Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B33/00—Silicon; Compounds thereof
  • C01B33/20—Silicates
  • C01B33/24—Alkaline-earth metal silicates
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B7/00—Hydraulic cements
  • C04B7/36—Manufacture of hydraulic cements in general
  • C04B7/43—Heat treatment, e.g. precalcining, burning, melting; Cooling
  • C04B7/434—Preheating with addition of fuel, e.g. calcining
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B7/00—Hydraulic cements
  • C04B7/345—Hydraulic cements not provided for in one of the groups C04B7/02 - C04B7/34
  • C04B7/3453—Belite cements, e.g. self-disintegrating cements based on dicalciumsilicate
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P40/00—Technologies relating to the processing of minerals
  • Y02P40/10—Production of cement, e.g. improving or optimising the production methods; Cement grinding

Definitions

• the present invention relates to a production method for obtaining a calcined product containing ⁇ -2CaO.SiO 2 . More specifically, the present invention provides a production method that enables effective utilization of waste (including by-products generated in cement production, etc.) and obtains a fired product containing ⁇ - 2CaO.SiO2 at a level equivalent to that of conventional methods.
• coal ash Among the wastes, coal ash, municipal refuse incineration ash, granulated blast furnace slag, slow-cooled blast furnace slag, etc., especially coal ash, has a large Al 2 O 3 content compared to the composition of ordinary cement clinker. Therefore, when the amount of such wastes used is increased, the content of 3CaO.Al 2 O 3 corresponding to the interstitial phase among the cement clinker components increases, which affects the physical properties of the cement. Therefore, the amount of waste used in cement production is limited by the amount of Al 2 O 3 component, and there is a problem that a large amount cannot be used.
• Patent Document 3 aims to obtain a product of higher purity, industrial productivity, and stable quality, and attempts to limit the presence of impurities in the raw materials for production.
• waste it is not assumed to use waste as a raw material for producing ⁇ - 2CaO.SiO2 .
• ⁇ -2CaO ⁇ SiO 2 is obtained by slightly adjusting the contents of Al 2 O 3 and Fe 2 O 3 with industrial alumina and ferric oxide having a purity of 99% or more. are manufacturing.
• waste with a high Al 2 O 3 content As described above, it was generally unthinkable to actively use waste with a high Al 2 O 3 content as a raw material for producing ⁇ -2CaO SiO 2 , but the present invention et al. dared to use waste such as coal ash having a high Al 2 O 3 content as a raw material.
• An object of the present invention is to provide a production method that enables the use of waste materials and obtains a baked product containing ⁇ -2CaO ⁇ SiO 2 at the same level as conventional methods.
• the inventors of the present invention have made intensive studies to solve the above problems, and have used waste as part of the raw materials for producing ⁇ -2CaO SiO 2 in addition to the conventional CaO raw materials and SiO 2 raw materials. also found a method for obtaining a baked product containing ⁇ -2CaO ⁇ SiO 2 at the same level as the conventional method, and completed the present invention.
• a raw material mixture containing a CaO raw material, a SiO 2 raw material and a waste is prepared, and the content of Al 2 O 3 after heating at 1000 ° C. is 5.0 mass% or less, and the sintering temperature is 1350 ° C. to 1600 ° C.
• the waste is preferably at least one waste selected from coal ash, blast furnace slag, concrete sludge, waste concrete, incineration fly ash, and municipal refuse incineration ash.
• the raw material mixture is preferably a raw material mixture in which the total content of Al 2 O 3 and Fe 2 O 3 after heating at 1000° C. is 5.0% by mass or more, and Al 2 O 3 after heating at 1000° C. is preferably a raw material mixture containing more than 1.7% by mass.
• waste as part of the raw materials for producing ⁇ -2CaO SiO 2 in addition to conventional CaO raw materials and SiO 2 raw materials, and to the same extent as conventional can be obtained. Therefore, according to the present invention, waste can be used more effectively.
• the content of Al 2 O 3 is higher than that of cement clinker composition, and it is effective for the use of waste whose amount of use is limited in cement production.
