Fluidized roasting furnace and fluidized roasting method

Abstract

To provide a flow roasting furnace which can perform roasting stably without limiting an object to be roasted, and to provide a flow roasting method.SOLUTION: In a flow roasting furnace 10, roasted sand is roasted in a fluid bed FB formed by causing the roasted sand to float in a gas to burn and remove combustibles contained in the roasted sand. A furnace body 11 includes: a fluidization nozzle 15 which is installed at a bottom part of a roasting chamber 12 and jets air to form the fluid bed; a first burner 51 which is installed in the roasting chamber 12 so as to be disposed at the upper part side relative to the fluid bed FB; and a second air supply system 52 which is connected to the upper part side relative to the fluid bed FB and supplies air to the roasting chamber 12. A controller 41 adjusts air supply to the roasting chamber 12 by the second air supply system 52 to control burning of the combustibles.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fluidized bed roasting furnace and a fluidized bed roasting method for burning and removing combustibles contained in roasted sand by fluidized bed roasting. [Background technology]

[0002] Used foundry sand and used MgO-C bricks usually contain impurities such as organic substances such as binders, adhesives, and pressure sensitive adhesives, and inorganic substances such as carbon. As most of these impurities are combustible, used foundry sand and crushed used MgO-C bricks are roasted (roasted) as roasted sand, and the combustible materials are burned and removed, allowing for reuse. As a roasting device, Patent Document 1 discloses a fluidized bed roasting furnace. This fluidized bed roasting furnace uses used foundry sand or the like as roasting sand, and roasts the sand by forming a fluidized bed of the roasting sand using air ejected from a nozzle. Patent Document 2 discloses that roasted sand is made from crushed MgO-C bricks used in steelmaking furnace linings, and is then fired (roasted) in a rotary kiln. This rotary kiln rotates a cylindrical furnace body to agitate the roasted sand within the furnace. In addition to fluidized bed roasting furnaces and rotary kilns, roasting equipment also includes shuttle kilns and electric furnaces that store carts or containers containing roasted sand inside the furnace and roast the sand. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 8-291977 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-249245 Summary of the Invention [Problem to be solved by the invention]

[0004] In roasting using a rotary kiln (see Patent Document 2), shuttle kiln, electric furnace, or the like, it is difficult to bring the roasted sand into uniform contact with air, which causes variations in the degree of roasting and makes it difficult to stabilize the quality after roasting, so the roasting time tends to be extended to resolve this issue. In particular, in a rotary kiln, as the roasting time is extended, the roasted sand rubs against itself during long periods of stirring and is mechanically worn down, resulting in a reduction in the particle size necessary for use as aggregate for foundry sand, bricks, etc., and thus a decrease in yield. A fluidized bed roaster (see Patent Document 1) allows roasted sand to come into uniform contact with air by forming a fluidized bed, which reduces variation in the roasting condition and causes no mechanical wear, making it more useful than a rotary kiln or the like. However, in order to stably roast using a conventional fluidized bed roaster, the roasting target is substantially limited to materials containing a relatively small amount of combustibles, such as used foundry sand, etc. In other words, when roasting materials containing a relatively large amount of combustibles, such as used MgO-C bricks, the amount of combustion heat increases, causing an overheating of the furnace, or there is a shortage of oxygen required for combustion, which may result in unstable roasting.

[0005] The present invention aims to solve the problems associated with the conventional techniques, and provides a fluidized bed roasting furnace and a fluidized bed roasting method that can stably roast any object without limiting the type of roasting target. [Means for solving the problem]

[0006] In order to solve the above problems, the invention of a fluidized bed roasting furnace described in claim 1 is a fluidized bed roasting furnace that roasts roasted sand in a gas, and burns and removes combustibles contained in the roasted sand, a furnace body having a roasting chamber for accommodating the roasted sand; a first air supply system connected to the furnace body and supplying air to the roasting chamber; an exhaust system connected to the furnace body for exhausting gas from the roasting chamber; a controller for controlling the roasting of the roasted sand in the roasting chamber; The furnace body is a fluidizing nozzle installed at the bottom of the roasting chamber, connected to the first air supply system, and configured to inject the air from the bottom side toward the top side of the roasting chamber to form the fluidized bed in the roasting chamber; a first burner installed in the roasting chamber so as to be disposed above the fluidized bed; a second air supply system connected to an upper side of the fluidized bed and supplying air to the roasting chamber, The controller controls the combustion of the combustibles by adjusting the supply of air to the roasting chamber by the second air supply system. The invention described in claim 2 is the invention described in claim 1, wherein the first burner is switchable between a heating mode in which combustion gas is ejected into the roasting chamber and an air supply mode in which air is ejected into the roasting chamber, the second air supply system is connected to the first burner, The supply of air to the roasting chamber by the second air supply system is performed via the first burner switched to the air supply mode. The invention described in claim 3 is the invention described in claim 1 or 2, wherein the furnace body includes a second burner installed in the roasting chamber so as to be disposed inside the fluidized bed, The gist is that the controller controls the combustion of the combustible material by adjusting the heating of the roasted sand by the second burner. The invention described in claim 4 is the invention described in claim 1 or 2, wherein the roasted sand contains, when the total amount is taken as 100 mass%, 5 to 20 mass% of powder having a particle size of 1 mm or less and 70 to 90 mass% of granules having a particle size of more than 1 mm and 5 mm or less, Bulk density is 1400 kg / m 3 More than 3500kg / m 3 The gist is as follows. The invention as set forth in claim 5 is the invention as set forth in claim 1 or 2, wherein the inner diameter of the lower part of the roasting chamber is smaller than the inner diameter of the upper part. The invention described in claim 6 is characterized in that, in the invention described in claim 1 or 2, the first burner is housed in the roasting chamber and installed above the fluidized bed, with the nozzle holes for ejecting combustion gas or air facing diagonally downward within a range of 20 to 50 degrees from the vertical direction. The invention as set forth in claim 7 is the invention as set forth in claim 1 or 2, wherein the controller adjusts the furnace temperature to a range of 650°C or higher and 1000°C or lower. The invention of claim 8 is the invention of claim 1 or 2, wherein the furnace body is provided with a measuring device for measuring the oxygen concentration and / or the carbon monoxide concentration in the roasting chamber. The invention described in claim 9 is the invention described in claim 1 or 2, further comprising a heat exchanger connected between the exhaust system and the first air intake system, The gist of the present invention is that the heat exchanger exchanges heat between the exhaust gas discharged from the roasting chamber and the air supplied to the roasting chamber, thereby preheating the air supplied to the roasting chamber to 200°C or higher. The invention described in claim 10 is the invention described in claim 1 or 2, wherein the exhaust system has a dust collector that removes dust from the exhaust gas exhausted from the roasting chamber. The invention described in claim 11 is the invention described in claim 1 or 2, wherein the roasted sand is obtained by crushing discarded magnesia bricks. The invention described in claim 12 is the invention described in claim 1 or 2, wherein the content of the combustible material contained in the roasted sand is 1% by mass to 30% by mass, with the total amount of the roasted sand being 100% by mass. The invention of claim 13 is a fluidized bed roasting method using the fluidized bed roasting furnace of claim 1 or 2, which roasts roasted sand and burns and removes combustibles contained in the roasted sand, a fluidization step of injecting air upward from the fluidization nozzle inside the roasting chamber of the furnace body to suspend the roasted sand in the air and fluidize the roasted sand; a combustion step of heating the roasted sand to cause combustibles contained in the roasted sand to react with oxygen in the air and burn, heating the roasted sand in the combustion step includes a preheating stage in which the roasted sand is preheated to a reaction temperature of the combustible material and the oxygen by the first burner, and a steady-state stage in which the roasted sand is heated by utilizing the combustion heat of the combustible material; The gist of the present invention is that in the steady state stage, when the furnace temperature of the roasting chamber becomes excessive and / or when there is a shortage of oxygen required for the combustion, the controller supplies air to the roasting chamber through the second air supply system to manage the combustion of the combustibles. The invention described in claim 14 is the invention described in claim 13, wherein the roasted sand contains, when the total amount is taken as 100 mass%, 5 to 20 mass% of powder having an average particle size of 1 mm or less and 70 to 90 mass% of granules having an average particle size of more than 1 mm and 5 mm or less, Bulk density is 1400 kg / m 3 More than 3500kg / m 3 The gist is as follows. The invention described in claim 15 is the invention described in claim 13 or 14, wherein the roasted sand is obtained by crushing discarded magnesia bricks. The invention described in claim 16 is the invention described in claim 13 or 14, wherein the content of the combustible material contained in the roasted sand is 1% by mass to 30% by mass, with the total amount of the roasted sand being 100% by mass. The invention described in claim 17 is the invention described in claim 13 or 14, wherein the controller adjusts the furnace temperature of the roasting chamber to a range of 650°C or higher and 1000°C or lower. [Effects of the Invention]

[0007] According to the present invention, a second air supply system is provided that is separate from the first air supply system that supplies gas to fluidize the roasted sand, and the combustion of combustible materials can be controlled by using the first burner to adjust the supply of air from the second air supply system to the roasting chamber, allowing roasting to be carried out stably without limiting the objects to be roasted. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram illustrating one embodiment of a fluidized bed roasting furnace according to the present invention. [Figure 2] 1 is a flowchart illustrating the fluidization step of the fluidized roasting method of the present invention. [Figure 3] 1 is a flowchart illustrating the combustion step of the fluidized roasting method of the present invention. [Figure 4] 4 is a flow chart illustrating the preheating stage of the combustion process. [Figure 5] 4 is a flowchart illustrating combustion management 1 in a steady state stage of the combustion process. [Figure 6] 10 is a flowchart illustrating combustion management 2 in the steady state stage of the combustion process. [Figure 7] 3 is a flow chart illustrating combustion management 3A during the steady state phase of the combustion process. [Figure 8] 3 is a flowchart illustrating combustion management 3B in the steady state phase of the combustion process. DETAILED DESCRIPTION OF THE INVENTION

[0009] The matters set forth herein are for illustrative purposes only and are intended to provide an illustrative description of the embodiments of the present invention, with the aim of providing what is believed to be the most effective and easily understandable explanation of the principles and conceptual features of the present invention. In this respect, it is not intended to show structural details of the present invention beyond the extent necessary for a fundamental understanding of the present invention, and the description, taken together with the drawings, will make clear to those skilled in the art how some aspects of the present invention may be actually embodied.

