Carbonation Slurry Production System

Abstract

A carbonation slurry production system is provided that can fix carbon dioxide in a slurry consisting of calcium-containing powder and water and can easily control the average residence time of the slurry. A carbonated slurry production system 1 including: a slurry tank 2 having first slurry storage portions 10a, 10b for contacting the slurry with a carbon dioxide-containing gas; a slurry supplying device 7 for supplying a slurry consisting of a calcium-containing powder and water; a carbon dioxide-containing gas supplying device 4 for supplying a carbon dioxide-containing gas at a pressure greater than atmospheric pressure to gas phases 9a, 9b consisting of the carbon dioxide-containing gas in the first slurry storage portion; a carbon dioxide-containing gas discharging device 5 for discharging the carbonated slurry; liquid level measuring means 6a, 6b, 6c for measuring the height of the liquid level consisting of the slurry; and a slurry control device 7 for controlling the average residence time of the slurry based on the heights of the first liquid levels 8a, 8b and the second liquid level 11.

Description

[Technical field]

[0001] The present invention relates to a carbonation slurry production system. [Background technology]

[0002] In recent years, reducing carbon dioxide emissions has become an important issue in order to prevent global warming. In relation to this, technology is being considered for fixing carbon dioxide captured from exhaust gases generated in cement manufacturing plants into concrete, etc. On the other hand, calcium-containing powders such as incineration ash generated during the incineration of municipal solid waste, including general waste and industrial waste, and clinker dust generated in cement plants are effectively reused as cement raw materials from the viewpoints of resource and environmental protection. Patent Document 1 describes a method for removing chlorine from incineration ash, clinker dust, etc., in order to make suitable use of such materials as cement raw materials, and the like. The method includes a washing step in which water is added to the chlorine-containing ash and the ash is stirred and washed; an ash slurry concentration step in which a polymer coagulant is added to the ash slurry that has undergone this washing step and the ash is allowed to settle and separate; a first dehydration step in which the concentrated ash slurry discharged from this concentration step is dehydrated using a vacuum belt filter; an advanced desalination step in which the dehydrated cake of ash discharged from this dehydration step is dispersed in water, and carbon dioxide-containing gas is added and heated; and a second dehydration step in which the slurry that has undergone this advanced desalination step is dehydrated using a filter press to produce a washed ash cake. Furthermore, as a method for efficiently contacting slaked lime with carbon dioxide and satisfactorily controlling and promoting the carbonation reaction, Patent Document 2 describes a method for producing calcium carbonate, which includes supplying a liquid containing calcium hydroxide and an auxiliary and an exhaust gas containing carbon dioxide to a reaction tank while mixing them with an injector, and in which a reaction liquid circulated from the reaction tank is used as the liquid containing calcium hydroxide. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6252653 [Patent Document 2] Patent No. 5426982 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a carbonation slurry production system that can continuously and efficiently fix carbon dioxide in a slurry consisting of calcium-containing powder and water, and further, can easily and stably control the average residence time of the slurry (the average time from when the slurry is supplied until it is discharged as a carbonated slurry). [Means for solving the problem]

[0005] As a result of intensive research into solving the above-mentioned problems, the inventors have found that the above-mentioned objects can be achieved by a carbonation slurry production system including a slurry tank for storing a slurry, a slurry supply device for continuously supplying the slurry to the slurry tank, a carbon dioxide-containing gas supply device for supplying a carbon dioxide-containing gas, a carbonated slurry discharge device for continuously discharging the carbonated slurry, a liquid level measuring means for measuring the height of a liquid level consisting of the slurry, and a slurry control device for controlling the average residence time of the slurry, and which controls the average residence time of the slurry by adjusting the amount of slurry supplied per unit time and the amount of carbonated slurry discharged per unit time based on the heights of the first liquid level and the second liquid level measured by the liquid level measuring means, and have completed the present invention. That is, the present invention provides the following [1] to [6].

