JPH0689883B2 - Combustion control method in a fluidized bed incinerator - Google Patents

Description

[Detailed Description of the Invention] Technical Field: The present invention relates to a method of controlling combustion in a fluidized bed incinerator, which incinerates materials for incineration while fluidizing a fluidized medium such as sand with air sent from the bottom of the hearth, and which is suitable for preventing the emission of unburned gas by controlling the combustion amount of materials fed into the furnace, i.e., the combustion amount per unit time, without varying the amount of combustion air or exhaust gas. Note that the term "fluidized bed incinerator" here includes a fluidized bed boiler for the purpose of heat recovery.

BACKGROUND ART Conventionally, fluidized bed furnaces have been used for incineration of municipal waste, etc.
When municipal solid waste is incinerated in a fluidized bed incinerator, the waste is continuously fed into the incinerator. However, due to its nature, municipal solid waste often becomes entangled and forms large clumps, resulting in a large amount of waste being fed into the incinerator at once. Fluidized bed incinerators have an extremely fast combustion rate, which is an advantage because they burn very well, but this can also be a drawback. Because of their high combustion performance, when materials are fed into the fluidized bed, they can burn in just a few seconds. Therefore, if the feeder that supplies materials to the incinerator does not have a constant feed rate, variations in the amount of materials fed directly lead to variations in the oxygen concentration in the combustion gas.

Depending on the type of fluidized bed furnace, if the oxygen concentration in the combustion exhaust gas falls below around 5%, carbon monoxide and hydrocarbons such as methane, ethylene, propylene, acetylene, and benzene will not be completely burned and will be emitted. In addition, substances such as ammonium chloride and ammonium hydroxide will be produced, causing white smoke to come out of the chimney.

Furthermore, because fluidized bed furnaces have such good combustion performance, they can burn the bed material even if the theoretical air ratio of the fluidizing air to the bed material is less than 1, as long as the superficial velocity of the bed material is sufficient to fluidize it, but as mentioned above, the air ratio is increased to prevent the generation of unburned gases such as carbon monoxide. Also, in anticipation of a case where the quantitative capability of the supply feeder is impaired, excess air is sometimes blown in beforehand to prevent the oxygen concentration from decreasing even if the amount of incineration material supplied increases.

Although it depends on the quantitative performance of the supply feeder, the amount of air blown into the furnace can be as much as twice the theoretical amount. However, even in this case, especially when handling municipal waste, the waste can become tangled and form large clumps, causing a so-called "downpour" of waste, resulting in a momentary lack of oxygen and the emission of unburned gases such as carbon monoxide from the chimney.

Conventionally, methods for preventing the emission of these unburned gases have been as follows:
The feeder that supplies the incineration material to the furnace is improved to improve the quantitative performance.
As disclosed in Japanese Patent Application Laid-Open No. 61-100612, a measuring means is provided to measure the amount of incineration material fed in, and when a large amount of incineration material is fed in, the number of revolutions of the feeder is reduced to reduce the amount fed in.

In addition, a method has been adopted in which an increase in the amount of incineration material being fed or a lack of oxygen is detected and new secondary air is blown in.

However, even with the use of supply feeders, which is one of the conventional methods for preventing the emission of unburned gas, there are limits to the improvements that can be made to improve quantitative performance, and as a result, there is a tendency to use feeders that are extremely expensive.

The system disclosed in the aforementioned Japanese Patent Application No. 59-223198 also uses a feed amount measurement device, but as a result, any material dropped into the furnace burns immediately, resulting in a lack of oxygen. If secondary air is introduced to compensate for this, the amount of exhaust gas increases due to the rapid combustion, and the introduction of secondary air further increases the amount of exhaust gas, causing the furnace pressure to become positive. This pressure is detected and the induced draft fan inlet damper opens to normalize the furnace pressure. However, when a large amount of material is added to the furnace, the furnace pressure fluctuates, and the positive pressure causes exhaust gas to be blown out from the exhaust gas duct flange and ash discharge rotary valve, dispersing dust particles in the exhaust gas, making the factory dusty.

Furthermore, the method of controlling the secondary air to maintain a certain oxygen concentration in the exhaust gas has the drawback that, because the combustion speed of a fluidized bed furnace is extremely fast, variations in the amount of incineration material supplied directly result in variations in the exhaust gas, causing the same problems as above. In addition, a large amount of combustion air requires larger combustion fans, exhaust gas induction fans, etc.
There are also problems with the driving power being increased. Furthermore, because the amount of exhaust gas fluctuates, when the amount of exhaust gas is large, large-capacity exhaust gas treatment equipment such as exhaust gas ducts, gas coolers, and electrostatic precipitators are required, which increases the size of the incineration facility and the overall construction costs.

Furthermore, in conventional fluidized bed boilers, particularly those used for power generation, the amount of fuel supplied, such as coal, is varied in response to fluctuations in the load, as disclosed in Japanese Patent Laid-Open Publication No. 1912/1984. When the amount of fuel supplied increases, there is a combustion control method for controlling the amount of fluidizing air sent from the bottom of the fluidized bed, thereby controlling combustion while preventing the temperature of the fluidizing medium in the fluidized bed from exceeding a predetermined level. However, even with this combustion control method, it has been impossible to prevent sudden fluctuations in the amount of combustion and to prevent the emission of unburned gas without changing the amount of combustion air and exhaust gas, especially in fluidized bed incinerators that burn a mixture of materials such as municipal waste that are heterogeneous in volume, shape, combustibility, and calorific value, when the amount of material fed into the furnace fluctuates.

Here, the amount of combustion refers to the calorific value (kcal/kg) x the amount of material to be burned (amount of material to be incinerated) (kg/hour).

The present invention has been made to solve the above-mentioned problems of the prior art, and aims to provide a combustion control method for a fluidized bed incinerator that can prevent the emission of unburned gas without using an expensive supply feeder with good quantitative accuracy, and that can prevent the emission of unburned gas even when combustible materials with different calorific values, properties such as combustibility, shapes, and volumes, i.e., coal, municipal waste, industrial waste, or mixtures of these, are fed into the fluidized bed incinerator, even if the amount of combustible material fed changes, without increasing the amount of combustion air or exhaust gas.

