JP2006175364A - Recovery method and apparatus of fluorine from fluorine-containing material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recovery method and apparatus of fluorine from fluorine-containing material which recover fluorine in a state of a reduction in the contamination of silicon compounds as low as possible when recovering fluorine from the fluorine-containing material as calcium fluoride. <P>SOLUTION: The recovery method of fluorine from fluorine-containing material recovers fluorine as a fluorine compound by cooling the fluorine compound obtained by adding an acidic substance to the fluorine-containing material and distilling it by heating, or by absorbing the obtained fluorine compound in water, an alkaline solution, a solution of a calcium compound, or a suspension of a calcium compound. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for recovering fluorine from a fluorine-containing material and a fluorine recovery device that recover fluorine from the fluorine-containing material as a fluorine compound with few impurities.

  In Japan, fluorite (calcium fluoride), which is a fluorine resource, is rarely produced, and so it depends on imports. Among the producing countries, China, which produces particularly high-quality ore, has started export restrictions and quotas, so the import volume has been decreasing year by year and the price has been rising. For this reason, utilization of fluorite from Mexico with low purity is desired, but in reality it cannot be used for hydrofluoric acid production that requires high purity fluorite. This is because high-purity hydrofluoric acid cannot be obtained by mixing impurities such as silicon contained in the ore when sulfuric acid is added to fluorite for distillation. For this reason, technologies for increasing the purity of low-grade fluorite, technologies for improving the purity by purifying low-purity hydrofluoric acid containing silicon compounds generated during hydrofluoric acid production, and silicon compounds from waste containing fluorine, etc. There is a strong demand for a technology for recovering raw materials for producing hydrofluoric acid with a low content.

  As a method for removing fluorine from fluorine-containing wastewater, a method is adopted in which a calcium compound is added to fluorine-containing wastewater, and precipitation is removed as sludge containing calcium fluoride. Sludge containing calcium fluoride obtained by removing fluorine has been disposed of as industrial waste without being collected. Although this sludge differs depending on the type of waste water, it usually contains silicon compounds, heavy metals, etc., which has hindered the reuse of sludge. However, if the silicon content of the sludge can be lowered and the calcium fluoride content can be increased, the sludge can be reused, and thus such a technique is strongly demanded.

As described in Patent Document 1, an invention in which a magnesium compound is added to fluorine-containing wastewater, precipitated as magnesium fluoride, the recovered fluorine-containing sludge is treated, and hydrogen fluoride is recovered by distillation. Is also open to the public.
JP 2004-000846 A Japanese Patent Application No. 2003-050121 Japanese Patent Application No. 2003-124483 Japanese Patent Application No. 2003-38591

  However, although the invention described in Patent Document 1 treats fluorine-containing wastewater with magnesium, the treatment with magnesium has a large amount of sludge, and sludge with good sedimentation cannot be obtained. This method is hardly applied in processing. Moreover, in the invention described in Patent Document 1, there are unrealistic elements in actual water treatment, such as sludge obtained by waste water treatment must be dried.

  Accordingly, the present invention has an object to provide a method and an apparatus for recovering fluorine from a fluorine-containing material that recovers the fluorine compound from the fluorine-containing material in a state where contamination of the silicon compound is as low as possible when the fluorine is recovered as calcium fluoride. It is what.

  The inventor of the present invention has intensively studied to solve the above-mentioned problems. As a result, the present invention has been completed, and the present invention has the following configuration.

  The method for recovering fluorine from fluorine-containing material is to add an acidic substance to the fluorine-containing material and heat to cool the fluorine compound that is distilled off, or by cooling water, an alkaline solution, a calcium compound solution or a calcium compound. Fluorine is recovered as a fluorine compound by being absorbed into the suspension.

  The fluorine-containing material is sludge obtained when fluorine-containing water such as fluorine-containing waste water or hydrofluoric acid waste liquid is treated. Therefore, in the fluorine-containing material, impurities such as heavy metals and silicon compounds are included in addition to the fluorine compound, but an acidic substance is added and heated to distill the fluorine compound, and the reduced fluorine compound of the impurity is removed. It is characterized by obtaining. The acidic substance is any one of sulfuric acid, hydrofluoric acid, hydrochloric acid, oxalic acid, phosphoric acid or perchloric acid, or a mixture of one or more acids thereof. Heating may be performed under normal pressure, but is preferably performed under reduced pressure.

