JP2005179771A - Agglomeration method of steel sludge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily agglomerate steel sludge, particularly an agglomeration method that can be uniformly mixed, has no uneven quality of agglomerates, and has a low agglomeration treatment cost and good yield. suggest.
SOLUTION: In mixing and agglomerating steelmaking dust with slurry-like ironmaking sludge generated in an ironmaking process, the amount of metallic iron in the steelmaking dust is 25 masses with respect to 100 mass parts of dry mass of the ironmaking sludge. A method for agglomerating slurry-like iron sludge, comprising mixing slurry-like iron-making sludge and steel-making dust so as to be a part or more to obtain a mixture, and drying and solidifying the mixture after dehydration.
[Selection] Figure 4

Description

  The present invention relates to a method for agglomerating iron sludge, and in particular, a slurried iron sludge such as pickling sludge and neutralized sludge containing metal hydroxide or metal oxide, such as a shaft furnace, a converter, an electric furnace, etc. The present invention relates to an agglomeration method for reuse as a steelmaking raw material.

  In a so-called iron making process for manufacturing steel, for example, a pickling process on the surface of a steel material, a waste liquid in which a large amount of metal is dissolved is generated. The waste liquid containing the metal component is then neutralized. At this time, the dissolved metal component is precipitated and iron-making sludge such as pickling sludge and neutralized sludge is generated. Although the metal content contained in such steelmaking sludge varies depending on the type of steel material to be treated, it is mainly iron (Fe), and in addition, useful metals such as Ni and Cr are included. Therefore, it is very significant if the metal content contained in the slurried iron sludge can be recovered and reused as a raw material for a converter. For this purpose, it is necessary to add a binder or the like to such steelmaking sludge to form briquettes or pellets and agglomerate them.

  However, the metal content in these steel sludges is mainly in the form of hydroxides, and is fine and highly hydrophilic, so even if it is subjected to dehydration treatment such as filter press, it still contains a lot of moisture. Since it is of a quality, it is extremely difficult to handle. Moreover, since this sludge is difficult to dry naturally, it is necessary to dry it using a dedicated dryer such as a rotary kiln, resulting in an increase in processing costs.

  For example, as a technique for effectively using the above-described iron-making sludge, dewatered iron-making sludge and dried, add dust and scale generated in other iron-making processes, add a binder to this, solidify, Methods used for ferroalloy production raw materials and the like are known (see, for example, Patent Document 1 and Patent Document 2). However, these methods are a method in which iron sludge is first dried using a special dryer such as a rotary kiln, and then dried dust or binder is added to form briquettes or pellets. There is a problem that the cost of auxiliary materials such as binder is high.

On the other hand, Patent Document 3 discloses a method of mixing and agglomerating steel-making sludge and steel-making dust containing metallic iron. This method agglomerates iron-making sludge using the oxidation exothermic reaction of metallic iron, which eliminates the need for agglomeration equipment such as briquette machines and pelletizers, greatly increasing the agglomeration cost. There is an advantage that it can be reduced. This method is also an excellent technique in that steelmaking dust, which is a byproduct of the iron making process, can be reused. However, in this agglomeration method, it is difficult to mix uniformly because iron sludge and steelmaking dust are stacked on the yard and mixed with a power shovel or the like. For this reason, the quality of the agglomerated material may vary in quality, such as strength or particle size, or the powder may remain in powder form without being agglomerated, and the ratio to be re-agglomerated may increase. There is a point.
JP-A-52-88519 JP-A-52-88520 JP 2001-316731 A

As described above, conventional steel sludge agglomeration techniques have problems in processing costs and quality of agglomerated products, and solutions to such problems have been demanded.
Therefore, in view of such circumstances, an object of the present invention is a method for easily agglomerating iron sludge, and in particular, the quality of the agglomerated material can be uniformly mixed and the agglomeration processing cost is low. The aim is to propose an agglomeration method with good yield.

