JPH06305702A - Method for starting gas reformer - Google Patents

Abstract

PURPOSE:To remarkably lower the heating temp. of a start-up heater or to start a gas reformer without heating by supplying a gas contg. H2 and CO2 or CO to a first reforming tube along with steam when the reformer is started. CONSTITUTION:A gaseous mixture of hydrocarbons and steam is primarily reformed, an oxygen-contg. gas is added to partially oxidize the reformed gas which is then secondarily reformed, and the obtained high-temp. gas is used as a heat source for the primary reforming reaction. When the gas reformer is started, a gaseous mixture of H2 and CO2, or CO is introduced from a passage 1 and steam from a passage 2 to bring about methanation reaction in the primary reforming tube 5, and the temp. in the tube 5 is raised. Consequently, a start-up heater 3 is greatly reduced in size, and the time until the O2-contg. gas is introduced is significantly reduced. Further, since the temp. of the tube 5 is raised, the tube 5 need not be heated by the gas from a secondary reforming part 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of starting an apparatus for producing a reformed gas from a hydrocarbon such as methane or natural gas. Specifically, the primary reforming reaction is carried out with a mixed gas of hydrocarbon and steam, and then the oxygen-containing gas is added to carry out the secondary reforming reaction after partial oxidation. The present invention relates to a method for starting a gas reforming device used in.

[0002]

2. Description of the Related Art Since hydrogen is used in large quantities as future clean energy and methanol is used as a cheap fuel that is low in pollution and is easy to transport, it is required to develop a large-scale apparatus for processing a large amount of gas with high thermal efficiency. ing.

As a gas reforming apparatus in a large-scale apparatus, a system combining steam reforming and partial oxidation has recently attracted attention. This is a mixture of natural gas and water vapor to carry out a primary reforming reaction, then oxygen is added to carry out partial oxidation and secondary reforming reaction, and the obtained high temperature gas is used as a heating source for the primary reforming reaction. It is a thing. According to this method, high-pressure reformed gas can be obtained without supplying heat from the other, and therefore high-pressure hydrogen can be easily produced. Further, in a methanol or ammonia production apparatus, a synthetic reaction can be carried out suddenly without using a reformed gas compressor to increase the pressure. Furthermore, since it is not necessary to use a reforming furnace that heats the reaction tube externally, and the reforming reaction is performed under high pressure, it is easy to upsize the apparatus. In this way, a self-heat exchange type reactor that performs the primary reforming reaction and the secondary reforming reaction
(Hereinafter referred to as adiabatic reformer)
Specific structures are shown in JP-A Nos. 60-186401, 1-261201, and 2-18303.

[0004]

When activating such an adiabatic reformer apparatus, generally, a startup heating furnace (hereinafter referred to as a "start-up heater") specially installed is used to heat steam to perform primary After being supplied to the reforming reaction tube and introducing hydrocarbon (natural gas or the like) to perform the primary reforming reaction, oxygen is introduced into the combustion chamber to perform partial oxidation. In this case, in order to ignite the primary reformed gas, 600
Since a temperature of about ℃ is required, it is necessary to heat the start-up heater to about 700 to 800 ℃. For this reason, the start-up heater becomes considerably large, and the heat transfer tube of the start-up heater requires a highly heat-resistant material, so that the equipment cost is high. It also takes a very long time (typically 24
(More than time), the amount of energy loss due to the use of steam and fuel at startup becomes large.

[0005]

Means for Solving the Problems As a result of earnest studies on a method for starting an adiabatic reformer having the above-mentioned problems, the inventor has found that hydrogen, carbon dioxide gas or carbon monoxide, or methanol vapor is used as a primary gas instead of hydrocarbon at the time of starting. By introducing it into the reforming reaction tube and introducing it into the combustion chamber after the methanation reaction, the heating temperature in the start-up heater can be remarkably lowered, and in some cases it can be started without using the start-up heater. The present invention has been achieved by finding out that it is also possible to perform the operation at the time of start-up and that the amount of energy loss at the time of start-up can be reduced.

