KR20150094925A - A method of manufacturing raw material for stainless steel using stainless neutalized sludge - Google Patents

Abstract

The present invention relates to a method for producing a raw material for stainless steel using stainless neutralized sludge increasing content of nickel (Ni) and removing harmful anoins (for example, F-, NO3-, SO42-). According to one embodiment of the present invention, the method for producing a raw material for stainless steel using stainless neutralized sludge comprises the steps of: water washing stainless neutralized sludge; removing an [S] ingredient among the sludge; applying HCL to a sludge solution where the [S] ingredient is removed to acid-dissolve; solid-liquid separating the acid-dissolved solution and the non-dissolved sludge through a filtering apparatus; inputting a neutralizing agent to the separated acid-dissolved solution to neutralize; firing and crushing a filtered material to generate powder; and agglomerating the generated powder.

Description

Technical Field [0001] The present invention relates to a method for producing a stainless steel raw material using a stainless steel neutralized sludge,

The present invention relates to a method of manufacturing a stainless steel raw material by using a stainless neutralized sludge, and more particularly, to selectively dissolve the water treatment neutralization sludge in the stainless steel pickling plants nickel (Ni) while increasing the content of harmful ion (e.g., F ^-, NO ₃ ^- , SO ₄ ^2-, and the like) is removed from the stainless steel sludge.

In a stainless steel pickling plant, pickling is carried out using sulfuric acid (H ₂ SO ₄ ) or a mixed acid of sulfuric acid (H ₂ SO ₄ ) and hydrofluoric acid (HF). In this pickling process, iron (Fe) Chromium (Cr) and nickel (Ni) are dissolved in the acid to generate waste acid, and then the waste acid is neutralized with sodium hydroxide (NaOH) and calcium hydroxide (Ca (OH) 2) to generate stainless neutralized sludge.

Since the concentration of nickel (Ni) contained in such stainless steel neutralized sludge is too low, it is considered that it is not economical to recycle the stainless neutralized sludge. Since stainless steel neutralized sludge contains harmful anions such as F ^- , NO ₃ ^- , and SO ₄ ^{2 -} contained in the acid tax, it is possible to remove NOx, HF, SOx, etc. during the heat treatment to be recycled as a stainless steel raw material. It was considered that environmental problems were caused. Therefore, stainless steel neutralized sludge can not be recycled and the entire amount is being landfilled.

Meanwhile, there has been proposed a method of separating and recycling an acid and a metal by reacting a waste acid with an organic solvent using a solvent extraction technique (see Japanese Patent Application Laid-Open No. 1985-206481, US Patent No. 4,565,675, etc.) There is a problem that the installation cost of the equipment and the expensive solvent cost are low and the economical efficiency is low. In addition, although a method of treating Fe, Ni, Cr and the like contained in the waste acid by varying the pH and the type of neutralizing agent has been proposed (see Korean Patent Laid-Open Publication No. 2000-0013354) (F ^- , NO ₃ ^- , SO ₄ ^{2 -,} etc.) contained in the separation of the sludge, and the concentration of the anion in the filtrate F ^- reprocessing problems, lowered recovery rate, and the like. In addition, a method of separating metal ions according to pH by adding a slag eluent to the spent acid has been proposed (Korean Patent Laid-Open Publication No. 2003-0052320). However, this method requires a lot of equipment investment, lowered processing speed, And the like.

Thus, the neutralized sludge is washed with water and hydrochloric acid to dissolve the acid, and the acid solution and the un-dissolved sludge are separated by solid-liquid separation. Then, the neutralizing agent is added to the separated solution containing Fe and Ni, (Korean Patent No. 10-0813579), which is obtained by drying, calcining, pulverizing and bulking. However, in the application of Korean Patent No. 10-0813579, there is a disadvantage that the pH range of hydrochloric acid is limited in dissolving the neutralized sludge by the [S] and [F] components contained in the stainless neutralized sludge.

Japanese Laid-Open Patent Publication No. 1985-206481 U.S. Patent No. 4,565,675 Korean Patent Publication No. 2000-0013354 Korean Patent Publication No. 2003-0052320 Korean Patent No. 10-0813579

The present invention relates to a method for producing a stainless steel raw material using stainless steel neutralized sludge which economically produces a raw material for producing a stainless steel by recycling the entire amount of stainless steel neutralized sludge that is buried due to environmental problems and improves the actual recovery rate of Ni, to provide.