DISCLOSURE OF THE INVENTION In order to achieve the above object, the combustion control method for a fluidized bed incinerator of the present invention is characterized in that, in a fluidized bed furnace in which air is sent from the lower part of the fluidized bed to fluidize a fluidized medium and combust material fed into the furnace, the amount of material burned in the fluidized bed furnace is monitored, and when the amount of combustion exceeds a predetermined amount, the amount of air sent from the lower part of the fluidized bed is reduced, thereby reducing the amount of material burned in the furnace and increasing the amount of air blown into the space above the fluidized bed, thereby controlling the amount of material burned to a constant level.

In addition, in a fluidized bed furnace configured to fluidize the fluidized medium by air sent from multiple air chambers below the furnace bed, when the amount of incineration material being added exceeds a predetermined amount, the amount of air sent from the air chamber at the point where the incineration material falls is reduced by a predetermined amount according to the amount of incineration material being added, and the amount of air sent from the air chamber is increased and sent into the space above the fluidized bed, thereby slowing the flow of the fluidized medium at the point where the incineration material falls according to the amount of incineration material being added, and activating the flow of the fluidized medium in the surrounding area, thereby controlling the amount of incineration material being burned.

BRIEF DESCRIPTION OF THE DRAWINGS Figures 1 (A), (B), and (C) are diagrams showing the results of measurements of the brightness inside a fluidized bed incinerator, the oxygen concentration in the exhaust gas, and fluctuations in the pressure inside the incinerator, respectively. Figure 2 is a diagram showing the schematic configuration of a fluidized bed incinerator in which the combustion control method according to the present invention is implemented.
FIG. 3 is a diagram showing the fluctuations of the combustion amount, oxygen concentration in the exhaust gas, exhaust gas amount, primary air amount, secondary air amount, and in-furnace temperature with respect to the time fluctuation of the incineration material input amount in a fluidized bed incinerator using a conventional combustion control method. FIG. 4 is a diagram showing the fluctuations of the combustion amount, oxygen concentration in the exhaust gas, exhaust gas amount, primary air amount, secondary air amount, and in-furnace temperature with respect to the time fluctuation of the incineration material input amount in a fluidized bed incinerator using a combustion control method according to the present invention. FIGS. 5(A), (B), and (C) are respectively diagrams showing the results of measurements of the primary air amount, in-furnace brightness, and oxygen concentration in the exhaust gas using a combustion control method according to the present invention using in-furnace brightness. FIG. 6 is a diagram showing the results of measurements of the acidity concentration in the exhaust gas, where FIG. 5(A) shows the case where the conventional combustion control method is used and FIG. 5(B) shows the case where the combustion control method according to the present invention is used. FIG. 7 is a diagram showing the relationship between the fluidization ratio G [U/Umf] and the heat transfer coefficient _hK in a fluidized bed incinerator.
and pressure loss _PL , Figs. 9(A) and (B) are diagrams showing the results of measurements of fluctuations in the oxygen concentration in the exhaust gas when municipal waste is incinerated in a fluidized bed incinerator with different fluidizing air volumes, Fig. 10 is a diagram showing the schematic configuration of another fluidized bed incinerator in which the combustion control method of the present invention is implemented, Figs. 11(A), (B), and (C) are diagrams showing the results of measurements of fluctuations in the primary air volume, furnace pressure, and oxygen concentration in the exhaust gas in the combustion control method based on furnace pressure of the present invention, Fig. 12 is a diagram showing the schematic configuration of another fluidized bed incinerator in which the combustion control method of the present invention is implemented, Fig. 13 is a diagram showing the schematic configuration of another fluidized bed incinerator in which the combustion control method of the present invention is implemented, Fig. 14 is a diagram showing the control flow of the combustion control method of the present invention, Fig. 15 is a diagram showing the control flow of the combustion control method of the present invention,
The figure shows the schematic configuration of another fluidized bed incinerator in which the combustion control method of the present invention is implemented, Figure 16 is a diagram showing the fluctuations in the exhaust gas volume, primary air volume, secondary air volume and oxygen concentration in the exhaust gas relative to the time fluctuations in the amount of incineration material input using a conventional combustion control method in a fluidized bed incinerator with the configuration shown in Figure 15, and Figure 17 is a diagram showing the fluctuations in the exhaust gas volume, primary air volume, secondary air volume and oxygen concentration in the exhaust gas relative to the time fluctuations in the amount of incineration material input using a combustion control method of the present invention in a fluidized bed incinerator with the configuration shown in Figure 15.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment for carrying out the present invention will be described with reference to the drawings.

In a fluidized bed incinerator, it is extremely difficult to directly measure the amount of combustion of the material being burned, and this amount is detected indirectly from the brightness inside the furnace, the oxygen concentration in the exhaust gas, the pressure inside the furnace, the temperature inside the furnace, and the amount or volume and properties of the material being incinerated inside the furnace.

1(A), (B), and (C) show the results of measurements of the brightness L inside the furnace, the oxygen concentration E in the exhaust gas, and the furnace pressure P, which represent the combustion amount in the above-mentioned fluidized bed incinerator. The horizontal axis in the figures represents time t (each division is 5 seconds). As shown in the figures, in a fluidized bed incinerator, the brightness L inside the furnace, the oxygen concentration E in the exhaust gas, and the furnace pressure P change in response to fluctuations in the combustion amount. Therefore, the present invention estimates the combustion amount based on the brightness L inside the furnace, the oxygen concentration E in the exhaust gas, and the furnace pressure P, and controls the amount of fluidizing air sent from the bottom of the fluidized bed. This suppresses sudden fluctuations in the combustion amount even if the amount of material fed into the furnace fluctuates, thereby controlling the combustion amount to remain constant.

