JPH0235683B2 - METANOORUNOSUIJOKIKAISHITSUHO - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is a method for steam reforming a raw material gas containing methanol vapor and steam as main components by bringing it into contact with a catalyst, in which a small amount of steam is used. The present invention relates to a method for producing a product gas containing hydrogen and carbon dioxide as main components and having a low carbon monoxide content.

[Prior Art] The method of bringing a mixed gas of methanol vapor and water vapor into contact with a suitable catalyst at the operating temperature of the catalyst and reforming it into a product gas mainly composed of hydrogen and carbon dioxide is well known to some extent. There is. In this reforming method, a large amount of steam is used for methanol, and carbon monoxide as a by-product is usually mixed into the product gas. That is, this modification reaction is as follows (1)
The reaction proceeds according to the formula: CH ₃ OH + H ₂ O → 3H ₂ + CO ₂ (1) Since the reaction of the following formula (2) proceeds simultaneously, water vapor and carbon monoxide are produced as by-products.

H ₂ + CO ₂ = CO + H ₂ O (2) Therefore, in this reforming reaction, the purpose of carrying out this reforming reaction is to reduce the amount of water vapor used, as well as to reduce the amount of water vapor in the product gas, such as the production of high-purity hydrogen. When using hydrogen, if the contamination of carbon monoxide is undesirable, it is important to obtain a product gas that contains less carbon monoxide, which requires more cost to remove than carbon dioxide. Become. As you know,
The reaction of formula (1) is a large endothermic reaction, and is preferably carried out at a high temperature within the allowable range of the heat resistance of the catalyst, both in terms of chemical equilibrium and reaction rate. or
In order to prevent the reaction in equation (2) from proceeding from the left side to the right side, a low reaction temperature and a large amount of water vapor are required.

Several documents, such as the November 1983 issue of Kagaku Keizai, page 49, disclose two types of methods, an adiabatic reaction method and an isothermal reaction method, as means for concretely carrying out such a steam reforming reaction of methanol. has been done. Among these disclosed adiabatic reaction methods, since the main reaction (1) is a large endothermic reaction, it is necessary to retain the heat required for the endothermic reaction in the reaction raw material as sensible heat.
It is essential to heat the raw material containing a large amount of water vapor to a high temperature and supply it as a reaction raw material.
As a result, even if an attempt is made to recover the condensation heat of excess steam from the product gas containing the excess steam, there are drawbacks such as the temperature of the recovered heat being too low to make effective use of it. Furthermore, in the isothermal reactions disclosed in these disclosures, if a high reaction temperature is selected, results similar to those of an adiabatic reaction will be produced, and conversely, if a low reaction temperature is selected, a large excess of water vapor will not be added.
Although it is possible to obtain a product gas with a low carbon monoxide content, it has the disadvantage that the reactor becomes large due to a decrease in the reaction rate, and the required amount of catalyst becomes large, making it uneconomical.

[Structure of the Invention] The present invention is an improved method for steam reforming methanol in order to correct the drawbacks of the conventional method as described above. That is, in the method of the present invention, the contact zone where the raw material gas mainly consisting of methanol vapor and water vapor contacts the catalyst is divided into a first contact zone on the upstream side and a second contact zone on the downstream side, and The temperature is selected separately, and the reaction in the second contact zone is an exothermic reaction at a relatively low temperature that causes equation (2) to proceed from the right side to the left side, and the reaction heat generated during this reaction is combined with the raw material gas. This method is based on recovery and reuse through heat exchange, and makes it possible to obtain a product gas with a low carbon monoxide content using an extremely small amount of excess steam and a small reactor. The method of this invention will be explained in detail below.

