JP2015113239A - Fuel reformer and fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To mix fuel gas and water vapor sufficiently before entering a reformation chamber 12.SOLUTION: An evaporation chamber 11 is filled inside with a heat transfer acceleration member, and evaporates the water upon introduction of fuel gas and water, to generate water vapor. A reformation chamber 12 is filled inside with reformation catalysis, communicates with the evaporation chamber 11, and reforms the mixture gas from the evaporation chamber 11, to generate reformed gas including hydrogen. The communicating part between the evaporation chamber 11 and the reformation chamber 12 is a first opening part 16 formed at a partition wall 15 which partitions these. In the evaporation chamber 11, provided is a shielding plate 17 facing to the partition wall 15. The shielding plate 17 is hung down from the upper wall of the evaporation chamber 11, and, between its lower end edge and the bottom wall of the evaporation chamber 11, formed is a second opening part 18 through which the fuel gas and the water can flow. The first opening part 16 is provided at a higher position than the second opening part 18.

Description

  The present invention relates to a fuel reformer that generates a reformed gas containing hydrogen from a fuel gas using a steam reforming reaction, and a fuel cell system that includes the fuel reformer.

Patent document 1 is disclosing the raw material mixer which produces | generates the mixed gas utilized for the electric power generation reaction of a fuel cell.
This will be described. A fuel gas (first raw material) introduction pipe and water (second raw material) introduction pipe penetrating and opening into the casing through one end wall of the casing constituting the raw material mixer are provided. . The entry length of the fuel gas introduction pipe is longer than the entry length of the water introduction pipe. The casing is partitioned by a barrier into a first raw material introduction chamber in which a fuel gas introduction pipe is opened and a second raw material introduction chamber in which a water introduction pipe is opened. Both chambers communicate with each other through a communication portion. Here, on the basis of the flow direction of the mixed gas, the communication portion is arranged behind the opening of the fuel gas introduction pipe.

JP2013-016401A

When the fuel gas is reformed using a steam reforming reaction, it is necessary to provide an evaporation chamber upstream from the reforming chamber and evaporate water to generate steam.
Further, in order to avoid coking of the reforming catalyst filled in the reforming chamber, the fuel gas and water vapor must be well mixed before being introduced into the reforming chamber.
However, when water is supplied to the evaporation chamber in a liquid phase, a liquid pool is formed in the evaporation chamber, and water is vaporized from this liquid pool, so that an upper fuel gas layer and a lower water vapor layer are formed in the evaporation chamber. In other words, there was a problem of insufficient mixing of fuel gas and water vapor.

In the technique described in Patent Document 1, a mixing chamber (first raw material introduction chamber) and an evaporation chamber (second raw material introduction chamber) are provided upstream of the reforming chamber, and three chambers including the reforming chamber are provided. Due to the structure, the fuel reformer is increased in size.
In addition, since the length of the fuel gas introduction pipe that is plunged is longer, the section for mixing with water vapor becomes shorter, and mixing tends to be insufficient.

  The present invention has been made in view of such a situation, and has a two-chamber structure of an evaporation chamber and a reforming chamber, and can mix fuel gas and water vapor well before reforming. It is an issue to provide.

The fuel reformer according to the present invention is filled with a heat transfer promoting member, and is filled with fuel gas and water, evaporates the water to generate water vapor, and the reforming catalyst. A reforming chamber that communicates with the evaporation chamber and generates a reformed gas containing hydrogen by reforming a mixed gas of fuel gas and water vapor from the evaporation chamber.
The communicating portion between the evaporation chamber and the reforming chamber is a first opening formed in a partition wall that partitions the evaporation chamber and the reforming chamber.
A shielding plate facing the partition wall is provided in the evaporation chamber, and the shielding plate is suspended downward from the upper wall of the evaporation chamber, and between the lower edge of the evaporation chamber and the bottom wall of the evaporation chamber. A second opening through which fuel gas and water can flow is formed.
The first opening is provided at a higher position than the second opening.

According to the present invention, the flow direction of the fuel gas pushed upward by the water vapor generated upward from the liquid pool in the evaporation chamber is changed downward by the shielding plate suspended from the upper wall of the evaporation chamber, and faces each other. Colliding with water vapor can promote mixing.
Further, the fuel gas and the water vapor that have passed through the second opening formed below the lower edge of the shielding plate collide with the partition wall and head toward the first opening above, so that the shielding plate and the partition wall Mixing is promoted between the two.

