JP2006028277A - Manufacturing method of coke and waste plastic grain - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for suppressing the expansion pressure of a coke oven by adding waste plastics in charging the waste plastics into the coke oven as a charging raw material of the coke oven. <P>SOLUTION: The manufacturing method of coke is characterized by enabling the roundness of the waste plastics to become 0.5 or less on average using the waste plastics together with coal as a charging raw material of the coke oven, provided that the roundness C is the modulus represented by C=4πA/U<SP>2</SP>wherein the perimeter length of the individual is designated as U and the cross sectional area is designated as A in the cross section vertical to the major axis of the individual. The method is further characterized by enabling the average of the average particle size to become the lower limit value or more of the following particle size of the waste plastics: the particle size lower limit value=L×thickness of softening molten layer (1), provided that L is the constant determined by the type and addition rate of the waste plastics and the average particle size is an average value of the major axis diameter and the minor axis diameter of the individual. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing coke and waste plastic particles using waste plastic together with coal as a coke oven charging raw material.

  Conventionally, most of waste plastics discharged in large quantities as plastic industrial waste and general plastic waste are treated in landfills and partly combusted. Waste plastic is generally not decomposed by soil bacteria or bacteria in landfills, and when incinerated, it generates a large amount of heat and adversely affects the incinerator. In the case of waste plastic containing chlorine, the treatment of chlorine in the exhaust gas is difficult. It 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 method of recycling waste plastic, in addition to the reuse of plastic, there can be considered a method of using heat or gas or oil obtained by pyrolysis as fuel or chemical raw material in addition to recycling of plastic. As a method of adding waste plastic to a coke oven and treating it, for example, Patent Literature 1 and Patent Literature 2 disclose a method of producing coke by adding waste plastic to coking coal charging coal. 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.

  In the method in which a large amount of plastic is uniformly mixed and used in coal, the coke strength is lowered. In Patent Document 2, the amount of waste plastic added is required to be 1% by mass or less. 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.

  In Patent Document 3, when the amount of waste plastic added is the same, the larger the average particle size of the waste plastic added, the smaller the area where coal and plastic are in contact with each other. By making the average particle size of the waste plastic charged into the coal more than 10 times the average particle size of coal, it is said that the reduction in coke strength can be suppressed even if the amount of waste plastic added is increased. The average particle size of coal is preferably 0.6 to 2.0 mm.

  On the other hand, in patent document 4, when the particle size of plastic was small enough, it discovered that the space | gap after plastic pyrolysis will be filled with the coal particle which expanded by softening and melting. According to this document, if the size of the plastic particles is such that it is almost completely absorbed into the softened melt layer, the voids are buried in the softened melt layer after plastic pyrolysis. The smaller the particle size, the smaller the adverse effect on coke strength. This is because, when the size of the plastic is larger than 30% of the thickness of the softened molten layer, the gas generated by the thermal decomposition of the waste plastic escapes to the outside of the softened molten layer, thereby promoting the expansion of the softened molten layer. This is because the material described in Patent Document 4 has a particle size small enough to be buried in the softened and melted layer. Then, a constant K that varies depending on the type of waste plastic and the addition rate is determined, the upper limit of particle size is determined as “K · softening melt layer thickness”, and the strength is obtained by using the waste plastic granular material adjusted to a size equal to or smaller than the upper limit of particle size. It is said that high blast furnace coke can be manufactured.

  From the above, it can be seen that the plastic particle size can be reduced as described in Patent Document 4 or increased as described in Patent Document 3 in order to suppress the reduction in coke strength due to the addition of waste plastic.

  In the process of producing coke by carbonizing coal in a coke oven, the coal expands when heated and exerts pressure on the coke oven wall. This pressure is generally called expansion pressure. Yes. If this expansion pressure becomes abnormally high, the furnace wall of the coke oven will be damaged directly, making it impossible to operate, or the resistance (extrusion resistance) will increase when the coke is discharged from the carbonization chamber (extruding), If an excessive load is applied to the furnace wall, it will cause damage to the furnace wall. For this reason, it is an important issue to manage the expansion pressure below the allowable limit value for coke oven damage in the operation of the coke oven. In particular, coke ovens have become aging in recent years, and the allowable limit value is lowered due to a decrease in furnace body strength. In addition, the introduction of coal pretreatment technology such as the humidity-controlling coal method in recent years has led to the introduction of coal into the coke oven carbonization chamber. As the bulk density rises and the expansion pressure tends to increase, expansion pressure management has become an increasingly important issue for extending the life of coke ovens.

