Method for producing carbonated sludge water, apparatus for producing carbonated sludge water, and method for producing mortar or concrete

Abstract

To provide a method for producing carbonated sludge water that can simply reduce the emission of carbon dioxide into the atmosphere, an apparatus for producing carbonated sludge water used in the production method, and a method for producing mortar or concrete using the carbonated sludge water obtained by using the production method as a material.SOLUTION: A method for producing carbonated sludge water according to the present invention comprises: (1) a step of obtaining sludge water containing carbon dioxide by blowing a gas containing carbon dioxide into sludge water; and (2) a step of obtaining carbonated sludge water by passing the sludge water containing carbon dioxide obtained in the step (1) through a reactor configured to be able to generate fine bubbles. The reactor includes a cylindrical member in which a flow path is formed and a plurality of protruding members provided so as to project inward from an inner circumferential surface of the cylindrical member.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for producing carbonated sludge water, an apparatus for producing carbonated sludge water, and a method for producing mortar or concrete. [Background technology]

[0002] At ready-mix concrete plants, concrete product plants, construction sites, etc., washing wastewater containing aggregate is generated when transport vehicles, mixer trucks, etc. The water from which the aggregate is separated and recovered from the washing wastewater is separated into supernatant water containing calcium ions and the like eluted from cement, and sludge water containing sludge solids, the majority of which are hydration products such as calcium hydroxide and calcium silicate hydrate.

[0003] Sludge water can be reused as mixing water for concrete. However, sludge solids contained in sludge water solidify due to a hydration reaction between the water and the sludge solids contained in the sludge water, making it difficult to store for long periods of time. For this reason, most sludge water is separated into water and sludge solids using a filter press or other device before being disposed of.

[0004] In recent years, one method for effectively utilizing sludge water has been investigated, which involves injecting carbon dioxide into the sludge water and reacting the calcium oxide contained in the sludge water with the carbon dioxide to produce calcium carbonate, thereby carbonated the sludge water. Carbonated sludge water obtained by this method (hereinafter referred to as carbonated sludge water) is not only reused as mixing water for concrete, but also attempts have been made to separate the carbonated sludge water into calcium carbonate, the hydration product, and water, and reuse the resulting calcium carbonate as a material for, for example, agricultural products such as fertilizer, industrial products such as paper, and building materials.

[0005] As a method for producing carbonated sludge water, for example, Patent Document 1 discloses a method of blowing carbon dioxide into sludge water, and more specifically describes blowing carbon dioxide by simple bubbling, as well as by bubbling with stirring and by bubbling with ultrasonic irradiation. Furthermore, Patent Document 2 discloses a method of precipitating calcium carbonate from sludge liquid using a precipitation reaction apparatus formed in a sealed atmospheric pressure vessel. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-163821 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-279552 Summary of the Invention [Problem to be solved by the invention]

[0007] In recent years, growing awareness of environmental issues has led to a demand for reducing carbon dioxide emissions into the atmosphere. However, for example, in the method described in Patent Document 1, the injected carbon dioxide does not react sufficiently with calcium oxide in the sludge water, and there is a risk that a large amount of carbon dioxide will be released into the atmosphere.

[0008] Furthermore, for example, in the method described in Patent Document 2, even if a precipitation reaction apparatus is formed in a sealed atmospheric pressure vessel, the atmospheric pressure vessel must be provided with a stirrer, a carbon dioxide inlet, and the like, and therefore it is difficult to completely seal the inside of such an atmospheric pressure vessel, and as a result, there is a risk that a large amount of carbon dioxide supplied into the main body of the precipitation reaction apparatus will be released into the atmosphere.

[0009] The present invention has been made in consideration of the above circumstances, and aims to provide a method for producing carbonated sludge water that can easily reduce the release of carbon dioxide into the atmosphere, a carbonated sludge water production apparatus used in the production method, and a method for producing mortar or concrete that uses carbonated sludge water obtained using the production method as a material. [Means for solving the problem]

[0010] The method for producing carbonated sludge water according to the present invention is a method for producing carbonated sludge water by reacting calcium oxide in sludge water with carbon dioxide, Step (1): A step of blowing a gas containing carbon dioxide into sludge water to obtain sludge water containing carbon dioxide; Step (2): Passing the carbon dioxide-containing sludge water obtained in step (1) through a reactor capable of generating fine bubbles to obtain carbonated sludge water; Equipped with The reactor includes a cylindrical member having a flow path formed therein, and a plurality of protruding members provided to protrude inward from the inner circumferential surface of the cylindrical member.

[0011] According to this configuration of the method for producing carbonated sludge water, sludge water containing carbon dioxide is passed through a reactor, whereby the sludge water comes into contact with a plurality of protruding members provided on the reactor, generating fine carbon dioxide bubbles. In this way, rather than injecting carbon dioxide as fine bubbles beforehand, fine carbon dioxide bubbles are generated while the sludge water containing carbon dioxide is passing through the reactor, allowing the carbon dioxide to sufficiently react with calcium oxide in the sludge water, thereby reducing the release of carbon dioxide into the atmosphere. Furthermore, this configuration does not require complex equipment such as a sealed atmospheric pressure vessel, and allows for a simple reduction in the release of carbon dioxide into the atmosphere.

