KR20140114200A - Treating methods of sulfuric acid lyes and apparatus - Google Patents

Abstract

The present invention relates to a method for treating sulfuric acid waste liquid and, more particularly, to a method for treating sulfuric acid waste liquid, in which purity of gypsum produced as a by-product is increased so that the gypsum may be recycled. The present invention provides a method for treating the sulfuric acid waste liquid containing sulfuric acid and heavy metals by producing gypsum as a by-product, the method being characterized by pre-treating the sulfuric acid waste liquid to remove heavy metals; and forming gypsum. The present invention produces high-purity gypsum as a by-product, thereby solving environmental problems caused by contaminated gypsum which is typically produced as a by-product and reducing costs in treatment of the contaminated gypsum.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for treating sulfuric acid,

The present invention relates to a method for treating a sulfuric acid waste solution, and more particularly, to a method for treating a sulfuric acid waste solution that can increase the purity of a gypsum produced as a by-product to be reused.

Generally, the waste plaster is generated in a large amount during the desulfurization process and phosphoric acid, hydrofluoric acid, boron, and titanium manufacturing process. Since the gypsum thus produced contains a large amount of harmful impurities in itself, it is directly used in products such as cement and gypsum board The strength and durability are deteriorated and the effect is not achieved due to the limit of the throughput.

In addition, since the particles of waste scoria contain heavy metals such as cadmium, arsenic, lead, and chromium, there is a risk of groundwater contamination when they are deposited in nature, and disposal treatment is required at a separate cost. As a result, methods have been developed to reprocess waste scraps containing heavy metals and regenerate them as high purity gypsum by lowering the heavy metal concentration to the same level as in Table 1.

division Reference purity (mg / kg) Cu 800 CD 50 Hg 2 Pb 150 As 50

Patent No. 0527177 issued to the Korea Institute of Geoscience and Mineral Resources discloses a pulverizing process in which a waste rock is put into a pulverizing machine and mixed with a ball to be crushed into particles; A cyclone process in which the crushed scum core particles are charged into a conventional cyclone apparatus to primarily separate impurities; A specific gravity selecting step of secondarily separating the impurities contained in the waste slag by selecting the waste slag from which the impurities are first separated by using a wet type separator; An ultrasonic treatment process for finely grinding the refined gypsum subjected to the secondary selection by ultrasound at 40 to 50 kHz to separate heavy metals remaining in the gypsum particles into fine particles; And separating and sorting the separated heavy metal fine particles and purified pure gypsum in a multi-mass separator.

In patent No. 4,40539 issued to LG NIKODOK Co., Ltd., the waste gypsum is picked and filtered with waste sulfuric acid to recover the gypsum components in the waste plaster, and the valuable metals in the liquid after filtration are recovered in the form of emulsions through a sulfurization process The post-filtration liquid is subjected to primary neutralization and filtration to recover the gypsum components, the post-filtration liquid is subjected to secondary neutralization and filtration to minimize the final waste, and the post-filtration liquid is subjected to wastewater treatment or pH adjustment and discharge Discloses a method for recovering a useful component in a waste rock.

In addition, in Patent No. 0597707 granted to the Korea Institute of Geoscience and Mineral Resources, in performing a sorting process for refining and recycling various foreign substances such as heavy metals contained in waste scraps, waste water is mixed with waste scum, A scrubbing step of scrubbing for a period of time; And a wet specific gravity selecting step of allowing the heavy and light mineral to be selected in the process of flowing the scrubbed raw material along with the water along the predetermined inclined surface from the upper part.

However, there is a problem in that the above methods are ineffective as a method of recycling the produced waste stones. Accordingly, a demand for a method for preventing the occurrence of waste stones in the process of treating a waste sulfuric acid solution with gypsum continues.

The present invention provides a method of converting a sulfuric acid waste solution into high-purity gypsum and treating the same.

In one aspect, the present invention provides a method for pretreating a sulfuric acid waste solution to convert it to high purity gypsum.

In one aspect, the present invention provides a method for producing high purity gypsum by treating a sulfuric acid waste liquid.

The method for treating sulfuric acid waste according to the present invention comprises

A method for treating a sulfuric acid waste solution containing sulfuric acid and a heavy metal component as a by-product, comprising the steps of pretreating the sulfuric acid waste solution with acid to remove heavy metals, and forming a gypsum using the pretreated sulfuric acid waste solution, As shown in FIG.