That is, according to the present invention, a primary reforming reaction is carried out with a mixed gas of hydrocarbon and steam, and then an oxygen-containing gas is added to carry out a secondary reforming reaction after partial oxidation. In a gas reformer used as a heating source for a reforming reaction, a method for starting a gas reformer characterized in that a gas containing hydrogen and carbon dioxide or carbon monoxide together with steam is supplied to a primary reforming reaction tube. is there.

Since a gas containing hydrogen and carbon dioxide or carbon monoxide is obtained by a reforming or decomposition reaction of methanol, a method of supplying methanol can be adopted. When starting the adiabatic reformer, if the gas from the secondary reforming catalyst layer is allowed to pass through the outside of the primary reforming reaction tube (side of the shell) as it is, the primary reforming reaction tube outlet (combustion chamber inlet) gas will reach a specified temperature. It takes a considerably long time to raise the temperature. That is, in this case, the primary reforming reaction tube is cooled by the gas of the temperature lowered by passing through the secondary reforming catalyst layer and the like, and the refractory material is attached to the inside of the shell of the heat exchange section. Since its heat capacity is large, it takes a considerably long time to raise the temperature to a predetermined temperature. Therefore, if the gas from the secondary reforming catalyst layer is discharged to the outside of the adiabatic reformer without being supplied to the outside of the primary reforming reaction tube at startup, the time required to raise the temperature to a predetermined temperature is significantly increased. As a result, the amount of energy loss at startup is reduced.

In the gas reformer used in the present invention, the primary reforming reaction is carried out by introducing the mixed gas of the raw material hydrocarbon and steam into the primary reforming reaction tube during normal operation. Natural gas containing methane as a main component is usually used for this hydrocarbon, but LPG, naphtha, etc. are also used depending on the site conditions.
Further, in order to improve the basic unit of the raw material, mixing of the barge gas from the synthesis system together with the hydrocarbon is performed. A nickel-based catalyst is usually used as the primary reforming catalyst, but it is necessary to desulfurize the hydrocarbon as a raw material in advance in order to avoid a decrease in the activity of the reforming catalyst. Steam is used so that the steam / carbon ratio of the mixed gas of hydrocarbon and steam is usually about 2.0 to 3.6, which is preheated to 400 to 600 ° C and supplied to the reactor.

The primary reforming reaction is carried out while being heated by the high temperature secondary reforming gas. The primary reforming reaction is pressure 50
The reaction is carried out at ~ 150kg / cm ² G, temperature 500 ~ 800 ℃, and 700 ~ 800 ℃ at the outlet of the primary reforming reaction tube. In the adiabatic reformer, the pressure difference between the inside and outside of the primary reforming reaction pipe is small, so the reforming reaction pressure can be increased, and high-pressure hydrogen can be easily obtained as described above, without using a reforming gas compressor. It can be used for methanol or ammonia synthesis reaction. Also, it is easy to increase the size.

The gas exiting the primary reforming reaction tube is then mixed with the oxygen-containing gas in the combustion chamber and a partial oxidation reaction is carried out. As the oxygen-containing gas, high-purity oxygen gas is usually used in the case of hydrogen production or methanol production, and air or oxygen-enriched air is used in the case of ammonia production. The amount of the oxygen-containing gas used varies depending on the composition of the raw material hydrocarbon, the supply temperature, etc., and is determined by the heat balance of the adiabatic reformer. If necessary, a part of the raw material hydrocarbons may be introduced into the combustion chamber together with the oxygen-containing gas, or a part of the steam may be introduced into the combustion chamber to control the temperature of the combustion chamber and prevent carbon deposition. Is done. The oxygen-containing gas and steam introduced into these combustion chambers are preferably preheated and supplied as much as possible in view of the heat balance of the adiabatic reformer, and usually supplied at 200 to 300 ° C.

The temperature of the combustion chamber is usually 1300 to 1500 ° C., although it varies depending on the supply temperature and the supply amount of the oxygen-containing gas. The partial combustion gas from the combustion chamber then undergoes a secondary reforming reaction. A nickel-based or platinum-based catalyst is usually used as the secondary reforming catalyst, and the reaction is performed at 900 to 1100 ° C.
This high-temperature secondary reformed gas is used as a heat source for the primary reforming reaction, then exits the adiabatic reformer and undergoes various heat recovery and is then cooled to produce hydrogen, methanol, ammonia, etc. Used in syngas for.

