JP4144024B2 - Boron separation and removal method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention mainly relates to a method for separating and removing boron such as coal ash.
[0002]
[Prior art]
Incineration ash such as coal ash generated from a thermal power plant and ash generated after incineration of waste contains high alkali components and toxic heavy metals. Must be landfilled.
[0003]
Here, incineration ash, especially plant-derived coal ash, contains a large amount of boron, and such boron is a useful element used in the fields of semiconductor materials and glass industry, but has a health hazard. It is a harmful element that causes it, and is designated as a hazardous heavy metal along with chromium, cadmium and nickel.
[0004]
Therefore, even after completion of landfill disposal, exudate water from incineration ash prevents such high alkali components and harmful heavy metals from leaching from coal ash and leaching into the groundwater system and diffusing into the environment. Collected in the drainage drainage laid on the bottom of the disposal site, and pumped up and monitored the exudate, and for exudate that has no problem, discharge it to rivers, etc. after appropriate pH treatment, etc. Yes.
[0005]
[Problems to be solved by the invention]
On the other hand, in a situation where it becomes increasingly difficult to secure a waste disposal site, it is also desired to effectively use a large amount of incinerated ash as a recycled material.
[0006]
However, a method for separating and removing incinerated ash, especially boron contained in coal ash, from the incinerated ash has not yet been established. At present, it cannot be used as recycled material.
[0007]
The present invention has been made in consideration of the above-mentioned circumstances, and it is possible to use incineration ash as a recycling material by separating and removing incineration ash, in particular, boron, which is abundant in coal ash, from the incineration ash. An object of the present invention is to provide a method for separating and removing boron.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the method for separating and removing boron according to the present invention provides a treatment object by adding a dilute hydrochloric acid solution to boron-containing coal ash as described in claim 1 and in the treatment object. The boron ash contained in the coal ash is eluted into the dilute hydrochloric acid solution by bringing the coal ash and the dilute hydrochloric acid solution into contact with each other. Solid-liquid separation is performed on the separated processing solids, and the processing liquid is further solid-liquid separated, and the solid content is dehydrated for waste treatment, while the processing solids are rinsed with water and washed. The dilute hydrochloric acid solution and the boron remaining in the treated solid are removed, and then the solid content remaining after rinsing is dehydrated.
[0009]
Further, the boron separation and removal method according to the present invention is a recycling material obtained by dehydrating the solid content remaining after rinsing and washing.
[0010]
In the method for separating and removing boron according to the present invention, first, an acidic solution is added to a boron-containing substance such as coal ash to obtain a treatment object, and the boron-containing substance and the acidic solution in the treatment object are obtained. Touch each other.
[0011]
If it does in this way, boron contained in a boron content substance will elute in an acidic solution promptly.
[0012]
For example, it is conceivable that the object to be treated is charged with a boron-containing substance in a treatment tank and an acidic solution is added in such a state.
[0013]
In order to bring the boron-containing substance and the acidic solution in the object to be treated into contact with each other, the boron-containing substance is related to the above-described addition form. For example, the boron-containing substance injected into the treatment tank is sprinkled with the acidic solution. A method of infiltrating the acidic solution into the contained material and a method of adding a large amount of the acidic solution into the treatment tank into which the boron-containing substance has been added and then stirring and mixing the inside of the treatment tank are conceivable. That is, the addition referred to in the present invention is arbitrary regardless of the amount thereof, and the contact method is arbitrary such as infiltration, stirring and mixing.
[0015]
Next, the object to be treated is solid-liquid separated into a treatment liquid from which boron has been eluted and a treatment solid from which boron has been separated and removed. For example, a known flocculant may be used for solid-liquid separation.
[0016]
Here, about the processing liquid produced by solid-liquid separation, this is further solid-liquid separated, the solid content is dehydrated, and waste processing is carried out. In such solid-liquid separation, it is desirable to coagulate and precipitate in an alkaline environment so that as much boron as possible is concentrated in the solid content.
