JP4959311B2 - Method and apparatus for producing hydrogen from biomass and iron oxide - Google Patents

Description

  The present invention relates to a method and apparatus for producing hydrogen from biomass and iron oxide.

A steam iron method is known as a method for producing hydrogen by bringing metallic iron into contact with water vapor. In this method, iron oxide is reduced with a reducing gas containing hydrogen and carbon monoxide, and hydrogen is produced by reacting the produced iron with water vapor. Since reductive oxidation of iron oxide (Fe ₃ O ₄ → Fe → Fe ₃ O ₄ ) is used, iron oxide can be reused. Furthermore, Patent Document 1 describes a method of preventing so-called sintering phenomenon by adding metal such as Ni or Cr to iron and aggregating metallic iron due to repeated reductive oxidation. As a method for reducing iron oxide to metallic iron, it is common to use hydrogen and carbon monoxide mixed gas or hydrogen as described in Patent Document 1.

Biomass resources, on the other hand, are finite resources and are reproducible and carbon neutral, unlike fossil fuels that emit large amounts of CO ₂ into the atmosphere. Therefore, many studies are currently being conducted on the effective use of biomass resources. However, most of the woody biomass such as waste wood and newspapers and saccharide biomass such as food residues are disposed of without being effectively used.

  As an effective utilization method of biomass resources, for example, in Patent Document 2, a mixture of waste containing biomass and iron oxide is rapidly heated at 1400 to 2200 ° C., and a metal iron, gas containing hydrogen and carbon monoxide is added. A method of manufacturing is described. However, this method has a problem that carbon monoxide is generated as a by-product with hydrogen.

On the other hand, as a technique using iron oxidation, Patent Document 3 discloses a nitrogen gas production in which compressed air and iron powder are brought into contact with each other to oxidize iron, thereby reducing oxygen in the air and increasing the concentration of nitrogen. A method is described.
International Publication No. 2002/081368 Pamphlet JP 2005-111394 A JP 2003-119209 A

  In view of the above problems, the present invention provides a hydrogen production method and apparatus that can produce high-purity hydrogen that does not contain by-products such as carbon monoxide, using biomass resources and iron oxide. With the goal.

  In order to achieve the above object, the present invention, as one aspect thereof, is a method for producing hydrogen from biomass and iron oxide, wherein the mixture of iron oxide particles and biomass is heated to reduce iron oxide. A first oxidation step in which a solid phase containing metallic iron and carbon obtained in the reduction step is brought into contact with water vapor at a temperature of 600 ° C. or less to generate hydrogen gas. A solid phase containing iron oxide obtained in the step is supplied to the reduction step to circulate iron and iron oxide.

Thus, in the reduction step, first, as shown in, for example, Equation 1, iron oxide (Fe ₂ O ₃ ) is reduced to metallic iron (Fe) using biomass (C _n H _m O _x ) as a reducing agent. . The solid phase obtained in this reduction step contains unreacted biomass in addition to the generated Fe and carbon (C). Further, the gas phase obtained in this reduction step includes H ₂ O, CO ₂ , CO, CH _{4 and the} like to be generated. The iron oxide may be Fe ₃ O ₄ or FeO in addition to Fe ₂ O ₃ shown in Formula 1.
Fe ₂ O ₃ + C _n H _m O _x → 2Fe + H ₂ O + CO ₂ + CO + CH ₄ + C (Formula 1)

Next, in the first oxidation step, by setting the reaction temperature to 600 ° C. or less, as shown in Formula 2, carbon (C) coexisting with Fe and unreacted biomass do not react, and CO or CO ₂ Generation is avoided. Therefore, high-purity H ₂ gas can be produced using biomass.
3Fe + 4H ₂ O → Fe ₃ O ₄ + 4H ₂ (Formula 2)

  The hydrogen production method according to the present invention preferably further includes a second oxidation step in which a solid phase containing iron oxide obtained in the first oxidation step is brought into contact with air at a temperature of 200 ° C. or higher. In this case, it is preferable to circulate the iron and iron oxide by supplying iron oxide in the solid phase obtained in the first oxidation step to the reduction step after further oxidation in the second oxidation step. .