[0010] [1] Fluidized roasting furnace The fluidized bed roasting furnace of the present invention is a fluidized bed roasting furnace 10 that roasts roasted sand in a fluidized bed FB formed by suspending the roasted sand in a gas, and burns and removes combustibles contained in the roasted sand, a furnace body 11 having a roasting chamber 12 for accommodating the roasted sand; a first air supply system 21 connected to the furnace body 11 and supplying air to the roasting chamber 12; an exhaust system 31 connected to the furnace body 11 for exhausting gas from the roasting chamber 12; a controller (41) for controlling the roasting of the roasted sand in the roasting chamber (12); The furnace body 11 is a fluidizing nozzle 15 that is installed at the bottom of the roasting chamber 12, is connected to the first air supply system 21, and injects the air from the bottom side toward the top side of the roasting chamber 12 to form the fluidized bed FB in the roasting chamber 12; A first burner 51 installed in the roasting chamber 12 so as to be disposed above the fluidized bed FB; a second air supply system (52) connected to an upper side of the fluidized bed (FB) and supplying air to the roasting chamber; The controller 41 controls the combustion of the combustibles by adjusting the supply of air to the roasting chamber 12 by the second air supply system 52 (see FIG. 1).

[0011] That is, the fluidized roasting furnace 10 roasts roasted sand to burn and remove combustible materials contained in the roasted sand, and as shown in Figure 1, it is equipped with a furnace body 11, a first air supply system 21 connected to the furnace body 11, an exhaust system 31 connected to the furnace body 11, and a controller 41. Furthermore, the fluidized bed roasting furnace 10 is designed so that the heat required for roasting the roasted sand can be provided by the heat generated by the combustion of combustible materials, without relying substantially on external heat.

[0012] The furnace body 11 is the main part of the fluidized bed roasting furnace 10, and has a roasting chamber 12 therein for accommodating roasted sand, and roasts the roasted sand in the roasting chamber 12. The first air supply system 21 is for supplying air to the roasting chamber 12 of the furnace body 11. The air supplied by the first air supply system 21 is used to fluidize the roasted sand in the roasting chamber 12 to form a fluidized bed FB, and the oxygen contained in the air is used to combust combustibles contained in the roasted sand. The exhaust system 31 is for exhausting exhaust gas generated by roasting the roasted sand from the roasting chamber 12 of the furnace body 11. The controller 41 is for controlling the roasting of the roasted sand in the roasting chamber 12 of the furnace body 11, and mainly controls the combustion of combustibles contained in the roasted sand.

[0013] Hereinafter, each component of the fluidized bed roasting furnace 10 will be described. (1) Furnace body The overall shape of the furnace body 11 is not particularly limited as long as it can have a roasting chamber 12 for accommodating roasted sand. Typically, the furnace body 11 can be shaped like a vertical cylinder so that the roasted sand accommodated in the roasting chamber 12 can be fluidized to form a fluidized bed FB (see FIG. 1). The furnace body 11 is equipped with a fluidizing nozzle 15 installed at the bottom of the roasting chamber 12. The fluidizing nozzle 15 is used to supply air from the first air supply system 21 to the roasting chamber 12 and to fluidize the roasted sand. The fluidizing nozzle 15 is attached to the bottom wall of the roasting chamber 12 so that the air supplied by the first air supply system 21 can be sprayed from the bottom side of the roasting chamber 12 toward the top side thereof.

[0014] A plurality of fluidizing nozzles 15 are installed at the bottom of the roasting chamber 12, and each can spray air toward the upper side of the roasting chamber 12. The roasted sand is blown upward from the bottom of the roasting chamber 12 by the air spray from the fluidizing nozzles 15, where it floats in the air and becomes fluidized, forming a fluidized bed FB. The roasted sand in the fluidized bed FB is suspended in the air and can come into uniform contact with the oxygen contained in the air.

[0015] The multiple fluidization nozzles 15 can be arranged at equal intervals in the width direction (radial direction) of the furnace body 11 in order to spray air into the inside of the roasting chamber 12 at a uniform speed (rising speed) and to uniformize the rise of the roasted sand due to fluidization, in other words, the vertical height of the fluidized bed FB that is formed. Specifically, the interval between the fluidizing nozzles 15 can be set to 50 to 150 mm, preferably 60 to 100 mm, in terms of the distance (pitch) between the centers of adjacent fluidizing nozzles 15.

[0016] When the spacing between multiple fluidizing nozzles 15 is within the above-mentioned range, the air rising speed can be made uniform at each fluidizing nozzle 15, so the rise of the roasted sand due to fluidization (the vertical height of the fluidized bed FB) can be made uniform, which is particularly useful when fluidizing roasted sand (coarse aggregate) with a particle size (φ) of 1 mm to 5 mm. The vertical height of the fluidized bed FB can be determined according to the rising speed of the gas ejected from the fluidizing nozzle 15, but can usually be set to a level that allows the fluidized bed FB to fit inside the roasting chamber 12, particularly inside the lower part 12A of the roasting chamber 12.

[0017] The furnace body 11 includes a first burner 51 installed in the roasting chamber 12. The first burner 51 is provided in the upper portion 12B of the roasting chamber 12, and is therefore disposed above the fluidized bed FB. The first burner 51 is provided to preheat the roasted sand before roasting and to supply air to the roasting chamber 12 during roasting.

[0018] When the furnace body 11 is not equipped with the second burner 71 described later, the first burner 51 can be used for so-called "preheating and heating" purposes, preheating the roasted sand before roasting and heating the roasted sand during roasting. In other words, if the amount of combustible material contained in the roasted sand is small after preheating the roasted sand before roasting with the first burner 51 to cause self-heating, the amount of heat generated by self-heating may be small and the amount of heat required for roasting (combustion of combustible material) may be insufficient. In such cases, the amount of heat required for combustion of combustible material can be compensated for by heating the roasted sand using the first burner 51. In other words, if the furnace body 11 is not equipped with the second burner 71, the first burner 51 is used for "preheating and heating" and can preheat the roasted sand before roasting and heat the roasted sand during roasting.

[0019] Alternatively, when the furnace body 11 is equipped with a second burner 71 described later, the first burner 51 can be used for so-called "preheating" purposes, which preheat the roasted sand before roasting. In other words, after the first burner 51 preheats the roasted sand before roasting and causes it to generate heat by itself, if the amount of heat required for roasting (combustion of combustible materials) is insufficient, the amount of heat required for combustion of combustible materials can be made up by heating the roasted sand using the second burner 71 without using the first burner 51. In other words, when the furnace body 11 is equipped with the second burner 71, the first burner 51 can be used for "preheating" purposes, preheating the roasted sand before roasting, and not actually heating the roasted sand after being used for preheating.

[0020] The furnace body 11 is provided with a second air supply system 52 connected to the upper part 12B of the roasting chamber 12 so as to be disposed above the fluidized bed FB. The second air supply system 52 is provided to supply air to the roasting chamber 12. The second air supply system 52 can be connected to the first burner 51. In this case, air can be supplied to the roasting chamber 12 via the first burner 51. A first fuel supply system 62A extending from the fuel supply unit 61 is connected to the first burner 51. The first fuel supply system 62A is for supplying fuel from the fuel supply unit 61 to the first burner 51. When the second air supply system 52 and the first burner 51 are connected, the first fuel supply system 62A can be connected to the first burner 51 via the second air supply system 52. The first fuel supply system 62A has a first fuel valve 63A. The first fuel valve 63A can allow or restrict the supply of fuel to the first burner 51 by opening and closing the first fuel supply system 62A. The first fuel valve 63A is not particularly limited in type as long as it can open and close the first fuel supply system 62A, and examples thereof include a solenoid valve, an electric valve, and an on-off valve. The type and state of fuel supplied from the fuel supply unit 61 are not particularly limited, but typically, flammable gases such as city gases such as 12A gas and 13A gas, and LP gas (propane gas) can be used, as they are easy to obtain, easy to use, and have favorable ignition properties and heat output.

[0021] The second air supply system 52 has a second air supplier 53. The second air supplier 53 can supply air to the roasting chamber 12 via the first burner 51. The second air supplier 53 is not particularly limited in type as long as it can supply air, and examples thereof include a blower, a pump, a compressor, etc. Among these, a blower is preferable as the second air supplier 53 because it can continuously supply air at a constant air volume and / or wind speed. The second air supply system 52 has an air supply valve 54 between the second air supplier 53 and the first burner 51. The air supply valve 54 can allow or restrict the supply of air, fuel, etc. to the first burner 51 by opening and closing the second air supply system 52. The type of air intake valve 54 is not particularly limited as long as it is capable of opening and closing the second air intake system 52, and examples include an electric valve and a solenoid valve.Of these, an electric valve is preferred because it can, for example, arbitrarily adjust the amount of air supplied from the second air supplier 53 to the first burner 51.

