Method for arranging raw materials in coke oven and method for producing coke

Abstract

To provide a technique capable of suppressing a decrease in coke strength when blending resin materials.SOLUTION: A method for arranging raw materials in a coke oven comprises, when charging molded resin materials and molded coal into the coke oven as coke raw materials together with non-molded coal, arranging the molded resin materials and the molded coal in proximity to each other. The method for arranging raw materials in the coke oven preferably comprises: unevenly distributing the molded resin materials and the molded coal in the vicinity of the M / S and the C / S of the carbonization chamber; equally dividing the carbonization chamber into four or more regions along the longitudinal direction and allocating more of the molded resin materials and the molded coal to the regions adjacent to the M / S and the C / S than to other regions; and ensuring that the sum of the amounts of the molded resin materials and the molded coal allocated to the regions adjacent to the M / S and the C / S is 75% or more of the total amount of the molded resin materials and the molded coal charged into the entire coke oven, respectively. The method for producing coke comprises dry-distilling the molded resin materials, the molded coal, and the non-molded coal charged by the method for arranging raw materials in the coke oven.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for recycling resins, such as waste plastics and biomass, into raw materials for steelmaking in a coke oven. 3 The units are expressed in kg. In this specification, "resins" include not only used plastics from general waste, known as "synthetic resins" and waste plastics, but also plastics that become industrial waste, such as scraps and defective synthetic resins generated in the manufacturing process, and used plastics. "Resins" also includes so-called "biomass," which is carbonaceous material derived from plants. [Background technology]

[0002] In recent years, marine pollution caused by waste plastic has become a global problem, with the amount of waste plastic that ends up in the oceans around the world estimated at approximately 8 million tons per year. Solving marine pollution is one of the goals of the Sustainable Development Goals (SDGs) adopted at the United Nations Summit in 2015. In response to this, Europe has launched the EU Plastics Strategy, which aims to strengthen plastic recycling and reduce single-use plastics.

[0003] In Japan, the Containers and Packaging Recycling Law was enacted in 1995, and the recycling of waste plastics has been promoted from an early stage. In response to the growing trend to further reduce waste plastics, the Act on Promotion of Resource Recycling Related to Plastics will come into effect in 2022, calling for further strengthening of waste plastic recycling. In the steel industry, a technology has been put into practical use to recycle waste plastics as raw materials for steelmaking by mixing it with coal and charging it into coke ovens. This is being implemented as a chemical recycling technology for waste plastics under the Containers and Packaging Recycling Law.

[0004] However, it is known that mixing waste plastics into coal to produce coke reduces the strength of the coke, and the upper limit of the waste plastic mixing ratio at which coke strength does not decrease is said to be approximately 1 mass% (Non-Patent Document 1). Therefore, various technologies have been developed to suppress the deterioration of coke strength due to the mixing of waste plastics.

[0005] For example, Patent Document 1 discloses a method for pyrolysis recycling in which waste plastics are charged above the raw materials in the coke oven chamber at least one hour after the raw materials are charged into the coke oven chamber. The method claims that by utilizing the space above the coke oven, a large amount of waste plastics can be recycled without affecting the strength of the coke.

[0006] Meanwhile, a technique for charging preformed coal into a coke oven has been developed as a technique for improving coke strength. For example, Patent Document 2 discloses a technique for charging coal briquettes, which are formed by briquetting coal, into the coke oven chamber together with powdered coal. This technique specifies the bulk density and dimensions of the briquettes and the particle size blend of the powdered coal. By eliminating the segregation of the briquettes, it is said that this suppresses variation in coke quality and prevents damage to the coke oven refractory due to a local increase in the amount of expansion of the charged coal.

[0007] Patent Document 3 discloses a raw coal segregation prevention device that can suppress the segregation of briquettes and prevent the deterioration of coke quality. The segregation prevention device is installed below the charging port and has a charging control member with a plurality of holes through which briquettes and coal pass. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2019-135281 [Patent Document 2] Japanese Patent Application Laid-Open No. 2018-168296 [Patent Document 3] Patent Publication No. 2021-028387 [Non-patent literature]

[0009] [Non-Patent Document 1] Nomura, Seiji, Kato, Kenji, Nakagawa, Tomoyuki, Furumaki, Ikuo Journal of the Japan Institute of Energy, Vol. 81, No. 8 (2002) pp. 728-737 Summary of the Invention [Problem to be solved by the invention]

[0010] However, the conventional technology has the following problems. In the conventional technology, the volume of resin granules is 6000 to 200,000 mm 3 It is said that if this is the case, the effect on the decrease in coke strength will be small, but in reality, adding large amounts of granular molded plastic will cause a decrease in coke strength.

