WO2004067784A1 - Process for producing sponge iron and reduced iron powder, sponge iron, and charging apparatus - Google Patents

Abstract

A process for producing sponge iron, which comprises charging an iron oxide powder and a reducing agent powder into a reaction vessel so that these powders are alternately stacked spirally and reducing the iron oxide. In the process, the efficiency of gas reaction is satisfactory, and high quality and high productivity are attained. The process is advantageous also in production adjustment, for example, because the amounts of the feed materials being charged can be regulated without being limited by reduction time. Also provided is a charging apparatus for the production. More preferably, the ratio of the carbon amount in the reducing agent to the oxygen amount in the iron oxide in the reaction vessel is 1.1 or higher by mole.

Description

 Description Method for manufacturing sponge iron reduced iron powder, sponge iron, and charging equipment

 The present invention relates to a method for producing sponge iron used as a raw material for producing iron powder, and a method for producing reduced iron powder using sponge iron produced by the method.

 The reduced iron powder is used not only as powder but also as a raw material for sintered products such as mechanical parts and magnetic materials.

 The present invention also relates to an apparatus for charging a raw material for producing sponge iron used in the method for producing sponge iron, and a high-purity sponge iron that can be produced by the method.

 The charge of the raw material into the reaction vessel is conventionally referred to as charging the raw material (however, translated into charge in the English translation). Words such as "filling" and "filling device" are mainly used. Background art

 A typical method for producing sponge iron is shown in FIGS. 1A and 1B. Here, FIG. 1A is a cross-sectional view showing the state of filling of the raw material in the container, and FIG. 1B is a horizontal cross-sectional view thereof.

 In producing sponge iron, iron oxide powder 2 and reducing agent powder 3 are concentrically placed in a cylindrical refractory reaction vessel 1 (sagar) with a lid attached to the lower surface. Then, the whole container is heated (indirect heating) to a temperature of 1050 to 1200 using a tunnel furnace or the like. By the heating in the above period, the iron oxide powder 2 in the reaction vessel 1 is reduced (coarsely reduced) and sintered together to form sponge-like metallic iron, that is, sponge iron. Here, as the iron oxide powder 2, powder obtained by pulverizing a mill scale, iron ore powder, or the like is used. Further, as the reducing agent powder 3, coke powder / coal powder or the like is used. Note that lime powder or the like is added to the reducing agent powder 3 as needed.

The above technology is disclosed in “Steel Handbook”, 3rd edition, Vol. 5, pp. 457 to 459 (especially, pp. 457, right column, lines 10 to 13). You. In the conventional sponge iron production technology as shown in FIGS. 1A and 1B, iron oxide powder 2 is filled into a reaction vessel 1 in a cylindrical shape (hereinafter referred to as a cylindrical iron oxide layer), and a reducing agent is used. Powder 3 is filled so as to surround the cylindrical iron oxide layer. Further, the reducing agent powder 3 is filled in the upper and lower portions of the cylindrical iron oxide layer and also in the central portion.

As a result, when the reaction vessel 1 is heated after filling the raw materials, first, in the initial stage, oxygen present in the voids in the packed bed of the reducing agent reacts with carbon in the reducing agent to form C o and ₂ gas, reacts as limestone or the like is added to the reducing agent and carbon in the co ₂ gas force reducing agents generated by decomposition (1), the CO gas as a reducing gas reducing agent Generated in the packed bed of powder 3 (reducing agent layer). '

C + C 0 ₂ → 2 CO (1)

 Then, the CO gas generated in this way reaches the packed layer (iron oxide layer) of the iron oxide powder 2 from the reducing agent layer, and the following equation (2):

 F e On + n C O → F e + n C O (2)

The reaction reduces iron oxide and generates co ₂ (carbon dioxide) gas. Further, the co ₂ gas diffuses partially through the reduced iron oxide layer, reaches the reducing agent layer again, and converts carbon into CO gas by the reaction of equation (1) in the layer. Then, CO gas this that generated diffuses into the re Pi iron oxide layer, causing a reaction of iron oxide and (2) of unreduced, iron generates the co ₂ gas while generate.

As a result, the reaction vessel:! The iron oxide powder 2 filled therein is reduced to iron powder by repeating the reaction of the equations (1) and (2) at regular intervals. Simultaneously with this reduction reaction, sintering of the reduced iron proceeds to form cylindrical sponge iron (sintered body). Figure 2 shows the appearance of sponge iron obtained by the conventional technology (the lower part is omitted). Here, the amount of CO gas necessary to reduce all the iron oxide is theoretically calculated from the equation (2) as the molar ratio (= mole number of carbon atoms in CO gas / " The number of moles of oxygen atoms) is 1. Therefore, the amount of reducing agent required to reduce all iron oxide is the molar ratio (= moles of carbon atoms in reducing agent / oxygen atoms in iron oxide) The number of moles of carbon atoms in the reducing agent / the number of moles of oxygen atoms in the iron oxide is hereinafter referred to as “carbon amount Z oxygen amount (molar ratio)”. Disclosure of the invention

 [Problems to be solved by the invention]

In the above reduction method, the diffusion of the CO gas and co ₂ gas generated in the reaction vessel 1 into the layers of the iron oxide powder 2 and the reducing agent powder 3 is a main factor that controls the progress of the reduction reaction. It is considered a factor. However, in the method of taking a packed structure shown in FIG. 1, the diffusion distance of CO Gas and co ₂ gas greatly there has been a problem that it takes a long time required for the reduction.

 If the reduction takes a long time, for example, in a manufacturing process on an industrial production scale using a tunnel furnace for heating, the reaction efficiency (gas utilization efficiency) is reduced, and the time required from the charging of raw materials to the extraction of the product is reduced. It takes days and leads to reduced productivity. In addition, the heating energy consumption required for the reduction is significantly increased.

 That is, in the filling method as shown in FIGS. 1A and 1B, it is necessary to increase the thickness (radial direction) of the layer of the oxidized iron powder 2 in order to increase the amount of sponge iron to be produced. Then the return time will be longer. However, if the thickness of the iron oxide powder 2 layer is reduced to shorten the reduction time, the amount of sponge iron that can be manufactured per reactor decreases, so it is not always necessary to increase the production per unit time. it dose not connect.

 Therefore, the combination of the thickness of the layer of iron oxide powder 2 and the reduction time that maximizes the production amount is uniquely determined, and not only is the production amount limited, but also the degree of freedom in adjusting the production amount is high. There was a problem of being small.

 In addition, in the filling method as shown in Figs. 1A and 1B, the CO gas generated by the above reaction tends to flow through the lower density layer of the reducing agent powder 3 and flow out of the reaction vessel 1. is there. Therefore, the CO gas does not efficiently contribute to the reduction reaction.

 In addition, the reducing agent powder 3 needs to be excessively filled between the reaction vessel 1 and the iron oxide powder 2 or inside the cylindrical iron oxide layer so that the layer of the iron oxide powder 2 does not collapse in the firing step.

 Under these circumstances, the conventional method requires a large amount of the reducing agent powder 3 in a molar ratio of 2.0 or more, and has a problem in that the basic unit of the reducing agent is poor.

Further, the lower portion of the cylindrical oxidized iron layer may swell under its own weight. For this reason, there was also a problem that the reduction of the iron oxide in the swollen portion did not proceed sufficiently within the planned reduction time, and an unreacted portion remained. SUMMARY OF THE INVENTION An object of the present invention is to advantageously solve the above-described various problems of the related art. That is, an object of the present invention is to propose a method for producing sponge iron which has high productivity and whose production amount can be easily adjusted.

 Another object of the present invention is to propose a device for filling a raw material into a reaction vessel, which is advantageously used in carrying out the above-mentioned production method.

[Means for solving the problem]

 The present inventors have conducted intensive research, and as a result, found that the above-mentioned problems can be advantageously solved by devising a filling form of the iron oxide powder and the reducing agent powder in the reaction vessel, and completed the present invention. . That is, a first aspect of the present invention provides a filling step of filling an oxidized iron powder and a reducing agent powder in a reaction vessel, and heating the iron oxide powder in the reaction vessel by heating from outside the reaction vessel. reduction

(Coarse reduction) and a step of reducing to a massive sponge iron, wherein the iron oxide powder and the reducing agent powder alternately form a spiral layer in the filling step. It is a method of producing sponge iron, which is filled to be deposited. In the first invention, it is preferable to employ one or more of the following preferable conditions (1) to (8) in any combination.