Particularly, by removing the harmful substances [S] and [F] separately from the process, it is possible to improve the quality of the recycled stainless steel raw material and to recover the valuable metals such as [Fe], [Cr] and [Ni] A method for producing a stainless steel raw material using stainless steel neutralized sludge which can be smoothly performed.

The method for producing a stainless steel raw material using stainless steel neutralized sludge according to an embodiment of the present invention includes the steps of: (a) preparing a stainless steel neutralized sludge produced by a pickling process of stainless steel until the nitric acid ion (NO ₃ ^- ) is 0.1 wt% Washing the neutralized sludge with water; (b) adding water at least two times the weight of the washed sludge, mixing and uniformly stirring an aqueous alkali solution having a pH of 13 or more, and filtering the generated precipitate to remove the [S] component in the sludge; (c) adding sulfuric acid (HCl) to the sludge solution from which the [S] component has been removed, and dissolving it in an acid solution (acid dissolution) (d) solid-liquid separation (solid-liquid separation) of the acid solution and the un-dissolved sludge through a filter; (e) neutralizing the solution to pH 9.0 to 12.5 by adding a neutralizing agent to the separated solution; (f) filtering and washing the neutralized sludge with water, and firing and pulverizing the filtrate to produce powder; And (g) agglomerating the resulting powder.

In particular, the method further comprises a step (b-1) of removing the [F] component in the sludge by filtering the fluoride generated by adding the fluorine scavenger between the steps (b) and (c).

In the step (b-1), the fluoride scavenger is characterized by using calcium hydroxide (Ca (OH) ₂ ) and an inorganic compound chelate compound.

The firing in the step (e) is performed at a temperature of 100 ° C to 1000 ° C.

The bulking in the step (f) is characterized by being carried out by pelletizing, briquetting or compacting.

According to the embodiment of the present invention, when [Fe], [Cr] and [Ni] components in the neutralized sludge are dissolved in the acid solution in an ionic state by separating and removing the components [S] and [F] The pH range of the acid solution can be applied to a wider range than in the prior art, thereby facilitating the process.

Further, since the step of separately removing the [S] component contained in the neutralized sludge is further carried out, it is possible to prevent the release of SOx which is a noxious gas during the heat treatment of the sludge. Especially, when the neutralized sludge is recycled and used for stainless steel It is possible to inhibit the recycled neutralized sludge from acting as an influx source of S, which is an impurity component.

1 is a flowchart showing a method of manufacturing a stainless steel raw material using stainless steel neutralized sludge according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It will be apparent to those skilled in the art that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, It is provided to let you know.

1 is a flowchart showing a method of manufacturing a stainless steel raw material using stainless steel neutralized sludge according to an embodiment of the present invention.

As shown in FIG. 1, a method of manufacturing a stainless steel raw material using stainless steel neutralized sludge according to an embodiment of the present invention includes (a) washing stainless steel neutralized sludge, (b) removing [S] (C) dissolving the acid in the sludge solution, (d) solid-liquid separating the acid solution and the un-dissolved sludge, (e) neutralizing the acid solution, (f) filtering the neutralized sludge Calcining and then pulverizing, and (g) agglomerating the pulverized powder. Particularly, the step (b) further includes a step (b-1) of removing the [F] component in the sludge.

First, the stainless steel neutralized sludge is produced by a neutralization reaction as shown in the following reaction formula (1).

[Reaction Scheme 1]

_{(Fe, Ni) SO 4 +} (Fe, Ni) F 2 + (Fe, Ni) (NO 3) 2 + 3Ca (OH) 2 + (Fe, Cr) 2 (SO 4) 3 + (Fe, Cr) F ₃ + (Fe, Cr) (NO ₃ ) ₃ + 6 Ca (OH) ₂

