JP7488677B2 - Method for producing fine clinker aggregate and method for producing cement clinker - Google Patents

Description

The present invention relates to a method for producing fine aggregate using cement clinker. The present invention also relates to a method for producing cement clinker using the fine aggregate produced by this method.

In recent years, various waste materials that are difficult to process have been used as raw materials for producing cement clinker. This allows for both industrial waste processing and cement production.

However, as demand for cement declines, the amount of cement produced will also decline. In this case, the amount of industrial waste that can be accepted at cement manufacturing plants will also decrease, which is undesirable from the perspective of building a recycling-based society.

As a result, it has been considered to use cement clinker as aggregate (see, for example, Patent Document 1). Aggregate is introduced together with cement when producing hardened cement products such as concrete and mortar. Therefore, if cement clinker could be used as aggregate, the consumption of cement clinker could be increased, and therefore the production volume of cement clinker could be increased.

In addition, through intensive research by the inventors, it has been confirmed that the use of cement clinker as fine aggregate can improve the physical properties of concrete, such as compressive strength, and durability, such as carbonation resistance (see Non-Patent Document 1 below).

Japanese Patent Application Laid-Open No. 8-231255 JP 2016-193805 A

Hayashi et al., "Study on the physical properties of mortar using clinker aggregate and its effect on improving the transition zone," Taiheiyo Cement Research Report No. 173 (2017)

At present, the use of cement clinker as aggregate to produce concrete or mortar has not yet been put to practical use.

The inventors believe that the following problems arise when using cement clinker as aggregate:

When producing aggregate for concrete, it is necessary to satisfy the particle size distribution stipulated by standards such as JIS. For this reason, when producing aggregate using cement clinker, it is necessary to adjust the particle size by carrying out processes such as coarse crushing and classification.

However, when this type of coarse crushing and classification process is carried out, fine powder is inevitably generated. At present, there is no established method for handling the fine powder that is generated when carrying out the above processes on cement clinker.

In addition, free lime (quicklime), which may be contained in small amounts in cement clinker, may cause harmful expansion failure in concrete depending on the amount. Free lime may be contained in cement clinker at about 1.5% or less, and at this content, when used as a fine powder like cement, most of it becomes calcium hydroxide in the reaction process between water and cement when mixing concrete, so it is not a harmful component. However, with coarse particles like clinker, the reaction of the free lime present inside the clinker does not finish during the concrete mixing process, and it reacts after the concrete hardens to form calcium hydroxide, which may cause expansion failure in the concrete.

From this perspective, when using cement clinker as aggregate, it is desirable that it contains as little free lime as possible, and even if it does contain free lime, it should be present on the surface of the clinker as much as possible so that it reacts before the hardened concrete is formed. For this reason, it is desirable to use cement clinker as a fine aggregate with a large specific surface area.

In view of the above problems, the present invention aims to provide a method for producing fine clinker aggregate that can effectively utilize the fine powder generated by adjusting the particle size of cement clinker and reduce the effects of free lime.

The method for producing clinker fine aggregate according to the present invention comprises the steps of:
A step (a) of calcining a cement raw material;
A step (b) of cooling the cement raw material fired in the step (a);
A step (c) of classifying the clinker produced through the step (b) into coarse particles and fine particles based on classification points within a predetermined range;
A step (d) of pulverizing the coarse particles obtained in the step (c) to obtain pulverized fine particles;
A step (e) of mixing the first-class fine powder having a particle size smaller than that of the fine particles produced during the execution of the step (c) with a material containing gypsum to obtain cement;
and a step (f) of obtaining a clinker fine aggregate from a mixture of the fine particles obtained in the step (c) and the pulverized fine particles obtained in the step (d).

When manufacturing fine aggregate for concrete, it is necessary to satisfy the particle size distribution stipulated by standards such as JIS. Generally, fine aggregate is defined as aggregate that passes entirely through a 10 mm mesh sieve, and furthermore, 85% or more by mass passes through a 5 mm mesh sieve (aggregate less than approximately 5 mm). For this reason, the above classification point is set to satisfy the standards. As an example, the classification point can be set within the range of 4 mm to 6 mm, and more specifically, it can be set to 5 mm.

