JP2008212923A - Exhaust gas treatment agent, and exhaust gas treating method and treatment system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas treatment agent capable of surely cleaning exhaust gas by using a small amount and stabilizing heavy metals, and to provide an exhaust gas treatment system. <P>SOLUTION: The exhaust gas treatment agent comprises a powder mixture of a slaked lime powder and a dawsonite powder, and can neutralize an acid component and stabilize a heavy metal contained in the exhaust gas. Preferably, the powder mixture contains 20-45% of the dawsonite powder and the specific surface area of the dawsonite powder and the slake lime powder is 30 m<SP>2</SP>/g or larger. The exhaust gas treatment method comprises the steps of adding the exhaust gas treatment agent to the exhaust gas to neutralize the acid component contained in the exhaust gas and adsorb the heavy metals, passing the exhaust gas to which the agent is added through a dust collector to precipitate dust, and adding water to the collected dust and kneading the dust with water to turn the dust into clay. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust gas treatment agent that can simultaneously perform neutralization treatment of exhaust gas and stabilization treatment of heavy metals, and can obtain an excellent treatment effect with a small amount of use, and a treatment method and treatment system thereof. In the present invention, exhaust gas treatment and dust treatment are collectively abbreviated as exhaust gas treatment, and acidic components and heavy metals in exhaust gas include those in dust, and exhaust gas neutralization treatment includes soot dust neutralization treatment.

  Usually, an exhaust gas treatment system of a garbage incineration facility is provided with equipment for treating acidic components and soot contained in the exhaust gas. Specifically, for example, as shown in FIG. 2, in the exhaust gas flow path 21 of the garbage incineration facility 20, an exhaust gas cooling unit 22, an alkaline chemical charging unit 23 for neutralizing acidic components in the exhaust gas, a dust collector 24, A blower 25 and the like are provided. On the other hand, the dust collector 24 is provided with a processing facility for collected dust. The treatment facility is provided with a storage tank 27 for retaining dust, a kneading device 30, a means 31 for adding a heavy metal treating agent to the dust in the kneading apparatus 30, a water supply means 32, a hopper 33 for discharging the treated material to the outside, and the like. .

  The combustion exhaust gas from the waste incineration facility 20 is cooled in the exhaust gas cooling unit 22 by a waste heat boiler or water spray. Next, an alkaline agent that neutralizes acidic components such as HCl and SOx contained in the exhaust gas is introduced. As this neutralizer, slaked lime powder is generally used. The exhaust gas to which the neutralizing agent has been added is guided to the dust collector 24 where dust such as fly ash is collected, and the exhaust gas from which the dust has been removed is sucked into the blower 25 and discharged from the chimney 26 to the outside.

  On the other hand, the dust collected by the dust collector 24 is stored in the storage tank 27 and introduced into the kneading apparatus 30 through the quantitative feeder 29. A chemical for insolubilizing heavy metals is added to the soot and dust of the kneading device 30 together with water so that a certain amount or flow rate is adjusted to insolubilize (stabilize) the heavy metals contained in the soot and knead the dusty dust. It is made in clay and made easy to handle.

  Conventionally, various drugs are known as stabilizers for heavy metals, such as (1) dithiocarbamic acid and piperazine chelating agents, (2) phosphoric acid drugs, and (3) silica and aluminum silicate adsorbents. (4) Aluminum compounds such as aluminum hydroxide and sulfuric acid band, and (5) water glasses such as sodium silicate are used.

  In conventional exhaust gas treatment equipment, slaked lime is added to neutralize acidic components in the exhaust gas, and heavy metal stabilizers are added to the dust collected after the neutralization treatment. Due to such a two-stage process, the conventional equipment has a problem in that the configuration is complicated and the processing operation is also troublesome.

