WO2019231004A1

WO2019231004A1 - Zero-liquid discharge process

Info

Publication number: WO2019231004A1
Application number: PCT/KR2018/006110
Authority: WO
Inventors: 박영민; 김택훈; 정명진
Original assignee: 주식회사 영풍
Priority date: 2018-05-28
Filing date: 2018-05-29
Publication date: 2019-12-05
Also published as: KR20190135268A; KR102063246B1

Abstract

Disclosed is a zero-liquid discharge process comprising the steps of: pretreating sulfuric acid wastewater containing heavy metal components to precipitate and remove the heavy metal components; preparing gypsum by adding calcium carbonate to the pretreated sulfuric acid wastewater; neutralizing the remaining process liquid after the gypsum is isolated; removing fluorine from the neutralized process liquid; removing chlorine from the process liquid from which the fluorine has been removed; and using the process liquid from which the chlorine has been removed to clean a sulphurous acid gas.

Description

2019/231004 1 »（： 1 ^ 1 {2018/006110

【Specification】

[Name of invention]

Zero discharge process

Technical Field

The present invention relates to a zero discharge process. More specifically, the present invention relates to a non-discharge process that can be operated without discharge by utilizing sulfuric acid wastewater generated from by-products such as a smelting process in the manufacture of gypsum and reusing the filtrate process liquid.

[Technique to become background of invention]

Korean Patent No. 10-1484575 discloses a method of treating sulfuric acid waste liquid containing sulfuric acid and heavy metal components by forming gypsum as a by-product. Specifically, a method of pretreating sulfuric acid waste liquid to remove heavy metals and forming gypsum is disclosed, but does not disclose any method for environmentally friendly treatment of remaining filtrate after gypsum production.

The remaining filtrate was produced and separated from the sulfuric acid waste solution,

Since heavy metals such as 1¾, 0 (3, etc. are contained, if they are discharged as they are, they can cause big environmental problems. Therefore, it is urgent to develop a process that can be operated without discharge of the filtrate containing heavy metals.

[Content of invention]

Problem to be solved

Sulfuric acid wastewater generated from by-products such as smelting process is used for the production of gypsum, and the process liquid as a filtrate is reused to provide a non-discharge process that can be operated without discharge.

[Measures of problem]

The non-discharge process according to an embodiment of the present invention comprises the steps of pretreating sulfuric acid wastewater containing a heavy metal component to remove and remove the heavy metal component; Preparing gypsum by adding calcium carbonate to the pretreated sulfuric acid wastewater; Neutralizing the remaining process solution after the gypsum is separated; Removing fluorine from the neutralized process solution; Chlorine is removed from the fluorine-free process solution _. Removing; And the process solution from which the chlorine is removed 2019/231004 1 »（： 1 ^ 1 {2018/006110

It includes a step used for cleaning.

In the step of depositing and removing the heavy metal component, ¾ 0 ₃ and 犯 Ye may be added to the spent sulfuric acid wastewater to co-precipitate the heavy metal.

The neutralizing of the process solution may include: neutralizing by adding hydrated lime to the remaining process liquid after the gypsum is separated, and removing the tidal gypsum generated by adding the hydrated lime; desulfurizing by adding sulfuric acid to the neutralized process solution. Doing; And neutralizing by adding slaked lime to the de-neutralized process solution, and removing tidal gypsum generated by adding slaked lime. In the step of neutralizing the sulfuric acid, after the sulfuric acid is added, alumina may be added to remove fluorine, and iron chloride may be added to remove arsenic.

The removing of fluorine may include firstly removing fluorine by introducing a lime and a polymer material into the neutralized process solution; Injecting aluminum ions into the process solution from which fluorine is first removed; And removing residual fluorine from the process solution into which the aluminum ions are added using cerium resin.

Injecting the aluminum ions may have a reaction temperature of 33 to 381 :.

After the step of removing the fluorine, the concentration of fluorine in the process solution in weight%,

It may be:

The removing of chlorine may include: electrolyzing the process solution from which the fluorine is removed to oxidize chlorine ions in the process solution to a chlorine gas state; Converting the chlorine gas into hypochlorous acid by reacting with water in the process solution; And phase change of the hypochlorous acid to a chlorine gas state by maintaining the process solution at less than 2.0, and then discharging it in water.

After removing the chlorine, the chlorine concentration of the process solution may be 30% by weight, or less.

