JP5554478B2 - Method for producing briquettes, method for producing reduced metals, and method for separating zinc or lead - Google Patents

Description

  The present invention relates to a method for producing an agglomerate (briquette) using a dust raw material containing a metal oxide (particularly iron oxide), a method for producing a reduced metal from the obtained agglomerate, and zinc or It can be applied to a method for separating and recovering volatile metals such as lead.

  Of course, iron ore raw materials are also used as raw materials for producing reduced iron. However, due to the price increase accompanying the recent increase in demand for iron ore raw materials, dust containing iron raw materials generated in ironworks is recycled. It is attracting attention. In the ironmaking and steelmaking processes, dust containing powdered iron and iron oxide blown up in a blast furnace, converter, melting furnace, etc. is collected by a dust collector. The recovered powder (hereinafter referred to as “steel dust”) contains iron and iron oxide, and thus is used as an iron raw material. There are various types of steelmaking dust, but steelmaking dust that volatilizes once from molten steel and then solidifies in gas, and electric furnace dust (electric furnace dust) generated from electric furnaces have a very small particle size of several μm. is there.

  In a rotary hearth furnace, one of the production facilities for reduced iron, it is necessary to supply raw materials containing metal oxides and carbonaceous materials as agglomerates in order to make the reduction reaction uniform. It is necessary to have a certain strength. However, when a carbonaceous material is included, carbon burns even at a relatively low temperature, and thus a method for increasing the strength of the agglomerated material by sintering cannot be taken. For this reason, the intensity | strength of the agglomerate was raised by using expensive binders (henceforth a "binder" may be described hereafter), such as starch and molasses.

  As equipment for producing agglomerated materials, it is common to use either pellet production equipment or briquette production equipment. In both of these equipments, agglomerates having a uniform size and high strength are possible. Need to manufacture. However, it was very difficult to produce an agglomerated material of fine powder material mainly for the following two reasons. The first is that it is difficult to produce a strong agglomerated material because the fine dust raw material has a small bulk density and a large number of voids. If the strength of the briquette is low, it cannot be stored in large quantities because it may collapse due to pressure, and cracks and the like also occur during transportation. Secondly, in order to increase the strength of briquettes, a fine powder raw material is mixed with a binder, but it is difficult to uniformly mix the binder. This is because the binder has the function of an adhesive and thus has a viscosity, which prevents uniform mixing. In addition, the binder material itself is expensive, and since it has an adhesive function, it may cause clogging of the material in the production or supply process (for example, an intermediate hopper) of the agglomerated material. If the raw material is clogged, the supply of the raw material to the rotary hearth furnace or the like is interrupted or suddenly a large amount is supplied, so that the operation of the reduction furnace becomes unstable. Therefore, it is desired to reduce the amount of binder used as much as possible.

  Hereinafter, a conventionally known method for producing fine dust particles and a method for producing briquettes will be described.

  In Patent Document 1, as shown in FIG. 1 of the same Patent Document, the raw material discharged from the raw material storage tank is kneaded by a kneading apparatus, and particles containing metal oxide and carbon are used as raw materials, and pellets are produced by a bread granulator. A method of manufacturing is known. In detail, a mixing ratio is determined from a plurality of raw material storage bins, and a plurality of raw materials are cut out on a raw material conveyor. The mixing ratio of the raw material particle size, chemical composition, and water content is determined. In particular, in order to appropriately perform the reduction reaction, the ratio of metal oxide to carbon is adjusted.

Patent Document 2 describes a method for producing a solidified product from steelmaking dust as shown in FIG. As can be seen in this figure, in this system, the dust that is mainly composed of iron and its oxides produced in the steel production process is mixed with the powder that is mainly composed of carbon, and granulated into pellets. Process, a water impregnation process for impregnating the mixed granulated body with water, a solidification process for forming a briquette by putting the water-impregnated pellets into a mold and press-molding, and this briquette into a melting furnace The zinc concentration of the dust is concentrated between the process of transporting as a raw material and the solidification process after the dust is obtained from the melting furnace, and the zinc in the concentrated state is dezinced. It includes processing steps. Furthermore, in this method, the surface of the mixed granulated body is softened by impregnating with water just before molding, and the granulated body is easily deformed during briquetting molding, thereby increasing the adhesive strength between the granulated bodies. Can do.
JP 2002-206120 A JP 2007-270229 A

  In the reduction furnace, since it is necessary to perform a homogeneous reduction reaction, the agglomerate supplied to the reduction furnace needs to be uniform in size. This is because if the size of the agglomerated material varies, the reduction reaction does not become homogeneous and the quality of the reduced iron becomes very low. In FIG. 1 of Patent Document 1, the pellets are classified by a pellet sieving apparatus to maintain uniformity as required in a reduction furnace. However, the pellet sieving device not only deteriorates the pellet supply efficiency, but also has a cost demerit of the pellet sieving device itself.

