JP6180252B2 - Hydrogen production system by ammonia decomposition - Google Patents

Description

  The present invention relates to a hydrogen production system using ammonia as a hydrogen source. More specifically, a reforming reaction that decomposes ammonia to produce hydrogen and an ammonia removal device that removes a small amount of ammonia from a gas containing hydrogen produced downstream are installed upstream of one flow reactor. Relates to a hydrogen production system.

  As global warming due to carbon dioxide and the like becomes serious, hydrogen is attracting attention as an energy source for the next generation instead of fossil fuels. In recent years, fuel cell power generation systems that generate power using hydrogen have been rapidly developed as a power source for various applications such as automobiles, household power generation equipment, vending machines, and portable devices. A fuel cell generates electricity when hydrogen and oxygen are reacted to form water, and can be used for hot water supply and air conditioning using thermal energy generated at the same time. In addition to fuel cells, internal combustion engines such as microturbines and microengines are also being developed.

  Hydrogen transportation, storage, and supply systems, which are indispensable for using hydrogen as a fuel, are a major issue. Since hydrogen is a gas at room temperature, it is difficult to store and transport compared to liquids and solids. Moreover, hydrogen is a flammable substance, and when it has a predetermined mixing ratio with air, the risk of explosion is very high.

  As a technique for solving such problems, a system for extracting hydrogen from a liquid compound containing hydrogen has attracted attention as a hydrogen storage method that is excellent in safety, transportability, storage capacity, and cost reduction. For example, ammonia, methylcyclohexane, decalin, and the like can be given. Among them, ammonia has a high hydrogen content of 17.8% by mass, and is easily liquefied at about 1 MPa at room temperature, so that it is excellent in storability and transportability.

As a technique for extracting hydrogen from ammonia, for example, it is disclosed that ammonia is decomposed into N ₂ and H ₂ at 900 to 950 ° C. using a Ni-based catalyst, and a small amount of remaining ammonia and moisture are adsorbed on the zeolite at room temperature. (Patent Document 1). In order to obtain pure H _2, it is also disclosed that the separation of N ₂ by liquefaction. Alternatively, an ammonia storage container that stores liquefied ammonia, and a reformer that contains a ruthenium catalyst or a rhodium catalyst and decomposes ammonia at 600 ° C. to 900 ° C. to generate a reformed gas mainly composed of hydrogen and nitrogen. An apparatus including an ammonia remover that dissolves and removes ammonia in the reformed gas in water is disclosed (Patent Document 2). In more detail, the present invention relates to a fuel cell system using ammonia as a fuel. More specifically, an ammonia oxidation zone and an ammonia decomposition zone for producing hydrogen by decomposing ammonia on the downstream side of the zone are provided in one flow reactor. A fuel cell system equipped with an installed hydrogen production apparatus is disclosed (Patent Document 3).

Japanese Patent Laid-Open No. 54-126589 JP 2009-35458 A JP 2010-282755 A

  An object of the present invention is to provide a highly efficient hydrogen production system by ammonia decomposition that sufficiently removes unreacted ammonia and does not require supply of reaction heat energy to the ammonia decomposition reaction.

  As a result of intensive studies in order to solve the above problems, the present inventors have found the following techniques and have completed the invention. The present invention comprises an ammonia decomposing apparatus that decomposes ammonia into hydrogen and nitrogen, and an ammonia removing apparatus that adsorbs and removes ammonia discharged from the decomposing apparatus, and the ammonia removing apparatus has an ammonia adsorption heat of 50 to 180 kJ. / Mole, an ammonia adsorption capacity of 0.1 to 4 mmol / g, and an ammonia adsorbent having a pore diameter of 50 nm to 10 μm in a volume of 0.1 to 1 mL / g.

  Preferably, (1) the ammonia adsorbent is at least one selected from zeolite, acidic clay mineral, silicon oxide-containing composite oxide, vanadium oxide-containing composite oxide, metal sulfate and metal phosphate. ) The adsorption device is composed of a plurality of adsorbers arranged in parallel to the gas flow, and when one adsorber adsorbs ammonia, the other adsorber adsorbs the adsorbed ammonia, When the adsorber adsorbs ammonia, the one adsorber can repeatedly discharge ammonia.

