JP2011016710A - Carbonation treatment method and apparatus of steel slag powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for carbonating calcium oxide and calcium hydroxide in steel slag homogeneously to calcium carbonate, and an apparatus for carrying out the method.SOLUTION: Calcium oxide and/or calcium hydroxide in steel slag is transformed to calcium carbonate by forming a fluid layer of steel slag powder by using a treating water in which a gas containing carbon dioxide is dispersed as microbubbles.

Description

  The present invention relates to a method for carbonizing calcium oxide or calcium hydroxide contained in steel slag and a carbonation processing apparatus for carrying out the method.

  In steelworks, steel slag is generated as a by-product when steel is produced. Steel slag is roughly classified into blast furnace slag discharged together with pig iron from the blast furnace and converter slag composed of oxides generated during oxidation refining in the converter. These steel slags are used for roadbed materials, cement materials, civil engineering materials, and the like.

Steel slag contains calcium oxide (CaO), and when it comes into contact with moisture, it produces calcium hydroxide [Ca (OH) ₂ ], causing a swelling phenomenon that increases the volume. When steel slag is used as a roadbed material, for example, the problem is that dimensional stability is poor due to swelling phenomenon. In order to suppress the swelling phenomenon during use, it is considered that CaO in steel slag may be hydrated in advance to complete the change to Ca (OH) ₂ .

As a method for changing CaO to Ca (OH) ₂ , atmospheric aging treatment, vapor aging treatment, and pressure aging treatment are known. Atmospheric aging treatment is a method in which steel slag is exposed to the atmosphere for several months to several years to fully hydrate CaO in the steel slag and change it to Ca (OH) ₂ . Under atmospheric pressure and under pressure, aging treatment is a method in which water vapor is brought into contact with steel slag to change CaO in the steel slag to Ca (OH) ₂ under pressure.

However, Ca (OH) ₂ produced by aging treatment is dissolved in water according to the following formula (1).
Ca (OH) ₂ → Ca ²⁺ + 2OH ⁻ (1)

When Ca (OH) ₂ is dissolved in seawater and the pH of the seawater rises to about 9.5 or more, Mg (OH) ₂ is precipitated, and the seawater becomes cloudy.

Further, CaO and contained in the iron and steel slag, since CaO remaining unreacted even after being subjected to an aging treatment to the steel slag to produce a Ca (OH) ₂ when in contact with seawater, the Ca (OH) ₂ is seawater As described above, it becomes a cause of causing the cloudiness phenomenon. Generation | occurrence | production of the cloudiness phenomenon of the seawater resulting from CaO or Ca (OH) ₂ becomes a factor which inhibits the use expansion of steel slag.

In order to make CaO and Ca (OH) ₂ contained in steel slag and aging-treated steel slag insoluble in water, carbonization treatment is applied to steel slag (or aging-treated steel slag) and oxidation in steel slag is performed. Methods for changing calcium or calcium hydroxide to calcium carbonate are known (for example, Patent Documents 1 to 4).

In Patent Document 1, the moisture content of steel slag powder having a particle size distribution with a particle size of 1 mm or less having a particle size distribution of 60% by mass or more and a volume expansion coefficient of 3% or more was adjusted to 10 to 25% by mass. Thereafter, a stabilization method for powdered steel slag in which a carbon dioxide-containing gas is brought into contact is described. Patent Document 2 discloses a metal in which a slag in a molten state, a semi-molten state, or a high-temperature solid state is injected into a rotating drum in which a metal ball group is accommodated, and the slag rolls in the rotating drum. A steelmaking slag having a step of pulverizing by contacting with a ball group, a step of bringing a slag pulverized product into contact with carbon dioxide or a gas containing carbon dioxide, and a step of reacting uncarbonized Ca contained in the slag pulverized product with carbon dioxide A processing method is disclosed. Patent Document 3 discloses that carbon dioxide added to a steelmaking slag that has been subjected to an aging treatment so as to be less than a moisture value at which free water begins to exist and to be in a range of 10% by mass or less than the moisture value. A method for stabilizing steelmaking slag is described, in which after adjusting the amount of water, carbon dioxide is contained and a gas having a relative humidity of 75 to 100% is flowed. In Patent Document 4 and Non-Patent Document 1, steelmaking slag particles accompanied with surface adhering water are brought into contact with CO ₂ -containing exhaust gas in a packed bed system (fixed bed system), and vibration for applying vibration to the reaction tank is disclosed. The installation of the device is described. Further, in Patent Document 5, a micro-bubble-containing water in which carbon dioxide-containing gas is dispersed as microbubbles in water is brought into contact with a blast furnace granulated slag to make it hard to consolidate. A manufacturing method is disclosed.

