JP3665483B2 - Combustion control device for incinerator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a combustion control device for an incinerator, for example, in a fluidized bed incinerator that incinerates, melts or pyrolyzes municipal waste, industrial waste, etc., and is injected to burn unburned gas generated in the furnace. The present invention relates to a combustion control device for an incinerator that controls the amount of secondary air.
[0002]
[Prior art]
Various incinerators have been developed in order to efficiently incinerate or thermally decompose municipal waste, industrial waste, etc., which have been increasing in recent years as lifestyles change. For example, in a fluidized bed incinerator, the sand is fluidized by primary air blown from below, such as sand filled in the furnace, and dust is introduced into it to uniformly heat and thermally decompose it. is there. FIG. 3 shows the schematic configuration of the fluidized bed incinerator.
As shown in FIG. 3, in the fluidized bed incinerator, the dust or the like charged into the incinerator 2 from the dust supply device 1 falls into the sand layer 30 filled in the lower part of the incinerator 2. Primary air is blown into the sand layer 30 from below to fluidize the sand layer 30, and the dust and the like are burned together with fuel in the fluidized sand layer 30. In addition, secondary air is blown into the unburned gas such as CO generated at that time above the sand layer 30, and the unburned gas is completely burned to be discharged from the incinerator 2 as exhaust gas.
By the way, in the incinerator as described above, the state in which a stable combustion state is ensured can be said to be a state in which the generation of the unburned gas is suppressed. For example, the oxygen concentration in the furnace has a correlation with the amount of the unburned gas. By controlling the oxygen concentration in the furnace to be constant, the generation amount of the unburned gas can be reduced. Is possible.
More specifically, the in-furnace oxygen concentration detection device 31 detects the in-furnace oxygen concentration, and according to the detected in-furnace oxygen concentration, the input amount of the dust etc. by the waste supply device 2 and the secondary air amount operation device. The combustion state can be controlled by changing the amount of secondary air by 3.
However, although the oxygen concentration in the furnace is correlated with the amount of combustion, there is a time delay in the correlation. This correlation delay is a control response delay. Therefore, when the base amount of the secondary air amount is controlled using the in-furnace oxygen concentration as a basic control amount, it is desirable to perform feedforward control.
However, even if the feedforward control is performed, for example, when unsteady fluctuations in the combustion state occur due to, for example, a large amount of garbage clogged in the charging path falling into the incinerator 2 at once. In this case, the control accuracy is lowered, and the supply amount of the secondary air amount may be excessive or insufficient.
[0003]
In this regard, the present inventors discriminate fluctuations in the unsteady combustion state using brightness in the furnace, which has a relatively fast response, and when the fluctuations in the unsteady combustion state are judged, A combustion control device for an incinerator that rapidly adjusts the amount of secondary air by changing the amount in an impulse form was proposed in a patent application (Japanese Patent Application No. 10-136992). FIG. 4 shows the schematic configuration, and FIG. 5 shows a time chart relating to the control of the secondary air amount based on the furnace brightness.
As shown in FIG. 4, the combustion control device for the incinerator is based on the brightness measuring device 4 for measuring the brightness in the incinerator 2 and the in-furnace brightness measured by the brightness measuring device 4. And a control arithmetic device 5 for operating the secondary air amount.
The brightness in the furnace measured by the brightness measuring device 4 corresponds to the amount of unburned gas generated, and responds relatively quickly to fluctuations in the combustion state. If it falls into the incinerator 2 at a time, as shown in FIG.
When the control arithmetic device 5 determines that the furnace brightness measured by the brightness measuring device 4 is, for example, a predetermined threshold value or more, the secondary air amount is shown in FIG. As shown, it is changed in an impulse shape. Here, changing the amount of secondary air in an impulse form means changing the amount of secondary air in a rectangular manner in a short time so as not to lower the temperature in the furnace.
