WO2005092528A1

WO2005092528A1 - Method for treatment of fly ash using sulfur dioxide

Info

Publication number: WO2005092528A1
Application number: PCT/JP2005/002379
Authority: WO
Inventors: Taro Aichi; Hiroshi Asada; Hideki Yatsuduka; Akiyoshi Horiuchi; Tetsuo Dohi
Original assignee: Dowa Mining Co., Ltd.
Priority date: 2004-03-29
Filing date: 2005-02-09
Publication date: 2005-10-06
Also published as: JP4639398B2; JP2005279446A

Abstract

A method for the treatment of a fly ash which comprises a process wherein a slurry of a fly ash is reacted with SO2, to thereby dissolve Ca and Zn in the fly ash into a solution, and these elements are separated from a residue containing Pb and are recovered in the solution; and the method which further comprises a process wherein the above solution containing Ca and Zn is reacted with an oxidizing agent (for example, a gas containing oxygen) or sulfuric acid, to thereby precipitate Ca selectively and allow Zn to remain in the solution in a dissolved state, and these elements, that is, Ca and Zn are recovered separately.

Description

Description Fly ash treatment method using sulfur dioxide

The present invention is intended for fly ash collected from combustion exhaust gas at the time of incineration of municipal waste or the like, or fly ash collected from exhaust gas generated at the time of melting and processing ash and dust during incineration. The present invention relates to a wet treatment method for separating and recovering Ca, Zn, pb, gangue components and the like contained in fly ash 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 and incinerated at municipal waste incineration facilities, industrial waste incineration plants, etc. . At that time, the 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 contains a large amount of heavy metals such as Zn, pb, Cu, and Cd, as well as CI, Na, and Ca. A way was sought. Various fly ash treatment methods are proposed in the following patent documents. '

Patent Document 1 Japanese Patent Application Laid-Open No. 7-1 Q9533

Patent Document 2 Japanese Patent Application Laid-Open No. Hei 8-1 1 7 7 2 4

Patent Literature 3 Japanese Patent Application Laid-Open No. H08-14141539

Patent Literature 4 Japanese Patent Application Laid-Open No. 2000-1-111 3 2 4 2

Patent Literature 5 JP 2 Q 0 1-3 4 8 6 2 7

Patent Document 6 Japanese Patent Application Laid-open No. 2003-16664 829 Problems the invention is trying to solve

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 collect, as the neutralization residue, those which are rich in Zn and are accompanied by other heavy metals, and which hardly contain Si and A 1. This residue has a high utility value as a raw material for supplying to wet zinc production. There is a problem with this treatment method. That is, since a solution having 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, the treatment using hydrochloric acid leaching is more expensive than the case of 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₎ many including intends want. Since Pb in fly ash is collected in this gangue residue, this residue is to be used for lead production. However, since it contains a large amount of gypsum, it should be used as a raw material for lead production. There is a problem. Also, a large amount of Ca in fly ash subjected to sulfuric acid leaching increases the load on the sulfuric acid leaching step, which is not preferable.

Therefore, the present applicant has created a method in which fly ash is washed in a liquid with a very low pulp concentration to remove most of Ca by dissolving it in the washing liquid before subjecting to sulfuric acid leaching. Were proposed as Japanese Patent Application No. 2004-595984 and Japanese Patent Application No. 2004-599852. In this case, by blowing C 0 ₂ gas during cleaning it could be achieved a more effective removal of C a.

This method requires a large amount of water for cleaning, and in a factory with a small facility, The disadvantage was that it was difficult to implement.

In view of such circumstances, the present invention is a treatment process capable of efficiently recovering valent metals such as Ca, Zn or Pb from fly ash in a form that can be easily used, regardless of the size of the equipment. The purpose is to develop and provide methods that can be implemented in many existing wet treatment sites. Means for solving the problem

Where we of extensive research, S0 ₂ when treated fly ash slurry using a gas, can be recovered in the form dissolved in the same time a solution of Ca and Zn, Pb, etc. in the stage of its It has been found that the residue containing valuable metals can be separated and recovered in a low Ca grade state. Furthermore, when a simple oxidation treatment such as blowing air into the solution in which Ca and Zn are dissolved, or a treatment in which sulfuric acid is added, the sulfate of Ca (gypsum) is insoluble and the sulfate of Zn is soluble. It was found that Ca and Zn can be easily separated and recovered by using the property described above. The present invention has been completed based on such findings.

