JP2008209041A - Combustion control method for gasification melting system and its system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a combustion control method of a gasification melting system and the system capable of reducing generation of CO and performing a stable operation. <P>SOLUTION: In this combustion control method of the gasification melting system where wastes 40 supplied into a gasification furnace 3 through a refuse feeding machine 2 is thermally decomposed, ash is melted by combustion heat of a thermal decomposition gas in a melting furnace 6, and an unburned component in a combustion exhaust gas is burned in a secondary combustion chamber 12, conditions of furnace internal pressure are set in a plurality of stages in advance corresponding to abnormality levels as the conditions of the furnace internal pressure indicating abnormal combustion in the gasification furnace 3, the supply of combustion air supplied to at least one of the gasification furnace 3, the melting furnace 6 and the secondary combustion chamber 12 is controlled when the furnace internal pressure detected in the gasification furnace 3 reaches the first furnace internal pressure condition, and the feeding of refuse to the gasification furnace 3 is controlled in addition to the control of the supply of the combustion air when the furnace internal pressure reaches the second furnace internal pressure condition having the abnormal level higher than that of the first furnace internal pressure condition. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a gasification and melting system in which waste is pyrolyzed to generate pyrolysis gas, and ash is melted by the combustion heat of the pyrolysis gas. The present invention relates to a combustion control method for a gasification and melting system capable of performing the operation and the system.

Conventionally, a gasification and melting system is known as a technology capable of processing a wide range of wastes such as municipal waste, non-combustible waste, incineration residue, sludge, landfill waste, and the like.
An outline of the gasification melting system is shown in FIG. The gasification melting system is a gasification furnace 3 that thermally decomposes and gasifies waste, and a swirl that burns the pyrolysis gas generated in the gasification furnace 3 at a high temperature and converts the ash content in the gas into molten slag. A melting furnace 6, a secondary combustion chamber 12 in which the exhaust gas of the swirling melting furnace 6 is introduced and unburned in the exhaust gas is combusted, a temperature reducing tower 14, a dust removing device 15, a steam heater 16, and a catalytic reaction device And an exhaust gas treatment facility consisting of 17 etc. In order to reduce the amount of waste, reduce the volume, and make it harmless, slag is taken out from the swivel melting furnace 6 and reused as civil engineering materials such as roadbed materials, or from the high-temperature exhaust gas in the secondary combustion chamber 13 The company collects waste heat and generates electricity.

In such a system, the waste is quantitatively supplied into the furnace by a dust feeder 2 provided in the gasification furnace 3. As the dust feeder 2, for example, a screw feeder or the like is used, and a predetermined amount of waste is supplied by controlling the rotational speed of a motor that rotationally drives the screw.
In the gasification furnace 3, the waste is thermally decomposed by the combustion air supplied from the furnace bottom. A pyrolysis gas containing combustible gas such as CO and H ₂ , char (carbide), and ash generated in the gasification furnace 3 is supplied to the swirl melting furnace 6 through a pyrolysis gas duct 25. In the slewing melting furnace 6, ash is melted by the combustion heat obtained by burning the pyrolysis gas. The exhaust gas generated in the melting furnace 3 is sent to a secondary combustion chamber 12 connected to the upper side of the melting furnace, where unburned components in the gas are burned. Combustion air for promoting combustion is supplied to the swirl melting furnace 6 and the secondary combustion chamber 12, respectively.

  As a combustion control method in a general melting furnace, as described in Patent Document 1 (Japanese Patent Laid-Open No. 11-351538) and the like, the temperature in the furnace is detected by a temperature sensor installed in the melting furnace, and the detected temperature is detected. A method of controlling the amount of combustion air supplied to the melting furnace based on the temperature is used. However, when waste is treated in such a gasification and melting system, combustion becomes unstable due to fluctuations in the amount of waste input and the amount of heat generated, and the CO concentration in the exhaust gas discharged from the secondary combustion chamber is high. Therefore, the adverse effect on the environment caused by this has been a problem.

Moreover, in patent document 2 (Unexamined-Japanese-Patent No. 2003-269712), a pressure detection apparatus is provided in a pyrolysis furnace, and based on the detection result of furnace pressure, the amount of pyrolysis furnace secondary combustion air, the amount of ash melting furnace combustion air, and A configuration for controlling at least one of the amount of combustion air in the secondary combustion chamber is disclosed. In this way, by controlling and supplying the necessary amount of combustion air in each part, a large amount of harmful gas resulting from a shortage of combustion air is prevented.
Further, Patent Document 3 (Japanese Patent Laid-Open No. 2001-201023) detects waste load fluctuations by measuring the furnace pressure of the pyrolysis gasification furnace, and burns in the melting furnace when a sudden increase in load is detected. The structure which prevents the incomplete combustion in a melting furnace by increasing supply_amount | feed_rate of the combustion air supplied to a melting furnace is disclosed.

