JPH07111911B2 - Control method of waste melting furnace - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for controlling a melting treatment furnace for melting waste by applying electric power.

[Prior Art] In many cases, municipal waste, sewage sludge, incinerated ash of industrial waste, etc., and residue (hereinafter simply referred to as waste) are landfilled. However, since it is becoming more difficult to secure landfill sites, there is a demand for a method of reducing the volume of landfill waste. Separately from this, toxic substances such as heavy metals are eluted from the landfill waste into rainwater, groundwater, etc., which causes secondary pollution, or unburned organic matter in the incinerated ash is decomposed. Pollute the surrounding area. Therefore, there is a demand for pollution-free treatment of waste.

Under such circumstances, a method has been proposed in which waste is put into a reverberatory furnace, an induction furnace, an arc heating furnace, etc., and the waste is melted. For example, a method using arc heating is disclosed in JP-A-52
-8676. According to this method, sludge is melted and solidified by arc heat to generate molten slag and molten metal, so that the rate of reduction in melting is large. In addition, the harmful substances dissolved in the molten slag do not elute into rainwater or the like, and there is no problem in pollution even if they are discarded as they are.

The melting furnace for waste by arc heating is one in which an electrode is inserted into the furnace and electric energy is input to convert the heat energy into heat energy for melting the waste at a high temperature.

The heating method by input power includes open arc heating method that generates an arc between the surface of the molten material of the waste and the electrode tip located in the space above the surface, the unmelted waste of the electrode tip. (Object to be treated) A resistance heating method in which the object to be melted is heated by Joule heat generated as a conductor to form a molten material of waste, and both the open arc heating method and the resistance heating method are adopted. There is a submerged arc heating method.

Here, the submerged arc heating method, for example, as described in JP-B-57-55476, the melting formed by melting waste such as municipal waste incineration ash put into the melting furnace. An arc is generated between the surface of the slag and the electrode to heat it, and the arm is covered with unmelted waste. Arc heat is generated because most of the electrode length is embedded in the unmelted material. Occurs and participates in heating. A melting furnace to which such a heating method is applied is generally called a submerged arc furnace.

[Problems to be Solved by the Invention] In the heating method for the three waste melting treatment furnaces described above, the open heating method opens the melted surface of the waste, so that the heat energy dissipated from the surface of the melt is big,
Along with this, the amount of power input increases, which is extremely uneconomical. Moreover, the damage caused by heating the furnace is also large. Further, since the arc hits the surface of the melt, dust is remarkably generated. In this method, the control of the amount of power input is performed by adjusting the distance between the electrode tip and the melt surface so that the arc voltage / arc current ratio (impedance) is constant.

On the other hand, in the resistance heating method, the tip of the electrode is buried in the waste to be melted, and the generated Joule heat is used to form the melt of the waste, so the surface of the melt is not open. . Therefore, unlike the open heating method, the surface of the melt is not hit by the arc and the generation of dust is not amplified. In addition, since the surface of the melt is covered with unmelted waste, the amount of dissipated heat energy is small, and accordingly, the amount of input power is also small and the heat damage to the furnace body is also small. However, the electric resistance value varies from batch to batch in the melting treatment of waste, such as municipal waste incineration ash, in which the iron content fluctuates greatly in the range of 0 to 45%, and when it is severe, the interelectrode resistance is too small. , Even resistance heat does not stand. In order to control the voltage therefor, a voltage tap change must be frequently performed, and in the submerged arc heating method using a conventionally known submerged arc furnace, the waste to be treated is, for example, municipal waste incineration ash. In the case of, since the resistance value related to the generation of Joule heat greatly varies depending on the content ratio of the metal component (mainly iron content), the tap changing for voltage control is also frequently performed like the resistance heating method. There is a need.

Therefore, the present invention is a submerged arc heating method that is less likely to cause dust generation, and is also suitable for treating municipal waste whose iron content greatly fluctuates, and is appropriately disposed of without frequent tap changing. The present invention provides a method of performing a melting process of an object, reducing input electric energy and manpower and preventing pollution of an operating environment, and at the same time, preventing damage to a furnace body.

