WO2005084837A1

WO2005084837A1 - Method for treatment of fly ash involving fixation of carbon dioxide

Info

Publication number: WO2005084837A1
Application number: PCT/JP2005/002375
Authority: WO
Inventors: Taro Aichi; Hiroshi Asada; Akiyoshi Horiuchi; Tetsuo Dohi
Original assignee: Dowa Mining Co., Ltd.
Priority date: 2004-03-03
Filing date: 2005-02-09
Publication date: 2005-09-15
Also published as: JP2005246225A

Abstract

A method for the treatment of a fly ash involving the fixation of carbon dioxide, which comprises [1] a step (washing step) of washing a fly ash in a fluid having a pulp concentration of 5 to 100 g/L, while blowing a CO2 gas into the fluid, to thereby dissolve a Ca component as Ca(HCO3)2, and [2] a step of subjecting the slurry formed in the above washing step to a solid-liquid separation, to thereby recover Ca(HCO3)2 in a solution after washing and also recover a solid component as a washing residue. The above solution after washing can be used for producing CaCO3. On the other hand, the above washing residue has a low Ca content, which results in the by-production of a Pb-containing residue having a low content of gypsum through subjecting the washing residue to the leaching with sulfuric acid, and the Pb-containing residue is useful in Pb refining. Further, the solution after the separation of the Pb-containing residue can be used as a raw material for Zn refining.

Description

Description Fly ash treatment method that also serves to fix carbon dioxide

The present invention is intended for fly ash collected from combustion exhaust gas at the time of incineration of municipal solid waste or the like, or fly ash collected from exhaust gas generated at the time of melting ash or dust during incineration or the like. This is a wet treatment method that also fixes carbon dioxide.Specifically, after a process that consumes a large amount of carbon dioxide, the C a component, pb component, gangue component, Zn component, etc. contained in the fly ash are removed. The present invention relates to a processing method for separating and recovering in a form that can be effectively used. Conventional technology

Waste from general establishments and households (referred to as “municipal waste” or “general waste”) is collected at municipal waste incineration facilities, industrial waste incineration plants, etc., and incinerated. I have. At that time, incineration ash and fly ash generated from the incinerator are deposited at the final disposal site through intermediate treatment such as chemical treatment, melting treatment, and cement kiln treatment.

However, in the intermediate treatment in the melting furnace and cement kiln, heavy metals such as Zn, pb, and Cd with high vapor pressure volatilize in the furnace and enter the exhaust gas, and then condense in the exhaust gas treatment equipment. Then, there was a problem that it became fly ash again. The fly ash contained a large amount of heavy metals such as Zn, pb, Cu, and Cd, as well as CI, Na, and Ca, and was stable including the recovery of these elements. A treatment method was required.

Various fly ash treatment methods are proposed in the following patent documents.

Patent Document 1: JP-A-7-1095333

Patent Literature 2: Japanese Patent Application Laid-Open No. H08-117177

Patent Literature 3: Japanese Patent Application Laid-Open No. H08-141459

Patent Document 4: Japanese Unexamined Patent Application Publication No. 2000-1-1103

Patent Document 5: Japanese Patent Application Laid-Open Publication No. 2000-1-3 4 8 6 2 7

Patent Document 6: Japanese Patent Application Laid-Open Publication No. 2003-16664 829 Patent Document 7: JP-A-8-36555

Patent Document 8: Japanese Patent Application Laid-Open No. 8-323231

Patent Document 9: Japanese Unexamined Patent Application Publication No. 2000-111

Patent Document 10: Japanese Patent Application Laid-Open No. 2000-2004-271

Patent Literature 11: Japanese Patent Application Laid-Open No. 200-02-111429

Patent Document 12: Japanese Patent Application Laid-Open Publication No. 2003-202015 Problem to be Solved by the Invention

It is considered that the wet treatment methods disclosed in the above patent documents are effective in separating and recovering heavy metals contained in fly ash in a stable form. These technologies focus on recovering heavy metals, and from the standpoint of effective use of Ca and effective use of gangue components, where further improvements are desired. is there.

