JP5148072B2 - Liquid raw fuel for fuel cell cogeneration system and fuel cell cogeneration system - Google Patents

Description

  The present invention relates to a liquid raw fuel used in a fuel cell cogeneration system, and more particularly to a liquid raw fuel for generating hydrogen in the system using a solid oxide fuel cell and the fuel cell cogeneration system. .

  For desulfurization of hydrocarbon oils such as kerosene used in stationary fuel cells for home use and commercial use, a chemisorption desulfurization method using a nickel-based desulfurizing agent at around 200 ° C has been studied. There are problems such as consuming energy for starting, taking time for starting, and complicating the system because it is necessary to carry out under pressurized conditions to prevent vaporization of hydrocarbon oil. The nickel-based desulfurizing agent to which copper is added has a certain activity even at a lower temperature of about 150 ° C., but has not yet been solved. In addition, nickel-based desulfurization agents need to be subjected to a reduction treatment in advance, and nickel-based desulfurization agents that have undergone reduction treatment are subject to rapid exothermic reactions due to contact with oxygen, resulting in decreased activity. There are also challenges. Furthermore, since nickel compounds are toxic, there is also a problem that the management method needs to be strict when they are spread to general households (Patent Documents 1 to 4).

  On the other hand, a physical adsorption desulfurization method using zeolite, activated carbon or the like at around room temperature is also being studied. However, commercially available kerosene contains aromatic compounds that compete with sulfur compounds, and there is no physical adsorbent with high removal performance, especially for benzothiophenes, which account for the majority of sulfur compounds. In order to reduce it to a very low level, a very large volume is required, which is not practical (Patent Documents 5 to 7).

The types of sulfur compounds contained in commercially available kerosene are mostly benzothiophenes and dibenzothiophenes, and especially the ratio of benzothiophenes is large. The ratio of benzothiophenes to the total sulfur compounds is 70% as the sulfur content. This is often the case. However, removal of dibenzothiophenes is more difficult than benzothiophenes, and it is known that removal of alkyldibenzothiophenes is particularly difficult (Patent Documents 8 and 9).
Therefore, a liquid raw fuel for a fuel cell cogeneration system that can be desulfurized relatively easily at a temperature from room temperature to about 150 ° C. that does not require reduction treatment or hydrogen and that does not require pressurization, and There has been a demand for a fuel cell cogeneration system using liquid raw fuel.

  The present inventors have also developed a desulfurization method that combines a chemical reaction and physical adsorption because sufficient desulfurization performance cannot be obtained by a simple physical adsorption method. It has been found that the thiophene ring is highly reactive and reacts with the benzene ring in the presence of an acidic catalyst even at 100 ° C. or lower to produce a heavier compound. The higher the temperature, the higher the reaction rate of the chemical reaction, but it was confirmed that the reaction proceeds even at a lower temperature by using a solid superacid catalyst having a high acid strength. A solid acid desulfurization agent having a large specific surface area can physically adsorb a heavy sulfur compound as a reaction product. By combining a chemical reaction and physical adsorption using a solid acid desulfurization agent with a large specific surface area, it was understood that benzothiophenes contained in commercial kerosene could be removed without hydrogen and near room temperature. However, alkyl dibenzothiophenes having a large number of alkyl groups have a problem that the desulfurization performance is rapidly reduced (Patent Document 10).

  The present inventors have also proposed an activated carbon-based desulfurization agent having high desulfurization performance for alkyldibenzothiophenes, but the adsorption mechanism of the activated carbon-based desulfurization agent is based on the graphite structure partially present in the activated carbon and the benzene ring. As the number of alkyl groups in alkyl dibenzothiophenes increases, the contribution ratio of the benzene ring decreases relatively, and desulfurization is still necessary for alkyl dibenzothiophenes having a large number of alkyl groups. There was a problem that the deterioration of performance was quick (Patent Document 5).

On the other hand, a solid polymer type or solid oxide type fuel cell cogeneration system using fuel gas such as city gas or LPG as a raw fuel has been proposed. In particular, it is known that the starting method in the case of a solid oxide fuel cell in which the raw fuel is fuel gas is relatively simple. For example, fuel gas is supplied to a solid oxide fuel cell via a steam reformer, and the fuel gas is burned in the solid oxide fuel cell, thereby ascending the solid oxide fuel cell and the steam reformer. It can be warmed up and activated in a short time (Patent Document 11). However, when the raw fuel is a liquid, whether it is a solid polymer fuel cell or a solid oxide fuel cell, the liquid raw fuel is kept in a high temperature part that is equal to or higher than the thermal decomposition temperature of the liquid raw fuel. Since carbon deposition occurs when supplied, it is necessary to supply it to the fuel cell after at least reducing the molecular weight by a reforming reaction or the like. For example, in the case of a solid oxide fuel cell, it is necessary to use a gas that does not contain hydrocarbons having 2 or more carbon atoms before being supplied to the cell. Therefore, even in the case of a solid oxide fuel cell in which the fuel gas supplied to the cell is more diverse than that of the solid polymer fuel cell, a sufficiently desulfurized raw fuel can be obtained by starting the desulfurizer. After that, unless the reformer is started to generate fuel gas such as hydrogen, the fuel gas cannot be supplied to the solid oxide fuel cell, and it takes time to start. .
Japanese Examined Patent Publication No. 6-65602 Japanese Patent Publication No.7-115842 Japanese Patent No. 3410147 Japanese Patent No. 3261192 WO2003-077771 JP 2003-49172 A JP 2005-2317 A JP 2001-294874 A JP 2004-319400 A PCT / JP05 / 01065 JP 2005-317405 A

  The present invention is a liquid raw fuel for a fuel cell, in particular, a solid oxide fuel cell, and can be efficiently desulfurized even under relatively mild conditions. An object is to provide a liquid raw fuel for a fuel cell cogeneration system that is relatively easy to maintain and that can simplify the fuel cell cogeneration system itself. Another object of the present invention is to provide a fuel cell cogeneration system using the liquid raw fuel for the fuel cell cogeneration system.

  The present inventor has conducted earnest research to solve the above problems, and as a result of examining in detail the relationship between the type of sulfur compound and the degree of adsorption desulfurization, the degree of difficulty of adsorption desulfurization of dimethyldibenzothiophene is not high. However, it was found that the difficulty of adsorptive desulfurization of sulfur compounds having a molecular weight higher than that of dimethyldibenzothiophene is extremely high. That is, it has been found that sulfur compounds having a molecular weight of 213 or more, particularly organic sulfur compounds having 15 or more carbon atoms, are extremely difficult to desulfurize, and further, sulfur compounds having a molecular weight of 213 or more, particularly organic sulfur compounds having 15 or more carbon atoms. The liquid raw fuel for a fuel cell cogeneration system having a sulfur content of 0.3 mass ppm or less as a sulfur content was efficiently desulfurized under relatively mild conditions and achieved the intended purpose, and the present invention was conceived. .

That is, the present invention is a liquid raw fuel for a fuel cell cogeneration system or a fuel cell cogeneration system as follows.
(1) A liquid raw fuel used in a fuel cell cogeneration system for generating electricity by supplying a fuel gas mainly composed of hydrogen obtained by desulfurization and reforming to a fuel cell, and having an end point in distillation properties of 220 ° C. A liquid raw fuel for a fuel cell cogeneration system, which is a hydrocarbon having a higher content of a sulfur compound having a molecular weight of 213 or more and a sulfur content of 0.3 mass ppm or less.
(2) The liquid raw fuel for a fuel cell cogeneration system according to the above (1), wherein the sulfur compound having a molecular weight of 213 or more is an organic sulfur compound having 15 or more carbon atoms.
(3) The liquid raw fuel for a fuel cell cogeneration system according to the above (1) or (2), wherein the sulfur content is 0.1 to 30 ppm by mass.
(4) The liquid raw fuel for a fuel cell cogeneration system according to any one of the above (1) to (3), wherein the main component is a kerosene fraction.
(5) The liquid raw fuel for a fuel cell cogeneration system according to any one of the above (1) to (3), wherein the main component is a light oil fraction.

