JP3478324B2 - Gasification method of plastic - 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 gasifying plastics, in which discarded plastics are mainly decomposed into useful gas such as hydrogen gas and reused.

[0002]

2. Description of the Related Art Conventionally, plastics, for example, thermoplastic resins such as polyethylene, polypropylene, polyvinyl chloride and polystyrene, and thermosetting resins such as polyurethane, melamine and PET (polyethylene terephthalate) have been enormous as domestic and industrial wastes. A large amount is discharged, and its disposal or reuse is an important issue. Therefore, various methods of gasifying and recycling the discarded plastic have been proposed. As one of the gasification methods, a method is known in which a plastic is contacted with high-temperature hot water containing supercritical water in a reaction vessel to cause a reaction, and gasified,
In this method, NaOH (alkali), sodium alkylbenzenesulfonate (surfactant), CH ₃ OH (alcohols) and the like are used as reaction catalysts (JP-A-6-299169).

[0003]

However, in the above-mentioned conventional method, there is a problem that the ratio of hydrogen gas in the gas generated by the decomposition of plastic is low and the amount of hydrogen gas itself generated is not practically sufficient. An object of the present invention is to provide a method for gasifying a plastic, which can efficiently decompose the plastic into hydrogen gas.

[0004]

The invention according to claim 1 is
Mainly hydrogen gas is generated by reacting plastic with water at a specified temperature.
It is a method of gasifying useful gases such as hydrogen, and uses a compound that releases halogen during the reaction as a reaction accelerator.
The reaction temperature is 250 to 500 ° C. and the reaction pressure is 5
It is a gasification method for plastics, which is characterized in that it is about 305.9 kg / cm ² . Reaction temperature and reaction pressure
Compounds that release halogen during reaction within the range of force react
Since it works effectively as a promoter , the plastic can be efficiently decomposed into hydrogen gas. The invention according to claim 2 is the invention according to claim 1, wherein the reaction promoting substance is a plastic containing chlorine or a halogen compound. When the plastic to be gasified is a chlorine-containing plastic, chlorine is released from the plastic itself during the reaction, so that a reaction- promoting substance is further added.
The plastic can be gasified without addition .

[0005]

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The reaction accelerator used in the present invention is a compound which releases halogen during the reaction, and specific examples thereof include plastic containing chlorine or hydrochloric acid, HBr .
And other halogen compounds. Examples of the chlorine-containing thermoplastics include polyvinyl chloride (PVC) and vinyl chloride / vinyl acetate copolymers. The aqueous solution containing the reaction promoting substance remaining after the completion of the gasification reaction can be recycled by recycling it. in this case,
It is not necessary to add new accelerating substances .

Next, in the present invention, the mechanism of the reaction in which the compound that releases halogen during the reaction acts as a reaction promoting substance will be described. For example, when the plastic is polyvinyl chloride, it acts as a reaction promoting substance by itself, so that it is not necessary to add a reaction promoting substance . First, polyvinyl chloride is mixed with water at a temperature of 250 to 500 ° C. for 5 to 30
By reacting at a pressure of 5.9 kg / cm ² , chlorine is desorbed from polyvinyl chloride to generate carbon radicals inside the polymer, and active chlorine is generated outside. Atmosphere is 250
Since it is water at ˜500 ° C. and 5-305.9 kg / cm ² , this water attacks a hydrogen atom bonded to a carbon atom adjacent to the carbon radical to desorb the hydrogen atom, and the carbon radical is Make a double bond with a carbon atom. Further, the active chlorine released to the outside attacks a hydrogen atom bonded to a carbon atom adjacent to the carbon radical to release the hydrogen atom, and the carbon radical forms a double bond with the carbon atom. The active chlorine remains without being consumed, attacks the remaining hydrogen atoms of the polymer to desorb the hydrogen atoms, and finally reacts with water to form a hydrochloric acid solution. The hydrogen atoms desorbed in this way become the desired hydrogen gas and are collected, and the residue mainly becomes carbon. Also, for example, when polypropylene is used as the plastic and hydrochloric acid is used as the reaction accelerating substance , the hydrochloric acid is first mixed with water at 250 to 500 ° C.
At a temperature of 5 to 305.9 kg / cm ^2, the hydrochloric acid decomposes to generate active chlorine, and this active chlorine attacks the hydrogen atoms bonded to the carbon atoms constituting the polymer to generate hydrogen. Detach an atom. Active chlorine remains without being consumed, attacks the remaining hydrogen atoms of the polymer to desorb the hydrogen atoms, and finally reacts with water to form a hydrochloric acid solution. The hydrogen atoms desorbed in this way become the target hydrogen gas, are collected, and the residue becomes carbon.

When carrying out the plastic gasification method of the present invention, for example, an apparatus as shown in FIG. 1 is used. As shown in FIG. 1, the gasifier comprises a reactor 10 to which a plastic material, water and a reaction promoting substance are supplied, a reaction promoting substance aqueous solution tank 11 containing water and a reaction promoting substance , and a gas generated in the reactor 10. A cooler 12 for cooling the fluid containing the gas, a gas capacity measuring instrument 13 for storing the fluid containing the gas from the cooler 12 and measuring the capacity of the gas, and a gas bag 14 for collecting and storing the gas from the gas capacity measuring instrument 13. With. A preheater 16 and a high-pressure pulseless flow pump 17 are provided between the reactor 10 and the reaction promoting substance aqueous solution tank 11. The water and the reaction promoting substance in the tank 11 are sucked and pressurized by the pump 17 and sent to the preheater 16 and then enter the reactor 10.
After the pressure in the reactor 10 reaches a predetermined value, the reactor 10
Then, the preheater 16 is put in a fluidized bed sand bath 18 shown by a broken line in the figure to rapidly heat it to a predetermined temperature. The reaction temperature of the reactor 10 can be directly measured by a thermocouple (not shown) inserted in the outlet of the reactor. The reactor 10 is filled with the plastic raw material shown by the arrow A before the reaction, and the reaction residue shown by the arrow B is taken out after the reaction. A pressure reducing valve 19 and a valve 20 are provided between the cooler 12 and the gas capacity measuring device 13.
Is provided et al is Ru. A pressure reducing valve 1 is provided between the cooler 12 and the tank 11.
9 and a valve 21 are provided, and a valve 20 and a valve 21 are provided between the gas capacity measuring device 13 and the tank 11. A valve 22 is provided between the gas capacity measuring device 13 and the gas bag 14.

In the gasifier constructed as described above, a lump of waste plastic is first prepared as a plastic raw material, the reactor 10 is filled with the waste plastic, and then the pump 17 is used.
To activate the water in the tank 11 and the reaction promoting substance in the reactor 1
0 and the reaction system including the preheater 16, and the pressure reducing valve 19 is adjusted to pressurize to a predetermined pressure. After the pressure and the flow rate of the water containing the reaction promoting substance are stabilized, the reactor 10 and the preheater 1
6 is put in the fluidized bed sand bath 18 and rapidly heated to a predetermined temperature. The fluid containing the gas generated from the reactor 10 is rapidly cooled by the cooler 12, and the pressure is reduced by the pressure reducing valve 19.
It passes through the valve 20 and flows into the gas volume measuring device 13, where the volume of gas is measured. The gas in the gas capacity measuring device 13 is sent to the gas bag 14 via the valve 22 and analyzed. The water and the liquid containing the reaction promoting substance in the gas capacity measuring device 13 are sent to the tank 11 via the valves 20 and 21 and used again for the gasification reaction. After continuing the reaction until the gas is substantially not generated from the outlet of the cooler 12 while keeping the temperature and pressure of the reaction system at predetermined values in this way,
The reactor 10 and the preheater 16 are pulled up from the fluidized bed sand bath 18 and quenched with water to stop the reaction.

[0010]

EXAMPLES Next, examples of the present invention will be described together with comparative examples in order to show specific embodiments of the present invention. <Example 1> Using the apparatus shown in FIG. 1, the reaction conditions shown in Table 1, that is,
Polypropylene (PP) is used as the waste plastic of the raw material , hydrochloric acid (HCl) is used as the reaction promoting substance ,
Reaction temperature of 400 ° C, 305.9 kg / cm ² (30 M
The plastic was gasified with the reaction pressure of Pa), the reaction time of 120 minutes and the flow rate of water containing hydrochloric acid of 4 ml / min. In this example, the internal volume of the reactor 10 was about 11 cm ³ . The results are shown in Table 1. In Table 1, the amount of generated gas (ml / g) shows the amount of gas containing hydrogen gas obtained per 1 g of waste plastic, and the hydrogen content (%) shows the ratio of hydrogen gas to the total amount of gas.

