JPH1180419A - Process and apparatus for supercritical hydroxylation decomposition of polyurethane waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decompose polyurethane wastes without causing cloggings of pumps and pipes by hydrolyzing the wastes under conditions in which water is present in an amount excessive over that of saturated steam in a closed system into a water-soluble substance and subjecting the substance to supercritical hydroxylation decomposition. SOLUTION: Polyurethane wastes in the form of foams, elastomers or fibers are fed into a closed reactor, an organic alkaline compound such as tetramethylammonium hydroxide is added, and the contents are treated with pressurized hot water at 150-200 deg.C to hydrolyze it into a water-soluble substance. Next, the hydrolyzate solution is mixed with a stoichiomelric or larger amount of an oxidizing agent selected among air, pure oxygen, hydrogen peroxide, etc., in a reactor such as a pipe-type one at 374 deg.C or above, particularly 550-650 deg.C under 22 Mpa or above, particularly 22-25 Mpa to form a homogeneous phase comprising supercritical water, the hydrolyzate solution and the oxidizing agent in the supercritical state of water and to effect its supercritical hydroxylation reaction and oxidative decomposition within a short time. The treated fluid is cooled, reduced in pressure and discharged from the system in the form of a carbon dioxide gas, a nitrogen gas and water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for supercritically hydrolyzing polyurethane waste.

[0002]

2. Description of the Related Art Polyurethane is a polymer obtained by reacting a polyisocyanate with an active hydrogen compound such as a polyol. By appropriately selecting a raw material, a polyurethane can be thermoset to thermoplastic, soft to hard, and fragile. Polyurethane having various properties such as toughness can be obtained.

[0003] Polyurethane has a shock absorbing property, elasticity,
Due to properties such as ease of molding, it is used in a wide range of fields such as foams, elastics, synthetic leather, and fibers. However, most methods of treating polyurethane waste are by incineration. Polyurethane can be processed relatively easily by incineration.

Various studies have been made on a method of hydrolyzing polyurethane and regenerating it as a raw material. For example, a method in which an alkylene oxide is addition-polymerized to a polyurethane foam decomposition solution to recover a polyol usable as a polyurethane raw material (Japanese Patent Laid-Open No. 51-74097)
No. 4), a method of decomposing a polyurethane foam into a polyamine in which an isocyanate group of a polyol and a polyisocyanate used in the production of the foam is changed to an amine (Japanese Patent Publication No. Sho 4)
2-10634), a method in which a polyurethane foam is decomposed in a decomposition reagent in which an amine compound is used in combination with an alkali metal hydroxide and the like, and polyether is recovered by liquid separation, distillation, and the like (Japanese Patent Publication No. 43-21079, Japanese Patent Publication No. Kossho 48-5
280).

Further, the organic substance is converted to a critical point of water (375 ° C.,
A method for oxidative decomposition in supercritical water exceeding 22 MPa) has been proposed (Japanese Patent Publication No. 1-38532, US Pat. No. 4,113,446, US Pat. No. 4,338,199).
No. 4,543,190). Water in a supercritical state has a high dissolving power for organic substances and gases, and the organic substances are completely mixed in the supercritical water to form a mixed fluid. In the supercritical state of water, they form a homogeneous phase, which is more advantageous in terms of mass transfer. As a result, when oxidative decomposition is performed in supercritical water, the oxidation rate is very high, and the decomposition time can be completed in the order of minutes or seconds. That is, the supercritical hydroxylation decomposition method is a method capable of performing complete oxidative decomposition in a short time for all organic substances.

[0006]

However, in the incineration method as a disposal treatment of polyurethane, nitrogen atoms constituting polyurethane molecules generate NOx gas, which causes a problem of air pollution. Must be provided, which increases the processing cost.