[0006] [1] A carbonation slurry production system for producing a carbonated slurry by carbonating a slurry containing a calcium-containing powder and water with a carbon dioxide-containing gas, comprising a slurry tank for storing the slurry, a slurry supply device for continuously supplying the slurry to the slurry tank, a carbon dioxide-containing gas supply device for supplying the carbon dioxide-containing gas, a carbonation slurry discharge device for continuously discharging the carbonated slurry from the slurry tank, a liquid level measuring means for measuring the height of a liquid level consisting of the slurry in the slurry tank, and a slurry control device for controlling an average residence time of the slurry, wherein the slurry tank stores the slurry and the carbon dioxide-containing gas such that a gas phase consisting of the carbon dioxide-containing gas is located above a first liquid level of the slurry, and includes a first slurry storage portion for contacting the slurry with the carbon dioxide-containing gas, and a second liquid level measuring means for measuring the height of a liquid level consisting of the slurry in the slurry tank. a second slurry storage portion which stores the first slurry in the first storage portion so that a gas phase is located above the liquid level of the first slurry, and which does not have a contact surface between the slurry and the carbon dioxide-containing gas, the carbon dioxide-containing gas supplying device supplies the carbon dioxide-containing gas to the gas phase consisting of the carbon dioxide-containing gas in the first slurry storage portion at a pressure greater than atmospheric pressure, the liquid level measuring means measures each height of a first liquid level in the first slurry storage portion and a second liquid level in the second slurry storage portion, and the slurry control device adjusts the amount of the slurry per unit time supplied from the slurry supplying device and the amount of the carbonated slurry discharged per unit time from the carbonated slurry discharging device based on the each height of the first liquid level in the first slurry storage portion and the second liquid level in the second slurry storage portion measured by the liquid level measuring means, thereby controlling an average residence time of the slurry.

[0007] [2] The carbonation slurry production system described in [1], wherein the carbonation slurry production system includes a slurry circulation path for returning at least a portion of the carbonation slurry discharged from the slurry tank to the slurry tank for circulating it. [3] The carbonation slurry production system according to [1] or [2], wherein the slurry tank has a stirring means for stirring and mixing the carbonation slurry in the slurry tank. [4] The carbonation slurry production system according to any one of [1] to [3], further comprising a pH measurement means for measuring the pH of the carbonation slurry. [5] The carbonation slurry production system according to any one of [1] to [4], further comprising a liquid temperature adjusting means for adjusting the liquid temperature of the carbonation slurry.

[0008] [6] A method for producing a carbonated slurry by carbonating a slurry containing a calcium-containing powder and water with a carbon dioxide-containing gas, comprising: a slurry preparation step of mixing the calcium-containing powder with the water to obtain the slurry; a slurry supply step of continuously supplying the slurry to a slurry tank for storing the slurry; a slurry containing step of storing the slurry and the carbon dioxide-containing gas in a first slurry storage portion of the slurry tank so that a gas phase consisting of the carbon dioxide-containing gas is located above a first liquid level of the slurry, and storing the slurry and the carbon dioxide-containing gas in a second slurry storage portion of the slurry tank so that a gas phase is located above a second liquid level of the slurry and so that there is no contact surface between the slurry and the carbon dioxide-containing gas; a carbonation slurry preparation step of supplying the carbon dioxide-containing gas at a pressure greater than atmospheric pressure to a gas phase consisting of the carbon dioxide-containing gas in the first slurry storage portion, thereby bringing the first liquid level into contact with the gas phase, thereby carbonating the slurry to obtain a carbonated slurry; a carbonation slurry discharge step of continuously discharging the carbonated slurry from the slurry tank; and a liquid level measurement step of measuring the height of the first liquid level in the first slurry storage portion and the second liquid level in the second slurry storage portion, wherein the supply amount of the slurry per unit time in the slurry supply step and the discharge amount of the carbonated slurry per unit time in the carbonation slurry discharge step are adjusted based on the measurement results obtained in the liquid level measurement step. Effect of the Invention

[0009] According to the carbonated slurry production system of the present invention, carbon dioxide can be continuously and efficiently fixed in a slurry containing a calcium-containing powder and water, and further, the average residence time of the slurry (the average time from when the slurry is supplied until it is discharged as a carbonated slurry) can be easily and stably controlled. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing a schematic diagram of an example of a carbonation slurry production system of the present invention. [Diagram 2] FIG. 1 is a diagram showing a schematic diagram of an example of a carbonation slurry production system of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The carbonation slurry production system of the present invention is a carbonation slurry production system for producing a carbonated slurry by carbonating a slurry containing a calcium-containing powder and water with a carbon dioxide-containing gas. The carbonation slurry production system of the present invention includes a slurry tank for storing a slurry, a slurry supply device for continuously supplying the slurry to the slurry tank, a carbon dioxide-containing gas supply device for supplying a carbon dioxide-containing gas, a carbonation slurry discharge device for continuously discharging the carbonated slurry from the slurry tank, a liquid level measurement means for measuring the height of the liquid level of the slurry in the slurry tank, and a slurry control device for controlling the average residence time of the slurry. The slurry tank has a first slurry storage portion for storing the slurry and the carbon dioxide-containing gas such that a gas phase of the carbon dioxide-containing gas is located above the first liquid level of the slurry, and for contacting the slurry with the carbon dioxide-containing gas, and a second slurry storage portion for storing the slurry such that a gas phase is located above the second liquid level of the slurry, and having no contact surface between the slurry and the carbon dioxide-containing gas. The carbon dioxide-containing gas supplying device supplies the carbon dioxide-containing gas at a pressure higher than atmospheric pressure to the gas phase consisting of the carbon dioxide-containing gas in the first slurry accommodating portion. The liquid level measuring means measures the heights of the first liquid level in the first slurry accommodating portion and the second liquid level in the second slurry accommodating portion. The slurry control device adjusts the amount of slurry supplied from the slurry supplying device per unit time and the amount of carbonated slurry discharged from the carbonated slurry discharging device per unit time based on the heights of the first liquid level in the first slurry accommodating portion and the second liquid level in the second slurry accommodating portion measured by the liquid level measuring means, thereby controlling the average residence time of the slurry. In this specification, the term "carbonation" refers to the absorption and fixation of carbon dioxide. Hereinafter, the carbonated slurry production systems 1, 21 of the present invention will be described in detail with reference to Figs.