JP 2008-214150 A JP 2008-100953 A JP-A-2005-47789 JP 2001-252525 A JP 2007-186364 A

Takahashi and five others, “FY 1998 New Energy and Industrial Technology Development Organization Immediate Proposal Public Offering Project Research and Development Results (final version) Carbon dioxide absorption by steel slag”, Nippon Steel Pipe Co., Ltd., March 2000

In Patent Documents 1 to 5 and Non-Patent Document 1, since carbonation of steel slag and aged steel slag is performed not in a fluid state but in a fixed layer, calcium oxide and calcium hydroxide contained in steel slag are used. It was difficult to uniformly carbonate. This is because the carbonization treatment is performed in the fixed layer, so that the slags are solidified or too much moisture is added to block the gas passage, and the gas is not uniformly dispersed in the slag layer. It is believed that there is. Further, the method of optimizing the amount of added water and the relative humidity of the gas is complicated.
According to Patent Document 4 and Non-Patent Document 1, it is also reported that in the case of a fixed layer, if the gas continues to flow, the packed layer contracts to create a gas passage, and gas blow-through occurs. Therefore, in these documents, the vibration device is attached, but it is desirable to reduce the additional equipment.

  The present invention has been made paying attention to the above circumstances, and its purpose is a carbonation treatment method capable of uniformly changing calcium oxide and calcium hydroxide in steel slag to calcium carbonate, And providing an apparatus for carrying out the method.

  The carbonation treatment method of the present invention that has achieved the above object is to form a fluidized bed of steel slag powder using water for treatment in which a carbon dioxide-containing gas is dispersed as microbubbles, thereby forming calcium oxide in steel slag. The point is that the calcium hydroxide is changed to calcium carbonate.

  As a preferable apparatus for carrying out the carbonation treatment method, calcium oxide in steel slag and / or by forming a fluidized bed of steel slag powder using water for treatment in which carbon dioxide-containing gas is dispersed as microbubbles. Or, it has a basic structure of a carbonation treatment tank for changing calcium hydroxide to calcium carbonate and a microbubble generator for preparing the treatment water, wherein the carbonation treatment tank includes the microbubble generator An inlet for introducing the prepared treatment water into the carbonation tank is provided, and an inclined surface part exceeding the angle of repose of the steel slag powder in water is formed below the inner wall surface of the carbonation tank. Is further provided as a characteristic configuration.

  The carbonation treatment tank is provided with a discharge part for discharging the treatment water to the outside of the carbonation treatment tank, and the steel slag powder is prevented from reaching the discharge part below the lowest point of the discharge part. A baffle member may be provided. An enlarged inner diameter portion may be provided above the carbonation tank. Also, by providing a rising pipe above the inlet and forming an upward flow of the treatment water in the rising pipe, the rising flow for raising the steel slag in the rising pipe and the lowering for lowering the outside of the rising pipe A convection including a flow may be generated in the carbonation tank.

  According to the carbonation treatment method of the present invention, by performing the carbonation treatment in a state where the steel slag powder is flowed using the treatment water in which the carbon dioxide-containing gas is dispersed as microbubbles, calcium oxide in the steel slag is obtained. And calcium hydroxide can be efficiently converted to calcium carbonate. For this reason, even when steel slag obtained by carbonation is used as a material for marine civil engineering, the pH of seawater is hardly increased, and the cloudiness phenomenon of seawater is hardly generated. According to the present invention, a carbonation treatment apparatus for carrying out the carbonation treatment method can also be provided.

