Operation method for rotary kiln and thermal treatment device

Abstract

To provide an operation method for a rotary kiln capable of removing deposits formed on a furnace wall surface in the rotary kiln without stopping an operation.SOLUTION: An operation method for a rotary kiln includes a heating process of irradiating and heating deposits formed on a furnace wall surface in the rotary kiln with microwaves.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for operating a rotary kiln and a heat treatment device. [Background technology]

[0002] Patent Document 1 discloses a method for operating a rotary kiln in ferronickel smelting, which dries and partially reduces a raw material nickel oxide ore, characterized in that a scoop feeder is provided midway through the rotary kiln, and coal with a moisture content of 2 to 5% by weight is fed into the rotary kiln through the scoop feeder. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-141719 A Summary of the Invention [Problem to be solved by the invention]

[0004] A rotary kiln has a roughly cylindrical shape, and typically, the raw material to be treated is loaded into one end, and heated from the other end by a heating means such as a burner. The rotary kiln is positioned so that the other end is lower, and as it rotates around the central axis, the loaded material is heated as it gradually moves toward the other end. The product obtained after the heat treatment is then discharged from an outlet provided at the other end.

[0005] During the operation of a rotary kiln, the raw materials supplied may melt in part at a high temperature near the heating means provided at the other end, adhere to the furnace wall, and form a deposit called a ring. The deposit may be formed, for example, in a ring shape on the furnace wall surface inside the rotary kiln, and as the deposit grows, the rotary kiln may become clogged. When the rotary kiln becomes clogged due to the deposit, the movement of the raw materials is hindered, making it impossible to continue operation.

[0006] To remove the solidified material adhering to the furnace walls, it was necessary to physically remove the solidified material by poking it with a stick or impacting the entire rotary kiln, or to bring a small burner into the furnace after stopping the heating means to melt the solidified material.

[0007] In view of the problems associated with the above-mentioned conventional techniques, one aspect of the present invention aims to provide a method for operating a rotary kiln that can remove deposits formed on the furnace wall surface inside the rotary kiln without stopping operation. [Means for solving the problem]

[0008] In order to solve the above problem, according to one aspect of the present invention, A method for operating a rotary kiln is provided, which includes a heating step in which microwaves are used to irradiate and heat deposits formed on the furnace wall surface inside the rotary kiln. Effect of the Invention

[0009] According to one aspect of the present invention, a method for operating a rotary kiln can be provided that can remove deposits formed on the surface of a furnace wall inside the rotary kiln without stopping operation. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a heat treatment apparatus according to an embodiment of the present invention. [Diagram 2]FIG. 2 is a cross-sectional view taken along line AA' in FIG. [Diagram 3] FIG. 3 is a cross-sectional view taken along line BB' in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the form for carrying out the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiment, and various modifications and substitutions can be made to the following embodiment without departing from the scope of the present invention. [How to operate a rotary kiln] The method for operating a rotary kiln according to this embodiment may include a heating step of irradiating microwaves to the deposits formed on the furnace wall surface in the rotary kiln to heat them.

[0012] According to the method for operating a rotary kiln of this embodiment, even if a deposit, also called a ring, is formed on the surface of the furnace wall in the rotary kiln, the deposit can be selectively heated by microwaves, and therefore the deposit can be peeled off and removed from the furnace wall without stopping the operation of the rotary kiln.

[0013] The configuration of a heat treatment device to which the rotary kiln operating method of this embodiment can be suitably applied will be described, and then the rotary kiln operating method of this embodiment will be described. (1) Heat treatment equipment An example of the configuration of a heat treatment device including a rotary kiln that can suitably carry out the rotary kiln operating method of this embodiment will be described with reference to Figs. 1 to 3. Fig. 1 is a perspective view of a heat treatment device 10, Fig. 2 is a cross-sectional view taken along line AA' in Fig. 1, and Fig. 3 is a cross-sectional view taken along line BB' in Fig. 2. All of these are schematic views for explaining the configuration of the device, and do not accurately indicate the size, etc. Also, in Figs. 2 and 3, the illustration of an overhead line 1053, which will be described later, is omitted. (1-1) About rotary kilns The heat treatment device 10 shown in FIG. 1 has a rotary kiln 100. The body 101, which is the furnace body of the rotary kiln 100, has a substantially cylindrical shape, and the body 101 is configured to be rotatable around a central axis CA parallel to the X-axis in the figure. The rotary kiln 100 is provided with a downward inclination from an inlet end 102, which is one end in the longitudinal direction, to a discharge end 103, which is the other end in the longitudinal direction. Therefore, the material to be treated, which is the raw material introduced from the inlet end 102 side, moves inside the rotating body 101 to the discharge end 103 side. That is, the X-axis direction in FIG. 1 is the conveying direction of the raw material. As described later, a burner 104 is provided on the discharge end 103 side, and the combustion heat of the fossil fuel burned by the burner 104 moves in the opposite direction to the movement direction of the raw material to be treated, that is, from the discharge end 103 side to the inlet end 102 side, thereby countercurrent heating the material to be treated.

[0014] The rotary kiln 100 has an inlet 1021 at an introduction end 102 which is one end in the longitudinal direction, and the material to be treated, which is the raw material, can be charged into the body portion 101 from the inlet 1021.

[0015] A discharge chute, which is a discharge port 1031, is provided at the other longitudinal end of the rotary kiln 100, and can be configured to discharge the workpieces that have completed the heat treatment inside the body 101. The workpieces that have completed the heat treatment can be transported to an apparatus such as an electric furnace for other processing as necessary. In addition, a burner 104 is provided at the discharge end 103, which can burn fossil fuels such as heavy oil to heat the workpieces and the like that have been placed inside the body 101 of the rotary kiln 100. (1-2) Microwave irradiation equipment The microwave irradiating device 105 can be configured so that, when an adherent matter 31 of raw materials or the like is formed, the adherent matter 31 can be irradiated with microwaves.

[0016] As shown in FIG. 3, the microwave irradiation device 105 can have an oscillator 1051 that generates microwaves, and a waveguide 23 that guides the microwaves generated by the oscillator 1051 into the rotary kiln.

[0017] The oscillator 1051 may be any device capable of oscillating microwaves, and may be, for example, a gyrotron, a magnetron, a klystron, a traveling wave tube, or the like. In this specification, microwaves refer to electromagnetic waves having a frequency of 300 MHz or more and 30 GHz or less, and the frequency of the microwaves oscillated by the oscillator 1051 may be a frequency that can be used for heating in accordance with regulations such as the Radio Law, and that is selected according to the raw materials and additives used. The output of the oscillator 1051 is not particularly limited, and may be selected according to the types of raw materials and additives, the heating temperature, and the like, and is preferably, for example, 1 kW or more.

[0018] The oscillator 1051 is preferably provided so as not to impede the rotation of the body 101 of the rotary kiln 100 as shown in Fig. 1, and can be provided, for example, on the outer surface of the body 101 as shown in Fig. 1. It is preferable to provide a heat insulating material or the like on the surfaces of the oscillator 1051 and the waveguide 23 so that they are not damaged by the heat of the rotary kiln 100.

[0019] As shown in FIG. 3, one end of the waveguide 23 is connected to the oscillator 1051, and the other end 23A is disposed within the rotary kiln 100. The waveguide 23 may be any structure capable of guiding microwaves, and may be, for example, a tubular waveguide or an electric wire. When the waveguide is a waveguide, it is preferable to dispose a microwave-transmitting plate at the end 23A disposed within the rotary kiln 100 so that raw materials and additives do not enter the waveguide. The material of the microwave-transmitting plate is not particularly limited, and may be, for example, one or more selected from quartz, alumina, zirconia, magnesia, silicon carbide, and the like.

[0020] Then, the microwaves that have passed through the waveguide 23 can be irradiated from the end 23A of the waveguide 23 that is arranged inside the rotary kiln 100. For this reason, the end 23A of the waveguide 23 that is arranged inside the rotary kiln 100 is preferably arranged at a position where the microwaves can be irradiated to the adherent material formed inside the rotary kiln 100.

[0021] The direction of microwave irradiation from the waveguide 23 is not limited as long as it is selected so that at least a portion of the adhering matter formed in the rotary kiln 100 can be irradiated.

[0022] The deposits are formed when a part of the raw materials melts in a high-temperature area near the burner 104, which is the heating means of the rotary kiln 100, and adheres (adheres) to the furnace wall. For this reason, the end 23A of the waveguide 23 can be directed toward the discharge end 103, for example, as shown in FIG. 3.

[0023] However, the position where the stuck matter occurs is not always constant, and may change depending on the operating conditions of the rotary kiln 100. Therefore, it is preferable that the microwave irradiating device 105 has a position changing device 24 that changes the position of the end 23A of the waveguide 23 arranged in the rotary kiln 100. By having the position changing device 24, the microwave irradiating device 105 can more appropriately heat and remove the stuck matter.

[0024] The configuration of the position changing device 24 is not particularly limited. For example, a rotary joint or the like can be used as the position changing device. The position changing device 24 may also be configured to have a rod-shaped body that supports the end 23A from the outer surface of the body 101 of the rotary kiln 100, and to change the position of the rod-shaped body to change the position of the end 23A. In this case, it is preferable that the waveguide 23 is configured to be deformable, and for example, a waveguide having a bellows structure or an electric wire can be used as the waveguide 23.

[0025] The position of the adhered matter formed in the rotary kiln 100 can be detected by observing it with an imaging device such as a camera arranged in the rotary kiln 100. The position of the adhered matter can also be detected from the temperature and temperature distribution measured by a temperature measuring device such as a thermocouple or a radiation thermometer installed on the outer wall of the rotary kiln 100.

[0026] When the adherent matter 31 is formed on the inner wall of the rotary kiln 100, the temperature distribution changes at the portion of the adherent matter 31 on the outer wall of the rotary kiln 100. Therefore, the position of the adherent matter 31 can be identified by measuring the temperature and temperature distribution of the outer wall of the rotary kiln 100 as described above.

[0027] Therefore, the heat treatment device 10 of this embodiment may also have one or more types selected from an imaging device installed in the rotary kiln 100 to detect the position of the adherent matter, and a temperature measuring device that measures the temperature or temperature distribution of the outer wall of the rotary kiln 100.

[0028] Then, the position changing device 24 can change and adjust the position of the end 23A of the waveguide 23 so that the fixed object 31, the position of which has been detected, can be irradiated with microwaves.

[0029] In addition, in order to supply power to the oscillator 1051 of the microwave irradiation device 105, the microwave irradiation device 105 may also have an overhead line 1053 and a current collector 1052. The overhead line 1053 may be arranged along the outer periphery of the rotary kiln 100 and may be connected to a power supply source (not shown). The current collector 1052 may be in contact with the overhead line 1053 to obtain power through the overhead line 1053. The configuration of the current collector 1052 is not particularly limited, but may have, for example, a conductive sliding part that contacts the overhead line 1053 and an expandable part that displaces the position of the sliding part and presses it against the overhead line 1053, and may have a configuration similar to that of a pantograph used in trains and the like.

[0030] 1 to 3 show an example in which one microwave irradiating device 105 is disposed near one of the scoop feeders 130, but the heat treatment device 10 of this embodiment may have multiple microwave irradiating devices depending on the degree of heating, etc. (1-3) Scoop feeder The heat treatment device 10 may also have a scoop feeder in the middle of the rotary kiln 100, i.e., between the inlet end 102 and the outlet end 103. This will be described with reference to FIG. 2, which shows a cross section taken along a plane perpendicular to the central axis CA at the position where the scoop feeder is provided, i.e., a cross section taken along line AA'.

[0031] As shown in Fig. 2, the rotary kiln 100 can have a rotating body 101 and an outer shell 110 that covers the body 101. Note that the outer shell 110 does not need to be provided so as to cover the entire surface of the body 101, and can be provided only where necessary, such as where a scoop feeder is provided, as shown in Fig. 1.

[0032] The material to be treated 21 is introduced into the body portion 101 through an inlet 1021 and can move toward the discharge end 103 as the body portion 101 rotates.

[0033] A space 120 is formed between the body 101 and the outer shell 110, and additives can be supplied to the space 120 via an additive supply port 111 provided in the outer shell 110. The additive supply port 111 can be connected to additive supply means 221 for supplying various additives as required.

[0034] The additive added by the additive supplying means 221 is not particularly limited, but may be, for example, one or more types selected from a reducing agent and an anti-fusing agent.

[0035] The configuration of the additive supplying means 221 is not particularly limited, and may be configured so that the opening degree of the opening provided on the additive supply port 111 side can be adjusted according to the supply amount of the additive, so that the supply amount of the additive that falls freely through the opening can be adjusted. Also, it may be configured so that it has a conveying means such as a screw conveyor, and the conveying speed of the additive by the conveying means can be adjusted, so that the supply amount of the additive can be adjusted by the conveying speed.

[0036] The scoop feeder 130 can be formed, for example, of an L-shaped pipe having a bent portion between a tip portion 131 and a straight portion 132.

[0037] The scoop feeder 130 can rotate clockwise (right-handed) together with the body portion 101, for example, as shown by the arrow in Fig. 2. During such rotation, the tip portion 131 can scoop up the additive material 22 supplied to the space portion 120, and the scooped additive material 22 can be passed through the straight portion 132 and fed into the body portion 101.

[0038] In the rotary kiln 100, the location where the scoop feeder is provided is not particularly limited, and the scoop feeder can be provided at any location depending on the temperature distribution inside the body portion 101 of the rotary kiln 100, the type of additive to be added, and the like.

[0039] The location where the scoop feeder is provided is not particularly limited. For example, the distance L110 from the discharge end 103 to the end of the outer shell 110 on the side of the introduction end 102 where the scoop feeder is provided is preferably 5% to 95% of the length L101 of the body 101 of the rotary kiln 100 in the longitudinal direction, more preferably 10% to 90%. (2) Operating conditions of rotary kilns The operating conditions of the rotary kiln are not particularly limited and can be arbitrarily selected depending on the type of material to be treated, that is, the raw material, the treatment to be carried out, and the like.

[0040] As described above, the heat treatment device 10 can also perform reduction treatment and the like.

[0041] The rotation speed of the rotary kiln 100, i.e., the rotation speed of the body portion 101 that constitutes the rotary kiln 100, is not particularly limited, but is preferably, for example, about 0.5 rpm or more and 1.5 rpm or less.

[0042] By setting the rotation speed of the rotary kiln 100 to 0.5 rpm or more, the stirring force in the rotary kiln 100 can be sufficiently increased, and the reaction can be sufficiently advanced while exposing additives and the like added during the reaction. In addition, by setting the rotation speed of the rotary kiln 100 to 0.5 rpm or more, it is possible to reduce deformation due to its own weight when the kiln body becomes soft due to high temperatures.

[0043] In addition, by setting the rotation speed of the rotary kiln to 1.5 rpm or less, the raw materials, i.e., the materials to be treated, introduced into the rotary kiln 100 can remain in the rotary kiln 100 for a sufficient period of time, thereby ensuring the desired heat treatment time. (3) About each process (3-1) Heating process In the heating process, the deposits formed on the furnace wall surface in the rotary kiln can be heated by irradiating them with microwaves.

[0044] In the heating step, microwaves can be irradiated from end 23A of waveguide 23 using microwave irradiation device 105 described above.

[0045] There is no particular limitation on the position and area of ​​the fixed object 31 to be irradiated with microwaves. However, in order to more efficiently heat and remove the fixed object 31, it is preferable to irradiate the microwaves in the heating step so that the microwave irradiation area includes the portion 311A ​​of the fixed object 31 located at the upper part in the rotary kiln, which is in contact with the rotary kiln.

[0046] By irradiating microwaves to the upper adherent 311, which is the adherent 31 located at the upper part of the rotary kiln, so that the irradiated area of ​​the microwaves includes the part 311A ​​in contact with the rotary kiln, the temperature of the part of the adherent close to the furnace wall is increased and the viscosity is reduced. By reducing the viscosity of the adhesive part between the furnace wall and the adherent 31 located at the upper part of the rotary kiln, the adherent can be dropped by its own weight and easily removed. This makes it possible to more reliably avoid troubles in which the adherent grows large and leads to clogging.

[0047] Since the rotary kiln 100 rotates, the adhered matter 31 located at the upper part inside the rotary kiln changes over time. Therefore, the part of the adhered matter located at the upper part inside the rotary kiln that contacts the rotary kiln means the part of the adhered matter located at the upper part inside the rotary kiln that contacts the rotary kiln during microwave irradiation.

[0048] 1 to 3 show an example in which one microwave radiating device 105 is disposed near one scoop feeder 130, but it may be similarly disposed near the other scoop feeder 130, etc.

[0049] As described above, the frequency of the microwaves used is not particularly limited, and can be selected according to the raw materials and additives used and can be used for heating in accordance with regulations such as the Radio Law.

[0050] The rotary kiln operating method of the present embodiment may include any step other than the heating step. The optional step will be described below. (3-2)Additive addition process As described above, the heat treatment device 10 can have a scoop feeder 130 between both ends in the longitudinal direction of the rotary kiln 100. The rotary kiln operating method of this embodiment can also have an additive introduction step of introducing additives into the rotary kiln, specifically into the raw materials in the body portion undergoing heat treatment, via the scoop feeder.

[0051] The additive introduction step can be carried out at any timing depending on the type of additive to be added, etc. (Regarding additives) The type of additive added in the additive introduction step is not particularly limited, and may be one or more selected from the reducing agent and the anti-fusing agent as described above. It is particularly preferable that the additive contains a reducing agent.

[0052] The reducing agent may be a carbon-containing material such as coal, wood pellets, or waste plastic.

[0053] The anti-fusing agent may be any material capable of preventing the raw material to be treated from adhering to the inner wall of the rotary kiln 100 to form a deposit and growing in a ring shape, and may be, for example, a ceramic material with a high melting point. By using a ceramic material with a high melting point as the anti-fusing agent, it is possible to coat the molten material to be treated, preventing the material from adhering to the inner wall of the furnace and growing into a deposit.

[0054] The anti-fusing agent can be selected according to the material to be treated so as not to adversely affect the components of the material to be treated, and is not particularly limited. It is preferable that the anti-fusing agent contains one or more types selected from, for example, silicon oxide, aluminum oxide, calcium oxide, and magnesium oxide. (About ingredients) The material to be treated, which is the raw material used in the rotary kiln operating method of this embodiment, is not particularly limited, and examples thereof include ores containing various metal components and ceramic raw materials.

[0055] In particular, the material to be treated may be various ores. In particular, metal ores that are required to be refined generally contain a lot of moisture and are oxidized. According to the rotary kiln operating method of this embodiment, various reducing agents are used to efficiently perform drying and reduction, so the material to be treated preferably includes metal ores. The material to be reduced may be composed of metal ores.

[0056] The metal contained in the metal ore is not particularly limited, but is preferably a metal containing a non-ferrous metal, and more preferably an ore containing one or more metals selected from nickel, zinc, etc.

[0057] In ferronickel refining, the ore (dried ore) from which part of the moisture adhering to the raw material nickel oxide ore has been removed by a dryer may be further subjected to a drying treatment and a reduction treatment. Therefore, the rotary kiln operating method of the present embodiment can suitably use nickel oxide ore as the raw material to be treated.

[0058] The nickel oxide ore (nickel oxide ore) is not particularly limited, but garnierite ore, etc. is preferably used. A typical composition of this garnierite ore is, in terms of dry ore, a Ni content of 2.1 mass% or more and 2.5 mass% or less, an Fe content of 11 mass% or more and 23 mass% or less, an MgO content of 20 mass% or more and 28 mass% or less, an SiO2 content of 29 mass% or more and 39 mass% or less, a CaO content of less than 0.5 mass%, and an ignition loss of 10 mass% or more and 15 mass% or less.

[0059] The object to be treated may be pre-dried in advance to reduce or remove some of the adhering moisture. (3-3) Adherence detection process, irradiation position adjustment process The rotary kiln operating method of this embodiment may also include a stuck-matter detection step of detecting the formation of stuck matter on the inner wall, which is the furnace wall surface inside the rotary kiln, or detecting the position of the stuck matter.

[0060] The formation of the stuck matter and the location of the stuck matter can be detected by observing the inside of the rotary kiln with an imaging device such as a camera, or by measuring the change in the temperature distribution on the outer wall of the rotary kiln.

[0061] When carrying out the stuck-on object detection process, an irradiation position adjustment process can also be carried out before or after starting the heating process, in which the position of the end 23A of the waveguide 23 is changed or adjusted depending on the position of the detected stuck object 31. [Heat treatment equipment] The heat treatment device of this embodiment may include a rotary kiln and a microwave irradiation device.

[0062] The microwave irradiation device can irradiate microwaves to deposits formed on the furnace wall surface inside the rotary kiln.

[0063] According to the heat treatment device of this embodiment, the above-mentioned rotary kiln operation method can be implemented, and therefore, the description of the matters already explained will be omitted.

[0064] The heat treatment device of this embodiment may also have a scoop feeder, which may be disposed between both ends of the rotary kiln in the longitudinal direction.

[0065] Since suitable configurations of the rotary kiln, microwave irradiation device, and scoop feeder have already been described, the description thereof will be omitted.

[0066] According to the heat treatment device of the present embodiment described above, the microwave irradiation device can irradiate the adhering matter with microwaves and heat it. Therefore, the adhering matter formed on the furnace wall surface in the rotary kiln can be removed without stopping the operation. [Explanation of symbols]

[0067] 10 Heat treatment device 100 Rotary Kiln 101 Torso 102 Introductory end 1021 Inlet 103 Discharge end 1031 Outlet 104 Burner 105 Microwave irradiation device 1051 Oscillator 1052 Current collector 1053 Overhead Line 110 Outer shell 111 Additive supply port 120 Space section 130 Scoop Feeder 131 Tip 132 Straight section 21 Processing object 22 Additives 221 Additive supply means 23 Waveguide 23A end 24 Position change device CA center axis L110 distance L101 Length 31 Sticking 311A part 311 Upper fixation

Claims

1. A method for operating a rotary kiln, comprising a heating step of irradiating with microwaves deposits formed on the furnace wall surface inside the rotary kiln to heat them.

2. A method for operating a rotary kiln as described in claim 1, wherein in the heating step, microwaves are irradiated so that the microwave irradiation area includes a portion of the adherent material located at the upper part in the rotary kiln that contacts the rotary kiln.

3. The method for operating a rotary kiln according to claim 1 or claim 2, further comprising a scoop feeder between both longitudinal ends of the rotary kiln, and an additive introduction step of introducing an additive into the raw materials in the rotary kiln via the scoop feeder.

4. 3. The method for operating a rotary kiln according to claim 1 or 2, wherein the raw material supplied to the rotary kiln is nickel oxide ore.

5. Rotary kiln and A heat treatment device having a microwave irradiation device that irradiates microwaves to the deposits formed on the furnace wall surface in the rotary kiln.

6. The microwave irradiation device includes an oscillator that generates microwaves, a waveguide that guides the microwaves generated by the oscillator into the rotary kiln, and a position changing device that changes the position of an end of the waveguide that is arranged in the rotary kiln. The heat treatment device according to claim 5.

7. The heat treatment device according to claim 5 or 6, wherein the microwave irradiation device comprises: an overhead line arranged along an outer periphery of the rotary kiln; and a current collector that contacts the overhead line to acquire electric power through the overhead line.

8. 7. The heat treatment apparatus according to claim 5, further comprising a scoop feeder disposed between both ends of the rotary kiln in the longitudinal direction.

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