JP2001263620A - Plasma arc melting furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma arc melting furnace in which local deterioration is suppressed effectively so that the joint part and brick have an equivalent deterioration strength and durability of brick constituting the inside of the melting furnace can be enhanced by avoiding replacement and repair of refractories themselves due to local deterioration. SOLUTION: Inner wall of a furnace is surrounded entirely or partially by regular refractories being a plurality of bricks, and a cooling jacket is provided on the outside thereof. In such a plasma arc melting furnace, a cooling member connected with the cooling jacket is provided along the vertical joint of the furnace for combining the bricks while touching each other. Alternatively, the vertical joint for combining the bricks while touching each other has a nonlinear structure from the core toward the outer wall of the furnace.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma arc melting furnace using a brick as a fixed refractory on the inner wall of a furnace, and more particularly to incineration ash for sewage sludge, municipal solid waste and industrial waste, and for industrial use. The present invention relates to a plasma arc type melting furnace for melting incineration ash discharged from a combustion furnace such as a thermal power plant by electric plasma.

[0002]

2. Description of the Related Art Conventionally, incinerated ash (powder inorganic substance) such as sewage sludge, municipal solid waste and industrial waste has been used as shown in FIG. It is melted by a simple plasma arc melting furnace 11 and taken out as slag. In order to melt the incineration ash in the furnace body using such a melting furnace 11, the incineration ash discharged from the refuse incinerator is screened by a dry ash extraction device, a magnetic separator, an incineration ash silo, a measuring device, and an ash. After passing through a pretreatment system such as a supply conveyor, the ash is supplied from the ash supply hopper 12 into the furnace body, and the supplied incinerated ash is melted by the high-temperature plasma 20.
At this time, fly ash similarly discharged from the incinerator is mixed with the incinerated ash discharged from the incinerator via a fly ash silo or a measuring instrument and supplied from an ash supply conveyor.

[0003] The molten slag 21 generated in the melting furnace 11
Is discharged from a slag port 23 through a slag gutter 24 to a dry slag apparatus, guided to a slag discharge system via a slag conveyor, and used for various uses. At the top and bottom of the furnace body 11,
Main electrode 1 of plasma electrode connected to DC power supply 13
8 and electrodes are provided, and nitrogen gas is supplied from the nitrogen gas generator to the upper part of the furnace main body. Further, the furnace main body of the plasma arc type melting furnace 11 is mainly composed of a refractory and a shell of a water cooling jacket (cooling structure 15) covering the outside thereof. Normally, the refuse incinerator is communicated with the chimney via a bag filter, while the exhaust gas generated in the melting furnace main body 11 passes through a secondary combustion chamber covered with a slag outlet cover 26, and then passes through a bag filter and a wet washing. It is being led to an exhaust gas treatment system consisting of a smoke tower and a chimney. Air is supplied from a combustion air fan to the secondary combustion chamber, and the bag filter is connected to a molten fly ash treatment device or the like.

[0004] By the way, usually, in a melting furnace, FIG.
As shown in the figure, the bricks 2 stacked vertically are
The joints are shifted so that the joints do not match up and down. A cooling jacket 4 as a cooling structure is provided on the outermost outer wall 5 of the melting furnace, and a stamp layer 7 made of an elastic refractory material is provided between the cooling jacket 4 and the brick 2. ing. The bricks 2 have a shape in which the width (thickness) becomes thinner from the outside of the furnace toward the center, and are arranged in a circle along the outer wall, so that the bricks 2 do not move inward (arch shape). It is organized in. In such a conventional melting furnace, cooling is performed only from the outer wall side 5 of the brick 2 which is a refractory material by a cooling action of water or the like flowing in the cooling jacket 4.

However, in the case of the conventional method for cooling a refractory in a melting furnace, the mortar joint 3 having a high porosity and a low thermal conductivity locally increases the surface temperature, so that the corrosion resistance is remarkably inferior. In other words, mortar is used for the joint (joint 3) between the bricks 2 and the mortar is a material similar to the brick, but the aggregate particles are fine, the moisture is large, and the mortar is soft. The joints 3 using this mortar have low strength and high moisture content as compared with bricks, and therefore have large pores. Therefore, if the operation of the melting furnace is performed for a long time, the erosion of the refractory starts from the joints,
There is a problem that the more round the corner of the brick 2 around the joint, the more the brick 2 deteriorates.

