JP3686448B2 - Waste melting furnace charge stock level control method - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a method for operating a waste melting furnace that thermally decomposes and melts general waste, industrial waste, or the like, and more particularly, to a charge stock level control method that keeps the stock level in the melting furnace properly.
[0002]
[Prior art]
Waste treatment using a shaft furnace type waste melting furnace takes out the waste as slag through the process of drying, pyrolysis, combustion and melting of general waste or industrial waste charged in the furnace. is there.
[0003]
The melting furnace is a shaft-type furnace body having a circular cross section, and in order to dry, pyrolyze, burn, and melt waste charged in the furnace, coke as a fuel is burned. For the coke combustion, a plurality of tuyere are provided in the lower part of the furnace body, and among these tuyere, the lower tuyere arranged near the hearth blows air enriched with oxygen. In order to burn the waste, the upper tuyere arranged above the lower tuyere is designed to blow air.
[0004]
In the operation of the waste melting furnace, the combustible matter in the charge is pyrolyzed in the furnace to generate a pyrolysis residue. The generated pyrolysis residue is combusted by the air sent from the tuyere or accumulated in the furnace, but among the fine ones, the pyrolysis residue that is not burned by the oxygen sent from the tuyere is an air flow It is scattered from the furnace as combustible dust.
[0005]
As a treatment technique for the flammable dust scattered, the present applicant has disclosed in Japanese Patent Application Laid-Open No. 5-340520, the fluctuation of the amount of flammable dust scattered after thermal decomposition in a waste melting furnace, and secondary combustion. In order to achieve stable energy recovery by controlling the amount of exhaust gas in the furnace and temperature, and to stabilize the exhaust gas treatment process, a combustible dust treatment technology in a waste melting furnace was proposed.
[0006]
In the waste melting furnace, as shown in FIG. 3, the exhaust gas containing the combustible dust scattered from the melting furnace 1 is collected by the dust remover 5 such as a cyclone provided in the exhaust gas pipe 4. The collected combustible dust is temporarily stored in the combustible dust hopper 6. The combustible dust hopper 6 is provided with a combustible dust cutting device 7. The combustible dust cut out by the cutting device 4 is sent to the secondary combustion furnace 8 and burned.
[0007]
[Problems to be solved by the invention]
In the above-described combustible dust treatment technology, the scattered combustible dust is completely burned in the secondary combustion furnace at the subsequent stage, but since the operation of the melting furnace itself is not improved, fluctuations in the amount of scattered char combustible dust This change is not preferable because it causes unburned CO to be generated in the secondary combustion chamber or clinker is generated.
[0008]
Therefore, as a result of investigating the fluctuation of the combustible dust scattering amount, it was found that the fluctuation of the combustible dust scattering amount was caused by the fluctuation of the thermal decomposition residue layer thickness in the furnace.
[0009]
In order to eliminate fluctuations in the amount of flammable dust scattered due to fluctuations in the pyrolysis residue layer thickness in the shaft furnace type waste melting furnace, the present invention sets the stock level of the charge in the melting furnace. The present invention provides a control method that keeps the composition appropriate even if the composition of the inclusion varies.
[0010]
[Means for Solving the Problems]
In the present invention, in order to keep the charge stock level in the shaft furnace type melting furnace appropriately, the aeration pressure loss in the melting furnace is detected, and the charge stock level is increased or decreased from the detection result. The ventilation pressure loss is determined from the furnace ventilation differential pressure, which is the difference between the pressures detected at the bottom and top of the furnace.
[0011]
When the ventilation pressure loss is large, the composition of the charge is low in moisture and contains many combustibles, so the drying completion level is high and the pyrolysis zone is widened. The layer becomes thicker. Therefore, at this time, in order to reduce the pyrolysis residue generated by narrowing the pyrolysis zone, if the charging of the waste is stopped and combustion is promoted, the stock level is lowered and the drying completion level is lowered. The thermal decomposition zone is narrowed, the generated thermal decomposition residue is reduced, and the thickness of the deposited thermal decomposition residue can be reduced.
[0012]
In the present invention, the target value of the stock level is set from the target value of the in-furnace differential pressure and the measured deviation in the in-furnace differential pressure, and the detected stock level is compared with the set stock level. The waste charging or the waste charging is stopped so that the stock level becomes the set level.
[0013]
[Action]
In the present invention, since the thickness of the pyrolysis residue layer can be controlled by controlling the stock level to make the air pressure loss appropriate, stable furnace operation can be achieved.