[0007] When polyurethane is hydrolyzed or alkali hydrolyzed, it is effective as a method for recovering and regenerating a small amount of polyurethane such as defective products and molding waste generated in the polyurethane molding process. However, when it comes to regenerating polyurethane waste with a large absolute amount, the hydrolysis method requires various treatments before regenerating polyurethane foams that absorb quality problems and various waste liquids. However, regeneration becomes inefficient because the cost required for the auxiliary equipment for the pretreatment increases.

Therefore, as a method for treating the polyurethane which has been disposed of, a method using supercritical hydroxylation is effective. In supercritical water, polyurethane is completely oxidatively decomposed, and the nitrogen atoms that make up the polyurethane molecules are decomposed into nitrogen gas, NOx is not contained in the exhaust gas, and the pre-nitrogen in the treated water is reduced to below the standard value. It is possible to

However, in the supercritical hydroxylation decomposition method, it is necessary to transport the object to be treated to the reactor under high pressure conditions, and the piping becomes thin due to the pressure resistance structure. Therefore, in the supercritical hydroxylation decomposition method, it is necessary to crush the object to be treated finely, but polyurethane is very difficult to crush due to its physical properties. Since polyurethane is an elastic body, it immediately returns to its original shape even when a force is applied, and is difficult to crush. Further, when heat is generated at the time of crushing, it is melted and further processed. Also, even if shredded, there is a danger of stagnation and blockage in the pump and piping.

[0010] An object of the present invention is to provide a method and apparatus for supercritically hydrolyzing polyurethane waste without clogging in pumps and piping.

[0011]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on a method of supercritically hydrolyzing polyurethane waste, and as a result, the polyurethane waste is hydrolyzed by hot pressurized water. The inventors have found that the above problems can be solved by performing a supercritical hydroxylation decomposition treatment after decomposing the substance, and have completed the present invention.

That is, the present invention is characterized in that polyurethane waste is hydrolyzed in a closed system in a state where water is present in excess of saturated steam to obtain a water-soluble substance, and then subjected to supercritical hydroxylolysis. Supercritical water hydroxylation decomposition method of polyurethane waste, and heating means to heat the mixed fluid of the processing object, a reactor to oxidatively decompose the processing object in a supercritical state of water, cooling means to cool the processing fluid, A supercritical hydroxylation / decomposition apparatus for polyurethane waste provided with a decompression means for depressurizing a cooled processing fluid, wherein the polyurethane waste is hydrolyzed in a closed system with pressurized hot water having excess water over saturated steam. A hydrolysis device, a unit for removing the aqueous solution of the hydrolyzed polyurethane waste from the hydrolysis device, and a pressurizing supply unit for supplying the removed hydrolysis treatment solution to the reactor under pressure are provided. It relates supercritical water oxidation decomposition apparatus of polyurethane waste characterized.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The polyurethane waste to be treated in the present invention can be treated with any of foams, elastic bodies, fibrous materials and the like. Further, the polyurethane waste can be used for any of used ones, defective products during molding, molding waste, and the like.

The present invention is characterized in that the polyurethane waste is hydrolyzed by a pressurized hot water treatment in a first stage in order to stably transport the polyurethane waste to a reactor for supercritical hydroxylation. Hydrolysis with pressurized hot water is performed under conditions in which water is present in excess of the saturated vapor pressure in a closed system. Hydrolysis with hot pressurized water is preferably performed, for example, within the range of 200 to 300 ° C.

By the hydrolysis treatment, the polyurethane waste is hydrolyzed to a water-soluble substance, and no residue or char is formed. Therefore, the hydrolysis treatment liquid can be stably supplied under pressure to the reactor of the supercritical hydroxylation decomposition apparatus, and there is no possibility that the piping or the reactor will be clogged. At the time of hydrolysis, hydroxides of alkali metals (eg, NaOH, KOH, Ca (OH) ₂
) Increases the rate of the hydrolysis reaction, but must be neutralized during the supercritical hydroxylation decomposition treatment. However, when the neutralization is performed, the solubility of the generated inorganic salt is significantly reduced in supercritical water, so that a mechanism for removing the inorganic salt is required. Therefore, it is preferable to hydrolyze without adding an inorganic alkali.

