JP2969417B2 - Decomposition method of waste plastic - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the recycling and effective use of waste plastic, and more particularly, to a decomposition method for recovering fuel gas, fuel oil, etc. as waste from waste plastic, mainly as paraffin-based components. It is about.

[0002]

2. Description of the Related Art Generally, wastes collected from homes and factories include various kinds of plastics. Such waste plastics can be reused as gas or fuel oil by thermally decomposing them from polymers to low molecules. However, the conventional waste plastic decomposition method is
Even though there are various problems and there is an urgent and strong demand, except for special cases, it can be said that a general practical device has not been operated until now. Many devices have been tested so far, but these are broadly divided into external heating systems and internal heating systems. The external heating method is to heat a reactor from the outside by a burner or the like to decompose waste plastic in the reactor, and is known as a pipe steel type, a retort type, or the like. This is often the case in relatively small reactors, mainly for sorted plastics. On the other hand, the internal heating method decomposes waste plastic in the reactor by introducing a heating gas serving as decomposition energy into the reactor, and is known as a fluidized bed type, a shaft furnace, or the like. Relatively large reactors have been tested, especially a number of fluidized bed systems.
In both the external heating method and the internal heating method, the pyrolysis products are recovered outside the reactor as steam. These are, in addition to the low marketability of the recovered material, various problems that hinder the practical use of the reactor. was there.

[0003]

However, according to such a conventional method of decomposing waste plastic, in the case of the external heating method, the thermal conductivity of the plastic is low, and the outer peripheral portion and the central portion in the reactor have a temperature difference between the outer peripheral portion and the central portion. Because of the difference, there are the following problems. The reactions occurring at the outer peripheral portion and the central portion are different from each other, and a violent decomposition reaction in which carbon is generated occurs at the outer peripheral portion of the reactor, and a moderate decomposition reaction such as the generation of wax occurs at the central portion. A carbon film is easily formed by coking on the inner wall of the reactor, and this carbon film hinders heat transfer to the inside, so the heating efficiency is greatly reduced and the supply of reaction energy is not efficient, and a large amount of ineffective energy Is consumed and uneconomical. The decomposition products have a relatively wide molecular weight distribution, and because the products are olefins, they tend to polymerize during storage or transportation to cause the components to be denatured, resulting in low economic efficiency. PVC in waste plastic
(Polyvinyl chloride), PET (polyethylene terephthalate) and other difficult-to-oil polymers include a large amount of solid residue remaining in the reactor, making it difficult to remove them.
Either the polymer was separated into only polyolefins that are advantageous for oiling, or an economically disadvantaged high-temperature decomposition reactor (600 ° C. or higher) was required.

In the case of the internal heating method, the gas flow rate of the heated air supplied as decomposition energy is relatively large, and as a result, the residence time is significantly shortened. For this reason, the reaction temperature must be raised to a high temperature (600 ° C. or higher), which causes the following problem. In general, the decomposition products are gaseous and contain a large amount of CO2 and CO, have low calories burned as fuel gas, and have low marketability of recovered products. The reactor for carrying out the high-temperature reaction becomes expensive, and the service life of the reactor is shortened. As a result, expensive components having low economical efficiency are recovered. For this reason, the conventional methods of decomposing waste plastic by the external heating method and the internal heating method do not solve fundamental problems such as the method of supplying the decomposition energy and the low marketability of the product. Very few practical devices are known. The development of practical equipment has almost been abandoned, and it is necessary to rely on incineration and landfill. The present invention has been made to solve such a problem. First, a method of supplying reaction energy for a decomposition reaction is basically solved in consideration of a reaction mechanism, and a heater is provided in a reactor. And selectively decomposes only the oilable plastics in the mixed waste plastics at a relatively low temperature, thereby providing a temperature distribution,
Decomposition method for waste plastics that enables the separation and decomposition of gas / oilified components and undecomposed products and recovers high-value components with marketability efficiently
The purpose is to provide.

