JPH0830569B2 - Combustion furnace combustion control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is a mixing method in which unburned gas and secondary air for combustion are mixed and stirred in an empty cylinder portion in order to satisfactorily burn municipal waste or industrial waste. The present invention relates to a combustion control method for a combustion furnace having a stirring area.

[Problems to be Solved by Prior Art and Invention]

In general, the characteristics of municipal waste and various industrial wastes are significantly different, so it is difficult to realize a duster that keeps the amount of supply to the furnace constant, and furthermore, the quality of these municipal wastes and various industrial wastes varies. Since there are many, the fluctuations in the quality and quantity of these incinerators charged into the furnace appear as fluctuations in the exhaust gas. That is, when the combustion furnace is operated with a constant amount of combustion air, oxygen shortage or excess oxygen occurs. When the oxygen is insufficient, unburned gas is discharged, and when the oxygen is excessive, excess combustion air enters, so that the combustion gas is cooled, and unburned gas that is not completely burned is discharged. Therefore, in the combustion furnace, it is common to control the amount of combustion air by measuring the oxygen concentration in the exhaust gas so as to prevent excess or deficiency of oxygen.

On the other hand, the shape of the hollow part of the furnace was devised so that the supplied combustion air could effectively contact the unburned gas, and the blowing air velocity of the combustion air was changed so that the combustion air and the unburned gas were mixed effectively. There are also some.

However, in the above-mentioned conventional method, if the amount of combustion air is changed and controlled, the blowing air velocity changes, so there is a problem that the shape of the furnace and the blowing air velocity do not match except at the design point.

The present invention has been made in view of the above points, and by guiding a part of the exhaust gas into the furnace, the unburned gas in the furnace and the secondary air for combustion are mixed and stirred even if the combustion state changes. Combustion control of a combustion furnace that keeps the flow rate of the mixed gas supplied to the mixing and stirring area within a predetermined range, activates the combustion reaction in the upper part of the hollow section when combustion is vigorous, and maintains the furnace top temperature within an appropriate range. To provide a method.

[Means for solving the problem]

In order to solve the above problems, the present invention provides an empty cylinder part directly above a hearth and a lower region of the empty cylinder part is a mixing and stirring region for mixing and stirring unburned gas and secondary air for combustion. In a combustion control method for a combustion furnace in which combustion control is performed by changing the amount of combustion air sent into the furnace of the combustion furnace, in the mixing and stirring area in the lower area of the hollow cylinder, the cross-sectional area of the mixing and stirring area is smaller than that of the hearth surface. It is characterized in that a part of the exhaust gas is blown into the mixing and stirring area in accordance with a change in the combustion air amount so that the flow rate of the mixed gas supplied to the mixing and stirring area is maintained within a predetermined range.

Further, in the combustion control method for the combustion furnace, when a part of the exhaust gas is blown into the upper portion of the empty cylinder portion and the amount of the exhaust gas blown into the mixing and stirring region is increased or decreased, the flow rate of the exhaust gas blown into the upper portion of the empty cylinder portion is increased or decreased by the increase or decrease. It is characterized in that the circulation flow rate of the exhaust gas sent from the exhaust gas into the furnace is maintained within a predetermined range.

Further, in the combustion control method for the combustion furnace, the furnace top temperature is monitored, and the exhaust gas flow rate blown into the upper part of the hollow cylinder is controlled,
A combustion control method for a combustion furnace, characterized in that the furnace top is maintained at 750 ° C to 950 ° C.

Also, in any one of the combustion control method of the combustion furnace, a part of the exhaust gas is mixed with secondary air blown horizontally or downward into the mixing and stirring area that is a throttle portion and mixed with secondary air. It is characterized by letting it blow.

In any one of the combustion control methods for the combustion furnace, a part of the exhaust gas is blown horizontally or downward into a mixing and stirring area that is a throttle to generate a swirling flow in the mixing and stirring area. It is characterized by being mixed with air and then blown.