[0012] In the present invention, the slurry to be carbonated is a mixture (slurry) containing a calcium-containing powder and water. The calcium-containing powder is not particularly limited as long as it is a powder containing calcium, and examples thereof include cement, crushed waste concrete, powdered fresh concrete sludge, powdered blast furnace slag, municipal waste incineration ash (fly ash, bottom ash), cement kiln dust, etc. These may be used alone or in combination of two or more. The cement is not particularly limited, and examples thereof include various Portland cements such as ordinary Portland cement, high-early-strength Portland cement, moderate-heat Portland cement, and low-heat Portland cement, mixed cements such as blast-furnace cement and fly ash cement, and ecocement. An example of the pulverized waste concrete is a powder containing cement hydrate and non-hydrated cement, which is obtained by crushing concrete waste generated during the demolition of concrete structures, etc., and then removing aggregate from the crushed concrete. The CaO content of the pulverized waste concrete is usually 15% by mass or more. Ready-mixed concrete sludge powder is a powder containing cement hydrates and non-hydrated cement, obtained by sieving sludge generated during the concrete manufacturing process at ready-mix concrete plants or concrete product plants. The CaO content of ready-mixed concrete sludge is usually 30% by mass or more. Examples of blast furnace slag powder include granulated slag obtained by quenching with water and crushing molten slag, which is a by-product of pig iron production in a blast furnace, and slowly cooled slag obtained by slowly cooling and crushing it. The CaO content of blast furnace slag powder is usually 35 mass% or more. The calcium content in the calcium-containing powder is preferably 15% by mass or more, more preferably 20% by mass or more, and particularly preferably 30% by mass or more, calculated as oxide (CaO). If the content is 15% by mass or more, the strength expression of the cement composition can be further improved when the obtained carbonated slurry is used as a part of the material of the cement composition such as concrete. The upper limit of the content is not particularly limited, but is usually 90% by mass.

[0013] The water is not particularly limited, and examples thereof include tap water, industrial water, and recovered water such as supernatant water and sludge water generated in concrete manufacturing plants. The water to calcium-containing powder ratio of the slurry (the mass ratio of water to calcium-containing powder (water / calcium-containing powder)) varies depending on the application of the carbonated slurry and the target concentration of the carbonated slurry, but is preferably 0.2 to 10.0, more preferably 0.4 to 9.5, even more preferably more than 0.6 and not more than 9.0, even more preferably 1.0 to 8.5, still more preferably 2.0 to 8.0, and particularly preferably 3.0 to 7.5. When the water / calcium-containing powder ratio is 0.2 or more, the viscosity of the slurry is reduced, improving workability and enabling carbon dioxide to be continuously and stably absorbed and immobilized in the slurry. When the water / calcium-containing powder ratio is 10.0 or less, the use of the carbonated slurry is not easily limited, and when the carbonated slurry is mixed as a part of a material such as concrete, it becomes easier to adjust the amount of other materials (e.g., water). Also, it is possible to prevent the device from becoming excessively large.

[0014] The calcium-containing powder and water are prepared into a slurry by stirring and mixing using a mixing means such as a stirring blade or a hand mixer disposed in a mixing tank (not shown) for mixing the calcium-containing powder and water to obtain a slurry. The prepared slurry is continuously supplied from the slurry supplying device 3, 23 to the slurry tank 2, 22 through the slurry inlet passage 13, 33. A dispersion plate or a nozzle may be disposed in at least one of the slurry inflow passages 13, 33 and the regions of the slurry tanks 2, 22 to which the slurry is supplied, for the purpose of further improving the efficiency of carbonation. The slurry tanks 2 and 22 are equipped with stirring means 19 and 39 for the purpose of preventing calcium-containing powder contained in the slurry from settling in the slurry tank. Examples of the stirring means include a stirring blade disposed in the slurry tank and a hand mixer. Furthermore, the slurry tanks 2, 22 have a tapered shape toward the carbonated slurry discharge passages 15, 35 (usually arranged in the vertical lower part of the slurry tanks 2, 22) in order to prevent the calcium-containing powder contained in the slurry from settling in the slurry tank. The stirring means may be omitted. The shape of the slurry tank is not particularly limited.