  When the fluorine compound to be distilled is hydrogen fluoride alone, by cooling it, a reduced impurity fluorine compound, that is, hydrogen fluoride is obtained, and if trapped in an alkaline solution, a fluoride salt is obtained. It is done. On the other hand, when the fluorine-containing material contains a silicon compound, the fluorine compound to be distilled is hydrogen fluoride, hexafluorosilicic acid and / or silicon fluoride, and contains a silicon compound in addition to the recovered fluorine compound.

  Fluorine is recovered as calcium fluoride by absorbing the distilling fluorine compound into a calcium compound solution or suspension. When a calcium carbonate suspension is used as the calcium compound, calcium fluoride having a lower silicon compound content than other calcium compounds can be obtained.

  When the fluorine compound distilled with calcium carbonate is recovered, a mixture of calcium fluoride and unreacted calcium carbonate is obtained. By treating this with hydrofluoric acid, the calcium carbonate is converted to calcium fluoride. The purity of calcium can be further increased.

  According to the present invention, it becomes possible to convert a fluorine-containing material containing impurities such as heavy metals and silicon compounds into a material having a low impurity content, and fluorine that has been disposed of as industrial waste without being reused so far. The sludge generated when the contained wastewater or the hydrofluoric acid waste liquid is treated can be reused.

  In the present invention, by adding an acidic substance to the fluorine-containing material and recovering the distilled fluorine compound, fluorine is recovered as a fluorine compound with few impurities. Any fluorine-containing material can be used as long as it reacts and dissolves with an acidic substance, but a material capable of ensuring the amount thereof is preferable.

  As such, for example, low-purity hydrofluoric acid containing a silicon compound generated during hydrofluoric acid production, fluorine-containing sludge obtained by treating fluorine-containing wastewater or hydrofluoric acid waste liquid, or various fluorine discharged from the fluorine industry There are fluorine-containing sludges obtained by processing the contained waste.

  In the present invention, fluorine-containing sludge is used as the fluorine-containing material, but the fluorine-containing sludge usually contains 80 to 95% of water. The fluorine-containing sludge may be used as it is, but it is preferable from the viewpoint of operability to use water in a slurry state of 90 to 99%.

  When an acidic substance is added to the slurry-like fluorine-containing sludge, fluorine is dissolved as hydrofluoric acid. Fluorine can be distilled as hydrogen fluoride by heating to 112.2 ° C. or higher, which is the boiling point of hydrofluoric acid. Moreover, it can also be distilled at a lower temperature by heating under reduced pressure.

  If the fluorine-containing material does not contain silicon, or if silicon content is low and contamination of silicon can be prevented during the reaction, the fluorine compound to be distilled out is only hydrogen fluoride, and does not contain impurities. Can be recovered. In addition, as a method for preventing contamination of silicon during the reaction, the reaction may be performed using a container made of a material that does not elute silicon even if it reacts with hydrofluoric acid.

  As a method of recovering the distilled fluorine compound, a method of cooling and recovering the distilled fluorine compound, absorbing water or an alkali such as sodium hydroxide or potassium hydroxide, and hydrofluoric acid or sodium fluoride And a method of recovering as calcium fluoride by absorbing the solution in a calcium compound solution or suspension.

  In the method in which the vaporized product of the distilled fluorine compound is absorbed in a solution or suspension of a calcium compound and fluorine is recovered as calcium fluoride, calcium carbonate, calcium hydroxide, calcium chloride, calcium nitrate, Any calcium compound such as calcium bromide or calcium iodide can be used.

  As a method of cooling the distilled fluorine compound, it can be carried out by a cooling operation used in a normal distillation operation, and an existing apparatus can be applied, and there is no particular limitation, but a material not affected by hydrofluoric acid is used. It is required to be a thing.

