Cement manufacturing method

Abstract

To provide a cement manufacturing method which can reduce CO2 emissions while using large amounts of waste as well as flexibly dealing with the kinds and amounts of waste to be disposed of.SOLUTION: A cement manufacturing method includes steps of: reacting waste involving 5 mass% or over of CaO with CO2 while separating them to a material involving calcium carbonate and a material involving aluminosilicates; and mixing a part or all of at least one of these to use as a cement admixture. The material involving separated calcium carbonate or the material involving separated aluminosilicates may be used as the cement admixture, and moreover, blast furnace slag and / or fly ash may be used as the cement admixture.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a cement manufacturing method capable of reducing CO2 emissions while using a large amount of industrial by-products and waste.

Background Art

[0002] CO2 generated by burning fossil fuels such as coal and oil is a type of greenhouse gas and has a great impact on global warming. Therefore, reduction of CO2 emissions is required on a global scale. In cement factories, CO2 derived from limestone used as a raw material for cement production is also emitted, and reduction of these CO2 emissions is required.

[0003] On the other hand, although some of fly ash, steel slag, etc. are used as by-product admixtures, waste that cannot be used up is landfilled in large quantities. However, due to the difficulty of finding new sites for final disposal sites, the remaining capacity of final disposal sites is becoming tight. Therefore, cement factories are also accepting and treating various types of waste. In recent years, a large amount of Ca·Al·Si-based waste containing relatively large amounts of Ca, such as waste concrete and raw sludge, has been generated, and an expansion of its recycling applications is required. It has been proposed to reduce CO2 emissions by bringing Ca·Al·Si-based waste into contact with exhaust gas and also absorbing CO2 in the exhaust gas (for example, Patent Documents 1 to 3).

[0004] Therefore, for example, as shown in FIG. 7, cement clinker is fired in a cement firing apparatus using natural raw materials such as limestone, clay, and silica stone, and a recycled material (hereinafter referred to as "low Ca-R material") containing less than 5% by mass of CaO and containing Al2O3 and SiO2, such as fly ash and construction-generated soil, as raw materials (Comparative Example 1), or by grinding / mixing by-product admixtures such as fly ash and blast furnace slag together with cement clinker to produce blended cement (Reference Example). Furthermore, a blended cement having the same strength development property as ordinary Portland cement or Type B blast furnace cement, which is a general-purpose cement, has also been found by grinding / mixing blast furnace slag and limestone together with cement clinker (for example, Patent Documents 4 to 6).

[0005] Further, as shown in FIG. 8, cement clinker is fired in a cement firing apparatus using the natural raw material, the low Ca-R material, and a recycled material containing 5% by mass or more of CaO and containing Al2O3 and SiO2 (hereinafter referred to as "high Ca-R material") as raw materials (Comparative Example 2).

[0006] Furthermore, as shown in FIG. 9, cement clinker is fired in a cement firing apparatus using the natural raw material and the low Ca-R material as raw materials, and CO2 is absorbed by bubbling the exhaust gas from the cement firing apparatus into the slurry of the high Ca-R material. At the same time, Ca substances (materials containing calcium carbonate) are obtained by carbonation of the high Ca-R material (for example, Patent Document 7), and Si·Al substances (materials containing aluminosilicate) containing Al2O3 and SiO2, which are residues from which alkaline earth metals have been extracted, are supplied to the cement firing apparatus as clinker raw materials, and it is assumed that Ca substances (materials containing calcium carbonate) mainly composed of alkaline earth metals are sold externally (Comparative Example 3).

[0007] Also, as shown in FIG. 10, cement clinker is fired in a cement firing apparatus using the natural raw material and the low Ca-R material as raw materials, and the Ca substances obtained by carbonation and separation of the high Ca-R material are supplied to the cement firing apparatus as clinker raw materials, and it has also been proposed to sell the Si·Al substances externally (Comparative Example 4) (Patent Document 8).

