JP5791429B2 - Exhaust gas treatment system and exhaust gas treatment method - Google Patents

Description

  The present invention relates to an exhaust gas treatment system and an exhaust gas treatment method for treating exhaust gas containing NOx generated in, for example, a waste incineration treatment facility.

  As shown in FIG. 2, in a conventional waste incineration treatment facility 51, waste is burned in a combustion furnace 52. The exhaust gas generated by the combustion of the waste in the combustion furnace 52 is cooled to a predetermined temperature in the gas cooling tower 54 after heat exchange in the boiler 53, and then is collected in a dust collector (BF) 55 using a bag filter. Sent. The exhaust gas from which the dust is removed by the dust collector 55 is once heated by the exhaust gas heating device (GRH) 56 and then sent to the catalyst denitration device (SCR) 57. The exhaust gas denitrated by the catalyst denitration device 57 is discharged out of the system through a chimney 59 by an induction fan (IDF) 58. Note that this kind of waste incineration treatment facility 51 is known, for example, from Patent Document 1.

JP 2004-309079 A

In the waste incineration treatment facility 51 described above, an exhaust gas heating device 56 and a catalyst denitration device 57 are incorporated in order to remove nitrogen oxides (NOx) contained in the exhaust gas from the combustion furnace 52.
The catalyst denitration device 57 is a device that causes ammonia (NH ₃ ) and NOx to react on the catalyst and decomposes NOx into N ₂ and H ₂ O. The decomposition rate greatly depends on the reaction temperature. Therefore, it is necessary to keep the exhaust gas temperature at 200 ° C. or higher.

On the other hand, the exhaust gas generated during waste incineration includes harmful substances such as dust, HCl and SOx derived from ash, chlorine and sulfur contained in the waste. Therefore, dust is removed by the dust collector 55, and an alkaline agent (mainly slaked lime) is blown upstream of the dust collector 55, so that acidic gases such as HCl and SOx are in the gas or on the filter cloth of the dust collector 55. To make it harmless.
The heat resistance of the filter cloth material (PTFE fiber or glass fiber is used) is up to about 200 ° C, and the reaction between acidic gas such as HCl and SOx and slaked lime is highly temperature dependent, and the exhaust gas temperature is high. Since the lower the efficiency, the lower the exhaust gas temperature, which is about 150 ° C., in consideration of countermeasures against corrosion of the equipment.

The exhaust gas treatment system in the waste incineration treatment facility 51 has a system configuration in which acid dust such as dust, HCl and SOx is first removed by the dust collector 55, and then NOx is removed by the catalyst denitration device 57. Therefore, the gas cooling tower 54 and the exhaust gas heating device 56 are arranged as shown in FIG.
In addition, the numerical value in the bracket | parenthesis in FIG. 2 shows the example of the exit gas temperature of each apparatus.

  The exhaust gas heating device 56 heats the exhaust gas of about 150 ° C. from the dust collector 55 to 210 ° C., and the heat source is superheated steam from the boiler 53 in the case of the waste incineration treatment facility 51 with a boiler. (400 ° C. or 300 ° C.) is used. In addition, in the case of a waste incineration processing facility not accompanied by the boiler 53, it is heated by a fuel burner or the like.

By the way, since the energy of the heat source used in the exhaust gas heating device 56 is lost energy, it is desired to reduce it. However, since the catalyst denitration reaction in the catalyst denitration device 57 is highly temperature dependent, it is difficult to lower the temperature. .
For this reason, for example, in the case of the waste incineration treatment facility 51 with a boiler (in the case of a trial calculation example), about 5.5% of the input waste heat amount is used for exhaust gas heating and is lost. This amount corresponds to about 9% of the steam from the boiler 53 that has recovered heat. On the other hand, in the case of a waste incineration treatment facility (100 t / day) that is not accompanied by the boiler 53, fuel such as kerosene is required to be 62 liters / h, and the operation cost increases accordingly.

  The present invention has been made in view of the above-described problems, and is capable of reducing the amount of superheated steam or fuel used as a heat source in an exhaust gas heating device while keeping the NOx concentration lower than a regulation value. It is an object of the present invention to provide a system and an exhaust gas treatment method.