That is, in the method of this invention, the contact zone between the catalyst and the raw material gas is divided into two, a first contact zone and a second contact zone located downstream of the first contact zone. This division allows the use of separate reaction temperatures for the first and second contacting zones, and
By keeping the temperature of the contact zone low, the reaction of equation (2) can proceed from the right side to the left side despite the use of a relatively small amount of water vapor, and a product gas with a low carbon monoxide content can be obtained. By using a higher temperature in the first catalytic zone than in the second catalytic zone, the total amount of catalyst used in both zones can be reduced. In this invention, the temperature of the raw material gas flowing into the first contact zone is 170°C.
Temperatures above 500°C, preferably above 230°C and below 280°C, are used. Further, the temperature of the gas flowing out of the first contact zone in the present invention is preferably 250°C or more and 350°C or less, preferably 250°C or more and 300°C or less. In this contact zone, if the temperature of the gas stream supplied to this contact zone as a raw material gas is maintained within the above temperature range, a reaction occurs in an isothermal reaction or a heat supply state intermediate between an adiabatic reaction and an isothermal reaction. mode (hereinafter referred to as intermediate reaction) can be used. When the reaction in the first contact zone is an isothermal reaction or an intermediate reaction, a desired temperature is selected from the above temperature range as the temperature of the raw material gas flowing into this zone and the temperature of the gas flowing out from this zone. However, in this case
It is necessary to supply the heat necessary for the endothermic reaction of equation (1), and the method for supplying heat for this will be described later. In this first contact zone, the endothermic reaction of equation (1) occurs very rapidly in the early stage of the reaction, so even if the heat supply method described later is carried out, some of the contact and this part of the catalyst The temperature of the gas in contact may drop below 250°C.

The catalyst in the first contacting zone is preferably a granular catalyst, and both fixed bed and fluidized bed systems can be used to support the granular catalyst. When a fixed bed is used as the catalyst support method, the structure of the reactor used in this contact zone is such that the catalyst is present in each tube of a group of tubes arranged in parallel at a desired interval. A structure that heats by passing a heat source fluid outside to supply reaction heat, or a structure that fills a catalyst in the space between the tubes of a group of tubes arranged in the same way and heats it by passing a heat source fluid inside the tubes. can be used. In the case where the catalyst is present in the tubes mentioned above, the catalyst may be filled over the entire cross section of the tube, but an inner tube is installed in the center of each tube, and the catalyst is placed between the tubes and the inner tube. The inner tube is filled with an annular space sandwiched between the inner tubes and has a structure in which a heat source fluid (containing the source gas or one of its components at a temperature higher than the temperature of the source gas when flowing into the first contact zone) flows through the inner tube. Often preferred. In addition, when a fluidized bed is used as a catalyst support method, the structure of the reactor is, for example, a group of tubes arranged vertically at a desired interval within the fluidized bed of the catalyst, and a heat source fluid is supplied into each tube. A structure can be used that allows the gas to flow through the catalyst and heat the gas during the reaction. In addition, when the first contact zone is used as an intermediate reaction, the catalyst layer is installed in a plurality of layers spaced apart in the vertical direction within the outer shell of the reactor, and a high temperature is applied to the space constituting each space. There is also a method of supplying heat by adding additional water vapor. In this case, the molar ratio described below at the inlet of the first contact zone is
It may be 1.0 or less.

If the raw material gas flowing into the first contact zone has a temperature of 500°C or higher, the life of the catalyst will be shortened, and conversely, if the temperature of this gas is 170°C or lower, heating as described above should not be performed. However, both are undesirable because a sufficient reaction rate cannot be obtained and a large amount of catalyst and a large first contacting zone must be used.
Furthermore, if the gas flowing out of the first contact zone has a temperature of 350°C or higher, the content of carbon monoxide in the gas flowing out of this contact zone increases, increasing the amount of catalyst in the second contact zone. The fact that the second contact zone is made larger and the temperature of the gas flowing out of the first contact zone is 250°C or less means that the latter half of this contact zone is relatively low temperature,
Both are undesirable because they create a need for an enlarged first contact zone.

The carbon monoxide content of the gas leaving this first catalytic zone depends on the performance of the catalyst used in this catalytic zone;
Although it varies slightly depending on the ratio of the raw material gas volume to the apparent volume of the catalyst and the ratio of the molar fraction of water vapor to the molar fraction of methanol vapor in the first contact zone described later, after unreacted methanol and water vapor are condensed and removed. The carbon monoxide content in the gas is approximately 2.0 mol%. Furthermore, a methanol modification rate of 90 mol% or more can be obtained in this first contact zone.