 (1) In the filling step, a layer made of the reducing agent powder is formed on the container side surface (referred to as an outer peripheral portion) and a vertical central axis portion in the reaction container, and the remaining portion (referred to as an intermediate portion) excluding the layer is formed. Filling to form said alternating and spiral layers. The outer peripheral portion and the central shaft portion correspond to the peripheral portion and the central portion, respectively, in the plan sectional view of the container. The middle part is preferably cylindrical or cylindrical. When the reaction vessel has a cylindrical shape, the vertical central axis is the axis of the cylinder.

 (2) As the iron oxide powder, at least one powder selected from iron ore, mill scale, and oxidized iron powder recovered from the pickling waste liquid is used.

 (3) As the reducing agent powder, at least one powder selected from coke, charcoal and coal is used.

(4) A carbon dioxide gas generating source is added to the reducing agent powder. Lime as a source of carbon dioxide Stone (including calcined lime) is particularly suitable. In this case, the reducing agent powder to be filled is a mixture of the reducing agent powder and the powder of the carbon dioxide gas generation source.

(5) The heating temperature in the reduction step is not less than 1000 ° C and not more than 1300 ° C.

 (6) In forming the spiral layer in the filling step, the layer thickness of the iron oxide powder layer and the layer of the reducing agent powder are variably controlled. Here, the variable control means that a different layer thickness can be set in at least one of the layers for each reaction vessel, and (1) the thickness of at least one of the layers is changed depending on the position in the reaction vessel. Obtaining, including both meanings.

 (7) In the filling step, the amount of the iron oxide powder in the reaction vessel or the amount of the reducing agent powder is determined by changing the amount of carbon contained in the reducing agent powder with respect to the amount of oxygen contained in the iron oxide powder. Should be controlled so that the molar ratio is 1.1 or more. Here, a preferable molar ratio is 1.15 or more, and a more preferable molar ratio is 1.2 or more.

 (8) In the filling step satisfying the above (1) and (7), the amount of the iron oxide powder and the amount of the reducing agent powder in the layer-filled portion are further included in the iron oxide powder. The amount of carbon contained in the reducing agent powder with respect to the amount of oxygen contained is controlled to be 0.5 or more in a molar ratio. Here, the “layer-filled portion” refers to a cylindrical region formed by a layer of spirally deposited iron oxide powder and reducing agent powder. This corresponds to the portion excluding each of the aforementioned “layers made of reducing agent powder”. The second invention is a method for producing reduced iron powder, in which the sponge iron produced according to the first invention is pulverized, reduced (finish reduction), and then further pulverized.

The preferred conditions (1) to (8) in the first present invention can be applied in any combination. A third aspect of the present invention is a sponge iron sintered into a helix-like mass, preferably a high-purity sponge iron having a metal iron content of 97 mass% or more. In the first aspect of the present invention, high-purity sponge iron can be produced even in a lump having a weight of 100 kg or more by, for example, applying a suitable condition (7) or the like and performing a reduction treatment for a sufficient time. A fourth aspect of the present invention is a filling device that fills a container with iron oxide powder and reducing agent powder, the insertion portion being inserted into the container, and capable of rotating and moving up and down in the container; Department An apparatus for filling sponge iron raw materials, comprising an iron oxide powder discharge port and a reducing agent powder discharge port rotatably provided with the insertion section at a lower end of the sponge iron.

 According to a fourth invention, in the method for producing sponge iron according to the first invention, the iron oxide powder and the reducing agent powder are alternately and spirally formed in a reaction vessel. It is suitable for use in filling for deposition. In the fourth aspect of the present invention, it is preferable that the opening areas of the iron oxide powder outlet and the reducing agent powder outlet are variable. Such a configuration can be suitably used in the first aspect of the present invention, particularly in order to satisfy the preferable condition (6).

 Further, in the fourth aspect of the present invention, the insertion part may be a cylindrical main body having a diameter of 85% or less of the inner diameter of the container, and a circle having a diameter of 90 to 95% of the inner diameter of the container. A lower end portion formed of a part of a cylinder having a cross-sectional shape, and the horizontal cross-sectional shape of the lower 耑 portion is a sector shape including the center of the circle and a part of the circumference, or a shape including the sector shape. It is preferable that there is. Such a configuration is suitable for the purpose of reducing the thickness of the reducing agent powder layer in the outer peripheral portion described in the preferred condition (1) in the first present invention. In addition, even if a projection is formed in the reaction vessel due to the attached matter, the insertion section can be inserted into the reaction vessel without interfering with the projection. BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is a cross-sectional view for explaining a conventional filling method of iron oxide powder and reducing agent powder. FIG. 1B is a horizontal sectional view showing a section taken along the line IB-IB of FIG. 1A.

 FIG. 2 is a perspective view showing the appearance of sponge iron obtained by a conventional method.

 FIG. 3A is a cross-sectional view illustrating an example of a filling method of the iron oxide powder and the reducing agent powder according to the present invention.

 FIG. 3B is a horizontal cross-sectional view showing a ΙΠΒ—: ΠΙ ′ cross section of FIG. 3A.

 FIG. 4 is a schematic diagram showing an example of the structure of the insertion portion (rotary charging cylinder) of the present invention.

 FIG. 4B is a cross-sectional view showing a filling state when the rotary charging cylinder of FIG. 4A is used.

FIG. 5 is a schematic diagram showing another example of the structure of the insertion portion (rotary charging cylinder) of the present invention. FIG. 6 is a cross-sectional view illustrating another example of the filling method of the iron oxide powder and the reducing agent powder according to the present invention. FIG. 7 is a perspective view showing the external shape of sponge iron obtained by the present invention.

 FIG. 8 is a cross-sectional view illustrating an experimental example of a filling method in which iron oxide powder and reducing agent powder are horizontally deposited in multiple layers.

 Figure 9 shows the relationship between the carbon content / oxygen content (molar ratio) (horizontal axis) and the required reduction time (vertical axis) in the alternate filling method for several different iron oxide layer thicknesses. FIG.

 FIG. 10 is a cross-sectional view illustrating another experimental example of a filling method in which iron oxide powder and reducing agent powder are horizontally deposited in multiple layers.

 Figure 11 shows the relationship between the amount of carbon in the alternating filling section, the amount of oxygen (molar ratio) (horizontal axis), and the required reduction time (vertical axis) in another alternating filling method. It is a figure which shows about thickness.

 Figure 12 shows the relationship between the amount of carbon / oxygen (mol ratio) (horizontal axis) and the required reduction time (vertical axis) in the whole reaction vessel in different alternate deposition methods. It is a figure showing about iron layer thickness.

Figure 1 3 is, in spiral alternately filling (hatching) and a cylindrical packing (open), amount increase iron oxide (wt%, abscissa) metallic iron purity obtained by the reduction (mas _S%, ordinate) of It is a figure showing a relation.

 FIG. 14A is a sectional view showing still another example of the structure of the insertion portion (rotary charging cylinder) of the present invention.

 FIG. 14B is an arrow view showing a section taken along the line XIVB—XIVB ′ of FIG. 14A (the thickness of the wall is omitted). Here, the meaning of each code is as follows.

 1, 1 1: reaction vessel (sagar)

 2, 1 2: iron oxide powder

 3, 1 3: reducing agent powder

 14: Raw material charging device

 1 4a, 1 4d: partition wall

 1 4 b: Rotary charging cylinder

1 4 c: Cut-out part 15: Iron oxide powder outlet

 16: Reducing agent powder outlet (for alternate filling)

 1 6 a: Reducing agent powder outlet for outer periphery

 1 6 b: Reducing agent powder outlet for shaft center

 17: Iron oxide powder container

 18: Reducing agent powder storage section

 1 9 a, 1 9 b: Holding plate

 a: Opening height Best mode for carrying out the invention

 (Raw material filling method and filling device)

 The present invention is characterized by a method for charging a raw material into a reaction vessel. Here, the raw materials are iron oxide powder and reducing agent powder, but if necessary, limestone or the like may be added together with the reducing agent.

 That is, conventionally, a method as shown in FIG. 1 is used.For example, a vertical cylindrical refractory reactor 1 is filled with an iron oxide powder 2 and a reducing agent powder 3 in a concentric cylindrical shape along the axial direction. The method is adopted. Instead, the present invention alternately fills the iron oxide powder and the reducing agent powder alternately and spirally with each other, that is, the structure in which both the containers are deposited is a spiral of iron oxide powder. The method is to employ a method in which the layers and the spiral layers of the reducing agent powder are filled alternately in a stacked state (hereinafter referred to as “helical alternating filling”). When the spiral alternate filling method is used, the filling with the iron oxide powder and the reducing agent powder can be performed simultaneously in parallel and continuously. For this reason, the thickness (filling amount) of each layer can be made constant. Therefore, the thickness ratio between the reducing agent layer and the iron oxide layer can be kept constant. This layer thickness ratio can be set to an arbitrary ratio for each reaction vessel depending on the purpose and situation.