Example 2 The method of Example 1 was repeated except that polyethylene (PE) was used as the waste plastic, and the plastic was gasified. The results are shown in Table 1.

Example 3 The method of Example 1 was repeated except that polyvinyl chloride (PVC) was used as the waste plastic and no reaction accelerator was used, and the plastic was gasified. The results are shown in Table 1.

Example 4 Polyvinyl chloride (PVC) was used as the waste plastic, except that a reaction accelerating substance was not used at a reaction pressure of 102 kg / cm ² (10 MPa) and a reaction time of 10 minutes. For example, the method of Example 1 was repeated to gasify the plastic. The results are shown in Table 1.

<Example 5> As waste plastics, polyvinyl chloride (PVC) 50% and polypropylene (PP)
The method of Example 1 was repeated except that a mixture consisting of 50% was used to gasify the plastic. The results are shown in Table 1.

Comparative Example 1 The method of Example 1 was repeated except that polypropylene (PP) was used as the waste plastic and no reaction accelerator was used, and the plastic was gasified. The results are shown in Table 1.

Comparative Example 2 Polyethylene (PE) was used as waste plastic,
Example 1 except that no reaction promoter was used
The above method was repeated to gasify the plastic. The results are shown in Table 1.

[0017]

[Table 1]

In Table 1, the mark * indicates that the hydrogen content could not be analyzed because the amount of generated gas was small.

<Comparative Evaluation> As is clear from Table 1, in each of Examples 1 to 5, the hydrogen content exceeds 90%, which shows that the plastic can be efficiently decomposed into hydrogen gas. Further, as shown in Examples 3 to 5, when the plastic is a chlorine-containing plastic, it can be understood that the plastic can be efficiently gasified without further adding a reaction promoting substance . On the other hand, using chlorine-free plastics PP and PE,
In addition, in Comparative Examples 1 and 2 in which the reaction promoting substance is not added, it is understood that the plastic cannot be efficiently decomposed into hydrogen gas.

[0020]

As described above, according to the present invention, a compound that releases a halogen during the reaction is used as a reaction promoting substance , and the plastic is treated with water at a temperature of 250 to 500 ° C.
And 5 to 305.9 kg / cm ² within the pressure range of the reaction to cause gasification, so that the plastic can be efficiently decomposed into hydrogen gas.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an apparatus used for carrying out a plastic gasification method of the present invention.

[Explanation of symbols]

10 Reactor 11 Reaction Accelerator Aqueous Solution Tank 12 Cooler 13 Gas Capacity Measuring Device 14 Gas Bag 16 Preheater 17 High-Pressure Pulse-Free Pump 18 Fluidized Bed Sand Bath 19 Pressure Reducing Valve 20, 21, 22 Valve

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Ken Iimura Inventor Ken Iimura Naka-machi, Naka-gun, Ibaraki Prefecture 6-headed six Mukaiyama, Naka-machi, Japan 14 Mitsubishi Materials Corporation Naka Energy Laboratory (72) Inventor Kenji Nishimura Naka-gun, Ibaraki Prefecture Nakamachi, Oita, Mukaiyama, Rokujinzu, No. 1002 14 14 Mitsubishi Materials Corporation, Naka Energy Laboratory (56) Reference JP-A-6-126744 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB) Name) C10J 3/00 C01B 3/02-3/48 C10B 57/00

Claims (2)

(57) [Claims] 1. A method for reacting plastic with water at a predetermined temperature to gasify mainly useful gas such as hydrogen gas, wherein a compound that releases halogen during the reaction is a reaction accelerator.
Used as a quality , the reaction temperature is 250 ~ 500 ℃,
Gasification method for a plastic, wherein the reaction pressure is 5~305.9kg / cm ^2. 2. The gasification method according to claim 1, wherein the reaction promoting substance is a chlorine-containing plastic or a halogen compound.