  In the method of Patent Document 2, briquettes are molded. Briquettes are more uniform than pellets and can form large agglomerates. However, since a briquette compresses a raw material by compression, it usually requires a binder as described above. In the method of Patent Document 2, water is impregnated immediately before forming a briquette in order to reduce the amount of binder used as much as possible. However, it is practically difficult to uniformly impregnate water throughout the aggregate of pellets. If even a part where moisture does not adhere remains, the surface of the mixed granulated body cannot be softened at that part, so the strength of the entire briquette does not increase. In addition, after briquetting, the moisture drying time also becomes longer.

  In view of such circumstances, an object of the present invention is to produce a briquette that can increase the strength even if the amount of binder and the amount of water used are reduced as much as possible.

  The manufacturing method of the briquette of this invention which could achieve the said objective forms a primary granular material using the powder of the metal oxide containing any one or more of zinc oxide, lead oxide, and titanium oxide, and iron oxide. And a step of forming a secondary granular material by pressurizing a plurality of primary granular materials in a state containing any one or more of zinc oxide, lead oxide, and titanium oxide.

  In the briquette manufacturing method, it is recommended that the primary granular material be formed by rolling granulation, kneading granulation, or pressure molding.

  In the manufacturing method of the briquette, it is recommended to contain at least 10% by mass of any one or more of zinc oxide, lead oxide, and titanium oxide.

  In the briquette manufacturing method, it is preferable to contain a reducing agent and moisture in the primary granular material.

  In the manufacturing method of the said briquette, it is preferable to make the moisture content of a primary granule into 50 to 95% with respect to before drying by drying a primary granule before shaping | molding into a secondary granule.

  It is preferable to further add a step of drying the secondary granular material to the briquette manufacturing method.

  In the briquette manufacturing method, the volume of the primary granular material is preferably set to 1/500 or more of the inner volume of the mold for molding the secondary granular material.

  A reduced metal can be produced by reducing the briquette obtained by the above-described briquette production method.

  Zinc can be separated by adding a step of volatilizing zinc by heating and reducing a briquette obtained by the above briquette manufacturing method and containing zinc oxide.

  Lead can be separated by adding a step of volatilizing lead by heating, heating, or reduction of a briquette obtained by the above briquette manufacturing method and containing lead oxide.

  In the above-described zinc separation method, both heating and reduction are required because zinc oxide has a low saturated vapor pressure, and therefore hardly volatilizes only by heating and needs to be reduced. It is.

  In the present invention, by adding at least one of zinc oxide, lead oxide, and titanium oxide to the metal oxide, any one or more of zinc oxide, lead oxide, and titanium oxide is a raw material containing a metal oxide. Since it acts as a binder, it is not necessary to use a binder such as molasses or water before forming the briquette, and a high-strength briquette can be efficiently produced without particularly complicating the equipment.

  The inventors of the present invention have included materials used as pigments such as paints such as zinc oxide, lead oxide, and titanium oxide in metal oxide powders, so that these work as metal oxide binders. It was found that the strength of the molded briquette is improved without mixing a binder or moisture. Further, it has been found that if the content of zinc oxide or the like is appropriately adjusted, the strength is sufficiently improved without drying the briquette after molding the briquette.

  Moreover, as a granulator which manufactures a pellet, a bread-type pelletizer or a drum-type pelletizer is normally used. Whichever granulator is used, the pellets obtained have a relatively wide particle size distribution due to the granulation principle. When pellets are formed by a bread granulator as described in Patent Document 1, it is usually necessary to provide an apparatus for classifying the formed pellets into a plurality of predetermined particle size ranges. It was. However, as a result of intensive studies by the present inventors, if the pellets are further pressed to form briquettes, small pellet grains enter the gaps between the large pellet grains, and the variation in pellet diameter is rather Ascertaining that it contributes to an increase in density, the present invention has been completed.