After the step of discharging in the water, the step of neutralizing by introducing the lime into the process solution from which the chlorine has been removed. 2019/231004 1 »（： 1 ^ 1 {2018/006110

In the step of neutralizing the slaked lime into the process solution, the neutralized process solution may be 6.5 to 8.5.

After the step of depositing and removing the heavy metal component, the step of mixing the wastewater generated in the smelting process to the pretreated sulfuric acid wastewater; may further comprise a. Before the precipitation of the heavy metal component, the step of washing the sulfurous acid gas generated in the roasting process with an alkaline solution; may further include.

In utilizing the process liquid to the cleaning of sulfur dioxide, some of the chlorine is removed, the process solution is to branch can be used as makeup water in the slag pit (3 _§山1 :).

【Effects of the Invention】

According to the non-discharge process according to an embodiment of the present invention, after the sulfuric acid wastewater generated from the by-products such as the smelting process and the like is used for the production of gypsum, it is possible to operate the process without discharge by reusing the process liquid as the filtrate. Accordingly, eco-friendly plant facilities can be operated.

[Brief Description of Drawings]

1 is a view showing a schematic diagram of a non-discharge process according to an embodiment of the present invention.

2 is a view showing a fluorine removal step of the process solution in a non-discharge process according to an embodiment of the present invention.

[Specific contents to carry out invention]

Terms such as first, second, and third are used to describe various parts, components, regions, layers, and / or sections, but are not limited to these. These terms are only used to distinguish one part, component, region, layer or section from another part, component, region, layer or section. Accordingly, the first portion, component, region, layer or section described below may be referred to as the second portion, component, region, layer or section without departing from the scope of the present invention.

The terminology used herein is for reference only to specific embodiments and is not intended to limit the invention. As used herein, the singular forms “a,” “an,” and “the” include plural forms as well, unless the phrases clearly indicate the opposite. As used in the specification, the meaning of “comprising” means certain characteristics, 2019/231004 1 »（： 1 ^ 1 {2018/006110

It specifies areas, integers, steps, actions, elements and / or components and does not exclude the presence or addition of other features, areas, integers, steps, actions, elements and / or components.

When a portion is referred to as being "on" or "on" another portion, it may be directly on or on the other portion or may be accompanied by another portion in between. In contrast, if you mention that a part is "just above" another part, no other part is intervened.

Although not defined otherwise, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. Commonly defined terms used are additionally interpreted to have a meaning consistent with the related technical literature and the presently disclosed contents, and are not interpreted in an ideal or very formal sense unless defined.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily practice. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

Zero discharge process

In a non-discharge process according to an embodiment of the present invention, as shown in FIG. 1, pretreatment of sulfuric acid wastewater containing a heavy metal component to remove streaks of heavy metal components is prepared by putting calcium carbonate into the pretreated sulfuric acid wastewater. Neutralizing the remaining process solution after the gypsum is separated, removing fluorine from the neutralized process solution, removing chlorine from the fluorine-free process solution, and using the chlorine-free process solution for cleaning sulfur dioxide. It includes. First, in the step of removing the heavy metal components, the heavy metal components contained in the sulfuric acid wastewater are removed by pretreating the sulfuric acid wastewater generated as a by-product of the smelting process. Specifically, in the step of precipitating and removing the heavy metal component, the heavy metal can be co-precipitated by adding (： 0 ₃ and 抑) to the sulfuric acid wastewater. Heavy metals removed in the pretreatment process may be Pb 0 (1, show (, ¾), etc.

Accordingly, the reaction may be performed by the following reaction formula. 2019/231004 1 »（： 1 ^ 1 {2018/006110

[Scheme]

丄 + ¾ ¥ ₃

[Scheme]

+ 犯₂ 30 ₄ 1 + ¾!

[Scheme 3] 2 他況 + 0 (保 0 ₄ 0 (13 + 此必 0 ₄ + ¾!

In the case of 1¾ contained in the sulfuric acid wastewater, the reaction with ¾) ₃ takes place and can be removed from the sulfuric acid wastewater. In the case of sulfuric acid wastewater, the reaction with [and 0 _(in the case _of 1, occurs and co-precipitation can be removed from sulfuric acid wastewater.