The fine particles classified in step (c) as having a diameter smaller than the above classification point are of a size that meets the standards for fine aggregate. Furthermore, the coarse particles extracted in step (c) as having a diameter larger than the above classification point are crushed in step (d) to become particles (crushed fine particles) having the same diameter as the fine particles obtained in step (c). Furthermore, the free lime contained in the cement clinker is crushed and appears on the surfaces of the fine particles and crushed fine particles. Therefore, these fine particles and crushed fine particles can be used as fine aggregate.

On the other hand, the classification process in step (c) inevitably produces fine powder (first-class fine powder) with a fine particle size. This fine powder contains more CaO than the fine particles obtained by classification in step (c). Therefore, by using this fine powder in cement, a cement with high strength can be obtained. In addition, this fine powder also contains a large amount of free lime, and the content of fine particles and pulverized fine particles is relatively small. More specifically, in step (e), cement can be obtained by mixing the first-class fine powder with a material containing gypsum. The fact that the fine powder is likely to contain a large amount of free lime and that fine powder containing a large amount of free lime has high strength development are described, for example, in the above-mentioned Patent Document 2.

In other words, according to the above method, the cement clinker is classified to produce fine aggregate, and the fine powder produced during this process can be used as cement.

The step (b) is a cooling step using an air quenching cooler,
The (e) may be a mixture of the first classified fine powder and spillage extracted from a cooling air inlet of the air quenching cooler.

The air quenching cooler is a device used to rapidly cool the cement raw materials after burning by introducing cooling air upward from a cooling air inlet. During this cooling process, some of the cooled material may fall downward from the cooling air inlet. This cooled material (hereinafter referred to as "spillage") is obtained by cooling more rapidly than the clinker extracted from the outlet side of the air quenching cooler, and has a high CaO content and high strength. Therefore, by using this spillage in the mixing and grinding process in step (e), it is possible to realize a high-strength cement. In addition, by not using this spillage as a raw material for fine aggregate, the free lime content in the fine aggregate can be reduced.

As described above, cement clinker (hereinafter, sometimes simply abbreviated as "clinker") is produced by burning cement raw materials and then cooling them. Here, clinker is an aggregate of particles whose main _components are cement compounds C3S, _C2S , C3A, and _C4AF , which are produced by burning the cement raw materials. In this specification, the terms " _C3S ", " _C2S ", " _C3A ", and _{" C4AF} " _are all abbreviations commonly used in the field of cement chemistry, and correspond to _3CaO.SiO2 , _2CaO.SiO2 , _3CaO.Al2O3 , _{and 4CaO.Al2O3.Fe2O3 , respectively} .

In the clinker produced through burning and cooling, there is inevitably some free, unreacted quicklime that does not form the above cement compounds. This is called free lime (f.CaO).

When cement clinker is used as cement, it is pulverized in a finishing mill to an average particle size of about 10 μm with gypsum and admixtures added.

As mentioned above in the "Problems to be Solved by the Invention" section, when clinker is used as aggregate, even fine aggregate has a coarse particle size of about 1mm to 5mm, so free lime can still be present inside the aggregate even after the concrete mixing process. For this reason, even after the concrete has hardened, there is a concern that over time, moisture will penetrate into the aggregate, causing a hydration reaction with the remaining free lime, resulting in the concrete expanding.

However, according to the above method, after the spillage with a high CaO content is removed in advance, fine aggregate is produced from the fine particles obtained in step (c) and the crushed fine particles obtained in step (d), so the free lime content in the fine aggregate can be reduced.

Furthermore, if fine aggregate contains a large amount of free lime, the setting time of the concrete will vary depending on the content. With this method, the free lime content in the fine aggregate is reduced, allowing the concrete to set in approximately the same time as when concrete is produced using conventional fine aggregate, so the quality of the concrete can be controlled in the same way as before.