If the joints 3 are further deteriorated, the thickness direction of the bricks 2 from the center of the furnace to the outer wall 5 may be completely eroded. Brick 2 had to be replaced by repair in the furnace before the erosion reached depth.
From the above, regarding the durability of the refractory constituting the interior of the melting furnace, the erosion that starts from the deterioration of the joints 3 greatly shortens the life of the brick 2. This has made it difficult to operate the melting furnace stably for a long period of time, causing problems such as frequent maintenance and inspection of refractory materials and a problem of cost burden for repair and replacement.

[0007]

DISCLOSURE OF THE INVENTION In view of the above-mentioned problems, the present inventors have effectively suppressed local deterioration, particularly of a mortar joint portion of the inner wall of a melting furnace, so that the joint portion and the brick are equivalent. In order to develop a plasma-arc-type melting furnace that can improve the durability of refractories while avoiding the replacement and repair of the refractories themselves due to local deterioration, while maintaining the deterioration strength . As a result, the present inventors have attached a cooling structure for cooling from the outside of the melting furnace to the mortar joint as a cooling member in order to prevent erosion deterioration of joints having high porosity and low thermal conductivity. It has been found that the above problems can be solved by strengthening the cooling, or by forming the mortar joint into a non-linear complex shape to achieve uniform cooling. The present invention has been completed from such a viewpoint.

[0008]

That is, according to the present invention, there is provided a plasma in which a whole or a part of a furnace inner wall is surrounded by a plurality of bricks which are a standard refractory, and a cooling jacket is provided outside the furnace to cool the furnace. An arc melting furnace, comprising: a plasma arc melting furnace provided with a cooling member connected to the cooling jacket along a vertical joint of the furnace in which the bricks are brought into contact with each other and combined. It is. Here, it is preferable that the cooling member does not reach the furnace inner wall surface. Further, the present invention is a plasma arc type melting furnace in which all or part of the furnace inner wall is surrounded by a plurality of bricks that are a standard refractory, and a cooling jacket is provided outside the furnace to cool the furnace. An object of the present invention is to provide a plasma arc type melting furnace in which vertical joints in which bricks are brought into contact with each other and have a non-linear structure from the furnace core toward the furnace outer wall.

[0009] By using the melting furnace of the present invention, local deterioration of joints can be effectively suppressed, and the joints and bricks can have the same deterioration strength. It is possible to improve the durability of the brick constituting the inside of the melting furnace by avoiding replacement and repair of the brick. here,
In the present invention, instead of cooling the entire refractory inside the furnace, the joints in the direction perpendicular to the liquid level of the molten slag are cooled. For this reason, a cooling member (cooling fin) is provided in the vertical direction in order to cool joints provided in the vertical direction of the furnace.

Generally, in a melting furnace, joints are provided in a vertical direction and a horizontal direction as shown in FIG. Among these joint portions, the most deteriorated portion is a portion 6 which is in contact with the upper surface portion (slag line) where the molten slag overflows, as shown in FIG. 3 which is a vertical sectional view. This is because the portion 6 is in contact with both the gas layer 8 and the molten slag layer 9 and it is necessary that the portion 6 can withstand contact from both components. Usually, in the slag line, the inner wall of the furnace is constituted by a refractory such as a brick because it is in contact with the molten slag layer 9, but since one of the gas layers 8 contains a little oxygen, the brick (SiC component) Are easily oxidized and easily deteriorated. On the other hand, even if the joints are the same, the joints in the horizontal direction are in contact with the same layer of slag, gas, or the like, and therefore, the joints in the horizontal direction do not deteriorate as in the portion 6 in contact with the slag line. Further, since the furnace inner wall located above the slag line contacts only the gas layer 8, it may be made of a material containing, for example, alumina. The cooling structure in the melting furnace of the present invention is to improve the durability of the refractory by supercooling particularly such vertical joints where deterioration is severe.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on illustrated embodiments. Embodiment (No. 1) FIG. 1 is a view showing a structure of an outer wall and a refractory of a melting furnace according to an embodiment of the present invention, in which a cooling fin 1 is provided as a cooling member. As shown in FIG. 5, the plasma arc type melting furnace of the present embodiment has a furnace body 11 formed in a cylindrical shape with a bottom.
A slag port 23 for extracting molten slag and exhaust gas is provided. In addition, a main electrode 18 of a plasma electrode connected to a DC power supply device is provided at an upper portion of the furnace main body 11 so as to hang therefrom. Nitrogen gas is supplied to the main electrode from a nitrogen gas generator. It is configured to be
The input waste incineration ash is heated and melted by the high-temperature plasma 20.

