JP2004175617A - Method for producing gas and production plant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To keep the amount of carbon monoxide in city gas (6C gas) or the like to a specified range without increasing the cost even when the production amount of the city gas (6C gas) or hydrogen gas is small. <P>SOLUTION: The plant to produce 6C gas or the like as a city gas from a crude gas includes: a reforming furnace 11 for steam reforming of 13A gas with water vapor to produce a reformed gas containing hydrogen and methane; and a carbon monoxide modifier 12 to modify carbon monoxide in the reformed gas into carbon dioxide to produce a crude gas. The plant is designed in such a manner that the reforming furnace is operated regardless of whether 13A gas is supplied as a source material to the reforming furnace or not, and that the crude gas can be circulated in a circulation passage 17 equipped with the reforming furnace and the carbon monoxide modifier. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a gas production method and a production plant, and more particularly to a gas production method and a production plant for producing city gas and the like using a low-pressure cyclic gas generator.
[0002]
[Prior art]
According to government policies, the conversion of city gas to a gas produced from liquefied natural gas (LNG), for example, to a 13A standard high calorific value gas (13A gas) stipulated by the City Gas Business Law is required. In this transition period, it is necessary to continuously supply the city gas consumer before the conversion with the city gas before the conversion, for example, a 6C gas having a low calorific value. Conventionally, this 6C gas has been produced using a 13A gas as a raw material by using a city gas production plant equipped with a low-pressure cyclic gas generator described in Patent Document 1.
[0003]
The low-pressure cyclic gas generator includes a reforming furnace and a carbon monoxide converter, and the reforming furnace contains hydrogen, methane, carbon monoxide and carbon dioxide by a steam reforming reaction of 13A gas and steam. Generated reformed gas. The carbon monoxide shifter converts the reformed gas from the reforming furnace into carbon dioxide by a carbon monoxide shift reaction using a carbon monoxide shift catalyst to produce a crude gas (shifted gas). After cooling the crude gas to room temperature, 13A gas and air are added to the crude gas to adjust the calorific value, thereby producing 6C gas.
[0004]
[Patent Document 1]
JP-A-3-197593
[Problems to be solved by the invention]
However, the demand for 6C gas has been gradually decreasing, and as a result, the city gas production plant does not need to be continuously operated, and has to be operated intermittently. When the city gas production plant is intermittently operated in this way, the temperature of the carbon monoxide converter at the time of restarting the operation may be lower than the activation temperature of the carbon monoxide conversion catalyst. In this case, the carbon monoxide concentration in the 6C gas produced at the beginning of the operation of the city gas production plant may exceed the specified range.
[0006]
It is conceivable to install a heater heating device in the carbon monoxide converter and heat the carbon monoxide converter using this heater heating device at the start of operation of the city gas production plant. However, in this case, since the carbon monoxide converter is large, the necessity of a heater heating facility increases, and the cost of the city gas production plant increases.
[0007]
The object of the present invention has been made in view of the above circumstances, and even when the amount of gas to be produced is small, the amount of carbon monoxide in the produced gas can be reduced without increasing the cost. An object of the present invention is to provide a gas production method and a production plant that can be maintained within a specified range.
[0008]
[Means for Solving the Problems]
According to the first aspect of the present invention, the reforming furnace generates a reformed gas containing hydrogen and methane by performing a steam reforming reaction on hydrocarbons, and the shifter converts carbon monoxide in the reformed gas into carbon dioxide. In a gas production method for converting crude gas to carbon to produce a crude gas and producing a desired gas from the crude gas, the reforming furnace is used regardless of whether hydrocarbons are supplied as a raw material to the reforming furnace. And operating a crude gas in a circulation path including the reforming furnace and the converter when hydrocarbons are not supplied as a raw material to the reforming furnace. is there.
[0009]
According to a second aspect of the present invention, in the first aspect of the present invention, the crude gas is transferred from the circulation path after a lapse of a predetermined time from the start of the circulation operation of the crude gas in the circulation path. A reforming gas and a crude gas are generated by a reforming furnace and a converter, respectively, and the crude gas is circulated again in the circulation path.
