JPH0812301A - Methanol reformer - Google Patents

Abstract

PURPOSE:To increase the reliability and safety and to use as a movable hydrogen supply source by compactly and easily constituting a methanol reformer of a combustor, a reforming tube, a liquid evaporator, a reforming catalyst, a CO conversion tube, a CO conversion catalyst and the like. CONSTITUTION:A methanol reforming tube 4 is arranged, bent in such a form that it surrounds a combustor 1. Near the inlet end part of the reforming tube 4, a liquid evaporating part 6 packed with foamed nickel as an air permeable packing 5 is installed and connected to a raw material fuel feeding pipe 7. In downstream of the liquid evaporating part 6 of the reforming tube 4, a packed part of a reforming catalyst 8 is installed. A CO conversion tube 9 is arranged in a coil shape on the outer periphery of the reforming tube 4, following the reforming tube 4, and is packed with a CO conversion catalyst 10. An outlet 11 of the conversion tube 9 is opened to the upper end. These elements are surrounded by an outer casing 12 consisting of an insulating material. Combustion is made in the combustor 1 to heat the reformer, and methanol and water are fed to the liquid evaporating part 6 of the reforming tube 4 from the raw material fuel feeding pipe 7 to perform methanol reforming and CO conversion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a methanol reformer for supplying hydrogen-rich gas using methanol as a raw fuel. This methanol reformer is used for mobile applications in general, and especially for fuel supply for low-temperature operation fuel cells.

[0002]

Methanol reforming technology is already widely used in chemical plant applications. The reforming method is as follows. First, a reforming gas containing H _{2 as a} main component is generated by a catalytic reforming reaction of the formula (1) or a steam reforming reaction of the formula (2) using a methanol reforming catalyst, and then the reforming gas is generated. It is general to use a so-called CO conversion reaction of the formula (3) in which CO contained in a gas in a considerable amount is reacted with H ₂ O to convert it into H ₂ and CO ₂ .

[0003]

Embedded image

The resulting H ₂ -rich gas contains:
Since CO ₂ , H ₂ O and CO are contained, a separation technique such as the PSA method is used in plants and the like in order to obtain H ₂ with higher purity. Methanol reforming generally performed is methanol reforming in these large-scale equipment,
Development of a small reformer is also being considered by some. For example, it is being developed as a fuel supply for hydrogen engine cars and small-scale fuel cells for remote areas. However, even with these relatively small-sized reformers, the purpose is to support an output of several kW or more, so even though they are small, they are still relatively large in scale, and efficiency is emphasized due to the nature of their applications, making them compact and lightweight. It has not been pursued so much for simplification and simplification.

On the other hand, in recent years, a small fuel cell which operates at a low temperature has been actively developed. These small fuel cells may be used as mobile power sources, but low-temperature fuel cells are limited to hydrogen gas, with some exceptions such as methanol direct fuel cells. . In addition, as the type of fuel cell, a polymer electrolyte fuel cell or the like is considered to be excellent because it is easy to obtain a high output density. However, low-temperature operation type fuel cells including this type have a problem that they are vulnerable to catalyst poisoning by CO in the fuel gas, since the Pt catalyst is used for the electrodes. Therefore, when the reformed gas is supplied to the fuel cell for use, it is necessary to reduce the CO concentration as much as possible. In a plant having a large scale to some extent, the CO concentration can be reduced to 1% or less by the CO conversion reaction. Therefore, in a system of several tens of kW or more of phosphoric acid fuel cells, which has a relatively high operating temperature of about 180, C
There is no problem with only O transformation. However, in a polymer electrolyte fuel cell, which is optimal as a mobile power source, the operating temperature is as low as around 70 ° C., so it is easily affected by CO, and it is necessary to further reduce the CO concentration. However, an extremely small-scale methanol reformer has not been developed, and there has been no methanol reformer capable of realizing low CO concentration with compactness, simplicity, and safety.