FIG. 1 is a schematic explanatory view showing a configuration example of a carbonation treatment apparatus according to the present invention. FIG. 2 is a schematic explanatory view showing another configuration example of the carbonation treatment apparatus according to the present invention. FIG. 3 is a schematic explanatory view showing still another configuration example of the carbonation treatment apparatus according to the present invention.

  The present inventors have intensively studied a method capable of uniformly carbonizing steel slag such as blast furnace slag and converter slag and an apparatus for carrying out the method. As a result, if carbonation treatment is performed while flowing steel slag powder using water for treatment in which carbon dioxide-containing gas is dispersed as microbubbles, calcium oxide and calcium hydroxide in steel slag (hereinafter referred to as calcium oxide, etc.) The present invention has been completed by finding that it can be uniformly changed to calcium carbonate.

  That is, the carbonation treatment method according to the present invention is characterized in that the calcium slag in the steel slag is changed to calcium carbonate while allowing the steel slag powder to flow in the liquid, and the steel slag powder is fluidized. In order to perform the carbonation treatment, it is important to use treatment water in which carbon dioxide-containing gas is dispersed as microbubbles.

On the other hand, in the said patent documents 1-5 and nonpatent literature 1, it is not considered at all about performing carbonation processing, making steel slag powder flow in a liquid, and it is fixing which does not flow substantially. Since the steel slag powder and the carbon dioxide-containing gas are in contact with each other, a large amount of unreacted CaO and Ca (OH) ₂ remains in the steel slag. Therefore, when this steel slag is used as a marine civil engineering material, as described above, the pH of seawater rises to about 9.5 or more, so that Mg (OH) ₂ is precipitated and the seawater becomes cloudy.

  Hereinafter, a carbonation treatment apparatus for carrying out the carbonation treatment method of the present invention will be described with reference to the drawings. However, the carbonation treatment apparatus of the present invention is not limited to the following drawings, and The design may be changed within a range that can be adapted to the purpose.

  FIG. 1 is a schematic explanatory view showing a configuration example of a carbonation treatment apparatus according to the present invention. In FIG. 1, 1 is a carbonation tank, 2 is a microbubble generator, 3 is a circulation pump, 4 is a circulation path, 5 is an oxygen dioxide-containing gas supply path, 6 is steel slag powder, 7 is water for treatment, and 8 is water for treatment. The baffle members are shown respectively. An inclined surface portion 1 a is provided below the inner wall surface of the carbonation treatment tank 1, and the treatment water prepared by the microbubble generator 2 is introduced into the carbonation treatment tank 1 below (bottom surface) of the carbonation treatment tank 1. In addition, a discharge port 1c for discharging the processing water to the outside of the carbonation treatment tank 1 is provided above the carbonation treatment tank 1. The treatment water 7 discharged from the discharge unit 1c to the outside of the carbonation treatment tank 1 is operated by the circulation pump 3 provided on the circulation path 4 to pass through the microbubble generator 2 and the carbonation treatment from the inlet 1b. It is configured to be returned into the tank 1. A path 5 is provided on the upstream side of the circulation pump 3, and a carbon dioxide-containing gas is supplied from the path 5. The carbon dioxide-containing gas is microbubbled by the microbubble generator 2 to prepare treatment water dispersed in water as microbubbles.

  In the carbonation treatment apparatus of the present invention, the inclination angle of the inclined surface portion 1a provided below the inner wall surface of the carbonation treatment tank 1 is an angle that exceeds the repose angle of the steel slag powder introduced into the carbonation treatment tank 1 in water. This is very important. This is because the fluidized bed (for example, fluidized bed) of the steel slag powder 6 introduced into the carbonation treatment tank 1 is stably formed and maintained, and the calcium oxide or the like in the steel slag powder 6 is uniformly changed to calcium carbonate.