At the time of starting the adiabatic reformer as described above in the present invention, a mixed gas of hydrogen and carbon dioxide or carbon monoxide is used in place of the raw material hydrocarbon. By introducing hydrogen and carbon dioxide or carbon monoxide into the nickel-based catalyst used for the primary reforming reaction, the methanation reaction shown by the following equations (1) and (2) occurs, and the primary heat is changed by the heat of reaction. The temperature in the quality reaction tube rises. At this time, the shift reaction of (3) also occurs, and it is considered that a state close to equilibrium is obtained.

[0013]

Embedded image CO ₂ + 4H ₂ → CH ₄ + 2H ₂ O + 39.4 kcal / mol (1) CO + 3H ₂ → CH ₄ + H ₂ O + 49.3 kcal / mol (2) CO + H ₂ O = CO ₂ + H ₂ + 9.8 kcal / mol (3)

It should be noted that the reaction gas from the primary reforming reaction tube must be heated to the combustion chamber at an autoignition temperature (about 600 ° C.) or higher.
In order to avoid carbon deposition and supply at such a temperature, it is necessary to introduce hydrogen and carbon dioxide or carbon monoxide together with steam into the primary reforming reaction tube. The amount of water vapor varies depending on the composition and temperature of the mixed gas of hydrogen and carbon dioxide or carbon monoxide to be introduced, and the reaction temperature and pressure, but it is preferably about 1 to 2 times the volume of the mixed gas.
The temperature to be supplied to the primary reforming reaction tube depends on the activity of the primary reforming catalyst, but it is necessary to consider the above reaction amount and the heat balance of the reaction gas, and it is usually about 250 to 450 ° C.

Such a mixed gas of hydrogen and carbon dioxide or carbon monoxide can be obtained by the following methanol reforming reaction (4) or methanol decomposition reaction (5).

CH ₃ OH + H ₂ O → CO ₂ + 3H ₂ − 11.8 kcal / mol (4) CH ₃ OH → CO + 2H ₂ − 21.7 kcal / mol (5)

In the methanol reforming reaction (4), a copper, chromium, manganese catalyst (Japanese Patent Publication No. 54-11274), a copper, zinc, aluminum catalyst (Japanese Patent Laid-Open No. 46-47281) and the like are used, and the temperature is generally The reaction is carried out at 180 to 350 ° C and a pressure of 1 to 30 kg / cm ² G. Further, in the methanol decomposition reaction of (5), copper, nickel, aluminum catalyst (JP-A-52-27085), copper, zinc, nickel catalyst (JP-A-62-49945), etc. are used,
The reaction is performed at almost the same temperature and pressure as in (4).

In the present invention, a catalyst that causes a methanol reforming reaction or a decomposition reaction as described above is installed at the upper portion (inlet portion) of the primary reforming reaction tube, and methanol is introduced at startup.
It is also possible to generate hydrogen and carbon dioxide gas or carbon monoxide by the reaction of (4) or (5), and heat by the methanation reaction of (1) or (2). The reaction of producing methane from methanol is known as a method for producing an alternative natural gas or city gas, as described in, for example, Japanese Patent Application Laid-Open No. 49-120902, and such a catalyst is similarly installed. It can also be reacted. When methanol is used as the raw material, the steam used is 4 to 5 times that of methanol, and the inlet temperature of the primary reforming reaction tube is 600 to 650.
It is necessary to set the temperature to about ℃.

Next, the present invention will be described with reference to the drawings. Figure 1
[Fig. 6] is an explanatory view of a flow at the time of starting the heat insulation reformer device, and shows an example of a case where an integrated heat insulation reformer device is used. In the conventional adiabatic reformer system, the starting hydrocarbons and steam are introduced into the start-up heater 3 from channel 1 and channel 2, respectively, and the heated gas is installed in the heat exchange section (primary reforming reaction section) 4. Into the primary reforming reaction tube 5.