[0015] The slurry tanks 2 and 22 have first slurry storage portions 10a, 10b, 30a, 30b for storing the slurry (including a slurry partly carbonated during the carbonation process) and carbon dioxide-containing gas stored in the slurry tanks 2 and 22 such that gas phases 9a, 9b, 29a, 29b consisting of the carbon dioxide-containing gas are positioned above the first liquid levels 8a, 8b, 28a, 28b of the slurry, and for contacting the slurry with the carbon dioxide-containing gas, and a second slurry storage portion for storing the slurry so that gas phases 12a, 12b, 12c, 32 (different from the gas phase consisting of the carbon dioxide-containing gas described above, usually a gas phase consisting of air) are positioned above the second liquid levels 11a, 11b, 11c, 31 of the slurry, and which does not have a contact surface between the slurry and the carbon dioxide-containing gas. The number of the first slurry storage portions that the slurry tanks 2 and 22 have needs to be at least one, and may be two or more. The first slurry containing portion may be disposed inside the slurry tank or outside the slurry tank.

[0016] 1, for example, the first slurry storage portions 10a, 10b are disposed so that at least a part of the first slurry storage portions is submerged in the slurry 18 stored in the slurry tank 2. The first slurry storage portions 10a, 10b may be fixed to a lid portion of the slurry tank 2, or may be fixed to an inner wall portion of the slurry tank 2 by a part of the first slurry storage portion or by using a fixing member (not shown). The gas phases 12a, 12b, and 12c are continuous spaces. The second liquid levels 11a, 11b, and 11c are liquid levels other than the first liquid levels 8a and 8b of the slurry 18, and the heights of the second liquid levels 11a, 11b, and 11c are the same. The slurry contained in the first slurry storage portions 10a, 10b passes through an outlet port that opens at the vertical lower end of the first slurry storage portions 10a, 10b and at a position vertically below the liquid level (second liquid level) of the slurry 18 contained in the slurry tank 2 (excluding the slurry contained in the first slurry storage portions 10a, 10b) and is contained in the first slurry storage portions 10a, 10b.

[0017] In Figure 2, the first slurry containing portions 30a, 30b are disposed on an outer wall portion of the slurry vessel 22. The first slurry containing portions 30a, 30b may form a region of the outer wall of the slurry vessel. The slurry contained in the first slurry storage portions 30a, 30b enters the first slurry storage portions 30a, 30b through outlet ports 40a, 40b which open at the vertically lower end of the first slurry storage portions 30a, 30b and at a position vertically below the liquid level (second liquid level) of the slurry 38 contained in the slurry tank 22 (excluding the slurry contained in the first slurry storage portions 30a, 30b). In FIG. 2, the first slurry storage portions 30a, 30b and the slurry tank 22 are connected at the inlet / outlet ports 40a, 40b. When the first slurry storage portion is disposed outside the slurry tank, an inlet / outlet passage may be provided which communicates from the inlet / outlet of the first slurry storage portion to the inlet / outlet of the slurry tank. The inlet / outlet of the slurry tank is usually disposed on the outer wall of the slurry tank at a position vertically below the liquid level of the slurry stored in the slurry tank (the second liquid level).

[0018] A portion of the slurry contained in the slurry tank passes through the outlet port and is contained in the first slurry containing portion. In the first slurry storage portion, the slurry and the carbon dioxide-containing gas are brought into contact (at the interface between the liquid surface and the gas phase) in an environment in which the pressure of the gas phase consisting of the carbon dioxide-containing gas is higher than atmospheric pressure (for example, a pressure difference of 0.02 MPa or more), whereby carbon dioxide can be efficiently absorbed and immobilized in the slurry in large quantities. The first slurry storage portion is usually a container having a structure capable of being pressurized. By supplying carbon dioxide gas to the gas phase of the first slurry storage portion under pressure (the internal pressure of the first slurry storage portion is made higher than atmospheric pressure), the amount of carbon dioxide fixed in the carbonated slurry can be increased, thereby obtaining a carbonated slurry in which a larger amount of carbon dioxide is fixed. Furthermore, from the viewpoint of efficiently absorbing and immobilizing a larger amount of carbon dioxide in the slurry, a stirring means such as a stirring blade may be provided in the first slurry storage section, and the slurry may be contacted with the carbon dioxide-containing gas while stirring the slurry using the stirring means or while circulating the slurry using a circulation means.

