WO2014207837A1 - Crystallization reactor - Google Patents

Crystallization reactor Download PDF

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Publication number
WO2014207837A1
WO2014207837A1 PCT/JP2013/067526 JP2013067526W WO2014207837A1 WO 2014207837 A1 WO2014207837 A1 WO 2014207837A1 JP 2013067526 W JP2013067526 W JP 2013067526W WO 2014207837 A1 WO2014207837 A1 WO 2014207837A1
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Prior art keywords
crystallization reaction
solid
water
raw water
liquid separation
Prior art date
Application number
PCT/JP2013/067526
Other languages
French (fr)
Japanese (ja)
Inventor
徹 中野
Original Assignee
オルガノ株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by オルガノ株式会社 filed Critical オルガノ株式会社
Priority to CN201380077825.7A priority Critical patent/CN105339063B/en
Priority to SG11201509658PA priority patent/SG11201509658PA/en
Priority to KR1020157033811A priority patent/KR101793809B1/en
Priority to PCT/JP2013/067526 priority patent/WO2014207837A1/en
Publication of WO2014207837A1 publication Critical patent/WO2014207837A1/en

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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C02F1/5236—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D9/0036—Crystallisation on to a bed of product crystals; Seeding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D9/005—Selection of auxiliary, e.g. for control of crystallisation nuclei, of crystal growth, of adherence to walls; Arrangements for introduction thereof
    • B01D9/0054—Use of anti-solvent
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/105—Phosphorus compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/12—Halogens or halogen-containing compounds
    • C02F2101/14—Fluorine or fluorine-containing compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/44—Time

Definitions

  • the present invention relates to a technology of a crystallization reaction apparatus for treating a crystallization target substance such as fluorine or phosphorus as a hardly soluble salt.
  • a crystallization method or the like is used as a method for recovering and reusing hardly soluble salts such as calcium fluoride and calcium phosphate.
  • the crystallization method for example, when fluorine in the fluorine-containing raw water is recovered as calcium fluoride, the fluorine-containing raw water is allowed to flow into the reaction tank, and the calcium agent is injected to react them, and in the reaction tank For example, calcium fluoride is precipitated on the seed crystal surface.
  • the raw water containing the crystallization target material such as fluorine-containing raw water is supplied to the reaction tank in an upward flow, and the fluidized bed type crystal is processed while flowing the hardly-soluble salt crystals in the reaction tank.
  • An agitation reaction apparatus for example, Patent Document 1
  • a stirrer type crystallization reaction apparatus for example, Patent Document 2
  • Etc. Etc.
  • the drawing step of drawing a part of the hardly soluble salt crystals from the reaction vessel and the replenishment step of newly replenishing seed crystals are repeated.
  • a method of continuously obtaining crystals of poorly soluble salts is employed.
  • JP 2003-225680 A JP 2008-73589 A JP 2002-292202 A JP 2009-226232 A JP 2010-207755 A
  • the surface area of the hardly soluble salt crystal or the like in the reaction tank is kept high, that is, the particles of the hardly soluble salt crystal in the reaction tank. It is important to keep the particle size fine.
  • As a method of keeping the particles (particle size distribution) of the sparingly soluble salt crystals in the reaction tank fine it is conceivable to supply a large amount of seed crystals having a fine particle size distribution in the tank, but the amount of seed crystals supplied increases. As a result, the processing cost increases.
  • an object of the present invention is to provide a crystallization reaction apparatus that can recover a hardly soluble salt at a high recovery rate without increasing the replenishment amount of seed crystals.
  • a crystallization reaction apparatus includes a crystallization reaction unit that includes a stirring unit having a stirring blade and generates a hardly soluble salt crystal by adding a calcium agent to raw water containing a crystallization target substance.
  • An crystallization reaction tank, and a water passage means for passing the raw water to the crystallization reaction part, and an inner peripheral wall facing the outer peripheral wall of the crystallization reaction tank is disposed in the crystallization reaction tank.
  • a solid-liquid separation unit that forms an upward flow between the inner and outer peripheral walls and performs solid-liquid separation between the crystal and the treated water, and the water flow means passes the raw water to the crystallization reaction unit. It is characterized by performing water intermittently.
  • the flow time of the raw water during intermittent water flow by the water flow means is 1 ⁇ 2 times to 5 times the residence time in the solid-liquid separation unit.
  • the flow stop time of the raw water during intermittent water flow by the water flow means is 1/5 times or more and 1 time or less of the residence time in the solid-liquid separation unit.
  • the flow time of the raw water during intermittent water flow by the water flow means is 1 to 24 times the residence time in the solid-liquid separation unit. More preferably, the flow stoppage time of the raw water during intermittent water flow by the water flow means is not less than 1/4 times and not more than 1/2 times the residence time in the solid-liquid separation unit.
  • the treated water is discharged to an outer peripheral wall of the crystallization reaction tank provided with the solid-liquid separation unit.
  • the upper end of the inner peripheral wall is at the same height as the discharge port or at a position lower than the discharge port within a range in which a part of the treated water can be discharged from the discharge port. It is preferable that a part of the treated water in the liquid separation part is returned to the crystallization reaction part across the inner peripheral wall.
  • the hardly soluble salt can be recovered at a high recovery rate without increasing the replenishment amount of the seed crystals.
  • FIG. 2 is a graph showing the particle size distribution of crystals in the crystallization reaction part of Example 1.
  • FIG. 4 is a graph showing a particle size distribution of crystals in a crystallization reaction part of Example 2.
  • FIG. 6 is a graph showing the particle size distribution of crystals in the crystallization reaction part of Example 3.
  • FIG. 6 is a graph showing a particle size distribution of crystals in a crystallization reaction part of Example 4.
  • FIG. 2 is a graph showing a particle size distribution of crystals in a crystallization reaction part of Comparative Example 1.
  • FIG. 6 is a graph showing a particle size distribution of crystals in a crystallization reaction part of Comparative Example 2.
  • FIG. 6 is a graph showing a particle size distribution of crystals in a crystallization reaction part of Comparative Example 3.
  • FIG. 1 is a schematic diagram showing an example of a crystallization reaction apparatus according to an embodiment of the present invention.
  • the crystallization reaction apparatus 1 includes a crystallization reaction tank 10, a seed crystal silo 12, a calcium agent addition line 14 as an example of addition means for adding a calcium agent to the crystallization reaction tank 10, and raw water.
  • a raw water passage line 16 and a valve 18 As an example of inflow means for flowing into the crystallization reaction tank 10, a raw water passage line 16 and a valve 18, a seed crystal addition line 20, a treated water discharge line 22, and a hardly soluble salt discharge line 24 are provided.
  • the crystallization reaction tank 10 is connected with a raw water passage line 16 from a raw water storage tank (not shown) and a calcium agent addition line 14 from a calcium agent storage tank (not shown).
  • a seed crystal addition line 20 is connected between the seed crystal silo 12 and the crystallization reaction tank 10.
  • a treated water discharge line 22 is connected to the treated water discharge port 21 of the crystallization reaction tank 10, and a hardly soluble salt discharge line 24 is connected to the hardly soluble salt discharge port of the crystallization reaction tank 10. .
  • a crystallization reaction section 28 for generating a hardly soluble salt crystal and a solid-liquid separation section 30 for performing a solid-liquid separation between the hardly soluble salt crystal and the treated water there are provided a crystallization reaction section 28 for generating a hardly soluble salt crystal and a solid-liquid separation section 30 for performing a solid-liquid separation between the hardly soluble salt crystal and the treated water.
  • an inner peripheral wall 26 facing the outer peripheral wall of the crystallization reaction tank 10 is provided, and a solid-liquid separation unit 30 is formed between the outer peripheral wall and the inner peripheral wall 26.
  • the inner peripheral wall 26 of this embodiment is provided in the predetermined area of the outer peripheral wall of the crystallization reaction tank 10, the inner peripheral wall 26 may be provided over the perimeter of the outer peripheral wall.
  • the crystallization reaction part 28 and the solid-liquid separation part 30 are partitioned by an inner peripheral wall 26, and a communication port 32 is formed in the lower part of the inner peripheral wall 26 for communication between the crystallization reaction part 28 and the solid-liquid separation.
  • the treated water discharge port 21 described above is provided on the outer peripheral wall of the crystallization reaction tank 10 where the solid-liquid separation unit 30 is formed, and the treated water discharge line 22 is connected to the treated water discharge port 21. ing.
  • the crystallization reaction section 28 of the crystallization reaction tank 10 includes a draft tube 36 and a stirring device 34 as an example of a stirring means for stirring the fluid in the crystallization reaction section 28.
  • the stirring device 34 includes a stirring blade 38, and the stirring blade 38 is disposed in the draft tube 36 and is rotated by a rotational force generated by a motor that is transmitted through the stirring shaft.
  • the valve 18 of the raw water passage line 16 is opened, and the raw water containing the substance to be crystallized such as fluorine and phosphorus (hereinafter sometimes simply referred to as “raw water”) is crystallized through the raw water passage line 16.
  • Water is passed through the crystallization reaction section 28 of the crystallization reaction tank 10.
  • the calcium agent is added to the crystallization reaction part 28 through the calcium agent addition line 14.
  • the seed crystal in the seed crystal silo 12 is preferably added to the crystallization reaction unit 28 through the seed crystal addition line 20 by a motor.
  • the crystallization target substances such as fluorine and phosphorus contained in the raw water react with the calcium agent to produce calcium fluoride and calcium phosphate (slightly soluble calcium salt). As a result, it precipitates on the surface of the seed crystal and forms a hardly soluble salt (slightly soluble calcium salt) crystal.
  • Crystals of sparingly soluble calcium salts such as calcium fluoride and calcium phosphate generated in the crystallization reaction unit 28 are periodically pulled out of the sparingly soluble salt discharge line 24 and discharged out of the system, for example.
  • the method of extracting the hardly soluble calcium salt crystal is not particularly limited, but may be a method of drawing the hardly soluble calcium salt crystal from the crystallization reaction tank 10 using a slurry pump such as a tube pump, As shown in FIG. 1, a method may be used in which a valve 24a is attached to the hardly soluble salt discharge line 24 and the crystal of the hardly soluble calcium salt is simply pulled out from the crystallization reaction tank 10 by gravity.
  • the treated water after the crystallization reaction in the crystallization reaction unit 28 flows into the solid-liquid separation unit 30 from the communication port 32. At this time, some of the crystals of the hardly soluble salt flow into the solid-liquid separation unit 30 together with the treated water.
  • the treated water after the crystallization reaction forms an upward flow to form a solid-liquid solution.
  • the hardly soluble salt crystal and the treated water contained in the treated water are solid-liquid separated after passing through the separation unit 30.
  • the treated water subjected to the solid-liquid separation is discharged out of the system through the treated water discharge line 22 as the final treated water of the present embodiment.
  • crystals of the hardly soluble calcium salt in the crystallization reaction part 28 (including the hardly soluble calcium salt crystals that could not be precipitated on the seed crystal surface), Part of seed crystals and the like replenished from the seed crystal silo 12 is stored in the solid-liquid separation unit 30 while flowing into the solid-liquid separation unit 30 together with the treated water after the crystallization reaction.
  • crystals and seed crystals crystals and seed crystals having a particularly small particle diameter are likely to flow to the solid-liquid separation unit 30.
  • the crystallization reaction unit 28 exists in the crystallization reaction unit 28.
  • the surface area per unit weight of the crystal or seed crystal to be kept cannot be kept large, and the recovery rate of the hardly soluble calcium salt crystal is lowered.
  • the raw water is intermittently passed through the crystallization reaction unit 28, that is, the water recovery and the water supply stop are repeated, thereby improving the recovery rate of the hardly soluble calcium salt crystals.
  • raw water is passed through the crystallization reaction unit 28 to obtain a hardly soluble calcium salt crystal.
  • a part of the crystals (including seed crystals) of the poorly soluble calcium salt obtained, particularly the crystals of the poorly soluble calcium salt having a fine particle diameter flow into the solid-liquid separation part 30 as described above, and are separated into solid and liquid. It is stored in the part 30.
  • the flow of the raw water to the crystallization reaction tank 10 is stopped, and crystals of a slightly soluble salt having a fine particle size staying in the solid-liquid separation unit 30 are naturally precipitated, and at least the crystals etc.
  • An operation is performed to return a part of this to the crystallization reaction unit 28. It is preferable to incline the bottom of the individual liquid separating unit 30 downward toward the crystallization reaction unit 28 so that the crystals or the like deposited on the individual liquid separating unit 30 can easily return to the crystallization reaction unit 28.
  • the operation of intermittently passing water was thought to be difficult to operate the apparatus stably while ensuring the recovery rate of hardly soluble salt crystals, but the apparatus configuration of this embodiment
  • the crystal of the slightly soluble calcium salt with a fine particle size is crystallized at the start of the next raw water flow. Since it is held in the part 28, the surface area per unit weight of the hardly soluble calcium salt crystals in the crystallization reaction part 28 is increased without increasing the replenishment amount of the seed crystal from the seed crystal silo 12, resulting in difficulty.
  • the recovery rate of soluble salt crystals can be improved.
  • the flow time and flow stop time of the raw water in the present embodiment are, for example, to ensure the time for generating crystals of sparingly soluble calcium salt and the time for naturally sedimenting the crystals etc. staying in the solid-liquid separation unit 30.
  • the valve 18 of the raw water flow line 16 is opened, and the raw water flow time to the crystallization reaction unit 28 is within a range of 1 ⁇ 2 times to 5 times the residence time in the solid-liquid separation unit 30. Water is passed to the crystallization reaction unit 28. Thereafter, the valve 18 of the raw water flow line 16 is closed, and the water supply stoppage time of the raw water to the crystallization reaction unit 28 is within the range of 1/5 to 1 time of the residence time in the solid-liquid separation unit 30. The flow of raw water to the reaction unit 28 is stopped. As a result, a sufficient time for the crystals of the slightly soluble calcium salt having a small particle size to settle in the crystallization reaction part 28 is secured and retained in the crystallization reaction part 28.
  • the recovery rate can be further improved. Since a larger number of crystals having a fine particle size of 50 ⁇ m or less are mainly retained in the crystallization reaction part 28, the recovery rate of the hardly soluble calcium salt crystals can be further improved. If all the particles in the device are the same size, the surface area per particle increases in proportion to the square of the particle diameter, but the number of particles per unit weight is inversely proportional to the cube of the particle diameter. Become bigger.
  • the residence time in the solid-liquid separation unit 30 is the residence time of the raw water flowing into the crystallization reaction tank 10, and the inflow amount of the raw water flowing into the crystallization reaction tank 10 by the volume of the solid-liquid separation unit 30. It is expressed as a divided value.
  • the valve 18 of the present embodiment may be opened or closed manually or automatically.
  • the flow time of the raw water to the crystallization reaction unit 28 is less than 1 ⁇ 2 times the residence time in the solid-liquid separation unit 30, the water flow time is short, the amount of water that can be treated by the apparatus is reduced, and the hardly soluble calcium salt The efficiency of recovering the crystals may deteriorate. Further, if the flow time of the raw water to the crystallization reaction unit 28 is more than 5 times the residence time in the solid-liquid separation unit 30, a large amount of finely soluble hardly soluble calcium salt crystals and the like are discharged out of the system, Crystals with a fine particle size may not be sufficiently retained in the crystallization reaction unit 28, and it becomes difficult to improve the recovery rate of the hardly soluble calcium salt crystals.
  • fine particles such as those of a replenished seed crystal having a too small particle diameter or crystals of a hardly soluble calcium salt that could not be precipitated on the surface of the seed crystal cannot be separated by the solid-liquid separation unit 30, and are caused by upward flow. It flows out with treated water and is discharged out of the system.
  • the discharged fine particles are disposed of as sludge without being recovered, but if the fine particles can be grown to a particle size capable of solid-liquid separation, the amount of generated sludge can be reduced. It is possible to reduce the replenishment amount of seed crystals.
  • the upper end of the inner peripheral wall 26 that separates the solid-liquid separation unit 30 and the crystallization reaction unit 28 is the same height as the treated water discharge port 21 or A part of the treated water is set at a position lower than the treated water discharge port 21 within a range where the treated water can be discharged from the treated water discharge port 21.
  • the water level of the crystallization reaction unit 28 is the same height as the treated water discharge port 21, if the upper end of the inner peripheral wall 26 is made the same height as the treated water discharge port 21 or lower than that height, Crystals or the like of the hardly soluble calcium salt in the precipitation reaction part 28 will flow over the inner peripheral wall 26 and to the solid-liquid separation part 30 side.
