JP2013082604A - Method for producing fired material, cement mixture, aggregate and earthwork material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method for producing a harmless fired material by using waste contaminated with radioactive cesium as a raw material.SOLUTION: In this method for producing a fired material including a heating process for obtaining the fired material by heating waste contaminated with radioactive cesium and a CaO source and/or an MgO source at 1,200-1,400°C to evaporate radioactive cesium in the waste, the obtained fired material includes CS and CAS, and the kind and the blending ratio of each of the waste, the CaO source and the MgO source are determined so that the total amount of CAS and CAF per 100 pts.mass CS falls into 10-100 pts.mass.

Description

  The present invention relates to a method for producing a harmless fired product using waste contaminated with radioactive cesium as a raw material, a cement mixture obtained by pulverizing the obtained fired product, and a bone comprising the fired product. Materials and earthwork materials.

Currently, in the cement industry, industrial waste and general waste are recycled as cement raw materials. For example, C ₂ S and C ₂ AS are essential components, 10 to 100 parts by weight of C ₂ AS + C ₄ AF is contained with respect to 100 parts by weight of C ₂ S, and the content of C ₃ A is 20 parts by weight or less. A certain fired product has been proposed (Patent Document 1). The fired product is made of at least one selected from industrial waste, general waste, and construction generated soil, and the fired product can be pulverized and used as a cement mixture.
On the other hand, there is a problem that radioactive cesium released into the external environment due to a major accident at a nuclear power plant may be contained in waste or soil. Since radioactive cesium (cesium 137) has a half-life of 30 years and can adversely affect the human body over a long period of time, it is often required to remove radioactive cesium from wastes and the like.
As a method for removing radioactive cesium, for example, radioactive waste existing in the form of nitrate is dissolved by electromagnetic induction heating in a cooled container having a slit having a current-carrying coil that circulates outside, and nitrate is decomposed. Of radioactive waste consisting of collecting the metal oxide produced in this way around the container, collecting the reduced white metal element in the middle of the container by electromagnetic pinch force, and then recovering the produced solidified material after cooling and condensation In the processing method, a method for separating and recovering long-lived nuclides such as cesium volatilized from radioactive waste during electromagnetic induction heating is described (Patent Document 2).
However, the method of Patent Document 2 is not intended for radioactive cesium released into the external environment due to an accident, but for radioactive waste generated in a limited area such as a nuclear power plant. Therefore, it is not suitable for processing a huge amount of contaminated soil and the like, and there is a problem that the apparatus is complicated and expensive, and the cost is high.

Japanese Patent No. 3559274 Japanese Patent Laid-Open No. 5-157897

  The present invention uses a waste contaminated with radioactive cesium as a raw material, a method for producing a harmless fired product, a cement mixture obtained by pulverizing the fired product, an aggregate made of the fired product, And to provide earthwork materials.

As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention are a method for producing a waste product contaminated with radioactive cesium and a fired product obtained by heating a CaO source and / or a MgO source. baked product comprises _{C 2} S and _C 2 _aS, by the method for manufacturing a baked product the total amount of _C 2 aS and _C 4 AF per C 2 S100 parts by mass determine the blending ratio so that 10 to 100 parts by weight The inventors have found that the above object can be achieved and completed the present invention.
That is, the present invention provides the following [1] to [8].
[1] A heating step of heating a waste contaminated with radioactive cesium and a CaO source and / or MgO source at 1200 to 1400 ° C. to volatilize the radioactive cesium in the waste to obtain a fired product. A method for producing a fired product, in which the obtained fired product contains C ₂ S and C ₂ AS, and the total amount of C ₂ AS and C ₄ AF per 100 parts by mass of C ₂ S is 10 to 100 parts by mass. And determining the type and the mixing ratio of each of the waste, CaO source and MgO source.
[2] Further, the above [1] defines the types and mixing ratios of the waste, the CaO source, and the MgO source so that the masses of CaO, MgO, and SiO ₂ satisfy the following formula (1): The manufacturing method of the baked product as described in any one of.
((CaO + 1.39 × MgO) / SiO ₂ ) = 1.0 to 2.2 (1)
(In the formula, CaO, MgO, and SiO ₂ represent the mass of calcium oxide, the mass of magnesium oxide, and the mass of silicon oxide, respectively.)
[3] The method for producing a fired product according to [1] or [2], wherein chloride is further used as a raw material.
[4] The method for producing a fired product according to any one of [1] to [3], wherein heating is performed in a reducing atmosphere in the heating step.
[5] The calcination according to any one of [1] to [4], including a mixing step of mixing the baked product obtained by the heating step and at least one selected from the group consisting of a reducing agent and an adsorbent. Manufacturing method.
[6] A cement mixed material obtained by pulverizing a fired product obtained by the method for producing a fired product according to any one of [1] to [5].
[7] An aggregate made of a fired product obtained by the method for producing a fired product according to any one of [1] to [5].
[8] An earthwork material comprising a fired product obtained by the method for producing a fired product according to any one of [1] to [5].

  According to the method for producing a fired product of the present invention, a harmless fired product from which radioactive cesium has been removed can be obtained. This fired product can be used as a cement mixture and aggregate for reconstruction concrete (embankments, breakwaters, wave-dissipating blocks, etc.), which will be required in large quantities in the future, and can protect natural resources. . In addition, it can be used as a backfill material for soil removed from soil as earthwork material.

Hereinafter, the present invention will be described in detail.
In the method for producing a fired product of the present invention, the waste contaminated with radioactive cesium and the CaO source and / or the MgO source are heated at 1200 to 1400 ° C. to volatilize the radioactive cesium in the waste and fire. A method for producing a fired product including a heating step for obtaining a product, wherein the obtained fired product contains C ₂ S and C ₂ AS, and the total amount of C ₂ AS and C ₄ AF per 100 parts by mass of C ₂ S is 10 It is characterized in that the types and blending ratios of the waste, CaO source, and MgO source are determined so as to be ˜100 parts by mass.

The object to be treated of the present invention is a waste contaminated with radioactive cesium.
Here, waste contaminated with radioactive cesium is, for example, general waste such as soil, sewage sludge dry powder, municipal waste incinerated ash, molten slag derived from garbage, shells, vegetation, sewage sludge, sewage slag, Industrial waste such as purified water sludge and construction sludge, and disaster waste such as debris, which contains radioactive cesium. These may be used individually by 1 type and may be used in combination of 2 or more type. In addition, the radioactive cesium-enriched product (intermediate treatment product) obtained by removing in advance a portion containing almost no radioactive cesium (for example, sand and stone in the case of soil) is also contaminated with radioactive cesium in the present invention. It is included in the concept of “waste”.
Examples of the CaO source include calcium carbonate, limestone, quicklime, slaked lime, limestone, dolomite, and blast furnace slag. Examples of the MgO source include magnesium carbonate, magnesium hydroxide, dolomite, serpentine, and ferronickel alloy slag. These examples may be used individually by 1 type, and may be used in combination of 2 or more type.
In the present invention, both the CaO source and the MgO source may be used, or only one of them may be used, but it is preferable to mix only the CaO source in order to enhance the activity as a cement mixture. .
Further, it is preferable to use a pulverized powder as the CaO source and the MgO source.