[0019] The carbon dioxide-containing gas is supplied from the carbon dioxide-containing gas supplying devices 4, 24 through the carbon dioxide-containing gas inlet passages 14, 34 to the gas phases 9a, 9b, 29a, 29b consisting of the carbon dioxide-containing gas in the first slurry accommodating portions 10a, 10b, 30a, 30b at a pressure greater than atmospheric pressure. The inlets for the carbon dioxide-containing gas in the first slurry storage portions 10a, 10b, 30a, and 30b are usually disposed at positions not in contact with the slurry (positions vertically above the first liquid level, such as the upper portion (e.g., the lid) of the first slurry storage portion) in order to prevent clogging due to scale formation. The carbon dioxide-containing gas may be a gas consisting of only carbon dioxide (carbonic acid gas), but may also be a gas containing carbon dioxide from the standpoint of ease of availability, etc. The ratio of carbon dioxide in the carbon dioxide-containing gas is preferably 5% by volume or more, more preferably 10% by volume or more, even more preferably 20% by volume or more, even more preferably 50% by volume or more, even more preferably 80% by volume or more, and particularly preferably 90% by volume or more. If the ratio is 5% by volume or more, the amount of carbon dioxide fixed in the slurry can be increased. In addition, the time required to prepare the carbonation slurry can be shortened. Examples of carbon dioxide-containing gases include liquefied carbon dioxide, exhaust gas generated in the cement manufacturing process (carbon dioxide concentration: approximately 20% by volume), exhaust gas generated in the steelmaking process (carbon dioxide concentration: approximately 20% by volume), exhaust gas generated in the thermal power generation process (carbon dioxide concentration: approximately 10% by volume), and gas separated and recovered from these exhaust gases (carbon dioxide concentration: approximately 100% by volume).

[0020] The difference between the gas phase to which the carbon dioxide-containing gas is supplied (the gas phase consisting of the carbon dioxide-containing gas in the first slurry-accommodating portion) and the atmospheric pressure is preferably 0.02 to 0.2 MPa, more preferably 0.03 to 0.18 MPa, and particularly preferably 0.04 to 0.15 MPa. If the pressure is 0.02 MPa or more, the amount of carbon dioxide fixed in the slurry per unit time can be increased, and the slurry can be carbonated more efficiently. In addition, the equipment such as a carbonation tank can be made smaller. If the pressure is 0.2 MPa or less, the cost of the equipment can be prevented from becoming excessive.

[0021] The carbonated slurry in the first slurry storage portion moves from the first slurry storage portion through an outlet port into a liquid phase consisting of slurry in the slurry tank (excluding the slurry stored in the first slurry storage portion). In this specification, the term "liquid phase" has a concept that includes a slurry obtained by mixing a liquid with a powder or granular material (specifically, water and a calcium-containing powder). The first slurry-containing portion may have any inlet and outlet as long as the slurry can move inside and outside the first slurry-containing portion. The first slurry-containing portion may have one inlet and may have a separate inlet for introducing the slurry into the first slurry-containing portion and a separate outlet for discharging the slurry out of the first slurry-containing portion.

[0022] The carbonated slurry discharge devices 5, 25 are devices for continuously discharging the slurry in which carbon dioxide has been sufficiently fixed in the first slurry storage portions 10a, 10b, 30a, 30b as carbonated slurry (carbonated slurry in which a target amount of carbon dioxide has been absorbed and fixed) from the slurry tanks 2, 22. The carbonated slurry is discharged from the slurry tanks 2, 22 through the carbonated slurry discharge paths 15, 17, 35, 37. The discharged carbonated slurry can be used as a material for cement compositions such as concrete.

[0023] The liquid level measuring means 6a, 6b, 26a, 26b are for measuring the heights of the first liquid levels 8a, 8b, 28a, 28b in the first slurry receiving portions 10a, 10b, 30a, 30b, respectively. The liquid level measuring means 6c and 26c are for measuring the heights of the second liquid levels 11b and 31 in the second slurry containing portions in the slurry tanks 2 and 32, respectively. The second slurry storage portion means a portion of the slurry tank that stores the slurry other than the slurry stored in the first slurry storage portion, and the second liquid level means a liquid level of the liquid phase consisting of the slurry in the slurry tank (excluding the slurry stored in the first slurry storage portion). Since the gas phase consisting of the carbon dioxide-containing gas in the first slurry containing portion has a higher pressure than the gas phase in the second slurry containing portion, the height of the first liquid level is usually vertically lower than the height of the second liquid level. When the slurry tank has a plurality of first slurry storage portions and the carbon dioxide-containing gas is supplied to the plurality of first slurry storage portions using a carbon dioxide-containing gas inlet passage branched off from a single carbon dioxide-containing gas inlet passage, etc., the pressure of the gas phase consisting of the carbon dioxide-containing gas in the plurality of first slurry storage portions can be controlled simultaneously, the height of the first liquid level may be measured using a liquid level measuring means for only one of the plurality of first slurry storage portions.