  In patent document 5, when estimating the expansion pressure of blended coal from the arithmetic mean value of the expansion pressure of each brand coal which comprises the conventional blended coal, instead of increasing the blending ratio of simple coal with low expansion pressure To reduce the expansion pressure by using a simple expansion pressure reduction method, to control the expansion pressure stably and reliably below the allowable limit value that does not damage the coke oven, and to produce coke with a certain strength or higher The coke oven operating method is disclosed.

JP 48-34901 A Japanese Patent Laid-Open No. 8-157834 JP 2001-49263 A JP 2002-327182 A JP 2001-214171 A

  Patent Document 5 discloses a method for estimating the blended coal expansion pressure, and a method for suppressing the expansion pressure by adding a binder, but the expansion pressure is further reduced while the coke oven aging progresses. There is a need for a means to suppress.

  On the other hand, as described above, various literatures disclose methods for charging waste plastic into a coke oven as a coke oven charging raw material. These documents focus only on the coke strength, and do not disclose any method for suppressing the expansion pressure of the coke oven by adding waste plastic.

  An object of the present invention is to provide a method for suppressing the expansion pressure of a coke oven by adding the waste plastic when the waste plastic is charged into the coke oven as a raw material charged in the coke oven.

That is, the gist of the present invention is as follows.
(1) A method for producing coke, wherein waste plastic is used together with coal as a raw material charged in a coke oven, and the roundness of waste plastic is 0.5 or less on average.
However, the roundness C is expressed by C = 4πA / U ^2, where U is the outer peripheral length of the individual and A is the cross-sectional area of the individual in a cross section perpendicular to the long axis of the individual and including the short axis. It is a coefficient. same as below.
Here, the long axis means that the particle is stabilized on a plane, and when the projected image of the particle on the plane is sandwiched between two parallel lines, the parallel line that maximizes the distance between the parallel lines is selected. The axis passing through the contact point between the parallel line and the particle means the axis having a direction perpendicular to the parallel line. The short axis means an axis that passes through the contact point between the parallel line and the particle when the particle is sandwiched between two parallel lines in a direction parallel to the long axis, and has a direction perpendicular to the long axis. .
(2) The method for producing coke according to (1) above, wherein an average of the average particle size of the waste plastic is not less than the following lower limit of particle size.
Particle size lower limit = L × softened melt layer thickness (1)
However, L is a constant determined by the type of waste plastic and the addition rate.
The average particle size is an average value of the long axis diameter and the short axis diameter of an individual. The long axis diameter stabilizes a particle on a plane and projects two parallel projection images of the particle on the plane. This means the width of the particle where the distance between the parallel lines is the largest when sandwiched between lines. The short axis diameter is when the particle is sandwiched between two parallel lines in the direction perpendicular to the parallel line when determining the long axis diameter. Means distance.
(3) Waste plastic particles for coke oven charging, wherein the roundness of the waste plastic particles is 0.5 or less on average.

  In the present invention, when waste plastic is used together with coal as a raw material for charging a coke oven, the roundness of the waste plastic is set to 0.5 or less on average, thereby suppressing the expansion pressure on the furnace wall of the coke oven. It becomes possible.

In the present invention, the roundness of the waste plastic charged into the coke oven together with coal is defined. The roundness is an index indicating how close the cross-sectional shape of a solid object is to a perfect circle. In the present invention, the roundness C is C = 4πA / U ² , where U is the outer perimeter of the individual and A is the cross-sectional area of the individual in a cross section perpendicular to the long axis of the individual and including the short axis. Is a coefficient represented by Here, the long axis means that the particle is stabilized on a plane, and when the projected image of the particle on the plane is sandwiched between two parallel lines, the parallel line that maximizes the distance between the parallel lines is selected. The axis passing through the contact point between the parallel line and the particle means the axis having a direction perpendicular to the parallel line. The short axis means an axis that passes through the contact point between the parallel line and the particle when the particle is sandwiched between two parallel lines in a direction parallel to the long axis, and has a direction perpendicular to the long axis. .