[0022] When the second air supply system 52 is connected, the first burner 51 can be freely switched between a heating mode in which combustion gas is sprayed into the roasting chamber 12 based on fuel supply from the first fuel supply system 62A, and an air supply mode in which air supplied from the second air supply system 52 is sprayed into the roasting chamber 12. The first burner 51 can be switched between the heating mode and the air supply mode mainly by switching between allowing and restricting the fuel supply to the first burner 51 by the first fuel valve 63A. In other words, the first burner 51 can be in heating mode when fuel supply from the first fuel supply system 62A is permitted, and can be in air supply mode when fuel supply from the first fuel supply system 62A is restricted. The type of the first burner 51 is not particularly limited, but from the viewpoint of enabling the supply of air to the roasting chamber 12 in the air supply mode, it is preferable to use a burner whose nozzle holes are open outward, such as a nozzle burner or a gun burner.

[0023] The first burner 51 can be installed so that the nozzle holes for ejecting combustion gas etc. face obliquely downward. That is, the first burner 51 in heating mode is used for "preheating" when the furnace body 11 is equipped with the second burner 71 described below, and is used for "preheating and heating" when the furnace body 11 is not equipped with the second burner 71. When using the first burner 51 in heating mode for such "preheating" or "preheating and heating", it is preferable to lick the surface of the roasted sand (fluidized bed FB) with the combustion gas (flame) ejected from the first burner 51 (to hit the surface directly) in order to improve the efficiency of heating the roasted sand. When the first burner 51 is installed with its nozzle facing diagonally downward, the combustion gas (flame) is ejected from the nozzle diagonally downward and diffused, thereby licking the surface of the roasted sand (fluidized bed FB) over a wide area. Specifically, the installation angle of the first burner 51 is preferably in the range of 20 degrees to 50 degrees, and more preferably in the range of 30 degrees to 45 degrees with respect to the vertical direction.

[0024] The first burner 51 in heating mode is used to preheat roasted sand before roasting, to preheat the roasted sand to a temperature (combustion start temperature) at which the combustibles contained in the roasted sand begin to react with oxygen in a combustion reaction. The roasted sand preheated by the first burner 51 in heating mode is in uniform contact with the oxygen contained in the air in the fluidized bed FB, and the combustible materials contained in the roasted sand undergo a combustion reaction with the oxygen and burn.

[0025] The heat of combustion generated by the combustion reaction of some of the combustibles contained in the roasted sand with oxygen heats other combustibles and induces combustion reactions. Therefore, roasted sand generates heat by itself due to the combustion heat generated by the chain reaction of combustibles, even without the need for external heat. Therefore, the heat required for roasting roasted sand can be met by the heat generated by the self-heating of the roasted sand. Since the heat required for roasting the roasted sand is provided by the heat generated by the self-heating of the roasted sand, the preheated roasted sand does not need to be constantly heated during roasting using the first burner 51 (or second burner 71) in heating mode. Therefore, the heating of the roasted sand by the fuel supply to the first burner 51 (or second burner 71) in heating mode can be kept to a minimum, and as a result, the amount of fuel used for roasting can be reduced.

[0026] The preheating temperature by the first burner 51 is preferably equal to or higher than the combustion initiation temperature of the combustible material contained in the roasted sand. The specific preheating temperature depends on the type of combustible material and is not particularly limited. However, from the viewpoint of ensuring safety and being equal to or higher than the spontaneous ignition temperature of the fuel supplied from the first fuel supply system 62A, the lower limit value is typically 650°C or higher when the fuel supplied from the first fuel supply system 62A is a liquid fuel, and 700°C or higher when the fuel is a gaseous fuel. The lower limit value of the preheating temperature is preferably 750°C or higher, more preferably 800°C or higher, and even more preferably 850°C or higher. The upper limit value of the preheating temperature is typically 1000°C or lower, preferably 950°C or lower, and more preferably 900°C or lower, from the viewpoint of reducing the amount of fuel required for roasting and preventing quality deterioration of the roasted sand due to exposure to high temperatures.

[0027] The first burner 51 in the air supply mode is used to supply air to the roasting chamber 12 during roasting, and specifically, can be used to cool the roasting chamber 12 when the furnace temperature becomes excessively high (hereinafter referred to as "overheating"), and / or to supplement oxygen when there is a shortage of oxygen required for combustion. In other words, roasted sand generates heat by itself due to the heat of combustion generated by the combustion reaction of combustible materials, and is roasted using the heat generated by this self-heating. However, the amount of heat generated and the amount of oxygen required for combustion vary depending on the amount of combustible materials contained in the roasted sand, etc.

[0028] For example, if the amount of combustible material contained in the roasted sand is large, the amount of heat generated by self-heating becomes large, and the furnace temperature of the roasting chamber 12 may rise excessively. Alternatively, when the roasted sand contains a large amount of combustible material, the amount of oxygen required for combustion may be insufficient with only the air supplied from the first air supply system 21. In such a case, by using the first burner 51 in the air supply mode as a so-called "air supply nozzle," air can be supplied (introduced) from the second air supply system 52 to the roasting chamber 12.

[0029] Specifically, if the furnace temperature of the roasting chamber 12 becomes excessively high, air at a temperature lower than the furnace temperature is introduced into the roasting chamber 12 from the second air supply system 52 via the first burner 51 in air supply mode, thereby cooling the roasting chamber 12. Alternatively, if the amount of oxygen required for combustion is insufficient, oxygen is replenished in the roasting chamber 12 by supplying air from the second air supply system 52 to the roasting chamber 12 via the first burner 51 in air supply mode. The supply of air to the roasting chamber 12 using the first burner 51 and the second air supply system 52 does not affect the amount of air supplied to the roasting chamber 12 by the first air supply system 21, because the second air supply system 52 is a separate system from the first air supply system 21, and this prevents any impact on the formation of the fluidized bed FB.

[0030] The fluidized bed roaster 10 has a dedicated line, such as the second air supply system 52, for supplying air for cooling when the furnace temperature of the roasting chamber 12 becomes excessive and / or for supplying air to assist combustion when there is a shortage of oxygen, etc. Therefore, the fluidized bed roaster 10 can appropriately and simply manage the combustion of combustible materials by appropriately supplying air to the roasting chamber 12 as needed. Furthermore, the fluidized bed roaster 10 can accommodate a wide variety of roasting targets without changing the device configuration by changing the connection destinations of various supply lines or increasing or decreasing the number of lines depending on the target to be roasted, thereby achieving high versatility in the types of targets that can be roasted.

[0031] As described above, when the second air supply system 52, which is a dedicated line for air supply related to the combustion management of combustible materials, is connected to the first burner 51, it is possible to obtain advantages such as simplifying the configuration and miniaturizing the device by consolidating or reducing the number of lines connected to the furnace body 11 into one. The second air supply system 52 is not necessarily limited to being connected to the first burner 51, and can be directly connected to the upper part 12B of the roasting chamber 12 of the furnace body 11. When the second air supply system 52 is directly connected to the furnace body 11, the advantages include being able to supply air in an amount greater than the capacity of the burner (first burner 51) and being able to reduce pressure loss that occurs when air passes through the burner (first burner 51).

[0032] Furthermore, when the second air supply system 52 is directly connected to the furnace body 11, the number of supply ports for supplying air to the roasting chamber 12 is not limited to one, but may be multiple. When multiple supply ports for supplying air are used, the end of the second air supply system 52 may be branched into multiple ports and connected to each supply port. Furthermore, when multiple supply ports for supplying air are used, the multiple supply ports can be arranged at approximately equal intervals along the circumferential direction (inner circumferential direction) of roasting chamber 12. In this case, air can be supplied evenly from the multiple supply ports to roasting chamber 12 from the circumferential direction, so that the combustibles contained in the roasted sand can come into uniform contact with the oxygen contained in the air throughout almost the entire roasting chamber 12 (lower part 12A), making it easier for the combustion reaction to occur evenly within roasting chamber 12 (lower part 12A).

[0033] The furnace body 11 may include a second burner 71 installed in the roasting chamber 12 . The second burner 71 can be a so-called "heating" burner that heats the roasted sand during roasting. The amount of heat generated by the self-heating of the roasted sand varies depending on the amount of combustible material contained in the roasted sand, but if the amount of combustible material contained in the roasted sand is small, the amount of heat generated by the self-heating may be small and the amount of heat required to burn the combustible material may be insufficient. In such cases, the second burner 71 can be used to heat the roasted sand and compensate for the amount of heat required to burn the combustible material. In other words, the second burner 71 is for "heating" and can heat the roasted sand during roasting.

[0034] The second burner 71 can be provided so as to be disposed inside the fluidized bed FB from the viewpoint of being able to heat the roasted sand with suitable heating efficiency. The heating efficiency of the roasted sand by the second burner 71 arranged inside the fluidized bed FB is much better than the heating efficiency of the roasted sand from the outside (top) of the fluidized bed FB by the above-mentioned first burner 51. Therefore, when the second burner 71 is provided, the first burner 51 in heating mode can be used only for "preheating," which preheats the roasted sand before roasting. Furthermore, when the first burner 51 is connected to the second air supply system 52, the first burner 51 in air supply mode can be used as a so-called "air supply nozzle" during roasting.

