JP2002235900A - Hydrogen gas supplying method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrogen gas supplying method capable of utilizing an existing town gas conduit network. SOLUTION: Mixed gas branched from a conduit 5 by piping 13a is supplied to a hydrogen separating device 15a. The mixed gas is sucked into the inside of the device by a vacuum pump (not shown in the figure) in the hydrogen separating device 15a, and separated into hydrogen gas and separated gas (inert gas and an odorless agent) by action of a hydrogen separating film (not shown in the figure). The hydrogen gas is supplied to a fuel battery 16a through the separating film. On the other hand, components except for the hydrogen gas remain because the components cannot pass through the separating film, and are returned to the conduit 5 through gas piping 14b. In the components structure of supplied gas, an inert gas component (carbon dioxide) and the odorless agent are enriched toward an end of the conduit 5 by the separated gas returned to the conduit 5. The supplied gas including inert gas as a main component is stored in an inert gas collecting device 8. The inert gas collected in the inert gas recovering device 8 is returned to an inert gas storing device 2 by inert gas collecting piping 9, and mixed with the hydrogen gas again to be supplied as the supplied gas to demanding homes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for supplying hydrogen gas, and more particularly, to a method for supplying hydrogen gas using an existing city gas pipe network.

[0002]

2. Description of the Related Art In recent years, attention has been paid to a system using hydrogen as a fuel. This is because even if hydrogen gas is burned, carbon dioxide which causes global warming is not generated. For this reason, hydrogen gas is expected to be widely used in the future as fuel for household fuel cell systems, fuel cell vehicles, and the like. Focusing on such advantages, a technique for supplying hydrogen gas using an existing city gas pipeline network has been proposed (for example, Japanese Patent Application Laid-Open No. H11-228101). However, hydrogen gas has a wide combustion range (4.0 in air).
% To 75.0% is in the flammable range), and there is a high risk of explosion when leaked, as compared with conventional city gas. For this reason,
There is a problem that it is difficult to use the conventional city gas pipeline network as it is. On the other hand, there is a problem that enormous investment is required to lay a new conduit exclusively for hydrogen gas.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for supplying hydrogen gas which can be used in existing city gas pipelines.

Another object of the present invention is to provide a hydrogen gas supply method free from explosion.

Another object of the present invention is to provide a city gas supply mode that is friendly to the global environment.

[0006]

A first aspect of the present invention is a hydrogen gas supply method for supplying a mixed gas containing a hydrogen gas and a non-combustible gas and adjusted to a combustion limit of the hydrogen gas or less by a conduit. And separating the hydrogen gas in the mixed gas at one or more points of the conduit, and returning the separated gas to the conduit again.

[0007] By adopting such a supply method, the hydrogen gas concentration in the mixed gas can always be kept below the combustion limit.
Even if leakage from the piping occurs at any point in the conduit network during construction or the like, the danger of explosion of the supplied gas can be avoided.

Further, since the non-combustible gas component after separation is returned to the conduit again, the inside of the conduit network can be constantly maintained below the combustion limit of hydrogen gas up to the end of the conduit.

In the present invention, the supply of hydrogen to a hydrogen fuel facility such as a fuel cell at a customer is performed by separating hydrogen gas in a mixed gas at a customer and supplying the separated hydrogen gas to the facility. Done.

[0010] The term "non-combustible gas" used herein refers to nitrogen gas,
Inert gases that do not participate in the combustion reaction, such as carbon dioxide gas and argon gas (Claims 4 to 6), and halogen-based fire extinguishing agents that actively participate in preventing the combustion reaction (Claims 7 and 8)
It is a concept including

The principle of making nonflammable gas (hydrogen) nonflammable by nonflammable gas is as follows. FIG. 2 shows a flammable gas,
FIG. 4 is a triangular diagram conceptually showing a combustion limit of a mixed gas containing a non-combustible gas and air as three components. Each side of the triangular diagram shows the mixing ratio of different types of gases located at two vertices opposed to each other with the triangle interposed therebetween. The distance between an arbitrary point in the triangular diagram and a line extending from the point in parallel with each side to one side indicates the mixing ratio of the three components. For example, the mixing ratio of the flammable gas, the inert gas and the air at the point P1 is X1: X2: X3 (where X1 + X2 + X3
(≡100%). Further, a portion T surrounded by oblique lines in the triangular diagram indicates a combustion range of the combustible gas. That is, when the mixture ratio of the flammable gas, the inert gas, and the air becomes the mixture ratio in the atmosphere in T, the mixture enters the combustion region, and there is a risk of explosion.