• CaO raw material and the SiO2 raw material as the raw materials for producing ⁇ -2CaO SiO2 , known CaO raw materials and SiO2 raw materials as raw materials for producing cement clinker can be used without limitation.
• Specific examples include CaO raw materials such as limestone, quicklime, and slaked lime, and SiO2 raw materials such as silica stone and silica fume.
• limestone (calcium carbonate) used as a CaO raw material for ⁇ -2CaO SiO 2 production emits carbon dioxide during firing.
• the waste it is possible to reduce the amount of limestone used, which causes carbon dioxide emissions, and to suppress carbon dioxide emissions during the production of ⁇ -2CaO ⁇ SiO 2 .
• the waste in the present invention means waste and by-products used in cement production and the like.
• Usable wastes are not particularly limited, but specific examples include granulated blast furnace slag, blast furnace slag such as slow-cooled blast furnace slag, steelmaking slag, non-ferrous slag, coal ash, concrete sludge (including returned concrete and residual concrete).
• waste concrete, sewage sludge, purified water sludge, paper sludge, construction soil, foundry sand, soot and dust incineration fly ash, molten fly ash, chlorine bypass dust, wood chips, waste clay, waste tires, shells, municipal waste and other Incineration ash and the like can be mentioned (some of these also serve as thermal energy sources).
• the waste containing Al 2 O 3 whose usage amount is restricted by the amount of Al 2 O 3 in the production of cement clinker is preferable from the viewpoint of further promoting the effective utilization of the waste.
• Typical wastes containing Al 2 O 3 include blast furnace slag, steelmaking slag, non-ferrous slag, coal ash, concrete sludge, waste concrete, sewage sludge, purified water sludge, paper sludge, foundry sand, incineration fly ash, melting Examples include fly ash, municipal waste and its incineration ash.
• the Al 2 O 3 content is higher than that of ordinary cement clinker compositions, and the main components are CaO, SiO 2 , and Al 2 O 3 , coal ash, blast furnace slag, concrete sludge, waste concrete , incineration fly ash, and municipal waste incineration ash are preferred. A combination of these wastes may also be used.
• the content of Al 2 O 3 in the raw material mixture is preferably 4.8% by mass or less, and 4.5% by mass or less. is more preferred. Within this range, a sintered product having a ⁇ -2CaO SiO 2 content that is almost the same as that produced by conventional ⁇ -2CaO SiO 2 using only the CaO raw material and the SiO 2 raw material can be obtained. .
• the lower limit of the content of Al 2 O 3 in the raw material mixture after heating to 1000 ° C. is not particularly limited, but since the CaO raw material and SiO 2 raw material used also contain Al 2 O 3 , the CaO raw material and SiO 2 raw material
• the content of Al 2 O 3 derived from the raw material may be more than the content, for example, more than 1.7% by mass.
• the higher the content of Al 2 O 3 in the raw material mixture the greater the amount of waste containing Al 2 O 3 used for producing the fired product containing ⁇ -2CaO ⁇ SiO 2 , This is preferable from the viewpoint of promoting effective utilization of waste, which is the most important factor in the present invention.
• the total content of Al 2 O 3 and Fe 2 O 3 in the raw material mixture after heating to 1000° C. is not particularly limited. Specifically, in the production method of the present invention, if the content of Al 2 O 3 in the raw material mixture after heating at 1000° C. is 5.0% by mass or less, the total of Al 2 O 3 and Fe 2 O 3 is 5.0% by mass or more, the calcined product having a ⁇ -2CaO SiO 2 content that is almost equivalent to the case of producing ⁇ -2CaO SiO 2 using only the conventional CaO raw material and SiO 2 raw material is obtained. That is, the present invention differs from the technical idea of Patent Document 3, which requires that the total content of Al 2 O 3 and Fe 2 O 3 be less than 5.0% by mass.
• the total content of Al 2 O 3 and Fe 2 O 3 is preferably 8.0% by mass or less, more preferably 7.0% by mass or less.
• Al 2 O 3 and “Fe 2 O 3 ” in the raw material mixture after heating to 1000° C. can be measured by methods based on JIS R 5204 “Fluorescent X-ray Analysis of Cement”.
