JP2019055904A - Production method of geopolymer molding body, and geopolymer molding body manufacturing system - Google Patents

Abstract

To provide a production method of a geopolymer molding body in which a time capable of mixing a solidification material and an alkali stimulant is long, less energy is required for manufacturing a solidified body, and a time required for manufacturing the solidified body is short.SOLUTION: A production method of a geopolymer molding body according to the embodiment, includes a mixing process and a compression process. In the mixing process, a mixture is obtained by mixing a solidification material and an alkali stimulant. In the compression process, a geopolymer molding body is formed by compressing and molding the mixture, in which the alkali stimulant contains hydrate. When compressing the mixture in the compression process, the mixture is heated so as to eliminate crystalline water from the hydrate, thus the reaction between the solidification material and the alkali stimulant is advanced.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing a geopolymer molded body and a geopolymer molded body manufacturing system.

  Radioactive waste is generally solidified using a solidifying material such as cement, glass, asphalt, or epoxy resin.

  Cement is often used because it is inexpensive and has excellent operability. However, since cement produces hydrated minerals and hardens, it has hydrates in the structure of the solidified body, and surplus water in the water during preparation exists in the solidified body. For this reason, when cement is exposed to a high dose of radiation, water may be decomposed by the radiation and hydrogen may be generated. Since asphalt and epoxy resin are organic substances, they may decompose and generate gas when exposed to a high dose of radiation over a long period of time. Therefore, in solidifying high-dose radiation waste, it is considered promising to solidify using inorganic material glass as a solidifying material. However, solidification using glass requires heat treatment at a temperature of about 1000 ° C., which is expensive and may deteriorate workability.

  As an alternative material for the above solidifying material, a geopolymer has attracted attention (for example, see Patent Document 1). A geopolymer is a polymer of an amorphous material mainly composed of aluminum (Al), silicon (Si), and the like, and is an inorganic material like cement. Unlike cement, the geopolymer has no hydrate in the structure of the solidified body. For this reason, when a geopolymer is used, even if it is a case where excess water is removed by drying by heating, an influence with respect to the structure of a solidified body is small. Therefore, when a geopolymer is used as a solidifying material, the amount of hydrogen generated can be reduced.

JP 2014-35202 A

  In the geopolymer, a solidifying material (binder) and an alkali stimulant are used as raw materials. The solidifying material is, for example, alumina silica containing aluminum (Al) and silicon (Si). The alkaline stimulant is, for example, an alkaline hydroxide (such as sodium hydroxide) or an alkaline silicate (such as sodium silicate). The geopolymer is formed as a solidified body by a condensation polymerization reaction occurring between the solidifying material and the alkaline stimulant.

  When producing a solidified body of a geopolymer, a reaction between the solidifying material and the alkaline stimulant occurs in a short time, and the viscosity of the mixture containing the solidifying material and the alkaline stimulant increases. For this reason, the mixing time is short.

  In addition, when producing a solidified body of geopolymer, when performing a drying process or a heat curing process, a large amount of energy is required for the process, and a long time is required for the execution of the process.

  Therefore, the problem to be solved by the present invention is that the time during which the solidifying material and the alkali stimulant can be mixed is long, less energy is required to produce the solidified body, and it is necessary to produce the solidified body. It is to provide a method for manufacturing a geopolymer molded body and a geopolymer molded body manufacturing system that have a short time.

  The manufacturing method of the geopolymer molding which concerns on embodiment has a mixing process and a compression process. In the mixing step, a mixture is obtained by mixing the solidifying material and the alkali stimulant. In the compression step, a geopolymer molded body is formed by compressing and molding the mixture. Here, the alkaline stimulant includes a hydrate. And when compression of a mixture is performed in a compression process, a mixture is heated so that crystal water may detach | desorb from a hydrate, and reaction between a solidification material and the said alkali stimulant advances.

  According to the present invention, a geopolymer having a long mixing time of a solidifying material and an alkali stimulator, a small amount of energy required for producing a solidified material, and a short time required for producing a solidified material. The manufacturing method of a molded object, and a geopolymer molded object manufacturing system can be provided.