  According to the present invention, ammonia can be decomposed at a very high space velocity with high efficiency of the reactor, the reaction heat of the reaction for decomposing ammonia can be supplied, and a small amount of ammonia contained in the reformer outlet gas can be used for the subsequent use. A hydrogen production system that can be removed without any problem can be realized.

FIG. 1 shows an embodiment according to the present invention, in which one ammonia decomposing apparatus and two ammonia adsorbents are installed.

  The present invention includes an ammonia decomposing apparatus for decomposing ammonia into hydrogen and nitrogen, and an ammonia adsorbing apparatus for adsorbing and removing ammonia discharged from the decomposing apparatus, and the ammonia removing apparatus has an ammonia adsorption heat of 50 to 180 kJ. / Mole, an ammonia adsorption capacity of 0.1 to 4 mmol / g, and an ammonia adsorbent having a pore diameter of 50 nm to 10 μm in a volume of 0.1 to 1 mL / g. This will be described in detail below.

(Ammonia decomposition system)
An ammonia decomposition apparatus is an apparatus that decomposes ammonia into hydrogen and nitrogen. Since the reaction for decomposing ammonia is a large endothermic reaction, it is necessary to supply this reaction heat. As a means for supplying reaction heat, a heater can be used. In addition, a mixed gas containing ammonia and oxygen as a reaction gas is introduced into the apparatus, and a heat necessary for burning a part of ammonia and decomposing ammonia. Can be obtained (autothermal method). Further, the mixed gas can be diluted with an inert gas. Air or oxygen can be used as the gas containing oxygen. Moreover, nitrogen, argon, and helium can be used as the inert gas. The volume of oxygen with respect to the volume of ammonia in the reaction gas is 0.05 to 0.5, preferably 0.1 to 0.3. If the volume ratio is less than 0.05, oxygen is insufficient and the necessary combustion heat cannot be obtained, which is not preferable. If the volume ratio is greater than 0.5, the reaction is runaway due to excess oxygen. In addition, since ammonia used for decomposition is excessively burned, it is not preferable from the viewpoint of fuel efficiency. Ammonia combustion reaction and ammonia decomposition reaction in the autothermal method are shown in Reaction Formula 1 and Reaction Formula 2.
Reaction Formula 1 NH ₃ + 3 / 4O ₂ → 1 / 2N ₂ + 3 / 2H ₂ O
Reaction Formula 2 NH ₃ → 1 / 2N ₂ + 3 / 2H ₂
From Reaction Formula 1 and Reaction Formula 2, this is a reaction in which nitrogen, water (steam), and hydrogen are generated as product gases by the combustion reaction and decomposition reaction of ammonia and oxygen. The space velocity is 1,000 to 100,000 h ⁻¹ , preferably 10,000 to 100,000 h ⁻¹ .

  As a method of heating the reaction gas, a method of heat exchange between the gas after ammonia decomposition and the reaction gas can be used. This is because the gas after ammonia decomposition is heated at the time of ammonia decomposition and has sufficient sensible heat to heat the reaction gas even after the decomposition reaction. On the other hand, since the gas after ammonia decomposition is sent to the ammonia adsorption device, it is preferable that the gas is cooled, and it is preferable for the gas after ammonia decomposition to be cooled by exchanging heat with the reaction gas.

(Ammonia decomposition catalyst)
The cracker can be filled with an ammonia cracking catalyst. For example, any substance can be used as long as it can normally decompose ammonia into hydrogen and nitrogen, but preferably noble metal, transition metal oxide, alkali metal oxide, alkaline earth metal oxide, rare earth It is an oxide, more preferably any element as long as it is at least one element of Group 8 to Group 10, but preferably consists of platinum, palladium, rhodium, ruthenium, iron, cobalt and nickel. And at least one selected from the group, aluminum oxide, cerium oxide, magnesium oxide, niobium oxide, titanium oxide, vanadium oxide, tantalum oxide, hafnium oxide, yttrium oxide, lanthanum oxide, neodymium oxide, more preferably aluminum oxide, oxide From the group consisting of cerium, magnesium oxide and titanium oxide It is a combination of at least one kind of barrel.

