Thermal decomposition device

Abstract

To provide a thermal decomposition device that separates gas in either a thermal decomposition part or a residue discharging part which discharges residue from the thermal decomposition part more securely, by which a gas volume coexisting with residue can be reduced on a post-stage of the residue discharging part.SOLUTION: A thermal decomposition device 1 comprises: a thermal decomposition part 20 which receives and thermally decomposes raw resin; a thermally decomposed gas separation part A which separates thermally decomposed gas generated by thermal decomposition in the thermal decomposition part 20; a gas treatment part 100 which treats thermally decomposed gas sent through the thermally decomposed gas separation part A; and a residue discharging part 30 which discharges undecomposed residue generated in the thermal decomposition part 20. The residue discharging part 30 includes a gear pump (positive displacement pump) 60 which absorbs and ejects undecomposed residue from an outlet part 23f of the thermal decomposition part 20.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a resin pyrolysis device. [Background technology]

[0002] In recent years, with the rise in resource prices and growing awareness of environmental issues, there has been a growing trend to collect and recycle resin molded products such as poly(meth)acrylic esters. One known example is a method in which poly(meth)acrylic esters are thermally decomposed (depolymerized) to recover the resulting monomer, which is then used to produce a new molded product. This type of resin recycling method is also called chemical recycling.

[0003] In chemical recycling, resin is thermally decomposed by heating it at a temperature of, for example, about 300°C to 500°C. For example, in the regeneration system described in Patent Document 1, pyrolysis gas generated in the pyrolysis section is extracted through a gas extraction section (vent). The pyrolysis gas is purified or cooled in a gas treatment device. Alternatively, impurities in the pyrolysis gas are adsorbed and removed in the gas treatment device. A residue discharge section is provided near the downstream end of the pyrolysis section to discharge residue generated in the pyrolysis section, including undecomposed components. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2024-48830 Summary of the Invention [Problem to be solved by the invention]

[0005] In the conventional system described above, the residue is discharged by a residue discharge section and is collected and stored in a storage tank through a connecting pipe. The storage tank is provided with a gas discharge section. Furthermore, in consideration of the flammability or combustibility of the gas present in the storage tank, safety measures are taken, such as cooling the residue in the storage tank or supplying an inert gas into the storage tank. As such, the more gas that may be generated or present in the residue storage device (or residue storage section), the more stringent safety measures are required.

[0006] The present disclosure describes a thermal decomposition apparatus that can more reliably separate gases in either the thermal decomposition section or the residue discharge section that discharges residue from the thermal decomposition section, thereby reducing the amount of gas that coexists with the residue in the downstream of the residue discharge section. [Means for solving the problem]

[0007] The present disclosure provides several aspects as follows. [1] A thermal decomposition unit that receives and thermally decomposes raw resin; a pyrolysis gas separation section that separates pyrolysis gas generated by pyrolysis in the pyrolysis section; a gas processing unit that processes the pyrolysis gas sent through the pyrolysis gas separation unit; a residue discharge section connected to an outlet of the thermal decomposition section and discharging undecomposed residue generated in the thermal decomposition section, The residue discharge section includes a positive displacement pump that sucks in and discharges the undecomposed residue from the outlet section.

[0008] According to the pyrolysis device of [1], by providing a positive displacement pump in the residue discharge section, even if gas is mixed with the undecomposed residue discharged from the outlet of the pyrolysis section, the gas is sealed by the internal structure of the positive displacement pump and is less likely to leak out the discharge side of the positive displacement pump. This sealing effect allows for more reliable gas separation in the pyrolysis section or residue discharge section. Furthermore, the amount of gas coexisting with the residue can be reduced in the stage following the residue discharge section (i.e., the residue storage section or granulation device connected to the discharge section of the positive displacement pump, etc.).

[0009] [2] The pyrolysis device according to [1], wherein the residue discharge unit further includes a flow path switching unit connected to the discharge unit of the positive displacement pump and switching the flow path of the undecomposed residue discharged by the positive displacement pump. With this configuration, even if a high-pressure state (such as a blockage) occurs downstream of the positive displacement pump, the flow path can be switched and the undecomposed residue can be discharged.

[0010] [3] The pyrolysis apparatus according to [1] or [2], wherein the residue discharge section further includes a chamber provided between the outlet of the pyrolysis section and the suction section of the positive displacement pump, having an internal space of a certain volume or more and having a gas outlet. With this configuration, gas can also be extracted from the chamber through the gas outlet. Furthermore, since a certain amount of undecomposed residue can be stored in the chamber, the positive displacement pump can be operated with a margin of error. Because the chamber functions as a volumetric buffer, the temperature of the undecomposed residue within the chamber can be lowered, allowing for more general-purpose specifications to be applied to the discharge side of the positive displacement pump (i.e., special specifications can be avoided).

[0011] [4] The pyrolysis device according to [3], wherein the residue discharge section further includes another positive displacement pump provided between the outlet section of the pyrolysis section and the chamber. With this configuration, multiple positive displacement pumps are provided (in two stages), further enhancing the gas sealing effect.

