JP2017040272A - Method for utilizing aluminum as fuel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide new renewable energy utilizing, as fuel, aluminum that is not harmful to the environment or human beings, and can be easily stored and supplied in a stable manner.SOLUTION: Aluminum powder and oxygen are fed into a combustion chamber to perform stationary combustion there, and the generated energy is taken out and utilized. The stationary combustion of aluminum is carried out under a certain control of one of an amount of aluminum powder to be fed into the combustion chamber and an amount of oxygen to be fed thereinto or both of them. The control of the amount of aluminum powder is carried out by controlling an amount of aluminum powder mixed into injection flow of carrier gas feeding the powder into the combustion chamber or by controlling an amount of impurities mixed into the aluminum powder. The control of the amount of oxygen is carried out by controlling a mixing ratio with an amount of dilution gas simultaneously fed into the combustion chamber. Alumina generated as a result of combustion is recovered and aluminum attained through its reduction can be utilized again as fuel.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method of using aluminum as a new energy resource by taking aluminum as a “fuel” or “energy source” and effectively utilizing the high heat generated when the aluminum burns. If the alumina (aluminum oxide) produced after the aluminum burns is recovered, and is recovered and reused, a new energy circulation system can be constructed as renewable energy using aluminum.

  The main source of power in Japan is about 60% of thermal power (coal, oil, natural gas), about 30% of nuclear power, and other sources of hydropower. Looking at the world as a whole, thermal power generation accounts for just under 70% and nuclear power generation about 15% (2009). Of these, thermal power generation, which accounts for the overwhelming share of the world, cannot avoid the generation of greenhouse gases associated with the combustion of fossil fuels. Therefore, an immediate energy supply system is necessary to cope with the recent global warming. Review is required. With regard to nuclear power generation, which was expected as one of the means to solve this problem, it started with the radiation leakage accident from the nuclear power plant caused by the Great East Japan Earthquake in March 2011. Crisis awareness and post-use nuclear fuel disposal issues are again highlighted, and in the future, the review of nuclear power dependence is inevitable.

  Where alternative power supply sources are required to replace thermal power generation and nuclear power generation, hydroelectric power generation, which was once the main power supply, has become a problem with environmental destruction caused by dam construction, and is relatively efficient (approximately 70%) ) For pumped-storage power generation, it is difficult to be an immediate solution, especially in Japan, where the country is small and there are few geographically suitable areas, such as the need to provide two reservoirs, an upper adjustment pond and a lower adjustment pond, across a dam. There may be similar circumstances in foreign countries. Renewable energies such as solar power generation and wind power generation are attracting attention, but the amount of power generation is greatly affected by the weather and seasons, so stable power supply cannot be expected, and the development of power storage technology corresponding to the amount of power generation It is an urgent issue. With existing power storage technologies such as lead-acid batteries and lithium-ion batteries, the energy storage density is low (two orders of magnitude lower than that of coal and oil) as the power level rises, even if small power levels are possible. Issues remain in terms of the amount of rare metal used, and no major development is likely.

  As for fuel cells, we cannot expect a big development from the viewpoint of the safe storage of hydrogen as a fuel. In addition, what can be said about batteries in general is constant due to changes over time due to repeated charging and discharging, and efficiency decreases. Renewal is necessary after the period, and there remains a problem in processing the battery after use. In the future, innovative power storage technology that eliminates these problems will be required. In order to maintain the production activities and living standards using the infrastructure that has been built up to now, there is a danger in the end, but it is necessary to be aware of this and rely on nuclear power generation for the time being.

  In order to overcome this situation and realize abundant energy supply without relying on conventional thermal power generation or nuclear power generation, establish a stable energy supply source supported by large-scale livestock electricity technology based on new ideas That is required on a global scale. The inventors of the present application have previously suggested that the energy cycle using aluminum as fuel, which has not been considered much before (see “Non-patent Document 1”), but at that time (1996) ) Still has many problems to be solved, and its feasibility is uncertain, so it has not been attracting attention. However, as a result of continuing steady research and development, the inventors of the present application have solved many problems in the process, and as a result, have finally been able to confirm its feasibility. The inventors of the present invention are extremely valuable inventions that give a single light toward the future of the earth, with the possibility that the present invention can simultaneously cope with the energy crisis and global warming phenomenon that can be expected in the near future. I believe that.

First, an outline of aluminum which is the main body of the present invention will be described. Aluminum is an element abundantly present on the surface of the earth's crust, and its Clark number, which expresses its composition by weight ratio, is 8.23, the third largest after oxygen (46.4) and silicon (28.15), This value is higher than other influential elements such as iron (5.63), calcium (4.15), sodium (2.63) and the like. In addition, the average chemical composition in the continental crust of alumina (Al ₂ O ₃ ), which is an oxide of aluminum, accounts for 15.5%, the second largest after 59,8% of silicon dioxide, which is calcium oxide. (6.4%), exceeding iron oxide (5.1%). In other words, it can be said that aluminum is an element that is usually present everywhere on the earth's surface.

