Method for removing phosphorus from ore

Abstract

A method for dephosphorization of ore according to one embodiment of the present disclosure includes a step of heating the ore at a temperature of 100°C or higher in a kiln-type or fluidized bed-type heating furnace. Preferably, during the step of heating the ore, a reducing gas or a non-reducing gas is supplied into the heating furnace. Preferably, the heating furnace is composed of a first heating furnace and a second heating furnace, and during the step of supplying a non-reducing gas to the first heating furnace and a reducing gas to the second heating furnace, the ore is first supplied to the first heating furnace and heated, and then the ore heated in the first heating furnace is supplied to the second heating furnace and heated.

Description

[Technical field]

[0001] The present invention relates to a method for removing phosphorus from an ore. [Background technology]

[0002] Phosphorus contained in sintered ore, which is a raw material for blast furnace steel, is one of the important components in controlling the quality of molten iron produced in blast furnaces. Phosphorus has a strong affinity with iron. Therefore, when steel is produced from sintered ore through molten iron, phosphorus tends to remain in the steel. Phosphorus remaining in the steel can cause low-temperature brittle fracture of the steel, impairing its quality.

[0003] As a method for reducing phosphorus contained in iron ore, Non-Patent Document 1 discloses a method for removing phosphorus as a gas by supplying a hydrogen-steam mixed gas to iron ore containing phosphorus to reduce it. Also, in Patent Document 1, a gas in the P2 gas equilibrium region and FeO equilibrium region of the CO gas reduction equilibrium diagram of iron oxide and diphosphorus pentoxide, the H2 gas reduction equilibrium diagram of iron oxide and diphosphorus pentoxide, and / or the CO-H2 mixed gas reduction equilibrium diagram of iron oxide and diphosphorus pentoxide is supplied to high phosphorus iron ore to reduce it, thereby reducing and vaporizing the phosphorus compounds to be removed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-20010 A [Non-patent literature]

[0005] [Non-Patent Document 1] "Direct removal of phosphorus from high phosphorus iron ore", Iron and Steel, Vol. 100 (2014) No. 2, pp. 325-330 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a method for removing phosphorus from an ore. [Means for solving the problem]

[0007] The gist of the present invention is as follows. (1) A method for dephosphorizing ore according to one embodiment of the present disclosure includes a step of heating ore at a temperature of 100°C or higher in a kiln-type or fluidized bed-type heating furnace. (2) In the method for dephosphorizing an ore according to (1) above, preferably, a reducing gas is supplied into the heating furnace during the step of heating the ore. (3) In the method for dephosphorizing an ore according to (1) or (2) above, preferably, a non-reducing gas is supplied into the heating furnace during the step of heating the ore. (4) Preferably, in the method for dephosphorization of ore described in any one of (1) to (3) above, the heating furnace is composed of a first heating furnace and a second heating furnace, a non-reducing gas is supplied to the first heating furnace, a reducing gas is supplied to the second heating furnace, and in the heating step, first, the ore is supplied to the first heating furnace and heated, and then the ore heated in the first heating furnace is supplied to the second heating furnace and heated. (5) Preferably, the method for dephosphorizing ore described in (4) above further includes a step of classifying the ore into a coarse particle fraction and a fine particle fraction finer than the coarse particle fraction after heating in the first heating furnace and before supplying the ore to the second heating furnace, and removing the coarse particle fraction from the ore supplied to the second heating furnace. (6) Preferably, in the method for dephosphorizing ore described in (5) above, in the step of classifying the ore after heating in the first heating furnace and before supplying it to the second heating furnace, a sieve having mesh sizes of 0.5 mm or more and 3.0 mm or less is used. (7) Preferably, the method for dephosphorizing ore according to any one of (1) to (6) above further comprises a step of classifying the ore into a coarse particle portion and a fine particle portion using a sieve having a mesh size of 3.0 mm or more and 5.0 mm or less before the step of heating the ore in the heating furnace, the heating furnace being a kiln-type heating furnace, only the coarse particle portion being supplied to the heating furnace, and the heating temperature of the coarse particle portion in the heating furnace being 400°C or more. (8) Preferably, in the method for dephosphorization of ore described in any one of (1) to (7) above, the ore includes two or more types of ore, the ore contains goethite, and the method further includes a step of selecting the ore having the highest phosphorus concentration in the goethite before the step of heating the ore in the heating furnace, and the ore having the highest phosphorus concentration in the goethite is preferentially supplied to the heating furnace. (9) Preferably, in the method for dephosphorizing an ore according to any one of (1) to (8) above, the ore contains goethite, and only the ore having a phosphorus concentration of 1.0 mass% or more in the goethite is supplied to the heating furnace. Effect of the Invention

[0008] According to the present invention, phosphorus contained in an ore can be separated from the ore. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating an example of equipment for carrying out a dephosphorization method. [Diagram 2] FIG. 2 is a diagram illustrating another example of equipment for carrying out a dephosphorization method. [Diagram 3] FIG. 2 is a diagram illustrating another example of equipment for carrying out a dephosphorization method. [Figure 4] FIG. 2 is a diagram illustrating another example of equipment for carrying out a dephosphorization method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The ore dephosphorization method according to the embodiment of the present disclosure involves heating the ore at a temperature of 100° C. or higher in a kiln or fluidized bed heating furnace. By heating the ore in a kiln or fluidized bed heating furnace, a physical impact is applied to the ore. This separates the phosphorus-containing fine powder from the ore. By physically separating the phosphorus-containing fine powder from the ore, phosphorus can be separated from the ore. Here, the "physical impact" refers to an impact applied to the ore by fluidizing the ore. In addition, the "fine powder" refers to ore having a diameter small enough to be removed by blowing gas. The dephosphorization method according to the present embodiment will be specifically described below.

[0011] (heating furnace) The heating furnace may be any furnace capable of heating the ore to a predetermined temperature of 100°C or higher and applying a physical shock to the ore. Specifically, a kiln-type or fluidized bed-type heating furnace may be used.

[0012] (Kiln-type heating furnace) In a kiln-type furnace, the furnace rotates to move the ore inside the furnace, which causes physical shocks to the ore, including shocks caused when the ore collides with the inner walls of the furnace and shocks caused when the ore particles collide with each other.

[0013] There are two types of kiln-type heating furnaces: internal combustion heating furnaces and external combustion heating furnaces. Internal combustion heating furnaces are heating furnaces in which combustion gas is introduced directly into the furnace. External combustion heating furnaces are heating furnaces in which heat is added from outside the furnace.