Depending on the temperature at which the gas exits the first contacting zone, it is cooled, if necessary, to the temperature at which it enters the second contacting zone, which will be described below. Methods for this cooling include countercurrent indirect heat exchange with the raw material gas at a lower temperature, one of the main component gases before being mixed with the raw material gas, or a small amount of liquid methanol, water, or a mixture of both. Examples include a method of adding and mixing the gas flowing out from the contact zone. In rare cases,
There may be cases where the temperature of the gas flowing out of the first contact zone is lower than the upper limit of the gas temperature that should flow into the second contact zone.
There is no need to heat the gas leaving the contact zone.
In this way, the temperature of the gas stream entering the second contact zone is between 200°C and 300°C, preferably between 200°C and 250°C.
Selected for temperatures below ℃.

In the second contact zone, as mentioned above, the main reaction is an exothermic reaction from the right side to the left side of equation (2), and the carbon monoxide and remaining water vapor react to reduce the carbon monoxide content. Decrease. The temperature of the gas during the progress of this reaction is such that the temperature of the gas flowing out of this second contact zone is preferably 170°C or more and 230°C or less.
It is best to select a temperature that is between 180°C and 220°C. As a means of temperature control in this process, for example, the reactor used in the second contact zone may be of a type in which a catalyst is filled in each tube of a group of tubes installed in parallel while maintaining a desired mutual spacing. Each of these tubes is used as a heat transfer surface, and the lower-temperature raw material gas or one of the main component gases constituting the raw material gas is allowed to flow outside the tube and countercurrently flows with the reacting gas flowing inside the tube. Examples of methods include heat exchange. However, if the temperature of the gas entering the second contacting zone is close to the lower limit of the temperature range, it may be possible to make this second contacting zone adiabatic. The first contact zone and the second contact zone in the above description may be installed as two divided catalyst beds in one reactor, or two catalyst beds that separately accommodate each contact zone. It may be installed as a reactor.

From the viewpoint of chemical equilibrium, the reaction of formula (2) tends to shift to the left-hand side as the temperature decreases. Therefore, in accordance with the purpose of this invention, when reducing the amount of water vapor used,
Since the amount of unreacted water vapor is small as described below, the second
It is preferable for the gas flowing into the contact zone to be at a temperature of 300°C or higher for the purpose of reducing carbon monoxide, since the reaction of equation (2) will proceed to the left side after this temperature drops to 300°C or lower. On the other hand, if this temperature is below 200°C, the reaction rate of this reaction will be slow, which will also lead to an increase in the amount of catalyst and the size of the second contact zone, which is undesirable. Furthermore, if the temperature of the gas flowing out of the second contact zone is 220°C or higher, the content of carbon monoxide in the product gas will not be sufficiently reduced due to chemical equilibrium reasons.
On the other hand, if the temperature of this gas is 170° C. or lower, the reaction rate becomes slow, resulting in an increase in the amount of catalyst used and an increase in the size of the second contact zone, which is not preferable.

In the method of the present invention as described above, the ratio of the molar fraction of water vapor to the molar fraction of methanol vapor in the first contact zone (hereinafter referred to as molar ratio) is 1.0 or more and 2.5 or less, preferably 1.3 or more and 1.7 or less. The fact that 1.0 can be used as the molar ratio in the first contact zone seems to go against chemical theory, but since the reaction in the first contact zone is accompanied by a reaction from the left side to the right side according to equation (2), the molar ratio Even if we use a ratio of 1.0, there will always be a small amount of water vapor present in the gas leaving the first contacting zone;
There is no hindrance to the progress of the reaction in the contact zone. Regarding this molar ratio, as for the method of adding water vapor, there are cases in which the molar ratio at the inlet of the first contact zone is within the above range and no additional water vapor is added in the first contact zone; Although the molar ratio at the inlet of the contacting zone is less than 1.0, it may be preferable to add hot steam during the reaction in the first contacting zone so that the molar ratio remains within the above range throughout the first contacting zone. be. The molar ratio in this invention method is 3, which is the molar ratio used in the conventional method.
Despite the use of such a low molar ratio, due to the selection of temperatures in the first and second contacting zones as described above, this is a significantly lower value compared to ~5.
The carbon monoxide content in the gas flowing out of the second contact zone can easily be 0.6 or less in terms of mole % in the gas after unreacted methanol and water vapor are condensed and separated.

With the above, the main steps of this invention are completed, but
The product gas obtained by the above-mentioned process of the present invention includes liquid methanol or water used as a raw material,
Alternatively, the product gas is cooled by heat exchange with vaporized methanol or water, or a mixture thereof, and unreacted methanol and water vapor contained in the product gas are condensed and separated. After carbon, carbon dioxide, or both are separated and removed, it is supplied to desired uses.
Moreover, at that time, the separated methanol and water mixture can be reused as a raw material.

