WO2002000813A1

WO2002000813A1 - Fuel for use in fuel cell system

Info

Publication number: WO2002000813A1
Application number: PCT/JP2001/005645
Authority: WO
Inventors: Kenichirou Saitou; Iwao Anzai; Osamu Sadakane; Michiro Matsubara
Original assignee: Nippon Oil Corporation
Priority date: 2000-06-29
Filing date: 2001-06-29
Publication date: 2002-01-03
Also published as: AU2001267883A1; US20030105369A1

Abstract

A fuel for use in a fuel cell system comprising a mixture of hydrocarbon compounds which is a gas at ordinary temperatures and contains saturated components in an amount of 60 mole % or more, olefin components in an amount of 40 mole % or less and butadiene components in an amount of 0.5 mole % or less, wherein saturated components having 4 or more carbon atoms contain iso-paraffins in an amount of 0.1 mole % or more. The fuel exhibits an increased energy output generated per its weight and per amount of CO2 formed, an improved fuel consumption, a decreased evaporative emission, good handling properties such as good storage stability and a suitable flash point, and reduced calories required for preheating. Further, the fuel allows a fuel cell system using the fuel to keep its initial performance for a long period of time, since it reduces the deterioration of a fuel cell system, that is, a reforming catalyst, a water gas shift reaction catalyst, a carbon monoxide removal catalyst, a fuel cell stack and the like.

Description

Description Fuel technology for fuel cell systems

The present invention relates to a fuel used for a fuel cell system. Background art

In recent years, the growing sense of danger to the global environment in the future has demanded the development of an energy supply system that is kind to the earth. JP (This, CO ₂ reduction for global warming, THC (unreacted hydrocarbons in the exhaust gas), NO x, PM (particulate matter in exhaust gas: soot, the fuel-lubricant high It is required to achieve a high degree of reduction of harmful substances such as boiling point and unburned polymer components) Specific examples of such systems include automobile power systems that replace conventional O.D. Another example is a power generation system that replaces thermal power.

Thus we have the energy efficiency close to the ideal, is basically a fuel cell which does not emit only between H ₂ O and C 0 ₂ has been expected promising systems also have to meet the needs of society. To achieve such a system, it is essential not only to develop equipment technology but also to develop the optimal fuel.

Conventionally, hydrogen, methanol, and hydrocarbon fuels have been considered as fuels for fuel cell systems.

As fuel for fuel cell systems, there is methanol in addition to hydrogen. Although methanol is advantageous in that it can be relatively easily reformed to hydrogen, it must be handled with care because it produces a small amount of power per weight and is toxic. In addition, since it is corrosive, special equipment is required for storage and supply.

Thus, no fuel has yet been developed to fully exploit the capabilities of the fuel cell system. In particular, heavy fuels for fuel cell systems It generation amount per amount is large, it generation amount of ₂ generation amount per co is large, that the fuel consumption of the entire fuel cell system is good, the evaporation gas (Ebapoemitsu Chillon) is small, the reforming catalyst, water gas shift reaction Catalysts, carbon monoxide removal catalysts, fuel cell stacks, etc., have low degradation of the fuel cell system and can maintain the initial performance for a long time, short system startup time, system loadability, storage stability, etc. Good handling properties such as flash point are required.

In the fuel cell system, it is necessary to keep the fuel and reformer at a given temperature. Therefore, the amount of power generated by subtracting the required amount of heat (the amount of heat that balances the heat generated and absorbed by the preheating and reaction) from the amount of generated power is This is the amount of power generated by the entire fuel cell system. Therefore, the lower the temperature required for reforming the fuel, the smaller the amount of preheating and the more advantageous the system, the shorter the startup time of the system, and the lower the amount of heat per weight required for the preheating of the fuel. Is also necessary. Insufficient preheating can lead to high levels of unreacted hydrocarbons (THC) in the exhaust gas, not only reducing power generation per weight, but also causing air pollution. Conversely, when operating the same system at the same temperature, it is advantageous to have less T H C in the exhaust gas and a higher conversion rate to hydrogen:

In view of such circumstances, an object of the present invention is to provide a fuel suitable for a fuel cell system that satisfies the above-mentioned required properties in a good balance. Disclosure of the invention

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a fuel composed of a hydrocarbon compound having a specific composition is suitable for a fuel cell system.

