Flow roasting furnace and flow 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 roasting furnace and a fluidized roasting method for burning and removing combustibles contained in roasted sand by fluidized roasting.

Background Art

[0002] Generally, used casting sand, used MgO-C bricks, etc. contain impurities such as organic substances such as binders, adhesives, and tackifiers, and inorganic substances such as carbon. Since most of these impurities are combustibles, the pulverized products of used casting sand and used MgO-C bricks are roasted (calcined) as roasted sand, and the combustibles are burned and removed to enable reuse and the like. As an apparatus for roasting, Patent Document 1 discloses a fluidized roasting furnace. This fluidized roasting furnace uses used casting sand etc. as roasted sand, and forms a fluidized bed of the roasted sand with air ejected from a nozzle to perform roasting. Also, Patent Document 2 discloses that pulverized products of used MgO-C bricks used for lining furnaces for steelmaking are used as roasted sand, and a firing process (roasting) is performed using a rotary kiln. This rotary kiln performs roasting while stirring the roasted sand in the furnace by rotating a cylindrical furnace body. In addition to fluidized roasting furnaces and rotary kilns, as apparatuses for roasting, there can be mentioned shuttle kilns, electric furnaces, etc. that roast by storing a trolley, a container, etc. into which roasted sand has been charged in a furnace.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Roasting using a rotary kiln (see Patent Document 2), a shuttle kiln, an electric furnace, etc. makes it difficult to uniformly contact the roasted sand with air, resulting in variations in the roasting condition and making it difficult to stabilize the quality after roasting. Therefore, in order to solve this problem, the roasting time tends to be lengthened. In particular, in the case of a rotary kiln, as the roasting time becomes longer, the roasted sand rubbed against each other by long-time stirring is mechanically worn and refined until the required particle size as an aggregate such as foundry sand or bricks cannot be obtained, resulting in poor yield. A fluidized roasting furnace (see Patent Document 1) can uniformly contact the roasted sand with air by forming a fluidized bed, making it difficult for variations to occur in the roasting condition, having no mechanical wear, and being more useful than a rotary kiln or the like. However, a normal fluidized roasting furnace is substantially limited to those with a relatively small amount of combustible substances such as used foundry sand as the object of roasting in order to perform roasting stably. That is, when a normal fluidized roasting furnace roasts an object with a relatively large amount of combustible substances such as used MgO-C bricks, the roasting may become unstable, such as the combustion heat amount increasing and causing an excessive rise in the furnace temperature, or the oxygen required for combustion being insufficient.

[0005] The present invention aims to solve the problems of such conventional technologies, and provides a fluidized roasting furnace and a fluidized roasting method capable of stably performing roasting without limiting the object of roasting.

Means for Solving the Problems

[0006] In order to solve the above problems, the invention of the fluidized roasting furnace according to claim 1 is a fluidized roasting furnace that roasts the roasted sand in a fluidized bed formed by suspending the roasted sand in a gas to burn and remove combustible substances contained in the roasted sand, comprising: a furnace body having a roasting chamber for accommodating the roasted sand; a first air supply system connected to the furnace body for supplying air to the roasting chamber; an exhaust system connected to the furnace body for exhausting gas from the roasting chamber; a controller configured to control the roasting of the roasted sand in the roasting chamber; The furnace body is installed at the bottom of the roasting chamber and connected to the first air supply system to form a fluidized bed in the roasting chamber by injecting the air from the bottom side to the upper side of the roasting chamber; a fluidizing nozzle a first burner installed in the roasting chamber so as to be disposed above the fluidized bed; a second air supply system connected above the fluidized bed to supply air to the roasting chamber; The gist of the invention is that the controller manages the combustion of the combustible material by adjusting the supply of air to the roasting chamber by the second air supply system. The invention according to claim 2 is the invention according to claim 1, wherein the first burner is switchable between a heating mode of ejecting combustion gas into the roasting chamber and an air supply mode of ejecting air into the roasting chamber, the second air supply system is connected to the first burner, The gist of the invention is that the supply of air to the roasting chamber by the second air supply system is performed through the first burner switched to the air supply mode. The invention according to claim 3 is the invention according to 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 of the invention is that the controller manages the combustion of the combustible material by adjusting the heating of the roasted sand by the second burner. The invention according to claim 4 is the invention according to claim 1 or 2, wherein the roasted sand contains 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 exceeding 1 mm and not exceeding 5 mm when the total amount is 100% by mass, The bulk specific gravity is 1400 kg / m 3 3500 kg / m or more 3 The gist of the invention is that it is below. The invention according to claim 5 is the invention according to claim 1 or 2, wherein the roasting chamber has an inner diameter at the lower part smaller than that at the upper part. The invention according to claim 6 is the invention according to claim 1 or 2, wherein the first burner is installed in the roasting chamber above the fluidized bed on the upper side of the roasting chamber, and the ejection holes for ejecting combustion gas or air are arranged obliquely downward in the range of 20 degrees to 50 degrees with respect to the vertical direction. The invention according to claim 7 is the invention according to claim 1 or 2, wherein the controller adjusts the furnace temperature to be in the range of 650 °C or more and 1000 °C or less. The invention according to claim 8 is the invention according to claim 1 or 2, wherein the furnace body is provided with a measuring device for measuring the oxygen concentration and / or carbon monoxide concentration in the roasting chamber. The invention according to claim 9 is the invention according to claim 1 or 2, which includes a heat exchanger connected between the exhaust system and the first air supply system. The gist is that heat exchange is performed between the exhaust gas exhausted from the roasting chamber and the air supplied to the roasting chamber by the heat exchanger to preheat the air supplied to the roasting chamber to 200 °C or more. The invention according to claim 10 is the invention according to claim 1 or 2, wherein the exhaust system has a dust collector for removing dust from the exhaust gas exhausted from the roasting chamber. The invention according to claim 11 is the invention according to claim 1 or 2, wherein the roasted sand is obtained by pulverizing discarded magnesia bricks. The invention according to claim 12 is the invention according to 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 the fluidized roasting method according to claim 13 is a fluidized roasting method using the fluidized roasting furnace according to claim 1 or 2, roasting roasted sand to burn and remove the combustible material 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 the combustible material contained in the roasted sand to react with oxygen in the air and burn, is provided. The heating of the roasted sand in the combustion step includes a preheating stage of preheating the roasted sand to the reaction temperature of the combustible material and oxygen by the first burner, and a steady stage of heating the roasted sand using the combustion heat of the combustible material. In the steady stage, when the furnace temperature in the roasting chamber rises excessively and / or when the oxygen required for combustion is insufficient, the controller supplies air to the roasting chamber by the second air supply system to manage the combustion of the combustible material. This is the gist. The invention according to claim 14 is the invention according to claim 13, wherein the roasted sand contains 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 exceeding 1 mm and 5 mm or less, when the total amount is 100% by mass. The bulk specific gravity is 1400 kg / m 3 3500 kg / m or more 3 The following is the gist. The invention according to claim 15 is the invention according to claim 13 or 14, wherein the roasted sand is obtained by pulverizing discarded magnesia bricks. This is the gist. The invention according to claim 16 is the invention according to claim 13 or 14, wherein the content of the combustible material contained in the roasted sand is 1 to 30% by mass, with the total amount of the roasted sand being 100% by mass. This is the gist. The invention according to claim 17 is the invention according to claim 13 or 14, wherein the controller adjusts the furnace temperature in the roasting chamber to a range of 650°C or more and 1000°C or less. This is the gist.

