JPH10204443A - Operation of apparatus for oil-making treatment of waste plastic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To recover light oil free from the contamination of heavy components by surely recycling the heavy components in cracked gas into a thermal decomposition tank in an oil-making treatment of waste plastics. SOLUTION: This apparatus consists of a thermal decomposition tank 1 for thermally decomposing waste plastics, a cooler 2 for cooling cracked gas generated in the thermal decomposition tank 1 to a specified temperature to liquefy a heavy component and recycling it to the thermal decomposition tank 1, a recycling tank 3 for removing misty heavy components from the cracked gas passed through the cooler 2, separating a heavy component from light gas and recycling the resultant heavy component to the thermal decomposition tank 1, a condenser 5 for cooling the light gas separated in the recycling tank 3 to condense and liquefy a part of the light gas to oil, and a gas-liquid separator 6 for separating the oil obtained in the condenser 5 from non-condensing gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating a waste plastic oil treatment apparatus.

[0002]

2. Description of the Related Art In recent years, treatment of waste plastic discharged in large quantities has become a serious social problem, and the need for recycling thereof has increased. One of the recycling methods of waste plastic is a method of thermally decomposing waste plastic into oil. However, the oil recovered by simple pyrolysis of waste plastic contains waxy components and high molecular weight components. Therefore, JP-A-3-86790 and JP-A-4-18.
As disclosed in JP-A-0995, there is a method of obtaining a low-boiling hydrocarbon oil by reforming a pyrolysis gas of waste plastic with synthetic zeolite. However, when synthetic zeolite is used, lightening of the pyrolysis gas is promoted and gasification proceeds, so that the oil recovery rate decreases. Further, the synthetic zeolite itself needs to be regenerated or replaced due to deterioration due to deposition of carbon and deactivation due to hydrogen chloride in the pyrolysis gas, which increases running costs.

As a method for lightening the recovered oil without using a synthetic zeolite, there is a method using a reflux tank described in Japanese Patent Application No. 7-183809. This is because the cracked gas of waste plastic generated in the pyrolysis tank is separated into heavy oil and light gas in the reflux tank, and the separated heavy oil is returned to the pyrolysis tank and repeatedly pyrolyzed. This is a way to reduce the weight.
The temperature of the reflux tank is set lower than the temperature of the decomposition gas generated in the thermal decomposition tank, and the decomposition gas is cooled to a predetermined temperature while passing through the reflux tank. A heater is installed on the outer wall of the reflux tank to compensate for supercooling due to heat radiation to the outside, and the heater output is adjusted at the outlet of the reflux tank by adjusting the heater output in accordance with fluctuations in the amount of cracked gas generated in the pyrolysis tank. The decomposition gas temperature is kept in a predetermined range. However, if the amount of cracked gas entering the reflux tank in a short time increases significantly, the output of the heater cannot be maintained within a predetermined temperature range by adjusting the output, so that the temperature inside the reflux tank rises and heavy components pass through the reflux tank. Would. As a result, when not only heavy components are mixed into the recovered oil, but also a chlorine fixation tank filled with a chlorine fixative is connected downstream of the reflux tank, heavy oil mist is added to the chlorine fixative. Adheres and closes the passage for the decomposition gas, making it impossible to obtain a sufficient chlorine fixing effect. Therefore, it is necessary to replace the chlorine fixing agent while leaving the unreacted chlorine fixing agent, which not only complicates the operation but also increases the running cost.

In order to solve this problem, a cooler is provided between the thermal decomposition tank and the reflux tank, and the above-mentioned problem is avoided by keeping the temperature of the cracked gas flowing into the reflux tank constant regardless of the thermal decomposition temperature. There is a way. However, when the thermal decomposition temperature increases, the components condensed and liquefied in the cooler increase, so that a thick liquid layer is formed on the heat exchange surface inside the cooler, and the heat transfer coefficient decreases. As a result, the high-temperature cracked gas flows into the reflux tank without being cooled to the predetermined temperature, and the same problem occurs. In addition, in order to surely cool a large amount of high-temperature cracked gas to a predetermined temperature, a cooler having a large heat exchange area is required, and there is a problem that equipment costs increase.

