JPH0252766B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for starting operation of a waste melting processing furnace. More specifically, the present invention provides a method for operating a waste melting furnace using electric resistance heating, which can minimize the generation of dust and facilitate the initial melting of input waste under stable power supply. This is related to the starting method.

[Prior Art] Recently, a waste treatment method has been proposed in which industrial waste such as sewage sludge, general waste such as municipal garbage, and waste such as incineration residue of these wastes are melted at high temperatures by arc heating. There is. To carry out this method, an arc is struck between the molten base metal in the furnace and the electrode using a closed furnace with a structure similar to that used for steel manufacturing. Inject waste such as dried sewage sludge. The waste undergoes thermal decomposition in the high-temperature reducing atmosphere inside the furnace, and the organic matter in the waste is gasified, the inorganic matter becomes molten slag, some metals are gasified, and the rest are distributed into slag and base metal. . When the molten slag obtained by this method is cooled and solidified, its volume is significantly reduced compared to the original waste, there is no release of heavy metals, and it can be effectively used as aggregate for concrete, etc. It is attracting attention as an effective waste treatment method. When starting a furnace using the above treatment method when a new furnace is installed or when the refractories of the furnace are repaired once every six months, first put a good conductor such as scrap iron into the furnace and energize the electrodes to create an arc. After melting to make the base metal, the waste can be thrown in, making it easy to generate an arc and start operation smoothly. However, when restarting the furnace after an emergency stop in a continuous operation furnace or after slag extraction in a batch operation furnace, if the slag coats the top surface of the base metal at the bottom of the furnace, this slag will reach a high temperature. Unless it is in a molten state, it has poor conductivity, making it difficult to generate an arc, and the same problem occurs when the top surface of the base metal that is not covered with slag becomes flat and solidified after slag is removed. It is difficult to generate an arc.

In order to solve this problem, the inventors of the present invention have discovered that no arc occurs even after a predetermined period of time has elapsed after lowering the electrode to a predetermined position and connecting it to a power source to enable arc discharge. A method for starting operation of a waste treatment furnace is provided, in which a predetermined amount of powdered or granular conductive material is detected, the conductive material supply device is operated, and an arc is generated between the conductive material and the electrode. I suggested it earlier.

[Problems to be Solved by the Invention] The above method can be used even when slag covers a conductive material such as base metal existing at the bottom of the furnace, or when base metal not covered by slag has solidified. It has the characteristics of being able to reliably generate an arc and start the operation of the furnace smoothly and without having to worry about obtaining it. However, when starting operation due to high temperatures such as arc heat, inorganic substances and other substances in the waste may become particulate dust and scatter outside the furnace.
When using a conductive material such as graphite powder, which has a low bulk specific gravity and turns into gas when heated, it is necessary to use a fairly large amount to form a spark when the waste is introduced into the furnace, in order to ensure smooth melting. Not progressing or
There were points that needed to be improved in terms of pollution control and operation, such as adjusting the electrode level position due to electrode consumption.

[Means for Solving the Problems] The present invention provides a melting furnace, such as an arc-type melting furnace, in which a plurality of electrodes are provided from the furnace lid toward the hearth, and when starting the operation, a submerged arc melting furnace is used. The operation of the arc-type waste melting furnace is started by automatically positioning the electrodes for melting, supplying the required amount of melting initiator having a specific resistance value and composition within a certain range, and energizing. This solves the above-mentioned problems at times. That is, the present invention provides a closed-type waste melting furnace in which a furnace shell is covered with a furnace lid and an electrode is inserted through the furnace lid. Confirm that the tip is grounded to the bottom of the furnace or the surface of the contents, then raise the electrode by a predetermined amount, and add a predetermined amount of a melting initiator made of a conductive material and a slagging agent and having a resistivity value of 1 to 200 Ωcm. A waste melting processing furnace characterized in that the tip of the electrode, which has been raised by a predetermined amount after grounding, is buried at a predetermined depth in the melting initiator by supplying the same, and then energized and melted by resistance heating. The outline is how to start operation.

[Function] When electricity is applied at the start of operation, for example, in the case of an arc type melting furnace, there is little arc generation, so there is little scattering of dust from the furnace and no flickering occurs. By adjusting the electrode height and using a melting initiator made of a mixture of a conductive material and a slagging agent, a spark called a slag pool (or hot water pool) is formed at the start of heating and melting, and the waste is disposed of here. Since the materials are added sequentially, melting starts gently and easily.