Fig. 2 is a diagram showing the schematic configuration of a fluidized bed incinerator for implementing the combustion control method in a fluidized bed incinerator according to the present invention. In the figure, 1 is a furnace, and inside the furnace 1, a fluidized bed 2 is formed in which a fluidizing medium such as sand flows. An air chamber 6 is provided below the fluidized bed 2, and the fluidizing medium is fluidized by sending fluidizing air from a fluidizing blower (not shown) through piping 5 into the furnace 1 via the air chamber 6. This blower is, for example, a centrifugal blower, and is preferably controlled so that the air volume is constant during operation. 11 is an incineration material input hopper into which materials for incineration such as municipal waste are input, and the incineration material input hopper
A supply feeder 12 is provided below the furnace 11 to supply materials to be incinerated into the furnace 1. 14-1 is a brightness detection sensor that detects the brightness of the furnace 1, and 13 is a regulator that adjusts the valve opening based on the measured brightness inside the furnace 1.
The wall of the fluidized bed 2 is provided with an air nozzle 8 for blowing air into the upper space of the fluidized bed 2, and the air nozzle 8 is connected to a pipe.
The control valve 7 is connected via the pipe 16. The control valve 7 may be attached to either the pipe 5 or the pipe 16.
Furthermore, instead of using the pipe 16 as a bypass pipe for the pipe 5, the pipe 16 and the pipe 5 may be connected to different blowers. In the figure, the reference numeral 9 denotes a freeboard section, and the reference numeral 18 denotes a secondary air supply pipe. The brightness detection sensor 14-1 is not affected by the brightness of the bed material or the furnace wall, etc., and detects the brightness of the furnace 1 due to the combustion of the incineration material A.
The detector should be installed at a position far above the secondary air inlet and where the entire cross section of the furnace can be seen so that the brightness inside can be detected. Also, in the figure, EG indicates the exhaust gas discharged from the exhaust gas outlet, and AS indicates the ash discharged from the ash outlet.

In the fluidized bed incinerator having the above-mentioned configuration, the incineration material A fed into the incinerator 1 from the feeder 12 is a certain portion of the fluidized bed 2,
In other words, it falls in the center.
Although not shown, a spreader may be used to disperse the materials A. When the amount of materials A fed into the furnace 1 is greater than usual, the amount of materials burned (per unit time) increases, making the furnace 1 brighter and causing the brightness detection sensor to detect the amount of materials A burned.
The output of 14-1 increases. When the brightness of the furnace 1 increases, the regulator 13 opens the control valve 7, and the reduced amount of air blown in from the air chamber 6 is blown through the pipe 16 and into the upper space of the fluidized bed 2 from the air nozzle 8. As a result, the amount of air sent in from the air chamber 6 decreases, the flow of the fluidized bed 2 becomes slower, the amount of heat transferred from the fluidized bed to the incineration material A decreases, and the gasification rate of the incineration material A slows down. In other words, the combustion rate slows down. At this time, by reducing the amount of air from the air chamber 6, the amount of oxygen in the fluidized bed 2 decreases, and the amount of unburned gas increases accordingly, but the amount of air blown in from the air nozzle 8
Since the amount of air blown in from the fluidized bed 2 is increased, this unburned gas is burned in the upper space of the fluidized bed 2 such as the freeboard section 9.

The amount of air that is reduced from the air chamber 6 may be blown into either the air nozzle 8 or the secondary air inlet, or may be distributed between them; the point is that only an amount of air sufficient to completely burn the unburned gases in the hollow cylindrical portion is blown in.

Fig. 3 is a diagram showing the fluctuations in the combustion amount, oxygen concentration in the exhaust gas, exhaust gas amount, fluidizing air amount (primary air amount), secondary air amount and in-furnace temperature with respect to the time fluctuations in the amount of incineration material fed into a fluidized bed incinerator using a conventional combustion control method, and Fig. 4 is a diagram showing the fluctuations in the combustion amount, oxygen concentration in the exhaust gas, exhaust gas amount, fluidizing air amount (primary air amount), secondary air amount and in-furnace temperature with respect to the time fluctuations in the amount of incineration material fed into a fluidized bed incinerator using a combustion control method according to the present invention. In these figures, the horizontal axis represents time t.

Conventionally, as shown in Figure 3, the amount of primary air C supplied from the bottom of the fluidized bed 2 through the air chamber 6 is constant, and when the incineration material A is introduced at time _t1 , it is immediately gasified, and combustion begins a few seconds later, and the combustion amount Q increases.
The oxygen concentration E in the exhaust gas decreases rapidly. When this oxygen concentration is low, unburned gas is discharged, so the amount of secondary air D increases in response to the decrease in the oxygen concentration E in the exhaust gas, and the amount of exhaust gas B also increases. In addition, the temperature T in the furnace also rises because the amount of combustion Q increases. As combustion progresses, the amount of unburned material in the furnace 1 decreases, and the oxygen concentration E in the exhaust gas increases, so
The amount of secondary air D is reduced, the amount of exhaust gas B is also reduced, and the temperature inside the furnace also drops.

In contrast, when the combustion control method of the present invention is used,
As shown in the figure, when the incineration material A is fed from time _t1 and the combustion amount Q increases, the brightness inside the furnace 1 increases, the output of the brightness detection sensor 14-1 increases, and the regulator 13 operates the control valve 7.
is opened, and air is blown into the upper space of the fluidized bed 2 as the primary air amount _C2 , so the primary air amount _C1 supplied from the air chamber 6 decreases. The decrease in the primary air amount _C1 supplied from the air chamber 6 reduces the rate of increase in the combustion amount Q. In other words, since the combustion speed slows down, the oxygen concentration E in the exhaust gas also decreases gradually rather than suddenly. Moreover, since the secondary air amount D increases in line with this decrease in the oxygen concentration E in the exhaust gas, the oxygen concentration E in the exhaust gas hardly changes. Furthermore, the decrease in the rate of increase in the combustion amount Q reduces the rate of increase in the furnace temperature T. When the combustion amount Q decreases, the control valve 7 is closed to reduce the primary air amount _C2 from the air nozzle 8 and increase the primary air amount _C1 from the air chamber 6. This primary air amount
The increase in _C1 causes the fluidization of the fluidized medium in fluidized bed 2 to become more active, and normal operation is resumed.

In this way, as the combustion amount Q increases, the primary air _C1 from the air chamber 6 is reduced, and the primary air C1 from the air nozzle 8 is
Since _C2 is increased and the amount of secondary air D is supplied in accordance with the gradual decrease in the oxygen concentration E in the exhaust gas, the increase in the amount of exhaust gas B is also extremely small.

