JP2017186579A - Method for storing clinker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide means that can suppress elution of lead from metallic iron and lead-containing clinker well below the desired control reference value and the means that can suppress elution of lead from clinker which can be implemented at a lower cost than before.SOLUTION: The method for storing clinker is a method for storing metallic iron and lead-containing clinker and includes steps of: temporary placement in which a clinker 1 is piled in a mountain shape to form a temporary placement clinker accumulation body 2; and agitation in which, after completion of the temporary placement step and after a predetermined period of time has passed, agitation is carried out so that the surface portion and inside portion of the temporary placement clinker accumulation body 2 are replaced.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a clinker storage method. More specifically, the present invention relates to a clinker storage method capable of suppressing elution of lead from a clinker containing metallic iron and lead.

  A typical example of a clinker containing metallic iron and lead is a clinker discharged as a residue when carrying out a reduction roasting method (Wertz method) for recovering crude zinc oxide from steel dust. Steel dust generated in the steel smelting process contains a relatively large amount of zinc, which is a valuable metal, in addition to iron. Conventionally, this steel dust is produced by a reduction roasting method using a rotary kiln, the so-called Wertz method. The process of recovering the crude zinc oxide from is widely performed.

  The clinker discharged as a residue at the time of carrying out the reduction roasting method (Weltz method) is repeated in the steel refining process as an iron raw material, or used as a landfill material as industrial waste. The main component of this clinker is iron, but trace amounts of zinc and lead that have not been volatilized during the reduction roasting also remain.

  With regard to clinker as industrial waste for landfill treatment, it is obliged by the Ordinance of the Ministry of the Environment that the lead elution standard amount is 0.3 mg / l or less in the dissolution test based on Notification No. 13 of the Environment Agency. For the clinker discharged from the above reduction roasting process, a control standard value that is sufficiently lower than the elution standard amount is set, and the leaching of lead from the clinker is not strictly controlled so as not to exceed this control standard value. Quality control of clinker is performed.

  As a general means for preventing elution of heavy metals from waste, for example, a chemical comprising 0.1 to 10% by weight of polyaluminum chloride and / or sulfate-containing polyaluminum chloride as an external component. And a small amount of water are added and kneaded to stabilize a heavy metal contained in the waste as a compound insoluble in water in a neutral or alkaline state and prevent its elution (Patent Document 1). reference).

  However, such a method for preventing elution of heavy metals requires a kneader for kneading the drug, and increases the cost of the drug and the operation cost of the kneader. Therefore, especially in the case where a large amount of clinker of about several thousand tons per month is discharged, such as the zinc recovery process by the reduction roasting method described above, the burden on cost becomes excessive.

  There has been a need for means that can stabilize clinker to suppress lead elution from lead-containing clinker without requiring special equipment and processes and without incurring chemical costs and operating costs. .

Japanese Patent Laid-Open No. 10-216678

  The present invention can suppress the elution of lead from a clinker containing metallic iron and lead to a prescribed control standard value or less, and can be implemented at a low cost. The purpose is to provide.

  As a result of intensive studies to achieve the above object, the present inventors have added a specific treatment to the clinker aggregate at a predetermined timing when storing the clinker containing metallic iron and lead, It has been found that the clinker can be stabilized and the lead elution value can be suppressed sufficiently low, and the present invention has been completed. Specifically, the present invention provides the following.

  (1) A method for storing clinker containing metallic iron and lead, wherein the clinker is stacked in a mountain shape to form a temporary clinker assembly, and after completion of the temporary placement process, a certain period of time has passed. A clinker storage method in which a stirring step is performed in which stirring is performed so that the surface portion and the inside of the temporary clinker assembly are replaced later.

  According to the invention of (1), the stabilization process for reducing the lead elution value of the clinker containing lead does not require special equipment and processes as in the conventional method, and the chemical cost and operation cost are reduced. Can be done without spending. Thereby, the lead elution value from the clinker containing lead can be further stably suppressed at a lower cost below the prescribed control reference value.