• the mixing ratio of CaO raw material, SiO 2 raw material and waste may be adjusted so that the CaO/SiO 2 molar ratio of the raw material mixture is 2.0, which is the stoichiometric ratio. If it is much less than 2.0, wollastonite and rankinite are by-produced, and if it is much more than 2.0, 3CaO ⁇ SiO 2 is by-produced.
• the CaO/SiO 2 molar ratio is preferably adjusted to 1.8-2.2, more preferably 1.9-2.1.
• a well-known method may be appropriately employed for preparing and mixing a raw material mixture for producing a fired product containing ⁇ -2CaO ⁇ SiO 2 .
• a raw material mixture for producing a fired product containing ⁇ -2CaO ⁇ SiO 2 .
• the particle size of the raw material mixture containing CaO raw material, SiO 2 raw material and waste is 90 ⁇ m because the smaller the particle size, the faster the firing reaction rate, but the worse the power unit generated when pulverizing each raw material and / or raw material mixture.
• the sieve residue may be adjusted to 10 to 30%, preferably 20 to 26%.
• the method of pulverizing each raw material and/or raw material mixture is not particularly limited, and may be pulverized by a known method.
• the firing temperature of the raw material mixture after preparation and mixing is 1350 to 1600 ° C., and from the viewpoint of the content of ⁇ -2CaO SiO 2 in the fired product, the firing temperature is more preferably 1400 to 1600 ° C., 1500 to 1500 ° C. 1600° C. is particularly preferred. If the firing temperature is less than 1350°C, the amount of free lime (f-CaO) tends to increase. Conversely, if the firing temperature exceeds 1600° C., the raw material melts and vitrifies, making the operation difficult and not preferable from the viewpoint of the amount of thermal energy used.
• the firing time depends on the firing temperature, but is generally 0.5 to 10 hours, preferably 1 to 5 hours.
• the firing method is not particularly limited, and rotary kilns, shaft kilns, electric furnaces, tunnel furnaces, fluidized bed incinerators, etc. can be used.
• a device capable of high-temperature heating such as a cement kiln typified by an SP kiln, can be suitably used. Also, from the viewpoint of mass production, it is preferable to use the cement manufacturing facility.
• the cooling operation is performed after firing, but the cooling conditions are not particularly limited. It can be cooled with a sprinkler).
• the content of ⁇ -2CaO SiO 2 contained in the fired product obtained by the production method of the present invention is preferably greater than the content of ⁇ -2CaO SiO 2 , and is 40% by mass or more of the entire fired product. is preferred, and more preferably 50% by mass or more.
• the fired product obtained by the production method of the present invention can be used, for example, as an admixture for cement.
• Concrete or mortar using cement containing this fired product has a densified surface layer portion and high durability due to carbonation curing during production. Furthermore, in the production of concrete and the like, since carbon dioxide is absorbed into concrete during carbonation curing, it is possible to reduce the amount of carbon dioxide emitted when obtaining concrete products.
• Example 1-3 Comparative Examples 1-3
• the CaO/SiO 2 molar ratio is 2.0, and Al 2 O 3 after heating at 1000 ° C.
• Raw material mixtures (90 ⁇ m sieve residue 20%) with different formulations with different total Fe 2 O 3 contents were prepared.
• Table 1 shows the ignition loss (ig.loss) and chemical composition of each raw material used
• Table 2 shows the mixing ratio of each raw material
• Table 3 shows the chemical composition of the raw material mixture after heating to 1000°C.
• the ignition loss (ig.loss) of each raw material was measured by weighing 3.0 g of the raw material in a crucible, heating it at 1000 ° C. for 1 hour in an electric furnace, and calculating the mass loss before and after the heating. I asked.
• the chemical composition of the raw material mixture was measured according to JIS R 5204 "Fluorescent X-ray analysis of cement", and 1.5 g of the raw material mixture after heating at 1000°C for 1 hour and lithium tetraborate (special grade)4. 0 g was mixed and melted at 1050° C. for 20 minutes, and the prepared glass beads were analyzed by a multi-element simultaneous fluorescent X-ray spectrometer (manufactured by Rigaku Corporation, Simultix15).