Thus, in the second oxidation step, as shown in Equation 3, Fe ₃ O ₄ in the solid phase obtained in the first oxidation step is further oxidized by oxygen in the air to become Fe ₂ O _3. . Moreover, since the oxygen concentration in air falls, an inert gas with a high nitrogen concentration can be obtained.
4Fe ₃ O ₄ + O ₂ → 6Fe ₂ O ₃ (ΔH = ca.−480 kJ) (Formula 3)

Therefore, when the reduction step is performed under the flow of an inert gas, it is preferable to supply the gas phase obtained in the second oxidation step as the inert gas in the reduction step. By performing the reduction process under the flow of an inert gas, gas phase products such as H ₂ O, CO ₂ , CO, and CH ₄ can always be removed from the reduction process. Moreover, since said Formula 3 is an exothermic reaction, it is preferable to assist the heating in the said reduction | restoration process with the heat | fever which generate | occur | produces in the said 2nd oxidation process.

Another aspect of the present invention is a hydrogen production apparatus, in which a mixture of biomass and iron oxide particles is supplied, a reduction reactor that heats the mixture to reduce iron oxide, and the reduction reactor is obtained. A first oxidation reactor for generating hydrogen gas by bringing a solid phase containing metallic iron and carbon into contact with water vapor at a temperature of 600 ° C. or lower, and a solid phase containing iron oxide obtained in the first oxidation reactor. Iron and iron oxide circulating means to be supplied to the reduction reactor are provided. This means for circulating iron and iron oxide further contacts the solid phase containing iron oxide obtained in the first oxidation reactor to further oxidize the iron oxide in the solid phase (for example, Fe ₃ O ₄ is converted to Fe _{A second} oxidation reactor (oxidized to ₂ O ₃ ), and iron and iron oxide transfer means for supplying the reduction reactor with a solid phase containing further oxidized iron oxide obtained in the second oxidation reactor. It is preferable to provide.

  Thus, according to the present invention, it is possible to provide a hydrogen production method and apparatus that can produce high-purity hydrogen that does not contain by-products such as carbon monoxide, using biomass resources and iron oxide.

Hereinafter, an embodiment of a hydrogen production method and apparatus according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic view showing an embodiment of a hydrogen production apparatus according to the present invention. As shown in FIG. 1, the hydrogen production apparatus of the present embodiment generates a hydrogen gas and Fe ₃ O ₄ by the reaction of Fe and water vapor through a reduction reactor 10 that reduces iron oxide to Fe using biomass as a reducing agent. The first oxidation reactor 20 is mainly configured. The reduction reactor 10 and the first oxidation reactor 20 are provided so as to be inclined toward the traveling direction of the solid raw material so that the solid raw material descends due to gravity.

  The reduction reactor 10 is provided with a mixture inlet 12 for supplying a mixture of biomass and iron oxide particles into the reactor. The mixture inlet 12 of the reduction reactor 10 is provided with a mixing means (not shown) for mixing the supplied biomass, the iron oxide particles generated in the oxidation reactor 20 and the remaining carbon to obtain these mixtures. Has been. As the mixing means, for example, a stirrer, a kneader and the like are preferable.

  Examples of biomass include cellulosic woody biomass such as small-diameter wood, thinned wood, sawdust, wood waste, waste paper, rice husk, rice straw, bagasse, natural fiber, newspaper, wrapping paper, tissue paper, toilet paper, cardboard, Sucrose biomass such as sugar cane and sugar beet, starch biomass such as rice, wheat, corn and potato, food processing residue (rice bran, okara, etc.), waste biomass such as waste cooking oil, sludge and waste plastic Can be used. The biomass is preferably processed into small pieces, granules or powders by crushing or grinding.

  As the iron oxide particles, those commercially available as fine iron oxide, iron oxide or iron dust discharged from an iron company, iron oxide fine particles prepared from various iron salts, and the like can be used. The average particle diameter of the iron oxide particles is preferably 1 nm to 100 μm from the viewpoint of reactivity. The mixing ratio of biomass and iron oxide particles is preferably 20 to 300 parts by weight of iron oxide particles with respect to 100 parts by weight of biomass. By setting the mixing ratio in this range, iron oxide can be sufficiently reduced to Fe.

  In addition, elements other than iron can be added to the iron oxide particles. As an element to be added, chromium (Cr), molybdenum (Mo), titanium (Ti), vanadium (V), zirconium (Zr), niobium (Nb), lanthanum (La), from the viewpoint of suppressing sintering of iron particles, At least one metal or metalloid selected from the first group consisting of cerium (Ce), aluminum (Al), gallium (Ga), germanium (Ge), and silicon (Si), or an improved reaction rate, so-called catalyst At least one metal selected from the second group consisting of cobalt (Co), nickel (Ni), copper (Cu), palladium (Pd), platinum (Pt), ruthenium (Ru), and rhodium (Rh) from the viewpoint. Is preferably added. Of course, a total of at least two metals or metalloids selected from at least one metal or metalloid from the first group and from the second group can be added. Each compounding ratio of the metals or metalloids of the first group and the second group is preferably 0.1 to 10 mol% when the metal and metalloid containing Fe are 100 mol%. As a method for preparing Fe and the metal or metalloid to be added, a physical mixing method, an impregnation method, a coprecipitation method or the like is used, and a coprecipitation method is particularly preferable.