[0006]

In order to solve the above-mentioned problems, the reformer has the following problems in order to realize a compact and simple structure and to realize low CO concentration as well as safety. First, the arrangement of the heat source and the reforming part, which are important for effective utilization of heat and efficient reforming, and the structure of the constituent elements. This optimization of the layout and structure greatly contributes to compactness. Further, as a problem related to simplicity, it is necessary to improve the controllability of the heat supply amount and the raw fuel supply amount and the handling convenience in consideration of versatility. Regarding the CO concentration, for example, it is necessary to reduce the CO concentration as much as possible in order to meet the usage conditions of the low temperature fuel cell, but this is also a problem for safety.
The problem is how to realize this in a small-scale device. In addition, considering the life and stable operation of the reformer, the purity of methanol, water, etc. becomes a problem, but unexpected use situations are expected in general applications, so it is necessary to prevent them in advance. . By solving these problems, it can be used as a mobile hydrogen supply source, for example, for low temperature operation fuel cell fuel processing.

[0007]

A methanol reformer according to the present invention comprises a combustor, a reforming pipe arranged so as to be bent to surround the periphery of the combustor, and an inlet end of the reforming pipe. A liquid evaporation part having a gas permeable filler provided therein, a reforming catalyst filled in the reforming pipe in a downstream flow of the liquid evaporation part, and bent to the outer peripheral portion of the reforming pipe continuously with the reforming pipe. And a CO shift catalyst filled in the shift shift pipe, and an outer casing made of a heat insulating material. Methanol and water are supplied from the liquid evaporation section of the reforming pipe to reform the methanol. And CO conversion.

Further, the methanol reforming tube of the present invention includes a combustor, a reforming tube bent to surround the combustor, and a ventilation provided near an inlet end of the reforming tube. Liquid evaporating section having a functional packing, a reforming catalyst filled in the reforming tube in a downstream flow of the liquid evaporating section, and being bent to the outer peripheral portion of the reforming tube continuously with the reforming tube. Placed C
An O shift pipe, a second liquid evaporation section having a gas permeable filler provided in a section between the reforming pipe and the shift pipe, a CO shift catalyst filled in the shift pipe, and an outer part made of a heat insulating material. A casing is provided, and methanol is supplied to the first liquid evaporation unit and water is supplied to the second liquid evaporation unit to perform methanol reforming and CO conversion.

Here, the combustor is preferably a catalytic combustor using methanol as a fuel. Also, two opposing diaphragms are provided as means for carrying and supplying a mixed liquid of methanol and water to the liquid evaporating section, or as means for carrying and supplying methanol and water to the first and second liquid evaporating sections, respectively. It is preferable to use a pair of pumps and use diaphragm pumps that operate in a coordinated manner so that each diaphragm has a motor-driven cam to reduce the pulsating flow of the delivery liquid.

Further, it is supplied from a mixture containing methanol and water to be supplied to the liquid evaporating section, or a container accommodating methanol and water to be supplied to the first liquid evaporating section and the second liquid evaporating section, respectively, and a shift pipe. Equipped with a purification column containing an adsorbent for purifying the reformed product gas, the container and the purification column are jointly housed in one cartridge, and raw fuel is supplied to the methanol reformer for a certain period of time. It is preferable that the reformed product gas be purified.

[0011]

In the methanol reformer according to the present invention, a reforming tube which requires a slightly high temperature (350 to 400 ° C.) for the reaction and in which an endothermic reaction takes place is installed in the vicinity of the periphery of the combustor, and a low temperature portion in the periphery thereof is installed. Is equipped with a CO shift pipe in which a relatively low temperature (about 250 ° C.) is preferable and an exothermic reaction occurs. With this structure, each reaction tube can tend to inevitably achieve a desired state of heat supply, temperature distribution, etc. from its spatial arrangement. Therefore, the temperature of the reforming pipe and the CO shift pipe can be maintained at a desired value only by fixing the calorific value of the combustor at the center to a certain constant value or by performing simple control.

Further, the raw fuel methanol and water are conveyed with a low pulsating flow and good controllability by a set of cam driven diaphragm pumps. This makes it possible to convey an extremely small amount of liquid with good reproducibility and control the reforming capacity and the amount of combustion. Further, the transported methanol or water is vaporized by the liquid evaporation section provided inside the reforming pipe and is naturally introduced into the reforming pipe, so that the structure is simple and the control is easy. In addition, a container for accommodating the fuel methanol and pure water, or a mixture of methanol and water, and a purification pipe containing a reformed gas purification adsorbent are provided.
By jointly storing them in individual cartridges, it is possible to supply the raw fuel whose purity is guaranteed for the operation of the reformer for a certain period of time, and at the same time, surely adsorb and remove CO and the like in the reformed gas.