• the raw material mixture after these preparations and mixtures is fired in a high-speed heating electric furnace (manufactured by Motoyama Co., Ltd., SUPER-BURN NH-2025D-OP) at a firing temperature of 1350 to 1600 ° C. for 1 hour at a rate of 10 ° C./min. After slowly cooling to 1300° C., it was taken out from the electric furnace and cooled to room temperature to obtain a fired product.
• a high-speed heating electric furnace manufactured by Motoyama Co., Ltd., SUPER-BURN NH-2025D-OP
• the baked product was subjected to X-ray diffraction analysis, and the content of ⁇ -2CaO ⁇ SiO 2 was determined by Rietveld analysis.
• Table 4 shows the firing temperature and the amount of ⁇ -2CaO ⁇ SiO 2 determined by Rietveld analysis of the fired product obtained at each firing temperature.
• Table 5 shows the chemical composition of the fired product obtained by Rietveld analysis when fired at 1500°C.
• a reference example is a case where ⁇ -2CaO SiO 2 is fired using only conventional CaO raw materials and SiO 2 raw materials, and the content of Al 2 O 3 after heating at 1000 ° C. is 2.5% by mass. .
• the quality of the results of each example and comparative example was judged based on the results of this reference example.
• Examples 1 to 3 are according to the present invention, and the content of ⁇ -2CaO ⁇ SiO 2 in the sintered product is almost the same as that of the reference example in any sintering temperature range of 1350 to 1600°C.
• Example 1 coal ash (calcium oxide containing) used as waste becomes a calcium source, and the amount of limestone used, which causes carbon dioxide emissions, is reduced (see Tables 1 and 2). Emission of carbon dioxide is suppressed. Converting from the raw material composition, the amount of carbon dioxide emissions is reduced by 1.2% in Example 1, by 1.6% in Example 2, and by 2.4% in Example 3.
• Example 4-5 Comparative Examples 4-5
• Tests were conducted in the same manner as in Examples 1 to 3 and Comparative Examples 1 to 3, except that blast furnace slag (annealed blast furnace slag) was used instead of coal ash as waste.
• Table 6 shows the chemical composition of each raw material used
• Table 7 shows the mixing ratio of each raw material
• Table 8 shows the chemical composition of the raw material mixture after heating at 1000°C.
• Table 9 shows the chemical composition of the fired product when fired at 1500°C obtained by Rietveld analysis.
• Examples 4 and 5 relate to the present invention, and similarly to the case of using coal ash, the content of ⁇ -2CaO ⁇ SiO 2 in the fired product is high.
• Example 4 the blast furnace slag (calcium oxide containing) used as waste becomes a calcium source, and the amount of limestone used, which causes carbon dioxide emissions, is reduced (see Tables 6 and 7). Emission of carbon dioxide is suppressed. Converting from the raw material composition, the amount of carbon dioxide emissions is reduced by 8.4% in Example 4, and by 14.6% in Example 5.
• Example 6 Comparative Examples 6-7
• Tests were conducted in the same manner as in Examples 1 to 5 and Comparative Examples 1 to 5 above, replacing coal ash or blast furnace slag as waste with concrete sludge (raw concrete sludge).
• Table 10 shows the chemical composition of each raw material used
• Table 11 shows the mixing ratio of each raw material
• Table 12 shows the chemical composition of the raw material mixture after heating at 1000°C.
• Table 13 shows the chemical composition of the fired product when fired at 1400°C obtained by Rietveld analysis.
• Example 6 relates to the present invention, and similarly to the case of using coal ash or blast furnace slag, the content of ⁇ -2CaO ⁇ SiO 2 in the fired product is high.
• Example 6 the concrete sludge (calcium oxide containing) used as waste becomes a calcium source, and the amount of limestone used, which causes carbon dioxide emissions, is reduced (see Tables 10 and 11), so that carbon dioxide emissions are suppressed.
• the amount of carbon dioxide emissions is reduced by 17.8%.

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• 2022
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