JPH08240310A - Treating apparatus for exhaust gas from melting furnace - Google Patents

Abstract

PURPOSE: To take-out useful heavy metal and salt component by providing a cooling and washing tower wherein exhaust gas is cooled and solid and mist component is washed by bringing washing-liquid into contact with the exhaust gas produced when fly ash or incineration ash is treated by melting, a solid-liquid separation means wherein liquid containing solid component is filtrated, and a heavy metal-separating and collecting means wherein metallic component is collected by electrolysis. CONSTITUTION: Fly ash or incineration ash is sent into a melting furnace 1, and molten matter and exhaust gas, which are produced therein, are sent into a cooling and washing tower 3. At this point, by washing-liquid sprayed from a spraying means 3a, the exhaust gas is cooled and solid and mist component being contained in the exhaust gas is washed away and is sent into a circulation liquid storage part 4 and a solid- liquid separation means 5 together with the washing liquid. The solid-liquid separation means 5 filtrates liquid containing sludge by a filter. Filtrate is sent into a heavy metal-separating and collecting means 6, and sludge component is sent into a sludge- conveying means 8. In the heavy metal-separating and collecting means 6, metallic component being contained in the filtrate is collected by electrolysis, and in the sludge- conveying means 8, the sludge component is again thrown into the melting furnace 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a melting furnace exhaust gas treatment apparatus, and more particularly, to a process for melting fly ash or incineration ash discharged from a waste incinerator for incinerating municipal waste, industrial waste, etc. It treats the contained metal and salt in the exhaust gas produced during the melting treatment.

[0002]

2. Description of the Related Art As an example of an incinerator for incinerating incinerators such as municipal waste, there is proposed a fluidized bed type incinerator of No. Kaikaihei 3-56027. In addition, as a related technology example of melting and processing fly ash or incineration ash (dust) in a melting furnace,
The following suggestions have been made. JP-A-58-030382 "Dust processing method" JP-A-58-040791 "Slag method" JP-A-60-053780 "Electrode insertion control device for direct current type melt processing furnace" JP-A-60- No. 054780 "Melting treatment furnace for dust" JP-B-63-051755 "Dust treatment method" JP-A-63-315187 "Incinerator exhaust gas treatment method" JP-A-02-099184 "Detoxification treatment of heavy metal-containing dust" Method ”These technologies solve various problems that occur during melting when fly ash or incinerator ash (dust) discharged from incinerators such as municipal solid waste is melted and solidified in a melting furnace. I am trying.

[0003]

According to the melting treatment technology for these dusts, the temperature at the time of melting the dust reaches 1200 to 1350 ° C., as described in the prior art example, and therefore the mercury contained in the dust. Low melting point metal such as HCl, HCl
Etc. will be discharged as a gas. Therefore, in addition to the conventional technology example, from the exhaust gas of the melting furnace,
It is necessary to recover low melting point metals, harmful substances or useful substances.

As a technique for removing heavy metals such as mercury contained in a general exhaust gas, for example, the exhaust gas is guided to a wet absorber and absorbed by an alkali such as NaOH and fixed by using a chelating agent for fixing heavy metals. There is a way. Further, as a technique for collecting soot and dust contained in exhaust gas, for example,
There is a way to use a bug filter.

However, with the former method of using a chelating agent, 1) it is difficult to completely fix mercury, and there are cases where wastewater treatment standards cannot be satisfied. 2) During long-term landfill disposal, the chelating agent deteriorates, and the exudation or dissolution phenomenon of mercury easily occurs. 3) Since the chelating agent is expensive, the cost for removing mercury increases. Problems to be solved are left. Further, in the latter method using the bag filter, when the temperature is too high, the metal gas cannot pass through and be collected, and when the temperature is too low, the solid content contains HCl.
Mist content such as, etc. mixes in, making it difficult to process the collected matter and easily causing clogging. In addition, the collected matter becomes waste and it is difficult to reduce the volume. Is left.

