JP5701141B2 - Method for producing fired product containing CaO · Al 2 O 3 · 2SiO 2 - Google Patents

Description

The present invention relates to a production method for obtaining a fired product containing 20% by mass or more of CaO · Al ₂ O ₃ · 2SiO ₂ . Specifically, in obtaining the waste and by-products, baked containing especially the _{CaO · Al 2 O 3 · 2SiO} 2 20% by mass or more of coal ash as a main material, provide effectively available manufacturing methods existing equipment To do.

  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.

Among such, as a main component the above coal ash, to produce a calcined product containing (if there is to be hereinafter abbreviated as _{CAS 2) CaO · Al 2 O} 3 · 2SiO 2 raw material as subcomponent including Ca, cement Techniques for using mixed materials and fine aggregates have been proposed (see Patent Documents 1 and 2).

When the ratio of the constituent components of general coal ash is compared with CAS ₂ , the ratio of Al ₂ O ₃ and SiO ₂ is high, while the ratio of CaO is low. Therefore, usually, a fired product containing CAS ₂ cannot be obtained unless a Ca-containing raw material is mixed and fired with respect to coal ash. The mixing ratio of the Ca-containing raw material is generally a small amount of 90 to 5 parts by mass with respect to 100 parts by mass of coal ash, although it depends on the type of the Ca-containing raw material.

  Here, in the production of ordinary Portland cement, various raw materials are mixed so as to have a predetermined baked (clinker) composition, pulverized and mixed by a mill such as a ball mill, a vertical mill, etc. Firing (see Non-Patent Document 1).

Japanese Patent No. 4494743 Japanese Patent No. 4456832

Cement Association HP, “Until Cement is Made (Manufacturing Process)”, [online], Cement Association, Internet, <URL: http://www.jcassoc.or.jp/cement/1jpn/jd3.html>

Here, when the CAS ₂ is to be produced from the coal ash and Ca-containing raw material, coal ash, it is alone seen when a fine powder, there is no advantage Kyosu to dare grinding process. Rather, mixing with a Ca-containing raw material and pulverizing in the same manner as the above-mentioned Portland cement production method only requires extra energy during pulverization, which is rather problematic from the viewpoint of energy saving.

On the other hand, as calcium-containing raw materials, industrially produced calcium carbonate, slaked lime, etc. can be obtained as powders, but considering the cost, the use of natural minerals such as limestone takes into account the grinding cost. It is also advantageous. However, as described above, when a fired product containing CAS ₂ is produced from coal ash and a Ca-containing raw material, the amount of Ca-containing raw material used is relatively small. And ball mills) and firing equipment (rotary kiln, etc.) are used to manufacture the CAS ₂ , the balance between the grinding equipment and the firing equipment is lost, and the grinding capacity becomes excessive. There is a problem that a facility for storing a large amount of water is required. In addition, if a pulverizing facility with a small capacity is provided in order to avoid the occurrence of such a problem, the cost of the apparatus is newly generated.

  The present inventors have conducted intensive research to solve the above problems. And attention is paid to the fact that most of the pulverized and blended raw materials used to manufacture existing Portland cement clinker are occupied by CaO sources such as limestone and are industrially produced in large quantities by existing equipment. Thus, the present invention has been completed.

That is, the present invention is a production method for obtaining a fired product containing 20 mass% or more of CaO · Al ₂ O ₃ · 2SiO ₂ by mixing and firing coal ash and a Ca-containing raw material,
As this Ca-containing raw material, when this is baked alone, C ₃ S is 30 to 75% , C ₂ S is 5 to 50% , C ₃ A is ₃ to 15%, and C ₄ AF is 5 to 15%. Said production method characterized in that a powder having a chemical composition prepared to produce a Portland cement clinker is used.

According to the production method of the present invention, a fired product containing CAS ₂ that enables effective use of a large amount of waste, by-products, etc. can be produced using the existing Portland cement production equipment as it is. Very useful in terms of cost.

The production method of the present invention is to obtain a fired product containing 20% by mass or more of CAS ₂ by mixing and firing coal ash and a Ca-containing raw material.

