Hydrocarbon fuel reformer to hydrogen with flameless combustion device

Abstract

FIELD: energy.SUBSTANCE: invention relates to autonomous power generating units with fuel cells using hydrogen as fuel. A reformer is proposed that includes a heat-insulated container with a catalyst for steam conversion of hydrocarbons, into which flameless combustion elements are inserted, providing heating of the catalyst. At the outlet of combustion gases from these elements, a recuperative heat exchanger is installed for heating the air used for combustion, and at the outlet of the reaction products from the catalytic reactor, a unit is installed for the diffusion separation of hydrogen, which then goes to the fuel element, and carbon monoxide, which is used as fuel for the flameless combustion elements. The claimed invention makes it possible to expand the range of fuels used to heat the steam reforming catalyst, including the possibility of recycling carbon monoxide and the hydrogen-comprising mixture from the fuel cell exhaust.EFFECT: improving the operational characteristics of a hydrocarbon fuel reformer, including improving heat exchange between a heat source and a steam reforming catalyst, which leads to a reduction in thermal energy losses during heating of the catalyst compared to similar reformers, where free-volume combustion is used to ensure the conversion process.1 cl, 4 dwg, 1 ex

Description

[0001] The invention relates to the field of energy, and more specifically, to autonomous fuel cell power plants using hydrogen as fuel. Therefore, an autonomous power plant operating on hydrocarbon fuel and hydrogen fuel cells requires a primary fuel reformer to produce hydrogen.

[0002] Fuel cells are currently considered the most promising energy conversion systems, potentially replacing traditional, less efficient power generation technologies. Fuel cells convert the chemical energy of fuel directly into electrical energy, providing a higher degree of efficiency compared to electricity generation using traditional heat engines based on the Carnot cycle. However, unlike internal combustion engines, fuel cell power plants have a higher energy efficiency in converting chemical energy into electrical energy.

[0003] The most common solid polymer fuel cell is, in general, an electrochemical device that produces electricity through an electrochemical reaction between a fuel, such as hydrogen obtained by reforming a hydrocarbon fuel, and an oxidizer. Therefore, generating electricity using this method requires appropriate power plants that include, in addition to the fuel cell, units for reforming the feedstock fuel into an intermediate energy carrier—hydrogen.

[0004] One such reformer is described in patent RU 176514 U1, published on January 22, 2018, in Bulletin No. 3. In this patent, the natural gas conversion monoblock is a thermally insulated volume, the lower portion of which contains a burner device, the hot gases of which sequentially heat a steam generator and then a membrane-catalytic unit, where the catalytic modules are installed alternately with the hydrogen diffusion separation modules.

[0005] The disadvantages of this design include the significant spatial separation between the heat generation zone in the burner and the heat consumption zone for the steam reforming reaction, which hinders heat transfer and reduces the efficiency of the entire unit. Furthermore, this separation of zones increases the overall dimensions of the structure, including the hot zone, leading to unnecessary heat loss.

[0006] Also known from the prior art is a hydrocarbon reformer design disclosed in document US 9102535 B1, published August 11, 2015, in which catalyst heating is provided by a single flameless combustion element inserted into a cylindrical volume filled with a steam reforming catalyst. The flameless combustion element is a structure consisting of several metal cylinders, nested within each other, for supplying fuel and air and removing combustion products.

[0007] The disadvantages of the above-mentioned design include uneven heating of the catalyst due to the use of only one flameless combustion element, which in turn complicates the heat transfer process. Furthermore, the presence of multiple metal cylinder shells and their bolted connections in the hot catalyst heating zone also complicates the heat transfer process and makes the design insufficiently heat-resistant. The upper temperature limitation of the design, in turn, limits the performance of the catalytic process.

[0008] Therefore, the task facing the authors of the present invention was the need to develop an efficient and compact reformer of hydrocarbon fuel into hydrogen for decentralized generation of electric power in autonomous power plants based on known batteries of solid polymer fuel cells with the possibility of obtaining high specific energy output.

[0009] The purpose of the present invention was to create a relatively simple in design, technologically advanced and efficient, i.e., having a high specific productivity, reformer of hydrocarbon fuel, such as methane, propane, liquid motor fuel or dimethyl ether for conversion into hydrogen for use in a fuel cell battery as part of mobile autonomous power generating units.