  That is, when the treatment water is introduced from the introduction port 1b provided below the carbonation treatment tank 1 (in the center of the bottom in FIG. 1), the steel slag powder 6 in the carbonation treatment tank 1 is reduced in water pressure and microbubbles at the time of introduction. The inside of the carbonation treatment tank 1 rises following the upward flow of the treatment water 7 formed by floating. A part of the rising treatment water 7 is discharged from the discharge part 1c to the outside of the system above the carbonation treatment tank 1, and the remaining part is reversed to form a downward flow. The steel slag powder 6 that reaches the upper side with the upward flow descends with the downward flow. At this time, if the bottom of the carbonation tank 1 is, for example, a flat bottom, the steel slag powder 6 that has descended stays at the bottom of the carbonation tank 1 to form a fixed layer, but the steel slag powder 6 is formed below the inner wall surface. If the inclined surface portion 1 a having an angle exceeding the angle of repose in water is provided, the steel slag powder 6 slides on the inclined surface portion 1 a and reaches the bottom surface of the carbonation treatment tank 1. The steel slag powder 6 that has reached the bottom surface of the carbonation treatment tank 1 rises again following the upward flow formed by the treatment water introduced from the introduction port 1b and continuously flows into the carbonation treatment tank 1. A state is formed (no stagnation at the bottom mentioned above). By causing the steel slag powder 6 to flow in this way, it is possible to prevent the steel slag powder 6 from aggregating and solidifying with each other.

In the present invention, since the treatment water in which the carbon dioxide-containing gas is dispersed as microbubbles is introduced from the introduction port 1b, the reaction with the steel slag powder 6 can be promoted, and calcium oxide and the like in the steel slag powder 6 can be obtained. It can be uniformly changed to calcium carbonate. Dispersing the carbon dioxide-containing gas in the water as microbubbles makes the rate of increase of the carbon dioxide-containing gas in the treatment water slower than in general bubbling, and the surface area of the carbon dioxide-containing gas can be increased. The dissolution efficiency of CO _{2 in} the water for treatment is increased, and carbonation of calcium oxide and the like is promoted. The size of the microbubbles is not particularly limited, and usually the diameter is in the range of about 1 μm to 100 μm.

  The angle of repose is a valley-like slope formed by steel slag powder remaining in the container when the steel slag and water are naturally dropped from the bottom center of a flat bottom transparent container containing steel slag powder and water. It is examined by measuring the angle. This measurement method is called the discharge method.

  In the carbonation treatment tank 1 shown in FIG. 1, a porous plate is provided as a baffle member 8 below the lowest point of the discharge part 1c. If the baffle member 8 is provided, the steel slag powder 6 that has risen with the upward flow can be forcibly separated from the upward flow and prevented from being discharged out of the tank from the discharge portion 1c.

  The baffle member 8 is not limited to a perforated plate, and for example, a plurality of plates may be combined in a staggered manner so that a clearance is provided to allow treatment water to pass.

  FIG. 2 is a schematic explanatory view showing another configuration example of the carbonation treatment apparatus of the present invention, and the same parts as those in FIG. In FIG. 2, instead of providing the baffle member 8 with respect to the configuration example shown in FIG. By providing an enlarged inner diameter portion 1 d wider than the inner diameter of the body portion 1 e of the carbonation treatment tank 1, the rising speed of the treatment water is relaxed to form a stagnation state above the carbonation treatment tank 1. Therefore, the timing at which the steel slag powder 6 begins to sink under its own weight (that is, the steel slag powder 6 descends) can be advanced, and the steel slag powder 6 can be prevented from reaching the discharge portion and flowing out of the tank.

  As another means for preventing the steel slag powder 6 from flowing out of the carbonation treatment tank 1, the carbonic acid so that the distance between the lowest point of the discharge part 1c and the highest point of the steel slag powder 6 in the fluidized state is increased. You may lengthen the trunk | drum 1e of the chemical conversion tank 1. FIG. Since the momentum of the upward flow of treatment water introduced from the inlet 1b is limited, if the body portion 1e is lengthened, the steel slag powder 6 flows out without providing the baffle member 8 and the enlarged inner diameter portion 1d. Can be prevented.