[0012] The method for producing carbonated sludge water according to the present invention further comprises: Step (3): A step of measuring the pH of the carbonated sludge water obtained in the step (2). The steps (1) to (3) may be repeated until the pH measured in the step (3) falls within the range of 6.0 to 7.0.

[0013] The inventors have found that the pH decreases as the amount of calcium oxide that reacts with carbon dioxide decreases, and that the injected carbon dioxide hardly reacts when the pH falls within the range of 6.0 to 7.0. Therefore, in the method for producing carbonated sludge water, steps (1) to (3) are repeated until the pH falls within the range of 6.0 to 7.0, making it possible to easily control the amount of carbon dioxide-containing gas that is not injected into the sludge water in excess, and thus making it possible to further easily reduce the release of carbon dioxide into the atmosphere.

[0014] In the method for producing carbonated sludge water of the present invention, in step (1), the ratio of the mass of sludge solids in the sludge water to the volume of carbon dioxide blown into the sludge water per minute may be 0.0200 kg / L or more.

[0015] The method for producing carbonated sludge water according to the present invention, with such a configuration, prevents excessive injection of gas containing carbon dioxide into the sludge water, thereby further reducing the release of carbon dioxide into the atmosphere.

[0016] In the method for producing carbonated sludge water according to the present invention, the reactor is a static mixer.

[0017] The method for producing carbonated sludge water according to the present invention has such a configuration that fine bubbles of carbon dioxide can be generated more effectively while passing carbon dioxide-containing sludge water through a static mixer, which makes it easier for the carbon dioxide to react with calcium oxide in the sludge water and further reduces the release of carbon dioxide into the atmosphere. Furthermore, this configuration does not require complex equipment such as a stirrer, making it possible to more simply reduce the release of carbon dioxide into the atmosphere.

[0018] The carbonated sludge water production apparatus according to the present invention is an apparatus for producing carbonated sludge water used in the above-mentioned method for producing carbonated sludge water, and includes: a flow path for distributing sludge water; a blowing unit that blows a gas containing carbon dioxide into the flow path; a reactor configured to allow sludge water containing carbon dioxide to pass through and generate fine bubbles; Equipped with The reactor includes a cylindrical member having a flow path formed therein, and a plurality of protruding members provided to protrude inward from the inner circumferential surface of the cylindrical member.

[0019] According to the configuration of the carbonated sludge water production apparatus of the present invention, by passing sludge water containing carbon dioxide through a reactor, the sludge water comes into contact with the multiple protrusions of the reactor, generating fine carbon dioxide bubbles. By generating fine carbon dioxide bubbles while passing sludge water containing carbon dioxide through the reactor, the carbon dioxide can sufficiently react with calcium oxide in the sludge water, thereby reducing the release of carbon dioxide into the atmosphere. Furthermore, this configuration does not require complex equipment such as a sealed atmospheric pressure vessel, and allows for a simple reduction in the release of carbon dioxide into the atmosphere.

[0020] The method for producing mortar or concrete according to the present invention includes a step of kneading the carbonated sludge water produced by the above-described method for producing carbonated sludge water, cement, and aggregate.

[0021] According to the above-described configuration, the method for producing mortar or concrete of the present invention can produce mortar or concrete using carbonated sludge water while easily reducing the release of carbon dioxide into the atmosphere. [Effects of the Invention]

[0022] According to the present invention, it is possible to provide a method for producing carbonated sludge water that can easily reduce the release of carbon dioxide into the atmosphere, a carbonated sludge water production apparatus used in the production method, and a method for producing mortar or concrete that uses carbonated sludge water obtained using the production method as a material. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a cross-sectional view of a reactor 1 taken along a flow direction S. [Figure 2] FIG. 2 is a schematic diagram showing one aspect of the carbonated sludge water production apparatus M according to this embodiment. [Figure 3] FIG. 3 is a schematic diagram showing another aspect of the carbonated sludge water production apparatus M according to this embodiment. [Figure 4] FIG. 4 is a graph obtained by plotting the CO2 supply time on the horizontal axis and the CO2 / CaO and pH of the sludge water on the vertical axis in Example 2-1. [Figure 5] FIG. 5 is a graph obtained by plotting the CO2 supply time on the horizontal axis and the CO2 / CaO and pH of the sludge water on the vertical axis in Example 2-2. [Figure 6] FIG. 6 is a graph obtained by plotting the CO2 supply time on the horizontal axis and the CO2 / CaO and pH of the sludge water on the vertical axis in Example 2-3. [Figure 7] FIG. 7 is a graph obtained by plotting the CO2 supply time on the horizontal axis and the CO2 / CaO and pH of the sludge water on the vertical axis in Example 2-4. [Figure 8] FIG. 8 is a graph obtained by plotting the CO2 supply time on the horizontal axis and the CO2 / CaO and pH of the sludge water on the vertical axis in Example 2-5. [Figure 9] FIG. 9 is a graph obtained by plotting the CO2 supply time on the horizontal axis and the CO2 / CaO and pH of the sludge water on the vertical axis in Example 2-6. DETAILED DESCRIPTION OF THE INVENTION

[0024] The following describes the method for producing carbonated sludge water, the apparatus for producing carbonated sludge water, and the method for producing mortar or concrete according to this embodiment.