JP 11-351538 A JP 2003-269712 A JP 2001-201023 A

  As described above, the gasification and melting system has a problem in that combustion becomes unstable due to fluctuations in the amount of waste input and the amount of heat generated, and the CO concentration of exhaust gas discharged from the secondary combustion chamber increases. However, as described in Patent Document 1, it is difficult to reduce the CO concentration only by controlling the amount of combustion air to the melting furnace based on the in-furnace temperature of the melting furnace. This is because when a large amount of pyrolysis gas is generated in the gasification furnace, it is impossible to completely burn it only by controlling the amount of combustion air supplied to the melting furnace and the secondary combustion chamber. This is because if a large amount of combustion air is supplied to the furnace, the temperature in the furnace decreases and the melting of ash is hindered.

On the other hand, Patent Documents 2 and 3 are configured to control the amount of combustion air based on the internal pressure of the gasification furnace. According to this method, the amount of pyrolysis gas generated can be accurately detected and the CO concentration can be reduced. However, it is difficult to stably maintain the combustion state only by controlling the amount of combustion air uniformly with respect to fluctuations in the furnace pressure. In addition, the control of the combustion air amount alone has not been sufficient for a large fluctuation in the furnace pressure. For example, if the furnace pressure rises significantly, even if the combustion air amount is increased to promote the combustion of pyrolysis gas, the amount of gas generated is so large that the CO concentration in the exhaust gas becomes high without complete combustion. There is a problem that the temperature of the melting furnace decreases because the amount of combustion air is excessively increased.
Therefore, in view of the above-mentioned problems of the prior art, the present invention is capable of accurately detecting even when the gas generation amount fluctuates in the gasifier and reducing the CO generation amount by performing accurate control. It is another object of the present invention to provide a combustion control method for a gasification and melting system that can cope with a large variation in gas generation amount and the system.

Therefore, in order to solve such a problem, the present invention thermally decomposes the waste supplied into the gasification furnace via a dust feeder and introduces the pyrolysis gas generated in the gasification furnace into the melting furnace. Combustion control of a gasification and melting system in which ash is melted by the combustion heat of pyrolysis gas in the melting furnace and then unburned in combustion exhaust gas is burned in a secondary combustion chamber connected to the melting furnace In the method
As a state of the furnace pressure indicating abnormal combustion in the gasification furnace, a plurality of stages of furnace pressure conditions are set in advance corresponding to the abnormal level,
The internal pressure of the gasification furnace is detected, and when the detected internal pressure reaches the first internal pressure condition, the gasification furnace is supplied to at least one of the gasification furnace, the melting furnace, and the secondary combustion chamber. The amount of combustion air supplied to the gasifier is controlled in addition to the control of the amount of combustion air supplied when the second furnace pressure condition, which is higher than the first furnace pressure condition, is reached. It is characterized by controlling the amount of dust supply.

In the present invention, in the first furnace pressure condition where the abnormal level of the furnace pressure is low, the combustion air supply amount is controlled, and the combustion state of the combustion gas is promoted or suppressed on the rear stage side of the gasification furnace. In the second furnace pressure condition where the abnormal level is high, the amount of dust supplied is controlled in addition to the amount of combustion air supplied. This suppresses generation of pyrolysis gas by lowering the amount of dust supplied and reducing the amount of waste supplied when the furnace pressure is high.
By controlling not only the combustion air supply amount but also the supply amount as in the present invention, it is possible to prevent a decrease in furnace temperature due to supplying a large amount of combustion air, and to reduce the CO concentration in the combustion exhaust gas. In addition to the suppression, it is possible to stably produce molten slag in the melting furnace.

Furthermore, a plurality of the first furnace pressure conditions and the second furnace pressure conditions are respectively set,
The control contents of the combustion air supply amount are respectively set corresponding to the plurality of first furnace pressure conditions, and when the first furnace pressure conditions are duplicated, the control contents are added,
When the contents of control of the supply amount are respectively set corresponding to the plurality of second furnace pressure conditions, and when the plurality of second furnace pressure conditions overlap, the larger one of the control contents is controlled. It is characterized by adopting it.

