Method for producing carbonated powder and granular material

Abstract

Provided is a method for producing a carbonated powder and granular material that reduces the load on the environment, enables stable operation, and makes it possible to achieve high carbonation efficiency. This method for producing a carbonated powder and granular material comprises: a step for supplying, to a fine bubble generation nozzle 16, a first fluid L1 obtained by mixing water and a to-be-carbonated powder and granular material C, and a gas containing carbon dioxide; a step for injecting, from the fine bubble generation nozzle 16, a second fluid L2 in which fine bubbles containing microbubbles of the abovementioned gas are dispersed in the first fluid L1; and a step for obtaining the carbonated powder and granular material by a carbonation reaction in which at least a portion of the to-be-carbonated powder and granular material C is carbonated by carbon dioxide eluted from the fine bubbles into the water in the second fluid L2.

Description

Method for producing carbonated powder

[0001] The present invention relates to a method for producing carbonated powder or granules.

[0002] Various decarbonization technologies are being considered to achieve carbon neutrality. Among them, carbonate or concrete-related carbon dioxide fixation technology is easier to put into practical use than other carbon dioxide-based technologies, and carbon dioxide fixation technology has great potential.

[0003] A method utilizing fine bubbles for immobilizing carbon dioxide has been reported. Patent Document 1 discloses a method for producing an inorganic carbonate, which comprises injecting a gas containing carbon dioxide and a liquid from a nozzle into a reaction vessel to generate ultrafine bubbles containing carbon dioxide, and precipitating an inorganic carbonate having an average primary particle size of 300 nm or less in the presence of the ultrafine bubbles.

[0004] Patent Document 2 discloses a method for producing calcium carbonate for immobilizing carbon dioxide as calcium carbonate, which includes the steps of: preparing a slurry containing calcium hydroxide; and generating fine bubbles containing carbon dioxide from a fine bubble generator equipped with a porous portion having fine pores in a container configured to prevent carbon dioxide from being released into the atmosphere, and supplying the carbon dioxide into the slurry containing calcium hydroxide, thereby precipitating the calcium carbonate, wherein the fine bubble generator supplies the carbon dioxide at a flow rate of 40 to 2500 ml / min per 1 mol of the calcium hydroxide.

[0005] Patent Document 3 describes a method in which a gas containing carbon dioxide is blown into a solution containing an organic amine molecule and a metal ion as a cation, to form a porous metal complex with a carbon dioxide-derived crosslinking ligand, and to form β-type dicalcium silicate (β-2CaO.SiO) in the pores and surrounding areas of the formed porous metal complex. ２ The document discloses a fine aggregate for concrete, which is characterized by producing a calcium carbonate composition by a carbonation reaction between calcium carbonate and a gas containing carbon dioxide.

[0006] JP 2018-039696 A JP 2023-028788 A JP 2023-076782 A

[0007] However, the technology disclosed in the above document has the following problems. In Patent Document 1, inorganic carbonates such as calcium hydroxide and magnesium hydroxide are formed on the surfaces of solid particles, which may cause the reaction to stop midway. Furthermore, when the suspension is sprayed from the nozzle, the generated inorganic carbonates may clog the nozzle, causing operation to stop. Furthermore, because ultrafine bubbles have a low buoyancy velocity and move only by Brownian motion, there is little opportunity for them to come into contact with the substance to be carbonated, which may prevent the carbonation reaction from proceeding efficiently.

[0008] In Patent Document 2, fine bubbles are generated from the porous portion, but if the particle size of the substance to be carbonated or the carbonate-containing substance is smaller than that of the porous portion, the porous portion may become clogged, preventing the generation of fine bubbles and resulting in a shutdown of the operation. Also, since only fine bubbles are injected from the porous portion, there is a risk that the carbonation reaction will not proceed efficiently.

[0009] In Patent Document 3, an amine-based porous metal complex is required to produce a calcium carbonate composition, but this cannot be used depending on the type of product from the viewpoint of environmental load.

[0010] In view of the above problems, the present invention aims to provide a method for producing carbonated powder and granules that imposes little burden on the environment, enables stable operation, and can achieve high carbonation efficiency.

[0011] The inventors of the present invention conducted extensive research to solve the above-mentioned problems and discovered the following: By supplying a first fluid, which is a mixture of water and powder to be carbonated, and a gas containing carbon dioxide to a fine bubble generating nozzle, it is possible to spray a second fluid from the fine bubble generating nozzle, in which fine bubbles containing microbubbles of the gas are dispersed in the first fluid. In the second fluid, at least a portion of the powder to be carbonated is carbonated by carbon dioxide dissolved from the fine bubbles into the water, resulting in carbonated powder. Furthermore, the carbonation efficiency can be further improved by irradiating the second fluid with ultrasonic waves or applying high-voltage pulses, or by stirring the second fluid vertically.

[0012] In the present invention, fine bubbles refer to bubbles defined in ISO 20480-1 and JIS B 8741-1. That is, fine bubbles consist of microbubbles with a diameter of 1 μm or more and less than 100 μm, and ultrafine bubbles (nanobubbles) with a diameter of less than 1 μm. The method for measuring the particle size of fine bubbles will be described later.

[0013] That is, the gist and configuration of the present invention are as follows.

[0014] [1] A method for producing carbonated powder and granular material, comprising the steps of: supplying a first fluid, which is a mixture of water and powder and granular material to be carbonated, and a gas containing carbon dioxide, to a fine bubble generating nozzle; spraying a second fluid, which is the first fluid into which fine bubbles containing microbubbles of the gas are dispersed, from the fine bubble generating nozzle; and obtaining carbonated powder and granular material by a carbonation reaction in which at least a part of the powder and granular material to be carbonated is carbonated in the second fluid by the carbon dioxide dissolved from the fine bubbles into the water.