[0025] (Method of producing carbonated sludge water) The method for producing carbonated sludge water according to the present embodiment is a method for producing carbonated sludge water by reacting calcium oxide in sludge water with carbon dioxide, Step (1): A step of blowing a gas containing carbon dioxide into sludge water to obtain sludge water containing carbon dioxide; Step (2): Passing the carbon dioxide-containing sludge water obtained in step (1) through a reactor configured to generate fine bubbles to obtain carbonated sludge water; Equipped with.

[0026] In this specification, sludge water refers to water containing sludge solids, which is obtained by removing aggregate from the wastewater used to wash vehicles, mixers, and other equipment in ready-mix concrete plants. The sludge solids are mostly composed of hydration products and also contain aggregate particles. The hydration products include calcium-based compounds, such as calcium oxide, calcium hydroxide, calcium silicate hydrate, and calcium aluminate hydrate.

[0027] The cement used as a raw material for ready-mixed concrete is not particularly limited, and examples thereof include Portland cements such as ordinary Portland cement, high-early-strength Portland cement, ultra-high-early-strength Portland cement, low-heat Portland cement, moderate-heat Portland cement, sulfate-resistant Portland cement, and white Portland cement, as specified in JIS R 5210:2019; blended cements such as blast-furnace cement, fly ash cement, and silica cement; ultra-rapid-hardening cement, and alumina cement. One type of cement may be used alone, or two or more types may be used in combination.

[0028] <Process (1)> In step (1), a gas containing carbon dioxide is blown into sludge water to obtain sludge water containing carbon dioxide.

[0029] Examples of the carbon dioxide-containing gas to be blown into the sludge water include industrial carbon dioxide, air, carbon dioxide generated during the burning of cement clinker, and exhaust gases containing nitrogen oxides.

[0030] The concentration of carbon dioxide contained in the carbon dioxide-containing gas is not particularly limited, and may be, for example, 0.004% by volume or more and 100% by volume or less.

[0031] The flow rate of the carbon dioxide-containing gas is not particularly limited, and may be, for example, 1 L / min or more and 1000 L / min or less.

[0032] The molar concentration of carbon dioxide per 1 L of sludge water is not particularly limited, and may be, for example, 0.001 mol / L or more and 0.2 mol / L or less.

[0033] The molar concentration of carbon dioxide can be calculated using the following formula (1) from the concentration of carbon dioxide, the flow rate of the gas containing carbon dioxide, the time for blowing the gas, and the volume of gas per mole under standard conditions (0°C, 1 atmosphere). Molar concentration of carbon dioxide (mol / L) = [(carbon dioxide concentration (volume%) / 100) ×Gas flow rate (L / min) × gas injection time (min)} / 22.4 / Amount of sludge water (L) (1)

[0034] The ratio of the mass of sludge solids in the sludge water to the volume of carbon dioxide injected into the sludge water per minute is preferably 0.0200 kg / L or more, and more preferably 0.0400 kg / L or more, from the viewpoint of preventing excessive injection of carbon dioxide-containing gas into the sludge water.

[0035] From the viewpoint of reducing carbon dioxide emissions into the atmosphere, the concentration of the sludge water is preferably 3% by mass or more and 50% by mass or less, and more preferably 5% by mass or more and 40% by mass or less. The concentration of the sludge water can be determined based on JIS A 1806:2011.

[0036] The content of calcium oxide contained in the sludge solid content is not particularly limited, but may be, for example, 10% by mass or more and 90% by mass or less relative to the total amount of the sludge solid content.

[0037] The calcium oxide content can be a value obtained by measurement using an X-ray fluorescence analyzer (for example, ZSX Primus IV manufactured by Rigaku Corporation) based on the method specified in JIS R 5204:2019.

[0038] The molar concentration of calcium oxide contained in 1 L of sludge water is not particularly limited, but may be, for example, 0.06 mol / L or more and 4.50 mol / L or less.

[0039] The molar concentration of calcium oxide can be calculated from the calcium oxide content (mass %), the molecular weight of calcium oxide, and the mass of the sludge solid content by using the following formula (2). Molar concentration of calcium oxide (mol / L) = [{amount of sludge water (g)] × (Sludge concentration (mass%) / 100)×0.8 × (calcium oxide content (mass%) / 100)} / 56] / Amount of sludge water (L) (2)

[0040] Step (1) can be carried out in a flow path that circulates sludge water through a reactor. In this case, the flow rate of the sludge water is not particularly limited and may be, for example, 1 L / min or more and 1000 L / min or less.

[0041] <Process (2)> In step (2), the sludge water containing carbon dioxide obtained in step (1) is passed through a reactor configured to generate fine bubbles to obtain carbonated sludge water.

