WO2013153846A1 - Method and device for manufacturing calcium fluoride - Google Patents

Method and device for manufacturing calcium fluoride Download PDF

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WO2013153846A1
WO2013153846A1 PCT/JP2013/053181 JP2013053181W WO2013153846A1 WO 2013153846 A1 WO2013153846 A1 WO 2013153846A1 JP 2013053181 W JP2013053181 W JP 2013053181W WO 2013153846 A1 WO2013153846 A1 WO 2013153846A1
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calcium fluoride
potassium
reaction product
fluoride
reaction
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PCT/JP2013/053181
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French (fr)
Japanese (ja)
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達夫 宮崎
敦之 徳永
利久 井手
赤松　佳則
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セントラル硝子株式会社
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D3/00—Halides of sodium, potassium or alkali metals in general
    • C01D3/02—Fluorides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D7/00—Carbonates of sodium, potassium or alkali metals in general
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F11/00—Compounds of calcium, strontium, or barium
    • C01F11/20—Halides
    • C01F11/22—Fluorides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/80—Compositional purity

Definitions

  • the present invention relates to a method and an apparatus for producing calcium fluoride suitable as a raw material for producing hydrofluoric acid by decomposing drainage containing silicohydrofluoric acid (H 2 SiF 6 ).
  • calcium fluoride is synthesized and recovered from wastewater containing hydrofluoric acid discharged in the semiconductor industry, chemical industry, etc., and recycled using the obtained calcium fluoride as a raw material for the production of hydrofluoric acid Technology is known.
  • hydrofluoric acid is produced by collecting calcium fluoride using this kind of recycling technology and reacting calcium fluoride and sulfuric acid as shown in the following reaction formula (1). ing.
  • hydrofluoric acid When manufacturing hydrofluoric acid using reaction like said Reaction formula (1), it is performed in a rotary kiln with the reaction temperature of 200 degreeC or more, for example. At this time, when calcium hydroxide or calcium carbonate is present in the calcium fluoride used as a raw material, as shown in the following reaction formula (2) and reaction formula (3), a reaction that produces water as a by-product occurs. .
  • reaction formula (2) and reaction formula (3) when calcium fluoride containing SiO 2 is used, as shown in the following reaction formula (4), H 2 SiF 6 is formed and synthesized by reaction with hydrofluoric acid generated in the kiln. It not only loses hydrofluoric acid but also produces water as a by-product.
  • the calcium fluoride used as a raw material when hydrofluoric acid is produced in a rotary kiln, the calcium fluoride used as a raw material must be sized to flow in the kiln.
  • the raw material calcium fluoride acid grade fluorite (mainly calcium fluoride) that is naturally present is generally used, and the natural fluorite can be flowed in a kiln, for example, 15 It is used after being pulverized to an average particle size of about 300 ⁇ m. Therefore, when recovering calcium fluoride by a recycling technique, it is preferable to obtain an average particle size of about 15 to 300 ⁇ m.
  • calcium fluoride is recovered using fluorine-containing wastewater recycling technology such as silicofluoric acid, and hydrofluoric acid is produced using the recovered calcium fluoride.
  • fluorine-containing wastewater recycling technology such as silicofluoric acid
  • hydrofluoric acid is produced using the recovered calcium fluoride.
  • Patent Document 1 when the silicohydrofluoric acid water and calcium carbonate are directly reacted, the concentration of silicohydrofluoric acid water and the pH during the reaction are controlled as shown in the following reaction formula (5). Discloses a technique for directly synthesizing calcium fluoride.
  • Patent Document 2 as shown in the following reaction formula (6), a fluorine-containing wastewater containing hydrofluoric acid and a sodium compound such as sodium carbonate are mixed to decompose hydrofluoric acid, thereby insoluble.
  • a technique is disclosed in which a mixture of silica and an aqueous solution of sodium fluoride is formed, and then calcium fluoride is recovered from the obtained aqueous solution of sodium fluoride by a crystallization technique or the like.
  • the method via a fluoride salt such as sodium fluoride as described in Patent Document 2 does not cause calcium fluoride and silica to precipitate simultaneously as in the above reaction formula (5). It is an excellent method for synthesizing and recovering calcium fluoride.
  • a fluoride salt such as sodium fluoride as described in Patent Document 2
  • Patent Document 2 since sodium fluoride has low solubility in water, it is necessary to enlarge the reaction system in order to form a sufficient amount of aqueous sodium fluoride solution. As a result, there has been a problem that the recovery device and the like are likely to be large and complicated, and the running cost for manufacturing and maintaining the device becomes high.
  • the present invention has been made in view of the above problems, and provides a simple method for producing calcium fluoride suitable as a raw material for producing hydrofluoric acid from wastewater containing hydrofluoric acid. With the goal.
  • the present invention is a method for producing calcium fluoride using silicohydrofluoric acid-containing water, wherein the first reaction includes insoluble silica and an aqueous potassium fluoride solution by reacting silicohydrofluoric acid-containing water with a potassium compound.
  • a method for producing calcium fluoride comprising a step [3] of generating a second reaction product containing an aqueous potassium carbonate solution and a step [4] of separating the aqueous potassium carbonate solution from the second reaction product.
  • the fluoride salt through which the fluorosilicic acid water fluorine is converted to calcium fluoride has sufficient solubility in water. Therefore, to provide calcium fluoride having a high purity and particle size suitable as a raw material for producing hydrofluoric acid with a simpler apparatus configuration without increasing the size of the apparatus in the calcium fluoride production process. Is possible.
  • a step [5] of reusing the potassium carbonate aqueous solution separated in the step [4] as a potassium compound raw material in the step [1] may be included. According to this configuration, since the separated potassium carbonate aqueous solution can be reused as a potassium compound raw material, the amount of potassium compound used in this step can be reduced, and the merit of manufacturing cost reduction can be obtained. It is done.
  • the apparatus 100 for producing calcium fluoride according to the present invention reacts hydrofluoric acid-containing water with a potassium compound to produce a first reaction product containing insoluble silica and an aqueous potassium fluoride solution by neutralization and decomposition.
  • a dehydrating device 30 for dehydrating the slurry liquid containing the solid liquid separation operation.
  • the neutralization / decomposition tank 60 includes a raw water supply pipe 61 for introducing wastewater containing hydrofluoric acid-containing water into the neutralization / decomposition tank 60 via a supply pump 60a, and a potassium compound that promotes the neutralization / decomposition reaction.
  • An alkali agent supply unit 62 for supplying an alkali agent and a silica separation water discharge pipe 63 for discharging silica separation water (first reaction product from which insoluble silica has been separated) as a supernatant of the reaction solution are provided via a discharge pump 60b. It is connected.
  • a first slurry discharge pipe 64 for discharging the precipitated insoluble silica slurry is connected to the bottom of the neutralization decomposition tank 60 via a discharge pump 67a.
  • the neutralization decomposition tank 60 you may make it install the stirrer 66 and the pH measuring device (not shown) which measures the pH of the reaction solution in the neutralization decomposition tank 60 via the motor 65.
  • a heat source may be secured by using steam instead of dilution water in order to dissolve the alkali agent and promote the neutralization reaction.
  • a dehydrator 67 for dehydrating the discharged insoluble silica slurry is connected to the downstream of the first slurry discharge pipe 64 via a discharge pump 67a. Furthermore, a circulation pipe 68 for returning the desorbed water separated by the dehydration to the neutralization decomposition tank 60 may be connected to the dehydrator 67. Since the desorbed water recovered via the circulation pipe 68 contains an alkali component derived from a potassium compound, it can be reused as a raw material liquid for the neutralization decomposition reaction. The separated silica cake (silica slurry having a low water content) is separately collected. Similarly, the desorbed water recovered via the circulation pipe 69 may be connected to the waste liquid storage tank 70 so that the desorbed water is reused as a raw material liquid.
  • a storage tank (not shown) for adding a flocculant for precipitating insoluble silica components that could not be separated may be provided as necessary.
  • a flocculant for precipitating insoluble silica components that could not be separated may be provided as necessary.
  • the aggregating agent to be used generally known ones such as an inorganic type and a polymer type can be used. For example, aluminum sulfate, polyaluminum chloride, sodium aluminate, iron (II) sulfate, chlorinated green vane, sodium caseinate, gelatin, gum arabic, dextrin, starch and the like can be mentioned.
  • a calcium fluoride synthesis tank 10 is connected downstream of the silica separation water discharge pipe 63 via a discharge pump 60b, and calcium carbonate is added to the calcium fluoride synthesis tank 10 in the calcium fluoride synthesis tank 10.
  • a calcium carbonate introduction device 40 to be introduced into the second slurry discharge pipe 14 is connected to a second slurry discharge pipe 14 for discharging a slurry liquid (second reaction product) containing synthetic calcium fluoride and a potassium carbonate component via a discharge pump 20b.
  • a dehydrator 30 is connected downstream of the second slurry liquid discharge pipe 22 via a discharge pump 20b.
  • a cleaning liquid supply pipe 31 for supplying a cleaning liquid for cleaning the slurry liquid sent via the second slurry liquid discharge pipe 22 is connected to the dehydrator 30 via a supply pump 30a as necessary.
  • an organic solvent such as water or ethanol can be used.
  • pure water having a chlorine component of 10 mg / L or less may be used from the viewpoint of the residual chlorine component.
  • the dehydrating device 30 is provided with a calcium fluoride recovery pipe 32, and the synthetic calcium fluoride 50 after dehydration and washing is recovered by the pipe 32.
  • a centrifugal separator is usually used, but as other methods, for example, a filter press dehydrator or a filtration dehydrator (nonwoven fabric filter type) may be used.
  • An outer jacket 12 through which a heat medium or the like can be circulated is provided around the outer periphery of the calcium fluoride synthesis tank 10, and the internal temperature is adjusted to promote the reaction between the aqueous potassium fluoride solution and calcium carbonate.
  • the method of the outer jacket 12 is not particularly limited, but for example, an electric heater using a Peltier element or the like may be used.
  • a stirrer 13 may be installed in the calcium fluoride synthesis tank 10 via a motor 15 to stir the inside. When an external jacket is not used, heated steam as a heat source may be directly fed into the calcium fluoride synthesis tank 10.
  • the material of the calcium fluoride synthesis tank 10 is not particularly limited, but for long-term durability, for example, a fluororesin such as PFA or PTFE, a resin such as FRP, or a rubber lining tank may be used.
  • the calcium carbonate introducing device 40 includes a granular calcium carbonate receiving popper 41 and a screw feeder 42 for supplying calcium carbonate, and the supply amount (supply speed) of calcium carbonate is adjusted by the screw feeder 42.
  • the supply rate of calcium carbonate is appropriately adjusted depending on the reaction situation.
  • a desorption water discharge pipe 71 for discharging desorption water (potassium carbonate aqueous solution) obtained by solid-liquid separation operation of the dehydration apparatus 30 is connected to the dehydration apparatus 30 via a discharge pump 70a.
  • a waste liquid storage tank 70 for storing desorbed water is provided downstream of the discharge pipe 71. Further, the waste liquid storage tank 70 is connected to a circulation pipe 72 for returning the stored desorbed water to the neutralization decomposition tank 60, and the desorbed water whose potassium carbonate concentration is adjusted is used as a raw material for the alkaline component. It can be reused in the sum decomposition tank 60.
  • a method using sun drying and membrane separation can be used.
  • FIG. 1 is a process schematic diagram of a method for producing calcium fluoride according to the present invention.
  • Step [1] is a step [1] in which silicohydrofluoric acid-containing water and a potassium compound are reacted to generate a first reaction product containing insoluble silica and an aqueous potassium fluoride solution.
  • hydrofluoric acid-containing water is supplied to the neutralization / decomposition tank 60 through the raw water supply pipe 61 from a tank that stores wastewater containing hydrofluoric acid.
  • a potassium compound such as potassium carbonate is added from the alkali agent supply unit 62, and as shown in the following reaction formula (7), hydrofluoric acid is neutralized and decomposed to contain insoluble silica and an aqueous potassium fluoride solution.
