JP3859926B2 - Method and apparatus for controlling combustion air in pyrolysis gasification melting system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pyrolysis gasification melting system, and more particularly to a method and apparatus for controlling combustion air supplied to a combustion melting furnace.
[0002]
[Prior art]
Conventionally, most of the waste such as municipal waste has been incinerated, but due to the lack of final disposal sites and the dioxin problem, the volume of waste can be reduced and replaced with incineration. There is a need for a more advanced waste disposal method that does not generate waste.
[0003]
As a corresponding technology, a pyrolysis gasification melting process that simultaneously incinerates waste and melts ash has been developed and is now operating as an actual machine. This pyrolysis gasification melting process is attracting attention because it can effectively use the energy held by waste by reducing the amount of exhaust gas while reducing harmful substances in the exhaust gas.
[0004]
In the pyrolysis gasification melting process, combustible materials are introduced into a fluidized bed furnace, for example, as a pyrolysis gasification furnace, via a dust feeder, and low temperature pyrolysis is performed in the sand layer where the sand layer temperature is maintained at 500 to 600 ° C. The valuable metal such as aluminum contained in the waste is extracted from the lower part of the sand layer and collected.
[0005]
The combustible gas, char, and ash generated in the fluidized bed furnace are then introduced into the combustion melting furnace, where the ash is melted and separated as slag by high-temperature combustion at 1200 ° C or higher, and harmful substances in the gas such as dioxin are decomposed. To do. The exhaust gas discharged from the combustion melting furnace is recovered by a heat exchanger and a waste heat boiler, cooled in an exhaust gas cooling process, finally removed by a bag filter and cleaned, and then diffused into the atmosphere.
[0006]
[Problems to be solved by the invention]
In order to completely burn the pyrolysis gas in the combustion melting furnace, it is necessary to maintain the oxygen concentration at the outlet of the combustion melting furnace at least about 5% (corresponding to an air ratio of about 1.3). In addition, in order to stabilize combustion in the combustion melting furnace, the waste pits are used to agitate the waste to a uniform quality, and the dust feeder is throwing the waste into the fluidized bed furnace at a constant volume. .
[0007]
However, garbage is composed of miscellaneous components having different densities, specifically, papers, plastics, incombustibles and other components, and it is extremely difficult to uniformly mix them. In addition, a wire or the like contained in the garbage may move the garbage in a lump shape. Therefore, it is practically impossible to make the waste quality and the input amount to the fluidized bed furnace constant.
[0008]
In such a situation, when the load suddenly increases (due to waste debris dropping) in the fluidized bed furnace, a large amount of pyrolysis gas generated by pyrolyzing the waste is sent to the combustion melting furnace. Insufficient oxygen to burn cracked gas. As a result, incomplete combustion occurs in the combustion melting furnace, and harmful carbon monoxide is generated.
[0009]
Conventionally, in order to compensate for the lack of oxygen in the combustion melting furnace, combustion control is performed in which the oxygen concentration is measured at the outlet of the combustion melting furnace and combustion air is replenished when oxygen shortage is detected. However, there is a time lag between the detection of a change in the oxygen concentration after the debris is dropped, and there is a delay in the operation of the damper for replenishing the combustion air that is opened after the decrease in the oxygen concentration is detected. Combustion control is not performed in real time, and a rapid increase in combustion load cannot be handled quickly. Therefore, the incomplete combustion in the combustion melting furnace could not be fundamentally eliminated.
[0010]
The present invention has been made in view of the problems in the conventional control method of combustion air as described above, and ensures complete combustion in the combustion melting furnace even when the load of the pyrolysis gasification furnace increases rapidly. The present invention provides a control method and apparatus for combustion air in a pyrolysis gasification and melting system.
[0011]
[Means for Solving the Problems]
The present invention of claim 1 is a combustion melting furnace in which the waste that has been input is pyrolyzed in a pyrolysis gasification furnace, and the pyrolysis gas discharged from the pyrolysis gasification furnace is combined with combustion air supplied separately. In the control method of combustion air in the pyrolysis gasification and melting system burned at, the load fluctuation of the waste supplied to the pyrolysis gasification furnace is detected, and when the load increases rapidly, the supply amount of combustion air is reduced. This is a method for controlling combustion air that is increased by a predetermined amount to prevent incomplete combustion in the combustion melting furnace.
