JPS6251674B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In recent years, as the production of plastics has increased, the disposal of plastic waste has become a major social problem. In addition, many methods for reusing and recycling plastics have been proposed due to the tendency to deplete petroleum resources and the rising price of crude oil.

The present inventors also discovered that when plastic is catalytically decomposed with a certain type of catalyst in an inert gas atmosphere, the hydrogen in the polymer that makes up the plastic is efficiently converted to hydrogen gas _H2 . I found out.

In addition, in the case of polymers containing nitrogen, in addition to efficiently converting the hydrogen contained in the polymer into H ₂ , the nitrogen contained in the polymer can also be converted into harmful components such as ammonia NH ₃ and hydrogen cyanide HCN that are generated during normal thermal decomposition. We have discovered that it is possible to extremely suppress the rate at which nitrogen gas changes into nitrogen gas and efficiently convert it into nitrogen gas, which is harmless to the human body. In this case, it has been found that since the thermal decomposition is carried out in a closed system in an atmosphere free of oxygen gas, there is almost no generation of harmful nitrogen oxides.

Subsequent research revealed that not only nitrogen-containing plastics but also nitrogen-containing organic compounds can be treated in a non-polluting manner with extremely low generation of harmful gases, just as in the case of nitrogen-containing plastics.

The invention relates to a device for carrying out the method described above.

The fundamentally important point of this device is that the thermal decomposition products are
The purpose is to effectively carry out catalytic pyrolysis with a heated catalyst, and because the catalytic effect of the catalyst decreases with the catalytic pyrolysis of the material to be thermally decomposed, the effect can be regenerated and used repeatedly. The apparatus of the present invention that basically takes these into consideration will be described in detail below.

In the thermal decomposition section, it is also possible to introduce the thermal decomposition products directly into the catalyst heated to a high temperature (over 600℃), but in this case, the thermal decomposition products are rapidly thermally decomposed on the catalyst near the inlet of the thermal decomposition section. As a result, decomposition residues adhere locally to the catalyst, clogging the system or even blocking the flow of gas, making it impossible to carry out thermal decomposition under uniform conditions. Therefore, it is preferable to separate the part that gasifies (evaporates or thermally decomposes) the thermal decomposition products from the part that catalytically decomposes them with the catalyst. In this way, the heating temperature of the part to be gasified can be adjusted to an appropriate temperature depending on the ease with which the pyrolyzed material is gasified, so rapid gasification can be suppressed, and the generated gas can be controlled at an appropriate flow rate. Since it can be fed to the catalyst, smooth catalytic thermal decomposition can be carried out. However, in this case, even if the pyrolysis chamber is the same, for example, if it is a tubular pyrolysis chamber, the catalyst filling part and the gasification part of the pyrolyzed material can be adjusted to different heating temperatures, so for this purpose can be achieved. In such a case, it is better to fill the part to be gasified with particles made of quartz, porcelain, or heat-resistant glass, which have no contact effect, rather than with a catalyst.

The catalytic thermal decomposition effect of the catalyst with the thermally decomposed substances gradually decreases (so-called poisoning) as the decomposition progresses because the thermally decomposed substances of the thermally decomposed substances adhere to the catalyst surface as a residue.

However, they discovered that by flowing oxygen-containing gas, such as air, at temperatures above 700°C, the poisoned metal surface could regain its contact effect. This is called regeneration. Therefore, it is necessary for the device to be able to easily regenerate this catalyst. For this reason, it is desirable to provide the catalyst filling section in a system that can carry out the above regeneration operation independently of other systems in the pyrolysis apparatus. In addition, two or more catalytic pyrolysis units each consisting of a catalyst filling unit are provided so that catalytic pyrolysis can be carried out continuously even when the catalyst is regenerated.
While one catalyst is being regenerated, it is convenient to be able to continue pyrolysis in another catalytic pyrolysis section.

Next, we will discuss the material of the pyrolysis chamber. First, the material for the catalyst filling part is required to have fairly excellent high temperature resistance. For example, catalytic pyrolysis temperature 800
℃, if air is flowed during regeneration, an oxidation reaction will occur on the catalyst, so the temperature of the catalyst will be 900℃.
It can be more than that. Therefore at least 1000℃
It is necessary to use a material that can withstand more than this. Desirable materials of this type include porcelain materials, quartz, stainless steel, and heat-resistant alloys. Further, since the material of the gasification chamber for the thermal decomposition material is not required to have the same heat resistance as the catalyst-packed part, it is generally sufficient that the material has heat resistance of 600° C. or higher. However, if the catalyst filling part and the gasification part of the thermally decomposed material are present in the same thermal decomposition chamber, the material should naturally meet the heat resistance required for the catalyst filling part.