[0035] When the second burner 71 is disposed inside the fluidized bed FB, it is exposed to heat generated by the combustion of combustible materials, and therefore, from the viewpoint of preventing abnormal combustion, it is preferable to use it in an atmosphere at a temperature equal to or higher than the temperature at which the fuel spontaneously ignites. Note that, since the fuel injected from the second burner 71 spontaneously ignites when exposed to heat generated by the combustion of combustible materials, the second burner 71 does not necessarily have to have an ignition function for igniting the fuel. The type of the second burner 71 is not particularly limited, and examples include a gun burner and a nozzle burner, but a gun burner is preferred from the viewpoint of being able to inject fuel at high pressure.

[0036] When the second burner 71 is disposed inside the fluidized bed FB, it is preferable that the fuel be supplied at high pressure so that the fuel can be injected into the fluidized bed FB where air is constantly flowing. Specifically, a third air supply system 72 is connected to the second burner 71, and a second fuel supply system 62B extending from the fuel supply unit 61 is connected to the third air supply system 72. Second fuel supply system 62B has second fuel valve 63B. Second fuel valve 63B opens and closes second fuel supply system 62B, thereby allowing or restricting fuel supply to second burner 71. There are no particular limitations on the type of second fuel valve 63B as long as it is capable of opening and closing second fuel supply system 62B, and examples of the type include a solenoid valve and an electric valve.

[0037] The third air supply system 72 has a compressed air supplier 73 that supplies compressed air to the second burner 71. There are no particular limitations on the type of this compressed air supplier 73 as long as it is capable of supplying compressed air, and examples of such a supplier include a high-pressure pump and a compressor, with a high-pressure pump being preferred among these because it can stably supply compressed air. The third air supply system 72 has a supply valve 74 between the compressed air supplier 73 and the second burner 71. The supply valve 74 can allow or restrict the supply of compressed air to the second burner 71 by opening and closing the third air supply system 72. The type of supply valve 74 is not particularly limited as long as it can open and close the third air supply system 72, and examples of the supply valve 74 include an electric valve and a solenoid valve. Of these, an electric valve is preferable because it can adjust the amount of compressed air supplied from the compressed air supplier 73 to the second burner 71, for example.

[0038] When the second burner 71 is in use, the second fuel valve 63B opens the second fuel supply system 62B, and fuel is supplied from the fuel supply unit 61 to the third air supply system 72, and compressed air is supplied from the compressed air supplier 73 to the third air supply system 72. The fuel and compressed air are mixed in the third air supply system 72 and supplied at high pressure to the second burner 71. When injected from the second burner 71 into the fluidized bed FB, they spontaneously combust in the fluidized bed FB, heating the roasted sand and supplementing the heat required to combustible materials. The second burner 71 is disposed in the fluidized bed FB, and therefore has good heating efficiency and can quickly replenish the heat required for combustion of combustible materials. When replenishment of heat by the second burner 71 is to be stopped, the supply valve 74 is used to close the third air supply system 72, thereby stopping the supply of fuel and compressed air to the second burner 71. That is, the second burner 71 is provided for the purpose of secondarily heating the roasted sand in the fluidized bed FB when the amount of heat required for roasting is insufficient, for example, because the amount of heat generated by the combustion of combustibles is small. In other words, the second burner 71 is provided for the purpose of supplementing the insufficient amount of heat. Therefore, the second burner 71 is not provided for the purpose of constantly heating the roasted sand for roasting, but rather, after supplementing the insufficient amount of heat, heating is promptly stopped.

[0039] The second burner 71, the third air supply system 72, etc. are provided as a system separate from the first burner 51 and the second air supply system 52. Therefore, when using the second burner 71, if it becomes necessary to supply air to the roasting chamber 12 due to an excessive rise in furnace temperature or a lack of oxygen, air can be supplied to the roasting chamber 12 using the first burner 51 and the second air supply system 52. Furthermore, since the second burner 71, the third air supply system 72, etc. are separate systems from the first air supply system 21, the use of the second burner 71, the third air supply system 72, etc. does not affect the amount of air supplied to the roasting chamber 12 by the first air supply system 21, and therefore, it is possible to prevent any impact on the formation of the fluidized bed FB.

[0040] The furnace body 11 can be equipped with a sand charging chute 13 for charging roasted sand before roasting into the roasting chamber 12. The sand charging chute 13 has, for example, a hopper 13A for charging roasted sand and a pipe 13B extending from the hopper 13A, and can be provided by arranging the hopper 13A outside the furnace body 11, inserting the pipe 13B inside the furnace body 11, and arranging the tip of the pipe 13B in the roasting chamber 12. Furnace body 11 can be equipped with a discharge nozzle 14 for removing the roasted sand from roasting chamber 12 after roasting. Discharge nozzle 14 can be provided, for example, at the bottom of roasting chamber 12, penetrating the furnace wall of furnace body 11. Discharge nozzle 14 can be made to open and close freely by connecting a valve such as a cone valve that discharges roasted sand at a constant rate.

[0041] In the roasting chamber 12 of the furnace body 11, the fluidized bed FB is formed in the lower part 12A of the roasting chamber 12. In other words, the fluidized bed FB is not formed throughout the entire interior of the roasting chamber 12, and the upper edge (top surface) of the fluidized bed FB does not easily reach the upper part 12B of the roasting chamber 12, but is contained within the lower part 12A of the roasting chamber 12. This is because the height (altitude) of the roasted sand that can be blown up and suspended by the air jet from the fluidizing nozzle 15 is limited depending on the weight, bulk density, etc. of the roasted sand. In the furnace body 11, the inner diameter of the lower portion 12A of the roasting chamber 12 can be smaller than the inner diameter of the upper portion 12B of the roasting chamber 12. When the inner diameter of the lower portion 12A of the roasting chamber 12 is smaller than the inner diameter of the upper portion 12B, the amount of air required to form the fluidized bed FB can be reduced.

[0042] When the inner diameters of the lower portion 12A and the upper portion 12B of the roasting chamber 12 are different, the flow speed of the air flowing through the roasting chamber 12 can also be different between the lower portion 12A and the upper portion 12B. If the inner diameter of the upper portion 12B of the roasting chamber 12 is made larger than the inner diameter of the lower portion 12A, the volume of the upper portion 12B will be larger than the volume of the lower portion 12A, and the air flow velocity in the upper portion 12B of the roasting chamber 12 will be slower than the air flow velocity in the lower portion 12A of the roasting chamber 12 (the air velocity in the fluidized bed FB). In this case, the air flow rate (rising speed) in the lower part 12A of the roasting chamber 12 is maintained at a rate sufficient to form a fluidized bed FB, while the air flow rate in the upper part 12B of the roasting chamber 12 is slowed down, thereby making it possible to optimize the residence time of the air in the roasting chamber 12.

[0043] Specifically, when the inner diameters of the lower portion 12A and the upper portion 12B of the roasting chamber 12 are different, the inner diameter (radius) of the lower portion 12A of the roasting chamber 12 is r1, and the inner diameter (radius) of the upper portion 12B is r2, and the square of r2 is: (r2) 2 is the square of r1:(r1) 2 1.3 times or more [1.3 × (r1) 2 ≦(r2) 2 ] is preferably 1.4 times or more [1.4 × (r1) 2 ≦(r2) 2 ] is more preferable, and 1.5 times or more [1.4 × (r1) 2 ≦(r2) 2 is more preferred. Also, the square of r2:(r2) 2 is the square of r1:(r1) 2 Less than three times (r2) 2 ≦3×(r1) 2 ], and is preferably 2.5 times or less [(r2) 2 ≦2.5×(r1) 2] is more preferable, and is 2 times or less [(r2) 2 ≦2×(r1) 2 is more preferred.

[0044] The furnace body 11 can be provided with an air supply chamber 16 below the roasting chamber 12. The air supply chamber 16 can be connected to the first air supply system 21 to temporarily store the air supplied from the first air supply system 21. The air supply chamber 16 communicates with the roasting chamber 12 via the fluidizing nozzle 15 , and the fluidizing nozzle 15 is connected to the first air supply system 21 via the air supply chamber 16 . The air supplied from the first air supply system 21 is temporarily stored in the air supply chamber 16, whereby the pressure and rising speed are made uniform, and the air can be ejected from the multiple fluidizing nozzles 15.

[0045] The furnace body 11 can be provided with an exhaust chamber 17 above the roasting chamber 12. By connecting the exhaust chamber 17 to the exhaust system 31, it is possible to temporarily store the exhaust gas discharged from the roasting chamber 12 to the exhaust system 31. This exhaust gas contains air that has passed through the fluidized bed FB, carbon dioxide produced by the combustion of combustible materials during the roasting of the roasted sand, impurities such as dust particles mixed in the roasted sand, and fine dust particles. A porous wall 18 can be provided between the exhaust chamber 17 and the roasting chamber 12. The porous wall 18 has a plurality of holes, which allows the exhaust gas from the roasting chamber 12 to pass through while preventing the passage of roasted sand mixed in the exhaust gas and dust particles and dirt contained in the roasted sand. The porous wall 18 also restricts the passage of the exhaust gas to the exhaust chamber 17 in an upward direction, thereby rectifying the flow of air (exhaust gas) inside the roasting chamber 12 so that it flows upward.

