JP7671798B2 - Waste treatment equipment and waste treatment method - Google Patents

Description

The present invention relates to a waste treatment facility and a waste treatment method.

Some waste treatment facilities that incinerate waste are equipped with a heat exchanger that exchanges heat between exhaust gas and a heat transfer medium (see, for example, Patent Documents 1 and 2).

The pressurized fluidized furnace system disclosed in Patent Document 1 includes a pressurized fluidized furnace for burning materials to be treated, an air preheater for heating the combustion gas to be supplied to the pressurized fluidized furnace with the combustion exhaust gas discharged from the pressurized fluidized furnace, a dust collector for removing dust and the like in the combustion exhaust gas discharged from the pressurized fluidized furnace, a turbocharger driven by the combustion exhaust gas and supplying combustion air to the pressurized fluidized furnace, a white smoke prevention heat exchanger for heating the white smoke prevention air with the combustion exhaust gas supplied from the turbocharger, and an exhaust smoke treatment device for removing impurities in the combustion exhaust gas. The white smoke prevention heat exchanger raises the temperature of the white smoke prevention air and lowers the temperature of the combustion exhaust gas by indirectly exchanging heat between the combustion exhaust gas discharged from the turbocharger turbine and the white smoke prevention air supplied from the white smoke prevention blower.

The equipment disclosed in Patent Document 2 comprises a boiler or refuse incinerator (hereinafter referred to as "incinerator"), an air preheater, a high-temperature heat exchanger, a wet flue gas treatment device, and a low-temperature heat exchanger, which are connected in this order to a gas duct through which the combustion gas generated in the incinerator flows. The low-temperature heat exchanger and the high-temperature heat exchanger are connected by an air duct through which air supplied by a forced draft fan flows. The combustion gas passes through the gas duct and enters the high-temperature heat exchanger, where it exchanges heat with the air from the low-temperature heat exchanger. The combustion gas leaving the high-temperature heat exchanger is desulfurized or denitrified in the wet flue gas treatment device and is then led to the low-temperature heat exchanger.

JP 2019-15485 A Japanese Unexamined Patent Publication No. 52-74133

In a heat exchanger that exchanges heat between exhaust gas and a heat medium as disclosed in Patent Documents 1 and 2, there may be a portion where the temperature of the heat transfer surface between the exhaust gas and the heat medium is below the sulfuric acid dew point. In the portion where the temperature of the heat transfer surface of the heat exchanger is below the sulfuric acid dew point, sulfur trioxide and the like contained in the SOx in the exhaust gas condenses and adheres to the heat transfer surface of the heat exchanger. If this condensate adheres to the heat transfer surface of the heat exchanger, corrosion of the heat transfer surface of the heat exchanger becomes a problem. In particular, the exhaust gas generated when combusting combustible materials with unstable properties such as waste contains various components, so condensates of various components adhere to the heat transfer surface, causing corrosion of the heat transfer surface of the heat exchanger. This phenomenon is likely to occur in relatively low-temperature exhaust gas that flows downstream of the dust collector in the exhaust gas flow direction.

For these reasons, it is desirable to suppress corrosion of heat exchangers.

The waste treatment facility according to the present invention is characterized in that it comprises an incinerator for incinerating waste, a dust collector for collecting dust contained in the exhaust gas discharged from the incinerator, a smoke scrubber that is provided downstream of the dust collector in the exhaust gas flow direction of the exhaust gas and performs a smoke scrubbing process to purify the exhaust gas, and a low-temperature heat exchanger that is provided between the dust collector and the smoke scrubber and recovers heat from the exhaust gas by performing heat exchange between the exhaust gas and a heat exchange gas. The low-temperature heat exchanger has a plurality of partition members that separate a heat exchange gas passage through which the heat exchange gas flows and an exhaust gas passage through which the exhaust gas flows, and a cleaning device that cleans the partition members with a cleaning liquid, the cleaning device includes a plurality of nozzles, and the supply amount of the cleaning liquid supplied from the plurality of nozzles is set based on the temperature of the partition members.

According to this configuration, the condensate adhering to the partition member is removed by washing it with a cleaning liquid by the washing device. Since this washing device is incorporated in the waste treatment facility, it is possible to wash the partition member with the condensate adhering thereto during operation, and it is possible to prevent the condensate from adhering to the partition member for a long period of time. As a result, it is possible to suppress acid corrosion of the partition member.

In addition, one method of removing condensate adhering to the heat transfer surface is to wash the heat transfer surface, but if the amount of washing liquid is increased to more effectively remove condensate adhering to the heat transfer surface (to increase the washing effect on the heat transfer surface), the temperature of the heat transfer surface drops and the heat recovery rate of the exhaust gas drops. In other words, there is a trade-off between the washing effect on the heat transfer surface and the heat recovery rate of the exhaust gas. With this configuration, the amount of washing liquid supplied from the multiple nozzles is set based on the temperature of the partition member, so it is possible to balance the washing effect on the partition member and the heat recovery rate of the partition member (heat transfer surface).

Furthermore, according to this configuration, since the low-temperature heat exchanger is provided downstream of the dust collector in the flow direction of the exhaust gas, it is possible to recover the thermal energy of the exhaust gas at a lower temperature. This allows the heat of the exhaust gas to be recovered without waste, improving the heat recovery rate of the exhaust gas. Moreover, since the low-temperature heat exchanger performs gas-to-gas heat exchange between the exhaust gas and the heat exchange gas via the partition member, it is possible to increase the temperature of the clean heat exchange gas and use it for various purposes such as power generation. Therefore, it is possible to suppress corrosion of the heat transfer surface and suppress a decrease in the heat recovery rate of the exhaust gas.

As another feature, the supply amount may be set based on the temperature change of the partition member caused by the supply of the cleaning liquid.

With this configuration, the supply amount is set based on the temperature change of the partition member caused by the supply of cleaning liquid, so the temperature drop of the partition member is moderate, and a balance can be achieved between the heat recovery rate of the exhaust gas and the cleaning effect on the partition member.

Another feature is that the device includes a temperature acquisition unit that acquires the temperature of the partition member, and a control unit that controls the operation of the cleaning device, and the control unit may set the supply amount based on the temperature of the partition member acquired by the temperature acquisition unit.

According to this configuration, the control unit sets the supply amount based on the temperature of the partition member. Therefore, compared to when the supply amount is set by an operator, for example, the supply amount can be set according to the operating conditions, and a balance can be achieved between the heat recovery rate of the exhaust gas and the cleaning effect on the partition member.

As another feature, the temperature acquisition unit may acquire the temperature of the partition member based on at least one of the inlet temperature of the exhaust gas introduced into the low-temperature heat exchanger, the outlet temperature of the exhaust gas discharged from the low-temperature heat exchanger, the flow rate of the exhaust gas, the inlet temperature of the heat exchange gas introduced into the low-temperature heat exchanger, the outlet temperature of the heat exchange gas discharged from the low-temperature heat exchanger, and the flow rate of the white smoke prevention air.

According to this configuration, the temperature acquisition unit acquires the temperature of the partition member based on at least one of the inlet temperature of the exhaust gas introduced into the low-temperature heat exchanger, the outlet temperature of the exhaust gas discharged from the low-temperature heat exchanger, the flow rate of the exhaust gas, the inlet temperature of the heat exchange gas introduced into the low-temperature heat exchanger, the outlet temperature of the heat exchange gas discharged from the low-temperature heat exchanger, and the flow rate of the heat exchange gas, so that, for example, there is no need to provide a separate device for measuring the temperature of the partition member. Therefore, a balance can be achieved between the heat recovery rate of the exhaust gas and the cleaning effect on the partition member with a simple configuration.

As another feature, at least one of the inlet temperature of the exhaust gas, the outlet temperature of the exhaust gas, the flow rate of the exhaust gas, the inlet temperature of the heat exchange gas, the outlet temperature of the heat exchange gas, and the flow rate of the heat exchange gas may be an actual measured value.

According to this configuration, at least one of the exhaust gas inlet temperature, exhaust gas outlet temperature, exhaust gas flow rate, heat exchange gas inlet temperature, heat exchange gas outlet temperature, and heat exchange gas flow rate is an actual measurement value. In other words, the exhaust gas inlet temperature, exhaust gas outlet temperature, exhaust gas flow rate, heat exchange gas inlet temperature, heat exchange gas outlet temperature, and heat exchange gas flow rate other than the actual measurement value may be an approximate value. Therefore, for example, the number of devices for measuring temperature and flow rate can be reduced. Therefore, a balance between the heat recovery rate of the exhaust gas and the cleaning effect on the partition member can be achieved with a simple configuration.