  Absorption of the distilled fluorine compound by water or an alkali such as sodium hydroxide or potassium hydroxide, or absorption in a solution or suspension of a calcium compound can be achieved by a method performed by a normal gas absorption operation. An existing apparatus can be applied and is not particularly limited, but is required to be made of a material that is not affected by hydrofluoric acid.

  If the fluorine-containing material does not contain a silicon compound, but only contains non-volatile impurities such as heavy metals, an acidic substance is added to the fluorine-containing material and treated under heat, so that heavy metals contained in the fluorine-containing material, etc. And can be recovered as pure hydrofluoric acid or sodium fluoride, or calcium fluoride.

  When the fluorine-containing material contains a silicon compound as an impurity, a part of the fluorine reacts with the silicon compound and distills as silicon fluoride and / or hexafluorosilicic acid. Silicon compounds such as hexafluorosilicic acid and silicon dioxide are mixed in sodium and calcium fluoride.

  The calcium fluoride recovered in the present invention is used for reuse, but the purity of calcium fluoride required varies depending on what is reused. For example, when the recovered calcium fluoride is reused as a raw material for producing hydrofluoric acid, high purity is required. In particular, the silicon content is desirably 1.0% or less with respect to calcium fluoride. If the silicon content exceeds 1.0%, the purity of the resulting hydrogen fluoride is reduced when hydrogen fluoride is produced.

  In the present invention, any calcium compound can be used when recovered as calcium fluoride, but the silicon compound content in the fluorine-containing material is high, and as a result, the silicon content in the recovered calcium fluoride becomes a problem. In this case, it is desirable that the silicon contamination in the recovered calcium fluoride is minimized.

  In the present invention, when an alkaline calcium compound such as calcium carbonate or calcium hydroxide is used as the calcium compound to be recovered as calcium fluoride, contamination of silicon into the recovered calcium fluoride can be reduced. In this case, the use of calcium carbonate as the calcium compound is particularly preferred.

  In the present invention, an alkaline calcium compound such as calcium carbonate or calcium hydroxide is used as a calcium compound for recovering calcium fluoride having a low silicon content from a fluorine-containing material containing silicon. It is desirable to be able to maintain a pH of 3 or higher, preferably 4 or higher, in which calcium fluoride can exist without dissolving.

  Moreover, since it is possible to further prevent the incorporation of the silicon compound when the added alkaline calcium compound is dissolved as much as possible, the pH after distillation is maintained from the neutral side to the acidic side, that is, pH 3 to 8, preferably Is preferably maintained at pH 3-7, more preferably at pH 4-5.5.

  The amount of calcium in the recovered liquid of the fluorine compound distilled in the present invention is 1 to 20 times, preferably 1 to 10 times, more preferably 1 to 5 times the amount of fluorine.

  In order to maintain the pH, the amount of calcium carbonate may be increased or adjusted by coexistence of calcium carbonate and a basic substance so that the pH is not lowered excessively by the distilled acidic fluorine compound. . In addition, sodium hydroxide, potassium hydroxide, calcium hydroxide, etc. can be utilized as a basic substance.

  In the present invention, when calcium fluoride is recovered from a fluorine-containing material that does not contain silicon or a fluorine-containing material that does not cause a problem even if silicon is contained, the calcium compound is not particularly limited, and after completion of distillation The pH of the is also not particularly limited.

  If the pH after distillation is reduced and calcium fluoride is dissolved and added, a basic substance is added and adjusted to pH 4-10, preferably pH 4-8, to produce calcium fluoride. good. As the basic substance, an alkaline substance such as sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide or calcium carbonate is used.

  The acidic substance used in the present invention is not particularly limited as long as the object of the present invention can be achieved, and examples thereof include mineral acids (inorganic acids) such as sulfuric acid, hydrofluoric acid, hydrochloric acid or nitric acid, phosphoric acid, oxalic acid or perchloric acid. Available.

  There is no particular problem with the purity of the acidic substance, and an unused acid may be used, or a waste acid once used may be used. Moreover, an acid may be used independently and it can also react using the mixed acid which consists of two or more acids. The addition amount of the acidic substance in the present invention is 1 to 20 times, preferably 1 to 10 times, more preferably 1 to 5 times in terms of molar ratio with respect to fluorine.