  (2) The clinker storage method according to (1), wherein the clinker is a clinker generated as a residue in a reduction roasting step of recovering crude zinc oxide dust from steel dust.

  According to the invention of (2), the clinker generated from the reduction roasting process of steel dust contains the reduced metal iron, and the lead elution suppression effect of the invention of (1) is achieved. It can be further increased. The invention of (2) makes it possible to more stably suppress the lead elution value from the clinker at a lower cost by making use of the “easy to be oxidized” characteristic of the clinker.

  Conventionally, among the above clinker generated as a residue in the reduction roasting process for recovering crude zinc oxide dust from steel dust, defective clinker exceeding the lead elution standard value is dealt with by repeatedly treating this in a rotary kiln. It was. Such a measure leads to a decrease in the processing amount of steel dust and an increase in processing costs in the reduction roasting step. According to invention of (2), generation | occurrence | production of a defective clinker can be reduced and it can contribute significantly also to the improvement of the productivity of the said reduction roasting process.

  (3) The clinker storage method according to (1) or (2), wherein the stirring is performed while water is sprayed on the clinker, or water is sprayed on the clinker immediately after the stirring is completed.

  According to the invention of (3), by performing watering on the clinker aggregate at an appropriate timing, the elution value of lead from the clinker that can be performed by the clinker storage method according to (1) or (2) The suppressing action can be promoted more efficiently. This process does not require an expensive drug or the like, and can be carried out only with simple watering means, so there is little additional burden in terms of cost. Therefore, the advantageous effects of these inventions can be enjoyed in a more preferred aspect while maintaining the cost advantage of the clinker storage method described in (1) or (2) over the conventional method.

  (4) The clinker storage method according to (3), wherein the water is seawater.

  According to the invention of (4), the water used in the clinker storage method according to (3) is seawater. Seawater can promote the above-mentioned lead elution suppression effect more efficiently than fresh water. In addition, when a factory or the like that requires the application of the method of the present invention is in a coastal area, the use of seawater is relatively easy. The method is also an advantageous method that is superior in terms of cost.

  (5) The clinker storage method according to any one of (1) to (4), wherein the predetermined period is 5 to 10 days.

  After the temporary placement step is completed, it takes about 5 days until a later-described firm consolidated layer is formed on the surface layer portion of the temporary placement clinker assembly. According to the invention of (5), after a strong consolidated layer is formed on the surface layer portion, it can be rapidly stirred. According to this, the progress efficiency of lead elution value reduction by this storage method can be made especially high.

  According to the present invention, elution of lead from a clinker containing metallic iron and lead can be stably suppressed to a specified control standard value or less, and can be carried out at a low cost. A means for suppressing lead elution can be provided.

It is process explanatory drawing which showed the embodiment of each process in the storage method of the clinker of this invention typically. It is a graph which shows the transition of the lead elution value from a clinker by the storage method of the clinker of this invention, and the actual condition of elution amount suppression.

  Hereinafter, preferred embodiments of the clinker storage method of the present invention will be described. However, the present invention is not limited to the following embodiments. Below, the outline | summary of the "reduction roasting process which collect | recovers crude zinc oxide from steel dust" assumed first as a preferable application target process of the storage method of the clinker of this invention is demonstrated first. Thereafter, a preferred embodiment of the present invention in which the clinker discharged from the step is stabilized by the present invention so as to suppress the lead elution value will be described in detail.

<Reduction roasting process>
In a process including a reduction roasting step for recovering crude zinc oxide from steel dust, steel dust and steel dust pellets (in the present specification, these are collectively referred to as “steel dust”) are used as raw materials. Iron and steel dust is mainly generated when iron scrap is used as a raw material for melting treatment in an electric furnace, but iron dust is a material generated when iron ore is used as a raw material for melting treatment in a blast furnace. Includes all dust generated from the smelting process. For example, since iron scrap includes galvanized steel sheets, steel dust contains a relatively large amount of zinc. Also in the blast furnace, recycled materials such as iron scrap are input. Therefore, a relatively large amount of zinc is contained in the steel dust. The chemical composition of steel dust is 18 to 35% by weight of zinc and 15 to 30% by weight of iron, and additionally contains impurities such as chlorine, fluorine and 0.2 to 2.5% by weight of lead. The above weight% is based on the dry amount.