As another feature, the device may further include a temperature adjustment unit that adjusts the temperature of the cleaning liquid, and the control unit may adjust the temperature of the cleaning liquid by controlling the operation of the temperature adjustment unit based on the temperature of the partition member.

With this configuration, the temperature of the cleaning liquid is adjusted, which prevents the cleaning liquid from taking heat from the partition member that comes into contact with the cleaning liquid, thereby preventing a decrease in the heat recovery rate of the exhaust gas.

As another feature, the cleaning device further includes a cleaning unit composed of a plurality of the nozzles, the cleaning unit includes a first cleaning unit and a second cleaning unit arranged at a position different from the first cleaning unit, and a first supply amount of the cleaning liquid supplied from the nozzles constituting the first cleaning unit to the partition member may be different from a second supply amount of the cleaning liquid supplied from the nozzles constituting the second cleaning unit to the partition member.

As described above, the region where the sulfuric acid components contained in the exhaust gas generated by burning waste with unstable properties can condense and the temperature can drop below the sulfuric acid dew point varies depending on the environment, etc. With this configuration, the cleaning conditions for the first cleaning unit and the second cleaning unit can be made different depending on the region where condensation is likely to adhere to the partition member (where the temperature can drop below the sulfuric acid dew point). This makes it possible to suppress acid corrosion of the partition member and suppress a decrease in the heat recovery rate of the exhaust gas.

As another feature, the waste may contain an ammonia component.

With this configuration, since the waste contains ammonia components, it is possible to lower the sulfuric acid dew point and suppress corrosion of the partition member caused by exhaust gas.

The waste treatment method according to the present invention is characterized in that it is a waste treatment method in a waste treatment facility equipped with an incinerator for incinerating waste, and includes a dust collection step for collecting dust contained in exhaust gas discharged from the incinerator, a heat recovery step for recovering heat from the exhaust gas by performing heat exchange between the collected exhaust gas and a heat exchange gas, and a smoke washing step for purifying the exhaust gas from which the heat has been recovered, and the heat recovery step includes a cleaning step for cleaning a plurality of partition members that separate a heat exchange gas passage through which the heat exchange gas flows and an exhaust gas passage through which the exhaust gas flows, by a cleaning device, and in the cleaning step, the amount of cleaning liquid supplied from a nozzle of the cleaning device is set based on the temperature of the partition members.

This method can achieve the same effects as the waste treatment facility described above.

As another feature, the waste may contain an ammonia component.

According to this method, since the waste contains ammonia components, it is possible to lower the sulfuric acid dew point and suppress acid corrosion of the partition members.

1 is a schematic diagram of a waste treatment facility according to an embodiment; FIG. 2 is a schematic diagram showing a configuration of a white smoke prevention reserve heat exchanger according to the embodiment. 5A and 5B are diagrams illustrating configurations of a heat exchange section and a cleaning section according to the embodiment. FIG. 4 is a perspective view showing a plate member according to the embodiment. FIG. 2 is a diagram showing a configuration of a cleaning unit according to the embodiment. FIG. 2 is a block diagram showing a configuration of a white smoke prevention reserve heat exchanger according to the embodiment. 5 is a flowchart showing a cleaning condition setting process performed by the control device according to the embodiment. 5 is a flowchart showing a supply amount adjustment process performed by a control device according to the embodiment. 5A to 5C are diagrams illustrating an erosion mechanism on a main surface of a plate member according to an embodiment. 13 is a diagram showing a configuration of a cleaning unit according to another embodiment. FIG. FIG. 11 is a block diagram showing a configuration of a white smoke prevention reserve heat exchanger according to another embodiment. 10 is a flowchart showing a temperature adjustment process performed by a control device according to another embodiment. FIG. 11 is a schematic diagram showing a configuration of a white smoke prevention reserve heat exchanger according to another embodiment. FIG. 13 is a diagram showing isotherms and a temperature sensor in a plate member according to another embodiment. FIG. 13 is a diagram showing isotherms and a temperature sensor in a plate member according to another embodiment. FIG. 11 is a diagram showing whether a parameter used in calculating a plate temperature according to the embodiment and another embodiment is an actual measured value or an estimated value.

The following describes an embodiment of a waste treatment facility and a waste treatment method equipped with a white smoke prevention spare heat exchanger as a low-temperature heat exchanger according to the present invention, with reference to the drawings. However, the present invention is not limited to the following embodiment, and various modifications are possible without departing from the spirit of the present invention.

[Outline of waste treatment facility]
As shown in FIG. 1 , the waste treatment facility 100 includes an incinerator 10, a combustion air supply device 20, a white smoke prevention main heat exchanger 30, a dust collection device 40, a white smoke prevention reserve heat exchanger 50 (an example of a low-temperature heat exchanger), a wet smoke washing device 60, and a power generation facility 70.

The waste treatment facility 100 further includes an exhaust gas passage R1 through which exhaust gas generated when the waste is burned in the incinerator 10 flows. The incinerator 10, the combustion air supply device 20, the white smoke prevention main heat exchanger 30, the dust collection device 40, the white smoke prevention reserve heat exchanger 50, the wet smoke washing device 60, and the chimney (not shown) are connected via the exhaust gas passage R1. Hereinafter, the flow direction of the exhaust gas flowing through the exhaust gas passage R1 is referred to as the "exhaust gas flow direction D1."

[Exhaust gas passage]
The incinerator 10 incinerates waste such as dehydrated sludge (for example, ammonia-containing waste such as dehydrated sludge obtained by dehydrating sewage sludge). Exhaust gas generated by burning the waste is discharged toward the combustion air supply device 20 via an exhaust gas passage R1. The exhaust gas contains chlorine compounds such as hydrogen chloride, and corrosive substances such as sulfur oxides. In this embodiment, the incinerator 10 is a fluidized bed incinerator. However, the incinerator 10 may be an incinerator other than a fluidized bed incinerator (for example, a stoker incinerator).

The combustion air supply device 20 supplies the incinerator 10 with combustion air that is used when burning waste in the incinerator 10. The combustion air supply device 20 is provided downstream of the incinerator 10 in the exhaust gas flow direction D1, and exhaust gas discharged from the incinerator 10 is introduced into the combustion air supply device 20.

The combustion air supply device 20 has a combustion air heat exchanger 21 and a turbocharger 22. The combustion air supply device 20 may have a fluidized bed blower instead of the turbocharger 22.

The combustion air heat exchanger 21 exchanges heat between the exhaust gas discharged from the incinerator 10 and the combustion air. This cools the exhaust gas and heats the combustion air. The combustion air heated by the combustion air supply device 20 is supplied to the incinerator 10 via the turbocharger 22.

The turbocharger 22 supplies compressed combustion air to the combustion air heat exchanger 21. The turbocharger 22 includes a turbine 221, a shaft 222, and a compressor 223. The turbine 221 rotates due to the pressure and thermal energy of the air heated by the combustion air heat exchanger 21. The shaft 222 transmits the rotational force of the turbine 221 to the compressor 223. The compressor 223 compresses the combustion air using the rotational force transmitted by the shaft 222. The combustion air compressed by the compressor 223 is introduced into the combustion air heat exchanger 21.

The white smoke prevention main heat exchanger 30 is provided downstream of the combustion air supply device 20 in the exhaust gas flow direction D1, and the exhaust gas after heat exchange in the combustion air supply device 20 is introduced into the white smoke prevention main heat exchanger 30. The white smoke prevention main heat exchanger 30 is a type of heat exchanger, and is a multi-tube heat exchanger or a plate heat exchanger.

The white smoke prevention main heat exchanger 30 is provided to prevent the exhaust gas discharged from the chimney from being cooled in the atmosphere and turning into white smoke. The white smoke prevention main heat exchanger 30 exchanges heat between the exhaust gas introduced from the combustion air supply device 20 and air (hereinafter referred to as "white smoke prevention air"). This cools the exhaust gas and heats the white smoke prevention air. The white smoke prevention air is introduced by being pushed out from a blower B further provided in the waste treatment facility 100. The path through which the white smoke prevention air flows (hereinafter referred to as "white smoke prevention air path R2") will be described later.

The dust collector 40 is provided downstream of the white smoke prevention main heat exchanger 30 in the exhaust gas flow direction D1, and the exhaust gas after heat exchange in the white smoke prevention main heat exchanger 30 is introduced into the dust collector 40. The dust collector 40 collects dust contained in the exhaust gas (dust collection step). In this embodiment, the dust collector 40 is composed of a bag filter. However, the dust collector 40 is not limited to being composed of a bag filter, and may be composed of a ceramic filter or the like.