 On the other hand, the layer thickness ratio can be changed arbitrarily and at any time during charging.

For this reason, the spiral alternating filling method is useful as a method that can greatly contribute to the improvement of production and production and the production volume. 3A and 3B show an example of the present invention. In the present invention, the raw material is charged by using a raw material charging device 14 in a cylindrical reaction vessel 11 (sagar) made of a refractory material such as SiC and the like. It is preferred to charge and fill 3 simultaneously.

 The preferred configuration of the raw material charging device 14 is as follows.

 The raw material charging device 14 is mainly composed of a rotary charging cylinder 14 b (charging portion) inserted into the reaction vessel 11. The axial direction of the cylindrical body of the rotary charging cylinder 14 b is divided into two by the partition wall 14 a, and the chambers are partitioned, that is, the iron oxide powder storage section 17 and the reducing agent powder storage section 18 Can be charged with iron oxide powder 12 and reducing agent powder 13 (the powder in each storage section is not shown). At the lower end (or near the lower end) of the rotary charging cylinder 14b, an iron oxide powder discharge port 15 and a reducing agent powder discharge port 16 are provided, respectively, to accommodate the storage sections 17 and 1 respectively. 8 are provided as openings. Although not shown, it is preferable that each discharge port can be adjusted in opening degree (for example, opening height a), that is, opening area by a gate such as a slide gate. The position and orientation of the discharge port may be determined as necessary.Any surface of the cutout provided on the bottom, side, or bottom of the rotary charging cylinder 14b should be an opening. Can be. In principle, it is preferable that each raw material powder is discharged by its own weight of the raw material powder charged in the storage section. FIG. 4A shows an example of a detailed view of the rotary charging cylinder 14b. In this example, a rectangular tubular cutout portion 14c protruding in a direction perpendicular to the partition wall 14a is provided at the extending position of the lower end portion of the tube. Discharge ports (openings) 15 and 16 that are connected to the storage sections 17 and 18 are provided on side walls of the cutout section 14c that are diagonal to each other. FIG. 4B is a cross-sectional view of the filling process using such a rotary charging cylinder.

 As a variation, the cut-out portion for the iron oxide powder and the cut-out portion for the reducing agent powder can be arranged diagonally with respect to each other as a substantially quarter-circle sector. Conceivable. In this case, at least a part of the two outlets 15 and 16 should be provided on the side corresponding to the fan-shaped straight portion and on the same plane with the axis of the rotary charging cylinder 14b interposed therebetween. (The state is the cross-sectional view of FIG. 3A). FIG. 5 is a detailed view showing another example of the rotary charging cylinder 14b.

In order to ensure that the raw material powder to be charged is controlled and spread to the circumference of the reaction vessel 11, It is preferable that the diameter of the rotary charging cylinder 14 b (especially at the lower end) be a value close to the inner diameter of the reaction vessel 11. However, since the reaction vessel is used repeatedly and a plurality of cylindrical units are stacked to form a reaction vessel, reduced iron and ash in the reducing agent adhere to the inside of the reaction vessel and become convex. A part may be formed. Also, the container may be slightly tilted due to the distortion caused by repeated use. Therefore, if the lower end of the rotary charging cylinder 14 b is almost the inner diameter of the reaction vessel 11, it may come into contact with the reaction vessel 11 when charging the rotary charging cylinder 14 b, which may cause damage. There is.

 By the way, the purpose of making the diameter of the lower end of the rotary charging cylinder 14 b closer to the inner diameter of the reaction vessel 11 is to secure an opening from near the center of the reaction vessel to near the circumference for each outlet. It is. Therefore, if the position of the discharge port is devised, the horizontal cross-sectional shape of the lower end of the rotary charging cylinder 14b does not need to be a perfect circle, but a sector that forms a part of this circle (virtual circle), or Is sufficient if it has a shape including at least the sector.

 FIG. 5 shows an example in which the lower end has a fan shape, and the iron oxide powder outlet 15 and the reducing agent powder outlet 16 are provided asymmetrically. Here, the outlet 15 for the iron oxide powder and the outlet 16 for the reducing agent powder are provided on the side surface (equivalent to the side of the sector) of the cutout portion 14c provided in the same manner as in FIG. I have. Although the bottom surface of the cutout portion 14c is also open, the powders 12 and 13 are mainly discharged from the side surface because the deposited powder serves as a bottom surface. 19 a and 19 b are holding plates.

 The center angle of the sector may be arbitrary, but should be about 180 ° (ie, a semicircle) or less. This is preferable for making the lower end sufficiently compact. More preferably, the maximum crossover of the horizontal cross-sectional shape of the cutout portion is smaller than the diameter of the virtual circle.

 In addition, the diameter of the virtual circle at the lower end is preferably closer to the inner diameter of the reaction vessel from the viewpoint of productivity, and is preferably about 90% or more of the inner diameter of the reaction vessel. On the other hand, from the viewpoint of operability, it is preferable that the diameter of the virtual circle is appropriately reduced, and it is preferable that the diameter is not more than about 95% of the inner diameter of the reaction vessel.

The diameter of the main body of the rotary insertion tube 14b is preferably about 85% or less of the inner diameter of the reaction vessel, and it is preferable to secure room for horizontal movement in the container in order to avoid contact. In addition, from the viewpoint of securing a feed path for the raw material powder to be charged, the diameter of the main body is preferably about 30% or more of the inner diameter of the reaction vessel. In order to spirally fill the raw material using such a raw material charging device 14, the opening area (opening degree) of the discharge outlets 15 and 16 is adjusted, and the rotary charging cylinder 14 is used. b is inserted into the reaction vessel 11 from above. Then, by rotating the rotary charging cylinder 14b (therefore, the outlets 15 and 16) at a constant speed while rotating, the iron oxide layer thickness and the reducing agent layer thickness are maintained at a constant ratio. In this case, it is preferable that the filling is performed through the outlet so that the two are spirally entangled with each other (alternate filling). In this way, a packed bed in which the oxidized iron powder 12 and the reducing agent powder 13 are alternately deposited in a spiral form together is formed in the reaction vessel 11. Feeding of the raw materials into each of the storage sections 17 and 18 is performed before or during filling in the reaction vessel as necessary. FIG. 6 shows another example of the filling method according to the present invention. Here, the raw material charging device 14 is shown in a simplified manner.

 As shown in FIG. 6, when filling the raw material powder into the reaction vessel, the position of the spiral alternate filling may be limited to a region excluding the outer peripheral portion along the axial direction of the cylindrical reaction vessel 11. . Further, the position where the spiral alternate filling is performed may be a region excluding the axial portion along the axial direction of the reaction vessel 11. Further, the position where the spiral alternate filling is performed may be a region excluding both the axial center portion and the outer peripheral portion along the axial direction of the reaction vessel. In any case, the region where the spiral alternate filling is performed is referred to as a cylindrical intermediate portion. The outer peripheral part and the axial center part correspond to the peripheral part and the central part, respectively, in the plan sectional view of the container.

 The reducing agent layer in the outer peripheral portion is used to prevent interference between the rotary charging portion 14 b of the raw material charging device 14 and the reaction vessel 11, and to prevent seizure at the contact portion between the reaction container and the iron oxide powder. In some cases, it is unavoidable from the viewpoint of setting. The reducing agent layer at the shaft center may be set for convenience in handling sponge iron from the container. As a result, a layer of only the reducing agent is present at the outer peripheral portion or at the axial center portion, thereby forming a passage for the reaction gas, thereby making the gas diffusion in the reaction vessel smooth and uniform. The effect of increasing the reduction reaction rate can also be expected. Further, when the outer peripheral portion is formed of a reducing agent layer, it is possible to prevent the product from being welded to the vessel wall. Therefore, if necessary, it is preferable to provide these reducing agent layers while optimizing the layer thickness (radial direction) in consideration of the yield of the reducing agent and the amount of carbon / oxygen (molar ratio).

In the case of a cylindrical container, the outer periphery is about 2.5% or more and about 5% or less of the inner diameter of the vessel (diameter of the inner surface). It is preferable that the thickness be in the range (radial direction). On the other hand, the diameter of the shaft center is preferably about 250 or less. For example, in order to form a reducing agent layer on the outer peripheral portion, an opening may be provided on the side of the rotary charging cylinder 14a, and the reducing agent powder forming the outer peripheral portion may be discharged from the opening. In addition, in order to form a reducing agent layer at the shaft center, a central cylindrical portion is further formed at a position where the partition wall 14c is provided in FIG. 4 and the like, and an opening is provided at a lower end of the central cylindrical portion. By discharging the reducing agent powder that forms the axis from the opening.

 These openings may be connected to the outlet 16 for forming the spiral layer or may be independent.

