JP2010029851A - Coal ash composition and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coal ash composition and a manufacturing method thereof capable of simply manufacturing at low cost and having sufficient adsorption ability in practical use. <P>SOLUTION: A coal ash composition is manufactured by heating a mixture of coal ash and water at the temperature of more than 150°C for more than 60 minutes. Alkaline aqueous solution also can be used instead of water. A mixing ratio of the mixture of coal ash 12 and water 14 is, for example, the coal ash 12 is 20 pts.wt. and the water 14 is 80 pts.wt. Also, for example, a high temperature pressurized oven (hereafter called as autoclave 16) is used for heating the mixture. It is preferable, for example, to use vapor which has been used for a power of vapor turbine 22 in a power plant as heat source for heating in the autoclave 16. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a coal ash composition having adsorptive capacity, and particularly to a technique that can be manufactured at low cost.

Zeolite and allophane are typical examples of environmental purification materials used for the purpose of water purification and the fixing or prevention of diffusion of harmful substances.
Zeolite is a naturally occurring mineral that has fine pores in the crystal and contains cations such as sodium in the fine pores, and thus has an adsorption ability, ion exchange ability, and a function as a catalyst. Allophane is composed of non-crystalline or low-crystalline clay components that appear in soils based on volcanic eruptions such as volcanic ash and pumice, and has a high specific surface area, so it has adsorption capacity and ion exchange. Have the ability.

  Since these zeolites and allophane contain silicon and aluminum as main constituent elements, techniques for artificially synthesizing zeolite and allophane from coal ash containing a large amount of these elements have been proposed (for example, Patent Document 1 or 2).

  Patent Document 1 discloses a method for producing zeolite by mixing coal ash and an alkaline substance, heating and melting the mixture, and then performing heat treatment.

  In addition, in Patent Document 2, the present inventors added an alkaline aqueous solution to an inorganic component containing silicic acid and aluminum, heated and dissolved, and then added an acidic solution that does not form a chelate compound with aluminum, and added a slightly acidic solution. After that, a method for producing allophane by heating is disclosed.

JP-A-6-34417 JP 2000-178021 A

  However, in the method for producing zeolite described in Patent Document 1, it is necessary to mix an alkaline substance and to set the heating and melting temperature to 1000 ° C. or more. In the method for producing allophane described in Patent Document 2, Since a large amount of both an aqueous solution and an acidic solution are used, energy costs and material costs increase.

  Moreover, in order to implement these manufacturing methods, the installation cost for introducing and maintaining equipment for heat and chemical resistance also occurs.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a coal ash composition that can be produced simply and at low cost, and has a practically sufficient adsorption capacity, and a method for producing the same.

In order to achieve the above object, the present invention provides a coal ash composition having adsorption capacity,
A mixture of coal ash and water is heated at a temperature of 150 ° C. or higher for 60 minutes or longer.

  According to the coal ash composition of the present invention, a silanol group is generated on the surface of the coal ash, so that it has a practically sufficient adsorption capacity.

  In addition, it is not necessary to heat the material to a high temperature (1000 ° C. or higher), and it can be produced without mixing an acid or an alkaline substance, which contributes to cost reduction of energy, material and equipment.

  In the present invention, alkaline water may be used as the water.

  According to the coal ash composition of the present invention, the hydration reaction between coal ash and water is promoted more than in a neutral environment, and more silanol groups having adsorption ability are generated, thereby improving adsorption ability. To do.

  In the present invention, fly ash may be used as the coal ash.

  In the present invention, the mixing ratio of the mixture may be 80 parts by weight of the water with respect to 20 parts by weight of the coal ash.

  Further, the present invention is a method for producing a coal ash composition having adsorption ability, characterized in that a mixture of coal ash and water or an alkaline solution is heated at a temperature of 150 ° C. or more for 60 minutes or more. To do.

  In the present invention, an autoclave may be used as a container for heating the mixture.

  In the present invention, the heat of steam after being used as power for the steam turbine may be used as a heat source for heating the mixture in the autoclave.