  In the present invention, duplicate control details are added in the control of the combustion air amount, and priority is given to the larger control amount among the duplicate control details in the control of the dust supply amount. This is because the increase / decrease in the combustion air supply amount does not affect the operation state of the system as much as the increase / decrease in the supply amount of the fuel, so that the control content can be added to enable significant control. On the other hand, since an increase or decrease in the amount of dust supply has a relatively large effect on the operating state of the system, priority is given to one of the control contents so as to minimize fluctuations in the amount of dust supply.

Further, assuming that the first furnace pressure condition is a suitable preset furnace pressure set as a reference value, when the first furnace pressure condition reaches a predetermined set value exceeding the reference value, the predetermined set value exceeding the reference value is set to a predetermined value. It is characterized by including at least one of the conditions when the time continues.
By setting such an in-furnace pressure condition, an abnormality in the combustion state can be accurately estimated from the in-furnace pressure, and appropriate control becomes possible.

Further, when the second furnace pressure condition is a preset appropriate furnace pressure, a predetermined set value exceeding the reference value is set to a predetermined value when reaching a predetermined set value exceeding the reference value. It includes at least one of the following conditions: when the time is continued, when the reversal of the time-series change in the furnace pressure is performed at a position deviating from the reference value, or when the rate of change in the furnace pressure exceeds a predetermined value It is characterized by.
According to the present invention, similarly to the first in-furnace pressure condition, an abnormality in the combustion state can be accurately estimated from the in-furnace pressure, and appropriate control can be performed.
In addition, a state in which the reversal of the time series change of the furnace pressure is continuously performed at a position deviating from the reference value, and a state in which the rate of change of the furnace pressure exceeds a predetermined value appear particularly when the abnormal level is high. Therefore, it is preferable to control the amount of dust supply when this condition is met.

Furthermore, after carrying out the dust supply amount control corresponding to the second furnace pressure condition, when returning the dust supply amount, it is gradually returned at a predetermined speed.
In this way, by gradually returning the supplied amount according to the set return speed, it is possible to prevent a sudden change in the supplied amount and stabilize the combustion state in the gasifier.

Also, a gasification furnace that generates pyrolysis gas by pyrolyzing waste supplied via a dust feeder, a melting furnace that melts ash by the combustion heat of the pyrolysis gas, and generated in the melting furnace In a gasification and melting system consisting of a secondary combustion chamber that burns unburned components in the exhaust gas
As a state of the furnace pressure indicating abnormal combustion in the gasification furnace, a plurality of stages of furnace pressure conditions are set in advance corresponding to the abnormal level,
A furnace pressure detecting means for detecting a furnace pressure of the gasification furnace;
Combustion air supply that is supplied to at least one of the gasification furnace, the melting furnace, and the secondary combustion chamber when the furnace pressure detected by the furnace pressure detection means reaches a first furnace pressure condition. The amount of dust supplied to the gasification furnace is controlled in addition to the control of the combustion air supply amount when the second furnace pressure condition that is abnormally higher than the first furnace pressure condition is reached. And a control means for controlling.

Further, a plurality of the first furnace pressure conditions and the second furnace pressure conditions are set in the control means, and the control means corresponds to the plurality of first furnace pressure conditions. When the control content of the combustion air supply amount is set respectively and the first furnace pressure condition is duplicated, the control content is added.
When the contents of control of the supply amount are respectively set corresponding to the plurality of second furnace pressure conditions, and when the plurality of second furnace pressure conditions overlap, the larger one of the control contents is controlled. It is characterized by adopting it.

In addition, when the first furnace pressure condition set in the control means reaches a predetermined set value exceeding the reference value, assuming that the appropriate furnace pressure set in advance is a reference value, the reference value is It is characterized by including at least one of the conditions when the predetermined set value exceeding the predetermined time continues.
In addition, when the second furnace pressure condition set in the control means is a preset appropriate furnace pressure as a reference value, when a predetermined set value exceeding the reference value is reached, the reference value is set. When the predetermined set value exceeds the predetermined time, when the reversal of the time series change of the furnace pressure is performed at a position deviating from the reference value, or when the rate of change of the furnace pressure exceeds the predetermined value Or a single condition.

  As described above, according to the present invention, when a large amount of pyrolysis gas is generated in the gasification furnace due to changes in the amount of waste input or the amount of heat generated, the amount of combustion air supplied and / or depending on the abnormal level Providing a combustion control method and system for a gasification and melting system that controls the amount of dust supplied, stabilizes the amount of gas generated, suppresses the generation of harmful gases due to shortage of combustion air, and enables stable operation can do.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.
1 is an overall configuration diagram of a gasification and melting system according to an embodiment of the present invention, FIG. 2 is a diagram showing a basic flow of a control method in the system of FIG. 1, and FIG. 3 is a specific example of a control method in the system of FIG. FIG.

