to store a large amount of natural gas. It is difficult to secure the site. Also, in the application of fuel tanks for automobiles and the like, the low energy density is fatal because the mounting space is limited. In order to increase the energy density, a high-pressure container or a pressure regulating valve that can withstand the storage pressure of CNG is required, and there is a problem that the equipment cost is significantly increased.

  In order to solve such a problem, a technique has been proposed in which natural gas is adsorbed and stored in an adsorbent disposed in a tank, and is desorbed and supplied from the adsorbent when used. According to this technique, gas molecules are adsorbed in the pores formed in the activated carbon or the like, so there is no need to perform cooling or compression at a high pressure.

  However, in the above technique, a single activated carbon is used as the adsorbent, and all components are adsorbed. Therefore, high carbon number components such as butane, propane, and ethane, which have strong adsorption power against activated carbon, are adsorbed on the activated carbon. As a result, there was a problem that the activated carbon was clogged. As a result, the amount of adsorption of methane, which is the main component, decreases, and the amount of methane gas stored decreases with repeated use.

  For such problems, a storage device (for example, Patent Document 1) in which adsorbent layers having different pore diameters are stacked in the storage tank in order of increasing pore diameter and the introduced natural gas is separated and adsorbed into the respective layers. And a storage device (for example, a patent) that includes a first adsorption container for adsorbing components other than methane and a second adsorption container for adsorbing methane, and further includes a heater for desorbing gas. Techniques such as Document 2 have been proposed.

  A schematic diagram of the former storage device is shown in FIG. According to this apparatus, since the adsorbents having different pore diameters are sequentially laminated, when the introduced natural gas passes through these layers, the butane adsorbent 41, the propane adsorbent 42, the ethane adsorbent 43, And each component can be made to adsorb | suck to the methane adsorption material 44, respectively. Further, according to the latter storage device, a high carbon number component having a strong adsorbing power other than methane can be adsorbed in the first adsorption vessel, and only methane can be introduced into the second adsorption vessel and adsorbed.

JP 2003-28397 A (abstract) JP 2002-327897 A (abstract)

  However, the former storage device has a problem that a difference in gas flow velocity occurs between the tank center C and the periphery P shown in FIG. 1 and the adsorption at the center C and the periphery P becomes uneven. It was. In the latter storage device, although the high carbon number component and the methane adsorption container are independent, the high carbon number component consisting of a plurality of gas components is trapped by one adsorption container, so that the methane storage There have been problems such as incomplete trapping of the high carbon number component that causes a decrease in the amount, and an increase in the size of the first adsorption vessel.

  The present invention has been made in view of the above situation, and an object thereof is to provide an adsorption-type natural gas fuel storage device in which the amount of storage does not decrease even when used repeatedly.

  The adsorption type natural gas fuel storage device of the present invention is an adsorption type natural gas fuel storage device provided with a natural gas supply port and a natural gas discharge port in a natural gas storage tank, and the natural gas storage tank has a maximum A first tank filled with an adsorbent having a pore diameter, a second tank filled with an adsorbent having a pore diameter next to the adsorbent filled in the first tank, and an adsorbent filled in the second tank. A third tank filled with an adsorbent having a pore diameter, and a fourth tank filled with an adsorbent having a minimum pore diameter, the first tank and the second tank in order from the natural gas supply port and the natural gas discharge port side; The tank, the third tank, and the fourth tank are connected in series via a gas passage.

  According to the adsorption type natural gas fuel storage device of the present invention having the above-described configuration, butane having the strongest adsorption power among natural gas components tends to be particularly adsorbed in the first tank filled with the adsorbent having the maximum pore diameter. Most of the water is adsorbed in the first tank, and the remaining propane, ethane, and methane are introduced into the next second tank. Similarly, most propane is selectively adsorbed in the second tank, and most ethane is selectively adsorbed in the third tank. The final fourth tank is introduced with methane containing trace amounts of other components (butane, propane, and ethane). As a result, each tank can be uniformly adsorbed for each component. In addition, since each tank is filled with an adsorbent having a pore size suitable for adsorbing each component, it is not a target as in a conventional storage device that adsorbs a plurality of gas components in the same tank. The adsorbent is not clogged due to the adsorption of the components, and the storage capacity does not decrease even after repeated use.