In other words,. The object, by the action of S 0 ₂ to a slurry of fly ash, dissolved Ca and Zn in carry ash into the liquid, these elements, the words Ca and Zn, the residue (e.g., Pb-containing This is achieved by a method for treating fly ash that has a step of separating it into liquid with the residue.

Here, "the action of S0 ₂ to a slurry of fly ash" is the solid component and water constituting the fly ash slurry, refers to the reaction of S0 _2.

S 0 ₂ as the fly ash slurry exerting, Na through washing, which was repulped fly ash obtained by subtracting the content of K, C1 can be used.

Here, the “repulp” refers to a solid that has been once separated by solid-liquid separation and re-mixed with a solvent mainly composed of water to form a slurry.

Furthermore, Ca separate from the residue by the action of S0 ₂ as described above, Zn-containing liquid, ie the liquid Ca and Zn are dissolved oxidizing agent (e.g., a gas containing oxygen), Oh Rui sulfate To precipitate Ca selectively and leave Zn dissolved in the liquid to separate these elements, that is, Ca and Zn. And a method for treating fly ash having a step of recovering the fly ash.

Further, the Ca, by blowing an inert gas into the Zn-containing solution, when precipitated as a tan sulfite Ca and Zn by using a degassed reaction of S 0 _2, followed by the action of sulfuric acid, Ca The present invention provides a method for treating fly ash, comprising the steps of selectively precipitating and dissolving Zn in a liquid, and separating and recovering these elements.

Further, the Ca separate from the residue by the action of S 0 ₂ as in Zn-containing liquid separated by selectively precipitate Ca and Zn-containing solution, precipitating Zn by neutralizing by adding an alkali The present invention provides a method for treating fly ash in which the separated liquid is reused as water for fly ash treatment.

The method of the present invention has the following advantages.

(1) Ca, Zn, or Pb can be separated and recovered from fly ash in a form that is industrially usable simply by reacting it with gas components such as S02 and air. Cost can be reduced by reduction.

(2) Since the Pb-containing residue separated and recovered has low Ca grade, it can be effectively used in Pb refining.

(3) Ca and Zn can be easily separated by further oxidizing the Ca- and Zn-containing liquid to be separated and recovered.

(4) Since there is no need to recycle a large amount of water, it is relatively easy to implement even small-scale factories.

Therefore, the present invention contributes to the spread of recycling processing for recovering valuable metals and gangue residues from fly ash. Brief Description of Drawings

FIG. 1 is a flowchart of a fly ash treatment process including the treatment of the present invention.

FIG. 2 is a flow chart of a fly ash treatment process including the treatment of the present invention. Preferred embodiments of the invention

The fly ash treatment method of the present invention is discharged from an incinerator or a melting furnace of a waste treatment facility or the like. It can be applied to various fly ash or mixed fly ash. Among them, it is particularly effective to apply fly ash having a relatively high Ca content of, for example, 5 to 30% by mass.

FIG. 1 shows an example of a fly ash processing flow including the processing of the present invention, and the present invention will be described below with reference to this example.

〔Washing〕

Fly ash should first be washed to remove salts, ie, elements such as Na, K, and CI. Usually, a method of dissolving salts in water by stirring the slurry mixed with water is adopted. If the fly ash is agglomerated and clumped, such as when the fly ash is conditioned, it is desirable to grind it in advance. If the pulp concentration is reduced, the effect of removing salts attached to fly ash is higher, but the wastewater treatment amount increases accordingly.If conditions are adopted to minimize costs according to the actual conditions of the equipment, Good. Generally, it can be carried out at a pulp concentration in the range of 50 to 500 g / L. The C 0 ₂ during washing has the effect of suppressing the elution of the burn them blown into the slurry one heavy metals, can also be to reduce the load in the subsequent step in the elution of C a is promoted.

The pH varies depending on the type of fly ash. The force calms down in the range of approximately 7 to 13. If you put the C 0 ₂ is about 5-7. Arbitrary pH may be adjusted by adding a mineral acid. The cleaning residence time is about 10 to 120 minutes, which is effective. However, it is generally considered economical to secure the residence time of about 60 minutes by stirring.

The slurry after washing may be separated into solid and liquid by a general method. For example, various means such as concentration by a thickener, a filter press, a belt-type vacuum filter, an Oliver, and a screw power center can be selected. However, care must be taken when only thickener is used, since solid-liquid separation becomes poor and a large amount of salts and the like dissolved by washing may be carried over to the solid content side. In general, good results are obtained with a filter-press.

