JP6364682B2 - Incineration plant and waste heat recovery method - Google Patents

Description

  The present invention relates to an incineration plant, and more particularly to an incineration plant and a waste heat recovery method that make it possible to effectively use exhaust heat of exhaust gas.

  Conventionally, incineration plants that incinerate waste such as sewage sludge, for example, exhaust gas generated in an incinerator is treated with an exhaust gas treatment facility, detoxified, and then discharged into the atmosphere (for example, Patent Document 1). , Patent Document 2 and Patent Document 3).

  Further, the exhaust gas treatment facility is equipped with a combustion air preheater and a white smoke prevention air preheater, and heat is recovered from the exhaust gas generated in the incinerator by the combustion air preheater and the white smoke prevention air preheater. And the heat collect | recovered with the combustion preheater is sent to an incinerator, and the retained heat of combustion exhaust gas is used effectively.

  On the other hand, in addition to the combustion air preheater and the white smoke prevention air preheater, the exhaust gas treatment facility includes an exhaust gas cooling tower, a dust collector such as a bag filter, an exhaust gas cleaning tower such as a scrubber, and a dehumidification tower. It is configured. And the exhaust gas heat-recovered by the combustion air preheater and the white smoke prevention air preheater is cooled by the exhaust gas cooling tower and subjected to dust removal by the dust collector. Further, the exhaust gas after being processed by the dust collector is subjected to alkali treatment in the exhaust gas cleaning tower to remove harmful substances such as SOx, NOx, and HCl, and dehumidified in the dehumidifying tower. The exhaust gas thus treated is heated with the heat recovered by the air preheater for white smoke prevention to give the white smoke prevention treatment, and is discharged from the chimney to the atmosphere.

  Here, as shown in FIG. 3, for example, the exhaust gas G discharged from the incinerator (not shown) has a temperature of about 850 ° C., and is a combustion air preheater (not shown), a white smoke prevention air preheater. The temperature is reduced to about 200 ° C. to 250 ° C. by treatment with (not shown). Thereby, the temperature of the exhaust gas G processed by the dust collector 1 and sent to the exhaust gas cleaning tower 2 is about 200 ° C. to 250 ° C., and the exhaust gas G after being processed in the exhaust gas cleaning tower 2 by the cleaning water W 1 of about 20 ° C. The temperature is about 70 ° C. Furthermore, the temperature of exhaust gas G becomes about 40 degreeC by processing with the dehumidification tower 3 using the cooling water W2 about 20 degreeC. And the temperature of the exhaust gas G rises to about 200 degreeC by carrying out the white smoke prevention process with the white smoke prevention air P about 300 degreeC sent from the air preheater for white smoke prevention, and it discharge | releases to air | atmosphere in this state.

  Further, in the exhaust gas cleaning tower 2, the temperature of the cleaning water W1 becomes about 70 ° C., and the cleaning water W1 is circulated to perform the cleaning process. Furthermore, a part of the washing water W1 is drained to the sewage treatment plant together with drainage (cooling water W2) of about 50 ° C. from the dehumidifying tower 3. At this time, a part of the drainage of the washing water and the drainage from the dehumidifying tower 3 are mixed, and the wastewater W3 at about 60 ° C. is discharged to the sewage treatment plant.

JP 2012-207617 A Japanese Patent No. 5444439 Japanese Patent No. 5524909

  On the other hand, in the conventional incineration plant, the heat of the high-temperature exhaust gas generated in the incinerator is recovered by the combustion air preheater and the white smoke prevention air preheater, and this exhaust heat is utilized in the incinerator. In some cases, high-temperature exhaust heat from the incinerator is used to generate steam and rotate the turbine to generate power.

  However, since the heat of the exhaust gas at about 200 ° C. after being processed by the dust collector and the heat of about 70 ° C. of the cleaning water of the exhaust gas cleaning tower are low temperatures, the exhaust gas after being processed by the dust collector When heat recovery is performed at the bottom, there is a risk of low-temperature corrosion due to sulfur in the gas.

  Furthermore, in the above conventional incineration plant, taking into account fluctuations in the incineration load and fluctuations in the outside air temperature, a large amount of heat energy is sent from the air preheater for white smoke prevention to prevent white smoke at higher temperatures than necessary. ing. For this reason, a part of the excellent thermal energy is released into the atmosphere together with the exhaust gas.

