JP6523142B2 - Preformed ash granulated material and roadbed material or filling material using this granulated material - Google Patents

Description

  BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an as-built granulated material that can be effectively used from as-formed ash and to obtain a roadbed material or a filling material using this granulated material.

  Coal ash generated in large quantities from coal-fired thermal power plants is composed of fresh ashes that are not landfilled and existing ashes that have been reclaimed in a designated landfill (hereinafter referred to as “disposal”) over a long period of time. It can be divided. Among them, as for the new ash, it is conventionally used as a coal ash granulated product subjected to a predetermined treatment by a method as disclosed in, for example, Japanese Patent Laid-Open Publication No. 2008-143740, for landfill work, ground improvement work, etc. It's being used.

  On the other hand, almost all of the as-built ash is in a state of being not used as it is being reclaimed in a disposal site, except when a portion thereof is used as a backfill material for a public quay, for example. Under such circumstances, after the earthquake disaster that occurred in 2011, due to the shutdown of the nuclear power plant, the amount of power generation by coal thermal power is increasing. As a result, the amount of coal ash that is generated tends to increase in landfills, but in the future there is a risk that it will be difficult to expand and secure the disposal site. Therefore, it is necessary to extend the life of the landfill site (disposal site) by digging up and using the existing ash (mass of the ashes) from the disposal site.

JP, 2008-143740, A

  However, because the characteristics of the as-built ash change over time under the influence of water, pressure, etc. in the landfill, it has characteristics different from those of the ashes, so the conventional method of treating ashes is used as it is If this is the case, there is a risk that it can not be used effectively after meeting environmental standards such as suppression of elution of harmful substances. For example, the water content in the formed ash may increase to about 30 wt% due to water absorption in the ground, and the adjustment of the water content is more strongly required in the treatment of the formed ash. There is also a desire to treat the as-built ash with a portion of the ashes, eg, fly ash.

  An object of the present invention is to obtain an as-built granulated material that can be effectively used from ashes, and more specifically, the water content is relatively high (for example, up to about 30%), and effective utilization is difficult With regard to utilization of the as-built ash, it is an object of the present invention to provide as-made ashes granulated products containing as-made ash which can suppress elution of harmful substances and can be effectively used regardless of whether as-formed ash alone or together with new ash. I assume. In addition, with "formed ash granulated material" used in this specification, a granulating machine is used to granulate a mixture consisting of plural kinds of powdery materials, granular materials, crushed materials, etc. containing formed ash. It means the granular material obtained.

  The present invention relates to an existing ash crushed material obtained by crushing a lump of existing ash excavated from a landfill site, cement, and waste gypsum for adjusting the water content in the existing ash crushed material The present invention is characterized by a formed ash granulated product obtained by granulating a mixture containing the mixture.

  According to the present invention, the granulation treatment and the as-formed granulated material obtained by the same are controlled by adjusting the water content of the as-made ash which holds a large water content as compared with the fresh ash by the amount of cement / waste gypsum. The required viscosity / viscosity can be obtained. At the same time, it is possible to suppress the elution amount of harmful arsenic, cadmium, fluorine, hexavalent chromium or boron and the like in the formed ash granulated product mainly by the solidification function of cement.

  In the present invention, the mixture contains water in the range of 22-25 wt%.

  According to the present invention, the physical properties (eg, viscosity etc.) and chemical properties (eg, viscosity, etc.) of the as-formed granulated material are adjusted by adjusting the water content (percentage) in the ashes having a large water content to a proper ratio for granulation treatment. For example, it is possible to stabilize and equalize the elution amount etc.).

  In the present invention, the mixture may further comprise fly ash.

  According to the present invention, fly ash, which is a form of fresh ash generated from a coal-fired power plant, is granulated together with the formed ash to obtain the formed ash granulated product, thereby achieving its effective use (amount reduction). Can.

  In the present invention, the mixture may further contain ferrous sulfate or magnesium oxide or both as an insolubilizer.

  According to the present invention, hexavalent chromium contained in cement and fly ash can be insolubilized by ferrous sulfate or magnesium oxide, and the amount of elution can be suppressed. Furthermore, the elution of harmful substances such as selenium, arsenic and fluorine, which are increased by the addition of fly ash, can be suppressed.