FIG. 1 is a flowchart showing a method for producing a geopolymer molded body in the first embodiment. FIG. 2 is a block diagram schematically showing a geopolymer molded body manufacturing system in the first embodiment. FIG. 3 is a diagram showing the results of X-ray structural analysis of the sample of the example, each sample of the comparative example, the solidifying material, the alkali stimulating agent, and the mixture of the solidifying material and the alkali stimulating agent.

<First Embodiment>
[A] Method for Producing Geopolymer Molded Body FIG. 1 is a flowchart showing a method for producing a geopolymer molded body in the first embodiment.

  In this embodiment, as shown in FIG. 1, a geopolymer molded body is produced by sequentially performing a mixing step ST10 and a compression step ST20. The details of each process will be described sequentially.

[A-1] Mixing step ST10
In the mixing step ST10, a mixture is obtained by mixing at least a solidifying material and an alkali stimulant as a raw material for the geopolymer.

[A-1-1] Solidified material The solidified material is, for example, alumina silica containing aluminum (Al) and silicon (Si). Alumina silica is, for example, metakaolin, blast furnace slag, incinerated ash, fly ash (including fly ash), zeolite, mordenite, silica fume, amorphous silicon dioxide, aluminum oxide, and aluminum hydroxide. Here, fly ash includes fly ash. Fly ash is fly ash collected after burning finely pulverized coal and is managed as a product.

[A-1-2] Alkali stimulator The alkali stimulator is, for example, an alkaline hydroxide or an alkaline silicate. The alkaline hydroxide is, for example, lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, or cesium hydroxide. Alkaline silicates are, for example, lithium silicate, sodium silicate, potassium silicate, rubidium silicate, cesium silicate. As the silicate, various forms such as orthosilicate and metasilicate can be used. In addition to the above, aluminate may be added as an alkali stimulant.

In this embodiment, the alkaline stimulant includes a hydrate. For example, silicate hydrates and aluminate hydrates are used as alkali stimulants. Hydrates are substances containing water of crystallization (hydration water) and act as a moisture providing material in the raw material of the geopolymer. That is, the alkali stimulant which is a hydrate acts as an alkali stimulator and also acts as a moisture providing material. Hydrates of silicates, for example, lithium silicate hydrate, (such as sodium metasilicate nonahydrate _{(Na 2 SiO 3 · 9H 2} O)) Sodium silicate hydrate, potassium silicate hydrate (Such as potassium tetrasilicate monohydrate), rubidium silicate hydrate, and cesium silicate hydrate. Aluminate hydrate includes, for example, lithium aluminate hydrate, sodium aluminate hydrate, potassium aluminate hydrate (potassium aluminate trihydrate, etc.), rubidium aluminate hydrate, cesium aluminate It is a hydrate.

Alkaline stimulant is a hydrate is preferably one having a melting point of 100 ° C. or less, for example, sodium metasilicate nonahydrate _{(Na 2 SiO 3 · 9H 2} O; mp 48 ° C.), sodium metasilicate pentahydrate A Japanese product (Na ₂ SiO ₃ .5H ₂ O; melting point 72 ° C.) is preferably used. At the same time, it is more preferable that the alkaline stimulant which is a hydrate has a melting point higher than the temperature of the workplace where the mixture is prepared and does not melt when the mixture is prepared. Specifically, the alkali stimulant that is a hydrate preferably has a melting point of 50 ° C. or higher and 100 ° C. or lower.

[A-1-3] Others In addition to the above, radioactive waste such as a radionuclide adsorbent used for purifying water may be mixed as a solidified material with the raw material of the geopolymer. Further, other pulverizable solid waste may be mixed as a solidified material with the raw material of the geopolymer.

  Moreover, in order to produce a geopolymer molded body as a solidified body, water may be appropriately added if necessary. Specifically, water may be added so that the weight of water is, for example, 1/20 or less of the total weight of solids in the mixture.