The primary reforming reaction tube 5 is filled with a primary reforming catalyst, and the primary reforming reaction is carried out in the reaction tube during normal operation. The obtained primary reformed gas is mixed with the oxygen-containing gas from the flow path 6, is partially oxidized in the combustion chamber 7, and is then introduced into the secondary reforming reaction section 8. The secondary reforming reaction section 8 is filled with the secondary reforming catalyst 9 to carry out an adiabatic reaction. The obtained high temperature secondary reformed gas is introduced to the body side of the heat exchange section 4 and used as a heat source for the primary reforming reaction.

This primary reforming reaction is an endothermic reaction and is heated by the high temperature secondary reforming gas by the above flow,
The oxygen-containing gas cannot be introduced unless the temperature of the primary reformed gas exceeds the self-ignition temperature (about 600 ° C) in the combustion chamber 7 at startup. Therefore, in the conventional adiabatic reformer apparatus, steam is first heated to about 700 to 800 ° C by the start-up heater 3 and introduced into the primary reforming reaction tube 5, and then the secondary reforming reactor 8 is passed through the shell of the primary reforming reactor 4. After the primary reforming reaction tube 5 is sufficiently heated by this steam introduced on the side, the raw material hydrocarbons are introduced to perform the primary reforming reaction, and the obtained gas has reached the self-ignition temperature sufficiently. After confirming that, the oxygen-containing gas is introduced.

In the conventional method for starting the adiabatic reformer apparatus, usually, an inert gas is first introduced into a start-up heater to ignite and heat it, and after reaching a temperature at which steam does not condense, the steam is switched to 700 to 800 ° C. Needs to be heated to a degree. The heating rate of the startup heater 3 is 30
Since it is limited to about ℃ / H, it takes about 10 hours to switch to steam, and more than one day is required to heat the material to 700 to 800 ℃ and introduce the raw material hydrocarbons. Since it takes several hours before the state of being able to be introduced, the start-up time is very long, and the amount of energy lost due to the use of the fuel for the start-up heater, hydrocarbons and steam of the raw material during that time is very large.

In the present invention, when starting, a mixed gas of hydrogen and carbon dioxide gas or carbon monoxide is introduced from channel 1 and steam is introduced from channel 2 in place of the raw material hydrocarbon, and the primary reforming reaction tube is introduced.
The temperature of the primary reforming reaction tube is raised by carrying out the methanation reaction in the reactor 5. This significantly reduces the start-up heater and greatly shortens the time until the oxygen-containing gas is introduced. That is, the temperature to be heated by the start-up heater 3 may be the start temperature of the methanation reaction (about 300 ° C), and after the start of the methanation reaction, the temperature of the primary reforming reaction tube 5 rises due to the adiabatic reaction, so the secondary reforming reaction It is not necessary to heat the primary reforming reaction tube 5 with the gas from the reaction section 8, and therefore the gas from the secondary reforming reaction section 8 does not pass through the heat exchange section 4 and is discharged in the method of the present invention. Eject from tube 10.

FIG. 2 is an explanatory diagram showing a flow in the case of producing a mixed gas of hydrogen and carbon dioxide or carbon monoxide at the time of start-up by a methanol reforming or decomposition reactor. Methanol, which is a raw material of the mixed gas of hydrogen and carbon dioxide or carbon monoxide, is introduced into the methanol reforming reactor or the methanol decomposition reactor 12 through the channel 11. Since the methanol reforming reaction and the methanol decomposition reaction are endothermic reactions, a heating medium boiler 13 is usually installed, and a heating medium circulating pump 14 introduces a high temperature heating medium into the reactor to heat the reaction tube installed inside. To do.

In FIG. 2, when a methanol reforming reactor is used, steam is introduced from the channel 15 because steam is used in the reforming reaction, and when a methanol decomposition reactor is used, steam is introduced from the channel 16. Will be introduced. The mixed gas of hydrogen and carbon dioxide or carbon monoxide from the methanol reforming reactor or the methanol decomposition reactor 12 is introduced into the start-up heater 3 via the flow path 17. The flow after the start-up heater 3 is the same as that in FIG. 1, and the start-up heater can be selected by suitably selecting the operating conditions of the methanol reforming reactor or the methanol decomposition reactor 12.
In some cases, 3 may not be needed.