[0013]

EXAMPLES Examples of the methanol reformer according to the present invention will be described below. [Example 1] Fig. 1 shows a schematic configuration of a methanol reformer of this example. The combustor 1 is a wick type combustor using methanol as a fuel, and a dispersion plate 2 is installed on the upper part thereof to disperse the flame 3 laterally. The amount of heat of combustion can be changed to some extent by adjusting the wick vertically. The methanol reforming tube 4 is composed of a slightly flat copper tube having a cross-sectional area of about 1.5 cm ² , and has a diameter of about 8 cm so as to surround the periphery of the combustor 1.
It is wound in a coil shape. A liquid vaporizing section 6 filled with foamed nickel as the air-permeable filler 5 is provided near the upper end serving as the inlet of the reforming tube 4 for a length of about 5 cm, and the raw fuel is supplied to the liquid vaporizing section 6. A raw fuel supply pipe 7 for supplying is connected. The reforming catalyst 8 is filled in the reforming pipe 4 downstream of the liquid evaporating portion over a length of about 40 cm. As the reforming catalyst, for example, a pellet-shaped catalyst in which Pt is supported on alumina is used.

The CO shift pipe 9 is composed of a copper pipe continuous with the reforming pipe 4, and is wound around the outer periphery of the reforming pipe 4 in a coil shape. After the reforming catalyst in the pipe 4, about 50
Cu / ZnO based pellet CO over a length of cm
The shift catalyst 10 is filled. The outlet 11 of the shift pipe 9 is open at the upper end. Reference numeral 12 is an outer casing made of a heat insulating material that surrounds the above-mentioned elements, and an exhaust port 13 for combustion exhaust gas is provided in the upper portion.

In order to operate this reformer, first, methanol is supplied to the combustor and burned to raise the temperature of the reformer. The temperature of the reforming tube is 350-
Although it is desirable that the temperature be 400 ° C., in the present embodiment, for simplicity, the combustion amount is fixed at a combustion amount that stabilizes at the temperature in the standard use state. When the temperature of the reforming tube rises, methanol and water are supplied to the liquid evaporation section 6 from the tube 7 at a rate of 2 g / min each. Methanol and water are vaporized here and flow into the reforming pipe 4, and due to the action of the reforming catalyst 8, contain H ₂ as a main component and 10% by number of CO ₂ , CO and H ₂ O. Generate a mixed gas. The mixed gas subsequently enters the CO shift pipe 9, but since the CO shift pipe is slightly away from the heat source and the reforming reaction is an endothermic reaction, the temperature is lower than that of the reforming pipe. It is in an advantageous state for CO conversion. Cu / Zn in the CO shift pipe
Since the CO conversion reaction between CO and H ₂ O proceeds due to the function of the O catalyst 10, the CO concentration at the outlet 11 becomes 0.5 to 2% and the H ₂ concentration becomes 70 to 75%. The flow rate of the produced gas is about 4 liters.

[Embodiment 2] FIG. 2 shows a schematic structure of a methanol reformer according to this embodiment. In this embodiment, the reforming tube 4
A second liquid evaporation section 14 is provided in the section from the CO conversion pipe 9 to the CO conversion tube 9, and a filling material 15 for promoting vaporization is provided inside the second liquid evaporation section 14.
Is filled. Methanol is supplied to the liquid evaporation section 6 of the reforming pipe, and water is supplied to the second liquid evaporation section 14 from the supply pipe 16. In this embodiment, the first liquid evaporating section for methanol is located above the reforming tube and the second liquid evaporating section for water is located below the reforming tube. The structure of the reforming pipe, the CO shift pipe and other elements is the same as that of the first embodiment.
Is similar to.