  The briquette manufacturing method of the present invention includes (1) a step of forming a primary granular material using a powder containing at least one of zinc oxide, lead oxide and titanium oxide and a metal oxide, and (2) zinc oxide. And a step of forming a secondary granular material by pressurizing a plurality of primary granular materials while containing at least one of lead oxide and titanium oxide.

  Examples of the method for forming the primary granular material include a method by rolling granulation, a method by kneading granulation, or a method by pressure molding. Here, the primary granular material formed by rolling granulation is referred to as “pellet”. The pressure-molded secondary granular material is sometimes called “briquette”. Hereinafter, embodiments of the present invention will be described with a focus on (1) pellet forming step and (2) briquette molding step. FIG. 1 is a process diagram according to an embodiment of the present invention, and FIG. 2 is a diagram illustrating an example of equipment for performing this process.

1. Process As shown in FIG. 1, (a) one or more of metal oxide, (b) zinc oxide, lead oxide, and titanium oxide, and (c) reducing agent, (d) binder, (if necessary) E) A pellet is formed from a mixture obtained by blending water. Next, after further (f) adding moisture as necessary, a briquette is molded by pressure compression while still containing any one or more of zinc oxide, lead oxide, and titanium oxide. Further, if necessary, (3) the briquette is dried. Thereafter, (4) the reduced briquette can be obtained by supplying the obtained briquette to a reduction furnace, and (5) when the supplied briquette contains zinc and / or lead, heat reduction in the reduction furnace Thus, zinc and / or lead can be recovered from the briquette.

(A) Metal oxide Since iron oxide is contained in a metal oxide, reduced iron can be manufactured by reducing the iron oxide briquette in a reduction furnace. Steelmaking dust can be used as the iron oxide. As the steelmaking dust, various sources and forms such as dust that volatilizes once from molten steel and solidifies in gas and electric furnace (electric furnace) dust generated from an electric furnace can be used.

(B) One or more of zinc oxide, lead oxide, and titanium oxide By containing zinc oxide, lead oxide, and titanium oxide, which are also used in pigments for paints, in the metal oxide, It acts as a binder for metal oxides, and the strength of the molded briquette is improved without mixing a binder or moisture. If the strength of briquettes is improved, various effects are brought about. For example, when briquettes are reduced, since the briquettes are not easily pulverized in the reduction step, the metal oxide reduction rate (reduction metal production rate) is improved. Moreover, when recovering volatile metals such as zinc and lead contained in briquettes, the recovery rate and purity are also improved. Furthermore, since mixing and deaeration of materials are promoted during granulation of pellets, an expensive mixer having a kneading function is not required for pelletizing metal oxides.

  For the above reasons, in the present invention, at least one of zinc oxide, lead oxide, and titanium oxide is contained in the metal oxide. The steelmaking dust usually contains a metal such as zinc oxide derived from galvanized steel or the like, although the amount varies depending on the type of dust source.

  Further, if the total content of zinc oxide, lead oxide, and titanium oxide is appropriately adjusted, a more reliable binding action is exhibited. Although it is a specific adjustment method, since the concentration of zinc oxide contained varies depending on the type of dust source as described above, zinc oxide, lead oxide, titanium oxide can be mixed by mixing an appropriate amount of steelmaking dust with different dust sources. It is possible to adjust the total content of. The total content of zinc oxide, lead oxide, and titanium oxide is, for example, 10% by mass or more, more preferably 15% by mass or more, and further preferably 20% by mass or more. On the other hand, the total content of zinc oxide, lead oxide and titanium oxide is not particularly limited, but considering the range that can be used industrially, it is, for example, 60% by mass or less, more preferably 50% by mass or less.

(C) Reducing agent When the molded briquette is supplied to a mobile reduction furnace, for example, a rotary hearth furnace, to reduce the metal oxide, a reducing agent necessary for the reduction reaction is mixed in the pellet forming stage. As the reducing agent, for example, carbon-containing substances such as coal, lignite, anthracite, coke powder, steelmaking dust including carbonaceous material, plastic, and wood powder can be used. From the viewpoint of maintaining the strength of briquettes, it is generally preferred to use a reducing agent with a low volatile content. However, according to the briquette manufacturing method of the present invention, the strength of briquettes is increased. Can be used.