[Action]

As described above, a part of the exhaust gas is blown into the mixing and stirring area where the cross-sectional area is a narrowed portion smaller than the hearth surface in accordance with the change in the combustion air amount, so that it is supplied into the combustion chamber, particularly in the mixing and stirring area. Since the flow rate of the mixed gas is maintained within a predetermined range, the unburned gas is agitated with a constant stirring force regardless of the amount of combustion air, so that the unburned gas and the combustion air are in good contact with each other. The unburned gas burns efficiently, and the discharge of the unburned gas is suppressed as much as possible.

Further, when the combustion in the furnace becomes vigorous, the secondary air for combustion blown into the mixing and stirring area increases, and the amount of exhaust gas blown into the mixing and stirring area decreases, the reduced amount is blown into the upper part of the hollow cylinder portion. The combustion reaction at the top can be activated. Further, when the combustion is vigorous as described above, the furnace top temperature also tends to rise, and an increase in circulating exhaust gas also has a cooling effect, that is, an effect of always maintaining the furnace top temperature within an appropriate range.

Further, since the furnace top temperature is monitored and the amount of exhaust gas blown into the upper part of the hollow cylinder is controlled to maintain the furnace top temperature at 750 ° C to 950 ° C, the furnace top temperature is always in an appropriate range.

Further, since a part of the exhaust gas is blown horizontally or downward into the throttle portion just above the hearth or horizontally or downward and mixed with the secondary air which causes a swirling flow in the throttle portion, the unburned gas is not burned. Even if the flow velocity rising vertically increases, the agitation is efficiently performed, and the discharge of unburned gas is further suppressed.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a system configuration when a combustion control method according to the present invention is applied to a fluidized bed combustion furnace apparatus. In the figure, 11 is a fluidized bed, an upper portion of the fluidized bed 11 is a combustion chamber 13, and a narrowed portion 12 having a small cross section is formed immediately above the combustion chamber 13. The furnace wall of the throttle 12 is provided with a secondary air supply port 14 for blowing secondary air for combustion downward. A tertiary air supply port 15 for supplying tertiary air or exhaust gas to the upper part of the throttle part 12, that is, the furnace wall of the upper part 28 of the hollow cylinder part.
Is provided. An air chamber 16 is provided below the fluidized bed 11, and a pipe for sending the primary air from the primary fan 17 is connected to the air chamber 16, and the primary air is sent from the primary fan 17 to the air chamber 16. Thereby, the fluidized medium of the fluidized bed 11 is fluidized. Combustibles such as municipal solid waste or various industrial wastes, which have been injected into the furnace from a fuel supply port (not shown), are burned in the fluidized bed 11 and the generated gas passes through the mixing and stirring area
It is discharged from the upper part 28 of the hollow cylinder portion, passes through the exhaust gas cooling device 19 and the exhaust gas processing device 20, is sucked by the induction fan 21, and is discharged from the chimney 22.

24 is an oxygen concentration controller that measures the oxygen concentration in the exhaust gas from the output of the oxygen concentration sensor 23, and controls this oxygen concentration to a predetermined value.The output value of the oxygen concentration controller 24 is the secondary air for combustion. The flow rate adjusting valve 27 is operated to perform a comparison calculation with the output of a flow rate sensor 26 which detects the secondary air for combustion sent to the throttle portion 12 as a set value of the flow rate controller 25, and the secondary air flow rate for combustion is adjusted.

29 is a mixed gas flow rate setting device that sets the total flow rate of the mixed gas of combustion secondary air and exhaust gas, and 30 is the output of the mixed gas flow rate setting device 29 and the output of the flow rate sensor 26 or the mixed gas flow rate setting device 29. Output and the secondary air controller for combustion 25 (not shown)
Is an exhaust gas flow rate calculator that calculates the amount of exhaust gas blown into the throttle portion 12 from the set value and converts the amount of exhaust gas into a damper opening, and the exhaust gas flow rate calculator 30 operates the flow rate adjusting valve 31 to reduce the throttle portion. Adjust the amount of exhaust gas blown into 12.

