JP5042364B2 - Gas supply system and supply method - Google Patents

Description

  The present invention relates to a gas supply system and a supply method, and in particular, for a gas consuming device affected by a methane number, even if the gas composition fluctuates, only gases within a predetermined methane number range are supplied to those gases. The present invention relates to a technology for ensuring and stabilizing the operation of a device by supplying the device group.

  Among gas consuming equipment that uses city gas as fuel, the methane number of the fuel gas affects the operation of the equipment. A gas engine is a typical example. When a gas having a low methane number is supplied, so-called knocking is likely to occur, and the operation of the equipment becomes unstable.

Here, the methane number is standardized by AVL as an index indicating resistance to knocking corresponding to the octane number of a gasoline engine, and was reported to the American Society of Mechanical Engineers in 1973. In general, the methane number is defined as 100 for methane and 0 for hydrogen, and a mixed gas having a methane number exceeding 100 can be adjusted by mixing a gas that does not easily cause knocking. Such an agent is called a “methane value adjusting gas”, and an example thereof is CO ₂ .

For example, Patent Document 1 describes a technique for increasing the output without causing knocking in a gas engine. By mixing CO ₂ with fuel gas, the methane number of the fuel gas is increased to suppress the occurrence of knocking. Thus, the amount of fuel gas supplied to the engine body is increased to improve the engine output.

Patent Document 2 describes a technique in which CO _{2 in} exhaust gas from a gas engine is recovered, and a gas reformed by reacting CO ₂ with methane gas as a main fuel is used as fuel. The technique described in Patent Document 2 aims to increase the amount of heat, but it can also be understood that the methane number of the fuel gas is increased by the addition of CO ₂ .

Patent Document 3 describes a fuel supply device for a gas engine. In order to enable operation of the gas engine using low-calorie gas fuel, the mixing ratio of each gas contained in the fuel gas is calculated, Based on the information, the total amount of heat of the gaseous fuel to be supplied is controlled. If necessary, it is also described that CO ₂ , compressed hydrogen, LPG, and butane are added to adjust the combustion rate and methane number (anti-knock property).

On the other hand, in Patent Document 4, in view of the fact that a gas having a high methane number is effective in a gas engine, the city gas is converted into a first gas having a high methane number and a methane number by pressure swing adsorption (PSA). An apparatus is described that separates into a second gas having a low gas content. By adopting this gas separation device in the gas engine cogeneration system, supplying the first gas with high methane number to the gas engine and supplying the second gas with high calorific value to the boiler, the output of the whole system increases and energy efficiency It is possible to improve.
JP 2002-180909 A JP 2002-13447 A JP 2004-278468 A JP 2006-326545 A

As described above, as a countermeasure against knocking of a gas engine, a technique for increasing the methane number of the fuel gas, a technique for adding CO ₂ to the fuel gas for that purpose, and further, a gas separator is used to convert the fuel gas that is city gas into methane. The technology that separates the first gas having a higher valence and the second gas having the lower methane number, supplying the first gas having a higher methane number to the gas engine, and supplying the second gas having a higher calorific value to the combustor such as a boiler Are known. However, each of them focuses on a specific gas consuming device (for example, a gas engine) and a fuel gas flow supplied to the specific gas consuming device, and attempts to adjust a methane number or the like of the gas flow. .

  In the actual city gas supply, many types of gas combustion devices of different types are connected downstream of the main gas supply line, and high methane fuel gas supplies such gas consuming devices in the entire system. Distinguish between gas consuming equipment groups (eg, gas engines) and other gas consuming equipment groups (eg, combustors) that are desirable to be used, without interrupting the gas flow in the main gas supply line In order to operate the entire system efficiently, it is required to continuously supply fuel gas suitable for each, but in the conventional technology, the methane number is efficiently contained in the gas supply system. No particular consideration is given to a technique for supplying an appropriate gas suitable for each consumer device group that ensures stable operation of the consumer device group while controlling the above.

  Here, the city gas refers to a hydrocarbon-based gas whose type is determined by the combustion speed and the Wobbe index, and is classified into 13A, 12A, 6A, etc. according to the combustibility classification. For example, 13A gas that is generally supplied at present is a city gas having a Wobbbe index in the range of 52.7 to 57.8 and a combustion speed MCP in the range of 35 to 47, and quality based on the index. Are strictly managed.

  The combustion speed MCP refers to a numerical value obtained by the calculation formula shown in Equation 1, and the Wobbbe index WI refers to a numerical value obtained by the calculation equation shown in Equation 2.

