JP3273316B2 - Plastic mixed waste treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating plastic waste, and more particularly, to a method for treating plastic waste using an alkaline solution.

[0002]

2. Description of the Related Art The production of plastic raw materials in Japan reaches about 14.66 million tons per year. Of these, plastics containing chlorine, such as polyvinyl chloride and polyvinylidene chloride, account for about 21%. At present, products produced from these chlorine-containing plastic raw materials are widely used for a wide range of applications. For example, polyvinyl chloride is widely used for industrial and general purposes because it is an inexpensive resin and has excellent workability and mechanical properties. In addition to chlorine-containing resins, polyethylene terephthalate (PE
Plastics such as T) and polyethylene have a very wide range of applications and are used in large quantities.

On the other hand, with the increase in plastic production, waste of plastic products is increasing year by year, which is a major social problem.

[0004] Plastic waste is usually discharged as mixed waste of various plastics. For example,
Various plastic products, such as vinyl chloride and pet materials, which are no longer needed in ordinary households, are usually discharged as general waste and collectively collected as plastic-mixed waste.

At present, the treatment of plastic mixed waste includes (1) landfill, (2) recycling, (3) incineration,
There are (4) thermal decomposition oil conversion, (5) solid fuel conversion, and (6) blast furnace raw material conversion.

[0006] The "landfill" of (1) typically includes a sea surface landfill and a lowland landfill. However, at present, it is difficult to secure a new landfill. Also,
Plastic does not rot. Therefore, the ground where plastic waste is landfilled is unstable.

[0007] The "recycling process" of (2) is a processing method in which only high-quality plastic waste is separated and collected, and processed into a desired product. Thus, in the recycling process, it is necessary to determine whether each of the plastic wastes is suitable for the recycling process. Therefore, it is very inefficient to apply this to mixed plastic waste. As described above, the recycling method cannot treat all plastic waste and is inefficient.

In contrast to the physical treatment methods (1) and (2), the treatment methods (3) to (6) decompose the plastic itself. Since the plastic containing chlorine is mixed in the plastic mixed waste, hydrochloric acid is generated during decomposition. Therefore, the waste treatment facility is rapidly deteriorated because it is exposed to hydrochloric acid at a high temperature. In addition, a small amount of an organic chlorine compound may be generated at the time of decomposing a plastic containing chlorine. Such an organic chlorine compound is not preferable for the environment, and may cause a problem of environmental pollution. In addition, many of the chlorine-containing plastics described above contain a plasticizer mixed to impart plasticity. Such plasticizers can behave as environmental hormones during plastic degradation and can cause problems during processing.
Even if waste containing no chlorine-containing plastics, sodium chloride, inorganic chlorine compounds and the like can be inevitably mixed into general waste. These can be formed as organochlorine compounds during waste incineration and pyrolysis.

[0009] In the case of the thermal decomposition oil conversion of (4), depending on the waste mixed, the operation of the equipment and the quality of the product are greatly affected. Therefore, beverage pet products and the like in the plastic waste are manually removed in advance, and metals such as aluminum are separated from the mixed waste by the eddy current generator. However, pet products for foods and detergents other than beverages can inevitably be mixed into waste. These cause clogging of piping and the like during operation of the equipment. In addition, moisture can inevitably enter the waste. Moisture has a significant effect on the quality of the product oil and must be removed during the pretreatment stage, thus requiring a step of sufficient drying. As described above, in the case of conventional thermal decomposition oiling and the like, a step of removing pet materials, metals, moisture, and the like is required in the pretreatment stage, and it is difficult to remove all of them in the pretreatment.

[0010]

SUMMARY OF THE INVENTION The object of the present invention is to treat plastic mixed waste with little pre-treatment and no emission of environmental pollutants.
It is an object of the present invention to provide a processing method for recovering and recycling high-purity hydrocarbons.

[0011]

According to the present invention, a plastic mixed waste mixed with a chlorine-containing resin and crushed and an aqueous sodium hydroxide solution having a concentration of 35 to 50% by weight are mixed with the plastic mixed waste. Containing the product in a reaction vessel in a state of being immersed in the aqueous sodium hydroxide solution, and allowing the plastic mixed waste in the reaction vessel to be immersed in the aqueous sodium hydroxide solution at 250 to 310 ° C.
To react the plastic mixed waste with the aqueous sodium hydroxide solution to remove chlorine and a plasticizer.
Desorb and add high purity hydrocarbon to aqueous sodium hydroxide solution
A method for treating plastic mixed waste, comprising: producing and suspending .

