JP4157436B2 - Waste plastic oil processing equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a waste plastic oil processing apparatus for thermally decomposing plastic waste and converting it into an oil, and relates to an improvement of a heating portion thereof.
[0002]
[Prior art]
In recent years, waste plastic oil converting apparatuses that thermally decompose plastic waste and extract oil components have come to be used.
[0003]
In this type of waste plastic oil processing apparatus, plastic waste is decomposed by a thermal decomposition apparatus, the generated cracked gas (oil vapor) is condensed, and the obtained decomposed oil is once recovered in a cracked oil drum. This cracked oil is sent to the product oil recovery tower (distillation tower), where it is fractionated into light oil, medium oil and heavy oil due to the difference in boiling point. It stores in an oil tank (for example, refer patent document 1).
[0004]
In this example, the cracked gas (oil vapor) generated in the thermal cracking device is condensed and recovered in the cracked oil drum. However, the contents described below are not limited to such a system, and the generated cracked gas (oil The present invention can also be applied to a case where (gas) is directly sent to a product oil recovery tower (distillation tower).
[0005]
When fractionating the cracked oil in the product oil recovery tower, the cracked oil is heated in the recovery tower heating furnace in order to apply heat to the cracked oil. At this time, in order to efficiently heat the cracked oil, it is passed through a relatively thin and bent heat transfer tube disposed in the recovery tower heating furnace, and a heat source provided outside the heat transfer tube Heated by.
[0006]
By the way, the cracked oil obtained by thermally decomposing plastic waste has many unsaturated components. For this reason, when distilling cracked oil in the product oil recovery tower (distillation tower), if it is heated in the recovery tower heating furnace as described above, re-decomposition / repolymerization occurs in the heat transfer tube in the recovery tower heating furnace. easy. In addition, due to the presence of corrosive substances, there is a problem that coking occurs in the heat transfer tube and corrosion progresses.
[0007]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-173690
[Problems to be solved by the invention]
Thus, in order to distill the cracked oil obtained in the waste plastic oil converting process, when the cracked oil is heated, coking may occur in the heat transfer tube of the heating furnace, or corrosion may develop.
[0009]
An object of the present invention is to provide a waste plastic oil converting apparatus that prevents coking in a heat transfer tube and can be stably operated without causing corrosion when heated in a heating furnace for distillation treatment of cracked oil. It is in.
[0010]
[Means for Solving the Problems]
The waste plastic oil converting apparatus according to the present invention comprises a product oil recovery tower for distilling cracked oil decomposed from plastic waste by thermal decomposition due to a difference in boiling point, a heat transfer tube, and a heat source for heating the heat transfer tube from the outside. A recovery tower heating furnace, a cracked oil supply path for sending the cracked oil to a lower stage of the generated oil recovery tower, and a portion through which the generated oil of the generated oil recovery tower is withdrawn by a pipe. Directly connected to the inlet side of the heat transfer tube, the outlet side of this heat transfer tube is connected to the lower stage of the product oil recovery tower through a conduit, and only the product oil generated in the product oil recovery tower is heated in the recovery tower heating furnace, And a heat circulation loop for supplying the heated product oil to the lower stage of the product oil recovery tower .
[0011]
In the present invention, the recovery tower heating furnace has a cylindrical shape, a burner serving as a heat source is installed below the inside thereof, has a furnace body that exhausts from the upper part, and the heat transfer tube is a lower part near the burner in the furnace body. It consists of a radiant heating pipe part arranged along the inner wall surface and a convection heating pipe part installed in the upper part of the furnace body and heated by the exhaust gas of the burner. The convection heating pipe part of the heat circulation loop is connected to the radiant heating pipe part, and the product oil extracted from the product oil recovery tower is radiated from the convection heating pipe part of the heat transfer pipe to the radiant heating pipe. flows in part, constitutes the flow so that the radiant heating tube portion at the bottom of the product oil recovery column.
[0012]
In the present invention, a pressure control valve is installed in the outlet side pipe of the thermal circulation loop, and the pressure in the pipe is adjusted so that the ratio of the liquid at the outlet portion of the heat transfer pipe from the recovery tower heating furnace is 30% wt or more. To do.
[0013]
In the present invention, the pressure regulating valve is configured to detect the pressure in the pipe line and to control the opening degree by the detected pressure.
[0015]
Furthermore, in the present invention, the operating pressure of the product oil recovery tower is reduced, and the heat transfer tube outlet temperature of the recovery tower heating furnace is preferably set to 350 ° C. or lower.
[0016]
In these inventions, a part of the product oil generated by the product oil recovery tower is heated by flowing through the heat transfer tube of the recovery tower heating furnace, and the heated product oil is supplied to the cracked oil reservoir of the product oil recovery tower. As a result, a stable distillation operation can be performed without coking in the heat transfer tube.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a waste plastic oil processing apparatus according to the present invention will be described with reference to the drawings.
[0018]
First, a system configuration of a general waste plastic oil processing facility will be schematically described with reference to FIG.
[0019]
The waste plastic oil treatment system includes a pretreatment step 11, a dehydrochlorination / thermal decomposition step 12, a hydrochloric acid treatment step 13, a product oil recovery step 14, and an exhaust gas treatment step 15.
[0020]
In the pretreatment step 11, the plastic waste 17 reduced in a pail shape is carried in, crushed by a crusher 18, and then dried by a dryer 19. Then, impurities are removed from the dryer cyclone 20 through the wind separator 21 and the magnetic separator 22, granulated by the granulator 23, and stored in the granulating silo 24.
[0021]
In the dehydrochlorination / pyrolysis step 12, the plastic granulated in the pretreatment step 11 is fed from the desalinator hopper 26 to the desalinator 27 and desalted, and then in the molten state into the melting tank 28. Once stored.
[0022]
The desalted gas separated by the desalting treatment is sent to the hydrochloric acid treatment step 13, treated in the desalting gas combustion furnace 32 and the hydrogen chloride absorption tower 33, and the generated hydrochloric acid is stored in the hydrochloric acid tank 34.
[0023]
In addition, the desalted processed material to be processed is supplied from the melting tank 28 to the thermal decomposition apparatus 29 where it is separated into decomposition gas (oil vapor) and residue. Of these, the residue is cooled by the residue cooling conveyor 30 and then discharged to a residue processing unit (not shown). On the other hand, the cracked gas is condensed into cracked oil and accumulated in the cracked oil drum 36 provided in the product oil recovery step 14.
[0024]
In the product oil recovery step 14, the cracked oil stored in the cracked oil drum 36 is sent to the product oil recovery tower 37, where it is fractionated into light oil, medium oil, and heavy oil according to the difference in boiling points. It is stored in a tank 38, a medium oil tank 39, and a heavy oil tank 40.
[0025]
The exhaust gas generated in the product oil recovery step 14 and the hydrochloric acid treatment step 13 is burned in the exhaust gas combustion device 42 in the exhaust gas treatment step 15, detoxified and released to the atmosphere.
[0026]
The present invention relates to the product oil recovery step 14 and will be described in detail below.
[0027]
In FIG. 1, the cracked oil decomposed from the plastic waste by pyrolysis is sent from the cracked oil drum 36 to the lower stage of the product oil recovery tower 37 through the cracked oil supply path 46 by the cracked oil pump 45. In the middle of the cracked oil supply passage 46, a cracked oil heater 47 is provided. The cracked oil heater 47 heats the cracked oil with the high-temperature heavy oil extracted from the product oil recovery tower 37.
[0028]
Reference numeral 50 denotes a recovery tower heating furnace (hereinafter simply referred to as a heating furnace), which includes a heat transfer tube 51 and a heat source 52 for heating the heat transfer tube 51. The detailed structure of the heating furnace 50 will be described later. The entrance side of the heat transfer tube 51 provided in the heating furnace 50 is a portion (for example, medium oil) from which the product oil (for example, medium oil) of the product oil recovery tower 37 is extracted by a pipe line 54A having a pump 53 in the middle part (for example, , Middle part). Also, the delivery side pipe 54B of the heat transfer tube 51, connected to the lower part of the product oil recovery tower 3 7, to form a heat circulation loop 54. The pipe 54A is referred to as the inlet side pipe of the thermal circulation loop 54, and 54B is referred to as the outlet side pipe.