(6) Desulfurization means for desulfurizing the liquid raw fuel for a fuel cell cogeneration system according to any one of (1) to (5) above, reforming the liquid raw fuel desulfurized by the desulfurization means, A fuel cell cogeneration system comprising: reforming means for generating fuel gas as a main component; and a fuel cell for generating electric power by reacting the fuel gas with oxygen.
(7) The fuel cell cogeneration system according to (6) above, wherein the desulfurization means is adsorptive desulfurization with one or more kinds of desulfurization agents selected from solid acid desulfurization agents, activated carbon desulfurization agents, and metal desulfurization agents.
(8) The solid acid desulfurizing agent is at least one solid superacid selected from the group consisting of sulfate group zirconia, sulfate group alumina, sulfate group tin oxide, sulfate group iron oxide, tungstate zirconia, and tungstate oxide tin. The fuel cell cogeneration system according to the above item (7).
(9) The activated carbon-based desulfurization agent has a specific surface area of 500 m ² / g or more, a micropore specific surface area Smicro [m ² / g], a micropore external pore volume Vext [cm ³ / g], and a micropore external specific surface area Sext [M ² / g] is the following formula (1):
Smicro × 2 × Vext / Sext> 0.7 (1)
The fuel cell cogeneration system according to the above item (7), which is a carbon material satisfying the above.
(10) The fuel cell cogeneration system according to (7), wherein the metal desulfurizing agent is a copper desulfurizing agent and / or a nickel desulfurizing agent.
(11) The fuel cell cogeneration system according to (7) above, wherein adsorptive desulfurization with a solid acid desulfurizing agent and / or activated carbon desulfurizing agent is performed at -30 to 150 ° C.
(12) In the desulfurization means, after desulfurization with a solid acid desulfurization agent and / or activated carbon desulfurization agent, the remaining trace sulfur compound is further removed with a metal desulfurization agent, The fuel cell cogeneration system according to the above (7) .
(13) The fuel cell cogeneration system according to (7) above, wherein the trace sulfur compound is removed by the metal desulfurizing agent at a temperature of 100 to 300 ° C.
(14) The fuel cell cogeneration system according to the above (6) to (13), wherein the liquid raw fuel desulfurized by the desulfurization means has a sulfur content of 50 mass ppb or less.
(15) The reforming means for reforming the liquid raw fuel desulfurized by the desulfurization means to generate a fuel gas containing hydrogen as a main component includes hydrogen and hydrocarbon gas from the liquid raw fuel, water and oxygen after the desulfurization treatment. A steam reformer that generates a fuel gas mainly composed of hydrogen, carbon monoxide, and carbon dioxide from a gas containing hydrogen and hydrocarbon gas and water. The fuel cell cogeneration system according to any one of (6) to (14) above.
(16) The fuel cell cogeneration system according to any one of (6) to (15), wherein the fuel cell is a solid oxide fuel cell.
(17) The fuel cell cogeneration system according to the above (16), wherein the steam reformer is heated by the exhaust heat of the solid oxide fuel cell.
(18) The fuel cell cogeneration system according to any one of (6) to (17), wherein the desulfurization means is heated when the fuel cell cogeneration system is activated by warm water in a hot water storage tank of the fuel cell cogeneration system.
(19) The fuel cell cogeneration system according to the above (6) to (18), wherein electricity is supplied to a heater for starting the desulfurizer and / or the autothermal reformer by a capacitor or a secondary battery.

  The liquid raw fuel for a fuel cell cogeneration system according to the present invention is selected from solid acid desulfurization agents, activated carbon desulfurization agents, and metal desulfurization agents because the content of a specific sulfur compound is regulated to a specific amount or less. By adsorptive desulfurization with more than one kind of desulfurization agent, sulfur content can be efficiently removed to a very low concentration under relatively mild conditions. For this reason, starting and maintenance of the fuel cell cogeneration system are relatively easy, and the number of auxiliary devices constituting the system can be reduced, so that the system itself can be made compact.

  The liquid raw fuel for a fuel cell cogeneration system of the present invention (hereinafter also simply referred to as liquid raw fuel or liquid raw fuel for a fuel cell) contains a sulfur compound having a distillation property higher than 220 ° C. and a molecular weight of 213 or more. The amount of hydrocarbon oil is 0.3 mass ppm or less as a sulfur content. A typical example of a sulfur compound having a molecular weight of 212 is dimethyldibenzothiophene, which is a sulfur compound in which two methyl groups are bonded to dibenzothiophene, and is an organic sulfur compound having 14 carbon atoms. The sulfur compound corresponds to an organic sulfur compound having 15 or more carbon atoms.

  The types and concentrations of sulfur compounds contained in liquid raw fuel are gas chromatograph (GC) -flame photometric detector (FPD), GC-atomic emission detector (AED), GC-sulfur. It can be analyzed using a chemiluminescence detector (SCD), a GC-inductively coupled plasma mass spectrometer (ICP-MS), etc., but for analysis at the mass ppb level, GC is used. -ICP-MS is most preferred. In the case of GC analysis, in the gas chromatogram as a measurement result, the longer the retention time, the larger the molecular weight. Dimethyldibenzothiophene has multiple isomers, of which 2,8-dimethyldibenzothiophene is detected later than 4,6-dimethyldibenzothiophene, and is the last isomer of dimethyldibenzothiophene. It appears to be the detected isomer. Therefore, the sulfur compound detected after 2,8-dimethyldibenzothiophene is considered to be a sulfur compound having a molecular weight of 213 or more. If the sulfur compound having a molecular weight of 213 or more is a dibenzothiophene, it has 15 or more carbon atoms. Examples of the dibenzothiophenes having 15 carbon atoms include trimethyldibenzothiophene.

  For example, the main sulfur compounds contained in the kerosene fraction are benzothiophenes and dibenzothiophenes, but may also contain thiophenes, mercaptans (thiols), sulfides, disulfides, carbon disulfide, etc. . Both thiophenes and benzothiophenes are sulfur compounds with high reactivity of heterocycles containing a sulfur atom as a heteroatom. When they come into contact with a solid acid desulfurization agent, the cleavage of the heterocycle or the reaction between the heterocycle and the aromatic ring, Alternatively, decomposition occurs easily. Dibenzothiophenes are stable sulfur compounds that are less reactive than thiophenes and benzothiophenes because benzene rings are bonded to both sides of the thiophene ring. In particular, dibenzothiophenes having many alkyl groups such as trimethyldibenzothiophene, tetramethyldibenzothiophene, and pentamethyldibenzothiophene are difficult to remove even with a solid acid desulfurization agent. That is, as a result of examining the relationship between the type of sulfur compound and the degree of difficulty of adsorptive desulfurization in detail, the present inventors have found that the degree of difficulty of adsorptive desulfurization of dimethyldibenzothiophene is not high, but the molecular weight is higher than that of dimethyldibenzothiophene. It has been found that the difficulty of adsorptive desulfurization becomes extremely high when the sulfur compound is large.

  When such sulfur compounds detected after 2,8-dimethyldibenzothiophene, that is, sulfur compounds having a molecular weight of 213 or more are contained in the liquid raw fuel for fuel cells in excess of 0.3 mass ppm as the sulfur content, In addition to the fact that the compound itself cannot be sufficiently desulfurized and removed because the degree of difficulty of adsorptive desulfurization is extremely high, the reason is not necessarily clear, but there is a tendency to inhibit adsorptive desulfurization for sulfur compounds having a molecular weight of less than 213, The life of the adsorptive desulfurization agent is shortened.

  The reason why an organic sulfur compound having a molecular weight of 213 or more has an adverse effect on adsorptive desulfurization is considered that the molecular size of the sulfur compound has an influence on two points. The first is the area occupied when sulfur compounds are adsorbed. In the adsorption to the adsorptive desulfurizing agent, not all sulfur atoms are extracted from the sulfur compounds and only the sulfur atoms are adsorbed, but the entire sulfur compound molecules are adsorbed. Therefore, a sulfur compound with a high molecular weight has a large occupied area per molecule because the molecule itself is large, and the number of molecules adsorbed per unit surface area of the adsorptive desulfurization agent decreases. The amount is also reduced. Second, the diffusion route of sulfur compounds in the pores of the adsorptive desulfurization agent is blocked, and the present inventor shows that when carbon-based adsorptive desulfurization agents are used, mesopores greatly affect the adsorption of sulfur compounds. I found. If the size of the adsorbed sulfur compound molecule is large, the diffusion route is likely to be blocked, and it is considered that the sulfur compound cannot reach the active point in the pore even if the surface sufficient for adsorption remains. It is considered that this indicates that not only the amount of the mesopore but also a mesopore having a sufficient diameter that is not blocked by the adsorption of the sulfur compound is necessary in the carbon material. This phenomenon is considered to be the same for desulfurizing agents other than carbon-based ones. If the molecular weight of the adsorbed sulfur compound is large and the size of the molecule is large, the diffusion route is likely to be blocked, and a surface sufficient for adsorption remains. Even if it does, it is thought that a sulfur compound cannot reach.