Advantages of the Invention

[0007] According to the present invention, by providing a second air supply system separate from the first air supply system that supplies gas for fluidizing the roasted sand, and adjusting the supply of air from the second air supply system to the roasting chamber using the first burner, the combustion of the combustible material can be managed, and roasting can be stably performed without being limited to the object of roasting.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

[0009] The matters shown here are illustrative and for exemplarily explaining the embodiments of the present invention, and are described for the purpose of providing an explanation that can most effectively and without difficulty understand the principles and conceptual features of the present invention. In this regard, it is not intended to show more structural details of the present invention than necessary for a fundamental understanding of the present invention, and it is to clarify for those skilled in the art how some forms of the present invention are actually embodied by the description in combination with the drawings.

[0010] [1] Fluidized Roasting Furnace The fluidized roasting furnace of the present invention is a fluidized roasting furnace 10 that roasts the roasting sand in a fluidized bed FB formed by suspending the roasting sand in a gas and burns and removes combustibles contained in the roasting sand, having a furnace body 11 having a roasting chamber 12 for accommodating the roasting 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, and a controller 41 for controlling the roasting of the roasted sand in the roasting chamber 12. The furnace body 11, is installed at the bottom of the roasting chamber 12 and is connected to the first air supply system 21 to form a fluidized bed FB in the roasting chamber 12 by injecting the air from the bottom side to the upper side of the roasting chamber 12. A fluidizing nozzle 15, A first burner 51 installed in the roasting chamber 12 so as to be arranged on the upper side of the fluidized bed FB, and a second air supply system 52 connected to the upper side of the fluidized bed FB for supplying air to the roasting chamber. The controller 41 is characterized in that it manages the combustion of the combustible material 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 the roasted sand and burns and removes the combustible material contained in the roasted sand. As shown in FIG. 1, it includes 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. In addition, the fluidized roasting furnace 10 is configured such that the heat required for roasting the roasted sand can be covered by the heat generated by the combustion of the combustible material without substantially relying on the application from the outside.

[0012] The furnace body 11 is the main part of the fluidized roasting furnace 10, has a roasting chamber 12 for accommodating roasted sand inside, and is for roasting 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 for the combustion of the combustible material contained in the roasted sand. The exhaust system 31 is for exhausting the 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 manages the combustion of combustibles contained in the roasted sand.

[0013] Hereinafter, each component included in the fluidized roasting furnace 10 will be described. (1) Furnace body The overall shape and the like of the furnace body 11 are not particularly limited as long as it can have a roasting chamber 12 for accommodating the roasted sand. Usually, the furnace body 11 can be formed in a vertical cylindrical shape 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 provided with a fluidization nozzle 15 installed at the bottom of the roasting chamber 12. The fluidization nozzle 15 is for supplying air from the first air supply system 21 to the roasting chamber 12 and for fluidizing the roasted sand. The fluidization 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 jetted from the bottom side to the upper side of the roasting chamber 12.

[0014] A plurality of fluidization nozzles 15 are installed at the bottom of the roasting chamber 12, and each can jet air toward the upper side of the roasting chamber 12. The roasted sand is blown upward from the bottom to the top of the roasting chamber 12 by the jet of air from the fluidization nozzle 15, floats in the air and is fluidized to form a fluidized bed FB. The roasted sand in the fluidized bed FB is in a state of floating in the air and can be uniformly and evenly contacted with the oxygen contained in the air.

[0015] From the viewpoints of jetting air into the roasting chamber 12 at a uniform speed (rising speed) and making the height of the roasted sand swelled by fluidization, in other words, making the vertical height of the formed fluidized bed FB uniform, the plurality of fluidization nozzles 15 can be arranged at equal intervals in the width direction (radial direction) of the furnace body 11. Specifically, the interval between the fluidization nozzles 15 can be 50 to 150 mm, preferably 60 to 100 mm, which is the distance (pitch) between the centers of adjacent fluidization nozzles 15.

[0016] When the intervals between the plurality of fluidization nozzles 15 are within the above-described range, the upward velocity of the air can be made uniform at each fluidization nozzle 15, so that the swelling of the roasted sand due to fluidization (the vertical height of the fluidized bed FB) can be made uniform, and it is particularly useful in the fluidization of roasted sand (coarse aggregate) having a particle size (φ) of 1 mm to 5 mm. The vertical height of the fluidized bed FB can be determined according to the upward velocity of the gas ejected from the fluidization nozzle 15, but usually, it can be set to such an extent that the fluidized bed FB is contained 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. This first burner 51 is provided in the upper part 12B of the roasting chamber 12, and thus is arranged on the upper side of the fluidized bed FB. The first burner 51 is provided for preheating the roasted sand before roasting and supplying air to the roasting chamber 12 during roasting.

[0018] When the furnace body 11 does not include the second burner 71 described later, the first burner 51 can be a so-called "preheating and heating" burner that preheats the roasted sand before roasting and heats the roasted sand during roasting. That is, after preheating the roasted sand before roasting by the first burner 51 to cause self-heating, if the amount of combustible matter contained in the roasted sand is small, the amount of heat generated by self-heating will be small, and the amount of heat required for roasting (combustion of the combustible matter) may be insufficient. In such a case, by using the first burner 51 to heat the roasted sand, the amount of heat required for the combustion of the combustible matter can be supplemented. In other words, when the furnace body 11 does not include the second burner 71, the first burner 51 is a "preheating and heating" burner and can preheat the roasted sand before roasting and heat the roasted sand during roasting.

[0019] Alternatively, when the furnace body 11 includes the second burner 71 described later, the first burner 51 can be a so-called "preheating" burner that preheats the roasted sand before roasting. That is, after preheating the roasting sand before roasting with the first burner 51 to cause self-heating, when the amount of heat required for roasting (combustion of combustibles) is insufficient, even without using the first burner 51, the second burner 71 can be used to heat the roasting sand, thereby compensating for the amount of heat required for the combustion of combustibles. In other words, when the furnace body 11 is provided with the second burner 71, the first burner 51 can be regarded as for "preheating", used to preheat the roasting sand before roasting, and after being used for preheating, it can be substantially not used for heating the roasting sand.

[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 arranged on the upper side of the fluidized bed FB. The second air supply system 52 is provided for supplying air to the roasting chamber 12. The second air supply system 52 can be connected to the first burner 51, and in this case, air can be supplied to the roasting chamber 12 through the first burner 51. A first fuel supply system 62A extending from the fuel supply section 61 is connected to the first burner 51. The first fuel supply system 62A is for supplying fuel from the fuel supply section 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 through 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 regulate the fuel supply to the first burner 51 by opening and closing the first fuel supply system 62A. The first fuel valve 63A is not particularly limited as long as the first fuel supply system 62A can be opened and closed, and examples include solenoid valves, motor-operated valves, on-off valves, etc. The type and state of the fuel supplied from the fuel supply section 61 are not particularly limited. Usually, from the viewpoints of easy availability, good usability, suitable ignition property, obtainable heat quantity, etc., for example, city gas such as 12A gas and 13A gas, and combustible gases such as LP gas (propane gas) can be used.

[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 type of the second air supplier 53 is not particularly limited 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 air velocity. 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 regulate the supply of air, fuel, etc. to the first burner 51 by opening and closing the second air supply system 52. The type of the air supply valve 54 is not particularly limited as long as the second air supply system 52 can be opened and closed, and examples thereof include an electric valve, a solenoid valve, etc. Among these, an electric valve is preferable because, for example, it can arbitrarily adjust the air supply amount 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 switched between a heating mode in which combustion gas is ejected into the roasting chamber 12 based on the 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 ejected into the roasting chamber 12. The switching between the heating mode and the air supply mode of the first burner 51 can be mainly executed by switching the allowance and regulation of the fuel supply to the first burner 51 by the first fuel valve 63A. That is, the first burner 51 can be set to the heating mode in a state where the fuel supply from the first fuel supply system 62A is allowed, and can be set to the air supply mode in a state where the fuel supply from the first fuel supply system 62A is regulated. 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, for example, those having ejection holes such as a nozzle burner or a gun burner that are open outward are preferable.

