JPH04349102A - Method for steam-reforming hydrocarbon - Google Patents

Abstract

PURPOSE:To produce a reformed gas contg. hydrogen and carbon oxides by the reaction of hydrocarbons with steam with high heat energy efficiency while stably and easily operating the reactor. CONSTITUTION:A gaseous mixture of hydrocarbons and steam is primarily reformed by using plural heat exchanger-type reformers, and the primarily reformed gaseous reactant is secondarily reformed with an internal combustion reactor-type reformer in the presence of oxygen and/or air or by using a heat exchanger. A part of the heat to be consumed in the heat exchanger-type reformer in the primary stage is replenished with the sensible heat of the secondarily reformed gas, and the remainder is replenished with the sensible heat of the compressed air. The heat to be consumed in the secondary stage is replenished with the sensible heat of the compressed air.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steam reforming method (steam reforming) for producing a reformed reaction gas containing hydrogen and carbon oxides by reacting hydrocarbons with steam.

[Prior art and its problems]

[0002] The production of a reformed reaction gas containing hydrogen and carbon oxides (CO2 and CO) by reacting hydrocarbons with steam is widely known as steam reforming. Conventionally, this steam reforming method generally uses a steam reforming furnace formed by standing up a large number of catalyst tubes filled with catalyst in a combustion furnace, and the preheated fuel and This is carried out by circulating a gas mixture with steam and heating the outer wall of the catalyst tube with a burner attached to a combustion furnace to supply the heat necessary for the reforming reaction. This steam reforming method is carried out by combining the steam reforming furnace with an appropriate secondary reformer for the purpose of producing ammonia synthesis gas, methanol synthesis gas, hydrogen production, etc. has been done. For example, when producing ammonia synthesis gas, an internal combustion reactor type reformer is combined as a secondary reformer with the steam reformer (primary reformer), and from the primary reformer The obtained primary reformed reaction gas is supplied to the secondary reformer together with pressurized air, where the primary reformed reaction gas and pressurized air are mixed, and the oxygen in the air is transferred to the primary reformed reaction gas. This reacts with the combustible components of the reactor to replenish the amount of heat required for the reaction in the secondary reformer, as well as to obtain the nitrogen gas necessary for the subsequent ammonia synthesis process. In addition, when producing methanol synthesis gas, as in the case of obtaining the ammonia synthesis gas, an internal combustion reactor-type secondary reformer is combined with the primary reformer, and the primary reformer is The primary reformed reaction gas obtained from the reactor is supplied to the secondary reformer together with oxygen, and this oxygen is mixed and reacted with combustible components in the reaction gas in the secondary reformer. supplies the amount of heat required for the reaction. in this case,
In the secondary reformer, part of the excess hydrogen in the reaction gas in the subsequent methanol synthesis step is removed by reacting with oxygen, and at the same time, the ratio of CO and CO2 is adjusted to the ratio desired for methanol synthesis. There is.

However, in the combination of the primary reformer and the secondary reformer as described above, the temperature of the secondary reformed reaction gas exiting the secondary reformer is high and contains a large amount of sensible heat. The energy efficiency of the entire device system is poor. Therefore, in recent years, in order to effectively utilize the large amount of sensible heat possessed by the reaction gas exiting the secondary reformer and improve the energy efficiency of the equipment system, multiple reformers have been installed in the vertical reaction vessel as the primary reformer. The use of a heat exchanger type reformer with upright catalyst tubes has come into use.

However, the steam reforming method using a conventional system in which a secondary reformer is combined with the heat exchanger type primary reformer described above is still not satisfactory. In this equipment system, it is extremely difficult to replenish the reaction heat required in the primary reformer using only the sensible heat possessed by the secondary reformed reaction gas that exits the secondary reformer; , excess air and/or oxygen is supplied to the secondary reformer, causing the combustible components in the primary reformed reaction gas from the primary reformer to react with oxygen, and the heat generated at that time causes the secondary reforming to occur. The reality is that it is replenishing the reaction heat in the vessel. However, supplying such excess air and/or oxygen to replenish the heat of reaction presents several disadvantages. For example, if excessive air is supplied in a reforming method to obtain gas for ammonia synthesis, excess nitrogen will be supplied to the subsequent ammonia synthesis process, so it is necessary to remove the excess nitrogen. In addition, there are further problems such as the useful hydrogen in the reformed gas reacting with excess oxygen and being consumed to a large extent. In addition, in reforming methods aimed at producing alcohol synthesis gas or hydrogen gas, if excess oxygen is supplied, the useful hydrogen in the reformed reaction gas will react with the excess oxygen and be significantly consumed. There is a problem. Furthermore, supplying excess air or oxygen has the problem that extra power is consumed for compression to obtain the reforming reaction pressure. As described above, the conventional steam reforming method using a device system that combines a heat exchange type reformer and an internal combustion reactor type reformer is still unsatisfactory and leaves room for improvement.

