JP2012236731A - Method for manufacturing fired material containing anorthite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a fired material containing anorthite (CaO-AlO-2SiO2) useful as a fine aggregate in manufacture of cement additives, mortars, concretes and the like from coal ash alone without using a separate Ca source.SOLUTION: A coal ash is used which contains, by mass as residues after ignition at 950°C, 34 to 63% of SiO, 22 to 42% of AlOand 10 to 35% of CaO in terms of oxide, especially preferably 40 to 55% of SiO, 27 to 37% of AlOand 15 to 23% of CaO, and is fired at 1,000 to 1,400°C for 0.5 to 10 hours.

Description

The present invention relates to a production method for obtaining a fired product containing 20 mass% or more of CaO.Al ₂ O ₃ .2SiO ₂ . Specifically, the present invention provides a production method for obtaining a fired product containing 20% by mass or more of anorthite (CaO.Al ₂ O ₃ .2SiO ₂ ) using only coal ash as a raw material.

  In connection with recent global environmental problems, effective utilization of waste, by-products, etc. has become an important issue. Taking advantage of the characteristics of the cement industry and cement production facilities, it is considered effective from the viewpoint of safe and mass disposal to effectively use or treat waste as raw material or fuel during cement production.

Among wastes, by-products, etc., coal ash, municipal waste incineration ash, blast furnace granulated slag, blast furnace slow-cooled slag, etc., especially coal ash, has a higher Al ₂ O ₃ content than ordinary cement clinker compositions. Therefore, when the amount of such wastes and by-products used is increased, the content of 3CaO.Al ₂ O ₃ corresponding to the interstitial phase of the cement clinker component is increased, which affects the cement physical properties. Therefore, there is a problem that the amount of waste, by-products, etc. used in cement production is restricted by the amount of Al ₂ O ₃ component and cannot be used in large quantities.

Under such circumstances, a calcined product containing CaO.Al ₂ O ₃ .2SiO ₂ (anorsite) is produced using the above coal ash as a main component and a Ca-containing raw material as a subcomponent, and the calcined product is used as a cement mixture or Techniques for making fine aggregates have been proposed (see Patent Documents 1 and 2).

Japanese Patent No. 4494743 Japanese Patent No. 4456832 JP 58-92490 A, page 4, table 2 Japanese Patent Laid-Open No. 62-13490, page 3, table 1 JP-A-8-1127, page 3, Table 1 Japanese Examined Patent Publication No. 62-19494, page 6, left column

The Chemical Society of Japan, “Coal and Petroleum”, Ninth Edition, Dainippon Library, August 15, 1965, p. 57

When the ratio of the constituent components of general coal ash is compared with anorthite, the ratio of Ca ₂ is low while the ratio of Al ₂ O ₃ and SiO ₂ is high (see Patent Documents 3 to 5). Therefore, normally, unless a Ca-containing raw material is mixed and calcined with coal ash, a calcined product mainly containing anorthite cannot be obtained, resulting in a calcined product mainly containing mullite.

  Limestone is often used as a Ca-containing raw material, but it has been required to use all of the raw material as a by-product / waste as a countermeasure against higher environmental problems.

  The present inventors have conducted intensive research to solve the above problems. And it pays attention that there is a thing with a comparatively high ratio of CaO in some coal ash (refer to patent documents 6 and nonpatent literature 1), and if it is such coal ash, Ca sources, such as limestone, will not be used separately. Both considered that a fired product containing anorthite could be obtained, and as a result of further investigation, the present invention was completed.

That is, in the present invention, the residue after ignition at 950 ° C. includes 34 to 63 mass% of SiO ₂ , 22 to 42 mass% of Al ₂ O ₃ and 10 to 35 mass% of CaO in terms of oxide. coal ash alone, firing at a temperature of 1000 to 1400 ° C., a manufacturing method of anorthite _{(CaO · Al 2 O 3 ·} 2SiO 2) a calcined product containing more than 20 wt%.

  According to the production method of the present invention, it is possible to obtain a fired product containing 20% by mass or more of anorsite useful as a cement mixed material or a fine aggregate using only waste as a raw material. Accordingly, a larger amount of waste can be treated as compared with the prior art, which is an advanced method for dealing with environmental problems.

In the production method of the present invention, the components after ignition at 950 ° C. include 34 to 63 mass% of SiO ₂ , 22 to 42 mass% of Al ₂ O ₃ and CaO in terms of oxides. Coal ash containing 10 to 35% by mass is used. If it is out of this range, anorthite will not be produced at all even if it is fired, or the amount produced will be so small that it will not have suitable physical properties as a cement mixture or fine aggregate.

  Here, the residue after ignition at 950 ° C. (hereinafter referred to as “ignition residue”) is a temperature of 1000 to 1400 ° C. by removing moisture, unburned carbon, etc. contained in coal ash. This is because it is more accurately reflected in the chemical composition when baked. That is, depending on the coal ash, there is a range from almost no moisture and unburned carbon to almost 30 wt%. Therefore, it is not possible to determine whether or not the composition is sufficient to produce anorthite unless the chemical composition excludes these.

To obtain a more anorthite high content fired product residue on ignition is a SiO ₂ 34 to 63 wt%, _Al 2 _{O 3} and 22 to 42 wt%, a 12 to 28% by weight of the coal ash of CaO it is preferable to use, the SiO ₂ 40 to 55 wt%, the _Al 2 _{O 3} 27 to 37 wt%, it is more preferable to use 15 to 23 wt% of coal ash to CaO.