  The reduction reactor 10 is provided with heating means (not shown) for heating the supplied mixture to a predetermined reduction reaction temperature. As a reduction reaction temperature, 400-800 degreeC is preferable and 600-800 degreeC is more preferable. By setting this temperature range, iron oxide can be sufficiently reduced to Fe. As the heating means, an electric heater, a natural gas burner, a biomass combustion burner, or the like can be used.

  A gas inlet 14 and a gas outlet 16 for constantly flowing an inert gas through the reactor into the reduction reactor 10 and discharging gas phase products such as water and carbon dioxide generated by the reduction reaction out of the system. Is provided. The gas inlet 14 and the gas outlet 16 are arranged so that the inert gas flows in the opposite direction to the flow of the mixture. The gas discharged from the gas outlet 16 contains hydrogen and carbon monoxide, which are flammable gases. Therefore, an exhaust gas combustion apparatus (not shown) for burning these and releasing them into the atmosphere is gas exhausted. It is desirable to install it after the outlet 16. Alternatively, in order to separate hydrogen in the gas discharged from the gas discharge port 16 from other gases and add it to the hydrogen obtained in the first oxidation reactor 20, a hydrogen separation membrane or the like (not shown) is used as a gas. You may install after the discharge port 16. A nitrogen gas cylinder or a generator (not shown) can be installed at the gas inlet 14 to introduce an inert gas.

The first oxidation reactor 20 is provided with an Fe supply port 22 for supplying a solid phase containing metallic iron produced in the reduction reactor 10 into the reactor. In addition, the first oxidation reactor 20 is provided with a water vapor inlet 24 for introducing water vapor into the reactor. In order for the metallic iron and water vapor in the solid phase to react at a predetermined oxidation reaction temperature, the first oxidation reactor 20 is provided with temperature adjusting means (not shown). The oxidation reaction temperature needs to be 600 ° C. or lower in order to prevent carbon in the solid phase and unreacted biomass from reacting to generate CO or CO _{2 as a} by-product. The oxidation reaction temperature is more preferably 200 to 600 ° C, particularly preferably 350 to 600 ° C.

Since the high-temperature solid phase of 400 to 800 ° C. is supplied from the reduction reactor 10 to the first oxidation reactor 20, it is not necessary to heat the first oxidation reactor 20 in order to maintain a predetermined oxidation reaction temperature. The temperature adjusting means is constituted by a cooling means such as a water cooling cooler. In addition, you may make it the structure which combined heating means, such as an electric heater, as needed. It is preferable to introduce a sufficient amount of water vapor from the water vapor inlet 24 so that all of the Fe in the solid phase becomes Fe ₃ O ₄ . For example, it is preferable to introduce 4 to 10 mol of water vapor with respect to 3 mol of metallic iron.

  The first oxidation reactor 20 is provided with a hydrogen discharge port 26 for discharging high-purity hydrogen gas generated by the reaction between metallic iron and water vapor. The hydrogen gas is supplied to an apparatus (not shown) that uses hydrogen, such as a fuel cell. Further, in order to sufficiently react the metallic iron in the solid phase supplied into the first oxidation reactor 20 with the water vapor, the water vapor inlet 24 is arranged so that the water vapor flows in the opposite direction to the flow of the solid phase. And a hydrogen outlet 26 is arranged.

The first oxidation reactor 20 is provided with a circulation port 28 for discharging a produced solid phase containing Fe ₃ O ₄ and remaining carbon and biomass. The circulation port 28 is connected to the mixture charging port 12 of the reduction reactor 10 via an iron oxide circulation line 40 that conveys the discharged solid phase. As the iron oxide circulation line 40, a conveyor, an air conveyance, etc. can be used.

  Each reactor of hydrogen production equipment is made of metal such as stainless steel or aluminum, ceramics such as alumina or zirconia, or heat-resistant plastic such as phenol resin or polyphenylene sulfide, etc., and can withstand heat and internal / external pressure Have taken. Moreover, each reactor can also be covered with a heat insulating material. As the heat insulating material, glass fiber, silica fiber, silica powder molded body and the like can be used.

