JP2021155271A - Manufacturing method of cement - Google Patents

Abstract

To provide a manufacturing method of cement which reduces CO2 discharge amount while using a large amount of waste and can flexibly deal according to a kind and an amount of the waste to be treated.SOLUTION: A method for manufacturing cement by reacting a waste containing 5 mass% or larger of CaO with CO2, and using a part or all of the resulting carbonate as a cement mixture. While the waste material containing 5 mass% or larger of CaO is reacted with CO2, followed by separating into a material containing calcium carbonate and a material containing aluminosilicate, and a part of at least any one or all can be used as the cement mixture. Furthermore, blast furnace slag or/and fly ash may be used as a cement mixture. Among the material containing calcium carbonate and the material containing aluminosilicate, the material that was not used as the cement mixture can be used as a cement clinker raw material.SELECTED DRAWING: Figure 1

Description

The present invention relates to a cement manufacturing method capable of reducing _{CO 2} emissions while using a large amount of industrial by-products and wastes.

_{CO 2} generated by burning fossil fuels such as coal and petroleum is a kind of greenhouse gas and has a great influence on global warming. Therefore, _{reduction of CO 2} emissions is required on a global scale. _{In cement factories, CO 2} derived from limestone used as a raw material for cement production is also emitted, and _{reduction of these CO 2} emissions is required.

On the other hand, some coal ash and steel slag are used as by-product mixture, but a large amount of waste that cannot be used is landfilled. However, the remaining capacity of the final disposal site is becoming tight due to the difficulty of newly locating the final disposal site. Therefore, the cement factory also accepts and treats various types of waste. Further, in recent years, a large amount of Ca / Al / Si-based waste containing a relatively large amount of Ca such as waste concrete and ready-mixed concrete has been generated, and expansion of its recycling use is required. _{It has been proposed to reduce CO 2} emissions by bringing Ca / Al / Si waste into contact with exhaust gas and _{absorbing CO 2 in} the exhaust gas (for example, Patent Documents 1 to 3).

Therefore, for example, as shown in FIG. 7, a recycled material containing less than 5% by mass of natural raw materials such as limestone, clay, and silica stone, and CaO such as coal ash and construction soil, and containing Al ₂ O ₃ and SiO _{2 (} (Hereinafter referred to as "low Ca-R material") is used as a raw material to fire a cement clinker with a cement calcination device (Comparative Example 1), or by-product mixed materials such as coal ash and blast furnace slag are crushed / mixed together with the cement clinker and mixed. Clay is being manufactured (reference example). Furthermore, mixed cement has been found in which blast furnace slag and limestone are crushed / mixed together with cement clinker and have the same strength development as ordinary Portland cement, which is a general-purpose cement, and blast furnace cement type B (for example, Patent Documents). 4-6).

Further, as shown in FIG. 8, the natural raw material, the low Ca-R material, _{and the recycled material containing 5% by mass or more of CaO and also containing Al 2} O ₃ and SiO ₂ (hereinafter referred to as "high Ca-R material"). ) Is used as a raw material to fire a calcium clinicer with a calcium firing device (Comparative Example 2).

Further, as shown in FIG. 9, the cement clinker is fired by the cement firing device using the natural raw material and the low Ca-R material as raw materials, and the exhaust gas from the cement firing device is bubbled on the slurry of the high Ca-R material. Then, _{while absorbing CO 2} , a Ca substance (material containing calcium carbonate) is obtained by carbonation of a high Ca-R material (for example, Patent Document 7), and Al, which is a residue obtained by extracting an alkaline earth metal. ₂ O ₃ , _{Si / Al containing SiO 2} (material containing aluminosilicate) is supplied to the cement firing equipment as a clinker raw material, and Ca (material containing calcium carbonate) containing alkaline earth metal as the main component is sold externally. It is assumed that this will be done (Comparative Example 3).

Further, as shown in FIG. 10, a cement clinker is fired with a cement firing device using the natural raw material and a low Ca-R material as raw materials, and the Ca product obtained by carbonation / separation of the high Ca-R material is used as a clinker. It has also been proposed to supply the Si / Al product to a cement firing device as a raw material and sell it to the outside (Comparative Example 4) (Patent Document 8).