[0015] [2] The method for producing carbonated powder and granules described in [1] above, wherein the second fluid is supplied to the fine bubble generating nozzle and sprayed again from the fine bubble generating nozzle, thereby continuing the carbonation reaction.

[0016] [3] The method for producing carbonated powder and granules described in [1] or [2] above, wherein the average diameter of the fine bubbles is 0.3 μm or more and less than 100.0 μm, and the number ratio of the microbubbles in the fine bubbles is 0.5% or more and 100.0% or less.

[0017] [4] The method for producing carbonated powder and granules according to any one of [1] to [3] above, wherein the fine bubble generating nozzle is any one of a swirling liquid flow type, a static mixer type, an ejector type, a Venturi type, a pressurized dissolution type, and a cooling dissolution type.

[0018] [5] A method for producing carbonated powder or granules according to any one of [1] to [4] above, comprising a step of irradiating the second fluid with ultrasonic waves or applying a high voltage pulse to the second fluid.

[0019] [6] The method for producing carbonated powder and granules described in [5] above, wherein the frequency of the ultrasonic waves is 20 kHz or more and 100 kHz or less.

[0020] [7] The method for producing carbonated powder or granules described in [5] above, wherein the voltage of the high voltage pulse is 1 kV or more and 200 kV or less.

[0021] [8] A method for producing carbonated powder or granules according to any one of [1] to [7] above, comprising a step of stirring the second fluid in the vertical direction.

[0022] [9] The method for producing carbonated powder and granules according to any one of [1] to [8] above, wherein the water supply flow rate to the fine bubble generating nozzle is 1 L / min or more and 2000 L / min or less.

[0023]

[10] The method for producing carbonated powder and granules according to any one of [1] to [9] above, wherein the flow rate of the gas supplied to the fine bubble generating nozzle is 0.1 to 1.5 times the flow rate of the water supplied to the fine bubble generating nozzle.

[0024]

[11] The method for producing carbonated powder or granules according to any one of [1] to

[10] above, wherein the viscosity of the first fluid and the second fluid at 20°C is 0.3 mPa·s or more and 40,000 mPa·s or less.

[0025]

[12] A method for producing carbonated powder or granules described in any one of [1] to

[11] above, wherein in the first fluid, the ratio of the mass of the water to the mass of the powder or granules to be carbonated is 1.0 or more and 100 or less.

[0026]

[13] The method for producing carbonated powder or granules according to any one of [1] to

[12] above, wherein the carbon dioxide content in the gas is 1% by volume or more and 100% by volume or less.

[0027]

[14] The method for producing carbonated powder or granules described in any one of [1] to

[13] above, wherein the minimum value of the inner diameter of the fine bubble generating nozzle is equal to or greater than the maximum particle size of the powder or granules to be carbonated.

[0028]

[15] The method for producing carbonated powder or granules according to any one of [1] to

[14] above, wherein the total time for the carbonation reaction is 1 minute or more and 1,440 minutes or less.

[0029]

[16] The method for producing carbonated powder or granules according to any one of [1] to

[15] above, wherein the powder or granules to be carbonated consist of particles containing at least one selected from CaO, MgO, MnO, and Fe.

[0030]

[17] The method for producing carbonated powder and granules described in

[16] above, wherein the powder and granules to be carbonated are steel slag.

[0031]

[18] The method for producing carbonated powder and granules described in

[17] above, wherein the steel slag is steelmaking slag.

[0032]

[19] The method for producing carbonated powder and granules described in

[16] above, wherein the powder and granules to be carbonated are waste concrete.

[0033]

[20] A method for producing carbonated powder or granules according to any one of [1] to

[19] above, wherein the powder or granules to be carbonated have a maximum particle size of 53 mm or less.

[0034] According to the present invention, it is possible to provide a method for producing carbonated powder and granules which places less strain on the environment, allows stable operation, and can achieve high carbonation efficiency.

[0035] FIG. 1 is a schematic diagram of a manufacturing apparatus 100 capable of carrying out a method for producing carbonated powder and granules according to one embodiment of the present invention. FIG. 2 is a schematic diagram of a manufacturing apparatus 102 capable of carrying out a method for producing carbonated powder and granules according to one embodiment of the present invention, and having an ultrasonic irradiation device 26 or a high-voltage pulse application device 28. FIG. 3 is a schematic diagram of a manufacturing apparatus 104 capable of carrying out a method for producing carbonated powder and granules according to one embodiment of the present invention, and having an ultrasonic irradiation device 26 or a high-voltage pulse application device 28. FIG. 4 is a diagram showing (a) a perspective view, (b) a cross-sectional view in a plane parallel to the length direction, and (c) the behavior of fine bubbles in a cross-section perpendicular to the length direction of a static mixer applicable to one embodiment of the present invention. FIG. 5 is a schematic diagram of a manufacturing apparatus 106 capable of carrying out a method for producing carbonated powder and granules according to one embodiment of the present invention.

[0036] Hereinafter, an embodiment of the method for producing carbonated powder and granules according to the present invention will be described. Note that the embodiment described below is an example of the present invention, and the configuration of the present invention is not limited to this specific example.

[0037] 1 is a schematic diagram of a manufacturing apparatus 100 capable of carrying out a method for manufacturing carbonated powder and granular material according to one embodiment of the present invention. The manufacturing apparatus 100 includes a sample supply pipe 10, a mixing tank 12, a first pipe 14, a fine bubble generating nozzle 16, a second pipe 18, a valve 20, a third pipe 22, and a pump 24. The sample supply pipe 10 and the second pipe 18 are connected to the mixing tank 12, and the first pipe 14 is connected to the bottom of the mixing tank 12. A valve 20 is installed midway through the first pipe 14, and the third pipe 22 branches off from it. A liquid delivery pump 24 is also installed midway through the first pipe 14. The first pipe 14 is connected to the supply port of the fine bubble generating nozzle 16, and the second pipe 18 is connected to the injection port.