  • the crystallization reaction unit 1 in order to keep the surface area of the crystals in the crystallization reaction unit 28 high, the crystallization reaction unit 1 is operated in a state where the crystal concentration is high. The specific gravity per unit volume tends to be higher than the specific gravity of the fluid in the solid-liquid separation unit 30.
  • a water level difference occurs between the crystallization reaction unit 28 and the solid-liquid separation unit 30.
  • This water level difference may be a water level difference of several meters depending on the size of the apparatus. Therefore, as in this embodiment, even if the position of the upper end of the inner peripheral wall 26 is lowered as described above, the raw water in the crystallization reaction unit 28 does not flow over to the solid-liquid separation unit 30, and the solid-liquid separation is performed. A part of the treated water in the part 30 can be returned to the crystallization reaction part 28.
  • the addition (injection point) of the calcium agent and raw water to the crystallization reaction unit 28 is preferably performed in the vicinity of the stirring blade 38.
  • the calcium agent and the raw water are immediately diffused when injected into the crystallization reaction unit 28, and the crystallization target substances such as the calcium agent concentration, fluorine, phosphorus, etc. Concentration drops quickly.
  • the formed hardly soluble salt is less likely to be directly deposited in the liquid, and the crystallization target substance (fluorine, phosphorus, etc.) in the liquid as the hardly soluble salt crystal on the seed crystal in the crystallization reaction unit 28. Can be captured carefully.
  • the draft tube 36 it is preferable to install the draft tube 36 so that the stirring blade 38 of the stirring device 34 is located in the cylinder. At this time, the stirring blade 38 preferably forms a downward flow.
  • the draft tube 36 is thus installed, a downward flow is generated toward the lower portion of the tube, and a zone having a relatively large diffusion flow rate is formed. For this reason, raw
  • an upward flow zone with a gentle flow is formed on the outer periphery of the tube.
  • the particles are classified and small particles rise along the outer surface of the tube, and re-enter from the upper end of the tube to the inside of the tube. Recirculate to the stirring zone. Since these small-sized crystals serve as nuclei to promote the crystallization reaction, the recovery rate of the hardly soluble salt crystals can be improved.
  • the crystal having a larger particle size due to the progress of the crystallization reaction does not rise due to the upward flow at the outer periphery of the tube, sinks down and does not enter the draft tube 36 again. Since it can prevent being destroyed by the collision with the blade 38, it can contribute to the improvement of the recovery rate of the hardly soluble salt crystal.
  • acid or alkali is added to the crystallization reaction unit 28 so that the pH of the crystallization reaction solution in the crystallization reaction unit 28 is in the range of 0.8 to 3. It is more preferable to set the range.
  • the raw water containing crystallization target substances such as fluorine and phosphorus in the present embodiment may be raw water of any origin as long as it contains fluorine, phosphorus and the like removed by crystallization treatment, for example, semiconductor related industries.
  • Fluorine, phosphorus, etc. which are crystallization target substances, can be present in the raw water in any state as long as they are crystallized by a crystallization reaction. From the viewpoint that it is dissolved in the raw water, the crystallization target substance is preferably in an ionized state.
  • the calcium agent used in the present embodiment for example, calcium chloride, calcium hydroxide and the like are used.
  • a powder state may be sufficient and a slurry state may be sufficient.
  • the injection amount of the calcium agent is preferably 0.8 to 2 times and 1 to 2 times that of fluorine and phosphorus as the chemical equivalent of calcium, but more preferably 1 to 1.2 times.
  • the chemical equivalent of calcium is more than twice the chemical equivalent of fluorine and phosphorus in the raw water, calcium fluoride and calcium phosphate are not easily deposited on the seed crystal and are easily formed as fine particles, and calcium fluoride and calcium phosphate are mixed into the treated water. If the ratio is less than 0.8 times, the proportion of fluorine and phosphorus in raw water that does not become calcium fluoride and calcium phosphate increases, and fluorine and phosphorus may be mixed into the treated water.
  • seed crystals may exist in advance in the crystallization reaction unit 28, or in the crystallization reaction unit 28 in advance. There may be no seed crystals. In order to perform a stable treatment, it is preferable that a seed crystal is present in the crystallization reaction unit 28 in advance.
  • the seed crystal may be any material as long as it can precipitate a hardly soluble calcium salt crystal formed on the surface thereof, and any material can be selected, for example, filtered sand, activated carbon, zircon sand, garnet sand, It is composed of particles containing oxides of metal elements such as Sac Random (trade name, manufactured by Nihon Cartrit Co., Ltd.) and hardly soluble calcium salts that are precipitates by crystallization reaction.
  • Sac Random trade name, manufactured by Nihon Cartrit Co., Ltd.
  • particles composed of the hardly soluble salt which is a precipitate by a crystallization reaction are preferable.
  • the particles comprising a hardly soluble calcium salt that is a precipitate by crystallization reaction include fluorite when depositing calcium fluoride, and phosphate ore when depositing calcium phosphate. Is mentioned.
  • the flow rate of the raw water flowing to the crystallization reaction unit 28 is preferably in the range of residence time 1 to 4 hours, and more preferably 2 to 4 hours.
  • the flow rate (LV) of the treated water flowing through the solid-liquid separation unit 30 is preferably in the range of 0.1 to 2.0 m / h, preferably 0.2 to 1.0 m / h, from the viewpoint of satisfactory solid-liquid separation. A range is more preferred.
  • FIG. 2 is a schematic diagram showing an example of the configuration of a crystallization reaction apparatus of a reference example.
  • a crystallization reaction apparatus 100 shown in FIG. 2 includes a crystallization reaction tank 110, a seed crystal silo 112, a calcium agent addition line 114 as an example of addition means for adding a calcium agent to the crystallization reaction tank 110, and a crystallization reaction of raw water.
  • a raw water flow line 116, a seed crystal addition line 118, a treated water discharge line 120, and a hardly soluble salt discharge line 122 are provided as an example of an inflow means for flowing into the tank 110.
  • the crystallization reaction tank 110 is connected to a raw water passage line 116 from a raw water storage tank (not shown) and a calcium agent addition line 114 from a calcium agent storage tank (not shown).
  • a seed crystal addition line 118 is connected between the seed crystal silo 112 and the crystallization reaction tank 110.
  • a treated water discharge line 120 is connected to the treated water discharge port 111 of the crystallization reaction tank 110, and a hardly soluble salt discharge line 122 is connected to the hardly soluble salt discharge port of the crystallization reaction tank 110. .
  • a crystallization reaction part 126 for generating a hardly soluble salt crystal and a solid / liquid separation part 128 for performing a solid / liquid separation between the hardly soluble salt crystal and the treated water.
  • an inner peripheral wall 124 facing the outer peripheral wall of the crystallization reaction tank 110 is provided, and a space between the outer peripheral wall and the inner peripheral wall 124 serves as a solid-liquid separation unit 128.
  • the inner peripheral wall 124 of this embodiment is provided in a predetermined section of the outer peripheral wall of the crystallization reaction tank 110, the inner peripheral wall 124 may be provided over the entire periphery of the outer peripheral wall.
  • the crystallization reaction unit 126 and the solid-liquid separation unit 128 are partitioned by an inner peripheral wall 124, and a communication port 130 through which the crystallization reaction unit 126 and the solid-liquid separation unit 128 communicate with each other is formed below the inner peripheral wall 124.
  • a communication port 130 through which the crystallization reaction unit 126 and the solid-liquid separation unit 128 communicate with each other is formed below the inner peripheral wall 124.
  • the treated water discharge port 111 described above is provided on the outer peripheral wall of the crystallization reaction tank 110 where the solid-liquid separation unit 128 is formed, and the treated water discharge line 120 is connected to the treated water discharge port 111. ing.
  • the upper end of the inner peripheral wall 124 that separates the solid-liquid separation unit 128 and the crystallization reaction unit 126 is the same height as the treated water discharge port 111 or a range in which a part of the treated water can be discharged from the treated water discharge port 111. Is set to a position lower than the treated water discharge port 111.
  • the crystallization reaction section 126 of the crystallization reaction tank 110 includes a draft tube 134 and a stirring device 132 as an example of a stirring means for stirring the fluid in the crystallization reaction section 126.
  • the stirring device 132 includes a stirring blade 136.
  • the stirring blade 136 is disposed in the draft tube 134 and is rotated by a rotational force generated by a motor transmitted through the stirring shaft.
  • raw water containing a target substance for crystallization of fluorine and phosphorus (hereinafter sometimes simply referred to as “raw water”) is passed through the raw water flow line 116 to the crystallization reaction unit 126.
  • the calcium agent is added to the crystallization reaction part 126 through the calcium agent addition line 114.
  • the seed crystal in the seed crystal silo 112 is added to the crystallization reaction unit 126 through the seed crystal addition line 118 by the motor.
  • the fluorine and phosphorus crystallization target substances contained in the raw water react with the calcium agent to produce calcium fluoride and calcium phosphate (slightly soluble calcium salt).
  • the calcium agent to produce calcium fluoride and calcium phosphate (slightly soluble calcium salt).
  • the crystals of the poorly soluble calcium salt of calcium fluoride and calcium phosphate generated in the crystallization reaction unit 126 are, for example, periodically pulled out from the hardly soluble salt discharge line 122 and discharged out of the system.
  • the method of extracting the hardly soluble calcium salt crystal is not particularly limited, but may be a method of extracting the hardly soluble calcium salt crystal from the crystallization reaction tank 110 using a slurry pump such as a tube pump, As shown in FIG. 1, a method may be used in which a valve 122a is attached to the hardly soluble salt discharge line 122 and the crystal of the hardly soluble calcium salt is simply extracted from the crystallization reaction tank 110 by gravity.
  • the treated water after the crystallization reaction in the crystallization reaction unit 126 flows into the solid-liquid separation unit 128 from the communication port 130. At this time, a part of the crystals of the hardly soluble salt flows into the solid-liquid separation unit 128 together with the treated water.
  • the treated water after the crystallization reaction forms an upward flow to form a solid-liquid liquid.
  • the hardly soluble salt crystal and the treated water contained in the treated water are separated into solid and liquid.
  • the treated water subjected to the solid-liquid separation is discharged out of the system through the treated water discharge line 120 as the final treated water of the present embodiment.
  • fine particles such as those of a replenished seed crystal having a too small particle diameter or crystals of a hardly soluble calcium salt that could not be precipitated on the seed crystal surface could not be separated by the solid-liquid separation unit 128, It flows out with treated water and is discharged out of the system.
  • the discharged fine particles are disposed of as sludge without being recovered, but if the fine particles can be grown to a particle size capable of solid-liquid separation, the amount of generated sludge can be reduced. It is possible to reduce the replenishment amount of seed crystals.
  • the upper end of the inner peripheral wall 124 that separates the solid-liquid separation unit 128 and the crystallization reaction unit 126 is the same height as the treated water discharge port 111, or A part of the treated water is set at a position lower than the treated water discharge port 111 within a range where the treated water can be discharged from the treated water discharge port 111.
  • the water level of the crystallization reaction part 126 is the same height as the treated water discharge port 111, if the upper end of the inner peripheral wall 124 is made the same height as the treated water discharge port 111 or lower than that height, Crystals or the like of the hardly soluble calcium salt in the precipitation reaction portion 126 will flow over the inner peripheral wall 124 to the solid-liquid separation portion 128 side.
  • the specific gravity per unit volume of the fluid in the crystallization reaction unit 126 tends to be higher than the specific gravity of the fluid in the solid-liquid separation unit 128.
  • the weight per liter of raw water containing the crystals in the crystallization reaction part 126 can be 2.0 kg / L.
  • the specific gravity in the solid-liquid separator 128 is at most about 1.0 kg / L to 1.2 kg / L.
  • the raw material water containing the crystallization target substance in the present embodiment contains fluorine and phosphorus that are removed by the crystallization treatment.
  • raw water of any origin may be used as long as it contains fluorine and phosphorus, for example, raw water discharged from the electronics industry including the semiconductor-related industry, the power plant, the aluminum industry, It is not limited to these.
  • Fluorine and phosphorus as crystallization target substances can be present in the raw water in any state as long as they are crystallized by a crystallization reaction. From the viewpoint of dissolving in raw water, fluorine and phosphorus are preferably in an ionized state.
  • the addition (injection point) of the calcium agent and raw water to the crystallization reaction unit 126 is preferably performed in the vicinity of the stirring blade 136.
  • the calcium agent and the raw water are immediately diffused when injected into the crystallization reaction unit 126, and the calcium agent concentration, the fluorine concentration, and the phosphorus concentration are quickly lowered.
  • the formed hardly soluble salt is less likely to be directly deposited in the liquid, and fluorine and phosphorus in the liquid can be taken in well as the hardly soluble salt crystal on the seed crystal in the crystallization reaction unit 126.
  • the draft tube 134 it is preferable to install the draft tube 134 so that the stirring blade 136 of the stirring device 132 is positioned in the cylinder. At this time, the stirring blade 136 preferably forms a downward flow.
  • the draft tube 134 is thus installed, a downward flow is generated toward the lower portion of the tube, and a zone having a relatively large diffusion flow rate is formed. For this reason, raw
  • an upward flow zone with a gentle flow is formed on the outer periphery of the tube.
  • the particles are classified and small particles rise along the outer surface of the tube, and re-enter from the upper end of the tube to the inside of the tube. Recirculate to the stirring zone. Since these small-sized crystals serve as nuclei to promote the crystallization reaction, the recovery rate of the hardly soluble salt crystals can be improved.
  • the crystals whose particle size has increased due to the progress of the crystallization reaction does not rise due to the upward flow at the outer periphery of the tube, sinks down and does not enter the draft tube 134 again. Since it can be prevented from being destroyed by the collision with the blade 136, it can contribute to the improvement of the recovery rate of the hardly soluble salt crystal.
  • acid or alkali is added to the crystallization reaction tank 110, and the pH of the crystallization reaction solution in the crystallization reaction unit 126 is preferably in the range of 0.8 to 3, preferably 1 to 1.5. It is more preferable to set the range.
  • the concentration of the crystallization target substance of fluorine and phosphorus in the treated water can be reduced.
  • the calcium agent used in the present embodiment for example, calcium chloride, calcium hydroxide and the like are used.
  • a powder state may be sufficient and a slurry state may be sufficient.
  • the injection amount of the calcium agent is preferably 0.8 to 2 times and 1 to 2 times that of fluorine and phosphorus as the chemical equivalent of calcium, but more preferably 1 to 1.2 times.
  • the chemical equivalent of calcium is more than twice the chemical equivalent of fluorine and phosphorus in the raw water, calcium fluoride and calcium phosphate are not easily deposited on the seed crystal and are easily formed as fine particles, and calcium fluoride and calcium phosphate are mixed into the treated water. If the ratio is less than 0.8 times, the proportion of fluorine and phosphorus in raw water that does not become calcium fluoride and calcium phosphate increases, and fluorine and phosphorus may be mixed into the treated water.
  • seed crystals may exist in advance in the crystallization reaction unit 126, or in the crystallization reaction unit 126 in advance. There may be no seed crystals. In order to perform a stable process, it is preferable that a seed crystal is present in the crystallization reaction unit 126 in advance.
  • the seed crystal may be any material as long as it can precipitate a hardly soluble calcium salt crystal formed on the surface thereof, and any material can be selected, for example, filtered sand, activated carbon, zircon sand, garnet sand, It is composed of particles composed of oxides of metal elements such as sacrandom (trade name, manufactured by Nihon Cartrit Co., Ltd.) and the like, and hardly soluble salts that are precipitates by crystallization reaction. Examples thereof include, but are not limited to, particles. From the viewpoint that a purer hardly soluble salt can be obtained as a pellet or the like, particles composed of the hardly soluble salt which is a precipitate by a crystallization reaction are preferable. Examples of the particles composed of a hardly soluble salt that is a precipitate by a crystallization reaction include fluorite when depositing calcium fluoride, and when depositing calcium phosphate, for example, phosphate ore. Etc.
  • Example 1 In Example 1, the crystallization reaction apparatus shown in FIG. 1 was used, and calcium fluoride was recovered from the fluorine-containing raw water under the following conditions.
  • Crystallization reaction part size 130 L (440 mm ⁇ ⁇ 880 mmH)
  • Solid-liquid separation part size 230L (440 ⁇ 590 ⁇ 880mmH)
  • Fluorine-containing raw water flow rate 50 L / h
  • Fluorine concentration of raw water containing fluorine 10000 mg / L
  • Calcium agent A solution in which 10% slurry of slaked lime is dissolved in hydrochloric acid.