The present invention has been made in view of the above circumstances, and aims to render the exhaust gas produced by the melting treatment of dust harmless and to remove useful heavy metals and salt from the system in a reusable state. It is intended to be taken out.

[0007]

[Means for Solving the Problems] As a device for treating exhaust gas produced by melting fly ash or incineration ash in a melting furnace, the cleaning liquid is connected to a pipeline for transferring the exhaust gas and a cleaning liquid is brought into contact with the cleaning liquid for cooling and cleaning. A cooling and washing tower, a solid-liquid separating means connected to the lower part of the cooling and washing tower for filtering a solid-content liquid, and a heavy metal separating and collecting means connected to the solid-liquid separating means for collecting metal by electrolysis. The configuration is adopted. A mist eliminator that collects the mist contained in the exhaust gas after cleaning the exhaust gas is arranged in a connected state in the gas phase portion of the cooling and cleaning tower, and the heavy metal separation and recovery means separates and recovers the salt content in the electrolytic solution. A salt separation means is provided. When the heavy metal separation / collection means is an electrolytic cell, a technique of adsorbing + ionized metal atoms to the negative electrode of the electrolytic cell is adopted, and as the salt separation means, −ionized salt content is adsorbed to the positive electrode of the electrolytic cell. The technology to make it adopted. In the electrolytic cell, an electrolytic potential is applied to each electrode under the condition of depositing only a specific metal or the condition of depositing a plurality of kinds of metals collectively. Between the melting furnace and the solid-liquid separation means, there is adopted a technology in which a sludge transfer means for transferring the sludge component collected at the time of filtering the solid content-containing liquid to the melting furnace and re-injecting is arranged, and a cooling and washing tower. Between the solid-liquid separation means and the solid-liquid separation means, there is added a technique of storing a cleaning liquid or a liquid containing a solid content and providing a circulating liquid storage part for sending at least one of these liquids as a cleaning liquid to a cooling and cleaning tower. .

[0008]

[Operation] When fly ash or incinerator ash discharged from an incinerator such as municipal solid waste is melted in a melting furnace, exhaust gas is generated together with the molten material. The exhaust gas is transferred to the cooling and washing tower through a pipe and cooled and washed while being in contact with the washing liquid. The solid content and mist content contained in the exhaust gas are sent to the solid-liquid separation means from the lower part of the cooling washing tower together with the washing liquid,
The filtrate obtained by filtering the solid-content liquid is supplied to the heavy metal separating and recovering means, and the metal content is recovered by electrolysis. On the other hand, the mist component in the exhaust gas is captured by sending the exhaust gas after exhaust gas cleaning to the mist eliminator from the gas phase portion of the cooling and cleaning tower. When the heavy metal separation / collection means is an electrolytic cell, the negative electrode adsorbs + ionized metal atoms, whereby the metal content is recovered from the electrolyte solution of the solid content-containing liquid, and the salt content in the electrolyte solution is recovered. Are separated and recovered by the salt separation means. And as a salt separation means,
When the positive electrode of the electrolytic cell is used, the ionized salt is adsorbed on the positive electrode and recovered. By applying the negative electrode of the electrolytic cell and setting the electrolysis potential, only a specific metal in a pure state is deposited or a plurality of kinds of metals are collectively deposited in a mixed state. The sludge component collected by filtering the solid-content liquid is transferred to the melting furnace by the sludge transfer means and is re-introduced, so that the sludge is brought into a molten state again. In addition, the circulation liquid storage unit stores the cleaning liquid or the solid-containing liquid, and circulates the cleaning liquid as a cleaning liquid to the cooling cleaning tower.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a melting furnace exhaust gas treating apparatus according to the present invention will be described below with reference to FIGS. FIG.
In FIG. 1, reference numeral A is an ash supply system (fly ash supply system), 1 is a melting furnace, 2 is a pipe line, 3 is a cooling and washing tower, 4 is a circulating liquid storage section, 5
Is a solid-liquid separating means, 6 is a heavy metal separating and collecting means, 7 is a salt separating means, 8 is a sludge transferring means, and 9 is a mist eliminator.