[0024] The slurry control devices 7, 27 adjust the amount of slurry supplied per unit time from the slurry supply devices 3, 23 and the amount of carbonated slurry discharged per unit time from the carbonated slurry discharge devices 5, 25 based on the heights (the first liquid level height and the second liquid level height) measured by the liquid level measuring means 6a, 6b, 6c, 26a, 26b, 26c, to control the average residence time of the slurry from supply to discharge (the average time required for the slurry to be discharged as carbonated slurry after it is supplied). When carbonating a slurry continuously under pressure, the quality of the resulting carbonated slurry (e.g., the degree of carbonation of the slurry) is affected by the average residence time of the carbonated slurry and the pressure of the gas phase consisting of carbon dioxide-containing gas, etc., so it is difficult to control the average residence time of the carbonated slurry to a constant value and to stably maintain the quality of the carbonated slurry. However, according to the present invention, by adjusting the supply amount of the slurry per unit time and the discharge amount of the carbonated slurry per unit time based on the height measured by the liquid level measuring means, the average residence time of the slurry can be controlled more easily and stably, and a sufficiently carbonated carbonated slurry can be continuously produced. More specifically, the total amount of slurry in the slurry tank is calculated from the capacity of the slurry tank (first slurry storage portion and second slurry storage portion) and the measurement results obtained from the liquid level measuring means, and the amount of slurry supplied per unit time and the amount of carbonated slurry discharged per unit time are adjusted so that the total amount of slurry remains constant, thereby stabilizing the average residence time of the slurry and continuously producing a sufficiently carbonated carbonated slurry.

[0025] The slurry control device may adjust the amount of slurry supplied per unit time from the slurry supply device and the amount of carbonated slurry discharged per unit time from the carbon dioxide-containing gas discharge device, as well as adjust the amount of carbon dioxide-containing gas supplied from the carbon dioxide-containing gas supply device (in other words, adjust the pressure of the gas phase consisting of the carbon dioxide-containing gas in the first slurry storage means by increasing or decreasing the supply amount).

[0026] The carbonated slurry production system 1, 21 has a slurry circulation path 16, 36 for returning at least a portion of the carbonated slurry discharged from the slurry tank 2, 22 to the slurry tank 2, 22 for circulation. The slurry circulation path may be omitted. In order to circulate the carbonated slurry, a circulation means such as a circulation pump may be provided in the slurry circulation paths 16, 36. Here, the carbonated slurry discharge devices 5, 25 may also serve as the circulation means. In addition, a distributor or nozzle (not shown) may be provided in at least one of the regions to which the slurry is supplied from the slurry circulation paths 16 and 36 for the purpose of further improving the efficiency of carbonation. The above circulation is usually carried out until the slurry becomes a carbonated slurry in which a target amount of carbon dioxide has been absorbed and immobilized (carbonated slurry in which a sufficient amount of carbon dioxide gas has been absorbed and immobilized). By carbonating the slurry while circulating the carbonated slurry, the amount of carbon dioxide fixed in the slurry per unit time can be increased, and the slurry can be carbonated more efficiently. Furthermore, even when the slurry is carbonated continuously, the time required for carbonation can be easily adjusted. The carbonated slurry circulated from the circulation pump may be returned into the first slurry containing means from the viewpoint of further improving the efficiency of carbonation.

[0027] The carbonated slurry production system may include a liquid temperature adjusting means (not shown) for adjusting the liquid temperature of the carbonated slurry. The degree of absorption and fixation of carbon dioxide in the slurry, as well as the properties of the carbonated slurry (e.g., viscosity, particle size of the calcium-containing powder contained in the carbonated slurry) are affected by the temperature of the carbonated slurry (including a slurry that is at least partially carbonated and contained in a slurry tank). By adjusting the liquid temperature of the carbonated slurry, it is possible to more efficiently and in greater amounts to absorb and fix carbon dioxide in the slurry, and to more easily manage (adjust) the properties of the carbonated slurry. The liquid temperature adjusting means is not particularly limited as long as it has a cooling means and a heating means. The liquid temperature adjusting means can be disposed in the slurry tank, the slurry circulation path, etc. The liquid temperature adjusting means adjusts the liquid temperature of the carbonation slurry based on the liquid temperature measured by a temperature measuring means (not shown) for measuring the liquid temperature of the carbonation slurry. The temperature measuring means can be appropriately disposed in the slurry tank, the slurry circulation path, etc. The liquid temperature of the carbonation slurry adjusted by the liquid temperature adjustment means is preferably 10 to 50° C., more preferably 20 to 40° C. If the liquid temperature is 10° C. or higher, it is possible to prevent the cost of cooling equipment from becoming excessive. If the liquid temperature is 50° C. or lower, it is possible to more efficiently absorb and immobilize a larger amount of carbon dioxide in the slurry. Furthermore, for the purpose of adjusting the temperature of the slurry when it is supplied to the slurry tank, a liquid temperature adjusting means and a liquid temperature measuring means may be provided in the mixing tank (not shown).