  • PH in the crystallization reaction part pH 2 (adjusted by adding NaOH)
  • Initially filled seed crystals in the crystallization reaction section 20 kg (without replenishment of seed crystals thereafter)
  • Slurry concentration in the crystallization reaction section 30 to 35 v / v% (appropriately withdrawn from the hardly soluble salt discharge pipe)
  • the residence time of the solid-liquid separation part of Example 1 was 4.6 h (230 (L) / 50 (L / h)), and the residence time of the crystallization reaction part was 2.6 h.
  • Example 1 the raw water was passed through the crystallization reaction section for 9.2 hours, and then the water flow was stopped for 2.3 hours. This water flow and water flow stop were repeated until the water flow time reached 400 hours.
  • the flow rate (LV) of the treated water in the solid-liquid separation part during water flow was 0.2 m / h. The test was conducted in such a manner that a part of the treated water in the solid-liquid separation part was not returned to the crystallization reaction part.
  • Example 2 In Example 2, the test was performed under the same conditions as in Example 1 except that the raw water was passed through the crystallization reaction section for 4.6 hours and then stopped for 1.15 hours.
  • Example 3 In Example 3, the test was performed under the same conditions as in Example 1 except that the raw water was passed through the crystallization reaction section for 4.6 hours and then the water supply was stopped for 2.3 hours.
  • Example 4 In Example 4, a crystallization reaction apparatus in which the solid-liquid separation part size was changed to 23 L (440 ⁇ 60 ⁇ 880 mmH) was used. In Example 4, the raw water was passed through the crystallization reaction section for 0.46 hours and then stopped for 0.23 hours. This water flow and water flow stop were repeated until the water flow time reached 400 hours. In addition, the flow rate (LV) of the treated water of the solid-liquid separation part at the time of water flow was 2.0 m / h.
  • Example 5 In Example 5, the test was performed under the same conditions as in Example 1 except that the raw water was passed through the crystallization reaction part for 18.4 hours and then stopped for 2.3 hours.
  • Comparative Example 1 In Comparative Example 1, the test was performed under the same conditions as in Example 1 except that the raw water was not stopped and the raw water was passed through the crystallization reaction part for 400 hours.
  • the flow rate (LV) of the treated water in the solid-liquid separation part during water flow was 0.2 m / h.
  • Comparative Example 2 In Comparative Example 2, using the crystallization reaction apparatus whose solid-liquid separation part size was changed to 23 L (440 ⁇ 60 ⁇ 880 mmH), the raw water was passed through the crystallization reaction part for 400 hours without stopping the flow of the raw water. The test was performed under the same conditions as in Example 1 except that. The flow rate (LV) of the treated water in the solid-liquid separation part during water flow was 2.0 m / h.
  • Table 1 shows the flow rate of treated water in the solid-liquid separation parts of Examples 1 to 5 and Comparative Examples 1 and 2, the time for passing raw water to the crystallization reaction part, the time for stopping water flow, and after 400 hours for water flow.
  • the recovery rates of calcium fluoride were summarized.
  • Example 6 In Example 6, in the crystallization reaction apparatus shown in FIG. 1, a part of the treated water in the solid-liquid separation unit was obtained using a crystallization reaction apparatus in which the upper end of the inner peripheral wall was set to the same height as the treated water discharge port. The test was performed under the same conditions as in Example 1 except that the sample was returned to the crystallization reaction part.
  • Example 7 In Example 7, the test was performed under the same conditions as in Example 6 except that the raw water was passed through the crystallization reaction section for 4.6 hours and then stopped for 2.3 hours.
  • Comparative Example 3 In Comparative Example 3, in the crystallization reaction apparatus shown in FIG. 2, using the crystallization reaction apparatus in which the upper end of the inner peripheral wall is set to the same height as the treated water discharge port, the raw water is not stopped without passing the raw water. The test was performed under the same conditions as in Example 5 except that water was passed through the crystallization reaction section for 400 hours.
  • Table 2 shows the flow rate of treated water in the solid-liquid separation sections of Examples 6 to 7 and Comparative Example 3, the flow time of raw water to the crystallization reaction section, the stop time of water flow, and the flow after 400 hours of water flow.
  • the recovery rate of calcium fluoride was summarized.
  • FIG. 3 is a diagram showing the particle size distribution of crystals in the crystallization reaction part of Example 1
  • FIG. 4 is a diagram showing the particle size distribution of crystals in the crystallization reaction part of Example 2
  • FIG. These are diagrams showing the particle size distribution of crystals in the crystallization reaction part of Example 3
  • FIG. 6 is a diagram showing the particle size distribution of crystals in the crystallization reaction part of Example 4
  • FIG. 8 is a diagram showing the particle size distribution of crystals in the crystallization reaction part of Comparative Example 1
  • FIG. 8 is a diagram showing the particle size distribution of crystals in the crystallization reaction part of Comparative Example 2
  • FIG. 9 is a comparative example.
  • FIG. 3 is a diagram showing a particle size distribution of crystals in a crystallization reaction part of 3.
  • the particle size distribution of the crystals in the crystallization reaction part was measured using a particle size distribution meter (LS230 manufactured by Beckman Coulter, Inc.) after 400 hours of water flow.
  • Comparative Example 1 in which calcium fluoride was recovered by continuous flow of raw water without replenishing seed crystals, as can be seen from the results of FIG. 7 and Table 1, crystals having a particle size of 100 ⁇ m or more were formed in the crystallization reaction part. Many were present and the recovery rate was as low as 65%. Furthermore, in Comparative Example 2 in which the flow rate of the treated water in the solid-liquid separation part was increased to 2.0 m / h, as can be seen from the results of FIG. 8 and Table 1, crystals having a particle size of 125 ⁇ m or more were formed in the crystallization reaction part. There were many, and the recovery rate was further reduced to 50%.
  • Example 3 in which the raw water was passed for one time the residence time of the solid-liquid separation unit, and the water passage was stopped for half the residence time of the solid-liquid separation unit.
  • Example 4 where the residence time of the solid-liquid separation unit was 1 time, and the water flow was stopped for 1/2 time of the residence time of the solid-liquid separation unit, the results shown in FIGS.
  • crystals having a particle size of 50 ⁇ m or less are present in the crystallization reaction part, and the recovery rate is 90% or higher, which is higher than in Examples 1 and 2. That is, the raw water is passed through for a time that is one time the residence time of the solid-liquid separation part, and the water passage is stopped for a time that is one-half the residence time of the solid-liquid separation part. It was found that it could be retained in the crystallization reaction part, and the recovery rate of calcium fluoride crystals was further improved.
  • 1,100 crystallization reaction apparatus 10,110 crystallization reaction tank, 12,112 seed silo, 14,114 calcium agent addition line, 16,116 raw water passage line, 18, 24a, 122a valve, 20,118 seeds Crystal addition line, 21,111 treated water discharge port, 22,120 treated water discharge line, 24,122 sparingly soluble salt discharge line, 26,124 inner wall, 28,126 crystallization reaction section, 30,128 solid-liquid separation section 32, 130 communication port, 34, 132 stirring device, 36, 134 draft tube, 38, 136 stirring blade.

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Abstract

　There is used a crystallization reactor provided with a crystallization reaction tank (10) which has a crystallization reaction unit (28) for adding a calcium preparation to raw water containing a substance to be crystallized and generating crystals of a poorly soluble salt. An inner peripheral wall (26) facing an outer peripheral wall of the crystallization reaction tank (10) is disposed in the crystallization reaction tank (10). A solid-liquid separator (30), which forms an upward flow between the inner and outer peripheral walls and performs solid-liquid separation on the crystals and the treated water, is provided in the crystallization reaction tank (10). A valve (18) provided to a raw water passage line (16) is opened so that the duration of raw water passage into the crystallization reaction tank (10) is half to five times the duration of retention in the solid-liquid separator (30). After the passage of the raw water, the valve (18) provided to the raw water passage line (16) is closed so that the duration for which the passage of raw water into the crystallization reaction tank (10) is stopped is one fifth to one times the duration of retention in the solid-liquid separator (30).

Description

晶析反応装置Crystallization reactor
　本発明は、フッ素、リン等の晶析対象物質を難溶性塩として処理する晶析反応装置の技術に関する。 The present invention relates to a technology of a crystallization reaction apparatus for treating a crystallization target substance such as fluorine or phosphorus as a hardly soluble salt.
　従来、フッ化カルシウムやリン酸カルシウム等の難溶性塩を回収再利用する方法として晶析法等が用いられる。晶析法としては、例えば、フッ素含有原水中のフッ素をフッ化カルシウムとして回収する場合、反応槽にフッ素含有原水を流入させ、またカルシウム剤を注入することにより、それらを反応させ、反応槽内の種晶表面にフッ化カルシウムを析出させる方法等である。 Conventionally, a crystallization method or the like is used as a method for recovering and reusing hardly soluble salts such as calcium fluoride and calcium phosphate. As the crystallization method, for example, when fluorine in the fluorine-containing raw water is recovered as calcium fluoride, the fluorine-containing raw water is allowed to flow into the reaction tank, and the calcium agent is injected to react them, and in the reaction tank For example, calcium fluoride is precipitated on the seed crystal surface.
　従来、晶析法には、フッ素含有原水等の晶析対象物質を含む原水を反応槽に上向流で供給し、反応槽内の難溶性塩の結晶を流動させながら処理する流動床式晶析反応装置（例えば、特許文献１）、反応槽内に攪拌機を設け、攪拌機の攪拌により反応槽内の難溶性塩の結晶を流動させながら処理する攪拌式晶析反応装置（例えば、特許文献２）等が用いられている。なお、通常、反応槽内の難溶性塩の結晶がある程度大きく成長すると、反応槽内から難溶性塩の結晶の一部を引き抜く引き抜き工程と、新たに種晶を補給する補給工程を繰り返し行い、連続的に難溶性塩の結晶を得る方法が採用されている。 Conventionally, in the crystallization method, the raw water containing the crystallization target material such as fluorine-containing raw water is supplied to the reaction tank in an upward flow, and the fluidized bed type crystal is processed while flowing the hardly-soluble salt crystals in the reaction tank. An agitation reaction apparatus (for example, Patent Document 1), a stirrer type crystallization reaction apparatus (for example, Patent Document 2) in which a stirrer is provided in the reaction tank and the hardly soluble salt crystals in the reaction tank are flowed by the agitator. ) Etc. are used. Normally, when the hardly soluble salt crystals in the reaction vessel grow to a certain extent, the drawing step of drawing a part of the hardly soluble salt crystals from the reaction vessel and the replenishment step of newly replenishing seed crystals are repeated. A method of continuously obtaining crystals of poorly soluble salts is employed.
特開２００３－２２５６８０号公報JP 2003-225680 A 特開２００８－７３５８９号公報JP 2008-73589 A 特開２００２－２９２２０２号公報JP 2002-292202 A 特開２００９－２２６２３２号公報JP 2009-226232 A 特開２０１０－２０７７５５号公報JP 2010-207755 A
　ところで、晶析反応装置において、高い回収率で難溶性塩を回収するためには、反応槽内の難溶性塩結晶等の表面積を高く保つこと、すなわち、反応槽内の難溶性塩結晶の粒子を細かい粒径に保つことが重要である。反応槽内の難溶性塩結晶の粒子（粒径分布）を細かく保つ方法としては、細かい粒径分布を有する種晶を多く槽内に補給することが考えられるが、種晶の補給量が増加する分だけ処理コストが上昇してしまう。 By the way, in the crystallization reaction apparatus, in order to recover the hardly soluble salt at a high recovery rate, the surface area of the hardly soluble salt crystal or the like in the reaction tank is kept high, that is, the particles of the hardly soluble salt crystal in the reaction tank. It is important to keep the particle size fine. As a method of keeping the particles (particle size distribution) of the sparingly soluble salt crystals in the reaction tank fine, it is conceivable to supply a large amount of seed crystals having a fine particle size distribution in the tank, but the amount of seed crystals supplied increases. As a result, the processing cost increases.
　そこで、本発明の目的は、種晶の補給量を増加することなく、高い回収率で難溶性塩を回収することができる晶析反応装置を提供することである。 Therefore, an object of the present invention is to provide a crystallization reaction apparatus that can recover a hardly soluble salt at a high recovery rate without increasing the replenishment amount of seed crystals.
　（１）本発明の晶析反応装置は、攪拌翼を有する攪拌手段を備え、晶析対象物質を含む原水にカルシウム剤を添加して難溶性塩の結晶を生成させる晶析反応部を有する晶析反応槽と、前記晶析反応部へ前記原水を通水する通水手段と、を備え、前記晶析反応槽内には、前記晶析反応槽の外周壁に対向する内周壁を配置し、内外周壁間で上向流を形成して、前記結晶と処理水との固液分離を行う固液分離部が設けられ、前記通水手段は、前記晶析反応部への前記原水の通水を間欠的に行うことを特徴とする。 (1) A crystallization reaction apparatus according to the present invention includes a crystallization reaction unit that includes a stirring unit having a stirring blade and generates a hardly soluble salt crystal by adding a calcium agent to raw water containing a crystallization target substance. An crystallization reaction tank, and a water passage means for passing the raw water to the crystallization reaction part, and an inner peripheral wall facing the outer peripheral wall of the crystallization reaction tank is disposed in the crystallization reaction tank. A solid-liquid separation unit that forms an upward flow between the inner and outer peripheral walls and performs solid-liquid separation between the crystal and the treated water, and the water flow means passes the raw water to the crystallization reaction unit. It is characterized by performing water intermittently.
　（２）上記（１）記載の晶析反応装置において、前記通水手段による間欠通水時の前記原水の通水時間は、前記固液分離部における滞留時間の１／２倍以上５倍以下であり、前記通水手段による間欠通水時の前記原水の通水停止時間は、前記固液分離部における滞留時間の１／５倍以上１倍以下の時間であることが好ましい。 (2) In the crystallization reaction apparatus described in (1) above, the flow time of the raw water during intermittent water flow by the water flow means is ½ times to 5 times the residence time in the solid-liquid separation unit. In addition, it is preferable that the flow stop time of the raw water during intermittent water flow by the water flow means is 1/5 times or more and 1 time or less of the residence time in the solid-liquid separation unit.
　（３）上記（１）記載の晶析反応装置において、前記通水手段による間欠通水時の前記原水の通水時間は、前記固液分離部における滞留時間の１倍以上２４倍以下であり、前記通水手段による間欠通水時の前記原水の通水停止時間は、前記固液分離部における滞留時間の１／４倍以上１／２倍以下の時間であることがより好ましい。 (3) In the crystallization reaction apparatus described in (1) above, the flow time of the raw water during intermittent water flow by the water flow means is 1 to 24 times the residence time in the solid-liquid separation unit. More preferably, the flow stoppage time of the raw water during intermittent water flow by the water flow means is not less than 1/4 times and not more than 1/2 times the residence time in the solid-liquid separation unit.
　（４）上記（１）～（３）のいずれか１つに記載の晶析反応装置において、前記固液分離部が設けられている前記晶析反応槽の外周壁に、前記処理水を排出する排出口が形成され、前記内周壁の上端は、前記排出口と同じ高さ、又は前記処理水の一部が前記排出口から排出可能な範囲で前記排出口より低い位置にあり、前記固液分離部内の処理水の一部は、前記内周壁を越えて前記晶析反応部に返送されることが好ましい。 (4) In the crystallization reaction apparatus according to any one of (1) to (3), the treated water is discharged to an outer peripheral wall of the crystallization reaction tank provided with the solid-liquid separation unit. And the upper end of the inner peripheral wall is at the same height as the discharge port or at a position lower than the discharge port within a range in which a part of the treated water can be discharged from the discharge port. It is preferable that a part of the treated water in the liquid separation part is returned to the crystallization reaction part across the inner peripheral wall.
　本発明によれば、種晶の補給量を増加することなく、高い回収率で難溶性塩を回収することができる。 According to the present invention, the hardly soluble salt can be recovered at a high recovery rate without increasing the replenishment amount of the seed crystals.
本発明の実施形態に係る晶析反応装置の一例を示す模式図である。It is a schematic diagram which shows an example of the crystallization reaction apparatus which concerns on embodiment of this invention. 参考例の晶析反応装置の構成の一例を示す模式図である。It is a schematic diagram which shows an example of a structure of the crystallization reaction apparatus of a reference example. 実施例１の晶析反応部内の結晶の粒径分布を示す図である。2 is a graph showing the particle size distribution of crystals in the crystallization reaction part of Example 1. FIG. 実施例２の晶析反応部内の結晶の粒径分布を示す図である。4 is a graph showing a particle size distribution of crystals in a crystallization reaction part of Example 2. FIG. 実施例３の晶析反応部内の結晶の粒径分布を示す図である。6 is a graph showing the particle size distribution of crystals in the crystallization reaction part of Example 3. FIG. 実施例４の晶析反応部内の結晶の粒径分布を示す図である。6 is a graph showing a particle size distribution of crystals in a crystallization reaction part of Example 4. FIG. 比較例１の晶析反応部内の結晶の粒径分布を示す図である。2 is a graph showing a particle size distribution of crystals in a crystallization reaction part of Comparative Example 1. FIG. 比較例２の晶析反応部内の結晶の粒径分布を示す図である。6 is a graph showing a particle size distribution of crystals in a crystallization reaction part of Comparative Example 2. FIG. 比較例３の晶析反応部内の結晶の粒径分布を示す図である。6 is a graph showing a particle size distribution of crystals in a crystallization reaction part of Comparative Example 3. FIG.