Aluminum's contribution to mankind begins with the discovery of alumina in the early 19th century. The bond between aluminum and oxygen in alumina is strong, and potassium, sodium, etc. were originally used to reduce the alumina and isolate the aluminum.・ Eru method was found, and this is still the mainstay of aluminum refining method. Specifically, alumina is extracted from bauxite, which is an ore rich in alumina, using sodium hydroxide or the like (Bayer method), and the alumina is an electrolytic bath (2,300K) using cryolite (Ga3AlF6). Aluminum is refined by electrolysis using a carbon electrode.
Al ₂ O ₃ + 3C → 2Al + 3CO
Al ₂ O ₃ + 3 / 2C → 2Al + 3 / 2CO ₂

  The Buyer method and the Hall-Eleu method are already established technologies and will not be described in detail. However, as is clear from the above chemical formula, the carbon electrode necessary for the reduction action is used, so carbon monoxide, carbon dioxide, etc. Cause a large amount of greenhouse gases. In addition, the electrolysis requires consumption of a large amount of power for separating a strong bond between aluminum and oxygen (power consumption for producing 1 ton of aluminum: 13,000 to 14,000 kWh). This is why it is commonly referred to as the “bulk of electricity”.

  Even now, the Hall-Eleu method is the mainstay for aluminum refining (reduction of alumina), and although various technical improvements are seen (see, for example, “Patent Document 1”), a large amount of electricity is consumed and greenhouse gases are consumed. Occurrence cannot be avoided. In recent years, direct carbothermic reduction methods have been proposed in place of the Hall-Eleu method (see, for example, “Patent Document 2” and “Patent Document 3”), but there is no change in using carbon as a reducing material. Therefore, the generation of greenhouse gases is inevitable.

Next, the potential when viewed as an energy resource (fuel) of aluminum will be described. Figures below are a comparison of the energy storage density of various materials, shown in kilojoules per gram units (kJ / g) and kilojoules per cubic centimeter (kJ / cm ^3).
Material kJ / g kJ / cm ³
Aluminum 15.5 41.9
Coal 41.3 57.8
Petroleum 60.4 47.2
LNG 76.9 33.7
Hydrogen (100MPa) 0.60 0.05
Lead-acid battery 0.13 0.29
Lithium ion battery 0.36 0.9

  Aluminum generates a high amount of heat when burned (oxidized). As is clear from the above comparison, when compared per volume, the energy storage density of aluminum is slightly inferior to coal, but antagonizes oil and is higher than LNG. Moreover, it is so high that it cannot be compared with hydrogen or a battery. In other words, it can be said that aluminum has characteristics comparable to those of coal and oil in storage and transportation. In addition, an excellent point of aluminum is that, even if the surface is oxidized by exposure to air, the oxide film is strong, so that the inside is kept as aluminum. While the potential energy declines due to coal and oil being altered and volatilized during storage, aluminum can withstand long-term storage and stockpiling.

JP 2005-536637 A US Pat. No. 6,440,193 JP 2006-519921 A

Research Institute for Energy Engineering, “Study Report on Feasibility Study on Development of Low Smoke Reactor Technology (FY1995 Commissioned by the Agency for Natural Resources and Energy)”

  The inventors of the present application pay attention to the potential as an “energy resource (fuel)” of aluminum as described above, establish a technology to extract energy by controlling the combustion of aluminum, and can use aluminum as “fuel” Furthermore, it aims at making it possible to construct an energy circulation cycle using aluminum as “fuel” by refining, storing, burning, recovering and regenerating aluminum. In particular, in the aluminum refining process, the provision of alumina reduction technology that does not generate exhaust gas that has a low energy and an adverse effect on the human body, such as low-energy environments and greenhouse gases, in place of the current Hall Elle method, and the aluminum combustion process The purpose of the present invention is to provide an aluminum steady-state combustion technique that can control explosive combustion of aluminum and effectively extract it as energy.

  The present invention achieves steady combustion by controlling the amount of aluminum and oxygen introduced into the combustion chamber of an aluminum combustion device when aluminum is burned, and also uses laser plasma technology and supersonic freezing flow for alumina reduction. It solves the above-mentioned problems by isolating aluminum by using, and specifically includes the following contents.

  That is, one aspect of the present invention is a method of using aluminum as a fuel by burning aluminum and taking out and utilizing the energy generated by the combustion, and introducing aluminum powder and oxygen into the combustion chamber. The present invention relates to a method of using aluminum as a fuel, characterized in that aluminum is burned, the combustion speed is controlled to make it a steady combustion, and the energy generated by the steady combustion is taken out from the combustion chamber and utilized.

  In the step of constantly burning aluminum, the burning rate of aluminum can be controlled by controlling one or both of the amount of powdered aluminum introduced into the combustion chamber and the amount of oxygen.

  The amount of aluminum powder introduced into the combustion chamber is controlled by controlling the amount of aluminum powder entrained by a jet of carrier gas for introducing the powder into the combustion chamber, or mixed with the aluminum powder. This can be done by controlling the amount of impurities. At this time, alumina powder can be used as the impurity.