[A-1-5] Mixing Each raw material described above is, for example, put into a container and then mixed using a stirrer. As a result, a mixture is obtained in the mixing step ST10.

[A-2] Compression step ST20
Next, as shown in FIG. 1, after the mixing step ST10, the compression step ST20 is performed.

  In compression process ST20, a geopolymer molded object is formed by compressing and shape | molding the mixture obtained by mixing process ST10. In compression process ST20 of this embodiment, when compressing a mixture, the mixture is heated. That is, the compression process ST20 of the present embodiment performs a thermal compression process. Here, when performing compression molding of the mixture using a compression molding machine, for example, the mixture is heated from the outside using a heater.

  As a result, in this embodiment, the solidifying material and the alkaline stimulant are brought into close contact with each other by compression, and the temperature of the solidifying material and the alkaline stimulant is increased by heating. In this embodiment, the alkaline stimulant includes a hydrate. For this reason, crystal water (hydration water) is desorbed from the hydrate by heating during compression, and the water generated by the desorption functions as a reaction field. As a result, in the present embodiment, the reaction between the solidifying material and the alkaline stimulant proceeds effectively, and a geopolymer is formed.

  In compression process ST20, it is preferable that the pressure applied to a mixture is 1 megapascal [MPa] or more, for example. Thereby, the density of a geopolymer molded object becomes high and the shape of a geopolymer molded object is stabilized.

  Moreover, in compression process ST20, the temperature of a mixture is a temperature which the hydrate which is an alkali stimulant melt | dissolves, for example, it is preferable that it is the range of 48 to 100 degreeC. When the temperature is lower than the lower limit of the above temperature range, water necessary for the solidification reaction is not generated, and thus there may be a problem that the solidification reaction does not proceed. On the other hand, when the temperature is higher than the upper limit of the above temperature range, there is a case where water necessary for the solidification reaction evaporates and the solidification reaction does not proceed.

[A-3] Other process Although illustration is abbreviate | omitted, you may perform a curing process and a drying process as needed after execution of compression process ST20.

  In the curing process, the reaction is further advanced by curing the geopolymer molded body obtained in the compression process ST20. Here, the water contained in the geopolymer molded body functions as a reaction field, and the reaction further proceeds.

  In the drying process, for example, water present in the geopolymer molded body that has been subjected to the curing process is removed by evaporation. In the drying step, drying may be performed by natural drying, or drying using a dryer may be performed.

[B] Geopolymer molded body manufacturing system FIG. 2 is a block diagram schematically showing a geopolymer molded body manufacturing system in the first embodiment.

  As shown in FIG. 2, the geopolymer molded body manufacturing system of this embodiment includes at least a mixing unit 10 and a compression molding unit 20. The detail of each part which comprises the geopolymer molded object manufacturing system of this embodiment is demonstrated sequentially.

[B-1] Mixing unit 10
The mixing unit 10 includes, for example, a container 11 and a stirrer 12 and executes the above-described mixing step ST10. That is, in the mixing part 10, a mixture is obtained by mixing a solidification material and an alkaline stimulant as a raw material of a geopolymer.

  Specifically, in the mixing unit 10, for example, after the respective raw materials described above are charged into the container 11, the respective raw materials are mixed using the stirrer 12.

[B-2] Compression molding part 20
The compression molding unit 20 includes, for example, a mold 21, a pressurizer 22, and a heater 23, and executes the above-described compression step ST20. That is, a geopolymer molded body is formed by compressing and molding the mixture obtained in the mixing unit 10. In the compression molding part 20 of this embodiment, when compressing a mixture, the mixture is heated.

  Specifically, in the compression molding unit 20, the mixture obtained in the mixing unit 10 is introduced into the mold 21, and the pressurizer 22 applies pressure to the mixture introduced into the mold 21 and compresses the mixture. At this time, the heater 23 heats the mixture introduced into the mold 21 from the outside of the mold 21.

