JP5060182B2 - Control method of plasma melting furnace - Google Patents

Description

  The present invention relates to an improvement in a control method for a plasma melting furnace used for melting a material to be melted such as incineration ash and fly ash discharged from a waste incinerator, for example.

In a plasma melting furnace, the inside of the furnace could not be monitored with a visible light camera due to fly ash, fume, etc. generated during melting.
For this reason, using a long wavelength (8 to 12 μm) infrared camera, the inside of the furnace is monitored from a viewing window installed at the outlet or the side wall, and the plasma arc is analyzed from the image of the infrared camera to detect the main electrode. A technique is known in which the tip is obtained and the main electrode is moved up and down to directly control the arc length (see Patent Documents 1 to 8).

However, in such a case, when the main electrode is immersed in the molten metal or when the inside of the furnace cannot be monitored because the dust concentration is high, the arc length is determined to be 0 mm. As the gas temperature inside the furnace rises too much, there is a risk of an increase in power consumption, damage to the refractory in the furnace ceiling and gas layer, and side arcs. When the electrode is raised, the main electrode may come off from the electrode seal portion.
In addition, since the main electrode is consumed with time, an appropriate upper limit of the electrode height cannot be set. Therefore, when the infrared camera or the image processing apparatus breaks down, there is a possibility that the same problem as described above may occur because the main electrode rises too much.

On the other hand, in a plasma melting furnace, one that performs control to make the voltage constant is also known (see Patent Document 9).
In the control, the ash supply amount (or input power) corresponding to the preset input power (or ash supply amount) is calculated as the input power or ash supply amount to the plasma melting furnace. The input power is (input power) = (input voltage) × (input current). As the input voltage, a preset input voltage is calculated according to the input power, and the control value of the main electrode position of the plasma melting furnace is calculated. It becomes. The applied current is calculated by (applied current) = (applied power) ÷ (applied voltage), and is controlled by the DC power supply device. The input voltage is determined based on past operating results and stable operating conditions, and the ash supply amount is calculated based on the calculated value from the bulk specific gravity of the ash and the actual measured value in the cold state. It is determined.

  However, in such a case, since the input voltage is calculated by (input voltage) = (input current) × (electric resistance value), the input voltage, that is, the electric resistance value is adjusted by moving the main electrode position up and down. ing. 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 input voltage is different. It was difficult to operate at an appropriate charging voltage because changes in ash properties and actual differences from the set value of ash supply cannot be determined in a short time. That is, the electrical resistance value due to the properties of the molten ash (molten metal) and the electrical resistance value of the molten metal part under the main electrode change due to excess or shortage of the ash supply amount. In some cases, it was deeply submerged in the molten metal.

JP-A-11-287426 JP 2002-81992 A Japanese Patent No. 3611299 JP 2002-81634 A Japanese Patent No. 3659903 JP 2003-28411 A JP 2003-343824 A JP 2004-156865 A JP 2004-251520 A

  In short, the conventional constant arc length control and constant input voltage control have their merits and demerits, and it has been difficult to achieve stable operation control of the plasma melting furnace.

  The present invention was devised in view of the above-mentioned problems, and was devised to solve this problem. The problem is that whether or not the control by the infrared camera is possible, based on the constant input voltage control. When the standard for judgment is set and control with an infrared camera is possible, plasma is designed to realize stable operation control by adding input voltage correction based on the deviation of the distance between electrodes (distance from the bottom of the electrode to the molten metal surface). It is in providing the control method of a melting furnace.

The method for controlling a plasma melting furnace of the present invention melts a material to be melted by a plasma arc generated by a voltage applied between a main electrode and a furnace bottom electrode provided in the furnace, and raises and lowers the main electrode. In a plasma melting furnace that controls the input voltage constant by making the input voltage constant, when the inside of the furnace can be observed with an infrared camera provided outside the furnace, the distance from the molten metal surface to the tip of the main electrode is constant. The inter-electrode distance constant control is performed to correct the applied voltage according to the above. When the inside of the furnace cannot be observed by the infrared camera, the applied voltage constant control is performed . Further, the inter-electrode distance constant control is performed by the infrared camera. The molten metal surface is photographed, and the lower and side edges of the main electrode and the molten metal surface are determined on the image, the distance between the electrodes from the molten metal surface to the leading edge of the main electrode, Measure the electrode width between the two side edges, calculate the actual interelectrode distance from the ratio of the measured electrode width to the actual electrode width, and apply the voltage according to the interelectrode distance depending on whether the electrode side end can be determined. The feature is that the correction of the applied voltage is performed based on the deviation between the measured value of the distance between the electrodes calculated as described above and the set value set in advance .

According to the present invention, the following excellent effects can be achieved.
(1) When the inside of the furnace cannot be observed with an infrared camera, the constant inter-electrode distance control is turned off, so that the power unit intensity increases due to excessively high main electrode (input voltage), refractory damage, side arc Generation and removal of the main electrode can be prevented.
(2) Since the control is not the electrode height control but the addition voltage correction, an abnormal increase of the main electrode (the input voltage) can be prevented by setting the upper limit of the input voltage.
(3) Since the control is based on the addition of the applied voltage correction, not the electrode height control, it is not necessary to change the control start set value if the control is turned off.
(4) Since the actual interelectrode distance is calculated, it is not necessary to change the interelectrode distance setting value even if the camera position or the like is changed. In addition, by using the actual distance between electrodes as a parameter, the relationship between the distance between electrodes and the operating state can be compared with other plans.
(5) By setting the height of the molten metal surface in advance, the distance between the electrodes can be measured if the tip of the main electrode can be determined even when unmelted ash drifts to the vicinity of the outlet and it is difficult to determine the molten metal surface.
(6) Since the control is based on the addition of the input voltage correction, there is little change from the conventional constant input voltage control, and the existing remodeling work is easy. In addition, the operator can easily cope with the change in the control method.