  FIG. 3 is a schematic explanatory view showing still another configuration example of the carbonation treatment apparatus according to the present invention. In the carbonation tank 1 shown in FIG. 3, the rising pipe 9 is provided immediately above the inlet 1b. In the configuration example shown in FIG. 3, the baffle member 8 shown in FIG. 1 is not provided.

  If the rising pipe 9 is provided directly above the inlet 1b and the processing water is introduced toward the rising pipe 9, an upward flow of the processing water can be formed in the rising pipe 9, and the steel slag powder 6 is An ascending flow that rises in the ascending pipe 9 and a convection that is discharged from the top of the ascending pipe 9 and turns into a descending flow can be formed in the carbonation treatment tank 1. At this time, a part of the carbon dioxide-containing gas dispersed as microbubbles in the treatment water 7 rising in the riser 9 floats as it is and reaches the water surface. It moves below the carbonation tank 1 along with the downward flow formed outside the ascending pipe 9. Since the microbubbles are very fine, the force to float in the water is weak, and it is considered that a part of the microbubbles also descends in the carbonation treatment tank 1 with the downward flow formed by the steel slag powder 6. Therefore, if the ascending pipe 9 is provided, the steel slag powder 6 and the carbon dioxide-containing gas can be brought into contact with each other for a longer time, so that the carbonation reaction of the steel slag powder 6 can be promoted.

  1-3, the opening diameter of the inlet 1b is not particularly limited, but if the opening diameter is too large, the momentum of the upward flow formed by the treatment water 7 becomes weak, and a part of the steel slag powder 6 is formed. There is a case where calcium oxide or the like in the steel slag powder 6 cannot be uniformly carbonated without flowing. Moreover, in order to increase the upward flow speed of the processing water 7, the equipment load increases, which is uneconomical. Furthermore, when the ascending flow speed of the treatment water in the carbonation treatment tank 1 becomes too large, the steel slag powder rises and is easily discharged out of the carbonation treatment tank 1. On the other hand, if the opening diameter is too small, the momentum of the upward flow formed by the treatment water 7 becomes too strong, and the flow state of the steel slag powder 6 becomes non-uniform, and stable carbonation may not be performed.

  What is necessary is just to set the flow volume of the process water introduce | transduced in the carbonation-treatment tank 1 from the said inlet 1b in the range which forms the flow state of the steel slag powder 6. FIG. For example, when the average particle size of the steel slag powder is about 75 μm, the liquid velocity of the treatment water at the inlet 1b is calculated from the Stokes equation assuming that the steel slag powder is a spherical particle having a particle size of 75 μm. What is necessary is just to make it larger than 0.006 m / sec which is a terminal sedimentation velocity.

  In FIGS. 1 to 3, the configuration example in which the introduction port 1 b is provided in the center of the bottom surface of the carbonation treatment tank 1 is shown, but the position where the introduction port 1 b is provided is not limited to the bottom (lowermost part) For example, one or more introduction ports may be provided in the inclined surface portion 1a. Furthermore, you may provide one or several inlets in a side surface. Water (that is, water in which the carbon dioxide-containing gas is not dispersed as microbubbles) is supplied from the bottom of the carbonation tank 1 to form an upward flow in the carbonation tank 1, while the bottom Steel slag powder 6 can be obtained by introducing treatment water in which carbon dioxide-containing gas is dispersed as microbubbles or introducing microbubbles of carbon dioxide-containing gas from an inlet provided in a place other than the above (for example, inclined surface portion 1a). The carbon dioxide-containing gas can be brought into contact with the steel slag powder 6. As a result, calcium oxide or the like contained in the steel slag can be uniformly carbonated.

  1 to 3, the carbon dioxide-containing gas may be supplied from the upstream side of the microbubble generator 2. For example, even if the path 5 is provided between the circulation pump 3 and the microbubble generator 2. Good. As the microbubble generator 2, a generator using a gas-liquid shearing method, a generator using a pressurized levitation method, or a diffuser-type generator can be used. For example, pure carbon dioxide gas may be supplied as the carbon dioxide-containing gas.