[0004]
[Problems to be solved by the invention]
By the way, if the magnitude of the secondary air amount when changing in an impulse shape as described above is not set appropriately, the secondary air amount may be excessive or insufficient, and unburned gas may be generated. .
However, since the brightness in the furnace and the amount of unburned gas are not in a strictly linear relationship, it is difficult to determine the amount of secondary air when changing in the impulse shape based on the brightness in the furnace.
In order to solve such problems in the prior art, the present invention improves the combustion control device of an incinerator and uses the above-mentioned impulse shape based on the oxygen concentration in the furnace which has a substantially linear relationship with the amount of unburned gas generated. By determining the amount of secondary air when changing to, even if unsteady fluctuations occur in the combustion state, an appropriate amount of secondary air can be supplied to suppress the generation of unburned gas. An object of the present invention is to provide a combustion control device for an incinerator that can be used.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 is directed to an in-furnace brightness measuring means for measuring an in-furnace brightness in an incinerator, and an in-furnace brightness measured by the in-furnace brightness measuring means. And a combustion state determination control means for determining an unsteady change in the combustion state in the incinerator and changing the amount of secondary air injected to burn the unburned gas in the furnace in an impulse manner. The incinerator combustion control apparatus comprises in-furnace oxygen concentration measuring means for measuring the in-furnace oxygen concentration of the incinerator, and the combustion state discrimination control means is measured by the in-furnace oxygen concentration measuring means. The incinerator combustion control apparatus is characterized in that the amount of secondary air to be changed in the impulse shape is determined based on the in-furnace oxygen concentration of the incinerator.
According to the combustion control apparatus for an incinerator according to claim 1, the amount of secondary air to be changed in an impulse shape is determined based on the in-furnace oxygen concentration having a substantially linear relationship with the amount of unburned gas generated. Therefore, even if unsteady fluctuations occur in the combustion state, it is possible to supply an appropriate amount of secondary air in an impulse form, which suppresses the decrease in furnace temperature and the generation of unburned gas. Stable combustion can be realized.
The invention according to claim 2 is the combustion control device for an incinerator according to claim 1, further comprising in-furnace temperature measuring means for measuring the in-furnace temperature of the incinerator, and the combustion state discrimination control. The gist of the invention is that the means corrects the gain related to the amount of secondary air to be changed in the impulse shape based on the in-furnace temperature of the incinerator measured by the in-furnace temperature measuring means.
According to the combustion control apparatus for an incinerator according to claim 2, even if the amount of secondary air determined based on the oxygen concentration in the furnace is somewhat inappropriate, the secondary air is based on the temperature in the furnace. Since the gain related to the quantity is corrected, the combustion state can be further stabilized.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention. The following embodiment is a specific example of the present invention, and is not of a nature that limits the technical scope of the present invention.
First, FIG. 1 shows a schematic configuration of an incinerator combustion control apparatus according to an embodiment of the present invention.
As shown in FIG. 1, the combustion control apparatus for an incinerator according to an embodiment of the present invention controls the combustion of an incinerator 2 that controls the amount of secondary air that is blown to burn unburned gas generated in the furnace. A brightness measuring device 4 (corresponding to the in-furnace brightness measuring means) for measuring the brightness in the incinerator 2 and the in-furnace brightness measured by the brightness measuring device 4. Conventional in that it comprises a control arithmetic unit 5 (corresponding to combustion state discrimination control means) that discriminates unsteady changes in the combustion state in the incinerator 2 and changes the secondary air amount in an impulse form. Is almost the same.
The combustion control device of the incinerator according to the present embodiment is different from the conventional one in that the in-furnace oxygen concentration measuring device 6 for measuring the in-furnace oxygen concentration of the incinerator 2 (corresponding to the in-furnace oxygen concentration measuring means) ), An in-furnace temperature measuring device for measuring the in-furnace temperature of the incinerator 2 (corresponding to the in-furnace temperature measuring means), the in-furnace oxygen concentration measured by the in-furnace oxygen concentration measuring device 6 and the in-furnace A correction value calculation device 8 that determines the amount of secondary air to be changed in an impulse shape based on the temperature in the furnace measured by the temperature measurement device 7, and an impulse-like secondary air value determined by the correction value calculation device 8 And an adding device 9 for adding an amount to the output of the control arithmetic device 5.