[S02 processing]

In this way Na, K, fly ash content of C 1 is reduced (cleaning residue) is re pulp, referred to as "process for applying a S 0 _2" (hereinafter "S 0 ₂ process" of the present invention ). To exert S 0 ₂ The slurry of fly ash directly into the slurry S 0 ₂ The simplest way is to blow gas. Put S 0 ₂ gas into water by equipment specifications, Ru mower when the easily performed better to supply those H ₂ S0 ₃ solution corresponds to the slurry. Thus it is indirectly possible to dissolve the Ca and Zn in the fly ash be allowed to act S 0 ₂ in the solution.

The reaction in S 0 ₂ process of the present invention is basically Pb is not eluted, Ca, a reaction in which Zn is eluted, although the reaction mechanism often part unexplained, Oyo its "sulfite And the formation of sulfurous acid ”+“ reaction between sulfite and sulfurous acid ”. Sulfites Ca or Zn is CaS 0 _{_3,} ZnS 0 ₃ in the form states, but they are insoluble in pure water either, the sulfite aqueous solution having the property of Ru soluble der. That Ca (HS 0 ₃₎ ₂ and Zn (HS 0 ₃₎ ₂ is soluble, it can be recovered in dissolved form is separated from the residual component, such as P, in a liquid.

When Ca content in the form of fly ash is taken as an example the case of CaO, Scheme in S0 ₂ process of the present invention are believed to be as follows.

S 0 ₂ + CaO → CaS 03 (neutralization reaction) (1)

S 02 + H ₂ 0- H ₂ S 0 ₃ (Sulfurous acid formation reaction) · · · · (2)

CaSOa + H ₂ S0 ₃ → Ca (HS0 ₃ ) ₂ (3)

According to the inventors' experiments, the form of Ca content not only of _{_{CaO, CaSi0 3, Ca 3 (}} P 04) 2, the CaC O 3, CaS Os, in any case of CaF ₂ S O2 Elution was possible. However, the CaS 0 ₄ (gypsum) has been difficult to the child eluted with S 0 _2.

Similarly for Zn, take the case form of Zn content is Ζηθ example, it is considered to reaction scheme at S 0 ₂ process is as follows.

S02 + Zn0 → ZnS0 ₃ (neutralization reaction) (4)

S 0 ₂ + H ₂ 0 → H 2 S 0 ₃ (Sulfurous acid formation reaction) · · · (2)

_{_{ZnS Oa + H 2 S0 3 →}} Zn (HS03) 2 (5)

In S 0 ₂ treatment may be a 5 0~5 0 0 gZL about a pulp consistency of fly ash. Although thinning is advantageous in increasing the amount of Ca and Zn eluted, it also reduces efficiency and increases the burden of solid-liquid separation work. Generally, it is realistic to set the pulp concentration to about 100 to 200 gZL. SO 2 gas may be S 0 ₂ concentration using those 5-1 0 0%. S0 ₂ gas generated from the example Eba made鍊原fee is available. S 0 ₂ concentration of the not necessarily mean that the reaction is advanced difficulty Kunar low.

When blowing directly S 0 ₂ gas into the slurry, G / L ratio (i.e. "volume of the gas blown into the reaction time (L) / slurry vol (L)") is preferably set to 1 or more. As the G / L ratio increases, the stirring effect by bubbling increases, but the upper limit is limited by the capacity of the equipment. A realistic G / L ratio of about 1 to 100 is appropriate.

During the reaction, it is desirable to perform strong mechanical stirring or publishing sufficient to sufficiently diffuse S 02 into the liquid.

Whether or not the reaction by S02 has proceeded sufficiently can be determined by a change in the pH of the solution. It is desirable to continue the reaction until the pH drops below 3.5. When the pH is higher, it can be seen that considerable amounts of undissolved Ca and Zn still remain. For example using pure S 0 ₂ gas, G / L ratio 5 0, when the initial temperature and 3 Q ° C, 1 pH at the reaction time of about 0 minutes than decreases to about 2, the dissolution reaction You can see that it has advanced. In this case, the oxidation-reduction potential (based on the Ag / AgCl electrode) is about 100 to 25 OmV. The temperature rises to about 40 ° C after 10 minutes and reaches about 50 ° C after 30 minutes.