[0029]
A return pipe 55 and a medium oil take-out pipe 56 are branched from the discharge side portion of the pump 53 of the inlet pipe 54A. The return pipe 55 returns a part of the medium oil extracted from the product oil recovery tower 37 to the middle stage of the product oil recovery tower 37. Further, the medium oil take-out pipeline 56 cools a part of the medium oil taken out from the product oil collecting tower 37 by the cooler 57 and sends it to a medium oil tank (not shown).
[0030]
A heavy oil take-out pipeline 59 is connected to the bottom of the product oil recovery tower 37, and heavy oil staying at the bottom of the product oil recovery tower 37 is taken out by the pump 60 during the distillation operation. The line 59 is provided with the cracked oil heater 47 and the cooler 61, and the extracted heavy oil is cooled by these and then sent to a heavy oil tank (not shown). A return pipe 62 branches off from the heavy oil take-out pipe 59, and a part of the taken-out heavy oil is returned to the lower stage of the product oil recovery tower 37.
[0031]
A tower top gas extraction pipe 64 is connected to the top of the product oil recovery tower 37, and is joined with a pipe 65 from the cracked oil drum 36 and connected to a tower top drum 67 through a condenser 66. ing. Therefore, the top gas of the product oil recovery tower 37 is condensed by the condenser 66 together with the gas components in the cracked oil drum 37 and stored in the top drum 67. The oil component stored in the climbing drum 67 is sent as light oil to a light oil tank (not shown) by a pump 68. A part of this light oil is returned to the upper stage of the product oil recovery tower 37 by the return pipe 69.
[0032]
The gas component staying in the tower top drum 67 is sucked by the vacuum pump 70 and sent to the exhaust gas treatment process as off-gas. Further, the vacuum pump 70 has a function of sucking the top gas in the product oil recovery tower 37 and can adjust the operating pressure in the product oil recovery tower 37.
[0033]
Next, a detailed configuration of the heating furnace 50 will be described with reference to FIG.
[0034]
A furnace body 71 has a cylindrical shape having a narrow neck portion, and a burner 52 serving as a heat source is installed below the inside of the furnace body. An exhaust pipe 72 is integrally connected to the upper part, and combustion exhaust gas from the burner 52 is exhausted from the upper part through the exhaust pipe 72. The heat transfer tube 51 includes a radiant heating tube portion 51A installed at the lower portion in the furnace body 71 and a convection heating tube portion 51B disposed above. The radiant heating tube portion 51A is disposed along the lower inner wall surface so as to surround the flame of the burner 52 in the furnace body 71, and is heated by the radiant heat of the burner flame. The convection heating pipe portion 51 </ b> B is installed in an exhaust passage formed by the exhaust cylinder 72 above the furnace body 71 and is heated by the exhaust gas from the burner 52.
[0035]
As shown in FIGS. 3A and 3B, the convection heating pipe portion 51B is formed by diffracting a large number of finned thin tubes so as to form a rectangular parallelepiped as a whole. As shown, it is installed so as to cross the exhaust passage formed by the exhaust cylinder 72. Further, as shown in FIG. 3B, one end 51Ba of the convection heating pipe portion 51B is connected to the inlet side conduit 54A of the thermal circulation loop 54 shown in FIG. 1, and the other end 51Bb is cross-over. It connects with the pipe | tube 51C, It connects with 51 A of radiation heating pipe parts arrange | positioned below via this crossover pipe | tube 51C.
