JP4088054B2 - Coke production method - Google Patents

Description

【００５９】
【発明の効果】
本発明により、石炭をコークス炉で乾留する際に、廃プラスチックを用いる高炉用コークスを製造する方法において、添加する廃プラスチックの粒度を所定値以下に制御して乾留することにより、廃プラスチックの種類などの製造条件に応じて強度の高い高炉用コークスを製造することが可能となった。
【００６０】
また、コークス製造に際して石炭に添加して所定のコークス強度を満足できるように用いることができる廃プラスチックの添加率を高くすることができるので、廃プラスチックのリサイクルをより有効化できるという利点が得られる。
【００６１】
これらのことにより、本発明によって、廃プラスチックが多量にリサイクル処理可能となり、その経済的効果は極めて大きい。
【図面の簡単な説明】
【図１】プラスチック粒度とドラム強度の関係を示す図である。
【図２】全膨張率ＴＤとドラム強度の関係を示す図である。
【図３】プラスチック粒度とプラスチックを添加した石炭のＴＤの関係を示す図である。
【図４】本発明の製造方法で用い得るコークス炉の設備の概略を示す図である。
【符号の説明】
１・・・コークス炉
２・・・装入原料ホッパー
３・・・上昇管
４・・・ベント管
５・・・ドライメーン
６・・・ガス冷却器
７・・・安水タンク
８・・・苛性ソーダ添加設備
９・・・脱安設備
１０・・・廃プラスチックを混合した石炭[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing coke by blending waste plastic with a raw material charged in a coke oven.
[0002]
[Prior art]
Regarding the disposal of waste plastics that are discharged in large quantities as plastic industrial waste and general plastic waste, most of them have been landfilled and partly combusted. In general, waste plastics are not decomposed by bacteria and bacteria in the soil just by landfilling. Further, when waste plastic is incinerated, the calorific value is large and adversely affects the incinerator. In the case of waste plastic containing chlorine, the treatment of chlorine in the exhaust gas is a problem. In view of the anticipated shortage of landfill sites in the future and growing environmental problems, it is desirable to promote the recycling of such waste plastics. As a recycling method, in addition to the reuse of plastics, a method of using gas or oil obtained by the use of heat during combustion or pyrolysis as a fuel or chemical raw material can be considered.
[0003]
As a method of processing waste plastic by adding it to a coke oven, for example, in Japanese Patent Laid-Open No. 48-34901 and Japanese Patent Laid-Open No. 8-157634, a method of producing coke by adding waste plastic to coking coal charging coal. Is disclosed. In these methods, most of the plastic waste is pyrolyzed at a high temperature during coke dry distillation, and recovered as a coke oven gas as a high calorie reducing cracking gas such as hydrogen, methane, ethane, and propane.
[0004]
[Problem to be solved]
By the way, as described in JP-A-48-34901, among the above-mentioned prior art problems, a method in which a large amount of plastic is uniformly mixed and used in coal causes a reduction in coke strength. It is said that the amount of waste plastic added needs to be 1% by mass or less as disclosed in Japanese Patent Laid-Open No. 8-157834. In order to prevent the coke strength from being lowered, it is necessary to increase the blending ratio of caking coal having high caking properties. However, caking coal is less expensive and more expensive than non-minor caking coal. Thus, in order to effectively use non-slightly caking coal that has a large amount of resources and is cheap, it has been desired to develop a method that uses more waste plastic without increasing the blending ratio of caking coal. .
[0005]
The present invention proposes a method for producing high-strength blast furnace coke even if waste plastic is added, by controlling the particle size of waste plastic added to the blast furnace coke raw coal to a predetermined level or less and performing dry distillation. It is.
[0006]
[Means for Solving the Problems]
The present invention has the following configuration.
[1] A method for producing coke using coal and waste plastic as a raw material charged in a coke oven, wherein the waste plastic is an aliphatic system that does not contain oxygen, and for producing coke having a drum strength of 84 or more. the addition rate of the waste plastic and 0.3 to 3 wt%, a = 0.013-0.026, and b = 1 to 2, the type of the waste plastics, the addition rate of the waste plastics, the total expansion rate of coal , and based on the coal charging Nyukasa density (1) determined the particle size upper limit of the waste plastics by type, the waste plastic is crushed to the particle size upper limit value or less of the particle size, evenly added waste plastics into the coal A method for producing coke for a blast furnace, characterized in that coke is produced.