  According to the method for producing a coal ash composition according to the present invention, the thermal energy of steam after use of the steam turbine can be used effectively, and the energy cost can be reduced.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to manufacture simply and at low cost, the coal ash composition which has practically sufficient adsorption capacity, and its manufacturing method can be provided.

It is explanatory drawing which shows the manufacturing method of the coal ash composition which concerns on this embodiment. It is the table | surface which put together the preparation conditions of each sample of a coal ash composition, and the various test results with respect to the sample. It is the table | surface which put together the fluctuation | variation of the preset temperature and saturated vapor pressure of an autoclave in the case of sample preparation. The example of the X-ray diffraction pattern of the material which has adsorption ability is shown, The figure (a) is an X-ray diffraction pattern of coal ash (fly ash) and artificial zeolite, The figure (b) is an X-ray diffraction pattern of allophane. . It is a graph which shows the example of the weight change by the temperature of the sample by thermal analysis, the figure (a) is a graph of coal ash (fly ash), the figure (b) is sample No. 12 graphs. It is explanatory drawing which shows the measurement result of a cation exchange capacity. It is explanatory drawing which shows the adsorption test result of the cadmium ion by a coal ash composition, (a) is a table | surface which shows a test result, (b) is a graph which shows a test result.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings.
This embodiment is related with the technique which manufactures the coal ash composition which has adsorption capacity from coal ash, for example in a coal thermal power station.

Drawing 1 is an explanatory view showing the manufacturing method of coal ash composition 10 concerning this embodiment.
As shown in FIG. 1, the coal ash composition 10 according to this embodiment is manufactured by heating a mixture of coal ash 12 and water 14 at a temperature of 150 ° C. or more for 60 minutes or more.

Here, the fly ash which is the fine particle collect | recovered from the combustion exhaust gas of the pulverized coal boiler 20 of a coal thermal power plant can be used for the coal ash 12. FIG.
The mixing ratio of the mixture of coal ash 12 and water 14 is, for example, 20 parts by weight of coal ash 12 and 80 parts by weight of water 14.

For heating the mixture, for example, a high-temperature pressure cooker (hereinafter referred to as autoclave 16) is used.
Here, it is preferable to use, for example, steam used as power for the steam turbine 22 of the power plant as a heat source for heating the autoclave 16.

  In addition, the heating of the mixture increases the adsorption capacity of the generated coal ash composition 10 as the temperature is increased or the heating time is lengthened. When the heat source is used, it is practical to set the heating temperature to 300 ° C. and the heating time to about 300 minutes in consideration of the steam temperature.

  In addition, you may adjust the water 14 of a mixture to alkalinity so that sodium hydroxide etc. may be mixed and pH may become about 12-13.

  In order to set the production conditions of the coal ash composition, the present inventor changed the heating set temperature, the heating time, or the liquid mixed with the coal ash to distilled water or an alkaline aqueous solution, Samples were prepared, and various tests were performed on these samples to evaluate whether or not the coal ash composition had a practically sufficient adsorption capacity. The details will be described below.

  FIG. 2 is a table summarizing the preparation conditions of each sample of the coal ash composition and various test results for the sample.

  As shown in FIG. 2, the set temperature is 150 to 300 ° C., the reaction time is 0 to 300 min, or the pH of the mixture is changed to 7 (neutral) or 12 to 13 (alkaline) by using water or NaOH solution. Thus, a total of 24 samples of the coal ash composition were prepared, and the bulk capacity, X-ray diffraction pattern, methylene blue adsorption amount, or silanol group weight ratio by thermal analysis was measured for these samples. Moreover, the same test was implemented also about the coal ash itself and natural allophane which are raw materials as a reference sample.

  As a specific test procedure, first, 20 g of coal ash and 80 g of distilled water or sodium hydroxide solution were put into an autoclave and stirred by rotating the rotor inside. In this evaluation, coal ash was used, and the type II of fly ash quality standard (JIS A6201-1999) was used. The autoclave used here had a capacity of 120 ml and a maximum working pressure of 120 MPa.

  Then, the inside of the autoclave was heated to a predetermined set temperature while stirring as described above, and when the set temperature was reached, the internal pressure of the autoclave was recorded.