  The reduction roasting process can be carried out in any roasting furnace such as a fixed bed roasting furnace, a fluidized bed roasting furnace, a rotary hearth furnace, etc., but generally a rotary kiln called the Welts method is used. Reducing roasting that has been widely performed. When performing reduction roasting with a rotary kiln (hereinafter also referred to as “RRK”), steel dust as a raw material is put into the RRK together with a carbonaceous reducing agent. As a specific example of RRK for reduction roasting, the outer diameter is 3.3 m, the length is 50 m, and the exterior is made of steel with a thickness of 25 mm, and the inside is 25 to 30 mm thick with a fixed refractory (brick) or The thing in which the refractory layer is formed with the irregular refractory (castable) can be mentioned. The inside of the RRK that performs reduction roasting is controlled so that the maximum temperature reached about 1100 to 1200 ° C. by combustion of fuel heavy oil and the carbonaceous reducing agent.

  The steel dust is reduced and roasted in the RRK for reduction roasting, and the volatilized metallic zinc is reoxidized and solidified in the RRK, and then recovered as a powdery crude zinc oxide dust by an electric dust collector or the like. On the other hand, the reduction roasting residue which remained in RRK without volatilizing by reduction | restoration roasting operation is discharged | emitted from the discharge end of a rotary kiln as a clinker. The clinker storage method of the present invention, which will be described in detail below, is a storage method in which clinker generated as a residue in the reduction roasting step (hereinafter also simply referred to as “clinker”) is assumed as a particularly preferable storage object.

<Clinker storage method>
FIG. 1 is a process explanatory view schematically showing an embodiment of each process in the clinker storage method of the present invention. As shown in FIGS. (A) to (d), the clinker storage method of the present invention is a temporary standing step (a), followed by a fixed standing period (b), and a stirring step (c), This is a method of sequentially performing the restacking step (d). However, the restacking step (d) is not necessarily an essential step in the implementation of the present invention, and may be appropriately performed according to storage conditions such as the area of the storage place. For example, after the stirring step (c), the clinker aggregates may be stored as they are without restacking. In addition, the clinker storage method of the present invention may be further performed as a method of performing the above stirring while spraying water on the clinker, or performing a process of spraying water on the clinker immediately after the completion of the stirring. More preferred.

[Clinker discharged from reduction roasting process]
The clinker generated in the process of recovering crude zinc oxide from steel dust is usually cooled in air or water and then stored in a mountain shape at the clinker yard and shipped to steel manufacturers as iron raw materials. Or paid to industrial waste disposal companies for landfill disposal. Usually, the storage period is about 1 to 2 months, but the iron content of the clinker after 1 to 2 months is generally about 35 to 55% by weight.

The iron compound form in the steel dust is ferric trioxide (Fe ₂ O ₃ ), but when the charged steel dust reaches near the discharge end of the rotary kiln, it is reduced to metallic iron (Fe ⁰ ) Therefore, the clinker, which is a residue in the reduction roasting step in the entire process of recovering crude zinc oxide from steel dust, contains a large amount of metallic iron. However, since the metal iron easily be extremely air oxidation, as soon as is discharged from the discharge end, the iron oxide from the portion touching the air (FeO), further to the oxidation proceeds diiron trioxide (Fe 2 _{O 3)} And is oxidized. On the other hand, about this clinker, the defective clinker which shows the lead elution test value exceeding the above-mentioned control reference value may be produced.

  The clinker storage method of the present invention intentionally promotes appropriate oxidation of clinker particles to stabilize the clinker by taking advantage of the property of the clinker being easily oxidized, thereby preventing the occurrence of the above-mentioned defective clinker. For the purpose.