 FIG. 14A shows an example of the rotary charging cylinder capable of filling shown in FIG. Fig. 14B is a cross-sectional view at the XIVB-XIVB 'position in Fig. 14A (wall thickness is omitted for simplicity). In this example, a reducing agent powder outlet 16 is provided on the bottom surface of the rotary charging cylinder 14b for alternate filling such as spiral alternate filling. In addition, an opening is provided on the lower side surface of the rotary charging cylinder 14b to form a reducing agent powder outlet 16a for the outer peripheral part. In addition, a reducing agent powder outlet 16b for the shaft center is provided on the bottom surface of the rotating loading cylinder 14b at the shaft center position, and a part of the reducing agent powder is guided by the partition wall 14d. It has become. Furthermore, as shown in Fig. 3A, the bottom layer usually forms only a layer of reducing agent powder (and limestone), ensuring the reduction of the bottom iron oxide layer, and the reaction vessel and iron oxide layer. It is preferable to prevent seizure. Similarly, it is preferable to form a layer of only the reducing agent powder for the uppermost layer. These reducing agent layers close the iron oxide powder outlet 15 (set the opening to zero) in the raw material charging device 14 or supply the iron oxide powder to the rotary charging cylinder 14b. It can be formed by means such as stopping. In the present invention, in performing the spiral alternate filling using the above-described apparatus or the like, it is preferable to variably control the thicknesses of the silicon oxide layer and the reducing agent layer. That is, it is preferable that the thickness of each layer is controlled to be constant within one reaction vessel, but it is preferable that the thickness can be adjusted, for example, by optimizing the thickness according to the raw material.

Such changes in the layer thickness include, for example, the rotation speed, the rising speed, It can be realized by adjusting any two or more of the opening degrees of the outlets 15 and 16. In particular, if the opening degree of the outlets 15 and 16 is controlled through gate opening / closing control, stable operation can be ensured without inducing gas diffusion resistance, prolonging the reduction time, and reducing production volume. It is preferable because it can be realized.

 Theoretically, it is possible to change the layer thickness continuously or intermittently in the height direction of the vertical reaction vessel 11, for example, at the bottom, middle, or near the top. It does not preclude a variety of applications. For example, an application form in which the thickness of the iron oxide layer is increased in an upper part where the progress of reduction tends to be fast may be considered. The thickness of the oxide layer and the reducing agent layer deposited spirally is preferably about 5 mm or more in each layer, and the sum of the two layers is preferably about 10 mm or more. More preferably, it is 40 or more thighs. If the layer thickness is excessively small, an unsteady portion tends to occur due to the fluctuation of the layer thickness. A more preferred lower limit is about 10 mm or more for each layer, and about 30 mm or more for each layer.

 On the other hand, if the layer thickness is excessively large, the reduction treatment time is prolonged and the raw material efficiency is reduced. Therefore, it is preferable that the thickness of each layer is about 100 mm or less, and the sum of each layer is about 200 thigh or less. A more preferable upper limit is about 80 mm or less for each layer, and about 150 or less for each layer.

 The layer thickness ratio between the iron oxide layer and the reducing agent layer is generally not represented by the thickness but by the amount of carbon and the amount of oxygen (molar ratio). Suitable ratios will be described later. The above-described raw material charging apparatus is an example. In short, the raw material charging apparatus has an insertion part that can be vertically moved and rotated. Is provided so as to rotate with the rotation of the inlet portion, and is inserted into the reaction vessel and raised while rotating the inlet portion, so that the iron oxide powder has a double helix from the outlet. Any structure may be used as long as it can deposit and fill the reducing agent powder.

 For example, the insertion portion is advantageously cylindrical, but is not limited to this. For example, a cylindrical body having a sectional shape such as a fan shape, a star shape, or a chrysanthemum shape depending on the shape of the reaction vessel may be used. Further, the storage section does not need to be formed of a partition plate, and its shape and position are arbitrary. It is not necessary that the iron oxide powder container and the reducing agent powder container have the same volume.

A fixed or movable guide plate, a holding plate, or the like is preferably provided around the discharge ports 15 and 16 in order to guide the raw material powder to be filled from the discharge ports in a target direction. You. (Raw material powder)

 In the method for producing sponge iron according to the present invention, at least an iron oxide powder and a reducing agent powder are required as raw materials to be charged into the reaction vessel, and the iron oxide powder may be iron ore or steel. It is preferable to use, as a powder, iron oxide such as a mill scale generated in the hot rolling step. Also, in the so-called pickling process of removing oxides and the like on the surface of steel with an acid such as hydrochloric acid, waste acid (pickling waste liquid) is generated, and the pickling waste liquid is obtained by roasting or the like. Iron oxide powder is also preferred as the iron oxide powder. The preferred average particle size of these iron oxide powders is about 0.05 mm to about 10 cm.

Further, finer iron oxide powder, such as hematite powder having a specific surface area of 2 m ² / g or more and a grain size of 0.01 μm or more industrially controlled, may be used in the above mill scale or iron ore. It is preferable to use the powder mixed with such a powder as it improves the quality of sponge iron. A so-called carbonaceous powder containing carbon is used as the reducing agent powder. As the carbonaceous powder, coatus powder, charcoal (a kind of volatile coal), coal powder (preferably non-coking), anthracite powder, charcoal powder and the like are suitable. From the viewpoint of reduction efficiency, the amount of carbon in the carbonaceous powder is preferably 60% or more. A suitable average particle size with the reducing agent powder is also about 0.05 瞧 to about 10 bandages.

 As the reducing agent powder, if necessary, there is no problem even if a powder serving as a carbon dioxide gas generating source is used as a part of the reducing agent layer and mixed and added. . Limestone (including calcined lime) powder is particularly preferable as a carbon dioxide gas generating source. (Reduction step)

The iron oxide powder 12 and the reducing agent powder 13 (including the carbon dioxide gas source powder to be added and mixed) are placed in the reaction vessel 11 in the raw material charging apparatus 14 shown in FIGS. Fill alternately with a spiral. As the reaction vessel 11, for example, it is preferable to use a cylindrical reaction vessel made of SiC called sagar. The shape of the reaction vessel 11 is not limited, but a cylindrical shape seems to be the most advantageous. Although there is no particular limitation on the dimensions of the reaction vessel, in the case of a cylindrical shape, the inner surface has a cross-sectional diameter of about 200 mm to about 800 mm and a height of about 100 mm to about 2000 strokes. It is suitable. Incidentally, one preferably at least about 10k _g amount of sponge iron ingot to produce per container, from the viewpoint of productivity, it is further preferable to further about 100kg more than about 50 kg,. The reaction vessel 11 filled with iron oxide powder 12, reducing agent powder 13, and limestone or the like used as required is then loaded in a baking furnace such as a tunnel furnace while being loaded on a bogie or the like. Then, the raw material filled in the container is heated together with the container for a predetermined time for reduction. This reduction is called crude reduction, and the target purity (the content of metallic iron in the reduced sponge iron) depends on the use of the reduced iron powder, but a high purity of at least about 90% mass _S is required. It is about 97 mass% or more for the intended use. There is no upper limit to the purity target, but the purity that can be _{achieved at} an acceptable cost is currently about _{99.5 maSS} % at maximum.

 If the heating temperature for the above reduction is insufficient, the reduction of iron oxide does not proceed sufficiently, and the purity of sponge iron decreases. The preferred lower limit of the heating temperature is about 1000. On the other hand, if the heating temperature is excessive, the sintering of sponge iron, which proceeds simultaneously with the reduction, proceeds excessively, causing the sponge iron to harden, resulting in an increase in power consumption in the subsequent coarse pulverization and wear of the crushing tool. This may lead to an increase in manufacturing costs. The preferred upper limit of the heating temperature is 1300 ° C. The preferred heating temperature is therefore in the range of 1000-1300 ° C.

 When a tunnel furnace is used as a firing furnace, the reaction vessel 11 (and the iron oxide inside), which is placed on a carriage and moves inside the firing furnace, first moves through a pre-tropical region where the temperature gradually increases for 24 hours. (Preferably 20 hours or more, 28 hours or less), and a firing zone at about 1000 ° C to about 1300 for about 60 hours (preferably 36 hours or more, more preferably 56 hours or more) , And preferably 72 hours or less, more preferably 64 hours or less. Thereafter, the reduction treatment is completed through a cooling zone region in which the temperature gradually decreases (preferably, passing through 20 to 28 hours). The inlet temperature in the pre-tropical zone and the outlet temperature in the cooling zone are about 200 ° C (about 20 ° C to about 400 ° C) .The outlet temperature in the pre-tropical zone and the inlet temperature in the cooling zone are Approximately 900 ° C (firing zone temperature-450 ° C-firing zone temperature-about 50 ° C) Force It is preferable from the viewpoint of protection of the reaction vessel (refractory).