  • a first reaction product is produced.
  • the reaction conditions of the reaction formula (7) are preferably such that the pH is 7 to 14, the reaction temperature is 40 to 100 ° C., more preferably 50 to 80 ° C., and the reaction time is at least 1 hour or more. .
  • the amount of the potassium compound to be added is preferably adjusted to 1.1 to 10 equivalents of the amount required for the reaction with silicohydrofluoric acid.
  • the pressure at the time of performing reaction does not have a restriction
  • reaction formula (7) does not proceed easily, and the reaction for producing potassium salt (K 2 SiF 6 ) as shown in reaction formula (8) proceeds, which is not preferable.
  • reaction temperature is lower than 40 ° C., a sufficient reaction of the following reaction formula (7) does not proceed and the reaction formula (8) proceeds, which is not preferable.
  • volatilization amount of the liquid increases or it may cause boiling, it is not suitable as the reaction temperature. If the reaction time is less than 1 hour, the reaction may not be completed.
  • a potassium compound has a very high solubility in water due to the high hydration energy of potassium ions.
  • the solubility of potassium fluoride (KF) is about 920 g / 1000 g-H 2 O at room temperature.
  • the fluoride salt (potassium fluoride) passed through in the process of the present invention is sodium fluoride (solubility: 40 g / 1000 g-H), which is a fluoride salt disclosed in JP2009-196858 (Patent Document 2).
  • the solubility is much higher than 2 O).
  • the potassium compound is not particularly limited as long as it has sufficient solubility in water.
  • common compounds such as potassium carbonate, potassium hydrogen carbonate, potassium oxide, and potassium hydroxide can be used. These compounds can be used as at least one kind or a mixture of two or more kinds thereof.
  • potassium carbonate is particularly suitable from the viewpoints of chemical stability and availability.
  • Step [2] is a step of separating insoluble silica from the first reaction product obtained in step [1].
  • a potassium fluoride-containing liquid is separated from the first reaction product by a sedimentation operation. As separate.
  • the separated supernatant liquid is discharged from the silica separated water discharge pipe 63 and is sent to the calcium fluoride synthesis tank 10 via the discharge pump 60b.
  • the method for the sedimentation operation is not particularly limited, and can be performed, for example, by an operation (such as decantation) of allowing the first reaction product to stand still for a predetermined time.
  • step [3] the first reaction product (potassium fluoride-containing liquid) obtained by separating the insoluble silica obtained in the step [2] is reacted with calcium carbonate, so that the second containing the calcium fluoride and the potassium carbonate aqueous solution.
  • This is a step of generating a reaction product.
  • the reaction proceeds as shown in the following reaction formula (9).
  • the reaction conditions of the reaction formula (9) are preferably carried out in the range of a reaction temperature of 40 to 80 ° C., more preferably 50 to 70 ° C., and a reaction time of at least 3 hours or more.
  • the potassium fluoride is preferably adjusted to 1.1 to 10 equivalents of the amount required for the reaction with the calcium carbonate to be added.
  • the pressure at the time of performing reaction does not have a restriction
  • the pH under the reaction conditions is not particularly limited, but may be appropriately set within a range where a processing burden such as a neutralizing agent is not applied (for example, pH is about 7 to 10).
  • reaction temperature When the reaction temperature is lower than 40 ° C., the reaction of the above reaction formula (9) does not proceed sufficiently, which is not preferable. On the other hand, when the reaction temperature is higher than 80 ° C., calcium fluoride collapses during synthesis. Is not preferable because calcium fluoride having an average particle size (15 to 300 ⁇ m) suitable as a raw material for producing hydrofluoric acid cannot be obtained. If the reaction time is less than 3 hours, the reaction may not be completed.
  • the “average particle diameter” means a particle diameter at an integrated value of 50% (median diameter) in a particle size distribution obtained by a laser diffraction / scattering method. A detailed method for measuring the average particle diameter will be described in Example 1 described later.
  • Calcium is introduced into the calcium fluoride synthesis tank 10 through the screw feeder 42 while adjusting the supply amount.
  • the method for introducing calcium carbonate is not limited to the above method, and is appropriately set.
  • the calcium carbonate introduction device 40 in addition to the method of directly adding granular calcium carbonate, a separate adjustment tank is provided, the calcium carbonate slurry solution is adjusted, and the calcium carbonate slurry solution is charged into the calcium fluoride synthesis tank 10.
  • the direct injection method of granular calcium carbonate is more preferable.
  • the average particle size of calcium carbonate is preferably 15 ⁇ m or more and 300 ⁇ m or less. Furthermore, it is particularly preferably 30 ⁇ m or more and 150 ⁇ m or less. The reason for this is that if it is larger than 300 ⁇ m, the conversion rate from calcium carbonate to calcium fluoride decreases, which is not efficient. Further, if the particle size of the synthesized calcium fluoride is smaller than 15 ⁇ m, it is not preferable because a problem is caused in the fluidity when a rotary kiln is used as a raw material for producing hydrogen fluoride.
  • a particle size of calcium carbonate of 30 ⁇ m or more and 150 ⁇ m or less is particularly suitable. By setting this range, it is possible to synthesize calcium fluoride having a suitable size.
  • Step [3] is different from the conventional step of growing calcium fluoride crystals by using a known crystallization technique from a hydrofluoric acid-containing solution and a calcium chloride aqueous solution (for example, Patent Document 2). It is not necessary to make the acidity of hydrochloric acid as large as possible, and the burden of processing and equipment such as mass use of chemicals such as hydrogen peroxide for neutralization and corrosion of equipment are small.
  • step [3] since a chlorine-containing compound such as calcium chloride is not used, there is no possibility that a trace amount of chlorine component derived from calcium chloride is mixed into calcium fluoride.
  • a chlorine-containing compound such as calcium chloride
  • the hydrochloric acid component is mixed into the produced hydrofluoric acid, and there is a concern that quality may deteriorate. Therefore, according to the step [3], it is possible to synthesize higher-purity calcium fluoride with less concern about impurities.
  • Step [4] is a step of separating the potassium carbonate solution from the second reaction product that has undergone step [3] and recovering the synthetic calcium fluoride obtained by the reaction of the above reaction formula (9).
  • the slurry liquid containing the synthetic calcium fluoride and the potassium carbonate component obtained in the step [3] is sent to the dehydrator 30 via the second slurry liquid discharge pipe 22 by the discharge pump 20b. And dehydrated by a solid-liquid separation operation such as a centrifuge. Further, the dehydrated synthetic calcium fluoride 50 is washed with a washing liquid such as water or ethanol, and the synthetic calcium fluoride is recovered. Note that dehydration and washing may be repeated as necessary. For example, the slurry liquid may be dehydrated to perform most of the dehydration, and then washed with a cleaning liquid such as water or ethanol, and then a dehydration operation may be performed to completely perform the dehydration process.
  • a washing liquid such as water or ethanol
  • the average particle size suitable as a raw material for producing hydrofluoric acid is 15 ⁇ m or more and 300 ⁇ m or less, High quality calcium fluoride having a purity of 95% wt or more can be obtained.
  • Step [5] is a step of reusing the potassium carbonate aqueous solution separated in step [4] as the potassium compound raw material in step [1].
  • the desorbed water (potassium carbonate aqueous solution) is sent and stored in the waste liquid storage tank 70 via the desorbed water discharge pipe 71 by the discharge pump 70a.
  • the potassium carbonate concentration of the desorbed water (potassium carbonate aqueous solution) is adjusted in the waste liquid storage tank 70 as necessary.
  • the liquid is sent by the discharge pump 70b through the circulation pipe 72 and reused as a calcium compound raw material.
  • the method for adjusting the concentration is not particularly limited, but moisture can be removed using sun drying, membrane separation, or the like.
  • step [2] the insoluble silica separated in step [2] is washed, and the washing liquid obtained by the washing is added to step [1] and / or step [3]. You may make it introduce.
  • the calcium fluoride separated in step [3] may be washed, and the cleaning liquid obtained by the washing may be introduced into step [1] and / or step [3].
  • the desorption water obtained in the process which concerns on this invention can be used efficiently, the usage-amount of the potassium compound used at this process can be reduced further, and manufacturing cost can be reduced. Reduction can be expected.
  • Calcium fluoride obtained in the present invention can be suitably used as a raw material for producing hydrofluoric acid.
  • the hydrofluoric acid or anhydrous hydrofluoric acid produced is used as a starting material for various fluorine compounds.
  • Calcium fluoride was manufactured using the calcium fluoride manufacturing apparatus 100 according to the present invention shown in FIG. As an evaluation of the calcium fluoride produced and recovered, the purity of calcium fluoride and the concentration of impurities contained in calcium fluoride were measured.
  • Example 1 As a calcium fluoride production apparatus 100 shown in FIG. 2, first, using a diaphragm type supply pump in a 2 liter PTFE reaction vessel (neutralization decomposition tank 60) having a PTFE stirrer installed therein, first, the concentration of hydrofluoric acid 0.72 kg of raw water adjusted to 10 wt% was supplied. Further, 0.4 kg of potassium carbonate was added as a potassium compound, and hydrofluoric acid was neutralized and decomposed with potassium carbonate as shown in the reaction formula (7) to generate an aqueous potassium fluoride solution and insoluble silica. The reaction conditions are shown below. In addition, pH of reaction conditions shows the value at the time of completion
  • the supernatant liquid (potassium fluoride aqueous solution) that had been subjected to sedimentation separation was collected to synthesize calcium fluoride.
  • a 2 L PFA-lined synthesis reaction vessel (calcium fluoride synthesis tank 10) around which an external jacket (silicon oil was used as a heat medium) capable of adjusting the temperature inside the reactor was used.
  • an external jacket sicon oil was used as a heat medium
  • calcium carbonate calcium carbonate having an average particle diameter of 60 ⁇ m was introduced into a receiving hopper, and a total of 0.1 kg was introduced while adjusting the supply amount with a screw feeder.
  • a PTFE stirrer was installed inside the reaction vessel to carry out the reaction while stirring.
  • reaction conditions are shown below.
  • pH of reaction conditions shows the value at the time of completion
  • the amount of calcium carbonate added was adjusted to be 0.6 equivalent of the amount required for the reaction with potassium fluoride.
  • Reaction conditions>-Reaction formula (9) Reaction temperature: 50 ° C Reaction time: 7 hours pH: 7 Calcium carbonate addition amount: 0.6 equivalent
  • the average particle size of the powder was measured using a laser diffraction particle size distribution analyzer SALD2200 manufactured by Shimadzu Corporation.
  • the particle size distribution is calculated from the data of the light intensity distribution of the diffracted / scattered light by the particles detected by the sensor.
  • the average particle size is obtained by multiplying the value of the measured particle size by the relative particle amount (difference%) and dividing by the total relative particle amount (100%).
  • the average particle diameter is the average diameter of the particles.
  • the “average particle diameter” means a particle diameter at an integrated value of 50% (median diameter) in a particle size distribution obtained by a laser diffraction / scattering method.
  • the powder sample was sufficiently ground with a mortar so that the calcium carbonate inside the crystal could be detected.
  • the standard reagents of calcium fluoride and calcium carbonate are mixed in advance at a predetermined concentration, thoroughly mixed on a mortar, and X-ray A calibration curve was prepared by performing diffraction measurement. Using the prepared calibration curve, the purity of the synthesized calcium fluoride and the concentration of calcium carbonate contained as impurities were calculated.
  • the purity of calcium fluoride was 98 wt% or more, and the average particle diameter was 55 ⁇ m.
  • the chlorine content in calcium fluoride was analyzed using a fluorescent X-ray analyzer (model number: SYSTEM 3270, manufactured by Rigaku Corporation), it was a sufficiently low value of less than 100 ppm.
  • FIG. 4 shows an X-ray diffraction pattern of the synthesized calcium fluoride. From the obtained diffraction pattern, the peak of calcium carbonate (CaCO 3 ) was not observed, and only the peak of calcium fluoride (CaF) was observed. Therefore, it turns out that the purity of the calcium fluoride manufactured in Example 1 is high.
