JP2008105895A - Reforming system - Google Patents

Abstract

The present invention provides a reforming system that stabilizes the amount of steam (S / C) with respect to hydrocarbons introduced into a reformer.
A reformer 15 that generates a reformed gas by reforming reaction of a boiler 13 that vaporizes water to generate steam, a hydrocarbon, and steam from the boiler 13; and a reformer 15 Shift reactor 16 that shifts the reformed gas from the gas, CO selective oxidizer 17 that selectively oxidizes carbon monoxide in the reformed gas after the shift reaction to generate a hydrogen-containing gas, and shift reactor The reforming system 1 includes a cooling water line 20 through which cooling water for heat exchange with both the CO 16 and the CO selective oxidizer 17 flows, and exchanges heat with both the shift reactor 16 and the CO selective oxidizer 17. Thus, the steam vaporized by the cooling water was merged with the steam from the boiler 13 toward the reformer 15.
[Selection] Figure 1

Description

  The present invention relates to a reforming system that generates a hydrogen-containing gas by reforming a hydrocarbon and steam.

In recent years, fuel cells have attracted attention as power generation devices with a low environmental load. Then, as a device for producing hydrogen to be supplied to the fuel cell, a reforming reaction is performed in which a hydrocarbon such as kerosene and water vapor are reformed under a reforming catalyst to generate a hydrogen-containing gas containing hydrogen as a main component. A system has been proposed (see Patent Document 1). Incidentally, the reforming system includes a reformer that performs a steam reforming reaction, a shift reactor that performs a shift reaction, and a CO selective oxidizer (PROX reactor) that selectively oxidizes CO. Then, since an exothermic reaction occurs in the shift reactor and the CO selective oxidizer, cooling water is passed so as to exchange heat with the shift reactor and the CO selective oxidizer.
JP 2004196611 A

However, in the reforming system of Patent Document 1, the steam vaporized by the cooling water is exchanged with the shift reactor and the CO selective oxidizer, so that the steam joins with the liquid water upstream of the boiler. In some cases, the flow rate of a mixture of water vapor (gas phase) and water (liquid phase) is not stable.
As a result, the amount of steam (S / C (moles / C-atom)) with respect to the hydrocarbons introduced into the reformer is not stable, and there is a possibility that the hydrocarbons will not be steam reformed well in the reformer. It was. Further, when the gas phase and the liquid phase merge, a so-called water hammer is generated, and there is a possibility that a negative effect such as a load acting on each device, piping and the like may occur.

  Then, this invention makes it a subject to provide the reforming system which can stabilize S / C.

  As a means for solving the above-mentioned problems, the present invention provides a modified gas generator for generating a reformed gas by reforming a boiler that vaporizes water to generate steam, a hydrocarbon, and steam from the boiler. A selective reaction part that selectively oxidizes carbon monoxide in the reformed gas after the shift reaction to generate a hydrogen-containing gas. And a cooling water line through which cooling water that exchanges heat with at least one of the shift reaction unit and the CO selective oxidation unit flows, wherein the reforming system includes at least the shift reaction unit and the CO selective oxidation unit. The reforming system is characterized in that the steam vaporized by the cooling water is merged with the steam from the boiler toward the reforming unit by heat exchange with one side.

According to such a reforming system, the vaporized steam of the cooling water merges with the steam from the boiler to the reforming section by exchanging heat with at least one of the shift reaction section and the CO selective oxidation section where an exothermic reaction occurs. To do. That is, since water vapor (gas phase) from the boiler and water vapor (gas phase) generated by heat exchange with at least one of the shift reaction unit and the CO selective oxidation unit merge, different phase states (gas phase, liquid Phase) water becomes difficult to merge. Thereby, the flow rate of water vapor to the reformer is stabilized, and S / C can be stabilized. As a result, it is possible to suitably cause the reforming reaction between hydrocarbon and steam in the reforming section.
At the same time, since at least one of the shift reaction unit and the CO selective oxidation unit can be cooled by the cooling water, an exothermic reaction in at least one of the shift reaction unit and the CO selective oxidation unit can be promoted.

  The reforming system is characterized in that all the cooling water is vaporized by exchanging heat with at least one of the shift reaction section and the CO selective oxidation section.