In the present invention, radioactive cesium means cesium 134 and cesium 137, which are radioactive isotopes of cesium. These radioactive cesiums are radioactive substances that are released into the external environment by accidents at nuclear power plants, and have half-lives of about 2 years and about 30 years, respectively.
In the present invention, the radioactive cesium that is the object to be removed is released into the external environment together with radioactive iodine in the form of cesium iodide, etc., from the nuclear power plant that caused the accident, and dropped from the sky to the ground surface. . Cesium iodide has a boiling point of 1200 ° C. or higher and is less likely to volatilize than cesium iodide having a boiling point of about 700 ° C. In addition, radioactive cesium that has fallen to the surface of the earth is trapped in clay minerals contained in the soil, becomes difficult to separate from the soil, and the form may change. In addition, radioactive cesium that adheres to disaster waste such as debris or falls to the ground surface is washed away by rain and concentrated in the process of sewage treatment, resulting in sewage sludge containing high concentration of radioactive cesium, etc. There is. Furthermore, by absorbing radioactive cesium contained in the soil, the vegetation is contaminated with radioactivity, and incineration ash generated by incineration of those containing vegetation contaminated with these radioactivity, radioactive cesium is contained in glass, etc. Sometimes it is trapped. In the present invention, it is intended to separate and recover these radioactive cesium compounds that are difficult to treat.

The fired product obtained after heating contains C ₂ S (2CaO · SiO ₂ ) and C ₂ AS (2CaO · Al ₂ O ₃ · SiO ₂ ), and C ₂ AS and C ₄ AF (4CaO per 100 parts by mass of C ₂ S). - the total amount of _{Al 2 O 3 · Fe 2 O} 3) is 10 to 100 parts by weight, preferably 20 to 90 parts by weight.
When the total amount of C ₂ AS and C ₄ AF is less than 10 parts by mass, the total volatilization amount of potassium and sodium in the mixture of the waste contaminated with radioactive cesium and the CaO source and / or MgO source is large. Therefore, the amount of radioactive material-containing waste, which is a solid content obtained by cooling the exhaust gas, increases. Moreover, even if heating temperature is raised at the time of a heating, the amount of free lime (the amount of unreacted CaO) is hard to fall and baking becomes difficult. Furthermore, the resulting C _{2 S} becomes likely to be no γ-type C _{2 S} hydration activity, when used as a cement mixing material etc., which may greatly reduce the strength of the cement. On the other hand, when the amount exceeds 100 parts by mass, the melt at a high temperature increases, so that the calcinable temperature is narrowed and the volatilization amount of radioactive cesium is reduced. Further, since C 2 _S is small, when used as a cement mixing material etc., the initial and long-term strength of the cement are both reduced.
Depending on the composition of the raw materials used (waste, CaO source, and MgO source), C ₄ AF may be produced, but of the total 100 parts by mass of C ₂ AS and C ₄ AF, C ₄ The content of AF is preferably 70 parts by mass or less. When the content of C ₄ AF exceeds this range, production management may be difficult.
Moreover, the content of C ₃ A per 100 parts by mass of C ₂ S is preferably 20 parts by mass or less, and more preferably 10 parts by mass or less. When it exceeds 20 parts by mass, the heat of hydration of the cement may increase and the fluidity may deteriorate when used as a cement mixture.

The mineral composition ratio of the fired product is calculated by calculating the mass ratio of each mineral according to the following formula from the contents (mass%) of CaO, SiO ₂ , Al ₂ O ₃ , and Fe ₂ O _{3 in} the raw materials used. Can be sought.
C ₄ AF = 3.04 × Fe ₂ O ₃
C ₃ A = 1.61 × CaO−3.00 × SiO ₂ −2.26 × Fe ₂ O ₃
C ₂ AS = −1.63 × CaO + 3.04 × SiO ₂ + 2.69 × Al ₂ O ₃ + 0.57 × Fe ₂ O ₃
C ₂ S = 1.02 × CaO + 0.95 × SiO ₂ -1.69 × Al ₂ O ₃ −0.36 × Fe ₂ O ₃
Therefore, the mixing ratio of the waste contaminated with radioactive cesium and the CaO source and / or MgO source is appropriately determined so that the composition of the fired product obtained is within the scope of the present invention, depending on the composition of the waste. Just decide.

Further, the waste contaminated with the radioactive cesium and the CaO source and / or the MgO source have a mass of each of calcium oxide (CaO), magnesium oxide (MgO), and silicon dioxide (SiO ₂ ) in the obtained mixture. In order to satisfy the following formula (1), it is preferable that the waste and the CaO source and / or the MgO source are determined and mixed and then mixed.
((CaO + 1.39 × MgO) / SiO ₂ ) = 1.0 to 2.2 (1)
(In the formula, CaO, MgO, and SiO ₂ represent the mass of calcium oxide, the mass of magnesium oxide, and the mass of silicon oxide, respectively.)
The numerical values derived from the respective masses of CaO, MgO and SiO ₂ of the above formula (1) and the above formula (1) are preferably 1.0 to 2.2, more preferably 1.1 to 1.9, particularly Preferably it is 1.2-1.8.
In addition, since the mass of 1 mol of CaO corresponds to the mass of 1.39 mol of MgO, in the above formula (1), the mass of MgO is multiplied by 1.39.
When the mass ratio is less than 1.0, a liquid phase is likely to be generated as the firing temperature is increased, and the volatilization amount of radioactive cesium may be reduced. When the mass ratio exceeds 2.2, the total volatilization amount of potassium and sodium in the mixture of the waste contaminated with radioactive cesium and the CaO source and / or MgO source increases, and the exhaust gas is cooled. In some cases, the amount of radioactive material-containing waste, which is a solid content, increases.