In the present invention, the pretreatment is performed in an acidic condition. The fact that the pretreatment is performed in an acidic condition means that pH of the sulfuric acid waste solution is maintained acidic and not converted to neutral or alkaline in the pretreatment for removing or reducing heavy metals in the sulfuric acid waste solution it means.

In the present invention, though not theoretically, the pretreatment is carried out by adding a compound which forms barium ions to a sulfuric acid waste liquid containing a transporting sludge, coprecipitating it with a heavy metal contained in the waste liquid, It is precipitated by sulfide.

In the present invention, the sulfuric acid waste solution is a waste solution containing heavy metals such as sulfuric acid and zinc (Zn), arsenic (As), lead (Pb), mercury (Hg), copper (Cu), and cadmium (Cd). The sulfuric acid waste liquid mainly occurs in the metal smelting process, but is not limited to the metal smelting process.

In the present invention, the pretreatment of the sulfuric acid waste solution is preferably performed in an acidic condition. Although it is not theoretically limited, CaCO ₃ , which is advantageous for gypsum production in terms of purity and price of raw materials, may increase in pH during the production of gypsum, resulting in elution of heavy metals or deterioration of efficiency due to decrease in solubility of CaCO ₃ . It is advantageous for the sulfuric acid waste solution to be acidic.

In the present invention, the sludge conveyed to the sulfuric acid waste liquid can be mixed and used in the pretreatment of the sulfuric acid waste liquid, and the conveyed sludge acts as a seed or growth point during the precipitation of barium sulfate, thereby improving the sedimentation efficiency.

In the present invention, in the pretreatment of the sulfuric acid waste liquid, a coagulant that coagulates so as to precipitate barium sulfate particles and metal sulfide particles in a floc form may be used. As the coagulant, a polymer coagulant, preferably an acrylic polymer coagulant, may be used .

In the present invention, the compound forming the barium ion and the compound forming the sulfur ion are added in the form of a precursor to form barium ions or sulfur ions in the waste solution. Barium chloride may be used as a compound forming barium ion in a sulfuric acid waste solution, and sodium hydrogen sulfide may be used as a compound forming sulfur ions.

The present invention, in one aspect,

A method of forming a waste solution of sulfuric acid containing sulfuric acid and a heavy metal component as a byproduct, comprising the steps of: introducing a compound forming barium ion into a sulfuric acid waste solution containing sludge conveyed to form barium sulfate; Introducing a compound forming sulfur ions to form a metal sulfide; Coagulating the barium sulfate and the metal sulfide by the coagulant to form flocs; And a step of forming a gypsum to form gypsum, and a pretreatment step of forming at least a part of the sludge which precipitates the formed flocs, and a step of producing gypsum. Each process will be described in detail.

1. Pre-processing step

Barium sulfate  Step of generating

In this step, a sludge carried in a reaction tank containing a sulfuric acid waste solution and a compound capable of forming barium ions are added to generate barium sulfate to precipitate and remove heavy metals.

In the present invention, the compound capable of forming barium ions is a precursor compound capable of forming barium ions through a chemical reaction such as dissociation, decomposition, oxidation, or reduction in a sulfuric acid waste solution, preferably barium chloride ₂ ) can be used. Barium chloride is reacted with sulfuric acid of sulfuric acid waste solution in the same manner as in the reaction formula (1) to form barium sulfate, and barium sulfate is reacted with heavy metal ions contained in the sulfuric acid waste solution, Effectively co-ordinates.

BaCl ₂ + H ₂ SO ₄ ---> BaSO ₄ ↓ + HCl (1)

Further, in order to increase the coprecipitation efficiency, it is preferable to improve contact between BaSO ₄ and lead (Pb) ions generated by stirring at high speed. In the present invention, the conveyed sludge acts as a growth point of seed particles or precipitated particles in the sediment.

Step of forming metal sulfide

In this step, heavy metal ions which are not coprecipitated by barium sulfate react with sulfur ions to form metal sulfides and remove them together with barium sulfate.

In the present invention, sulfur ions can be formed by introducing a compound such as sodium hydrosulfide (NaSH), and the formed sulfide forms a metal sulfide as shown in the following reaction formula (2), and a high solubility Nevertheless, the barium sulfate particles contained in the reaction tank are effectively co-precipitated together to remove heavy metal components. do. Preferably, Cd, Hg and the like are effectively removed during the precipitation of MeS.

Me ^{2 +} + NaSH + H ₂ O ---> MeS ↓ + Na ⁺ + OH ^- (2)

In the practice of the present invention, it is preferable that the reaction vessel is rapidly stirred so that the metal sulfide sufficiently contacts with the metal sulfide to be produced, so that the metal sulfide can effectively remove the heavy metal component.