  In addition, in the case of the autothermal method, it is necessary to use a catalyst having both ammonia decomposability and oxidation ability. Specifically, a catalyst in which rhodium, platinum or the like is supported on a carrier as a noble metal, cobalt, nickel or the like is supported. A catalyst supported on the catalyst is suitable.

  As a method for preparing the ammonia decomposition catalyst. A mixing method in which oxides of each component are mixed together, a loading method in which a material having a large specific surface area is loaded with a material having a small specific surface area, a precipitate in which the precursor of each component is dissolved in an aqueous solution and then adjusted to pH and precipitated as a hydroxide. The method etc. can be used. These preparation methods can be appropriately used as an ammonia decomposition catalyst after drying and baking. When preparing materials with ammonia-degrading ability and oxidizing ability, in addition to mixing individual materials, use a coprecipitation method in which the precursors of each component are dissolved in an aqueous solution and then adjusted to pH and precipitated as a hydroxide. be able to.

(Ammonia removal device)
The ammonia decomposing apparatus decomposes ammonia into hydrogen and nitrogen, but ammonia may be discharged from the apparatus due to unreacted, etc., in order to adsorb the ammonia and prevent discharge of ammonia out of the system. What is used for this is an ammonia removal device.

(Ammonia adsorbent)
The ammonia removing device is filled with an ammonia adsorbent and adsorbs ammonia. As the ammonia adsorbent, the ammonia adsorption heat is 50 to 180 kJ / mol, the total ammonia adsorption capacity at the adsorption heat is 0.1 to 4 mmol / g, and the volume of pore diameter 50 nm to 10 μm is 0.1 to 1 mL / g. It takes a thing.

  The heat of ammonia adsorption is 50 to 180 kJ / mol, preferably 90 to 150 kJ / mol, and more preferably 100 to 140 kJ / mol. Ammonia adsorption heat is the amount of heat generated when ammonia is adsorbed on the solid surface. If the heat of ammonia adsorption is less than 50 kJ / mol, the ammonia adsorption power is too weak, and ammonia cannot be sufficiently adsorbed and removed due to the effect of competitive adsorption with coexisting water vapor. On the other hand, if it is higher than 180 kJ / mol, the adsorption is too strong and the desorption operation becomes difficult.

  The total amount of ammonia adsorbed in the ammonia adsorption heat is 0.1 to 4 mmol / g, preferably 0.5 to 3 mmol / g, and more preferably 0.6 to 2 mmol / g. When the total adsorption capacity is less than 0.1 mmol / g, a large amount of adsorbent necessary for ammonia adsorption is required and the adsorber becomes too large. Also, adsorbents larger than 4 mmol / g are often thermally unstable and are not suitable for practical use.

  The volume of the pore diameter of 50 nm to 10 μm (meso to macropores) is 0.1 to 1 mL / g, preferably 0.3 to 1 mL / g. If the volume is smaller than 0.1 mL / g, the diffusion of ammonia into the adsorbent is slowed and the adsorption characteristics are deteriorated, which is not preferable. If the volume is larger than 1 mL / g, the bulk density is too small and the volume per volume is too small. This is because the adsorption capacity becomes small and the strength of the adsorbent becomes small, which is not preferable.

  When the adsorbent is a zeolite having a micropore having a pore diameter of 1 nm or less, the crystallite diameter is preferably 10 nm to 1 μm, more preferably 10 nm to 500 nm. When the crystallite diameter is 10 nm or less, the crystallinity is poor and sufficient adsorption ability may not be obtained. This is because when the crystallite diameter is 1 μm or more, the micropore diffusion may be rate-limiting.

