JP7653464B2 - 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 to supply 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 indirectly exchanges heat between the combustion exhaust gas discharged from the turbocharger turbine and the white smoke prevention air supplied from the white smoke prevention blower, thereby raising the temperature of the white smoke prevention air and lowering the temperature of the combustion exhaust gas.

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 burning a combustible material whose properties are unstable, 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.

A first waste treatment facility according to the present invention is characterized in that it comprises an incinerator for incinerating waste, a dust collecting device for collecting dust contained in the exhaust gas discharged from the incinerator, a smoke washing device that is provided downstream of the dust collecting device in the exhaust gas flow direction of the exhaust gas and performs a smoke washing process to purify the exhaust gas, and a low-temperature heat exchanger that is provided between the dust collecting device and the smoke washing device and recovers heat from the exhaust gas by performing heat exchange between the exhaust gas and a heat exchange gas, wherein 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, and the cleaning device includes a plurality of nozzles that spray the cleaning liquid, and the nozzles spray the cleaning liquid so that the portions of the partition members that face the multiple exhaust gas passages are included in the spray range .
A second 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 an exhaust gas discharged from the incinerator, a smoke scrubbing device provided downstream of the dust collector in a flow direction of the exhaust gas, the smoke scrubbing device performing a smoke scrubbing process for purifying the exhaust gas, and 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 having a plurality of partition members separating 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 for cleaning the partition members with a cleaning liquid, the cleaning device including a plurality of nozzles for spraying the cleaning liquid, the nozzles being arranged such that a portion of the partition member facing a plurality of the exhaust gas passages is a cleaning liquid. the cleaning liquid is sprayed so that the cleaning liquid is included in a spray range, the partition member includes a flat plate member having a flat heat transfer surface, the exhaust gas passage is formed between a pair of the plate members, the heat exchange gas passage is formed between adjacent ones of the exhaust gas passages, and the nozzles spray the cleaning liquid so that the cleaning liquid is rectangular in a virtual plane perpendicular to a main spray direction in which the nozzles spray the cleaning liquid, when the number of surfaces of the plate member on the exhaust gas passage side that are the target onto which the cleaning liquid is sprayed from the multiple nozzles is Na, the length (m) in a direction perpendicular to the main spray direction among directions along the heat transfer surface of the plate member that is the target onto which the cleaning liquid is sprayed from the multiple nozzles is PLa, the amount of sprayed water (L/min) of one nozzle is Q, and the number of the multiple nozzles is i
Q = α × Na × PLa / i ... formula (11)
The nozzle and the plate member are set so that α in the above formula (11) satisfies the relationship of 0.5 to 4.9.
A third 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 an exhaust gas discharged from the incinerator, a smoke scrubbing device provided downstream of the dust collector in a flow direction of the exhaust gas, the smoke scrubbing device performing a smoke scrubbing process for purifying the exhaust gas, and 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 having a plurality of partition members for separating 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 for cleaning the partition members with a cleaning liquid, the cleaning device including a plurality of nozzles for spraying the cleaning liquid, the nozzles being arranged so that portions of the partition members facing the plurality of exhaust gas passages are included in the spray range. the cleaning liquid is sprayed, the partition member includes a flat plate member having a flat heat transfer surface, the exhaust gas passage is formed between a pair of the plate members, the heat exchange gas passage is formed between adjacent ones of the exhaust gas passages, the nozzles spray the cleaning liquid so as to form a rectangular shape in a virtual plane perpendicular to a main spraying direction in which the nozzles spray the cleaning liquid, when the number of the exhaust gas passages onto which the cleaning liquid is sprayed from the multiple nozzles is Ma, the flow path width which is the length of the exhaust gas passage in a direction perpendicular to the heat transfer surface is C, the length (m) in a direction along the heat transfer surface of the plate member onto which the cleaning liquid is sprayed from the multiple nozzles in a direction perpendicular to the main spraying direction is PLa, the amount of water sprayed (L/min) of one nozzle is Q, and the number of the nozzles is i,
Q = β × Ma × C × PLa / i ... formula (12)
The nozzle and the plate member are set so that β shown in the above formula (12) satisfies the relationship of 90 to 816.