As a raw material of the above mixture for the purpose of accelerating the volatilization of radioactive cesium by chlorination and reducing the volume of volatile recovery, further, chlorides such as calcium chloride (CaCl ₂ ), potassium chloride (KCl), and sodium chloride (NaCl) May be used. Of these, calcium chloride is preferred from the viewpoint of promoting chlorination.
The amount of chloride is such that the molar ratio of chlorine, cesium and potassium (Cl / (Cs + K)) is preferably 1.0 or less, more preferably 0.3 or less. When the molar ratio is 1.0 or less, potassium and sodium do not volatilize and a large amount of radioactive cesium volatilizes, so that the volume of radioactive material-containing waste can be reduced.
Moreover, it is preferable that the chlorine content in the said mixture is 1500 mg / kg or less. When the amount of chlorine is 1500 mg / kg or less, a liquid phase is hardly generated even at a high temperature, and a large amount of radioactive cesium is volatilized.
Preferably, the molar ratio (Cl / (Cs + K)) is 1.0 or less, and the amount of chlorine in the mixture is 1500 mg / kg or less, more preferably, the molar ratio is 0.5 or less. If the amount of chlorine in the inside is 1250 mg / kg or less, the volatilized cesium can be easily volatilized in the form of cesium chloride, and the volume of recovered material described later can be reduced.
When mixing the above-mentioned waste with the CaO source and / or MgO source, if necessary, crushing, pulverizing, etc. also serving as mixing, or combining the crusher or pulverizer with a mixer, A two-stage process may be performed. When firing using a rotary kiln, which will be described later, since each material is rotationally mixed in the rotary kiln, a part of the above-mentioned CaO source, MgO source, waste, etc. may be put into the kiln kiln as it is. Moreover, it is preferable that the said mixture is smaller than the granular material of about 5 mm. Further, stones of 5 mm or more that do not contain much cesium may be removed in advance while washing with water.

The heating temperature of the mixture of the waste contaminated with radioactive cesium and the CaO source and / or MgO source is 1200 to 1400 ° C, preferably 1200 to 1350 ° C.
By heating within the above temperature range, radioactive cesium contained in the waste can be volatilized efficiently. When the heating temperature is less than 1200 ° C., the volatilization amount of radioactive cesium decreases. If it exceeds 1400 ° C., a liquid phase is formed, and radioactive cesium is taken in and becomes difficult to volatilize.
The heating time of the mixture is preferably 15 minutes or more, more preferably 30 minutes or more from the viewpoint of obtaining a sufficient volatilization amount of radioactive cesium. The upper limit of the heating time is not particularly limited, but is preferably 180 minutes or less, more preferably 120 minutes or less. When the heating time exceeds 180 minutes, the volatilization amount of potassium and sodium increases with the radioactive cesium in the mixture. When the raw material rolls, such as a rotary kiln, the contact rate between the gas and the radioactive cesium is increased and the thermal conductivity is improved, so that a high volatilization rate can be obtained in a shorter firing time than the standing condition.
As the heating means, either a continuous type or a batch type can be used.
A rotary kiln etc. are mentioned as an example of a continuous heating means.
Examples of the batch type heating means include an incinerator, an electric furnace, a microwave heating device, and the like.
Among these, the continuous heating means is preferably used in the present invention from the viewpoint of increasing the processing efficiency. In particular, a rotary kiln is preferable because a heating temperature suitable for volatilization of radioactive cesium and a residence time of waste can be easily provided.

The atmosphere during heating is preferably heated in air containing water vapor because the volatilization amount of alkali metals (potassium and sodium) can be reduced and the volatilization amount of radioactive cesium can be increased.
On the other hand, when heated under air that does not contain water vapor (pure air), the volatilization amount of alkali metals (potassium and sodium) increases, but more radioactive cesium can be volatilized.
By adjusting the amount of chloride, the heating temperature, the time, and the amount of water vapor at the time of heating, the volatilization amount of radioactive cesium can be increased while reducing the volatilization amount of alkali metals (potassium and sodium). .

Moreover, when the waste contaminated with radioactive cesium contains chromium, the fired product obtained may contain hexavalent chromium (Cr ⁶⁺ ).
When such a fired product is used as a cement mixture, aggregate, earthwork material, etc. (especially when used as an earthwork material), hexavalent chromium contained in the fired product is eluted, causing water pollution, soil pollution, etc. May cause.
Therefore, in the heating step, heating may be performed in a reducing atmosphere. By heating in a reducing atmosphere, even if chromium is contained in the waste, it is possible to prevent the formation of hexavalent chromium that is likely to occur in an oxidizing atmosphere, and in the step of heating the waste, Even if the waste is temporarily heated in an oxidizing atmosphere to produce hexavalent chromium, it is reduced to trivalent chromium (Cr ³⁺ ), so the obtained fired product can be used safely as an earthwork material. Can be used. In addition, you may perform combining the method heated in the air containing the water vapor | steam mentioned above, and the method heated in a reducing atmosphere. In the following, the method of heating in a reducing atmosphere will be explained using an example of an internal combustion type device (such as an internal combustion rotary kiln) that uses a counter-current type (combusted at the raw material outlet side) as an example. However, the present invention is not limited to these forms.

As an example of a method of heating waste contaminated with radioactive cesium in a reducing atmosphere, a method of burning a combustible substance when heating the waste is mentioned. By burning the combustible substance, the periphery of the waste can be maintained in a reducing atmosphere. Moreover, even if chromium is contained in the waste, the production of hexavalent chromium can be prevented, and even if hexavalent chromium is produced in the step of heating the waste, trivalent chromium is produced. Reduced to
Here, the combustible material includes, for example, waste solid lump obtained by compressing and / or solidifying waste such as coal, coke, activated carbon, waste wood, waste plastic, heavy oil sludge, and municipal waste.
As a method of supplying the combustible material, it may be mixed in advance with waste contaminated with radioactive cesium. When a rotary kiln is used as a heating device, the combustible material is disposed on the waste inlet side, You may supply from the exit side or the middle of a rotary kiln.
When combustible materials are mixed with raw materials in advance, the amount of combustible materials is preferably larger as long as the combustible materials do not remain in the unburned state in the fired product obtained by heating. A larger particle size is preferred.

Here, a case where the combustible substance is supplied on the waste kiln waste side or in the middle of the rotary kiln will be described.
In this case, the combustible substance is preferably one that can maintain the reducing atmosphere for a long time. Specifically, for example, a combustible material having a slower combustion speed than the main fuel of a rotary kiln or a combustion speed similar to that of the main fuel and having coarser grains than the main fuel can be mentioned. Specific examples include petroleum coke, coal coke, and anthracite. The slower the burning rate, the better because the combustible material can be made finer.
The average particle size of the combustible material is preferably 0.5 to 20 mm, more preferably 1 to 5 mm. If the average particle diameter is less than 0.5 mm, the reducing atmosphere may not be maintained for a long time because it burns out in the very initial stage during combustion. If the average particle diameter exceeds 20 mm, a large amount of unburned combustible material remains in the obtained fired product, so that the supplied combustible material is wasted. When used as a concrete aggregate, the remaining unburned carbon adsorbs the AE agent, so that the air entrainment of the mortar concrete deteriorates, or when compacted, the unburned carbon appears on the surface, and the mortar concrete Problems such as deterioration in appearance may occur.
The amount of the combustible material is preferably 5 to 40 kg, more preferably 10 to 40 kg, and particularly preferably 12 to 40 kg per 1000 kg of the fired product obtained by heating. If the amount is less than 5 kg, the effect of making a reducing atmosphere may be small. When the amount exceeds 40 kg, a large amount of unburned combustible material remains in the obtained fired product, and when the fired product is used as a cement mixture or a concrete aggregate, the air entrainment and appearance of mortar concrete May get worse.
In addition, when supplying a combustible substance in the middle of a rotary kiln, it is preferable to supply in the middle from the position which becomes the highest temperature in a rotary kiln to the waste inlet side.
The oxygen (O ₂ ) concentration in the furnace when burning the combustible material is preferably 5% by mass or less, more preferably 3% by mass or less, from the viewpoint that the combustible material is not immediately lost.
By adjusting the above-described conditions and the residence time, it is possible to prevent the formation of hexavalent chromium and prevent the combustible substance from remaining. Moreover, when using the obtained baked product as a cement mixed material or a concrete aggregate, the above-described conditions, residence time, and the like are adjusted so as not to adversely affect the air entrainment and appearance of the mortar concrete.