Such a change in pH or redox potential, can be take advantage in the control of the S0 ₂ processing time.

More specifically, the reaction may be terminated after 11 is 3.5 or less, preferably 2.5 or less, after the introduction of SO ₂ gas into the slurry.

Alternatively, the reaction may be terminated when the oxidation-reduction potential (based on the Ag / AgCl electrode) has settled, for example, between 100 and ₂₀₀ mV after the introduction of the SO ₂ gas into the slurry. Since the oxidation-reduction potential fluctuates depending on the type of fly ash, the processing time can be controlled by, for example, previously defining the potential region at the end of the reaction according to the fly ash to be applied.

The slurry having been subjected to the S 0 ₂ treatment, by solid-liquid separation, can be recovered from the liquid and residue Ca, Zn is dissolved. If the original fly ash contains Pb, this The residue is collected as “Pb-containing residue”. This residue remaining part also Ca, which is intended CaS 0 ₄ (gypsum) mainly contained in the fly ash from the beginning. However, as compared to Pb-containing residue is separated and recovered by conventional sulfuric acid leaching CaS 0 ₄ content is made as significantly less, it can be suitably used as a raw material for Pb made kneaded.

(Oxidation treatment)

The “Ca, Zn-containing liquid” obtained by removing the residue after the S 02 treatment is subjected to, for example, “treatment with an oxidizing agent” (hereinafter referred to as “oxidation treatment”) to separate and recover Ca and Zn. can do. The Ca, the Zn-containing solution, believed to be present in the form C a as described above as Ca (HS0 ₃₎ _2, also Zn is dissolved in each sulfite aqueous solution as Zn (HS 0 ₃₎ ₂ Can be When the Ca (HS 0 ₃₎ ₂ and Zn (HSO 3) is an oxidizing agent to 2, both changes relatively easily sulfate. At this time, the sulfate of Ca CaS 0 ₄ (gypsum) is insoluble, sulfate ZnS_rei_4 of Zn in order to be soluble, it is possible to solid-liquid separation of Ca and Zn. That is, Ca can be selectively precipitated by causing an oxidizing agent to act on the Ca- and Zn-containing liquid.

This oxidation reaction is considered to be represented by the following reaction formula.

_{_{Ca (HS 0 3) 2 (}} aq) + 0 2 + 2 H 2 0 → CaS 04 - 2 EO (s) + H2S 04 - - (7) Ca (HS 0 3) 2 (aq) + l / 202 + H 20 → C a S 04 · 2 H 2 0 (s) + S 0 2 (g) - · (7), Zn (HS 0 3) 2 (aq) + 02 → ZnS 04 (aq) + H 2 S 04

_{_{Zn (HS 0 3) 2 (}} aq) + l / 202 → ZnS 04 (aq) + S 02 (g) + H2O · · · (8), the little initial reaction: white precipitate forms up the pH Therefore, it is considered that both reactions (7) and (7) 'are occurring. The same applies to (8) and (8) '.

These reactions can be advanced by blowing an oxygen-containing gas such as air as an oxidant into the liquid. Other oxidizing agents may be used such as H ₂ 0 ₂ and 0 _3. However, if a Μη compound such as ΚΜηΟ is used, it is necessary to devise a way to recover Μη and treat Μη present in the attached water.

During the reaction, it is desirable to perform strong mechanical stirring or bubbling sufficient to sufficiently diffuse the oxidizing agent into the solution. When this oxidation reaction is performed by blowing air, the GZL ratio can usually find an optimum value in the range of 1 to 1000. The temperature is preferably about 20 to 50 ° C. Regarding the reaction time, it is preferable to control the end point of the reaction by the oxidation-reduction potential. In the case of air blowing, the oxidation-reduction potential was initially 100 to 200 mV (based on the Ag / AgCl electrode, the same applies hereinafter), but since 0 ₂ was consumed in the initial stage of the reaction, 35 It rises to around O mV, then gradually rises, and calms down at about 400 to 75 O mV. If there is almost no change in the potential, it can be seen that the oxidation reactions of the above equations (7) and (8) are almost completed.

H ₂ S 03 → H ₂ 0 + S 0 ₂ (degassing reaction)... (9)

For [rho Eta is elevated 0.5-2.0 degree from the initial S 0 ₂ degassed by temporarily original p H (e.g. 2 before and after), get dropped at slightly below the subsequent original pH.

