JP2013129543A - Method and system for producing calcium carbonate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and system for producing calcium carbonate, wherein fine powder consisting of waste concrete, obtained after separating an aggregate from the waste concrete, is recovered.SOLUTION: A method for producing calcium carbonate includes: a step of extracting a calcium ion in fine powder consisting of waste concrete by supplying water, acetic acid, and the fine powder to the inside of a main reaction container 1 and stirring them; a step of separating a reaction residue from a solution containing the calcium ion by using first filtration equipment 18; a step of feeding the solution from which the reaction residue is separated, to the inside of a sub-reaction container 23; a step of causing calcium carbonate deposition by supplying carbon dioxide to the inside of the sub-reaction container and stirring the solution and the carbon dioxide; and a step of recovering the calcium carbonate deposited, by using second filtration equipment 36.

Description

  TECHNICAL FIELD The present invention relates to a calcium carbonate manufacturing method and a calcium carbonate manufacturing system for reusing residual waste fine powder after separating aggregate from waste concrete.

  The total amount of waste concrete generated when demolishing concrete structures reaches 400 million tons per year. This total amount is expected to increase to 500 million tons in 2025 with the aging of concrete buildings built after the period of high economic growth.

  Currently, the generated concrete waste is reused as a roadbed material or processed at a final disposal site. However, the increase in the amount of concrete waste generated in the future cannot be covered by the demand for roadbed materials alone, and it is expected to exceed the processing capacity of the final disposal site, and there is a need for a method of reusing concrete waste. .

  As a method of reusing waste concrete, there is a method in which the discharged waste concrete is pulverized, the aggregate and the waste concrete fine powder (filler) are separated, and the removed aggregate is reused as the concrete aggregate. The filler generated in large quantities when separated from the aggregate is discarded as it is, and is hardly reused.

  In Patent Document 1, the waste cement fine powder is dissolved in a hydrochloric acid solution to precipitate impurities, and ammonia water is dropped into the solution from which impurities are removed to precipitate metal ions in the solution as hydroxides. Furthermore, the structure which makes a carbon dioxide gas conduct | electrically_connect to the solution which removed the impurity, or deposits calcium carbonate by dripping the ammonium carbonate aqueous solution is disclosed.

JP 2008-143765 A

  In view of such circumstances, the present invention provides a calcium carbonate manufacturing method and a calcium carbonate manufacturing system for reusing waste concrete fine powder after separating aggregate from waste concrete.

  The present invention provides a step of extracting calcium ions in waste concrete fine powder by supplying water, acetic acid and waste concrete fine powder into a main reaction vessel and stirring, and a first filtration from a solution containing calcium ions. A step of separating the reaction residue by an apparatus, a step of feeding the solution from which the reaction residue has been separated into the sub-reaction vessel, and supplying the carbon dioxide into the sub-reaction vessel and stirring to precipitate calcium carbonate. The present invention relates to a method for producing calcium carbonate, which includes a step and a step of recovering precipitated calcium carbonate by a second filtration device.

  Further, the present invention includes a step of separating acetic acid-containing water as a residual liquid in the step of recovering calcium carbonate by the second filtration device, circulating the separated acetic acid-containing water, and supplying it again into the main reaction vessel. Further, the present invention relates to a method for producing calcium carbonate.

  The present invention also includes a main reaction vessel that stirs water, acetic acid and waste concrete fine powder to extract calcium ions, a water supply system that supplies water into the main reaction vessel, and acetic acid in the main reaction vessel. Acetic acid supply system for supplying, waste concrete fine powder supply system for supplying waste concrete fine powder into the main reaction vessel, a first filtration device for separating a reaction residue from a solution containing calcium ions, and the reaction residue A carbon dioxide-containing gas introduced into the separated solution to precipitate calcium carbonate, a carbon dioxide supply system for supplying the carbon dioxide-containing gas into the secondary reaction vessel, and deposition in the secondary reaction vessel The present invention relates to a calcium carbonate production system comprising a second filtration device that collects the calcium carbonate that has been collected.