As the melting furnace 1, for example, a direct current type melting furnace described in the prior art example is applied, and dust supplied to the ash supply system (for example, fly ash supply system) A is fed into the inside. Dust inlet 1a for
And an exhaust port 1b for discharging the exhaust gas generated by melting the dust through the pipe line 2, and a sludge charging for charging the sludge connected to the sludge transfer means 8 into the inside. It has a mouth 1c.

The cooling and washing tower 3 is connected to the pipe line 2,
It has spray means 3a for bringing the exhaust gas into contact with a spray-like cleaning liquid for cooling and cleaning.

The circulating liquid storage section 4 is connected between the lower portion of the cooling and washing tower 3 and the solid-liquid separating means 5 to wash either the washing liquid or the supernatant liquid of the solid content-containing liquid, or both of them. It is connected to the spraying means 3a with the function of a pump or the like for discharging as.

The solid-liquid separating means 5 is connected to the lower part of the circulating-liquid storing section 4 with the circulating-liquid storing section 4 interposed, and has a function of filtering or separating the solid-content liquid, a hydrocyclone, and a sedimentation separation. A tank etc. is built in.

The heavy metal separating / collecting means 6 is connected to the solid-liquid separating means 5 and has a function of collecting at least a metal component. For example, the electrolytic cell 6A shown in FIG. 2 is applied as the one having the metal content recovery function.
The electrolytic cell 6A has a negative electrode 6a and a positive electrode 6b arranged therein, a DC power source 6c connected to the negative electrode 6a and the positive electrode 6b for applying a DC voltage, a ceramic for partitioning and separating the inside, and the like. The porous semipermeable membrane 6d and the electrolytic solution 6e filled therein are provided.

The salt separating means 7 is arranged in a connected state between the heavy metal separating / collecting means 6 and the circulating liquid storage part 4, and in FIG. 2, in the electrolytic solution 6e by the positive electrode 6b in the electrolytic cell 6A. The salt separation and recovery function of is used.

The sludge transfer means 8 is arranged in a connected state between the melting furnace 1 and the solid-liquid separation means 5, and transfers the sludge component collected during the filtration in the solid-liquid separation means 5 to the sludge input port 1c. Then, it has a function of charging the inside of the melting furnace 1.

The mist eliminator 9 is arranged in a connected state in the gas phase portion of the cooling and cleaning tower 3 and collects the mist contained in the exhaust gas after cleaning the exhaust gas.

In the melting furnace exhaust gas treating apparatus having the above-mentioned structure, fly ash or incineration ash discharged from an incinerator such as municipal solid waste is sent from the ash supply system A to the melting furnace 1. When the melting process is performed by the operation of the melting furnace 1, exhaust gas is generated together with the melt, and the exhaust gas is discharged from the exhaust port 1b to the pipeline
Is sent to the cooling and washing tower 3 via.

In the cooling and washing tower 3, spray means 3a
When the cleaning liquid is jetted out by the operation of, and the cleaning liquid and the exhaust gas are brought into contact with each other, the exhaust gas is cooled and the solid content and mist contained in the exhaust gas are washed away, and the cleaning liquid is circulated from the lower part of the cooling cleaning tower 3. It is sent out to the liquid storage section 4 and the solid-liquid separation means 5.

In the circulating liquid storage section 4, the cleaning liquid containing solids and mist, that is, the liquid containing solids is temporarily stored to separate the separated liquid phase portion such as the supernatant liquid in the liquid containing solids. The cooling / washing tower 3 is circulated to return to the spraying means 3a, and the sludge-containing liquid containing a large amount of solids and the like is sent to the solid-liquid separating means 5.

In the solid-liquid separation means 5, the sludge containing liquid is sent to the heavy metal separation and recovery means 6 by a method of sending the sludge-containing liquid to a filter and filtering the same, and the accumulated sludge is sent to the sludge transfer means 8 It will be sent at an appropriate time.