Here, a configuration in which all of the cooling water is vaporized by heat exchange with at least one of the shift reaction unit and the CO selective oxidation unit is, for example, a heat exchange capacity of at least one of the shift reaction unit and the CO selective oxidation unit. There is a configuration in which the flow rate of the cooling water is controlled (restricted) so that all of the cooling water is vaporized based on the temperature and the like.
According to such a reforming system, heat exchange with at least one of the shift reaction unit and the CO selective oxidation unit causes all of the cooling water to evaporate into steam, and this steam joins. The flow rate of water vapor can be further stabilized.

  The cooling water line is configured so that the cooling water exchanges heat with both the shift reaction unit and the CO selective oxidation unit, and the cooling water flows in the order of the CO selective oxidation unit and the shift reaction unit. It is the reforming system characterized by being.

  According to such a reforming system, since the cooling water flows in the order of the CO selective oxidation unit and the shift reaction unit that operates at a higher temperature than the CO selective oxidation unit, the cooling water can be efficiently vaporized. it can.

In addition, when the system is started, the Pt and Ru-based CO selective oxidation catalyst (PROX catalyst) built in the CO selective oxidation unit quickly rises in temperature when oxygen is injected, but is built into the shift reaction unit. Fe-Cr-based and Cu-Zn-based shift catalysts tend to be difficult to increase in temperature. Therefore, by adopting a configuration in which the cooling water flows in the order of the CO selective oxidation unit and the shift reaction unit, the shift reaction unit and the CO selective oxidation unit have a suitable temperature distribution not only during system startup but also during steady operation. It becomes easy. Thereby, the performance of a shift catalyst and a CO selective oxidation catalyst can be exhibited efficiently.
That is, for example, when the cooling water flows in the order of the shift reaction unit and the CO selective oxidation unit at the time of starting the system, the normal temperature (for example, 10 ° C.) cooling water is directly introduced into the shift reaction unit, and the shift reaction unit Although it is difficult to raise the temperature, since the cooling water that has been heated by exchanging heat with the CO selective oxidation unit is introduced into the shift reaction unit, the shift reaction unit can be raised in temperature satisfactorily and quickly started up.

  According to the present invention, it is possible to stabilize the amount of steam (S / C) with respect to the hydrocarbon introduced into the reformer.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 1, the reforming system 1 according to the present embodiment is a system for producing hydrogen (hydrogen-containing gas) by reforming the desulfurized reformed kerosene (liquefied hydrocarbon) and steam. The water tank 11, the pump 12, the boiler 13, the vaporizer 14, the reformer 15 (reformer), the shift reactor 16 (shift reactor), and the CO selective oxidizer 17 (CO And a cooling water line 20 for cooling the shift reactor 16 and the CO selective oxidizer 17.

  The water tank 11 is a tank that stores water therein. The water tank 11 is connected to the boiler 13 via a pipe 11a, a pump 12, and a pipe 12a. When the pump 12 is activated, the water in the water tank 11 is pumped to the boiler 13.

  The boiler 13 is a device that vaporizes water (liquid phase) fed from the water tank 11 to generate water vapor (gas phase). And the produced | generated water vapor | steam is sent to the vaporizer | carburetor 14 via the piping 13a.

The vaporizer 14 is a device that vaporizes reformed kerosene (liquid phase), which is a hydrocarbon, to generate vaporized kerosene. The vaporizer 14 is a device that mixes vaporized kerosene and water vapor from the boiler 13 and a cooling water line 20 to be described later so as to obtain a desired S / C.
And the mixed gas with which vaporized kerosene and water vapor | steam were mixed is sent to the reformer 15 via the piping 14a.