According to the above configuration, first, nitrogen gas is circulated into the reduction reactor 10 from the gas inlet 14 and the inside of the reduction reactor 10 is heated to a predetermined reduction reaction temperature. Then, a mixture of biomass, iron oxide particles, and coexisting carbon is introduced into the reduction reactor 10 from the mixture inlet 12. In the reduction reactor 10, the mixture is heated to a reduction reaction temperature, and iron oxide is reduced to Fe using biomass as a reducing agent. Vapor phase products such as H ₂ O, H ₂ , CO, CO ₂ , and CH ₄ generated by the reduction reaction are discharged out of the system from the gas discharge port 16 together with nitrogen gas.

Next, Fe reduced in the reduction reactor 10 is introduced into the first oxidation reactor 20 as a solid phase together with carbon and unreacted biomass. In the first oxidation reactor 20, hydrogen is generated in contact with the steam introduced from the steam inlet 24. Since the inside of the first oxidation reactor 20 is maintained at an oxidation reaction temperature of 600 ° C. or less, CO and CO ₂ are not generated from carbon and unreacted biomass coexisting in the solid phase. The high purity hydrogen gas thus obtained is discharged out of the system through the hydrogen discharge port 26.

Further, Fe ₃ O ₄ produced by oxidation of Fe in the first oxidation reactor 20 is discharged from the circulation port 28 as a solid phase together with the remaining carbon and biomass, and is supplied to the mixture inlet 12 through the iron oxide circulation line 40. To the reduction reactor 10. Then, it is mixed with newly introduced biomass, and Fe ₃ O ₄ is reduced again to Fe by a reduction reaction. Carbon coexisting with Fe ₃ O ₄ in the solid phase functions as a reducing agent in the reduction reactor 10.

Depending on the type of biomass to be used, there is a possibility that the solid derived from the biomass itself _{(e.g., SiO 2, CaO, MgO,} Na 2 O, K 2 O, etc. Al ₂ O ₃₎ is accumulated. When such solids accumulate due to the recycling of iron and iron oxide, the recycling of iron and iron oxide is stopped and replaced with fresh iron oxide particles.

Thus, since the iron oxide particles thrown into the reduction reactor 10 become iron oxide particles again through the Fe particles, the iron material can be reused repeatedly. When 100 kg of Fe is circulated per hour (143 kg for Fe ₂ O _{3 and} 138 kg for Fe ₃ O ₄ ), 4.8 kg (54 Nm ³ ) of hydrogen is generated per hour. When this hydrogen is supplied to the fuel cell, the electrical output is 77 kWh.

As described above, according to the present embodiment, since iron and iron oxide can be circulated and reused, it is possible to simply use inexpensive and abundant biomass, water, and air as raw materials, and do not include CO and CO ₂ byproducts. Pure hydrogen can be produced continuously. In addition, the present embodiment is an environmentally friendly process that does not require a large amount of electric energy.

  In the above description, an inert gas is always flowed through the reduction reactor 10, but reduction is performed if the inside of the reduction reactor 10 is maintained in a reducing atmosphere even if the inert gas is not always flowed. be able to. In this case, in order to prevent the gas generated in the reduction reactor 10 from flowing into the oxidation reactor 20, the hydrogen pressure in the oxidation reactor 20 is controlled to be higher than the gas pressure generated in the reduction reactor 10. It is preferable to do. As a result, part of the hydrogen generated in the oxidation reactor 20 flows into the reduction reactor 10 and the gas generated in the reduction reactor 10 flows out from the discharge port 16, thus promoting the reduction of iron oxide by biomass. can do. Furthermore, the hydrogen flowing into the reduction reactor 10 from the oxidation reactor 20 serves not only for purging the gas generated in the reduction reactor 10 but also as a reducing agent for iron oxide.

Another embodiment of the present invention will be described. FIG. 2 is a schematic view showing another embodiment of the hydrogen production apparatus according to the present invention. The same components as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted. As shown in FIG. 2, in addition to the reduction reactor 10 and the first oxidation reactor 20 described above, the hydrogen production apparatus of the present embodiment brings Fe ₃ O ₄ into contact with air to make Fe ₂ O ₃ and a second oxidation reactor 30 for obtaining nitrogen gas is provided. The second oxidation reactor 30 is also provided with an inclination toward the traveling direction of the solid raw material so that the solid raw material descends due to gravity.

