JP5135964B2 - Blowing synthetic resin into blast furnace - Google Patents

Description

  The present invention relates to a technology for blowing a synthetic resin material into a blast furnace together with pulverized coal, and particularly to a technology for blowing waste plastic, which is a plastic discarded as general waste or industrial waste, into the blast furnace as a synthetic resin material.

  Conventionally, coke has mainly been used as iron ore reducing material in blast furnaces, but in recent years, auxiliary reducing materials such as pulverized coal, heavy oil and natural gas have been blown from the tuyere to reduce the use of expensive coke. It has been broken. Among them, pulverized coal obtained by simply pulverizing coal (a particle size of 75 μm or less is about 80 mass% or more (about 50 μm for D50 described later)) contributes to a reduction in the amount of expensive coke used, In order to extend the life of the coke oven by reducing the operating rate of the coke oven, there has also appeared an ultra-large quantity pulverized coal injection blast furnace in which the monthly pulverized coal injection ratio in a given blast furnace records 266 kg / t (for example, Non-patent document 1).

  Natural gas has a higher calorific value than pulverized coal and has a high hydrogen content, so that it is used from the viewpoint of reducing carbon dioxide emissions in addition to reducing coke.

  On the other hand, combustible solids, such as a synthetic resin material, can be used as an auxiliary reducing material of a blast furnace other than the above. In particular, it would be desirable from the viewpoint of energy saving, recycling, and environmental protection if it is possible to use municipal waste that has been incinerated or disposed of in landfills, or used plastic (waste plastic) mixed in industrial waste. .

A technology for blowing waste plastic into a vertical furnace such as a blast furnace from a tuyere is known (for example, see Patent Document 1 and Patent Document 2). By blowing waste plastic from the tuyere, it is possible to effectively recycle the waste plastic as a coke substitute. According to Patent Document 1, in order to improve the combustion rate in the raceway of the furnace, it is important to control the strength and particle size of the plastic particles blown into the furnace. Manufactured and blown into the furnace. Further, in Patent Document 2, in order to improve the combustibility of granular plastic which is a synthetic resin material, pulverized coal is attached to the surface of the granular plastic, and the granular plastic having the pulverized coal attached to the surface is connected to the tuyere. There is disclosed a technique in which fuel is injected from a blow lance for auxiliary fuel, the tip of which is located inside the blower branch or the tuyere, and blown into the furnace of the blast furnace through the tuyere.
JP 2001-220589 A JP 2002-146416 A “Materials and Process 11” 1998, p. 834

  In order to recycle a large amount of waste plastic in a blast furnace, etc., it is important not only to ensure the combustibility of the waste plastic, but also to maintain the stable operation of the furnace and to increase the replacement rate of waste plastic for coke. It is. However, the present inventors have found that when the amount of waste plastic blown into the blast furnace is increased, the breathability of the furnace deteriorates in addition to the combustibility problem. That is, since the air permeability of the furnace is deteriorated and the blowing pressure is increased, it is necessary to perform an operation for increasing the coke ratio in order to ensure the air permeability, and the replacement rate of the waste plastic with respect to the coke is eventually reduced. When operation is performed to increase the coke ratio, the fuel consumption rate increases and productivity also decreases. Therefore, it is not preferable for the operation of the blast furnace to increase the amount of waste plastic blown into the blast furnace under such conditions.

  The techniques described in Patent Document 1 and Patent Document 2 are methods for improving the combustibility of waste plastic having poor combustibility and achieving a high combustion rate, but have the following problems.

  Patent Document 1: It is possible to form waste plastic to be blown into a furnace into a cylindrical lump using a granulator (compression extruder), but because the waste plastic is a mixture of many types of plastic, the granulator When the operating conditions are constant, it is difficult to always produce a lump with a constant condition (strength).

  In order to always produce a lump with a certain condition, it is necessary to appropriately measure the properties (plastic type, composition, moisture, etc.) of the waste plastic to be supplied and feed back the results to the production conditions. Frequent changes are difficult.

  When viewed locally, the properties (strength) fluctuate for each granulated product produced, and there are concerns about fluctuations when blown into a blast furnace.

  When blowing waste plastic waste into the blast furnace, it is blown into the bottom of the blast furnace by air transport, enters the raceway from the tuyere with hot air of 1000 ° C or higher, and burns and gasifies at high speed to generate reducing gas. To do. Since the gas flow rate of hot air at the tip of the tuyere is 200 m / s or more, the residence time of the blown particulate matter is as short as about 0.01 seconds, and highly efficient combustion and gasification is important. However, if the amount of waste plastic injected into the blast furnace increases, the combustion and gasification rate decreases, char from unburned plastic is generated, impairing the air permeability in the blast furnace, and hindering blast furnace operation. May cause Therefore, in order to recycle a large amount of waste plastic in a blast furnace or the like, it is necessary to improve the combustibility of the waste plastic more than before.