The crushed plastic mixed waste
Preferably has a maximum length of 5 to 15 mm .

[0013]

[0014] The ratio of the <br/> plastic mixed waste for the sodium hydroxide aqueous solution, preferably 1-8% by weight.

[0015]

[0016]

Embodiments of the present invention will be described below.

In the present invention, the plastic mixed waste to be treated is waste mixed with plastic and discharged from ordinary households and / or waste discharged from various industries, and at least chlorine-containing resin is contained. Mixed waste can be targeted.

For example, garbage discharged from ordinary households often contains a mixture of pet materials such as PET bottles and metals such as aluminum lids for PET bottles. According to the present invention, these pet materials, metals, and the like may remain mixed in the waste, and a pretreatment step for removing them in advance is not particularly required. That is, a pet material can be hydrolyzed by an alkali, and a metal such as aluminum can be dissolved in an alkali solution. Further, in the present invention, since the treatment is a wet treatment, a step of removing moisture in the waste in advance is not required.

According to the present invention, as the pretreatment, it is desirable to crush the plastic mixed waste in advance with a cutter or the like. The finer the degree of crushing,
The subsequent contact reaction with an alkaline solution can be performed more sufficiently. However, crushing that is too fine is undesirable from an efficiency point of view. According to the invention, it is preferred that the crushed plastic is crushed such that the maximum length is between 5 mm and 15 mm. With such a degree of crushing, the subsequent contact reaction with an alkaline solution can be sufficiently performed.

In the present invention, a pretreatment such as removal of pet material or metal and removal of water as in the above-mentioned prior art is not particularly required, and a simple pretreatment such as crushing as described above is preferable. . Of course, when the individual size of the plastic is small in advance, it is needless to say that the plastic does not have to be crushed.

Next, the plastic mixed waste, preferably crushed as described above, and an alkaline solution are accommodated in a reaction vessel.

In the present invention, since an alkaline solution is used, the reaction vessel is preferably alkali-resistant. Further, a container having a lined inner surface, for example, a reaction container lined with Teflon or the like is also preferable. In addition, since heating is performed as described below, it is more preferable that the material be alkali-resistant and heat-resistant.

As the alkali used in the present invention, those exhibiting weak alkalinity such as calcium hydroxide slurry can be used. However, in such weak alkalis, the rates of dechlorination and dephthalic acid from plastics, pet materials, Has a low decomposition rate and is not very practical in terms of processing efficiency. Therefore, those showing strong alkalinity such as caustic are preferred, and sodium hydroxide is more preferred. Potassium hydroxide is also suitable, as is sodium hydroxide, but is more expensive than sodium hydroxide and sodium hydroxide is more preferred from an economic standpoint. When caustic alkali is used, the eliminated phthalic acid can be recovered as sodium phthalate or potassium phthalate. Such phthalates can be reused as desired chemical raw materials.

When a caustic alkali as described above is used,
It is important for the treatment efficiency that the concentration is such that chlorine and phthalic acid can be rapidly eliminated. The lower the concentration, the higher the water vapor pressure. Therefore, when using a closed container, it may be necessary to use a container having a strength that can cope with heating and holding described below. In the present invention, taking these factors into account, the alkali concentration is preferably 15% by weight or more, more preferably 35 to 50% by weight. Within such a concentration range, dechlorination and dephthalic acid can proceed efficiently. In addition, since the water vapor pressure cannot be increased, when a closed container is used, it is not necessary to use a pressure-resistant container.

The alkaline solution whose concentration has been adjusted as described above,
Preferably, a predetermined amount of the crushed plastic mixed waste is stored in the reaction vessel.

In the present invention, since the reaction is a solid-liquid contact reaction, an appropriate solid-liquid ratio is desirable. Here, in the present specification, the solid-liquid ratio indicates a ratio of the weight of the solid to the weight of the liquid. This solid-liquid ratio is desirably a large value from the viewpoint of processing efficiency, but since the specific gravity of the plastic is smaller than that of the alkaline solution, depending on the amount of the plastic, the amount that floats on the alkaline solution may be increased. Therefore, solid-liquid contact may not be sufficiently performed. In the present invention, in consideration of such points, the solid-liquid ratio is preferably 1% by weight or more, more preferably 1 to 8% by weight.

In storing the crushed plastic waste and the alkaline solution in the reaction vessel, it is preferable from the viewpoint of safety that the atmosphere in the reaction vessel be an inert gas atmosphere. That is, a metal such as aluminum that can be mixed into the waste can react with the alkaline solution to generate hydrogen gas. However, since it depends on the amount of metal such as aluminum in the waste, the atmosphere is not necessarily limited to the inert gas atmosphere.