[0038] First, the powder C to be carbonated is supplied to the mixing tank 12 through the sample supply pipe 10 and mixed with water (not shown) separately supplied into the mixing tank 12 to form a first fluid L1.

[0039] <Carbonated Powder C> The carbonated powder C is a substance to be carbonated. That is, the carbonated powder C reacts with carbon dioxide to produce carbonated powder. The carbonated powder C is preferably a substance containing at least one selected from CaO, MgO, MnO, and Fe. When the carbonated powder C contains at least one selected from CaO, MgO, MnO, and Fe, Ca, Mg, Mn, and Fe can be dissolved as ions from the carbonated powder C into water when water is supplied. Furthermore, the carbonated powder C preferably contains T-Fe as Fe. The total content of CaO, MgO, MnO, and T-Fe in the carbonated powder C is preferably 1 to 100% by mass.

[0040] As the powder to be carbonated C, it is preferable to use steel slag, and more preferably steelmaking slag, because it contains CaO, MgO, MnO, and T-Fe. Examples of steelmaking slag include converter slag, secondary refining slag, electric furnace slag, and hot metal pretreatment slag. For the same reason, it is preferable that the powder to be carbonated C be waste concrete. In addition to steel slag and waste concrete, sludge, dust, etc. can also be used as the powder to be carbonated C because the metal ions contained therein can be dissolved in water by supplying water.

[0041] If the maximum particle size of the powder to be carbonated C is 53 mm or less, the carbonation reaction in water can be suitably promoted. Therefore, the maximum particle size of the powder to be carbonated C is preferably 53 mm or less, more preferably 4.75 mm or less, and even more preferably 2.36 mm or less. Here, the maximum particle size means that when sieved using a sieve with a nominal mesh size specified in JIS Z 8801-1:2019, the entire amount of the powder to be carbonated C passes through the sieve with the corresponding nominal mesh size. On the other hand, there is no particular lower limit for the maximum particle size of the powder to be carbonated C, but the maximum particle size is generally 0.001 mm or more.

[0042] <Water> The type of water is not particularly limited and may be any common water type. Examples of water that can be used include tap water, distilled water, ion-exchanged water, pure water, rainwater, well water, lake water, river water, brackish water, salt water, seawater, and hot spring water.

[0043] [First Fluid L1] A fluid obtained by mixing powder and granules C to be carbonated and water is referred to as the first fluid L1. In the first fluid L1, if the ratio of the mass of water to the mass of powder and granules C to be carbonated is 1.0 or more, the fluidity of the first fluid L1 can be favorably obtained, and the carbonation reaction described below can be favorably progressed. Therefore, the ratio of the mass of water to the mass of powder and granules C to be carbonated is preferably 1.0 or more, and more preferably 3 or more. On the other hand, if the ratio of the mass of water to the mass of powder and granules C to be carbonated is 100 or less, the carbonation reaction can be favorably prevented from becoming inefficient. Therefore, the ratio of the mass of water to the mass of powder and granules C to be carbonated is preferably 100 or less, and more preferably 5 or less.

[0044] When the viscosity of the first fluid L1 at 20°C is 0.3 mPa·S or more, the generation of fine bubbles described below can be suitably achieved. Therefore, the viscosity of the first fluid L1 at 20°C is preferably 0.3 mPa·S or more, and more preferably 1.0 mPa·S or more. On the other hand, when the viscosity of the first fluid L1 at 20°C is 40,000 mPa·S or less, the generation of bubbles with a particle size larger than 100 μm can be suitably prevented. Therefore, the viscosity of the first fluid L1 at 20°C is preferably 40,000 mPa·S or less, and more preferably 30 mPa·S or less.

[0045] The viscosity of the first fluid L1 can be measured using a rotational viscometer as described in JIS Z 8803 "Liquid viscosity - measurement method."

[0046] (Supplying Step) The first fluid L1 passes through the first pipe 14 connected to the bottom of the mixing tank 12, is pumped by the pump 24, and is supplied to the fine bubble generating nozzle 16. Furthermore, a gas containing carbon dioxide is supplied from the gas supply pipe 30 to the fine bubble generating nozzle 16. As a result, water contained in the first fluid L1 and the gas containing carbon dioxide are supplied to the fine bubble generating nozzle 16. The gas containing carbon dioxide is supplied to the nozzle 16 via the gas supply pipe 30 and the gas supply pump 32. The supplied gas is received in the mixing tank 12 from the second pipe 18 after completion of the carbonation reaction described below, and unreacted gas containing carbon dioxide can also be recovered from the mixing tank 12 via the gas recovery pipe 34. The recovered gas can be supplied again to the nozzle 16 by switching the valve 36.

[0047] When the flow rate of water supplied to the fine bubble generating nozzle 16 is 1 L / min or more, fine bubbles are suitably generated. Therefore, the flow rate of water supplied to the fine bubble generating nozzle 16 is preferably 1 L / min or more, and more preferably 10 L / min or more. On the other hand, when the flow rate of water supplied to the fine bubble generating nozzle 16 is 2000 L / min or less, the generation of bubbles with a particle size larger than 100 μm is suitably prevented. Therefore, the flow rate of water supplied to the fine bubble generating nozzle 16 is preferably 2000 L / min or less, and more preferably 100 L / min or less.