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

[0009] However, in the use of high Ca-R materials as raw materials for cement clinker, there is a limit value of the CO2 reduction rate depending on the Ca amount and the treatment amount of the high Ca-R materials. In addition, with the use of high Ca-R materials, the treatable amount of other low Ca-R materials currently accepted decreases. Furthermore, in recent years, there is also a problem that the amount of fly ash and blast furnace slag, which are industrial by-products contributing to strength, is decreasing.

[0010] Therefore, the present invention has been made in view of the problems in the prior art, and an object thereof is to provide a cement manufacturing method capable of reducing the CO2 emission amount while using a large amount of waste (including industrial by-products) and flexibly corresponding to the types and amounts of the waste to be treated. [Means for Solving the Problems]

[0011] To achieve the above object, the cement manufacturing method according to the present invention reacts CaO with 20 mass% or more Contains 50 mass% or less and Al 2 O 3 , SiO 2 Recycled material containing and CO2, separates the product into a material containing calcium carbonate and a material containing aluminosilicate, and Recycled material uses the product as a cement admixture. According to the The method of separating the recycled material into a material containing calcium carbonate and a material containing aluminosilicate is carried out by bringing a gas containing CO 2 into contact with water, an aqueous solution obtained from the recycled material and a salt of a weak base and a strong acid, selling the separated material containing calcium carbonate on the external market, and the separated material containing aluminosilicate invention, by corresponding according to the amount for each type of . This , further reacts CaO with Recycled material mass% or more 20 mass% or more Contains 50 mass% or less and Al 2 O 3, SiO 2 Recycled material containing promote the utilization of Recycled material and increase the unit of use of

[0014] Furthermore, by using blast furnace slag and / or fly ash as cement admixtures, CO2 can be further reduced.

[0017] Pre Record Recycled material can be made into waste concrete powder and / or waste fresh sludge.

[0018] Furthermore, the blast furnace slag mixed in blast furnace cement type B 、 Before The above-mentioned a material containing luminosilicate material can be replaced. When the amount of blast furnace slag for blast furnace cement decreases , A Replacing it with a material containing luminosilicate can produce cement of the same strength and lead to a reduction in CO2 emissions.

Advantages of the Invention

[0020] As described above, according to the cement manufacturing method of the present invention, while using a large amount of waste, the CO2 emissions can be reduced, and it can flexibly respond according to the types and amounts of waste to be processed.

Brief Description of the Drawings

[0021]

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Mode for Carrying Out the Invention

[0022] Next, the cement manufacturing method according to the present invention will be described in detail.

[0023] The cement manufacturing method according to the present invention is characterized in that waste containing 5% by mass or more of CaO is reacted with CO2, and part or all of the obtained carbonates are used as a cement admixture. Here, the waste containing 5% by mass or more of CaO includes the above-mentioned high Ca-R materials, blast furnace slag, steelmaking slag, paper sludge, waste concrete powder, waste fresh sludge, municipal waste ash, fluidized bed biomass fly ash, fluidized bed coal fly ash, chlorine bypass dust, and the like.

[0024] The high Ca-R material is waste or the like containing 5% or more of CaO, and preferably contains 10% or more, more preferably 20% or more of CaO in order to absorb a large amount of CO2. Further, when the CaO derived from calcium carbonate in the CaO is less than half, a large amount of CO2 is absorbed in the carbonation step, so it is preferable because it contributes to CO2 reduction. On the other hand, for the high Ca-R material, it is preferable that CaO is 50% or less in order to effectively utilize the Al2O3·SiO2 component as a cement raw material.