[0005]

[Problems to be Solved by the Invention] The present invention aims to solve the above-mentioned problems found in the conventional steam reforming method that combines a heat exchanger type reformer and an internal combustion reactor type reformer. That is the issue.

[0006]

[Means for Solving the Problems] The present inventors have conducted extensive research to solve the above problems, and as a result, have completed the present invention.

That is, according to the present invention, there is a primary reforming step in which a mixed gas of hydrocarbon and steam is subjected to a reforming reaction using a plurality of heat exchanger type reformers, and It consists of a secondary reforming process in which a plurality of primary reformed reaction gases are subjected to a reforming reaction using an internal combustion reactor type reformer in the presence of oxygen and/or air, and the plurality of primary reforming reaction gases used in the primary reforming process are Of the amount of heat consumed in the heat exchanger type reformer, part of it is replenished by the sensible heat possessed by the secondary reformed reaction gas obtained in the secondary reforming process, and the remainder is replenished by the sensible heat possessed by the secondary reformed reaction gas obtained in the secondary reforming step, and the remainder is Provided is a method for steam reforming hydrocarbons characterized by replenishment using retained sensible heat.

Further, according to the present invention, there is provided a primary reforming step in which a mixed gas of hydrocarbons and steam is subjected to a reforming reaction using a heat exchanger type reformer, and a primary reforming step obtained in the primary reforming step. It consists of a secondary reforming process in which the reformed reaction gas undergoes a reforming reaction using a heat exchanger type reactor, and the amount of heat consumed in the heat exchanger type reformer used in the primary reforming process is converted into the secondary reforming process. The amount of heat consumed in the heat exchanger type reformer used in the secondary reforming process is replenished by the sensible heat possessed by the compressed heated air. A method for steam reforming hydrocarbons is provided.

In the present invention, a heat exchanger type reformer is used as the primary reformer. This heat exchanger type reformer has a structure in which a large number of catalyst tubes are installed upright in a reaction vessel, and heated gas flows through the catalyst tubes while being in contact with the catalyst tubes, and is a conventionally known type. The catalyst used in this reformer is, for example, one in which nickel is supported on a heat-resistant carrier such as magnesia or alumina.

[0010] Furthermore, in the present invention, an internal combustion reactor type reformer or a heat exchanger type reformer is used as the secondary reformer. It has a gas combustion reaction section in which the gas subjected to the combustion reaction flows through a reforming catalyst layer disposed in the container, and is a conventionally known structure.

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a flow sheet for a steam reforming method using an apparatus system in which a plurality of heat exchanger type primary reformers are combined with an internal combustion reactor type secondary reformer. In FIG. 1, 1 and 2 are heat exchanger type reformers, 3 is an internal combustion reactor type reformer, 4 is a heat exchanger, 5 is a compressor, and 6 is a heat exchanger type reformer.
7 is a combustor, and 8 is a gas turbine. The mixed gas of hydrocarbon and steam is sent through line 10 to heat exchanger 4, where it is preheated to 400-650°C, and then extracted through line 11, and a part of it is sent through line 12. through line 13 to the first heat exchanger type primary reformer 1, and the remainder is sent through line 13 to the second heat exchanger type primary reformer 2.
sent to. The proportion of hydrocarbons in the steam/hydrocarbon gas mixture is usually H2O/carbon in a molar ratio of 1.5 to 6.
The ratio is such that it becomes 0. On the other hand, compressor 5 has 6 to 18
Air compressed to atmospheric pressure passes through line 14 to first combustor 6
After being heated to 900 to 1300° C., it is sent to the first primary reformer 1 through a line 15. The compressed air in the first combustor 6 is heated by causing a gaseous or liquid fuel introduced through the line 16 to undergo a combustion reaction with a part of the compressed air, and using the combustion heat generated at that time. do. The first primary reformer 1 has a large number of catalyst tubes, and the hydrocarbon/steam mixture gas introduced into the reformer 1 through the line 12 flows downward inside the catalyst tubes. On the other hand, the compressed heated air introduced into the reformer 1 through the line 15 flows upward while contacting the outer wall of the catalyst tube, so that the hydrocarbon/steam mixed gas flowing inside the catalyst tube is 600 to 900 C. to undergo a reforming reaction, producing a primary reformed reaction gas containing hydrogen and carbon oxides, as well as unreacted fuel. The conversion rate of hydrocarbons in this reformer 1 is usually 20 to 60 mol%.

