Method for treating waste plastic

Abstract

The present invention pertains to a method for treating waste plastic, the method being characterized in that when producing coke by charging waste plastic into a furnace top space above charged carbon which has been charged into a carbonization chamber after dry distillation of coal in a coke oven, a charging test is performed in advance on a full-scale model of a carbonization chamber 2, the bulk density ρ (kg / m3) of the waste plastic and the repose angle θ (°) of a mound formed by charged waste plastic 12 are determined in advance, the height y of the waste plastic 12 to be charged into a furnace top space 5 is determined on the basis of the furnace top space height hspace, and the amount x (kg) of waste plastic charged per charging port is estimated and determined on the basis of the formulas (1) and (2) below.　(1) y = k × x0.5 (2) k = (tan θ / (ρ × d))0.5, where d is the furnace width (mm) of the carbonization chamber.

Description

How to dispose of waste plastic

[0001] The present invention relates to a method for treating waste plastics by charging coal for coke production (charging coal) and waste plastics into a carbonization chamber of a coke oven and carrying out carbonization.

[0002] Conventionally, the vast amounts of waste plastic generated as industrial plastic waste and general plastic waste have been disposed of by landfilling or partial incineration. When landfilled, waste plastics are not decomposed by bacteria in the soil, and when incinerated, the high heat output has a negative impact on incinerators. Furthermore, in the case of chlorine-containing waste plastics, the disposal of the chlorine in the exhaust gas poses a problem. Given the predicted future shortage of landfill sites and growing environmental concerns, there is a desire to promote the recycling of waste plastics. Possible recycling methods include reuse as plastic, utilization of the heat generated during combustion, and the use of gases and oils obtained through thermal decomposition during heating as fuels or chemical raw materials.

[0003] For example, Patent Document 1 discloses a method for recycling waste plastics by mixing plastic granules molded at 100 to 160°C with coal and dry distilling the mixture in a coke oven. On the other hand, Patent Document 2 describes that mixing a large amount of plastic reduces the strength of the resulting coke, and that to keep the reduction in coke strength to a few percent, the mass ratio of plastic to coal needs to be 1% or less, and that the amount that can be recycled is limited depending on the target level of coke strength.

[0004] One known method for processing waste plastics by adding them to a coke oven is to charge them into the space above the coal charged in the coke oven. According to Patent Document 3, this method allows most of the waste plastics to be pyrolyzed in the high-temperature coke oven, resulting in the production of high-calorie pyrolysis gases containing hydrogen, methane, ethane, propane, and the like. These pyrolysis gases are recovered as part of the coke oven gas generated in the coke oven chamber by the pyrolysis of coal, and are reused as an energy source.

[0005] For example, Patent Document 4 discloses a method for producing coke by carbonizing coal in a coke oven and then charging waste plastics into the upper space of the coke oven. It is recommended that the waste plastics be charged during the coke maturation period (approximately 2 hours) between the end of the fire (completion of carbonization) and the coke extrusion, which is usually called the storage time. This is because, during this time, the amount of coke oven gas generated is small and the heat dissipated from the coke oven is large and can be utilized as heat for gas decomposition.

[0006] Patent Document 5 relates to a method for treating waste plastics, which involves preparing a coke oven charge coal or a coke oven charge coal containing 0.1 to 1.0 wt% of waste plastics, charging the prepared coal into a coke oven, and then charging waste plastics into the top space above the charged coal. The waste plastics are then pyrolyzed during carbonization to recover tar, diesel, and gas. Two methods for treating waste plastics are disclosed: one in which waste plastics are charged into the top space above the charged coal through a charging port after the coal is charged, and another in which waste plastics are supplied from a supply device connected to the top space of the coke oven from after the coal is charged until the end of carbonization. These methods are said to enable the treatment of the same amount of waste plastic as when approximately 5 wt% of waste plastics is mixed into the top space. On the other hand, Patent Document 2 states that in the method described in Patent Document 5, the raw material charging lid is opened and waste plastic is charged while coal is being carbonized in the carbonization chamber of the coke oven, so 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.