  On the other hand, the liquid raw fuel for fuel cells of the present invention preferably has a total sulfur content of 0.1 to 30 ppm by mass, particularly 3 to 10 ppm by mass. If the sulfur content is high, the necessary amount of adsorbent increases, and this is not preferable because there are restrictions on installation space particularly in the case of a household fuel cell system. Even hydrodesulfurization which is a conventional technique, for example, hydrocarbon oil corresponding to a kerosene fraction can be desulfurized relatively easily up to about 30 mass ppm, and the use of a highly active catalyst and low liquid space are possible. Since 10 mass ppm is possible if a slight cost increase such as speed (LHSV) is allowed, the sulfur content of the liquid raw fuel for fuel cells of the present invention is preferably 30 mass ppm or less, and particularly preferably 10 mass ppm or less. . Further, since sulfur compounds having a molecular weight of less than 213 can be adsorbed and desulfurized relatively easily, it is not necessary to remove them in advance to a very low concentration. In addition, for example, in the case of kerosene used in a heating appliance or the like, a sulfur content of several tens of mass ppm is allowed. Therefore, it is not necessary to desulfurize in advance to a low concentration of 0.1 mass ppm or less for the liquid raw fuel for fuel cells, and it is not economical to desulfurize to 3 mass ppm or less. The sulfur content of the liquid raw fuel for a fuel cell of the present invention is preferably 0.1 mass ppm or more, particularly preferably 3 mass ppm or more.

  The liquid raw fuel for the fuel cell cogeneration system of the present invention is a hydrocarbon oil in which the content of a sulfur compound having a molecular weight of 213 or more is 0.3 mass ppm or less as a sulfur content, distillation properties, and the end point exceeds 220 ° C. The end point of the distillation property is preferably 240 ° C. or higher, more preferably 260 ° C. or higher. If the end point exceeds 220 ° C, the boiling point range (initial boiling point to end point) is preferably 80 to 390 ° C, more preferably 100 to 305 ° C, and particularly preferably 120 to 270 ° C. If the initial boiling point is less than 80 ° C., there are many fractions that are easily gasified and the vapor pressure is high. More preferably, it is 100 degreeC or more, Especially 120 degreeC or more. When the end point exceeds 390 ° C., the reforming reaction becomes extremely difficult, which is not preferable. The upper limit of the end point is more preferably 305 ° C. or lower, particularly 270 ° C. or lower, lower than the distillation temperature of the sulfur compound having a molecular weight of 213 or higher. If the lower limit of the end point is 220 ° C. or lower, the yield will be reduced if the flash point is 40 ° C. or higher and the smoke point is 23 mm or higher (21 mm or higher for cold weather) so that it can be shared with kerosene used in heating appliances. It is not economical.

  Specific fractions include kerosene fractions, light oil fractions, intermediate products used to produce them, petroleum fractions such as blend base materials, and naphtha fractions and heavy oil fractions mixed with them. Is mentioned. More preferably, a kerosene fraction, a mixed oil of a kerosene fraction and a naphtha, a mixed oil of a kerosene fraction and a light gas oil fraction, a kerosene fraction having a slightly lower end point than a commercial kerosene, and an end point more than a commercial kerosene Examples include kerosene fractions that are low and have a high initial boiling point, and kerosene fractions obtained by removing specific components such as aromatics from commercial kerosene. Among them, kerosene fractions that have a lower end point than commercial kerosene are heating appliances. It is preferable because it can be shared with kerosene used in the

A typical commercial kerosene is an oil mainly composed of hydrocarbons having about 12 to 16 carbon atoms, a density (15 ° C.) of 0.790 to 0.850 g / cm ³ , and a boiling point range of about 150 to 320 ° C. Although it contains a lot of paraffinic hydrocarbons, it contains about 0 to 30% by volume of aromatic hydrocarbons and about 0 to 5% by volume of polycyclic aromatics. Generally, it is No. 1 kerosene defined in Japanese Industrial Standard JIS K2203 as a fuel for lamps, heating, and kitchen. As for quality, flash point 40 ° C or higher, 95% distillation temperature 270 ° C or lower, sulfur content 0.008 mass% (80 mass ppm) or lower, smoke point 23mm or higher (21mm or higher for cold weather), copper plate corrosion ( 50 ° C., 3 hours) 1 or less, color (Saebold) +25 or more. Usually, the sulfur content is from several ppm to 80 ppm or less, and the nitrogen content is from several ppm to 10 ppm.

  A typical diesel oil is an oil mainly composed of hydrocarbons having about 16 to 20 carbon atoms, has a density (15 ° C.) of 0.820 to 0.880 g / cm 3, a boiling point range of about 140 to 390 ° C., and paraffin. Although it contains a lot of hydrocarbons, it contains about 0 to 30% by volume of aromatic hydrocarbons and about 0 to 10% by volume of polycyclic aromatic compounds. In general, JIS K2204 defines a standard property as “light oil” as fuel for automobile diesel engines.

  Therefore, as a method for producing a liquid raw fuel for a fuel cell of the present invention, the content of a sulfur compound having a distillation property, an end point exceeding 220 ° C., and a molecular weight of 213 or more from the petroleum fraction is 0 as a sulfur content. It can be obtained by separating those satisfying 3 mass ppm or less, or by mixing two or more fractions at an appropriate ratio so as to satisfy the above physical properties. Furthermore, fractions that do not satisfy the above physical properties are treated by distillation separation, hydrodesulfurization, adsorption separation, oxidative desulfurization, and the like, and combinations thereof, so that the end point exceeds 220 ° C. and the molecular weight is 213 or more. The sulfur compound content can be adjusted to 0.3 mass ppm or less as the sulfur content.

  For example, regarding the content of sulfur compounds, in the case of kerosene included in the general JIS K2203 No. 1 standard, do not include a fraction containing a sulfur compound having a molecular weight of 213 or more by distillation separation, Or it can manufacture by lowering the content of the said fraction. Specifically, when the kerosene fraction is distilled and separated using a distillation apparatus having a large number of theoretical plates, dibenzothiophenes are distilled at about 305 to 310 ° C., but in a distillation apparatus having a small number of theoretical plates, it is distilled at about 270 ° C. To do. That is, in order not to include a sulfur compound having a molecular weight of 213 or more, preferably by using a distillation apparatus having a large number of theoretical plates in order to increase the yield, the end point of the kerosene fraction is adjusted to the low temperature side, It is sufficient that the high-boiling fraction containing 213 or more organic sulfur compounds is not included. In this case, it is preferable to improve the recovery rate of the liquid raw fuel by precise distillation separation using a distillation apparatus having a theoretical plate number of 12 or more. .

In addition, when blended and prepared as a kerosene fraction, the distillation properties of each blend base material are adjusted in advance so that the content of the organic sulfur compound having a molecular weight of 213 or more falls within the predetermined range of the present invention. It can also be produced by blending.
The content of the organic sulfur compound having a molecular weight of 213 or more in each blend base and kerosene fraction varies depending on the properties of crude oil as a raw material, the configuration of the desulfurizer, the operating conditions of the desulfurizer, the production amount, etc. When adjusting the distillation property of each blend base material, the initial boiling point and / or end point thereof are appropriately adjusted according to the content of the organic sulfur compound having a molecular weight of 213 or more. Obtained may be kerosene fraction of more invention and appropriately adjusted child ratio and compounding of each blend substrate. In short, as a liquid raw fuel for fuel cells, it is important that the content of an organic sulfur compound having a molecular weight of 213 or more is 0.3 mass ppm or less as a sulfur content.

  In the case of adsorptive separation, for example, it is possible to reduce sulfur compounds having a molecular weight of 213 or more with an activated carbon-based desulfurization agent that excels in adsorption of a compound having a large number of benzene rings by a π electron adsorption mechanism. In particular, since a sulfur compound having a molecular weight of 213 or more has a large molecule, an activated carbon-based desulfurization agent having a large average pore size and a large number of mesopores and macropores as diffusion routes is preferable. Specifically, it is preferable to use a desulfurization agent containing a carbon material previously proposed by the present applicant (see International Patent Publication No. WO03097777).

As the carbon material, the specific surface area is preferably 500 m ² / g or more, more preferably 2000 m ² / g or more, and the micropore specific surface area Smicro [m ² / g] and the micropore external pore volume Vext are [cm ³ / g] and the micropore external specific surface area Sext [m ² / g] preferably satisfy the following formula (1).
Smicro × 2 × Vext / Sext> 0.7 (1)
The carbon material preferably has sufficient mesopores with a large specific surface area and a pore diameter of about 20 to 500 mm. For example, by bringing kerosene included in No. 1 standard of JIS K2203 into contact with an activated carbon desulfurizing agent made of activated carbon fiber having a large average pore diameter, the content of sulfur compounds having a molecular weight of 213 or more is set to 0. It can be adjusted to 3 mass ppm or less.