The step (f) may include a step (f1) of subjecting the mixture to an aging treatment.

According to the above method, the free lime contained in the mixture can be converted into slaked lime, etc., so that fine aggregate that does not cause expansion in concrete can be produced. In this step (f1), a method of reacting the mixture with water, _CO2 gas, exhaust gas, etc. can be adopted.

The step (f) may also include a step (f2) of subjecting the mixture to an anti-caking treatment.

Since cement clinker is hydraulic, when fine aggregate produced from this clinker is stored, it may absorb moisture from the air to produce hydrates, causing the fine aggregate to harden together. In contrast, the above method produces fine aggregate that has been treated to prevent caking, so even if it is stored outdoors, the progress of caking can be inhibited.

This anti-caking treatment can be achieved by mixing non-hydraulic aggregate or fine powder into the mixture.

In the above method, the classification process can be performed multiple times.

For example, the step (c) is
(c1) classifying the clinker into first coarse particles and the fine particles;
A step (c2) of subjecting the coarse particles to a pre-pulverization treatment to reduce their particle size;
The method includes a step (c3) of classifying the pre-pulverized product obtained in the step (c2) into second coarse particles and the fine particles,
The step (d) is a step of pulverizing the second coarse particles,
The step (f) may be a step of producing the clinker fine aggregate from the fine particles obtained in the steps (c1) and (c3).

In this case, the step (e) may be a step of obtaining the cement from the first classified fine powder obtained in at least one of the steps (c1) and (c2).

In addition, classification may be performed again after step (d).
The method for producing the clinker fine aggregate comprises:
The method includes a step (g) of classifying the product obtained in the step (d) into residual coarse particles and the fine particles,
The step (d) is a step of grinding the residual coarse particles obtained in the step (g) together with the coarse particles obtained in the step (c),
The step (e) may be a step in which second-class fine powder, which has a particle size smaller than that of the fine particles and which is produced during the execution of the step (g), is mixed with the first-class fine powder.

The fine clinker aggregate obtained by the above method can be recovered after use as concrete or mortar and reused as a cement raw material. In other words, this cement raw material can be used to produce cement clinker.

That is, the method for producing cement clinker according to the present invention is as follows:
obtaining the clinker fine aggregate by the method described above;
A step (h1) of mixing cement, the clinker fine aggregate obtained in the step (f), and coarse aggregate to produce concrete;
A step (i) of separating the coarse aggregate after the completion of use of the concrete obtained in the step (h1);
The method may further include a step (j1) of burning the residue obtained in the step (i) as a cement clinker raw material.

Further, the method for producing cement clinker according to the present invention comprises the steps of:
obtaining the clinker fine aggregate by the method described above;
A step (h2) of mixing cement with the clinker fine aggregate obtained in the step (f) to produce mortar;
After the mortar obtained in the step (h2) is used for sharing, the method may further include a step (j2) of burning the mortar as a cement clinker raw material.

In the above-mentioned method for producing cement clinker, the cement used in step (h1) or step (h2) may be the cement obtained in step (e) in the method for producing fine clinker aggregate according to the present invention, or may be the cement obtained in another cement plant.

In addition, in the above-mentioned method for producing cement clinker, the burning step in step (j1) or step (j2) can be the step (a) in the method for producing fine clinker aggregate according to the present invention, or can be a cement clinker burning step carried out in general cement production that is not intended to produce fine clinker aggregate.

According to the present invention, it is possible to effectively utilize the fine powder generated during classification processing, while producing fine aggregate from cement clinker in which the effects of free lime are mitigated.

1 is a flowchart showing an example of a procedure of a method for producing clinker fine aggregate according to the present invention. FIG. 2 is a block diagram illustrating an example of a system for implementing the method for producing fine clinker aggregate illustrated in FIG. 1 .

The present invention will now be described in more detail with reference to the drawings. However, the present invention is not limited to the embodiments described with these drawings.

Figure 1 is a flow chart showing the steps of the method for producing fine clinker aggregate according to the present invention. Also, Figure 2 is a block diagram showing an example of a system for implementing the method for producing fine clinker aggregate shown in Figure 1 (hereinafter referred to as the "fine clinker aggregate production system").