　本発明の実施の形態について以下説明する。本実施形態は本発明を実施する一例であって、本発明は本実施形態に限定されるものではない。 Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.
　図１は、本発明の実施形態に係る晶析反応装置の一例を示す模式図である。図１に示すように、晶析反応装置１は、晶析反応槽１０、種晶サイロ１２、カルシウム剤を晶析反応槽１０へ添加する添加手段の一例としてのカルシウム剤添加ライン１４、原水を晶析反応槽１０へ流入させる流入手段の一例としての原水通水ライン１６及びバルブ１８、種晶添加ライン２０、処理水排出ライン２２、難溶性塩排出ライン２４、を備えている。 FIG. 1 is a schematic diagram showing an example of a crystallization reaction apparatus according to an embodiment of the present invention. As shown in FIG. 1, the crystallization reaction apparatus 1 includes a crystallization reaction tank 10, a seed crystal silo 12, a calcium agent addition line 14 as an example of addition means for adding a calcium agent to the crystallization reaction tank 10, and raw water. As an example of inflow means for flowing into the crystallization reaction tank 10, a raw water passage line 16 and a valve 18, a seed crystal addition line 20, a treated water discharge line 22, and a hardly soluble salt discharge line 24 are provided.
　晶析反応槽１０には、原水貯槽（不図示）からの原水通水ライン１６、カルシウム剤貯槽（不図示）からのカルシウム剤添加ライン１４が接続されている。また、種晶サイロ１２と晶析反応槽１０との間は、種晶添加ライン２０が接続されている。さらに、晶析反応槽１０の処理水排出口２１には、処理水排出ライン２２が接続され、晶析反応槽１０の難溶性塩排出口には、難溶性塩排出ライン２４が接続されている。 The crystallization reaction tank 10 is connected with a raw water passage line 16 from a raw water storage tank (not shown) and a calcium agent addition line 14 from a calcium agent storage tank (not shown). A seed crystal addition line 20 is connected between the seed crystal silo 12 and the crystallization reaction tank 10. Further, a treated water discharge line 22 is connected to the treated water discharge port 21 of the crystallization reaction tank 10, and a hardly soluble salt discharge line 24 is connected to the hardly soluble salt discharge port of the crystallization reaction tank 10. .
　晶析反応槽１０内には、難溶性塩の結晶を生成させる晶析反応部２８と、難溶性塩結晶と処理水との固液分離を行う固液分離部３０とが設けられている。晶析反応槽１０内には、晶析反応槽１０の外周壁に対向する内周壁２６が設けられており、この外周壁と内周壁２６間を固液分離部３０としている。本実施形態の内周壁２６は晶析反応槽１０の外周壁の所定区間に設けられているが、内周壁２６は外周壁の全周にわたって設けられていてもよい。 In the crystallization reaction tank 10, there are provided a crystallization reaction section 28 for generating a hardly soluble salt crystal and a solid-liquid separation section 30 for performing a solid-liquid separation between the hardly soluble salt crystal and the treated water. In the crystallization reaction tank 10, an inner peripheral wall 26 facing the outer peripheral wall of the crystallization reaction tank 10 is provided, and a solid-liquid separation unit 30 is formed between the outer peripheral wall and the inner peripheral wall 26. Although the inner peripheral wall 26 of this embodiment is provided in the predetermined area of the outer peripheral wall of the crystallization reaction tank 10, the inner peripheral wall 26 may be provided over the perimeter of the outer peripheral wall.
　晶析反応部２８と固液分離部３０とは内周壁２６により区画されており、内周壁２６の下部には、晶析反応部２８と固液分離とが連通する連通口３２が形成されている。また、前述した処理水排出口２１は、固液分離部３０が形成されている晶析反応槽１０の外周壁に設けられており、この処理水排出口２１に処理水排出ライン２２が接続されている。 The crystallization reaction part 28 and the solid-liquid separation part 30 are partitioned by an inner peripheral wall 26, and a communication port 32 is formed in the lower part of the inner peripheral wall 26 for communication between the crystallization reaction part 28 and the solid-liquid separation. Yes. Further, the treated water discharge port 21 described above is provided on the outer peripheral wall of the crystallization reaction tank 10 where the solid-liquid separation unit 30 is formed, and the treated water discharge line 22 is connected to the treated water discharge port 21. ing.
　晶析反応槽１０の晶析反応部２８には、ドラフトチューブ３６、晶析反応部２８内の流体を撹拌する攪拌手段の一例としての攪拌装置３４を備える。攪拌装置３４は攪拌翼３８を備え、攪拌翼３８は、ドラフトチューブ３６内に配置され、撹拌軸を介して伝達されるモータが発生する回転力によって回転する。 The crystallization reaction section 28 of the crystallization reaction tank 10 includes a draft tube 36 and a stirring device 34 as an example of a stirring means for stirring the fluid in the crystallization reaction section 28. The stirring device 34 includes a stirring blade 38, and the stirring blade 38 is disposed in the draft tube 36 and is rotated by a rotational force generated by a motor that is transmitted through the stirring shaft.
　本実施形態に係る晶析反応装置１の動作について説明する。 The operation of the crystallization reaction apparatus 1 according to this embodiment will be described.
　まず、原水通水ライン１６のバルブ１８を開放し、原水通水ライン１６を通して、フッ素、リン等の晶析対象物質を含有する原水（以下、単に「原水」と呼ぶ場合がある。）を晶析反応槽１０の晶析反応部２８に通水する。また、カルシウム剤添加ライン１４を通して、カルシウム剤を晶析反応部２８に添加する。さらに、モータにより種晶サイロ１２中の種晶が種晶添加ライン２０を通して晶析反応部２８に添加されることが好ましい。 First, the valve 18 of the raw water passage line 16 is opened, and the raw water containing the substance to be crystallized such as fluorine and phosphorus (hereinafter sometimes simply referred to as “raw water”) is crystallized through the raw water passage line 16. Water is passed through the crystallization reaction section 28 of the crystallization reaction tank 10. Further, the calcium agent is added to the crystallization reaction part 28 through the calcium agent addition line 14. Further, the seed crystal in the seed crystal silo 12 is preferably added to the crystallization reaction unit 28 through the seed crystal addition line 20 by a motor.
　そして、晶析反応槽１０の晶析反応部２８において、原水に含まれるフッ素、リン等の晶析対象物質がカルシウム剤と反応して、フッ化カルシウム、リン酸カルシウム（難溶性カルシウム塩）が生成して、種晶表面に析出し、難溶性塩（難溶性カルシウム塩）の結晶が生成する。 And in the crystallization reaction part 28 of the crystallization reaction tank 10, the crystallization target substances such as fluorine and phosphorus contained in the raw water react with the calcium agent to produce calcium fluoride and calcium phosphate (slightly soluble calcium salt). As a result, it precipitates on the surface of the seed crystal and forms a hardly soluble salt (slightly soluble calcium salt) crystal.
　晶析反応部２８内で生成したフッ化カルシウム、リン酸カルシウム等の難溶性カルシウム塩の結晶は、例えば定期的に難溶性塩排出ライン２４から引き抜かれ、系外へ排出される。難溶性カルシウム塩の結晶の引き抜き方法は、特に制限されるものではないが、チューブポンプ等のスラリ用ポンプを用いて、晶析反応槽１０から難溶性カルシウム塩の結晶を引き抜く方法でも良いし、図１に示すように難溶性塩排出ライン２４にバルブ２４ａを取り付け、単に重力によって晶析反応槽１０から難溶性カルシウム塩の結晶を引き抜く方法でもよい。 Crystals of sparingly soluble calcium salts such as calcium fluoride and calcium phosphate generated in the crystallization reaction unit 28 are periodically pulled out of the sparingly soluble salt discharge line 24 and discharged out of the system, for example. The method of extracting the hardly soluble calcium salt crystal is not particularly limited, but may be a method of drawing the hardly soluble calcium salt crystal from the crystallization reaction tank 10 using a slurry pump such as a tube pump, As shown in FIG. 1, a method may be used in which a valve 24a is attached to the hardly soluble salt discharge line 24 and the crystal of the hardly soluble calcium salt is simply pulled out from the crystallization reaction tank 10 by gravity.
　一方、晶析反応部２８内の晶析反応後の処理水は、連通口３２から固液分離部３０に流入する。この際、処理水と共に、難溶性塩の結晶の一部が固液分離部３０に流入するが、固液分離部３０では、晶析反応後の処理水が上向流を形成して固液分離部３０を通過し、処理水中に含まれる難溶性塩結晶と処理水とが固液分離される。固液分離された処理水は、処理水排出ライン２２を通して、本実施形態の最終処理水として系外に排出される。 On the other hand, the treated water after the crystallization reaction in the crystallization reaction unit 28 flows into the solid-liquid separation unit 30 from the communication port 32. At this time, some of the crystals of the hardly soluble salt flow into the solid-liquid separation unit 30 together with the treated water. In the solid-liquid separation unit 30, the treated water after the crystallization reaction forms an upward flow to form a solid-liquid solution. The hardly soluble salt crystal and the treated water contained in the treated water are solid-liquid separated after passing through the separation unit 30. The treated water subjected to the solid-liquid separation is discharged out of the system through the treated water discharge line 22 as the final treated water of the present embodiment.
　ここで、晶析反応部２８への原水の通水を継続すると、晶析反応部２８内の難溶性カルシウム塩の結晶（種晶表面に析出できなかった難溶性カルシウム塩結晶等も含む）や種晶サイロ１２から補給された種晶等の一部は、晶析反応後の処理水と共に固液分離部３０に流れたまま、固液分離部３０内に溜められる。これらの結晶や種晶のうち特に粒径の細かい結晶や種晶は固液分離部３０に流れやすい。したがって、晶析反応槽１０への原水の通水を継続すると、晶析反応部２８内に粒径の細かい結晶や種晶を保持することが困難となるため、晶析反応部２８内に存在する結晶や種晶の単位重量当たりの表面積を大きく保つことができずに、難溶性カルシウム塩の結晶の回収率が低下してしまう。 Here, if the raw water flow to the crystallization reaction part 28 is continued, crystals of the hardly soluble calcium salt in the crystallization reaction part 28 (including the hardly soluble calcium salt crystals that could not be precipitated on the seed crystal surface), Part of seed crystals and the like replenished from the seed crystal silo 12 is stored in the solid-liquid separation unit 30 while flowing into the solid-liquid separation unit 30 together with the treated water after the crystallization reaction. Among these crystals and seed crystals, crystals and seed crystals having a particularly small particle diameter are likely to flow to the solid-liquid separation unit 30. Accordingly, if the raw water flow into the crystallization reaction tank 10 is continued, it becomes difficult to maintain crystals and seed crystals having a small particle size in the crystallization reaction unit 28, and therefore, the crystallization reaction unit 28 exists in the crystallization reaction unit 28. The surface area per unit weight of the crystal or seed crystal to be kept cannot be kept large, and the recovery rate of the hardly soluble calcium salt crystal is lowered.
　そこで、本実施形態では、晶析反応部２８への原水の通水を間欠的に行う、すなわち通水と通水停止を繰り返し行うことにより、難溶性カルシウム塩の結晶の回収率を向上させている。まず、本実施形態では、晶析反応部２８への原水の通水を行い、難溶性カルシウム塩の結晶を得る。この際、得られる難溶性カルシウム塩の結晶（種晶も含む）の一部、特に細かい粒径の難溶性カルシウム塩の結晶は、前述したように固液分離部３０内に流れ、固液分離部３０内に溜められる。しかし、本実施形態では、晶析反応槽１０への原水の通水停止を行い、固液分離部３０内に滞留した細かい粒径の難溶性塩の結晶等を自然沈降させ、少なくともその結晶等の一部を晶析反応部２８に戻す操作を行う。個液分離部３０に堆積した結晶等が晶析反応部２８内に戻りやすいように、個液分離部３０の底部を晶析反応部２８に向かって下るように傾斜させることが好ましい。 Thus, in the present embodiment, the raw water is intermittently passed through the crystallization reaction unit 28, that is, the water recovery and the water supply stop are repeated, thereby improving the recovery rate of the hardly soluble calcium salt crystals. Yes. First, in the present embodiment, raw water is passed through the crystallization reaction unit 28 to obtain a hardly soluble calcium salt crystal. At this time, a part of the crystals (including seed crystals) of the poorly soluble calcium salt obtained, particularly the crystals of the poorly soluble calcium salt having a fine particle diameter, flow into the solid-liquid separation part 30 as described above, and are separated into solid and liquid. It is stored in the part 30. However, in the present embodiment, the flow of the raw water to the crystallization reaction tank 10 is stopped, and crystals of a slightly soluble salt having a fine particle size staying in the solid-liquid separation unit 30 are naturally precipitated, and at least the crystals etc. An operation is performed to return a part of this to the crystallization reaction unit 28. It is preferable to incline the bottom of the individual liquid separating unit 30 downward toward the crystallization reaction unit 28 so that the crystals or the like deposited on the individual liquid separating unit 30 can easily return to the crystallization reaction unit 28.
　通常、通水を間欠的に行うような操作は、難溶性塩結晶の回収率を確保しながら装置を安定して運転することが困難であると考えられていたが、本実施形態の装置構成を採用すると共に、該装置を稼働させながら原水の通水を間欠的に行うと、次の原水の通水の開始の際には、細かい粒径の難溶性カルシウム塩の結晶等が晶析反応部２８内に保持されているため、種晶サイロ１２から種晶の補給量を増やすことなく、晶析反応部２８内の難溶性カルシウム塩の結晶等の単位重量当たりの表面積が大きくなり、難溶性塩結晶の回収率を向上させることができる。本実施形態における原水の通水時間及び通水停止時間は、例えば、難溶性カルシウム塩の結晶を生成させる時間及び固液分離部３０内に滞留する結晶等を自然沈降させる時間を確保するために適宜設定されるものであるが、原水の通水時間及び通水停止時間は以下の条件に設定されることが好ましい。 Usually, the operation of intermittently passing water was thought to be difficult to operate the apparatus stably while ensuring the recovery rate of hardly soluble salt crystals, but the apparatus configuration of this embodiment When the raw water is intermittently passed while the apparatus is in operation, the crystal of the slightly soluble calcium salt with a fine particle size is crystallized at the start of the next raw water flow. Since it is held in the part 28, the surface area per unit weight of the hardly soluble calcium salt crystals in the crystallization reaction part 28 is increased without increasing the replenishment amount of the seed crystal from the seed crystal silo 12, resulting in difficulty. The recovery rate of soluble salt crystals can be improved. The flow time and flow stop time of the raw water in the present embodiment are, for example, to ensure the time for generating crystals of sparingly soluble calcium salt and the time for naturally sedimenting the crystals etc. staying in the solid-liquid separation unit 30. Although appropriately set, it is preferable to set the water passage time and the water passage stop time under the following conditions.