As a heating means for the catalyst, heating using an electric furnace or a gas burner is easy, but heating using an electric furnace is superior in that it is easier to maintain a constant decomposition temperature. However, the burner method has the advantage that the gas obtained by this method can be used as heating fuel. However, if the capacity of the catalyst filling section is large, heating from outside the pyrolysis chamber using an electric furnace or burner will result in a large temperature difference between the portion of the catalyst in the pyrolysis chamber near the chamber wall and the center of the chamber. For example, in the case of a cracking tube with an inner diameter of 50 mm, there is a temperature difference of several tens of degrees or more at 800 degrees Celsius. Therefore, the temperature of the catalyst cannot be maintained uniformly, making it difficult to carry out thermal decomposition under certain conditions. Such a case can be solved by inserting a sheathed heater into the pyrolysis chamber to heat the catalyst. Also,
Uniform heating of the catalyst can also be achieved by using a combination of external heating using an electric furnace or the like and internal heating using a sheathed heater.

Next, the catalyst used in this device is nickel-chromium stainless steel, typified by stainless steel SUS316.

On the other hand, it can be said that it is desirable for the shape of the catalyst to have as large a surface area as possible in order to enhance the contact effect, but in the case of this device, if the effectiveness of the catalyst decreases, a gas containing oxygen such as air is passed through the catalyst, and the catalyst is repeatedly used. One of its characteristics is that it is regenerated and used (in this case, the surface of the catalyst deteriorates slightly each time it is regenerated), so if the catalyst is too fine or too thin, the number of times it can be regenerated will decrease. , which is inconvenient in practice. Therefore, if it is flat,
At least 50μ, if rod-shaped, at least 50mm thick
More than μ is required. In the case of a catalyst with a shape smaller than this, for example a 40μ flat plate (however, a curved one was used for the reason explained later), use nylon-6.
When catalytic cracking and regeneration were repeated at 800°C, the shape of the catalyst changed significantly within a few cycles. In addition to such restrictions on thickness or thickness, it is possible to fill as much as possible into a given volume, and by filling the gas flow, the gas flow will not be significantly hindered (for example, if it is a flat plate, there will be no overlapping In addition, when regenerating, heated air is flowed through the surface to oxidize the surface and remove deposits, but in this case, the catalyst is easily removed. The catalyst must have a shape that allows the entire surface of the catalyst to be regenerated, and furthermore, when the catalyst is heated in a filled state, pressure will be applied inside the pyrolysis chamber due to the thermal expansion of the catalyst, and the shape will not damage the pyrolysis chamber. Many constraints are required on the shape of the catalyst, including a shape that can absorb the expansion within the filling metal.

Taking the above into consideration, the shape of the catalyst suitable for this device is one made by weaving wires with a thickness of 50 μm or more into a net shape and then rolling it up, such as Dixon.
Items shaped like packing or woven into shapes such as Heli packing, items cut into an appropriate size and curved from a flat plate with a thickness of 50μ or more, used for metal drilling. The resulting cuticle-like shape is good.

Next, in this device, since the contact effect of the catalyst is finite, the material to be thermally decomposed is thermally decomposed catalytically while this effect lasts, and when the contact effect disappears, it is regenerated as described above. We have a method. Therefore, in this apparatus, the contact effect of the catalyst must be constantly grasped by some method. Therefore, the gas produced by catalytic pyrolysis is sampled continuously or at appropriate intervals, and components in the gas whose production amount changes greatly depending on the magnitude of the contact effect, such as hydrogen, are extracted.
It is necessary to quantitatively analyze H ₂ , ammonia NH ₃ , hydrogen cyanide HCN, etc. As means for analyzing these components, gas chromatography is suitable for H ₂ , and infrared absorption spectroscopy, ion electrode method, etc. are suitable for NH ₃ and HCN. In this case, the process from gas collection to analysis is automated, and the analysis value is automatically read and, for example, if the analysis value exceeds a certain standard, it is determined that regeneration is required, and the process is switched from catalytic pyrolysis operation to regeneration operation. It is also possible to switch automatically.