  In addition to the reducing agent, the method of the present invention is also effective when a preconditioner (such as lime or dolomite) necessary for the melting furnace is premixed.

(D) Binder In order to improve the strength of the pellet, an appropriate amount of a binder such as starch or molasses may be mixed if necessary.

(E) Moisture (before pelletization, during pelletization process)
In order to improve the strength of the pellet, an appropriate amount of water may be mixed as necessary. Before pelletization, at a stage in the pelletization process, water can be mixed uniformly relatively easily. There is also an effect of reducing the amount of binder used.

(F) Moisture (before briquetting)
In the present invention, since any one of zinc oxide, lead oxide, and titanium oxide serves as a binder as described above, it is basically unnecessary to add moisture before briquetting. However, when a reducing agent is mixed in the pellet, it is of course one of the embodiments that can be practiced to supplementarily add moisture depending on the amount and type of the reducing agent.

  Although drying of briquettes is not an essential requirement of the present invention, the strength of briquettes can be further increased by drying. High strength can prevent powdering due to collapse after the briquette molding process, and it can also suppress surface tackiness by drying, so a large amount of intermediate briquettes can be stored in storage such as bottles and piles. Can be stored. The drying method may be any method such as heat drying, ventilation drying, and natural drying. However, when carbon is contained in the briquette, it is important to set the temperature so that the carbon does not ignite spontaneously.

  As mentioned above, although the manufacturing method of the briquette of this invention was demonstrated, it is desirable to dry a pellet before shaping | molding into a briquette. This is because, if the surface of the pellet is dry, it is difficult to adhere to the inside of the apparatus when the pellet is supplied to the briquette manufacturing apparatus. As a drying method, forced drying or natural drying (for example, 4 hours, preferably 1 day or more) can be considered. Even if the surface of the pellet is dried, the moisture present inside the pellet is dispersed throughout the briquette, which contributes to the improvement of the briquette strength. As the degree of drying, it is desirable that the moisture content of the pellets is 50 to 95% of that before drying. The reason why it is 95% or less is to effectively obtain the effect of preventing adhesion to the briquette manufacturing apparatus, and it is more preferably 90% or less. On the other hand, 50% or more is for maintaining the briquette strength to some extent, and more preferably 70% or more. The pellet-containing water content used as an index representing the degree of drying does not measure a part such as the surface or inside of the pellet, but measures the water content of the whole pellet.

2. Facility Example Next, a facility example according to the embodiment of the present invention will be described with reference to FIG. The following facilities are merely examples, and the briquette manufacturing method of the present invention is not limited by the functions of the following facilities.

  As shown in FIG. 2, steel storage dust, a reducing agent, and a binder are stored in each of the three storages 1. Each material discharged from the storage 1 is mixed by the mixer 2 and then supplied to the bread granulator 3 which is a rolling granulator. As described in Patent Document 1, the bread granulator 3 is a rotating pan having a diameter of 2 to 6 m in the shape of a wok. The pan is tilted at about 45 degrees, and the steel-making dust and reducing agent containing water roll in this, and pellets grow while new powder material is sprinkled around the generated core. . Fully grown pellets come out of the bread under their own weight.

  The pelletized material is inserted into the briquetting device 4. In the briquetting apparatus 4, the pellet material is solidified (briquette) by being pressed and compressed by two rollers having concave portions, and sequentially discharged as briquettes.

  In addition, it is preferable that the volume of primary granular materials, such as a pellet, is 1/500 or more of the internal volume of the type | mold (usually called a "pocket") for shape | molding a briquette. If it is less than 1/500, the contact area between the briquette and the inner wall of the pocket is too large, and adhesion to the inner wall of the pocket increases. The upper limit of the briquette volume is not particularly limited, but is practically less than the inner volume of the pocket.