  In the present invention, the waste gypsum added to the mixture can include gypsum ranging from 5 to 10 wt%.

According to the present invention, it is possible to reuse dihydrate gypsum (CaSO ₄ .2H ₂ O) which is generated in large amounts as waste gypsum and treated as an unnecessary substance.

  In the present invention, the cement can include blast furnace cement B in the range of 5 to 10 wt%. In addition, fly ash can be included in the mixture in the range of 5 to 10 wt%.

It is a figure which shows the process of manufacturing the ready-made ash granule which can be utilized from the lump of the ready-made ash of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram in the case of utilizing the pre-formed ash granulated material of this invention as a base material for asphalt paving. It is a schematic diagram in the case of utilizing the pre-formed ash granulated material of this invention as a filling material.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing the steps of producing an available ready-made ash granulate according to one embodiment of the present invention. In steps S2 to S6 excluding excavated lumps of the built-up ash in step S1 in the manufacturing process of FIG. It can carry out using the equipment of "Zero Emi plant" etc. owned by Co., Ltd.). In addition, since the as-built ash is held for a long period of at least several years to several decades, sometimes 100 years or more in the landfill, it is also called as aging ash.

  In step S1 of FIG. 1, a lump of formed ash is excavated from a disposal site which is a landfill site of formed ash. The as-built ash (mass of as-made ash) has characteristics different from those of the ashes due to the effects of water, pressurization, etc. in the landfill. For example, as a result of pozzolanic action due to water and pressure, as-built ash has less pozzolanic reaction than fresh ash, or the grain size distribution is coarse due to the granulating action in the ground, ie, a grain size having a large median diameter It has features such as having a distribution.

  In addition, the as-made ash has a large amount of water content compared to the fresh ash, and holds at least 20 wt% or more of water, and sometimes holds about 30 wt% of water content. Therefore, in the mixing step or granulation step described below, those treatments can be performed without adding water at all. In other words, when the water content is high, it is necessary to adjust the amounts of other additives in consideration of the absorption. The properties of these formed ashs vary depending on the properties of the landfilled coal ash (newly produced ash), the location environment of the landfill site, the elapsed time after the landfill (also called "aging time"), and the like. Therefore, when digging and processing, it is desirable to investigate / analyze the properties in advance.

  In step S2, the lump of the already formed ash obtained in step S1 is crushed. This crushing has a pre-treatment implication for improving the mixing state with the additive in the mixing of the next step and for performing the treatment in the granulation step properly. The crushing process of the pre-formed ash is carried out so as to at least have a granulizable size (such as a particle size range) in the granulator used.

  In step S3, various additives are mixed to form a mixture as described after crushing. The additive may include, for example, cement as a solidifier, waste gypsum as a caking additive, or an insolubilizer. In addition, it is possible to mix fly ash which is one of the fresh ash. The mixing ratio of fly ash can be, for example, 6 to 8 wt%. By mixing fly ash, it is possible to achieve effective use (reduction of the amount) of fly ash which is a form of fresh ash generated from a coal-fired power plant.

  For example, blast furnace cement type B is used as cement which is a solidifying material. The mixing ratio of cement can be varied in the range of several wt% to about 10 wt%, preferably 6 to 10 wt%. The cement is adjusted to the appropriate amount (for example, 22-25 wt%) by adjusting the moisture amount of the existing ash which holds a large amount of water (for example, about 30 wt%) compared to the fresh ash, like the waste gypsum Have the ability to By its function, it is possible to obtain the viscosity / viscosity required in the granulation process and the resulting pre-formed ash granules. At the same time, it is possible to suppress the elution amount of harmful arsenic, cadmium, fluorine, boron or the like in the formed ash granulated material by the solidification function of cement. As a result, it is possible to obtain a low elution amount (rate) conforming to the environmental standard described later.