Next, the case where a combustible substance is supplied from the waste outlet side will be described.
The combustible material can be easily pumped from the waste outlet side into the furnace using air. A dedicated inlet may be provided on the outlet side of the rotary kiln. Further, a coarse combustible substance (having an average particle diameter of about 1 to 10 mm) may be dropped as part of the fuel of the main burner.
The combustible substance is preferably one that can be in a reduced state stronger than when it is supplied on the waste inlet side or in the middle of the rotary kiln. Specifically, for example, a combustible material having a higher combustion speed than the main fuel of a rotary kiln can be used. Examples of the combustible material having a high combustion rate include waste solids obtained by compressing and / or solidifying waste wood, waste plastic, heavy oil sludge, and municipal waste.
The average particle size of the combustible substance is preferably 0.1 to 10 mm, more preferably 1 to 5 mm. If the average particle size is less than 0.1 mm, the reducing atmosphere may not be maintained because it burns out at the very beginning during firing. If the average particle diameter exceeds 10 mm, a large amount of unburned combustible material remains in the obtained fired product, and the supplied combustible material is wasted, and the fired product is used as a cement mixture or concrete bone. When used as a material, the air entrainment and appearance of mortar concrete may deteriorate. In addition, the time which can maintain a reducing atmosphere can be adjusted with the average particle diameter of a combustible substance. For example, a combustible substance having a high combustion rate can increase the time during which the reducing atmosphere can be maintained by increasing (roughening) the average particle size.
The amount of heat of the combustible substance can be usually 2 to 40% of the amount of heat of the whole fuel used for the main burner. If the amount of heat of the combustible material is less than 2%, the effect of the reducing atmosphere may be small. When the amount of heat of the combustible material exceeds 40%, a large amount of unburned combustible material remains in the obtained fired product, and the supplied combustible material is wasted, and the fired product is used as a cement mixture or concrete. When used as an aggregate, the air entrainment and appearance of mortar concrete may deteriorate.
Compared with the case where the above-mentioned combustible substance is supplied from the waste inlet side or in the middle of the rotary kiln, when the waste is supplied from the waste outlet side, the reducing atmosphere in the rotary kiln is part of the furnace. In addition to maintaining the reducing atmosphere for a long time, the flammable substance supply position (falling position) is higher than the position where the maximum temperature is reached in the rotary kiln so that the reducing atmosphere is maintained in a high temperature zone where the reduction speed is fast. It is preferable to adjust to the side. The supply position is preferably preferably deeper than a point 4D from the kiln outlet, where D is the inner diameter of the kiln. Moreover, when the position which becomes the highest temperature in a kiln becomes the exit side more according to setting conditions, such as a main burner, a back | inner side is preferable from the point of 3D from the exit of a kiln. The supply position (falling position) is preferably adjusted by the angle of the inlet of the combustible substance, the position of the inlet, the speed at which the combustible substance is introduced, the particle size of the combustible substance, and the density of the combustible substance.
The oxygen (O ₂ ) concentration in the furnace when the combustible substance is added is preferably 5% by mass or less, more preferably 3% by mass or less from the viewpoint that the combustible substance does not disappear immediately.
By adjusting the above-described conditions, it is preferable to prevent the formation of hexavalent chromium and prevent the combustible substance from remaining.

As another method of heating the waste contaminated with radioactive cesium in a reducing atmosphere, a method in which a flame is brought into direct contact with the waste is mentioned.
Specifically, in an internal combustion type apparatus (internal heating rotary kiln or the like), the waste contaminated with radioactive cesium during heating (during firing) is fired so that the flame of the burner is in direct contact (hereinafter, referred to as “burning”). Also referred to as “flame film firing”). Flame film firing using an internally heated rotary kiln includes (a) a main burner for heating at the bottom and heating (firing) so that the flame licks waste, etc., (b) fuel quantity Or by adjusting the air velocity to dissipate the flame and heat (fire) the flame so that it licks the waste, etc. (c) The flame is lengthened by turning the angle of the main burner downward. Examples of the method include heating (firing) so as to lick waste and the like. Moreover, you may install the auxiliary burner for flame film baking other than the main burner for heating. By adjusting each condition, the reduction effect is improved as the contact time between the waste and the flame becomes longer. Moreover, even if chromium is contained in the waste, the production of hexavalent chromium can be prevented, and even if hexavalent chromium is produced in the step of heating the waste, trivalent chromium is produced. Reduced to
From the viewpoint of generating more flame film, the oxygen concentration at the time of flame film baking is preferably 5% by mass or less, more preferably 3% or less.
By adjusting the conditions described above, the hexavalent chromium elution preventing effect can be further increased. In addition, you may use together combustion of the combustible substance mentioned above, and flame film baking.

Moreover, it can also be under a reducing atmosphere by adjusting the atmosphere at the time of heating.
For example, as another method of heating waste contaminated with radioactive cesium in a reducing atmosphere, a method of burning a fuel used for heating with an amount of air smaller than the theoretical amount of air can be given.
Specifically, in an internal combustion type apparatus (such as an internal heat rotary kiln), the air ratio in the furnace (ratio of the supply air amount to the theoretical air amount) is 0.8 to 1.0, and the oxygen concentration in the furnace is The fuel is burned at 1% by mass or less or at a carbon monoxide concentration of 0.1 to 1.0% by mass.
When the air ratio is less than 0.8 or the carbon monoxide concentration exceeds 1.0 mass%, combustion necessary for heating may be difficult. When the air ratio exceeds 1.0, when the oxygen concentration exceeds 1% by mass, or when the carbon monoxide concentration is less than 0.1% by mass, the reduction effect is reduced.
Fuel used for heating includes heavy oil, pulverized coal, reclaimed oil, LPG, NPG, flammable waste, etc. as the main fuel (burner fuel), with the particle size adjusted to burn in space Is used.
Furthermore, it can be used in combination with the above-described combustion of combustible materials and / or flame film firing.
Moreover, the method of substituting or distribute | circulating the inside (external heating type rotary kiln, an electric furnace, etc.) used for a heating with inert gas, such as nitrogen gas, is mentioned. Further, the inert gas mixed with a reducing gas such as carbon monoxide gas may be replaced or circulated.