In addition, according to the present invention, by performing the melting treatment while continuously feeding the treated material, and performing the melting treatment while keeping the residue level in the furnace constant, a substance such as municipal waste incineration residue is thrown in. In consideration of the fact that unburned substances and water are contained in the gas, a large amount of these unburned substances and water are injected at a time depending on the temperature in the furnace and vaporized, rapidly increasing the pressure in the furnace. By preventing such a situation, it is intended to stabilize the temperature control of the furnace and prevent environmental problems such as ducts blowing out of the slag outlet outside the furnace. is there.

[Means for Solving the Problem] The present invention, which has been made to achieve the above object, provides a method for controlling a waste melting treatment furnace in which a treatment material is melt-treated by input electric energy in a submerged arc furnace, As long as the height of the processed material in the furnace does not exceed the limit, the processed material is continuously charged, and while the temperature at the furnace top is lower than the specified temperature, the height of the processed material is the specified upper limit value (HL) or more. To less than the limit value (ML), the input power is increased, and the height of the processed object becomes a predetermined lower limit value (L
Input power is held between L) and less than the upper limit value (HL), and control is performed to reduce the input power when the height of the processed object is less than the specified lower limit value (LL). When the temperature of the object is above the predetermined temperature, the height of the processed object is not rising, and when the input power is above the lower limit value, the control to reduce the input power is executed, and the height of the processed object is not rising. The control method of the waste melting treatment furnace is characterized in that the control for increasing the input amount of the processed material is executed when the input electric power is less than the lower limit value.

Next, an example of an apparatus to which the present invention is applied will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a submerged arc furnace, in which 1 is a furnace body, and a lid 2 is provided on an upper portion of the furnace body 1. Has been. The three-phase arc main electrodes 4A, 4B, 4C penetrate through the lid body 2 so that the impedance can be controlled at a constant level, and the lower tip is buried in the deposited layer 5a of the waste material 5, which is the leading edge. 4a, 4b and 4c are positioned with a gap for adjustment with the melting surface 5b of the waste, and an arc covered with the deposited layer 5a is generated between them. Also, the lid 2
Is provided with input ports 6A, 6B for waste 5, level meters 8A, 8B and thermometers 10A, 10B.

The level gauges 8A and 8B above are the heavy weight 8 attached to the wire 8a.
b is raised and lowered by the hoisting motor 8c, and the level of the waste 5 is detected by the torque fluctuation at that time. Further, the thermometers 10A and 10B are, for example, thermocouples, and the accumulated layer 5a of the waste 5 is eliminated and the thermometers 8b are removed.
Due to contact of the molten surface 5b with the radiant heat of the molten surface 5b
To prevent damage to the
When a temperature of 800 ° C. or higher is detected, a detection signal for retracting the heavy slag 8b to the furnace top 1b is output.

Auxiliary electrodes 12A and 12B are installed above the discharge port 1d of the furnace main body 1 to prevent solidification of the melt due to heat dissipation to allow continuous outflow and discharge, and discharge the melt to the slag forming device 13. It is like this.

The output signals of the above level meters 8A, 8B and thermometers 10A, 10B are
Control device composed of microcomputer, etc.
The control device 20 controls the rise and fall of the level meters 8A and 8B, and the main electrode 4 via the power supply device 30.
The electric energy to A, 4B, 4C is controlled stepwise.

Next, the processing method will be described.

The waste 5 is input through the input ports 6A and 6B, and the level of the waste is detected by the level meters 8A and 8B. Here, the average value of the level meters 8A and 8B is adopted as the waste level, and the detection value above the waste input limit value ML is 1
The detection value of one level meter 8A, 8B is adopted.

Then, the detection values of the level meters 8A and 8B are calculated by the control device 20, and when the input power amount is small, even if the level of the waste 5 is equal to or higher than the predetermined upper limit value HL, the power amount is reduced. On the other hand, the amount of electric power is increased stepwise, and when the amount of input electric power is large, even if it is below a predetermined lower limit, the amount of electric power is decreased stepwise.

Here, the reason why the amount of electric power is increased or decreased in steps is to shorten the time flag until melting and to increase the responsiveness to melting of the waste.

The waste 5 dissolved by the above process is discharged to the melt slag forming device 13 from the discharge port 1d.

On the other hand, when the temperature detected by the thermometers 10A and 10B is 600 ° C. or higher, step-down of the input power or increase of the input amount of waste is executed as the process of lowering the temperature.