[0012] [5] A pressure gauge is provided at or near the outlet of the thermal decomposition section, The pyrolysis device according to any one of [1] to [4], wherein the positive displacement pump operates and stops in response to the pressure value detected by the pressure gauge. With this configuration, the positive displacement pump operates (by controlling the number of reciprocating motions or the number of rotations) and stops in response to the pressure value, thereby ensuring the discharge of undecomposed residue and sealing the system by leaving a certain amount of residue in the pyrolysis section. This prevents excessive pressure buildup and prevents blockage due to undecomposed residue. Furthermore, it prevents the leakage of flammable gases to the outside of the system and the intrusion of oxygen gas and the like from the outside of the system.

[0013] [6] The thermal decomposition device according to any one of [1] to [5], wherein the positive displacement pump is operated intermittently or so as to vary the number of rotations or the number of reciprocating motions of the movable part. This configuration makes it possible to suppress fluctuations in the amount of undecomposed residue inside the thermal decomposition section.

[0014] [7] The pyrolysis apparatus according to any one of [1] to [6], wherein the positive displacement pump is a gear pump. Gear pumps transport fluids by the meshing of multiple gears, which are rotating parts, and therefore have excellent gas sealing capabilities among positive displacement pumps. [Effects of the Invention]

[0015] According to the present disclosure, the sealing effect of the positive displacement pump allows for more reliable gas separation in the thermal decomposition section or the residue discharge section, and also reduces the amount of gas coexisting with the residue downstream of the residue discharge section. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a flow diagram of a pyrolysis apparatus according to one embodiment of the present disclosure. [Figure 2] FIG. 2 is a diagram showing a first example of the configuration of the residue discharge unit and its periphery. [Figure 3] FIG. 3 is a diagram showing a second example of the configuration of the residue discharge unit and its periphery. [Figure 4] FIG. 4 is a diagram showing a third example of the configuration of the residue discharge unit and its periphery. [Figure 5] FIG. 5 is a diagram showing a fourth example of the configuration of the residue discharge unit and its periphery. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicate explanations will be omitted. Each drawing is created for explanatory purposes and is drawn to particularly emphasize the portions to be described. Therefore, the dimensional proportions of each component in the drawings do not necessarily correspond to the actual proportions.

[0018] The resin pyrolysis apparatus 1 according to one embodiment of the present disclosure is an apparatus for obtaining monomers by thermally decomposing (depolymerizing) used resin molded bodies (e.g., recovered products from the market) or discarded resin molded bodies (e.g., factory waste). The pyrolysis apparatus 1 can also process post-consumer recycled plastic (PCR), in addition to resins originating from factories. The monomers obtained by the pyrolysis apparatus 1 are repolymerized in a separate device to obtain polymers (or recycled monomers). The monomers obtained by pyrolysis, i.e., pyrolyzed monomers, may contain several types of impurities. The pyrolysis apparatus 1 according to this embodiment, combined with a separate repolymerization apparatus, enables chemical recycling of any resin. In this specification, "used or discarded resin" may also be referred to as "raw material" or "raw material resin."

[0019] The type of resin to be recovered by the thermal decomposition apparatus 1 is not particularly limited. The thermal decomposition apparatus 1 may thermally decompose (meth)acrylic resins, styrene-based resins, polycarbonate, or polyethylene terephthalate. For example, when polymethyl methacrylate (PMMA), which is one type of resin, is thermally decomposed, the monomer methyl methacrylate (MMA) is obtained. At this time, several low-boiling-point impurities are contained. For example, impurities may include methyl propionate, methyl isobutyrate, methyl acrylate, ethyl acrylate, butyl acrylate, methanol, etc. Note that with regard to methyl acrylate, it is believed that the influence of the raw material origin is significant.

[0020] Even when recycling a single type of resin, there are various types of impurities. The impurities may include typical impurities such as those described above, or may include special impurities. The impurities may be low-boiling point impurities or high-boiling point impurities. Low-boiling point impurities are substances with a lower boiling point than the monomers of the resin to be recovered (i.e., the resin to be recycled). High-boiling point impurities are substances with a higher boiling point than the monomers of the resin to be recovered (i.e., the resin to be recycled). The pyrolysis device 1 can handle any type of impurity.

[0021] The types and amounts of impurities that can be tolerated in pyrolysis monomers may vary (or may be set appropriately) depending on the type of resin, or may vary (or may be set appropriately) for the same resin depending on the intended use after recycling. When the manner of use of recycled resins differs, the required level of impurity concentration in recycled resins often differs. The pyrolysis device 1 of this embodiment is applicable to all impurities and all concentration levels (the above-mentioned required levels).

[0022] The configuration of the pyrolysis apparatus 1 will be described with reference to Fig. 1. As shown in Fig. 1, the pyrolysis apparatus 1 includes a pre-treatment section 10, a pyrolysis section 20, a pyrolysis gas separation section A, and a gas treatment section 100. Although Fig. 1 does not show valves, instruments, detailed piping configurations, etc., each section of the pyrolysis apparatus 1 may employ a known detailed configuration for realizing the function of each section, which will be described later.

[0023] The pre-treatment section 10 pre-treats the raw resin before it is supplied to the pyrolysis section 20. Examples of pre-treatment include conventionally known processes such as a fine powder removal process, a metal removal process, and a process for separating or sorting different resins. The pre-treatment section 10 includes a pre-treatment device 11 that performs pre-treatment such as fine powder removal, and a first feeder 12 that supplies the pre-treated raw material to the pre-treatment section 10. The type of the first feeder 12 is not particularly limited and can be selected from known devices.