Next, in the step of preparing gypsum, calcium carbonate ⁽ : 030) ₃ ) is added to the pretreated sulfuric acid wastewater. The production of gypsum is achieved by the reaction of sulfuric acid wastewater with calcium carbonate. This can remove 30 ₄ ions in the sulfuric acid wastewater, produce high-quality product gypsum, and suppress the generation of waste. Accordingly, the reaction can be made by the following reaction scheme.

[Scheme 4] ¾30 ₄ +。 Size. + ¾0 0 _¾ 30 ₄ · 2¾0 1 + ¥ ₂ !

The gypsum production reaction can take place at 45-50 ^° 0 and about 3.0.

Next, in the step of neutralizing the process solution, the process solution in the acidic solution state is neutralized with alkali. Specifically, the step of neutralizing the process solution is neutralized by adding hydrated lime (0 Li ₂ ) to the remaining process solution after the gypsum is separated, removing the tidal gypsum generated by the addition of hydrated lime, sulfuric acid in the neutralized process solution It may include the step of de-neutralizing by inputting the neutralized by the addition of hydrated lime to the de-neutralized process solution, the step of removing the gypsum generated by the input of hydrated lime.

In the step of adding hydrated lime to the pretreated process solution, gypsum is separated and hydrated lime can be added to the remaining process solution to neutralize it, and the resulting tidal gypsum can be separated and removed. Å11, 0 (1, 01, metals such as Pb), and ₄ ,, II ions can be removed from the process solution.

Accordingly, the reaction can be made by the following reaction scheme.

[Scheme 5] ¾ 엤 ₄ (301) + ◦3 (0 ₂ (3 (1) 0350 ₄

[Scheme 6] ¾30 ₄ (3 (1) 代： 3 ((¾) 2 (3 (1) + 2¾0 (1)

_{11 (0} 0 2 (3} ) +0330 4 · 2¾0 (

Scheme 7 ¾ 엤 ₄ (3 (1) 此_& (0} 1) ₂ + 2¾0 (1) ® 2019/231004 1 »(： 1 ^ 1 {2018/006110

_{1¾ (011) 2 (3)} 4 330 4 · 2¾0 (3)

Equation 8 0130 ₄ (3 <¾) <3_ ₂ (3 (1) + 2¾0 (1)

(： 11_ ₂ (3) ^^ 042 2¾0 (3)

[Scheme 9] 0 wire 30 ₄ (明 _ ₂ ) + 2¾0 (1)

_{0 (1 (0} 0 2} (3) 30 4 · 2¾0 (3)

[Scheme 10] 0 ₄ (明) _ ₂ (3 (1) + 2¾0 (1)

_ ₂ (0 ₄ - 2¾0 (

Scheme 11

1 _§ (0 ratio _{_{2 (3)祀330 4 -}} 2¾0)

[Scheme 12] 630 ₄ (3 (1)) urine (0 ₂ (3 (1) + 2¾0 (1)

_{? 6 (011) 2 (3} )此330 4 · 2¾0 (

[Scheme 13] 2 ^ (3 (!) + ◦k (010 ₂ (3 (1) ® ◦)) + 2¾0 (1)

[Scheme]

As shown in the above reaction scheme, the addition of slaked lime may neutralize the process solution with the removal of heavy metals and 80 ₄ ions.

In the step of neutralizing by adding sulfuric acid, sulfuric acid may be added to the neutralized process solution to change the process solution into a weakly acidic state. Specifically, after neutralizing the process solution, alumina sulfate (hour ₂ ( ₄ ) 3) may be added to remove fluorine, and iron chloride may be added to remove residual traces of arsenic.

Accordingly, the reaction may be performed by the following reaction formula.

[Scheme]

The precipitated system can be separated and removed by the reaction of fluorine ions and alumina sulfate. On the other hand, the reverse reaction of the reaction scheme 6 to 12 may occur by reverse neutralization.

In the step of neutralizing by adding the slaked lime to the de-neutralized process solution, it is possible to neutralize the slaked lime by adding it again to the de-neutralized process solution. Metals such as 1 ^, 06, 01, ¾ and 30 ₄ II ions can be removed from the process solution.

The reaction of Schemes 5 to 14 may be made again.

Next, in the step of removing fluorine, as shown in FIG. 2019/231004 1 »（： 1 ^ 1 {2018/006110

Eliminate fluoride present. The fluorine content in the process solution after the pretreatment and the multi-stage neutralization process may be 26% by weight or less. Through the step of removing fluorine, the content of fluorine can be lowered to less than 1 如，. Specifically, the step of removing fluorine may include firstly removing fluorine by adding calcium hydroxide and a polymer material to the neutralized process solution, firstly adding aluminum ions to the process solution from which fluorine is removed, and cerium resin. It may include the step of removing the residual fluorine from the process solution into which the aluminum ion is added.