The second oxidation reactor 30 is provided with an Fe ₃ O ₄ supply port 32 for supplying the solid phase obtained in the first oxidation reactor 20 into the reactor. The second oxidation reactor 30 is provided with an air inlet 34 for introducing air into the reactor. The oxidation reaction temperature for oxidizing Fe ₃ O ₄ in the supplied solid phase to Fe ₂ O ₃ is preferably 200 ° C. or higher, and more preferably 200 to 500 ° C.

The oxidation reaction of Fe ₃ O ₄ is an exothermic reaction, and in the second oxidation reactor 30, residual carbon and residual biomass in the solid phase are completely oxidized to CO ₂ , and this reaction is also an exothermic reaction. Furthermore, the solid phase supplied from the first oxidation reactor 20 is as high as 200 to 600 ° C. Therefore, in the second oxidation reactor 30, a predetermined oxidation reaction temperature is maintained without heating by particularly providing a heating means, and the oxidation reaction of Fe ₃ O ₄ proceeds spontaneously (note that if necessary, electric heating is performed) A heating means such as a heater may be installed). In addition, in order to effectively use the heat generated in the second oxidation reactor 30, in the present embodiment, the heat generated in the second oxidation reactor 30 can be used as a heat source for the heating means of the reduction reactor 10. Thus, the reduction reactor 10 and the second oxidation reactor 30 are configured.

From the air inlet 34, all the oxygen in the air is consumed, Fe ₃ O ₄ in the solid phase is oxidized to Fe ₂ O ₃ , and the remaining carbon and biomass are oxidized to CO, CO ₂ , H ₂ O. It is preferable to introduce such an amount of air. For example, it is preferable to introduce 5 to 20 moles of air with respect to 4 moles of Fe ₃ O ₄ .

The second oxidation reactor 30 discharges a gas phase in which oxygen in the air is removed and nitrogen is present at a high concentration, and a solid phase containing Fe ₂ O ₃ and remaining carbon and unreacted biomass. A circulation port 36 is provided for this purpose. The circulation port 36 includes a nitrogen gas supply line 42 for supplying the obtained gas phase as an inert gas to the gas inlet 14 of the reduction reactor 10, and the obtained solid phase to the mixture inlet 12 of the reduction reactor 10. A supply Fe ₂ O ₃ transfer line 44 is branched.

The gas phase obtained in the second oxidation reactor 30 may contain CO, CO ₂ , H ₂ O, and O ₂ in addition to nitrogen. In this case, a gas purification device (not shown) using a PSA (pressure swing adsorption) method or the like is installed in the nitrogen gas supply line 42, and the high-purity nitrogen gas obtained by refining the gas phase is reduced. Supply to the vessel 10.

According to the above configuration, first, a mixture of biomass, iron oxide particles and coexisting carbon is introduced into the reduction reactor 10 from the mixture inlet 12 and heated to the reduction reaction temperature under a nitrogen gas flow. Thereby, iron oxide is reduced to Fe using biomass as a reducing agent. Next, the solid phase containing Fe, carbon, and unreacted biomass obtained in the reduction reactor 10 is introduced into the first oxidation reactor 20, and is passed through the water vapor inlet 24 at an oxidation reaction temperature of 600 ° C. or lower. Contact with the introduced water vapor. As a result, hydrogen is generated without producing CO or CO _{2 as a} by-product. This high-purity hydrogen gas is discharged from the hydrogen discharge port 26 to the outside of the system.

Further, Fe ₃ O ₄ produced by oxidation of Fe in the first oxidation reactor 20 is introduced into the second oxidation reactor 30 as a solid phase together with carbon and unreacted biomass. In the second oxidation reactor 30, it reacts with oxygen in the air introduced from the air inlet 34 and is oxidized to Fe ₂ O ₃ . At this time, since oxygen in the air is consumed, the nitrogen concentration is relatively increased, and a high-concentration nitrogen gas is obtained. In addition, if residual carbon and biomass are oxidized, oxygen consumption is accelerated.

Nitrogen gas is supplied from the gas inlet 14 into the reduction reactor 10 through a nitrogen gas supply line 42 having a gas purifier. Fe ₂ O ₃ is introduced into the reduction reactor 10 through the Fe ₂ O ₃ transfer line 44 from the mixture inlet 12 together with the remaining carbon and biomass. Then, it is mixed with newly input biomass, and Fe ₂ O ₃ is reduced again to Fe by a reduction reaction. Carbon coexisting with Fe ₂ O ₃ functions as a reducing agent in the reduction reactor 10.