Further, in order to reduce the glass phase and increase the amount of anorthite generated, the coal ash has an alkali content (Na ₂ O + K ₂ O) in the ignition residue of 2.0% by mass or less, It is preferable to use a material of 1.5% by mass or less.

Similarly, from the viewpoint of increasing the anorthite generation rate, as a metal element other than SiO ₂ , Al ₂ O ₃ and CaO, the total in the ignition residue is 15% by mass or less in terms of oxide. Is preferable, and it is more preferable that it is 10 mass% or less.

  Coal ash has a different chemical composition depending on the origin of the original coal. Therefore, whether or not the chemical composition of the ignition residue is within the above range is determined according to JI R5202 “Chemical analysis method of Portland cement” or JI R5204 “X-ray fluorescence analysis method of cement”. Measurement and confirmation may be performed by a compliant method. The ignition at 950 ° C. is performed according to “5. Method for quantifying loss on ignition” in JIS R5202.

  Moreover, the coal ash in the present invention does not need to use coal ash from a single emission source (for example, a thermal power plant) or a coal-producing area, and appropriately mixes coal ash from different emission sources or coal-producing areas, and falls within the above composition range. It is also possible to prepare and use it.

In the present invention, the coal ash firing temperature is 1000 ° C. or higher. When the firing temperature is lower than 1000 ° C., the formation of anorthite is insufficient. A more preferable firing temperature is 1150 ° C. or higher. On the other hand, when the firing temperature exceeds 1400 ° C., the raw material melts and vitrifies, so that it becomes difficult to crystallize anorthite. Accordingly, the maximum temperature during firing is 1400 ° C. or lower, preferably 1350 ° C. or lower.
Although the firing time depends on the firing temperature, it is generally 0.5 to 10 hours, preferably 1 to 5 hours.

  The firing method is not particularly limited as long as it is an apparatus capable of obtaining the above temperature, but from the viewpoint that an existing Portland cement production facility can be used, NSP kiln, high temperature heating such as cement kiln represented by SP kiln, etc. The apparatus which can be used can be used conveniently. Moreover, it is preferable to use the said cement manufacturing equipment also from a viewpoint of mass production or mass processing.

  The anorthite in the fired product may be contained in an amount of 20% by mass or more of the whole, but considering physical properties when used as a cement mixed material, it is preferably 50% by mass or more, and 70% by mass or more. Particularly preferred. On the other hand, due to the characteristics of using coal ash as the main raw material, it is difficult to make 100% anorthite, and it may be 90% by mass or less, and usually 80% by mass or less is sufficient.

The baked organisms containing anorthite produced by the production method of the present invention can be made into a hydraulic composition by pulverization with Portland clinker and gypsum, or pulverization individually and then mixing. As for the gypsum to be used, known gypsum as a raw material for producing cement such as dihydrate gypsum, hemihydrate gypsum, and anhydrous gypsum can be used without particular limitation. The amount of gypsum added is preferably such that the amount of SO ₃ in the hydraulic composition is 1.5 to 5.0% by mass, and more preferably 1.8 to 3% by mass. preferable. Known methods can be used for the baked product containing the anorthite, the Portland cement clinker, and the gypsum pulverization method without any particular limitation. Any known Portland cement clinker can be used without limitation in its production method and composition.

  Further, the hydraulic composition may further be appropriately mixed, mixed and pulverized with a blast furnace slag, a siliceous mixed material, fly ash, calcium carbonate, limestone and other mixed materials and a grinding aid. Further, chlorine bypass dust or the like may be mixed.

The fineness of the hydraulic composition is not particularly limited, but is preferably adjusted to 2800-4500 cm ² / g.

  Further, if necessary, blast furnace slag, fly ash or the like can be mixed after pulverization to obtain blast furnace slag cement, fly ash cement or the like.

  Of course, the fired product of the present invention may be used as a raw material for manufacturing cement or a cement-based solidified material other than JIS standards.

  Furthermore, the fired product obtained by the production method of the present invention can be used as a fine aggregate for producing mortar and concrete by pulverizing the particles to 2.5 mm or less by a sieving method.

  EXAMPLES Hereinafter, examples will be shown to specifically describe the present invention, but the present invention is not limited to only these examples.

  The coal ash used was discharged from a thermal power plant in Japan. The composition of the ignition residue of the coal ash is shown in Table 1. The chemical composition was determined by fluorescent X-ray analysis. The loss on ignition was 22 wt%.

  The coal ash was fired at 1200 ° C. for 0.5 hours to obtain a fired product. The obtained fired product was determined for the chemical composition by fluorescent X-ray analysis and the amount of anorthite contained by Rietveld analysis using an internal standard for powder X-ray diffraction. The results are shown in Table 2.

Claims (4)

The residue after ignition at 950 ° C. is coal ash containing 34 to 63% by mass of SiO ₂ , 22 to 42% by mass of Al ₂ O ₃ and 10 to 35% by mass of CaO in terms of oxides. the method of calcining containing 1000-1400 calcined at a temperature of ° C., anorthite _{(CaO · Al 2 O 3 ·} 2SiO 2) and 20 mass% or more.   A method for producing a hydraulic composition, comprising obtaining a fired product containing 20% by mass or more of anorthite by the production method according to claim 1, and mixing the pulverized product, Portland cement clinker and gypsum.   Furthermore, the manufacturing method of the hydraulic composition of Claim 2 which mixes at least 1 type of mixed material chosen from blast furnace slag, fly ash, a siliceous raw material, and limestone.   The manufacturing method of the fine aggregate which obtains the baked material which contains 20 mass% or more of anorthite with the manufacturing method of Claim 1, and grind | pulverizes this until it becomes a particle size of 2.5 mm or less (sieving method).