  The amount of oxygen introduced into the combustion chamber can be controlled by controlling the mixing ratio with the amount of dilution gas introduced simultaneously with oxygen.

  The step of extracting the amount of heat generated during the steady combustion can be configured to drive either one or both of the gas turbine and the steam turbine with the combustion gas. Thereby, the energy obtained by burning aluminum can be used for power generation or used as power.

  The method of using the aluminum as a fuel includes an alumina reduction step of reducing the alumina to produce aluminum before the step of steady burning the aluminum, or an aluminum regeneration in which the aluminum waste material is treated and regenerated into aluminum powder. Any one of these steps may be further added.

  In the alumina reduction step, the alumina powder is heated by a heating means such as a laser beam to separate the aluminum and oxygen by making the alumina into a plasma state, and this is spouted at a supersonic speed to isolate the aluminum. can do. At this time, hydrogen can be added to the working gas, and the reduction of alumina can be promoted by the action of hydrogen.

  After the alumina reduction step or the aluminum regeneration step, before the steady combustion step of the aluminum, any step of transporting, storing and stocking the aluminum powder obtained by the alumina reduction or aluminum regeneration is performed. You can add more. Further, after the step of taking out the energy generated during the steady combustion, a step of recovering the alumina generated by the steady combustion of aluminum can be further added. The alumina recovered in this step can be recycled for use in the alumina reduction step. Also, by adding these steps, an energy cycle utilizing aluminum can be constructed.

  By implementing the present invention, it is possible to effectively use energy obtained by burning aluminum as fuel. For example, when it is used for power generation, it does not emit greenhouse gas and other renewable energy. Thus, stable power can be supplied without being affected by the weather. In addition, aluminum can be recovered and reused after combustion, and more stable and long-term storage is possible, providing a potential energy resource candidate for the future energy crisis. .

It is a flowchart which shows the outline | summary of the aluminum energy cycle which concerns on embodiment of this invention. It is the schematic of the apparatus which carries out the steady combustion of the aluminum which concerns on other embodiment of this invention. It is a schematic block diagram of the combined electric power generating apparatus which burns aluminum and generates electric power. It is explanatory drawing which shows the outline | summary of the reduction | restoration method of aluminum which concerns on other embodiment of this invention.

  About the novel energy circulation method (henceforth an "aluminum energy cycle") which produces | generates energy by circulating aluminum, including the method of using aluminum as a fuel according to the first embodiment of the present invention. This will be described with reference to the drawings. FIG. 1 shows an overall outline of an aluminum energy cycle using aluminum according to the present embodiment. In the figure, step (abbreviated as “S” in the drawing) 0 is a process of extracting alumina (aluminum oxide) from an aluminum-containing ore (bauxite, etc.), which is based on the prior art (for example, the buyer method). It's okay.

In step 1, alumina is reduced to extract aluminum. Aluminum used as a fuel in the present invention does not have to be high-purity aluminum such as 99.9% as in the case of refining industrial aluminum, and impurities or alumina or other elements are limited to a certain limit. May be included. Here, alumina reduction by the Hall-Eleu method according to the prior art may be used, or a novel alumina reduction method related to the present invention as described later (third embodiment) may be used. Since power is consumed for the reduction of alumina, this step is preferably carried out in an area where the electricity charge is low. For example, if a solar power generation facility is prepared by selecting an area where the sun's irradiation time is long and the weather changes little throughout the year, and alumina reduction is performed using the power generated there, the obtained aluminum will be fueled. It includes the possibility of becoming an “energy producing country (region)” that can be compared to the conventional “oil producing country” by shipping.

  Next, in step 2, the aluminum obtained in step 1 is transported to an area (country) where energy is required as “fuel (energy source)” and stored. Aluminum forms an oxide film on the surface and protects the inside, so that the state becomes stable thereafter and storage is easy. Furthermore, when compared with conventional fossil fuels, there are no alterations due to storage, no reduction due to volatilization, and no off-flavors, and it is suitable for long-term storage (stockpile). Aluminum in this state can be called “aluminum fuel” and can be regarded as an energy resource. When handling powder, there is always a common problem of preventing dust explosions. For this reason, it is necessary to manage the storage amount, temperature, humidity, etc., but unlike materials that ignite simply by watering, such as magnesium, aluminum is in a stable state, so the risk is relatively high. There is no.

  Next, in step 3, the aluminum fuel stored in step 2 is burned to extract energy. The combustion of aluminum is known to be explosive, which makes it difficult to extract energy in the prior art. There are examples of aluminum being used in rocket engines, etc., using explosives such as light bullets and flash bullets, or rapid expansion due to explosions, but the idea of using aluminum as an energy resource or fuel for steady combustion and effective use Was not. In the present invention, the combustion speed during aluminum combustion is controlled and combustion is performed in a steady state to enable effective extraction of energy. This will be described in detail in the second embodiment. In this step 3, aluminum is oxidized by combustion and returns to alumina (aluminum oxide).