[Other Ca / Zn separation methods]

Fig. 1 shows the step of precipitating Ca by oxidation.Another method for separating and recovering Ca and Zn is to selectively treat Ca by directing sulfuric acid on the Ca- and Zn-containing liquid. There is a method to precipitate as gypsum (sulfuric acid substitution treatment). The reaction equation is considered as follows.

About Ca;

_{_{Ca (HS 0 3) 2 (}} aq) + H 2 S 04 → CaS 0 4 - 2 H 2 0 (s) + 2 S O2 · · (10) for Zn;

_{_{Zn (HS 0 3) 2 (}} aq) + HhS 04 → ZnS_rei_4 (aq) + 2 H2O + 2 S O2 · · (11) Others, by blowing an inert gas such as N ₂ in the liquid, S0 ₂ There is a method in which the degassing reaction is allowed to proceed, and then sulfuric acid is added to selectively precipitate Ca. This reaction formula is considered to be as follows.

About Ca;

_{_{Ca (HS 0 3) 2 →}} CaS0 3 (s) + H 2 0 + S 02 (12)

_{CaS 0 3 (s) + H} 2 S 04 + H 2 0 → CaS 04 - 2 H2O (s) + S0 2 · - ( about 13 Zn;

Zn (HS 0 ₃ ) ₂ → ZnS 0 ₃ (s) + H20 + S O2 (14) _{ZnS 0 3 (s) + H2} S 04 - ZnS O (aq) + H2O + S O2 · · · (15) i.e., Ca (HS0 ₃₎ by degassing the reaction ₂ and Zn (HS 0 ₃₎ ₂ Once sulfite It precipitates as a salt, and when sulfuric acid acts on it, Ca becomes an insoluble sulfate (gypsum) and Zn becomes a soluble sulfate. As a result, it is thought that Ca can be selectively separated as a precipitate.

After selective precipitation of Ca as described above, solid-liquid separation recovers Ca as gypsum. When commercializing this gypsum as gypsum that meets industrial standards, it is desirable to remove moisture sufficiently. It is advisable to use a filter press or a centrifuge for draining.

(Neutralization)

The liquid after the separation and removal Ca (Zn-containing liquid), Zn is dissolved in the form of ZnS 0 _4. This liquid can be directly introduced into the zinc production process, but in consideration of handling properties during transport and recycling of the liquid, neutralization, sulfidation, and solvent extraction are used to recover Zn as a solid. Is desirable.

In the case of neutralization, an alkali such as CaO, Ca (OH) ₂ , or CaCOa may be added to the Zn-containing liquid as a neutralizing agent. When 11 is 7 to 10, Zn precipitates. When the original liquid (Zn-containing liquid) is a liquid obtained through the above-mentioned oxidation treatment, the Zn residue is mainly composed of Ζηθ. The use of NaOH or として as a neutralizing agent can form Zn precipitates, but if the solution after neutralization is returned to the previous step and used repeatedly, the Na and K sulfates become soluble. Therefore, a crystallization step is required.

By solid-liquid separation of the neutralized slurry, a Zn-containing residue is recovered. This residue can be used as a raw material for zinc production. On the other hand, the after-liquid can be reused as water for washing or S02 treatment. However, if the reuse of the solution is repeated, NaC1 and KC1 will be concentrated due to the carry-in of attached salts. Therefore, it is desirable to bleed off part of the wastewater and treat it.

The Figure 2 shows an example of a fly ash treatment flow for carrying out the S0 ₂ process of the present invention without first washing. In this case, since the solution after removing the Zn-containing residue has a high salt concentration, it is desirable to send most of the solution to the C1 removal step for wastewater treatment. Example

Example 1

Using A fly ash shown in Table 1, if this was treated with sulfuric acid leach and neutralization without the use of S 0 ₂ (Comparative Example), when treated with S 0 ₂ (invention according to the invention For Example), each liquid after treatment and each residue were compared. Further, in the case of the invention, an oxidation treatment step and then a neutralization step were performed.

Table 1 (A fly ash)

(Comparative example)

100 g of fly ash was weighed, and 3 L (liter) of distilled water was added thereto to obtain mixed fly ash water. After this fly ash mixed water was stirred for 60 minutes, it was subjected to solid-liquid separation with 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 (referred to as “wash residue”). Approximately 3 L of a mixture of the filtrate a and the filtrate b (referred to as “post-wash solution”) was obtained.

