JP2007271206A - Operation control method of gasification melting system, and system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an operation control method of a gasification melting system and the system capable of reducing its running cost by reducing the use of fuel such as an auxiliary fuel in starting, performing economical operation, and being stably started without blockage of a slag cinder notch of a melting furnace. <P>SOLUTION: In this operation control method of the gasification melting system wherein a thermal decomposition gas is generated by thermally decomposing wastes 31 in a fluidized bed gasification furnace 3, the thermal decomposition gas 31 is introduced into the melting furnace 6, and ash content is melted by combustion heat of the thermal decomposition gas 31 in the melting furnace 6, fluidization of a bed material is started by combustion air 32 introduced from a bottom of the gasification furnace 3 while synchronously raising temperatures of the gasification furnace 3 and the melting furnace 6, a fluidized state in the gasification furnace 3 is detected after the lapse of a prescribed time from the start of temperature rise, and the temperature rise of the melting furnace 6 is stopped when the fluidization is not established. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a gasification melting system in which waste is pyrolyzed to generate pyrolysis gas, and ash is melted by the combustion heat of the pyrolysis gas, and in particular, the fuel cost required at startup is reduced, In addition, the present invention relates to an operation control method for a gasification and melting system that enables smooth start-up 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 includes a gasification furnace 3 that thermally decomposes and gasifies, and a swirl melting furnace that combusts the pyrolysis gas 33 generated in the gasification furnace 33 at a high temperature and converts the ash content in the gas into molten slag. 6, the secondary combustion chamber 12 in which the exhaust gas of the swirling melting furnace 6 is introduced and the unburned portion in the exhaust gas is combusted, the temperature reducing tower 14, the reaction dust collector 15, the steam heater 16, the catalytic reactor And an exhaust gas treatment facility consisting of 17 etc. In order to recycle waste, reduce its 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 high temperature exhaust gas from the secondary combustion chamber 12 13 recovers waste heat and generates power.

  In the gasification and melting system as described above, an operation for fluidizing the fluidized medium (fluidized bed 30) filled in the bottom of the gasification furnace 3 at the time of start-up and an operation for raising the temperature in the system are required. In the gasification furnace 3, combustion air 32 is supplied to fluidize the fluidized bed 30, and the auxiliary fuel burner 21 is ignited to raise the temperature in the furnace. In addition, the swirl melting furnace 6 is heated by the high-temperature gas flowing from the gasification furnace 3, and the insufficient heat quantity is compensated by the seed flame burner 24 and the auxiliary fuel burner 25. Similarly, in the secondary combustion chamber 12, the temperature is raised by igniting the auxiliary fuel burner 27 together with the temperature rise by the high temperature gas.

In the gasification and melting system, the temperature inside the gasification furnace 3, the melting furnace 6, and the secondary combustion chamber 12 connected in series is optimized to raise the temperature inside the furnace uniformly, and to reduce the fuel cost. Is required.
In Patent Document 1 (Japanese Patent Application Laid-Open No. 2003-302023), excessive combustion air is supplied into the melting furnace before ignition of the temperature raising burner of the melting furnace, and the temperature raising burner is ignited in this state. Discloses an operation method in which the temperature is gradually raised according to a preset temperature rise table while detecting the temperature in the furnace. The temperature rise is controlled by the output control of the temperature raising burner and the introduction flow rate of the combustion air. Thereby, a large amount of hot gas can be generated by excess combustion air in the melting furnace, and the furnace temperature is made uniform.

Moreover, in patent document 2 (Unexamined-Japanese-Patent No. 2002-22126), after starting up temperature by burning a fuel with excess air using the starting burner of a gasifier, this fuel is air-released using a fuel blowing nozzle. There has been proposed a method in which a combustible gas is generated by burning in a shortage, and the temperature inside the furnace is increased by burning the combustible gas using an ignition pilot burner provided in a melting furnace. Thereby, the temperature rising timing of a gasification furnace and a melting furnace can be match | combined, and fuel cost can be reduced.
Furthermore, Patent Document 3 (Japanese Patent Laid-Open No. 2001-296013) proposes a configuration in which the amount of air supplied to the respective start burners of the gasification furnace and the melting furnace is adjusted independently of the fuel amount. This prevents cooling of the melting furnace by not supplying excess air to the entire system, and shortens the time to reach the target temperature with the minimum amount of fuel used.