Thus, since the iron oxide particles thrown into the reduction reactor 10 become iron oxide particles again through the Fe particles, the iron material can be reused repeatedly. The amount of hydrogen generated per weight of Fe used in circulation is the same as that in the embodiment of FIG. Moreover, according to this Embodiment, the nitrogen gas used as an inert gas can be manufactured from air. When 138 kg of Fe ₃ O ₄ particles are processed per hour in the second oxidation reactor 30, the amount of oxygen removed from the air is 3.34 Nm ³ . Therefore, the production amount of nitrogen gas is 13.4 Nm ³ / h, and the calorific value is 71,520 kJ / h.

  1 and 2 are embodiments in which raw materials are continuously supplied and the reaction is continuously performed, the present invention is not limited to such a continuous process, and for example, a reaction After completion of the reaction in the reactor, a batch-type process in which the obtained solid phase is supplied to the next reactor may be used.

(Test Example 1)
0.45 g of pulp mill material (Havix) generated in the manufacturing process in a pulp nonwoven fabric factory, and Ni—Cr—Fe ₂ O ₃ particles (particle diameter: 0.01 μm to 100 μm. Each amount of Ni and Cr: 5 mol%) And 5 mol%) was mixed in a mortar with 0.45 g (the weight of only Fe ₂ O ₃ in the particles was 0.41 g). And the test which produces | generates hydrogen from the sample of said mixture was done using the normal pressure fixed bed flow type reactor. The sample was heated to 700 ° C. at a temperature rising rate of 5 ° C./min, and kept at this temperature for 1 hour to carry out a reaction for reducing Fe ₂ O ₃ to Fe. And the component of the gaseous phase product produced | generated by this reduction reaction and its production amount were measured. The gas phase product was always discharged out of the reactor together with Ar gas.

Next, water vapor was supplied into the reaction apparatus using Ar gas as a carrier gas, and the solid phase product remaining in the reaction apparatus was brought into contact with water vapor to oxidize Fe to Fe ₃ O ₄ . And the component of the gaseous phase product produced | generated by this oxidation reaction and its production amount were measured. The temperature in the reactor was maintained at 350 ° C., and the oxidation reaction was performed for 1 hour. The measurement results of the above reduction reaction and oxidation reaction are shown in FIG.

As shown in FIG. 3, when the temperature increased with the passage of time, hydrogen, carbon monoxide, carbon dioxide, and methane were generated, and the Fe ₂ O ₃ reduction reaction started. When the reduction reaction was completed about 200 minutes after the start of the test, and then water vapor was supplied, a large amount of hydrogen was generated due to the oxidation reaction of Fe. The amount of hydrogen produced in this 60-minute oxidation reaction was 3000 μmol. In the oxidation reaction, carbon monoxide, carbon dioxide and methane were not detected.

(Test Examples 2 to 6)
An experiment was conducted in which hydrogen was generated in the same procedure as in Test Example 1 except that the amount of iron oxide used was changed to 0.45 g and changed to 5 g, 1.35 g, 0.3 g, and 0.15 g. In addition, when the usage-amounts of iron oxide were 5g and 1.35g, the reaction temperature of the reductive reaction was 650 degreeC. For comparison, the same procedure was used to test a sample to which no iron oxide was added. The results are shown in Table 1. In Table 1, the results of Test Example 1 are also shown.

As shown in Table 1, in Test Example 4 in which the amount of iron oxide used was 0.3 g, the amount of hydrogen produced in the oxidation reaction was 2784 μmol. This is the amount of hydrogen produced when iron oxide (Fe ₂ O ₃ ) is reduced to 100% Fe (hereinafter referred to as the theoretical amount produced, taking into account the amount of NiO and Cr ₂ O ₃ added). The rate of hydrogen production (hereinafter, hydrogen production yield) was 61.71%, and the hydrogen production yield was higher than Test Example 1 in which 0.45 g of iron oxide was used. On the other hand, in Test Example 6 in which no iron oxide was added, the pulp scrap was decomposed by the reaction at 700 ° C. to generate hydrogen, carbon monoxide, carbon dioxide, and methane. Hydrogen was not generated even when the water vapor was contacted.

(Test Examples 7 to 10)
The solid phase product that has finished the oxidation reaction is heated as it is, and after the reduction reaction is performed again, the oxidation reaction is performed by adding water vapor, and the first reduction reaction is set to 650 ° C. The second and subsequent reductions An experiment for generating hydrogen was performed in the same procedure as in Test Example 1 except that the reaction was performed at 700 ° C. The results are shown in Table 2. In addition, the test which repeats a reduction reaction and an oxidation reaction twice using the rice bran instead of the pulp scrap was also performed. In the case of rice bran, the first reduction reaction was 700 ° C. The results are also shown in Table 2.

