Carbon dioxide adsorption method, regenerated building material generation method, and asphalt mixture manufacturing method

Abstract

To provide a carbon dioxide adsorption method, regenerated building material generation method, and an asphalt mixture manufacturing method, capable of efficiently consuming concrete sludge by adsorbing carbon dioxide.SOLUTION: The carbon dioxide adsorption method, regenerated building material generation method, and asphalt mixture manufacturing method include the steps of: a) molding a dehydrated cake of concrete sludge to obtain a carbon dioxide adsorbent block; and b) bringing the carbon dioxide adsorbent block into contact with an exhaust gas stream containing carbon dioxide and dust. This ensures that carbon dioxide is adsorbed and the concrete sludge can be efficiently consumed.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a method for adsorbing carbon dioxide, a method for producing recycled building materials, and a method for producing an asphalt mixture. [Background technology]

[0002] In so-called ready mixed concrete manufacturing plants and secondary concrete product factories, unused ready mixed concrete such as return concrete or residual concrete remains, and washing wastewater (sludge water) from concrete mixers, agitator vehicles, etc. is generated. This return concrete, residual concrete, and sludge water are called concrete sludge.

[0003] After the aggregates such as gravel and sand are collected from the concrete sludge, the solid and liquid phases are separated using a filter press, etc. The solid phase containing the cement particles after separation is generally called the dewatered cake.

[0004] As is well known, ready-mix concrete is made up of calcium oxide (and various minerals), a component of cement, which hardens through hydration and acts as a binder. Therefore, dehydrated cake derived from concrete sludge contains a lot of calcium hydroxide, which is a hydrate of cement particles, and is a highly alkaline waste product, making disposal of it difficult.

[0005] In recent years, reducing carbon dioxide, a greenhouse gas, has become an urgent issue, and concrete sludge and its dehydrated cake have attracted attention as carbon dioxide adsorbents. Calcium hydroxide (and various hydration products) derived from concrete sludge reacts chemically with carbon dioxide (neutralization) to produce calcium carbonate and other carbonate minerals, and this neutralization process fixes carbon dioxide. For this reason, concrete sludge can be used as a carbon dioxide adsorbent.

[0006] A conventional carbon dioxide adsorbent derived from concrete sludge is disclosed in Patent Document 1. Specifically, Patent Document 1 discloses a technology in which concrete sludge is dehydrated, dried and finely granulated to increase the surface area and adsorption capacity, thereby efficiently consuming carbon dioxide in exhaust gas. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 7-8796 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the technology of Patent Document 1 requires a considerable amount of man-hours for the process of forming the concrete sludge in advance (by pulverizing or granulating it, etc.). Concrete sludge is generated in large quantities, and even when it is used as a carbon dioxide adsorbent, it is desirable to consume it efficiently with as little effort as possible.

[0009] The present invention has been made in consideration of the above-mentioned points, and an object of the present invention is to provide a carbon dioxide adsorption method, a recycled building material production method, and an asphalt mixture production method that can adsorb carbon dioxide and efficiently consume concrete sludge. [Means for solving the problem]

[0010] In order to solve the above problems, a first invention of the present application provides a method for adsorbing carbon dioxide in flue gas, comprising the steps of: a) molding a dehydrated cake of concrete sludge to obtain a carbon dioxide adsorbent mass; and b) bringing the carbon dioxide adsorbent mass into contact with a flow of flue gas containing carbon dioxide and dust.

[0011] A second invention of the present application is a method for producing recycled building materials, comprising the steps of: a) molding a dehydrated cake of concrete sludge to obtain a carbon dioxide adsorbent lump; b) bringing the carbon dioxide adsorbent lump into contact with an airflow of exhaust gas containing carbon dioxide and dust; and c) recovering sludge powder from which a surface layer of the carbon dioxide adsorbent lump has peeled off due to collision with the dust contained in the airflow in step b).

[0012] A third invention of the present application is the recycled building material generating method of the second invention, characterized in that in the step c), the sludge powder is collected using a dust collector.

[0013] The fourth invention of the present application is a method for producing recycled building materials according to the third invention, characterized in that the dust collector is provided in an exhaust path that discharges the exhaust gas from a source of the exhaust gas to the outside, and the carbon dioxide adsorbent mass is installed inside the exhaust path upstream of the dust collector in the exhaust air direction.

[0014] A fifth aspect of the present invention is a method for producing recycled building materials according to any one of the second to fourth aspects of the present invention, wherein the dust contains minerals derived from aggregate for asphalt mixtures.

[0015] A sixth invention of the present application is a method for producing recycled building materials, comprising: a) a step of molding a dehydrated cake of concrete sludge to obtain carbon dioxide adsorbent lumps; b) a step of contacting the carbon dioxide adsorbent lumps with an airflow of exhaust gas containing carbon dioxide and dust; and d) a step of crushing the carbon dioxide adsorbent lumps after step b).

[0016] The seventh invention of the present application is a method for producing an asphalt mixture, comprising: A) a step of obtaining the sludge powder by the recycled building material production method of any one of the second to fourth inventions; and B) a step of producing an asphalt mixture by blending the sludge powder obtained in step A) as a filler with aggregate for asphalt mixture and molten asphalt. Effect of the Invention

[0017] According to the first to seventh aspects of the present application, carbon dioxide can be adsorbed and concrete sludge can be efficiently consumed.

[0018] In particular, according to the second to fifth inventions of the present application, by recovering the sludge powder generated by the collision of dust contained in the exhaust gas, it is possible to obtain powdered sludge powder that can be used as recycled building material without crushing.

[0019] In particular, according to the sixth aspect of the present invention, the remaining carbon dioxide adsorbing material chunks that have not been peeled off due to the collision with dust can be used as recycled building materials.