[0024] The pyrolysis section 20 performs pyrolysis of the raw material supplied from the pretreatment section 10. In other words, the pyrolysis section 20 receives and pyrolyzes raw material resin. The pyrolysis section 20 includes, for example, a resin receiving section 21, a second feeder 22, and a pyrolysis gasification device 23. The resin receiving section 21 can also be considered a resin inlet into which resin is introduced. The resin receiving section 21 is a raw material supply section that supplies raw material to the pyrolysis gasification device 23. The type of the second feeder 22 is not particularly limited and can be selected from known devices. Any of the pretreatment section 10, the resin receiving section 21, and the second feeder 22 may be provided with a device for processing the raw material, such as crushing, a detector for detecting foreign matter contained in the raw material, or a meter for controlling the amount of raw material introduced.

[0025] The pyrolysis gasification apparatus 23 thermally decomposes the raw material resin to obtain a gaseous pyrolysis product (hereinafter also referred to as pyrolysis gas). As the pyrolysis gasification apparatus 23, for example, an extrusion type apparatus or a fluidized bed type apparatus may be used. A kneader may also be used as the pyrolysis gasification apparatus 23. As the pyrolysis gasification apparatus 23, any known (arbitrary and suitable) apparatus capable of thermally decomposing the target raw material resin may be used.

[0026] Suitable examples of the pyrolysis gasification device 23 include twin-screw extruders such as a twin-screw co-rotating extruder and a twin-screw counter-rotating extruder. These extruders are equipped with a raw material inlet, a cylinder, and a screw 23a (see FIG. 2, etc.) disposed inside the cylinder, and are devices that can transport the raw material fed from the inlet in a predetermined direction while heating it.

[0027] An example of the pyrolysis gasification apparatus 23 being a kneader is the apparatus described in U.S. Patent No. 10,301,235. An example of the pyrolysis gasification apparatus 23 being a fluidized bed heater is the apparatus described in Japanese Patent Laid-Open No. 2009-112902.

[0028] The temperature at which the poly(meth)acrylic acid ester is thermally decomposed in the thermal decomposition section 20 may be selected from the range of, for example, 300°C to 500°C, 400°C to 500°C, or 450°C to 500°C.

[0029] A residue storage unit 70 is connected to the pyrolysis unit 20 (specifically, to the pyrolysis gasification apparatus 23) via a residue discharge unit 30, which will be described later, etc. The residue storage unit 70 stores the residue (undecomposed residue) discharged from the pyrolysis gasification apparatus 23 by the residue discharge unit 30. The method for storing the residue is not particularly limited and can be selected from known methods. The residue storage unit 70 may be equipped with a processing device or the like that processes the residue into a disposable state. In addition to or instead of the residue storage unit 70, a granulation device or the like that granulates the undecomposed residue may be provided.

[0030] 2, the pyrolysis gas separation unit A includes, for example, a pyrolysis gas outlet pipe L1 provided at an upper portion near the outlet 23f of the pyrolysis gasifier 23. The pyrolysis gas outlet pipe L1 extends, for example, upward from the pyrolysis gasifier 23 and discharges the pyrolysis gas generated by pyrolysis in the pyrolysis gasifier 23. That is, the pyrolysis gas separation unit A separates the pyrolysis gas generated by pyrolysis in the pyrolysis unit 20. The internal structure of the pyrolysis gasifier 23 is capable of separating the pyrolysis gas and the undecomposed residue generated in the pyrolysis gasifier 23.

[0031] As shown in Fig. 1, the gas processing unit 100 processes the pyrolysis gas sent through the pyrolysis gas separation unit A. The gas processing unit 100 has, for example, a condensation unit 40 and a purification unit 50. In Fig. 1, the downstream end of the pyrolysis gas discharge pipe L1 is connected to, for example, the condensation unit 40.

[0032] A partial condenser may be provided between the thermal decomposition section 20 and the condensation section 40. The partial condenser, for example, condenses (liquefies) and removes high-boiling-point impurities contained in the gaseous thermal decomposition product obtained in the thermal decomposition section 20. By disposing the partial condenser downstream of the thermal decomposition section 20, the load of the purification process in the purification section can be further reduced. The removal of high-boiling-point impurities by the partial condenser is carried out, for example, at a temperature that is equal to or higher than the boiling point and lower than the ignition point of the substance contained in the thermal decomposition product to be recovered, and that is lower than the boiling point and higher than the melting point of the high-boiling-point impurities. In other words, the high-boiling-point impurities are removed while the thermal decomposition product as a whole remains in a gaseous state.

[0033] The condensation section 40 liquefies the pyrolysis gas discharged from the pyrolysis section 20. The condensation section 40 includes a cooling section. The condensation section 40 cools and liquefies the pyrolysis gas obtained in the pyrolysis section 20 to obtain a condensed liquid.

[0034] The temperature to which the pyrolysis gas is cooled is preferably lower than the boiling point of the substance to be recovered. For example, when the pyrolysis gas contains methyl methacrylate or methyl acrylate to be recovered, the pyrolysis gas is cooled to a temperature lower than 101°C, the boiling point of methyl methacrylate, or lower than 80°C, the boiling point of methyl acrylate. The configuration of the condenser 40 is not particularly limited, and a known device such as a condenser can be used.