[0023] The first burner 51 can be installed with the ejection holes for ejecting combustion gas or the like facing obliquely downward. That is, the first burner 51 in the heating mode is used as "for preheating" when the furnace body 11 is provided with a second burner 71 described later, and is used as "for preheating and heating" when the furnace body 11 is not provided with the second burner 71. When using the first burner 51 in the heating mode as such "for preheating" or "for preheating and heating", from the viewpoint of improving the efficiency of heating the roasted sand, it is preferable to let the combustion gas (flame) ejected from the first burner 51 lick (directly hit) the surface of the roasted sand (fluidized bed FB). When the first burner 51 is installed with the ejection holes facing obliquely downward, the combustion gas (flame) ejected obliquely downward from the ejection holes diffuses, so that the surface of the roasted sand (fluidized bed FB) can be licked over a wide range. Specifically, the installation angle of the first burner 51 is preferably in the range of 20 degrees to 50 degrees, more preferably in the range of 30 degrees to 45 degrees, with respect to the vertical direction.

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

[0025] The heat of combustion generated by the combustion reaction of a part of the combustible substances contained in the roasted sand with oxygen heats other combustible substances and induces a combustion reaction. Therefore, the roasted sand self-heats by the heat of combustion generated by the chain combustion reaction of the combustible substances without external heat addition. Thus, the amount of heat required for roasting the roasted sand can be covered by the heat generated by the self-heating of the roasted sand. Since the amount of heat required for roasting the roasted sand is covered by the heat generated by the self-heating of the roasted sand, the roasted sand after preheating does not need to be constantly heated during roasting using the first burner 51 (or the second burner 71) in the heating mode. Therefore, the heating of the roasted sand by supplying fuel to the first burner 51 (or the second burner 71) in the heating mode can be minimized, 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 start temperature of the combustible substances contained in the roasted sand. The specific preheating temperature depends on the type of combustible substances and is not particularly limited. However, from the perspective of ensuring safety and setting the lower limit to be equal to or higher than the spontaneous ignition temperature of the fuel supplied from the first fuel supply system 62A, when the fuel supplied from the first fuel supply system 62A is a liquid fuel, the lower limit can usually be set to 650 °C or higher, and when the fuel is a gaseous fuel, it can be set to 700 °C or higher. Also, the lower limit of the preheating temperature can preferably be 750 °C or higher, more preferably 800 °C or higher, and even more preferably 850 °C or higher. The upper limit of the preheating temperature can usually be set to 1000 °C or lower, preferably 950 °C or lower, and more preferably 900 °C or lower, from the perspectives of reducing the amount of fuel used 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 for supplying air to the roasting chamber 12 during roasting. Specifically, it can be used for cooling when the furnace temperature of the roasting chamber 12 becomes excessively high (hereinafter referred to as "over-temperature rise"), and / or for replenishing oxygen when the oxygen required for combustion is insufficient. That is, the roasted sand self-heats by the combustion heat generated in the combustion reaction of the combustible substances, 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 substances contained in the roasted sand and the like.

[0028] For example, when the amount of combustible substances 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 experience over-temperature rise. Alternatively, when the amount of combustible matter contained in the roasted sand is large, 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, when the furnace temperature in 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 through the first burner 51 in the air supply mode, thereby cooling the roasting chamber 12. Alternatively, when the amount of oxygen required for combustion is insufficient, air is supplied from the second air supply system 52 to the roasting chamber 12 through the first burner 51 in the air supply mode, thereby replenishing oxygen in the roasting chamber 12. 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 system separate from the first air supply system 21, and it is possible to prevent the influence on the formation of the fluidized bed FB.

[0030] The fluidized roasting furnace 10 has a dedicated line for supplying air for cooling when the furnace temperature in the roasting chamber 12 becomes excessively high and / or for assisting combustion in case of oxygen deficiency, such as the above-mentioned second air supply system 52. Therefore, the fluidized roasting furnace 10 can suitably and simply manage the combustion of combustible matter by appropriately supplying air to the roasting chamber 12 as needed. And the fluidized roasting furnace 10 can correspond to a wide variety of roasting objects without changing the device configuration, such as changing the connection destination of various supply lines or increasing or decreasing the number of lines, and can be made highly versatile for the roasting objects it can handle.

[0031] The second air supply system 52, which is a dedicated line for air supply related to the combustion management of combustible matter, as described above, when connected to the first burner 51, can obtain advantages such as simplification of the configuration and miniaturization of the device by collecting or reducing the number of lines connected to the furnace body 11 to 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 with respect to the furnace body 11. When the second air supply system 52 is directly connected to the furnace body 11, advantages include that air with a capacity greater than that of the burner (the first burner 51) can be supplied, and the pressure loss generated when passing through the burner (the first burner 51) can be reduced, etc.

[0032] Also, when the second air supply system 52 is directly connected to the furnace body 11, the supply port for supplying air to the roasting chamber 12 is not limited to only one, and can be plural. When there are plural supply ports for supplying air, the second air supply system 52 can branch at its end into plural parts and be connected to each supply port. Furthermore, when there are plural supply ports for supplying air, the plural supply ports can be arranged at substantially equal intervals along the circumferential direction (inner circumferential direction) of the roasting chamber 12. In this case, since air can be evenly supplied to the roasting chamber 12 from the circumferential direction through the plural supply ports, the combustibles contained in the roasted sand can come into uniform contact with the oxygen contained in the air throughout substantially the entire roasting chamber 12 (lower part 12A), so that the combustion reaction can easily occur evenly within the roasting chamber 12 (lower part 12A).

[0033] The furnace body 11 can be provided with a second burner 71 installed in the roasting chamber 12. The second burner 71 can be a so-called "heating type" for heating the roasted sand during roasting. That is, the amount of heat generated by the self-heating of the roasted sand varies according to the amount of combustibles contained in the roasted sand, etc. For example, when the amount of combustibles contained in the roasted sand is small, the amount of heat generated by self-heating is small, and there may be a case where the amount of heat required for the combustion of the combustibles is insufficient. In such a case, by using the second burner 71, the roasted sand can be heated to supplement the amount of heat required for the combustion of the combustibles. In other words, the second burner 71 is a "heating type" and can heat the roasted sand during roasting.

[0034] The second burner 71 can be provided so as to be arranged 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 extremely good compared to the heating efficiency of the roasted sand from the outside (upper part) of the fluidized bed FB by the above-described first burner 51. For this reason, when the second burner 71 is provided, the first burner 51 in the heating mode can be used only as "for preheating" for preheating the roasted sand before roasting. Further, when the first burner 51 is connected to the second air supply system 52, the first burner 51 in the air supply mode can be used as a so-called "air supply nozzle" during roasting.

[0035] When the second burner 71 is arranged inside the fluidized bed FB, since it is exposed to the heat generated by the combustion of the combustible material, it is preferably used in an atmosphere at a temperature equal to or higher than the temperature at which the fuel spontaneously ignites from the viewpoint of preventing abnormal combustion. Note that since the fuel injected from the second burner 71 spontaneously ignites by being exposed to the heat generated by the combustion of the combustible material, the second burner 71 does not necessarily need to be provided with an ignition function or the like for igniting the fuel. The type of the second burner 71 is not particularly limited, and examples thereof include a gun burner and a nozzle burner. However, a gun burner is preferable from the viewpoint of being able to inject fuel at high pressure.

