JP2008096067A - Control method for plasma melting furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain reasonable balance between electric power and an ash supply amount, and to prevent side arcs from being generated by excessive increase of voltage in regard to a control method for a plasma melting furnace used in a melting process of incineration residues (incinerated ash and fly ash) discharged from an incinerator or the like. <P>SOLUTION: When there is property change of ash or excess and deficiency of the ash supply amount that can not be judged in a short period of time, by regarding an internal gas temperature changed by these factors as an object to be controlled, the electric power or the ash supply amount is adjusted. The object to be controlled may be a radiation amount of a melting furnace gas layer part, or an front end position of an upper electrode. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an improvement in a control method of a plasma melting furnace used when melting incineration residues (incineration ash and fly ash) discharged from a waste incinerator or the like.

  Conventionally, as a method for controlling this type of plasma melting furnace, for example, the method described in Patent Document 1 and the method described in Patent Document 2 are known.

In the former case, the power supply amount or the ash supply amount to the plasma melting furnace is calculated as an ash supply amount (or an electric supply amount) corresponding to a preset power supply amount (or ash supply amount). The power is (power) = (voltage) × (current), and the voltage is a preset voltage corresponding to the power, and becomes a control value for the position of the upper electrode of the plasma melting furnace. The current is calculated by (current) = (power) / (voltage) and is controlled by the DC power supply device. The voltage is determined based on past operating results and stable operating conditions, and the ash supply amount is determined from the calculated value from the bulk specific gravity of the ash and the actual measured value in the cold. Is done.
In the latter, the tip of the upper electrode is recognized by an infrared camera image, and the position of the upper electrode is controlled so that the plasma arc length of the tip of the upper electrode is constant. Has been calculated. Therefore, the voltage is uniquely determined from the relationship of (voltage) = (current) × (electric resistance value) by the electric resistance value between the upper electrode and the lower electrode.
In any method, the power and current are corrected and adjusted according to the measurement result of the melting temperature.

However, in the former method, since the voltage is calculated by (voltage) = (current) × (electric resistance value), the electric resistance value, that is, the voltage is adjusted by moving the upper electrode position up and down (FIG. 1). ). The voltage is a value determined based on actual operation and stable operating conditions. However, the voltage is appropriate depending on the operating conditions of the melting furnace (changes in the properties of the ash to be processed, excess or deficiency due to actual differences in the set value of the ash supply amount, etc.) The voltage is different. It was difficult to operate at an appropriate voltage because changes in ash properties and actual differences from the set value of the ash supply amount cannot be judged in a short time. In other words, the electrical resistance value due to the properties of the molten ash (molten metal) and the excess or shortage of the ash supply amount change the electrical resistance value of the molten metal part under the upper electrode. In some cases, it was deeply submerged in the molten metal.
In the latter method, since the plasma arc length is constant, the electric resistance value of the molten metal part under the upper electrode changes due to the change in the electric resistance value due to the properties of the molten ash (molten metal) and the excess or shortage of the ash supply amount. Depending on the relationship of (voltage) = (current) × (electric resistance value), the voltage becomes excessively high or low. In particular, when the voltage is high, a side arc is likely to be generated at the penetrating portion of the upper electrode (see FIG. 3), which may cause damage to the furnace body.

JP 2004-251520 A JP 2002-81634 A

  In short, all of the conventional ones change the electric resistance value due to the properties of the molten ash (molten metal) and the ash supply amount, so that the electric resistance value of the molten metal part under the upper electrode changes. The supply balance could not be maintained.

  The present invention was devised in view of the above-mentioned problems, and was devised to solve this problem. The subject of the present invention is control of a plasma melting furnace capable of maintaining a balance between an appropriate electric power and an ash supply amount. Is in providing a way.

  The control method of the plasma melting furnace of the present invention basically adjusts the power or ash supply amount with the furnace gas temperature as the control target in order to set the balance between the power and the ash supply amount to an appropriate value. There is a feature in doing.

  When operating the plasma melting furnace, if there is a change in ash properties or excess or deficiency in the amount of ash supplied, the gas temperature in the furnace changes due to these factors. Thus, it is possible to determine the change in the ash properties and the excess or deficiency of the ash supply amount in a short time, and adjust the power or the ash supply amount based on this to make the balance between the power and the ash supply amount appropriate.