In order to achieve the above object, an exhaust gas treatment system according to the first invention comprises:
In an exhaust gas treatment system comprising an exhaust gas heating device that heats exhaust gas containing NOx, and a catalyst denitration device that injects NH ₃ gas into the exhaust gas from the exhaust gas heating device and denitrates,
A bypass pipe branched from a pipe connected to the exhaust gas inlet of the exhaust gas heating device and connected to a pipe connected to the exhaust gas outlet of the catalyst denitration device;
An exhaust gas temperature control means for controlling heating in the exhaust gas heating device so that the temperature of the exhaust gas from the exhaust gas heating device becomes a predetermined temperature;
In the catalyst denitration device, the NOx concentration of the exhaust gas from the catalyst denitration device before the exhaust gas from the catalyst denitration device and the exhaust gas from the bypass pipe merge is equal to or lower than a first predetermined percentage of a regulation value. NH ₃ gas injection amount control means for controlling the injection amount of NH ₃ gas;
The flow rate of the exhaust gas flowing through the bypass pipe is controlled so that the NOx concentration of the exhaust gas after the exhaust gas from the catalyst denitration apparatus and the exhaust gas from the bypass pipe are merged is equal to or less than a second predetermined percentage of the regulation value. Bypass gas amount control means;
It is characterized by providing.

Next, an exhaust gas treatment method according to the second invention is as follows.
From an exhaust gas heating device that heats exhaust gas containing NOx, a catalyst denitration device that injects NH ₃ gas into the exhaust gas from the exhaust gas heating device to denitrate, and a pipe connected to the exhaust gas inlet of the exhaust gas heating device In an exhaust gas treatment system comprising a bypass pipe that branches and leads to a pipe connected to the exhaust gas outlet of the catalyst denitration device,
Controlling the heating in the exhaust gas heating device so that the temperature of the exhaust gas from the exhaust gas heating device becomes a predetermined temperature,
In the catalyst denitration device, the NOx concentration of the exhaust gas from the catalyst denitration device before the exhaust gas from the catalyst denitration device and the exhaust gas from the bypass pipe merge is equal to or lower than a first predetermined percentage of a regulation value. Control the injection amount of NH ₃ gas,
The flow rate of the exhaust gas flowing through the bypass pipe is controlled so that the NOx concentration of the exhaust gas after the exhaust gas from the catalyst denitration apparatus and the exhaust gas from the bypass pipe are merged is equal to or less than a second predetermined percentage of the regulation value. It is characterized by this.

In the present invention, heating in the exhaust gas heating device is controlled so that the temperature of the exhaust gas from the exhaust gas heating device becomes a predetermined temperature (for example, 210 ° C.). Thereby, the catalyst denitration reaction in the catalyst denitration apparatus having high temperature dependence is favorably performed.
Further, the NOx concentration of the exhaust gas from the catalyst denitration device before the exhaust gas from the catalyst denitration device and the exhaust gas from the bypass line merge is set to be equal to or lower than a first predetermined percentage (for example, 30%) of the regulation value. The injection amount of NH ₃ gas in the catalyst denitration device is controlled, and the NOx concentration of the exhaust gas after the exhaust gas from the catalyst denitration device and the exhaust gas from the bypass line merge is less than the first predetermined percentage of the regulation value. The flow rate of the exhaust gas flowing through the bypass pipe is controlled so as to be equal to or less than a second predetermined percentage (for example, 90%) which is large and less than 100%. Thereby, the NOx concentration is suppressed to be lower than the regulation value.
In addition, a part of the exhaust gas that goes to the exhaust gas inlet of the exhaust gas heating device flows through a bypass pipe to a pipe connected to the exhaust gas outlet of the catalyst denitration device. Or fuel can be reduced.
According to the present invention, while kept below the regulation value of the NOx concentration, since Ru can reduce superheated steam or fuel used as a heat source in the exhaust gas heating device, for example, in the case of a boiler with waste incineration facilities In the case of waste incineration facilities that do not have boilers, use the reduced steam heat for other equipment (for example, increase the amount of steam sent to the steam turbine generator to increase power generation). , Fuel consumption can be reduced and operating expenses can be reduced.

Schematic system configuration diagram of a waste incineration treatment facility equipped with an exhaust gas treatment system according to an embodiment of the present invention Schematic system configuration diagram of a waste incineration facility equipped with a conventional exhaust gas treatment system

  Next, specific embodiments of the exhaust gas treatment system and the exhaust gas treatment method according to the present invention will be described with reference to the drawings.

  FIG. 1 shows a schematic system configuration diagram of a waste incineration treatment facility equipped with an exhaust gas treatment system according to an embodiment of the present invention.

<Description of schematic configuration of waste incineration facility>
In the waste incineration treatment facility 1 shown in FIG. 1, the waste is burned in a combustion furnace 2. The exhaust gas generated by the combustion of the waste in the combustion furnace 2 is cooled to a predetermined temperature in the gas cooling tower 4 after heat exchange in the boiler 3 and then collected in a dust collector (BF) 5 using a bag filter. Sent. The exhaust gas from which the dust is removed by the dust collector 5 is once heated by the exhaust gas heating device (GRH) 6 and then sent to the catalyst denitration device (SCR) 7. The exhaust gas denitrated by the catalyst denitration device 7 is discharged out of the system through a chimney 9 by an induction fan (IDF) 8. In addition, the numerical value in the bracket | parenthesis in FIG. 1 shows the example of the exit gas temperature of each apparatus.