  • FIG. 5 shows an XRD diffraction pattern of the sediment component when the sedimentation is performed by the reaction formula (7). The peak of K 2 SiF 6 is not confirmed and is only a peak that is considered to be amorphous silica. Accordingly, reaction formula (8) does not proceed and only reaction formula (7) occurs. It could be confirmed.
  • Example 1 Calcium fluoride was produced using the same calcium fluoride production apparatus and operating conditions as in Example 1 except that no potassium compound (potassium carbonate) was added. As a result, the purity of calcium fluoride was 55 wt% only by directly reacting silicofluoric acid and calcium fluoride, and calcium fluoride with sufficient purity could not be obtained.

Abstract

Provided is a method for manufacturing, from drain water containing hydrosilicofluoric acid, calcium fluoride having a particle size and high purity suitable as a material for manufacturing hydrofluoric acid. This manufacturing method comprises: a step [1] of reacting hydrosilicofluoric acid-containing water with a potassium compound and producing a first reaction product that includes insoluble silica and a potassium fluoride aqueous solution; a step [2] of separating the insoluble silica from the first reaction product; a step [3] of reacting the first reaction product, from which the insoluble silica has been separated, with calcium carbonate and producing a second reaction product that includes calcium fluoride and a potassium carbonate aqueous solution; and a step [4] of separating the potassium carbonate aqueous solution from the second reaction product.

Description

フッ化カルシウムの製造方法及び装置Method and apparatus for producing calcium fluoride
　本発明は、ケイフッ化水素酸（Ｈ2ＳｉＦ6）を含有する排水を分解して、フッ化水素酸製造用の原料として好適なフッ化カルシウムを製造する方法及び装置に関する。 The present invention relates to a method and an apparatus for producing calcium fluoride suitable as a raw material for producing hydrofluoric acid by decomposing drainage containing silicohydrofluoric acid (H 2 SiF 6 ).
　従来、半導体産業や化学産業等において排出されるケイフッ化水素酸を含有する排水からフッ化カルシウムを合成、回収して、得られたフッ化カルシウムをフッ化水素酸の製造用原料として利用するリサイクル技術が知られている。 Conventionally, calcium fluoride is synthesized and recovered from wastewater containing hydrofluoric acid discharged in the semiconductor industry, chemical industry, etc., and recycled using the obtained calcium fluoride as a raw material for the production of hydrofluoric acid Technology is known.
　この種のリサイクル技術を利用してフッ化カルシウムを回収し、下記の反応式（１）に示すように、フッ化カルシウムと硫酸を反応させて、フッ化水素酸の製造が一般的に行われている。
Figure JPOXMLDOC01-appb-C000001
 In general, hydrofluoric acid is produced by collecting calcium fluoride using this kind of recycling technology and reacting calcium fluoride and sulfuric acid as shown in the following reaction formula (1). ing.
Figure JPOXMLDOC01-appb-C000001
　上記の反応式（１）のような反応を用いてフッ化水素酸を製造する場合、例えば、２００℃以上の反応温度で、ローターリーキルン内にて行われる。この時、原料となるフッ化カルシウム中に水酸化カルシウムや炭酸カルシウムが存在した場合、下記の反応式（２）および反応式（３）に示すように、水を副生する反応が生じてしまう。
Figure JPOXMLDOC01-appb-C000002
Figure JPOXMLDOC01-appb-C000003
 　また、ＳｉＯ2を含むフッ化カルシウムを使用した場合、下記の反応式（４）に示すように、キルン内で生成したフッ化水素酸との反応により、Ｈ2ＳｉＦ6を形成し、合成するフッ化水素酸をロスするばかりか、水を副生してしまう。
Figure JPOXMLDOC01-appb-C000004
 　上記の反応式（２）～（４）のように水が副生した場合、キルン内はフッ酸環境下であるため、キルン装置に通常用いられている鉄系金属材料を腐食させてしまう。このことにより、フッ酸製造装置の装置寿命が短くなってしまうため、できるだけフッ化カルシウムは純度の高いものが好ましい。 When manufacturing hydrofluoric acid using reaction like said Reaction formula (1), it is performed in a rotary kiln with the reaction temperature of 200 degreeC or more, for example. At this time, when calcium hydroxide or calcium carbonate is present in the calcium fluoride used as a raw material, as shown in the following reaction formula (2) and reaction formula (3), a reaction that produces water as a by-product occurs. .
Figure JPOXMLDOC01-appb-C000002
Figure JPOXMLDOC01-appb-C000003
 When calcium fluoride containing SiO 2 is used, as shown in the following reaction formula (4), H 2 SiF 6 is formed and synthesized by reaction with hydrofluoric acid generated in the kiln. It not only loses hydrofluoric acid but also produces water as a by-product.
Figure JPOXMLDOC01-appb-C000004
 When water is by-produced as in the above reaction formulas (2) to (4), since the inside of the kiln is in a hydrofluoric acid environment, the iron-based metal material usually used in the kiln apparatus is corroded. This shortens the device life of the hydrofluoric acid production apparatus, so that calcium fluoride having a purity as high as possible is preferable.
　また、ロータリーキルンでフッ化水素酸を製造する際、原料として使用するフッ化カルシウムは、キルン内で流動可能な大きさにする必要がある。原料のフッ化カルシウムとしては、一般的に天然に存在するアシッドグレードの蛍石（フッ化カルシウム主成分）が用いられ、この天然の蛍石を、キルン内で流動可能なように、例えば、１５～３００μｍ程度の平均粒径まで粉砕し、使用される。したがって、リサイクル技術によってフッ化カルシウムを回収する場合には、１５～３００μｍ程度の平均粒径のものが得られると好ましい。 Also, when hydrofluoric acid is produced in a rotary kiln, the calcium fluoride used as a raw material must be sized to flow in the kiln. As the raw material calcium fluoride, acid grade fluorite (mainly calcium fluoride) that is naturally present is generally used, and the natural fluorite can be flowed in a kiln, for example, 15 It is used after being pulverized to an average particle size of about 300 μm. Therefore, when recovering calcium fluoride by a recycling technique, it is preferable to obtain an average particle size of about 15 to 300 μm.
　このような背景のもと、ケイフッ化水素酸などのフッ素含有排水のリサイクル技術を利用して、フッ化カルシウムを回収し、この回収したフッ化カルシウムを用いて、フッ化水素酸の製造を行うには、フッ化カルシウムの粒子径を適度に揃えること、および、不純物を含まない高い純度をもつフッ化カルシウムを用いることが重要な要素となる。 Against this backdrop, calcium fluoride is recovered using fluorine-containing wastewater recycling technology such as silicofluoric acid, and hydrofluoric acid is produced using the recovered calcium fluoride. For this, it is important to make the particle size of calcium fluoride moderately and to use calcium fluoride having high purity not containing impurities.
　ケイフッ化水素酸を含有する排水からフッ化カルシウムを回収する技術として、主に、１）ケイフッ化水素酸含有水と炭酸カルシウムとを直接反応させフッ化カルシウムを合成する方法、２）ケイフッ化水素酸含有水に含まれるフッ素を、フッ化物塩を経由させることによってフッ化カルシウムを合成する方法、などが知られている。 As a technique for recovering calcium fluoride from wastewater containing silicofluoric acid, mainly, 1) a method of directly synthesizing hydrofluoric acid-containing water and calcium carbonate to synthesize calcium fluoride, and 2) hydrogen silicofluoride A method of synthesizing calcium fluoride by passing fluorine contained in acid-containing water through a fluoride salt is known.
　例えば、特許文献１には、下記の反応式（５）のように、ケイフッ化水素酸水と炭酸カルシウムを直接反応させる際に、ケイフッ化水素酸水の濃度と反応中のｐＨをコントロールすることによって、フッ化カルシウムを直接合成する技術が開示されている。
Figure JPOXMLDOC01-appb-C000005
 For example, in Patent Document 1, when the silicohydrofluoric acid water and calcium carbonate are directly reacted, the concentration of silicohydrofluoric acid water and the pH during the reaction are controlled as shown in the following reaction formula (5). Discloses a technique for directly synthesizing calcium fluoride.
Figure JPOXMLDOC01-appb-C000005
　また、特許文献２には、下記の反応式（６）のように、ケイフッ化水素酸を含むフッ素含有排水と炭酸ナトリウムなどのナトリウム化合物を混合して、ケイフッ化水素酸を分解し、不溶性のシリカとフッ化ナトリウムの水溶液との混合物を生じさせ、次いで、得られたフッ化ナトリウムの水溶液から、晶析技術などによって、フッ化カルシウムを回収する技術が開示されている。
Figure JPOXMLDOC01-appb-C000006
 Further, in Patent Document 2, as shown in the following reaction formula (6), a fluorine-containing wastewater containing hydrofluoric acid and a sodium compound such as sodium carbonate are mixed to decompose hydrofluoric acid, thereby insoluble. A technique is disclosed in which a mixture of silica and an aqueous solution of sodium fluoride is formed, and then calcium fluoride is recovered from the obtained aqueous solution of sodium fluoride by a crystallization technique or the like.
Figure JPOXMLDOC01-appb-C000006
米国特許第２７８０５２３号明細書U.S. Pat. No. 2,780,523 特開２００９－１９６８５８号公報JP 2009-196858 A
　特許文献１のような、ケイフッ化水素酸水と炭酸カルシウムを直接反応させ、フッ化カルシウムを直接合成する方法では、反応式（５）に示すように、フッ化カルシウムとシリカが同時に析出し混合してしまい、現実的に、高い純度のフッ化カルシウムを回収することが難しい。 In the method of directly synthesizing calcium fluoride by directly reacting silicohydrofluoric acid water and calcium carbonate as in Patent Document 1, as shown in the reaction formula (5), calcium fluoride and silica are simultaneously precipitated and mixed. In reality, it is difficult to recover high-purity calcium fluoride.
　特許文献２に記載のような、フッ化ナトリウムなどのフッ化物塩を経由する方法は、上記の反応式（５）のようにフッ化カルシウムとシリカが同時に析出することがなく、高い純度のフッ化カルシウムを合成、回収する優れた方法である。しかしながら、特許文献２に記載の方法では、フッ化ナトリウムは水に対する溶解度が低いため、十分な量のフッ化ナトリウム水溶液を形成させるためには、反応系を大きくする必要がある。その結果、回収装置等が大型で煩雑なものになりやすく、装置の製作や維持などのランニングコストが高くなる問題点があった。 The method via a fluoride salt such as sodium fluoride as described in Patent Document 2 does not cause calcium fluoride and silica to precipitate simultaneously as in the above reaction formula (5). It is an excellent method for synthesizing and recovering calcium fluoride. However, in the method described in Patent Document 2, since sodium fluoride has low solubility in water, it is necessary to enlarge the reaction system in order to form a sufficient amount of aqueous sodium fluoride solution. As a result, there has been a problem that the recovery device and the like are likely to be large and complicated, and the running cost for manufacturing and maintaining the device becomes high.
　このように、ケイフッ化水素酸などのフッ素含有排水からフッ化カルシウムを回収し再利用する種々の技術について開示されているが、回収したフッ化カルシウムの粒径、純度、回収装置のコストなどの問題点があり、回収物の再利用技術が未だ確立されていないのが現状である。 As described above, various techniques for recovering and reusing calcium fluoride from fluorine-containing wastewater such as silicohydrofluoric acid have been disclosed. However, the recovered particle size, purity, cost of the recovery device, etc. There is a problem, and the recycling technology of the collected material has not been established yet.
　本発明は、上記の問題点に鑑みてなされたものであり、ケイフッ化水素酸を含有する排水からフッ化水素酸製造用の原料として好適なフッ化カルシウムを製造する簡便な方法を提供することを目的とする。 The present invention has been made in view of the above problems, and provides a simple method for producing calcium fluoride suitable as a raw material for producing hydrofluoric acid from wastewater containing hydrofluoric acid. With the goal.