Japanese Unexamined Patent Publication No. 2020-0156559 Japanese Unexamined Patent Publication No. 2000-197810 Japanese Unexamined Patent Publication No. 7-323299 Japanese Unexamined Patent Publication No. 2016-08768 Japanese Unexamined Patent Publication No. 2012-254909 Japanese Unexamined Patent Publication No. 2001-240445 Japanese Unexamined Patent Publication No. 2005-073310 Japanese Unexamined Patent Publication No. 2005-097072

However, when the high Ca-R material is used as a raw material for cement clinker, there is a limit value of the _{CO 2 reduction rate depending on the Ca amount and the processing amount of the high Ca-R material.} In addition, with the use of high Ca-R materials, the amount of other low Ca-R materials currently accepted can be reduced. Furthermore, in recent years, there is also a problem that the amount of waste of coal ash and blast furnace slag, which are industrial by-products that contribute to strength, is decreasing.

Therefore, the present invention has been made in view of the problems in the prior art, and is a waste to be treated _{while reducing CO 2 emissions while using a large amount of waste (including industrial by-products).} It is an object of the present invention to provide a cement manufacturing method that can flexibly respond to the type and amount of the above.

In order to achieve the above object, the cement manufacturing method according to the present invention _{reacts CO 2} with a waste containing 5% by mass or more of CaO, and uses a part or all of the obtained carbonic acid oxide as a cement mixture. It is characterized by that.

_{According to the present invention, CO 2} emissions can be reduced while utilizing waste containing 5% by mass or more of CaO.

_{Further, in the cement manufacturing method according to the present invention, while reacting CO 2} with a waste containing 5% by mass or more of CaO, the waste is separated into a material containing calcium carbonate and a material containing aluminosilicate, and at least eventually. It is characterized in that a part or all of one of them is used as a cement mixture. Either one or a part of the material containing calcium carbonate or the material containing aluminosilicate may be sold to the outside. According to the present invention, it is possible to further promote the utilization of waste containing 5% by mass or more of CaO and increase the basic unit of waste by responding to the amount of each type of waste.

In addition, the separated material containing calcium carbonate can be used as a cement mixture, and CO ₂ emissions can be further reduced.

Further, the material containing the separated aluminosilicate can be used as a cement mixture, and the utilization of waste can be further promoted.

Furthermore, by using blast furnace slag and / and fly ash as a cement mixture, CO ₂ can be further reduced.

Of the above-mentioned materials containing calcium carbonate and materials containing aluminosilicate, a material not used as a cement mixture can be used as a raw material for cement clinker, thereby responding according to the amount of each type of waste. This will lead to further utilization of waste and reduction of the amount of natural resources used.

The reaction between the waste and CO ₂ can be carried out using water, and the waste can be waste concrete fine powder and / and waste consludge, fluidized bed fly ash or vegetation-based biomass ash.

Further, the blast furnace slag mixed with the blast furnace cement type B can be replaced with one or more of the above-mentioned carbon oxide, a material containing calcium carbonate, and a material containing aluminosilicate. When the amount of blast furnace slag for blast furnace cement is reduced, cement of the same strength can be produced even if it is replaced with the material containing carbon oxide, calcium carbonate, or aluminosilicate, and CO ₂ can be reduced. Connect.

When the amount of waste containing less than 5% by mass of CaO as a cement clinker raw material is small, the material containing aluminosilicate is used as a clinker raw material, and the amount of waste containing less than 5% by mass of CaO as a cement clinker raw material is large. Occasionally, by using the material containing aluminosilicate as a cement mixture or selling it outside, it is possible to efficiently utilize waste and reduce the amount of natural resources used.

As described above, according to the cement manufacturing method according to the present invention, it is possible _{to reduce CO 2} emissions while using a large amount of waste, and to flexibly respond to the type and amount of waste to be treated. can.

It is a flow chart which shows Example 1 of the cement manufacturing method which concerns on this invention, and the modified example thereof. It is a flow chart which shows Example 2 of the cement manufacturing method which concerns on this invention, and the modified example thereof. It is a flow chart which shows Example 4 and Example 5 of the cement manufacturing method which concerns on this invention. It is a flow chart which shows Example 6 of the cement manufacturing method which concerns on this invention, and the modified example thereof. It is a flow chart which shows Example 7 of the cement manufacturing method which concerns on this invention. It is a flow chart which shows Example 8-10 of the cement manufacturing method which concerns on this invention. It is a flow chart which shows the comparative example 1 and the reference example of the cement manufacturing method which concerns on this invention. It is a flow chart which shows the comparative example 2 of the cement manufacturing method which concerns on this invention. It is a flow chart which shows the comparative example 3 of the cement manufacturing method which concerns on this invention. It is a flow chart which shows the comparative example 4 of the cement manufacturing method which concerns on this invention. _{It is a graph of the CO 2} reduction rate and the total amount of recycled material usable in an Example and a comparative example which concerns on this invention.