The method of bringing the activated carbon desulfurizing agent into contact with the kerosene fraction, etc., may be batch type (batch type) or distribution type, but the container (desulfurization tank) is filled with the activated carbon desulfurizing agent of the molded product and the hydrocarbon oil The distribution type which distribute | circulates is more preferable. In the case of the flow type, the contact condition is a normal pressure to 5 MPaG, preferably a normal pressure to 1 MPaG, particularly 0.01 to 0.3 MPaG, and a temperature of −30 to 100 ° C., preferably −10 to 10 ° C. 80 ° C., particularly 0 to 50 ° C., and LHSV is preferably 0.01 to 100 hr ⁻¹ , particularly 0.05 to 20 hr ⁻¹ . Moreover, it is preferable to install two or more desulfurization tanks. First, the hydrocarbon oil to be desulfurized is circulated in one desulfurization tank, and when the desulfurization performance of the desulfurizing agent is lowered and sufficient desulfurization performance cannot be obtained, the desulfurization tank is switched to another desulfurization tank. Is preferably a method in which the desulfurization agent having a lowered desulfurization performance is regenerated or replaced with a new desulfurization agent and this operation is repeated. Furthermore, two or more desulfurization tanks are connected in series, and when the desulfurization performance of the desulfurization tank on the most upstream side is completely lost or significantly deteriorated, the desulfurization tank is separated and regenerated, or a new desulfurization tank is obtained. It is particularly preferable to connect a desulfurization tank filled with a regenerated or new desulfurization agent at the most downstream side after the replacement with the agent, and repeat this.

  It is preferable that the desulfurization agent removes a small amount of adsorbed moisture in advance as a pretreatment. If moisture or the like is adsorbed, not only the adsorption of sulfur compounds is inhibited, but moisture desorbed from the desulfurizing agent immediately after the introduction of hydrocarbons is mixed into the hydrocarbon. In an oxidizing atmosphere such as air, it is preferable to dry at about 100 to 200 ° C, preferably about 120 to 150 ° C. If it is 200 ° C. or higher, it reacts with oxygen and the mass decreases, which is not preferable. On the other hand, it can be dried at about 100 to 800 ° C. in a non-oxidizing atmosphere such as nitrogen. It is particularly preferable to perform the heat treatment at 400 to 800 ° C. because organic substances and oxygen contained therein are removed and the adsorption performance is improved.

  In the case of oxidative desulfurization, the alkyl-substituted product generally has a higher relative reactivity than dibenzothiophene, and is effective as a method for removing dibenzothiophenes having many alkyl groups. For example, by using a polar solvent such as acetic acid, using an acid such as sulfuric acid as a catalyst, oxidizing agent such as hydrogen peroxide and kerosene of No. 1 standard of JIS K2203 are mixed using, for example, a static mixer, etc. The sulfur compound having a molecular weight of 213 or more can be reduced by reacting the agent with a sulfur compound having a molecular weight of 213 or more in kerosene and extracting and / or adsorbing and separating the generated oxide. Examples of the oxidative desulfurization method include JP-A Nos. 11-14462, 2001-151748, 2001-354978, 2003-268385, 2004-195445, and JP-A-2004-195445. The method described in 2004-196927 gazette, Unexamined-Japanese-Patent No. 2004-231701, Unexamined-Japanese-Patent No. 2006-36944, etc. can be taken.

  In this way, the liquid raw fuel for a fuel cell of the present invention prepared by removing a specific sulfur compound is further desulfurized by a desulfurization means and then reformed to produce a fuel gas used in the fuel cell. The fuel gas is made of hydrogen, carbon monoxide or the like and sent to the means, and the fuel gas is sent to the fuel cell and reacts with oxygen to generate power. The present invention also provides a desulfurization means for desulfurizing the liquid raw fuel for a fuel cell, a reforming means for reforming the liquid raw fuel desulfurized by the desulfurization means to generate a fuel gas mainly containing hydrogen, and a fuel A fuel cell core comprising a fuel cell that generates electricity by reacting gas and oxygen, and preferably means for recovering exhaust heat of the fuel cell, for example, exhaust heat recovery means such as a hot water tank for producing and storing hot water It is a generation system.

  FIG. 2 is a flow sheet showing a simplified example of the fuel cell cogeneration system of the present invention. In FIG. 2, kerosene, which is a typical petroleum fraction as the liquid raw fuel for fuel cells of the present invention, is first sent to the desulfurization means 1 to remove sulfur that poisons the reforming catalyst at the subsequent stage. The kerosene from which the sulfur content has been removed is then converted into a gas containing hydrogen, light hydrocarbon gas, carbon monoxide, and carbon dioxide by the reaction of water and oxygen in the autothermal reformer 2.

  In FIG. 2, the solid oxide fuel cell housing 3 is indicated by a frame surrounded by a dotted line, and heat exchange is performed to recover the heat generated in the steam reformer 4, the solid oxide fuel cell 5 and the fuel cell with hot water. It consists of a container (not shown). In the solid oxide fuel cell 5, a plurality of cell stacks in which a plurality of fuel cells (cells) are stacked are arranged at an appropriate interval and accommodated in the housing 3. The gas containing hydrogen and light hydrocarbon gas obtained by the self-heat reformer 2 is sent to the steam reformer 4 in the housing 3 and uses an endothermic reaction while utilizing the heat generated by the fuel cell. The light hydrocarbon gas is further steam reformed to produce hydrogen, which is converted into fuel gas for a fuel cell. The solid oxide fuel cell 5 can reform methane gas or the like in the cell stack, but if hydrocarbons having 2 or more carbon atoms remain, it may cause carbon deposition. In the mass container 4, it is preferable not to leave hydrocarbons having 2 or more carbon atoms. In addition, since the solid oxide fuel cell 5 can also use carbon monoxide as a fuel, it is not necessary to adjust the CO content by CO shift after steam reforming.

The hydrogen-based fuel gas obtained in the steam reformer 4 is sent to the fuel cell 5 to generate electricity when it reacts with oxygen in the air. Exhaust heat of the solid oxide fuel cell 5 during power generation is used for the endothermic reaction of the steam reformer 4, and hot water is produced by a heat exchanger provided inside the housing wall or the like to produce hot water storage tank 6. Can be stored. The hot water in the hot water tank 6 is normally used as hot water supply, but when the fuel cell cogeneration system is stopped at night, the hot water can be used for heating the desulfurizer when the fuel cell cogeneration system is started. In addition, if a capacitor or secondary battery 7 is installed, it is charged during power generation, and when the fuel cell cogeneration system is stopped and then restarted, it is used for heating the desulfurizer, vaporizer and autothermal reformer. It can also be used as a power source for heaters.
These desulfurization means, reforming means, and fuel cell will be sequentially described in more detail below.

  In order to prevent poisoning of the reforming catalyst that reforms the fuel gas directly supplied to the fuel cell, the liquid raw fuel for the fuel cell of the present invention is usually used in a fuel cell cogeneration system. Desulfurization is preferably performed to 20 mass ppb or less, more preferably 5 mass ppb or less. This desulfurization means does not have to be incorporated in the fuel cell cogeneration system, and may be disposed outside the fuel cell cogeneration system. The desulfurization means for desulfurizing the liquid raw fuel for a fuel cell of the present invention is preferably adsorption desulfurization with one or more kinds of desulfurization agents selected from solid acid desulfurization agents, activated carbon desulfurization agents, and metal desulfurization agents. Preferably there is. Since the liquid raw fuel of the present invention has a low content of an organic sulfur compound having a molecular weight of 213 or more which is extremely difficult to desulfurize, the liquid raw fuel can be used more efficiently in a fuel cell cogeneration system when used in combination with the desulfurization means of the present invention. Therefore, the desulfurization means can be made compact and the life of the desulfurization agent can be improved.

  Adsorption desulfurization with a solid acid desulfurization agent and / or an activated carbon desulfurization agent is preferably performed at a temperature of 150 ° C. or lower. Heating to a temperature exceeding 150 ° C. not only requires time for startup, but also reduces energy efficiency. Therefore, in the desulfurization means, it is preferable that the solid acid desulfurization agent and / or the activated carbon desulfurization agent filled in the desulfurizer remove sulfur from the liquid raw fuel at a temperature of −30 to 150 ° C.