[0007]
Upper limit of particle size (mm) = (a · TD + b) · BD (1)
TD (%): a total expansion index measured in the dilatometer method in accordance with the dilatometer method specified in JIS M8801,
BD (t / m ³ ): coal bulk density (based on dry coal),
a, b: Constants determined according to the type and addition rate of waste plastic.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be specifically described.
[0009]
In order to solve the above-mentioned problems, the present invention obtains an upper limit value of the particle size according to several production conditions, and uses waste plastic having a particle size of a predetermined upper limit value or less as a coke oven charging raw material. A method for producing high blast furnace coke is proposed. As a usage mode of the waste plastic, it is desirable that the waste plastic is uniformly mixed with all or a part of the coal charged into the coke oven and then charged into the coke oven.
[0010]
The waste plastic used in the present invention is only required to have a predetermined particle size, and specifically, a lump of waste plastic adjusted to a predetermined particle size by pulverization or the like can be used. Heat the film, foam, and powdery waste plastic in the temperature range of 80 ° C to 190 ° C, apply compression in the heated state, cool again and solidify by volume reduction, then pulverize as necessary What was agglomerated by processing etc. and adjusted to a predetermined particle size can be used. As the volume reduction and solidification method, those conventionally used such as a resin kneader, a pulverizer, and a drum-type heater can be used. By doing in this way, the troubles, such as a small bulk specific gravity and the difficulty of charging when the waste plastics of the film, foam and powder are crushed as they are, can be solved. Further, the particle size may be adjusted by sieving as necessary.
[0011]
In this specification, “granular” mainly means to specify the size. The shape of the granular material includes a spherical shape, an elliptical shape, a cylindrical shape, and the like. In addition, the “particle size” of one granular material means the maximum width of the granular material, for example, the diameter of a spherical shape, and the maximum width of vertical and horizontal or thickness if the shape is not spherical. The particle size of the waste plastic used in the present invention is determined by predetermined requirements as described below.
[0012]
Generally, coal is classified into caking coal with high caking properties and non-minor caking coal with low caking properties. In the coke production process, caking coal and non-caking caking coal are used so that a predetermined coke quality can be obtained. It is blended and used at a predetermined ratio.
[0013]
Non-coking coal is a coal whose maximum fluidity is 10 ddpm or less in the fluidity test by the Gisela plastometer method specified in JIS M 8801, or whose average reflectivity of vitrinite is 0.8 or less. Show.
[0014]
Conventionally, since the strength of blast furnace coke is reduced when the amount of waste plastic added is too large, the upper limit of the amount of waste plastic added is usually considered to be 1% by mass.
[0015]
In contrast, the inventors of the present inventors have intensively studied strength reduction mechanism coke upon addition waste plastics, when homogeneously mixed and dry distillation of waste plastic raw material coal, as well as the addition rate of the waste plastic, waste plastic click particle size also affect coke strength, coke strength waste plastics granularity at the same addition rate differs found different. Based on this knowledge, the inventor has invented a method for producing high-strength blast furnace coke by adjusting the waste plastic particle size.
[0016]
This knowledge will be specifically described below. FIG. 1 shows the results of examining the change in coke strength due to the difference in the particle size of waste plastics when coking is performed by adding 2% by mass of polyethylene and polystyrene of various particle sizes to coal. Here, the coal used 50% by mass of caking coal and 50% by mass of non-slightly caking coal. Using a test coke oven with a furnace width of 425 mm, a furnace height of 400 mm, and a furnace length of 600 mm, plastic was added and charged at a charging density of 0.83 dry-t / m ³ , furnace temperature of 1250 ° C., dry distillation time Dry distillation was carried out under conditions of 18.5 hours. For coke after calcination After cooling in nitrogen was measured coke drum strength (DI ¹⁵⁰ _15). In this specification, the drum strength (DI ¹⁵⁰ ₁₅ ) of coke is charged with 10 kg of coke into a drum tester (diameter and length: 1,500 mm, 4 blades) as described in JIS K 2151. Then, after rotating 150 times, it is sieved with a 15 mm sieve, and the mass remaining on the sieve is expressed as a percentage.
