JP2013011384A - Microwave heating furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microwave heating furnace which can produce molten pig iron at high energy efficiency in place of a blast furnace pig iron production method, can recover noble metal or the like from a so-called urban mine, and can manufacture a silicon substrate at high efficiency.SOLUTION: A microwave beam is irradiated toward a reaction vessel 11 of a melting furnace 10 which is arranged in a cylinder center of a cylindrical support plate from the cylindrical support plate, and increases power density during the irradiation. The microwave beam is introduced into the melting furnace 10 from a microwave window 14 of the melting furnace 10, reflected on a sub-reflecting mirror 16, progresses toward a main reflecting mirror 13, is reflected at the main reflecting mirror 13 and progresses toward an accommodated material 12 in a vessel space of the reaction vessel 11. Infrared light is emitted from the accommodated material 12 and the reaction vessel 11, and on the other hand, the infrared light is reflected by a step reflecting face 15 formed at a part of the main reflecting mirror 13, and returned to the accommodated material 12. The microwave beam and the infrared light are confined in a clearance between the main reflecting mirror 13 and the reaction vessel 11, and the accommodated material 12 is heated.

Description

  The present invention relates to a microwave smelting furnace such as an iron making furnace that obtains pig iron from iron ore, or a microwave heating furnace such as a melting furnace or a sintering furnace, and in particular, a carbon source such as iron ore and coal or coke by microwaves. A microwave smelting furnace that heats and melts raw materials containing iron and reduces iron ore with carbon to obtain molten pig iron, a so-called melting furnace that recovers precious metals and rare metals from urban mines, and silicon to produce silicon substrates The present invention relates to a microwave heating furnace suitable for use in a sintering furnace for sintering powder.

  In the field of steel, molten pig iron is usually obtained by a blast furnace ironmaking method. That is, iron ore that is iron oxide and coke as a carbon source that is the reducing agent and limestone pellets are charged into the blast furnace (blast furnace) from the top, and hot air is blown from the tuyeres at the bottom of the blast furnace. (Air) is blown to form an upward flow of hot air in the blast furnace, and the falling pellets are heated by hot air, and the iron ore is reduced by the reaction between iron ore and coke. The reduced iron melts and becomes molten pig iron and accumulates at the bottom of the blast furnace. After a certain amount of pig iron is stored, pig iron at the bottom of the furnace is taken out from the hot water outlet at the bottom of the furnace, flows through the runner, and is stored in a ladle (for example, Patent Document 1).

However, in the conventional blast furnace ironmaking method, the reduction or melting of iron ore takes 6 hours or more at a temperature of about 1500 ° C. or more, and the production efficiency is low, and 2 tons of CO ₂ gas per ton of pig iron. There is a problem of discharging.

On the other hand, Patent Document 2 discloses a method for producing iron powder by heating and reducing iron oxide using microwaves. This iron powder manufacturing method includes iron ore and milled iron oxide, a carbon source which is a microwave high derivative mainly composed of carbon such as coke, char charcoal, activated carbon and pulverized coal, and calcium carbonate. , And carbonates such as magnesium carbonate and sodium carbonate are mixed, and the mixture is irradiated with microwaves to cause the carbon source to generate heat internally to a temperature exceeding 900 ° C., and CO generated by pyrolysis of the carbonate in the mixture. This is a method for producing iron powder by reacting with _two gases to convert to CO gas and reducing iron oxide with this CO gas.

However, in the method for producing iron powder using microwaves described in Patent Document 2, a mixture of an iron oxide such as iron ore, a carbon source such as coke and a carbonate is heated by microwaves, and the carbon source Is heated to a temperature exceeding 900 ° C., CO ₂ gas decomposed from the carbonate in the mixture is reacted with a carbon source to generate CO gas, and this CO gas reduces iron oxide. It does not melt iron ore or coke. Therefore, this method can only produce iron powder and cannot efficiently produce a large amount of molten pig iron.

  Therefore, the inventors of the present application have previously proposed a technique capable of producing a large amount of molten pig iron with high efficiency using a microwave (Patent Document 3).

JP-A-11-229007 JP-A-6-116616 JP 2007-205639 A

  In the conventional microwave smelting furnace described in Patent Document 3, iron ore and coke are melted only by microwaves, and the intended purpose has been achieved, but for the practical application of microwave smelting, A further increase in heating efficiency is desired.