The flowchart shown in FIG. 1 includes some steps that can be omitted. The clinker fine aggregate manufacturing system 1 shown in FIG. 2 also includes some device configurations that can be omitted. This will be explained below.

The processing contents of each process shown in Figure 1 will be described in detail below, with reference to the clinker fine aggregate manufacturing system 1 shown in Figure 2 as appropriate.

(Firing process S1)
The calcination process S1 is a process for calcining the supplied cement raw material M1. This calcination process is carried out using a rotary kiln 5 equipped with a preheater 3 as necessary. This cement raw material M1 may be a general cement raw material, or it may be a recycled raw material RM recovered from concrete or mortar containing the clinker fine aggregate FA produced by the method of the present invention.

This firing process S1 corresponds to process (a).

(Cooling treatment step S2)
The cement raw material (calcined product M2) calcined in the calcination process S1 is cooled in the cooling process S2 and converted into cement clinker (clinker C1). This cooling process S2 can utilize a cooling device such as a drum cooler or an air quenching cooler, but an air quenching cooler is preferably used from the viewpoint of obtaining high-strength clinker C1 by rapid cooling. FIG. 2 shows an example in which the cooling device is configured as an air quenching cooler 7.

The air quenching cooler 7 rapidly cools the high-temperature sintered material M2 supplied from the rotary kiln 5 by blowing cooling air upward from a slit (cooling air inlet) formed on the bottom side. At this time, some of the sintered material M2 may fall in a rapidly cooled state through the slit. This falling material is called "spillag CS." The treatment of this spillage CS will be described later.

This cooling process step S2 corresponds to step (b).

(Coarse crushing process S3)
The clinker C1 obtained through the cooling process S2 is crushed (coarsely crushed) by a coarse crusher 9 to a particle size of, for example, about 40 mm or less. This coarse crushing process S3 is performed for the purpose of crushing the clinker C1 to a size that can be transported by a transport mechanism such as a belt conveyor. As the coarse crusher 9, for example, a jaw crusher or a hammer crusher can be used.

The clinker C1 that has been through this coarse crushing process S3 includes clinker with a particle size of 5 mm or less. In other words, this clinker C1 with a particle size of 5 mm or less is classified into fine particles FC2 in the subsequent classification process S4.

If the particle size of the clinker C1 obtained through the cooling treatment step S2 remains within the range of 40 mm or less, this step S3 can be omitted.

(Classification process S4)
The clinker C1 is classified by a classifier 11 into coarse particles CC2 (corresponding to "first coarse particles") having a particle size larger than a predetermined classification point, and fine particles FC2 having a finer particle size. The classifier 11 may be a sieve whose mesh size indicates the size of the classification point, or a centrifugal air classifier with rotating blades such as an air separator. The classification point may be set to, for example, 5 mm.

When the classification process is performed by the classifier 11, fine powder of clinker C1 is inevitably generated. In the following of this specification, the fine powder generated during the classification process is called "classified fine powder CF". The classified fine powder CF has a particle size sufficiently finer than the fine particles FC2, for example, 2 mm or less. The classification point, including the classification process described below, can be set appropriately depending on the free lime content of the classified fine powder CF obtained in each classification process and the strength when made into cement. In addition, if there is a classification process at a later stage, it is not necessarily necessary to perform a classification process before that. The processing of this classified fine powder CF will be described later.

The fine particles FC2 classified by the classification process S4 become the clinker fine aggregate raw material MFA. In addition, the coarse particles CC2 classified by the classification process S4 are subjected to a pre-crushing process in a later stage.

This classification process S4 corresponds to process (c1). Note that this classification process S4 can be omitted. In other words, the subsequent pre-crushing process S5 can be performed on all of the clinker C1 obtained in the coarse crushing process S3.

