JP2010172812A - Method for decreasing elution amount of heavy metal of steelmaking dust - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for decreasing the elution amount of heavy metals to a standardized value of a specially controlled industrial wastes or less within a shorter water-sprinkling time than before in a detoxification method for steelmaking dust by water-sprinkling treatment. <P>SOLUTION: In water-sprinkling treatment for steelmaking dust for suppressing the elution amount of heavy metals of the steelmaking dust, the method for decreasing the elution amount of heavy metals of steelmaking dust is carried out as follows: hot water at 35 to 80°C is used for carrying out water-sprinkling to the steelmaking dust granulated into pellets by mixing the steelmaking dust with water or more preferably before hot water at 35 to 80°C is used for carrying out water-sprinkling to the steelmaking dust granulated into pellets by mixing the steelmaking dust with water, water-sprinkling is carried out using water at normal temperature for 20 to 50 hours in the initial stage of water-sprinkling and thereafter further water-sprinkling is carried out using hot water at 35 to 80°C for 20 to 80 hours and thus water-sprinkling is carried out for 40 to 100 hours in total to remove heavy metals from steelmaking dust in advance. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technique for reducing the heavy metal elution amount of steelmaking dust containing heavy metals, and particularly to a technique for reducing the elution amount of these heavy metals when a hexavalent chromium compound, a selenium compound or a mercury compound is contained as the heavy metal.

  Conventionally, steelmaking dust has been dechlorinated by watering and used as a cement raw material by a cement manufacturer, or after a zinc recovery manufacturer recovers zinc, the residue is used as a cement raw material. However, in recent years, steelmaking dust having a high chromium content has been reduced in use as a raw material for cement, and steelmaking dust has to be disposed of in landfills.

  However, steelmaking dust contains harmful heavy metals, and the amount of elution of heavy metals complies with the “Ministerial Ordinance for Establishing Judgment Criteria for Industrial Waste Containing Metals” shown in Prime Minister Ordinance No. 5 promulgated in 1973 If the specified value is exceeded, it will be treated as specially controlled industrial waste, which requires very strict management and must be disposed of in a closed final disposal site.

  For this reason, a method of heat-mixing steelmaking dust and sulfur containing harmful substances to 95 to 120 ° C. and cooling and solidifying them to render them harmless has been proposed (for example, see Patent Document 1) or harmful. A method for preventing elution of toxic metals such as cadmium and lead by adding 0.5 to 6% of potassium carbonate or sodium carbonate alone or in combination to steelmaking dust has been proposed (for example, (See Patent Document 2).

  On the other hand, it has been shown that when steelmaking dust is dechlorinated by watering, heavy metals such as hexavalent chromium compounds are also dissolved in water, and the amount of elution is reduced (see, for example, Patent Document 3). .) However, since the purpose of this method is dechlorination, water spraying for a long period of 6 to 20 days is required, which is not an efficient treatment as a method for detoxifying heavy metals.

Japanese Patent Publication No. 61-15759 JP-A 64-90082 Japanese Patent Laid-Open No. 5-58686

  The problem to be solved by the present invention is to provide a method for reducing the amount of elution of heavy metals below the reference value for specially controlled industrial waste in a detoxification method by watering treatment of steelmaking dust in a shorter watering time than before. That is.

  The heavy metal here refers to heavy metals such as mercury or a compound thereof, cadmium or a compound thereof, lead or a compound thereof, hexavalent chromium compound, arsenic or a compound thereof, selenium or a compound thereof. The amount of elution of these heavy metals is measured based on the verification method for metals contained in industrial waste described in Environmental Agency Notification No. 13 promulgated in 1973.

  The means of the present invention for solving the above-mentioned problems is the steelmaking granulated into pellets while mixing with water in the watering treatment for the steelmaking dust for suppressing the heavy metal elution amount of the steelmaking dust. It is a method for reducing the heavy metal elution amount of steelmaking dust, wherein heavy metal in steelmaking dust is removed in advance by sprinkling water with hot water of 35 to 80 ° C.

  In the invention of claim 2, in the sprinkling treatment for the steelmaking dust for suppressing the heavy metal elution amount of the steelmaking dust, the hot water of 35 to 80 ° C. is used for the steelmaking dust granulated into pellets while mixing with water. The heavy metal of the steelmaking dust according to the means of claim 1, wherein the heavy metal in the steelmaking dust is removed in advance by watering for 100 hours to suppress the elution amount of heavy metal below the reference value of specially controlled industrial waste. This is a method for reducing the amount of elution.