　本発明者らは、上記問題点を解決するために、鋭意検討した結果、ケイフッ化水素酸水のフッ素をフッ化カルシウムに変換する際に経由させるフッ化物塩の水に対する溶解度に着目し、水に対する溶解度の大きいカリウム化合物をケイフッ化水素酸水と反応させることによって、フッ化水素酸製造用の原料として好適な高い純度と粒径のフッ化カルシウムを製造できることを見出し、本発明に至った。 As a result of intensive studies to solve the above problems, the present inventors have paid attention to the solubility in water of a fluoride salt that is passed through when the fluorine of silicofluoric acid water is converted to calcium fluoride. It has been found that high purity and particle size calcium fluoride suitable as a raw material for the production of hydrofluoric acid can be produced by reacting a potassium compound having a high solubility with respect to silicic hydrofluoric acid water.
　すなわち、本発明は、ケイフッ化水素酸含有水を用いたフッ化カルシウムの製造方法であって、ケイフッ化水素酸含有水とカリウム化合物を反応させ、不溶性シリカとフッ化カリウム水溶液を含む第１反応生成物を生成させる工程［１］と、前記第１反応生成物から不溶性シリカを分離する工程［２］と、不溶性シリカを分離した第１反応生成物と炭酸カルシウムを反応させ、フッ化カルシウムと炭酸カリウム水溶液を含む第２反応生成物を生成させる工程［３］と、前記第２反応生成物から炭酸カリウム水溶液を分離する工程［４］を含むフッ化カルシウムの製造方法である。 That is, the present invention is a method for producing calcium fluoride using silicohydrofluoric acid-containing water, wherein the first reaction includes insoluble silica and an aqueous potassium fluoride solution by reacting silicohydrofluoric acid-containing water with a potassium compound. A step [1] of generating a product, a step [2] of separating insoluble silica from the first reaction product, a reaction of the first reaction product from which the insoluble silica has been separated with calcium carbonate, and calcium fluoride, A method for producing calcium fluoride comprising a step [3] of generating a second reaction product containing an aqueous potassium carbonate solution and a step [4] of separating the aqueous potassium carbonate solution from the second reaction product.
　本発明によれば、ケイフッ化水素酸水のフッ素をフッ化カルシウムに変換する際に経由させるフッ化物塩は、水に対する十分な溶解度を有している。そのため、フッ化カルシウムの製造工程において、装置を大型化することなく、より簡便な装置構成にて、フッ化水素酸製造用の原料として好適な高い純度と粒径のフッ化カルシウムを提供することが可能となる。 According to the present invention, the fluoride salt through which the fluorosilicic acid water fluorine is converted to calcium fluoride has sufficient solubility in water. Therefore, to provide calcium fluoride having a high purity and particle size suitable as a raw material for producing hydrofluoric acid with a simpler apparatus configuration without increasing the size of the apparatus in the calcium fluoride production process. Is possible.
　また、本発明において、前記工程［４］にて分離した炭酸カリウム水溶液を、前記工程［１］のカリウム化合物原料として再利用する工程［５］を含むようにしてもよい。本構成によれば、分離した炭酸カリウム水溶液を、カリウム化合物原料として、再利用することができるため、本工程にて使用するカリウム化合物の使用量を低減させることができ製造コスト低減のメリットが得られる。 Further, in the present invention, a step [5] of reusing the potassium carbonate aqueous solution separated in the step [4] as a potassium compound raw material in the step [1] may be included. According to this configuration, since the separated potassium carbonate aqueous solution can be reused as a potassium compound raw material, the amount of potassium compound used in this step can be reduced, and the merit of manufacturing cost reduction can be obtained. It is done.
本発明に係るフッ化カルシウムの製造方法の工程概略図である。It is process schematic of the manufacturing method of the calcium fluoride which concerns on this invention. 本発明に係るフッ化カルシウムの製造装置の一例を示す概略図である。It is the schematic which shows an example of the manufacturing apparatus of the calcium fluoride which concerns on this invention. 本発明に係るフッ化カルシウム合成槽近傍の詳細図である。It is detail drawing of the calcium fluoride synthesis tank vicinity which concerns on this invention. 実施例１にて得られたフッ化カルシウムのＸ線回折パターンである。2 is an X-ray diffraction pattern of calcium fluoride obtained in Example 1. FIG. 実施例１にて得られた沈降成分のＸ線回折パターンである。2 is an X-ray diffraction pattern of a sedimentation component obtained in Example 1. FIG.
　以下、図面を参照して、本発明の実施形態について説明する。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
　まず、図２、３を参照して、本発明の実施の形態に適用可能なフッ化カルシウムの製造装置１００の一例について説明する。 First, an example of a calcium fluoride production apparatus 100 that can be applied to the embodiment of the present invention will be described with reference to FIGS.
　本発明のフッ化カルシウムの製造装置１００は、ケイフッ化水素酸含有水とカリウム化合物を反応させ、中和分解によって不溶性シリカとフッ化カリウム水溶液を含む第１反応生成物を生成させる中和分解槽６０と、不溶性シリカを分離した第１反応生成物と炭酸カルシウムを反応させ、フッ化カルシウムと炭酸カリウム水溶液を含む第２反応生成物を生成させるフッ化カルシウム合成槽１０と、合成したフッ化カルシウムを含むスラリー液を固液分離操作によって脱水する脱水装置３０と、を備える。 The apparatus 100 for producing calcium fluoride according to the present invention reacts hydrofluoric acid-containing water with a potassium compound to produce a first reaction product containing insoluble silica and an aqueous potassium fluoride solution by neutralization and decomposition. 60, a calcium fluoride synthesis tank 10 for reacting calcium carbonate with a first reaction product from which insoluble silica has been separated to produce a second reaction product containing calcium fluoride and an aqueous potassium carbonate solution, and synthesized calcium fluoride And a dehydrating device 30 for dehydrating the slurry liquid containing the solid liquid separation operation.
　中和分解槽６０には、供給ポンプ６０ａを介して、ケイフッ化水素酸含有水を含む排水を中和分解槽６０に導入する原水供給配管６１と、中和分解反応を進行させるカリウム化合物等のアルカリ剤を供給するアルカリ剤供給部６２と、反応液の上澄み液としてのシリカ分離水（不溶性シリカを分離した第１反応生成物）を排出するシリカ分離水排出配管６３が排出ポンプ６０ｂを介して接続されている。さらに、中和分解槽６０の底部には、沈殿した不溶性シリカスラリーを排出する第１スラリー排出配管６４が排出ポンプ６７ａを介して接続されている。なお、中和分解槽６０内には、モーター６５を介して攪拌機６６と、中和分解槽６０内の反応溶液のｐＨを測定するｐＨ測定器（図示せず）を設置するようにしてもよい。また、必要に応じて、中和分解槽６０内に希釈水を供給する希釈水供給部（図示せず）を設けてもよい。希釈水供給部の好適な一例として、アルカリ剤の溶解、中和反応の促進のために、希釈水の代わりに水蒸気を用いて熱源を確保するようにしてもよい。 The neutralization / decomposition tank 60 includes a raw water supply pipe 61 for introducing wastewater containing hydrofluoric acid-containing water into the neutralization / decomposition tank 60 via a supply pump 60a, and a potassium compound that promotes the neutralization / decomposition reaction. An alkali agent supply unit 62 for supplying an alkali agent and a silica separation water discharge pipe 63 for discharging silica separation water (first reaction product from which insoluble silica has been separated) as a supernatant of the reaction solution are provided via a discharge pump 60b. It is connected. Further, a first slurry discharge pipe 64 for discharging the precipitated insoluble silica slurry is connected to the bottom of the neutralization decomposition tank 60 via a discharge pump 67a. In addition, in the neutralization decomposition tank 60, you may make it install the stirrer 66 and the pH measuring device (not shown) which measures the pH of the reaction solution in the neutralization decomposition tank 60 via the motor 65. . Moreover, you may provide the dilution water supply part (not shown) which supplies dilution water in the neutralization decomposition tank 60 as needed. As a preferred example of the dilution water supply unit, a heat source may be secured by using steam instead of dilution water in order to dissolve the alkali agent and promote the neutralization reaction.
　第１スラリー排出配管６４の下流には、排出ポンプ６７ａを介して、排出された不溶性シリカスラリーの脱水を行う脱水装置６７が接続されている。さらに、脱水装置６７には、脱水によって分離された脱離水を中和分解槽６０に戻す循環配管６８を接続するようにしてもよい。循環配管６８を経由して回収される脱離水は、カリウム化合物に由来するアルカリ成分を含むため、中和分解反応の原料液として再利用することができる。なお、分離されたシリカケーキ（含水率を低くしたシリカスラリー）は別途回収される。また、同様に、循環配管６９を経由して回収される脱離水を廃液貯留槽７０に接続して、脱離水を原料液として再利用するようにしてもよい。 A dehydrator 67 for dehydrating the discharged insoluble silica slurry is connected to the downstream of the first slurry discharge pipe 64 via a discharge pump 67a. Furthermore, a circulation pipe 68 for returning the desorbed water separated by the dehydration to the neutralization decomposition tank 60 may be connected to the dehydrator 67. Since the desorbed water recovered via the circulation pipe 68 contains an alkali component derived from a potassium compound, it can be reused as a raw material liquid for the neutralization decomposition reaction. The separated silica cake (silica slurry having a low water content) is separately collected. Similarly, the desorbed water recovered via the circulation pipe 69 may be connected to the waste liquid storage tank 70 so that the desorbed water is reused as a raw material liquid.
　シリカ分離水排出配管６３の経路には、必要に応じて、分離しきれなかった不溶性シリカ成分を沈殿させるための凝集剤を添加する貯留槽（図示せず）を設けるようにしてもよい。使用する凝集剤としては、無機系、高分子系などの一般的に公知のものを用いることができる。例えば、硫酸アルミニウム、ポリ塩化アルミニウム、アルミン酸ナトリウム、硫酸鉄（ＩＩ）、塩素化緑バン、カゼイン酸ナトリウム、ゼラチン、アラビアゴム、デキストリン、デンプンなどを挙げることができる。 In the path of the silica separation water discharge pipe 63, a storage tank (not shown) for adding a flocculant for precipitating insoluble silica components that could not be separated may be provided as necessary. As the aggregating agent to be used, generally known ones such as an inorganic type and a polymer type can be used. For example, aluminum sulfate, polyaluminum chloride, sodium aluminate, iron (II) sulfate, chlorinated green vane, sodium caseinate, gelatin, gum arabic, dextrin, starch and the like can be mentioned.
　さらに、シリカ分離水排出配管６３の下流には、排出ポンプ６０ｂを介して、フッ化カルシウム合成槽１０が接続されており、フッ化カルシウム合成槽１０には、炭酸カルシウムをフッ化カルシウム合成槽１０に導入する炭酸カルシウム導入装置４０と、合成フッ化カルシウムと炭酸カリウム成分を含むスラリー液（第２反応生成物）を排出する第２スラリー排出配管１４が排出ポンプ２０ｂを介して接続されている。 Further, a calcium fluoride synthesis tank 10 is connected downstream of the silica separation water discharge pipe 63 via a discharge pump 60b, and calcium carbonate is added to the calcium fluoride synthesis tank 10 in the calcium fluoride synthesis tank 10. A calcium carbonate introduction device 40 to be introduced into the second slurry discharge pipe 14 is connected to a second slurry discharge pipe 14 for discharging a slurry liquid (second reaction product) containing synthetic calcium fluoride and a potassium carbonate component via a discharge pump 20b.