Therefore, a composite treatment agent in which an exhaust gas neutralizer and a heavy metal stabilizer are mixed has been proposed. In this composite treatment agent, slaked lime is mainly used as an exhaust gas neutralizing agent, and various chemicals are used as an insolubilizing agent for heavy metals. For example, slaked lime powder and a processing agent (patent document 1) formed by mixing a neutralizing agent such as cement or sulfate, a chelating agent, water glass or phosphate, slaked lime and an aluminum compound such as aluminum hydroxide. Treatment agent obtained by mixing (Patent Document 2), Treatment agent obtained by mixing sulfate substance such as gypsum and aluminum compound such as aluminum hydroxide in lime powder (Patent Document 3 and Patent Document 4), and slaked lime powder A treatment agent (Patent Document 5) obtained by mixing aluminum hydroxide and / or activated alumina powder is known.
JP 09-99234 A (Patent No. 3867307) JP 2000-42360 A JP 2000-301101 A JP 2001-327834 A JP 2003-311122 A

  Most of the conventional composite treatment agents use slaked lime as an exhaust gas neutralizing component and are mixed with a heavy metal stabilizer, which is a mixture of so-called special labor chemicals. However, compared with the conventional method which uses an exhaust gas neutralizer and a heavy metal treating agent separately, it did not decrease so much and there were few merit as a composite treating agent.

  The present invention solves the above-mentioned conventional problems with exhaust gas treatment agents, and an exhaust gas treatment agent capable of reliably performing exhaust gas neutralization treatment and heavy metal stabilization treatment with a smaller amount of use and the treatment thereof Provide a system.

The present invention relates to an exhaust gas treatment agent having the following configuration and a treatment system thereof.
[1] An exhaust gas treatment agent comprising a mixed powder of slaked lime powder and dawsonite powder, which neutralizes acidic components in exhaust gas and stabilizes heavy metals in exhaust gas.
[2] The exhaust gas treating agent according to [1], wherein the mixed powder contains 20% to 45% of dawsonite powder.
[3] The exhaust gas treating agent according to [1] or [2] above, wherein the specific surface areas of the slaked lime powder and the dosonite powder are 30 m ² / g or more.
[4] The exhaust gas treating agent described in any one of [1] to [3] above is added to the exhaust gas to neutralize acidic components contained in the exhaust gas and adsorb heavy metals, and then the exhaust gas is passed to a dust collector. A method for treating exhaust gas, comprising collecting dust and exhaust gas treatment agent in the exhaust gas through the mixture, and hydromixing the collected powder into clay.
[5] Means for adding an exhaust gas treatment agent comprising a mixed powder of slaked lime powder and dosonite powder to the exhaust gas, a dust collector for collecting the soot and the exhaust gas treatment agent contained in the exhaust gas, and the collected powder An exhaust gas treatment system comprising means for kneading.

  The exhaust gas treatment agent of the present invention contains slaked lime powder and dawsonite powder, and the dowsonite powder has an action of adsorbing and stabilizing heavy metals and neutralizing acidic components in the exhaust gas. A synergistic neutralization effect by the powder can be obtained, and the dosonite powder has an excellent effect of stabilizing heavy metals, so that the exhaust gas can be reliably neutralized and the heavy metals can be stabilized.

  The dosonite contained in the exhaust gas treating agent of the present invention is stable without being decomposed at 300 ° C. or less, and is stable without reacting even when mixed with alkali powder. Therefore, the exhaust gas treating agent of the present invention is stable even if it is put into the exhaust gas of a garbage incineration facility, and is suitable as a blowing agent for exhaust gas flue. In addition, since dosonite has the effect of sufficiently insolubilizing heavy metals even after reacting with acidic components in the exhaust gas, it is mixed with slaked lime powder to assist its neutralizing action, and as a heavy metal stabilizer Can be used. For this reason, it is possible to neutralize the acidic components contained in the exhaust gas and to insolubilize (stabilize) heavy metals by using a much smaller amount than the conventional treating agent.

  Since the exhaust gas treating agent of the present invention has both a neutralizing action on acidic components contained in the exhaust gas and an insolubilizing action on heavy metals, it can be introduced into the exhaust gas only once, simplifying the processing operation and processing equipment. it can. Moreover, the thing using the exhaust gas treating agent of the present invention is insolubilized with heavy metals and is lower than the landfill elution reference value, so it can be disposed as landfill.

  Hereinafter, the present invention will be specifically described. In addition,% is mass% except the case intrinsic | native to a unit, and a specific surface area is a BET specific surface area.

  The exhaust gas treatment agent of the present invention is an exhaust gas treatment agent comprising a mixed powder of slaked lime powder and dawsonite powder, which neutralizes acidic components contained in the exhaust gas and stabilizes heavy metals.