In this case, the decrease (increase) in the secondary air amount due to the decrease (increase) in the primary air amount is preferably equal to the decrease (increase) in the primary air amount, but may be ±30% of the decrease (increase) in the primary air amount.

FIG. 5 shows the brightness L in the furnace, i.e., the brightness sensor 14
Fig. 1 shows the results of actual measurements in which the amount of primary air _C1 supplied from the air chamber 6 was controlled by the output of -1, and the amount of combustion was controlled. Fig. 1(A) shows the fluctuation state of the amount of primary air _C1 [ ^Nm3 / ^m2 ·H], Fig. 1(B) shows the fluctuation state of the brightness L [%] inside the furnace, and Fig. 1(C) shows the oxygen concentration E in the exhaust gas.
This is a diagram showing the fluctuation state of [%]. The horizontal axis indicates time t (1 scale represents 17 seconds).

As shown in the figure, by controlling the amount of primary air _C1 supplied from the air chamber 6 using the brightness L inside the furnace, the fluctuations in the oxygen concentration E in the exhaust gas become extremely gentle. In other words, it can be confirmed that combustion becomes gentle (the combustion speed becomes slower) and stable.

Figure 6 shows the results of measurements of the oxygen concentration E in exhaust gas using a conventional combustion control method and the combustion control method of the present invention, with (A) showing the case where the conventional combustion control method was used and (B) showing the case where the combustion control method of the present invention was used. In the figure, the vertical axis shows the oxygen concentration E [%] in the exhaust gas, and the horizontal axis shows time t (1 division represents 200 seconds). As shown in the figure, it was confirmed that the fluctuation range of the oxygen concentration E in the exhaust gas was smaller when using the combustion control method of the present invention than when using the conventional combustion control method.

The combustion control method of the present invention will be further explained with reference to Figures 7 and 8. Figure 7 shows the relationship between the fluidization ratio G [U/Umf] and the heat transfer coefficient _hK in a fluidized bed incinerator, and Figure 8 shows the relationship between the fluidization ratio G [U/Umf] and the pressure loss _pL , where U is the superficial velocity and Umf is the minimum fluidization superficial velocity (the minimum superficial velocity required for fluidizing the bed material).

In a typical fluidized bed furnace, the superficial velocity U of the fluidizing air is such that the fluidization ratio G is 4 to 10 [U/Umf] (700 to 1500 Nm ³ /m ² .
Therefore, in a fluidized bed incinerator implementing the combustion control method of the present invention, the superficial velocity _U of the fluidizing air is set to a fluidization ratio of 1 to 4 [U/Umf] (250 to 700 Nm3), and the heat transfer coefficient hK is kept at a substantially constant value, so there is a limit to how much the gasification of the incinerated material can be controlled even if the superficial velocity U of the fluidizing air is changed ^.
When the amount of combustion Q of the incineration material exceeds a predetermined amount, the superficial velocity of the fluidizing air is changed to a range where the fluidization factor G slightly exceeds 1 [U/Umf], ^i.e. , the range of the shaded area in Figure 7. This makes it possible to change the heat transfer coefficient _hK. Therefore, by adding this method to the method of simply controlling gasification by changing the superficial velocity of the fluidizing air, it is possible to better control the gasification rate of the incineration material.

FIG. 9 shows the change in the oxygen concentration E in the exhaust gas when municipal waste is incinerated in a fluidized bed incinerator by changing the amount of ^fluidizing air ^.
・H], and (B) in the same figure shows the case of a flowing air volume of 420 [Nm ³
/m ² H]. In the figure, the horizontal axis represents time t
(One scale represents 100 seconds). As shown in the figure,
When the flowing air volume is as high as 970 [ ^Nm3 / ^m2 ·H], the waste fed in is gasified all at once, and fluctuations in the amount fed directly lead to fluctuations in the oxygen concentration E in the exhaust gas. Therefore, when controlling the combustion speed, the fluctuations are too large, resulting in large fluctuations in the oxygen concentration and carbon monoxide. In contrast, when the flowing air volume is 420 [ ^Nm3 / ^m2 ·H], combustion becomes gentler (the combustion speed becomes slower) and more stable, so these fluctuations become smaller.

By controlling combustion in the fluidized bed incinerator as described above, even if the combustion target is coal, municipal waste, industrial waste, or a mixture of these combustion materials, which have different calorific values, shapes, and volumes such as flammability, the amount of combustion air,
Combustion is possible without significant fluctuations in the amount of exhaust gas, the oxygen concentration in the exhaust gas, unburned gas, etc. It also makes it possible to incinerate materials by feeding them into a fluidized bed incinerator without crushing them.

Fig. 10 is a schematic diagram of a fluidized bed incinerator in which the combustion rate of materials in the incineration furnace is controlled by detecting the pressure inside the furnace 1. In the figure, parts with the same reference numerals as in Fig. 2 indicate the same or corresponding parts. As shown in the figure, a pressure detection sensor 14-2 is provided above the fluidized bed 2 to detect the pressure inside the furnace, and the output of the pressure detection sensor 14-2 is input to a regulator 13.

By configuring the combustion amount control as described above, when a large amount of material A is fed into the furnace 1, the combustion amount (per unit time) of the material A increases, so the amount of exhaust gas generated increases, and the internal pressure of the furnace 1 increases as can be seen from Figure 1 (C), and the output of the pressure detection sensor 14-2 increases. When the internal pressure of the furnace 1 increases, the regulator 13 operates the control valve 7
The nozzle 8 is opened to increase the amount of air blown into the upper space above the fluidized bed 2. This reduces the amount of air sent from the air chamber 6, slowing the flow of the fluidized bed material in the fluidized bed 2, reducing the amount of heat transferred from the fluidized bed material to the material A, and slowing the gasification rate of the material A. In other words, the combustion rate slows down. At this time, reducing the amount of air blown from the air chamber 6 reduces the amount of oxygen in the fluidized bed 2, and the amount of unburned gas increases accordingly. However, since the air is blown into the upper space above the fluidized bed 2, such as the freeboard section 9, using the air nozzle 8 and/or the secondary air inlet, this unburned gas is combusted.

In this case, an amount of primary air equal to the amount of the decrease in primary air may be supplied from the air nozzle 8 as primary air _C2 .