　図３に示すように、第２スラリー液排出配管２２の下流には、排出ポンプ２０ｂを介して脱水装置３０が接続されている。脱水装置３０には、必要に応じて、第２スラリー液排出管２２を介して送液されたスラリー液を洗浄するための洗浄液を供給する洗浄液供給配管３１が供給ポンプ３０ａを介して接続される。なお、洗浄液としては、水やエタノールなどの有機溶媒を使用することができ、例えば、残留塩素成分の観点から、塩素成分が１０ｍｇ／Ｌ以下の純水を用いるとよい。 As shown in FIG. 3, a dehydrator 30 is connected downstream of the second slurry liquid discharge pipe 22 via a discharge pump 20b. A cleaning liquid supply pipe 31 for supplying a cleaning liquid for cleaning the slurry liquid sent via the second slurry liquid discharge pipe 22 is connected to the dehydrator 30 via a supply pump 30a as necessary. . As the cleaning liquid, an organic solvent such as water or ethanol can be used. For example, pure water having a chlorine component of 10 mg / L or less may be used from the viewpoint of the residual chlorine component.
　また、脱水装置３０には、フッ化カルシウムの回収配管３２が設けられ、この配管３２によって、脱水、洗浄後の合成フッ化カルシウム５０が回収される。脱水装置３０としては、通常、遠心分離機をすればよいが、その他の方式として、例えば、フィルタプレス脱水装置、ろ過式脱水装置（不織布フィルター型）を使用してもよい。 In addition, the dehydrating device 30 is provided with a calcium fluoride recovery pipe 32, and the synthetic calcium fluoride 50 after dehydration and washing is recovered by the pipe 32. As the dehydrator 30, a centrifugal separator is usually used, but as other methods, for example, a filter press dehydrator or a filtration dehydrator (nonwoven fabric filter type) may be used.
　フッ化カルシウム合成槽１０の外周には、熱媒等を流通可能な外部ジャケット１２が周設されており、フッ化カリウム水溶液と炭酸カルシウムの反応を促進させるために内部の温度が調整される。外部ジャケット１２の方式は、特に限定されないが、例えば、ペルチェ素子などを利用した電気的ヒータを使用してもよい。また、フッ化カルシウム合成槽１０内には、モーター１５を介して攪拌機１３を設置して内部を攪拌するようにしてもよい。外部ジャケットを使用しない場合は、熱源として加熱水蒸気を直接、フッ化カルシウム合成槽１０の内部に投入するようにしてもよい。 An outer jacket 12 through which a heat medium or the like can be circulated is provided around the outer periphery of the calcium fluoride synthesis tank 10, and the internal temperature is adjusted to promote the reaction between the aqueous potassium fluoride solution and calcium carbonate. The method of the outer jacket 12 is not particularly limited, but for example, an electric heater using a Peltier element or the like may be used. In addition, a stirrer 13 may be installed in the calcium fluoride synthesis tank 10 via a motor 15 to stir the inside. When an external jacket is not used, heated steam as a heat source may be directly fed into the calcium fluoride synthesis tank 10.
　フッ化カルシウム合成槽１０の材質は特に限定されないが、長期耐久性から、例えば、ＰＦＡ、ＰＴＦＥなどのフッ素樹脂やＦＲＰなどの樹脂あるいはゴム製のライニング槽を使用するとよい。 The material of the calcium fluoride synthesis tank 10 is not particularly limited, but for long-term durability, for example, a fluororesin such as PFA or PTFE, a resin such as FRP, or a rubber lining tank may be used.
　炭酸カルシウム導入装置４０は、粒状の炭酸カルシウムの受入ポッパー４１と、炭酸カルシウムを供給するためのスクリューフィーダ４２と、を備えており、スクリューフィーダ４２によって炭酸カルシウムの供給量（供給速度）が調整される。なお、炭酸カルシウムの供給速度は、反応状況により適宜調整される。 The calcium carbonate introducing device 40 includes a granular calcium carbonate receiving popper 41 and a screw feeder 42 for supplying calcium carbonate, and the supply amount (supply speed) of calcium carbonate is adjusted by the screw feeder 42. The The supply rate of calcium carbonate is appropriately adjusted depending on the reaction situation.
　脱水装置３０には、排出ポンプ７０ａを介して、脱水装置３０の固液分離操作によって得られた脱離水（炭酸カリウム水溶液）を排出するための脱離水排出配管７１が接続されており、脱離水排出配管７１の下流には、脱離水を貯留する廃液貯留槽７０が設けられている。さらに、廃液貯留槽７０には、貯留した脱離水を中和分解槽６０に戻すための循環配管７２が接続されており、炭酸カリウムの濃度が調整された脱離水をアルカリ成分の原料として、中和分解槽６０に再利用することができる。廃液貯留槽７０にて、貯留された脱離水の炭酸カリウム濃度を調整する（例えば、濃縮するなど）には、天日干し、膜分離による方法を用いることができる。 A desorption water discharge pipe 71 for discharging desorption water (potassium carbonate aqueous solution) obtained by solid-liquid separation operation of the dehydration apparatus 30 is connected to the dehydration apparatus 30 via a discharge pump 70a. A waste liquid storage tank 70 for storing desorbed water is provided downstream of the discharge pipe 71. Further, the waste liquid storage tank 70 is connected to a circulation pipe 72 for returning the stored desorbed water to the neutralization decomposition tank 60, and the desorbed water whose potassium carbonate concentration is adjusted is used as a raw material for the alkaline component. It can be reused in the sum decomposition tank 60. In order to adjust (for example, concentrate) the potassium carbonate concentration of the stored desorbed water in the waste liquid storage tank 70, a method using sun drying and membrane separation can be used.
　次に、フッ化カルシウムの製造方法（工程［１］～［５］）について説明する。図１は、本発明に係るフッ化カルシウムの製造方法の工程概略図である。 Next, a method for producing calcium fluoride (steps [1] to [5]) will be described. FIG. 1 is a process schematic diagram of a method for producing calcium fluoride according to the present invention.
　まず、本発明の工程［１］について説明する。工程［１］は、ケイフッ化水素酸含有水とカリウム化合物を反応させ、不溶性シリカとフッ化カリウム水溶液を含む第１反応生成物を生成させる工程［１］である。 First, step [1] of the present invention will be described. Step [1] is a step [1] in which silicohydrofluoric acid-containing water and a potassium compound are reacted to generate a first reaction product containing insoluble silica and an aqueous potassium fluoride solution.
　具体的には、図２に示すように、ケイフッ化水素酸を含有した排水などを貯留したタンクから、ケイフッ化水素酸含有水が、原水供給配管６１を介して中和分解槽６０に供給される。次いで、アルカリ剤供給部６２から、炭酸カリウムなどのカリウム化合物を添加し、下記の反応式（７）に示すように、ケイフッ化水素酸を中和分解し、不溶性シリカとフッ化カリウム水溶液を含む第１反応生成物を生成させる。 Specifically, as shown in FIG. 2, hydrofluoric acid-containing water is supplied to the neutralization / decomposition tank 60 through the raw water supply pipe 61 from a tank that stores wastewater containing hydrofluoric acid. The Next, a potassium compound such as potassium carbonate is added from the alkali agent supply unit 62, and as shown in the following reaction formula (7), hydrofluoric acid is neutralized and decomposed to contain insoluble silica and an aqueous potassium fluoride solution. A first reaction product is produced.
　反応式（７）の反応条件は、ｐＨが７～１４、反応温度は、４０～１００℃、より好ましくは、５０～８０℃、反応時間は、少なくとも１時間以上、の範囲で行うことが好ましい。また、投入するカリウム化合物の量は、ケイフッ化水素酸との反応に必要な量の１．１～１０当量に調整することが好ましい。なお、反応を行う際の圧力は特に制限はなく、常圧にて行うとよい。 The reaction conditions of the reaction formula (7) are preferably such that the pH is 7 to 14, the reaction temperature is 40 to 100 ° C., more preferably 50 to 80 ° C., and the reaction time is at least 1 hour or more. . The amount of the potassium compound to be added is preferably adjusted to 1.1 to 10 equivalents of the amount required for the reaction with silicohydrofluoric acid. In addition, the pressure at the time of performing reaction does not have a restriction | limiting in particular, It is good to carry out at a normal pressure.
　ｐＨが７より小さい場合は、反応式（７）が進行しにくく、反応式（８）に示すようなカリウム酸塩（Ｋ2ＳｉＦ6）が生成する反応が進行してしまうため好ましくない。反応温度が４０℃より低い場合は、下記の反応式（７）の十分な反応が進行せず、反応式（８）が進行してしまうため好ましくなく、一方、１００℃より高い場合は、水分の揮発量が大きくなる、あるいは沸騰をまねく恐れがあるため反応温度としては適さない。反応時間は、１時間より少なくなると、反応が完了しない場合があるので好ましくない。
Figure JPOXMLDOC01-appb-C000007
Figure JPOXMLDOC01-appb-C000008
 When the pH is smaller than 7, reaction formula (7) does not proceed easily, and the reaction for producing potassium salt (K 2 SiF 6 ) as shown in reaction formula (8) proceeds, which is not preferable. When the reaction temperature is lower than 40 ° C., a sufficient reaction of the following reaction formula (7) does not proceed and the reaction formula (8) proceeds, which is not preferable. As the volatilization amount of the liquid increases or it may cause boiling, it is not suitable as the reaction temperature. If the reaction time is less than 1 hour, the reaction may not be completed.
Figure JPOXMLDOC01-appb-C000007
Figure JPOXMLDOC01-appb-C000008
　カリウム化合物は、カリウムイオンの水和エネルギーが高いため水に対する溶解性が非常に高く、例えば、フッ化カリウム（ＫＦ）の溶解度は、常温で約９２０ｇ／１０００ｇ－Ｈ2Ｏである。本発明の工程にて経由するフッ化物塩（フッ化カリウム）は、特開２００９－１９６８５８（特許文献２）にて開示されるフッ化物塩である、フッ化ナトリウム（溶解度：４０ｇ／１０００ｇ－Ｈ2Ｏ）に比べて溶解度が極めて大きい。そのため、フッ化カリウムの場合、溶解度の低さに起因するフッ化ナトリウムのような結晶析出（沈降）が起こりにくく、より少量の水で、より多くのフッ素源を水溶液中に存在させることができ、反応系を大型化する必要がない。また、特許文献２のような析出したフッ化ナトリウム結晶を溶解するための希釈水配管などを別途設置する必要がなく、製造設備を簡便化することができる。さらに、本発明によれば、フッ化物塩の濃度を高くできるため、より純度の高いフッ化カルシウムを合成することが可能となる。 A potassium compound has a very high solubility in water due to the high hydration energy of potassium ions. For example, the solubility of potassium fluoride (KF) is about 920 g / 1000 g-H 2 O at room temperature. The fluoride salt (potassium fluoride) passed through in the process of the present invention is sodium fluoride (solubility: 40 g / 1000 g-H), which is a fluoride salt disclosed in JP2009-196858 (Patent Document 2). The solubility is much higher than 2 O). Therefore, in the case of potassium fluoride, crystal precipitation (precipitation) unlike sodium fluoride due to low solubility is unlikely to occur, and more fluorine source can be present in the aqueous solution with a smaller amount of water. It is not necessary to enlarge the reaction system. Further, it is not necessary to separately install a dilution water pipe for dissolving the precipitated sodium fluoride crystal as in Patent Document 2, and the manufacturing equipment can be simplified. Furthermore, according to the present invention, since the concentration of the fluoride salt can be increased, calcium fluoride with higher purity can be synthesized.
　カリウム化合物としては、水に対する溶解度が十分なものであれば特に制限されないが、例えば、炭酸カリウム、炭酸水素カリウム、酸化カリウム、水酸化カリウムなどの一般的なものを使用することができる。これらの化合物は少なくとも１種もしくはこれらの２種以上の混合物として使用することも可能である。中でも、炭酸カリウムは、化学的安定性、入手し易さなどの観点から、特に好適である。 The potassium compound is not particularly limited as long as it has sufficient solubility in water. For example, common compounds such as potassium carbonate, potassium hydrogen carbonate, potassium oxide, and potassium hydroxide can be used. These compounds can be used as at least one kind or a mixture of two or more kinds thereof. Among these, potassium carbonate is particularly suitable from the viewpoints of chemical stability and availability.
