JP2013202464A - Solidification treatment method and solidification treated body of combustible waste incineration ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an easy cement solidification treatment method of combustible waste incineration ash, capable of being applied even to solidification treatment of incineration ash of general waste such as rubble including radioactive waste or municipal refuse, preventing the generation of hydrogen gas in time of inclination ash treatment, suppressing even the elution of a heavy metal or radioactive substance such as cesium in a solidified body, and allowing the securement of solidified body strength.SOLUTION: In this cement solidification treatment method of incineration ash of combustible waste, a part of cement used for the incineration ash and solidification is subjected to a stirring processing together with water, amphoteric metal inside the waste is ionized or is changed into an amphoteric metal hydroxide, thereafter residual cement is put in and kneaded, and is molded and solidified.

Description

  The present invention relates to a method of solidifying flammable waste incineration ash generated when incinerated flammable waste such as rubble and municipal waste.

  Combustible waste such as rubble and municipal waste can be reduced in volume by incineration in a dedicated incinerator, and a technique for solidifying and stabilizing the incinerated ash with cement is being studied.

On the other hand, amphoteric metals such as aluminum exist in rubble and municipal waste incineration ash. It is known that amphoteric metals generate hydrogen gas in the high pH range generated by the hydration reaction of cement. In particular, when aluminum is mixed in debris incineration ash and municipal waste incineration ash, for example, about 0.5% by weight or more, for example, unconstrained formwork due to hydrogen gas bubbles by the age of one day after kneading. Part rises to a foamed caramel state and subsequent densification is difficult. In addition, after that, hydrogen gas is generated for a relatively long period of time, preventing the formation of a dense solidified body, reducing the solidified body strength, and reducing the elution suppressing effect of heavy metals and the like. In addition, this hydrogen gas may cause the pressure inside the container to rise when a sealed waste container filled with incinerated ash of combustible waste is stored in an intermediate storage facility for a long period of time or disposed of in a landfill site. is assumed.

Therefore, as disclosed in Patent Document 1, “a method of obtaining an inorganic material that is advantageously used as a cement raw material by subjecting the incineration ash generated in a municipal waste incinerator to wet pulverization and desalination. , A method of removing the metallic aluminum material before the wet pulverization process "is disclosed, but the waste liquid treated with the metallic aluminum is discharged out of the system. Therefore, it is essential to treat the radioactive substance in the system. It was not applicable to waste.

Patent Document 2 states that “a radioactive waste containing an amphoteric metal is mixed with water to form a turbid liquid, ozone is injected into the turbid liquid, and the amphoteric metal contained in the radioactive waste in the turbid liquid is stabilized. A method of chemically changing to a form and kneading the ozone-treated turbid liquid with cement to form a kneaded product, and molding and solidifying the kneaded product to obtain a solidified product is disclosed. Additional equipment was required, the process was not easy, and it was not suitable for mass processing.

JP 2003-080106 A JP 2005-195497 A

  Therefore, in view of the above, the present invention is applicable to solidification of incineration ash of general waste such as debris containing waste and municipal waste, and prevents generation of hydrogen gas during incineration ash treatment, It aims to provide a simple cement solidification treatment method that can be applied to radioactive waste incineration ash that can suppress elution of radioactive substances such as cesium and heavy metals, and can secure solidified strength. To do.

  In addition, when municipal waste is processed in a normal waste incineration facility, non-combustible substances are concentrated by reducing the volume of municipal waste. When municipal waste contains radioactive materials, the level of radioactivity increases per unit weight, but the radioactive materials in municipal waste incineration ash are contained, cracked solidified bodies, soundness that does not cause expansion, and appropriate compressive strength It is possible to maintain a large amount of solidified material that can be applied to radioactive waste ash.

A method for cement solidification treatment of combustible waste incineration ash, wherein the incineration ash and a part of cement used for solidification are agitated together with moisture, and at least part of the amphoteric metal in the waste incineration ash is removed. There is provided a cement solidification treatment method characterized by ionizing or forming an amphoteric metal hydroxide, and then charging and kneading the remaining cement, and molding and solidifying.

Furthermore, calcium hydroxide and / or quick lime is added to a part of the cement used for incineration ash and solidification, and after stirring with moisture, the remaining cement is added and kneaded and molded. There is provided a cement solidification processing method characterized by solidifying.

Furthermore, sodium hydroxide or potassium hydroxide is added to a part of the cement used for incineration ash and solidification, and after stirring with moisture, the remaining cement is added and kneaded, molded and solidified. And a cement solidification processing method characterized by the above.

Further, the present invention provides a method for solidifying cement, wherein the combustible waste contains a radioactive substance.