The steady combustion state control in the combustion control device of the incinerator is performed based on the in-furnace oxygen concentration measured by the in-furnace oxygen concentration measuring device 6, for example.
[0007]
In the combustion control device of the incinerator described above, so-called stagnation or the like, in which dusts fall into the furnace all at once, is monitored by the brightness in the furnace. The in-furnace brightness Ii is sequentially measured by the brightness measuring device 6 at a constant sampling interval. The in-furnace brightness Ii measured by the brightness measuring device 6 is output to the control arithmetic device 5.
In the control arithmetic unit 5, the furnace brightness Ii and the preset threshold value Is are sequentially compared.
For example, as shown in FIGS. 2 (a) and 2 (b), at the time T1 when the control arithmetic unit 5 detects a drop, the period of the drop (T1 to T1 + Ta1), the set value Ai of the secondary air amount Is changed from the base secondary air amount As to an impulse by a predetermined amount ΔA according to the following equations (1) and (2).
Ai = As + ΔA (T1 <i <T1 + Ta1) (1)
Ai = As (T1 + Ta1 <i) (2)
By changing the set value Ai in this way, the generation of unburned gas accompanying the deterioration of the combustion state is suppressed, and further by changing it to an impulse shape, the inside of the furnace due to the secondary air that occurs when changing to a step shape A decrease in temperature is suppressed. Also, by controlling using the brightness in the furnace, a change in the combustion state is detected with almost no delay time, so that highly responsive control becomes possible.
The secondary air amount Ai calculated by the control arithmetic device 5 based on the equations (1) and (2) is output to the secondary air amount operating device 3 via the adding device 9.
Further, the in-furnace oxygen concentration measuring device 6 sequentially measures the in-furnace oxygen concentration of the incinerator 2 and outputs it to the correction value computing device 8. In the correction value calculation device 8, the differential value DOi is sequentially calculated from the oxygen concentration value Oi according to the following equation (3).
DOi = Oi-Oi-1 (3)
Then, the in-furnace oxygen concentration value of N steps ahead is calculated according to the following equation from the current value and the differential value of the oxygen concentration.
O _est = Oi + α _n × DOi (4)
Here, O _est is a predicted value of the change in oxygen concentration when the secondary air amount is maintained as it is using the current furnace oxygen concentration, and this predicted value and the target oxygen concentration target value O _taget. It can be said that a constant multiple of (O _taget −O _est ) calculated using the above is the amount of air required to generate unburned gas.
Accordingly, the correction value calculation device 8 calculates an appropriate increase amount ΔA of air according to the following equation (5), and corrects the increase amount ΔA set in the control calculation device 5 based on this. The correction amount is calculated.
ΔA = K × (O _taget −O _est ) (5)
Then, the correction value output from the correction value calculation device 8 is added to the output of the control calculation device 5 by the adding device 9 and output to the secondary air amount operating device 3.
As a result, as shown in FIGS. 2A and 2C, the increase amount ΔA of the secondary air amount is determined from the predicted value and target value of the in-furnace oxygen concentration. According to the control device, stable combustion can be realized.
[0008]
However, if the gain K in the above equation (5) is inappropriate, the air amount increase ΔA may become more than necessary, reducing the furnace temperature, making combustion unstable and generating unburned gas. .
Therefore, in the combustion control device for the incinerator, the gain K is adjusted using the in-furnace temperature sequentially measured by the in-furnace temperature measuring device 7. When the influence on the furnace temperature based on the increase amount ΔA of the air amount is determined to be Δtemp by the furnace temperature measuring device 7 and the correction value calculating device 8, the following adjustments (A) to (C) Is added to the gain K.