[0010] The technical result of the claimed invention is to improve the performance characteristics of a hydrocarbon fuel reformer, including improved heat exchange between the heat source and the steam reforming catalyst, resulting in reduced thermal energy losses during catalyst heating compared to similar reformers that utilize free-flow combustion to ensure the reforming process, as described in the patents described above. The claimed invention also expands the range of fuels used to heat the steam reforming catalyst, including the possibility of recycling carbon monoxide and the hydrogen-containing mixture from the fuel cell exhaust.

[0011] The said problem is solved and the technical result is achieved thanks to the proposed design of a hydrocarbon fuel reformer, including a catalytic reactor for the steam conversion of hydrocarbons, made integral with a recuperative heat exchanger, wherein the reactor consists of a housing, inside which a heat-insulated cylindrical sleeve is placed, filled with a catalyst for the steam conversion of hydrocarbons, into the layer of which flameless combustion elements are inserted, each of which is made in the form of a tube-housing, filled with a flameless combustion catalyst in the zone of the catalyst layer for the steam conversion of hydrocarbons and including an air distributor, a fuel gas distributor and an ignition element, wherein the tube-housings pass through the entire layer of the catalyst for the steam conversion and exit with their ends free from the flameless combustion catalyst into the recuperative heat exchanger, where the products of the reaction of the steam conversion and the combustion products,formed in the flameless combustion element are separated by these tube-housings.

[0012] This solution ensures the simplicity and high temperature resistance of the reformer design.

[0013] The terms and definitions used here and below generally correspond to the wording given in GOST R 56188.1-2023 (IEC 60050-485:2020). National standard of the Russian Federation. Fuel cell technologies. Part 1. Terminology.

[0014] A hydrocarbon, typically paraffin-based (methane, propane, butane, kerosene), is introduced along with water vapor into a steam reforming catalyst bed, which fills a certain reaction volume and is heated to a temperature of 800-1100°C. The heating temperature will depend on the activity, volume of the catalyst, and reagent consumption.

[0015] In the steam reforming catalyst bed, an endothermic steam reforming reaction will occur, shown using methane as an example (reaction I), with the absorption of heat:

[0016]

[0017] The heat required for the catalytic steam reforming process is supplied by multiple flameless combustion elements arranged uniformly in a hexagonal, axisymmetric pattern within the steam reforming catalyst bed, thereby ensuring uniform heating of the entire steam reforming catalyst bed. The presence of multiple flameless combustion elements ensures optimal, uniform heating of the reaction zone of the steam reforming process.

[0018] Initially, heat for the steam reforming process is generated in the flameless combustion catalyst bed during fuel combustion. Subsequently, the heat generated during combustion enters the steam reforming catalyst bed through heat exchange through the sealed walls of the flameless combustion elements.

[0019] The resulting mixture of hydrogen and carbon monoxide from the steam reforming process must be converted into a hydrogen-containing gas suitable for further use in a fuel cell. To this end, the hydrogen and carbon monoxide mixture obtained from reaction I is sent to a hydrogen-carbon monoxide diffusion separator or to a separate carbon monoxide steam reforming reactor (the "shift reactor"), where the catalytic oxidation of carbon monoxide occurs, producing additional hydrogen (reaction II).

[0020]

[0021] This exothermic process with the release of heat occurs at a lower temperature than the process of steam reforming of hydrocarbons, since at a lower temperature the thermodynamic equilibrium is shifted towards the formation of CO2.

[0022] To cool the reaction gases exiting the steam reforming reactor, it is necessary to install a recuperative heat exchanger, such as a tube-in-tube heat exchanger, in which both the reaction products and the combustion gases coming from the flameless combustion elements are cooled, while simultaneously heating the air supplied to the inlet of the flameless combustion elements.

[0023] A novel feature of the proposed catalytic hydrocarbon fuel reformer design is the structural integration of the recuperative heat exchanger with the steam reforming reactor. This integration can be achieved by using tubes, which also serve as the housings for the flameless combustion elements, passing through the entire steam reforming catalyst bed, protruding from the reaction volume, and running inside the jackets of a tube-in-tube heat exchanger. This proposed solution eliminates the need for complex connecting elements in hot zones and enhances the thermal stability of the design.