→ 2 (Fe, Ni) ( OH) 2 + 2 (Fe, Cr) (OH) 3 + 4CaSO 4 + 2.5Ca (NO 3) 2 + 2.5CaF 2

Metal ions such as Fe ^{2 +} , Fe ^{2 +,} and Fe ^{3 +} and Cr ^{3 +} , which exist as divalent ions, dissociate with anions such as SO ₄ ^{2 -} , F ^- , NO ^{3 -} Through the neutralization reaction, metal ions are precipitated as hydroxides and neutral salts are formed. Of the compounds produced by the neutralization reaction, all compounds except Ca (NO ₃ ) ₂ are not soluble in water and precipitate and become sludge. Since Ca (NO ₃ ) ₂ is soluble in theory, it can not be included in the sludge, but when the precipitated reaction sludge is filtered, it is included in the moisture in the filtrate and partially incorporated into the sludge. When the sludge containing NO ^{3 -} is heat-treated, it is preferable to remove the sludge as low as possible because NO x is discharged. F ^- theoretically precipitates in the form of CaF ₂ , but can also be precipitated in the form of Fe (OH) F, Cr (OH) ₂ F, and the like. The heat treatment of the sludge containing F ^- desorbs HF as much as possible. SO ₄ ^{2 -} precipitates in the form of gypsum, but acts as a source of SOx emissions during the heat treatment of SO ₄ ^{2 -} containing sludge. In particular, since the impurity component of stainless steel may be the source of S, .

Therefore, nitrate ions (NO ₃ ^- ), sulfate ions (SO ₄ ^{2 -} ) and fluorine ions (F ^- ) contained in the stainless neutralized sludge are sequentially removed.

First, stainless steel neutralized sludge is washed with water until the nitric acid ion (NO ₃ ^- ) in the stainless neutralized sludge produced in the pickling process of the stainless steel becomes 0.1 wt% or less (step a)

Since NO ₃ ^- ions in the stainless steel neutralized sludge are dissolved in the form of Ca (NO ₃ ) _{2 in} the liquid phase, it is possible to remove NO ₃ ^{- in} the sludge by adding water to the sludge and washing it. Such a method of washing with water includes a repeated washing method in which water is added to the sludge, the water is added to the sludge, the water is added again, and the resultant is filtered, a method in which water is passed through the sludge in the sludge, There are various methods such as sedimentation of post sludge and warming of water. The concentration of NO ₃ ^- ions in the sludge after washing is to be 0.1 wt% or less. If the concentration of NO ₃ ^- ions in the sludge after washing is not more than 0.1 wt%, the NO ₃ ^- is further reduced in the subsequent wet process so that the NO x emission is lower than the legal limit standard, and the subsequent process after the wet process This is because the nitrogen content in the wastewater is very small and does not require a separate biological nitrogen treatment.

Then, water is added twice or more of the weight of the washed sludge, and then an alkali aqueous solution having a pH of 13 or more is mixed and uniformly stirred. Then, the generated precipitate is filtered to remove the [S] component in the sludge.

In step (b), more than twice the weight of the sludge is added to the washed sludge in order to improve the reactivity of the sludge. Then, in order to remove the [S] component, an alkali aqueous solution having a pH of 13 or more (preferably, a pH of 14.0 or more, more preferably, a pH of 14.5 or more) is mixed to extract the [S] component.

In such a high pH range, the amount of sulfur oxides dissolved in the sludge becomes very large, while the amount of other basic oxides dissolve is small. In addition, the solubility of neutral oxides and acidic oxides increases, S] component can be selectively dissolved and removed.

In order to selectively remove the [F] component from the sludge in which the [S] component has been removed, the fluoride generated by adding the fluoride removing agent is filtered. (Step b-1)

At this time, calcium fluoride (Ca (OH) ₂ ) and an inorganic compound chelate compound are used together. In this process, calcium hydroxide (Ca (OH) ₂ ) is bound to fluorine (F) in the form of CaF ₂ , but CaF ₂ has a solubility of 10 to 15 ppm, which makes it difficult to satisfy the discharge water quality standards. The solubility can be easily influenced by ions or the like. Therefore, it is preferable to use an inorganic compound-based chelate compound as the fluorine removing agent.

(HCl) is added to the sludge solution in which the [NO ₃ ], [S] and [F] components are sequentially removed.