  Patent Document 2: Combustion of pulverized coal consists of two steps of volatile matter release (gasification) in the first step, combustion, and fixed carbon combustion in the second step. Since the body residence time is extremely short (less than 20 ms), the combustion rate depends on the amount of volatile matter in the pulverized coal, and the combustion rate is 50 to 70%. In addition, in order to generate volatile components from pulverized coal, it is necessary to supply decomposition heat (about 200 kcal / kg) from the surroundings. On the other hand, in the combustion of a synthetic resin material having a dense polymer structure, heat (about 380 kcal / kg) necessary for decomposition (gasification) of a polymer compound is supplied to the particle surface, and volatile matter is generated and burned. . Therefore, if pulverized coal with fast ignition is attached to the surface of the synthetic resin material and the exterior is put on the exterior, the combustion heat of the synthetic resin material is improved by the combustion heat of the pulverized coal, but conversely the combustion rate of the pulverized coal decreases. There is a concern to do.

  The method described in Patent Document 2 is a method in which pulverized coal is sheathed on the surface of a synthetic resin material by utilizing the difference in the conveying gas velocity between the pulverized coal and the synthetic resin material. This is a safety issue.

  As described above, it is difficult to use waste plastic as a granulated material having a constant strength for blast furnace injection using conventional techniques, and it is necessary to increase the combustibility of plastic particles for stable operation. . In addition, when a large amount of synthetic resin material is blown into the furnace, it is necessary to improve the combustibility of the plastic particles in order to prevent deterioration of the air permeability of the furnace. In addition, when the pulverized coal and the synthetic resin material are blown from the tuyere at the same time, the combustion rate of the pulverized coal is lowered, which may cause a safety problem.

  The object of the present invention is to solve such problems of the prior art and provide a method for blowing a synthetic resin material into a blast furnace without deteriorating the air permeability of the blast furnace even when a large amount of synthetic resin material is blown into the furnace. There is to do. Another object of the present invention is to provide a method for blowing a synthetic resin material into a blast furnace in which the combustibility of the pulverized coal does not decrease even when the pulverized coal and the synthetic resin material are simultaneously blown from the tuyere. Another object of the present invention is to provide a method for blowing a synthetic resin material having a stable combustibility even when waste plastic is used as the synthetic resin material. And, it is to enable operation of a blast furnace with an increased replacement rate of synthetic resin for coke.

The features of the present invention for solving such problems are as follows.
(1) When the synthetic resin material is blown into the furnace from the tuyere of the blast furnace, the synthetic resin material containing a particle size of 3 mm or more and 90 mass% or more is heated and melted, and after cooling and solidification, pulverization is performed. A method of blowing a synthetic resin material into a blast furnace, wherein the synthetic resin material having a particle diameter of less than 1.2 mm is simultaneously blown.
(2) A synthetic resin material having a particle size of less than 1.2 mm is blown at a ratio of 33 to 300 parts by mass with respect to 100 parts by mass of a synthetic resin material containing 90% by mass or more of a particle size of 3 mm or more (1 ) The method of blowing a synthetic resin material into the blast furnace.
(3) When the synthetic resin material is blown into the furnace from the tuyere of the blast furnace, the cylindrical granulated plastic produced by the extrusion method and / or the synthetic resin material crushed by the crusher and the synthetic resin material are heated. A method of blowing a synthetic resin material into a blast furnace, characterized by simultaneously blowing a synthetic resin material that has been melted and cooled and solidified and then pulverized.
(4) The method for injecting a synthetic resin material into a blast furnace according to (3), wherein the particle size of the synthetic resin material produced by pulverization is less than 1.2 mm.
(5) The method for blowing a synthetic resin material into a blast furnace according to any one of (1) to (4), wherein pulverized coal is blown simultaneously with the synthetic resin material.
(6) The method for blowing a synthetic resin material into a blast furnace according to any one of (1) to (5), wherein waste plastic is used as the synthetic resin material.
(7) A synthetic resin for a blast furnace according to any one of (1) to (6), wherein a synthetic resin material containing chlorine is heated and melted to dechlorinate, and then cooled and solidified, and then pulverized. Material blowing method.

  According to the present invention, the finely pulverized synthetic resin material is blown into the blast furnace at the same time as the synthetic resin material having a large particle size, whereby the air permeability of the furnace can be improved and the combustibility of the granulated plastic can be improved. For this reason, the substitution rate with respect to the coke of a synthetic resin material can be increased, and waste plastic can be used effectively as a blast furnace raw material.

  The present inventors have intensively studied to solve the above problems. And in order to improve the combustibility of the synthetic resin material having a relatively large particle size used for blowing in the blast furnace, it was considered preferable to simultaneously blow the synthetic resin material having a small particle size into the furnace. In order to improve the combustibility of a synthetic resin material having a relatively large particle size, ignition is faster than pulverized coal, decomposition heat is lower than that of a synthetic resin material and pulverized coal having a large particle size, and the combustion rate in the raceway is low. This is because it is preferable to blow a high material into the furnace simultaneously with the synthetic resin material. Then, as a synthetic resin material having a small particle diameter, it was found that a synthetic resin material obtained by subjecting a synthetic resin material to heat melting, cooling and solidification and then pulverizing was suitable, and the present invention was completed.

  By heat-melting and cooling and solidifying the synthetic resin material, a fine pulverization process is facilitated, and a finely pulverized synthetic resin material having a high combustion rate can be manufactured. In particular, the synthetic resin material containing chlorine is heated, melted, dechlorinated, and cooled and solidified to lower the molecular weight of the original synthetic resin material, so that the heat of decomposition can be reduced, which is preferable. Furthermore, the obtained synthetic resin material that has been heat-melted, dechlorinated, and cooled and solidified is easily reduced in molecular weight because of its low molecular weight.