  After desulfurization with a solid acid desulfurization agent and / or activated carbon desulfurization agent, it is preferable to further remove residual trace sulfur compounds with a metal desulfurization agent. Since the amount of residual trace sulfur compounds is very small, poisoning of the reforming catalyst is slight if it takes a short time, so desulfurization is not always necessary immediately after the start of the fuel cell cogeneration system. However, desulfurization after heating to a higher temperature is sufficient, and can be performed at a temperature of 100 to 300 ° C. The metal-based desulfurizing agent is preferably a copper-based desulfurizing agent and / or a nickel-based desulfurizing agent.

  As the liquid hydrocarbon to be supplied to the reforming means, it is preferable that the sulfur content is desulfurized by the above desulfurization means and removed to 50 mass ppb or less, and further to 20 mass ppb or less. The sulfur content is successively reduced by adsorptive desulfurization with a solid acid desulfurizing agent and / or an activated carbon desulfurizing agent, and further with a metal desulfurizing agent. The sulfur content may be finally desulfurized to the above-mentioned concentration, but in the case of a solid acid desulfurization agent and / or activated carbon desulfurization agent, desulfurization to about 0.1 mass ppm to 50 mass ppb or less and about 20 mass ppb. Furthermore, it may be desulfurized to 50 mass ppb to 20 mass ppb or less with a metal desulfurization agent.

  In the fuel cell in which the raw fuel for a fuel cell of the present invention can be preferably used, the solid acid desulfurization agent provided as a desulfurization means is a reaction between sulfur compounds in hydrocarbon oil and / or sulfur compounds and aromatic hydrocarbons ( In other words, the reaction between the thiophene ring and the benzene ring is catalyzed to promote the formation of heavy sulfur compounds, and also serves as an adsorbent that adsorbs sulfur compounds in hydrocarbon oils, especially the generated heavy sulfur compounds. Is. In the present invention, the heaviness of the sulfur compound is a reaction between the sulfur compounds or mainly between the thiophene ring and the benzene ring. Therefore, the sulfur compound contained in the naphtha is removed in the presence of an alkylating agent (such as an olefin). This is different from the method of alkylating with a solid acid to make it heavy, and in the present invention, a special alkylating agent such as olefin is not required.

Specific examples of solid acid desulfurization agents include zeolite, silica / alumina, activated clay and other solid acids, sulfate zirconia, sulfate radical alumina, sulfate radical tin oxide, sulfate radical iron oxide, tungstate zirconia, tungsten Solid superacids such as tin oxide can also be mentioned.
The solid acid desulfurizing agent is preferably at least one zeolite selected from proton type faujasite type zeolite, proton type mordenite and proton type β zeolite. In particular, these zeolites preferably have a silica / alumina ratio of 100 mol / mol or less, more preferably 30 mol / mol or less, because the smaller the silica / alumina ratio, the greater the amount of acid that becomes an adsorption site. .

Zeolite has the general formula: xM _{2 / n} O · Al ₂ O ₃ · ySiO ₂ · zH ₂ O (where n is the valence of the cation M, x is a number of 1 or less, y is a number of 2 or more, z is a general term for a crystalline hydrous aluminosilicate represented by a number of 0 or more. Charge-compensating cations such as alkali metals and alkaline earth metals are held in the pores and cavities. The charge compensating cation can be easily exchanged for another cation such as a proton. In addition, due to the acid treatment or the like, the SiO ₂ / Al ₂ O ₃ molar ratio is increased, the acid strength is increased, and the solid acid amount is decreased. Since acid strength does not significantly affect the adsorption of sulfur compounds, it is preferable not to reduce the amount of solid acid.

  The charge-compensating cation of the zeolite used for the desulfurization means is a proton, that is, hydrogen, and the cation content other than protons such as sodium, potassium, magnesium and calcium is preferably 5% by mass or less, more preferably 3 It is 1 mass% or less, More preferably, it is 1 mass% or less.

As the properties of the above-mentioned zeolite crystals, the crystallinity is preferably 80% or more, particularly preferably 90% or more, the crystallite diameter is preferably 5 μm or less, particularly preferably 1 μm or less, and the average particle diameter is 30 μm or less, particularly 10 μm or less. Further, the specific surface area is preferably 300 m ² / g or more, particularly preferably 400 m ² / g or more.

Moreover, there exists a solid super strong acid catalyst as a desulfurization agent used for the desulfurization means of this invention. The solid superacid catalyst refers to a catalyst made of a solid acid having a higher acid strength than 100% sulfuric acid having a Hammett acidity function H ₀ of −11.93, and includes silicon, aluminum, titanium, zirconium, tungsten, Hydroxides or oxides such as molybdenum and iron, or a support made of graphite, ion exchange resin, etc., with sulfate radical, antimony pentafluoride, tantalum pentafluoride, boron trifluoride etc. attached or supported, oxidation Zirconium (ZrO ₂ ), stannic oxide (SnO ₂ ), titania (TiO ₂ ), ferric oxide (Fe ₂ O ₃ ) or the like supporting tungsten oxide (WO ₃ ), and further fluorinated sulfonic acid Resin etc. can be illustrated. Among these, in particular, zirconia, alumina, tin oxide, iron oxide or titania sulfate radical zirconia, sulfate radical alumina, sulfate radical tin oxide, sulfate radical iron oxide, sulfate radical titania previously proposed by the present applicant is proposed. Alternatively, it is preferable to use zirconia tungstate, tin oxide tungstate, or the like in which a plurality of metal hydroxides and / or hydrated oxides are mixed and fired. (For example, Japanese Patent Publication No. 59-6181, Japanese Patent Publication No. 59-40056, Japanese Patent Application Laid-Open No. 04-187239, Japanese Patent Application Laid-Open No. 04-187241, Japanese Patent No. 2566814, Japanese Patent No. 2929772, Japanese Patent No. 3251313, (See Japanese Patent No. 3328438, Japanese Patent No. 3432694, Japanese Patent No. 3517696, Japanese Patent No. 3553878, and Japanese Patent No. 3568372.)

The acid strength (H ₀ ) is defined by the ability of an acid point on the catalyst surface to give a proton to a base or the ability to receive an electron pair from a base, and is expressed by a pKa value. It can be measured by a method such as a method. For example, the acid strength of the solid acid desulfurization agent can be directly measured using an acid-base conversion indicator having a known pKa value. p-nitrotoluene (pKa value; -11.4), m-nitrotoluene (pKa value; -12.0), p-nitrochlorobenzene (pKa value; -12.7), 2,4-dinitrotoluene (pKa value; -13.8) 2,4-dinitrofluorobenzene (pKa value; -14.5), 1,3,5-trichlorobenzene (pKa value; -16.1), etc. When the color change of the indicator on the catalyst surface to the acidic color is observed, the value is the same as or lower than the pKa value at which the color changes to the acidic color. When the catalyst is colored, it cannot be measured with an indicator, so it has been reported that it can be estimated from the isomerization activity of butane and pentane ["Studies in Surface Science and Catalysis" Vol. 90, ACID-BASE CATALYSIS II , p.507 (1994)].

  As the solid acid desulfurizing agent, the above-mentioned zeolite or solid superacid catalyst can be used as it is, but a molded body containing 30% by mass or more, particularly 60% by mass or more of these zeolite or solid superacid catalyst is preferably used. As the shape, in order to increase the concentration gradient of the sulfur compound, in the case of the flow type, a small shape, particularly a spherical shape, is preferable as long as the differential pressure before and after the container filled with the desulfurizing agent does not increase. In the case of a spherical shape, the diameter is preferably 0.5 to 5 mm, particularly preferably 1 to 3 mm. In the case of a columnar shape, the diameter is preferably 0.1 to 4 mm, particularly 0.12 to 2 mm, and the length is preferably 0.5 to 5 times, particularly 1 to 2 times the diameter.

The specific surface area of the solid acid-based desulfurization agent is preferably 100 m ² / g or more, more preferably 200 m ² / g or more, particularly 300 m, since it has a great influence on the adsorption capacity of sulfur compounds, including the case of a solid superacid catalyst. ² / g or more is preferable. The pore volume having a pore diameter of 10 mm or less is preferably at least 0.10 ml / g, particularly preferably at least 0.20 ml / g, in order to increase the adsorption capacity of the sulfur compound. In addition, the pore volume having a pore diameter of 10 mm or more and 0.1 μm or less should be 0.05 ml / g or more, particularly 0.10 ml / g or more in order to increase the diffusion rate of sulfur compounds in the pores. Is preferred. The pore volume having a pore diameter of 0.1 μm or more is preferably 0.3 ml / g or less, particularly preferably 0.25 ml / g or less, in order to increase the mechanical strength of the molded article. In general, the specific surface area and the total pore volume are measured by a nitrogen adsorption method, and the macropore volume is measured by a mercury intrusion method.