The white smoke prevention reserve heat exchanger 50 is provided downstream of the dust collector 40 in the exhaust gas flow direction D1, and exhaust gas after dust collection by the dust collector 40 is introduced into the white smoke prevention reserve heat exchanger 50. The white smoke prevention reserve heat exchanger 50 is a type of heat exchanger, and in this embodiment is a plate-type heat exchanger. Because the white smoke prevention reserve heat exchanger 50 is a plate-type heat exchanger, heat exchange is performed over a wide heat transfer surface.

The white smoke prevention reserve heat exchanger 50 is provided to prevent the exhaust gas discharged from the chimney from being cooled in the atmosphere and turning into white smoke. Exhaust gas at a lower temperature than the exhaust gas introduced into the white smoke prevention main heat exchanger 30 is introduced into the white smoke prevention reserve heat exchanger 50. For this reason, the white smoke prevention reserve heat exchanger 50 is sometimes called the "low-temperature heat exchanger" and the white smoke prevention main heat exchanger 30 is sometimes called the "high-temperature heat exchanger."

The white smoke prevention reserve heat exchanger 50 uses the thermal energy of the introduced exhaust gas to heat the white smoke prevention air (an example of a heat exchange gas). In detail, the white smoke prevention reserve heat exchanger 50 exchanges heat between the exhaust gas introduced from the dust collector 40, i.e., the exhaust gas after dust has been removed, and the white smoke prevention air. This cools the exhaust gas (recovers the heat of the exhaust gas) and heats the white smoke prevention air (heat recovery step). The temperature of the exhaust gas introduced into the white smoke prevention reserve heat exchanger 50 is 160 degrees or more and 250 degrees or less. By performing heat exchange in the white smoke prevention reserve heat exchanger 50, the temperature of the exhaust gas is reduced to 50 degrees or more and 150 degrees or less.

The wet smoke scrubbing device 60 is provided downstream of the white smoke prevention reserve heat exchanger 50 in the exhaust gas flow direction D1, and the exhaust gas after heat exchange in the white smoke prevention reserve heat exchanger 50 is introduced into the wet smoke scrubbing device 60. The wet smoke scrubbing device 60 (an example of a smoke scrubbing device) performs a smoke scrubbing process to purify the exhaust gas (smoke scrubbing step). In this embodiment, the wet smoke scrubbing device 60 purifies the exhaust gas by the wet smoke scrubbing process and removes moisture in the exhaust gas by dehumidification and cooling. Circulating water containing a chemical agent is used to purify the exhaust gas. Cooling water is used to dehumidify and cool the exhaust gas. The amount of exhaust gas is reduced by removing moisture in the exhaust gas by dehumidification and cooling. The purified exhaust gas flows toward a chimney (not shown).

[White smoke prevention air path]
The waste treatment facility 100 further includes a white smoke prevention air passage R2 through which the white smoke prevention air flows. Hereinafter, the flow direction of the white smoke prevention air flowing through the white smoke prevention air passage R2 will be referred to as "air flow direction D2".

The white smoke prevention air path R2 connects the blower B, which sends out white smoke prevention air, the white smoke prevention reserve heat exchanger 50, the white smoke prevention main heat exchanger 30, the power generation equipment 70, and the chimney (not shown).

The white smoke prevention reserve heat exchanger 50 is provided downstream of the blower B in the air flow direction D2, and the white smoke prevention air sent out from the blower B is introduced into the white smoke prevention reserve heat exchanger 50. The temperature of the white smoke prevention air introduced into the white smoke prevention reserve heat exchanger 50 is the same as the outside air temperature, and is between 0 and 50 degrees. The temperature of the white smoke prevention air rises to between 50 and 220 degrees by exchanging heat with the exhaust gas.

The white smoke prevention main heat exchanger 30 is provided downstream of the white smoke prevention reserve heat exchanger 50 in the air flow direction D2, and the white smoke prevention air after heat exchange in the white smoke prevention reserve heat exchanger 50 is introduced into the white smoke prevention main heat exchanger 30. The temperature of the white smoke prevention air introduced into the white smoke prevention main heat exchanger 30 is 50 degrees or more and 220 degrees or less (for example, around 125 degrees). The temperature of the white smoke prevention air increases to 220 degrees or more and 550 degrees or less by performing heat exchange in the white smoke prevention main heat exchanger 30. It is preferable that the heat recovery amount of the white smoke prevention main heat exchanger 30 is configured to be equal to or greater than the heat recovery amount of the white smoke prevention reserve heat exchanger 50 (for example, 1 to 5 times).

The power generation equipment 70 is provided downstream of the white smoke prevention main heat exchanger 30 in the air flow direction D2, and the white smoke prevention air that has been heat exchanged (heated) in the white smoke prevention main heat exchanger 30 is introduced into the power generation equipment 70. The power generation equipment 70 generates electricity by using the thermal energy of the white smoke prevention air that has been heated in the white smoke prevention main heat exchanger 30.

The power generation facility 70 includes a hot water boiler 71, a circulation path 72, and a power generation device 73.

The hot water boiler 71 uses the thermal energy of the white smoke prevention air to heat water. The heated water (hot water) is introduced to the power generation device 73 via the circulation path 72.

The circulation path 72 connects the hot water boiler 71 and the power generation device 73, and circulates water between the hot water boiler 71 and the power generation device 73.

The power generation device 73 generates power using water (hot water) introduced from the hot water boiler 71 via the circulation path 72 as a heat source. After being used for power generation, the water is introduced into the hot water boiler 71 via the circulation path 72. In this embodiment, the power generation device 73 is a binary power generation device.

The white smoke prevention air from which thermal energy has been recovered in the hot water boiler 71 is introduced downstream of the wet smoke scrubbing device 60 in the exhaust gas passage R1 and merges with the exhaust gas discharged from the wet smoke scrubbing device 60. The temperature of the white smoke prevention air that merges with the exhaust gas is between 100°C and 200°C.

The exhaust gas discharged from the wet smoke scrubbing device 60 is heated by merging with the white smoke prevention air. The exhaust gas heated by the white smoke prevention air is discharged into the atmosphere from a chimney (not shown). As described above, the exhaust gas is cooled stepwise by the white smoke prevention main heat exchanger 30 and the white smoke prevention reserve heat exchanger 50, and is finally cooled by the wet smoke scrubbing device 60, and then heated by the white smoke prevention air that has passed through the power generation equipment 70 before being discharged from the chimney. The reduced moisture content of the exhaust gas before being discharged from the chimney and the increased temperature of the exhaust gas prevent the exhaust gas from turning into white smoke when discharged from the chimney.

[White smoke prevention spare heat exchanger]
2, the white smoke prevention preliminary heat exchanger 50 has a housing 51, a heat exchange unit 52, and a cleaning unit 53 (an example of a cleaning device). The heat exchange unit 52 and a part of the cleaning unit 53 are accommodated in the housing 51.

[Heat exchange section]
The heat exchange section 52 includes a heat exchange unit 521 that exchanges heat between the exhaust gas and the white smoke prevention air. The heat exchange unit 521 includes a plurality of plate members 522 (an example of a partition member).

[Plate member]
3, the plate member 522 separates a heat exchange exhaust gas passage R51 (an example of an exhaust gas passage) through which exhaust gas flows and a heat exchange air passage R52 (an example of a heat exchange gas passage) through which white smoke prevention air flows inside the white smoke prevention reserve heat exchanger 50. Inside the white smoke prevention reserve heat exchanger 50, a plurality of heat exchange exhaust gas passages R51 and a plurality of heat exchange air passages R52 are formed in parallel, and the heat exchange exhaust gas passages R51 and the heat exchange air passages R52 are provided alternately. The heat exchange exhaust gas passage R51 is the exhaust gas passage R1 inside the white smoke prevention reserve heat exchanger 50, and the heat exchange air passage R52 is the white smoke prevention air passage R2 inside the white smoke prevention reserve heat exchanger 50.

As shown in Figures 3 and 4, the plate member 522 is flat and has a main surface 522s. The multiple plate members 522 are spaced apart so that the main surfaces 522s are parallel to each other. In this embodiment, the main surfaces 522s are flat, but at least one of the main surfaces 522s may have minute irregularities such as grooves or protrusions.

The heat exchange exhaust gas passage R51 is formed between opposing plate members 522. As shown in FIG. 4, the heat exchange exhaust gas passage R51 is formed, for example, by joining one end 522e (hereinafter referred to as the "first end 522e") of the opposing plate members 522 by welding or the like. Note that the dashed dotted line shown in FIG. 4 indicates the welded portion. Hereinafter, the two plate members 522 opposing each other across the heat exchange exhaust gas passage R51 are referred to as a "pair of plate members 522t."