 By this reduction reaction by heating, the iron oxide is reduced by the reducing agent to form massive sponge iron. The sponge iron obtained naturally forms a spiral mass. Fig. 7 shows an example of the external shape of sponge iron obtained by the method of the present invention (the upper and lower ends are omitted).

It is preferable that the height (axial direction) of the sponge iron ingot obtained is large, but there is no restriction on the size of the reaction vessel or the decrease in thermal efficiency due to the large firing furnace when the height of the reaction vessel is increased. In consideration of such factors, the size is preferably about 2000 mm or less. According to the method of the present invention, high-purity sponge iron having a purity of 97 mass% or more can be obtained. When the purity is 97 ma _SS % or more, it is advantageous in guaranteeing the product characteristics of sintered parts such as mechanical parts and magnetic materials, or reduced iron powder used as powder. However, since the method of the present invention has advantages other than purity, the purity is not limited to a method for producing high-purity sponge iron of 97 mass% or more. That is, it is applicable to general crude reduction with a purity of about 90 raass% or more. In addition, as components other than metallic iron, impurities (Si, Mn, P, S, etc.) of less than l mass% in total are generally contained. After heating for the crude reduction, the sponge iron produced is separated from the reaction vessel 11 and removed from the reducing agent. The sponge iron taken out of the reaction vessel 11 is then coarsely pulverized, usually to about 150 ni or less, for further reduction, thereby obtaining coarse reduced particles. Thereafter, the coarsely reduced particles are charged into a finishing reduction furnace in a reducing atmosphere and subjected to finish reduction, and are further pulverized into reduced iron powder.

(Ratio of iron oxide and reducing agent)

 In filling the raw materials into the reaction vessel, the ratio of the amount of iron oxide and the amount of reducing agent (solid reducing agent) when performing the above-mentioned spiral alternating filling, particularly the amount of oxygen in the iron oxide, is required. The ratio of the amount of carbon in the reducing agent has already been described together with the formula (2). In other words, the reduction reaction of iron oxide is determined as a reaction of one C atom in the reducing agent and one O atom in the iron oxide (carbon content / oxygen content (molar ratio) = 1. 0). However, in general, a larger amount of carbon than the amount of oxygen in iron oxide is required as a reducing agent. In the conventional method, the reducing agent is excessively charged for the reason already described, and the reducing agent is 2.0 to 2.5 times (carbon content / oxygen content (molar ratio) = 2.0 to 2.5). ) Is filled. In this case, the reduction ratio (target purity of sponge iron) is 90 mass% or more for metallic iron, and preferably 97 mass% or more. The present inventors investigated the relationship between the carbon amount / oxygen amount (molar ratio) and the required reduction time in the spiral alternating filling method of the present invention by the following experiment.

In the experiment, as shown in Fig. 8, for simplicity, it was filled almost horizontally instead of spiral. A horizontal alternating filling method was adopted, in which the layers of iron oxide powder 12 (iron oxide layer) and the layer of reducing agent powder 13 (reducing agent layer) were alternately filled. The horizontal alternating filling is complicated because the sponge iron obtained by reduction has multiple disc shapes, and the spiral alternating filling is superior to the suitability for actual equipment, but the carbon content and the oxygen content (molar ratio) In relation to the progress of the reduction reaction, it is equivalent to spiral alternating packing. Hereinafter, the spiral alternating filling and the horizontal alternating filling are collectively referred to as alternate filling.

 The inner diameter of the reaction vessel used for the experiment was 370, and the filling height was 1400 mm. The same iron oxide powder and reducing agent powder as those used in Example 1 described later were used. The reduction treatment was performed at a maximum temperature of 1150 ° C. The reduction time refers to the holding time at this maximum temperature. Figure 9 shows how to obtain carbon content (molar ratio) and oxygen content in iron oxide in a plurality of horizontal alternating filling systems with different iron oxide layer thicknesses and to obtain 97 mass% iron (metallic iron) sponge iron. It is a graph which shows the relationship with the required reduction time. The molar ratio is the ratio between the total iron oxide and the total reducing agent in the container.

 In FIG. 9, an example of the result of performing the same reduction treatment using the conventional cylindrical filling method (FIG. 1) is indicated by a circle (conventional example: Association). In this conventional method, the thickness of the iron oxide layer was set to 55 and the amount of carbon / oxygen (molar ratio) was set to 2.2, but the reduction time was as long as 53 hours.

 On the other hand, in the layered alternating packing (Fig. 8), the thickness of the iron oxide layer was 15 (Experimental example 4: X mark), 20 (Experimental example 3: triangle mark), 30 mm (Experimental example 2: square mark (, Reduction experiments were performed for each case of 50 mm (Experimental example 1: rhombus mark (♦)). As a result, the reduction time was shortened by reducing the thickness of the iron oxide layer. It was found that when the molar ratio was 1.2 or more, the reduction time became almost constant, and it was not necessary to secure a molar ratio of 2.0 or more as in the conventional case.

If the molar ratio is less than 1.2, the reduction time tends to be long, but the effect of changing from the cylindrical filling method to the alternating filling method and reducing the layer thickness surpasses the above tendency. In other words, since the spiral method can fill more iron oxide, for example, in this example, the spiral alternate filling method with an iron oxide layer thickness of 30 oz. Is filled with almost the same amount of iron oxide as the conventional cylindrical filling method. Have been. Therefore, the effects of the present application are sufficiently obtained in the experimental range of the molar ratio of 1.1 or more. In addition, if the molar ratio is 1.15 or more, the degree of prolongation of the reduction time is relatively small. Then, it is roughly effective. Of course, when the molar ratio is 1.2 or more, the effect of reducing the reduction time can be further obtained. When the thickness of the iron oxide layer was 15 mm, the reduction time was almost constant at a molar ratio of 1.6 or more. The experiment was repeated under different conditions. As a result, it was found that the following relationship was satisfied when the thickness of iron oxide was less than 20 corruption.

 Molar ratio X iron oxide layer thickness (圆) = 2.3-2.5 (3)

 If the thickness of the iron oxide layer is less than 20 mm, the filling is performed so as to satisfy the above formula (3) .If the thickness of the oxidized iron layer is determined, the reduction time is determined and the operation is stabilized. However, the quality of sponge iron obtained is also stable. However, this relationship may be due to the fact that the thickness of the reducing agent layer becomes thinner, making it difficult to control the layer thickness stably, rather than to the essential relationship based on the reaction rate. It is expected that the above restrictions will be relaxed with the improvement.

 From the viewpoint of the yield of the reducing agent, it is preferable not to increase the amount of carbon and the amount of oxygen (molar ratio). If the molar ratio is less than 2.0, there is an advantage over the conventional cylindrical filling method, and it is preferably 1.8 or less. As shown in Fig. 6, when the reducing agent layer is provided on the outer peripheral portion or the axial center portion of the container, only the amount of carbon and the amount of oxygen (molar ratio) in the entire container are regulated, and the reducing agent layer is added. The present inventors thought that it was necessary to investigate whether or not the thickness ratio with the iron oxide layer was sufficient as a guide for designing. Therefore, the inventors of the present invention set the required amount of the reducing agent in the portion of the raw material deposition layer (cylindrical intermediate portion) in the reaction vessel as a ratio of the thickness of the iron oxide and the reducing agent to some tendency in the reduction behavior. We examined the power and experiment to see if it could be seen. The experiments and results are described below.

 That is, the molar ratio of the amount of carbon in the reducing agent to the amount of oxygen in the iron oxide charged in the reaction vessel was kept constant at 1.2, and the vicinity of the wall (outer periphery) and the center of the axis of the reaction vessel were An experiment was conducted in which the amount of carbon in the reducing agent was changed with respect to the amount of oxygen in the iron oxide in the portion where the reducing agent was removed, that is, the portion where both were deposited in layers.

In the experiment, the horizontal filling method was used as in the previous experiment. Fig. 10 shows a schematic cross-sectional view of the filling method used in the experiment. The reduction layer covering the upper and lower surfaces of the cylindrical intermediate portion also It shall be included in the intervening part. The raw materials and experimental conditions were the same as in the previous experiment.

 FIG. 11 shows the change in the reduction time with respect to the carbon content and the oxygen content (molar ratio) at several different iron oxide layer thicknesses. The circles (hata) in the figure are the values when the laminating method shown in Fig. 8 is used without providing the reducing agent layer on the outer periphery and the axial center.