[0005]

A problem to be solved by the present invention is to prevent a large amount of high-temperature pyrolysis gas from being generated in the pyrolysis and oiling treatment of waste plastics, and to prevent heavy waste in the reflux tank. It is an object of the present invention to provide a means for reliably separating components from light components.

[0006]

According to the present invention, there is provided a pyrolysis tank for thermally decomposing waste plastics, and a decomposed gas generated in the pyrolysis tank is cooled to a predetermined temperature to remove heavy components in the decomposed gas. A cooler to be condensed and liquefied, the heavy component condensed and liquefied by the cooler and the gaseous light component are separated, and the mist-like heavy component mixed in the gaseous light component is further removed.
A reflux tank for returning to the pyrolysis tank together with the heavy component liquefied in the cooler, a condenser for cooling the light gas separated in the reflux tank and partially condensing and liquefying it as oil, and In a method for operating a waste plastic oil liquefaction apparatus including a gas-liquid separator for separating oil and a non-condensable gas obtained in a cooler, the temperature of the gaseous light component at the outlet of the cooler is within a predetermined range. The heating amount of the pyrolysis tank is controlled so as to take a value. Specifically, a means for detecting the temperature of the light gas that has passed through the cooler is provided, and when the detected temperature reaches the upper limit of the predetermined temperature range, the heating amount of the pyrolysis tank is reduced, and When the lower limit is reached, the heating amount of the pyrolysis tank is to be increased.

[0007] When the pyrolysis residue stored in the pyrolysis tank is extracted from the pyrolysis tank, the operation of raising the pyrolysis temperature, evaporating the can solution, and drying the residue is conventionally called burning-off. While monitoring the temperature of the solution, the temperature was raised in one step to a temperature required for evaporating and drying the can solution. In this method, a large amount of decomposed gas having a high temperature level was temporarily generated immediately after entering the burning operation, and the cooling capacity of the cooler could not keep up and the decomposed gas flowed into the reflux tank at a high temperature in some cases. . As a result, a predetermined reflux performance was not obtained, and heavy components were sometimes mixed into the recovered oil. However, by controlling the heating amount of the pyrolysis tank while monitoring the temperature of the decomposition gas that has passed through the cooler according to the present invention, the gasification rate of the can solution in the burning operation can be reduced, and the waste plastic can be supplied to the pyrolysis tank. Since the gasification rate of the waste plastic during the supply can be controlled to the same level, a predetermined reflux lightening effect can be obtained even in the burning-off operation. Furthermore, since the mist-like heavy components are reliably separated and removed from the light gas in the reflux tank, the chlorine fixing agent is not contaminated by the heavy components, so that the dechlorination effect can be obtained continuously. became. Further, when there is a variation in the generation rate of the cracked gas, the selection of the cooler is performed on the basis of the case where the cracked gas is generated at a high temperature and in a large amount, so that the scale becomes large. In the present invention, since the generation speed of the decomposition gas can be averaged, the size of the cooler can be reduced.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the contents of the present invention will be specifically described with reference to examples.

FIG. 1 shows an embodiment of a waste plastic oil treatment system having the basic structure of the present invention. This system consists of a pyrolysis tank 1, a cooler 2, a reflux tank 3, a chlorine fixing tank 4, a condenser 5, a gas-liquid separator 6, an oil recovery tank 7, an oil feed pump 8, an air pump 9, a burner 10, and a valve. 11 to 13, temperature sensors 20 to 22, a controller 30, and the like.

First, the operation of this embodiment will be described.
In FIG. 1, waste plastic 100 is supplied to a pyrolysis tank 1. The waste plastic 100 is burned into the burner 1 in the pyrolysis tank 1.
0 to generate decomposition gas 101. The cracked gas 101 is introduced into the cooler 2, cooled to an arbitrary predetermined temperature by the cooling water 201, and the heavy components are condensed and liquefied, and then introduced into the reflux tank 3. In the reflux tank 3, the liquid heavy component 10
2 is separated from the gaseous light component 103 and the heavy component 102
Is returned to the thermal decomposition tank 1. The gaseous light component 10
After being completely separated from the mist-like heavy components in the reflux tank 3 under a predetermined temperature condition, the liquid 3 is introduced into the chlorine fixing tank 4. The chlorine fixing tank 4 is maintained at a temperature equal to or higher than that of the reflux tank 3 by 5 to 10 ° C. so that the light gas 103 is not condensed and liquefied in the chlorine fixing tank 4.
In the unlikely event that the liquid heavy component 104 generated in the chlorine immobilization tank is
It is refluxed to the thermal decomposition tank 1. The gaseous light component 105 that has passed through the chlorine fixing tank 4 is introduced into the condenser 5,
After being cooled to an arbitrary predetermined temperature by 02, it is separated into oil 106 and non-condensable gas 107 by the gas-liquid separator 6. A part of the oil 106 is transferred to the burner 10 by the oil feed pump 8 and burned together with the air supplied by the air pump 9 to serve as a heat source for thermally decomposing the waste plastic 100. The non-condensable gas 107 is released outside the system.