<Description of bypass pipeline>
The pipeline 10 connecting the exhaust gas outlet of the dust collector 5 and the exhaust gas inlet of the exhaust gas heating device 6 and the pipeline 11 connecting the exhaust gas outlet of the catalyst denitration device 7 and the exhaust gas inlet of the induction fan 8 are bypassed. They are connected by a pipe 12. As a result, a part of the exhaust gas from the dust collector 5 toward the exhaust gas heating device 6 flows to the pipeline 11 via the bypass pipeline 12 branched from the pipeline 10, and merges with the exhaust gas from the catalyst denitration device 7. Guided to the induction fan 8.

<Description of exhaust gas temperature control means>
The exhaust gas heating device 6 heats about 150 ° C. exhaust gas from the dust collector 5 to 210 ° C., and superheated steam (400 ° C. or 300 ° C.) from the boiler 3 is used as a heat source.
The exhaust gas heating device 6 is provided with exhaust gas temperature control means 13 for controlling the heating in the exhaust gas heating device 6 so that the temperature of the exhaust gas from the exhaust gas outlet becomes a predetermined temperature (for example, 210 ° C.).
The exhaust gas temperature control means 13 includes a control valve 14 and a controller 15, and is heated by a signal from the controller 15 so that the exhaust gas outlet temperature of the exhaust gas heating device 6 becomes a predetermined temperature (for example, 210 ° C.). The supply amount of steam is controlled by the control valve 14.

<Description of NH ₃ gas injection amount control means>
The catalyst denitration device 7 is a device that causes ammonia (NH ₃ ) and NOx to react on the catalyst and decomposes NOx into N ₂ and H ₂ O.
The catalyst denitration device 7 includes the catalyst so that the NOx concentration of the exhaust gas from the exhaust gas outlet is not more than a first predetermined percentage (for example, 30%) of a regulation value (for example, 100 ppm (converted to 12% of O ₂ )). NH ₃ gas injection amount control means 16 for controlling the injection amount of the NH ₃ gas in the denitration unit 7 is attached.
This NH ₃ gas injection amount control means 16 includes a control valve 17 and a controller 18, and the catalyst denitration device 7 receives a signal from the controller 18 so that the NOx concentration at the exhaust gas outlet of the catalyst denitration device 7 becomes 30 ppm. The control valve 17 is configured to control the supply amount of NH ₃ gas.

<Description of bypass gas amount control means>
In the bypass line 12, the NOx concentration of the exhaust gas after the exhaust gas from the catalyst denitration device 7 and the exhaust gas from the bypass line 12 merge is equal to or lower than the second predetermined percentage (for example, 90%) of the regulation value. Thus, a bypass gas amount control means 19 for controlling the flow rate of the exhaust gas flowing through the bypass pipeline 12 is attached.
The bypass gas amount control means 19 is provided in the middle of the bypass pipe 12 and adjusts the flow rate of the exhaust gas according to the rotation angle of the bypass gas, and a motor 21 that drives the bypass damper 20 to rotate. A controller 22 for controlling the motor 21, and the controller 22 controls the motor 21 so that the NOx concentration of the exhaust gas after the exhaust gas from the catalyst denitration device 7 and the exhaust gas from the bypass line 12 merge is 90 ppm. The rotation angle of the bypass damper 20 is adjusted by the drive control signal to control the flow rate of the exhaust gas flowing through the bypass conduit 12.
Incidentally, _{O 2} measurement signal is sent from the _{O 2} meter 23 for _{O 2} converted concentration is to the controller 18, 22.

<Description of effects>
In the present embodiment, the supply steam to the exhaust gas heating device 6 by a signal from the controller 15 so that the exhaust gas outlet NO. Temperature of the exhaust gas heating device 6 becomes 210 ° C. with exhaust gas standard NOx 100 ppm (O ₂ 12% conversion). The amount is controlled by the control valve 14. The exhaust gas from the exhaust gas heating device 6 flows to the catalyst denitration device 7. The control valve 17 controls the NH ₃ gas supply amount by a signal from the controller 18 so that the NOx concentration at the exhaust gas outlet of the catalyst denitration device 7 is 30 ppm, and the NOx concentration at the exhaust gas outlet of the catalyst denitration device 7 is about 30 ppm. To do. The flow rate of the exhaust gas flowing through the bypass line 12 is controlled by adjusting the rotation angle of the bypass damper 20 with a signal from the controller 22 so that the NOx concentration after merging with the bypass line 12 becomes 90 ppm. 12 and the NOx concentration after merging are about 90 ppm. Thereby, the NOx concentration is suppressed to be lower than the regulation value (100 ppm).

