JP3329243B2 - Supercritical water treatment apparatus and treatment method for waste - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for treating plastics, shredder dusts and the like discharged by treating waste industrial products using supercritical water.

[0002]

2. Description of the Related Art Industrial products include plastics, metals, glass, and the like, which complicate the disposal of waste products after use. Until now, a technology has been developed in which waste industrial products are crushed and pulverized, and valuable metals are selected by magnetic force, eddy current, and wind power, and separated into plastics, valuable metals, and residues (dust). After sorting, the volume of organic matter is generally reduced by incineration or thermal decomposition. Dust is made harmless by a concrete solidification method, a chemical solidification method, a melting method, or the like. The above technique is described in, for example, JP-A-8-57853.

[0003]

The above-mentioned prior art was developed for the purpose of sorting waste industrial products into plastics, valuable metals and dusts. Among these, the sorted metals are collected and collected. It is being reused. On the other hand, the sorted plastic and dust are incinerated, thermally decomposed, or rendered harmless and disposed of in landfill. However, such a processing system has a limit in recovering useful materials and the like. The first reason is that plastics and dusts can be separated very finely by combining known techniques such as specific gravity selection, but the methods and processing conditions for treating the substances thus selected are not so many in practice. There is that. For example, in the case of incineration and melting, which are common treatment methods, the operating conditions of the equipment are constant regardless of the properties of plastics and dust. A detailed system for setting operating conditions according to the conditions has not been established. For this reason, conventionally, even if plastics and dusts were finely sorted, they could not be fully utilized and were often treated under almost the same conditions. The second reason is that the material selected for the scale is incinerated depending on its properties,
Even if they are processed by methods such as thermal decomposition and melting, they have different device shapes, etc., and there are few parts that can be shared as a device. For example, by installing them collectively, high efficiency such as heat use and power consumption can be achieved. I can't expect to do that.

[0004] On the other hand, the supercritical water treatment can treat a wide range of target substances uniformly in an aqueous system, and can not only treat a single substance at a higher decomposition rate than the conventional method, but also treat various plastics. Even if the type is finely selected, the useful substance can be recovered from each by finely changing the conditions such as additives, pH, oxidizing agent, and temperature. For this reason, in the supercritical water treatment, various useful substances can be collected by finely selecting the types of plastic and shredder dust and setting various treatment conditions in accordance with the classification.

However, there are the following technical problems in order to put a supercritical water treatment system into practical use. First, as a material of the supercritical processing unit, a temperature of about 380 to 600 ° C. and a pressure of 2
It not only withstands high-temperature and high-pressure conditions of supercritical water of about 8 to 40 Mpa, but also withstands corrosive substances such as chlorine contained in waste and oxidizing agents added to increase the efficiency of treatment. You need something you can withstand. Until now, it has been difficult to develop a material that satisfies all of these heat resistance, strength, and corrosion resistance conditions. Therefore, a system for supercritical water treatment of plastics such as vinyl chloride, which causes strong corrosion, has become practical. Was difficult. Second, since a high-temperature and high-pressure supercritical water treatment apparatus consumes a large amount of energy, it is necessary to devise high efficiency in order to systematize it. If you simply process the substances selected in the previous stage in parallel,
For this purpose, high-temperature and high-pressure pressure vessels must be provided by the number of types of the selected substances, so that there is no merit of high efficiency at all.
In comparison with the case where treatment is performed in one reaction vessel, energy is consumed more.

[0006] As described above, in order to realize a supercritical water treatment system, a device must withstand both high-temperature, high-pressure and strongly corrosive conditions, which have been difficult in the past, and must be capable of reacting at various temperatures and additives. It is necessary that the conditions can be realized at the same time, and that the heat and energy utilization as a whole are highly efficient.

[0007]

SUMMARY OF THE INVENTION The present invention is a result of intensive research and development of a method and an apparatus for converting plastic and dust obtained after crushing and sorting waste industrial products into recyclable forms. It is. In other words, it withstands the temperature and pressure conditions of supercritical water and the conditions of highly corrosive environments, and converts plastics and dusts into reusable substances and recovers them, stabilizes harmful metals in dusts, A system that can increase the efficiency of use of heat and energy in these series of processes has been found. The present invention provides the following means for that purpose.