  Furthermore, the present invention is provided with a plurality of subsystems each including the main reaction vessel, the first filtration device, the sub-reaction vessel, and the second filtration device, and sequentially operating the subsystems. Thus, the present invention relates to a calcium carbonate production system that enables pseudo continuous operation.

  According to the present invention, the step of extracting calcium ions in the waste concrete fine powder by supplying water, acetic acid, and the waste concrete fine powder into the main reaction vessel and stirring, and the first solution from the solution containing calcium ions. The step of separating the reaction residue by the filtration device of step 1, the step of feeding the solution from which the reaction residue has been separated into the side reaction vessel, and supplying carbon dioxide into the side reaction vessel and stirring the calcium carbonate. Since it has a step of precipitating and a step of recovering the precipitated calcium carbonate by the second filtration device, it is possible to reduce the amount of waste by producing calcium carbonate from the waste concrete fine powder, Carbon dioxide can be treated at low cost.

  Further, according to the present invention, a main reaction vessel that stirs water, acetic acid and waste concrete fine powder to extract calcium ions, a water supply system that supplies water into the main reaction vessel, and the main reaction vessel An acetic acid supply system for supplying acetic acid; a waste concrete fine powder supply system for supplying waste concrete fine powder into the main reaction vessel; a first filtration device for separating a reaction residue from a solution containing calcium ions; A sub-reaction vessel that introduces a carbon dioxide-containing gas into the solution from which the reaction residue has been separated to precipitate calcium carbonate, a carbon dioxide supply system that supplies the carbon dioxide-containing gas into the sub-reaction vessel, and the sub-reaction vessel And a second filtering device that collects calcium carbonate precipitated in step (b), thereby reducing the total amount of waste discarded by producing calcium carbonate from the waste concrete fine powder. Rutotomoni, there is exhibited an excellent effect that the treatment of carbon dioxide can be carried out at a low cost.

It is a block diagram of the calcium carbonate manufacturing system which concerns on the Example of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  With reference to FIG. 1, a calcium carbonate production system according to an embodiment of the present invention will be described.

  In FIG. 1, reference numeral 1 denotes a main reaction vessel. The main reaction vessel 1 is connected to a water supply source 3 such as a water storage tank via a water supply pipe 2 and is connected to an acetic acid storage tank etc. via an acetic acid supply pipe 4. The acetic acid supply source 5 is connected to a waste concrete crusher (not shown) via a filler supply pipe 6. A waste concrete fine powder supply system 7 is constituted by the filler supply pipe 6 and the waste concrete crusher.

  The water supply pipe 2 is provided with a water supply pump 8 for supplying water from the water supply source 3 into the main reaction vessel 1, and a heat exchanger 9 using steam obtained from factory exhaust gas as a heat source. The water supplied into the main reaction vessel 1 is heated to a predetermined temperature, for example, 60 ° C. by the heat exchanger 9. The water supply pipe 11, the water supply source 3, the water supply pump 8, and the heat exchanger 9 constitute a water supply system 11.

  The acetic acid supply pipe 4 is provided with an acetic acid supply pump 12 for supplying acetic acid from the acetic acid supply source 5 into the main reaction vessel 1, and the acetic acid supply pipe 4, the acetic acid supply source 5, and the acetic acid supply pump. 12 constitutes an acetic acid supply system 13.

  The main reaction vessel 1 is provided with a first stirring mechanism 15 that is rotated by a first drive motor 14, and water supplied into the main reaction vessel 1 by the first stirring mechanism 15 Acetic acid and waste concrete fine powder are stirred.

  Further, the main reaction vessel 1 is connected to a first filtration device 18 via a mixed solution feed pipe 17 provided with a pump 16. The first filtration device 18 has a structure in which a required filter 21 such as a filter press or a Hundback filter is provided in an airtight container 19, and consists of a calcium ion solution and a reaction residue described later by the filter 21. The mixed solution is filtered.

