JP2016160153A - Separation and recovery method of hydrogen fluoride and separation and recovery apparatus of hydrogen fluoride - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separation and recovery method of hydrogen fluoride and a separation and recovery apparatus of hydrogen fluoride, with which hydrogen fluoride is efficiently recovered from calcium fluoride discharged from various steps.SOLUTION: A separation and recovery method includes: a gas separation step to separate fluorine ingredients as a hydrogen fluoride-based gas by filling a closed type vertical reactor R with a calcium fluoride-based raw material (recovered calcium fluoride) and vertically stirring the raw material with a stirring blade 2a of stirring means 2 while adding sulfuric acid etc. thereto; a step to make an ejector E generate negative pressure by circulating an aqueous absorbent stored in a recovery storage tank T through the ejector E by using a pump P; a gas recovery step to suck out the hydrogen fluoride-based gas generated in the vertical reactor R by using the negative pressure and to recover and feed the gas into the recovery storage tank T; and a hydrogen fluoride concentration step to repeat circulation of the aqueous absorbent and recovery of the generated hydrogen fluoride-based gas in batches.SELECTED DRAWING: Figure 1

Description

  The present invention efficiently separates hydrogen fluoride, hydrogen silicofluoride, and the like from calcium fluoride-based dehydrated solids obtained by precipitation treatment of fluorine-containing waste liquids such as hydrogen fluoride and hydrogen silicofluoride. The present invention relates to a hydrogen fluoride separation and recovery method that can be recovered and a hydrogen fluoride separation and recovery device used therefor.

  In the process of etching glass or silicon wafers for liquid crystal (LCD) panels, the process of processing fluorine-containing organic substances such as alternative chlorofluorocarbons, the factory for manufacturing metal surface treatment and various fluorinated derivatives, etc. Waste liquid (treatment liquid) containing hydrogen fluoride or the like at a high concentration is discharged. This aqueous solution containing hydrofluoric acid (hydrofluoric acid or hydrofluoric acid) as a waste liquid is designated as a poisonous and poisonous medicine for poisonous substances under the Act on the Control of Deleterious Substances. , Calcium hydroxide, calcium oxide, calcium carbonate, calcium chloride and other calcium compounds were mixed and reacted with the above effluent, and hydrogen fluoride was precipitated as hardly soluble (insoluble) calcium fluoride and removed. On the other hand, drainage containing almost no residual hydrogen fluoride is discharged out of the process.

  In addition, the calcium fluoride-based soft water-containing solid material removed from the drainage liquid is made into a cake-like or plate-like solid matter by a dehydration operation using compression or centrifugation, and further, a drying step, a pulverizing step, etc. In general, porous particles or powder (sponge-like) having a water content of 20% or less (preferably 10% or less) are taken out of the process as industrial waste (hereinafter referred to as “ "Recovered calcium fluoride"). And this recovered calcium fluoride is usually used as a part of raw materials (flux) such as iron making, a raw material of cement, a raw material of optical lenses, etc. is the current situation.

  On the other hand, attempts have been made to separate and take out hydrogen fluoride from the recovered calcium fluoride, recover it as hydrofluoric acid (an aqueous solution of hydrogen fluoride), and reuse it. For example, in an industrially established conventional process for producing hydrogen fluoride using fluorite (natural calcium fluoride mineral), a small amount of recovered calcium fluoride powder is used as a raw material for the fluorite ( Addition (mixing) is performed (several percent) (see Patent Document 1).

  Further, in Patent Document 2, the recovered calcium fluoride carried from another process (factory) or the like is put into a horizontal reaction furnace (a small rotary kiln having a cylindrical external heating type inclined furnace), and there Concentrated sulfuric acid or fuming sulfuric acid is mixed and heated in a state where it is heated to 250 ° C. or lower (preferably 80 to 150 ° C.) while slowly rotating (stirring) the cylindrical furnace body (residence time: about 1 A method for producing hydrogen fluoride using recovered calcium fluoride that can continuously generate 40% or more of the stoichiometric amount of hydrogen fluoride in a temperature range in which decomposition of sulfuric acid does not occur. It is disclosed.

Japanese Patent No. 4316393 Japanese Patent No. 4652948

  However, the method of mixing the recovered calcium fluoride with the conventional hydrogen fluoride production process using fluorite is the main raw material fluorite because the recovered calcium fluoride is porous particles having a low bulk specific gravity. In addition to worsening the fluidity in the furnace, problems such as volatilization of sulfuric acid and increase in impurities due to long-term ignition (about 500 to 600 ° C.) occur.

  In addition, in the method for producing hydrogen fluoride described in Patent Document 2, since the recovered calcium fluoride is in the form of light particles and the manufacturing method is continuous, the recovered calcium fluoride and concentrated sulfuric acid or the like There was a problem that it was difficult to keep the mixing ratio constant (keep mutual contact opportunities uniform), and the separation efficiency (recovery rate) of hydrogen fluoride was not easily increased. Therefore, improvement of a method for recovering and regenerating hydrogen fluoride from recovered calcium fluoride is desired.

  The present invention has been made in view of such circumstances, and a method for separating and recovering hydrogen fluoride, which can efficiently recover hydrogen fluoride from calcium fluoride discharged from various processes, and hydrogen fluoride The purpose is to provide a separation and recovery device.

  In order to achieve the above object, the present invention comprises a cylindrical reaction vessel, a stirring means for stirring the powder in the reaction vessel up and down, a recovery storage tank for storing an absorption liquid for absorbing gas, Gas suction means comprising an ejector and a pump for supplying a negative pressure generating fluid to the ejector, and the reaction vessel is a sealed vertical reaction vessel capable of containing the generated gas. A calcium fluoride-based raw material is filled in a mold-type reaction vessel, and while adding sulfuric acid, these are stirred up and down with a stirring blade of a stirring means, and a fluorine component is removed from the calcium fluoride-based raw material by a hydrogen fluoride-based gas. Gas separation step of separating as follows, and a water-based absorption liquid that absorbs hydrogen fluoride gas is stored in the recovery storage tank, and this water-based absorption liquid is returned to the recovery storage tank via the ejector using a pump. Circulation A step of generating a negative pressure for gas suction in the ejector, and using the negative pressure of the ejector, the hydrogen fluoride gas generated in the vertical reaction vessel is sucked out, and the gas is discharged into the ejector. In the gas recovery step, the mixture is recovered in the recovery storage tank, the aqueous absorption liquid is circulated via the ejector using the pump, and the hydrogen fluoride gas generated in the vertical reaction vessel. And a hydrogen fluoride concentration step of continuously collecting the hydrogen fluoride until the concentration of the hydrogen fluoride-based component absorbed in the aqueous absorbent in the recovery storage tank reaches a predetermined concentration. The method is the first gist.

