Method for treating waste plastics

Abstract

Coke manufacturing coal, or coke manufacturing mixed coal containing coal and mixed waste plastics is charged into a carbonization chamber (2) of a coke oven (1) to perform dry distillation to produce coke (13), after the dry distillation is completed, using a part or all of a plurality of charging ports (4 (4a-4d)) provided in the carbonization chamber of the coke oven, waste plastics (14 (14b-14d)) are sequentially charged into an upper space portion (5) in the carbonization chamber on the upper side from the charging port on the side close to the riser (3) to the charging port on the side away from the riser (3), thereby providing a waste plastic treatment method capable of inhibiting leakage or emission of thermal decomposition gas of waste plastics from the charging port.

Description

Technical Field

[0001] This invention relates to a method for treating waste plastics, and particularly to a method for treating waste plastics using a coking oven. Background Technology

[0002] Waste plastics, which are discharged in large quantities as industrial waste and general plastic waste, have traditionally been mostly disposed of through landfill or partially through incineration. Even when landfilled, waste plastics are not decomposed by microorganisms and bacteria in the soil. Incineration generates a large amount of heat, negatively impacting incinerators. Furthermore, the treatment of chlorine in the exhaust gases during incineration becomes a problem, especially given the presence of chlorine in the waste plastics. Anticipating future landfill shortages and increasing awareness of environmental issues, there is a desire to promote the recycling of waste plastics. Recycling methods, in addition to reusing the plastics themselves, include utilizing the heat from combustion and using the gases and oils obtained from the thermal decomposition during heating as fuels and chemical feedstocks.

[0003] For example, Patent Document 1 discloses a method for reusing waste plastics by mixing plastic granules formed at 100-160°C with coal and then dry-distilling the mixture in a coking oven (hereinafter referred to as the coal mixing and charging method). On the other hand, Patent Document 2 describes that if a large amount of plastic is mixed in the coal mixing and charging method, the strength of the resulting coke will decrease. In order to keep the decrease in coke strength to around a few percent, the mass ratio of plastic to coal needs to be less than 1%. Depending on the target coke strength grade, the amount that can be reused is limited.

[0004] In addition, as a method for treating waste plastics to suppress the reduction of coke strength, a method is known (hereinafter referred to as the upper space loading method): instead of mixing waste plastics into coal, waste plastics are loaded into the space above the coal or a mixture of coal and waste plastics (hereinafter, the mixture of coal and waste plastics is also referred to as mixed coal) loaded into the carbonization chamber (the upper (furnace top side) space in a carbonization furnace that is not filled with coal or mixed coal). According to Patent Document 3, in this upper space loading method, most of the waste plastics can be thermally decomposed in a high-temperature coking furnace, resulting in the production of high-calorie thermal decomposition gases containing hydrogen, methane, ethane, propane, etc. These thermal decomposition gases are contained in the coke oven gases generated in the coking furnace carbonization chamber through the thermal decomposition of coal and are thus recovered and reused as raw materials for various products. The following technology is disclosed regarding the upper space loading method.

[0005] Patent Document 4 discloses a method for treating waste plastics, characterized by preparing coke-making coal or coke-making coal containing 0.1 to 1.0 wt% waste plastics, loading it into a coking oven, and then further loading waste plastics into the overhead space above the coal. During dry distillation, the waste plastics are thermally decomposed and recovered as tar, light oil, gas, and coke (residue). This waste plastic treatment method discloses a method for loading waste plastics into the overhead space above the coal after loading, and a method for supplying waste plastics from the coal loading point until the end of dry distillation via a supply device leading to the coking oven's overhead space. Through these methods, in the example of this document where waste plastics are loaded into the overhead space, the same amount of waste plastics can be treated as when approximately 5 wt% waste plastics are added. The method described in Patent Document 4 involves opening the raw material loading cover and loading waste plastic during the dry distillation of coal in the carbonization chamber of a coking oven. Therefore, it is necessary to ensure that the amount of gas generated in the carbonization chamber does not exceed the gas recovery capacity of the riser pipe.

[0006] Patent Document 5 discloses a method for manufacturing coke by loading waste plastics into the upper space of the carbonization chamber after dry distillation of coal in a coke oven. In this document, as a means of loading polymeric waste into the carbonization chamber under atmospheric isolation, a method is described using a hopper on a loading vehicle and a cylindrical chute at the coal feed port of the coke oven for loading (see Figure 5 of this document). The loading time is preferably during the coke maturation period (approximately 2 hours), known as the normal settling time, from the end of dry distillation to the expulsion of coke. This is because during this time, the amount of gas generated in a typical coke oven is relatively small, and the heat dissipation from the coke oven is relatively large, which can be utilized as heat of gas decomposition.

[0007] Patent Document 6 discloses a method for treating waste plastics in the carbonization chamber of a coke oven. The method, applicable to coke ovens equipped with leveling coal levelers, involves supplying waste plastics or a mixture of waste plastics and recycled coal to the leveling coal leveler at the end of coal loading into the carbonization chamber or after coal loading, thereby treating the waste plastics. In the method described in Patent Document 4, a new dedicated waste plastic supply device needs to be installed at each loading inlet. In the method described in Patent Document 5, the coal loading car needs to be modified to allow waste plastics to be fed in a way that isolates it from the atmosphere. In contrast, the method described in Patent Document 6 eliminates these problems.

[0008] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2001-49261 Patent Document 2: Japanese Patent Application Publication No. 2019-135278 Patent Document 3: Japanese Patent Application Publication No. 2002-47494 Patent Document 4: Japanese Patent Application Publication No. 8-157834 Patent Document 5: Japanese Patent Application Publication No. 4-41588 Patent Document 6: Japanese Patent Application Publication No. 2002-371285 Summary of the Invention

[0009] The problem that the invention aims to solve As mentioned above, the top-space loading method can increase the amount of waste plastics processed compared to the coal-mixed loading method. Therefore, given the current desire to promote the recycling of waste plastics, the top-space loading method is more effective. Furthermore, in the top-space loading method, the form of the waste plastics to be loaded is not limited to molded plastic granules; waste plastics kept in a crushed state can also be loaded for thermal decomposition.