The said coal ash can use well-known coal ash, ie, what is discharged | emitted from a thermal power plant etc., without being restrict | limited in particular. Common coal ash contains 35 to 76% by mass of SiO ₂ as a main component and 17 to 40% by mass of Al ₂ O ₃ , and other minor components include CaO, Fe ₂ O ₃ , MgO, TiO ₂ and Na. ₂ O, K ₂ O and the like are included. In order to produce a larger amount of CAS ₂ , it is preferable to contain 20% by mass or more of Al ₂ O ₃ . Coal ash is in the form of powder as the term indicates.

In the present invention, as a Ca-containing raw material, the chemical composition is prepared so as to produce a Portland cement clinker mainly composed of C ₃ S, C ₂ S, C ₃ A and C ₄ AF when fired alone. (Hereinafter, this unfired Portland cement clinker raw material powder is referred to as “clinker raw material powder”).

The chemical composition of the C ₃ S, C ₂ S, C ₃ A and C ₄ AF, and the raw materials that produce these minerals upon firing are well known to those skilled in the art, but will be described briefly below. .

C ₃ S is also called alite and is a mineral represented by 3CaO · SiO ₂ . C ₂ S, also called belite, is a mineral represented by 2CaO · SiO ₂ . C ₃ A is also called an aluminate, also called an aluminate phase represented by 3CaO · Al ₂ O ₃ , and is a component constituting a gap phase in the clinker together with C ₄ AF also called a ferrite phase.

In ordinary Portland cement typical as Portland cement, C ₃ S is 30 to 75%, C ₂ S is 5 to 50%, C ₃ A is ₃ to 15%, and C ₄ AF is about 5 to 15%. Thus, various raw materials are mixed and fired. Of course, the clinker raw material powder in the present invention is not limited to those prepared for the above ordinary Portland cement, but may be those prepared for early strong, moderately hot, low heat, sulfate resistant Portland cement.

  A known raw material can be used as the raw material of the clinker raw material powder. Specifically, mineral raw materials such as limestone, silica, clay, blast furnace slag, steelmaking slag, non-ferrous iron slag, sewage sludge, purified water sludge, papermaking sludge, construction generated soil, foundry sand, dust, incineration fly ash, molten By-products and waste materials such as fly ash, chlorine bypass dust, wood scrap, waste white clay, waste, tires, shells, municipal waste and incinerated ash. Moreover, what is necessary is just to perform the method of mixing and grind | pulverizing these raw materials by a well-known method as a manufacturing method of a Portland cement clinker (for example, refer nonpatent literature 1). For example, the fineness of the clinker raw material powder is desirably less than 50% of the 90 μm sieve residue.

When the clinker raw material powder is fired alone at 1350 to 1550 ° C., the above-mentioned Portland cement clinker is produced. However, in the present invention, the clinker raw material powder is mixed with the coal ash and fired. the al ₂ O ₃ · 2SiO ₂ and calcined product containing more than 20 wt%.

As described above, the clinker raw material powder is mainly composed of a CaO source such as limestone, and as other components, there are a lot of constituent components of CAS _{2 such} as SiO ₂ and Al ₂ O ₃ and a large amount industrially. In combination with the property of being a powder, it has extremely excellent advantages as a Ca-containing raw material.

  As a method for mixing the coal ash and the clinker raw material powder, a known technique such as a known mixer or other mixing method can be used without any particular limitation. The mixing ratio varies slightly depending on the chemical composition of the coal ash and the like, but usually the clinker raw material powder may be 90 to 5 parts by mass with respect to 100 parts by mass of the coal ash.

In order to stably obtain a fired product having a higher CAS ₂ content, the Ca amount in terms of CaO in a mixture of coal ash and clinker raw material powder (hereinafter also referred to as “mixed raw material”) is preferably 10 to 10%. Both raw materials are controlled and mixed so as to be in the range of 35% by mass, more preferably 12 to 28% by mass, and particularly preferably 15 to 23% by mass.

The calcination temperature for producing CAS ₂ from a mixed raw material, usually, 1000 to 1400 ° C., preferably from 1,150-1,350 ° C.. Although the firing time depends on the firing temperature, it is generally 0.5 to 10 hours, preferably 1 to 5 hours.

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

CAS ₂ 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 mixture, it is preferably 50% by mass or more, and 70% by mass or more. Particularly preferred. On the other hand, it is difficult to make 100% CAS _{2 due} to the characteristics of using coal ash as the main raw material, and it is usually sufficient if 80 to 90% by mass is CAS ₂ . The ratio of CAS ₂ can be increased by first firing the mixture in an appropriate temperature range and time as described above by bringing the chemical composition of the mixed raw material closer to the chemical composition of CAS ₂ .