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

The cement manufacturing method according to the present invention is characterized in that a waste containing 5% by mass or more of CaO is _{reacted with CO 2} and a part or all of the obtained carbon oxide is used as a cement mixture. Here, the waste containing 5% by mass or more of CaO contains the high Ca-R material as described above, and includes blast furnace slag, steelmaking slag, paper sludge, waste concrete fine powder, waste cons sludge, city waste ash, and fluid bed. Type biomass fly ash, liquid bed type coal fly ash, chlorine bypass dust, etc.

The high Ca-R material is a waste 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 CO 2.} Further, it is preferable that CaO due to calcium carbonate is less than half of CaO because it absorbs a _{large amount of CO 2} in the carbonation step and contributes to _{CO 2 reduction.} On the other hand, the high Ca-R material preferably has a CaO content of 50% or less in order to effectively utilize the _{Al 2} O ₃ and SiO _{2 components as a cement raw material.}

Waste concrete is a fine powder containing cement hydrate and cement unhydrate by sieving sludge generated in the concrete manufacturing process in a ready-mixed concrete factory or concrete product factory using an appropriate open-opening sieve. Is taken out as. In waste concrete, cement hydrate and cement _{unhydrate are easily carbonated in CO 2} gas and slurry, and since the CaO content is 30% or more, the _{amount of CO 2} absorbed is large, and CaO Is suitable as a waste containing 5% by mass or more. In addition, waste concrete contains Ca (OH) ₂ and cement unhydrate, which cause fluctuations in fluidity and coagulation, but when these are carbonated and disappear, cement mixed with carbon oxide of waste concrete is mixed. Reduces fluctuations in fluidity and coagulation, and facilitates quality control of cement and concrete. Further, when the waste concrete is carbonated in the slurry, it is preferable because it absorbs sulfur content, so that the exhaust gas can be easily purified, and the water-soluble Cr ⁶⁺ , which is a harmful substance, can be removed by washing with water.

Waste concrete fine powder is used by crushing concrete waste generated when dismantling a concrete structure, recovering aggregate from the crushed material, and then taking it out as fine powder containing cement hydrate and cement unhydrate. do. Since the other properties of the waste concrete fine powder are the same as those of the waste concrete fine powder, the waste concrete fine powder is easy to carbonate, and since the CaO content is 15% or more, the _{amount of CO 2} absorbed is large, and the CaO is 5 It is suitable as a waste containing mass% or more. In addition, the cement mixed with the carbon oxide of the waste concrete fine powder like the waste concrete has less fluctuation in fluidity and coagulation, the quality control of the cement and concrete is easy, and the waste concrete is carbonated in the slurry. ^{In the case of concrete} , it is suitable because it absorbs sulfur content, so that it is easy to purify the exhaust gas, and water-soluble Cr 6+, which is a harmful substance, can be removed by washing with water.

The fluidized bed type flying ash is ash generated when biomass such as plants and livestock manure or coal is burned in a circulating fluidized bed type or a pressurized fluidized bed type fluidized bed furnace to generate power. Limestone is added for the purpose of desulfurization in the furnace, and the CaO content is 10% or more, and most of them are about 20%. The fluidized bed type fly ash is suitable as a waste containing 5% by mass or more of CaO because quicklime is generated without CaO being incorporated into the glass and the _{amount of CO 2 absorbed is large.} In addition, the fluidized bed fly ash contains quicklime and Ca (OH) ₂ generated by moisture absorption, which cause fluctuations in fluidity and coagulation. When these are carbonated and disappear, the carbon oxide of the fluidized bed fly ash Cement mixed with the above reduces fluctuations in fluidity and coagulation, and facilitates quality control of cement and concrete. Furthermore, when the liquid bed type fly ash is carbonated in the slurry, it absorbs sulfur so that the exhaust gas can be easily purified, and the harmful substances such as water-soluble selenium and Cr ⁶⁺ and chlorine harmful to concrete are washed with water. It can be removed and is suitable.