According to these configurations, the condensate adhering to the partition member is removed by being washed with a cleaning liquid by the cleaning device. Since this cleaning 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. Furthermore, according to the second and third configurations, it is possible to optimize the settings of the nozzle and plate member in order to efficiently clean the heat transfer surface. As a result, it is possible to reduce the consumption of cleaning liquid.

In addition, according to this configuration, the nozzle sprays the cleaning liquid over the portion of the partition member that faces the multiple exhaust gas passages, so the partition member can be cleaned efficiently. Note that if the amount of cleaning liquid is increased, the temperature of the heat transfer surface decreases, and the heat recovery rate of the exhaust gas decreases. In other words, there is a trade-off between the cleaning effect on the heat transfer surface and the heat recovery rate of the exhaust gas. According to this configuration, the nozzle sprays the cleaning liquid over the portion of the partition member that faces the multiple exhaust gas passages, so the cleaning liquid spreads over the heat transfer surface of the partition member, and it is possible to balance the cleaning effect on the partition member and the heat recovery rate of the partition member (heat transfer surface). Therefore, it is possible to suppress acid corrosion of the heat transfer surface and suppress a decrease in the heat recovery rate of the exhaust gas.

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.

As another feature, the direction in which the nozzle sprays the cleaning liquid may be along the gas flow direction of the exhaust gas flowing through the exhaust gas passage.

Since there is less condensate on the upstream side of the exhaust gas passage than on the downstream side, the cleaning liquid that passes through the partition member on the upstream side of the exhaust gas passage, where there is relatively little condensate, has relatively little condensate and is relatively high in purity. With this configuration, the partition member on the downstream side, where there is relatively more condensate, can be intensively cleaned with a cleaning liquid of relatively high purity. Furthermore, by cleaning the downstream side, where there is relatively more condensate, with a cleaning liquid of relatively high purity, the consumption of cleaning liquid can be reduced. Furthermore, by spraying the cleaning liquid from the nozzle in a direction that is parallel to the gas flow direction of the exhaust gas flowing through the exhaust gas passage, it is possible to prevent the flow of exhaust gas from being obstructed by the cleaning liquid.

As another feature, the partition member may include a flat plate member having a flat heat transfer surface, the exhaust gas passage may be formed between a pair of the plate members, and the heat exchange gas passage may be formed between adjacent exhaust gas passages.

With this configuration, the heat of the exhaust gas and the heat of the heat exchange gas can be exchanged on the flat heat transfer surface of the flat plate member, improving the heat recovery rate of the exhaust gas.

As another feature, the nozzle may spray the cleaning liquid in a rectangular shape on a virtual plane perpendicular to a main spray direction in which the nozzle sprays the cleaning liquid.

With this configuration, the nozzle sprays the cleaning liquid in a rectangular shape similar to the shape of the top surface of the plate member, allowing the partition member to be cleaned efficiently.

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, a nozzle included in the cleaning device sprays a cleaning liquid over the portions of the partition members that face the plurality of exhaust gas passages.

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

1 is a schematic diagram of a waste treatment facility according to a first embodiment. FIG. FIG. 2 is a schematic diagram showing a configuration of a white smoke prevention reserve heat exchanger according to the first embodiment. 3 is a diagram showing the configuration of a heat exchange section and a cleaning section according to the first embodiment; FIG. FIG. 2 is a perspective view showing a plate member according to the first embodiment. FIG. 2 is a diagram showing a configuration of a cleaning unit according to the first embodiment. FIG. 2 is a block diagram showing a configuration of a white smoke prevention reserve heat exchanger according to the first embodiment. 4 is a diagram showing the configuration of a heat exchange section and a cleaning section as viewed from a direction perpendicular to a main surface of a plate member in embodiment 1. FIG. 4 is a diagram showing the configuration of a heat exchange section and a cleaning section as viewed from a direction perpendicular to the exhaust gas flow direction in a direction along a main surface of a plate member in the first embodiment. FIG. 5A to 5C are diagrams illustrating an erosion mechanism on a main surface of the plate member according to the first embodiment. FIG. 11 is a diagram showing the configuration of a white smoke prevention preliminary heat exchanger and a wet smoke washing device according to another embodiment.