[0036]
As shown in FIG. 4, the radiant heating tube portion 51A is formed in a flat shape by diffracting a large number of narrow tubes as shown in FIG. 4, and is installed in a cylindrical shape along the inner wall surface of the furnace body 71 as shown in FIG. is doing. And one end 51Aa shown in FIG. 4 is connected to the crossover pipe 51C, and communicates with the convection heating pipe section 51B disposed above via the crossover pipe 51C. Further, the other end 51Ab shown in FIG. 4 is connected to the outlet side conduit 54B of the thermal circulation loop 54 shown in FIG.
[0037]
Therefore, a part of the medium oil from the product oil recovery tower 37 enters the convection heating pipe part 51B of the heat transfer pipe 51 in the heating furnace 50, and flows from the convection heating pipe part 51B to the radiant heating pipe part 51A. A part of the radiant heating tube portion 51A is vaporized.
[0038]
In the above configuration, the cracked oil in the cracked oil drum 36 is directly sent to the lower stage of the product oil recovery tower 37 through the cracked oil supply passage 46. During the distillation operation, medium oil is extracted from the middle stage of the product oil recovery tower 37 by the pump 53 provided in the pipeline 54A. The medium oil extracted from the middle stage of the product oil recovery tower 37 is recovered by a medium oil take-out line 56 to a medium oil tank (not shown) via a medium oil cooler 57. A part of the refrigerant is circulated to the middle stage of the product oil recovery tower 37 through the return pipe 55 and is sent to the heating furnace 50 to be heated.
[0039]
That is, the medium oil sent from the middle stage of the product oil recovery tower 37 by the pump 53 and flowing into the heating furnace 50 first flows through the convection heating pipe portion 51B installed at the upper part of the heating furnace 50 and is heated. . Then, it further heats by flowing through the radiation heating pipe part 51A arranged in a cylindrical shape in the lower part. Then, a part of the medium oil is vaporized in the radiant heating pipe portion 51A to become a gas-liquid two-phase flow and flows out from the heating furnace 50 to the pipe line 54B.
[0040]
The medium oil heated in the heating furnace 50 and partially vaporized into a gas-liquid two-phase flow is returned to the lower stage of the product oil recovery tower 37 through the pipe 54B. That is, a thermal circulation loop 54 is formed from the middle stage of the product oil recovery tower 37 through the heating furnace 50 to the lower stage of the product oil recovery tower 37. Therefore, the cracked oil can be distilled in the product oil recovery tower 37 while constantly supplying heat to the product oil recovery tower 37.
[0041]
As described above, since the stable produced oil (for example, medium oil) after the distillation treatment is heated in the heating furnace 50 and the heat is supplied to the produced oil recovery tower 37, the conventional unsaturated oil is used. The cracked oil can be prevented from re-polymerizing or coking in the recovery tower heating furnace, causing it to thicken and clogging the heat transfer tubes, as in the case of sending a large amount of cracked oil directly to the recovery tower heating furnace. . That is, the produced oil (medium oil) that has flowed into the heating furnace 50 flows from the convection heating tube portion 51B continuously formed by the narrow tube to the radiant heating tube portion 51A. The product oil stays and coking, and it does not thicken and clog the inside of the heat transfer tube, preventing repolymerization and coking in the heating furnace 50, and always stable. The product oil recovery tower 37 can be heated.
[0042]
The light oil is recovered from the top gas extracted from the top of the product oil recovery tower 37, and the heavy oil is extracted from the bottom bottom of the product oil recovery tower 37 and recovered.
[0043]
In addition, when the distillation operation is started, the generated oil cannot be taken out from the generated oil recovery tower 37. Therefore, the separately prepared generated oil may be supplied to the heating furnace 50 and heated by a starting pipe (not shown).
[0044]
Here, the medium oil which is heated in the heating furnace 50 and supplies heat to the product oil recovery tower 37 through the pipe 54B is a gas-liquid two-phase flow partially vaporized. This is because the gas component containing the gas component can be well mixed with the cracked oil stored in the lower stage of the product oil recovery tower 37 and heated efficiently. Therefore, it can be considered to control the ratio of the gas and liquid to a preferable ratio.