1 and 2, the primary reforming reaction section 4, the combustion chamber 7 and the secondary reforming reaction section 8 are shown as an integrated unit. The method of the invention can be carried out. In addition, as described above, when a catalyst for the methanol reforming or decomposition reaction or the reaction for producing methane from methanol is installed in the upper part of the primary reforming reaction tube 5 to carry out each reaction, in FIG. Methanol vapor will be introduced from here. Since the start-up heater of the conventional adiabatic reformer has a high heating temperature, a combustion furnace is generally used, but in the case of the method of the present invention, this is used as a heat exchanger for high pressure steam, or a methanol reforming reactor or a methanol decomposition reactor. The heat medium used in the above can also be used as the heat source.

[0026]

EXAMPLES Next, the present invention will be described more specifically by way of examples. However, the present invention is not limited to these examples.

Comparative Example 1 The adiabatic reformer reactor shown in FIG. 1 was started up by a conventional method. This reactor is an adiabatic reformer test device, and the primary reforming reaction tube (inner diameter 48 mm,
19 pieces (8 m long) are installed, and natural gas (composition CH ₄ 86.9%, C ₂ H ₆ 7.6%, C ₃ H ₈ 3.0%) at a pressure of about 80 kg / cm ² G
, C ₄ H ₁₀ 1.4%, C ₅ H ₁₂ 0.6%, CO ₂ 0.5%, N ₂ 0.1%) to obtain a gas for hydrogen production.

The starting operation of the adiabatic reformer reactor is as follows. First, nitrogen gas is introduced into the start-up heater and ignited.
Heated to 300 ° C at ° C / H. Next, steam at 300 ° C 137.5
kg-mol / H was introduced at a pressure of the primary reforming reaction tube of 20 kg / cm ² G, heated to 800 ° C. at the same heating rate, and natural gas was introduced. Since the gas discharge pipe 10 of FIG. 1 is not used, the introduced nitrogen gas, water vapor and natural gas pass through the combustion chamber and the secondary reforming catalyst layer and all pass through the shell side of the primary reforming reaction pipe. As a result, it took about 30 hours from the introduction of water vapor until the primary reformed gas introduced into the combustion chamber reached the ignition temperature (590 ° C). Table 1 shows the steam and natural gas flow rates used at startup, the combustor inlet gas flow rate, and the operating conditions of the start-up heater.

Example 1 In the same adiabatic reformer reactor as in Comparative Example 1, a starting operation was carried out using a mixed gas of hydrogen and carbon dioxide according to the method of the present invention. Table 1 shows the main operating conditions. During the startup operation, the gas from the secondary reforming catalyst layer was released from the system through the gas release pipe 10. In this case, the outlet temperature of the start-up heater can reach the ignition temperature (590 ° C) of the primary reformed gas by performing the methanation reaction at 413 ° C. After introducing steam into the adiabatic reformer reactor, this ignition is performed. It took about 4 hours to reach the temperature.

Example 2 In an adiabatic reformer reactor similar to Comparative Example 1, FIG.
The starting operation was performed using the gas obtained by the methanol reforming reaction according to the flow of 1. Table 1 shows the main operating conditions. For the methanol reforming reaction, pressure 20 kg / cm ² G, temperature 3
The reaction was performed at 00 ° C., and the gas from the secondary reforming catalyst layer was released from the system through the gas release pipe 10 during the startup operation. Table 1 shows the main operating conditions. In this case, the ignition temperature of the primary reformed gas (590 ° C) can be reached by performing the methanation reaction with the outlet temperature of the startup heater set at 380 ° C, and after introducing steam into the adiabatic reformer reactor, this ignition is performed. It took about 3.5 hours to reach the temperature.

