JP2002265956A - Liquefaction apparatus for polymer waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquefaction apparatus for a polymer waste which can recover, stably at a low cost, an oily component having stable qualities from a polymer waste. SOLUTION: A polymer waste PW charged into the container 20 of a thermal decomposition apparatus 2 is brought into direct contact with a non-oxygen gas NG heated to a high temperature by a heat exchanger 1 and supplied into the container 20, thus being thermally decomposed in a non-oxygen state while generating a thermal decomposition gas DG. The thermal decomposition gas DG is cooled with a condenser 3, and the resultant condensed oil component OL is recovered. Then, the residual gas is circulated as a non-oxygen gas to the heat exchanger 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel oil conversion facility for recovering oils usable as various fuels from polymer waste.

[0002]

2. Description of the Related Art Conventionally, as a facility for thermally decomposing a polymer waste to recover an oil component, for example, a facility as shown in FIG. 3 is generally used. In the equipment shown in the figure, first, in a pretreatment equipment 90, a polymer waste PW as a raw material is pulverized into an appropriate size (coarse pulverization 90a, fine pulverization 90a).
b), after removing mixed metal components (iron removal 90c),
A pretreatment of washing with water 90d and drying 90e is performed.

[0003] Next, the pretreated polymer waste P
W is introduced into the heating furnace 91a of the oiling facility 91, and is heated to about 250 ° C. and melted by the heat of the burner 91b through the furnace wall. Next, the melted polymer is supplied to a pyrolysis furnace 91c, and in the pyrolysis furnace 91c, the heat is further heated to a high temperature by the heat of the burner 91b through the furnace walls, whereby the pyrolysis is performed. Generate gas. After the generated pyrolysis gas passes through the catalyst 91d, it is cooled by the condenser 91e, and the condensed oil OL is recovered. The collected oil OL is stored in an oil storage tank 91f. Since the residual gas after recovering the oil is flammable, the burner 91
b as auxiliary fuel.

In the equipment shown in the figure, polymer waste PW
In order to prevent stagnation in the heating furnace 91a and the pyrolysis furnace 91c, the melt in the furnaces 91b and 91c is circulated by the circulation pump 91g. In the figure, reference numeral 91h denotes an exhaust gas treatment device for cooling, dust-removing, washing low-molecular-weight gas generated during heating and melting of the polymer-based waste PW in the heating furnace 91a, and then releasing the gas into the atmosphere.

[0005]

In the above-mentioned conventional equipment,
There are various problems as described below. For example, heating furnace 91a
First, the polymer waste supplied to the apparatus must be pretreated in the pretreatment facility 90 as described above, so that the facility cost and running cost become enormous when viewed as a whole facility, which is not economical. There's a problem. Heating furnace 9
In 1a, the heat of the burner 91b is transferred to the polymer in the furnace mainly by conduction. This is because the polymer melt has high viscosity and convection hardly occurs in the furnace. In addition, polymers have low thermal conductivity and are difficult to transmit heat. Therefore, it takes a long time to melt the polymer waste in the heating furnace 91a. In other words, from the start of equipment operation,
It takes a long time before the oil recovery actually starts. In consideration of the energy consumed during that time, there is a problem that the energy use efficiency is poor.

Further, since the heat is not easily transmitted to the polymer-based waste, the number of cases in which the heating furnace 91a is excessively heated increases. Polymer-based waste is a mixture of various types of polymers having various molecular weights. Even if it is put into the heating furnace 91a as it is, it does not dissolve uniformly, but dissolves in order from the one that is easily dissolved. I do. For this reason, the heating furnace 91a moves from the pyrolysis furnace 9
The composition of the melt supplied to 1c changes every moment, which causes a problem that the composition of the pyrolysis gas generated in the pyrolysis furnace 91a and the oil OL recovered therefrom fluctuate unstablely.

In order to prevent this problem from occurring, it is necessary to add a polymer separation step to the pretreatment step in the pretreatment equipment. is not. For this reason, there arises a problem that the running cost further increases. Further, the polymer melt tends to stay in the heating furnace 91a and the pyrolysis furnace 91c. Therefore, in order to prevent this stagnation, the melt in both furnaces 91b and 91c is passed through circulation pump 9 as described above.
Circulated with 1 g. However, when the heating is stopped, the melt in the piping solidifies and the circulation pump 91g cannot be restarted. For this reason, there is a problem that once the equipment is started, it must be continuously operated for a long time, for example, until the next maintenance of the circulation pump 91g.