  As the synthetic resin material containing chlorine, chlorine-containing plastics such as PVC (polyvinyl chloride) and PVDC (polyvinylidene chloride), and mixtures thereof can be used. If the total chlorine content is, for example, about 1.7 mass% or more, a mixture of a synthetic resin material containing no chlorine and a synthetic resin material containing chlorine can also be used as a synthetic resin material containing chlorine. It is.

  The heat melting treatment is to melt and knead a synthetic resin material by heating it to a melting temperature or higher. Whether or not to perform the dechlorination treatment after heating and melting depends on the chlorine content of the synthetic resin material and the tolerance of the chlorine content in the subsequent process (blowing into the blast furnace). In the case of performing dechlorination treatment, it is preferable to melt and knead the synthetic resin material containing chlorine while heating it to 300 ° C. or higher while performing dechlorination treatment. In the cooling and solidification, the molten synthetic resin material obtained by heating and melting / dechlorination treatment is cooled and solidified by water cooling or the like. In the fine pulverization treatment, the synthetic resin material whose pulverizability is improved by the above-described treatment is pulverized to produce a finely pulverized synthetic resin material having a particle diameter of preferably less than 1.2 mm.

  If a synthetic resin material having a low chlorine content (for example, a chlorine concentration of less than 1.7 mass%) is used, the dechlorination step is omitted if it is allowed in the subsequent step even without dechlorination. It is preferable to melt and knead at a temperature which is not lower than ° C. and does not generate combustible decomposition gas. It is preferable to omit the dechlorination step and to melt and knead the mixture at a temperature of 160 ° C. or higher at which the combustible decomposition gas is not generated. The temperature at which the combustible decomposition gas is not generated varies slightly depending on the type of waste plastic, but is usually 270 ° C. or lower. By heating and melting and kneading the synthetic resin material at a temperature at which no flammable decomposition gas is generated, a decomposition gas processing facility such as a combustion furnace becomes unnecessary, and the synthetic resin material can be processed at low cost. When plastic is heated at a low temperature, the pulverizability of the solidified product produced by heating and melting and cooling and solidification may be reduced, but it is solidified by mixing the additive with the plastic before forming the solidified product. The grindability of the body can be improved, and the reduction in the productivity of the plastic grind can be prevented. It is preferable to mix an additive having an aspect ratio of 2 or more with a synthetic resin material in a mass ratio of 3 to 50% before forming a solidified body. Or, before forming the solidified body, it is preferable to mix the additive having an average particle size of the average particle size ± 50% targeted by the pulverized product with a synthetic resin material in a mass ratio of 3 to 50%. The additive is preferably one or more selected from rice husk, pulverized coal, sawdust, wood, tea husk, coffee extract, fiber waste, coke, shells, ore.

  A synthetic resin material (hereinafter referred to as “synthetic resin material B”) that has been finely pulverized after being heated and melted and cooled and solidified is a synthetic resin material having a relatively large particle size, that is, a particle size containing 90 mass% or more of a particle size of 3 mm or more. The combustibility of the synthetic resin material A can be improved by blowing into the furnace simultaneously with the distribution of the synthetic resin material (hereinafter referred to as “synthetic resin material A”).

  As the synthetic resin material A having a relatively large particle size, it is appropriate to use a cylindrical granulated plastic produced by an extrusion method and / or a synthetic resin material crushed by a crusher. Combustibility is improved by being blown into the blast furnace at the same time as the relatively large particle size granulated plastic, the crushed synthetic resin material, and the synthetic resin material B, which are usually used as raw materials for blowing into the blast furnace. . The granulated plastic (granulated plastic) is usually produced mainly from a film-like plastic, as will be described in detail below. Synthetic resin materials (hereinafter referred to as “crushed plastic”) that have been crushed by a crusher are usually produced mainly from solid plastic that can be easily crushed by a crusher. Both of them usually have a particle size distribution containing a particle size of 3 mm or more and 90 mass% or more. The crushed plastic is processed only by normal crushing without performing processing such as heating and melting, and the synthetic resin material B is not included.

  The upper limit of the particle size of the synthetic resin material A typified by granulated plastic and crushed plastic is determined by facility restrictions for blowing. That is, the upper limit value of the synthetic resin material A is a size that can be blown into the blast furnace. For example, when the inner diameter of the blast furnace tuyere is about 140 mm and the inner diameter of the blowing lance is about 40 A, the particle size is preferably 20 mm or less (usually 10 mm or less), and a sieve having a sieve mesh of 20 mm (or 10 mm) It is preferable to use an under-sieving that has passed through. Note that some of the granulated plastic and crushed plastic may contain particles having a particle size of less than 1.2 mm. As the granulated plastic, for example, those produced by extrusion from an extruder having a die having a die diameter of 6 mm, which will be described later, have a very small proportion of particles having a particle size of less than 1.2 mm. The particle size of less than 3 mm is less than 5 mass%. For example, if the crushing plastic is manufactured using a crusher with a screen size of 10 mm after crushing, the proportion of particles less than 1.2 mm is very small. The particle size of less than 3 mm is less than 5 mass%. In this case, the 50% passing particle diameter (D50) is calculated to be 4 to 6 mm. Therefore, the particle size of the granulated plastic and crushed plastic is preferably 4 mm or more at D50.