  In the present invention, an acidic substance is added to the fluorine-containing material and heated, but the heating may be performed under normal pressure or under reduced pressure. In addition, it is sufficient to perform under reduced pressure, heating temperature may be low, and it can also prevent that a silicon compound adheres to a vessel wall. Further, the reduced pressure is more preferable because the fluorine recovery rate is high.

  When heating is performed under normal pressure, the heating temperature is 100 to 150 ° C, preferably 100 to 130 ° C, more preferably 110 to 130 ° C. When the reaction is carried out under normal pressure, it is preferable to carry out the reaction while sending gas in order to smoothly send the generated vaporized product to the calcium compound solution or suspension.

  As the gas, any gas other than flammable or harmful gas can be used, but it is preferable to use a gas that can be obtained easily and inexpensively, such as air or nitrogen. The method of sending the gas is not particularly limited, and air bubbles may be jetted, or a method of sucking the gas by sucking from the absorption container side containing the calcium compound solution or suspension may be used.

  When heating is performed under reduced pressure, the pressure is reduced by suction from the side of the absorption container containing the calcium compound solution or suspension. The vacuum device is not particularly limited as long as it can be sucked, such as an existing vacuum pump.

  The degree of vacuum should be as high as possible, and is −60 to −76 cmHg, preferably −65 to −76 cmHg, more preferably −70 to −76 cmHg. Moreover, although heating temperature changes also with vacuum degrees, it is 30-100 degreeC, Preferably it is 40-90 degreeC, More preferably, it is 50-80 degreeC.

  As the fluorine-containing material, sludge generated when fluorine-containing wastewater is treated can be used. There are various methods for treating fluorine-containing wastewater, and sludge obtained by any of the treatment methods can be used.

  For example, sludge obtained by a method of adding calcium to precipitate as calcium fluoride or a method of coprecipitation or adsorption by an aluminum or magnesium hydroxide precipitation method can be used.

  In addition, in the state where rare earth element ions and harmless polyvalent metal ions are present in fluorine-containing wastewater, the pH is adjusted to 5 to 9 to precipitate and separate dissolved fluorine ions as a hardly soluble substance. The sludge obtained by the method can also be used.

  Furthermore, harmless polyvalent metal ions are present in the fluorine-containing waste water, alkali is added to adjust the pH of the treated water to 10 or more, rare earth ions are added, aluminum ions are added as necessary, and acidic substances are added. The sludge obtained by the method described in Patent Document 3 in which dissolved fluorine ions are precipitated and separated as a hardly soluble substance by adjusting the pH to 6 or more and less than 10 can also be used.

  In addition, by adding calcium compounds to the fluorine wastewater, which is the raw water, and adjusting the pH to 5-9, the precipitate generated by making it alkaline is returned to new raw water to remove fluorine to a low concentration. And the sludge obtained by the method of patent document 4 which also reduces the quantity of the deposit to generate | occur | produce can also be utilized.

  In the present invention, when the recovered calcium fluoride is subjected to solid-liquid separation, it is preferable to use a flocculant for aggregating the calcium fluoride to facilitate separation.

  As the flocculant, polyacrylamide cationized modified product, polyacrylic acid dimethylaminoethyl ester, polymethacrylic acid dimethylaminoethyl ester, cationic organic flocculant such as polyethyleneimine or chitosan, nonionic organic type such as polyacrylamide There are flocculants, or anionic organic flocculants such as polyacrylic acid, a copolymer of acrylamide and acrylic acid, or a salt of the copolymer.

  The amount of the flocculant used is 0.1 to 100 milligrams, preferably 0.1 to 50 milligrams, and more preferably 0.5 to 25 milligrams per liter of water in the concentration in water.

  The coagulated and precipitated calcium fluoride is subjected to solid-liquid separation treatment and reused. Examples of the solid-liquid separation method include conventional methods such as filtration separation, centrifugal separation, and sedimentation separation.

  Next, a fluorine recovery method and a fluorine recovery apparatus from a fluorine-containing material according to the present invention will be described in detail with reference to the attached drawings. FIG. 1 is a diagram showing a method for recovering fluorine from a fluorine-containing material according to the present invention.