In the heavy metal separating / collecting means 6, the metal component contained in the filtrate is collected by electrolyzing the filtrate. The filtrate sent to the electrolytic cell 6A shown in FIG. 2 has an acidity of, for example, pH by adding an alkaline solution based on the type of metal deposited by electrolysis.
After adjusting the pH to about 6, power was supplied from the DC power supply 6c to apply a potential corresponding to the type of metal between the negative electrode 6a and the positive electrode 6b, and the negative electrode 6a was + ionized. Adsorb metal atoms. In the case of adhering Cu to the surface of the negative electrode 6a in the electrolytic solution of pH 6, the potential of the negative electrode 6a slightly to the right of the peak shown in the position of FIG. 3, that is, about −0.15 to − 0.
When the precipitation of Cu is promoted by maintaining the electrolytic potential of about 3 V and Pb is attached to the surface of the negative electrode 6a, the negative electrode is slightly shifted to the right of the peak shown in the position of FIG. 6a to -0.45--0.
When the deposition of Pb is promoted by maintaining the voltage at about 55 V and Zn is attached to the surface of the negative electrode 6a, the potential of the negative electrode 6a is adjusted so as to be slightly to the right of the peak shown in FIG. To -1.05 to -1.15V
By keeping the content to some extent, precipitation of Zn is promoted.
Therefore, a plurality of negative electrodes 6a are installed inside the electrolytic cell 6A, and p of the electrolytic solution (filtrate) inside the electrolytic cell 6A is
By sequentially adjusting H and setting the potential of the negative electrode 6a, a desired metal can be separated and recovered in a state of being deposited on the surface of the negative electrode 6a. In this case, similar recovery can be performed for cations such as other metals As and Hg.

Further, the heavy metal separating / collecting means 6 is composed of the electrolytic cell 6
When the metal is deposited on the negative electrode 6a in A, it is possible to recover the salt content using the positive electrode 6b in parallel with the deposition of the metal. In this case, when the positive electrode 6b is at + potential, the salt ionized by electrolysis is attracted to the positive electrode 6b and is deposited on the surface. Therefore, by using a part of the electrolytic cell 6A as the salt separating means 7,
Similar recovery can be performed for anions such as Cl and Na having a desired salt content.

The electrolytic solution 6e from which the metal and salt are removed in the electrolytic bath 6A is returned to the circulating solution storage section 4 and reused as a cleaning solution, as shown by the arrow in FIG.

On the other hand, in the sludge transfer means 8, the sludge component collected by the solid-liquid separation means 5 is transferred to the melting furnace 1.
Is carried out and re-input is carried out via the sludge charging port 1c, and the solid content is repeatedly dissolved and re-processed as a molten material.

Next, in the mist eliminator 9, the exhaust gas after exhaust gas cleaning is sent from the gas phase part of the cooling and cleaning tower 3, and the mist component contained in the exhaust gas is collected to collect air components and carbon dioxide gas. Processing such as releasing only the above into the atmosphere is performed.

[Other Embodiments] The present invention includes the following techniques in addition to the embodiments. a) Instead of the technique of sequentially depositing Cu, Pb, etc. described with reference to FIG. 3, Cu, Pb, Cd, etc. are collectively separated and recovered by a potential suitable for Zn deposition, for example. b) Precipitating a specific metal, for example, only Cu, in the state of pure Cu, separating and recovering, and then collecting and recovering the remaining plural kinds of metals collectively. c) The temperature, pH, etc. of the electrolyte solution should be changed for the specific metal and separated and collected under the optimum conditions.

[0028]