　次に、本発明における工程［２］について説明する。工程［２］は、工程［１］で得られた第１反応生成物から、不溶性シリカを分離する工程であり、第１反応生成物から、フッ化カリウム含有液を、沈降分離操作によって上澄み液として分離する。分離された上澄み液は、シリカ分離水排出配管６３から排出され、排出ポンプ６０ｂを介して、フッ化カルシウム合成槽１０に送液される。なお、沈降分離操作の方法は、特に限定はされないが、例えば、第１反応生成物を所定時間静止させる操作（デカンテーションなど）によって行うことができる。 Next, step [2] in the present invention will be described. Step [2] is a step of separating insoluble silica from the first reaction product obtained in step [1]. A potassium fluoride-containing liquid is separated from the first reaction product by a sedimentation operation. As separate. The separated supernatant liquid is discharged from the silica separated water discharge pipe 63 and is sent to the calcium fluoride synthesis tank 10 via the discharge pump 60b. The method for the sedimentation operation is not particularly limited, and can be performed, for example, by an operation (such as decantation) of allowing the first reaction product to stand still for a predetermined time.
　次に、本発明における工程［３］について説明する。工程［３］は、工程［２］で得られた不溶性シリカを分離した第１反応生成物（フッ化カリウム含有液）と、炭酸カルシウムを反応させ、フッ化カルシウムと炭酸カリウム水溶液を含む第２反応生成物を生成させる工程である。フッ化カルシウムの合成は、下記の反応式（９）のように反応が進行する。
Figure JPOXMLDOC01-appb-C000009
 Next, process [3] in this invention is demonstrated. In the step [3], the first reaction product (potassium fluoride-containing liquid) obtained by separating the insoluble silica obtained in the step [2] is reacted with calcium carbonate, so that the second containing the calcium fluoride and the potassium carbonate aqueous solution. This is a step of generating a reaction product. In the synthesis of calcium fluoride, the reaction proceeds as shown in the following reaction formula (9).
Figure JPOXMLDOC01-appb-C000009
　反応式（９）の反応条件は、反応温度は、４０～８０℃、より好ましくは５０～７０℃、反応時間は、少なくとも３時間以上、の範囲で行うことが好ましい。また、フッ化カリウムは、投入する炭酸カルシウムとの反応に必要な量の１．１～１０当量になるように調整することが好ましい。なお、反応を行う際の圧力は特に制限はなく、常圧にて行うとよい。また、反応条件におけるｐＨは、特に制限はないが、中和処理剤などの処理上の負担が掛からない範囲（例えば、ｐＨが７～１０程度）で適宜設定するとよい。 The reaction conditions of the reaction formula (9) are preferably carried out in the range of a reaction temperature of 40 to 80 ° C., more preferably 50 to 70 ° C., and a reaction time of at least 3 hours or more. The potassium fluoride is preferably adjusted to 1.1 to 10 equivalents of the amount required for the reaction with the calcium carbonate to be added. In addition, the pressure at the time of performing reaction does not have a restriction | limiting in particular, It is good to carry out at a normal pressure. Further, the pH under the reaction conditions is not particularly limited, but may be appropriately set within a range where a processing burden such as a neutralizing agent is not applied (for example, pH is about 7 to 10).
　反応温度が４０℃より低い場合は、上記の反応式（９）の十分な反応が進行しないため、好ましくなく、一方、８０℃より高い場合は、合成する際にフッ化カルシウムが崩れてしまい微粒子状のフッ化カルシウムが生成してしまうため、フッ化水素酸製造用の原料として好適な平均粒径（１５～３００μｍ）のフッ化カルシウムが得られなくなるため好ましくない。反応時間は、３時間より少なくなると、反応が完了しない場合があるので好ましくない。 When the reaction temperature is lower than 40 ° C., the reaction of the above reaction formula (9) does not proceed sufficiently, which is not preferable. On the other hand, when the reaction temperature is higher than 80 ° C., calcium fluoride collapses during synthesis. Is not preferable because calcium fluoride having an average particle size (15 to 300 μm) suitable as a raw material for producing hydrofluoric acid cannot be obtained. If the reaction time is less than 3 hours, the reaction may not be completed.
　なお、本明細書において、「平均粒径」とは、レーザー回折・散乱法によって求めた粒度分布における積算値５０％（メジアン径）での粒子径を意味する。また、平均粒径の詳細な測定方法は、後述の実施例１にて説明する。 In the present specification, the “average particle diameter” means a particle diameter at an integrated value of 50% (median diameter) in a particle size distribution obtained by a laser diffraction / scattering method. A detailed method for measuring the average particle diameter will be described in Example 1 described later.
　具体的には、図３に示すように、フッ化カルシウム合成槽１０に送液された不溶性シリカを分離した第１反応生成物（フッ化カリウム水溶液）に受入ホッパー４１に収容された粒状の炭酸カルシウムが、スクリューフィーダ４２を介して供給量を調整しながらフッ化カルシウム合成槽１０に投入される。 Specifically, as shown in FIG. 3, the granular carbonic acid contained in the receiving hopper 41 in the first reaction product (potassium fluoride aqueous solution) obtained by separating the insoluble silica sent to the calcium fluoride synthesis tank 10. Calcium is introduced into the calcium fluoride synthesis tank 10 through the screw feeder 42 while adjusting the supply amount.
　なお、本発明において、炭酸カルシウムの導入方法は上記の方法に限定されるものではなく、適宜設定されるものである。また、工程［３］は、炭酸カルシウムからフッ化カルシウムの転化反応を完全に進行させるために、十分な反応時間を確保しやすいバッチプロセスを用いるとよい。 In the present invention, the method for introducing calcium carbonate is not limited to the above method, and is appropriately set. In addition, for the step [3], it is preferable to use a batch process that easily secures a sufficient reaction time in order to cause the conversion reaction of calcium fluoride from calcium carbonate to proceed completely.
　炭酸カルシウム導入装置４０としては、粒状の炭酸カルシウムを直接投入する方式以外に、別途調整槽を設け、炭酸カルシウムのスラリー溶液を調整し、フッ化カルシウム合成槽１０に炭酸カルシウムスラリー溶液を投入する方式も採用可能であるが、本発明においては、粒状の炭酸カルシウムを直接投入方式がより好ましい。 As the calcium carbonate introduction device 40, in addition to the method of directly adding granular calcium carbonate, a separate adjustment tank is provided, the calcium carbonate slurry solution is adjusted, and the calcium carbonate slurry solution is charged into the calcium fluoride synthesis tank 10. However, in the present invention, the direct injection method of granular calcium carbonate is more preferable.
　その理由としては、炭酸カルシウムのスラリー溶液を投入する場合、別途、スラリー溶液を調整する調整槽を設けたり、フッ化カルシウム合成槽１０の容積を大きくする必要があり装置が煩雑になる。加えて、スラリー液を供給する配管の液詰まりが懸念されるため１０ｗｔ％程度のスラリー液にする必要がある。また、１０ｗｔ％程度の濃度の薄いスラリー液を用いた場合、フッ化カルシウム合成槽１０の反応溶液の濃度調整がしにくくなるためである。 The reason is that when a slurry solution of calcium carbonate is added, it is necessary to provide a separate adjustment tank for adjusting the slurry solution or to increase the volume of the calcium fluoride synthesis tank 10, which complicates the apparatus. In addition, since there is a concern about clogging of piping for supplying the slurry liquid, it is necessary to make the slurry liquid about 10 wt%. Further, when a thin slurry liquid having a concentration of about 10 wt% is used, it is difficult to adjust the concentration of the reaction solution in the calcium fluoride synthesis tank 10.
　炭酸カルシウムの平均粒子径は、１５μｍ以上、３００μｍ以下、とすることが好ましい。さらには、３０μｍ以上、１５０μｍ以下とすることが特に好ましい。その理由としては、３００μｍより大きくなると、炭酸カルシウムからフッ化カルシウムへの転化率が減少し、効率的でない。また、合成後のフッ化カルシウムの粒径が、１５μｍより小さくなると、ローターリーキルンを使用してフッ化水素製造の原料として投入した場合、流動性に問題点が生じやすいため好ましくない。ロータリーキルンによるフッ化水素製造用原料として使用するには、３０μｍ以上、１５０μｍ以下の炭酸カルシウムの粒径が特に好適である。この範囲にすることによって、好適な大きさのフッ化カルシウムを合成することができる。 The average particle size of calcium carbonate is preferably 15 μm or more and 300 μm or less. Furthermore, it is particularly preferably 30 μm or more and 150 μm or less. The reason for this is that if it is larger than 300 μm, the conversion rate from calcium carbonate to calcium fluoride decreases, which is not efficient. Further, if the particle size of the synthesized calcium fluoride is smaller than 15 μm, it is not preferable because a problem is caused in the fluidity when a rotary kiln is used as a raw material for producing hydrogen fluoride. For use as a raw material for producing hydrogen fluoride by a rotary kiln, a particle size of calcium carbonate of 30 μm or more and 150 μm or less is particularly suitable. By setting this range, it is possible to synthesize calcium fluoride having a suitable size.
　工程［３］は、従来、公知のフッ酸含有液と塩化カルシウム水溶液からの晶析技術を駆使してフッ化カルシウムの結晶を成長させる工程（例えば、特許文献２）と異なり、反応溶液を比較的大きな塩酸酸性条件化にする必要がなく、中和するための過酸化水素など薬剤の大量使用や装置の腐食などの処理上の負担や装置の負担が少ない。 Step [3] is different from the conventional step of growing calcium fluoride crystals by using a known crystallization technique from a hydrofluoric acid-containing solution and a calcium chloride aqueous solution (for example, Patent Document 2). It is not necessary to make the acidity of hydrochloric acid as large as possible, and the burden of processing and equipment such as mass use of chemicals such as hydrogen peroxide for neutralization and corrosion of equipment are small.
　また、工程［３］は、塩化カルシウムなどの塩素を含有した化合物を使用することがないため、塩化カルシウムに由来する微量の塩素成分がフッ化カルシウムに混入する恐れがない。特に、微量の塩素成分が混入したフッ化カルシウムを使用してフッ化水素酸を製造した場合、製造したフッ化水素酸中に塩酸成分が混入してしまい品質の悪化が懸念される。そのため、工程［３］によれば、不純物の懸念が少ない、より高純度なフッ化カルシウムを合成することが可能となる。 Further, in the step [3], since a chlorine-containing compound such as calcium chloride is not used, there is no possibility that a trace amount of chlorine component derived from calcium chloride is mixed into calcium fluoride. In particular, when hydrofluoric acid is produced using calcium fluoride in which a small amount of chlorine component is mixed, the hydrochloric acid component is mixed into the produced hydrofluoric acid, and there is a concern that quality may deteriorate. Therefore, according to the step [3], it is possible to synthesize higher-purity calcium fluoride with less concern about impurities.
　次に、本発明の工程［４］について説明する。工程［４］は、工程［３］を経た第２反応生成物から炭酸カリウム溶液を分離して、上記反応式（９）の反応にて得られた合成フッ化カルシウムを回収する工程である。 Next, step [4] of the present invention will be described. Step [4] is a step of separating the potassium carbonate solution from the second reaction product that has undergone step [3] and recovering the synthetic calcium fluoride obtained by the reaction of the above reaction formula (9).
　具体的には、工程［３］にて得られた合成フッ化カルシウムと炭酸カリウム成分を含むスラリー液が、排出ポンプ２０ｂによって、第２スラリー液排出配管２２を介して、脱水装置３０に送液され、遠心分離機などの固液分離操作によって脱水される。さらに、脱水された合成フッ化カルシウム５０は、水やエタノールなどの洗浄液によって洗浄されて合成フッ化カルシウムは回収される。なお、脱水と洗浄は、必要に応じて適宜繰り返し行うようにしてもよい。例えば、スラリー液を脱水して大部分の脱水を行い、次いで、水やエタノールなどの洗浄液で洗浄し、さらに、脱水操作を行い、完全に脱水処理を施すようにしてもよい。 Specifically, the slurry liquid containing the synthetic calcium fluoride and the potassium carbonate component obtained in the step [3] is sent to the dehydrator 30 via the second slurry liquid discharge pipe 22 by the discharge pump 20b. And dehydrated by a solid-liquid separation operation such as a centrifuge. Further, the dehydrated synthetic calcium fluoride 50 is washed with a washing liquid such as water or ethanol, and the synthetic calcium fluoride is recovered. Note that dehydration and washing may be repeated as necessary. For example, the slurry liquid may be dehydrated to perform most of the dehydration, and then washed with a cleaning liquid such as water or ethanol, and then a dehydration operation may be performed to completely perform the dehydration process.