[0042] In this specification, fine bubbles are bubbles with a volume-equivalent diameter of less than 100 μm, as defined in JIS B 8741-1:2019 and ISO 20480-1:2017. Fine bubbles are classified into two types, microbubbles and ultrafine bubbles, depending on the diameter of the bubbles. As defined in JIS B 8741-1:2019 and ISO 20480-1:2017, microbubbles are fine bubbles with a volume-equivalent diameter in the range of 1 μm or more and less than 100 μm, and ultrafine bubbles are fine bubbles with a volume-equivalent diameter of less than 1 μm.

[0043] From the viewpoint of allowing carbon dioxide to react sufficiently with calcium oxide in the sludge water, the volume-equivalent diameter of the fine bubbles is preferably 0.001 μm or more and 100 μm or less, and more preferably 1 μm or more and 100 μm or less. The volume-equivalent diameter of the fine bubbles can be determined by dynamic image analysis using, for example, a flow-type image analysis particle size / shape measurement device (manufactured by Shimadzu Science East Japan Co., Ltd.; Particle Insight).

[0044] The reactor, which is configured to generate fine bubbles, is provided with a cylindrical member having a flow path formed therein and a plurality of protrusion members protruding inward from the inner peripheral surface of the cylindrical member, from the viewpoint of reducing the release of carbon dioxide into the atmosphere.

[0045] Fig. 1 is a diagram showing an example of a reactor 1, and is a cross-sectional view taken along a flow direction S. The flow direction is the direction in which sludge water flows, and is the direction indicated by the arrow S in Fig. 1.

[0046] As shown in Fig. 1, the reactor 1 includes a cylindrical member 11 having a flow path formed therein, and a plurality of protruding members 12 provided so as to protrude inward from the inner peripheral surface of the cylindrical member 11. The protruding members 12 are blade members having a shape twisted by 180° in a spiral shape around the axis of the cylindrical member 11, and six of them are arranged consecutively along the flow direction S. Adjacent blade members may be arranged so as to be offset by a predetermined angle around the axis of the cylindrical member 11, and may be configured to be discontinuous overall. Adjacent blade members may also be arranged so as to rotate in opposite directions around the axis of the cylindrical member 11.

[0047] The number of protrusion members 12 is not particularly limited as long as it is capable of generating fine bubbles, and may be, for example, 8 or more or 58 or less.

[0048] From the viewpoint of facilitating the reaction between carbon dioxide and calcium oxide in the sludge water, such a reactor is preferably a static mixer. Examples of the static mixer include a static mixer.

[0049] The reaction temperature in the reaction between carbon dioxide and calcium oxide is preferably 1°C or higher and 50°C or lower, more preferably 1°C or higher and 35°C or lower, from the viewpoint of reducing the release of carbon dioxide into the atmosphere.

[0050] The reaction temperature can be adjusted, for example, by adjusting the temperature of the sludge water, for example, by leaving the sludge water in a thermostatic chamber or in the natural environment, by using a cooler in a water storage tank for storing the sludge water, or by arranging a cooler in the flow path of the sludge water.

[0051] <Process (3)> The method for producing carbonated sludge water according to this embodiment preferably further includes the following step (3), from the viewpoint of easily managing the gas containing carbon dioxide so that it is not blown into the sludge water in excess.

[0052] In step (3), the pH of the carbonated sludge water obtained in step (2) above can be measured.

[0053] The pH can be measured using a pH meter (for example, a glass electrode hydrogen ion concentration indicator manufactured by Toko Scientific Research Institute Co., Ltd.).

[0054] In the method for producing carbonated sludge water according to this embodiment, steps (1) to (3) can be repeated until the pH measured in step (3) is in the range of 6.0 or more and 7.0 or less, preferably 6.3 or more and 6.8 or less, from the viewpoint of easily controlling the amount of carbon dioxide-containing gas that is not blown into the sludge water in excess.

[0055] The method for producing carbonated sludge water according to this embodiment includes the above steps (1) and (2), and the reactor includes a cylindrical member having a flow path formed therein and a plurality of protruding members protruding inward from the inner circumferential surface of the cylindrical member, thereby reducing the release of carbon dioxide into the atmosphere. Furthermore, the method for producing carbonated sludge water according to this embodiment does not require complex equipment such as a sealed atmospheric pressure vessel, and can easily reduce the release of carbon dioxide into the atmosphere. Therefore, the method for producing carbonated sludge water according to this embodiment can easily reduce the release of carbon dioxide into the atmosphere, especially in an open system.

[0056] In addition, the method for producing carbonated sludge water according to this embodiment further includes the above-mentioned step (3), and by repeating the above-mentioned steps (1) to (3) until the pH measured in the above-mentioned step (3) falls within the range of 6.0 or more and 7.0 or less, it is possible to easily prevent excessive blowing of gas containing carbon dioxide into the sludge water, and in other words, it is possible to easily further reduce the release of carbon dioxide into the atmosphere.

[0057] (Carbonated sludge water production equipment) Hereinafter, a carbonated sludge water manufacturing apparatus M according to an embodiment of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are given the same reference numerals, and the description thereof will not be repeated.