[0010]
According to a third aspect of the present invention, in the first or second aspect, the desired gas is city gas or hydrogen gas.
[0011]
The invention described in claim 4 is a reforming furnace for producing a reformed gas containing hydrogen and methane by performing a steam reforming reaction of a hydrocarbon, and converting carbon monoxide in the reformed gas into carbon dioxide. A gas producing plant for producing a desired gas from the crude gas, regardless of whether or not hydrocarbons are supplied as raw materials to the reforming furnace. The furnace is operated, and crude gas is circulated in a circulation path including the reforming furnace and the converter.
[0012]
According to a fifth aspect of the present invention, in the invention of the fourth aspect, after a lapse of a predetermined time from the start of the circulation operation of the crude gas in the circulation path, the crude gas can be transferred from the circulation path. A reforming furnace and a shift converter generate reformed gas and crude gas, respectively, and the crude gas is configured to be circulated again in the circulation path.
[0013]
The invention described in claim 6 is the invention according to claim 4 or 5, wherein the desired gas is city gas or hydrogen gas.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a system diagram showing a city gas production plant to which an embodiment of a gas production plant according to the present invention is applied.
A city gas production plant 10 shown in FIG. 1 includes a low-pressure cyclic gas generator including a reforming furnace 11, a carbon monoxide converter 12, an exhaust heat recovery device 19, and a water type holder 13, and a compression for delivery. It comprises a machine 14, a calorie adjuster 15, a delivery holder 16, and a circulation path 17.
[0015]
To the reforming furnace 11, a 13A standard high-calorific value city gas (hereinafter referred to as 13A gas) specified by the City Gas Business Law is supplied from a 13A gas holder 18 as a raw material and a fuel. The 13A gas holder 18 also supplies the 13A gas to the calorie adjuster 15 and sends the 13A gas to the city. The city gas production plant 10 uses the 13A gas as a raw material to produce a low calorific value city gas (hereinafter, referred to as 6C gas) of the 6C standard defined by the City Gas Business Law.
[0016]
Here, the 13A gas is generated by vaporizing liquefied natural gas (LNG) and stored in the 13A gas holder 18. The 13A gas is a representative composition, by using the volume percent methane _CH 4: 87.78%, ethane _C 2 _H 6: 5.24%, propane _C 3 _H 8: 5.73%, butane C ₄ H ₁₀ : 1.12%, nitrogen N ₂ : 0.13%, and the standard calorific value is 46.0 MJ / m ³ N (N means a standard state; the same applies hereinafter). Further, 6C gas a representative composition, by using the volume percent carbon dioxide _CO 2: 7.94%, hydrocarbon _C m _H n: 4.38%, oxygen _O 2: 5.25%, one carbon monoxide CO: 1.38% hydrogen _H 2: 28.90% methane _CH 4: 32.85% nitrogen _N 2: a 19.30%, and the standard calorific value 20.93025MJ / ^{m 3} N Has become.
[0017]
Meanwhile, the reforming furnace 11 mixes 13A gas as a raw material and steam at a temperature of about 700 ° C., and makes a steam (eg, a nickel-based catalyst) come into contact with the catalyst to perform a steam reforming reaction to generate a reformed gas. I do. This reformed gas contains hydrogen H ₂ , methane CH ₄ , carbon dioxide CO ₂ , carbon monoxide CO, carbon C, and water H ₂ O. Further, the steam reforming reaction is an endothermic reaction.
[0018]
The reforming furnace 11 includes a blow step of burning the 13A gas to raise the temperature of the catalyst, a blow purge step of discharging exhaust gas generated in the blow step, and a make step of producing a reformed gas using the 13A gas as a raw material. And a make purge step of discharging the reformed gas remaining in the make step are sequentially performed for several minutes (for example, 4 minutes), and by repeating these steps, a reformed gas is generated.
