JP2021115511A - Method for producing zinc-containing solid matter from molten fly ash - Google Patents

Abstract

To provide a method for producing a solid matter having high zinc concentration from molten fly ash.SOLUTION: A method for producing a zinc-containing solid matter includes: a mixing step of mixing molten fly ash with water; a separation step of separating mixed liquid obtained by the mixing step into heavy mixed liquid having a large mass per unit volume and light mixed liquid having a small mass per unit volume than the heavy mixed liquid, by centrifugal separation; and a dehydration step of dehydrating the light mixed liquid to obtain a zinc-containing solid matter.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing a zinc-containing solid from molten fly ash.

Conventionally, molten fly ash is generated by melting treatment of general waste and industrial waste, and molten fly ash is generated by melting treatment of incinerated fly ash generated by incinerating general waste and industrial waste. It is known (for example, Patent Document 1). It is generally known that these molten fly ashes contain zinc, lead, chromium, and the like (for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2008-253949

However, when these metals are reused, it is difficult to reuse them unless the concentration exceeds a certain level, and the melting treatment, which is a general concentration method, has a problem that energy consumption is large.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for producing a solid substance having a high zinc concentration from molten fly ash.

The present invention has been made to solve the above problems, and can be realized as the following forms.

(1) According to one embodiment of the present invention, a method for producing a zinc-containing solid matter is provided. In this method for producing a zinc-containing solid, a mixing step of mixing molten flying ash and water and a heavy mixed solution having a large mass per unit volume are obtained by centrifuging the mixed solution obtained by the mixing step. It includes a separation step of separating into a light mixed liquid having a smaller mass per unit volume than the heavy mixed liquid, and a dehydration step of obtaining a zinc-containing solid by dehydrating the light mixed liquid.

According to the method for producing a zinc-containing solid product of this form, a solid content having a high zinc concentration can be obtained by going through a separation step.

(2) In the method for producing a zinc-containing solid of the above embodiment, an adjustment step of adjusting the pH of the mixed solution may be further provided after the mixing step and before the separation step.

According to the method for producing a zinc-containing solid of this form, by providing an adjusting step before the separation step, the pH of the mixed solution is adjusted at once as compared with the case where the adjusting step is provided after the separation step. be able to.

(3) In the method for producing a zinc-containing solid of the above embodiment, in the separation step, centrifugation may be performed by a decanter type centrifuge.

According to the method for producing a zinc-containing solid in this form, separation can be performed even when the solid content in the mixture is high.

(4) In the method for producing a zinc-containing solid of the above embodiment, a centrifugal force of 100 G or more and 500 G or less may be applied in the separation step.

According to the method for producing a zinc-containing solid product in this form, a solid content having a higher zinc concentration can be obtained.

(5) In the method for producing a zinc-containing solid of the above embodiment, the step of dehydrating the heavy mixed solution and the melted fly ash by melting the solid obtained by dehydrating the heavy mixed solution are further performed. It may be provided with a step of obtaining the above.

According to the method for producing a zinc-containing solid in this form, the zinc contained in the heavy mixture can be reused.

The flowchart of the manufacturing method which manufactures a zinc-containing solid substance from molten fly ash which is an embodiment of this invention. Explanatory drawing of apparatus 100 used in this experiment.

FIG. 1 is a flowchart of a production method for producing a zinc-containing solid substance from molten fly ash according to an embodiment of the present invention. The manufacturing method of the present embodiment includes a mixing step (step P100), a separation step (step P120), and a dehydration step (step P130).

First, the manufacturer performs a mixing step (step P100). The mixing step (step P100) is a step of mixing water with the molten fly ash. In the present embodiment, as the melt fly ash, fly ash volatilized in a melting furnace and repaired by a filter is used, but the present invention is not limited to this. As the molten fly ash, for example, molten fly ash collected at an incinerator, a metal smelting factory, or the like may be used.

Next, the manufacturer performs an adjustment step (step P110). The adjusting step (step P110) is a step of adjusting the pH of the mixed solution obtained in the mixing step (step P100). In this embodiment, the pH is adjusted to 9.0 or more and 11.0 or less by using slaked lime or sodium hydroxide. By doing so, precipitation of heavy metals can be suppressed.

After the adjustment step (step P110), the manufacturer performs a separation step (step P120). In the separation step (step P120), the mixed solution obtained in the adjusting step (step P110) is centrifuged to separate a heavy mixed solution having a large mass per unit volume into a heavy mixed solution and a unit volume larger than that of the heavy mixed solution. This is a step of separating into a light mixed solution having a small mass per unit.