3, the heat exchange air passage R52 is formed between the adjacent heat exchange exhaust gas passages R51. As shown in FIG. 4, the heat exchange air passage R52 is formed by joining the second end 522f of the first joining plate 522A and the second joining plate 522B of the adjacent pair of plate members 522t. The second end 522f is an end in a direction perpendicular to the first end 522e of the plate member 522, and is formed between the adjacent first end 522e in a plan view (viewed in a direction along the main surface 522s). The first joining plate 522A is one plate member 522 of the pair of plate members 522t. The second joining plate 522B is a plate member 522 of the pair of plate members 522t adjacent to the first joining plate 522A that faces the first joining plate 522A through the heat exchange air passage R52.

When viewed from a direction perpendicular to the main surface 522s of the plate member 522, the heat exchange exhaust gas passage R51 and the heat exchange air passage R52 overlap with each other so as to sandwich the main surface 522s. Therefore, the main surface 522s of the plate member 522 functions as a heat transfer surface for heat exchange between the exhaust gas flowing through the heat exchange exhaust gas passage R51 and the white smoke prevention air flowing through the heat exchange air passage R52.

The plate member 522 can be made of a material selected from pure titanium, titanium alloy, stainless steel, nickel alloy, etc. Nickel alloys include, for example, Hastelloy (registered trademark) (Hastelloy C-22, Hastelloy C-276, Hastelloy C-4, Hastelloy C-22HS, Hastelloy C-2000, Hastelloy HYBRID-BC1, other Hastelloys), ALLOY (ALLOY 22, ALLOY C-276), Inconel (registered trademark) (Inconel 600, Inconel 625, Inconel 718), etc. Nickel alloys are suitable as materials for the plate member 522 because of their excellent resistance to acid corrosion.

[Cleaning section]
As shown in Fig. 3, the cleaning unit 53 cleans the plate member 522 with a cleaning liquid L1 (cleaning step). The cleaning liquid L1 is a liquid for removing deposits (condensate) attached to the plate member 522, and in this embodiment, is water (tap water, industrial water, sand filtration water, sewage treatment water, etc.). The cleaning liquid L1 may be an alkaline aqueous solution containing sodium hydroxide or the like. The cleaning unit 53 cleans the plate member 522 at a predetermined interval (preset frequency). This removes deposits attached to the plate member 522, and acid corrosion of the plate member 522 can be suppressed.

As shown in FIG. 5, the cleaning section 53 includes a first tank 531, a cleaning liquid supply section 532, and a cleaning unit 533.

As shown in FIG. 5, the first tank 531 stores cleaning liquid L1. The first tank 531 is provided outside the housing 51 (see FIG. 2).

The cleaning liquid supply unit 532 includes a first pump 532a and a cleaning liquid supply path 532b. The first pump 532a transfers the cleaning liquid L1 stored in the first tank 531. The cleaning liquid supply path 532b is connected to the cleaning unit 533, and the cleaning liquid L1 flowing through the cleaning liquid supply path 532b is supplied to the cleaning unit 533.

The cleaning unit 533 includes a nozzle pipe 535, a plurality of nozzles 536, and a control valve 537. The nozzle pipe 535 and the plurality of nozzles 536 are provided inside the housing 51, and the control valve 537 is provided outside the housing 51.

The nozzle pipe 535 is connected to the cleaning liquid supply path 532b via the control valve 537, and cleaning liquid L1 is supplied from the cleaning liquid supply path 532b.

As shown in FIG. 3, the nozzle pipe 535 extends in a direction perpendicular to the main surface 522s of the plate member 522, and multiple nozzles 536 are provided along the extension direction.

The nozzle 536 sprays the cleaning liquid L1. In this embodiment, the nozzle 536 sprays the cleaning liquid L1 at high pressure. However, the nozzle 536 may be a nozzle that sprays the cleaning liquid L1 at low pressure.

The control valve 537 controls the flow rate of the cleaning liquid L1 flowing through the nozzle pipe 535. The control valve 537 controls the amount of cleaning liquid L1 supplied from the nozzle 536 to the plate member 522 (hereinafter referred to as the "supply amount") by controlling the flow rate of the cleaning liquid L1 flowing through the nozzle pipe 535. In this embodiment, the control valve 537 is configured by combining a manual valve whose valve opening can be adjusted to a predetermined opening between fully open and fully closed, and an electromagnetic valve that switches ON (fully open)/OFF (fully closed) by timer operation.

The supply amount here is the amount of cleaning liquid L1 supplied to the heat exchange unit 521 per unit time (e.g., 24 hours) from the multiple nozzles 536 constituting the cleaning unit 533 corresponding to that heat exchange unit 521. Specifically, the supply amount is calculated based on a value obtained by multiplying the number of nozzles 536 constituting the cleaning unit 533, the amount of cleaning liquid L1 sprayed from one nozzle 536 at a time (L/piece), and the frequency at which the nozzles 536 spray the cleaning liquid L1 per unit time (e.g., 24 hours) (hereinafter referred to as the "spray frequency"). The spray amount (L/piece) is calculated by multiplying the amount of cleaning liquid L1 sprayed from one nozzle 536 per unit time (L/min.piece) by the spray time (min) of one nozzle 536.

The supply amount is set, for example, based on the total area (hereinafter referred to as the "total sulfuric acid condensation area") of the plate member 522 included in the sulfuric acid condensation area of the heat exchanger 52 (the area where the temperature of the heat transfer surface of the plate member 522 can be below the sulfuric acid dew point). The supply amount is set to be larger as the total sulfuric acid condensation area is larger, and set to be smaller as the total sulfuric acid condensation area is smaller. For example, if the total sulfuric acid condensation area is less than the threshold, the supply amount of the cleaning unit 533 is set to zero, and if the total sulfuric acid condensation area is equal to or greater than the threshold, the supply amount of the cleaning unit 533 is increased in proportion to the area. This makes it possible to balance the heat recovery rate of the exhaust gas and the cleaning effect on the plate member 522. Since the properties of waste are unstable, it is not easy to estimate the concentration of sulfuric acid components (e.g., sulfur trioxide) in the exhaust gas generated by burning waste compared to the exhaust gas generated by burning fossil fuels such as coal, and it is also not easy to estimate the total sulfuric acid condensation area of the plate member 522. For this reason, in this embodiment, an experimental heat exchanger may be installed in an existing waste treatment facility, and the total sulfuric acid condensation area of the plate member 522 may be calculated based on the experimental results. The total sulfuric acid condensation area and the supply amount may be previously associated based on, for example, the experimental results using the experimental heat exchanger, the results obtained from a trial run, etc.

The injection conditions (cleaning conditions) of injection frequency, injection amount, and injection time are set to obtain the set supply amount. In this embodiment, the injection conditions (supply amount) are set by a control device 55 further provided in the white smoke prevention reserve heat exchanger 50, as shown in FIG. 6. This allows the supply amount to be easily set.

The control device 55 controls the operation of the cleaning unit 53 (control valve 537). The control device 55 is composed of a processor such as a CPU (Central Processing Unit). The control device 55 also includes a storage area composed of a semiconductor memory such as a ROM (Read Only Memory). A control program for controlling the operation of the cleaning unit 53 is stored in the storage area. The control device 55 functions as a temperature acquisition unit 551, a supply amount setting unit 552, a condition setting unit 553, and a cleaning control unit 554 (an example of a control unit) by the processor executing the control program.

The temperature acquisition unit 551 acquires the plate temperature. Although the heat exchange unit 521 includes a plurality of plate members 522, the temperature acquisition unit 551 acquires the plate temperature assuming that the temperature change of the plurality of plate members 522 is uniform. The temperature acquisition unit 551 acquires the plate temperature based on the inlet temperature of the exhaust gas introduced into the white smoke prevention reserve heat exchanger 50, the outlet temperature of the exhaust gas discharged from the white smoke prevention reserve heat exchanger 50, the inlet temperature of the white smoke prevention air introduced into the white smoke prevention reserve heat exchanger 50, the outlet temperature of the white smoke prevention air discharged from the white smoke prevention reserve heat exchanger 50, the flow rate of the exhaust gas, and the flow rate of the white smoke prevention air. This eliminates the need to provide a separate device for measuring the temperature of the plate member 522, and allows for a simple configuration to balance the heat recovery rate of the exhaust gas and the cleaning effect on the plate member 522. In this embodiment, the actual measured values are used for the exhaust gas inlet temperature, exhaust gas outlet temperature, white smoke prevention air inlet temperature, white smoke prevention air outlet temperature, exhaust gas flow rate, and white smoke prevention air flow rate.

The temperature of the exhaust gas and the temperature of the white smoke prevention air are obtained based on information output from a temperature sensor S further provided in the white smoke prevention reserve heat exchanger 50. The temperature sensor S is, for example, a thermocouple, a resistance temperature detector, etc. The temperature sensor S obtains the temperature of the object to be measured and outputs information indicating the temperature.

