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

Abstract

A method for producing carbonated sludge water according to the present disclosure comprises: obtaining sludge water that contains carbon dioxide by blowing a gas which contains carbon dioxide into sludge water; and obtaining carbonated sludge water by passing the obtained sludge water that contains carbon dioxide through a reactor configured to be able to generate fine bubbles, wherein the reactor is provided with a cylindrical member inside which a flow path is formed and a plurality of protruding members which are provided so as to protrude inward from the inner peripheral surface of the cylindrical member.

Description

TITLE OF INVENTION: METHOD FOR PRODUCING CARBONATED SLUDGE WATER, DEVICE FOR PRODUCING CARBONATED SLUDGE WATER, AND METHOD FOR PRODUCING MORTAR OR CONCRETE CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to Japanese Patent Application No. 2024-054516, the disclosure of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present disclosure 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

[0003] At ready-mixed concrete plants, concrete product plants, construction sites, and the like, wastewater containing aggregate is generated by cleaning transport vehicles, mixer trucks, and the like. The water obtained after aggregate is separated and recovered from the wastewater is divided into supernatant water containing calcium ions and the like eluted from cement and sludge water containing sludge solids composed mostly of hydration products such as calcium hydroxide and calcium silicate hydrate.

[0004] The sludge water can be reused as mixing water for concrete. However, the sludge water is difficult to store for a long period because a hydration reaction occurs between the sludge solids contained in the sludge water and water, causing the sludge solids to solidify. Therefore, most sludge water is separated into water and sludge solids by a filter press or the like, and then discarded.

[0005] In recent years, as one method of effectively utilizing the sludge water, a method of carbonating the sludge water by blowing carbon dioxide into the sludge water and causing calcium oxide contained in the sludge water to react with the carbon dioxide to generate calcium carbonate has been studied. Attempts have been made not only to reuse the carbonated sludge water obtained by the method (hereinafter, referred to as 5 “carbonated sludge water”) as mixing water for concrete, but also to separate the carbonated sludge water into calcium carbonate, the above-described hydration products, and water and to reuse the obtained calcium carbonate, for example, as a material for agricultural products such as fertilizers, industrial products such as paper, building materials, and the like. 10

[0006] As a method for producing the carbonated sludge water, Patent Literature No. 1, for example, discloses a method of blowing carbon dioxide into the sludge water and, more specifically, describes blowing carbon dioxide by simple bubbling, bubbling while stirring, and bubbling while irradiating with ultrasonic waves. In addition, Patent Literature No. 2 discloses a method of precipitating calcium carbonate from a sludge 15 liquid using a precipitation reaction apparatus formed using a sealed ambient-pressure vessel.

[0007] In recent years, with growing awareness of environmental issues, there has been a demand to reduce the release of carbon dioxide into the atmosphere. However, in the method described in Patent Literature No. 1, for example, the carbon dioxide blown into 20 the sludge water cannot sufficiently react with calcium oxide in the sludge water and may be released into the atmosphere in a large amount.

[0008] Further, in the method described in Patent Literature No. 2, for example, even when the precipitation reaction apparatus is formed using a sealed ambient-pressure vessel, because the precipitation reaction apparatus requires a stirrer, a carbon dioxide inlet, and the like to be provided in the ambient-pressure vessel, it is difficult to completely seal the interior of such an ambient-pressure vessel, and as a result, a large amount of carbon dioxide supplied into the main body of the precipitation reaction apparatus may be released into the atmosphere. Citation List Patent Literatures

[0009] Patent Literature No. 1: Japanese Unexamined Patent Application, First Publication No. 2020-163821 Patent Literature No. 2: Japanese Unexamined Patent Application, First Publication No. 2009-279552 SUMMARY OF INVENTION Technical Problem

[0010] The present disclosure has been made in view of such circumstances, and an object of the present disclosure is to provide a method for producing carbonated sludge water that can easily reduce release 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, as a material, carbonated sludge water obtained using the production method. Solution to Problem

[0011] In order to provide a basic understanding of some features of the present disclosure, a brief summary of the present disclosure is set forth below. This summary is not intended to provide an extensive overview of the present disclosure. It is not intended to identify key or critical elements of the present disclosure or to delineate the scope thereof. The sole purpose is to present some basic concepts of the present disclosure in a simplified form as a prelude to the more detailed description that follows.

[0012] A method for producing carbonated sludge water according to the present disclosure includes: blowing a gas containing carbon dioxide into sludge water to obtain carbon dioxide-containing sludge water; and passing the carbon dioxide-containing sludge water obtained by the obtaining of the carbon dioxide-containing sludge water through a reactor configured to generate fine bubbles to obtain carbonated sludge water, in which the reactor includes a cylindrical member inside which a flow path is formed and a plurality of protruding members provided to protrude inward from an inner circumferential surface of the cylindrical member.