In order to operate this reformer, when the temperature of the reforming pipe rises to 350 to 400 ° C., 2 g of methanol is added to the first liquid evaporation section 6 installed near the inlet of the reforming pipe.
The second liquid evaporator 1 located between the reforming pipe and the CO shift pipe 1
4 is supplied with water at a rate of 2 g / min. In the reforming tube, a catalytic thermal decomposition reaction of methanol occurs, and a mixed gas containing H ₂ as a main component is generated as in Example 1, but in this case, the concentration of CO is higher than 20% and the amount of CO ₂ is small. . Subsequently, water vapor is added to the mixed gas in the process of passing through the second liquid evaporation unit 14, and the gas temperature is lowered due to the heat of vaporization of water. The mixed gas added with H ₂ O causes a CO shift reaction in the CO shift pipe 9, and the CO concentration drops to 1% or less. This is related to the fact that the CO conversion reaction is an exothermic reaction and it is advantageous that the temperature is as low as around 250 ° C. That is, as described above, in the structure of the present embodiment, the temperature of the gas at around 350 ° C. passing through the reforming tube is lowered by the cooling effect by vaporization, and compared with the case where H ₂ O is added from the reforming stage. Since H ₂ O is added just before the CO conversion, the partial pressure of H ₂ O is high and the reaction is advantageous, so that C 2
The O concentration can be greatly reduced.

[Embodiment 3] In the above embodiment, the core type combustor is used as the combustor of the methanol reformer.
Here, an embodiment using a catalytic combustor using methanol as a fuel will be described. In this embodiment, as shown in FIG. 3, a cylindrical honeycomb combustor carrying a noble metal catalyst is used. Inorganic fiber block 17 for fuel methanol
After being vaporized and uniformly distributed by the diffusion plate 18, the surface of the cylindrical honeycomb catalyst 19 comes into contact with air to cause catalytic combustion. In catalytic combustion, since the heat generating part can be formed in a planar shape, the uniformity of heating of the reforming pipe and the like is improved, and the combustion temperature is also lower than that of the flame. Problems such as methane generation and carbon deposition can be prevented. Further, the control of the combustion heat amount can be performed by controlling the amount of methanol to be supplied, and since there are few problems such as incomplete combustion, there are advantages such as superior safety and controllability as compared with the case of using a flame. .

[Embodiment 4] In this embodiment, an example of the structure of the liquid carrying and supplying section will be described. The liquid carrying and supplying section is used as a means for carrying and supplying methanol, water, etc. to the liquid evaporating section, or as a means for supplying methanol to the combustor. The configuration consists of two diaphragm pumps facing each other,
It consists of operating each diaphragm cooperatively by a cam driven by a motor. With such a configuration, it is possible to control the liquid transfer with a minute flow rate and reduce the pulsating flow. Furthermore, the reproducibility is not deteriorated due to the deformation of the tube found in the tube pump and the like.

The structure of the diaphragm pump will be described with reference to FIG. A diaphragm 26 is provided in a main body 25 provided with an inlet 22 having a valve 21 and an outlet 24 having a valve 23, and the diaphragm 26 is provided with a rod 27 driven by a cam 32. 28 is a return spring. The pair of pumps 20a, 20b includes a drive unit 31 as shown.
The rod 27 is pressed by the cam 32 driven by the diaphragm 26 moves, and the valve operates to supply the liquid from the outlet 24 to the supply pipe 28. Both of them are displaced by half the rotation of the cam 32. Works. Similarly, the pair of pumps 30 a and 30 b is driven by the cam 32.

In a single diaphragm pump, there is a period in which the liquid delivery is stopped, but continuous liquid delivery can be performed by operating the two pumps in a state in which the operations are shifted by a half cycle, and the pulsating flow is a cam shape. The degree can be significantly reduced by optimizing. The cam drive unit 31 is composed of a DC servo motor and a reduction gear in this embodiment, and the flow rate can be adjusted within the range of 0.3 to 2 g / min by controlling the motor rotation speed. The material of the diaphragm is polytetrafluoroethylene, and the movable part has a diameter of about 2.5c.
m. With such a mechanism, it is possible to realize a liquid supply with a small flow rate and a small pulsating flow, and a stable reforming operation can be performed. The pumps 20a and 20b are for methanol, for example, and the pumps 30a and 30b are for water, and may be used for supplying methanol for combustion, if necessary.