The temperature of the reformed gas leaving the first primary reformer 1 is usually 600 to 900°C, and this reformed gas passes through the line 17 to the internal combustion reactor type secondary reformer. is introduced into the combustion reaction section a of the vessel 3. On the other hand, the temperature of the compressed air that exits the first primary reformer 1 is usually 500 to 700°C, and this compressed air passes through the line 18 and further heat exchanger 4.
After passing through, it is introduced into the second combustor 7, where the line 2
The fuel introduced through 0 is combusted and heated to 900-1300°C by the heat of combustion. This heated compressed air is introduced into the gas turbine 8, where it is expanded to near atmospheric pressure, and the expansion force at that time drives the compressor 5 to compress the air introduced from the line 21. In addition, the surplus expansion energy at this time is used to rotate a generator to generate electricity. The temperature of the air leaving the gas turbine 8 is between 400 and 700°C, and this heated air is passed through a line 22 for its heat recovery, e.g. steam, air, hydrocarbons, which are introduced into this equipment system. It is used for preheating, etc., or for generating steam, and then released into the atmosphere at 140 to 250°C. In the present invention, when there are a plurality of primary reformers similar to the primary reformer 1 heated by compressed air, the compressed air heated by the second combustor 7 is sequentially distributed through the primary reformers. Let me,
Each primary reformer can also be heated. In this case, the compressed air exiting each primary reformer is heated in the combustor and introduced into the next primary reformer in the same manner as described above, and the compressed air exiting the last primary reformer is After heating this in a combustor, it is introduced into the gas turbine 8.

The hydrocarbon/steam mixture gas introduced into the second primary reformer 2 through line 13 is now subjected to a secondary reforming reaction which is withdrawn from the secondary reformer 3 through line 25. It is heated by the sensible heat of the gas and undergoes a reforming reaction,
The primary reformed reaction gas generated in the primary reformer 2 is introduced into the combustion reaction section a of the secondary reformer 3 through a line 26. The temperature of the secondary reformed reaction gas exiting the secondary reformer 3 and passing through line 25 is typically 900 to 1100°C; The temperature of the secondary reformed reaction gas is 500 to 800°C, and this secondary reformed reaction gas is sent to a heat recovery system. Further, the temperature of the primary reformed reaction gas from the second primary reformer 2 passing through the line 26 is 600 to 900°C. This primary reformed reaction gas contains hydrogen and carbon oxides, and further contains unreacted fuel. The conversion rate of hydrocarbons is usually 20 to 60 mol%
It is. In the secondary reformer 3, the primary reformers from the first primary reformer 1 and the second primary reforming reactor 2 pass through lines 17 and 26 to the upper combustion reaction section a. The reactant gas is introduced, as well as air and/or oxygen optionally in a mixture with steam through line 28. The temperature of this air and/or oxygen is usually 400 to 700°C. This secondary reformer 3
In the combustion reaction part a, the combustible components (hydrogen, carbon monoxide, hydrocarbons) contained in the primary reformed reaction gas are
An exothermic reaction between the gas and the air and/or oxygen occurs to replenish the amount of heat required for the reforming reaction. At the same time, a reforming reaction between steam and hydrocarbons also occurs. The temperature of the reaction gas obtained in the combustion reactor section a of the secondary reformer 3 is usually 1000
~1300° C., and this reaction gas flows through the catalyst tube of the catalytic reaction section b in the lower part thereof, and then is sent to the second primary reformer 2 as a heating medium through the line 25.

In the combustion reaction section a of the secondary reformer 3,
Most of the unreacted hydrocarbons in the primary reforming reaction gas react with the steam, and in the lower catalytic reaction section b, a reaction occurs so that an equilibrium state of the reforming reaction is obtained, and the secondary reforming In the outlet gas of vessel 3, the reforming reaction has almost reached an equilibrium state. The steam reforming method according to the flow sheet shown in FIG. 1 described above is suitable as a method for producing a reformed reaction gas for synthesizing ammonia and methanol. That is, when obtaining a reformed reaction gas for ammonia synthesis, air is introduced into the combustion reaction section a of the secondary reformer 3 to obtain a reformed reaction gas containing nitrogen as well as hydrogen and carbon oxides. In addition, when obtaining a reformed reaction gas for methanol synthesis, oxygen is introduced into the combustion reaction section a of the secondary reformer 3 to produce a reformed reaction gas containing hydrogen and carbon oxides but not nitrogen. obtain. Various changes are possible in the steam reforming method shown in FIG. 1. For example, the number of primary reformers can be 3 to 5, and the number of secondary reformers can also be 2 to 5. There can be three pieces.

