Rotary kiln operation method, heat treatment equipment

Abstract

To provide a rotary kiln operation method which is capable of heating an additive material to be added in the middle of a rotary kiln.SOLUTION: Provided is a rotary kiln operation method in which scoop feeders are provided between both end parts in a longitudinal direction of a rotary kiln. The rotary kiln operation method includes an addition material input step of inputting an addition material into raw material inside the rotary kiln through the scoop feeders and an addition material heating step of irradiating the addition material with microwaves so as to be heated while the addition material passes through the scoop feeders and inputted into the raw material at the inside of the rotary kiln.SELECTED DRAWING: Figure 1

Description

Technical Field

[0006] , ,

[0005] ,

[0001] The present invention relates to an operating method of a rotary kiln and a heat treatment apparatus.

Background Art

[0002] Patent Document 1 discloses an operating method of a rotary kiln for drying and partially reducing nickel oxide ore as a raw material in ferronickel smelting, wherein a scoop feeder is provided in the middle of the rotary kiln, and coal with a moisture content of 2 to 5% by weight is introduced into the rotary kiln through the scoop feeder.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The rotary kiln has a substantially cylindrical shape. Usually, the object to be processed as a raw material is introduced from one end side, and heated by heating means such as a burner from the other end side. The rotary kiln is arranged such that the other end side is lower, and by rotating about the central axis, the introduced object to be processed is heated while gradually moving to the other end side. Then, the product obtained after the heat treatment is discharged from the discharge port provided on the other end side.

[0005] For example, as disclosed in Patent Document 1, a scoop feeder is provided in the middle of the rotary kiln, and an additive is added into the rotary kiln through the scoop feeder.

[0006] However, when additives with high water content or volatile components were added to the rotary kiln midway through the process via a scoop feeder, problems such as the additives absorbing heat from the raw materials in the rotary kiln and preventing the reaction from proceeding sufficiently could occur.

[0007] Therefore, in view of the problems of the above-mentioned prior art, one aspect of the present invention aims to provide a rotary kiln operation method that allows for the heating of additives added during the rotary kiln process. [Means for solving the problem]

[0008] To solve the above problems, according to one aspect of the present invention, The rotary kiln has scoop feeders between its longitudinal ends, and the process includes an additive feeding step in which additives are introduced into the raw material inside the rotary kiln via the scoop feeders, During the time that the additive passes through the scoop feeder and is fed into the raw material in the rotary kiln, the additive undergoes a process that Using a microwave irradiation device The process involves heating the additive by irradiating it with microwaves. death, The microwave irradiation apparatus comprises an oscillator that emits microwaves, a waveguide that guides the microwaves emitted by the oscillator into the rotary kiln, including the scoop feeder, and a position changing device that changes the position of the end of the waveguide located inside the rotary kiln. This document provides a method for operating a rotary kiln. [Effects of the Invention]

[0009] According to one aspect of the present invention, a method for operating a rotary kiln is provided that allows for heating of additives added during the rotary kiln process. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic diagram of a heat treatment apparatus according to an embodiment of the present invention. [Figure 2] Figure 2 is a cross-sectional view along line AA' in Figure 1. [Figure 3] Figure 3 is a cross-sectional view along line BB' in Figure 2. [Modes for carrying out the invention]

[0011] The embodiments for carrying out the present invention will be described below with reference to the drawings, but the present invention is not limited to the embodiments described below, and various modifications and substitutions can be made to the embodiments described below without departing from the scope of the present invention. [Rotary Kiln Operation Method] The rotary kiln operation method of this embodiment may include an additive input step and an additive heating step.

[0012] The additive feeding process involves having a scoop feeder between the longitudinal ends of the rotary kiln, through which the additive can be fed into the raw material inside the rotary kiln.

[0013] The additive heating process allows the additive to be heated by irradiating it with microwaves while it is passing through the scoop feeder and before it is fed into the raw materials in the rotary kiln.

[0014] According to the rotary kiln operation method of this embodiment, additives can be introduced into the rotary kiln via a scoop feeder installed in the middle of the rotary kiln. The additives can then be heated by irradiating them with microwaves as they pass through the scoop feeder and before they are introduced into the raw materials in the rotary kiln. Therefore, for additives added to the raw materials in the middle of the rotary kiln, the additives can be heated before they come into contact with the raw materials, thereby increasing the temperature of the additives. As a result, the amount of heat absorbed by the additives when they come into contact with the raw materials can be reduced. Furthermore, for example, if the additives contain volatile components, these volatile components can be separated by heating, and the separated combustible gases can be ignited by contact with the high-temperature exhaust air from the burner, contributing to the temperature increase. The volatile components mentioned above refer to the gases, oils, and tar (coal tar) generated when coal is heated. In addition, "in the middle of the rotary kiln" refers to the middle of the transport route of the raw materials processed in the rotary kiln.