With reference to FIG. 1, the whole structure of the gasification melting system which concerns on a present Example is demonstrated. In addition, the numerical value shown below is an example and is not limited to these.
The waste 40 input from the waste input hopper 1 is quantitatively supplied to the fluidized bed gasifier 3 through the dust feeder 2. In the fluidized bed gasification furnace 3, combustion air 41 having a temperature of about 120 to 230 ° C. and an air ratio of about 0.2 to 0.7 is blown into the furnace through the wind box 4 from the lower part of the furnace, and the fluidized bed temperature is 550. It is maintained at about ˜650 ° C.
The waste 40 is pyrolyzed and gasified in the fluidized bed gasification furnace 3 and decomposed into gas, tar, and char (carbide). Tar is a component that becomes liquid at room temperature, but is present in a gaseous state in the gasification furnace. The incombustible material in the gasification furnace 3 is sequentially discharged from the incombustible material discharge port 5.
The char is gradually pulverized in the fluidized bed, and is introduced into the swirl melting furnace 6 along with gas and tar. Hereinafter, these components introduced into the melting furnace 6 are collectively referred to as a pyrolysis gas.
In addition, although the fluidized bed type gasification furnace 3 was mentioned as an example as a gasification furnace in the present Example, it is not limited to this, Any if it is a furnace which has the structure which pyrolyzes and gasifies waste. But you can.

The pyrolysis gas discharged from the top of the fluidized bed gasification furnace 3 is introduced into the pyrolysis gas burner of the swirling melting furnace 6 through the pyrolysis gas duct 25. In the pyrolysis gas burner, the pyrolysis gas is mixed with the combustion air 42 and introduced into the furnace to form a swirling flow. At this time, the combustion air may have an air ratio of 0.9 to 1.1, preferably about 1.0.
In the swirl melting furnace 6, the mixed gas of the pyrolysis gas and the combustion air 42 is combusted, and the furnace temperature is maintained at 1300 to 1500 ° C. by the seed flame burner 26 and the auxiliary fuel burner 27 as necessary. The ash in the gas melts and slags. The molten slag adheres and flows down on the inner wall surface of the swirl melting furnace 6 and is discharged from the slag outlet 7 at the bottom of the furnace through the slag extraction chute 8. The slag discharged from the slewing melting furnace 6 is rapidly cooled in the water granulating tank 9, carried out by the slag conveyor 10, and collected as granulated slag. The recovered granulated slag can be effectively used for roadbed materials and the like. In this embodiment, the swirl melting furnace 6 is taken as an example of the melting furnace. However, the present invention is not limited to this, and any furnace may be used as long as it is configured to burn and melt pyrolysis gas containing ash. .

  On the other hand, the combustion exhaust gas discharged from the swirl melting furnace 6 is introduced into the secondary combustion chamber 12 through the connecting portion 11. In the secondary combustion chamber 12, the combustion air 43 is supplied so as to have an air ratio of 1.2 to 1.5, and is heated to a predetermined temperature by the auxiliary fuel burner 32 as necessary. The unburned portion is completely burned here.

  The fluidized bed gasification furnace 3 includes a waste charging hopper 1 on a side wall and a dust feeder 2 connected to the lower side of the hopper 1. The dust feeder 2 is composed of a rotating shaft inserted into the casing, a screw blade fixed to the rotating shaft, and a motor 2a connected to an end of the rotating shaft and rotating the rotating shaft. . In this dust feeder, in principle, the rotation amount of the rotating shaft and screw blades are controlled by the motor 2a to adjust the supply amount (supply speed) of waste to be supplied into the furnace.