[0007] Patent Document 3 discloses a coke production method in which coke raw materials are first charged into the carbonization chamber of a coke oven and then waste plastics are charged into the furnace top space, suppressing dust generation during extrusion and reducing extrusion resistance. The document states that it is desirable to charge the waste plastics after the fire has died out (when carbonization is complete). This is because, if the waste plastics are charged after the fire has died out, gas generation due to thermal decomposition of the coke raw materials decreases, and, although the heat dissipated from the coke oven body usually increases after the fire has died out, this heat can be utilized for the thermal decomposition of the waste plastics.

[0008] Patent Document 6 describes a leveling device that has the function of leveling unevenness on the top of the charged coal charged into the coke oven carbonization chamber. The leveling device is composed of multiple boxes separated by partitions and without bottom plates. Return coal is supplied into the leveling device boxes, and by moving the leveling device forward into the carbonization chamber, the return coal falls according to the unevenness of the top of the charged coal, thereby leveling the top of the charged coal. When the leveling device moves backward, excess charged coal and return coal are moved into the leveling device boxes and collected, and are reused as return coal in the next charge.

[0009] Patent Documents 7 and 8 disclose a method for accurately controlling the coal charging height of coal charged into a coke oven carbonization chamber and a method for maintaining the coal charging height as constant as possible throughout the coke oven. Therefore, Patent Documents 7 and 8 describe a method for estimating the relationship between the volume and mass of the charged coal and the charging pile height in advance and setting the amount of charged coal according to the target charging pile height. Therefore, Patent Documents 7 and 8 do not describe a method for adding waste plastics to a coke oven for processing. Furthermore, both Patent Documents 7 and 8 consider the shape of the top of the charged coal before carbonization to be a horizontal plane.

[0010] JP 2001-49261 A JP 2019-135278 A JP 2002-47494 A JP 4-41588 A JP 8-157834 A JP 2002-371285 A JP 2014-088528 A JP 2-235988 A

[0011] The present invention relates to a method for treating waste plastics in which coal for coke production (charging coal) and waste plastics are charged into the carbonization chamber of a coke oven and carbonized, and after carbonization of the coal in the coke oven, the waste plastics are charged into the furnace top space above the produced coke layer in the carbonization chamber.

[0012] When waste plastics are charged into the furnace top space after carbonization of coal, it is necessary to charge as much waste plastics as possible to increase the productivity of waste plastic processing. On the other hand, if too much waste plastics is charged into the furnace top space, the gap between the top of the charged waste plastics and the ceiling of the coke chamber becomes insufficient, resulting in insufficient heating and clogging in the upper layer. When charging waste plastics, it is necessary to accurately grasp the height of the top of the coke layer after carbonization, accurately predict the upper limit of the amount of waste plastics that can be charged, and then charge the maximum amount of waste plastics possible.

[0013] The first object of the present invention is to provide a method for treating waste plastics that enables the maximum amount of waste plastics to be charged into the furnace top space above the charged coal in a coke oven after carbonization of coal, and a second object of the present invention is to accurately estimate the volume of the furnace top space after carbonization.