  One end of a solution feed pipe 22 is connected to the sealed container 19, and the other end of the solution feed pipe 22 is connected to a sub-reaction vessel 23, and the solution feed pipe 22 is connected to the solution feed pipe 22. A valve 20 capable of closing 22 is provided.

  The side reaction container 23 is provided with a second stirring mechanism 25 that is rotated by a second drive motor 24 and stirs the solution supplied into the side reaction container 23. The secondary reaction vessel 23 is connected to a carbon dioxide supply source 27 via a carbon dioxide supply pipe 26, and liquefied carbon dioxide is stored in the carbon dioxide supply source 27.

  The carbon dioxide supply pipe 26 is provided with a heat exchanger 28 for blowing normal temperature air by a fan or the like to vaporize the liquefied carbon dioxide, and the pressure is adjusted so that the inside of the side reaction vessel 23 becomes atmospheric pressure. An adjustment valve 29 and a pressure regulator 31 are provided. The carbon dioxide supply pipe 26, the carbon dioxide supply source 27, the heat exchanger 28, the adjustment valve 29, and the pressure regulator 31 constitute a carbon dioxide supply system 32.

  Further, a second filtration device 36 composed of a sealed container 34 and a filter 35 provided in the sealed container 34 and the side reaction container 23 are connected via a turbid liquid feed pipe 33, and the turbidity is obtained. The turbid liquid agitated and generated in the side reaction vessel 23 is fed to the second filtration device 36 by a pump 37 provided in the liquid feed pipe 33. As the filter 35 in the second filtration device 36, a required filter such as a filter press or a Hundback filter is used.

  The second filtration device 36 is connected to a residual liquid storage section 39 via a residual liquid supply pipe 38, and one end of a residual liquid circulation pipe 41 is connected to the residual liquid storage section 39. The other end of the liquid circulation pipe 41 is connected to the water supply pipe 2. The residual liquid circulation pipe 41 is provided with a circulation pump 42, and the residual liquid in the residual liquid reservoir 39 is circulated through the residual liquid circulation pipe 41 by the circulation pump 42, and the residual water circulation pipe 41 is connected to the residual liquid circulation pipe 41. The main reaction vessel 1 is supplied. The residual liquid storage section 39, the residual liquid circulation pipe 41, and the circulation pump 42 constitute a residual liquid circulation system 43.

Here, calcium in the filler supplied to the main reaction vessel 1 exists mainly in the form of calcium silicate (CaSiO ₃ ) or the like, and calcium oxide (CaO) and silicon oxide ( The ratio of SiO ₂ ) is about 6: 4.

  Therefore, it is considered that the following formula is established by reacting calcium silicate and carbon dioxide.

CaSiO ₃ + CO ₂ → CaCO ₃ ↓ + SiO ₂

  Below, the manufacturing process of the calcium carbonate which advances the said reaction using the calcium carbonate manufacturing system mentioned above is demonstrated.

  First, among the waste concrete pulverized by a waste concrete pulverizer (not shown), the filler after the aggregate is removed is supplied to the main reaction vessel 1 through the filler supply pipe 6 and the acetic acid is supplied. Acetic acid is supplied from the source 5 to the main reaction vessel 1 through the acetic acid supply pipe 4. Further, water heated to, for example, 60 ° C. by the heat exchanger 9 so as to promote the reaction and to make acetic acid at an appropriate concentration and temperature is supplied from the water supply source 3 through the water supply pipe 2 to the main reaction. It is supplied to the container 1.

  In a state where filler, water, and acetic acid are supplied into the main reaction vessel 1, the first stirring motor 15 is driven by the first drive motor 14, and the filler, water, and acetic acid are mixed with the first stirring mechanism 15. 15 is stirred for a required time, for example, about 60 minutes.

  As the filler in the main reaction vessel 1 reacts with acetic acid, calcium ions are extracted from calcium silicate and dissolved in water, and silicon oxide is separated and precipitated as shown in the following formula. Moreover, the following reaction is promoted by stirring the filler, water, and acetic acid by the first stirring mechanism 15.