[0035] The liquid pyrolyzate (condensate) that has passed through the condensation section 40 is supplied to the downstream purification section 50. A storage section (not shown) for storing the condensate may be provided between the condensation section 40 and the purification section 50. A dehydration section may be provided at any location within the storage section.

[0036] The purification section 50 has multiple purification columns (first purification column 51 and second purification column 52) and a cooling mechanism 53. FIG. 1 is a diagram showing an embodiment in which low-boiling-point impurities are removed in the first purification column 51 and high-boiling-point impurities are removed in the second purification column 52. The purification section 50 purifies the condensate. Each of the first purification column 51 and the second purification column 52 purifies the liquid pyrolysate (condensate) obtained in the condensation section 40. In this specification, "purification of the pyrolysate" means increasing the proportion of the components to be recovered among the components contained in the pyrolysate.

[0037] In the first purification column 51, low-boiling-point impurities are removed from the liquid pyrolysate (condensate) obtained in the condensation section 40. Specifically, by purifying the pyrolysate in the first purification column 51, a gas mainly containing low-boiling-point impurities is discharged from the top of the first purification column 51, and a liquid containing a large amount of the components to be recovered is sent from the bottom of the first purification column 51 to the second purification column 52. The gas mainly containing low-boiling-point impurities discharged from the top of the first purification column 51 is cooled and liquefied by the cooling mechanism 53. From the viewpoint of purification efficiency, it is preferable to discard a portion of the cooled liquid (downward arrow in FIG. 1 ) and return the remainder to the first purification column 51.

[0038] In the second purifier 52, high-boiling-point impurities are removed from the liquid delivered from the bottom of the first purifier 51. Specifically, the liquid delivered from the bottom of the first purifier 51 is purified in the second purifier 52, so that a gas containing mainly the components to be recovered is discharged from the top of the second purifier 52, and a liquid containing high-boiling-point impurities accumulates at the bottom of the second purifier 52. The liquid that accumulates at the bottom of the second purifier 52 can be discarded by a known method. For example, the liquid that accumulates at the bottom of the second purifier 52 may be stored in a waste liquid tank 57 and then discarded. The gas that contains a large amount of the components to be recovered and that is delivered from the top of the second purifier 52 is cooled and liquefied by a cooling mechanism 53 and is sent as a product to a packing section (not shown).

[0039] 1 shows a configuration in which low boiling point impurities are removed in the first purification column 51 and high boiling point impurities are removed in the second purification column 52, but the configuration of the purification section 50 is not limited to this example. It is also possible to adopt a configuration in which high boiling point impurities are removed in the first purification column 51 and low boiling point impurities are removed in the second purification column 52. In that case, an appropriate device configuration may be adopted so that a liquid containing a large amount of the component to be recovered is stored in the packed section.

[0040] The liquid pyrolysate introduced into the purification section 50 (first purification column 51 and second purification column 52) may or may not contain water. When the liquid pyrolysate introduced into the purification section 50 contains water, the water may or may not be removed in the purification section 50. The configuration of the purification section 50 is not particularly limited, and a known purification device such as a purification column can be applied.

[0041] The cooling mechanism 53 cools and liquefies the gas discharged from the first purification column 51 and the second purification column 52. The temperature to which the gas is cooled may be set appropriately depending on the gas discharged from the first purification column 51 and the second purification column 52, but is preferably a temperature lower than the boiling point of the main components contained therein. The configuration of the cooling mechanism 53 is not particularly limited, and known devices such as condensers (for example, double-pipe type, shell-and-tube type, plate type, spiral type, etc.) can be applied. As described above, the purified monomer storage tank 57 is a tank for storing and disposing of monomers containing a large amount of high-boiling-point impurities.

[0042] The above-described configuration is an example of the gas processing unit 100. The gas processing unit 100 may have a different configuration for processing pyrolysis gas. Only the condensation unit 40 may be provided, omitting the purification unit 50, or only the purification unit 50 may be provided, omitting the condensation unit 40. The liquid pyrolyzed product that has passed through the condensation unit 40 may be filled in a filling unit (not shown). The filling unit may include a storage container such as a tank and a filling container such as a drum. The pyrolyzed product may be filled in a drum or the like and then shipped as needed. In addition to the above, the gas processing unit may include a collection process for collecting droplets, a process for removing impurities by contact with an adsorbent, a process for removing ions using an ion exchange unit, and a dehydration process using a dehydration unit. At least one of these processes may be combined as appropriate, or the gas processing unit may include all of these processes.

[0043] As shown in FIGS. 1 and 2, the pyrolysis apparatus 1 further includes a residue discharge section 30 connected to the outlet 23f of the pyrolysis gasification apparatus 23. The residue discharge section 30 is provided between the pyrolysis gasification apparatus 23 and the residue storage section 70 and discharges undecomposed residue generated in the pyrolysis section 20. Here, the term "undecomposed residue" refers to components generated by pyrolysis of methyl (meth)acrylate and the like, other than pyrolysis gas. The undecomposed residue is generally a liquid substance. Examples of undecomposed residue include decomposed or undecomposed components other than methyl poly(meth)acrylate contained in the raw resin, such as polymethyl (meth)acrylate that was not gasified by pyrolysis, colorants, diffusing agents, and inorganic fillers, as well as undecomposed other resins and pyrolyzed, non-volatile copolymer components.

[0044] As shown in FIG. 2 , the residue discharge section 30 has a gear pump (positive displacement pump) 60 connected directly or indirectly to the outlet 23f of the pyrolysis gasification apparatus 23. An appropriate connection section 25 may be provided between the gear pump 60 and the outlet 23f. The connection section 25 is an adapter for connecting the pyrolysis gasification apparatus 23 and the gear pump 60. For example, the connection section 25 may have a cylindrical shape. A flow path 25a is formed inside the connection section 25, which guides the undecomposed residue discharged from the outlet 23f of the pyrolysis gasification apparatus 23 to downstream devices such as the gear pump 60. The shape and size of the flow path 25a are appropriately determined so as to accommodate both the outlet 23f and the suction section 61 of the gear pump 60. An external heater may also be provided inside the connection section 25. A static mixer may also be provided inside the connection section 25 to induce fluid flow. Furthermore, a breaker plate may also be provided inside the connection section 25 to protect the gear pump 60. Note that "(two parts) are indirectly connected" means that another member is interposed between the two parts. The connecting part 25 may be omitted, and the suction part 61 of the gear pump 60 may be directly connected to the outlet part 23f. The outlet part 23f of the pyrolysis gasification apparatus 23 and the gear pump 60 are connected so that a fluid can move (flow) between them.

[0045] The gear pump 60 includes a motor (not shown) and uses the driving force of the motor to suck in and discharge undecomposed residue from the outlet 23f of the pyrolysis gasification apparatus 23. The gear pump 60 includes a suction section 61 directly or indirectly connected to the outlet 23f of the pyrolysis gasification apparatus 23, a first gear 64A and a second gear 64B that rotate due to the driving force of the motor, and a discharge section 62 located on the opposite side of the suction section 61. The gear pump 60 is, for example, an external gear pump. The suction section 61 and the discharge section 62 are integrally formed at one end and the other end of the casing 63, respectively, and are shaped to be connectable to the connection section 25 or other piping material. The residue discharge section 30 further includes a residue discharge pipe 39 connected to the discharge section 62. The residue discharge pipe 39 connects the discharge section 62 of the gear pump 60 to the residue storage section 70.

[0046] The first gear 64A and the second gear 64B are housed in a casing 63 and rotate while meshing with each other. Fluid is sucked from the suction port 61 into a clearance (gap) having a predetermined volume between the first gear 64A and the second gear 64B and the inner wall surface of the casing 63, and is discharged to the discharge port 62 as the first gear 64A and the second gear 64B rotate. The gear pump 60, which is a positive displacement pump, enables a constant flow of fluid depending on the rotation speed of the first gear 64A and the second gear 64B. The gear pump 60 has specifications that allow it to withstand at least predetermined high-temperature conditions and predetermined pressures, and is sealed against pyrolysis gas. A known pump that can be used to handle undecomposed residue generated in the pyrolysis gasification system 23 may be used as the gear pump 60.

[0047] A thermometer 27 for measuring the temperature inside the pyrolysis gasification apparatus 23 and a pressure gauge 28 for measuring the pressure inside the pyrolysis gasification apparatus 23 are provided at appropriate locations near the outlet 23f of the pyrolysis gasification apparatus 23. The pyrolysis apparatus 1 may also include a controller (not shown) that receives measurement values ​​output from the thermometer 27 and the pressure gauge 28 and controls the operation of the gear pump 60. The controller may be provided outside the residue discharge unit 30, or may be provided attached to the gear pump 60 as part of the residue discharge unit 30. The controller receives information about the temperature (temperature value) measured by the thermometer 27 and information about the pressure (pressure value) measured by the pressure gauge 28. The controller controls the motor of the gear pump 60 based on the received temperature and pressure values, and activates or stops (turns on or off) the gear pump 60. The controller also controls the rotation speed of the motor of the gear pump 60 based on the received temperature and pressure values. Note that the temperature value may not be used in the control of the controller, and only the pressure value may be used.

[0048] The thermometer 27 and the pressure gauge 28 may be provided at the outlet 23f instead of near the outlet 23f, or may be provided near the connection part 25 or the suction part 61 of the gear pump 60.

[0049] In the pyrolysis apparatus 1, the pyrolysis gasification apparatus 23 is operated continuously. On the other hand, the gear pump 60 is operated intermittently or continuously while controlling the rotation speed (the rotation speed of the moving part). In other words, a rotary positive displacement pump is operated intermittently or so that the rotation speed of the moving part is variable. The purification unit 50 is controlled, for example, by the controller and is activated and stopped at least in accordance with the pressure value detected by the pressure gauge 28. "Activation" means both control of the motor rotation speed to a constant value and control of the motor rotation speed to a variable value. Therefore, the controller stores a pressure threshold as an activation condition (and a stop condition) of the gear pump 60. When the controller controls the gear pump 60 using a temperature value in addition to a pressure value, the temperature value may be added to the activation condition of the gear pump 60. By operating the apparatus while controlling the rotation speed of the gear pump 60 so that the value of the pressure gauge becomes constant (or approximately constant), the amount of undecomposed residue inside the pyrolysis unit 20 can be kept constant (or approximately constant).

[0050] In the pyrolysis apparatus 1 described above, the raw material resin is sequentially pyrolyzed in the pyrolysis gasifier 23. The pyrolysis gas and uncracked residue are generated in the pyrolysis gasifier 23. The pyrolysis gas is discharged from the pyrolysis gasifier 23 through the pyrolysis gas discharge pipe L1 and sent to the condenser 40. When the pressure near the outlet 23f (or at the outlet 23f) in the pyrolysis gasifier 23 is equal to or greater than a predetermined pressure threshold, the gear pump 60 is activated or its rotation speed is increased, causing the uncracked residue to be discharged from the outlet 23f and sucked in and discharged by the gear pump 60. When the pressure near the outlet 23f (or at the outlet 23f) in the pyrolysis gasifier 23 is less than the predetermined pressure threshold, the gear pump 60 is stopped or its rotation speed is reduced, causing the uncracked residue to accumulate near the outlet 23f or in the space between the outlet 23f and the suction section 61. In this way, by operating the gear pump 60 by turning it on and off or by controlling the rotation speed of the gear pump 60, the undecomposed residue is reliably discharged and a certain amount of residue is accumulated in the thermal decomposition section.

[0051] In the pyrolysis device 1, gas may be mixed in with the uncracked residue discharged from the outlet 23f of the pyrolysis section 20. By providing the gear pump 60, which is a positive displacement pump, in the residue discharge section 30, even if gas is mixed in with the uncracked residue discharged from the outlet 23f, the internal structure of the gear pump 60 seals the gas, making it less likely to leak to the discharge section 62 side (discharge side) of the gear pump 60. This sealing effect allows the gas mixed in with the uncracked residue to be discharged to the pyrolysis gas discharge pipe L1, allowing for more reliable gas separation in the pyrolysis section 20 or the residue discharge section 30. Furthermore, the amount of gas coexisting with the residue can be reduced downstream of the residue discharge section 30 (i.e., the residue storage section 70 connected upstream of the discharge section 62 of the gear pump 60).

[0052] The effect of the residue discharge section 30 will be explained in more detail. By providing the gear pump 60 immediately after the pyrolysis gasification apparatus 23, the vicinity of the outlet section 23f of the pyrolysis gasification apparatus 23 is sealed with resin. This prevents gas from leaking downstream. By preventing gas from leaking downstream, almost all (or most) of the gas is treated in the gas treatment section 100. This contributes to improving yield and ensuring safe operation by preventing hazardous gas from leaking outside the system. Furthermore, the above-mentioned sealing effect prevents oxygen from outside the system from entering the system, greatly reducing the risk of explosions and other problems within the system.

[0053] If the gear pump 60 were not provided, it would be impossible to seal the gas if the amount of undecomposed residue generated in the pyrolysis gasification apparatus 23 was small. This is because the resin would flow only in the lower portion of the pyrolysis gasification apparatus 23, while the gas would pass through the upper portion and reach the outlet 23f. The gear pump 60 can block the resin, sealing the gas with the blocked resin. On the other hand, if a sealing function is provided by providing a damming section or a backflow section in a screw configuration, a decrease in the decomposition rate could cause the undecomposed residue to clog the system, leaving the gas with nowhere to go. As a result, the internal pressure of the pyrolysis gasification apparatus 23 would increase, increasing the risk of explosion. According to this embodiment, the undecomposed residue can be quantitatively discharged, ensuring safety.

[0054] Furthermore, the gear pump 60 operates (on or speed controlled) and stops (off) according to the pressure value detected by the pressure gauge 28. By operating (on or speed controlled) and stopping (off) the gear pump 60 according to the pressure value, it is possible to reliably discharge the undecomposed residue. This prevents the pressure from increasing too much, and prevents blockage due to the undecomposed residue. In other words, by providing the pressure gauge 28 on the suction side (inlet side) of the gear pump 60, it is possible to estimate the amount of resin accumulated on the suction side. This allows the discharge rate of the gear pump 60 to be controlled, and the undecomposed residue to be discharged from the pyrolysis gasification device 23 while maintaining an almost constant accumulated amount.

[0055] As mentioned above, the thermometer 27 can be omitted, but its use offers advantages. The thermometer 27 allows for more accurate control. For example, using both the pressure gauge 28 and the thermometer 27 for control allows for more precise adjustment of the amount of residue filling the pyrolysis gasification system 23. In other words, when the temperature is low, the viscosity of the residue increases, which can result in high pressure even when the amount of residue is small. Conversely, when the temperature is high, the viscosity of the residue decreases, which can result in low pressure even when the amount of residue is large. Controlling with both the thermometer and the pressure gauge allows for prediction of the viscosity of the residue, eliminating discrepancies in the filling amount due to viscosity. If the pressure gauge 28 malfunctions, the gear pump may become too fast, causing all of the undecomposed residue to be discharged. As a result, the pyrolysis gas may reach the inlet of the gear pump 60. Because the temperature of the pyrolysis gas is higher than that of the undecomposed residue, the thermometer 27 can detect abnormalities. As an example of control, the gear pump 60 can be stopped (turned off) or the rotation speed of the gear pump 60 can be reduced using the signal output from the thermometer 27. Furthermore, by installing a thermometer, abnormally high temperatures due to runaway reactions inside the pyrolysis gasification device can be detected quickly and a quick response can be made.

[0056] The gear pump 60 is operated intermittently or at a variable rotation speed, which makes it possible to suppress fluctuations in the amount of undecomposed residue inside the pyrolysis gasification apparatus 23 even when the apparatus is operated continuously.

[0057] The gear pump 60 transfers fluid by meshing of the first gear 64A and the second gear 64B, which are rotating parts, and therefore has an excellent gas sealing ability among positive displacement pumps.

[0058] Because most of the raw material is gasified by pyrolysis in the pyrolysis gasifier 23, very little residue is discharged (discharged) from the outlet 23f (tip). By using an extrusion-type device such as a twin-screw extruder as the pyrolysis gasifier 23 and filling the space between the tip of the screw 23a and the cylinder with residue, the tip of the screw 23a can be fixed. This is also advantageous from the perspective of protecting the device. In a typical extrusion processing device, the same amount of raw material is discharged from the tip, filling the device with raw material. However, in the pyrolysis gasifier 23, the tip of the screw 23a becomes starved, which can create a gap between the tip of the screw 23a and the cylinder. Screw vibration can cause damage to the device, but the presence of residue as described above can be used to protect the device.

[0059] Next, other configuration examples of the residue discharge unit and its periphery will be described with reference to Figure 3 and subsequent figures. The residue discharge unit 30A shown in Figure 3 is connected to the discharge unit 62 of the gear pump 60 and further includes a flow path switching unit 33 that switches the flow path of the undecomposed residue discharged by the gear pump 60. The flow path switching unit 33 includes a main flow path 35 formed inside the main body unit 34 and connected to the residue discharge pipe 39, and an alternative flow path 36 that connects to an external pipe or the like other than the residue discharge pipe 39. The flow path switching unit 33 includes a switching unit 32 interposed between the discharge unit 62 and the main body unit 34 and serving as an actuator that switches the flow path through which the fluid is introduced between the main flow path 35 and the alternative flow path 36. A known diverter valve, for example, can be used as the flow path switching unit 33. Even if a high pressure state (such as blockage due to adhesion of undecomposed residue) occurs in the downstream residue discharge pipe 39 due to some kind of trouble, the flow path switching unit 33 switches the flow path from the main flow path 35 to the alternative flow path 36 to discharge the undecomposed residue. The flow path switching unit 33 operates and switches the flow path according to, for example, a pressure value detected by a pressure gauge (not shown) provided downstream.

[0060] The configuration including the residue discharge unit 30A provides the same functions and effects as the pyrolysis device 1 including the residue discharge unit 30. Furthermore, even if a high-pressure state (such as a blockage) occurs downstream of the gear pump 60, the flow path can be switched from the main flow path 35 to the alternative flow path 36 to discharge the undecomposed residue.

[0061] The residue discharge section 30B shown in FIG. 4 further includes a chamber 37 disposed between the outlet 23f of the pyrolysis gasification apparatus 23 and the suction section 61 of the gear pump 60. The chamber 37 includes an inlet 37a directly or indirectly connected to the outlet 23f, an internal space S having a certain volume or greater and communicating with the inlet 37a, a gas outlet 37b formed above the internal space S, and a residue discharge port 37c formed below the internal space S. The volume of the internal space S in the chamber 37 is preferably in the range of, for example, 1 / 6 to 1 / 2 of the raw material supply rate per hour. If the volume is too large, the residue may cool and solidify after long storage in the chamber, making discharge using a positive displacement pump difficult. If the volume is too small, it is undesirable because it does not function as a volumetric buffer. The chamber may also have a temperature control function for heating, maintaining, or cooling the residue. For example, a pyrolysis gas outlet pipe L30 is connected to the gas outlet 37b. 1, or may be connected to a part of the gas treatment unit 100, such as the condensation unit 40, separately from the pyrolysis gas discharge pipe L1. In this case, the pyrolysis gas discharge pipe L30 functions as a part of the pyrolysis gas separation unit A that separates the pyrolysis gas generated by pyrolysis in the pyrolysis gasification apparatus 23. The residue discharge port 37c is connected to the suction unit 61 of a gear pump 60.

[0062] A more detailed explanation will be given of an example of how to determine the volume of the chamber 37. The volume of the chamber 37 is determined so that one of the following two conditions is satisfied. <First condition> The capacity must be equal to or greater than the internal volume of the pyrolysis gasification device 23. For example, if the pyrolysis gas outlet pipe L1, which is a vent pipe, becomes clogged due to some kind of trouble, the supply of raw material to the pyrolysis gasification apparatus 23 will be stopped. At this time, in order to safely stop operation, the resin accumulated inside the pyrolysis gasification apparatus 23 can be discharged into the chamber 37. <Second condition> The capacity is set to 30 minutes of the maximum supply amount [kg / h] of the pyrolysis gasification device 23. For example, if the maximum supply rate of the pyrolysis gasification apparatus 23 is 100 L / h, the capacity of the chamber 37 should be 50 L or more. As explained in the first condition, even if the pyrolysis gas outlet pipe L1, which is the vent pipe, becomes blocked due to some kind of trouble and all of the gas or residue in the pyrolysis gasification apparatus 23 is discharged into the chamber 37, time can be secured for an operator to move to the site and the trouble can be dealt with manually (switching from automatic operation to manual operation, safely shutting down the operation, etc.).

[0063] The configuration including the residue discharge unit 30B achieves the same effects and advantages as the pyrolysis apparatus 1 including the residue discharge unit 30. Furthermore, gas can be extracted from the gas outlet 37b in the chamber 37. The gas can be treated as a useful component in a chemical recycling system, similar to the pyrolysis gas recovered through the pyrolysis gas outlet pipe L1. Furthermore, since a certain amount of undecomposed residue can be stored in the chamber 37, the gear pump 60 can be operated with a certain margin. Specifically, even if the downstream side of the gear pump 60 is blocked for some reason, the chamber 37 provides a time allowance before the pyrolysis apparatus 1 needs to be shut down. Furthermore, since the chamber 37 functions as a volumetric buffer, the temperature of the undecomposed residue in the chamber 37 can be lowered, allowing for more general-purpose specifications to be applied to the discharge side of the gear pump 60 (i.e., special specifications can be avoided).

[0064] 5 includes the same configuration as residue discharge section 30B including chamber 37, and further includes another gear pump (positive displacement pump) 60A provided between outlet 23f of pyrolysis gasification apparatus 23 and chamber 37. The configuration including residue discharge section 30C provides the same functions and effects as pyrolysis apparatus 1 including residue discharge section 30 described above. Furthermore, since two gear pumps 60, 60A are provided (positive displacement pumps are provided in two stages), the gas sealing effect described above is further enhanced.

[0065] Although the embodiments of the present disclosure have been described above, the present invention is not limited to the above embodiments. For example, the positive displacement pump is not limited to the gear pump 60. The positive displacement pump in the residue discharge section may be a screw pump, vane pump, rotary pump, plunger pump, piston pump, or the like. In a pump with a reciprocating moving part, such as a plunger pump or piston pump, the "operation" of the pump includes both control of the moving part to a constant reciprocating rate and control of the moving part to a variable reciprocating rate. In other words, a reciprocating positive displacement pump may also be operated intermittently or with a variable reciprocating rate. This allows for suppressing fluctuations in the amount of undecomposed residue within the pyrolysis gasification apparatus 23, even when the apparatus is operated continuously.

[0066] In the control of the controller, a weight scale may be used instead of or in addition to the pressure gauge. The weight scale measures the weight of the fluid inside the pyrolysis gasifier 23. The controller receives the measurement value measured by the weight scale and controls the operation of the gear pump 60.

[0067] The controller may be omitted. In that case, for example, the gear pump 60 is operated (on or rotation speed controlled) and stopped (off) based on a predetermined operation schedule.

[0068] A flow path switching unit 33 may be further applied to the residue discharge unit 30B including the chamber 37. In this case, the flow path switching unit 33 is connected to the discharge unit 62 of the gear pump 60.

[0069] The screw 23a of the pyrolysis gasification apparatus 23 may extend into the inside of the connecting part 25. Furthermore, a part of the tip of the screw 23a may protrude into the chamber 37. By extending the screw 23a and making the tip protrude, the possibility of resin stagnation inside the connecting part 25 can be reduced.

[0070] The pyrolysis device 1 may also include a secondary-side gas separator connected to the discharge port 62 of the gear pump 60 to separate the gas component contained in the undecomposed residue discharged by the gear pump 60. Examples of secondary-side gas separators include a suction blower and a reduced-pressure gas suction device. The secondary-side gas separator can further reduce the amount of gas coexisting with the residue downstream of the residue discharge port. Even when connecting a granulation facility or the like downstream of the secondary-side gas separator (liquid side), the connection is easy. [Explanation of symbols]

[0071] 1...pyrolysis device, 20...pyrolysis section, 23...pyrolysis gasification device, 23f...outlet section, 27...thermometer, 28...pressure gauge, 30, 30A, 30B, 30C...residue discharge section, 33...flow path switching section, 37...chamber, 37b...gas outlet, 40...condensation section, 50...purification section, 60...gear pump (positive displacement pump), 61...suction section, 62...discharge section, 100...gas processing section, A...pyrolysis gas separation section, S...internal space.

Claims

1. a thermal decomposition section that receives and thermally decomposes raw material resin; a pyrolysis gas separation section that separates pyrolysis gas generated by pyrolysis in the pyrolysis section; a gas processing unit that processes the pyrolysis gas sent through the pyrolysis gas separation unit; a residue discharge section connected to an outlet of the thermal decomposition section and discharging undecomposed residue generated in the thermal decomposition section, The residue discharge section includes a positive displacement pump that sucks in and discharges the undecomposed residue from the outlet section.

2. The pyrolysis device according to claim 1 , wherein the residue discharge unit further includes a flow path switching unit connected to a discharge unit of the positive displacement pump and switching a flow path for the undecomposed residue discharged by the positive displacement pump.

3. 2. The pyrolysis apparatus according to claim 1, wherein the residue discharge section is provided between the outlet section of the pyrolysis section and the suction section of the positive displacement pump, and further includes a chamber having an internal space of a certain volume or more and having a gas outlet.

4. The pyrolysis apparatus according to claim 3 , wherein the residue discharge section further includes another positive displacement pump provided between the outlet of the pyrolysis section and the chamber.

5. a pressure gauge is provided at or near the outlet of the thermal decomposition section; The pyrolysis apparatus according to any one of claims 1 to 4, wherein the positive displacement pump is activated and stopped in response to a pressure value detected by the pressure gauge.

6. The pyrolysis apparatus according to any one of claims 1 to 4, wherein the positive displacement pump is operated intermittently or so as to vary the number of rotations or reciprocating motions of the movable part.

7. The pyrolysis apparatus according to any one of claims 1 to 4, wherein the positive displacement pump is a gear pump.

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