Coagulate Flock  Forming step

In this step, coagulation of barium sulphate with the produced sulfide or coprecipitates thereof is carried out by administering a flocculant.

In the present invention, the flocculant is preferably a polymer flocculant, for example, an acrylic polymer flocculant. It is preferable that the coagulation process is carried out at a constant speed so as to prevent the coagulated particles from being unwound again.

The step of settling

In order to precipitate the generated flocs, it is preferable that the sedimentation area is widened so as to increase the sedimentation rate. In the preferred embodiment, the sedimentation tank is preferably formed in the sedimentation tank to increase the sedimentation rate.

The flocs settled in the settling tank are preferably returned to the reaction tank where at least a part of the barium sulphate is formed to improve the coprecipitation efficiency of the barium sulfate reaction tank. In addition, the remaining precipitates are discharged to chemical sludge and treated.

2. Gypsum production process

It is preferable to add calcium carbonate to the pretreated sulfuric acid waste solution as shown in the following reaction formula (3) to form the gypsum and adjust the charging rate according to the pH of the gypsum tank so as to prevent the pH from rising as the gypsum is introduced.

CaCO ₃ + H ₂ SO ₄ ---> CaSO ₄ ↓ + H ₂ O + CO ₂ ... (3)

The resulting gypsum is separated from the sedimentation tank by solid-liquid separation, transferred to a dehydration plant, dehydrated and dried, and separated into gypsum. The separated filtrate is treated with hydroxide precipitation method, and most of the acidity is removed in the gypsum production process, and the amount of alkali is greatly reduced.

The present invention, in another aspect,

There is provided a method for pretreating a sulfuric acid waste solution containing sulfuric acid and a heavy metal component to remove heavy metals and adding a compound which forms calcium ions to a pretreated waste solution of sulfuric acid to form a high purity gypsum.

The high-purity gypsum is understood to mean gypsum containing heavy metals below the regulatory level so that no additional reprocessing is required for industrial use. In the practice of the invention, the high-purity gypsum means that it contains 50 mg / kg or less of Cd, 2 mg / kg of Hg, and 150 mg / kg or less of Pb.

The present invention, in another aspect,

Reacting a sulfuric acid waste solution with barium ions to produce barium sulfate;

Forming a metal sulfide;

Agglomerating barium sulfate and sulfide to form flocs; And

And precipitating the generated flocs. The present invention also provides a pretreatment method of a sulfuric acid waste liquid.

According to another aspect of the present invention,

Sulfuric acid waste solution collection tank; A primary reaction tank into which a compound containing a transporting sludge and barium ions is introduced; A secondary reaction tank into which a compound containing sulfur ions is introduced; A slow aggregation tank into which a polymer flocculant is introduced; A settling tank in which barium sulphate and metal sulfide are flocculated, wherein at least a portion of the sludge is returned to the first reaction tank and at least a portion is disposed of as chemical sludge; A gypsum reaction tank in which gypsum is formed; A settling tank in which gypsum is deposited; And a final treatment furnace for precipitating the precipitate filtrate as a hydroxide.

In the practice of the present invention, the compound containing barium ions is barium chloride, the compound containing sulfur ions is sodium hydrogen sulfide, and in the settling tank in which the gypsum is precipitated, calcium carbonate is injected to form high purity gypsum.

In a preferred embodiment of the present invention, it is preferable that the swash plate settler uses a sludge circulating tubular swash plate settler known in Japanese Patent No. 1133316.

The method for treating sulfuric acid waste according to the present invention can solve the environmental problem caused by contaminated gypsum generated as a by-product in the prior art by producing high-purity gypsum as a by-product and reduce the cost of the treatment.

In addition, the method for treating sulfuric acid waste according to the present invention can reduce the amount of alkali used by removing the heavy metal contained in the sulfuric acid waste solution without using an alkaline neutralizing agent, and can maintain an acidic pH favorable for the gypsum production process without any additional treatment .

FIG. 1 is a flow chart of a high purity gypsum production process according to the present invention.
2 is a flow chart of a gypsum production process according to one embodiment of the prior art.
3 is a flowchart of a high-purity gypsum production process according to one embodiment of the prior art.
4 is a cross-sectional view of a pretreatment tank used in the high-purity gypsum production process according to the present invention.
5 is the solubility of the sulfide used in the present invention with respect to pH.
6 is the solubility of the lead component removed according to the present invention.

