JPH10253266A - Method for re-starting plasma melting furnace and plasma melting furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a sure re-starting of a melting furnace to be carried out by a method wherein after conductive particles are fed between plasma torches on a slag solidified on base metal when the re-starting is carried out after a plasma melting furnace is stopped in its operation, a voltage is applied to the plasma torches so as to form a plasma arc. SOLUTION: In the case that a plasma ash melting furnace is to be re-started after its operation is stopped, a predetermined amount of granular carbon C fed from a conductive material supplying device 21 into a main body 3 of the furnace is accumulated on a solidified layer CS where molten slag formed on a condensing base metal 4 is solidified. Then, operating gas is supplied from an operating gas supplying device 18 into the main body 3 of the furnace through plasma torches 15A, 15B. A starting voltage is applied from a DC power supply device 17 to plasma torches 15A, 15B to generate a plasma arc between the granular carbon layer C and the plasma torches 15A, 15B, and then the solidified slag layer CS is heated and melted and further the base metal 4 is melted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is directed to harmless solid waste such as incineration ash and construction waste discharged from a waste incinerator.
The present invention relates to a restart method and a plasma melting furnace in a plasma melting furnace for heating and melting for the purpose of volume reduction.

[0002]

2. Description of the Related Art A conventional twin torch type or a plasma type melting furnace having three or more plasma torches accommodates a base metal at the bottom of a furnace body and a plurality of plasma torches at a top wall of the furnace body. Hang down freely
By generating a plasma arc between the base metal and the plasma torch, the incineration ash and waste put on the base metal are heated and melted, the molten slag overflows and is put into the cooling water tank to form granulated slag By doing so, the incineration ash and waste are made harmless and the volume is reduced.

[0003]

When the plasma melting furnace is started (started), an iron piece serving as a base metal is put into the bottom of the furnace body, and a plasma arc is generated between the iron piece and the plasma torch. After heating and melting to form a base metal, ash and waste are charged.

However, the base metal and the molten slag after the operation is stopped are solidified by cooling the furnace body, and a solidified slag layer is formed on the solidified base metal. This slag has conductivity in a molten state, but loses conductivity when solidified. Therefore, when restarting (restarting), there is a problem that a plasma arc cannot be formed and restarting becomes difficult.

The invention according to claim 1 of the present invention solves the above-mentioned problems and provides a method for restarting a plasma-type melting furnace and a plasma-type melting furnace capable of easily restarting even if there is a residual solidified slag layer. It is intended to provide a furnace.

[0006]

According to a first aspect of the present invention, there is provided a method for restarting a plasma-type melting furnace, comprising: A plasma melting furnace in which the plasma torch hangs down close to the base metal, generates a plasma arc between the base metal and the plasma torch, and heats and melts ash and waste put on the base metal to produce slag When restarting after stopping, conductive particles are charged between the plasma torches on the slag layer solidified on the base metal, and then a voltage is applied to the plasma torch to form a plasma arc. In the plasma melting furnace according to the fourth aspect, the base metal is housed in the furnace bottom, and a plurality of plasma torches hang down from the furnace top in close proximity to the base metal. In a plasma-type melting furnace that generates slag by heating and melting ash and waste put on the base metal by generating a plasma arc, the plasma on the slag layer solidified on the base metal when the furnace is restarted A conductor supply device for supplying conductive particles between the torches is provided.

[0007] According to the above configuration, a conductive particle layer having conductivity is formed by the conductive particles charged on the solidified slag layer, and a plasma arc is easily generated between the plasma torch and the conductive particle layer. And the solidified slag layer and the base metal can be re-melted by this plasma arc to stably continue the plasma arc, and the melting furnace can be restarted reliably. .

Further, in the inventions according to claims 2 and 5, the conductive particles are made of granular carbon.

According to the above structure, granular carbon is inexpensive, has a low operating cost, is easy to put into and handle in a furnace, and has a small effect on operation.

Further, according to the third aspect of the present invention, the input amount of the granular carbon is set to be 1 to the distance L (m) between the electrodes.
It is not less than 0 × L (kg) and not more than 30 × L (kg).

According to the above configuration, by supplying an appropriate amount of granular carbon, there is no interruption or discontinuity of the plasma arc at the time of startup, and the amount of the charged granular carbon remaining in the furnace is reduced. be able to.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a plasma type ash melting furnace according to the present invention will be described with reference to FIGS.