[0024] The connection of the proposed reformer to other units of the system for preparing a hydrogen-containing mixture for use in a power plant as fuel for a fuel cell has two options depending on the type of fuel cell used.

[0025] In the first embodiment of installing a reformer in a power plant with a low-temperature solid polymer fuel cell based on sulfided fluoroplastic (MF4-SK membrane), which prevents even small amounts of carbon monoxide from being present in hydrogen, a special unit—a diffusion separator—is required for the thorough purification of hydrogen from impurities, including carbon monoxide. In this case, hydrogen is separated from a mixture of hydrogen and carbon monoxide heated to 450-500°C in diffusion elements with a palladium membrane, which feeds the fuel cell, while the carbon monoxide is returned to the flameless combustion elements as fuel.

[0026] Carbon monoxide enters the flameless combustion elements from the separator block and burns, releasing 281 kJ of heat per mole of CO. This heat is transferred through the flameless combustion element housing walls to the hydrocarbon steam reforming catalyst bed. Thus, the flameless combustion elements, thanks to the recovery of the released CO, are almost completely supplied with fuel. This design eliminates the need for a carbon monoxide post-oxidation unit.

[0027] However, for the hydrogen separation diffusion membrane unit to operate, elevated pressure of the hydrogen-containing mixture in the hydrocarbon fuel catalytic reformer is required. In this version of the power plant with a low-temperature solid polymer fuel cell, the pressure in the catalyst chamber should be 7-10 atm.

[0028] In the second version of the power plant, using a high-temperature solid polymer fuel cell based on polybenzimidazole (PBI) impregnated with phosphoric acid, a carbon monoxide content of up to 4% in the hydrogen-containing fuel gas entering the fuel cell is permissible. Therefore, a fine diffusion gas purification unit may be unnecessary.

[0029] The difference from the previous version of the power plant is the use of carbon monoxide not as fuel for the steam reforming process, but as a source for producing additional hydrogen. For this purpose, an additional unit for the oxidation of CO to CO2 (a "shift reactor") must be installed. The output of this unit can be a hydrogen mixture containing approximately 20% vol. CO2. This hydrogen-containing mixture can be used as fuel in a fuel cell.

[0030] It is necessary to periodically purge the fuel cell of accumulated CO2 by opening the outlet of the fuel cell's hydrogen circuit to vent the accumulated gas mixture, enriched with CO2 to 60-80% vol. The H2 and CO2 gas mixture exiting the fuel cells can be additionally used as fuel in flameless combustion elements. If necessary, the original hydrocarbon can be added to this mixture.

[0031] The second version of the power plant does not require high gas pressure, since there is no hydrogen diffusion purification unit, the pressure in the reformer can be 0-1 atm.

[0032] Brief description of drawings.

[0033] Fig. 1 - internal section of the design of the claimed catalytic reactor for steam reforming of hydrocarbons with internal flameless combustion elements and a recuperative heat exchanger.

[0034] Fig. 2 - section A-A of the catalytic reactor for steam reforming of hydrocarbons, indicated in Fig. 1.

[0035] Fig. 3 - structural diagram of the connection of hydrocarbon fuel reformer blocks for the option of operating as part of a power plant with a low-temperature polymer fuel cell requiring hydrogen that is maximally purified from carbon monoxide.

[0036] Fig. 4 - structural diagram of the connection of hydrocarbon fuel reformer blocks for the option of operating as part of a power plant with a high-temperature solid polymer fuel cell, allowing the presence of a limited amount of carbon monoxide (up to 4% vol.) in the fuel, hydrogen-containing gas.

[0037] The provided drawings are intended to further explain the invention and illustrate preferred embodiments of the present invention.