　まず、原水通水ライン１６のバルブ１８を開放し、晶析反応部２８への原水の通水時間を固液分離部３０における滞留時間の１／２倍以上５倍以下の範囲で、原水を晶析反応部２８へ通水する。その後、原水通水ライン１６のバルブ１８を閉じ、晶析反応部２８への原水の通水停止時間を固液分離部３０における滞留時間の１／５倍以上１倍以下の範囲で、晶析反応部２８への原水の通水を停止する。これにより、細かい粒径の難溶性カルシウム塩の結晶等が晶析反応部２８内に沈降する時間が十分に確保され、晶析反応部２８内で保持されるため、難溶性カルシウム塩の結晶の回収率をより向上させることができる。晶析反応部２８内には、主に５０μｍ以下の細かい粒径の結晶がより多く保持されるため、難溶性カルシウム塩の結晶の回収率をより向上させることができる。仮に、装置内の粒子が全て同じ大きさだとすると、粒子1個当たりの表面積は、粒子径の２乗に比例して大きくなるが、単位重量当たりの粒子個数は、粒子径の３乗に反比例して大きくなる。そのため、単位重量当たりの表面積は、（粒子径）３／（粒子径）２＝粒子径に反比例して大きくなるため、本実施形態の条件で原水の通水及び停止を行い、粒径の小さい難溶性カルシウム塩の結晶等を晶析反応部２８内により多く存在させることにより、晶析反応部２８内の結晶の単位重量当たりの表面積は飛躍的に上昇し、難溶性塩結晶の回収率を大幅に向上させることができる。ここで、固液分離部３０における滞留時間とは、晶析反応槽１０へ流入する原水の滞留時間であり、固液分離部３０の容積を晶析反応槽１０へ流入する原水の流入量で割った値で表される。なお、本実施形態のバルブ１８の開閉は手動であっても自動であってもよい。 First, the valve 18 of the raw water flow line 16 is opened, and the raw water flow time to the crystallization reaction unit 28 is within a range of ½ times to 5 times the residence time in the solid-liquid separation unit 30. Water is passed to the crystallization reaction unit 28. Thereafter, the valve 18 of the raw water flow line 16 is closed, and the water supply stoppage time of the raw water to the crystallization reaction unit 28 is within the range of 1/5 to 1 time of the residence time in the solid-liquid separation unit 30. The flow of raw water to the reaction unit 28 is stopped. As a result, a sufficient time for the crystals of the slightly soluble calcium salt having a small particle size to settle in the crystallization reaction part 28 is secured and retained in the crystallization reaction part 28. The recovery rate can be further improved. Since a larger number of crystals having a fine particle size of 50 μm or less are mainly retained in the crystallization reaction part 28, the recovery rate of the hardly soluble calcium salt crystals can be further improved. If all the particles in the device are the same size, the surface area per particle increases in proportion to the square of the particle diameter, but the number of particles per unit weight is inversely proportional to the cube of the particle diameter. Become bigger. Therefore, since the surface area per unit weight increases in inverse proportion to (particle diameter) 3 / (particle diameter) 2 = particle diameter, the raw water is passed and stopped under the conditions of this embodiment, and the particle diameter is small By causing more crystals of hardly soluble calcium salt or the like to exist in the crystallization reaction portion 28, the surface area per unit weight of the crystals in the crystallization reaction portion 28 is dramatically increased, and the recovery rate of the hardly soluble salt crystals is increased. It can be greatly improved. Here, the residence time in the solid-liquid separation unit 30 is the residence time of the raw water flowing into the crystallization reaction tank 10, and the inflow amount of the raw water flowing into the crystallization reaction tank 10 by the volume of the solid-liquid separation unit 30. It is expressed as a divided value. Note that the valve 18 of the present embodiment may be opened or closed manually or automatically.
　晶析反応部２８への原水の通水時間が固液分離部３０における滞留時間の１／２倍未満であると、通水時間が短く、装置で処理できる水量が少なくなり、難溶性カルシウム塩の結晶を回収する効率が悪くなる場合がある。また、晶析反応部２８への原水の通水時間が固液分離部３０における滞留時間の５倍超であると、細かい粒径の難溶性カルシウム塩の結晶等が系外へ多く排出され、晶析反応部２８内に細かい粒径の結晶を十分に保持することができない場合があり、難溶性カルシウム塩の結晶の回収率を向上させることが困難となる。晶析反応部２８への原水の通水停止時間が固液分離部３０における滞留時間の１／５倍未満であると、固液分離部３０内に滞留している粒径の細かい結晶が晶析反応部２８内へ戻りきれず、晶析反応部２８内に細かい粒径の結晶を十分に保持することができない場合があり、難溶性カルシウム塩の結晶の回収率を向上させることが困難となる。また、晶析反応部２８への原水の通水停止時間が固液分離部３０における滞留時間の１倍超であると、停止時間が長く、装置で処理できる水量が少なくなり、難溶性カルシウム塩の結晶を回収する効率が悪くなる場合がある。 When the flow time of the raw water to the crystallization reaction unit 28 is less than ½ times the residence time in the solid-liquid separation unit 30, the water flow time is short, the amount of water that can be treated by the apparatus is reduced, and the hardly soluble calcium salt The efficiency of recovering the crystals may deteriorate. Further, if the flow time of the raw water to the crystallization reaction unit 28 is more than 5 times the residence time in the solid-liquid separation unit 30, a large amount of finely soluble hardly soluble calcium salt crystals and the like are discharged out of the system, Crystals with a fine particle size may not be sufficiently retained in the crystallization reaction unit 28, and it becomes difficult to improve the recovery rate of the hardly soluble calcium salt crystals. When the flow stoppage time of the raw water to the crystallization reaction unit 28 is less than 1/5 times the residence time in the solid-liquid separation unit 30, fine crystals having a small particle size staying in the solid-liquid separation unit 30 are crystallized. It is difficult to improve the recovery rate of the hardly soluble calcium salt crystals because it may not be possible to fully return to the crystallization reaction part 28 and the fine crystallization crystals may not be sufficiently retained in the crystallization reaction part 28. Become. In addition, when the stoppage time of the raw water to the crystallization reaction unit 28 is more than 1 time of the residence time in the solid-liquid separation unit 30, the stop time is long, and the amount of water that can be treated by the apparatus is reduced. The efficiency of recovering the crystals may deteriorate.
　次に、固液分離部３０で処理水と分離されず、処理水と共に通過してしまう微細な難溶性カルシウム塩の結晶等について考える。 Next, let us consider fine, insoluble calcium salt crystals that are not separated from the treated water by the solid-liquid separation unit 30 and pass along with the treated water.
　例えば、補給した種晶のうち微細すぎる粒径のものや、種晶表面に析出できなかった難溶性カルシウム塩の結晶等の微細粒子は、固液分離部３０で分離しきれず、上向流によって処理水と共に流出し、系外に排出されてしまう。一般的に、この排出された微細粒子は、回収されずに汚泥として処分されてしまうが、この微細粒子を固液分離可能な粒径にまで成長させることができれば、発生汚泥量を削減することができ、かつ種晶の補給量も削減することが可能となる。従来、処理水と共に流出する微細粒子を固液分離可能な粒径にまで成長させるために、処理水中の微細粒子を晶析反応部に戻す方法が提案されている（例えば、特開２００２－２９２２０２、特開２００９－２２６２３２、特開２０１０－２０７７５５）。 For example, fine particles such as those of a replenished seed crystal having a too small particle diameter or crystals of a hardly soluble calcium salt that could not be precipitated on the surface of the seed crystal cannot be separated by the solid-liquid separation unit 30, and are caused by upward flow. It flows out with treated water and is discharged out of the system. In general, the discharged fine particles are disposed of as sludge without being recovered, but if the fine particles can be grown to a particle size capable of solid-liquid separation, the amount of generated sludge can be reduced. It is possible to reduce the replenishment amount of seed crystals. Conventionally, a method for returning fine particles in the treated water to the crystallization reaction part has been proposed in order to grow the fine particles flowing out together with the treated water to a particle size capable of solid-liquid separation (for example, JP-A-2002-292202). JP 2009-226232 A, JP 2010-207755 A).
　本実施形態では、図１に示す晶析反応装置１のように、固液分離部３０と晶析反応部２８とを隔てる内周壁２６の上端が、処理水排出口２１と同じ高さか、または処理水の一部が処理水排出口２１から排出可能な範囲で処理水排出口２１より低い位置に設定する。 In the present embodiment, as in the crystallization reaction apparatus 1 shown in FIG. 1, the upper end of the inner peripheral wall 26 that separates the solid-liquid separation unit 30 and the crystallization reaction unit 28 is the same height as the treated water discharge port 21 or A part of the treated water is set at a position lower than the treated water discharge port 21 within a range where the treated water can be discharged from the treated water discharge port 21.
　一般的に、晶析反応部２８の水位は処理水排出口２１と同じ高さであるため、内周壁２６の上端を処理水排出口２１と同じ高さかその高さより低くしてしまうと、晶析反応部２８内の難溶性カルシウム塩の結晶等が内周壁２６を越えて固液分離部３０側に越流してしまう。しかし、本実施形態の晶析反応装置１においては、晶析反応部２８内の結晶の表面積を高く維持するために、結晶濃度が高い状態で運転するため、晶析反応部２８内の流体の単位体積当たりの比重は固液分離部３０内の流体の比重より高くなり易い。このように、晶析反応部２８と固液分離部３０に比重差が生じると、晶析反応部２８と固液分離部３０に水位差が生じる。この水位差は、装置の大きさ等によって数ｍの水位差となる場合がある。したがって、本実施形態のように、内周壁２６の上端の位置を上記のように下げても、晶析反応部２８内の原水が固液分離部３０に越流することはなく、固液分離部３０内の処理水の一部を晶析反応部２８に戻せることになる。これにより、処理水中に含まれる微細粒子（難溶性カルシウム塩の結晶や種晶等）を、何の動力機器も使うことなく、晶析反応部２８に返送することが可能となるため、より晶析反応部２８内の難溶性カルシウム塩の結晶や種晶の粒径分布を細かく維持することが可能となる。その結果、更に難溶性カルシウム塩の結晶の回収率を向上させることが可能となる。 Generally, since the water level of the crystallization reaction unit 28 is the same height as the treated water discharge port 21, if the upper end of the inner peripheral wall 26 is made the same height as the treated water discharge port 21 or lower than that height, Crystals or the like of the hardly soluble calcium salt in the precipitation reaction part 28 will flow over the inner peripheral wall 26 and to the solid-liquid separation part 30 side. However, in the crystallization reaction apparatus 1 of the present embodiment, in order to keep the surface area of the crystals in the crystallization reaction unit 28 high, the crystallization reaction unit 1 is operated in a state where the crystal concentration is high. The specific gravity per unit volume tends to be higher than the specific gravity of the fluid in the solid-liquid separation unit 30. Thus, when a specific gravity difference occurs between the crystallization reaction unit 28 and the solid-liquid separation unit 30, a water level difference occurs between the crystallization reaction unit 28 and the solid-liquid separation unit 30. This water level difference may be a water level difference of several meters depending on the size of the apparatus. Therefore, as in this embodiment, even if the position of the upper end of the inner peripheral wall 26 is lowered as described above, the raw water in the crystallization reaction unit 28 does not flow over to the solid-liquid separation unit 30, and the solid-liquid separation is performed. A part of the treated water in the part 30 can be returned to the crystallization reaction part 28. This makes it possible to return fine particles (refractory calcium salt crystals, seed crystals, etc.) contained in the treated water to the crystallization reaction unit 28 without using any power equipment. The particle size distribution of the hardly soluble calcium salt crystals and seed crystals in the precipitation reaction portion 28 can be maintained finely. As a result, it becomes possible to further improve the recovery rate of crystals of the hardly soluble calcium salt.
　次に、本実施形態の晶析反応装置１のその他の条件等について説明する。 Next, other conditions of the crystallization reaction apparatus 1 of the present embodiment will be described.
　本実施形態において、カルシウム剤及び原水の晶析反応部２８への添加（注入点）は、攪拌翼３８の近傍に行われることが好ましい。カルシウム剤及び原水を攪拌翼３８の近傍に添加することにより、カルシウム剤及び原水は、晶析反応部２８へ注入されると直ちに拡散せしめられ、カルシウム剤濃度やフッ素、リン等の晶析対象物質濃度が素早く低下する。このため、形成された難溶性塩が液中に直接析出することが少なくなり、晶析反応部２８内の種晶上の難溶塩結晶として液中の晶析対象物質（フッ素、リン等）をじっくり取り込むことができる。 In this embodiment, the addition (injection point) of the calcium agent and raw water to the crystallization reaction unit 28 is preferably performed in the vicinity of the stirring blade 38. By adding the calcium agent and the raw water in the vicinity of the stirring blade 38, the calcium agent and the raw water are immediately diffused when injected into the crystallization reaction unit 28, and the crystallization target substances such as the calcium agent concentration, fluorine, phosphorus, etc. Concentration drops quickly. For this reason, the formed hardly soluble salt is less likely to be directly deposited in the liquid, and the crystallization target substance (fluorine, phosphorus, etc.) in the liquid as the hardly soluble salt crystal on the seed crystal in the crystallization reaction unit 28. Can be captured carefully.
　本実施形態においては、筒内に攪拌装置３４の攪拌翼３８が位置するようにドラフトチューブ３６を設置することが好ましい。このとき、攪拌翼３８は下降流を形成するものであることが好ましい。このようにドラフトチューブ３６を設置すると、チューブ下部に向けて下降流が生じ、拡散流速が比較的大きいゾーンが形成される。このため、原水やカルシウム剤等をより素早く拡散させることができ、原水やカルシウム剤の濃度が局所的に濃い領域同士が接触せずに、難溶性カルシウム塩粒子の直接生成が抑制される。 In this embodiment, it is preferable to install the draft tube 36 so that the stirring blade 38 of the stirring device 34 is located in the cylinder. At this time, the stirring blade 38 preferably forms a downward flow. When the draft tube 36 is thus installed, a downward flow is generated toward the lower portion of the tube, and a zone having a relatively large diffusion flow rate is formed. For this reason, raw | natural water, a calcium agent, etc. can be diffused more rapidly, and the direct production | generation of a sparingly soluble calcium salt particle | grain is suppressed, without the area | regions where the density | concentration of raw | natural water or a calcium agent is locally concentrated.
　また、上記のようにドラフトチューブ３６および攪拌翼３８を設置すると、チューブ外周部には流れのゆるやかな上向流ゾーンが形成される。このゾーンでは、粒子が分級されて小粒径の粒子はチューブ外側面に沿って上昇すると共に、チューブ上端からチューブ内部に再侵入して下降し、原水やカルシウム剤等の注入点付近やその下部の撹拌ゾーンへと再循環する。これら小粒径の結晶が核となって晶析反応を促進せしめるため、難溶性塩結晶の回収率を向上させることができる。 Also, when the draft tube 36 and the stirring blade 38 are installed as described above, an upward flow zone with a gentle flow is formed on the outer periphery of the tube. In this zone, the particles are classified and small particles rise along the outer surface of the tube, and re-enter from the upper end of the tube to the inside of the tube. Recirculate to the stirring zone. Since these small-sized crystals serve as nuclei to promote the crystallization reaction, the recovery rate of the hardly soluble salt crystals can be improved.
　さらに、晶析反応が進んで粒径が大きくなった結晶は、チューブ外周部の上向流によっては上昇せず、下に沈んで再びドラフトチューブ３６内には入り込まないため、成長した結晶が攪拌翼３８との衝突により破壊されてしまうことを防止することができるため、難溶性塩結晶の回収率の向上に寄与することができる。 Further, the crystal having a larger particle size due to the progress of the crystallization reaction does not rise due to the upward flow at the outer periphery of the tube, sinks down and does not enter the draft tube 36 again. Since it can prevent being destroyed by the collision with the blade 38, it can contribute to the improvement of the recovery rate of the hardly soluble salt crystal.
　本実施形態では、晶析反応部２８に酸又はアルカリを添加し、晶析反応部２８における晶析反応液のｐＨを０．８～３の範囲とすることが好ましく、１～１．５の範囲とすることがより好ましい。酸又はアルカリを添加して晶析反応部２８のｐＨを０．８～３の範囲で運転することにより、例えば、処理水のフッ素、リン等の晶析対象物質濃度を低減させることができる。 In the present embodiment, it is preferable that acid or alkali is added to the crystallization reaction unit 28 so that the pH of the crystallization reaction solution in the crystallization reaction unit 28 is in the range of 0.8 to 3. It is more preferable to set the range. By adding acid or alkali and operating the crystallization reaction section 28 at a pH in the range of 0.8 to 3, for example, the concentration of a substance to be crystallized such as fluorine and phosphorus in the treated water can be reduced.
　本実施形態におけるフッ素、リン等の晶析対象物質含有原水は、晶析処理により除去されるフッ素、リン等を含むものであれば、如何なる由来の原水であっても良く、例えば、半導体関連産業をはじめとする電子産業、発電所、アルミニウム工業等から排出される原水が挙げられるが、これらに限定されるものではない。 The raw water containing crystallization target substances such as fluorine and phosphorus in the present embodiment may be raw water of any origin as long as it contains fluorine, phosphorus and the like removed by crystallization treatment, for example, semiconductor related industries. Raw water discharged from the electronics industry, including power plants, power plants, aluminum industries, etc., but is not limited thereto.
　晶析対象物質となるフッ素、リン等は、晶析反応により晶析するのであれば、任意の状態で原水中に存在することが可能である。原水中に溶解しているという観点から、晶析対象物質はイオン化した状態であるのが好ましい。 Fluorine, phosphorus, etc., which are crystallization target substances, can be present in the raw water in any state as long as they are crystallized by a crystallization reaction. From the viewpoint that it is dissolved in the raw water, the crystallization target substance is preferably in an ionized state.