[0014] (Fluidized bed heating furnace) In a fluidized bed furnace, hot gas is blown onto the ore particles. The gas causes the ore particles to move and form a fluidized bed. The gas also heats the ore. In a fluidized bed furnace, the ore is subjected to physical shocks by moving it around in the furnace. These physical shocks include shocks caused when the ore collides with the inner walls of the furnace and shocks caused when the ore particles collide with each other.

[0015] Fluidized bed furnaces include direct heating furnaces and indirect heating furnaces. Direct heating furnaces are furnaces that apply heat directly to the ore in the furnace. Indirect heating furnaces are furnaces that apply heat indirectly to the ore in the furnace. Fluidized bed furnaces may also be furnaces that circulate the ore.

[0016] (Ore heating temperature) The heating temperature of the ore in the heating furnace is 100°C or higher. By heating the ore to a specified temperature of 100°C or higher, the ore can be dried and the fine powder attached to the ore by water can be easily removed. By applying a physical impact to the ore in a dry state, the fine powder can be efficiently removed from the ore. Since the fine powder tends to contain a high concentration of phosphorus, the phosphorus can be removed from the ore by physically separating the fine powder from the ore. In addition, by heating the ore to a specified temperature of 100°C or higher in a fluidized bed or kiln heating furnace, a dehydration reaction can be caused and the phosphorus in the goethite contained in the ore can be removed. Goethite is a type of mineral that constitutes ore, and its chemical composition is FeO(OH). JIS M 8700:2013 "Iron ore and reduced iron - Terminology" classifies goethite as a hydrous iron oxide.

[0017] The ore may be heated to a predetermined temperature of 300°C or more. This is preferable because it further evaporates the crystal water contained in the ore and embrittles the goethite portion, which is the portion containing the crystal water. In a state in which the portion containing the crystal water is embrittled, the embrittled portion can be pulverized by applying a physical impact to the ore. This further promotes separation of the fine powder from the ore. The portion containing the crystal water is likely to contain a high concentration of phosphorus. Therefore, as described above, the pulverized fine powder is likely to contain a high concentration of phosphorus. Therefore, by physically separating the pulverized fine powder from the ore, phosphorus can be separated from the ore.

[0018] The upper limit of the predetermined temperature for heating the ore is not particularly limited. For example, in consideration of the durability of the heating furnace and the phosphorus removal efficiency described in the examples below, the heating temperature is preferably 1000 [°C] or less. In addition, as will be described in detail in the examples, in the range where the heating temperature exceeds 750 [°C], the ratio of the increase rate of the dephosphorization rate to the increase amount of the temperature is lower than in the range of 750 [°C] or less. In other words, in the temperature range above 750 [°C], the improvement of the phosphorus removal effect with respect to the increase in the heating temperature is limited compared to the case of 750 [°C] or less. This phenomenon occurs whether the atmosphere of the heating furnace is non-reducing or reducing. Therefore, more preferably, the heating temperature can be 750 [°C] or less. Furthermore, as will be described later, even in the range of about 100 [°C] to 500 [°C], the dephosphorization effect can be obtained regardless of the atmosphere of the heating furnace. Therefore, taking into consideration the energy costs in the heating furnace, the ore may be heated in the range of 100° C. to 500° C., or in the range of 100° C. to 300° C.

[0019] The rate of temperature rise when the ore is heated to a predetermined temperature can be determined appropriately. The time for which the ore is heated to the predetermined temperature, i.e., the time for which the temperature of the ore is maintained at the predetermined temperature, is not particularly limited, but is preferably a time that allows the water of crystallization contained in the ore to evaporate sufficiently, as described below. This time can be, for example, 5 min or more.

[0020] (Type of gas supplied to the furnace) The atmosphere in the heating furnace can be appropriately determined. For example, the atmosphere in the heating furnace can be a non-reducing atmosphere or a reducing atmosphere. The term "non-reducing atmosphere" is a concept that includes both an oxidizing atmosphere and an inert atmosphere.

[0021] For example, the atmosphere in the heating furnace can be made into an oxidizing atmosphere by supplying a gas containing oxygen gas, which is a type of oxidizing gas, or the air into the heating furnace. Also, the atmosphere in the heating furnace can be made into an inert atmosphere by supplying nitrogen gas, argon gas, or the like, which is a type of inert gas, into the heating furnace. Hereinafter, the term "non-reducing gas" is used as a concept that includes both inert gas and oxidizing gas.

[0022] Furthermore, by supplying a type of reducing gas, such as a gas containing hydrogen gas or a gas containing carbon monoxide, into the heating furnace, the atmosphere in the heating furnace can be made a reducing atmosphere. By making the atmosphere in the heating furnace a reducing atmosphere, in addition to the phosphorus removal by the phosphorus removal method of this embodiment, i.e., phosphorus removal accompanying heating of the ore and physical impact on the ore, the phosphorus removal described in Non-Patent Document 1, i.e., phosphorus removal from the ore as a gas, can be performed. That is, by heating the ore in a reducing atmosphere, the phosphates contained in the ore can be reduced, decomposed, and removed.

[0023] There is no particular limitation on the means for supplying the reducing gas or non-reducing gas into the heating furnace. When the heating furnace is of a fluidized bed type, the gas for fluidizing the ore may be a reducing gas or a non-reducing gas. When the heating furnace is of a kiln type, as exemplified in FIG. 1, the reducing gas or non-reducing gas may be sprayed toward the ore from the inlet or outlet of the heating furnace. Note that by supplying a reducing gas or non-reducing gas to the heating furnace and fluidizing the gas inside the heating furnace, the fine powder separated from the ore can be moved together with the gas, that is, the fine powder can be transported by airflow. This also has the effect of making it easier to remove the fine powder from the ore.

[0024] (Classification after heating) The ore discharged from the heating furnace may be subjected to a classification process. The classification process allows the ore to be separated from the fine powder separated from the ore. This allows the fine powder separated from the ore to be removed. Unlike the intermediate classification process described below, it is not expected that the ore will be further heated after the classification process after heating. If the ore is heated two or more times, the classification process after heating is performed after all of the heating processes are completed.

[0025] As a means for carrying out the classification treatment after heating, for example, a sieve can be used. The mesh size of the sieve can be appropriately determined in consideration of the particle size of the fine powder separated from the ore. For example, in the classification treatment after heating, the mesh size can be 0.125 [mm] to 0.25 [mm].

[0026] Next, an example of equipment for carrying out the method for dephosphorizing ore according to the present embodiment will be described with reference to FIG.