  The adsorbent is preferably an inorganic compound having water resistance. This is because, in the case of an inorganic compound having no water resistance, ammonia adsorption ability is lost because water vapor is generated in the ammonia decomposition apparatus. Specific components of the adsorbent include zeolite (metallosilicates such as aluminosilicate and ferricsilicate and metalloaluminophosphates such as silicoaluminophosphate), acidic clay minerals, silicon oxide-containing composite oxides, vanadium oxide It is at least one selected from the containing composite oxide, metal sulfate, and metal phosphate. A material having a strong ammonia adsorption ability is preferable, for example, a zeolite having a high ammonia adsorption performance is preferable. As zeolite, Y zeolite, mordenite, ZSM-5, β zeolite, SAPO-11, SAPO-34 and the like can be used.

  The adsorbent can be used by supporting it on a carrier or adding a binder to form a molded body. In order to produce a large amount of hydrogen, it is necessary to process a large amount of raw material gas. Therefore, the pressure loss of the catalyst and adsorbent filled in the cracking reactor may become too large if ordinary pellet-shaped molded bodies are used. is there. In that case, it is preferable to form a honeycomb-shaped carrier by supporting it on a honeycomb-shaped carrier or adding a binder.

(Ammonia adsorption method)
Although the ammonia adsorption temperature varies depending on the performance of the adsorbent used, it is preferably 50 to 350 ° C., more preferably 100 to 300 ° C. When the adsorption temperature is lower than 50 ° C., diffusion is delayed and ammonia combustion is caused. The generated water vapor may condense inside the adsorber. Further, if the adsorption temperature is higher than 350 ° C., the adsorption equilibrium becomes disadvantageous and the ammonia adsorption amount decreases.

  On the other hand, the temperature at which ammonia adsorbed on the adsorbent is desorbed varies depending on the performance of the adsorbent used, but is preferably 50 to 250 ° C. higher than the temperature at which ammonia is adsorbed, more preferably 100 to The temperature is 200 ° C. higher. If the desorption temperature is not higher than the adsorption temperature by 50 ° C. or more, the desorption equilibrium does not sufficiently reach the desorption side, and a long time is required for the desorption operation. On the other hand, if the temperature is higher than 250 ° C., it is necessary to heat the regeneration gas to a high temperature, and there is a possibility that a problem arises in the thermal stability of the adsorbent.

It is preferable to use air as the desorption gas. This is because, since the desorption gas is air, the desorbed gas can be used as a reaction gas in the ammonia decomposition reaction, and there is no need for heat exchange of excess gas, so that the thermal efficiency of the entire system is good. Moreover, since ammonia contained in the gas after desorption is treated again by the ammonia decomposition apparatus, it is possible to prevent ammonia from being released into the atmosphere. The supply amount of desorption gas space velocity is 1,000～100,000H ^-1, preferably 5,000~50,000h ^-1.

(Switching method)
Ammonia adsorption / desorption consists of a plurality of adsorbers arranged in parallel to the gas flow. When one adsorber adsorbs ammonia, it discharges the ammonia adsorbed by the other adsorber, When the adsorber adsorbs ammonia, the one adsorber preferably discharges ammonia (switching method). If the ammonia adsorber is saturated with ammonia, it can no longer be adsorbed, so it is necessary to desorb and regenerate the adsorbed ammonia. Therefore, the adsorption device is composed of a plurality of adsorbers, and it is possible to prevent ammonia from being discharged out of the system for a long time by using a system in which ammonia adsorption and ammonia desorption are alternately performed in each adsorber. It becomes.

  When performing alternately, it is preferable to measure the amount of ammonia adsorbed by the ammonia adsorbent used in advance and the amount of ammonia discharged from the ammonia decomposition apparatus, and switch until the ammonia adsorbed amount in the ammonia adsorbent reaches saturation.

  In addition, when ammonia adsorption and ammonia desorption are alternately performed, it is preferable that the desorption gas inlet during the ammonia desorption operation be in the opposite direction to the adsorption gas inlet during the ammonia adsorption operation. If the adsorption gas inlet during the ammonia adsorption operation and the desorption gas inlet during the ammonia desorption operation are in the same direction, the desorbed ammonia will be re-adsorbed to the ammonia non-adsorbed part, making it difficult to regenerate the ammonia adsorbent. Because it becomes.