[0010] In the upper space loading method, methods have been proposed for loading waste plastics before (or during) the dry distillation of already loaded coal or mixed coal (Patent Documents 4 and 6, hereinafter also referred to as the upper space pre-loading method), and for loading waste plastics after the dry distillation of coal or mixed coal (hereinafter also referred to as coal, etc.) is completed (Patent Document 5, hereinafter also referred to as the upper space post-loading method). In the upper space post-loading method, the upper space (furnace top side space) of the carbonization chamber, which expands due to the sintering (burn-off) of the coal, etc. after dry distillation, can be utilized, thus enabling the processing of more waste plastics.

[0011] Furthermore, in the pre-loading method in the upper space, thermal decomposition gases from coal or mixed coal (such as coal) are generated simultaneously with those from waste plastics during the dry distillation process. In contrast, in the post-loading method in the upper space, thermal decomposition gases from coal are generated during the dry distillation process, and those from waste plastics are generated after the dry distillation process, when the amount of thermal decomposition gases from coal is reduced. Therefore, the generation of thermal decomposition gases can be dispersed, increasing the amount of waste plastics that can be processed.

[0012] In the upper space post-loading method, waste plastics can be loaded through multiple loading inlets located on the furnace top using a coal charging car. Currently, since the coal charging car has a mechanism (such as the auxiliary hopper described later) to load (feed) waste plastics through the loading inlets in a manner that prevents coal from scattering, waste plastics can be loaded in a state of near-isolation from the atmosphere. However, in the upper space pre-loading and upper space post-loading methods, it is difficult to supply waste plastics using a leveling coal feeder. This is because most waste plastics soften and melt at relatively low temperatures (generally less than 200°C), and therefore, the waste plastics may adhere to the leveling coal feeder. This adhesion may pull the waste plastics out of the kiln, or cause the leveling coal feeder to malfunction.

[0013] Here, when waste plastics are charged from multiple inlets at the top of the furnace, multiple piles of waste plastics (hereinafter also referred to as waste plastic piles) are formed on top of the carbonized coal and other materials after dry distillation in the carbonization chamber. When waste plastics are charged simultaneously from all inlets, the amount of pyrolysis gas from the waste plastics increases suddenly, exceeding the gas recovery capacity of the riser pipe. This causes the gas pressure in the carbonization chamber to rise, and pyrolysis gas to leak from the inlets, gaps in the furnace cover, etc. (hereinafter referred to as inlets, etc.), potentially leading to fires and damage to the metal components of the coking furnace and the coal charging cars. Furthermore, if pyrolysis gas leaks outside the coking furnace, the amount of pyrolysis gas recovered by the riser pipe decreases. Although reducing the amount of waste plastics charged itself is considered to prevent the gas pressure from rising and to prevent the leakage of pyrolysis gas, this results in a decrease in the amount of waste plastics processed. Additionally, if time is spent charging waste plastics, the operating rate of the coking furnace will decrease.

[0014] The purpose of this invention is to provide a method for processing waste plastics, which ensures operational safety when waste plastics are loaded into the upper space of the carbonization chamber from the loading inlet at the top of the carbonization chamber after the dry distillation of coal or mixed coal.

[0015] Methods for solving problems (1) A method for treating waste plastics, characterized in that, Coke is produced by dry distillation of coal used in coke production, or a mixture of coal and waste plastics used in coke production, in the carbonization chamber of a coking oven. After the dry distillation is completed, waste plastic is loaded into the upper space of the carbonization chamber above the coke using some or all of the multiple loading inlets provided in the carbonization chamber of the coke, from the loading inlet on the side closer to the riser pipe to the loading inlet on the side farther away from the riser pipe.

[0016] (2) The waste plastic treatment method as described in (1), characterized in that, In all the loading ports into which the waste plastic is loaded, two or more loading ports that are sequentially connected and are less than the total number of loading ports are grouped together. For each loading port of the group, the waste plastic is loaded simultaneously instead of loading the waste plastic in the specified sequence.

[0017] (3) The waste plastic treatment method according to (2) is characterized in that, Multiple groups are set up to load the waste plastic.

[0018] According to the present invention, by determining the loading sequence of waste plastics from the loading inlet, the safety of the operation can be ensured. Attached Figure Description

[0019] Figure 1 This is a cross-sectional view showing an example of the state in which the coal loaded into the carbonization chamber has completed its dry distillation.

[0020] Figure 2A It represents the total amount of gas produced (m³) 3 The graph showing the relationship between / h and the loading time interval is for a loading time interval of β seconds.

[0021] Figure 2B It represents the total amount of gas produced (m³) 3 The graph showing the relationship between / h) and the loading time interval is for a loading time interval of γ seconds.

[0022] Figure 3 This is an explanatory diagram illustrating a method of loading waste plastic sequentially from the side furthest from the riser pipe to the side closest to the riser pipe using multiple loading inlets.

[0023] Figure 4 This is an explanatory diagram illustrating a method of loading waste plastic sequentially from the side closest to the riser pipe to the side furthest from the riser pipe using multiple loading inlets.

[0024] Figure 5 This is a graph showing the temperature measurement results of the space temperature inside the auxiliary hopper in Comparative Example 1 of Example 1.

[0025] Figure 6 This is a graph showing the temperature measurement results of the space temperature inside the auxiliary hopper in Example 1 of the invention.

[0026] Figure 7 This is a graph showing the temperature measurement results of the space temperature inside the auxiliary hopper in Example 3 of the invention.

[0027] Figure 8 This is a graph showing the temperature measurement results of the space temperature inside the auxiliary hopper in Comparative Example 3 of Example 3. Detailed Implementation

[0028] This invention relates to a method for processing waste plastics. The method involves loading coal for coke production, or a mixture of coal and waste plastics (coal mixed with waste plastics), into the carbonization chamber of a coking oven for dry distillation to produce coke. After dry distillation, waste plastics are sequentially fed into the upper space of the carbonization chamber above the coke using some or all of the multiple loading inlets located in the carbonization chamber of the coking oven, from the loading inlet closest to the riser pipe to the loading inlet furthest from the riser pipe. The invention will now be described with reference to the accompanying drawings.