 As shown in Fig. 11, the thickness of the iron oxide layer was 60 mm (Experimental example 11: diamond-shaped mark (decree)), 50 mm (Experimental example 12: Square mark (solid)), 30 mm (Experimental example) The reduction was carried out at four levels of 13: triangle mark and 20 mm (Example 14: X mark). As a result, the reduction time is shortened by reducing the thickness of the oxidized iron layer, and the reduction time becomes almost constant when the amount of carbon / oxygen (molar ratio) becomes 0.5 or more. It was found that the reduction time was prolonged when the ratio was less than 0.5.

 Therefore, in order to maximize the effect of setting the amount of carbon and the amount of oxygen (molar ratio) in the entire vessel to 1.2 or more, the cylindrical intermediate portion, which is the portion of the spirally packed layer (alternately filled portion), is required. It was found that it is preferable to set the amount of carbon and the amount of oxygen (molar ratio) to 0.5 or more. For confirmation, the molar ratio of the amount of carbon in the reducing agent to the amount of oxygen in the iron oxide in the cylindrical intermediate portion was kept constant at 0.8, and the reduction to be filled in the axial center portion and the outer peripheral portion of the reaction vessel was performed. An experiment was performed in which the amount of the agent was changed. The results of the experiment are shown in Fig. 12 as a graph of the change in reduction time with respect to the total amount of carbon Z and the total amount of oxygen (molar ratio) in the entire reaction vessel. The symbols used correspond to the same plate thickness as in FIG.

 As can be seen from Fig. 12, when the molar ratio of the total amount of carbon and oxygen in the reaction vessel becomes 1.2 or more, the reduction time becomes almost constant and becomes stable. It turned out to be long.

However, as described above, the effect of the present invention can be sufficiently obtained with less than 1.2 and more than 1.1, preferably more than 1.15. Summarizing the above, in the present invention, in the case of alternate layered filling (such as spiral alternating filling) of iron oxyferrate and the reducing agent into the reaction vessel 11, these raw materials are put into the reaction vessel 11. The charging ratio of the iron oxide and the reducing agent as a whole in the reaction vessel 11 including the axial center portion, the outer peripheral portion, and the cylindrical intermediate portion is the total amount of the reducing agent with respect to the oxygen amount in the iron oxide. The molar ratio of the amount of carbon is preferably 1.1 or more, more preferably 1.15 or more, and even more preferably 1.2 or more. The thickness ratio between the iron oxide and the reducing agent in the cylindrical intermediate portion in which the raw material was filled into a spiral layer is shown by the molar ratio of the amount of carbon in the reducing agent to the amount of oxygen in the iron oxide. In this case, it is preferable that the value be 0.5 or more.

〔Example〕

 (Example 1)

 In this example, each experimental level as shown in Table 1 was set, and an oxide layer and a reducing agent layer were filled in a reaction vessel 11 made of SiC by a method conforming to each of the above levels, and a crude reduction treatment was performed. Then, sponge iron was manufactured. That is, levels A to C and H in the table are examples of the cylindrical filling method shown in FIG. 1, levels D to F are examples of the spiral alternating filling method shown in FIG. 6, and level G is an example of the horizontal alternating filling method.

 Here, the 20% increase in the filling amount for levels A and D means that the total thickness of the mill scale in the reaction vessel 11 increases by 20%, and the 40% increase in the filling amount for levels B and E. Means that the total thickness of the mill scale in the reaction vessel 11 is increased by 40% in total, and the 60% improvement in the filling amount of the levels C and F means that the mill scale in the reaction vessel 11 is This means that the total layer thickness increases by a total of 60%. Table 2 shows the details of each condition. Under these conditions, each level filled was examined and the filling method, suitable layer thickness and purity were determined. In this experiment, the iron oxide, the main raw material, was prepared by drying the mill scale generated in the hot rolling process, pulverizing it, and sieving it. The obtained mill scale powder was used (the average particle size was confirmed to be between 0.05 mm and 10 mm). In addition, a mixture of limestone powder and carbonaceous powder was used as a reducing agent as an auxiliary material. The carbonaceous powder used was an anthracite with a ratio of about 7: 3, and the average particle size of coke was 85 m and the average particle size of anthracite was 2.4 mm. The limestone powder added limestone powder having an average particle size of 80 μπι to the reducing agent powder by about 14 mass%.

In addition, the reaction vessel is a cylindrical vessel with an inner diameter of 400. In the case of cylindrical filling, the iron oxide layer has an outer diameter of 320 thighs, the thickness shown in Table 2 and the height (axial direction) of about 1500 mm. Filled so that In the case of spiral filling, a reducing agent layer with a diameter of about 80 mm at the center of the shaft and a thickness of about 15 at the outer periphery is formed. Direction) about 1500 As a packed layer. The carbon content / oxygen content (molar ratio) in the container and in the cylindrical intermediate portion were 1.2 or more and 0.5 or more, respectively. table 1

Table 2

The horizontal alternating filling was performed for the purpose of confirming the filling efficiency. That is, using the same raw material charging apparatus as that used for the helical alternating charging, the rotary charging cylinder is swirled while charging only one of the iron oxide powder and the reducing agent powder, and the rotary charging is performed. After the cylinder was raised, the procedure of filling the other powder in the same manner was repeated. As shown in Table 1, continuous filling is not possible in horizontal alternating filling, and the filling time is longer than in cylindrical filling and spiral alternating filling. In the case of spiral alternating filling, the filling time can be shortened most.

 Each reaction vessel 11 filled with the raw materials based on each experimental level was loaded on the same bogie and charged into a tunnel furnace. The loaded trolley passed through the pre-tropical zone (200 ° C to 900 ° C) in about 1 day and passed through the firing zone (at 1150) in about 3 days. After that, it passed through the cooling zone (200 ° C to 900 ° C) for about one day, the bogie was discharged from the tunnel furnace, and the sponge iron was taken out of the vessel and its purity was measured. Each sponge iron weighed 200 kg or more.

The purity of sponge iron is determined by converting the metallic Fe content from the chemical components determined by oxygen analysis. I did. Figure 13 shows the results. As shown in Fig. 13, in the case of spiral alternating filling (hatching), reduction is good and the purity is 97 mass% or 98 mass% when the iron oxide layer thickness is up to 60 鹏, that is, up to 40% in productivity improvement allowance. High-purity sponge iron has been obtained, indicating that productivity can be adjusted by layer thickness up to 40% increase compared to the conventional method. On the other hand, with cylindrical packing, if the aim is to improve productivity by 20%, the layer thickness will reach 75 mm, and the purity will be 95.65 mass%, so it is impossible to improve productivity as much as spiral alternating packing.

(Example 2)

 Sponge iron was produced by the methods of Invention Examples 1 to 5 and Conventional Example 1 below. The filling method was substantially that shown in Fig. 3A, and the carbon content / oxygen content (molar ratio) was 1.2 or more.

 [Invention Example 1]

 In this example, the reaction vessel was spirally and alternately filled at an equal thickness ratio where the layer thickness of iron oxide was 50 mm and the total thickness of the reducing agent was 50 mm. The reaction vessel used was a cylindrical vessel with a height of 1.8 m and an inner diameter of 40 cm. As the reducing agent powder, a mixture of limestone of 16 mass% (average particle size of about 95 m) mixed with a coatus powder having a particle size of less than 1 bun was used. The iron oxide powder used was a mill scale pulverized to less than 0.1 thigh (which was pulverized, sieved, and adjusted so that particles passing through 60 111 mesh became about 40 mass%). The average particle size of both mill scale powder and coke powder is 0.05 mn! It was in the range of ~ 10 tons. The raw material charging device shown in Fig. 4A was used.The opening height of the iron oxide powder outlet 15 was set to 50 mm, and the opening height of the reducing agent powder outlet 16 was set to 50 mm. After adjustment, the rotating cylinder 14b was filled at a rotational speed of 4 revolutions per minute for 4 revolutions and a rising speed of 400 bpm.

 As the packing result, a 17-turn spiral alternating packed bed with an iron oxide layer thickness of 50 mm and a solid reducing agent layer of 50 mm was obtained. At this time, the charged amount of iron oxide was 339 kg.

[Invention Example 2]

In this example, the reaction vessel was spirally and alternately filled with an equal thickness ratio of iron oxide layer thickness of 35 mm and reducing agent layer thickness of 65 mm. Same reaction vessel, raw material powder and raw material as in Invention Example 1 Using a charging device, the oxidized iron and the solid reducing agent were charged. The opening height of the iron oxide powder outlet 15 is 35 hidden, the opening height of the reducing agent powder outlet 16 is adjusted to 65 thighs, and the rotation speed of the rotary charging cylinder 14 b is set to 4 The rotation and the ascending speed were filled as 400 marauders Z minutes.