[0005]

Decomposition method of waste plastics of the present invention to its SUMMARY trying to achieve the above, the waste plastic in the reactor
To supply heat of decomposition to the waste plastic by the internal heating method.
A method of recovering the thermal decomposition product of the heat outside the reactor.
Te, the next step A~E, A. A moving bed made of heat storage medium is formed inside the reactor.
That process, B. Introducing waste plastic into the reactor, the moving bed
With the heat of the heat storage medium
B. decomposing the waste plastic; The volatile decomposition product of the waste plastic is transferred to the reactor.
A step of taking out and collecting at the top, D. High temperature steam is introduced into the lower part of the moving bed of the reactor.
Into the waste plastic decomposed product
It acts as a rear gas and heats high-temperature steam
A. re-decomposition for lightening by lug; From the lower part of the reactor, decomposition products, non-volatile
The process consists of discharging the disassembled material and heat storage medium.
Sign.

Further, the method for decomposing waste plastic of the present invention.
Is heated by the heater built in the reactor and
It is advisable to add a step of heating the waste plastic. Ma
Further, the method for decomposing waste plastic according to the present invention comprises the reactor
Outside, the heat storage heat medium and the waste plastic are selected.
And heat regeneration of the heat storage heat medium,
It is advisable to add a step of re-introducing and recycling the reactor.
It is desirable that the heat storage heat medium is granular. The accumulation
It is desirable that all or part of the heating medium is a catalyst.
No. The temperature in the reactor may be 500 ° C. or less.
desirable.

[0007]

Decomposition method of waste plastics of the [action] The present invention, waste plastics
The decomposition energy of the stick is stored as a heat storage medium and high-temperature water vapor
Feed into the reactor by air. Thermal storage medium transfer floor
In the upper part, waste plastic is mainly generated by the heat of the heat storage heat medium.
Decomposes and some vapors evaporate above the moving bed
You. On the other hand, in the lower part of the moving bed,
Undegraded waste plastics and heavy oil
You. The high-temperature steam is undecomposed and separated in the lower part of the moving bed.
While acting as a carrier gas for the lightened oil,
Plays a role in promoting the re-decomposition of heavy oil components in cracked products
You. In other words, the supply of decomposition energy is
Decomposition required for reaction control in the reactor
Efficient supply of energy streamlines decomposition reactions
Can be controlled. Also, when disassembling, waste plastic
Only volatiles that have a vapor pressure in the system
Gas through the heat transfer medium to remove it outside the system.
And non-decomposed products are easily separated. In addition, in the reactor
When the heating temperature of the moving bed is controlled by the storage heater,
Easy distribution of temperature distribution in reactors that is disadvantageous for control
Waste blasting in the upper and lower layers of the moving floor.
The cracking reaction efficiently according to its decomposition reaction mechanism
Can proceed.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 shows an apparatus for decomposing waste plastic according to a first embodiment of the present invention. As shown in FIG. 1, the decomposition apparatus 10 includes a reactor 20, a heating medium regeneration furnace 14, a separation apparatus 16 for separating a heating medium and a residue, and a heating medium supply apparatus 18. The waste plastic is thermally decomposed by introducing a heat storage medium. The heat storage heat medium for thermally decomposing the waste plastic circulates through the reactor 20 and the heat medium regeneration furnace 14 as shown by arrows a to e in FIG. 1, and transfers the heat recovered by the heat medium regeneration furnace 14 to the reactor 20. It is supplied as decomposition energy together with high-temperature gas (usually steam). Here, as the heat storage heat medium, for example, it is desirable to use a granular solid acid catalyst made of silica-alumina or the like, and as the shape of the heat medium particles, for example, spherical,
Cylinder, cylinder, triangular prism, quadrangular prism, regular tetrahedron, and the like can be used. In this case, those having an average particle diameter of the heat medium particles of about 2 to 3 mm are effective. In particular, when a cylindrical material is used, the decomposition reaction of the waste plastic can be efficiently promoted because the surface area of the particles is large.