  The present invention also provides a sealed vertical reaction vessel having a suction port for hydrogen fluoride gas at the top and a discharge port for reacted powder at the bottom, and calcium fluoride in the vertical reaction vessel. A stirring means for stirring the raw material of the system up and down, a recovery storage tank for storing an aqueous absorption liquid for absorbing the hydrogen fluoride gas, and a vertical reaction vessel and a recovery storage tank An ejector, an absorption liquid circulation channel for returning the aqueous absorbent in the recovery storage tank to the storage tank via the ejector, and a pump for pumping the aqueous absorbent in the recovery storage tank to the ejector as a fluid for generating negative pressure And a gas recovery passage that is provided between the suction port of the vertical reaction vessel and the ejector and sucks out the hydrogen fluoride-based gas generated in the vertical reaction vessel. Is the second gist.

  That is, the present inventor has intensively studied to solve the above problems. As a result, by using a vertical (vertical) reaction vessel with excellent powder agitation and mixing properties, separation operation of fluorine-based components (hydrogen fluoride) from calcium fluoride in batch mode instead of continuous type, It has been found that fluorine can be separated with a high yield even in a short reaction time as compared with the conventional continuous separation operation. In addition, the process of recovering fluorine-based components (gas) has also been devised, and there is no moving part in the device part that comes in contact with highly corrosive hydrogen fluoride or hydrofluoric acid (aqueous solution), so that the liquid seal (shaft seal) By using an ejector, pump, etc. that do not require air flow, and the entire flow path is made of resin lining (or made of resin), prevention of leakage of hydrogen fluoride outside the system and recovery process The service life was extended. Combined with the fact that hydrogen fluoride can be separated with high efficiency (energy saving) as described above, the initial equipment investment and running cost of hydrogen fluoride separation and recovery process (equipment) as a whole are at a practical level. I was convinced that it can be reduced up to this point and came to propose the present invention.

  The calcium fluoride-based raw material used in the present invention is called “recovered calcium fluoride” obtained by treating drainage discharged from various processes using a fluorine-based component. There are a solid solid, a sponge obtained by drying the solid, or a powder obtained by pulverizing the solid (including a state in which the powder or particles are secondarily aggregated). In addition, the term “recovery” in the separation and recovery of hydrogen fluoride includes the meaning of recovering the fluorine-based component in the “recovered calcium fluoride” and subjecting it to “regeneration” or “reuse”.

  According to the method for separating and recovering hydrogen fluoride of the present invention, a calcium chloride-based raw material is charged into a sealed vertical reaction vessel capable of containing the generated gas, and sulfuric acid is added to the stirring means. A gas separation step of separating the fluorine component as a hydrogen fluoride gas from the calcium fluoride material by stirring up and down with a stirring blade is provided. As a result, the calcium fluoride-based raw material filled in the vertical reaction vessel is quickly and sufficiently added to the sulfuric acid added because the mixing (reaction) method is a batch type and stirred up and down. (Concentrated sulfuric acid, fuming sulfuric acid, etc.) are mixed and contacted, and separation of fluorine-based components (desorption of hydrogen fluoride) can be completed in a short time. Moreover, the above reaction (separation of the fluorine-based component) does not require high temperatures (250 ° C. or more exceeding the decomposition temperature of sulfuric acid) as in the conventional production method using a rotary kiln, and the low temperature range of 150 ° C. or less. Therefore, it is advantageous from the viewpoint of energy consumed in the reaction (running cost of the process).

  Further, the method for separating and recovering hydrogen fluoride of the present invention circulates the water-based absorbent stored in the recovery storage tank using a pump so as to return to the recovery storage tank via the ejector, and this ejector is used for gas suction. Using the negative pressure of the ejector and the negative pressure of the ejector, the hydrogen fluoride-based gas generated in the vertical reaction vessel is sucked out, and this gas is mixed with the aqueous absorbent in the ejector. A gas recovery step for recovering this mixed liquid in the recovery storage tank, circulation of the water-based absorbent via the ejector using the pump, and recovery of the hydrogen fluoride-based gas generated in the vertical reaction vessel, in batch units, A hydrogen fluoride concentration step that is continuously performed until the concentration of the hydrogen fluoride-based component absorbed in the aqueous absorbent in the recovery storage tank reaches a predetermined concentration.

  By cooperation of these processes, the hydrogen fluoride gas generated in the vertical reaction vessel in the gas separation process can be quickly absorbed into the aqueous absorbent and concentrated. Moreover, since the ejector used for generating the negative pressure has no movable part or shaft seal part in the negative pressure generation mechanism, harmful liquid may leak even through highly corrosive hydrofluoric acid (aqueous solution). Is low. Furthermore, there is an advantage that the hydrogen fluoride-based gas sucked from the vertical reaction vessel is immediately mixed with the water-based absorbent injected in the ejector and absorbed.

  The hydrogen fluoride separation and recovery method of the present invention is based on a synergistic effect of the action and effect obtained from the hydrogen fluoride gas separation step and the action and effect obtained from the hydrogen fluoride gas recovery (concentration) step. Compared with the conventional continuous hydrogen fluoride production equipment, the fluorine component (hydrogen fluoride) in the calcium fluoride raw material can be separated and recovered with significantly shorter reaction time, higher efficiency and lower cost. it can.

  In the method for separating and recovering hydrogen fluoride according to the present invention, the inner surface of the vertical reaction vessel has an inverted conical shape in which the diameter gradually decreases from the upper part toward the lower part, and the stirring blade of the stirring means includes What precesses along the inner surface of the inverted conical shape can be suitably used. Further, at least the inner surface of the vertical reaction vessel that contacts with the hydrogen fluoride, the inner surface of the recovery storage tank, the contact surface with the water-based absorbent in the gas suction means, and the inner surface of the pipe through which the hydrogen fluoride-based gas passes, It is desirable to be covered with a resin lining or resin film having corrosion resistance.

