KR20050058535A - A treatment method of waste water from incineration plant - Google Patents

Abstract

The present invention relates to a method for treating wastewater containing fluorine and heavy metals discharged from an incinerator, and an object thereof is a wastewater treatment process for maintaining a fluorine concentration below environmental regulations while minimizing the use of a fluorine remover whose main component is an expensive rare earth compound. In providing.

The present invention comprises the steps of adjusting the wastewater containing heavy metals and fluorine to acidic (approximately pH: 4) using sulfuric acid; Adjusting to alkaline (approximately pH: 10.5) using slaked lime; Immobilizing the heavy metal using a heavy metal stabilizer; Using calcium alumina to adjust to neutral (approximately pH: 7) and simultaneously adding calcium chloride; Injecting a polymer flocculant; A heavy metal removal process consisting of removing sludge produced in the settling tank,

Adjusting the wastewater which has undergone the heavy metal removal process to acidic (approximately pH: 4-5) using sulfuric acid; Injecting a fluorine remover having a rare earth compound as a main component; Adjusting to neutral (approximately pH: 7) using slaked lime; Injecting a polymer flocculant; The technical subject matter is to include a fluorine removal process consisting of removing sludge produced in the settling tank.

Description

A treatment method of waste water from incineration plant

The present invention relates to a method for treating wastewater containing fluorine and heavy metals discharged from an incinerator, and more particularly, to wastewater treatment to maintain fluorine concentrations below environmental regulations while minimizing the use of fluorine removers whose main components are expensive rare earth compounds. It is about a method.

Due to industrialization and urbanization, the generation of general waste and workplace waste is on the rise, and waste disposal by incineration is indispensable due to the narrow domestic environment. As a result, an increasing number of incineration facilities are incinerated with general waste and workplace waste. In the incineration plant, many wastewaters such as wastewater, floor ash and cooling water are generated during the operation of the absorption tower to prevent secondary environmental pollutants generated during incineration. These wastewaters contain a lot of heavy metals and fluorine, which are the main factors of environmental pollution, so the wastewater must be treated in accordance with environmental standards. 1 shows a wastewater treatment process for purifying wastewater generated at the present A incineration plant. Wastewater treatment process can be divided into heavy metal removal process and fluorine removal process. The heavy metal removal process adjusts the wastewater to acidity using acid (approximately pH: 4) and alkaline (approximately pH: 10.5) using calcined lime (Ca (OH) ₂ ) and uses heavy metal capture agents such as chelate compounds. To stabilize the heavy metals, adjust neutral (approximately pH: 7) with alumina sulfate (Al ₂ (SO ₄ ) ₃ ), which controls pH and flocculates, and flocs with a polymer flocculant. Remove heavy metal deposits from the settling tank. The fluorine-containing wastewater from which heavy metals have been removed is introduced into the fluorine removal process. In order to remove fluorine, sulfuric acid is used to adjust acidity (approximately pH: 4 to 5), and a fluorine remover (HITISOL), UNI TECHNOLOGY) is added to solidify the fluorine and then neutralized using slaked lime (Ca (OH) ₂ ) to neutral (approximately pH: 7), and then the wastewater treatment sludge is removed from the settling tank and the purified wastewater is discharged.

Solidifying agents of fluorine in wastewater include Ca compounds, Al compounds, and rare earth compounds. However, Ca and Al compounds use a fluorine remover whose main component is a rare earth compound, which can be lowered to 15 ppm or less because its solubility is over 15 ppm. You must do it. Fluoride ions contained in the wastewater input to the wastewater treatment process are about 300-500ppm, and the fluorine concentration is reduced to about 150-200ppm by the heavy metal removal process. Fluorine ions in the heavy metal removal process were converted into Ca (F ₂ ), AlF ₃ , Na ₃ AlF ₆ (Crystal) by (Ca (OH) ₂ ) and alumina sulfate (Al ₂ (SO ₄ ) ₃ ) added as a pH regulator. To precipitate.