The pellet inserted into the briquetting apparatus 4 has the following two characteristics.
(1) In a state containing any one or more of zinc oxide, lead oxide, and titanium oxide, the pellets remain in the briquette apparatus 4 while containing any one or more of zinc oxide, lead oxide, and titanium oxide. Inserted. Therefore, the strength of the briquette produced by the binding action of zinc oxide, lead oxide, and titanium oxide is improved. Therefore, it is possible to reduce the amount of binder used. Reduction of the amount of binder used leads to prevention of material adhesion to the inner wall of the facility such as an intermediate hopper. In addition, when a reducing agent such as a carbonaceous material is blended with a metal oxide, the strength of briquettes tends to decrease, so the method of the present invention that can improve the strength due to the inclusion effect of zinc oxide or the like is particularly useful. is there.

(2) As granulated pellets As a preferred embodiment of the present invention, the granulated pellets can be inserted into the briquette apparatus 4 without being classified according to their size without being classified (pelletized). Recommended. As described above, since there are considerable variations in the particle size of the pellets, the particle size is usually made uniform using a pellet sieving apparatus. In the aggregate of pellets having a large variation in particle size in the present embodiment, small pellets enter the gaps between the large pellets, and the bulk density is large and the voids are small. By pressure-compressing (aggregating) such an aggregate of pellets, a briquette having a high bulk density and high strength can be obtained. Further, there is no need to install a pellet sieving apparatus as described above, and there is no need to provide equipment for recycling pellets that are no longer necessary for classification.

  The briquettes molded as described above are evaporated into the rotary hearth furnace 6 after the moisture is evaporated by the dryer 5 and heated on the hearth, thereby reducing metal (reduction) by the action of the reducing agent (carbon). Iron) is produced. The rotary hearth furnace 6 is heated by a burner 7. Zinc or lead vaporized by heating in the rotary hearth furnace 6 is recovered by a dust recovery device 8 (for example, one equipped with a bag filter) and recycled as a zinc raw material or a lead raw material. The remaining gas is exhausted by the exhaust fan 9. A heat exchanger 10 is provided in the middle of the exhaust path, and is effectively used as a heat source for hot air supplied to the dryer 5 and the burner 7.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, and appropriate modifications are made within a range that can be adapted to the above-described purpose. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

Example 1
As a steelmaking dust raw material, the total iron content is 22.7% by mass (hereinafter sometimes simply referred to as “%”), the zinc oxide content is 38.4% by mass, the lead oxide content is 2.1% by mass, and the titanium oxide content is 0.8%. An electric furnace dust raw material containing 1% by mass (hereinafter sometimes simply referred to as “dust raw material”) was used. The particle size distribution of this dust raw material is as shown in FIG. 3, and the peak particle size is about 4.3 μm. Moreover, the bulk density of this electric furnace dust raw material was 0.76 g / cm < ³ >. Coke powder (86% fixed carbon) was blended as a reducing agent. The amount of the dust raw material was 85.7%, and the amount of the coke powder was 14.3%.

  In the raw material mixing step before the pelletizing step, mixing was performed for 5 minutes with a twin-screw ribbon stirrer (manufactured by Chemical Engineering Co., Ltd.), and 4% water and 2% binder (molasses) were added and further mixed for 5 minutes. The stirrer container had a width of 45 cm, a length of 36 cm, and a height of 35 cm, and the rotation speed was 77 rpm.

In the pelletizing step, the mixed raw material is supplied to a pan pelletizer (manufactured by Maya Special Industrial Co., Ltd.) having a diameter of 900 mm, a rim height of 160 mm, an inclination angle of 47 °, and a rotation speed of 17 rpm. In addition, pellets were produced. As for the particle size of the pellets, 15.2% belonged to a diameter range of 3.0 to 6.0 mm, and 84.8% belonged to a diameter range of 6.0 to 9.5 mm. The bulk density of the pellets (apparent reference density: 2.44 g was / cm ³⁾ 1.39g / cm ³ and had increased than 0.76 g / cm ³ at the raw material stage. The moisture content of the pellets was 10.8% by mass. The zinc oxide content of the pellet was 32.9% by mass, the lead oxide content was 1.8% by mass, and the titanium oxide content was 0.09% by mass.

The pellets produced as described above are not classified, and, unlike Patent Document 2, without being dezinced, a briquette molding machine with a screw feeder (manufactured by Shinto Kogyo Co., Ltd., molding pressure: 160 kg / cm) ² (linear pressure about 4 t / cm), roll rotation speed: 2.5 rpm), and pressure compression to obtain a briquette.