FIG. 11 shows the pressure P in the furnace, i.e., the pressure detection sensors 14-
Fig. 2 shows the results of measurements in which the amount of primary air _C1 supplied from the air chamber 6 was controlled by the output of the ignition coil 2, thereby controlling the combustion amount. Fig. 2(A) shows the fluctuations in the amount of primary air _C1 [ ^Nm3 / ^m2 ·H], Fig. 2(B) shows the fluctuations in the furnace pressure P [mmaq], and Fig. 2(C) shows the fluctuations in the oxygen concentration E [%] in the exhaust gas. The horizontal axis is time t (1 division represents 17 seconds).
Shows.

As shown in the figure, the pressure inside the furnace P causes the air chamber 6
By controlling the amount of primary air _C1 supplied from the exhaust gas, the change in the oxygen concentration E in the exhaust gas becomes extremely gradual. In other words, it can be confirmed that combustion becomes gentle (the combustion speed becomes slower) and becomes stable.

Fig. 12 is a schematic diagram of a fluidized bed incinerator in which the combustion rate of materials in the incinerator is controlled by detecting the oxygen concentration in the exhaust gas. In this figure, parts with the same reference numerals as in Fig. 2 indicate the same or corresponding parts. As shown in the figure, an oxygen concentration detection sensor 14- for detecting the oxygen concentration in the exhaust gas is provided at the exhaust gas outlet.
3, and the output of the oxygen concentration detection sensor 14-3 is adjusted by a regulator
I'm entering 13.

By configuring the combustion amount control as described above, when the amount of material A to be incinerated is greater than normal, as can be seen in Figure 1, the amount of material A burned (per unit time) increases, increasing the amount of exhaust gas generated.
The oxygen concentration in the exhaust gas decreases, and the oxygen concentration detection sensor 14
When the oxygen concentration decreases, the regulator 13 opens the control valve 7 to allow air to flow from the air nozzle 8 to the fluidized bed 2.
This increases the amount of air blown into the upper space of the incineration chamber 6. This reduces the amount of air sent from the air chamber 6, slowing down the flow of the fluidized bed 2 fluidizing material, reducing the amount of heat transferred from the fluidized bed to the incineration material A, and slowing down the gasification rate of the incineration material A. In other words, the combustion rate slows down.
By reducing the amount of air blown in from the air chamber 6, the amount of oxygen in the fluidized bed 2 decreases, and the amount of unburned gas increases accordingly. However, since air is blown into the upper space of the fluidized bed 2, such as the freeboard section 9, using the air nozzle 8 or the secondary air inlet or both, this unburned gas is combusted.

In this case, the amount of primary air _C1 is reduced by the amount of air flowing through the air nozzle 8.
The primary air amount _C2 may be supplied from the

Fig. 13 is a schematic diagram of a fluidized bed incinerator in which the amount of material burned in the incineration furnace is controlled by detecting the temperature inside the furnace. In this figure, parts with the same reference numerals as in Fig. 2 indicate the same or corresponding parts. As shown in the figure, a temperature detection sensor 14-4 is provided above the fluidized bed 2 to detect the temperature of the furnace 1, and the output of the temperature detection sensor 14-4 is input to a regulator 13.

By configuring the combustion amount control as described above, when the amount of material A to be incinerated is larger than normal, the combustion amount (per unit time) of material A to be incinerated increases, so the temperature inside the furnace rises and the output of the temperature detection sensor 14-4 increases. When the temperature inside the furnace increases, the regulator 13 opens the control valve 7, and the air nozzle 8
Therefore, the amount of air blown into the upper space of the fluidized bed 2 is increased.
As a result, the amount of air sent from the air chamber 6 decreases, the fluidization of the fluidized bed 2 slows down, the amount of heat transferred from the fluidized bed to the incineration material A decreases, and the amount of heat transferred from the fluidized bed to the incineration material A decreases.
The gasification rate of the fuel is reduced, i.e. the combustion rate is slowed down.
At this time, by reducing the amount of air blown in from the air chamber 6, the amount of oxygen in the fluidized bed 2 decreases, and the amount of unburned gas increases accordingly. However, by using the air nozzle 8 and/or the secondary air inlet, the amount of unburned gas in the fluidized bed 2 in the freeboard section 9, etc. can be reduced.
Air is blown into the upper space of the furnace, causing this unburned gas to burn.

In this case, the amount of primary air _C1 is reduced by the amount of air flowing through the air nozzle 8.
The primary air amount _C2 may be supplied from the

In the above embodiment, the amount of combustion of the material in the furnace 1 is detected and controlled using the brightness detection sensor 14-1, pressure detection sensor 14-2, oxygen concentration detection sensor 14-3 and temperature detection sensor 14-4, but there is also a control method using brightness detection means such as the brightness detection sensor 14-1 shown in Figure 14(A).
In this method, the brightness signal is multiplied by a coefficient k (0 to 2.0) using a calculator _Y01 to which the output value _PV01 of ₁ is assigned the symbol a, and the opening of the control valve 7 is adjusted using an output signal y01 proportional to the brightness.

In this case, there is no problem if municipal waste and other incinerated materials are continuously fed into the furnace, but due to the nature of municipal waste, the so-called "big drop" caused by sticking can cause sudden combustion, generating smoke and other substances, and even though combustion is vigorous, the inside of the furnace can become dark, causing the brightness detection sensor 14-1 to output an erroneous signal indicating that combustion is sluggish, which can cause malfunctions in the opening adjustment of the control valve 7.

To solve the above problem, since the pressure inside the furnace tends to rise when combustion becomes active, there is a control method that combines brightness detection means such as brightness detection sensor 14-1 and furnace pressure detection means such as pressure detection sensor 14-2 as shown in Figure 14 (B).

This is because when the output signal value _PV02 of the pressure detection sensor 14-2 corresponding to the furnace pressure becomes equal to or greater than a certain set value, a calculator _Y02 with a symbol b calculates an output signal value _y02 such that the opening of the control valve 7, which has been at its minimum opening until now, is opened to a certain opening.
Since the pressure inside the furnace is normally controlled, it immediately drops below the set value.
If the output signal value _PV02 of -2 drops and remains below a certain set value for a predetermined time, an output signal value _y02 of the minimum opening is output to the control valve 7. The output signal values _y01 and _y02 are compared by a calculator _Y03 marked with the symbol c, which outputs the larger signal value as the output signal value _y03 , and the opening of the control valve 7 is adjusted according to the output signal value _y03 .