(Expression 1) MCP = Σ (Si × fi × Ai) / Σ (fi × Ai) × (1−K)
However, Si is a burning rate of each combustible gas in gas, and is 282 for hydrogen, 36 for methane, 41 for ethane, 41 for propane, and 38 for butane. fi is a coefficient relating to each combustible gas in the gas, and is 1.00 for hydrogen, 8.72 for methane, 16.6 for ethane, 24.6 for propane, and 32.7 for butane. Ai is the content (percentage by volume) of each combustible gas in the gas. K is an attenuation coefficient.

(Equation 2) WI = H / √a
Where a is the specific gravity of the gas relative to the air. H is the amount of heat (megajoules) of the gas.

  For example, even if the city gas is a city gas classified as 13A (hereinafter referred to as 13A gas), the definition thereof has a wide range as described above, and thus the gas composition satisfies the conditions of the combustion speed and the Wobbe index. It changes with.

  On the other hand, in the case of city gas, it is not possible to avoid the flow of natural gas (Note 1) from localities with different methane values depending on the time. Even if the city gas satisfies the conditions of the combustion speed and the Wobbbe index, For example, the methane number, which is 66 in the average composition, varies within a certain range. In addition, when natural gas (Note 2) from various production areas flows into the same pipeline, as in the actual international gas pipeline in Europe, it is inevitable that the methane number fluctuates. In addition, a gas supply company that supplies city gas with a methane value that falls within the standard value range may have a gas other than the gas supply company (for example, biogas) Even when surplus gas can be supplied, the methane number of the gas flowing through the main gas supply line varies.

(Note 1) Brunei natural gas has a methane number of 66.6, Indonesian natural gas has a methane number of 66.7, and Malaysian natural gas has a methane number of 70.7.

(Note 2) Russian natural gas is a gas with a very high methane number with a methane concentration of 90% or more. On the other hand, natural gas from Algeria has a lower methane concentration.

  Even in such a case, it is desirable for customers who use consumer equipment affected by methane number to supply fuel gas with methane number suitable for their own gas consumer equipment, but in the main gas supply line It is practically difficult to control the methane number of gas uniformly or according to individual customer requirements, and a realistic solution is required.

  The present invention has been made in view of the above circumstances, and even when a gas having any gas composition of any methane number flows in a gas supply pipeline (main gas supply line), at the customer site or It is desirable to control the methane number at an intermediate point close to the customer and supply high methane number fuel gas to the gas consuming equipment group where it is desirable to supply high methane number fuel gas, and other gas consuming equipment group ( For example, it is an object of the present invention to provide a gas supply system and a gas supply method that can reliably supply a low methane number fuel gas to a combustor.

According to a first aspect of the present invention for solving the above problems, the gas flowing in the main gas supply line is supplied to the first gas consuming device group via the first branch path, and the second gas is consumed via the second branch path. a gas supply system for supplying to the device group, a methane number measuring means for measuring a methane number of the gas flowing through the main gas supply line, compared to be compared with the predetermined threshold methane number of the methane number measuring means to measure Means, a gas flow path switching means provided in the main gas supply line between a position of the methane number measuring means and a branch point of the first branch path and the second branch path, and the gas flow path When the branch gas supply line that supplies the gas flow switched by the switching means to the first gas consuming equipment group and the second gas consuming equipment group, and the comparing means determine that the methane number exceeds the threshold value In The gas flowing through the gas supply lines directly supplied to the first branch passage and the second branch passage, wherein the methane number is the branch the gases flowing through the main gas supply line when it is determined that less than or equal to the threshold value A switching control means for switching the gas flow path switching means so as to supply to the supply line, and a first gas having a high methane number that is provided in the branch gas supply line and whose methane number exceeds the threshold value. And a gas separation device that separates the second gas having a low methane number that is equal to or lower than the threshold value, and a first gas that supplies the first gas having a high methane number separated by the gas separation device to the first gas consuming device group. And a second bypass line that supplies the second gas having a low methane number separated by the gas separation device to the second gas consuming device group. A gas supply system for.

  In the gas supply system, a buffer tank for the first gas having a high methane number may be provided downstream of the first bypass line. In the gas supply system, the second gas buffer tank having a low methane number may be provided downstream of the second bypass line.

Further, the gas supply system is capable of supplying a methane number adjusting gas to the gas flowing through the first bypass line when the comparing means determines that the methane number does not exceed a predetermined threshold. A valence adjusting gas supply means may be further provided.

