JP2011111662A - Method for producing molded raw material for producing reduced iron - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for advantageously producing a molded raw material with a proper water content required for molding and firing without requiring the construction of new equipment and complicated operational control. <P>SOLUTION: In the method for obtaining a molded raw material for producing reduced iron, when water and a binder are added to an iron-containing raw material, they are stirred and mixed by a mixer, and the mixed raw material is molded to produce a molded raw material for producing reduced iron, the water content in the mixed raw material prior to the molding is adjusted to 6±0.5 mass%, and, after that, the molding by a molding machine is performed to adjust the water content to 5±0.5 mass%. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a molding raw material for producing reduced iron, and in particular, a method for pre-treating a molded product (molding raw material) of an iron-containing raw material made of iron-making dust or the like, which is charged into a rotary hearth type reduction furnace or the like. In particular, the method is characterized by a method for adjusting the moisture content of the forming raw material.

  In recent years, iron resources have been depleted, and reduced iron produced by effectively using iron production by-products has attracted attention. The reduced iron is obtained by reducing powdered iron-containing raw materials that are iron by-products such as blast furnace dust and converter dust by, for example, a rotary hearth type reduction furnace (hereinafter simply referred to as “rotary hearth furnace”). It is manufactured.

  The powdered iron-containing raw material used as the main raw material in the operation of the rotary hearth furnace is likely to be scattered in the transportation process if handled as it is in powder form, causing loss and environmental problems. However, there was a problem that was exhausted with the exhaust gas. Therefore, conventionally, such a powdery iron-containing raw material is briquetted with a molding machine in advance or pelletized with a granulator before being charged into a rotary hearth furnace. In general, it is generally charged into a rotary hearth furnace.

  For the conventional forming raw materials, the strength when pellets or briquettes may be insufficient, and it is easy to crack and pulverize in the transportation process, so it may not be charged into the rotary hearth furnace as it is. there were. In addition, since such a molding material (agglomerated material) has a large amount of adhering moisture and the moisture may explode due to rapid evaporation in a high-temperature furnace, the molding material is once dried and then loaded. It was common to enter (see Patent Documents 1, 2, 3, 4, and 5).

  In the operation of an electric furnace or converter, the mixed raw material may be directly fed without being dried, but in this case, a problem that heavy metals such as Zn remain in the molten steel occurs.

JP 2002-167624 A JP 2005-272895 A JP-A-2005-97665 JP 2001-234256 A Japanese Patent Laid-Open No. 11-12624

  By the way, the molding raw material charged in the rotary hearth furnace is generally agglomerated into briquettes and pellets by humidifying and kneading the powdered iron-containing raw material, and then heating the agglomerate. What is dried and adjusted in moisture by the apparatus is charged into the furnace. (Exemplified in Patent Documents 1 and 2). However, in this method, it is necessary to newly provide a drying facility, and there are problems such as an increase in facility cost and an increase in dry fuel cost. Moreover, it replaces with the drying after agglomeration, and the method of drying to the moisture content of 3 mass% or less is also proposed by adding dry powder in the step before a shaping | molding process (refer patent document 3). ) Had the same problem as above.

  Furthermore, a powdered iron-containing raw material is made into a slurry form, and this is stirred and mixed. After that, a method of dehydrating so that the water content is 15 to 30 mass% and then forming (see Patent Document 4) or a high-speed stirring mixer is used. There are also proposals such as a method of forming after processing (see Patent Document 5), but all of them require slurry processing equipment, dehydration equipment, or special agitators, which increases equipment costs and complicated operation control. There was a problem that it was necessary.

  Therefore, an object of the present invention is to propose a technique for producing a molding raw material that provides appropriate moisture both at the time of molding and at the time of firing without requiring the construction of new equipment and complicated operation control. It is in.

  The inventors first studied a method capable of overcoming the above-described problems of the prior art, and as a result, found that it can be solved by adopting the following means, and the present invention. It came to develop. That is, the present invention manufactures a forming raw material for reduced iron production by adding at least water and a binder to a powdered iron-containing raw material which is a main raw material, stirring and mixing in a mixer, and forming the mixed raw material. In doing so, the moisture content of the mixed raw material prior to molding is adjusted to 6 ± 0.5 mass%, and then the moisture content after molding by a molding machine is adjusted to 5 ± 0.5 mass%. It is a manufacturing method of the shaping | molding raw material for reduced iron manufacture.

In the present invention,
(1) The moisture content of the mixed raw material is adjusted by drying or dehumidifying by adjusting the addition amount of wet powder or the addition amount of dry powder in addition to the addition of moisture to the mixer,
(2) The wet powder is any one of iron-making wet dust, mill scale powder, and sludge containing iron such as blast furnace dust, converter dust, and electric furnace dust that have been wet collected.
(3) The dry powder is dry powder recovered iron-making dry dust containing iron, such as blast furnace dust and converter dust, and sieving powder such as return to a sintered factory,
(4) For the moisture content of the mixed raw materials, install a moisture meter on the inlet and outlet sides of the mixer, feed back the measured moisture value to the inlet moisture meter, By adjusting the cutout amount,
Is a more preferable solution.