[0017]
On the other hand, the treated solid material generated by the solid-liquid separation is rinsed with water to remove the acidic solution and boron remaining in the treated solid material, and the solid content remaining after the rinse is removed. Dehydrated.
[0018]
Here, if the solid content remaining after the rinsing and washing is dehydrated to be recycled materials, the coal ash can be effectively used and the amount of waste can be greatly reduced.
In the present invention, the boron-containing substance means coal ash containing boron, and the acidic solution means a dilute hydrochloric acid solution.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a method for separating and removing boron according to the present invention will be described below with reference to the accompanying drawings. Note that components that are substantially the same as those of the prior art are assigned the same reference numerals, and descriptions thereof are omitted.
[0020]
FIG. 1 is a flowchart showing a processing procedure of a boron separation and removal method according to this embodiment. As can be seen from the figure, in the method for separating and removing boron according to the present embodiment, first, a dilute hydrochloric acid solution, which is an acidic solution, is added to coal ash, which is a boron-containing substance, to obtain a treatment object, and the treatment object The coal ash therein and the dilute hydrochloric acid solution are brought into contact with each other (step 101).
[0021]
In this way, boron contained in the coal ash is immediately eluted in the dilute hydrochloric acid solution, and about 80% of the boron initially contained in the coal ash is eluted in the dilute hydrochloric acid solution. Can do.
[0022]
For example, the coal ash may be appropriately carried out from a thermal power plant.
[0023]
For example, coal ash is charged into the treatment tank and the diluted hydrochloric acid solution is added in this state. Moreover, the coal ash and the dilute hydrochloric acid solution in the object to be treated can be brought into contact with each other by being added to a treatment tank constituted by a mixer or the like and stirred and mixed in such a state.
[0024]
In the treatment tank, it is desirable to maintain the pH around 4.
[0025]
Next, the processing object is subjected to solid-liquid separation into a processing liquid from which boron is eluted and a processing solid from which boron has been separated and removed (step 102). In order to perform the solid-liquid separation, for example, a known flocculant may be added to the treatment tank, and the supernatant liquid may be used as the treatment liquid, and the aggregated precipitate may be treated solid matter.
[0026]
Next, the processing liquid generated by the solid-liquid separation is further subjected to solid-liquid separation (step 103), and then the solid content is dehydrated (step 104). Process (step 105).
[0027]
Note that dilute hydrochloric acid may be added to the water generated in the dehydration process in step 104 and refluxed as a dilute hydrochloric acid solution to be added to the treatment tank.
[0028]
On the other hand, the treated solid material generated by the solid-liquid separation is rinsed with water to remove dilute hydrochloric acid and boron remaining in the gaps in the treated solid material (step 106).
[0029]
In such a step, the remaining about 10% of boron is removed. Although a slight amount of boron is still contained in the treated solid material, such boron is hardly eluted from the treated solid material after being eluted in the dilute hydrochloric acid solution. do not do. As described above, the boron removed by the rinsing cleaning is boron remaining in the gaps in the treated solid, and is not newly eluted boron.
[0030]
Next, the used washing water is subjected to water treatment in the same manner as in Steps 103 to 105 to perform solid-liquid separation. The liquid separated into solid and liquid is reused as washing water, the solid content is disposed of as waste (step 107), and the solid content remaining after rinsing is dehydrated to be recycled (step 108). .
[0031]
The used washing water may be refluxed to the diluted hydrochloric acid solution in Step 101. If it does in this way, the fresh water addition amount mentioned above can be saved.
[0032]
As described above, according to the boron separation and removal method according to the present embodiment, a dilute hydrochloric acid solution, which is an acidic solution, is added to coal ash, which is a boron-containing substance, to obtain a treatment object, and in the treatment object By bringing the coal ash and dilute hydrochloric acid solution into contact with each other by stirring and mixing, it becomes possible to elute boron contained in the coal ash to about 80% in the dilute hydrochloric acid solution.
