JPH09314091A - Waste treatment method - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a waste treatment method capable of reliably encapsulating heavy metals in soot and dust generated during waste incineration to prevent re-elution. SOLUTION: Soot and dust generated during waste incineration and containing heavy metals such as Pb react with aqueous solution A containing soluble silicate and carbonate containing no polyvalent metal, and hydroxide ion. Is a waste treatment method comprising adding an aqueous solution B containing a polyvalent metal cation that forms an insoluble or sparingly soluble hydroxide, and further adding water as necessary, and mixing the heavy metal in the dust. Encapsulate securely to prevent re-elution. Furthermore, in the exhaust gas treatment device attached to the waste incineration facility, soot and dust have a specific surface area of 30 m ² / for the purpose of neutralizing and reducing acidic gas such as hydrogen chloride gas.
When the slaked lime of g or more or the powdery calcium silicate compound having a specific surface area of 20 m ² / g or more is blown into the exhaust gas and captured by the electrostatic precipitator or the bag filter from the exhaust gas, the above effect is more easily exhibited.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for stabilizing waste, and more particularly, to a heavy metal (Pb, Cd, Cr) contained in dust produced from exhaust gas generated during incineration of waste. ⁶⁺ , As, Hg, Cu, Z
n), etc., is effective in stabilizing wastes, and in particular, hazardous heavy metals in soot and dust discharged from municipal waste incineration facilities where it is difficult to prevent lead (Pb) elution The present invention relates to a waste treatment method effective for stabilization.

[0002]

2. Description of the Related Art Conventionally, in the disposal of soot and dust generated when incinerating waste, humidification treatment has been performed to prevent scattering during transportation, and cement treatment has been performed mainly for solidification molding. However, these methods have various problems from the viewpoint of suppressing the elution of harmful metals from soot and dust, and unless careful attention is paid to their handling, heavy metals will be eluted from discarded soot and dust. The next pollution may occur.

[0003] For example, a general waste incineration facility is typically an incinerator, a heat exchanger for cooling exhaust gas, a water spray device, and slaked lime blowing for neutralizing acid gases such as hydrogen chloride gas. Device (blowing into the exhaust gas guide pipe),
And a dust collector and the like, and a device / device for removing harmful components such as sulfur oxides (SOx), nitrogen oxides (NOx) and dioxins may be added.
As described above, slaked lime for neutralizing acid gas is blown into the exhaust gas generated during waste incineration, and the dust collected from such exhaust gas includes dust, slaked lime and hydrogen chloride gas. The reaction product with the acidic gas, unreacted slaked lime, and heavy metals such as Pb are contained. This soot and dust is landfilled in the final disposal site after being subjected to an intermediate treatment so that the heavy metal is not eluted. However, it cannot be said that the stabilization of the heavy metal has been sufficiently performed conventionally. Pb for waste treatment as described above
The problem of elution of heavy metals such as the above was particularly remarkable in the soot and dust generated from the exhaust gas generated during the incineration of waste such as general waste and captured by the dust collector.

[0004]

As described above, in the prior art, it is possible to suppress the elution of harmful metals from wastes containing heavy metals such as Pb, in particular, soot and dust collected from exhaust gas generated during incineration of wastes. It was difficult to do. Therefore, there has been a demand for a treatment method in which heavy metals and the like are reliably enclosed even during landfill disposal and do not re-elute. Therefore, the present invention, in view of the current state of such waste treatment, especially the dust treatment that is collected during waste incineration, waste that can reliably stabilize various heavy metals in dust and suppress the elution thereof. It is intended to provide a method for treating a product.

[0005]