At this time, when the pH is more than 4.5, only a part of Fe and Ni are dissolved and dissolved in (Fe, Ni) Cl ₂ , and a considerable amount of Ni ions are not dissolved, which adversely affects the recovery rate of final Ni (see the following reaction formula 2); (ii) When the pH is 1.0 to 4.5 or less, most of Fe and Ni present as divalent ions are almost completely dissolved, so that most of Ni can be recovered.

On the other hand, when the pH is lower than 1.0, CaF ₂ and CaSO ₄ are decomposed to CaCl ₂ , and all metals are in an ionic state, so that selective metal recovery is impossible (see Scheme 4 below). However, in the present invention, since the components [S] and [F] are previously removed before step (c), even when the pH is less than 1.0, it is possible to recover more Fe and Ni present as divalent ions It is.

[Reaction Scheme 2]

{(Fe, Ni) (OH ) 2} + {(Fe, Cr) (OH) 3} + {CaSO 4} + Ca (NO 3) 2 + {CaF 2} + 0.8HCl →

{0.6 (Fe, Ni) ( OH) 2} + 0.4 (Fe, Ni) Cl 2 + {(Fe, Cr) (OH) 3} + {CaSO 4} + Ca (NO 3) 2 + {CaF 2}

[Reaction Scheme 3]

{(Fe, Ni) (OH) ₂ } + {(Fe, Cr) (OH) ₃ } + {CaSO ₄ } + Ca (NO ₃ ) ₂ + {CaF ₂ }

_{(Fe, Ni) Cl 2 +} {0.1 (Fe, Cr) Cl 3} + {0.9 (Fe, Cr) (OH) 3} + {CaSO 4} + Ca (NO 3) 2 + {CaF 2}

[Reaction Scheme 4]

{(Fe, Ni) (OH ) 2} + {(Fe, Cr) (OH) 3} + {CaSO 4} + Ca (NO 3) 2 + {CaF 2} + 5HCl →

_{(Fe, Ni) SO 4 +} 3/2 (Fe, Cr) F 3 + 1/3 (Fe, Cr) Cl 3 + CaCl 2 + Ca (NO 3) 2 + CaCl 2

In the above Reaction Schemes 2 to 4, the symbol {} indicates a solid state.

Particularly, in order to describe the characteristics of the present invention in the above-mentioned Reaction Schemes 2 to 4, {CaSO ₄ }, Ca (NO ₃ ) ₂ and {CaF ₂ } in _{b-1) [NO 3]} , because it removes the [S] and _{[F] {CaSO 4},} Ca (NO 3) _2, and a _{2} the amount of CaF insufficient level.

Therefore, when the acid is dissolved while maintaining the pH within the range of 4.5 or less, the Fe and Ni can be dissolved in an acid and recovered in the form of an ion. That is, when acid dissolution is carried out in such a pH range, most of Ni, Fe and Cr are dissolved in the ion phase and the remainder is converted into sludge.

In this way, most of the Ni, Fe and Cr are dissolved in the ionic phase and the remaining solution is sludge, and the acid solution and the un-dissolved sludge are subjected to solid-liquid separation (solid-liquid separation) through a filter. (Step d)

Then, a neutralizing agent is added to the separated acid solution to neutralize the solution to pH 9.0 to 12.5. (Step e)

In addition, a neutralizing agent (for example, sodium hydroxide, calcium hydroxide, sodium carbonate or the like) is added to an Fe, Ni and Cl aqueous solution to adjust the pH to 9.0 to reach an equivalent point (for example, molar amount of slaked- Raising to 12.5 gives the reaction shown in Scheme 5 below.

[Reaction Scheme 5]

_{(Fe, Ni) Cl 2 +} Ca (OH) 2 → (Fe, Ni) (OH) 2 + CaCl 2

(Fe, Ni) Cl ₂ + ₂ NaOH → (Fe, Ni) (OH) ₂ + 2 NaCl

(Fe, Ni) Cl ₂ + Na ₂ CO ₃ → (Fe, Ni) CO ₃ + 2 NaCl

When the neutralization pH is less than 9.0, the re-precipitation of Ni is not easy and the recovery rate (Ni loss) occurs. The pH of 12.5 corresponds to the saturation solubility of the slaked lime.