[0038] In Fig. 1-4, positions indicate:

[0039] 1 - steam reforming reactor vessel;

[0040] 2 - internal high-temperature thermal insulation;

[0041] 3 - sleeve;

[0042] 4 - catalyst for steam reforming of hydrocarbons;

[0043] 5 - flameless combustion element;

[0044] 6 - tube-body;

[0045] 7 - flameless combustion catalyst;

[0046] 8 - air distributor of flameless combustion element;

[0047] 9 - Flameless combustion element fuel distributor;

[0048] 10 - recuperative heat exchanger;

[0049] 11 - outer jacket of heat exchanger;

[0050] 12 - flow swirler;

[0051] 13 - outlet pipe for hydrocarbon steam conversion products;

[0052] 14 - air inlet pipe to the flameless combustion element;

[0053] 15 - fuel inlet pipe to the flameless combustion element;

[0054] 16 - reagent supply pipe;

[0055] 17 - air inlet pipe;

[0056] 18 - outlet pipe for heated air from the recuperative

[0057] heat exchanger;

[0058] 19 - combustion products outlet pipe;

[0059] 20 - catalytic reactor for steam reforming of hydrocarbons;

[0060] 21 - combustion products discharge line;

[0061] 22 - water evaporator;

[0062] 23 - hydrogen and carbon monoxide diffusion separator unit;

[0063] 24 - low-temperature solid polymer fuel cell;

[0064] 25 - Carbon monoxide return line;

[0065] 26 - throttle;

[0066] 27 - valve;

[0067] 28 - compressor;

[0068] 29 - heated air supply line;

[0069] 30 - water vapor supply line;

[0070] 31- carbon monoxide steam reforming reactor;

[0071] 32 - High temperature solid polymer fuel cell;

[0072] 33 - residual hydrogen gas return line;

[0073] 34 - Residual hydrogen gas return line throttle.

[0074] Fig. 1 schematically shows a sectional view of the design of the claimed hydrocarbon fuel reformer with internal flameless combustion elements and a recuperative heat exchanger.

[0075] The hydrocarbon fuel reformer, implemented in a single structural unit with a recuperative heat exchanger, consists of a steam reforming reactor vessel (1), which is a sealed metal cylinder with internal high-temperature thermal insulation (2) made of fibrous thermal insulation material such as fibrous alumina or mullite-siliceous fibrous material. Inside the cylindrical vessel of the steam reforming reactor (1), a thermally insulated cylindrical metal sleeve (3) of smaller diameter is placed, filled with bulk catalyst for the steam reforming of hydrocarbons (4) and separating the internal high-temperature thermal insulation (2) from the catalyst volume.

[0076] The bulk steam reforming catalyst (4) is nanosized active particles of Pt, Ni, Mn, Cu or their mixtures, or oxides of Ni, Mn, Cu or their mixtures, supported on porous spherical granules of a ceramic carrier, which is corundum porous spherical granules with a diameter of 1-5 mm.

[0077] Several identical flameless combustion elements (5) are inserted into the hydrocarbon steam reforming catalyst layer (4), each of which is a heat-resistant ceramic or metal tube-housing (6) of the flameless combustion element (5), partially filled with a flameless combustion catalyst (7) to ensure the flameless combustion reaction of the fuel. The heat released during the flameless combustion reaction is transferred through the walls of the tube-housings (6) to the layer of bulk steam reforming catalyst (4), thereby ensuring the endothermic steam reforming reaction.

[0078] The bulk flameless combustion catalyst (7) is a porous spherical ceramic carrier granule with a diameter of 1-5 mm, which can be coated with Pt or Ni particles.

[0079] Each flameless combustion element (5) includes an air distributor (8) and a fuel gas distributor (9), which are inserted into the flameless combustion catalyst layer (7), and an ignition element, which is not shown in Fig. 1.

[0080] The ignition element may be a glow (incandescent) element, which includes a spiral made of heat-resistant material, heated by an electric current, wound on a ceramic rod and in contact with the first layers of the flameless combustion catalyst (7) on the air and fuel supply side.

[0081] To ensure the most uniform heat transfer throughout the heated volume of the steam reforming catalyst (4), several flameless combustion elements (5) are arranged uniformly in a hexagonal, axially symmetrical pattern. This arrangement is possible with 3, 7, or 14 elements.

[0082] Each flameless combustion element (5) has a standard set of inlet and outlet pipes.

[0083] The integrated design of the hydrocarbon fuel reformer includes a recuperative heat exchanger (10) for cooling the reaction gases exiting the steam reforming catalyst bed (4). This heat exchanger is a "tube-in-tube" type, cooling both the reaction products and the combustion gases emitted by the flameless combustion elements, while simultaneously heating the air supplied to the inlet of the flameless combustion elements (5).