Fluorine-containing wastewater undergoing heavy metal removal process is to remove the rare earth compound as LnF ₃ by the main component fluorine remover (wherein Ln refers to rare earth elements such as La and Ce). LnF ₃ is insoluble in water and can be lowered below 15ppm. However, since the fluorine remover whose main component is a rare earth compound is expensive, a large amount of expensive fluorine remover is consumed in the wastewater treatment process.

The present invention has been made to solve the above-mentioned conventional problems, the object of the wastewater to maintain the fluorine concentration below the environmental regulation value (fluorine concentration: 15ppm) while minimizing the use of a fluorine remover whose main component is an expensive rare earth compound In providing a treatment process.

The present invention to achieve the object as described above and to perform the task for eliminating the conventional drawbacks comprises the steps of adjusting the waste water containing heavy metals and fluorine acidic (approximately pH: 4) using sulfuric acid; Adjusting to alkaline (approximately pH: 10.5) using slaked lime; Immobilizing the heavy metal using a heavy metal stabilizer; Using calcium alumina to adjust to neutral (approximately pH: 7) and simultaneously adding calcium chloride; Injecting a polymer flocculant; A heavy metal removal process consisting of removing sludge produced in the settling tank,

Adjusting the wastewater which has undergone the heavy metal removal process to acidic (approximately pH: 4-5) using sulfuric acid; Injecting a fluorine remover having a rare earth compound as a main component; Adjusting to neutral (approximately pH: 7) using slaked lime; Injecting a polymer flocculant; It characterized in that it comprises a fluorine removal process consisting of the step of removing the fish sludge in the sedimentation tank.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a flow chart of a wastewater treatment process according to the present invention, which includes a first step (1) of adjusting wastewater containing heavy metals and fluorine to acidic (approximately pH: 4) using sulfuric acid; A second step (2) of adjusting to alkaline (approximately pH: 10.5) using slaked lime; A third step (3) of immobilizing the heavy metal using a heavy metal stabilizer; A fourth step (4) of adjusting calcium to neutral (approximately pH: 7) and adding calcium chloride at the same time by using alumina; A fifth step (5) of introducing a polymer flocculant; A heavy metal removal process comprising a sixth step (6) for removing sludge produced in the settling tank,

A seventh step (7) of adjusting the wastewater which has undergone the heavy metal removal process to acidic (approximately pH: 4 to 5) using sulfuric acid; An eighth step (8) of introducing a fluorine remover having a rare earth compound as a main component; A ninth step (9) of adjusting to neutral (approximately pH: 7) using slaked lime; A tenth step (10) of introducing a polymer flocculant; It comprises a fluorine removal process consisting of an eleventh step (11) for removing the sludge produced in the sedimentation tank.

On the other hand, the slaked lime in the second step (2) and 9 step (9) is introduced at about 600-1000ppm and 300ppm with respect to the waste water source 80 m ³ / min, respectively, the reaction time is about 1 hour.

In addition, in the third step (3), the heavy metal stabilizer usually uses a chelated compound, and is introduced at about 2000 to 3000 ppm with respect to 80 m ³ / min of wastewater, and the reaction time is about 1 hour.

In addition, in the fourth step (4), alumina sulfate is introduced at about 600 to 1200 ppm with respect to 80 m ³ / min of wastewater, and the reaction time is about 1 hour. Meanwhile, in the fourth step (4), calcium chloride is added, and the action of calcium chloride is insoluble as CaF ₂ by incorporation of fluorine and CaF ₂ without significantly affecting pH. In the next step, the flocculant becomes large and precipitates in the polymer coagulant input process, so that the fluorine concentration in the heavy metal removal process is lowered to a lower value, thereby reducing the amount of fluoride remover used in the fluorine removal process.

Table 1 shows the concentration of fluorine in the sedimentation tank which is the final stage of the heavy metal removal process when the calcium chloride is added at different concentrations of alumina sulfate.