  As a result, the energy recovery efficiency of the incineration plant as a whole is low, and in order to control greenhouse gases, there is a method for recovering such low-temperature exhaust heat and improving the energy recovery efficiency of the incineration plant as a whole. It was strongly desired.

  The incineration plant of the present invention includes a dust collector for removing exhaust gas generated in an incinerator, an exhaust gas cleaning device for cleaning exhaust gas processed by the dust collector, and a dehumidification process for exhaust gas processed by the exhaust gas cleaning device. In the incineration plant including the dehumidifying device, the dehumidifying device includes an electrothermal conversion device that generates a temperature difference from a voltage, and is a low heat source that is cooled by supplying electric power to the electrothermal conversion device. The exhaust gas treated by the exhaust gas cleaning device is cooled and dehumidified, the heat of the high heat source heated by supplying power to the electrothermal converter is used, and the exhaust gas subjected to the dehumidification treatment is heated. It is configured to prevent white smoke.

  The waste heat recovery method of the present invention includes a dust collector that removes exhaust gas generated in an incinerator, an exhaust gas cleaner that cleans the exhaust gas treated by the dust collector, and an exhaust gas treated by the exhaust gas cleaner. A waste heat recovery method for an incineration plant comprising a dehumidifying device for performing a moisture treatment, comprising: an electrothermal conversion device that generates a temperature difference from a voltage as the dehumidifying device, and supplying electric power to the electrothermal conversion device The low-temperature heat source cooled by the exhaust gas cleaning device cools and dehumidifies the exhaust gas, and uses the heat of the high heat source heated by supplying electric power to the electrothermal conversion device. The treated exhaust gas is heated to prevent white smoke.

  In these inventions, as a dehumidifying device, an electrothermal conversion device that generates a temperature difference from a voltage is used, and when electric power is supplied to the electrothermal conversion device, the low heat source of the electrothermal conversion device is cooled, and the exhaust gas is exhausted by the low heat source. It becomes possible to cool and dehumidify the exhaust gas treated by the cleaning device.

  Moreover, outside air of about 20 ° C., for example, is supplied to a high heat source heated by supplying electric power to the electrothermal converter, and the outside air is heated by heat exchange. And it becomes possible to perform the white smoke prevention process of the waste gas discharged | emitted from the chimney etc. to air | atmosphere by heating the exhaust gas which carried out the dehumidification process with this heated external air.

  Further, the incineration plant of the present invention includes a first generator that generates electricity using the exhaust gas sent from the dust collector to the exhaust gas cleaning device as a high heat source, and the electric power generated by the first generator is It is desirable to be configured to supply to the electrothermal conversion device.

  In this invention, for example, an exhaust gas of about 200 ° C. sent from the dust collector to the exhaust gas cleaning device is used as a high heat source, water of about 20 ° C. is used as a low heat source, and a generator or ORC generator provided with a thermoelectric element is used. Can be used to generate electricity.

  Thereby, the heat | fever of the waste gas after processing with a dust collector can be collect | recovered and electric power generation can be performed. That is, it is possible to effectively use the heat of the exhaust gas after being treated by a dust collector that has been radiated. Then, by supplying the electric power generated by the first generator to the electrothermal conversion device, it is not necessary to provide a separate power source, and a more efficient waste heat recovery system can be constructed.

  Further, the incineration plant of the present invention includes a second generator that generates electricity using the washing water used in the exhaust gas cleaning device as a high heat source, and the electric power generated by the second generator is supplied to the electrothermal conversion device. More preferably, it is configured to supply.

  In the present invention, for example, washing water at about 70 ° C. can be used as a high heat source, water at about 20 ° C. can be used as a low heat source, and power can be generated using a generator or an ORC generator equipped with a thermoelectric element.

  Thereby, the heat of the cleaning water of the exhaust gas cleaning device can be recovered to generate power. That is, it is possible to effectively use the heat of the washing water that has been conventionally radiated. By supplying the electric power generated by the second generator to the electrothermal conversion device, it is not necessary to provide a separate power source, and it becomes possible to construct a more efficient waste heat recovery system.