  Further, among the hydrogen fluoride separation and recovery methods of the present invention, in particular, a hydrogen fluoride-based gas generated in the vertical reaction vessel provided with two or more gas recovery units comprising the recovery storage tank and the gas suction means. When the gas recovery unit connected to this vertical reaction vessel is switched and recovered in response to the change in type and concentration, the calcium fluoride-based raw material discharged from various processes is Even if it is a mixed system with different fluorine content, or a mixed system of two or more calcium fluorides, these can be recovered (regenerated) by sorting by type or concentration (purity). it can.

  Next, the hydrogen fluoride separation and recovery apparatus of the present invention used in the separation and recovery method is a sealed type having a suction port for hydrogen fluoride gas at the top and a discharge port for the reacted powder at the bottom. A vertical reaction vessel and a stirring means for stirring the calcium fluoride-based material in the vertical reaction vessel up and down, and the calcium fluoride-based material and sulfuric acid are mixed in the vertical reaction vessel. Thus, hydrogen fluoride gas is generated. With this configuration, as described above, the separation and recovery apparatus of the present invention can quickly and sufficiently add the sulfuric acid (concentrated sulfuric acid, concentrated calcium fluoride-based raw material filled in the vertical reaction vessel). It can be mixed and contacted with fuming sulfuric acid and the like, and the separation of the fluorine-based component (desorption of hydrogen fluoride) can be completed in a short time. Moreover, the above reaction (separation of the fluorine-based component) does not require high temperatures (250 ° C. or more exceeding the decomposition temperature of sulfuric acid) as in the conventional production method using a rotary kiln, and the low temperature range of 150 ° C. or less. It is energy saving because it completes with.

  The separation and recovery device includes a recovery storage tank that stores an aqueous absorption liquid for absorbing the hydrogen fluoride gas, an ejector disposed between the vertical reaction container and the recovery storage tank, An absorption liquid circulation channel for returning the aqueous absorbent in the recovery storage tank to the storage tank through the ejector, a pump for pumping the aqueous absorbent in the recovery storage tank to the ejector as a negative pressure generating fluid, and the vertical A gas recovery passage that is provided between the suction port of the vertical reaction container and the ejector, and sucks out the hydrogen fluoride-based gas generated in the vertical reaction container, and is generated in the vertical reaction container. Hydrogen fluoride gas is sucked using the negative pressure generated by the ejector, and absorbed by the water-based absorbent (the fluid for generating negative pressure in the ejector) that circulates between the recovery storage tank and the ejector. Collect and fix (concentrate) To have.

  With this configuration, the hydrogen fluoride gas generated in the vertical reaction vessel can be quickly and reliably absorbed. In addition, as described above, the ejector used for generating the negative pressure is different from a general suction (vacuum) pump or the like in that the negative pressure generating mechanism has no movable part and a shaft seal (liquid Since there is no sealing part, harmful liquids are prevented from leaking even through highly corrosive hydrofluoric acid (aqueous solution). Furthermore, since the hydrogen fluoride-based gas sucked from the vertical reaction vessel is immediately mixed with and absorbed by the water-based absorbent that passes (circulates) through the ejector, the volume is reduced due to absorption (dissolution). In other words, there is also an effective effect that the negative pressure generated in the ejector naturally increases (negative pressure increases).

  In the hydrogen fluoride separation and recovery apparatus of the present invention, the inner surface of the vertical reaction vessel has an inverted conical shape that gradually decreases in diameter from the upper part toward the lower part. In addition, the one that precesses along the inner surface of the inverted conical shape consists of a calcium fluoride-based raw material (powder) and concentrated sulfuric acid or the like (liquid) stirred by the stirring blade. Then, it flows so as to be concentrated along the inner peripheral surface (inverted conical shape) of the vertical reaction vessel toward the center of the bottom of the vessel. Therefore, the mixing operation (separation operation of hydrogen fluoride gas) of calcium fluoride-based raw material and sulfuric acid or the like using the vertical reaction vessel of the above shape is compared with the case of using a reaction vessel of another shape, Since the chance of contacting these calcium fluoride-based raw materials with concentrated sulfuric acid and the like increases, the reaction can be completed in a shorter time.

  Further, among the hydrogen fluoride separation and recovery apparatus of the present invention, in particular, at least the inner surface of the vertical reaction vessel, the inner surface of the recovery storage tank, the contact surface with the fluid inside the ejector, which is in contact with the hydrogen fluoride, and If the pipe inner surfaces of the absorption liquid circulation channel and gas recovery channel are covered with a corrosion-resistant resin lining or resin film, fluid leaking out of the system due to the corrosion of hydrogen fluoride will occur. It is difficult to generate, and the maintenance cost of the apparatus can be reduced. Further, there is an advantage that the entire apparatus can have a long life.

  In the hydrogen fluoride separation and recovery apparatus of the present invention, two or more gas recovery units including the recovery storage tank and ejector, the absorption liquid circulation flow path, and the pump are provided, and the unit end of the gas recovery flow path is provided at the unit end. The recovery unit switching means for switching the gas recovery unit connected to the gas recovery flow path corresponding to the change in the type and concentration of the hydrogen fluoride gas generated in the vertical reaction vessel is provided. Even if the calcium fluoride-based raw materials discharged from various processes are low in fluorine content, high in impurities, or mixed with two or more calcium fluorides, It is possible to collect (regenerate) by sorting by type or concentration (purity).

It is a figure explaining the structure of the separation-and-recovery apparatus used for the separation-and-recovery method of hydrogen fluoride of 1st Embodiment of this invention. It is a figure which shows the structure of the vertical reaction container used for the said separation-and-recovery apparatus of hydrogen fluoride. It is a figure explaining the structure of the separation-and-recovery apparatus used for the separation-and-recovery method of hydrogen fluoride of 2nd Embodiment of this invention.

  Next, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to this embodiment.

  FIG. 1 is a configuration diagram for explaining the outline of the hydrogen fluoride separation and recovery method according to the first embodiment of the present invention, and FIG. 2 is a schematic configuration diagram of a vertical reaction vessel used in the separation and recovery method. Note that the storage tank and transport piping for raw materials (calcium fluoride, sulfuric acid, etc.) used in the process, the support member (base) and the base for supporting the vertical reaction vessel are not shown.