  The present invention has been made in view of such problems, and instead of the blast furnace ironmaking method, it can produce molten pig iron with high energy efficiency, and can recover precious metals and the like from so-called city mines, Furthermore, it aims at providing the microwave heating furnace which can manufacture a silicon substrate with high efficiency.

The microwave heating furnace according to the present invention is
A reaction vessel for storing, melting and smelting raw materials;
A microwave unit disposed on an inner surface of a circumferential surface surrounding the reaction vessel and emitting a microwave beam toward a specific point in the reaction vessel;
A main reflector that is disposed above the reaction vessel and whose paraboloid focusing on the specific point is a microwave reflecting surface;
It is characterized by having.

  In this microwave heating furnace, it is preferable that the main reflecting mirror has a step reflection surface in which a part of the paraboloid is stepped on the paraboloid.

  Further, for example, the width of the stepped reflection surface in the circumferential direction of the paraboloid is 5 to 50 times the infrared wavelength, and the stepped reflection surface reflects light having a wavelength of visible light from infrared rays. And microwaves with a frequency of 1 to 100 GHz are reflected.

  Furthermore, it is preferable to have a sub-reflecting mirror that is provided at the peripheral edge of the reaction vessel and reflects the microwave incident from the microwave unit toward the main reflecting mirror.

  Furthermore, it is preferable to have an auxiliary reflecting mirror provided at the peripheral portion of the reaction vessel for returning infrared rays and visible rays radiated from the contents in the reaction vessel into the reaction vessel.

  According to the present invention, the raw reflector can be heated with high efficiency by confining the microwave inside the main reflector and using the energy of the microwave with high efficiency. Therefore, in iron making, molten pig iron can be manufactured with high efficiency, and precious metals can be recovered with high efficiency in urban mines. Furthermore, the silicon substrate can be manufactured with high efficiency.

It is a perspective view which shows the melting furnace vicinity of the microwave smelting furnace which concerns on embodiment of this invention. Similarly, it is a figure which shows a level | step difference reflective mirror. Similarly, it is a perspective view showing the whole microwave smelting furnace.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 is a front sectional view showing the vicinity of a melting furnace, and FIG. 3 is a perspective view showing the entire inside of a microwave heating furnace (smelting furnace). As shown in FIG. 3, a microwave unit 3 that radiates a plurality of microwave beams is installed on the inner surface of a support plate 1 that forms a circumferential surface around a melting furnace 10. The unit 3 irradiates the microwave toward the center C of the storage space of the reaction vessel 11 in the melting furnace 10. The support plate 1 has an inner surface that is curved inward in the longitudinal section, and the inner surface is located on a circumference centered on the melting furnace 10 in a plan view and outward in an elevation view. The bulge and the inner surface are slightly curved toward the inner side of the support plate in the vertical direction. The microwave unit 3 is, for example, a 10 kW highly directional microwave source unit in which the semiconductor 500 W module 2 is provided at a lattice position of 4 columns and 5 rows. The microwave unit 3 is a 10 kW wave source combined radial phased array antenna. It constitutes a radiator. The power density of the microwave unit 3 is about an incandescent bulb. The microwave units 3 are arranged on the inner surface of the cylindrical support plate 3 in a plurality of rows in the circumferential direction, for example, in two upper and lower stages. The number of the microwave units 3 is not limited to the above numerical value. As an example, the microwave smelting furnace of this embodiment has an overall height of 3 to 4 m including a melting furnace 10 described later, a diameter of 8 m, and the size of the microwave unit 3 is about 20 cm long and about 25 cm wide. It is.

  In the melting furnace 10, as shown in FIG. 1, a reaction vessel 11 is installed at the center, and in the accommodation space of the reaction vessel 11, when the contents 12 are molten pig iron, Mixed powder such as coke powder, graphite powder and coal powder is charged. This raw material is heated by microwave irradiation, melts, undergoes a smelting reaction, and becomes molten pig iron. The material of the reaction vessel 11 is a refractory material. In addition, the raw material is not limited to iron ore or the like that smelts hot metal, and the containment 12 may be electronic equipment waste as a so-called city mine, and recover precious metals and rare metals by dissolving this waste. Can do. Moreover, when the metal silicon powder is accommodated as the container 12, the metal silicon powder can be heated and sintered. Since the thermal conductivity of the raw material is increased by this sintering, it becomes easy to heat by induction heating and can be efficiently heated.