[0027] The ore to be dephosphorized is stored in the storage tank 1. The ore discharged from the storage tank 1 is transported to a kiln-type heating furnace 2. The ore is supplied into the heating furnace 2 from a supply port 2a located at one end of the heating furnace 2. The ore is then heated to a predetermined temperature of 100°C or higher, and is subjected to a rolling action by the rotation of the heating furnace 2, giving it physical impact. Inside the heating furnace 2, the above-mentioned evaporation and pulverization of the water of crystallization separates the fine powder from the ore. The ore moves from the supply port 2a of the heating furnace 2 toward the discharge port 2b located at the other end of the heating furnace 2, and is discharged from the discharge port 2b.

[0028] The gas supplier 3 supplies gas to the inside of the heating furnace 2. The gas is a non-reducing gas or a reducing gas. The gas from the gas supplier 3 is supplied to the inside of the heating furnace 2 from the exhaust port 2b of the heating furnace 2, moves along the rotation axis direction of the heating furnace 2, and is then discharged from the supply port 2a of the heating furnace 2. As the gas flows inside the heating furnace 2, the fine powder separated from the ore moves together with the gas as described above. The exhaust gas, which is the gas discharged from the heating furnace 2, and the fine powder are guided to the dust collector 4. The fine powder discharged from the heating furnace 2 is collected in the dust collector 4. In the equipment shown in FIG. 1, the gas flows from the exhaust port 2b toward the supply port 2a, but the gas can also flow from the supply port 2a toward the exhaust port 2b.

[0029] The ore discharged from the discharge port 2b of the heating furnace 2 may be transported to a sieve 5 for classification. The sieve 5 has meshes of a predetermined size. The meshes of the sieve 5 are, for example, within a range of 0.125 [mm] to 0.25 [mm]. The sieve 5 removes fine particles of a predetermined size or less from the ore transported to the sieve 5. The ore on the sieve of the sieve 5 is from which phosphorus has been removed. The ore from which phosphorus has been removed is used to produce sintered ore or pellets, which are iron raw materials to be charged into a blast furnace.

[0030] The heating furnace 2 may be a fluidized bed type heating furnace as described above. The gas supplied to the heating furnace causes the ore to flow, which can give the ore a physical shock. Therefore, the fluidized bed type heating furnace can separate fine powder from the ore and remove phosphorus, just like the kiln type.

[0031] (Combined use of a first heating furnace with a non-reducing atmosphere and a second heating furnace with a reducing atmosphere) In the above embodiment illustrated in Fig. 1, the ore is heated in the heating furnace once in either a non-reducing atmosphere or a reducing atmosphere. However, the method for dephosphorization of ore according to the present embodiment is not limited to this configuration. For example, the ore may be heated in a non-reducing atmosphere and then heated in a reducing atmosphere.

[0032] The heating in a non-reducing atmosphere and the heating in a reducing atmosphere may be performed in different heating furnaces. The first heating furnace and the second heating furnace may be the same in volume, type, etc., or may be different. For example, one heating furnace may be a kiln type heating furnace and the other heating furnace may be a fluidized bed type heating furnace.

[0033] On the other hand, heating in a non-reducing atmosphere and heating in a reducing atmosphere may be performed in the same heating furnace. In this case, after the first heating, the type of gas supplied to the heating furnace is changed, and then the second heating is performed. In this case, the heating furnace in which the non-reducing gas is blown in is regarded as the first heating furnace, and the heating furnace in which the reducing gas is blown in is regarded as the second heating furnace.

[0034] A case where heating in a non-reducing atmosphere and heating in a reducing atmosphere are performed in separate heating furnaces will be described with reference to FIG. 2. In the facility shown in FIG. 2, the heating furnace is composed of two furnaces, a first heating furnace 21 and a second heating furnace 22. The first heating furnace 21 and the second heating furnace 22 are connected in series. In the following description, the description will be omitted for the parts that overlap with the case of FIG. 1. Also, as an example, the first heating furnace 21 and the second heating furnace 22 will be described as being of the kiln type. On the other hand, either or both of the first heating furnace 21 and the second heating furnace 22 may be of the fluidized bed type.

[0035] First, the ore is supplied from the storage tank 1 to the first heating furnace 21. In the first heating furnace 21, the ore is heated to a predetermined temperature of 100°C or more. A non-reducing gas is supplied from the non-reducing gas supplying device 31 to the first heating furnace 21. In the first heating furnace 21, the ore is heated in a non-reducing atmosphere. Then, the ore is subjected to a rolling action by the rotation of the first heating furnace 21 and a physical impact is given to the ore. As a result, fine powder is separated from the ore. The fine powder is discharged together with the gas and collected in the dust collector 41. The gas discharged together with the fine powder is called exhaust gas. As a result, a part of the phosphorus contained in the ore is separated. In FIG. 2, the non-reducing gas is caused to flow from the exhaust port 21b of the first heating furnace 21 toward the supply port 21a, but the exhaust gas may be caused to flow from the supply port 21a toward the exhaust port 21b.

[0036] The ore discharged from the discharge port 21b of the first heating furnace 21 is supplied into the second heating furnace 22 from the supply port 22a located at one end of the second heating furnace 22. Thereafter, in the second heating furnace 22, the ore is heated in a reducing atmosphere at a predetermined temperature of 100°C or more, and is subjected to a rolling action by the rotation of the second heating furnace 22, giving rise to a physical shock. Inside the second heating furnace 22, the ore moves from the supply port 22a toward the discharge port 22b located at the other end, and is discharged from the discharge port 22b.

[0037] The reducing gas supplier 32 supplies reducing gas to the inside of the second heating furnace 22. The reducing gas from the reducing gas supplier 32 is supplied to the inside of the second heating furnace 22 from the exhaust port 22b of the second heating furnace 22, moves along the rotation axis direction of the second heating furnace 22, and is then discharged from the supply port 22a. As the gas flows inside the second heating furnace 22, the fine powder separated from the ore moves together with the gas as described above. The exhaust gas, which is the gas discharged from the second heating furnace 22, and the fine powder are guided to the dust collector 42. Then, the fine powder discharged from the second heating furnace 22 is collected by the dust collector 42. In the equipment shown in FIG. 2, the gas flows from the exhaust port 22b of the second heating furnace 22 toward the supply port 22a, but the gas can also flow from the supply port 22a toward the exhaust port 22b.

[0038] The ore discharged from the discharge port 22b of the second heating furnace 22 may be transported to a sieve 5 for classification. The sieve 5 has meshes of a predetermined size. The meshes of the sieve 5 are, for example, within a range of 0.125 mm to 0.25 mm. The sieve 5 removes fine particles of a predetermined size or less from the ore transported to the sieve 5. The ore on the sieve of the sieve 5 is from which phosphorus has been removed. The ore from which phosphorus has been removed is used to produce sintered ore or pellets, which are iron raw materials to be charged into a blast furnace.