However, any organic alkaline compound which does not produce an inorganic salt by supercritical hydroxylation decomposition can be used without any problem. Examples of the organic alkaline compound include monoethanolamine, diethanolamine, triethanolamine, tetramethylammonium hydroxide and the like. For example, by adding tetramethylammonium hydroxide and performing hot water treatment under pressure, hydrolysis can be performed at a lower reaction temperature of about 150 to 200 ° C. than in the case of using water alone. Even if the processing solution is subjected to supercritical hydroxylation and decomposition, there is no element that generates an inorganic salt, so that an inorganic salt removing mechanism is unnecessary.

Particularly, in a factory for producing electronic parts and components such as semiconductors, although separate systems, waste water of tetramethylammonium hydroxide and polyurethane waste may be discharged at the same time. Since the hydrolysis can be performed using the ammonium hydroxide waste liquid, extremely efficient waste treatment can be achieved.

In the latter stage of the supercritical hydroxylation, water-soluble compounds obtained by hydrolysis in the supercritical state of water are oxidatively decomposed. The temperature and pressure conditions for bringing water into a supercritical state are not limited. For example, the temperature is 374 ° C. or more, preferably 550 to 650 ° C., and the pressure is 22 MPa or more.
Preferably, the condition is 22 to 25 MPa. Examples of the oxidizing agent include air, pure oxygen, hydrogen peroxide, and liquid oxygen. These oxidizing agents may be used in a stoichiometrically required amount or more. The reactor for performing the supercritical hydroxylation decomposition may be any of a pipe (tubular) type and a vessel type.

Since water becomes a good solvent in the supercritical state, the supercritical water, the hydrolyzed solution and the oxidizing agent form a homogeneous phase in the reactor, and the supercritical hydroxylation reaction proceeds. It is oxidatively decomposed in a short time. The processing fluid obtained by supercritically hydrolyzing and decomposing the hydrolysis treatment liquid of polyurethane waste is cooled and decompressed and discharged out of the system as carbon dioxide, nitrogen gas and water.

When the polyurethane contains water, it is inherently difficult to self-combust (energy-free) in the supercritical water oxidation reaction due to a low calorific value, and further, by hydrolyzing the polyurethane waste, Since water is added to decrease the organic matter concentration, it is necessary to add an auxiliary fuel to supercritically hydrolyze the hydrolyzed solution. The auxiliary fuel is not particularly limited as long as it has combustion heat capable of sustaining supercritical hydroxylation decomposition.For example, isopropyl alcohol, kerosene, and the like may be used, but the above tetramethylammonium hydroxide waste liquid, crushed waste It is preferable to use plastics, sludge, and the like to be disposed of as auxiliary fuel. The organic substance serving as such an auxiliary fuel may be any substance as long as it can be transported by a pump.

One embodiment of the apparatus for supercritically hydrolyzing and decomposing polyurethane waste of the present invention will be described with reference to FIG. 1 and FIG.

In FIG. 1, first, polyurethane waste is supplied from a hopper 2 to a hydrolysis chamber 1 by a supply chamber 3.
Supplied to The hydrolysis device 1 is maintained at 200 to 300 ° C. and hermetically sealed, and hydrolyzes polyurethane waste in a state where water is present in excess of saturated steam to obtain a water-soluble hydrolysis treatment liquid. The hydrolysis treatment liquid is supplied to the hydrolysis apparatus 1
Is taken out from the bottom by the take-out pump 5 and sent to the storage tank 6. The hydrolysis treatment liquid temporarily stored in the storage tank 6 is pressurized to a predetermined pressure (for example, 25 MPa) by the pressure pump 7 and sent to the tubular reactor 9 together with the auxiliary fuel. On the other hand, air as an oxidizing agent is pressurized by a high-pressure compressor 8, mixed with a hydrolysis solution, and sent to a tubular reactor 9. The mixed fluid is heated to a predetermined temperature (for example, 550 ° C.) by a preheater 10 provided at the entrance of the tubular reactor 9 to be in a supercritical state of water, and a supercritical hydroxylation decomposition reaction proceeds in the reactor 9, The hydrolysis products of polyurethane are rapidly oxidatively decomposed. Alternatively, supercritical water can be prepared in advance and supplied to the reactor together with hydrolysis of the polyurethane. The processing fluid subjected to the supercritical hydroxylation decomposition is cooled by a cooler 11 and decompressed by a pressure reducing valve 12, whereby carbon dioxide and nitrogen gas, which are decomposition products, are released to the atmosphere, and the processing water is discharged out of the system. You.