[0058] The carbonated sludge water production apparatus M according to this embodiment will be described with reference to Figure 2. Figure 2 is a schematic diagram showing one embodiment of the carbonated sludge water production apparatus M according to this embodiment. As shown in Figure 2, one embodiment of the carbonated sludge water production apparatus M according to this embodiment comprises a flow path 2 for circulating sludge water, an inlet section 3 for injecting a gas containing carbon dioxide into the flow path, and a reactor 1 configured to pass the sludge water containing carbon dioxide and generate fine bubbles. In Figure 2, the flow direction is indicated by an arrow S.

[0059] The flow path 2 is configured to allow gas containing carbon dioxide to be blown in from the blowing section 3 described later, and is connected to the lower part of a water storage tank 4 that stores sludge water on the upstream side in the flow direction S, and is connected to a reactor 1 described later on the further downstream side in the flow direction S, so that sludge water can be supplied to the reactor 1. A pump (not shown) is provided in the flow path 2 to allow the sludge water to flow. The shortest distance between the blowing section 3 and the reactor 1 in the flow path 2 may be 0.5 cm or more and 5000 cm or less.

[0060] The blowing section 3 is configured to be able to blow a gas containing carbon dioxide into the flow path 2, upstream of the reactor 1 described below in the flow direction S. The blowing section 3 has an adjusting section (not shown) configured to be able to adjust the flow rate of the gas. Examples of the adjusting section include a valve, a regulator, etc.

[0061] The reactor 1 is the same as that used in the carbonated sludge water production method according to the present embodiment. The reactor 1 is connected to the upper side of the water storage tank 4 on the downstream side in the flow direction S, and is configured so that the carbonated sludge water obtained by passing through the reactor 1 can be stored in the water storage tank 4. As a result, the carbonated sludge water production apparatus M according to the present embodiment is configured so that sludge water and / or carbonated sludge water can be circulated.

[0062] The water storage tank 4 may be provided with a pH measurement unit (not shown). The pH measurement unit may be provided above the sludge water storage tank 4 or below the sludge water storage tank 4. The pH measurement unit may use the same pH meter as in the method for producing carbonated sludge water according to the present embodiment.

[0063] The carbonated sludge water manufacturing apparatus M according to this embodiment is used in the carbonated sludge water manufacturing method according to the embodiment described above.

[0064] Specifically, the carbonated sludge water manufacturing apparatus M performs the above step (1) by blowing gas containing carbon dioxide from blowing section 3 into sludge water flowing through flow path 2 to obtain sludge water containing carbon dioxide.

[0065] In addition, the carbonated sludge water manufacturing apparatus M performs step (2) by passing the sludge water containing carbon dioxide obtained in step (1) through the reactor 1, generating fine bubbles of carbon dioxide, and obtaining carbonated sludge water.

[0066] In the carbonated sludge water manufacturing apparatus M of this embodiment, the water tank 4 is connected to the reactor 1 above the water tank 4 and to the flow path 2 below the water tank 4, so that the step (3) is carried out by measuring the pH of the carbonated sludge water obtained in the step (2) in the pH measuring unit, and the steps (1) to (3) can be repeated until the pH measured in the step (3) falls within the range of 6.0 to 7.0.

[0067] In addition, as another aspect of the carbonated sludge water manufacturing apparatus M of this embodiment, as shown in Figure 3, the flow path 2 may be connected to a water tank 4 on the upstream side of the flow direction S, and the reactor 1 may be connected to a carbonated sludge water storage tank 4' capable of storing carbonated sludge water on the downstream side of the flow direction S.

[0068] The carbonated sludge water production apparatus M according to this embodiment may be provided with a swirling flow section (not shown) downstream of the reactor 1 in the flow direction S, which is configured to extend the reaction time between carbon dioxide and the sludge water by adding a swirling flow to the carbonated sludge water obtained in step (2) above. The carbonated sludge water production apparatus M may also be provided with a pressure vessel (not shown) downstream of the reactor 1 in the flow direction S, which is configured to apply pressure to the carbonated sludge water.

[0069] Furthermore, when the carbonated sludge water manufacturing apparatus M is equipped with a swirling flow section, the pressure vessel may be arranged downstream of the swirling flow section in the flow direction S, or upstream of the swirling flow section in the flow direction S.

[0070] The carbonated sludge water production apparatus M according to this embodiment may also include a temperature adjustment unit (not shown) to adjust the temperature of the sludge water and / or the carbonated sludge water. The temperature adjustment unit may be provided in at least one of the reactor 1, the flow path 2, and the water storage tank 4.

[0071] The temperature adjustment unit may be, for example, a cooler such as a chiller.