The reactor 20 is made of a refractory brick, ceramic, or the like, and includes a mixing section 22 (when the waste plastic and the heat medium are homogenized by a stirrer) and a reaction section 24. The waste plastic inlet 26 and the heat medium inlet 28 are provided at predetermined positions of the mixing unit 22. As an example, waste plastics that have been appropriately pulverized are screw feeders 3
0, the heat storage medium is introduced into the reactor 20 from the waste plastic input port 26 by the heat medium supply port 28 by the heat medium supply device 18. In addition,
The waste plastic may be supplied directly to the heating medium from a waste plastic inlet provided separately in the upper part of the reactor without using a screw feeder. Then, a heating medium is supplied onto the waste plastic, and this is repeatedly performed. Mixing section 2
A decomposition gas discharge port 31 is provided on the ceiling wall of No. 2. Of course, this can be provided on the side surface of the reactor 20, but in any case, the decomposition gas discharge port 31 is provided with a gas cooling jacket 3 made of, for example, a spiral stainless pipe.
2 are provided. By adjusting the temperature of the jacket 32, the molecular weight of the decomposed gas discharged to the outside can be controlled to give selectivity to the properties of the product.

The reaction section 24 is preferably provided with a partition wall 34 made of, for example, ceramic along the inner peripheral wall surface. The partition wall 34 prevents the inner wall of the reactor 22 from being worn by the movement of the heat storage medium. The partition wall 34 can be replaced after being used for a predetermined period, which contributes to increasing the durability of the device. At the bottom of the reaction section 24, an outlet 36 for the undecomposed material and the heat storage heat medium is provided. A lower part of the outlet 36 is provided with a separating device 1 for separating the undecomposed material and the heat storage heat medium.
6 are provided. The non-volatile non-decomposed material and the heat storage heat medium generated by the thermal decomposition of the waste plastic are discharged from the outlet 36 and introduced into the separation device 16. When the heat storage heat medium and the heavy oil containing undecomposed substances are separately taken out, as shown in a second embodiment described later, an outlet may be provided on the lower side surface of the reactor. These are all arbitrarily selected according to the ratio of the polyolefin in the waste plastic.

The separating device 16 comprises, for example, a screw type extractor 40, a drive motor 42, a sorter 44 and a transfer means 46. The undecomposed material and the heat storage heat medium are sent to the separator 44 by the screw type extractor 40, where they are separated, and the undecomposed material is separated and collected in the separator 44,
The heat storage heat medium is sent to the heat medium regeneration furnace 14 through the transfer means 46.

The heat medium regeneration furnace 14 has, for example, a heating gas supply unit 51 and a stalker 52 in a furnace body 50.
The heat storage medium is regenerated by heating and burning when moving the stalker 52. The combustion gas generated in the combustion chamber 54 is
After the heat is recovered and cooled, it is discharged out of the furnace by the chimney 56. The heat medium supply device 18 is, for example, an elevator 6
0, an elevator drive motor 62, a heat medium cabinet 64, a screw feeder 66, a screw feeder drive motor 68, and a transfer means 69. The heat storage heat medium regenerated in the heat medium regeneration furnace 14 is transferred to the heat medium cabinet 64 by the elevator 60 and adjusted to a predetermined temperature, and then transferred by the screw feeder 66 to the transfer means 69.
Through to the reactor 20.

A heat exchanger 80 is provided in the heat medium regeneration furnace 14, a pipe 82 is connected from the heat exchanger 80 to the heat medium cabinet 64, and a pipe 83 is connected from the heat medium cabinet 64 to the reactor 20. Is connected. The high-temperature steam heated by the heat exchanger 80 is used for adjusting the temperature of the heat medium cabinet 64, and then further heated, and if necessary, is converted into steam at a predetermined temperature in the reactor 20.
The gas is blown from the high-temperature gas inlet 81 as decomposition energy. The controller 84 provided in the pipe 83 controls the flow rate of steam introduced into the reactor 20. The heating gas supply port 75 attached to the heating medium cabinet 64 controls the temperature of the heating medium supplied to the reactor 20. Further, as another example, the heat storage heat medium is transferred to the heat medium cabinet 64 by the transfer means 46 directly without passing through the heat medium regeneration furnace 14, and the heat storage medium is transferred by the heating gas introduced into the heat medium cabinet 64. Playback is also possible. This is arbitrarily selected depending on the composition of the waste plastic.