FIG. 2 is the same as the apparatus of FIG. 1 in that the polyurethane waste is hydrolyzed by pressurized hot water treatment and then subjected to supercritical hydroxylation. The difference is that heat is recovered through a heat exchange device. That is, the processing fluid flowing out of the reactor 9 is supplied to the heat exchanger 1
Introduce to 3. The high-temperature processing fluid exchanges heat with the cooling water 14 by the heat exchange device 13. After the treatment liquid is cooled, the pressure is reduced by the pressure reducing valve 12. The hot water heat-exchanged by the heat exchanger 13 can be returned to the hydrolysis device 1 via the return line 14 to be used for inflow of polyurethane waste from the supply chamber 3 or effective thermal energy can be recovered.

FIG. 3 shows an embodiment of a polyurethane waste hydrolysis apparatus. The polyurethane waste is supplied semi-continuously from the hopper 2 to the supply chamber 3. The polyurethane waste is put into the supply chamber 3 under normal pressure, the supply control plate 29 is closed, and the steam of the hydrolysis device 1 is supplied into the supply chamber 3. With the pressure in the supply chamber 3 equal to the pressure in the hydrolysis device 1,
The pressure adjusting plate 3a is opened to flow into the hydrolysis device 1. At that time, air may be supplied from the hopper 2 side by a blower or the like and press-fitted, or hot water heat-exchanged by the heat exchanger in FIG. 2 may be used. A heater 4 is provided at a lower portion of the hydrolysis device 1 and is configured to heat water existing at a lower portion of the hydrolysis device 1 to 200 to 300 ° C.

In order to receive the polyurethane waste flowing into the hydrolysis apparatus 1, a porous horizontal flat plate 1b such as a rough steel plate is provided at the center of the apparatus. The polyurethane waste on the porous horizontal flat plate 1b is hydrolyzed in a closed system in the presence of water in excess of saturated steam, completely decomposes to a water-soluble substance in about 30 minutes, and is liquefied at the bottom of the hydrolysis device 1. Stored as things.

[0026]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to the examples.

Example 1 A polyurethane foam was autoclaved (with an internal volume of 100
cc) was charged so that water was present in excess of the saturated vapor pressure, and heated to 150 to 300 ° C. in an electric furnace to perform hydrolysis. Table 1 shows the results.

[0028]

[Table 1]

As a result of hydrolysis under the conditions shown in Table 1,
No. At a reaction temperature of 150 ° C. in 1, polyurethane was not hydrolyzed and remained in almost its original form. No. When the reaction temperature of Step 2 reached 200 ° C., the polyurethane was rapidly decomposed into a water-soluble substance. Furthermore, when the temperature was raised to 250 ° C. and 300 ° C., there was almost no residue. Also 30
It was confirmed that hydrolysis was performed without any problem even when the reaction time was set at 10 minutes at 0 ° C. Therefore, if the polyurethane is hydrolyzed by hot pressurized water, the piping and the reactor will not be clogged even after the supercritical hydroxylation decomposition treatment.

Further, in the case of As shown in FIG. 6, when the polyurethane was hydrolyzed in an aqueous solution of tetramethylammonium hydroxide (25%), it was found that the residue disappeared at 150 ° C. and the water-soluble substance was decomposed. This is presumably because the hydrolysis of the polyurethane was promoted by the addition of the alkali. In addition, when this tetramethylammonium hydroxide is decomposed by supercritical hydroxylation, inorganic salts are not generated, and it is completely decomposed by supercritical hydroxylation. When waste liquid comes out, it is preferably used to increase the hydrolysis rate of polyurethane waste.