[0048] Fine bubbles are preferably generated when the flow rate of the gas containing carbon dioxide supplied to the fine bubble generating nozzle 16 is 0.1 L / min or more. Therefore, the flow rate of the gas containing carbon dioxide supplied to the fine bubble generating nozzle 16 is preferably 0.1 L / min or more, and more preferably 1 L / min or more. On the other hand, fine bubbles are preferably generated when the flow rate of the gas containing carbon dioxide supplied to the fine bubble generating nozzle 16 is 3000 L / min or less. Therefore, the flow rate of the gas containing carbon dioxide supplied to the fine bubble generating nozzle 16 is preferably 3000 L / min or less, and more preferably 1000 L / min or less.

[0049] Fine bubbles are preferably generated when the flow rate of the gas containing carbon dioxide supplied to the fine bubble generating nozzle 16 is 0.1 times or more the flow rate of the water supplied to the fine bubble generating nozzle 16. Therefore, the flow rate of the gas supplied to the fine bubble generating nozzle 16 is preferably 0.1 times or more, more preferably 0.5 times or more, the flow rate of the water supplied to the nozzle. On the other hand, when the flow rate of the gas supplied to the fine bubble generating nozzle 16 is 1.5 times or less the flow rate of the water supplied to the nozzle, the generation of bubbles with a particle size larger than 100 μm is preferably prevented. Therefore, the flow rate of the gas supplied to the fine bubble generating nozzle 16 is preferably 1.5 times or less, more preferably 1.0 times or less, the flow rate of the water supplied to the nozzle. The flow rate of the gas supplied to the fine bubble generating nozzle 16 should be sufficient to generate carbonated powder and granules from the powder and granules to be carbonated C, as described below.

[0050] [Gas Containing Carbon Dioxide] The gas containing carbon dioxide can be a mixed gas containing other gases such as nitrogen, oxygen, carbon monoxide, and water vapor. In this case, if the carbon dioxide content in the gas is 1% by volume or more, the carbon dioxide necessary for the carbonation reaction can be suitably supplied. Therefore, the carbon dioxide content in the gas is preferably 1% by volume or more, more preferably 5% by volume or more, and even more preferably 10% by volume or more. On the other hand, the upper limit of the carbon dioxide concentration in the gas is not particularly limited, and the carbon dioxide content in the gas may be 100% by volume.

[0051] [Fine Bubble Generating Nozzle 16] In the present invention, the fine bubble generating nozzle 16 is a nozzle that can spray a fluid containing fine bubbles by supplying water and gas. The fine bubble generating nozzle 16 preferably generates fine bubbles by any of the following methods: swirling liquid flow, static mixer, ejector, Venturi, pressurized dissolution, and cooling dissolution. Furthermore, the fine bubble generating nozzle 16 can be an aeration tube, which is an example of a static mixer. Note that the fine bubble generation conditions in this specification (such as the amount of water and gas supplied and the viscosity of the first fluid L1 and the second fluid L2) refer to the conditions that apply to the ejector-type fine bubble generating nozzle 16.

[0052] If the minimum value of the inner diameter of the fine bubble generating nozzle 16 is equal to or larger than the maximum particle size of the powder to be carbonated C, clogging of the fine bubble generating nozzle 16 can be suitably prevented. Therefore, the inner diameter of the fine bubble generating nozzle 16 is preferably equal to or larger than the maximum particle size of the powder to be carbonated C. On the other hand, the upper limit of the inner diameter of the fine bubble generating nozzle 16 is not particularly limited, but the inner diameter is generally equal to or smaller than 200 mm.

[0053] (Injection Step) Next, a step is performed in which a second fluid L2, which is a first fluid L1 dispersed with fine bubbles containing gas microbubbles containing carbon dioxide, is injected from the fine bubble generating nozzle 16. By injecting the first fluid L1 and fine bubbles from the fine bubble generating nozzle 16, the fine bubbles can be suitably dispersed within the first fluid L1. The injection port of the fine bubble generating nozzle 16 is connected to the second pipe 18, and the injected second fluid L2 returns to the mixing tank 12 through the second pipe 18.

[0054] [Fine Bubbles] When the average diameter of the fine bubbles sprayed from the fine bubble generating nozzle 16 is 0.3 μm or more, the fine bubbles move significantly through the second fluid L2, ensuring a favorable contact frequency with the powder C to be carbonated. Furthermore, the bursting of the fine bubbles generates cavitation, which peels off the carbonated material formed on the surface of the powder C to be carbonated, creating new unreacted areas and promoting the carbonation reaction, improving carbonation efficiency. Therefore, the average diameter of the fine bubbles is preferably 0.3 μm or more, and more preferably 0.5 μm or more. On the other hand, if the average diameter of the fine bubbles is less than 100.0 μm, they do not rise too much and remain in the second fluid L2, which is preferable. Therefore, the average diameter of the fine bubbles is preferably less than 100.0 μm, and more preferably 10.0 μm or less.

[0055] The average diameter of fine bubbles can be determined as follows: The particle size of each fine bubble contained in the fluid to be measured is determined by laser diffraction / scattering. The measured particle size and number are divided into 10 equally spaced intervals, and the volume average diameter is calculated using the following formula (1), which is the average diameter of the fine bubbles. Here, i is an integer of 1 to 100, and x ｉ is the representative particle size (mm) of the i-th particle size interval, and n ｉ is the number of particles in the i-th particle size interval. The representative particle size is the average of the maximum and minimum values ​​in that particle size interval.