[0020] In particular, according to the seventh aspect of the present invention, the sludge powder can be used as a filler for asphalt mixtures as a recycled building material. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a diagram showing the configuration of an asphalt plant. [Diagram 2] 1 is a flowchart showing a flow of a carbon dioxide adsorbing material lump production process. [Diagram 3] 1 is a flowchart showing the flow of a first asphalt mixture production process accompanied by a carbon dioxide adsorption process and a first recycled building material production process. [Figure 4] 10 is a flowchart showing the flow of a second asphalt mixture production process accompanied by a second recycled building material production process. [Diagram 5] FIG. 2 is a diagram showing an example of a carbon dioxide adsorbent mass. [Figure 6] FIG. 2 is a cross-sectional perspective view showing a cylindrical carbon dioxide adsorbent mass arranged in a cylindrical portion of a first exhaust flue. [Figure 7] FIG. 13 is a diagram showing a state in which a block of carbon dioxide adsorbing material according to a first modified example is fitted inside a rectangular cylindrical portion of a first exhaust flue. [Figure 8] FIG. 13 is a diagram showing a state in which a block of carbon dioxide adsorbing material according to a second modified example is fitted inside a rectangular cylindrical portion of a first exhaust flue. [Figure 9] FIG. 11 is a cross-sectional view showing a state in which a block of carbon dioxide adsorbing material according to a third modified example is fitted inside a rectangular cylindrical portion of a first exhaust flue. [Figure 10] FIG. 13 is a cross-sectional view showing a state in which a mass of carbon dioxide adsorbing material according to a fourth modified example is arranged along a wall surface of a bent portion of a first exhaust flue. [Figure 11] FIG. 4 is a cross-sectional view showing a state in which a mass of carbon dioxide adsorbing material is arranged in a portion of a first exhaust flue having a small inner diameter. [Figure 12] FIG. 4 is a cross-sectional view showing the state in which the carbon dioxide adsorbing material block is arranged in a damper installation portion of the first exhaust flue. [Figure 13] FIG. 4 is a cross-sectional view showing the state in which the carbon dioxide adsorbing material block is arranged in a damper installation portion of the first exhaust flue. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[0023] <1. Embodiment> <1-1. Asphalt plant configuration> Fig. 1 is a diagram showing the configuration of an asphalt plant 1. This asphalt plant 1 produces an asphalt mixture by mixing new material, waste material, molten asphalt, and filler (stone powder). As shown in Fig. 1, the asphalt plant 1 includes a new material hopper 10, a waste material hopper 20, a new material dryer 30, a regenerated dryer 40, an exhaust path 50, and a plant main body 90.

[0024] The new material hopper 10 temporarily stores new aggregate for asphalt mixture (hereinafter referred to as “new material”) carried into the asphalt plant 1. The new material hopper 10 supplies the new material to a drum 31 of the new material dryer 30.

[0025] As new aggregates, various natural coarse aggregates (natural gravel), crushed stone, natural fine aggregates (natural sand), crushed sand, etc. are used. However, aggregates that are particularly susceptible to abrasion loss when heated, or aggregates that are destroyed when heated, are generally considered unsuitable for paving applications. For this reason, it is preferable that the aggregate be a paving aggregate having a certain degree of hardness (at least the degree required as a road paving material). For example, hard basalt, andesite, quartz trachyte, sandstone, or various hard rocks of similar materials are preferably used.

[0026] In addition, the new materials are classified according to particle size as follows: No. 4 crushed stone with a particle size of 30mm to 20mm, No. 5 crushed stone with a particle size of 20mm to 13mm, No. 6 crushed stone with a particle size of 13mm to 5mm, No. 7 crushed stone with a particle size of 5mm to 2.5mm, coarse sand with a particle size of 5mm to 0mm, and fine sand with a particle size of 2mm to 0mm.

[0027] New materials of each particle size are stored in new material hoppers 10 by particle size, and after the required amount of new materials according to the mix design of the asphalt mixture to be manufactured is cut out from each new material hopper 10, all the cut new materials are supplied together to the drum 31 of the new material dryer 30. Therefore, the new materials in the drum 31 contain aggregates of each particle size (coarse aggregate and fine aggregate), and also contain fine particles derived from aggregates with small particle sizes.

[0028] The new wood dryer 30 is a device that heats and dries new wood that is supplied from the new wood hopper 10 and contains at least water inside the aggregate. The average moisture content of new wood is, for example, around 3 to 15%. Aggregates with small particle sizes tend to have particularly high moisture contents, and most of them are in a wet state containing surface water. In addition, some new wood may be in a so-called surface-dried or air-dried state, which contains water inside the aggregate but does not have surface water, due to the effects of sunlight, etc.

[0029] The new material dryer 30 comprises a drum 31, a machine base 32, and a burner 33. The drum 31 is located in the center of the new material dryer 30. The machine base 32 is provided to support the drum 31 from below so that it can rotate freely. The burner 33 is located at one end of the new material dryer 30. In other words, the new material dryer 30 has the burner 33 at one end of the drum 31. The new material dryer 30 is connected to the plant main body 90 by a vertical conveying device 101. In addition, the new material dryer 30 is connected to a first exhaust flue 51 of the exhaust path 50, which will be described later.

[0030] The new wood dryer 30 has a scraper blade (not shown) on the inner periphery of the drum 31. The scraper blade rotates at a predetermined speed by a drive device (not shown) and stirs the new wood supplied to the drum 31. The burner 33 heats the new wood supplied to the drum 31 to a predetermined temperature and heats and dries the wood to an absolutely dry state with a moisture content of approximately 0%.

[0031] During the heating and drying process of new wood, the burner 33 generates carbon dioxide in the process of burning various carbon-containing fuels. Therefore, carbon dioxide is contained in the exhaust gas discharged from the new wood dryer 30. The carbon-containing fuel may be, for example, a fossil fuel such as heavy oil or city gas, or a biomass fuel.

[0032] Also, new wood originally contains a certain amount of dust derived from fine particles. Furthermore, at least a part of the new wood may be slightly worn away and generate dust during the process of being exposed to hot air and stirred in the drum 31. Therefore, the exhaust gas discharged from the new wood dryer 30 contains dust derived from the aggregate.

[0033] Furthermore, due to the heating and drying process of the new wood, almost all of the water contained in the new wood is contained as water vapor in the exhaust gas discharged from the new wood dryer 30. In other words, the new wood dryer 30 is a source of exhaust gas containing carbon dioxide generated with the combustion of fuel, dust derived from the aggregate, and moisture derived from the aggregate.