  Next, in step 4, the alumina after combustion is recovered. The melting point of alumina is 2,300K. For example, the combustion gas containing molten alumina is cooled after it is effectively used to drive a gas turbine or a steam turbine, and then the alumina solidified as dust is solidified using a filter. And can be recovered. The other components contained in the combustion gas are only oxygen and an inert gas such as argon used as a carrier gas or a diluent gas, and do not contain substances that are harmful to the environment or the human body. The recovered alumina can be collected and transported and returned to the “reduction of alumina” step of step 1 as shown. As described above, an “aluminum energy cycle” in which steps 1 to 4 are circulated with aluminum interposed therebetween is configured.

  Step 5 shows the process of using regenerated aluminum as a fuel without or requiring the reduction of alumina. Aluminum is already on the market in large quantities as industrial products, building materials, beverage cans, etc., and it is still practiced to recover these and regenerate aluminum. According to this aluminum regeneration technology, it is said that the power consumption is only about 3% compared to the conventional alumina reduction method (Hall-Eleu method) shown in Step 1. If it can be regenerated, it will play an extremely important role as an energy resource. In the flow shown in FIG. 1, the regeneration of aluminum in step 5 is connected to the combustion of aluminum in step 3, but this may be connected to the transportation and storage of aluminum in step 2.

The method of extracting energy using aluminum as described above, and also the entire aluminum energy cycle that burns, recovers, reduces, and reuses aluminum is remarkable when compared with the conventional energy generation method. The advantages are summarized as follows.
1. Aluminum as a fuel is abundant as a resource, and recycled aluminum can also be used. Until now, resources such as coal, oil, and LNG have been unevenly distributed on the earth, but as long as there is alumina refining technology, there is a possibility that any country will become an “energy producing country”. This also does not require a rare metal such as lithium, which is unevenly distributed.
2. Aluminum is recyclable and is fundamentally different from other fossil fuels in this respect.
3. Aluminum is easy to store because it has an oxide film on its surface and the interior is protected and stable. Unlike other fossil fuels, there is no phenomenon of alteration or volatilization. For this reason, it is also suitable for stockpiling.
4). By using aluminum, the power supply can be stabilized. Other renewable energies, such as solar power and wind power, are susceptible to natural phenomena such as the weather and the power supply fluctuates, while when using aluminum as fuel, it is appropriate to meet the demand. An amount of power can be supplied at any time. For this reason, power storage equipment such as a battery is not necessarily required.
5). Aluminum is harmless as a fuel and does not pollute the environment. It has nothing to do with radioactivity and is fundamentally different from nuclear power generation. The result of combustion is an innocuous stable substance called aluminum oxide. In this respect, it is different from fossil fuels that generate large amounts of greenhouse gases, as well as power storage technology that uses harmful substances such as lead and lithium. It is also different.

  The overall outline of the “aluminum energy cycle” according to the present embodiment has been described above, but this shows the basic concept of the present invention, which is intended to effectively utilize aluminum as an energy resource by circulating aluminum. . However, not all the elements from Step 0 to Step 5 shown in FIG. 1 are necessarily essential elements of the present invention. The core part of the present invention is in the “steady combustion of aluminum” in step 3 and the other elements can be viewed as the components associated therewith. For example, the reduction of alumina in step 1 is not limited to the already established Hall-Eleu method, although there are problems, and other reduction technologies are seen. Aluminum obtained by reduction using these technologies can be reduced. It may be used for the steady combustion of aluminum in Step 3. In addition, the aluminum transport and storage process in Step 2 is an element required when it is assumed that alumina reduction and aluminum combustion are performed in different countries and regions, or when aluminum is stored as fuel. It is not always necessary when the reduction of alumina and the steady combustion of aluminum are performed consistently.

  Further, even though the recovery of alumina in step 4 is an element for carrying out the aluminum energy cycle according to the present embodiment, the alumina generated after combustion is not recovered here, and is already distributed in large quantities on the ground surface. May be discarded as part of the aluminum-containing component. Like oxygen and working gas (inert gas) which are other components contained in the combustion gas, alumina is harmless to the environment and the human body, and basically it does not pose a problem even if it is released into the atmosphere as it is.

  Until now, the technology that captured aluminum as an energy resource or fuel has been very limited. In particular, combustion of aluminum is not explosive combustion, and obtaining energy as steady combustion is a new technical idea. At the same time, the entire aluminum energy cycle that burns, recovers, reduces, and reuses aluminum is also a new technical idea. Moreover, it can be said that these are novel technical ideas that can be used very effectively in the industry.

  Next, a second embodiment of the present invention will be described with reference to the drawings. Here, it relates to the “aluminum combustion” technique of Step 3 indicated by a double frame in the aluminum energy cycle shown in FIG. As described above, the combustion of aluminum is explosive, and in order to extract it as effective energy, combustion in a steady state by controlling the combustion speed (hereinafter referred to as “steady combustion” in this specification). ) Must be. “Steady combustion” is the counter electrode of “explosive combustion (unsteady combustion)”. The combustion speed can be controlled and combustion in that state can be continued for a certain period of time. Refers to combustion.