Hereinafter, the adsorption type natural gas fuel storage device of the present invention will be described in detail.
FIG. 2 shows a schematic diagram of the adsorption type natural gas fuel storage device of the present invention. In FIG. 2, reference numeral 11 is a natural gas supply port for taking in natural gas from the outside, and reference numeral 12 is a natural gas discharge port for supplying natural gas stored in the storage device to an external engine or the like. is there. Reference numerals 21 and 22 are cocks for opening and closing the natural gas supply port 11 and the natural gas discharge port 12, respectively.

  A first tank 31, a second tank 32, a third tank 33, and a fourth tank 34 are successively connected via the gas passage 13 in order from the natural gas supply port 11 and the discharge port 12 side. Each tank is filled with a butane adsorbent 41, a propane adsorbent 42, an ethane adsorbent 43, and a methane adsorbent 44, respectively. The first tank 31, the second tank 32, and the third tank 33 are provided with heaters 50.

  Natural gas supplied from the natural gas supply port 11 with the supply port opening / closing cock 21 opened and the discharge port opening / closing cock 22 closed is first introduced into a first tank 31 provided on the most upstream side. Butane having the strongest adsorption force is mainly adsorbed by the butane adsorbent 41 filled in the tank. Propane, ethane, and methane, which are the remaining components, have a lower adsorption power than butane and have a lower molecular weight, so that they pass through the tank without being adsorbed by the butane adsorbent 41 and pass through the gas passage 13. Then, it is introduced into the next second tank 32. In this tank, propane is mainly easily selectively adsorbed by the propane adsorbent 42 having the pore diameter next to the butane adsorbent 41, and ethane and methane having a weaker adsorbing force and smaller molecular weight pass through the gas passage 13 to the next. It is introduced into the third tank 33. In this tank, ethane is mainly selectively adsorbed by the ethane adsorbent 43 having the pore size next to the propane adsorbent 42, and the last remaining component, methane, and a small amount of other components (butane, propane, and ethane) are first added. The methane adsorbent 44 in the four tanks 34 is adsorbed.

  When the stored natural gas is supplied to an external engine or the like, heating is performed by the heater 50 with the supply port opening / closing cock 21 closed and the discharge port opening / closing cock 22 opened. By heating the adsorbent in each tank by the heater 50, the gas component adsorbed on the adsorbent is desorbed, and gas is supplied to the outside from the natural gas outlet 12. The heater 50 is not particularly limited, such as an electric heater or a heater that uses waste heat of the radiator liquid.

  In the adsorption type natural gas fuel storage device of the present invention, since the tank for each component is provided independently, the non-uniform gas flow generated in the conventional storage device that adsorbs each gas in the same tank. Has been resolved. In addition, since a dedicated adsorbent whose pore diameter is adjusted for each component is packed, each component, particularly a component having 2 or more carbon atoms, can be reliably adsorbed. Therefore, the high carbon number component can be prevented from flowing into the fourth tank (methane tank), and the clogging of the methane adsorbent can be prevented. As a result, the use is repeated as in the conventional storage device. However, the storage capacity does not decrease.

  The detailed structural drawing of the 1st tank 31-the 2nd tank 33 which adsorb | sucks a high carbon number component (butane, propane, and ethane) among each adsorption tank which constitutes the adsorption type natural gas fuel storage device of the present invention is shown. 3 shows. As shown in FIG. 3, the first tank 31 to the third tank 33 are connected to a gas passage 13 that is an inlet / outlet of natural gas. The interiors of the first tank 31 to the third tank 33 are divided into a plurality of spaces by a partition wall 60, and each space is filled with adsorbents 41 to 43, respectively. A plurality of holes serving as gas flow paths are formed in the partition wall 60. Adjacent partition holes are offset from each other so that more gas molecules are in contact with the adsorbent as the gas passes between the partitions. A heater 50 is sandwiched and fixed for each partition wall 60 facing each other.

  As a material for the partition wall, it is preferable to use a metal having a good thermal conductivity represented by aluminum or copper, a ceramic represented by SiC, or the like. If the thermal conductivity is good, the heat of the heater can be transmitted to the entire partition wall, and the adsorbent can be heated uniformly. As a result, it exerts a great effect on desorption of high carbon components.

  In FIG. 4, the schematic diagram of the connection part of a gas passage and a tank is shown. As shown in FIG. 4, it is preferable that the inner surface of the tank end portion has a taper structure so that the gas flow velocity in the central portion and the peripheral portion becomes uniform and the gas can be uniformly dispersed inside the tank.

  The volume ratio of the tank used in the present invention is appropriately selected according to the component ratio of the supplied natural gas. For example, in the case of Japanese natural gas 13A, ratios of 100 L for methane, 10.2 to 11.2 L for ethane, 0.8 to 0.9 L for propane, and 0.8 to 0.9 L for butane are required.

  In the present invention, activated carbon having a pore diameter peak of 1.10 to 1.30 nm is placed in the first tank, and activated carbon having a pore diameter peak of 0.95 to 1.05 nm is placed in the third tank. Is preferably filled with activated carbon having a pore diameter peak of 0.75 to 0.85 nm. Activated carbon having a pore diameter peak in this range can suitably adsorb each gas. FIG. 5 shows the relationship between the pore diameter peak of activated carbon and the gas trap (adsorption) ability.

The activated carbon used as the adsorbent of the present invention will be described.
Examples of the raw material for activated carbon include a wide range of materials such as wood, coconut shell, coal, and phenol resin. There are two types of production methods: gas activation such as steam activation and carbon dioxide activation, and chemical activation such as phosphoric acid activation and KOH activation. When gas activation is performed, first, a carbonization process for carbonizing the raw material and an activation process for growing pores therein are continuously performed. In the case of chemical activation, the chemical is added to the raw material and heated, and carbonization and activation are performed at once, followed by washing and neutralization. When steam activation is performed, the time is in the range of 600 to 1000 ° C. for about 1 to 8 hours. In the case of carbon dioxide activation, it is 1 to 10 hours at 600 to 1000 ° C., and in the case of phosphoric acid activation and KOH activation, 500 to 900. It is about 1 to 8 hours at ° C.

  In the adsorption type natural gas fuel storage device of the present invention, the ratio of the inner diameter A of the tank and the inner diameter B of the gas passage shown in FIG. 2 is preferably in the range of 2: 1 to 40: 1. By adopting such a configuration, pressure loss occurs between the tank and the gas passage, and each gas component can be more uniformly adsorbed.

  As described above, the adsorption type natural gas fuel storage device has been described. However, the application of the adsorption type natural gas fuel storage device of the present invention is not particularly limited, and for example, for an installation type fuel storage device or a natural gas vehicle. It can be used for any application such as a fuel tank device.

Hereinafter, the adsorption type natural gas fuel storage device of the present invention will be described in detail by way of examples.
Activated carbon having the following properties was filled in each tank, and the tanks were connected in series in the order schematically shown in FIG.
-Activated carbon for butane (peak pore size 1.2 ± 0.1 nm)
・ Activated carbon for propane (1.0 ± 0.05nm)
・ Activated carbon for ethane (0.8 ± 0.05 nm)

  In this adsorption type natural gas fuel storage device, the composition of methane: 87.6%, ethane: 5.44%, propane: 4.69%, butane: 1.76% (total of i-butane and n-butane) A mixed gas having a ratio was introduced. When the composition ratio of the mixed gas introduced into the fourth tank through the first tank, the second tank, and the third tank (the three tanks are collectively referred to as a filter) was examined, methane: 99.4 %, Ethane: 0.25%, propane: 0.21%, and butane: 0.13%, and it can be seen that the purity of methane is improved to 99.4% (analysis time 0 to FIG. 6). See the 16 minute range).