[0012]
According to the second aspect of the present invention, while adjusting the amount of combustion air supplied to the combustion melting furnace based on the oxygen concentration at the outlet of the combustion melting furnace, the amount of combustion air exceeding the normal control range is supplied when the load suddenly increases. This is a method for controlling combustion air.
[0013]
The present invention of claim 3 is a combustion air control method for detecting a sudden increase in load by a pressure change in a pyrolysis gasification furnace.
[0014]
The present invention of claim 4 is a method for controlling combustion air, in which a sudden increase in load is detected by a change in luminance in the pyrolysis gasification furnace.
[0015]
In the present invention of claim 5, the input waste is thermally decomposed in a pyrolysis gasification furnace, and the pyrolysis gas discharged from the pyrolysis gasification furnace is supplied to the combustion melting furnace together with combustion air. In a control apparatus for combustion air in a pyrolysis gasification and melting system to be combusted, a load detection means for detecting a load fluctuation of waste supplied to the pyrolysis gasification furnace, and a sudden increase in load is detected by the load detection means. A combustion air control device is provided with incomplete combustion preventing means for preventing incomplete combustion in the combustion melting furnace by increasing the supply amount of combustion air supplied to the combustion melting furnace by a predetermined amount.
[0016]
The present invention of claim 6 has an adjusting means for adjusting the amount of combustion air supplied to the combustion melting furnace based on the oxygen concentration at the outlet of the combustion melting furnace, and the incomplete combustion preventing means is usually used by the adjusting means when the load suddenly increases. It is a combustion air control apparatus comprised so that the quantity of combustion air exceeding the control range may be supplied.
[0017]
The present invention according to claim 7 is the combustion air control device in which the load detecting means comprises a pressure sensor for detecting the pressure in the pyrolysis gasification furnace.
[0018]
The present invention of claim 8 is the combustion air control device in which the load detecting means is an optical sensor for measuring the luminance in the pyrolysis gasification furnace.
[0019]
As the combustion melting furnace, it is preferable to use a swirl flow combustion melting furnace in which a pyrolysis gas containing dust is swirled to burn.
[0020]
According to the first and fifth aspects of the present invention, when the load fluctuation of the pyrolysis gasifier is detected and a sudden increase in load is detected, the supply amount of combustion air to the combustion melting furnace is increased. As a result, before the excessive pyrolysis gas reaches the combustion melting furnace outlet, an amount of air corresponding to the pyrolysis gas amount can be supplied to the combustion melting furnace to prevent the occurrence of incomplete combustion.
[0021]
According to the present invention of claims 2 and 6, while adjusting the combustion air supplied to the combustion melting furnace based on the oxygen concentration at the outlet of the combustion melting furnace, the amount exceeding the normal control range when the load increases rapidly Since the combustion air is supplied to the combustion melting furnace, incomplete combustion can be prevented more accurately.
[0022]
According to the present invention of claims 3 and 7, a rapid increase in load can be detected by detecting a pressure change in the pyrolysis gasifier. Specifically, when the load increases rapidly, the pyrolysis gasification reaction is excessively performed in the pyrolysis gasification furnace, and the pressure in the sealed pyrolysis gasification furnace rises higher than the normal pressure. Thereby, a sudden increase in load can be detected.
[0023]
According to the present invention of claims 4 and 8, a rapid increase in load can be detected quickly by detecting a change in luminance in the pyrolysis gasification furnace. Specifically, when the load increases rapidly, black smoke is generated in the pyrolysis gasification furnace and the inside of the furnace becomes dark. Therefore, for example, if the brightness in the furnace is measured with an optical sensor, a sudden increase in load can be detected.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on the embodiments shown in the drawings.
[0025]
FIG. 1 shows an overall configuration of a waste treatment facility to which a combustion air control method according to the present invention is applied. A fluidized bed furnace was used as the pyrolysis gasification furnace.
[0026]
In the figure, waste as waste is temporarily stored in a waste pit 1 and is put into a hopper 1b by a crane 1a. Garbage discharged from the hopper 1b is introduced into the crusher 1c and finely crushed, and then sent to the dust feeder 2 via the garbage conveyor 1d. .
[0027]
In the fluidized bed furnace 3, partial combustion is performed under conditions of an air ratio of 0.2 to 0.4, and low temperature pyrolysis is performed with the sand layer temperature maintained at 500 to 600 ° C. All of the waste that has been thrown in, other than the non-combustible material extracted from the bottom of the hearth, is led to the combustion melting furnace 4 that is directly connected (downstream) to the fluidized bed furnace 3.