Below, 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 will be described 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.

[Embodiment 1]
First, a waste treatment facility and a waste treatment method according to a first embodiment will be described with reference to FIG.
[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 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 dewatered 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 an "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 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 into 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 effect of reducing the moisture content of the exhaust gas before being discharged from the chimney and increasing the temperature of the exhaust gas prevents the exhaust gas discharged from the chimney from becoming white smoke.

[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 pair of adjacent 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.

The first tank 531 stores the 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.

2, the cleaning unit 533 includes a plurality of nozzle pipes 535, which are arranged in a virtual plane parallel to the main surface 522s of the plate member 522 in a direction perpendicular to the exhaust gas flow direction D1. In this embodiment, the cleaning unit 533 includes two nozzle pipes 535, which are connected to one control valve 537.

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. Note that FIG. 3 illustrates one of the two nozzle pipes 535 connected to one control valve 537.

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.

Here, the supply amount 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 the 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 nozzle 536 sprays 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. In the following, the amount of cleaning liquid L1 sprayed from one nozzle 536 per unit time (L/min-piece) may be referred to as the spray water amount.

The injection conditions (supply amount) such as injection frequency, injection amount, and injection time may be predetermined constant conditions, or may be set by a control device 55 further provided in the white smoke prevention reserve heat exchanger 50, as shown in FIG. 6.

The control device 55 controls the operation of the cleaning unit 53 (control valve 537). The control device 55 is, for example, a programmable logic controller (sequencer) or part of a distributed control system (DCS). Alternatively, the control device 55 may be a hard timer that measures the cleaning time or other time. The control device 55 may include a memory area that is made up of a processor such as a central processing unit (CPU) and a semiconductor memory such as a read only memory (ROM). A control program for controlling the operation of the cleaning unit 53 may be stored in the memory area.

[Nozzle configuration]
Next, the configuration of the nozzle 536 will be described with reference to Figs. 7 and 8. Fig. 7 is a diagram showing the configuration of the heat exchanger 52 and the cleaning unit 53 as viewed from a direction perpendicular to the main surface 522s of the plate member 522. Fig. 8 is a diagram showing the configuration of the heat exchanger 52 and the cleaning unit 53 as viewed from a direction perpendicular to the exhaust gas flow direction D1 along the main surface 522s of the plate member 522. Hereinafter, the direction perpendicular to the main surface 522s of the plate member 522 is referred to as the X direction, the direction perpendicular to the exhaust gas flow direction D1 along the main surface 522s of the plate member 522 is referred to as the Y direction, and the direction parallel to the exhaust gas flow direction D1 is referred to as the Z direction. Note that the multiple plate members 522 are arranged along the X direction, and the heat exchange exhaust gas passages R51 are provided in parallel in the X direction.

As shown in Figures 7 and 8, the nozzle 536 sprays the cleaning liquid L1 so that the spray shape (diffusion shape) is fan-shaped when viewed from the X or Y direction. The main spray direction D3 in which the nozzle 536 sprays the cleaning liquid L1 is the -Z axis direction. In other words, the main spray direction D3 of the nozzle 536 is a direction along the exhaust gas flow direction D1.