DISCLOSURE OF THE INVENTION As a result of intensive studies made by the present inventors for the purpose of solving the above-mentioned problems in the prior art, as a result, waste or a large amount of waste that cannot substantially prevent the elution of heavy metals such as Pb. It has been found that waste products that require heavy metal stabilizers have common characteristics. That is, since the soot and dust generated during incineration of waste contains a large amount of unreacted slaked lime that is blown to reduce acid gases such as hydrogen chloride gas in the exhaust gas, the soot and dust becomes highly alkaline. It was found that this promotes the elution of amphoteric metals such as Pb and inhibits the effect of the heavy metal stabilizer. That is, as described above, in the exhaust gas treating apparatus of the waste incinerator, slaked lime is blown as the neutralizing agent in order to satisfy the emission standard of acidic gas such as hydrogen chloride gas. However, since the slaked lime that has been used conventionally does not always have sufficient reaction efficiency with the acidic gas, it is often blown in an amount equal to or more than the equivalent amount of the generated acidic gas. Therefore, the soot and dust collected from such exhaust gas contains a large amount of unreacted slaked lime and becomes highly alkaline. Therefore, it was conceived that the hydroxide ions derived from the slaked lime are reduced to effectively suppress the elution of Pb and the like. Further, in place of conventionally used slaked lime, use of slaked lime or powdered calcium silicate hydrate, which has a higher specific surface area and excellent reaction efficiency, in place of conventional slaked lime in an exhaust gas treatment apparatus The present invention has been completed based on the idea that the amount of unreacted slaked lime contained in soot and dust can be reduced, and thereby the elution of heavy metals such as Pb can be suppressed more easily. Is.

That is, the present invention provides a waste containing a heavy metal such as Pb and a soluble alkaline polyvalent metal compound, an aqueous solution A containing a soluble silicate and a carbonate containing no polyvalent metal as a main component, An aqueous solution B containing a polyvalent metal cation that reacts with a hydroxide ion to form an insoluble or sparingly soluble hydroxide, and further, if necessary, water is added and the waste is mixed. The content of the method is the processing method. Furthermore, in an exhaust gas treatment device attached to a waste incineration facility, a specific surface area of 30 m ² / g for the purpose of neutralizing and reducing acidic gas such as hydrogen chloride gas.
Above slaked lime (calcium hydroxide) or specific surface area 20
Dust that is generated by blowing powdered calcium silicate hydrate (m ² / g or more) into the exhaust gas, treating the slaked lime or powdered calcium silicate hydrate by blowing it, and trapped by an electrostatic precipitator or a bag filter By carrying out the same treatment as described above, the effect of stabilizing harmful metals in soot and dust is more remarkably exhibited.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The waste treatment method according to the present invention will be described in more detail. Aqueous solution A in the treatment method of the present invention
The action of the aqueous solution B and the aqueous solution B is not clear, but it can be estimated as follows. First, the action of the aqueous solution A will be described. When a waste containing a heavy metal such as Pb and a soluble alkaline polyvalent metal compound is treated according to the present invention, the soluble silicate in the aqueous solution A and the heavy metal ion such as Pb in the waste are represented by the following formula (1). As described above, insoluble heavy metal silicate is generated and the elution of heavy metal is suppressed. Pb ²⁺ + SiO ₃ ^2- → PbSiO ₃ (1) In addition, the silicate in the aqueous solution A and Ca eluted from the waste
And the like react with polyvalent metal ions such that heavy metal such as Pb in the waste is included in the reaction product or the heavy metal is adsorbed on the surface of the reaction product and stabilized. The heavy metal inclusion capacity and adsorption capacity of this reaction product depend on the quantitative relationship between the silicate in the aqueous solution A and the polyvalent metal ion in the waste, and it is almost clear that an optimum value exists. . The optimum value varies depending on the properties of the waste and the amount of silicate, but in most cases, the polyvalent metal ion such as Ca in the waste is excessive relative to the amount of silicate in the aqueous solution A. The better the tendency, the better. Therefore, the carbonate containing no polyvalent metal in the aqueous solution A reacts with the polyvalent metal ion such as Ca in the waste, and the amount thereof is controlled to be smaller, whereby the heavy metal by the silicate as described above is used. The stabilizing effect is promoted.