[0013] An apparatus for producing carbonated sludge water according to the present disclosure, which is an apparatus for producing carbonated sludge water used in the above-described method for producing carbonated sludge water, includes: a flow path through which sludge water is circulated; a blowing unit configured to blow a gas containing carbon dioxide into the flow path; and a reactor configured to allow carbon dioxide-containing sludge water to pass therethrough and to generate fine bubbles, in which the reactor includes a cylindrical member inside which a flow path is formed and a plurality of protruding members provided to protrude inward from an inner circumferential surface of the cylindrical member.

[0014] A method for producing mortar or concrete according to the present disclosure includes kneading carbonated sludge water produced by the above-described method for producing carbonated sludge water, with cement and aggregate. BRIEF DESCRIPTION OF DRAWINGS

[0015] The foregoing and other features of the present disclosure will become apparent from the following description of illustrated embodiments of the present disclosure and the drawings. [FIG. 1] A cross-sectional view of a reactor 1 taken along a flow direction S. [FIG. 2] A schematic view representing one aspect of an apparatus M for producing carbonated sludge water according to the present embodiment. [FIG. 3] A schematic view representing another aspect of the apparatus M for producing carbonated sludge water according to the present embodiment. [FIG. 4] A graph obtained in Example 2-1 by plotting CO2 supply time on the horizontal axis and CO2 / CaO and the pH of sludge water on the vertical axis. [FIG. 5] A graph obtained in Example 2-2 by plotting CO2 supply time on the horizontal axis and CO2 / CaO and the pH of sludge water on the vertical axis. [FIG. 6] A graph obtained in Example 2-3 by plotting CO2 supply time on the horizontal axis and CO2 / CaO and the pH of sludge water on the vertical axis. [FIG. 7] A graph obtained in Example 2-4 by plotting CO2 supply time on the horizontal axis and CO2 / CaO and the pH of sludge water on the vertical axis. [FIG. 8] A graph obtained in Example 2-5 by plotting CO2 supply time on the horizontal axis and CO2 / CaO and the pH of sludge water on the vertical axis. [FIG. 9] A graph obtained in Example 2-6 by plotting CO2 supply time on the horizontal axis and CO2 / CaO and the pH of sludge water on the vertical axis. DESCRIPTION OF EMBODIMENTS

[0016] Hereinafter, the method for producing carbonated sludge water, the apparatus for producing carbonated sludge water, and the method for producing mortar or concrete 6 according to the present embodiment will be described.

[0017] (Method for 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 causing calcium oxide in sludge water to react with carbon dioxide, and includes the following: step (1): a step of blowing a gas containing carbon dioxide into sludge water to obtain carbon dioxide-containing sludge water; and step (2): a step of passing the carbon dioxide-containing sludge water obtained in the step (1) through a reactor configured to generate fine bubbles to obtain carbonated sludge water.

[0018] In the present specification, the term “sludge water” refers to the portion of water that contains sludge solids after aggregate has been removed from wastewater generated by cleaning transport vehicles, mixers, and the like at a ready-mixed concrete plant. The sludge solids are composed mostly of hydration products and also contain fine particles of aggregate and the like. The hydration products contain calcium-based compounds. Examples of the calcium-based compounds include calcium oxide, calcium hydroxide, calcium silicate hydrate, calcium aluminate hydrate, and the like.

[0019] Cement used as a raw material for ready-mixed concrete is not particularly limited, and examples of cement that may be used include Portland cements specified in JIS R 5210:2019, 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; blended cements such as blast-furnace slag cement, fly ash cement, and silica cement; and known cements such as ultra-rapid-hardening cement and alumina cement. One type of cement may be used alone, or two or more types thereof may be used in combination.

[0020] <Step (1)> In the step (1), which is the obtaining of carbon dioxide-containing sludge water, a gas containing carbon dioxide is blown into sludge water to obtain carbon dioxidecontaining sludge water.

[0021] Examples of the gas containing carbon dioxide blown into the sludge water include industrial-grade carbon dioxide, air, and exhaust gas and the like generated during firing of cement clinker and containing carbon dioxide and nitrogen oxides.

[0022] The concentration of carbon dioxide contained in the gas containing carbon dioxide is not particularly limited, and may be, for example, 0.004% by volume or more and 100% by volume or less.

[0023] The flow rate of the gas containing carbon dioxide is not particularly limited, and may be, for example, 1 L / min or more and 1000 L / min or less.

[0024] The molar concentration of carbon dioxide with respect to 1 L of the sludge water is not particularly limited, and may be, for example, 0.001 mol / L or more and 0.2 mol / L or less.

[0025] The molar concentration of carbon dioxide described above can be determined using an equation (1) below from the concentration of carbon dioxide, the flow rate of the gas containing carbon dioxide, the gas blowing time, and the molar volume of a gas under standard conditions (0°C and 1 atm). Molar concentration of carbon dioxide (mol / L) = [{(Carbon dioxide concentration (% by volume) / 100) x Gas flow rate (L / min) x Gas blowing time (min)} / 22.4] 8 / Amount of sludge water (L) ... (1)

[0026] 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 preferably 0.0200 kg / L or more and more preferably 0.0400 kg / L or more, from the viewpoint of suppressing excessive blowing of the gas containing carbon dioxide into the sludge water.