[0034] The vertical conveying device 101 conveys the heated new lumber to the plant body 90. Exhaust gas generated by heating the new lumber is discharged to the first exhaust flue 51. The exhaust gas in the first exhaust flue 51 contains carbon dioxide generated in association with the heating and drying process of the new lumber, dust, and moisture derived from the aggregate. The dust contains minerals derived from the aggregate.

[0035] By heating and drying aggregate (new material) that can withstand heat treatment (grain size does not change significantly due to heat treatment) and has a hardness that can be used as a paving material in the new material dryer 30, the mineral phase contained in the dust also has an appropriate hardness. As a result, it is considered that the surface peeling effect of the carbon dioxide adsorbent mass described below will also be increased. For this reason, it is desirable that each aggregate has an abrasion loss value of at least about 40% or less, as measured by JIS A 1121 "Test method for abrasion of coarse aggregate using a Los Angeles tester".

[0036] The waste material hopper 20 temporarily stores the recycled aggregate (waste material) brought into the asphalt plant 1. The waste material hopper 20 supplies the waste material to a drum 41 of the regenerative dryer 40.

[0037] The waste material used is recycled aggregate R13-0, which is made by crushing and classifying pavement waste material removed during road construction, etc., into a specified particle size, for example, 13mm to 10mm. After crushing and classification, part of the aggregate is exposed as a fracture surface, while part of the aggregate is covered with the old asphalt. The rock type of aggregate contained in the waste material varies depending on the mix used at the time of construction, but it can be assumed that it is at least one of the pavement aggregates mentioned above. The waste material also mainly contains fine particles generated during crushing.

[0038] The regenerative dryer 40 is a device that heat-treats waste material containing water, which is supplied from the waste material hopper 20 in the asphalt plant 1. The average moisture content of the waste material is, for example, about 3 to 15%, similar to that of new material, and at least water is contained inside the aggregate. The regenerative dryer 40 includes a drum 41, a machine base 42, a burner 43, a regenerative material storage bin 44, and a regenerative material measuring tank 45. The drum 41 is located between the burner 43 and the regenerative material storage bin 44. The machine base 42 is provided so as to support the drum 41 from below so as to be freely rotatable. The burner 43 is located at one end of the regenerative dryer 40. That is, the regenerative dryer 40 has the burner 43 at one end of the drum 41. The regenerative material storage bin 44 is located at the other end of the regenerative dryer 40. The regenerative material measuring tank 45 is located at the lower end of the regenerative material storage bin 44. The regenerative dryer 40 is connected to the plant main body 90 by an input chute 102. In addition, the regenerative dryer 40 is connected to a second exhaust flue 52 of the exhaust path 50, which will be described later.

[0039] The regenerative dryer 40 has a scraper blade (not shown) on the inner periphery of the drum 41. The scraper blade rotates at a predetermined speed by a drive device (not shown) and stirs the waste material supplied to the drum 41. The burner 43 heats the waste material supplied to the drum 41 to a predetermined temperature and heats and dries the waste material to an absolute dry state with a moisture content of approximately 0%.

[0040] During the heat drying process of the waste material, the burner 43 generates carbon dioxide in the process of burning various carbon-containing fuels. Therefore, the exhaust gas discharged from the regenerative dryer 40 contains carbon dioxide.

[0041] Also, waste materials originally contain a certain amount of dust derived from fine particles. Furthermore, at least a portion of the waste materials may be slightly worn away (for example, the fractured surfaces of aggregates) during the process of being exposed to hot air and stirred inside the drum 31, generating dust. Therefore, the exhaust gas discharged from the regenerative dryer 40 contains dust derived from the aggregates. The dust generated by the regenerative dryer 40 has a certain degree of stickiness due to the old asphalt components of the waste materials adhering thereto, and it is considered that the amount of dust generated is less than that of the new material dryer 30.

[0042] Furthermore, due to the heat drying process of the waste material, almost all of the water contained in the waste material is contained as water vapor in the exhaust gas discharged from the regenerative dryer 40. In other words, the regenerative dryer 40 is a source of exhaust gas containing carbon dioxide generated with the combustion of fuel, dust derived from the aggregate, and moisture derived from the aggregate.

[0043] The recycled material storage bin 44 temporarily stores the heated waste material. In other words, the recycled material storage bin 44 is an aggregate storage section that stores aggregate (waste material) dried by the regenerative dryer 40. The recycled material measuring tank 45 measures a predetermined amount of waste material stored in the recycled material storage bin 44 and supplies it to the input chute 102. The input chute 102 transports the predetermined amount of waste material to the plant main body 90. Exhaust gas generated by heating the waste material is discharged from the recycled material storage bin 44 to the second exhaust flue 52.

[0044] The exhaust path 50 is a gas exhaust path composed of piping and the like, which discharges exhaust gas from the new material dryer 30 and the regenerative dryer 40, which are the sources of exhaust gas, to the outside. The exhaust path 50 has a first exhaust flue 51, a second exhaust flue 52, and a common flue 53. The upstream end of the first exhaust flue 51 is connected to the top of the drum 31 of the new material dryer 30. The upstream end of the second exhaust flue 52 is connected to the top of the regenerative material storage bin 44 of the regenerative dryer 40. The downstream end of the first exhaust flue 51 and the downstream end of the second exhaust flue 52 are connected to the upstream end of the common flue 53. As a result, the exhaust gas discharged from the new material dryer 30 and the exhaust gas discharged from the regenerative dryer 40 join together and flow through the common flue 53.

[0045] In the common flue 53, an inertial dust collector 61, a filter dust collector 62, and an exhaust fan 63 are inserted in this order from the upstream side. The downstream end of the common flue 53 is connected to a chimney 64. The exhaust fan 63 generates a flow of exhaust gas from the upstream side to the downstream side in the common flue 53. As a result, the exhaust gas that has flowed into the common flue 53 from the first exhaust flue 51 and the second exhaust flue 52 is discharged from the chimney 64 after dust has been removed in the inertial dust collector 61 and the filter dust collector 62.