In a preferred aspect of the above gas supply system, the first gas consuming device group includes a gas engine, and the second gas consuming device group includes a combustor. In this aspect, when the first gas consuming device group is a gas engine, the gas supply system according to the present invention further includes means for separating CO ₂ contained in the exhaust gas from the gas engine, and the methane number adjustment gas supply The means is means for supplying the CO ₂ separated by the CO ₂ separation means into the first bypass line.

According to a second aspect of the present invention for solving the above problems, the gas flowing in the main gas supply line is supplied to the first gas consuming device group via the first branch path, and the second gas is consumed via the second branch path. a gas supply method for supplying to the device group, comprising: a measurement step of measuring methane number of the gas flowing through the main gas supply line, and a comparison step of comparing the measured methane number predetermined threshold, the measurement If the methane number thus obtained exceeds the threshold value, the gas flowing through the main gas supply line is directly supplied to the first gas consuming device group and the second gas consuming device group via the first and second branch paths. supplied, if the measured methane number is equal to or less than the threshold value, the methane number of the gas flowing through the main gas supply line is low methane number which is less than the high methane number of the first gas which exceeds said threshold value threshold 2 separated into a gas, wherein after separation Methane number of the first gas is supplied to the first through the bypass line first gas consuming device group, supplied to the low methane number second gas and the second through the bypass line second gas consuming device group The gas supply method is characterized in that:

The above gas supply method may further include a step of temporarily storing the first gas having a high methane number downstream of the first bypass line . In addition, the method may further include a step of temporarily storing the second gas having a low methane number downstream of the second bypass line .

Furthermore, the method of gas supply, in the comparing step, the methane number methane number control gas supplies methane number adjusted to gas flowing through the first bypass line when it is determined that does not exceed the predetermined threshold value A gas supply step can be further provided.

In one aspect of the above gas supply method, the first gas consuming device group includes a gas engine, and the second gas consuming device group includes a combustor. In this aspect, when the first gas consuming device group is a gas engine, the methane number adjustment gas is CO 2 contained in the exhaust gas from the gas engine.

In the gas supply system and the gas supply method according to the present invention, the main gas supply line is a gas supply line to the first gas consuming device group, and the gas supply line to the second gas consuming device group. The methane number of the gas flowing through the main gas supply line is measured on the upstream side of the branch point at which the second branch is branched. If the measured methane number exceeds a predetermined threshold value, even if a gas consuming device (first gas consuming device group) that affects the operation of the device is connected downstream, the methane number of the fuel gas is connected. Since the gas consuming equipment is not adversely affected, the gas supply is continued as it is.

When the measured methane number is less than or equal to the threshold value, there is a risk of adversely affecting gas consuming equipment (a first gas consuming equipment group, such as a gas engine) connected to the downstream side. Therefore, the main methane number of the gas flowing in the gas supply line, a process for separating a low methane number of the second gas is a high methane number of the first gas which exceeds the threshold value the threshold value or less, after separation The first gas having a high methane number is supplied to a first gas consuming device group, and the second gas having a low methane number is supplied to a second gas consuming device group. Thereby, even if the methane number of the gas flowing through the main gas supply line fluctuates, it is possible to supply a gas suitable for device operation to both the first gas consuming device group and the second gas consuming device group. it can. Further, the process of separating the gas flowing through the main gas supply line from the first gas having a methane number exceeding the threshold value and the second gas having the threshold value equal to or less than the threshold value may be performed only when necessary, and the processing cost can be reduced.

  As described above, in the gas supply system and the gas supply method according to the present invention, the fuel gas to be supplied in the large gas supply system in which a large number of different types of gas combustion devices are connected downstream of the main gas supply line. Even when multiple gas consuming devices with different optimum values of methane number are connected, by performing the above methane number measurement process and gas separation process for each gas consuming device, all It is possible to continuously supply a suitable gas to the gas consuming equipment. That is, even if the methane number of the mixed gas supplied to the upstream side (main gas supply line) fluctuates, only the gas within the range of the predetermined methane number in the predetermined gas equipment group in each customer It is possible to supply to the system, and it is possible to guarantee and stabilize all the device operations.

  As a specific example, the gas engine used in the cogeneration system is not only made in Japan but also many imported products are distributed in Japan. For example, the specifications of gas engines produced in Europe are determined according to the fuel gas with a high methane number (methane number: 70), but if it is used as it is in Japan, a gas with a low methane number (methane No. 66) becomes the fuel and there is a concern about the occurrence of knocking, so the specification is currently being changed to lower the rated output. However, by using the gas supply system and the gas supply method according to the present invention, Japanese city gas users who have a low methane number compared to natural gas in Europe can use high methane number gas. The possibility of selecting not only a Japanese-specification gas engine that assumes about 66 fuel gas but also a European-specification gas engine, for example, will expand. As a result, the output of the gas engine can be increased, and as a result, the initial investment can be reduced.