Next, a method of decomposing waste plastic using the decomposer 10 will be described. First, a predetermined amount of heat storage medium heated to a temperature slightly higher than the reaction set temperature is input from the heat medium inlet 28, and the heat storage medium is moved from the upper part to the lower part to form a moving bed. A predetermined amount of pulverized waste plastic is injected from a plastic input port 26 onto a heat medium serving as a moving bed. The operation of sequentially charging the heat storage medium and the waste plastic onto the waste plastic is repeated, and as shown in FIG.
The inside is laminated. Here, in FIG.
e indicates a heat storage medium layer, and 88a to 88e indicate waste plastic layers.

The reaction set temperature is, for example, about 400 to 500 ° C. in the case of a thermal decomposition reaction. 250-500
This is because when the temperature is in the range of about ° C, waste plastic is decomposed into useful oil components, and the molecular weight distribution of the decomposed product can be narrowed to reduce the molecular weight. However, in this reaction, when a heat storage heat medium having a catalytic function is used as described later, the temperature in the reactor is in the range of 250 to 400 ° C.
A so-called low-temperature oiling reaction is possible. When the polymer constituting the waste plastic comes into contact with the heat storage medium, the polyolefin and polystyrene are first melted, and the viscosity of the polymer decreases, and the polymer flows down between the particles of the heat storage medium. Then, decomposition and reduction of the molecular weight further progress between these particles, and a heavy oil is generated from the high viscosity polymer. The heavy oil causes a decrease in molecular weight while permeating and diffusing through the heat storage medium layers 86a to 86e.

When the heat storage heat medium is a catalyst, the heavy decomposition product is
The molecular weight is further reduced by catalytic cracking, and vaporized in the reactor 20. Then, the vaporized product passes through, for example, the heat storage heat medium layers 86a to 86e in FIG. 1 and moves to the low-pressure side decomposition gas discharge port 31 by the vapor pressure. That is, only the component having a vapor pressure is filtered and separated into the heat storage heat medium layers 86a to 86e in the reactor 20, and then moves as steam to the cracked gas discharge port 31, and is discharged outside the reactor 20 and collected. You. On the other hand, the controller 84
When high-temperature steam is blown into the lower part of the moving bed , the steam acts as the reaction energy for thermal decomposition and as a carrier gas, and promotes the re-decomposition of high-viscosity heavy substances that remain between the particles of the heat storage heat medium.

In the above embodiment, since a solid acid catalyst such as silica-alumina is usually used as a heat storage heat medium, carbonization of decomposition products proceeds on the catalyst surface, and hydrogen atoms released in the carbonization process Performs hydrogenation of the olefin component in the decomposition product. That is, during the decomposition reaction,
A hydrogen transfer reaction occurs. Therefore, when the decomposition product generated in the heat storage heat medium layer rises through the catalyst layer,
Furthermore, it is re-decomposed and hydrogenated at the same time to become a stable paraffinic gas or oil. It is one of the features of the present invention to make such a hydrogen transfer reaction dominantly proceed,
For this purpose, the amount of catalyst and the amount of waste plastic supplied are adjusted. In this case, it is desirable to make the catalyst concentration relative to the reactant relatively high. In addition, a solid acid catalyst causes a large amount of carbonaceous material to precipitate on the catalyst surface as the reaction time increases,
This carbonaceous material becomes a fuel for regenerating the heat medium.

The heat storage medium obtained by thermally decomposing the waste plastic accumulates in the lower part of the reactor 20. The heat storage heat medium layer contains undecomposed products of waste plastic. Then, the heat storage heat medium containing the undecomposed material is extracted from the heat medium outlet 36 and collected in the separator 44. Thus, the reactor 20
The thermal storage medium and the waste plastic are charged from the upper part of the reactor 20 to continuously perform the operation of separating and recovering the decomposition gas from the upper part of the reactor 20 and the thermal storage medium and the decomposition products and undecomposed products from the lower part. The decomposed gas and undecomposed products of the waste plastic are separated and collected.

