JP3973940B2 - Waste plastic combustion burner for electric furnace - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a waste plastic combustion burner provided on a furnace wall and a furnace lid of an electric furnace used for melting a metal material and / or refining a molten metal.
[0002]
[Prior art]
In recent years, the number of waste plastics exhausted as industrial waste or general waste has been increasing. On the other hand, as a major theme for environmental conservation on a global scale, there is an increasing demand for carbon dioxide gas instantly, and instead of processing waste plastics in landfills by conventional incineration, material waste is recycled as a heat source. More and more cases are tackling.
In particular, while the current waste plastics are mixed with many types of plastics, thermal recycling is attracting attention from the viewpoint of processing costs, and in many industrial furnaces, practical application or research into practical use of thermal recycling of waste plastics has been made. Various burners for efficiently burning waste plastic have been proposed.
[0003]
For example, in Japanese Patent Application Laid-Open No. 7-71728, by disposing a nozzle for spraying liquid fuel on the outer periphery of a nozzle for blowing waste plastic powder having a particle diameter of 1 mm or less, the waste plastic powder is reliably ignited. A burner structure for stable combustion has been proposed.
Further, in Japanese Patent Laid-Open No. 10-185115, as a conventional technique, waste plastic with a metal coating of about 1 to 2 mm, which has been finely divided by primary combustion air for fuel supplied from an ignition burner, is formed into a cylindrical combustion cylinder. There has been proposed a method in which a swirling flow is generated inside and sprayed into an incinerator, and further, by blowing secondary combustion air, the plastic waste is combusted and sprayed into the incinerator.
However, according to these methods, since the refractory constituting the combustion cylinder is overheated by the combustion of the waste plastic, the metal-coated waste plastic is ejected linearly from the rear end of the burner into the incinerator to prevent it. An improved technique for combusting waste plastic by providing an ejection nozzle and an ignition burner around the nozzle is proposed.
[0004]
All of the burners proposed in the above publications are targeted for blowing powdery waste plastic of about 1 to 2 mm, but generally it costs processing costs when the waste plastic is crushed to about 1 to 2 mm, and the bulk specific gravity increases. There is a problem that the merit of using waste plastic as a heat source is reduced because the size is reduced and transportation costs are increased. In order to enjoy sufficient cost merit by thermal recycling of waste plastic, it is desirable that the size of the waste plastic used for blowing is about several mm to several tens of mm.
[0005]
The burner is assumed to be used in a furnace having a space inside the furnace in front of the burner such as an exhaust incinerator. For this reason, the burner proposed in Japanese Patent Laid-Open No. 7-71728 does not have a combustion chamber in the burner itself, and the burner of the improved technique of Japanese Patent Laid-Open No. 10-185115 is in the description thereof. The waste plastic blown from the jet nozzle does not need to be burned sufficiently in the burner, and it is proposed to protect the refractory in the burner's combustion cylinder by constructing a proportion of the waste plastic to burn in the furnace. Has been.
[0006]
Thus, various types of waste plastic combustion burners have been proposed in the past, but most of them are used in incinerators, and few are used in electric furnaces.
[0007]
In an electric furnace, raw material scrap is charged into the furnace so that the scrap is melted mainly by arc energy generated at the center of the furnace, and assists melting of scrap near the furnace wall far from the arc generating part. In addition, oil and gaseous fuel combustion burners are used. Therefore, it is assumed that scrap exists on the front surface of the burner, and there is almost no space on the front surface of the burner, particularly at the initial stage of scrap melting.
Under such conditions, when a waste plastic combustion burner as proposed in the above publication is used as an alternative to an oil or gas fuel burner, especially the flow rate of waste plastic and the flow rate of gas such as air for carrying it. When the amount of gas increases, the waste plastic ejected from the burner center and the waste plastic formed by the combustion of fuel collide with the scrap near the furnace wall, bounce off, adhere to the water-cooled furnace wall, and burn. Alternatively, dust is collected from the furnace through a small space between the scrap near the furnace wall and the water-cooled furnace wall, which causes a problem that the combustion heat does not sufficiently contribute to melting of the scrap.
[0008]
Naturally, when waste plastic having an economical size of about several millimeters to several tens of millimeters is blown, the combustion speed is slow, so that the efficiency of the combustion heat is further reduced. .