CaSiO ₃ + 2CH ₃ COOH → Ca ²⁺ + 2CH ₃ COO ⁻ + H ₂ O + SiO ₂

  Although not described in the above formula, calcium ions that could not be dissolved in water precipitate as calcium oxide (CaO) in the same manner as silicon oxide, and the precipitated calcium oxide and silicon oxide in the above formula. Reaction residue.

  After stirring for about 60 minutes by the first stirring mechanism 15 and sufficiently reacting calcium silicate and acetic acid, the valve 20 is opened, the pump 16 is driven, and the mixed solution feed pipe 17 is connected. Then, a mixed solution composed of the calcium ion solution and the reaction residue is fed to the first filtration device 18.

  The mixed solution fed to the first filtration device 18 is filtered by the filter 21, and the filtered calcium ion solution is fed to the side reaction vessel 23 via the solution feeding pipe 22. The reaction residue is separated by the filter 21.

  When the reaction residue is sufficiently separated from the mixed solution by the filter 21 and the calcium ion solution is sufficiently fed into the side reaction vessel 23, the pump 16 is stopped and the valve 20 is closed. Thereafter, the reaction residue separated by the filter 21 is discharged from an outlet formed at the lower end of the sealed container 19.

  Further, after the valve 20 is closed, liquefied carbon dioxide is supplied from the carbon dioxide supply source 27 and vaporized by the heat exchanger 28, and then carbon dioxide is converted into the side reaction through the carbon dioxide supply pipe 26. It is supplied into the container 23 and introduced into the calcium ion solution. Carbon dioxide introduced into the calcium ion solution may be other gas as long as it contains carbon dioxide, but pure carbon dioxide is used in this embodiment. At this time, the pressure in the secondary reaction vessel 23 is adjusted by the adjusting valve 29 and the pressure regulator 31 so that it becomes equal to a predetermined pressure, for example, atmospheric pressure.

  Further, in a state where carbon dioxide is introduced into the calcium ion solution, the second stirring mechanism 25 is driven by the second driving motor 24, and the calcium ion solution is required for a required time, for example, about 10 minutes by the second stirring mechanism 25. Stir.

  When carbon dioxide is introduced into the calcium ion solution, calcium ions and carbon dioxide react as shown in the following formula, and calcium carbonate is precipitated. Further, the following reaction is promoted by stirring the calcium ion solution by the second stirring mechanism 25.

Ca ²⁺ + 2CH ₃ COOH ⁻ + CO ₂ + H ₂ O → CaCO ₃ ↓ + 2CH ₃ COOH

  When calcium carbonate is sufficiently precipitated by the stirring of the second stirring mechanism 25, the second stirring mechanism 25 is stopped and the pump 37 is driven.

  When the pump 37 is driven, a turbid liquid composed of calcium carbonate, water, and acetic acid in the side reaction vessel 23 is fed to the second filtration device 36 through the turbid liquid feeding pipe 33. Calcium carbonate in the turbid liquid is separated by the filter 35 in the second filtration device 36.

  The residual liquid after calcium carbonate is recovered by the second filtration device 36, that is, acetic acid-containing water composed of acetic acid and water, is supplied to the residual liquid storage section 39 via the residual liquid supply pipe 38. And is stored in the residual liquid storage unit 39. Finally, by recovering the calcium carbonate remaining in the second filtration device 36, a series of calcium carbonate manufacturing steps is completed.

  Further, when calcium carbonate is produced again, the circulation pump 42 is driven to circulate the residual liquid stored in the residual liquid storage section 39 via the residual liquid circulation pipe 41, and the water supply pipe 2 is sent. The residual liquid supplied to the water supply pipe 2 is supplied again into the main reaction vessel 1 through the water supply pipe 2.