Since CaCl ₂ and NaCl are water-soluble salts in the reaction scheme 5, they are removed by neutralization and filtration, thereby obtaining sludges containing (Fe, Ni) (OH) ₂ and (Fe, Ni) CO ₃ . When the sludge containing (Fe, Ni) (OH) ₂ and (Fe, Ni) CO ₃ is dried and fired at a firing temperature of 100 to 1000 ° C and pulverized, (Step f) < RTI ID = 0.0 >

When the powder is put into a furnace such as a melting furnace, it is discharged as dust and must be agglomerated. (Step g)

The agglomeration can be carried out by pelletizing, briquetting or compacting while adding a small amount of water and a binder. Examples of the binder used in the agglomeration include cement binders (3CaOSiO2, 2CaOSiO2, 3CaOAl2O3, 4CaOAl2O3), polyvinyl alcohol (PVA), molasses, starch and the like.

The agglomerated product can be used not only as a raw material for melting stainless steel but also as a raw material for ferronickel smelting.

Hereinafter, the present invention will be described by way of examples.

2,500 g of stainless steel neutralized sludge containing 0.5% by weight of nitric acid ions (NO 3 ^- ) was washed with 10 liters of water, 100 g of washed sludge was weighed into a beaker, 400 g of water was added and stirred until the sludge was loosened.

Then, the alkali such that a pH above 13 in the loose sludge solution (e.g., NaOH, Ca (OH) _2, Na ₂ CO _3, etc.) is added, and then calcium hydroxide (Ca (OH) ₂₎ and the chelates based inorganic compound with fluorine scavenger Based compound were sequentially added.

After that, different amounts of hydrochloric acid were added and the pH of solution was varied from 0 to 8 to obtain each aqueous solution. This aqueous solution was filtered, and the neutralized product was obtained by adding alkali to the filtered aqueous solution until the equivalence point (pH 9.0 or higher at which the pH increase sharply increased) was changed by varying the type of neutralizing agent, and the neutralized product was dried at 100 ° C.

The contents of cations and anions were determined by inductively coupled plasma (ICP) and ion chromatography. Also, the recovery rate of Ni was determined by the following formula (1), and the results are shown in Table 1 below.

[Equation 1]

Ni recovery rate = [initial sludge input amount (100 g) before sludge x Ni content in sludge (wt%)] / [recovery amount produced by neutralization / neutralization / filtrate water / drying x recovery amount in water] x 100

[Table 1] Table 1 shows the results of the experiments of Examples 1 to 2 and Comparative Examples 1 to 11 of the present invention for the removal of nitric acid, the removal of [S], the removal of [F] , The content of Ni and the like, and the recovery rate of Ni.

division Whether nitric acid can be washed or not [S]
Whether to remove [F]
Whether to remove Hydrochloric acid
input
Maintenance pH Neutralization
pH Component (wt%) Fe Cr Ni SO ₄ F NO ₃ Al +
Si Ni
Recovery rate Comparative Example 1 X X X - - 20.4 5.8 2.2 8.9 16.8 0.5 8.8 0% Comparative Example 2 X X X 2.3 11.8 42.1 0.6 16.8 0.3 0.3 0.12 0.05 91% Comparative Example 3 ○ X X 5.5 11.8 36.2 0.05 37 0.1 0.2 0.03 or less 0.15 40% Comparative Example 4 ○ X X 0.5 11.9 26.2 3.5 7.2 5.4 11.3 0.03 or less 0.08 98% Comparative Example 5 ○ X X 0 12.5 22.3 4.5 2.5 7.7 15.5 0.03 or less 0.05 98% Comparative Example 6 ○ X X 2.2 8.4 38.4 0.5 18.8 0.2 0.2 0.03 or less 0.02 65% Comparative Example 7 ○ X X 3.5 12.3 38.4 0.23 22.1 0.3 0.3 0.03 or less 0.14 82% Comparative Example 8 ○ X X 2.2 11.9 43.2 0.6 17.1 0.3 0.4 0.03 or less 0.14 90% Comparative Example 9 ○ X X 1.8 11.8 38.3 1.2 11.3 0.6 0.7 0.03 or less 0.11 97% Comparative Example 10 ○ X X 2.3 9.5 36.4 0.6 14.2 0.3 0.9 0.03 or less 0.08 91% Comparative Example 11 ○ X X 2.6 11.0 42.8 0.6 17.3 0.2 0.8 0.03 or less 0.04 88% Inventory 1 ○ ○ ○ 0.9 11.8 39.7 0.9 15.3 0.1
Below 0.1 or less 0.03 or less 0.07 98% Inventory 2 ○ ○ ○ 0.5 12.1 40.7 1.1 16.2 0.1 or less 0.1 or less 0.03 or less 0.06 98%