After the washing residue was sufficiently dried at 105 ° 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 g / L, and adjusted to pH == 2 by adding sulfuric acid. This was stirred at 30 ° C for 60 minutes to perform sulfuric acid leaching. Then was adjusted to p H = 4 by adding CAC0 ₃ to the treatment liquid (slurry after leaching), it was neutralized by stirring for 6 0 minutes. The liquid temperature was kept at 30 ° C. After that, solid-liquid separation was performed to obtain a Zn-containing post-solution and a Pb-containing residue. Table 4 shows the results of analysis of the solution containing Ζπ. After the Pb-containing residue was sufficiently dried at 105 ° C, the composition was analyzed. Table 5 shows the results. ' (Washing residue)

Table 3 (After washing)

Table 5 [Pb-containing residue] Comparative example

(Invention example)

100 g of fly ash A was weighed and washed in the same manner as in the comparative example to obtain a washing residue and a liquid after washing. The washed residue was repulped with pulp 1 0 0 g / L, were conducted "S 0 ₂ process" by blowing pure SO ₂ gas to the slurry 8 L. S 0 ₂ gas blowing speed was 8 L / min. In this case, the G / L ratio is 60. Liquid temperatures ranged from 15 to 40 ° C. During gas blowing, mechanical stirring was also performed. During the reaction, the redox potential (based on the Ag / AgCl electrode) and pH were monitored. According to the results, it was considered that the reaction was almost completed in about 10 to 20 minutes, but after that, gas blowing and mechanical stirring were continued, and the reaction time was finally set to 60 minutes. The final redox potential was 150 mV and pH was 2.2.

The resulting slurry was solid-liquid separated through a filter to obtain S 0 ₂ treatment after solution (Ca, Zn-containing liquid) and S 0 ₂ processing residue (Pb-containing residue). Table 6 shows the composition analysis results of the back solution. The residue was sufficiently dried at 105 ° C. and analyzed for composition. The results are shown in Table 7.

Replacement paper 26 Table 6 [S 0 ₂ treatment after solution (Ca, Zn-containing liquid)] one invention embodiment

Table 7 [S 0 ₂ processing residue (Pb-containing residue)] one invention embodiment

Table 4 (Comparative Example) In comparison to Table 6 (invention examples), in the inventive examples it can be seen that was recovered in the form dissolved in the liquid Zn and Ca by S 0 ₂ treatment. Also, comparing Table 5 (Comparative Example) and Table 7 (Inventive Example), it can be seen that in the inventive example, the amount of the Pb-containing residue was significantly reduced, and the amount and content of Ca in the residue were reduced. Understand. Directly by S 0 ₂ process according to Sunawa Chi present invention, a low Pb-containing residue Pb quality of high Ca quality occurs, since the amount is reduced, the lead made鍊process side to reuse the same The load can be greatly reduced.

Was then carry out the oxidation treatment in a method of blowing air into the S 0 ₂ treatment after solution (Ca, Zn-containing solution). The air blowing speed was 60 L / min. In this case, the GZL ratio is 600. The temperature was controlled at 45 ° C. Mechanical stirring was also used. In addition, the redox potential (based on the Ag / AgCl electrode) and pH were monitored. According to the results, the oxidation-reduction potential once decreased to 10 OmV 10 minutes after the start of the reaction, and the pH increased to more than 3.5. Thereafter, the redox potential increased and the pH gradually decreased. At the elapse of 60 minutes, the oxidation-reduction potential was 40 OmV and the pH was 2, and the fluctuation was small. At this point, the reaction was considered to be almost complete, but air blowing and mechanical stirring were continued for up to 120 minutes to observe the situation. Finally, the oxidation-reduction potential was 450 mV and the pH was 2.0. A white precipitate was formed in the liquid, which was separated into solid and liquid by a filter to obtain a cake of the liquid after oxidation treatment (Zn-containing liquid) and the oxidation treatment residue (Ca-containing residue). Table 8 shows the analysis results of the back solution, and Table 9 shows the analysis results of the residue.

Table 8 [Oxidized solution (Zn-containing solution)]

Replacement Form '(Rule 26) Table 9 [Residue of oxidation treatment (residue containing Ca)]

Total Zn Pb Ca S Na K CI Grade (% by mass) 0.23 0.00 25.69 21.49 0.24 0.24 0.60 Quantity (g) 398 1 0 102 86 1 1 2 From Tables 8 and 9, Ca was selectively precipitated by oxidation treatment. It can be seen that Ca and Zn could be separated and recovered. That is, the combination of oxidation and S 0 ₂ treatment, and Ca, were able to separate and recover Zn Pb, from fly ash by a simple operation of blowing gas. As a result of X-ray diffraction, it was confirmed that the cake containing Ca-containing residue was gypsum.