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 a view showing a captured image of the infrared camera. FIG. 3 is a block diagram of the control device. FIG. 4 is a diagram illustrating the concept of the input voltage correction calculation.

  The plasma melting furnace 1 melts the melted material A such as incineration ash and fly ash discharged from a garbage incinerator such as municipal waste and industrial waste, and a furnace main body 2 formed of refractory or the like. A main electrode 3 penetrating the ceiling of the furnace body 2 so as to be movable up and down, a furnace bottom electrode 4 made of a conductive refractory disposed at the bottom of the furnace body 2, and a cathode connected to the main electrode 3 And a DC power supply device 6 whose anode is connected to the furnace bottom electrode 4 via the current collector plate 5, an electrode lifting / lowering device 7 that supports the main electrode 3 so that it can be lifted and lowered, and a material A to be melted A A melt supply device 8, an outlet 9 through which molten metal B made of molten slag and molten metal overflows, and an infrared camera 10 for detecting the tip position 3 ′ of the main electrode 3 and the molten metal surface B ′. An image processing device 11 for processing an image from the infrared camera 10, and a signal from the image processing device 11. And a control device 12 for controlling the DC power supply device 6 and the electrode lifting / lowering device 7 on the basis of the number.

  The infrared camera 10 is installed outside a viewing window 13 provided in the furnace body 2 on the outlet 9 side.

  In the image processing apparatus 11, the electrode width measurement window 15, the electrode tip position measurement window 16, and the position of the molten metal surface B ′ are set on the camera screen 14.

  The control device 12 performs a power-voltage calculation unit 17 in which a preset input voltage is calculated according to the input power, a manual input unit 18 for manually inputting the input voltage correction value, and a constant input voltage control. The input voltage correction value is determined by the control unit 19 and the deviation PV-SV between the measured value PV of the interelectrode distance (distance from the lower end 3 ′ of the main electrode 3 to the molten metal surface B ′) and the preset set value SV. An input voltage correction value calculation unit 20 for calculation, and a changeover switch 21 for connecting or disconnecting the input voltage correction value calculation unit 20 with respect to the power-voltage calculation unit 17 and the manual input unit 18 are provided.

Next, the operation will be described based on such a configuration.
(1) Edge processing is performed by determining the side edge of the main electrode 3 based on the luminance difference in the electrode width measurement window 15 on the camera screen 14 photographed by the infrared camera 10 and processed by the image processing device 11. Then, the electrode width is measured. In addition, the applied voltage is corrected according to the distance between the electrodes only when the edge processing is possible.
(2) When the visibility is good, the molten metal surface B ′ is set to have a constant height. Edge processing is performed based on the luminance difference in the electrode tip position measurement window 16, and the tip 3 'of the main electrode 3 is determined, thereby measuring the distance between the electrodes.
(3) The actual inter-electrode distance is calculated from the measured inter-electrode distance, electrode width, and actual electrode width.
(4) When performing the inter-electrode distance constant control, the input voltage correction value is calculated from the measured value PV of the inter-electrode distance and the deviation PV-SV of the set value SV.
(5) When it is determined that the interelectrode distance constant control is difficult, such as when the side end of the main electrode 3 cannot be confirmed, the input voltage correction is set to “OFF” by the changeover switch 21, and the normal input voltage constant control is performed. .

The schematic diagram which shows the plasma melting furnace used for implementation of this invention. The figure which shows the picked-up image of an infrared camera. The block diagram of a control apparatus. The figure which shows the concept of the input voltage correction calculation.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Plasma melting furnace, 2 ... Furnace main body, 3 ... Main electrode, 3 '... Tip position of main electrode, 4 ... Furnace bottom electrode, 5 ... Current collecting plate, 6 ... DC power supply device, 7 ... Electrode raising / lowering device, 8 DESCRIPTION OF SYMBOLS ... Melt supply apparatus, 9 ... Outlet, 10 ... Infrared camera, 11 ... Image processing apparatus, 12 ... Control apparatus, 13 ... Viewing window, 14 ... Camera image, 15 ... Electrode width measurement window, 16 ... Electrode tip position Measurement window, 17 ... power-voltage calculation unit, 18 ... manual input unit, 19 ... charge voltage constant control unit, 20 ... charge voltage correction value calculation unit, 21 ... switch, A ... melted material, B ... melt, B ´… The molten metal surface.

Claims (1)

Melting the molten material by a plasma arc generated by the voltage applied between the main electrode and the furnace bottom electrode provided in the furnace, and making the input voltage constant by raising and lowering the main electrode In the controlled plasma melting furnace, when the inside of the furnace can be observed by an infrared camera provided outside the furnace, the distance between the molten metal surface and the tip of the main electrode is constant, and the interelectrode distance is corrected for the input voltage according to this distance. When the inside of the furnace cannot be observed with an infrared camera, the applied voltage is controlled with constant control.In addition, the interelectrode distance control is performed by photographing the main electrode and the molten metal surface with an infrared camera. Determine the lower end and side ends of the main electrode and the molten metal surface, measure the distance between the molten metal surface and the tip of the main electrode, and the electrode width between the main electrode side edges, and perform the measurement The actual distance between the electrodes is calculated from the ratio of the measured electrode width and the actual electrode width, and the applied voltage correction is turned on / off according to the distance between the electrodes depending on whether the electrode side edge can be determined. A method for controlling a plasma melting furnace, wherein the input voltage is corrected based on a deviation between the measured value of the distance between the electrodes and a preset value .