Hereinafter, the present invention will be described in detail. The following examples illustrate the invention in detail, but are intended to illustrate the invention and are not intended to limit the scope of the invention.

1, the sulfuric acid waste solution treatment process according to the present invention includes a wastewater collecting tank 1, a first reaction tank 2, a second reaction tank 3, a complete flocculation tank 4, a sludge circulating slope plate settling tank 5, a gypsum reaction tank 6, a settling tank 7, and a final treatment tank 8. Here, the primary reaction tank 2, the secondary reaction tank 3, the complete flocculation tank 4, and the sludge recirculating slope plate settling tank 5 are pretreatment processes for pretreating the sulfuric acid wastewater. The gypsum reaction tank 6, 7), and the final treatment tank 8 are gypsum production steps.

The sludge discharged from the sludge recirculating swash plate settling tank 5 is partially returned to the first reaction tank 2 through a conduit connected to the first reaction tank 2 and the remainder is disposed of as chemical sludge. In addition, the high-purity gypsum separated from the sedimentation tank 7 is separated into solid-liquid and transferred to a dewatering unit for treatment. The apparatus for disposing chemical sludge and the dewatering apparatus for gypsum can use conventional sludge treatment and dehydration drying apparatus by those skilled in the art.

The wastewater collection tank (1) is used to control the stability of the process by controlling the fluctuation of the water quality and the flow rate constantly. The sulfuric acid wastewater generated in the nonferrous smelting process is collected, stored and transferred to the first reaction tank (2).

In the first reaction tank 2, barium sulfate (BaCl.sub.2) is added and barium sulfate (BaSO.sub.4) is produced by the same reaction as in the reaction formula (1), and lead having a similar ion size is effectively coprecipitated with the precipitation of barium sulfate. The resulting barium sulphate was rapidly stirred at 180 rpm for 60 minutes for the contact reaction of lead (Pb). The sludge returned from the slope plate settler was introduced to improve the coprecipitation efficiency.

In the secondary reaction tank 3, NaSH is injected into the waste liquid containing heavy metal sulfate coprecipitated with heavy metal and heavy metals (mainly Cd, Hg, etc.) which are not co-precipitated in the first reaction tank 2. The input NaSH forms a metal sulphide which is not coprecipitated by the reaction similar to the reaction formula (2). The metal sulphide is introduced into the first reaction tank (2) even in the pH range of 1 where the metal sulphide has a high solubility, Particles are formed efficiently by using the barium sulfate particles as seeds. In the second reaction vessel (3), sodium sulfide (NaSH) is injected into the reaction metal equivalent to induce sulfide formation and rapid stirring (180 rpm) for about 30 minutes ensures that the generated sulfide sufficiently contacts with barium sulfate.

As the slow flocculation tank 4, the waste liquid containing the transport sludge, barium sulphate, metal sulfide, or coprecipitate thereof is introduced from the secondary reaction tank 3, and a polymer flocculant such as a conventional organic polymer flocculant or an inorganic polymer flocculant And the like, the particles contained in the waste liquid flocculate, and as the organic polymer flocculant, an acrylic polymer flocculant can be commercially purchased and used. In the slow flocculation tank (4), acrylic polymer flocculant is injected and it is agitated slowly (60 rpm) for 15 minutes to aggregate barium sulphate and sulfide precipitated with heavy metals.

As shown in FIG. 4, the primary reaction tank 2, the secondary reaction tank 3, and the slow aggregation tank 4 may be divided into a single reaction tank and a stirring tank, respectively. As shown in FIG. 4 (refer to Japanese Patent No. 133316), a sludge circulating swash plate settling apparatus introduced from the slow settling tank 4 is provided with a tubular swash plate on the top of the settling tank, a sludge outlet is formed in the bottom of the settling tank, Is returned to the reaction tank (2), and the remainder is discharged and processed.

In the gypsum reaction tank 6, waste liquid of strong acid from which the heavy metal components are sufficiently removed is introduced from the sludge recirculating swash plate settling tank 5 and reacted with CaCO ₃ to produce high-purity gypsum (CaSO ₄ ). At this time, the amount of calcium carbonate injected is determined by the pH of the gypsum tank 6 measured using a pH meter, and is adjusted to a pH of 2.5 or lower, preferably a pH of 2.5 The reaction is maintained.