(Pre-grinding process S5)
The coarse particles CC2 classified in the classification process S4 are crushed (coarsely crushed) by a pre-crusher 13 to a particle size of, for example, about 20 mm or less. This process is performed to reduce the particle size of the coarse particles CC2 in advance in order to shorten the processing time in the crushing process S7 described later. Therefore, if the coarse particles CC2 (or clinker C1) have a particle size fine enough to be directly crushed in the crushing process S7, the pre-crushing process S5 can be omitted.

The pre-crusher 13 can be, for example, a vertical mill or a jaw crusher.

This pre-grinding process step S5 corresponds to step (c2).

(Classification process S6)
The pre-pulverized material CC3 obtained in the pre-pulverization process S5 is classified by a classifier 15 into coarse particles CC4 (corresponding to "second coarse particles") having a particle size larger than a predetermined classification point, and fine particles FC4 having a finer particle size. The classifier 11 may be a sieve whose mesh size indicates the size of the classification point. For example, a sieve with a mesh size of 5 mm may be used.

When classification is performed by the classifier 15, fine powder (classified fine powder CF) of the pre-ground material CC3 is inevitably generated. The processing of this classified fine powder CF will be described later.

The fine particles FC4 classified in the classification process S6 become the clinker fine aggregate raw material MFA. The second coarse particles CC4 classified in the classification process S6 are crushed in the subsequent crushing process S7.

This classification process S6 corresponds to process (c3). If the preceding pre-crushing process S5 is omitted, this classification process S6 may be performed on the clinker C1 instead of the pre-crushed material CC3.

In other words, the process group consisting of the classification process S4, the pre-grinding process S5, and the classification process S6 is carried out for the purpose of classifying the clinker C1 into coarse particles and fine particles based on a predetermined classification point, and all of these correspond to process (c).

(Crushing process S7)
Most of the second coarse particles CC4 classified in the classification step S6 are pulverized to a particle size of, for example, about 5 mm or less by a pulverizer 17. The pulverizer 17 may be a vertical mill, a tube mill, a ball mill, or the like.

The crusher 17 is preferably a tube mill having two chambers. In this case, it is preferable that the balls (medium) in the first chamber located at the front stage are made larger in diameter than the balls (medium) in the second chamber located at the rear stage. It is also possible that the second chamber does not have balls.

In the above configuration, the second coarse particles CC4 are atomized by the balls in the first chamber, and then sent to the second chamber where the corners of the particles are rounded and the particles are sized uniformly. This is preferable because the fluidity of the concrete is increased by forming fine aggregate from the sized fine particles.

This grinding process step S7 corresponds to step (d).

(Classification process S8)
If there is a possibility that the pulverized material CC5 obtained in the pulverization process S7 contains particles with a large particle size, it may be further classified by a classifier 19, and the coarse particles CC6 (corresponding to the "residual coarse particles") may be returned to the pulverization process S7 (corresponding to step (g)). The fine particles FC6 (pulverized fine particles FC6) classified by the classifier 19 become the clinker fine aggregate raw material MFA.

When classification is performed by the classifier 19, fine powder (classified fine powder CF) of the pulverized material CC5 is inevitably generated. The processing of this classified fine powder CF will be described later.

If the particle size of the pulverized material CC5 obtained by the pulverization process S7 is approximately 5 mm or less, that is, if the second coarse particles CC4 have been sufficiently pulverized by the pulverization process S7 and the fine powder (classified fine powder CF) of the pulverized material CC5 is within an acceptable range for fine aggregate, this classification process S8 is not necessary. In this case, all of the pulverized material CC5 obtained by the pulverization process S7 corresponds to the pulverized fine particles FC6 and becomes the clinker fine aggregate raw material MFA.

(Aggregate post-treatment process S10)
The fine particles (FC2, FC4) obtained by the classification process S4 or S6 and the pulverized fine particles FC6 obtained by the classification process S8 are mixed to become the clinker fine aggregate raw material MFA. This clinker fine aggregate raw material MFA can be used as the clinker fine aggregate FA as it is, but by performing the aggregate formation post-processing process S10 in the post-processing device 20, a better quality clinker fine aggregate FA can be obtained.