Here, in the present invention, the electrode tip is once grounded and then raised by a predetermined amount, so that the electrode tip can always be reliably held at the optimal position depending on the situation inside the furnace. As a result, thereafter, simply by supplying a predetermined amount of the melting initiator, the tip of the electrode is reliably buried to a predetermined depth. Therefore, even when restarting operation after an emergency stop or the like, there is no need to visually check the situation inside the furnace, and the electrodes can always be placed at optimal positions.

In addition, since the electrode tip is placed in the optimal position at the start of operation, the distance between the electrode tip and the bottom of the furnace can be accurately determined.Also, since the melting initiator is used in a predetermined amount, the amount of embedding of the electrode tip can also be understood. Therefore, when lowering the electrode later, it is useful to know the current position.

[Example] The present invention will be explained below based on the drawings.

In FIG. 1, 1 is a closed-type arc furnace, 2 is a furnace shell thereof, and 3 is a furnace lid placed over this furnace shell.
Reference numeral 4 denotes an electrode that penetrates the furnace lid 3, and is supported by an electrode support arm (not shown) that can be raised and lowered. 5 is a slag gutter, which is filled from the slag outlet 6 with refractory bricks or stamp material. 7 is a waste inlet provided in the furnace lid 3; 8
9 is a waste hopper containing waste W, and 9 is a screw conveyor. Reference numeral 10 denotes a gas discharge port provided in the furnace lid 3, and a generated gas processing device (not shown) consisting of a gas scrubbing tower, a gas cooler, a blower, etc.
It is connected to the. Reference numeral 11 is a powder or pellet melting initiator consisting of a conductive material and a slagging agent. Examples of conductive materials that are constituent components include coke with a particle size of 1 to 4 mm, graphite, iron oxide powder, iron powder, etc., and slagging agents that are other constituents include Particle size of 4 mm or less when slag whose main components are SiO ₂ , CaO, Al ₂ O ₃ , Fe ₂ O _{3 ,} etc. generated from an arc furnace or a direct energized waste melting furnace is released into water. Examples include granulated slag, glass cullet, and small lumps of incineration residue. It is necessary that the above-mentioned melt initiator is blended and adjusted so that its specific resistance value is 1 to 200 Ωcm.
When the resistivity value is outside this range, for example, smaller than 1 Ωcm, the resistance heating state shifts to an arc heating state or a submerged arc heating state, and the generation of dust and flicker relatively increases. Also,
On the other hand, if it is larger than 200 Ωcm, the resistance between the electrodes will be too large, so
Even if a voltage of around 400V is applied, no current flows and no heating can be created.

FIG. 2 is a graph showing the relationship between the blending ratio of each component of several examples of the melt initiator and the specific resistance value of the melt initiator obtained by the blending. As is clear from this figure, the blending ratio of the melt initiator having a resistivity value in the range of 1 to 200 Ωcm is 50 to 90% of the conductive material.
% by weight, the slagging agent ranges from 10 to 50% by weight.

Returning to FIG. 1, 12 is a melting initiator supply device, which includes a hopper 13, a rotary leaf feeder 14 provided at the outlet of this hopper, an electric motor 15 for driving the rotary leaf feeder, and a melting initiator that communicates with the inside of the furnace. It consists of an input chute 16. Reference numeral 17 denotes a support arm that repositions the electrode 4 perpendicularly to the direction of the hearth bottom; 18 is an electrode position adjustment device; a wire 19 that suspends the support arm 17; a wheel 20 that winds the wire; and a wheel 20 that rotates the wheel 20 in forward and reverse directions. It consists of an electric motor 21 that lifts and lowers the support arm 17, and a slack detector 22 that detects loosening of the wire 19. 23 is a controller with a built-in timer.

