JPH01232671A - Fuel battery modifying device - Google Patents

Abstract

PURPOSE:To modify a fuel gas by using the exhaust heat of a fuel battery and the heat obtained through combustion of the uncombusted fuel gas exhausted as a heat source for heat-absorbing reactions. CONSTITUTION:The exhaust heat as surplus reaction heat produced at the time of discharging is emitted from the battery body 2 in the form of sensible heat using oxygen gas chiefly as the heat medium. This exhaust heat is supplied to the low-temp. modification reaction part 12 of a modifier device 10 and utilized as the modification reaction heat necessary to modify alcohols or hydrocarbons as crude fuel. The low-temp. modification reaction part 12 makes modifying reaction at 550-600 deg.C, and approx. 50% methane is modified and introduced to a high-temp. modification reaction part 13. Uncombusted fuel gas exhausted from the body 2 is combusted, and the heat is supplied to this high-temp. modification reaction part 13. If the fuel gas utilization of the body 2 is assumed to be 85%, the max. temp. attains 850-920 deg.C. The reaction heat in the reaction part 13 can be reduced to a great extent, as approx. 50% modification is finished in the reaction part 12, and the power generating efficiency is improved by approx. 5% of a conventional modifier.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention effectively utilizes surplus energy by-produced in a fuel cell reformer, particularly in a power generation system, as the heat of a fuel gas reforming reaction. This relates to a reformer.

[Conventional technology]

FIG. 5 is a diagram showing a system flow of a fuel cell power generation system using a conventional reformer disclosed in, for example, Japanese Unexamined Patent Publication No. 1986-23'73'70. is a reforming device for reforming raw fuel (4) such as hydrocarbons or alcohols into fuel gas (6) containing a large amount of hydrogen, which is the main fuel component.
1a) and a heating section (1) that supplies reforming reaction heat through combustion.
b) consists of (2) is the main body of the fuel cell that is supplied with the fuel gas (6) and the oxidizing gas (7) from the air supply M (51) to cause an electrochemical reaction. Gas side In and oxidizing gas (7)
It is constructed by stacking unit cells in multiple stages, each consisting of an oxidizing gas-side electric oven for reacting oxidizing gas and an electrolyte plate interposed between these two electrodes. In the conventional example above, the reformer (1) is housed in the same unit as the fuel cell main body (2). In Figure 5, which explains factors that can improve power generation efficiency, the raw fuel hydrocarbons or alcohols are
First, in the reformer (fl) VC, the fuel gas is reformed into a fuel gas whose main component is water, which undergoes an electrochemical reaction in the fuel cell body (2). The reaction formula for the reforming reaction of methane, a typical hydrocarbon, is shown in equation (1).

As shown in (2), this is a large endothermic reaction as a whole.

OH4+H2O-Co+3H2+ 49.3Kca
l/mol fl)Co +H2O-002+H2
-9.8 Kcal/mol [2] A reforming device (1) that performs such a reforming reaction accompanied by endothermy (1) A reforming reaction section (1a) that is equipped with a reforming catalyst inside and allows the reforming reaction to proceed.
and a heating part (1b) that supplies the reforming reaction heat necessary for carrying out the reforming reaction. In particular, the heated part (1
b) includes a normal combustor, in which unburned combustible gas contained in the fuel gas discharged from the fuel cell main body (2) is combusted, and the combustion that occurs at this time is The heat is used as reforming reaction heat.

On the other hand, in the fuel cell main body, during discharging, the fuel gas side electric oven and the oxidant gas side electric oven each satisfy equation (3).

The reaction shown in (4) progresses, and the chemical 'r-energy of the fuel gas (hydrogen) is converted into electrical energy with a total heat reaction.

Fuel gas side electrical resistance H2 + 003 - JO + 002 + 2e - (3) Oxidizing gas side electrical resistance 02 + 002 + 2e - - + CO32 - (4) In such a fuel cell main body system, the % constant current efficiency is:
It can be roughly calculated using the following equation (5).