[0008] 1. As a structure of the supercritical processing apparatus, by providing multiple reaction chambers such as by providing concentric multiple cylindrical partition plates inside the reaction vessel, each fractionated product of plastic and shredder dust can be separated in one pressure vessel. The treatment can be performed under various reaction conditions depending on the type.

[0009] 2. In order to solve the two problems of high-temperature and high-pressure strength and corrosion resistance required for the material of the supercritical processing apparatus, as described above, the apparatus structure has multiple reaction chambers provided in one pressure vessel. By having a structure,
It is not necessary to meet these issues with one material at the same time.
That is, for example, for a reaction chamber for processing a sorted material containing a vinyl chloride-based plastic that causes strong corrosion,
It is necessary to make the material of the partition wall strong in corrosion resistance, but since this partition wall only partitions the reaction chamber in the entire pressure vessel, it is pressure-resistant like the pressure vessel that houses the whole equipment. There is no need to have sex. On the other hand, the pressure vessel that houses the entire apparatus must have pressure resistance to withstand the supercritical pressure, but because the caustic substance that causes strong corrosion is treated in the reaction chamber partitioned as described above. This avoids contact with the pressure vessel itself and does not require as much corrosion resistance as the partition walls of the reaction chamber for treating the corrosive substances described above. In this way, both conditions of pressure resistance and corrosion resistance at high temperature and high pressure can be satisfied.

[0010] 3. Further, by providing and adjoining multiple reaction chambers in one pressure vessel in this way, for example, heat energy generated in a supercritical water oxidation reaction chamber is transferred from a partition wall of the reaction chamber, and the adjacent reaction chambers are heated. The thermal energy can be used effectively, for example, for heating a supercritical water splitting reaction in an oxygen-free state. Further, since the heat energy is closely exchanged between the adjacent reaction chambers as described above, there is an effect of stabilizing the reaction temperature of the entire reaction system even if the components of each selected material fluctuate with time.

4. Furthermore, the processing conditions with water in a supercritical state can be set in accordance with the component composition of the plastic selected as described in 1 above, so that the plastic is converted into a monomer, oil, or gas, and collected as a useful substance. In addition, by oxidizing the selected dust in supercritical water, heat can be recovered from organic components in the dust.

5. In the above item 4, plastics are classified into four types, each of which is mainly composed of polyvinyl chloride, polyethylene and polypropylene, polystyrene, ABS resin, and PET resin. And gasification treatment methods can be selected.

6. In the case of the above 5, the plastic containing polyvinyl chloride as a main component can be recovered as gas or oil by introducing it into water in a supercritical state after dechlorination in advance. Plastics based on polyethylene and polypropylene, plastics based on polystyrene and ABS resin, and plastics based on PET resin,
By decomposing into a monomer by a solvent reaction in supercritical water, it can be recovered as a plastic raw material.

7. In the above item 4, the content of polyvinyl chloride in the plastic containing polyvinyl chloride as a main component is 60% or more by weight, and the content of polyethylene and polypropylene in the plastic containing polyethylene and polypropylene as a main component is 95%. % Or more, the content of polystyrene and ABS resin in a plastic containing polystyrene and ABS resin as a main component is 95% or more, PET
If the content of the PET resin in the resin-based plastic is 95% or more, the treatment can be performed with high efficiency.

[8] In the above item 4, after crushing the dust, introducing it into supercritical water in the presence of an oxidizing agent, thereby oxidizing plastic to reduce its volume, and stabilizing by changing metals to oxide. Can be.

In the treatment system of the present invention, the supercritical treatment apparatus has a multi-layer structure in which a plurality of reaction chambers are provided in one pressure vessel, so that the supercritical water has a high temperature and high pressure condition and the wastewater contains Conventionally difficult conditions such as strong corrosive conditions derived from vinyl chloride plastics can be overcome. Further, plastics and dusts that have not been reused can be recovered as monomers, oils, and gases that can be reused by treating them with water under various supercritical conditions after sorting.
Further, by oxidizing the plastic contained in the dust, the harmful metal can be stabilized as an oxide by utilizing the generated heat. In addition, since the respective reaction chambers having the above-described apparatus shape can be adjacent to each other, in such a series of processes, the reaction heat and energy can be effectively used to increase the efficiency.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described.
The processing object, system configuration, and processing method will be described in this order.