As shown in FIGS. 1 and 2, on the gantry 1,
The furnace main body 3 is disposed via a tilting device 2 for discharging a base metal, which can be tilted about a support pin 2a by a tilting cylinder 2b. A metal housing 5 for housing the base metal 4 is formed on the bottom wall 3 a of the furnace main body 3.
Also. At the front wall 3b of the furnace body 3 on the side of the tilt cylinder 2b, an ash supply port 6 for charging incineration ash A onto the base metal 4 of the furnace body 3 is formed. A supply hopper 7 and an ash pusher 8 are provided.
A slag discharge passage 9 for discharging the molten slag FS melted on the base metal 4 is formed in the rear wall 3c of the furnace body 3 on the support pin 2a side, and the molten slag FS is water-cooled below the slag discharge passage 9. A slag cooling device 11 for generating granulated slag WS is provided. Reference numeral 12 denotes a preheating burner disposed opposite to a discharge weir 9a provided at the entrance of the slag discharge passage 9.

The upper part of the furnace body 3 is covered with a water-cooling jacket 13 and, for example, two torch insertion ports 14A and 14B are formed on the top wall 3d at a predetermined distance in the front-rear direction, and the torch on the ash supply port 6 side. An anode torch 15A, which is a plasma torch, is inserted into the insertion port 14A, and a cathode torch 1, which is a plasma torch, is inserted into the torch insertion port 14B on the slag discharge passage 9 side.
5B is hung. These two plasma torches 15
An inexpensive carbon electrode is used for A and 15B, and the torch elevating device 16 is lowered in accordance with the consumption of the lower end portion to maintain a predetermined distance from the base metal 4 or the molten slag FS.
Each is supported. Furthermore, both plasma torches 1
A DC power supply device 17 is connected to 5A and 15B, and a working gas supply device 18 is connected to supply working gas (for example, nitrogen gas) into the furnace main body 3 through both plasma torches 15A and 15B. Have been. 1
Reference numeral 9 denotes an exhaust gas port formed in one side wall 3e, which is connected to an exhaust gas treatment device.

On the top wall 3d of the furnace main body 3, there is provided a conductor supply device 21 for feeding granular carbon C onto the solidified slag layer CS at the time of restart. The conductor supply device 21 is provided with the torch insertion ports 14A, 1 near the side wall 3e.
4B, a conductor supply nozzle 21 that is inclined and penetrates toward the center of the lower end of the plasma torches 15A, 15B.
a and a conductive particle hopper 21c disposed at the upper end of the conductive material supply nozzle 21a via a charging valve 21b.

In the above configuration, when the furnace is stopped and then restarted, the molten slag is solidified on the solidified base metal 4 to form a solidified slag layer CS, and the plasma torch 15A is moved by the torch elevating device 16. , 15B are respectively slightly raised, and then the charging valve 21b of the conductor supplying device 21 is opened to supply a predetermined amount of granular carbon C into the furnace main body 1 and deposited on the solidified slag layer CS between the plasma torches 15A, 15B. Thus, a granular carbon layer C is formed. Then, the plasma torch 1 is supplied from the working gas supply device 18.
The working gas is supplied into the furnace main body 3 via 5A and 15B, and the DC torch
A starting voltage is applied to A and 15B to generate a plasma arc between the granular carbon layer C and the plasma torches 15A and 15B, and the heat heats and solidifies the solidified slag layer CS to further melt the base metal 4.

The appropriate amount of granular carbon used in the restart is determined by the experiment using the above-mentioned ash melting furnace. As a result, the relationship between the input amount of granular carbon C and the remaining amount of carbon is shown in FIG.
Became clear. The vertical axis of this graph shows the amount of carbon remaining in the furnace body 3 after 10 hours of restart, and the horizontal axis shows the amount of granular carbon injected per meter of the distance L between the electrodes. . Here, at the point a of 3 kg / m where the input amount was small, no plasma arc was generated and ignition was not possible.
Further, at the point b where the input amount was 6 kg / m, a plasma arc was generated but was unstable and intermittent, and the plasma arc disappeared halfway. Point c with input of 10 kg / m and input of 17 kg
At the point d of / m, the plasma arc was generated favorably and the restart was smoothly performed. In addition, 33kg / m of input e
In terms of the point, although the plasma arc was generated favorably and the restart could be performed smoothly, it was confirmed that the carbon residue was about 10% of the input amount in a solid state 10 hours after the restart. Furthermore, at the point f of the charged amount of 33 kg / m, the restart was smooth, but it was confirmed that the residual carbon amount after 10 hours was about 75% of the charged amount in a solid state.