　上記工程［１］～［４］にて、フッ化カルシウムの製造および回収を行うと、フッ化水素酸製造用の原料として好適な、平均粒径が、１５μｍ以上、３００μｍ以下、であって、純度が９５％ｗｔ以上の高品質なフッ化カルシウムを得ることができる。 When calcium fluoride is produced and recovered in the above steps [1] to [4], the average particle size suitable as a raw material for producing hydrofluoric acid is 15 μm or more and 300 μm or less, High quality calcium fluoride having a purity of 95% wt or more can be obtained.
　さらに、本発明の工程［５］について説明する。工程［５］は、工程［４］にて分離した炭酸カリウム水溶液を、工程［１］におけるカリウム化合物原料として再利用する工程である。 Furthermore, the process [5] of the present invention will be described. Step [5] is a step of reusing the potassium carbonate aqueous solution separated in step [4] as the potassium compound raw material in step [1].
　具体的には、脱離水（炭酸カリウム水溶液）が、排出ポンプ７０ａによって、脱離水排出配管７１を介して、廃液貯留槽７０に送液され貯留される。次いで、必要に応じて、廃液貯留槽７０にて、脱離水（炭酸カリウム水溶液）の炭酸カリウム濃度が調整される。さらに、排出ポンプ７０ｂによって、循環配管７２を介して送液され、カルシウム化合物原料として再利用される。なお、濃度を調整方法（濃縮する方法）は、特に限定されないが、天日干し、膜分離などを使用して水分を除去することができる。 Specifically, the desorbed water (potassium carbonate aqueous solution) is sent and stored in the waste liquid storage tank 70 via the desorbed water discharge pipe 71 by the discharge pump 70a. Next, the potassium carbonate concentration of the desorbed water (potassium carbonate aqueous solution) is adjusted in the waste liquid storage tank 70 as necessary. Further, the liquid is sent by the discharge pump 70b through the circulation pipe 72 and reused as a calcium compound raw material. The method for adjusting the concentration (concentration method) is not particularly limited, but moisture can be removed using sun drying, membrane separation, or the like.
　さらに、上記工程［１］～［４］に加えて、工程［２］にて分離された不溶性シリカを洗浄し、当該洗浄によって得られた洗浄液を工程［１］及び／又は工程［３］に導入するようにしてもよい。同様に、工程［３］にて分離されたフッ化カルシウムを洗浄し、当該洗浄によって得られた洗浄液を工程［１］及び／又は工程［３］に導入するようにしてもよい。 Further, in addition to the above steps [1] to [4], the insoluble silica separated in step [2] is washed, and the washing liquid obtained by the washing is added to step [1] and / or step [3]. You may make it introduce. Similarly, the calcium fluoride separated in step [3] may be washed, and the cleaning liquid obtained by the washing may be introduced into step [1] and / or step [3].
　上記の構成によれば、本発明に係る工程において得られる脱離水を効率的に使用することができるため、本工程にて使用するカリウム化合物の使用量をさらに低減させることができ、製造コストの低減が期待できる。 According to said structure, since the desorption water obtained in the process which concerns on this invention can be used efficiently, the usage-amount of the potassium compound used at this process can be reduced further, and manufacturing cost can be reduced. Reduction can be expected.
　本発明にて得られたフッ化カルシウムは、フッ化水素酸製造用の原料として好適に使用することができる。なお、製造されるフッ化水素酸または無水フッ化水素酸は、さまざまなフッ素化合物の出発原料として使用される。 Calcium fluoride obtained in the present invention can be suitably used as a raw material for producing hydrofluoric acid. The hydrofluoric acid or anhydrous hydrofluoric acid produced is used as a starting material for various fluorine compounds.
　以下、実施例によって本発明を詳細に説明するが、本発明は係る実施例に限定されるものではない。 Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the examples.
　図２に示す本発明に係るフッ化カルシウムの製造装置１００を用いてフッ化カルシウムの製造を行った。製造して回収したフッ化カルシウムの評価として、フッ化カルシウムの純度とフッ化カルシウムの含有不純物濃度の測定を行った。 Calcium fluoride was manufactured using the calcium fluoride manufacturing apparatus 100 according to the present invention shown in FIG. As an evaluation of the calcium fluoride produced and recovered, the purity of calcium fluoride and the concentration of impurities contained in calcium fluoride were measured.
　［実施例１］
　図２に示すフッ化カルシウム製造装置１００として、ＰＴＦＥ攪拌機を内部に設置した容積２ＬのＰＴＦＥ製反応容器（中和分解槽６０）にダイヤフラムタイプの供給ポンプを用いて、まず、ケイフッ化水素酸濃度１０ｗｔ％に調整した原水を０．７２ｋｇ供給した。さらに、カリウム化合物として炭酸カリウムを０．４ｋｇ投入し、反応式（７）に示すように、ケイフッ化水素酸を炭酸カリウムで中和分解して、フッ化カリウム水溶液と不溶性シリカを生成させた。以下に、反応条件について示す。なお、反応条件のｐＨは、反応終了時の値を示す。また、投入する炭酸カリウムの量は、ケイフッ化水素酸との反応に必要な量の２当量となるように調整した。
　＜反応条件＞－反応式（７）
　反応温度　：　７０℃
　反応時間　：　３時間
　ｐＨ　　　：　１０
　炭酸カリウム添加量：　２当量 [Example 1]
As a calcium fluoride production apparatus 100 shown in FIG. 2, first, using a diaphragm type supply pump in a 2 liter PTFE reaction vessel (neutralization decomposition tank 60) having a PTFE stirrer installed therein, first, the concentration of hydrofluoric acid 0.72 kg of raw water adjusted to 10 wt% was supplied. Further, 0.4 kg of potassium carbonate was added as a potassium compound, and hydrofluoric acid was neutralized and decomposed with potassium carbonate as shown in the reaction formula (7) to generate an aqueous potassium fluoride solution and insoluble silica. The reaction conditions are shown below. In addition, pH of reaction conditions shows the value at the time of completion | finish of reaction. The amount of potassium carbonate to be added was adjusted to be 2 equivalents of the amount required for the reaction with silicohydrofluoric acid.
<Reaction conditions>-Reaction formula (7)
Reaction temperature: 70 ° C
Reaction time: 3 hours pH: 10
Potassium carbonate addition amount: 2 equivalents
　次いで、沈降分離処理した上澄み液（フッ化カリウム水溶液）を採取して、フッ化カルシウムの合成を行った。反応槽として、反応器内部の温度調整が可能な外部ジャケット（熱媒体にはシリコンオイルを使用）を周設した容積２ＬのＰＦＡライニング合成反応容器（フッ化カルシウム合成槽１０）を使用した。炭酸カルシウムの導入手段（炭酸カルシウム導入装置）としては、平均粒子径６０μｍの炭酸カルシウムを受入ホッパーに導入し、スクリューフィーダにて供給量を調整しながら、合計０．１ｋｇ投入した。また、反応容器の内部には、ＰＴＦＥ攪拌機を設置して攪拌しながら反応を行った。以下に、反応条件について示す。なお、反応条件のｐＨは、反応終了時の値を示す。また、投入する炭酸カルシウムの量は、フッ化カリウムとの反応に必要な量の０．６当量となるように調整した。
　＜反応条件＞－反応式（９）
　反応温度　：　５０℃
　反応時間　：　７時間
　ｐＨ　　　：　７
　炭酸カルシウム添加量：　０．６当量 Next, the supernatant liquid (potassium fluoride aqueous solution) that had been subjected to sedimentation separation was collected to synthesize calcium fluoride. As a reaction tank, a 2 L PFA-lined synthesis reaction vessel (calcium fluoride synthesis tank 10) around which an external jacket (silicon oil was used as a heat medium) capable of adjusting the temperature inside the reactor was used. As a means for introducing calcium carbonate (calcium carbonate introducing device), calcium carbonate having an average particle diameter of 60 μm was introduced into a receiving hopper, and a total of 0.1 kg was introduced while adjusting the supply amount with a screw feeder. Further, a PTFE stirrer was installed inside the reaction vessel to carry out the reaction while stirring. The reaction conditions are shown below. In addition, pH of reaction conditions shows the value at the time of completion | finish of reaction. The amount of calcium carbonate added was adjusted to be 0.6 equivalent of the amount required for the reaction with potassium fluoride.
<Reaction conditions>-Reaction formula (9)
Reaction temperature: 50 ° C
Reaction time: 7 hours pH: 7
Calcium carbonate addition amount: 0.6 equivalent
　粒状の炭酸カルシウム投入後、７時間の反応時間を経た後、攪拌を止め、合成反応容器に接続された排出配管（第２スラリー配管１４）より反応後のスラリー液を引き抜き、遠心分離機（脱水装置３０）に送液し脱水を行い、さらに純粋で合成フッ化カルシウムを洗浄し不純物を除去した。得られたサンプルは、１００℃で乾燥処理を施し、Ｘ線回折測定および粒度分布測定を実施した。 After 7 hours of reaction time after the granular calcium carbonate was added, the stirring was stopped, the slurry liquid after the reaction was drawn out from the discharge pipe (second slurry pipe 14) connected to the synthesis reaction vessel, and the centrifuge (dehydration) The solution was sent to the apparatus 30) for dehydration, and the pure and synthetic calcium fluoride was washed to remove impurities. The obtained sample was dried at 100 ° C. and subjected to X-ray diffraction measurement and particle size distribution measurement.
　なお、粉体の平均粒径の測定は、島津製作所製レーザー回折式粒度分布測定装置ＳＡＬＤ２２００を用いて測定を実施した。レーザー回折式粒度分布測定装置では、センサで検出した粒子による回折／散乱光の光強度分布のデータから粒度分布を計算する。平均粒子径は測定される粒子径の値に相対粒子量（差分％）を掛けて、相対粒子量の合計（１００％）で割って求められる。なお、平均粒子径は粒子の平均直径である。本実施例および明細書において、「平均粒子径」とは、レーザー回折・散乱法によって求めた粒度分布における積算値５０％（メジアン径）での粒径を意味する。 The average particle size of the powder was measured using a laser diffraction particle size distribution analyzer SALD2200 manufactured by Shimadzu Corporation. In the laser diffraction type particle size distribution measuring device, the particle size distribution is calculated from the data of the light intensity distribution of the diffracted / scattered light by the particles detected by the sensor. The average particle size is obtained by multiplying the value of the measured particle size by the relative particle amount (difference%) and dividing by the total relative particle amount (100%). The average particle diameter is the average diameter of the particles. In this example and specification, the “average particle diameter” means a particle diameter at an integrated value of 50% (median diameter) in a particle size distribution obtained by a laser diffraction / scattering method.
　Ｘ線回折測定の際には、粉体サンプルを十分に乳鉢で磨り潰し、結晶内部の炭酸カルシウムについても検出できるようにした。また、合成したフッ化カルシウムの純度および不純物として含まれる炭酸カルシウムの濃度の分析については、予め、フッ化カルシウムおよび炭酸カルシウムの標準試薬を所定濃度で混合し、すり鉢上十分に混合し、Ｘ線回折測定を行うことで検量線を作成した。この作成した検量線によって、合成したフッ化カルシウムの純度および不純物として含まれる炭酸カルシウムの濃度について算出した。 In the X-ray diffraction measurement, the powder sample was sufficiently ground with a mortar so that the calcium carbonate inside the crystal could be detected. For the analysis of the purity of the synthesized calcium fluoride and the concentration of calcium carbonate contained as impurities, the standard reagents of calcium fluoride and calcium carbonate are mixed in advance at a predetermined concentration, thoroughly mixed on a mortar, and X-ray A calibration curve was prepared by performing diffraction measurement. Using the prepared calibration curve, the purity of the synthesized calcium fluoride and the concentration of calcium carbonate contained as impurities were calculated.