  In the incineration plant and the waste heat recovery method of the present invention, an electrothermal converter that generates a temperature difference from a voltage is used as a dehumidifier, and when electric power is supplied to the electrothermal converter, the low heat source of the electrothermal converter is cooled. This low heat source makes it possible to cool and dehumidify the exhaust gas treated by the exhaust gas cleaning device.

  Moreover, outside air of about 20 ° C., for example, is supplied to a high heat source heated by supplying electric power to the electrothermal converter, and the outside air is heated by heat exchange. And it becomes possible to perform the white smoke prevention process of the waste gas discharged | emitted from the chimney etc. to air | atmosphere by heating the exhaust gas which carried out the dehumidification process with this heated external air.

This makes it possible to perform exhaust gas dehumidification treatment and white smoke prevention treatment by using an electrothermal conversion device, and is heated with the heat recovered by the white smoke prevention air preheater as in the past. It is unnecessary to perform the prevention process. For this reason, for example, the heat of white smoke prevention air at 300 ° C. (about 400 ° C.) (excellent energy obtained from the white smoke prevention air preheater) can be used for power generation, hot water replacement, and the like. .
Therefore, it becomes possible to improve the energy recovery efficiency as the whole incineration plant.

It is a figure which shows the waste gas processing equipment of the incineration plant which concerns on one Embodiment of this invention. It is a figure which shows the waste gas processing equipment of the incineration plant which concerns on one Embodiment of this invention. It is a figure which shows the waste gas treatment equipment of the conventional incineration plant.

  Hereinafter, with reference to FIG.1 and FIG.2, the incineration plant and waste heat recovery method which concern on one Embodiment of this invention are demonstrated.

  First, incineration plant A of this embodiment is a plant which incinerates sewage sludge, for example, as shown in Drawing 1 and Drawing 2, and processes exhaust gas G generated in an incinerator (not shown) and incinerator. The exhaust gas treatment equipment B for discharging the detoxified exhaust gas G into the atmosphere is provided.

  Further, the incineration plant A of the present embodiment includes a combustion air preheater (not shown) and a white smoke prevention air preheater (not shown), and a combustion air preheater, white gas from exhaust gas G generated in the incinerator. Heat is collected by the air preheater for smoke prevention, and the collected heat is sent to the incinerator to effectively use the retained heat of the combustion exhaust gas G in the incinerator. For example, the temperature of the exhaust gas G discharged from the incinerator is about 850 ° C., and the temperature is reduced to about 200 ° C. (˜250 ° C.) by processing with the combustion air preheater and the white smoke prevention air preheater. .

  Further, the exhaust gas treatment facility B includes an exhaust gas cooling tower, a dust collecting device 1 such as a bag filter, an exhaust gas cleaning tower (exhaust gas cleaning device) 2 such as a scrubber, a dehumidification tower (dehumidification device) 3 and the like. Yes.

  Then, the exhaust gas G recovered by the combustion air preheater and the white smoke prevention air preheater is cooled by the exhaust gas cooling tower and subjected to dust removal treatment by the dust collector 1. Further, the exhaust gas G after being processed by the dust collector 1 is alkali-treated by the exhaust gas cleaning tower 2 to remove harmful substances such as SOx, NOx, and HCl, and dehumidified by the dehumidifying tower 3.

Further, in the exhaust gas cleaning tower 2, the cleaning water W1 is supplied from above, the cleaning water W1 accumulated in the lower part is sent upward by the circulation pump 4, and the exhaust gas G is cleaned while circulating the cleaning water W1 in the circulation flow path. Further, the cleaning water W1 accumulated below the exhaust gas cleaning tower 2 evaporates by circulation and gradually decreases. For this reason, for example, cleaning water W1 such as sewage treatment water is replenished at any time at 40 m ³ / h. In addition, an overflow pipe 5 for controlling the amount of the wash water W1 accumulated below is attached, and the overflow wash water W1 is led to the tank 6 so that the overflow wash water W1 is further discharged from the tank 6 to the outside. It is configured.

  Here, for example, the exhaust gas G processed by the dust collector 1 and sent to the exhaust gas cleaning tower 2 has a temperature of about 200 ° C., and has been processed by the exhaust gas cleaning tower 2 with cleaning water W 1 of about 20 ° C. The temperature of the exhaust gas G is about 70 ° C.