40 is a circulation exhaust gas flow rate setting device for setting the circulation exhaust gas flow rate, 32 is an exhaust gas flow rate for calculating the exhaust gas flow rate blown into the upper part 28 of the hollow cylinder portion from the output of the circulation exhaust gas flow rate setting device 40 and the output of the exhaust gas amount calculator 30. It is an arithmetic unit.

35 is a furnace top temperature controller that measures the furnace top temperature from the output of the temperature sensor 34 that detects the furnace top temperature, and outputs an output that keeps the furnace top temperature at 750 ° C to 950 ° C, and 33 is the furnace top temperature adjustment A low selector that selects either the output of the total 35 or the output of the exhaust gas flow rate calculator 32, which is the lower one, and the low selector 33 operates the flow rate adjustment valve 39 to adjust the exhaust gas flow rate blown into the upper part 28 of the hollow cylinder portion. To do. 36 is a cyclone and 37 is an exhaust gas circulation fan.

In addition, 41 is a primary air flow rate controller that indicates the primary air flow rate blown into the lower part of the fluidized bed 11 or into the lower part and the immediately upper part (not shown), and measures the primary air flow rate from the output of the flow rate sensor 42, Operate the adjusting valve 43 to adjust the primary air flow rate to the set value. In the fluidized bed combustion furnace device of the above system configuration, the oxygen concentration controller 24 performs a comparative calculation of the detected value and the set value of the oxygen concentration of the exhaust gas, and outputs the value to the set value of the secondary air controller for combustion 25. . The combustion secondary air controller 25 calculates the excess or deficiency of the combustion secondary air from the output of the flow rate sensor 26 and the output of the oxygen concentration controller 24, operates the flow rate adjusting valve 27, and causes the throttle unit 12 to operate. Adjust the secondary air for combustion to be blown. That is, when the secondary air for combustion is insufficient, the flow rate adjusting valve 27 is loosened to increase the shortage, and when it is excessive, the flow rate adjusting valve 27 is throttled to reduce the excess amount.

The exhaust gas flow rate calculator 30 is either the output of the flow rate sensor 26 and the output of the mixed gas flow rate setter 29, or the mixed gas flow rate setter.
29 output and setting value of secondary air controller 25 for combustion, or throttle
The flow rate of exhaust gas blown into 12 is calculated, and the flow rate adjusting valve 31 is operated to adjust the amount of exhaust gas blown into the throttle 12. That is, when the secondary air for combustion increases, the flow rate adjustment valve 31
When the combustion secondary air decreases, the flow rate adjusting valve 31 is loosened to increase the exhaust gas flow rate by the decrease amount. As a result, the gas flow rate passing through the throttle portion 12 is always the flow rate set by the mixed gas flow rate setter 29.

The exhaust gas flow rate calculator 32 calculates the shortage of the exhaust gas flow rate to be circulated from the output of the exhaust gas flow rate calculator 30, that is, the exhaust gas flow rate blown into the throttle unit 12 and the output of the circulating exhaust gas flow rate setting device 40, via the low selector 33. The flow rate adjusting valve 39 is operated to adjust the flow rate of the exhaust gas blown into the upper portion 28 of the hollow cylinder portion.
That is, when the amount of exhaust gas sent to the throttle portion 12 through the flow rate adjusting valve 31 is decreased, the flow rate adjusting valve 39 is loosened to increase the amount of exhaust gas corresponding to the decrease and sent to the upper part 28 of the hollow cylinder portion. When the amount of exhaust gas sent to the throttle unit 12 increases, the flow control valve 39 is throttled to reduce the amount of exhaust gas corresponding to this increase. As a result, the amount of circulating exhaust gas is controlled to the exhaust gas circulation flow rate set by the circulation exhaust gas flow rate setting device 40. In addition, the low selector 33 is provided with the output of the furnace top temperature controller 35 and the exhaust gas flow rate calculator 32.
The lower one of the outputs is selected, and the flow rate adjusting valve 39 is operated according to the selected output. This allows
For example, when the exhaust gas flow rate sent to the upper part 28 of the hollow cylinder increases and the furnace top temperature falls below the lower limit of the appropriate range (750 ° C to 950 ° C), the circulating exhaust gas to the upper part 28 of the hollow cylinder is throttled to lower the temperature. Can be prevented.