[0027] 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, from the viewpoint of reducing the release of carbon dioxide into the atmosphere. The concentration of the sludge water can be determined in accordance with JIS A 1806:2011.

[0028] The content of calcium oxide contained in the sludge solids is not particularly limited and may be, for example, 10% by mass or more and 90% by mass or less based on the total mass of the sludge solids.

[0029] As the content of calcium oxide, a value measured using an X-ray fluorescence analyzer (for example, ZSX Primus IV manufactured by Rigaku Corporation) in accordance with the method specified in JIS R 5204:2019 may be used.

[0030] The molar concentration of calcium oxide contained in 1 L of the sludge water is not particularly limited, and may be, for example, 0.06 mol / L or more and 4.50 mol / L or less.

[0031] The molar concentration of calcium oxide can be determined using an equation (2) below from the content of calcium oxide (% by mass), the molecular weight of calcium oxide, and the mass of the sludge solids. Molar concentration of calcium oxide (mol / L) = [{Amount of sludge water (g) x (Concentration of sludge water (% by mass) / 100) x 0.8 x (Content of calcium oxide (% by mass) / 100)} / 56] / Amount of sludge water (L) ... (2)

[0032] The step (1) can be performed in a flow path through which the sludge water is circulated to the reactor. In this case, the flow rate of sludge water is not particularly limited, and may be, for example, 1 L / min or more and 1000 L / min or less.

[0033] <Step (2)> In the step (2), which is the obtaining of carbonated sludge water, the carbon dioxide-containing sludge water obtained in the step (1) is passed through a reactor configured to generate fine bubbles to obtain carbonated sludge water.

[0034] In the present specification, the fine bubbles are bubbles having a volumeequivalent diameter of less than 100 pm, as specified in JIS B 8741-1:2019 and ISO 20480-1:2017. The fine bubbles are classified into two types, microbubbles and ultrafine bubbles, based on bubble diameter. As specified in JIS B 8741-1:2019 and ISO 20480-1:2017, the microbubbles are fine bubbles having a volume-equivalent diameter of 1 pm or more and less than 100 pm, and the ultrafine bubbles are fine bubbles having a volume-equivalent diameter of less than 1 pm.

[0035] The volume-equivalent diameter of fine bubbles is preferably 0.001 pm or more and 100 pm or less, and more preferably 1 pm or more and 100 pm or less, from the viewpoint of promoting sufficient reaction between carbon dioxide and calcium oxide in the sludge water. The volume-equivalent diameter of fine bubbles can be determined by dynamic image analysis using, for example, a flow-type imaging particle size and shape analyzer (manufactured by Shimadzu Science East Japan Corporation; Particle Insight).

[0036] From the viewpoint of reducing the release of carbon dioxide into the atmosphere, the reactor configured to generate fine bubbles includes a cylindrical member inside 10 which a flow path is formed and a plurality of protruding members provided to protrude inward from an inner circumferential surface of the cylindrical member.

[0037] FIG. 1 is a cross-sectional view showing an example of a reactor 1 taken along a flow direction S. The flow direction is a direction in which the sludge water is circulated, and is indicated by an arrow S in FIG. 1.

[0038] As shown in FIG. 1, the reactor 1 includes a cylindrical member 11 inside which a flow path is formed and a plurality of protruding members 12 provided to protrude inward from an inner circumferential surface of the cylindrical member 11. The protruding members 12 are blade members each having a shape helically twisted by 180° about an axis of the cylindrical member 11, and six protruding members 12 are consecutively arranged along the flow direction S. Adjacent blade members may be arranged with a predetermined angular offset about the axis of the cylindrical member 11, and may be configured to be discontinuous as a whole. In addition, adjacent blade members may be arranged with opposite directions of twist about the axis of the cylindrical member 11.

[0039] The number of protruding members 12 is not particularly limited as long as the fine bubbles can be generated, and may be, for example, 8 or more or 58 or less.

[0040] Such a reactor is preferably a stationary mixer from the viewpoint of facilitating the reaction between carbon dioxide and calcium oxide in the sludge water. Examples of the stationary mixer include static mixers and the like.

[0041] The reaction temperature of the reaction between carbon dioxide and calcium oxide is preferably 1°C or higher and 50°C or lower, and more preferably 1°C or higher and 35°C or lower, from the viewpoint of reducing the release of carbon dioxide into the atmosphere.

[0042] The above-described reaction temperature can be adjusted, for example, by adjusting the water temperature of the sludge water. Examples of a method for adjusting the water temperature include leaving the sludge water to stand in a constanttemperature bath or under natural environmental conditions, using a cooler in a water storage tank that stores the sludge water, and placing a cooler in a flow path for the sludge water.

[0043] <Step (3)> It is preferable that the method for producing carbonated sludge water according to the present embodiment further includes a step (3) below from the viewpoint of facilitating control to prevent the gas containing carbon dioxide from being excessively blown into the sludge water.

[0044] In the step (3), as the measuring of the pH, the pH of the carbonated sludge water obtained in the step (2) can be measured.