The nozzle 536 sprays the cleaning liquid L1 so that it has a rectangular shape (or a nearly rectangular shape) when viewed from the Z direction. In other words, the nozzle 536 sprays the cleaning liquid L1 so that it has a rectangular shape (or a nearly rectangular shape) on an imaginary plane VS perpendicular to the main spray direction D3. This imaginary plane VS has a shape that is nearly identical to the cross section of the flow path in the spray range at the distance h from the nozzle 536 to the upper surface of the plate member 522. Hereinafter, the range in which the cleaning liquid L1 is sprayed from one nozzle 536 is referred to as the "spray range." Note that the nozzle 536 may spray the cleaning liquid L1 so that it has an elliptical shape close to a rectangle.

In this embodiment, the nozzle 536 sprays the cleaning liquid L1 over multiple (three in the example shown in FIG. 8) heat exchange exhaust gas channels R51. That is, the cleaning liquid L1 is sprayed so that the spray range includes the portions of the main surfaces 522s of multiple (three in the example shown in FIG. 8) plate members 522 that face the heat exchange exhaust gas channels R51 (six heat transfer surfaces in the example shown in FIG. 8). This allows the cleaning liquid L1 to spread along the height H (see FIG. 7) of the portions of the main surfaces 522s of the plate members 522 that face the heat exchange exhaust gas channels R51.

The nozzles 536 are set based on the range of water volume density in the spray range that is equal to or greater than a specified value and the size of the heat exchange unit 521 (plate member 522) that is the target of spraying from one nozzle 536. The water volume density is indicated as a relative amount to the water volume in the range (the center of the spray range) where the amount of cleaning liquid L1 is the greatest in the spray range.

In this embodiment, the performance (spray volume, spray angle, flow rate distribution, etc.) and arrangement (position relative to the plate member 522) of the nozzle 536 are set based on the range of water flow density in the spray range that is equal to or greater than a specified value and the size of the heat exchange unit 521 (plate member 522) that is the target of spray from one nozzle 536.

Specifically, the performance and arrangement of the nozzle 536 are set so that the length aL of the long side of the projected image when a range where the water density is a preset specified value (e.g., 25% or more) is projected in the Z direction, in other words, the length aL of the long side (hereinafter referred to as the "first side a") of the spray range on the virtual plane VS where the water density is a preset specified value, is greater than or equal to the cleaning target length PL, and the length bL of the short side of the projected image, in other words, the length bL of the short side (hereinafter referred to as the "second side b") of the spray range on the virtual plane VS where the water density is a preset specified value, is greater than or equal to the cleaning target width PW. As shown in FIG. 7, the cleaning target length PL indicates the length in the Y direction (a direction along the main surface 522s that is perpendicular to the main spray direction D3) of the heat exchange unit 521 (plate member 522) onto which cleaning liquid L1 is sprayed from one nozzle 536, and the cleaning target width PW indicates the length in the X direction (a direction perpendicular to the main surface 522s) of the heat exchange unit 521 (multiple plate members 522) onto which cleaning liquid L1 is sprayed from one nozzle 536, as shown in FIG. 8.

The cleaning target width PW is calculated based on the number of heat exchange exhaust gas channels R51 onto which the cleaning liquid L1 is sprayed from one nozzle 536 (hereinafter referred to as the "number of exhaust gas channels M"), the distance between the opposing plate members 522, i.e., the width of the heat exchange exhaust gas channel R51 in the X direction (hereinafter referred to as the "flow path width C"), the width of the heat exchange air channel R52 in the X direction, and the thickness of the plate member 522 (length in the X direction).

The nozzles 536 and the plate member 522 are set based on the amount of sprayed water Q (L/min.pieces) of cleaning liquid L1 sprayed per unit time from one nozzle 536, the number of surfaces to be cleaned N, and the length PL (m) of the surface to be cleaned. Note that the number of surfaces to be cleaned N is the number of surfaces on the heat exchange exhaust gas passage R51 side of the main surface 522s of the plate member 522 onto which cleaning liquid L1 is sprayed from one nozzle 536.