The slaked lime powder contained in the exhaust gas treating agent of the present invention has an action of reacting with and neutralizing acidic components (sulfur oxides such as HCl, SO ₂ and SO ₃ ) contained in the exhaust gas.

The dosonite [NaAlCO ₃ (OH) ₂ ] contained in the exhaust gas treating agent of the present invention has an action of reacting with and neutralizing the acidic component contained in the exhaust gas, and further against heavy metals contained in soot dust. This is carbonated and stabilized, and unreacted slaked lime remaining in the dust and dosonite react to form a Ca-Al compound, and this reaction product stabilizes by taking in heavy metals by ion exchange or the like. Has an effect.

  Since the neutralization effect of the acid components in the exhaust gas of dosonite is about half that of slaked lime, it is appropriate to use it together with slaked lime rather than just using dosonite. The exhaust gas treating agent of the present invention comprises a mixed powder of slaked lime powder and dosonite powder.

  The content of the dosonite powder contained in the exhaust gas treating agent of the present invention is preferably 20% to 45%, and the content of the slaked lime powder is preferably 55% to 80%. When the dosonite content is less than 20%, the effect of dosonite becomes insufficient. On the other hand, if the dosonite content is more than 45%, the content of slaked lime is relatively reduced, so the neutralization effect on the acidic components of the exhaust gas is reduced, and therefore the required amount of the exhaust gas treatment agent increases, This is not preferable because the cost increases and the amount of processed material to be discarded in the landfill site increases.

The specific surface area of the slaked lime powder and dawsonite powder is preferably not less than 30 m ² / g, the specific surface area of the slaked lime powder is 30 to 50 m ² / g approximately, a specific surface area of dawsonite powder is more preferably about 60~100m ² / g. When the specific surface areas of the slaked lime powder and the dawsonite powder are smaller than the above range, the contact with the acidic components and heavy metals contained in the exhaust gas may be insufficient.

  The dosonite contained in the exhaust gas treating agent of the present invention has an effect of neutralizing the acidic gas component contained in the exhaust gas and insolubilizing heavy metals. On the other hand, conventional exhaust gas treating agents are known to contain aluminum compounds such as aluminum hydroxide, aluminum chloride, and aluminum sulfate together with slaked lime powder, although these aluminum compounds have the effect of immobilizing heavy metals, It has no or very little action to neutralize the acidic components of the exhaust gas. On the other hand, since dawsonite also has the effect of fixing heavy metals and neutralizing acidic components, unlike aluminum compounds contained in conventional treatment agents, it can exhibit excellent treatment effects even with a small amount of use. .

  The exhaust gas treatment agent of the present invention is added to the exhaust gas to neutralize acidic components contained in the exhaust gas and adsorb heavy metals, and the exhaust gas to which this treatment agent is added is passed through a dust collector to remove dust and treatment in the exhaust gas. It can be suitably used as an exhaust gas treatment method that collects an agent and hydrates and kneads the collected powder to form a clay.

  Since the exhaust gas treating agent of the present invention has both a neutralizing action on acidic components contained in the exhaust gas and an insolubilizing action on heavy metals, it can be introduced into the exhaust gas only once. On the other hand, in the conventional processing system that collects dust after adding slaked lime powder, and kneads the collected dust by adding a heavy metal treatment agent and water, the treatment agent is added in two stages. In the treatment system using the treatment agent of the present invention, the treatment agent may be added in one step, and the step of adding the treatment agent after collecting the dust can be omitted.

  Specifically, for example, as shown in FIG. 1, the exhaust gas treatment system of the present invention contains an exhaust gas treatment agent comprising a mixed powder of slaked lime powder and dawsonite powder in the exhaust gas downstream of the exhaust gas cooling unit 11 of the incineration facility 10. Means 12 for adding to the dust, a dust collector 13 for collecting dust contained in the exhaust gas and the exhaust gas treating agent, a storage tank 14 for storing the collected powder, and the soot and dust discharged from the storage tank 14 through the quantitative feeder 19 It is only necessary to have a means 15 for supplying water, a water supply means 17 and a blower 18 for sucking exhaust gas, and it is not necessary to provide means for adding a treating agent for heavy metals after collecting dust. The storage tank 14 may be omitted. The purified exhaust gas is discharged outside through the chimney 16.