On the other hand, as a fly ash treatment method intended to recover Zn in fly ash in the most preferable form that can be used in a wet zinc production process, a process of leaching fly ash with an aqueous hydrochloric acid solution is proposed. A processing method that employs the above-mentioned method is proposed as Japanese Patent Application No. 2003-36567706. According to this method, it is possible to recover the neutralized residue which is rich in Zn and enriched with other heavy metals and hardly contains Si and Al. This residue is highly useful as a raw material for supplying to the wet zinc production process.

However, there is a problem with this method. That is, since a liquid with a high salt concentration adheres to the obtained residue, the amount of the residue used is limited by the amount of chlorine that can be accepted in the production process. In order to avoid this limitation, a process for removing the adhering liquid is required. In addition, treatment using hydrochloric acid leaching is more expensive than sulfuric acid leaching.

On the other hand, if it is attempted to separate and recover Zn resources that can be supplied to wet zinc production using a sulfuric acid leaching process that is advantageous in terms of cost, fly ash contains a large amount of Ca, so it is not possible to obtain in the intermediate process. is the gangue residue byproducts gypsum (C a S 0 ₄₎ and contains a lot Mau. Since this residue has high Pb quality, it is desired to use it effectively for lead production. However, since it has a large gypsum content, its use as a raw material for lead production has a problem in terms of thermal energy. By the way, if carbon dioxide released into the atmosphere can be used for wet processing of fly ash and fixed by changing its form into reaction products, it can contribute to the prevention of global warming. Carbon dioxide and this varying the Ca content in Patent Document 7-1 2 forces both basically process for performing blowing of carbon dioxide in the process of fly ash are disclosed in the direct Ca C0 ₃ lees product is It is only used and consumes very little carbon dioxide. From the viewpoint of global warming prevention, a treatment method that consumes more carbon dioxide is desired.

Therefore, the present invention relates to a process for recovering heavy metals by treating fly ash,

ii) Effective use of Pb-containing gangue components,

iii) promotion of carbon dioxide fixation,

iv) Lower cost than hydrochloric acid leaching process,

The goal is to achieve these all at once. Means for solving the problem

Fly ash contains a large amount of Zn and often Pb. To use these metals effectively, it is preferable to use Zn for wet zinc smelting and Pb for lead sintering together with other gangue components. The present inventors have conducted intensive studies on the process of treating fly ash that makes it possible to use Zn and pb, and as a result, firstly, in the washing step, as much Ca as possible was dissolved in “liquid” as much as possible and separated and collected. It has been found that it is extremely advantageous to reduce the amount of Ca remaining on the solids side of the washed fly ash as much as possible.

The dissolved in a liquid in Ca content in the first washing step, a) pulp concentration of fly ash to make a very thin fly ash mixture, b) by blowing a large amount of C0 ₂ gas to the fly ash mixture once more Ca (H C0 ₃₎ the Ca C0 ₃ insoluble generating 2 by changing it to dissolve to a, it was divide is very effective.

At this time, it is necessary to blow the C0 ₂ gas in a large amount, which leads to a fixed promoting carbon dioxide. Also, since the amount of residue after washing is greatly reduced, the amount of gangue residue generated when this is treated by sulfuric acid leaching is also reduced, and the amount of gangue residue accompanying the gangue residue is reduced. Gypsum amount can be greatly reduced. Ca is calcium carbonate (Ca CO

3) and gypsum (Ca S04) can be separated and collected.

The present invention has been completed based on these findings.

That is, according to the present invention, in order to achieve the above object,

[1] fly ash by washing with write attempts blowing of CO ₂ gas in the liquid of the pulp concentration 5~1 0 0 gZL (liters), as E dissolving the Ca content as Ca (HC0 ₃₎ ₂ ( Washing process),

[2] by solid-liquid separation of the resulting slurry at the cleaning step, the recovering of Ca (HC 0 ₃₎ ² during washing after liquid, recovering the solids as the washing residue,

A method for treating fly ash, which also serves to fix carbon dioxide, is provided.

At that time, the use of C 0 ₂ gas generated in the manufacturing鍊工park steps of [1], it is possible to reduce the amount of carbon dioxide released into the atmosphere from the manufacturing鍊工field. In addition, it is desirable to perform stirring during washing.