 As a result, a 17-turn spiral alternating packed bed with an iron oxide layer thickness of 35 mm and a reducing agent layer thickness of 65 thighs was obtained. At this time, the filling amount of iron oxide was 237 kg.

[Invention Example 3]

 This example is an example in which the reaction container is spirally and alternately filled at an equal thickness ratio where the thickness of the iron oxide is 60 and the thickness of the reducing agent is 40. The reaction vessel, raw material powder and raw material charging apparatus used were the same as in Invention Example 1, and were charged with iron oxyacid and a reducing agent. The opening height of the iron oxide powder outlet 15 is set to 60 mm, the opening height of the reducing agent powder outlet 16 is adjusted to 40 mm, and the rotation speed of the rotary charging cylinder 14 b is increased by 4 minutes. The rotation and the ascending speed were filled at 400 o'clock.

 As a result of packing, a 17-turn spiral alternating packed bed with an iron oxide layer thickness of 60 mm and a solid reducing agent layer of 50 mm was obtained. At this time, the filling amount of the iron oxide was 406 kg.

[Invention Example 4]

 In this embodiment, the reaction vessel is spirally filled alternately at an equal thickness ratio with the layer thickness of iron oxide being 25 mm and the layer thickness of the reducing agent being 25 mm. The used reaction vessel, raw material powder and raw material charging device were the same as in Invention Example 1, and were charged with iron oxide and a reducing agent. Adjust the opening height of the iron oxide powder outlet 15 to 25 mm, adjust the opening height of the reducing agent powder outlet 16 to 25 thighs, and adjust the rotation speed of the rotary charging cylinder 14 b to 4 The rotation and ascending speed were filled at 200 strokes Z.

 As a result of filling, a 34-turn spiral alternating packed bed with a thickness of 25 layers of iron oxide layer and 25 mm of reducing agent layer was obtained. At this time, the charged amount of iron oxide was 339 kg.

[Invention Example 5]

This example shows an example in which the thickness of the iron oxide layer is 57.5 mm and the reducing agent is 50 mm in the reaction vessel. The same reaction vessel, raw material powder and raw material charging apparatus as those of Invention Example 1 were used, and were charged with iron oxide and a reducing agent. The opening height of the iron oxide powder outlet 15 is 57.5 mm, The rotating charging cylinder 14b with the opening height of the reducing agent powder outlet 16 adjusted to 50 thighs was filled at a rotation speed of 4 rotations per minute and a rising speed of 430 mm / min.

 As a result of packing, a 16-turn spiral alternating packed bed with an iron oxide layer thickness of 57.5 mm and a reducing agent layer thickness of 50 mm was obtained. At this time, the filling amount of iron oxide was 366 kg.

[Conventional example 1] 0)

 In this example, a cylindrical vessel was filled based on the conventional method shown in Fig. 1.The same reaction vessel as in Example 1 was used, and iron oxide was formed into a cylindrical shape with a thickness of 57.5 mm and an outer diameter of 310 mm φ. A powder layer was formed, and the reducing agent powder was filled around the iron oxide layer (including the inside of the cylinder). The same reaction vessel and raw material powder as those of Invention Example 1 were used. The amount of carbon in the container and the amount of oxygen (molar ratio) were about 2.2. The reduction treatment was performed using a tunnel furnace, and the time required for the reduction was examined.

 The above results are summarized in Table 3.

 Here, the time required for reduction refers to a retention time in a calcination zone (1150 ° C) for obtaining sponge iron having a purity of 95% or more. The productivity per hour is the value obtained by dividing the weight of iron oxide charged by the time required for reduction. o t

 CO

 As can be seen from the results in Table 3, in the case of the method of the present invention, a significant improvement in o0 productivity is obtained as compared with the conventional method. Table 3

 Invention example 1 Invention example 2 Invention example 3 Invention example 4 Invention example 5 Conventional example 1 Filling method Spiral alternating filling Cylindrical filling Iron oxide layer thickness

 50 35 60 25 57.5

 (mm)

 Reducing agent layer thickness

 50 65 40 25 50 50 or more (mm)

 Iron oxide weight

 339 237 406 339 366 227 (kg)

 When it falls

 62 52 78 40 74 75 (h)

 Per hour

 4.55 8.47 4.94

Productivity (kg / h) (Example 3)

 [Invention Example 6]

 Using the raw material charging device disclosed in FIG. 4A, reducing agent powder 13 (coke powder) was deposited on the bottom of the reaction vessel 11 to a thickness of 30 strokes. On top of this, the rotating charging cylinder 14 b having the iron oxide powder discharge port 15 and the reducing agent powder discharge port 16 is rotated upwards while rotating, so that the iron oxide powder having a thickness of 40 mm is obtained. 1 2 (mill case) and a reducing agent powder 13 having a thickness of 充填 were alternately and continuously filled in a spiral manner in the reaction vessel. Finally, the upper end of the reaction vessel 11 was filled with reducing agent powder (Cotas powder) 13. In this filling, the molar ratio of the amount of carbon in the reducing agent to the amount of oxygen in the oxidized iron was 1.6. The other conditions were the same as in Example 2.

[Comparative Example 1]

 Filling was performed in the same manner using the horizontal filling method shown in FIG. In this example, the filling schedule is as follows. In the raw material feeding device 14 shown in Fig. 4, the reducing agent powder (coats powder) 3 is first filled into the bottom of the reaction vessel 11 to a thickness of 50 mm. Iron oxide powder (mill scale) 12 was cut out to a thickness of 40 mm and deposited thereon, and was repeatedly filled up to the upper end of the reaction vessel 11 according to such a filling schedule. Note that the upper end of the reaction vessel 11 is filled with a reducing agent powder (copper powder) 13. In this filling, the molar ratio of the amount of carbon in the reducing agent to the amount of oxygen in the iron oxide was 1.6.

[Conventional example 2]

Filling was performed in the same manner using the cylindrical filling method shown in Figs. 1A and 1B. The conditions were the same as in Conventional Example 1 of Example 2 except that the carbon content and the oxygen content (molar ratio) were set to 2.5. Next, the refractory reaction vessel 11 filled with the raw materials was placed on a cart and passed through a tunnel furnace to heat and reduce the iron oxide. The total length of the tunnel furnace used was 100 m, of which the central 40 m area was adjusted to an ambient temperature of 1150 ° C. Table 4 summarizes the results of a sponge iron production operation with an iron ratio of 97 mas _S % under these conditions. As is clear from Table 4, in the example of the present invention, the bogie speed is 1.3 mZhr, 18% faster than the conventional example of 1. lm / hr. The amount of mill scale filled was 220 kg 16% larger than the container, 256 kgZ container. As a result, productivity increased by 38%. Along with this, the amount of heat required for heating per unit mass of sponge iron was reduced by about 30% from 11470 MJ / ton to 8820 MJ / ton. Table 4

(Example 4)

 The sponge iron was manufactured using the raw material charging device shown in Fig. 5. The raw materials used are the same as in Example 2. The cutout 14c was semicircular (sector-shaped with a central angle of about 180 °). The reaction vessel was 400 thigh in diameter and 2,000 mm in height, and the rotary charging cylinder was inserted without intentionally removing the convex part (maximum height of about 20 mm) due to the welded reaction product slag. The outer shape of the rotating charging cylinder main body was 310 mm (77.5% of the inner diameter of the container), and the diameter of the imaginary circle in the plane cross section of the cutout was 360 mm (90% of the inner diameter of the container).

Even if the tip of the rotary charging cylinder is slightly in contact with the convex part and the reaction vessel, it can be moved to the opposite side, so that it can be inserted without problems to the lowermost end of the reaction vessel, and there is no problem in inserting the raw material powder. The anti-reaction container vessel, the iron oxide powder 260kg could filled without problems (layer of iron oxide thickness: 50 strokes, reducing agent layer thickness: 30 thigh) ₀

 After the filling, reduction was performed in a tunnel furnace in the same manner as in Example 2, but there was no particular problem, and a spiral sponge iron mass having a purity of 95 mass% or more was obtained.

(Example 5)

 Inventive Examples 7 to 11, Comparative Example 2 and Conventional Example 3 were used to produce sponge iron. Figure 6 shows the filling method.

In this example, the iron oxide powder used as the main raw material was mill scale or iron ore powder. Was appropriately pulverized. Further, as the reducing agent powder, at least one kind of a single substance or a mixture of a powder of coal, a powder of charcoal, a powder of charcoal and the like was used by appropriately pulverizing and adjusting the particle size. Each has an average particle size of about 70 μπ! 9090 m.