  In the gas supply system and the gas supply method according to the present invention, any conventionally known gas separation method can be used for the process of separating the gas. As an example, the pressure swing adsorption method (PSA) described in Patent Document 4 is raised. In addition, a membrane separation method, an absorption separation method, a cryogenic separation method, a gas hydride separation method, and the like can be used. For such a technique, for example, “Gas Separation / Purification Technology” issued by Toray Research Center, Inc., April 2007 is referred to.

  As one specific example of the gas separation process in the gas supply system and the gas supply method according to the present invention, there is an aspect in which the first gas having a high methane number is separated from the 13A gas which is city gas. When the high methane number gas is separated from the 13A gas, as a result, the remaining gas has a high composition ratio of propane, butane or the like that causes the methane number to decrease. Since propane and butane have a higher calorie than methane, the calorific value of the remaining gas (second methane number second gas) is higher than that of the separated high methane number gas. For this purpose, a high methane number gas (first gas) is supplied to, for example, a gas engine to improve engine output, while a low methane number gas (second gas) is supplied to a combustion heat utilization system such as a boiler, thereby The overall efficiency of the engine cogeneration system can be improved. Further, since propane and butane are more reducible to nitrogen oxides than methane, a low methane number gas (second gas) can be suitably applied to the denitration treatment. Furthermore, if the high methane number gas (first gas) is supplied to the gas engine, the output of the gas engine is improved and an output margin is generated. Therefore, the fuel efficiency can be further improved by controlling the output of the gas engine. .

In the gas supply system and the gas supply method according to the present invention, when a methane number adjusting gas is used, a conventionally known methane number adjusting gas can be appropriately used. Representative examples include CO2 and nitrogen gas. Table 1 shows an example of the change in methane number when the mixing ratio of methane and nitrogen gas is changed, and Table 2 shows the case where the mixing ratio of methane and nitrogen gas is changed. The table shows the effectiveness of adding the methane number adjusting gas to the mixed gas in the present invention.

Furthermore, in the gas supply system and the gas supply method according to the present invention, when the methane number adjustment gas is used, the methane number adjustment gas is discharged from other combustion equipment or the like in addition to CO2 contained in the exhaust gas from the gas engine. CO2 can also be used. CO2 emitted from various combustors and the like is one of the greenhouse gases, and it is currently required to reduce them. As described above, in the present invention, the use of exhausted CO2 as the methane number adjusting gas is It will also contribute to environmental conservation.

  In the gas supply system and the gas supply method according to the present invention, any conventionally known appropriate means can be used as the methane number meter, that is, the means for measuring the methane number. Examples include a means using a calorimeter GasPT (manufactured by Advantica), a means for quantitatively analyzing a gas composition by a mass spectrometer or gas chromatography, and calculating by a software Methane from AVL.

FIG. 1 is a system diagram illustrating a gas supply system and a gas supply method according to the present invention. FIG. 2 is a flowchart for explaining an operation process of the system of FIG. FIG. 3 is a diagram for explaining an example of gas separation by pressure swing adsorption (PSA). FIG. 4 is a graph showing a result of separating the city gas 13A into a high methane number first gas and a low methane number second gas by the pressure swing adsorption method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Main gas supply line, 2 ... Sub line, 3 ... Gas branch point, 4 ... 1st branch path, 5 ... 2nd branch path, 6 ... Methane number meter, 7 ... Gas flow path switching valve, 8 ... Branch gas supply line, 10: Gas consuming equipment group (first gas consuming equipment group) in which the methane number of fuel gas typified by a gas engine affects the operation of equipment, 20 ... Fuel gas typified by a combustor Gas consumption equipment group (second gas consumption equipment group) in which the methane number does not affect the operation of the equipment, 30 ... gas separator, 31 ... first bypass line, 32 ... second bypass line, 33 ... high methane number gas buffer tank, 34 ... low methane number gas buffer tank, 35 ... computer, 36 ... methane number threshold storage section, 37 ... comparator, 38 ... CPU (control means), 40 ... CO ₂ separation device, 50 ... CO ₂ adding device, A B, C, D ... customer

BEST MODE FOR CARRYING OUT THE INVENTION

  Hereinafter, each invention of the present application will be described based on embodiments with reference to the drawings.