Volatilized radioactive cesium in the exhaust gas generated by the heating method described above can be recovered by a dust collector or a scrubber after being cooled and solidified. Moreover, when the preheater is attached to the kiln, the radioactive cesium which became solid can also be collect | recovered by extracting and cooling a part of waste gas which contains the volatilized radioactive cesium in high concentration. The collected radioactive cesium can be stored in a concrete container or the like after further volume reduction treatment by washing, adsorption or the like, if necessary. As a result, waste containing radioactive materials can be reduced in volume and stored without leaking outside.
When chloride is added to a mixture of waste and a CaO source and / or MgO source, radioactive cesium can be recovered in the form of radioactive cesium chloride. The radioactive cesium chloride can be easily dissolved in water and can be recovered as an aqueous solution.
The fired product obtained after heating is crushed as necessary, and used as cement mixture, aggregate (concrete aggregate, asphalt aggregate), earthwork material (backfill material, embankment material, roadbed material, etc.) can do.

The fired product obtained after heating is a fired product having an absolute dry density of preferably 1.5 to 3.0 g / cm ³ , more preferably 2.0 to 3.0 g / cm ³ .
Moreover, the amount of free lime (free lime) in the calcined product is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, and particularly preferably 0.2% by mass or less. When the amount of free lime exceeds 1.0% by mass, when the fired product is used as a concrete aggregate or earthwork material, the concrete may expand and break, or the fired product itself may collapse.
The particle size of the fired product may be adjusted by sieving or the like in consideration of the required particle size, compactness, etc., and used for a cement mixed material or the like.
In addition, when the waste contains chromium, in addition to the method in which heating is performed in a reducing atmosphere in the above-described heating step, the obtained fired product is subjected to the following treatment, whereby the hexavalent chromium is converted from the fired product. Can be prevented from eluting. In particular, when using a fired product as an earthwork material, it is preferable to take measures against elution of hexavalent chromium from the viewpoint of preventing water pollution and soil pollution. Hereinafter, a specific method for countermeasures against elution of hexavalent chromium will be described.

When hexavalent chromium is contained in the obtained fired product, as a countermeasure against elution of hexavalent chromium, a method of mixing the high-temperature fired product obtained by the heating step and a combustible substance can be mentioned. By mixing and cooling the high-temperature fired product and the combustible material after the heating step, hexavalent chromium in the fired product can be reduced to trivalent chromium, and hexavalent chromium in the fired product can be reduced. .
Specifically, a method of mixing the fired product after the heating step with a combustible substance while keeping the temperature of the fired product at a high temperature in a hot air furnace, or a high-temperature fired product and a combustible material after the heating step in the container There is a method in which the mixture is filled and then left standing while maintaining the temperature of the mixture of the fired product and the combustible substance at a high temperature.

Moreover, you may mix a high temperature baked material and a combustible substance in the cooling process using an air quenching cooler, a rotary cooler, etc. performed after a heating process. Among them, it is preferable to use a rotary cooler that is less in contact with oxygen and has a high degree of mixing of combustible substances.
When mixing a combustible substance in a cooling process, the mixing method of a combustible substance is not specifically limited, However, It is preferable to mix immediately after a heating process from a viewpoint of maintaining high temperature conditions and reducing atmosphere for a long time. For example, when heating is performed using a rotary kiln, a method in which a combustible substance is dropped and mixed at the outlet of the rotary kiln is preferable.
The higher the temperature of the fired product at the time of mixing the combustible substance, the greater the effect of reducing hexavalent chromium, preferably 800 ° C. or higher, more preferably 1000 ° C. or higher. In addition, when heating using a rotary kiln, the temperature of the baked product at the time of mixing in a rotary cooler can be made high by making the position where the calcination temperature in a rotary kiln becomes the maximum close to the outlet.
The longer the time until the fired product cools after mixing the combustible material, the greater the effect of reducing hexavalent chromium, but the time from mixing to the temperature of the fired product becoming 600 ° C. or lower is preferably 1 More than 3 minutes, more preferably more than 3 minutes.
The combustible material is preferably mixed in an amount corresponding to a heat amount of 2 to 20% with respect to the heat amount of the entire mixture of the fired product and the combustible material. When the amount corresponds to a heat amount of less than 2%, the effect of reducing hexavalent chromium is reduced. When the amount corresponds to an amount of heat exceeding 20%, a large amount of unburned combustible material remains in the fired product after cooling.
Examples of the combustible material include solid waste lump obtained by compressing and / or solidifying waste such as coal, coke, activated carbon, waste wood, waste plastic, heavy oil sludge, and municipal waste. Especially, what can be made into a stronger reduction state is preferable. Specifically, a combustible substance having a high burning rate can be used. Examples of the combustible material having a high combustion rate include waste solids obtained by compressing and / or solidifying waste wood, waste plastic, heavy oil sludge, and municipal waste.
The average particle size of the combustible substance is preferably 0.1 to 10 mm, more preferably 1 to 5 mm. If it exceeds 10 mm, a large amount of combustible material remains in the fired product after cooling. When the thickness is less than 0.1 mm, the effect of reducing hexavalent chromium is reduced, and when it is introduced, it is scattered by the wind speed of the cooling air and the amount mixed with the fired product is reduced.
The combustible material having a high combustion rate described above can increase (roughen) the average particle size. By increasing the average particle size, it is possible to lengthen the time during which the reducing atmosphere can be maintained, and to prevent the combustible material from being scattered due to the wind speed of the cooling air when being charged.
The oxygen concentration at the time of mixing a combustible substance is not specifically limited. Further, if possible, exhaust gas may be used from the viewpoint of reducing contact with oxygen or reducing the amount of flammable substance added.
It is preferable to adjust the above-described conditions so that the effect of reducing hexavalent chromium is large and combustibles do not remain. Moreover, when using a baked material as a cement mixing material, it is preferable to adjust so that the color of the cement using this baked material may not change by making a reducing atmosphere too strong.

Moreover, as a countermeasure against elution of hexavalent chromium, a method of further heating and melting the fired product obtained in the heating step can be mentioned.
By melting the fired product, hexavalent chromium contained in the fired product is sealed in the glass, and when it is used for earthwork materials, the elution amount of hexavalent chromium becomes the environmental standard value or less.
After the fired product is further heated and melted, the melt is cooled to become a granular material. The obtained granular melt has a low water absorption rate and high strength, and therefore can be used as an aggregate for concrete. The melt may be cooled rapidly or slowly.
Moreover, it is preferable from a viewpoint of energy cost to melt | dissolve the high-temperature-baked material obtained by the heating process (for example, the fired material immediately after coming out of the kiln) directly.