[0039] The heating temperatures of the first heating furnace 21 and the second heating furnace 22 may be the same or different. In addition, both heating in a non-reducing atmosphere and heating in a reducing atmosphere may be performed in the same heating furnace. In that case, the heating temperatures in each atmosphere may be the same or different. However, the heating temperature in the second heating, which is heating in a reducing atmosphere, is preferably 300 [°C] or higher. That is, it is preferable that the first heating temperature is 100 [°C] or higher and the second heating temperature is 300 [°C] or higher. The "second heating" means both the heating in the second heating furnace 22 in the case where the ore is heated sequentially using two heating furnaces, and the second heating in the case where the ore is heated twice using one heating furnace. By setting the second heating temperature to 300 [°C] or higher, the remaining phosphorus can be more efficiently separated from the ore from which phosphorus has been partially separated from the goethite portion by the first heating.

[0040] In addition, the heating time of the first heating and the heating time of the second heating are not particularly limited. In addition, the heating time of the first heating and the heating time of the second heating may be the same or different. Note that the "first heating" refers to both the heating in the first heating furnace 21 in the case where the ore is heated sequentially using two heating furnaces, and the first heating in the case where the ore is heated twice using one heating furnace.

[0041] As described above, phosphorus contained in the ore may be removed by first heating in a non-reducing atmosphere and then heating in a reducing atmosphere. Compared to the case of heating once in either a non-reducing atmosphere or a reducing atmosphere, the combination of heating in a non-reducing atmosphere and heating in a reducing atmosphere can remove more phosphorus from the ore. In addition, first, heating in a non-reducing atmosphere, which is generally cheaper than a reducing atmosphere, is performed to remove phosphorus by thermal decomposition of goethite, in which most of the phosphorus is present, and then the phosphorus and phosphorus oxides that remain after the heating are removed by heating in a reducing atmosphere, thereby minimizing the use of reducing gas, which is more expensive, and removing phosphorus more efficiently. Therefore, according to the embodiment method in which heating is performed twice as described above, further energy and cost savings can be achieved compared to the case of heating once. That is, when the step of heating the ore includes performing a first heating on the ore in a non-reducing atmosphere and performing a second heating on the ore in a reducing atmosphere after the first heating, the amount of reducing gas required to reduce and decompose the phosphates present in the ore can be reduced. Since non-reducing gas is cheaper than reducing gas, reducing the amount of reducing gas used using the first heating furnace reduces the dephosphorization cost.

[0042] In addition, when heating in a reducing atmosphere, reduction of iron oxide in the ore may occur. Metallic iron produced by reduction binds with phosphorus, so heating in a reducing atmosphere may actually decrease the dephosphorization rate. Therefore, by making a part of the heating process a non-reducing atmosphere, it is possible to suppress the reduction reaction to metallic iron, which leads to a decrease in the dephosphorization rate, and to obtain the advantage of allowing only the dephosphorization reaction to proceed efficiently.

[0043] (Intermediate classification process) An intermediate classification process may be further performed between the first heating furnace 21 and the second heating furnace 22. The intermediate classification process is a process for separating the ore discharged from the first heating furnace 21 into a coarse particle portion and a fine particle portion. Unlike the classification process after heating described above, the intermediate classification process is always followed by a second heating of the ore. The intermediate classification process is defined as a process for classifying the ore after it is heated in the first heating furnace and before it is supplied to the second heating furnace.

[0044] 3 is a process diagram showing the process of the ore dephosphorization method according to an embodiment when intermediate classification is performed. The ore heated and discharged in the first heating furnace 21 is supplied to a sieve 6, which is a classification device. The sieve 6 performs intermediate classification, classifying the ore heated in the first heating furnace 21 into a coarse particle portion and a fine particle portion. The coarse particle portion of the ore classified by the sieve 6 is then supplied to a second heating furnace 22 and reduced. The fine particle portion is removed from the ore supplied to the second heating furnace 22.

[0045] In the sieve 6 used in the intermediate classification process, the size of the sieve mesh is preferably 0.5 mm or more and 3.0 mm or less. In the sieve 6, particles that do not pass through the sieve mesh are the coarse particle portion, and particles that pass through the sieve mesh are the fine particle portion. The particle size can be adjusted by adjusting the size of the mesh of the sieve 6. By using a sieve with a mesh range of 0.5 mm to 3.0 mm, the particle size of the fine particle portion can be set to 0.5 mm to 3.0 mm. The mesh of the sieve 6 that performs the intermediate classification process is larger than the mesh of the sieve 5 that performs the classification process after heating to remove fine powder. The classification device that performs the intermediate classification process is not limited to a sieve, and other classification devices may be used.

[0046] Usually, in the ore heated in the first heating furnace 21 and from which fine powder has been removed, the smaller the particle size, the lower the phosphorus content. In other words, the smaller the particle size of the ore, the higher the dephosphorization rate. Therefore, by the above-mentioned intermediate classification process, the ore discharged from the first heating furnace 21 can be separated into a coarse particle part with a relatively low dephosphorization rate and a fine particle part with a relatively high dephosphorization rate. Then, by performing the intermediate classification process, only the coarse particle part that needs dephosphorization can be preferentially supplied to the second heating furnace 22. In this way, the dephosphorization target can be narrowed down to the part of the whole iron ore that needs further dephosphorization by reduction, in other words, the part where dephosphorization is difficult to proceed and where dephosphorization by reduction should be performed with higher priority, and the dephosphorization can be performed more effectively. Then, by heating only the coarse particle part in the second heating furnace 22, the dephosphorization can be performed more efficiently in terms of overall energy efficiency and gas consumption than when all the ore is heated in the second heating furnace 22. That is, when the ore is classified after the first heating and before the second heating, the fine powder is removed from the ore, thereby increasing the reaction efficiency between the ore particles and the reducing gas, and thus further reducing the amount of reducing gas required to reduce and decompose the phosphates present in the ore.

[0047] The fine particles separated by the intermediate classification process in this embodiment have a sufficiently high dephosphorization rate, and can be used as dephosphorized iron ore as it is for pellets, briquettes, or as a raw material for sintering, etc. The classification process after heating using a sieve 5 shown in Fig. 3 may be omitted.

[0048] (Classification before heating) The method for dephosphorization of ore according to the present embodiment may further include a step of classifying the ore into a coarse particle portion and a fine particle portion before the step of heating the ore in a heating furnace. Hereinafter, the classification process of the ore before heating is referred to as "classification process before heating". Figure 4 shows an exemplary process diagram of the method for dephosphorization of ore that performs classification process before heating.