[0019]
The carbon monoxide shifter 12 converts carbon monoxide in the reformed gas from the reforming furnace 11 to carbon dioxide at a temperature of about 400 ° C. by a carbon monoxide shift reaction using a carbon monoxide shift catalyst. Then, a crude gas (that is, a modified gas) is generated. As the carbon monoxide conversion catalyst, for example, an iron oxide-chromium oxide catalyst is used. The carbon monoxide shift reaction is an exothermic reaction represented by CO + H ₂ O → CO ₂ + H ₂ . By this carbon monoxide conversion reaction, more than 10% of carbon monoxide in the reformed gas is reduced to about 5%.
The exhaust heat recovery unit 19 recovers heat from the crude gas generated in the carbon monoxide converter 12 and cools the crude gas to room temperature. The crude gas cooled to room temperature is temporarily stored in the water-containing holder 13.
[0020]
The delivery compressor 14 raises the pressure of the crude gas in the water-type holder 13 by the delivery compressor 14 and sends the pressurized gas to the delivery holder 16 via the calorie controller 15. The calorie adjuster 15 mixes 13A gas and air with the crude gas, adjusts the calorific value, specific gravity, combustion rate, etc., and dilutes carbon monoxide to 6C gas. Thereby, carbon monoxide in the 6C gas is reduced to 3% or less (for example, about 1.38%). The delivery holder 16 stores the 6C gas and enables the 6C gas to be delivered to the city.
[0021]
Now, the circulation path 17 includes a reforming furnace 11, a carbon monoxide converter 12, an exhaust heat recovery device 19, a water type holder 13, a first on-off valve 21, a circulation compressor 20, a circulation holder 23, The two on-off valve 22 and the reforming furnace 11 are sequentially connected by piping to form a loop.
[0022]
The circulation compressor 20 is started when the first opening / closing valve 21 is opened, and supplies the crude gas in the water-type holder 13 to the circulation holder 23. The circulation holder 23 is configured to be able to store a crude gas. The second on-off valve 22 is opened when the crude gas in the circulation holder 23 is supplied to the reforming furnace 11.
[0023]
In the city gas production plant 10 of this embodiment, the reforming furnace 11 is not limited to the case where the raw material supply valve 24 is opened and the 13A gas is supplied from the 13A gas holder 18 as the raw material. , The blow operation, the blow purge operation, the make operation, and the make purge operation are repeatedly performed even when the 13A gas is not supplied as the raw material due to the closing operation. On the other hand, 13A gas as fuel is always supplied from the 13A gas holder 18 to the reforming furnace 11. Therefore, when the 13A gas is not supplied as a raw material, the reforming gas is not generated in the making process, and the 13A gas as the fuel is burned in the blowing process, and the temperature in the reforming furnace 11 reaches a predetermined temperature. Be raised.
[0024]
During the operation of the reforming furnace 11 when the 13A gas is not supplied to the reforming furnace 11, the first on-off valve 21 and the second on-off valve 22 are opened and the circulation compressor 20 is started. Thus, the crude gas stored in the water-containing holder 13 is configured to be able to circulate in the circulation path 17 as shown in FIG. As a result, the crude gas heated by the reforming furnace 11 flows into the carbon monoxide converter 12, and the temperature of the carbon monoxide converter 12 becomes about 400 ° C. which is the activation temperature of the carbon monoxide conversion catalyst. Temperature is maintained.
[0025]
As a result, when the raw material supply valve 24 is opened to supply the 13A gas as the raw material to the reforming furnace 11, and when the reformed gas starts to be supplied from the reforming furnace 11 to the carbon monoxide converter 12, The carbon monoxide converter 12 can convert carbon monoxide in the reformed gas into carbon dioxide by the action of the carbon monoxide conversion catalyst immediately after the supply of the reformed gas.
[0026]
When the 13A gas is supplied to the reforming furnace 11 as a raw material, a reformed gas is produced during the operation of the reforming furnace 11, and the reformed gas has a high temperature (about 300 ° C. or higher). By supplying the reformed gas to the carbon monoxide converter 12, the temperature of the carbon monoxide converter 12 is maintained at a temperature of about 400 ° C. which is the activation temperature of the carbon monoxide conversion catalyst. .