Next, the action of the aqueous solution B will be described.
When the waste is treated according to the present invention, the hydroxide ion derived from the alkali component in the waste and the polyvalent metal cation in the aqueous solution B are reacted by the reactions shown in the following formulas (2) and (3). It produces insoluble or sparingly soluble hydroxides, lowering the pH of waste products. M ²⁺ + 2OH ⁻ → M (OH) ₂・ ・ ・ (2) M ³⁺ + 3OH ⁻ → M (OH) ₃・ ・ ・ (3) At this time, the solubility of heavy metals in the waste to be treated is If the pH drops to a sufficiently low range, aqueous solution B
It is possible to suppress the elution of heavy metals such as Pb only by the action of. When treating soot and dust collected in an incinerator, high specific surface area slaked lime or powdered calcium silicate hydrate is used to treat the amount of unreacted slaked lime in the soot and dust when treating exhaust gas. As a result, this effect is very likely to be exhibited. However, the heavy metals contained in the waste are not limited to amphoteric metals such as Pb,
There are many heavy metals that are newly eluted with a decrease in pH. Therefore, depending on the pH range changed by the action of the aqueous solution B, the elution of the heavy metal which has not been eluted originally may be promoted. In this respect, in the method of the present invention, synergistic effect can be expected by using the aqueous solution A together even if there is no decrease in pH until the elution of the heavy metal is sufficiently suppressed in the aqueous solution B, and high stabilization performance of heavy metals is obtained. Express. That is,
By slightly adjusting the pH range of the waste from alkaline to acidic, the action of the above-mentioned aqueous solution A is dramatically accelerated. This depends on the morphology of the reaction product of the silicate in the aqueous solution A and the polyvalent metal ion such as Ca eluted from the waste depending on the pH, and the pH slightly decreases from the highly alkaline region. Thereby, the gelling time of the aqueous solution of soluble silicate is significantly shortened. Under such conditions, it is considered that the reaction between the silicate in the aqueous solution A and the heavy metal ions in the waste is promoted, and the adsorption ability and inclusion ability of the produced reaction product for heavy metals are improved. Further, the reaction product produced by the reaction between the polyvalent metal cation in the aqueous solution B and the silicate in the aqueous solution A contains the heavy metal more than the reaction product with the polyvalent metal ion eluted from the waste. It seems that a suitable reaction product is produced by adsorption or adsorption. Therefore, aqueous solution A
By using both and the aqueous solution B in combination, even if the heavy metal cannot be sufficiently stabilized, a synergistic effect is exerted and high performance can be exhibited in each of the individual performances.

Next, each of the treating agents used in the present invention will be described. First, the soluble silicate used in the present invention may be a general-purpose one, and examples thereof include lithium silicate, sodium silicate (sodium silicate), potassium silicate, and ammonium silicate. Generally, the solid content of soluble silicate is represented by M ₂ O.nSiO ₂ (M is a cation of silicate), and n (SiO ₂ / M ₂ O composition ratio) represents the molar ratio of the silicate. Since the performance of the soluble silicate depends on the solid content in the case of its aqueous solution, when the addition amount is the same, the higher the silicate concentration is, the higher the heavy metal stabilizing performance is. Regarding the concentration of the soluble silicate, the upper limit of the concentration that can be adjusted varies depending on the type of the soluble silicate, the molar ratio, and the temperature of the solution. On the other hand, as the temperature of the aqueous solution of the soluble silicate becomes higher, the viscosity becomes higher and the handling property may be significantly lowered. Therefore, it is necessary to set the concentration of the soluble silicate in the aqueous solution A after sufficiently considering the performance and the handling property.

Although various kinds of soluble silicates are industrially produced as exemplified above, sodium silicate is a sodium silicate from the viewpoints of stabilizing performance of heavy metals, industrial availability, and cost. It is preferable. It is known that the soluble silicate generally has a faster gelation reaction with heavy metals and polyvalent metals as the molar ratio is higher. In the case of sodium silicate, the molar ratio of commercially available products is in the range of about 0.5 to 4.2, but the higher the molar ratio is, the more excellent the performance is. Therefore, the value is about 2.0 or more. preferable. Furthermore, stabilizing performance of heavy metals, industrial availability,
Considering price, handling property, etc., it is generally preferable in the present invention to select JIS standard product sodium silicate No. 3.

Next, the carbonate used in the present invention may be any carbonate which does not contain a polyvalent metal salt.
The higher the solubility is, the more preferable it is in consideration of being dissolved therein. As the carbonate containing no polyvalent metal salt,
Sodium carbonate, potassium carbonate, sodium hydrogen carbonate,
Examples thereof include potassium hydrogen carbonate, but sodium hydrogen carbonate and potassium hydrogen carbonate release hydrogen ions (H ⁺ ) when dissolved in the aqueous solution A. Therefore, depending on the blending amount, the soluble silicate in the aqueous solution A Gelation is promoted and the entire aqueous solution A may be solidified during storage, which is not preferable. Further, sodium carbonate has a low solubility in water, and cannot be completely dissolved unless it is sufficiently diluted and mixed. On the other hand, potassium carbonate has a very high solubility and can be sufficiently dissolved without being diluted too much. However, it should be noted that when the soluble silicate is sodium silicate, the sodium ion of sodium silicate and the carbonate ion of potassium carbonate react with each other to form sodium carbonate.