  FIG. 1 is a system diagram illustrating a gas supply system and a gas supply method according to the present invention. In the figure, reference numeral 1 denotes a main gas supply line, and a mixed gas of a gas having a high methane number and a gas having a low methane number, which is appropriately mixed by a gas supplier, flows through the main gas supply line 1. Although it is desirable that the methane number of the mixed gas is within a certain range, as described above, it is inevitable that the mixed gas varies depending on the time or region. In addition, a gas having a low calorie but a high methane number may enter from the auxiliary line 2 like biogas. This also changes the methane number of the mixed gas flowing through the main gas supply line 1.

  Many gas consuming devices are connected to the downstream side of the main gas supply line 1, and are roughly classified into, for example, a gas consuming device group 10 such as a gas engine in which the methane number of the fuel gas affects the operation of the device. (In the present invention, these are collectively referred to as “first gas consuming equipment group”) and, for example, a gas consuming equipment group 20 represented by a combustor in which the methane number of the fuel gas does not affect the operation of the equipment. (In the present invention, they are collectively referred to as “second gas consuming equipment group”).

  There are a large number of customers who receive the supply of mixed gas from gas suppliers, and each customer (for example, a plurality of factories, etc.) uses the first gas consuming device group 10 and the second gas consuming device group 20 described above. It is normal to have. In the example of FIG. 1, the customer A includes a gas engine as the first gas consuming device group 10, a combustor and a denitration catalyst as the second gas consuming device group 20, and the customer B has the first gas consuming device group 10. As a second gas consuming device group 20 and a combustor. The customer A and customer B may have the same or different methane numbers for fuel gas supplied to their own gas engines. The same is true between customer C and customer D.

  The main gas supply line 1 includes a first branch 4 for supplying gas to the first gas consuming device group 10 and a second gas consuming device at a gas branch point 3 provided at each customer or a place close thereto. A branch is made to the second branch path 5 that supplies gas to the group 20, and gas is supplied from the branch paths 4 and 5 to the gas consuming devices 10 and 20. Such a gas piping system is the same as the conventional one.

  In the present invention, a methane number meter 6 is provided upstream of the branch point 3, and a switching valve 7 that switches a gas flow path is provided between the position of the methane number meter 6 and the branch point 3. The switching valve 7 has a first position for continuously flowing the mixed gas flow down to the main gas supply line 1 and a second position for switching the mixed gas flow to the branch gas supply line 8 branched from the main gas supply line 1. Positions can be taken selectively.

The branch gas supply line 8 is provided with a gas separation device 30 as described in Patent Document 4, for example. The gas separation device 30, the mixed gas flowing through the branch gas supply line 8, a predetermined first gas is a methane number exceeding the threshold value (high methane number gas) and the second gas is equal to or less than the threshold (low methane number Gas ) And are separated. The high methane number first gas separated by the gas separation device 30 is supplied to the first gas consuming device group 10 through the first bypass line 31, and at the same time, the low methane number second gas is supplied to the second bypass. The gas is supplied to the second gas consuming equipment group 20 through the line 32.

In the above system, the measured value of the methane number meter 6 is sent to the computer 35. The computer 35 has a methane number threshold storage means 36, a comparison means 37, and a control means (CPU) 38. The threshold of the methane number stored in the threshold storage means 36 is determined by the fuel gas supplied to the first gas consuming equipment group 10 (gas engine) owned by each customer A, B, C, D,. The lowest methane number is usually determined, but a higher value or a lower value may be set as the threshold value. The comparison unit 37 compares the methane number measured by the methane number meter 6 with the threshold value of the methane number stored in the threshold value storage unit 36, and the control unit 38 transmits the result to the switching valve 7.

  In the example shown in FIG. 1, in the piping system of customer A, a buffer tank 33 for high methane number gas that temporarily stores a high methane number first gas is disposed in the first bypass line 31, and The second bypass line 32 is provided with a low methane number gas buffer tank 34 for temporarily storing the second gas having a low methane number. Whether or not the buffer tanks 33 and 34 are arranged is a matter of choice. In the example of FIG. 1, the customer B does not have such a buffer tank. Only one of the buffer tanks may be arranged.

Further, the customer A's piping system is provided with a CO ₂ separation device 40 and a CO ₂ addition device 50 that constitute an example of the “methane number adjusting gas supply means” in the present invention. Here, the CO ₂ separation device 40 is for separating CO ₂ contained in the exhaust gas from the gas engine which is the first gas consuming equipment group 10, and any conventionally known CO ₂ separation device is used. Can be used. For example, a chemical absorption method, the amine method, pressure swing adsorption (PSA: Pressure Swing Adsorption) by gas separation method, membrane separation method, absorption separation method, examples cryogenic separation method, the CO ₂ separation device by gas hydrate separation method Can be mentioned.