[0046] The porous wall 18 functions as a partition wall that thermally insulates the roasting chamber 12 from the exhaust chamber 17. That is, by thermally insulating the roasting chamber 12 from the exhaust chamber 17, the porous wall 18 can make the temperature inside the exhaust chamber 17 lower than the furnace temperature of the roasting chamber 12. Furthermore, the inner diameter of exhaust chamber 17 can be made larger than the inner diameter of lower portion 12A of roasting chamber 12. In this case, the flow velocity of the exhaust gas flowing upward in exhaust chamber 17 (the velocity of the ascending air current in exhaust chamber 17) can be made slower than the flow velocity of the air flowing upward in lower portion 12A of roasting chamber 12 (the velocity of the air in fluidized bed FB). In the exhaust chamber 17, the internal temperature is lower than the furnace temperature of the roasting chamber 12, so the amount of exhaust gas discharged (volume) can be reduced. Also, in the exhaust chamber 17, the speed of the ascending air current is slower than the speed of the air in the fluidized bed FB, so fine dust mixed in the exhaust gas can be allowed to settle.

[0047] The furnace body 11 can be provided with a furnace temperature measuring device 42 that measures the furnace temperature of the roasting chamber 12. This furnace temperature measuring device 42 can be disposed in the roasting chamber 12 and electrically connected to the controller 41. The furnace body 11 can be provided with an oxygen concentration measuring device 43 that measures the oxygen concentration in the roasting chamber 12. This oxygen concentration measuring device 43 can be disposed in the roasting chamber 12 and electrically connected to the controller 41. The furnace body 11 can be provided with an oxygen concentration meter 43 that measures the carbon monoxide concentration in the roasting chamber 12. The oxygen concentration meter 43 is disposed in the roasting chamber 12 and can be electrically connected to the controller 41.

[0048] (2) 1st air supply system The first air supply system 21 is used to supply air to the roasting chamber 12 of the furnace body 11 in order to fluidize the roasted sand and to burn the combustible materials contained in the roasted sand using the oxygen contained in the air. The first air supply system 21 may have a first air supplier 22. The first air supplier 22 is for supplying air to the furnace body 11 at a predetermined flow rate and / or flow velocity. That is, the first air supplier 22 supplies air to the furnace body 11 at a predetermined flow rate, thereby adjusting the amount of air supplied to the roasting chamber 12 and supplying oxygen required for the combustion reaction of combustibles to the roasting chamber 12.

[0049] In addition, the first air supplier 22 supplies air to the furnace body 11 at a predetermined flow rate, thereby adjusting the rising speed of the air ejected from the fluidizing nozzle 15 and fluidizing the roasted sand. The first air supplier 22 is not particularly limited in type as long as it can supply air to the furnace body 11 at a predetermined flow rate and / or flow velocity, and examples thereof include a blower, a pump, a compressor, etc. Among these, a blower is preferable as the first air supplier 22 because it can adjust not only the flow rate (air volume) of air to the roasting chamber 12 but also the flow velocity (air speed).

[0050] Specifically, the amount of air supplied (A) to the roasting chamber 12 is the sum (A=A1+A2) of the amount of air supplied (A1) by the first air supply system 21 and the amount of air supplied (A2) by the second air supply system 52. The amount of air supplied (A) to the roasting chamber 12 per unit time is 3 / s) is the volume of the roasting chamber 12, B (m 3 ), the relationship between the residence time T (s) of air in the roasting chamber 12 and A is A=B / T. The residence time T (s) is preferably 0.6 seconds or more, more preferably 1 second or more, from the viewpoint of sufficiently burning the combustibles. Therefore, the amount of air supplied to the roasting chamber 12 per unit time A (m 3 / s) can be determined according to the volume of the roasting chamber 12 so that the residence time T(s) falls within the above range.

[0051] As described above, the volume of the roasting chamber 12 can be reduced by reducing the inner diameter of the lower portion 12A of the roasting chamber 12 and increasing the inner diameter of the upper portion 12B, thereby reducing the volume of the lower portion 12A where the fluidized bed FB is formed and increasing the volume of the upper portion 12B. That is, in the lower portion 12A of the roasting chamber 12, which has a small volume, it is possible to maintain the air flow velocity (rising speed) sufficient to form the fluidized bed FB. On the other hand, in the upper portion 12B of the roasting chamber 12, which has a large volume, the air flow velocity can be appropriately slowed by adjusting the volume, etc., so that the residence time of the air in the roasting chamber 12 can be kept within the above-mentioned preferred range.

[0052] The rising speed (Nm / s) of the air ejected from the fluidizing nozzle 15 can be appropriately set depending on the specific gravity and particle size (grain size) of the roasted sand, and is not particularly limited, but the lower limit is usually 0.2 Nm / s or more, and preferably 0.5 Nm / s or more. The upper limit of the rising speed (Nm / s) can usually be 2 Nm / s or less, and preferably 1.5 Nm / s or more. The rising speed can be set appropriately depending on the amount of air supplied (A1) by the first air supply system 21. In other words, the amount of air supplied (A1) by the first air supply system 21 can be adjusted so that the rising speed falls within the above range. The amount of air supplied by the second air supply system 52 (A2) is the amount of air supplied to the roasting chamber 12 per unit time A (m 3 / s), the sum of the air supply amount (A1) by the first air supply system 21 is the supply amount A (m 3 The range can be adjusted so that it does not exceed 1 / s.

[0053] As described above, by reducing the inner diameter of the lower portion 12A of the roasting chamber 12, the amount of air supplied (A1) by the first air supply system 21 required to form the fluidized bed FB can be reduced, and the volume of the fluidized bed FB formed can be made compact. In this way, if the air supply amount (A1) is reduced and the capacity of the fluidized bed FB is made compact, the capacity and size of the first air supplier 22 can be reduced, and as a result, it is possible to reduce equipment costs and operating costs such as electricity costs.

[0054] Moreover, the rising speed becomes faster as the furnace temperature of the roasting chamber 12 becomes higher. On the other hand, the velocity of the fluid (air) when the roasted sand starts to fluidize (hereinafter referred to as the "minimum fluidization velocity") decreases as the furnace temperature of the roasting chamber 12 increases. In consideration of the rise speed and the minimum fluidization speed, it is preferable to increase the amount of air supplied (A1) by the first air supply system 21 until roasting starts (i.e., while the furnace temperature is at room temperature), and to decrease the amount of air after roasting starts, especially during roasting (i.e., while the furnace temperature is high due to the combustion of combustibles). That is, it is preferable to reduce (throttle) the flow rate (A1) of the air supplied by the first air supply system 21 in at least two stages as the furnace temperature rises from room temperature to a high temperature (the temperature range during operation). In this case, it is possible to obtain advantages such as a reduction in the amount of heat generated by the air, suppression of scattering of roasted sand outside the furnace, and reduction in power consumption of the first air supplier 22.

[0055] A heat exchanger 34 can be connected between the first air intake system 21 and the exhaust system 31 . Specifically, the first air supply system 21 has an intake system 23 through which the first air supplier 22 draws in air. The exhaust system 31 and the intake system 23 are connected to the heat exchanger 34. The heat exchanger 34 exchanges heat between the exhaust gas discharged from the roasting chamber 12 by the exhaust system 31 and the air drawn into the first air supplier 22 from the intake system 23 and supplied to the roasting chamber 12, thereby preheating the air using the heat contained in the exhaust gas. The preheating temperature of the air is not particularly limited, but from the viewpoint that the higher the temperature of the air sprayed from the fluidizing nozzle 15, the more active the fluidization of the roasted sand becomes, the preferably it can be 200°C or higher, more preferably 230°C or higher, and even more preferably 270°C or higher.

[0056] When the air supplied from the first air supply system 21 to the roasting chamber 12 (furnace body 11) is preheated using the above-mentioned heat exchanger 34 or the like, the amount of air supplied (A1) by the first air supply system 21 required to form the fluidized bed FB can be reduced compared to when air is supplied without preheating. In other words, preheating the air can reduce the amount of air supplied (A1) to the roasting chamber 12 (furnace body 11), which in turn can reduce the capacity and size of the first air supplier 22, which is useful from the perspective of energy conservation and reduction of equipment capacity. Furthermore, by reducing the inner diameter of the lower portion 12A of the roasting chamber 12, the amount of air supplied (A1) can be reduced, which allows the heat exchanger 34 to be made smaller, which is particularly useful from the perspective of energy conservation of the equipment and reduction of equipment capacity.

[0057] (3) Exhaust system The exhaust system 31 is used to exhaust gas from the roasting chamber 12 of the furnace body 11, thereby facilitating the supply (introduction) of air into the roasting chamber 12, and also to exhaust carbon dioxide and other gases generated by roasting (combustion of combustible materials) as exhaust gases. The exhaust system 31 may have a damper 32. This damper 32 is for keeping the amount of exhaust from the furnace body 11 constant. Therefore, it is preferable to arrange the damper 32 in the immediate vicinity of the furnace body 11. The amount of air exhausted by the exhaust system 31 is not particularly limited as long as it is an amount that can introduce into the roasting chamber 12 an amount of air that can maintain the formed fluidized bed FB. Specifically, the displacement C (m 3 / s) is the amount of air supplied to the roasting chamber 12, A (m 3 / s) (C≈A), and more preferably within ±20% of the supply amount A [(0.8×A)≦C≦(1.2×A)].

