KR101015906B1 - Natural gas reformer for fuel cell with high thermal efficiency - Google Patents

Abstract

The present invention relates to a natural gas reformer for a fuel cell. More specifically, the present invention relates to a self-heating reformer in which natural gas causes an autothermal reforming reaction with water vapor and oxygen, a first heat exchanger in which heat exchange occurs in which steam and natural gas are heated by heat of the reformed gas obtained from the reformer. 1 A high temperature steam reforming reactor in which a high temperature steam reforming reaction of a reformed gas passing through a heat exchanger occurs, a second heat exchanger in which heat exchange to heat steam by heating the reformed gas obtained from the high temperature steam reforming reactor, and passes through the second heat exchanger A low temperature steam reforming reactor in which a low temperature steam reforming reaction of one reforming gas occurs, a third heat exchanger in which heat exchange to heat steam by heating the reformed gas obtained from the low temperature steam reforming reactor, and a reformed gas having passed through the third heat exchanger Part of converting carbon monoxide to carbon dioxide The fourth heat exchanger in which heat exchange occurs in which heat is heated by the heat of the reformed gas obtained from the oxidation reactor, the partial oxidation reactor, and the reformed gas from which the moisture is removed are removed by removing the moisture from the reformed gas passing through the fourth heat exchanger. It relates to a natural gas reformer for a fuel cell, characterized in that it comprises a water separator for supplying.

Autothermal reforming, steam reforming, partial oxidation, heat exchanger

Description

Natural gas reformer for fuel cell with high thermal efficiency {NATURAL GAS REFORMER FOR FUELCELL WITH HIGH THERMAL EFFICIENCY}

The present invention relates to a natural gas reformer for a fuel cell having a high thermal efficiency. More specifically, the present invention is a natural gas supplied through the city gas supply compressor and the desulfurizer autothermal reformer to cause the catalytic thermal reaction with oxygen in the air supplied through the steam and the first air supply compressor (Auto Thermal Reaction), A first heat exchanger in which heat exchange for heating steam and natural gas occurs by the heat of the reformed gas obtained from the reformer, and high temperature steam in which a high temperature steam reforming reaction of the reformed gas passing through the first heat exchanger occurs. A reforming reactor, a second heat exchanger in which heat exchange takes place by heating the steam from the reformed gas obtained from the high temperature steam reforming reactor, and a low temperature steam reforming reaction of the reformed gas passing through the second heat exchanger Low temperature steam reforming reactor produced, the low temperature steam A third heat exchanger in which heat exchange takes place in which heat of the steam is heated by the residual heat of the reformed gas obtained from the quality reactor, a partial oxidation reactor converting carbon monoxide in the reformed gas passing through the third heat exchanger into carbon dioxide through a selective oxidation reaction, the portion A fourth heat exchanger in which heat exchange takes place in which heat is heated by the residual heat of the reformed gas obtained from the oxidation reactor, and for removing the moisture of the reformed gas passing through the fourth heat exchanger and supplying the reformed gas from which the moisture has been removed to the fuel cell. It relates to a natural gas reformer for a fuel cell comprising a; separator.

Due to resource depletion and environmental pollution, many researches are underway to find alternative energy for fossil fuels. Among them, the hydrogen fuel cell has high power generation efficiency and low emission of impurities, and can supply hydrogen as fuel through various raw materials including fossil fuel, so that industrialization methods in power generation, home / commercial, portable, etc. Actively researched.

Hydrogen, the main fuel of a hydrogen fuel cell, does not exist in nature itself, so it must be obtained from fossil fuel, water, biomass, etc. using heat, light, and electricity. Domestic production of hydrogen is more than 400,000 tons per year, most of which are mainly used for industrial purposes in petroleum refineries, chemical plants, semiconductors and steel industries, and due to high production costs, hydrogen production for energy purposes is still The situation is not active.

Specific hydrogen energy production techniques include 1) hydrogen production method using steam reforming, partial oxidation, autothermal reaction, pyrolysis of fossil fuels such as natural gas, LPG, naphtha and coal, and 2) renewable energy such as wind and solar power. Various methods such as electrolysis of water, photoelectrochemical or photobiological hydrogen production method, and 3) hydrogen production method by thermochemical or electrolysis method of water using nuclear energy have been studied.

Among them, industrialization researches on the production of hydrogen for fuel cells from fossil fuels, which are economical in the short term, are most actively conducted. Among them, various efforts have been made to reduce manufacturing prices, particularly for technical commercialization.