The control method will be described in detail with reference to the flowchart of FIG.
It is determined whether the temperature is 600 ° C. or lower. When the temperature is 600 ° C. or lower, the process proceeds to step 50. At step 50, the waste level is the limit value
When it is determined whether or not it is equal to or more than the ML, and when it is determined that the value is equal to or more than the limit value ML, the process proceeds to step 51, the input of waste is stopped, and when it is determined that the value is equal to or less than the limit value ML, step 52 Go to. When it is determined in step 52 that the waste level is equal to or higher than the upper limit value HL, and when it is determined in step 54 that it is equal to or lower than the maximum allowable power amount, the input power amount is increased (step 56).

On the other hand, in step 52 above, the waste level is judged to be below the upper limit value HL, and in step 58 it is judged to be below the lower limit value LL, and in step 60 the minimum allowable electric power (solidification of the melt in the furnace If it is determined that the amount is equal to or higher than the amount of electric power held by the melting furnace (which is not allowed), the input electric power is stepped down (step 62). When stepping down to the allowable minimum power amount, the power amount is maintained as it is and the melting furnace holding operation is performed (step 63).

Further, when it is determined in steps 52 and 58 that the value is between the upper and lower limit values HL and LL, the applied power is held (step 64).

Therefore, since the electric power is increased or decreased according to the level of waste in the furnace to melt and process the waste, continuous quantitative output can be realized by the automatic operation of the furnace.

Moreover, even if wastes having different compositions are sequentially input, it is detected as a change in the waste level, so that wastes having different compositions can be dealt with quickly.

On the other hand, when it is determined in step 40 that the detected temperature value is, for example, 600 ° C. or higher, in steps 70 to 80, the process of reducing the temperature of the furnace top to 600 ° C. or lower is executed. That is, in step 70, it is determined whether the waste level is equal to or higher than the limit value ML, and when it is determined that the waste level is equal to or higher than the limit value ML, the process proceeds to step 72, and the input of waste is stopped. At this time, when the waste reaches the limit value ML and the temperature shielding effect of the waste is small, that is, when the waste is large and has good air permeability, the input power is stepped down if it is not over 600 ° C. Then, the temperature of the furnace is lowered (step 74). On the other hand, in step 70, when the waste level is less than or equal to the limit value ML, the routine proceeds to step 76, where it is judged whether or not there is a rise in the waste level. By utilizing the effect of lowering, the input power is not immediately stepped down, while when there is no level increase, that is, when there is more waste to be processed even if waste is input, proceed to step 78. . Then, in step 78, when the input power amount is equal to or more than the lower limit value, the input power is stepped down (step 74). On the other hand, when the input power amount is at the lower limit value and the input power cannot be further stepped down, Increase the waste input (step 80) to take advantage of the temperature drop due to the waste input.

Therefore, even if the waste has good air permeability, the temperature of the furnace top can be reliably suppressed to a predetermined value or less. As a result, heat dissipation from the melting surface can be reduced, power saving can be achieved, and dust volatilization from the melting surface can be reduced.

The temperature at the top of the furnace has a correlation with the temperature of the generated gas (measured in the exhaust gas outlet pipe of the furnace). Therefore, instead of measuring the temperature at the top of the furnace, measure the temperature of the generated gas so that the temperature at the top of the furnace falls below a specified value. It is also possible to control the input power amount.

Next, according to the flow chart of FIG. 3, a method of detecting the level of the waste to be processed accumulated in the furnace in the present invention with a level meter and controlling the impedance of the input electric power constant only based on the detected value is shown in FIG. More specifically, first, at step 50, it is judged whether or not the waste level is equal to or higher than the limit value ML, and when it is judged to be equal to or higher than the limit value ML, the process proceeds to step 51 to stop the waste input. On the other hand, if it is determined that the value is equal to or less than the limit value ML, the process proceeds to step 52. When it is determined in step 52 that the waste level is equal to or higher than the upper limit value HL, and when it is determined in step 54 that it is equal to or lower than the maximum allowable power amount, the input power amount is increased (step 56).

On the other hand, in step 52 above, the waste level is judged to be below the upper limit value HL, and in step 58 it is judged to be below the lower limit value LL, and in step 60 the minimum allowable electric power (solidification of the melt in the furnace If it is determined that the amount is equal to or higher than the amount of electric power held by the melting furnace (which is not allowed), the input electric power is stepped down (step 62). When stepping down to the allowable minimum power amount, the power amount is maintained as it is and the melting furnace holding operation is performed (step 63).

Further, when it is determined in steps 52 and 58 that the value is between the upper and lower limit values HL and LL, the applied power is held (step 64).