Next, No. 2 to 6 hydrolysis treatment liquids
As a result of supercritical hydroxylation decomposition in a 0 cc autoclave,
At a temperature of 650 ° C. and a pressure of 25 MPa, a theoretical amount of oxygen is supplied only for 1 minute, the TOC is 1 ppm or less, the nitrogen content does not remain in the form of nitrous acid, nitric acid or ammonia, and the nitrogen removal rate is 99%. A good result of 0.8% was obtained.

[0032]

The method and apparatus of the present invention exhibit the following excellent effects.

(1) When performing supercritical hydroxylation decomposition treatment of polyurethane waste, a difficult crushing step of polyurethane waste is not required.

(2) Since the supercritical hydroxylation decomposition treatment is performed after the polyurethane waste is hydrolyzed to a water-soluble substance, the treatment can be performed stably without clogging in the piping and the reactor.

(3) Since an alkali metal hydroxide that generates an inorganic salt is not used, a neutralization treatment is not required in the supercritical water oxidation treatment, and a salt removing mechanism is not required.

(4) By adding an organic alkali when hydrolyzing polyurethane waste, polyurethane waste can be efficiently hydrolyzed, and even if neutralized, inorganic salts are not generated. No salt removal mechanism is required.

(5) When the polyurethane waste and the tetramethylammonium hydroxide waste liquid come out at the same time, the tetramethylammonium hydroxide waste liquid can be used for the hydrolysis treatment of the polyurethane waste, so that efficient disposal can be achieved. .

[Brief description of the drawings]

FIG. 1 is a flow chart showing one embodiment of the apparatus for supercritically decomposing polyurethane waste according to the present invention.

FIG. 2 is a flowchart showing another embodiment of the apparatus for supercritically decomposing polyurethane waste according to the present invention.

FIG. 3 is an explanatory view showing one embodiment of a polyurethane waste hydrolysis apparatus used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hydrolysis apparatus 2 Hopper 3 Supply chamber 4 Heater 5 Discharge pump 6 Hydrolysis solution storage tank 7 High pressure pump 8 High pressure compressor 9 Tubular reactor 10 Preheater 11 Cooler 12 Pressure reducing valve 13 Heat exchanger 14 Cooling water

Claims (6)

[Claims] 1. A polyurethane waste, which is obtained by hydrolyzing a polyurethane waste in a closed system in a state where water is present in excess of saturated steam to obtain a water-soluble substance, and then performing supercritical hydroxylation decomposition. Supercritical water splitting method. 2. The method of claim 1, wherein the hydrolysis is carried out at 200 to 300 ° C. 3. The method for supercritically hydrolyzing polyurethane waste according to claim 1, wherein the hydrolysis is carried out in the presence of an organic alkaline compound. 4. The supercritical hydroxylation decomposition method according to claim 3, wherein the organic alkaline compound is tetramethylammonium hydroxide. 5. The supercritical hydroxylation decomposition method according to claim 3, wherein the hydrolysis is performed at 150 to 200 ° C. 6. A heating means for heating a mixed fluid of an object to be processed, a reactor for oxidizing and decomposing an object to be processed in a supercritical state of water, a cooling means for cooling a processing fluid, and a decompression of the cooled processing fluid. A supercritical hydroxylation / decomposition apparatus for polyurethane waste provided with a decompression means for performing hydrolysis, wherein the hydrolysis apparatus hydrolyzes polyurethane waste in a closed system with hot pressurized water having an excess of saturated steam. Supercritical water oxidation of polyurethane waste, comprising: means for removing the aqueous solution of the discharged polyurethane waste from the hydrolysis apparatus; and pressure supply means for pressurizing and supplying the extracted hydrolysis treatment liquid to the reactor. Disassembly device.