Moreover, you may perform the mixing process which mixes at least 1 sort (s) chosen from the baked material obtained by the heating process, and the group which consists of a reducing agent and an adsorbent as a countermeasure against elution of hexavalent chromium.
For example, by mixing a fired product and a reducing agent, hexavalent chromium contained in the fired product or hexavalent chromium eluted from the fired product can be reduced to trivalent chromium.
Examples of the reducing agent include sulfites such as sodium sulfite, iron (II) salts such as iron (II) sulfate and iron (II) chloride, sodium thiosulfate, and iron powder.
In addition, by mixing the fired product and the adsorbent, hexavalent chromium eluted from the fired product can be adsorbed, and insolubilization of hexavalent chromium or elution can be suppressed.
Examples of the adsorbent include zeolites, clay minerals, layered double hydroxides such as hydrotalcite compounds such as Mg-Al and Mg-Fe, Ca-Al hydroxides, ettringite, and monosulfates. Ca-Al compounds, hydrous oxides such as iron oxide (hematite) and bismuth oxide, magnesium compounds such as magnesium hydroxide, light calcined magnesium, calcined dolomite and magnesium oxide, iron sulfide, iron powder, Schwermanite, FeOOH, etc. And an iron compound, a mixture of one or more of silicon oxide, aluminum oxide, iron oxide and the like, or a fired product, a compound containing cerium, and a rare earth element.
A reducing agent and an adsorbent may be used individually by 1 type, and may be used in combination of 2 or more type.
As a method of mixing the calcined product and the drug (reducing agent and / or adsorbent), the calcined product and the powdered drug may be mixed. The drug is mixed with water in advance, and a slurry or an aqueous solution (hereinafter, “ Also referred to as “slurry or the like”), and a method of mixing the fired product with the slurry, spraying the slurry or the like on the fired product, or immersing the fired product in the slurry or the like.
The amount of the drug used is such that the amount of metal salt per 100 kg of the fired product is preferably 0.01 to 10 kg, more preferably 0.1 to 7 kg, particularly preferably 0.2 to 5 kg. The amount of the powdered drug, the concentration of the slurry, etc., the spray amount of the slurry, etc., and the input amount of the fired product into the slurry are adjusted. When the amount of the metal salt per 100 kg of the fired product is less than 0.01 kg, the effect of reducing the elution amount of hexavalent chromium is reduced. If the amount exceeds 10 kg, the effect of reducing the elution amount of hexavalent chromium is saturated, which is not economical.
The temperature of the fired product during mixing is preferably 100 to 800 ° C, more preferably 125 to 600 ° C, and particularly preferably 150 to 400 ° C. When the temperature of the baked product exceeds 800 ° C., cracks or the like are generated in the baked product, or the baked product is atomized, resulting in a decrease in strength. When the temperature is lower than 100 ° C., it is not preferable because the drug hardly adheres to the surface of the fired product.
A method of spraying a slurry containing a drug or the like on a high-temperature fired product is preferable because the drug adheres to the surface of the fired product and is difficult to peel off. Moreover, when there are pores in the fired product, a method of immersing the fired product in a slurry or the like is preferable because the drug penetrates well into the inside and adheres to the surface.

Furthermore, as a countermeasure against elution of hexavalent chromium, there is a method of washing the fired product obtained in the heating step with water.
As washing methods, (i) a method in which a cleaning liquid is sprayed on a fired product in a container or on a belt conveyor by a sprinkler or the like, and (ii) a fired product and a cleaning liquid are put in a container, and the fired product is washed for a certain period (Iii) A method of repeatedly washing and supplying new cleaning liquid after immersion, (iii) Using trommel, etc., sequentially replacing the fired products while immersing the fired products in the cleaning liquid Examples include a cleaning method.
The cleaning liquid may be ordinary tap water or an aqueous solution of the above-described drug (reducing agent or adsorbent). The washing liquid after washing with water may be reused as the washing liquid, or may be discarded after being treated.
The washing time, the number of washings, and the amount of washing solution used for washing are not particularly limited, and the washing may be performed until the elution amount of hexavalent chromium satisfies the environmental standard value (Environment Agency Notification No. 46).
These methods may be performed in combination with the method of heating in a reducing atmosphere in the heating step described above.

  In addition, since the fired product obtained by the heating process of the present invention is excellent in the ability to fix heavy metals (lead, arsenic, etc.) other than hexavalent chromium inside, the above-described treatment for preventing elution of hexavalent chromium is performed. If done, it can be suitably used as earthwork material (backfill material, embankment material, roadbed material, etc.).

The fired product can be pulverized and used as a cement mixture. Further, 1 to 6 parts by mass of gypsum in terms of SO ₃ can be added to 100 parts by mass of the pulverized product of the fired product.
The pulverization method is not particularly limited, and may be pulverized by a normal method using, for example, a ball mill.
The pulverized product of the fired product preferably has a Blaine specific surface area of 2500 to 5000 cm ² / g from the viewpoint of reducing bleeding of mortar and concrete, fluidity, and strength development.
The pulverization may be performed simultaneously with the fired product, cement clinker and gypsum. The brane specific surface area of the cement when pulverized at the same time is preferably 2500 to 4500 cm ² / g from the viewpoints of reducing bleeding of mortar and concrete, fluidity, and strength development.
When the cement mixture is mixed with cement to obtain a cement composition, the heat of hydration of the cement composition can be lowered and the fluidity can be improved.

Further, the fired product can be pulverized or classified as necessary, and used as an aggregate (concrete aggregate, aggregate for asphalt) or earthwork material.
When fired products containing hexavalent chromium are used as aggregates, hexavalent chromium is incorporated into the hardened cement, and therefore preventing elution of hexavalent chromium by preventing rainwater during transportation and storage of aggregates. Can do. Moreover, you may perform the process which prevents elution of the hexavalent chromium mentioned above.
The obtained fired product can be used for both fine aggregate and coarse aggregate. When used as a coarse aggregate, the particle size is adjusted to 5 mm or more by sieving or the like.
Moreover, when using as earthwork material, considering compaction property etc., it adjusts and uses for 0.1-100 mm.
When used as an aggregate, the absolute dry density of the fired product is preferably 2.0 to 3.0 g / cm ³ . When the absolute dry density is less than 2.0 g / cm ³ , the strength of the concrete may be reduced. The water absorption rate of the fired product is preferably 15% or less. If the water absorption is greater than 15%, the strength of the concrete may be reduced.
In particular, when used as an aggregate for concrete, it is preferable that the absolutely dry density of the fired product is 2.5 to 3.0 g / cm ³ and the water absorption is 3% or less.
The amount of free lime is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, and particularly preferably 0.2% by mass or less. If the amount exceeds 1.0% by mass, concrete may expand and break.