[0072] In the carbonated sludge water production apparatus M according to this embodiment, the reactor 1 includes a cylindrical member 11 having a flow path formed therein and a plurality of protruding members 12 protruding inward from the inner circumferential surface of the cylindrical member 11. By passing carbon dioxide-containing sludge water through the reactor 1, the sludge water comes into contact with the plurality of protruding members 12 provided on the reactor 1, generating fine carbon dioxide bubbles. By generating fine carbon dioxide bubbles while passing carbon dioxide-containing sludge water through the reactor 1, the carbon dioxide can sufficiently react with calcium oxide in the sludge water, thereby reducing the release of carbon dioxide into the atmosphere. Furthermore, by including the reactor 1, the carbonated sludge water production apparatus M according to this embodiment can easily reduce the release of carbon dioxide into the atmosphere without requiring a complex device such as a sealed atmospheric pressure vessel.

[0073] (Method of manufacturing cement molded body) The method for producing mortar or concrete according to this embodiment includes a step of kneading the carbonated sludge water produced by the above-described method for producing carbonated sludge water, cement, and aggregate.

[0074] The method for producing mortar or concrete according to this embodiment includes carbonated sludge water produced by the method for producing carbonated sludge water. Note that the method for producing mortar or concrete according to this embodiment may also include mixing the carbonated sludge water with other water, such as tap water, industrial water, recycled water, groundwater, river water, or rainwater.

[0075] The amount of the carbonated sludge water to be blended is, for example, a unit amount (kg / m 3 : Cement composition 1m 3 Mass per unit mass) is 0.5 kg / m 3 More than 300kg / m 3 It is possible to set the amount as follows: When the other water is mixed with the carbonated sludge water, the amount of water blended is the total amount of water blended.

[0076] The cement is not particularly limited, and may be any of the above cements.

[0077] The blending amount of the cement is, for example, a unit amount (kg / m 3 : Cement composition 1m 3 Mass per unit mass) is 200 kg / m 3 More than 500kg / m 3 When two or more cements are contained, the above blending amount is the total blending amount of the cements.

[0078] Fine aggregate and / or coarse aggregate can be used as aggregate. Fine aggregate is defined as aggregate that passes entirely through a 10 mm mesh sieve and at least 85% by mass passes through a 5 mm mesh sieve, while coarse aggregate is defined as aggregate that is retained by at least 85% by mass on a 5 mm mesh sieve (JIS A 0203:2019).

[0079] Examples of fine aggregates include natural sands such as river sand, land sand, mountain sand, sea sand, crushed sand, and crushed limestone sand, as specified in JIS A 5308:2019 Appendix A Aggregates for Ready-Mixed Concrete, and blast furnace slag. Silica sand produced by crushing and classifying silica may also be used. One type of fine aggregate may be used alone, or two or more types may be used in combination.

[0080] The amount of the fine aggregate to be mixed is, for example, a unit amount (kg / m 3 : Cement composition 1m 3 mass per unit mass), 600 kg / m 3 More than 1300kg / m 3 When two or more types of fine aggregate are contained, the above blending amount is the total blending amount of the fine aggregate.

[0081] Examples of coarse aggregate include natural aggregates such as river gravel, mountain gravel, and sea gravel, as specified in JIS A 5308:2019 Appendix A Aggregates for Ready-Mixed Concrete, artificial aggregates such as crushed stone such as sandstone, hard limestone, basalt, and andesite, and recycled aggregate. One type of coarse aggregate may be used alone, or two or more types may be used in combination.

[0082] The amount of the coarse aggregate to be mixed is, for example, a unit amount (kg / m 3 : Cement composition 1m 3 mass per unit mass), 600 kg / m 3 More than 1300kg / m 3 When two or more types of coarse aggregate are contained, the above blending amount is the total blending amount of the coarse aggregate.

[0083] In the method for producing a cement molded product according to this embodiment, mortar or concrete can be obtained by kneading the carbonated sludge water, cement, and aggregate.

[0084] The method for producing a cement molded body according to this embodiment includes carbonated sludge water produced from the above-mentioned carbonated sludge water, thereby making it possible to produce mortar or concrete while easily reducing the release of carbon dioxide into the atmosphere.

[0085] The method for producing carbonated sludge water, the apparatus for producing carbonated sludge water, and the method for producing mortar or concrete according to this embodiment are not limited to the above embodiments, and various modifications can be made within the scope that does not deviate from the gist of the present invention.

[0086] The present invention includes the following aspects. [1] A method for producing carbonated sludge water by reacting calcium oxide in sludge water with carbon dioxide, Step (1): A step of blowing a gas containing carbon dioxide into sludge water to obtain sludge water containing carbon dioxide; Step (2): Passing the carbon dioxide-containing sludge water obtained in step (1) through a reactor configured to generate fine bubbles to obtain carbonated sludge water; Equipped with A method for producing carbonated sludge water, wherein the reactor comprises a cylindrical member having a flow path formed therein and a plurality of protrusion members protruding inward from the inner surface of the cylindrical member. [2] Furthermore, Step (3): A step of measuring the pH of the carbonated sludge water obtained in the step (2). The method for producing carbonated sludge water according to [1], further comprising repeating steps (1) to (3) until the pH measured in step (3) falls within a range of 6.0 to 7.0. [3] A method for producing carbonated sludge water described in [1] or [2], wherein in step (1), the ratio of the mass of sludge solids in the sludge water to the volume of carbon dioxide blown into the sludge water per minute is 0.0200 kg / L or more. [4] The method for producing carbonated sludge water according to any one of [1] to [3], wherein the reactor is a static mixer. [5] An apparatus for producing carbonated sludge water used in the method for producing carbonated sludge water according to any one of [1] to [4], a flow path for distributing sludge water; a blowing unit that blows a gas containing carbon dioxide into the flow path; a reactor configured to allow sludge water containing carbon dioxide to pass through and generate fine bubbles; Equipped with The reactor is a carbonated sludge water manufacturing apparatus comprising a cylindrical member having a flow path formed therein and a plurality of protrusion members protruding inward from the inner surface of the cylindrical member. [6] A method for producing mortar or concrete, comprising a step of kneading carbonated sludge water produced by the method for producing carbonated sludge water described in any one of [1] to [4], cement, and aggregate. [Example]