[0025] Waste fresh sludge is taken out as fine powder containing cement hydrates and unhydrated cement by sieving the sludge generated in the concrete manufacturing process using a sieve with an appropriate mesh size in a fresh concrete factory or a concrete product factory. Waste fresh sludge is suitable as a waste containing 5% by mass or more of CaO because cement hydrates and unhydrated cement are easily carbonated in CO2 gas or slurry, and the CaO content is 30% or more, so the CO2 absorption amount is large. In addition, waste fresh sludge contains Ca(OH)2 and unhydrated cement, which are factors causing fluctuations in fluidity and setting, but when these are carbonated and disappear, the cement mixed with the carbonated product of waste fresh sludge has smaller fluctuations in fluidity and setting, making it easier to manage the quality of cement and concrete. Furthermore, when waste fresh sludge is carbonated in slurry, it absorbs sulfur components, making it easy to purify exhaust gas, and water-soluble Cr 6+ which is a harmful substance can be removed by washing with water, which is preferable.

[0026] Waste concrete fine powder is used by crushing concrete waste generated when disassembling concrete structures, recovering aggregates from the crushed material, and then taking out and using it as fine powder containing cement hydrates and unhydrated cement. Since other properties of waste concrete fine powder are the same as those of waste fresh sludge, waste concrete fine powder is easily carbonated, and since the CaO content is 15% or more, the CO2 absorption amount is large, making it suitable as a waste containing 5% by mass or more of CaO. Also, similar to waste fresh sludge, the cement mixed with the carbonated product of waste concrete fine powder has smaller fluctuations in fluidity and setting, making it easy to manage the quality of cement and concrete. Furthermore, when waste fresh sludge is carbonated in slurry, it absorbs sulfur components, making it easy to purify exhaust gas, and water-soluble Cr 6+ which is a harmful substance can be removed by washing with water, which is preferable.

[0027] Fluidized bed fly ash is the ash generated when burning biomass such as plants and animal manure, or coal, in a circulating fluidized bed type and pressurized fluidized bed type fluidized bed furnace for power generation or the like. Limestone is added for the purpose of desulfurization in the furnace, and the CaO content is 10% or more, and often about 20%. In fluidized bed fly ash, quicklime is generated without CaO being incorporated into the glass, and since the CO2 absorption amount is large, it is suitable as a waste containing 5 mass% or more of CaO. Further, fluidized bed fly ash contains quicklime and Ca(OH)2 generated by moisture absorption, which are factors causing fluctuations in fluidity and condensation. However, when the carbonates of fluidized bed fly ash are mixed in cement, the fluctuations in fluidity and condensation are reduced, and the quality control of cement and concrete becomes easier. Furthermore, when fluidized bed fly ash is carbonated in a slurry, it absorbs sulfur components, so it is easy to purify exhaust gas, and water-soluble selenium and Cr 6+ , which are harmful substances, and chlorine harmful to concrete can be removed by washing with water, which is suitable.

[0028] Among fluidized bed fly ashes, plant-based biomass fluidized bed fly ash has a high K2O content, and most of it is incorporated into the glass. In biomass power plants, co-firing of biomass and coal may be carried out. In the case of co-firing with coal, usually the ratio of biomass in the fuel is 70 mass% or more, and the K2O content is 2 to 10 mass%.

[0029] For the reaction between a waste containing 5 mass% or more of CaO and CO2, that is, the carbonation of this waste, existing methods can be used, such as injecting it into the exhaust gas of a cement firing device, or bubbling the exhaust gas into a slurry-like waste.

[0030] The grinding / mixing of the carbonates used as cement admixtures and cement clinker may be carried out by adding gypsum, or further, by simultaneously grinding and mixing by-product admixtures, or by separately grinding and mixing. These admixtures may be added at a ready-mixed concrete plant. In the case of separate grinding, higher strength can be obtained by increasing the grinding degree of the admixtures and by-product admixtures according to the present invention. Quicklime, slaked lime, limestone, and chlorine bypass dust may be added during the grinding / mixing.

[0031] The by-product admixture is an existing latent hydraulic substance or pozzolan, and examples thereof include blast furnace slag, fly ash, and silica fume. Among them, blast furnace slag is preferable because the strength reduction is small even when used simultaneously with carbonates.