(A) When Δtemp> 0, K is not changed (B) When Δtemp = 0, K is not changed (C) When Δtemp <0, K is changed to (1−β) K where β Is a constant of 0 <β <1.
As a result, when the temperature in the furnace is lowered, it is determined that the amount of increase in air is large, and the gain K is adjusted in a decreasing direction. Further, by repeating this, an appropriate gain K can be determined for the specific device.
As described above, according to the combustion control apparatus for an incinerator according to the present embodiment, the secondary air when changing in an impulse form based on the in-furnace oxygen concentration having a substantially linear relationship with the amount of unburned gas generated. Because the amount is determined, even if unsteady fluctuations occur in the combustion state, an appropriate amount of secondary air can be supplied in an impulse manner, reducing the furnace temperature and generating unburned gas. Suppressing and stable combustion can be realized. Moreover, even if the amount of secondary air determined based on the oxygen concentration in the furnace is somewhat inappropriate, the gain related to the amount of secondary air is corrected based on the temperature in the furnace, so that the combustion state is further stabilized. be able to.
[0009]
【Example】
In the above embodiment, the fluidized bed incinerator has been described as an example. However, the combustion of the incinerator according to the present invention can be applied to other incinerators that completely burn unburned gas by blowing secondary air. The control device is applicable.
[0010]
【The invention's effect】
As described above, according to the combustion control device for an incinerator according to the first aspect of the present invention, the 2 in the case of changing in an impulse form based on the in-furnace oxygen concentration having a substantially linear relationship with the amount of unburned gas generated. Because the amount of secondary air is determined, even if unsteady fluctuations occur in the combustion state, an appropriate amount of secondary air can be supplied in an impulse manner, the furnace temperature can be lowered, and unburned gas Generation can be suppressed and stable combustion can be realized.
Further, according to the combustion control device for an incinerator according to the second aspect, even if the amount of secondary air determined based on the oxygen concentration in the furnace is somewhat inappropriate, the 2 Since the gain related to the amount of secondary air is corrected, the combustion state can be further stabilized.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of an incinerator combustion control apparatus according to an embodiment of the present invention.
FIG. 2 is a time chart for explaining control of the secondary air amount of the combustion control device for the incinerator.
FIG. 3 is a diagram showing an example of a conventional combustion control device for an incinerator.
FIG. 4 is a view showing another example of a conventional combustion control device for an incinerator.
FIG. 5 is a time chart for explaining control of the amount of secondary air in another example of a conventional combustion control device for an incinerator.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Waste supply apparatus 2 ... Incinerator 4 ... Brightness detection apparatus (in-furnace brightness detection means)
5. Control arithmetic unit (combustion state determination control means)
6 ... In-furnace oxygen concentration measuring device (in-furnace oxygen concentration measuring means)
7 ... Furnace temperature measuring device (furnace temperature measuring means)
8 ... Correction value calculation device 9 ... Addition device

Claims (2)

In-furnace brightness measuring means for measuring the in-furnace brightness in the incinerator;
The amount of secondary air that is blown in order to discriminate unsteady changes in the combustion state in the incinerator based on the brightness in the furnace measured by the brightness measuring means in the furnace and to burn unburned gas in the furnace In a combustion control apparatus for an incinerator comprising combustion state discrimination control means for changing the pressure in an impulse shape,
In-furnace oxygen concentration measuring means for measuring the in-furnace oxygen concentration of the incinerator,
The incineration characterized in that the combustion state discrimination control means determines the amount of secondary air to be changed in the impulse shape based on the in-furnace oxygen concentration of the incinerator measured by the in-furnace oxygen concentration measuring means. Furnace combustion control device. A furnace temperature measuring means for measuring the furnace temperature of the incinerator;
The said combustion state discrimination | determination control means correct | amends the gain regarding the secondary air amount changed to the said impulse form based on the in-furnace temperature of the said incinerator measured by the said in-furnace temperature measurement means. Incinerator combustion control device.

Images