In the present embodiment, in the separation step (step P120), centrifugation is performed by a decanter type centrifuge. Here, the decanter type centrifuge is a centrifuge having an inner cylinder and an outer cylinder, and the rotation directions are the same, and the speed difference between the outer cylinder and the screws provided on the outer periphery of the inner cylinder is slight. It is a centrifuge that rotates at high speed with a. Of the mixed liquid supplied to the inside of the outer cylinder, the agglomerates having a heavy specific gravity become stuck to the inner wall of the rotating cylinder by centrifugal force, and the part separated from the liquid component is scraped off by the screw conveyor and removed. .. There are "vertical type" and "horizontal type" in the decanter type centrifuge depending on the installation direction of the rotating body. In the present invention, both can be used, but from the viewpoint of efficient separation, the "horizontal type" is used. preferable. In addition, as the liquid feeding method into the device, the "concurrent flow type" in which the liquid feeding direction and the liquid moving direction in the rotating body are the same, and the liquid feeding direction and the liquid moving direction in the rotating body are opposite to each other. There is a "counterflow type", but any of them may be used.

When a decanter type centrifuge is used, the centrifugal force to be applied is not particularly limited, but from the viewpoint of obtaining a solid content having a higher zinc concentration, it is preferably 100 G or more and 500 G or less, and more preferably 200 G or more and 400 G or less. When a decanter type centrifuge is used, the supply speed to the decanter type centrifuge is preferably 0.50 m / S or more and 2.80 m / S or less, and the residence time in the decanter type centrifuge is 7 seconds or more and 20. Seconds or less is preferable.

In the present embodiment, in the separation step (step P120), a centrifuge other than the decanter type centrifuge may be used. As another centrifuge, for example, a wet cyclone may be used. According to this embodiment, since a decanter type centrifuge is used, separation can be performed even when the solid content in the mixed solution is large.

After the separation step (step P120), the manufacturer performs a dehydration step (step P130) for the light mixture (step P125: YES) among the light mixture and the heavy mixture separated by the centrifuge. .. The dehydration step (step P130) is a step of obtaining a zinc-containing solid by dehydrating the light mixed solution.

Further, the manufacturer obtained the heavy mixture separated in the separation step (step P120) by dehydrating the heavy mixture after undergoing the dehydration step (step P140) (step P125: NO). Molten fly ash is obtained by going through a step of melting the solid material (step P150). Then, the manufacturer uses this molten fly ash in the mixing step (step P100). By doing so, the heavy mixture can be reused.

As described above, according to the production method of the present embodiment, a solid content having a high zinc concentration can be obtained by going through the separation step (step P120). Although this mechanism is not clear, as an estimation mechanism, since the particle size of the zinc-containing compound is small, it is conceivable that a solid substance having a high zinc concentration can be obtained by dehydrating the light mixture.

Further, in the present embodiment, by providing the adjusting step before the separation step, the pH of the mixed solution can be adjusted at once as compared with the case where the adjusting step is provided after the separation step. Further, by adjusting the pH, elution of heavy metals can be suppressed.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.

FIG. 2 is an explanatory diagram of the device 100 used in this experiment. The device 100 includes a supply tank 10, a supply pump 20, a flow indicator 25, a centrifuge 30, a heavy mixture tank 40, and a light mixture tank 50. In this experiment, molten fly ash collected by a bag filter, which was ash volatilized in a melting furnace, was used.

In this experiment, first, in the supply tank 10, molten fly ash and industrial water are mixed and then stirred for 30 minutes to obtain a slurry having a solid content of 26% by mass (hereinafter, also referred to as “raw material slurry”). Obtained. Since the pH of the molten fly ash used in this experiment was 9.5, which is a preferable range, the pH was not particularly adjusted.

Next, the raw material slurry was supplied to the centrifuge 30 using the supply pump 20. The flow rate of the raw material slurry supplied to the centrifuge 30 is measured by the flow indicator 25. In this experiment, a decanter type centrifuge was used as the centrifuge 30. More specifically, a decanter type centrifuge SID-200S manufactured by Saito Centrifuge Industry Co., Ltd. was used. Table 1 shown below shows the numerical values showing the performance and functions of the decanter type centrifuge SID-200S, and Table 2 shown below shows the operating conditions in the present invention.