Further, in order to treat the post-washing solution of the above [2], after the steps of [1] and [2],

[3] the step of changing the Ca (HC 03) 2 a CAC0 ₃ by adding CaO or Ca (OH) ₂ to cleaning after solution of the [2],

[4] the by solid-liquid separation and the resulting slurries in the process of [3], the step of separating and recovering the CaC 0 ₃ as a solid,

If necessary, the solution after decalcification obtained in the step [4] is returned to the step [1] and reused as a liquid for washing fly ash. A method for treating fly ash is also provided.

On the other hand, in order to treat the washing residue of [2], after the steps of [1] and [2],

[5] A step of leaching the washing residue of the above [2] with a sulfuric acid-containing aqueous solution having a pH of 1 to 3.5 to transfer Zn to the leaching solution side (sulfuric acid leaching step 1),

[6] a step of adding alkali to the leached slurry (solid-liquid mixture) of the above [5] to neutralize so that the pH becomes 3.5 to 5 (neutralization step 1);

[7] a step of recovering the Zn-containing post-solution and the P-containing residue by solid-liquid separation of the neutralized slurry of the above [6],

And a method for treating fly ash that also serves to fix carbon dioxide. In order to recover Zn and Ca S 04, after the step [1] [2] [5] [6] [7], [8] CaO or Ca was added to the post-Zn-containing solution of [7]. (OH) ₂ is added to make ρ 5 5 ~

By neutralizing to be 9, Zn compounds, the step of generating a CaS 0 ₄

(Neutralization step 2),

[9] the by solid-liquid separation of the slurry after neutralization of [8], recovering the Zn compound and CaS 0 ₄ as solid content,

And a method for treating fly ash that also serves to fix carbon dioxide.

In this case, the after-liquid obtained in the step [9] can be reused by returning it to the step [6] or [8] as [1] or [5], or as repulping water.

Further, in order to collect a ZnS 0 * -containing liquid that can be used for wet zinc production, after the steps [1] [2] [5] [6] [7] [8] [9]

[10] the by leaching with sulfuric acid-containing aqueous solution solids containing the Zn compound and CaS 0 ₄ obtained in step [9], the step of shifting the Zn leachate side (sulfuric leaching step 2) ,

[11] by slurrying the solid-liquid separation after leaching of the [10], ZnS 0 ₄ and containing perforated after solution, CaS 0 ₄ (gypsum) of the principal (ie CaS 0 ₄ 8 0 wt% 'or more free The process of collecting solids,

And a method for treating fly ash that also serves to fix carbon dioxide.

The present invention has the following advantages.

(1) Most of the Ca contained in the fly ash in large quantities will be dissolved in the liquid in the cleaning process first, so the amount of cleaning residues to be treated can be reduced.

(2) Since the Ca content of the cleaning residue is reduced, the gypsum content in the Pb-containing gangue residue obtained as a by-product can be reduced when treated by a process using sulfuric acid immersion. Therefore, the Pb-containing residue is obtained in a form that can be easily used for lead production, and recycling can be promoted.

(3) Zn contained in fly ash can be recovered in a form that can be easily used for wet zinc smelting by a treatment process using sulfuric acid immersion. Therefore, the processing cost can be reduced as compared with the case of hydrochloric acid immersion.

(4) C a in fly ash, as from the wash after liquid CAC0 _3, also from the cleaning residual渣側is Since it is separated and recovered as CaS 04, it can be effectively used for various purposes.

(5) In the washing step Ca (HC0 ₃₎ ₂ blow a large amount of C0 ₂ gas sufficient to generate write Munode, it can contribute to the fixed promoting carbon dioxide. Moreover, the C0 ₂ gas can be utilized which is discharged Cu, from manufacturing鍊工field such as Zn. Brief Description of Drawings

FIG. 1 is a flowchart showing an example of a fly ash treatment process to which the present invention is applied. Preferred embodiments of the invention

The fly ash treatment method of the present invention can be applied to various fly ash discharged from incinerators and melting furnaces of waste treatment facilities and the like, or mixed fly ash thereof. Above all, it is effective to apply to fly ash having a high Ca content of, for example, 15 to 30% by mass.