[0056] If the fine bubbles do not contain microbubbles, i.e., if the number rate of microbubbles in the fine bubbles is 0.0%, high carbonation efficiency cannot be achieved. Furthermore, if the number rate of microbubbles in the fine bubbles is 0.5% or more, the frequency of contact with the powder / granule C to be carbonated can be favorably obtained, and carbonation can be promoted. Therefore, the number rate of microbubbles in the fine bubbles should be greater than 0.0%, preferably 0.5% or more, and more preferably 5.0% or more. On the other hand, the higher the number rate of microbubbles in the fine bubbles, the more preferable it is, and the number rate may even be 100.0%. The number rate of microbubbles in the fine bubbles is the ratio of the number of microbubbles to the total number of microbubbles and ultrafine bubbles contained in the fine bubbles.

[0057] The number rate of microbubbles among fine bubbles can be calculated as follows. For fine bubbles contained in the fluid to be measured, the particle size of each fine bubble is determined by the laser diffraction / scattering method, as described above. From the measurement results, bubbles with a particle size of 1 μm or more but less than 100 μm are defined as microbubbles, and bubbles with a particle size less than 1 μm are defined as ultrafine bubbles, and the number of each is calculated. The ratio of the number of microbubbles to the total number of microbubbles and ultrafine bubbles is defined as the number rate (%) of microbubbles among fine bubbles.

[0058] [Second Fluid L2] A fluid obtained by dispersing fine bubbles including microbubbles of a gas including carbon dioxide in the first fluid L1 is referred to as the second fluid L2.

[0059] If the viscosity of the second fluid L2 at 20°C is 0.3 mPa·S or more, the generation of fine bubbles described below can be suitably achieved. Therefore, the viscosity of the second fluid L2 at 20°C is preferably 0.3 mPa·S or more, and more preferably 1.0 mPa·S or more. On the other hand, if the viscosity of the second fluid L2 at 20°C is 40,000 mPa·S or less, the generation of bubbles with a particle size larger than 100 μm can be suitably prevented. Therefore, the viscosity of the second fluid L2 at 20°C is preferably 40,000 mPa·S or less, and more preferably 30 mPa·S or less.

[0060] The viscosity of the second fluid L2 can be measured in the same manner as the viscosity of the first fluid L1 described above.

[0061] (Carbonation step) Next, in the second fluid L2, at least a portion of the powder C to be carbonated is carbonated by carbon dioxide dissolved into the water from the fine bubbles through a carbonation reaction to obtain carbonated powder. The carbonation reaction progresses while the second fluid L2 passes through the second pipe 18, etc. After the carbonation reaction has progressed sufficiently, the second fluid L2 is contained in the mixing tank 12 and can be taken out from the third pipe 22 by switching the valve 20.

[0062] It is preferable to continue the carbonation reaction by supplying the second fluid L2 that has returned from the second pipe 18 to the mixing tank 12 again via the first pipe 14 to the fine bubble generating nozzle 16 and spraying it again from the fine bubble generating nozzle 16. By spraying the second fluid L2 again from the fine bubble generating nozzle 16, the total time for the carbonation reaction can be suitably secured.

[0063] When the total time for the carbonation reaction is 1 minute or longer, the carbonation reaction in water can be sufficiently promoted, and carbonated powder and granules can be suitably obtained. Therefore, the total time for the carbonation reaction is preferably 1 minute or longer, and more preferably 10 minutes or longer. On the other hand, when the total time for the carbonation reaction is 1,440 minutes or shorter, energy loss due to a decrease in carbonation efficiency can be suitably avoided. Therefore, the total time for the carbonation reaction is preferably 1,440 minutes or shorter, and more preferably 240 minutes or shorter.

[0064] (Ultrasonic irradiation step) It is preferable to have a step of irradiating the second fluid L2 with ultrasonic waves. By irradiating the second fluid L2 with ultrasonic waves, the collapse of the microbubbles is promoted by cavitation, and the effect of scraping the reacted surface of the powder / granules C to expose the unreacted surface can be enhanced. In addition, by irradiating the powder / granules C with ultrasonic waves and vibrating the powder / granules C to be carbonated, the outer shell can be destroyed, exposing the unreacted portion. Ultrasonic irradiation can be performed using a Hielscher UIP2000hdT.

[0065] FIG. 2 is a schematic diagram of a manufacturing apparatus 102 having an ultrasonic irradiation device 26, which can be used to implement a method for manufacturing carbonated powder and granular materials according to one embodiment of the present invention. In FIG. 2, after the second fluid L2 is sprayed from the fine bubble generating nozzle 16, the second fluid L2 is irradiated with ultrasonic waves from the ultrasonic irradiation device 26. FIG. 3 is a schematic diagram of a manufacturing apparatus 104 having an ultrasonic irradiation device 26, as another embodiment. In the manufacturing apparatus 104, the second fluid L2 is returned from the second pipe 18 to the mixing tank 12, and before it is sprayed again from the fine bubble generating nozzle 16 via the first pipe 14, the second fluid L2 is irradiated with ultrasonic waves from the ultrasonic irradiation device 26 within the first pipe 14. As such, the installation location of the ultrasonic irradiation device 26 is not limited, and it can be installed in any location where ultrasonic waves can be irradiated to the second fluid L2.

[0066] When the frequency of the ultrasonic waves is 20 kHz or more and 100 kHz or less, cavitation can be suitably generated. Therefore, the frequency of the ultrasonic waves is preferably 20 kHz or more and 100 kHz or less. Furthermore, from the viewpoint of improving carbonation efficiency, the output of the ultrasonic waves is preferably 1000 W or more, or preferably 16000 W or less.

[0067] Generally, the temperature of the water in the second fluid L2 increases over time due to vibrations caused by ultrasonic irradiation. In particular, when the temperature of the water in the second fluid L2 exceeds 100°C, the water evaporates and cavitation no longer occurs. Therefore, it is preferable to maintain the temperature of the water in the second fluid L2 below 100°C. On the other hand, although there is no particular lower limit for the temperature of the water in the second fluid L2, the water temperature is generally 20°C or higher.