E3 + 14 where, Fli]: Electrical energy generated by the fuel cell main body (2) E2: Electrical energy consumed by equipment such as auxiliary machines that purchase the core in the power generation system E3: Fuel Energy possessed by the raw fuel necessary to generate hydrogen consumed in the battery body (2) π4: Energy possessed by the raw fuel corresponding to the fuel gas consumed in the heating part (1b) At eight, E-engineer. E3 and E2 are roughly determined by the characteristics of the fuel cell body (2) and the characteristics of the equipment used in the power generation system, respectively. Therefore, in order to systematically improve the constant current efficiency of the power generation system, The challenge is how to obtain a reformer that requires less fuel gas for heating.

- According to the trial calculation, the proportion of the supplied raw fuel that is used to generate the hydrogen consumed in the fuel cell itself is V'165 ((6), and the remaining 35 (@ is the heating part) It is theoretically impossible to reduce the ratio of the fuel that is burned in the fuel cell body to 10
・However, from the viewpoint of fuel gas distribution and operational stability,
The appropriate utilization ratio is, for example, about 75 to 9o(4). Therefore, by effectively utilizing the Q″c′5 by-product energy in the fuel cell power generation system, the fuel gas consumed in the heating section can be reduced to 10 to 25 (chi) of the total amount of raw fuel input to the entire power generation system. If it can be suppressed to less than 2 degrees or less, it will be possible to improve the electrical efficiency without consuming excess raw fuel in the heating section.

From this point of view, in the power generation system disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 61-237370, the power generation efficiency is improved by preheating the fuel gas with exhaust combustion, which is the excess reaction heat generated in the fuel cell main body. I spend hours trying to improve.

[Problem to be solved by the invention]

In the conventional fuel cell reformer as mentioned above.

The raw fuel is reformed using a heat source that is a mixture of exhaust heat from the fuel cell and combustion heat. - As a trial calculation, the temperature of the mixed heat source is 73
The temperature is about 0 to 800℃, so I-t7 in the reformer.
When the reforming reaction progresses at around 00°C, for example, when the fuel gas is methane, the reforming reaction rate is highly dependent on the reforming reaction temperature and reaction pressure, as shown in Figure 6, an example of its dependence. However, when the reaction pressure is increased to improve the performance of a special VC battery, the reforming reaction rate decreases, which is a problem with equation (5) indicating the power generation efficiency described above, that is, the reduction of fuel gas for heating V
The problem with C was that it had limits.

This invention was made to solve the above problems, and the object is to obtain a reformer that increases the power generation efficiency of a fuel cell power generation system over a wide reaction pressure operating range. Means] The fuel cell reformer according to the present invention introduces the raw fuel into the reformer that obtains heat for reforming, reforms the raw fuel into fuel gas containing a large amount of main fuel components, and supplies the fuel gas to the fuel cell. The exhaust heat of the fuel cell is the heat obtained by burning the first reforming reaction part to be reformed and the unburned fuel gas discharged from the fuel cell, which is reformed using the heat obtained and led to the fuel cell. [Function] In this invention vc, the exhaust heat from the fuel cell and the heat obtained by burning the discharged unburned fuel gas serve as the heat source for the endothermic reaction. and reform the fuel gas.

〔Example〕

FIG. 1 is a diagram showing a system flow of a fuel cell power generation system using a reformer according to an embodiment of the present invention.
2), [41 to (7) are similar to the conventional example.

αυ is a reformer that reforms raw fuel (4) into fuel gas (6a) with a high hydrogen component, which is the main fuel component, and supplies it to the fuel cell main body (2). It consists of a low-temperature reforming reaction section @ that performs the reforming reaction and a high-temperature reforming reaction section α3 that performs the reforming reaction at a relatively high temperature.

In the low-temperature reforming reaction section (2), the reaction heat of the fuel cell body (2) is transported in the form of sensible heat of the circulating oxidizing gas to the reformer αO by a heat medium (2) such as a blower α9 or a heat pump. The reforming reaction can be carried out using the obtained exhaust heat as the heat source for the endothermic reaction. On the other hand, unburned fuel gas (6b) discharged from the fuel cell main body (2) at the high temperature reforming reaction part (end) The reforming reaction is carried out using the heat obtained by burning the combustible components contained in the fuel gas in the heating section as the heat source for the endothermic reaction. In addition, heat exchangers and the like are installed at necessary locations such as the recovery section in the oxidizing gas circulation path.