 The equipment has a rotating charging cylinder as shown in Fig. 14.At the start of operation, first, a reducing agent powder 13 is spread on the bottom of the reaction vessel 11 and iron oxide powder 12 is reduced on top of it. The agent powder 13 is charged alternately in a spiral layer at the same time while rotating the swirl charging cylinder 14 b of the raw material charging device 14, and is alternately charged into the spiral layer. I went up. Then, the top of the reaction vessel 11 was filled with a reducing agent powder 13 and covered. In order to prevent the removal of the product (sponge iron) and the adhesion of the sponge iron to the container, and to enhance the diffusion efficiency of the reaction gas, the outer periphery of the shaft center and the vicinity of the container wall is a reducing agent. Only filled.

[Conventional example 3]

This example is the conventional filling method shown in FIG. In other words, a refractory reaction vessel 1 (inner diameter 400, length 1800 mm) contains an iron oxide layer with an outer diameter of 310 mm, an inner diameter of 200 mm, and a length of 1600 (the other parts are reducing agents) Was charged. The amount of carbon in the container and the amount of oxygen (molar ratio) were set to 2.2, and the reduction time (1150 ° C, the same applies hereinafter) with the target purity of 97.0 ma _SS % was 53 hours.

[Invention Example 7]

In this example, using the helical alternate filling method, the iron oxide has an outer diameter of 390 mm, an inner diameter of 60 mm, thickness ⁶ 0 Yuzuru spiral, the other as a similar spiral in the reducing agent layer thickness 45 mm, Both were filled at the same time. The molar ratio of the carbon content and the oxygen content of the iron oxide and the reducing agent in the cylindrical intermediate portion was 0.8, and the carbon content and the oxygen content (molar ratio) of all the filling materials were 1.2. In this example, the filling amount was first increased by 35% compared to Conventional Example 3, but the reduction time was only 60 hours. The sponge iron did not adhere to the inner surface of the container and was easily removed.

[Invention Example 8]

In this example, a spiral spiral filling method is used.The iron oxide is a spiral with an outer diameter of 365 mm, an inner diameter of 100 mm, and a layer thickness of 60 mm.The reducing agent has a layer thickness of 28 mm. Both were filled at the same time. The molar ratio of the carbon content and the oxygen content of the oxidizing iron and the reducing agent at the cylindrical intermediate portion was 0.5, and the molar ratio to the total filling was 1.2. In this example, first, the filling amount increased by 35% compared to Conventional Example 3, The payback time stopped at 59 hours. The sponge iron did not adhere to the inner surface of the container and was easily removed.

[Invention Example 9]

 In this example, the spiral alternating filling method is used.The iron oxide is a spiral with an outer diameter of 350 mm, the inner diameter is 100 mm, and the layer thickness is 60 mm. Both were filled at the same time. The carbon content of the iron oxide and the reducing agent in the intermediate portion of the cylinder, the molar amount of the Z oxygen amount was 0.3, and the molar ratio to the total charge was 1.2. In this example, first, it took 70 hours for the power reduction time, in which the filling amount was increased by 35% compared to the conventional example 1. The sponge iron did not adhere to the inner surface of the container and was easily removed. However, the reduction time was almost the same as in Conventional Method 3 even if the increase was considered.

[Invention Example 10]

 In this example, a spiral spiral filling method is used, iron oxide is a spiral with an outer diameter of 375 mm, an inner diameter of 100 mm, and a layer thickness of 60 mm. Both were charged at the same time. The molar ratio of the carbon content of the iron oxide and the reducing agent and the oxygen content of the oxygen in the cylindrical intermediate part was 0.8, and the molar ratio to the total charge was 1.5. In this example, first, the filling amount increased by 20% compared to Conventional Example 3 and stopped at a reduction time of 59 hours. The sponge iron did not adhere to the inner surface of the container and was easily removed. Inventive Example 7, in which the amount of carbon / oxygen (molar ratio) in the container is relatively low, has a higher production efficiency per reduction time, but also in this example, better results are obtained than in the prior art.

[Invention Example 11]

In this example, a spiral spiral filling method is used.The iron oxide is a spiral with an outer diameter of 395 mm, an inner diameter of 40 mm, and a layer thickness of 60 mm. Both were filled simultaneously as a spiral. The molar ratio of carbon / oxygen in the middle part of the cylinder was 0.8, the molar ratio to the total charge was 1.1, and the charge was 40% higher than in Conventional Example 3, but the reduction time was 78 hours. The sponge iron did not adhere to the inner surface of the container and was easily removed. In this example, the reduction time was slightly longer, and the reduction time was almost the same as in Conventional Method 3 even if the increased amount was considered. Table 5 summarizes the above results. Table 5

 *) Iron oxide:: Amount (relative ratio) / Reduction time (h)

Industrial potential

 As described above, according to the present invention, sponge iron can be manufactured while ensuring high productivity and quality (for example, purity of 97% or more) by employing the spiral alternating filling technique. In addition, since the raw material filling structure in the reaction vessel can be changed arbitrarily, easily and quickly, it is easy to adjust the quality “quantity” reduction time and the like, and it is possible to realize a remarkable improvement in production efficiency. Consequently, high-purity sponge iron can be produced at low cost.

Claims

The scope of the claims

1. a charging step of charging the iron oxide powder and the reducing agent powder into the reaction vessel;

 A heating step of heating from the outside of the reaction vessel to reduce the iron oxide powder in the reaction vessel to form a massive sponge iron; and

 A method for producing sponge iron having

 In the charging step, a method for producing sponge iron in which the iron oxide powder and the reducing agent powder are charged so as to be deposited alternately and in a spiral layer.

2. In the charging step, a layer made of the reducing agent powder is formed on the side surface (referred to as an outer peripheral portion) and the vertical center axis portion of the reaction container, and the remaining portion (the middle portion) excluding the layer is formed. The method for producing sponge iron according to claim 1, wherein charging is performed so as to form the alternating and spiral layers.

3. The method for producing sponge iron according to claim 1, wherein as the iron oxide powder, at least one powder selected from iron ore, mill scale, and iron oxide powder recovered from pickling waste liquid is used.

4. The method for producing sponge iron according to claim 1, wherein at least one powder selected from the group consisting of coatas, charcoal and coal is used as the reducing agent powder.

5. The method for producing sponge iron according to claim 1, wherein a carbon dioxide gas generation source is added to the reducing agent powder.

6. The method for producing sponge iron according to claim 1, wherein the heating temperature in the reduction step is from 1000 ° C to 1300 ° C.

7. The method for producing sponge iron according to claim 1, wherein, in forming the spiral layer in the charging step, the layer thicknesses of the iron oxide powder layer and the reducing agent powder layer are variably controlled.

8. In the charging step, the amount of the iron oxide powder in the reaction vessel and / or the amount of the reducing agent powder are determined by calculating the amount of carbon contained in the reducing agent powder with respect to the amount of oxygen contained in the iron oxide powder. 2. The method for producing sponge iron according to claim 1, wherein the molar ratio is controlled to be 1.1 or more.

9. In the charging step, the amount of the iron oxide powder in the reaction vessel may be determined by changing the amount of the reducing agent powder to the amount of carbon contained in the reducing agent powder with respect to the amount of oxygen contained in the iron oxide powder. 3. The method for producing sponge iron according to claim 2, wherein the amount is controlled to be 1.1 or more in a molar ratio.

10. In the charging step, the amount of the iron oxide powder in the intermediate portion or the amount of the reducing agent powder is determined by the amount of carbon contained in the reducing agent powder with respect to the amount of oxygen contained in the iron oxide powder. 10. The method for producing sponge iron according to claim 9, wherein the molar ratio is controlled to be 0.5 or more.

11. A method for producing reduced iron powder in which sponge iron produced by the method of claim 1 is pulverized, reduced, and then further pulverized.

1 2. Sponge iron, a helix-like mass.

13. The sponge iron according to claim 12, having a metallic iron content of 97 mass% or more.

14. A charging device for charging iron oxide powder and reducing agent powder into a container, wherein the insertion portion is inserted into the container, and is rotatable and vertically movable in the container;

 An iron oxide powder discharge port and a reducing agent powder discharge port rotatably provided with the insertion section at a lower end of the insertion section;

 An apparatus for charging raw materials for producing sponge iron.

15. The charging device for raw materials for producing sponge iron according to claim 14, wherein the opening areas of the iron oxide powder outlet and the reducing agent powder outlet are variable.

1 6. The insertion portion is

 A cylindrical body having a diameter of not more than 85% of the inner diameter of the container;

 A lower end portion formed of a part of a cylinder having a horizontal cross-sectional shape of a circle having a diameter of 90 to 95% of the inner diameter of the container, and

 15. The charging device for raw materials for producing sponge iron according to claim 14, wherein the horizontal cross-sectional shape of the lower end portion is a sector shape including a part of the center of the circle or a shape including the sector shape. .