Next, the solution after the oxidation treatment (Zn-containing solution) was neutralized by adding NaOH. A solution having a Na concentration of 100 g / L was prepared, added to the solution after the oxidation treatment, and neutralized so that the pH became 8. The consumption of NaOH solution was 43 OmL. Since a white precipitate was generated by the neutralization, the precipitate was separated into solid and liquid to obtain a cake of a liquid after the neutralization and a neutralization residue (Zn-containing residue). Table 10 shows the analysis results of the back solution, and Table 11 shows the analysis results of the residue.

Table 10 [After neutralization]-Inventive example

[Neutralization residue (Zn-containing residue)]

Table 1 As can be seen from 0, the after liquid Ca, Zn, low content of pb, is the first washing step, or even capable enough reused as water to be supplied to the S0 ₂ process to. Further, as can be seen from Table 11, the cake of the neutralized residue has a high Zn content and is preferable as a raw material for zinc production. Example 2

(Invention example)

Using fly ash A, having conducted a washing and S 0 ₂ processed in the same way as the invention examples of Examples 1. Each obtained S 0 ₂ treatment after solution and S 0 ₂ processing residues Tables 6 and 7

Replacement form (Rule 26) It is the same as that shown. Here, the S 0 ₂ treatment after solution (Ca, Zn-containing liquid) by a method for applying a sulfuric acid, attempts to selective precipitation of Ca.

Table 6 similar S 0 ₂ treatment after solution (Ca, Zn-containing solution) to 6.2 L, it was added 2 3 7 g sulfuric acid. pH became 0.9. Since a white precipitate was formed, the mixture was stirred for 10 minutes and then subjected to solid-liquid separation. The analysis results after the obtained (referred to as “sulfuric acid replacement solution”) are shown in Table 12, and the analysis results for the residue (referred to as “sulfuric acid replacement residue”) are shown in Table 13.

Table 12 [Sulfuric acid replacement solution (Zn-containing solution)] An example of the invention

Table 13 [Sulfuric acid substitution residue (Ca-containing residue)] An example of the invention

Tables 12 and 13 show that Ca was selectively precipitated by the action of sulfuric acid and that Ca and Zn could be separated and recovered. As a result of X-ray diffraction, it was confirmed that the cake of the sulfuric acid substitution residue (Ca-containing residue) was gypsum.

Next, the solution after sulfuric acid replacement (Zn-containing solution) was neutralized by adding quicklime CaO here. While the mechanical stirring was being performed, quicklime was gradually poured into the liquid in a powdery state, and the pH was adjusted to 8. The total amount of CaO added was 74 g. The reaction time was 60 minutes. The oxidation-reduction potential (based on the Ag / AgCl electrode) finally reached 100 OmV. Since a white precipitate was generated by the neutralization, this was subjected to solid-liquid separation to obtain a cake of a liquid after the neutralization and a neutralization residue (Zn-containing residue). Table 14 shows the analysis results of the post-solution and Table 15 shows the analysis results of the residue.

Table 14 [Liquid after neutralization] An example of the invention

Table 15 [Neutralization residue (Zn-containing residue S)]

Replacement paper ('J26) Table 1 4 As can be seen, this after liquid Ca, Zn, low content of pb, is the first washing step, or even an S 0 ₂ can sufficiently reused as water to be supplied to the treatment step of. Further, as can be seen from Table 15, the cake of the neutralized residue has a high Zn content and is preferred as a raw material for zinc smelting. Example 3

(Invention example)

Using fly ash A, cleaning and SO ₂ treatment were performed in the same manner as in the invention example of Example 1. The resulting S0 ₂ treatment after solution and S 0 ₂ processing residues are the same as those shown in Tables 6 and 7. Here, the S 0 ₂ treatment after solution (Ca, zn-containing liquid) is allowed to proceed degassed reaction of S 0 ₂ by blowing an inert gas (N ₂ gas) to, by then in method of reacting sulfuric acid , Ca was attempted to precipitate selectively.