The temperature sensors S include a first temperature sensor S1, a second temperature sensor S2, a third temperature sensor S3, and a fourth temperature sensor S4. The first temperature sensor S1 is inserted into a duct (not shown) connected to the inlet 50a through which the exhaust gas shown in FIG. 2 is introduced, and measures the center of the exhaust gas flow in the duct. Similarly, the second temperature sensor S2 is inserted into a duct connected to the outlet 50b through which the exhaust gas is discharged, the third temperature sensor S3 is inserted into a duct connected to the inlet 50c through which the white smoke prevention air is introduced, and the fourth temperature sensor S4 is inserted into a duct connected to the outlet 50d through which the white smoke prevention air is discharged, and measures the center of the exhaust gas flow in those ducts.

The flow rates of the exhaust gas and the white smoke prevention air are obtained based on information output from a flow meter F further provided in the white smoke prevention reserve heat exchanger 50. The flow meter F includes a first flow meter F1 and a second flow meter F2. The first flow meter F1 is provided, for example, inside a duct connected to the inlet 50a through which the exhaust gas is introduced. The second flow meter F2 is provided, for example, inside a duct connected to the outlet through which the white smoke prevention air is discharged from the power generation equipment 70. The positions at which the first flow meter F1 and the second flow meter F2 are provided can be changed as desired.

6 acquires the inlet temperature of the exhaust gas acquired by the first temperature sensor S1 and the outlet temperature of the exhaust gas acquired by the second temperature sensor S2. Similarly, the temperature acquisition unit 551 acquires the inlet temperature of the white smoke prevention air acquired by the third temperature sensor S3 and the outlet temperature of the white smoke prevention air acquired by the fourth temperature sensor S4. Furthermore, the temperature acquisition unit 551 acquires the flow rate of the exhaust gas acquired by the first flow meter F1 and the flow rate of the white smoke prevention air acquired by the second flow meter F2. The temperature acquisition unit 551 calculates the plate temperature based on the acquired inlet temperature and outlet temperature of the exhaust gas, the inlet temperature and outlet temperature of the white smoke prevention air, the flow rate of the exhaust gas, and the flow rate of the white smoke prevention air. For example, if the exhaust gas inlet temperature is 200 degrees, the exhaust gas outlet temperature is 100 degrees, the white smoke prevention air inlet temperature is 20 degrees, and the white smoke prevention air outlet temperature is 125 degrees, the temperature acquisition unit 551 estimates that the temperature of the plate member 522 changes roughly linearly in the range of 160 degrees to 60 degrees along the exhaust gas flow direction, taking into account the amount of heat transfer, and calculates the plate temperature.

The supply amount setting unit 552 sets the supply amount of cleaning liquid L1 based on the plate temperature acquired by the temperature acquisition unit 551. In this embodiment, the supply amount setting unit 552 sets the supply amount based on the total sulfuric acid condensation area of the plate. Note that association information between the total sulfuric acid condensation area and the supply amount is stored in advance in the memory area of the control device 55. The supply amount setting unit 552 sets the supply amount of cleaning liquid L1 by referring to the association information between the total sulfuric acid condensation area and the supply amount stored in the memory area.

The supply amount setting unit 552 adjusts the supply amount based on the change (decrease) in the plate temperature caused by the supply of the cleaning liquid L1. For example, if the temperature drop of the plate member 522 caused by one injection from the nozzle 536 is equal to or higher than the first temperature drop threshold, the supply amount is set to a value smaller than the set supply amount (the supply amount is reduced). On the other hand, if the temperature drop of the plate member 522 caused by one injection from the nozzle 536 is equal to or higher than the second temperature drop threshold and lower than the first temperature drop threshold, the supply amount is set to the same value as the set supply amount (the supply amount is maintained). Furthermore, if the temperature drop of the plate member 522 caused by one injection from the nozzle 536 is lower than the second temperature drop threshold, the supply amount is set to a value larger than the set supply amount (the supply amount is increased). This makes it possible to suppress the temperature drop of the plate member 522 and suppress the decrease in the heat recovery rate of the exhaust gas. The first temperature drop threshold is a value larger than the second temperature drop threshold. Furthermore, information indicating the first temperature drop threshold and information indicating the second temperature drop threshold are stored in advance in the memory area of the control device 55.

The condition setting unit 553 sets the spray conditions (spray amount, spray time, and spray frequency) of the nozzle 536 so that the set supply amount of cleaning liquid L1 is supplied to the plate member 522.

The cleaning control unit 554 controls the operation of the control valve 537. More specifically, the cleaning control unit 554 controls the operation (opening frequency, opening time, and valve opening) of the control valve 537 so that the injection frequency, injection time, and injection amount set by the condition setting unit 553 are achieved. The cleaning control unit 554 also controls the operation of the first pump 532a. As a result, the cleaning liquid L1 is injected from the nozzle 536 so as to achieve the set supply amount.

The cleaning condition setting process executed by the control device 55 will be described below with reference to FIG. 7. The cleaning condition setting process is started when the control device 55 receives a signal from an input device (not shown) such as an input button or touch sensor by an operator such as a worker or driver when the waste treatment facility 100 starts operating and then reaches steady operation (for example, the exhaust gas introduction temperature acquired by the first temperature sensor S1 is 200 degrees or higher). Before the cleaning condition setting process is started, information required to set the supply amount (information indicating the experimental results using an experimental heat exchanger, etc.) is input in advance to the control device 55 by an input device (not shown).

As shown in FIG. 7, the temperature acquisition unit 551 acquires the plate temperature (step S102). In this embodiment, the temperature acquisition unit 551 determines the plate temperature based on the information output from the temperature sensor S. The temperature acquisition unit 551 stores information indicating the plate temperature in the memory area of the control device 55.

Next, the supply amount setting unit 552 sets the supply amount of cleaning liquid L1 based on the plate temperature obtained by the temperature acquisition unit 551 (step S104). In detail, the supply amount setting unit 552 obtains the total sulfuric acid condensation area based on the information indicating the plate temperature obtained by the temperature acquisition unit 551 and stored in the memory area of the control device 55, and sets the supply amount corresponding to the total sulfuric acid condensation area based on the association information as the supply amount of cleaning liquid L1 supplied from the nozzle 536. The total sulfuric acid condensation area can be obtained from the plate temperature obtained by the temperature acquisition unit 551.

Next, the condition setting unit 553 sets the spray conditions (spray amount, spray time, and spray frequency) of the nozzle 536 so that the set supply amount of cleaning liquid L1 is supplied to the plate member 522 (step S106), and the cleaning control unit 554 controls the operation of the control valve 537 (cleaning unit 53) (step S108), and the cleaning process is performed under the set spray conditions.

Next, the supply amount setting unit 552 determines whether the cleaning process has been performed (whether the cleaning liquid L1 has been sprayed from the nozzle 536) (step S110). If the supply amount setting unit 552 determines that the cleaning process has not been performed (step S110; No), the process proceeds to step S114.

On the other hand, if the supply amount setting unit 552 determines that the cleaning process has been performed (step S110; Yes), it executes the supply amount adjustment process shown in FIG. 8 (step S112).

In the supply amount adjustment process shown in FIG. 8, the supply amount setting unit 552 determines whether the drop in temperature of the plate member 522 due to a single spray from the nozzle 536 is equal to or greater than a first drop temperature threshold (e.g., any value between 10 degrees and 30 degrees) (step S202).

When the supply amount setting unit 552 determines that the temperature drop of the plate member 522 is equal to or greater than the first drop temperature threshold (step S202; Yes), it sets the supply amount to a value smaller than the set supply amount (step S204) and terminates the supply amount adjustment process.

On the other hand, when the supply amount setting unit 552 determines that the decreased temperature of the plate member 522 is less than the first decreased temperature threshold (step S202; No), it determines whether the decreased temperature of the plate member 522 is equal to or greater than a second decreased temperature threshold (e.g., any value between 1 degree and 5 degrees) that is smaller than the first decreased temperature threshold (step S206).

When the supply amount setting unit 552 determines that the temperature drop of the plate member 522 is less than the second drop temperature threshold (step S206; No), it sets the supply amount to a value greater than the set supply amount (step S208) and terminates the supply amount adjustment process.

On the other hand, if the supply amount setting unit 552 determines that the temperature drop of the plate member 522 is equal to or greater than the second drop temperature threshold (step S206; Yes), it ends the supply amount adjustment process without changing the set supply amount value. When the supply amount adjustment process ends, the process returns to the cleaning condition setting process shown in FIG. 7, and the process of step S114 is executed.

