Manufacturing method of carbide

Abstract

To suppress carbon dioxide emissions when manufacturing carbide using waste including a thermoplastic resin.SOLUTION: A method for manufacturing carbide using waste including a thermoplastic resin comprises: the carbonization step of carbonizing a material to be processed including the waste by heating; and the temperature lowering step of lowering the temperature of the material to be processed after the carbonization step. The method for manufacturing carbide includes deciding a timing moving to the temperature lowering step from the carbonization step on the basis of the reduction of a speed of decreasing the weight of the material to be processed.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a waste recycling technology. [Background technology]

[0002] Incineration of waste emits a large amount of carbon dioxide, which causes a greenhouse effect. In response to this, Patent Documents 1 and 2 disclose waste treatment technologies that can suppress carbon dioxide emissions. These technologies fix carbon through carbonization treatment, making it possible to suppress the carbon contained in the waste from being emitted as carbon dioxide.

[0003] However, in the carbonization process of waste described in Patent Document 1, the processing temperature is high, at 400°C or higher, resulting in a large amount of carbon dioxide emissions due to fuel consumption.In contrast, in the carbonization process of waste described in Patent Document 2, concentrated sulfuric acid or fuming nitric acid is used as a catalyst to promote carbonization, making it possible to lower the processing temperature. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-272203 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-143396 Summary of the Invention [Problem to be solved by the invention]

[0005] Thermoplastic resins are known to be difficult to carbonize. During the carbonization process of waste containing thermoplastic resins, carbon derived from the thermoplastic resins is not fixed and is easily emitted as carbon dioxide. Therefore, a technology that can reduce carbon dioxide emissions during the carbonization process of waste containing thermoplastic resins is desired.

[0006] The present invention relates to a technique for reducing carbon dioxide emissions when producing a carbonized product using waste containing a thermoplastic resin. [Means for solving the problem]

[0007] A method for producing a carbonized material using waste containing a thermoplastic resin according to one embodiment of the present invention includes a carbonization step in which a treated material containing the waste is carbonized by heating, and a temperature reduction step in which the treated material is cooled after the carbonization step. In this method for producing a carbonized material, the timing of transition from the carbonization step to the temperature-lowering step is determined based on a decrease in the rate of weight loss of the workpiece. [Effects of the Invention]

[0008] According to the present invention, it is possible to reduce the amount of carbon dioxide emitted when producing a carbonized product using waste containing a thermoplastic resin. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram illustrating the configuration of a stirring device that can be used in one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram illustrating the configuration of the stirring device. [Figure 3] 3 is a flowchart showing a method for manufacturing the carbide according to the embodiment. [Figure 4] 10 is a graph showing an example of a change in weight of a workpiece over time. [Figure 5] 1 is a photograph of the carbides obtained in Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Outline of an embodiment of the present invention] In one embodiment of the present invention, when waste containing a thermoplastic resin is carbonized, the remaining portion of the thermoplastic resin that does not become a char is intentionally left in the thermoplastic resin state, thereby reducing carbon dioxide emissions. For example, the charred material containing the thermoplastic resin obtained in this embodiment can be effectively used as a recycled material, such as a fuel. Furthermore, by subjecting the charred material containing the thermoplastic resin obtained in this embodiment to a further carbonization treatment, the carbon constituting the thermoplastic resin can be fixed in the char, which can be used to produce a charred material with higher purity. The charred material obtained in this embodiment can be effectively used as a recycled material, such as a soil conditioner, water treatment agent, or fuel. Furthermore, the charred material containing the thermoplastic resin obtained in this embodiment can be used not only as a char but also as a carbon dioxide source by recovering the carbon constituting the thermoplastic resin as carbon dioxide.