By controlling as described above, for example, when the oxygen concentration in the exhaust gas rises, the flow control valve 27 is throttled to reduce the amount of secondary air. As a result, the exhaust gas flow rate calculator 30 loosens the flow rate adjusting valve 31 and increases the circulation amount of the exhaust gas by the decrease of the secondary air, regardless of the secondary air amount that fluctuates according to the change in oxygen concentration, Since the flow rate of the mixed gas of the secondary air and the exhaust gas supplied from the secondary air supply port 14 becomes substantially constant, the agitated state of the unburned gas in the throttle portion 12 depends on the secondary air amount (combustion air amount). It becomes almost constant regardless of fluctuations.

Since the flow velocity of the gas supplied from the secondary air supply port 14 is generally around 40 m / s when the exhaust gas amount is zero and only the secondary air is supplied,
When the exhaust gas oxygen concentration rises, the secondary air is throttled,
The gas flow rate from the secondary air supply port 14 may decrease in some cases. At this time, the unburned gas is agitated and mixed in the throttle portion 12, so that the unburned gas is discharged. When the secondary air is throttled in this way, the flow rate sensor 26 detects that the flow rate of the secondary air supplied to the throttle unit 12 decreases, and the exhaust gas flow rate calculator 31 is used to loosen the flow rate adjusting valve 31 to control the exhaust gas circulation flow rate. By increasing the amount, the amount of decrease in the secondary air amount is compensated. As a result, the flow rate of the mixed gas supplied to the throttle portion 12 becomes substantially constant, so that the combustion gas and the combustion air are constantly stirred with a constant stirring force, and the contact between the unburned gas and the combustion air becomes good. The emission of unburned gas is suppressed as much as possible. That is, even in a fluidized bed combustion furnace in which the oxygen concentration in the exhaust gas is measured and the amount of combustion air is controlled so that excess or deficiency of oxygen does not occur, unburned gas is not discharged as in the conventional case.

Further, since the mixed gas flow rate setting device 29 is provided and the secondary air for combustion is preferentially blown into the throttle portion 12,
It is also possible to prevent the oxygen concentration from becoming thin in the throttle portion 12 which is the mixing and stirring area of the combustion gas. When the combustion becomes vigorous and the amount of secondary air sent to the throttle portion 12 increases, the exhaust gas that is no longer needed is supplied to the upper part 28 of the hollow cylinder portion, so that the combustion reaction at the furnace top can be activated. Further, when the combustion is vigorous in this way, the furnace top temperature also tends to rise, and an increase in the flow rate of the exhaust gas sent to the upper part 28 of the hollow cylinder cools the furnace top and maintains the furnace top temperature in an appropriate range. Also plays. Also, the furnace top temperature is in the proper range (750 ° C to 950 ° C).
If the temperature falls below the lower limit of (.degree. C.), the flow rate of exhaust gas blown into the upper portion 28 of the hollow cylinder portion is reduced to prevent the temperature from dropping.

In the above embodiment, the secondary air blown from the secondary air supply port 14 or the mixed gas of the secondary air and the exhaust gas is blown downward to improve the stirring force, but the stirring force is slightly sacrificed. Of course, the secondary air supply port 14 may be provided so that the secondary air or the mixed gas of the secondary air and the exhaust gas is blown horizontally as shown in FIG.

In addition, the secondary air or the mixed gas of the secondary air and the exhaust gas blown downward or horizontally as described above forms a swirl flow in the throttle 12 as shown in FIG. 14 may be provided at a predetermined angle with respect to the tangential direction of the furnace wall in the cross section of the furnace, which further improves the stirring effect.

Further, in the above embodiment, the secondary air supply port 14 has two stages in the vertical direction of the furnace, but the present invention is not limited to this, and it may have one stage or a plurality of stages, and the plurality of stages are blown. The gas may be configured to form a swirl flow.