[0049] First, the configuration of a method for dephosphorizing ore by performing classification before heating will be described with reference to Fig. 4. Ore to be dephosphorized is stored in a storage tank 1. The ore discharged from the storage tank 1 is transported to a sieve 7 before being transported to a kiln-type heating furnace 2. The sieve 7 for classification before heating has sieve openings of 3.0 mm or more and 5.0 mm or less. The sieve 7 classifies the ore before heating into a coarse particle portion and a fine particle portion.

[0050] After classification before heating, the coarse particle portion is supplied to the heating furnace 2. The fine particle portion is preferably removed from the ore supplied to the heating furnace 2. The fine particle portion may be added to the ore discharged from the heating furnace 2. The fine particle portion does not have to be used as the ore for steel making. The heating furnace 2 is a kiln-type heating furnace. The heating temperature of the coarse particle portion in the heating furnace 2 is set to 400°C or higher. More preferably, the heating temperature is set to a range of 600 to 1000°C.

[0051] The atmosphere inside the heating furnace 2 is not particularly limited. For example, it is preferable to supply a reducing gas to the heating furnace 2 to create a reducing atmosphere inside the heating furnace 2. Examples of the reducing gas include hydrogen gas, CO gas, and a mixed gas of these. In a kiln-type heating furnace, the best dephosphorization efficiency is achieved by heating the ore to 400°C or higher while blowing in a reducing gas.

[0052] The various configurations described above may be combined with a configuration in which classification treatment is performed before heating.

[0053] For example, when the heating furnace is composed of the first heating furnace 21 and the second heating furnace 22, the ore may be classified before being supplied to the first heating furnace 21. In this case, at least one of the first heating furnace 21 and the second heating furnace 22 may be a kiln type, and the heating temperature may be set to 400° C. or higher. More preferably, the first heating furnace 21 is a kiln type, and the heating temperature may be set to 400° C. or higher.

[0054] For example, in addition to the classification before heating, one or both of intermediate classification and classification after heating may be performed. When classification is performed multiple times, all classifications may be performed with one sieve. However, the sieve suitable for classification before heating does not necessarily match the sieve suitable for intermediate classification and classification after heating. This is because the state of the ore to be classified and the purpose of these classifications are different. In particular, the classification before heating has the purpose of maintaining the rolling property in the furnace and improving the reactivity with gas, while the classification after heating has the purpose of selectively putting only particles in which phosphorus removal has not progressed into the heating furnace 2 by excluding particles in which phosphorus removal has progressed, thereby enabling efficient phosphorus removal. Therefore, it is most preferable to independently install the sieve 7 for classification before heating, the sieve 6 for intermediate classification, and the sieve 5 for classification after heating.

[0055] Next, the technical concept and the effects of the method for dephosphorizing ore by performing classification before heating will be described. The inventors have found that when dephosphorizing ore using a kiln-type heating furnace at 400°C or higher, if the particle size of the ore fed into the heating furnace falls below a certain threshold, the dephosphorization efficiency decreases. This is a phenomenon that contradicts the technical common sense of those skilled in the art. When reducing ore using a kiln-type heating furnace, it is believed that the smaller the particle size of the ore, the higher the reduction efficiency. This is because the smaller the particle size of the ore, the larger the surface area per weight of the ore. Therefore, according to the technical common sense, it was expected that the smaller the particle size of the ore, the easier it would be to dephosphorize the ore.

[0056] Based on the above findings of the present inventors, it is preferable to remove the fine particles of the ore before dephosphorizing the ore using a kiln-type heating furnace at 400°C or higher. By dephosphorizing only the coarse particles, which are the parts where it is easy to increase the dephosphorization rate, the dephosphorization efficiency can be increased, and a more efficient dephosphorization process can be carried out in terms of overall energy efficiency and gas consumption. As clarified through experiments by the present inventors, the above-mentioned effects can be preferably obtained by performing classification using a sieve with meshes of 3 mm to 5 mm and supplying only the coarse particles remaining on the sieve meshes to the heating furnace.

[0057] (Selection of ore before heating) The method for dephosphorizing ore according to the present embodiment may further include a step of selecting an ore having the highest phosphorus concentration of goethite before the step of heating the ore in a heating furnace when there are two or more types of ore, and the ore having the highest phosphorus concentration of goethite may be preferentially supplied to the heating furnace. A specific configuration of an embodiment in which the ore is selected before being heated will be described in detail below.

[0058] Ore types are distinguished, for example, based on the face formed when the ore is mined in the deposit. A face is a working area in a coal, metal, or other mine where coal, ore, etc. are mined or tunnels are excavated (see JIS M 0102:2000 "Mining Terminology"). The grade of the ore may differ depending on the face where the ore is mined. Ore types may also be distinguished based on the place of origin of the ore.

[0059] When there are two or more types of ores, the ore with the highest phosphorus concentration in the goethite is selected as the target for dephosphorization. It should be noted that the criterion for selecting the ore is the phosphorus concentration in the goethite in the ore, not the phosphorus content of the ore. For example, when there are ore A with a low goethite content but a high phosphorus concentration in the goethite and ore B with a high goethite content but a low phosphorus concentration in the goethite, ore A is selected as the target for dephosphorization. Even if the total amount of phosphorus contained in ore B is greater than that of ore A, ore A is preferentially subjected to dephosphorization based on the phosphorus concentration in the goethite contained in the ore from the viewpoint of efficiency and energy saving.

[0060] When the phosphorus concentration of goethite in the ore is unknown, the method for dephosphorization of the ore may further include a step of measuring the phosphorus concentration of goethite. The means for measuring the phosphorus concentration of goethite may be, for example, a mineral liberation analyzer (MLA). The mineral liberation analyzer includes a scanning electron microscope (SEM) having an energy dispersive X-ray analyzer (EDS), and a computer that controls the SEM and stores the EDS spectrum of each mineral species as data. JP 2015-40724 A discloses an example of an MLA. JP 2020-34372 A discloses an example of an analysis method using an MLA.

[0061] By performing elemental analysis of cross-sectional polished samples of iron ore using MLA, the amount of goethite per unit mass of iron ore and the arrangement of goethite can be determined. In addition, by cross-sectional analysis using MLA, the amount of phosphorus per unit mass of iron ore and the arrangement of phosphorus can also be determined. By comparing the analysis results of goethite and phosphorus, the phosphorus concentration of goethite can be determined.