In the apparatus having the above configuration, the operation of the furnace is started as follows when a layer of base metal 24 in a molten state or a solidified state is present at the bottom of the furnace. First, the electric motor 21 is driven by turning on the switch, and the wire 19 around which the wheel 20 is wound is wound down, and the support arm 17 is lowered. In other words, when the electrode 4 is brought close to the surface of the base metal 24 and the tip of the electrode is grounded thereto, the wire 19 becomes slack. Looseness detector 22 detects this and receives the signal from controller 23. According to the command,
The electric motor 21 stops, and after a certain period of time under timer control has elapsed, the motor 21 rotates in the opposite direction in order to lift the support arm 17, that is, to separate the tip of the electrode 4 from the surface of the base metal 24 by a certain distance. In this case, the distance between the surface of the base metal 24 and the tip of the electrode is approximately 10 to 100 mm, depending on the diameter of the electrode 4.
It is preferable to control the setting so that it becomes mm. If the surface of the base metal 24 and the tip of the electrode 4 are in contact, when alternating current is applied to the electrode, an arc is generated between the two, making it difficult to control the current flow and causing flicker, making operation difficult. Furthermore, if the distance between the surface of the base metal 24 and the tip of the electrode is greater than the above-mentioned setting range, it is necessary to use a large amount of the melting initiator 11, which is uneconomical in terms of power consumption. In addition, the above is
This is an example of processing waste that has a low metal content and requires the use of base metal, but for example, in the case of a material to be processed that has a high metal content, such as municipal waste incineration residue, base metal 24 loading is required. ,do not need. Therefore, in that case, the distance between the tip of the electrode 4 and the bottom of the furnace should be 100 to 200 mm. If the interval is less than this, when alternating current is applied, the vicinity of the electrodes will become high temperature and there is a risk of damaging the hearth bottom. On the other hand, if the distance between the tip of the electrode 4 and the bottom of the furnace exceeds the above-mentioned setting range, it is necessary to use a large amount of the melting initiator 11, which is uneconomical in terms of power consumption. When the adjustment of the height position of the electrode 4 is completed and the reverse rotation of the electric motor 21 is stopped, the electric motor 15 for operating the rotary feeder is driven for a certain period of time in response to a command from the controller 23 that receives the signal, and the electric motor 15 is driven for a certain amount of time. of melt initiator 11 is supplied.
The supply amount is set so that the electrode 4 is buried 10 mm to 300 mm from the tip. In other words, the amount of electrode buried by the melting initiator is resistance (R) = specific resistance (ρ) × distance between electrodes.
(l)/fused area (A) is related to the resistance value, and R is related to I and V from voltage (V) = current (I) x resistance (R). If the amount of burial is small, R needs to be large, and in terms of equipment, it is necessary to have a large number of voltage taps for the power transformer. It is possible to increase A and decrease R and V, but this requires a large amount of melting initiator, which is not a good idea.

In this way, it is desirable to supply the melting initiator 11 in an amount sufficient to make the tip of the electrode 4 optimally buried, and in an amount that is not wasted. Here, in this embodiment, as a result of adopting a configuration in which the electrode is grounded to the bottom of the furnace and then raised by a predetermined amount, the electrode 4
The distance between the tip of the furnace and the bottom of the furnace is always kept within the set range. Therefore, as the supply amount of the melting initiator 11, the minimum amount necessary to sufficiently bury the tip of the electrode 4 can be easily determined. Therefore, it is sufficient to set the supply amount of the melt initiator 11 to the required minimum amount, and there is no waste. In this way, the optimum supply amount of the melt initiator 11 can be easily and reliably determined.

Next, a certain amount of melting initiator 11 is supplied into the furnace, and upon receiving a signal that the motor 15 for operating the rotary feeder has stopped driving, a timer commands AC current to be applied to the electrode 4 after a certain period of time has elapsed.
A voltage of 100 to 400 V is applied to generate Joule heat, and the supplied melting initiator is melted to form a molten puddle in the electrode buried region. Thereafter, the waste to be treated is inputted from the hopper 8, and the melting process is started without generating any dust under stable power consumption.

Next, an embodiment example of starting the furnace operation will be described. First, 85% by weight of a conductive material made of coke powder (Special A type) with a particle size of 1 to 4 mm and 15% by weight of a slagging agent made of molten slag of garbage incineration ash with a particle size of 4 mm or less are mixed, and the mixture is heated at room temperature. A melt initiator with a specific resistance value of 68 Ωcm was prepared. Next, it is equipped with three electrodes with a diameter of 100 mm and made of artificial graphite, and the distance between the electrodes is 180 mm.
PCD (pitch circle diamond)
Using a 220 mm arc heating type melting furnace as shown in FIG. 1, the electric motor 21 was turned on and the electrode 4 fixed to the support arm 17 was lowered. The tip of the electrode is connected to the surface of the base metal 24 (in the case of melting municipal waste incineration ash, base metal is not used, so the furnace bottom surface is used) and receives a signal from the loosening detector 22 which detects the loosening of the wire 19. The electric motor 21 stops in response to a command from the controller, and then rotates in the opposite direction after a certain period of time under timer control to raise the electrode 4 to a preset height (15 mm to 20 mm).
mm) and stopped it. Next, electric motor 2
The motor 15 for operating the rotary feeder receives a stop signal from the controller 23 under timer control, and the motor 15 for operating the rotary feeder is driven for a certain period of time under timer control. The prepared melt initiator 11 was fed into the furnace. The controlled supply amount was 9.8 kg (11.5 kg), and the buried depth of the electrode was approximately 100 mm. AC current supply to the electrode 4 was started in response to a command from the controller 23 which received a signal to stop the supply of the melting initiator, that is, to stop driving the electric motor 15 . The voltage was 100V tap, and there were variations in each phase, but a current of 1.6 to 75A flowed.
The resistance value at that time was 5.9Ω. At this time,
No arcing was observed, and almost no dust was observed. After 4 minutes, as the molten area expands and a puddle is formed, the resistance value becomes 2 Ω, the state becomes a submerged arc heating state, and the energization state becomes stable. From then on, the waste to be treated is supplied from the hopper 8. was able to start.