[0032] It is preferable to use the carbonate that has absorbed CO2 as a cement admixture because the absorbed CO2 is reduced and immobilized. For carbonates containing calcium carbonate, if the content rate in the blended cement is 10% by mass or less, the strength of the produced concrete does not change. When mixed with blast furnace slag, if the content rate is 20% by mass or less, the strength of the produced concrete does not change. When using carbonates, it is a method that is easier and has less environmental impact than the method of using chemicals such as acids described later. Even if a part of the blast furnace slag of blast furnace slag cement type B, preferably half or less of the blast furnace slag, is replaced, the strength is equivalent, which is preferable.

[0033] Further, the cement manufacturing method according to the present invention is characterized in that while reacting the waste containing 5% by mass or more of CaO with CO2, it is separated into a Ca substance (a material containing calcium carbonate) mainly composed of an alkaline earth metal and a Si·Al substance (a material containing aluminosilicate) that is a residue from which the alkaline earth metal has been extracted, and either one or a part of both is used as a cement admixture.

[0034] The reaction of the waste with CO2 (carbonation) and the separation of the Ca substance and the Si·Al substance can be carried out by conventional methods such as bringing a gas containing CO2 into contact with an aqueous solution obtained from water, waste, and a salt of a weak base and a strong acid. The gas containing CO2 only needs to contain a carbon dioxide concentration, but the exhaust gas from a cement factory is easily available, and carbonates, Ca substances, and Si·Al substances can be used on-site, so it is suitable. Also, the exhaust gas from a fluidized bed furnace can obtain a fluidized bed fly ash, which is a waste containing 5% by mass or more of CaO as an exhaust gas containing CO2 on-site, and carbonates, Ca substances, and Si·Al substances can be delivered according to the application, so it is suitable.

[0035] Gels containing SiO2 and Al2O3, which are the main components of Si·Al substances, have pozzolanic hydraulicity similar to fly ash. When mixed with cement, they will have the same strength as when not mixed in the long term, and the durability will be improved.

[0036] Ca substances and Si·Al substances can also be used as substitutes for natural raw materials as cement clinker raw materials. Since their chemical components are separated, it is easy to adjust the chemical composition. The components lacking in the existing waste raw materials can also be supplemented by Si·Al substances and Ca substances. Also, Ca substances and Si·Al substances may be sold externally.

[0037] When the amount of low Ca-R material as a cement clinker raw material is small and insufficient, Si·Al substances are used as clinker raw materials. When the amount of low Ca-R material is large and sufficient, Si·Al substances are used as cement admixtures or sold externally, so that it is possible to flexibly respond according to the types and amounts of waste to be treated.

[0038] Next, examples of the cement manufacturing method according to the present invention will be described in detail with reference to the drawings.

[0039] As shown in FIG. 1, natural raw materials such as limestone, clay, and silica stone, and a recycled material (low Ca-R material) containing less than 5% by mass of CaO and containing Al2O3 and SiO2 are used as raw materials to bake cement clinker in a cement baking apparatus. Also, a recycled material (high Ca-R material) containing 5% by mass or more of CaO and containing Al2O3 and SiO2 is carbonated and separated using the exhaust gas from the cement baking apparatus to absorb CO2, and the Si·Al substance (material containing aluminosilicate) containing Al2O3 and SiO2, which is the residue from which the separated alkaline earth metal is extracted, is supplied to the cement baking apparatus as a clinker raw material. On the other hand, a Ca substance (material containing calcium carbonate) mainly composed of the separated alkaline earth metal is pulverized / mixed with the cement clinker as an admixture to produce a mixed cement. This is Example 1. In addition, by-products admixtures such as fly ash and slag may be further pulverized / mixed with the cement clinker (modification example).

[0040] The natural raw material is mainly limestone for the CaO component, but clay or the Al2O3·SiO2 component of silica stone may also be used. Further, the low Ca-R material is currently fly ash or the like used as the Al2O3·SiO2 component, but slag or the like containing the CaO component may also be used.