[0087] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0088] (Materials used) Cement: Ordinary Portland cement (manufactured by Sumitomo Osaka Cement Co., Ltd.) was used. Water: Tap water was used.

[0089] (Sludge water preparation) Cement (1.5 kg, 4.0 kg, 7.9 kg, 16.7 kg, or 26.5 kg) was added to 150 L of tap water, mixed, and left for 30 minutes to obtain sludge water so that the concentration of the sludge water reached the specified concentration shown in each example and comparative example in Tables 1 and 2 below.

[0090] (Reactor) A static mixer (1-N33-131-F manufactured by Noritake Co., Ltd., protruding member: spirally twisted shape, number of blades: 6) was used as the reactor. The static mixer was the same as that shown in Figure 1.

[0091] The reactor was also confirmed to be capable of generating microbubbles using the following method. First, 100% carbon dioxide gas by volume was blown into tap water (flow rate: 25 L / min) at 20 L / min, and the resulting carbon dioxide-containing water was passed through the reactor to generate microbubbles. The microbubble diameter and number ratio were then measured using dynamic image analysis with a flow-type image analyzer for particle size and shape (Particle Insight, manufactured by Shimadzu Science East Japan Co., Ltd.). The results showed that the average bubble diameter was 57.1 μm and the number concentration was 940 bubbles / mL, confirming the generation of microbubbles. Furthermore, microbubbles were also confirmed to be generated when carbon dioxide-containing water was passed through the reactor and then further passed through a swirling flow section and a pressure vessel, where a pressure of 0.2 MPa was applied.

[0092] (Test 1) <Examples 1-1 to 1-7, 1-9 to 1-10, Comparative Example 1> Using a carbonated sludge water production apparatus M in another aspect of this embodiment, as shown in Figure 3, carbon dioxide gas with a concentration of 100% by volume was blown into 150 L of sludge water according to the conditions listed in Table 1, and the resulting sludge water containing carbon dioxide was passed through a reactor to obtain carbonated sludge water.

[0093] The carbonated sludge solids obtained by dehydrating the resulting carbonated sludge water were subjected to differential thermal analysis (TG-DTA) to determine the amount of carbon dioxide (unit: mass%) immobilized in the carbonated sludge solids through reaction with calcium oxide. The amount of carbon dioxide released was calculated using the following formula (I) and evaluated based on the following criteria. The results are shown in Table 1. ◎: The amount of carbon dioxide released is less than 1.0 L / min. ○: The amount of carbon dioxide released is 1.0 L / min or more and 10.0 L / min or less. ×: The amount of carbon dioxide released exceeds 10.0 L / min.

[0094]

number

[0095] <Example 1-8> The same procedure as in Example 1-1 was carried out, except that the sludge water containing carbon dioxide was passed through a reactor, and then passed through a swirl section and a pressure vessel to apply a pressure of 0.2 MPa. The results are shown in Table 1.

[0096] <Comparative Example 1> The same procedure as in Example 1-1 was carried out, except that the sludge water containing carbon dioxide was not passed through the reactor. The results are shown in Table 1.

[0097] [Table 1]

[0098] As can be seen from the results in Table 1, the methods for producing carbonated sludge water in each example that satisfied all of the configurations of the present invention released less than 10 L / min of carbon dioxide, meaning that most of the supplied carbon dioxide was carbonated. From this, it can be said that the methods for producing carbonated sludge water in each example can easily reduce the release of carbon dioxide into the atmosphere.

[0099] (Test 2) <Examples 2-1 to 2-5> Using a carbonated sludge water production apparatus M according to one embodiment of the present invention, as shown in Figure 2, 150 L of sludge water was blown with 100% by volume of carbon dioxide gas, the resulting sludge water containing carbon dioxide was passed through a reactor, and the resulting carbonated sludge water was discharged into a water tank and the pH in the water tank was measured using a pH meter (a glass electrode hydrogen ion concentration indicator manufactured by Toko Scientific Research Institute Co., Ltd.) according to the conditions of Examples 2-1 to 2-5 listed in Table 2. This procedure was repeated until the pH of the carbonated sludge water fell within the range of 6 to 7.