  As a result of diligent research aimed at solving the above-described problems of the prior art, the inventors have found that the steelmaking sludge is mixed and agglomerated by mixing the steelmaking dust with the slurry-like steelmaking sludge generated in the ironmaking process. To the dry mass of 100 parts by mass, the amount of metallic iron in the steelmaking dust is 25 parts by mass or more so that the slurry-like iron sludge and the steelmaking dust are mixed to form a mixture, and the mixture is dried after dehydration, We have developed a method for agglomerating slurry iron sludge characterized by solidification.

  In the agglomeration method of the present invention, the steelmaking dust contains 20 mass% or more of metallic iron in terms of dry mass, contains 90 mass% or more of particles having a particle size of 1 mm or less, and is mixed with ironmaking sludge. The steelmaking dust used in this process is characterized by mixing the slurry-like dust as it is with the slurry-like iron-making sludge.

  Further, in the agglomeration method of the present invention, when the dehydrated mixture is dried and solidified, the mixture is left in a piled state or in a flat state at a certain height and left standing for a certain period, preferably After a certain period of time from the start of drying, mechanically coarsely crushed and agitated so that the surface layer part and the inner layer part are interchanged, and then, after a certain period of time, this crushed and adjusted to the desired particle size And

  In the present invention, steelmaking sludge generated in the ironmaking process is dehydrated, and then dried, solidified and agglomerated. Before the dewatering process, the steelmaking dust containing metallic iron is preferably contained in the slurry-like ironmaking sludge. Is characterized in that it is mixed as a slurry-like steelmaking dust in a fluidized state and dehydrated after the mixing step. When treated in such a process, the steel sludge and steel dust are uniformly mixed, and the dried and solidified material is also homogenized, so there is no unevenness in the strength of the agglomerated material and, in turn, the product yield can be improved. Moreover, in the method of the present invention, steelmaking dust generated in a slurry state can be used as it is, so that not only homogenization of the agglomerated material but also the processing process is simplified, and the by-product generated in the ironmaking process is reduced. Since recycling becomes easy, it contributes to reduction of manufacturing cost.

  In the present invention, steelmaking dust containing metallic iron is mixed with slurry-like steelmaking sludge. The reason for this is that the particle size of general steelmaking dust containing metallic iron is several tens of microns, which is about 10 times the particle size of ironmaking sludge. This is because iron sludge mixed with metal iron-containing steel dust having a large particle size is easier to dewater than small iron sludge alone.

  Further, the amount of steelmaking dust added to the slurry ironmaking sludge must be added so that the amount of metallic iron in the steelmaking dust is 25 parts by mass or more with respect to 100 parts by mass of the dry mass of the slurry ironmaking sludge. . This is because, in the present invention, it is assumed that the agglomerate obtained from the mixture of the steelmaking sludge and the steelmaking dust is reused as a raw material for ironmaking. It must be strong enough not to be pulverized by handling such as loading and unloading. The strength of such agglomerates is that the metallic iron contained in the steelmaking dust is oxidized during the drying process after dehydration, and the parts other than the metallic iron in the steelmaking sludge and steelmaking dust are consolidated by the oxidation exothermic reaction at that time. (Solidified). Therefore, when the amount of metallic iron is relatively small, sufficient caking force cannot be obtained, and the strength of the agglomerated material is lowered.

  Inventors investigated the relationship between the crushing strength of the agglomerated material described later and the pulverization rate when transported by a truck or the like in order to grasp the strength necessary for the agglomerated material, as shown in FIG. The result was obtained. From this result, if the crushing strength is 2.5 MPa or more, the pulverization rate is constant at about 5%, and if the crushing strength is 2.5 MPa or more, it is used as a steelmaking raw material in a converter or shaft furnace. However, it was confirmed that problems such as an increase in generated powder did not occur. And in order to make the crushing strength of the agglomerate obtained from the mixture of steelmaking sludge and steelmaking dust 2.5 MPa or more, the amount of metallic iron in the steelmaking dust is 100 parts by mass of the dry mass of the slurry-like steelmaking sludge. The present inventors have found that it is necessary to add steelmaking dust so that the amount is 25 parts by mass or more.