[0036] When the second burner 71 is arranged inside the fluidized bed FB, it is preferable to supply fuel at high pressure so that the fuel can be injected into the fluidized bed FB in which air is always 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. The second fuel supply system 62B has a second fuel valve 63B. By opening and closing the second fuel supply system 62B with this second fuel valve 63B, the fuel supply to the second burner 71 can be permitted or restricted. The type of the second fuel valve 63B is not particularly limited as long as the second fuel supply system 62B can be opened and closed, and examples thereof 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. This compressed air supplier 73 is not particularly limited in terms of its type or the like as long as it can supply compressed air, and examples include a high-pressure pump, a compressor, etc. Among these, a high-pressure pump is preferable 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 regulate the supply of compressed air to the second burner 71 by opening and closing the third air supply system 72. The supply valve 74 is not particularly limited in terms of its type as long as it can open and close the third air supply system 72, and examples include an electric valve, a solenoid valve, etc. Among these, an electric valve is preferable because, for example, it can adjust the supply amount of compressed air from the compressed air supplier 73 to the second burner 71.

[0038] When the second burner 71 is in use, the second fuel supply system 62B is opened by the second fuel valve 63B, and fuel is supplied from the fuel supply unit 61 to the third air supply system 72, and at the same time, compressed air is supplied from the compressed air supplier 73 to the third air supply system 72. The fuel and the compressed air are mixed in the third air supply system 72 and supplied to the second burner 71 at high pressure. When they are injected from the second burner 71 into the fluidized bed FB, they ignite spontaneously in the fluidized bed FB, heating the roasted sand and supplementing the heat required for the combustion of combustibles. Since the second burner 71 is arranged in the fluidized bed FB, the heating efficiency is good, and the heat required for the combustion of combustibles can be supplemented in a short time. When stopping the heat supplementation by the second burner 71, the supply of fuel and compressed air to the second burner 71 is stopped by closing the third air supply system 72 with the supply valve 74. That is, the second burner 71 is provided for the purpose of secondarily heating the roasted sand in the fluidized bed FB, in other words, for the purpose of supplementing the insufficient heat, when the heat required for roasting is insufficient, such as when the heat generated by the combustion of combustibles is small. Therefore, the second burner 71 is not provided for the purpose of constantly heating the roasted sand for roasting, and after supplementing the insufficient heat, the heating is quickly stopped.

[0039] The second burner 71, the third air supply system 72, etc. are provided as systems separate from the first burner 51 and the second air supply system 52. Therefore, when it is necessary to supply air to the roasting chamber 12 due to overheating of the furnace temperature or lack of oxygen during the use of the second burner 71, the first burner 51 and the second air supply system 52 can be used to supply air to the roasting chamber 12. Also, 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 it is possible to prevent the influence on the formation of the fluidized bed FB.

[0040] The furnace body 11 can be provided with a sand input chute 13 for introducing the roasting sand before roasting into the roasting chamber 12. The sand input chute 13 has, for example, a hopper 13A for introducing the roasting sand and a pipe 13B extending from the hopper 13A. The hopper 13A is arranged outside the furnace body 11, the pipe 13B is inserted into the furnace body 11, and the tip of the pipe 13B is arranged in the roasting chamber 12, whereby it can be provided. The furnace body 11 can be provided with a discharge nozzle 14 for taking out the roasted sand after roasting from the roasting chamber 12. The discharge nozzle 14 can be provided, for example, at the bottom of the roasting chamber 12 so as to penetrate the furnace wall of the furnace body 11. Also, the discharge nozzle 14 can be made openable and closable, for example, by connecting a valve such as a cone valve for discharging the roasting sand in a fixed amount.

[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. That is, the fluidized bed FB is not formed throughout the inside of the roasting chamber 12, and the upper edge (upper surface) of the fluidized bed FB hardly reaches the upper part 12B of the roasting chamber 12 and is contained within the lower part 12A of the roasting chamber 12. This is because the height (altitude) of the roasting sand that can be blown up and suspended by the injection of air from the fluidization nozzle 15 is limited according to the weight, bulk specific gravity, etc. of the roasting sand. In the furnace body 11, the inner diameter of the lower part 12A of the roasting chamber 12 can be made smaller than the inner diameter of the upper part 12B of the roasting chamber 12. When the inner diameter of the lower part 12A of the roasting chamber 12 is made smaller than the inner diameter of the upper part 12B, the amount of air required to form the fluidized bed FB can be reduced.

[0042] When the inner diameters of the lower part 12A and the upper part 12B of the roasting chamber 12 are different, the flow velocity of the air flowing through the roasting chamber 12 can also be made different between the lower part 12A and the upper part 12B. When the inner diameter of the upper part 12B of the roasting chamber 12 is made larger than the inner diameter of the lower part 12A, since the volume of the upper part 12B of the roasting chamber 12 expands more than the volume of the lower part 12A, the flow velocity of the air in the upper part 12B of the roasting chamber 12 becomes slower than the flow velocity of the air in the lower part 12A of the roasting chamber 12 (the velocity of the air in the fluidized bed FB). In this case, by slowing down the flow velocity of the air in the upper part 12B of the roasting chamber 12 while maintaining the flow velocity of the air (the rising velocity) sufficient to form the fluidized bed FB in the lower part 12A of the roasting chamber 12, the residence time of the air in the roasting chamber 12 can be made suitable.

[0043] Specifically, when the inner diameters of the lower part 12A and the upper part 12B of the roasting chamber 12 are different, taking the inner diameter (radius) of the lower part 12A of the roasting chamber 12 as r1 and the inner diameter (radius) of the upper part 12B as r2, the square of r2: (r2) 2 is 1.3 times or more the square of r1: (r1) 2 〔1.3×(r1) 2 ≦(r2) 2 〕 is preferable, 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 even more preferable. Also, the square of r2: (r2) 2 is 3 times or less the square of r1: (r1) 2 〔(r2) 2 ≦3×(r1) 2 〕 is preferably, 2.5 times or less 〔(r2) 2 ≦2.5×(r1) 2〕 is more preferable, and 2 times or less [(r2) 2 ≦2×(r1) 2 〕 is even more preferable.

[0044] The furnace body 11 can be provided with an air supply chamber 16 at the lower part of the roasting chamber 12. The air supply chamber 16 can temporarily store the air supplied from the first air supply system 21 by connecting to the first air supply system 21. The air supply chamber 16 communicates with the roasting chamber 12 through the fluidization nozzles 15, and the fluidization nozzles 15 are connected to the first air supply system 21 through the air supply chamber 16. The air supplied from the first air supply system 21 is temporarily stored in the air supply chamber 16, so that the pressure and the rising speed can be made uniform and ejected from a plurality of fluidization nozzles 15.

[0045] The furnace body 11 can be provided with an exhaust chamber 17 above the roasting chamber 12. The exhaust chamber 17 can temporarily store the exhaust gas exhausted from the roasting chamber 12 to the exhaust system 31 by connecting to the exhaust system 31. This exhaust gas contains the air that has passed through the fluidized bed FB, carbon dioxide generated by the combustion of combustibles during the roasting of the roasting sand, impurities such as dust mixed in the roasting sand, and fine dust. 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, allows the exhaust gas from the roasting chamber 12 to pass through, and can suppress the passage of the roasting sand mixed in the exhaust gas and the dust and dirt contained in the roasting sand. Further, the porous wall 18 rectifies the flow direction of the air (exhaust gas) inside the roasting chamber 12 to be upward by restricting the passage direction of the exhaust gas to the exhaust chamber 17 upward.