  As a preferred example, a hydrogen production system is shown in FIG. The raw material ammonia (11) is heated via the heat exchanger (4) and introduced into the ammonia decomposition apparatus (1). On the other hand, after the ammonia combustion air (12) is heated through the heat exchanger (4), it is introduced into the ammonia adsorber B (3) where ammonia is adsorbed by the three-way valve, and the ammonia is desorbed and then the ammonia decomposing apparatus. Introduced in (1). A part of ammonia is combusted by the ammonia decomposing apparatus (1), and ammonia is decomposed into hydrogen and nitrogen. Hydrogen, nitrogen and unreacted ammonia are discharged from the ammonia decomposing apparatus (1), cooled by the heat exchanger (4), introduced into the ammonia adsorber A (2) through the three-way valve, and the gas after ammonia adsorption is the three-way valve. Through the ammonia removal treatment hydrogen-containing gas outlet (13). The discharged gas can be used as hydrogen by separating other gases.

  By using these processes, it is possible not only to prevent an increase in the size of the apparatus by supplying reaction heat energy necessary for ammonia decomposition reaction from the outside, but also a compact hydrogen production system that does not unnecessarily increase the number of equipment. Can be provided.

  In addition, heat exchange can be performed in countercurrent between the ammonia decomposition apparatus outlet gas, the raw material ammonia, and the regeneration air to cool the hydrogen-containing gas, and at the same time, the raw material ammonia and the regeneration air can be efficiently heated to a required temperature.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to the following examples, and may be implemented with appropriate modifications within a range that can be adapted to the gist of the invention. All of these are possible within the scope of the present invention.

(Ammonia decomposition catalyst preparation example 1)
58.2 g of cobalt nitrate hexahydrate, 10.8 g of cerium nitrate hexahydrate were dissolved in 500 g of pure water, and then 10.3 g of water-dispersed zirconia sol (manufactured by Nissan Chemical Co., Ltd., “Nanouse ( (Registered trademark) ZR-30AL ", containing 30% by mass as zirconium oxide) was added (aqueous solution A). Separately, an aqueous solution B in which 74 g of potassium hydroxide was dissolved in 1.5 L of pure water was prepared. While the aqueous solution B5 was irradiated with ultrasonic waves at 25 ° C. and vigorously stirred with a three-one motor, the aqueous solution A was added dropwise thereto to synthesize a fine precipitate. The precipitate was collected by filtration, sufficiently washed with water, and dried overnight at 120 ° C. The dried precipitate was pulverized in an agate mortar, filled in an annular furnace, and reduced at 450 ° C. for 1 hour using 10 vol% hydrogen gas (diluted with nitrogen) to obtain catalyst A1.

(Ammonia adsorbent preparation example 1)
50.0 g of Y-zeolite (high silica zeolite HSZ-331HSA manufactured by Tosoh Corporation) was formed into a disk shape at a pressure of 20 MPa with a hydraulic press, and the disk was roughly crushed and sized to about 1 μm to adsorb ammonia. Agent B1 was obtained. The heat of adsorption and adsorption capacity of the Y-zeolite used are shown in Table 1. Further, the pore volume within the pore diameter range of 50 nm to 10 μm was 0.41 mL / g, and the zeolite crystal diameter was 400 nm.

(Ammonia decomposition reaction process)
Using a 10 mmφ SUS316 reaction tube, 1 mL of ammonia decomposition catalyst A1 was charged to perform ammonia decomposition reaction in the presence of oxygen. Under normal pressure, the space velocity per hour was 40,000 h ⁻¹ , the reaction tube was heated in an electric furnace, and the ammonia decomposition rate at an electric furnace set temperature of 600 ° C. was measured. The ammonia decomposition reaction was carried out with the composition of the inlet gas supplied to the catalyst being 50 volume% ammonia and 50 volume% air. The internal temperature of the reactor was 400 ° C. at the inlet, and the maximum temperature rose to a maximum of 850 ° C. by ammonia combustion.