  As shown in Table 2, hydrogen was generated in the second oxidation reaction in any of the test examples. Further, in Test Example 10 using rice bran instead of the pulp scrap, hydrogen was generated with a yield equivalent to that of the pulp scrap. However, since the amount of hydrogen generated in the third oxidation reaction was remarkably small (Test Example 9), carbon or unreacted biomass capable of reducing iron oxide was present in the solid phase after the second oxidation reaction. It seems that almost no iron remains, mainly iron oxide.

(Test Examples 11 and 12)
An experiment was conducted to generate hydrogen in the same procedure as in Test Example 1 except that Cu—Cr—Fe ₂ O ₃ particles or Fe ₂ O ₃ particles were used instead of Ni—Cr—Fe ₂ O ₃ particles. . The results are shown in Table 3. When Cu—Cr—Fe ₂ O ₃ particles were used, the amount of iron oxide used was 0.3 g.

  As shown in Table 3, in Test Example 12 in which a metal other than iron was not added, although the yield was low, a large amount of hydrogen was generated by the oxidation reaction. In Test Example 11 in which Cu and Cr were added, the hydrogen production yield was improved as compared with Test Example 12 in which Cu and Cr were not added. In addition, in Test Example 4 in which Ni and Cr were added in Table 1, the hydrogen generation yield was higher than Test Example 11 in which Cu and Cr were added.

(Test Examples 13 and 14)
An experiment was conducted in which hydrogen was generated in the same procedure as in Test Example 1 except that the mixing method of biomass and iron oxide was changed to the mixing method by lamination or sandwich lamination instead of the mixing method by mortar. The results are shown in Table 3. As shown in Table 3, in Test Examples 13 and 14, which were laminated or sandwiched, the yield was low, but a large amount of hydrogen was generated by the oxidation reaction.

(Test Examples 15 and 16)
An experiment was conducted to generate hydrogen in the same procedure as in Test Example 1 except that the reaction temperature at 700 ° C. in the reduction reaction was changed to 500 ° C. or 400 ° C. The results are shown in Table 3. As shown in Table 3, in Test Example 15 having a reaction temperature of 500 ° C., although the yield was low, a certain amount of hydrogen was generated by the oxidation reaction. In Test Example 16 having a reaction temperature of 400 ° C., hydrogen was generated by the oxidation reaction, but the amount was very small.

(Test Example 17)
An experiment was conducted to generate hydrogen in the same procedure as in Test Example 4 except that the reaction temperature in the reduction reaction and the oxidation reaction was 500 ° C., respectively. The results are shown in Table 3. As shown in Table 3, even when the reduction reaction was performed at 500 ° C., Test Example 17 in which the oxidation reaction was performed at 500 ° C. was more hydrogen than Test Example 15 in which the oxidation reaction was performed at 350 ° C. The yield of was significantly improved.

(Test Examples 18 and 19)
An experiment was conducted to generate hydrogen in the same procedure as in Test Example 4 except that the reaction time in the oxidation reaction was changed from 60 minutes to 250 minutes or 158 minutes. The results are shown in Table 3. As shown in Table 3, the amount of hydrogen produced increased because hydrogen production continued even when the reaction time exceeded 60 minutes. However, the hydrogen generation rate increases dramatically with the start of the oxidation reaction, reaches a peak when about 30 minutes have elapsed from the start of the oxidation reaction, and then gradually decreases, and then reaches 60 minutes after the start of the oxidation reaction. After the lapse, it was very low.

(Test Examples 20 to 22)
An experiment was conducted to generate hydrogen in the same procedure as in Test Example 4 except that the reaction temperature in the oxidation reaction was changed from 350 ° C. to 450 ° C., 500 ° C., and 600 ° C. The results are shown in Table 3. As shown in Table 3, even when the reaction temperature in the oxidation reaction was increased to 600 ° C., CO, CO ₂ , and CH ₄ were not generated. In addition, the higher the reaction temperature in the oxidation reaction, the higher the amount of hydrogen produced.

(Test Examples 23 to 25)
Next, in order to perform the reaction of further oxidizing Fe ₃ O ₄ to Fe ₂ O ₃ by bringing oxygen in the air into contact with the solid phase product remaining in the reactor after the oxidation reaction of Test Example 1, Air was supplied into the reactor. And the color of the solid phase product produced | generated by this further oxidation reaction was observed. The temperature inside the reactor was kept at 200 ° C., 350 ° C. or 500 ° C., and the oxidation reaction was carried out for 1 hour. The rate of temperature increase was 5 ° C./min.