[0015] After explaining the configuration of the heat treatment apparatus to which the operation method of the rotary kiln of the present embodiment can be preferably applied, the anti-fusion agent addition step of the present embodiment will be described. (1) Heat treatment apparatus A configuration example of a heat treatment apparatus including a rotary kiln in which the operation method of the rotary kiln of the present embodiment can be preferably implemented will be described using FIGS. 1 to 3. FIG. 1 is a perspective view of the heat treatment apparatus 10, FIG. 2 is a cross-sectional view taken along line A-A' of FIG. 1, and FIG. 3 is a cross-sectional view taken along line B-B' of FIG. 2. All are schematic diagrams for explaining the configuration of the apparatus and do not accurately show sizes and the like. Also, in FIGS. 2 and 3, the description of the overhead wire 1053 to be described later is omitted. (1-1) Regarding the rotary kiln The heat treatment apparatus 10 shown in FIG. 1 has a rotary kiln 100. The body portion 101 that forms the furnace body of the rotary kiln 100 has a substantially cylindrical shape, and the body portion 101 is configured to be rotatable about a central axis CA parallel to the X axis in the figure as a rotation axis. The rotary kiln 100 is provided so as to incline downward from the introduction end 102, which is one end in the longitudinal direction, toward the discharge end 103, which is the other end in the longitudinal direction. For this reason, the object to be processed, which is the raw material introduced from the introduction end 102 side, moves to the discharge end side inside the rotating body portion 101. As will be 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 moving direction of the object to be processed, that is, from the discharge end 103 side to the introduction end 102 side, thereby heating the object to be processed in countercurrent.

[0016] The rotary kiln 只要保持原文格式,这里的内容似乎不完整,你可以检查一下原文是否完整。若完整,可继续追问我。]] has an inlet 1021 at the introduction end 102, which is one end in the longitudinal direction, and the object to be processed can be introduced into the inside of the body portion 101 through the inlet 1021.

[0017] At the discharge end 103, which is the other longitudinal end of the rotary kiln 100, a discharge chute, which is the discharge port 1031, is provided so that the object to be processed that has completed the heat treatment inside the body part 101 can be discharged. The object to be processed that has completed the heat treatment can be conveyed to a device such as an electric furnace that performs other processes as necessary. Further, a burner 104 is provided at the discharge end 103, and fossil fuel such as heavy oil is burned to heat the object to be processed and the like introduced into the body part 101 of the rotary kiln 100. (1-2) About the scoop feeder The heat treatment device 10 can have a scoop feeder in the middle of the rotary kiln 100, that is, between the introduction end 102 and the discharge end 103. FIG. 2 shows a cross-section of the position where the scoop feeder is provided, that is, a cross-sectional view taken along the line A-A'.

[0018] As shown in FIG. 2, the rotary kiln 100 can have a rotating body part 101 and an outer shell part 110 that covers the body part 101. Note that the outer shell part 110 does not need to be provided so as to cover the entire surface of the body part 101, and for example, as shown in FIG. 1, it can also be provided only at necessary locations such as the location where the scoop feeder is provided.

[0019] The object to be processed 21 introduced from the inlet 1021 is introduced into the body part 101 and can move toward the discharge end 103 side as the body part 101 rotates.

[0020] A space part 120 is formed between the body part 101 and the outer shell part 110, and an additive can be supplied to the space part 120 through the additive supply port 111 provided in the outer shell part 110. An additive supply means 221 for supplying various additives as necessary can be connected to the additive supply port 111.

[0021] The additives added by the additive supply means 221 are not particularly limited, and examples include one or more selected from a reducing agent and an anti-fusion agent.

[0022] The configuration of the additive supply means 221 is not particularly limited. The opening of an opening provided on the additive supply port 111 side may be configured to be adjustable according to the amount of additive to be supplied, thereby allowing adjustment of the amount of additive supplied as it falls freely through the opening. Alternatively, the system may include a conveying means such as a screw conveyor, and the conveying speed of the additive by the conveying means may be adjustable, thereby allowing adjustment of the amount of additive supplied by the conveying speed.

[0023] The scoop feeder 130 can be formed, for example, as an L-shaped tube with a bend between a tip portion 131 and a straight portion 132. The material of the scoop feeder 130 is not particularly limited, but when microwaves are irradiated onto the additive material inside the scoop feeder 130 using a microwave irradiation device described later, it is preferable that the material be able to transmit microwaves, and for example, various ceramic materials can be used. The scoop feeder 130 can rotate together with the body portion 101, for example, clockwise (right-hand rotation) as shown by the arrow in Figure 2. During such rotation, the tip portion 131 scoops up the additive material 22 supplied to the space portion 120, and the scooped-up additive material 22 can be passed through the straight portion 132 and fed into the body portion 101.

[0024] In the rotary kiln 100, the location where the scoop feeder is installed is not particularly limited and can be installed at any location depending on the temperature distribution inside the body 101 of the rotary kiln 100, the type of additive to be added, etc.

[0025] The location where the scoop feeder is installed is not particularly limited. For example, the distance L110 from the discharge end 103 to the end of the outer shell portion 110 on the introduction end 102 side where the scoop feeder is installed is preferably 5% to 95% of the longitudinal length L101 of the body portion 101 of the rotary kiln 100, and more preferably 10% to 90%. (1-3) About microwave irradiation equipment The microwave irradiation device 105 can be configured to irradiate the additive material fed from the scoop feeder 130 with microwaves. The microwave irradiation device 105 can have an oscillator 1051 that emits microwaves and a waveguide 23 that guides the microwaves emitted by the oscillator 1051 into the rotary kiln, including the inside of the scoop feeder.

[0026] The oscillator 1051 can be any device capable of emitting microwaves, such as a gyrotron, magnetron, klystron, traveling wave tube, etc. In this specification, microwaves refer to electromagnetic waves with a frequency of 300 MHz or more and 30 GHz or less. The frequency of the microwaves emitted by the oscillator 1051 can be selected according to the additives used, etc., and is suitable for heating in accordance with the Radio Law and other regulations. The output of the oscillator 1051 is not particularly limited and can be selected according to the type of additive and the heating temperature, etc., and is preferably, for example, 1 kW or more.

[0027] The oscillator 1051 is preferably installed so as not to obstruct the rotation of the body 101 of the rotary kiln 100, as shown in Figure 1, etc. For example, it can be installed on the outer surface of the body 101 as shown in Figure 1. It is also preferable to provide insulating material or the like on the surface of the oscillator 1051 and the waveguide 23 so that they are not damaged by the heat of the rotary kiln 100.

[0028] Waveguide 23 has one end connected to oscillator 1051, and the other end 23A is placed inside rotary kiln 100. Waveguide 23 only needs to be able to guide microwaves, and its configuration is not particularly limited, but it can be, for example, a tubular waveguide or an electric wire. If the waveguide is a waveguide, it is preferable to place a microwave-transmitting plate at the end 23A located inside rotary kiln 100 to prevent raw materials or additives from entering the inside of the waveguide. The material of the microwave-transmitting plate is not particularly limited, but one or more types selected from, for example, quartz, alumina, zirconia, magnesia, silicon carbide, etc. can be used.

[0029] Furthermore, microwaves that have passed through the waveguide 23 can be irradiated from the end 23A of the waveguide 23, which is located inside the rotary kiln 100. For this reason, it is preferable that the end 23A of the waveguide 23, which is located inside the rotary kiln 100, be positioned so that microwaves can be irradiated from the additive 22 until it passes through the scoop feeder 130 and is fed into the raw material inside the rotary kiln 100. Note that the period from when the additive 22 passes through the scoop feeder 130 and is fed into the raw material inside the rotary kiln 100 means the period from when the additive 22 is scooped up by the scoop feeder 130 and placed inside the scoop feeder 130 until it comes into contact with the raw material.

[0030] The microwave irradiation device 105 may also have a position changing device 24 for changing the position of the end 23A of the waveguide 23 located inside the rotary kiln 100. The configuration of the position changing device 24 is not particularly limited. For example, it may have a rod-shaped body that supports the end 23A from the outer surface of the body portion 101 of the rotary kiln 100, and the position of the end 23A may be changed by changing the position of the rod-shaped body. In this case, it is preferable that the waveguide 23 is configured to be deformable.

[0031] Furthermore, 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 wire 1053 and a current collector 1052. The overhead wire 1053 can be arranged along the outer circumference of the rotary kiln 100 and can be connected to a power supply source (not shown). The current collector 1052 can acquire power through the overhead wire 1053 by making contact with it. The configuration of the current collector 1052 is not particularly limited, but for example it may have a conductive sliding part that makes contact with the overhead wire 1053 and an expandable part that displaces the position of the sliding part and presses against the overhead wire 1053, and can have a configuration similar to a pantograph used in electric trains, etc.

[0032] Figures 1 to 3 show an example where one microwave irradiation device 105 is placed near one scoop feeder 130, but it is preferable to place it similarly near the other scoop feeder 130 as well. (2) Operating conditions of the rotary kiln The operating conditions for a rotary kiln are not particularly limited and can be arbitrarily selected depending on the type of material to be processed and the processing to be performed.

[0033] As previously described, the heat treatment apparatus 10 can also perform reduction treatment and the like.

[0034] The rotational speed of the rotary kiln 100, that is, the rotational speed of the body portion 101 that constitutes the rotary kiln 100, is not particularly limited, but it is preferably, for example, 0.5 rpm or more and 1.5 rpm or less.

[0035] By setting the rotation speed of the rotary kiln 100 to 0.5 rpm or higher, the stirring force within the rotary kiln 100 is sufficiently increased, allowing the reaction to proceed sufficiently while exposing the additives added during the process. Furthermore, by setting the rotation speed of the rotary kiln 100 to 0.5 rpm or higher, the deformation caused by the weight of the kiln body when it softens due to the high temperature can be reduced.

[0036] Furthermore, by setting the rotation speed of the rotary kiln to 1.5 rpm or less, the material to be treated introduced into the rotary kiln 100 can remain inside the rotary kiln 100 for a sufficient amount of time, thereby ensuring the desired heat treatment time. (3) Regarding each process (3-1)Additive addition process In the additive input process, the additive can be introduced into the rotary kiln, specifically into the body section where the material to be processed is heat-treated, via the aforementioned scoop feeder.

[0037] The additive addition process can be carried out at any time depending on the type of additive being added. (Regarding additives) The type of additive added in the additive addition process is not particularly limited, and as mentioned above, one or more types selected from reducing agents and anti-fusion agents are examples. It is especially preferable that the additive includes a reducing agent.

[0038] Examples of reducing agents include carbon-containing materials such as coal, wood pellets, and waste plastics. In particular, according to the rotary kiln operation method of this embodiment, the additive can be heated by irradiating it with microwaves during the additive heating process. Therefore, reducing agents that previously required pretreatment to remove moisture and volatile components can be used without pretreatment, resulting in particularly high effectiveness. For this reason, wood pellets and waste plastics can be suitably used as additives.

[0039] Normally, when performing reduction treatment, air is not supplied to maintain a reducing atmosphere inside the body 101 of the rotary kiln 100. However, when using a material containing a large amount of volatile components as a reducing agent, the system may be configured to supply air into the body 101 via a scoop feeder 130, and the flammable gas separated by heating is then supplied into the body 101 of the rotary kiln 100.

[0040] Furthermore, the anti-fusion agent can be any material that can suppress the adhesion of the workpiece to the inner wall of the rotary kiln 100 and prevent it from growing in a ring shape. For example, a high-melting-point ceramic material can be suitably used. By using a high-melting-point ceramic material as an anti-fusion agent, for example, the molten workpiece can be coated, preventing the workpiece from adhering to the inner wall of the furnace and preventing the growth of ring-shaped deposits.

[0041] The anti-fusion 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, but preferably contains one or more selected from, for example, silicon dioxide, aluminum oxide, calcium oxide, and magnesium oxide. (Regarding raw materials) The material to be processed, which is the raw material used in the rotary kiln operation method of this embodiment, is not particularly limited and can include, for example, ores containing various metal components or ceramic raw materials.

[0042] In particular, various types of ores can be used as materials to be processed. Metal ores, especially those of metals that require refining, generally contain a high amount of moisture and are oxidized. Furthermore, the rotary kiln operation method of this embodiment allows for efficient drying and reduction using various reducing agents that were previously difficult to use; therefore, it is preferable that the materials to be processed include metal ores. The material being reduced may also consist of metal ores.

[0043] The metals contained in the metal ore are not particularly limited, but it is preferable that the ore contains non-ferrous metals, and more preferably that it contains one or more metals selected from nickel, zinc, etc.

[0044] In ferronickel refining, the ore (dried ore) from which some of the moisture adhering to the nickel oxide ore raw material has been removed by a dryer may undergo further drying and reduction treatments. For this reason, the rotary kiln operation method of this embodiment is suitable for using nickel oxide ore as the material to be processed.

[0045] While there are no particular limitations on the nickel oxide ore (nickel oxide ore), garnierite or the like is preferably used. Typical compositions of this garnierite ore include those with a Ni grade of 2.1% to 2.5% by mass, a Fe grade of 11% to 23% by mass, a MgO grade of 20% to 28% by mass, a SiO2 grade of 29% to 39% by mass, a CaO grade of less than 0.5% by mass, and a burnt-down loss of 10% to 15% by mass (on a dry ore basis).