Schematic of a fuel cell system showing an embodiment of the present invention Detailed view of the fuel reformer in the same embodiment The figure which shows the relationship between the distance H from a vaporization chamber bottom wall to a shielding-plate lower end edge, and a mixing index value The figure which shows the relationship between the distance S of a partition wall and a shielding board, and a mixing index value

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 is a schematic view of a fuel cell system showing an embodiment of the present invention.
The fuel cell system includes a fuel reformer 1 and a fuel cell 2.
The fuel cell system of the present embodiment is a solid oxide fuel cell (SOFC) system, and the fuel reformer 1 and the fuel cell 2 are placed in a casing (combustion chamber partition member) 4 together with the off-gas combustion unit 3. Be placed.

The fuel reformer 1 reforms a fuel gas using a steam reforming reaction to generate a reformed gas containing hydrogen. Details will be described later.
In addition, as fuel gas here, hydrocarbon gas, specifically, city gas, LPG, gas derived from shale gas, methane, propane, butane, and a mixture thereof can be exemplified. Moreover, methanol, dimethyl ether, etc. may be contained in these as an additive.
Examples of the fuel gas include low-boiling hydrocarbon compounds and ethers. Specifically, pentane, hexane, dimethyl ether, diethyl ether and the like.
Examples of the fuel gas further include alcohols having a low boiling point. Specifically, methanol, ethanol and the like.

  The fuel cell 2 is an assembly (fuel cell stack) of a plurality of solid oxide fuel cells.

Each fuel cell includes an anode (fuel electrode) and a cathode (oxidant electrode) on both sides of an electrolyte made of a solid oxide. The reformed gas is supplied from the fuel reformer 1 to the anode. An oxidant gas (generally air) is supplied to the cathode from an oxidant supply device (not shown) outside the housing 4.
The electrolyte conducts oxide ions at high temperatures. The anode reacts oxide ions with hydrogen in the fuel to generate electrons and water. The cathode reacts oxygen and electrons in the oxidant to generate oxide ions.
Therefore, the electrode reaction of the following formula (1) is caused at the cathode of each fuel cell, and the electrode reaction of the following formula (2) is caused at the anode to generate electric power.
Cathode: 1 / 2O ₂ + 2e ⁻ → O ²⁻ (electrolyte) (1)
Anode: O ²⁻ (electrolyte) + H ₂ → H ₂ O + 2e ⁻ (2)

  The fuel cell 2 includes many fuel cells as described above, and these are electrically connected in series (and in parallel) to generate a power generation output.

The off-gas combustion unit 3 burns off-gas discharged from the fuel cell 2 (hydrogen-containing fuel discharged as power generation unreacted gas) in the presence of an oxidant, and the fuel cell in the casing (combustion chamber partition member) 4 2 is maintained at a high temperature. Here, the upper end portion of the fuel cell 2 serves as a discharge portion for the off gas from the fuel cell 2, and this off gas is ignited and burned by an ignition device (not shown). Accordingly, the upper end portion side of the fuel cell 2 becomes the off-gas combustion portion 3. The fuel cell 2 is maintained in a high-temperature state capable of generating power by the combustion heat in the off-gas combustion unit 3.
The fuel reformer 1 is disposed above the fuel cell 2 in the housing 4 so as to be heated by the combustion heat in the off-gas combustion unit 3. In other words, the off-gas combustion unit 3 is disposed below the fuel reformer 1.

  High-temperature exhaust gas generated by combustion in the housing 4 is discharged to the housing 4 side through the exhaust passage. The waste heat is appropriately recovered and used as heat.

Next, the fuel reformer 1 will be described with reference to FIG.
The fuel reformer 1 includes an evaporation chamber 11 filled with a heat transfer promotion member (not shown) such as a heat transfer bead and a reforming catalyst (not shown) filled with a pellet shape or the like inside. It is a two-chamber structure with a pawn chamber 12.
Specifically, the fuel reforming apparatus 1 includes the evaporating chamber 11 and the reformer in the direction of fuel flow from the inlet portion 13 of the fuel gas and water before reforming to the outlet portion 14 of the reformed gas after reforming. A quality chamber 12 is provided in this order, and these chambers 11 and 12 are partitioned by a partition wall 15 having a communication portion.