[0062] The ore having the highest phosphorus concentration in goethite selected by the above procedure is preferentially supplied to the heating furnace for dephosphorization. Specifically, the ore having the highest phosphorus concentration in goethite is supplied to the heating furnace first. Next, after all of the ores have been supplied to the heating furnace, the ore having the highest phosphorus concentration in goethite among the remaining ores is selected and supplied to the heating furnace. In other words, the order in which the ores are supplied to the heating furnace is determined in descending order of the phosphorus concentration in goethite. If another type of ore arrives before all types of ore have been supplied to the heating furnace, the ore to be dephosphorized is selected from the group including the new ore by the above method.

[0063] Next, the effect of the embodiment in which the ore is sorted before being heated will be described. In the method for dephosphorizing ore according to the present embodiment, the criterion for selecting the type of ore to be supplied to the heating furnace is the phosphorus concentration of goethite in the ore. This is because it is difficult to remove phosphorus contained in minerals other than goethite using a kiln-type or fluidized bed heating furnace. On the other hand, the phosphorus concentration of goethite has a significant effect on the efficiency of dephosphorization of ore using a kiln-type or fluidized bed heating furnace. The higher the phosphorus concentration of goethite in the ore, the easier it is to perform dephosphorization using a kiln-type or fluidized bed heating furnace.

[0064] According to the method for dephosphorizing ore of the present embodiment, it is possible to preferentially dephosphorize ores having high dephosphorization efficiency, thereby further increasing the efficiency of the dephosphorization process.

[0065] Instead of relatively comparing the phosphorus concentrations of goethite of multiple types of ores, dephosphorization may be performed only when the phosphorus concentration of goethite of the ore is equal to or higher than a predetermined value. Specifically, only ores with a goethite phosphorus concentration of 1.0 mass% or more may be supplied to the heating furnace. In this case, only one type of ore may be used. If there is no ore with a goethite phosphorus concentration of 1.0 mass% or more, the dephosphorization may be stopped.

[0066] According to the results of experiments conducted by the inventors, by subjecting only goethite ores having a phosphorus concentration of 1.0 mass% or more to dephosphorization treatment using a kiln-type or fluidized bed heating furnace, it is possible to further increase the dephosphorization efficiency and reduce the energy required for dephosphorization.

[0067] The various configurations described above may be appropriately combined with the configuration of selecting the ore before heating. EXAMPLES

[0068] The effects of one embodiment of the present disclosure will be explained in more detail with reference to examples. However, the conditions in the examples are merely examples of conditions adopted to confirm the feasibility and effects of the present disclosure. The present disclosure is not limited to these examples of conditions. Various conditions may be adopted in the present disclosure as long as the purpose is achieved without departing from the gist of the disclosure.

[0069] (Experiment 1) (ore) In the comparative example and examples 1 to 5 described later, ore having the composition shown in Table 1 was used. In the comparative example, 2 kg of ore was charged into a batch-type heating furnace described later. In examples 1 to 4, the ore was supplied to a kiln-type heating furnace described later at a constant supply rate of 300 kg / h.

[0070] [Table 1]

[0071] (heating furnace) In the comparative example, a batch-type box furnace that only heats the ore without fluidizing it was used as the heating furnace. The inner diameter of the box furnace was 300 mm in width, 300 mm in depth, and 300 mm in height. In the examples 1 to 4, an external combustion kiln was used as the heating furnace. The inner space of the kiln had a diameter of 0.90 m and a length of 2.0 m. The kiln rotation speed was 2.0 rpm.

[0072] (Number of heating furnaces and heating atmosphere conditions) In the comparative example and the embodiment 1, the number of heating furnaces was 1. In the comparative example and the embodiment 1, the oxidizing gas, air, was fed at 15 [Nm 3 / h] into the heating furnace to make the atmosphere in the heating furnace a non-reducing atmosphere. In Example 2, the number of heating furnaces was 1. In Example 2, a reducing gas containing 33% H2 and the remainder N2 was used at 15 [Nm 3 / h] into the heating furnace to create a reducing atmosphere in the heating furnace. In Examples 3 and 4, the number of heating furnaces was two. In the first heating furnace, heat treatment was performed in a non-reducing atmosphere under the conditions of Example 1. The ore was then cooled to room temperature. Then, in the second heating furnace, heat treatment was performed in a reducing atmosphere under the conditions of Example 2.

[0073] (Heating temperature conditions) In the comparative example and examples 1 to 4, a plurality of temperatures were set as the temperature to which the ore was heated. Specifically, in the heating furnace, the temperature was raised to 100[°C], 300[°C], 500[°C], 750[°C], 1000[°C], and 1100[°C], and then this temperature was maintained. In examples 3 and 4, the heating temperature in the non-reducing atmosphere was the same as the heating temperature in the reducing atmosphere.

[0074] (Heating time conditions) In Examples 1 and 2, the residence time of the ore in the heating furnace was set to 120 min. In Examples 3 and 4, the total residence time of the ore in the first heating furnace and the second heating furnace was 120 [min]. In Examples 3 and 4, heating in a non-reducing atmosphere in the first heating furnace was performed for 60 [min], and heating in a reducing atmosphere in the second heating furnace was performed for 60 [min]. In the comparative example, the heating time in the heating furnace was set to 120 min.

[0075] (Intermediate classification process) In Example 5, after heat treatment in a non-reducing atmosphere in the first heating furnace, the ore was discharged from the first heating furnace and subjected to intermediate classification using a sieve with a mesh size of 3.0 mm. In the intermediate classification, the ore was separated into a fine particle portion and a coarse particle portion. Then, only the coarse particle portion was put into the second heating furnace and subjected to heat treatment in a reducing atmosphere. Note that in the comparative example and Examples 1 to 4, the intermediate classification was not performed.

[0076] In none of the examples was classification performed before or after heating.

[0077] Table 2 below summarizes the test conditions described above.

[0078] [Table 2]

[0079] (Measurement of dephosphorization rate) The dephosphorization rate was measured for the ore that had been heat-treated in a heating furnace. In the comparative example and examples 1 to 3, the dephosphorization rate of the ore discharged from the heating furnace was measured. The dephosphorization rate of Example 4 was calculated by the following procedure. First, the dephosphorization rate of the fine particle portion obtained by intermediate classification treatment after heating in a non-reducing atmosphere in the first heating furnace was calculated. In addition, the dephosphorization rate of the coarse particle portion obtained by heating in a reducing atmosphere in the second heating furnace after intermediate classification treatment was calculated. The overall dephosphorization rate of Example 5 was calculated from both the dephosphorization rate of the fine particle portion and the dephosphorization rate of the coarse particle portion after heating. The overall dephosphorization rate was calculated as the sum of the values ​​obtained by multiplying the mass ratio of the coarse particle portion and the fine particle portion by each dephosphorization rate. That is, the overall dephosphorization rate was calculated by the following formula. (Total dephosphorization rate) = {(Dephosphorization rate of fine particle part) x (Weight of fine particle part) + (Dephosphorization rate of coarse particle part) x (Weight of coarse particle part)} / {(Weight of fine particle part) + (Weight of coarse particle part)}

[0080] The dephosphorization rate is expressed by the following formula (1).