[0045]
FIG. 6 is based on such an idea. A pressure control valve 74 is installed in the outlet side pipe 54B of the thermal circulation loop 54, and the ratio of the liquid at the outlet of the heat transfer pipe from the heating furnace 50 is 30% wt or more ( The pressure in the pipeline is adjusted so that the vapor component is less than 70% wt. That is, by controlling the opening degree of the pressure control valve 74 and increasing the pressure in the heat transfer pipe 51 including the pipe 54B, the ratio of the liquid at the outlet in the heat transfer pipe 51 is set to 30% wt or more. The pressure control valve 74 should be installed as close as possible to the product oil recovery tower 37. This is because the pressure should be uniform over as wide a range as possible from the outlet of the heat transfer tube 51 to the product oil recovery tower 37.
[0046]
In this way, by installing the pressure control valve 74 on the outlet side of the heat transfer tube 51 of the heating furnace 50, the ratio of the liquid at the outlet in the heat transfer tube 51 can be adjusted, and the ratio of the liquid at the outlet in the heat transfer tube 51 is lowered. As a result, the heating temperature increases in the heat transfer tube 51. For this reason, it is possible to prevent coking of the generated oil on the inner wall of the heat transfer tube 51, to prevent the heat transfer tube 51 from being blocked due to coking, and to stably heat the generated oil recovery tower 37.
[0047]
The opening degree of the pressure adjustment valve 74 may be manually operated. However, as shown in the figure, the pressure in the conduit 54B is detected by the pressure sensor 75, and the opening degree of the pressure adjustment valve 74 is automatically detected based on the detected pressure. You may control. With this configuration, the opening degree of the pressure control valve 74 is automatically controlled with respect to the pressure fluctuation in the pipe line 54B, so that the ratio of the liquid at the outlet of the heat transfer pipe 51 during operation can always be adjusted to be constant. Thus, the ratio of the liquid at the outlet of the heat transfer tube 51 can be prevented from becoming extremely low, and a more stable operation can be performed.
[0048]
The diameter of the heat transfer tube 51 of the heating furnace 50 was set to be narrow so that the flow velocity in the tube was always in a turbulent region even at the time of startup and at the time of shutdown. That is, although it varies depending on the flow rate in the tube, if the diameter of the heat transfer tube 51 is narrowed, the flow velocity in the tube is increased to become a turbulent flow region, heat transfer efficiency is increased, and repolymerization and coking in the heat transfer tube 51 can be effectively prevented. .
[0049]
In addition, the outlet temperature of the heat transfer tube 51 provided in the heating furnace 50 is desirably 350 ° C. or lower. That is, when the outlet temperature of the heat transfer tube of the heating furnace 50 exceeds 350 ° C., the produced oil that has flowed into the heating furnace 50 is overheated and becomes a condition where coking is easily performed immediately. Thus, in order to restrict | limit the exit temperature of the heat exchanger tube 51, what is necessary is just to adjust the pressure in the pipe line containing the heat exchanger tube 51. FIG. Thus, the operating pressure of the product oil recovery tower 37 may be reduced in order to reduce the pressure in the pipe line.
[0050]
Normally, the product oil recovery tower 37 is operated under a negative pressure or a state close to a negative pressure by the vacuum pump 70 shown in FIG. The medium oil is extracted from the product oil recovery tower 37 by the pump 53 provided in the inlet side pipe 54A of the thermal circulation loop 54, and the inside of the pipe including the heat transfer pipe 51 in the heating furnace 50 after this pump has a positive pressure. Maintained. When the pressure in the pipe line is increased, the ratio of the liquid at the outlet in the heat transfer pipe 51 can be increased to 30% wt or more as described above, but the outlet temperature also increases. Therefore, the operating pressure of the product oil recovery tower 37 is reduced so that the outlet temperature of the heat transfer tube 51 is 350 ° C. or lower even in such a state where the pressure is increased.
[0051]
That is, the operating pressure of the product oil recovery tower 37 is reduced by the vacuum pump 70 so that the heat transfer tube outlet temperature of the heating furnace 50 is 350 ° C. or lower. As a result, repolymerization and coking in the heat transfer tube 51 can be prevented. In addition, the ratio of the liquid at the outlet of the heat transfer tube 51 can be easily adjusted to be constant, and the liquid ratio can be prevented from becoming extremely low.
[0052]
【The invention's effect】
According to the present invention, when the cracked oil is heated in order to distill the cracked oil of the waste plastic, it is possible to effectively prevent re-aggregation and coking in the heat transfer tube of the recovery tower heating furnace. Oiling can be performed.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of a waste plastic oil converting apparatus according to the present invention.
FIG. 2 is a cross-sectional view of a recovery tower heating furnace used in the embodiment.
FIGS. 3A and 3B show a convection heating unit used in the embodiment, in which FIG. 3A is a front view, and FIG. 3B is a side view.
FIG. 4 is a developed front view showing a radiation heating unit used in the embodiment.
FIG. 5 is a cross-sectional plan view showing a mounting state of the radiation heating unit according to the embodiment.
FIG. 6 is a system diagram showing another embodiment of the present invention.
FIG. 7 is a schematic diagram showing an overall configuration of a general waste plastic oil processing apparatus.
[Explanation of symbols]
36 Cracked oil drum 37 Generated oil recovery tower 46 Cracked oil supply path 50 Recovery tower heating furnace 51 Heat transfer pipe 51A Radiation heating pipe part 51B Convection heating pipe part 52 Heat source (burner)
54 Thermal circulation loop 54A Thermal circulation loop entry side 54B Thermal circulation loop exit side 71 Furnace body 74 Pressure regulating valve 75 Pressure sensor

Claims (5)

A product oil recovery tower that distills cracked oil decomposed from plastic waste by pyrolysis according to the difference in boiling point;
A recovery tower heating furnace having a heat transfer tube and a heat source for heating the heat transfer tube from the outside;
A cracked oil supply passage for sending the cracked oil to the lower stage of the generated oil recovery tower;
The portion from which the product oil of the product oil recovery tower is extracted is directly connected to the inlet side of the heat transfer tube of the recovery tower heating furnace through a conduit, and the outlet side of the heat transfer tube is connected to the lower stage of the product oil recovery tower by the conduit. A thermal circulation loop that heats only the product oil generated in the product oil recovery tower in a recovery tower heating furnace and supplies the heated product oil to the lower stage of the product oil recovery tower;
A waste plastic oil processing apparatus characterized by comprising: Recovery tower heating furnace
It has a cylindrical shape, a burner serving as a heat source is installed below the inside, and has a furnace body that exhausts from the top,
The heat transfer tube is composed of a radiant heating tube portion arranged along the lower inner wall surface near the burner in the furnace body, and a convection heating tube portion installed on the upper portion of the furnace body and heated by the exhaust gas of the burner,
The inlet side pipe of the heat circulation loop is connected to the convection heating pipe part of the heat transfer pipe, and the outlet side pipe of the heat circulation loop is connected to the radiation heating pipe part,
The product oil extracted from the product oil recovery tower flows from the convection heating pipe part of the heat transfer pipe to the radiation heating pipe part, and flows from the radiation heating pipe part to the lower part of the product oil recovery tower. The waste plastic oil processing apparatus of Claim 1. A pressure control valve is installed in the outlet pipe of the thermal circulation loop, and the pressure in the pipe is adjusted so that the ratio of the liquid at the outlet of the heat transfer pipe from the recovery tower heating furnace is 30% wt or more. The waste plastic oil processing apparatus according to claim 1. The waste plastic oil converting apparatus according to claim 3, wherein the pressure regulating valve is configured to detect the pressure in the pipe line and control the opening degree by the detected pressure. 2. The waste plastic oil treatment apparatus according to claim 1, wherein the operating pressure of the product oil recovery tower is reduced and the heat transfer tube outlet temperature of the recovery tower heating furnace is set to 350 ° C. or lower.

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