  The fluorine recovery method 1 from fluorine-containing material comprises the steps of fluorine-containing material preparation 1a, acidic substance addition 1b, distillation 1c, recovery 1d, and solid-liquid separation 1e.

  In the fluorine-containing material preparation 1a step, fluorine-containing sludge or fluorine-containing slurry that is a target of fluorine recovery treatment is prepared. As the fluorine-containing sludge, the one generated when the fluorine-containing wastewater is treated can be used.

  In the acidic substance addition 1b step, an acidic substance is added to the fluorine-containing material and reacted. Add water if necessary. By the reaction, fluorine in the fluorine-containing material is changed to hydrofluoric acid or the like.

  In the distillation 1c step, the fluorine-containing material is heated and the generated hydrofluoric acid is evaporated and separated. If distillation 1c is performed under reduced pressure, it can be distilled at a temperature lower than that under normal pressure.

  In the recovery 1d step, fluorine is recovered. There are a method of recovering the distilled fluorine compound by cooling, a method of absorbing it in water or an alkaline solution, and a method of recovering it by absorbing it in a calcium compound solution or suspension.

  When the distilled fluorine compound contains a silicon compound, the compound is absorbed and recovered in a calcium compound solution or suspension. When calcium carbonate is used as the calcium compound, calcium fluoride having a low silicon content can be obtained.

  In the solid-liquid separation 1e step, precipitated calcium fluoride is separated from the liquid and collected by a method such as filtration. Fluorine can be recovered as calcium fluoride from which impurities such as silicon have been removed.

  FIG. 2 is a diagram showing a fluorine recovery apparatus according to the present invention. The fluorine recovery device 2 includes a distillation unit 3 for evaporating fluorine-containing material and a receiving unit 5 connected to the distillation unit 3. A location where the distillation unit 3 and the receiving unit 5 are connected is referred to as a connection unit 4.

  The distillation unit 3 includes a distiller 3a for containing a fluorine-containing material, a heater 3c for heating the distiller 3a, and a stirrer 3d for distiller for stirring the distiller 3a.

  The connecting portion 4 includes a vent pipe 4a through which the vapor of the fluorine compound passes, a pipe 4c on the distillation section 3 side of the vent pipe 4a, and a pipe 4d on the receiving section 5 side of the vent pipe 4a. The vent pipe 4a is desirably as short as possible, and can also have a structure in which the distiller 3a and the receiver 5a are integrated. The vent pipe 4a can be heated by attaching a heater 4b for heating the vent pipe 4a as necessary.

  The receiver 5 includes a receiver 5a into which a fluorine compound vapor enters, a receiver stirrer 5b for stirring the receiver 5a, and a vacuum device 6 for reducing the pressure in the receiver 5a. Distillation is performed by vacuum distillation.

  The distiller 3a is a container for containing a distillate 3e, which is made of a material that does not elute silicon by reacting with hydrofluoric acid, for example, a distillation flask made of Teflon (registered trademark), or a distillation coated with Teflon (registered trademark). A flask or the like is used. The distillate 3e is a fluorine-containing wastewater, and is a slurry (slurry) wastewater in which a fluorine-containing material is suspended.

  There is a thermometer 3b as an instrument for measuring the temperature when the distillate 3e in the distiller 3a is heated, and a Teflon (registered trademark) coated thermometer or the like is used. The thermometer 3b is inserted from the inlet of the distiller 3a and measured.

  The heater 3c is an instrument for heating the distillate 3e in the distiller 3a, and a mantle heater or the like is used. The mantle heater is suitable for heating a round bottom flask or the like.

  The receiver 5a is a container in which the absorption liquid 5c is put, and an absorption flask or the like is used. The vapor | steam sent from the distiller 3a is absorbed by the absorption liquid 5c of the receiver 5a, and a residual liquid remains in the distiller 3a.

  The distiller stirrer 3d is a device that stirs the distiller 3a, and the receiver stirrer 5b is a device that stirs the receiver 5a. A magnetic stirrer or the like is used for the stirrer 3d for the still and the stirrer 5b for the receiver.