  The control target is not only the gas temperature in the furnace, but also the amount of heat released from the furnace body gas layer, the tip position of the upper electrode, or a combination of these. If it does in this way, like the above, electric power or ash supply amount can be adjusted, and the balance of electric power and ash supply amount can be made into an appropriate value.

According to the present invention, the following excellent effects can be achieved.
(1) When there is a change in ash properties that cannot be determined in a short period of time or an excess or deficiency in the amount of ash supplied, the appropriate gas and ash supply amount can be controlled by controlling the furnace gas temperature that changes due to these factors. Can keep the balance.
(2) Since the tip position of the upper electrode can be set to an appropriate position, it is possible to prevent the tip position of the upper electrode from becoming excessively high or conversely sinking deeply into the molten metal.
(3) Since the voltage can be set to an appropriate value, the voltage does not become excessively high or low, and there is no danger that a side arc will occur due to the high voltage.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view showing a plasma melting furnace used for carrying out the present invention. FIG. 2 is an enlarged view of a main part of FIG. FIG. 3 is an electric circuit diagram of the plasma melting furnace of FIG.

Referring to FIG. 1, a plasma melting furnace 1 is for melting a molten material such as incineration ash and fly ash discharged from a garbage incinerator such as municipal waste or industrial waste, and is formed of a refractory or the like. The furnace body 2, the upper electrode (main electrode) 3 penetrating the ceiling of the furnace body 2, and the lower electrode (furnace) made of conductive refractory disposed at the bottom of the furnace body 2 Bottom electrode) 4, a DC power supply device 6 whose cathode is connected to the upper electrode 3 and whose anode is connected to the lower electrode 4 via the current collector plate 5, and an electrode lifting device which supports the upper electrode 3 in a freely movable manner 7, a melt supply device 8 for supplying melt (incinerated ash and fly ash), a molten metal 9 made of molten slag and molten metal, and an outlet 10 through which the molten metal 9 overflows and flows out , Temperature detection means 11 for detecting the gas temperature in the furnace body 2 and the detection signal from the temperature detection means 11 And a control unit 12 or the like for controlling the DC power supply 6 and the electrode lifting device 7 and the melt feeder 8 based.
The temperature detection means 11 is a thermocouple or the like that is provided in the furnace body 2 and can detect the gas temperature in the furnace.

  In FIG. 2, the furnace body 2 includes an iron part 13 and a refractory 14, and a seal for sealing the upper electrode 3 so as to be movable up and down via an insulator 15 on the outside of the iron part 13. A device 16 is provided. A current I directed to the DC power supply device 6 flows through the upper electrode 3, and a side arc 17 that flows from the upper electrode 3 to the iron portion 13 of the furnace body 2 is also depicted.

  In FIG. 3, V is a charging voltage, I is a charging current, Ra is an arc resistance (electric resistance value of plasma arc), and Rm is a molten metal resistance (electric resistance value of the molten metal).

FIG. 4 is a flowchart showing the control method of the plasma melting furnace of the present invention, which is controlled in the following manner.
(1) The electric energy (ash supply amount) corresponding to the ash supply amount (electric power amount) is set from the relationship between the preset ash supply amount and electric power, and the plasma melting furnace 1 is operated. That is, a predetermined voltage and current are calculated from the set power, and the voltage is controlled by the upper and lower positions of the upper electrode 3 and the current is controlled by the DC power supply device 6 (step S1).
(2) When the properties of the ash to be treated change, the electrical resistance value of the molten metal changes due to the component change, or the change in bulk specific gravity causes a difference from the ash supply amount setting value, so that the actual ash supply amount is excessive or insufficient (Step S2).
(2) As a result, the electric resistance value Rm of the molten metal under the upper electrode 3 increases or decreases (step S3).
(3) When the electric resistance value Rm of the molten metal increases, the upper electrode 3 is lowered (step S4).
(4) When the upper electrode 3 is lowered, the radiant heat from the plasma arc is reduced and the furnace gas temperature is lowered (step S5).
(5) When the in-furnace gas temperature decreases, this is detected by the temperature measuring means 11, and the controller 12 controls the DC power supply device 6 or the melt supply device 8 to increase the electric energy or set the ash supply amount set value. Reduction is performed (step S6).
(6) It is determined whether or not the value of the gas temperature in the furnace is an appropriate value, and if it is appropriate, the process returns to step S1 (step S7).
(7) In step S3, when the electrical resistance value Rm of the molten metal decreases, the upper electrode 3 is raised (step S8).
(8) When the upper electrode 3 is raised, the radiant heat from the plasma arc increases and the furnace gas temperature rises (step S9).
(9) When the gas temperature in the furnace rises, this is detected by the temperature measuring means 11, and the controller 12 controls the DC power supply device 6 or the melt supply device 8 to reduce the electric energy or set the ash supply amount set value. An increase is made (step S10).
(10) In step S7, it is determined whether or not the value of the in-furnace gas temperature is an appropriate value. If the value is not appropriate, the process returns to step S3 and steps S3 to S10 are repeated until the appropriate value is reached. And the ash supply amount set value is increased or decreased.