[0041] Next, Example 2 of the present invention and its modified examples will be described with reference to FIG. 2.

[0042] In this example, cement clinker is fired in a cement firing apparatus using a natural raw material and a low Ca-R material as raw materials. Further, the high Ca-R material is carbonated and separated using the exhaust gas from the cement firing apparatus to absorb CO2, and the separated Ca substance is pulverized / mixed with the cement clinker as a mixing material to produce a mixed cement. Furthermore, the Si·Al substance is sold externally as a filler or the like (Example 2). Incidentally, by-products such as fly ash and slag may be further pulverized / mixed with the cement clinker (modified example).

[0043] Next, Example 3 of the present invention will be described.

[0044] Although the illustration of this example is omitted, Example 3 is a combination of the configurations of Example 1 and Example 2, and by-products are pulverized / mixed with the cement clinker. That is, in this example, cement clinker is fired in a cement firing apparatus using a natural raw material and a low Ca-R material as raw materials. Further, the high Ca-R material is carbonated and separated using the exhaust gas from the cement firing apparatus to absorb CO2, and the separated Ca substance is replaced with an existing by-product and pulverized / mixed with the cement clinker as a mixing material to produce a mixed cement. Furthermore, the Si·Al substance is supplied to the cement firing apparatus as a clinker raw material and sold externally as a filler or the like. Also, by-products are pulverized / mixed with the cement clinker.

[0045] Next, Example 4 and Example 5 of the present invention will be described with reference to FIG. 3.

[0046] In Example 4, cement clinker is fired in a cement firing apparatus using natural raw materials and low Ca-R materials as raw materials. Further, the high Ca-R material is carbonated and separated using the exhaust gas from the cement firing apparatus, and the Ca substance obtained by separation is supplied as a clinker raw material to the cement firing apparatus. On the other hand, the Si·Al substance is pulverized / mixed together with the cement clinker as an admixture to produce a blended cement. Further, Example 5 includes a step of further pulverizing / mixing a by-product admixture together with the cement clinker.

[0047] Next, Examples 6 of the present invention and modifications thereof will be described with reference to FIG. 4.

[0048] In this example, cement clinker is fired in a cement firing apparatus using natural raw materials and low Ca-R materials as raw materials. Further, the high Ca-R material is carbonated and separated using the exhaust gas from the cement firing apparatus, and the Si·Al substance obtained by separation is pulverized / mixed together with the cement clinker as an admixture to produce a blended cement. Further, the Ca substance is sold externally as a filler or the like (Example 6). Incidentally, a by-product admixture may be further pulverized / mixed together with the cement clinker (modification).

[0049] Next, Example 7 of the present invention will be described with reference to FIG. 5.

[0050] In this example, cement clinker is fired in a cement firing apparatus using natural raw materials and low Ca-R materials as raw materials. Further, the high Ca-R material is carbonated and separated using the exhaust gas from the cement firing apparatus, and the Si·Al substance obtained by separation and substituted for the existing by-product admixture is pulverized / mixed together with the cement clinker as an admixture to produce a blended cement. Further, the Ca substance is supplied as a clinker raw material to the cement firing apparatus and sold externally as a filler or the like.

[0051] Next, Examples 8 to 10 of the present invention will be described with reference to FIG. 6.

[0052] In Example 8, cement clinker is fired in a cement firing apparatus using natural raw materials and a low-Ca-R material as raw materials. Further, exhaust gas from the cement firing apparatus is bubbled through a slurry of the high-Ca-R material to absorb CO2, and the carbonates obtained by carbonation of the high-Ca-R material are pulverized / mixed with the cement clinker as a mixing material to produce a blended cement. Furthermore, in Example 9, a by-product mixing material was pulverized / mixed with the cement clinker. In Example 10, the carbonates were replaced with blast furnace slag of blast furnace cement type B.