[0046] The inertial dust collector 61 separates dust particles having a relatively large particle size from dust particles contained in the exhaust gas. For example, a cyclone type dust collector is used as the inertial dust collector 61. The dust particles having a relatively large particle size separated in the inertial dust collector 61 are transported to a filler storage bin 94 (described later) of the plant main body 90 via a pressure transfer pipe 103. The exhaust gas discharged from the inertial dust collector 61 is introduced into a filter dust collector 62 downstream.

[0047] The filter dust collector 62 separates fine dust (particles) contained in the exhaust gas. The filter dust collector 62 captures and removes the fine dust using a filter cloth. The fine dust removed by the filter cloth is transported to a filler storage bin 94 (described later) of the plant main body 90 via a pressure feed pipe 103. The filter dust collector 62 discharges the exhaust gas from which the dust has been removed to the downstream side of the common flue 53. The exhaust gas from which the dust has been removed by the inertial dust collector 61 and the filter dust collector 62 is discharged from a chimney 64.

[0048] The plant body 90 is a facility for producing an asphalt mixture by mixing new wood that has been heated and dried, waste wood that has been heated and dried, filler, and molten asphalt. The plant body 90 includes a vibrating sieve 91, an aggregate storage bin 92, an aggregate measuring tank 93, a filler storage bin 94, a filler measuring tank 95, a molten asphalt tank 96, a supply pump 97, an asphalt measuring tank 98, and a mixer 99.

[0049] The vibrating sieve 91 receives new material supplied from the vertical conveying device 101. The vibrating sieve 91 sifts the received new material and supplies it to the aggregate storage bin 92 by grain size. In other words, the aggregate storage bin 92 is an aggregate storage section that stores the aggregate (new material) dried by the new material dryer 30. The aggregate measuring tank 93 weighs each of the new materials stored in the aggregate storage bin 92 by grain size and supplies it to the mixer 99.

[0050] The filler storage bin 94 is a filler storage section that temporarily stores the stone powder brought into the asphalt plant 1 and the sludge powder transported from the pressure feed pipe 103. In the following explanation, the stone powder brought into the asphalt plant 1 and the dust containing the sludge powder transported from the pressure feed pipe 103 are collectively referred to as "filler". The filler measuring tank 95 measures a predetermined amount of filler stored in the filler storage bin 94 and supplies it to the mixer 99.

[0051] The molten asphalt tank 96 is a molten asphalt storage unit that temporarily stores the molten asphalt, which is a material for the asphalt mixture. The supply pump 97 is an asphalt transport unit that transports the molten asphalt from the molten asphalt tank 96 to the asphalt metering tank 98. The asphalt metering tank 98 measures the asphalt transported by the supply pump 97 and supplies it to the mixer 99.

[0052] The mixer 99 produces an asphalt mixture by mixing new material supplied from the aggregate metering tank 93, waste material supplied from the recycled material metering tank 45, filler supplied from the filler metering tank 95, and molten asphalt supplied from the asphalt metering tank 98 for a predetermined period of time.

[0053] <1-2. Carbon dioxide adsorption process, recycled building material production process, and asphalt mixture manufacturing process> Next, a method for performing carbon dioxide adsorption treatment of exhaust gas and recycled building material production treatment in conjunction with the asphalt mixture production treatment in the asphalt plant 1 will be described with reference to Figs. 2 to 4. Fig. 2 is a flowchart showing the flow of the carbon dioxide adsorbent block production treatment. Fig. 3 is a flowchart showing the flow of the first asphalt mixture production treatment accompanied by the carbon dioxide adsorption treatment and the first recycled building material production treatment. Fig. 4 is a flowchart showing the flow of the second asphalt mixture production treatment accompanied by the second recycled building material production treatment.

[0054] In the method shown in Figures 2 to 4, a method for adsorbing carbon dioxide in exhaust gas generated in asphalt plant 1, a first recycled building material production method, and a first asphalt mixture production method are performed by the carbon dioxide adsorbent lump production process (step S1) shown in Figure 2 and the first asphalt mixture production process (step S2) shown in Figure 3. Also, in addition to the carbon dioxide adsorbent lump production process (step S1) shown in Figure 2 and the first asphalt mixture production process (step S2) shown in Figure 3, a second recycled building material production method and a second asphalt mixture production method are performed by performing the second asphalt mixture production process (step S3) shown in Figure 4.

[0055] As shown in Fig. 2, in the carbon dioxide adsorbent lump production process (step S1), first, aggregates such as gravel and sand are classified and removed from the concrete sludge (step S101). At this time, the removal of the aggregates may be performed in two stages, that is, the removal of coarse aggregate and the removal of fine aggregate. Thereafter, a filter press or the like is used to separate the solid phase and the liquid phase (step S102). As a result, a dehydrated cake, which is a solid phase containing cement particles, is obtained.

[0056] Next, the dehydrated cake is molded into a predetermined shape to obtain a carbon dioxide adsorbent lump (step S103). Specifically, the dehydrated cake is packed into a mold for molding and left to stand for a while. In this way, a carbon dioxide adsorbent lump having a desired shape can be obtained. Figure 5 is a diagram showing an example of a carbon dioxide adsorbent lump 80. This carbon dioxide adsorbent lump 80 is molded into a cylindrical shape.

[0057] Concrete sludge contains cement. Cement is produced by mixing and firing limestone, which is mainly composed of calcium carbonate, silica sand, which is mainly composed of quartz, clay containing oxides of aluminum and silicon, and oxides containing iron, at high temperatures of over 900°C. During the firing process at such high temperatures, the calcium carbonate contained in the limestone is thermally decomposed into carbon dioxide and calcium oxide. After firing, cement is composed mainly of tricalcium silicate (CaO)3 (SiO2), dicalcium silicate (CaO)2 (SiO2), tricalcium aluminate (CaO)3 (Al2O3), and tetracalcium aluminate ferroferro (CaO)4 (Al2O3) (Fe2O3), and the content ratio of each component varies depending on the type of cement. The average particle size of cement particles is approximately 10 μm (0.01 mm) or less, which is roughly compatible with the required particle size of the filler.