Therefore, since the electric power is increased or decreased according to the level of waste in the furnace to melt and process the waste, continuous quantitative output can be realized by the automatic operation of the furnace.

Moreover, even if wastes having different compositions are sequentially input, it is detected as a change in the waste level, so that wastes having different compositions can be dealt with quickly.

[Operation] In the submerged arc heating method, since the surface of the melt of the waste is covered with the deposited layer of the waste, the corrugation due to the arc generation does not occur, and the heat dissipation is suppressed. Therefore, while suppressing the generation of dust from the surface of the melt,
The input electric power is saved, and the pollution of the working environment and the heat damage of the furnace are prevented.

Moreover, even if wastes having different compositions are sequentially input, it is detected as a change in the waste level, so that wastes having different compositions can be quickly dealt with. As a result, the tap changer is not required, and the complexity due to frequent tap changing can be prevented.

Then, based on the continuous feeding of treated materials, by setting the residue level to fall within a predetermined range, for example, when something like municipal waste incineration residue is fed, unburned materials and moisture contained in it are included. Eliminates the situation of sudden vaporization to raise the pressure inside the furnace. This facilitates the control of the temperature inside the furnace and prevents the occurrence of a situation in which dust is blown out of the furnace along with hot air.

[Effects] As described above, according to the present invention, it is possible to prevent contamination of the work environment in which the generation of dust is suppressed, and to reduce the amount of heat that is dissipated, thereby saving input power energy.

For example, in the conventional open arc heating method, a power amount of 700 to 800 KWh / 1 ton is required in the melting process of incineration ash, whereas according to the present invention, a power amount of 570 to 660 KWh / ton is sufficient, and a significant power reduction is achieved. Is possible. Further, unlike the conventional resistance heating method, there is no troublesome tap change operation for voltage adjustment corresponding to the variation of the metal component contained in the waste to be treated.

Furthermore, it is possible to cut out an appropriate amount of waste to be processed into the furnace and to quantitatively discharge the melted processed product from the furnace, and the furnace top temperature that fluctuates due to the shape change of the waste cut out into the furnace. Is suppressed to a predetermined value or less to suppress the consumption of input power due to heat dissipation, and to prevent dust from volatilizing out of the furnace.

[Example] Using a submerged arc furnace having an inner diameter of 900 m / m and having a three-phase transformer of 360 KVA as shown in FIG. 1, 100 to 150 kg / h
Municipal rubber incineration ash with various iron contents as shown in Table 1 was treated at a treatment rate of r. Power requirement is 120-150KW
The h and voltage were 100 V or 125 V, and the impedance was controlled to be constant. The results are shown in Table 1.

From the above results, the situation in which it is impossible to control the impedance constant with the input power does not occur.
However, with the increase of iron content, the phenomenon that the fine arc blade generated between the molten slag surface and the electrode changed and the power factor decreased was observed. Incidentally, the improvement of the power factor can be solved without problems by installing a phase-shifting condenser or the like. Moreover, although the generated gas concentration was somewhat high, there was no practical problem.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a submerged arc heating furnace for carrying out the method according to the present invention, and FIGS. 2 and 3 are flowcharts showing an embodiment of the present invention. 1 …… Furnace body 2 …… Lid 4A, 4B, 4C …… Main electrode 5 …… Waste 8A, 8B …… Level meter 10A, 10B …… Thermometer

Claims (2)

[Claims] 1. A method of controlling a waste melting furnace in which a processed material is melt-processed by input electric energy in a submerged arc furnace, unless the height of the processed material in the furnace exceeds a limit. Is continuously charged, and when the temperature at the furnace top is below the specified temperature, the input power is increased when the height of the processed material is between the specified upper limit (HL) and less than the limit (ML). , The height of the processed material is a predetermined lower limit (L
Input power is held between L) and less than the upper limit value (HL), and control is performed to reduce the input power when the height of the processed object is less than the specified lower limit value (LL). When the temperature of the object is above the predetermined temperature, the height of the processed object is not rising, and when the input power is above the lower limit value, the control to reduce the input power is executed, and the height of the processed object is not rising. The method for controlling a waste melting furnace is characterized by executing control to increase the input amount of the processed material when the input power is less than the lower limit value. 2. The method for controlling a waste melting treatment furnace according to claim 1, wherein the treated material is municipal waste incineration ash.