As shown in FIG. 2, the centrifuge 30 includes an outer cylinder 70 provided on the outer circumference, an inner cylinder 60 provided inside the outer cylinder 70, and a screw 65 provided on the outer circumference of the inner cylinder 60. To be equipped. The outer cylinder 70 includes a cylindrical portion 72 having a substantially constant cross-sectional area, and a conical portion 75 whose cross-sectional area decreases toward the end. The outer cylinder 70 is provided with discharge holes 77 and 79 at both ends. The discharge hole 77 is provided in the cylindrical portion 72, and the discharge hole 79 is provided in the conical portion 75.

First, the raw material slurry is supplied into the inner cylinder 60 of the centrifuge 30 from the supply hole 31 of the centrifuge 30 provided on the left side of the paper surface. Then, the raw material slurry is supplied to the outer cylinder 70 from the discharge hole 35 provided near the center of the inner cylinder 60 in the axial direction. Centrifugal force is applied to the raw material slurry in the outer cylinder 70 by rotating about the axis while the inner cylinder 60 and the outer cylinder 70 have a difference in speed. Due to this centrifugal force and the external force of the screw 65, the heavy mixed liquid, which is a mixed liquid having a large mass per unit volume, is discharged from the discharge hole 79, and is a light mixed liquid having a smaller mass per unit volume than the heavy mixed liquid. The mixed liquid is discharged from the discharge hole 77. Then, the heavy mixed liquid is supplied to the heavy mixed liquid tank 40, and the light mixed liquid is supplied to the light mixed liquid tank 50.

In Table 3 below, the solid content concentration and the element concentration in the solid content of each of the raw material slurry, the light mixed solution, and the heavy mixed solution are shown. Here, the solid content concentration was measured in a state where the raw material slurry was filtered and then dried. The solid content concentration of the heavy mixture could not be measured because the filtration could not be performed normally.

The element concentration in the solid content was analyzed by the following method. As the zinc analysis method, an EDTA titration method based on JIS M 8228 was used. As the chlorine analysis method, an ion chromatograph method based on JIS M 5011 was used. As the method for analyzing silicon dioxide, a silicon dioxide method based on JIS M 8214 was used. As the method for analyzing calcium oxide, an atomic absorption method based on JIS M 8221 was used. As the analysis method of aluminum oxide, an atomic absorption method based on JIS M 8220 was used.

From the results shown in Table 3, it was found that the zinc concentration of the light mixture was about 10% by mass higher than the zinc concentration of the raw material slurry. On the other hand, it was found that the zinc concentration of the heavy mixture was about 12% by mass lower than the zinc concentration of the raw material slurry.

The present invention is not limited to the above-described embodiment, and can be realized with various configurations within a range not deviating from the gist thereof. For example, the embodiment corresponding to the technical feature in each embodiment described in the column of the outline of the invention, the technical feature in the embodiment may be used to solve a part or all of the above-mentioned problems, or the above-mentioned above. It is possible to replace or combine them as appropriate to achieve some or all of the effects. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.

10 ... Supply tank 20 ... Supply pump 25 ... Flow indicator 30 ... Centrifuge 31 ... Supply hole 35 ... Discharge hole 40 ... Heavy mixture tank 50 ... Light mixture tank 60 ... Inner cylinder 65 ... Screw 70 ... Outer cylinder 72 ... Cylindrical part 75 ... Conical part 77, 79 ... Discharge hole 100 ... Device

Claims (5)

A method for producing zinc-containing solids,
A mixing process that mixes molten fly ash and water,
A separation step of separating the mixed solution obtained by the mixing step into a heavy mixed solution having a large mass per unit volume and a light mixed solution having a smaller mass per unit volume than the heavy mixed solution by centrifugation. ,
A method for producing a zinc-containing solid, comprising a dehydration step of obtaining a zinc-containing solid by dehydrating the light mixture. The method for producing a zinc-containing solid according to claim 1, further comprising:
After the mixing step and before the separation step,
A method for producing a zinc-containing solid, which comprises an adjusting step for adjusting the pH of the mixed solution. The method for producing a zinc-containing solid according to claim 1 or 2.
A method for producing a zinc-containing solid, which is subjected to centrifugation by a decanter type centrifuge in the separation step. The method for producing a zinc-containing solid according to claim 3.
A method for producing a zinc-containing solid, which applies a centrifugal force of 100 G or more and 500 G or less in the separation step. The method for producing a zinc-containing solid according to any one of claims 1 to 4, further comprising:
The process of dehydrating the heavy mixture and
A method for producing a zinc-containing solid, comprising a step of obtaining the molten fly ash by melting the solid obtained by dehydrating the heavy mixture.

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