The polyvalent metal cation in the aqueous solution B will be described. Most of the hydroxide ions eluted from the waste are derived from the alkaline components blown in to neutralize the acidic gas generated during waste incineration when the waste is dust collected in an incinerator. Therefore, in the polyvalent metal cation contained in the aqueous solution B, the hydroxide produced by the reaction with the hydroxide ion needs to have a lower solubility than calcium hydroxide. As long as this condition is satisfied, any polyvalent metal cation may be selected, but in consideration of industrial availability and handling, aluminum ion, magnesium ion, iron (II) ion,
It is preferred to choose among iron (III) ions. Among them, aluminum sulfate (sulfuric acid band), aluminum chloride, polyaluminum chloride (PA) is particularly taken into consideration in terms of industrial availability, stabilizing performance of heavy metals, price and the like.
C), sodium aluminate, iron (II) sulfate, iron (III) chloride, magnesium sulfate and magnesium chloride are preferable. Further, a plurality of these substances may be used in combination, if necessary. It is also preferable to use a waste liquid discharged from a chemical plant or the like as the aqueous solution containing the polyvalent metal cation from the viewpoint of recycling useful substances. When the pH of the aqueous solution B is low, corrosion may be promoted depending on the material of the pipes and the kneader that use the aqueous solution B. If this poses a problem, it is desirable to change the material of the equipment or adjust the pH of the aqueous solution B from neutral to alkaline range before use. In that respect, when sodium aluminate is used, it is not necessary to pay attention to these points, which is preferable.

The amount of the above-mentioned aqueous solution A and aqueous solution B added to the waste in the treatment method of the present invention depends on the properties of the waste, particularly the amount of heavy metal elution without treatment, the amount of alkaline components remaining in the waste, and the target. The allowable elution amount of the heavy metal, further, the compounding ratio of the soluble silicate and carbonate in the aqueous solution A,
It depends on the addition ratio of the aqueous solution A and the aqueous solution B to the waste. Practically, the selection of the addition amounts of the aqueous solution A and the aqueous solution B that achieves the lowest cost for achieving the target elution amount is a factor that determines the addition amount. In a normal case, the solid content of the aqueous solution A is 3 to 30 parts by weight and the solid content of the aqueous solution B is 5 parts by weight with respect to 100 parts by weight of the waste.
It is possible to suppress the elution amount of heavy metals to be equal to or less than the legally regulated value with an addition amount such that the amount becomes ˜40 parts by weight.

In the method of the present invention, the method of adding the aqueous solution A and the aqueous solution B to the waste is arbitrarily selected, such as a method of sequentially adding the aqueous solutions A and B to the waste, a method of simultaneously adding the aqueous solutions A and B, and the like. However, the preferable addition method differs depending on the properties of soot and dust, and therefore it is preferable to examine it in advance by a preliminary test or the like. Since the aqueous solution A and the aqueous solution B may be solidified if they are mixed before being added to the waste, it is preferable to store the aqueous solution A and the aqueous solution B separately until they are added to the waste. .

In carrying out the waste treatment method of the present invention, there is a possibility that inconvenience may occur in handling, especially in cold regions. That is, when the temperature during the use of the aqueous solution A is remarkably lowered, the viscosity is remarkably increased and the fluidity is lowered. Also in the aqueous solution B, a salt of a polyvalent metal may be precipitated due to a decrease in temperature. In such a case, by keeping the storage tank for the treatment agent warm, the above-mentioned problems are almost eliminated.