By carrying out the above control, smoke and other issues are generated,
Even if the inside of the furnace becomes dark, the control valve 7 remains open at a constant opening and operates effectively, providing a desirable combustion control method. The calculator marked with the symbol a may use a regulator to control the brightness inside the furnace to be constant. Furthermore, the control valve 7 may be provided with a flow regulator to control the bypass flow rate in addition to adjusting the opening.

Similarly, the combination is not limited to the above, as long as a control system that can adequately follow rapid changes in the combustion amount can be constructed by combining any of the factors that change with fluctuations in the combustion amount, such as brightness, furnace pressure, oxygen concentration in the exhaust gas, furnace temperature, etc. In short, more desirable control can be achieved by constantly monitoring the outputs of sensors that detect brightness, furnace pressure, oxygen concentration in the exhaust gas, furnace temperature, etc., ignoring the output values of sensors whose outputs do not correspond to the furnace conditions, and controlling using the outputs of sensors that are operating normally.

Fig. 15 is a diagram showing the schematic configuration of another fluidized bed incinerator for implementing the combustion control method in a fluidized bed incinerator according to the present invention. In the figure, 21 is a furnace, inside which a fluidized bed 22 is formed, and below the fluidized bed 22, a plurality of air chambers 28, 26 are provided, and fluidizing air is sent from a fluidizing blower (not shown) through piping 25 into the furnace 21 via the air chambers 28, 26 to fluidize the fluidized medium. 31 is an incineration material charging hopper into which materials for incineration such as municipal waste are charged, and the incineration material charging hopper 31
A supply feeder 32 is provided at the bottom of the furnace 21 to supply the incineration material into the furnace 21, and a material input amount measuring device 33 is provided at the tip of the supply feeder 32 to detect the amount of incineration material A input from the supply feeder 32 into the furnace 21. 39 is an air volume adjusting device. Air nozzles 38 are provided on the furnace wall of the furnace 21 to blow air into the space above the fluidized bed 22,
An on-off valve 35 is connected to the air nozzle 38 via a pipe 34. An on-off valve 36 is connected to the central air chamber 28 via a pipe 27. Also, in the figure, 37 is a minimum flow valve that sends in the minimum amount of air.

In the figure, 29 is the freeboard section, 30 is the exhaust gas cooling section,
23 and 24 are outlets for non-combustible materials.

In the fluidized bed incinerator having the above-mentioned configuration, the incineration material A fed into the furnace 21 from the feeder 32 is usually dropped into a certain part of the fluidized bed 22, i.e., the center part. In this case, although not shown, a spreader is used to spread the incineration material A.
The amount of incineration material input can be measured by the incineration material input measuring device 33.
If the amount or volume of the incineration material A fed into the furnace 21 is greater than normal or is deemed to be highly combustible in nature, the air volume regulator 39 immediately closes the on-off valve 36 and opens the on-off valve 35. As a result, the amount of air sent to the air chamber 28 in the center becomes the amount of air sent through the minimum flow valve 37, i.e., the minimum amount of air that prevents a portion of the fluidized medium from leaking to the bottom of the furnace, and the flow of the fluidized medium in this part of the fluidized bed 22 becomes slow. At the same time, air is sent from the air nozzle 38 to the fluidized bed 22
Air is blown into the upper space of the bed 22. Furthermore, the material A measured by the material input measuring device 33 falls into the center of the fluidized bed 22, where the fluidized bed material flow has slowed. This slows the flow of the fluidized bed material A at the point where the material A falls, slowing the gasification (i.e., combustion) rate of the material A and preventing a sudden increase in exhaust gas. Furthermore, by reducing the amount of air fed into the fluidized bed 22, the oxygen concentration _O2 in the fluidized bed 22 decreases slightly, resulting in an increase in unburned gas. However, since air is blown into the upper space of the fluidized bed 22, such as the freeboard section 29, using the air nozzle 38 and/or secondary air inlet, this increased unburned gas is combusted.

In this case, the amount of primary air _C1 is reduced by the amount of air flowing through the air nozzle 8.
It may be supplied as primary air _C2 from

FIG. 16 shows the fluctuations in the exhaust gas volume B, the primary air volume C, the secondary air volume D, and the oxygen concentration E in the exhaust gas with respect to the time fluctuations in the input amount of incineration material A by the conventional combustion control method in the fluidized bed incinerator of the construction shown in FIG. 15. FIG. 17 shows the fluctuations in the exhaust gas volume B, the primary air volume (C ₁ , C ₂ ), and the secondary air volume D with respect to the time fluctuations in the input amount of incineration material A by the combustion control method according to the present invention.
10 is a graph showing the fluctuation of the oxygen concentration E in the exhaust gas.

According to the conventional combustion control method, when the incineration material A is input at time _t1 , combustion starts immediately, and the oxygen concentration E in the exhaust gas
In response to this decrease in the oxygen concentration E in the exhaust gas, the amount of secondary air D increases and the amount of exhaust gas B also increases.
As combustion progresses, the amount of unburned material in the furnace 21 decreases, and the oxygen concentration E in the exhaust gas increases, so the amount of secondary air D is reduced and the amount of exhaust gas B decreases. When material A is added to the furnace at time _t2 , the same operation as above is repeated. That is, the amount of secondary air D, the amount of exhaust gas B, and the oxygen concentration E in the exhaust gas change according to the material A.
This causes a large fluctuation in the oxygen concentration E in the exhaust gas, resulting in the emission of unburned gas when the oxygen concentration E in the exhaust gas is low.