[0058] The carbon dioxide adsorbent lump 80 contains a large amount of calcium hydroxide, which is a hydrate of cement particles, and various hydration products. The calcium hydroxide and other substances contained in the carbon dioxide adsorbent lump 80 react with carbon dioxide to cause a chemical reaction and neutralize to produce various carbonate minerals such as calcium carbonate. Therefore, the carbon dioxide adsorbent lump 80 can adsorb and fix carbon dioxide.

[0059] 3, in the first asphalt mixture manufacturing process (step S2), first, the carbon dioxide adsorbent lump 80 obtained in the carbon dioxide adsorbent lump generation process (step S1) is placed inside the first exhaust flue 51 (step S201). That is, the carbon dioxide adsorbent lump 80 is installed inside the exhaust path 50, which discharges exhaust gas containing carbon dioxide, dust, and moisture derived from aggregate generated in the new material dryer 30 to the outside, on the upstream side in the exhaust air direction from the dust collectors 61, 62.

[0060] In this embodiment, the carbon dioxide adsorbent mass 80 is disposed inside the first exhaust flue 51, but the location of the carbon dioxide adsorbent mass 80 is not limited to inside the first exhaust flue 51. The carbon dioxide adsorbent mass 80 may be disposed anywhere upstream of the dust collectors 61, 62 of the exhaust path 50 in the exhaust direction. In other words, the location of the carbon dioxide adsorbent mass 80 is not limited to inside the first exhaust flue 51. The carbon dioxide adsorbent mass 80 may be disposed inside the second exhaust flue 52, or inside the common flue 53 upstream of the dust collectors 61, 62 in the exhaust direction.

[0061] Fig. 6 is a cross-sectional perspective view showing a cylindrical carbon dioxide adsorbent mass 80 disposed in a cylindrical portion of the first exhaust flue 51. In Fig. 6, the carbon dioxide adsorbent mass 80 is disposed along the inner wall surface of the first exhaust flue 51. That is, the cylindrical outer circumferential surface of the carbon dioxide adsorbent mass 80 is disposed along the cylindrical inner wall surface of the first exhaust flue 51. As a result, the inner wall surface of the first exhaust flue 51 is covered by the carbon dioxide adsorbent mass 80. For this reason, the carbon dioxide adsorbent mass 80 can be expected to have the effect of acting as a liner to protect the inner wall surface of the first exhaust flue 51 at the location where it is disposed.

[0062] After the installation of the carbon dioxide adsorbent block 80 is completed, the asphalt plant 1 is operated to start the production of an asphalt mixture. That is, the heating and drying process of the new material in the new material dryer 30 is also started. As a result, exhaust gas containing carbon dioxide, dust, and moisture derived from the aggregate, generated in the new material dryer 30, is discharged into the first exhaust flue 51. Then, in the first exhaust flue 51, the exhaust gas flow comes into contact with the carbon dioxide adsorbent block 80 (step S202).

[0063] When the exhaust gas flow comes into contact with the carbon dioxide adsorbent lump 80, the calcium hydroxide and various hydration products contained in the carbon dioxide adsorbent lump 80 chemically react (neutralize) with carbon dioxide to produce various carbonate minerals including calcium carbonate, and carbon dioxide is fixed by this neutralization action. In this manner, the method for adsorbing carbon dioxide in exhaust gas is carried out by the carbon dioxide adsorbent lump generation process (step S1) and steps S201-S202 of the first asphalt mixture production process (step S2).

[0064] The exhaust gas discharged from the new material dryer 30 and the regenerator dryer 40 and flowing into the first exhaust flue 51 and the second exhaust flue 52 contains a considerable amount of water derived from the aggregate due to the heat drying process of the aggregate. At this time, in order to achieve both energy efficiency and condensation suppression, the exhaust gas temperature is adjusted to about 100°C to 120°C, which is near the dew point temperature, and the humidity of the exhaust gas is in a substantially saturated state close to 100%. In this way, the exhaust gas of the asphalt plant 1 is kept below the temperature (about 900°C) at which calcium carbonate decomposes. Therefore, if the carbon dioxide adsorbent mass 80 installed inside the first exhaust flue 51 and the second exhaust flue 52 has already been neutralized, there is little risk of it being thermally decomposed again (carbon dioxide being desorbed). On the other hand, it is considered that the thermal energy of the exhaust gas contributes to improving the reaction speed of the neutralization reaction. These operating conditions are considered to be favorable conditions for proceeding with the neutralization reaction in which carbon dioxide is adsorbed into the carbon dioxide adsorbent mass 80, which contains a large amount of unneutralized, unreacted calcium oxide.

[0065] On the other hand, the first exhaust flue 51 and the second exhaust flue 52 are designed in terms of flow resistance and the like so that the wind speed of the exhaust gas is, for example, 5 m / sec to 20 m / sec. The dust contained in the exhaust gas airflow collides with the carbon dioxide adsorbent mass 80 at a speed close to the wind speed, causing the surface layer of the carbon dioxide adsorbent mass 80 to peel off. As a result, the surface layer of the carbon dioxide adsorbent mass 80 that has been neutralized by adsorbing carbon dioxide is peeled off. By scraping off the surface layer that has undergone the neutralization reaction, a part that contains a large amount of unreacted calcium oxide that has not been neutralized is exposed as a new surface layer, and carbon dioxide is easily adsorbed by the unreacted part. That is, the dust contained in the exhaust gas from the asphalt plant 1 and suitable wind speed conditions promote the metabolism of the carbon dioxide adsorbent mass 80, and stable adsorption of carbon dioxide is promoted.

[0066] When the surface layer of the carbon dioxide adsorbent lump 80 is peeled off due to the collision of the dust, it becomes sludge powder and is transported downstream of the first exhaust flue 51 together with the exhaust gas flow. In particular, the dust of the exhaust gas flowing through the first exhaust flue 51 contains minerals derived from the aggregate (new material) for the asphalt mixture. Since the dust containing minerals has a certain degree of hardness or more, the surface layer of the carbon dioxide adsorbent lump 80 is likely to peel off. Then, in the inertial dust collector 61 and the filtration dust collector 62, the dust contained in the exhaust gas and the sludge powder are collected (step S203).