The fluidized bed gasification furnace 3 is formed with a fluidized bed 20 filled with fluidized sand at the bottom of the furnace, and an auxiliary fuel burner 21 is provided above the fluidized bed 20. A plurality of wind boxes 4 are arranged in parallel at the bottom of the furnace, and combustion air 41 is introduced into the furnace through the wind boxes 4. The fluidized bed 20 during normal operation is maintained at a temperature of about 450 to 650 ° C.
The combustion air 41 is supplied by the blower 23, and an FDF damper (push-in blower damper) 24 is disposed on the supply line. The FDF damper 24 adjusts the amount of combustion air supplied to the wind box 4 by controlling the opening. The opening degree control of the FDF damper 24 is performed by the control device 35.
A pyrolysis gas duct 25 connected to the swirling melting furnace 6 is disposed above the fluidized bed gasification furnace 3. A furnace pressure sensor 22 for detecting the furnace pressure is provided on the pyrolysis gas outlet side above the fluidized bed gasification furnace 3, and continuously detects and transmits the detected value to the control device 35. To do. In the control device 35, based on the detected value of the furnace pressure, the opening degree of the FDF damper 24, the secondary FDF damper (secondary blower damper) 30, and the OFA damper (secondary air damper) 31 to be described later are controlled. The opening degree is controlled, and the amount of combustion air supplied into each device is adjusted.

  The swirl melting furnace 6 has a furnace body having a circular cross section, and one or more pyrolysis gas burners extending from the pyrolysis gas duct 25 and blowing pyrolysis gas into the furnace are disposed on the side walls. The In the vicinity of the pyrolysis gas burner, a seed flame burner 26 and an auxiliary fuel burner 27 are disposed. Further, the upper part of the furnace communicates with the secondary combustion chamber 12 via the connecting portion 11 having a throttle structure, and the combustion exhaust gas generated in the swirling melting furnace 6 is sent to the secondary combustion chamber 12. A slag outlet 7 is provided at the bottom of the furnace, and molten slag is discharged through a slag extraction chute 8 extending downward from the slag outlet 7. The slag extraction chute 8 is provided with a melt-solidified melt burner 28 toward the slag outlet 7 so as to heat the molten slag discharged from the slag outlet 7 so that it does not solidify and become blocked. It has become.

Combustion air 42 is supplied to the pyrolysis gas duct 25. The combustion air 42 is supplied by a blower 29, and a secondary FDF damper 30 is disposed on the supply line. The secondary FDF damper 30 adjusts the amount of combustion air supplied to the swirling melting furnace 6 and the secondary combustion chamber 12 by controlling the opening degree. The opening degree control of the secondary FDF damper 30 is performed by the control device 35.
One or a plurality of auxiliary fuel burners 32 are provided on the side wall of the secondary combustion chamber 12 so as to maintain the temperature in the secondary combustion chamber as necessary.
Further, combustion air 43 is supplied to the secondary combustion chamber 12. The combustion air 43 is supplied by the same blower 29 as the combustion air 42 supplied to the swirl melting furnace 6. The combustion air supplied from the blower 29 is branched after passing through the secondary FDF damper 30, one is supplied to the secondary combustion chamber 12 via the OFA damper 31, and the other is supplied to the pyrolysis gas duct 25 for melting furnace. Introduced in. The OFA damper 31 adjusts the ratio of combustion air supplied to the secondary combustion chamber 12 and the melting furnace 6 by opening degree control. The control of the OFA damper 31 is performed by the control device 35.

  In the fluidized bed gasification furnace 3 as described above, the amount of pyrolysis gas generated varies due to changes in the heat generation amount and input amount of waste. When a large amount of pyrolysis gas is generated in the fluidized bed gasification furnace 3, the pyrolysis gas is not completely burned in the downstream melting furnace 6 and exhaust gas containing a large amount of CO is generated. Therefore, in the present embodiment, a configuration is provided in which combustion in the fluidized bed gasification furnace 3, the swirl melting furnace 6, and the secondary combustion chamber 12 is optimized and the CO concentration in the exhaust gas is reduced.

In this embodiment, a furnace pressure sensor 22 for detecting the furnace pressure is provided in the upper part of the fluidized bed gasification furnace 3. Furthermore, as a state of the furnace pressure indicating abnormal combustion in the gasification furnace 3, a plurality of stages of furnace pressure conditions are set in advance corresponding to the abnormal level.
As shown in the basic flow of FIG. 2, when the furnace pressure detected by the furnace pressure sensor 22 reaches the first furnace pressure condition, at least one of the gasification furnace 3, the melting furnace 6, and the secondary combustion chamber 12. The amount of combustion air supplied to any of the above is controlled, and when the detected furnace pressure reaches the second furnace pressure condition, the combustion air supply amount is controlled and the dust supply amount (supply) in the feeder is controlled. (Reel speed) is controlled.
In this embodiment, the control of the amount of combustion air and the amount of dust supply are performed by the control device 35. However, the present invention is not limited to this configuration, and each control may be performed by separate control devices, and these control devices may be cascade-controlled.