[0027]
As described above, the first on-off valve 21 and the second on-off valve 22 are opened, the circulating compressor 20 is started, and the circulating operation in which the crude gas in the water-type holder 13 circulates in the circulating path 17. After a lapse of a predetermined time from the start of the operation, the first on-off valve 21 is closed, the circulation compressor 20 is stopped, and the delivery compressor 14 is started. Thereby, the crude gas in the circulation holder 23 is transferred to the calorie controller 15 through the second on-off valve 22, the reforming furnace 11, the carbon monoxide converter 12, the exhaust heat recovery unit 19, and the water-type holder 13. Then, the calorie adjuster 15 adjusts the calorific value of the 13A gas and the air with the 13A gas and the air to produce 6C gas. The 6C gas is sent to and stored in the delivery holder 16, and the delivery holder can be delivered from the 16 to the city.
[0028]
In this way, the crude gas in the circulation holder 23 of the circulation path 17 is transferred to the calorie controller 15 and stored in the delivery holder 16 as 6C gas, then the delivery compressor 14 is stopped, and the second opening / closing is performed. The valve 22 is closed, the raw material supply valve 24 and the first on-off valve 21 are opened, and the circulation compressor 20 is started. As a result, a reformed gas is generated in the reforming furnace 11, a crude gas is generated in the carbon monoxide converter 12, and the crude gas is supplied to the exhaust heat recovery device 19, the water type holder 13, the first opening / closing valve. 21 and can be stored in the circulation holder 23. Thus, by the same crude gas is circulated only within a predetermined time in the circulation path 17, the amount of the nitrogen gas N ₂ occurring crude gas to the circulation is suppressed within a permissible range .
[0029]
Next, the operation of the city gas production plant 10 will be described with reference to FIGS.
As shown in FIG. 2, the raw material supply valve 24 and the first on-off valve 21 are opened, the second on-off valve 22 is closed, and the circulation compressor 20 is started. Thereby, the reforming furnace 11 uses the 13A gas as a raw material and steam as a reformed gas by a steam reforming reaction, and the carbon monoxide converter 12 converts the carbon monoxide in the reformed gas into a carbon monoxide reforming reaction. To generate a crude gas as carbon dioxide, and press-in a predetermined amount of the crude gas into the circulation holder 23 through the exhaust heat recovery device 19, the water type holder 13, and the first opening / closing valve 21 (crude gas injection operation). .
[0030]
As shown in FIG. 3, next, the raw material supply valve 24 is closed and the second on-off valve 22 is opened to circulate the crude gas stored in the circulation holder 23 in the circulation path 17 (crude gas). Gas circulation operation). In this case, no reformed gas is produced in the reforming furnace 11, but since the reforming furnace 11 is in an operating state, the crude gas is heated while passing through the reforming furnace 11 to convert carbon monoxide. The temperature of the carbon monoxide shift converter 12 is maintained at the activation temperature of the carbon monoxide shift catalyst.
[0031]
As shown in FIG. 4, after a lapse of a predetermined time from the start of the circulation operation of the crude gas, the first on-off valve 21 is closed, the compressor 20 for circulation is stopped, and the compressor 14 for delivery is started. . As a result, the crude gas in the circulation holder 23 is transferred to the calorie controller 15 through the second on-off valve 22, the reforming furnace 11, the carbon monoxide converter 12, the exhaust heat recovery unit 19, and the water holder 13 in this order. Then, the crude gas is calorie-adjusted using the 13A gas and air by the calorie adjuster 15 to obtain 6C gas, and the 6C gas is supplied to the delivery holder 16 and stored therein (6C gas supply operation).
[0032]
The above-described crude gas injection operation, crude gas circulation operation, and 6C gas supply operation are sequentially repeated, and the 6C gas stored in the delivery holder 16 is appropriately delivered to the city.
[0033]
Further, when the 6C gas is full in the delivery holder 16 and the circulation operation of the crude gas has been performed for the above-described predetermined time, in order to avoid an increase in the amount of nitrogen gas in the circulated crude gas. Then, the operation of the city gas production plant 10 is stopped by stopping the circulation compressor 20. Thereafter, when the city gas production plant 10 is operated again, the reforming furnace 11 is brought into the operating state, the compressor for circulation 20 is started, and the crude gas circulation operation is first performed. Thereby, the crude gas is heated by the reforming furnace 11, and after a certain time has elapsed after the temperature of the crude gas supplied to the carbon monoxide converter 12 has become equal to or higher than the activation temperature of the carbon monoxide conversion catalyst. The 6C gas supply operation is performed.