FIG. 1 is a flowchart showing an embodiment of the processing apparatus according to the present invention. This equipment consists of vinyl chloride plastic 2, olefin plastic 3, styrene plastic 4, PE
For each of the four types of plastics composed of the T-resin-based plastic 5 and the shredder dust 1, in a single pressure vessel 220, the reaction conditions such as additives and temperatures are set according to the properties of each of these fractions. And process at the same time. Here, vinyl chloride plastic 2
The term "predominantly" means that the content is, for example, 60% or more by weight, mainly of vinyl chloride. The olefin-based plastic 3 is mainly composed of polyethylene or polypropylene, and has a content of, for example, 95% or more. Styrene plastic 4
Is mainly composed of polystyrene or ABS resin, and the content thereof is, for example, 95% or more. The PET resin-based plastic 5 refers to a resin whose main component is a PET resin and whose content is, for example, 95% or more. The shredder dust 1 is mainly a residue remaining after sorting the above-mentioned various plastics from waste. The configuration of the present apparatus is largely as shown in FIG. 1, a supply means 1000 for supplying each fraction to the reaction means 2000 under supercritical water reaction conditions suitable for each,
Reaction means 2 for treating these simultaneously in a single pressure vessel
And recovery means 3000 for separating and recovering the substances generated by the reaction means 2000 respectively.

The supply means 1000 is provided with supply pipes 101 to 105 arranged corresponding to the above-mentioned separated material and water 100M.
Pressurizing means 21 to 25 for increasing the supercritical pressure to Pa or higher, and each of supply devices 11 to 15 for supplying the above-mentioned fractions into a supply pipe.
And means for supplying additives such as alkali 32 and oxidizing agents 51 and 52, and dechlorination means for pre-treating the vinyl chloride plastic 2 and the like.

As shown in FIG. 2, the reaction means 2000 is a cylindrical pressure vessel 220, which is formed concentrically with the partition walls 211 to 214 and the outer wall 21 along the flow of the object to be treated.
By providing 5, the inside is partitioned into a plurality of reaction chambers 201 to 205 having a multi-cylindrical shape. As shown in FIG. 3, for example, as shown in FIG. 3, the reaction chamber 201 is divided into five reaction chambers 201 to 205 from the inside, and the reaction chamber 201 has a reaction chamber 202 outside and the reaction chamber 202 has a reaction chamber 202 outside. Room 20
3. The outside of the reaction chamber 203 is the reaction chamber 204 and the reaction chamber 204.
The reaction chamber 205 surrounds the outside of the reactor, and the supply pipe 101 is connected to the reaction chamber from each supply pipe.
The reaction pipe 201 is connected to the reaction chamber 201 from the partition wall 211 through the partition walls 212 to 214 and the outer wall 215.
02 is connected to the reaction chamber 202 from the partition 212 through the partitions 213, 214 and the outer wall 215 of the reaction chambers 203 to 205, and the supply pipe 103 is connected to the partition 2 of the reaction chambers 204 to 205.
14 is connected to the reaction chamber 203 from the partition wall 213 through the outer wall 215, and the supply pipe 104 is connected to the reaction chamber 204 through the outer wall 215 of the reaction chamber 205 from the partition wall 214.
5 has a structure in which it is directly connected to the reaction chamber 205 from the outer wall 215. The outer wall 215 of the reaction chamber 205 may also serve as a pressure vessel 220 that accommodates the entire reaction chambers 201 to 205 as shown in FIGS.

The recovery means 3000 is provided in each of the reaction chambers 20 described above.
Discharge pipes 301 to 305 for discharging supercritical water and reaction products entrained therein (hereinafter collectively referred to as products) after the treatment at 1 to 205, and cooling for cooling the products to near room temperature Means 311 to 315, pressure reducing valves 321 to 325 for lowering the pressure of the product to normal pressure, and vapor-salt separating means 331 for recovering a product which separates into a gas phase and a liquid phase at a temperature close to normal temperature and normal pressure, respectively. To 335, and solid-liquid separation means 341 for separating and removing solid components contained in the liquid phase.
345. The connection from each of the reaction chambers to the discharge pipe has a structure in which the outlet end of the reaction chamber is multiplexed in the same manner as the above-mentioned inlet end, and the discharge pipe is connected from the end of each reaction chamber.

The processing method in this apparatus is as follows.