JP 2003-302023 A Japanese Patent Laid-Open No. 2002-22126 JP 2001-296013 A

As described in Patent Documents 1 to 3, in the gasification and melting system, the temperature of the melting furnace is raised at the same time as the gasification furnace, and the gasification furnace and the melting furnace are operated in a synchronized manner. However, in a system equipped with a fluidized bed gasification furnace, when fluidization is not established and the gasification furnace is not properly started up, only the melting furnace continues to be heated and supplied to the melting furnace. There was a problem that fuel costs were wasted. In this case, the melting furnace is maintained at a high temperature until the fluidization of the gasification furnace becomes normal, and the running cost may increase due to the fuel used therefor.
Further, when the system is restarted, a slag coat layer coated with molten slag is formed on the furnace wall of the melting furnace, and this slag coat layer may be melted at the temperature rising stage of the melting furnace. In a furnace where the temperature has not been raised completely, the slag coat layer melt may block the slag outlet, so there is a risk that stable startup will not be performed.
Therefore, in view of the above-described problems of the prior art, the present invention reduces the amount of fuel used such as auxiliary fuel at the time of start-up, reduces running costs, enables economical operation, and provides a slag outlet for a melting furnace. It is an object of the present invention to propose an operation control method for a gasification and melting system capable of stable start-up without causing any blockage of the gas, and the system.

Therefore, in order to solve such a problem, the present invention thermally decomposes waste in a fluidized bed gasification furnace to generate pyrolysis gas, introduces the pyrolysis gas into the melting furnace, In the operation control method of the gasification and melting system for melting ash by the combustion heat of the pyrolysis gas,
While raising the temperature of the gasification furnace and the melting furnace synchronously, introducing combustion air from the bottom of the gasification furnace,
A fluidization state in the gasification furnace is detected after a predetermined time has elapsed from the start of the temperature increase, and when the fluidization is not established, the temperature increase of the melting furnace is stopped.
According to the present invention, it is judged that fluidization of the gasification furnace is completely established, and the temperature of the melting furnace is increased only when the fluidization is established. The fuel is not used, and it is possible to reduce the fuel cost and perform an economical operation.

Further, in the case of restarting the gasification melting system, a self-coat layer in which molten slag is adhered and solidified on the furnace wall of the melting furnace is formed,
The temperature in the furnace is detected when the melting furnace is heated, and before the furnace temperature reaches the melting temperature of the self-coat layer, the molten solidified melting burner that heats the slag outlet of the melting furnace is ignited. It is characterized by doing.
As a result, even when the self-coating layer is melted during the temperature rising process of the melting furnace, the slag tap outlet can be prevented from being blocked by heating the slag tap outlet with a melt-solidified product melting burner. it can.

Further, the temperature raising stop of the melting furnace is performed by stopping the output increase of the already ignited burner or stopping the ignition of the unignited burner.
In this way, for burners that have already ignited, the output increase is stopped, and for burners that have not ignited, ignition is stopped, so that only the temperature rise is stopped without the temperature in the melting furnace dropping extremely. Is possible.

Further, the fluidization state is detected based on a temperature distribution of a fluidized bed formed in the gasification furnace.
This is because the temperature distribution in the fluidized bed is detected, and if the temperature distribution is substantially uniform, it can be determined that sufficient fluidization has been established. Therefore, according to this configuration, fluidization of the fluidized bed can be accurately detected.
Furthermore, when the fluidization is not established, the supply amount of the combustion air is temporarily increased over the entire bottom or part of the gasification furnace.
Thereby, fluidization can be promoted without stopping the gasification furnace, and smooth start-up becomes possible.

And a fluidized bed gasification furnace that thermally decomposes waste to generate pyrolysis gas, and a melting furnace that melts ash by the combustion heat of the pyrolysis gas, and the melting furnace converts the pyrolysis gas into In a gasification and melting system comprising a pyrolysis gas burner introduced into a furnace, a seed flame burner that promotes ignition of the pyrolysis gas burner, and an auxiliary fuel burner that introduces auxiliary fuel into the melting furnace,
Fluidization detection means for detecting a fluidization state after a predetermined time has elapsed from the start of temperature rise of the gasification furnace;
And a control device for controlling ignition or output of the auxiliary fuel burner and the seed burner based on the fluidization state detected by the fluidization detection means.

Further, the control device controls the auxiliary fuel burner and the seed fire burner so as to stop the temperature rise of the melting furnace when the fluidization detection means does not detect the establishment of fluidization. Features.
Furthermore, the fluidization detection means is a temperature sensor group that detects a temperature distribution in a fluidized bed of the gasification furnace.

As described above, according to the present invention, it is determined that the fluidization of the gasifier is completely established, and the melting furnace is heated only when the fluidization is established. In this case, useless fuel is not used, and it is possible to reduce the fuel cost and perform economical operation.
In addition, even when the self-coat layer adhering to the melting furnace wall melts during the temperature rising process of the melting furnace, the slag outlet is closed by heating the slag outlet with a molten solidified melting burner. Can be prevented.