  EXAMPLES Hereinafter, the present invention will be specifically described by examples, and comparative examples and reference examples will be shown together with examples. Table 1 shows the components of the exhaust gas treating agent used in each of these examples. Table 2 shows an overview of incineration facilities using exhaust gas treatment agents.

Slaked lime having a specific surface area of 39.5 m ² / g was used. Aluminum hydroxide having an amorphous surface area with a specific surface area of 90 m ² / g was used. Dorsonite having a specific surface area of 79 m ² / g was used. The average particle size was measured using a laser diffraction particle size distribution measuring device (LA-920) manufactured by Horiba. The bulk specific gravity was measured using a powder tester made by Hosokawa Micron.

[Exhaust gas neutralization treatment] Example 1, Comparative Examples 1 to 3, Reference Example The treatment agent (Nos. 1 to 5) shown in Table 1 was introduced into the exhaust gas passage of the facility I, and the exhaust gas neutralization treatment test was conducted. Carried out. In the existing slaked lime supply pipe shown in FIG. 3, each treatment agent is disposed between the slaked lime quantitative supply machine A and the slaked lime transfer blower B and the slaked lime supply port C located upstream of the dust collector and the exhaust gas treatment agent tank D and the fixed quantity. A supply feeder E was provided, and the treatment agent of the example was quantitatively supplied from the tank D, and the slaked lime of the comparative example was quantitatively supplied from the feeder A. In the test method, the waste separation in the incineration facility I is progressing, and the waste gas in the waste pit is sufficiently stirred, so the acid gas concentrations of HCl and SO ₂ present in the exhaust gas are extremely stable. The fixed amount (X kg / hr) of the treating agent that can maintain the operation control standard values of HCl and SO ₂ in the exhaust gas (HCl <30 ppm, SO ₂ <30 ppm) continuously for one week was determined. The results are shown in Table 3.

  As shown in Table 3, the necessary amount of the treating agent of Example 1 of the present invention is considerably reduced as compared with Comparative Examples 1 and 2. Specifically, the amount of slaked lime required for the neutralization treatment of the exhaust gas is 34.7 kg / hr to 35 kg / hr in Comparative Examples 1 and 2 and Reference Example 1, but in Example 1, dosonite is neutralized. Therefore, the amount of slaked lime used is small, 29.6 kg / hr is sufficient, and the amount of slaked lime can be reduced by about 15%.

  In addition, although the amount of the exhaust gas treating agent of Reference Example 1 is small, the total amount is slaked lime, and the amount of slaked lime necessary for the neutralization treatment is almost the same as in Comparative Examples 1 and 2. Moreover, since the processing agent of Reference Example 1 does not contain a heavy metal stabilizer, as shown in the results of the following heavy metal processing (Table 4), the amount of Pb eluted is remarkably large and heavy metals cannot be insolubilized. For this reason, for example, as shown in Reference Example 3, a chemical treatment or the like for insolubilizing heavy metals is required separately.

[Heavy metal treatment] Example 2, Comparative Examples 4-6, Reference Examples 2-3
After performing the exhaust gas neutralization treatment, a certain amount of water is added to the dust collected by the dust collector and introduced into the same kneading apparatus as the conventional treatment, and the conventional heavy metal treatment agent is not supplied except in Reference Example 3. Only water kneading was performed. These treated products were subjected to Environmental Agency Notification No. 13 test in 1973, and the amount of Pb elution and pH were measured. The results are shown in Table 4.

  As shown in Table 4, in Example 2 of the present invention, the elution amount of Pb was reduced to the same extent as Comparative Example 4 and Comparative Example 6. On the other hand, as shown in Table 3, Comparative Example 4 (Comparative Example 1 in Table 3) and Comparative Example 6 (Comparative Example 3 in Table 3) are treatment agents necessary for exhaust gas neutralization treatment and dust heavy metal stabilization treatment. Therefore, when a series of treatments from neutralization treatment to heavy metal treatment is performed, the treating agent of Example 2 is Comparative Example 4 (Comparative Example 1 in Table 3) and Comparative Example 6 (Table 3). The same treatment effect is achieved with a smaller amount used than in Comparative Example 3). Further, Comparative Example 2 in Table 3 contains almost the same amount of aluminum hydroxide in place of dosonite. However, as shown in Comparative Example 5 in Table 4 (Comparative Example 2 in Table 3), the elution amount of Pb In many cases, heavy metals cannot be sufficiently stabilized.