In FIG. 1, the aggregate post-processing process S10 is illustrated as including the granulation process S11, the aging process S12, and the caking prevention process S13, but it may include only some of these processes. In other words, the post-processing device 20 shown in FIG. 2 may include only some of the devices among the granulator 21, the aging process device 23, and the caking prevention process device 25.

<Grain sizing process S11>
The granulator 21 rounds off the corners of the fine particles (FC2, FC4, FC6) supplied as the clinker fine aggregate raw material MFA, thereby changing the fine particles into rounded particles with high fluidity. The granulator 21 is configured, for example, by a tube mill (drum) without balls, similar to the above-mentioned crusher 17.

However, if the fine particles FC6 have been sized by the above-mentioned crushing process S7 and the amount of fine particles (FC2, FC4) is relatively small and/or nonexistent, the sizing process S11 can be omitted.

<Aging treatment step S12>
The aging treatment device 23 performs aging treatment on the free lime (f.CaO) contained in the clinker fine aggregate raw material MFA, and changes the free lime to slaked lime, etc. After this treatment is performed, the clinker fine aggregate FA has a reduced free lime content, so that after it is used as concrete, the phenomenon of concrete expanding due to hydration reaction over time can be suppressed.

The aging treatment device 23 can be composed of a device or a warehouse that can pass steam, _CO2 gas, exhaust gas, etc. through the clinker fine aggregate raw material MFA. In particular, passing exhaust gas through the clinker fine aggregate raw material MFA is preferable because free lime is converted to calcium carbonate and disappears.

When carrying out the above-mentioned sizing process S11, the aging process S12 and the sizing process S11 can be carried out in parallel by carrying out processes such as spraying water on the sizing machine 21 and passing exhaust gas through it. In this case, the sizing machine 21 also serves as the aging treatment device 23.

This aging treatment step S12 corresponds to step (f1).

<Anti-caking treatment step S13>
The anti-caking treatment device 25 is a device that performs a treatment to prevent caking of the clinker fine aggregate raw material MFA, and performs a treatment to mix, for example, non-hydraulic aggregate such as blast furnace slag aggregate or limestone sand, or fine powder of limestone, γ- _C2S , coal ash, or incineration ash. This mixing treatment is realized by a device such as a mixer or drum.

In particular, when the coarse aggregate is separated from the concrete after the end of the shared use in the coarse aggregate separation step S51 described later, _SiO2 derived from the coarse aggregate is mixed into the recycled raw material RM. Therefore, from the viewpoint of bringing the recycled raw material RM closer to the cement raw material M1, it is preferable to mix limestone sand or limestone fine powder in the anti-caking treatment step S13 to increase the content of the CaO component.

The clinker that constitutes the clinker fine aggregate raw material MFA has hydraulic properties. Therefore, when the clinker fine aggregate raw material MFA is stored, it absorbs moisture from the air and generates hydrates, which can reduce the fluidity of the concrete and, in some cases, can cause the fine aggregates to harden together. According to the anti-caking treatment process S13, powder and aggregate made of materials with low hydraulic properties are mixed, so that the clinker fine aggregate FA that has undergone this treatment suppresses the generation of hydrates and the progression of hardening during storage.

Fine aggregates usually contain a small amount of fine powder, so when fine powder is mixed in this anti-caking treatment step S13, it is also possible to replenish the fine powder removed in the previous classification step.

This anti-caking treatment step S13 corresponds to step (f2).

(Cement finishing treatment S21)
The fine powder (classified fine powder CF) obtained in the classification process (S4, S6, S8) is mixed and pulverized together with the gypsum PL and other small amounts of mixed components Z1 by the finishing mill 31. In this process S21, if the spillage CS is obtained in the cooling process S2, this spillage CS is also mixed together with the classified fine powder CF and pulverized by the finishing mill 31.

The classified fine powder CF may be sent to the finishing mill 31 by collecting dust using a bag filter or the like during each classification process (S4, S6, S8).