C ₂ S in the obtained fired product has hydraulic properties, and has an effect of slowly reacting in the concrete to densify the concrete and improve the strength. C ₂ AS does not have hydraulic properties, but becomes dense when carbonated, and thus has an effect of suppressing neutralization.
Therefore, by using the fired product as an aggregate, it is possible to produce concrete having excellent durability such as strength development and neutralization resistance.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
[Synthesis Example 1; Preparation of Cesium-Adsorbed Clay A]
After immersing 500 g of bentonite in 2 liters of an aqueous solution containing cesium at a concentration of 250 mg / liter for 1 day, the solid content was collected by centrifugation, and the solid content was washed with water and centrifuged again. As a result, cesium-adsorbed clay A containing cesium at a concentration of 1060 mg / kg was obtained.
[Synthesis Example 2; Preparation of Cesium-Adsorbed Clay B]
After immersing 500 g of bentonite in 2 liters of an aqueous solution containing cesium at a concentration of 500 mg / liter for 1 day, the solid content was recovered by centrifugation, and the solid content was further washed with water and centrifuged again. As a result, cesium-adsorbed clay B containing cesium at a concentration of 2200 mg / kg was obtained.
The chemical composition of the raw materials used is as shown in Table 1.

[Example 1]
9 g of cesium adsorption clay A obtained in Synthesis Example 1 and 11 g of limestone powder were mixed. The obtained mixture was heated at a heating temperature and a heating time described in Table 2 under air (water content: 7%) obtained by bubbling by passing it through water at 60 ° C. using a tubular electric furnace, A fired product was obtained. The Cs content of each of the mixture before heating and the fired product obtained by heating was measured using a wet method, and the volatilization rate (mass%) of Cs was determined. Moreover, each amount of Na ₂ O and K ₂ O was measured by X-ray fluorescence analysis (XRF), and the volatilization rate (mass%) of Na and K was determined. Further mineral composition ratio of the obtained baked product _{(C 2 S, C 2 AS} , C 4 AF, C 3 A) of _CaO in use in the raw material, the content of _{SiO 2, Al 2 O 3,} Fe 2 O 3 From (mass%), it calculated and calculated | required by the formula described in the paragraph 0016. The results are shown in Table 2.
[Example 2]
9 g of cesium adsorption clay A obtained in Synthesis Example 1 and 11 g of limestone powder were mixed. The obtained mixture was heated using a tubular electric furnace under air (pure air) not containing water vapor at the heating temperature and heating time described in Table 2 to obtain a fired product. For the mixture before heating and the fired product obtained by heating, the volatilization amount and the like were determined in the same manner as in Example 1. The results are shown in Table 2.
[Example 3]
8 g of cesium adsorption clay A obtained in Synthesis Example 1 and 12 g of limestone powder were mixed. The obtained mixture was heated at a heating temperature and a heating time described in Table 2 under air (water content: 7%) obtained by bubbling by passing it through water at 60 ° C. using a tubular electric furnace, A fired product was obtained. For the mixture before heating and the fired product obtained by heating, the volatilization amount and the like were determined in the same manner as in Example 1. The results are shown in Table 2.
[Example 4]
8 g of cesium adsorption clay A obtained in Synthesis Example 1 and 12 g of limestone powder were mixed. The obtained mixture was heated in pure air using a tubular electric furnace at the heating temperature and heating time described in Table 2 to obtain a fired product. For the mixture before heating and the fired product obtained by heating, the volatilization amount and the like were determined in the same manner as in Example 1. The results are shown in Table 2.
[Example 5]
The cesium adsorption clay A6.6g obtained by the synthesis example 1 and limestone powder 13.2g were mixed. The obtained mixture was heated at a heating temperature and a heating time described in Table 2 under pure air using a tubular electric furnace to obtain a fired product. For the mixture before heating and the fired product obtained by heating, the volatilization amount and the like were determined in the same manner as in Example 1. The results are shown in Table 2.
[Example 6]
The cesium adsorption clay A6.6g obtained by the synthesis example 1 and limestone powder 13.2g were mixed. The obtained mixture was heated at a heating temperature and a heating time described in Table 2 under air (water content: 7%) obtained by bubbling by passing it through water at 60 ° C. using a tubular electric furnace. As a result, a fired product was obtained. For the mixture before heating and the fired product obtained by heating, the volatilization amount and the like were determined in the same manner as in Example 1. The results are shown in Table 2.

[Comparative Example 1]
Cesium adsorption clay A11g obtained by the synthesis example 1 and limestone powder 9g were mixed. The obtained mixture was heated at a heating temperature and a heating time described in Table 2 under air (water content: 7%) bubbled with 60 ° C. water using a tubular electric furnace to obtain a fired product. For the mixture before heating and the fired product obtained by heating, the volatilization amount and the like were determined in the same manner as in Example 1. The results are shown in Table 2.
[Comparative Example 2]
10 g of cesium adsorption clay A obtained in Synthesis Example 1 and 10 g of limestone powder were mixed. The obtained mixture was heated at a heating temperature and a heating time described in Table 2 under air (water content: 7%) bubbled with 60 ° C. water using a tubular electric furnace to obtain a fired product. For the mixture before heating and the fired product obtained by heating, the volatilization amount and the like were determined in the same manner as in Example 1. The results are shown in Table 2.
[Comparative Example 3]
10 g of cesium adsorption clay A obtained in Synthesis Example 1 and 10 g of limestone powder were mixed. The obtained mixture was heated at a heating temperature and a heating time described in Table 2 under pure air using a tubular electric furnace to obtain a fired product. For the mixture before heating and the fired product obtained by heating, the volatilization amount and the like were determined in the same manner as in Example 1. The results are shown in Table 2.
[Comparative Example 4]
10 g of cesium adsorption clay A obtained in Synthesis Example 1 and 10 g of limestone powder were mixed. The obtained mixture was heated at a heating temperature and a heating time described in Table 2 under air (water content: 7%) bubbled with 60 ° C. water using a tubular electric furnace to obtain a fired product. For the mixture before heating and the fired product obtained by heating, the volatilization amount and the like were determined in the same manner as in Example 1. The results are shown in Table 2.