[Temporary placement process]
In the clinker storage method of the present invention, first, as shown in FIG. 1A, a temporary placement step is performed in which the clinker 1 is stacked in a mountain shape to form a temporary placement clinker assembly 2.

  Immediately after discharge from the RRK, the surface layer portion of the temporary clinker assembly 2 stacked in a mountain shape undergoes rapid air oxidation accompanied by heat generation, so that after about 5 days, as shown in FIG. A strong consolidated layer 21 is formed on the surface layer portion. The consolidated layer 21 becomes an air blocking layer, and the oxidation inside the temporary clinker assembly 2 stacked in a mountain shape is inhibited. The surface layer portion of the temporary clinker assembly 2 stacked in a mountain shape is oxidized and becomes ferric trioxide (reddish brown). However, in the temporary clinker assembly 2, a consolidated layer 21 is formed. After the oxidation, the progress of oxidation inside the mountain is very slow, and for this part, iron oxide or metallic iron (black) is the major part.

[Stirring step]
After completion of the temporary placement step, after a certain period of time, a stirring step is performed in which the surface portion and the inside of the temporary placement clinker assembly 2 are stirred. As shown in FIG. 1C, this stirring is performed in such a manner that the surface portion and the inside of the temporary clinker assembly 2 are replaced while the consolidated layer 21 is broken. This agitation and subsequent re-stacking operation can be performed by a general-purpose construction machine such as a normal hydraulic excavator, a power shovel, a backhoe or the like. This agitation and subsequent re-stacking operation replaces the air in the entire clinker aggregate.

  The above-mentioned “certain period” in which the temporary placement clinker assembly 2 is left is not limited to a specific period, but the formation of a cured film by oxidation has spread throughout the entire surface portion of the temporary placement clinker assembly 2. Thereafter, it is preferable to carry out as soon as possible. Specifically, although it depends on the state of the clinker and the environment of the accumulation location, as described above, it is preferable to perform stirring after 5 to 10 days have passed after the temporary placing step is completed.

  As shown in FIG. 1 (c), the stirring step is performed while spraying water 5 with the watering means 4, or is performed in a mode in which the water 5 is sprayed onto the clinker immediately after the completion of stirring. Is preferred. At this time, the sprayed water 5 may be fresh water or seawater, but seawater is preferred in that it can promote oxidation more efficiently. In any case, the adhesion of the sprayed water can significantly promote the oxidation of metallic iron, so-called rust generation. Further, the water spraying means 4 for spraying water does not need to be provided with special additional equipment as long as it has a hose and a tip nozzle, and can be easily and inexpensively deployed. Note that “immediately after completion” does not mean strictly within a specific time after completion of stirring, but can be stored at the same time as completion of stirring or within 2 to 3 days at the latest. An appropriate oxidation promoting effect by watering at the initial stage can be sufficiently exerted even inside the aggregate.

[Restacking process]
After completion of the agitation step, as shown in FIG. 1 (d), the agitated clinker may be restacked as necessary to form a storage clinker aggregate 3 for restacking. preferable. Note that the storage clinker assembly 3 is not necessarily limited to the re-stack as described above. For example, when the clinker after the stirring step is stored without being re-stacked after the stirring step, for example, when the clinker after the stirring step is stored while being left in a state of being spread almost flat, It shall be regarded as a storage clinker aggregate on the invention.

  The details of the clinker stabilization mechanism in the storage clinker aggregate 3 are not necessarily clear, but are considered to be due to the progress of appropriate oxidation throughout the clinker aggregate. More specifically, an oxide film is formed on the surface of the clinker particles, and this acts as a protective film. Further, secondary consolidation of the clinker particles proceeds by oxidation, resulting in an increase in particle size and crushing strength. It is presumed to be due to the action such as the rise of.

  In the storage clinker assembly 3, unlike the temporary storage clinker assembly 2 stacked in a mountain shape immediately after discharge, rapid air oxidation with heat generation does not occur. Therefore, a strong consolidated layer is not formed on the surface layer portion. In addition, in the storage clinker assembly 3 that has been piled up again in a mountain shape, appropriate oxidation proceeds even inside the mountain unless a strong consolidated layer is formed in the surface layer portion. It is presumed that the elution of lead from the storage clinker aggregate 3 is suppressed by these actions.