CO ₂ separated by the CO ₂ separation device 40, as one of the methane number conditioning gas through the CO ₂ adding device 50 is added to the high methane number of the gas flowing through the first bypass line 31. Although not shown, if necessary, CO ₂ separation device may be arranged towers for storing the CO ₂ separated. Note that whether or not the CO ₂ separation device 40 and the CO ₂ addition device 50 are provided, that is, whether or not the “methane number adjustment gas supply means” is provided is a matter of choice. In the example of FIG. No adjustment gas supply means ”is provided.

FIG. 2 is a flow for explaining the operation process of the above system in the customer A. The customer A starts supplying gas to the gas consuming devices (the first gas consuming device group 10 and the second gas consuming device group 20) managed by the customer A (s101). The supplied mixed gas is desirably a mixed gas of a methane number gas exceeding the methane number threshold value stored in the threshold value storage means 36 and a methane number gas less than that. At the beginning, the switching valve 7 is set to the first position.

Simultaneously with the start of gas supply, the methane number meter 6 starts measuring the methane number of the mixed gas (s102). The measured value is sent to the computer 35, and the comparing means 37 compares whether or not the measured methane number exceeds the methane number threshold value stored in the threshold value storing means 36 (s103).

  When the measured value exceeds the threshold value, the gas engine which is the first gas consuming device group 10 is in a state where it can operate without causing knocking, and the control means 38 sends a switching signal to the switching valve 7. Do not send. Therefore, the mixed gas is continuously sent to the main gas supply line 1 (s104). The mixed gas is branched into the first branch path 4 and the second branch path 5 at the gas branch point 3, and the branch paths 4 and 5 are connected to the gas consuming devices 10 and 20 (gas engine, combustor, etc.). Is supplied (s105).

When the measured value is less than or equal to the threshold value, the control means 38 of the computer 35 starts the gas separation device 30 (s106) and sends a switching signal to the switching valve 7. The switching valve 7 is switched to the second position, and the mixed gas is sent to the gas separation device 30 (s107). The gas separation device 30 separates the mixed gas into a first gas having a high methane number that is a methane number exceeding a predetermined threshold value and a second gas having a low methane number that is equal to or lower than the threshold value. The gas is supplied to the gas engine which is the first gas consuming equipment group 10 and the second gas having a low methane number is supplied to the combustor or the like (s108). If necessary, the high methane number first gas is temporarily stored in the high methane number gas buffer tank 33, and the low methane number second gas is temporarily stored in the low methane number gas buffer tank 34. When required, the first bypass line 31 or the second bypass line 32 is supplied.

Hereinafter, during the operation of the gas consuming device, the methane number measurement of the mixed gas supplied by the methane number meter 6 is continuously performed, and the process from s103 onward is executed according to the change in the methane number of the mixed gas.

  The above processing can be performed independently for each of the customers B, C, D,..., By setting different methane number thresholds individually, that is, separately from the customer A. Therefore, even if the methane number changes in the mixed gas supplied to the main gas supply line 1, only customers who have gas consuming equipment (first gas consuming equipment group 10) affected by the fluctuation range. However, it is only necessary to take necessary measures, and the gas piping system as a whole can be operated at low cost and with high efficiency.

  As described above, in the present invention, whether the mixed gas is separated into the first gas having a high methane number and the second gas having a low methane number that is equal to or lower than the threshold by the gas separation device 30 depends on whether the mixed gas is the first gas. Judgment is made based on whether or not the methane number is suitable for the consumer equipment group 10, and a gas amount corresponding to the demand of the first gas consumer equipment group 10 is supplied. Therefore, there may be a case where the amount of the second gas having a low methane number obtained from the separated gas is smaller than the demand of the second gas consuming equipment group 20. In order to cope with this, a bypass line (not shown) is provided, and when necessary, a part of the mixed gas in the main gas supply line 1 is directly supplied to the second gas consuming device group 20 through the bypass line. it can.

In FIG. 1, the “methane number adjusting gas supply means” provided by the customer A, that is, the CO ₂ separation device 40 and the CO ₂ addition device 50 are used as follows. That is, when the gas engine is operating, the exhaust gas is captured, CO ₂ in the exhaust gas is separated, and stored in a tank (not shown) as necessary. By adding the separated CO ₂ to the first branch 4, the methane number of the fuel gas flowing therethrough can be further increased. Further, when the gas engine is operated by the first gas having a high methane number separated by the gas separation device 30 disposed in the branch gas supply line 8, the separated CO ₂ is added into the first bypass line 31. By doing so, the methane number of the fuel gas flowing therethrough can be further increased. In either case, it is possible to prevent the CO ₂ in the exhaust gas from being released to the atmosphere.