  FIG. 3 is a table summarizing fluctuations in the autoclave set temperature and saturated vapor pressure during sample preparation. As shown in FIG. 3, the internal saturated vapor pressure increases as the set temperature increases.

  Next, after heating at a predetermined set temperature for a predetermined time, the cover of the autoclave was removed and the air was cooled by a fan. When the temperature in the autoclave was cooled to 60 ° C. or lower, the slurry was taken out from the autoclave, transferred to a centrifuge tube, and solid-liquid centrifugation was performed with a centrifuge. Here, centrifugation with a centrifuge was performed at 3000 rpm for 5 minutes.

  Next, the supernatant liquid centrifuged in the centrifuge tube is removed to leave a solid content, and then about 30 ml of distilled water is added to the centrifuge tube and shaken to wash the solid content. Then, the centrifuge is centrifuged again. The supernatant liquid centrifuged in the centrifuge tube was removed to leave a solid content. When a sodium hydroxide solution was used, these washing and centrifugation were repeated 5 times.

  And it adjusted so that the mass might be set to 20g with respect to the solid content which remained in the centrifuge tube in this way, and the bulk capacity (ml) at that time was measured.

  In addition, after measuring the bulk capacity, the solid content in the centrifuge tube is collected in an evaporating dish and sufficiently dried at 110 ° C. Using the dried sample, silanol groups by X-ray diffraction pattern, methylene blue adsorption amount, and thermal analysis The weight percentage was measured.

  Hereinafter, each test result is considered.

<Measurement of bulk capacity>
In the measurement of the bulk capacity, the amount of silanol groups that is a factor of the adsorption capacity of the coal ash composition can be evaluated. This is because the volume increases from the raw coal ash by the generation of silanol groups on the surface of the coal ash composition.

Bulk capacity measurements were performed on all 24 samples and the coal ash itself.
As a result, the bulk capacity of the raw material coal ash (fly ash) was 19 ml.

  On the other hand, among samples (sample Nos. 1 to 12) prepared using distilled water, sample No. About 1-9, bulk capacity was 19 ml of the same quantity as coal ash (fly ash), and the change was not recognized. This is considered that when the set temperature is relatively low at 150 to 250 ° C., silanol groups were not generated so as to affect the bulk capacity.

  On the other hand, the sample temperature of 300 ° C. For samples 10-12, sample no. 10 (reaction time 0 min) and sample no. 11 (reaction time 60 min) was 20 ml. The bulk capacity increases as the reaction time is extended, as 12 is 21 ml. This is considered that the silanol group is increasing according to reaction time.

  Moreover, the sample (sample No. 13-24) produced using alkaline aqueous solution is the same preset temperature and the same reaction time as the sample (sample No. 1-12) produced using distilled water. In comparison, it can be seen that the bulk capacity is generally increased. This is presumably because the hydration reaction between coal ash and water was promoted by the alkaline environment, and more silanol groups were generated. In addition, for samples prepared using these alkaline aqueous solutions, a tendency that the bulk capacity increases as the set temperature rises, the reaction time extends, or the PH value increases is recognized. Will increase.

<Measurement of X-ray diffraction pattern>
In the measurement of the X-ray diffraction pattern, the crystal structure of the coal ash composition can be confirmed.
FIG. 4 shows an example of an X-ray diffraction pattern of a material having an adsorption capacity. FIG. 4A shows an X-ray diffraction pattern of coal ash (fly ash) and artificial zeolite, and FIG. 4B shows an X-ray of allophane. It is a diffraction pattern. In the figure, the horizontal axis represents the diffraction angle indicated by 2θ.

  In the X-ray diffraction pattern of coal ash (fly ash) in FIG. 4 (a), a diffraction peak indicating the presence of crystals of mullite (M) having a single chain structure appears, and in the X-ray diffraction pattern of artificial zeolite Shows a diffraction peak indicating the existence of crystals of philipite (P) peculiar to artificial zeolite.

  On the other hand, in the X-ray diffraction pattern of allophane in FIG. 4B, no sharp peak is observed at any diffraction angle. This indicates that allophane is amorphous amorphous.