First, water 100 is supplied to a supply pipe 101 corresponding to each processing of shredder dust 1, vinyl chloride plastic 2, olefin plastic 3, styrene plastic 4, and PET resin plastic 5.
To 105. Of these, the alkali 32 may be further added to the supply pipe 102 corresponding to the treatment of the vinyl chloride plastic 2 by the alkali supply means 42. This is for neutralization in the reaction chamber 202 in the latter stage. As the alkali, for example, caustic soda may be used. Next, the water 10 in these supply pipes 101 to 105 is
0 is introduced into each of the pressure raising means 21 to 25 and the pressure 22
The pressure is increased to a supercritical pressure of not less than MPa, and shredder dust 1, a polyvinyl chloride plastic 2,
The olefin-based plastic 3, the styrene-based plastic 4, and the PET resin-based plastic 5 are respectively supplied from the supply devices 11 to 15. In the feeders 11 to 15, shredder dust 1 and various plastics 2 to 5 to be supplied are provided.
May be supplied in a state of being heated and melted at a temperature of about 100 to 200 ° C. However, before the vinyl chloride plastic 2 is introduced into the supply unit 12, the dechlorination means 8
It is desirable to introduce chlorine into the polyvinyl chloride-based plastic in the thickener to remove the chlorine content in advance. This is to prevent hydrogen chloride from being generated and corroding the reaction vessel in the subsequent processing, particularly in the processing in the reaction chamber 202, and the method is as follows. It is advisable to heat the mixture to a temperature of not higher than about ° C. and desorb chlorine as hydrogen chloride by a chemical reaction. Further, since the PET resin-based plastic 5 has a property that it is hard to be melted even when heated, it is preferable to supply the finely pulverized particles having a particle size of about 1 mm or less in advance.

The oxidizing agents 51 and 62 are supplied to the shredder dust 1 and the vinyl chloride-based plastic 2 by the oxidizing agent supplying means 61 and 62, from among the objects to be treated, that is, the separated materials, supplied into the water 100 in this manner. 52. Oxygen or hydrogen peroxide may be used as the oxidizing agent.
Since the supply of the processing object and the oxidizing agents 51 and 52 to the water 100 is performed while being heated by the preheating means 71 to 75, the mixed fluid of the water 100 and the processing object is supplied to the supply pipes 101 to While 105 passes through the preheating means 71 to 75, the temperature is raised to a critical temperature of about 380 ° C., and the condition becomes near supercritical. The preheating method in the preheating means 71 to 75 includes, for example, a reaction product cooling means 31 described later.
The waste heat generated in 1 to 315 may be exchanged with heat.

The following reaction chambers 201 to 201 in the reaction means 2000
In 205, in the water near the supercritical state, the shredder dust 1 and the vinyl chloride-based plastic 2 to be treated are partially oxidatively decomposed by reacting with the oxidizing agents 61 and 62, respectively, to form oil or gas. Is converted. In addition, olefin plastic 3, styrene plastic 4, PE
The T resin-based plastic 5 is decomposed and monomerized by reacting with water that has almost reached a supercritical state. The temperatures in the reaction chambers 201 to 205 are maintained by heat generated by oxidation and decomposition reactions. Also, the reaction chambers 201 and 2
The temperature of each reaction chamber can be controlled to some extent by utilizing the heat transfer between them.

The reaction products generated in the reaction chambers 201 to 205 are led out of the reaction means by discharge pipes 301 to 305, respectively. Discharge pipe 301 from reaction chambers 201-205
The connection to 305 is the same as the connection from the supply pipes 101 to 105 to the reaction chambers 201 to 205 as shown in FIG. Next, these reaction products are supplied to the cooling means 31.
It is cooled to near normal temperature by 1 to 315, and the pressure reducing valve 32
The pressure is reduced to near normal pressure by 1 to 325. As a cooling method, heat exchange may be performed with water or the like. Since the reaction product in the normal temperature and normal pressure state is separated into a gas phase and a liquid phase, the reaction product is introduced into gas-liquid separation means 331 to 335, and the recovered gas 401 to 405 and the recovered liquid 501 to Separated and collected as 505. The shape of the gas-liquid separation means 331 to 335 is basically a tank type, and may be any as long as it can collect, from the upper part and the lower part, reaction products in which gas and liquid are vertically separated into phases. The recovered liquids 501 to 505 are further introduced into solid-liquid separation means 341 to 345 to remove solids contained in the liquids.