  A cylindrical microwave window 14 is erected on the periphery of the reaction vessel 11, and a main reflecting mirror 13 is installed above the reaction vessel 11 so as to cover the microwave window 14. ing. The main reflecting mirror 13 has a parabolic surface that forms a parabola in its longitudinal section, and the microwaves reflected by the inner surface forming the parabolic surface gather at the center C that is the focal point of the parabolic surface.

  The main reflecting mirror 13 is formed of a metal that reflects a microwave beam. For example, copper or copper alloy, gold-plated stainless steel, ceramic coated with a conductive film, or the like can be used. Since the reflecting surface of the main reflecting mirror 13 is made of copper, a copper alloy, gold, or a conductive film, the microwave beam can be reflected. The microwave window 14 is formed of glass that transmits a microwave beam. For example, Neoceram (registered trademark) having a small thermal expansion can be used.

  The main reflecting mirror 13 is formed with a step reflecting surface 15 as shown in FIG. FIG. 2 is an enlarged view of point A in FIG. The step reflecting surface 15 is formed by stepping a part of the paraboloid, and the width D in the circumferential direction of the paraboloid is 5 to 50 times the wavelength of infrared rays. Thereby, the infrared rays radiated from the reaction container 11 and the container 12 are reflected by the step reflection surface 15 and returned to the container 12 in the reaction container 11. As described above, the step reflecting surface 15 is formed by a series of minute surfaces having a width D that is 5 to 50 times the infrared wavelength, and has a property of reflecting infrared light and visible light. Accordingly, the inclination angle of the step reflection surface 15 is determined such that the infrared rays radiated from the surface of the molten container 12 and the infrared rays radiated from the surface of the reaction vessel 11 are reflected by the step reflection surface 15 to the container 12. Design to go back. Thereby, the infrared rays radiated from the reaction vessel 11 and the container 12 can be confined between the main reflection surface 13 and the reaction vessel 11. Since the microwave has a long wavelength, it is not affected by the step reflecting surface 15. That is, the microwave beam is reflected toward the focal position of the paraboloid without being affected by the step on the paraboloid of the main reflecting mirror 13. Therefore, even if the step reflection surface 15 is provided over the entire area of the main reflection mirror 13, it does not hinder the reflection of the microwave beam. As shown in FIG. 1, at least the step reflecting surface 15 is provided on the inner surface of the main reflecting mirror 13 in a region where infrared rays radiated from the container 12 and the reaction container 11 reach (at least directly above the container 12 or the like). If provided, infrared rays can be reflected efficiently. The step reflection surface 15 may be a flat surface or may be curved to the same extent as the main reflection surface 13.

  The microwave window 14 is formed of a material that transmits microwaves, and introduces the microwave beam emitted from the microwave unit 3 into the melting furnace 10. The melting furnace 10 has a space surrounded by the reaction vessel 11, the main reflecting mirror 13, and the microwave window 14. The atmosphere inside this space may be an inert gas atmosphere such as nitrogen, It may be an atmospheric atmosphere.

  A sub-reflecting mirror 16 that reflects the microwave beam introduced from the outside through the microwave window 14 toward the main reflecting mirror 13 is formed at the peripheral edge of the reaction vessel 11. The microwave beam reflected by the sub-reflecting mirror 16 is reflected by the main reflecting mirror 13 and gathers toward the center C in the reaction vessel 11.

  Further, infrared rays and visible rays radiated from the liquid surfaces of the reaction container 11 and the container 12, which are the peripheral part of the reaction container 11 and between the container 12 and the sub-reflecting mirror 16, An auxiliary reflecting mirror 17 that reflects toward the main reflecting mirror 13 is provided. Infrared light and visible light reflected by the auxiliary reflecting mirror 17 are reflected by the main reflecting mirror 13 and gathered toward the accommodating portion 12 of the reaction vessel 11.

  Next, the operation of the microwave smelting furnace configured as described above will be described. When producing molten pig iron, powder or lumps of raw materials such as iron ore, coke, graphite, and coal are accommodated in the accommodating space of the reaction vessel 11 and the interior is made into a nitrogen atmosphere, or the atmosphere is kept in an air atmosphere. A microwave beam is irradiated from the wave unit 3 toward the melting furnace 10. The microwave beam travels from the cylindrical support plate 1 toward the reaction vessel 11 of the melting furnace 10 disposed at the center of the cylinder, and during this time, the power density is increased. In the present embodiment, the microwave unit 3 is arranged with its emission direction directed toward the circumferential center of the support plate 1 and the inner surface of the support plate 1 is curved up and down. The direction of the emitted microwave beam is directed to the reaction vessel 11 arranged at the center of the support plate 1 in the vertical direction as well as the horizontal direction. For this reason, the power density of the microwave beam can be significantly increased in the vicinity of the reaction vessel 11. The support plate 1 does not necessarily have a shape that extends in the circumferential direction and swells in the vertical direction, but the microwave is emitted so that the emission direction of the microwave beam of the microwave unit 3 is directed to the reaction vessel 11. If the unit 3 is installed, the power density of the microwave beam can be increased.