[0045] The pH can be measured using a pH meter (for example, a glass-electrode-type hydrogen ion concentration indicator manufactured by Toko Kagaku Kenkyusho Co., Ltd.).

[0046] In the method for producing carbonated sludge water according to the present embodiment, the above-described steps (1) to (3) can be repeated until the pH measured in the step (3) falls within a 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 facilitating control to prevent the gas containing carbon dioxide from being excessively blown into the sludge water.

[0047] The method for producing carbonated sludge water according to the present embodiment includes the step (1), which is the obtaining of carbon dioxide-containing sludge water, and the step (2), which is the obtaining of carbonated sludge water, and the reactor includes a cylindrical member inside which a flow path is formed and a plurality of protruding members provided to protrude inward from an inner circumferential surface of the cylindrical member, whereby the release of carbon dioxide into the atmosphere can be reduced. In addition, the method for producing carbonated sludge water according to the present embodiment does not require a complex apparatus such as a sealed ambientpressure vessel, and can reduce the release of carbon dioxide into the atmosphere in a simple manner. For this reason, the method for producing carbonated sludge water according to the present embodiment can reduce the release of carbon dioxide into the atmosphere in a simple manner, particularly even in an open system.

[0048] In addition to the step (1), which is the obtaining of the carbon dioxide-containing sludge water, and the step (2), which is the obtaining of the carbonated sludge water, the method for producing carbonated sludge water according to the present embodiment further includes the step (3), which is the measuring of the pH, and repeats the steps (1) to (3) until the pH measured in the step (3) falls within a range of 6.0 or more and 7.0 or less. This facilitates control to prevent the gas containing carbon dioxide from being excessively blown into the sludge water; that is, the release of carbon dioxide into the atmosphere can be reduced even more easily.

[0049] (Apparatus for Producing Carbonated Sludge Water) Hereinafter, an apparatus M for producing carbonated sludge water according to an embodiment of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

[0050] The apparatus M for producing carbonated sludge water according to the present embodiment will be described with reference to FIG. 2. FIG. 2 is a schematic view showing one aspect of the apparatus M for producing carbonated sludge water according to the present embodiment. As shown in FIG. 2, in one aspect, the apparatus M for producing carbonated sludge water according to the present embodiment includes a flow path 2 through which sludge water is circulated, a blowing unit 3 configured to blow a 5 gas containing carbon dioxide into the flow path 2, and a reactor 1 configured to allow carbon dioxide-containing sludge water to pass therethrough and to generate fine bubbles. In FIG. 2, the flow direction is indicated by an arrow S.

[0051] The flow path 2 is configured to allow the gas containing carbon dioxide to be blown thereinto from the blowing unit 3 described later, is connected to a lower portion 10 of a water storage tank 4 that stores the sludge water on an upstream side in the flow direction S, is connected to the reactor 1 described later further downstream in the flow direction S, and is configured to supply sludge water to the reactor 1. A pump (not shown) is provided in the flow path 2 to circulate the sludge water. The shortest distance between the blowing unit 3 and the reactor 1 along the flow path 2 may be 0.5 15 cm or more and 5000 cm or less.

[0052] The blowing unit 3 is configured to blow the gas containing carbon dioxide into the flow path 2 at a position upstream of the reactor 1 described later in the flow direction S. The blowing unit 3 includes an adjustment unit (not shown) configured to adjust the flow rate of the gas. Examples of the adjustment unit include a valve, a regulator, and 20 the like.

[0053] The reactor 1 is the same as that used in the method for producing carbonated sludge water according to the present embodiment described above. The reactor 1 is connected to an upper portion of the water storage tank 4 on the downstream side in the flow direction S, and is configured such that the carbonated sludge water obtained by passage through the reactor 1 can be stored in the water storage tank 4. With this configuration, the apparatus M for producing carbonated sludge water according to the present embodiment is configured to allow the sludge water and / or the carbonated sludge water to circulate. 5

[0054] The water storage tank 4 may be provided with a pH measuring unit (not shown). The pH measuring unit may be provided above or below the sludge water storage tank 4. In addition, the pH measuring unit may use the same type of pH meter as that used in the method for producing carbonated sludge water according to the present embodiment described above. 10

[0055] The apparatus M for producing carbonated sludge water according to the present embodiment is used in the method for producing carbonated sludge water according to the present embodiment described above.

[0056] Specifically, the apparatus M for producing carbonated sludge water performs the above-described step (1) by blowing the gas containing carbon dioxide from the blowing 15 unit 3 into the sludge water flowing through the flow path 2 to obtain carbon dioxidecontaining sludge water.

[0057] Further, the apparatus M for producing carbonated sludge water performs the above-described step (2) by allowing the carbon dioxide-containing sludge water obtained in the step (1) to pass through the reactor 1 while generating fine bubbles of 20 carbon dioxide, thereby obtaining carbonated sludge water.