That is, the fuel for a fuel cell system according to the present invention is:

(1) Saturated content of 60 mol% or more, Olefin content of 40 mol% or less, butadiene content of 0.5 mol% or less, isoparaffin in saturated content of 4 or more carbon atoms Is at least 0.1 mol% and is a hydrocarbon compound which is a gas at normal temperature and normal pressure.

It is more preferable that the fuel composed of the hydrocarbon compound having the above specific composition further satisfies the following additional requirements.

(2) The sulfur content is 50 mass ppm or less.

(3) 5 mol% or less of hydrocarbons having 2 or less carbon atoms, 90 mol% or more of hydrocarbons having 3 carbon atoms and hydrocarbons having 4 carbon atoms, 5 mol% of hydrocarbons having 5 or more carbon atoms It is as follows.

(4) The vapor pressure at 40 is 1.55MPa or less.

(5) The density at 15 is 0.500 to 0.620 g / cm ³ .

(6) The copper plate corrosion rate for 1 hour at 40 ° C is 1 or less.

(7) The gas has a heat capacity at 15 ° C of 1.7 kJZkg ' BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a flowchart of a steam reforming fuel cell system used for evaluating fuel for a fuel cell system of the present invention. FIG. 2 is a front chart of a partial oxidation fuel cell system used for evaluating the fuel for a fuel cell system of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the contents of the present invention will be described in more detail.

In the present invention, a hydrocarbon compound having a specific composition is defined as having a saturated component (M (S)) of 60 mol% or more, an olefin component (M (O)) of 40 mol% or less, and a butadiene component (M (B (B)). )) Is 0.5 mol% or less, and isoparaffins (M (IP)) in the saturated component having 4 or more carbon atoms are 0.1 mol% or more, and are hydrocarbon compounds which are gaseous at ordinary temperature. Hereinafter, these will be individually described. The saturation (M (S)) indicates that the amount of power generation per weight is large, the amount of power generation per CO ₂ generation is large, and the fuel efficiency of the entire fuel cell system is good. In addition, the amount of THC in the exhaust gas is small, and the system startup time is short. Therefore, it is preferable to use at least 60 mol%, preferably at least 80 mol%, and more preferably at least 95 mol%. Preferably, it is at least 99 mol%, most preferably.

The olefin component (M (O)) has a large amount of power generation per weight, a large amount of power generation per CO ₂ generation, good fuel efficiency of the fuel cell system as a whole, and low THC in the exhaust gas. In view of the fact that the system startup time is short, the deterioration of the reforming catalyst is small and the initial performance can be maintained for a long time, and the storage stability, etc., the content is preferably 40 mol% or less, and more preferably 10 mol% or less. Most preferably, it is 1 mol% or less.

Butadiene (M (B)) has a large amount of power generation per weight, a large amount of power generation per CO ₂ generation, good fuel economy of the fuel cell system as a whole, and low THC in exhaust gas. It should be less than 0.5 mol% and less than 0.1 mol% from the viewpoint of short system start-up time, low deterioration of the reforming catalyst, long-lasting initial performance, and storage stability. Is preferred.

Isoparaffins (M (IP)) in saturated components with 4 or more carbon atoms are considered to be zero due to their good fuel efficiency as a whole fuel cell system, low THC in exhaust gas, and short system startup time. 1 mol% or more, preferably 1 mol% or more, more preferably 10 mol% or more, still more preferably 20 mol% or more, and preferably 30 mol% or more. Most preferred.

The above M (S), M (B), M (IP) and M (O) are values measured by JIS K 2240 “liquefied petroleum gas 5.9 composition analysis method”.

Although there is no limitation on the sulfur content of the fuel of the present invention, the deterioration of the fuel cell system such as a reforming catalyst, a water gas shift reaction catalyst, a carbon monoxide removal catalyst, a fuel cell stock, etc. is small, and Since the performance can be maintained for a long time, it is preferable that the mass be 50 mass ppm or less based on the total amount of fuel. 10 mass! ) It is more preferably at most pm, even more preferably at most 1 ppm by mass.