The method of the present invention will be explained in more detail below using the attached FIG. 1. Although FIG. 1 is a diagram showing an example of a process according to the present invention, the present invention is not limited to this process example. This process example has a structure in which each tube of a group of tubes arranged in parallel at a desired interval is filled with a catalyst in both a first contact zone and a second contact zone housed in one reactor. This is an example where . In the figure, numerals 1 and 2 are pumps for supplying liquid methanol and water, respectively, to the downstream process according to the method of the present invention. Methanol and water supplied by both pumps pass through pipes 3 and 4, join into pipe 5, and are preheated in a heat exchanger 6 by exchanging heat with the product gas obtained by the method of the present invention. The mixture of methanol and water preheated in the heat exchanger 6 further flows into the next evaporator 7, where it exchanges heat with the heat source medium supplied from the tube 8 and is evaporated. The evaporated mixed vapor is supplied through the pipe 9 to the lower part of the space outside the catalyst tube group 11 installed in the second contact zone 10, and is heat exchanged with the gas undergoing reaction in the second contact zone inside the tube. and heated. In each tube of the catalyst tube group 11, as shown in the figure, only the lower half of the tube length is filled with catalyst, but the upper half is not filled with catalyst.
It serves as a heat exchanger for cooling the gas exiting from the first contacting zone 16 to the above temperature. The mixed steam whose temperature has increased due to this heat exchange further flows into the heat exchanger 13 via the pipe 12, and then flows into the heat exchanger 13.
At 3, the raw material gas is further heated by the heat source medium 14 to become a raw material gas at a desired temperature, and is supplied to each of the first contact zones 16 inside the tube group 17 via the tubes 15. In the raw material gas that has come into contact with the catalyst in the first contact zone, most of the methanol is reformed by the main reaction of equation (1). The heat necessary for this reforming reaction is supplied by the heat source fluid supplied from 18, and the temperature of the first contacting zone is maintained within the above temperature range. As the heat source fluid for the first contact zone in the example shown in this figure, combustion gas is used which is circulated by the blower 22 from the combustion zone 21 to the heat source fluid pipes 18, 20, the blower 22, and the pipe 26. . This circulating combustion gas is maintained at the required temperature by replenishing the high temperature combustion gas produced by combustion of air and fuel supplied from the pipes 23 and 24 in the combustion chamber 25, and the surplus circulating combustion gas is It is configured so that exhaust air is exhausted from 27.

The gas exiting the first contacting zone is, as described above,
It flows into each tube of the catalyst tube group 11, and in the upper part of each of these tubes where the catalyst is not filled, the tube 9
After being cooled to a predetermined temperature by countercurrent heat exchange with a mixed gas of methanol and steam supplied from
Subsequently, it enters the catalyst-filled portion of each tube of the tube group 11, that is, the second contacting zone, and the reaction in the second contacting zone is completed before exiting each of these tubes. The gas that has undergone the reaction in the second contact zone is cooled by exchanging heat with the mixture of methanol and water in the heat exchanger 6 as described above, and is taken out through the pipe 29 and indirectly cooled by water (this cooling After unreacted methanol and water are condensed in a vessel (the vessel is not shown in the drawings), the condensed unreacted methanol and water are separated in a separator 30 and taken out from a pipe 31 as a product gas. The mixed liquid of methanol and water separated in the separator 30 is transferred to the pipe 3
2 and returned as a raw material through a pipe 33 by a pump 34.

In the method of the invention, liquid methanol and liquid water are evaporated separately without being mixed, and only one of the vapors is used as a gas for cooling the second contact zone, upstream of the heat exchanger 13. Alternatively, both may be mixed downstream and supplied to the first contact zone. If it is possible to introduce water vapor at an appropriate temperature and pressure from outside the system, only liquid methanol is evaporated and used as described above, and the water vapor introduced from outside the system is evaporated depending on its temperature and pressure. , may be supplied upstream or downstream of the heat exchanger 13. In the above example, cooling during transition from the first contact zone to the second contact zone was performed by heat exchange with the raw material gas or one of the main components of the raw material gas. 1st besides
There is a method of adding liquid methanol, liquid water, low temperature steam, low temperature methanol vapor and/or mixtures of two or more thereof to the gas exiting the contact zone. When using such a method, there are two methods: when the additive is in a gaseous state, the additive gas is directly added to and mixed with the gas flowing out of the first contact zone, and when the additive is in a liquid state, In this case, a well-known gas-liquid contacting device such as a packed column or a tray column can be used.

In the method of this invention, the pressure in the first and second contact zones is 0 to 30 Kg/cm ² G, and the catalyst is a well-known catalyst, such as a copper-zinc system supported on alumina or a copper-zinc-chromium system. , a copper-chromium catalyst is used as a heat source fluid such as steam having a desired temperature and pressure, a mixture of diphenyl and diphenyl oxide, an alkylbenzene, an alkylnaphthalene, an aliphatic saturated hydrocarbon fraction, etc. Fluid vapor having a desired temperature and pressure, combustion gas, etc. can be used.

[Advantages and Effects of the Invention] As described above, the advantage of the present invention is that, compared to the conventional method, by using a small amount of steam, the carbon monoxide content after condensing and removing unreacted methanol and steam is 0.6. % or less of product gas, and the amount of catalyst required at that time is approximately 1 ton/hour in terms of apparent volume for processing 1 ton/hour of methanol.
It is relatively small at 3.5 m ³ , which allows the reactor to be downsized and is easy to operate. Therefore, compared to the conventional methanol reforming method or the method of producing hydrogen using natural gas, liquefied petroleum gas, naphtha, etc. and a large amount of steam as raw materials, the method of this invention is relatively easy to produce hydrogen. It is useful as a method. An example of such advantages of the present invention will be explained below using examples.

Example A methanol reforming test according to the process shown in FIG. 1 was carried out under a pressure of about 5.0 Kg/cm ² G. The reactor consists of 420 chromo-molybdenum steel tubes with an inner diameter of 27.53 mm, an outer diameter of 31.8 mm, and a length of 3600 mm, which are fixed vertically to two substantially horizontal tube plates (upper and lower) as a first contact zone, and a second contact zone. As a zone, 420 chromium-molybdenum steel tubes having the same inner and outer diameters as above and a length of 1200 mm were fixed vertically to two other approximately horizontal tube sheets, upper and lower, below the first contact zone. A reactor was used in which both were incorporated into one vertical cylindrical reactor. In the first contact zone, copper-zinc based spherical catalyst particles with a diameter of 4 to 6 mm are filled in the tubes over almost the entire length of each tube, and in the second contact zone, the same catalyst particles are filled in the tubes. was filled in the lower half of each tube length. The apparent volume of the packed catalyst is
The first contact zone is 0.9 m ³ and the second contact zone is 0.3 m ³ . In the space outside the catalyst tubes of the first contact zone, the combustion gas mentioned above was circulated at a flow rate of 4500 Nm ³ /h, the temperature of which was controlled at 270° C. at the reactor inlet. In addition, 21.63 kg mol/hour of the above-mentioned mixture of methanol and steam having a molar ratio of 1.5 at 149° C. flowing out of the evaporator was allowed to flow countercurrently into the extratubular space of the second contacting zone as shown. This mixed vapor is heated to 270°C after heat exchange in the second contact zone, a heat exchange section between the first contact zone and the second contact zone, and a downstream heat exchanger, and is further heated to 270°C in the first contact zone. Supplied to the catalyst layer. The gas temperature at the outlet of the first contacting zone was 270°C. A small amount of the gas at the outlet of the first contact zone was sampled and analyzed. As a result, 98.5% of the supplied methanol was reformed, and after condensing and removing unreacted methanol and water vapor, the gas contained
It contained 1.9% carbon monoxide. The temperature of the gas at the inlet of the catalyst bed in the second contact zone was 230°C. The temperature of the gas at the exit of the second contact zone is 200℃
After cooling this gas and condensing and separating unreacted methanol and water vapor, carbon monoxide is 0.6, carbon dioxide is 24.4, hydrogen is 74.7, and methanol vapor is 0.3.
Product gas consisting of 758 Nm ³ /h of each mol % and condensate 79.3 of each mol % of methanol 2.2 and water 97.8 mol %
/ Time was obtained. This condensate was returned to the raw material mixture of methanol and water.