Further, in the above embodiment, the exhaust gas to be circulated was configured to be mixed with the secondary air and blown in, but the structure becomes complicated, but the exhaust gas to be circulated is supplied from the exhaust gas supply port provided separately from the secondary air supply port. Of course, it may be configured to supply.

Further, in the above-mentioned embodiment, the mixing and stirring area of the combustion gas is a narrowed portion having a small cross-sectional area, but the mixing and stirring area is not limited to this, and if the mixing and stirring can be effectively performed, the cross-sectional area is not always required. Does not have to be small.

Further, in the above embodiment, the combustion state in the furnace is detected by measuring the oxygen concentration of the exhaust gas with the oxygen concentration sensor 23 and the oxygen concentration controller 24, but the combustion state detection means in the furnace is The brightness and pressure in the furnace are not limited, and change according to the combustion state (for example, if the combustion is vigorous, the brightness and pressure are high, and if the combustion is not vigorous, these are low). The above control may be performed by detecting these and detecting the combustion state. Further, since the relationship between the combustion state in the furnace and the temperature also has a correlation, it is possible to detect the combustion state from the temperature in the furnace. However, in this case, there is a time delay, and this point is sacrificed to some extent.

Although the combustion control method of the present invention has been described by taking the combustion control of the fluidized bed combustion furnace as an example in the above embodiment, the combustion control method of the present invention is not limited to the combustion control of the fluidized bed combustion furnace. Of course.

FIG. 4 is a diagram showing a system configuration of a combustion furnace having a stoker type hearth to which the combustion control method of the present invention is applied.
In the figure, the parts designated by the same reference numerals as those in FIG. 1 indicate the same or corresponding parts and have the same functions. In the figure, 12 is a mixing and stirring area portion, and 28 is an upper hollow cylinder portion. Further, 51 is a feeder, 52 is a dry stoker, 53 is a combustion stoker, and 54 is a post-combustion stoker.

The operation of the combustion furnace system having the structure shown in FIG. 4 is substantially the same as the operation of the fluidized bed system having the structure shown in FIG.

〔The invention's effect〕

As described above, according to the invention described in claim (1), a part of the exhaust gas becomes a narrowed portion having a cross-sectional area smaller than the hearth surface in accordance with a change in the combustion air amount. By blowing into the mixing and stirring area, the gas flow rate in the mixing and stirring area is maintained within a predetermined range, so that the oxygen concentration in the exhaust gas is measured and the combustion air amount is controlled so that excess or deficiency of oxygen does not occur. Even in a combustion furnace, the combustion gas is agitated with a constant agitation force regardless of the amount of combustion air. Therefore, the unburned gas and the combustion air are in good contact with each other, and the discharge of the unburned gas is minimized. It can be suppressed.

Further, according to the invention as set forth in claim (2), when the secondary air for combustion sent to the mixing and stirring area increases, the exhaust gas that is no longer needed is supplied to the upper part of the empty cylinder portion, The combustion reaction at the furnace top can be activated.
Further, when the combustion is vigorous as described above, the furnace top temperature also tends to rise, and an increase in the flow rate of the exhaust gas fed into the upper part of the hollow cylinder portion can maintain the furnace top temperature in an appropriate range.

Further, according to the invention as set forth in claim (3), the furnace top temperature is monitored, the amount of exhaust gas blown into the upper part of the empty cylinder is controlled, and the furnace top temperature is maintained at 750 ° C to 950 ° C. From
The furnace top temperature can always be kept in an appropriate range.

Further, according to the invention as set forth in claim (4), a part of the exhaust gas is mixed with the secondary air blown horizontally or downward into the mixing and stirring area to be mixed with the secondary air blown therein. And then blown in, the effect of mixing and stirring in the mixing and stirring area is further improved.

According to the invention as set forth in claim (5), secondary air for blowing a part of the exhaust gas horizontally or downward into the mixing and stirring area to generate a swirling flow in the mixing and stirring area. The effect of mixing and stirring in the mixing and stirring area is further improved by mixing and blowing with.