[0058] The exhaust system 31 may have a dust collector 33. In addition to gas, the exhaust gas discharged by the exhaust system 31 contains solid matter such as scattered fine roasted sand, dust particles mixed in the roasted sand, and other particles. The dust collector 33 captures and removes the solid matter mixed in the exhaust gas, preventing it from being released to the outside together with the exhaust gas. The dust collection method of the dust collector 33 is not particularly limited, and examples include cyclones, scrubbers, bag filters, and electrostatic dust collectors. Of these, bag filters are preferred because they can handle large volumes of exhaust gas and can capture fine solids. When a heat exchanger 34 is connected between the exhaust system 31 and the first air supply system 21, it is possible to cool the exhaust gas that is discharged to the outside from the exhaust system 31. At this time, the temperature of the exhaust gas can be set preferably to 250°C or less, more preferably to 200°C or less. The position of the dust collector 33 in the exhaust system 31 is not particularly limited, but for example, when the dust collector 33 is a bag filter, it is preferable that the temperature of the exhaust gas is low. In such a case, the position of the dust collector 33 in the exhaust system 31 is preferably downstream of the heat exchanger 34.

[0059] (4) Controller The controller 41 is used to control the roasting of the roasted sand. Specifically, the controller 41 has a built-in electronic calculator (computer) equipped with an arithmetic processing unit such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit) and a memory area unit such as an HDD, SSD, or ROM, and executes a program stored in the memory area unit to control the roasting of the roasted sand. The controller 41 is electrically connected to a furnace temperature measuring instrument 42, an oxygen concentration measuring instrument 43, and an oxygen concentration measuring instrument 43. The controller 41 is also electrically connected to an air intake valve 54 and a supply valve 74.

[0060] The controller 41 can manage the combustion of combustibles contained in the roasted sand under the control of the roasting of the roasted sand by operating the air intake valve 54 and the supply valve 74 based on the furnace temperature measuring instrument 42, the oxygen concentration measuring instrument 43, and the detected value of the oxygen concentration measuring instrument 43. In managing the combustion of combustibles, the controller 41 can adjust the furnace temperature of the roasting chamber 12 to a predetermined temperature range. Specifically, the lower limit of the furnace temperature of the roasting chamber 12 can be preferably 700°C or higher, more preferably 800°C or higher. The upper limit of the furnace temperature of the roasting chamber 12 can be preferably 950°C or lower, more preferably 900°C or lower.

[0061] The controller 41 can be electrically connected to the first fuel valve 63A. In this case, the controller 41 can control the switching of the first burner 51 between the heating mode and the air supply mode by operating the first fuel valve 63A. The controller 41 can be electrically connected to the first air supplier 22. In this case, the controller 41 can operate the first air supplier 22 to appropriately adjust the amount of air supplied to the roasting chamber 12 by the first air supply system 21, the rising speed of the air ejected from the fluidizing nozzle 15, and the like. The controller 41 can be electrically connected to the second air supplier 53. In this case, the controller 41 can appropriately adjust the amount of air supplied to the roasting chamber 12 by the second air supply system 52 by operating the second air supplier 53.

[0062] (5) Roasted sand The fluidized bed roasting furnace 10 of the present invention is not particularly limited in terms of the type of roasted sand to be roasted, and any roasted sand containing combustible material can be roasted. Examples of roasted sand include used foundry sand, discarded firebricks (magnesia bricks, magnesia-carbon bricks, etc.), and ores such as sulfide ores and arsenide ores. The combustible material contained in the roasted sand is not particularly limited as long as it undergoes a combustion reaction (oxidation reaction) with oxygen. Typical combustible materials include organic materials such as binders, adhesives, and pressure-sensitive adhesives, and inorganic materials such as carbon, graphite, alkali metals (sodium, lithium, etc.), sulfur, and arsenic.

[0063] The fluidized bed roasting furnace 10 has a furnace body 11 equipped with a first burner 51, a second air supply system 52, etc., and can deal with the problem of the furnace temperature in the roasting chamber 12 rising excessively when the amount of combustible material contained in the roasting sand is large, or the problem of a lack of oxygen required for combustion. From this perspective, it can be said that the roasted sand useful as the object of roasting in the fluidized roasting furnace 10 contains a large amount of combustible material. The specific content of combustibles can be 1% by mass to 30% by mass, preferably 1.5% by mass to 25% by mass, and more preferably 2% by mass to 20% by mass, with the total amount of roasted sand being 100% by mass.

[0064] Roasted sand is preferred because it is easily fluidized and has a good yield. For example, if the roasted sand is made up of only small particle size powder, it is easy to fluidize, but the yield tends to decrease because the particles are easily blown away by the air and discharged outside the furnace. On the other hand, if the roasted sand is made up of only large particle size powder, the yield is good, but it is difficult to fluidize, and the operating costs increase due to the increased air supply. Therefore, it is preferable that the roasted sand contains both powder with a small particle size and particles with a large particle size. Specifically, when the total amount of roasted sand is taken as 100% by mass, it preferably contains 5 to 20% by mass of powder having an average particle size (D50) of 1 mm or less, and 70 to 90% by mass of granules having an average particle size (D50) of more than 1 mm and 5 mm or less.

[0065] In addition, roasted sand with a low bulk density is easy to fluidize, but is easily blown away by air and discharged outside the furnace, while roasted sand with a high bulk density has a good yield but is difficult to fluidize and requires an increased amount of air supply, resulting in higher operating costs. Therefore, it is preferable that the bulk density of the roasted sand is within a predetermined range. Specifically, the bulk density of the roasted sand is preferably 1400 kg / m 3 More than 3500kg / m 3 Less than or equal to 1500 kg / m 3 More than 3300kg / m 3 or less, more preferably 1600 kg / m 3 More than 3100kg / m 3 It can be as follows:

[0066] An example of roasted sand that can easily satisfy the above conditions is magnesia bricks (magnesia carbon bricks), which are discarded refractory bricks. Magnesia bricks mainly contain magnesia (MgO) and also contain 15% to 20% by mass of carbon or graphite as a combustible material. When magnesia bricks are made into roasted sand, the combustible carbon or graphite is removed to obtain magnesia (MgO). Although the magnesium (Mg) contained in magnesia (MgO) is used in a wide range of fields and applications, most of it is imported, and most magnesia bricks are discarded without being recycled. From the above, it is preferable that the roasted sand is obtained by crushing discarded magnesia bricks, and it is very useful from the viewpoints of economical effect, recycling effect, etc.

[0067] [2] Fluidized roasting method The fluidized bed roasting method of the present invention is a fluidized bed roasting method in which roasted sand is roasted using the above-mentioned fluidized bed roasting furnace 10, and combustible materials contained in the roasted sand are burned and removed, a fluidization step of injecting air upward from the fluidization nozzle 15 inside the roasting chamber 12 of the furnace body 11 to suspend the roasted sand in the air and fluidize the roasted sand; a combustion step of heating the roasted sand to cause combustibles contained in the roasted sand to react with oxygen in the air and burn, heating the roasted sand in the combustion step includes a preheating stage in which the roasted sand is preheated to a reaction temperature of the combustible material and the oxygen by the first burner 51, and a steady stage in which the roasted sand is heated by utilizing the combustion heat of the combustible material; In the steady state, the controller controls the combustion of the combustibles by supplying air to the roasting chamber through the second air supply system when the furnace temperature of the roasting chamber becomes excessive and / or when there is a shortage of oxygen required for the combustion.

[0068] (1) Fluidization process The fluidization step is a step of fluidizing the roasted sand to form a fluidized bed. FIG. 2 is a flow chart showing a specific example of the fluidization step. The fluidization step includes an operation (W1) of injecting air from the fluidization nozzle 15 in the roasting chamber 12 of the furnace body 11 of the fluidized roasting furnace 10, and an operation (W2) of charging roasted sand.

[0069] In operation (W1), air sent out from first air supplier 22 is supplied from first air supply system 21 to fluidizing nozzle 15 via air supply chamber 16 of furnace body 11. Fluidizing nozzle 15 injects the air supplied from first air supply system 21 toward the top of roasting chamber 12, and this injection forms an air flow from the bottom to the top of roasting chamber 12. In operation (W2), roasted sand is introduced into the roasting chamber 12 using the sand introduction chute 13. At this time, since an air flow from the bottom to the top of the roasting chamber 12 is formed in operation (W11), the roasted sand is dispersed in the air, floats, and fluidizes, forming a fluidized bed FB.

[0070] (2) Combustion process The combustion process involves burning combustible materials contained in the roasted sand by reacting them with oxygen in the air (combustion reaction, oxidation reaction). FIG. 3 is a flow chart showing an example of the combustion process. The combustion process includes a preheating stage (W3) and a steady-state stage (W4).

[0071] In the preheating stage (W3), the roasted sand is preheated in the roasting chamber 12 of the furnace body 11 of the fluidized roasting furnace 10. FIG. 4 is a flow chart illustrating an example of the preheating stage of the combustion process. The preheating stage includes the steps of switching the first burner 51 to heating mode (W31), preheating the roasted sand with the first burner 51 (W32), determining whether the furnace temperature has reached the combustion start temperature (W33), and switching the first burner 51 to air supply mode (W34). The operation (W31) of switching the first burner 51 to the heating mode and the operation (W34) of switching the first burner 51 to the air supply mode are performed when the second air supply system 52 is connected to the first burner 51. Therefore, when the second air supply system 52 is directly connected to the furnace body 11, the operations (W31) and (W34) can be omitted.