[0081]

number

[0082] In the above formula (1), η p is the dephosphorization rate [mass%], (C p )0 is the phosphorus concentration [mass%] in the ore before heating and reduction, (C p ) t is the phosphorus concentration [mass%] in the ore after heating and reduction.

[0083] The phosphorus concentration C shown in the above formula (1) pis expressed by the following formula (2). That is, the phosphorus concentration C p is the phosphorus content standardized by the iron content.

[0084]

number

[0085] In the above formula (2), %P is the phosphorus content (measured value) [mass %], %T.Fe is the iron content (Fe 2+ , Fe 3+ The phosphorus content (%P) was measured in accordance with the JIS M8216 standard. 2+ The FeO content [mass%] was measured according to the JIS M8213 standard. 3+ The (Fe2O3) content [mass%] was measured by fluorescent X-ray analysis. The M.Fe content [mass%] was measured in accordance with the JIS M8212 standard.

[0086] The measurement results of the phosphorus removal rate are shown in Table 3 below.

[0087] [Table 3]

[0088] When the heating temperature is 100°C, the dephosphorization rate η in Examples 1 and 2 p is the dephosphorization rate η in the comparative example p It is presumed that when the heating temperature is less than 100°C, the surface of the ore does not dry sufficiently, making it difficult to separate the phosphorus-containing fine powder (fine powder with a particle size of 0.25 mm or less) from the surface of the ore, and therefore the dephosphorization effect is small.

[0089] In all cases, the higher the heating temperature is above 100°C, the higher the dephosphorization rate η p When the heating temperature was 300°C, the dephosphorization rate η in Examples 1 to 4 p is the dephosphorization rate η in the comparative examplep This is presumably because at temperatures above 300°C, the water of crystallization in the goethite part of the ore evaporated (dehydrated), causing embrittlement, and the fine powder containing phosphorus was further separated and removed by physical impact.

[0090] As mentioned above, the higher the heating temperature, the higher the dephosphorization rate η p However, when the rate of increase in the dephosphorization rate relative to the increase in the heating temperature is taken into consideration, the heating temperature does not need to be too high. Table 4 below shows the rate of increase in the dephosphorization rate Δη when the heating temperature is increased by 10°C based on the results shown in Table 3 above. p The calculated value is [mass% / 10°C].

[0091] [Table 4]

[0092] According to the results shown in Table 4 above, if the heating temperature is up to 750[℃], the increase rate Δη p However, when the heating temperature exceeds 750°C, the rate of increase Δη p Therefore, taking into account the rate of increase, the upper limit of the heating temperature can be set to 750°C. On the other hand, taking into account the points described below, the upper limit of the heating temperature can be set to 1000°C.

[0093] When the heating temperature is higher than 1000°C, the temperature of the ore exceeds 950°C, which is the measurement standard temperature in the Karl Fischer method (see JIS M 8211:1995 "Method for determining the amount of water of synthesis in iron ore"). Therefore, in the ore heated to 950°C or higher, the embrittlement caused by the evaporation of the water of crystallization described above has already been completed. In addition, when the ore is heated in a reducing atmosphere, at a heating temperature higher than 1000°C, the reduction reaction is excessively promoted, and the production of metallic iron progresses, which is likely to hinder the release of phosphorus from the ore. Considering these points, the upper limit of the heating temperature can be set to 1000°C.

[0094] In Example 2, in which the atmosphere in the heating furnace was a reducing atmosphere, the dephosphorization rate η p In addition, Example 3 also had a higher dephosphorization rate η than Example 1 in the range of 750°C or higher. p The dephosphorization rate η p On the other hand, in Examples 1 to 3, in the heating temperature range of 100° C. or more and 500° C. or less, the dephosphorization rate η at the same temperature was improved regardless of the atmosphere in the heating furnace. p were equivalent.

[0095] At the same heating temperature, the dephosphorization rate η in Example 4 among Examples 1 to 4 p The dephosphorization rate was the highest. By carrying out intermediate classification to separate the fine and coarse particles after the initial heating in a non-reducing atmosphere, the dephosphorization rate can be further improved.

[0096] (Experiment 2) The effect of classification before heating is verified below using the results of offline experiments.

[0097] (raw materials) The ore to be dephosphorized was Australian iron ore fines, with the following composition: Fe: 62.6%, P: 0.29%, SiO2: 2.7%, alumina: 2.2%, and crystal moisture [CW]: 4.5%.

[0098] (Classification method) The classification before heating was performed using a sieve with mesh sizes of 2 mm, 3 mm, 5 mm, or 7 mm.

[0099] (Heat treatment device, heating conditions) The heating furnace was a kiln type. The heating conditions were as follows: - Furnace internal space size: diameter 0.90m, length 2.0m Furnace speed: 2.0 rpm Number of furnaces: 1 - Amount of ore fed into the heating furnace: 1kg / h (constant feeding rate) Gas type supplied to the furnace: Reducing gas (N2-33%H2) Gas flow rate supplied to the furnace: 15Nm 3 / h ·Heating temperature: 700℃ Residence time at the above heating temperature: 60 min

[0100] The method for measuring the dephosphorization rate was the same as in Example 4 of Experiment 1. That is, the dephosphorization rate of the fine particle portion obtained by classification before heating and the dephosphorization rate of the coarse particle portion after heating were measured. The values ​​obtained by substituting these values ​​into the following formula are shown in Table 5 as the dephosphorization rate. (Total dephosphorization rate) = {(Dephosphorization rate of fine particle part) x (Weight of fine particle part) + (Dephosphorization rate of coarse particle part) x (Weight of coarse particle part)} / {(Weight of fine particle part) + (Weight of coarse particle part)} The experimental results are shown in Table 5.

[0101] [Table 5]

[0102] The dephosphorization rates of Examples 12 and 13, in which the sieve mesh was in the range of 3 to 5 mm, were higher than those of Example 11, in which the sieve mesh was 2 mm, and Example 14, in which the sieve mesh was 7 mm. In Example 11, ores with diameters of 2 to 3 mm, which are difficult to dephosphorize, were also subjected to dephosphorization, so it is presumed that the dephosphorization rate was lower than that of Examples 12 and 13. In Example 14, the amount of ores subjected to dephosphorization was small, so it is presumed that the dephosphorization rate was lower than that of Examples 12 and 13.