Incinerated ash from incinerated combustible waste contains amphoteric metals such as aluminum. The amphoteric metal is a metal typified by aluminum or zinc and is ionized even in a high pH region.

On the other hand, a clinker mineral having a calcium component in cement produces calcium hydroxide which is an alkaline component in the hydration process. Therefore, when amphoteric metal is present during the solidification treatment with cement, calcium hydroxide produced by the hydration reaction reacts with the amphoteric metal in the incinerated ash of the combustible waste. At this time, hydrogen gas is generated.

In particular, there is metallic aluminum in the incineration ash, and if this is solidified as it is, it will foam into unconstrained parts such as molds to produce cellular concrete by hydrogen gas bubbles by the age of one day. The body part is raised and formed, and subsequent densification and encapsulation of radioactive elements and heavy metals becomes difficult. Further, when hydrogen gas is not released to the outside of the solidified body, it stops and accumulates inside the solidified body, and the solidified body expands, cracks, or continuously voids, and the containment effect is diminished.

In addition, if amphoteric metal oxides such as zinc and lead are mixed in the incineration ash, calcium hydroxide and hydroxides and double salts are formed from the cement mineral, and the surface of the cement mineral or cement hydrate is formed. It may be considered that the hydration of the cement is hindered by coating or the like, the setting time of the cement is remarkably delayed, and if the mixing amount is increased, a hardening failure is caused. Furthermore, if metal ions such as iron and magnesium that form a hydroxide with low solubility upon contact with an alkaline solution are contained, the setting time of the cement is delayed and a satisfactory solidified product cannot be obtained.

Moreover, when pretreating incinerated ash with an alkali hydroxide solution, there is a problem that the influence of residual counter ions, sodium and potassium, on cement hydration cannot be eliminated.

Therefore, prior to the kneading of most of the cement used for solidification, a portion of the cement used for forming a hydroxide or a double salt with these amphoteric metals and amphoteric metal oxides (hereinafter, some cements). ) Or, if necessary, calcium hydroxide and / or quicklime are used together to increase the reaction rate, and it has been found that good results can be obtained. Moreover, when quicklime is used, the reaction can be promoted by the heat generated by the hydration of quicklime by raising the water temperature of the suspension during the treatment from 20 ° C. to about 80 ° C. Even without using quicklime, the reaction can be promoted by heating.

The details of the mechanism are not clear, but in the process of hydration of the remaining cement to be added later, the generated hydroxide and double salt do not cover the surface of the cement particles, so that inhibition of hydration can be prevented. That is, it is considered that the formation of a hydroxide having a low solubility concentrates on a part of the cement and deposits to prevent hydration. Therefore, even if a metal salt compound that can generate this kind of hydroxide is contained in the incineration ash, the treatment of the present invention is carried out in advance to convert the amphoteric metal hydroxide into some cement. When deposited, it is thought that hydroxide deposition on the surface of cement particles disappeared during the hydration process of most cements, preventing inhibition of the hydration reaction.

Furthermore, calcium hydroxide produced from some cement reacts with metal aluminum to form a hydroxide, and if there is cement hydrate or cement powder there is easier formation on the surface, I think it will be possible at high speed. Still, when there is a large amount of aluminum metal to be treated, the reaction takes time, so it is effective to add heat or to add calcium hydroxide and / or quicklime. Furthermore, when the amount of metallic aluminum is more than the equivalent of calcium hydroxide generated from some cement, potassium hydroxide and sodium hydroxide can be used in combination in order to further shorten the time.

Some cements are thought to include the role of supplying calcium hydroxide that reacts with aluminum in the incinerated ash and the role of stabilizing by providing a site for the formation of amphoteric metal hydroxides.

Calcium hydroxide and / or quicklime are also added to accelerate the reaction with amphoteric metals. When quicklime is added, the heat generated by the hydration of quicklime can be used, and the processing time can be further shortened. At this time, calcium hydroxide from quick lime reacts with aluminum and further generates heat.

Sodium hydroxide and potassium hydroxide are effective when added in excess of the equivalent amount of metallic aluminum in the incinerated ash.

The present invention is an incineration ash having a high content of metallic aluminum, and can be applied to solidification treatment of general waste or industrial waste incineration ash containing radioactive waste. This completely suppresses the foaming phenomenon caused by hydrogen gas and suppresses elution of heavy metals and / or elution of radioactive substances such as cesium in incineration ash, and further suppresses the subsequent generation of hydrogen gas, thereby solidifying the product. A simple cement solidification method for combustible waste incineration ash capable of ensuring strength can be provided.

It is a schematic diagram of the figure which shows the flow which processes combustible waste incineration ash. It is a figure of the example which solidified the combustible waste incineration ash using normal Portland cement.