[0072] In operation (W31), the first fuel valve 63A opens the first fuel supply system 62A, fuel and air are sent from the second air supply system 52 to the first burner 51, and the first burner 51 is set to the heating mode. Note that if operation (W31) is omitted, the controller 41 operates the first fuel valve 63A to open the first fuel supply system 62A, and fuel and air are sent from the fuel supply unit 61 to the first burner 51 via the first fuel supply system 62A. In operation (W32), fuel is ignited by the first burner 51, and combustion gas (flame) is ejected from the first burner 51, thereby preheating the roasted sand on the surface (upper surface) of the fluidized bed FB. In operation (W33), it is determined whether the furnace temperature of the roasting chamber 12 has reached the combustion start temperature of the combustibles contained in the roasting sand, based on measurements by the furnace temperature measuring device 42. If it is determined in operation (W33) that the furnace temperature has not reached the combustion start temperature of the combustibles (no in W33), the preheating of the roasting sand by operation (W32) continues. If it is determined that the furnace temperature has reached the combustion start temperature of the combustibles (yes in W33), operation (W34) is executed. In operation (W34), the first fuel valve 63A closes the first fuel supply system 62A, and only air is sent from the second air supply system 52 to the first burner 51, placing the first burner 51 in air supply mode. Note that if operation (W34) is omitted, the controller 41 operates the first fuel valve 63A to close the first fuel supply system 62A, thereby stopping the preheating of the roasted sand by the first burner 51 and ending the preheating stage.

[0073] The roasted sand, which has been preheated to the combustion initiation temperature of the combustibles in the preheating stage, generates heat by itself due to the heat of combustion generated by the combustion of the combustibles. In the steady state stage (W4), the roasted sand is heated in the roasting chamber 12 of the furnace body 11 of the fluidized roasting furnace 10 using the heat of combustion of combustibles, that is, the roasted sand is roasted using the heat generated by self-heating. In this steady state stage (W4), combustion management 1, combustion management 2, and combustion managements 3A and 3B are executed to manage the combustion in accordance with the state of the roasting chamber 12 caused by the combustion of combustibles (see FIG. 3). Any one of combustion management 1, combustion management 2, and combustion management 3A and 3B may be executed depending on the state of the roasting chamber 12, or two or more selected from combustion management 1, combustion management 2, and combustion management 3A and 3B may be executed. Regarding combustion management 3A and 3B, in the above-mentioned fluidized roasting furnace 10, combustion management 3A is performed when the furnace body 11 is equipped with a second burner 71, and combustion management 3B is performed when the furnace body 11 is not equipped with a second burner 71.

[0074] Combustion management 1 is executed when the furnace temperature of the roasting chamber 12 becomes excessively high due to the combustion of combustibles. FIG. 5 is a flowchart showing a specific example of combustion management 1 in the steady state stage (W4). Combustion management 1 includes the steps of checking whether the furnace temperature of the roasting chamber 12 has risen too high (W411), supplying air from the second air supply system 52 (W412), checking whether the furnace temperature of the roasting chamber 12 has reached the specified value (W413), and stopping the air supply from the second air supply system 52 (W414).

[0075] In operation (W411), the furnace temperature of the roasting chamber 12 is measured by the furnace temperature measuring instrument 42, and the measured value is sent to the controller 41. The controller 41 determines whether the furnace temperature of the roasting chamber 12 has risen too high based on the measured value from the furnace temperature measuring instrument 42. If it is determined in operation (W411) that the furnace temperature has not risen too high (W411; no), combustion management 1 ends. If it is determined that the furnace temperature has risen too high (W411; yes), operation (W412) is executed. In operation (W412), air is supplied from second air supply system 52 to roasting chamber 12. In this operation (W412), controller 41 operates air supply valve 54 to open second air supply system 52, and sends air supplied from second air supplier 53 into roasting chamber 12 while adjusting the supply amount, etc., using air supply valve 54. The operation (W412) can be performed using the first burner 51 switched to the air supply mode in the operation (W34) of the preheating stage (W3) when the second air supply system 52 is connected to the first burner 51. In this case, air from the second air supply system 52 is supplied to the roasting chamber 12 via the first burner 51.

[0076] In operation (W413), the controller 41 determines whether the furnace temperature of the roasting chamber 12 has reached a specified value based on the measurement value from the furnace temperature measuring device 42. If it is determined in operation (W413) that the furnace temperature has not reached the specified value (W413; no), operation (W412) continues to be executed. If it is determined that the furnace temperature has reached the specified value (W413; yes), operation (W414) is executed. The specified value of the furnace temperature in operation (W413) can be specifically set to 650°C or higher and 1000°C or lower, preferably 750°C or higher and 950°C or lower, and more preferably 800°C or higher and 900°C or lower. In operation (W414), the controller 41 operates the air intake valve 54 to close the second air intake system 52, thereby stopping the air supply to the roasting chamber 12.

[0077] Combustion management 2 is executed when the amount of oxygen required for burning combustibles in the roasting chamber 12 becomes insufficient. FIG. 6 is a flowchart showing a specific example of combustion management 2 in the steady state stage (W4). Combustion management 2 includes the steps of checking whether the carbon monoxide (CO) value in the roasting chamber 12 is rising (W421), supplying air from the second air supply system 52 (W422), checking whether the oxygen (O2) value in the roasting chamber 12 is at a specified value (W423), and stopping the air supply from the second air supply system 52 (W424).

[0078] In operation (W421), the carbon monoxide concentration in the roasting chamber 12 is measured by the oxygen concentration measuring instrument 43, and the measured value is sent as a CO value to the controller 41. Based on the CO value sent from the oxygen concentration measuring instrument 43, the controller 41 determines whether there is a shortage of oxygen required for burning combustible materials in the roasting chamber 12. Specifically, in the combustion reaction of combustibles, if the atmosphere is sufficiently oxygen-rich, carbon dioxide (CO2) is produced and almost no carbon monoxide (CO) is produced, whereas if the atmosphere is insufficient in oxygen, carbon monoxide (CO) is produced and almost no carbon dioxide (CO2) is produced. Therefore, an increase in the CO value means that carbon monoxide (CO) is being produced and there is a shortage of oxygen. In operation (W421), if it is determined that the CO value is not rising (W421; no), combustion management 2 ends. If it is determined that the CO value is rising (W421; yes), operation (W422) is executed.

[0079] In operation (W422), air is supplied from second air supply system 52 to roasting chamber 12. In this operation (W422), controller 41 operates air supply valve 54 to open second air supply system 52, and sends air supplied from second air supplier 53 into roasting chamber 12 while adjusting the supply amount, etc., using air supply valve 54. The operation (W422) can be performed using the first burner 51 switched to the air supply mode in the operation (W34) of the preheating stage (W3) when the second air supply system 52 is connected to the first burner 51. In this case, air from the second air supply system 52 is supplied to the roasting chamber 12 via the first burner 51. In operation (W423), the oxygen concentration in the roasting chamber 12 is measured by the oxygen concentration measuring device 43, and the measured value is sent to the controller 41 as an O2 value. Based on the O2 value sent from the oxygen concentration measuring device 43, the controller 41 determines whether a sufficient amount of oxygen has been supplied to the roasting chamber 12 to burn the combustible material. In operation (W423), if it is determined that the O2 value has not reached the specified value (W423; no), operation (W422) continues to be executed. If it is determined that the O2 value has reached the specified value (W423; yes), operation (W424) is executed. In operation (W424), the controller 41 operates the air intake valve 54 to close the second air intake system 52, thereby stopping the air supply to the roasting chamber 12.

[0080] Combustion management 3A and 3B are performed when the furnace temperature of the roasting chamber 12 drops during roasting, i.e., even while combustible materials are being burned. Combustion management 3A and 3B are essentially the same process, except that the second burner 71 is used to heat the fluidized bed FB in combustion management 3A, while the first burner 51 is used in combustion management 3B. FIG. 7 is a flowchart showing a specific example of combustion management 3A in the steady state stage (W4). Combustion management 3A includes the steps of checking whether the furnace temperature of the roasting chamber 12 is decreasing (W431), heating the fluidized bed FB with the second burner 71 (W432), checking whether the furnace temperature of the roasting chamber 12 is at a specified value (W433), and stopping heating by the second burner 71 (W434).

[0081] In operation (W431), the furnace temperature of the roasting chamber 12 is measured by the furnace temperature measuring instrument 42, and the measured value is sent to the controller 41. Based on the measured value from the furnace temperature measuring instrument 42, the controller 41 determines whether the furnace temperature of the roasting chamber 12 is maintained within a predetermined temperature range. In operation (W431), if it is determined that the furnace temperature is maintained within the predetermined temperature range and has not decreased (W431; no), combustion management 3A ends. If it is determined that the furnace temperature is not maintained within the predetermined temperature range and has decreased (W431; yes), operation (W432) is executed. In operation (W432), the controller 41 operates the supply valve 74 to open the third air supply system 72, and sends compressed air supplied from the compressed air supplier 73 and fuel sent from the fuel supply unit 61 via the second fuel supply system 62B to the second burner 71. The second burner 71 injects the sent compressed air and fuel into the fluidized bed FB, igniting the fuel with the self-heat generated by the roasted sand during roasting, thereby heating the fluidized bed FB.

[0082] In operation (W433), the controller 41 determines whether the furnace temperature of the roasting chamber 12 has reached a specified value based on the measurement value from the furnace temperature measuring device 42. If it is determined in operation (W433) that the furnace temperature has not reached the specified value (W433; no), operation (W432) continues to be executed. If it is determined that the furnace temperature has reached the specified value (W433; yes), operation (W434) is executed. Specifically, the specified value of the furnace temperature in operation (W433) can be preferably 650°C or higher, more preferably 750°C or higher, even more preferably 800°C or higher, and particularly preferably 850°C or higher. In operation (W434), the controller 41 operates the supply valve 74 to close the third air supply system 72, thereby stopping heating by the second burner 71.