[0058] Because the water storage tank 4 is connected to the reactor 1 at an upper portion of the water storage tank 4 and to the flow path 2 at a lower portion of the water storage tank 4, the apparatus M for producing carbonated sludge water according to the present embodiment can perform the above-described step (3) by measuring, with the pH measuring unit, the pH of the carbonated sludge water obtained in the step (2), and can repeat the steps (1) to (3) until the pH measured in the step (3) falls within a range of 6.0 or more and 7.0 or less.

[0059] In another aspect, as shown in FIG. 3, the flow path 2 of the apparatus M for 5 producing carbonated sludge water according to the present embodiment may be connected to the water storage tank 4 on the upstream side in 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 in the flow direction S.

[0060] The apparatus M for producing carbonated sludge water according to the present 10 embodiment may include a swirling-flow unit (not shown) disposed downstream of the reactor 1 in the flow direction S and configured to lengthen the reaction time between carbon dioxide and sludge water by imparting a swirling flow to the carbonated sludge water obtained in the step (2). In addition, the apparatus M for producing carbonated sludge water may include a pressure vessel (not shown) disposed downstream of the 15 reactor 1 in the flow direction S and configured to apply pressure to the carbonated sludge water.

[0061] When the apparatus M for producing carbonated sludge water includes the swirling-flow unit, the pressure vessel may be disposed downstream or upstream of the swirling-flow unit in the flow direction S. 20

[0062] In addition, the apparatus M for producing carbonated sludge water according to the present embodiment may include a temperature adjustment unit (not shown) to enable adjustment of the temperature of sludge water and / or 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.

[0063] A cooler such as a chiller may be used as the temperature adjustment unit.

[0064] In the apparatus M for producing carbonated sludge water according to the present embodiment, because the reactor 1 includes the cylindrical member 11 inside which the flow path is formed and the plurality of protruding members 12 provided to protrude inward from the inner circumferential surface of the cylindrical member 11, when the carbon dioxide-containing sludge water is passed through the reactor 1, the plurality of protruding members 12 in the reactor 1 come into contact with the sludge water, thereby generating fine bubbles of carbon dioxide. In this manner, the generating of fine bubbles of carbon dioxide while passing the carbon dioxide-containing sludge water through the reactor 1 allows carbon dioxide to react sufficiently with calcium oxide in the sludge water and reduces the release of carbon dioxide into the atmosphere. In addition, by including the above-described reactor 1, the apparatus M for producing carbonated sludge water according to the present embodiment does not require a complex apparatus such as a sealed ambient-pressure vessel and can reduce the release of carbon dioxide into the atmosphere in a simple manner.

[0065] (Method for Producing Mortar or Concrete) The method for producing mortar or concrete according to the present embodiment includes kneading carbonated sludge water produced by the abovedescribed method for producing carbonated sludge water with cement and aggregate.

[0066] The method for producing mortar or concrete according to the present embodiment includes the use of the carbonated sludge water produced by the abovedescribed method for producing carbonated sludge water. In the method for producing mortar or concrete according to the present embodiment, the carbonated sludge water may be mixed with other water such as tap water, industrial water, recovered water, 17 groundwater, river water, and rainwater.

[0067] The amount of the carbonated sludge water to be blended may be, for example, 0.5 kg / m3 or more and 300 kg / m3 or less, expressed as a unit amount (kg / m3: mass per 1 m3 of cement composition). When the other water is mixed with the carbonated sludge water, the above-described blending amount is the total amount of water blended.

[0068] The cement is not particularly limited and may be the cement described above.

[0069] The amount of the cement to be blended may be, for example, 200 kg / m3 or more and 500 kg / m3 or less, expressed as a unit amount (kg / m3: mass per 1 m3 of cement composition). When two or more types of cement are contained, the above-described blending amount is the total amount of cement blended.

[0070] Fine aggregate and / or coarse aggregate may be used as the aggregate. The fine aggregate means aggregate all of which passes through a 10-mm wire-mesh sieve and 85% by mass or more of which passes through a 5-mm wire-mesh sieve; and the coarse aggregate means aggregate 85% by mass or more of which is retained on a 5-mm wiremesh sieve (JIS A 0203:2019).

[0071] Examples of the fine aggregate include, among aggregates for ready-mixed concrete specified in Annex A of JIS A 5308:2019, natural-origin sands such as river sand, land sand, mountain sand, sea sand, crushed sand, and crushed limestone sand, and blast-furnace slag. Silica sand or the like produced by crushing and classifying silica stone may also be used. One type of fine aggregate may be used alone, or two or more types thereof may be used in combination.

[0072] The amount of the fine aggregate to be blended may be, for example, 600 kg / m3 or more and 1300 kg / m3 or less, expressed as a unit amount (kg / m3: mass per 1 m3 of cement composition). When two or more types of fine aggregate are contained, the 18 above-described blending amount is the total amount of fine aggregate blended.

[0073] Examples of the coarse aggregate include, among aggregates for ready-mixed concrete specified in Annex A of JIS A 5308:2019, natural aggregates such as river gravel, mountain gravel, and sea gravel; artificial aggregates such as crushed stone 5 produced from sandstone, hard limestone, basalt, and andesite; and recycled aggregate. One type of coarse aggregate may be used alone, or two or more types thereof may be used in combination.