As described above, when the furnace pressure of the gasification furnace 3 reaches the first furnace pressure condition, the amount of combustion air supplied is controlled as the control content.
When a plurality of first in-furnace pressure conditions are set and an appropriate in-furnace pressure is set as a reference value, when a predetermined absolute value with respect to the reference value is exceeded, a predetermined absolute value with respect to the reference value is continued for a predetermined time, etc. These conditions are listed.
Control contents corresponding to the first furnace pressure condition include conditions such as one or a combination of opening control of the secondary FDF damper, opening control of the FDF damper, and opening control of the OFA damper. Can be mentioned.

Further, in this embodiment, when a plurality of first furnace pressure conditions are duplicated, control is performed to add duplicate control details. That is, when the opening degree of the secondary FDF damper is controlled to + 10% and then the opening degree of the damper is controlled to + 15% before returning, the opening degree of the secondary FDF damper is added to + 25%. To control.
In this manner, the overlapping control contents are added because the increase or decrease in the combustion air supply amount does not affect the operation state of the system as much as the increase or decrease in the supply amount of the fuel, and therefore, a large control is possible.
After implementing this control content, when the preset return condition is reached, the opening degree of the damper is returned to the original state. The return condition includes conditions such as when a predetermined furnace pressure indicating a normal state is reached, when a predetermined furnace pressure continues for a predetermined time, or when a control continuation time reaches a predetermined time.

On the other hand, when the furnace pressure of the gasification furnace 3 reaches the second furnace pressure condition, the amount of dust supplied is controlled as a control content.
When a plurality of second furnace pressure conditions are set and an appropriate furnace pressure is used as a reference value, when a predetermined absolute value with respect to the reference value is exceeded, when a predetermined absolute value with respect to the reference value is continued for a predetermined time, etc. These conditions are listed.
Further, the second furnace pressure condition includes a rate of change of the furnace pressure. In this case, when a change in the furnace pressure exceeding a predetermined range appears continuously several times within a predetermined time, it is determined that the abnormal level of the combustion state is high, and the amount of dust supplied is controlled. For example, when a change of 0.05 kPa or more within 1 second continues for 3 seconds or more, it is estimated that a large amount of pyrolysis gas is generated in the gasification furnace 3, and in order to suppress this, As the amount of combustion air on the side increases, the amount of dust supplied on the inlet side decreases to suppress the amount of pyrolysis gas generated.

  Furthermore, the second in-furnace pressure condition includes an inversion condition of the in-furnace pressure. This is because if the time-series change in the furnace pressure is reversed above or below the reference value and does not return to the reference value, it is determined that the abnormal level of the combustion state is high, and the amount of dust supplied is controlled. To do. For example, when reversal is repeated at a value higher than the reference value, it is presumed that the amount of pyrolysis gas generated continues to increase, and in order to suppress this, the amount of dust supplied with the increase in the amount of combustion air on the rear stage side To reduce the amount of pyrolysis gas generated.

The control content corresponding to the second furnace pressure condition includes rotation speed control of the dust feeder motor 2a.
At this time, since the abnormal level of the second furnace pressure condition is higher than that of the first furnace pressure condition, the amount of combustion air is inevitably controlled. Therefore, when the second furnace pressure condition is reached, in addition to controlling the amount of combustion air, the amount of dust supplied is controlled.

Further, in this embodiment, when a plurality of second furnace pressure conditions are duplicated, the control content with the larger control amount is executed among the duplicated control details. That is, if the feed rate is controlled to -18% before returning after the feed rate is controlled to -10%, the feed rate of -18% is adopted.
In this way, giving priority to the larger control amount among the duplicated control contents is because the increase or decrease in the amount of dust supply has a relatively large effect on the operating state of the system, so the fluctuation in the amount of dust supply is minimized. Because.

  After implementing this control content, when the preset return condition is reached, the opening degree of the damper is returned to the original state. The return condition includes conditions such as when a predetermined furnace pressure indicating a normal state is reached, when a predetermined furnace pressure continues for a predetermined time, or when a control continuation time reaches a predetermined time. Further, in the control of the dust supply amount, it is preferable to provide a return speed when returning. By gradually returning the dust supply amount according to a predetermined return speed, it is possible to prevent a sudden change in the dust supply amount and to stabilize the combustion state in the gasifier.