The mixing ratio of waste gypsum as a caking additive is 10 wt% or less, preferably 6 to 9 wt%. The ratio can be adjusted according to the amount of water contained in the formed ash or according to the amount of cement and fly ash to be added. As waste gypsum, one or more selected from dihydrate gypsum (CaSO ₄ · 2H ₂ O), hemihydrate gypsum (CaSO ₄ · 0.5H ₂ O), and anhydrous gypsum (CaSO ₄ ) It can be selected and used timely. Among them, gypsum dihydrate (CaSO ₄ .2H ₂ O) is most preferable from the viewpoint of reuse of unwanted matter. Further, from the viewpoint of absorption of moisture, hemihydrate gypsum _(CaSO 4 · 0.5H ₂ O) is highly absorptive of water can also be used mainly.

  As the insolubilizer, ferrous sulfate or oxide for suppressing the elution of hexavalent chromium, selenium, lead, arsenic, fluorine or boron contained in cement or fly ash mainly mixed as a solidifying material Containing reducing agents such as magnesium. In each insolubilized material, the elution amount from the granulated ashes is shown by the environmental standard (“Ordinance on Soil Contamination Countermeasures Law Enforcement Regulations” (Dec. 26, 2002, Ministry of the Environment Ordinance No. 29)). It is added in a predetermined amount (proportion) so as to fall below the same. On the environmental basis, for example, the elution amount (content) of hexavalent chromium is 0.05 mg / L or less, the elution amount of arsenic is 0.01 mg / L or less, the elution amount of boron is 1.0 mg / L or less, or The elution amount of selenium is set to 0.01 mg / L or less.

  The predetermined amount (percentage) of the insolubilizing material is preferably 5 wt% or less, and more specifically, for example, 0.5 to 1.0 wt% and 2 to 5 wt% of ferrous sulfate and magnesium oxide in order. be able to. These proportions can be adjusted according to the amount (percentage) of cement and fly ash to be added. When each additive is added in the above ratio (range), it becomes possible to meet (fall below) the above environmental standard.

  In step S4, the mixture obtained in the mixing step S3 is granulated in a granulator to produce an already formed ashes granulate. The particle size of the pre-formed ash granules changes according to the rotation speed and rotation time (that is, granulation time) of the blades of the granulator, etc., and the proportion of granules with large particle size is increased by prolonging the rotation time. be able to. The particle size of the already-formed ash granule is appropriately set according to the use of the already-formed ash granule.

  In this granulation treatment, the addition of water, which is essential in the case of treatment of fresh ash, can be eliminated. This is because, as already mentioned, since the as-made ash contains water of at least 20 wt% or more, it is not necessary to add water again. On the other hand, as described above, it is necessary to adjust the viscosity by absorbing the water in the ashes from the added cement and waste gypsum, that is, adjusting the water content to, for example, 22-25 wt% It has the feature of. The mixing of step S3 may be performed simultaneously (as a part thereof) in this granulation step.

  In step S5, the formed ash granulated material is cured. Curing is important in improving the strength of the formed ash granules, and is also important in the sense of reducing the elution amount of hexavalent chromium, and further, arsenic and fluorine. In experiments conducted by the present inventors, it was found that various elution amounts can be reduced to or below the respective environmental standard values by securing a curing period of at least several days to several tens of days. The length of the curing period (days, hours) can be selected according to the application of the granulated material and the like.

  In step S6, the quality control of the generated ashes granulated matter is performed. Quality control inspects / confirms whether the existing ash granulated material meets the specification (particle size, particle size, clear of environmental standard etc.) suitable for the application. The already formed ashes and granules that have passed the inspection are mixed with, for example, a recycling crusher orchid (RC 40) at a predetermined ratio, and effectively used as a roadbed material or as an embankment material for filling of land or the like.

  FIG. 2: is a schematic diagram in the case of utilizing the preformed ash granulated material of this invention as a base material for asphalt pavement. Asphalt paving material means a road material 20 disposed under the surface layer / base layer 10 including asphalt in asphalt paving, and in particular means the material of the lower material of the road material. As shown in FIG. 2, the preformed ash granules are mixed so as to fill the space between the RCs 40 (22) as a road base material 20.

  FIG. 3: is a schematic diagram in the case of utilizing the preformed ash granulated material of this invention as a filling material. A filling material 40 containing formed ash granules is formed on the foundation layer 30. It goes without saying that other embankment materials (new ash, sand, soil, clay, etc.) can be added together with the granulated material to make the embankment material 40.