  The ammonia decomposition rate is determined by collecting unreacted ammonia in the catalyst outlet gas with an aqueous boric acid solution for a certain period of time, and quantitatively analyzing the ammonia concentration in the collected liquid with a cation chromatograph, and the amount of ammonia remaining in the outlet gas. Asked. In addition, as a pretreatment of the catalyst, 10% hydrogen diluted with nitrogen was reduced at 450 ° C. for 1 hour while flowing at 100 ml per minute, and then an ammonia decomposition reaction was carried out in the presence of water vapor. Most of the raw material ammonia was decomposed, hydrogen in the cracking reactor outlet gas was 38.5% by volume, water vapor was 15.0% by volume, and nitrogen was 46.2% by volume. A slight amount of remaining ammonia was 0.2% by volume in the cracking reactor outlet gas.

(Ammonia adsorption removal step 1)
Using a 10 mmφ SUS316 reaction tube, 3.0 mL of ammonia adsorbent B1 was filled. The ammonia decomposition process outlet gas was cooled to 250 ° C. and passed through the adsorber. The adsorption temperature was maintained at 250 ° C. by installing an adsorption tube in an electric furnace. The ammonia in the adsorber outlet gas was kept at 1 ppm or less for 10 minutes after the start of the adsorption removal process, and the ammonia could be removed sufficiently.

(Ammonia desorption regeneration process 1)
After the adsorption operation for 10 minutes, the temperature of the adsorber is changed to 500 ° C., and air having the same flow rate as that used in the ammonia decomposition reaction step is circulated from the opposite direction to the adsorption time of the adsorber to perform the desorption regeneration operation. Went for a minute. After the start of desorption, the adsorbed ammonia was desorbed and detected in the outlet gas. After 10 minutes, it was confirmed that ammonia was 1 ppm or less in the adsorption tube outlet gas, and it was confirmed that the adsorbent was regenerated.

(Measurement of ammonia decomposition rate and removal rate in ammonia decomposition reaction process and adsorption removal process)
Ammonia decomposition rate / removal rate is determined by collecting unreacted ammonia contained in the reactor / adsorber outlet gas with a boric acid aqueous solution (boric acid concentration 10 g / L) for a certain period of time, and ammonium ions contained in the collected solution. The amount of ammonia remaining in the outlet gas was determined by quantitatively analyzing the amount with a cation chromatograph (ion chromatograph IC-2001 manufactured by Tosoh Corporation). A calibration curve was prepared using an ammonium ion standard solution (manufactured by Wako Pure Chemical Industries, Ltd.), and the amount of ammonium ions was quantified by comparison with the calibration curve.

(Measurement of heat of adsorption and adsorption capacity)
The heat of adsorption and the adsorption capacity were measured by the methods described in the literature “Zeolite, 45 (5), 388-394 (2003)”. The details will be described below.

The heat of adsorption and adsorption capacity can be obtained by analyzing the data obtained by ammonia temperature programmed desorption analysis. For ammonia temperature programmed desorption analysis, a catalyst analyzer (catalyst analyzer BEL-CAT-A manufactured by Nippon Bell Co., Ltd., detector: quadrupole mass spectrometer) was used. First, the adsorbent was filled in a sample tube, held at 500 ° C. for 1 hour under a helium flow, and then cooled to 100 ° C. Next, ammonia was adsorbed to the adsorbent by flowing 10% NH ₃ / N ₂ gas through the tube for 30 minutes while maintaining the sample tube at 100 ° C. Subsequently, a humidified helium gas was allowed to flow through the adsorbent for 30 minutes, and then a dry helium gas was allowed to flow for 30 minutes (water vapor treatment). After the steam treatment was repeated twice, the temperature was increased to 600 ° C. at a temperature increase rate of 10 K / min while flowing helium gas at a flow rate of 30 mL / min, and ammonia temperature desorption was performed. The ammonia fragment mass number of the quadrupole mass spectrometer was 16. The obtained ammonia temperature-programmed desorption pattern was determined by a parameter fitting method using adsorption heat and adsorption capacity as parameters.