  Further, in the exhaust gas cleaning tower 2, the temperature of the cleaning water W1 becomes about 70 ° C., and the cleaning processing is performed by circulating the cleaning water W1. Furthermore, a part of the washing water W1 is drained to the sewage treatment plant.

  On the other hand, in the exhaust gas treatment facility B of the incineration plant A of the present embodiment, as a dehumidifying device of the dehumidifying tower 3, for example, an electrothermal conversion device (such as a Peltier effect) that generates a temperature difference from a voltage of a thermoelectric element unit / thermoelectric element module or the like. The electrothermal conversion device 10) that generates a temperature difference is used.

  Specifically, for example, when the electrothermal conversion device 10 such as a thermoelectric element unit supplies power from a power source to a semiconductor element or the like, the pipe side on which the exhaust gas G treated in the exhaust gas cleaning tower 2 circulates, that is, the inner side (low heat source 10a). Lowers the temperature and cools the exhaust gas G. In this way, the low heat source 10a absorbs heat and cools the exhaust gas G, so that the exhaust gas temperature decreases from 70 ° C. to about 10 ° C.

And by absorbing heat from the exhaust gas G and reducing the exhaust gas temperature, moisture in the exhaust gas G is condensed to form water droplets, and the exhaust gas G is dehumidified.
In addition, by providing the electrothermal conversion device 10 in a vertical pipe, water droplets fall and are collected in the exhaust gas cleaning tower 2.

At this time, the outside (high heat source 10b) of the electrothermal conversion device 10 is heated. And in this embodiment, about 20 degreeC outside air M is supplied to the high heat source 10b side of the electrothermal conversion apparatus 10, and this outside air M is heated to about 80 degreeC by performing heat exchange. Further, the heated outside air M is sent as white smoke prevention air N to the exhaust gas G after dehumidification.
As a result, the white smoke is not recovered from the low-temperature exhaust gas G after being processed in the exhaust gas cleaning tower 2 without being heated with the heat recovered by the air preheater for preventing white smoke as in the prior art. Prevention processing can be performed.

  For this reason, in the exhaust gas treatment facility B of the incineration plant A of this embodiment, the heat of the white smoke prevention air P of about 300 ° C. sent from the conventional white smoke prevention air preheater is separately used for power generation, hot water replacement, etc. To do.

  Further, in the exhaust gas treatment facility B of the incineration plant A of the present embodiment, the heat of about 200 ° C. of the exhaust gas G sent from the dust collector 1 such as a bag filter to the exhaust gas cleaning tower 2 is recovered / utilized, and the thermoelectric element unit / Electric power is generated by a first generator 12 such as a thermoelectric element module, a binary power generation system, or an ORC power generation system (organic Rankine cycle power generation system).

  Specifically, in the present embodiment, the first generator 12 is provided in the exhaust gas supply pipe 11 that sends the exhaust gas G from the dust collector 1 to the exhaust gas cleaning tower 2. Furthermore, in this embodiment, the vertical pipe part 11a extended in an up-down direction is provided in the exhaust gas supply pipe 11, and the 1st generator 12 is provided in this vertical pipe part 11a.

  The first generator 12 is provided inside the exhaust gas supply pipe 11. At this time, the 1st generator 12 is comprised using the thermoelectric element unit / thermoelectric element module etc. which coat | covered the semiconductor element with the insulating layer which uses the ceramic etc. which have high corrosion resistance and thermal conductivity as a raw material, for example. . As a result, power generation / heat recovery can be reliably performed while preventing low-temperature corrosion due to sulfur in the exhaust gas G.

  Furthermore, in this embodiment, about 20 degreeC water W2, such as sewage treated water, is sent to the 1st generator 10 as a low heat source. Then, the exhaust gas G sent from the dust collector 1 to the exhaust gas cleaning tower 2 is used as a high heat source, sewage treated water is used as a low heat source, and power is generated by the Seebeck effect using the temperature difference between the low temperature water W2 and the high temperature exhaust gas G. Do.