As shown in FIG. 1, the hydrogen fluoride separation and recovery method according to the first embodiment includes a gas separation step of generating and separating hydrogen fluoride (HF) gas in a vertical reaction vessel R, and a recovery storage tank. The generated hydrogen fluoride gas is sucked out from the vertical reaction vessel R by utilizing the negative pressure generated in the ejector E by the absorption liquid (water: H ₂ O) in T circulating, and this gas is absorbed into the absorption liquid. A gas recovery step of storing in the recovery storage tank T in a state of being mixed (absorbed) with (water). When separating and recovering the hydrogen fluoride gas, a vertical reaction vessel R having excellent stirring properties, which is different from a conventional horizontal kiln furnace, is used. Efficient generation of hydrogen is the greatest feature of the separation and recovery method and separation and recovery apparatus for hydrogen fluoride of the present invention.

  In addition, the absorption liquid in the said collection | recovery storage tank T uses water as a main component, and may contain some components, such as an antifreezing agent.

  The process of separating and collecting the hydrogen fluoride will be described in the order of the apparatus configuration. First, the gas separation process for generating hydrogen fluoride gas is a vertical type as shown in the left side of FIG. 1 and an enlarged view of FIG. The reaction vessel R is used. The vertical reaction vessel R is hermetically sealed so that corrosive hydrogen fluoride (HF) gas can be trapped, and the inner surface 1a of the vessel R extends from the upper portion of the vessel to the lower portion (bottom portion 1b). It has an inverted conical shape that gradually decreases in diameter.

In addition, in the upper part (upper surface) of the container body of the vertical reaction vessel R, a powder inlet 1w for introducing a calcium fluoride-based material (main component CaF ₂ ) as a gas generation material, and a liquid material A liquid inlet 1x for introducing sulfuric acid (H ₂ SO ₄ : concentrated sulfuric acid, fuming sulfuric acid, etc.) and a gas inlet 1y for sucking out the hydrogen fluoride (HF) gas generated inside In the lower part (bottom 1b) of the container main body, residual anhydrous calcium sulfate (CaSO ₄ ) produced by the reaction (generation of HF gas) of the calcium fluoride-based raw material with concentrated sulfuric acid or the like is provided. A powder discharge port 1z for discharging powder [so-called “anhydrous gypsum”] is provided.

  The material of the container body of the vertical reaction container R is not particularly limited, but in the case of a material that is corroded by hydrogen fluoride gas generated inside, the entire inner surface 1a of the container R is a resin lining having corrosion resistance. Or it is preferable to coat with a resin film (film). Furthermore, a heat jacket 3 for keeping the whole container R warm and warm is attached to the outer surface of the container body of the vertical reaction container R (see FIGS. 1 and 2).

  In the inside (inside) of the vertical reaction vessel R, two different rotations are provided for efficiently stirring the calcium fluoride raw material (powder or granule) and sulfuric acid (liquid) as raw materials. A stirring means 2 having a shaft (spinning shaft-revolving shaft) is disposed. This is also one of the features of the hydrogen fluoride separation and recovery apparatus of the present invention.

The stirring means 2, as shown in FIG. 2, the driving of the motor M _1, the vertical reaction vessel angled autonomous rotation along the inner surface 1a of the R (rotation) of stirring blades 2a (spiral screw blade or Helical ribbon blades) and the stirring blade 2a are rotated (spinned), and this is revolved along the inner surface 1a of the container R together with the motor M ₁ (rotating shaft) [precession motion (so-called “slashing motion”). The arm 2b and the rotating shaft 2c are rotated as shown in FIG.

  When the stirring means 2 configured as described above is operated, the calcium fluoride-based material (not shown in FIG. 2) charged into the vertical reaction vessel R is rotated by the rotation of the stirring blade 2a (screw blade) itself. Then, stirring is performed so as to rise along the inner wall (inner surface 1a) from the container bottom 1b to the upper part. In addition, since the entire stirring blade 2a rotates and revolves (precession) along the inner surface 1a of the container, the calcium fluoride raw material and the concentrated liquid introduced from the upper liquid inlet 1x. The sulfuric acid and the like are sufficiently stirred and mixed in a short time.

  The heat jacket 3 arranged on the outer surface of the vertical reaction vessel R circulates the fluid (heat medium such as oil: about 100 to 150 ° C.) heated inside from the medium inlet 3b toward the medium outlet 3a. As a result, the entire container R is kept warm and heated during the stirring and mixing of the calcium fluoride material and concentrated sulfuric acid. The set temperature of the heat jacket 3 is usually 100 to 150 ° C, more preferably 110 to 130 ° C.

  In the hydrogen fluoride separation and recovery method (gas separation step) and apparatus in the present embodiment having the above-described configuration, the configuration of the stirring means 2 and the inner surface 1a of the vertical reaction vessel R have an inverted conical shape. In combination, the mixing of the calcium fluoride-based raw material with concentrated sulfuric acid and the accompanying separation of the fluorine-based components (desorption of hydrogen fluoride gas) can be completed in a shorter time than the conventional method. . In addition, since calcium fluoride and an equivalent amount of concentrated sulfuric acid are mixed evenly and quickly inside the container, the generation efficiency (yield) of hydrogen fluoride (HF) gas by the reaction can be increased.

In addition, the configuration of the vertical reaction vessel R and the stirring means 2 is coupled with the shape of the inner surface 1a (reverse conical shape) of the vessel R to reverse the stirring blade 2a (screw blade) (reverse to the rotation direction). The powder of anhydrous calcium sulfate (CaSO ₄ ) produced after the calcium fluoride raw material and concentrated sulfuric acid react with each other can be easily removed from the powder outlet 1z on the bottom 1b side. There is also an advantage that it can be discharged easily.

  Next, each step of sucking, collecting and concentrating (retaining) the hydrogen fluoride gas generated in the vertical reaction vessel R is shown in the right side of FIG. 1 as a hydrogen fluoride gas recovery storage tank T, ejector E, circulation. Using the pump P and the absorption liquid circulation passage 11 connecting them, and the gas recovery passage 10 for sucking out hydrogen fluoride (HF) gas generated in the vertical reaction vessel R (leading to the ejector E) Configured.

First, the step of sucking the hydrogen fluoride gas uses the circulation pump P to remove the hydrogen fluoride absorbing liquid (in this case, water: H ₂ O) stored in the recovery storage tank T as shown in FIG. Then, it is pumped to the passage fluid inlet 4 side (the upper side in the figure) of the ejector E through the absorption liquid circulation channel 11, and the passage fluid outlet 5 is passed through an orifice (narrowed portion or small hole: not shown) inside the ejector E. A negative pressure for gas suction is generated at the suction fluid inlet 6 that is passed toward the side (the lower side in the drawing) and connected to the side gas recovery flow path 10, and absorption that has flowed out of the passage fluid outlet 5 The liquid is collected in the circulation collection storage tank T through the absorption liquid circulation channel 11. By circulating the absorption liquid (water), a negative pressure for sucking hydrogen fluoride gas can be continuously generated at the suction port (suction fluid inlet 6) of the ejector E.

  Next, in the recovery step of sucking out the hydrogen fluoride (HF) gas, as shown in FIG. 1, the hydrogen fluoride (HF) gas generated in the vertical reaction vessel R is discharged from the upper gas suction port 1y. The gas is sucked out using the negative pressure generated in the ejector E through the gas recovery flow path 10 connected to the gas, and the gas is sucked into the ejector E from the suction fluid inlet 6 of the ejector E that is the source of the negative pressure. The mixed liquid (water + HF) is collected in the collection storage tank T while being sucked and mixed with the absorbing liquid (water) passing through the ejector E through the orifice (not shown).

  The step of generating the negative pressure for gas suction and the step of sucking out the hydrogen fluoride gas and absorbing (mixing) it into the absorption liquid are absorbed by the absorption liquid (water) in the recovery storage tank T. The hydrogen fluoride (HF) component is continuously operated (operated) until the concentration of the hydrogen fluoride (HF) component reaches a predetermined concentration, and the hydrogen fluoride taken out from the vertical reaction vessel R is concentrated in the recovery storage tank T. (Hydrogen fluoride concentration step).

  The ejector E used in each of the above steps has the same structure (shape) as that of a general-purpose one, but is formed using a resin having corrosion resistance against hydrogen fluoride, or a hydrogen fluoride-based one. The surface (mainly the inner surface) of the ejector E that is in contact with the fluid is provided with a resin lining (resin film) that is resistant to hydrogen fluoride as described above. This is also one of the features of the present invention.

  Examples of the resin used for forming or lining the ejector E include synthetic resins such as Teflon (registered trademark) and polyethylene. In addition to the ejector E formed of Teflon (registered trademark) and polyethylene, it can be made of FRP using carbon fiber or organic fiber (glass fiber may be used).

  According to the ejector E having the above configuration, since there is no movable part (shaft seal part) compared to a conventional suction (vacuum) pump or the like, there is less risk of leakage of hydrogen fluoride, and the suction operation can be continued safely. it can. Further, since there is no risk of leakage of the shaft seal or hydrogen fluoride, the maintenance frequency of the ejector E and the entire apparatus is low, and the apparatus can have a long life.

  Further, as shown in FIG. 1, the hydrogen fluoride recovery storage tank T used in each of the above steps includes a recovery tank 7 in which a filler (filler for gas-liquid contact) is disposed, a degassing tank 8, The recovered hydrogen fluoride (HF) is stored in a state of being dissolved in an absorption liquid whose main component is water.

  The recovery storage tank T also has a sealed structure in order to prevent leakage of hydrogen fluoride, and the exhaust gas (including a small amount of hydrogen fluoride) is sent to a dedicated exhaust gas facility (not shown). Similarly to the ejector E, a resin lining (resin film) having corrosion resistance against hydrogen fluoride is applied to the surface (mainly the inner surface) of the recovery tank T in contact with the hydrogen fluoride fluid. It is desirable. Furthermore, you may provide the concentration detection means (illustration omitted) which can measure the hydrogen fluoride density | concentration of the absorption liquid in the said collection | recovery storage tank T (deaeration tank 8).

  On the other hand, the circulation pump P used to circulate the absorption liquid (water) containing hydrogen fluoride must not cause leakage of the absorption water. In this embodiment, the liquid seal (shaft seal) is used. An electromagnetic pump (induction type electromagnetic pump), a diaphragm type pump, a piston type pump, or the like having no part) is preferably used. The type (type) of the pump is not particularly limited, but the internal volume portion and piping portion of the pump that comes into contact with hydrogen fluoride, as well as the rotor, diaphragm, piston, etc., like the ejector E and the recovery storage tank T A resin lining (resin film) having corrosion resistance against hydrogen fluoride is preferable. Further, instead of the electromagnetic pump, there may be used a normal pumping pump configured using a corrosion-resistant metal (alloy) such as Hastelloy (registered trademark).

  In addition, the inner surface of the piping and the connecting portion of the absorption liquid circulation channel 11 connected to the circulation pump P and the gas recovery channel 10 for sucking out hydrogen fluoride (HF) gas are also resistant to hydrogen fluoride. It is desirable to provide a resin lining having corrosive properties. Thus, by making the entire apparatus have a corrosion resistant structure, it is possible to improve the life of the apparatus and the safety for the person (operator) who operates the apparatus.

  According to the hydrogen fluoride separation and recovery method (gas recovery / concentration step) and apparatus configured as described above, hydrogen fluoride can be safely and quickly absorbed into the absorption liquid (water) without leakage. In addition, by continuing to circulate the absorption liquid, the hydrogen fluoride concentration of the absorption liquid is combined with the high generation efficiency of hydrogen fluoride (HF) gas in the gas separation step (vertical reaction vessel R). Can be easily increased to a concentration (about 50 to 60% by weight) that can be taken out as a product (hydrofluoric acid as a recycled product). Therefore, according to the method and apparatus for separating and recovering hydrogen fluoride of the present embodiment, the cost (running cost) required for regeneration (reuse) of hydrogen fluoride can be pushed down to a level according to practical use.

  Finally, the calcium fluoride-based raw material (recovered calcium fluoride) used in the hydrogen fluoride separation and recovery method (regeneration of hydrogen fluoride) and apparatus will be described.

Usually, as described above, the recovered calcium fluoride used in the present embodiment is obtained by draining a waste liquid (treatment liquid) containing hydrogen fluoride, hydrogen silicofluoride or the like at a high concentration. Calcium fluoride (CaF ₂ ), calcium silicofluoride [Ca [SiF ₆ ]: hexafluorosilicic acid (silicic acid) calcium] and the like obtained are dehydrated and dried. This recovered calcium fluoride is once made into a soft water-containing solid such as cake by a dehydration operation using compression or center separation, etc., and further through a drying or pulverization step, etc., and usually the water content is 20% by weight or less. It is made into a lump of sponge-like powder or granules (preferably 10% by weight or less) and is carried out of the process (factory) as industrial waste.

  Among them, as the recovered calcium fluoride used in the present embodiment, one having a purity (content of calcium fluoride with respect to other ash) of usually 70% by weight or more, preferably 80% by weight or more is used. The reason is that if the purity (content rate) of calcium fluoride is too low, the production amount of hydrofluoric acid (regenerated product) per batch decreases, and the production efficiency tends to decrease. Moreover, since the purity of anhydrous gypsum, which is a reaction residue, is lowered, there is an adverse effect that its use and value are lowered.

  Also, if the water content of the recovered calcium fluoride is too high, the water contained in the recovered calcium fluoride will boil when sulfuric acid or the like is added (mixed) together with the generated hydrogen fluoride (HF) gas. The negative pressure of the ejector E enters the circulation line (absorption liquid circulation flow path 11) from the recovery line (gas recovery flow path 10), and hydrogen fluoride of the absorption liquid in the recovery storage tank T (deaeration tank 8). There is a risk of reducing the concentration.

  However, in this case, or when the purity of the calcium fluoride is low, when the fuming sulfuric acid is added to the concentrated sulfuric acid added to the recovered calcium fluoride and used together, the absorption in these “recovery storage tank T (deaeration tank 8)” It is possible to solve the problem that the hydrogen fluoride concentration in the liquid is difficult to increase (the efficiency / yield per batch is poor). The concentration of hydrofluoric acid as a product (recycled product) stored in the recovery storage tank T (target: about 50 to 60% by weight) is a series of separation, recovery and concentration of the hydrogen fluoride. It may be prepared by repeating the process (number of batches).

Next, a second embodiment of the present invention, in which a plurality of types of hydrogen fluoride gases [in this case, hydrogen fluoride (HF) and silicofluoride (H ₂ [SiF ₆ ])] can be separated and recovered. A form is demonstrated.

FIG. 3 is a configuration diagram for explaining the outline of the method for separating and recovering hydrogen fluoride according to the second embodiment of the present invention. Note that the support member (base) and the base for supporting the vertical reaction vessel, the raw material storage tank and the transportation piping, and the exhaust and drainage systems provided in the respective recovery storage tanks T ₁ and T ₂ are not shown. Moreover, the same reference numerals are given to the constituent members having the same functions as those in the first embodiment, and detailed description thereof will be omitted.

The hydrogen fluoride separation and recovery method (apparatus) according to the second embodiment uses calcium silicofluoride [Ca [SiF ₆ ]: hexafluorosilicic acid (silicate) calcium] as a calcium fluoride-based raw material, The hydrogen silicofluoride (H ₂ [SiF ₆ ]) and the hydrogen fluoride (HF) generated by mixing these are separated and collected in two stages.

The apparatus used in the hydrogen fluoride separation (separation) recovery method is different from the first embodiment in that two sets of gas recovery steps (ejector E ₁ , recovery storage tank T ₁ and circulation as shown in FIG. 3). the first gas recovery step consisting pump P _1, and is 2 units) comprising the point of the ejector E ₂ and the collection tank T ₂ and a second gas recovery step consisting circulation pump P _2. These two sets of gas recovery steps are connected in parallel so as to branch into two from the end of the gas recovery flow path 10 for sucking out the hydrogen fluoride gas generated in the vertical reaction vessel R (leading to the ejector). and, in the branch point, the flow control valve V _1, the switching valve V ₂ for switching the flow-down destination of the hydrogen fluoride gas flowing in the gas recovery channel 10 tubes _(three-way cock: recovery unit switching means) are disposed Has been.

Incidentally, in the gas recovery channel 10 'in the first gas recovery step (shown above) are not in the second gas recovering step lower, clogging prevention means 9 of the ejector E _{1 (orifice)} is, ejector E ₁ [The second gas recovery step (the lower side in the drawing) has the same configuration as the gas recovery step of the first embodiment. ]. Further, a concentration detection means (not shown) for measuring (monitoring) the concentration of the hydrogen fluoride-based gas is disposed in the gas recovery flow path 10 immediately after the vertical reaction vessel R (gas inlet 1y), The component (main component) of the gas flowing in the gas recovery channel 10 can be measured in real time (on time).

The hydrogen fluoride separation / recovery method using the separation (separation) recovery device having the above-described configuration also begins with the calcium silicofluoride from the powder inlet 1w in the reaction vessel R having the inner surface 1a having an inverted conical shape. (Ca [SiF ₆ ]) powder is charged, and concentrated sulfuric acid (or a mixture of concentrated sulfuric acid and fuming sulfuric acid) is added from the liquid charging port 1x while stirring with the stirring means 2 having the stirring blade 2a. As a result, a hydrogen fluoride-based gas is generated.

In this reaction (mixing of calcium silicofluoride and concentrated sulfuric acid), according to the knowledge of the present inventor, hydrogen silicofluoride (H ₂ [SiF ₆ ]) is preferentially high in the first half immediately after stirring and mixing. It has been found that hydrogen fluoride (HF) is subsequently generated at a high concentration as the main component of the gas after it has been generated and almost completely finished. Further, the inventor has empirically known that the hydrogen silicofluoride gas is more easily precipitated (crystallized) than the hydrogen fluoride gas, and the orifice of the ejector is easily clogged.

Therefore, in the hydrogen fluoride separation and recovery method of the second embodiment, first, the first gas recovery step (including the clogging prevention means 9) at the end of the gas recovery flow path 10 (the switching valve V ₂ ) ( shown above) is connected, it precipitated easily silicic hydrogen fluoride clogged with (H ₂ [SiF _6]) gas, via the ejector E _1, the recovery tank 7 for recovery storage tank T ₁ 'and the deaeration tank 8 It is collected and concentrated.

Subsequently, if the switching of the component of the gas flowing in the gas recovery passage 10 is confirmed by the hydrogen fluoride gas concentration detecting means (not shown), a switching valve (terminal valve) at the end of the gas recovery passage 10 ( Three-way cock) The connection destination of V ₂ is switched, and the gas generated in the vertical reaction vessel R [at this time, hydrogen fluoride (HF) gas similar to that of the first embodiment] is the second lower side in the drawing. Flowed towards the gas recovery process. Thus, the hydrogen fluoride generated is recovered and concentrated in the collection tank 7 and degassing tank 8 of the collection tank T _2.

  Then, generation of hydrogen fluoride gas by the above vertical reaction vessel R-switching of gas recovery process (first ← → second) by monitoring gas components-recovery / concentration of hydrogen fluoride gas in batch units By repeating, the hydrogen silicofluoride and hydrogen fluoride generated from the calcium silicofluoride can be efficiently recovered while being separated.

  Note that the concentration detecting means for measuring (monitoring) the gas concentration and the clogging preventing means 9 may be attached to the second gas recovery step having the same configuration as that of the first embodiment, respectively. You may arrange | position in the middle of the gas collection | recovery flow path 10 before performing.

  Next, examples (demonstration tests) performed using the hydrogen fluoride separation and recovery apparatus (FIG. 1) of the present invention will be described.

[Example 1]
<Raw material: recovered calcium fluoride>
In a semiconductor manufacturing factory or the like, calcium hydroxide was added to the discharged liquid containing hydrogen fluoride, and a soft solid having a water content of 33% by weight was obtained by centrifugal dehydration and compression. Then, it was dried by heating and pulverized to obtain recovered calcium fluoride having a water content of 10% by weight (granularity in which calcium fluoride was secondarily aggregated: average particle size 5.4 μm, particle size distribution 1 to 50 μm). . The components of the recovered calcium fluoride (solid content excluding moisture) are 82.5% by weight of calcium fluoride, 10% by weight of calcium sulfate, 2% by weight of aluminum oxide, 1% by weight of silicon oxide, and other ash content. It was 5% by weight. Further, the particle size (distribution) of the recovered calcium fluoride is measured by a particle size measuring method defined in JIS M 8100 “Powder mixture-General rules of sampling method”. Rate) according to the moisture content (105 ° C x 5 hours after absolute drying) specified in JIS K 1468-1 “Method for analyzing fluorite for hydrofluoric acid (Part 1 Determination of moisture content of lot)” It is measured.

<Hydrogen fluoride separation process>
100 kg of the recovered calcium fluoride (water content 10% by weight) is put into a vertical reaction vessel R (see FIG. 1), and oil heated to 110 ° C. is circulated through the heat jacket 3 surrounding the vessel R, Got ready. Next, while stirring the recovered calcium fluoride (powder) by operating the stirring means 2, a prescribed amount (molar equivalent) of concentrated sulfuric acid is added to the charged calcium fluoride (net 74.25 kg) for 30 minutes. Then, it was slowly charged (added) into the vertical reaction vessel R at a constant flow rate. Stirring was continued after completion of the addition of concentrated sulfuric acid, and the final stirring time was 2 hours from the start of the addition of concentrated sulfuric acid until the generation of hydrogen fluoride gas was completed (1 batch = 2 hours). ).

<Hydrogen fluoride recovery process>
The gas generated in the vertical reaction vessel R over the entire operation time (2 hours) of the one batch using the negative pressure generated in the ejector E by operating the circulation pump P simultaneously with the start of the addition of the concentrated sulfuric acid. (Mainly hydrogen fluoride) was absorbed in the absorption liquid (water: 30 kg) and recovered in the recovery storage tank T. After 2 hours of 1 batch, the remaining gypsum in the vertical reaction vessel R is extracted from the powder discharge port 1z at the bottom of the vessel R, and the reaction vessel R is emptied to prepare for the next (next batch). went.

<Hydrogen fluoride concentration process>
One cycle (one batch) of charging the calcium fluoride, charging the sulfuric acid, and recovering the hydrogen fluoride was repeated three times to obtain a regenerated hydrofluoric acid (aqueous solution) having a hydrogen fluoride concentration of 56% by weight.

  The concentration of hydrogen fluoride was 35.5% by weight at the end of the first batch and 48.8% by weight at the end of the second batch. The hydrofluoric acid having a concentration of 56% by weight (product shipment standard: 55% by weight or more) obtained in the third batch is industrially sufficient and can be reused. Further, when the gypsum extracted from the lower part of the vertical reaction vessel R was analyzed (fluorescence X-ray analysis), it was found that no fluorine remained and 97% by weight of the gypsum was industrially usable anhydrous gypsum. Incidentally, the regenerated hydrofluoric acid having a concentration of 56% by weight was used for etching glass, but it could be used without any problem.

[Example 2]
<Raw material: recovered calcium fluoride>
In the incineration (disposal) process of fluorine-containing compounds, calcium hydroxide is added to the drained liquid containing hydrogen fluoride, and a soft solid with a moisture content of 33% by weight is obtained by centrifugal dehydration and compression. It was. Then, it was dried by heating and pulverized to obtain recovered calcium fluoride having a water content of 5% by weight (particles in which calcium fluoride was secondarily aggregated: average particle size 10.7 μm, particle size distribution 1 to 100 μm). . The components of the recovered calcium fluoride (solid content excluding water) were 94% by weight of calcium fluoride, 1% by weight of calcium sulfate, 1% by weight of silicon oxide, and 4% by weight of other ash. The particle diameter (distribution) and water content (moisture content) of the recovered calcium fluoride are, as described above, JIS M 8100 “Powder mixture-General sampling method” and JIS K 1468-1 “Hydrogen fluoride”. It is measured by “Analysis method for acid fluorite”.

<Hydrogen fluoride separation process>
100 kg of the recovered calcium fluoride (water content 5% by weight) is put into a vertical reaction vessel R (see FIG. 1), and oil heated to 110 ° C. is circulated through the heat jacket 3 surrounding the vessel R, Got ready. Next, while stirring the recovered calcium fluoride (powder) by operating the stirring means 2, a specified amount (molar equivalent) of concentrated sulfuric acid is added to the charged calcium fluoride (net 89.3 kg) for 30 minutes. Then, it was slowly charged (added) into the vertical reaction vessel R at a constant flow rate. Stirring was continued after completion of the addition of concentrated sulfuric acid, and the final stirring time was 2 hours from the start of the addition of concentrated sulfuric acid until the generation of hydrogen fluoride gas was completed (1 batch = 2 hours). ).

<Hydrogen fluoride recovery process>
The gas generated in the vertical reaction vessel R over the entire operation time (2 hours) of the one batch using the negative pressure generated in the ejector E by operating the circulation pump P simultaneously with the start of the addition of the concentrated sulfuric acid. (Mainly hydrogen fluoride) was absorbed in the absorption liquid (water: 30 kg) and recovered in the recovery storage tank T. After 2 hours of 1 batch, the remaining gypsum in the vertical reaction vessel R is extracted from the powder discharge port 1z at the bottom of the vessel R, and the reaction vessel R is emptied to prepare for the next (next batch). went.

<Hydrogen fluoride concentration process>
One cycle (1 batch) of the above calcium fluoride input, sulfuric acid input and hydrogen fluoride recovery was repeated three times to obtain regenerated hydrofluoric acid (aqueous solution) having a hydrogen fluoride concentration of 64.8% by weight. It was.

  The concentration of hydrogen fluoride was 41.4% by weight at the end of the first batch and 56.8% by weight at the end of the second batch. The hydrofluoric acid having a concentration of 64.8% by weight (product shipment standard: 55% by weight or more) obtained in the third batch is industrially sufficient and can be reused. Further, when the gypsum extracted from the lower part of the vertical reaction vessel R was analyzed (fluorescence X-ray analysis), it was found that no fluorine remained and 97% by weight of the gypsum was industrially usable anhydrous gypsum. Incidentally, the regenerated hydrofluoric acid having a concentration of 64.8% by weight could also be used for glass etching without problems.

  According to the hydrogen fluoride separation and recovery method and the hydrogen fluoride separation and recovery apparatus of the present invention, hydrogen fluoride can be efficiently recovered from calcium fluoride discharged from various processes in a safe and maintenance-free manner. Can do. Therefore, a hydrogen fluoride recycling system can be put to practical use at a sustainable low running cost by adding to a process or factory for discharging waste liquid and waste containing fluorine.

2 Stirring means 2a Stirring blade E Ejector P Pump R Vertical reaction vessel T Collection storage tank

Claims (8)

  A cylindrical reaction vessel, a stirring means for stirring the powder in the reaction vessel up and down, a recovery storage tank for storing an absorbing liquid for absorbing gas, an ejector, and a fluid for generating negative pressure are supplied to this And a gas suction means comprising a pump that performs the above operation, and the reaction vessel is a sealed vertical reaction vessel that can contain the generated gas, and a calcium fluoride-based raw material is placed in the vertical reaction vessel. A gas separation step in which the fluorine component is separated as a hydrogen fluoride gas from the calcium fluoride raw material by stirring up and down with a stirring blade of a stirring means while adding and adding sulfuric acid, and in the recovery storage tank Aqueous absorption liquid that absorbs hydrogen fluoride gas is stored, and this aqueous absorption liquid is circulated back to the recovery storage tank via the ejector using a pump, and the negative pressure for gas suction is returned to the ejector. And using the negative pressure of the ejector, the hydrogen fluoride gas generated in the vertical reaction vessel is sucked out, and the gas is mixed with the aqueous absorbent in the ejector. A gas recovery step for recovering the liquid in the recovery storage tank, circulation of the water-based absorbent via the ejector using the pump, and recovery of the hydrogen fluoride-based gas generated in the vertical reaction vessel. And a hydrogen fluoride concentration step that is continuously performed until the concentration of the hydrogen fluoride-based component absorbed in the absorption liquid reaches a predetermined concentration.   The inner surface of the vertical reaction vessel has an inverted cone shape that gradually decreases in diameter from the upper part toward the lower part, and the stirring blade of the stirring means precesses along the inner circumferential surface of the inverted cone shape. The method for separating and recovering hydrogen fluoride according to claim 1.   At least the inner surface of the vertical reaction vessel in contact with the hydrogen fluoride, the inner surface of the recovery storage tank, the contact surface with the water-based absorbent in the gas suction means, and the inner surface of the pipe through which the hydrogen fluoride-based gas passes are corrosion resistant. The method for separating and recovering hydrogen fluoride according to claim 1 or 2, wherein the method is covered with a resin lining or resin film having a property.   Two or more gas recovery units consisting of the recovery storage tank and gas suction means are provided and connected to the vertical reaction vessel according to changes in the type and concentration of the hydrogen fluoride gas generated in the vertical reaction vessel. The method for separating and recovering hydrogen fluoride according to any one of claims 1 to 3, wherein the gas recovery unit is switched for recovery.   A closed vertical reaction vessel having a suction port for hydrogen fluoride gas at the top and a discharge port for reacted powder at the bottom, and a calcium fluoride material in the vertical reaction vessel up and down Stirring means for stirring, a recovery storage tank for storing an aqueous absorbing liquid for absorbing the hydrogen fluoride gas, an ejector disposed between the vertical reaction container and the recovery storage tank, and the recovery storage tank An absorption liquid circulation channel for returning the aqueous absorbent in the storage tank through the ejector, a pump for pumping the aqueous absorbent in the recovery storage tank to the ejector as a negative pressure generating fluid, and the vertical reaction A hydrogen fluoride separation and recovery device, comprising: a gas recovery channel that is provided between a suction port of the container and the ejector and sucks out a hydrogen fluoride-based gas generated in the vertical reaction container.   The inner surface of the vertical reaction vessel has an inverted conical shape that gradually decreases in diameter from the upper part to the lower part, and the stirring blades of the stirring means precess along the inner peripheral surface of the inverted conical shape. The apparatus for separating and recovering hydrogen fluoride according to claim 5.   At least the inner surface of the vertical reaction vessel, the inner surface of the recovery tank, the contact surface with the fluid inside the ejector, and the inner surfaces of the absorption liquid circulation channel and the gas recovery channel, which are in contact with the above hydrogen fluoride, are corrosion resistant. The hydrogen fluoride separation and recovery device according to claim 5 or 6, wherein the hydrogen fluoride separation and recovery device is covered with a resin lining or a resin film.   Two or more gas recovery units comprising the recovery storage tank and ejector, absorption liquid circulation channel, and pump are provided, and the type of hydrogen fluoride gas generated in the vertical reaction vessel at the unit side end of the gas recovery channel Separation of hydrogen fluoride according to any one of claims 5 to 7, further comprising recovery unit switching means for switching a gas recovery unit connected to the gas recovery flow path in response to a change in concentration. Recovery device.

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