[Embodiment 5] In this embodiment, an outline of a cartridge in which a purification column containing methanol, pure water, and an adsorbent for purifying a reformed product gas is integrally housed,
The usage state when connected to the methanol reforming portion will be described. FIG. 5 shows a schematic structure of the cartridge, and FIG. 6 shows a connection state with the methanol reforming portion. The cartridge is integrated with a methanol tank 40 that stores methanol and pure water in an amount that can be used for the methanol reformer for a certain period of time, a pure water tank 41, and a purification column 42 that is filled with a gas purification adsorbent. Has been done. The gas purification adsorbent 43 is mainly intended to remove CO by adsorption.
As the adsorbent, a solid adsorbent using monovalent copper is used. Liquid outlets 44 and 45 are installed at the bottom of the methanol tank 40 and the pure water tank 41, respectively, and a simple valve for adjusting the tank internal pressure is installed at the upper part (not shown). The gas purification column portion is also provided with a reformed gas inlet 46 and an outlet 47, and a joint that can be connected to the reformer main body side without leakage. These openings are sealed so as to prevent leakage and the like during the storage period prior to transportation and use, and the seals are breached before use.

Next, the connection between the cartridge and the reformer will be described with reference to FIG. Methanol supply pipe 48 connected to the outlet 44 of the methanol tank 40
Is branched into a pipe 48a connected to the inlet of the reformer tube of the reformer 49 and a pipe 48b connected to the fuel supply port of the combustor 50. A water supply pipe 51 connected to the outlet 45 of the pure water tank 41 is connected to the water inlet of the reformer. A flow rate control unit 52 for controlling the flow rate is provided in the middle of these pipes 48, 51. A pipe 53 for sending the gas generated by the reformer 49 is connected to the inlet of the refining column 42, and an air cooler 54 for condensing excess steam and a drain tank 55 for discharging condensed water are provided in the middle of the pipe 53. Is provided. Reference numeral 56 is a pipe for supplying the modified glass purified by the column 44.

One of the advantages of integrally storing and supplying the raw material in the cartridge is that the purity of the raw material can be secured.
That is, when a catalyst is used, impurities in the substance to be treated affect the life and performance of the catalyst.For example, if general city water is used as the water to be used, chlorine ions or the like may be mixed in. On the other hand, when methanol of low purity or completely different hydrocarbon liquid is mixed in, there is a possibility of causing rapid deterioration of the catalyst. On the contrary,
Fill such a cartridge with methanol and pure water,
By supplying this, the purity is assured and the error of liquid supply is prevented. Further, it is possible to prevent malfunction of the reformer due to such a mistaken supply of raw materials, and it is possible to enhance safety.

Regarding the refining column, the reformed gas obtained from the reformer contains 0.5 to 2% of CO as described above, and therefore it is necessary to reduce CO. That is, in order to supply and use a low temperature fuel cell such as a polymer electrolyte fuel cell without shortening its life, it is necessary to greatly reduce the CO concentration, and a purification column is necessary for this purpose. Becomes In the case of this purification tube, the CO concentration in the refined reformed gas can be removed to about several tens of ppm, so that it can be used in a fuel cell. Also,
It is necessary to remove CO from the viewpoint of safety,
At this concentration level, there are no safety issues. The adsorbent may be recyclable in some cases, but it is difficult to regenerate it when considering general applications, and it is appropriate to use it only once in order to guarantee the processing capacity. In view of the above circumstances, the cartridge of this embodiment can play a useful role in terms of safety and performance guarantee.

Although copper pipes are used as the reforming pipes and CO shift pipes in the above-mentioned embodiments, other materials may be used, such as a circular pipe, a rectangular pipe, and a fin pipe. It can be anything. Further, the gas permeable filling material of the liquid vaporization section may be made of a material other than the foam metal, for example, a porous metal sintered body or a porous ceramic. The methanol reforming catalyst and CO shift catalyst used are not limited to those in the examples, and the shape is not limited to pellets. Further, the catalyst used for catalytic combustion is not limited to the noble metal catalyst, and the shape does not have to be a cylindrical honeycomb. For the cam-operated diaphragm pump, in the embodiment, methanol,
Although it is separate from water, it may be for a mixed solution of methanol and water, and the diaphragm may have any material and shape. Regarding the cartridges of methanol, pure water, and the purification column, the tanks, the arrangement of the columns, the materials, and the like may be of any type, and the structure of the fluid connecting portion is not limited. Further, the CO adsorbent packed in the gas purification column does not have to be copper or the like, and the form thereof is not limited to solid but may be impregnated with a liquid into a porous body.
Further, the use of the reformer is not limited to the fuel cell, but may be other uses such as an engine.