FIG. 1 shows an example of the processing flow of the present invention. [1] to [11] in FIG. 1 correspond to the steps [1] to [11] described in the claims. Hereinafter, description will be given along the steps [1] to [11]. <Process [1] (Washing process)>

First, make a fly ash mixture with a low pulp concentration. If the fly ash is agglomerated and agglomerated, as in the case where the fly ash is conditioned, it is desirable to grind it in advance. This is because if the fly ash does not become well dispersed in the liquid at the time of washing, the dissolution of Ca will not proceed easily. The liquid for washing may be water, but after the step [4], the liquid can be reused.

In the present invention, a fly ash mixture having a very low pulp concentration (PD) of 5 to 100 g / L is used as the washing ash mixture during washing. The higher the pulp concentration, the higher the apparent Ca solubility, but as a result of various experiments, it was found that the lower the pulp concentration, the more the total Ca dissolved in the washing water was more advantageous. The pulp concentration can be in the range of 0.01 to 100 g / L, but if the pulp concentration is too low, the amount of liquid to be treated by solid-liquid separation increases and it becomes uneconomical. It is better to do within the range. Practically, it is preferably from 10 to 100 g / L, and more preferably from 30 to 50 g / L.

Blown C 0 ₂ gas into the liquid. Salts such as NaCl and KC1 are contained in fly ash Since it is present, CaO, which is an alkaline component in fly ash, dissolves in a large amount beyond the solubility when no salts are present. Once dissolved Ca reacts with C0 _2, forms a non-soluble calcium carbonate CaC 0 ₃ of, for thinner pulp, calcium bicarbonate Ca (HC0 ₃₎ by continuing to introduce additional excess C0 ₂ It changes to ₂ and dissolves (see the following reaction formula).

Ca (0H) ₂ (D + C O2 (g) → CaC Οα (s) | + Η2Ό

CaC 03 (s) + C Ο2 (g) + H ₂₀ → Ca (HC 03) 2 (1)

In order to make this reaction proceed smoothly, it is desirable to stir vigorously. Bubbling by blowing C02 gas may be used. Specifically, the fly ash is dispersed in the liquid, and film mass transfer coefficient of Ca and C 0 ₂ gas in the fly ash is important that the stirring to a negligible level the liquid.

When starting the blowing of C_〇 ₂ gas, pH is stabilized at usually about 1 0 minutes. The pH value varies depending on the salt concentration depending on the type of fly ash. If the G / L ratio (ie, “volume of gas blown per minute (L) / volume of slurry (L)”) is about 1, the reaction is considered to be almost completed by treatment for about 10 minutes. It is also desirable to secure a processing time of about 60 minutes.

Specifically, GZL ratio 0.01 ~; L. 0, temperature 5 ~ 50 ° C, treatment time 10 ~: pH stable within 5 ~ 60 minutes after the start of treatment It is desirable to perform the stirring with such strength as to cause

Carbon dioxide in this step is fixed as Ca (HC0 ₃₎ _2. On the other hand, in the case of conventional processing methods disclosed in, Patent Document 7, 8, carbon dioxide remains in fixed as CaC 0 _3. Comparing the case where the same amount of fly ash of the same composition is treated, the amount of carbon dioxide fixed in the washing step of the present invention is about twice the amount fixed by the conventional method such as Patent Documents 7 and 8, The effect of fixing carbon dioxide is great. When the C0 ₂ gas generated in about manufacturing鍊工such as Cu or Zn utilized in the present process, it can contribute to reducing carbon dioxide emissions complexes.

The slurry after washing is subjected to solid-liquid separation. Since Ca (HC0 ₃₎ ₂ is dissolved in the liquid, It can be recovered as a solution after washing. In addition, the amount of cleaning residue is greatly reduced compared to the original fly ash due to the decrease in the amount of Ca.

In this process, various means can be selected, such as thickening by thickener, filter press, belt type vacuum filter, Oliver, screw counter, etc. However, care must be taken when using only a thickener, since solid-liquid separation is poor, and a large amount of Ca and salts dissolved by washing may be carried over to the solids side. In general, good results are obtained with a Phil Yuichi press.