[0068] If the ultrasonic irradiation time is 1 second or more from the time the second fluid L2 is sprayed from the fine bubble generating nozzle 16 until it is sprayed again, the carbonation reaction in the water will proceed and carbonated powder and granules will be obtained. Therefore, when the ultrasonic irradiation step is performed, the ultrasonic irradiation time is preferably more than 0 seconds, and 1 second or more. On the other hand, if the ultrasonic irradiation time is 10 seconds or less from the time the second fluid L2 is sprayed from the fine bubble generating nozzle 16 until it is sprayed again, the water temperature will be prevented from becoming too high and degassing will be prevented. Therefore, the irradiation time is preferably 10 seconds or less. In the present invention, the ultrasonic irradiation time is defined as the time during which the ultrasonic irradiation device 26 is operated.

[0069] After being irradiated with ultrasonic waves, the second fluid L2 is allowed to cool while being fed through the manufacturing apparatus until it is irradiated with ultrasonic waves again. That is, in the present invention, the cooling time can be calculated by dividing the total volume of the piping of the manufacturing apparatus by the water supply flow rate. From the viewpoint of suppressing carbonate decomposition, the cooling time of the second fluid L2 is preferably 30 seconds or more. On the other hand, from the viewpoint of treatment efficiency, the cooling time of the second fluid L2 is preferably 60 seconds or less. The cooling time of the second fluid L2 can be adjusted by adjusting the feeding speed of the second fluid L2.

[0070] (High-Voltage Pulse Application Step) It is preferable to have a step of applying a high-voltage pulse to the second fluid L2. By applying a high-voltage pulse to the second fluid L2, an electric discharge occurs in the liquid, and a current flows in the powder C to be carbonated, causing cracks along the reacted / unreacted interface, exposing the unreacted portion of the powder C to be carbonated. In addition, cavitation caused by the electric discharge promotes the collapse of microbubbles, enhancing the effect of scraping the reacted surface of the powder C to expose the unreacted surface. The high-voltage pulse can be applied using a SELFRAG ​​Lab manufactured by SELFRAG ​​AG.

[0071] FIG. 2 is a schematic diagram of a manufacturing apparatus 102 having a high-voltage pulse application device 28, which can be used to implement a method for manufacturing carbonated powder and granular material according to one embodiment of the present invention. In FIG. 2, after the second fluid L2 is sprayed from the fine bubble generating nozzle 16, a high-voltage pulse is applied to the second fluid L2 from the high-voltage pulse application device 28. FIG. 3 is a schematic diagram of a manufacturing apparatus 104 having a high-voltage pulse application device 28, as another embodiment. In the manufacturing apparatus 104, the second fluid L2 returns from the second pipe 18 to the mixing tank 12, and before it is sprayed again from the fine bubble generating nozzle 16 via the first pipe 14, a high-voltage pulse is applied from the high-voltage pulse application device 28 to the second fluid L2 within the first pipe. As such, the installation location of the high-voltage pulse application device 28 is not limited, and it can be installed anywhere where a high-voltage pulse can be applied to the second fluid L2.

[0072] If the voltage of the high-voltage pulse is 1 kV or more and 200 kV or less, electric disruption and cavitation can be suitably performed. Therefore, the voltage of the high-voltage pulse is preferably 1 kV or more and 200 kV or less. Furthermore, from the viewpoint of carbonation efficiency, the output of the high-voltage pulse is preferably 1000 W or more. On the other hand, the output of the high-voltage pulse is generally 6000 W or less.

[0073] From the viewpoint of power, the application time of the high-voltage pulse from the time when the second fluid L2 is sprayed from the fine bubble generating nozzle 16 until the time when the second fluid L2 is sprayed again is preferably 3.0 μs or less, and more preferably 1.0 μs or less. On the other hand, the application time of the high-voltage pulse is generally 0.1 μs or more. In the present invention, the application time of the high-voltage pulse is defined as the time during which current is flowed from the high-voltage pulse application device.

[0074] When the total application time for the entire carbonation reaction is 0.1 milliseconds or more, the carbonation reaction in water can proceed and carbonated powder and granules can be suitably obtained. Therefore, when the high-voltage pulse application step is performed, the total application time of the high-voltage pulses is more than 0.0 milliseconds, and preferably 0.1 milliseconds or more. On the other hand, the total application time for the entire carbonation reaction is approximately 10 milliseconds or less.

[0075] (Stirring Step) A method for producing carbonated powder and granules according to one embodiment of the present invention preferably includes a step of stirring the second fluid L2 in the vertical direction. Stirring in this manner increases the contact opportunity between the fine bubbles in the second fluid L2 and the powder and granules C to be carbonated, thereby accelerating the carbonation reaction. Stirring in the vertical direction also increases the time that the fine bubbles in the second fluid L2 remain in water. The stirring method should not cause the fine bubbles to escape from the water, and static stirring, such as with a static mixer, is preferred.

[0076] Figure 4(a) shows a perspective view of a static mixer that can be used in one embodiment of the present invention. Figure 4(b) shows a cross-sectional view of the static mixer taken along a plane parallel to its longitudinal direction and including its central axis. When a second fluid passes through a static mixer with this structure, fine bubbles in the second fluid are stirred vertically. Figure 4(c) shows the behavior of fine bubbles in a cross-section perpendicular to the longitudinal direction of the static mixer. The static mixer rotates the second fluid clockwise, and the fine bubbles in the second fluid rise vertically upward due to gravity. As a result, the fine bubbles behave as shown in the right diagram of Figure 4(c), allowing them to be suitably stirred in the second fluid. The installation location of a stirring device such as a static mixer is not particularly limited, and they can be installed inside the first pipe 14 or the second pipe 18.