  FIG. 2 shows an example of an aluminum combustion apparatus 1 that enables steady combustion of aluminum. In FIG. 2, the aluminum combustion apparatus 1 is mainly composed of an aluminum supply unit 10 and an aluminum combustion unit 30. Among them, the aluminum fuel supply unit 10 supplies an appropriate amount of aluminum powder (hereinafter also referred to as “aluminum fuel”) 5 to the aluminum combustion unit 30, and the turntable 11 and the turntable 11 are arranged from below. A fuel container 12 for placing the aluminum fuel 5 placed thereon, a fuel discharge pipe 13 for supplying the aluminum fuel 5 into the fuel container 12, a fuel supply pipe 14 for taking out the aluminum fuel 5 from the fuel container 12, and aluminum The carrier gas supply pipe 16 supplies a carrier gas for taking out and transporting the fuel 5.

  The turntable 11 is rotationally driven by a motor 17, and the number of rotations can be controlled by a control device (not shown). The aluminum fuel 5 is appropriately discharged from the fuel discharge pipe 13 into the fuel container 12. For example, a sensor (not shown) can be attached to the tip of the fuel discharge pipe 13, and the level of the aluminum fuel 5 in the fuel container 12 can be detected and supplied to keep it at a constant level. The fuel discharge pipe 13 can be replenished with the aluminum fuel 5 from above. The fuel supply pipe 14 and the carrier gas supply pipe 16 have a double-pipe structure in the illustrated example, and carrier gas such as argon and helium is directed downward from above through the carrier gas supply pipe 16 on the outer periphery. It can be supplied. The double pipe is at or near the height in contact with the aluminum fuel 5 in the fuel container 12, and the aluminum fuel 5 entrained by the pressure of the carrier gas moves from the lower side to the upper side inside the fuel supply pipe 14 together with the carrier gas. Then, it is pushed out and sent to the aluminum combustion section 30 through the connecting pipe 20.

  On the other hand, the aluminum combustion section 30 has a double-tube structure in which a fuel nozzle 31 that discharges a fuel mixed gas in which the aluminum fuel 5 and the carrier gas are mixed into the combustion chamber 40 and oxygen that mainly supplies oxygen from the surroundings. It is comprised from the supply pipe | tube 32 and the ignition mechanism 33 which ignites the aluminum fuel 5 using a torch flame here. The oxygen supply pipe 32 is connected to an external oxygen supply source (not shown). In the drawing, only one nozzle having a double tube structure is drawn, but a large number of small nozzles having the same structure may be arranged.

  The operation of the aluminum combustion apparatus 1 according to the present embodiment configured as above will be described together with a control measure for realizing steady combustion in particular. First, the aluminum fuel 5 is discharged from the fuel discharge pipe 13 of the aluminum supply unit 10 into the fuel container 12, and the turntable 11 is rotationally driven by the motor 17. Next, pressurized carrier gas is supplied from above the carrier gas supply pipe 16, and the aluminum fuel 5 entrained in the flow of the carrier gas at the lower end of the double pipe is pushed into the fuel supply pipe 14, and the mixed gas. Is supplied to the aluminum combustion section 30 through the connecting pipe 20. In the aluminum combustion section 30, oxygen is supplied into the oxygen supply pipe 32 and is ignited by the ignition mechanism 33 in a state where the fuel mixed gas containing the aluminum fuel 5 and oxygen are mixed, and combustion of the aluminum fuel 5 starts. Is done. Thereafter, the aluminum fuel 5 supplied one after another burns, becomes high-temperature and high-pressure gas, is guided from the combustion chamber 40 to the right in the figure, and is led to an energy generating device such as a power generation gas turbine described later.