  Further, in the exhaust gas treatment facility B of the incineration plant A of the present embodiment, as shown in FIG. 1, the heat of about 200 ° C. of the exhaust gas G sent from the dust collector 1 such as a bag filter to the exhaust gas cleaning tower 2 is recovered / It is configured to generate power using another first generator (electrothermal conversion device) 13 such as a thermoelectric element unit / thermoelectric element module, binary power generation system, ORC power generation system.

  Specifically, in the exhaust gas cleaning tower 2, a pipe (circulation flow path) that circulates by supplying the cleaning water W <b> 1 from below to the upper side by driving the circulation pump 4 is branched, and a part of the cleaning water W <b> 1 at about 70 ° C. is supplied. The exhaust gas G is sent from the dust collector 1 to the exhaust gas cleaning tower 2 to the heat exchanger 14 provided in the exhaust gas supply pipe 11, and the cleaning water W 1 is heated to about 90 ° C. by the heat of the exhaust gas G. At this time, in this embodiment, since the cleaning water W1 evaporates when the temperature is raised to 100 ° C. or higher, the heating temperature is suppressed to about 90 ° C.

  A heat exchanger 14 is provided inside the exhaust gas supply pipe 11, and a ceramic heat exchanger 14 having high corrosion resistance against sulfur in the exhaust gas G and high thermal conductivity is provided as the heat exchanger 14. It is desirable to use it. In addition, it is desirable to increase the heat exchange efficiency between the cleaning water W1 and the exhaust gas G, for example, by applying heat insulation coating to the piping that forms the circulation flow path of the cleaning water W1.

  Further, as described above, the cleaning water W1 heated at the heat exchanger 14 provided in the exhaust gas supply pipe 11 for sending the exhaust gas G from the dust collector 1 to the exhaust gas cleaning tower 2 is used as a thermoelectric element unit / thermoelectric element module or the like. Send to the first generator 13. Then, this washing water W1 is used as a high heat source, and water W4 of about 20 ° C. such as sewage treated water is sent as a low heat source to the first generator 13 to generate power by the Seebeck effect using these temperature differences. In addition, the washing water W1 lowered to about 40 ° C. by the first generator 13 is returned to the exhaust gas washing tower 2.

  Next, in the exhaust gas treatment facility B of the incineration plant A of the present embodiment, as shown in FIG. 2, the heat of about 70 ° C. of the cleaning water (overflowed cleaning water) W1 used in the exhaust gas cleaning tower 2 is recovered / The power is generated by the second generator 15 such as a thermoelectric element unit / thermoelectric element module, binary power generation system, or ORC power generation system.

  Moreover, in this embodiment, about 20 degreeC water W2, such as sewage treated water, is sent to the 2nd generator 15 as a low heat source. Then, the cleaning water W1 used in the exhaust gas cleaning tower 2 is used as a high heat source, the sewage treated water is used as a low heat source, and power is generated by the Seebeck effect using the temperature difference between the low temperature water W2 and the high temperature cleaning water W1.

  In the present embodiment, the electric power generated by the first generators 12 and 13 and the second generator 15 in this way is supplied to the electrothermal conversion device 10.

  Therefore, in the incineration plant A and the waste heat recovery method of the present embodiment, when the electrothermal conversion device 10 that generates a temperature difference from the voltage is used as the dehumidifying device and electric power is supplied to the electrothermal conversion device 10, the electrothermal conversion device. The ten low heat sources 10a are cooled, and the low heat source 10a allows the exhaust gas G processed in the exhaust gas cleaning tower 2 to be cooled and dehumidified.

  In addition, outside air M of about 20 ° C., for example, is supplied to the high heat source 10b heated by supplying electric power to the electrothermal converter 10, and the outside air M is heated by heat exchange. Then, by heating the dehumidified exhaust gas G with the heated outside air M, it is possible to perform a white smoke prevention process for the exhaust gas G released from the chimney or the like to the atmosphere.

  Further, a first generator such as a generator or an ORC generator provided with a thermoelectric element using an exhaust gas G of about 200 ° C. sent from the dust collector 1 to the exhaust gas cleaning tower 2 as a high heat source and water of about 20 ° C. as a low heat source. Electric power can be generated using the generators 12 and 13.