[0033]
Further, according to the boron separation and removal method according to the present embodiment, the object to be treated is solid-liquid separated into a treatment liquid from which boron is eluted and a treatment solid from which boron has been separated and removed, and the solid-liquid separation results. The solid content was further separated into solid and liquid, and the solid content was dehydrated, and the dehydrated solid content was treated as waste. It becomes possible to concentrate considerably, and the amount of industrial waste can be greatly reduced.
[0034]
Further, according to the method for separating and removing boron according to the present embodiment, the treatment solid matter generated by the solid-liquid separation is rinsed with water so as to remove dilute hydrochloric acid and boron remaining in the treatment solid matter. Therefore, if the solid content remaining after rinsing and washing is dehydrated, it can be effectively used as various civil engineering and building materials such as embankment materials, landfill materials, and backfill materials as recycled materials.
[0035]
That is, after boron is eluted in dilute hydrochloric acid, boron hardly elutes from the treated solid, so that the solid content remaining after rinsing and cleaning does not elute boron, and the environmental standards can be sufficiently cleared. Further, by bringing coal ash into contact with dilute hydrochloric acid solution, not only boron but also other toxic heavy metals can be eluted into dilute hydrochloric acid solution and removed from the coal ash, so that there is no problem as a recycled material. In addition, high alkali components such as Ca, Na, K, and Mg are also eluted from the coal ash. However, since the alkali components are eluted from the coal ash to neutralize with the dilute hydrochloric acid solution added first, there is no problem. Does not occur.
[0036]
Moreover, since the landfill material etc. as a recycling material are detoxified as mentioned above, it becomes possible to use the landfill immediately for the use of a green space etc., for example after completion of landfill.
[0037]
Although not specifically mentioned in the present embodiment, if the dilute hydrochloric acid and boron remaining in the gap between the treated solids cannot be sufficiently removed only by the rinsing cleaning in step 106, they are contained in the solid content remaining after the rinsing cleaning. What is necessary is just to repeat the above-mentioned rinse washing | cleaning suitably, adding makeup water suitably as needed until the quantity of boron falls below an environmental standard.
[0038]
Further, in the present embodiment, the contents until the production of the recycled material is described, but after dehydrating the solid content remaining after the rinsing and washing, it is not necessarily used as the recycled material. It does not exclude the composition of landfill disposal.
[0039]
Even in such a configuration, boron and other harmful heavy metals are not eluted from the solid content disposed of in landfill, and the pH is almost neutral, so that it can be used immediately for various purposes after landfill is completed. It becomes possible.
[0040]
【The invention's effect】
As described above, according to the method for separating and removing boron according to the present invention, a dilute hydrochloric acid solution is added to coal ash containing boron to obtain a treatment object, and the coal ash and the dilute hydrochloric acid solution in the treatment object. Are brought into contact with each other, boron contained in the coal ash can be eluted into the dilute hydrochloric acid solution .
[0041]
[Brief description of the drawings]
FIG. 1 is a flowchart showing a processing procedure of a method for separating and removing boron according to the present embodiment.

Claims (2)

The boron contained in the coal ash by contacting the dilute hydrochloric acid solution and the coal ash of the processing object in each other along with a dilute hydrochloric acid solution was added to the processing object in the coal ash containing boron Elution into a dilute hydrochloric acid solution , followed by solid-liquid separation of the treatment object into a treatment liquid from which the boron has been eluted and a treatment solid from which the boron has been separated and removed, and the treatment liquid is further separated into solid and liquid. The treated solid is rinsed with water to remove the dilute hydrochloric acid solution and the boron remaining in the treated solid, and then the solid remaining after the rinse is washed. A method for separating and removing boron, which comprises dehydrating the material.   The method for separating and removing boron according to claim 1, wherein the solid content remaining after the rinsing and washing is dehydrated to obtain a recycled material.

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