According to the manufacturing method of the forming raw material according to the present invention configured as described above, the drying equipment after forming the powdered iron-containing raw material is not necessary, and the burden of equipment investment cost can be reduced.
Moreover, according to the present invention, not only the moisture content suitable for molding can be adjusted, but also the moisture of the molded product (molding raw material) after molding is charged into a high-temperature rotary hearth furnace and heated. Since it can be adjusted to an appropriate moisture concentration that does not explode, product yield and metallization rate can be improved.
Furthermore, according to the present invention, by adjusting the blending of dry powder and wet dust, the water content is adjusted to a low water content by adding a relatively small amount of water, so an economical and environmentally friendly technique can be proposed. it can.

It is a basic diagram which shows an example of the shaping | molding raw material manufacturing process which concerns on this invention. 3 is a graph showing changes in mixed powder moisture during adjustment of water content in Example 1. FIG. It is a graph which shows the change of the mixed-powder water | moisture content at the time of the amount of water adjustment in another Example. It is a graph which shows the change of the mixed-powder water | moisture content at the time of the amount of water adjustment in another Example. 6 is a graph showing changes in mixed powder moisture when adjusting the amount of water added in Example 2. FIG. It is a graph which shows the influence on the briquette water | moisture content after yield adjustment in Example 1, a yield, drop strength, and a powder rate.

FIG. 1 is a process diagram showing an example in which a forming raw material manufactured by applying the present invention is charged into a rotary hearth furnace 1. As shown in this process drawing, in the method for producing a forming raw material of the present invention, from one to plural kinds of iron-containing raw material powder hoppers 2a, 2b, limestone powder hopper 2c, and binder hopper 3, The raw material powder is cut out on the cutting conveyor 4 so as to have a required composition, and then these raw material powders are charged into one or two mixers 5 and 6 and stirred and mixed. After passing through the mixed raw material hopper 7, it is formed into a required shape of, for example, 33 mm long × 23 mm wide × 13-15 mm thick (6-7 cm ³ ) by a molding machine 8, and then, for example, 15 mm or more sieve mesh Through the screen 9, a molded product (molding raw material) having a particle size of about 20 to 40 mm is obtained. The molding raw material thus adjusted and adjusted to a required size is charged into the rotary hearth furnace 1 via the charging conveyor 10.

  In the above equipment configuration, on the conveyor 4, an initial moisture measuring device 11 for measuring the initial (before mixing) moisture of the cut out various raw material powders is disposed, and the after the mixing step The mixture hopper 7 is provided with a post-treatment moisture measuring device 12 for measuring the moisture content of the mixture, and a moisture adding device 13 is provided in the mixer, preferably the mixer 6 in the subsequent stage.

  Hereinafter, using the above-mentioned equipment, moisture adjustment according to the method of the present invention, that is, adjusting the moisture content of the mixed raw material to a preferable amount of moisture to form (granulate), and for the molded product (molding raw material) after molding, A method for producing a desired raw material for producing reduced iron by controlling the amount of moisture so as to be stably melted and reduced without explosion in a high temperature furnace will be described.

(1) Method by adding water This method is preferable for forming by adding an appropriate amount of water to the mixed raw material with a water adding device 13 such as a spray nozzle disposed in the subsequent mixer 6. The amount is adjusted to 6 ± 0.5 mass%, and is realized by feedback-controlling the measured value of the moisture measuring device 11 on the cutting conveyor 4.
(2) Method by blending dry powder and wet powder Similar to the above method, by performing feedback control using the moisture measuring device 11 on the cutting conveyor 4, the moisture content of the mixed raw material in the mixer 6 at the subsequent stage is 6 ±. Dry powder such as dry dust removal from the blast furnace, under-sieving powder (returning, etc.) generated at the sintering plant, or wet-recovered blast furnace dust, converter dust, electric dust, or mill scale to 0.5 mass% This is a method of mixing and adjusting wet powder such as powder and sludge by adding predetermined amounts to each other. Specifically, by adding an auxiliary material added to the iron-containing raw material powder, such as iron dust, for the purpose of adjusting the component consisting of the dry / wet powder, together with a binder such as lime or starch, desired moisture The amount is set to 6 ± 0.5 maa%.
(3) Combined use of addition of moisture and addition of component adjustment aid By adjusting by both the method (1) and the method (2) described above, the most suitable moisture content (6 ± 0. 5 maa%).

  In the present invention, the reason for adjusting the moisture content of the mixed raw material powder before molding to 6 ± 0.5 mass% is that, as described above, appropriate moisture is required for molding, and if it is 5.5 mass% or more, This is because the compaction function in the molding machine functions sufficiently to allow molding. On the other hand, if it exceeds 6.5 mass%, not only explosion may occur during firing in a high-temperature furnace or the like, but also powder adheres to the inner wall of the molding machine, and the production efficiency decreases. Preferably, the water content is set to 5.5 mass% to 6.0 mass%.