[0084] The outlet of gases - combustion products from the flameless combustion catalyst layer (7) occurs through the free internal part of the continuation of the tube-housings (6), which pass through the recuperative heat exchanger (10), which has external jackets (11), inside which there are tube-housings (6) of flameless combustion elements (5) protruding from the steam conversion catalyst layer (4).

[0085] Thus, the steam reforming reactor body (1) is combined with the recuperative heat exchanger (10), and the body tubes (6) pass through both the steam reforming catalyst bed (4) and the outer jackets (11) of the recuperative heat exchanger (10), connecting the reactor and the heat exchanger into a simple and heat-resistant structure.

[0086] Inside each of these tube-housings (6) running in the recuperative heat exchanger (10), a flow swirler (12) is inserted to enhance the convective and radiative heat transfer from the cooled gases to the walls of the heat exchanger.

[0087] The products of the reaction of steam reforming of hydrocarbons are released through the recuperative heat exchanger (10) through the gap between the tube-housings (6) and the internal tubes of the jackets of the recuperative heat exchanger (10), and then through the outlet pipes of the products of steam reforming of hydrocarbons (13).

[0088] High-temperature sealing gaskets are installed on the flange connections of the ends of the tube-housings (6) to separate the media of the gas flows of flameless combustion products and the flows of products of steam conversion of hydrocarbons from the catalyst layer of steam conversion of hydrocarbons (4).

[0089] Air is supplied to the flameless combustion elements (5) through the air inlet pipes of the flameless combustion element (14), and gaseous fuel is supplied to the flameless combustion elements through the fuel inlet pipes of the flameless combustion elements (15), which are directly connected inside the flameless combustion elements (5) to the fuel distributor (9).

[0090] Water vapor and the initial hydrocarbon fuel are supplied to the steam reforming catalyst bed (4) through the reagent supply pipes (16).

[0091] The air inlet into the recuperative heat exchanger (10) is carried out through the air inlet pipe (17) into the outer jackets of the recuperative heat exchanger, and the air heated in the recuperative heat exchanger (10) is released through the heated air outlet pipe from the recuperative heat exchanger (18). This pipe supplies heated air to the air inlet pipes of the flameless combustion element (14).

[0092] The outlet of combustion product gases (flue gases) from the flameless combustion elements (5) is carried out through the combustion product outlet pipes (19) to the combustion product discharge line (21).

[0093] Figure 2 shows a cross-section A-A of a catalytic reactor for steam reforming of hydrocarbons with internal flameless combustion devices, which shows the arrangement of flameless combustion elements (5) in the tube housings (6), located in an axisymmetric, hexagonal geometry relative to each other. In the preferred embodiment, the number of flameless combustion elements (5) is 7, which ensures uniform external heating of the steam reforming catalyst (3).

[0094] The proposed design of a catalytic steam reforming reactor can be applied to work with various types of fuel cells, which determine fundamentally different compositions of hydrogen-containing gas required for use in fuel cells as fuel.

[0095] Fig. 3 schematically shows the structural diagram of the connection of hydrocarbon fuel reformer blocks for the option of operating as part of a power plant with a low-temperature polymer fuel cell (24), which requires hydrogen that is maximally purified from carbon monoxide.

[0096] The catalytic reactor for steam reforming of hydrocarbons (20) is made in a single structural unit with a recuperative heat exchanger (10). The outlet of the reaction gas mixture from the unit of this design is connected to the inlet of the water evaporator (22), after which the cooled reaction gases (hydrogen-containing mixture) go to the hydrogen and carbon monoxide diffusion separator unit (23), which has separate outlets: one for the target, high-purity hydrogen for further use in the fuel cell (24), the other for the residual gas mixture: carbon monoxide with an admixture of a small amount of CO2 and residual hydrogen, which is returned as fuel through the carbon monoxide return line (25) to the flameless combustion element. A throttle (26) is installed on this line to relieve pressure from the reaction circuit to a lower fuel gas pressure level in the flameless combustion element (5).

[0097] If necessary, some amount of the original hydrocarbon can be added to the carbon monoxide return line (25) as additional fuel through the valve (27).