In contrast, when the combustion control method of the present invention is used, the on-off valve is opened at the same time as the incineration material A is input at each time t ₁ , t ₂ , . . .
36 is closed, and the on-off valve 35 is opened, and the primary air is sent in fixed amounts above and below the fluidized bed 22 (the primary air amount _C2 blown in from the air nozzle 38, and the primary air amount _C1 blown in from the air chamber 28), and the secondary air amount D is controlled by feedback control based on the oxygen concentration E in the exhaust gas. Therefore, when the material A to be incinerated is added at time _t1 , the primary air amount _C1 from the lower part of the fluidized bed 22 where the material A has fallen decreases, and the flow of the fluidized medium becomes slower,
The amount of heat transfer from the bed material to the incineration material A is reduced, suppressing gasification of the incineration material A, i.e., combustion, and slowing the combustion rate. Furthermore, because the combustion rate is slow, there is no sudden drop in the oxygen concentration E in the exhaust gas. Although a slight drop occurs, the oxygen concentration E in the exhaust gas hardly fluctuates because the secondary air flow rate D is controlled and the oxygen concentration E in the exhaust gas is controlled. After a certain time has passed, the injection of the primary air flow rate _C2 from the air nozzle 38 is stopped, and the same primary air flow rate _C2 is injected from below the fluidized bed 22. This activates fluidization in the center of the fluidized bed 22, and normal operation is restored. At this point, the volatile matter in the hearth has already been burned, so combustion is gentle, and a stable furnace environment is achieved without sudden fluctuations in the oxygen concentration or the exhaust gas flow rate B.

In the fluidized bed of the construction shown in Fig. 15, for example, a control valve may be connected to the pipe 25, and when the amount of material A to be incinerated fed into the furnace 21 is equal to or greater than a predetermined amount, the on-off valve 36 may be closed and the control valve may be throttled at the same time, reducing the amount of primary air _C1 sent through the air chamber 26 and increasing the amount of air blown into the upper space of the fluidized bed 22 from the air nozzle 38. A combustion control method similar to the combustion control of the present invention in the fluidized bed incinerator of Fig. 1 may also be used in combination. Furthermore, in this case,
An amount of primary air _C2 equal to the amount of reduction in the amount of primary air _C1 may be supplied from the air nozzle 8. The schematic configuration of the fluidized bed incinerator for carrying out the above control method is not limited to that shown in FIG.

In the above examples, the combustion control method was explained using a fluidized bed incinerator. However, this fluidized bed incinerator may of course be a so-called fluidized bed boiler for the purpose of heat recovery, and therefore the fluidized bed incinerator of the present invention includes a fluidized bed boiler.

As explained above, the combustion control method for a fluidized bed incinerator according to the present invention maintains the amount of combustion air and the amount of exhaust gas at a substantially constant level even when coal, municipal waste, industrial waste, or a mixture of these combustible materials, which have different calorific values, flammability, shapes, and volumes, are fed into the fluidized bed furnace as incineration materials, and the oxygen concentration in the exhaust gas can also be maintained at a substantially constant level. Therefore, in incineration facilities for municipal waste and the like that use a fluidized bed incinerator, the peripheral equipment of the fluidized bed incinerator, such as primary and secondary air blowers and exhaust gas treatment equipment, can be made compact, reducing construction costs, and it is possible to minimize the release of unburned gas into the atmosphere, which is also effective in preventing air pollution.

As described above, the combustion control method for a fluidized bed incinerator according to the present invention can minimize fluctuations in the oxygen concentration in the exhaust gas and the amount of exhaust gas even if the amount of combustion input to the fluidized bed incinerator fluctuates, and can prevent the emission of unburned gas, so it is effective as a combustion control method for incineration facilities equipped with a fluidized bed incinerator.
When the combustion target is municipal waste, industrial waste, or a mixture of these, the method can easily achieve particularly remarkably stable combustion control, and is suitable as a combustion control method for municipal waste incineration facilities equipped with fluidized bed incinerators.

───────────────────────────────────────────────────────── Continued from the front page (51) Int.Cl. ⁵ Identification symbol Internal reference number FI Technical marking location F23G 5/50 P 8409-3K Q 8409-3K

Claims (15)