The waste treatment method of the present invention comprises:
Aqueous solution A and aqueous solution B and, if necessary, water are added and mixed to exhibit sufficient effect. Further, kneading these mixtures is a more preferable method. In addition, curing the treated material for a certain period of time at a certain temperature or higher is an effective means for further exhibiting the effect of the treating agent. In this way, the effect of the treatment agent is further expressed by curing, that the treatment agent used in the present invention is
It suggests that the reaction is instantly initiated by contact with the waste components and the effect is exhibited, but the reaction gradually proceeds thereafter. Generally, the longer the curing time, the better. It is also possible to further accelerate the effect by heating the treated material during curing, shortening the curing time by curing the compounded mixture of the waste and the treatment agent at a predetermined temperature, It becomes possible to promptly dispose of the product.

The waste treatment method of the present invention is applicable to any waste as long as it contains a heavy metal such as Pb and a soluble alkaline polyvalent metal compound. Dust captured by an electric dust collector or a bag filter attached to an incinerator contains unreacted components of slaked lime blown for the purpose of neutralizing acid gas such as hydrogen chloride gas, and the treatment method of the present invention is , Especially effective against such dust. Further, in this dust treatment, as an alkaline substance blown in to neutralize the acidic gas such as hydrogen chloride in the exhaust gas generated at the time of waste disposal as described above, a specific surface area of 30 m is used instead of the conventionally used slaked lime. ^{By using} slaked lime of ² / g or more or powdery calcium silicate hydrate with a specific surface area of 20 m ² / g or more, the amount of unreacted slaked lime contained in soot and dust is reduced, and the effect of the treatment agent is more effective. Is expressed.

Therefore, the high specific area slaked lime and calcium silicate hydrate used for the exhaust gas treatment will be described. First, the specific surface area used in the present invention is 30 m ² / g
The above-mentioned slaked lime is preferred to have a larger specific surface area in consideration of reaction efficiency with an acidic gas such as hydrogen chloride gas, but from the viewpoint of industrial availability, a specific surface area of about 30 to 60 m ² / g is preferred. The slaked lime having such a specific surface area can be produced by, for example, the method disclosed in Japanese Patent Publication No. 06-8194.

The method of Japanese Patent Publication No. 06-8194 will be described. That is, in the method for producing slaked lime disclosed herein, finely lumped or crushed lightly calcined lime is strongly and uniformly mixed with a slaked liquid consisting of an organic solvent that delays the reaction with water. Thus, in the method for producing dry calcium hydroxide by soaking lime, a mixture of a soaking liquid consisting of 30 to 50 parts by volume of water and 50 to 70 parts by volume of an organic solvent and lime is mixed in a mixing container. At a temperature of 45 ° C. or lower. The reaction mixture is then transferred to the main reaction vessel in which it is brought to a temperature of 50-70 ° C. by means of a heating device and the final reaction is carried out in a second
In the reaction vessel of. The proportion of lime to slaked liquid in the mixing vessel is then selected so that a reaction temperature of 85 to 110 ° C. is achieved in the second reaction vessel. Further, in a subsequent degassing step, the adhering solvent is removed from the finished calcium hydroxide by applying a vacuum and / or purging with an inert gas.

As the slaked lime having a high specific surface area as described above, it is industrially preferable to use slaked lime "Tamacalc" manufactured by Okutama Kogyo Co., Ltd. The effect of the high specific surface area slaked lime can be confirmed if the specific surface area is 20 m ² / g or more, but the effect is more remarkable as the specific surface area is higher.
It is preferably m ² / g or more. It should be noted that other than "Tamacalc", any one having a specific surface area within the above range can of course be used.

The amount of slaked lime having a specific surface area of 30 m ² / g or more should be appropriately set according to the concentration of hydrogen chloride gas in the exhaust gas, the temperature of the exhaust gas, the flow rate, and the concentration of hydrogen chloride gas finally discharged to the outside. No, but JIS special slaked lime (specific surface area 14.5m)
² / g), the specific surface area is about twice as high, so the reaction efficiency with hydrogen chloride gas is also high, and it is finally discharged with an addition amount of about half (weight) of JIS Special Issue slaked lime. The hydrogen chloride gas concentration can be made similar.