  The measurement of the X-ray diffraction pattern in this evaluation was performed using Sample No. 1 to 17 and the raw material coal ash itself.

  As a result, sample no. In the X-ray diffraction patterns 1 to 17, a diffraction peak indicating the presence of crystals of mullite (M) having a single chain structure similar to the coal ash (fly ash) of FIG. There was no difference in crystal structure from the coal ash itself. This indicates that the crystal structure of the raw material coal ash is not affected by the mixing or heating of water or an aqueous alkaline solution. That is, sample no. Nos. 1 to 17 have crystal structures different from those of general environmental purification materials such as zeolite and allophane.

  Sample No. No measurement of X-ray diffraction pattern was performed for 18 to 24, but among the samples (Nos. 13 to 24) prepared using an alkaline aqueous solution, the set temperature was high and the reaction time was long. From the results of X-ray diffraction patterns for the samples (Nos. 13 to 17) in which the dynamic hydration reaction was promoted, the difference in crystal structure from the coal ash itself was not recognized. Since the reaction time is short, the sample No. It is presumed that the results of the X-ray diffraction patterns for 18 to 24 also show results in which the same crystal structure difference is not recognized.

<Measurement of methylene blue adsorption amount>
The amount of methylene blue adsorption was measured in accordance with Japanese Industrial Standard JIS K1474. In the measurement of the methylene blue adsorption amount, the degree of adsorption ability of the coal ash composition can be evaluated.
Measurement of the amount of methylene blue adsorbed was measured using sample no. It carried out about 12-14, coal ash, and natural allophane.
As a result, no adsorption capacity was shown for the raw coal ash (no adsorption).
In contrast, sample no. Adsorption amounts of 12 to 14 (0.89 to 1.04 g / kg) were inferior to those of natural allophane (0.92 g / kg).

  Sample No. The adsorption amount of 12-14 shows the tendency for the adsorption amount to increase, so that PH value becomes high. This is probably because the higher the alkalinity, the more the hydration reaction between coal ash and water is promoted, and the amount of silanol groups in the produced coal ash composition increases.

<Measurement of silanol group weight ratio by thermal analysis>
The measurement of the silanol group weight ratio by thermal analysis is based on the characteristic that the silanol group in the coal ash composition burns completely until it is heated to about 500 ° C. The weight of possible silanol groups can be grasped. Specifically, a thermogravimetric / differential thermal analysis method (TG-DTA) was adopted, and a 10 mm sample was heated from room temperature to 1000 ° C. at 20.0 ° C./min. From the recorded weight of the sample at each temperature at that time The weight reduction rate from room temperature to 500 ° C. was calculated.

The measurement of the weight ratio of silanol groups by thermal analysis was performed using Sample No. 2,3,5,6,8,9,11-14 and coal ash.
5 is a graph showing an example of a change in weight due to the temperature of the sample by thermal analysis. FIG. 5 (a) is a graph of coal ash (fly ash), and FIG. 12 graphs.

  As shown in FIG. 5 (a), coal ash (fly ash) hardly shows a decrease in weight from room temperature, whereas as shown in FIG. In FIG. 12, it can be seen that the weight gradually decreases with heating from room temperature. This is considered that the hydroxy group (OH) is desorbed from the silanol group produced in the coal ash and the weight is reduced. Sample No. 12, the weight decreased by -2.02%.

  Sample No. As shown in the results of 12 to 14 (see FIG. 2), the weight reduction rate tended to increase as the PH value increased. This is probably because the higher the alkalinity, the more the hydration reaction between coal ash and water is promoted, and the amount of silanol groups in the produced coal ash composition increases.

  In addition, such a decrease in weight is caused by the relatively low set temperature and the short reaction time. 2, 3, 5, 6, 8, 9, and 11 were also observed. This result indicates that silanol groups are reliably generated on the surface of the coal ash, although no significant increase can be confirmed by measuring the bulk capacity.

  Considering these results, it is possible to generate silanol groups on the surface by heating at least 150 ° C. for 60 minutes or more and hydrating coal ash in an environment with a pH of 7 or more. A coal ash composition having an adsorptive capacity can be produced.