[Brief description of drawings]

FIG. 1 is a diagram showing a system configuration of a fluidized bed combustion furnace apparatus to which a combustion control method according to the present invention is applied, FIG. 2 is a diagram showing the arrangement of other secondary air supply ports of the fluidized bed combustion furnace, and FIG. FIG. 4 is a diagram showing a gas flow in a narrowing portion of a fluidized bed combustion furnace, and FIG. 4 is a diagram showing a system configuration of a combustion furnace device having a stoker type hearth to which a combustion control method according to the present invention is applied. In the figure, 11 ... fluidized bed, 12 ... mixing and stirring area (lower hollow cylinder), 13 ... combustion chamber, 14 ... secondary air supply port, 15 ... secondary air supply port, 16 ... Air chamber, 17 ... Primary fan, 18 ...
… Secondary fan, 19 …… Exhaust gas cooling device, 20 …… Exhaust gas treatment device, 21 …… Induction fan, 22 …… Chimney, 23 …… Oxygen concentration sensor, 24 …… Oxygen concentration controller, 25 …… For combustion Secondary air controller, 26 ... Flow sensor, 27 ... Flow control valve,
28 …… Upper empty cylinder part, 29 …… Mixed gas flow rate setting device, 30 ……
Exhaust gas flow rate calculator, 31 …… Flow rate adjusting valve, 32 …… Exhaust gas flow rate calculator, 33 …… Low selector, 34 …… Temperature sensor, 35 …… Top temperature controller, 36 …… Cyclone, 37 ……
Exhaust gas recirculation fan, 39 …… Flow control valve, 40 …… Circulating exhaust gas flow setter, 51 …… Feeder, 52 …… Drying stoker, 53 …… Combustion stoker, 54 …… Post-combustion stoker.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keiichi Sato 11-1 Haneda-Asahi-cho, Ota-ku, Tokyo Inside the EBARA CORPORATION (56) Reference JP-A-53-90672 (JP, A) JP-A-62 -202925 (JP, A)

Claims (5)

[Claims] 1. A furnace of a combustion furnace in which an empty cylinder is provided immediately above a hearth and a lower region of the empty cylinder is a mixing and stirring area for mixing and stirring unburned gas and secondary air for combustion. In a combustion control method of a combustion furnace that performs combustion control by changing the amount of combustion air sent to, a mixing and stirring region in the lower region of the hollow cylinder part is a narrowed portion whose cross-sectional area is smaller than the hearth surface, By blowing a part of the exhaust gas into the mixing and stirring area according to the change in the combustion air amount, the flow rate of the mixed gas supplied to the mixing and stirring area is maintained within a predetermined range. Combustion control method. 2. The invention according to claim (1), wherein a part of the exhaust gas is blown into the upper part of the empty cylinder part, and when the amount of the exhaust gas blown into the mixing and stirring area is increased or decreased, the empty cylinder part A combustion control method for a combustion furnace, characterized in that the flow rate of exhaust gas blown into the upper part is increased / decreased to maintain the circulation flow rate of exhaust gas sent from the exhaust gas into the furnace within a predetermined range. 3. The invention according to claim (2), wherein the furnace top temperature is monitored and the flow rate of the exhaust gas blown into the upper part of the hollow cylinder part is controlled to bring the furnace top part to 750 ° C. to 950 ° C. A combustion control method for a combustion furnace characterized by maintaining the same. 4. The invention according to any one of claims (1) to (3), wherein a part of the exhaust gas is horizontally or lower in a mixing and stirring area which is the throttle portion. A combustion control method for a combustion furnace, comprising: mixing with secondary air blown in a direction and mixing with secondary air blown in; and blowing the mixture. 5. The invention according to any one of claims (1) to (4), wherein a part of the exhaust gas is horizontally or lower in a mixing / stirring region which is the throttle unit. A combustion control method for a combustion furnace, characterized in that the mixture is mixed with secondary air that blows in the opposite direction to generate a swirling flow in the mixing and stirring region, and then the mixture is blown.