Vegetation based biomass fluidized bed fly ash Among fluidized bed fly ash has a high K 2 _O content of, most of which incorporated into the glass. The biomass power plant, there is a case where the mixed combustion of biomass and coal, if a co-combustion with coal, usually the ratio of the biomass in the fuel is not less than 70 mass%, K 2 _O content, 2 It becomes 10% by mass.

_{For the reaction of CO 2} with waste containing 5% by mass or more of CaO, that is, carbonation of this waste, an existing method can be used, and it can be put into the exhaust gas of a cement firing device or in the form of a slurry. There is a method of bubbling exhaust gas to waste.

The carbonic acid oxide used as the cement mixture and the cement clinker may be crushed / mixed by adding gypsum, the by-product mixture may be crushed at the same time and mixed, or the by-product mixture may be crushed and mixed separately. .. These mixed materials may be added at the ready-mixed concrete factory. In the case of separate pulverization, higher strength can be obtained by increasing the degree of pulverization of the mixed material and the by-product mixed material according to the present invention. Quick lime, slaked lime, limestone, and chlorine bypass dust may be added during the pulverization / mixing.

The by-product mixture is an existing latent hydraulic substance or pozzolan, and examples thereof include blast furnace slag, fly ash, and silica fume. Above all, blast furnace slag is preferable because its strength does not decrease even when it is used at the same time as carbon oxide.

It is preferable to use a carbon oxide that has absorbed CO ₂ as a cement mixture because the absorbed CO ₂ is reduced and immobilized. As for the carbonic acid containing calcium carbonate, the strength of the produced concrete does not change as long as the content in the mixed cement is 10% by mass or less. When mixed with blast furnace slag, the strength of the produced concrete does not change if the content is 20% by mass or less. When carbon oxide is used, it is a method that is easier and has less environmental load than the method using a chemical such as acid described later, and replaces a part of the blast furnace slag of blast furnace slag cement type B, preferably less than half of the blast furnace slag. However, it is preferable because the strength is the same.

Further, in the cement production method according to the present invention, a Ca product (material containing calcium carbonate) containing an alkaline earth metal as a main component and a Ca product (material containing calcium carbonate) containing an alkaline earth metal as a main component while reacting the _{waste containing 5% by mass or more of CaO with CO 2. Alkaline earth metal is separated into Si / Al substances (materials containing aluminosilicate) containing Al 2} O ₃ and SiO _2, which are the extracted residues, and either one or a part of both is used as a cement mixture. It is characterized by doing.

The reaction (carbonation) of the waste with CO ₂ and the separation of the Ca and Si / Al substances _{turn the gas containing CO 2} into an aqueous solution obtained from water, waste, and a salt of a weak base and a strong acid. It can be done by a conventional method such as contacting. The _{gas containing CO 2} may contain carbon dioxide concentration, but the exhaust gas of the cement factory is suitable because it is easily available and carbon oxides, Ca substances and Si / Al substances can be used on the spot. .. Further, the exhaust gas of the fluidized bed furnaces, the fly fluidized bed fly ash is a waste containing exhaust gas and CaO containing CО ₂ 5 wt% or more was obtained with a carbonate or Ca compound and Si · Al compound It is suitable because it can be delivered according to the application.

_{Gels containing SiO 2} and Al ₂ O _3, which are the main components of Si and Al, have pozzolan hydraulic hardness similar to fly ash, and when mixed with cement, they have the same strength as when not mixed in the long term. , Durability is improved.

The Ca product and the Si / Al product can also be used as substitutes for natural raw materials as cement clinker raw materials, and since the chemical components of these are separated, it is easy to formulate the chemical composition. It is also possible to supplement the components lacking in the conventional waste raw materials with Si / Al products and Ca products. In addition, Ca products and Si / Al products may be sold outside.

When the amount of low Ca-R material as a cement clinker raw material is small and insufficient, Si / Al material is used as a clinker raw material, and when the amount of low Ca-R material is large and insufficient, Si / Al material is used. By using it as a cement mixture or selling it externally, it is possible to flexibly respond to the type and amount of waste to be treated.