[0053] Furthermore, regarding Example 10, a specific case where herbaceous biomass fluidized bed fly ash is used as the high-Ca-R material will be described.

[0054] [Test Example 1] Fly ash was obtained from a biomass power generation facility A that conducts power generation using wood as fuel in a circulating fluidized bed furnace, and it was slurried and washed with water (reference example), and CO2 gas was introduced into the slurry to produce carbonates (test example). Specifically, 100 g of biomass ash and 400 g of tap water were put into a beaker, made into a slurry, and stirred with a stirrer at 400 rpm for 30 minutes. At this time, those with CO2 gas bubbling (test example) and those without (reference example) were prepared. The pH after stirring of those with bubbling was 9, and those without was 12. After stopping the stirring, filtration was performed using a Buchner funnel, and 400 g of tap water was further added to the cake on the obtained filter paper to wash the slurry, and then it was recovered. The recovered cake was naturally dried, its weight was measured, and various analyses were performed.

[0055] Table 1 shows the chemical compositions of the fly ash before and after treatment. The chemical compositions were measured by the FP method (fundamental parameter method) using the above-mentioned fluorescent X-ray analyzer. Since this ash is fluidized bed fly ash, it has a high CaO content. Also, it can be seen that the CO2 content in the test example is higher than that of the original ash, and CO2 has been absorbed by the carbonation treatment.

[0056]

Table 1

[0057] In addition, the existence form of calcium components in fly ash was analyzed by the XRD method (X-ray diffraction method). As a result, in the raw ash, the existence of each Ca compound such as CaO (quicklime), Ca(OH)2 (slaked lime), CaCO3 (limestone), and CaSO4 (gypsum) was confirmed as the form of calcium components. On the other hand, in the washed reference example, the existence of CaO (quicklime) disappeared, but a trace amount of Ca(OH)2 was present. In the test example with CO2 gas injection, both CaO and Ca(OH)2 disappeared. Therefore, it can be seen that when fluidized bed fly ash is carbonated, Ca(OH)2, which is a factor causing fluctuations in fluidity and coagulation, disappears and becomes CaCO3. The cement mixed with this has less abnormal fluctuations in fluidity and coagulation, making it easier to control the quality of cement and concrete.

[0058] Table 2 shows the chemical composition by quantitative wet analysis of herbaceous biomass fluidized bed fly ash and the elution amount according to JIS K 0058-1 "Test Method for Chemical Substances in Slags - Part 1: Elution Test Method 5. Test by Utilization Form". It can be seen that the K2O content of herbaceous biomass fluidized bed fly ash is high and is not removed even by washing or carbonation. The glass of incineration ash mixed with cement contributes to the strength development of the hardened body by the pozzolanic reaction. However, the herbaceous biomass fluidized bed fly ash in which most of the K2O is incorporated into the glass has higher reactivity of the glass, so it has higher strength development than fly ash without K2O. Therefore, the carbonates of herbaceous biomass fluidized bed fly ash containing glass contribute more to strength development than fine limestone powder or pulverized coal combustion-type coal ash. In addition, when the glass reacts and potassium, which is an alkali component, is released, the reaction of slag also progresses more due to the alkali promotion reaction, resulting in higher strength development.

[0059] Therefore, based on previous findings when at least calcium carbonate and blast furnace slag are mixed into cement, if cement is produced by mixing carbonates of biomass fluidized bed fly ash from plants and blast furnace slag instead of calcium carbonate, it is possible to produce cement having strength development equal to or higher than that of current blast furnace cement. Specifically, when the output of blast furnace slag has decreased, if at least half of the blast furnace slag contained in Blast Furnace Cement Type B specified in JIS R 5211 with an addition amount of blast furnace slag of about 40% is replaced with carbonates of biomass fluidized bed fly ash from plants as needed, cement with fluidity and strength equal to or higher than those of Blast Furnace Cement Type B can be obtained. As for the formulation, with cement clinker and carbonates as 100 parts by mass, the total of blast furnace slag and carbonates of biomass fluidized bed fly ash from plants is 30 to 60 parts by mass, and the carbonates of biomass fluidized bed fly ash from plants is 5 to 25% by mass, resulting in a blended cement.