[0074] The amount of the coarse aggregate to be blended may be, for example, 600 kg / m3 or more and 1300 kg / m3 or less, expressed as a unit amount (kg / m3: mass per 1 m3 10 of cement composition). When two or more types of coarse aggregate are contained, the above-described blending amount is the total amount of coarse aggregate blended.

[0075] With the method for producing mortar or concrete according to the present embodiment, it is possible to obtain mortar or concrete by kneading the above-described carbonated sludge water with cement and aggregate. 15

[0076] The method for producing mortar or concrete according to the present embodiment includes the use of the carbonated sludge water produced by the abovedescribed carbonated sludge water, thereby making it possible to produce mortar or concrete while reducing the release of carbon dioxide into the atmosphere in a simple manner. 20

[0077] The method for producing carbonated sludge water, the apparatus for producing carbonated sludge water, and the method for producing mortar or concrete according to the present embodiment are as described above; however, the present disclosure is not limited to the above-described embodiments, and various modifications may be made without departing from the spirit of the present disclosure. Further, the packaging bag according to the present disclosure is not limited by the operations and effects of the above-described embodiments. That is, the embodiments disclosed herein are to be considered in all respects as illustrative and not restrictive. The scope of the present disclosure is indicated by the claims rather than by the foregoing description. The scope of the present disclosure is intended to include all modifications within the meaning and scope equivalent to those of the claims.

[0078] The present disclosure includes the following aspects. [1] A method for producing carbonated sludge water by reacting calcium oxide in sludge water with carbon dioxide, the method including: step (1): a step of blowing a gas containing carbon dioxide into sludge water to obtain carbon dioxide-containing sludge water; and step (2): a step of passing the carbon dioxide-containing sludge water obtained in the step (1) through a reactor configured to generate fine bubbles to obtain carbonated sludge water, in which the reactor includes a cylindrical member inside which a flow path is formed and a plurality of protruding members provided to protrude inward from an inner circumferential surface of the cylindrical member. [2] The method for producing carbonated sludge water according to [1], further including: step (3): a step of measuring the pH of the carbonated sludge water obtained in the step (2), in which the steps (1) to (3) are repeated until the pH measured in the step (3) falls within a range of 6.0 or more and 7.0 or less. [3] The method for producing carbonated sludge water according to [1] or [2], in 20 which, in the step (1), a 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], in which the reactor is a stationary 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], the apparatus including: a flow path through which sludge water is circulated; a blowing unit configured to blow a gas containing carbon dioxide into the flow path; and a reactor configured to allow carbon dioxide-containing sludge water to pass therethrough and to generate fine bubbles, in which the reactor includes a cylindrical member inside which a flow path is formed and a plurality of protruding members provided to protrude inward from an inner circumferential surface of the cylindrical member. [6] A method for producing mortar or concrete, including a step of kneading carbonated sludge water produced by the method for producing carbonated sludge water according to any one of [1] to [4] with cement and aggregate. Examples

[0079] Examples of the present disclosure will be described below; however, the present disclosure is not limited to the following examples.

[0080] (Materials Used) • Cement: Ordinary Portland cement (manufactured by Sumitomo Osaka Cement Co., Ltd.) was used. • Water: Tap water was used.

[0081] (Preparation of Sludge Water) Sludge water was obtained by adding cement (1.5 kg, 4.0 kg, 7.9 kg, 16.7 kg, or 26.5 kg) to 150 L of tap water, mixing the resultant mixture, and allowing the mixture to stand for 30 minutes such that the concentration of the sludge water was the predetermined concentration indicated for each of Examples and Comparative Examples in Tables 1 and 2 below.

[0082] (Reactor) A static mixer (1-N33-131-F manufactured by Noritake Co., Limited; protruding members: helically twisted shape; number of blades: six) was used as a reactor. The static mixer is the same as that shown in FIG. 1.

[0083] In addition, it was confirmed by the following method that the above-described reactor was capable of generating microbubbles. First, carbon dioxide gas having a concentration of 100% by volume was blown at 20 L / min into tap water (flow rate: 25 L / min), and the obtained carbon dioxide-containing water was passed through the reactor to generate microbubbles. Next, the bubble diameter and number ratio of the microbubbles were measured by a dynamic image analysis method using a flow-type imaging particle size and shape analyzer (Particle Insight manufactured by Shimadzu Science East Japan Corporation). As a result, the average particle diameter of bubbles was 57.1 gm and the number concentration of bubbles was 940 bubbles / mL, and it was confirmed that the microbubbles were generated. Even when the carbon dioxidecontaining water, after being passed through the reactor, was further passed through a swirling-flow unit and a pressure vessel and subjected to a pressure of 0.2 MPa, it was confirmed that the microbubbles were generated.

[0084] (Test 1) <Examples 1-1 to 1-7, 1-9, and 1-10, and Comparative Example 1> Using the apparatus M for producing carbonated sludge water according to another aspect of the present embodiment as shown in FIG. 3, carbon dioxide gas having a concentration of 100% by volume was blown into 150 L of sludge water under the conditions described in Table 1, and the obtained carbon dioxide-containing sludge water was passed through the reactor to obtain carbonated sludge water.