  It is preferable to use waste plastic (used plastic) as the synthetic resin material. Waste plastic is a waste generated in large quantities, and an increase in the amount of recycling is desired. Waste plastic usually consists of a mixture of multiple types of plastics. As the chlorine-containing waste plastic, it is desirable to use a waste plastic having a particularly high chlorine content. Examples thereof include chlorine-containing plastics such as PVC (polyvinyl chloride) and PVDC (polyvinylidene chloride), and waste plastics having a high content ratio thereof. It is particularly desirable to use PVC, PVDC, etc. as industrial waste. It is also desirable to use a waste plastic having a high chlorine concentration, which has been subjected to a treatment such as specific gravity separation and separated as a high specific gravity component. Since waste plastic is a mixture of multiple types of plastics, it is heated and melted and mixed thoroughly, increasing the interface between different plastics, generating stress during cooling, improving crushability, and facilitating pulverization. The grindability is also improved.

The ignition characteristics of pulverized coal and the plastic (synthetic resin material B) finely pulverized as described above were evaluated using the apparatus shown in FIG. In FIG. 1, air at 1200 ° C. was blown from the top of the furnace through a preheater 2 at a gas velocity of 4 m / s into the vertical electric furnace 1 to be heated to the same blowing temperature (1200 ° C.) as the blast furnace. In the electric furnace, the powder is supplied from the powder supply device 3 from above, and the ignition characteristics of the powder are evaluated. The furnace length L ₁ is 2400 mm, and the length L ₂ of the powder combustion part is 100 to 1500 mm which can be changed by moving the upper powder blowing pipe up and down. 4 is an exhaust gas discharge passage, and 5 is an unburned powder sampling portion. Using coal or waste plastic pulverized and classified to each particle size as powder, each ignition start time was measured. As the plastic, waste plastic having a chlorine content concentration of 1 mass% or less was used.

  The results are shown in FIG. FIG. 2 also shows the ignition start time of a granulated plastic (6 mmφ × 5 mmL) that is a cylindrical granulated plastic manufactured by the extrusion method that is the synthetic resin material A. According to FIG. 2, it can be seen that the synthetic resin material B finely pulverized to a particle diameter of less than 1.2 mm has a short ignition start time and good combustibility.

  The ignition start time of pulverized coal (particle size of about 50 μm) that is usually used as an auxiliary reducing material is also shown in FIG. The ignition start time of pulverized coal is equivalent to or shorter than the ignition start time of plastics with a particle size of less than 1.2 mm, but in the case of pulverized coal, the volatile component is ignited, but the overall combustion rate is about 60%. The flame temperature does not rise because the amount of heat generated by the entire stay (FIG. 4 to be described later) is small. Therefore, it has been found that the combustibility of the synthetic resin material A is not improved.

Next, the combustion rate of pulverized coal and the plastic (synthetic resin material B) pulverized as described above was evaluated. The combustion rate was evaluated using a combustion apparatus simulating the lower part of the blast furnace shown in FIG. In FIG. 3, a combustion test apparatus 6 having a blowing direction length of 600 mm, a tuyere 7 with a diameter of 65 mm, and a blow pipe 8 with a diameter of 90 mm was used. A probe 9 measures and collects the raceway temperature and gas composition. Waste plastic crushed material 10 or the like was blown into the combustion test apparatus from the tuyere 7 through the lance 11 and burned in the raceway 12 formed in front of the tuyere. 13 is a coke supply apparatus. Pulverized coal and sieving using heat smelted, dechlorinated, cooled solidified, finely pulverized waste plastic sieves are blown into the combustion test device from the tuyere 7 to measure the combustion rate did. Combustion rate is: Coke consumption rate when plastic is not blown (kg / h): G _CA , Coke consumption rate when plastic is blown (kg / h): G _CP , carbon content in coke (−): C _C , plastic blowing speed (kg / h): G _P , carbon content in plastic (−): C _P , combustion rate = (G _CA −G _CP ) × It was defined as C _C / (G _P × C _P ) × 100.

  The results are shown in FIG. The particle size of the pulverized coal and the pulverized plastic was measured by microtrack measurement, and the value of D50 was used. Plastics having a particle diameter of 1.2 mm or more were classified by sieving, and the 50% passage diameter was D50. FIG. 9 shows the particle size distribution of the granulated plastic used in FIG. The 50% passage particle diameter (D50) of the granulated plastic calculated from FIG. 9 is 5.8 mm. According to the relationship between the particle size and the combustion rate in FIG. 4, if the particle size of the synthetic resin material B is less than about 1.2 mm, the combustion rate exceeds that of pulverized coal.

  FIG. 4 also shows that the combustibility of the granulated plastic can be greatly improved by blowing the synthetic resin material B having a particle size of less than 1.2 mm simultaneously with the granulated plastic. The D50 of the mixture of the synthetic resin material B and the granulated plastic is calculated to be 3.1 mm, and if the additivity is satisfied, the combustion rate should be over 40%, but the measurement result is over 50%, and mixing The effect by blowing is recognized. Here, the mixing ratio of the synthetic resin material B having a particle diameter of less than 1.2 mm and the granulated plastic is 1: 1 by mass ratio.