In a power generation system according to an embodiment of the present invention, the operation of which will be explained next, the raw fuel input is combined with exhaust heat, which is excess reaction heat generated in the fuel cell main body (2), and the fuel cell main body (2). In the embodiment shown in Fig. Wc1, the fuel gas is reformed by effectively combining the combustion heat generated by burning the discharged unburned fuel gas and using both as reforming reaction heat. Fuel cell main body (2) f Exhaust heat, which is surplus reaction heat generated during discharge, is discharged from the fuel cell main body (2) in the form of sensible heat, mainly using oxidizing gas as a heat medium. Exhaust heat, which is surplus reaction heat discharged in the form of sensible heat, is supplied to the low-temperature reforming reaction section (2) of the reformer αO to reform the raw fuel, hydrocarbons or alcohols. For example, in a power generation system using a molten carbonate fuel cell, the temperature of the circulating oxidant gas is around 65oC (YVi) at the time of discharge, but the temperature of the circulating oxidant gas is used as the necessary heat of the reforming reaction. Then it fell slightly to 55.
The modification reaction can be carried out at a reaction temperature of about 0 to 600°C. This reaction temperature fij, methane gas, as shown in the sixth factor.

About 50% is reformed and then led to the high-temperature reforming reaction section (end). This part is provided with a heating part 04, which burns unburned fuel gas discharged from the fuel cell main body (2), and this combustion heat is used as reforming reaction heat to reach the high temperature reforming reaction part (towards the high temperature reforming reaction part). The maximum temperature obtained by burning the unburned fuel gas supplied to the tank will vary depending on various operating conditions and the purchase of each equipment. If the utilization rate of fuel gas is 85%, the temperature will reach 850-920°C. Therefore, in the high-temperature reforming reaction section α3, it is possible to advance the reforming reaction at a higher temperature than in the low-temperature reforming reaction section α,
Furthermore, even under high pressure operating conditions, it is possible to reform methane almost completely as shown in Figure 6. In addition, since the reforming of raw fuel 501 has already been completed in the low-temperature reforming reaction section (c), the high-temperature reforming reaction section (1:1 [
The reforming reaction heat required in the reforming reactor can be significantly reduced compared to conventional reforming reactors, and the amount of fuel gas to be supplied to the heated portion aavc can be significantly reduced.

- Depending on the trial calculation example, the reformer according to the embodiment of the present invention may be used.
In the fuel tank power generation system, the proportion of fuel gas supplied to the heating section (14) out of the raw fuel supplied to the entire military system is about 15 inches, and the proportion of fuel gas supplied to the heating section α4 is about 15. By reducing the amount of gas, the constant current efficiency of the power generation system can be improved by about 5 cm.

In this way, the surplus energy by-produced in the VC system is effectively used as the heat of the reforming reaction of the fuel gas, and the reaction power fIJf/F is wide and high in the range of 1. A power generation efficiency can be obtained.

FIG. 2 shows an example of the structural concept of a reformer 00 having two reaction parts as described above. In the figure, the raw fuel is supplied with exhaust heat that has been transported by a heat medium (2) in a low-temperature reforming reaction section (2), for example, a cylinder, and then undergoes high-temperature reforming in a tube-shaped When passing through the reaction part (to), combustion heat of the unburned fuel gas [6b] is not supplied, and a reforming reaction can be carried out. Since such a reforming system involves a large endothermic reaction, it is necessary to pay attention to the internal heat transfer method in order to realize it. Regarding the low-temperature reforming reaction part, the reaction heat from the iib normal fuel 1 &1' pond body is transported in the form of sensible heat or latent heat using a heating medium, so the heating medium and the fuel gas to be subjected to the reforming reaction are transported. It is a type of heat exchanger that exchanges heat.

In order to downsize the device and perform sufficient heat exchange, filler particles such as finned tubes and ceramic particles should be used. On the other hand, regarding the high temperature reforming reaction part.

Direct heating using a burner-type combustor or catalytic combustor, heating by exchanging heat between high-temperature combustion gas and a reaction tube, or a combination of the two can be used.

FIG. 3 is a diagram showing a system flow of a fuel cell power generation system using a reformer according to another embodiment of the present invention.