In the pyrolysis gas generated by the pyrolysis of the polymer waste in the pyrolysis furnace 91c, the carbon number of the constituent component varies depending on the temperature of the pyrolysis. In other words, the higher the thermal decomposition temperature, the smaller the carbon number of the constituent component and the narrower the range of the variation. However, the higher the temperature, the more often the pyrolysis furnace 91c is heated excessively, so that the furnace body is easily damaged. In addition, a caulking phenomenon occurs near the inner wall surface of the thermal decomposition furnace 91c, and precipitates that hinder heat transfer adhere to the inner wall surface, which tends to cause problems such as a reduction in the efficiency of thermal decomposition.

Therefore, usually, the thermal decomposition temperature in the thermal decomposition furnace 91c is set to less than 500 ° C., specifically, about 300 to 400 ° C., and the generated pyrolysis gas is a low molecular weight component having one digit of carbon. To components having a high molecular weight of about 40 carbon atoms, various mixed components are mixed. Therefore, in order to improve the quality of oil by narrowing the range of variation in the number of carbon atoms of the components constituting the pyrolysis gas, by passing through the catalyst 91d as described above, the decomposition of components having a large molecular weight is promoted. I have. Specifically, the decomposition of the high molecular weight component is promoted through the catalyst 91d such that the carbon number of the constituent component of the pyrolysis gas is about 4 to 10 in terms of hydrocarbon.

[0010] However, the catalyst 91d such as nickel or zeolite, for example, tends to lose its activity particularly due to the presence of chloride ions contained in a large amount in polyvinyl chloride waste. The composition of the recovered oil OL and the oil O per unit time
There is also a problem that the recovery amount of L tends to fluctuate unstablely. SUMMARY OF THE INVENTION An object of the present invention is to solve these problems and to stably recover oil of high quality from polymer waste at a low cost. Is to provide.

[0011]

Means for Solving the Problems and Effects of the Invention In order to solve the above-mentioned problems, the present invention provides an apparatus for liquefying polymer waste, comprising: a heat exchanger for increasing the temperature of oxygen-free gas; Is provided with a container composed of water-cooled walls open to the container, and the polymer waste filled in this container is brought into direct contact with the high-temperature oxygen-free gas supplied into the container from the heat exchanger. A pyrolyzer for generating pyrolysis gas by pyrolysis in a state, a condenser for cooling the pyrolysis gas generated by the pyrolysis device and recovering condensed oil, and an oil recovered by the condenser And a circulation path for circulating the remaining gas as an oxygen-free gas to the heat exchanger.

[0012] In the oil conversion equipment of the present invention, the polymer waste is thermally decomposed by directly contacting the high temperature oxygen-free gas in the heat exchanger with the heat exchanger in the vessel. Therefore, all of the above-mentioned problems associated with the melting of the polymer can be solved. That is, conventionally, as described above, the polymer is melted as quickly and uniformly as possible, and the melted polymer is melted in the heating furnace 91a and the pyrolysis furnace 91.
It was necessary to carry out thermal decomposition while circulating smoothly with c. Therefore, pretreatment is performed in the pretreatment equipment 90 in order to remove components other than the polymer, to adjust the size, and to adjust the composition as needed.

However, in the present invention, there is no need for these, and the polymer waste is directly placed in the container of the pyrolysis apparatus as it is or when it is simply coarsely pulverized as necessary. Since it can be filled and thermally decomposed, no pretreatment equipment is required. In addition, the polymer-based waste is thermally decomposed sequentially from the portion in contact with the high-temperature oxygen-free gas, so that oil recovery starts in a short time after the operation of the equipment is started. For this reason, energy use efficiency is improved.

Further, since the container does not directly participate in the heat transfer to the polymer-based waste, there is no possibility that the container is excessively heated and may be damaged. Therefore, the temperature of the thermal decomposition reaction is set to 500 ° C. or more, preferably 60 ° C.
The temperature can be raised to about 0 to 900 ° C. Therefore, without using a catalyst, a pyrolysis gas having a carbon number of about 4 to 10 in terms of hydrocarbon can be mainly generated.

For example, polyethylene, polypropylene, polyvinyl chloride, polystyrene and other general-purpose plastics or natural rubber and other general-purpose rubbers are brought into direct contact with an oxygen-free gas heated to 600 to 900 ° C. as described above. The pyrolysis gas obtained by pyrolysis in an oxygen-free state generally has the following compositions (a) to (c). The component (a) is condensed by a condenser and recovered as an oil. The components (b) and (c), that is, the residual gas after removing the oil component, are circulated through the heat exchanger as oxygen-free gas. (a) A component having 4 to 10 carbon atoms in terms of hydrocarbon: about 80
% By volume (b) A component having a carbon number of 3 or less in terms of hydrocarbon: about 10% by volume (c) Hydrogen gas: about 10% by volume In the present invention, the container is constituted by a water-cooled wall opened to the atmosphere. Therefore, the temperature during pyrolysis does not exceed 100 ° C., and is maintained in the range of about 90 to 100 ° C.,
It functions to stabilize the thermal decomposition reaction of polymer waste.

Therefore, the composition of the pyrolysis gas and the oil recovered from the pyrolysis gas and the amount of recovered oil per unit time can be stably maintained without fluctuation. By the way, when the container is made of refractory such as firebrick, the temperature of the container gradually rises with the operation of the device, and when the temperature exceeds the thermal decomposition temperature of the polymer, Then, heat transfer from the wall to the reaction system occurs. For this reason, the thermal decomposition reaction may run out of control and fall out of control.

On the other hand, in the present invention, as described above, the container is constituted by a water-cooled wall opened to the atmosphere, and its temperature is always kept at 100 ° C. or lower, so that the burner of the heat exchanger is stopped. Then, if the temperature of the oxygen-free gas supplied into the container is lowered, the thermal decomposition reaction can be stopped immediately.
Therefore, runaway of the thermal decomposition reaction can be prevented beforehand, which is a great advantage in terms of safety and operability. In addition, since there are no moving parts in the container of the pyrolysis device, the operation is stopped once during the pyrolysis reaction, and then restarted without any trouble simply by restarting the blowing of high-temperature oxygen-free gas. can do. Therefore, it is not necessary to continue the operation of the equipment for a long time.

Thus, according to the present invention, it is possible to provide a novel polymer-based waste liquefaction facility capable of stably recovering oil of stable quality from a polymer-based waste at low cost. It becomes possible.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG.
It is a block diagram showing an example of an embodiment. The oiling equipment in the example shown in the figure includes a heat exchanger 1 for exchanging heat with oxygen-free gas with a high-temperature combustion gas generated by the flame of the burner 11 to increase the temperature, and a container 20. The polymer waste PW charged into the container 20 is brought into direct contact with the high-temperature oxygen-free gas NG supplied from the heat exchanger 1 into the container 20, thereby thermally decomposing in an oxygen-free state to generate a pyrolysis gas DG. , A condenser 3 for cooling the pyrolysis gas DG generated by the pyrolysis apparatus 2 and recovering the condensed oil OL, and an oil OL by the condenser 3.
And a circulation path 4 for circulating the residual gas from the heat exchanger 1 as oxygen-free gas NG. The piping is connected between the devices so that the oxygen-free gas NG and the pyrolysis gas DG are circulated between the devices by the blowing pressure of the circulating blower 41 provided on the circulation path 4.

As the fuel FL of the burner 11 of the heat exchanger 1, kerosene, waste oil or the like is mainly used. Also,
The oil OL recovered by the condenser 3 can be used as fuel. Further, in the oiling equipment of this example, the surplus gas generated during the circulation of the residual gas is also transferred to the circulation blower 41.
Is supplied to the burner 11 as auxiliary fuel.

That is, of the components (a) to (c) generated by thermal decomposition of the polymer waste, (b)
The component (c) circulates through the facility as oxygen-free gas NG due to the blowing pressure of the circulating blower 41, and its amount gradually increases as the thermal decomposition of the polymer waste PW proceeds. Therefore, in this example, residual gas exceeding the amount required for circulation is branched off from the circulation path 4 and supplied to the cleaning device 5 as surplus. Then, in the cleaning device 5, by washing with sodium hydroxide solution CS, HCl, such as SO _2, after removing the components which can cause air pollution, the burner 11 as described above, and supplies that as auxiliary fuel .

The components (b) and (c), which are the main components of the residual gas, are all flammable and, since the components that may cause air pollution are removed as described above, are reused as auxiliary fuel. You can. Moreover, the combustion flame of the burner 11 has a high temperature of about 1000 ° C. or higher. For this reason, even if dioxin is contained in the residual gas, it is decomposed. Therefore, even if the residual gas is reused as an auxiliary fuel, there is no problem of environmental pollution due to dioxin.

The high-temperature combustion gas generated by the burner 11 is
The air flows through the heat exchanger 1 by the blowing pressure of the blower 12, and first, the oxygen-free gas is heated to a high temperature by heat exchange in the heat exchange unit 13, and then is released from the chimney 14 into the atmosphere. As the heat exchange unit 13, any of conventionally known various types such as a multi-tube type, a high-temperature combustion gas generated by the burner 11 in the pipe, and an oxygen-free gas flowing outside the pipe are used. It is possible.

The container 20 of the thermal decomposition device 2 is constituted by a water-cooled wall open to the atmosphere as described above. That is, the inner cylinder 20a forming the container inner wall and the outer cylinder 20 forming the container outer wall
and b are concentrically arranged so as not to contact each other. At the same time, a space 20c between the two cylinders 20a and 20b is opened to the atmosphere through an opening 20d above the container.
The container 20 is constituted by filling the inside of c with water W. In the figure, the reference numeral 23 is for supplying new water W when the water W evaporates from the opening 20d and the water level drops to a certain level in order to keep the water level of the water W in the space 20c constant. Water supply means. If the amount of water supplied by the water supply means 23 at one time is large, the temperature of the container 20 may drop sharply, which may affect the thermal decomposition reaction of the polymer waste PW in the container 20. Therefore, it is preferable that the level of the water level at which the water supply is started by the water supply means 23 is set so that the amount of water supplied at one time is as small as possible.

Above the container 20, there is provided an inlet 20e for charging the polymer waste PW into the container 20. The inlet 20 e is provided with a cover 21 to maintain the interior of the container 20 in an oxygen-free state during thermal decomposition of the polymer waste PW.
To close. In addition, a grid 22 for supporting the charged polymer waste PW from below is provided below the inside of the container 20 so as to provide a void 20f below the region in the container 20 where the polymer waste PW is filled. Provided. The gap 20f is provided with a pipe inlet 20g for supplying the high-temperature oxygen-free gas NG from the heat exchanger 1. Then, the oxygen-free gas NG heated to a high temperature in the heat exchanger 1 is first supplied to the space 20 f from the inlet 20 g by the blowing pressure of the circulating blower 41, and then the inside of the container 20 is raised to raise the height on the grid 22. It is configured to be brought into contact with the molecular waste PW.

With this configuration, the liquid polymer heated and melted by contact with the oxygen-free gas NG is dropped through the grid 22 into the gap 20f therebelow to be removed from the gap of the polymer waste PW. can do. Therefore, the gap can be prevented from being clogged by the liquefied polymer. Therefore, the oxygen-free gas N
The thermal decomposition of the polymer waste PW by G can be constantly and smoothly performed while maintaining a constant reaction rate.

Moreover, the liquid polymer dropped into the gap 20f is sequentially cooled by the high-temperature oxygen-free gas NG supplied from the inlet 20g into the gap 20f, and the polymer waste PW on the polymer waste PW is placed thereon.
Earlier, it is rapidly pyrolyzed and removed. Therefore, the inside of the space 20f is not filled with the dropped polymer. Next, the pyrolysis gas DG generated in the container 20 is supplied to the container 2 by the blowing pressure of the circulation blower 41.
0 is supplied to the condenser 3 which is the next step from the outlet 20h provided on the upper side surface.