[0011] Furthermore, as described in Patent Document 1, charging a large amount of waste plastic into a coke oven reduces the strength of the coke. The technology disclosed in Patent Document 1 has a unique problem: after charging coal, the raw material charging lid must be opened and synthetic resin molded materials must be charged. To prevent gas leakage, it is necessary to ensure that the amount of gas generated does not exceed the amount of gas suction. However, if the amount of gas generated in the coke chamber increases due to fluctuations in coal quality or other causes, there is a risk that the generated gas will leak to the outside and cause abnormal combustion. Furthermore, since synthetic resin molded materials are charged after the raw materials are charged into the coal tower, a dedicated hopper for waste plastics must be provided on top of the coal car. Furthermore, the additional steps required for raw material charging reduce the productivity of the coke oven.

[0012] Furthermore, the techniques disclosed in Patent Documents 2 and 3 are intended to avoid adverse effects when blending molded coal, and are primarily aimed at preventing segregation of the molded coal. In addition, adopting the measures disclosed in Patent Documents 2 and 3 also poses the problem of increased production costs. Furthermore, no specific method has been considered for blending molded coal to improve the deterioration of coke strength caused by blending resins into raw materials.

[0013] The present invention has been made in consideration of the above circumstances, and aims to propose a method for arranging raw materials in a coke oven and a method for producing coke that can suppress a decrease in coke strength when resins are blended. [Means for solving the problem]

[0014] The method of arranging raw materials in a coke oven according to the present invention, which advantageously solves the above-mentioned problems, is characterized in that when resin molded products and molded coal are charged into a coke oven together with non-molded coal as coke raw materials, the molded coal optionally contains less than 1.0 mass% of resins excluding binders, and the resin molded products and the molded coal are arranged in close proximity to each other.

[0015] The method for placing raw materials in a coke oven according to the present invention is as follows: (a) distributing the molded resins and the molded coal unevenly in the vicinity of the machine side and the vicinity of the coke side of the carbonization chamber; (b) dividing the carbonization chamber into four or more equal regions in the longitudinal direction, and allocating more of the resin moldings and the molded coal to the region in contact with the machine side and the region in contact with the coke side than to other regions; (c) the sum of the amounts of the molded resins allocated to the area in contact with the machine side and the area in contact with the coke side is 75% or more of the amount of the molded resins charged to the entire coke oven, and the sum of the amounts of the molded coals allocated to the area in contact with the machine side and the area in contact with the coke side is 75% or more of the amount of the molded coals charged to the entire coke oven; would be a more preferable solution.

[0016] The coke manufacturing method of the present invention, which advantageously solves the above-mentioned problems, is characterized by carbonizing molded resin products, molded coal, and non-molded coal that have been charged using any of the above-mentioned raw material arrangement methods for a coke oven. [Effects of the Invention]

[0017] In the present invention, the decrease in coke strength caused by the addition of resin moldings can be suppressed by adding molded coal together with the resin moldings. Resins are mostly composed of volatile components, and when carbonized together with coal, the volatile components escape as gas, which is thought to cause holes to form inside the coke. By placing the resin moldings and molded coal close to each other in the carbonization chamber, the voids created by the gasification of the resin moldings absorb the local expansion of the molded coal, suppressing the decrease in coke strength and reducing the risk of damage to the furnace body. Furthermore, the constraints on the bulk density of the molded coal can be relaxed.