  As the iron-making sludge generated in the iron-making process, it is necessary to use the iron-making sludge in a slurry state before passing through the dewatering process. The reason is that in order to obtain an agglomerated material having a high strength and a uniform component, it is indispensable to uniformly mix iron-making sludge generated in an iron-making factory and steel-making dust containing metallic iron. However, when steelmaking sludge is dehydrated before mixing, it becomes a clay state, and even if steelmaking dust containing metallic iron is added to the steelmaking sludge in such a clay state, it is difficult to mix them uniformly. . That is, in order to solve this problem, it is necessary to add steelmaking dust containing metallic iron to ironmaking sludge in a slurry state before dehydration.

  The steelmaking dust to be mixed with the ironmaking sludge preferably has a metallic iron content of 20 mass% or more in terms of dry mass and 90 mass% or more of particles having a particle size of 1 mm or less. By using steelmaking dust under such conditions as a raw material, an agglomerate having a particle diameter of 20 mm to 50 mm that can be easily used as an ironmaking raw material can be produced with high yield.

  Such steelmaking dust is preferably used in a slurry state. The reason is that, in the same way as in the case of steelmaking sludge, it is preferable to be in a slurry state for uniform mixing, and steelmaking dust is often collected in a wet manner, so that the slurry form is easier to obtain. It depends on things. Further, since the slurry-like steelmaking dust is alkaline, it is advantageous in that the amount of alkali added necessary for neutralization of acidic ironmaking sludge can be reduced.

  The mixing method of iron-making sludge and steel-making dust is not particularly limited, and can be performed by putting each in a tank and stirring. Moreover, since the mixture of iron-making sludge and steel-making dust is in a slurry state, it is necessary to perform a dehydration treatment as a pretreatment for drying and solidifying to agglomerate. Although the method of this dehydration process is not specifically limited, For example, a filter press method etc. can be used suitably.

  The mixture of steelmaking sludge and steelmaking dust is dehydrated and then dried and solidified. Drying and solidification can be done by using a power shovel or the like in a steel factory yard, etc., or piled up in a pile, or 30-70 cm in height and 7-10 m in length and width. It is preferable to carry out in a stacked state. However, when the mixture is dried and solidified, especially when it is dried and solidified in a piled state, the frequency with which the mixture comes into contact with air (oxygen) is greatly different between the surface layer portion and the inner layer portion. Differences may occur in the degree of progress of the oxidation reaction, and as a result, the quality of the agglomerates may vary.

  In order to solve this problem, after a certain period of time has passed since the start of drying and solidification (for example, after about two weeks), the initial stacking state is once destroyed using a power shovel, etc. It is preferable that the mixture of the inner layer portion is roughly crushed and agitated, and then is returned to the original state again, and further dried and solidified for a certain period (for example, about one week). By carrying out this stirring treatment, the agglomeration in the surface layer portion and the inner layer portion proceeds uniformly, and the period required for drying and solidification can be greatly shortened. If the drying and solidification period is too long, weathering of the surface of the agglomerated material starts, so it is preferable to use it as a raw material for ironmaking immediately after drying and solidification, preferably within 5 weeks from the start of drying and solidification. It is preferable to use it.

  In addition, even if it performs drying and solidification in any state of a pile or a flat, if the said stirring process is performed appropriately, the intensity | strength of the obtained agglomerate will become substantially the same. However, the pulverization rate due to handling or the like when used as a steelmaking raw material is advantageous because flat stacking in which drying and solidification proceed relatively uniformly tends to be slightly lower. However, in the case of flat stacking, leveling work with a power shovel or the like is required, and a larger site is required compared to pile stacking. Therefore, when processing steelmaking sludge in a process, it is necessary to select whether to pile up or to pile up in consideration of the yard condition and work load.