[0028]
On the other hand, the non-combustible material extracted from the bottom of the hearth is separated into non-combustible material, non-ferrous metal, iron, and fluidized sand through the screw conveyor 5, the vibrating vibrator 6 and a magnetic separator (not shown). Then, the fluidized sand is returned to the sand layer of the fluidized bed furnace 3 and reused.
[0029]
The pyrolysis gas containing ash generated in the fluidized bed furnace 3 is guided to the combustion melting furnace 4 and further combusted under the condition of a total air ratio of 1.3. In the combustion melting furnace 4, high-temperature combustion at 1200 ° C. or higher is performed, and the ash is melted and separated as slag, and harmful substances in gas such as dioxin are decomposed. 7 is a slag discharge device, and 8 is a slag drainage conveying device for cooling and solidifying the slag.
[0030]
The melting furnace exhaust gas discharged from the combustion melting furnace 4 is heat-recovered by the waste heat boiler 10, then the temperature is further lowered in the gas cooling chamber 11, and dust is removed by the bag filter 12. The purified exhaust gas then passes through the induction fan 13, passes through the denitration device 14, and is discharged from the chimney 15.
[0031]
FIG. 2 is an enlarged view of the fluidized bed furnace 3 and the combustion melting furnace 4.
[0032]
In the figure, a dispersion plate 3 a having a large number of air injection ports is provided at the bottom of the fluidized bed furnace 3, and an air box 3 b is formed therebelow. When fluidized air is introduced into the wind box 3b by the forced air blower 3c, fluidized air is injected upward through the air injection port of the dispersion plate 3a, and a fluidized bed made of sand particles is formed above the dispersion plate 3a. .
[0033]
Above this fluidized bed is provided a dust inlet 3d and a starting main burner (not shown), and a free board 3e is formed above it.
[0034]
Further, a pyrolysis gas discharge port 3f and a pressure sensor 3g are provided at the top of the furnace. The pressure sensor 3g has detected pressure in the fluidized bed furnace 3 at all times, the detection result is supplied to a controller 20 to be described later as a furnace pressure signal S _1. The pressure sensor 3g functions as a load detection means.
[0035]
On the other hand, in the combustion melting furnace 4, the pyrolysis gas flows tangentially into the primary combustion region 4a and burns while swirling, and ash is collected on the wall surface to be melted into slag. Next, the combustion gas that has passed through the throttle 4b collides with the bottom surface 4c of the slag separation part, collects fine ash, and forms molten slag. These slags are continuously discharged from the outlet 4d.
[0036]
An oxygen concentration meter 40 for measuring the oxygen concentration is provided at the outlet 4 e of the combustion melting furnace 4, and an oxygen concentration signal S ₂ output from the oxygen concentration meter 40 is given to the controller 20.
[0037]
Primary air is introduced from the blower 41 through the first pipe 42 to the primary combustion region 4a, and secondary air is introduced from the blower 41 through the second pipe 43 to the outlet 4e. . The control of the combustion air in the present invention controls the supply of the secondary air.
[0038]
The second pipe 43 is provided with a flow meter 44 and a damper 45 controlled by the controller 20 in the air flow direction, and a flow rate signal S ₃ output from the flow meter 44 is given to the controller 20.
[0039]
The controller 20 includes a first control unit 20a and a second controller 20b, the first control unit 20a receives the oxygen density signal S ₂ and the flow rate signal S _3, the opening of the damper 45 in accordance with the oxygen concentration The secondary air supply amount is adjusted by adjusting the degree. Specifically, the oxygen concentration at the outlet 4e of the combustion melting furnace 4 is always maintained at 5%, whereby complete combustion is performed when the pyrolysis gasification furnace 3 is under normal load.
[0040]
The said 1st control part 20a and the damper 45 controlled by the 1st control part 20a function as an adjustment means.
[0041]
The second control unit 20b receives a furnace pressure signal S _1, and compared with the set furnace pressure stored in advance, the damper 45 in response to the excess amount stepwise opened so when exceeds the set furnace pressure It has become. However, the second control unit 20b performs an interrupt process for the first control unit 20a, and resumes the suspended process of the first control unit 20a when the process of the second control unit 20b is completed. Shall be allowed to.
[0042]
The second control unit 20b and the damper 45 controlled by the second control unit 20b function as incomplete combustion preventing means.