Next, a method for collecting the generated gas will be described.
The simplest collection method is to collect the generated gas as is in a gas tank, but as proposed earlier, first liquefy a portion of the generated gas with liquid nitrogen, etc. Thereafter, if the gas that is not liquefied is collected in a gas tank, it can be separated based on the difference in boiling point, which is convenient when using the generated gas. In addition, when nitrogen-containing organic compounds are thermally decomposed using this device, the nitrogen contained can be efficiently converted into harmless nitrogen gas _N2 .
The contact effect of the catalyst decreases, and immediately before regeneration, trace amounts of harmful gases such as NH ₃ and HCN begin to be produced. Therefore, if you are extremely concerned about this type of harmful gas, it is best to remove the generated gas by bubbling it through the water or by passing it through a shower of water before it is collected.

Next, embodiments of the present invention will be described. FIG. 1 shows an outline of the configuration of this device. This device is suitable for cases where the gasification section and catalytic cracking section of the pyrolysis target section are separate, and when the component is easily gasified, that is, has a low boiling point, or when the boiling point of the component produced by pyrolysis is low. This equipment is suitable for catalytic pyrolysis of pyrolysis products. This device was suitable for catalytic thermal decomposition of amines with boiling points below 150°C, such as ethylenediamine, diethylamine, triethylamine, and isopropylamine. In Fig. 1, 1 is the gasification part of the material to be pyrolyzed, and 2 is a pyrolysis tube made of quartz, with a diameter of 20 mmφ and a length of
It has a diameter of 15 cm, and its interior is filled with quartz beads 3 having a size of 4 mmφ x 4 mm to increase heat capacity. The pyrolysis tube 2 is heated by an electric furnace 4. Further, 5 and 5' are catalytic pyrolysis sections, each consisting of quartz pyrolysis tubes 6 and 6' with an inner diameter of 20 mmφ and a length of 20 cm, and electric furnaces 7 and 7'. Catalysts 8, 8' made of Dixon packing made of stainless steel SUS316 are filled in the inside. The pyrolysis tubes 6 and 6' are heated by electric furnaces 7 and 7', respectively. Reference numeral 9 denotes a monitor section for checking the contact effect of the catalysts 8 and 8', the details of which will be described later. Reference numeral 10 denotes a collection section for the generated gas, and a piston-cylinder type collector with a volume of about 4 was used.

Next, the operating procedure for carrying out catalytic thermal decomposition of ethylenediamine having a boiling point of 117°C using the apparatus shown in FIG. 1 will be described.

(i) When the voltage of the electric furnace 4 is set to 150, the temperature inside the pyrolysis tube 2 is
The voltage of the electric furnaces 7 and 7' is set so that the temperature of the catalysts 8 and 8' becomes 800°C.

(ii) Introduce nitrogen gas from the gas inlet 11 to replace the inside of the system with nitrogen gas. At this time, the connection part 12 is kept separated and connected to the collection part 10 having the cylinder after nitrogen gas replacement.

(iii) Open the pots 13 and 14 and open the gasification section 1 →
The system path from the catalytic pyrolysis section 5 to the gas collection section 10 is opened, while the locks 13' and 14' are closed.
→5'→10 system is cut off.

(iv) Ethylenediamine is introduced into the gasification section 1 from the thermally decomposed product inlet 15 at intervals of 0.1 g.

(v) Every time 0.1 g of ethylenediamine is introduced, a portion of the generated gas is collected from the monitor section 9, its infrared absorption spectrum is determined, and hydrogen cyanide is quantitatively analyzed.

(vi) When 0.1 g of ethylenediamine is subjected to catalytic pyrolysis about 10 times, the catalytic effect of the catalyst decreases, and normal pyrolysis, that is, without a catalyst and in a nitrogen gas atmosphere, is performed.
At 800°C, the production rate of hydrogen cyanide is approximately 5%. At this point, the catalytic cracking section 5
terminating the catalytic pyrolysis at

(vii) Immediately after the operation in (vi) is completed, catalytic pyrolysis is continued in the catalytic pyrolysis section 5'. In other words, Kotoku 13
and 14, and Kotoku 13 and 1
4 is gas inlet 16 → Kotoku 13 → Kotoku 1
4→Adjust so that the gas inlet 17 line is opened. On the contrary, open the locks 13' and 14', that is, from the gasification section 1 to the catalytic pyrolysis section 5'.
→The system line of the gas collection section 10 is opened, and catalytic pyrolysis of ethylenediamine is continued in the catalytic pyrolysis section 5'.

(viii) While the operation in (vii) is being carried out, the catalyst 8 in the catalytic pyrolysis section 5 is regenerated. That is, air is introduced from the gas inlet 16 or 17 at a rate of approximately 1/min.
After that, nitrogen gas is passed through the gas inlet 16 or 17 to replace the inside of the catalytic pyrolysis section 5 with nitrogen gas, and the tanks 18 and 19 are closed.

(ix) Continue the operations (iv) to (vi) in the catalytic pyrolysis section 5', and when the catalyst 8' in the catalytic pyrolysis section 5' deteriorates,
(vii) Repeat the following operations.

The above is the operating procedure for the apparatus shown in Figure 1. This apparatus can be used when the boiling point of the thermally decomposed material is high, or when the components obtained by primary thermal decomposition contain many high-boiling point components, such as polymers. In such cases, these high boiling point components may liquefy and condense between the gasification section 1 and the catalytic pyrolysis sections 5 and 5', or when heated to prevent condensation, these high boiling point components may decompose. It may solidify and cause clogging of the system. In order to eliminate such inconveniences, a device as shown in FIG. 2 is used.

The apparatus shown in FIG. 2 has two pyrolysis sections 20 and 2.
0', a monitoring section 22 for the composition of produced gas, and a gas collecting section 23. The pyrolysis sections 20 and 20' are respectively made of quartz pyrolysis tubes 24 and 24' (inner diameter 20 mmφ x 70 cm) and electric furnaces 25 and 25' with a length of 30 cm for heating the pyrolysis tubes 24 and 24'. , electric furnace 26 with a length of 15 cm
and 26′, electric furnace 27 and 2 with a length of 20 cm.
The inside of the decomposition tube 24, 24' is made of stainless steel SUS316.
Catalysts 28 and 28' made of Dixonpacking and quartz beads 29, 2 with a diameter of about 4 mmφ and a length of 4 mm.
9' is filled. Pyrolysis section 20 and 2
The gas generated at 0' is collected by a gas collecting section 23. Note that the monitor section 22 will be described later.

Next, we will describe the operating procedure for catalytic thermal decomposition of triethanolamine (boiling point 360°C) using this device.

(i) The insides of the two pyrolysis tubes 24 and 24' are replaced with nitrogen gas. At this time, the connection part 30 is removed and connected to the post-replacement gas collection part 23.

(ii) Adjust the inside of the pyrolysis tubes 24, 24' to a predetermined temperature using an electric furnace. That is, the tubes 24, 24' near the electric furnaces 25 and 25' are heated to 800°C.
The temperature near the electric furnaces 26 and 26' is adjusted to 400°C, and the temperature near the electric furnaces 27 and 27' is adjusted to 800°C.

(iii) Close the pot 31' to cut off the connection between the thermal decomposition section 20' and the gas collection section 23.

(iv) 0.1 g of triethanolamine is introduced into the pyrolysis tube 24 from the pyrolysis product inlet 32 at intervals.

(v) When about 1.5 g of triethanolamine is catalytically decomposed, the catalytic effect of the catalyst 28 is reduced, and the product is not produced by normal thermal decomposition, i.e., without using a catalyst, at 800° C. in a nitrogen gas atmosphere. The catalytic pyrolysis in the pyrolysis section 20 is terminated when about 5% of the amount of hydrogen cyanide produced is produced. The production rate of hydrogen cyanide was determined in exactly the same manner as in the case of the apparatus shown in FIG.

(vi) After completing the operation in (v), immediately close Kotoku 31,
The pot 31' is opened and the catalytic thermal decomposition of triethanolamine is continued using the thermal decomposition unit 20' in exactly the same manner as in the case of the thermal decomposition unit 20.

(vii) While the operation in (vi) is being performed, the catalyst 28 in the thermal decomposition section 20 is regenerated. In other words, Kotoku 2
1, 31, 33 and 34 to open the system of gas inlet 35 → gas inlet 21 → gas inlet 31 → gas inlet 36, and air is introduced from gas inlet 35 or 36 at a flow rate of 1/min for about 20 minutes. After that, the system is replaced with nitrogen gas again.

(viii) When the contact effect of the catalyst 28' in the thermal decomposition section 20' decreases, the catalytic decomposition is continued by switching to the thermal decomposition section 20' again, while the catalyst 28' in the thermal decomposition section 20' is ) to playback. Catalytic thermal decomposition of triethanolamine is accomplished by repeating these operations.

In the above example, when introducing ethylenediamine and triethanolamine, which are thermally decomposed products, into the thermal decomposition parts 20 and 20', a certain amount was introduced intermittently. A similar effect was found when the substance was introduced continuously at a constant flow rate using a microtube pump.