The melting furnace 11 includes a refractory 16 and a cooling structure 15 including a cooling jacket that covers the outside of the refractory, and the cooling jacket is formed of a steel shell (iron plate) and has a closed cross section. . Non-oxide bricks such as SiC bricks and carbon bricks are widely used as refractories constituting the inner wall surface in the melting furnace 2. A through-hole (through-hole) for the main electrode is formed in the upper center of the melting furnace 11, and an insulating sleeve and a nozzle (wind box) for blowing a sealing gas (nitrogen gas) are provided in the through-hole. ing. When the slag is discharged from the accompanying slag gutter 24, the slag overflows and is sequentially discharged.

The internal structure of the furnace according to the present embodiment is such that the cooling fins 1 extend from the cooling jacket 4 along joints perpendicular to the surface of the slag layer 9 from the furnace core to the outer wall 5.
And mortar is applied on both sides. The stamp layer 7 is penetrated by the cooling fin 1.
Since cooling such as water cooling is performed in the cooling fin 1 similarly to the cooling structure of the cooling jacket 4, the joint portion of the mortar is also cooled. As described above, by supercooling the joint portion made of mortar by the cooling fins 1, the durability of the mortar and the durability of the brick portion can be made substantially the same, and local deterioration of the joint portion can be prevented. . And the durability of the brick 2 itself can also be improved.

Here, the length of the cooling fin 1 in the direction of the core is not particularly limited.
May be about the same as the total thickness of the brick and stamp layers so that it comes out of a part of the brick wall of the furnace inner wall, or may be embedded in the brick without reaching the furnace inner wall as shown in FIG. Such a structure may be used. However, from the viewpoint that the material of the cooling fin 1 does not directly contact the high-temperature molten slag or the like, a structure in which the cooling fin does not reach the inner wall of the furnace is preferable. Although the thickness of the cooling fin 1 is not particularly limited, the thickness of the joint 3 itself is usually about 2 to 3 mm, and therefore, a range larger than that, for example, about 2 to 10 mm is preferable. The cooling fin 1 is made of a material having excellent thermal conductivity, such as iron or copper.

The location where the cooling fins 1 are provided is not particularly limited, and can be widely used as long as it is a vertical joint in the furnace. For the reasons described above, the joints connecting the bricks 2 in contact with the slag line are particularly preferred. Is preferably provided. However, since the slag line itself rises and falls to some extent (about ± 50 mm), a structure in which a plurality of cooling fins are provided in a certain range in the vertical direction is also preferable. In the melting furnace of the present invention, the cooling of the joints and the mortar portion is directly enhanced by the cooling fins 1, and the durability of the refractory material made of brick or the like is improved. In addition, the provision of the cooling fins 1 makes the joints non-linear, so that the time required for erosion is lengthened, and in that respect, the durability of the refractory material is improved.
This is a further effect when the cooling fin 1 does not reach the inner wall of the furnace, and has a role of stopping the erosion of the joint at the location of the cooling fin.

Embodiment (No. 2) FIG. 2 is a view showing a structure of an outer wall and a refractory of a melting furnace according to an embodiment of the present invention, and a joint 3 is bent from a furnace core to an outer wall. have. In the present embodiment, a part of the furnace inner wall is surrounded by a brick that is a standard refractory, and cooling is provided by providing a cooling jacket on the outside thereof. It has a non-linear structure from the furnace core to the furnace outer wall. Here, the non-linear structure includes not only a bent structure as shown in FIG. 2 but also various shapes having a plurality of steps in a linear portion, such as an uneven shape or a step shape. However, a simple curved shape is not preferable because it is not enough to prevent deterioration from erosion. By thus forming the joint portion 3 in a complicated shape (non-linear shape), the cooling effect can be made uniform, and local intrusion of slag can be prevented.