Specifically, the nozzle 536 and the plate member 522 are set so as to satisfy the relationship α=1.63 when expressed by the following formula (1).
Q=α×N×PL...Formula (1)
However, α may be 0.5 (α=30% of 1.63) or more and 4.9 (α=300% of 1.63) or less, preferably 0.8 (α=50% of 1.63) or more and 3.3 (α=200% of 1.63) or less, and more preferably 1.3 (α=80% of 1.63) or more and 2.0 (α=120% of 1.63) or less. That is, when expressed by the above formula (1), the nozzle 536 and the plate member 522 are set so that α is 0.5 or more and 4.9 or less, preferably 0.8 or more and 3.3 or less, and more preferably 1.3 or more and 2.0 or less. This allows the settings of the nozzle 536 and the plate member 522 to be optimized in order to efficiently clean the main surface 522s (heat transfer surface) of the plate member 522. Furthermore, the above formula (1) simplifies the arrangement standard of the plate member 522 according to the performance of the nozzle 536, and enables efficient cleaning of the main surface 522s of the plate member 522. Note that the above value of α is a value when the unit of the length to be cleaned PL is m (meters) and the unit of the amount of jetted water Q is L/min. The value of α changes depending on the unit of the length to be cleaned PL and the amount of jetted water Q.

Alternatively, instead of the method (Equation 1) based on the amount of water sprayed Q, the number of surfaces to be cleaned N, and the length to be cleaned PL, the nozzle 536 and the plate member 522 may be set based on the amount of water sprayed Q, the number of exhaust gas channels M, the width of the exhaust gas flow path C, and the length to be cleaned PL.

Specifically, the nozzle 536 and the plate member 522 are set so that β=272 when expressed by the following equation (2).
Q=β×M×C×PL...Formula (2)
However, β may be 90 (β=30% of 272) or more and 816 (β=300% of 272) or less, preferably 136 (β=50% of 272) or more and 544 (β=200% of 272) or less, and more preferably 217 (β=80% of 272) or more and 327 (β=120% of 272) or less. That is, when expressed by the above formula (2), the nozzle 536 and the plate member 522 are set so that β is 90 or more and 816 or less, preferably 136 or more and 544 or less, and more preferably 217 or more and 327 or less. This allows the settings of the nozzle 536 and the plate member 522 to be optimized in order to efficiently clean the main surface 522s (heat transfer surface) of the plate member 522. In addition, the above formula (2) simplifies the arrangement standard of the plate member 522 according to the performance of the nozzle 536, and the main surface 522s of the plate member 522 can be efficiently cleaned. The above value of β is a value when the unit of the cleaning target length PL is m (meters) and the unit of the jet water volume Q is L/min. The value of β changes depending on the unit of the cleaning target length PL and the jet water volume Q.

[Effects of the First 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 of lower temperature exhaust gas. As a result, the heat of the exhaust gas can be recovered without waste, and the heat recovery rate of the exhaust gas is improved.

In addition, the white smoke prevention reserve heat exchanger 50 exchanges heat between the exhaust gas and the white smoke prevention air through the plate member 522, so the temperature of the clean white smoke prevention air can be increased and used for various purposes such as power generation.

In addition, according to this embodiment, the condensate adhering to the plate member 522 is removed by washing with the washing liquid L1 by the washing unit 53. Since this washing unit 53 is incorporated in the waste treatment equipment 100, it is possible to wash the plate member 522 with the condensate adhering thereto during operation, and it is possible to prevent the condensate from adhering to the plate member 522 for a long period of time. As a result, it is possible to suppress acid corrosion of the plate member 522.