[Effects of the Invention] As described above, the method of the present invention adjusts the height position of the electrode and adjusts the height of the conductive material and slagging agent when starting the operation of the arc heating type waste melting processing furnace. The tip of the electrode is buried in a compound (having a specific resistance value in a specific range), and then an alternating current is applied to the electrode, and with the melting initiator as a conductor, Joule heat is generated and submerged arc heating is performed. The process involves forming a molten puddle, then introducing the waste to be treated and starting melting. Therefore, compared to the conventional method, the method of the present invention does not scatter dust, so that contamination of the working environment is prevented and the problem of contamination of the living environment is solved. Further, there is an advantage that the power consumption at the start of operation is stable, and the melting heat treatment can be started mildly and uniformly due to the stable generation of Joule heat.

In order to enable such a smooth and favorable start of operation, a configuration is adopted in which the electrode is lowered once and then raised by a predetermined amount after touching the ground, so that the distance between the electrode tip and the hearth bottom etc. is always constant. Therefore, the amount of melting initiator required to bury the electrode tip to a predetermined depth is determined automatically. As a result, in the present invention, it is sufficient to simply supply a predetermined amount of melting initiator after lowering and raising the electrode, making the preparation work for starting operation extremely simple.
Particularly in cases where the situation inside the reactor cannot be easily predicted, such as in the case of an emergency shutdown, the effect of simplifying the preparation work is that it does not require complicated labor such as checking the situation inside the reactor. noticeable.

In addition, since the optimum amount of melting initiator can be easily determined and the electrode tip can be reliably buried in the desired state, there is no need to supply a large amount of melting initiator due to fear of insufficient embedding, and there is no wastage of materials. There is.

In addition, since the distance between the electrode tip and the bottom of the furnace, etc. is known, and the amount of the electrode buried in the melting initiator is also known, the electrode can be lowered as the melting initiator melts through. In such cases, it is possible to easily select the optimum lowering speed that will not cause the electrode to break due to excessive thrusting or expose the electrode due to a lowering delay. According to the present invention, such secondary effects after the start of operation are also quite remarkable.

[Brief explanation of the drawing]

Figure 1 is a schematic cross-sectional view of an arc-heating waste melting furnace used to implement the method of the present invention, and Figure 2 is a graph showing the relationship between the blending ratio of each component of the melting initiator and the specific resistance value. It is. 1... Arc furnace, 2... Furnace shell, 3... Furnace cover, 4
...Electrode, 5...Slag gutter, 6...Slag outlet, 7...
Waste input port, 8...Waste hopper, 9...Screw conveyor, 10...Gas discharge port, 11...
...Melting initiator, 12...Melting initiator supply device, 1
3...Hopper, 14...Rotary feeder, 15...Electric motor, 16...Chute for introducing melting initiator, 17...Support arm, 18...Electrode position adjustment device, 19...Wire, 20...Wheel ,2
1... Looseness detector, 23... Controller, 24...
base metal.

Claims (1)

[Scope of Claims] 1. In a closed waste melting furnace equipped with a furnace shell covered with a furnace lid and an electrode penetrating the furnace lid, when the furnace starts operating, the electrode is lowered,
Confirm that the tip of the electrode is grounded to the bottom of the furnace or the surface of the contents, and then raise the electrode by a predetermined amount.
By supplying a predetermined amount of a melting initiator having a resistivity value of A method for starting operation of a waste melting processing furnace characterized by melting. 2. The method for starting operation of a waste melting furnace according to claim 1, wherein the composition ratio of the melting initiator is 50 to 90% by weight of the conductive material and 10 to 50% by weight of the slagging agent. 3 Among the components of the melt initiator, the conductive material is coke powder,
One or two of graphite powder, iron oxide powder, and iron powder
or more, or pellets thereof, and the slagging agent is granulated slag generated from an electric arc furnace for melting waste.
Method for starting the operation of the waste melting processing furnace described in Section 1.