As described in Patent Document 2, it has been confirmed that the smaller the particle size of clinker C1, the higher the CaO content. For this reason, the classified fine powder CF obtained in each of the above classification processes (S4, S6, S8) can be used as cement CM to obtain a cement with high strength. In addition, the spillage CS obtained in the cooling process S2 is cooled more rapidly than the clinker C1, and therefore has a higher strength. Therefore, by using it as cement CM, a cement with high strength can be obtained.

In other words, the classified fine powder CF obtained in the classification process (S4, S6, S8) and the spillage CS obtained in the cooling process S2 are not used as clinker fine aggregate FA, but are mixed and crushed with gypsum PL, etc. in process S21 and used as cement CM.

This allows the classified fine powder CF obtained in the classification process (S4, S6, S8) to be effectively utilized.

This cement finishing process S21 corresponds to step (e).

If necessary, a classifier 33 may be used to classify large particles, and the particles may then be sent back to the finishing mill 31 for grinding to produce cement CM.

In addition, the classified fine powder CF that has already become fine enough to be used as cement can be used as cement CM by simply mixing with gypsum PL, etc., without grinding. In other words, this cement finishing process S21 may involve only the mixing process, without including the grinding process.

(Concrete processing S31, mortar processing S32)
When the clinker fine aggregate FA is used as concrete, it is mixed with cement CM, coarse aggregate CA, and water (step S31). When the clinker fine aggregate FA is used as mortar, it is mixed with cement CM and water (step S32). Note that water is omitted in FIG. 1 for convenience of illustration.

Process S31 corresponds to step (h1), and process S32 corresponds to step (h2).

The cement CM mixed in steps S31 and S32 can be any type of cement CM. That is, it is possible to use fine powder (classified fine powder CF) obtained in the classification process (S4, S6, S8) in parallel with the production of the clinker fine aggregate FA described above, or cement CM produced from spillage CS in the cooling process S2, or cement CM produced at another cement plant.

(Shared process S40)
The concrete or mortar is shipped as a product and used on-site.

(Recycling step S50)
From the used concrete, the coarse aggregate RCA is separated in a coarse aggregate separation mechanism 51 (corresponding to a coarse aggregate separation step S51, step (i)). The recovered material remaining after separation of the coarse aggregate RCA from the used mortar or the used concrete is mixed with other raw materials Y1 as necessary to prepare the components, thereby obtaining the recycled raw material RM (raw material mixing step S52).

In addition, if the recovered material has a raw material composition almost the same as that of the original cement raw material M1, recycled raw material RM can be obtained without going through the raw material mixing step S52. In the concrete processing step S31 and the mortar processing step S32, limestone fine powder or limestone aggregate may be mixed into the recovered material after the shared use is completed so that the raw material composition is almost the same as that of the original cement raw material M1.

The recycled raw material RM obtained in the recycling step S50 is used as the cement raw material M1 and is calcined in the calcination step S1 to obtain the cement clinker C1 again. In this case, the amount of limestone raw material that emits _CO2 when heated can be reduced, so that the amount of _CO2 generated in the calcination step S1 is reduced and the amount of energy required for this process can be reduced, which contributes to the prevention of global warming.

The recycled raw material RM can also be applied to systems other than the clinker fine aggregate manufacturing system 1 shown in FIG. 2. That is, the recycled raw material RM can be used again as a raw material for the clinker fine aggregate FA after passing through the above-mentioned processes, or can be used as a cement clinker raw material in a general cement manufacturing process that does not manufacture the clinker fine aggregate FA. In the former case, the recycled raw material RM is used in the above-mentioned firing process S1, and the clinker fine aggregate FA is obtained again after passing through the above-mentioned processes after step S2. In the latter case, the recycled raw material RM is used in the firing process (corresponding to steps (j1) and (j2)) in a general cement manufacturing process to obtain cement clinker, and cement is produced from this cement clinker.