[0085] Differential thermal analysis (TG-DTA) was performed on the carbonated sludge solids obtained by dewatering the obtained carbonated sludge water to determine the amount of carbon dioxide (unit: % by mass) fixed in the carbonated sludge solids through reaction with calcium oxide. The amount of carbon dioxide released was determined using an equation (I) below and evaluated based on the criteria below. The results are shown in Table 1. ◎: The amount of carbon dioxide released was less than 1.0 L / min. o: The amount of carbon dioxide released was 1.0 L / min or more and 10.0 L / min or less. x: The amount of carbon dioxide released was more than 10.0 L / min.

[0086] [Math. 1] Here, in the equation (I), A represents the amount of carbon dioxide blown (L / min), B represents the flow rate of sludge solids (kg / min), and C represents the amount of carbon dioxide fixed in the carbonated sludge solids (% by mass). In addition, 1.97 in the equation (I) is the density of carbon dioxide gas (kg / m3).

[0087] <Example 1-8> The same procedure as in Example 1-1 was performed, except that, after the carbon dioxide-containing sludge water was passed through the reactor, it was further passed through a swirling-flow unit and a pressure vessel and subjected to a pressure of 5   0.2 MPa.  The results are shown in Table 1.

[0088] <Comparative Example 1> The same procedure as in Example 1-1 was performed, except that the carbon dioxide-containing sludge water was not passed through the reactor. The results are shown in Table 1. 10

[0089] [Table 1] Microbubble Pressure (MPa) Concentration of sludge water (%) Flow rate of sludge water (L / min) Flow rate of sludge solids (kg / min) Mass of sludge solids / volume of CO2 (kg / L) Amount of CO2 blown (L / min) Amount of CO2 fixed (% by mass) Amount of CO2 released (L / min) Evaluation Example 1-1 Y 0 5.0 25 1.25 0.0625 20 3.05 0 ◎ Example 1-2 Y 0 10.0 25 2.5 0.1250 20 1.53 0.3 ◎ Example 1-3 Y 0 15.0 25 3.75 0.1875 20 1.02 0.4 ◎ Example 1-4 Y 0 2.5 25 0.625 0.0313 20 5.80 0.5 ◎ Example 1-5 Y 0 5.0 25 1.25 0.1250 10 1.49 0.4 ◎ Example 1-6 Y 0 5.0 25 1.25 0.0417 30 4.51 0 ◎ Example 1-7 Y 0 5.0 25 1.25 0.0313 40 5.22 5.1 0 Example 1-8 Y 0.2 5.0 25 1.25 0.0625 20 2.98 0.5 ◎ Example 1-9 Y 0 5.0 25 1.25 0.0156 80 10.05 9.1 0 Example 1 10 Y 0 1.0 25 0.25 0.0125 20 7.40 9.9 0 Comparative Example 1 N 0 5.0 25 1.25 0.0625 20 0.90 14.2 X

[0090] As can be seen from the results in Table 1, in the method for producing carbonated sludge water of each of Examples satisfying all the configurations of the present disclosure, the amount of carbon dioxide released was less than 10 L / min, so that most of the supplied carbon dioxide underwent carbonation. Accordingly, it can be said 15 that the method for producing carbonated sludge water of each of Examples could reduce the release of carbon dioxide into the atmosphere in a simple manner.

[0091] (Test 2) <Examples 2-1 to 2-5> Using the apparatus M for producing carbonated sludge water according to one aspect of the present embodiment as shown in FIG. 2, an operation was performed under the conditions for Examples 2-1 to 2-5 described in Table 2, in which carbon dioxide gas having a concentration of 100% by volume was blown into 150 L of sludge water, the obtained carbon dioxide-containing sludge water was passed through the reactor, the obtained carbonated sludge water was discharged into the water storage tank, and the pH in the water storage tank was measured using a pH meter (a glass-electrode-type hydrogen ion concentration indicator manufactured by Toko Kagaku Kenkyusho Co., Ltd.). At this time, the above-described operation was repeated until the pH of the carbonated sludge water fell within a range of 6 or more and 7 or less.

[0092] Using a carbon dioxide measuring instrument (a CO2 concentration, temperature, and humidity data logger manufactured by T&D Corporation), the concentration of carbon dioxide in the atmosphere at a point approximately 30 cm from the outlet of the reactor was measured when the pH of the carbonated sludge water fell within the range of 6 or more and 7 or less, and was evaluated based on the criteria below. The results are shown in Table 2. o: The concentration of carbon dioxide was less than 1500 ppm. x: The concentration of carbon dioxide was 1500 ppm or more.

[0093] <Example 2-6> The same procedure as in Example 2-1 was performed, except that the water temperature of the sludge water was set to 5°C. The results are shown in Table 2.