<Measurement of cation adsorption capacity>
In addition to the above tests, the cation adsorption capacity of the coal ash composition prepared by the above procedure was also measured. As the measurement of the cation adsorption capacity, the measurement of cation exchange capacity (CEC) and the adsorption test of cadmium which is a kind of trace harmful substances were performed.

The cation exchange capacity was measured according to the following procedure. First, a CaCl ₂ aqueous solution was added to a predetermined amount of sample and stirred, and then left overnight. Washing with pure water was repeated 5 times using a centrifuge. The precipitate was repeatedly washed with an aqueous ethanol solution until Cl ⁻ was not detected with the aqueous silver nitrate solution in the supernatant. Next, the operation of adding an aqueous NH ₄ Cl solution and centrifuging to collect the supernatant was repeated 5 times. The concentration of Ca ²⁺ contained in the collected supernatant was measured with an atomic absorption photometer to obtain a cation exchange capacity. The unit of the cation exchange capacity is [cmol · kg ⁻¹ ].

FIG. 6 shows the cation exchange capacity of the coal ash and the cation exchange capacity of the coal ash composition. While the cation exchange capacity of coal ash was 7.1 [cmol · kg ⁻¹ ], the cation exchange capacity of the coal ash composition 10 was 81.6 [cmol · kg ⁻¹ ]. From this result, it is possible to understand the high cation adsorption capacity in the coal ash composition.

  FIG. 7 shows the results of the cadmium adsorption test. In the initial test, the cadmium concentration in the sample solution was measured. The concentration of cadmium was measured according to Japanese Industrial Standard JIS K0102 (2008) 55.4. In the adsorption test, (1) a step of adding a predetermined amount of the coal ash composition to the sample solution, (2) a step of shaking the sample solution to which the coal ash composition has been added for a predetermined time, (3) after shaking The sample solution was centrifuged to separate the solid and liquid, (4) the supernatant was filtered, and (5) the cadmium concentration in the supernatant was measured.

  In addition, 1 g of the coal ash composition was added to 1 L of the sample solution. Shaking was performed for 20 hours.

  Further, the initial test and the adsorption test described above were performed for each of the pH 7 and pH 10 sample solutions. And as a sample solution of pH 7, those prepared by adjusting the initial concentration of cadmium to 2.0 mg / L, 4.0 mg / L, 8.0 mg / L, 10.0 mg / L, 25.0 mg / L were prepared. . For the sample solution at pH 10, the initial concentration of cadmium was 2.0 mg / L, 4.0 mg / L, 8.0 mg / L, 10.0 mg / L, 25.0 mg / L, 50.0 mg / L, 100. What adjusted to 0 mg / L, 150.0 mg / L, and 200.0 mg / L was prepared.

  And the removal rate of cadmium was calculated | required about each sample solution from the cadmium density | concentration in an initial test, and the cadmium density | concentration in an adsorption test.

  In the case of pH 7, the removal rate with a sample solution with a concentration of 2.0 mg / L is 45%, the removal rate with a sample solution with a concentration of 4.0 mg / L is 12.5%, and the sample solution with a concentration of 6.0 mg / L. The removal rate of was 5.1%. The removal rate with a sample solution with a concentration of 8.0 mg / L is 10.0%, the removal rate with a sample solution with a concentration of 10.0 mg / L is 0.0%, and the sample solution with a concentration of 25.0 mg / L. The removal rate of was 2.0%.

  On the other hand, in the case of pH 10, the removal rate in the sample solution having a concentration of 2.0 mg / L is 84.6%, the removal rate in the sample solution having a concentration of 4.0 mg / L is 75.8%, and the concentration is 6.0 mg / L. The removal rate in the sample solution was 53.8%, and the removal rate in the sample solution with a concentration of 8.0 mg / L was 34.3%. The removal rate with a sample solution with a concentration of 10.0 mg / L was 30.3%, the removal rate with a sample solution with a concentration of 25.0 mg / L was 2.4%, and the sample solution with a concentration of 50.0 mg / L. Was 6.3%, and the removal rate of the sample solution with a concentration of 100.0 mg / L was 5.4%. The removal rate with the sample solution having a concentration of 150.0 mg / L was 4.7%, and the removal rate with the sample solution having a concentration of 200.0 mg / L was 1.5%.