  When using zeolite as a molded product, as described in JP-A-4-198011, after the semi-finished product is molded, it may be dried and calcined. The binder may be mixed and molded, and then dried and fired.

  Examples of the binder include clays such as alumina and smectite, and inorganic binders such as water glass. These binders may be used to such an extent that they can be molded, and are not particularly limited, but usually about 0.05 to 30% by mass with respect to the raw material is used. Mixing inorganic fine particles such as silica, alumina, other zeolites, and organic substances such as activated carbon to improve the adsorption performance of sulfur compounds that are difficult for zeolite to adsorb, and increasing the abundance of mesopores and macropores. The diffusion rate of the compound may be improved. Moreover, you may improve adsorption | suction performance by compounding with a metal. In the case of particles, the adsorbent generally has an irregular shape mainly having an average diameter of 0.8 to 1.7 mm, and the fracture strength of the carrier is 3.0 kg / pellet or more, particularly 3.5 kg / pellet or more. This is preferable because it does not cause cracking. Usually, the breaking strength is measured by a compressive strength measuring device such as a Kiya-type tablet breaking strength measuring device (Toyama Sangyo Co., Ltd.).

As the activated carbon-based desulfurization agent, it is preferable to use a desulfurization agent containing a carbon material previously proposed by the present applicant (see International Publication No. WO03 / 097771).
As the carbon material, the specific surface area is preferably 500 m ² / g or more, more preferably 2000 m ² / g or more, and the micropore specific surface area Smicro [m ² / g] and the micropore external pore volume Vext are [cm ³ / g] and the micropore external specific surface area Sext [m ² / g] preferably satisfy the following formula (1).
Smicro × 2 × Vext / Sext> 0.7 (1)
In particular, it is more preferable that the following formula (2) is satisfied.
Smicro × 2 × Vext / Sext> 3.0 (2)

  The carbon material preferably has sufficient mesopores with a large specific surface area and a pore diameter of about 20 to 500 mm. Parameters such as specific surface area, pore diameter and pore volume used in the analysis of carbon materials are generally determined by gas adsorption methods using physical adsorption based on intermolecular forces acting between gas molecules and solid surfaces, especially nitrogen adsorption. Measured using the method. Since many carbon materials have an average pore diameter of 20 mm or less, care must be taken in their analysis.

A commonly used BET (Brunauer-Emmett-Teller) method is a method for obtaining the specific surface area of a carbon material based on the following equation (3).
x / V / (1-x) = 1 / Vm / C _B + (C _B -1) x / Vm / C _B (3)
Here, x is a relative pressure, the adsorption amount when V is the relative pressure is x, Vm is monolayer adsorption amount, and, C _B are constants (> 0).

In addition, micropores can be quantified by the t plot method. In the t plot method, the horizontal axis represents the adsorption layer thickness t (function of relative pressure), and the vertical axis represents the adsorption amount, and the change in the adsorption amount of the carbon material with respect to the adsorption layer thickness t is plotted. In the plotted characteristics, there exists an adsorption layer thickness region t _{B in} which the slope of the t plot continuously decreases. In the area t _B, with the progress of the multi-molecule layer adsorption, the fine pore (micropore) is met adsorbed gas (nitrogen), it does not contribute as a surface. Since this phenomenon is caused by the micropore filling in the adsorption layer thickness region t _B , in the region where the adsorption layer thickness t is smaller and larger than the region near the region t _B , Since the filling into the micropores and the capillary condensation have not occurred, the slope of the t plot is constant. Therefore, the thickness t is larger than the area t _B region of the adsorption layer, i.e. draw a straight line in the region where the filling of the micropores of the gas molecules is completed, the contribution from the slope as the surface other than the micropores of the carbon material The specific surface area (external specific surface area) is determined. Further, when converted to intercept of the vertical axis of the line thickness t of the adsorption layer is pulled at a greater area than t _B to the liquid, micropore volume is obtained.

In summary, the carbon material adsorption amount V, the micropore external specific surface area Sext [m ² / g], the micropore specific surface area Smicro [m ² / g], the micropore volume Vmicro [cm ³ / g] and The micropore external pore volume Vext [cm ³ / g] is obtained by the following formulas (4) to (8).
V = αt + β (t> t _B ) (4)
Sext = α × 10 ³ × D (5)
Vmicro = β × D (6)
Smicro = Sa-Sext (7)
Vext = Va-Vmicro (8)
Here, α [cm ³ (STP) / g / nm] is the slope of the straight line of the t plot in the region where the thickness t of the adsorption layer is larger than the region t _B , and β [cm ³ (STP) / g] is the adsorption. The intercept of the straight line of the t plot in the region where the layer thickness t is larger than the region t _B , D is the density conversion coefficient (0.001547 when nitrogen is used as the gas) [cm ³ liq / cm ³ (STP )], Sa is the total specific surface area [m ² / g], and Va is the total pore volume [cm ³ / g]. However, Sa is the total specific surface area as determined by etc. BET method described above. Va can be defined as a value obtained by converting the amount of adsorbed gas at a pressure close to the saturated vapor pressure into a liquid. For example, the adsorbed amount [cm ³ (STP) / g] when the relative pressure is 0.95. The value multiplied by D.

Many of the carbon materials are mainly micropores, and there are almost no mesopores outside the micropores. However, it has been found that a small amount of mesopores greatly affects the adsorption of sulfur compounds. The inventor has found that a value of 2 × Vext / Sext is used as an index representing the influence of mesopores. A value of 2 × Va / Sa represents the average pore half diameter when the pores is assumed to be cylindrical (Da / 2). That is, 2 × Vext / Sext is an index representing a value close to the average pore radius (Dext / 2) of the mesopores. For the adsorption of sulfur compounds, the larger the micropore specific surface area and mesopore average pore diameter of the carbon material, the better, and the larger the product of both (Smicro × 2 × Vext / Sext), the more preferably 3.0 cm ³ / g. As described above, the carbon material adsorption performance of 5.0 cm ³ / g or more is more excellent. Although the cause of this is not clear, it is considered that it is not simply the amount of mesopores but represents that a mesopore having a sufficient diameter that does not become clogged by adsorption of sulfur compounds is necessary.

  The activated carbon-based desulfurization agent may carry a transition metal and / or a transition metal oxide. Examples of the transition metal include silver, mercury, copper, cadmium, lead, molybdenum, zinc, cobalt, manganese, nickel, platinum, palladium, and iron.

  The activated carbon-based desulfurization agent can be used in any shape such as granular, fibrous, powdery, honeycomb, matte or felt. It is particularly preferable to use a molded product. Usually, it is mainly indefinite with an average diameter of 0.8 to 1.7 mm. In order not to cause cracking of the adsorbent, the breaking strength is preferably 3.0 kg / pellet or more, particularly 3.5 kg / pellet or more.

As the metal-based desulfurizing agent, a material in which a metal component is supported on a porous carrier such as alumina, or a product obtained by mixing alumina and the metal component and the like can be used. Examples of the metal include silver, mercury, copper, cadmium, lead, molybdenum, zinc, cobalt, manganese, nickel, platinum, palladium, and iron, and these oxides can also be used. From the viewpoint of safety and economy, copper, zinc, and nickel are preferable. Among them, copper is inexpensive and can be used in a wide temperature range from around normal temperature to about 300 ° C. It also has excellent performance for adsorption of sulfur compounds even in the absence of hydrogen in the state of copper oxide without reduction. Is particularly preferable. An adsorbent having a specific surface area of 150 m ² / g or more, preferably 200 m ² / g or more in which a copper component is supported on a porous carrier can be used. In particular, it is preferable to use the copper oxide-based desulfurization agent previously proposed by the present applicant (see Patent 3324746).

  In order to remove sulfur compounds having relatively low reactivity such as sulfides and carbon disulfide, it is preferable to use a nickel-based desulfurizing agent. The nickel-based desulfurization agent is particularly preferably one that has been reduced in a hydrogen atmosphere before use. Even if sulfides and carbon disulfide are contained in kerosene, they are generally very little, so a small amount of nickel-based desulfurizing agent is sufficient. Further, the nickel-based desulfurization agent has very low desulfurization activity unless it is at a high temperature of 150 ° C. or higher, but has a slight desulfurization performance even at room temperature. Even when the temperature is low such as at the time of start-up, the amount of sulfides and carbon disulfide originally contained in kerosene is very small, so that it can be desulfurized to a sufficient level with a small amount of desulfurizing agent.

  The method of bringing the two or three types of desulfurizing agent into contact with the hydrocarbon oil may be a batch type (batch type) or a flow type, but a flow type in which the hydrocarbon oil is passed through the packed bed of the desulfurizing agent is more preferable. preferable.