  Thereby, the heat | fever of the waste gas G after processing with the dust collector 1 can be collect | recovered, and electric power generation can be performed. That is, it is possible to effectively use the heat of the exhaust gas G after being processed by the dust collector 1 that has been radiated. By supplying the electric power generated by the first generators 12 and 13 to the electrothermal conversion device 10, it is not necessary to provide a separate power source, and a more efficient energy recovery system can be constructed.

  Furthermore, the washing water W1 at about 70 ° C. is used as a high heat source, the water W2 at about 20 ° C. is used as a low heat source, and power can be generated using the second generator 15 such as a generator equipped with a thermoelectric element or an ORC generator. it can.

  Thereby, the heat | fever of the washing water W1 of the exhaust gas washing tower 2 can be collect | recovered and electric power generation can be performed. That is, the heat of the washing water W1 that has been conventionally radiated can be effectively used. Then, by supplying the electric power generated by the second generator 15 to the electrothermal conversion device 10, it is not necessary to provide a separate power source, and a more efficient energy recovery system can be constructed.

Therefore, in the incineration plant A and the waste heat recovery method of the present embodiment, by using the electrothermal conversion device 10, it is possible to perform the dehumidification treatment of the exhaust gas G and the white smoke prevention treatment. It is unnecessary to perform the white smoke prevention treatment by heating with the heat recovered by the smoke prevention air preheater. For this reason, for example, the heat of white smoke prevention air at 300 ° C. (about 400 ° C.) (excellent energy obtained from the white smoke prevention air preheater) can be used for power generation, hot water replacement, and the like. .
Thereby, it becomes possible to improve the energy recovery efficiency of the incineration plant A as a whole.

  As mentioned above, although one embodiment of the incineration plant and waste heat recovery method concerning the present invention was described, the present invention is not limited to the above-mentioned one embodiment, and can be changed suitably in the range which does not deviate from the meaning. .

1 Dust collector 2 Exhaust gas cleaning tower (Exhaust gas cleaning device)
3 Dehumidification tower (dehumidification device)
4 Circulation pump 5 Overflow pipe 6 Tank 7 Bypass pipe 8 Piping 10 Electrothermal converter 10a Low heat source 10b High heat source 11 Exhaust gas supply pipe 11a Vertical pipe section 12 First generator 13 First generator 14 Heat exchanger 15 Second generator A Incineration plant B Exhaust gas treatment facility G Exhaust gas W1 Wash water W2 Water W3 Waste water W4 Water

Claims (4)

A dust collector for removing dust from the exhaust gas generated in the incinerator, an exhaust gas cleaning device for cleaning the exhaust gas processed by the dust collector, and a dehumidifier for dehumidifying the exhaust gas processed by the exhaust gas cleaner In an incineration plant
As the dehumidifier, an electrothermal converter that generates a temperature difference from voltage is provided,
A low heat source that is cooled by supplying electric power to the electrothermal converter, cools the exhaust gas treated by the exhaust gas cleaning device, dehumidifies it,
An incineration plant configured to use the heat of a high heat source that is heated by supplying electric power to the electrothermal converter, and to heat the dehumidified exhaust gas to prevent white smoke. . Incineration plant according to claim 1,
A first generator that generates power using the exhaust gas sent from the dust collector to the exhaust gas cleaning device as a high heat source;
An incineration plant configured to supply power generated by the first generator to the electrothermal converter. In the incineration plant according to claim 1 or claim 2,
A second generator for generating electricity using the washing water used in the exhaust gas cleaning device as a high heat source;
An incineration plant configured to supply power generated by the second generator to the electrothermal converter. A dust collector for removing dust from the exhaust gas generated in the incinerator, an exhaust gas cleaning device for cleaning the exhaust gas processed by the dust collector, and a dehumidifier for dehumidifying the exhaust gas processed by the exhaust gas cleaner A waste heat recovery method for an incineration plant,
As the dehumidifier, an electrothermal converter that generates a temperature difference from the voltage,
A low heat source that is cooled by supplying electric power to the electrothermal converter, cools the exhaust gas treated by the exhaust gas cleaning device, dehumidifies it,
A waste heat recovery method characterized in that heat from a high heat source heated by supplying electric power to the electrothermal converter is used to heat the dehumidified exhaust gas to prevent white smoke.

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