  If the said carbonation processing apparatus is used, since the carbonization process can be performed while making the steel slag powder 6 flow, the calcium oxide etc. in steel slag can be changed uniformly to calcium carbonate. Steel slag obtained by carbonation treatment does not increase the pH of water even when it comes into contact with water, and does not generate sea turbidity even when it comes into contact with seawater, so it is particularly suitable as a material for marine civil engineering. Available to: This marine civil engineering material is used for, for example, submerged dike materials, seaweed bed construction materials, raising materials (for example, raising materials when building seaweed bed construction materials), sand-capping materials, backfill materials for deep digging traces it can. The steel slag subjected to the carbonation treatment can be used as, for example, a roadbed material, a cement material, and a civil engineering material.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

[Experiment 1 (Invention)]
Using the carbonation treatment apparatus shown in FIG. 1, the converter slag is steam-aged according to the following procedure to change the calcium oxide contained in the converter slag into calcium hydroxide, and then the steam-aged converter slag is used. The calcium oxide and calcium hydroxide contained were changed to calcium carbonate.

  First, steam aging was performed by blowing steam to the converter slag for 48 hours, and 1 kg of steam-aged converter slag was prepared. The particle size of steam-aged converter slag was 75 to 420 μm.

  Next, the prepared steam-aged converter slag was introduced into the carbonation treatment tank 1. As the carbonation treatment tank 1, an acrylic cylindrical tube having an inner diameter of 180 mm and a height of 1200 mm attached to an acrylic cone having a bottom diameter of 180 mm as shown in FIG. 1 was used. The apex angle of the acrylic cone is 60 °, and the angle of the inclined surface portion is 60 °. The angle of the inclined surface portion exceeds the angle of repose of steam-aged converter slag in water.

  The apex portion of the acrylic cone is cut off, and an inlet 1b having an opening diameter of 18 mm is provided. The total length of the carbonation treatment tank 1 (distance from the inlet 1b to the uppermost end) was 1340 mm, and the discharge part 1c was provided at a position where the height from the inlet 1b was 1000 mm. As shown in FIG. 1, a baffle member 8 (a perforated plate filter) was provided at a position where the height from the inlet 1b was 700 mm.

  Pure carbon dioxide gas is supplied from the path 5 at a flow rate of 0.1 NL / min, and the circulation pump 3 and the microbubble generator 2 (gas-liquid shear mixing / dispersing device) are operated to disperse the pure carbon dioxide gas as microbubbles. The carbonation treatment is carried out by preparing the treated water, supplying the treatment water from the inlet 1b at a flow rate of 8 L / min, and changing the calcium oxide and calcium hydroxide in the steam-aged converter slag to calcium carbonate. Went for hours. During the carbonation treatment, the steam-aged converter slag introduced into the carbonation treatment tank 1 was flowing over the entire lower portion of the baffle member 8.

After 10 hours, the slag was taken out from the carbonation tank 1 and dried. When the calcium carbonate content in the slag before and after the carbonation treatment was examined as follows, the CO ₂ absorption amount per 1 ton of slag (measured CO ₂ absorption amount) was 119 kg. The reaction rate (= measured CO ₂ absorption amount / theoretical CO ₂ absorption amount. The theoretical CO ₂ absorption amount means that all Ca contained in the slag before carbonation treatment can react with CO ₂ and be converted to CaCO _3. Assuming that the theoretical amount of CO ₂ required for this is 33%, the CO ₂ utilization rate (= the amount of supplied CO ₂ / the amount of absorbed CO _{2. The} amount of supplied CO ₂ is the unit time of CO ₂ . The product of the per unit flow rate and the supply time was divided by the mass of the slag, and the absorbed CO ₂ amount was the measured CO ₂ absorbed amount) was 88%.

[Measurement method of calcium carbonate content in slag]
After the slag was crushed, hydrochloric acid was added to chemically decompose CaCO ₃ in the slag. CO ₂ generated by this decomposition was collected and the amount thereof was determined. Assuming that all CaCO ₃ was decomposed to CO ₂ , the amount of CaCO _{3 in} the slag was determined.