　本実施形態において用いられるカルシウム剤としては、例えば塩化カルシウム、水酸化カルシウム等が用いられる。カルシウム剤を添加する形態としては、粉末状態でもよいし、スラリ状態であってもよい。 As the calcium agent used in the present embodiment, for example, calcium chloride, calcium hydroxide and the like are used. As a form which adds a calcium agent, a powder state may be sufficient and a slurry state may be sufficient.
　カルシウム剤の注入量としては、カルシウムの化学当量としてフッ素、リンの０．８倍～２倍、１倍～２倍までがよいが、１倍～１．２倍がよりよい。カルシウムの化学当量が原水のフッ素、リンの化学当量の２倍より多いとフッ化カルシウム、リン酸カルシウムが種晶上に析出せずに微粒子として生成しやすく、処理水にフッ化カルシウム、リン酸カルシウムが混入する場合があり、０．８倍より少ないと、原水中のフッ素、リンのうちフッ化カルシウム、リン酸カルシウムとならない割合が多くなり、処理水にフッ素、リンが混入する場合がある。 The injection amount of the calcium agent is preferably 0.8 to 2 times and 1 to 2 times that of fluorine and phosphorus as the chemical equivalent of calcium, but more preferably 1 to 1.2 times. When the chemical equivalent of calcium is more than twice the chemical equivalent of fluorine and phosphorus in the raw water, calcium fluoride and calcium phosphate are not easily deposited on the seed crystal and are easily formed as fine particles, and calcium fluoride and calcium phosphate are mixed into the treated water. If the ratio is less than 0.8 times, the proportion of fluorine and phosphorus in raw water that does not become calcium fluoride and calcium phosphate increases, and fluorine and phosphorus may be mixed into the treated water.
　本実施形態においては、原水とカルシウム剤とを晶析反応部２８に添加する前に、あらかじめ、晶析反応部２８に種晶が存在していてもよいし、あらかじめ晶析反応部２８内に種晶が存在していなくてもよい。安定した処理を行うためには、晶析反応部２８にあらかじめ種晶が存在していることが好ましい。 In the present embodiment, before adding raw water and calcium agent to the crystallization reaction unit 28, seed crystals may exist in advance in the crystallization reaction unit 28, or in the crystallization reaction unit 28 in advance. There may be no seed crystals. In order to perform a stable treatment, it is preferable that a seed crystal is present in the crystallization reaction unit 28 in advance.
　種晶は、その表面に生成した難溶性カルシウム塩の結晶を析出させることができるものであればよく、任意の材質が選択可能であり、例えば、ろ過砂、活性炭、およびジルコンサンド、ガーネットサンド、サクランダム（商品名、日本カートリット株式会社製）などをはじめとする金属元素の酸化物を含んで構成される粒子、ならびに、晶析反応による析出物である難溶性カルシウム塩を含んで構成される粒子等が挙げられるが、これらに限定されるものではない。より純粋な難溶性塩をペレット等として入手できるという観点から、晶析反応による析出物である難溶性塩を含んで構成される粒子が好ましい。晶析反応による析出物である難溶性カルシウム塩を含んで構成される粒子としては、例えば、フッ化カルシウムを析出させる場合には蛍石等が挙げられ、リン酸カルシウムを析出させる場合にはリン鉱石等が挙げられる。 The seed crystal may be any material as long as it can precipitate a hardly soluble calcium salt crystal formed on the surface thereof, and any material can be selected, for example, filtered sand, activated carbon, zircon sand, garnet sand, It is composed of particles containing oxides of metal elements such as Sac Random (trade name, manufactured by Nihon Cartrit Co., Ltd.) and hardly soluble calcium salts that are precipitates by crystallization reaction. However, it is not limited to these. From the viewpoint that a purer hardly soluble salt can be obtained as a pellet or the like, particles composed of the hardly soluble salt which is a precipitate by a crystallization reaction are preferable. Examples of the particles comprising a hardly soluble calcium salt that is a precipitate by crystallization reaction include fluorite when depositing calcium fluoride, and phosphate ore when depositing calcium phosphate. Is mentioned.
　晶析反応部２８へ通水する原水の流量は、晶析反応を良好に行う観点から、滞留時間１～４時間の範囲であることが好ましく、２～４時間であることがさらに好ましい。 From the viewpoint of satisfactorily performing the crystallization reaction, the flow rate of the raw water flowing to the crystallization reaction unit 28 is preferably in the range of residence time 1 to 4 hours, and more preferably 2 to 4 hours.
　固液分離部３０を流れる処理水の流速（ＬＶ）は、固液分離を良好に行う観点から、０．１～２．０ｍ／ｈの範囲が好ましく、０．２～１．０ｍ／ｈの範囲がより好ましい。 The flow rate (LV) of the treated water flowing through the solid-liquid separation unit 30 is preferably in the range of 0.1 to 2.0 m / h, preferably 0.2 to 1.0 m / h, from the viewpoint of satisfactory solid-liquid separation. A range is more preferred.
　図２は、参考例の晶析反応装置の構成の一例を示す模式図である。図２に示す晶析反応装置１００は、晶析反応槽１１０、種晶サイロ１１２、カルシウム剤を晶析反応槽１１０へ添加する添加手段の一例としてのカルシウム剤添加ライン１１４、原水を晶析反応槽１１０へ流入させる流入手段の一例としての原水通水ライン１１６、種晶添加ライン１１８、処理水排出ライン１２０、難溶性塩排出ライン１２２、を備えている。 FIG. 2 is a schematic diagram showing an example of the configuration of a crystallization reaction apparatus of a reference example. A crystallization reaction apparatus 100 shown in FIG. 2 includes a crystallization reaction tank 110, a seed crystal silo 112, a calcium agent addition line 114 as an example of addition means for adding a calcium agent to the crystallization reaction tank 110, and a crystallization reaction of raw water. A raw water flow line 116, a seed crystal addition line 118, a treated water discharge line 120, and a hardly soluble salt discharge line 122 are provided as an example of an inflow means for flowing into the tank 110.
　晶析反応槽１１０には、原水貯槽（不図示）からの原水通水ライン１１６、カルシウム剤貯槽（不図示）からのカルシウム剤添加ライン１１４が接続されている。また、種晶サイロ１１２と晶析反応槽１１０との間は、種晶添加ライン１１８が接続されている。さらに、晶析反応槽１１０の処理水排出口１１１には、処理水排出ライン１２０が接続され、晶析反応槽１１０の難溶性塩排出口には、難溶性塩排出ライン１２２が接続されている。 The crystallization reaction tank 110 is connected to a raw water passage line 116 from a raw water storage tank (not shown) and a calcium agent addition line 114 from a calcium agent storage tank (not shown). A seed crystal addition line 118 is connected between the seed crystal silo 112 and the crystallization reaction tank 110. Further, a treated water discharge line 120 is connected to the treated water discharge port 111 of the crystallization reaction tank 110, and a hardly soluble salt discharge line 122 is connected to the hardly soluble salt discharge port of the crystallization reaction tank 110. .
　晶析反応槽１１０内には、難溶性塩の結晶を生成させる晶析反応部１２６と、難溶性塩結晶と処理水との固液分離を行う固液分離部１２８とが設けられている。晶析反応槽１１０内には、晶析反応槽１１０の外周壁に対向する内周壁１２４が設けられており、この外周壁と内周壁１２４間を固液分離部１２８としている。本実施形態の内周壁１２４は晶析反応槽１１０の外周壁の所定区間に設けられているが、内周壁１２４は外周壁の全周にわたって設けられていてもよい。 In the crystallization reaction tank 110, there are provided a crystallization reaction part 126 for generating a hardly soluble salt crystal and a solid / liquid separation part 128 for performing a solid / liquid separation between the hardly soluble salt crystal and the treated water. In the crystallization reaction tank 110, an inner peripheral wall 124 facing the outer peripheral wall of the crystallization reaction tank 110 is provided, and a space between the outer peripheral wall and the inner peripheral wall 124 serves as a solid-liquid separation unit 128. Although the inner peripheral wall 124 of this embodiment is provided in a predetermined section of the outer peripheral wall of the crystallization reaction tank 110, the inner peripheral wall 124 may be provided over the entire periphery of the outer peripheral wall.
　晶析反応部１２６と固液分離部１２８とは内周壁１２４により区画されており、内周壁１２４の下部には、晶析反応部１２６と固液分離部１２８とが連通する連通口１３０が形成されている。また、前述した処理水排出口１１１は、固液分離部１２８が形成されている晶析反応槽１１０の外周壁に設けられており、この処理水排出口１１１に処理水排出ライン１２０が接続されている。 The crystallization reaction unit 126 and the solid-liquid separation unit 128 are partitioned by an inner peripheral wall 124, and a communication port 130 through which the crystallization reaction unit 126 and the solid-liquid separation unit 128 communicate with each other is formed below the inner peripheral wall 124. Has been. Further, the treated water discharge port 111 described above is provided on the outer peripheral wall of the crystallization reaction tank 110 where the solid-liquid separation unit 128 is formed, and the treated water discharge line 120 is connected to the treated water discharge port 111. ing.
　また、固液分離部１２８と晶析反応部１２６とを隔てる内周壁１２４の上端は、処理水排出口１１１と同じ高さか、または処理水の一部が処理水排出口１１１から排出可能な範囲で処理水排出口１１１より低い位置に設定する。 Further, the upper end of the inner peripheral wall 124 that separates the solid-liquid separation unit 128 and the crystallization reaction unit 126 is the same height as the treated water discharge port 111 or a range in which a part of the treated water can be discharged from the treated water discharge port 111. Is set to a position lower than the treated water discharge port 111.
　晶析反応槽１１０の晶析反応部１２６には、ドラフトチューブ１３４、晶析反応部１２６内の流体を撹拌する攪拌手段の一例としての攪拌装置１３２を備える。攪拌装置１３２は攪拌翼１３６を備え、攪拌翼１３６は、ドラフトチューブ１３４内に配置され、撹拌軸を介して伝達されるモータが発生する回転力によって回転する。 The crystallization reaction section 126 of the crystallization reaction tank 110 includes a draft tube 134 and a stirring device 132 as an example of a stirring means for stirring the fluid in the crystallization reaction section 126. The stirring device 132 includes a stirring blade 136. The stirring blade 136 is disposed in the draft tube 134 and is rotated by a rotational force generated by a motor transmitted through the stirring shaft.
　本実施形態に係る晶析反応装置１００の動作について説明する。 The operation of the crystallization reaction apparatus 100 according to this embodiment will be described.
　まず、原水通水ライン１１６を通して、フッ素、リンの晶析対象物質を含有する原水（以下、単に「原水」と呼ぶ場合がある。）を晶析反応部１２６に通水する。また、カルシウム剤添加ライン１１４を通して、カルシウム剤を晶析反応部１２６に添加する。さらに、モータにより種晶サイロ１１２中の種晶が種晶添加ライン１１８を通して晶析反応部１２６に添加されることが好ましい。 First, raw water containing a target substance for crystallization of fluorine and phosphorus (hereinafter sometimes simply referred to as “raw water”) is passed through the raw water flow line 116 to the crystallization reaction unit 126. Further, the calcium agent is added to the crystallization reaction part 126 through the calcium agent addition line 114. Furthermore, it is preferable that the seed crystal in the seed crystal silo 112 is added to the crystallization reaction unit 126 through the seed crystal addition line 118 by the motor.
　そして、晶析反応槽１１０の晶析反応部１２６において、原水に含まれるフッ素、リンの晶析対象物質がカルシウム剤と反応して、フッ化カルシウム、リン酸カルシウム（難溶性カルシウム塩）が生成して、種晶表面に析出し、難溶性塩（難溶性カルシウム塩）の結晶となる。 Then, in the crystallization reaction part 126 of the crystallization reaction tank 110, the fluorine and phosphorus crystallization target substances contained in the raw water react with the calcium agent to produce calcium fluoride and calcium phosphate (slightly soluble calcium salt). , Precipitated on the seed crystal surface to form crystals of a hardly soluble salt (hardly soluble calcium salt).
　晶析反応部１２６内で生成したフッ化カルシウム、リン酸カルシウムの難溶性カルシウム塩の結晶は、例えば定期的に難溶性塩排出ライン１２２から引き抜かれ、系外へ排出される。難溶性カルシウム塩の結晶の引き抜き方法は、特に制限されるものではないが、チューブポンプ等のスラリ用ポンプを用いて、晶析反応槽１１０から難溶性カルシウム塩の結晶を引き抜く方法でも良いし、図１に示すように難溶性塩排出ライン１２２にバルブ１２２ａを取り付け、単に重力によって晶析反応槽１１０から難溶性カルシウム塩の結晶を引き抜く方法でもよい。 The crystals of the poorly soluble calcium salt of calcium fluoride and calcium phosphate generated in the crystallization reaction unit 126 are, for example, periodically pulled out from the hardly soluble salt discharge line 122 and discharged out of the system. The method of extracting the hardly soluble calcium salt crystal is not particularly limited, but may be a method of extracting the hardly soluble calcium salt crystal from the crystallization reaction tank 110 using a slurry pump such as a tube pump, As shown in FIG. 1, a method may be used in which a valve 122a is attached to the hardly soluble salt discharge line 122 and the crystal of the hardly soluble calcium salt is simply extracted from the crystallization reaction tank 110 by gravity.
　一方、晶析反応部１２６内の晶析反応後の処理水は、連通口１３０から固液分離部１２８に流入する。この際、処理水と共に、難溶性塩の結晶の一部が固液分離部１２８に流入するが、固液分離部１２８では、晶析反応後の処理水が上向流を形成して固液分離部１２８を通過し、処理水中に含まれる難溶性塩結晶と処理水とが固液分離される。固液分離された処理水は、処理水排出ライン１２０を通して、本実施形態の最終処理水として系外に排出される。 On the other hand, the treated water after the crystallization reaction in the crystallization reaction unit 126 flows into the solid-liquid separation unit 128 from the communication port 130. At this time, a part of the crystals of the hardly soluble salt flows into the solid-liquid separation unit 128 together with the treated water. In the solid-liquid separation unit 128, the treated water after the crystallization reaction forms an upward flow to form a solid-liquid liquid. After passing through the separation unit 128, the hardly soluble salt crystal and the treated water contained in the treated water are separated into solid and liquid. The treated water subjected to the solid-liquid separation is discharged out of the system through the treated water discharge line 120 as the final treated water of the present embodiment.
　ところで、補給した種晶のうち微細すぎる粒径のものや、種晶表面に析出できなかった難溶性カルシウム塩の結晶等の微細粒子は、固液分離部１２８で分離しきれず、上向流によって処理水と共に流出し、系外に排出されてしまう。一般的に、この排出された微細粒子は、回収されずに汚泥として処分されてしまうが、この微細粒子を固液分離可能な粒径にまで成長させることができれば、発生汚泥量を削減することができ、かつ種晶の補給量も削減することが可能となる。従来、処理水と共に流出する微細粒子を固液分離可能な粒径にまで成長させるために、処理水中の微細粒子を反応部分に戻す方法が提案されている（例えば、特開２００２－２９２２０２、特開２００９－２２６２３２、特開２０１０－２０７７５５）。 By the way, fine particles such as those of a replenished seed crystal having a too small particle diameter or crystals of a hardly soluble calcium salt that could not be precipitated on the seed crystal surface could not be separated by the solid-liquid separation unit 128, It flows out with treated water and is discharged out of the system. In general, the discharged fine particles are disposed of as sludge without being recovered, but if the fine particles can be grown to a particle size capable of solid-liquid separation, the amount of generated sludge can be reduced. It is possible to reduce the replenishment amount of seed crystals. Conventionally, a method for returning fine particles in the treated water to the reaction portion has been proposed in order to grow the fine particles flowing out with the treated water to a particle size that can be separated into solid and liquid (for example, JP-A-2002-292202; 2009-226232, JP 2010-207755).
　本実施形態では、図２に示す晶析反応装置１００のように、固液分離部１２８と晶析反応部１２６とを隔てる内周壁１２４の上端が、処理水排出口１１１と同じ高さか、または処理水の一部が処理水排出口１１１から排出可能な範囲で処理水排出口１１１より低い位置に設定する。 In the present embodiment, as in the crystallization reaction apparatus 100 shown in FIG. 2, the upper end of the inner peripheral wall 124 that separates the solid-liquid separation unit 128 and the crystallization reaction unit 126 is the same height as the treated water discharge port 111, or A part of the treated water is set at a position lower than the treated water discharge port 111 within a range where the treated water can be discharged from the treated water discharge port 111.