[0098] Air from the compressor (28) is supplied to the inlet of the recuperative heat exchanger (10) through the air inlet pipe (17) into the outer jacket of the recuperative heat exchanger (11). Heated to 200-300°C in the recuperative heat exchanger (10), the air is supplied as an oxidizer to the flameless combustion elements (5) through the heated air supply line (29).

[0099] Water vapor from the water evaporator (22) enters through the steam supply line (30) to the inlet of the reagent supply pipe (16) in the catalytic steam reforming reactor (20).

[0100] Fig. 4 schematically shows the structural diagram of the connection of hydrocarbon fuel reformer blocks for the variant of operation as part of a power plant with a high-temperature solid polymer fuel element (32), allowing the presence of a limited amount of carbon monoxide (up to 4% vol.) in the fuel, hydrogen-containing gas.

[0101] In this embodiment of the reformer block connection, the hydrogen and carbon monoxide diffusion separator block can be replaced by a carbon monoxide steam reforming reactor (31) to produce additional hydrogen.

[0102] In this case, when feeding a hydrogen mixture with a noticeable (about 20% when converting natural gas) CO2 content to the fuel cell, it is necessary to periodically purge the fuel cell and feed residual gas containing unused hydrogen from the fuel cell outlet (32) to the input of the flameless combustion elements (5) as additional fuel through the residual hydrogen gas return line (33) through the throttle of the residual hydrogen gas return line (34).

[0103] The invention is implemented as follows.

[0104] A mixture of the feedstock hydrocarbon and steam enters the reaction volume of the catalytic hydrocarbon steam reforming reactor (20) through the reactant feed pipe (16). The reactor is filled with a hydrocarbon steam reforming catalyst (4), in which an endothermic steam reforming reaction occurs with the consumption of thermal energy supplied to the hydrocarbon steam reforming catalyst (4) from flameless combustion elements (5), uniformly inserted into the volume of the hydrocarbon steam reforming catalyst (4).

[0105] The flameless combustion elements (5), separately from the hydrocarbon flow to the reformer, receive fuel gas coming from the hydrogen and carbon monoxide diffusion separator unit (23) via the carbon monoxide return line (25) through the throttle (26), when using the connection diagram of the hydrocarbon fuel reformer units for the option of operating as part of a power plant with a low-temperature polymer fuel cell (24), shown in Fig. 3. The fuel gas for the flameless combustion elements (5) in this case consists of a mixture of carbon monoxide and residual hydrogen. If necessary, a small amount of the original hydrocarbon can be mixed with the fuel gas through the valve (27).

[0106] When using the connection diagram of the hydrocarbon fuel reformer units for the variant of operation in the power plant with a high-temperature solid polymer fuel cell (32), shown in Fig. 4, the residual hydrogen mixture, coming from the outlet of the high-temperature fuel cell (32) along the residual hydrogen gas return line (33) through the throttle of the residual hydrogen gas return line (34), serves as the fuel. The residual hydrogen mixture is a mixture of hydrogen not completely used in the fuel cell and CO2.

[0107] Air heated to 150-200°C and coming from the recuperative heat exchanger (10) is supplied to the inlet of the flameless combustion elements (5) through the air inlet pipes into the flameless combustion elements (14). Fuel gas is also supplied to the inlet of the flameless combustion elements (5) through the fuel inlet pipes into the flameless combustion element (15).

[0108] After the fuel gas and air enter the flameless combustion elements (5), combustion of the fuel gas occurs inside the tube-housings (6) of the flameless combustion element on the flameless combustion catalyst (7) with the release of heat, which is transferred through the walls of the tube-housings (6) to the hydrocarbon steam reforming catalyst (4), thereby ensuring the reaction of hydrocarbon steam reforming.

[0109] To ensure uniform combustion of the fuel gas, a flameless combustion element air distributor (8) and a flameless combustion element fuel distributor (9), shown in Figs. 1 and 2, are inserted inside each layer of the flameless combustion catalyst (7).

[0110] The combustion products from the flameless combustion catalyst layer (7) pass through the inner part of the extension of the tube-housings (6) into the recuperative heat exchanger (10), and the products of the reaction of steam conversion of hydrocarbons are released through the recuperative heat exchanger (10) along the outer side of the tube-housings (6) and the inner side of the jackets of the recuperative heat exchanger (10).