According to the method for decomposing waste plastic in the above embodiment, since the waste plastic is decomposed by the heat storage medium, a temperature difference due to heat absorption occurs in the reactor 20 due to the temperature of the heat storage medium and the high temperature. By adjusting the temperature of the steam and the supply amount thereof, the inside of the reactor 20 can be maintained at a reaction condition suitable for the decomposition reaction. Also,
According to the above embodiment, by adjusting the supply amount and the discharge amount of the waste plastic and the heat storage heat medium, the residence time of the reactant in the reaction system can be appropriately controlled. The composition of the reaction product can be controlled. For example, if the contact time is set to a relatively long time, the amount of recovered multi-branched paraffin-based components can be increased. These components are not generated by the conventional waste plastic decomposition apparatus, and have various advantages such as excellent combustibility and a new use as a high boiling point solvent.

In general, among waste plastics, those which generate volatile components when decomposed at low temperature (400 ° C. or lower) are made of polyolefin or polystyrene.
VC and PET hardly generate vapor pressure components, and solid residues increase. In addition, in the method of decomposing waste plastic using a high-temperature gas as a heat medium as seen in a conventional apparatus (fluidized bed), the calorie of the recovered decomposed gas is low,
The external heating method is not practical because energy loss is large and the added value of the product is low. On the other hand, according to the waste plastic decomposition method according to the above embodiment, the energy supply method for heat decomposition is rational, and the undecomposed material is easily separated into the decomposed gas and the undecomposed material in the reactor 20. So that a so-called mixed plastic decomposition treatment is possible. In particular, the recovered gas and oil are paraffinic and chemically stable unlike conventional olefinic components. is there.

Therefore, the waste plastic charged into the reactor 20 may be of any composition, especially PVC
There is no problem even if it is 100%. That is, PVC which is the most difficult in the decomposition treatment of waste plastic
Can be easily decomposed to recover useful components. For example, in the case of PVC 100%, a small amount of oil and a large amount of HCl gas are generated by thermal decomposition, but most of PVC is recovered from the outlet 36 together with the heat storage medium as fixed carbonaceous matter. The carbonaceous residue can be used as a useful activated carbon by being activated with steam, so that the field of use is wide. In particular, when recovering as activated carbon, the moving bed can be stopped to promote the dehydrochlorination reaction of PVC as a fixed bed, and the generated carbide can be brought into contact with high-temperature steam (600 to 700 ° C. or higher) to be recovered as activated carbon.

In the above embodiment, the reactor has a relatively simple structure and is made of a heat-insulating material such as refractory brick or refractory ceramic, so that it is hardly corroded by an acid such as PVC and the life of the apparatus is extended. be able to. further,
Since a carbon film due to coking is hardly generated on the inner wall of the reactor, special techniques and materials for preventing the formation of a carbon film as in the conventional reactor are not required.

Next, the results of an experiment in which waste plastics were decomposed using the above-described embodiment are shown in Table 1.

[Table 1] As a result of the experiment, as shown in Table 1, in the above example, high value-added components such as gasoline and kerosene fractions were efficiently and largely recovered at a relatively low temperature.

In the first embodiment, the waste plastic inlet 26 is provided on the side wall of the reactor, and the outlet 36 for the heat medium and the undecomposed substances is provided on the bottom wall.
For example, as shown in the second embodiment shown in FIG.
A heat medium outlet 92 may be provided on the side wall of the heat medium. Further, as a third embodiment of the present invention, for example, as shown in FIG.
0 and 102 are provided to allow a fluid at an appropriate temperature to flow through these tubes, and the flowing fluid serves as a supply source of decomposition energy, and at the same time, controls the temperature distribution in the reactor 20. In addition, these built-in heaters may be installed in any direction of the vertical axis and the horizontal axis of the reactor. Further, in the above embodiment, the waste plastic and the heat storage heat medium were laminated and reacted, but as another embodiment of the present invention, for example, when only polystyrene is treated, the waste plastic and the heat storage heat medium are placed in the reactor. May be charged and mixed with a stirrer installed in the reactor. More preferably, the decomposition reaction may be performed by removing the built-in heater of the reactor, stopping the blowing of the high-temperature gas, and supplying the decomposition energy only from the moving bed heat storage heat medium. Conversely, the reaction can be carried out only by the heater built into the reactor and the decomposition energy from the high-temperature gas as a fixed bed with the moving bed stopped. Of course, as can be easily understood from the above examples, for example, a waste plastic supply port is provided at the lower part of the reactor, a heat medium outlet is provided at the upper part of the reactor, and a decomposition gas outlet is provided at the reactor. The decomposition reaction can be carried out continuously while being provided at the upper portion or side surface of the reactor and moving the heat medium from the lower portion to the upper portion by a screw blade. These merely replace the heating medium stirrer with screw blades and use the usual inlet / outlet provided in the reactor in reverse. These are arbitrarily selected depending on the composition of the waste plastic and the treatment amount.