  Table 1 shows a comparison result in a 100 t / day incineration process between the conventional waste incineration facility 51 and the waste incineration facility 1 of the present embodiment. As shown in Table 1, the amount of steam used in the exhaust gas heating device (GRH) 6 can be reduced by about 50%. When the steam power generation efficiency on the scale of 100 t / day is 15%, the power generation amount is about 1400 kW. The increase in power generation amount due to this reduced steam amount is about 90 kW, and the power generation amount is about 6%. The power generation efficiency is improved by about 1%.

  According to this embodiment, it is possible to reduce superheated steam used as a heat source in the exhaust gas heating device 6 while suppressing the NOx concentration to be lower than the regulation value (reduction of about 50% in heat loss in the exhaust gas heating device 6). . As a result, it is possible to increase the amount of power generation by increasing the amount of steam sent to, for example, a steam turbine generator (not shown) attached to the waste incineration treatment facility 1 (increase by about 6% in power generation amount).

  The exhaust gas treatment system and the exhaust gas treatment method of the present invention have been described based on one embodiment. However, the present invention is not limited to the configuration described in the above embodiment, and is appropriately within a range not departing from the gist thereof. The configuration can be changed.

  The exhaust gas treatment system and the exhaust gas treatment method of the present invention have a characteristic that the superheated steam or fuel used as a heat source in the exhaust gas heating device can be reduced while keeping the NOx concentration lower than the regulation value. Therefore, it can be suitably used for an exhaust gas treatment application in a waste incineration treatment facility.

DESCRIPTION OF SYMBOLS 1 Waste incineration processing facility 6 Exhaust gas heating apparatus 7 Catalytic denitration apparatus 10 Pipe line 11 Pipe line 12 Bypass line 13 Exhaust gas temperature control means 14 Control valve 15 Controller 16 NH ₃ gas injection amount control means 17 Control valve 18 Controller 19 Bypass gas amount control means 20 Bypass damper 21 Motor 22 Controller

Claims (2)

In an exhaust gas treatment system comprising an exhaust gas heating device that heats exhaust gas containing NOx, and a catalyst denitration device that injects NH ₃ gas into the exhaust gas from the exhaust gas heating device and denitrates,
A bypass pipe branched from a pipe connected to the exhaust gas inlet of the exhaust gas heating device and connected to a pipe connected to the exhaust gas outlet of the catalyst denitration device;
An exhaust gas temperature control means for controlling heating in the exhaust gas heating device so that the temperature of the exhaust gas from the exhaust gas heating device becomes a predetermined temperature;
In the catalyst denitration device, the NOx concentration of the exhaust gas from the catalyst denitration device before the exhaust gas from the catalyst denitration device and the exhaust gas from the bypass pipe merge is equal to or lower than a first predetermined percentage of a regulation value. NH ₃ gas injection amount control means for controlling the injection amount of NH ₃ gas;
The flow rate of the exhaust gas flowing through the bypass pipe is controlled so that the NOx concentration of the exhaust gas after the exhaust gas from the catalyst denitration apparatus and the exhaust gas from the bypass pipe are merged is equal to or less than a second predetermined percentage of the regulation value. Bypass gas amount control means;
An exhaust gas treatment system comprising: From an exhaust gas heating device that heats exhaust gas containing NOx, a catalyst denitration device that injects NH ₃ gas into the exhaust gas from the exhaust gas heating device to denitrate, and a pipe connected to the exhaust gas inlet of the exhaust gas heating device In an exhaust gas treatment system comprising a bypass pipe that branches and leads to a pipe connected to the exhaust gas outlet of the catalyst denitration device,
Controlling the heating in the exhaust gas heating device so that the temperature of the exhaust gas from the exhaust gas heating device becomes a predetermined temperature,
In the catalyst denitration device, the NOx concentration of the exhaust gas from the catalyst denitration device before the exhaust gas from the catalyst denitration device and the exhaust gas from the bypass pipe merge is equal to or lower than a first predetermined percentage of a regulation value. Control the injection amount of NH ₃ gas,
The flow rate of the exhaust gas flowing through the bypass pipe is controlled so that the NOx concentration of the exhaust gas after the exhaust gas from the catalyst denitration apparatus and the exhaust gas from the bypass pipe are merged is equal to or less than a second predetermined percentage of the regulation value. An exhaust gas treatment method characterized by that.

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