[0011] Furthermore, from the viewpoint of storage and transportability, recycled materials are preferably in granular form. Generally, a heating and stirring process is used to granulate waste. However, waste containing thermoplastic resins tends to form clumps after the heating and stirring process, as the fragments bond together due to the thixotropy of the thermoplastic resin. Therefore, a separate crushing process is required after the heating and stirring process. In contrast, this embodiment is configured to obtain carbonized granules using waste containing thermoplastic resins without performing a separate crushing process after the stirring process. In other words, this embodiment can efficiently produce carbonized granules that are easy to handle as recycled material using waste containing thermoplastic resins. Therefore, the carbonized product manufacturing method according to this embodiment contributes to promoting the recycling of waste containing thermoplastic resins and ultimately contributes to the realization of a resource-circulating society.

[0012] In this embodiment, "granular" refers to the shape of each fragment of the crushed material. Furthermore, "granular body" refers to an aggregate of multiple fragments that are separated from each other. Furthermore, "granulation" refers to converting the material to be processed into granules. The smaller the fragments that make up the granules, the more preferable they are as recycled material. From this perspective, in this embodiment, the maximum diameter of each fragment that makes up the granules obtained by granulating the material to be processed is preferably 5 cm or less, more preferably 1 cm or less, and even more preferably 0.5 cm or less.

[0013] In this embodiment, the term "softening point" refers to the temperature at which the thermoplastic resin contained in the workpiece begins to rapidly soften. When the workpiece contains multiple thermoplastic resins, the softening point is determined based on the softening point of the thermoplastic resin with the lowest softening point contained in the workpiece. In other words, the softening point of the workpiece is determined as the softening point of the thermoplastic resin with the lowest softening point contained in the workpiece. When the thermoplastic resin contained in the workpiece can be identified, the softening point can be determined by measuring the Vicat softening temperature in advance. The Vicat softening temperature can be measured in accordance with JIS K 7206:2016 (ISO 306:2013). When the thermoplastic resin contained in the workpiece cannot be identified, the softening point of the thermoplastic resin contained in the workpiece can be determined by removing the resin from the workpiece and measuring its Vicat softening temperature.

[0014] [Agitator 100] First, we will explain an agitator 100 that can be used in the carbonized material manufacturing method according to this embodiment. FIG. 1 shows the agitator 100 from the front, and FIG. 2 shows the agitator 100 from the side. The agitator 100 has a treatment tank 101. The treatment tank 101 has a wall 101a and a storage section 101b. The storage section 101b can store the object to be carbonized by the agitator 100 and is configured as an internal space of the treatment tank 101 surrounded by the wall 101a. FIGS. 1 and 2 each show a vertical cross section of the wall 101a, breaking it vertically, to show the interior of the storage section 101b. The agitator 100 is configured to be able to measure the weight of the object to be treated in the storage section 101b of the treatment tank 101 at any time. Furthermore, in the treatment tank 101, a portion of the wall 101a is configured to be openable and closable, allowing external access to the storage section 101b for loading and unloading the object to be treated.

[0015] The agitator 100 further includes an agitator shaft 102. The agitator shaft 102 includes a shaft portion 102a and multiple blade portions 102b. The shaft portion 102a is configured as a round bar-shaped member that can rotate around a rotation axis C that extends horizontally to the side. Both ends of the shaft portion 102a are supported by the wall portion 101a on the sides of the storage portion 101b, and the portion between the both ends supported by the wall portion 101a is located within the storage portion 101b. The multiple blade portions 102b are provided at intervals along the longitudinal direction, with no substantial bias, over the entire portion of the shaft portion 102a located within the storage portion 101b. Furthermore, each blade portion 102b protrudes in various radial directions from the outer circumferential surface of the shaft portion 102a.

[0016] The agitator 100 further includes a heater 103. The heater 103 is attached to the outside of the wall 101a of the treatment tank 101. The heater 103 is configured to be able to increase the temperature inside the storage section 101b through the wall 101a when power is applied to the heater 103. That is, in the agitator 100, the heater 103 can heat the object to be treated stored in the storage section 101b. Note that the configuration of the heater 103, such as the heating method and installation position, can be determined in various ways depending on the configuration of the treatment tank 101 and the properties of the object to be treated.