[Claims] [Claim 1] A combustion control method for a fluidized bed incinerator, which fluidizes a fluidized medium with air sent from the lower part of the fluidized bed and burns materials fed into the incineration furnace, comprising: a combustion amount detection means for detecting the combustion amount in the entire incineration furnace, including the inside of the fluidized bed and the upper part of the fluidized bed; and a control means for controlling the combustion amount based on the combustion amount detected by the combustion amount detection means, wherein when the detected combustion amount is equal to or greater than a predetermined amount, the control means reduces the amount of air sent from the lower part of the fluidized bed and increases the amount of air blown into the space above the fluidized bed; and when the combustion amount falls below the predetermined amount, the control means restores the amount of air sent from the lower part of the fluidized bed and reduces the amount of air blown into the space above the fluidized bed, thereby maintaining and controlling the combustion amount at the predetermined amount. However, the combustion amount is defined as the calorific value per weight of material to be incinerated [kcal
al/kg × amount of material incinerated (kg/hour). [Claim 2] A combustion control method for a fluidized bed incinerator as described in claim 1, characterized in that when the combustion amount is equal to or greater than a predetermined amount, the amount of air blown into the space above the fluidized bed is equal to the decrease in the amount of air sent from the lower part of the fluidized bed, and when the combustion amount is equal to or less than the predetermined amount, the decrease in the amount of air blown into the space above the fluidized bed is equal to the increase in the amount of air sent from the lower part of the fluidized bed. 3. The fluidized bed incinerator has a fluidization ratio of 1 to 4.
3. The method for controlling combustion in a fluidized bed incinerator according to claim 1, wherein the fluidized bed incinerator is operated at a superficial velocity in the range of 1. [Claim 4] A combustion control method in a fluidized bed incinerator as described in any one of claims 1 to 3, characterized in that the combustion amount detection means is a brightness detection means that detects the brightness within the freeboard section above the fluidized bed, and the control means controls the combustion amount based on the output of the brightness detection means. 5. A method for controlling combustion in a fluidized bed incinerator according to claim 4, wherein the brightness detection means of the combustion amount detection means is provided above the secondary air blowing position in the freeboard section above the fluidized bed. [Claim 6] A method for controlling combustion in a fluidized bed incinerator, which fluidizes a fluidized medium with air sent from the lower part of the fluidized bed and burns materials fed into the incineration furnace, comprising: a detection means for detecting the amount or volume of materials fed into the incineration furnace, including the fluidized bed and the upper part of the fluidized bed, and a control means for controlling the amount of combustion based on the amount or volume of materials detected by said detection means, wherein said control means, when the amount or volume of materials to be incinerated is equal to or greater than a predetermined amount, reduces the amount of air sent from the lower part of the fluidized bed and increases the amount of air blown into the space above the fluidized bed, and when the amount or volume of materials to be incinerated falls below the predetermined amount, restores the amount of air sent from the lower part of the fluidized bed and reduces the amount of air blown into the space above the fluidized bed, thereby maintaining and controlling the amount of combustion at a predetermined amount. However, said amount of combustion is defined as the calorific value per weight of materials to be incinerated [kc
al/kg × amount of material incinerated (kg/hour). [Claim 7] A combustion control method for a fluidized bed incinerator, which fluidizes a fluidized medium with air sent from the lower part of the fluidized bed and burns materials fed into the incinerator, comprising: a temperature detection means for detecting the temperature inside the incinerator above the fluidized bed; and a control means for controlling the amount of combustion based on the temperature detected by said temperature detection means, wherein said control means, when the temperature inside the incinerator above the fluidized bed is equal to or higher than a predetermined value, reduces the amount of air sent from the lower part of the fluidized bed and increases the amount of air blown into the air above the fluidized bed; and, when the temperature falls below said predetermined value, restores the amount of air sent from the lower part of the fluidized bed and decreases the amount of air blown into the space above the fluidized bed, thereby maintaining and controlling the amount of combustion at a predetermined amount. However, said amount of combustion is defined as the calorific value per weight of material to be incinerated [kc
al/kg × amount of material incinerated (kg/hour). [Claim 8] A combustion control method for a fluidized bed incinerator in which a fluidized bed material is fluidized by air sent from the bottom of the fluidized bed and materials to be incinerated are burned in the incinerator, the method comprising: oxygen concentration detection means for detecting the oxygen concentration in the exhaust gas; and control means for controlling the amount of combustion based on the oxygen concentration detected by the oxygen concentration detection means, wherein when the oxygen concentration in the exhaust gas is equal to or higher than a predetermined value, the control means:
A combustion control method for a fluidized bed incinerator, characterized in that the amount of air sent from the lower part of the fluidized bed is reduced and the amount of air blown into the space above the fluidized bed is increased, and when the oxygen concentration falls below the predetermined value, the amount of air sent from the lower part of the fluidized bed is restored and the amount of air blown into the space above the fluidized bed is reduced, thereby maintaining and controlling the amount of combustion at a predetermined amount. However, the amount of combustion is defined as the calorific value per weight of the incinerated material [kc
al/kg × amount of material incinerated (kg/hour). [Claim 9] A combustion control method for a fluidized bed incinerator in which a fluidized medium is fluidized by air sent from the lower part of the fluidized bed and materials to be incinerated are combusted, comprising a pressure detection means for detecting the pressure inside the incinerator, and a control means for controlling the amount of combustion based on the pressure inside the incinerator detected by said pressure detection means, wherein said control means, when the pressure inside the incinerator is equal to or higher than a predetermined value, reduces the amount of air sent from the lower part of the fluidized bed and increases the amount of air blown into the space above the fluidized bed, and when the pressure falls below said predetermined value, restores the amount of air sent from the lower part of the fluidized bed and reduces the amount of air blown into the space above the fluidized bed, thereby maintaining and controlling the amount of combustion at a predetermined amount. However, said amount of combustion is defined as the calorific value per weight of materials to be incinerated [kc
al/kg × amount of material incinerated (kg/hour). [Claim 10] A method for controlling combustion in a fluidized bed incinerator, which fluidizes a fluidized medium with air sent from the lower part of the fluidized bed and burns materials fed into the incineration furnace, comprising a control means for controlling the amount of combustion based on the properties of the materials fed into the entire incineration furnace, including the fluidized bed and the upper part of the fluidized bed, wherein when the amount of combustion exceeds a predetermined amount based on the properties of the materials, the control means reduces the amount of air sent from the lower part of the fluidized bed and increases the amount of air blown into the space above the fluidized bed, and when the amount of combustion falls below the predetermined amount, restores the amount of air sent from the lower part of the fluidized bed and reduces the amount of air blown into the space above the fluidized bed, thereby maintaining and controlling the amount of combustion at the predetermined amount. However, the amount of combustion is defined as the calorific value per weight of material to be incinerated [kc
al/kg × amount of material incinerated (kg/hour). 11. A method for controlling combustion in a fluidized bed incinerator in which material fed into the incinerator is fluidized by air fed from the lower part of the fluidized bed, and material fed into the incinerator is combusted, comprising: first means for outputting a signal reflecting the amount of combustion from the output of a brightness detection means for detecting the brightness in the freeboard above the fluidized bed; second means for outputting a signal reflecting the amount of combustion from the output of an internal pressure detection means for detecting the pressure inside the incinerator; and control means for controlling the amount of combustion by giving priority to the larger of the output signals from the first and second means, wherein the control means reduces the amount of air fed from the lower part of the fluidized bed and increases the amount of air blown into the space above the fluidized bed when the prioritized output signal is equal to or greater than a predetermined value; and when the output signal falls below the predetermined value, restores the amount of air fed from the lower part of the fluidized bed and reduces the amount of air blown into the space above the fluidized bed, thereby maintaining and controlling the amount of combustion at a predetermined level. The combustion amount is defined as the calorific value per weight of material to be incinerated [kcal].
al/kg × amount of material incinerated (kg/hour). [Claim 12] A combustion control method in a fluidized bed incinerator as described in any one of claims 1 to 11, characterized in that the fluidized bed incinerator is provided with a plurality of air chambers below the fluidized bed and is configured to send air through said air chambers. [Claim 13] A combustion control method for a fluidized bed incinerator as described in any one of claims 1 to 12, characterized in that the materials to be incinerated have different calorific values or different properties, shapes, and volumes. 14. A method for controlling combustion in a fluidized bed incinerator according to any one of claims 1 to 13, wherein the input combustion material is coal, industrial waste, municipal waste or a mixture thereof. 15. A method for controlling combustion in a fluidized bed incinerator according to any one of claims 1 to 14, wherein the fluidized bed incinerator is a fluidized bed boiler.