When a mixed gas of a combustible gas and a non-flammable gas flows into a conduit as in the present invention, this corresponds to the case where the air component is zero in FIG. Therefore, the mixture ratio of combustible gas and noncombustible gas in the conduit is shown as a point on the side connecting the vertices of combustible gas and noncombustible gas. For example, when the gas composition in the conduit is P2, that is, when the mixing ratio between the combustible gas and the nonflammable gas is X1 ′: X2 ′, when this two-component gas diffuses into the atmosphere, The mixing ratio of the ternary mixed gas containing air changes according to a straight line connecting P2 and P1. With the change, the proportion of air increases to reach the point P3, and when entering the region T, the mixture ratio becomes within the combustion limit.

Thus, there is no danger of explosion if the mixture ratio of the combustible gas and the inert gas is such that it does not always enter the combustible gas region T even if it is diffused into the atmosphere. You can see that. Such a mixing ratio is a point inside the triangle LMN in FIG. That is, in the production process of the supply gas, the mixture ratio of the combustible gas and the nonflammable gas is set to X1 ″: X
If it is adjusted to 2 "or less, the mixed gas will always be out of the combustion range even if diffused into the air, so that even if it leaks from the conduit, it will not explode in the atmosphere.

FIG. 3 shows H2 (hydrogen gas) as a combustible gas and N2 (nitrogen gas) or CO2 as a noncombustible gas.
It is a triangular diagram in the case of using (carbon dioxide). In the figure, curve Q is the explosion limit line of nitrogen gas, and curve R is the explosion limit line of carbon dioxide gas. According to the figure, in the case of nitrogen gas, the three components are {L'M '
If the mixture ratio is indicated by an arbitrary point in N ', it is possible to always maintain the mixture ratio at or below the combustion limit. Such a mixing ratio in the case of a two-component gas of hydrogen gas-nitrogen gas is in a range such that the ratio of hydrogen gas is always about 30% or less (point M '). If the mixing ratio is within this range, there is no possibility of explosion even if it leaks into the atmosphere. Similarly, in the case of carbon dioxide, the value is about 43% (point P4) or less.

According to a second aspect of the present invention, there is provided a hydrogen gas supply method according to the first aspect, further comprising recovering the separated gas at one or more predetermined points in the conduit.

According to the first aspect of the present invention, since each customer uses the hydrogen by separating the mixed gas, the separated gas returned toward the supply end has a high proportion of nonflammable gas. Along with this, the gas composition in the conduit also has a high nonflammable gas concentration. If the supply gas is collected at the end point of the conduit where the concentration of the non-flammable gas is equal to or higher than the predetermined value,
The nonflammable gas can be reused. Thereby, even if the nonflammable gas is an expensive gas, it becomes practical. Even if the nonflammable gas is a gas (for example, carbon dioxide gas) that causes global warming, there is no problem in use because it is not released into the atmosphere.

The recovery of the separated gas can be performed, for example, by providing a recovery tank at the end of the conduit.
As the installation point of the recovery tank, an appropriate point can be selected, for example, based on the actual consumption of hydrogen gas by the customer, analysis of the conduit network, and the like. Also, a plurality of points in the conduit may be set as collection points, and gas components analysis may be periodically performed at each point to collect the separated gas from the points where the non-combustible gas is high.

Further, a fourth aspect of the present invention provides the hydrogen gas supply method according to the first or second aspect, wherein the recovered separated gas is returned to the mixed gas production step. For recovery, for example, a non-flammable gas can be continuously recovered by using a recovery conduit, and a large storage holder is not required.

Further, it is also possible to liquefy, compress, etc., the gas mainly composed of non-combustible gas at the collection point, and collect it with a vehicle or the like.

[0020]

Embodiments of the present invention will be specifically described below with reference to the drawings. Here, in each of the drawings, the same components are denoted by the same reference numerals, and redundant description will be omitted. Further, the following embodiments are exemplifications, and the scope of the present invention is not limited to each embodiment.

FIG. 1 is a diagram showing a hydrogen gas supply system according to this embodiment. The hydrogen gas supply system 1 according to the present invention includes a hydrogen gas production plant 2, a supply gas production process 4 having an incombustible gas storage device 3, a conduit 5, a hydrogen separation device, and a customer 6 having a hydrogen gas utilization device. And 7, a nonflammable gas recovery device 8, and a nonflammable gas recovery pipe 9. Carbon dioxide gas is stored in the nonflammable gas storage device 2. The hydrogen gas supply system 1 includes necessary production and supply equipment such as a booster, an odor device, a gas holder, a governor, etc. other than the above equipment, but these are omitted. The conduits constitute a network, but are represented by conduits 5. Further, a number of customer groups are connected to the conduit, and are represented by the customers 6 and 7.