Next, the operation of the control system will be described. First, the temperature control of the decomposition gas 101 while the waste plastic 100 is continuously supplied to the pyrolysis tank 1 will be described. The heating temperature of the waste plastic is detected by a temperature sensor 20 installed inside the pyrolysis tank 1. The temperature detected by the temperature sensor 20 is input to the controller 30 and, based on an output signal from the controller 30, a valve 12 provided on a supply line of oil and air to the burner 10 heating the pyrolysis tank, 13 is adjusted so that the internal temperature of the pyrolysis tank 1 is controlled to be constant. The decomposition gas 101 generated in the thermal decomposition tank 1 is introduced into the cooler 2. The temperature of the decomposition gas 101 that has passed through the cooler 2 is detected by a temperature sensor 21. The temperature detected by the temperature sensor 21 is controlled by the controller 30.
And a valve 11 provided in a supply line of the cooling water 201 supplied to the cooler 2 in accordance with an output signal therefrom.
Is adjusted, and the decomposition gas 101 after passing through the cooler 2 is adjusted.
Is controlling the temperature.

Next, the control for evaporating the can solution in the pyrolysis tank 1 will be described. When the supply of the waste plastic 100 ends, the generation amount of the decomposition gas 101 gradually decreases. Cooling water 20 supplied to the cooler 2 by the controller 30
The opening degree of the valve 11 for adjusting the supply amount of 1 is reduced. Valve 1
1 reaches an arbitrary lower limit, the output signals from the controller 30 increase the opening degrees of the valves 12 and 13 that regulate the supply amounts of oil and air to the burner 10, and the burner 10 The supply of oil and air to the tank increases. As a result, the heating amount of the burner 10 increases, the temperature of the pyrolysis tank 1 increases, and gasification of the can solution starts. The temperature of the cooling water 201 detected by the temperature sensor 22 increases, and the opening of the valve 11 whose opening is adjusted by the controller 30 increases. When the opening of the valve 11 reaches an arbitrarily set threshold value, the opening of the valves 12 and 13 for adjusting the supply amounts of oil and air by the output signal from the controller 30 while maintaining the opening of the valve 11. Is squeezed. As a result, the output of the burner 10 decreases, and the generation amount of the decomposition gas 101 decreases. Since the opening of the valve 11 for adjusting the supply amount of the cooling water is maintained at the opening of the threshold value, the temperature of the decomposition gas 101 detected by the temperature sensor 21 decreases as the generation amount of the decomposition gas 101 decreases. I do. When the temperature of the cracked gas 101 reaches a preset threshold value, a signal for increasing the opening of the valves 12 and 13 for adjusting the supply amounts of oil and air is output. As a result, the heating amount of the burner 10 increases, the temperature of the pyrolysis tank 1 increases, and gasification of the can solution is promoted. The temperature of the decomposed gas 101 detected by the temperature sensor 21 increases as the gas amount increases, and reaches a threshold value preset in the controller 30. Therefore, the controller 30 outputs a signal for reducing the opening degree of the valves 12 and 13 for adjusting the supply amounts of oil and air. As described above, based on the temperature of the decomposed gas 101 after passing through the cooler detected by the temperature sensor 21,
By adjusting the supply amounts of oil and air to the burner 10 that heats the pyrolysis tank 1, the amount of generated decomposition gas 101 can be averaged.

An embodiment using the waste plastic oil treatment system of FIG. 1 will be described. 45 kg of waste plastic, 22 kg of polyethylene, 7 kg of polystyrene
g, 1 kg of polyvinyl chloride, 18 kg of epoxy resin, and 7 kg of phenol resin. The reflux tank 3 was filled with porcelain balls having a diameter of 15 mm in order to promote the separation of the liquid heavy component and the gaseous light component. The chlorine fixing tank 4 was filled with calcium hydroxide pellets having a diameter of 4.8 mm as a chlorine fixing agent. Waste plastic 100
kg was put into the pyrolysis tank 1 and turned into oil by the operation. The waste plastic was supplied to the pyrolysis tank 1 in 20 divided portions of 5 kg each. Temperature sensor 2 while supplying waste plastic
The temperature of the pyrolysis tank 1 detected at 0 is 420 ° C. to 43 ° C.
The temperature of the decomposition gas 101 at the outlet of the cooling bath 2 detected by the temperature sensor 21 was set to 270 ° C. After the supply of the waste plastic was completed, the temperature of the pyrolysis tank 1 was finally raised to 580 ° C. in order to evaporate the can solution. The temperature of the reflux tank 3 was maintained at 270 ° C., and the temperature of the chlorine fixing tank 4 was maintained at 280 ° C.

Table 1 shows the results of a distillation test of the oil recovered in this example.

[0015]

[Table 1]

The total chlorine content of the oil was 80 ppm.

As a comparative example, after the supply of the waste plastic was completed, the temperature of the pyrolysis tank 1 detected by the temperature sensor 20 was raised in one step from 430 ° C. to 580 ° C. As a result, the generation amount of the decomposition gas 101 increases rapidly, the cooling capacity of the cooler 1 cannot keep up, and the decomposition gas temperature detected by the temperature sensor 21 cannot be maintained at 270 ° C., and the maximum is 350 ° C.
Rose to. Table 1 shows the results of the distillation test of the oil recovered in the comparative example. The total chlorine content of the oil is 1200pp
m.

As shown in Table 1, the oil recovered in this example had a 95% distillation point of 283 ° C., whereas the oil recovered in the comparative example had a 95% distillation point of 87 ° C. 370 ℃
Met.

From these results, according to this embodiment, the boiling point is 3
It can be seen that heavy components having a temperature of 00 ° C. or higher are refluxed and transformed. When the total chlorine content of the oil was compared, the oil recovered according to this example had a low value of 80 ppm, whereas the recovered oil of the comparative example had a high value of 1200 ppm. From these results, it can be seen that the chlorine removing agent of the present invention maintains the chlorine removing effect.

[0020]

According to the present invention, it is possible to provide a means for preventing a large amount of high-temperature pyrolysis gas from being generated and for reliably separating heavy and light components in the reflux tank.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a basic system of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Thermal decomposition tank, 2 ... Cooler, 3 ... Reflux tank, 4 ... Chlorine fixation tank, 5 ... Condenser, 6 ... Gas-liquid separator.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Norio Arashi 7-1-1, Omikacho, Hitachi City, Ibaraki Prefecture Inside Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Hisao Yamashita 7-1 Omikamachi, Hitachi City, Ibaraki Prefecture No. 1 Inside the Hitachi Research Laboratory, Hitachi, Ltd.

Claims (1)

[Claims] 1. A pyrolysis tank for pyrolyzing waste plastics,
A cooler that cools the decomposition gas generated in the thermal decomposition tank to a predetermined temperature and condenses and liquefies heavy components in the decomposition gas,
The heavy component condensed and liquefied in the cooler is separated from the gaseous light component, the mist-like heavy component mixed in the gaseous light component is further removed, and the heavy component liquefied in the cooler is removed. A reflux tank for returning to the pyrolysis tank together with the condenser, a condenser for cooling the light gas separated in the reflux tank and partially condensing and liquefying the oil, and non-condensing with the oil obtained in the condenser. A method for operating a waste plastic oil liquefaction apparatus including a gas-liquid separator for separating gas from the gas, wherein the temperature of the gaseous light component at the outlet of the cooler takes a value within a predetermined range. A method for operating a waste plastic oil treatment apparatus, wherein the rate of generation of cracked gas is averaged by controlling the amount of heating of the waste plastics.