  The shortage of water supplied into the main reaction vessel 1 is supplied into the main reaction vessel 1 from the water supply source 3 via the water supply pipe 2 by separately driving the water supply pump 8, and acetic acid. This deficiency is separately supplied into the main reaction vessel 1 from the acetic acid supply source 5 through the acetic acid supply pipe 4 by driving the acetic acid supply pump 12 separately. Therefore, for the second and subsequent treatments, the amount of water supplied from the water supply source 3 and the amount of acetic acid supplied from the acetic acid supply source 5 may be small.

  Subsequent steps are the same as those described above, and thus description thereof is omitted.

  As described above, in this embodiment, since calcium carbonate is produced from the filler of waste concrete that has been conventionally discarded as it is, the amount of waste after pulverization treatment of waste concrete can be reduced.

  Further, in this embodiment, pure carbon dioxide is used as the carbon dioxide-containing gas, so that the calcium carbonate produced is of high purity and can be used for various applications such as using concrete again. .

  Further, in this embodiment, acetic acid-containing water is discharged as a residual liquid after the production of calcium carbonate, but when the calcium carbonate is produced again, the acetic acid-containing water that is the residual liquid is circulated and again in the main reaction vessel 1. In the second and subsequent treatments, the amount of acetic acid supplied can be reduced and the running cost can be reduced.

  In this example, pure carbon dioxide obtained by vaporizing liquefied carbon dioxide is used. However, any gas containing carbon dioxide may be used, for example, by using factory exhaust gas instead of pure carbon dioxide, In addition to the effect, the amount of carbon dioxide emitted from the factory is reduced, and the environmental load can be reduced. In addition, since waste concrete is used as a raw material for producing calcium carbonate, carbon dioxide in exhaust gas can be treated at low cost.

  Furthermore, in this embodiment, the main reaction vessel 1, the first filtration device 18, the sub-reaction vessel 23, the second filtration device 36, etc. are provided one by one and are operated in a batch manner. By providing multiple subsystems and operating them alternately, the next calcium carbonate manufacturing process can be executed without waiting for the completion of a series of calcium carbonate manufacturing processes. Pseudo continuous operation can be performed.

DESCRIPTION OF SYMBOLS 1 Main reaction container 7 Waste concrete fine powder supply system 11 Water supply system 13 Acetic acid supply system 18 1st filtration apparatus 23 Side reaction container 32 Carbon dioxide supply system 36 2nd filtration apparatus 43 Residual liquid circulation system

Claims (4)

  Supplying water, acetic acid and waste concrete fine powder into the main reaction vessel and stirring to extract calcium ions in the waste concrete fine powder, and reaction residue from the solution containing calcium ions by the first filtration device A step of separating the reaction residue, a step of feeding the solution from which the reaction residue is separated into the side reaction vessel, a step of depositing calcium carbonate by supplying carbon dioxide into the side reaction vessel and stirring, and a step of precipitation. And a step of recovering the calcium carbonate that has been caused to collect by a second filtration device.   The step of recovering calcium carbonate by the second filtration device further comprises the step of separating acetic acid-containing water as a residual liquid, circulating the separated acetic acid-containing water and supplying it again into the main reaction vessel. 1. A method for producing calcium carbonate.   A main reaction vessel for extracting calcium ions by stirring water, acetic acid and waste concrete fine powder, a water supply system for supplying water into the main reaction vessel, and an acetic acid supply system for supplying acetic acid into the main reaction vessel A waste concrete fine powder supply system for supplying waste concrete fine powder into the main reaction vessel, a first filtration device for separating a reaction residue from a solution containing calcium ions, and a solution from which the reaction residue is separated A carbon dioxide-containing gas into which the carbon dioxide is precipitated, a carbon dioxide supply system for supplying the carbon dioxide-containing gas into the secondary reaction vessel, and the calcium carbonate deposited in the secondary reaction vessel is recovered. And a second filtration device. A calcium carbonate production system comprising:   A plurality of subsystems including the main reaction vessel, the first filtration device, the sub-reaction vessel, and the second filtration device are provided. The calcium carbonate production system according to claim 3, which enables operation.

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