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

As shown in FIG. 1, a cement firing apparatus using natural raw materials such as limestone, clay, and silica stone, and recycled materials (low Ca-R materials) _{containing less than 5% by mass of CaO and Al 2} O ₃ and SiO _{2 as raw materials.} Bake the cement clinker in. In addition, a recycled material (high Ca-R material) containing 5% by mass or more of CaO and containing Al ₂ O ₃ and SiO ₂ is carbonized and separated by using the exhaust gas from the cement firing apparatus to absorb _{CO 2. , Si / Al material (material containing aluminosilicate) containing Al 2} O ₃ and SiO ₂ which is the residue extracted from the separated alkaline earth metal is supplied to the cement firing apparatus as a clinker raw material. On the other hand, a separated Ca substance (material containing calcium carbonate) containing an alkaline earth metal as a main component is crushed / mixed with a cement clinker as a mixing material to produce a mixed cement. This is Example 1. Further, a by-product mixture such as coal ash and slag may be crushed / mixed together with cement clinker (modification example).

The natural raw material is mainly limestone for the CaO component, but the Al ₂ O ₃ · SiO ₂ component of clay or silica stone may be used. The low Ca-R material is _{coal ash or the like currently used as the Al 2} O ₃ / SiO ₂ component, but slag or the like containing the Ca O component may be used.

Next, Example 2 of the present invention and a modified example thereof will be described with reference to FIG.

In this embodiment, the cement clinker is fired by a cement firing device using a natural raw material and a low Ca-R material as raw materials. In addition, the high Ca-R material is carbonated and separated using the exhaust gas from the cement firing device to _{absorb CO 2} , and the separated Ca material is crushed / mixed with the cement clinker as a mixed material to form a mixed cement. To manufacture. Further, the Si / Al product is sold outside as a filler or the like (Example 2). Further, a by-product mixture such as coal ash and slag may be crushed / mixed together with cement clinker (modification example).

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

Although not shown in this example, Example 3 combines the configurations of Example 1 and Example 2 and pulverizes / mixes the by-product mixture together with cement clinker. That is, in this embodiment, the cement clinker is fired by a cement firing device using a natural raw material and a low Ca-R material as raw materials. In addition, the high Ca-R material is carbonized and separated using the exhaust gas from the cement firing device to _{absorb CO 2} , and the separated Ca material is replaced with the existing by-product mixture material as the cement clinker. Grind / mix with to produce mixed cement. Further, Si / Al products are supplied to cement firing equipment as clinker raw materials and sold externally as fillers and the like. Also, the by-product mixture is crushed / mixed with cement clinker.

Next, Examples 4 and 5 of the present invention will be described with reference to FIG.

In Example 4, a cement clinker is fired by a cement firing device 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, and the Ca product obtained by the separation is supplied to the cement firing apparatus as a clinker raw material. On the other hand, a mixed cement is produced by crushing / mixing a Si / Al product together with a cement clinker as a mixed material. Further, in the fifth embodiment, the step further includes a step of pulverizing / mixing the by-product mixture together with the cement clinker.

Next, Example 6 of the present invention and a modified example thereof will be described with reference to FIG.

In this embodiment, the cement clinker is fired by a cement firing device 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, and the Si / Al product obtained by the separation is crushed / mixed with a cement clinker as a mixed material to produce a mixed cement. .. Further, the Ca product is sold outside as a filler or the like (Example 6). Further, the by-product mixture may be pulverized / mixed together with the cement clinker (modification example).

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

In this embodiment, the cement clinker is fired by a cement firing device using a natural raw material and a low Ca-R material as raw materials. Further, the high Ca-R material is carbonized and separated using the exhaust gas from the cement firing device, replaced with an existing by-product mixed material, and the Si / Al product obtained by separation is used as a mixed material and crushed together with cement clinker. / Mix to produce mixed cement. Further, the Ca product is supplied to the cement firing apparatus as a clinker raw material and sold externally as a filler or the like.

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

In Example 8, a cement clinker is fired by a cement firing apparatus using a natural raw material and a low Ca-R material as raw materials. _{In addition, CO 2} is absorbed by bubbling the exhaust gas from the cement firing device to the slurry of the high Ca-R material, and the carbon oxide obtained by carbonation of the high Ca-R material is used as a mixed material together with the cement clinker. Crush / mix to produce mixed cement. Further, in Example 9, the by-product mixture was pulverized / mixed together with the cement clinker. Further, in Example 10, the coal oxide was replaced with the blast furnace slag of the blast furnace cement type B.