[0100] Using a carbon dioxide meter (a CO2 concentration, temperature, and humidity data logger manufactured by T&D Corporation), the concentration of carbon dioxide in the atmosphere was measured approximately 30 cm from the reactor outlet when the pH of the carbonated sludge water reached between 6 and 7, and the results were evaluated based on the following criteria. The results are shown in Table 2. ○: The carbon dioxide concentration is less than 1500 ppm. ×: The carbon dioxide concentration is 1500 ppm or more.

[0101] <Example 2-6> The same procedure as in Example 2-1 was carried out, except that the temperature of the sludge water was set to 5° C. The results are shown in Table 2.

[0102] The time it took for carbon dioxide to be injected into the sludge water was taken as the carbon dioxide supply time (hereinafter also referred to as CO2 supply time). For Examples 2-1 to 2-6, graphs were created in which the CO2 supply time was plotted on the horizontal axis and the ratio of the molar mass of carbon dioxide reacted with calcium oxide to the molar mass of calcium oxide in the sludge water (hereinafter also referred to as CO2 / CaO) and the pH of the sludge water were plotted on the vertical axis. Regarding CO2 / CaO, the value obtained using the molar mass of carbon dioxide obtained in an actual test was taken as the actual value, and the value obtained using the theoretical molar mass of carbon dioxide reacted with calcium oxide was taken as the theoretical value, and the respective values ​​were plotted. The results are shown in Figures 4 to 9.

[0103] [Table 2]

[0104] As can be seen from the results in Table 2, the methods for producing carbonated sludge water in each example that satisfied all of the configurations of the present invention had a carbon dioxide concentration of less than 1500 ppm, and therefore reduced the amount of carbon dioxide released. This shows that the methods for producing carbonated sludge water in each example allow the injected carbon dioxide to sufficiently react with the calcium oxide in the sludge water, and as a result, can easily reduce the release of carbon dioxide into the atmosphere.

[0105] 4 to 9, in the carbonated sludge water production methods of Examples 2-1 to 2-6, the pH gradually decreases when carbon dioxide is injected into the sludge water, and by injecting carbon dioxide into the sludge water until the pH of the carbonated sludge water falls within the range of 6 to 7, the release of large amounts of carbon dioxide can be suppressed. From this, the inventors discovered that the pH decreases as the amount of calcium oxide that reacts with carbon dioxide decreases, and that when the pH falls within the range of 6.0 to 7.0, the injected carbon dioxide hardly reacts at all. Therefore, in the carbonated sludge water production methods of each Example, by repeating the above steps (1) to (3) until the pH falls within the range of 6.0 to 7.0, it is possible to easily control the amount of carbon dioxide-containing gas injected into the sludge water so that it is not excessively injected. In other words, the release of carbon dioxide into the atmosphere can be further easily reduced.

[0106] Furthermore, since the carbonated sludge water produced using the carbonated sludge water of each example can reduce the release of carbon dioxide into the atmosphere, it can be said that the carbonated sludge water can be used to produce mortar or concrete while easily reducing the release of carbon dioxide into the atmosphere. [Explanation of symbols]

[0107] 1. Reactor 11 Cylindrical member 12 Protruding member 2 Flow path 3. Blowing section 4. Water tank 4' Carbonated Sludge Water Storage Tank M Carbonated sludge water production equipment S Distribution direction

Claims

1. A method for producing carbonated sludge water by reacting calcium oxide in sludge water with carbon dioxide, comprising: Step (1): A step of blowing a gas containing carbon dioxide into sludge water to obtain sludge water containing carbon dioxide; Step (2): Passing the carbon dioxide-containing sludge water obtained in step (1) through a reactor configured to generate fine bubbles to obtain carbonated sludge water; Equipped with A method for producing carbonated sludge water, wherein the reactor comprises a cylindrical member having a flow path formed therein and a plurality of protrusion members protruding inward from the inner surface of the cylindrical member.

2. moreover, Step (3): A step of measuring the pH of the carbonated sludge water obtained in the step (2). The method for producing carbonated sludge water according to claim 1, wherein steps (1) to (3) are repeated until the pH measured in step (3) is in the range of 6.0 to 7.

0.

3. A method for producing carbonated sludge water as described in claim 1 or 2, wherein in step (1), the ratio of the mass of sludge solids in the sludge water to the volume of carbon dioxide blown into the sludge water per minute is 0.0200 kg / L or more.

4. The method for producing carbonated sludge water according to claim 1 or 2, wherein the reactor is a static mixer.

5. 2. A carbonated sludge water producing apparatus used in the carbonated sludge water producing method according to claim 1, a flow path for distributing sludge water; a blowing unit that blows a gas containing carbon dioxide into the flow path; a reactor configured to allow sludge water containing carbon dioxide to pass through and generate fine bubbles; Equipped with The reactor is a carbonated sludge water manufacturing apparatus comprising a cylindrical member having a flow path formed therein and a plurality of protrusion members protruding inward from the inner surface of the cylindrical member.

6. A method for producing mortar or concrete, comprising a step of kneading carbonated sludge water produced by the method for producing carbonated sludge water according to claim 1, cement, and aggregate.

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