[0067] The sludge powder collected in the inertial dust collector 61 and the filter dust collector 62 is transported to the filler storage bin 94 via the pressure delivery pipe 103. As a result, the sludge powder obtained in step S203 is mixed with the filler (step S204). That is, the sludge powder obtained in step S203 is used as a recycled building material. The pressure delivery pipe 103 plays the role of a sludge powder transport path that transports the sludge powder collected in the dust collectors 61 and 62 to the filler storage bin 94 as a filler. In this way, the first recycled building material production method is implemented by the carbon dioxide adsorbent lump production process (step S1) and steps S201 to S203 of the first asphalt mixture production process (step S2).

[0068] Thereafter, the filler containing the sludge powder obtained in step S203 is supplied to a mixer 99 via a filler measuring tank 95, and mixed with new material supplied from the aggregate measuring tank 93, waste material supplied from the recycled material measuring tank 45, and molten asphalt supplied from the asphalt measuring tank 98 to produce an asphalt mixture (step S205). In this manner, the carbon dioxide adsorbent lump generation process (step S1) and the first asphalt mixture production process (step S2) carry out the first asphalt mixture production method in which sludge powder is blended as a filler.

[0069] After the carbon dioxide adsorbent block generation process (step S1) and the first asphalt mixture production process (step S2) are completed, the carbon dioxide adsorbent block 80 used in the first asphalt mixture production process (step S2) is recovered and a second asphalt mixture production process (step S3) is carried out.

[0070] As shown in FIG. 4, in the second asphalt mixture manufacturing process (step S3), first, the carbon dioxide adsorbent block 80 that was placed inside the first exhaust flue 51 in the first asphalt mixture manufacturing process (step S2) is removed from the first exhaust flue 51 and recovered (step S301).

[0071] The recovered carbon dioxide adsorbent lump 80 is in contact with the exhaust gas in the first exhaust flue 51 for a long period of time, and carbon dioxide is also fixed inside the lump. Furthermore, the surface of the carbon dioxide adsorbent lump 80 is peeled off by dust, reducing the thickness, and carbon dioxide fixation easily progresses up to the outer circumferential surface side of the carbon dioxide adsorbent lump 80. Furthermore, the carbon dioxide adsorbent lump 80 is dried by being in contact with the high-temperature exhaust gas for a long period of time.

[0072] Next, the collected carbon dioxide adsorbent lumps 80 are crushed to a predetermined particle size or less (step S302). In this way, crushed recycled building materials are obtained. At this time, if the carbon dioxide adsorbent lumps 80 are not sufficiently dry, a drying process may be performed on the crushed carbon dioxide adsorbent lumps 80. In this way, the second recycled building material production method is carried out by steps S301 and S302 of the carbon dioxide adsorbent lumps production process (step S1), the first asphalt mixture production process (step S2), and the second asphalt mixture production process (step S3).

[0073] After completion of step S302, the crushed recycled building materials generated in step S302 are input into the filler storage bin 94 of the asphalt plant 1. As a result, the crushed recycled building materials generated in step S302 are mixed into the filler (step S303).

[0074] When the crushed recycled building materials are used as a filler, the particle size of the crushed recycled building materials is a predetermined particle size or less, for example, 100 μm (0.1 mm) or less, more preferably 75 μm (0.075 mm) or less. When the crushed recycled building materials are used as a filler, the moisture content is preferably, for example, 1% or less. Therefore, after crushing the carbon dioxide adsorbent block, the crushed recycled building materials may be subjected to a drying process.

[0075] Then, in step S303, the filler mixed with the crushed recycled building materials is supplied to the mixer 99 via the filler metering tank 95, and is mixed with new material supplied from the aggregate metering tank 93, waste material supplied from the recycled material metering tank 45, and molten asphalt supplied from the asphalt metering tank 98 to produce an asphalt mixture (step S304).

[0076] The crushed recycled building materials generated in step S302 may be used for purposes other than filler used in asphalt mixtures. For example, they may be used as embankments, backfill materials, spread sand, etc. They may also be used for fine particle adjustment (gradation adjustment) of gradation-adjusted crushed stone (RM40-0, etc.), as well as for various recycled aggregates and recycled roadbed materials.

[0077] <2. Modification> Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment.

[0078] <2-1. Modifications of the shape and arrangement of the carbon dioxide adsorbent mass> Fig. 7 is a diagram showing a state in which a carbon dioxide adsorbent mass 80A according to a first modified example is fitted inside a rectangular tubular portion of a first exhaust flue 51. In Fig. 7, only a cut-away portion of the first exhaust flue 51 is shown, and the carbon dioxide adsorbent mass 80A is shown in its entirety. In the example of Fig. 7, the carbon dioxide adsorbent mass 80A is formed into a substantially flat plate shape. Two carbon dioxide adsorbent masses 80A are arranged in the flow path of the first exhaust flue 51 along the exhaust air direction indicated by the arrow in Fig. 7. The two carbon dioxide adsorbent masses 80A are arranged side by side at an interval at the same position in the exhaust air direction.

[0079] With this arrangement, the exhaust gas comes into contact with both sides of the carbon dioxide adsorbent block 80A. Therefore, the carbon dioxide adsorbent block 80A can efficiently absorb the carbon dioxide in the exhaust gas. Also, dust in the exhaust gas collides with both sides of the carbon dioxide adsorbent block 80A. This allows the surface of the carbon dioxide adsorbent block 80A that has adsorbed the carbon dioxide to be efficiently peeled off. Therefore, sludge powder can be efficiently produced.

[0080] In the above embodiment, the carbon dioxide adsorbent mass 80 is formed in a cylindrical shape, but as shown in Fig. 7, the shape of the carbon dioxide adsorbent mass is not limited to a cylindrical shape. Furthermore, the location of the carbon dioxide adsorbent mass in the exhaust path is not limited to along the inner wall. The carbon dioxide adsorbent mass may be placed in any position in the exhaust path as long as it does not interfere with the flow of exhaust gas.