  Therefore, when the synthetic resin material is blown into the furnace from the tuyere of the blast furnace, it is effective to simultaneously blow the synthetic resin material A and the synthetic resin material B instead of pulverized coal. The synthetic resin material B is preferably blown at a rate of 33 to 300 parts by mass with respect to 100 parts by mass of the synthetic resin material A. If it is less than 33 parts by mass, a coke replacement ratio of 0.8 or more cannot be secured, and the ventilation resistance in the blast furnace increases. Blowing in excess of 300 parts by mass is not very different from the effect of increasing the combustion rate, and is not necessary from the viewpoint of treating a large amount of waste plastic. In addition, when a synthetic resin material A having a relatively large particle size, such as granulated plastic or crushed plastic, and pulverized coal are blown into a blast furnace, a part of the pulverized coal is subjected to the above synthetic resin material B. Is also effective. In this case, the synthetic resin material A, the synthetic resin material B having a particle size of less than 1.2 mm, and pulverized coal are simultaneously blown. If it does in this way, since the combustion heat of pulverized coal contributes to the improvement of the combustibility of the synthetic resin material A, it is preferable. When blowing pulverized coal at the same time, the amount of pulverized coal with respect to the synthetic resin material need not be specified. The amount of pulverized coal can be appropriately determined according to the amount of synthetic resin material that can be used. Therefore, for example, if blast furnace injection is performed with the total amount of synthetic resin material and pulverized coal kept constant, blast furnace operation can be continued under certain conditions without adjusting the amount of coke charged from the top of the furnace. And stable blast furnace operation is possible.

  Next, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 5 shows a process 1 for granulating waste plastic by a granulation process to obtain a granulated plastic, a process 2 for obtaining a finely pulverized plastic obtained by heating, melting, dechlorination, and a fine pulverization process, and a crushed plastic by a crushing process. It is explanatory drawing of one Embodiment of this invention which blows the granulated plastic, the crushing plastic, and the fine crushing plastic into a furnace simultaneously which consists of the process 3 which obtains.

  In FIG. 5, in step 1, the waste plastic is first subjected to foreign matter removal using magnetic separation, wind separation, etc. and washed with water in advance in the pretreatment step 20 to remove foreign matters other than plastic as much as possible. Next, it is supplied to the granulating step 21 and processed into a granulated plastic. In step 2, foreign substances other than plastic are first removed by the simple pretreatment step 24, but cleaning is not necessary. Next, it is heated at about 370 ° C. in the heating / melting / dechlorination step 25 and melt-kneaded while performing dechlorination. The plastic obtained from the heating and melting / dechlorination step 25 is cooled and solidified by water cooling or the like in the cooling step 26, cut into a predetermined length and pelletized. The manufactured pellets are made into a finely pulverized plastic in the coarsely pulverizing step 27 and the finely pulverizing step 28. The granulated plastic and finely pulverized plastic obtained in this manner are blown into the blast furnace 23 by the blowing means 22 and 29 to obtain a blast furnace blowing raw material. In step 3, the waste plastic is first removed in advance by a pretreatment step 60 using magnetic separation, wind separation, etc. to remove foreign matter other than plastic as much as possible, and then crushed in the crushing step 61 to be crushed plastic. Processed. The crushed plastic thus obtained is also blown into the blast furnace 23 by the blowing means 62 together with the finely pulverized plastic, or together with the granulated plastic and finely pulverized plastic, and used as a blast furnace blown raw material.

  The granulating step 21 may use a known method that is usually used when granulating waste plastic (used plastic). For example, a granulation method such as the following compression molding granulation method can be used, particularly a film. It is suitable for granulating waste plastic. It is desirable to crush the waste plastic into a suitable size for the granulation process in advance.

  In the compression molding granulation method, waste plastic is granulated by compressing and extruding waste plastic from a hole of a ring die having a plurality of die holes penetrating therethrough. For example, a compression molding apparatus including a ring die having a plurality of die holes penetrating the entire periphery thereof, and a rolling roller that is rotatably disposed in contact with the inner peripheral surface of the ring die inside the ring die The waste plastic thrown into the ring die is pressed into the die hole of the ring die while being compressed and crushed by the rolling roller with the inner peripheral surface of the ring die, and passes through the die hole. By cutting or scraping off the plastic molding extruded to the outer surface side of the ring die from the outer surface of the ring die, a granular plastic molding serving as a blast furnace blowing material is obtained. A plastic molding (granular material) is obtained mainly by at least a part of the waste plastic being semi-molten or melted by frictional heat in the die hole and then solidified.

  As a granulating apparatus used in the compression molding granulation method, for example, a ring die having a plurality of die holes penetrating the entire circumference and rotatably supported by the apparatus main body and rotated by a driving apparatus, and an apparatus main body It is known to have one or two or more rolling rollers that are rotatably supported and arranged in contact with the inner peripheral surface of the ring die inside the ring die. The rolling roller is pressed and granulated into the die hole of the ring die while being compressed and crushed between the inner peripheral surface of the ring die.