  A dry powder of metal iron-containing steelmaking dust having the component composition shown in Table 2 was added to the slurry-like iron sludge having the component composition shown in Table 1 generated in a stainless rolling mill to obtain a 20 kg mixture. Under the present circumstances, the addition amount of the steelmaking dust was adjusted so that the metal iron part derived from the steelmaking dust in a mixture might be 5-85 mass parts with respect to 100 mass parts of dry mass of ironmaking sludge. In addition, the composition value of each component shown in Table 1 and Table 2 is measured by a regular chemical analysis, and is included in the form of compounds such as oxides and hydroxides in addition to those included as simple metals. It is a value including All the mixtures prepared as described above were dehydrated with a filter press at a dehydration pressure of 0.4 MPa. A 100 g sample was immediately taken from the dehydrated mixture, and the water content was measured. Here, the moisture content is the difference between the initial mass and the mass of the mixture when the 100 g sample is dried while being held in an atmosphere of 110 ° C. This is regarded as a percentage of the initial mixture mass.

  The remaining dehydrated mixture used for measuring the moisture content was flattened to a thickness of 10 cm, kept in the room for one month, naturally dried, and solidified. This solidified mixture was placed on a steel mesh (screen) having an opening of 50 mm and crushed with a hammer until the entire amount was under the mesh, and then the crushing strength of the agglomerated product was measured. The crushing strength was measured by selecting 20 from the agglomerated agglomerated material after passing through a sieve with a mesh opening of 50 mm and remaining on the sieve with a mesh opening of 20 mm, and reducing them with a press. The maximum load until breakage was measured, and the arithmetic average of 18 pieces excluding the maximum value and the minimum value among the 20 maximum loads was obtained and used as the crushing strength.

  FIG. 2 shows the relationship between the part by mass of metallic iron in steelmaking dust added to the dry mass of 100 parts by mass of the steelmaking sludge and the water content after dehydration of the mixture. From FIG. 2, the higher the ratio of metallic iron in the mixture, that is, the higher the ratio of steelmaking dust added to the ironmaking sludge, the lower the water content after dehydration by the filter press, that is, the ironmaking sludge. Shows that it becomes easier to dehydrate by adding steelmaking dust.

  FIG. 3 shows the influence of the mass part of the metal iron in the steelmaking dust added to the dry mass of 100 parts by mass of the ironmaking sludge on the crushing strength of the agglomerated material. FIG. 3 shows that the larger the amount of metallic iron added to the steel sludge, the higher the crushing strength of the agglomerated product after drying and solidification. In addition, from FIG. 3, in order to obtain the crushing strength (2.5 MPa or more) necessary for reusing the agglomerate described above as an iron-making raw material, the iron metal content in the mixture is 100 mass of dry mass of iron-making sludge. It can be seen that steelmaking dust may be added so as to be 25 parts by mass or more with respect to the part.

  In order to investigate the preferable characteristics of steelmaking dust added to steelmaking sludge, the steelmaking dust shown in Table 2 was heated and oxidized, and untreated steelmaking dust was mixed as appropriate so that the metal iron content was 20.0 mass%, 15.0 mass% steelmaking dust was adjusted. In addition, the oxidized steelmaking dust was partially condensed to form coarse grains when heated, so the particle size distribution measuring device (Microtrac: manufactured by Nikkiso Co., Ltd.) measured the particle size of the steelmaking dust after heating by the laser diffraction scattering method. ).