By changing the mixing ratio, a plurality of samples (formed ash granules) were actually produced and quality evaluation (analysis) was performed. The example is shown below. In the following, “water” is the total value of the water content in each component of the mixture, and does not indicate the amount (ratio) of water added.
(1) Example 1
(A) Mixing ratio (wt%):
・ Attached ash: 59.5
・ Cement: 6.9
・ Fly ash: 9.7
・ Moisture: 23.9
(B) Analysis result (mg / L):
Hexavalent chromium: 0.01
Selenium: 0.002
Arsenic: 0.001
・ Fluorine: 0.28
· Boron: 0.1

(2) Example 2
(A) Mixing ratio (wt%):
・ Attached ash: 62.3
・ Cement: 7.1
・ Dihydrate plaster: 8.1
・ Moisture: 22.5
(B) Analysis result (mg / L):
Hexavalent chromium: 0.04
Selenium: 0.01
Arsenic: 0.005
・ Fluorine: 0.14
・ Boron: 0.4

(3) Example 3
(A) Mixing ratio (wt%):
・ Formed ash: 58.5
・ Cement: 6.9
・ Fly ash: 9.6
・ Ferrous sulfate water salt: 0.7
・ Moisture: 24.3
(B) Analysis result (mg / L):
Hexavalent chromium: <0.01
Selenium: 0.002
Arsenic: 0.001
・ Fluorine: 0.4
-Boron: <0.1

(4) Example 4
(A) Mixing ratio (wt%):
・ Formed ash: 58.2
・ Cement: 6.9
・ Fly ash: 9.6
・ Ferrous sulfate water salt: 0.7
Magnesium oxide: 0.7
・ Moisture: 23.9
(B) Analysis result (mg / L):
Hexavalent chromium: 0.01
Selenium: 0.003
Arsenic: 0.001
・ Fluorine: 0.38
· Boron: 0.2

(5) Comparative Example Water was added to the sample (mixture) to prepare a sample (mixture) having a water content of 30 wt% or more, and the granulation treatment in step S4 was performed. In this case, the mixture was in the form of a dumpling in the granulator, and it was not possible to obtain suitable and relatively uniform sized granules. In addition, after the sample was allowed to dry and the water content became 20 wt% or less, the granulation process of step S4 was similarly performed. In this case, the mixture was relatively crispy and low in viscosity and powdery, and it was not possible to obtain granules of a suitable size. Therefore, it was not possible to obtain reusable ready-made ash granules at high or low water content. If the amount of water is large, it is possible to increase the amount of cement used as a solidifying material to absorb the water in step S2 or the amount of waste gypsum used as a caking agent, but the production cost is increased, which is preferable. Absent.

  Embodiments of the present invention have been described with reference to the drawings. However, the present invention is not limited to these embodiments. The present invention can be practiced in variously modified, modified or modified forms based on the knowledge of those skilled in the art without departing from the scope of the invention.

10 Asphalt-containing surface layer / base layer 20 Base material (lower base material)
22 RC40
24 Pre-formed ash granules 30 Underlayer 40 Embankment material containing pre-formed ash granules

Claims (7)

A mixture comprising an existing ash crushed material obtained by crushing a lump of existing ash excavated from a landfill site, cement, and waste gypsum for adjusting the water content in the existing ash crushed material Preformed ash granules obtained by granulation treatment ,
The above mixture comprises the cement in the range of 6 to 10 wt% and the waste gypsum in the range of 6 to 9 wt% .   The preformed ash granulate according to claim 1, wherein the mixture comprises water in the range of 22-25 wt%. The pre-formed ash granulate according to claim 1 or 2, wherein the mixture further comprises fly ash in the range of 6 to 8 wt% . The formed ash granule according to any one of claims 1 to 3, wherein the mixture further contains, as an insolubilizer, one or both of ferrous sulfate and magnesium oxide in the range of 5 wt% or less . The gypsum contains gypsum, prefabricated ash granules of any one of claims 1-4. The cement comprises a high furnace cement type B, preformed ash granules of any of claims 1-5. A roadbed material or embankment material containing the already formed ashes granulated material according to any one of claims 1 to 6 .

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