[0043]
Next, the control operation of the controller 20 will be described.
[0044]
When the waste introduced into the fluidized bed furnace 3 is agglomerated and temporarily put in a large amount, the excess waste introduced is gasified, and pyrolysis gas containing CO, H ₂ , CH _{4 and the} like is generated. At this time, the furnace pressure of the fluidized bed furnace 3 rapidly increases, and the furnace pressure signal S ₁ output from the pressure sensor 3g greatly fluctuates.
[0045]
The peak of the furnace pressure signal S ₁ is compared with the set furnace pressure by the second control unit 20b. When the set furnace pressure is exceeded, the controller 20 controls the damper 45 at the current opening (controlled by the first control unit 20a). The predetermined opening is further opened than the damper opening), and the oxygen concentration at the combustion melting furnace outlet 4e is temporarily increased from 5% to 8%, for example.
[0046]
When the damper 45 is opened, the control of the second control unit 20b is finished, and the control by the first control unit 20a is resumed.
[0047]
At this time, since the oxygen concentration output from the oximeter 40 appears high, the first control unit 20a attempts to close the damper 45. At this time, the pyrolysis gas discharged from the fluidized bed furnace 3 has already combusted. It has reached the melting furnace 4. Therefore, high-temperature combustion is performed in an atmosphere having an oxygen concentration higher than usual, whereby the pyrolysis gas introduced into the combustion melting furnace 4 is completely combusted.
[0048]
Thereafter, the first control unit 20a performs control so as to maintain the oxygen concentration of the outlet 4e at 5%.
[0049]
FIG. 3 is a timing chart for explaining the control of the combustion air. FIG. 3A shows the conventional control shown for comparison, and FIG. 3B shows the control according to the present embodiment.
[0050]
In FIG. 3A, in the conventional control, when the amount of waste input increases rapidly (point B in the figure), the oxygen concentration meter reacts with a delay of t ₁ seconds and the oxygen concentration starts to decrease (point C in the figure). Although the secondary combustion air is replenished based on the decrease in the oxygen concentration, the operation of the damper is delayed, so replenishment of the secondary combustion air starts from point D in the figure.
[0051]
At this time, the pyrolysis gas has already reached the outlet of the combustion melting furnace 4 due to the sudden increase in the amount of dust input, and the oxygen concentration begins to decrease before the secondary combustion air is replenished (point E in the figure). ). As a result, oxygen shortage actually occurs in the combustion melting furnace. A high concentration of CO is generated during the period until the shortage of oxygen in the furnace is resolved by supplying the secondary combustion air.
[0052]
In contrast, in the control according to the present embodiment, the waste input amount is rapidly increased (in the drawing point F), outputted from the pressure sensor 3g provided in the fluidized bed furnace 3 is a furnace pressure signal S ₁ is greater deflection (FIG. The middle G point), the damper 45 is further opened than the normal opening degree according to the magnitude of the furnace pressure signal S ₁ , and replenishment of secondary combustion air to the outlet portion 4 e of the combustion melting furnace 4 is started. (Point H in the figure).
[0053]
This temporarily increases the oxygen concentration at the combustion melting furnace outlet 4e (point I in the figure). As can be seen from FIG. 5B, the timing at which the amount of dust input suddenly increases substantially coincides with the timing for supplying the secondary combustion air.
[0054]
Therefore, when the amount of waste input increases rapidly and the pyrolysis gas reaches the combustion melting furnace 4 (after t ₃ seconds), the secondary combustion air supply to the combustion melting furnace 4 has already been completed. Generation of combustion can be prevented.
[0055]
In the above-described embodiment, the adjustment means for adjusting the amount of combustion air supplied to the combustion melting furnace 4 based on the oxygen concentration in the combustion melting furnace 4 and the non-replenishment of detecting the sudden increase in load and further supplying combustion air. Although the damper 45 and the secondary air supply second pipe 43 are shared in the complete combustion prevention means, the combustion melting furnace 4 may be configured to supply secondary air independently for each means. it can.
[0056]
Further, the load detecting means of the present invention is configured by the pressure sensor in the above embodiment, but is not limited thereto, and may be configured by, for example, a CCD image sensor shown in FIG. 4 or a microwave oscillator and a microwave receiver. .