  As described above, with respect to the steelmaking dust adjusted in particle size and particle size, the amount of metal iron derived from the steelmaking dust is 40 parts by mass with respect to the dry mass of 100 parts by mass of the slurry-like ironmaking sludge shown in Table 1. These were mixed and mixed to obtain a 20 kg mixture, which was dehydrated with a filter press, then flattened to a height of 10 cm, dried and solidified for 3 weeks to obtain an agglomerated product. Since the agglomerated material thus obtained contains large agglomerates, it is crushed with a hammer until all the agglomerated material falls under a 50 mm square steel screen (screen). The agglomerated material passed through the screen is sieved with a 20 mm square screen, and the mass remaining without falling from the sieve is measured. The ratio of this mass to the total agglomerated material amount (on the sieve + under the sieve) is expressed as a percentage. The value was taken as the yield. Further, the crushing strength of the agglomerate remaining on the 20 mm square screen was measured in the same manner as in Example 1.

  Table 3 shows the results of the above measurement. From Table 3, the agglomerate with a particle size of 20 to 50 mm (50 mm screen under) in the agglomerated condition suitable for the present invention has a crushing strength of 2.5 MPa or more. It turns out that there is no problem. In addition, when the metal iron content in the steelmaking dust is 20 mass% or more and the steelmaking dust with a particle size of 1 mm or less is a fine particle size exceeding 90 mass%, the agglomerate yield is 90% or more. It can be seen that an agglomerated product that can be efficiently used as an ironmaking raw material is obtained by the agglomeration method of the present invention.

  The recovered slurry-like steelmaking dust is mixed with the slurry-like ironmaking sludge so that the amount of metal iron derived from the steelmaking dust with respect to 100 parts by mass (dry mass) of the ironmaking sludge is 40 parts by mass. Agglomeration was performed under the conditions, and the crushing strength was measured. The results are shown in Table 4, but almost the same crushing strength is obtained when dry steelmaking dust is used and when slurry steelmaking dust is used. However, when slurry-like steelmaking dust is used, there is an advantage that problems such as ignition due to oxidation heat generation of metallic iron in the steelmaking dust can be avoided in addition to omitting the drying step of the wet collected steelmaking dust. Further, since the solvent of the slurry-like steelmaking dust is alkaline, there is also an advantage that the amount of alkali added necessary for neutralization of acidic ironmaking sludge can be reduced.

  Table 2 was prepared so that the amount of metal iron derived from steelmaking dust was 25 parts by mass with respect to the dry mass of 100 parts by mass of the steelmaking sludge in the slurry-like steelmaking sludge having the composition shown in Table 1 generated in a stainless steel rolling mill. A metal iron-containing steelmaking dust having the composition shown in FIG. 5 is added in a slurry form and mixed to form a mixture, and then about 50 t of a mixture dehydrated by a filter press is prepared, and this is about 3 m in height using a power shovel. Pile up to height, collect agglomerates of the upper layer (less than 30 cm from the surface) and lower layer (more than 30 cm from the surface), and measure the crushing strength in the same manner as in Example 1. The change with time was examined.

  As a result, as shown in FIG. 4, the crushing strength after about 2 weeks increased to around the target 2.5 MPa in the upper layer (surface), whereas it was only 1.6 MPa in the lower layer. As a result of investigating the reason, since air (oxygen) does not reach the inside in a piled state, as shown in FIG. 5 and FIG. 6, in the lower layer, the moisture in the agglomerate is high, and the oxidation reaction of metallic iron It was thought that was not progressing sufficiently. Therefore, two weeks after the start of drying, the mountain was crushed with a power shovel and the mixture of the surface layer portion and the inner layer portion was mechanically agitated and then piled up again, and the change in crushing strength was continuously investigated. As a result, it was found that the crushing strength exceeded the target 2.5 MPa after 1 week of re-stacking both the upper layer and the lower layer.