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.
FIG. 1 is a schematic diagram showing the overall configuration of a gasification and melting system according to an embodiment of the present invention, FIG. 2 is a graph showing temperature control at startup, (a) is a gasification furnace, (b) is a melting furnace, (C) shows a secondary combustion chamber, respectively, and FIG. 3 is a diagram showing a control flow of a gasification melting system according to an embodiment of the present invention.

With reference to FIG. 1, schematic structure of the gasification melting system which concerns on a present Example is demonstrated.
The waste 31 input from the waste input hopper 1 is crushed and dried as necessary, and then quantitatively supplied to the fluidized bed gasifier 3 through the dust feeder 2. In the fluidized bed gasification furnace 3, combustion air 32 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 500. It is maintained at about ~ 600 ° C.
The waste 31 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 33.

The pyrolysis gas 33 discharged from the top of the fluidized bed gasification furnace 3 is introduced into the pyrolysis gas burner 29 of the swirling melting furnace 6 through a lining duct. In the pyrolysis gas burner 29, the pyrolysis gas 33 is mixed with the combustion air 34 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 swirling melting furnace 6, the mixed gas of the pyrolysis gas 33 and the combustion air 34 is combusted, so that the furnace temperature is maintained at 1300 to 1500 ° C., and the ash content in the pyrolysis gas 33 is melted and slagged. 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.

On the other hand, the combustion exhaust gas discharged from the swirling melting furnace 6 is introduced into the secondary combustion chamber 12 via the connecting portion 11. In the secondary combustion chamber 12, the combustion air 35 is supplied so as to have an air ratio of 1.2 to 1.5, and if necessary, the temperature is raised to a predetermined temperature by the auxiliary fuel burner 27. The unburned portion is completely burned here.
Combustion exhaust gas is heat-recovered by the boiler part 13, and is cooled to about 200-250 degreeC. The combustion exhaust gas discharged from the boiler unit 13 is introduced into the temperature reducing tower 14 and cooled to about 150 ° C. by direct water spray. The combustion exhaust gas discharged from the temperature reducing tower 14 is sprayed with slaked lime and activated carbon in the flue as necessary, and is introduced into the reaction dust collector 15. The reaction dust collector 15 removes soot, acid gas, DXNs and the like in the combustion exhaust gas. The dust ash discharged from the reaction dust collector 15 is treated with chemicals and disposed of in landfill. The combustion exhaust gas is reheated by the steam heater 16 and NO _x is removed by the catalyst reactor 17. The air is discharged from the chimney 19 through the air.

In the fluidized bed gasification furnace 3, a fluidized bed 30 in which fluidized sand is filled at the bottom of the furnace is formed, and an auxiliary fuel burner 21 is provided thereabove. A plurality of wind boxes 4 are arranged in parallel at the furnace bottom, and combustion air 32 is introduced into the furnace via the wind boxes 4. In addition, although the fluidized medium 30 at the initial stage of startup may not be fluidized, it is also referred to as the fluidized bed 30 in this embodiment. The fluidized bed 30 during normal operation is maintained at a temperature of about 500 to 600 ° C.
Furthermore, in this embodiment, at least one temperature sensor 22 located in the fluidized bed 30 at the time of activation is provided. Preferably, a temperature sensor group including a plurality of temperature sensors 22 arranged at a plurality of horizontal sections in the fluidized bed and spaced apart on the same horizontal section is provided. This temperature sensor group can detect the temperature distribution in the horizontal direction and the vertical direction of the fluidized bed.

The swirl melting furnace 6 has a furnace body having a circular cross section, and one or a plurality of pyrolysis gas burners 29 for blowing the pyrolysis gas 33 are disposed on the side walls. In the vicinity of the pyrolysis gas burner 29, an auxiliary burner 25 is 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 23 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. Although the melted solid melt melting burner 23 is not normally used, it is ignited when the slag outlet 7 is clogged or tends to be clogged, and the slag outlet 7 is heated while adjusting the burner output depending on the degree of clogging. Prevent clogging due to solidification of molten slag.
Combustion air 35 is supplied to the secondary combustion chamber 12 to completely burn the combustion exhaust gas from the swirling melting furnace 6. One or more auxiliary fuel burners 27 are provided on the side wall of the secondary combustion chamber 12 so as to maintain the temperature in the secondary combustion chamber.