  In both pH 7 and pH 10, the removal rate tended to decrease as the cadmium concentration in the sample solution increased. This is considered to be because the amount of adsorption of cadmium by the coal ash composition was saturated. That is, the amount of cadmium adsorbed by the coal ash composition is considered to be approximately the same. In the above test, only 1 g of the coal ash composition is added to 1 L of the sample solution. Considering that the addition amount is small, it can be said that the coal ash composition has a practically sufficient adsorption capacity for cadmium. In other words, it is considered that a sufficient removal rate can be obtained even with a high-concentration sample solution by increasing the amount of the coal ash composition added.

  Comparing the results of pH 7 and pH 10, the removal rate at pH 10 is sufficiently higher than the removal rate at pH 7. One possible reason for this is that the H of the silanol group is easily released by making the sample solution alkaline.

<About modification>
In said embodiment, the case where a coal ash composition was manufactured from coal ash was mentioned as an example, and was demonstrated. Here, both coal ash and glass are common in that network modification ions (alkali metal or alkaline earth metal) are contained in the network structure of SiO ₂ . For this reason, it replaces with coal ash, and a silanol group can be formed in the glass surface by heating a mixture, such as glass and water, at a temperature of 150 ° C. or more for 60 minutes or more (by subcritical water treatment). it is conceivable that. That is, it is thought that the glass composition which has adsorption ability can be produced | generated.

<Summary>
As described above, according to the coal ash composition of the present embodiment, the coal ash composition has an adsorbing ability, and a mixture of coal ash and water or an alkaline solution at a temperature of 150 ° C. or higher. By heating for 60 minutes or more, silanol groups are generated on the surface of coal ash, so that it has a practically sufficient adsorption capacity.

  In addition, according to the coal ash composition of the present embodiment, as described in Patent Document 1 or 2, the material is heated to a high temperature (1000 ° C. or higher), or a large amount of an acid or alkaline substance is used. This can contribute to the cost reduction of materials, energy and equipment.

  Moreover, the adsorption capacity of the manufactured coal ash composition can be improved by using alkaline aqueous solution with the manufacturing method of the coal ash composition of this embodiment.

  Moreover, according to the manufacturing method of the coal ash composition of this embodiment, by using the steam used as the power of the steam turbine as a heat source for heating the mixture of coal ash and water, The thermal energy of the steam can be used effectively, and the energy cost can be reduced.

  In addition, the coal ash composition manufactured as mentioned above can be used as, for example, an agricultural soil improvement material or a heavy metal elution suppression material for cement.

  Moreover, it can replace with coal ash and can produce | generate the glass composition which has adsorption capacity by using glass.

DESCRIPTION OF SYMBOLS 10 Coal ash composition 12 Coal ash 14 Water 16 Autoclave 20 Pulverized coal boiler 22 Steam turbine

Claims (8)

A coal ash composition having adsorption capacity,
A coal ash composition obtained by heating a mixture of coal ash and water at a temperature of 150 ° C. or more for 60 minutes or more.   The coal ash composition according to claim 1, wherein alkaline water is used as the water.   The coal ash composition according to claim 1 or 2, wherein fly ash is used as the coal ash.   The coal ash composition according to any one of claims 1 to 3, wherein a mixing ratio of the mixture is 80 parts by weight of the water with respect to 20 parts by weight of the coal ash. A method for producing a coal ash composition having adsorption capacity,
A method for producing a coal ash composition, comprising heating a mixture of coal ash and water or an alkaline solution at a temperature of 150 ° C. or more for 60 minutes or more.   6. The method for producing a coal ash composition according to claim 5, wherein an autoclave is used as a container for heating the mixture.   The method for producing a coal ash composition according to claim 6, wherein heat of steam after being used as power for a steam turbine is used for the autoclave as a heat source for heating the mixture. A glass composition having an adsorption capacity,
A glass composition obtained by heating a mixture of glass and water at a temperature of 150 ° C. or more for 60 minutes or more.

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