During the operation as described above, the following control means can be taken in order to realize steady combustion at a controlled combustion speed, not aluminum explosion combustion.
1. Control of carrier gas supply pressure: A pressure adjusting valve is provided upstream of the carrier gas supply pipe 16 to control the supply pressure of the carrier gas. The level of the supply pressure increases or decreases the amount of the aluminum fuel 5 caught in the fuel supply pipe 14. As an example, the pressure is controlled at about 100 kPa to 1 MPa, preferably about 300 to 600 kPa.
2. Control of the rotational speed of the turntable 11: By controlling the rotational speed, the amount of aluminum fuel 5 entrained by the carrier gas can be controlled. Alternatively, instead of the turntable 11, the table is configured to be movable up and down, and the relative height of the lower ends of the fuel container 12 and the fuel supply pipe 14 is controlled to penetrate the fuel supply pipe 14 into the aluminum fuel 5. May be adjusted. The supply amount of the aluminum fuel 5 is controlled at an equivalent ratio of about 0.2 to 1.1, preferably about 0.5 to 0.8 with respect to the supply oxygen amount. Further, the particle diameter of aluminum used as the aluminum fuel 5 is about 0.1 to 30 μm, preferably about 1 to 10 μm.
3. Addition of an element having a combustion mitigating effect to the aluminum fuel 5: As an example, the aluminum fuel 5 is not limited to pure aluminum particles, but alumina particles are added at a constant rate. When alumina is reduced by heat at the time of combustion, part of the energy is absorbed and combustion is promoted to become steady combustion. For supplying alumina, a predetermined amount is mixed with aluminum fuel in advance, or another discharge pipe similar to the fuel discharge pipe 13 is provided in the aluminum supply section 10 to control the required discharge amount of alumina in the fuel container 12. It may be supplied. In addition to alumina, other impurities having an effect of mitigating combustion, such as water (water vapor), may be added.
4). Control of supply amount of mixed gas of carrier gas and aluminum fuel: A pressure adjusting valve is provided in the middle of the connecting pipe 20, and the supply amount of the mixed gas is controlled like a throttle.
5). Control of the oxygen concentration in the oxygen supply pipe 32: A switching valve 34 is provided upstream of the oxygen supply pipe 32, and a dilution gas composed of an inert gas such as argon is controlled and mixed into oxygen to dilute the oxygen concentration. The volume ratio of oxygen and dilution gas is such that the oxygen is supplied to the oxygen supply pipe 32 in a specified amount (equivalent ratio to the aluminum fuel supply amount is about 0.2 to 1.1, preferably about 0.5 to 0.8. The mixture is mixed so that the injection pressure is about the same as that of the dilution gas (100 kPa to 1 MPa, preferably 300 kPa to 600 kPa).
6). Control of the combustion chamber temperature of the aluminum combustion section: In the aluminum combustion section 30, the temperature exceeding the autoignition temperature of aluminum is maintained, and the wall surface of the combustion chamber 40 is thermally insulated by a low thermal conductive material 41 such as ceramics. This heat insulating material 41 is kept at a high temperature by radiation by aluminum combustion, and contributes to stable combustion. Further, a heat exchanging portion 42 is provided upstream of the oxygen supply pipe 32, and the supplied oxygen is heated by a part of the heat generated in the combustor 40, thereby contributing to preheating of the aluminum combustion portion. As an example, the aluminum combustion section temperature is controlled at about 600K to 1200K, preferably about 800K to 1000K.

  It is possible to control the combustion rate of aluminum by arbitrarily combining any one of the above control means, or any combination thereof, and to make this a steady combustion. As a control system for this purpose, a temperature sensor and a pressure sensor (not shown) are provided in the combustion chamber 40, and these are input to the control device so that necessary control means can be operated. In an emergency in which the aluminum fuel 5 is being burned, the combustion of the aluminum fuel can be stopped immediately by stopping the supply of the aluminum fuel 5 and the supply of the carrier gas. At this time, no radioactivity or noxious gas is released.

  FIG. 3 shows an example of a power generation device 50 that generates power using high-temperature, high-pressure gas obtained from aluminum fuel. The figure shows an example of a combined power generation apparatus including a power generation region by a left gas turbine and a power generation region by a right steam turbine. 3, in the gas turbine power generation region on the left side, the aluminum combustion apparatus 1 shown in FIG. 2 is connected to the gas turbine 51, and the gas turbine 51 is rotationally driven by the combustion gas. The rotation of the gas turbine 51 is transmitted to a compressor 52 connected via a shaft (may be via a gear or the like) and further to a first generator 53, and electricity is generated by the first generator 53. The The pressure generated by the compressor 52 is returned to the aluminum combustion apparatus 1 and used as the combustion gas pressurization pressure.

  On the other hand, in the steam turbine power generation region, the combustion gas after driving the gas turbine 51 is guided to the heat exchanger 56 where steam is generated. The combustion gas after the heat exchange may be released to the atmosphere as indicated by an arrow A, or may be recovered and recycled. The steam generated in the heat exchanger 56 rotates the steam turbine 57, whereby electricity is generated by the second generator 58. Subsequent steam is returned to water by the condenser 59 and circulated for use. The amount of heat obtained by the condenser 59 may be effectively used for other purposes. The basic configuration of the power generator 50 described above is the same as that of the combined power generator that uses fossil fuel, except for the aluminum combustion apparatus 1. In the above example, the energy obtained by the combustion of aluminum is used for power generation. For example, it is used as a stationary industrial gas / steam turbine engine or a power engine for ships. May be.

  Next, a third embodiment of the present invention will be described with reference to the drawings. The present embodiment relates to the alumina reduction method shown in Step 1 of FIG. As described above, the aluminum used for combustion in the present invention can be aluminum reduced by the Hall Eru method according to the prior art, but a large amount of electric power is required for the reduction of alumina by the Hall Eru method. And a large amount of greenhouse gas is generated. When aluminum is used as a fuel, it is particularly preferable to obtain the energy source by a method that does not emit environmental pollutants. In this embodiment, the aluminum used in the aluminum energy cycle shown in FIG. The new alumina reduction method is used so that it can be obtained by a method that totally avoids the emission of greenhouse gases and leads to an improvement in power consumption.

  The alumina reduction method is not necessarily an indispensable requirement for the method of using aluminum according to the present invention as a fuel or the aluminum energy cycle. The invention of the alumina reduction method is dealt with in another independent application parallel to the present application, and in this embodiment, the method is applied to the aluminum energy cycle of the present application.