The baked goods containing CAS ₂ produced by the production method of the present invention can be made into a hydraulic composition by pulverizing or individually pulverizing with Portland clinker and gypsum and then mixing them. About the gypsum used, well-known gypsum can be used without a restriction | limiting especially as cement manufacturing raw materials, such as a two-water gypsum, a half-water gypsum, and anhydrous gypsum. 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, more preferably 1.8 to 3% by mass. preferable. For the pulverized product of CAS ₂ , the Portland cement clinker and the gypsum, known techniques can be used without 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 chemical composition and mineral composition of the raw material and the fired product were determined by Rietveld analysis using the internal standard of powder X-ray diffraction by subjecting the raw material or fired product to fluorescent X-ray analysis.

  As the clinker raw material powder, various raw materials for general-purpose Portland cement clinker such as limestone, waste, etc. were prepared and pulverized to produce a cement clinker having the mineral composition shown in Table 1 when fired as it is. . The fineness was adjusted to less than 35% with 90 μm residue.

Example 1
Coal ash and clinker raw material powder were mixed so that the Ca content in the mixed raw material was 17.5% by mass in terms of CaO to obtain mixed raw material powder. Firing was performed in a small electric furnace at a maximum temperature of 1250 ° C. for 1 hour. Table 2 shows the chemical analysis results of the obtained fired product. The amount of CaO · Al ₂ O ₃ · 2SiO ₂ was 80% by mass.

Example 2
Using the existing raw material process for cement production, the above clinker raw material powder was prepared and stored in a silo. On the other hand, the coal ash was subjected to chemical analysis as needed and stored in another silo. The coal ash used was composed of about 61% SiO _{2 and} about 25.5% Al ₂ O ₃ as main components.

  From each silo, the amount of coal ash and Portland cement obtained by calculating from the CaO value contained in each raw material so that the Ca content in the mixed raw material is constant at 14 ± 0.5% by mass in terms of CaO. Tonklinker powder raw material was cut out and simultaneously put into a raw material storage silo for fired products. The silo was charged at 400 t / h as the total amount of coal ash and CaO-containing powder raw material. At this time, the raw material in the fired material storage silo was extracted from the bottom and re-input from the top while circulating at 300 t / h to prepare a raw material of about 3000 t.

This blended raw material was fed to the kiln at about 90 t / h. Sample collection was started when the fired product fired in the kiln began to come out of the cooler. The maximum temperature in the kiln was varied in the range of 1000 to 1300 ° C. in order to see the change in the manner of generation of CaO.Al ₂ O ₃ .2SiO ₂ . The calcined product was collected every 0.5 or 1 hour from the start of sampling and analyzed. Table 3 shows the CaO content of the obtained fired product and the results of the CaO · Al ₂ O ₃ · 2SiO ₂ content.

Example 3
The clinker raw material powder was fired to obtain a Portland cement clinker having the mineral composition shown in Table 1.

To this Portland clinker, the calcined product obtained in Example 1 was added so that it would be 0, 5 or 10% by mass (inner percentage), and further, 2 gypsum so as to be 2 ± 0.2% by mass in terms of SO _3. Was added and mixed and ground so that the specific surface area by the Blaine method would be 3200 ± 50 cm ² / g, and a cement was manufactured.

  Using these trial cements, the mortar compressive strength was measured by a method based on JIS R 5201. The results are shown in Table 4.

Claims (4)

Coal ash and a Ca-containing raw material are mixed and fired to obtain a fired product containing 20% by mass or more of CaO · Al ₂ O ₃ · 2SiO ₂ ,
As this Ca-containing raw material, when this is baked alone, C ₃ S is 30 to 75% , C ₂ S is 5 to 50% , C ₃ A is ₃ to 15%, and C ₄ AF is 5 to 15%. The method as described above, wherein a powder having a chemical composition prepared so as to produce a Portland cement clinker is used.
A calcined product containing 20 mass% or more of CaO · Al ₂ O ₃ · 2SiO ₂ by the production method according to claim 1, and mixing this with Portland cement clinker and gypsum. Manufacturing method.   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 a baked material with the manufacturing method of Claim 1, and grind | pulverizes this baked material until it becomes a particle size of 2.5 mm or less (sieving method).