Accordingly, the evaporation chamber 11 is defined by the upstream fuel reformer end wall 1a and the downstream partition wall 15, and has an inlet 13 in the end wall 1a. Communication portion (first opening 16 described later).
The reforming chamber 12 is defined by an upstream partition wall 15 and a downstream fuel reformer end wall 1b, and has an outlet 14 in the downstream end wall 1b.
A communicating portion between the evaporation chamber 11 and the reforming chamber 12 is a first opening 16 formed at a relatively upper portion of the partition wall 15 that partitions the evaporation chamber 11 and the reforming chamber 12. The reason why it is provided in the relatively upper part is to prevent the water in the evaporation chamber 11 from flowing directly.

  Further, the evaporation chamber 11 and the reforming chamber 12 are arranged in the horizontal direction, and the off-gas combustion unit 3 is disposed below them. The horizontal direction here may be almost the same height, and is not necessarily provided on a straight line.

The evaporation chamber 11 (and the reforming chamber 12) will be described in more detail.
The evaporation chamber 11 has an inlet portion 13 in the end wall 1a, and fuel gas and water are introduced. Here, the fuel gas and water are premixed in an introduction pipe (not shown) and introduced from a single inlet portion 13, but may be introduced separately.
The evaporation chamber 11 is filled with a heat transfer promoting member (not shown) such as a heat transfer bead. In the evaporation chamber 11, water is evaporated to generate water vapor.

Here, a shielding plate 17 is provided in the evaporation chamber 11 on the upstream side of the partition wall 15. The shielding plate 17 hangs downward from the upper wall of the evaporation chamber 11 and forms a second opening 18 between the lower edge of the evaporation plate 11 and the bottom wall of the evaporation chamber 11 through which fuel gas and water can flow.
In addition, it is needless to say that the space between the shielding plate 17 and the partition wall 15 is a part of the evaporation chamber 11 and is filled with a heat transfer promoting member.

  The second opening 18, particularly the upper edge (the lower edge of the shielding plate 17), is provided at a lower position than the first opening 16 provided in the partition wall 15 that partitions the evaporation chamber 11 and the reforming chamber 12. In other words, the first opening 16 is provided at a higher position than the second opening 18.

Reference is made to the height relationship between the fuel gas and water inlet 13 to the evaporation chamber 11 and the first opening 16 and the second opening 18.
The first opening 16 is provided at a position higher than the inlet 13 for the fuel gas and water to the evaporation chamber 11.
The second opening 18, particularly the upper edge (the lower edge of the shielding plate 17), is provided at a position lower than the fuel gas and water inlet 13 to the evaporation chamber 11.
Therefore, the height relationship between the fuel gas and water inlet 13, the second opening 18, and the first opening 16 into the evaporation chamber 11 is the second opening 18, the inlet 13, and the first opening in descending order. The order is 16.

The reforming chamber 12 is filled with a reforming catalyst (not shown). In the reforming chamber 12, the mixed gas from the evaporation chamber 11 is reformed to generate a reformed gas containing hydrogen.
The reforming chamber 12 has an outlet 14 in the end wall 1b, and supplies the generated reformed gas to the fuel cell 2 (FIG. 1).

According to the fuel reformer 1 described above, fuel gas and water are introduced into the evaporation chamber 11 from the inlet 13, and the water introduced in the liquid phase forms a liquid pool in the evaporation chamber 11, and is vaporized from the liquid pool. To do. Accordingly, the fuel gas is pushed upward in the evaporation chamber 11. For this reason, a fuel gas layer is formed on the upper side and a water vapor layer is formed on the lower side in the evaporation chamber 11.
However, since there is a shielding plate 17 suspended from the upper wall of the evaporation chamber 11 on the upstream side of the partition wall 15, the fuel gas collides with the shielding plate 17, becomes a downward flow, and collides with water vapor. Mixing of fuel gas and water vapor is promoted.
The liquid level of the puddle oscillates irregularly due to repeated generation and disappearance of bubbles. The fuel gas collides with the shielding plate 17 to form a downward flow, and is guided to the irregular rocking portion, so that the mixing of the fuel gas and water vapor is promoted.
The fuel gas that has collided with the water vapor then passes through the second opening 18 formed between the lower edge of the shielding plate 17 and the bottom wall of the evaporation chamber 11. Therefore, when passing through the narrow second opening 18, the fuel gas and the water vapor are further mixed well.
Further, the fuel gas and the water vapor collide with the lower part of the partition wall 15 after passing through the second opening 18, and the mixing is promoted here. Then, the fuel and water vapor are changed upward in the space between the shielding plate 17 and the partition wall 15, and then flow into the reforming chamber 12 from the second opening 16. Therefore, the fuel gas and the water vapor are well mixed between the shielding plate 17 and the partition wall 15 to form a good air-fuel mixture and flow into the reforming chamber 12.