(Test Examples 26 and 27)
The solid phase product remaining in the reactor after the oxidation reaction of Test Example 9 and Test Example 12 was subjected to an oxidation reaction with air under the same conditions as in Test Example 25 (Test Examples 26 and 27). The results of the above Test Examples 23 to 27 are shown in Table 4.

(Test Examples 28 to 32)
For comparison, the solid phase product remaining in the reactor after the oxidation reaction of Test Example 6 in which no iron oxide was added was subjected to an oxidation reaction with air under the same conditions as in Test Example 25 (Test Example 28). ). For reference, 0.30 g of Fe ₃ O ₄ particles as a reagent is heated at 100 ° C., 200 ° C., 300 ° C., and 350 ° C. for 1 hour, and the color of the solid phase product is also observed. (Test Examples 29 to 32). These results are also shown in Table 4.

As shown in Table 4, in Test Example 23 in which the reaction temperature was 200 ° C., the color of the solid phase product remained black. However, as shown in Test Examples 29 to 32, since the oxidation of Fe ₃ O ₄ to Fe ₂ O ₃ started at a temperature of 200 ° C., in Test Example 23, although oxidation occurred, in the solid phase It is presumed that the carbon remaining in the black was black. In Test Example 24 in which the reaction temperature was 350 ° C., the color of the solid phase product was slightly reddish, and most of Fe ₃ O ₄ was oxidized to Fe ₂ O ₃ . Furthermore, in Test Examples 25 to 27 in which the reaction temperature was 500 ° C., the solid phase product was red, and most of Fe ₃ O ₄ was oxidized to Fe ₂ O ₃ . On the other hand, in Test Example 28 in which no iron oxide was added, the solid phase product exhibited a white color because of the ash content of biomass.

It is a schematic diagram which shows one Embodiment of the hydrogen production apparatus which concerns on this invention. It is a schematic diagram which shows another embodiment of the hydrogen production apparatus which concerns on this invention. Is a graph showing the production of gas-phase products in Test Example 1, the mixture was reduced and oxidized pulp scrap and Fe ₂ O _3.

Explanation of symbols

10 reduction reactor 12 mixture inlet 14 gas inlet 16 gas outlet 20 first oxidation reactor 22 Fe supply port 24 steam inlet 26 hydrogen outlet 28 circulation port 30 and the second oxidation reactor 32 Fe ₃ O ₄ Supply port 34 Air introduction port 36 Circulation port 40 Iron oxide circulation line 42 Nitrogen gas supply line 44 Fe ₂ O ₃ transfer line

Claims (4)

A method for producing hydrogen from biomass,
A reduction step of heating the mixture of iron oxide particles and biomass to reduce iron oxide;
A first oxidation step in which a solid phase containing metallic iron and carbon obtained in the reduction step is brought into contact with water vapor at a temperature of 600 ° C. or less to generate hydrogen gas ;
A solid phase containing iron oxide obtained in the first oxidation step, and a second oxidation step in which the solid phase containing iron oxide obtained in the first oxidation step is brought into contact with air at a temperature of 200 ° C. or higher. Is supplied to the reduction step to circulate iron and iron oxide ,
A method for producing hydrogen in which solid-phase iron oxide obtained in the first oxidation step is further oxidized in the second oxidation step and then supplied to the reduction step to circulate the iron and iron oxide . It performs the reduction step under flow of inert gas, the gas phase obtained at the second oxidation step, hydrogen production method according to claim 1 for supplying as the inert gas in the reduction step. The hydrogen production method according to claim 1 or 2 , wherein heating in the reduction step is performed with heat generated in the second oxidation step. A mixture of biomass and iron oxide particles is supplied, and a reduction reactor that heats the mixture to reduce iron oxide and a solid phase containing metallic iron and carbon obtained in the reduction reactor are steamed at a temperature of 600 ° C. or less. A first oxidation reactor for generating hydrogen gas in contact with the iron, and an iron and iron oxide circulation means for supplying a solid phase containing iron oxide obtained in the first oxidation reactor to the reduction reactor ,
The iron and iron oxide circulation means is a second method in which air is brought into contact with a solid phase containing iron oxide obtained in the first oxidation reactor at a temperature of 200 ° C. or more to further oxidize iron oxide in the solid phase. And an iron oxide transfer device for supplying a solid phase containing further oxidized iron oxide obtained in the second oxidation reactor to the reduction reactor .

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