By adding CaO or Ca (OH) ₂ in the washing after liquid to precipitate Ca and (HC 0 ₃₎ ₂ as CAC0 ₃ insoluble. It is advisable to add CaO or Ca (OH) 2 so that 11 becomes 7 to 11, preferably 9 to 10. When using Al force NaOH as a re added generated by the NaH C 0 _3, which is difficult to recover as § alkali solids because it is water soluble. Although _{_{N a 2 C 0 3 Ca C}} 03 be added can be recovered, it is difficult recovery of Na content. In this regard, when CaO or Ca (OH) 2 is added, (lime) only changes lime into calcium carbonate, so that it can be recovered as alkali solids while maintaining the effect of fixing carbon dioxide. is there.

It is desirable to control the addition amount of CaO or Ca (OH) ₂ so as not to be excessive. If added in excess, Ca dissolves in the solution, and this solution reduces the Ca dissolution rate when reused as washing water as described below. It is important that the stirring be vigorously agitated to a level where the membrane mass transfer coefficient of Ca is negligible. The treatment time may be such that the added Ca0 or Ca (0H) ₂ reacts and the pH is settled (for example, 5 to 60 minutes). The temperature may be about 10 to 50 ° C.

The step [3] obtained in CaC_〇 ₃ containing slurry was solid-liquid separation, separating and recovering CAC0 ₃ as solids. This can be used as a neutralizing agent in the production process. On the other hand, since Ca is removed from the post-solution, it can be returned to step [1] and used for washing. However, if this solution after decalcification is reused repeatedly, salts (NaCl and KC1) will be concentrated, so it is desirable to partially drain off the wastewater. Process [5] (Sulfuric acid leaching process 1)>

On the other hand, the cleaning residue obtained in the step [2] is subjected to a process of recovering a Pb-containing gangue residue usable for lead production and a Zn-containing liquid usable for wet sub-dust production. First, in step [5], repulp and sulfuric acid leaching are performed. The pulp concentration is preferably about 100 to 300 g / L before leaching. By using sulfuric acid, Zn is transferred to the leaching solution side, and Pb and gangue components are retained on the leaching residue side. However, some gangue components also migrate to the leachate side. The pH during leaching is controlled between 1 and 3.5. Increasing the acid concentration so that the pH is less than 1 does not significantly change the leaching rate of Zn. Leaching at a pH of 1.5 to 2.5 is more preferred, including economics. It is desirable that the temperature be 20 to 90 ° C and the leaching time be 30 to 120 minutes.

Process [6] (Neutralization process 1)>

Neutralization is performed following leaching. This process precipitates gangue components that have been leached once. As the neutralizing agent and NaOH, CaO, Ca (OH) 2, CaC 0 3 can be used. The pH at the time of middle-handed mouth is controlled to 3.5 to 5, preferably 3.5 to 4. Most of the Ca in the fly ash has been removed by the previous washing process, so a large amount of gypsum will not be generated in this neutralization process. The temperature can be between 20 and 90 ° C.

Process [7]>

The neutralized slurry is subjected to solid-liquid separation to recover the post-solution containing Zn and the residue containing Pb. The after-solution containing Zn can be used as a raw material for wet zinc production. Pb-containing residue includes Pb component and Si0 _2, gangue components such as AI2O3 mainly comprising pb S 0. Since this Pb-containing residue has a small amount of accompanying gypsum, it can be suitably used as a raw material for lead production.

Process [8] (Neutralization process 2)>

After solution excluding the Pb-containing residue is the [7] (Zn-containing after liquid), further pH neutralized with the liquid which had increased to 5-9 and to produce a Zn compound and CaS 0 ₄ such Zetaitashita. When the pH exceeds 9, Zn moves in the direction of redissolution. More preferably, the pH is 7 to 8. CaO or Ca (OH) ₂ can be used as a neutralizing agent. The temperature can be 20 to 90 ° C, and the reaction time can be 5 to 120 minutes. Process [9]>

The slurry after neutralization with solid-liquid separation, to recover the solids containing Zn compound and CaS 0 _4. This solid content is used as a raw material for wet zinc production by, for example, treating it in the following step [10]. The back solution can be used as [1] or [5], or returned to the process of [6] or [8] as repulp water.