Next, the configuration of the customer 5 will be described. The customer 5 includes a hydrogen separation device 15a and a hydrogen gas utilization device 16
a. The hydrogen gas separation device 15a is a device for selectively separating and extracting hydrogen from the supplied mixed gas. In order to separate hydrogen gas from the mixed gas, a hydrogen separation membrane (not shown) is provided inside the hydrogen separation device 15a. As a material for the hydrogen separation membrane, a known palladium, palladium alloy membrane, polymer membrane, or the like can be used. In addition to the hydrogen separation membrane, the hydrogen gas separation system is not limited to PS.
An A (Pressure Swing Absorption) device can also be used. The hydrogen gas utilization device 16a includes, for example, a fuel cell system.

Next, the configuration of the customer 7 will be described. It is the same as the customer 6 in that the hydrogen separator 15b and the return gas pipe 14b for returning the separated gas to the conduit 5 are provided. The configuration of the customer 7 is different from that of the customer 6 in that a hydrogen gas supply stand 18 is provided. The hydrogen gas supply stand 18 may be of a type that stores hydrogen gas by a hydrogen storage alloy, compression, or the like.

Next, the supply gas production process in the supply gas production process 4 and the supply process using the conduit 5 will be described. Hydrogen gas is produced in the hydrogen gas production plant 2. As a method for producing hydrogen gas, for example, solar power generation,
It can be based on electrolysis of seawater by wind power, wave power or the like. Hydrogen can also be produced by steam reforming of a fossil fuel, for example, natural gas. The hydrogen gas produced in the hydrogen gas production plant 2 is temporarily stored in a storage device (not shown), and then supplied via a conduit 5 according to demand. The hydrogen gas supplied from the storage device is mixed with the carbon dioxide gas supplied from the incombustible gas storage device 2 in the mixing device 11, and after adding an odorant such as, for example, TBM, to the customer via the conduit 5. 6 and 7.

The mixture ratio of hydrogen gas and carbon dioxide gas in the mixed gas is adjusted to 44:56 (that is, point P5 in FIG. 3).
Composition). In addition, the feed gas contains a very small amount of odorant. Although the supply pressure of the supply gas can take any value, there are three stages of high pressure (1 MPa or more), medium pressure (0.1 MPa or more, less than 1 MPa), and low pressure (less than 0.1 MPa), similarly to the conventional city gas. can do.

Next, the manner of using the supplied gas in the customer 6 will be described. The mixed gas branched from the conduit 5 by the pipe 13a is supplied to the hydrogen separator 15a. The mixed gas is sucked into the hydrogen separation device 15a by a vacuum pump (not shown) in the device, and separated from the hydrogen gas (nonflammable gas and deodorant) by the action of a hydrogen separation membrane (not shown). Is separated into The hydrogen gas passes through the separation membrane and is supplied to the fuel cell 16a. On the other hand, components other than the hydrogen gas cannot pass through the separation membrane and stay there, and return to the conduit 5 via the gas pipe 14b. The hydrogen separation device 15a
The pressurized device may be used to introduce the mixed gas into the gas. The return of the separated gas to the conduit 5 can also be performed via a pressure increasing device or the like as necessary.

Next, the usage of the supplied gas in the customer 7 will be described. The hydrogen gas separated and extracted in the hydrogen separator 15b is temporarily stored in a hydrogen gas supply stand 18 via a pipe 20, and supplies the hydrogen gas to a vehicle using hydrogen gas as a fuel, for example, a fuel cell vehicle 19.

Next, a method for recovering nonflammable gas will be described. As described above, the hydrogen gas component contained in the supply gas is separated by the hydrogen separation device at the customers 6, 7 connected to the conduit 5 via the pipes and a large number of other customers (not shown). It is used in the equipment used. On the other hand, the component composition of the supply gas is such that the noncombustible gas component (carbon dioxide gas) and the deodorant component are concentrated toward the end of the conduit 5 by the separated gas returned to the conduit 5. The supply gas mainly composed of the nonflammable gas is stored in the nonflammable gas recovery device 8. The incombustible gas recovery device 8 is provided with a compressor (not shown), and is configured to store the separated gas rich in CO2 component at a high pressure.

The non-combustible gas recovered by the non-flammable gas recovery device 8 is returned to the non-flammable gas storage device 2 by the non-flammable gas recovery pipe 9, and is again mixed with hydrogen gas and supplied to the customer as a supply gas. Is done.

In this embodiment, an example in which carbon dioxide gas is used has been described. However, when nitrogen gas is used as the nonflammable gas, the mixing ratio of hydrogen gas and nitrogen gas in the production stage is set to 3
By adjusting the ratio to be 0:70 or less (that is, the composition at the point P4 in FIG. 3), it is possible to maintain the temperature at or below the combustion limit.

When a halogen-based fire extinguisher is used as the non-flammable gas, the mixture ratio of the non-flammable gas can be further reduced. That is, in FIG. 4, curve 1 is a diagram showing the combustion limit of halon 114B2 in the air. (Source: P
revention of detonation burning in hydrogen-air mi
xtures with high efficient inhibitor, HydrogenEne
rgy Prog. XII, Proc. World Hydrogen Energy Conf.,
12th (1998), Vol., 1965-1976).