Furthermore, the mixed gas is a mixed gas having a methane number equal to or lower than the methane number threshold stored in the threshold storage means 36, and the methane number of the first gas having a high methane number separated by the CO ₂ separation device 40 is stored as the threshold. Even if the methane number threshold value stored in the means 36 is not exceeded, the threshold value was exceeded by adding separated CO ₂ into the first bypass line 31 or the first branch 4. It is also possible to supply methane number gas to the gas engine.

Next, 1 of a method and apparatus for separating a gas flowing through the branch gas supply line 8 into a low methane number of the second gas methane value is below the high methane number of high first gas which exceeds said threshold value threshold One specific example will be described by taking as an example a case where city gas called 13A in Japan is separated by the pressure swing adsorption method (PSA) described in Patent Document 4.

In Japan, city gas called 13A is methane (CH ₄ ) 87.7%, ethane (C ₂ H ₆ ) 6%, propane (C ₃ H ₈ ) 4.9%, butane (C ₄ H ₁₀ ) Having an average composition of 1.4%. Each gas has an adsorption pressure dependency of the amount adsorbed on an adsorbent (for example, activated carbon). In methane, ethane, propane, and butane, there is a great difference in the pressure dependency of the adsorption amount between methane gas and butane gas. . That is, the amount of butane gas adsorbed is much larger than that of methane gas. Both methane gas and butane gas increase in adsorption amount as the adsorption pressure increases, but there is a pressure range in which the increase in adsorption amount per unit pressure increases in butane gas as compared to methane gas. Propane gas exhibits almost the same characteristics as butane gas.

  When 13A gas is introduced and passed through an adsorption tower packed with activated carbon, more butane gas is adsorbed than methane gas, and the butane gas ratio of the passing gas becomes smaller than the butane gas ratio of the input gas. In other words, the methane number of the passing gas increases. Since the adsorption amount of this butane gas increases as the adsorption pressure increases, the methane number of the passing gas increases as the processing pressure when the 13A gas passes through the adsorption tower increases. That is, the methane number of the passing gas is controlled by swinging the pressure of the 13A gas passing through the adsorption tower filled with the adsorbent and repeating adsorption and regeneration (the adsorbent is regenerated to some extent by reducing the pressure). It becomes possible to make it. Since the butane gas adsorbed during the regeneration is released, the methane number of the passing gas decreases. Thereby, the gas separation which uses a methane number as a parameter is realizable.

  FIG. 3 shows an example of an apparatus capable of constantly separating and taking out a mixed gas into a high methane number gas and a low methane number gas using two of such adsorption towers. , One adsorption tower A takes the flow of pressurization → adsorption → desorption → desorption as shown in (i) to (iv), and the adsorption tower B correspondingly moves the flow of desorption → desorption → pressure increase → adsorption. Take. When the pressure in the adsorption tower is increased, the difference in the amount of adsorption of gases that are difficult to adsorb and difficult to absorb can be greatly increased. Therefore, a “pressure increase” process is provided, and the gas is desorbed when the pressure is decreased. In the “desorption” process, suction is performed with a vacuum pump or the like.

  FIG. 4 shows the results of experiments conducted by the present inventors with time, focusing on the left adsorption tower A in FIG. As shown in FIGS. 3 and 4, the high methane number gas and the low methane number gas do not flow in the pressure increasing process of (i). In the adsorption process (ii), a high methane number gas (HG) in which a heavy component (for example, butane) is adsorbed flows out, and a low methane gas does not flow. (Iii) In the desorption process (iv), low methane gas (LG) containing a large amount of heavy components (for example, butane) is discharged as desorption gas, and high methane number gas (HG) does not flow. As described above, by repeating this process, the 13A gas described above is converted into a high methane number gas having a methane number exceeding 70 (first gas having a high methane number in the present invention) and a methane number of 65 or less. It turns out that it can isolate | separate into low methane number gas (2nd gas of the low methane number said by this invention).

  Further, in the gas engine cogeneration system, the separated second gas having a low methane number can be used as a reducing agent in an exhaust gas denitration treatment facility of the gas engine. That is, in the denitration process using the silver-alumina catalyst, it is possible to use hydrocarbon gas as a reducing agent, and the second gas having a low methane number separated by the gas separation device 30 is more than methane gas. It contains a lot of propane gas and butane gas, which have excellent reducing properties. Therefore, if the second gas having a low composition ratio of propane gas or butane gas is used, an efficient denitration process can be performed. If hydrocarbon gas is used as the reducing agent, it is not necessary to use high-cost ammonia or urea, and cost can be reduced. Therefore, the customer A incorporates a denitration catalyst as one of the second gas consuming equipment group 20 and uses the low methane number gas separated by the gas separation device 30 as the reducing agent.