Next, after the plastic mixed waste and the alkaline solution are contained in the reaction vessel, they are heated to a predetermined temperature. In the present invention, to extract chlorine from the chlorine-containing resin by contact reaction with an alkali, and to extract phthalic acid and the like by decomposition of the plasticizer and pet material contained in the chlorine-containing resin, as the reaction temperature, It is desirable from the viewpoint of efficiency that the temperature is such that these chlorine and phthalic acid can be rapidly extracted. This reaction temperature is related to the alkali concentration described above. However, if the reaction temperature is set to a low temperature, only phthalic acid can be extracted from the plastic, or only phthalic acid can be extracted first, and it is difficult to extract chlorine. This can be time consuming. Since the dechlorination from the chlorine-containing resin proceeds at 200 ° C. or higher, the reaction temperature is preferably 200 ° C. or higher. However, even if the temperature is too high, deterioration due to corrosion is apt to proceed depending on the reaction vessel, and energy consumption increases, which is not economical. Therefore, in the present invention, in consideration of these points, the reaction temperature is from 200 ° C. to 310 ° C.
C. is more preferable. Most preferably, 250
The reaction temperature is in the range of from 0 ° C. to 310 ° C., and dechlorination as well as dephthalic acid can proceed more efficiently.

The heating can be carried out by heating the reaction vessel with electric heat, a gas burner or superheated steam.

After heating to a predetermined temperature as described above, the temperature is maintained for a predetermined time. During this holding time, chlorine is extracted from the crushed plastic mixed waste, and at the same time phthalic acid is extracted. The time for complete extraction of chlorine and phthalic acid can be determined by the alkali concentration and / or reaction temperature mentioned above. This holding time can be increased as the concentration of the alkaline solution is lower, and can be shortened as the alkali concentration is higher, and longer as the reaction temperature is lower,
Higher temperatures can be shorter. In the present invention, the retention time can be set to 0.5 to 5 hours if the above-mentioned preferable alkali concentration and reaction temperature are used.

In the present invention, the difference in density between the crushed plastic and the alkaline solution is large. For this reason, in a state where the crushed plastic and the alkaline solution are stationary or a state where the reaction container is left still, the crushed plastic and the alkaline solution may not sufficiently come into contact with each other, and the reaction may not be promoted. Therefore, during the temperature hold,
In order to promote the reaction, it is desirable to bring the alkaline solution and the crushed plastic into sufficient contact as much as possible. In the present invention, it is preferable to increase the chance of contact between the crushed plastic in the reaction vessel and the alkaline solution by shaking or rotating the reaction vessel itself, or by using a stirring device or the like. As an example, when a stirrer is used, the number of rotations of the stirrer is preferably about 400 to 1000 rpm, depending on the stirring performance of the stirring blades and the like.

As described above, chlorine can be extracted from the chlorine-containing resin in the plastic mixed waste, and at the same time, the plasticizer contained in the chlorine-containing resin can be decomposed. Can be recovered and recycled. Further, phthalic acid can be obtained by decomposition of the plasticizer.

Further, pet materials that can be contained in waste can be decomposed, and terephthalic acid and ethylene glycol can be obtained. Thus, according to the present invention, conventionally, it is possible to treat a pet material which is a problem in a treatment method such as thermal decomposition oiling while mixing it in the waste,
In addition, a decomposition product can be obtained as a chemical raw material.

The above phthalic acid, terephthalic acid and ethylene glycol can each be separated purely from the alkaline solution by any suitable method known in the art. Each of these can be reused as a chemical raw material or a raw fuel for a desired compound.

Hydrocarbons can also be recovered from the alkaline solution, and can be reused as a blast furnace reducing agent, solid fuel, etc. by purifying. Further, it can be reused as a raw material for thermal decomposition oilification or gasification.

[0036]

EXAMPLES Examples of the present invention will be described below.

As a sample, a plastic mixed waste containing a chlorine-containing resin separated from general waste was used.

First, the plastic mixed waste was crushed to about 10 mm by a crushing cutter. Then, 15 g each of the crushed plastic mixed waste was divided into three samples. Subsequently, the sample and a 50% by weight aqueous sodium hydroxide solution were accommodated in a reaction vessel at a solid-liquid ratio of 3% by weight. An autoclave made of SUS304 having an internal volume of 1 L (liter) was used as a reaction vessel.