Next, a control flow at the time of activation of the present system will be described based on FIG. FIG. 2 is a graph showing temperature changes in the gasification furnace 3, the melting furnace 6, and the secondary combustion chamber 12 corresponding to the time series of the control flow shown in FIG.
First, the fluidized sand is charged into the gasification furnace 3 by an initial filling amount (S1), the supply of the combustion air 32 is started (S2), and the auxiliary fuel burner 21 of the gasification furnace 3 (in the figure, the auxiliary burner and (Abbreviated) is ignited (S3). In FIG. 2, combustion air supply and auxiliary fuel burner ignition are indicated by point A.
Then, by controlling the output of the auxiliary burner 21 of the gasification furnace 3, the temperature of the free board part above the gasification furnace is raised at a constant temperature increase rate (S4). It is determined whether or not the temperature of the free board portion of the gasification furnace 3 is equal to or higher than a preset temperature (S5). (S6). Fixing the output of the auxiliary burner 21 of the gasification furnace 3 in FIG. 2 is carried out at point B since the temperature at this time is t _2. In addition, a steady value is a value equivalent to the time of normal operation after completion of starting. When the temperature is equal to or lower than the set temperature, the temperature control by the output of the auxiliary burner 21 of the gasification furnace 3 is continued (S4). Furthermore, additional supply of fluidized sand is sequentially performed as necessary.

When the temperature of the gasification furnace 3 is increased, a high-temperature gas flows into the subsequent melting furnace 6 and the secondary combustion chamber 12 and gradually starts to increase in temperature. The secondary combustion chamber 12 preferably ignites the auxiliary fuel burner 27 at a relatively early stage, and performs output control of the auxiliary fuel burner 27 so that the temperature is raised at a constant temperature increase rate. Ignition of the auxiliary fuel burner 27 in FIG. 2 is performed in point G, the temperature at this time is t _1.
In the melting furnace 6, the seed flame burner 24 is ignited (S7), and then the auxiliary fuel burner 25 is ignited (S8). When there are a plurality of seed flame burners 24 and auxiliary fuel burners 25, they may be ignited sequentially. Ignition of the pilot flame burner 24 in Figure 2 the temperature in the furnace is indicated by point C is t _2. Also, ignition of the auxiliary fuel burner 25 is the furnace temperature is shown by point D is t _3.

Further, by controlling the output of the auxiliary fuel burner 25 of the melting furnace 6 (S9), the temperature in the melting furnace is increased at a constant rate of temperature increase.
After a predetermined time has elapsed from the start of temperature increase, fluidization of the gasification furnace 3 is confirmed based on the temperature detected by the temperature sensor 22 (S10), and the presence or absence of fluidization is determined by the control device 20 (S11). . In FIG. 2, confirmation of fluidization is indicated by point E, which is time t ₄ .
When it is determined by the control device 20 that fluidization has been established, the temperature inside the melting furnace is continuously increased. On the other hand, if it is determined that fluidization has not been established, the temperature rise in the melting furnace is stopped (S12). The temperature rise is stopped by igniting the seed flame burner 24 and the auxiliary fuel burner 25 of the melting furnace 6 and controlling the output. For example, the burner that has already been ignited stops the output increase and maintains the current state, and the burner that has not been ignited stops the ignition. At this time, it is preferable not to extinguish an already ignited burner so as to prevent an extreme temperature drop in the furnace. In FIG. 2, when fluidization is not confirmed at point E, the temperature rise is stopped to maintain the temperature up to point E ′ where fluidization is confirmed. When fluidization is confirmed at point E ′ at time t ₄ ′, the temperature rise is resumed.

  Further, on the gasification furnace 3 side, in order to promote fluidization of the fluidized bed 30, the amount of combustion air supplied from all or a part of the plurality of wind boxes 4 at the lower part of the gasification furnace 3 is increased. Fluidization is promoted by supplying fresh combustion air 32 (S13). This operation may be repeated a plurality of times until fluidization is stably established. In the confirmation of fluidization, a method of detecting the temperature distribution by the temperature sensor 22 installed in the fluidized bed 30 is detected in the same manner as described above, and a part where the temperature detected by the temperature sensor 22 does not rise at the initial stage of temperature rise is detected. The method etc. are mentioned.