  FIG. 4 shows an outline of the method for reducing alumina according to the present embodiment. The step of thermally dissociating alumina in the region A shown on the left side of the drawing distinguished by a broken line, aluminum in the central region B And separating oxygen and isolating aluminum, and recovering the isolated aluminum in the C region shown on the right side. The flow of each step moves from the left side to the right side of the figure.

  First, in the step of thermally dissociating alumina in the region A on the left side of the figure, a throat portion 111 for restricting the flow is provided inside the reducing apparatus 100 used, and alumina is introduced upstream (left side of the figure). The port 112 is further provided with a working gas inlet 113 upstream thereof. Alumina powder is introduced into the apparatus together with a carrier gas such as argon from the alumina introduction port 112, and a pressurized working gas composed of an inert gas such as oxygen and argon gas is introduced from the working gas introduction port 113. In the mixture of alumina and carrier gas introduced from the alumina introduction port 112, the content of alumina in the whole is appropriately controlled within a range of, for example, about 0.1 to 0.6 g / l (l: liter). The pressure of the working gas introduced from the working gas introduction port 113 is preferably about 10 atmospheres. The mixture of alumina and carrier gas is pumped by the working gas from the left to the right in the figure toward the throat portion 111.

The throat portion 111 is irradiated with laser light 114 from the left side of the drawing with a focus on the throat portion 111. In this embodiment, a carbon dioxide gas laser with a maximum output of 2 kW, a wavelength of 10.6 μm, and a beam diameter of 34 mm is used. There may be. The vicinity of the focal point of the laser beam locally reaches a high temperature of 12,000 K, and the alumina is melted by the high heat (the melting point of alumina is 2,300 K). Here, a phenomenon called reverse bremsstrahlung, where electrons are absorbed and accelerated, occurs, and the plasma is heated by repeated Coulomb collisions between the electrons and ions.
Al ₂ O ₃ = 2Al + 3 / 2O ₂ −838 kJ

  Next, the gas in the plasma state is moved to the B region in the center of the figure, heated and expanded, and is squeezed by the throat part 111, and then becomes a jet from the nozzle 116 which is the outlet of the throat part 111. Is released towards The flow velocity at this time is a supersonic flow of 1,000 to 3,000 m / s, and the air flow is rapidly cooled by rapid expansion. Here, according to the conventional Hall-Elu method, oxygen is attracted to the anode and separated into carbon dioxide by being combined with carbon in the electrolyzed alumina component, and only the remaining aluminum is precipitated in the melting furnace. And recovered. However, in the absence of a reducing agent such as a carbon electrode, even when alumina is thermally dissociated and separated into aluminum and oxygen, aluminum and oxygen, which have strong bonding strength, are recombined during the cooling process and returned to alumina. It tends to end up. According to the method according to the present embodiment, aluminum and oxygen separated as plasma are rapidly cooled to room temperature with a supersonic air flow in which the separated aluminum and oxygen are frozen. As a result, the aluminum and oxygen are separated without recombination. It can be maintained in a state. This fact can be confirmed by measuring the frozen flow with an emission spectrum and observing the peak of the emission spectrum peculiar to aluminum.

  After that, the process moves to the C region on the right side of the figure, and only the isolated aluminum is recovered. In the illustrated example, a cooled copper tube 117 is used, and the oxygen in the separated gas body is released by flowing a fluid therethrough, and aluminum is deposited on the tube wall of the copper tube 117 and recovered. it can. This recovery method is an example, and for example, it is possible to recover by using a filter that transmits oxygen and captures aluminum powder.

  In order to guide and inject an appropriate amount of alumina powder controlled at the time of alumina reduction to the alumina inlet 112, as an example, a mechanism equivalent to the aluminum supply unit 10 shown in FIG. Can do. At this time, the fuel container 12 of FIG. 2 becomes an alumina container, and the fuel discharge pipe 13 is used as the alumina discharge pipe. In the present embodiment, alumina powder having a diameter of about 0.03 to 3 μm can be used, but in order to control the supply amount of alumina powder in a stable state, the alumina powder used for one treatment is It is desirable to select and use the particles having almost the same particle size.

As one of the modifications to the above-described alumina reduction method according to the present embodiment, it is conceivable that hydrogen is contained in the working gas introduced from the working gas inlet 114 to promote alumina reduction using hydrogen. By adding hydrogen, oxygen in the alumina is combined with hydrogen to discharge H ₂ O, but this does not discharge harmful gases to the environment.
_{Al 2 O 3 + 3H = 2Al} + 3H 2 O-112kJ

  When hydrogen is additionally used for reduction of alumina, alumina reduction can be performed with lower energy than in the case where only alumina is directly melted and separated, and the amount of heat can be saved. According to the calculation by the inventors of the present application, in order to perform alumina reduction (20 mg / kJ) with the same amount of heat as electrolysis by the current Hall-Eleu method, in the case of directly thermally dissociating alumina, the laser light calorific value is reduced. If 30% is effectively used, and if hydrogen is added, the same efficiency can be achieved if the heat amount of 4% is actually effectively used. In the alumina reduction method according to the present embodiment, a thermal efficiency of about 35% is possible. Therefore, in any of these cases, efficiency exceeding the Hall-Eru method is achieved, and generation of greenhouse gases is avoided. In addition, the power required for reduction can be saved.