In step S114, the control device 55 repeats the processes from step S102 to step S114 until it receives a signal from the input device (not shown) input by the operator instructing the end of the cleaning condition setting process (step S114; No). On the other hand, when the control device 55 receives a signal from the input device (not shown) instructing the end of the cleaning condition setting process (step S114; Yes), it ends the cleaning condition setting process. Note that the cleaning condition setting process is not limited to the order described above. For example, the step of determining whether the cleaning process has been performed (step S110) and the step of performing the supply amount adjustment process (step S112) may be performed before the step of setting the spray conditions (step S106). In this case, it is possible to set the spray conditions after performing a trial cleaning once.

[Effects of the embodiment]
As described above, according to this embodiment, since the white smoke prevention reserve heat exchanger 50 is provided downstream of the dust collector 40 in the exhaust gas flow direction D1, it is possible to recover thermal energy from lower temperature exhaust gas. As a result, it is possible to recover heat from the exhaust gas without waste, and the heat recovery rate of the exhaust gas is improved. Moreover, since the white smoke prevention reserve heat exchanger 50 performs gas-to-gas heat exchange between the exhaust gas and the white smoke prevention air via the plate member 522, it is possible to increase the temperature of the clean white smoke prevention air and use it for various purposes such as power generation.

The concentration of sulfuric acid components (sulfur trioxide) contained in exhaust gas generated by burning coal (fossil fuel) such as coal boilers is higher than the concentration of sulfuric acid components (sulfur trioxide) contained in exhaust gas generated by burning waste. On the other hand, the concentration of sulfuric acid components in exhaust gas generated by burning waste is lower than that of exhaust gas from fossil fuels, and the effect of acid corrosion is less of a problem in heat exchangers conventionally installed in waste treatment facilities compared to the case of fossil fuels. However, in this embodiment, it has been found that there is an area in the white smoke prevention reserve heat exchanger 50 where condensate of sulfuric acid components contained in exhaust gas is likely to adhere to the partition member due to a decrease in temperature of the heat transfer surface (the temperature of the heat transfer surface of the partition member may be below the sulfuric acid dew point), and it is possible to remove the condensate by washing with the washing liquid L1 by the washing unit 53. Since this washing unit 53 is incorporated in the waste treatment facility 100, it is possible to wash the plate member 522 to which the condensate has adhered during operation, and it is possible to prevent the condensate from continuing to adhere to the plate member 522 for a long time. As a result, it is possible to suppress acid corrosion of the plate member 522.

In addition, the amount of cleaning liquid L1 supplied from the multiple nozzles 536 is set based on the temperature of the plate member 522, so it is possible to balance the cleaning effect of the plate member 522 and the heat recovery rate of the plate member 522 (heat transfer surface). Therefore, it is possible to suppress a decrease in the heat recovery rate of the exhaust gas.

In addition, in the case where the waste is ammonia-containing waste such as dehydrated sludge obtained by dehydrating sewage sludge, ammonia derived from the waste still exists without adding NH ₃ (ammonia) to the exhaust gas flowing through the white smoke prevention preliminary heat exchanger 50, and as shown in FIG. 9, SOx in the exhaust gas reacts with NH ₃ on the main surface 522s (heat transfer surface) of the plate member 522 and in the vicinity thereof, and SOx changes to (NH ₄ ) ₂ SO ₄ (ammonium sulfate), which is relatively less corrosive than SOx. In addition, HCl (hydrochloric acid) in the exhaust gas reacts with NH ₃ and changes to NH ₄ Cl (ammonium chloride). FIG. 9 is a diagram showing a schematic diagram of the erosion mechanism when the main surface 522s (heat transfer surface) of the plate member 522 is not washed. The vertical axis shown in Fig. 9 indicates the temperature of the main surface 522s (heat transfer surface) of the plate member 522, and the horizontal axis indicates the relative amount of products generated near the main surface 522s of the plate member 522. The temperature is lower on the vertical axis. From the left in Fig. 9, the _black ink hatching indicates the relative amount of _Fe2O3 (iron oxide (III)), the left-leaning hatching indicates the relative amount of _NH4Cl , the right-leaning hatching indicates the relative amount _{of (NH4)2SO4 , and} the light ink hatching indicates the relative amount of _H2O . As shown in Fig. 9, _Fe2O3 and ( _NH4 ) _{2SO4 are} less _susceptible to acid corrosion of the plate member 522 than sulfuric acid, and also have the effect of reducing the sulfuric acid concentration, so that the durability of the plate member 522 can be improved. In particular, it has been found that below the sulfuric acid dew point Ts, sulfuric acid starts to condense and reacts with NH ₃ depending on the amount of condensed water to change to (NH ₄ ) ₂ SO _4. According to these findings, when the waste is ammonia-containing waste such as sewage sludge, even near the sulfuric acid dew point Ts where the amount of condensed water is small and the sulfuric acid concentration is likely to increase, the generation of (NH ₄ ) ₂ SO ₄ instead of sulfuric acid becomes dominant, making it possible to lower the sulfuric acid concentration below the sulfuric acid dew point Ts. As a result, the acid corrosion of the plate member 522 can be suppressed by cleaning with the cleaning liquid L1 sprayed from the nozzle 536 described above. In addition, although the pH of NH ₄ Cl increases when dissolved in water, the adhesion of the NH ₄ Cl aqueous solution can be prevented by cleaning with the cleaning liquid L1 sprayed from the nozzle 536. It has also been confirmed that if the plate member 522 is not washed with the cleaning liquid L1, solid substances mainly composed of Fe ₂ O ₃ adhere to the entire main surface 522s of the plate member 522, so cleaning with the cleaning liquid L1 is also effective from the viewpoint of preventing rust.

[Another embodiment]
The present invention may be configured as follows other than the above-described embodiment (common numbers and symbols as in the embodiment are used to designate components having the same functions as in the embodiment).

(1) For example, as shown in FIG. 10 and FIG. 11, the cleaning unit 533 may further include a heating section 538 (an example of a temperature adjustment section). The heating section 538 is provided outside the housing 51. The cleaning control section 554 may adjust the temperature of the cleaning liquid L1 by controlling the operation of the heating section 538 based on the plate temperature. This prevents the heat of the plate member 522 in contact with the cleaning liquid L1 from being taken away by the cleaning liquid L1, and prevents a decrease in the heat recovery rate of the exhaust gas.

The heating unit 538 is provided to adjust (heat) the temperature of the cleaning liquid L1. The heating unit 538 is, for example, a heater, and heats the cleaning liquid L1. In detail, as shown in FIG. 10, the heating unit 538 is provided upstream of the multiple nozzles 536 in the flow direction of the cleaning liquid L1 flowing through the nozzle pipe 535, and heats the cleaning liquid L1 flowing through the nozzle pipe 535. Note that the heating unit 538 is disposed downstream of the control valve 537 in the flow direction of the cleaning liquid L1, but the heating unit 538 may be disposed upstream of the control valve 537.

When the cleaning control unit 554 acquires the plate temperature in a predetermined area (e.g., an area downstream of the exhaust gas flow direction D1), it executes the temperature adjustment process shown in FIG. 12. Note that the cleaning condition setting process described with reference to FIG. 7 and the temperature adjustment process may be executed at the same timing, or may be executed at different timings.

As shown in FIG. 12, the cleaning control unit 554 determines whether the plate temperature is less than a preset first heating threshold (e.g., the plate temperature on the exhaust gas outlet 50b side is 50 degrees) (step S302).

If the plate temperature is less than the first heating threshold (step S302; Yes), the cleaning control unit 554 controls the heating unit 538 (step S304) so that the heating unit 538 is turned ON. In particular, if the heating unit 538 is in the OFF state, the cleaning control unit 554 transitions it to the ON state. Note that if the heating unit 538 is in the ON state, it is maintained in the ON state. Next, the temperature adjustment process proceeds to step S310.

On the other hand, if the plate temperature is equal to or higher than the first heating threshold (step S302; No), the cleaning control unit 554 determines whether the plate temperature is lower than a preset second heating threshold (for example, the plate temperature on the exhaust gas outlet 50b side is 60 degrees) (step S306). The second heating threshold is set to a value greater than the first heating threshold. Information indicating the first heating threshold and the second heating threshold (set temperature range) is stored in advance in the memory area of the control device 55.

If the plate temperature is less than the second heating threshold (step S306; Yes), the cleaning control unit 554 does not control the operation of the heating unit 538, and the cleaning condition setting process proceeds to step S310.