FIG. 3 shows an example of the control method. FIG. 3A shows the time-series change of the furnace pressure measured by the furnace pressure sensor 22, FIG. 3B shows the control of the combustion air amount, and FIG. 3C shows the control of the dust supply amount. The reference value P of the furnace pressure is the furnace pressure in an appropriate combustion state, and the set values P _{1 to} P ₅ exceed the reference value P, and the furnace pressure indicates an abnormal combustion state, and P ₁ <P ₂ <P ₃ < P ₄ <P ₅ . Further, P−P ₆ is a value lower than the reference value P by P ₆ .
In the same figure, at points A and B that have reached the first furnace pressure condition, the control content relating to the amount of combustion air corresponding to each furnace pressure condition is executed. In point A, since the furnace pressure exceeds the set value P _1, and controls the secondary FDF damper open. In point B for the pressure in the furnace exceeds the set value P _2, and controls the OFA damper open. At this time, since the control contents are added, the secondary FDF damper remains open. Thereafter, these damper controls are returned under the return condition. The point C, since the furnace pressure is higher than a setting P _1, performs the same control as the point A.

At point D, as the second furnace pressure condition, since the time-series change in the furnace pressure is reversed above the reference value, control is performed to reduce the feed amount (motor rotation speed). At this time, the control of the combustion air amount continues.
The point E, since the furnace pressure as the first furnace pressure conditions exceed the set value P _3, as the control content corresponding thereto, to control the OFA damper open.
At point F, as the first in-furnace condition, the in-furnace pressure exceeds P-P ₆ and continues for time T _1. Therefore, the secondary FDF damper and OFA damper are controlled to be opened as the corresponding control content. At this time, control is performed by adding to the control content at point E.

At point G, as the first furnace pressure condition and the second furnace condition, the furnace pressure exceeded P-P ₆ and continued for a time T ₂ , and as a control content corresponding to these, the secondary FDF damper and OFA The damper is controlled to be opened and the amount of dust supplied is reduced.
The point H, since the furnace pressure as the first furnace pressure conditions exceed the set value P _4, as control contents corresponding thereto, to control the FDF damper closed.
The point I, since the furnace pressure as a second furnace pressure conditions exceed the set value P _5, as the control content corresponding to this, the control to decrease the feed dust amount is carried out.
The J point, as a first furnace pressure conditions, since continued for a time T ₃ the furnace internal pressure exceeds the set value P _3, as the control content corresponding thereto, and controls the OFA damper open.
Further, when returning the dust supply amount control at the point I, as indicated by the gradient K, it is gradually returned at a predetermined return speed.
The combination of the furnace pressure condition and the control content described above is merely an example, and the present invention is not limited to this.

As described above, in this embodiment, under the first furnace pressure condition where the abnormal level of the furnace pressure is low, the combustion air supply amount is controlled, and the combustion of the pyrolysis gas is promoted on the rear side of the gasification furnace or the heat By suppressing the generation amount of cracked gas, the combustion state is stabilized, and in the second furnace pressure condition where the abnormal level is high, in addition to controlling the supply amount of combustion air, the amount of dust supplied is controlled, The amount of generation is stabilized. For example, when the pressure in the furnace is high, the combustion air supply amount is increased to promote combustion at the latter stage of the gasification furnace, and the amount of pyrolysis gas is reduced by lowering the supply amount and reducing the waste supply amount. Occurrence is suppressed.
As in the present invention, when there is a significant fluctuation in the furnace pressure, the furnace temperature is prevented from being lowered by supplying a large amount of combustion air by controlling not only the combustion air supply amount but also the dust supply amount. In addition to suppressing the CO concentration in the combustion exhaust gas, it is possible to stably produce molten slag in the melting furnace.
As a result, it is possible to provide a system that can cope with large fluctuations in the internal pressure of the furnace, and even during control, stable operation is possible without hindering the operation of the system.

1 is an overall configuration diagram of a gasification melting system according to an embodiment of the present invention. It is a figure which shows the basic flow of the control method in the system of FIG. It is a figure which shows the specific example of the control method in the system of FIG. It is a whole block diagram of the conventional gasification melting system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 Dust feeder 2a Motor 3 Fluidized bed gasifier 6 Swivel melting furnace 12 Secondary combustion chamber 13 Boiler part 22 Furnace pressure sensor 24 FDF damper 30 Secondary FDF damper 31 OFA damper 35 Control apparatus

Claims (9)