Furthermore, according to this embodiment, the nozzle 536 sprays the cleaning liquid L1 over the portion of the plate member 522 facing the multiple heat exchange exhaust gas passages R51, so that the plate member 522 can be efficiently cleaned. Note that, if the amount of cleaning liquid L1 is increased, the temperature of the heat transfer surface (main surface 522s) decreases, and the heat recovery rate of the exhaust gas decreases. In other words, there is a trade-off between the cleaning effect on the heat transfer surface and the heat recovery rate of the exhaust gas. According to this configuration, the nozzle 536 sprays the cleaning liquid L1 over the portion of the plate member 522 facing the multiple heat exchange exhaust gas passages R51, so that the cleaning liquid L1 spreads over the heat transfer surface of the plate member 522, and it is possible to balance the cleaning effect on the plate member 522 and the heat recovery rate of the plate member 522 (heat transfer surface). Therefore, it is possible to prevent corrosion of the heat transfer surface and suppress a decrease in the heat recovery rate of the exhaust gas.

However, 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. As shown in FIG. 9, SOx and NH ₃ in the exhaust gas react 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.

[Embodiment 2]
Next, a description will be given of a waste treatment facility and a waste treatment method according to embodiment 2. In embodiment 2, the formulas for setting the performance and arrangement of the nozzle 536 are different from those in embodiment 1 (formulas 1 and 2). Only the points different from embodiment 1 will be described below.

In the second embodiment, the nozzle 536 and the plate member 522 are set based on the amount of sprayed water Q (L/min.pieces) of the cleaning liquid L1 sprayed from one nozzle 536 per unit time, the number of surfaces to be cleaned Na, the length of the entire surface to be cleaned PLa (m), and the number of nozzles i included in the heat exchange unit 521. The number of surfaces to be cleaned Na indicates the number of surfaces on the heat exchange exhaust gas passage R51 side of the main surface 522s of the plate member 522 onto which the cleaning liquid L1 is sprayed from the nozzles 536 included in the heat exchange unit 521, and the length of the entire surface to be cleaned PLa indicates the length in the Y direction (the direction perpendicular to the main spray direction D3 among the directions along the main surface 522s) of the heat exchange unit 521 (plate member 522) onto which the cleaning liquid L1 is sprayed from the nozzles 536 included in the heat exchange unit 521, as shown in FIG. 7.

Specifically, the nozzle 536 and the plate member 522 are set so as to satisfy the relationship α=1.63 when expressed by the following equation (11).
Q = α × Na × PLa / i ... formula (11)
However, α may be 0.5 (α=30% of 1.63) or more and 4.9 (α=300% of 1.63) or less, preferably 0.8 (α=50% of 1.63) or more and 3.3 (α=200% of 1.63) or less, and more preferably 1.3 (α=80% of 1.63) or more and 2.0 (α=120% of 1.63) or less. That is, when expressed by the above formula (11), the nozzle 536 and the plate member 522 are set so that α is 0.5 or more and 4.9 or less, preferably 0.8 or more and 3.3 or less, and more preferably 1.3 or more and 2.0 or less. This allows the settings of the nozzle 536 and the plate member 522 to be optimized in order to efficiently clean the main surface 522s (heat transfer surface) of the plate member 522. Furthermore, the above formula (11) simplifies the arrangement standard of the plate member 522 according to the performance of the nozzle 536, and enables efficient cleaning of the main surface 522s of the plate member 522. Note that the above value of α is a value when the unit of the length PLa to be cleaned is m (meters) and the unit of the amount of jetted water Q is L/min. The value of α changes depending on the unit of the length PLa to be cleaned and the amount of jetted water Q.

Alternatively, instead of the method (Equation 11) based on the water injection amount Q, the number of surfaces to be cleaned overall Na, and the overall cleaning length PLa, the nozzle 536 and the plate member 522 may be set based on the water injection amount Q, the total number of exhaust gas channels Ma, the exhaust gas flow path width C, and the overall cleaning length PLa. The total number of exhaust gas channels Ma is the number of heat exchange exhaust gas channels R51 onto which the cleaning liquid L1 is sprayed from the multiple nozzles 536 included in the heat exchange unit 521. The overall cleaning width PWa shown in FIG. 8 indicates the length in the X direction (direction perpendicular to the main surface 522s) of the heat exchange unit 521 (multiple plate members 522) onto which the cleaning liquid L1 is sprayed from the multiple nozzles 536 included in the heat exchange unit 521, and is calculated based on the total number of exhaust gas channels Ma, the flow path width C, the width of the heat exchange air channel R52 in the X direction, and the thickness (length in the X direction) of the plate member 522.