　一般的に、晶析反応部１２６の水位は処理水排出口１１１と同じ高さであるため、内周壁１２４の上端を処理水排出口１１１と同じ高さかその高さより低くしてしまうと、晶析反応部１２６内の難溶性カルシウム塩の結晶等が内周壁１２４を越えて固液分離部１２８側に越流してしまう。しかし、フッ化カルシウム、リン酸カルシウムの結晶を得る場合、晶析反応部１２６内の流体の単位体積当たりの比重は固液分離部１２８内の流体の比重より高くなり易い。例えばフッ化カルシウムの結晶を得る場合、晶析反応部１２６内の結晶を含んだ原水１Ｌ当たりの重さは２．０ｋｇ／Ｌになり得る。これに対し、固液分離部１２８内の比重はせいぜい１．０ｋｇ／Ｌ～１．２ｋｇ／Ｌ程度である。 Generally, since the water level of the crystallization reaction part 126 is the same height as the treated water discharge port 111, if the upper end of the inner peripheral wall 124 is made the same height as the treated water discharge port 111 or lower than that height, Crystals or the like of the hardly soluble calcium salt in the precipitation reaction portion 126 will flow over the inner peripheral wall 124 to the solid-liquid separation portion 128 side. However, when obtaining crystals of calcium fluoride and calcium phosphate, the specific gravity per unit volume of the fluid in the crystallization reaction unit 126 tends to be higher than the specific gravity of the fluid in the solid-liquid separation unit 128. For example, when obtaining calcium fluoride crystals, the weight per liter of raw water containing the crystals in the crystallization reaction part 126 can be 2.0 kg / L. On the other hand, the specific gravity in the solid-liquid separator 128 is at most about 1.0 kg / L to 1.2 kg / L.
　このように、晶析反応部１２６と固液分離部１２８に比重差が生じると、晶析反応部１２６と固液分離部１２８に水位差が生じる。したがって、本実施形態のように、内周壁１２４の上端の位置を上記のように下げても、晶析反応部１２６内の原水が固液分離部１２８に越流することはなく、固液分離部１２８内の処理水の一部を晶析反応部１２６に戻せることになる。これにより、処理水中に含まれる微細粒子（難溶性カルシウム塩の結晶や種晶等）を、何ら動力機器を使用することなく晶析反応部１２６に返送することが可能となるため、より晶析反応部１２６内の難溶性カルシウム塩の結晶や種晶の粒径分布を細かく維持することが可能となる。その結果、更に難溶性カルシウム塩の結晶の回収率を向上させることが可能となる。 Thus, when a specific gravity difference occurs between the crystallization reaction unit 126 and the solid-liquid separation unit 128, a water level difference occurs between the crystallization reaction unit 126 and the solid-liquid separation unit 128. Therefore, as in this embodiment, even if the position of the upper end of the inner peripheral wall 124 is lowered as described above, the raw water in the crystallization reaction unit 126 does not flow into the solid-liquid separation unit 128, and the solid-liquid separation is performed. A part of the treated water in the unit 128 can be returned to the crystallization reaction unit 126. This makes it possible to return fine particles (crystals or seed crystals of sparingly soluble calcium salt) contained in the treated water to the crystallization reaction unit 126 without using any power equipment. The particle size distribution of the hardly soluble calcium salt crystals and seed crystals in the reaction section 126 can be maintained finely. As a result, it becomes possible to further improve the recovery rate of crystals of the hardly soluble calcium salt.
　次に、本実施形態の晶析反応装置１００のその他の条件について説明する。 Next, other conditions of the crystallization reaction apparatus 100 of this embodiment will be described.
　本実施形態における晶析対象物質含有原水は、晶析処理により除去されるフッ素、リンを含むものである。しかし、フッ素、リンを含むものであれば、如何なる由来の原水であっても良く、例えば、半導体関連産業をはじめとする電子産業、発電所、アルミニウム工業等から排出される原水が挙げられるが、これらに限定されるものではない。 The raw material water containing the crystallization target substance in the present embodiment contains fluorine and phosphorus that are removed by the crystallization treatment. However, raw water of any origin may be used as long as it contains fluorine and phosphorus, for example, raw water discharged from the electronics industry including the semiconductor-related industry, the power plant, the aluminum industry, It is not limited to these.
　晶析対象物質となるフッ素、リンは、晶析反応により晶析するのであれば、任意の状態で原水中に存在することが可能である。原水中に溶解しているという観点から、フッ素、リンはイオン化した状態であるのが好ましい。 Fluorine and phosphorus as crystallization target substances can be present in the raw water in any state as long as they are crystallized by a crystallization reaction. From the viewpoint of dissolving in raw water, fluorine and phosphorus are preferably in an ionized state.
　本実施形態において、カルシウム剤及び原水の晶析反応部１２６への添加（注入点）は、攪拌翼１３６の近傍に行われることが好ましい。カルシウム剤及び原水を攪拌翼１３６の近傍に添加することにより、カルシウム剤及び原水は、晶析反応部１２６へ注入されると直ちに拡散せしめられ、カルシウム剤濃度やフッ素、リン濃度が素早く低下する。このため、形成された難溶性塩が液中に直接析出することが少なくなり、晶析反応部１２６内の種晶上の難溶塩結晶として液中のフッ素、リンをじっくり取り込むことができる。 In this embodiment, the addition (injection point) of the calcium agent and raw water to the crystallization reaction unit 126 is preferably performed in the vicinity of the stirring blade 136. By adding the calcium agent and the raw water in the vicinity of the stirring blade 136, the calcium agent and the raw water are immediately diffused when injected into the crystallization reaction unit 126, and the calcium agent concentration, the fluorine concentration, and the phosphorus concentration are quickly lowered. For this reason, the formed hardly soluble salt is less likely to be directly deposited in the liquid, and fluorine and phosphorus in the liquid can be taken in well as the hardly soluble salt crystal on the seed crystal in the crystallization reaction unit 126.
　本実施形態においては、筒内に攪拌装置１３２の攪拌翼１３６が位置するようにドラフトチューブ１３４を設置することが好ましい。このとき、攪拌翼１３６は下降流を形成するものであることが好ましい。このようにドラフトチューブ１３４を設置すると、チューブ下部に向けて下降流が生じ、拡散流速が比較的大きいゾーンが形成される。このため、原水やカルシウム剤等をより素早く拡散させることができ、原水やカルシウム剤の濃度が局所的に濃い領域同士が接触せずに、難溶性カルシウム塩粒子の直接生成が抑制される。 In this embodiment, it is preferable to install the draft tube 134 so that the stirring blade 136 of the stirring device 132 is positioned in the cylinder. At this time, the stirring blade 136 preferably forms a downward flow. When the draft tube 134 is thus installed, a downward flow is generated toward the lower portion of the tube, and a zone having a relatively large diffusion flow rate is formed. For this reason, raw | natural water, a calcium agent, etc. can be diffused more rapidly, and the direct production | generation of a sparingly soluble calcium salt particle | grain is suppressed, without the area | regions where the density | concentration of raw | natural water or a calcium agent is locally concentrated.
　また、上記のようにドラフトチューブ１３４および攪拌翼１３６を設置すると、チューブ外周部には流れのゆるやかな上向流ゾーンが形成される。このゾーンでは、粒子が分級されて小粒径の粒子はチューブ外側面に沿って上昇すると共に、チューブ上端からチューブ内部に再侵入して下降し、原水やカルシウム剤等の注入点付近やその下部の撹拌ゾーンへと再循環する。これら小粒径の結晶が核となって晶析反応を促進せしめるため、難溶性塩結晶の回収率を向上させることができる。 In addition, when the draft tube 134 and the stirring blade 136 are installed as described above, an upward flow zone with a gentle flow is formed on the outer periphery of the tube. In this zone, the particles are classified and small particles rise along the outer surface of the tube, and re-enter from the upper end of the tube to the inside of the tube. Recirculate to the stirring zone. Since these small-sized crystals serve as nuclei to promote the crystallization reaction, the recovery rate of the hardly soluble salt crystals can be improved.
　さらに、晶析反応が進んで粒径が大きくなった結晶は、チューブ外周部の上向流によっては上昇せず、下に沈んで再びドラフトチューブ１３４内には入り込まないため、成長した結晶が攪拌翼１３６との衝突により破壊されてしまうことを防止することができるため、難溶性塩結晶の回収率の向上に寄与することができる。 Furthermore, the crystals whose particle size has increased due to the progress of the crystallization reaction does not rise due to the upward flow at the outer periphery of the tube, sinks down and does not enter the draft tube 134 again. Since it can be prevented from being destroyed by the collision with the blade 136, it can contribute to the improvement of the recovery rate of the hardly soluble salt crystal.
　本実施形態では、晶析反応槽１１０に酸又はアルカリを添加し、晶析反応部１２６における晶析反応液のｐＨを０．８～３の範囲とすることが好ましく、１～１．５の範囲とすることがより好ましい。酸又はアルカリを添加して晶析反応部１２６のｐＨを０．８～３の範囲で運転することにより、例えば、処理水のフッ素、リンの晶析対象物質濃度を低減させることができる。 In the present embodiment, acid or alkali is added to the crystallization reaction tank 110, and the pH of the crystallization reaction solution in the crystallization reaction unit 126 is preferably in the range of 0.8 to 3, preferably 1 to 1.5. It is more preferable to set the range. By adding acid or alkali and operating the crystallization reaction section 126 at a pH in the range of 0.8 to 3, for example, the concentration of the crystallization target substance of fluorine and phosphorus in the treated water can be reduced.
　本実施形態において用いられるカルシウム剤としては、例えば塩化カルシウム、水酸化カルシウム等が用いられる。カルシウム剤を添加する形態としては、粉末状態でもよいし、スラリ状態であってもよい。 As the calcium agent used in the present embodiment, for example, calcium chloride, calcium hydroxide and the like are used. As a form which adds a calcium agent, a powder state may be sufficient and a slurry state may be sufficient.
　カルシウム剤の注入量としては、カルシウムの化学当量としてフッ素、リンの０．８倍～２倍、１倍～２倍までがよいが、１倍～１．２倍がよりよい。カルシウムの化学当量が原水のフッ素、リンの化学当量の２倍より多いとフッ化カルシウム、リン酸カルシウムが種晶上に析出せずに微粒子として生成しやすく、処理水にフッ化カルシウム、リン酸カルシウムが混入する場合があり、０．８倍より少ないと、原水中のフッ素、リンのうちフッ化カルシウム、リン酸カルシウムとならない割合が多くなり、処理水にフッ素、リンが混入する場合がある。 The injection amount of the calcium agent is preferably 0.8 to 2 times and 1 to 2 times that of fluorine and phosphorus as the chemical equivalent of calcium, but more preferably 1 to 1.2 times. When the chemical equivalent of calcium is more than twice the chemical equivalent of fluorine and phosphorus in the raw water, calcium fluoride and calcium phosphate are not easily deposited on the seed crystal and are easily formed as fine particles, and calcium fluoride and calcium phosphate are mixed into the treated water. If the ratio is less than 0.8 times, the proportion of fluorine and phosphorus in raw water that does not become calcium fluoride and calcium phosphate increases, and fluorine and phosphorus may be mixed into the treated water.
　本実施形態においては、原水とカルシウム剤とを晶析反応部１２６に添加する前に、あらかじめ、晶析反応部１２６に種晶が存在していてもよいし、あらかじめ晶析反応部１２６内に種晶が存在していなくてもよい。安定した処理を行うためには、晶析反応部１２６にあらかじめ種晶が存在していることが好ましい。 In the present embodiment, before adding raw water and calcium agent to the crystallization reaction unit 126, seed crystals may exist in advance in the crystallization reaction unit 126, or in the crystallization reaction unit 126 in advance. There may be no seed crystals. In order to perform a stable process, it is preferable that a seed crystal is present in the crystallization reaction unit 126 in advance.
　種晶は、その表面に生成した難溶性カルシウム塩の結晶を析出させることができるものであればよく、任意の材質が選択可能であり、例えば、ろ過砂、活性炭、およびジルコンサンド、ガーネットサンド、サクランダム（商品名、日本カートリット株式会社製）などをはじめとする金属元素の酸化物を含んで構成される粒子、ならびに、晶析反応による析出物である難溶性塩を含んで構成される粒子等が挙げられるが、これらに限定されるものではない。より純粋な難溶性塩をペレット等として入手できるという観点から、晶析反応による析出物である難溶性塩を含んで構成される粒子が好ましい。晶析反応による析出物である難溶性塩を含んで構成される粒子としては、フッ化カルシウムを析出させる場合には、例えば蛍石等が挙げられ、リン酸カルシウムを析出させる場合には、例えばリン鉱石等が挙げられる。 The seed crystal may be any material as long as it can precipitate a hardly soluble calcium salt crystal formed on the surface thereof, and any material can be selected, for example, filtered sand, activated carbon, zircon sand, garnet sand, It is composed of particles composed of oxides of metal elements such as sacrandom (trade name, manufactured by Nihon Cartrit Co., Ltd.) and the like, and hardly soluble salts that are precipitates by crystallization reaction. Examples thereof include, but are not limited to, particles. From the viewpoint that a purer hardly soluble salt can be obtained as a pellet or the like, particles composed of the hardly soluble salt which is a precipitate by a crystallization reaction are preferable. Examples of the particles composed of a hardly soluble salt that is a precipitate by a crystallization reaction include fluorite when depositing calcium fluoride, and when depositing calcium phosphate, for example, phosphate ore. Etc.
　以下、実施例および比較例を挙げ、本発明をより具体的に詳細に説明するが、本発明は、以下の実施例に限定されるものではない。 Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.
（実施例１）
　実施例１では、図１に示す晶析反応装置を用い、以下の条件で、フッ素含有原水からフッ化カルシウムの回収を行った。 (Example 1)
In Example 1, the crystallization reaction apparatus shown in FIG. 1 was used, and calcium fluoride was recovered from the fluorine-containing raw water under the following conditions.
＜晶析反応装置＞
　晶析反応部サイズ：１３０Ｌ（４４０ｍｍφ×８８０ｍｍＨ）
　固液分離部サイズ：２３０Ｌ（４４０×５９０×８８０ｍｍＨ）
＜試験条件＞
　フッ素含有原水流量：５０Ｌ／ｈ
　フッ素含有原水のフッ素濃度：１００００ｍｇ／Ｌ
　カルシウム剤：消石灰１０％スラリを塩酸で溶解した溶液
　晶析反応部内のｐＨ：ｐＨ２（ＮａＯＨを添加して調整）
　晶析反応部内の初期充填種晶：２０ｋｇ（その後の種晶の補給無し）
　晶析反応部内のスラリ濃度：３０～３５ｖ／ｖ％（難溶性塩排出管から適宜引き抜く） <Crystal crystallization reactor>
Crystallization reaction part size: 130 L (440 mmφ × 880 mmH)
Solid-liquid separation part size: 230L (440 × 590 × 880mmH)
<Test conditions>
Fluorine-containing raw water flow rate: 50 L / h
Fluorine concentration of raw water containing fluorine: 10000 mg / L
Calcium agent: A solution in which 10% slurry of slaked lime is dissolved in hydrochloric acid. PH in the crystallization reaction part: pH 2 (adjusted by adding NaOH)
Initially filled seed crystals in the crystallization reaction section: 20 kg (without replenishment of seed crystals thereafter)
Slurry concentration in the crystallization reaction section: 30 to 35 v / v% (appropriately withdrawn from the hardly soluble salt discharge pipe)
　実施例１の固液分離部の滞留時間は４．６ｈ（２３０（Ｌ）／５０（Ｌ／ｈ））となり、晶析反応部の滞留時間は２．６ｈとなった。 The residence time of the solid-liquid separation part of Example 1 was 4.6 h (230 (L) / 50 (L / h)), and the residence time of the crystallization reaction part was 2.6 h.
　実施例１では、原水を晶析反応部へ９．２時間通水した後、２．３時間通水を停止した。通水時間が４００時間に達するまで、この通水及び通水停止を繰り返した。通水時の固液分離部の処理水の流速（ＬＶ）は０．２ｍ／ｈであった。なお、固液分離部の処理水の一部は晶析反応部へ返送されない態様で試験を行った。 In Example 1, the raw water was passed through the crystallization reaction section for 9.2 hours, and then the water flow was stopped for 2.3 hours. This water flow and water flow stop were repeated until the water flow time reached 400 hours. The flow rate (LV) of the treated water in the solid-liquid separation part during water flow was 0.2 m / h. The test was conducted in such a manner that a part of the treated water in the solid-liquid separation part was not returned to the crystallization reaction part.