  In addition, when we continued to measure the change in crushing strength after 3 weeks, when more than 5 weeks have passed since the start of drying, the surface of the agglomerated material began to weather and the crushing strength decreased. It was also confirmed that the powdering rate tends to increase when transported by truck. Furthermore, as can be seen from FIG. 6, the ratio of metallic Fe in the agglomerate after 5 weeks or more is lower than that after 3 weeks, and this is a steelmaking raw material to be reduced in the subsequent steps. This is not preferable. From the above results, when the mixture is dried and solidified at least in a piled state, after about 2 weeks, the mountain is broken and roughly crushed with a power shovel, etc., and the surface layer and inner layer are mechanically agitated and mixed. After about 1 week has passed, after sufficient contact between the air and the air, the material is crushed and adjusted to an appropriate particle size and used as a raw material for iron making as quickly as possible (within 5 weeks from the start of drying and solidification). It has been confirmed that it is preferable.

  In addition, as for the state of stacking when the mixture was dried and solidified, a comparative experiment was performed for the case of stacking as described above and the case of stacking about 8 m in length and width at a height of about 50 cm. As a result, the crushing strength after 3 weeks from the dehydration of the agglomerated material was almost the same between the case of flat stacking and the case of stacking if the stirring process was performed. However, it was confirmed that the product yield of 5 mm or more after the main pulverization is 5 to 10% higher in the case of flattening.

  The steel sludge agglomerate thus produced was charged into the furnace from the top of the coke packed bed type smelting reduction furnace as an iron production raw material, and a sponge iron melt production experiment was conducted. No valuable metal was recovered.

  If the technology of the present invention is applied, not only iron-making sludge and steel-making dust generated in the iron-making process but also agglomeration of various other by-products generated from the ironworks and including metal components is possible.

It is a graph which shows the relationship between the crushing strength of an agglomerated material, and the powdering rate after the agglomerated material conveyance (occurrence rate of powder of 5 mm or less). It is a graph which shows the relationship between the ratio (mass part) of the metal iron content in the steelmaking dust with respect to 100 mass parts of dry mass of ironmaking sludge, and the moisture content after dehydration of ironmaking sludge. It is the graph which showed the relationship between the ratio (mass part) of the metal iron content in the steelmaking dust with respect to the dry mass of 100 mass parts of iron-making sludge, and the crushing strength of an agglomerate. It is a graph which shows the relationship between the elapsed days and the crushing strength of an agglomerate when it puts in the state of a pile after dehydration. It is a graph which shows the relationship between the elapsed days and the moisture content in an agglomerated material when it puts in the state of a pile after dehydration. It is a graph which shows the relationship between elapsed days and the metal iron ratio in an agglomerate when it puts in a pile state after dehydration.

Claims (5)

  When the steelmaking dust is mixed and agglomerated with the slurry-like ironmaking sludge generated in the ironmaking process, the amount of metallic iron in the steelmaking dust is 25 parts by mass or more with respect to 100 parts by mass of the dry mass of the ironmaking sludge. Thus, a method for agglomerating slurry-like iron-making sludge, comprising mixing slurry-like iron-making sludge and steel-making dust into a mixture, and drying and solidifying the mixture after dehydration.   The slurry steelmaking sludge according to claim 1, wherein the steelmaking dust has a metallic iron content of 20 mass% or more in terms of dry mass, and 90 mass% or more of particles having a particle size of 1 mm or less. Agglomeration method.   The method for agglomerating slurry-like iron sludge according to claim 1 or 2, wherein the steel-making dust used for mixing with the iron-made sludge is a slurry.   4. The method according to claim 1, wherein when the dehydrated mixture is dried and solidified, the mixture is left in a piled state or in a flat state at a certain height and left standing for a certain period of time. The agglomeration method of the slurry-like iron-making sludge as described. When drying and solidifying the mixture, mechanically coarsely pulverize after a certain period of time from the start of drying, stir so that the surface layer part and the inner layer part are interchanged, and then pulverize after a certain period of time to obtain the desired particle size The method for agglomerating a slurry-like iron sludge according to any one of claims 1 to 4, wherein the agglomeration method is characterized in that:

Images