[0046] The porous wall 18 has a function as a partition wall that thermally insulates the roasting chamber 12 and the exhaust chamber 17. That is, the porous wall 18 can thermally insulate the roasting chamber 12 and the exhaust chamber 17, so that the temperature inside the exhaust chamber 17 can be made lower than the furnace temperature of the roasting chamber 12. Further, the exhaust chamber 17 can have an inner diameter larger than that of the lower portion 12A of the roasting chamber 12. In this case, the flow velocity of the exhaust gas flowing upward in the exhaust chamber 17 (the velocity of the upward airflow in the exhaust chamber 17) can be made slower than the flow velocity of the air flowing upward in the lower portion 12A of the roasting chamber 12 (the velocity of the air in the fluidized bed FB). In the exhaust chamber 17, since the internal temperature is lower than the furnace temperature of the roasting chamber 12, the exhaust gas discharge amount (volume amount) can be reduced. Further, in the exhaust chamber 17, since the velocity of the upward airflow is slower than the velocity of the air in the fluidized bed FB, fine dust mixed in the exhaust gas can be sedimented.

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

[0048] (2) First air supply system The first air supply system 21 is used for the purpose of fluidizing the roasting sand by supplying air to the roasting chamber 12 of the furnace body 11 and burning the combustible substances contained in the roasting sand with the oxygen contained in the air. The first air supply system 21 can have a first air supply device 22. The first air supply device 22 is for supplying air to the furnace body 11 at a predetermined flow rate and / or flow velocity. That is, the first air supply device 22 can adjust the supply amount of air to the roasting chamber 12 by supplying air to the furnace body 11 at a predetermined flow rate, and send the oxygen required for the combustion reaction of the combustible substances into the roasting chamber 12.

[0049] In addition, the first air supply device 22 can fluidize the roasted sand by adjusting the rising speed of the air ejected from the fluidization nozzle 15 by supplying air to the furnace main body 11 at a predetermined flow rate. The first air supply device 22 is not particularly limited as long as it can supply air to the furnace main body 11 at a predetermined flow rate and / or flow velocity, and examples thereof include blowers, pumps, compressors, etc. Among these, a blower is preferable as the first air supply device 22 because it can adjust not only the flow rate (air volume) but also the flow velocity (wind speed) of the air to the roasting chamber 12.

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

[0051] As described above, the volume of the roasting chamber 12 can be made such that the inner diameter of the lower part 12A of the roasting chamber 12 is small and the inner diameter of the upper part 12B is large, so that the volume of the lower part 12A where the fluidized bed FB is formed is small and the volume of the upper part 12B is large. That is, in the lower part 12A of the roasting chamber 12 with a small volume, the flow velocity (rising speed) of the air sufficient to form the fluidized bed FB can be maintained. On the other hand, in the upper part 12B of the roasting chamber 12 with a large volume, by adjusting the volume or the like to appropriately slow down the flow velocity of the air, the residence time of the air in the roasting chamber 12 can be made within the preferable above range.

[0052] The rising velocity (Nm / s) of the air ejected from the fluidization nozzle 15 can be appropriately set according to the specific gravity and particle size (grain size) of the roasted sand, etc., and is not particularly limited. However, usually, the lower limit value can be 0.2 Nm / s or more, preferably 0.5 Nm / s or more. The upper limit value of the rising velocity (Nm / s) can usually be 2 Nm / s or less, preferably 1.5 Nm / s or less. The rising velocity can be appropriately set according to the supply amount (A1) of the air by the first air supply system 21. That is, the supply amount (A1) of the air by the first air supply system 21 can be adjusted so that the rising velocity is within the above range. And the supply amount (A2) of the air by the second air supply system 52 is such that the sum with the supply amount (A1) of the air by the first air supply system 21 is within a range that does not exceed the supply amount A (m 3 / s) of the air to the roasting chamber 12 per unit time. 3 That is, it can be adjusted so that the sum does not exceed the supply amount A (m

[0053] In addition, as described above, by reducing the inner diameter of the lower part 12A of the roasting chamber 12, the supply amount (A1) of the air by the first air supply system 21 required to form the fluidized bed FB can be reduced, and the capacity of the formed fluidized bed FB can be made more compact. In this way, when the supply amount (A1) of the air is reduced and the capacity of the fluidized bed FB is made more compact, it is possible to reduce the capacity and size of the first air supply device 22, and as a result, it is also possible to reduce the equipment cost and the operation cost such as the power cost.

[0054] Also, the rising velocity increases as the furnace temperature in the roasting chamber 12 increases. On the other hand, the velocity of the fluid (air) when the roasted sand starts to fluidize (hereinafter, "minimum fluidization velocity") decreases as the furnace temperature in the roasting chamber 12 increases. In view of the rising velocity and the minimum fluidization velocity, the supply amount (A1) of the air by the first air supply system 21 preferably increases until roasting starts (that is, while the furnace temperature is normal temperature), and decreases after roasting starts, especially during roasting (that is, while the furnace temperature becomes high due to the combustion of combustibles). That is, the supply amount of air (A1) by the first air supply system 21 preferably reduces (narrows down) the flow rate in at least two or more stages while the furnace temperature changes from normal temperature to high temperature (the temperature range during operation). In this case, advantages such as reduction of the heating heat quantity of air, suppression of the scattering of roasted sand outside the furnace, and reduction of the power consumption of the first air supply device 22 can be obtained.

[0055] A heat exchanger 34 can be connected between the first air supply system 21 and the exhaust system 31. Specifically, the first air supply system 21 has an intake system 23 through which the first air supply device 22 intakes air. The heat exchanger 34 is connected to the exhaust system 31 and the intake system 23. The heat exchanger 34 performs heat exchange between the exhaust gas exhausted from the roasting chamber 12 by the exhaust system 31 and the air inhaled from the intake system 23 by the first air supply device 22 and supplied to the roasting chamber 12, and can preheat the air with the heat possessed by the exhaust gas. The preheating temperature of the air is not particularly limited. However, from the viewpoint that the higher the temperature of the air ejected from the fluidization nozzle 15, the more active the fluidization of the roasted sand, it can be preferably 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 supply amount of air (A1) by the first air supply system 21 required for the formation of the fluidized bed FB can be reduced as compared with the case where air is supplied without preheating. That is, preheating of the air can reduce the supply amount of air (A1) to the roasting chamber 12 (furnace body 11), and thereby the capacity reduction and miniaturization of the first air supply device 22 can also be achieved. Therefore, it is useful from the viewpoints of energy saving of the equipment and reduction of the equipment capacity. Furthermore, since the supply amount of air (A1) can be reduced by reducing the inner diameter of the lower part 12A of the roasting chamber 12, the heat exchanger 34 can be miniaturized, which is particularly useful from the viewpoints of energy saving of the equipment and reduction of the equipment capacity.

[0057] (3) Exhaust system The exhaust system 31 is used for the purpose of facilitating the supply (introduction) of air into the roasting chamber 12 by exhausting gas from the roasting chamber 12 of the furnace body 11, and exhausting carbon dioxide and the like generated by roasting (combustion of combustibles) as exhaust gas. The exhaust system 31 can have a damper 32. This damper 32 is for making the exhaust amount from the furnace body 11 a certain amount. Therefore, the damper 32 is preferably arranged at the position closest to the furnace body 11. The exhaust amount by the exhaust system 31 is not particularly limited as long as it is an amount that can introduce an amount of air capable of maintaining the formed fluidized bed FB into the roasting chamber 12. Specifically, the exhaust amount C (m 3 / s) by the exhaust system 31 is preferably approximately the same amount as the supply amount A (m 3 / s) of air to the roasting chamber 12 described above (C≒A), and more preferably within the range of ±20% of the supply amount A [(0.8×A)≦C≦(1.2×A)].