[Example 7]
30 g of the cesium adsorption clay B obtained in Synthesis Example 2, 60 g of limestone powder, and 0.0246 g of calcium chloride were pulverized and mixed. 20 g of the obtained mixture was heated at a heating temperature and a heating time described in Table 3 under air (water content: 7%) bubbled with 60 ° C. water using a tubular electric furnace to obtain a fired product. . For the mixture before heating and the fired product obtained by heating, the volatilization amount and the like were determined in the same manner as in Example 1. The results are shown in Table 3.
[Example 8]
30 g of the cesium adsorption clay B obtained in Synthesis Example 2, 60 g of limestone powder, and 0.0492 g of calcium chloride were pulverized and mixed. 20 g of the obtained mixture was heated at a heating temperature and a heating time described in Table 3 under air (water content: 7%) bubbled with 60 ° C. water using a tubular electric furnace to obtain a fired product. . For the mixture before heating and the fired product obtained by heating, the volatilization amount and the like were determined in the same manner as in Example 1. The results are shown in Table 3.
[Example 9]
30 g of the cesium adsorption clay B obtained in Synthesis Example 2, 60 g of limestone powder, and 0.0984 g of calcium chloride were pulverized and mixed. 20 g of the obtained mixture was heated at a heating temperature and a heating time described in Table 3 under air (water content: 7%) bubbled with 60 ° C. water using a tubular electric furnace to obtain a fired product. . For the mixture before heating and the fired product obtained by heating, the volatilization amount and the like were determined in the same manner as in Example 1. The results are shown in Table 3.
[Example 10]
30 g of the cesium adsorption clay B obtained in Synthesis Example 2, 60 g of limestone powder, and 0.246 g of calcium chloride were pulverized and mixed. 20 g of the obtained mixture was heated at a heating temperature and a heating time described in Table 3 under air (water content: 7%) bubbled with 60 ° C. water using a tubular electric furnace to obtain a fired product. . For the mixture before heating and the fired product obtained by heating, the volatilization amount and the like were determined in the same manner as in Example 1. The results are shown in Table 3.
[Example 11]
30 g of the cesium adsorption clay B obtained in Synthesis Example 2, 60 g of limestone powder, and 0.492 g of calcium chloride were pulverized and mixed. 20 g of the obtained mixture was heated at a heating temperature and a heating time described in Table 3 under pure air using a tubular electric furnace to obtain a fired product. The volatilization amount and the like were determined in the same manner as in Example 2 for the mixture before heating and the fired product obtained by heating. The results are shown in Table 3.
[Example 12]
30 g of the cesium adsorption clay B obtained in Synthesis Example 2, 60 g of limestone powder, and 0.492 g of calcium chloride were pulverized and mixed. 20 g of the obtained mixture was heated at a heating temperature and a heating time described in Table 3 under air (water content: 7%) bubbled with 60 ° C. water using a tubular electric furnace to obtain a fired product. . For the mixture before heating and the fired product obtained by heating, the volatilization amount and the like were determined in the same manner as in Example 1. The results are shown in Table 3.

[Comparative Example 5]
10 g of cesium adsorbing clay B obtained in Synthesis Example 2, 10 g of limestone powder, and 0.49 g of calcium chloride were mixed. 20 g of the obtained mixture was heated at a heating temperature and a heating time described in Table 3 under an air bubbled with 60 ° C. water (water content: 7%) using a tubular electric furnace to obtain a fired product. It was. For the mixture before heating and the fired product obtained by heating, the volatilization amount and the like were determined in the same manner as in Example 1. The results are shown in Table 3.

[Example 13]
A fired product was obtained in the same manner as in Example 5 except that heating was performed at 1300 ° C. for 120 minutes under air (pure air) not containing water vapor. The respective contents of cesium (Cs), chlorine (Cl), Na ₂ O, and K ₂ O of the mixture before heating and the fired product obtained by heating were measured in the same manner as in Example 1. , Cs, Na, and K volatilization rates (% by mass) were determined. The results are shown in Table 4.
[Example 14]
A fired product was obtained in the same manner as in Example 5 except that heating was performed at 1300 ° C. for 30 minutes under air (pure air) not containing water vapor. The respective contents of cesium (Cs), chlorine (Cl), Na ₂ O, and K ₂ O of the mixture before heating and the fired product obtained by heating were measured in the same manner as in Example 1. , Cs, Na, and K volatilization rates (% by mass) were determined. The results are shown in Table 4.
[Example 15]
A fired product was obtained in the same manner as in Example 5 except that heating was performed at 1250 ° C. for 60 minutes under air (pure air) not containing water vapor. The respective contents of cesium (Cs), chlorine (Cl), Na ₂ O, and K ₂ O of the mixture before heating and the fired product obtained by heating were measured in the same manner as in Example 1. , Cs, Na, and K volatilization rates (% by mass) were determined. The results are shown in Table 4.
[Example 16]
A fired product was obtained in the same manner as in Example 5 except that heating was performed at 1250 ° C. for 120 minutes under air (pure air) not containing water vapor. The respective contents of cesium (Cs), chlorine (Cl), Na ₂ O, and K ₂ O of the mixture before heating and the fired product obtained by heating were measured in the same manner as in Example 1. , Cs, Na, and K volatilization rates (% by mass) were determined. The results are shown in Table 4.
[Example 17]
A fired product was obtained in the same manner as in Example 5 except that heating was performed at 1350 ° C. for 30 minutes under air (pure air) not containing water vapor. The respective contents of cesium (Cs), chlorine (Cl), Na ₂ O, and K ₂ O of the mixture before heating and the fired product obtained by heating were measured in the same manner as in Example 1. , Cs, Na, and K volatilization rates (% by mass) were determined. The results are shown in Table 4. The volatilization rates in Tables 1 to 4 are rounded off to the first decimal place.

Claims (8)

The waste contaminated with radioactive cesium and the heating step of heating the CaO source and / or MgO source at 1200 to 1400 ° C. to volatilize the radioactive cesium in the waste to obtain a fired product. A manufacturing method comprising:
The above-mentioned waste, CaO source, and so that the obtained fired product contains C ₂ S and C ₂ AS, and the total amount of C ₂ AS and C ₄ AF per 100 parts by mass of C ₂ S is 10 to 100 parts by mass. A method for producing a fired product, characterized in that each kind of MgO source and a mixing ratio thereof are determined. Further, CaO, MgO, and each of the mass of SiO ₂ is, so as to satisfy the following formula (1), firing of claim 1 for determining the types and blending ratio of each of the waste, CaO source and MgO source Manufacturing method.
((CaO + 1.39 × MgO) / SiO ₂ ) = 1.0 to 2.2 (1)
(In the formula, CaO, MgO, and SiO ₂ represent the mass of calcium oxide, the mass of magnesium oxide, and the mass of silicon oxide, respectively.)   The manufacturing method of the baked product of Claim 1 or 2 which uses a chloride further as a raw material.   The manufacturing method of the baked product of any one of Claims 1-3 which heats in a reducing atmosphere in the said heating process.   The manufacturing method of the baked product of any one of Claims 1-4 including the mixing process which mixes the baked product obtained by the said heating process, and at least 1 sort (s) chosen from the group which consists of a reducing agent and an adsorbent. .   The cement mixed material obtained by grind | pulverizing the baked product obtained by the manufacturing method of the baked product of any one of Claims 1-5.   The aggregate which consists of a baked product obtained by the manufacturing method of the baked product of any one of Claims 1-5.   The earthwork material which consists of a baked product obtained by the manufacturing method of the baked product of any one of Claims 1-5.