[0017] In addition, the agitator 100 further includes a blower mechanism 104. The blower mechanism 104 includes an air supply section 104a and an exhaust section 104b. The air supply section 104a and the exhaust section 104b are respectively provided on the wall section 101a of the treatment tank 101 and laterally face each other across the storage section 101b. The blower mechanism 104 is configured to supply air into the storage section 101b from the air supply section 104a and exhaust air from the treatment tank 101 through the exhaust section 104b, thereby blowing air into the storage section 101b. Therefore, in the agitator 100, the blower mechanism 104 can accelerate a decrease in the temperature inside the storage section 101b, which means that the temperature of the heated workpiece in the storage section 101b can be quickly decreased. In addition, the gas used for blowing air by the blower mechanism 104 in the agitator 100 is not limited to air, and may be, for example, an inert gas such as nitrogen.

[0018] With the above configuration, the agitator 100 rotates the shaft 102a around the rotation axis C, thereby effectively agitating the workpieces in the storage section 101b through the interaction of gravity and the force applied by the multiple blades 102b. Therefore, the agitator 100 can perform two processes on the workpieces stored in the storage section 101b: a stirring / carbonization process in which the workpieces are heated by the heater 103 and carbonized while being stirred, and a temperature-reducing stirring process in which the heated workpieces are stirred while being cooled. During the temperature-reducing stirring process, the agitator 100 can control the temperature-reducing rate of the workpieces by blowing air using the air blowing mechanism 104. However, it is not essential for the agitator 100 to use the air blowing mechanism 104 during the temperature-reducing stirring process.

[0019] The configuration of the agitator 100 is not limited to the above and can be modified in various ways. For example, in the agitator 100, the rotation axis C of the shaft 102a does not necessarily have to extend horizontally, and may be tilted relative to the horizontal plane. However, to effectively obtain the agitation effect due to gravity in the agitator 100, it is necessary that at least the rotation axis C of the shaft 102a be tilted relative to the vertical direction, and it is preferable that the angle of the rotation axis C of the shaft 102a with respect to the horizontal plane is small. Specifically, in the agitator 100, it is preferable that the angle of the rotation axis C of the shaft 102a with respect to the horizontal plane is 30° or less.

[0020] [Basic structure of carbide manufacturing method] As shown in FIG. 3, the method for producing a carbonized material according to this embodiment includes a storage step S01 and a stirring step S02. The method for producing a carbonized material according to this embodiment uses the stirring device 100 described above. In the storage step S01, the material to be treated, including waste containing thermoplastic resin, is stored in the storage section 101b of the treatment tank 101. The material to be treated preferably contains an easily carbonizable component such as cellulose. In the stirring step S02, the material to be treated stored in the storage section 101b of the treatment tank 101 in the storage step S01 is stirred by rotating the stirring shaft 102.

[0021] The stirring step S02 includes a carbonization step S21. In the carbonization step S21, the workpiece contained in the container 101b is heated by the heater 103 to carbonize the workpiece. In the carbonization step S21, the temperature of the workpiece is maintained, for example, at 200°C or higher and 500°C or lower, thereby carbonizing the workpiece. By maintaining the temperature of the workpiece below the decomposition point or volatilization point of the thermoplastic resin, decomposition or volatilization of the thermoplastic resin is suppressed, allowing a larger amount of thermoplastic resin to remain in the workpiece. Furthermore, in the carbonization step S21, the stirring shaft 102 is rotated to stir the heated workpiece. By maintaining the temperature of the workpiece above the softening point of the thermoplastic resin to soften the thermoplastic resin, stirring of the workpiece proceeds smoothly. In the carbonization step S21, the carbonization of the material to be treated progresses as the water contained in the material evaporates and the solid components are crushed, and the material to be treated becomes a granular carbonized material consisting of mutually separated fragments.