（実施例２）
　実施例２では、原水を晶析反応部へ４．６時間通水した後、１．１５時間通水を停止したこと以外は実施例１と同様の条件で試験を行った。 (Example 2)
In Example 2, the test was performed under the same conditions as in Example 1 except that the raw water was passed through the crystallization reaction section for 4.6 hours and then stopped for 1.15 hours.
（実施例３）
　実施例３では、原水を晶析反応部へ４．６時間通水した後、２．３時間通水を停止したこと以外は実施例１と同様の条件で試験を行った。 (Example 3)
In Example 3, the test was performed under the same conditions as in Example 1 except that the raw water was passed through the crystallization reaction section for 4.6 hours and then the water supply was stopped for 2.3 hours.
（実施例４）
　実施例４では、固液分離部サイズを２３Ｌ（４４０×６０×８８０ｍｍＨ）に変更した晶析反応装置を用いた。また、実施例４では、原水を晶析反応部へ０．４６時間通水した後、０．２３時間通水を停止した。通水時間が４００時間に達するまで、この通水及び通水停止を繰り返した。なお、通水時の固液分離部の処理水の流速（ＬＶ）は２．０ｍ／ｈであった。 Example 4
In Example 4, a crystallization reaction apparatus in which the solid-liquid separation part size was changed to 23 L (440 × 60 × 880 mmH) was used. In Example 4, the raw water was passed through the crystallization reaction section for 0.46 hours and then stopped for 0.23 hours. This water flow and water flow stop were repeated until the water flow time reached 400 hours. In addition, the flow rate (LV) of the treated water of the solid-liquid separation part at the time of water flow was 2.0 m / h.
（実施例５）
　実施例５では、原水を晶析反応部へ１８．４時間通水した後、２．３時間通水を停止した以外は実施例１と同様の条件で試験を行った。 (Example 5)
In Example 5, the test was performed under the same conditions as in Example 1 except that the raw water was passed through the crystallization reaction part for 18.4 hours and then stopped for 2.3 hours.
（比較例１）
　比較例１では、原水の通水停止を行わず、原水を晶析反応部へ４００時間通水したこと以外は実施例１と同様の条件で試験を行った。通水時の固液分離部の処理水の流速（ＬＶ）は０．２ｍ／ｈであった。 (Comparative Example 1)
In Comparative Example 1, the test was performed under the same conditions as in Example 1 except that the raw water was not stopped and the raw water was passed through the crystallization reaction part for 400 hours. The flow rate (LV) of the treated water in the solid-liquid separation part during water flow was 0.2 m / h.
（比較例２）
　比較例２では、固液分離部サイズを２３Ｌ（４４０×６０×８８０ｍｍＨ）に変更した晶析反応装置を用いて、原水の通水停止を行わず、原水を晶析反応部へ４００時間通水したこと以外は実施例１と同様の条件で試験を行った。通水時の固液分離部の処理水の流速（ＬＶ）は２．０ｍ／ｈであった。 (Comparative Example 2)
In Comparative Example 2, using the crystallization reaction apparatus whose solid-liquid separation part size was changed to 23 L (440 × 60 × 880 mmH), the raw water was passed through the crystallization reaction part for 400 hours without stopping the flow of the raw water. The test was performed under the same conditions as in Example 1 except that. The flow rate (LV) of the treated water in the solid-liquid separation part during water flow was 2.0 m / h.
　表１に、実施例１～５及び比較例１～２の固液分離部の処理水の流速、晶析反応部への原水の通水時間、通水停止時間、及び通水４００時間経過後のフッ化カルシウムの回収率をまとめた。 Table 1 shows the flow rate of treated water in the solid-liquid separation parts of Examples 1 to 5 and Comparative Examples 1 and 2, the time for passing raw water to the crystallization reaction part, the time for stopping water flow, and after 400 hours for water flow. The recovery rates of calcium fluoride were summarized.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
（実施例６）
　実施例６では、図１に示す晶析反応装置において、内周壁の上端を処理水排出口と同じ高さに設定した晶析反応装置を用いて、固液分離部の処理水の一部を晶析反応部へ返送したこと以外は実施例１と同様の条件で試験を行った。 (Example 6)
In Example 6, in the crystallization reaction apparatus shown in FIG. 1, a part of the treated water in the solid-liquid separation unit was obtained using a crystallization reaction apparatus in which the upper end of the inner peripheral wall was set to the same height as the treated water discharge port. The test was performed under the same conditions as in Example 1 except that the sample was returned to the crystallization reaction part.
（実施例７）
　実施例７では、原水を晶析反応部へ４．６時間通水した後、２．３時間通水を停止したこと以外は実施例６と同様の条件で試験を行った。 (Example 7)
In Example 7, the test was performed under the same conditions as in Example 6 except that the raw water was passed through the crystallization reaction section for 4.6 hours and then stopped for 2.3 hours.
（比較例３）
　比較例３では、図２に示す晶析反応装置において、内周壁の上端を処理水排出口と同じ高さに設定した晶析反応装置を用いて、原水の通水停止を行わず、原水を晶析反応部へ４００時間通水したこと以外は実施例５と同様の条件で試験を行った。 (Comparative Example 3)
In Comparative Example 3, in the crystallization reaction apparatus shown in FIG. 2, using the crystallization reaction apparatus in which the upper end of the inner peripheral wall is set to the same height as the treated water discharge port, the raw water is not stopped without passing the raw water. The test was performed under the same conditions as in Example 5 except that water was passed through the crystallization reaction section for 400 hours.
　表２に、実施例６～７及び比較例３の固液分離部の処理水の流速、晶析反応部への原水の通水時間、通水停止時間、及び通水４００時間経過後のフッ化カルシウムの回収率をまとめた。 Table 2 shows the flow rate of treated water in the solid-liquid separation sections of Examples 6 to 7 and Comparative Example 3, the flow time of raw water to the crystallization reaction section, the stop time of water flow, and the flow after 400 hours of water flow. The recovery rate of calcium fluoride was summarized.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　図３は、実施例１の晶析反応部内の結晶の粒径分布を示す図であり、図４は、実施例２の晶析反応部内の結晶の粒径分布を示す図であり、図５は、実施例３の晶析反応部内の結晶の粒径分布を示す図であり、図６は、実施例４の晶析反応部内の結晶の粒径分布を示す図であり、図７は、比較例１の晶析反応部内の結晶の粒径分布を示す図であり、図８は、比較例２の晶析反応部内の結晶の粒径分布を示す図であり、図９は、比較例３の晶析反応部内の結晶の粒径分布を示す図である。晶析反応部内の結晶の粒径分布は、通水４００時間後の晶析反応部内の粒径分布を、粒度分布計（ベックマン・コールター社製　ＬＳ２３０）を用いて測定した。 3 is a diagram showing the particle size distribution of crystals in the crystallization reaction part of Example 1, and FIG. 4 is a diagram showing the particle size distribution of crystals in the crystallization reaction part of Example 2, and FIG. These are diagrams showing the particle size distribution of crystals in the crystallization reaction part of Example 3, FIG. 6 is a diagram showing the particle size distribution of crystals in the crystallization reaction part of Example 4, and FIG. FIG. 8 is a diagram showing the particle size distribution of crystals in the crystallization reaction part of Comparative Example 1, FIG. 8 is a diagram showing the particle size distribution of crystals in the crystallization reaction part of Comparative Example 2, and FIG. 9 is a comparative example. FIG. 3 is a diagram showing a particle size distribution of crystals in a crystallization reaction part of 3. The particle size distribution of the crystals in the crystallization reaction part was measured using a particle size distribution meter (LS230 manufactured by Beckman Coulter, Inc.) after 400 hours of water flow.
　種晶の補給を行わず原水の連続通水によりフッ化カルシウムを回収した比較例１では、図７及び表１の結果から判るように、晶析反応部内に、粒径が１００μｍ以上の結晶が多く存在し、回収率も６５％と低かった。さらに、固液分離部の処理水の流速を２．０ｍ／ｈに上げた比較例２では、図８及び表１の結果から判るように、晶析反応部内に、粒径が１２５μｍ以上の結晶が多く存在し、回収率も５０％とさらに低くなった。一方、原水の通水を間欠的に行った実施例、具体的には、原水の通水を固液分離部の滞留時間の１／２倍以上５倍以下の時間行い、通水停止を固液分離部の滞留時間の１／５倍以上１倍以下の時間行った実施例１～５では、図３～６及び表１の結果から判るように、晶析反応部内に、粒径が１００μｍ以下の結晶が多く存在し、回収率も７５％以上となり比較例１及び２より高い回収率を得ることができた。特に、原水の通水を固液分離部の滞留時間の１倍の時間、通水停止を固液分離部の滞留時間の１／２倍の時間の間行った実施例３、原水の通水を固液分離部の滞留時間の１倍の時間、通水停止を固液分離部の滞留時間の１／２倍の時間行った実施例４では、図５、図６及び表１の結果から判るように、晶析反応部内に、５０μｍ以下の粒径の結晶が存在するようになり、回収率も９０％以上と実施例１，２より高い回収率を得ることができた。すなわち、原水の通水を固液分離部の滞留時間の１倍の時間行い、通水停止を固液分離部の滞留時間の１／２倍の時間行うことにより、より細かい粒径の結晶を晶析反応部内に保持することができ、フッ化カルシウム結晶の回収率もより向上することがわかった。 In Comparative Example 1 in which calcium fluoride was recovered by continuous flow of raw water without replenishing seed crystals, as can be seen from the results of FIG. 7 and Table 1, crystals having a particle size of 100 μm or more were formed in the crystallization reaction part. Many were present and the recovery rate was as low as 65%. Furthermore, in Comparative Example 2 in which the flow rate of the treated water in the solid-liquid separation part was increased to 2.0 m / h, as can be seen from the results of FIG. 8 and Table 1, crystals having a particle size of 125 μm or more were formed in the crystallization reaction part. There were many, and the recovery rate was further reduced to 50%. On the other hand, an example in which the raw water was intermittently passed, specifically, the raw water was passed for a time that was 1/2 times to 5 times the residence time of the solid-liquid separation unit, and the water flow was stopped. In Examples 1 to 5, which were conducted for a time that was 1/5 times or more and 1 time or less of the residence time of the liquid separation part, as can be seen from the results of FIGS. 3 to 6 and Table 1, the particle size was 100 μm in the crystallization reaction part. Many of the following crystals existed, and the recovery rate was 75% or more, and a higher recovery rate than Comparative Examples 1 and 2 could be obtained. In particular, Example 3 in which the raw water was passed for one time the residence time of the solid-liquid separation unit, and the water passage was stopped for half the residence time of the solid-liquid separation unit. In Example 4 where the residence time of the solid-liquid separation unit was 1 time, and the water flow was stopped for 1/2 time of the residence time of the solid-liquid separation unit, the results shown in FIGS. As can be seen, crystals having a particle size of 50 μm or less are present in the crystallization reaction part, and the recovery rate is 90% or higher, which is higher than in Examples 1 and 2. That is, the raw water is passed through for a time that is one time the residence time of the solid-liquid separation part, and the water passage is stopped for a time that is one-half the residence time of the solid-liquid separation part. It was found that it could be retained in the crystallization reaction part, and the recovery rate of calcium fluoride crystals was further improved.
　表２の結果から判るように、実施例６，７では、原水の通水を間欠的に行うとともに、固液分離部内の処理水の一部を内周壁を超えて晶析反応部に返送することにより、回収率は９５％以上とさらに向上することがわかった。 As can be seen from the results in Table 2, in Examples 6 and 7, the raw water is intermittently passed, and part of the treated water in the solid-liquid separation part is returned to the crystallization reaction part beyond the inner peripheral wall. As a result, it was found that the recovery rate was further improved to 95% or more.
　１，１００　晶析反応装置、１０，１１０　晶析反応槽、１２，１１２　種晶サイロ、１４，１１４　カルシウム剤添加ライン、１６，１１６　原水通水ライン、１８，２４ａ，１２２ａ　バルブ、２０，１１８　種晶添加ライン、２１，１１１　処理水排出口、２２，１２０　処理水排出ライン、２４，１２２　難溶性塩排出ライン、２６，１２４　内周壁、２８，１２６　晶析反応部、３０，１２８　固液分離部、３２，１３０　連通口、３４，１３２　攪拌装置、３６，１３４　ドラフトチューブ、３８，１３６　攪拌翼。 1,100 crystallization reaction apparatus, 10,110 crystallization reaction tank, 12,112 seed silo, 14,114 calcium agent addition line, 16,116 raw water passage line, 18, 24a, 122a valve, 20,118 seeds Crystal addition line, 21,111 treated water discharge port, 22,120 treated water discharge line, 24,122 sparingly soluble salt discharge line, 26,124 inner wall, 28,126 crystallization reaction section, 30,128 solid- liquid separation section 32, 130 communication port, 34, 132 stirring device, 36, 134 draft tube, 38, 136 stirring blade.

Claims (4)

  1. 　攪拌翼を有する攪拌手段を備え、晶析対象物質を含む原水にカルシウム剤を添加して難溶性塩の結晶を生成させる晶析反応部を有する晶析反応槽と、前記晶析反応部へ前記原水を通水する通水手段と、を備え、
    　前記晶析反応槽内には、前記晶析反応槽の外周壁に対向する内周壁を配置し、内外周壁間で上向流を形成して、前記結晶と処理水との固液分離を行う固液分離部が設けられ、
    　前記通水手段は、前記晶析反応部への前記原水の通水を間欠的に行うことを特徴とする晶析反応装置。     A crystallization reaction tank having a crystallization reaction section that includes a stirring means having a stirring blade and adds a calcium agent to raw water containing a crystallization target substance to form crystals of a hardly soluble salt, and to the crystallization reaction section Water flow means for passing raw water,
    In the crystallization reaction tank, an inner peripheral wall facing the outer peripheral wall of the crystallization reaction tank is disposed, and an upward flow is formed between the inner and outer peripheral walls to perform solid-liquid separation between the crystal and treated water. A solid-liquid separation unit is provided,
    The crystallization reaction apparatus, wherein the water passing means intermittently passes the raw water through the crystallization reaction section.
  2. 　前記通水手段による間欠通水時の前記原水の通水時間は、前記固液分離部における滞留時間の１／２倍以上５倍以下であり、前記通水手段による間欠通水時の前記原水の通水停止時間は、前記固液分離部における滞留時間の１／５倍以上１倍以下の時間であることを特徴とする請求項１記載の晶析反応装置。 The flow time of the raw water during intermittent water flow by the water flow means is ½ to 5 times the residence time in the solid-liquid separation unit, and the raw water during intermittent water flow by the water flow means 2. The crystallization reaction apparatus according to claim 1, wherein the water passage stop time is 1/5 to 1 time of the residence time in the solid-liquid separation unit.
  3. 　前記通水手段による間欠通水時の前記原水の通水時間は、前記固液分離部における滞留時間の１倍以上４倍以下であり、前記通水手段による間欠通水時の前記原水の通水停止時間は、前記固液分離部における滞留時間の１／４倍以上１／２倍以下の時間であることを特徴とする請求項１記載の晶析反応装置。 The flow time of the raw water during intermittent water flow by the water flow means is 1 to 4 times the residence time in the solid-liquid separator, and the flow of the raw water during intermittent water flow by the water flow means. 2. The crystallization reaction apparatus according to claim 1, wherein the water stop time is a time that is not less than 1/4 times and not more than 1/2 times the residence time in the solid-liquid separation unit.
  4. 　前記固液分離部が設けられている前記晶析反応槽の外周壁に、前記処理水を排出する排出口が形成され、
    　前記内周壁の上端は、前記排出口と同じ高さ、又は前記処理水の一部が前記排出口から排出可能な範囲で前記排出口より低い位置にあり、前記固液分離部内の処理水の一部は、前記内周壁を越えて前記晶析反応部に返送されることを特徴とする請求項１～３のいずれか１項に記載の晶析反応装置。     A discharge port for discharging the treated water is formed on the outer peripheral wall of the crystallization reaction tank provided with the solid-liquid separation unit,
    The upper end of the inner peripheral wall is at the same height as the discharge port or at a position lower than the discharge port within a range in which a part of the treated water can be discharged from the discharge port, and the treated water in the solid-liquid separation unit The crystallization reaction apparatus according to any one of claims 1 to 3, wherein a part of the crystallization reaction apparatus is returned to the crystallization reaction section beyond the inner peripheral wall.
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JP2001038370A (en) * 1999-08-03 2001-02-13 Maezawa Ind Inc Waste water treatment device
JP2002292204A (en) * 2001-03-30 2002-10-08 Japan Organo Co Ltd Crystallization reaction apparatus provided with means for controlling amount of raw water to be supplied and crystallization method to use the same

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