  In invention of Claim 3, in the watering process with respect to the steelmaking dust for suppressing the heavy metal elution amount of steelmaking dust, it sprinkles using the hot water of 35-80 degreeC to the steelmaking dust granulated to the pellet, mixing with water. Prior to spraying, water is sprayed for 20 to 50 hours at room temperature using normal temperature water, and then water is sprayed for 20 to 80 hours using warm water of 35 to 80 ° C. for a total of 40 to 100 hours. The method for reducing heavy metal elution in steelmaking dust according to the means of claim 1, wherein heavy metal elution in steelmaking dust is removed in advance to suppress the elution amount of heavy metal below a reference value for specially controlled industrial waste. It is.

  The above-mentioned detoxification treatment of steelmaking dust by watering is a method of reducing the amount of elution of heavy metals by dissolving heavy metals in water and removing them in advance. By the way, the solubility of heavy metals in water generally increases as the water temperature increases. Thus, if high-temperature water is used in watering, heavy metals are often dissolved in water and removed, so that the amount of elution is reduced in a short time.

  In this case, if the water temperature sprayed onto the steelmaking dust is less than 35 ° C., the effect of reducing the amount of heavy metal elution is reduced, so the lower limit of the water temperature is 35 ° C. Further, the upper limit of the water temperature for watering is 80 ° C., preferably 60 ° C. from the viewpoint of cost and safety.

  Wastewater used for watering treatment is sent to treatment facilities, and the heavy metals contained in the wastewater are precipitated as sparingly soluble salts to make them harmless. By the way, if the watering temperature is kept constant from the start to the end of watering, heavy metals dissolve in water more and more at the start of watering, and the concentration of heavy metals in the wastewater becomes higher. Also grows. In addition, the higher the water spray temperature, the higher the heavy metal concentration in the wastewater. Therefore, if high-temperature water is used immediately after the start of watering, the heavy metal concentration in the wastewater at the start of watering will further increase, and the ability to perform proper wastewater treatment. High processing equipment is required. Therefore, in order to disperse the load of wastewater treatment, in the means of the invention of claim 3, as a preferable method, after the amount of elution of heavy metals is reduced to some extent by using water at room temperature at the start of watering, It is assumed that hot water of 80 ° C. is used.

  By spraying steelmaking dust using the hot water of 35 to 80 ° C. according to the means of claim 1 of the present invention, the amount of elution of heavy metals can be reduced compared to the conventional watering alone with the same watering time. it can. In addition, the means of claim 2 is to sprinkle steelmaking dust for 20 to 100 hours using hot water of 35 to 80 ° C., and specially control the elution amount of heavy metals in steelmaking dust by watering for a shorter time than before. It can be reduced below the standard value for industrial waste. Furthermore, water at normal temperature is sprayed at the beginning of the means of claim 3, and after the amount of dissolution has been reduced, water is sprayed on the steelmaking dust using hot water of 35 to 80 ° C., thereby leveling the wastewater treatment load. The method of the present application has an excellent effect that has not been achieved so far.

It is a perspective view showing typically the place of steelmaking dust which sprinkles the pellet of steelmaking dust, and shows through.

  EMBODIMENT OF THE INVENTION The form for implementing this invention is demonstrated below with reference to a table | surface and drawing. Since the steelmaking dust generated in the steelmaking factory is a fine particle, if it is sprinkled as it is, it tends to flow out due to the momentum of the sprinkling water. A steelmaking dust pellet 4 having a height of 2 m and a thickness of about 500 t was stacked on a 14 m × 14 m steelmaking dust place 1 and sprinkled with water. As shown in FIG. 1, the steelmaking dust storage place 1 is partitioned in three directions by walls 2 and has a drainage groove (not shown) on the floor surface. Watering was performed using six watering nozzles 3 so that water was uniformly applied to the steelmaking dust pellets 4. The amount of water sprayed was 100 kg per square meter per hour for stacked dust. In addition, the waste water sprayed on the pellet 4 was collected from the drainage groove and sent to a detoxification treatment facility provided elsewhere.

  Examples and Comparative Examples of the present invention are shown in Tables 1 to 3. The amount of elution of heavy metals was measured based on the method for testing metals contained in industrial waste described in Environmental Agency Notification No. 13 promulgated in 1973. In Tables 1 to 3, the unit of the elution amount of heavy metal and the reference value is mg / L.