  A schematic diagram of an example of a granulating apparatus used in the compression molding granulation method is shown in FIG. The plastic compression molding apparatus includes a ring die 31 having a plurality of die holes 30 penetrating the entire periphery thereof, and a rolling element disposed rotatably inside the ring die 31 so as to be in contact with the inner peripheral surface of the ring die. Rollers 32 a and 32 b and a cutter 33 disposed outside the ring die 31 are provided.

  The ring die 31 is composed of a ring body having an appropriate width, is rotatably supported by a device body (not shown), and is rotationally driven by a drive device (not shown). A plurality of die holes 30 are provided in the circumferential direction and the width direction of the ring die 31. These die holes 30 are provided so as to penetrate between the inner side (inner peripheral surface) and the outer side (outer peripheral surface) of the ring die 31 along the radial direction of the ring die 31. The hole diameter (diameter) of the die hole 30 is determined according to the size (diameter) of the granular plastic molding to be granulated, but is usually about 3 to 15 mm. The length of the die hole 30 (the thickness of the ring tie 31) is usually about 30 to 150 mm.

  The rolling rollers 32a and 32b are rotatably supported by the apparatus main body and are disposed in a state of facing the inner side of the ring die 31 by 180 °. These rolling rollers 32 a and 32 b are non-driving free roller bodies and are in contact with the inner peripheral surface of the ring die 31, and therefore rotate with the rotation of the ring die 31 due to friction with the inner peripheral surface. The number of the rolling rollers 32 is arbitrary, and one or three or more may be provided.

  The cutter 33 is provided so that the cutting edge thereof is in contact with the outer peripheral surface of the ring die 31 or is positioned in the vicinity of the outer peripheral surface, and a plastic molded product extruded in a rod shape from the die hole 30 to the outside of the ring die 31 has an appropriate length. It is cut into pieces (or scraped off from the outer peripheral surface of the ring die).

  In the plastic compression molding apparatus as described above, the ring die 31 is driven to rotate in the direction of the arrow in the figure, and the rolling rollers 32a and 32b are rotated accordingly. Waste plastic is put into the ring die 31, and the thrown plastic is mixed in the ring die 31 and is compressed and crushed between the inner peripheral surface of the ring die 31 by the rolling rollers 32a and 32b. It is pushed into 30. The waste plastic pushed into the die hole 30 passes through the die hole and is sequentially extruded in the form of a rod on the outer surface side of the ring die 31, and this plastic molding is made into an appropriate length by the cutter 33. By cutting, a granular plastic molding 35 is obtained. Reference numeral 36 denotes a discharge port.

  In the heat melting / dechlorination treatment step 25, it is preferable to carry out using an extruder when the waste plastic is heated and melted, melted and kneaded, and dechlorinated. An example of an extruder used in the heat melting / dechlorination treatment step 25 is shown in FIG. Even when the dechlorination treatment is not performed, it is preferable to heat and melt the synthetic resin material using an extruder.

  The extruder is an apparatus having an extrusion screw 41 in a cylinder 40 as shown in FIG. 7, and melt-kneading by transferring the plastic into the cylinder while heating. Since the power of the screw of the extruder is large and the waste plastic is melt-kneaded while moving in a narrow cylinder, a good mixing state can be obtained with sufficient stirring force. Moreover, since the residence time in an extruder can be easily adjusted by changing the diameter and rotation speed of a screw, controllability is high and it is easy to implement predetermined operating conditions. In addition, the degree of freedom in designing the production line is large, such as arranging a plurality of extruders. Although any number of screws can be used for the extruder, it is desirable to use an extruder having two or more screws from the viewpoint of processing efficiency.

  Further, by using an extruder, it can be transported simultaneously with stirring and can be processed efficiently. Therefore, it is possible to easily cope with a continuous process, and it is possible to perform processing of waste plastic having high thermal efficiency and high productivity.

  Waste plastic usually consists of a mixture of multiple types of plastics. When the waste plastic is sufficiently mixed, the interface between different plastics increases, stress is generated during cooling, and pulverization is improved. The grindability is further improved by using a waste plastic having a high chlorine content.

  As shown in FIG. 7, it is desirable that the extruder includes a first extruded portion 43 that removes moisture from the waste plastic and a second extruded portion 44 that removes hydrogen chloride.

  Since it is a waste, the waste plastic contains moisture and the like, and in the present invention, a material containing chlorine can be suitably used. Since plastic containing chlorine generates chlorine gas by heat treatment and corrodes the furnace and piping, it is desirable to inject into a blast furnace after dehydrochlorination treatment. Therefore, it is desirable to dechlorinate waste plastic when it is heated using an extruder. However, if water and hydrogen chloride are removed at the same time, hydrochloric acid is generated, which is undesirable because it causes corrosion problems. It is desirable to perform a dechlorination treatment after removing.

  In the first extruded portion 43, when the waste plastic is heated and melted, moisture is evaporated and removed. The higher the heating temperature, the smaller the heat loss in the next step, but it must be lower than the temperature at which chlorine is generated, and is preferably about 160 to 200 ° C. If a pipe that discharges water vapor is made of a corrosion-resistant material, processing at a higher temperature is possible. The purpose of the treatment is dehydration and melting, and the treatment can be performed in a shorter time than the second extruded portion 44.

  In the second extruding portion 44, the plastic remaining without being melted in the first extruding portion 43 is melted and mixed sufficiently to remove the chlorine component contained in the plastic. It is efficient to perform the dechlorination treatment at 300 ° C. or higher, and the higher the temperature, the higher the processing efficiency. Is preferably about 350 to 390 ° C. This treatment is intended for dechlorination and requires a longer time than the first extruded portion 43.

  When performing such a degassing treatment, it is desirable that the area of the interface between the molten plastic and the outside air is large, but the amount of waste plastic input should be set so that the liquid level of the molten plastic is sufficiently formed in the extruder. It is possible to perform sufficient degassing by adjusting or providing the convex portion 45 on the cylinder upper portion of the extruder to form a gas-liquid interface. In addition, the gas-liquid interface is updated at any time by the rotation of the screw, and there is an effect that the gas such as hydrogen chloride generated can be more easily separated.

  Therefore, the extruder used for the second extrusion portion 44 has a degassing space 45 at the top of the extruder cylinder, and has a pipe 46 for removing hydrogen chloride gas generated from the waste plastic from the degassing space 45. It is desirable. Due to the presence of the degassing space 45, an interface between the molten plastic and the outside air can be formed to improve the dechlorination efficiency. It is also possible to supply an inert gas such as nitrogen into the degassing space and actively discharge hydrogen chloride out of the system. It is desirable that the pipe 46 be heated to the same level or higher than the heating temperature of the extruder.

  In the cooling step 26, the plastic extruded from the extruder using a die or the like is cooled and solidified. What is necessary is just to cool using well-known methods, such as direct water cooling by the water tank 47 as shown in FIG. 7, or indirect cooling like a steel belt cooler. The treated plastic after cooling may be appropriately cut and pelletized or formed into a plate shape.

  In the coarse pulverization step 27 and the fine pulverization step 28, the treated plastic after cooling is used as a fine pulverization plastic. The pulverization may be performed using a normal pulverizer. Depending on the degree of pulverization, the pulverization step can be performed in one step.

  By using the above processing method, in step 2, the waste plastic can be pulverized to a particle size of less than 1.2 mm. By setting the particle size distribution of the pulverized product so that the particle size of 600 μm or less is 60 mass% or more, the pulverized product has particularly excellent combustibility.

  The granulated plastic obtained in step 1, the finely pulverized plastic obtained in step 2, and the crushed plastic obtained in step 3 are blown into the blast furnace 23 by the blowing means 22, 29, 62. It may be mixed in the middle of the piping for the purpose, and after mixing and storing in one storage tank, it can be blown into the blast furnace.

  Granulated plastic, crushed plastic, and finely crushed plastic were manufactured according to the flow of FIG. The heat melting / dechlorination treatment was performed using an extruder having a first extruded portion and a second extruded portion shown in FIG. The heating temperature in the first extrusion part was 180 ° C., and the heating temperature in the second extrusion part was 335 ° C. The resulting granulated plastic (diameter 7 mm, length 10-15 mm), crushed plastic (maximum particle size 10 mm and particle size 3 mm or more, 95 mass% or more), finely pulverized plastic (particle size 0 Table 1 shows the properties (composition, calorific value, heat of decomposition) of the used pulverized coal (75 μm or less, 80 mass% or more).

Blast furnace injection test (operation Nos. 1 to 9) using the above granulated plastic, crushed plastic, finely pulverized plastic with a particle size of less than 1.2 mm, and pulverized coal, coke replacement rate (combustibility) and blast furnace lower aeration The resistance index (breathability) was measured. The test was performed in a practical blast furnace with an internal volume of 5000 m ³ , changing the blowing method under the conditions shown in Table 2. FIG. 8 shows a method of blowing granulated plastic, crushed plastic, finely pulverized plastic, and pulverized coal. In FIG. 8, reference numeral 50 denotes a furnace wall of the blast furnace, and the right side of the furnace wall 50 toward the paper surface is inside the blast furnace. FIG. 8A shows a state in which the granulated plastic and / or crushed plastic is blown from the pipe 51 and the finely pulverized plastic is blown from the pipe 52, and the granulated plastic and / or crushed plastic and the finely pulverized plastic are mixed in the pipe 51. In this case, the blast furnace 54 is blown together with the pulverized coal blown from another pipe 53. 55 is hot air. FIG. 8B shows a case where the granulated plastic and finely pulverized plastic mixed in advance are blown from the pipe 51 and blown from the tuyere 54 of the blast furnace together with pulverized coal blown from another pipe 53. FIG. 8C shows a case where the granulated plastic is blown from the pipe 51 and pulverized coal is blown from the pipe 52, and the granulated plastic and pulverized coal are mixed in the pipe 51 and then blown from the tuyere of the blast furnace. FIG. 8D shows a case where the granulated plastic or crushed plastic is blown from the tuyere tuyeres 54 together with the pulverized coal blown from another pipe 53. The carrier gas speed of granulated plastic, crushed plastic and finely pulverized plastic was 20 m / s, and the carrier gas speed of pulverized coal was 15 m / s. When the crushing plastic and the granulated plastic were blown simultaneously, the crushing plastic and the granulated plastic were mixed and blown.

The blast furnace lower ventilation resistance index is an index indicating the pressure loss at the lower part of the blast furnace, and the larger the blast furnace lower ventilation resistance index, the greater the pressure loss. The blast furnace lower ventilation resistance index (K _l ) is calculated from the following equation (e).

K _l = (P _blast ² −P ₄ ² ) × 10 ⁶ / V _bosh (e)
Here, P _blast and P ₄ are the _blowing pressure, shaft four-stage pressure (Kg / cm ² ), and V _bosh is the Bosch gas amount (Nm ³ / min).

  The coke replacement ratio is: coke replacement ratio = (coke ratio during all coke operation−coke ratio when powder is blown) / (granulated plastic + crushed plastic + fine pulverized plastic + pulverized coal). Since the replacement rate of the total amount of plastic, finely pulverized plastic, and pulverized coal is coke, the larger the coke replacement rate, the higher the plastic combustion rate.

Operation No. 1 to 5 is the blowing method of FIG. 8 (a). When the ratio of granulated plastic and / or crushed plastic and finely pulverized plastic is changed and mixed in the middle of piping, operation No. 1-5 is performed. 6 is the blowing method of FIG. 8 (b). When the granulated plastic and the finely pulverized plastic are charged into the same reservoir and blown, the operation No. 6 is performed. 7 is the blowing method of FIG. 8 (d). When granulated plastic and pulverized coal are blown from different lances, operation No. 7 is performed. 8 is the blowing method of FIG.8 (c), and is a case where granulated plastic and pulverized coal are mixed in the middle of piping. Operation No. 9 is the blowing method of FIG. 8 (d), in which crushed plastic and pulverized coal are blown from different lances. 7 to 9 are all comparative examples. Table 2 also shows the measurement results of the coke replacement rate and the blast furnace lower ventilation resistance index (K _l ) in each operation.

Operation No. 1 in which granulated plastic and crushed plastic were mixed with pulverized coal and blast furnace was injected. Compared with 7-9, operation No. 1 in which pulverized plastic was mixed with pulverized coal after mixing finely pulverized plastic with granulated plastic and crushed plastic. In 1-6, the coke substitution rate increased and the blast furnace lower air flow resistance index ( _Kl ) decreased. From these results, it was found that the use of finely pulverized plastics improves the combustibility and breathability of granulated plastics and crushed plastics.

Schematic of a test apparatus for evaluating ignition characteristics. The graph which shows the measurement result of ignition start time. Schematic of a combustion test apparatus that evaluates the combustion rate. The graph which shows the measurement result of a combustion rate. Explanatory drawing of one Embodiment of this invention. Schematic of an example of a granulator used in the compression molding granulation method (ring die granulator). Schematic which shows an example of the extruder used at a heat-melting / dechlorination process. Explanatory drawing which shows the blowing method of the granulation plastic in the Example, fine grinding plastic, and pulverized coal. The graph which shows the particle size distribution of granulated plastic.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vertical electric furnace 2 Preheater 3 Powder supply apparatus 4 Exhaust gas discharge passage 5 Unburned powder sampling part 6 Combustion test apparatus 7 Tuyere 8 Blow pipe 9 Probe 10 Waste plastic ground material 11 Lance 12 Raceway 13 Coke supply apparatus 20 Pretreatment process 21 Granulation process 22 Blowing means 23 Blast furnace 24 Simple pretreatment process 25 Heat melting / dechlorination process 26 Cooling process 27 Coarse grinding process 28 Fine grinding process 29 Blowing means 30 Die hole 31 Ring die 32a, 32b Moving roller 33 Cutter 34 Input port 35 Granular plastic molding 36 Discharge port 40 Cylinder 41 Extrusion screw 43 First extrusion portion 44 Second extrusion portion 45 Convex portion (degassing space)
46 Piping 47 Water Tank 50 Blast Furnace Wall 51 Piping 52 Piping 53 Piping 54 Tuyere 55 Hot Air 60 Pretreatment Step 61 Crushing Step 62 Blowing Means L ₁ Furnace Length L ₂ Powder Combustion Length

Claims (4)

When a synthetic resin material is blown into the furnace from the tuyere of the blast furnace, a synthetic resin material having a chlorine concentration of less than 1.7 mass% is heated and melted at a temperature of 160 ° C. or more and 270 ° C. or less, and pulverized after cooling and solidification. A method of blowing a synthetic resin material into a blast furnace, wherein the synthetic resin material having a particle size of less than 1.2 mm and a synthetic resin material containing a particle size of 3 mm or more and 90 mass% or more are simultaneously blown.   The synthetic resin material having a particle size of less than 1.2 mm is blown at a ratio of 33 to 300 parts by mass with respect to 100 parts by mass of the synthetic resin material containing 90% by mass or more of a particle size of 3 mm or more. Method of injecting synthetic resin into the blast furnace. The method for blowing a synthetic resin material into a blast furnace according to claim 1 or 2, wherein pulverized coal is blown simultaneously with the synthetic resin material. The method for blowing a synthetic resin material into a blast furnace according to any one of claims 1 to 3 , wherein waste plastic is used as the synthetic resin material.

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