  Depending on the degree of progress of the oxidation on the surface and inside of the storage clinker aggregate 3 after the restacking step, the stirring and restacking in the above embodiment may be repeated again as necessary. . In addition to performing the above watering at the above timing, the watering may be additionally performed as appropriate. In the surface layer portion of the storage clinker aggregate 3, it is difficult to form a strong consolidated layer that inhibits the penetration of water into the inside. Therefore, by performing an appropriate amount of additional watering as necessary, Appropriate oxidation inside can be further promoted.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example.

Example 1
As Example 1, the clinker storage method of the present invention was carried out in the following manner. That is, in the process of recovering crude zinc oxide from steel dust, the clinker, which is the residue discharged from the rotary kiln that performs the reduction roasting step, is piled up in a mountain shape as shown in FIG. An aggregate was obtained. Stirring was performed so that the surface portion and the inside of the temporary placement clinker assembly were replaced as shown in FIG. After sufficiently stirring the entire clinker, as shown in FIG. 1 (d), the clinker was again piled up to form a storage clinker aggregate. Then, at the start of the implementation of the above storage method, clinker sampling was performed 0.5 months after the start and 1 month after the start, and the lead elution value was measured for each sample collected. Sampling 0.5 months later and 1 month after the start was performed by sampling five clinker samples having a depth of 10 cm from the surface of each clinker aggregate peak. The lead elution value was measured by the elution test method based on Notification No. 13 of the Environment Agency. In FIG. 2, the average value of the measured lead elution values is plotted.

(Example 2)
As Example 2, except that the above stirring process was performed while sprinkling seawater on the clinker, the clinker accumulation for stirring and storage was performed in the same procedure as in Example 1 from the accumulation of the temporary clinker aggregate. A series of work was done until the body was piled up. The transition of the lead elution value of the clinker was also measured by the same method as in Example 1.

(Comparative example)
After the step of stacking the temporary placement clinker aggregate was performed in the same manner as in Example 1, the aggregate was left as it was as a storage clinker aggregate without performing the stirring step. The transition of the lead elution value of the clinker was measured by the same method as in Examples 1 and 2.

  In the clinker aggregate of the comparative example, it took 1 month for the lead elution value to become the control standard value of 0.1 mg / l or less. On the other hand, in Example 1 and Example 2, the management reference value could be satisfied in 0.5 months. In particular, in Example 2, as in the comparative example and Example 1, the rate of reduction of the lead elution value does not become dull after one month has elapsed, and the linear elution value decreases significantly after one month. It was reduced. As mentioned above, the storage method of the clinker of the present invention can suppress the elution of lead from the clinker containing metallic iron and lead below the prescribed control standard value, and can be carried out at a low cost. It turns out that it is a suppression means of lead elution from a clinker.

DESCRIPTION OF SYMBOLS 1 Clinker 2 Temporary placing clinker aggregate 21 Consolidation layer 3 Storage clinker aggregate 4 Watering means 5 Water

Claims (5)

A storage method for clinker containing metallic iron and lead,
Temporary placement step of stacking the clinker in a mountain shape to form a temporary clinker assembly;
A clinker storage method, comprising: a stirring step in which stirring is performed so that the surface portion and the inside of the temporary placement clinker assembly are replaced after a predetermined period of time after the temporary placement step is completed.   The clinker storage method according to claim 1, wherein the clinker is a clinker generated as a residue in a reduction roasting step of recovering crude zinc oxide dust from steel dust.   The clinker storage method according to claim 1 or 2, wherein the stirring is performed while water is sprayed on the clinker, or water is sprayed on the clinker immediately after the stirring is completed.   The clinker storage method according to claim 3, wherein the water is seawater.   The clinker storage method according to any one of claims 1 to 4, wherein the predetermined period is 5 to 10 days.

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