  In the above-described example, the laser beam 114 is used as a heating means when reducing alumina by thermal dissociation instead of electrolysis according to the prior art, but the present invention is not limited to this, A heating means may be used. Examples thereof include arc discharge and inductively coupled plasma. However, when arc discharge is used, the electrodes (tungsten, copper) are consumed, and there is a problem that the operation is limited particularly in an oxygen atmosphere. When inductively coupled plasma is used, the operating pressure is 1 In addition to being restricted to below atmospheric pressure, there is a problem of interference with aluminum which is a generated metal. According to the laser plasma system according to the present embodiment, since there is no consumable part such as an electrode, the operation in an oxygen atmosphere is possible, and the operation pressure can be maintained high (up to about 10 atm), so that the supersonic speed is high. It can be said that it is more suitable for obtaining a frozen flow.

The steady combustion of aluminum shown in the second embodiment was performed with the following contents.
-Carrier gas supply pressure: 110 kPa
-Supply amount of aluminum powder: Equivalent ratio with respect to oxygen amount 0.7
-Supply oxygen temperature: 750K
-Aluminum particle size: 1 μm
-Aluminum combustion chamber temperature: The combustion chamber wall is covered with ceramics and maintained at the 800K target. A mixture of aluminum powder and oxygen is injected from the nozzle under the above conditions and ignited with a torch flame. Combustion was confirmed.

The alumina reduction shown in Embodiment 3 was performed with the following specifications.
-Laser specification: A continuous oscillation type carbon dioxide laser with an output of 1 KW is used. Wavelength: 10.6 μm, beam diameter: 34 mm, lens: f95.
-Throat specification: Throat diameter: 1 mm, nozzle outlet: 10 mm
-Alumina powder flow rate: 10% mass ratio to carrier gas (argon).
-Alumina powder diameter: 3 μm
As a result, emission peaks (257 nm, 309 nm, and 396 nm) indicating the presence of aluminum atoms were observed in the frozen flow, confirming the isolation of aluminum.

  The method of using aluminum as a fuel according to the present invention includes all industries that supply energy mainly for power generation, industries that use power sources such as industrial and marine use, as well as those that generate energy or consume energy. It can be widely used in various industrial fields.

1. 4. Aluminum combustion device 10. Aluminum fuel (aluminum powder) 10. aluminum supply section; Turntable, 12. Fuel container, 13. Fuel discharge pipe, 14. Fuel supply pipe, 16. Carrier gas supply pipe, 17. Motor, 20. Connecting pipe, 30. Aluminum combustion section, 31. Fuel nozzle, 32. Oxygen supply pipe, 33. Ignition mechanism, 34. Switching valve, 40. Combustion chamber, 41. Low thermal conductivity material, 42. Heat exchange section, 50. Power generator, 51. Gas turbine, 52. Compressor, 53. First generator, 56. Heat exchanger, 57. Steam turbine, 58. Second generator, 59. Condenser, 100. Reduction device, 111. Throat section, 112. 114. Alumina inlet, 114. working gas inlet; Laser light, 116. Nozzle, 117. Copper tube.

Claims (6)

In a method of using aluminum as a fuel that burns aluminum and uses the energy generated by the combustion,
Aluminum powder and oxygen are introduced into the combustion chamber to burn aluminum. At this time, the pressure of the carrier gas for introducing the aluminum powder into the combustion chamber is about 100 kPa to 1 MPa, and the supply amount of the aluminum powder is The equivalence ratio with respect to the supply amount of oxygen is set to about 0.2 to 1.1, and the particle size of the aluminum powder is set to about 0.1 to 30 μm so as to control the combustion rate, thereby setting the steady combustion, A method of using aluminum as a fuel, characterized by extracting and utilizing energy generated by steady combustion.   2. The aluminum according to claim 1, wherein the aluminum burning rate is controlled by controlling either one or both of an amount of aluminum powder and an amount of oxygen introduced into the combustion chamber when the aluminum is steadily burned. To use as fuel.   The amount of aluminum powder introduced into the combustion chamber is controlled by controlling the amount of aluminum powder entrained by a jet of carrier gas for introducing the powder into the combustion chamber, or mixed with the aluminum powder. The method of using aluminum as a fuel according to claim 2, wherein the method is performed by controlling the amount of impurities.   4. The method of using aluminum as a fuel according to claim 3, wherein the impurity is alumina powder, water, or water vapor.   The method of using aluminum as a fuel according to claim 2, wherein the amount of oxygen introduced into the combustion chamber is controlled by controlling a mixing ratio with the amount of dilution gas introduced simultaneously with oxygen. . The method of using aluminum as a fuel according to claim 1, wherein the means for taking out the amount of heat generated during the steady combustion comprises driving one or both of a gas turbine and a steam turbine with combustion gas.

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