[0022] Here, we will explain the case where the agitation step S02 ends with only the carbonization step S21, i.e., after the carbonization step S21, the heating of the workpiece by the heater 103 is stopped and the agitation of the workpiece by the agitation shaft 102 is also stopped. In this case, the thermoplastic resin contained in the workpiece, which has been turned into granules in the carbonization step S21, simultaneously hardens as the temperature drops and increases in viscosity due to its thixotropic nature. As a result, the workpiece after the carbonization step S21 tends to become agglomerated as the thermoplastic resin bonds between the carbide fragments that make up the granules during the temperature drop. Therefore, if the agitation step S02 ends with only the carbonization step S21, a separate crushing process must be performed after the agitation step S02 to obtain carbide granules.

[0023] In contrast, the stirring step S02 according to this embodiment further includes a temperature-reducing step S22, which is performed in the same storage section 101b of the treatment tank 101 following the carbonization step S21. In the temperature-reducing step S22, heating of the workpiece by the heater 103 is stopped after the carbonization step S21, while stirring of the workpiece by the stirring shaft 102 is continued. In the temperature-reducing step S22, stirring of the workpiece is continued at least until the temperature of the workpiece drops below the softening point of the thermoplastic resin contained in the workpiece. As a result, in the temperature-reducing step S22, hardening of the thermoplastic resin progresses as the temperature is reduced, but the viscosity of the thermoplastic resin is maintained low due to its thixotropy as stirring is continued. Therefore, in the temperature-reducing step S22, carbonized fragments constituting the carbonized granules are less likely to bond together via the thermoplastic resin. Furthermore, even if carbonized fragments are bonded together via the thermoplastic resin, they are re-crushed by stirring, preventing agglomeration. Therefore, in the temperature-reducing step S22, the thermoplastic resin hardens while wrapping around each of the carbide fragments, so that the object to be treated is maintained as carbide granules composed of fragments separated from each other. Note that, in the method for producing carbide according to this embodiment, it is preferable to reduce the temperature of the object to at least below 100°C in the temperature-reducing step S22 before recovering the carbide granules from the storage section 101b.

[0024] As described above, the carbonized material manufacturing method according to this embodiment can produce carbonized granules from materials containing waste containing thermoplastic resin without a separate crushing process. The carbonized granules obtained in this embodiment are densified by granulation, significantly reducing the volume required for storage. This allows the granules of material obtained in this embodiment to be easily stored and transported. Furthermore, in the temperature-reducing step S22, the time it takes for the temperature of the material to drop below the softening point of the thermoplastic resin by blowing air from the blower mechanism 104 can be shortened, thereby reducing the amount of carbon dioxide emitted from the carbon that constitutes the thermoplastic resin.

[0025] [Timing of transition from carbonization step S21 to temperature-reducing step S22] To fully carbonize the workpiece, it is necessary to maintain the workpiece in a heated state. Therefore, the carbonization step S21 requires a relatively long time. Meanwhile, during the carbonization step S21, carbon from the carbon-resistant thermoplastic resin contained in the heated workpiece slowly combines with oxygen to release carbon dioxide. Therefore, the longer the carbonization step S21 lasts, the greater the amount of carbon dioxide released. Therefore, from the perspective of reducing carbon dioxide emissions, it is preferable to complete the carbonization step S21 as quickly as possible. In other words, it is preferable to transition from the carbonization step S21 to the temperature-reducing step S22 immediately after the carbonization of the workpiece has fully progressed. Therefore, it is important to accurately determine whether the carbonization of the workpiece has fully progressed in the carbonization step S21. In response to this, the inventors of the present application have succeeded in accurately determining whether the carbonization of the workpiece has fully progressed by monitoring the rate at which the weight of the workpiece decreases.

[0026] In the carbonization step S21 according to this embodiment, the weight of the workpiece in the storage section 101b is measured sequentially to monitor the rate of weight loss of the workpiece. FIG. 4 is a graph showing an example of the change in the weight of the workpiece over time when the carbonization step S21 is performed for a long period of time, 30 hours or more. The horizontal axis represents the elapsed time in logarithmic terms, and the vertical axis represents the weight of the workpiece in relative terms. The graph in FIG. 4 also plots the weight of the workpiece at each time point, and the rate of weight loss of the workpiece can be determined by the slope of the curve connecting the plots. Referring to FIG. 4, it can be seen that the slope of the curve changes significantly between times t1 and t2. At time t1, the evaporation of water contained in the workpiece, which had been progressing up to time t1, is considered to have been substantially completed, and active carbonization of the easily carbonizable components contained in the workpiece has begun. At time t2, the carbonization of the easily carbonizable components contained in the workpiece, which had been progressing since time t1, is considered to have been substantially completed. After time t2, the weight of the workpiece becomes almost constant, and it is considered that the carbon that constitutes the thermoplastic resin is discharged as carbon dioxide, and the carbonization of the carbonization-resistant thermoplastic resin proceeds very slowly. In this embodiment, whether the carbonization of the workpiece has proceeded sufficiently is determined by whether time t2, at which the carbonization of the carbonizable components of the workpiece is substantially completed, has been reached.

[0027] That is, in this embodiment, the process proceeds from the carbonization step S21 to the temperature-reducing step S22 promptly after it is determined that time t2 has passed. As a result, in the carbonized material manufacturing method according to this embodiment, carbonization of at least the easily carbonizable components of the object to be treated can be minimized under conditions in which they are sufficiently carbonized. In this embodiment, various methods can be employed to determine whether time t2 has passed based on the rate of weight loss of the object to be treated. Specifically, for example, the weight of the object to be treated is measured every 30 minutes, and the difference between the weight measured 30 minutes prior is calculated. When the calculated weight difference is 1% or less of the total weight of the object to be treated accommodated in the accommodation section 101b in the accommodation step S01, it can be determined that time t2 has passed. As another specific example, the weight of the object to be treated is measured every 30 minutes, and the weight loss rate relative to the weight measured 30 minutes prior is calculated. When the calculated weight loss rate is 1 / 100 or less of the maximum weight loss rate calculated up to that point, it can be determined that time t2 has passed. By adopting this method, it is possible to accurately determine whether or not time t2 has passed.

[0028] [Details of the carbide manufacturing method] In the storage step S01, waste that can be stored as the material to be processed in the storage section 101b includes, for example, general waste containing thermoplastic resins generated by households, businesses, etc. Specific examples of waste containing thermoplastic resins include used packaging containers (food containers, bottles, etc.), used absorbent articles (disposable diapers, sanitary napkins, etc.), and marine debris. The carbonized material production method according to this embodiment is advantageous for waste containing many thermoplastic resins, and is particularly effective for waste containing, for example, 40% or more by weight of thermoplastic resins. The thermoplastic resin contained in the waste is not limited to a specific type, and examples include polyolefin, polyester, polyacrylic acid, and sodium polyacrylate. The material to be processed may also contain two or more types of thermoplastic resins derived from the waste. In this case, the softening point of the thermoplastic resin contained in the material to be processed is the softening point of the thermoplastic resin with the lowest softening point contained in the material to be processed.

[0029] In the storage step S01, it is preferable that the amount of workpieces stored in the storage section 101b be relatively large. Specifically, the amount of workpieces stored in the storage section 101b in the storage step S01 is preferably set so that the volume of the granular material in the storage section 101b at the end of the agitation step S02 exceeds the shaft portion 102a. The volume of the granular material in the storage section 101b is obtained, for example, as shown in FIGS. 1 and 2, as the vertical height L of the surface of the granular material smoothed along a horizontal plane in the storage section 101b. In this way, by determining the amount of workpieces stored in the storage section 101b in the storage step S01 based on the state at the end of the agitation step S02, when the volume of the workpieces is at its lowest due to the progress of crushing, the shaft portion 102a is maintained submerged in the workpieces being agitated throughout the entire agitation step S02. This allows the workpieces to be efficiently agitated in the agitation step S02. From the viewpoint of efficiently stirring the material to be processed, it is preferable that the volume of the granular material to be processed exceeds the entire shaft portion 102a in the storage portion 101b at the end of the stirring step S02, that is, the shaft portion 102a is completely buried in the granular material to be processed. However, in cases such as when the shaft portion 102a is tilted relative to the horizontal plane as described above, the effect of efficiently stirring the material to be processed can be obtained as long as the volume of the granular material to be processed exceeds at least a portion of the shaft portion 102a in the storage portion 101b at the end of the stirring step S02.

[0030] The materials to be processed contained in the storage section 101b in the storage step S01 may consist solely of waste containing thermoplastic resin, or may contain materials other than waste containing thermoplastic resin. In particular, if the amount of materials to be processed is insufficient with only waste containing thermoplastic resin, a bulking agent may be stored in the storage section 101b along with the waste. The bulking agent can be selected arbitrarily. For example, an object made of a heat-resistant, hard material such as ceramics that does not change during the mixing step S02 (e.g., ceramic balls such as alumina balls, zirconia balls, silicon nitride balls, and silicon carbide balls) can be used as the bulking agent. By leaving such a bulking agent in the storage section 101b after the mixing step S02, it can be repeatedly used as a bulking agent. Additionally, any object that does not contain thermoplastic resin (e.g., food waste, agricultural waste, etc.) can be used as the bulking agent. Furthermore, by using materials whose main component is cellulose (e.g., wood pellets, paper scraps, selected branches, etc.) that are carbonized together with the waste, or already carbonized materials (e.g., carbonized fuel pellets, activated carbon, etc.) as secondary materials, the carbonization of the material to be treated in the carbonization step S21 can be promoted.

[0031] Furthermore, the carbide granules obtained in the mixing step S02 in a previous process for producing carbide can be used as a secondary material for a subsequent process. In particular, when multiple processes for producing carbide are performed consecutively, the carbide granules obtained in the previous process can be used as a secondary material by leaving at least a portion of the carbide granules in the storage section 101b after the mixing step S02 in the previous process and introducing new waste in the storage step S01. This allows the carbide granules obtained in the previous process to be used as a secondary material. Even if the amount of waste newly introduced in the storage step S01 varies, the amount of material to be treated in the storage section 101b can be kept constant by recovering the carbide granules from the storage section 101b in an amount calculated backward from the amount of waste newly introduced. This allows for a stable carbide production process to be repeatedly performed.

[0032] Furthermore, in the carbonization step S21, it is preferable to fix as much of the carbon constituting the carbon-resistant thermoplastic resin as part of the charcoal. This reduces the amount of carbon dioxide emitted from the carbon constituting the thermoplastic resin. From this perspective, it is preferable to add at least one of phosphoric acid and a phosphate as a catalyst to the material to be treated in the storage section 101b. Phosphoric acid and a phosphate have the effect of promoting the desorption of hydrogen, water, and other elements from the thermoplastic resin. Therefore, by using phosphoric acid or a phosphate as a catalyst, the desorption of hydrogen, water, and other elements from the thermoplastic resin contained in the waste material progresses during the carbonization step S21, making it easier for the thermoplastic resin to be fixed integrally as elemental carbon on the surface of the charcoal. The phosphate added to the material to be treated as a catalyst can be, for example, at least one of ammonium phosphate, potassium phosphate, and sodium phosphate. Examples of ammonium phosphate include ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and triammonium phosphate. Examples of potassium phosphate include potassium dihydrogen phosphate, dipotassium hydrogen phosphate, and tripotassium phosphate. Examples of sodium phosphate include sodium dihydrogen phosphate, disodium hydrogen phosphate, and trisodium phosphate. Phosphoric acid and phosphates are condensed by heating to become polyphosphoric acid and polyphosphates, but polyphosphoric acid and polyphosphates soften in the carbonization step S21 and have the property of bonding fragments together during the temperature drop process, similar to thermoplastic resins. However, in the agitation step S02 according to this embodiment, the temperature drop step S22 is performed, so that the material to be treated remains as a granular body composed of fragments that are separated from each other.

[0033] In the carbide manufacturing method according to the present embodiment, granulating the carbide as described above is not essential. In other words, the resulting carbide does not have to be granular; for example, it may be a lump. In this case, the carbonization step S21 and the temperature-reducing step S22 may be performed without stirring. That is, the carbide manufacturing method according to the present embodiment may not include the stirring step S02, but may include independent carbonization steps S21 and S22 performed without stirring. Even in this case, in the present embodiment, by determining the timing of the transition from the carbonization step S21 to the temperature-reducing step S22 as described above, it is possible to obtain a high-quality carbide, albeit in a lump, while suppressing carbon dioxide emissions. When the stirring step S02 is not performed, the carbonization step S21 and the temperature-reducing step S22 may be performed in the accommodation section 101b of the treatment tank 101 of the stirring device 100 without driving the stirring shaft 102, or may be performed using another heating device capable of carbonizing the workpiece without using the stirring device 100.

[0034] [Examples and Comparative Examples] Examples and comparative examples of the carbonized material manufacturing method according to the present embodiment are described below. In each example and comparative example, a sample of the material to be treated was prepared, simulating the actual waste material. Table 1 shows the composition of the sample for each example and comparative example. Specifically, in the samples for each example and comparative example, unused disposable diapers containing thermoplastic resin were used as the component corresponding to the waste material containing thermoplastic resin. The unused disposable diapers were also soaked in tap water to simulate a used state. The tape-type disposable diapers used were Merries M size (manufactured by Kao Corporation), and the pants-type disposable diapers were Merries Pants L size (manufactured by Kao Corporation). The types (tape-type or pants-type) and weights of unused disposable diapers, as well as the amount of tap water absorbed, were varied in each example and comparative example. Furthermore, in each example and comparative example, a predetermined amount of alumina balls (product name HD-5, manufactured by Nikkato Corporation) or wood pellets (manufactured by Peteye Co., Ltd.) was used as a secondary material constituting the material to be treated, as appropriate. Furthermore, in the samples according to each of the examples and comparative examples, a predetermined amount of ammonium dihydrogen phosphate (manufactured by Wako Pure Chemical Industries, Ltd.) or potassium dihydrogen phosphate (manufactured by Wako Pure Chemical Industries, Ltd.) was used as a catalyst constituting the material to be treated, as appropriate.

[0035] [Table 1]

[0036] Carbonized materials were produced for each sample according to each example and comparative example. Table 2 shows the timing of the transition from the carbonization step S21 to the temperature-lowering step S22 in the stirring step S02 for each example and comparative example. The timing in examples 1 to 5 was immediately after time t2, as in the above-described embodiment. The timing in comparative examples 1 and 3 was before time t2, i.e., earlier than the above-described embodiment. The timing in comparative example 2 was after a long time had elapsed since time t2, i.e., significantly later than the above-described embodiment.

[0037] FIG. 5 shows photographs of the charcoal obtained in Examples 1 to 5 and Comparative Examples 1 to 3. A scale is provided in FIG. 5 to indicate the size of the charcoal components. The vials containing the charcoal obtained in Examples 1 to 5 and Comparative Examples 1 to 3 each had a diameter of 2 cm. Table 2 shows the evaluation results of the charcoal obtained in Examples 1 to 5 and Comparative Examples 1 to 3, including their state, color, O / C element ratio, and carbon emission ratio. The O / C element ratio is the ratio of the weight of oxygen atoms to the weight of carbon atoms obtained by elemental analysis of the charcoal. It can be seen that the lower the O / C element ratio, the more carbonized the charcoal. The carbon emission ratio is the ratio of the weight of carbon emitted as carbon dioxide to the weight of carbon atoms contained in the charcoal. It can be seen that the lower the carbon emission ratio, the more thermoplastic resin remains in the charcoal.

[0038] Referring to Table 2, black or brown charcoal particles were obtained in all of Examples 1 to 5. On the other hand, black or brown charcoal particles were obtained in Comparative Examples 2 and 3, while gray charcoal lumps were obtained in Comparative Example 1. Furthermore, when Examples 1, 3 to 5 and Comparative Examples 1 and 2, which did not use wood pellets as the secondary material, were compared, the O / C element ratios of Examples 1, 3 to 5 and Comparative Example 2 were lower than that of Comparative Example 1. Furthermore, when Example 2 and Comparative Example 3, which used wood pellets as the secondary material, were compared, the O / C element ratio of Example 2 was lower than that of Comparative Example 3. These results indicate that in Examples 1 to 5 and Comparative Example 2, the transition from the carbonization step S21 to the temperature-lowering step S22 occurred after time t2, so that sufficient carbonization progressed. Furthermore, the C emission ratio was lower in Examples 1 to 5 and Comparative Examples 1 and 3 than in Comparative Example 2. From these results, it can be seen that in Examples 1 to 5 and Comparative Examples 1 and 3, the transition from the carbonization step S21 to the temperature-reducing step S22 was sufficiently fast, thereby reducing the amount of carbon dioxide emitted and leaving a large amount of thermoplastic resin in the carbonized material. Thus, it was found that by transitioning from the carbonization step S21 to the temperature-reducing step S22 immediately after time t2, carbonization progresses sufficiently and carbonized material granules with a large amount of remaining thermoplastic resin can be obtained.

[0039] [Table 2] [Explanation of symbols]

[0040] 100...Stirring device 101... Treatment tank 101b...container 102...Agitator shaft 102a...Shaft part 102b...wing part 103...Heater 104...Blower mechanism C...Rotation axis

Claims

1. A method for producing a carbonized material using waste containing a thermoplastic resin, comprising: a carbonization step of carbonizing the object to be treated including the waste by heating, and a temperature-reducing step of reducing the temperature of the object to be treated after the carbonization step, After it is determined that a predetermined time has elapsed, the carbonization step is promptly transitioned to the temperature-lowering step, The predetermined time has passed, The weight of the workpiece is measured every 30 minutes, and the difference between the weight measured 30 minutes before and the weight measured 30 minutes before is calculated, and the calculated weight difference is 1% or less of the total weight of the workpiece before the carbonization step; or The weight of the object to be treated is measured every 30 minutes, and the weight loss rate relative to the previous weight measured 30 minutes prior is calculated, and the calculated weight loss rate is 1 / 100 or less of the maximum weight loss rate calculated up to that point. judge by Method for producing carbides.

2. The method further includes a step of storing the waste material in a treatment tank, and a step of stirring the waste material stored in the treatment tank, the carbonization step and the temperature reduction step are included in the stirring step, In the carbonization step, the temperature of the object to be treated is maintained at a softening point of the thermoplastic resin or higher, In the temperature lowering step, the temperature of the object to be treated is lowered to below the softening point of the thermoplastic resin. A method for producing the carbide according to claim 1.

3. In the temperature lowering step, air is blown into the treatment tank. The method for producing the carbide according to claim 2.

4. In the carbonization step, the temperature of the object to be treated is maintained at 200° C. or higher and 500° C. or lower. The method for producing the carbide according to any one of claims 1 to 3.

5. In the temperature lowering step, the temperature of the object to be treated is lowered to less than 100°C. The method for producing the carbide according to any one of claims 1 to 4.

6. The waste material includes cellulose. The method for producing the carbide according to any one of claims 1 to 5.

7. The waste includes absorbent articles. The method for producing the carbide according to any one of claims 1 to 6.

8. The waste contains 40% by weight or more of a thermoplastic resin. The method for producing the carbide according to any one of claims 1 to 7.

9. The object to be treated includes a secondary material for increasing the volume of the object to be treated. The method for producing the carbide according to any one of claims 1 to 8.

10. The material to be treated contains at least one of phosphoric acid and a phosphate. A method for producing the carbide according to any one of claims 1 to 9.

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