[0058] The exhaust system 31 can have a dust collector 33. In the exhaust gas exhausted by the exhaust system 31, in addition to gas, there are solids such as finely dispersed roasted sand, dust mixed in the roasted sand, and dust. The dust collector 33 captures and removes the solids mixed in the exhaust gas to prevent them 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 cyclone, scrubber, bag filter, and electrostatic precipitation. Among these, the bag filter is preferable from the viewpoint of being able to handle a large volume of exhaust gas and capture fine solids. When a heat exchanger 34 is connected between the exhaust system 31 and the first air supply system 21, the exhaust gas discharged from the exhaust system 31 to the outside can be cooled. The temperature of the exhaust gas at this time can preferably be 250°C or lower, and more preferably 200°C or lower. Note that the position of the dust collector 33 in the exhaust system 31 is not particularly limited. 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 on the downstream side of the heat exchanger 34.

[0059] (4) Controller The controller 41 is used for the purpose of controlling the roasting of roasted sand. Specifically, the controller 41 incorporates an electronic computer (computer) equipped with an arithmetic processing unit such as a CPU (Central Processing Unit) or MPU (Micro Processing Unit), and a storage area unit such as an HDD, SSD, or ROM. It executes the program stored in the storage area unit to control the roasting of roasted sand. A furnace thermometer 42, an oxygen concentration measuring device 43, and an oxygen concentration measuring device 43 are electrically connected to the controller 41. Also, the controller 41 is electrically connected to an air supply valve 54 and a supply valve 74.

[0060] Based on the detected values of the furnace thermometer 42, the oxygen concentration measuring device 43, and the oxygen concentration measuring device 43, 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 supply valve 54 and the supply valve 74. In the management of the combustion of combustibles, the controller 41 can adjust the furnace temperature of the roasting chamber 12 to a predetermined temperature range. The specific lower limit value of the furnace temperature of the roasting chamber 12 can preferably be 700 °C or higher, more preferably 800 °C or higher. The upper limit value of the furnace temperature of the roasting chamber 12 can preferably be 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 between the heating mode and the air supply mode of the first burner 51 by operating the first fuel valve 63A. The controller 41 can be electrically connected to the first air supply device 22. In this case, the controller 41 can appropriately adjust the amount of air supplied to the roasting chamber 12 by the first air supply system 21 and the rising speed of the air ejected from the fluidization nozzle 15 by operating the first air supply device 22. 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 roasting furnace 10 of the present application is not particularly limited with respect to the roasted sand to be roasted, and any roasted sand containing combustibles can be roasted. Examples of the roasted sand usually include waste materials such as used casting sand and discarded refractory bricks (magnesia bricks, magnesia carbon bricks, etc.), and ores such as sulfide ores and arsenide ores. In addition, the combustibles contained in the roasted sand are not particularly limited as long as they can undergo a combustion reaction (oxidation reaction) with oxygen. Examples of the combustibles usually include organic substances such as binders, adhesives, and tackifiers, and inorganic substances such as carbon, graphite, alkali metals (sodium, lithium, etc.), sulfur, and arsenic.

[0063] The above fluidized roasting furnace 10 has a furnace body 11 equipped with a first burner 51, a second air supply system 52, etc., and can cope with an excessive temperature rise in the roasting chamber 12 and a shortage of the amount of oxygen required for combustion when the amount of combustibles contained in the roasted sand is large. From such a perspective, it can be said that the roasted sand for which the fluidized roasting furnace 10 is useful as a roasting target is one containing a large amount of combustibles. The specific content of the combustibles can be 1 mass% to 30 mass%, preferably 1.5 mass% to 25 mass%, more preferably 2 mass% to 20 mass%, with the total amount of the roasted sand being 100 mass%.

[0064] Preferred roasted sand can include those that are easy to fluidize and have a good yield. For example, when the roasted sand consists only of fine powders with a small particle size, fluidization is easy, but it is easily blown away by air and discharged outside the furnace, so the yield is likely to deteriorate. On the other hand, when the roasted sand consists only of granules with a large particle size, the yield is good, but it is difficult to fluidize, and the operation cost increases due to an increase in the air supply amount or the like. Therefore, the roasted sand preferably contains both fine powders with a small particle size and granules with a large particle size. Specifically, when the total amount of the roasted sand is 100% by mass, it preferably contains powders with an average particle size (D50) of 1 mm or less; 5 to 20% by mass, and granules with an average particle size (D50) exceeding 1 mm and 5 mm or less; 70 to 90% by mass.

[0065] In addition, for the roasted sand, for example, those with a small bulk specific gravity are easy to fluidize, but are easily blown away by air and discharged outside the furnace, and those with a large bulk specific gravity have a good yield, but are difficult to fluidize, and the operation cost increases due to an increase in the air supply amount or the like. Therefore, the roasted sand preferably has a bulk specific gravity within a predetermined range. Specifically, the bulk specific gravity of the roasted sand is preferably 1400 kg / m 3 or more and 3500 kg / m 3 or less, more preferably 1500 kg / m 3 or more and 3300 kg / m 3 or less, and even more preferably 1600 kg / m 3 or more and 3100 kg / m 3 or less.

[0066] Examples of the roasted sand that can easily satisfy the above conditions include magnesia bricks (magnesia carbon bricks) as waste refractory bricks. Magnesia bricks mainly contain magnesia (MgO) and contain 15% to 20% by mass of carbon (carbon) or graphite (graphite) as combustibles. When magnesia bricks are used as roasted sand, carbon or graphite, which is a combustible, can be removed to obtain magnesia (MgO). Here, although magnesium (Mg) contained in magnesia (MgO) is used in a very wide range of fields and applications, most of it relies on imports. Also, most of the magnesia bricks are discarded without being recycled, etc. From the above, the calcined sand is preferably obtained by pulverizing the discarded magnesia bricks, and is very useful from the viewpoints of economic effects, recycling effects, etc.

[0067] [2] Fluidized roasting method The fluidized roasting method of the present invention is a fluidized roasting method that uses the above-mentioned fluidized roasting furnace 10 to roast the calcined sand and burn and remove the combustibles contained in the calcined sand, and a fluidization step of injecting air upward from the fluidization nozzle 15 inside the roasting chamber 12 of the furnace body 11 and floating the calcined sand in the air to fluidize the calcined sand; a combustion step of heating the calcined sand and reacting the combustibles contained in the calcined sand with oxygen in the air to burn, and the heating of the calcined sand in the combustion step has a preheating stage of preheating the calcined sand to the reaction temperature of the combustibles and oxygen by the first burner 51, and a steady stage of heating the calcined sand using the combustion heat of the combustibles, and in the steady stage, when the furnace temperature of the roasting chamber becomes overheated and / or when the oxygen required for the combustion is insufficient, the controller supplies air to the roasting chamber by the second air supply system to control the combustion of the combustibles.

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

[0069] In operation (W1), the air delivered from the first air supply device 22 is supplied from the first air supply system 21 to the fluidization nozzle 15 via the air supply chamber 16 of the furnace body 11. The fluidization nozzle 15 injects the air supplied from the first air supply system 21 upward above the roasting chamber 12, and by this injection, an air flow from the bottom to the top of the roasting chamber 12 is formed. In operation (W2), roasted sand is introduced into the roasting chamber 12 using the sand input 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 floats and fluidizes while being dispersed in the air, forming a fluidized bed FB.