[0025]

As described above , according to the waste plastic decomposition method of the present invention, waste plastic is brought into contact with the heat storage heat medium forming the moving bed to supply waste plastic decomposition energy , and the waste plastic is decomposed. High-temperature steaming on the lower part of the floor
Supply heat of re-decomposition of decomposition products of waste plastic
To feed, the reactor is held at a suitable temperature distribution, it is possible to obtain a high high quality value-added decomposition products. In addition, since the heat storage heat medium functions as a filter material, volatile substances generated during decomposition and undecomposed substances can be easily separated and recovered. Not only can be made into a low-temperature oil (400 ° C. or lower), but also is effective in treating PVC itself. In particular, there is an effect that a decomposition product of a chemically stable paraffin-based component having excellent storage properties and flammability can be selectively recovered as a point different from the conventional one. Furthermore, since the heat storage heat medium is heated and incinerated and regenerated outside the reactor and recycled, the reaction energy for the decomposition reaction can be easily supplied and the reaction can be continuously performed.
There is an effect that a large amount of waste plastic can be efficiently treated.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an apparatus for decomposing waste plastic according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing an apparatus for decomposing waste plastic according to a second embodiment of the present invention.

FIG. 3 is a schematic configuration diagram showing an apparatus for decomposing waste plastic according to a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Decomposition apparatus 14 Regeneration furnace 16 Separation apparatus 18 Heat medium supply apparatus 20 Reactor 28 Heat medium input port 30 Waste plastic input port 31 Decomposition gas discharge port 36 Discharge port 40 Screw type extractor 86a-86e Heat storage heat medium layer 88a-86e Waste plastic layer 100, 101 Fluid flow pipe (reactor built-in heater)

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-59-111815 (JP, A) JP-A-54-83002 (JP, A) JP-A-53-126777 (JP, A) JP-A-53-111 26480 (JP, A) JP-A-49-99960 (JP, A) JP-A-53-101074 (JP, A) JP-A-49-95470 (JP, A) (58) Fields investigated (Int. ⁶ , DB name) C10G 1/10 B09B 3/00

Claims (6)

(57) [Claims] 1. An internal heating method for waste plastic in a reactor
The decomposition heat is supplied according to the formula to thermally decompose the waste plastic.
A method of recovering a substance outside the reactor, comprising:
AE, A. A moving bed made of heat storage medium is formed inside the reactor.
Process, B. Introducing waste plastic into the reactor, the moving bed
With the heat of the heat storage medium
Decomposing the waste plastic, C. The volatile decomposition product of the waste plastic is transferred to the reactor.
The process of taking out and collecting at the top, D. High temperature steam is introduced into the lower part of the moving bed of the reactor.
Into the waste plastic decomposed product
It acts as a rear gas and heats high-temperature steam
Process to re-decompose for lighter, E. FIG. From the lower part of the reactor, decomposition products, non-volatile
The process consists of discharging the disassembled material and heat storage medium.
A method of decomposing waste plastic. 2. The heat storage heat medium by a heater built in a reactor.
Adding a step of heating the body and the waste plastic
The method for decomposing waste plastic according to claim 1. 3. The heat storage heat medium and the heat storage medium outside the reactor.
And the waste plastics, and the heat storage heat
The medium is heated and regenerated, re-introduced into the reactor and recycled.
3. The waste plus according to claim 1, further comprising a step of adding
How to break tics. 4. The thermal storage medium according to claim 1, wherein the thermal storage medium is granular.
4. The method for decomposing waste plastic according to 2 or 3. 5. All or a part of the heat storage heat medium is a catalyst.
The waste plastic according to claim 1, 2, 3, or 4,
Decomposition method. 6. The temperature in the reactor is 500 ° C. or less.
Waste plastic according to claim 1, 2, 3, 4 or 5.
Decomposition method.