The specific surface area used in the present invention is 20 m.
Regarding the powdery calcium silicate hydrate of ² / g or more, considering the reaction efficiency of hydrogen chloride gas, etc., it is preferable that the specific surface area is large, but from the viewpoint of industrial availability, the specific surface area is 2
It is preferably about 0 to 60 m ² / g. Specifically, “HP: Sunparfer” manufactured by Asahi Kasei Corporation (typically represented by 5CaO · 6SiO ₂ · 5H ₂ O)
Is industrially preferable. The powder calcium silicate hydrate may be used by dispersing it in a solvent and spraying it into the exhaust gas guide passage, and also from the viewpoint of reactivity with hydrogen chloride gas, water may be used. It is a preferred embodiment to disperse and use. When spraying into the exhaust gas guide pipe, the particle size of calcium silicate hydrate is 1000 μm in order to prevent clogging in the spray pipe.
The following is preferred.

The amount of the powdery calcium silicate hydrate having a specific surface area of 20 m ² / g or more depends on the concentration of hydrogen chloride gas in the exhaust gas, the temperature of the exhaust gas, the flow rate and the hydrogen chloride gas finally discharged to the outside. Although it must be set appropriately according to the concentration, etc., the reaction efficiency with hydrogen chloride gas is large because it has a large specific surface area as compared with JIS special slaked lime (specific surface area 14.5 m ² / g) that is commonly used in the past. Is high, JIS
Despite having less alkali component per unit weight than special slaked lime, it has the same ability to neutralize acidic gases such as hydrogen chloride gas, and as a result, it is possible to obtain the same amount from the exhaust gas treated with this calcium silicate hydrate. It is possible to reduce the amount of unreacted residual alkali components in the captured soot and dust. In addition,
Although the mechanism of action is not clear, it should be additionally noted that the powdery calcium silicate hydrate used in the present invention has an effect of adsorbing and stabilizing a heavy metal such as Pb.

[0024]

The mechanism by which the waste treatment method of the present invention stabilizes heavy metals such as Pb is not clear, but it can be estimated as follows. (1) The soluble silicate in the aqueous solution A reacts with the heavy metal eluted from the waste to produce an insoluble substance. (2) The silicate in the aqueous solution A reacts with the polyvalent metal eluted from the waste, and the reaction product adsorbs and contains the heavy metal in the waste. (3) The carbonate in the aqueous solution A controls the amount of polyvalent metal eluted from the waste, and the action of (2) above is promoted. (4) The polyvalent metal cation of the aqueous solution B reacts with the hydroxide ion eluted from the waste to be insolubilized, and the pH is lowered. Accordingly, the actions 1) and 2) are synergistically promoted. (5) By treating the exhaust gas generated during waste incineration with slaked lime or powdery calcium silicate hydrate having a large specific surface area, the soot and dust collected from this exhaust gas have less residual alkaline components. Therefore, the action (4) is easily exhibited, and the actions (1) and (2) are synergistically promoted.

[0025]

EFFECT OF THE INVENTION Using the waste treatment method of the present invention, Pb
By treating the waste containing heavy metals such as Pd, the heavy metals, especially Pb in the dust is stabilized, and the elution amount is reduced. In addition, the mixture of the waste and the treatment crack obtained in the present invention can be reused as a material having a very small amount of heavy metal eluted, such as a roadbed material or an aggregate of cement, and can be a valuable resource.

[0026]

EXAMPLES The present invention will be described in more detail with reference to examples of actual salts, but the present invention is not limited thereto.

(Comparative Example) Dissolution tests of soot and dust I and II produced in a municipal solid waste incineration facility and captured by a bag filter, without treatment, according to the Environmental Agency Notification No. 13 method (Japan) The test results are shown in Table 1.

[0028]

[Table 1]

(Composition of Treatment Agent) The composition of the treatment agent used in the examples is shown in Table 2.

[0030]

[Table 2]

(Comparative Examples 2 to 7 and Example 1) Dust I was diluted with a predetermined amount of the treating agent so that the amount of water added was approximately 60 to 80 parts by weight with respect to the dust, and the mixture was added and kneaded. The product was cured and solidified for 1 day. After solidification, the crushed product was classified with a sieve having an opening of 5 mm, and 50 g of the product that passed through the sieve was collected and a dissolution test was conducted. Table 3 shows the type of treatment agent used, the amount of treatment agent added to the waste (solid content), and the Pb concentration.

[0032]

[Table 3]

Comparison between Comparative Examples 1 to 3 and Comparative Example 4 showed that a treating agent comprising a soluble silicate and an aqueous solution containing a carbonate containing no polyvalent metal as a main component is effective.
Further, from the comparison between Comparative Examples 4 and 5 and Example 1, by carrying out the waste treatment method of the present invention, an aqueous solution A containing a soluble silicate and a carbonate not containing a polyvalent metal as main components is obtained.
And an aqueous solution B containing a polyvalent metal cation that reacts with hydroxide ions to form insoluble or sparingly soluble hydroxides.
It was shown that and produce a synergistic effect. Further, from the comparison between Comparative Examples 6 and 7 and Example 1, as the aqueous solution A, a solution containing a soluble silicate and a carbonate not containing a polyvalent metal as the main components was used as the aqueous solution A.
It was shown to be more effective than each of the carbonates containing no polyvalent metal alone.

(Comparative Examples 8 to 18 and Examples 2 to 9) The same procedure as in the above Comparative Examples and Examples was carried out except that Dust II was used. Table 4 shows the type of treatment agent used, the amount added, and the Pb concentration.

[0035]

[Table 4]

As can be seen from the comparison between Comparative Examples 8 to 17 and Examples 2 to 9, the combined use of the treatment agents A and B produced synergistic effects, and the treatments were carried out independently. The performance exceeded that of the case. Therefore, it contains an aqueous solution A containing a soluble silicate and a carbonate containing no polyvalent metal as main components, and a polyvalent metal cation that reacts with a hydroxide ion to form an insoluble or sparingly soluble hydroxide. It was shown that the waste treatment method of the present invention using the aqueous solution B and Comparison between Comparative Example 18 and Examples 2 to 9 revealed that aluminum, iron (II), iron (III) and magnesium were effective as the polyvalent metal cation contained in the liquid B. . Further, in the case where a solution containing calcium ions similar to the alkaline component remaining in the soot and dust was added as the solution B (Comparative Example 18),
As is clear from the above comparison, it is not preferable.

(Comparative Example 19 and Example 10) Soot and dust generated when the incinerator and the exhaust gas treatment device were operated while adjusting the slaked lime so that the hydrogen chloride gas temperature in the outdoor exhaust gas was kept constant in the municipal waste incineration facility It was collected and treated with dust. Soot and dust is JI as slaked lime
Two types were collected: one using S special slaked lime (Comparative Example 19) and one using slaked lime “Tamacalc” manufactured by Okutama Kogyo Co., Ltd. (Example 10). For each of the above two kinds of dust, the addition amount (solid content) of the treating agent A and the treating agent B shown in Table 5 and further water were added and kneaded.
After curing at ℃ for 1 day, Pb dissolution test according to the Environmental Agency Notification No. 13 method (Japan). Table 5 shows the results.

[0038]

[Table 5]

From the results of Table 5 above, it is possible to effectively elute Pb by carrying out the method for treating soot and dust of the present invention on soot and dust collected from exhaust gas treated with slaked lime having a large specific surface area. It has become clear that That is, even if the Pb concentration cannot be reduced to 0.3 mg / L or less of the landfill standard value in the dust collected by performing the exhaust gas treatment by the conventional method such as JIS special slaked lime,
In the soot and dust of the example obtained by performing the exhaust gas treatment of the present invention, the performance of the heavy metal stabilizer is remarkably exhibited, and the level can be set to the standard value or less. As a result, it is clear that the waste treatment method of the present invention is extremely effective in preventing the elution of heavy metals in dusts generated during waste incineration.

(Comparative Example 20 and Example 11) In an incineration facility for municipal waste, an incineration facility while adjusting the amount of slaked lime or powdered calcium silicate hydrate so that the concentration of hydrogen chloride gas in the outdoor exhaust gas is constant. And the dust when the exhaust gas treatment equipment was operated was collected and treated. As for the soot and dust, when JIS special slaked lime was used (Comparative Example 20) and as powdered calcium silicate hydrate "HP: Sunparfer, specific surface area 35 m ² /
g) was used (Example 11).
To the above-mentioned two kinds of dust, the treating agent A and the treating agent B in the amounts shown in Table 6 were respectively added, and water was added and kneaded. After curing at 20 ° C. for 1 day, the Environmental Agency Notification Method No. 13 A Pb dissolution test by (Japan) was conducted. The results are shown in Table 6.