[0014] That is, the gist of the present invention is as follows: [1] A method for treating waste plastics in which coal for coke production (hereinafter referred to as "charging coal") and waste plastics are charged into the carbonization chamber of a coke oven and carbonized, the method determining the amount of waste plastics to be charged based on the height (hereinafter referred to as the "top space height") of the space from the top end of the coke layer produced in the carbonization chamber to the top end of the carbonization chamber after carbonization of the charged coal is completed (hereinafter referred to as the "top space height"), the method determining the height y of the pile of waste plastics to be charged into the top space from each charging port based on the top space height, and determining the amount of waste plastics to be charged by estimating the amount x (kg) of waste plastics to be charged for each charging port based on the following equations (1) and (2) which show the relationship between the amount x (kg) of waste plastics to be charged for each charging port and the height y (mm) of the waste plastics: y = k × x ０．５ (1) k=(tanθ / (ρ×d)) ０．５ (2) Where ρ: bulk density of waste plastic (kg / mm ３), d: furnace width of the carbonization chamber (mm), θ: angle of repose (°) of the pile formed by the waste plastics charged from each charging port, and the bulk density ρ (kg / mm ３ ) is measured in advance by a charging test using a full-scale model of a coke chamber, or by a method of filling a container of known volume with a sample and measuring the mass as specified in JIS K2151, and the angle of repose θ (°) is measured in advance by a charging test using the full-scale model. [2] The method for treating waste plastics according to [1], characterized in that the height of the furnace top space is determined based on an estimate of the height of the top end of the coke layer after carbonization, and the estimation of the height of the top end of the coke layer after carbonization is carried out by measuring the height of the top end of the coke layer after carbonization based on multiple past treatment results, and deriving in advance an estimate formula for the relationship between the amount of coal to be charged and the height of the top end of the coke layer after carbonization. [3] The method for treating waste plastics according to [1], characterized in that the height of the furnace top space is determined based on an estimate of the height of the upper end of the coke layer after carbonization, and the estimation of the height of the upper end of the coke layer after carbonization is carried out by measuring the height of the upper end of the coke layer after carbonization based on multiple past treatment results, and deriving in advance an estimation formula for the relationship between the amount of coal to be charged, the moisture content of the charged coal, and the height of the upper end of the coke layer after carbonization. [4] The method for treating waste plastics according to [1], characterized in that the height of the upper end of the coke layer after carbonization is determined by measuring it using a level meter, and the height of the furnace top space is determined based on the determined height of the upper end of the coke layer after carbonization.

[0015] In the present invention, when producing coke by carbonizing coal in a coke oven and then charging waste plastics into the furnace top space above the charged coal charged into the carbonization chamber, a charging test is conducted in advance on a full-scale model of the carbonization chamber to measure the bulk density ρ of the waste plastics and the angle of repose θ of the pile formed by the charged waste plastics, and the relationship between the amount x of waste plastic charged at each charging port and the height y of the waste plastics is estimated based on a predetermined formula to determine the amount of waste plastic to be charged, thereby enabling the maximum amount of waste plastic to be charged.

[0016] Fig. 1 is a cross-sectional view showing an example of a state in which waste plastics are charged into a furnace top space of a carbonization chamber. Fig. 2 is a cross-sectional view showing a state in which the upper end position of a coke layer after carbonization is completed and before waste plastics are charged into the carbonization chamber. Fig. 3 is a cross-sectional view showing a state in which the upper end position of a coke layer after carbonization is measured with a level meter.

[0017] FIG. 1 shows the state in which waste plastics 12 have been charged into the furnace top space 5. FIG. 2 shows a cross-section of the coke chamber 2 of the coke oven 1 after carbonization is complete. The post-charging coal layer top position 14 (the top end position of the charged coal before carbonization) is indicated by a two-dot chain line. A produced coke layer 11 (the charged coal after carbonization is complete) is formed in the coke chamber 2, and the generated gas is discharged through the riser 3. A charging port 4 is located in the ceiling of the coke chamber 2. Burn-down occurs during carbonization, and the height decreases from the post-charging coal layer top position 14 before carbonization to the post-carbonization coke layer top position 13. The top end of the produced coke layer 11 is the post-carbonization coke layer top position 13, and the space above the produced coke layer 11 is the furnace top space 5. FIG. 3 shows the state in which the post-carbonization coke layer top position 13 is measured with a level meter 6 through the charging port 4 after carbonization is complete.

[0018] First, a test was conducted in advance to load waste plastic into a full-scale model of a carbonization chamber. ３ The bulk density ρ (kg / mm ３) was calculated by calculating the volume of the pile of charged waste plastics in a full-scale model test and dividing it by the mass of the charged waste plastics. The bulk density ρ of waste plastics may be evaluated by a method such as that specified in JIS K2151, in which a sample is filled into a container of known volume and its mass is measured. In addition, the angle of repose θ (°) of the slope of the pile of piled waste plastics charged into the carbonization chamber in the furnace length direction was measured in a test of charging waste plastics into a full-scale model of the carbonization chamber. The angle of repose θ may be measured directly with a protractor or the like, or may be measured by data processing of an image of the shape of the pile of piled waste plastics. Here, when observing the shape of the pile of waste plastics accumulated in the furnace top space of the coke chamber, in a full-scale model experimental device with a furnace width of d (mm), waste plastics were charged from a position simulating a charging port, and when the amount of waste plastic charged was x (kg), the pile of waste plastics, when viewed from the furnace width direction, formed an isosceles triangle with a height of y (mm) and an angle of repose of the inclined surface in the furnace length direction of θ (°). The area of ​​this triangle was defined as A (mm ２ ) then A = y ２ / tan θ (3) ρ×d×A=x (4) This relation can be transformed to k=(tan θ / (ρ×d)) ０．５ (2) Then, y = k × x ０．５ The following relational expression is obtained: (1) This relational expression shows the relationship between the amount of waste plastic charged x (kg) and the height y (mm) of the waste plastic pile.

[0019] A waste plastic charging test was conducted using a full-scale model experimental device, with the width d of the coke chamber, the distance from the charging port to the top end position 13 of the coke layer after carbonization, and the waste plastic charging rate set to the same values ​​as in a real coke oven. Two types of waste plastic were used: "low-density" and "high-density." When charging the waste plastic into the coke oven, it was compressed and molded using a volume reduction molding machine to improve handling during transportation and increase the plastic charging density. Depending on the molding conditions, the waste plastic is classified into a hard pellet-like "high-density" product and a softer "low-density" product. As a result, the bulk density ρ of the waste plastic and the angle of repose θ of the slope of the waste plastic pile were measured as shown in Table 1.

[0020]

[0021] That is, once the height y of the waste plastic pile is determined, the amount x of waste plastic charged per charging port required to achieve this height of the pile can be determined based on equations (1) and (2). If the carbonization chamber has multiple charging ports, the amount x of waste plastic charged for each charging port can be determined by the above method, and then the amounts x of waste plastic charged from each charging port can be added together to determine the amount of waste plastic charged for the entire carbonization chamber.

[0022] Next, as shown in FIG. 1, the height y of the pile of waste plastic is calculated by dividing the height h of the furnace top space by the height y of the pile of waste plastic. ｓｐａｃｅ The height of the waste plastic pile (y) and the height of the furnace top space (h) are determined by the following equation. ｓｐａｃｅ Regarding the relationship with ｓｐａｃｅ From the viewpoint of operational efficiency, it is preferable to maximize the height y of the waste plastic pile, and y is set to the range where h ｓｐａｃｅ The closer it is to this, the better.

[0023] <<Embodiment 2>> The coal charged into the coke oven contains moisture, and the coal charge amount t is expressed as the amount of coal charged containing moisture (wet-t / ch). Here, wet-t is the mass of the coal charge in a moisture-containing state. Also, ch is the amount of coal charged per coke chamber. The height of the top end of the coke layer after carbonization h ｃｏｋｅThe height (mm) of the coke layer after carbonization can be measured by lowering a measuring rod or the like from above the furnace. By measuring the level under multiple conditions with different charging amounts, the coal charging amount t (wet-t / ch) and the top height of the coke layer after carbonization h ｃｏｋｅ For example, the above measurement was performed in a specific coking chamber, and the relationship between h ｃｏｋｅ = 141.17 × t + 1453.3 (5) was obtained. This is the result of changing the coal charge amount t (wet-t / ch) in the range of 12 to 15 (wet-t / ch). The moisture content of the coal used was approximately 2%. As shown in Figure 1, the coking chamber height h ｏｖｅｎ Since the furnace top space height h (mm) is known, ｓｐａｃｅ For (mm), h ｓｐａｃｅ =h ｏｖｅｎ -h ｃｏｋｅ (6) can be calculated as follows.

[0024] That is, in the waste plastic processing method of the present invention, the furnace top space height h ｓｐａｃｅ The height of the top of the coke layer after carbonization h ｃｏｋｅ The height of the top of the coke layer after carbonization h ｃｏｋｅ The estimation of the height of the coke layer after carbonization h was based on the past results of multiple treatments. ｃｏｋｅ Measure the amount of coal to be charged t and the height of the top of the coke layer after carbonization h ｃｏｋｅ An estimation formula for the relationship between the above can be derived and determined in advance.

[0025] <<Embodiment 3>> When carbonizing charged coal in a coke oven carbonization chamber, the coal height h immediately after charging ｃａｏｌ In contrast, the height of the top of the coke layer after carbonization h ｃｏｋｅ The reduction amount is h ｄｒｏｐ (mm). This phenomenon is called "burn-down." The burn-down rate r (%) is calculated using the following formulas (7) and (8). h ｄｒｏｐ =h ｃａｏｌ -h ｃｏｋｅ (7) r = h ｄｒｏｐ / h ｃａｏｌ ×100 (8)

[0026] Coal height immediately after charging hｃａｏｌ and the height of the top of the coke layer after carbonization h ｃｏｋｅ is measured by lowering a measuring rod or similar tool from above the furnace. By measuring the level under multiple conditions with different moisture contents w (%) of charged coal, the change in the amount of burn-down depending on the moisture content was clarified. The amount of burn-down (burn-down rate r) differs depending on the moisture content of the coke. The relationship between the burn-down rate r (%) and the moisture content w (%) of charged coal was calculated as follows: r = 0.33 × w + 0.66 (9)

[0027] Moisture content of charged coal w (%) and coal height h immediately after charging ｃａｏｌ If this is known, the height of the top of the coke layer after carbonization h ｃｏｋｅ can be calculated using the above formula (9) and the following formula (10). ｃｏｋｅ =h ｃａｏｌ ×(1-r / 100) (10)

[0028] Coal height immediately after charging h ｃａｏｌ The coal height (mm) can be measured by lowering a measuring rod or the like from above the furnace immediately after charging. By measuring the level under multiple conditions with different charging amounts, the coal charging amount t (wet-t / ch) and the coal height h immediately after charging can be calculated. ｃａｏｌ The relationship between the distance (mm) can be derived in advance as a first-order estimation equation.

[0029] That is, in the waste plastic processing method of the present invention, the furnace top space height h ｓｐａｃｅ The height of the top of the coke layer after carbonization h ｃｏｋｅ The height of the top of the coke layer after carbonization h is determined based on the estimate of ｃｏｋｅ The estimation of the coal height h immediately after charging was based on the past results of multiple treatments. ｃａｏｌ , the height of the top of the coke layer after carbonization h ｃｏｋｅ The moisture content w of the charged coal is measured at the coal height h immediately after charging. ｃａｏｌ and the height of the top of the coke layer after carbonization h ｃｏｋｅ The coal height h immediately after charging is calculated. ｃａｏｌ Using the actual measured values ​​of the moisture content w of the charged coal, the height h of the coke layer after carbonization is calculated by the above estimation formula. ｃｏｋｅ can be estimated and determined.

[0030] As another modification of the third embodiment, the following method can be used. That is, the coal charge amount t (wet-t / ch) and the moisture content w (%) of the charged coal are used as variables, and the coke layer top height h after carbonization is calculated. ｃｏｋｅ It is assumed that the relationship holds as a two-dimensional linear estimation equation for the formula expressing the coke layer height (mm) after carbonization. ｃｏｋｅ Then, the coefficients of the two-variable linear estimation equation can be obtained by applying a technique such as multiple regression analysis. The two-variable linear equation is determined in advance based on the above observation results, and once the moisture content w of the charged coal is determined, the coal charging amount t (wet-t / ch) is determined and substituted into the two-variable linear equation determined in advance, the height h of the top end of the coke layer after carbonization can be obtained. ｃｏｋｅ can be calculated.

[0031] That is, in the waste plastic processing method of the present invention, the furnace top space height h ｓｐａｃｅ The height of the top of the coke layer after carbonization h ｃｏｋｅ The height of the top of the coke layer after carbonization h ｃｏｋｅ The estimation of the height of the coke layer after carbonization h was based on the past results of multiple treatments. ｃｏｋｅ The amount of coal to be charged (t), the moisture content (w) of the charged coal, and the height of the top end of the coke layer after carbonization (h) were measured. ｃｏｋｅ The estimated equation for the relationship between the above can be derived and determined in advance as a linear equation with two unknowns.

[0032] Next, in addition to the amount of coal to be charged t and the moisture content w of the charged coal, other processing conditions are determined as follows: the top height of the coke layer after carbonization h ｃｏｋｅAs in the above experiment, the post-carbonization coke layer top position 13 was measured for multiple coke chambers 2, and the relationship between the amount of coal charged and various processing conditions was investigated. As a result, it was revealed that even with the same coal charge amount, the post-carbonization coke layer top position 13 changes when the crushed particle size of the charged coal, the volatile matter content of the coal, the degree of carbonization of the coal, the coal composition (C / N / O, etc.), the carbonization conditions (furnace temperature, carbonization time), the coal charging rate, etc. vary. The effect of these parameters on the post-carbonization coke layer top position 13 can be expressed as a multi-dimensional linear function. The estimation accuracy can be improved by taking these parameters into account.

[0033] The measured post-carbonization coke layer upper end position 13 has a linear correlation with the amount of coal charged, and even with the same amount of coal charged, the post-carbonization coke layer upper end position 13 may differ for each coke chamber 2. In such cases, it is preferable to provide an estimation formula for the post-carbonization coke layer upper end position 13 for each coke chamber 2. For each coke chamber 2, the post-carbonization coke layer upper end position 13 is measured based on multiple past processing results, and an estimation formula for the relationship between the amount of coal charged and the post-carbonization coke layer upper end position 13 is derived as a linear formula. The post-carbonization coke layer upper end position 13 in the coke chamber 2 for the target process can be estimated by substituting the coal charging amount for the process into the estimation formula. When deriving an estimation formula from multiple past processing results, a highly accurate estimation formula can be obtained by including processes with as many different coal charging amounts as possible. The estimation accuracy may be improved by taking these parameters into consideration.

[0034] In addition to investigating the behavior of each coke chamber, the post-carbonization coke layer upper end position 13 was measured for each charging port 4 of each coke chamber 2, and the relationship with the processing parameters was investigated. As a result, even for the same coke chamber 2, the estimation formula for estimating the post-carbonization coke layer upper end position 13 may differ for each charging port 4. In such cases, it is more preferable to derive an estimation formula based on multiple past processing results for each coke chamber 2 and each charging port 4, and estimate the post-carbonization coke layer upper end position 13 according to the measured values ​​for each charging port 4. Here, the coke chamber top deck thickness, tapered portion height, non-tapered portion height, leveler height, and charging port dimensions may be common to all charging ports. Then, the amount of waste plastic 12 to be charged into the top space 5 above the produced coke layer for each charging port 4 is determined according to the estimated value of the post-carbonization coke layer upper end position 13 estimated for each charging port 4. This makes it possible to more accurately estimate the volume of the furnace top space 5, and to maximize the amount of waste plastics 12 charged into the furnace top space 5. The estimation accuracy may be improved by taking these parameters into consideration.

[0035] The post-carbonization coke layer top position 13 may be measured manually as in the above experiment when creating the estimation equation. However, it is more preferable to directly measure the position at each charging inlet 4 using a level meter 6. The level meter 6 can be a differential pressure or microwave type. A differential pressure level meter measures the depth of the nozzle descent by measuring the change in air pressure at the nozzle when the nozzle, which descends telescopically while spraying a small amount of gas from above, comes into contact with the object to be measured. A microwave level meter measures the round-trip propagation time of a microwave pulse emitted from the sensor antenna, reflected by the surface of the object to be measured and received again by the antenna as a reflected pulse, thereby measuring the distance. The level meter 6 is placed above the charging inlet 4 of the coke chamber 2, and the post-carbonization coke layer top position 13 in the coke chamber can be measured when the charging inlet 4 is open.

[0036] Regarding the charging of waste plastics into the coke chamber, in addition to charging waste plastics 12 into the furnace top space 5 above the coke layer produced in the coke chamber after carbonization is complete, waste plastics can also be mixed into the charged coal before charging. The mixing of waste plastics into the charged coal can cause fluctuations in the top height of the coke layer after carbonization. Therefore, in multiple processing trials, waste plastics were mixed into the charged coal before being charged, and the effects of the waste plastic content rate and properties of the waste plastic on the estimation of the top height of the coke layer after carbonization were investigated. The properties of the waste plastics may be parameterized as the particle size, apparent specific gravity, bulk density, and angle of repose of the waste plastic. As a result, the effects of the waste plastic content rate and the above waste plastic property parameters on the top height of the coke layer after carbonization were clarified, and both parameters can be incorporated into the estimation equation as a linear equation. These parameters may be taken into account to improve the estimation accuracy.

[0037] In the present invention, when estimating the height of the top end of the coke layer after carbonization based on an estimation equation, the created estimation equation can be stored in a computer system, parameters to be input into the estimation equation can be input into the computer system, and the estimated value of the height of the top end of the coke layer after carbonization can be calculated by the computer system. Preferably, the parameters to be input into the estimation equation are automatically input into the computer system online. Furthermore, it is preferable that after the estimated value of the height of the top end of the coke layer after carbonization is calculated by the computer system, the amount of waste plastics to be charged into the furnace top space is determined by the computer system based on the calculated estimated value of the height of the top end of the coke layer after carbonization. Automatic control by the computer system can be performed for each coke chamber or even for each charging port. More preferably, a measured value of the top end position 13 of the coke layer after carbonization can be input into the computer system, and the estimation equation can be automatically corrected online using this measured value.

[0038] REFERENCE SIGNS LIST 1 Coke oven 2 Carbonization chamber 3 Riser pipe 4 Charging port 5 Furnace top space 6 Level gauge 11 Produced coke layer 12 Waste plastic 13 Upper end position of coke layer after carbonization 14 Upper end position of coal layer after charging

Claims

1. A method for treating waste plastics in which coal for coke production (hereinafter referred to as "charging coal") and waste plastics are charged into the carbonization chamber of a coke oven and carbonized, and the amount of waste plastics to be charged is determined based on the height (hereinafter referred to as the "top space height") of the space from the top of the coke layer produced in the carbonization chamber to the top of the chamber after carbonization of the charged coal is complete (hereinafter referred to as the "top space height"), and the height y of the pile of waste plastics to be charged into the top space from each charging port is determined based on the top space height, and the amount of waste plastics to be charged is determined by estimating the amount of waste plastics to be charged per charging port x (kg) based on the following equations (1) and (2) which show the relationship between the amount of waste plastics charged per charging port x (kg) and the height y (mm) of the waste plastics. y = k × x ０．５ (1) k=(tanθ / (ρ×d)) ０．５ (2) Where ρ: bulk density of waste plastic (kg / mm ３ ), d: furnace width of the carbonization chamber (mm), θ: angle of repose (°) of the pile formed by the waste plastics charged from each charging port, and the bulk density ρ (kg / mm ３ ) is measured in advance by a charging test using a full-scale model of the coke chamber, or by a method specified in JIS K2151 in which a container of known volume is filled with a sample and the mass is measured, and the angle of repose θ (°) is measured in advance by a charging test using the full-scale model.

2. The method for treating waste plastics according to claim 1, characterized in that the height of the furnace top space is determined based on an estimate of the height of the top end of the coke layer after carbonization, and the estimation of the height of the top end of the coke layer after carbonization is carried out by measuring the height of the top end of the coke layer after carbonization based on multiple past processing results, and deriving in advance an estimation formula for the relationship between the amount of coal to be charged and the height of the top end of the coke layer after carbonization.

3. The method for treating waste plastics described in claim 1, characterized in that the height of the furnace top space is determined based on an estimate of the height of the top end of the coke layer after carbonization, and the estimation of the height of the top end of the coke layer after carbonization is carried out by measuring the coal height immediately after charging and the height of the top end of the coke layer after carbonization based on multiple past processing results, deriving in advance an estimation formula for the effect of the moisture content of the charged coal on the relationship between the coal height immediately after charging and the height of the top end of the coke layer after carbonization, and estimating and determining the height of the top end of the coke layer after carbonization using the actual measured values ​​of the coal height immediately after charging and the moisture content of the charged coal according to the estimation formula.

4. A method for treating waste plastics as described in claim 1, characterized in that the height of the top of the coke layer after carbonization is determined by measuring it using a level meter, and the height of the furnace top space is set based on the determined height of the top of the coke layer after carbonization.

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