The condenser 3 exchanges heat between the pyrolysis gas DG sent from the pyrolysis apparatus 2 and cooled while passing through the piping but still having a high temperature of about 200 ° C. and the cooling water CW. Do. That is, by heat exchange,
The pyrolysis gas DG is cooled to about 30 ° C., and a component having a boiling point lower than that and having a hydrocarbon equivalent of 4 or more (the component (1) as a main component) is condensed as an oil OL, Liquefy. The liquefied oil OL is once separated and collected in a separation tank 61 provided below the condenser 3 to remove a precipitate, and then sent to an oil storage tank 63 by a pump 62 to be stored in the storage and transportation 63.

The residual gas not condensed and liquefied by the heat exchange is separated and supplied to the cleaning device 5 as a surplus gas by the blowing pressure of the circulation blower 41 as described above, and then the oxygen-free gas NG Is supplied to the heat exchanger 1 again. By repeating the above steps, the polymer waste PW put into the container 20 of the thermal decomposition apparatus 2 is efficiently thermally decomposed, and the oil having stable quality is recovered stably and at low cost. Can be.

When starting the operation of the above equipment, it is desirable to replace the inside of the pipe with, for example, nitrogen gas in order to remove oxygen from the pipe. FIG. 2 is a block diagram showing another example of the embodiment of the oiling equipment of the present invention. The oil conversion equipment shown in the figure is provided with an exhaust gas treatment device 7 instead of the surplus gas cleaning device 5, and the gas treated by the exhaust gas treatment device 7 is diffused into the atmosphere. The other configuration is the same as that of the example of FIG.

The exhaust gas treatment device 7 prevents the resynthesis of dioxin by rapidly cooling the temperature to 300 ° C. or less by spraying water on the surplus gas. Next, after dust removal, HC was washed with caustic soda solution CS.
l, such as SO _2, a component which can be a cause of air pollution is removed. After passing through these steps, the surplus gas is purified so as to sufficiently satisfy the emission standard stipulated by the Air Pollution Control Law, and then released into the atmosphere through a chimney (not shown) or the like.

Then, the surplus gas can be treated without causing the problem of air pollution and environmental pollution due to dioxin. Note that the configuration of the oiling equipment of the present invention is not limited to the examples in the two figures described above.
Various design changes can be made without changing the gist of the present invention.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of an embodiment of an oiling facility of the present invention.

FIG. 2 is a block diagram showing another example of the embodiment of the oiling equipment of the present invention.

FIG. 3 is a block diagram showing an example of a conventional oiling facility.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heat exchanger 2 Pyrolysis apparatus 20 Container 3 Condenser 4 Circulation path PW Polymer waste NG Oxygen-free gas DG Pyrolysis gas OL Oil

Claims (4)

[Claims] 1. A heat exchanger for increasing the temperature of oxygen-free gas, and a container constituted by a water-cooled wall opened to the atmosphere, and polymer waste filled in the container is discharged from the heat exchanger. A pyrolysis device that generates pyrolysis gas by being thermally decomposed in an oxygen-free state by directly contacting the high-temperature oxygen-free gas supplied into the container, and cooling the pyrolysis gas generated by the pyrolysis device A condenser for collecting condensed oil, and a circulation path for circulating the residual gas after collecting the oil with the condenser as an oxygen-free gas to the heat exchanger. Oil-based equipment for molecular waste. 2. A space is provided in a vessel of the thermal decomposition apparatus below a region filled with polymer waste, and high-temperature oxygen-free gas from a heat exchanger is first supplied to the space, and then the vessel is heated. The polymer waste liquefaction facility according to claim 1, wherein the inside is raised to be brought into contact with the polymer waste. 3. A cleaning device for cleaning excess gas generated during circulation of residual gas, wherein the gas cleaned by the cleaning device is supplied to a burner as a heat source of a heat exchanger as auxiliary fuel. Item 4. An apparatus for converting polymer waste into oil according to item 1. 4. An exhaust gas treatment device for cooling, dust-removing, and cleaning surplus gas generated during the circulation of residual gas, wherein the gas treated by the exhaust gas treatment device is released into the atmosphere. Oil-based equipment for molecular waste.