On the other hand, when the cleaning control unit 554 determines that the plate temperature is equal to or higher than the preset second heating threshold (step S306; No), it controls the heating unit 538 so that the heating unit 538 is in the OFF state (step S308), and proceeds to step S310. In more detail, if the heating unit 538 is in the ON state, the cleaning control unit 554 transitions it to the OFF state. Note that if the heating unit 538 is in the OFF state, it is maintained in the OFF state.

In step S310, the control device 55 repeats the processes from step S302 to step S310 until it receives a signal from an input device (not shown) input by an operator, for example, instructing the end of the temperature adjustment process (step S310; No). On the other hand, when the control device 55 receives a signal from the input device (not shown) instructing the end of the cleaning condition setting process (step S310; Yes), it ends the heating adjustment process.

The above process prevents the heat of the plate member 522 in contact with the cleaning liquid L1 from being taken away by the cleaning liquid L1, thereby preventing a decrease in the heat recovery rate of the exhaust gas.

(2) In the present embodiment, the white smoke prevention reserve heat exchanger 50 is a cross-flow plate-type heat exchanger. However, the white smoke prevention reserve heat exchanger 50 may be a counterflow, parallel flow, or other plate-type heat exchanger. In addition, the exhaust gas inlet 50a, exhaust gas outlet 50b, white smoke prevention air inlet 50c, and white smoke prevention air outlet 50d (see FIG. 2) in the white smoke prevention reserve heat exchanger 50 are not limited to those described in the embodiment and can be changed as appropriate. In this case, the flow direction of the exhaust gas and white smoke prevention air in the white smoke prevention reserve heat exchanger 50 can be changed as appropriate.

(3) In this embodiment, the case where there is one white smoke prevention main heat exchanger 30 has been described, but there may be multiple white smoke prevention main heat exchangers 30.

(4) In this embodiment, the white smoke prevention main heat exchanger 30 and the white smoke prevention reserve heat exchanger 50 are configured to heat the white smoke prevention air to prevent white smoke. However, the white smoke prevention main heat exchanger 30 and the white smoke prevention reserve heat exchanger 50 may be heat exchangers provided simply to recover heat from exhaust gas.

(5) In this embodiment, the dust collector 40 is provided downstream of the white smoke prevention main heat exchanger 30 in the exhaust gas flow direction D1, but the dust collector 40 may be provided upstream of the white smoke prevention main heat exchanger 30 in the exhaust gas flow direction D1.

(6) In this embodiment, the power generation equipment 70 includes a hot water boiler 71, a circulation path 72, and a power generation device 73. However, the power generation equipment 70 may also include a steam boiler, a water supply pump, a water supply tank, etc.

(7) In the present embodiment, the cleaning unit 533 is described as being one, but the cleaning unit 533 may be two or more. For example, as shown in FIG. 13, the cleaning unit 533 may include a first cleaning unit 533a and a second cleaning unit 533b provided at a position different from the first cleaning unit 533a. In the example shown in FIG. 13, the heat exchange section 52 includes a first heat exchange unit 521a and a second heat exchange unit 521b arranged downstream of the first heat exchange unit 521a in the exhaust gas flow direction D1, and the first cleaning unit 533a is provided corresponding to the first heat exchange unit 521a to clean the first heat exchange unit 521a, and the second cleaning unit 533b is provided corresponding to the second heat exchange unit 521b to clean the second heat exchange unit 521b. In the second heat exchange unit 521b, the total area (total sulfuric acid condensation area) of the part included in the region where the temperature of the heat transfer surface (main surface 522s) of the plate member 522 is equal to or lower than the sulfuric acid dew point is larger than the total sulfuric acid condensation area of the plate member 522 included in the first heat exchange unit 521a. Therefore, the supply amount (hereinafter referred to as the "first supply amount") of the cleaning liquid L1 sprayed from the nozzle 536 (hereinafter referred to as the "first nozzle 536a") constituting the first cleaning unit 533a to the plate member 522 (hereinafter referred to as the "first plate member 522a") is different from the supply amount (hereinafter referred to as the "second supply amount") of the cleaning liquid L1 sprayed from the nozzle 536 (hereinafter referred to as the "second nozzle 536b") constituting the second cleaning unit 533b to the plate member 522 (hereinafter referred to as the "second plate member 522b"), and the second supply amount may be set to be larger than the first supply amount. However, the deposits of the exhaust gas generated by burning sewage sludge among waste materials are mainly ammonium sulfate, which is less soluble in water than the deposits of the exhaust gas generated by burning fossil fuels (ammonium hydrogen sulfate). For this reason, the amount of cleaning liquid L1 supplied to the first heat exchange unit 521a including the area where ammonium sulfate is likely to adhere (130 degrees or more and 250 degrees or less) may be greater than the amount supplied to the second heat exchange unit 521b including the area where ammonium sulfate is unlikely to adhere. This makes it possible to reliably remove the deposits attached to the heat transfer surface and suppress blockage of the heat exchange air passage R52. In addition, when there are two or more cleaning units 533, the heating unit 538 may be provided for each cleaning unit 533, or only one may be provided to heat the first tank 531 of the cleaning unit 53.

(8) The number of nozzle pipes 535 included in the cleaning unit 533 can be changed as desired. In addition, the number of nozzles 536 provided on the nozzle pipes 535 can also be changed as desired. In addition, the number of nozzle pipes 535 connected to one control valve 537 can also be changed as desired.

(9) In this embodiment, the cleaning unit 53 includes the first tank 531, but the cleaning unit 53 can omit the first tank 531. In this case, tap water, industrial water, sand filtration water, sewage treatment water, etc. are supplied to the nozzle 536. Also, although the control valve 537 is a combination of a manual valve and a solenoid valve, the control valve 537 may be any valve whose valve opening degree can be controlled.

(10) In this embodiment, the heating unit 538 is a heater. However, the heating unit 538 is not limited to a heater as long as it can adjust the temperature of the cleaning liquid L1. In addition, the heating unit 538 may have a function other than heating the cleaning liquid L1, such as a heat exchanger, for example, a cooling function.

(11) In this embodiment, the case where the spray conditions (cleaning conditions) of the nozzle 536 are set by the control device 55 has been described, but the spray conditions may be set manually. For example, in a periodic inspection that is performed periodically, such as once a year or every six months, an engineer may set the spray conditions of the nozzle 536 based on the degree of corrosion of the plate member 522, etc. Note that the spray conditions are not limited to being set by an engineer, and may also be set by an operator, a worker, or the like.

(12) In this embodiment, the temperature acquisition unit 551 acquires the plate temperature based on the inlet temperature of the exhaust gas introduced into the white smoke prevention reserve heat exchanger 50, the exhaust temperature of the exhaust gas discharged from the white smoke prevention reserve heat exchanger 50, the inlet temperature of the white smoke prevention air introduced into the white smoke prevention reserve heat exchanger 50, the exhaust temperature of the white smoke prevention air discharged from the white smoke prevention reserve heat exchanger 50, the flow rate of the exhaust gas, and the flow rate of the white smoke prevention air. However, the method in which the temperature acquisition unit 551 acquires the plate temperature is not limited to this. For example, as shown in FIG. 14 and FIG. 15, the white smoke prevention reserve heat exchanger 50 further includes a temperature sensor 54 for acquiring the temperature of the plate member 522. The temperature sensor 54 is provided on a plate member 522 that is previously set from among the multiple plate members 522, and outputs information indicating the temperature of the plate member 522. The temperature acquisition unit 551 may acquire the plate temperature based on the information output from the temperature sensor 54. FIG. 14 is a diagram showing the isotherm T1 and the temperature sensor 54 in the plate member 522, and FIG. 15 is a diagram showing the isotherm T1 and the temperature sensor 54 in a configuration in which the position of the white smoke prevention air inlet 50c is different from that in FIG. 14. In the example shown in FIG. 14 and FIG. 15, two temperature sensors 54 are provided on one plate member 522. The number of temperature sensors 54 is not limited to two, and may be one or three or more. When there are two or more temperature sensors 54, the multiple temperature sensors 54 may be provided on one plate member 522, or may be provided on different plate members 522. The more temperature sensors 54 are provided on one plate member 522, the higher the accuracy. The temperature acquisition unit 551 acquires the maximum value, the minimum value, or the average value of the temperatures of the multiple plate members 522 acquired by the multiple temperature sensors 54 as the plate temperature.