[0014]
【Example】
An embodiment of the present invention will be described with reference to FIGS.
[0015]
A shaft furnace type waste melting furnace 1 for carrying out the control method of the present invention shown in FIG. 1 has a lower tuyere 2 and an upper tuyere 3 around the furnace at the lower part of the shaft portion 1a. A plurality are provided. The lower tuyere 2 is provided in the hearth 1b, and oxygen-enriched air is blown into the furnace from the lower tuyere 2 in order to burn the coke that has descended to the furnace bottom. On the other hand, the upper tuyere 3 is provided in the morning glory part 1c in the upper part of the hearth part, and the air for burning a charge is blown in. It is effective to set the installation level of the upper tuyere 3 near the dry completion level 1d of the charge. The upper tuyere 3 may be provided in two or more stages.
[0016]
The ventilation differential pressure in the furnace is measured by the ventilation differential pressure gauge PT, and the measurement signal is sent to the level controller. The stock level 1e in the furnace is measured by a stock level detector (LT), and the measurement signal is sent to the level controller.
[0017]
Next, the control of the stock level will be described using the block diagram shown in FIG.
[0018]
The target value (+ SV) of the furnace air flow differential pressure and the differential pressure control amount periodically sent by the monitoring timer are input to the controller to calculate the deviation (ε) of the furnace air flow differential pressure. In the stock level setting device, the target value (SV1) of the stock level is set in a range between an upper limit and a lower limit set in advance based on the deviation of the furnace air flow differential pressure obtained by the controller. The stock level target value (SV1) is input to the waste charging necessity determination unit and compared with the actual value (PV1) of the stock level detected by the stock level detector.
[0019]
The waste charging necessity determination unit needs to raise the stock level to the set level when the actual value (PV1) of the stock level is lower than the target value (SV1) of the stock level (when SV1 ≧ PV1). Then, a charging operation signal is sent to the charging device, and the device is operated to charge the waste. Conversely, when the actual stock level value (PV1) is higher than the target stock level value (SV1) (when SV1 <PV1), it is necessary to lower the stock level to the set level. The combustion in the furnace is promoted.
[0020]
As a result of waste charging or combustion in the furnace, the actual value of the changed stock level is detected by a stock level detector, input to a waste charging necessity determination unit, and compared with a target level. This control is repeated to maintain an appropriate stock level.
[0021]
【The invention's effect】
The effects of the present invention are as follows.
[0022]
(1) The stock level can be controlled to an appropriate level according to the composition of the charge, and the ventilation pressure loss in the furnace can be lowered and the furnace can be stabilized. Unsteady phenomena such as reduction, blow-through, and unloading failure can be suppressed.
[0023]
(2) Since the thermal decomposition zone in the furnace can be narrowed, scattering of combustible dust can be suppressed, and the partial combustion ratio in the furnace can be increased.
[Brief description of the drawings]
FIG. 1 is a schematic view of a waste melting furnace for carrying out the present invention.
FIG. 2 is a block diagram of a stock level control method according to the present invention.
FIG. 3 is a schematic view of a conventional waste treatment furnace.
[Explanation of symbols]
1 shaft furnace type waste melting furnace, 1a shaft part, 1a morning glory part, 1b hearth part, 1c drying completion level, 1e stock level, 2 lower tuyere, 3 upper tuyere, 4 exhaust pipe, 5 dust remover, 6 Combustible dust hopper, 7 Cutting device, 8 Secondary combustion furnace

Claims (1)

Enter the target value of the in-furnace differential pressure of the shaft furnace type waste melting furnace and the differential pressure control amount periodically sent by the monitoring timer to calculate the deviation of the in-furnace differential pressure,
Set the target value of the stock level in the range between the upper limit and the lower limit set in advance by the stock level setter based on the deviation of the furnace air flow differential pressure obtained by the controller,
The set stock level target value is input to the waste charging necessity determination device and compared with the actual value of the stock level detected by the stock level detector,
As a result of the comparison, when the actual value of the stock level is lower than the target value of the stock level, the waste charging necessity determination device sends a charging operation signal to the charging device and operates the charging device to load the waste. On the contrary, when the actual value of the stock level is higher than the target value of the stock level, the pyrolysis residue that prevents combustion fluctuations in the combustible dust by promoting the combustion in the furnace without charging the waste A method for controlling the charge stock level of a waste melting furnace, characterized in that the thickness is controlled to a layer thickness .

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