As can be seen from Table 1, the nitrate ion (NO ₃ ^-) washing with water for the removal of (水洗), [S] removed, and [F] removing, the manufacture year, the sample was dried for stainless neutralized sludge without the process of neutralization, such as is It is difficult to recycle since harmful anions such as F-, NO3- and SO42- are not effectively removed. (Comparative Example 1)

A sample not subjected to a washing process for removing nitrate ions (NO 3 -) is not preferable due to environmental problems due to NO x emitted during the heat treatment. (Comparative Example 2)

When the pH of the solution is more than 4.5, the Ni component to be recovered is not sufficiently dissolved and the Ni recovery rate is significantly lowered. (Comparative Example 3)

When the pH is lowered to 4.5 or less, the recovery rate of Ni is increased. However, when the pH is lowered too much and becomes less than 1.0, F ^- and SO ₄ ^{2 -} are re-introduced into the acid solution and the recovered compound, (Comparative Example 4 and Comparative Example 5)

When the neutralization pH is less than 9.0, the precipitation of Ni can not be carried out and the recovery of Ni is decreased. (Comparative Example 6)

On the other hand, when the acid solution pH is maintained at 1.0 to 4.5, the recovery rate of Ni is increased, and F ^- and SO ₄ ^{2 -} are prevented from re ^- entering into the acid solution and recovered compound, (Comparative Example 7 to Comparative Example 11) However, in order to prevent the re ^- entry of F ^- and SO ₄ ^{2 -} while knowing that the recovery rate of Ni tends to increase as the acid solution pH is lowered, ~ 4.5. ≪ / RTI >

However, when [S] and [F] were removed before the acid treatment, the recovery of Ni was found to be increased again without F ^- and SO ₄ ^{2 -} Honor 1 and Honor 2)

Although the present invention has been described with reference to the accompanying drawings and the preferred embodiments described above, the present invention is not limited thereto but is limited by the following claims. Accordingly, those skilled in the art will appreciate that various modifications and changes may be made thereto without departing from the spirit of the following claims.

Claims (5)

(a) washing stainless steel neutralized sludge with nitric acid ions (NO ₃ ^- ) in a stainless steel neutralized sludge generated in a pickling process of stainless steel to 0.1 wt% or less;
(b) adding water at least two times the weight of the washed sludge, mixing and uniformly stirring an aqueous alkali solution having a pH of 13 or more, and filtering the generated precipitate to remove the [S] component in the sludge;
(c) adding sulfuric acid (HCl) to the sludge solution from which the [S] component has been removed, and dissolving it in an acid solution (acid dissolution)
(d) solid-liquid separation (solid-liquid separation) of the acid solution and the un-dissolved sludge through a filter;
(e) neutralizing the solution to pH 9.0 to 12.5 by adding a neutralizing agent to the separated solution;
(f) filtering and washing the neutralized sludge with water, and firing and pulverizing the filtrate to produce powder; And
(g) agglomerating the resulting powder. The method of producing a stainless steel raw material using the stainless neutralized sludge.
The method according to claim 1,
Further comprising the step (b-1) of removing the [F] component in the sludge by filtering a fluoride generated by adding a fluorine scavenger between the step (b) and the step (c) to remove a component of the stainless steel raw material Gt;
The method of claim 2,
Wherein the fluoride scavenger is used in combination with calcium hydroxide (Ca (OH) ₂ ) and an inorganic compound chelate compound in the step (b-1).
The method according to claim 1,
Wherein the firing in the step (e) is performed at a temperature of 100 ° C to 1000 ° C.
The method according to claim 1,
Characterized in that the agglomeration in step (f) is carried out by pelletizing, briquetting or compacting. 2. A method of producing a stainless steel raw material using stainless steel neutralized sludge according to claim 1, Way.

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