[0046] Furthermore, the material to be treated can be pre-dried to reduce or remove some of the adhering moisture. (3-2) Additive heating process In the additive heating process, the additive can be heated by irradiating it with microwaves while it passes through the scoop feeder and is fed into the rotary kiln.

[0047] In the additive heating process, microwaves can be irradiated from the end 23A of the waveguide 23 using the microwave irradiation device 105 described above. Although Figures 2 and 3 show an example in which the end 23A of the waveguide 23 is placed in the middle of the scoop feeder 130, the system is not limited to this configuration. For example, it may be placed near the end on the body portion 101 side of the scoop feeder 130, and microwaves may be irradiated onto the additive discharged from the scoop feeder 130. Furthermore, microwaves may be irradiated not only onto the additive but also onto fine powders such as raw materials in the gas phase portion of the rotary kiln.

[0048] Furthermore, while Figures 1 to 3 show an example where one microwave irradiation device 105 is placed near one scoop feeder 130, it can also be placed similarly near the other scoop feeder 130 to irradiate the additive with microwaves.

[0049] As previously mentioned, the frequency of the microwaves used is not particularly limited and can be selected according to the regulations of the Radio Law and other laws, as it can be used for heating and depends on the additives used.

[0050] The additive heating process may be carried out continuously during the additive addition process, or it may be carried out intermittently.

[0051] Furthermore, since different materials have different microwave absorption characteristics, in the additive heating process, only some of the components of the additive may absorb microwaves and be heated. [Heat treatment equipment] The heat treatment apparatus of this embodiment may include a rotary kiln, a scoop feeder positioned between the longitudinal ends of the rotary kiln, and a microwave irradiation device that irradiates microwaves onto the additive material introduced into the rotary kiln via the scoop feeder.

[0052] The heat treatment apparatus of this embodiment allows for the operation of the rotary kiln described above. Therefore, the matters already explained will be omitted from this explanation.

[0053] As described with reference to Figures 1 to 3, the heat treatment apparatus of this embodiment may include a rotary kiln, a scoop feeder, and a microwave irradiation device.

[0054] Since suitable configurations of rotary kilns, scoop feeders, microwave irradiation devices, and heat treatment equipment have already been described, we will omit further explanation.

[0055] According to the heat treatment apparatus of this embodiment described above, the additive material fed from the scoop feeder can be heated by irradiating it with microwaves using a microwave irradiation device. Therefore, the additive material added midway through the rotary kiln process can be heated. Consequently, even if the additive material contains a large amount of volatile components or moisture, the removal of heat from the raw materials in the rotary kiln when the additive material is added can be suppressed, and the reaction between the additive material and the raw materials can be promoted. [Explanation of symbols]

[0056] 10 Heat treatment equipment 100 Rotary Kilns 101 Torso 102 Introductory end 1021 Inlet 103 Discharge end 1031 Outlet 104 burners 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. Items to be processed 22 Additives 221 Additive supply means 23 Waveguides 24 Position changing device CA center axis L110 distance L101 Length

Claims

1. The rotary kiln has scoop feeders between its longitudinal ends, and the process includes an additive feeding step in which additives are introduced into the raw material inside the rotary kiln via the scoop feeders, The process includes an additive heating step in which the additive is heated by irradiating it with microwaves using a microwave irradiation device while it is passing through the scoop feeder and being fed into the raw material in the rotary kiln, A method for operating a rotary kiln, comprising: an oscillator that emits microwaves; a waveguide that guides the microwaves emitted by the oscillator into the rotary kiln, including the scoop feeder; and a position changing device that changes the position of the end of the waveguide located inside the rotary kiln.

2. The method for operating a rotary kiln according to claim 1, wherein the raw material is nickel oxide ore and the additive contains a reducing agent.

3. Rotary kiln and, A scoop feeder is positioned between the longitudinal ends of the rotary kiln, The system includes a microwave irradiation device that irradiates microwaves onto the additive material fed into the rotary kiln via the scoop feeder, The microwave irradiation apparatus is a heat treatment apparatus comprising: an oscillator that emits microwaves; a waveguide that guides the microwaves emitted by the oscillator into the rotary kiln, including the scoop feeder; and a position changing device that changes the position of the end of the waveguide located inside the rotary kiln.

4. The heat treatment apparatus according to claim 3, wherein the microwave irradiation apparatus comprises overhead wires arranged along the outer circumference of the rotary kiln and a current collector that acquires power via the overhead wires by contacting the overhead wires.

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