  The dried slag was immersed in artificial seawater having a mass 10 times the mass of the dried slag, and the change with time in pH of the artificial seawater was measured. The pH of the artificial seawater used is 8.5. In the present invention, the case where the pH of the seawater after the slag is immersed for 1000 hours is less than 9.5 is regarded as acceptable. As a result, the pH of the seawater after the slag was immersed for 1000 hours was about 9. Moreover, even if the seawater after slag immersion was visually observed, the seawater was not cloudy.

[Experiment 2 (Comparative Example)]
In the said experiment 1, the converter slag which carried out the steam aging on the same conditions except the point which used the carbonation treatment tank 1 shown below was carbonized.

  The carbonation treatment tank 1 used in this experiment 2 was one in which an acrylic cone having a bottom diameter of 180 mm was attached to the lower end of an acrylic cylindrical tube having an inner diameter of 180 mm and a height of 600 mm as shown in FIG. The apex angle of the acrylic cone is 120 °, and the angle of the inclined surface portion is 30 °. The angle of the inclined surface portion is equal to or less than the angle of repose of steam-aged converter slag in water. The apex portion of the acrylic cone is cut off, and an inlet 1b having an opening diameter of 18 mm is provided. The total length (distance from the inlet 1b to the uppermost end) of the carbonation treatment tank 1 is 1340 mm, and the discharge part 1c is provided at a position where the height from the inlet 1b is 1000 mm. As shown in FIG. 1, a baffle member 8 (a perforated plate filter) was provided at a position where the height from the inlet 1b was 700 mm.

  Using the carbonation tank 1, the carbonization of the steam-aged converter slag was performed for 10 hours under the same conditions as in Experiment 1. During the carbonation treatment, it was recognized that a part of the converter slag stayed at the bottom of the carbonation treatment tank 1 to form a fixed layer.

  After the carbonation treatment, the slag was taken out from the carbonation treatment tank 1 and dried. The dried slag was immersed in artificial seawater for 1000 hours under the same conditions as in Experiment 1, and the change over time in the pH of the artificial seawater was measured. As a result, the pH of seawater after slag was immersed for 24 hours was about 12, and the pH of seawater was about 12 even after 1000 hours of immersion. Moreover, when the seawater after slag immersion was observed visually, the seawater was cloudy.

DESCRIPTION OF SYMBOLS 1 Carbonation processing tank 2 Microbubble generator 3 Circulation pump 4 Circulation path 5 Oxygen dioxide containing gas supply path 6 Steel slag powder 7 Water for treatment 8 Baffle member

Claims (5)

  It is characterized in that calcium oxide and / or calcium hydroxide in steel slag is changed to calcium carbonate by forming a fluidized bed of steel slag powder using treatment water in which carbon dioxide-containing gas is dispersed as microbubbles. Carbonation treatment method. A carbonation treatment tank in which calcium oxide and / or calcium hydroxide in steel slag is changed to calcium carbonate by forming a fluidized bed of steel slag powder using treatment water in which carbon dioxide-containing gas is dispersed as microbubbles; A microbubble generator for preparing the treatment water,
The carbonation tank is provided with an inlet for introducing the treatment water prepared by the microbubble generator into the carbonation tank,
A carbonation treatment apparatus, wherein an inclined surface portion exceeding an angle of repose of the steel slag powder in water is formed below the inner wall surface of the carbonation treatment tank.   The carbonation treatment tank is provided with a discharge part for discharging the treatment water to the outside of the carbonation treatment tank, and prevents the steel slag powder from reaching the discharge part below the lowest point of the discharge part. The carbonation processing apparatus of Claim 2 which has provided the baffle member for performing.   The carbonation treatment apparatus according to claim 2 or 3, wherein an enlarged inner diameter portion is provided above the carbonation treatment tank.   By providing a rising pipe above the inlet and forming an upward flow of the treatment water in the rising pipe, an upward flow for raising the steel slag in the rising pipe and a downward flow for lowering the outside of the rising pipe The carbonation processing apparatus in any one of Claims 2-4 comprised so that the convection containing this may be produced | generated in the said carbonation processing tank.

Images