Degradation of fuel cell systems, such as reforming catalysts, water gas shift reaction catalysts, carbon monoxide removal catalysts, and fuel Kameike stacks, is such that the above-mentioned preferable range of the sulfur content and the preferable range of the above composition are both satisfied. It is most preferred because of its small size and long-term initial performance.

Here, the sulfur content means the sulfur content measured according to JIS K2240 “Liquid petroleum gas 5.5 or 5.5 sulfur content test method”. In the fuel of the present invention, the composition for each carbon number is not limited at all, but the hydrocarbons having 2 or less carbon atoms are 5 mol% or less, and the total amount of the hydrocarbons having 3 carbon atoms and the hydrocarbons having 4 carbon atoms is 9%. It is preferable that the content of hydrocarbons having 0 mol% or more and 5 or more carbon atoms is 5 mol% or less.

The hydrocarbon having 2 or less carbon atoms is preferably at most 5 mol%, more preferably at most 3 mol%, from the viewpoint of mountability, flammability, evaporation and the like. The total amount of hydrocarbons hydrocarbons and 4 carbon atoms of 3 carbon atoms, often power generation amount per weight, it generation amount of ₂ generation amount per CO is large, that overall fuel consumption of the fuel cell system is good, Since the amount of THC in the exhaust gas is small, the startup time of the system is short, the deterioration of the reforming catalyst is small, and the initial performance can be maintained for a long time, the content is preferably 90 mol% or more. Mole% or more is more preferable. 5 or more hydrocarbon atoms are often power generation amount per weight, it often power generation amount of ₂ generation amount per C_〇, good fuel economy as a whole燃钭cell system, small, THC in the exhaust gas It is preferably 5 mol% or less, more preferably 2 mol% or less, because the starting time of the system is short, the deterioration of the reforming catalyst is small, and the initial performance can be maintained for a long time.

The above composition for each carbon number is a value measured by JIS K2240 “liquefied petroleum gas 5.9 composition analysis method”.

Further, the vapor pressure of the fuel of the present invention is not limited at all, but the vapor pressure at 40 is 1.55 from the viewpoint of mountability, flammability, evaporation and the like. It is preferably at most 1.5 MPa, more preferably at most 1.5 MPa. .

The vapor pressure at 40 ° C is measured according to JIS K 2240 “liquefied petroleum gas 5.4 vapor pressure test method”.

Although there is no any restriction on the density of the fuel of the present invention, many power generation amount per weight, more power generation amount of ₂ generation amount per C_〇, that fuel consumption of the fuel cell system overall is good, exhaust gas it THC in a small, etc. that startup time the system is short, in view of the small initial performance degradation of the reforming catalyst can be long lasting, 0. 6 2 0 gZcm ³ the following 1 5 ^ In order to achieve the effects of the present invention, those having 0.5 000 gZcm ³ or more are most preferable.

The density at 15 ° C is measured according to JIS K 2240 “Liquefied petroleum gas 5.7 or 5.8 density test method”.

Further, there is no limitation on the copper plate corrosivity of the fuel of the present invention, but the fuel cell system, such as a reforming catalyst, a water gas shift reaction catalyst, a carbon monoxide removal catalyst, and a fuel cell stack, has little deterioration and has a long initial performance. From the point of view that it can be maintained for a long time, it is preferable that the corrosion rate of the copper plate per hour at 40 is 1 or less.

The copper plate corrosion rate at 40 for 1 hour is measured by the liquefied petroleum gas 5.10 copper plate corrosion test method of JIS 2240.

In the present invention, the heat capacity of the fuel is not limited at all. However, since the fuel efficiency of the entire fuel cell system is good, the heat capacity at 15 ° C of gas is 1.7 kJ g Is preferred.

This heat capacity is measured by a calorimeter such as a water calorimeter, an ice calorimeter, a vacuum calorimeter, or an adiabatic calorimeter. .

There is no particular limitation on the method for producing the fuel of the present invention. Specifically, for example, a straight-line propane fraction mainly composed of propane obtained from a crude oil distillation unit, a naphtha reformer, etc., a straight-line desulfurized propane fraction obtained by desulfurizing it, a crude oil distillation unit, a naphtha reformer Straight-run butane fraction centered on butane obtained from coal-processing equipment, alkylation equipment, etc., and a straight run obtained by desulfurizing the straight-run butane fraction. Desulfurized butane fraction, cracked propane fraction mainly composed of propane and propylene obtained from catalytic cracking unit, butane fraction derived mainly from butane and butene obtained from catalytic cracking unit, etc. It is manufactured using one or more base materials.

Among them, preferred as a base material for producing the fuel of the present invention include a straight-run desulfurized propane fraction, a straight-run desulfurized butane fraction, and the like. The fuel of the present invention is used as a fuel for a fuel cell system. The fuel cell system referred to in the present invention includes a fuel reformer, a carbon monoxide purifier, a fuel cell, and the like, and the fuel of the present invention is suitably used in any fuel cell system.

The fuel reformer is for reforming the fuel to obtain hydrogen, which is the fuel of the fuel cell. As a reformer, specifically, for example,

(1) A steam reforming reformer that mixes heated and vaporized fuel with steam and reacts by heating in a catalyst such as copper, nickel, platinum, and ruthenium to obtain hydrogen-based products. ,

(2) Partial oxidation reforming that mixes heated and vaporized fuel with air and reacts with or without a catalyst such as copper, nickel, platinum, and ruthenium to obtain a product containing hydrogen as a main component. Bowl,

(3) The heated and vaporized fuel is mixed with steam and air, and the partial oxidation reforming of (2) is performed in the preceding stage of the catalyst layer of copper, nickel, platinum, ruthenium, etc., and the partial oxidation reaction is performed in the subsequent stage. By performing the water-gas reforming of (1) using heat generation, a partial oxidation / steam reforming reformer that obtains a product containing hydrogen as a main component is obtained.

And the like.

The carbon monoxide purifier removes carbon monoxide contained in the gas generated by the above reformer and becomes a catalyst poison of the fuel cell.

(1) Mix reformed gas and heated vaporized steam and react in a catalyst such as copper, nickel, platinum, ruthenium, etc. to reduce carbon monoxide and steam. Water gas shift reactor to obtain carbon dioxide and hydrogen as products,

(2) Selective oxidation reactors that convert carbon monoxide to carbon dioxide by mixing reformed gas with compressed air and reacting in a catalyst such as platinum or ruthenium, etc. Used.

Specific examples of the fuel cell include polymer electrolyte fuel cells (PEFC), phosphoric acid fuel cells (PAFC), molten carbonate fuel cells (MCFC), and solid oxide fuel cells ( SOFC).

Further, the fuel cell system as described above is used for electric vehicles, hybrid vehicles of conventional engines and electric vehicles, portable power sources, distributed power sources, home power sources, cogeneration systems, and the like. Example

Table 1 shows the properties of the base material (LPG) used for each fuel in Examples and Comparative Examples.

Table 2 shows the composition and properties of each fuel used in Examples and Comparative Examples.

Table 1 Straight run system Straight run system Decomposition system Decomposition system DME

Proha. Sulfur fraction Desulfurized butane fraction Pro A fraction Frethane fraction

Crude oil distillation equipment, crude oil distillation equipment, catalytic cracking equipment, etc. Catalytic cracking equipment, etc. S-methyl naphtha naphtha reforming equipment Naphtha reforming equipment

Furnacation equipment obtained from products such as propylene

Fractions obtained mainly from Rohan, etc.

Tatana

Was desulfurized

Thorium Sulfur star ppm 7 <1 5 34 ku 1 Density @ 1 5 ° C g / m3 0.509 0.577 0.518 0.591 0.600 Vapor pressure @ 40 ° C MPa 1.33 0.34 1.50 0.39 0.88 Copper plate corrosion 1 a1 a1 a1

2 following hydrocarbon molar carbon atoms ^_0/0 2.5 0.0 0.0 0.0

CD

Hydrocarbon mole of 3 carbon atoms ^_0/0 96.6 0.0 99.8 2.4

Hydrocarbon mole of 4 carbon atoms ^_0/0 0.9 99.9 0.2 92.4

5 or more hydrocarbon mole carbon ^_0/0 0.0 0.1 0.0 5.2

Saturation mol% 99.9 99.9 19.7 53.9

Olefin mole% 0.1 0.1 80.3 46.1

Butadiene mol% 0.0 0.0 0.0 0.2

Isoperafin mol% in C4 or higher saturated content 78.2 35.8 100.0 81.4

Table 2 Example 1-Example ク Example 3 Comparative Example 1 Comparative Example 2 Mixing ratio (volume »%)

Straight run ° Rohan fraction 100 25

Straight run system · Desulfurized butane fraction 100 75

Decomposition system Rohan fraction 94

Cracking system 'Tan fraction 100 ethane 6

Property analysis results

Sulfur content ¾kppm 7 <1 2 5 34 Density g / cm3 0.509 0.577 0.560 0.508 0.591

Mpa 1.33 0.34 0.60 1.75 0.36 Carbon number distribution (hydrocarbon part) Hydrocarbons with 2 or less carbon mole% 2.5 0.0 0.7 5.8 0.0

Hydrocarbons with 3 carbons mol% 96.6 0.0 27.1 94.0 2.4 Hydrocarbons with 4 carbons mol% 0.9 99.9 72.1 0.2 92.4 Hydrocarbons with 5 or more carbons mol% 0.0 0.1 0.1 0.0 5.2

組成 Composition Saturation mol% 99.9 99.9 99.9 24.4 53.9

Olefin content mol% 0.1 0.1 0.1 75.6 46.1 'Fatashien'-mol% 0.0 0.0 0.0 0.0 0.2

Isohafin raffin mol% in C4 or more saturated content 78.2 35.8 35.9 100.0 80.6 Copper plate corrosion 1 a 1 a 1 a 1 a 1 Net calorific value kJ / kg 46 330 45 670 45 820 45 930 45 440 Heat capacity 3 kJ / kg- ° C 1.62 1.62 1.62 1.52 1.55.

For each of these fuels, a fuel cell system evaluation test was performed.

Fuel cell system evaluation test

(1) Steam reforming type

The fuel and water were vaporized by electric heating, led to a reformer filled with a noble metal catalyst and maintained at a predetermined temperature by an electric heater, and a reformed gas rich in hydrogen was generated.

The temperature of the reformer was set to the lowest temperature at which reforming was completely performed in the initial stage of the test (the lowest temperature at which THC was not contained in the reformed gas).

The reformed gas is led to a carbon monoxide treatment device (water gas shift reaction) together with water vapor to convert carbon monoxide in the reformed gas into carbon dioxide, and the generated gas is guided to a polymer electrolyte fuel cell to generate electricity. Was.

Diagram of the flow chart of the steam reforming type fuel cell system used for evaluation

Shown in 1.

(2) Partial oxidation type

The fuel was vaporized by electric heating, and the preheated air was charged with a precious metal catalyst and led to a reformer maintained at 1100 with an electric heater to generate a hydrogen-rich reformed gas.

The reformed gas is led together with water vapor to a carbon treatment device (water gas shift reaction) to convert carbon monoxide in the reformed gas to carbon dioxide, and the generated gas is led to a polymer electrolyte fuel cell to generate electricity. Done.

Figure 2 shows a flowchart of the partial oxidation fuel cell system used for the evaluation.

(3) Evaluation method

Immediately after the start of the evaluation test, the amounts of H ₂ , CO, CO ₂ , and THC in the reformed gas generated from the reformer were measured. Similarly, measurements were made on the amounts of H ₂ , CO, CO _2. , And THC in the reformed gas generated from the carbon monoxide treatment equipment immediately after the start of the evaluation test.

Immediately after and 100 hours after the start of the evaluation test, the amount of power generated by the fuel cell, the amount of fuel consumed, and the amount of CO ₂ emitted from the fuel cell were measured. became.

The amount of heat (preheat) required to guide each fuel to the specified reformer temperature was calculated from the heat capacity and latent heat of vaporization.

In addition, the performance degradation rate of the reforming catalyst (the amount of power generated 100 hours after the start of the test / the amount of power generated immediately after the test), the thermal efficiency (the amount of power generated immediately after the start of the test), The fuel calorific value) and the preheating amount ratio (preheating amount / power generation amount) were calculated.

Table 3 shows the measured values and calculated values.

Table 3 Example 1 Example 2 Example 3 Comparative example 1 Comparative example 2 Evaluation result

Power generation by steam reforming (reformer temperature = = optimal reformer temperature ¹ )

Optimal reformer temperature ¹⁾ ° c 650 640 640 680 670 Electric energy KJ / fuel kg 31 140 30 700 30 800-29 180 29 460

100 hours 31 1 10 30 690 30 780 28 700 28 520 Performance degradation rate 100 hours 0.10% 0.03% 0.06% 1.64% 3.19% Thermal efficiency ²⁾ 67% 67% 67% 64% 65%

G02 generation kg / fuel kg Initial performance 2.993 3.029 3.021 3.102 3.079

C02 this rienerki * 1 KJ / C02-kg.Initial performance 10404 10135 10195 9407 9568 Preheating amount ³⁾ KJ / twisting material kg 1010 1000 1000 1000 1000 Preheating amount ratio ⁴⁾ 3.2% 3.3% 3.2% 3.4% 3.4% Partial oxidation modification Power generation (reformer temperature 1100 ° C)

Electric energy KJ / twisting material kg Initial performance 16200 15590 15730 14020 14420

100 hours 16190 15590 15720 13910 14220 Performance degradation ratio 100 hours 0.06% 0.00% 0.06% 0.78% 1.39% Thermal efficiency ²⁾ Initial performance 35%-34% 34% 30% 32%

C02 generation kg / fuel kg Initial performance 2.992 3.028 3.019 3.101 3.077

Per C02: E Nerki 'one KJ / C02-kg Initial performance 5414 ― 5149 5210 4521 4686 Preheat amount ³⁾ KJ / fuel kg 1740 1750 1740 1630 1670 Preheat ratio ⁴⁾ 10.7% 1 1.2% 1 1.1% 1 1.6% 1 1.6%

1) Minimum temperature at which THC is not contained in the reformed gas

HQ

2) Electric energy Z fuel heating value

3) The amount of heat required to bring the fuel to the specified reformer temperature

4) Preheating amount Electric energy

Industrial applicability

As described above, the fuel comprising the hydrocarbon compound having the specific composition according to the present invention can obtain electric energy with a small performance deterioration ratio at a high output by being used in a fuel cell, and can have various performances for a fuel cell. To be satisfied.

Four

Claims

The scope of the claims

1. Saturated component is 60 mol% or more, olefin component is 40 mol% or less, putagen component is 0.5 mol% or less, isoparaffin in saturated component having 4 or more carbon atoms is 0.1 mol% or more Fuel for fuel cell systems consisting of hydrocarbon compounds that are gases at normal temperature and pressure.

2. The fuel for a fuel cell system according to claim 1, having a sulfur content of 50 mass ppm or less.

3. 5 mol% or less of hydrocarbons having 2 or less carbon atoms, 90 mol% or more of hydrocarbons having 3 carbon atoms and 4 carbon atoms, 5 mol% or less of hydrocarbons having 5 or more carbon atoms 3. The fuel for a fuel cell system according to claim 1 or 2, which is:

4. The fuel for a fuel cell system according to any one of claims 1 to 3, wherein the vapor pressure at 40 is 1.55 MPa or less.

5. The fuel for a fuel cell system according to any one of claims 1 to 4, wherein the density at 15 ° C is from 0,500 to 0.620 gZcm ³ .

6. The fuel for a fuel cell system according to any one of claims 1 to 5, wherein a copper plate corrosion rate per hour at 40 is 1 or less.

7. The fuel for a fuel cell system according to any one of claims 1 to 6, wherein the gas has a heat capacity at 15 of 1.7 kJZkg * ° C or less.