[0081] FIG. 8 is a diagram showing a state in which a carbon dioxide adsorbent block 80B according to the second modified example is fitted inside a rectangular tubular portion of the first exhaust flue 51. In FIG. 8, only a cut portion of the first exhaust flue 51 is shown. In the example of FIG. 8, the carbon dioxide adsorbent block 80B is formed into a substantially flat plate shape. The carbon dioxide adsorbent block 80B has a plurality of holes 81B penetrating in the thickness direction. As shown in FIG. 8, the two carbon dioxide adsorbent blocks 80B are arranged substantially perpendicular to the exhaust direction of the first exhaust flue 51. That is, the two carbon dioxide adsorbent blocks 80B are arranged side by side with an interval therebetween in the exhaust direction. When arranged in this manner, the holes 81B penetrate the carbon dioxide adsorbent block 80B in the exhaust direction.

[0082] In this second modified example, the exhaust gas flowing through the first exhaust flue 51 collides with the surface of the carbon dioxide adsorbent mass 80B on the upstream side in the exhaust air direction. This makes the surface of the carbon dioxide adsorbent mass 80B more likely to be peeled off by dust contained in the exhaust gas. In other words, sludge powder can be efficiently produced. The exhaust gas also flows downstream of the carbon dioxide adsorbent mass 80B through the holes 81B.

[0083] Fig. 9 is a cross-sectional view showing how a carbon dioxide adsorbing material block 80C according to a third modified example is fitted inside a rectangular tubular portion of the first exhaust flue 51. This carbon dioxide adsorbing material block 80C is molded into a substantially flat plate shape. One surface of the carbon dioxide adsorbing material block 80C is molded flat. The other surface of the carbon dioxide adsorbing material block 80C has an uneven portion. As shown in Fig. 9, the carbon dioxide adsorbing material block 80C is arranged so that the flat surface fits along the inner wall of the first exhaust flue 51.

[0084] In this third modified example, the surface of carbon dioxide adsorbent block 80C that comes into contact with the exhaust gas has unevenness. This makes it easier for dust in the exhaust gas to collide with the surface of carbon dioxide adsorbent block 80C when the exhaust gas passes through first exhaust flue 51. This makes the surface of carbon dioxide adsorbent block 80C easier to peel off due to dust contained in the exhaust gas.

[0085] Fig. 10 is a cross-sectional view showing a state in which a carbon dioxide adsorbent lump 80D according to the fourth modified example is arranged along the wall surface of a bent portion of the first exhaust flue 51. As shown in Fig. 10, the carbon dioxide adsorbent lump 80D is arranged along the inner wall of the outer side (part with a large radius of curvature) of the bent portion of the first exhaust flue 51. This makes it easier for the exhaust gas coming from the upstream side of the bent portion in the exhaust air direction and the dust contained in the exhaust gas to collide with the carbon dioxide adsorbent lump 80D. This makes it easier for the surface of the carbon dioxide adsorbent lump 80D to be peeled off by the dust contained in the exhaust gas. That is, sludge powder can be efficiently generated.

[0086] The inner wall surface on the outside of the bent portion of the first exhaust flue 51 is easily worn (eroded) by collision with exhaust gas coming from the upstream side of the bent portion in the exhaust air direction and dust contained in the exhaust gas. For this reason, by covering the inner wall surface on the outside of the bent portion with the carbon dioxide adsorbing material mass 80D, the inner wall surface of the first exhaust flue 51 is protected.

[0087] FIG. 11 is a cross-sectional view showing a state where the carbon dioxide adsorbent lump 80E is arranged in a portion of the first exhaust flue 51 having a smaller inner diameter than the other portions. That is, the inner diameter of the portion of the first exhaust flue 51 where the carbon dioxide adsorbent lump 80E is arranged is smaller than the inner diameter of the other portions. As a result, the flow velocity of the exhaust gas is faster at the portion of the first exhaust flue 51 where the carbon dioxide adsorbent lump 80E is arranged than at the other portions. Therefore, the dust contained in the exhaust gas collides with the carbon dioxide adsorbent lump 80E with force. Therefore, the surface of the carbon dioxide adsorbent lump 80E is easily peeled off by the dust contained in the exhaust gas. That is, the sludge powder can be efficiently generated.

[0088] 12 and 13 are cross-sectional views showing the state where the carbon dioxide adsorbent mass 80F is arranged at a portion of the first exhaust flue 51 where the damper 510F is installed. FIG. 12 shows the state when the damper 510F is not rotating. Also, FIG. 13 shows the state when the damper 510F is rotating. In the example of FIG. 12 and FIG. 13, two dampers 510F and two carbon dioxide adsorbent masses 80F are arranged side by side at an interval from each other at the same position in the exhaust air direction in the first exhaust flue 51. Specifically, the two carbon dioxide adsorbent masses 80F are arranged along the inner wall surface of the first exhaust flue 51. Also, the two dampers 510F are arranged in the space between the two carbon dioxide adsorbent masses 80F.

[0089] The damper 510F is a plate-shaped member that rotates about an axis 511F that extends in a direction perpendicular to the exhaust air direction. As shown in Fig. 12, when the damper 510F is not rotating, it is disposed parallel to the exhaust air direction. Therefore, when the damper 510F is not rotating, the damper 510F does not obstruct the flow in the first exhaust flue 51.

[0090] 13, during rotation, the upstream ends of the two dampers 510F each move closer to the inner wall of the first exhaust flue 51 and the carbon dioxide adsorbent block 80F, while the downstream ends move away from the inner wall of the first exhaust flue 51 and the carbon dioxide adsorbent block 80F. This brings the damper 510F and the upstream end of the carbon dioxide adsorbent block 80F closer to each other, narrowing the flow path between the damper 510F and the upstream end of the carbon dioxide adsorbent block 80F. As a result, the flow velocity of the exhaust gas between the damper 510F and the upstream end of the carbon dioxide adsorbent block 80F increases, accelerating peeling of the surface of the carbon dioxide adsorbent block 80F.