Further, with respect to Example 10, a specific example in the case where vegetation-based biomass fluidized bed fly ash is used as a high Ca-R material will be described.

[Test Example 1]
When fly ash is obtained from biomass power generation facility A, which uses wood as fuel to generate electricity using a circulating fluidized bed furnace, and this is slurried and washed with water (reference example), CO ₂ gas is added to the slurry. A carbon oxide (test example) was produced. Specifically, 100 g of biomass ash and 400 g of tap water were put into a beaker to make a slurry, which was stirred with a stirrer at 400 rpm for 30 minutes. At this time, _{one with bubbling with CO 2} gas (test example) and one without bubbling (reference example) were prepared. The pH after stirring was 9 with bubbling, and 12 without bubbling. After stopping the stirring, the cake was filtered using a Buchner funnel, and 400 g of tap water was further added to the obtained cake on the filter paper to wash the slurry and then recovered. After the collected cake was naturally dried, the weight was measured and various analyzes were performed.

Table 1 shows the chemical composition of fly ash before and after the treatment. The chemical composition was measured by the FP method (fundamental parameter method) using the above fluorescent X-ray analyzer. Since this ash is a fluidized bed fly ash, it has a high CaO content. _{In addition, the CO 2} content of the test example is higher than that of the raw ash, and it can be seen that _{CO 2} is absorbed by the carbonation treatment.

Moreover, the existence form of the calcium component in fly ash was analyzed by the XRD method (X-ray diffraction method). As a result, it was confirmed that each Ca compound of CaO (quick lime), Ca (OH) ₂ (slaked lime), CaCO ₃ (limestone), and CaSO _{4 (plaster) was present as the form of calcium component in the raw ash.} On the other hand, in the reference example washed with water, the presence of CaO (quick lime) disappeared, but a trace amount of _{Ca (OH) 2 was present.} In the _{test example in which CO 2} gas was blown, both CaO and Ca (OH) _{2 disappeared.} Therefore, when the liquid bed fly ash is carbonated, Ca (OH) _{2 which} is a factor of fluctuation in fluidity and coagulation disappears and becomes CaCO ₃ , and the cement mixed with this has small abnormality and fluctuation in fluidity and coagulation. It can be seen that quality control of cement and concrete becomes easier.

Table 2 shows the chemical composition of vegetation-based biomass fluid bed flying ash by quantitative wet analysis and JIS K 0058-1 "Test method for chemical substances of slag-Part 1: Dissolution test method 5. Test by actual use". Indicates the amount of elution. Content of K _{2 O} of vegetation biomass fluidized bed fly ash is high, and it can be seen that not removed by water washing or carbonation. Glass ash mixed with cement, contributes to strength development of the cured body by pozzolanic reaction, mostly vegetation based biomass fluidized bed fly ash is incorporated into the glass of K 2 _O is, the reactivity of the glass since higher high strength development than fly ash without the K _{2 O.} Therefore, the coal oxide of the vegetation-based biomass fluidized bed fly ash containing glass contributes to the development of strength more than the limestone fine powder and the pulverized coal combustion type coal ash. In addition, when the glass reacts and potassium, which is an alkaline component, is released, the slag reaction proceeds further due to the alkali-promoting reaction, so that the strength development becomes high.

Therefore, at least based on the previous knowledge when calcium carbonate and blast furnace slag are mixed with cement, if cement is produced by mixing carbon oxide of vegetation-based biomass fluidized bed flying ash and blast furnace slag instead of calcium carbonate, the current state of affairs It is possible to produce cement having a strength equal to or higher than that of blast furnace cement. Specifically, when the amount of blast furnace slag produced decreases, less than half of the blast furnace slag contained in the blast furnace cement type B specified in JIS R 5211, which is about 40% of the amount of blast furnace slag added, is required. If the slag-based biomass fluidized bed flying ash is replaced with charcoal oxide accordingly, cement having fluidity and strength equal to or higher than that of blast furnace cement type B can be obtained. As for the composition, the total amount of carbon oxides of blast furnace slag and vegetation-based biomass fluidized bed fly ash is 30 to 60 parts by mass, with cement clinker and carbon oxide as 100 parts by mass, and the amount of vegetation-based biomass fluidized bed fly ash is 5 parts by mass. It becomes a mixed cement of ~ 25% by mass.