In the first step of removing fluorine, the fluorine component may be removed due to some precipitation by adding slaked lime ratio 3 (0 ² ₂ ) and a polymer material to the neutralized process solution. The polymeric material may be an anionic precipitater.

In the step of adding aluminum ions, aluminum ions (hour ³⁺ ) are first added to the fluorine-free process solution to co-precipitate fluorine ions, and fluorine in the form of a combined fluorine present in the process solution. It can cause the bonds of compounds to break.

Accordingly, ¾ reaction according to the following reaction formula can be made.

[Scheme 16] Poetry ³⁺ + 3 Poetic |

[Reaction Scheme 17] 4 ³ + + 3011 one +? One hour (010 ₃ ·

[Reaction Scheme 18] 13 ^4- + 4 hours ^31- + 3¾0 ¾¾） ₃ + 4 hours ⁺ + 3 ^

Coprecipitation as in Scheme 16 and Scheme 17 may be made, and as shown in Scheme 18, the binding of the bond fluorine may be broken. Specifically, the reaction in which the fluorine bond is broken by aluminum ions is

It can be activated from above. More specifically,

The reaction can take place at 3.0, 35 to 38 for about 4 hours.

The cerium resin may be used to adsorb and remove the residual fluorine ions in the process solution into the process solution into which aluminum is added. This can be done in a fluorine adsorption tower.

Accordingly, the reaction may be performed by the following reaction formula.

[Scheme 19] ◦ Ke + 06 ^ + 0 『

The reaction scheme 19 may be a reaction at 3.5 or less. With this 2019/231004 1 »（： 1 ^ 1 {2018/006110

Through the same process, the fluorine content in the process solution may be 2 wt% or less in weight%. On the other hand, after the reaction with the cerium resin, the suspended solids are removed from the fluorine adsorption tower, ion is desorbed by injecting ions, and then one is discharged from the fluorine saw tower. Can be played.

Next, in the step of removing chlorine, chlorine components present in the process solution are removed. By removing chlorine, the content of chlorine can be lowered to 30¾）, or less. Specifically, the step of removing chlorine includes the steps of electrolyzing a process solution from which fluorine is removed to oxidize chlorine ions in the process solution to a chlorine gas state, converting chlorine gas into hypochlorous acid by reacting with water in the process solution, and Maintaining the process solution at less than 2.0 to convert the hypochlorous acid into a chlorine gas state, and may include the step of discharging in water.

In the step of electrolyzing the process solution, the fluorine-free process solution can be electrolyzed and converted to chlorine gas ratio1 ₂ by oxidizing chlorine ions (<: 厂) present in the process solution. Chlorine gas can react with water in the process solution to convert hypochlorous acid 0¾).

Accordingly, the reaction may be performed by the following reaction formula.

Scheme 20 01 ₂

Subsequently, hypochlorous acid can be phase-changed to a chlorine gas state by keeping the process liquid at less than 2.0. The reaction in which hypochlorous acid phase changes to a chlorine gas state may be a reverse reaction of Scheme 20. The removal of chlorine can then be completed by abandoning the chlorine gas and draining it from the process liquid. Through this process, the chlorine content in the process solution may be less than or equal to 30% by weight).

Next, the step of neutralizing by adding the lime to the process solution from which chlorine has been removed. The chlorine-free process solution is acidic, so it can be neutralized and removed to make it reusable by removing sulfate ions. Neutralized

6.5 to 8.5.

Next, in the step of using the process solution for cleaning sulfurous acid gas, the process solution from which all heavy metals, fluorine and chlorine have been removed is circulated and reused. In other words, 2019/231004 1 »（： 1 ^ 1 {2018/006110

A process liquid from which heavy metals, fluorine and chlorine have been removed can be used for the cleaning process of sulfurous acid gas (X ₂ ). Based on FIG. 1, the process solution may be reused as a weak acid supplement. Sulfurous acid gas is generated in the roasting process, and the sulfurous acid gas and

You can prevent it from being released into the atmosphere.