The step [9] Zn compound obtained in, repulped solids containing CaS 0 _4, leaching with sulfuric acid. This transfers Zn to the leachate side in the form of ZnS O ^. No ,. The lump concentration is preferably about 100 to 100 g / L before leaching. The pH during leaching should be controlled between 0.1 and 4. The temperature can be between 20 and 90 ° C and the leaching time can be between 5 and 120 minutes.

Process [11]>

The leached slurry is subjected to solid-liquid separation to recover the post-solution containing ZnS O and the solid content of CaS C (gypsum). ZnS 0 ₄ containing after liquid can be used as an electrolyte of the wet zinc made鍊. CaS0 ₄ is available in a variety of industrial fields. Example

(Example 1)

Using A fly ash shown in Table 1, when the washing in the usual manner without this blown a C0 ₂ gas (Comparative Example), while narrowing blowing C0 ₂ gas with a thin water of fly ash concentration in accordance with the present invention For the case of washing (invention example), the solution after washing and the washing residue were respectively processed.

table 1

(A fly ash)

(Comparative example)

A Weigh 100 g of fly ash, add 3 L (liter) of distilled water to this and mix with fly ash. Got water. After this fly ash mixed water was stirred for 60 minutes, solid-liquid separation was performed using a filter to obtain a filtrate a and a solid content a. The solid a was further washed with 0.3 L of distilled water to obtain a filtrate b and a solid (hereinafter referred to as “wash residue”). Approximately 3 L of a mixture of the filtrate a and the filtrate b (referred to as “liquid after washing”) was obtained.

After the washing residue was sufficiently dried at 1 Q at 5 ° C, composition analysis was performed. The results are shown in Table 2. On the other hand, a composition analysis was also performed on the solution after washing. The results are shown in Table 3.

Next, the washed residue was repulped at a pulp concentration of 100 gZL, and adjusted to p1-1 = 2 by adding sulfuric acid. This was stirred at 30 ° C. for 60 minutes to perform sulfuric acid leaching (step [5]). Then was adjusted to pH = 4 by adding CAC0 ₃ to the treatment liquid (slurry after leaching), it was neutralized by stirring for 6 0 minutes (step [6]). The liquid temperature was 30 ° C. Thereafter, solid-liquid separation was performed (step [7]) to obtain a Zn-containing post-solution and a Pb-containing residue. Table 4 shows the analysis results of the solution containing Zn. After the Pb-containing residue was sufficiently dried at 105 ° C, the composition was analyzed. Table 5 shows the results.

Table 2

[Washing residue (Comparative Example)]

Table 3

[Solution after washing (Comparative Example)]

Table 4

[Zn-containing solution (Comparative Example)]

[Pb-containing residue (Comparative Example)]

Total Zn Pb Ca S Na K CI

Grade (mass%) 0.86 1.61 30.56 8.92 1.09 0.89 0.97

Quantity (g) 576 5 9 176 51 6 5 6 (Invention example)

100 g of fly ash A was weighed, and 30 L of water to be used repeatedly was added thereto, and 3 L of distilled water was further added to obtain mixed fly ash water. The water to be used repeatedly is defined as [30] after about 30 L of the post-solution obtained in the step [4] of Example 2 is returned as washing water each time, and after the same treatment process has already been repeated for 4 charges, This is the post-liquid obtained in step 4) (however, distilled water is used for the first charge). The mixture was stirred at 30 ° C for 60 minutes while blowing C02 gas into the mixed fly ash at a flow rate of 30 L / min. The C0 ₂ gas was used to collect the gas discharged from the neutralization step of the Zn-made鍊工field. C0 ₂ blow write Mikara 1 0 minutes and p H in less 1 3 force, changes to La 6.5, it was not thereafter most change. Reactions Ca content is changed to Ca (HC0 ₃₎ ₂ was felt that this in that not nearly completed, but the 6 0 min treatment time also serves as an aging.

The obtained slurry was subjected to solid-liquid separation with a filter to obtain a liquid after washing and a washing residue.

The above is the process [1] and the process [2].

After the washing residue was sufficiently dried at 105 ° C., composition analysis was performed. Table 6 shows the results. On the other hand, a composition analysis was also performed on the solution after washing. Table 7 shows the results.