Comparative Example The reactor, the catalyst, and the filling part thereof were the same as in the above example, and tests of substantially adiabatic reaction and isothermal reaction were carried out as a comparative example.

In the case of an adiabatic reaction, the extratubular spaces of the catalyst tubes of the first contact zone and the second contact zone are closed at the outlet and inlet of the heat exchange gas, respectively;
The test was conducted under substantially adiabatic reaction conditions without flowing a heat exchange fluid into the extratubular space. Steam was added at a molar ratio of 2.6 to the same amount of methanol vapor supplied as in the example, and the temperature of the mixed vapor supplied to the reactor was set at 400°C. The temperature of the effluent at the reactor outlet in this test was 220°C, but after cooling the effluent and separating the condensate, the gas contained 0.4% carbon monoxide and was used to reform methanol. The rate was 43%. Decreasing the temperature of the mixed vapor at the reactor inlet reduces the carbon monoxide content in the gas after cooling the reactor effluent and separating the condensate, but further reduces the methanol reforming rate; Good results as in the Examples were not obtained.

In the case of an isothermal reaction, the test was carried out by supplying Dowtherm steam at a constant temperature to both the spaces outside the catalyst tubes of the first and second contact zones. Molar ratio for the same amount of methanol vapor supplied as in the example
Add 1.5% water vapor and bring the temperature of this mixed steam to 210%
and 270° C., and the temperature of the Dowtherm vapor was approximately equal to the two inlet temperatures. The test results show that when the temperature of the mixed steam supplied to the reactor is 210℃,
The carbon monoxide content in the gas after separating the unreacted condensate shows a relatively low value of 0.7 mol%, but the methanol reforming rate shows a low value of 81%, and the supply temperature of the mixed steam is At a high temperature of 270°C, the same carbon monoxide content as above increases to 1.9 mol%, and the methanol modification rate improves to 99%. In both cases, good results as in the example were not obtained. I couldn't help it.

[Brief explanation of drawings]

FIG. 1 is an example of a process according to the present invention. Symbol, 1...methanol pump, 2...water pump, 3, 4, 5...tube, 6...heat exchanger, 7...
Evaporator, 8... Heat source fluid, 9... Tube, 10... Second contact zone, 11... Catalyst tube group, 12... Tube, 1
3... Heat exchanger, 14... Heat source fluid, 15...
Pipe, 16...first contact zone, 17...catalyst tube group,
18...heat source fluid, 19...batsful plate,
20...Pipe, 21...Combustion zone, 22...Blower, 23, 24...Pipe, 25...Combustion chamber, 26,
27, 28, 29...tube, 30...separator, 3
1, 32, 33...tube, 34...pump.

Claims (1)

[Claims] 1. A method in which a raw material gas containing methanol vapor and water vapor as main components is brought into contact with a catalyst and reformed into a product gas containing hydrogen and carbon dioxide as main components, comprising: The contact zone with the raw material gas is a first contact zone and a second contact zone located downstream of the first contact zone.
The temperature of the gas flowing into the first contact zone is 170°C.
The temperature of the gas flowing out of the first contact zone is 250°C or more and 500°C or less.
The temperature of the gas flowing into the second contact zone is 200°C or more and 350°C or less.
The temperature of the gas flowing out of the second contact zone is 170°C or more and 300°C or less.
℃ or more and 230°C or less, and the gas in the process of transitioning from the first contact zone to the second contact zone and/or the gas in the process of reaction in the second contact zone is the raw material gas or one gas constituting the raw material gas. methanol cooled by countercurrent indirect heat exchange with the main component gas, wherein the ratio of the mole fraction of water vapor to the mole fraction of methanol vapor in the first contact zone is 1.0 or more and 2.5 or less. steam reforming method. 2. In the first contact zone, the catalyst is present in each tube of a group of tubes installed in parallel while maintaining a desired mutual spacing, and between the space outside each tube and the combustion zone of the desired fuel. 2. The steam reforming method according to claim 1, wherein the catalyst in each tube is heated by the circulating combustion gas. 3 Intermediately between the first contacting zone and the second contacting zone, water, steam, liquid methanol, or methanol vapor is added to the gas exiting the first contacting zone and causing the gas to flow into the second contacting zone. The steam reforming method according to claim 1, wherein the temperature of the steam reforming method is controlled. 4. The steam reforming method according to claim 1, wherein the second contact zone is an adiabatic reaction.