[0077] Figure 5 shows another embodiment of a manufacturing apparatus 106 capable of carrying out the method for manufacturing carbonated powder and granular materials according to the present invention. In Figure 5, the same components as those in Figure 1 are denoted by the same reference numerals. As shown in Figure 5, the fine bubble generating nozzle 16 may be installed inside the mixing tank 12 so as to be immersed in the first fluid L1. In this case, the first piping 14, pump 24, and second piping 18 are omitted. The first fluid L1 is introduced into the fine bubble generating nozzle 16 through a supply port located below the fine bubble generating nozzle 16, and a gas containing carbon dioxide is supplied to the fine bubble generating nozzle 16 via the gas supply piping 30 to generate fine bubbles. The generated second fluid L2 can then be sprayed from a spray port located above the fine bubble generating nozzle 16.

[0078] The method for producing carbonated powder granules according to one embodiment of the present invention can efficiently produce carbonated powder granules from powder granules C to be carbonated. In other words, the method for producing carbonated powder granules according to one embodiment of the present invention has high carbonation efficiency. Here, carbonation efficiency refers to the ratio of the amount of carbonate contained in the actually produced carbonated powder granules to the amount of carbonate that can be produced (carbonate produceable amount) calculated from the total amount of CaO, MgO, MnO, and Fe contained in the powder granules C to be carbonated. In the present invention, the carbonation efficiency is 5.0% or more, preferably 60.0% or more, and more preferably 80.0% or more. Meanwhile, there is no particular upper limit to the carbonation efficiency, and the carbonation efficiency may be 100.0%.

[0079] Carbonation efficiency can be measured by the following method. First, the amount of carbonate that can be produced is calculated from the total amount of CaO, MgO, MnO, and Fe contained in the powder to be carbonated. After producing carbonated powder from the powder to be carbonated, the carbonate content in the carbonated powder is measured by thermogravimetric analysis. The carbonation efficiency can be calculated by dividing the measured carbonate content by the amount of carbonated material that can be produced.

[0080] For steps and conditions not described in this specification, conventional methods can be used.

[0081] A carbonation test was conducted using the manufacturing apparatus shown in Figure 1, Figure 2, or Figure 3 according to the following procedure. Converter furnace slag and waste concrete with a maximum particle size of 2.36 mm were prepared as powders to be carbonated. Table 1 shows the composition of the powders to be carbonated used.

[0082]

[0083] In each example, water and powder to be carbonated were mixed to form a first fluid. The first fluid and a gas containing carbon dioxide were then supplied to a fine bubble generating nozzle, and the second fluid was sprayed. The second fluid was circulated through the manufacturing apparatus until the total time of the carbonation reaction reached the time shown in Table 2, and the second fluid was sprayed again from the fine bubble generating nozzle. The temperature of the water in the second fluid was maintained at 20°C in the examples without ultrasonic irradiation, as described below. Table 2 shows the types of powder to be carbonated and water used, the supply flow rates of water and gas, the ratio of the gas supply flow rate to the water supply flow rate, the carbon dioxide concentration in the gas, the viscosity of the first fluid, L / S (the ratio of the mass of water to the mass of the powder to be carbonated in the first fluid), the maximum temperature of the water in the second fluid, and the total time of the carbonation reaction.

[0084] The fine bubble generating nozzle used was a YJ-6 manufactured by EnviroVision Co., Ltd. The YJ-6 is an ejector-type nozzle. The minimum inner diameter of the YJ-6 is 6 mm.

[0085] In some examples, ultrasonic waves were irradiated to the second fluid. The ultrasonic irradiation device used was a Hielscher UIP2000hdT, and the output was 2000W. In the "Ultrasonic Irradiation" column of Table 2, examples in which ultrasonic waves were irradiated are marked "Yes", and examples in which ultrasonic waves were not irradiated are marked "No". Table 2 shows the frequency of the ultrasonic waves irradiated, the ultrasonic irradiation time, and the cooling time for the examples in which ultrasonic waves were irradiated. The ultrasonic irradiation device was installed at a position corresponding to 26 in Figure 2.

[0086] Furthermore, in some examples, a high voltage pulse was applied to the second fluid. The high voltage pulse application device used was a SELFRAG ​​Lab manufactured by SELFRAG ​​AG, and the output was 1000 W. In the "High Voltage Pulse" column of Table 2, examples in which a high voltage pulse was applied are marked "Yes," and examples in which a high voltage pulse was not applied are marked "No." Table 2 shows the voltage of the applied high voltage pulse and the application time of the high voltage pulse for the examples in which a high voltage pulse was applied. The high voltage pulse application device was installed at a position corresponding to 28 in Figure 2.

[0087] Furthermore, in some examples, a stirring device was used to stir the second fluid when it was delivered. The stirring device used was a static mixer N10 manufactured by Noritake Co., Ltd. In the "Stirring" column of Table 2, examples in which a stirring device was used are marked "Yes," and examples in which a stirring device was not used are marked "No." The stirring device was installed at a position corresponding to 18 in Figure 2.

[0088] In Comparative Example No. 43, the same procedure as above was carried out except that no nozzle was used. In Comparative Example No. 44, the same procedure as above was carried out except that water was not supplied. In Comparative Example No. 46, the same procedure as above was carried out except that no gas was supplied. In Comparative Example No. 48, the same procedure as above was carried out except that gas not containing carbon dioxide was supplied. Furthermore, in Comparative Examples Nos. 45, 47, and 49, no fine bubbles were generated from the fine bubble generating nozzle. In Comparative Example No. 53, a nozzle (model: OKE-MB04FJ-A10L) manufactured by OK Engineering Co., Ltd. was used as the fine bubble generating nozzle, and all of the bubbles sprayed from the fine bubble generating nozzle were ultrafine bubbles.