  The distance S between the partition wall 15 and the shielding plate 17 is sufficiently reduced (about 1 to 3 times the diameter of the heat transfer beads), and the fuel gas and water vapor that have passed through the second opening 18 of the shielding plate 17 are separated from the partition wall. The lower part of 15 may be vigorously collided to promote mixing.

  After mixing in the evaporation chamber 11, the mixed gas of the fuel gas and water vapor that has entered the reforming chamber 12 has been improved in its mixing property, and thus is reformed and hardly contains coking. A reformed gas is generated.

In the fuel cell system of the present embodiment, when the power generation output is about 1 kW, the position of the lower end edge of the shielding plate 17 (distance H from the bottom wall of the evaporation chamber 11 to the lower end edge of the shielding plate 17), and The distance S between the partition wall 15 and the shielding plate 17 is as follows.
The distance H from the bottom wall of the evaporation chamber 11 to the lower end edge of the shielding plate 17 is preferably 7 mm or less in order to exhibit a sufficient mixing effect. However, it should be set higher than the liquid level in the puddle.
The distance S between the partition wall 15 and the shielding plate 17 is preferably 7 mm or less in order to exhibit a sufficient mixing effect.

The simulation result will be described with reference to FIGS.
FIG. 3 is a diagram showing the relationship between the distance H (mm) from the bottom wall of the evaporation chamber to the lower edge of the shielding plate and the mixing index value as a simulation.
In the simulation, the distance S between the partition wall and the shielding plate was fixed to 7 mm, the distance H from the bottom wall of the evaporation chamber to the lower edge of the shielding plate was changed, and the mixing property was evaluated by the mixing property index value.
The mixing index value was calculated as follows. The steam / carbon ratio (S / C) of each part (plural locations) in the reforming chamber is detected, and the minimum value of these, that is, the S / C at the location where the S / C is the lowest is used as the mixing index value. . Therefore, the smaller the mixability index value, the smaller the S / C portion in the reforming chamber, which means that the mixture is not mixed.
As a result, the upper limit value Hmax of the distance from the bottom wall of the evaporation chamber to the lower end edge of the shielding plate is 7 mm. If the upper limit value Hmax is exceeded, a sufficient impact effect cannot be obtained, and the mixing index value becomes small. It turned out to get worse. Note that the distance H from the bottom wall of the evaporation chamber to the lower edge of the shielding plate needs to be higher than the liquid level of the liquid pool, and there is also a lower limit value Hmin.

FIG. 4 is a diagram showing the relationship between the distance S between the partition wall and the shielding plate and the mixing index value as a simulation.
In the simulation, the distance H from the bottom wall of the evaporation chamber to the lower edge of the shielding plate is fixed to 7 mm, the distance S between the partition wall and the shielding plate is changed, and the mixing property is evaluated by the above-described mixing index value. .
As a result, the distance S between the partition wall and the shielding plate needs to be 7 mm or less, and if it exceeds 7 mm, the gas mixing becomes insufficient, the mixing index value becomes small, and the mixing property deteriorates. I understood.

  However, the above simulation is a case where the power generation output is about 1 kW, and when the power generation output exceeds 1 kW, the amount of fuel gas and water required for reforming increases, so both the distance H and the distance S are It can be larger than 7 mm.

According to this embodiment, the flow direction of the fuel gas pushed upward by the water vapor generated upward from the liquid pool in the evaporation chamber 11 is lowered by the shielding plate 17 suspended from the upper wall of the evaporation chamber 11. Alternatively, it can be made to collide with the opposing water vapor and promote mixing of the fuel gas and water vapor.
Further, the fuel gas and water vapor that have passed through the second opening 18 formed on the lower side of the lower end edge of the shielding plate 17 collide with the partition wall 15 and travel toward the upper first opening 16, thereby shielding. Mixing is also promoted between the plate 17 and the partition wall 15.
Therefore, the mixing property of the fuel gas and the water vapor is improved, and the coking of the reforming catalyst in the reforming chamber 12 can be suppressed. In addition, the structure is extremely simple and low cost, and can be easily implemented.