[Exhaust gas neutralization treatment] Examples 3 to 5 and Comparative Examples 7 to 8
In the incineration facility (II), the treatment agents shown in Table 5 were supplied in the same manner as in the facility (I), and the exhaust gas was neutralized. The required amount of treating agent is the fixed amount of treating agent (X kg / hr) that can maintain the operation control standard values of HCl and SO ₂ in exhaust gas (HCl <200 ppm, SO ₂ <35 ppm) continuously for one week. ). The results are shown in Table 5.

As shown in Table 5, the concentration of the acidic gas components of HCl and SO ₂ contained in the exhaust gas was sufficiently below the operation management standard for all the treatment agents and was satisfactory. However, as the blending ratio of dosonite increases, the required amount of exhaust gas treating agent tends to increase. Therefore, considering No. 23 and No. 24 in Table 5, the dosonite content is preferably less than 45%. .

[Heavy metal treatment] Examples 3 to 5 and Comparative Examples 7 to 8
After the exhaust gas neutralization treatment in Examples 3 to 5 and Comparative Examples 7 to 8, a certain amount of water was added to the dust collected by the dust collector and introduced into the same kneading apparatus as the conventional treatment, and the conventional heavy metal Only water kneading was performed without supplying the treatment agent. These treated products were subjected to Environmental Agency Notification No. 13 test in 1973, and the amount of Pb elution and pH were measured. The results are shown in Table 6.

  As shown in Table 6, all of the samples No. 26 to No. 29 having a dosonite content of 20% or more have sufficiently small elution amounts of Pb and satisfy the landfill elution standard. For example, the Pb elution amount of sample No. 26 is 0.02 mg / L, which is about 1/10 or less of the landfill elution standard of 0.3 mg / L, which sufficiently satisfies the landfill standard. On the other hand, Sample No. 25 having a dosonite content of 10% has a large Pb elution amount of 5.6 mg / L and does not satisfy the landfill elution standard. Accordingly, the content of dosonite is suitably 20% or more from the results in Table 6, and when the results in Table 5 are taken together, it is understood that the content of dawsonite is preferably 20% to 45%.

Schematic which shows the exhaust gas processing system of this invention. Schematic which shows the conventional waste gas processing system. Schematic which shows the exhaust gas processing system used in the test.

Explanation of symbols

10-incineration facility, 11-exhaust gas cooling section, 12-exhaust gas treatment agent addition means, 13-dust collector, 14-storage tank 14, 15-hydrokneading means, 16-chimney, 17-water supply means, 18-blower, 19- Metering feeder, 20-incineration facility, 21-exhaust gas flow path, 22-exhaust gas cooling unit, 23-alkali chemical charging unit, 24-dust collector, 25-blower, 26-chimney, 27-storage tank, 29-quantitative feeder, 30 -Kneading device, 31-Heavy metal treatment agent addition means, 32-Water supply means, 33-Hopper. A-slaked lime feeder, B-blower, C-treatment agent supply port, D-treatment agent tank, E-quantitative feeder.

Claims (5)

An exhaust gas treatment agent comprising a mixed powder of slaked lime powder and dawsonite powder, which neutralizes acidic components in exhaust gas and stabilizes heavy metals in exhaust gas.
The exhaust gas treating agent according to claim 1, wherein the mixed powder contains 20% to 45% of dawsonite powder.
The exhaust gas treating agent according to claim 1 or ² , wherein the specific surface areas of the slaked lime powder and the dosonite powder are 30 m ² / g or more.
The exhaust gas treating agent according to any one of claims 1 to 3 is added to the exhaust gas to neutralize acidic components contained in the exhaust gas and adsorb heavy metals, and then the exhaust gas is passed through a dust collector to A method for treating exhaust gas, comprising collecting dust and an exhaust gas treating agent, and hydromixing the collected powder to form a clay.
Means for adding an exhaust gas treatment agent composed of a mixed powder of slaked lime powder and dosonite powder to the exhaust gas, a dust collector for collecting the soot and exhaust gas treatment agent contained in the exhaust gas, and means for hydro-kneading the collected powder An exhaust gas treatment system characterized by comprising:

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