[0028] The carbonated cement slurry production system may include a pH measurement means (not shown) for measuring the pH of the carbonated slurry (including the slurry that is at least partially carbonated and contained in the slurry tank). Based on the measured pH value of the carbonated slurry, it is possible to determine whether or not a carbonated slurry in which a target amount of carbon dioxide has been absorbed and immobilized has been obtained (whether or not a sufficient amount of carbon dioxide gas has been absorbed and immobilized in the slurry). For example, if the measured pH value of the carbonated slurry in the slurry tank (slurry that is at least partially carbonated and contained in the slurry tank) is within a predetermined numerical range, it may be determined that a sufficient amount of carbon dioxide gas has been absorbed and fixed in the carbonated slurry, and the carbonated slurry in the slurry tank may be discharged as carbonated slurry in which a target amount of carbon dioxide (carbon dioxide gas) has been absorbed and fixed. In addition, the preparation of the carbonated slurry can be managed (adjusted) by adjusting the amount of carbon dioxide-containing gas supplied from the carbon dioxide-containing gas supply device (in other words, adjusting the pressure of the gas phase consisting of carbon dioxide-containing gas in the first slurry storage means by increasing or decreasing the supply amount) based on the measured pH value of the carbonated slurry, adjusting the circulation of the slurry, etc. Furthermore, with regard to the above-mentioned slurry control device, the amount of slurry supplied per unit time from the slurry supply device and the amount of carbonated slurry discharged per unit time from the carbonated slurry discharge device may be adjusted based on the heights (the first liquid level height and the second liquid level height) measured by the liquid level measuring means and the pH of the carbonated slurry measured by the pH measuring means. The pH measuring means can be disposed in a member in which the carbonated slurry is stored or transported, such as a slurry tank or a slurry circulation path. Furthermore, each component constituting the above-mentioned carbonated slurry production system may be equipped with various measuring means such as a thermometer for measuring the temperature of the gas phase in the slurry tank, a carbonate ion concentration measuring device, an oxygen concentration measuring device, a carbon dioxide concentration measuring device, and a pressure gauge, for the purpose of managing the preparation of the carbonated slurry. Furthermore, these measurement results may be used for control by a slurry control device.

[0029] An example of a method for producing a carbonated slurry by carbonating a slurry containing a calcium-containing powder and water with a carbon dioxide-containing gas using the above-mentioned carbonated slurry production system includes a slurry preparation step of mixing a calcium-containing powder with water to obtain a slurry, a slurry supply step of continuously supplying the slurry to a slurry tank for storing the slurry, and a slurry storage step of storing the slurry and the carbon dioxide-containing gas in a first slurry storage portion of the slurry tank so that a gas phase consisting of the carbon dioxide-containing gas is located above a first liquid level of the slurry, and in a second slurry storage portion of the slurry tank so that a gas phase is located above a second liquid level of the slurry and there is no contact surface between the slurry and the carbon dioxide-containing gas. a carbonation slurry preparation step of supplying a carbon dioxide-containing gas at a pressure greater than atmospheric pressure to a gas phase consisting of a carbon dioxide-containing gas in a first slurry storage portion, and bringing the first liquid level into contact with the gas phase, thereby carbonating the slurry to obtain a carbonated slurry; a carbonation slurry discharge step of continuously discharging the carbonated slurry from the slurry tank; and a liquid level measurement step of measuring the height of the first liquid level in the first slurry storage portion and the second liquid level in the second slurry storage portion, and adjusting the amount of slurry supplied per unit time in the slurry supply step and the amount of carbonated slurry discharged per unit time in the carbonation slurry discharge step based on the measurement results obtained in the liquid level measurement step. [Explanation of symbols]