[0041]

[Table 6]

From the results shown in Table 6 above, the specific surface area of 20 m ² /
By applying the waste treatment method of the present invention to the dust collected from the exhaust gas treated using the powdery calcium silicate hydrate in an amount of g or more, it is clear that the elution of Pb can be effectively suppressed. became. That is, in the case of dust collected by performing exhaust gas treatment by a conventional method such as JIS special slaked lime, even if the Pb leak rate cannot be less than 0.3 mg / L of the landfill standard value, the exhaust gas treatment of the present invention is performed and collected. In the case of soot and dust, the performance of the heavy metal stabilizer is remarkably exhibited, and it can be reduced to the standard value or less. As a result, it has been clarified that the waste treatment method of the present invention is extremely effective in preventing the elution of heavy metals in dusts generated during waste incineration.

Claims (13)

[Claims] 1. A waste containing a heavy metal such as Pb and a soluble alkaline polyvalent metal compound, an aqueous solution A containing a soluble silicate and a carbonate containing no polyvalent metal as main components, and hydroxylation. A method for treating wastes, which comprises mixing an aqueous solution B containing a polyvalent metal cation that reacts with a product ion to form an insoluble or sparingly soluble hydroxide and water if necessary, and mixing. 2. The waste treatment method according to claim 1, wherein the waste is dust collected by an electrostatic precipitator or a bag filter attached to a waste incineration facility. 3. A slaked lime having a specific surface area of 30 m ² / g or more is blown into the exhaust gas for the purpose of neutralizing and reducing acidic gas such as hydrogen chloride gas in an exhaust gas treatment apparatus attached to a waste incineration facility. Reacts with aqueous solution A containing soluble silicate and carbonate containing no polyvalent metal as main components, and dust ions generated from exhaust gas after being blown in and treated, and captured by an electrostatic precipitator or a bag filter. A method for treating wastes, which comprises mixing an aqueous solution B containing a polyvalent metal cation that forms an insoluble or sparingly soluble hydroxide with water, and further adding water if necessary. 4. A powdery calcium silicate hydrate having a specific surface area of 20 m ² / g or more for neutralizing and reducing acidic gas such as hydrogen chloride gas in an exhaust gas treatment device attached to a waste disposal facility. Blown into the exhaust gas, generated from the exhaust gas after processing by blowing this powdery calcium silicate hydrate,
Dust captured by electric dust collectors and bag filters,
An aqueous solution A containing a soluble silicate and a carbonate containing no polyvalent metal as a main component, and an aqueous solution B containing a polyvalent metal cation that reacts with a hydroxide ion to form an insoluble or sparingly soluble hydroxide. A method for treating wastes, further comprising adding water as needed and mixing. 5. The waste treatment method according to claim 1, wherein the waste, the aqueous solution A and the aqueous solution B are mixed and further kneaded. 6. The waste treatment method according to claim 1, wherein the waste, the aqueous solution A and the aqueous solution B are mixed and further cured. 7. The waste treatment method according to claim 1, wherein the soluble silicate is sodium silicate. 8. The waste treatment method according to claim 7, wherein JIS standard product sodium silicate No. 3 is used as the soluble silicate. 9. The carbonate containing no polyvalent metal salt is potassium carbonate, claim 3, or claim 4.
The waste treatment method according to any one of 1. 10. The polyvalent metal cation in the aqueous solution B is aluminum ion, magnesium ion, iron (I
The waste treatment method according to claim 1, wherein the waste treatment method is at least one selected from the group consisting of I) ions and iron (III) ions. 11. The aqueous solution B comprises aluminum sulfate (sulfate band), aluminum chloride, polyaluminum chloride (PAC), sodium aluminate, iron sulfate (I).
I), iron (III) chloride, magnesium sulfate, and at least one selected from the group consisting of magnesium chloride as a main component, claim 1, claim 3, or claim 4. Waste treatment method. 12. The solid content of the aqueous solution A is 3 to 30 relative to 100 parts by weight of waste or soot and dust.
Claims 1, 3 which are added so that it becomes a weight part.
Alternatively, the waste treatment method according to claim 4. 13. The solid content of the aqueous solution B is 5 to 40 relative to 100 parts by weight of waste or soot and dust.
Claims 1, 3 which are added so that it becomes a weight part.
Alternatively, the waste treatment method according to claim 4.