In this system, the fuel cell main body is connected to the upstream fuel cell (2
This system is divided into two parts, a) and a downstream fuel cell (2b), each of which is equipped with a reformer for supplying fuel gas in a cascade connection. Here, the upstream reformer α0 to which the raw fuel is supplied is equipped with a low-temperature reforming reaction section ■ and a high-temperature reforming reaction section @.
By supplying the oxidizing gas that has not been discharged from the upstream fuel cell (2a), the reaction heat generated in the upstream fuel cell (2a) is used as a heat source for the reforming reaction to perform reforming again. Supplying to the downstream fuel cell (2b), in this case,
For molten carbonate fuel cells, the operating temperature is generally V1650.
Since the temperature is around ℃, tL75650 is emitted from the fuel cell.
Considering the finite temperature difference required for practical i'cVi heat exchange, exhaust heat around ℃ is used as reforming reaction heat. Here, the reforming reaction in the reformer is As shown in the above equations +1) and (2), the hydrogen concentration in the fuel gas is low and the water vapor concentration is promoted to a high degree, so the upstream fuel cell (2a) consumes hydrogen and generates water vapor. Since the fuel gas discharged from the fuel gas is introduced into the reformer [3], the steam-methane ratio increases and the reforming reaction is promoted.

Figure $4 is a diagram showing a system 70- of a fuel cell power generation system using a reformer according to an embodiment of the present invention. In this system, the fuel cell main body is divided into two and connected in a cascade configuration, and is equipped with an upstream reformer (lla) K low-temperature reforming reaction section υ and high-temperature reforming reaction section α3, and further downstream The side reformer (IIN) is also provided close to this, and the reforming reaction temperature of the downstream reformer @ (11b) is also made easier to raise.

In the above embodiments, a molten carbonate type fuel cell has been described as the main body of the fuel cell, but a power generation system using a phosphoric acid type fuel cell may also be used.

For example, phosphoric acid fuel cells typically have an operating temperature of 200°C.
The reaction heat of around 180 to 200°C can be used for polyelectrification. On the other hand, there are examples in which alcohols such as methanol are used as the raw fuel, but the preferred reforming reaction temperature for methanol is approximately 230 to 300°C. The temperature level of the exhaust heat from the fuel cell is reduced to 30-10 using the combustion heat from the combustion of unburned fuel gas.
By increasing the final reaction temperature by about 0°C to 230 to 300°C, the exhaust heat from the fuel cell can be effectively utilized for the reforming reaction.

〔Effect of the invention〕

This invention has been explained above! 11. ．． In the reformer, which obtains heat for reforming and reforms the raw fuel into fuel gas with a large amount of main fuel components and supplies it to the fuel tank, the first stage is where the raw fuel is introduced and reformed using the exhaust heat of the fuel cell. The structure includes a reforming reaction part and a second reforming reaction part that reforms the unburned fuel gas discharged from the fuel cell using the heat obtained by burning it and leads it to the fuel cell, thus creating a single power generation system. The surplus energy by-produced within the reactor can be effectively used for the heat of the reforming reaction of the fuel gas, and has the effect of obtaining high Vh power generation efficiency over a wide reaction pressure operating range.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a system flow of a fuel cell power generation system using a reformer according to an embodiment of the present invention, and FIG. 2 is a diagram showing the structure of the reformer according to an embodiment of the present invention used in FIG. A diagram showing an example of the concept, FIG. 3 is a diagram showing a system flow of a fuel-N battery power generation system using a reformer according to another embodiment of the present invention, and FIG. Figure 5 shows the system flow of a fuel cell power generation system using a reformer; Figure 6 shows the system flow of a fuel cell power generation system using a conventional reformer. It can't be used as a type of gas. FIG. 2 is a diagram showing the relationship between the methane reforming reaction rate and the reaction temperature and reaction pressure. Figure shows percentage (2) fuel cell, αOVi reformer a1@
The reforming reaction part of lt@-, α3, is the second reforming reaction part. In addition, in each figure, the same reference numeral indicates the same overlapping portion.

Claims (1)

[Claims] In a fuel cell reformer, the raw fuel is introduced into a fuel cell reformer that obtains heat for reforming, reforms the raw fuel into a fuel gas containing a large amount of main fuel components, and supplies the fuel gas to the fuel cell, where the raw fuel is introduced and reformed using the exhaust heat of the fuel cell. The fuel cell is characterized by comprising a first reforming reaction part and a second reforming reaction part that reforms unburned fuel gas discharged from the fuel cell using heat obtained by burning it and leads it to the fuel cell. fuel cell reformer.