  The vent pipe 4a is an instrument that connects the distiller 3a and the receiver 5a, and a plastic tube or the like is used. However, the vent pipe 4a is made of a material that does not elute silicon by reacting with hydrofluoric acid, for example, made of Teflon (registered trademark). Those coated with Teflon (registered trademark) are desirable.

  The pipe 4c of the vent pipe 4a is passed through the stopper of the distiller 3a and fixed so as not to touch the distillate 3e, and the pipe 4d of the vent pipe 4a is passed through the stopper of the receiver 5a and put into the absorbing liquid 5c. And fix. The vapor generated in the distiller 3a is sent from the pipe 4c through the vent pipe 4a to the receiver 5a, and is discharged from the pipe 4d into the absorbing liquid 5c.

  The heater 4b is an instrument that heats the steam passing through the ventilation pipe 4a so as not to cool, and a ribbon heater or the like is used. In the case of a ribbon heater, it is heated by being spirally wound around the vent pipe 4a.

  The vacuum device 6 is a device that depressurizes the receiver 5a, and a vacuum pump, a water flow pump, or the like is used. The vacuum device 6 is connected by passing the pressure reducing connecting pipe 6a through the stopper of the receiver 5a, and sucks gas from the receiver 5a.

  Next, a method for recovering fluorine from a fluorine-containing material and a fluorine recovery apparatus according to the present invention will be described in detail with reference to examples.

  The suspended solid content (SS) concentration of the fluorine-containing slurry was 7.1%, the fluorine concentration in the suspended material was 31.5%, the calcium concentration was 39.9%, and the silicon concentration was 5.4%. Using this slurry, a fluorine recovery experiment was conducted.

  The distiller 3a is a Teflon (registered trademark) distillation flask, the thermometer 3b is a Teflon (registered trademark) coated thermometer, the heater 3c is a mantle heater, the vent tube 4a is a plastic tube, the heater 4b is a ribbon heater, and a receiver. An absorption flask was used as the vessel 5a, a water flow pump as the vacuum device 6, a magnetic stirrer as the stirrer 3d for the still, and a stirrer 5b as the receiver.

  Take 44.6 ml of fluorine-containing slurry (1 gram as fluorine) in a distillation flask (capacity 250 ml), add 10 ml of water and 19.5 ml of sulfuric acid (molar concentration 10.25M), and heat with a mantle heater. Distilled.

  As a distillate absorption solution, a suspension of 3.16 grams of calcium carbonate (1.2 times the amount equivalent to fluorine) suspended in 500 milliliters of water was placed in a 1 liter eggplant-shaped flask. In addition, an equivalent is the quantity of the fluorine and calcium which form calcium fluoride (CaF2).

  The distillation flask and the absorption flask were connected with a plastic tube having an inner diameter of 12 mm. The tip of the plastic tube is open in the absorbent. The plastic tube is heated to about 50 ° C. with a ribbon heater.

  The temperature of the distillate is measured with a thermometer. In order to depressurize the absorption flask to a vacuum, a pressure reducing connecting pipe 6a was connected. The distillate and absorption liquid were stirred with a magnetic stirrer.

  The distillation flask was heated with a mantle heater, the temperature of the distillate was adjusted to about 70 to 80 ° C., and vacuum distillation was started by reducing the pressure by about −75 cmHg with a water flow pump. Bubbles are generated from the tip of the plastic tube in the absorbent. After 1 hour, the generation of bubbles stopped and the experiment was terminated.

  The absorption liquid (pH 6.1) was subjected to solid-liquid separation, and fluorine in the filtrate was 4.5 mg, silicon was 36.3 mg, and calcium was 248 mg. The fluorine in the absorbed sludge was 577 milligrams, silicon was 1.4 milligrams, calcium was 722 milligrams, and the silicon content was 0.1%.

  In the residual liquid (18 milliliters) in the distillation flask, 73.9 milligrams of fluorine, 7.1 milligrams of silicon, and 1318 milligrams of calcium remained.

  In Example 1, it experimented by changing the quantity of the calcium carbonate in the absorption liquid of a distillate vapor | steam. Experiments were carried out using suspensions of 2.63 grams of calcium carbonate (equivalent to fluorine) and 2.86 grams (1.1 times the amount equivalent to fluorine) in 500 ml of water.

  As a result of the experiment, the pH of the absorbing solution was 1.5 and 1.9, respectively. The fluorine concentrations in the filtrate obtained by solid-liquid separation of the absorption liquid were 603 mg / L and 419 mg / L, respectively.

  When the amount of calcium carbonate is small, the pH of the absorbing solution is lowered and the amount of fluorine dissolved in water is increased. Calcium carbonate more than 1.2 times the amount of fluorine in the raw sludge is required.

  In Example 1, an experiment was conducted in the same manner as in Example 1 except that the distillate absorption liquid was 500 ml of a suspension containing 2.22 g of calcium hydroxide (1.14 times the equivalent of fluorine).

  The absorption liquid (pH 10.0) was subjected to solid-liquid separation to obtain 2.275 g of a recovered product containing fluorine. The composition of the recovered material was 787 milligrams of fluorine, 35.7 milligrams of silicon, 1007 milligrams of calcium, and the silicon content was 1.6%. This recovered material contains calcium fluoride as a main component and also contains unreacted calcium hydroxide.

  In Example 1, an experiment was performed in the same manner as in Example 1 except that the absorption liquid of the distillate was changed to 500 ml of a suspension containing 2.63 g of calcium carbonate (equivalent to fluorine) and 12 mmol of sodium hydroxide. .

  The absorption liquid (pH 9.1) was subjected to solid-liquid separation to obtain a recovered product containing fluorine. The composition of 2.095 grams of this recovered material was 812 milligrams of fluorine, 2.0 milligrams of silicon, 957 milligrams of calcium, and the silicon content was 0.1%.

  This result shows that even if the absorption liquid does not have 1.2 times the amount of fluorine in the raw sludge and the equivalent amount of calcium carbonate, if there is an equivalent amount of calcium carbonate, the decrease in pH should be suppressed with sodium hydroxide. This shows that the silicon content in the absorbed sludge can be lowered.

  The recovered material obtained in Example 1 contains calcium fluoride as a main component and also contains unreacted calcium carbonate. After adding 0.5 ml of hydrofluoric acid (2% aqueous solution) to 0.5 gram of this recovered material and stirring and mixing, solid-liquid separation was performed to obtain 0.465 gram of recovered material containing calcium fluoride.

  The composition of this recovered material was 226 mg of fluorine, 0.45 mg of silicon, and 237 mg of calcium, and the silicon content was 0.1%. Therefore, the content of calcium fluoride in the recovered material is 99.5%.

  Fluorine-containing model wastewater (9.4 grams of hydrogen fluoride for 1 liter of wastewater, 8.9 grams as fluorine) was added with 24 grams of calcium hydroxide to pH 9 and stirred for 10 minutes. 2.2 ml of a molar concentration 1.28M) was added, 3 ml of a polymer flocculant (manufactured by Daianitrix, AP120C, concentration 0.2%) was added, and the mixture was stirred for 1 minute, followed by solid-liquid separation.

  The suspended solid amount (SS) concentration of the fluorine-containing sludge was 32.2%, the fluorine concentration in the suspended material was 29.2%, the calcium concentration was 42.5%, and the silicon concentration was 0.15%. Using this sludge, a fluorine recovery experiment was conducted. The experimental apparatus is the same as in Example 1.

  Fluorine-containing sludge (1 gram as fluorine) is placed in a distillation flask (volume: 250 ml), and 20 ml of water and 19.5 ml of sulfuric acid (molar concentration: 10.25 M) (molar ratio to fluorine: 3.8 times). Added, heated with a mantle heater and distilled.

  As a distillate absorption solution, a suspension of 3.16 grams of calcium carbonate (1.2 times the amount equivalent to fluorine) suspended in 500 milliliters of water was placed in a 1 liter eggplant-shaped flask.

  The distillation flask was heated with a mantle heater, the temperature of the distillate was adjusted to about 70 to 80 ° C., and vacuum distillation was started by reducing the pressure by about −75 cmHg with a water flow pump. Bubbles are generated from the tip of the plastic tube in the absorbent. After 1 hour, the generation of bubbles stopped and the experiment was terminated.