Example 3 In an adiabatic reformer reactor similar to Comparative Example 1, FIG.
A starting operation was performed using the gas obtained by the methanol decomposition reaction according to the flow of 1. Table 1 shows the main operating conditions. For the methanol decomposition reaction, pressure 20 kg / cm ² G, temperature 2
The reaction was carried out at 80 ° C, and the ignition temperature of the primary reformed gas was reached by the obtained methanation reaction of methanol decomposition, so that the startup operation could be performed without using the startup heater. During the startup operation, the gas from the secondary reforming catalyst layer was released from the system through the gas release pipe 10. Table 1 shows the main operating conditions. The time required from the introduction of steam and methanol decomposition gas to the adiabatic reformer reactor until the ignition temperature was reached was about 3 hours.

[0032]

[Table 1]

Example 4 In the same adiabatic reformer reactor as in Comparative Example 1, methanol was supplied to the reactor to carry out a starting operation, and during the starting operation, the gas from the secondary reforming catalyst layer was released from the gas releasing pipe 10. Before being introduced into the outside of the primary reforming reaction tube, it was released outside the system. Table 1 shows the main operating conditions. In this case, in order for the primary reformed gas to reach the ignition temperature (590 ° C), it is necessary to supply methanol and steam at about 623 ° C, and after reaching the ignition temperature after introducing steam into the adiabatic reformer reactor. It took about 12 hours.

[0034]

By starting the adiabatic reformer by the method of the present invention, the methanation reaction is carried out at a low temperature supplied to the primary reforming reaction tube, so that the heating temperature of the start-up heater is remarkably lowered and the start-up heater is started up. It is also possible to perform the starting operation without using a heater.
This not only significantly reduces the construction cost of the start-up heater, but also significantly shortens the start-up time of the adiabatic reformer and reduces the energy loss amount required for start-up operation.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a flow at startup of an adiabatic reformer device, showing an example of a case where an integrated adiabatic reformer device is used.

FIG. 2 is an explanatory diagram showing a flow in the case of producing a mixed gas of hydrogen and carbon dioxide gas or carbon monoxide at the time of startup by a methanol reforming reactor or a methanol decomposition reactor.

[Explanation of symbols]

1 Supply channel for mixed gas of hydrogen and carbon dioxide gas or carbon monoxide at startup, or methanol vapor (hydrocarbon supply channel during normal operation) 2 Steam supply channel 3 Start-up heater 4 Heat exchange section (primary Reforming reaction part) 5 Primary reforming reaction pipe 6 Oxygen-containing gas supply flow path 7 Combustion chamber 8 Secondary reforming reaction part 9 Secondary reforming catalyst layer 10 Gas discharge pipe from secondary reforming reaction part 11 Methanol Supply channel 12 Methanol reforming reactor or methanol decomposition reactor 13 Heat medium boiler 14 Heat medium circulation pump 15 Steam supply channel (during methanol reforming reaction) 16 Steam supply channel (during methanol decomposition reaction)

Claims (5)

[Claims] 1. A primary reforming reaction using a mixed gas of hydrocarbon and water vapor, and then oxygen-containing gas is added to carry out a secondary reforming reaction after partial oxidation, and the resulting high temperature gas is subjected to a primary reforming reaction. In a gas reformer used as a heating source for a gas reformer, a gas containing hydrogen and carbon dioxide or carbon monoxide is supplied to a primary reforming reaction tube together with steam, 2. A method for starting a gas reforming apparatus according to claim 1, wherein a gas containing hydrogen and carbon dioxide gas obtained by a steam reforming reaction of methanol is used. 3. A method for starting a gas reforming apparatus according to claim 1, wherein a gas containing hydrogen and carbon monoxide obtained by a decomposition reaction of methanol is used. 4. A primary reforming reaction using a mixed gas of hydrocarbon and water vapor, and then oxygen-containing gas is added to carry out a secondary reforming reaction after partial oxidation, and the resulting hot gas is subjected to a primary reforming reaction. In a gas reformer used as a heating source of a gas, a method for starting a gas reformer characterized by supplying a gas containing methanol and steam to a primary reforming reaction tube 5. A primary reforming reaction using a mixed gas of hydrocarbon and water vapor, then oxygen-containing gas is added to carry out a secondary reforming reaction after partial oxidation, and the resulting high temperature gas is subjected to a primary reforming reaction. In a gas reformer used as a heating source for a gas reformer, the gas from the secondary reforming catalyst layer is released to the outside of the system at the time of start-up.