[0094] In addition, the time during which the carbon dioxide was blown into the sludge water was defined as the carbon dioxide supply time (hereinafter, also referred to as a CO2 supply time), and, for Examples 2-1 to 2-6, graphs were created by plotting the CO2 supply time on the horizontal axis and the ratio of the molar mass of carbon dioxide that 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 on the vertical 5 axis. With regard to CO2 / CaO, the value calculated using the molar mass of the carbon dioxide obtained in the actual test was taken as the measured value, and the value calculated using the molar mass of the carbon dioxide that theoretically reacted with the calcium oxide was taken as the theoretical value, and both values were plotted. The results are shown in FIGS. 4 to 9. 10

[0095] [Table 2] Microbubble Pressure (MPa) Water temperature of sludge water (°C) Concentration of sludge water (%) Flow rate of sludge water (L / min) Flow rate of sludge solids (kg / min) Flow rate of CO2 (L / min) Mass of sludge solids / volume of CO2 (kg / L) Concentration of CO2 (ppm) Evaluation Example 2-1 Y 0 20 5.0 25 1.25 20 0.0625 1250 0 Example 2-2 Y 0 20 10.0 25 2.5 20 0.1250 1350 0 Example 2-3 Y 0 20 2.5 25 0.625 20 0.0313 1200 0 Example 2-4 Y 0 20 5.0 25 1.25 10 0.1250 1250 0 Example 2-5 Y 0.2 20 5.0 25 1.25 20 0.0625 1150 0 Example 2-6 Y 0 5 5.0 25 1.25 20 0.0625 1100 0

[0096] As can be seen from the results in Table 2, in the method for producing carbonated sludge water of each of Examples satisfying all the configurations of the present disclosure, the concentration of carbon dioxide was less than 1500 ppm, so that the amount of carbon dioxide released was reduced. Accordingly, in the method for 15 producing carbonated sludge water of each of Examples, the blown carbon dioxide sufficiently reacted with calcium oxide in the sludge water, and, as a result, the release of carbon dioxide into the atmosphere could be reduced in a simple manner.

[0097] Further, FIGS. 4 to 9 show that, in the methods for producing carbonated sludge water of Examples 2-1 to 2-6, the pH gradually decreased when the carbon dioxide was blown into the sludge water and that the blowing of carbon dioxide into the sludge water until the pH of the carbonated sludge water fell within a range of 6 or more and 7 or less suppressed the release of a large amount of carbon dioxide. Accordingly, the present inventors found that the pH decreased as the amount of calcium oxide that reacted with carbon dioxide decreased, and that the blown carbon dioxide hardly reacted when the pH fell within a range of 6.0 or more and 7.0 or less. Therefore, by repeating the abovedescribed steps (1) to (3) until the pH fell within the range of 6.0 or more and 7.0 or less, with the method for producing carbonated sludge water of each of Examples, it was possible to easily control the blowing of the gas containing carbon dioxide so that the gas was not excessively blown into the sludge water; that is, the release of carbon dioxide into the atmosphere could be reduced even more easily.

[0098] Furthermore, since the carbonated sludge water produced by the carbonated sludge water of each of Examples could reduce the release of carbon dioxide into the atmosphere, it can be said that the carbonated sludge water could be used to produce mortar or concrete while reducing the release of carbon dioxide into the atmosphere in a simple manner. REFERENCE SIGNS LIST

[0099] 1 Reactor 11 Cylindrical member 12 Protruding member 2 Flow path 3 Blowing unit 4 Water storage tank 4' Carbonated sludge water storage tank M Apparatus for producing carbonated sludge water S Flow direction 5

Claims

28 CLAIMS

1. A method for producing carbonated sludge water, comprising:blowing a gas containing carbon dioxide into sludge water to obtain carbon dioxide-containing sludge water; andpassing the carbon dioxide-containing sludge water obtained by the obtaining of the carbon dioxide-containing sludge water through a reactor configured to generate fine bubbles to obtain carbonated sludge water,wherein the reactor comprises a cylindrical member inside which a flow path is formed and a plurality of protruding members provided to protrude inward from an inner circumferential surface of the cylindrical member.

2. The method for producing carbonated sludge water according to Claim 1, further comprising:measuring the pH of the carbonated sludge water obtained by the obtaining of the carbonated sludge water,wherein the obtaining of the carbon dioxide-containing sludge water, the obtaining of the carbonated sludge water, and the measuring of the pH are repeated until the pH measured by the measuring of the pH falls within a range of 6.0 or more and 7.0 or less.

3. The method for producing carbonated sludge water according to Claim 1 or 2, wherein in the obtaining of the carbon dioxide-containing sludge water, a 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 or2, wherein the reactor is a stationary mixer.29

5. An apparatus for producing carbonated sludge water, comprising:a flow path through which sludge water is circulated;a blowing unit configured to blow a gas containing carbon dioxide into the flow path; and5            a reactor configured to allow carbon dioxide-containing sludge water to passtherethrough and to generate fine bubbles,wherein the reactor comprises a cylindrical member inside which a flow path is formed, and a plurality of protruding members provided to protrude inward from an inner circumferential surface of the cylindrical member.10

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

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