[0034]
When the demand for 6C gas increases, the above-described crude gas injection operation, crude gas circulation operation, and 6C gas supply operation are not performed. In this case, the feed compressor 14 is started, the raw material supply valve 24 is opened, and the reforming furnace 11 continues to generate reformed gas while the raw material supply valve 24 is opened, and the carbon monoxide converter 12 generates crude gas. Then, the crude gas is led to the calorie controller 15 via the exhaust heat recovery device 19 and the water type holder 13 to be converted into 6C gas, and the 6C gas is stored in the delivery holder 16. Send out to the city.
[0035]
With the configuration described above, according to the above embodiment, the following effects (1) to (3) can be obtained.
(1) Regardless of whether or not 13A gas is supplied as a raw material to the reforming furnace 11 via the raw material supply valve 24, the reforming furnace 11 is brought into an operating state, and the 13A gas is supplied to the reforming furnace 11 When the crude gas is not supplied, the crude gas is circulated in the circulation path 17 including the reforming furnace 11, the carbon monoxide converter 12, the circulation holder 23, and the like. Since a high-temperature reformed gas or crude gas is supplied, the temperature of the carbon monoxide converter 12 can be maintained at the activation temperature of the carbon monoxide conversion catalyst. As a result, even when the production amount of the city gas (6C gas) by the city gas production plant 10 is small, immediately after the reforming gas starts to be supplied from the reforming furnace 11 to the carbon monoxide converter 12, Since the carbon monoxide converter 12 can satisfactorily reduce the carbon monoxide in the reformed gas, the carbon monoxide concentration in the produced 6C gas can be kept within a specified range.
[0036]
(2) The reformed gas or crude gas heated from the reforming furnace 11 is constantly supplied to the carbon monoxide converter 12, and the carbon monoxide converter 12 is maintained at the activation temperature of the carbon monoxide conversion catalyst. Therefore, an increase in cost can be avoided as compared with the case where the carbon monoxide converter 12 is heated by the heater heating equipment.
[0037]
{Circle around (3)} When the same crude gas is circulated in the circulation path 17 for a long time, the nitrogen gas N ₂ taken in from the air during the operation of the reforming furnace 11 increases in the crude gas, and The nitrogen gas concentration increases. However, in the city gas production plant 10, after a lapse of a predetermined time from the start of the circulation operation of the crude gas in the circulation path 17, the circulating crude gas is transferred from the circulation path 17 to the calorie controller 15, and thereafter, the reforming furnace A reformed gas is generated at 11, the reformed gas is converted to crude gas by the carbon monoxide converter 12, and the newly generated crude gas is introduced into the circulation holder 23 of the circulation path 17. Therefore, the nitrogen gas concentration in the crude gas circulated in the circulation path 17 can always be maintained within an allowable range, and 6C gas having a suitable composition can be produced.
[0038]
As described above, the present invention has been described based on the above embodiment, but the present invention is not limited to this.
For example, in the above-described embodiment, an example in which 6C gas as city gas is produced from crude gas has been described. However, the present invention may be applied to a hydrogen gas production plant that produces hydrogen (H ₂ ) gas. In this hydrogen gas production plant, the calorie adjuster 15 in the city gas production plant 10 is replaced with a PSA device, and the produced hydrogen gas is stored in the delivery holder 16.
[0039]
The PSA device is an abbreviation of a Pressure Swing Adsorption device, and removes methane, carbon dioxide and carbon monoxide in crude gas. This PSA apparatus is provided with a plurality of adsorption columns (4 to 10 columns) filled with an adsorbent which selectively adsorbs components other than hydrogen gas under high pressure and desorbs under reduced pressure. In addition to performing the cyclic operation in which the process, the desorption process, the replacement process, and the pressure increasing process are one cycle, the adsorption operation is continuously performed as a whole of the apparatus by shifting the cycle between the columns in time.