  The absorption liquid (pH 6.6) was subjected to solid-liquid separation to obtain 2.544 g of a recovered product containing fluorine. The composition of the recovered material was 960 mg of fluorine, 1.8 mg of silicon, 1217 mg of calcium, and the silicon content was 0.1%. The recovered material contains calcium fluoride as a main component and contains unreacted calcium carbonate.

  In Example 6, an experiment was performed by adding silicon dioxide (SiO2) to the raw sludge so as to be 5% and 10% of the amount of sludge (dry).

  As a result of the experiment, the content of silicon in the absorbed sludge was 0.1 to 0.2%. This result shows that even if the amount of silicon in the raw sludge is large, the silicon content in the absorbed sludge distilled and absorbed in the calcium carbonate suspension can be reduced.

  In Example 6, the amount of sulfuric acid added to the raw sludge was experimented by adding 2 times and 3 times the molar ratio of fluorine.

  As a result of the experiment, the fluorine recovery rate was about 5% in the case of the double amount, but the recovery rate was about 80% in the case of the triple amount. It can be seen that it is preferable to add 3 times or more of sulfuric acid in a molar ratio with respect to fluorine.

It is a figure which shows the fluorine recovery method from the fluorine containing material which is this invention. It is a figure which shows the structure of the fluorine collection | recovery apparatus which is this invention.

Explanation of symbols

1 Fluorine recovery method from fluorine-containing material 1a Fluorine-containing material preparation 1b Acidic substance addition 1c Distillation 1d Recovery 1e Solid-liquid separation 2 Fluorine recovery device 3 Distillation unit 3a Distiller 3b Thermometer 3c Heater 3d Distiller agitator 3e Distillate 4 Connection portion 4a Ventilation tube 4b Heater 4c tube 4d tube 5 Receiving portion 5a Receiving device 5b Receiving stirrer 5c Absorbing liquid 6 Vacuum device 6a Decompression connecting tube

Claims (8)

  Adding an acidic substance to a fluorine-containing material and evaporating and distilling the fluorine compound by heating, or by cooling or absorbing it in water, an alkaline solution, a calcium compound solution or a calcium compound suspension To recover fluorine from fluorine-containing material, wherein fluorine is recovered as a fluorine compound.   The method for recovering fluorine from a fluorine-containing material according to claim 1, wherein the fluorine-containing material is sludge obtained when fluorine-containing water such as fluorine-containing waste water or hydrofluoric acid waste liquid is treated.   The acidic substance is any one of sulfuric acid, hydrofluoric acid, hydrochloric acid, nitric acid, oxalic acid, phosphoric acid and perchloric acid, or a mixture of one or more of these acids. A method for recovering fluorine from a fluorine-containing material as described in 1.   The method for recovering fluorine from a fluorine-containing material according to claim 1, wherein heating is performed under reduced pressure.   The fluorine-containing material contains a silicon compound, and the distilled fluorine compound contains a silicon compound such as hexafluorosilicic acid and / or silicon fluoride in addition to hydrogen fluoride. The method for recovering fluorine from the fluorine-containing material according to claim 3 or 4.   6. The fluorine recovery from the fluorine-containing material according to claim 1, wherein the calcium compound for recovering the distilling fluorine compound is calcium carbonate. Method.   A mixture of calcium fluoride and calcium carbonate obtained when a fluorine compound distilled with calcium carbonate is recovered is treated with hydrofluoric acid to increase the purity of calcium fluoride. The method for recovering fluorine from the fluorine-containing material according to claim 3, 4, 5 or 6. A distiller for containing a fluorine-containing material, a heater for heating the distiller, and a distiller for evaporating the fluorine-containing material comprising a stirrer for a distiller for stirring the distiller, a receiver for receiving steam from the distilling unit, Consists of a receiver stirrer that stirs the receiver and a vacuum device that decompresses the interior of the receiver, a receiver that can be distilled under reduced pressure, a vent pipe that connects the distillation part and the receiver, and a heater attached to the vent pipe A fluorine recovery device comprising a connection portion capable of heating the inside of a vent pipe.

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