JP4456832B2 - Method for producing crystallized aggregate from coal ash - Google Patents

Description

【表２】

【表３】

【表４】

【発明の効果】
以上の説明より理解されるように、本発明は、石炭灰の安全かつ多量処理を可能とする新規な結晶化骨材の製造方法及び結晶化骨材を提供するものである。石炭灰のみならず、多量の廃棄物、副産物の処理を可能とする本発明は、工業的見地のみならず、地球環境問題の観点からも極めて価値の高いものである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a novel crystallized aggregate. More specifically, the present invention provides a method for producing a crystallized aggregate that can be used easily and in large quantities as coal ash (including fly ash) discharged from a thermal power plant or a coal-fired boiler. .
[0002]
[Prior art]
From the viewpoint of global environmental problems, effective use of waste and by-products has become an important issue. The amount of coal ash emitted from thermal power plants and coal-fired boilers is also increasing year by year, and the development of safe and large-scale treatment methods is an urgent issue. The most effective treatment method as the current technology is the application to raw materials for cement production, and many coal ash has already been used.
[0003]
However, since coal ash has a higher content of Al ₂ O ₃ than cement clinker, its use amount is limited, and the upper limit of the use amount as a normal cement clinker raw material is 5 to 10% of the entire raw material. It remains to the extent. Therefore, the development of technology that can effectively use more coal ash is desired.
[0004]
Application as a raw material for artificial aggregates that can be used in large quantities as materials such as mortar and concrete is promising as a new effective utilization technology.
[0005]
In view of the above requirements, there has been proposed a method of obtaining an artificial aggregate mainly composed of wollastonite and anorthite by firing from coal ash, glass powder and cement as raw materials (see Patent Document 1).
[0006]
In addition, an artificial aggregate in which coal ash and glass powder are fired as raw materials and both are combined with anorthite generated in the firing process has also been proposed (Patent Document 2).
[0007]
[Problems to be solved by the invention]
However, although the artificial aggregate described in Patent Document 1 increases the strength of the aggregate by generating wollastonite and anorthite, the glass powder used as a raw material remains as a glass phase. Therefore, the density is lower than that of natural aggregate, the water absorption rate is relatively high, and the workability when pumping mortar, concrete, etc. is reduced, and the weight of piers, machine foundation concrete, etc. is required. There was a problem that the use to things was restricted. Moreover, since a glass phase remains, there exists a possibility that alkali-aggregate reaction may arise and we are anxious about the fall of durability of a structure.
[0008]
On the other hand, since the artificial aggregate described in Patent Document 2 has a short firing time when it is produced, crystallization is not sufficient, and the density is low compared to natural aggregate, and the water absorption rate is also high. ing. Therefore, like the artificial aggregate, there are problems of workability and applicability to structures. Moreover, since the glass phase is included as a production | generation phase, like the said artificial aggregate, there is a concern about the problem of the alkali aggregate reaction by the remaining glass phase.
[Patent Document 1]
Japanese Patent No. 3055899 [Patent Document 2]
Japanese Patent Laid-Open No. 2002-255613 [Means for Solving the Problems]
The present inventors have conducted intensive research to solve the above problems. As a result, by using coal ash as a main raw material and mixing an inorganic substance containing CaO, the crystallized aggregate has a CaO content of 10 to 35% by weight and an alkali content (Na ₂ O + K ₂ O) of 2.0. adjusted to a weight% or less, the composition after the adjustment and fired at 1000 to 1400 ° C., as a main component _{CaO · Al 2 O 3 · 2SiO} 2 ( hereinafter abbreviated as CAS ₂₎ by cooling high The present inventors have found a method for producing a crystallized aggregate having a density and low water absorption.
[0010]
Furthermore, by using at least one kind of inorganic waste selected from blast furnace slow cooling slag, blast furnace granulated slag, municipal waste incineration ash, and sewage sludge incineration ash as an inorganic substance containing CaO, In addition, we found that more waste and by-products can be used effectively.
[0011]
That is, the present invention mixes coal ash with an inorganic substance containing CaO, which is at least one selected from blast furnace slow-cooled slag, blast furnace granulated slag, municipal waste incineration ash, and sewage sludge incineration ash. The composition prepared by adjusting the CaO content to 10 to 35% by weight and the alkali content (Na ₂ O + K ₂ O) to 2.0% by weight or less is calcined at 1000 to 1400 ° C. This is a method for producing a crystallized aggregate mainly composed of Al ₂ O ₃ .2SiO ₂ .