Similar S 0 ₂ treatment after solution and Table 6 (Ca, Zn-containing solution) to 6.2 L, was bubbled 1 2 0 min N ₂ gas at a flow rate of 6 0 L / min. In an N ₂ gas blowing, S 0 ₂ gas was released from the generated solution. The pH was 3.9 and a white precipitate formed. The oxidation-reduction potential (based on the Ag / AgCl electrode) was 230 mV. Sulfuric acid were added 3 5 6 g to S 0 ₂ and degassed liquid (slurry) 6.2 L subsequently. The pH was 1.9, and the oxidation-reduction potential was 30 OmV. The white precipitate was apparently intact. After stirring for 60 minutes, the slurry was subjected to solid-liquid separation.

The results of analysis of the resulting solution (referred to as “N ₂ + sulfuric acid replacement solution”) are shown in Table 16, and the residue (referred to as “N ₂ + sulfuric acid replacement residue”) was sufficiently dried at 105 ° C. The results of the later analysis are shown in Table 17.

Table 16 [N ₂ + sulfuric acid S solution (Zn-containing solution)] An example of the invention

Total Zn Pb Ca S Na K CI

Grade (mass%) 0.30 0.00 26.73 23.29 0.28 0.22 0.58

Quantity (g) 365 1 0 98 85 1 1 2 Tables 16 and 17 It can be seen that Ca was selectively precipitated by injecting inert gas and adding sulfuric acid, and Ca and Zn could be separated and recovered. As a result of X-ray diffraction, it was confirmed that the cake of the N ₂ + sulfuric acid substitution residue (Ca-containing residue) was gypsum.

Next, the solution after the replacement with N ₂ + sulfuric acid (Zn-containing solution) was again neutralized by adding quicklime Ca 0. The quicklime was gradually poured into the liquid in a powdery state with mechanical stirring, and the pH was adjusted to 8. The total amount of CaO added was 89 g. The reaction time was 60 minutes. The oxidation-reduction potential (based on the Ag / AgCl electrode) was 30 OmV. Since a white precipitate was generated by the neutralization, this was subjected to solid-liquid separation to obtain a cake of the neutralized liquid and a neutralized residue (Zn-containing residue). Table 18 shows the analysis results of the back solution and Table 19 shows the analysis results of the residue.

Table 18 [After neutralization] Example of invention

Table 19 [Neutralization residue (Zn-containing residue)] —Example of invention

Table As can be seen from 1 8, this after liquid Ca, Zn, low content of P b,. The first washing step, or S is 0 ₂ treatment also the possible sufficiently reused as water to be supplied to the process. Further, as can be seen from Table 19, the cake of the neutralized residue has a high Zn content and is preferred as a raw material for zinc production.

Replacement form (Rule 26)

Claims

The scope of the claims

1. slurry one fly ash by the action of S 0 _2, fly ash having a step is dissolve Ca and Zn in fly ash into the liquid, recovered in the liquid separated from the residue of these elements Processing method.

2. The slurry is reacted with S 0 ₂ of fly ash, fly with step was dissolve Ca and Zn in fly ash into the liquid, to recover these elements in the liquid separated from the Pb-containing residue Ash treatment method.

3. The fly ash processing method according to claim 1, wherein the fly ash slurry is obtained by repulping fly ash having a reduced content of Na, K, and C1 through washing.

4. By causing an oxidizing agent to act on the Ca- and Zn-containing liquid recovered through any of the steps of claims 1 to 3, Ca is selectively precipitated and Zn is dissolved in the liquid. A method for treating fly ash that has a step of separating and recovering these elements while leaving them in a state of being left.

5. The method for treating fly ash according to claim 4, wherein the oxidizing agent is a gas containing oxygen.

6. By causing sulfuric acid to act on the Ca- and Zn-containing liquid recovered through any one of the steps of claims 1 to 3, Ca is selectively precipitated and Zn is dissolved in the liquid. A method for treating fly ash, comprising a step of separating and recovering these elements while leaving them in a state.

7. Inert gas is blown into the Ca- and Zn-containing liquid recovered through any one of claims 1 to 3 to advance the degassing reaction of SO ₂ , and then sulfuric acid is removed. A fly ash treatment method comprising the steps of selectively precipitating Ca and dissolving Zn in a liquid by causing the element to act to separate and recover these elements.

8. Alkali is added to neutralize the Zn-containing liquid separated and recovered from Ca through any of the steps 4 to 7 to precipitate and recover Zn. A method of treating fly ash in which the liquid after separation is reused as water for fly ash treatment.