In the case of the flow type, the contact condition is 0 (normal pressure) to 50 kg / cm ² G, preferably 0 (normal pressure) to 10 kg / cm ² G, particularly 0.1 to 3 kg / cm ^2. G is preferred. Flow rate, 0.1~100hr ^-1, particularly preferably 0.5～20Hr ^-1 in LHSV. The temperature for performing the desulfurization treatment is preferably −30 to 150 ° C., more preferably 40 to 120 ° C., and particularly preferably 60 to 100 ° C. for the solid acid desulfurization agent. The activated carbon-based desulfurization agent is preferably −30 to 150 ° C., −10 to 100 ° C., more preferably 0 to 80 ° C. Moreover, 100-300 degreeC is preferable and, as for a metal-type desulfurization agent, 150-250 degreeC is more preferable.

The adsorbent preferably removes a small amount of adsorbed moisture in advance as a pretreatment of the adsorbent. When moisture is adsorbed, not only the adsorption of sulfur compounds is inhibited, but moisture desorbed from the adsorbent immediately after the start of hydrocarbon introduction is mixed into the hydrocarbon. The solid acid desulfurizing agent is preferably dried at about 130 to 500 ° C, preferably about 350 to 450 ° C. The activated carbon desulfurization agent is preferably dried at about 100 to 200 ° C. under an oxidizing atmosphere such as air. If it is 200 ° C. or higher, it reacts with oxygen and the mass decreases, which is not preferable. On the other hand, it can be dried at about 100 to 800 ° C. in a non-oxidizing atmosphere such as nitrogen. It is particularly preferable to perform the heat treatment at 400 to 800 ° C. because organic substances and oxygen contained therein are removed and the adsorption performance is improved. The metal desulfurizing agent is preferably dried at about 100 to 200 ° C.
By desulfurizing the liquid raw fuel with a low content of the specific sulfur compound of the present invention using the above-described desulfurization means equipped with the desulfurizing agent, it is possible to perform efficient desulfurization even at a relatively low temperature. The fuel cell cogeneration system can exhibit excellent functions and effects, such as downsizing of the desulfurization means, improvement of the life of the desulfurization agent, improvement of energy efficiency, simplification of the system, and shortening of start and stop times.

The liquid raw fuel for a fuel cell of the present invention is supplied to reforming means for generating fuel gas for the fuel cell after being desulfurized as described above. Examples of means for reforming hydrocarbon oil to hydrogen-rich gas include steam reforming, partial oxidation reforming, and autothermal reforming, but steam reforming and autothermal reforming are more effective. preferable.
The autothermal reforming method is a method for producing hydrogen while controlling heat generation by partial oxidation and heat absorption by steam reforming to balance the heat balance, and has a feature of short start-up time. The liquid raw fuel after desulfurization is reacted with water and oxygen at a temperature of 600 to 1000 ° C. in the presence of an oxidation catalyst and a reforming catalyst, and the hydrocarbon compound of the liquid raw fuel is decomposed while partially burning to generate hydrogen. It produces lighter hydrocarbon compounds with carbon monoxide and carbon dioxide.

  The steam reforming method is a method that has been widely used in the fields of refineries and petrochemicals as a method for producing hydrogen from a light hydrocarbon compound, and a high-concentration and high-quality hydrogen gas can be obtained. In the steam reforming method, hydrocarbons with high C / H (carbon / hydrogen ratio) such as heavy hydrocarbons, hydrocarbons containing a large amount of naphthene and aromatic components are likely to deteriorate the reforming catalyst due to carbon deposition, etc. A hydrocarbon having a smaller C / H is preferred as a raw material. Highly desulfurized kerosene and steam are brought into contact with the reforming catalyst at a high temperature and reacted to produce a hydrogen-rich gas for a fuel cell. However, although it is a reaction in an atmosphere of water vapor, when using liquid raw fuel, the hydrocarbons of the vaporized lamp / light oil fraction can be pyrolyzed and coked in piping and reactors. is there. Since the steam reforming reaction is an endothermic reaction that requires a large amount of energy, it is important to effectively use the heat generated in the fuel cell for the reforming reaction in order to improve the energy efficiency of the system. By uniformly controlling the entire stack within a temperature range effective for power generation, the power generation efficiency of the fuel cell can also be improved.

  In general, the hydrogen-rich gas after reforming in both the autothermal reforming method and the steam reforming method contains carbon monoxide (CO) on the order of percent, and this carbon monoxide (CO) deteriorates the performance of the fuel cell. Therefore, it is necessary to reduce the CO concentration to 10 ppm or less by performing CO shift reaction and CO selective oxidation after normal reforming. The solid oxide fuel cell that can be preferably used in the present invention has an advantage that CO can be used as a fuel without using an expensive catalyst such as platinum.

  In particular, it is preferable to reform by combining the autothermal reforming method and the steam reforming method. For example, water and oxygen are first added to the liquid hydrocarbon after desulfurization of the liquid raw fuel for the fuel cell in the autothermal reformer. A gas containing hydrogen and hydrocarbon gas is generated by reaction, and then steam reforming the gas containing the hydrogen and light hydrocarbon gas generated by the autothermal reformer with a steam reformer. The reforming treatment is preferably performed in series in the order of autothermal reforming and steam reforming so as to generate a fuel gas containing hydrogen as a main component and also containing carbon monoxide and carbon dioxide. A fuel gas for a fuel cell can be produced only by steam reforming. However, although it is a reaction in an atmosphere of water vapor, when using liquid raw fuel, the hydrocarbons of the vaporized lamp / light oil fraction can be pyrolyzed and coked in piping and reactors. is there. In addition, since steam reforming alone has a problem that it takes time to start, by combining autothermal reforming and steam reforming and performing autothermal reforming on the upstream side of steam reforming, liquid can be obtained in a short time. The raw fuel can be reformed, converted into fuel gas, and supplied to the fuel cell.

  In the reforming and gasification of kerosene, etc. by autothermal reforming reaction, when the steam reforming reaction is performed downstream, it is not necessary to reform the hydrocarbon compound of kerosene and light oil fraction to hydrogen gas. For example, it is preferable to limit the conversion to a light hydrocarbon gas having about 1 to 3 carbon atoms. By doing so, since a relatively light hydrocarbon compound is processed in the steam reforming reactor, the energy required for gasification is reduced and the coking problem in the steam reforming reactor is also avoided. The In addition, if the fuel gas supplied to the steam reforming reactor in the solid oxide fuel cell housing is a light hydrocarbon gas having about 3 or less carbon atoms, the integrated solid oxidation incorporating the steam reforming reactor It is also possible to share the material fuel cell housing with those using city gas or LPG as the raw fuel, thereby reducing the manufacturing cost.

  Furthermore, when it is necessary to desulfurize the liquid raw fuel at a high temperature, in order to avoid this, it takes a long time until the desulfurizer becomes hot and sufficiently desulfurized kerosene flows out to the outlet of the desulfurizer. In order to use desulfurized kerosene that has been highly desulfurized at the time of starting the fuel cell cogeneration system, inconvenience and countermeasures such as providing an intermediate tank and storing desulfurized kerosene are required. However, since the liquid raw fuel of the present invention can perform desulfurization at a low temperature, a sufficiently desulfurized kerosene can be obtained immediately after the fuel cell cogeneration system is activated, and it can be started without providing an intermediate tank for storing the desulfurized kerosene. It is possible to shorten the time.

Examples of the fuel cell used in the present invention include a phosphoric acid fuel cell (PAFC), a molten carbonate fuel cell (MCFC), a solid oxide fuel cell (SOFC, also known as a solid electrolyte fuel cell), and a solid polymer fuel. Among them, a solid oxide fuel cell is preferable because it has higher power generation efficiency than a solid polymer fuel cell.
In order to further improve the efficiency of the fuel cell cogeneration system, it is important to make the temperature distribution in the housing uniform so as not to generate abnormally high temperatures, and to avoid excessively high temperatures. In order to achieve efficiency, it is important to effectively use the exhaust heat of the fuel cell. For example, it is effective to use the heat generated in the fuel cell as a heat source for the steam reforming reaction which is an endothermic reaction. Accordingly, in order to maximize the exhaust heat of the fuel cell, the steam reformer is disposed inside the solid oxide fuel cell housing and can be heated by utilizing the exhaust heat of the fuel cell to the maximum. preferable.
Further, it is preferable to heat the desulfurizer with warm water in the hot water storage tank when the fuel cell cogeneration system is activated. As a power source for a heater that heats the desulfurizer and / or the autothermal reformer for a short time when the fuel cell cogeneration system is started up, it is also preferable to use a capacitor or a secondary battery provided in the system.

  Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto.

(Preparation of test oil)
Five types of kerosene (Examples 1 and 2 and Comparative Examples 1 to 3) were prepared as test oils as follows. Table 1 shows the physical properties such as the content of sulfur compounds and the boiling range contained therein.
Test oil of Example 1 1 part by weight of a fraction having a distillation temperature of 215 to 260 ° C. obtained by distilling the commercial kerosene B used as the test oil of Comparative Example 3, and the commercial kerosene B with a sulfur content of 0. It was prepared by mixing 1 part by weight of kerosene hydrodesulfurized to 05 mass ppm or less.
Sample oil of Example 2 500 g of the sample oil of Example 1 was mixed with 20 mg of the reagent benzothiophene and 20 mg of 2,8-dimethyldibenzothiophene.
A commercial kerosene (commercial kerosene A) having a test oil density (15 ° C.) of Comparative Example 1 of 0.7928 g / cm ³ and an aromatic content of 17.9 vol% was used.
Test oil of Comparative Example 2 13 parts by weight of kerosene obtained by hydrodesulfurizing commercial kerosene B to a sulfur content of 0.05 mass ppm or less and a distillation temperature 260 obtained by distilling commercial kerosene B used in Example 1 It was prepared by mixing 1 part by weight of a high-boiling fraction having a temperature not lower than ° C.
A commercial kerosene (commercial kerosene B) having a test oil density of Comparative Example 3 (15 ° C.) of 0.7982 g / cm ³ and an aromatic content of 17.5 vol% was used.

(Desulfurization test)
The above five types of test oils were subjected to a desulfurization test using a solid acid desulfurization agent. As the solid acid desulfurizing agent, sulfate zirconia-alumina (specific surface area 162 m ² / g, pore volume 0.305 ml / g, median pore diameter 56.4 mm, zirconia 59 mass%, alumina 31 mass%, sulfur 2.9 Mass%) was used. Sulfate zirconia-alumina was packed in a column having a length of 300 mm and an internal volume of 27 ml. At the column inlet temperature of 70 ° C., five kinds of test oils were passed through the column at 1 ml / min. The sulfur content of each sample oil that was desulfurized with zirconia sulfate / alumina and flowed out was measured. The result is shown in FIG. 1 by the correlation between the sulfur content (vertical axis) of the spilled kerosene and the supply amount (horizontal axis) of the sulfur content.

(Analysis method)
The sulfur content was analyzed using a fuel oxidation-ultraviolet fluorescence sulfur analyzer, and the type of sulfur compound was analyzed using a gas chromatograph-inductively coupled plasma mass spectrometer (GC-ICP-MS). . All sulfur contents are shown as sulfur content (mass ppm-S) including the content of alkyl dibenzothiophenes, sulfur compounds having a molecular weight of less than 213 and a molecular weight of 213 or more. In addition, alkyl dibenzothiophenes are sulfur compounds that contain 4-methyldibenzothiophene (molecular weight 198) and flow out thereafter in the gas chromatography as alkyl dibenzothiophenes, and 2,8-dimethyldibenzothiophene (molecular weight 212). The sulfur compound that flowed out later was a sulfur compound having a molecular weight of 213 or more. That is, a sulfur compound having a molecular weight of 213 or more is a part of alkyl dibenzothiophenes.

(Test results)
FIG. 1 shows the relationship between the supply amount (mg) of sulfur content to the column packed with sulfate radical zirconia / alumina and the sulfur content (mass ppm) of the column outflow kerosene. In the sample oils of Comparative Examples 1 to 3 in which a sulfur compound having a molecular weight of 213 or more is contained in an amount of 0.4 mass ppm or more, the sulfur content of the spilled kerosene is 0.1 mass ppm or more from the initial outflow, but the molecular weight is 213 or more. In the test oils of Examples 1 and 2 in which the sulfur compound was 0.1 mass ppm or less, the sulfur content could be desulfurized to 0.05 mass ppm or less up to about 0.6 mg, and the fuel of the present invention It can be seen that the liquid raw fuel for batteries (the test oils of Examples 1 and 2) clearly shows a remarkable effect as compared with the test oils of Comparative Examples 1 to 3.
There is no correlation between the content of alkyldibenzothiophenes and the sulfur content of the column spilled kerosene.

Sulfur content supply amount (mg) and spilled kerosene fraction when 5 types of kerosene fractions of Examples and Comparative Examples were passed through a column of solid acid desulfurization agent (sulfuric acid zirconia / alumina) and desulfurized. It is a graph which shows the relationship with a sulfur content (mass ppm). It is a flow sheet which simplifies and shows an example of the fuel cell cogeneration system of the present invention suitable for using the liquid raw fuel for fuel cells of the present invention.

Explanation of symbols

1 Desulfurization means (desulfurizer)
2 autothermal reformer 3 solid oxide fuel cell housing 4 steam reformer 5 fuel cell 6 the hot water tank 7 rechargeable battery or capacitor over

Claims (16)

Distillation end point in the texture is higher than 220 ° C., the desulfurization unit content desulphurizing 0.3 mass ppm or less der Ru fuel cell cogeneration liquid fuel for the system as a sulfur content of molecular weight 213 or more sulfur compounds, desulfurization treatment Self-heat reformer for generating hydrogen and hydrocarbon gas-containing gas from liquid raw fuel, water and oxygen, and hydrogen, carbon monoxide and carbon dioxide from gas and water containing hydrogen and hydrocarbon gas Reforming means including a steam reformer that generates a fuel gas containing as a main component, a fuel cell that generates electricity by reacting the fuel gas and oxygen, and a desulfurizer and / or self-heating reformer with a capacitor or secondary battery. fuel cell cogeneration system which comprises means for supplying electricity to the heater for starting quality unit. Fuel cell cogeneration system according to claim 1 molecular weight 213 or more sulfur compound is an organic sulfur compound of the above 15 carbon atoms. Sulfur liquid fuel in the fuel cell cogeneration system according to claim 1 or 2 is 0.1 to 30 mass ppm. Fuel cell cogeneration system according to any one of claims 1 to 3 liquid fuel is mainly composed of a kerosene fraction. Fuel cell cogeneration system according to any one of claims 1 to 3 liquid fuel is mainly composed of a gas oil fraction. The fuel cell cogeneration system according to any one of claims 1 to 5, wherein the desulfurization means is adsorptive desulfurization using at least one desulfurization agent selected from a solid acid desulfurization agent, an activated carbon desulfurization agent, and a metal desulfurization agent. The solid acid desulfurization agent is at least one solid superacid selected from the group consisting of sulfate zirconia, sulfate radical alumina, sulfate radical tin oxide, sulfate radical iron oxide, tungstate zirconia, and tungstate oxide. Item 7. The fuel cell cogeneration system according to Item 6. Activated carbon desulfurization agent has a specific surface area of 500m ² / G or more, micropore specific surface area Smicro [m ² / G], micropore external pore volume Vext [cm ^Three / G] and micropore external specific surface area Sext [m ² / G] is the following formula (1):
Smicro × 2 × Vext / Sext> 0.7 (1)
The fuel cell cogeneration system according to claim 6, wherein the carbon material satisfies the following requirements. The fuel cell cogeneration system according to claim 6, wherein the metal desulfurizing agent is a copper desulfurizing agent and / or a nickel desulfurizing agent. The fuel cell cogeneration system according to claim 6, wherein adsorptive desulfurization with a solid acid desulfurizing agent and / or an activated carbon desulfurizing agent is performed at -30 to 150 ° C. The fuel cell cogeneration system according to claim 6, wherein in the desulfurization means, after the desulfurization with the solid acid desulfurization agent and / or the activated carbon desulfurization agent, the remaining trace sulfur compound is further removed with the metal desulfurization agent. The fuel cell cogeneration system according to claim 6, wherein the trace sulfur compound is removed by the metal desulfurizing agent at a temperature of 100 to 300 ° C. The fuel cell cogeneration system according to any one of claims 1 to 12, wherein the sulfur content of the liquid raw fuel desulfurized by the desulfurization means is 50 mass ppb or less. The fuel cell cogeneration system according to any one of claims 1 to 13, wherein the fuel cell is a solid oxide fuel cell. The fuel cell cogeneration system according to claim 14, wherein the steam reformer is heated by exhaust heat of the solid oxide fuel cell. The fuel cell cogeneration system according to any one of claims 1 to 15, wherein the desulfurization means is heated by hot water in a hot water storage tank of the fuel cell cogeneration system when the fuel cell cogeneration system is activated.