[0070] (2) Combustion process The combustion process is a process of reacting (combustion reaction, oxidation reaction) the combustibles contained in the roasted sand with oxygen in the air to cause combustion. Figure 3 is a flowchart showing a specific example of the combustion process. The combustion process has 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. Figure 4 is a flowchart showing a specific example of the preheating stage of the combustion process. The preheating stage has an operation (W31) of switching the first burner 51 to the heating mode, an operation (W32) of preheating the roasted sand with the first burner 51, an operation (W33) of determining whether the furnace temperature has reached the combustion start temperature, and an operation (W34) of switching the first burner 51 to the air supply mode. Note that 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 operations when the second air supply system 52 is connected to the first burner 51. Therefore, in the case of a configuration where 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 supply system 62A is opened by the first fuel valve 63A, fuel and air are fed from the second air supply system 52 to the first burner 51, and the first burner 51 is set to the heating mode. When 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 fed from the fuel supply unit 61 to the first burner 51 via the first fuel supply system 62A. In operation (W32), fuel is ignited in the first burner 51, combustion gas (flame) is ejected from the first burner 51, and the roasting sand is preheated on the surface (upper surface) of the fluidized bed FB. In operation (W33), based on the measurement by the furnace thermometer 42, it is determined whether the furnace temperature of the roasting chamber 12 has reached the combustion start temperature of the combustible material contained in the roasting sand. In operation (W33), if it is determined that the furnace temperature has not reached the combustion start temperature of the combustible material (W33; no), the preheating of the roasting sand by operation (W32) is continued. If it is determined that the furnace temperature has reached the combustion start temperature of the combustible material (W33; yes), operation (W34) is executed. In operation (W34), the first fuel supply system 62A is closed by the first fuel valve 63A, only air is fed from the second air supply system 52 to the first burner 51, and the first burner 51 is set to the air supply mode. When 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 roasting sand by the first burner 51 and ending the preheating stage.

[0073] The roasting sand preheated until it reaches the combustion start temperature of the combustible material in the above preheating stage self-heats by the combustion heat generated by the combustion of the combustible material. In the steady state stage (W4), in the roasting chamber 12 of the furnace body 11 of the fluidized roasting furnace 10, the roasting sand is heated using the combustion heat of the combustible material, that is, the roasting sand is roasted by the amount of heat generated by self-heating. In this steady state stage (W4), combustion management 1, combustion management 2, and combustion management 3A, 3B for managing the combustion are executed according to the state generated in the roasting chamber 12 by the combustion of the combustible material (see FIG. 3). Any one of Combustion Management 1, Combustion Management 2, Combustion Management 3A, and 3B may be executed according to the state of the roasting chamber 12, or two or more selected from Combustion Management 1, Combustion Management 2, 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 executed when the furnace body 11 is provided with the second burner 71, and Combustion Management 3B is executed when the furnace body 11 is not provided with the second burner 71.

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

[0075] In the operation (W411), the furnace temperature of the roasting chamber 12 is measured by the furnace temperature measuring device 42, and the measured value is sent to the controller 41. Based on the measured value from the furnace temperature measuring device 42, the controller 41 determines whether the furnace temperature of the roasting chamber 12 is overheated. In the operation (W411), if it is determined that the furnace temperature is not overheated (W411; no), Combustion Management 1 ends. If it is determined that the furnace temperature is overheated (W411; yes), the operation (W412) is executed. In the operation (W412), air is supplied from the second air supply system 52 to the roasting chamber 12. In this operation (W412), the controller 41 operates the air supply valve 54 to open the second air supply system 52, and sends the air supplied from the second air supply device 53 into the roasting chamber 12 while adjusting the supply amount and the like by the air supply valve 54. Operation (W412) can be executed using the first burner 51 that has been switched to the air supply mode in the preheating stage (W3) when the second air supply system 52 is connected to the first burner 51. In this case, the 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 measured value from the furnace thermometer 42. In operation (W413), if it is determined that the furnace temperature has not reached the specified value (W413; no), operation (W412) is continuously executed. If it is determined that the furnace temperature has reached the specified value (W413; yes), operation (W414) is executed. Note that the specified value of the furnace temperature in operation (W413) can specifically be 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 can operate the air supply valve 54 to close the second air supply system 52, thereby stopping the air supply to the roasting chamber 12.

[0077] Combustion management 2 is executed when the state occurs where the oxygen required for the combustion of combustibles in the roasting chamber 12 is insufficient. FIG. 6 is a flowchart showing a specific example of combustion management 2 in the steady state stage (W4). Combustion management 2 includes an operation (W421) to check whether the carbon monoxide (CO) value in the roasting chamber 12 is increasing, an operation (W422) to supply air from the second air supply system 52, and an operation (W423) to check whether the oxygen (O 2 ) value in the roasting chamber 12 has reached the specified value, and an operation (W424) to stop the air supply from the second air supply system 52.

[0078] In operation (W421), the carbon monoxide 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 the CO value. The controller 41 determines whether the oxygen required for the combustion of combustibles in the roasting chamber 12 is insufficient based on the CO value sent from the oxygen concentration measuring device 43. Specifically, in the combustion reaction of combustibles, if the atmosphere has sufficient oxygen, carbon dioxide (CO 2 ) is generated and carbon monoxide (CO) is hardly generated. On the other hand, if the atmosphere is oxygen-deficient, carbon monoxide (CO) is generated and carbon dioxide (CO 2 ) is hardly generated. Therefore, when the CO value increases, it means that carbon monoxide (CO) is being generated, indicating a state of oxygen deficiency. In operation (W421), if it is determined that the CO value has not increased (W421; no), the combustion control 2 ends. If it is determined that the CO value has increased (W421; yes), operation (W422) is executed.

[0079] In operation (W422), air is supplied from the second air supply system 52 to the roasting chamber 12. In this operation (W422), the controller 41 operates the air supply valve 54 to open the second air supply system 52, and sends the air supplied from the second air supply device 53 into the roasting chamber 12 while adjusting the supply amount and the like by the air supply valve 54. When the second air supply system 52 is connected to the first burner 51, operation (W422) can be executed using the first burner 51 switched to the air supply mode in operation (W34) of the preheating stage (W3). In this case, the 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 of the roasting chamber 12 is measured by the oxygen concentration measuring device 43, and the measured value is sent to the controller 41 as the O 2 value. Based on the O 2 value sent from the oxygen concentration measuring device 43, the controller 41 determines whether a sufficient amount of oxygen for burning the combustibles has been replenished in the roasting chamber 12. In operation (W423), if it is determined that the O 2 value has not reached the specified value (W423; no), operation (W422) continues to be executed. If it is determined that the O 2 value has reached the specified value (W423; yes), operation (W424) is executed. In operation (W424), the controller 41 can stop the air supply to the roasting chamber 12 by operating the air supply valve 54 to close the second air supply system 52.

[0080] Combustion controls 3A and 3B are executed when, during roasting, that is, even while the combustible material is burning, the furnace temperature in the roasting chamber 12 decreases. Combustion controls 3A and 3B are used to heat the fluidized bed FB. The difference is that the second burner 71 is used in combustion control 3A and the first burner 51 is used in combustion control 3B, but the processes are substantially the same otherwise. FIG. 7 is a flowchart showing a specific example of combustion control 3A in the steady state stage (W4). Combustion control 3A includes an operation (W431) to check whether the furnace temperature in the roasting chamber 12 is decreasing, an operation (W432) to heat the fluidized bed FB with the second burner 71, an operation (W433) to check whether the furnace temperature in the roasting chamber 12 has reached a specified value, and an operation (W434) to stop the heating by the second burner 71.