A reaction for producing hydrogen, which is a fuel used in a fuel cell, from fossil fuel is called reforming. The reforming apparatus is divided into a reforming unit for reforming fuel and a carbon monoxide removal unit for removing the generated carbon monoxide. The reforming unit converts the fuel into hydrogen-rich reforming gas by means of a catalyst using steam reforming, partial oxidation, and autothermal reaction.In the carbon monoxide removing unit, catalytic reactions such as aqueous conversion and selective oxidation methods, and membranes It is used to remove carbon monoxide from the reformed gas by using hydrogen purification.

For example, the reforming reaction of methanol is shown in the table below.

Reforming Type reaction (1) decomposition reaction
(Decomposition Reaction) CH ₃ OH-> CO + 2 H ₂
(ΔH = +90.0 kJ / mol) (2) steam reforming reaction
(Steam Reforming Reaction) CH ₃ OH + H ₂ O-> CO ₂ + 3 H ₂
(ΔH = + 49.5 kJ / mol) (3) partial oxidation reaction
(Partial Oxidation Reaction) CH ₃ OH + 1/2 O _2- > CO ₂ + 2 H ₂
(ΔH = −189.5 kJ / mol) (4) autothermal reforming reaction
(Autothermal Reforming Reaction) CH ₃ OH + X (1/2 O ₂ ) + (1-X) H ₂ O-> CO ₂ + (3-X) H ₂

Hydrocarbon decomposition reaction is a method of thermally decomposing hydrogen and carbon by supplying heat to hydrocarbon without introducing water or oxygen, but it is possible to obtain relatively pure hydrogen economically and simply. Due to this, there is a problem that the activity of the catalyst is reduced and the flow path of the gas is blocked. In contrast, the steam reforming reaction has advantages such as using a less expensive catalyst as a method of obtaining hydrogen through the reaction of a hydrocarbon fuel and steam, and obtaining a high concentration of hydrogen to increase the output of the fuel cell. Because of this, the heat must be supplied from the outside and the reaction rate is slow.

Partial oxidation reaction is exothermic, and the reaction rate is fast, and the response speed according to the load fluctuation is fast and the reactor can be miniaturized. There is a disadvantage that the dilution lowers the output of the fuel cell.

The autothermal reforming reaction reforms a part of the fuel to be partially oxidized and steam reforms the rest of the fuel with heat from the fuel. The heat reforming reaction does not require external heat supply, and the response speed according to load fluctuation is fast. A reformed gas having a medium hydrogen concentration of the partial oxidation method can be obtained. However, there are disadvantages in that the catalyst is relatively expensive, and the amount of reactants needs to be precisely controlled to complicate the process.

On the other hand, CO is inevitably generated in the process of reforming fossil fuels, and CO generated in the reforming process poisons platinum used as a cathode catalyst in the case of PEMFC, thereby rapidly reducing the performance of the fuel cell, thereby supplying reformed gas to PEMFC. A process for removing CO is required beforehand. Therefore, it is required to remove the CO of the reformed gas flowing into the PEMFC to about 20 ppm or less, ideally 10 ppm or less, and this treatment is performed in the carbon monoxide removal unit.

The following methods may be used to remove CO in the reformed gas for fuel cells.

CO removal method Contents (1) water gas conversion
(water gas shift) CO + H ₂ O → CO ₂ + H ₂ , ΔH =-40.5kJ / mol (2) CO selective oxidation CO + 1/2 O ₂ → CO ₂ , ΔH =-279.5 kJ / mol (3) methanation
(methanation) CO + 3 H ₂ → CH ₄ + H ₂ O, ΔH = -206.4 kJ / mol (4) hydrogen separation membrane Separation and purification of hydrogen from reforming gas, mostly Pd-based membranes. Advantageous for reducing the size of the reformer but requires pressurization and very expensive Pd separator (5) CO adsorption separation An adsorbent that can be resorbed and desorbed at room temperature to 100 ° C is used. Bigger capacity

The reforming and hydrogen refining techniques described above are already commercialized in the existing petrochemical processes, but studies are being conducted to make them suitable for fuel cell systems. In particular, the use of natural gas as a fuel for reforming hydrogen can utilize the existing city gas supply line, thereby reducing the cost of infrastructure construction. Therefore, many studies on the reformer for fuel cells using natural gas have been made.

As described above, the reformer generates hydrogen gas through a chemical catalytic reaction from a fuel containing hydrogen atoms, and is composed of various parts such as a heat source, a water vapor and oxygen supply device, and a carbon monoxide reduction device.

The reforming reaction unit and the carbon monoxide reducing unit require a heat source to form a unique reaction temperature range required for each reaction, and in the case of the reforming reaction, an appropriate supply of steam and air is required. However, the conventional reformer has a problem that the structure of the reformer is complicated due to the existence of a separate structure such as a heat source part, so that the size of the overall system is too large and the thermal efficiency and the reaction efficiency are lowered.

In order to solve these problems, a reformer using the above-described autothermal reforming reaction has been developed, but this also has similar problems due to the supply of air and steam and additional equipment. For example, Korean Patent Laid-Open Publication No. 10-2007-0050322 refers to a reformer using an autothermal reforming catalytic reaction, but measured by a heat source part and a sensor separately installed on one side of the reforming reaction part to provide a heat source to the reaction part. There is a problem in that the efficiency of the overall system is lowered due to additionally installed structures or complicated processes such as a controller for controlling the reactor valve and the air supply unit according to the temperature.

That is, the existing reformers have a large heat loss of the reformer due to separate structures and complex processes, thereby reducing the overall thermal efficiency and reaction efficiency, and also delaying the initial start-up time until normal operation by the autothermal reforming reaction. There have been some improvements that need to be made, such as a decrease in the overall reformer efficiency.

Thus, the present inventors in the reformer using the autothermal reforming reaction, to minimize the initial start-up time and to minimize the additional equipment for supplying air, steam, etc. to solve the inconvenience of limiting the installation space and management, thermal efficiency and reaction efficiency Invented a natural gas reformer for fuel cells that can maximize the

An object of the present invention is to reformate a natural gas reformer using an autothermal reforming reaction that does not require a separate heat source, to minimize the additional equipment for the supply of air and steam to maximize the thermal efficiency and reaction efficiency and simplify the structure of the overall reforming system To provide.

In addition, an object of the present invention is to provide a reformer that can be easily controlled to switch between the initial operation and the normal operation while minimizing the initial starting time until the normal operation by the autothermal reforming reaction by the use of a burner.

It is also an object of the present invention to provide a reformer that can increase the thermal efficiency of the entire system by heat-exchanging the water separated in the separator.

The object of the present invention as described above is that the natural gas is the autothermal reformer (1), which causes a catalytic autothermal reaction with oxygen in the water vapor and air, steam and natural gas by the heat of the reformed gas obtained from the reformer (1) A first heat exchanger (3) in which heat exchange takes place, a high temperature steam reforming reactor (4) in which a high temperature steam reforming reaction of the reformed gas passed through the first heat exchanger (3) occurs; The low temperature steam reforming reaction of the reformed gas passed through the second heat exchanger (5) and the second heat exchanger (5) in which heat exchange for heating the steam by heating of the reformed gas obtained from the high temperature steam reforming reactor (4) takes place ( A low temperature steam reforming reactor (6) in which a low temperature steam reforming reaction occurs, and the steam is heated by the heat of the reformed gas obtained from the low temperature steam reforming reactor (6). A third heat exchanger (7) in which exchange takes place, a partial oxidation reactor (8) for converting carbon monoxide in the reformed gas passing through the third heat exchanger (7) into carbon dioxide through a selective oxidation reaction, and the partial oxidation reactor (8) A fourth heat exchanger (10) in which heat exchange takes place in order to heat water with a residual heat of the reformed gas obtained from the fuel cell, and the reformed gas from which moisture is removed by removing moisture from the reformed gas passing through the fourth heat exchanger (10). It is achieved by providing a natural gas reformer for a fuel cell, characterized in that it comprises a separator 13 for feeding to the cell.

It is also an object of the present invention to achieve by providing a natural gas reformer for a fuel cell, further comprising a burner (2) for reducing the initial operating time before normal operation.

Further, an object of the present invention is to provide a city gas supply compressor 18 for supplying natural gas to the autothermal reformer 1 and a first air supply compressor for supplying air to the desulfurizer 16 and the autothermal reformer 1 ( It is achieved by providing a natural gas reformer for a fuel cell, characterized in that it further comprises 17).

In addition, an object of the present invention, the three-way valve 15 is mixed with the natural gas supplied through the city gas supply compressor 18 and the desulfurizer 16 and the air supplied through the first air supply compressor (17). It is achieved by providing a natural gas reformer for a fuel cell, characterized in that it further comprises.

In the conventional reformer, the overall size increases according to the attachment of individual heaters for heating water with water vapor, thereby reducing thermal efficiency, and there is a problem in that the configuration of the entire system is complicated. However, by using the natural gas reformer for the fuel cell of the present invention, it is possible to reduce the overall reformer size and simplify the overall process, thereby increasing thermal efficiency and solving inconveniences such as limitation and management of installation space.

In addition, the reformer of the present invention is used to recover the heat of the reforming reaction using heat exchangers to make steam, and the water separated from the water separator can increase the thermal efficiency of the entire system, such as using hot water in the domestic fuel cell system. have.

In addition, it is possible to reduce the time required for the initial operation by using the burner during the initial operation, and to improve the thermal efficiency by simplifying the equipment and reducing the starting load by using the burner as the flow path without the need for a separate heat source during the normal operation. Can be.

An embodiment of a natural gas reformer for a fuel cell of the present invention will be described in more detail with reference to the drawings.

1 is an overall process diagram of a natural gas reformer according to the present invention. As can be seen in Figure 1, the natural gas reformer for a fuel cell according to the present invention is a natural gas reformer (1) obtained from the reformer (1), which causes a catalytic autothermal reaction (Auto Thermal Reaction) with oxygen and steam in the air The first heat exchanger (3) in which heat exchange for heating steam and natural gas occurs by the heat of the reformed gas, and the High Temperature Steam Reforming Reaction of the reformed gas passing through the first heat exchanger (3) The hot steam reforming reactor 4 takes place, the second heat exchanger 5 and the second heat exchanger 5 where heat exchange takes place in order to heat the steam by the heat of the reformed gas obtained from the hot steam reforming reactor 4. A low temperature steam reforming reactor (6) in which a low temperature steam reforming reaction of a reforming gas takes place, obtained from the low temperature steam reforming reactor (6). A third heat exchanger 7 in which heat exchange takes place in order to heat water vapor by the heat of the vaginal gas, and a partial oxidation reactor converting carbon monoxide in the reformed gas passed through the third heat exchanger 7 into carbon dioxide through a selective oxidation reaction ( 8) a fourth heat exchanger 10 in which heat exchange occurs in which heat is exchanged by heating the reformed gas obtained from the partial oxidation reactor 8, and the moisture of the reformed gas passed through the fourth heat exchanger 10; And a separator 13 for supplying the reformed gas from which the moisture is removed and the moisture is removed to the fuel cell.

At this time, the reformer preferably further includes a burner (2) in order to reduce the initial operating time before normal operation.

In addition, the reformer may further include a city gas supply compressor 18 for supplying natural gas, a desulfurizer 163 for removing sulfur from natural gas, and an air supply compressor 17 for supplying air. have.

Looking at the process using each of the above configuration, the natural gas supplied through the city gas pipe network passes through the city gas supply compressor (18) to be applied to the apparatus, desulfurization to remove the sulfur contained in the city gas Fed to the unit 16. The sulfur-free city gas is mixed and supplied to the air supplied through the first air supply compressor 17 and to the three-way valve 15 line.

The valve is operated so that the mixed gas mixed in the three-way valve 15 is supplied to the burner 2 at the initial operation. On the other hand, after the initial operation time, when the self-heating reaction is sufficiently possible, that is, in the normal operation state, the three-way valve 16 supplies the mixed gas to the first heat exchanger 3 to preheat the mixed gas through heat exchange. The preheated mixed gas moves to the burner (2).

At this time, the burner 2 in the normal operation state acts only as a flow path, not as a combustion device, and may be used as equipment for increasing gas mixing efficiency. In addition, the water vapor heated while passing through a series of heat exchangers passes through the first heat exchanger (3) and then moves to the burner together with the mixed gas for the autothermal reaction.

The mixed gas and water vapor passing through the burner 2 in both the initial operation state and the normal operation state cause an autothermal reaction using a catalyst in an autothermal reactor (ATR). The gas passing through) is heated up to about 700 ° C. The heated gas passes through the first heat exchanger 3 again, and serves as a heat source for heating the mixed gas and water vapor, and the temperature is lowered to about 400 ° C.

The gas at 400 ° C. is supplied to the high temperature steam reforming reactor 4 to increase the ratio of hydrogen through the high temperature steam reforming reaction. The gas passing through the high temperature steam reforming reactor (4) is used as a heat source for heating the steam while passing through the second heat exchanger (5), and the gas passing through the second heat exchanger (5) is lowered to 200 ° C and then the low temperature steam It is fed to the reforming reactor 6.

The gas supplied to the low temperature steam reforming reactor (6) further increases the ratio of hydrogen through the Low Temperature Steam Reforming Reaction, and the gas passed through the low temperature steam reforming reactor (6) is a third heat exchanger. It passes through (7) and is used as a heat source for heating water vapor, and the gas passed through the third heat exchanger (7) is lowered to 150 ° C and then supplied to the partial oxidation reactor (8).

Partial oxidation reactor (8) is supplied with air for the oxidation reaction through the second air supply compressor (9), in which the process of oxidizing CO to CO ₂ to remove the CO. The gas passing through the partial oxidation reactor 8 passes through the fourth heat exchanger 10 and is used as a heat source for heating the water supplied from the pure water supply pump 11 and the gas passed through the fourth heat exchanger 10. Is lowered to 100 ° C. or lower and then supplied to the water separator 13 (Water Separator).

Water condensed in the reformed gas supplied to the separator 13 is supplied to the water tank 14, and the reformed gas from which the moisture is removed is moved to the reformed gas supply line 12 to be supplied to the fuel cell. The water separated in the separator can be reintroduced into the system through heat exchange to increase the thermal efficiency of the entire system.

In addition, it may be configured to further include a device for increasing the overall efficiency by heat exchange of the heat of water separated from the separator to the water tank, the method of using the water separated from the separator as hot water in the domestic fuel cell system This can increase the overall thermal efficiency of the system.

In addition, each of the heat exchangers 10, 7, 5, and 3 used in the reformer preferably has a sufficient heat transfer area so that sufficient heat can be recovered.

In the above description of the preferred embodiments of the present invention, the present invention is not limited to these embodiments, and the embodiments of the present invention together with the embodiments in which the above embodiments are simply combined with the existing known art are described in the claims and the detailed description of the present invention. Naturally, it should be understood that the present invention includes the equivalent technical scope that can be modified and used by those skilled in the art.

1 is an overall process diagram of a natural gas reformer for a fuel cell of the present invention.

<Description of Major Symbols Used in Drawings>

1: autothermal reactor 2: burner

3: first heat exchanger 4: high temperature steam reforming reactor

5: second heat exchanger 6: low temperature steam reforming reactor

7: third heat exchanger 8: partial oxidation reactor

9: second air supply compressor 10: fourth heat exchanger

11: pure water supply pump 12: reforming gas supply line

13: water separator 14: water tank

15: three-way valve 16: desulfurizer

17: first air supply compressor 18: city gas supply compressor

Claims (9)

A autothermal reformer 1 in which natural gas causes a catalytic autothermal reaction with oxygen in steam and air; A first heat exchanger (3) in which heat exchange for heating water vapor and natural gas takes place by the residual heat of the reformed gas obtained from the reformer (1); A high temperature steam reforming reactor (4) in which a high temperature steam reforming reaction of the reformed gas passing through the first heat exchanger (3) occurs; A second heat exchanger (5) in which heat exchange for heating the steam by heating the reformed gas obtained from the high temperature steam reforming reactor (4) takes place; A low temperature steam reforming reactor (6) in which a low temperature steam reforming reaction of the reformed gas passing through the second heat exchanger (5) occurs; A third heat exchanger (7) in which heat exchange for heating the steam by heating the reformed gas obtained from the low temperature steam reforming reactor (6) takes place; A partial oxidation reactor (8) for converting carbon monoxide in the reformed gas passed through the third heat exchanger (7) into carbon dioxide through a selective oxidation reaction; A fourth heat exchanger (10) in which heat exchange occurs in which water is heated by the residual heat of the reformed gas obtained from the partial oxidation reactor (8); A water separator (13) for removing moisture from the reformed gas passing through the fourth heat exchanger (10) and supplying the reformed gas from which the moisture is removed to the fuel cell; And A burner 2 for reducing initial operating time before normal operation; Natural gas reformer for a fuel cell comprising a. delete 2. A natural gas reformer for a fuel cell according to claim 1, further comprising a first air supply compressor (17) for supplying air to said autothermal reformer (1). 2. The natural gas reformer for a fuel cell according to claim 1, further comprising a city gas supply compressor (18) for supplying natural gas to the autothermal reformer (1). 2. The natural gas reformer of claim 1, further comprising a desulfurizer (16) for removing sulfur from the natural gas supplied to the autothermal reformer (1). The three-way valve (15) according to claim 1, wherein the natural gas supplied through the city gas supply compressor (18) and the desulfurizer (16) and the air supplied through the first air supply compressor (17) are mixed. A natural gas reformer for a fuel cell, characterized in that it further comprises. 7. The flow path according to claim 6, wherein the flow path is switched so that the mixed gas is supplied to the burner 2 when the three-way valve 15 is initially operated, and the mixed gas is supplied to the first heat exchanger 3 during normal operation. A natural gas reformer for a fuel cell, wherein the flow path is switched as much as possible. 2. A natural gas reformer for a fuel cell according to claim 1, further comprising a second air supply compressor (9) for supplying air for the partial oxidation reaction of the partial oxidation reactor (8). 2. A natural gas reformer for a fuel cell according to claim 1, further comprising a supply pump (11) for supplying pure water heated while passing through the heat exchangers (10, 7, 5, 3).

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