As described above, in the system of the present invention, the inside of the pressure vessel 220 is provided with a plurality of reaction chambers 201 to 201 having a multi-cylindrical shape.
205, the single pressure vessel 2
In 20, the treatment is carried out under the reaction conditions such as the temperature and the oxidizing agent according to the properties of the fractionated material, and it is possible to cope with both the high-temperature, high-pressure and strongly corrosive conditions, which were conventionally difficult. In addition, since the reaction chamber has a multi-layer structure, the necessary heat can be supplied to adjacent reaction chambers by effectively utilizing the heat transfer of the reaction heat. is made of.

As for the selection of the material, the partition wall 21 inside the reaction chamber 202 for processing the vinyl chloride plastic is used.
The first and outer partition walls 212 may be made of, for example, Inconel or Hastelloy, which have corrosion resistance, but their pressure resistance may not be as strong as the pressure vessel 220. Also,
If the pressure vessel 220 itself is distinguished from the outer wall 215 of the reaction chamber, the supercritical water does not need to come into contact with the object to be treated.
The material may be selected from high strength stainless steel, etc.
Corrosion resistance like the above-mentioned partition walls 211 and 212 is not required.

[0029]

The supercritical water treatment system of the present invention can withstand both of the conventionally difficult conditions of high temperature and pressure caused by supercritical water and the presence of strongly corrosive substances in waste. In addition, plastics and dusts that have not been reused before are treated with water under various supercritical conditions after sorting, so that monomers, oils,
It can be recovered as gas. Further, by oxidizing the plastic contained in the dust, the harmful metal can be stabilized as an oxide by utilizing the generated heat. Furthermore, the efficiency of the entire system can be improved by effectively utilizing the reaction heat and the energy generated in the series of processes.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating an embodiment of the present invention.

FIG. 2 is a perspective view showing an embodiment of the reaction vessel of the present invention.

FIG. 3 is a sectional view showing an embodiment of the reaction vessel of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Shredder dust, 2 ... Vinyl chloride plastic, 3 ... Olefin plastic, 4 ... Styrene plastic, 5 ... PET resin plastic, 21-2
5 ... Pressurizing means, 71-75 ... Preheating means, 100 ... Water, 1
01-105 ... supply pipe, 201-205 ... reaction chamber, 21
1-214 ... partition wall, 215 ... outer wall, 220 ... pressure vessel,
301-305 ... discharge pipe, 311-315 ... cooling means,
321 to 325 pressure reducing valve, 331 to 335 gas-liquid separation means, 341 to 345 solid-liquid separation means, 401 to 405
Collected gas, 501 to 505: Collected liquid, 1000: Supply means, 2000: Reaction means, 3000: Collection means.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Tobita 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Hisao Yamashita 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture No. 1 Hitachi, Ltd. Investigator in Hitachi Research Laboratory Tadahiro Sanada (56) References JP-A-9-85075 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 11/14 B09B 3/00 B01J 3/00 B01J 3/02

Claims (4)

(57) [Claims] An apparatus for supercritical water treatment of waste plastics separated into a plurality of types or shredder dusts individually and at once, comprising: a reaction vessel for supercritical water treatment; It has means for supplying plastic and shredder dust, respectively, and means for discharging each product generated in the reaction vessel. A multi-cylindrical pipe is provided in the reaction vessel, and independent reaction is performed for each cylinder. A waste supercritical water treatment apparatus, wherein a chamber is formed. 2. A method for treating a plurality of types of waste plastics or shredder dusts individually and at once with supercritical water, wherein a multi-cylindrical tube is provided in a reaction vessel for supercritical water treatment. Forming an independent reaction chamber for each cylinder, individually supplying the plastic or shredder dust to any of the reaction chambers, and performing supercritical water treatment under unique conditions for each reaction chamber. Supercritical water treatment method for waste. 3. The method according to claim 2, wherein the separated plastics are polyvinyl chloride, polyethylene and polypropylene, polystyrene and ABS resin, PET
A waste material characterized by four types of plastics, each of which contains resin as a main component. In supercritical water, the method of monomerization, oilification, and gasification is selected according to the type of the main component of the plastic. Supercritical water treatment method. 4. The supercritical water treatment method for waste according to claim 2, wherein the shredder dust is oxidized in supercritical water to recover heat.