[0057]
The configuration shown in FIG. 4 is configured such that a monitoring window 3h is provided on the side wall of the fluidized bed furnace 3, and the brightness in the furnace is monitored by the CCD image sensor 50 as an optical sensor through the monitoring window 3h. In this configuration, when the amount of dust input increases rapidly and black smoke is generated, the inside of the furnace becomes dark, and a decrease in luminance is detected by the CCD image sensor 50, whereby a rapid increase in the amount of dust input can be detected.
[0058]
【The invention's effect】
As is apparent from the above description, according to the present invention of claims 1 and 5, the load fluctuation of the waste supplied to the pyrolysis gasification furnace is detected, and if a sudden increase in the load is detected, the combustion The amount of combustion air supplied to the melting furnace is increased. Therefore, before the excessive pyrolysis gas reaches the combustion melting furnace, an amount of air corresponding to the amount of the pyrolysis gas can be supplied to the combustion melting furnace to prevent the occurrence of incomplete combustion.
[0059]
According to the present invention of claims 2 and 6, while adjusting the combustion air supplied to the combustion melting furnace based on the oxygen concentration at the outlet of the combustion melting furnace, the amount exceeding the normal control range when the load increases rapidly Since the combustion air is supplied to the combustion melting furnace, incomplete combustion can be prevented more accurately.
[0060]
According to the present invention of claims 3 and 7, a rapid increase in load can be detected by detecting a pressure change in the pyrolysis gasification furnace.
[0061]
According to the present invention of claims 4 and 8, a rapid increase in load can be detected quickly by detecting a change in luminance in the pyrolysis gasification furnace.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a configuration of a waste treatment facility to which an exhaust gas treatment method according to the present invention is applied.
FIG. 2 is an explanatory diagram showing a configuration of a combustion air control device according to the present invention.
FIG. 3 is a timing chart for explaining a control operation of the controller shown in FIG. 2;
FIG. 4 is a principle diagram showing another embodiment of the load detection means.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Garbage pit 2 Dust feeder 3 Fluidized bed furnace 3g Pressure sensor 4 Combustion melting furnace 20 Controller 20a 1st control part 20b 2nd control part 40 Oxygen concentration meter 41 Blower 42 1st pipe line 43 2nd pipe line 44 Flowmeter

Claims (8)

Pyrolysis gasification and melting is performed by pyrolyzing the input waste in a pyrolysis gasification furnace and burning the pyrolysis gas discharged from the pyrolysis gasification furnace together with combustion air supplied separately in the combustion melting furnace. In a method for controlling combustion air in a system,
Detecting the load fluctuation of the waste supplied to the pyrolysis gasification furnace, and when the load increases rapidly, increase the supply amount of the combustion air by a predetermined amount to prevent incomplete combustion in the combustion melting furnace. A method for controlling combustion air, characterized by: The combustion according to claim 1, wherein the amount of combustion air supplied to the combustion melting furnace is adjusted based on the oxygen concentration at the outlet of the combustion melting furnace, and an amount of combustion air exceeding the normal control range is supplied when the load suddenly increases. Air control method. The method for controlling combustion air according to claim 1 or 2, wherein a sudden increase in the load is detected by a pressure change in the pyrolysis gasification furnace. The method for controlling combustion air according to claim 1 or 2, wherein the sudden increase in load is detected by a change in luminance in the pyrolysis gasification furnace. A pyrolysis gasification and melting system that pyrolyzes the input waste in a pyrolysis gasification furnace and supplies the pyrolysis gas discharged from the pyrolysis gasification furnace together with combustion air to the combustion melting furnace for combustion. In the control device for combustion air in
A load detection means for detecting a load fluctuation of waste supplied to the pyrolysis gasification furnace, and a supply amount of combustion air to be supplied to the combustion melting furnace when a sudden increase in load is detected by the load detection means. A combustion air control apparatus comprising: an incomplete combustion preventing means for increasing a predetermined amount to prevent incomplete combustion in the combustion melting furnace. The adjusting means for adjusting the amount of combustion air supplied to the combustion melting furnace based on the oxygen concentration at the outlet of the combustion melting furnace, the incomplete combustion preventing means exceeding the normal control range by the adjusting means when the load suddenly increases 6. The combustion air control device according to claim 5, wherein the combustion air control device is configured to supply an amount of combustion air. The combustion air control device according to claim 5 or 6, wherein the load detection means comprises a pressure sensor that detects a pressure in the pyrolysis gasification furnace. The combustion air control device according to claim 5 or 6, wherein the load detection means comprises an optical sensor that measures the luminance in the pyrolysis gasification furnace.

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