Specifically, in the step of using the process solution for the cleaning of sulfurous acid gas, some of the process solution from which chlorine has been removed are branched to make slag pits (for 3

Can be reused as supplemental water.

As described above, in the non-discharge process according to an embodiment of the present invention, sulfuric acid wastewater generated from by-products such as a smelting process may be used to manufacture gypsum, and then the process may be operated by circulating the filtrate without discharge. . Accordingly, it is possible to operate eco-friendly plant facilities. This is enough to remove the fluorine and chlorine components in the process solution, the process can be operated without discharge.

The non-discharge process according to an embodiment of the present invention may further include washing the sulfurous acid gas generated in the roasting process with an alkaline solution before the step of depositing and removing heavy metal components. After removing the sulfurous acid gas (3¾) generated in the roasting process with sulfuric acid in the crude acid process, it can be washed with alkaline solution so that the remaining trace amount of sulfurous acid gas and 此 are not released into the atmosphere.

The gypsum generated in the step of washing the sulfurous acid gas with an alkaline solution may be prepared and the remaining process solution may be neutralized with the remaining process solution after preparing gypsum from the pretreated sulfuric acid wastewater. The alkaline solution may include calcium carbonate.

In addition, after the step of depositing and removing the heavy metal component, it may further comprise the step of mixing the wastewater generated in the smelting process to the pretreated sulfuric acid wastewater. The wastewater generated in the smelting process may be, for example, waste acid generated from the zinc residue treatment process or iron waste water. Such waste acid or waste water can be put together in a non-discharge process and treated together.

Hereinafter, specific examples of the present invention will be described. However, the following examples 2019/231004 1 »（： 1 ^ 1 {2018/006110

The present invention is not limited to the following examples, only specific examples of the present invention.

Example

1) Operation of discharge-free process

Sulfuric acid wastewater containing a heavy metal component according to the non-discharge process according to an embodiment of the present invention

And pretreatment through the addition of%, calcium carbonate was added to the process solution from which the heavy metal was removed to prepare gypsum and then separated. Thereafter, waste acid and indium wastewater were added to the process solution in which the gypsum was separated and mixed.

Sintered lime was first neutralized by adding lime to the process solution, and sulfuric acid was added to neutralize it, and then slaked lime was added to neutralize it. In reverse neutralization, alumina and iron chloride were added to the process solution to remove fluorine and arsenic.

After the neutralization of the process solution, hydrated lime and a polymer were added to remove fluorine. Then, aluminum ions were added thereto, followed by removal of residual fluorine in the process solution using cerium resin. After addition of aluminum ions, the reaction temperature was maintained at 381 :.

After the electrolysis of the process solution after the removal of fluorine, the process solution was kept at 1.81. Through this, the generated chlorine gas was given up and discharged from the water. Sintered lime was added to the process solution after the removal of chlorine to neutralize it, and the generated tides were separated and removed. The neutralized process solution was about 7.0. It was added to neutralize the process solution with sulfur dioxide (et ₂₎ replacement of the cleaning process, and some by the branch was used as makeup water in the slag pit (greater _§ 1)).

2) Component measurement at each step

The process solution was measured at each step, and heavy metal components such as 1x1, ¾, 0 (1) were measured. And its content was measured. The results are shown in Table 1 below.

Table 1

2019/231004 1 »(： 1 ^ 1 {2018/006110

① refers to sulfuric acid wastewater before pretreatment, ② refers to process solution after pretreatment and separation of gypsum production. ③ means 此 waste acid / indium ½ waste water, ④ means process liquid mixed with 공정 waste acid / indium waste water.

⑤ means the process liquid after the first neutralization, and ⑥ means the process liquid after the second neutralization. ⑦ means process solution after fluorine removal, and ⑧ means process solution after chlorine removal. ⑨ means the process solution after neutralization by adding slaked lime to the process solution from which chlorine is removed.

3) Verification of no discharge process

In general, the content of fluorine ions and chlorine ions is the most important item in water quality standards for reuse of process liquids in smelter processes. This is because the quality of the product is affected during the smelting process. The content standards of 1 out, heavy metal ions, including the content of fluorine ions and chlorine ions are shown in Table 2 below.

[Table 2]

In Table 2, the non-discharge process treated water is heavy metal, according to one embodiment of the present invention. 2019/231004 1 »（： 1 ^ 1 {2018/006110

It means the process liquid which neutralized after removal of fluorine and chlorine.