  Then, the microwave beam with the increased power density is introduced into the melting furnace 10 from the microwave window 14 of the melting furnace 10, reflected by the sub-reflecting mirror 16 and directed to the main reflecting mirror 13, and by the main reflecting mirror 13. Reflected toward the contents in the container space of the reaction vessel 11. In particular, since the main reflecting mirror 13 forms a paraboloid, this microwave beam gathers toward the focal position (center C) of the paraboloid. As a result, the raw material is heated by being irradiated with high-density microwaves and melted. Due to the melting of the raw material, the iron ore is reduced by the carbon to become pig iron, and the molten pig iron is stored in the reaction vessel 11 as the storage 12.

  From the molten pig iron and the reaction vessel 11, infrared rays are radiated. The infrared rays are reflected by the step reflecting surface 15 provided in a part of the main reflecting mirror 13 and return to the accommodation 12. The microwave beam applied to the container 12 is also reflected by the container 12, then travels toward the main reflecting mirror 13, is reflected by the main reflecting mirror 13, and returns to the container 12. In this way, the microwave beam and infrared rays are confined around the container 12 in the reaction vessel 11, and the container 12 is heated with high efficiency. Therefore, pig iron can be smelted from iron ore with high efficiency. In the case of the microwave heating furnace of the above-mentioned size, it is possible to produce 1000 tons of molten pig iron per day.

  In addition, waste of electronic equipment can be heated with high efficiency to recover precious metals and rare metals.

  Furthermore, by heating and sintering the metal silicon powder in the microwave heating furnace of this embodiment, the sintered body has a higher thermal conductivity than the powder. By induction heating the bonded body in an induction heating furnace, it can be dissolved with high efficiency. And the ingot which this molten silicon solidified can be sliced into a silicon substrate, and it can be set as the silicon substrate used for a solar cell. Conventionally, since the silicon substrate of the solar cell was manufactured in an electric furnace, a great deal of time was required for manufacturing, but by heating with the microwave heating furnace of this embodiment, The silicon substrate can be efficiently melted, and the silicon substrate can be manufactured in 1/10 of the conventional time, and the input energy can be reduced accordingly.

  INDUSTRIAL APPLICABILITY The present invention is extremely effective for steel smelting with low energy and recovery of precious metals and rare metals in city mines.

1: Support plate 2: Semiconductor 500W module 3: Microwave unit 10: Melting furnace 11: Reaction vessel 12: Containment 13: Main reflector 13a: Area 14: Microwave window 15: Step reflector 16: Sub reflector 17 : Auxiliary reflector

Claims (5)

A reaction vessel for storing, melting and smelting raw materials;
A microwave unit disposed on an inner surface of a circumferential surface surrounding the reaction vessel and emitting a microwave beam toward a specific point in the reaction vessel;
A main reflector that is disposed above the reaction vessel and whose paraboloid focusing on the specific point is a microwave reflecting surface;
A microwave heating furnace characterized by comprising: The microwave heating furnace according to claim 1, wherein the main reflecting mirror has a stepped reflecting surface in which a part of the paraboloid is stepped on the paraboloid. The width of the stepped reflecting surface in the circumferential direction of the parabolic surface is 5 to 50 times the infrared wavelength, and the stepped reflecting surface reflects light having a wavelength of visible light from infrared, and the reflecting surface has a frequency of 1 The microwave heating furnace according to claim 2, wherein microwaves of up to 100 GHz are reflected. 4. The sub-reflector according to claim 1, further comprising a sub-reflector provided at a peripheral portion of the reaction vessel and configured to reflect the microwave incident from the microwave unit toward the main reflector. The microwave heating furnace as described. 5. An auxiliary reflecting mirror provided at a peripheral portion of the reaction vessel for returning infrared rays and visible rays radiated from the contents in the reaction vessel into the reaction vessel. The microwave heating furnace of any one of these.

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