[Embodiment]
As the cement, ordinary ordinary Portland cement, early-strength Portland cement, low heat Portland cement, and cement such as blast furnace slag cement, ecocement, and jet cement can be used. Ordinary Portland cement is preferred as a cement that reacts with metallic aluminum at an early stage. In addition, when blast furnace slag cement is used, the hexavalent chromium in the incinerated ash is reduced to trivalent chromium and replaced with aluminum in ettringite, which is the initial hydrate, and the fixing effect may increase. ,preferable.

In addition, these various cements may be used in combination. Separately, calcium hydroxide and / or quicklime is further added, or sodium hydroxide and / or potassium hydroxide (hereinafter referred to as a composite material) is added as necessary. Further added.

(Initial addition amount)
First, all of the water to be kneaded and all of the incinerated ash containing amphoteric metals are mixed. A part of the cement is added to this. When a part of cement or a composite material is added (hereinafter, part of cement, etc.), the total amount is 5 to 20 parts by weight with respect to 100 parts by weight of cement finally used for solidification. Is preferred. If it is 5 parts by weight or less, the inhibitory effect of amphoteric metals and the like cannot be sufficiently suppressed, and if it is 20 parts by weight or more, the strength of the cement solidified as a whole may not be sufficient. Some cements and the remaining cements can be of different types.

(Amount of reaction with aluminum)
Since 20 parts by weight of cement is the upper limit of the amount of cement used, 20% of the CaO component (60% by weight of cement) is roughly estimated as 15 parts by weight that can potentially provide Ca (OH) 2. .6 parts by weight (100 parts by weight of cement produces 130 parts by weight of hydrate, 0.6 * 0.2 times that of 15.6 parts by weight) 15.6 × 27/101 (equivalent ratio), and 4.17 parts by weight of metallic aluminum is the upper limit of the potential processable amount. When incineration ash with a metal aluminum content exceeding this is treated, it is preferable to use calcium hydroxide and / or quick lime, and further, sodium hydroxide and / or potassium hydroxide is added to increase the reaction rate. Is preferably increased.

The incineration ash to be used is not particularly required to be pretreated. However, it is preferable that the incinerated ash is subjected to normal dry pulverization and from which coarse particles are removed by a vibration sieve or the like. This is because when a large particle size of metallic aluminum or the like is mixed, a relatively large amount of some cement or the like is required. In addition, when the incinerated ash after pulverization is immediately transferred to the mixing step with a part of cement, the fresh surface by pulverization of the metal partly promotes the reaction with the cement.

(Initial mixing method)
Put all the moisture, incineration ash, some cement, etc. into a normal kneading container (mixer) and stir well. At this time, in order to obtain a stirring effect, it is preferable to use a container with a stirrer. The stirring temperature may be room temperature (about 20 ° C.) or the outside air temperature, but if it is 20 to 80 ° C., the completion of the reaction can be accelerated.

(Determination of the amount of partial cement in the initial mixing and end point of the reaction)
If the amount of partial cement is 20 parts by weight, 4.2 parts by weight of metal aluminum can be processed. Therefore, measure the amount of metal aluminum in the incinerated ash in advance and set the amount of partial cement. Is preferred. When the amount of metallic aluminum contained in the incinerated ash exceeds 4.2 parts by weight or when the reaction is accelerated, a double material was added. The stirring time was 12 to 24 hours as a guide. Specifically, the completion of the reaction with some cement can be determined empirically by grasping in advance the amount of metallic aluminum in consideration of the origin of the incinerated ash to be treated and the variation between lots.

Next, the remaining cement used for solidification was added and kneaded. The charging is preferably performed while driving the stirrer.

The chemical composition of the simulated incineration ash shown in Table 1 is shown. For the simulated incineration ash, clay minerals kaolin, talc, and wax were mixed at a predetermined ratio, fired at about 1000 ° C., and ground to 1 mm under a ball mill. As the powder metal aluminum, a reagent (purity 97%: Daiwa Metal Powder Co., Ltd.) was used. As an alternative to unburned carbon, 4 parts by weight of graphite powder was used. The stable isotope cesium was added in the form of cesium chloride in an amount of 1.24 / 1000 parts by weight. (Incineration ash of rubble contaminated with 400,000 Bq / kg of cesium 137 is concentrated 1000 times. Therefore, assuming that 1 kg of incineration ash is treated, the amount of cesium is calculated to be 0.124 mg from the half-life of cesium. Therefore, assuming a case where high-concentration contaminants are treated with a stable isotope cesium chloride reagent, the test was conducted with cesium of 12.4 mg / kg incinerated ash equivalent to 100 times, that is, 400,000 Bq / kg. (Equivalent to 40 million Bq)).