As can be seen from the contents of fluorine ions and chlorine ions, 1, heavy metal ions in ⑨ of Table 1 and the contents of fluorine ions and chlorine ions, 1 出, heavy metal ions in the non-discharge process water of Table 2, It can be seen that the content of heavy metal components such as 1 出, 1 ^, 1¾, 0 (1, etc., and □ all satisfy the reusability criterion, that is, the process can be operated without discharge.

The present invention is not limited to the above embodiments and / or embodiments, but may be manufactured in various forms, and a person of ordinary skill in the art to which the present invention pertains may change the technical spirit or essential features of the present invention. It will be appreciated that it can be practiced in other specific forms without doing so. Therefore, it is to be understood that the embodiments and / or embodiments described above are illustrative in all respects and not restrictive.

Claims

2019/231004 1 »（： 1 ^ 1 {2018/006110

[Claim]

[Claim 11

Pretreating sulfuric acid wastewater containing a heavy metal component to remove and remove the heavy metal component;

Preparing gypsum by adding calcium carbonate to the pretreated sulfuric acid wastewater;

Neutralizing the remaining process solution after the gypsum is separated;

Removing fluorine from the neutralized process solution;

Removing chlorine from the fluorine-free process solution; And using the process solution from which the chlorine has been removed to wash the sulfurous acid gas.

[Claim 2]

The method of claim 1,

In the step of removing and removing the heavy metal component,

A non-discharge step of coprecipitation removal of the heavy metal by adding ¥ ₃ and 此況 to the sulfuric acid wastewater.

[Claim 3]

The method of claim 1,

Neutralizing the process solution,

Neutralizing by adding slaked lime to the remaining process solution after the gypsum is separated, and removing the gypsum generated by the slaked lime;

De-neutralizing by adding sulfuric acid to the neutralized process solution; And

And neutralizing the hydrated lime by injecting the hydrated lime into the de-neutralized process solution, and removing the crude tide generated by the addition of the lime.

[Claim 4]

According to claim 13,

In the step of neutralizing by adding the sulfuric acid,

After the addition of sulfuric acid, alumina-free is a process in which alumina sulfate is added, fluorine is removed, and iron chloride is added to remove arsenic.

[Claim 5] 2019/231004 1 »（1 ^ 1 {2018/006110

The method of claim 1,

Removing the fluorine is,

Firstly removing fluorine by adding slaked lime and a polymer material to the neutralized process solution;

Injecting aluminum ions into the process solution from which fluorine is first removed; And

And removing residual fluorine from the process solution into which the aluminum ions are injected using cerium resin.

[Claim 6]

The method of claim 5,

The step of injecting the aluminum ions is a non-discharge process wherein the reaction temperature is 33 to 38 X :.

[Claim 7]

The method of claim 1,

After removing the fluorine,

Fluoride concentration of the process solution is weight percent, no discharge process less than 2 ^.

[Claim 8]

The method of claim 1,

Removing the chlorine,

Electrolyzing the process solution from which the fluorine is removed to oxidize chlorine ions in the process solution to a chlorine gas state;

Converting the chlorine gas into hypochlorous acid by reacting with water in the process solution; And

Maintaining the process solution at less than or equal to 2.0 to change the hypochlorous acid into a chlorine gas state, and then discharging it in water.

[Claim 9]

The method of claim 1,

After removing the chlorine,

The chlorine concentration of the process solution is weight percent, no discharge process less than 30 如.

[Claim 10] 2019/231004 1 »（： 1 ^ 1 {2018/006110

The method of claim 7,

After the step of discharging in water,

Neutralization by adding the lime in the process solution from which the chlorine has been removed.

[Claim 11]

The method of claim 10,

In the step of neutralizing by adding slaked lime to the process solution,

Neutralized

Zero discharge process with 6.5 to 8.5.

[Claim 12]

The method of claim 1,

After the step of removing and removing the heavy metal component,

Mixing the wastewater generated in the smelting process to the pretreated sulfuric acid wastewater;

[Claim 13]

The method of claim 1,

Before the step of removing and removing the heavy metal component,

Non-discharge step further comprising the step of washing the sulfurous acid gas generated in the roasting process with an alkaline solution.

[Claim 14]

The method of claim 1,

In the step of using the process solution for the cleaning of sulfurous acid gas,

A part of the process liquid from which the chlorine has been removed is branched so that it can be used as a conserved water of slag pits.