[0083] FIG. 8 is a flowchart showing a specific example of combustion management 3B in the steady state stage (W4). Combustion management 3B includes the steps of checking whether the furnace temperature of the roasting chamber 12 is decreasing (W441), switching the first burner 51 to heating mode (W442), heating the fluidized bed FB with the first burner 51 (W443), checking whether the furnace temperature of the roasting chamber 12 is at a specified value (W444), stopping heating by the first burner 51 (W445), and switching the first burner 51 to air supply mode (W446). The operation (W442) of switching the first burner 51 to the heating mode and the operation (W446) of switching the first burner 51 to the air supply mode are performed when the second air supply system 52 is connected to the first burner 51. Therefore, when the second air supply system 52 is directly connected to the furnace body 11, the operations (W442) and (W446) can be omitted.

[0084] Operation (W441) is substantially the same as operation (W431) of the above-described Combustion Management 3A. If operation (W441) determines that the furnace temperature is maintained within the predetermined temperature range and has not decreased (W441; no), Combustion Management 3B ends. If operation (W441) determines that the furnace temperature is not maintained within the predetermined temperature range and has decreased (W441; yes), operation (W442) is executed. In operation (W442), the second air supplier 53 is stopped, the first fuel supply system 62A is opened by the first fuel valve 63A, fuel and air are sent from the second air supply system 52 to the first burner 51, and the first burner 51 is set to heating mode.

[0085] In operation (W443), the controller 41 operates the air intake valve 54 to open the second air intake system 52, and sends the fuel and air sent from the fuel supply unit 61 via the first fuel supply system 62A to the first burner 51. The first burner 51 ignites the sent air and fuel to inject combustion gas (flame) into the roasting chamber 12, and heats the fluidized bed FB by licking the surface (upper surface) of the fluidized bed FB with the combustion gas (flame). In addition, in operation (W443), when the second air supply system 52 is not connected to the first burner 51, the controller 41 operates the first fuel valve 63A to open the first fuel supply system 62A, and sends the fuel and air sent from the fuel supply unit 61 via the first fuel supply system 62A to the first burner 51.

[0086] Operation (W444) is substantially the same as operation (W431) of the above-described Combustion Management 3A. If operation (W444) determines that the furnace temperature has not reached the specified value (W444; no), operation (W443) continues to be executed. If operation (W444) determines that the furnace temperature has reached the specified value (W444; yes), operation (W445) is executed. In operation (W445), the controller 41 operates the air intake valve 54 to close the second air intake system 52, thereby stopping heating by the first burner 51. Note that in a configuration in which the second air intake system 52 is not connected to the first burner 51, operation (W445) can be performed by the controller 41 operating the first fuel valve 63A to close the first fuel supply system 62A, thereby stopping heating by the first burner 51. In operation (W446), the first fuel supply system 62A is closed by the first fuel valve 63A, only air is sent from the second air supply system 52 to the first burner 51, and the first burner 51 is set to the air supply mode. [Industrial Applicability]

[0087] The present invention is highly versatile and can stably roast any roasted sand containing combustible material, making it particularly useful for recycling waste materials into recycled materials. [Explanation of symbols]

[0088] 10;Fluidized torrefaction furnace, FB;Fluidized bed, 11; furnace body, 12; roasting chamber, 13; sand injection chute, 14; discharge nozzle, 15; fluidization nozzle, 16; air supply chamber, 17; exhaust chamber, 18; perforated wall, 19; preheating system, 21; first air supply system, 22; first air supplier, 23; intake system, 31; exhaust system, 32; damper, 33; dust collector, 34; heat exchanger, 41;Controller, 42;Furnace temperature measuring instrument, 43;Oxygen concentration measuring instrument, 44;Carbon monoxide concentration measuring instrument, 51; first burner, 52; second air supply system, 53; second air supplier, 54; air supply valve, 61; fuel supply unit, 62A; first fuel supply system, 63A; first fuel valve, 62B; second fuel supply system, 63B; second fuel valve, 71; second burner, 72; third air supply system, 73; compressed air supplier, 74; supply valve.

Claims

1. A fluidized bed roasting furnace in which roasted sand is suspended in gas and roasted in a fluidized bed, and combustible materials contained in the roasted sand are burned and removed, a furnace body having a roasting chamber for accommodating the roasted sand; a first air supply system connected to the furnace body to supply air to the roasting chamber; an exhaust system connected to the furnace body for exhausting gas from the roasting chamber; a controller for controlling the roasting of the roasted sand in the roasting chamber; The furnace body is a fluidizing nozzle installed at the bottom of the roasting chamber, connected to the first air supply system, and configured to inject the air from the bottom side toward the top side of the roasting chamber to form the fluidized bed in the roasting chamber; a first burner installed in the roasting chamber so as to be disposed above the fluidized bed; a second air supply system connected to an upper side of the fluidized bed and supplying air to the roasting chamber, the controller adjusts the supply of air to the roasting chamber by the second air supply system to control the combustion of the combustibles; the roasted sand is obtained by crushing discarded magnesia bricks, and the magnesia bricks contain carbon or graphite as the combustible material; The content of the combustible material contained in the roasted sand is 15% by mass to 20% by mass, with the total amount of the roasted sand being 100% by mass, The fluidized bed roasting furnace is characterized in that the second air supply system is a dedicated line for supplying cooling air when the furnace temperature of the roasting chamber becomes excessively high and for supplying air to assist combustion when there is a shortage of oxygen.

2. the first burner is switchable between a heating mode in which combustion gas is ejected into the roasting chamber and an air supply mode in which air is ejected into the roasting chamber, the second air supply system is connected to the first burner, 2. The fluidized bed roasting furnace according to claim 1, wherein the supply of air to the roasting chamber by the second air supply system is performed via the first burner switched to the air supply mode.

3. The furnace body includes a second burner installed in the roasting chamber so as to be disposed inside the fluidized bed, 3. The fluidized bed roasting furnace according to claim 1, wherein the controller controls the combustion of the combustible material by adjusting the heating of the roasted sand by the second burner.

4. The roasted sand contains, when the total amount is taken as 100% by mass, 5 to 20% by mass of powder having a particle size of 1 mm or less and 70 to 90% by mass of granules having a particle size of more than 1 mm and 5 mm or less, Bulk density is 1400 kg / m ３ More than 3500kg / m ３ 3. The fluidized roasting furnace according to claim 1 or 2, wherein:

5. 3. The fluidized bed roasting furnace according to claim 1, wherein the roasting chamber has a lower portion with a smaller inner diameter than an upper portion.

6. The fluidized roasting furnace according to claim 1 or 2, wherein the first burner is accommodated in the roasting chamber and is installed above the fluidized bed, with the nozzle holes for ejecting combustion gas or air facing diagonally downward at an angle of 20 to 50 degrees relative to the vertical direction.

7. The fluidized bed roasting furnace according to claim 1 or 2, wherein the controller adjusts the furnace temperature to a range of 650°C to 1000°C.

8. 3. The fluidized bed roasting furnace according to claim 1, wherein the furnace body is provided with a measuring device for measuring the oxygen concentration and / or the carbon monoxide concentration in the roasting chamber.

9. a heat exchanger connected between the exhaust system and the first air intake system, 3. The fluidized bed roasting furnace according to claim 1, wherein the heat exchanger exchanges heat between the exhaust gas discharged from the roasting chamber and the air supplied to the roasting chamber, thereby preheating the air to be supplied to the roasting chamber to 200°C or higher.

10. 3. The fluidized bed roasting furnace according to claim 1, wherein the exhaust system includes a dust collector for removing dust from the exhaust gas discharged from the roasting chamber.

11. A fluidized bed roasting method for roasting roasted sand by using the fluidized bed roasting furnace according to claim 1 or 2, and burning and removing combustibles contained in the roasted sand, a fluidization step of injecting air upward from the fluidization nozzle inside the roasting chamber of the furnace body to suspend the roasted sand in the air and fluidize the roasted sand; a combustion step of heating the roasted sand to cause combustibles contained in the roasted sand to react with oxygen in the air and burn, The roasted sand is obtained by crushing discarded magnesia bricks, and the magnesia bricks contain carbon or graphite as the combustible material. The content of the combustible material contained in the roasted sand is 15% by mass to 20% by mass, with the total amount of the roasted sand being 100% by mass, heating the roasted sand in the combustion step includes a preheating stage in which the roasted sand is preheated to a reaction temperature of the combustible material and the oxygen by the first burner, and a steady-state stage in which the roasted sand is heated by utilizing the combustion heat of the combustible material; a fluidized bed roasting method, characterized in that in the steady state, when the furnace temperature of the roasting chamber becomes excessive, the controller controls the combustion of the combustibles by supplying cooling air to the roasting chamber through the second air supply system, and when the oxygen required for the combustion is insufficient, the controller controls the combustion of the combustibles by supplying combustion-assisting air to the roasting chamber through the second air supply system.

12. The roasted sand contains, when the total amount is taken as 100% by mass, 5 to 20% by mass of powder having an average particle size of 1 mm or less and 70 to 90% by mass of granules having an average particle size of more than 1 mm and 5 mm or less, Bulk density is 1400 kg / m ３ More than 3500kg / m ３ The fluidized roasting method according to claim 11, wherein:

13. The fluidized roasting method according to claim 11, wherein the controller adjusts the furnace temperature of the roasting chamber to a range of 650°C to 1000°C.

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