Comparing Table 2 (Comparative Example) and Table 6 (Inventive Example), it can be seen that the amount of the generated cleaning residue in the inventive example is significantly smaller than that in the comparative example. In addition, the amount of Ca in the cleaning residue is also greatly reduced in the case of the invention example.

Also, comparing Table 3 (Comparative Example) and Table 7 (Inventive Example), in the inventive example, both the Ca amount and the Ca concentration in the solution after washing are significantly higher than those in the comparative example. This, it was diluted with fly ash mixed water, and by bubbled with C0 ₂ gas, C a indicates that that dissolved in a large amount in the wash water.

Next, as in the comparative example, the washed residue was repulped at a pulp concentration of 100 g / L, and then adjusted to pH = 2 by adding sulfuric acid. Sulfuric acid leaching was performed by stirring (step [5]). Next, CaCOa was added to the treatment liquid (the slurry after leaching) to adjust the pH to 4, and the mixture was stirred for 60 minutes to perform neutralization (step [6]). The liquid temperature was 30 ° C. Thereafter, solid-liquid separation was performed (Step [7]) to obtain a Zn-containing post-solution and a Pb-containing residue. Table 8 shows the analysis results of the solution containing Zn. After the Pb-containing residue was sufficiently dried at 105 ° C, the composition was analyzed. Table 9 shows the results. Comparing Table 4 (Comparative Example) and Table 8 (Inventive Example), in the inventive example, the Zn concentration in the liquid after Zn-containing was higher than that in the comparative example, and the C1 concentration was lower. In other words, in the invention example The resulting Zn-containing post-solution is very advantageous for use as a raw material for wet zinc production.

Further, when Table 5 (Comparative Example) and Table 9 (Inventive Example) are compared, the inventive example is higher than the comparative example of the Pb quality in the Pb-containing residue. Also, the amount of Ca was greatly reduced. In other words, the amount of gypsum accompanying the by-product Pb-containing residue is greatly reduced by using the washing residue in which most of the Ca is dissolved and removed to the liquid side in the washing step. This Pb-containing residue can be effectively used together with gangue components in powdered products.

(Example 2)

Processing the wash after liquid obtained in the washing step in the above [Inventive Example] An experiment was conducted to collect the CaC 0 _3. That C 0 ₂ in washing after liquid after cleaning by blowing gas, was added with stirring slurried lime CaO (step [3]). At that time, the pH was monitored so that the pH became 8. The consumed CaO was 140 g per 33 L of the back solution. The temperature was 30 ° C, and the reaction time was 60 minutes in consideration of the reaction delay of CaO. Since the liquid became cloudy, this slurry was subjected to solid-liquid separation (step [4]).

After the obtained solid was sufficiently dried at 105 ° C., the composition was analyzed. Table 10 shows the results. Composition analysis was also performed on the after solution (after Ca removal). Table 11 shows the results. As described above, the analyzed post-Ca-removed solution was used as described above, and at this stage, 30 de-Ca-removed solution was returned as washing water, and about 3 L of the bleed-off operation was already repeated four times. This is a solution obtained by performing the above charge, that is, a solution after removing Ca after performing five consecutive charges, and the composition fluctuation due to repetition is almost stable. Table 1 0, as can be seen from Table 1 1, the CaC 0 ₃ available in the resulting species s field from the wash after liquid quality is recovered according to the present invention. In addition, the amount of Ca dissolved in the solution after Ca removal was significantly smaller than that in the solution after washing even though Ca 0 was added, confirming that the solution can be used repeatedly as washing water. Was done. In addition, the carbon dioxide consumed in the cleaning process was consequently fixed in the form of CaCO ₃ , and an effect of reducing the amount released to the atmosphere was recognized.

Table 6

Table 7

[Liquid after washing (Invention example)]

[Zn-containing post-solution (Invention example)]

Table 9

[Pb-containing residue (Invention example)]

Table 11

[After Ca removal (Invention example)]

(Example 3)

In the [Inventive Example] of Example 1, the post-treatment liquid containing Zn obtained in the step [7] (the one in Table 8) was subjected to the treatment of the step [8] and thereafter. That is, slurried lime Ca 0 was added to the solution after the Zn content while stirring to neutralize (step [8]). At that time, the pH was monitored so that the pH became 9. The temperature was 40 ° C and the reaction time was 60 minutes. This slurry was subjected to solid-liquid separation (step [9]), and a Zn compound mainly composed of Zn◦ and CaSO ⁴ were recovered as solids. In addition, the post-solution was recovered. The liquid after this could be reused as water, for example, returned to step [1] or step [5].