The reformer 15 is an apparatus that generates a reformed gas containing hydrogen as a main component by performing a steam reforming reaction between vaporized kerosene and steam (see Expression (1)). Such a reformer 15 incorporates a Ni-based or Ru-based reforming catalyst. Incidentally, the reformed gas contains carbon dioxide (CO ₂ ), carbon monoxide (CO), methane (CH ₄ ), water vapor (H ₂ O) and the like in addition to hydrogen. The reformed gas is sent to the shift reactor 16 through the pipe 15a.
_{C n H m + H 2 O} → H 2 + CO + CO 2 ... (1)

The shift reactor 16 is a device that shifts the carbon monoxide and steam in the reformed gas (see Formula (2)) to generate hydrogen and increase the amount of hydrogen in the reformed gas. Such a shift reactor 16 incorporates an Fe—Cr-based or Cu—Zn-based shift catalyst. The reformed gas after the shift reaction is sent to the CO selective oxidizer 17 through the pipe 16a. The shift reactor 16 includes a heat exchange unit 16b through which cooling water flows.
CO + H ₂ O → H ₂ + CO ₂ (2)

The CO selective oxidizer 17 (also referred to as PROX) is a device that selectively oxidizes carbon monoxide in the reformed gas after the shift reaction (see Formula (3)) to generate a hydrogen-containing gas. Such a CO selective oxidizer 17 incorporates a Pt-based and Ru-based CO selective oxidation catalyst. The reformed gas having a reduced carbon monoxide concentration is sent to a fuel cell (not shown) via the pipe 17a. In the present embodiment, the reformer 1 and the fuel cell constitute a reformer-mounted fuel cell system. Moreover, as an oxygen source in Formula (3), the injector which injects air (oxygen) to the piping 16a is provided, for example. Furthermore, the CO selective oxidizer 17 includes a heat exchange unit 17b through which cooling water flows.
CO + O ₂ → CO ₂ (3)

  The preferred operating temperature (for example, 150 ° C.) of the CO selective oxidizer 17 is generally set lower than the preferred operating temperature (for example, 250 ° C.) of the shift reactor 16.

  Next, the cooling water line 20 for cooling the shift reactor 16 and the CO selective oxidizer 17 will be described. The cooling water line 20 includes a pump 21, pipes 21 a to 21 d, a heat exchange unit 16 b of the shift reactor 16, and a heat exchange unit 17 b of the CO selective oxidizer 17. And from the water tank 11, the piping 21a, the pump 21, the piping 21b, the heat exchange part 17b, the piping 21c, the heat exchange part 16b, and the piping 21d are connected in order. The downstream end of the pipe 21d is connected to a connection point J in the middle of the pipe 13a.

According to such a reforming system 1, the cooling water sequentially passes through the CO selective oxidizer 17 and the shift reactor 16 in series, and by exchanging heat with these devices, all of the cooling water is vaporized to become steam. Since this water vapor (gas phase) joins the water vapor (gas phase) flowing through the pipe 13a from the boiler 13 toward the vaporizer 14 (reformer 15), the flow rate of water vapor introduced into the vaporizer 14 is Stabilize. That is, since water (liquid phase) and water vapor (gas phase) do not merge, bumping of water and condensation of water vapor are prevented.
Therefore, in the vaporizer 14, vaporized kerosene and water vapor are easily mixed at a desired S / C. As a result, the S / C of the mixed gas of vaporized kerosene and steam sent to the reformer 15 is stabilized, and the steam reforming reaction can be suitably caused in the reformer 15.

  Further, the cooling water passes through the CO selective oxidizer 17 having a low operating temperature (for example, 150 ° C.) and the shift reactor 16 having a high operating temperature (for example, 230 ° C.) in series in this order. The CO selective oxidizer 17 and the shift reactor 16 are preferably cooled and controlled to their preferred operating temperatures. Then, the CO selective oxidation catalyst and the shift catalyst are efficiently exhibited, and each reaction (see formulas (2) and (3)) is promoted. Can be generated.

Incidentally, the amount of steam to be introduced into the reformer 15 is the reforming load (the operating state of the reformer 15) corresponding to the power generation amount required for the fuel cell (not shown) downstream of the CO selective oxidizer 17. ).
The flow rate of the cooling water through the shift reactor 16 and the CO selective oxidizer 17 (that is, the rotational speed of the pump 21) is excessively increased by the shift reactor 16 (shift catalyst) and the CO selective oxidizer 17 (CO selective oxidation catalyst). The CO selective oxidizer 17 and the shift are controlled based on the heat exchange capacities of the shift reactor 16 and the CO selective oxidizer 17, these temperatures, the temperature of the gas introduced into them, and the like while being controlled to a suitable temperature without being heated. It is set so that all the cooling water via the reactor 16 is vaporized.
Then, the rotation speed of the pump 12 is determined so that steam obtained by subtracting steam from the steam to be introduced into the reformer 15 via the shift reactor 16 and the CO selective oxidizer 17 is supplied via the boiler 13. .

As mentioned above, although one suitable embodiment of the present invention was described, the present invention is not limited to the above-mentioned embodiment, and can be changed as follows, for example, in the range which does not deviate from the meaning of the present invention.
In the above-described embodiment, the reforming system 1 in which the cooling water passes in series in the order of the CO selective oxidizer 17 and the shift reactor 16 is exemplified. However, as shown in FIG. The reforming system 2 provided with the cooling water line 30 that passes through the reactor 17 and the shift reactor 16 in parallel may be used.

  More specifically, the cooling water line 30 mainly includes flow rate adjusting valves 32 and 33 and pipes 31a to 34a. The pipe 12 a is provided with a flow rate adjustment valve 31, and the upstream end of the pipe 31 a is connected to the pipe 12 a between the pump 12 and the flow rate adjustment valve 31. The downstream side of the pipe 31a is bifurcated, and each downstream end is connected to the flow rate adjusting valves 32 and 33, respectively. The flow rate adjusting valve 32 is connected to the inlet of the heat exchanging part 16b via the pipe 32a, and the flow rate adjusting valve 33 is connected to the heat exchanging part 17b via the pipe 33a. The outlet of the heat exchanging part 16b and the outlet of the heat exchanging part 17b are connected to the pipe 13a via a joining pipe 34a that joins in the middle.

  Therefore, in the reforming system 2 including such a cooling water line 30, vaporization is performed in the boiler 13 at the connection point J by controlling the flow rate adjusting valves 31, 32, 33 while operating one pump 12. The steam that has been vaporized from the cooling water by heat exchange with the shift reactor 16 and the CO selective oxidizer 17 can be merged.

  In addition, only the water vapor heat-exchanged with one of the shift reactor 16 and the CO selective oxidizer 17 is vaporized in the boiler 13 without joining the cooling water (steam) downstream of the shift reactor 16 and the CO selective oxidizer 17. It is good also as a structure merged with the water vapor | steam which performed.

In the above-described embodiment, the vaporizer 14 has a function of vaporizing the reformed kerosene and a function of mixing the vaporized kerosene and water vapor. It is good also as a structure which arrange | positions a mixer and equips the upstream with the vaporizer which vaporizes reformed kerosene separately.
Further, in the above-described embodiment, the case where the reformer 15, the shift reactor 16, and the CO selective oxidizer 17 are formed as separate units is illustrated, but the present invention is not limited to this, and is integrally configured. There may be.

It is a figure which shows the structure of the reforming system which concerns on this embodiment. It is a figure which shows the structure of the reforming system which concerns on a modification.

Explanation of symbols

1 reforming system 11 water tank 12 pump 13 boiler 14 vaporizer 15 reformer (reforming section)
16 Shift reactor (shift reaction section)
17 CO selective oxidizer (CO selective oxidation unit)
20 Cooling water line 21 Pump

Claims (3)

A boiler that vaporizes water to produce water vapor;
A reforming section for reforming a hydrocarbon and steam from the boiler to generate a reformed gas;
A shift reaction unit that shift-reacts the reformed gas from the reforming unit;
A CO selective oxidation unit that selectively oxidizes carbon monoxide in the reformed gas after the shift reaction to generate a hydrogen-containing gas;
A cooling water line through which cooling water that exchanges heat with at least one of the shift reaction unit and the CO selective oxidation unit flows;
A reforming system comprising:
The reforming system characterized in that the steam vaporized by the cooling water is merged with the steam from the boiler toward the reforming section by exchanging heat with at least one of the shift reaction section and the CO selective oxidation section. .   The reforming system according to claim 1, wherein all of the cooling water is vaporized by exchanging heat with at least one of the shift reaction unit and the CO selective oxidation unit. The cooling water line is configured such that the cooling water exchanges heat with both the shift reaction unit and the CO selective oxidation unit, and the cooling water flows in the order of the CO selective oxidation unit and the shift reaction unit. The reforming system according to claim 1 or 2, characterized in that.

Images