(Pore analysis)
For the pore distribution analysis of the adsorbent, a pore distribution measuring device (AutoPore IV9520 manufactured by Micromeritics) was used. Upon measurement, the adsorbent powder was filled into a vinyl chloride ring and pressed using a hydraulic press at a pressure of 20 MPa, and the resulting disc-shaped adsorbent was roughly crushed, and the pore size distribution of the adsorbent was measured. The pore volume was obtained.

(Crystal diameter measurement)
The crystal diameter of the adsorbent was estimated from an electron microscope image of a scanning electron microscope (Electron Microscope JSM-7600F manufactured by JEOL Ltd.). A carbon tape was affixed to a copper sample stand, and a small amount of adsorbent powder was affixed on the tape, and then dried with a 120 ° C. dryer overnight. As an electron microscope measurement condition, the observation was performed with an acceleration voltage of 2.0 kV.

(Heat balance)
When the heat balance of the system is determined according to FIG. 1 and Example 1, the fluid flowing into the system is 11 raw material ammonia at room temperature and 12 combustion air, and the outflow is 13 hydrogen-containing gas at 250 ° C. . The enthalpy inflow rate of the inflowing raw material gas is −33.0 kJ / h from the standard heat of formation of each substance at 25 ° C., and the enthalpy outflow rate of the outflowing hydrogen-containing gas is −58.7 kJ / h. The difference is −25.7 kJ / h, the amount of heat of the outlet gas is larger, and it is not necessary to supply heat into the system. The amount of heat required for air heating for desorption regeneration can be supplied by heat exchange with the decomposition reactor outlet gas.
(Comparative example)

(Ammonia adsorbent preparation example, ammonia adsorption removal, desorption regeneration process 2)
The ammonia adsorbent B2 is prepared by forming 50.0 g of activated carbon powder containing ammonia and used as a general adsorbent into a disk shape at a pressure of 20 MPa with a hydraulic press, crushing the disk roughly, and adjusting the particle size to about 1 μm. Obtained. When the ammonia adsorption capacity of the used activated carbon was measured, the ammonia adsorption capacity was 0.1 mmol / g under the measurement conditions without steam treatment. This is presumably because ammonia adsorbing ability disappears under conditions where water vapor coexists. In the ammonia adsorption removal process 1 and the ammonia desorption regeneration process 1, the same operation was performed by changing the ammonia adsorbent B1 to the ammonia adsorbent B2. However, in the adsorption removal process, the ammonia concentration in the adsorber outlet gas is always It was 0.2% by volume, and the outlet gas ammonia could not be adsorbed. This is presumably because the ability to adsorb ammonia is lost under conditions where water vapor coexists.

  The present invention is a hydrogen production method and can be used as a hydrogen supply source in a plant that requires hydrogen, particularly in an energy-saving and compact space.

(1): Ammonia decomposition device (2): Ammonia adsorber A (during ammonia adsorption operation)
(3): Ammonia adsorber B (during ammonia desorption operation)
(4): Heat exchangers (5) to (10): Three-way valve (11): Raw material ammonia inlet (12): Ammonia combustion air inlet (13) Ammonia removal treatment hydrogen-containing gas outlet

Claims (3)

An ammonia decomposing apparatus that decomposes ammonia into hydrogen and nitrogen, and an ammonia adsorbing apparatus that adsorbs and removes ammonia discharged from the decomposing apparatus. The ammonia adsorbing apparatus has an ammonia adsorption heat of 50 to 180 kJ / mol, ammonia. An ammonia adsorbent having an adsorption capacity of 0.1 to 4 mmol / g and a pore diameter of 50 nm to 10 μm (hereinafter also referred to as “macropore”) is contained in an amount of 0.1 to 1 ml / g. Hydrogen production system. The ammonia adsorbent is at least one selected from zeolite, acidic clay mineral, silicon oxide-containing composite oxide, vanadium oxide-containing composite oxide, metal sulfate and metal phosphate. Hydrogen production system. The ammonia is adsorbed at an ammonia adsorption temperature of 50 to 350 ° C during operation of the ammonia adsorbent, and the adsorbent is regenerated at an ammonia desorption temperature of 50 to 250 ° C higher than the ammonia adsorption temperature. Item 2. The hydrogen production system according to Item 1.

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