Further, in the prior art disclosed in Japanese Patent Laid-Open No. 10-185115, cylindrical plastic is used to dispose of a 1 to 2 mm metal wire-covered waste plastic finely divided by primary combustion air for combustion supplied from an ignition burner. There has been proposed a method in which waste plastic is burned by being blown out so as to generate an internal swirling flow in a cylinder, and further blown in secondary combustion air, and then blown into an incinerator.
[0009]
However, in this method, most of the waste plastic ejected to the combustion cylinder is combusted, but since it is gasified along the swirl flow and burns in the vicinity of the inner wall of the combustion cylinder, the refractory constituting the inner wall of the combustion cylinder is waste plastic There is a problem that it is overheated by combustion.
In addition, the above-mentioned conventional burner uses air for combustion and completely burns waste plastic in a large space, so it is applicable to electric furnaces where it is difficult to secure sufficient space around the furnace. Can not.
[0010]
[Problems to be solved by the invention]
Therefore, according to the present invention, waste plastic combustion for electric furnaces that enables the introduction of waste plastics of several tens of millimeters, simplifies pretreatment equipment for thermal recycling of waste plastics, and greatly reduces equipment costs. The problem is to provide a burner.
[0011]
[Means for Solving the Problems]
The present invention has been made in order to solve the above-mentioned problems, and the gist thereof is the following contents as described in the claims.
[0012]
(1) A flow path for ejecting oxygen for scrap cutting is disposed at the center, and a flow path for ejecting fuel and a flow path for ejecting oxygen for fuel combustion are disposed on the outer periphery of the flow path. and a combustion space provided between the electric furnace furnace chamber, wherein the plurality electric furnace waste plastics combustion burner blowing port blowing waste plastics pneumatically transported into the combustion space, of the plurality of blowing openings An electric furnace characterized in that waste plastic to be conveyed by air is blown from at least one blowing port, only gas is blown from the other blowing port, and spiral blades are disposed on the inner wall of the combustion space. Waste plastic combustion burner for use.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described in detail with reference to FIGS.
1 is a longitudinal sectional view of an electric furnace in which the waste plastic combustion burner of the present invention is arranged, FIG. 2 is a detailed sectional view of the waste plastic combustion burner of the present invention, and FIG. 3 is a view taken along arrow BB in FIG. 4 and FIG. 4 are AA arrow views of FIG. 2, and FIG. 5 is a CC arrow view of FIG. In FIG. 1, the electric furnace is composed of a furnace body 1 and a furnace lid 3 through which a movable electrode 2 for generating an arc 4 passes. The furnace body 1 and the furnace lid 3 can withstand the heat generated by the arc 4. A water-cooled panel 5 is attached. The furnace lid 3 is provided with a duct 6 for sucking gas generated in the furnace.
[0015]
In the electric furnace, the raw material scrap 7 is charged in the furnace, and the scrap 7 is melted by the energy of the arc 4 generated in the center of the furnace. Further, in order to assist the melting of the scrap near the furnace wall far from the arc 4 generation part, an oil or gas fuel combustion burner has been conventionally installed. In FIG. 1, instead of the oil or gas fuel combustion burner. The state which installed the waste plastic combustion burner 8 is shown. When the scrap 7 is being melted, the scrap 7 exists on the front surface of the burner 8 particularly in the initial stage of melting, and the space 9 between the burner 8 and the scrap 7 is in a very small state. Under these conditions, the blown waste plastic does not burn or is heated, and hits and bounces off the scrap near the furnace wall, adheres to the panel 5 on the furnace wall, and burns or scraps 7 near the furnace wall It is important to burn the waste plastic as much as possible inside the burner 8 so that it is not sucked from the duct 6 through a small space in the furnace wall panel 5 and to fully utilize its heat for melting the scrap. .
[0016]
FIG. 2 shows the waste plastic combustion burner of the present invention installed on the side wall of an electric furnace furnace body. In FIG. 2, a burner block 10 is formed by providing an oxygen flow path 13 for scrap cutting at the center, and arranging a plurality of fuel flow paths 11 and an oxygen flow path 12 for fuel combustion around it. .
In the case shown in FIG. 3, the fuel flow paths 11 and the oxygen flow paths 12 are alternately arranged around the scrap cutting oxygen flow path 13 in the center. A note space 20 surrounded by the combustion cylinder 14 is formed between the jet nozzle tip of the burner block 10 and the furnace chamber. The combustion cylinder 14 is provided with a blowing port 15 for blowing waste plastic.