[0030] 1, 21 Carbonation slurry production system 2, 22 Slurry tank 3, 23 Slurry supply device 4, 24 Carbon dioxide-containing gas supply device 5, 25 Carbonation slurry discharge device 6a, 6b, 6c, 26a, 26b, 26c Liquid level measurement means 7, 27 Slurry control device 8a, 8b, 28a, 28b First liquid level 9a, 9b, 29a, 29b Gas phase consisting of carbon dioxide-containing gas 10a, 10b, 30a, 30b First slurry storage section 11a, 11b, 11c, 31 Second liquid level 12a, 12b, 12c, 32 Gas phase 13, 33 Slurry inlet 14, 34 Carbon dioxide-containing gas inlet 15, 17, 35, 37 Carbonated slurry discharge channel 16, 36 Slurry circulation path 18, 38 Slurries (including partially carbonated slurries) 19, 39 Stirring means 40a, 40b Outlet inlet

Claims

1. A carbonation slurry production system for producing a carbonated slurry by carbonating a slurry containing a calcium-containing powder and water with a carbon dioxide-containing gas, a slurry tank for containing the slurry; a slurry supply device for continuously supplying the slurry to the slurry tank; A carbon dioxide-containing gas supply device for supplying the carbon dioxide-containing gas; a carbonation slurry discharge device for continuously discharging the carbonated slurry from the slurry tank; a liquid level measuring means for measuring the liquid level of the slurry in the slurry tank; a slurry control device for controlling the average residence time of the slurry; The slurry tank has a first slurry storage portion for storing the slurry and the carbon dioxide-containing gas such that a gas phase consisting of the carbon dioxide-containing gas is located above a first liquid level of the slurry, and for contacting the slurry with the carbon dioxide-containing gas, and a second slurry storage portion for storing the slurry such that a gas phase is located above a second liquid level of the slurry, and does not have a contact surface between the slurry and the carbon dioxide-containing gas, The carbon dioxide-containing gas supplying device supplies the carbon dioxide-containing gas at a pressure higher than atmospheric pressure to the gas phase of the carbon dioxide-containing gas in the first slurry accommodation portion, the liquid level measuring means measures the height of each of a first liquid level in the first slurry receiving portion and a second liquid level in the second slurry receiving portion; A carbonated slurry production system characterized in that the slurry control device controls the average residence time of the slurry by adjusting the amount of the slurry supplied per unit time from the slurry supply device and the amount of the carbonated slurry discharged per unit time from the carbonated slurry discharge device based on the respective heights of the first liquid level in the first slurry storage portion and the second liquid level in the second slurry storage portion measured by the liquid level measuring means.

2. The carbonation slurry production system according to claim 1, further comprising a slurry circulation path for returning at least a portion of the carbonation slurry discharged from the slurry tank to the slurry tank for circulating the same.

3. 3. The system for producing a carbonated slurry according to claim 1 or 2, wherein the slurry tank has an agitation means for agitating and mixing the carbonated slurry in the slurry tank.

4. The carbonation slurry production system according to claim 1 or 2, further comprising a pH measuring means for measuring a pH of the carbonation slurry.

5. The carbonated slurry production system according to claim 1 or 2, further comprising a liquid temperature adjusting means for adjusting the liquid temperature of the carbonated slurry.

6. A method for producing a carbonated slurry by carbonating a slurry containing a calcium-containing powder and water with a carbon dioxide-containing gas, comprising: a slurry preparation step of mixing the calcium-containing powder with the water to obtain the slurry; a slurry supplying step of continuously supplying the slurry to a slurry tank for containing the slurry; a slurry containing step of containing the slurry and the carbon dioxide-containing gas in a first slurry containing portion of the slurry tank such that a gas phase consisting of the carbon dioxide-containing gas is located above a first liquid level of the slurry, and containing the slurry and the carbon dioxide-containing gas in a second slurry containing portion of the slurry tank such that a gas phase is located above a second liquid level of the slurry and there is no contact surface between the slurry and the carbon dioxide-containing gas; a carbonation slurry preparation step of supplying the carbon dioxide-containing gas at a pressure higher than atmospheric pressure to a gas phase consisting of the carbon dioxide-containing gas in the first slurry accommodation portion, thereby bringing the first liquid surface into contact with the gas phase, thereby carbonating the slurry to obtain a carbonated slurry; a carbonation slurry discharge step of continuously discharging the carbonated slurry from the slurry tank; A liquid level measuring step of measuring the height of the first liquid level in the first slurry containing portion and the height of the second liquid level in the second slurry containing portion, A method for producing a carbonated slurry, characterized in that the amount of the slurry supplied per unit time in the slurry supply process and the amount of the carbonated slurry discharged per unit time in the carbonation slurry discharge process are adjusted based on the measurement results obtained in the liquid level measurement process.

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