[0018] In addition, due to their shapes, molded resins and molded coal tend to roll and segregate. However, since the segregation of both materials in the same area cancels out the adverse effects on coke strength, no special measures to prevent segregation are required. Therefore, application of the present invention improves coke productivity, extends the life of equipment, and contributes to environmental conservation, making it industrially useful. [Brief explanation of the drawings]

[0019] [Figure 1] 1A and 1B are schematic diagrams illustrating a method for disposing raw materials in a coke oven according to one embodiment of the present invention, in which (a) is a plan view and (b) is a side view. [Figure 2] 5A and 5B are schematic diagrams illustrating a method for disposing raw materials in a coke oven according to another embodiment of the present invention, in which (a) is a plan view and (b) is a side view. DETAILED DESCRIPTION OF THE INVENTION

[0020] The following is a detailed description of embodiments of the present invention. The following embodiments are intended to exemplify equipment and methods for embodying the technical concept of the present invention, and are not intended to limit the configuration to those described below. In other words, the technical concept of the present invention can be modified in various ways within the technical scope defined in the claims.

[0021] In this embodiment, for example, a resin molded product molded by a twin-screw extruder is mixed with coal and used as a coke raw material. In this case, in order to suppress a decrease in coke strength after carbonization, molded coal is also added as a coke raw material, and the resin molded product and the molded coal are placed in close proximity. Note that the molded coal may be molded using a molding device such as that described in Patent Document 2, for example.

[0022] The molded coal contains a few mass percent of pitch or tar as a binder. This binder is used to improve the adhesion between coal particles when molding before charging into a coke oven, thereby improving coke strength. The use of a binder in molded coal is important for improving the strength of molded coal. In contrast, in this embodiment, molded coal and molded resins are placed in close proximity to each other to offset the expansion of the molded coal and the shrinkage due to gasification of the resins. To achieve a similar effect with molded coal alone, it is also possible to incorporate resins in addition to the binder into the molded coal. In this case, adding a large amount of non-binder resins to the molded coal reduces the adhesion between coal particles. Even if the expansion of the molded coal can be suppressed, this will actually result in a decrease in coke strength. Therefore, it is preferable to limit the content of non-binder resins in the molded coal used in this embodiment to less than 1.0 mass percent. It is more preferable to eliminate non-binder resins.

[0023] During development, the inventors used waste plastics as an example of resins in a test carbonization furnace under various conditions, mixed the waste plastics with molded coal, and investigated the effect of adding molded waste plastics on coke strength. The amount of molded waste plastics added is a major factor that affects strength reduction. When waste plastics are carbonized in coal, they contain a large amount of volatile matter, which causes voids to form after volatilization, resulting in voids within the coke after carbonization. Since voids are the starting point for cracks within the coke, it is thought that the more voids there are, the more cracks will form, and the lower the coke strength will be.

[0024] Meanwhile, molded coal is produced by compacting coal, which melts and expands during carbonization. By placing waste plastic and molded coal together, it was thought that it would be possible to fill the voids that occur in the waste plastic during carbonization with the expansion of the molded coal. Furthermore, since biomass also has a high volatile content, the same effect can be achieved when biomass is included in molded resin products.

[0025] In this embodiment, a carbonaceous material containing resins is molded, and then a predetermined amount is mixed with coal and molded coal and charged into a coke oven. Resins include used plastics from general waste, commonly known as waste plastics, as well as industrial waste plastics such as scraps and defective products of synthetic resins generated in the manufacturing process, and also biomass.

[0026] In this embodiment, the amount of resin molded material added to the coke oven is not particularly limited, but it is preferable to use as much as possible from the viewpoint of environmental protection. As a guideline, the amount is 0.1 mass% or more relative to the total raw materials charged to the coke oven. There is no particular upper limit, but adding more than 20 mass% may reduce the strength of the coke.

[0027] In this embodiment, the amount of molded resins mixed with coal can be selected depending on the size of the coke oven, the mass of resins added per mass of raw materials charged to the coke oven, the required strength of the coke, and other factors. For example, a coke oven with a coal loading capacity of 30 to 40 t, a coke oven width of 35 to 50 cm, and a coke strength of 84 or higher as measured by the DI (150 / 15) index (a 15 mm sieve index) after 150 rotations as specified in JIS K2151:2004 is used. When mixing molded resins in this coke oven, a content of more than 20% by mass of the raw materials charged to the coke oven is preferably 20% by mass or less, since a significant decrease in coke strength occurs when the content exceeds 20% by mass. The amount of molded resins varies depending on the amount of molded coal charged at the same time, the size of the coke oven, and operating conditions, so it is preferable to set it individually.

[0028] (How raw materials are arranged in a coke oven) In this embodiment, when coal, molded resins, and molded coal are supplied as raw materials to the carbonization chamber of a coke oven, the molded resins and molded coal are placed in close proximity to each other. This allows the expansion of the molded coal to fill voids created by the vaporization of the resins during carbonization, thereby maintaining the strength of the coke. As a method for placing the molded resins and molded coal in close proximity to each other, for example, the molded resins and molded coal may be supplied to the coke oven simultaneously, separately from the coal to be molded.

[0029] The molded resins are often cylindrical, while the molded coal is often ellipsoidal. These tend to roll and segregate more easily than molded coal in a coke oven. In this embodiment, as long as the molded resins and the molded coal are placed close to each other, even if segregation occurs, the expansion of the molded coal is absorbed by the voids in the vaporized resins, and the furnace body is not damaged.

[0030] In this embodiment, it is preferable to dispose the resin molded products and molded coal unevenly at the ends of the coke chamber in the longitudinal direction. That is, they are disposed so that the mixture ratio of resins and molded coal on the coke discharge side (hereinafter referred to as the coke side (C / S)) and the coke extrusion side (hereinafter referred to as the machine side (M / S)) is as high as possible. The mixture ratio of resins is calculated as a percentage by mass, using the formula: mass of resins / (mass of non-molded coal + mass of resins + mass of molded coal) × 100. The mixture ratio of molded coal is calculated as a percentage by mass, using the formula: mass of molded coal / (mass of non-molded coal + mass of resins + mass of molded coal) × 100.

[0031] In this embodiment, the interior of the coke chamber is divided into four or more equal regions along the longitudinal direction of the coke chamber. The resins and briquettes are preferably charged so that the mixing ratios of the resins and briquettes in the region adjacent to the coke side and the region adjacent to the machine side exceed those in the other inner regions. Furthermore, it is more preferable that the mixing ratios are three times or more. In this case, the total mass of the resins and briquettes charged in the region adjacent to the coke side and the region adjacent to the machine side is preferably 75% or more of the total. In this case, the mixing ratios of the resins and briquettes in the other inner regions are each 50% or less of the average mixing ratio of the resins and briquettes. Therefore, the strength decrease of the coke after carbonization in this region can be suppressed to at least 50% or less compared to when the resins are uniformly distributed. Furthermore, if the resins and briquettes are closely arranged in this region, the decrease in coke strength can be further suppressed. Although there is no upper limit to the number of regions in the coking chamber, taking into consideration the installation load of the raw material charging equipment, it is preferable to divide the coking chamber into 10 or less regions, and more preferably 6 or less regions.

[0032] Typically, the coke oven chamber has a long, narrow, roughly rectangular parallelepiped shape (for example, 0.6m W x 15m D x 7m H). To distribute the raw materials evenly throughout the chamber, coal is charged through multiple coal inlets aligned along the chamber's length (direction D). By increasing the mixing ratio of resins and molded coal with the raw materials charged through the inlet closest to the coke side or machine side, it is possible to concentrate the resins and molded coal unevenly near the coke side or machine side.

[0033] (Coke manufacturing method) The molded resins and molded coal are loaded into a hopper, then fed at a constant speed by a metering feeder onto the coal on a belt conveyor that supplies blended coal to the coke oven. By adjusting the amount of molded resins added so that the value obtained by dividing the amount of molded coal by the mass of the raw materials is below a certain level, it is possible to suppress a decrease in coke strength after carbonization. Furthermore, by adjusting the value obtained by dividing the amount of molded coal by the mass of the raw materials, it is also possible to increase the upper limit of the amount of molded resins added.

[0034] As an index of coke strength, the drum strength index (DI(150 / 15)) can be used according to the drum strength measurement method specified in JIS K2151:2004, a coke testing method. The drum strength index (DI(150 / 15)) is measured by charging coke into a drum testing machine, rotating it 150 times, and then sieving it through a 15-mm sieve to measure the mass fraction of the remaining coke. When using the drum strength index (DI(150 / 15)), it is preferable to ensure that the decrease in DI(150 / 15) is less than 1 point. The DI(150 / 15) index is known to have a measurement error of approximately 0.5 points, and a decrease in strength of 1 point or more clearly indicates a decrease in coke strength. In coke oven operation, a decrease in coke strength (DI(150 / 15)) of 1 point or more is recognized as a decrease in coke strength, and measures such as improving the quality of the coking coal may be taken.

[0035] The amount of resin moldings added can be measured by placing a camera above the conveyor belt after the moldings have been added, taking pictures, and analyzing the images. A simpler method is to measure the mass of each resin molding multiple times. The amount of molded charcoal added can also be evaluated in a similar manner.

[0036] The cut-out position for the molded resins is preferably at a low point on the conveyor belt after passing through the coal drying facility (CMC). Because the coal is heated and dried in the CMC, if molded resins are added before the CMC, there is a risk that they will melt inside the CMC. The molded resins are fed to the carbonization chamber via a coal tower and coal transport car along with the blended coal. The resins and biomass are thermally decomposed in the carbonization chamber, and some remain as charcoal, but most are by-produced as gas and tar.

[0037] The position of the molded charcoal may be the same as that of the molded resin material. However, unlike the molded resin material, there is no risk of melting, so there is no problem even if the molded charcoal is cut out before CMC. [Example]

[0038] A mixture of waste plastics mainly composed of thermoplastic resins was crushed and molded into a cylindrical shape using a twin-screw extruder. Furthermore, coal was molded into a Massek mold using a double-roll molding machine as described in Patent Document 2. The resulting molded waste plastics were mixed with approximately 40 kg of blended coal used as a coke raw material in the mixing ratio (addition amount a [mass %]) shown in Table 1, and molded coal was mixed with the mixing ratio (addition amount b [mass %]) shown in Table 1. When waste plastics were added to molded coal, the amount of the mixture (resin content [mass %]) shown in Table 1 was mixed into the molded coal.

[0039] (equal distribution) When arranging the molded waste plastics and briquettes, the amount of blended coal was divided into eight parts, and 1 / 8 of the blended coal was first laid out in the carbonization vessel. Then, a predetermined amount (1 / 4 of the planned amount to be charged) of molded waste plastics and briquettes was laid out at 1 / 4 and 3 / 4 positions from one end of the carbonization vessel in the longitudinal and width directions, respectively. Next, another 1 / 8 of the blended coal was charged, and the density of the charged coal was 830 kg / m 3 This process was repeated four times so that when the carbonization tank 3 was divided into four sections in the longitudinal direction, the mixture ratio of the waste plastic molded products and molded coal was the same in each section. Figure 1 shows an example in which the waste plastic molded products 1 and molded coal 2 are packed into the carbonization tank 4 in a uniform arrangement close to each other among the non-molded coal 3.

[0040] (segregation arrangement) When arranging the molded waste plastics and briquettes, the amount of blended coal was divided into eight parts, and first, 1 / 8 of the blended coal was laid out in the carbonization vessel. After that, a predetermined amount (1 / 4 of the planned amount to be charged) of molded waste plastics and briquettes was placed so that they were in contact with one end of the carbonization vessel in the longitudinal direction. Next, another 1 / 8 of the blended coal was charged, and the density of the charged coal was 830 kg / m 3 This process was repeated four times, and the waste plastic moldings and molded coal were arranged so that they were concentrated at one end of the can in the longitudinal direction. Figure 2 shows an example in which waste plastic moldings 1 and molded coal 2 are segregated and placed close to each other among non-molded coal 3 and packed into a carbonization can 4.

[0041] The moisture content of the coal blend was adjusted to 8%. After carbonization at 700 to 1100°C for 20 hours, the coal was rapidly cooled by pouring water over it from above, and then dried to obtain coke. The obtained coke was charged into a drum testing machine and rotated 150 times according to the drum strength measurement method specified in JIS K2151:2004, a coke testing method. The mass fraction of the remaining coke after sieving through a 15 mm mesh sieve was measured as the drum strength index DI (150 / 15).

[0042] Table 1 shows the relationship between the amount of waste plastic moldings (a), the amount of molded coal (b), and the arrangement method and the change in coke DI intensity, ΔDI (150 / 15). In the arrangement column, "evenly isolated" indicates that the moldings or molded coals are evenly arranged. "evenly adjacent" indicates that the moldings and molded coals are evenly arranged in close proximity. "segregated isolated" indicates that the moldings or molded coals are segregated in close proximity. "segregated adjacent" indicates that the moldings and molded coals are segregated in close proximity. The segregation rate indicates the proportion of moldings or molded coals present in the two end regions when the carbonization can is divided into four sections longitudinally. The expansion evaluation was performed by observing the cans containing the raw materials after carbonization to determine whether the cans were damaged due to the expansion of the raw materials. A "◎" indicates that the cans retained their original shape. A "〇" indicates that the cans were slightly bulging but not damaged. A "△" indicates that the cans were bulging and had scratches. Cans that have expanded significantly and are damaged are indicated with an "X" mark. For waste plastic moldings and molded coal, segregation measures are necessary to ensure uniform distribution, and are marked as "required." Others are marked as "not required."

[0043] For the overall evaluation, the standard conditions in which no waste plastic molded products or molded coal were charged were rated C. A case in which the DI strength decreased by 0.5 points or more from the standard conditions, or the expansion rating was "△" or "×", was rated E. A case in which the DI strength decreased by less than 0.5 points and the expansion rating was "〇" was rated D. A case in which the DI strength improved and the expansion rating was "〇" was rated B. A case in which the DI strength improved by less than 0.5 points and the expansion rating was ◎ was also rated B. A case in which the DI strength improved by 0.5 points or more and the expansion rating was ◎ was rated A.

[0044] [Table 1]

[0045] The results in Table 1 show that Tests 9 to 17, in which resin moldings and molded coal are placed in close proximity, can produce coke without compromising expansion properties while suppressing or improving the decrease in coke strength. In particular, by placing the resin moldings and molded coal in close proximity and segregating them, coke strength can be improved even when a large amount of resin moldings (3 to 20 mass%) is blended. When the resin moldings and molded coal are placed in a segregated manner, it was found that a segregation rate of 75% or more is highly effective in improving coke strength. Placing the resin moldings in close proximity at a mass exceeding 10% of the mass of the molded coal resulted in excellent expansion properties.

[0046] Tests Nos. 2 to 6, which contained only molded resins, showed a significant decrease in coke strength. Tests Nos. 7 and 8, which contained only molded coal and arranged in a segregated manner, resulted in can damage. Test No. 18, which contained only molded coal and arranged evenly, showed the greatest improvement in coke strength, but can expansion was observed. Test No. 19 showed a decrease in coke strength and can damage. Test No. 20 showed no noticeable decrease in coke strength, but the can expanded slightly. [Explanation of symbols]

[0047] 1. (Waste plastic) Molded products 2 Molded coal 3 Unmolded coal 4. Carbonization chamber

Claims

1. When resin molded products and molded coal are charged into a coke oven together with non-molded coal as coke raw materials, The molded coal optionally contains less than 1.0% by weight of resins, excluding binders; The resin molded product and the molded charcoal are placed in close proximity to each other. How materials are arranged in a coke oven.

2. 2. The method for arranging raw materials in a coke oven according to claim 1, wherein the molded resin products and the molded coal are unevenly distributed in the vicinity of the machine side and in the vicinity of the coke side of the carbonization chamber.

3. A method of arranging raw materials in a coke oven as described in claim 2, wherein the carbonization chamber is divided equally into four or more regions in the longitudinal direction, and more of the resin moldings and the molded coal are allocated to the region adjacent to the machine side and the region adjacent to the coke side than to other regions.

4. the sum of the amount of the molded resins distributed to the area in contact with the machine side and the area in contact with the coke side is 75% or more of the amount of the molded resins charged to the entire coke oven; 4. The method of claim 3, wherein the sum of the amount of molded coal allocated to the area in contact with the machine side and the area in contact with the coke side is 75% or more of the amount of molded coal charged to the entire coke oven.

5. A method for producing coke, comprising carbonizing molded resins, molded coal, and non-molded coal charged into a coke oven by the method for disposing raw materials in the coke oven according to any one of claims 1 to 4.

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