[0027]

As described above, the methanol reformer of the present invention has a compact and simple structure, but is capable of performing small-scale methanol reforming, and controls the amount of raw fuel supplied to control the amount of processing. Is also possible. Further, by making the methanol, pure water, and gas purification columns into cartridges, stable operation and reduction of CO concentration in the gas are possible, and reliability and safety are improved. Further, by supplying the hydrogen-rich gas having a sufficiently low CO concentration generated in the methanol reformer to the low temperature operation fuel cell, it becomes possible to construct a compact and movable power supply system.

[Brief description of drawings]

FIG. 1 is a front view in which a part of a reformer according to an embodiment of the present invention is cut away.

FIG. 2 is a front view in which a part of a reformer according to another embodiment of the present invention is cut away.

FIG. 3 is a front view in which a part of a reformer using a catalytic combustor according to another embodiment of the present invention is cut away.

FIG. 4 is a perspective view in which a part of the diaphragm pump used in the embodiment of the present invention is cut away.

FIG. 5 is a perspective view in which a part of the cartridge used in the embodiment of the present invention is cut away.

FIG. 6 is a view showing a connection state between the cartridge and the reformer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Combustor 2 Dispersion plate 3 Flame 4 Methanol reforming pipe 5 Breathable packing 6 Liquid evaporation part 7 Raw fuel supply pipe 8 Reforming catalyst 9 CO shift pipe 10 CO shift catalyst 11 Reformation pipe outlet 12 Outer casing 13 Combustion gas Exhaust port 14 Second liquid evaporation part 15 Breathable filler 16 Water supply pipe 17 Inorganic fiber block 18 Diffusion plate 19 Cylindrical honeycomb catalyst

Claims (5)

[Claims] 1. A liquid combustor having a combustor, a reforming pipe bent to surround the periphery of the combustor, and a gas permeable filler provided near an inlet end of the reforming pipe, A reforming catalyst filled in the reforming pipe in the downstream of the liquid evaporating section,
A CO shift pipe arranged continuously with the reforming pipe and bent around the outer circumference of the reforming pipe, and CO filled in the shift pipe.
A methanol reformer comprising an outer casing composed of a shift catalyst and a heat insulating material, and supplying methanol and water from a liquid evaporating portion of the reforming tube to perform methanol reforming and CO shift. 2. A first liquid having a combustor, a reforming tube arranged so as to be bent so as to surround the periphery of the combustor, and an air-permeable filler provided near an inlet end of the reforming tube. Evaporation section,
A reforming catalyst filled in the downstream of the liquid vaporizing section in the reforming pipe, a CO shift pipe continuous with the reforming pipe and bent around the outer periphery of the reforming pipe, and the reforming pipe. A second liquid evaporating portion having a gas permeable filler provided in a section between the shift pipe and the shift pipe; a CO shift catalyst filled in the shift pipe; and an outer casing made of a heat insulating material. The methanol reformer characterized in that methanol is supplied to the liquid evaporating section and water is supplied to the second liquid evaporating section to perform methanol reforming and CO shift conversion. 3. The methanol reformer according to claim 1, wherein the combustor is a catalytic combustor using methanol as a fuel. 4. A means for conveying and supplying a mixture of methanol and pure water or a mixture of methanol and water to a liquid evaporating section is a set of two diaphragm pumps facing each other, and each diaphragm is delivered by a motor-driven cam. The methanol reformer according to claim 1 or 2, comprising a diaphragm pump that operates in a coordinated manner so as to reduce the pulsating flow of the liquid. 5. A purification column containing a container containing methanol and pure water or a mixture of methanol and water to be supplied to the liquid evaporation section, and an adsorbent for purifying the reformed product gas supplied from the shift pipe. The methanol reformer according to claim 1 or 2, further comprising: a container, the container and the purification column are housed together in one cartridge, and the raw fuel is supplied to the methanol reformer for a certain period of time to simultaneously purify the reformed product gas. Pawn.