  Comparative Example 1 shows the elution amount of heavy metal in steelmaking dust before watering, and the elution amount of mercury or its compound, hexavalent chromium compound, selenium or its compound exceeds the standard value of specially controlled industrial waste . On the other hand, Example 1 and Comparative Example 2 show the subsequent elution amount of heavy metal in the case where heavy steel was removed in advance by watering the steelmaking dust of Comparative Example 1. Example 1 is a result of removing heavy metals in advance by watering at room temperature for 24 hours and then watering at 40 ° C. for 48 hours to remove heavy metals. The elution amount of the heavy metal of the valent chromium compound, selenium or the compound is less than the standard value of specially controlled industrial waste. However, Comparative Example 2 uses only water at room temperature of 25 ° C., and in the case of watering for 72 hours, mercury or a compound thereof is not reduced below the reference value for specially managed industrial waste. About the hexavalent chromium compound and selenium or its compound, although it has reduced to below the standard value of special management industrial waste also in the comparative example 2, the direction of Example 1 is a lower value, and the elution amount by warm water It shows that the effect of reduction is great.

  Comparative Example 3 in Table 2 shows the elution amount of mercury or its compound among heavy metals of steelmaking dust before watering, and the elution amount of mercury or its compound exceeds the standard value of specially controlled industrial waste. . On the other hand, Example 2, Example 3 and Comparative Example 4 show the subsequent elution amount of mercury or a compound thereof in the case where heavy metal was removed in advance by performing watering treatment on the steelmaking dust of Comparative Example 3. . Example 2 is the result of water removal for 72 hours using only warm water at 40 ° C., and the elution amount of mercury or its compound is less than the standard value for specially controlled industrial waste after 72 hours of water spraying. 0.0034 mg / L. In addition, Example 3 is a result obtained by spraying water at room temperature of 30 ° C. for 48 hours, and then spraying water at 60 ° C. for 48 hours to remove heavy metals in advance. The elution amount of the compound is 0.0028 mg / L which is lower than the standard value of specially controlled industrial waste. However, Comparative Example 4 uses only water at room temperature of 30 ° C., and watering for 72 hours reduces mercury or its compound to 0.005 mg / L or less, which is the standard value for specially controlled industrial waste. This indicates that the effect of reducing the amount of elution with warm water is great.

  Comparative Example 5 in Table 3 shows the elution amount of mercury or its compound among heavy metals in steelmaking dust before watering, and the elution amount of mercury or its compound exceeds the standard value of specially controlled industrial waste. . On the other hand, Example 4 and Comparative Example 6 show the subsequent elution amount of mercury or a compound thereof in the case where the steelmaking dust of Comparative Example 5 is subjected to watering treatment to remove heavy metals in advance. Example 4 is a result of removing heavy metals in advance by watering with warm water of 30 ° C. for 24 hours and then watering with warm water of 60 ° C. for 24 hours, and elution of mercury or its compound by watering for a total of 48 hours. The amount is 0.0011 mg / L below the standard value for specially managed industrial waste. However, Comparative Example 6 uses only water at room temperature of 30 ° C., and watering for 48 hours reduces mercury or its compound to 0.005 mg / L or less, which is below the standard value for specially controlled industrial waste. This indicates that the effect of reducing the amount of elution with warm water is great.

1 Place for steelmaking dust 2 Wall 3 Watering nozzle 4 Pellet

Claims (3)

  In sprinkling treatment of steelmaking dust to suppress the amount of heavy metal elution from steelmaking dust, heavy metal in steelmaking dust is sprinkled using hot water of 35 to 80 ° C to steelmaking dust granulated into pellets while mixing with water. A method for reducing the amount of heavy metal leaching of steelmaking dust, characterized by previously removing.   By sprinkling water for 20 to 100 hours using 35 to 80 ° C. hot water on steelmaking dust granulated into pellets while mixing with water in watering treatment for steelmaking dust to suppress heavy metal elution of steelmaking dust The heavy metal elution amount of steelmaking dust according to claim 1, wherein heavy metals in steelmaking dust are removed in advance to suppress the elution amount of heavy metals below a reference value for specially controlled industrial waste.   In sprinkling treatment for steelmaking dust to reduce the amount of heavy metal elution of steelmaking dust, watering the steelmaking dust granulated into pellets while mixing with water using 35-80 ° C warm water, After watering for 20 to 50 hours using water at room temperature, watering is further performed for 20 to 80 hours using warm water of 35 to 80 ° C., and watering is performed for 40 to 100 hours in total in the steelmaking dust. The method for reducing the heavy metal elution amount of steelmaking dust according to claim 1, wherein the heavy metal elution amount is suppressed in advance to suppress the elution amount of heavy metal below a reference value for specially controlled industrial waste.

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