In the figure, the horizontal axis represents the incombustible agent, the vertical axis represents the volume ratio (%) of hydrogen, and the air ratio is a value obtained by subtracting the ratio of hydrogen and the incombustible agent at an arbitrary point from 100%. The inside of the curve is the combustion range. Therefore, in the curve 1, the mixed gas does not explode in the air at any mixing ratio on the right side of P6. The critical mixing ratio of hydrogen gas and halon 114B2 in P6 is about 20:16
Therefore, it can be seen that the amount of non-combustible gas used can be reduced as compared with the use of the above-described carbon dioxide gas and nitrogen gas.

For reference, FIG. 4 also shows the explosion limit of AKAM-3 (curve 2). AK as nonflammable gas
If AM-3 is used, the mixing ratio of hydrogen can be further increased (the limit mixing ratio in this case is about 13:10).
Becomes).

As the halogen-based extinguishing agent, for example, CF3Br or CHF3 gas may be used in addition to the extinguishing agent.

[0035]

According to the present invention, it is possible to supply hydrogen gas using an existing city gas supply pipeline without laying a new pipeline. A smooth transition to supply is possible at low cost.

Further, even in the event of a leak, there is no explosion or combustion, so that gas can be transported at a higher pressure. As an example of the advantage of gas supply at a high pressure, there is an effect that the amount of heat supplied can be increased while using the current gas pipe as it is. For example, in the current 13A gas supply, the low-pressure gas pipe at the end is supplied with a 200 mm water column, but if this can be supplied with a 2000 mm water column comparable to Europe and the United States, the transport gas volume increases by one digit and the nitrogen gas volume ratio increases. 56%
Hydrogen transport rate is 4.4 times that of 200 mm water column supply.

Furthermore, since it is a non-combustible gas, it is possible to cut and process the gas pipe without interrupting the gas supply, which has the effect of reducing the construction cost.

Further, since a hydrogen separation device is provided for each consumer, a natural gas reforming device that is burdensome for the operation of the fuel cell becomes unnecessary, and a quick start of the fuel cell becomes possible.

Since hydrogen can be supplied to each home, office, and the like, it is possible to supply a hydrogen source for a hydrogen-fueled fuel cell vehicle without a dedicated stand, which contributes to the spread of the fuel cell vehicle.

[Brief description of the drawings]

FIG. 1 is a diagram showing a city gas production and supply system according to an embodiment of the present invention.

FIG. 2 is a triangular diagram conceptually showing a combustion limit of a three-component mixed gas.

FIG. 3 is a triangular diagram showing a combustion limit of a hydrogen-ternary mixed gas (hydrogen-nitrogen or carbon dioxide-air).

FIG. 4 Hydrogen-halogen fire extinguisher (Halon 114B2)
FIG. 3 is a view showing a combustion limit of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Hydrogen gas supply system, 2 ... Hydrogen gas production plant, 3 ... Non-combustible gas storage device, 4 ... Supply gas production process, 5 ... Conduit, 6, 7 ... Consumer, 8 ... Non-flammable gas recovery device, 9 ... Non-flammable gas recovery pipe, 10, 55 ...
... hydrogen gas storage device, 12 ... pipeline, 14a
14b ... Return gas pipe, 15a / 15b ... Hydrogen separator, 16a ... Hydrogen gas utilization equipment, 18 ... Hydrogen gas supply stand

Claims (8)

[Claims] 1. A method for supplying a mixed gas containing hydrogen gas and a non-combustible gas and adjusted to a combustion limit of hydrogen gas or lower by a conduit, wherein at one or more points in the conduit, Separating the hydrogen gas in the mixed gas,
A method for supplying a hydrogen gas, wherein a gas rich in a noncombustible gas component after separation (hereinafter, referred to as a separated gas) is returned to the conduit again. 2. The hydrogen gas supply method according to claim 1, further comprising recovering the separated gas at one or more predetermined points. 3. The hydrogen gas supply method according to claim 2, wherein the recovered separated gas is returned to the step of adjusting the mixed gas. 4. The hydrogen gas supply method according to claim 1, wherein said non-flammable gas contains an inert gas. 5. The hydrogen gas supply method according to claim 4, wherein said inert gas is nitrogen gas. 6. The hydrogen gas supply method according to claim 4, wherein said inert gas is carbon dioxide gas. 7. The hydrogen gas supply method according to claim 1, wherein said non-flammable gas contains a halogen-based fire extinguishing agent. 8. The halogen-based extinguishing agent is Halon 114B2.
The method for supplying hydrogen gas according to claim 7, wherein: