JPH09174019A - Treatment of general waste incineration ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a solid containing a heavy metal whose eluted concentration is limited within the range of a reference value and at a low cost by adding, and mixing water-granulated fine powder containing gypsum, produced at a blast furnace, to generate waste incineration ash together with water, then extruding the mixture and molding it using a molding machine. SOLUTION: Water-granuated fine powder containing gypsum, produced at a blast furnace, is added to and mixed with general waste incineration ash together with water, and the mixture is extruded and molded using a molding machine. In addition to the water-granulated fine powder originating from the blast furnace, a molten steel mill slag or a fibrous material such as sawdust is added and mixed depending on occasion. Further, to continue a hydration reaction, a recovered water at water temperatures of 60-80 deg.C used for slow- cooling a molten slag from a blast furnace is sprayed onto the top part of a stack of the moldings while curing the moldings by steam. About 1-10wt.% of the molding thus treated is added as such or in the form of a crushed product adjusted to the grain size of 5-0mm, to and mixed with a natural broken stone or the steel mill slag for the use as a road macadam.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating general waste incineration ash (hereinafter referred to as incineration ash),
Specifically, it relates to a method of suppressing elution of heavy metals in incinerated ash.

[0002]

2. Description of the Related Art Incinerated ash is often disposed of in landfills, but now that it is difficult to secure landfill sites, it is becoming increasingly difficult to dispose of it, and even if incinerated ash is used for landfills, , Hazardous substances such as heavy metals from incinerated ash may elute into groundwater etc. due to rainwater etc. and cause secondary pollution. In addition, since the incineration ash is a very fine powder, there are restrictions such as stabilization of the heavy metals contained, volume reduction, and prevention of incineration ash dust scattering during landfill work. There are many examples of performing grain or molding / solidification treatment.

As a general method for treating incinerated ash, a cement solidification method, an asphalt solidification method, a melt solidification method, etc. have been proposed and partially put into practical use. Therefore, each incineration ash solidification method will be described below.

The cement solidification method includes hydroxide conversion of heavy metals by alkali components in cement, adsorption of heavy metals by cement solidification products, chemical bonding between components in cement solidification products and heavy metals, physical encapsulation by cement gel, etc. Therefore, the harmful substance is fixed in the solidified substance, and in many cases, it is effective in preventing the elution of the harmful substance.

In the asphalt solidification method, since the fluidity is improved by heating the asphalt, the incineration ash and the asphalt can be kneaded well and the molded product can be made uniform. Since there is also an increase, the yield of molded products is high. In addition, the water repellency of the asphalt itself makes it difficult for water to enter the inside of the molded product, so it has the advantage of having long-term strength at the landfill.

The melt-solidification method is a method in which a material to be melted (incinerated ash) is heated to 1200 to 1500 ° C. in a furnace by fuel or electricity to melt the incinerated ash to form a slag. Of the heavy metals in the incinerated ash, those with a low boiling point are partially volatilized in the gas, but other heavy metals migrate into the slag and become glassy slag, which prevents the elution of heavy metals from the cooled and solidified slag. it can. That is, when the silica in the incineration ash melts, it becomes a network structure of SiO ₂ , but the heavy metals that have migrated into the slag are solidified while being wrapped in this network and become an extremely safe glassy material, which makes it difficult Solubilization is possible.

[0007]

However, in the cement solidification method, the elution concentration of heavy metals in the elution test of the solidified product may not partially meet the criterion standard value. In such a case, ordinary cement and ultra-rapid hardening are used. It is necessary to use a large amount of special cement such as cement or to apply a special treatment method, which is a cost disadvantage. In addition, there is currently no method of using the solidified material by the cement-based solidification method due to the problem of heavy metal elution concentration, etc., and the current situation is that it is dumped, and eventually there is a problem that the dump site becomes tight.

[0008] In the asphalt solidification method, it is necessary to carry out compression molding in order for the asphalt to enter the voids of the incineration ash and sufficiently coat and solidify the surface of the particles. However, since the molding process is complicated and continuous treatment is difficult, the initial cost is higher than that of the cement solidification method.
Further, this method only means that the harmful substance is physically wrapped, and there is a drawback that the harmful substance is eluted when the coating is broken.

Compared with the cement solidification method and the asphalt solidification method, the melting and solidification method requires a melting furnace or its auxiliary equipment in the post-process of the refuse incinerator, which increases construction costs and running costs such as fuel costs. There is a problem that it is considerably expensive compared to.

The present invention has been made in view of the above problems, and provides a method for treating and utilizing incinerated ash, which is capable of obtaining a solidified product having a heavy metal elution concentration within a reference value range at low cost. The purpose is to

[0011]

According to the present invention, blast furnace granulated fine powder containing gypsum is added to and mixed with incinerator ash of general waste together with water, and the mixture is molded by an extrusion molding machine.
In addition to ground granulated blast furnace powder containing gypsum, a crushed steelmaking slag product may be added and mixed. Further, a fiber substance such as sawdust may be added and mixed. If the shape of the molding hole of the extrusion molding machine is made different, the surface area can be increased. Further, in order to maintain the hydration reaction, while recovering the molded product with steam, the recovered water used when slowly cooling the blast furnace molten slag having a water temperature of 60 to 80 ° C. is provided to the upper layer portion of the pile where the molded product is stacked. Sprinkle water. The molded product treated as described above may be used as it is or as a crushed product having a particle size of the molded product of 5 to 0 mm, and then about 1 to 10% by weight is added to and mixed with natural crushed stone or steel slag to prepare a roadbed. It can be used as a material.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In a municipal solid waste incineration plant, slaked lime is added to the exhaust gas for the purpose of removing harmful gases. At that time, hydrogen chloride gas and sulfur components in the gas react with slaked lime. , Calcium chloride and anhydrous gypsum are produced, and unreacted slaked lime is changed into quick lime by high temperature gas. These products are collected by a dust collector and mixed into incinerated ash. When the incinerated ash containing this product, the ground granulated blast furnace fine powder containing gypsum and water are added and kneaded, a reaction form as shown in the following formula is exhibited.

[0013] _{C 5 AS 3 + 2C + 16H} → C 4 AH 13 + 3CSH (1) ‥‥‥‥‥‥‥ C 5 AS 3 + 2Cs + 76 / 3H → 3CSH (1) +2/3 [C ₃ ACs ₃ H _32] + 2 / 3Al (OH) ₃ ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ C = CaO, A = Al ₂ O ₃ , S = SiO ₂ , H
= H ₂ O and Cs = CaSO ₄ . C ₅ AS ₃ is ground granulated blast furnace powder, CSH (1) is calcium hydrosilicate, C ₄ AH ₁₃ is calcium aluminate, C ₃ ACs
₃ H ₃₂ is ettringite.

When the incinerated ash is solidified with cement, heavy metals in the incinerated ash, particularly lead, cadmium, etc., are solid-dissolved by substitution with calcium aluminate produced by the cement hydration reaction and Al atoms in ettringite, and are insoluble salts. On the other hand, the ground granulated blast furnace fine powder containing gypsum, unlike the structure and composition of Portland cement, is vitreous and has a low basicity.
Since it contains 15% of 1 ₂ O ₃ , it has a strong hydration property, and when gypsum-containing granulated blast furnace fine powder is added and mixed with incinerated ash together with water, calcium aluminate and ettringite in the reaction form of the above formula are added. Is produced in large quantities over a long period of time. As described above, the gypsum-containing granulated fine powder of blast furnace is superior to Portland cement in the ability to fix heavy metals in incinerated ash.

Next, the case of adding and mixing granulated blast furnace fine powder containing no gypsum with water together with water will be described. As described above, in a general waste incineration plant, calcium chloride, anhydrous gypsum, and quick lime produced from the flue gas desulfurization process are mixed in the incineration ash. The production rates of the anhydrous gypsum and quick lime were compared. In this case, since the amount of quick lime produced is larger than that of anhydrous gypsum, the reaction of the formula is sufficiently promoted and a large amount of calcium aluminate is produced. However, the amount of anhydrous gypsum produced is less than that of quicklime, and the amount of ettringite produced in the above formula is not stable because the amount produced varies depending on factors such as the behavior in the incinerator, etc. The elution of heavy metals from granulated fine powder blended molded products may deviate from the standard value. That is, it is necessary to add a certain amount or more of gypsum-containing granulated blast furnace fine powder in order to constantly and stably suppress the heavy metal elution of the solidified product within the prescribed range.

On the other hand, steelmaking slag contains lime (CaO) and silica (SiO ₂ ) as main components, and other magnesia (M
gO), iron oxide (FeO, Fe ₂ O ₃ ) and manganese oxide (MnO). Lime is used as an auxiliary raw material during the refining of steel making, and remains in the slag in an unstable state if not sufficiently slagged. This lime component is called free lime (free-CaO), and this free lime reacts with blast furnace granulated fine powder neutral component C ₅ AS ₃ to give C as shown in the equation.
_A large amount of ₄ AH ₁₃ calcium aluminate is produced for a long period of time, and as described above, the heavy metal substitutes for the Al atom of C ₄ AH _{13 to form} a solid solution and is immobilized as a sparingly soluble salt.

Regarding the method of molding the specimen, when other molding methods such as a pan type granulator or a briquette machine are used, the optimum granulation / molding water content is 10 to 15%. Since the required water content is not obtained in the initial stage of the reaction and the mixture is pressed to increase the density and the strength, the extrusion method is adopted as the molding method in the present invention.

The curing method may be atmospheric curing, underwater curing, etc. In consideration of economic efficiency such as the problem of treated water, the initial curing method was air curing. However, since air curing causes a problem of requiring a long curing time and a vast curing yard associated therewith, the present invention focused on the accelerated curing described above.

Regarding the steam curing method, a steam pipe is provided on the floor, and a so-called molded object is stacked on it.
The steam from the floor does not reach the upper layers of the loading mountain,
There is a drawback that the temperature of the atmosphere in the upper layer becomes low and the reaction of the above equations and equations is not promoted. Therefore, in the present invention, attention was paid to the recovered water of the water used when gradually cooling the blast furnace molten slag having a water temperature of 60 to 80 ° C. Since the recovered water also has a high PH and a water temperature of 60 to 80 ° C., if water is appropriately sprayed to the upper layer portion of the pile, the upper layer portion retains an alkaline atmosphere, a temperature atmosphere of 60 to 80 ° C., and an appropriate amount of water. The reaction of the formula is accelerated.

Further, as a method of further promoting the reaction of the formula, the forming hole at the time of extrusion molding is made to have a different shape, thereby increasing the contact area between the molded product and steam at the time of steam curing to improve the steam curing effect. The present invention has devised a way to improve.
However, in Example 4 described later, the unit volume mass of the molded product was adopted as an index of the increase in the surface area of the molded product. This is because when the incineration ash and the gypsum-containing granulated blast furnace fine powder of the same composition have different shapes, they are better meshed with each other and the unit volume mass is increased. When the molded products are packed during steam curing, they have a large surface area and accelerate the reaction of the formula.

As a method of accelerating the reaction of other formulas, if the molded product is made into a porous shape, the steam easily spreads inside the molded product during steam curing, and further water sprinkled appropriately during steam curing (blast furnace molten slag). It also has an effect of improving the water absorption of the molded product of the recovered water used for the slow cooling), and accelerates the reaction of the formula. This means:
A fibrous substance such as sawdust is added at the time of mixing and kneading the gypsum-containing granulated blast furnace fine powder into incinerated ash to roughen the surface of the molded product and to make it internal porous. In order to confirm the effect of this method, in Example 5, in the same mixture of incinerated ash and gypsum-containing granulated blast furnace fine powder, it was confirmed that the formed article was porous by comparing the water absorption rate of the molded product with and without the addition of sawdust.

On the other hand, since the molded product subjected to the steam treatment is relatively lower in strength than natural crushed stone or steel slag, it is possible to add a predetermined amount to natural crushed stone or steel slag and mix it to obtain a good particle size as a roadbed material. A compaction effect can be obtained. Further, this molded product is blended with ground granulated blast furnace powder, and the water sprinkled during steam curing (recovered water of water used when gradually cooling the blast furnace molten slag) is retained in the molded product. Therefore, the hydration reaction continues for a long period of time, and has the effect of stably maintaining the strength of the roadbed material. Further, water sprinkled during steam curing is retained in the molded article having high water absorbency, and in that state, it is constructed with natural crushed stone or steel slag at the site, and after the construction, the molded article removes moisture of natural crushed stone or steel slag. Since there is no risk of absorbing water and breaking the optimum water content ratio state,
It is possible to easily adjust the optimum water content of the roadbed material. However, when the molded product is applied on site in a dry state, the molded product absorbs water and it is difficult to maintain the optimum water content ratio.

When a molded product crushed to a grain size of 5 to 0 mm is added to and mixed with natural crushed stone or steel slag, the natural crushed stone or steel slag is added more than when the molded product is tangibly added and mixed. It is dispersed in the gaps of No. 1 without segregation to further improve the above effects.

[0024]

Embodiments of the present invention will be described below.

(Example 1) Incinerator ash generated from a municipal solid waste incineration plant was used, and as test 1, 0 to 5 granulated blast furnace fine powder (Blaine value: about 4000 cm ² , the same applies hereinafter) was used.
After mixing in 0% and extruding and curing in air, a heavy metal elution test was performed. The results are shown in Table 1.

[0026]

[Table 1]

The sample preparation method was as follows: Granulated gypsum-containing granulated blast furnace powder and incinerated ash (kneading temperature was raised at about 50 ° C. in a dryer according to actual equipment) According to the mixing ratio, dry kneading is carried out for 5 minutes by a kneading machine described in JISR5201, then the air kneading raw material is adjusted to a water content of 30% and kneaded again for 3 minutes, and then the kneading machine is temporarily stopped. After kneading, the raw materials adhering to the bottom of the bee and the paddle were scraped off for 30 seconds, and then kneaded again for 3 minutes. Next, the kneading raw material was processed by a twin-screw extrusion molding machine having a processing capacity of 400 kg / hr to have a diameter of 10 mm and a length of about 30 to 5
The sample was molded into a size of 0 mm.

Regarding the heavy metal elution test, from the results of the elution test of the cement solidified body shown in Table 2, since the only non-regular component is lead, the target component was lead this time and the Environmental Agency Notification No. 1
It carried out by No. 3. The particle size of the dissolution test sample was set to 0.5 to 0 mm in consideration of safety.

[0029]

[Table 2]

Next, in Test 2, the slag crushed steelmaking product (size: 1.2 to 0 mm, the same hereinafter) including 10, including the reduction of the addition amount of the granulated blast furnace fine powder in Test 1,
Only 15% and 10% crushed steelmaking slag product was added and mixed with granulated blast furnace fine powder 5%, and extrusion molding was carried out. After curing in air, heavy metal elution test was carried out. Table 3 shows the results.

[0031]

[Table 3]

With respect to the test results, in Test 1, the addition of 20% of granulated blast furnace fine powder and lead leaching test results after 6 weeks of curing were not detected. Also, in Test 2, 10% and 15% of the crushed converter slag were added to 5% of granulated blast furnace powder.
As a result, the lead elution test result of ash alone was 1.05 mg / l in Test 1 and about 3 times in Test 2 2.
Despite the value of 94 mg / l, the new water quality environmental standard value (lead: 0.01 mg at the 5th week of curing)
/ L or less) was satisfied. Here, Table 4 shows examples of the components of steelmaking (converter) slag.

[0033]

[Table 4]

Further, 5% of granulated blast furnace fine powder and 10% of crushed steelmaking slag were blended and cured in air for 10 weeks. Main water quality environmental standard items (cadmium, cyanide compound, organophosphorus compound, lead, hexavalent) Chromium, total mercury, alkyl mercury, PCB)
When the dissolution test was conducted, all were not detected.

(Example 2) Incinerator ash generated from a municipal solid waste incineration plant, solidified cement produced from a municipal solid waste incineration plant and gypsum-containing ground granulated blast furnace fine powder were used in accordance with Example 1. Mixed and molded similarly. While appropriately spraying the recovered water of the water used when slowly cooling the blast furnace molten slag having a water temperature of 80 ° C., a steam pressure of 2 kgf / cm
Only ² in 6 hours curing, 12 hours curing and steam curing in aged in steam pressure 2 kgf / cm ² for 6 hours curing, 12 hours a dissolution test was performed for each. Table 5 shows the results.

[0036]

[Table 5]

(Example 3) Incinerator ash and gypsum-containing granulated blast furnace differential powder generated from a general waste incineration plant were molded according to Example 1. However, the extrusion was performed in two forms, that is, the case where the forming hole of the extruder is a normal circle and the case where the forming hole is a different shape. The molded product was aged at a steam pressure of 2 kgf / cm ² for 12 hours while appropriately spraying recovered water of water used for gradually cooling the blast furnace molten slag having a water temperature of 80 ° C. Therefore, the dry unit volume mass of the cured molded article was measured and compared. Table 6 shows the results.

[0038]

[Table 6]

(Example 4) Incinerator ash and gypsum-containing granulated blast furnace fine powder generated from a municipal solid waste incineration plant were molded according to Example 1. However, when adding / mixing granulated gypsum-containing granulated blast furnace powder, two forms, one with and without sawdust added, are formed into normal circular shaped holes, and the formed product is a blast furnace molten slag with a water temperature of 80 ° C. Steam pressure of 2k while sprinkling the recovered water used for slow cooling
It was aged at gf / cm ² for 12 hours. Therefore, the water absorption of the cured molded article was measured and compared. Table 7 shows the results.

[0040]

[Table 7]

(Example 5) A molded product obtained by steam curing for 12 hours while appropriately spraying the recovered water in Example 2 and crushed to a size or 5 to 0 mm (uniaxial compressive strength of molded product in 4 weeks) 70 kgf / cm ² or more) was added to the steel slag roadbed material MS25 at 4% and 10%, respectively, and the uniaxial compressive strength was measured. As a result, the base MS25 had a uniaxial compressive strength of 9.6 kgf / cm ² . 13.9 kg with 4% appearance
^{f / cm 2, 17.1kgf / cm} 2 at Yusugata 10% 15.8kgf / cm ^2, and in 5~0mm crushed product 4%, 5
With 0% crushed product 10%, 18.8 kgf / cm ²
The result was that the standard value of 12 kgf / cm ² or more was sufficiently satisfied. Incidentally, HMS25 in the normal production at this time was 14.5 kgf / cm ² . In addition, this uniaxial compressive strength test method is a method in which about 15 kg of a steel slag roadbed material mixed with an additive material is held at an optimum water content ratio (obtained by a compaction test, usually 9 to 10%) for 24 hours, and the "JIS A
"5015 Road steel slag" was crushed in a 10 cm mold with a 4.5 kg Rammer for 3 layers 42 times, and placed in a constant temperature and humidity room at a temperature of 20 ° C and a humidity of 60% for 13 days, and then immersed in water for 1 day for compression. It is a thing. The results are shown in Table 8.