In general, in a plasma arc type melting furnace, main ash generated by ordinary incineration and fly ash such as dust remaining in the gas are mixed and thrown in from an ash supply hopper. A screw is provided at the lower part of the hopper, and is supplied from the screw through the ash inlet into the melting furnace. The furnace is in a nitrogen atmosphere at about 1000 ° C. In the furnace, there is a molten slag layer 9 in which main ash and fly ash are melted, and the supplied ash is also deposited thereon. The temperature of the molten slag is about 1600 ° C. The melted ash is discharged from the slag port. When dissolving the ash, the main electrode (upper) in the furnace is minus and the plus electrode is located below, so that current flows and plasma is generated, and current also flows to molten metal and slag (transfer type) plasma). Plasma temperature is about 10,000 ℃
And the inside of the electrode is hollow.

The inside of the melting furnace is surrounded by a brick or the like which is a standard refractory, and a water cooling jacket is provided on the outside thereof,
Cooling. Generally, bricks are used for a portion (slag portion) where the molten slag layer contacts the inner wall of the furnace, but an irregular refractory (for example, cement) is used for a portion where the gas layer contacts. The boundary between these refractories is located slightly above the liquid level (slag line) of the molten slag. Normally, a refractory such as a brick is used in the upper portion of the slag portion and for one more stage. Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications and changes can be made without departing from the spirit of the present invention. is there.

[0019]

According to the plasma arc type melting furnace of the present invention, the local deterioration of the mortar joint, particularly the inner wall of the melting furnace, is effectively suppressed, and the joint and the brick have the same deterioration strength. I can do it. In addition, it is possible to avoid the replacement or repair of the refractory material itself due to local deterioration, and to improve the durability of the brick constituting the inside of the melting furnace. Further, the melting process in the plasma arc type melting furnace can be performed continuously and stably over a long period of time.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a refractory and an outer wall structure of a melting furnace according to the present invention.

FIG. 2 is a diagram showing another example of the refractory and outer wall structure of the melting furnace according to the present invention.

FIG. 3 is a sectional view of the inside of a plasma arc type melting furnace.

FIG. 4 is a diagram showing an example of a conventional refractory and outer wall structure.

FIG. 5 is a configuration diagram schematically showing a plasma arc type melting furnace and a system associated therewith.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cooling fin (cooling member) 2 Refractory (brick) 3 Joint 4 Cooling jacket 5 Furnace outer wall 6 Erosion location (erosion location of slag line) 7 Stamp layer 8 Gas layer 9 Slag layer 10 Metal layer 11 Melting furnace 12 Ash hopper 13 Power supply 14 Ash inlet 15 Cooling structure 16 Refractory 17 Sleeve 18 Main electrode 20 Plasma arc 21 Molten slag 22 Molten metal 23 Outlet 24 Outlet gutter 25 Outlet cleaner 26 Outlet cover

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F27B 3/14 F27B 3/24 3/24 F27D 1/00 K F27D 1/00 1/12 A 1/12 B09B 3/00 303L (72) Inventor Naoyuki Ito 1-8-1 Koura, Kanazawa-ku, Yokohama-shi, Kanagawa Prefecture F-term in Yokohama Research Laboratory, Mitsubishi Heavy Industries, Ltd. 3K061 AA18 AA23 AB03 AC01 AC02 AC03 CA14 DA13 DB12 DB19 DB20 NB02 NB13 NB24 NB27 NB28 3K065 AA18 AA23 AB03 AC01 AC02 AC03 FA03 FA15 FB02 FC02 4D004 AA36 CA08 CA09 CA29 CA32 CA43 CB31 4K045 AA04 BA10 RA06 RA16 RB02 4K051 AA05 AB03 BD07 HA04 HA06

Claims (3)

[Claims] 1. A plasma arc melting furnace in which a whole or a part of a furnace inner wall is surrounded by a plurality of bricks which are a fixed refractory, and a cooling jacket is provided outside the furnace to be cooled. A plasma arc melting furnace, comprising: a cooling member connected to the cooling jacket along a vertical joint of the furnace in which the furnaces are brought into contact with each other. 2. The plasma arc melting furnace according to claim 1, wherein the cooling member does not reach the inner wall surface of the furnace. 3. A plasma arc melting furnace in which a whole or a part of a furnace inner wall is surrounded by a plurality of bricks which are a standard refractory, and is cooled by providing a cooling jacket on the outside thereof. A plasma arc melting furnace characterized in that vertical joints to be brought into contact with each other have a non-linear structure from the furnace core toward the furnace outer wall.