[0012]
The crystallized aggregate obtained by the present invention is widely applicable as a constituent material for mortar, concrete, building materials, etc. due to its high density and low water absorption, and enables safe and large-scale treatment of coal ash. .
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail.
[0014]
In the present invention, coal ash can be used without particular limitation as long as it is discharged from a thermal power plant or a coal-fired boiler. The chemical components of coal ash are not particularly limited, but those having an Al ₂ O ₃ content of 10% by weight or more, particularly 14 to 36% by weight, are preferably used.
[0015]
In the present invention, the inorganic substance containing CaO can be used without any particular limitation. Specific examples include limestone, slaked lime, quicklime, blast furnace slow-cooled slag, blast furnace granulated slag, chlorine bypass dust, municipal waste incineration ash, concrete waste, sewage sludge, sewage sludge incineration ash, and the like. Among these, at least one selected from blast furnace slow-cooled slag, blast furnace granulated slag, municipal waste incineration ash, and sewage sludge incineration ash can be suitably used from the viewpoint of effective utilization of waste and by-products.
[0016]
In the present invention, the firing raw material is obtained by mixing coal ash and an inorganic substance containing CaO. The CaO content of the firing raw material needs to be adjusted to 10 to 35% by weight, more preferably 15 to 30% by weight. That is, in this range, generation of CAS ₂ becomes difficult, it is impossible to obtain a dense crystallized aggregate composed mainly of CAS _2.
[0017]
In addition, since the alkali content (Na ₂ O + K ₂ O) suppresses generation of a glass phase in the obtained crystallized aggregate, increases the density of the crystallized aggregate, and suppresses the water absorption rate. It is necessary to adjust to 0% by weight or less, particularly 1.5% by weight or less.
[0018]
In addition, you may mix the inorganic substance which does not contain CaO in the range which does not inhibit the effect of this invention at the time of mixing of a baking raw material.
[0019]
In the present invention, a method of firing a composition comprising a mixture of the coal ash and an inorganic substance containing CaO to produce a crystallized aggregate is preferably performed at 1000 to 1400 ° C., more preferably 1000 to 1300. A method of firing at 0 ° C. and natural cooling or slow cooling is employed. That is, when the firing temperature is lower than 1000 ° C., the production of CAS ₂ is insufficient, and when it is higher than 1400 ° C., the raw material melts and vitrifies, so that crystallization becomes difficult and high-density crystal The aggregate cannot be obtained and the object of the present invention cannot be achieved.
[0020]
The firing time is not particularly limited, but is preferably 1 hour or longer. If it is less than 1 hour, crystallization may not be performed sufficiently.
[0021]
Furthermore, the baking apparatus for performing the baking is not particularly limited, but an electric furnace, a rotary kiln type crystallization furnace, or the like is preferably used.
[0022]
The crystallized aggregate obtained by the method of the present invention contains CAS ₂ as a main component, and the content of CAS ₂ is 50 depending on the amount of CaO in the composition as a raw material, firing conditions, and the like. It is adjusted to be at least wt%, particularly at least 70 wt%.
[0023]
In the present invention, the crystallization aggregate as a main component the above CAS _2, depending on the raw materials used in the construction of the composition, CaO, _Al 2 _{O 3} and oxides such as SiO _2, CaO, Al ₂ A compound composed of two or more of O ₃ and SiO ₂ or a compound other than these may be contained, but there is no particular problem as long as the effect of the present invention is not impaired. These compounds are _{specifically, 2CaO · Al 2 O 3 ·} SiO 2, CaO · SiO 2, 3CaO · SiO 2, 2CaO · SiO 2, CaO · Al 2 O 3, 3CaO · Al 2 O 3, 3Al 2 _{O 3 · 2SiO 2, 2CaO ·} Fe 2 O 3, 3CaO · Fe 2 O 3, Na 2 O · Al 2 O 3 · 6SiO 2, K 2 O · Al 2 O 3 · 6SiO 2 and the like. _Further, it may also contain _{CaO, Al 2 O 3, SiO} 2, MgO, Fe 2 O 3, Na 2 O, the glass phase to component _{K 2} O or the like within the scope of the alkali content.
[0024]
The use of the crystallized aggregate of the present invention is not particularly limited. Typical applications include fine aggregates for mortar, fine aggregates for concrete and coarse aggregates, aggregates for interlocking blocks, aggregates for terrazzo tiles, and the like.
[0025]
【Example】
Hereinafter, although an example explains composition and an effect of the present invention, the present invention is not limited to these examples.
[0026]
Various tests in Examples and Comparative Examples were performed according to the following methods.