[0060] Furthermore, although biomass fluidized bed fly ash from plants contains more chlorine, which is a cement-repellent component, than ordinary fly ash, it has been found that it can be removed at a high rate by carbonation and dehydration with slurry. Also, elution components of harmful selenium and chromium are removed by more than half by carbonation with slurry, indicating that it becomes safer and easier to use as a blending material.

[0061]

Table 2

[0062] The simulation results of Examples 1 to 10 and Comparative Examples 1 to 4 and the Reference Example described in the column of the Background Art are shown in Table 3. In this simulation, the CaO content of the high Ca-R material was set to 20% by mass. The CO2 reduction rate is the total of the CO2 absorption amounts by raw materials, fuel, and carbonation treatment. The total amount of recyclable materials is the total amount of low Ca-R material, high Ca-R material, and by-product blending materials.

[0063] The CaO content of Portland cement was set at 63%, and the remaining 37% mainly contained SiO2 and Al2O3. The CO2 emissions from limestone during the production of Portland cement were calculated to be 505 kg / t based on the above-mentioned CaO content. Regarding the CO2 emissions from thermal energy sources, it was set at 348 kg / t based on the summary of the LCI data of cement issued by the Cement Association of Japan (February 19, 2019). Also, it was assumed that 50% of the CO2 emissions from thermal energy sources accounted for the CO2 emissions used in the decarbonation reaction of limestone. The CO2 absorption amount by carbonation was assumed that all Ca in the high Ca-R material became CaCO3, and it was assumed to absorb 80% by mass with respect to the CaO content.

[0064]

Table 3

[0065] Also, the CO2 reduction rates and the total amount of recyclable materials used in the above-mentioned examples and comparative examples are shown in Fig. 11. From Fig. 11, in both the CO2 reduction rate and the total amount of recyclable materials used, almost all of the examples exceeded the comparative examples, and Examples 3, 5, and 7 exceeded the reference examples.

[0066] In addition, although the CaO content rate of the high Ca-R material was set at 20% by mass in the above simulation, as described above, those with a CaO content rate of 5% by mass or more can be treated as high Ca-R materials. As an example, in Example 4, when the CaO content rate of the high Ca-R material was 10%, the CO2 reduction rate was 30%, and the total amount of recyclable materials used was 570 kg / t. Also, in Example 4, when the CaO content rate of the high Ca-R material was 30%, the CO2 reduction rate was 29%, and the total amount of recyclable materials used was 592 kg / t. Therefore, even when the CaO content rate of the high Ca-R material is different, although the generation amount of each treated product changes, by appropriately selecting the manufacturing method, the CO2 reduction rate and the total amount of recyclable materials used hardly fluctuate.

Claims

1. A recycling material containing 20% by mass or more and 50% by mass or less of CaO and containing Al₂O₃ and SiO₂ and CO 2 react with each other, and separate the recycling material into a material containing calcium carbonate and a material containing aluminosilicate. The method for separating the recycling material into a material containing calcium carbonate and a material containing aluminosilicate is carried out by bringing a gas containing CO₂ into contact with an aqueous solution obtained from water, the recycling material, and a salt of a weak base and a strong acid. The separated material containing calcium carbonate is sold on the external market, and the separated material containing aluminosilicate is used as a cement admixture. A cement manufacturing method characterized by this.

2. The cement manufacturing method according to claim 1, wherein the recycling material is waste concrete fine powder or / and waste raw sludge.

3. The cement manufacturing method according to claim 1 or 2, further characterized in that blast furnace slag or / and fly ash is used as a cement admixture.

4. The cement manufacturing method according to claim 1 or 2, characterized in that the blast furnace slag mixed in the blast furnace cement type B is replaced with the material containing the aluminosilicate.

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