[0089] The second fluid after the reaction was removed, and the average diameter of the fine bubbles and the number rate of microbubbles among the fine bubbles were measured using the method described above. Furthermore, the viscosity of the second fluid at 20°C was measured using the method described above. Furthermore, the carbonate content and carbonation efficiency of the solid content of the obtained second fluid, i.e., the carbonated powder, were determined using the method described above. Table 2 shows the viscosity, average bubble diameter, microbubble number rate, carbonate production amount, carbonate content, and carbonation efficiency of the second fluid at 20°C.

[0090]

[0091] As shown in Table 2, in the inventive examples that satisfied the requirements of the present invention, the carbonation efficiency was 5.0% or more, and carbonated powder and granules were produced with high carbonation efficiency. On the other hand, in the comparative examples that did not satisfy the requirements of the present invention, the carbonation efficiency was less than 5.0%, and sufficient carbonate was not produced. Furthermore, particularly high carbonation efficiencies were obtained in inventive examples Nos. 33, 34, 51, and 52, which were irradiated with ultrasound, Nos. 35 and 36, which were applied with high-voltage pulses, and No. 37, which used a stirrer.

[0092] According to the present invention, it is possible to provide a method for producing carbonated powder and granules which places less strain on the environment, allows stable operation, and can achieve high carbonation efficiency.

[0093] 100 Manufacturing apparatus 102 Manufacturing apparatus 104 Manufacturing apparatus 106 Manufacturing apparatus 10 Sample supply pipe 12 Mixing tank 14 First pipe 16 Fine bubble generating nozzle 18 Second pipe 20 Valve 22 Third pipe 24 Pump 26 Ultrasonic irradiation device 28 High voltage pulse application device 30 Gas supply pipe 32 Gas supply pump 34 Gas recovery pipe 36 Valve C Powder to be carbonated L1 First fluid L2 Second fluid

Claims

1. A process of supplying a first fluid, which is a mixture of water and a carbonation-to-carbonate powder, and a gas containing carbon dioxide to a fine bubble generating nozzle, A step of injecting a second fluid from the fine bubble generating nozzle, in which fine bubbles containing microbubbles of the gas are dispersed within the first fluid, A step of obtaining carbonated powder by a carbonation reaction in which at least a portion of the powder to be carbonated is carbonated by carbon dioxide dissolved from the fine bubbles into the water in the second fluid, A method for producing carbonated granules having the following characteristics.

2. The method for producing carbonated granules according to claim 1, wherein the carbonation reaction is continued by supplying the second fluid to the fine bubble generating nozzle and spraying it again from the fine bubble generating nozzle.

3. A method for producing carbonated powder according to claim 1 or 2, wherein the average diameter of the fine bubbles is 0.3 μm or more and less than 100.0 μm, and the number ratio of microbubbles in the fine bubbles is 0.5% or more and 100.0% or less.

4. The method for producing carbonated powder according to claim 1 or 2, wherein the fine bubble generating nozzle is of any of the following types: swirling liquid flow type, static mixer type, ejector type, venturi type, pressurized dissolution type, and cooling dissolution type.

5. A method for producing carbonated granules according to claim 1 or 2, comprising the step of irradiating the second fluid with ultrasonic waves or applying high-voltage pulses.

6. The method for producing carbonated granules according to claim 5, wherein the frequency of the ultrasonic waves is 20 kHz or more and 100 kHz or less.

7. The method for producing carbonated powder according to claim 5, wherein the voltage of the high-voltage pulse is 1 kV or more and 200 kV or less.

8. A method for producing carbonated granules according to claim 1 or 2, comprising the step of stirring the second fluid in a vertical up-and-down direction.

9. A method for producing carbonated powder according to claim 1 or 2, wherein the water supply flow rate to the fine bubble generating nozzle is 1 L / min or more and 2000 L / min or less.

10. A method for producing carbonated powder according to claim 1 or 2, wherein the flow rate of the gas supplied to the fine bubble generating nozzle is 0.1 times or more and 1.5 times or less the flow rate of the water supplied to the fine bubble generating nozzle.

11. A method for producing carbonated powder according to claim 1 or 2, wherein the viscosity of the first fluid and the second fluid at 20°C is 0.3 mPa·s or more and 40,000 mPa·s or less.

12. The method for producing carbonated granules according to claim 1 or 2, wherein in the first fluid, the ratio of the mass of water to the mass of the carbonated granules is 1.0 or more and 100 or less.

13. A method for producing carbonated powder according to claim 1 or 2, wherein the carbon dioxide content in the gas is 1% by volume or more and 100% by volume or less.

14. The method for producing carbonated powder according to claim 1 or 2, wherein the minimum value of the inner diameter of the fine bubble generating nozzle is equal to or greater than the maximum particle size of the powder to be carbonated.

15. A method for producing carbonated powder according to claim 1 or 2, wherein the total time of the carbonation reaction is 1 minute or more and 1440 minutes or less.

16. The method for producing carbonated powder according to claim 1 or 2, wherein the carbonated powder consists of particles containing at least one selected from CaO, MgO, MnO, and Fe.

17. The method for producing carbonated powder according to claim 16, wherein the powder to be carbonated is steel slag.

18. The method for producing carbonated granular material according to claim 17, wherein the steel slag is steelmaking slag.

19. The method for producing carbonated granules according to claim 16, wherein the carbonated granules are waste concrete.

20. The method for producing carbonated powder or granules according to claim 1 or 2, wherein the maximum particle size of the carbonated powder or granules is 53 mm or less.