The apparent density of the briquette produced here was 2.61 g / cm ³ . The strength of the briquette should be such that it is difficult to powder even when transported in a stored state, but the drop strength (the number of times until the briquette collapses when repeatedly dropped from a height of 45 cm) ) Showed a sufficient strength of 22 times. The crushing strength was 49 kN / P.

  When this briquette was dried at 105 ° C. all day and night, the strength further increased and the drop strength was 30 times. Note that the drop strength of 30 times is sufficient in view of the necessity of transportation and storage of briquettes, and therefore, the drop test exceeding the number of times is not performed.

  Moreover, the crushing strength of the briquettes after drying was dramatically improved to 765 kN / P. From this, it was confirmed that the strength of the briquette was improved even with the same binder amount (2%) as the binder amount used in Comparative Examples 1 to 4 described later.

(Example 2)
Pellets were produced in the same manner as in Example 1, and briquettes were obtained from the pellets. The difference from Example 1 is that in Example 1, 4% of water and 2% of binder (molasses) were mixed in the raw material mixing step before the pelletizing step, whereas in Example 2, no binder was used. , 6% water was mixed.

The particle size of the produced pellets was 23.0% in the range of 3.0 to 6.0 mm in diameter, and 77.0% in the range of 6.0 to 9.5 mm in diameter. Or because it does not use a binder in Example 2, the bulk density of the pellets (apparent reference density ^{2.48g / cm 3) 1.36g / cm} 3 , and this value is that of Example 1 (1. Compared to 39 g / cm ³ ), it was slightly lower. Nevertheless, it was sufficiently increased because it was 0.76 g / cm ³ at the dust raw material stage. The moisture content of the pellets was 11.0%, which was slightly higher than that of Example 1.

The apparent density of the briquette produced in Example 2 was 2.65 g / cm ³ . The briquette strength is required to be such that powdering is unlikely to occur even when transported in a stored state as described above, but the drop strength was 20 times. The crushing strength was 98 kN / P.

  When this briquette was dried at 105 ° C. all day and night, the strength further increased and the drop strength became 30 times. Note that the drop strength of 30 times is sufficient in view of the necessity of transportation and storage of briquettes, and therefore, the drop test exceeding the number of times is not performed.

  Further, the crushing strength of the briquettes after drying was 729 kN / P, which was dramatically improved as in Example 1. From this, it was confirmed that the strength of the briquette was improved without using a binder.

  In Example 1 and Example 2, the raw material having the particle size distribution shown in FIG. 3 was used, but the same effect can be obtained by mixing about 5% by mass of zinc oxide with iron ore having an average particle diameter of about 100 μm. It has been found that it can be obtained. Moreover, although the result when a pellet diameter is 3.0-9.5 mm was shown, since a pellet fits in a pocket favorably if it is a volume smaller than the type | mold of the pocket of a pressure molding machine, the same effect is shown. Obtained.

  Moreover, although the method to add a reducing agent at the time of pellet manufacture was described, it is not limited to this, You may press-mold after mixing a reducing agent, a binder, or both a reducing agent and a binder after pellet manufacture.

  In Examples 1 and 2, the briquette was dried by heating. However, the drying method is not limited, and air drying (forced drying) or natural drying may be used. Strength improvement was seen by making it into% or less, or by making a water content into half or less before drying.

(Example 3)
Pellets were produced in the same manner as in Example 2, and briquettes were obtained from the pellets. The difference from Example 2 is that various types of steelmaking dust as a raw material were changed.

  Table 1 shows the results of experiments similar to Example 2 using 13 types of dust raw materials.

  As can be seen from Table 1, regardless of the type of dust raw material, briquette after drying without using a binder by using a metal oxide powder containing at least one of zinc oxide, lead oxide and titanium oxide. Showed a drop strength of 6 times or more, and a strength of 3 times or more without any problem in transportation.

  Furthermore, by containing 10% by mass or more of zinc oxide, lead oxide and titanium oxide, the briquette after drying is sufficiently strengthened with a drop strength of 10 times or more, and there is a problem in transporting the briquette even before drying the briquette. Not more than 3 times strength was shown.

(Example 4)
A part of the pellet produced in Example 2 was left, and a briquette was obtained using the pellet which was naturally dried for 7 days. It was 6.7 mass% when the moisture content of the pellet was measured before briquetting. The apparent density of the manufactured briquette was 2.83 g / cm ³ . The average drop strength of the briquettes was 8 times, indicating that there was no problem in transportation. The crushing strength was 303 kN / P.