  Under a pressure of 1 MPa, the tank in which the mixed gas was adsorbed was heated (filter regeneration process) as indicated by the heater temperature and activated carbon temperature in FIG. As shown in the analysis time of 16 to 40 minutes in FIG. 6, the desorbed gas composition ratio when the adsorbed gas was desorbed with heating and the activated carbon temperature reached 50 ° C. was methane: 88.6. %, Ethane 5.81%, propane 3.91%, and butane 1.65%, which is substantially equal to the composition ratio of the mixed gas before adsorption. As described above, according to the adsorption type natural gas fuel storage device of the present invention, almost all the high carbon number components are adsorbed when the gas is introduced, and these adsorbed components are almost completely desorbed when the gas is desorbed. Can be played.

  The heating temperatures required at 1 MPa are ethane: 35 ° C., propane: 45 ° C., and butane: 50 ° C. When considering practical use, the heating temperatures are 55 ° C., 65 ° C., and 70 respectively at 3.5 MPa. ° C.

It is a schematic diagram which shows the conventional fuel storage apparatus. It is a schematic diagram which shows the adsorption type natural gas fuel storage apparatus of this invention. It is a schematic diagram which shows the tank for high carbon number components in the adsorption type natural gas fuel storage apparatus of this invention. It is a schematic diagram which shows the gas inlet in the tank of FIG. It is a graph which shows the relationship between the pore diameter of an adsorbent, and a component gas trap capability. It is a graph which shows the time-dependent change of the gas composition in a fuel tank in an Example, and the desorption gas composition in a filter reproduction | regeneration process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Natural gas supply port 12 Natural gas discharge port 13 Gas passage 21 Supply port opening / closing cock 22 Discharge port opening / closing cock 31 1st tank 32 2nd tank 33 3rd tank 34 4th tank 41 Butane adsorbent 42 Propane adsorbent 43 Ethane adsorption Material 44 Methane adsorbent 50 Heater 60 Bulkhead A Tank diameter B Gas passage diameter C Tank center P Tank periphery

Claims (5)

An adsorption-type natural gas fuel storage device having a natural gas supply port and a natural gas discharge port in a natural gas storage tank,
The natural gas storage tank includes a first tank filled with an adsorbent having a maximum pore diameter, a second tank filled with an adsorbent having a pore diameter next to the adsorbent filled in the first tank, A third tank filled with an adsorbent having a pore size next to the adsorbent filled in the second tank, and a fourth tank filled with an adsorbent having a minimum pore diameter;
The first tank, the second tank, the third tank, and the fourth tank are connected in series via a gas passage in order from the natural gas supply port and the natural gas discharge port side. Adsorption type natural gas fuel storage device.   The adsorption type natural gas fuel storage device according to claim 1, wherein heating means is provided in each of the first tank, the second tank, and the third tank.   The inside of the first tank is filled with activated carbon having a pore diameter peak of 1.10 to 1.30 nm, and the inside of the second tank is filled with activated carbon having a pore diameter peak of 0.95 to 1.05 nm, 3. The adsorption type natural gas fuel storage device according to claim 1, wherein the third tank is filled with activated carbon having a pore diameter peak of 0.75 to 0.85 nm.   The adsorption type natural gas fuel storage device according to any one of claims 1 to 3, wherein an inner diameter ratio of each tank and the gas passage is 2: 1 to 40: 1.   The adsorption type natural gas fuel storage device according to claim 1, wherein the adsorption type natural gas fuel storage device is a fuel tank device for a natural gas vehicle.

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