Specifically, the nozzle 536 and the plate member 522 are set so that β=272 when expressed by the following equation (12).
Q = β × Ma × C × PLa / i ... formula (12)
However, β may be 90 (β=30% of 272) or more and 816 (β=300% of 272) or less, preferably 136 (β=50% of 272) or more and 544 (β=200% of 272) or less, and more preferably 217 (β=80% of 272) or more and 327 (β=120% of 272) or less. That is, when expressed by the above formula (12), the nozzle 536 and the plate member 522 are set so that β is 90 or more and 816 or less, preferably 136 or more and 544 or less, and more preferably 217 or more and 327 or less. This allows the settings of the nozzle 536 and the plate member 522 to be optimized in order to efficiently clean the main surface 522s (heat transfer surface) of the plate member 522. In addition, the above formula (12) simplifies the arrangement standard of the plate member 522 according to the performance of the nozzle 536, and the main surface 522s of the plate member 522 can be efficiently cleaned. The above value of β is a value when the unit of the cleaning target length PLa is m (meters) and the unit of the jet water volume Q is L/min. The value of β changes depending on the unit of the cleaning target length PLa and the jet water volume Q.

[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 for components having the same functions as in the embodiment).

(1) In this 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.

(2) 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.

(3) 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.

(4) 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.

(5) The concentration of sulfuric acid components (sulfur trioxide) contained in exhaust gas generated by burning coal (fossil fuel) such as in a coal boiler is higher than the concentration of sulfuric acid components 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. For this reason, in the past, the effect of acid corrosion was less of a problem in heat exchangers installed in waste treatment facilities than in the case of fossil fuels. However, in the heat recovery of exhaust gas in the white smoke prevention reserve heat exchanger 50, the temperature of the heat transfer surface (main surface 522s) of the plate member 522 decreases, and it has been found that there is an area in the white smoke prevention reserve heat exchanger 50 where condensate of the sulfuric acid components contained in the exhaust gas is likely to adhere to the plate member 522 due to the temperature decrease of the heat transfer surface (the temperature of the heat transfer surface of the plate member 522 may be below the sulfuric acid dew point). Therefore, as shown in FIG. 10, the waste treatment facility 100 may include two or more heat exchange units 521 and cleaning units 533, and the amount of cleaning liquid L1 supplied to each heat exchange unit 521 may be different. In the example shown in FIG. 10, 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 cleaning unit 533 includes a first cleaning unit 533a provided in correspondence with the first heat exchange unit 521a to clean the first heat exchange unit 521a, and a second cleaning unit 533b provided in correspondence with the second heat exchange unit 521b to clean the second heat exchange unit 521b.

The heat exchange unit 521 arranged downstream in the exhaust gas flow direction D1 may include an area where the temperature of the heat transfer surface (main surface 522s) of the plate member 522 may be equal to or lower than the sulfuric acid dew point. For this reason, 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") may be 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"). For example, the second supply amount may be set to be greater than the first supply amount. The second supply amount may be the same as the first supply amount.

(6) 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.

(7) In this embodiment, the nozzle 536 sprays the cleaning liquid L1 over three heat exchange exhaust gas passages R51. However, the range over which the nozzle 536 sprays the cleaning liquid L1 can be changed as appropriate, and the cleaning liquid L1 may be sprayed over two or four or more heat exchange exhaust gas passages R51.

(8) 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.

(9) 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 every 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.

(10) 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.

(11) 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.

(12) 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 incline 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.

(13) 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.