Pa was repulped residue containing Zn compound and CaS 0 ₄ recovered as solids Sulfuric acid was added to the mixture to adjust the pH to 2, and the mixture was stirred at 60 ° C. for 20 minutes to perform sulfuric acid leaching (step [10]). Then solid-liquid fraction leaving the performed (step [11]), were recovered after liquid and CAS0 ₄ (gypsum) solids principal containing ZnS04. The post-solution containing ZnSO was gradely usable as a raw material for wet zinc production. On the other hand, the obtained gypsum had relatively few impurities and could be used in various fields.

Claims

The scope of the claims

1. [1] fly ash a is Do blowing C0 ₂ gas in the liquid of the pulp concentration 5 to 1 0 0 GZL by al wash, the Ca component as the step (washing E dissolving as Ca (HC0 ₃₎ ₂ ) , and

[2] by solid-liquid separation of the resulting slurry at the cleaning step, the recovering of Ca (HC 0 ₃₎ ₂ during washing after liquid, recovering the solids as the washing residue,

A method for treating fly ash that also serves to fix carbon dioxide.

2. [1] fly ash at a pulp concentration 5 to 0 0 8. / Shino liquid (: 0 _{by 2} Do blowing gas al stirred wash, dissolve the Ca content as Ca (HC0 ₃₎ ₂ Process (cleaning process), and

[2] by solid-liquid separation of the resulting slurry at the cleaning step, the recovering Ca (HC0 ₃₎ ₂ during washing after liquid, recovering the solids as the washing residue,

A method for treating fly ash that also serves to fix carbon dioxide.

3. Made鍊工the C 0 ₂ gas generated by field by using the process of [1], according to claim 1 or 2 claims to reduce the amount of carbon dioxide released into the atmosphere from Sei鍊E field Fly ash treatment method that also fixes carbon dioxide.

4. [3] The by adding CaO or Ca (OH) ₂ to cleaning after solution of [2], the step of changing of Ca (HC 0 ₃₎ ₂ in CaC 0 _3,

[4] a step of separating and collecting CaC Os as a solid content by subjecting the slurry obtained in the step [3] to solid-liquid separation,

3. The method for treating fly ash according to claim 1, wherein the method comprises:

5. The fly ash treatment according to claim 4, wherein the solution after decalcification obtained in the step [4] is returned to the step [1] and reused as a liquid for washing fly ash. Method.

6. [5] Leach the washing residue of [2] with an aqueous solution containing sulfuric acid with a pH of 1 to 3.5. Thus, the step of transferring Zn to the leaching solution side (sulfuric acid leaching step 1),

[6] pH is adjusted by adding alkali to the leached slurry (solid-liquid mixture) of [5].

Neutralization step (neutralization step 1) to be 3-5-5,

[7] By subjecting the slurry after the neutralization of the above [6] to solid-liquid separation,

A process for collecting P-containing residues,

7. [8] by pH with the addition of CaO or Ca (OH) ₂ in the Zn-containing after solution of the [7] is neutralized to be 5-9, to produce a Zn compound and CaS 0 ₄ Process (neutralization process 2),

[9] a step of recovering the Zn compound and Ca S 04 as a solid content by subjecting the slurry after the neutralization of the above [8] to solid-liquid separation,

7. The method for treating fly ash according to claim 6, comprising:

8. The fly ash treatment method according to claim 7, wherein the after-liquid obtained in the step [9] is returned to the step [1] or [5] for reuse.

9.

[10] the [9] of the Zn compound and solid content containing CaS 0 ₄ obtained by leaching with sulfuric acid-containing aqueous solution to a step, the step of Ru transitions the Zn leachate side (sulfuric leaching step 2),

[11] a step of recovering the ZnSC-containing liquid and the solid component mainly composed of CaS04 (gypsum) by solid-liquid separation of the leached slurry of the above [10];

8. The method for treating fly ash according to claim 7, comprising: