JP5133029B2 - Method for removing inorganic particles in liquid - Google Patents

Description

  The present invention relates to a method for removing inorganic particles contained in a liquid that is phase-separable from water from the liquid.

A method in which a resin (waste plastic, etc.) is brought into contact with high-temperature inorganic particles (sand, etc.), the resin is thermally decomposed, and a gas containing the generated decomposition products is cooled to recover a liquid (monomer, oil, etc.) It has been known.
However, since the recovered liquid contains inorganic particles (including crushed pieces of inorganic particles), when the liquid is purified by distillation as it is, the inorganic particles accumulate in the distillation tower. Or inorganic particles are mixed into the purified product.

As a method for solving this problem, the following method has been proposed.
(1) Solid between a pyrolysis means that thermally decomposes waste plastic by adding high-temperature sand to waste plastic and a gas-liquid separation means that separates high-boiling oil contained in the pyrolysis gas from low-boiling components. A method of providing a minute removing means (Patent Document 1).

  However, in the method (1), the fine solids (sand crushed pieces) contained in the pyrolysis gas trapped in the solid content removing means (packing material) are converted into high-boiling oil obtained by the gas-liquid separation means. This is a method for preventing clogging of the solid content removing means (filler) by washing off. The crushed pieces of sand that cannot be captured by the solid content removing means are more easily brought into the subsequent process than the gas-liquid separating means, and the liquid recovered by cooling the pyrolysis gas contains a lot of crushed pieces of sand. However, the problem has not been solved.

In addition, the following method is also known as a method for removing impurities contained in waste oil.
(2) A method in which a specific linear low polymer is dissolved in a lipophilic organic solvent and added to waste oil to agglomerate or solidify and remove impurities (Patent Document 2).
(3) Add one or more selected from saturated or unsaturated monohydric, divalent, trivalent or higher polyhydric alcohols and polyalkylene glycols, and then add an amide bond or urea bond in the main chain. Alternatively, a method of adding a lipophilic organic solvent solution of a linear polymer having a low degree of polymerization having a urethane bond, or adding both simultaneously (Patent Document 3). Examples of impurities include metal powders, resins, pigments, and dyes.

However, the methods (2) and (3) require a step of separating the aggregated or coagulated impurities by a method such as filtration or centrifugation. During the separation, waste oil may be lost. In addition, extra labor such as machine maintenance is required. Furthermore, when the treated waste oil is refined in order to newly add an organic solvent, it is expected that the load on the distillation column will increase.
JP 2000-336203 A JP-A-49-84974 Japanese Patent Laid-Open No. 50-22006

  The present invention provides a method capable of sufficiently removing inorganic particles contained in a liquid that is phase-separable from water from the liquid.

The method for removing inorganic particles in a liquid according to the present invention is a method for removing inorganic particles contained in a liquid that can be phase-separated from water from a liquid, wherein a liquid containing inorganic particles and a substance capable of aggregating the inorganic particles The inorganic particles are removed from the liquid by mixing the water to be contained and then separating the phase into a liquid phase and an aqueous phase.

Substances which are capable of aggregating the pre-inorganic particles is preferably an amine.
The amine is preferably triethylenetetramine.
The inorganic particles are preferably sand.

The liquid containing inorganic particles is preferably a liquid that is phase-separable from water recovered by cooling a gas containing a decomposition product obtained by thermally decomposing a resin in the presence of the inorganic particles. .
The liquid containing the inorganic particles is preferably a liquid after the collected liquid is further passed through a filter.

  According to the method for removing inorganic particles in a liquid of the present invention, inorganic particles contained in a liquid that can be phase-separated from water can be sufficiently removed from the liquid.

  In this specification, (meth) acrylic acid means acrylic acid or methacrylic acid.

  The present invention is a method for removing inorganic particles contained in a liquid that can be phase-separated from water from the liquid, and the liquid containing the inorganic particles and water are mixed and then separated into a liquid phase and an aqueous phase. To remove the inorganic particles from the liquid.

  The liquid capable of phase separation with water refers to a liquid having a solubility in water at 20 ° C. of 10% by mass or less. If the solubility in water is 10% by mass or less, the liquid and water can be phase-separated after mixing the liquid and water.

The liquid preferably has a specific gravity at 20 ° C. smaller than that of water. If the specific gravity is smaller than water, when the liquid and water are phase-separated, the liquid phase is above the water phase, so that the inorganic particles that have moved to the water phase do not settle and return to the liquid phase. The specific gravity of the liquid is preferably 0.98 or less. The specific gravity of the liquid is obtained from the following formula.
Specific gravity of liquid = liquid density / water density.

  Although it does not specifically limit as this liquid, For example, the liquid which can be phase-separated with the water collect | recovered by cooling the gas containing the decomposition product obtained by thermally decomposing resin in presence of an inorganic particle is mentioned. The liquid after the collected liquid is further passed through a filter is preferable. The liquid after passing through the filter contains crushed pieces of inorganic particles that are difficult to remove by the conventional method. However, according to the method of the present invention, the crushed pieces can be sufficiently removed.

  Examples of the resin include acrylic resin, olefin resin (polyethylene, polypropylene, etc.), polyvinyl chloride, polyester (polyethylene terephthalate, etc.), polycarbonate, polystyrene, and the like. It is meaningful to apply the method of the present invention to an acrylic resin because it is easy to recover the monomer by depolymerization.

  In the case of an acrylic resin, the liquid recovered by cooling the gas containing the decomposition product obtained by thermally decomposing the resin is a liquid containing (meth) acrylic acid ester, etc., and in the case of an olefin resin In the case of polyethylene terephthalate, it is a liquid containing terephthalic acid, in the case of polycarbonate, it is a liquid containing phenols, and in the case of polystyrene, it is a liquid containing styrene.

  Examples of the (meth) acrylic acid ester include methyl methacrylate (solubility in water at 20 ° C .: 1.59% by mass, specific gravity at 20 ° C .: 0.94), ethyl methacrylate (solubility in water at 20 ° C .: 0 .46 mass%, specific gravity at 20 ° C .: 0.91), butyl methacrylate (solubility in water at 20 ° C .: 0.6 mass%, specific gravity at 20 ° C .: 0.90), methyl acrylate (at 20 ° C. Solubility in water: 6.00% by mass, specific gravity at 20 ° C .: 0.95), ethyl acrylate (solubility in water at 20 ° C .: 1.5% by mass, specific gravity at 20 ° C .: 0.92), acrylic Acid butyl (solubility in water at 20 ° C .: 2.00 mass%, specific gravity at 20 ° C .: 0.92) and the like.

  Examples of inorganic particles include sand, ceramic particles, metal particles, metal oxide particles, metal hydroxide particles, metal halide particles, and the like, which are easily available and inexpensive, and inert to resins and liquids. Therefore, sand is preferable.

As the inorganic particles, particles having a specific gravity at 20 ° C. larger than that of water are preferable. If the specific gravity is greater than that of water, when the liquid and water are phase-separated, the inorganic particles that have moved to the water phase will not settle and return to the liquid phase. The specific gravity of the inorganic particles is obtained from the following formula.
Specific gravity of inorganic particles = true density of inorganic particles / density of water.

  It is preferable that water contains the substance which can aggregate an inorganic particle from the point which improves the removal effect of an inorganic particle. By aggregating the inorganic particles, the inorganic particles easily move from the liquid phase to the aqueous phase.

A water-soluble substance is used as the substance capable of aggregating the inorganic particles.
Examples of the substance capable of aggregating the inorganic particles include a polymer-based flocculant, an inorganic flocculant, and an amine-based flocculant.

Examples of the polymer flocculant include an anionic flocculant, a cationic flocculant, and a nonionic flocculant.
Examples of the anionic polymer flocculant include sodium polyacrylate.
Examples of the cationic polymer flocculant include polydimethylaminoethyl methacrylate.
Examples of nonionic polymer flocculants include polyacrylamide.

  Examples of the inorganic flocculant include polyaluminum chloride, aluminum sulfate, ferric chloride, ferrous sulfate, sodium hydroxide, and iron sulfide.

Examples of amine-based flocculants include monoamines and polyvalent amines.
Examples of the monoamine include ethylamine, diethylamine, triethylamine, ethanolamine, diethanolamine, and triethanolamine.
Examples of the polyvalent amine include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine.

  The substance capable of aggregating the inorganic particles is preferably an amine-based aggregating agent (hereinafter, also simply referred to as “amine”) because of its high solubility in water and a high removal effect of the inorganic particles. Ethylenetetramine is particularly preferred. Moreover, when an amine is used, there exists an effect by which the acid component contained in a liquid is removed by neutralization.

  The mass ratio of amine to inorganic particles (amine / inorganic particles) is preferably 1 to 100. If the number of amine / inorganic particles is 1 or more, the effect of removing inorganic particles is sufficiently exhibited. If the amine / inorganic particles are 100 or less, the amount of amine contained in the liquid after the inorganic particles are removed can be suppressed.

  The mass ratio of water containing amine and liquid containing inorganic particles ((amine + water) / (inorganic particles + liquid)) is preferably 0.05 to 1.0. If (amine + water) / (inorganic particles + liquid) is 0.05 or more, the effect of removing inorganic particles is sufficiently exhibited. If (amine + water) / (inorganic particles + liquid) is 1.0 or less, the amount of water contained in the liquid after the inorganic particles are removed can be suppressed.

  Hereinafter, taking a method of recovering (meth) acrylic acid ester from acrylic resin using sand as inorganic particles as an example, a method for removing sand in a liquid containing (meth) acrylic acid ester will be specifically described.

  FIG. 1 is a schematic view showing an example of an apparatus for recovering (meth) acrylic acid ester from an acrylic resin. The apparatus includes a decomposition tank 10 for thermally decomposing an acrylic resin by bringing the acrylic resin into contact with high-temperature sand, a resin supply device 12 for supplying the acrylic resin to the decomposition tank 10, and a high temperature for the decomposition tank 10. From a sand supply device 14 for supplying sand, a sand discharge device 16 for discharging sand from the bottom of the decomposition tank 10, a sand heating device 18 for heating sand, and a gas containing decomposition products discharged from the decomposition tank 10. The cyclone 20 for removing sand, the first cooling device 22 for recovering the liquid by cooling the gas discharged from the cyclone 20, and the liquid discharged by cooling the gas discharged from the first cooling device 22 The second cooling device 24, the mist separator 26 that collects the liquid mist contained in the gas discharged from the second cooling device 24, the first cooling device 22, the second cooling device 24, and the mist separator 26 A third cooling device 28 that cools a part of the recovered liquid, and a first filter 30 that filters the remaining liquid recovered by the first cooling device 22, the second cooling device 24, and the mist separator 26. A container 32 for storing an aqueous solution in which water or a substance capable of aggregating inorganic particles is stored, a mixing tank 34 for mixing the liquid discharged from the first filter 30 with water or an aqueous solution, and a mixed liquid of the mixing tank 34 From the phase separation tank 36 for phase-separating the liquid phase 102 and the aqueous phase 104, the first distillation column 38 for distilling the liquid discharged from the phase separation tank 36, and the bottom of the first distillation column 38. The second distillation column 40 for distilling the liquid to be discharged, the gas discharged from the top of the second distillation column 40 as a liquid, the second filter 42 for filtering the liquid, and the decomposition tank 10 Fluidization to supply fluidized gas to the bottom of the Body supply flow path 44, sand supply flow path 46 for supplying sand heated by the sand heating device 18 to the sand heating device 18, and sand discharged from the bottom of the decomposition tank 10 by the sand discharge device 16 18, the first gas flow path 50 for supplying the gas containing the decomposition products discharged from the decomposition tank 10 to the cyclone 20, and the gas discharged from the cyclone 20 to the first cooling device 22. The second gas flow path 52 to be supplied to the second gas flow path, the third gas flow path 54 to supply the gas discharged from the first cooling apparatus 22 to the second cooling apparatus 24, and the second cooling apparatus 24 to be discharged. A fourth gas flow path 56 for supplying the gas to be supplied to the mist separator 26, a gas discharge flow path 58 for discharging the gas that has passed through the mist separator 26, the first cooling device 22, the second cooling device 24, and Mist separator 2 6, a first liquid channel 60 that supplies the liquid collected in 6 to the first filter 30, and a branch from the middle of the first liquid channel 60, and a part of the liquid is supplied to the third cooling device 28. The liquid branching channel 62 that performs cooling, the cooling liquid channel 64 that supplies the liquid cooled by the third cooling device 28 to the first cooling device 22, and the liquid that has passed through the first filter 30 is mixed into the mixing tank 34. A second liquid channel 66 for supplying water, a water supply channel 68 for supplying an aqueous solution dissolving a substance capable of aggregating water or inorganic particles from the container 32 to the mixing tank 34, and a phase separation tank 36 from the mixing tank 34. A third liquid flow path 70 for sending the mixed liquid to the waste water flow path 72 for discharging the waste water from the phase separation tank 36, and a liquid for discharging the liquid discharged from the phase separation tank 36 to the first distillation column 38. 4 and the low-boiling point impurities from the top of the first distillation column 38 are discharged. A low-boiling-point impurity discharge channel 76, a fifth liquid channel 78 for supplying the liquid discharged from the bottom of the first distillation column 38 to the second distillation column 40, and the second distillation column 40 The high-boiling-point impurity discharge flow path 80 for discharging high-boiling-point impurities from the bottom of the column and the gas discharged from the top of the second distillation column 40 are converted into a liquid, and then the liquid is supplied to the second filter 42. A sixth liquid channel 82 and a liquid recovery channel 84 that recovers the liquid ((meth) acrylic acid ester) that has passed through the second filter 42 are provided.

The decomposition tank 10 includes a main body 86, a conical dispersion plate 88 that is provided at a lower portion of the main body 86 and gradually decreases in diameter toward the bottom, and a flow of sand that is formed on the dispersion plate 88. A layer 90, a stirring device 92 having a stirring blade for stirring the fluidized bed 90, a resin supply port 94 formed on a side surface of the main body 86 in contact with the lower part of the fluidized bed 90, and connected to the resin supply device 12; A sand supply port 96 connected to the sand supply device 14 and a sand discharge port 98 connected to the sand discharge device 16 formed at the top of the conical shape of the dispersion plate 88; A fluidizing gas chamber 100 for uniformly feeding the fluidizing gas supplied to the bottom of the decomposition tank 10 to the entire surface of the dispersion plate 88 is provided.
Examples of the dispersion plate 88 include a perforated plate, a slit plate, a mesh plate, and a sintered filter. A nozzle, a nozzle with a cap, or the like may be used instead of the dispersion plate.
Note that the stirrer 92 is not necessarily provided as long as the fluidized bed 90 is sufficiently fluidized by the fluidized gas blown from the dispersion plate 88.

As the resin supply apparatus 12, the sand supply apparatus 14, and the sand discharge apparatus 16, a uniaxial screw is mentioned.
An example of the sand heating device 18 is a heating furnace. Examples of the fuel for the heating furnace include heavy oil, light oil, kerosene, and liquid recovered by thermal decomposition of acrylic resin.

The first cooling device 22 is a scrubber. As the first cooling device 22, a tube condenser, a plate condenser, a spray tower, or the like may be used.
The second cooling device 24 is a tubular condenser. As the second cooling device 24, a plate condenser, a scrubber, a spray tower, or the like may be used.
The third cooling device 28 is a tubular heat exchanger. As the third cooling device 28, a plate-type capacitor or the like may be used.

Examples of the first filter 30 include a wind filter, a nonwoven fabric filter, a sintered filter, a plastic foam filter, and a metal mesh filter. The pore size (nominal) of the first filter 30 is preferably 1 to 2000 μm.
Examples of the second filter 42 include a wind filter, a nonwoven fabric filter, a sintered filter, a plastic foam filter, and a metal mesh filter. The pore diameter (nominal) of the second filter 42 is preferably 0.1 to 25 μm.

  Examples of the first distillation tower 38 and the second distillation tower 40 include a plate tower, a perforated plate tower, a bubble bell tower, and a packed tower. Connected to the top of the distillation column is a condenser (not shown) that cools the gas discharged from the top of the column to make it liquid. In addition, a reboiler (not shown) that heats the liquid discharged from the bottom of the distillation tower and turns it into a gas is connected to the bottom of the distillation tower.

Recovery of the (meth) acrylic acid ester from the acrylic resin using the apparatus is performed through the following steps (a) to (d).
(A) A step of thermally decomposing an acrylic resin to obtain a gas containing a decomposition product.
(B) A step of cooling the gas containing the decomposition product to obtain a liquid containing the decomposition product.
(C) A step of removing sand contained in the liquid.
(D) A step of distilling the liquid to recover the (meth) acrylic acid ester.

Step (a):
The high-temperature sand heated by the sand heating device 18 is supplied to the sand supply device 14 via the sand supply flow path 46, and is connected to the sand supply port 96 of the decomposition vessel 10 to the fluidized bed of the decomposition vessel 10. 90 is continuously supplied at a predetermined speed. At the same time, the sand of the fluidized bed 90 of the decomposition tank 10 is continuously discharged at a predetermined speed from the sand discharge device 16 connected to the sand discharge port 98 at the bottom of the decomposition tank 10, and is transferred to the sand heating device 18 by the conveyor 48. Transport.
The fluidizing gas from the fluidizing gas supply channel 44 is supplied to the fluidizing gas chamber 100 at the bottom of the decomposition tank 10.
The fluidized bed 90 of the decomposition tank 10 is fluidized by a fluidizing gas blown from the dispersion plate 88 and a fluidizing gas blown from the dispersion plate 88.

Acrylic resin pulverized pieces crushed by a pulverization apparatus (not shown) are supplied to the resin supply apparatus 12 connected to the resin supply port 94 of the decomposition tank 10, and are transferred from the resin supply apparatus 12 to the fluidized bed 90 of the decomposition tank 10. Supply continuously at a predetermined supply rate.
Since the acrylic resin has a specific gravity smaller than that of sand, it rises in the fluidized bed 90 together with the fluidized gas. At this time, the acrylic resin comes into contact with hot sand and is thermally decomposed.
The decomposition product generated by the thermal decomposition of the acrylic resin is discharged from the decomposition tank 10 together with the fluidized gas.
A gas containing a decomposition product discharged from the gas phase part of the decomposition tank 10 is supplied to the cyclone 20 via the first gas flow path 50, and relatively large sand contained in the gas is removed by the cyclone 20.

  The temperature of the fluidized bed 90 is preferably 350 to 500 ° C. When the temperature of the fluidized bed 90 is 350 ° C. or higher, the thermal decomposition rate of the acrylic resin is increased. When the temperature of the fluidized bed 90 is 500 ° C. or lower, the quality of the recovered liquid is improved.

The average particle diameter of the sand supplied to the fluidized bed 90 is preferably 0.01 mm to 1 mm, and more preferably 0.05 mm to 0.8 mm.
The temperature of the sand supplied to the fluidized bed 90 is preferably (the temperature of the fluidized bed 90 + 50 ° C.) or more and (the temperature of the fluidized bed 90 + 250 ° C.) or less. If the temperature of the sand is equal to or higher than the temperature of the fluidized bed 90 + 50 ° C., the thermal decomposition rate of the acrylic resin is increased. If the temperature of the sand is equal to or lower than (temperature of fluidized bed 90 + 250 ° C.), the quality of the recovered liquid is improved.

  The ratio (sand / acrylic resin) between the sand supply rate (kg / hour) and the acrylic resin supply rate (kg / hour) is preferably 1-20. If the sand / acrylic resin is 1 or more, the acrylic resin can be efficiently thermally decomposed. If the sand / acrylic resin is 20 or less, the circulation amount of sand between the decomposition tank main body 86 and the sand heating device 18 is suppressed, and an increase in cost due to the increase in size of the sand heating device 18 is suppressed.

  The fluidizing gas is preferably a gas that does not substantially contain oxygen from the viewpoint of the stability of thermal decomposition and the yield of decomposition products. Examples of the gas include nitrogen, carbon dioxide, water vapor, and a gas discharged without becoming a liquid in the step (b).

  The temperature of the fluidizing gas supplied to the fluidized bed 90 is preferably not lower than the temperature of the acrylic resin supplied to the fluidized bed 90 and not higher than 500 ° C. If the temperature of the fluidizing gas is equal to or higher than the temperature of the acrylic resin, an excessive temperature drop of the fluidized bed 90 can be suppressed. When the temperature of the fluidizing gas is 500 ° C. or lower, the quality of the recovered liquid is improved.

  The ratio (fluidization gas / acrylic resin) of the fluidization gas supply rate (kg / hour) to the acrylic resin supply rate (kg / hour) is preferably 0.4 to 3.0. If the fluidizing gas / acrylic resin is 0.4 or more, the fluidity of the fluidized bed 90 can be maintained. If the fluidized gas / acrylic resin is 3.0 or less, the load on the cooling device in step (b) can be reduced.

  1-20 mm is preferable and, as for the average particle diameter of the grinding | pulverization piece of acrylic resin, 3-10 mm is more preferable. If the average particle diameter of the pulverized pieces of acrylic resin is 1 mm or more, adhesion and fusion between the acrylic resins can be suppressed. If the average particle diameter of the pulverized pieces of acrylic resin is 20 mm or less, the dispersibility of the acrylic resin and sand will be good.

  The temperature of the acrylic resin supplied to the fluidized bed 90 is preferably 0 ° C. or higher and (the glass transition temperature of the acrylic resin or the melting point −50 ° C.) or lower. If the temperature of acrylic resin is 0 degreeC or more, the temperature fall of the fluidized bed 90 will be suppressed and the fluidity | liquidity of the fluidized bed 90 will become favorable. When the temperature of the acrylic resin is equal to or lower than (the glass transition temperature of the acrylic resin or the melting point −50 ° C.), the adhesion between the acrylic resins is suppressed, and the mixing of the acrylic resin and the sand is good.

The acrylic resin is a polymer having a structural unit derived from the above (meth) acrylic acid ester.
The acrylic resin may have a structural unit derived from another monomer other than the (meth) acrylic acid ester. Examples of other monomers include (meth) acrylic acid, maleic anhydride, styrene, α-methylstyrene, acrylonitrile, and polyfunctional monomers.

  A polyfunctional (meth) acrylic acid ester is mentioned as a polyfunctional monomer. Polyfunctional (meth) acrylic acid esters include ethylene glycol diacrylate, propylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, ethylene glycol dimethacrylate, Examples include propylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, and neopentyl glycol dimethacrylate.

  The acrylic resin preferably has 50% by mass or more of methyl methacrylate units in 100% by mass of all the structural units from the viewpoint of recovering the (meth) acrylic acid ester in a high yield, and 70% by mass of methyl methacrylate units. % Or more is more preferable.

The acrylic resin may be mixed with other resins.
The acrylic resin may contain a filler. Examples of the filler include aluminum hydroxide, silica, calcium carbonate, glass fiber, talc, and clay.
The acrylic resin may contain an additive excluding the filler. Examples of additives include pigments, dyes, reinforcing agents, antioxidants, and various stabilizers.

  When there is undecomposed matter in the fluidized bed 90, the undecomposed matter is discharged from the decomposition tank 10 together with sand and transferred to the sand heating device 18. The undecomposed product is an acrylic resin itself, a low molecular weight acrylic resin, a carbide, or the like. Undecomposed matter is removed from the sand by pyrolysis or combustion in the sand heating device 18.

Step (b):
The gas discharged from the cyclone 20 is supplied to the first cooling device 22 via the second gas flow path 52. At the same time, the liquid cooled by the third cooling device 28 is supplied to the first cooling device 22 via the cooling liquid flow path 64, and the gas supplied from the cyclone 20 is cooled by the liquid to be used as a liquid. to recover.

The gas that has not become liquid in the first cooling device 22 is supplied from the gas phase portion of the first cooling device 22 to the second cooling device 24 via the third gas channel 54, and the gas is supplied to the second cooling device 24. The liquid is recovered by cooling with the second cooling device 24.
The gas discharged from the second cooling device 24 is supplied to the mist separator 26 via the fourth gas flow path 56, and the liquid mist contained in the gas is recovered by the mist separator 26.
The gas that has passed through the mist separator 26 is discharged via the gas discharge channel 58. A part of the gas is detoxified by the combustion treatment and then discharged outside the apparatus, and the remaining part is reused as a fluidized gas.

  A part of the liquid recovered by the first cooling device 22, the second cooling device 24 and the mist separator 26 is supplied to the third cooling device 28 via the liquid branch flow path 62, and the remainder is the first cooling device. It is supplied to the first filter 30 in the step (c) via the liquid channel 60. The supply of the liquid to the third cooling device 28 and the first filter 30 is performed by a liquid feed pump (not shown) provided in the middle of the first liquid channel 60.

The temperature of the cooling liquid supplied from the third cooling device 28 to the first cooling device 22 is preferably (recovered liquid freezing point + 10 ° C.) to (recovered liquid boiling point−10 ° C.).
The temperature of the gas flowing through the third gas channel 54 is preferably (the freezing point of the liquid to be recovered + 10 ° C.) to (the boiling point of the liquid to be recovered−20 ° C.). Further, it is preferable that a medium of (the freezing point of the recovered liquid + 10 ° C.) to (the boiling point of the recovered liquid−30 ° C.) flows through the second cooling device 24.

Step (c):
The liquid collected in the step (b) is filtered by the first filter 30 to remove relatively large pieces of crushed sand contained in the liquid.
A liquid containing crushed pieces of sand that could not be removed by the first filter 30 is supplied to the mixing tank 34 via the second liquid channel 66.
Further, the water in the container 32 or an aqueous solution in which a substance that can be aggregated is dissolved is sent to the mixing tank 34 through the water supply channel 68.

After mixing the liquid and the aqueous solution in which the substance capable of aggregating water or sand is mixed in the mixing tank 34, the liquid is sent to the phase separation tank 36 by the third liquid channel 70, and the liquid phase and the aqueous phase are mixed. Separate. At this time, the crushed pieces of sand contained in the liquid move from the liquid phase 102 to the aqueous phase 104 or gather near the interface between the liquid phase 102 and the aqueous phase 104.
By collecting only the liquid phase 102 (excluding the vicinity of the interface with the aqueous phase), the crushed pieces of sand are removed from the liquid.
The aqueous phase 104 is discharged from the phase separation tank 36 via the waste water channel 72 as waste water.

The mixing time of the liquid and the aqueous solution in which the substance capable of aggregating water or sand is dissolved is preferably 5 to 60 minutes. Sand can be sufficiently removed by setting the mixing time to 5 minutes or more. Setting the mixing time to 60 minutes or less shortens the time required for mixing, which is advantageous in terms of productivity.
Examples of the mixing method in the mixing tank 34 include a method using a mixing device. Examples of the mixing device include a stirring device having a stirring blade, a magnetic stirrer, a static mixer, vertical vibration disk stirring, low frequency vibration stirring, rocking stirring, jet stirring, and the like.

The mixing tank 34 may be a batch type or a continuous type.
In the batch type, an aqueous solution in which water or a substance capable of agglomerating sand and a liquid containing sand are placed in the mixing tank 34 and mixed for a predetermined time, and after mixing, the mixed liquid is mixed with the mixing tank 34. It is a method of discharging from.
In the continuous type, water or an aqueous solution in which a substance capable of agglomerating sand or a liquid containing sand is continuously supplied to the mixing tank 34, and the mixed liquid is continuously supplied from the mixing tank 34. It is a method of discharging.

  The mixing temperature of the liquid and the aqueous solution in which the substance capable of aggregating water or sand is dissolved is preferably 5 to 90 ° C. By setting the mixing temperature to 5 ° C. or higher, water can be prevented from freezing and sand can be easily removed. By setting the mixing temperature to 90 ° C. or less, water evaporation can be prevented.

The water preferably contains an amine. When water contains an amine, the sand removal effect is enhanced, and (meth) acrylic acid contained as an impurity in the liquid is neutralized and transferred to the aqueous phase, thereby improving the quality of the liquid.
As the amine, triethylenetetramine is preferable.
The mass ratio between the amine and sand (inorganic particles) and the mass ratio between the water containing amine and the liquid containing sand (inorganic particles) are preferably within the above ranges.

  In the phase separation tank 36, the time for phase separation of the liquid mixture of the liquid and the aqueous solution in which the substance capable of aggregating water or sand is preferably 5 to 60 minutes. By setting the phase separation time to 5 minutes or longer, the liquid phase 102 and the aqueous phase 104 can be sufficiently separated. By setting the phase separation time to 60 minutes or less, the time required for phase separation is shortened, which is advantageous in terms of productivity.

The phase separation tank 36 may be a batch type or a continuous type.
In the batch type, a liquid mixture of a liquid and an aqueous solution in which water or a substance capable of agglomerating sand is dissolved is allowed to stand for a predetermined time, and after standing, the liquid phase 102 is sent to the first distillation column 38, This is a method of draining the water phase 104 via the waste water flow path 72. Standing is an operation of leaving the mixed solution as it is and waiting for separation.
In the continuous type, a liquid mixture of a liquid and an aqueous solution in which water or a substance capable of agglomerating sand is dissolved is continuously sent to the phase separation tank 36 near the interface between the liquid phase 102 and the water phase 104. In this method, the liquid phase 102 is sent to the first distillation column 38 and the water phase 104 is continuously discharged via the waste water flow path 72.

Step (d):
The liquid discharged from the phase separation tank 36 is supplied to the first distillation column 38 via the fourth liquid channel 74, and is distilled in the first distillation column 38.
Low boiling point impurities from the top of the first distillation column 38 are discharged out of the apparatus via the low boiling point impurity discharge passage 76.

The liquid discharged from the bottom of the first distillation column 38 is supplied to the second distillation column 40 via the fifth liquid channel 78 and is distilled in the second distillation column 40.
High boiling point impurities from the bottom of the second distillation column 40 are discharged out of the apparatus via the high boiling point impurity discharge passage 80. High boiling impurities include crushed sand.

The gas discharged from the top of the second distillation column 40 is converted into a liquid by a condenser (not shown), and then the liquid is supplied to the second filter 42 via the sixth liquid channel 82. The liquid is filtered by the second filter 42 to remove the crushed pieces of sand remaining to the end.
The liquid ((meth) acrylic acid ester) that has passed through the second filter 42 is recovered via the liquid recovery channel 84 as a purified product.

  According to the method for removing inorganic particles in the liquid of the present invention described above, the liquid containing inorganic particles and water are mixed and then separated into a liquid phase and an aqueous phase. The particles move from the liquid phase to the aqueous phase or gather near the interface between the liquid phase and the aqueous phase. Therefore, the inorganic particles contained in the liquid can be sufficiently removed by collecting the liquid phase (except for the vicinity of the interface with the aqueous phase).

Examples are shown below.
Various measurement methods in the examples are as follows.

(Measurement method of sand content in liquid)
A scavenger was added to the liquid containing sand, and ashing was performed in air under the conditions of an ashing temperature: 650 ° C. and an ashing time: 1 hour, and then melted with potassium hydrogen sulfate. After dissolving in dilute nitric acid, using an ICP emission analyzer (ICPS-8100, manufactured by Shimadzu Corporation), the amount of Si obtained was determined by ICP emission analysis (high frequency plasma emission analysis). It was multiplied by 14 to calculate the mass% of sand (SiO ₂ ) contained in the liquid.

(Method for measuring the concentration of methyl methacrylate in liquid)
The concentration (mass%) of methyl methacrylate (hereinafter referred to as MMA) in the liquid was measured by gas chromatography. As the gas chromatography, GC-17A manufactured by Shimadzu Corporation was used. N, N-dimethylformamide was used as the solvent. A calibration curve was prepared in advance, and the MMA concentration in the liquid was calculated from the gas chromatography results of the sampled liquid. When the liquid was injected into the gas chromatography, the sand was removed with a syringe filter.

[ Comparative Example 1]
A molded plate made of polymethyl methacrylate (MMA unit: 100% by mass, mass average molecular weight: 400,000, glass transition temperature: 100 ° C.) was pulverized to obtain pulverized pieces. A screen having an opening of 10 mm was installed under the crusher. The crushed pieces were sieved with another 6 mm screen. The crushed pieces remaining on the screen were used for resin decomposition. Therefore, the average particle diameter of the crushed pieces was 8 mm.
As the sand, natural river sand (manufactured by Changei Material Co., Ltd., trade name: Ebaralozuna, average particle size: 0.3 mm, bulk density: 1600 kg / m ³ , true density of 2500 kg / m ³ ) was prepared.

Using the decomposition tank 10 shown in FIG. 1, polymethyl methacrylate was thermally decomposed.
As the decomposition tank 10, one having a diameter of 350 mm and a height of 1400 mm was used. As the stirring blade of the stirring device 92, two inclined paddle blades (diameter: 310 mm, width: 20 mm, inclination angle: 45 degrees) with five stages (pitch between paddles: 140 mm) were used. The stirring speed was 25 revolutions per minute (25 rpm). As the dispersion plate 88, a disperser (thickness 1.6 mm, made of stainless steel) made of a sintered metal filter (Fuji Filter Industrial Co., Ltd.) was arranged in a conical shape. The diameter of the cone was 350 mm, and the cone height was 100 mm. A sand outlet 98 was connected to the apex of the disperser cone.
As the sand heating device 18, a heating furnace having a fluidized bed for fluidizing sand with hot air was used, and 60 kg of sand was previously placed in the sand heating device 18.

After 70 kg of sand was put into the decomposition tank 10, the inside of the decomposition tank 10 was replaced with nitrogen.
The sand in the fluidized bed 90 of the decomposition tank 10 was continuously discharged from the sand discharger 16 at 120 kg / hour and transferred to the sand heating unit 18.
The set temperature of the sand heating device 18 was set to 400 ° C., and the heated high-temperature sand was continuously supplied from the sand supply device 14 to the fluidized bed 90 of the decomposition tank 10 at 120 kg / hour. The amount of sand stayed in the decomposition tank 10 was always 70 kg. The average residence time of the sand in the decomposition tank 10 was 0.58 hours.

The fluidizing gas was supplied from the fluidizing gas supply channel 44 to the fluidizing gas chamber 100 at the bottom of the decomposition tank 10 at 20 kg / hour.
As the fluidizing gas, a gas discharged from the mist separator 26 via the gas discharge channel 58 was used. Between the gas discharge channel 58 and the fluidizing gas supply channel 44, a gas extraction device (not shown), a circulation blower (not shown), a flow meter (not shown), a flow rate control device (not shown), A nitrogen supply blower (not shown) and a heating device (not shown) for heating the gas were provided, and a fluidized gas at 50 ° C. was supplied to the fluidized gas chamber 100 at the bottom of the decomposition tank 10 at 20 kg / hour.
The ratio of the fluidizing gas supply rate (kg / hour) to the sand supply rate (kg / hour) was 0.167.
The fluidized bed 90 of the decomposition tank 10 was fluidized by the fluidizing gas blown up from the stirring device 92 and the dispersion plate 88.

When the temperature of the fluidized bed 90 in the decomposition tank 10 is stabilized at about 400 ° C., the temperature of the sand supplied from the sand heating apparatus 18 to the fluidized bed 90 in the decomposition tank 10 is changed by changing the set temperature of the sand heating apparatus 18. The pulverized pieces of polymethyl methacrylate at 20 ° C. were continuously supplied from the resin supply device 12 to the fluidized bed 90 of the decomposition tank 10 at 12 kg / hour.
The ratio of the fluidization gas supply rate (kg / hour) to the polymethyl methacrylate supply rate (kg / hour) was 1.67.
After 30 minutes from the start of the supply of polymethyl methacrylate, the temperature of the fluidized bed 90 in the decomposition tank 10 became a steady state. The temperature was 405 ° C.

  The gas containing the decomposition product of polymethyl methacrylate and nitrogen discharged from the decomposition tank 10 was supplied to the first cooling device 22. A scrubber was used as the first cooling device 22. The liquid at 50 ° C. coming out of the third cooling device 28 was sprayed into the first cooling device 22 using a nozzle. The third cooling device 28 is a multi-tube heat exchanger, and 5 ° C. cold water was allowed to flow through the shell.

The gas at 60 ° C. coming out of the first cooling device 22 was supplied to the second cooling device 24. The second cooling device 24 is a multi-tube heat exchanger, and 5 ° C. cold water was allowed to flow through the shell.
A 30 ° C. gas coming out of the second cooling device 24 was supplied to the mist separator 26. As the mist separator 26, a cyclone type was used. Cold water at 10 ° C. was passed through a jacket provided on the mist separator 26. The liquid was recovered from each cooling device and the mist separator 26 into a container (not shown) via the first liquid channel 60.

This operation was continued for 24 hours from the start of the supply of polymethyl methacrylate. A liquid containing 268 kg of crushed pieces of sand in a container was recovered with respect to a total supply amount of polymethyl methacrylate of 288 kg.
It was 0.065 mass% when content of the sand in a liquid was measured. That is, the ratio of the liquid was 99.935% by mass.
The mass of liquid 100 cm ³ containing sand at 20 ° C. was 94.20 g. Of the 94.20 g, the liquid mass was calculated to be 94.20 × 99.935 / 100 = 94.14 g. Therefore, the specific gravity of the liquid was calculated as 0.9414.

  The liquid collected in the container was a liquid containing 92.5% by mass of MMA. The liquid was passed through the first filter 30 (manufactured by Hayward, trade name: RBT, nominal pore diameter: 25 μm). The amount of sand contained in the liquid after passing through the first filter 30 was 0.050% by mass.

250 g of water was added to 2500 g of the liquid containing the crushed sand pieces, and the mixture was stirred for 30 minutes with a magnetic stirrer.
Both the liquid containing the crushed pieces of sand and water were set to 20 ° C.
The mass ratio of water to the liquid containing sand was 250 g / 2500 g = 0.1.
After stirring, the mixed solution was allowed to stand for 30 minutes to separate into a liquid phase and an aqueous phase. Most of the sand gathered at the bottom of the aqueous phase and near the interface between the aqueous and liquid phases.
The liquid phase (excluding the vicinity of the interface with the aqueous phase) was recovered. The amount of sand contained in the recovered liquid was 0.0020% by mass (20 ppm).

When this liquid was passed through the first distillation column 38 and the second distillation column 40, the amount of sand contained in the liquid in the sixth liquid channel 82 was 0.0000045% by mass (45 ppb). .
When this liquid was passed through the second filter 42 (manufactured by Fuji Filter Industry Co., Ltd., trade name: sintered metal filter, nominal pore diameter: 0.5 μm), the amount of sand contained in the liquid in the liquid recovery channel 84 was 0.0000032 mass% (32 ppb). This liquid was a liquid containing MMA 99.75%.

[Example 2]
The same operation as in Comparative Example 1 was performed except that 250 g of a 3.0% by mass triethylenetetramine aqueous solution was used instead of 250 g of water. As triethylenetetramine, Aldrich product number 90460 was used.

To 2500 g of the liquid after passing through the first filter 30 (the amount of sand contained is 0.050% by mass), 250 g of a 3.0% by mass triethylenetetramine aqueous solution is added and stirred for 30 minutes with a magnetic stirrer. did.
Both the liquid containing the crushed pieces of sand and the aqueous triethylenetetramine solution were set to 20 ° C.
2500 g of liquid containing crushed pieces of sand contained 2500 g × 0.05 / 100 = 1.25 g of sand. In addition, 250 g of the 3.0 mass% triethylenetetramine aqueous solution contained 250 g × 3.0 / 100 = 7.5 g of triethylenetetramine. Therefore, the mass ratio of amine to sand (amine / sand) was 7.5 g / 1.25 g = 6.0.
The mass ratio of water containing triethylenetetramine and liquid containing sand was 250 g / 2500 g = 0.1.

After stirring, the mixed solution was allowed to stand for 30 minutes to separate into a liquid phase and an aqueous phase. Most of the sand gathered at the bottom of the aqueous phase and near the interface between the aqueous and liquid phases.
The liquid phase (excluding the vicinity of the interface with the aqueous phase) was recovered. The amount of sand contained in the recovered liquid was 0.00015% by mass (1.5 ppm).
When this liquid was passed through the first distillation column 38 and the second distillation column 40, the amount of sand contained in the liquid in the sixth liquid channel 82 was 0.0000030% by mass (30 ppb). .
When this liquid was passed through the second filter 42, the amount of sand contained in the liquid in the liquid recovery channel 84 was 0.0000025% by mass (25 ppb). This liquid was a liquid containing 99.81% of MMA.

Example 3
The same operation as in Example 2 was carried out except that 250 g of a 3.0% by mass diethanolamine aqueous solution was used instead of 250 g of the 3.0% by mass triethylenetetramine aqueous solution. The product number 398179 made by Aldrich was used as diethanolamine.

250 g of a 3.0% by mass diethanolamine aqueous solution was added to 2500 g of the liquid after passing through the first filter 30 (the amount of sand contained was 0.050% by mass), and the mixture was stirred with a magnetic stirrer for 30 minutes.
Both the liquid containing the crushed pieces of sand and the diethanolamine aqueous solution were set to 20 ° C.
2,500 g of sand was contained in 2500 g of the liquid containing the crushed pieces of sand. Further, 250 g of 3.0 mass% diethanolamine aqueous solution contained 7.5 g of diethanolamine. Therefore, the mass ratio of amine to sand (amine / sand) was 7.5 g / 1.25 g = 6.0.
The mass ratio of water containing diethanolamine and liquid containing sand was 250 g / 2500 g = 0.1.

After stirring, the mixed solution was allowed to stand for 30 minutes to separate into a liquid phase and an aqueous phase. Most of the sand gathered at the bottom of the aqueous phase and near the interface between the aqueous and liquid phases.
The liquid phase (excluding the vicinity of the interface with the aqueous phase) was recovered. The amount of sand contained in the recovered liquid was 0.00051% by mass (5.1 ppm).
When this liquid was passed through the first distillation column 38 and the second distillation column 40, the amount of sand contained in the liquid in the sixth liquid channel 82 was 0.0000038% by mass (38 ppb).
When this liquid was passed through the second filter 42, the amount of sand contained in the liquid in the liquid recovery channel 84 was 0.0000029% by mass (29 ppb). This liquid was a liquid containing 99.79% MMA.

[Comparative Example 2 ]
The same operation as in Comparative Example 1 was performed except that 7.5 g of triethylenetetramine itself was used instead of 250 g of water.
7.5 g of triethylenetetramine was added to 2500 g of the liquid after passing through the first filter 30 (the amount of sand contained was 0.050 mass%), and the mixture was stirred for 30 minutes with a magnetic stirrer.
After stirring, the mixture was allowed to stand for 30 minutes, but the liquid, sand and triethylenetetramine remained mixed. It was not possible to separate the sand from the liquid.

[Comparative Example 3 ]
Without passing through the mixing tank 34 and the phase separation tank 36, 2500 g of the liquid that passed through the first filter 30 (the amount of sand contained is 0.050% by mass) is directly passed through the first distillation column 38 and the second distillation column 38. The same operation as in Comparative Example 1 was performed except that it was passed through the distillation column 40.
The amount of sand contained in the liquid of the sixth liquid channel 82 was 0.000011% by mass (110 ppb). In addition, after the distillation was finished, when the shelf of each distillation tower was confirmed, sedimentation of sand was observed.
When this liquid was passed through the second filter 42, the amount of sand contained in the liquid in the liquid recovery channel 84 was 0.0000090 mass% (90 ppb).

  The method for removing inorganic particles in a liquid according to the present invention is a liquid which can be phase-separated from water recovered by cooling a gas containing a decomposition product obtained by thermally decomposing waste plastic in the presence of inorganic particles. Inorganic particles can be removed from the liquid, so that it is useful for the purification of liquid monomers, oils, etc. recovered from waste plastics.

It is the schematic which shows an example of the apparatus which collect | recovers (meth) acrylic acid ester from acrylic resin.

Explanation of symbols

30 First filter 34 Mixing tank 36 Phase separation tank 102 Liquid phase 104 Water phase

Claims (6)

A method of removing inorganic particles contained in a liquid capable of phase separation from water from the liquid,
Inorganic particles in a liquid, in which a liquid containing inorganic particles and water containing a substance capable of aggregating inorganic particles are mixed and then separated into a liquid phase and an aqueous phase to remove inorganic particles from the liquid. Removal method. The method for removing inorganic particles in a liquid according to claim 1 , wherein the substance capable of aggregating the inorganic particles is an amine. The method for removing inorganic particles in a liquid according to claim 2 , wherein the amine is triethylenetetramine. Wherein the inorganic particles are sand, the method of removing the inorganic particles in the liquid according to any one of claims 1-3. Liquid containing the inorganic particles is a liquid which is recovered by cooling the gas containing decomposition products of the resin obtained by thermally decomposing in the presence of the inorganic particles, any of claims 1-4 The removal method of the inorganic particle in the liquid as described in 2. The method for removing inorganic particles in a liquid according to claim 5 , wherein the liquid containing the inorganic particles is a liquid after the collected liquid is further passed through a filter.

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