Next, the reaction vessel was heated to 250 ° C. and held for a predetermined time. The holding time was 1 hour, 3 hours, and 5 hours for each sample. 1000 rpm by electromagnetic induction type rotating flat blades
Stir with m.

Thereafter, the mixture was cooled to room temperature, the content in the autoclave was passed through a glass filter, the liquid was filtered off, and the filtrate was diluted. Subsequently, the diluted filtrate was passed through a cation exchange column to remove sodium ions. Then, the amount of chlorine and the amount of phthalic acid in the liquid after the removal were quantified by ion chromatography. As ion chromatography equipment, DIONEX (Dionex)
DX100 manufactured by the company was used.

Further, with respect to the contents held for 5 hours, the residue filtered off with a glass filter was pulverized with a pulverizer. After thoroughly mixing the ground residue, about 124
Three samples each of 3 μg were separated and subjected to elemental analysis. Elemental analysis was performed by Yanaco Analytical Industry Co., Ltd.
Using CO CHN Corder MT5 type, C
(Carbon), H (hydrogen) and N (nitrogen) were measured, and Cl was determined by potentiometric titration using a silver nitrate solution as a standard solution.
(Chlorine) was measured. Table 1 shows the measurement results.
In addition, the value in Table 1 shows the average value of the measurement results of three samples.

[0042]

[Table 1]

As is clear from Table 1, the chlorine content in the residue was below the detection limit for all three elemental analysis samples.
It turns out that chlorine was able to be extracted sufficiently. Table 1 also shows that the main elements in the residue are only carbon and hydrogen, and the residue after the reaction is a high-purity hydrocarbon.

With respect to the weight of chlorine and the weight of phthalic acid determined by ion chromatography, the ratio of the weight of dechlorinated and the weight of dephthalic acid to the weight of the sample at the time of storage was determined as a percentage. In addition, the dechlorination rate was determined. The results are shown in Table 2 below.

From the results shown in Table 1, the dechlorination rate was based on the sample having a retention time of 5 hours (dechlorination rate: 100%), and the samples having a retention time of 1 hour and 3 hours were dechlorinated. The rate was calculated.

[0046]

[Table 2]

From the results shown in Table 2, it was found that the dechlorination rate increased with the retention time.
However, as described above, it was found that chlorine could be completely extracted with a retention time of 5 hours.

Further, from the results shown in Table 2, the weight of dephthalic acid has the same value for each retention time. In other words, the amount of dephthalic acid in each sample at the retention time has reached a plateau,
Since phthalic acid proceeds at a temperature lower than the dechlorination temperature, it may be considered that phthalic acid has been completely extracted. At the same time, the pet material may also be considered completely degraded to produce phthalic acid (terephthalic acid).

As is evident from the above, according to the method of the present invention in which the plastic mixed waste is brought into contact with an alkaline solution, preferably after pretreatment, preferably only by crushing, the phthalic acid contained in the plastic mixed waste And chlorine can be completely extracted, and the residue can be recovered as a high-purity hydrocarbon. At the same time, the pet material can be completely decomposed.

[0050]

As described above, according to the present invention, it is only necessary to crush the plastic-mixed waste, preferably as a pretreatment, and the chlorine-containing resin is converted from the chlorine-containing resin by the contact reaction with the alkaline solution. Phthalic acid resulting from decomposition of a plasticizer that may be contained in the resin can be completely extracted into the alkaline solution, and a high-purity hydrocarbon can be obtained. At the same time, the pet material can be completely decomposed, and the decomposition product can be reused as a chemical raw material or a raw fuel.

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-8-259728 (JP, A) JP-A-48-96503 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 11/00 B09B 3/00 C10G 1/10

Claims (3)

(57) [Claims] 1. A plastic mixed waste mixed with a chlorine-containing resin and crushed and an aqueous sodium hydroxide solution having a concentration of 35 to 50% by weight are immersed in the aqueous sodium hydroxide solution. Heating the aqueous sodium hydroxide solution in which the plastic mixed waste in the reaction vessel is immersed to a temperature of 250 to 310 ° C. Reacts with sodium aqueous solution to remove chlorine and plasticizer
To produce high-purity hydrocarbons in aqueous sodium hydroxide solution.
Forming and floating the plastic mixed waste. 2. The method according to claim 1, wherein the crushed plastic mixed waste has a maximum length of 5 to 15 mm. 3. The method according to claim 1, wherein a ratio of the plastic mixed waste to the aqueous sodium hydroxide solution is 1 to 8% by weight.