　以上の方法で、合成したフッ化カルシウムの純度および平均粒子径を測定したところ、フッ化カルシウムの純度は、９８ｗｔ％以上であり、平均粒子径は５５μｍであった。またフッ化カルシウム中の塩素含有量を、蛍光Ｘ線分析装置（型番：ＳＹＳＴＥＭ３２７０、株式会社リガク製）を用いて、分析したところ１００ｐｐｍ未満と十分に低い値であった。 When the purity and average particle diameter of the synthesized calcium fluoride were measured by the above method, the purity of calcium fluoride was 98 wt% or more, and the average particle diameter was 55 μm. Moreover, when the chlorine content in calcium fluoride was analyzed using a fluorescent X-ray analyzer (model number: SYSTEM 3270, manufactured by Rigaku Corporation), it was a sufficiently low value of less than 100 ppm.
　また、合成したフッ化カルシウムのＸ線回折パターンを図４に示す。得られた回折パターンより、炭酸カルシウム（ＣａＣＯ3）のピークは観測されず、フッ化カルシウム（ＣａＦ）のピークのみ観測された。したがって、実施例１にて製造したフッ化カルシウムの純度は高いことがわかる。また、反応式（７）で沈降分離した際の沈降成分のＸＲＤ回折パターンを図５に示す。Ｋ2ＳｉＦ6のピークは確認されず、非晶質なシリカと考えられるピークのみであり、これにより反応式（８）は進行しておらず、反応式（７）のみが生じていることが確認できた。 Further, FIG. 4 shows an X-ray diffraction pattern of the synthesized calcium fluoride. From the obtained diffraction pattern, the peak of calcium carbonate (CaCO 3 ) was not observed, and only the peak of calcium fluoride (CaF) was observed. Therefore, it turns out that the purity of the calcium fluoride manufactured in Example 1 is high. Further, FIG. 5 shows an XRD diffraction pattern of the sediment component when the sedimentation is performed by the reaction formula (7). The peak of K 2 SiF 6 is not confirmed and is only a peak that is considered to be amorphous silica. Accordingly, reaction formula (8) does not proceed and only reaction formula (7) occurs. It could be confirmed.
　［比較例１］
　カリウム化合物（炭酸カリウム）を加えない、とする以外は、実施例１と同様なフッ化カルシウムの製造装置および運転条件にて、フッ化カルシウムの製造を行った。その結果、ケイフッ化水素酸とフッ化カルシウムを直接反応させるだけでは、フッ化カルシウムの純度は５５ｗｔ％であり、十分な純度のフッ化カルシウムを得ることができなかった。 [Comparative Example 1]
Calcium fluoride was produced using the same calcium fluoride production apparatus and operating conditions as in Example 1 except that no potassium compound (potassium carbonate) was added. As a result, the purity of calcium fluoride was 55 wt% only by directly reacting silicofluoric acid and calcium fluoride, and calcium fluoride with sufficient purity could not be obtained.
　［比較例２］
　実施例１と同じ装置を用い、炭酸カリウムから炭酸ナトリウムに原料を変更して反応を行った。反応（７）を行った後の沈降成分をＸＲＤ分析したところ、ＳｉＯ2以外にＮａＦ成分が確認された。したがって、溶液中にＮａＦが溶解しきれずに析出してしまっていること確認された。 [Comparative Example 2]
Using the same apparatus as in Example 1, the reaction was carried out by changing the raw material from potassium carbonate to sodium carbonate. An XRD analysis of the precipitated component after performing the reaction (7) revealed a NaF component in addition to SiO 2 . Therefore, it was confirmed that NaF was precipitated in the solution without being completely dissolved.
　１００　　フッ化カルシウムの製造装置
　１０　　　フッ化カルシウム合成槽
　３０　　　脱水装置
　４０　　　炭酸カルシウム導入装置
　５０　　　フッ化カルシウム
　６０　　　中和分解槽
　７０　　　廃液貯留槽 DESCRIPTION OF SYMBOLS 100 Calcium fluoride manufacturing apparatus 10 Calcium fluoride synthesis tank 30 Dehydration apparatus 40 Calcium carbonate introduction apparatus 50 Calcium fluoride 60 Neutralization decomposition tank 70 Waste liquid storage tank

Claims (11)

  1. ケイフッ化水素酸含有水を用いたフッ化カルシウムの製造方法であって、
    　ケイフッ化水素酸含有水とカリウム化合物を反応させ、不溶性シリカとフッ化カリウム水溶液を含む第１反応生成物を生成させる工程［１］と、
    　前記第１反応生成物から不溶性シリカを分離する工程［２］と、
    　不溶性シリカを分離した第１反応生成物と炭酸カルシウムを反応させ、フッ化カルシウムと炭酸カリウム水溶液を含む第２反応生成物を生成させる工程［３］と、
    　前記第２反応生成物から炭酸カリウム水溶液を分離する工程［４］と、を含む、フッ化カルシウムの製造方法。     A method for producing calcium fluoride using siliceous hydrofluoric acid-containing water,
    Reacting silicofluoric acid-containing water with a potassium compound to produce a first reaction product containing insoluble silica and an aqueous potassium fluoride solution [1];
    Separating the insoluble silica from the first reaction product [2];
    Reacting the first reaction product from which insoluble silica has been separated with calcium carbonate to form a second reaction product containing calcium fluoride and an aqueous potassium carbonate solution [3];
    Separating the aqueous potassium carbonate solution from the second reaction product [4].
  2. さらに、前記工程［４］にて分離した炭酸カリウム水溶液を、前記工程［１］のカリウム化合物原料として再利用する工程［５］を含む、請求項１のフッ化カルシウムの製造方法。 Furthermore, the manufacturing method of the calcium fluoride of Claim 1 including the process [5] which reuses the potassium carbonate aqueous solution isolate | separated at the said process [4] as a potassium compound raw material of the said process [1].
  3. 前記工程［５］が、炭酸カリウム水溶液の濃縮処理を含む、請求項２のフッ化カルシウムの製造方法。 The manufacturing method of the calcium fluoride of Claim 2 in which the said process [5] includes the concentration process of potassium carbonate aqueous solution.
  4. さらに、前記工程［２］にて分離された不溶性シリカを洗浄し、当該洗浄によって得られた洗浄液を前記工程［１］及び／又は前記工程［３］に導入する、請求項１から請求項３の何れかのフッ化カルシウムの製造方法。 Further, the insoluble silica separated in the step [2] is washed, and the cleaning liquid obtained by the washing is introduced into the step [1] and / or the step [3]. The manufacturing method of any one of these.
  5. さらに、前記工程［３］にて分離されたフッ化カルシウムを洗浄し、当該洗浄によって得られた液を前記工程［１］及び／又は前記工程［３］に導入する、請求項１から請求項４の何れかのフッ化カルシウムの製造方法。 Furthermore, the calcium fluoride separated in the step [3] is washed, and the liquid obtained by the washing is introduced into the step [1] and / or the step [3]. 4. The method for producing calcium fluoride according to any one of 4 above.
  6. 前記工程［３］に用いる炭酸カルシウムの平均粒径が、１５～３００μｍである、請求項１から請求項５の何れかのフッ化カルシウムの製造方法。 The method for producing calcium fluoride according to any one of claims 1 to 5, wherein an average particle diameter of calcium carbonate used in the step [3] is 15 to 300 µm.
  7. 前記工程［１］の反応温度が、４０～１００℃である、請求項１から請求項６の何れかのフッ化カルシウムの製造方法。 The method for producing calcium fluoride according to any one of claims 1 to 6, wherein the reaction temperature in the step [1] is 40 to 100 ° C.
  8. 前記工程［３］の反応温度が、４０～８０℃である、請求項１から請求項７の何れかのフッ化カルシウムの製造方法。 The method for producing calcium fluoride according to any one of claims 1 to 7, wherein a reaction temperature in the step [3] is 40 to 80 ° C.
  9. 前記カリウム化合物が、炭酸カリウム、炭酸水素カリウム、酸化カリウム、水酸化カリウムからなる群より選ばれる少なくとも１種の化合物である、請求項１から請求項８の何れかのフッ化カルシウムの製造方法。 The method for producing calcium fluoride according to any one of claims 1 to 8, wherein the potassium compound is at least one compound selected from the group consisting of potassium carbonate, potassium hydrogen carbonate, potassium oxide, and potassium hydroxide.
  10. ケイフッ化水素酸含有水を用いたフッ化カルシウムの製造装置であって、
    　ケイフッ化水素酸含有水とカリウム化合物を反応させ、不溶性シリカとフッ化カリウム水溶液を含む第１反応生成物を生成させる中和分解槽と、
    　該中和分解槽に連結され、不溶性シリカを分離した第１反応生成物と炭酸カルシウムを反応させ、フッ化カルシウムと炭酸カリウム水溶液を含む第２反応生成物を生成させるフッ化カルシウム合成槽と、
    　該フッ化カルシウム合成槽に連結され、前記第２反応生成物から炭酸カリウム水溶液を分離する分離装置と、を備えた、フッ化カルシウムの製造装置。     An apparatus for producing calcium fluoride using silicohydrofluoric acid-containing water,
    A neutralization decomposition tank for reacting hydrofluoric acid-containing water with a potassium compound to produce a first reaction product containing insoluble silica and an aqueous potassium fluoride solution;
    A calcium fluoride synthesis tank connected to the neutralization decomposition tank and reacting calcium carbonate with a first reaction product from which insoluble silica has been separated to produce a second reaction product containing calcium fluoride and an aqueous potassium carbonate solution;
    An apparatus for producing calcium fluoride, comprising: a separator connected to the calcium fluoride synthesis tank and separating an aqueous potassium carbonate solution from the second reaction product.
  11. さらに、前記分離装置に連結され、前記第２反応生成物から分離された炭酸カリウム水溶液を貯留するための貯留槽を備え、該貯留槽は、前記中和分解槽と前記貯留槽を結び、前記炭酸カリウム水溶液を前記中和分解槽に送液するための循環配管を有する、請求項１０のフッ化カルシウムの製造装置。 Further, the storage device is connected to the separation device and includes a storage tank for storing the potassium carbonate aqueous solution separated from the second reaction product, the storage tank connecting the neutralization decomposition tank and the storage tank, The manufacturing apparatus of the calcium fluoride of Claim 10 which has a circulation piping for sending potassium carbonate aqueous solution to the said neutralization decomposition tank.
PCT/JP2013/053181 2012-04-13 2013-02-12 Method and device for manufacturing calcium fluoride WO2013153846A1 (en)

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CN110642282A (en) * 2019-09-23 2020-01-03 湖北祥云(集团)化工股份有限公司 Method for preparing calcium fluoride and potassium bicarbonate by using carbon dioxide
CN112897562A (en) * 2021-01-05 2021-06-04 上海大学 Method for purifying calcium fluoride from calcium fluoride sludge
CN114031100A (en) * 2021-12-20 2022-02-11 湖北祥云(集团)化工股份有限公司 Method for preparing fluoride salt from phosphorus ore associated fluorine

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CN110642282A (en) * 2019-09-23 2020-01-03 湖北祥云(集团)化工股份有限公司 Method for preparing calcium fluoride and potassium bicarbonate by using carbon dioxide
CN112897562A (en) * 2021-01-05 2021-06-04 上海大学 Method for purifying calcium fluoride from calcium fluoride sludge
CN114031100A (en) * 2021-12-20 2022-02-11 湖北祥云(集团)化工股份有限公司 Method for preparing fluoride salt from phosphorus ore associated fluorine

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