FIG. 5 is an example of operation data of the plasma melting furnace when a constant electric power (not shown) is supplied according to the set ash supply amount.
In this example, the actual ash supply amount is larger than the set value, and the ash supply amount is excessive (power shortage).
As the ash supply amount is excessive (power shortage), the ash that has not melted to near the lower part of the upper electrode approaches, the electric resistance value of the molten metal under the upper electrode increases, and the set voltage (not shown) There is a case where the upper electrode whose position is adjusted so as to fall rapidly.
When the position of the upper electrode is lowered, the furnace gas temperature decreases. In this example, when the furnace gas temperature falls below the set temperature, the ash supply is stopped and the furnace gas temperature rises above the set value. The ash supply is restarted (that is, the average ash supply is reduced). By carrying out such an operation, the balance between the appropriate power and the ash supply amount is achieved.

In the previous example, the gas temperature in the furnace is the control target. For example, the heat dissipation amount of the melting furnace gas layer and the tip position of the upper electrode can be controlled, or a plurality of these can be combined. good.
When the heat release amount of the melting furnace gas layer is to be controlled, the heat release amount detection means 18 is provided in the furnace body 2 as shown by the chain line in FIG. Although not shown in the figure, the heat radiation amount detecting means 18 may be one that detects the flow rate of the cooling medium that cools the furnace body 2 or the temperature difference of the cooling medium and calculates the heat radiation amount therefrom.
When the tip position of the upper electrode 3 is to be controlled, the position detection means 19 is provided in the furnace body 2 as shown by the chain line in FIG. As the position detection means 19, an infrared camera or the like that is installed outside the furnace body 2 and observes the tip of the upper electrode 3 can be used.

  The present invention can also be applied to, for example, an electric furnace for steelmaking.

The schematic diagram which shows the plasma melting furnace used for implementation of this invention. The principal part enlarged view of FIG. The electric circuit diagram of the plasma melting furnace of FIG. The flowchart which shows the control method of the plasma melting furnace of this invention. The graph which shows an example of the operation data of a melting furnace.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Plasma melting furnace, 2 ... Furnace main body, 3 ... Upper electrode, 4 ... Lower electrode, 5 ... Current collecting plate, 6 ... DC power supply device, 7 ... Electrode raising / lowering device, 8 ... Molten material supply apparatus, 9 ... Molten metal DESCRIPTION OF SYMBOLS 10 ... Outlet, 11 ... Temperature detection means, 12 ... Control apparatus, 13 ... Iron part, 14 ... Refractory material, 15 ... Insulator, 16 ... Sealing device, 17 ... Side arc, 18 ... Radiation amount detection means, 19 ... position detecting means, V ... charging voltage, I ... charging current, Ra ... arc resistance, Rm ... molten metal resistance, S1-S10 ... control step.

Claims (3)

  A control method for a plasma melting furnace, characterized in that the power or ash supply amount is adjusted with the furnace gas temperature as a control target in order to set the balance between the electric power and the ash supply amount to an appropriate value.   A control method for a plasma melting furnace, characterized in that the power or ash supply amount is adjusted with the furnace body gas layer heat release amount as a control target in order to set the balance between the electric power and the ash supply amount to an appropriate value. A control method for a plasma melting furnace, wherein the power or ash supply amount is adjusted with the position of the tip of the upper electrode as a control target in order to set the balance between the power and the ash supply amount to an appropriate value.

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