The temperature sensor 54 is a thermocouple, a resistance temperature detector, or the like. The temperature sensor 54 is provided on the main surface 522s of the plate member 522 on the heat exchange air passage R52 side. As shown in FIG. 14 and FIG. 15, the cable Ca connecting each of the temperature sensors 54 and the control device 55 connects the temperature sensor 54 and the control device 55 via, for example, a duct Da through which the white smoke prevention air flows. The cable Ca may connect the temperature sensor 54 and the control device 55 via the outside of the housing 51 without via a duct. In this embodiment, the duct Da includes a first duct Da1 connected to an inlet 50c through which the white smoke prevention air is introduced into the white smoke prevention reserve heat exchanger 50 and a second duct Da2 connected to an outlet 50d through which the white smoke prevention air is discharged from the white smoke prevention reserve heat exchanger 50, and the cable Ca includes a first cable Ca1 arranged in the first duct Da1 and a second cable Ca2 arranged in the second duct Da2.

(13) In this embodiment, the temperature acquisition unit 551 acquires the plate temperature based on the inlet temperature of the exhaust gas introduced into the white smoke prevention reserve heat exchanger 50, the exhaust temperature of the exhaust gas discharged from the white smoke prevention reserve heat exchanger 50, the inlet temperature of the white smoke prevention air introduced into the white smoke prevention reserve heat exchanger 50, the exhaust temperature of the white smoke prevention air discharged from the white smoke prevention reserve heat exchanger 50, the flow rate of the exhaust gas, and the flow rate of the white smoke prevention air. However, the temperature acquisition unit 551 may acquire the plate temperature based on at least one of the inlet temperature of the exhaust gas, the exhaust temperature of the exhaust gas, the inlet temperature of the white smoke prevention air, the exhaust temperature of the white smoke prevention air, the flow rate of the exhaust gas, and the flow rate of the white smoke prevention air. In other words, the temperature acquisition unit 551 may acquire the plate temperature based on the temperature of the exhaust gas (at least one of the inlet temperature and the exhaust temperature), or may acquire the plate temperature based on the temperature of the white smoke prevention air (at least one of the inlet temperature and the exhaust temperature).

(14) At least one of the exhaust gas inlet temperature, exhaust gas outlet temperature, exhaust gas flow rate, white smoke prevention air inlet temperature, white smoke prevention air outlet temperature, and white smoke prevention air flow rate may be an actual measurement value, and the other temperatures or flow rates may be approximate values. For example, as shown in FIG. 16, at least one of the exhaust gas inlet temperature Tg1, exhaust gas outlet temperature Tg2, exhaust gas flow rate Vg, white smoke prevention air inlet temperature Ta1, white smoke prevention air outlet temperature Ta2, and white smoke prevention air flow rate Va may be an actual measurement value, and the other temperatures and flow rates may be approximate values calculated based on experiments, etc. The temperature acquisition unit 551 acquires approximate values of each value based on information such as experimental results stored in advance in the memory area of the control device 55. This allows the waste treatment facility 100 to be reduced in cost. Note that FIG. 16 is a diagram showing whether the parameters used to calculate the plate temperature are actual measurements or approximate values.

(15) In this embodiment, the cleaning unit 53 cleans the plate member 522 with the cleaning liquid L1 by spraying the cleaning liquid L1 from the multiple nozzles 536, but the method by which the cleaning unit 53 cleans the plate member 522 is not limited to this. For example, the cleaning unit 53 may clean the plate member 522 by dripping the cleaning liquid L1 from a hole provided in a pipe.

(16) In this embodiment, the flat plate member 522 is used as a partition member. However, instead of the flat plate member 522, a plate member having a bent portion, such as a plate member bent in an uneven shape, may be used.

(17) In this embodiment, the pair of plate members 522t are arranged in parallel with a space between them so that the opposing main surfaces 522s are parallel to each other. However, the opposing main surfaces 522s of the pair of plate members 522 may be arranged at an angle so that they approach each other downstream in the exhaust gas flow direction D1. This allows, for example, the cleaning liquid L1 to remain on the downstream side of the opposing main surfaces 522s in the exhaust gas flow direction D1, and as a result, deposits attached to the main surfaces 522s can be more reliably removed.

(18) In this embodiment, the supply amount setting unit 552 executes a supply amount adjustment process (step S112 in FIG. 7) to adjust the supply amount. However, step S112 in FIG. 7 can be omitted, and the supply amount setting unit 552 does not need to adjust the supply amount (does not need to execute the supply amount adjustment process).

The present invention can be used in waste treatment facilities and waste treatment methods.

10: Incinerator 40: Dust collector 50: White smoke prevention spare heat exchanger (low-temperature heat exchanger)
53: Cleaning section (cleaning device)
60: Smoke cleaning device (wet type smoke cleaning device)
100: Waste treatment equipment 522: Plate member (partition member)
533: cleaning unit 533a: first cleaning unit 533b: second cleaning unit 536: nozzle 538: heating unit (an example of a temperature adjustment unit)
551: Temperature acquisition unit 554: Cleaning control unit (an example of a control unit)
D1: exhaust gas flow direction L1: cleaning liquid R51: heat exchange exhaust gas path (exhaust gas path)
R52: Heat exchange air passage (heat exchange gas passage)
Ta1: inlet temperature of heat exchange gas Ta2: outlet temperature of heat exchange gas Tg1: inlet temperature of exhaust gas Tg2: outlet temperature of exhaust gas Va: flow rate of heat exchange gas Vg: flow rate of exhaust gas

Claims (10)

An incinerator for incinerating waste;
A dust collector that collects dust contained in the exhaust gas discharged from the incinerator;
a smoke washing device that is provided downstream of the dust collecting device in a flow direction of the exhaust gas and performs a smoke washing process to purify the exhaust gas;
a low-temperature heat exchanger provided between the dust collector and the smoke scrubbing device, for recovering heat from the exhaust gas by performing heat exchange between the exhaust gas and a heat exchange gas;
the low-temperature heat exchanger includes a plurality of partition members that separate a heat exchange gas passage through which the heat exchange gas flows and an exhaust gas passage through which the exhaust gas flows, and a cleaning device that cleans the partition members with a cleaning liquid,
The cleaning device includes a plurality of nozzles;
A waste treatment facility, wherein the amount of the cleaning liquid supplied from the plurality of nozzles is set based on the temperature of the partition member. The waste treatment facility according to claim 1, wherein the supply amount is set based on a temperature change of the partition member caused by the supply of the cleaning liquid. a temperature acquisition unit that acquires a temperature of the partition member;
A control unit for controlling the operation of the cleaning device,
The waste treatment facility according to claim 1 , wherein the control unit sets the supply amount based on the temperature of the partition member acquired by the temperature acquisition unit. The waste treatment facility according to claim 3, wherein the temperature acquisition unit acquires the temperature of the partition member based on at least one of the inlet temperature of the exhaust gas introduced into the low-temperature heat exchanger, the outlet temperature of the exhaust gas discharged from the low-temperature heat exchanger, the flow rate of the exhaust gas, the inlet temperature of the heat exchange gas introduced into the low-temperature heat exchanger, the outlet temperature of the heat exchange gas discharged from the low-temperature heat exchanger, and the flow rate of the heat exchange gas. The waste treatment facility according to claim 4, wherein at least one of the inlet temperature of the exhaust gas, the outlet temperature of the exhaust gas, the flow rate of the exhaust gas, the inlet temperature of the heat exchange gas, the outlet temperature of the heat exchange gas, and the flow rate of the heat exchange gas is an actual measured value. A temperature adjusting unit that adjusts the temperature of the cleaning liquid is further provided.
The waste treatment facility according to claim 3 , wherein the control unit adjusts the temperature of the cleaning liquid by controlling an operation of the temperature adjustment unit based on the temperature of the partition member. The cleaning device further includes a cleaning unit configured with a plurality of the nozzles,
the cleaning unit includes a first cleaning unit and a second cleaning unit disposed at a position different from that of the first cleaning unit;
2. The waste treatment facility according to claim 1, wherein a first supply amount of the cleaning liquid supplied to the partition member from a nozzle constituting the first cleaning unit is different from a second supply amount of the cleaning liquid supplied to the partition member from a nozzle constituting the second cleaning unit. The waste treatment facility according to claim 1 or 2, wherein the waste contains an ammonia component. A waste treatment method in a waste treatment facility equipped with an incinerator for incinerating waste, comprising:
A dust collection step of collecting dust contained in exhaust gas discharged from the incinerator;
a heat recovery step of recovering heat from the exhaust gas by performing heat exchange between the exhaust gas from which dust has been collected and a heat exchange gas;
A scrubbing step of purifying the exhaust gas from which heat has been recovered,
the heat recovery step includes a cleaning step of cleaning a plurality of partition members that separate a heat exchange gas passage through which the heat exchange gas flows and an exhaust gas passage through which the exhaust gas flows, by a cleaning device;
A waste treatment method, wherein in the cleaning step, an amount of cleaning liquid supplied from a nozzle of the cleaning device is set based on a temperature of the partition member. The waste treatment method according to claim 9, wherein the waste contains an ammonia component.

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