[0029] Figure 1 This is a cross-sectional view showing an example of the completed dry distillation state of coke-making coal (hereinafter also referred to as charged coal) that has been loaded into the carbonization chamber. Additionally, in Figure 1 The example shown is a carbonization chamber 2 with four loading inlets 4, but the number of loading inlets 4 is not limited to this example; there can be multiple inlets. For example, there could be five or six loading inlets 4. Alternatively, instead of loading coal 11, a mixed coal for coke manufacturing (hereinafter also referred to as mixed coal 12) containing coal and mixed waste plastics can be loaded for dry distillation. The process is the same as when loading coal 11, so for convenience, only the loading of coal 11 will be described in the following description.

[0030] In the carbonization chamber 2 of coke oven 1, from the length of the furnace at the top ( Figure 1 Multiple loading inlets 4 are set on the horizontal side, and coal 11 is loaded into the coal loading car 31 (in the horizontal direction). Figure 1 (Diagram with double-dotted lines). As the dry distillation proceeds, the coal 11 is thermally decomposed to produce coke oven gas (COG). The generated coke oven gas passes through the upper space 5 (furnace top side space) of the carbonization chamber, and is then transported via the coke pusher side (PS) side (…). Figure 1 The riser pipe 3 on the top of the furnace (on the left side) is recycled. Figure 1 In the diagram, the double-dotted line represents the upper surface of the coal 11 before dry distillation, and the solid line represents the upper surface of the coke 13 (the coal 11 after dry distillation). After dry distillation, the volume of the coal 11 decreases due to sintering, and the upper space 5 becomes larger. In addition, the upper space 5 is the space in the carbonization chamber that is above the upper end (upper surface) of the coal.

[0031] In this invention, waste plastic 14 is loaded onto the upper surface of coke 13 (coal 11 after dry distillation) through the loading inlet 4, and thermal decomposition occurs in the upper space 5 of the carbonization chamber 2. The waste plastic 14 is loaded under conditions where the furnace temperature rises due to the dry distillation of the coal 11. Thermal decomposition of the waste plastic 14 occurs during the time from the completion of the dry distillation of the coal 11 (fire extinguishing) to its ejection by the ejector (placement time). The thermal decomposition gas generated by the thermal decomposition of the waste plastic 14 flows towards the riser pipe 3 and is recovered by the riser pipe 3.

[0032] This invention utilizes some or all of the multiple loading inlets 4 located in the carbonization chamber of a coking oven, sequentially loading waste plastics 14 from the loading inlet closest to the riser pipe 3 towards the loading inlet furthest from the riser pipe 3. Loading experiments conducted in a coking oven have shown that by loading sequentially from the side closest to the riser pipe to the side furthest from the riser pipe, it is possible to suppress fires or accidents caused by leakage or ejection of thermal decomposition gases from the loading inlets. The rationale for this assumption will be explained below with reference to the accompanying drawings.

[0033] The following Figure 3 and Figure 4 This diagram illustrates a method for loading waste plastics using multiple loading inlets located on the top of the furnace. Furthermore, in Figure 3 and Figure 4 In this process, the four loading inlets 4 are sequentially designated as 4a, 4b, 4c, and 4d, starting from the side furthest from the riser pipe 3 (the coke side (CS) side). Furthermore, the waste plastics formed into pile shapes when loaded from loading inlets 4a, 4b, 4c, and 4d are respectively designated as waste plastics 14a, 14b, 14c, and 14d. Additionally, the thermal decomposition gases generated from waste plastics 14a, 14b, 14c, and 14d (waste plastic piles 14a, 14b, 14c, and 14d) are respectively designated as thermal decomposition gases 24a, 24b, 24c, and 24d.

[0034] Here, the amount of waste plastic charged from each loading inlet and the total amount charged can be set to meet the following conditions, for example. Specifically, the conditions are as follows: when waste plastic is charged into each loading inlet, the amount of waste plastic already charged is such that it does not rise to the top of the kiln (the allowable waste plastic charging amount α or less, as described later); in addition, the total amount of gas generated when waste plastic is charged is within the allowable range of the high-pressure ammonia water suction capacity (hereinafter referred to as the riser gas suction capacity) of the riser pipe 3 in the kiln. These two conditions will be explained below.

[0035] The upper limit α (kg) of the allowable loading amount of waste plastic in each loading port 4 (allowable waste plastic loading amount) can be calculated, for example, based on the following formula (1). Formula (1) is a formula that expresses the relationship between the loading amount x (kg) of waste plastic when it is loaded into the high-temperature space (hot state) of the carbonization chamber and the loading height of the waste plastic (hot plastic loading height) y′ (m). In formula (1), y (m) represents the loading height of waste plastic at room temperature (room temperature plastic loading height), and a (-) represents the sinking rate of the waste plastic in the vertical direction immediately after loading into the high-temperature space. In addition, θ (°) represents the angle of repose of the waste plastic, and ρ (kg / m 3) represents the bulk density of the waste plastic, d (m) represents the distance in the furnace width direction of the internal space of the carbonization chamber, and x (kg) represents the amount of waste plastic loaded (waste plastic loading amount). The cross-section of the waste plastic 14 pile loaded into the upper space 5 is a triangle with height = y and base = 2y / tanθ, and is a plate-shaped shape with width d. Based on the formula for calculating the volume of this plate-shaped shape, the following formula (1) is derived.

[0036] y´=a×y=a×((x×tanθ) / (ρ×d)) 1 / 2 …(1) In the above formula (1), the height h (m) of the upper space 5 after sintering of coal 11 is substituted into the thermoplastic loading height y′ to calculate the waste plastic loading amount x. h (kg), the amount of waste plastic loaded is x h The maximum allowable amount of waste plastic to be loaded is assumed to be α (kg). By loading a quantity of waste plastic close to the allowable amount of waste plastic to be loaded into each loading inlet 4 in a manner not exceeding the allowable amount of waste plastic α, it is possible to prevent waste plastic from overflowing from the loading inlet and to ensure the amount of waste plastic processed.

[0037] In setting the amount of waste plastic loaded into each inlet 4, the gas suction capacity of the riser pipe is also considered, that is, the amount of gas that the riser pipe can attract, i.e., the allowable amount of gas generated δ (m). 3 / h). Specifically, by ensuring that the total amount of gas generated when waste plastics are loaded into the high-heat space after the dry distillation of coal (coal or mixed coal) from the loading inlet 4 does not exceed the allowable gas generation amount δ, leakage of waste plastic thermal decomposition gas can be prevented, ensuring operational safety and also ensuring the recovery of thermal decomposition gas. Furthermore, the allowable gas generation amount δ (m³) 3 The force ( / h) can be increased or decreased by adjusting the attractive force of the blower.

[0038] Here, referring to the attached diagram, the total amount (m³) of the generated gas (thermal decomposition gas) is... 3 Explain the time variation of / h). Figure 2A , Figure 2B This indicates the total amount of gas produced (m³) when, for the sake of simplicity, there are two loading inlets, meaning waste plastic is loaded once from each inlet (a total of two times). 3 A graph showing the relationship between (h) and the loading time interval (seconds) for loading waste plastic from the loading inlet. Regarding the loading time intervals for the first and second loading operations... Figure 2A The graph represents the case for β seconds. Figure 2B The graph represents the case where the loading time interval is γ seconds. Figure 2A , Figure 2B The amount of gas generated from coal after dry distillation is represented by a dashed line. The amount of gas generated when the first batch of waste plastic is added is represented by a single-dotted line. Even after the second batch of waste plastic is added, the amount of gas generated from the first batch is continuously recorded using a single-dotted line. The total amount of gas generated when the second batch of waste plastic is added, and the combined amount generated from the first and second batches, is represented by a double-dotted line. To understand the total amount of gas generated over time, a cumulative line graph is used. Equal amounts of α kg of waste plastic are added in both batches. Since the amount of waste plastic added in the first and second batches is the same, it is assumed that the amount of gas generated over time in the first and second batches is approximately the same, and the two graphs (single-dotted line and the difference between the double-dotted line and the single-dotted line) are set to the same shape. The allowable amount of gas generated δ (m³) is given above. 3 The figure ( / h) is represented by a thick solid line. It shows the time-varying changes in gas production after the first and second loading of waste plastics. Immediately after loading, gas production rapidly increases to its maximum value, then decreases over time. (and...) Figure 2A Compared to the loading time interval β, Figure 2B The loading time interval γ becomes longer. For example... Figure 2A As shown, when the loading time interval is set to β seconds, after time β from the first loading, the amount of gas generated by the first loading is still close to its maximum. Therefore, the total amount of gas generated during the time interval t1~t2 (minutes) exceeds the allowable amount of gas generated δ, which may cause leakage of the generated gas (thermal decomposition gas). On the other hand, as... Figure 2B As shown, when the loading time interval is set to γ ​​seconds, after time γ from the first loading, the gas production rate from the first loading is decreasing, and the total gas production will not exceed the allowable gas production rate δ. Figure 2B As shown, the loading time interval is set so that the total amount of gas generated does not exceed the allowable amount of gas generated, δ.

[0039] Furthermore, as mentioned above, in Figure 2A , Figure 2BThe text describes the case where the same amount of waste plastic is sequentially loaded from two loading inlets at intervals. However, when the carbonization chamber has four loading inlets, loading is performed four times (or more than twice in the case of grouping) using each inlet. As long as the loading interval is set such that the total amount of gas generated does not exceed the allowable gas generation rate δ from the initial loading of waste plastic until the time exceeding the peak value of the gas generation rate caused by the final loading of waste plastic. Here, the loading intervals can be the same or different. For example, the time interval between the first and second loading can be the same or different from the time interval between the second and third loading. Furthermore, regarding the amount of waste plastic loaded from each inlet, as long as it is set such that the total amount of gas generated does not exceed the allowable gas generation rate δ from the initial loading of waste plastic until the time exceeding the peak value of the gas generation rate caused by the final loading of waste plastic, it can be the same or different.

[0040] In addition, the amount of waste plastics charged from each loading inlet and the total amount charged are preferably the amount of waste plastics that have been fully decomposed within the time until the coke is discharged from the furnace. Furthermore, the allowable range of the discharge load at the time of discharge and the amount of chlorine contained in the decomposition gas of the waste plastics are also preferably taken into consideration.

[0041] Even when considering the aforementioned maximum allowable amount of waste plastic 14 (α) and the allowable amount of gas generated (δ), and the waste plastic 14 is sequentially loaded into multiple loading inlets 4, leakage of pyrolysis gases from the loading inlets 4 still exists depending on the loading order. The inventors of this application conducted a loading experiment in a coke oven and found that by loading sequentially from the side closest to the riser pipe to the side furthest from the riser pipe, the occurrence of fires or accidents caused by leakage or ejection of pyrolysis gases from the loading inlets can be suppressed. The reasons for this assumption will be explained below with reference to the accompanying drawings.

[0042] Figure 3 This diagram illustrates the sequential loading of waste plastic 14 from the side away from the riser pipe 3 (opposite to the riser pipe side) to the side closer to the riser pipe 3 (riser pipe side) among the four loading inlets 4 (4a→4b→4c→4d). It also shows the state after the loading of waste plastic 14a from loading inlet 4a and waste plastic 14b from loading inlet 4b has ended, and waste plastic 14c is being loaded from loading inlet 4c.

[0043] In the thermal decomposition reaction of waste plastic 14, the amount of thermal decomposition gas produced is highest immediately after being placed at a high temperature, and then decreases to approximately a constant amount (refer to...). Figure 2A , Figure 2B (The single-dotted line). Waste plastics 14a and 14b undergo thermal decomposition over time, resulting in a decrease in volume. Figure 3 In the diagram, regarding waste plastics 14a and 14b, the double-dotted lines represent their initial loading time, while the solid lines represent the time elapsed after loading (when waste plastic 14c is loaded). The solid line for waste plastic 14c represents its initial loading time. As shown in the diagram for waste plastics 14a and 14b, the volume of the waste plastic decreases as time passes after loading. On the other hand, since thermal decomposition is not complete after the time elapsed after loading, therefore... Figure 3 As indicated by the middle arrow, thermal decomposition gases 24a and 24b are continuously generated from waste plastics 14a and 14b.

[0044] When waste plastic 14c is loaded into the inlet 4c, the waste plastic 14c narrows the flow path (space) of pyrolysis gases 24a and 24b towards the riser pipe. Furthermore, the pyrolysis gases 24c generated from the waste plastic 14c all at once combine, resulting in an excess of gas near the inlet 4c. As a result, the gas pressure increases, and for example, as shown by the dashed arrow, pyrolysis gases 24a and 24b leak or spray out from the inlet 4c during the loading of the waste plastic 14c. Additionally, although not shown in the diagram, depending on the situation (the degree of narrowing of the flow path and the cumulative amount of gas generated), the following situations may also be considered: not only pyrolysis gases 24a and 24b, but also pyrolysis gas 24c leaks from the inlet 4c; or not only from the inlet 4c, but also pyrolysis gases 24a and 24b, etc., leak from the inlets 4b and 4a.

[0045] Figure 4 This diagram illustrates the sequential loading of waste plastic 14 from the side closest to the riser pipe 3 (riser pipe side) to the side furthest from the riser pipe 3 (opposite to the riser pipe side) (4d→4c→4b→4a) of the four loading inlets 4. It also shows the state at the moment when the loading of waste plastic 14d from loading inlet 4d and waste plastic 14c from loading inlet 4c has ended, and waste plastic 14b is being loaded from loading inlet 4b.

[0046] Waste plastics 14d and 14c undergo thermal decomposition over time, such as... Figure 4 As shown by the double-dotted line (when waste plastics 14d and 14c are loaded) and the solid line (when waste plastic 14b is loaded), the volume decreases, but because thermal decomposition is incomplete, thermal decomposition gases 24d and 24c continue to be generated from waste plastics 14d and 14c, as indicated by the arrows. When waste plastic 14b is loaded through inlet 4b, since it is before waste plastic 14a is loaded through inlet 4a, no thermal decomposition gases are generated on the side opposite to the riser pipe side compared to waste plastic 14b. Figure 3 Unlike waste plastic 14c, the loading of waste plastic 14b will not reduce the flow path (space) towards the riser pipe side. Additionally, when loading waste plastic 14b, if... Figure 4As shown, the accumulation of waste plastics 14d and 14c and the generation of thermal decomposition gases 24d and 24c are reduced. Therefore, the flow path (space) of thermal decomposition gas 24b generated from waste plastic 14b to the riser side is ensured. As a result, the gas pressure will not increase, and the leakage and ejection of thermal decomposition gas 24b can be suppressed.

[0047] In this way, by sequentially loading waste plastic 14 from the loading inlet on the side closest to the riser pipe 3 (riser pipe side) towards the loading inlet on the side furthest from the riser pipe 3 (opposite to the riser pipe side), it is possible to prevent the narrowing of the flow path (space) towards the riser pipe side and suppress the leakage and ejection of pyrolysis gas 24. In the above... Figure 4 The example shown illustrates how waste plastic 14 can be loaded sequentially from the side closest to the riser pipe 3 to the side furthest from the riser pipe 3, but it is also possible to load waste plastic from only some of the loading ports. Even if there are loading ports 4 where waste plastic is not loaded, as long as the waste plastic is loaded sequentially from the loading port closest to the riser pipe 3 to the loading port furthest from the riser pipe 3, leakage and ejection of pyrolysis gas 24 can be prevented.

[0048] Additionally, the following situations may be considered for the loading port 4, where waste plastics are not loaded. For example, if a portion of the upper wall of the coking oven's carbonization chamber is damaged, waste plastics may not be loaded to avoid placing a burden on that portion. Also, if the upper surface level of a portion of the coke that has been dry-distilled after being loaded with coal is higher than the specified level, waste plastics may not be loaded into that portion.

[0049] Furthermore, in cases where it is necessary to further shorten the loading time of waste plastics, the allowable gas generation amount δ (m³) can be considered to be no more than the aforementioned permissible amount. 3 Based on the premise of the method described in ( / h), the following method is adopted. That is, among all the loading ports for loading waste plastic, two or more loading ports that are consecutively arranged from the side closest to the riser pipe to the side furthest from the riser pipe, and which are less than the total number of loading ports, are grouped together. For loading ports belonging to the same group, waste plastic can be loaded simultaneously, instead of loading waste plastic sequentially. The number of groups should be two or more and less than the total number of loading ports, but from an operational point of view, the fewer the better. For example, the number of groups can be set to two or three.

[0050] Here, "simultaneously" simply means that they are loaded at the same time. For example, it could also mean that they are loaded at the same time. Figure 4In the carbonization chamber 2 with four loading inlets 4, loading inlets 4d and 4c are grouped together. Waste plastics 14d and 14c are loaded sequentially from the side closer to the riser pipe 3 (riser pipe side) to the side farther away from the riser pipe 3 (opposite to the riser pipe side) through loading inlets 4d and 4c, which are grouped together. Then, waste plastic 14b is loaded through loading inlet 4b, and then waste plastic 14a is loaded through loading inlet 4a. In addition, loading into loading inlets belonging to different groups is not carried out simultaneously.

[0051] Multiple loading inlets can also be set up to simultaneously load waste plastics into a group. For example, in a system with... Figure 4 In the carbonization chamber 2 with four loading inlets 4, loading inlets 4d and 4c can be grouped as the first group, and loading inlets 4b and 4a as the second group. Waste plastics 14d and 14c are simultaneously loaded into loading inlets 4d and 4c, and then waste plastics 14b and 14a are simultaneously loaded into loading inlets 4b and 4a. Alternatively, loading inlets 4c, 4b, and 4a can be grouped as one group, with waste plastic 14d loaded into loading inlet 4d, and then waste plastics 14c, 14b, and 14a simultaneously loaded into loading inlets 4c, 4b, and 4a.

[0052] In addition, Figure 3 In the scenario shown, if waste plastic 14c is loaded only when the generation of pyrolysis gases 24a and 24b has become sufficiently low, leakage or ejection of pyrolysis gases 24a and 24b will not occur. However, the total loading time of waste plastic for each kiln is constrained by the coking oven's operating rate. If the loading of waste plastic for one kiln takes time, the original coke discharge rate is also delayed, thus reducing coke production and the total amount of waste plastic processed.

[0053] Furthermore, as described above, groups of two or more consecutive loading inlets, each smaller than the total number of loading inlets, are established sequentially from the side closest to the riser pipe toward the side furthest from the riser pipe. When waste plastic is loaded into each loading inlet of the group simultaneously, an upper limit is set on the amount of waste plastic loaded, except for the loading inlet furthest from the riser pipe in the group. Specifically, for example, it is preferable to calculate, based on the loading height (thermoplastic loading height) y′ (m) of the waste plastic formed when loading the waste plastic, the longitudinal cross-sectional area (section perpendicular to the kiln length direction (m)) of the upper space of the waste plastic pile formed when loading the waste plastic is obtained, i.e., the flow path (space) to the riser pipe 3 side, except for the loading inlet furthest from the riser pipe. 2 ), so that the cross-sectional area is the cross-sectional area C of the riser pipe 3 (the cross-sectional area perpendicular to the central axis (m²)). 2The above method determines the loading amount at each inlet. Therefore, the preferred number of inlets in a group is determined as follows: based on the properties of the waste plastic to be loaded, the kiln temperature, the loading amount of waste plastic into each inlet, and the loading time interval, the total amount of gas generated is predicted, such that the total amount of gas generated becomes the allowable gas generation amount δ (m³). 3 The longitudinal cross-sectional area (m²) of the flow path on the ascending pipe 3 side below (the upper space of the waste plastic pile) below / h 2 The cross-sectional area C (m²) of the riser pipe 3 becomes the cross-sectional area of ​​the riser pipe 3. 2 The above applies. From an efficiency standpoint, it is preferable to implement this method by minimizing the number of times waste plastic is fed into the inlet of a single kiln. However, as mentioned above, since an upper limit is set on the amount of waste plastic to be fed, there may be a reduction in the amount of waste plastic processed. For each case with different numbers of feedings, feeding intervals, and total feeding amounts, it is preferable to determine the operating conditions based on the productivity.

[0054] Typical chamber coking ovens have 4 to 5 inlets, making them suitable for this invention. Furthermore, this invention can be applied to special types of stamping ovens with multiple top gas intakes. On the other hand, for ovens with jumper pipes or standpipes installed at the inlet positions on the opposite side of the riser at the top of the oven, the gas flow within the carbonization chamber is significantly different, making it difficult to achieve sufficient results even with this invention.

[0055] Example (Example 1) In a carbonization chamber with five loading inlets, an experiment was conducted to load waste plastics after the dry distillation of coal for coke production (Invention Example 1, Comparative Example 1). The carbonization chamber had a furnace height of 5.0 m, a furnace length of 14.62 m, and a furnace width of 0.45 m. The waste plastics were volume-reduced molded products made from recycled container packaging plastics produced based on the container packaging recycling method (laws related to the classified collection and promotion of resale of container packaging). The waste plastics had dimensions of approximately 26 mm in diameter, approximately 50 mm in height, and a bulk density of approximately 0.29 t / m³. 3 Cylindrical granular material. Furthermore, in Example 1 and Example 2 described later, the total amount of waste plastic loaded and the amount loaded at each loading inlet are the aforementioned maximum allowable waste plastic loading amount α (kg). Additionally, the time interval between loading from each loading inlet (loading time interval) is set as follows: the amount of gas generated when waste plastic is loaded from the loading inlet (m³ / kg). 3 The total amount of gas produced per hour (m³) will not exceed the permissible gas production rate δ (m³). 3 The shortest time ( / h).

[0056] A coal loading car was used for loading waste plastics. The coal loading car has a hopper for receiving coal from the coal tower, a feeder (tabletop feeder) located at the bottom of the hopper, and an auxiliary hopper for loading the coal supplied from the feeder into the loading inlet. Waste plastics were fed into the hopper of the coal loading car in the same way as coal, and loaded through the loading inlet. The total loading capacity of waste plastics was 300 kg. 60 kg of waste plastics were loaded sequentially through each loading inlet by opening the loading cover, and the loading cover was closed immediately after loading was completed.

[0057] In Invention Example 1, the waste plastics are loaded sequentially from the side closest to the riser pipe towards the side furthest from the riser pipe among the five loading inlets. In Comparative Example 1, the waste plastics are loaded sequentially from the side furthest from the riser pipe towards the side closest to the riser pipe among the five loading inlets. The initial loading of waste plastics occurs at a time when the generation of COG gas caused by coal dry distillation disappears or decreases sufficiently (e.g., 200 Nm in the case of a coke oven with a furnace height of 6 m). 3 The process is carried out within an hour (or less). Waste plastic is loaded into the inlet in 5 seconds, and then transferred to the next inlet in sequence, repeating this process to load into all five inlets. In addition, to shorten the overall loading time, the lid of the next inlet is opened at the same time as the lid of the previous inlet is closed.

[0058] Regarding the test results, to evaluate the risk of ignition of waste plastics into the hopper of the coal loading car caused by gas leakage from the loading inlet, thermocouples were installed in the auxiliary hopper of the coal loading car (the auxiliary hopper was fixed by inserting thermocouples into the side openings), and the evaluation was conducted by temperature measurement. Additionally, the presence of pyrolysis gas leakage from the loading inlet was visually confirmed. Furthermore, it was determined that waste plastics in containerized recycled products, when exceeding approximately 300°C, may soften and ignite depending on the properties of the various plastics constituting the waste plastics; this was confirmed by offline visual observation using a homogenizing furnace and a thermoviewer. Therefore, the upper limit for waste plastic combustion risk management was set at 300°C. Furthermore, in the event of a fire in the waste plastics in the auxiliary hopper, rapid water spraying for fire extinguishing is required; therefore, tests were conducted considering safety.

[0059] Figure 5 This represents the temperature measurement results obtained using thermocouples in Comparative Example 1. Figure 6 The temperature measurement results of the thermocouple in Example 1 are shown. The vertical axis represents the temperature of the space inside the auxiliary hopper (°C), and the horizontal axis represents the elapsed (dry distillation) time (time: minutes) from the moment the coal is loaded. Figure 5 and Figure 6 In the diagram, #1 to #5 represent inlets 1 to 5, numbered sequentially from the side furthest from the riser pipe towards the side closest to it, with the inlet closest to the riser pipe being inlet number 5. In Comparative Example 1 ( Figure 5In Example 1, waste plastics are loaded at 20 hours 45 minutes 48 seconds, 20 hours 47 minutes 54 seconds, 20 hours 49 minutes 00 seconds, 20 hours 51 minutes 06 seconds, and 20 hours 53 minutes 12 seconds, respectively, in the order of loading port 1 to loading port 5 (waste plastic loading start times #1~#5). Additionally, in Invention Example 1 ( Figure 6 In the sequence, at 20 hours 54 minutes 34 seconds, 20 hours 55 minutes 53 seconds, 20 hours 58 minutes 20 seconds, 20 hours 59 minutes 49 seconds, and 21 hours 06 minutes 26 seconds, waste plastics are loaded in the order of loading port 5 → loading port 1 (waste plastic loading start times #1~#5). The entire process from the start to the end of waste plastic loading takes approximately 5 seconds. Figure 5 and Figure 6 As shown, the temperature of the auxiliary hopper space before the waste plastic is loaded is 10~15℃, which is roughly the same as the temperature of the outside air above the coking oven.

[0060] In Invention Example 1, such as Figure 6 As shown, the temperature inside each auxiliary hopper of the coal charging car above the loading inlet did not rise by more than 15°C throughout the entire measurement process. Furthermore, only a slight gas leak was visually confirmed. As described above, a riser pipe 3 is installed in the carbonization chamber 2 of the coking oven, and gas is drawn in using the riser pipe 3, creating a negative pressure inside the carbonization chamber 2. In Example 1 of the Invention, the temperature did not rise after the waste plastic was loaded because even when waste plastic was loaded from loading inlets 1 to 5, the negative pressure generated by the gas drawing in through the riser pipe 3 was maintained, and external gas was drawn into each auxiliary hopper.

[0061] In Comparative Example 1, such as Figure 5 As shown, when waste plastics were sequentially loaded from port 1, which is furthest from the riser pipe, a temperature rise was observed in the auxiliary hoppers at ports 4 and 5. Furthermore, a large amount of gas was visually observed being ejected from ports 4 and 5. In Comparative Example 1, the temperature rise after waste plastics were loaded into ports 4 and 5 was because, when waste plastics were loaded into each of the ports 4 and 5, the negative pressure generated by the gas suction from the riser pipe 3 could not be maintained, and the thermal decomposition gases from the waste plastics were blown upwards into the auxiliary hopper directly above ports 4 and 5.

[0062] Furthermore, in Invention Example 1 and Comparative Example 1, environmental conditions such as temperature varied due to different weather conditions, but the carbonization chamber was used to investigate the effect of thermal decomposition gases generated at high temperatures from melting waste plastics; therefore, a difference of a few degrees Celsius would not be a problem. Moreover, it can be assumed that since the amount of waste plastic loaded at each loading inlet is constant, the pressure distribution of the thermal decomposition gases will not change significantly relative to slight deviations in the loading interval.

[0063] Furthermore, it is speculated that when waste plastic is simultaneously loaded into all the loading ports, compared to the case where the loading timing of each loading port is different, gas is generated rapidly, making it impossible to ensure the flow path to the riser pipe side. Consequently, it is difficult to maintain the negative pressure generated by the gas suction of the riser pipe 3, and gas is confirmed to be ejected from each loading port.

[0064] (Example 2) A loading experiment using waste plastics was conducted in a carbonization chamber with four loading inlets after the dry distillation of coal for coke production. The carbonization chamber had a height of 4.0 m, a length of 13.40 m, and a width of 0.40 m. The waste plastics used were volume-reduced molded products of recycled plastic containers, with dimensions of approximately 29 mm in diameter, approximately 60 mm in height, and a bulk density of approximately 0.3 t / m³. 3 The waste plastics were cylindrical granules. The coal loading car used the same structure as in Example 1. The total loading amount of waste plastics was 80 kg, with 20 kg of waste plastics loaded through each loading inlet.

[0065] In Example 2, the four loading inlets were sequentially designated as inlets 1 through 4, moving from the side furthest from the riser pipe towards the side closest to it. Inlets 1 and 2 were designated as group A, and inlets 3 and 4 as group B. In this experiment, firstly, 20 kg of waste plastic (totaling 80 kg) was loaded into each of the four loading inlets (from the coal loading car) in a two-stage loading method, following the order of group B closest to the riser pipe and group A furthest from the riser pipe (loading simultaneously into inlets of the same group). After loading, the loading covers of all the inlets were temporarily closed. After moving the coal loading car, the pressure values ​​directly below each loading inlet were measured by inserting a long-handled probe into the inlet to confirm the gas retention status (pressure distribution) and visually confirm the flame ejection status.

[0066] As described above, in the waste plastic loading operation using a coal loading car with group B (closest to the riser pipe) as the front and group A (farthest from the riser pipe) as the rear, no pyrolysis gas or flame is emitted from any loading inlet, allowing all waste plastic to be loaded. After loading all the waste plastic, when the loading covers of the loading inlets of group A (inlets 1 and 2) are opened simultaneously, almost no flame is emitted from any loading inlet, confirming that the pressure directly below both loading inlets is approximately negative. On the other hand, when the loading covers of the loading inlets of group B (inlets 3 and 4) are opened simultaneously, a significant flame is observed emanating from inlet 3. Furthermore, the pressure directly below inlet 3 is also relatively high. The pressure directly below inlet 4 is a stable negative pressure, and no flame is observed.

[0067] In Example 2, it is believed that the highest pressure directly below the loading inlet of port 3 is due to the cumulative effect of the gases generated from the loading of waste plastics through ports 1, 2, and 3, which are located far from the riser pipe. Furthermore, the pressure directly below the loading inlet of port 4 is negative, which is believed to be because it is closest to the riser pipe, thus ensuring a flow path for the generated gases. Conversely, in the case where group A, which is far from the riser pipe, is loaded first, followed by group B, which is close to the riser pipe, it is believed that during the operation of loading waste plastics by opening the loading cover of port 3, the cumulative effect of the gases generated from the loading of waste plastics through ports 1, 2, and 3 causes the thermal decomposition gases of the waste plastics to blow upwards into the auxiliary hopper of the coal loading car, potentially causing a fire. In addition, during the loading operation of waste plastics with group B, which is closer to the riser pipe, as the front and group A, which is farther away from the riser pipe, as the back, waste plastics are loaded from ports 1 and 2 after the loading cover of port 3 is closed. Therefore, it is believed that no thermal decomposition gases or the like are emitted during the entire loading operation.

[0068] (Example 3) Similar to Example 2, a waste plastic loading experiment was conducted in a carbonization chamber with four loading inlets after the dry distillation of coal for coke production. The size of the carbonization chamber, the shape of the waste plastic used, and the shape of the coal loading car were also the same as in Example 2.

[0069] In embodiment 3, the four loading ports are also designated as ports 1 to 4 in sequence from the side away from the riser pipe toward the side closer to the riser pipe. Ports 1 and 2 are designated as group A, and ports 3 and 4 are designated as group B.

[0070] As an example of the invention, a loading operation was carried out on a coal loading car based on loading waste plastics from group B (ports 3 and 4) which is closer to the riser pipe as the front and group A (ports 1 and 2) which is farther from the riser pipe as the rear. Since ports 3 and 4 of group B are loaded simultaneously, compared to loading at each port individually, the height of the waste plastics near port 4, closer to the riser pipe, is not completely reduced, and the gas path for the waste plastics at port #3 becomes narrower. As a result, as... Figure 7 As shown, with Figure 5 , Figure 6 Compared to the previous chart, a small amount of high-temperature gas was ejected from port 3, causing a slight increase in the temperature of the auxiliary hopper. However, this temperature was lower than the 300°C limit set for waste plastic combustion risk management, and therefore not a level that would hinder actual operation. Furthermore, the gas accumulating at port 3 consisted solely of waste plastic gas from port 3.

[0071] In Invention Example 3, the waste plastic is loaded in two assemblies simultaneously through ports 1 and 2. Therefore, the height of the waste plastic near port 2, closer to the riser pipe, is not completely reduced compared to loading through each port individually. The waste plastic gas path at port 1 is narrower. Similarly, a small amount of high-temperature gas is ejected from the port furthest from the riser pipe, causing a slight increase in the auxiliary hopper temperature. However, this temperature is lower than the 300°C limit for waste plastic combustion risk management, a level that does not hinder actual operation. Furthermore, the gas collected at port 1 consists only of the waste plastic gas from port 1.

[0072] As a comparative example 3, the loading operation was performed first on group A (ports 1 and 2), which is farther from the riser pipe, and then on group B (ports 3 and 4), which is closer to the riser pipe. If loading is performed from the side opposite to the riser pipe, then group A (ports 1 and 2) will be loaded in a way that is... Figure 7 The same state. This is because the gas gathered at port 1 is only the waste plastic gas from port 1. On the other hand, when group B (ports 3 and 4) is loaded, the generated gases from ports 1, 2, and 3 are concentrated at port 3, therefore... Figure 8 As shown, high-temperature gas was ejected on a large scale, and the temperature of the auxiliary hopper rose sharply, exceeding 300°C, which is the upper limit for risk management of waste plastic combustion.

[0073] Based on the above results, in order to avoid the risk of thermal decomposition gas ejection when loading waste plastics, it is preferable to load the waste plastics sequentially from the loading port closest to the riser pipe to the far side. Specifically, when establishing groups to load waste plastics simultaneously to shorten the loading time, it is preferable to load the waste plastics simultaneously into ports 1 and 2, followed by ports 3 and 4 (group A → group B), rather than loading them simultaneously into ports 3 and 4, followed by ports 1 and 2 (group B → group A).

[0074] Explanation of reference numerals in the attached figures 1: Coke oven; 2: Carbonization chamber; 3: Ascension pipe; 4: Loading inlet (4a, 4b, 4c, 4d); 5: Upper (top side) space; 11: Coal (coal for coke manufacturing); 12: Mixed coal (mixed coal for coke manufacturing: a mixture containing coal and waste plastics for mixing); 13: Coke; 14: Waste plastics (14a, 14b, 14c, 14d); 24: Thermal decomposition gases (24a, 24b, 24c, 24d); 31: Coal loading car.

Claims

1. A method for treating waste plastics, characterized in that, Coke is produced by dry distillation of coal used in coke production, or a mixture of coal and waste plastics used in coke production, in the carbonization chamber of a coking oven. After the dry distillation is completed, waste plastic is sequentially loaded into the upper space of the carbonization chamber from some or all of the multiple loading inlets provided in the carbonization chamber of the coking oven, from the loading inlet on the side closer to the riser pipe toward the loading inlet on the side farther away from the riser pipe. The upper space of the carbonization chamber is the space above the upper end of the coke, i.e., the coal loaded after the dry distillation is completed.

2. The method for treating waste plastics as described in claim 1, characterized in that, In all the loading ports into which the waste plastic is loaded, one or more loading ports are set as a group. For each loading port belonging to the same group, the waste plastic is loaded into all of each loading port simultaneously. The group of loading ports is any number of loading ports that are two or more consecutive in the order of loading the waste plastic and are less than the total number of loading ports.

3. The method for treating waste plastics as described in claim 2, characterized in that, The waste plastic is loaded into two or more of the aforementioned groups.

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