[0081] In operation (W431), the furnace temperature of the roasting chamber 12 is measured by the furnace thermometer 42, and the measured value is sent to the controller 41. Based on the measured value from the furnace thermometer 42, the controller 41 determines whether the furnace temperature in 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 not decreasing (W431; no), combustion control 3A ends. If it is determined that the furnace temperature is not maintained within the predetermined temperature range and is decreasing (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 the compressed air supplied from the compressed air supply 73 and the fuel sent from the fuel supply unit 61 through the second fuel supply system 62B to the second burner 71. The second burner 71 injects the supplied compressed air and fuel into the fluidized bed FB, ignites the fuel with the self-heat generated from the roasting sand during roasting, and heats the fluidized bed FB.

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

[0083] FIG. 8 is a flowchart showing a specific example of the combustion management 3B in the steady state stage (W4). The combustion management 3B includes an operation (W441) for checking whether the furnace temperature in the roasting chamber 12 is in a decreasing state, an operation (W442) for switching the first burner 51 to the heating mode, an operation (W443) for heating the fluidized bed FB with the first burner 51, an operation (W444) for checking whether the furnace temperature in the roasting chamber 12 has reached the specified value, an operation (W445) for stopping the heating by the first burner 51, and an operation (W446) for switching the first burner 51 to the air supply mode. Note that the operation (W442) for switching the first burner 51 to the heating mode and the operation (W446) for switching the first burner 51 to the air supply mode are operations when the second air supply system 52 is connected to the first burner 51. Therefore, in the case of a configuration in which 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. In operation (W441), if it is determined that the furnace temperature is maintained within a predetermined temperature range and has not decreased (W441; no), the combustion management 3B ends. If it is determined 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 supply 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 the heating mode.

[0085] In operation (W443), the controller 41 operates the air valve 54 to open the second air supply 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 supplied air and fuel and injects 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). Note that in the case where the second air supply system 52 is not connected to the first burner 51 in operation (W443), 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 control 3A. In operation (W444), when it is determined that the furnace temperature has not reached the specified value (W444; no), operation (W443) is continuously executed. When it is determined that the furnace temperature has reached the specified value (W444; yes), operation (W445) is executed. In operation (W445), the controller 41 operates the air valve 54 to close the second air supply system 52, thereby enabling the heating by the first burner 51 to be stopped. Note that in the case where the second air supply system 52 is not connected to the first burner 51 in operation (W445), the controller 41 operates the first fuel valve 63A to close the first fuel supply system 62A, thereby enabling the heating by the first burner 51 to be stopped. In operation (W446), the first fuel supply system 62A is closed by the first fuel valve 63A, and 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 can stably perform roasting without any limitation on the object of roasting as long as it is roasted sand containing combustibles, and thus has high versatility and is particularly useful for applications in which waste materials are recycled into recycled materials.

Explanation of Reference Numerals

[0088] 10; fluidized roasting furnace, FB; fluidized bed 11; furnace body, 12; roasting chamber, 13; sand input chute, 14; discharge nozzle, 15; fluidizing nozzle, 16; air supply chamber, 17; exhaust chamber, 18; porous wall, 19; preheating system 21; first air supply system, 22; first air supply, 23; intake system 31; exhaust system, 32; damper, 33; dust collector, 34; heat exchanger 41; controller, 42; furnace thermometer, 43; oxygen concentration detector, 44; carbon monoxide concentration detector 51; first burner, 52; second air supply system, 53; second air supply, 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 supply, 74; supply valve

Claims

1. A fluidized roasting furnace for roasting roasted sand in a fluidized bed formed by suspending the roasted sand in a gas to burn and remove combustibles contained in the roasted sand, comprising: a furnace body having a roasting chamber for containing the roasted sand; a first air supply system connected to the furnace body for 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, wherein the furnace body is installed at the bottom of the roasting chamber and is connected to the first air supply system, and forms the fluidized bed in the roasting chamber by injecting the air from the bottom side to the upper side of the roasting chamber; a fluidization nozzle; a first burner installed in the roasting chamber so as to be disposed above the fluidized bed; a second air supply system connected above the fluidized bed for supplying air to the roasting chamber, wherein the controller manages the combustion of the combustibles by adjusting the supply of air to the roasting chamber by the second air supply system. A fluidized roasting furnace characterized by the above.

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, The fluidized roasting furnace according to claim 1, wherein the supply of air to the roasting chamber by the second air supply system is performed through 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, The fluidized roasting furnace according to claim 1 or 2, wherein the controller manages the combustion of the combustibles by adjusting the heating of the roasted sand by the second burner.

4. When the total amount of the roasted sand is 100% by mass, it contains 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 exceeding 1 mm and 5 mm or less. The bulk specific gravity is 1400 kg / m ３ or more and 3500 kg / m ３ or less, and the fluidized roasting furnace according to claim 1 or 2.

5. The fluidized roasting furnace according to claim 1 or 2, wherein the roasting chamber has a smaller inner diameter at the lower part than at the upper part.

6. The first burner is installed in the roasting chamber and has an ejection hole for ejecting combustion gas or air obliquely downward in a range of 20 degrees to 50 degrees with respect to the vertical direction on the upper side of the roasting chamber above the fluidized bed. The fluidized roasting furnace according to claim 1 or 2.

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

8. The fluidized roasting furnace according to claim 1 or 2, wherein the furnace body is provided with a measuring device for measuring the oxygen concentration and / or carbon monoxide concentration in the roasting chamber.

9. Comprising a heat exchanger connected between the exhaust system and the first air supply system, The fluidized roasting furnace according to claim 1 or 2, wherein heat exchange is performed between the exhaust gas exhausted from the roasting chamber and the air supplied to the roasting chamber by the heat exchanger to preheat the air supplied to the roasting chamber to 200°C or higher.

10. The fluidized roasting furnace according to claim 1 or 2, wherein the exhaust system has a dust collector for removing dust from the exhaust gas exhausted from the roasting chamber.

11. The fluidized roasting furnace according to claim 1 or 2, wherein the roasted sand is obtained by pulverizing discarded magnesia bricks.

12. The fluidized roasting furnace according to claim 1 or 2, wherein the content of the combustible material contained in the roasted sand is 1% by mass to 30% by mass based on 100% by mass of the total amount of the roasted sand.

13. A fluidized roasting method using the fluidized roasting furnace according to claim 1 or 2, roasting roasted sand to burn and remove the combustible material 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 react the combustible material contained in the roasted sand with oxygen in the air to burn, comprising: The heating of the roasted sand in the combustion step includes a preheating stage of preheating the roasted sand to the reaction temperature of the combustible material and oxygen by the first burner, and a steady stage of heating the roasted sand using the combustion heat of the combustible material. In the steady stage, when the furnace temperature in the roasting chamber rises excessively and / or when the oxygen required for combustion is insufficient, the controller supplies air to the roasting chamber by the second air supply system to manage the combustion of the combustible material. The fluidized roasting method is characterized by this.

14. When the total amount of the roasted sand is 100% by mass, the roasted sand contains 5% to 20% by mass of powder with an average particle size of 1 mm or less and 70% to 90% by mass of granules with an average particle size exceeding 1 mm and 5 mm or less. The bulk specific gravity is 1400 kg / m ３ or more and 3500 kg / m ３ or less, and the fluidized roasting method according to claim 13.

15. The fluidized roasting method according to claim 13 or 14, wherein the roasted sand is obtained by pulverizing discarded magnesia bricks.

16. The content of the combustible material contained in the roasted sand is 1% by mass to 30% by mass based on 100% by mass of the total amount of the roasted sand, according to the fluidized roasting method described in claim 13 or 14.

17. The controller adjusts the furnace temperature of the roasting chamber to a range of 650°C or higher and 1000°C or lower, according to the fluidized roasting method described in claim 13 or 14.

Images