In the above system, the CO ₂ contained in the exhaust gas from the gas engine is used as the methane number adjusting gas, which is one example, and CO ₂ discharged from other combustion equipment or the like is used. You can also. In that case, CO ₂ discharged from another combustion device or the like can be stored in a tank (not shown). In any case, the use of exhausted CO ₂ as the methane number adjusting gas as described above can contribute to the preservation of the global environment.

Claims (12)

A gas supply system for supplying a gas flowing through a main gas supply line to a first gas consuming device group via a first branch path and to a second gas consuming device group via a second branch path,
Methane number measuring means for measuring the methane number of the gas flowing through the main gas supply line,
A comparing means for comparing the methane number measured by the methane number measuring means with a predetermined threshold;
A gas flow path switching means provided in the main gas supply line between a position of the methane number measuring means and a branch point of the first branch path and the second branch path;
A branch gas supply line for supplying the gas flow switched by the gas flow path switching means to the first gas consuming device group and the second gas consuming device group;
When the comparison means determines that the methane number exceeds the threshold, the gas flowing through the main gas supply line is supplied to the first branch path and the second branch path as it is, and the methane number is A switching control means for switching the gas flow path switching means to supply the gas flowing through the main gas supply line to the branch gas supply line when it is determined that the gas flow is below the threshold;
The branch gas supply is provided with a line, a gas separation apparatus for separating a low methane number of the second gas is a high methane number of the first gas methane number of the gas to be supplied exceeds the threshold value the threshold value or less When,
A first bypass line for supplying the first gas with a high methane number separated by the gas separator to the first gas consuming device group;
A second bypass line for supplying the second gas having a low methane number separated by the gas separation device to the second gas consuming device group;
A gas supply system comprising at least 2. The gas supply system according to claim 1, further comprising a buffer tank for the first gas having a high methane number, downstream of the first bypass line . 2. The gas supply system according to claim 1, wherein the second gas buffer tank having the low methane number is provided downstream of the second bypass line . When the comparison means determines that the methane number does not exceed a predetermined threshold, the apparatus further comprises a methane number adjustment gas supply means capable of supplying a methane number adjustment gas to the gas flowing through the first bypass line. The gas supply system according to any one of claims 1 to 3, wherein: The gas supply system according to claim 4 , wherein the first gas consuming device group includes a gas engine, and the second gas consuming device group includes a combustor. The first gas consuming equipment group is a gas engine, and further includes means for separating CO ₂ contained in exhaust gas from the gas engine, and the methane number adjusting gas supply means is CO separated by the CO ₂ separation means. 6. The gas supply system according to claim 5, wherein the gas supply system is a means for supplying ₂ into the first bypass line. A gas supply method for supplying a gas flowing through a main gas supply line to a first gas consuming device group via a first branch path and to a second gas consuming device group via a second branch path,
A measurement process for measuring the methane number of the gas flowing through the main gas supply line;
Comparing the measured methane number with a predetermined threshold,
If the measured methane number exceeds the threshold, the gas flowing through the main gas supply line is sent to the first gas consuming device group and the second gas consuming device group via the first and second branch paths. as it is supplied, the measured methane number is when: the threshold value, the main gas methane number of the gas flowing through the supply line is low methane number which is less than the high methane number of the first gas which exceeds said threshold value threshold separated into a second gas, the high methane number of the first gas after separation was supplied through the first bypass line to the first gas consuming device group, the low methane number of the second gas in the second A gas supply method comprising supplying to a second gas consuming device group via a bypass line . The gas supply method according to claim 7, further comprising a step of temporarily storing the first gas having a high methane number downstream of the first bypass line . The gas supply method according to claim 7, further comprising a step of temporarily storing the second gas having a low methane number downstream of the second bypass line . The comparison step further includes a methane number adjustment gas supply step of supplying a methane number adjustment gas to the gas flowing through the first bypass line when it is determined that the methane number does not exceed a predetermined threshold value. The gas supply method according to any one of claims 7 to 9. The gas supply method according to claim 10 , wherein the first gas consuming device group includes a gas engine, and the second gas consuming device group includes a combustor. The gas supply method according to claim 10 , wherein the first gas consuming device group is a gas engine, and the methane number adjustment gas is CO ₂ contained in exhaust gas from the gas engine.

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