[0017]
As shown in FIG. 1, it can be seen that there is a plastic particle size at which the coke strength has a minimum value. The reason is considered as follows.
[0018]
When plastic is added to coal (in this example, polyethylene and polystyrene) and the carbon is pyrolyzed, the thermal decomposition temperature of the plastic is lower than or equal to the softening and melting temperature range of the coal. Therefore, since at most 20-30% by mass remains as a residue, if the plastic particle size is large, large voids remain after pyrolysis. For this reason, when the coal that has been in contact with the plastic is softened and melted, the coal expands freely toward the gap, and a foamed brittle coke structure is formed. Furthermore, in the case of plastics that inhibit coal caking, such as polystyrene, the caustic properties of coal in contact with the plastics are hindered by the chemical action of the pyrolysis gas, resulting in the formation of weaker and weaker coke structures. Is done.
[0019]
However, as the size of waste plastic added increases, the area where coal and plastic per unit waste plastic added mass decrease and the number of places that become weak coke structures decreases. If the size of the coke is exceeded, the coke strength increases.
[0020]
On the other hand, when the particle size of the plastic is small, it is included in the softened and melted layer, so that the expansibility of the softened and melted coal is inhibited. Here, the expansibility is a total expansivity index measured in an expansibility test by the dilatometer method defined in JIS M8801. The reason why the expansibility is hindered is that there is a physical effect that the actual charge bulk density of coal is reduced due to void formation after plastic pyrolysis, and plastics that inhibit coal caking (eg polystyrene) This is thought to be due to the chemical effect of the coal itself being altered by the pyrolysis gas of polyethylene terephthalate. When the expansibility is inhibited, the fusion bond between coals is inhibited, and the coke strength is lowered.
[0021]
However, the inventors have found that when the particle size of the waste plastic to be added is smaller than a predetermined size, the inhibition of expansibility is suppressed. This is presumably because when the plastic particle size is reduced, the plastic pyrolysis gas is trapped between the molten coal particles, and conversely, the effect of promoting the expansion of the coal occurs. For this reason, the smaller the plastic particle size, the smaller the adverse effect on coke strength.
[0022]
The reason why there is a plastic particle size at which the coke strength has a minimum value is considered to be as described above.
[0023]
Based on the above knowledge, in order to suppress the reduction of coke strength due to the addition of plastic, avoid the particle size of the plastic that can cause the coke strength to be lower than the predetermined strength, make the particle size smaller or larger than that particle size You can see that
[0024]
In the case where the plastic particle size is larger than a predetermined size, the inventors have already specifically (1) characterized in that the particle size of the waste plastic added to the coal is 10 times or more the average particle size of the coal. (2) The method for producing coke according to (1), wherein the average particle size of the coal is 0.6 to 2.0 mm, (3) Volume reduction of waste plastic A coke production method characterized by being solidified and used as a coke oven charging raw material has been invented (Japanese Patent Laid-Open No. 2001-49263).
[0025]
On the other hand, in the case where the plastic particle size is smaller than the predetermined size, it has been unknown until what particle size the plastic should be crushed.
[0026]
The present inventor has further researched and found that when the particle size of the waste plastic is made smaller than a predetermined size, not only the reduction of the coke strength is suppressed but also the coke strength may be improved. And when this inventor examined the upper limit of the waste plastic particle size, it discovered that an upper limit changed with the expansibility of coal, the charging bulk density of coal, a plastic kind, and the addition rate of a plastic.
[0027]
According to the inventor's study, in order to produce coke with high strength, it is necessary for the softened and melted coal to be bonded to each other. For this purpose, the coal bulk density and the coal expansibility are predetermined. It is necessary to exceed the value. In other words, even if the charge bulk density is low, if the coal expandability is sufficiently large, or if the charge bulk density is sufficiently high even if the coal expandability is small, it is possible to produce high strength coke. It is.
[0028]
The inventors have found that when coal with high expansibility is used, the plastic particle size giving the minimum coke strength shifts to the large particle size side. This is because, in the plastic particle size range where the coke strength decreases as the plastic particle size increases, the larger the plastic particle size, the more the coal expandability is inhibited. This is because, even if the properties are hindered, the expandability after the plastic addition is sufficient to produce coke with high strength.
[0029]
It was also found that the plastic particle size giving the minimum coke strength shifts to the large particle size side even when the coal bulk density is improved. This is because, in the plastic particle size range where the coke strength decreases as the plastic particle size increases, the larger the plastic particle size, the more the coal expandability is inhibited. This is because it is sufficient to produce coke with high strength.
[0030]
It was also found that the plastic particle size giving the minimum coke strength varies depending on the type of plastic. For example, as shown in FIG. 1, aromatic polystyrene has a smaller plastic particle size that gives a minimum coke strength than polyethylene. This is because polystyrene has an action of inhibiting the caking property of coal and suppresses the expansion of coal.
[0031]
According to the study of the present inventor, there are plastics that are difficult to inhibit coking caking and those that are likely to be inhibited. Typical examples of plastics that do not easily inhibit coking caking properties include aliphatic plastics that do not contain oxygen, such as polyethylene, vinyl chloride, polypropylene, and polyvinylidene chloride. On the other hand, typical examples of plastics that easily inhibit coking caking are aromatic compounds such as polystyrene and polyethylene terephthalate, and plastics that contain oxygen atoms in structural formulas such as polyester and polyvinyl acetate. Etc.
[0032]
Aliphatic plastics that do not contain oxygen have no inhibitory effect on coal caking properties because the gas generated by plastic pyrolysis is an aliphatic gas that contains a large amount of hydrogen. This is because the action is small.
[0033]
Based on the above knowledge, in order to obtain the desired high strength coke, the inventors according to the production conditions such as the total expansion rate of coal, the bulk density of coal charge, the type of waste plastic, the addition rate of waste plastic. The present invention invented a method for producing coke by adjusting the particle size of waste plastic to a particle size upper limit value or less (for example, pulverization) determined by the equation (1) and adding this waste plastic to raw coal for coke production.
[0034]
Upper limit of particle size (mm) = (a · TD + b) · BD (1)
(1) where
TD (%): a total expansion index measured in the dilatometer method in accordance with the dilatometer method specified in JIS M8801,
BD (t / m ³ ): coal bulk density (based on dry coal),
a, b: constants that vary depending on the type and addition rate of waste plastics,
It is.
[0035]
Here, the constants a and b vary depending on the target coke strength, but specifically, they may be obtained by the following method.
[0036]
First, at a constant charge bulk density BD, various blended coals are dry-distilled without adding plastic, and the relationship between TD and drum strength is obtained to maintain a predetermined drum strength as shown in FIG. Find the minimum required TDmin. For example, in the example of FIG. 2, when the charging bulk density BD = 0.83 (t / m ³ ) and the drum strength is 84 or more, TDmin = 45%.
[0037]
Next, TD is measured by adding a predetermined ratio of plastics having different particle sizes to the above blended coal, and a particle size upper limit Dmax such that TD is equal to or greater than TDmin as shown in FIG. Ask. For example, in the example of FIG. 3, when the plastic addition rate is 2% by mass, TDmin = 45%, whereas when the blended coal TD = 50%, the particle size upper limit Dmax = 2.1 mm.
[0038]
Thus, Dmax was obtained for each blended coal TD, and the relationship between TD and Dmax was obtained by changing BD. The inventors found that Dmax is proportional to BD and is a linear function of TD. I found that I can represent it. Therefore, the particle size upper limit Dmax can be expressed in the form of the product of the primary expression of BD and TD as in the above expression (1), and the constants a and b in the expression (1) can be expressed from the graph as shown in FIG. If it asks for, even if charging bulk density BD and compounding total expansion index TD change, if the plastic particle size is adjusted below the upper limit particle size defined by the formula (1), coke with high strength can be obtained.
[0039]
The constants a and b in the equation (1) may be obtained by the same method as described above even when the type of waste plastic and the addition rate change.
[0040]
For example, according to the study example of the present inventor, when 2 mass% of aliphatic waste plastic not containing oxygen is added to coal, if a = 0.0193 and b = 1.547, the drum strength is 84. It was possible to produce the above coke.
[0041]
Furthermore, according to the study example of the inventors, when producing coke having a drum strength of 84 or more with an addition rate of 0.3 to 3% by mass of an aliphatic waste plastic not containing oxygen , a = 0.013 to 0 .026, b = 1-2.
[0044]
Further, the lower limit value of the waste plastic particle size is not theoretical, and may be determined in consideration of actual processes such as pulverization and transportation.
[0045]
The upper limit value of the waste plastic addition rate is not particularly defined as long as it is within a range in which coke having the desired strength can be produced. According to the study by the inventors, when the addition rate exceeds 5% by mass, the blast furnace Since it becomes difficult to produce coke having a strength that can be used in the above, the addition rate is desirably 5% by mass or less. Furthermore, since the amount of coke produced decreases due to the treatment of waste plastic, it is necessary to consider the balance between the amount of coke produced and the amount of waste plastic stick to be treated.
[0046]
Further, if the target coke strength is the same level, a large amount of waste plastic can be treated in the case of aliphatic waste plastic not containing oxygen. This is because aliphatic plastics that do not contain oxygen do not inhibit coal caking, while aromatic plastics such as polystyrene and polyethylene terephthalate and plastics containing oxygen such as polyester inhibit caking. Because there is.
[0047]
When coal is carbonized in a coke oven, the maximum temperature is about 1,350 ° C. On the other hand, polyvinyl chloride and polyvinylidene chloride begin to thermally decompose at about 250 ° C., gasify at about 400 ° C., and almost completely decompose at 1,350 ° C. Therefore, as long as the chlorine-containing waste plastic is pyrolyzed together with the coal in the coke oven, the pyrolysis or the carbonization temperature and the carbonization pattern may be the same as those of the conventional coal carbonization.
[0048]
Chlorine gas derived from waste plastic generated when the waste plastic is heated reacts with excess ammonia generated during the carbonization of coal. Therefore, a large amount of ammonium chloride accumulates in the aqueous solution taken out of the coke oven from the system. By adding a strong base such as sodium hydroxide (caustic soda), ammonium chloride is harmless to sodium chloride. It is possible to convert to It is desirable to add sodium hydroxide in an amount equal to or greater than that of ammonium chloride.
[0049]
In the dewatering equipment outside the system, the water is evaporated after free ammonia is removed by steam stripping, and then activated sludge is discharged. If ammonium chloride in the water is converted into sodium chloride and ammonia with sodium hydroxide before entering the safeguard, all nitrogen components contained in the safewater can be removed as ammonia, and the safe water that has exited the safeguard Only harmless sodium chloride remains, and even if it is discharged as it is, there is no fear of increasing the nitrogen content in the seawater.
[0050]
The coke production method of the present invention can be produced by a commonly used coke production facility. FIG. 4 shows an outline of an example of a coke facility that can implement the production method of the present invention.
[0051]
【Example】
Using a test coke oven with a furnace width of 400 mm, a furnace height of 1000 mm, and a furnace length of 10600 mm, waste plastics were uniformly added under the conditions shown in Table 1, and a charge bulk density BD = 0.83 dry-t / m ³ was added. It was charged at a charge density, and carbonized under conditions of a furnace temperature of 1200 ° C. and a carbonization time of 18 hours. About the coke after baking, after cooling with nitrogen, the drum strength index (+15 mm index after 150 rotations) of the coke according to JIS K2151 was measured. Table 1 shows the drum strength.
[0052]
Base conditions are the case where it dry-distills without adding a plastic only with the blended coal of caking coal 60 mass% and non-slightly caking coal 40 mass%.
[0053]
Example 1 consists of 60% by weight caking coal, 40% by weight non-caking coal, and 100% waste plastic consisting of 50% by weight polyethylene, 25% by weight polypropylene, and 25% by weight vinyl chloride. coal blend (TD = 50%) to be added 2 wt% for a case where the dry distillation. From the type of waste plastic and the addition rate, a and b are obtained by the method described in the above-mentioned “Embodiment of the Invention”, and the total expansion rate of coal and the bulk density of coal charge are calculated by the equation (1). The upper limit value of the particle size of the waste plastic is 2.1 mm, and the particle size of the waste plastic used in Example 1 is not more than the upper limit value.
[0054]
A reference example is a blended coal (TD = 50%) composed of 100% waste plastic consisting of 50% by mass of polyethylene and 50% by mass of polystyrene and 100% or less of 100% caking coal and 40% by mass of non-coking coal. This is a case where 2% by mass is added to dry distillation. From the type of waste plastic and the addition rate, a and b are obtained by the above method, and the upper limit of the particle size of the waste plastic is obtained from equation (1) from the total expansion rate of coal and the bulk density of coal charge. The particle size of the waste plastic used in the reference example is below the upper limit.
[0055]
Comparative Example 1 is a blended coal (TD = 50) consisting of 100% waste plastic consisting of 50% by mass of polyethylene and 50% by mass of polystyrene and having 100% or less of 100 mm of caking coal and 60% by mass of caking coal and 40% by mass of non-caking caking coal. %), And 2% by mass is added to dry distillation. When the upper limit value of the particle size of the waste plastic is determined from the type of waste plastic, the total expansion rate of coal, and the bulk density of coal charge according to the equation (1), it is 1.3 mm, and the particle size of the waste plastic used in Comparative Example 1 The upper limit is outside the scope of the present invention. In the comparative example 1 column of “waste plastic particle size” in Table 1, “1.5 mm or less 100%” means that 1.5 mm is adjusted to be the maximum particle size. , Waste plastic having a particle size exceeding 1.3 mm was included.
[0056]
As can be seen from Table 1, the drum intensity in Example 1 is greater than the drum strength of the dry distillation and base conditions without the addition of waste plastics, coke strength by the addition of waste plastics is improved. On the other hand, the drum strength in Comparative Example 1 is smaller than the drum strength in the base condition obtained by dry distillation without adding waste plastic. This is because the upper limit value of the waste plastic particle size used in Comparative Example 1 is outside the scope of the present invention.
[0057]
From the above, in the method of producing waste blast furnace coke by blending waste plastic with coal and carbonizing in a coke oven, it was possible to produce high strength blast furnace coke by adding waste plastic.
[0058]
[Table 1]

[0059]
【The invention's effect】
According to the present invention, in the method of producing coke for blast furnace using waste plastic when coal is carbonized in a coke oven, the type of waste plastic is obtained by controlling the particle size of waste plastic to be a predetermined value or less and performing carbonization. It became possible to produce high-strength blast furnace coke depending on the production conditions.
[0060]
Moreover, since the addition rate of the waste plastic which can be used so that predetermined | prescribed coke intensity | strength can be satisfy | filled by adding to coal at the time of coke manufacture can be made high, the advantage that recycling of waste plastic can be made more effective is acquired. .
[0061]
For these reasons, according to the present invention, a large amount of waste plastic can be recycled, and its economic effect is extremely large.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between plastic particle size and drum strength.
FIG. 2 is a diagram showing a relationship between a total expansion rate TD and drum strength.
FIG. 3 is a diagram showing the relationship between plastic particle size and TD of coal to which plastic is added.
FIG. 4 is a diagram showing an outline of equipment of a coke oven that can be used in the production method of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Coke oven 2 ... Charge raw material hopper 3 ... Rising pipe 4 ... Vent pipe 5 ... Dry main 6 ... Gas cooler 7 ... Water tank 8 ... Caustic soda addition equipment 9 ... de-safe equipment 10 ... coal mixed with waste plastic

Claims (1)

A method for producing coke using coal and waste plastic as a raw material for charging a coke oven, wherein the waste plastic is an aliphatic system containing no oxygen, and the waste plastic is used to produce coke having a drum strength of 84 or more. the addition rate of the 0.3 to 3 wt%, a = from .013 to .026, and b = 1 to 2, the type of the waste plastics, the addition rate of the waste plastics, the total expansion ratio of the coal, and coal It obtains a particle size upper limit of the waste plastics by based on instrumentation Nyukasa density (1), by crushing the waste plastic into the particle size upper limit value or less of the particle size, the coke was uniformly added to the waste plastics into the coal A method for producing coke for blast furnace, characterized in that the coke is produced.
Upper limit of particle size (mm) = (a · TD + b) · BD (1)
TD (%): a total expansion index measured in the dilatometer test according to JIS M8801
BD (t / m 3): Charging bulk density of coal (based on dry coal),
a, b: Constants determined according to the type and addition rate of waste plastic.

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