  Next, the mixed raw material powder whose moisture has been adjusted as described above is sent to the molding process in the molding machine 8, but due to the heat generated during the molding process, the moisture content of the molding raw material is exactly 5 ± 0.5 mass. As a result, it will be adjusted to about%. As a result, the forming raw material can be charged as it is into the rotary hearth furnace 1 without going through a drying step, and even in this case, the required strength is ensured, so that the material is exploded in the furnace. Such a thing disappears.

(1) In this embodiment, the equipment shown in FIG. 1 is used to measure the water content attached to the mixed raw material hopper 7 on the outlet side of the mixer 6 by a method of adding a predetermined amount of water from the water adder 13. The water content of the mixed powder was measured with the vessel 12, and the appearance when the forming raw material (briquette) was produced with the roll forming machine 8 was visually observed.

The results are shown in FIG. 2, FIG. 3, and FIG.
a. In the example shown in FIG. 2, blast furnace dry dust (BDC): returning (sintered powder): starch was blended at a ratio of 89: 11: 2.5, respectively, and operated at a water content of 3.5 to 4.0 mass%. As an example, the briquette in which the water content of the mixed powder was less than 4.5 mass% was low in strength and resulted in a high ratio of −15 mm powder at the conveyor 10 outlet.
b. The example of FIG. 3 is a case where the amount of water is increased to 4.0 to 4.5 mass% in the blend of BDC: returning: 90: 10: 2.5, but the mixed powder moisture is 6.5 mass%. The powder adhered to the forming roll and caused roll clogging.
c. In the example of FIG. 4, in the blend of BDC: returning: limestone: starch = 81: 14: 5: 2.5, when the water content is 4.0 mass% at the maximum, the mixed powder moisture becomes 7.0 mass%. The adhesion of powder to the roll surface was observed. On the other hand, when the moisture content of the mixed raw material powder aimed at by the present invention was adjusted to a moisture content of 6.5 ± 0.5 ma%, no adhesion of the powder to the roll surface occurred and it was confirmed that the present invention was effective.

(2) In this example, the binder (starch) is constant (2.5), and the ratio of BDC (74-89) and return mineral (11-26) is largely changed, while the amount of water added is slightly The water content was adjusted by a method in which the ratio of the wet powder (BDC) and the dry powder (returning) was adjusted while suppressing the fluctuation of the above.

  The result is shown in FIG. As can be seen from FIG. 5, when the mixing ratio of the raw materials was changed (A) and the mixed powder moisture was greatly changed, the moisture content decreased by 5.0 mass%, and the briquette strength was lowered. I needed it. On the other hand, when the amount of return ore is suppressed (B, C), the mixed powder moisture becomes high without increasing the amount of water added too much, and when it exceeds 6.5 mass%, powder roll adhesion becomes conspicuous. It was.

Next, FIG. 6 shows the measurement of the moisture content of the molding raw material (briquette) after the above-mentioned AC raw materials are molded by the roll molding machine 8, and the moisture content is 5.5 ± 0. For those in the range of 0.5 mass%, the molding yield and drop strength are high, while the powder ratio (-15 mm ratio at the conveyor 10 outlet) is low. A forming raw material that can be charged into the rotary hearth furnace as the raw material can be obtained.
The briquette drop strength is a ratio of +15 mm after dropping the briquette three times on the iron plate from a height of 50 cm for 30 briquettes.

  The technology of the present invention is not only effective as a method for producing a forming raw material for charging into a rotary hearth furnace, but also, for example, as a technology for producing a forming raw material for a sintering machine or a raw material for forming another reducing furnace. Useful.

DESCRIPTION OF SYMBOLS 1 Rotary hearth furnace 2 Raw material hopper 3 Binder hopper 4 Cutting conveyor 5, 6 Mixer 7 Mixed raw material hopper 8 Forming machine 9 Screen 10 Loading conveyor 11, 12 Moisture measuring device 13 Water adding device

Claims (3)

In producing the reduced iron production molding raw material by adding at least water and a binder to the powdery iron-containing raw material which is the main raw material, stirring and mixing in a mixer, and molding the mixed raw material,
For reducing iron production, characterized in that the moisture content of the mixed raw material prior to molding is adjusted to 6 ± 0.5 mass%, and thereafter the moisture content after molding by a molding machine is adjusted to 5 ± 0.5 mass%. Manufacturing method of molding raw material. The moisture content of the mixed raw material is adjusted by drying or dehumidifying by adjusting the addition amount of wet powder or the addition amount of dry powder in addition to the addition of moisture to the mixer. The manufacturing method of the shaping | molding raw material for reduced iron manufacture of description. For the moisture content of the mixed raw material, install a moisture meter on the inlet and outlet sides of the mixer, feed back the measured moisture value on the inlet side to the inlet moisture meter, and determine the amount of humidification or dry powder and moisture powder cut-out. It adjusts by adjusting, The manufacturing method of the shaping | molding raw material for reduced iron manufacture of Claim 1 or 2 characterized by the above-mentioned.

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