EFFECTS OF THE INVENTION The melting furnace exhaust gas treatment apparatus according to the present invention has the following effects. (1) The cleaning liquid is brought into contact with the exhaust gas discharged from the melting furnace, and cooling and cleaning are performed to remove metal mist and harmful substances mixed in the exhaust gas, thereby making the exhaust gas harmless. . (2) By removing the mist component mixed in the exhaust gas at the time of cleaning the exhaust gas with the mist eliminator, it is possible to reduce the mixing of the mist component in the released gas outside the system and improve the safety. (3) Useful heavy metals, etc. can be individually separated and recovered by electrolyzing the filtrate of the solid-containing liquid generated by the cleaning of the exhaust gas, and can be reused as a single metal. It can be taken out of the system in the state. (4) By re-charging the sludge component collected at the time of filtering the solid-containing liquid into the melting furnace, the sludge can be redissolved and the metal recovery rate can be improved. (5) By separating and recovering the filtrate from which sludge has been removed, and by using the positive electrode of the electrolytic cell as the salt separating means, it is possible to recover metal and salt at the same time. (6) By applying the negative electrode of the electrolytic cell, the flexibility of depositing a specific metal in a pure state and separating and collecting it, or collectively separating and collecting a plurality of kinds of metals in a mixed state is provided. Can be increased.

[Brief description of drawings]

FIG. 1 is a block connection diagram showing an embodiment of a melting furnace exhaust gas treatment apparatus according to the present invention.

FIG. 2 is a front cross-sectional view showing an example of a heavy metal separating and collecting means and a salt separating means in FIG.

FIG. 3 is a relationship curve diagram between an electrolytic potential of a deposited metal and an electrolytic current.

[Explanation of symbols]

 A Ash supply system (fly ash supply system) 1 Melting furnace 1a Dust input port 1b Exhaust port 1c Sludge input port 2 Pipe line 3 Cooling and washing tower 3a Spray means 4 Circulating liquid storage section 5 Solid-liquid separation means 6 Heavy metal separation and recovery means 6A Electrolyzer 6a Negative electrode 6b Positive electrode 6c DC power source 6d Semipermeable membrane 6e Electrolyte 7 Salt separation means 8 Sludge transfer means 9 Mist eliminator

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location B03C 3/16 B09B 3/00 303L B09B 3/00 (72) Inventor Hiroshi Aramaki Isogo Yokohama, Kanagawa Prefecture Shin-Nakahara-cho, Ichi-Ku, Ishikawajima-Harima Heavy Industry Co., Ltd. Technical Research Institute (72) Inventor Kenichi Tahara, Shin-Nakahara-cho, Isogo-ku, Yokohama, Kanagawa Prefecture

Claims (6)

[Claims] 1. A device for treating exhaust gas produced by melting and processing fly ash or incineration ash in a melting furnace (1), which is connected to a pipe line (2) for transferring the exhaust gas to contact the cleaning liquid with the exhaust gas. A cooling and washing tower (3) for cooling and washing, a solid-liquid separating means (5) connected to a lower part of the cooling and washing tower for filtering a solid-content liquid, and a metal component by electrolysis connected to the solid-liquid separating means. And a heavy metal separation and recovery means (6) for recovering the gas. 2. The mist eliminator (9) for collecting the mist contained in the exhaust gas after cleaning the exhaust gas is connected to the gas phase portion of the cooling cleaning tower (3). Equipment for melting furnace exhaust gas. 3. Treatment of exhaust gas from a melting furnace according to claim 1 or 2, wherein the heavy metal separating / collecting means (6) is provided with a salt separating means (7) for separating and collecting salt in the electrolytic solution. apparatus. 4. A sludge transfer means (8) for transferring, to the melting furnace (1) and the solid-liquid separation means (5), sludge components collected at the time of filtration of the solid-content liquid to the melting furnace. ) Is provided, The apparatus for treating melting furnace exhaust gas according to claim 1 or 2, characterized in that. 5. A cooling and washing tower (3) and a solid-liquid separation means (5)
A circulating liquid storage section (4) for storing a cleaning liquid or a liquid containing a solid content and sending at least one of these liquids as a cleaning liquid to a cooling and cleaning tower is provided between The processing apparatus for melting furnace exhaust gas according to 2, 3, or 4. 6. An electrolytic cell (6A) is applied as the heavy metal separating and recovering means (6), and the negative electrode (6a) of the electrolytic cell is mixed with a condition for precipitating only a specific ionized metal or a mixture of plural kinds of metals. 2. The apparatus for treating a melting furnace exhaust gas according to claim 1, wherein an electrolytic potential under a condition of collectively precipitating in this state is applied.