Therefore, the input amount of the granular carbon C is
An appropriate amount is 10 to 30 kg per 1 m of the distance between the electrodes, and in this range, a plasma arc is satisfactorily generated and restart can be performed smoothly. However, the input amount of granular carbon C is 1
If it is less than 0 kg, the plasma arc is unstable and the plasma arc tends to disappear. When the amount of the granular carbon C is 30 kg or more, the granular carbon C spreads not only between the plasma torches 15A and 15B, but also throughout the furnace, and the reason is not clear. This is because a phenomenon occurs in which a granular carbon layer is formed on the upper part of the molten slag layer without melting the carbon, and the ash charged thereon does not melt on the carbon layer. If the amount of the granular carbon C exceeds 65 kg, the amount of carbon remaining in the furnace main body 3 in the form of a solid material increases significantly.

According to the above-described embodiment, a predetermined amount of granular carbon C is injected onto the non-conductive solidified slag layer CS to form a conductive granular carbon layer C, and the plasma torches 15A, 15B and Since the plasma arc is formed between the carbon layer and the granular carbon layer C, the plasma arc can be easily and stably formed, and the heat solidifies the surrounding solidified slag layer CS and the solidified base metal 4 to further form a conductive layer. Performance can be improved and restart can be performed reliably.

In the above configuration, the granular carbon C is used as the conductive particles. However, it is of the same quality as the electrodes, is inexpensive, has a small operating cost, is easy to put into and handle in the furnace, and is easy to operate. The effect is small. As other conductive particles, iron chips, steel chips, chips, and the like can also be used.

[0021]

As described above, according to the first and fourth aspects of the present invention, the conductivity is imparted by the conductive particles put on the solidified slag layer, and the plasma torch and the conductive particles are provided. A plasma arc can be easily formed between the layers, and the solidified slag layer and the base metal can be re-melted by this plasma arc to stably maintain the plasma arc. It can be done reliably.

Further, according to the second and fifth aspects of the present invention, the cost is low, the operating cost is low, the charging and handling into the furnace are easy, and the influence on the operation is small.

According to the third aspect of the present invention,
By supplying an appropriate amount of granular carbon, there is no interruption or discontinuity of the plasma, and the amount of charged granular carbon remaining in the furnace can be reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of an ash melting furnace according to the present invention.

FIG. 2 is a sectional view taken along the line II shown in FIG.

FIG. 3 is a graph showing the amount of granular carbon charged and the amount of residual carbon after 10 hours.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 3 Furnace main body 3d Top wall part 4 Base metal 6 Ash supply port 9 Slag discharge passage 14A, 14B Torch insertion port 15A Plasma torch (anode torch) 15B Plasma torch (cathode torch) 16 Torch elevating device 21 Conductor supply device 21a Conductor Supply nozzle 21b Input valve 21c Conductive granular material hopper A Ash FS Melted slag CS Solidified slag layer C Granular carbon (granular carbon layer)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazunori Nakamura 5-3-28 Nishikujo, Konohana-ku, Osaka-shi, Osaka Inside Hitachi Zosen Corporation (72) Inventor Toshiro Sakata 5 Nishikujo, Konohana-ku, Osaka-shi, Osaka Hitachi Shipbuilding Co., Ltd. (72) Inventor Hiroshi Kosaka 5-3-28 Nishikujo, Konohana-ku, Osaka City, Osaka, Japan

Claims (5)

[Claims] A base metal is accommodated in a furnace bottom, and a plurality of plasma torches are hung down from the furnace top to approach the base metal to generate a plasma arc between the base metal and the plasma torch. When the plasma type melting furnace that generates slag by heating and melting the ash and waste put on top was restarted after stopping, conductive particles were injected between the plasma torches on the slag layer solidified on the base metal Thereafter, a voltage is applied to the plasma torch to form a plasma arc. 2. The method according to claim 1, wherein the conductive particles are granular carbon. 3. The amount of granular carbon charged is determined by the distance L between the electrodes.
(M) and 10 × L (kg) or more and 30 × L (k
g) The method for restarting a plasma melting furnace according to claim 2, wherein: 4. A base metal is accommodated in a furnace bottom, and a plurality of plasma torches are hung down from the furnace top in proximity to the base metal to generate a plasma arc between the base metal and the plasma torch. In a plasma-type melting furnace that generates slag by heating and melting the ash and waste put on top, conductive particles are placed in the furnace body between the plasma torches on the slag layer solidified on the base metal during restart. A plasma-type melting furnace comprising a conductor supplying device to be charged. 5. The plasma type melting furnace according to claim 4, wherein said conductive particles are granular carbon.