The temperature in the melting furnace 6 is sequentially detected by the temperature sensor 26 (S14), and it is determined whether or not the furnace temperature has been raised to a set temperature or higher (S15). The set temperature is lower than the melting temperature of the slag coat layer in the melting furnace, for example, about 1000 ° C. When the furnace temperature becomes equal to or higher than the set temperature, the melt-solidified melt burner 23 is ignited (S16). Ignition of molten solidified melt burner 23 in FIG. 2 are indicated by the point F at time t _5.
When the temperature is lower than the set temperature, the output control of the auxiliary fuel burner 25 of the melting furnace 6 is continued.
By controlling the output of the auxiliary fuel burner 25, the temperature is increased at a constant temperature increase rate until the temperature in the melting furnace reaches about 1300 ° C., and when the temperature in the melting furnace reaches about 1300 ° C., waste is input. Normal operation is started (S17).

As in this configuration, when igniting the various burners required at the start-up and supplying the combustion air to perform the start-up operation, the fluidization of the gasification furnace 3 is confirmed after a predetermined time from the temperature rise, and the fluidization is performed. Is not established, it is possible to avoid supplying unnecessary fuel in the melting furnace 6 by stopping the temperature rise of the melting furnace 6 and to reduce the fuel cost.
Moreover, since it was set as the structure which ignites the molten solidified material fusion burner 23 and heats the slag outlet 7 if the inside of the melting furnace 6 becomes more than predetermined temperature, obstruction | occlusion of the slag outlet 7 can be prevented.

It is the schematic which shows the whole structure of the gasification melting system which concerns on the Example of this invention. It is a graph which shows the temperature control at the time of starting, (a) shows a gasification furnace, (b) shows a melting furnace, (c) shows a secondary combustion chamber, respectively. It is a figure which shows the control flow of the gasification melting system which concerns on the Example of this invention. It is the schematic which shows the whole structure of the conventional gasification melting system.

Explanation of symbols

3 Gasification furnace 6 Swivel melting furnace 7 Slag outlet 12 Secondary combustion chamber 20 Controller 21 Auxiliary fuel burner (gasification furnace)
22, 26 Temperature sensor 24 Seed fire burner 25 Auxiliary fuel burner (melting furnace)
27 Auxiliary fuel burner (secondary combustion chamber)
29 Pyrolysis gas burner 30 Fluidized bed

Claims (8)

The waste is pyrolyzed in a fluidized bed gasification furnace to generate pyrolysis gas, the pyrolysis gas is introduced into the melting furnace, and the ash is melted by the combustion heat of the pyrolysis gas in the melting furnace. In the operation control method of the gasification melting system,
While raising the temperature of the gasification furnace and the melting furnace synchronously, introducing combustion air from the bottom of the gasification furnace,
A gasification and melting system characterized by detecting a fluidization state in the gasification furnace after a lapse of a predetermined time from the start of temperature rise, and stopping temperature rise of the melting furnace when fluidization is not established. Operation control method. In the case of restarting the gasification melting system, a self-coat layer in which molten slag adheres and solidifies on the furnace wall of the melting furnace is formed,
The temperature in the furnace is detected when the melting furnace is heated, and before the furnace temperature reaches the melting temperature of the self-coat layer, the molten solidified melting burner that heats the slag outlet of the melting furnace is ignited. The operation control method for a gasification and melting system according to claim 1.   The operation control method of the gasification melting system according to claim 1, wherein the temperature rise stop of the melting furnace is performed by stopping the increase in output of the already ignited burner or stopping the ignition of the unignited burner.   The operation control method for a gasification and melting system according to claim 1, wherein the detection of the fluidization state is determined based on a temperature distribution of a fluidized bed formed in the gasification furnace.   2. The gasification and melting system according to claim 1, wherein when the fluidization is not established, the supply amount of the combustion air is temporarily increased over the entire bottom or part of the gasification furnace. Operation control method. A fluidized bed gasification furnace that thermally decomposes waste to generate pyrolysis gas, and a melting furnace that melts ash by the combustion heat of the pyrolysis gas, and the melting furnace converts the pyrolysis gas into the furnace In a gasification and melting system comprising a pyrolysis gas burner to be introduced into a gas, a seed flame burner that promotes ignition of the pyrolysis gas burner, and an auxiliary fuel burner that introduces auxiliary fuel into the melting furnace,
Fluidization detection means for detecting a fluidization state after a predetermined time has elapsed from the start of temperature rise of the gasification furnace;
A gasification and melting system comprising: a control device that controls ignition or output of the auxiliary fuel burner and the seed flame burner based on a fluidization state detected by the fluidization detection means.   The control device controls the auxiliary fuel burner and the seed fire burner so as to stop the temperature rise of the melting furnace when the establishment of fluidization is not detected by the fluidization detection means. The gasification melting system according to claim 6. The gasification and melting system according to claim 6 or 7, wherein the fluidization detection means is a temperature sensor group that detects a temperature distribution in a fluidized bed of the gasification furnace.

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