Next, an outline of the monitor sections 9 and 22 in the apparatus shown in FIGS. 1 and 2 will be described with reference to FIG. 3. That is, the pyrolysis sections 5, 5' and 2
A gas sampling port 37 is provided between 0 and 20' and the gas collection sections 10 and 23, and a gas sampling port 37 is provided between the
ml Teflon bag 38 is connected, and the spring material 3
Stop at 9 and open the caps 40 and 41 to collect some of the gas produced in the bag 38. A certain amount of the collected gas is introduced into a gas cell for infrared spectroscopic analysis, and the infrared absorption spectrum is measured.
Quantitative analysis of hydrogen cyanide was performed from the hydrogen cyanide absorption band at 14.01μ.

Next, a preferred embodiment of the catalytic thermal decomposition section will be described where the capacity of the packed section of the catalysts 8, 8' and 28, 28' is large. In the catalytic pyrolysis of thermally decomposed products, temperature control of the catalyst has a large effect on the composition of the gas produced. That is, for example, when triethanolamine is catalytically decomposed using the apparatus shown in FIG. 2, the amounts of ammonia a and hydrogen cyanide b produced are as shown in FIG. 4. Therefore, it can be seen that the preferable temperature condition in this case is between 800°C and 850°C. However, when the capacity of the catalytic pyrolysis section is large, as described above, a large temperature difference occurs between the part near the electric furnace and the central part. That is, during thermal decomposition, the temperature is generally lower in the center. In such a case, a catalytic thermal decomposition section as shown in FIG. 5 is preferable because it can make the temperature of the catalyst uniform.

In FIG. 5, 42 is an inlet for the gas generated in the gasification section, and 43 is a catalytic pyrolysis gas outlet for gas collection. 44 is stainless steel
It is a pyrolysis tube made of SUS321 with an inner diameter of 55 mmφ, and the center part has a thickness of 8 mm, and the surface material is stainless steel.
A SUS321 sheathed heater 45 is embedded.
Stainless steel as catalyst 46 in space
Filled with SUS316 chips. This chip has a thickness of 0.4 mm and is shaped like a curved board approximately 4 mm square. This catalyst 46 is heated by a sheathed heater 45 and an electric furnace 47.

It has been found that in a catalytic pyrolysis section having such a configuration, the temperature difference between the internal catalysts can be controlled within several degrees.

As described above, the organic substance thermal decomposition apparatus of the present invention is capable of effectively catalytically decomposing a thermally decomposed substance with a heated catalyst, and the catalyst can be used repeatedly and good contact can be maintained at all times. It is recyclable and can stably thermally decompose organic compounds so that it retains its effectiveness.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an organic substance thermal decomposition device according to an embodiment of the present invention, FIG. 2 is a schematic configuration diagram showing another embodiment of the same device, and FIG. 3 is a schematic cross-sectional diagram showing a monitor section provided in the same device. FIG. 4 is a diagram showing the relationship between the thermal decomposition temperature and the amount of gas produced in the same apparatus, and FIG. 5 is a schematic diagram showing another embodiment of the thermal decomposition section. 1... Gasification section, 2... Pyrolysis tube, 4... Electric furnace,
5, 5'... Catalytic pyrolysis section, 6, 6'... Pyrolysis tube,
7, 7'... Electric furnace, 8, 8'... Catalyst, 9... Monitor section, 10... Collection section, 20, 20'... Pyrolysis section, 2
2...Monitor section, 23...Gas collection section, 24,2
4'...Pyrolysis tube, 25, 25', 26, 26', 2
7,27'...Electric furnace, 28,28'...Catalyst, 44...
Pyrolysis tube, 45... Sheathed heater, 46... Catalyst, 4
7...Electric furnace.

Claims (1)

[Claims] 1. A pyrolysis chamber having an inlet for pyrolyzable materials, a heating device for heating the interior of the pyrolysis chamber, and a gasification section for gasifying the pyrolyzable materials, a catalyst made of nickel-chromium stainless steel, and a catalyst. At least two parts, each having a heating device for heating, and bringing the gas generated in the gasification section into contact with the catalyst to decompose the gas.
the first and second catalytic pyrolysis sections, and a means for collecting and analyzing the gas generated in the catalytic pyrolysis section; The connections can be switched between each other using the gas passage,
An apparatus for thermally decomposing organic substances, which is configured so that when one catalytic thermal decomposition section is in operation, a catalyst is regenerated in the other, and the switching is performed based on the analysis result of the sampling and analyzing means.