(14) In this embodiment, 25% or more is given as an example of the specified value, but the specified value is not limited to 25% or more and can be set arbitrarily to, for example, 15% or more, 20% or more, etc.

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)
522s: Main surface (heat transfer surface)
536: Nozzle C: Flow path width D1: Exhaust gas flow direction D3: Main injection direction L1: Cleaning liquid M: Number of exhaust gas passages N: Number of surfaces to be cleaned PL: Length of cleaning object PW: Width of cleaning object Q: Amount of water injected R51: Exchanger exhaust gas passage (exhaust gas passage)
R52: Exchanger air passage (heat exchange gas passage)
VS: Virtual plane

Claims (7)

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 for spraying the cleaning liquid,
The nozzle sprays the cleaning liquid so that the portions of the partition member facing the exhaust gas passages are included in the spray range . The waste treatment facility according to claim 1, wherein the direction in which the nozzle sprays the cleaning liquid is along the gas flow direction of the exhaust gas flowing through the exhaust gas passage. The partition member includes a flat plate member having a flat heat transfer surface,
3. The waste treatment facility according to claim 1, wherein the exhaust gas passage is formed between a pair of the plate members, and the heat exchange gas passage is formed between adjacent ones of the exhaust gas passages. The waste treatment facility according to claim 3, wherein the nozzle sprays the cleaning liquid in a rectangular shape on a virtual plane perpendicular to a main spray direction in which the nozzle sprays the cleaning liquid. 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 for spraying the cleaning liquid,
the nozzle sprays the cleaning liquid so that the portions of the partition member facing the plurality of exhaust gas passages are included in the spray range;
The partition member includes a flat plate member having a flat heat transfer surface,
The exhaust gas passage is formed between a pair of the plate members, and the heat exchange gas passage is formed between adjacent ones of the exhaust gas passages,
the nozzle sprays the cleaning liquid so as to form a rectangular shape on a virtual plane perpendicular to a main spraying direction in which the nozzle sprays the cleaning liquid;
Q=α×Na×PLa/i (11) where Na is the number of surfaces of the plate member on the exhaust gas passage side, onto which the cleaning liquid is sprayed from the plurality of nozzles, PLa is the length (m) of the direction perpendicular to the main spray direction among the directions along the heat transfer surface of the plate member onto which the cleaning liquid is sprayed from the plurality of nozzles, Q is the amount of sprayed water (L/min) from one nozzle, and i is the number of the plurality of nozzles.
The waste treatment facility, wherein the nozzle and the plate member are set so that α shown in the above formula (11) satisfies the relationship of 0.5 to 4.9. 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 for spraying the cleaning liquid,
the nozzle sprays the cleaning liquid so that the portions of the partition member facing the plurality of exhaust gas passages are included in the spray range;
The partition member includes a flat plate member having a flat heat transfer surface,
The exhaust gas passage is formed between a pair of the plate members, and the heat exchange gas passage is formed between adjacent ones of the exhaust gas passages,
the nozzle sprays the cleaning liquid so as to form a rectangular shape on a virtual plane perpendicular to a main spraying direction in which the nozzle sprays the cleaning liquid;
Let Ma be the number of the exhaust gas passages onto which the cleaning liquid is sprayed from the multiple nozzles, C be a flow path width which is the length of the exhaust gas passage in a direction perpendicular to the heat transfer surface, PLa be a length (m) in a direction perpendicular to the main spray direction among directions along the heat transfer surface of the plate member onto which the cleaning liquid is sprayed from the multiple nozzles, Q be the amount of sprayed water (L/min) from one nozzle, and i be the number of the nozzles.
Q = β × Ma × C × PLa / i ... formula (12)
The waste treatment facility, wherein the nozzle and the plate member are set so that β shown in the above formula (12) satisfies the relationship of 90 to 816. 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, a nozzle included in the cleaning device sprays a cleaning liquid so that portions of the partition member facing the multiple exhaust gas passages are included in the spray range.

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