[B-3] Others Although not shown, the geopolymer molded body manufacturing system may include a curing unit that performs the curing process described above and a drying unit that performs the drying process described above. The curing unit includes, for example, an air conditioner that adjusts the temperature and humidity of the curing room. The drying unit includes, for example, an air conditioner that adjusts the temperature and humidity of the drying chamber.

[C] Summary As described above, in this embodiment, when a mixture of a solidifying material and an alkali stimulant is compressed and molded, the mixture is heated using a heater. In this embodiment, the alkaline stimulant includes a hydrate. For this reason, in this embodiment, as described above, crystal water (hydrated water) is desorbed from the hydrate by heating at the time of compression molding, and the water generated by the desorption functions as a reaction field. That is, in this embodiment, the reaction between the solidifying material and the alkaline stimulant is unlikely to proceed before the crystal water (hydrated water) is desorbed from the hydrate by heating during compression. Therefore, in this embodiment, in mixing process ST10, the time which can mix a solidification material and an alkaline stimulant can be lengthened.

  Further, in the present embodiment, as described above, the reaction between the solidifying material and the alkaline stimulant is effectively performed by removing crystal water (hydrated water) from the hydrate by heating at the time of compression molding. Since the process proceeds, it is not necessary to perform the curing process and the drying process. Even if the curing process and the drying process are performed, the time for performing the process can be shortened. Therefore, in the present embodiment, less energy is required for producing the solidified body, and the time required for producing the solidified body can be shortened.

Second Embodiment
[A] Method for Producing Geopolymer Molded Body In this embodiment, a geopolymer molded body is produced by sequentially performing the mixing step ST10 and the compression step ST20, as in the case of the first embodiment. However, in the mixing step ST10 of the present embodiment, unlike the case of the first embodiment, a mixture is obtained by further mixing the exothermic substances. The exothermic substance is a metal powder formed of a metal material selected from iron, zinc, aluminum, nickel, and tin, and generates heat by an oxidation reaction. For this reason, in the compression step ST20 of the present embodiment, unlike the case of the first embodiment, the mixture is heated by the heat generated by the heat generating material. That is, the mixture is heated with heat generated by the exothermic substance inside the mold 21.

[B] Summary As described above, in this embodiment, since the mixture is obtained by further mixing the exothermic substance in the mixing step ST10, the mixture is heated by the exothermic substance in the compression step ST20. Therefore, in this embodiment, the time which can mix a solidification material and an alkaline stimulant can be lengthened similarly to the case of 1st Embodiment. Further, in the present embodiment, as in the case of the first embodiment, the energy required for producing the solidified body is small, and the time required for producing the solidified body can be shortened.

  In addition to the addition of the exothermic substance, components such as activated carbon may be added as appropriate. When activated carbon is added, since air is taken into the pores of the activated carbon, supply of oxygen necessary for the oxidation reaction of the exothermic substance is promoted.

  Hereinafter, examples will be described with reference to Table 1. In Table 1, Example 1 (Examples 1-1 to 1-3) corresponds to the case of the first embodiment described above. Example 2 corresponds to the case of the second embodiment described above.

[1] Preparation of sample (Example 1-1)
In Example 1-1, as shown in Table 1, the mixture was obtained by performing mixing process ST10 which mixes the raw material of the geopolymer shown below.

-Solidifying material: metakaolin ... 17.1g
・ Alkali stimulant: Sodium metasilicate nonahydrate 34g

  Next, as shown in Table 1, a geopolymer molded body was formed by executing a compression step ST20 for compressing and molding the above mixture.

  Specifically, 20 g of the mixed powder obtained as a mixture was put in a mold having a diameter of 30 mm. Then, compression molding was performed under compression molding conditions where the pressure was 20.0 MPa and the compression time was 10 minutes. When performing this compression molding, the mixture was heated from the outside using a heater so that the center temperature of the mixture would be 50 ° C. Thereafter, the mixture compressed from the mold was taken out as a geopolymer molded body.

(Example 1-2)
In Example 1-2, as shown in Table 1, in the compression step ST20, a geopolymer molded body was produced under the same conditions as in Example 1-1 except that the compression time was 30 min. It was.