FIG. 2 shows a flow sheet of a steam reforming method using an apparatus system in which a heat exchanger type primary reformer is similarly combined with a heat exchanger type secondary reformer. In Figure 2, 3
Reference numeral 1 indicates a heat exchanger type primary reformer, and 32 indicates a heat exchanger type secondary reformer. Note that in the symbols shown in FIG. 2, the same symbols as those shown in FIG. 1 have the same meanings. The hydrocarbon/steam mixture gas passing through line 10 is preheated to 400-650°C through heat exchanger 4, and then introduced through lines 11 and 13 to primary reformer 31, where the obtained The primary reformed reaction gas is sent to the secondary reformer 32 through line 26. The air compressed by the compressor 5 is
In a manner similar to that shown in FIG. , line 1
8 and undergoes processing similar to that shown in FIG. The primary reformed reaction gas introduced into the secondary reformer 32 through line 26 undergoes a reforming reaction here. The secondary reformed reaction gas obtained in the secondary reformer 32 is extracted through the line 17 and is used as a heating medium in the primary reformer 31.
, where the hydrocarbon/steam mixture introduced through line 13 is heated and then withdrawn through line 27 . The temperature of the primary reformed reaction gas introduced into the secondary reformer 32 through line 26 is 600 to 750°C, and the secondary reformed reaction gas is extracted from the secondary reformer 32 through line 17. The temperature of the gas is 750-850°C. The heated compressed air introduced into the secondary reformer 32 through the line 15 has a pressure of 8 to 20 atmospheres and a temperature of 900 to 1
The temperature is 300°C. The temperature of the compressed air extracted from the secondary reformer 32 through line 18 is 700-950°C. The steam reforming method according to the flow sheet shown in FIG. 2 is suitable for obtaining a reformed reaction gas for the purpose of producing hydrogen.

[0016]

Effects of the Invention The steam reforming method of the present invention uses a device system in which a plurality of heat exchanger type primary reformers are combined with a mixed reactor type secondary reformer. Since heating of a part of the reformer is performed using compressed heated air, there is no need to supply excess oxygen or air to the combustion reaction section of the secondary reformer, and there is no need to supply excess oxygen or air to the combustion reaction section of the secondary reformer By heating the subsequent compressed and heated air to a high temperature again and driving the gas turbine, the energy of the compressed and heated air can be efficiently utilized. Therefore, in the present invention, the energy required per unit amount of hydrogen can be significantly saved. Furthermore, since the multiple heat exchanger-type primary reformers are heated using compressed heated air as described above, the degree of freedom in operating the equipment system is significantly increased, and the resulting reformed reaction gas The composition can be easily adjusted. In addition, the steam reforming method of the present invention uses a device system that combines a heat exchanger type primary reformer and a heat exchanger type secondary reformer,
As the equipment system is downsized and compressed heated air is used as the heating medium for the secondary reformer, the energy required per unit amount of hydrogen produced can be significantly reduced. The degree of freedom in operating the device system is also significantly increased.

[Brief explanation of the drawing]

FIG. 1 shows a flow sheet for one embodiment of the invention.

FIG. 2 shows a flow sheet for another embodiment of the invention.

[Explanation of symbols]

1, 2, 31, 32 Heat exchanger type reformer 3 Internal combustion reactor type reformer 4 Heat exchanger 5 Compressor 6, 7 Combustor 8 Gas turbine

Claims (3)

[Claims] [Claim 1] A primary reforming step in which a mixed gas of hydrocarbon and steam undergoes a reforming reaction using a plurality of heat exchanger type reformers, and a plurality of primary reformers obtained in the primary reforming step. It consists of a secondary reforming process in which a reaction gas is subjected to a reforming reaction using an internal combustion reactor type reformer in the presence of oxygen and/or air, and includes a plurality of heat exchanger type reformers used in the primary reforming process. In the amount of heat consumed in the reformer, part of it is replenished by the sensible heat possessed by the secondary reformed reaction gas obtained in the secondary reforming process, and the remainder is replenished by the sensible heat possessed by the compressed heated air. A method for steam reforming hydrocarbons, characterized by: 2. A primary reforming step in which a mixed gas of hydrocarbons and steam undergoes a reforming reaction using a heat exchanger type reformer, and a primary reforming reaction gas obtained in the primary reforming step is heated. It consists of a secondary reforming process in which a reforming reaction is carried out using an exchanger type reactor, and the amount of heat consumed in the heat exchanger type reformer used in the primary reforming process is converted into the amount of heat obtained in the secondary reforming process. The secondary reforming reaction gas is supplied with sensible heat, and the amount of heat consumed in the heat exchanger type reformer used in the secondary reforming process is replenished with the sensible heat possessed by the compressed heated air. A method for steam reforming hydrocarbons. 3. The compressed air flowing through the heat exchanger type reformer and having a lower temperature is heated by the combustion heat of the fuel and then expanded to recover the energy of the heated compressed air. the method of.