  For example, after determining the short axis and long axis of waste plastic, the roundness is cut by a cross section perpendicular to the long axis and including the short axis, and the area (A) and the outer peripheral length (C) of the cut surface are measured. Find it. The area and the outer peripheral length can be obtained by a method such as image analysis. When the shape of the waste plastic varies, the roundness of several samples may be measured and the average value may be obtained.

  When the waste plastic charged in the coke oven is made into a granular material by a normal method, the cross-sectional shape thereof is as shown in FIG. 1 (a), and the roundness is about 0.9 at most. On the other hand, the waste plastic used in the present invention has an average roundness of 0.5 or less. The cross-sectional shape of the waste plastic particles having a roundness of 0.5 has a shape as shown in FIG.

  As a result of the roundness of the waste plastic being 0.5 or less on average, fine irregularities are formed on the surface of the waste plastic. In this way, when waste plastic particles having irregularities on the surface are charged into a coke oven together with coal and subjected to dry distillation, the contact area between the softened and melted coal and the plastic becomes large during the softening and melting of the coal. For this reason, it becomes easy for gas to escape from the softened and melted coal to the outside of the softened and melted layer, the gas pressure in the softened and melted layer is lowered, and as a result, the expansion pressure applied to the furnace wall of the coke oven can be suppressed. .

  When waste plastic is added to the coke oven charge, the gas in the softened and melted coal bed escapes mainly at the interface between the softened and melted coal and the waste plastic. In the present invention, since the roundness of waste plastic is as small as 0.5 or less on average, the interface between coal and waste plastic is widened. As the contact area is larger, the number of paths through which the gas flows is increased. As a result, the pressure in the softened and melted layer can be reduced, and the expansion pressure can be suppressed.

  Further, the waste plastic particles for charging a coke oven characterized in that the roundness of the waste plastic particles according to the present invention is 0.5 or less on average is loaded into a coke oven together with coal as a coke oven charging raw material. By entering, the expansion pressure can be suppressed.

  Waste plastic with roundness ≦ 0.5 can be manufactured by changing the die shape of the extruder to an appropriate shape when extruding waste plastic that has been heated and semi-molten, for example. is there. Alternatively, it can be produced by compacting waste plastic into an appropriate shape from the outside immediately after the extrusion molding.

  Furthermore, in order to further suppress the expansion pressure, it has been found that there is a suitable range for the particle size of the waste plastic to be charged.

  The cause of the expansion pressure is due to the pressure of the gas accumulated in the softened and melted layer. However, by setting the average particle size of the waste plastic to be charged to a value larger than a predetermined ratio with respect to the softened melt layer thickness, the gas in the softened melt layer can easily escape to the outside through the waste plastic, resulting in softening. It becomes possible to suppress the expansion pressure by reducing the gas pressure in the molten layer.

Here, when the average of the average particle size of the waste plastic is set to a value larger than the following particle size lower limit value, preferable results can be obtained.
Particle size lower limit = L × softened melt layer thickness (1)
However, L is a constant determined by the type of waste plastic and the addition rate. The average particle size is an average value of the long axis diameter and the short axis diameter of an individual. The long axis diameter stabilizes a particle on a plane and projects two parallel projection images of the particle on the plane. This means the width of the particle where the distance between the parallel lines is the largest when sandwiched between lines. The short axis diameter is when the particle is sandwiched between two parallel lines in the direction perpendicular to the parallel line when determining the long axis diameter. Means distance. That is, fine irregularities on the surface are not reflected. Specifically, the outer diameter may be measured with a measuring tool such as a caliper.

  Specifically, the value of L can be obtained by the following method. Mixing waste plastics of different types and particle sizes into blended coal at a specified ratio and then including waste plastic in a movable wall type test distillation furnace that can directly measure the expansion pressure applied to the furnace wall with a load cell etc. Charcoal is charged and the expansion pressure during dry distillation is measured. Here, the plastic particle diameter when the expansion pressure is drastically reduced is obtained, and the plastic particle diameter (mm) / softened molten layer thickness (mm) at this time may be set to a constant L.

  The value of L varies depending on the type of plastic and the addition rate. This is because the gas releasing properties from the softened and molten layer differ depending on the type of plastic. For example, according to the study example of the present inventor, in the range of the softened melt layer thickness of 3 to 7 mm and the waste plastic addition rate of 0.3 to 3% by mass, in the case of waste plastic of aliphatic resin or aliphatic organic compound, L = 2 to 6, L = 1 to 4 in the case of an aromatic resin such as polystyrene or a waste plastic of an aromatic organic compound, a resin containing oxygen such as polyethylene terephthalate, or a waste plastic of an organic compound. Specifically, when 2% by mass of plastic is added to coal and the thickness of the softened molten layer is 5.7 mm, L = 2.5 in the case of aliphatic waste plastic, aromatic type such as polystyrene For plastics containing oxygen, such as plastic and polyethylene terephthalate, L = 1.5.

  When waste plastic is actually used, since waste plastic is a mixture of various plastics (resin or organic compound), the value of L may be determined in consideration of the mixing ratio of various plastics.

  In a coke oven, the thickness of the layer in the softened and molten state varies depending on the dry distillation conditions and the position in the coke oven width direction, and is thicker near the furnace wall where the temperature gradient is large and thicker at the center of the carbonization chamber where the temperature gradient is gentle. However, the thickness is almost constant in most regions within the carbonization chamber. Assuming various operating conditions, the thickness of the softened molten layer is calculated by a heat transfer model. The thickness of the softened molten layer formed on the one side of the furnace width direction excluding the wall surface 10% and the central side 10% is almost constant. I know that there is. Therefore, as the thickness of the softened molten layer, an average value of the thickness of the softened molten layer formed in a portion excluding the wall side 10% and the center side 10% on one side in the furnace width direction may be used.

  For example, in a coke oven having a furnace width of 450 mm (one side of 225 mm), the thickness of the softened molten layer at each position in the furnace width direction is calculated by a heat transfer model under the conditions of a furnace temperature of 1150 ° C. and a softening melting temperature range of coal of 100 ° C. In the vicinity of the furnace wall where the temperature gradient is large, the thickness is about 2 mm, and in the center of the carbonization chamber where the temperature gradient is gentle, the thickness is about 20 mm. However, the thickness is almost constant in most regions in the carbonization chamber. Here, on the one side in the furnace width direction, the average value of the thickness of the softened molten layer formed on the portion excluding the wall side 10% (22.5 mm from the wall) and the center side 10% (22.5 mm from the center) is 5 mm. is there. When the thickness of the softened and melted layer is obtained under various operating conditions, the thickness is in the range of about 3 to 7 mm.

  Here, the softening melting temperature range of coal is a temperature difference between a softening start temperature and a solidification temperature measured in a fluidity test by the Gisela plastometer method defined in JIS M8801, and is usually 60 ° C to 100 ° C. The value is about ℃.

The thickness of the softened and melted layer is about 5 mm as described above, but differs depending on the softening and melting temperature range of the blended coal for coke oven charging, the bulk density of the coal charge, and the furnace temperature of the coke oven. The softened melt layer thickness becomes thicker as the softening melt temperature range is wider, the coal charging bulk density is higher, and the furnace temperature of the coke oven is lower, the charging bulk density BD, the furnace temperature T of the coke oven, the softening melting temperature. It is expressed as a linear function of each of the ranges ΔT. Furthermore, using these three parameters, the thickness of the softened molten layer can be obtained by the following equation (2).
Softened melt layer thickness (mm) = [a · BD + b · T + c] × (ΔT + 25) / 100 (2)
ΔT (° C.): Softening and melting temperature range of coal blend for coke oven charging. It can be defined as the temperature difference between the softening temperature and the solidification temperature measured in the fluidity test by the Gisela plastometer method defined in JIS M8801.
BD (t / m ³ ): Charging bulk density of coal (based on dry coal).
T (° C.): The temperature of the coke oven.
a, b, c: constants.
Here, the constants a, b, and c vary depending on the coke oven type and operation mode, but in the study by the present inventors, a = 4.5 to 5.3, b = −0.0076 to −0.0088, c = 8.9 to 10.4.

  In patent document 3, since the area which coal and a plastics contact decreases as the average particle diameter of the waste plastic to add is large, it is supposed that a weak point can be reduced. It has been found that the size of the plastic itself has a greater influence on the “contact area” described in Patent Document 3 than the unevenness of the surface. For this reason, even if the particle size of the waste plastic is the same as that described in Patent Document 3, it is possible to maintain the same strength as that described in Patent Document 3 by using waste plastic having a different surface shape (unevenness). It was possible to reduce the expansion pressure.

In the present invention, the roundness of the waste plastic is set to 0.5 or less on average, and it is not a waste plastic having a large particle size as described above, but a size equal to or less than the upper limit of the particle size obtained by the equation (3) It is good also as using the granular material prepared further.
Upper limit of particle size (mm) = K. Softened melt layer thickness (3)
K: A constant determined by the type of waste plastic and the addition rate.

  In the present invention, as a result of setting the roundness of the waste plastic to 0.5 or less on average, gas is likely to escape from the softened and melted coal to the outside of the softened and melted layer, and the gas pressure in the softened and melted layer is reduced. As a result, the expansion pressure applied to the furnace wall of the coke oven can be suppressed. In addition, since the particle size of the waste plastic is made fine, the gas generated by the thermal decomposition of the waste plastic is included in the softened and melted layer, and as a result, the expansion of the softened and melted layer is promoted (the expansion coefficient of coal becomes high). As a result, the fusion bond between the softened and melted coals is strengthened by the gas pressure inside the softened and melted layer. By reducing the roundness of the waste plastic, the expansion pressure is suppressed. On the other hand, by reducing the particle size of the waste plastic, the expansion coefficient is increased and the coke strength is ensured. Although it seems that the expansion pressure is suppressed while the expansion coefficient is high, it seems contradictory at first. However, the expansion coefficient is an index that shows how much coal expands under the condition that there is no restriction. It is a mechanical force that acts on the furnace wall under specified conditions, and is a completely different concept. If the coal particles are bonded and fused together, the coke strength is improved, so that the coke strength is affected by the expansion coefficient, not the expansion pressure. When the roundness of the waste plastic is set to 0.5 or less on average, and the granular material prepared to have a particle size not more than the upper limit of the particle size obtained by the equation (3) is used, the coal particles swell and come into contact with each other. Until then, the gas generated from the waste plastic acts on the expansion of the coal, but once the coal particles stick together, the waste plastic added to this time acts as a degasser to release excess gas. The expansion pressure decreases.

  Here, the constant K in the equation (3) varies depending on the thickness of the softened molten layer and the plastic addition rate, but specifically, it may be obtained by a method of measuring the expansion coefficient of coal as described below.

  That is, a polyethylene particle having a predetermined particle size is added to a coal in a retort having a diameter of 12 mm (bottom sealed, top open type) with respect to coal, and then the mixture is charged to a height corresponding to the assumed softened melt layer thickness. Heat uniformly from the outside, measure the expansion behavior of the coal bed during heating, determine the plastic particle size when the expansion rate is drastically reduced, and determine the plastic particle size (mm) / charging height (mm) as a constant K

  For example, in the range of softened melt layer thickness of 3 to 7 mm and plastic addition rate of 0.3 to 3% by mass, in the case of aliphatic waste plastic, K = 0.3 to 0.7, aromatic plastic such as polystyrene For plastics containing oxygen such as polyethylene terephthalate, K = 0.075 to 0.175. Specifically, when 2% by mass of plastic is added to coal and the thickness of the softened molten layer is 5.7 mm, K = 0.5 in the case of aliphatic waste plastic, aromatic type such as polystyrene In the case of plastics containing oxygen such as plastic and polyethylene terephthalate, K = 0.125. If the waste plastic particle size is adjusted to be equal to or lower than the particle size upper limit defined by the formula (3) and added to the coal, coke having the same strength as the coke drum strength when the waste plastic is not added can be produced. Is possible.

  The reason why the value of K varies depending on the type of plastic is that the caking property of the coal itself may be hindered by the chemical interaction between the pyrolysis gas of the plastic and the coal. Of the main plastics that make up waste plastics, aliphatic plastics such as polyethylene and vinyl chloride have no inhibitory effect on coal caking, and aromatic plastics such as polystyrene and polyethylene terephthalate Plastics containing oxygen have a caking inhibiting effect. When the waste plastic is a mixture of an aliphatic plastic and an aromatic plastic and waste plastic containing oxygen, the coefficient K for determining the upper limit value may be changed according to the ratio of the two.

  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.

  In the present invention, the upper limit value of the waste plastic addition rate is not particularly defined, and it is preferable as long as the coke having the desired strength can be produced. If the addition rate exceeds 5% by mass, it can be used in a blast furnace. Since it becomes difficult to produce coke having strength, 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 to be treated.

  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 coal in a coke oven, the pyrolysis or the carbonization temperature and the carbonization pattern may be the same as those of conventional coal carbonization.

  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. 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.

  Using a movable wall type test coke oven having a furnace width of 400 mm, a furnace height of 600 mm, and a furnace length of 600 mm, coal and waste plastics were uniformly mixed and subjected to dry distillation under conditions of a dry distillation time of 18.5 hours. About the coke after baking, after cooling with nitrogen, the drum strength index (after 150 rotations +15 mm index) of the coke according to JIS K2151 was measured. Further, the expansion pressure was measured by a load cell installed outside the movable wall. As charging coal, blended coal of 70% by weight caking coal and 30% by weight non-caking coal was used. As the waste plastic to be charged together with coal, the one composed of 50% by mass of polyethylene and 50% by mass of polystyrene was used. The waste plastic addition rate was 2% in all cases.

  The waste plastic used was a solid made by extruding the heated and semi-molten waste plastic. In addition, waste plastics with different roundness were manufactured by changing the die shape of the extrusion molding machine. Here, the average of the average particle size of the waste plastic was set to 10, 20, 30, and 40 mm. The average roundness is calculated according to Example No. of the present invention. 1-4 is 0.5, comparative example No. 1-4 was 0.9.

  At this time, the thickness of the softened molten layer obtained by the equation (2) from the softened melting temperature range of the blended coal for coke oven charging, the coal charging bulk density, and the furnace temperature of the coke oven is 4.7 mm, (1 ) The lower limit value of the waste plastic particle size obtained from the formula is 9.4 mm as L = 2, and the waste plastic particle size is within the scope of the present invention. Here, as constants of the formula (2), a = 5.04, b = −0.08, and c = 9.9 were used.

  Comparative Example No. 1 to 4 all had high inflation pressures of 10 to 12 kPa. 1 to 4 had a good expansion pressure of 7 to 8 kPa. On the other hand, the coke strength was almost the same between the inventive example and the comparative example, that is, the coke strength similar to the conventional one could be secured.

It is a figure explaining roundness, (a) is a figure which shows the case where roundness is 0.9, (b) is the case where roundness is 0.5.

Claims (3)

A method for producing coke, wherein waste plastic is used together with coal as a raw material for charging a coke oven, and the roundness of waste plastic is 0.5 or less on average.
However, the roundness C is expressed by C = 4πA / U ^2, where U is the outer peripheral length of the individual and A is the cross-sectional area of the individual in a cross section perpendicular to the long axis of the individual and including the short axis. It is a coefficient. same as below.
Here, the long axis means that the particle is stabilized on a plane, and when the projected image of the particle on the plane is sandwiched between two parallel lines, the parallel line that maximizes the distance between the parallel lines is selected. The axis passing through the contact point between the parallel line and the particle means the axis having a direction perpendicular to the parallel line. The short axis means an axis that passes through the contact point between the parallel line and the particle when the particle is sandwiched between two parallel lines in a direction parallel to the long axis, and has a direction perpendicular to the long axis. . The method for producing coke according to claim 1, wherein the average particle size of the waste plastic is equal to or greater than the following lower limit of particle size.
Particle size lower limit = L × softened melt layer thickness (1)
However, L is a constant determined by the type of waste plastic and the addition rate.
The average particle size is an average value of the long axis diameter and the short axis diameter of an individual. The long axis diameter stabilizes a particle on a plane and projects two parallel projection images of the particle on the plane. This means the width of the particle where the distance between the parallel lines is the largest when sandwiched between lines. The short axis diameter is when the particle is sandwiched between two parallel lines in the direction perpendicular to the parallel line when determining the long axis diameter. Means distance.   Waste plastic particles for coke oven charging, wherein the roundness of the waste plastic particles is 0.5 or less on average.

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