[0111] To enhance convective and radiative heat transfer from the cooled gases to the walls of the recuperative heat exchanger (10), a flow swirl device (12) is inserted inside each tube-housing (6) running inside the heat exchanger. The tube-housings (6) are common elements of both the flameless combustion elements (5) and the recuperative heat exchanger (10).

[0112] In the recuperative heat exchanger (10), the steam reforming products are cooled to a temperature of 700-800°C, which then enter the water evaporator (22), where they are further cooled to a temperature of 500°C, which is optimal for the operation of the hydrogen and carbon monoxide diffusion separator unit (23), when using the reformer block connection diagram (Fig. 3) to provide the low-temperature fuel cell with hydrogen.

[0113] In case of using the reformer block connection diagram shown in Fig. 4, the gas mixture should be cooled to a temperature of 300-450°C, which is optimal for the operation of the carbon monoxide steam reforming reactor (31).

[0114] When using the reformer block connection diagram shown in Fig. 3, the pressure of the hydrocarbon steam reforming product gases obtained on the hydrocarbon steam reforming catalyst (4) should be from 7 to 10 atm to ensure efficient operation of the hydrogen and carbon monoxide diffusion separator (23).

[0115] To relieve the pressure from the reaction circuit to a lower fuel gas pressure level in the flameless combustion element (5), a throttle valve (26) is installed on the carbon monoxide return line (25). The pressure of high-purity hydrogen supplied from the hydrogen and carbon monoxide diffusion separator (23) to the fuel cell inlet is close to atmospheric pressure.

[0116] When using a high-temperature solid polymer fuel cell (32) in the circuit diagram of the reformer blocks shown in Fig. 4, the hydrogen-containing gas from the outlet of the recuperative heat exchanger (10) through the water evaporator (22) enters the inlet of the carbon monoxide steam reforming reactor (31), where the steam reforming of carbon monoxide CO into CO2 occurs according to reaction 2.

[0117] The resulting hydrogen-containing gas (a mixture of CO2 and H2 with residual amounts of carbon monoxide CO) is fed as fuel to the input of a high-temperature solid polymer fuel cell (32). This type of fuel cell tolerates the presence of up to 4% vol. CO in the hydrogen-containing gas without significant loss of performance.

[0118] Example.

[0119] The insulated vessel of the catalytic steam reforming reactor is filled with a catalyst consisting of NiO particles (10% by weight) supported by porous spherical Al2O3 granules with a granule size of 2 mm. The volume of the catalytic bed, including flameless combustion elements, is 30.77 liters.

[0120] The reactor uses internal thermal insulation made of mullite-siliceous fiber material in a stainless steel casing. The thermal insulation thickness is 100 mm.

[0121] Seven flameless combustion elements with ceramic tube housings with an outer diameter of 45 mm were installed in the steam reforming catalyst bed. These tube housings were filled with a flameless combustion catalyst consisting of nanosized Pt particles deposited on a carrier—porous Al2O3 granules with a granule size of 2-3 mm. The amount of deposited Pt was approximately 0.5% by weight.

[0122] Methane was used as the initial fuel to be converted, with a flow rate of 1 to 5 l / s. The temperature of the steam reforming catalyst's catalytic bed was 800-850°C.

[0123] At the outlet of the recuperative heat exchanger, the composition of the gas samples after condensation of residual water vapor: H2 - 74% vol., CO - 23% vol., CO2 - 2.5% vol., N2 - 0.5% vol.

[0124] The volumetric output of hydrogen-containing gas mixture is from 4 to 20 l / s, which can provide hydrogen to a hydrogen fuel cell with a power range of 10 - 200 kW.

[0125] Summarizing the above, it can be concluded that the reformer design proposed in the claimed invention has a greater uniformity of heat distribution over the reaction catalytic volume of the steam reforming catalyst compared to the converter described in document US 9102535 B1, which leads to an increase in the specific productivity per unit volume of the catalytic layer by at least 1.3 times.

[0126] The increase in specific productivity, accordingly, leads to the compactness of the reactor and the reduction of heat loss in a more compact design.

Images