[0017]
In the combustion space 20 of the burner, an oxygen flow 17 for scrap cutting is formed at the center. The fuel injected from the fuel flow path 11 becomes a fuel jet flow 18 in the combustion space 20 of the combustion cylinder 14, and the oxygen jetted from the oxygen flow path 12 becomes an oxygen jet flow 19 in the combustion space 20, and both jet flows are mixed. Fire.
As shown in FIG. 4, the waste plastic blow-in port 15 is provided so that the waste plastic that is gas-conveyed in the combustion cylinder 14 turns.
[0018]
Four waste plastic injection ports are installed in the combustion cylinder 14 so as to inject waste plastic, but the waste plastic is injected from only one of the four injection ports, and the other three are You may make it blow only gas. In this way, the waste plastic blown into the combustion cylinder is more likely to generate a swirling flow due to the gas blown from the other three, and the combustion efficiency of the waste plastic can be improved.
[0019]
FIG. 5 is a view in which a spiral blade 21 is provided on the inner wall of the combustion cylinder 14, and the waste plastic blown into the blade 21 together with the gas from the waste plastic blowing port 15 swirls and passes through the combustion cylinder 14. . The blade 21 causes the swirl and swirl at the waste plastic blowing port to have a synergistic effect, and the waste plastic blown into the combustion cylinder 14 further swirls and passes.
[0020]
Copper was used for the blade fixed to the inner wall of the combustion cylinder 14. By fixing to the inner wall of the combustion cylinder 14, the blades are cooled by water cooling of the outer periphery of the combustion cylinder 14, and even if the waste plastic flame directly contacts in the combustion cylinder 14, it does not melt.
[0021]
As described above, in the present invention, the waste plastic is disposed around the high temperature flame 16 formed by the scrap cutting oxygen flow 17 formed in the central portion and the surrounding fuel and combustion oxygen. The waste plastic blown into the combustion space 20 while swirling into the blade 21 fixed to the inner wall 14 swirls and passes through the combustion cylinder 14, so that the passage time of the waste plastic in the combustion cylinder can be maintained for a long time. Even if the size is several millimeters to several tens of millimeters, it can be efficiently burned in the combustion tower 14.
[0022]
【The invention's effect】
As described above, conventionally, it has been necessary to put waste plastic into a powder and put it into a burner. However, according to the present invention, it is possible to put in waste plastic of several tens of millimeters, and it is possible to perform thermal recycling of waste plastic in advance. Processing facilities can be simplified, and equipment costs can be greatly reduced.
In addition, since the swirl vanes that swirl the waste plastic are fixed to the inner wall of the combustion cylinder, the residence time of the waste plastic in the combustion cylinder is extended, and even a few tens of millimeters of waste plastic can be burned completely. It is effective and has significant industrially useful effects.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an electric furnace in which a waste plastic combustion burner of the present invention is arranged.
FIG. 2 is a detailed sectional view of the waste plastic combustion burner of the present invention.
FIG. 3 is a view taken along arrow BB in FIG. 2;
4 is an AA arrow view of FIG. 2;
FIG. 5 is a view taken along the line CC in FIG. 2;
[Explanation of symbols]
1: Furnace body 2: Movable electrode 3: Furnace lid 4: Arc 5: Water cooling structure panel 6: Duct 7: Scrap 8: Burner 9: Space 10: Burner block 11: Fuel flow path 12: Oxygen flow path for combustion 13: Scrap cutting oxygen flow path 14: Combustion cylinder 15: Waste plastic injection port 16: Flame 17: Oxygen flow 18 for scrap cutting 18: Fuel jet stream 19: Combustion oxygen jet stream 20: Combustion space 21: Blade

Claims (1)

A flow path for ejecting oxygen for scrap cutting is disposed at the center, and a flow path for ejecting fuel and a flow path for ejecting oxygen for fuel combustion are disposed on the outer periphery of the flow path. A waste plastic combustion burner for an electric furnace in which a combustion space is provided between the furnace chamber and a plurality of blowing ports for blowing waste plastic that is air-conveyed into the combustion space is provided . At least one of the plurality of blowing ports. Waste plastic for electric furnace , wherein waste plastic to be conveyed by air is blown from a single blow inlet, only gas is blown from the other blow openings, and spiral blades are disposed on the inner wall of the combustion space. Burning burner.

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