JP3082796B2 - Steam reforming reactor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrogen separation type steam reforming reactor.

[0002]

2. Description of the Related Art In a steam reforming reactor, a raw material gas composed of hydrocarbons such as methane and methanol or oxygen-containing hydrocarbons is converted into hydrogen, carbon monoxide and carbon dioxide by a steam reforming reaction and a CO shift reaction using a catalyst. Decompose into For example,
A raw material gas composed of a hydrocarbon such as methane is mixed with steam, introduced into a catalyst layer, and decomposed into hydrogen, carbon monoxide and carbon dioxide by the following reaction. _{CnHm + nH 2 O = nCO +} (n + m / 2) H 2 (1) CnHm + 2nH 2 O = nCO 2 + (2n + m / 2) H 2 (2) CnHm + nCO 2 = 2nCO + m / 2 H 2 (3)

[0003] The steam reforming reaction of these source gases is an equilibrium reaction involving endotherm, and the reaction proceeds as the temperature increases. Further, the reaction amount and reaction rate are affected by the concentration of the raw material gas, the concentrations of hydrogen and carbon monoxide as reaction products, the reaction temperature and the pressure.
For example, in order to improve the reaction amount of the source gas, it is necessary to increase the concentration of the source gas, decrease the concentration of the reaction product, and perform the reaction at low pressure and high temperature. Therefore, in the conventional steam reforming reactor, the reaction amount of the raw material gas was secured mainly by setting the reaction temperature high. For example, in a methane steam reforming reactor, the outlet temperature is set at about 800 ° C. For this reason, such a reactor requires a material capable of withstanding high temperatures as a reactor material, and has a problem that it is expensive.

[0004] In order to react at a lower temperature than conventional reactors, there has been proposed a reactor of a type that promotes decomposition of a raw material gas while breaking the reaction equilibrium, that is, a hydrogen separation type steam reforming reactor. This reactor has a built-in membrane for selectively separating hydrogen in the catalyst layer of the reactor. The hydrogen generated as a result of the progress of the steam reforming reactions (1) to (3) is converted into the built-in hydrogen. It has the function of selectively separating out of the reaction system through the separation membrane. Therefore, the reaction proceeds without reaching equilibrium as long as hydrogen is separated even at a low temperature.

[0005] Hydrogen separation membranes include palladium alone, palladium-silver alloy, or the like, or a metal coated with a porous inorganic material such as ceramics, or a porous material formed of a metal material such as a sintered metal. Is used. In these hydrogen separation membranes, hydrogen is separated by utilizing the phenomenon that hydrogen moves in the membrane due to the hydrogen partial pressure difference between the permeate side and the non-permeate side, and a pressure difference is created between the reaction side and the permeate side. There is a need.

A conventional example of a hydrogen separation type steam reactor is shown in FIGS.
This will be described with reference to FIG. 6 is an explanatory view of one embodiment of a conventional hydrogen separation type steam reforming reactor, FIG. 7 is an explanatory view of one embodiment of a hydrogen separation membrane set in FIG. 6, and FIG. 8 is another hydrogen separation type steam reforming reactor. It is explanatory drawing of one aspect of a reactor.

[0007] The structure and function of the reactor will be described below by taking a steam reforming reaction of methane as an example. Reference numeral 1 denotes a shell-and-tube type hydrogen separation type steam reforming reactor, which comprises a plurality of catalyst tubes 2 (see FIG. 7) and a body 22. The catalyst tube 2 has a hydrogen separation membrane 3 substantially at the center of the reforming catalyst layer 4 and is fixed to the body 22 by tube sheets 20 and 20 ′. The hydrogen separation membrane 3 is tubular, and a region outside the catalyst layer 4 is constituted by a raw tube 3 ′, and is fixed to a body 22 by a tube sheet 21. The mixed gas 5 of methane and steam is supplied from the reaction gas inlet nozzle 6 to the upper space 19 of the reactor 1, and after dispersion, is introduced into the reforming catalyst layer 4 as a dispersed mixed gas 5 '. In the catalyst layer 4, the reforming reactions (1) to (3)
Progresses to produce mainly hydrogen and carbon dioxide. Of these, only hydrogen is passed through the hydrogen separation membrane 3 to the permeation side 7 of the separation membrane 3.
Separated into The unreacted gas 9 after the reaction flows out of the catalyst layer 4, collects in the space 23, and is discharged from the reaction gas outlet nozzle 10 to the outside of the reactor 1 as an unreacted gas 9 ′.

On the other hand, the separated hydrogen flows out from the permeation side 7 and is discharged as separated hydrogen 8 through a lower space 18 separated by a tube plate 21 of the reactor 1 from a hydrogen outlet nozzle 17 as separated hydrogen 8 ′. You. At this time, the pressure on the permeation side 7 is kept lower than that of the catalyst layer 4, and the operation is performed so that the hydrogen partial pressure is lower than that of the catalyst layer 4.

The steam reforming reaction is an endothermic reaction involving a large amount of reaction heat as described above, and it is necessary to supply reaction heat by heating the catalyst tube 2 from outside the tube. For this reason, in this case, the high temperature combustion exhaust gas 11 is supplied to the heating gas inlet nozzle 12.
The reaction heat is supplied by being introduced into the body side 13 of the reactor 1. The combustion gas 11 ′ supplied to the barrel 13 is controlled by a baffle 14 disposed in the barrel so that its flow path is substantially perpendicular to the catalyst tube 2 and flows. Thereby, heat transfer between the combustion exhaust gas 11 'and the catalyst tube 2 is promoted, and the catalyst tube 2 can be efficiently heated. Combustion gas 1
After heating the catalyst tube 2, the exhaust gas 1 ′ is discharged from the combustion gas outlet nozzle 15 as exhaust gas 16.

The embodiment shown in FIG. 8 shows a case where an inert gas 24 is used to discharge hydrogen separated by the hydrogen separation membrane 3 to the permeation side 7. Here, an inert gas inlet nozzle 25 is provided in the body 22 to supply the inert gas 24, and an inert gas supply pipe 26 is provided in the tubular hydrogen separation membrane 3.
Other structures and functions are the same as those in the above-described embodiments of FIGS.

[0011]

FIGS. 9 and 10 show hydrogen partial pressures in the catalyst layer and on the permeation side of the hydrogen separation membrane. FIG.
7 shows a change in hydrogen partial pressure in FIGS. 7 and 8, and FIG. 10 shows a change in FIG. In both cases, the hydrogen partial pressure gradually increases on the catalyst layer side, but the hydrogen partial pressure peaks at a position where the hydrogen permeation rate from the hydrogen separation membrane and the hydrogen generation rate in the catalyst layer are balanced. After that, most of the raw material gas is decomposed and approaches the reaction equilibrium, so that the reaction proceeds by an amount that allows hydrogen to permeate, and the hydrogen partial pressure gradually decreases, but becomes almost constant. On the other hand, on the permeate side, the hydrogen partial pressure at the catalyst layer inlet is high and the outlet side is low, and at the inlet side, the hydrogen partial pressure on the catalyst layer side is lower than that on the permeate side. This leads to the following problems.

(1) At the inlet side of the catalyst layer, the hydrogen partial pressure is lower than that at the permeation side, and backflow of hydrogen from the permeation side to the catalyst layer side occurs, so that the reaction speed in the catalyst layer decreases. (2) Also, the amount of recovered hydrogen is reduced by the amount of the backflow, and the efficiency of the hydrogen separation membrane is reduced.

[0013]

SUMMARY OF THE INVENTION The present invention is a reactor for producing hydrogen by a steam reforming reaction in which a hydrocarbon or an oxygen-containing hydrocarbon is supplied as a raw material. In a hydrogen separation type steam reforming reactor in which a reaction proceeds while selectively separating hydrogen by a pressure difference, a region not containing the hydrogen separation membrane is provided on the upstream side of the catalyst layer. A steam reforming reactor, wherein the hydrogen separation membrane is built in a region downstream of the region.

That is, in the steam reforming reactor of the present invention, a heat transfer section without a hydrogen separation membrane is provided at the inlet of the catalyst layer, and the hydrogen separation membrane is set after the heat transfer section.

[0015]

By arranging the hydrogen separation membrane in this manner, the hydrogen partial pressure reversing portion at the catalyst layer inlet is eliminated.
Since the backflow of hydrogen is prevented, a reduction in the reaction rate in the catalyst layer and a reduction in the separation efficiency of the membrane can be prevented.

[0016]

【Example】

(Embodiment 1) An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an explanatory view of an apparatus according to an embodiment of the present invention, and FIG. 2 is an explanatory view of an embodiment of the hydrogen separation membrane installed in FIG. 1, and FIG. 6 and FIG. 7, the differences between the structures according to the present invention and the operation thereof will be mainly described below.

A mixed gas 5 of methane and steam as a raw material gas is introduced into the reactor 1 through a raw material gas inlet nozzle 6 and supplied to the catalyst layer 4. At the inlet of the catalyst layer 4, a region where the hydrogen separation membrane 3 is not provided, that is, a heat transfer portion 4a is provided, and the raw material gas and steam are mainly converted into hydrogen by the steam reforming reactions (1) to (3). Decomposed into carbon dioxide. Since there is no hydrogen separation membrane 3 in this region, hydrogen does not flow backward from the permeation side 7 of the hydrogen separation membrane 3 to increase the hydrogen partial pressure of the catalyst layer 4 and reduce the reaction rate.

The hydrogen partial pressure after passing through the heat transfer section 4a is
Is higher than the hydrogen partial pressure of the catalyst layer 4, and hydrogen is efficiently transferred to the catalyst layer 4 through the hydrogen separation membrane 3 provided downstream of the heat transfer section 4 a.
The light is further transmitted to the transmission side 7.

As described above, according to the embodiment of the present invention, by providing the heat transfer section without the hydrogen separation membrane at the inlet of the catalyst layer, the backflow of hydrogen from the permeation side to the catalyst layer side is prevented. In addition, the steam reforming reaction can be promoted and the efficiency of hydrogen separation can be improved.

(Embodiment 2) Next, another embodiment will be described with reference to FIG. This embodiment is an improvement of the conventional example shown in FIG. Since the structure and function are basically the same as those of the conventional example, detailed description will be omitted, and the difference between the structure and the operation according to the present invention will be mainly described.

In this embodiment, the heat transfer portion 4a of only the catalyst layer without the hydrogen separation membrane 3 is provided at the inlet of the catalyst layer 2, and therefore, as in the first embodiment, the heat in the catalyst layer 4 due to the backflow of hydrogen is provided. There is no reduction in hydrogen partial pressure and the reaction rate associated therewith. This leads to promotion of the steam reforming reaction and improvement of hydrogen separation.

FIGS. 4 (Embodiment 1) and FIG. 5 (Embodiment 2) show changes in the hydrogen partial pressure. The hydrogen partial pressure between the catalyst layer and the permeate side at the inlet of the catalyst layer as shown in the conventional example is shown. There is no reversal.

[0023]

According to the present invention, a heat transfer section having no hydrogen separation membrane is provided at the inlet of the catalyst layer, and the hydrogen separation membrane is set at a position after the heat transfer section. By arranging the hydrogen separation membrane in this way, the partial pressure of hydrogen does not reverse at the inlet of the catalyst layer, and there is no backflow of hydrogen. Can be. Therefore, it leads to the improvement of the performance of the apparatus and helps to make the reactor compact.

[Brief description of the drawings]

FIG. 1 is an explanatory view of Embodiment 1 of a steam reforming reactor of the present invention.

FIG. 2 is an explanatory view of one embodiment of the hydrogen separation membrane of the present invention.

FIG. 3 is an explanatory view of Embodiment 2 of the steam reforming reactor of the present invention.

FIG. 4 is an explanatory diagram of the operation and effect of the first embodiment of the present invention.

FIG. 5 is an explanatory diagram of the operation and effect of the second embodiment of the present invention.

FIG. 6 is an explanatory view of one embodiment of a conventional steam reforming reactor.

FIG. 7 is an explanatory view of one embodiment of a conventional hydrogen separation membrane.

FIG. 8 is an explanatory view of another embodiment of the conventional steam reforming reactor.

FIG. 9 is an explanatory diagram of the operation of the steam reforming reactor of FIG. 6;

FIG. 10 is a diagram illustrating the operation of the steam reforming reactor in FIG.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-219001 (JP, A) JP-A-4-121197 (JP, A) JP-A-5-132301 (JP, A) 13363 (JP, B1) (58) Field surveyed (Int. Cl. ⁷ , DB name) C01B 3/32 C01B 3/38

Claims (1)

(57) [Claims] 1. A reactor in which a hydrocarbon or an oxygen-containing hydrocarbon is supplied as a raw material to produce hydrogen by a steam reforming reaction, wherein a hydrogen separation membrane is built in a steam reforming reaction catalyst layer, and a pressure difference In a hydrogen separation type steam reforming reactor in which the reaction proceeds while selectively separating hydrogen by
A steam reforming reactor comprising: a region in which the hydrogen separation membrane is not provided upstream of the catalyst layer; and the hydrogen separation membrane in a region downstream of the region.