(Example 1-3)
In Example 1-3, as shown in Table 1, in the compression step ST20, the geopolymer molded article was formed under the same conditions as in Example 1-1 except that the center temperature of the mixture was 85 ° C. Fabrication was performed.

(Example 2)
In Example 2, as shown in Table 1, in the mixing step ST10, unlike the case of Example 1-1, 10 g of iron powder was added as a heat generating material. In Example 2, the mixture was heated by the heat generated by the exothermic material without external heating in the compression step ST20. That is, heating from the inside was performed. Except for these points, in Example 2, a geopolymer molded body was produced under the same conditions as in Example 1-1.

(Comparative Example 1)
In Comparative Example 1, as shown in Table 1, when performing the compression step ST20, unlike the case of Example 1-1, the mixture was not heated. And after execution of compression process ST20, unlike the case of Example 1-1, curing process ST30 was performed. In the curing step ST30, a geopolymer molded body was produced by performing curing under the curing conditions shown in Table 1.

(Comparative Example 2)
In Example 2, as shown in Table 1, in the compression step ST20, a geopolymer molded body was produced under the same conditions as in Example 1-1 except that the center temperature of the mixture was 30 ° C. went.

[2] Test contents As shown in Table 1, the uniaxial compressive strength, the average solidified body height, and the average solidified body diameter were measured for the samples of each example produced as described above. At the same time, the presence or absence of a hydrate peak was confirmed for the samples of each example.

[2-1] Measuring method of uniaxial compressive strength The measurement of uniaxial compressive strength was performed as follows. First, a cylindrical specimen having a diameter of 3 cm was loaded into a testing machine. In the test machine, pressure was applied to the specimen, and the pressure value when the specimen was broken was measured. And the uniaxial compressive strength was computed by converting the measured pressure value per unit area.

[2-2] Method of measuring average solidified body height, average solidified body diameter, and density Measurement of average solidified body height, average solidified body diameter, and density was performed as follows. The average height of the solidified body and the average diameter of the solidified body were obtained as average values by measuring the height and diameter of the solidified body using two calipers at two or more points. Moreover, the density was calculated from the volume calculated from the measured value of the weigh scale, the average height, and the average diameter.

[2-3] Confirmation of presence or absence of hydrate peak The confirmation of the presence or absence of the hydrate peak was performed using the results of X-ray structural analysis. The X-ray structural analysis was performed by the X-ray diffraction method on the pulverized product obtained by pulverizing the sample of each example. The presence or absence of a hydrate peak is determined by whether or not there is a peak due to the hydrate in a portion where the incident angle (diffraction angle 2θ) of the incident beam is around 31 ° in the X-ray diffraction spectrum obtained for each example. Judged accordingly. Here, for reference, the X-ray structural analysis was also performed for each of the solidifying material, the alkali stimulating agent, and the mixture of the solidifying material and the alkali stimulating agent.

  FIG. 3 is a diagram showing the results of X-ray structural analysis of the sample of the example, each sample of the comparative example, the solidifying material, the alkali stimulating agent, and the mixture of the solidifying material and the alkali stimulating agent. In FIG. 3, (1) is an X-ray diffraction spectrum relating to metakaolin used as a solidifying material. (2) is an X-ray diffraction spectrum for sodium metasilicate nonahydrate used as an alkali stimulant. (3) is an X-ray diffraction spectrum for a mixture (before compression) of metakaolin and sodium metasilicate nonahydrate. (4) is an X-ray diffraction spectrum for the sample of Comparative Example 1. (5) is an X-ray diffraction spectrum for the sample of Comparative Example 2. (6) is an X-ray diffraction spectrum for the sample of Example 1-1. (7) is an X-ray diffraction spectrum for the sample of Example 1-3. In FIG. 3, the horizontal axis represents the diffraction angle 2θ, and the vertical axis represents the diffraction intensity normalized according to the maximum value. In addition, since the X-ray-diffraction spectrum regarding Example 1-2 and Example 2 is substantially the same as the case of Example 1-1, illustration is abbreviate | omitted.