Furthermore, it can be seen that the vegetation-based biomass fluidized bed fly ash contains more chlorine, which is a cement repellent component, than ordinary coal ash, but it was removed at a high rate by carbonation and dehydration with a slurry. In addition, it can be seen that more than half of the harmful elution components of selenium and chromium have been removed by carbonation with the slurry, which makes the mixture safer and easier to use.

Table 3 shows the simulation results of Examples 1 to 10 and Comparative Examples 1 to 4 and Reference Examples described in the column of background technology. In this simulation, the CaO content of the high Ca-R material was set to 20% by mass. The CO ₂ reduction rate is the total amount of _{CO 2} absorbed by raw materials, fuel, and carbonation treatment. The total amount of recycled material that can be used is the total amount of low Ca-R material, high Ca-R material and by-product mixture.

The amount of CaO in Portland cement was 63%, and the remaining 37% mainly contained _{SiO 2} and Al ₂ O _{3. The CO 2} emission from limestone during the production of Portland cement was calculated to be 505 kg / t from the CaO amount described above. The CO ₂ emissions from thermal energy were set at 348 kg / t based on the outline of LCI data for cement issued by the Cement Association (February 19, 2019). _{Moreover, it was assumed that the CO 2} emissions used for the decarboxylation reaction of limestone account for 50% of _{the CO 2} emissions originating from thermal energy. The amount of CO ₂ absorbed by carbonation was assumed to be 80% by mass with respect to the CaO content, assuming that all Ca of the high Ca-R material _{became CaCO 3.}

_{Further, FIG. 11 shows the CO 2} reduction rate and the total amount of recycled material that can be used in the above-mentioned Examples and Comparative Examples. From FIG. 11, in _{terms of both the CO 2} reduction rate and the total amount of recycled material that can be used, almost all the examples exceed the comparative examples, and the examples 3, 5 and 7 exceed the reference examples.

Although the CaO content of the high Ca-R material was set to 20% by mass in the simulation, as described above, a material having a CaO content of 5% by mass or more can be treated as a high Ca-R material. As an example, in Example 4, when the CaO content of the high Ca-R material is 10%, the CO ₂ reduction rate is 30%, and the total usable amount of the recycled material is 570 kg / t. Further, in Example 4, when the CaO content of the high Ca-R material is 30%, the CO ₂ reduction rate is 29%, and the total usable amount of the recycled material is 592 kg / t. Therefore, even if the CaO content of the high Ca-R material is different, the amount of each processed product generated will change, but by appropriately selecting the manufacturing method, the CO ₂ reduction rate and the total amount of recycled material that can be used will be almost the same. Does not fluctuate.

Claims (12)

A cement manufacturing method characterized in that a waste containing 5% by mass or more of CaO is _{reacted with CO 2} and a part or all of the obtained carbon oxide is used as a cement mixture. _{While reacting CO 2} with a waste containing 5% by mass or more of CaO, the waste is separated into a material containing calcium carbonate and a material containing aluminosilicate, and at least a part or all of one of them is a cement mixture. A cement manufacturing method characterized by being used as. The cement manufacturing method according to claim 2, wherein the separated material containing calcium carbonate is used as a cement mixture. The cement manufacturing method according to claim 2, wherein the separated material containing aluminosilicate is used as a cement mixture. The cement manufacturing method according to any one of claims 1 to 4, further comprising using blast furnace slag and / and fly ash as a cement mixture. The cement manufacturing method according to any one of claims 2 to 5, wherein the material containing calcium carbonate and the material containing aluminosilicate, which is not used as a cement mixture, is used as a raw material for cement clinker. .. The cement manufacturing method according to any one of claims 1 to 6, wherein the reaction between the waste and CO _{2 is carried out using water.} The cement manufacturing method according to any one of claims 1 to 7, wherein the waste is waste concrete fine powder and / or waste consludge. The cement manufacturing method according to any one of claims 1 to 7, wherein the waste is a fluidized bed fly ash. 6. Cement manufacturing method. The cement manufacturing method according to any one of claims 1 to 7, wherein the waste is vegetation-based biomass ash. When the amount of waste containing less than 5% by mass of CaO as a raw material for cement clinker is small, the material containing aluminosilicate is used as a raw material for clinker, and the amount of waste containing less than 5% by mass of CaO as a raw material for cement clinker is large. The cement manufacturing method according to any one of claims 2 to 11, wherein the material containing the aluminosilicate is sometimes used as a cement mixture or sold to the outside.

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