In the settling tank 7, the generated gypsum is settled, and the settled gypsum is moved to a separate dewatering facility to obtain high-purity gypsum. In addition, the molten trace heavy metals contained in the solid-liquid separated liquid are treated by applying the hydroxide precipitation method. At this time, since most acidity is removed through the gypsum production process, only a small amount of alkali is required.

Claims (19)

A method for treating a sulfuric acid waste solution containing sulfuric acid and a heavy metal component as a byproduct of gypsum, wherein the sulfuric acid waste solution is pretreated to remove heavy metals and form gypsum. The method of treating sulfuric acid waste solution according to claim 1, wherein the pretreatment is performed in an acidic condition. The method of treating sulfuric acid waste solution according to claim 1 or 2, wherein the pretreatment is carried out by introducing a compound forming barium ion and a compound forming sulfur ion into a sulfuric acid waste liquid containing the transporting sludge. The method for treating sulfuric acid waste solution according to claim 3, wherein the polymer flocculant is further added to precipitate. The method for treating sulfuric acid waste solution according to claim 1 or 2, wherein calcium carbonate is added to the pretreated sulfuric acid waste solution to form gypsum. A method for treating a sulfuric acid waste solution containing sulfuric acid and a heavy metal component by forming gypsum as a byproduct,
Introducing a compound forming barium ion into the sulfuric acid waste liquid containing the sludge conveyed to form barium sulfate;
Introducing a compound forming sulfur ions to form a metal sulfide;
Coagulating the barium sulfate and the metal sulfide by the coagulant to form flocs; And
Forming sludge to precipitate the resulting flock, and conveying at least a portion
And a pretreatment step including a pretreatment step. 7. The method of treating sulfuric acid waste solution according to claim 6, wherein calcium carbonate is added to the pretreated sulfuric acid waste solution to form gypsum. The method according to claim 6 or 7, wherein the step of forming barium sulfate and the step of forming metal sulfide are stirred at a higher rate than the step of forming flocs. The method according to claim 6 or 7, wherein the compound forming the barium ion is barium chloride, the compound forming the sulfur ion is sodium hydrogen sulfide, or the flocculating tank is an acrylic polymer flocculant. The method for treating a sulfuric acid waste solution according to claim 6 or 7, wherein hydroxide is added to the filtrate from which the precipitated gypsum is separated. A method for pretreating a sulfuric acid waste solution containing sulfuric acid and a heavy metal component to remove heavy metals and a compound for forming calcium ions in a pretreated waste solution of sulfuric acid to form a high purity gypsum. 12. The method of claim 11, wherein the pretreatment is in acidic. The method of claim 11 or 12, wherein the calcium ion forming compound is CaCl ₂ , Ca (OH) ₂ , CaCO ₃ , CaO, or a mixture of at least one of the foregoing. The method according to claim 11 or 12, wherein the heavy metal comprises at least one of zinc (Zn), arsenic (As), lead (Pb), mercury (Hg), copper (Cu) To form a high purity gypsum. The method for forming high purity gypsum according to claim 11 or 12, wherein the sulfuric acid waste solution is pre-treated by adding a compound forming barium ion and a compound forming sulfur ion. 15. The method of forming a high purity gypsum according to claim 14, wherein the sulfuric acid waste solution is further pretreated with sludge and a flocculant. Sulfuric acid waste solution collection tank;
A primary reaction tank into which a compound which forms a carrier sludge and a barium ion is introduced into a sulfuric acid waste solution;
A secondary reaction tank into which a compound forming sulfur ions is introduced;
A slow aggregation tank into which a polymer flocculant is introduced;
A settling tank in which barium sulphate and metal sulfide are flocculated, wherein at least a portion of the sludge is returned to the first reaction tank and at least a portion is disposed of as chemical sludge;
A gypsum reaction tank in which gypsum is formed;
A settling tank in which gypsum is deposited;
A final treatment tank for precipitating the precipitate filtrate with hydroxide
Wherein the sulfuric acid-containing waste solution treatment apparatus comprises: 18. The method according to claim 17, wherein the first reaction tank into which the compound forming the barium ion is transported and the second reaction tank into which the compound forming the sulfur ion is charged is stirred at a higher rate than the slow aggregation tank into which the polymer flocculant is introduced Characterized in that the sulfuric acid waste liquid treatment device 18. The method according to claim 17, wherein the first reaction tank into which the compound forming the barium ion and the carrier sludge are charged, the secondary reaction tank into which the compound forming the sulfur ion is charged, and the slow aggregation tank into which the polymer flocculant is introduced, And a separate stirring tank is formed in the lower part of the reaction vessel.

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