The 13A gas and air in the case of the calorie adjuster 15 are not supplied to the PSA device. This PSA device produces hydrogen gas having a purity of 99.99% or more by volume percentage from crude gas fed by the delivery compressor 14.
[0040]
In the hydrogen gas production plant according to the other embodiment, an operation in which the word of city gas or 6C gas is replaced with hydrogen gas in paragraph numbers (0029) to (0034), such as a crude gas circulation operation shown in FIG. Execute. As a result, according to this hydrogen gas production plant, the same effects as the effects (1) to (3) of the above embodiment, that is, in the paragraph numbers (0035) to (0037), the word of the city gas or 6C gas is replaced with hydrogen This has the effect of replacing the gas.
[0041]
【The invention's effect】
According to the gas production method according to the first to third aspects of the present invention, even if the production amount of the gas to be produced is small, the amount of carbon monoxide in the produced gas is regulated without increasing the cost. Can be kept within the range.
According to the gas production plant according to the invention as set forth in claims 4 to 6, even when the production amount of the gas to be produced is small, the amount of carbon monoxide in the produced gas is regulated without increasing the cost. Can be kept within the range.
[Brief description of the drawings]
FIG. 1 is a system diagram showing a city gas production plant to which an embodiment of a gas production plant according to the present invention is applied.
FIG. 2 is an operation diagram showing a crude gas press-in operation for press-in a crude gas into a circulation holder in the city gas production plant of FIG.
FIG. 3 is an operation diagram showing a crude gas circulation operation of circulating crude gas in a circulation path in the city gas production plant of FIG. 1;
FIG. 4 is an operation diagram showing a 6C gas supply operation of supplying a 6C gas to a delivery holder 2 by adjusting a calorific value of a crude gas in a circulation path in the city gas production plant of FIG. .
[Explanation of symbols]
10 City gas production plant (gas production plant)
Reference Signs List 11 reforming furnace 12 carbon monoxide converter 15 calorie controller 17 circulation path 20 circulation compressor 23 circulation holder 21 first on-off valve 22 second on-off valve 24 raw material supply valve

Claims (6)

A reforming furnace produces a reformed gas containing hydrogen and methane by performing a steam reforming reaction on hydrocarbons, and a shifter transforms carbon monoxide in the reformed gas into carbon dioxide to produce crude gas. Then, in a gas production method for producing a desired gas from the crude gas,
Irrespective of whether or not hydrocarbon is supplied as a raw material to the reforming furnace, the reforming furnace is in an operating state, and when the hydrocarbon is not supplied as a raw material to the reforming furnace, the reforming furnace is And circulating a crude gas in a circulation path comprising the above-mentioned transformer. After a lapse of a predetermined time from the start of the circulation operation of the crude gas in the circulation path, the crude gas is transferred from the circulation path,
2. The gas production method according to claim 1, wherein a reforming gas and a crude gas are generated by a reforming furnace and a shifter, respectively, and the crude gas is circulated again in the circulation path. 3. The gas production method according to claim 1, wherein the desired gas is city gas or hydrogen gas. A reforming furnace for producing a reformed gas containing hydrogen and methane by performing a steam reforming reaction on hydrocarbons, and a reformer for transforming carbon monoxide in the reformed gas into carbon dioxide to produce a crude gas. In a gas production plant that produces a desired gas from crude gas,
Regardless of whether or not hydrocarbons are supplied as a raw material to the reforming furnace, the reforming furnace is operated, and crude gas is circulated in a circulation path including the reforming furnace and the shift converter. A gas production plant characterized in that it is configured to obtain a gas. After a lapse of a predetermined time from the start of the circulation operation of the crude gas in the circulation path, the crude gas can be transferred from the circulation path,
5. The apparatus according to claim 4, wherein a reforming gas and a crude gas are generated by a reforming furnace and a converter, respectively, and the crude gas can be circulated again in the circulation path. Gas production plant. The gas production plant according to claim 4, wherein the desired gas is city gas or hydrogen gas.

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