1: Clinker fine aggregate manufacturing system 3: Preheater 5: Rotary kiln 7: Air quenching cooler 9: Crusher 11: Classifier 13: Pre-crusher 15: Classifier 17: Crusher 19: Classifier 20: Post-treatment device 21: Granulator 23: Aging treatment device 25: Anti-caking treatment device 31: Finishing mill 33: Classifier 51: Coarse aggregate separation mechanism C1: Clinker CA: Coarse aggregate CC2: Coarse particles (first coarse particles)
CC3: Pre-ground material CC4: Coarse particles (second coarse particles)
CC5: Crushed material CC6: Coarse grain CF: Classified fine powder CM: Cement CS: Spillage FA: Clinker fine aggregate FC2: Fine grain FC4: Fine grain FC6: Fine grain (crushed fine grain)
M1: Cement raw material M2: Burnt product MFA: Clinker fine aggregate raw material PL: Gypsum RCA: Coarse aggregate RM: Recycled raw material Y1: Raw material Z1: Small amount of mixed component

Claims (7)

A step (a) of calcining a cement raw material;
A step (b) of cooling the cement raw material fired in the step (a);
A step (c) of classifying the clinker produced through the step (b) into coarse particles and fine particles using a classifier based on a classification point within a range of 4 mm to 6 mm, and obtaining a first-class fine powder having a particle size of 2 mm or less that is finer than the fine particles to such an extent that it can be collected during classification;
A step (d) of pulverizing the coarse particles obtained in the step (c) to obtain pulverized fine particles;
A step (e) of collecting the first-class fine powder obtained during the execution of the step (c) and then mixing it with a material containing gypsum to obtain cement;
and (f) obtaining a clinker fine aggregate from a mixture of the fine particles obtained in the step (c) and the pulverized fine particles obtained in the step (d),
The step (b) is a cooling step using an air quenching cooler having a slit-shaped cooling air inlet and configured to blow cooling air upward from the cooling air inlet,
The method for producing clinker fine aggregate (e) is characterized in that spillage, which is the burned product of the step (a) that has fallen downward through the cooling air inlet of the air quenching cooler, is mixed with the first classified fine powder. The method for producing clinker fine aggregate according to claim 1, characterized in that the step (f) includes a step (f1) of performing an aging treatment by passing water vapor, _CO2 gas, or exhaust gas through the mixture. The step (c)
(c1) classifying the clinker into first coarse particles and the fine particles;
A step (c2) of subjecting the coarse particles to a pre-pulverization treatment to reduce their particle size;
The method includes a step (c3) of classifying the pre-pulverized product obtained in the step (c2) into second coarse particles and the fine particles,
The step (d) is a step of pulverizing the second coarse particles,
3. The method for producing clinker fine aggregate according to claim 1 or 2, wherein the step (f) is a step of producing the clinker fine aggregate from the fine particles obtained in the steps (c1) and (c3). The method for producing fine clinker aggregate according to claim 3, characterized in that the step (e) is a step of obtaining the cement from the first classified fine powder obtained in at least one of the steps (c1) and (c2). The method includes a step (g) of classifying the product obtained in the step (d) into residual coarse particles and the fine particles,
The step (d) is a step of grinding the residual coarse particles obtained in the step (g) together with the coarse particles obtained in the step (c),
The method for producing clinker fine aggregate according to any one of claims 1 to 4, characterized in that the step (e) is a step of mixing second-classified fine powder, which is generated during the execution of the step (g) and has a particle size smaller than that of the fine particles, with the first-classified fine powder. Obtaining the clinker fine aggregate by the manufacturing method according to any one of claims 1 to 5;
A step (h1) of mixing cement, the clinker fine aggregate obtained in the step (f), and coarse aggregate to produce concrete;
A step (i) of separating the coarse aggregate after the completion of use of the concrete obtained in the step (h1);
and a step (j1) of burning the residue obtained in the step (i) as a cement clinker raw material. Obtaining the clinker fine aggregate by the manufacturing method according to any one of claims 1 to 5;
A step (h2) of mixing cement with the clinker fine aggregate obtained in the step (f) to produce mortar;
and after completion of sharing of the mortar obtained in the step (h2), a step (j2) of burning the mortar as a cement clinker raw material.

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