[0027]
(1) Aggregate test For crystallized fine aggregate, the density and water absorption rate were measured according to JIS A 1109 “Test method for fine aggregate density and water absorption rate”, and the coarse particle ratio was measured according to JIS A 1102 “Aggregate screening test. The test was conducted according to “Method”.
[0028]
(2) Compressive strength test of mortar using crystallized fine aggregate 70% by weight of standard sand for compressive strength test defined in JIS R 5201 “Cement physical test method” was replaced with crystallized aggregate. The compressive strength was measured according to the above test method. As the cement, ordinary Portland cement was used.
[0029]
Reference example 1
A composition having a composition shown in Table 1 in which coal ash and limestone were mixed at a blending ratio shown in Table 1 was fired at 1200 ° C. for 2 hours in an electric furnace, and then naturally cooled to obtain a crystal. The obtained crystal was crushed with a crusher to obtain a crystallized fine aggregate.
[0030]
The content of CAS _{2 in} the obtained crystallized aggregate is also shown in Table 1.
[0031]
Table 3 shows the results of the aggregate test, and Table 4 shows the results of the compressive strength test.
[0032]
Example 1
A composition having the composition shown in Table 1 in which coal ash and slowly cooled slag were mixed at the blending ratio shown in Table 1 was fired under the same conditions as in Reference Example 1 to obtain crystallized fine aggregate.
[0033]
The content of CAS _{2 in} the obtained crystallized aggregate is also shown in Table 1.
[0034]
Table 3 shows the results of the aggregate test, and Table 4 shows the results of the compressive strength test.
[0035]
Reference example 2
As a reference example, Table 2 shows the results of the aggregate test and Table 3 shows the results of the compressive strength test for the Genkai sea sand generally used as fine aggregate for concrete. Show.
[0036]
Comparative Example 1
A crystallized fine aggregate was prepared in the same manner as in Reference Example 1 except that the composition having the composition shown in Table 1 in which coal ash and limestone were mixed at the blending ratio shown in Table 1 was fired at 1300 ° C. for 2 hours in an electric furnace. Obtained.
[0037]
The content of CAS _{2 in} the obtained crystallized aggregate is also shown in Table 1.
[0038]
Table 3 shows the results of the aggregate test, and Table 4 shows the results of the compressive strength test.
[0039]
Comparative Example 2
In Reference Example 1, a crystallized aggregate was produced in the same manner except that the firing temperature was 900 ° C.
[0040]
The content of CAS _{2 in} the obtained crystallized aggregate is also shown in Table 1.
[0041]
Table 3 shows the results of the aggregate test, and Table 4 shows the results of the compressive strength test.
[0042]
Example 2 and Comparative Example 3
In Example 1 , a crystallized fine aggregate was obtained in the same manner as in Example 1 except that the composition having the composition shown in Table 1 in which coal ash and slowly cooled slag were mixed at the blending ratio shown in Table 1 was used. It was.
[0043]
The content of CAS _{2 in} the obtained crystallized aggregate is also shown in Table 1.
[0044]
Table 3 shows the results of the aggregate test, and Table 4 shows the results of the compressive strength test.
[0045]
Comparative Example 4
The composition of the composition shown in Table 2 in which coal ash, slow-cooled slag and glass powder are mixed at the blending ratio shown in Table 2 is the same as in Reference Example 1 except that the composition is baked at 1100 ° C. for 2 hours in an electric furnace. A fine aggregate was obtained.
[0046]
The content of CAS _{2 in} the obtained crystallized aggregate is also shown in Table 1.
[0047]
Table 3 shows the results of the aggregate test, and Table 4 shows the results of the compressive strength test.
[0048]
[Table 1]

[Table 2]

[Table 3]

[Table 4]

【The invention's effect】
As will be understood from the above description, the present invention provides a novel method for producing a crystallized aggregate and a crystallized aggregate that enable safe and large-scale treatment of coal ash. The present invention capable of processing not only coal ash but also a large amount of waste and by-products is extremely valuable not only from an industrial standpoint but also from the viewpoint of global environmental problems.

Claims (1)

Coal ash is mixed with an inorganic substance containing CaO, which is at least one selected from blast furnace slow-cooled slag, blast furnace granulated slag, municipal waste incineration ash, and sewage sludge incineration ash. CaO · Al ₂ O ₃ · 2SiO, characterized by calcining a composition adjusted to 35 wt% and alkali content (Na ₂ O + K ₂ O) to 2.0 wt% or less at 1000 to 1400 ° C. _A method for producing a crystallized aggregate containing ₂ as a main component.