  When this briquette was dried at 105 ° C. all day and night, the strength further increased and the drop strength became 30 times. As in the case of Examples 1 to 3, the drop strength of 30 times is sufficient in view of the necessity for transportation and storage of briquettes, and therefore, the drop test exceeding the number is not performed. Moreover, the crushing strength of the briquettes after drying was dramatically improved to 1416 kN / P.

  In addition, when the inside of the briquette apparatus was confirmed after the briquette was molded, almost no material adhered to the inside of the apparatus (in Example 2, it was slightly adhered).

(Example 5)
Pellets were produced under the same conditions as in Example 2, and briquettes were obtained from the pellets. The reducing agent used is different from Example 2. As the reducing agent, coal containing 28.0% by mass of volatile matter (61.6% by mass of fixed carbon) was used. The amount of the dust raw material was 80.9% by mass, and the amount of coal was 19.1% by mass.

The particle size of the pellets was 21.4% in the range of diameter 3.0 to 6.0 mm, and 78.6% in the range of diameter 6.0 to 9.5 mm. The bulk density of the pellets increased to 1.29 g / cm ³ . The moisture content of the pellets was 12.7% by mass. The apparent density of the briquette was 2.33 g / cm ³ . The average drop strength of the briquette was 14 times, indicating that there was no problem in transportation. The crushing strength was 122 kN / P.

  When this briquette was dried at 105 ° C. all day and night, the strength further increased and the drop strength averaged 19 times. Moreover, the crushing strength of the briquettes after drying was dramatically improved to 1031 kN / P. Therefore, it was found that the briquette strength was sufficiently improved even when coal with a large amount of volatile matter was used.

(Example 6)
Pellets were produced under the same conditions as in Example 2, and briquettes were obtained from the pellets. The reducing agent used is different from Example 2. As the reducing agent, coal containing 43.6% by mass of volatile matter (fixed carbon 51.9% by mass) was used. The amount of the dust raw material was 78.1% by mass, and the amount of coal was 21.9% by mass.

The particle size of the pellets was 31.6% in the range of 3.0 to 6.0 mm in diameter, and 68.4% in the range of 6.0 to 9.5 mm in diameter. The bulk density of the pellets increased to 1.28 g / cm ³ . The moisture content of the pellets was 12.1% by mass. The apparent density of this briquette was 2.17 g / cm ³ . The average drop strength of the briquettes was four times, indicating that there was no problem in transportation. The crushing strength was 113 kN / P.

  When this briquette was dried at 105 ° C. all day and night, the strength further increased and the drop strength averaged 15 times. Moreover, the crushing strength of the briquettes after drying was dramatically improved to 575 kN / P. Therefore, also from this example, it was found that the briquette strength was sufficiently improved even when coal with a large amount of volatile matter was used.

(Example 7)
In Examples 1 to 6, the dust material was first pelletized and then briquetted, but in this reference example, briquetting was performed instead of pelletizing. That is, the briquette was directly molded from a mixture of the dust raw material, the reducing agent, and the binder by applying pressure molding twice. As a result, the apparent density of the briquette was 2.3 g / cm ³ on average, and the drop strength could be achieved 30 times before and after the briquette was dried. In this example, 12% by mass of molasses was contained as a binder.

(Comparative Example 1)

  The test which shape | molds a briquette using 13 types of dust raw materials shown in Example 3 was done. However, in the test of Comparative Example 1, briquettes were directly molded from the dust raw material without forming pellets from the dust raw material. The same conditions as in Example 3 were applied except that the pelletizing step was omitted. As a result, the briquette shape was formed once in all dust raw materials, but it was very brittle, and even physical properties tests such as drop strength could not be performed as shown in Table 2.

(Comparative Example 2)
As Comparative Example 2, the same test as Comparative Example 1 was performed. That is, briquettes were directly molded from dust raw materials without forming pellets from the dust raw materials. The difference from Comparative Example 1 is that 2% binder (molasses) was used as in Example 1. In Comparative Example 2, the bulk density of the dust raw material mixed with the reducing agent and the binder was slightly increased to 0.80 g / cm ³ , but this mixture was used as a briquette molding machine with a screw feeder (Examples 1 to 6, Comparative Examples). As a result, the briquette was once molded, but it was very brittle and could not even be tested for physical properties such as drop strength.