The effects of improved mixing are as follows.
1) Even if water is introduced in any of a gas phase, a liquid phase, and a mixed phase, the miscibility with the fuel gas is improved and coking of the reforming catalyst in the reforming chamber 12 can be suppressed. Therefore, it is possible to reduce the amount of water that has been set to a large amount, thereby improving the power generation efficiency. Also, if the amount of water supplied is reduced, the temperature of the reforming catalyst rises and the reforming reaction rate increases, so that the amount of reforming catalyst filling required to complete the reforming reaction can be reduced. It becomes possible. In addition, since the fuel reformer can be downsized, the fuel cell system can also be downsized. Since the heat capacity of the fuel reformer and the fuel cell system is reduced by downsizing, the amount of fuel required to maintain the fuel reformer and the fuel cell system at a predetermined temperature is reduced, and the power generation efficiency is improved. Can do.
2) When the flow rate increase / decrease rate of the fuel gas and water at the time of power generation output fluctuation etc. is increased, there is a concern that the water vapor supply amount temporarily decreases due to the delay in vaporization of water in the evaporation chamber 11 when the power generation output increases. By improving the mixing property, local reduction of the water vapor amount in the reforming chamber 12 does not occur, and coking can be suppressed. Therefore, the flow rate increase / decrease speed of the fuel gas and water can be increased, and the response of the power generation output can be improved.

  Further, according to the present embodiment, the first opening 16 of the partition wall 15 is provided at a position higher than the inlet 13 of the fuel gas and water to the evaporation chamber 11 so that the water in the evaporation chamber 11 is modified. It is possible to reliably prevent direct flow into the quality chamber 12.

  Further, according to the present embodiment, the second opening 18 of the shielding plate 17 is provided at a position lower than the inlet 13 of the fuel gas and water to the evaporation chamber 11, so that the fuel gas is surely directed downward. Can collide with water vapor.

  The illustrated embodiments are merely examples of the present invention, and the present invention is not limited to those directly described by the described embodiments, and various improvements and modifications made by those skilled in the art within the scope of the claims. Needless to say, it encompasses changes.

DESCRIPTION OF SYMBOLS 1 Fuel reformer 2 Fuel cell 3 Off-gas combustion part 4 Case (combustion chamber division member)
DESCRIPTION OF SYMBOLS 11 Evaporation chamber 12 Reforming chamber 13 Inlet part 14 Outlet part 15 Partition wall 16 1st opening part 17 Shielding plate 18 2nd opening part

Claims (6)

An evaporation chamber that is filled with a heat transfer promotion member, fuel gas and water are introduced, water is evaporated, and water vapor is generated;
A reforming chamber that is filled with a reforming catalyst, communicates with the evaporation chamber, reforms a mixed gas of fuel gas and water vapor from the evaporation chamber, and generates a reformed gas containing hydrogen;
With
The communicating portion between the evaporation chamber and the reforming chamber is a first opening formed in a partition wall that partitions the evaporation chamber and the reforming chamber,
In the evaporation chamber, a shielding plate facing the partition wall is provided,
The shielding plate is suspended downward from the upper wall of the evaporation chamber, and forms a second opening through which fuel gas and water can flow between a lower edge of the evaporation plate and a bottom wall of the evaporation chamber,
The fuel reformer according to claim 1, wherein the first opening is provided at a position higher than the second opening.   2. The fuel reformer according to claim 1, wherein the first opening is provided at a position higher than an inlet of fuel gas and water to the evaporation chamber.   3. The fuel reformer according to claim 1, wherein the second opening is provided at a position lower than an inlet of fuel gas and water into the evaporation chamber. The fuel reformer according to any one of claims 1 to 3,
A fuel cell for generating electricity by reacting hydrogen in the reformed gas from the fuel reformer and oxygen in the oxidant gas;
A fuel cell system comprising:   The said evaporation chamber and the said modification | reformation chamber are arrange | positioned along with the horizontal direction, and the off gas combustion part which burns the off gas discharged | emitted from the said fuel cell is arrange | positioned under these. Fuel cell system.   6. The fuel cell system according to claim 4, wherein the fuel cell is a solid oxide fuel cell.