[0091] Furthermore, as a result of the flow path between the damper 510F and the upstream end of the carbon dioxide adsorbent block 80F becoming narrower, a vortex of the exhaust gas is generated between the damper 510F and the carbon dioxide adsorbent block 80F, as shown in Fig. 13. This makes it easier for dust contained in the exhaust gas to collide with the carbon dioxide adsorbent block 80F, further accelerating peeling of the surface of the carbon dioxide adsorbent block 80F.

[0092] In the example of Fig. 12 and Fig. 13, two dampers 510F are installed, but the present invention is not limited to this. One damper may be arranged in the center of the first exhaust flue 51. In the example of Fig. 12 and Fig. 13, the damper 510F is arranged at the same position in the exhaust direction as the carbon dioxide adsorbent mass 80F, but the present invention is not limited to this. In the first exhaust flue 51, one or more dampers may be arranged on the upstream side of the carbon dioxide adsorbent mass in the exhaust direction, on the downstream side of the carbon dioxide adsorbent mass in the exhaust direction, or on both the upstream side and downstream side of the carbon dioxide adsorbent mass in the exhaust direction. In addition, the carbon dioxide adsorbent mass may be installed on the surface of the damper (preferably the surface facing the inner wall surface of the exhaust flue).

[0093] <2-2. Other Modifications> In the above embodiment, the asphalt plant 1 uses new materials and waste materials as aggregates, and uses sludge powder and crushed recycled building materials as part of the filler to produce an asphalt mixture. However, the asphalt plant 1 may use only either new materials or waste materials as aggregates to produce an asphalt mixture. For example, when only new materials are used as aggregates, the waste materials are not heat-treated, and the regenerative dryer 40 is not operated.

[0094] In the above embodiment, the carbon dioxide adsorbent mass 80 is fitted in the first exhaust flue 51, but the present invention is not limited to this. The carbon dioxide adsorbent mass 80 may be fitted in any position in the exhaust path 50 as long as it is upstream of the dust collectors 61, 62. That is, the carbon dioxide adsorbent mass 80 may be fitted in the second exhaust flue 52 or in a position upstream of the dust collectors 61, 62 in the common flue 53. The carbon dioxide adsorbent mass 80 may also be fitted in the vicinity of the inlet of the inertial dust collector 61, that is, upstream of a portion of the inertial dust collector 61 that has a dust collection function.

[0095] In the above embodiment, the dust collectors 61, 62 are provided in the common flue 53 connected to both the first exhaust flue 51 and the second exhaust flue 52. However, in the asphalt plant 1, a dust collector may be provided in each of the first exhaust flue 51 and the second exhaust flue 52.

[0096] Furthermore, the asphalt plant 1 may produce an asphalt mixture containing only one of sludge powder and crushed recycled building materials as a filler, or neither. When sludge powder is not included as a filler, the sludge powder collected by the dust collectors 61, 62 may be stored and used for other purposes. The crushed recycled building materials may also be used for purposes other than the production of asphalt mixtures after crushing the carbon dioxide adsorbent masses that have adsorbed carbon dioxide by contacting exhaust gas to obtain crushed recycled building materials.

[0097] Furthermore, the elements appearing in the above-described embodiments and modifications may be combined as appropriate to the extent that no contradiction arises. [Industrial Applicability]

[0098] INDUSTRIAL APPLICABILITY The present invention can be used in a carbon dioxide adsorption method, a recycled building material manufacturing method, and an asphalt mixture manufacturing method, which can adsorb carbon dioxide and efficiently consume concrete sludge. [Explanation of symbols]

[0099] 1: Asphalt plant 10: New material hopper 20: Waste hopper 30: New wood dryer 31: Drums 33: Burna 40: Regenerative dryer 41: Drums 43: Burna 44: Recycled material storage bin 50: Exhaust route 51: First exhaust flue 52: Second exhaust flue 53: Common flue 61:Inertial dust collector 62:Filtration dust collector 63:Exhaust fan 64: Chimney 80, 80A, 80B, 80C, 80D, 80E: Carbon dioxide adsorbent mass 81B: Hole 92: Aggregate storage bin 94: Filler storage bin 96: Molten Asphalt Tank 99: Mixer 103: Pressure pipe

Claims

1. a) forming a dehydrated cake of concrete sludge to obtain a carbon dioxide adsorbent mass; b) contacting the mass of carbon dioxide sorbent with a stream of exhaust gas containing carbon dioxide and dust; A method for adsorbing carbon dioxide in exhaust gas, comprising:

2. a) forming a dehydrated cake of concrete sludge to obtain a carbon dioxide adsorbent mass; b) contacting the mass of carbon dioxide sorbent with a stream of exhaust gas containing carbon dioxide and dust; c) recovering sludge powder resulting from the surface layer of the carbon dioxide adsorbent mass being peeled off due to collision of the dust contained in the airflow in step b); and A method for producing recycled building materials, comprising:

3. The method for producing recycled building materials according to claim 2, characterized in that in the step c), the sludge powder is collected using a dust collector.

4. The dust collector is provided in an exhaust path that discharges the exhaust gas from a generation source of the exhaust gas to the outside, 4. The method for producing recycled building materials according to claim 3, wherein the carbon dioxide adsorbent mass is installed inside the exhaust path, upstream of the dust collector in the exhaust air direction.

5. The method for producing recycled building materials according to any one of claims 2 to 4, wherein the dust contains minerals derived from aggregate for asphalt mixtures.

6. a) forming a dehydrated cake of concrete sludge to obtain a carbon dioxide adsorbent mass; b) contacting the mass of carbon dioxide sorbent with a stream of exhaust gas containing carbon dioxide and dust; d) after step b), crushing the carbon dioxide adsorbent mass; A method for producing recycled building materials, comprising:

7. A) obtaining the sludge powder by the method for producing recycled building materials according to any one of claims 2 to 4; B) A step of producing an asphalt mixture by mixing the sludge powder obtained in step A) as a filler with an aggregate for asphalt mixture and molten asphalt; A method for producing an asphalt mixture comprising the steps of:

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