(Comparative Example 3)
As Comparative Example 3, a test with the same composition as Comparative Example 2 was performed. Differences from Comparative Example 2 are as follows. In Comparative Example 2, the mixing of the raw material dust, reducing agent, binder, etc. may be insufficient, and the mixing time after adding 4% water and 2% binder (molasses) is extended to 30 minutes. did. The bulk density of the raw material after the mixing was 0.81 g / cm ³ , which was slightly increased as compared with the case of Comparative Example 2. This mixture was supplied to a briquette molding machine with a screw feeder (the same conditions as in Examples 1 to 6 and Comparative Examples 1 and 2) without passing through the pellets as in Comparative Example 2. The result was the same as that of Comparative Example 2, and the briquette was once molded but very brittle and could not even be tested for physical properties such as drop strength. Therefore, increasing the mixing time did not lead to a significant improvement in strength.

(Comparative Example 4)
As Comparative Example 4, a test with the same composition as Comparative Example 2 was performed. However, a twin-screw type ribbon stirrer (mixer used in Examples 1 to 3 and Comparative Examples 1 to 3) was changed, and a mixed muller mixer (container size: diameter 254 mm × width 73 mm, compressive load) with higher kneading ability. : 181 to 275 N, spring load system, rotation speed: 44 rpm). The procedure for blending and mixing the raw material dust is the same as in Comparative Example 2.

That is, 85.7% of fine dust raw material and 14.3% of coke powder were mixed for 5 minutes with a biaxial ribbon stirrer, 4% of water and 2% of binder (molasses) were added and further mixed for 5 minutes. The bulk density of the dust raw material after the mixing was slightly increased to 1.01 g / cm ³ . This mixture was further mixed for 15 minutes in a mix muller mixer. And it supplied to the briquette molding machine with the screw feeder (same conditions as Example 1) without going through the pellet. The results were the same as those of Comparative Examples 2 and 3, and the briquette was molded once, but it was very brittle and could not even be tested for physical properties such as drop strength. Therefore, even if a mix muller mixer having a high kneading capacity was used, the strength was not significantly improved.

It is a process figure concerning an embodiment of the invention. It is a figure which shows the example of an installation for implementing the process. It is a graph which shows the particle size distribution of the electric furnace dust used in the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Storage 2 Mixer 3 Bread granulator 4 Briquette apparatus 5 Dryer 6 Rotary hearth furnace 7 Burner 8 Dust collection apparatus 9 Exhaust fan 10 Heat exchanger

Claims (9)

Forming a primary particulate using a powder of a metal oxide containing at least one of zinc oxide, lead oxide, and titanium oxide, and iron oxide;
The zinc oxide, lead oxide, in a state of containing any one or more of titanium oxide, see contains a step of molding the secondary granules by pressurizing a plurality of primary granules,
A method for producing briquettes containing at least 10% by mass of any one or more of zinc oxide, lead oxide and titanium oxide .   The method for producing briquettes according to claim 1, wherein the primary granular material is formed by rolling granulation, kneading granulation, or pressure molding. The manufacturing method of the briquette of Claim 1 or 2 which makes a reducing agent and a water | moisture content contain in the said primary granular material. The briquette manufacturing method according to claim 3 , wherein the primary granule is dried before being formed into the secondary granule, so that the water content of the primary granule is 50 to 95 mass% with respect to that before drying. Method. The manufacturing method of the briquette of Claim 3 or 4 which has the process of drying the said secondary granular material. The manufacturing method of the briquette in any one of Claims 1-5 whose volume of the said primary granular material is 1/500 or more of the internal volume of the type | mold for shape | molding the said secondary granular material. The manufacturing method of a reduced metal including the process of reduce | restoring the briquette manufactured by the method as described in any one of Claims 1-6 . A method for separating zinc, comprising a step of volatilizing zinc by heating and reduction of a briquette produced by the method according to any one of claims 1 to 6 and containing zinc oxide. A method for separating lead, comprising a step of volatilizing lead by heating, heating, or reduction of a briquette manufactured by the method according to any one of claims 1 to 6 .