[0042]

[Table 8]

(Example 6) A molded product similar to that of Example 2 was added to steel slag MS25 in the form of 4% and 10%, respectively, and a 15 cm mold was used to form a 4.5 kg Rammer in three layers 9
In the CBR test conducted by tamping twice and soaking in water for 4 days, the original CBR value of MS25 was 4% compared to 287%.
Addition of 322% and addition of 10% resulted in a value of 400%, which was effective in improving the strength as a road material. In addition, the test piece was approximately 10 kg with a mixture of additive materials and a water content ratio of 9 in accordance with the JIS A1211 subgrade soil bearing capacity (CBR) test method.
What was held for 10% to 10% for 24 hours was prepared by the method of compaction test of soil by tamping with JIS A1210. The results are shown in Table 9.

[0044]

[Table 9]

[0045]

INDUSTRIAL APPLICABILITY The present invention is one in which general waste incineration ash and a small amount of gypsum-containing ground granulated blast furnace fine powder, steel slag crushed products, and fibrous substances such as sawdust are mixed and molded or shaped into different shapes. Elution of heavy metals from incinerated ash can be suppressed by using waste materials that are available at low cost. In addition, all waste materials, including general waste incineration ash, can be regenerated as molded articles that are highly safe and do not elute heavy metals, and that have excellent economic efficiency and water absorption.

After the molding, the hydration reaction can be maintained for a long period of time by steam-curing while appropriately adding the recovered water of the water used for slowly cooling the blast furnace molten slag. Further, a molded product or a product obtained by crushing and molding the molded product into 5 to 0 mm is added to natural crushed stone or steel slag.
By mixing, it can be effectively used as a roadbed material.

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[Procedure amendment]

[Submission date] July 23, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0036

[Correction method] Change

[Correction contents]

[0036]

[Table 5]

Front Page Continuation (72) Inventor Noriyuki Kato 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Co., Ltd. Kimitsu Works Co., Ltd. Service Center Building Stock company, Mr. Kimitsu Branch, (72) Inventor Hiroaki Okumura Kimitsu, Chiba Prefecture Kimitsu No. 1 Kimitsu Steel Works, Nippon Steel Co., Ltd.

Claims (7)

[Claims] 1. A general waste incineration ash, characterized in that blast furnace granulated fine powder containing gypsum is added to and mixed with general waste incineration ash, and the mixture is molded by an extrusion molding machine. Processing method. 2. A blast furnace granulated fine powder containing gypsum and a steel slag crushed product are added and mixed with water to municipal waste incineration ash, and the mixture is molded by an extrusion molding machine. General waste incineration ash treatment method. 3. A blast furnace granulated fine powder containing gypsum is added and mixed with water to general waste incineration ash, and fibrous substances such as sawdust are added and mixed, and the mixture is molded by an extrusion molding machine. A method for treating municipal waste incineration ash, characterized by: 4. A blast furnace granulated fine powder containing gypsum and a crushed steelmaking slag product are added and mixed with water to municipal waste incineration ash, and fibrous substances such as sawdust are added and mixed, and the mixture is mixed. A method for treating general waste incineration ash, which comprises molding with an extrusion molding machine. 5. The method for treating general waste incineration ash according to claim 1, 2, 3 or 4, wherein the shape of the molding hole of the extrusion molding machine is made different. 6. The water used for slowly cooling the blast furnace molten slag having a water temperature of 60 to 80 ° C. to the upper layer portion of the pile on which the molded product is stacked while steam-curing the molded product molded by an extrusion molding machine. Collected water is sprinkled, Claim 1 characterized by the above-mentioned.
The method for treating municipal waste incineration ash according to 2, 3, 4 or 5. 7. A molded product treated according to claim 1, 2, 3, 4, 5 or 6, or a crushed product obtained by adjusting the molded product to a grain size of 5 to 0 mm in a range of 1 to 10% by weight for natural crushed stone or A method for treating general waste incineration ash, which is characterized by adding to and mixing with steel slag to make roadbed material.