The waste supplied into the gasification furnace through the dust feeder is pyrolyzed, the pyrolysis gas generated in the gasification furnace is introduced into the melting furnace, and the heat of combustion of the pyrolysis gas in the melting furnace In the combustion control method of the gasification and melting system, after the ash is melted by the above, the unburned content in the combustion exhaust gas is burned in the secondary combustion chamber connected to the melting furnace.
As a state of the furnace pressure indicating abnormal combustion in the gasification furnace, a plurality of stages of furnace pressure conditions are set in advance corresponding to the abnormal level,
The internal pressure of the gasification furnace is detected, and when the detected internal pressure reaches the first internal pressure condition, the gasification furnace is supplied to at least one of the gasification furnace, the melting furnace, and the secondary combustion chamber. The amount of combustion air supplied to the gasifier is controlled in addition to the control of the amount of combustion air supplied when the second furnace pressure condition, which is higher than the first furnace pressure condition, is reached. A combustion control method for a smelting and melting system, characterized by controlling a dust supply amount. A plurality of the first furnace pressure conditions and the second furnace pressure conditions are respectively set,
The control contents of the combustion air supply amount are respectively set corresponding to the plurality of first furnace pressure conditions, and when the first furnace pressure conditions are duplicated, the control contents are added,
When the contents of control of the supply amount are respectively set corresponding to the plurality of second furnace pressure conditions, and when the plurality of second furnace pressure conditions overlap, the larger one of the control contents is controlled. The combustion control method for a gasification and melting system according to claim 1, wherein the combustion control method is employed.   Assuming that the first furnace pressure condition is a preset appropriate furnace pressure as a reference value, when the first furnace pressure condition reaches a predetermined set value exceeding the reference value, the predetermined set value exceeding the reference value continues for a predetermined time. The combustion control method for a gasification and melting system according to claim 1, wherein at least one of the conditions is included.   Assuming that the second furnace pressure condition is a predetermined preset furnace pressure as a reference value, when a predetermined set value exceeding the reference value is reached, the predetermined set value exceeding the reference value continues for a predetermined time. When the reversal of the time series change of the furnace pressure is performed at a position deviating from the reference value, it includes at least one of the conditions when the rate of change of the furnace pressure exceeds a predetermined value. A combustion control method for a gasification and melting system according to claim 1 or 2.   3. The method according to claim 1, wherein after the dust supply amount control corresponding to the second in-furnace pressure condition is performed, the dust supply amount is gradually returned at a predetermined speed when returning. Control method for gasification and melting system A gasification furnace that generates pyrolysis gas by pyrolyzing waste supplied via a dust feeder, a melting furnace that melts ash by the combustion heat of the pyrolysis gas, and combustion generated in the melting furnace In a gasification and melting system consisting of a secondary combustion chamber that burns unburned components in exhaust gas,
As a state of the furnace pressure indicating abnormal combustion in the gasification furnace, a plurality of stages of furnace pressure conditions are set in advance corresponding to the abnormal level,
A furnace pressure detecting means for detecting a furnace pressure of the gasification furnace;
Combustion air supply that is supplied to at least one of the gasification furnace, the melting furnace, and the secondary combustion chamber when the furnace pressure detected by the furnace pressure detection means reaches a first furnace pressure condition. The amount of dust supplied to the gasification furnace is controlled in addition to the control of the combustion air supply amount when the second furnace pressure condition that is abnormally higher than the first furnace pressure condition is reached. A gasification and melting system comprising a control means for controlling. A plurality of the first furnace pressure conditions and the second furnace pressure conditions are set in the control means, and combustion air corresponding to the plurality of first furnace pressure conditions is set by the control means. When the contents of control of the supply amount are respectively set and the first furnace pressure condition is duplicated, the control contents are added,
When the contents of control of the feed amount are set corresponding to the plurality of second furnace pressure conditions, respectively, and when the plurality of second furnace pressure conditions overlap, the larger of the control contents of the control contents is selected. The gasification and melting system according to claim 6, wherein the gasification and melting system is adopted.   Assuming that the first furnace pressure condition set in the control means is a suitable preset furnace pressure set as a reference value, and reaches a predetermined set value exceeding the reference value, a predetermined value exceeding the reference value is reached. 8. The gasification and melting system according to claim 6, wherein at least one of the conditions is included when the set value continues for a predetermined time.   Assuming that the second furnace pressure condition set in the control means is a pre-set appropriate furnace pressure as a reference value, when it reaches a predetermined set value exceeding the reference value, a predetermined value exceeding the reference value is reached. When the set value of the furnace pressure continues for a predetermined time, when the reversal of the time series change of the furnace pressure is performed at a position deviating from the reference value, or at least one of the cases where the rate of change of the furnace pressure exceeds the predetermined value The gasification melting system according to claim 6 or 7, characterized in that it includes two conditions.

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