[3] Test Results The test results of each example performed as described above will be sequentially described.

[3-1] About uniaxial compressive strength As shown in Table 1, the uniaxial compressive strength is higher in Example 1-1, Example 1-2, Example 1-3, and Example 2 than in Comparative Example. It is sufficiently larger than 1 and Comparative Example 2. That is, when the mixture is compressed in the compression step ST20, the mixture is heated so that water of crystallization is desorbed from the hydrate, and the reaction between the solidifying material and the alkali stimulant is advanced, thereby the curing step. Even if it does not perform, a geopolymer molded object with sufficiently large uniaxial compressive strength can be produced.

  As can be seen by comparing the results of each Example and the results of Comparative Example 2, when the mixture is compressed, the internal temperature of the mixture is set to 50 ° C. or higher so that the uniaxial compressive strength is sufficiently large. A molded body was produced. As can be seen by comparing the results of Example 1-1 and the results of Example 1-3, the uniaxial compressive strength of the geopolymer molded body can be increased by increasing the internal temperature of the mixture. Furthermore, the uniaxial compressive strength of a geopolymer molded object can be enlarged by lengthening compression time so that it may understand by comparing the result of Example 1-1 and the result of Example 1-2.

  In addition, as can be seen by comparing the results of Example 1-1 and the results of Example 2, the uniaxial compressive strength of the geopolymer molded body is also sufficient when the mixture is heated by the heat generated by the exothermic material. Can be large.

[3-2] Presence / absence of hydrate peak As shown in Table 1, the hydrate peak was present in the case of Comparative Example 2, but was not present in the other examples. From this result, in the case of Comparative Example 2, it can be seen that the reaction between the solidifying material and the alkaline stimulant does not sufficiently proceed because the hydrate which is the alkaline stimulant remains. On the other hand, in each of the other examples, since the hydrate which is an alkali stimulant does not remain, it can be seen that the reaction between the solidifying material and the alkali stimulant is sufficiently advanced. As a result, Example 1-1, Example 1-2, Example 1-3, and Example 2 were considered to have sufficiently higher uniaxial compressive strength than Comparative Example 1 and Comparative Example 2. It is done.

  Note that the present invention is not limited to the above-described embodiments as they are, and can be implemented in various forms other than the above-described examples in the implementation stage. The present invention can be variously omitted, added, replaced, and changed without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 10 ... Mixing part, 11 ... Container, 12 ... Stirrer, 20 ... Compression molding part, 21 ... Mold, 22 ... Pressurizer, 23 ... Heater.

Claims (6)

A mixing step of obtaining a mixture by mixing a solidifying material and an alkali stimulant;
A compression step of forming a geopolymer molding by compressing and molding the mixture,
The alkaline stimulant includes a hydrate,
When the mixture is compressed in the compression step, the mixture is heated so that water of crystallization is desorbed from the hydrate, and the reaction between the solidifying material and the alkali stimulant proceeds. ,
A method for producing a geopolymer molding. In the compression step, the mixture is heated using a heater.
The manufacturing method of the geopolymer molded object of Claim 1. In the mixing step, a pyrogen is added to the mixture,
In the compression step, the mixture is heated by the heat generated by the exothermic material.
The manufacturing method of the geopolymer molded object of Claim 1 or 2. The exothermic substance is a metal powder formed of a metal material selected from iron, zinc, aluminum, nickel, and sud,
The manufacturing method of the geopolymer molded object of Claim 3. The alkali stimulant has a melting point of 50 ° C. or higher and 100 ° C. or lower.
The manufacturing method of the geopolymer molded object in any one of Claim 1 to 4. A mixing section for obtaining a mixture by mixing the solidifying material and the alkali stimulant;
A compression molding part that forms a geopolymer molding by compressing and molding the mixture,
The alkaline stimulant includes a hydrate,
When the mixture is compressed in the compression molding section, the mixture is heated so that water of crystallization is desorbed from the hydrate, and the reaction between the solidifying material and the alkali stimulant proceeds. To
Geopolymer molding production system.

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