[0103] (Experiment 3) The effectiveness of ore sorting before heating is verified below using the results of offline experiments.

[0104] (raw materials) The high-phosphate ores targeted for dephosphorization were two types of Australian iron ore fines A and B. The components of high phosphorus rock A were iron: 62.6%, P: 0.29%, SiO2: 2.7%, alumina: 2.2%, and crystal moisture [CW]: 4.5%. The phosphorus concentration in the goethite contained in high phosphorus rock A was 1.33%. High phosphorus rock A was used as the ore of the invention example. The components of high phosphorus rock B were iron: 61.6%, P: 0.19%, SiO2: 1.6%, alumina: 1.8%, and crystal moisture [CW]: 7.1%. The phosphorus concentration in the goethite contained in high phosphorus rock B was 0.37%. High phosphorus rock B was used as a comparative example.

[0105] The ores used in the comparative example and the invention example were both dried at 105° C. for 2 hours and then sized to 5 to 10 mm using a vibrating sieve. The weight of the ores was approximately 3 kg.

[0106] (Heat treatment equipment and method) The heating furnace was a kiln type. The heating conditions were as follows: - Furnace internal space size: diameter 0.90m, length 2.0m Furnace speed: 2.0 rpm Number of furnaces: 1 - Amount of ore fed into the heating furnace: 1kg / h (constant feeding rate) Gas type supplied to the furnace: Air (N2-21% O2) or reducing gas (N2-30% H2) Flow rate of gas supplied to the furnace: 15 Nm if the gas is a reducing gas 3 / h, 6Nm if the gas is air 3 / h Heating temperature: 700℃ if the gas is a reducing gas, 280℃ if the gas is air Residence time at steam heating temperature: 55 min if the gas is a reducing gas, 22 min if the gas is air - Classification after heating: The iron ore discharged from the heating furnace is classified using a sieve with 0.25 mm mesh.

[0107] (Calculation of phosphorus removal amount) The amount of phosphorus removed was calculated by multiplying the obtained dephosphorization rate by the initial phosphorus content of the iron ore. The initial phosphorus content of the iron ore is the phosphorus content of the iron ore after drying at 105°C for 2 hours as described above and then sieving to 5 to 10 mm particles using a vibrating sieve. The dephosphorization rate was expressed as the difference in the phosphorus content standardized by the iron content (P / Fe) before and after treatment, expressed as a percentage. The results are shown in Table 6.

[0108] [Table 6]

[0109] When goethite ore with a high phosphorus concentration was fed into a kiln-type heating furnace, the dephosphorization rate and amount of phosphorus removed were far greater than those of goethite ore with a low phosphorus concentration. [Explanation of symbols]

[0110] 1: storage tank, 2: heating furnace, 21: first heating furnace, 22: second heating furnace, 2a, 21a and 22a: supply port, 2b, 21b and 22b: exhaust port, 3: gas supplier, 31: non-reducing gas supplier, 32: reducing gas supplier, 4, 41 and 42: dust collector, 5, 6 and 7: sieves

Claims

1. A method for dephosphorizing ore, comprising the step of heating ore at a temperature of 100°C or higher and lower than 750°C in a kiln-type or fluidized bed-type heating furnace.

2. 2. The method for dephosphorizing ore according to claim 1, further comprising the step of supplying a reducing gas into the heating furnace during the step of heating the ore.

3. 2. The method for dephosphorizing ore according to claim 1, further comprising the step of supplying a non-reducing gas into the heating furnace during the step of heating the ore.

4. The heating furnace is composed of a first heating furnace and a second heating furnace, Supplying a non-reducing gas to the first heating furnace; Supplying a reducing gas to the second heating furnace; In the heating step, first, the ore is supplied to the first heating furnace and heated, and then the ore heated in the first heating furnace is supplied to the second heating furnace and heated. The method for removing phosphorus from an ore according to claim 1 .

5. The method includes a step of heating the ore at a temperature of 100° C. or more in a kiln-type or fluidized bed-type heating furnace, The heating furnace is composed of a first heating furnace and a second heating furnace, Supplying a non-reducing gas to the first heating furnace; Supplying a reducing gas to the second heating furnace; In the heating step, first, the ore is supplied to the first heating furnace and heated, and then the ore heated in the first heating furnace is supplied to the second heating furnace and heated; The method further includes a step of classifying the ore into a coarse particle portion and a fine particle portion finer than the coarse particle portion after heating in the first heating furnace and before supplying the ore to the second heating furnace, The fine particle portion is removed from the ore supplied to the second heating furnace. A method for removing phosphorus from ores.

6. In the step of classifying the ore after heating in the first heating furnace and before supplying it to the second heating furnace, a sieve having a mesh size of 0.5 mm or more and 3.0 mm or less is used. The method for removing phosphorus from an ore according to claim 5 .

7. The method includes a step of heating the ore at a temperature of 100° C. or more in a kiln-type or fluidized bed-type heating furnace, The method further includes a step of classifying the ore into a coarse particle portion and a fine particle portion using a sieve having a mesh size of 3.0 mm or more and 5.0 mm or less before the step of heating the ore in the heating furnace, The heating furnace is a kiln-type heating furnace, Supplying only the coarse particle portion into the heating furnace; The heating temperature of the coarse grain portion in the heating furnace is set to 400° C. or higher. A method for removing phosphorus from ores.

8. The type of ore is two or more, The ore contains goethite, Prior to the step of heating the ore in the heating furnace, the step of selecting the ore having the highest phosphorus concentration in the goethite is further included; The ore having the highest phosphorus concentration in the goethite is preferentially supplied to the heating furnace. The method for removing phosphorus from an ore according to any one of claims 1 to 6.

9. The ore contains goethite, The method for dephosphorizing ore according to any one of claims 1 to 6, characterized in that only the ore having a phosphorus concentration in the goethite of 1.0 mass% or more is supplied to the heating furnace.

10. The method for dephosphorizing ore according to any one of claims 1 to 6, further comprising a step of removing fine powder generated from the ore heated in the heating furnace.

11. 11. The method for removing phosphorus from ore according to claim 10, wherein the fine powder is removed by supplying a reducing gas or a non-reducing gas to the heating furnace and flowing the gas inside the heating furnace.

12. 11. The method for removing phosphorus from an ore according to claim 10, wherein the fine powder is removed by subjecting the ore discharged from the heating furnace to a classification process.

13. 7. The method for dephosphorizing an ore according to claim 1, wherein the ore is heated in the heating furnace at a temperature of 100° C. or more and 500° C. or less.

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