Experimental example A1
First, as a blank test, 100 parts by weight of this simulated incineration ash, 110 parts by weight of ordinary Portland cement, and 110 parts by weight of water were added, and after kneading using a mortar mixer at room temperature of 20 ° C., the kneaded product was used as a mold. It was injected, filled, and cured at 20 ° C. in a wet atmosphere.

Experimental example B1
100 parts by weight of this simulated incinerated ash, 10 parts by weight of ordinary Portland cement, and 110 parts by weight of water were added, suspended at a room temperature of 40 ° C. using a mortar mixer, and allowed to react for 24 hours with gentle stirring.
Thereafter, 100 parts by weight of ordinary Portland cement was further added thereto, and the mixture was put into the same mortar mixer. After kneading, the kneaded material was poured into a mold, filled, and cured at 20 ° C. .

Experiment C1, Experiment C2
100 parts by weight of this simulated incineration ash, 10 parts by weight of ordinary Portland cement, 10 parts by weight of slurry liquid suspended in 10% by weight of calcium hydroxide solids, and 100 parts by weight of water were added. The mixture was suspended using a mortar mixer at room temperature of 40 ° C., and reacted for 12 hours (C1) and 24 hours (C2) with gentle stirring to obtain two mixtures.
Thereafter, 100 parts by weight of ordinary Portland cement was additionally added to a mortar mixer, and after kneading, the kneaded product was poured into a mold, filled, and cured by aerobic conditions.

Experiment D1, Experiment D2, Experiment D3
100 parts by weight of this simulated incineration ash, 10 parts by weight of ordinary Portland cement, 10 parts by weight of a suspension of 10% by weight of calcium hydroxide solids, and 100 parts by weight of sodium hydroxide were dissolved in 100 parts by weight of water. 1 part by weight of the solution and 99 parts by weight of water were added. The mixture was suspended using a mortar mixer at room temperature of 40 ° C., and reacted for 12 hours (D1), 24 hours (D2), and 48 hours (D3) with gentle stirring to obtain a three-level mixture.
Thereafter, 100 parts by weight of ordinary Portland cement was additionally added to the mortar mixer, and after kneading, the kneaded product was poured into a mold, filled, and cured at 20 ° C. in a wet atmosphere.

Experimental example E1
In Experiment D1 (12 hours stirring), the same experiment except that 7.57 parts by weight of quicklime powder was used instead of 10 parts by weight of the slurry liquid in which the calcium hydroxide solid content was suspended by 10% by weight. Went.

Experimental example F1
In Experiment D1 (12 hours stirring), instead of ordinary Portland cement, the same part by weight of Class B blast furnace slag cement (some parts of the cement and the remaining cement are the same part by weight as in Experiment D1) is used. A similar experiment was conducted except that 7.57 parts by weight of quicklime powder was used as an alternative to 10 parts by weight of the slurry liquid suspended by 10% by weight.

Table 2 shows the state observation results of the specimens and the uniaxial compressive strength test results (the test method conforms to JISR5201).

Experimental examples B1 to E1 were subjected to a metal elution test (tank leaching test based on Environment Agency Notification No. 46) and elemental analysis by ICP. Ions were not detected. Moreover, FIG. 2 is a state of one day age in which the ash which incinerated the combustible waste was solidified with normal Portland cement. On the left is solidified using 100 parts by weight of cement at once, and on the right is the daily material age in this experimental example B1 (10 parts by weight of cement was added and 90 parts by weight was added after stirring). It is a state. On the right, there is no expansion, and dense curing is in progress.

The present invention relates to a method for solidifying flammable waste incineration ash generated when incinerated flammable waste such as rubble and municipal waste, and a solidified body thereof .

Claims (5)

A method for cement solidification treatment of combustible waste incineration ash, wherein the incineration ash and a part of cement used for solidification are agitated together with moisture, and at least part of the amphoteric metal in the waste incineration ash is removed. A cement solidification treatment method characterized by ionizing or forming an amphoteric metal hydroxide, then charging the remaining cement, kneading, molding and solidifying. The cement solidification processing method according to claim 1, wherein the combustible waste contains a radioactive substance. In Claim 1 or Claim 2, calcium hydroxide and / or quicklime are further added to a part of the cement used for incineration ash and solidification, and after stirring with moisture, the remaining cement is added. A cement solidification treatment method, characterized by being charged, kneaded, molded and solidified. The remaining cement according to any one of claims 1 to 3, wherein sodium hydroxide or potassium hydroxide is further added to a part of the cement used for incineration ash and solidification, and the mixture is stirred with water. A cement solidification treatment method characterized in that, the mixture is kneaded, molded, and solidified. The cement solidification treatment method according to any one of claims 1 to 4, wherein the stirring treatment is performed at 20 ° C to 80 ° C.