Calcium chloride dosage 0 ppm 1000 ppm 2000 ppm 3000 ppm Fluorine Concentration in Precipitation Tank of Heavy Metal Removal Process 210 ppm 78 ppm 68 ppm 60 ppm

                        TABLE 1

The initial concentration of fluorine in the wastewater treatment process was 350ppm, and the concentration of fluorine in the sedimentation tank, the final stage of the heavy metal removal process, was 210ppm when calcium chloride was not added in the alumina sulphate input. In the fluorine removal process, the fluorine concentration was removed even though the slaked lime added to adjust the pH and the alumina sulfate added as a flocculant reacted with fluorine to precipitate as CaF ₂ , AlF ₃ , Na ₃ AlF ₆ (cryolite), respectively. Is reduced. When the amount of calcium chloride was added to the alumina sulfate input process as in the present invention, fluorine concentration of 68 ppm was added when 2000 ppm of calcium chloride was added and 60 ppm was added when 3000 ppm of calcium chloride was added. Increasing the amount of calcium chloride increases the production of sludge, so the amount of calcium chloride is preferably 1000 ppm.

In addition, in the fifth step (5) and the ten step (10), the polymer flocculant is introduced at about 10 ppm and 20 ppm with respect to the waste water source 80 m ³ / min in each step, the reaction time is about 1 hour.

In addition, in the eighth step (8), the fluorine remover is added with calcium chloride, so that the fluorine concentration is lowered to about 50 to 80 ppm, and as a result, less fluorine remover is used than the conventional wastewater treatment method in which calcium chloride is not added. Comparing the amount of fluoride remover with and without the use of calcium chloride, the conventional method without calcium chloride is about 2000 ppm of fluoride remover when the reaction time of the fluorine remover is 1 hour. 15ppm or less can be set. However, when the reaction time of the fluorine remover is the same as 1 hour and 1000 ppm of calcium chloride is added in the alumina sulfate input process, the fluorine concentration can be adjusted to 15 ppm or less even if the amount of the fluorine remover is 1000 ppm. Therefore, the use of calcium chloride has the effect of reducing the amount of fluoride remover in half.

The present invention is not limited to the above-described specific preferred embodiments, and various modifications can be made by any person having ordinary skill in the art without departing from the gist of the present invention claimed in the claims. Of course, such changes will fall within the scope of the claims.

As described above, in the present invention, when calcium chloride is simultaneously added to the alumina sulfate input step of the heavy metal removal process, calcium ions are combined with fluorine to form CaF ₂ , insolubilized and co-precipitate with the introduced alumina sulfate, and then a polymer coagulant is added. In the process, flocs become larger and settle. Accordingly, fluorine ions are reduced to 50 to 80 ppm in the heavy metal removal process, thereby reducing the amount of fluorine remover used in the fluorine removal process.

1 is a conventional wastewater treatment process diagram

2 is a process chart of wastewater treatment according to the present invention.

<Description of the symbols for the main parts of the drawings>

(1 '): Step 1 (2'): Step 2

(3 ′): Step 3 (4 ′): Step 4

(5 '): Step 5 (6'): Step 6

(7 ′): 7th Step (8 ′): 8th Step

(9 '): 9th step (10'): 10th step

(11 ’): Eleventh stage

(1): first stage (2): second stage

(3): third stage (4): fourth stage

(5): 5th step (6): 6th step

(7): 7th step (8): 8th step

(9): 9th step (10): 10th step

(11): eleventh step

Claims (1)

Adjusting the wastewater containing heavy metals and fluorine to acidic (approximately pH: 4) using sulfuric acid; Adjusting to alkaline (approximately pH: 10.5) using slaked lime; Immobilizing the heavy metal using a heavy metal stabilizer; Using calcium alumina to adjust to neutral (approximately pH: 7) and simultaneously adding calcium chloride; Injecting a polymer flocculant; A heavy metal removal process consisting of removing sludge generated in the settling tank, and adjusting the wastewater which has undergone the heavy metal removal process to acidic (approximately pH: 4 to 5) using sulfuric acid; Injecting a fluorine remover having a rare earth compound as a main component; Adjusting to neutral (approximately pH: 7) using slaked lime; Injecting a polymer flocculant; A method of treating wastewater discharged from an incineration plant comprising a fluorine removal process comprising the step of removing sludge produced in the settling tank.