Waste treatment equipment and waste treatment method

Abstract

To provide a waste processing facility which can inhibit deterioration of a heat recovery rate while inhibiting corrosion of a heat exchanger.SOLUTION: A waste processing facility includes: an incinerator; a dust collector which collects dust contained in exhaust gas exhausted from the incinerator; a smoke washing device which is provided at a downstream side relative to the dust collector in an exhaust gas circulation direction D1 of the exhaust gas and performs smoke washing processing for purifying the exhaust gas; and a low temperature heat exchanger 50 which is provided between the dust collector and the smoke washing device and conducts heat exchange between the exhaust gas and heat exchange gas to recover heat of the exhaust gas. The low temperature heat exchanger 50 has: multiple partition members 522 each of which partitions a heat exchange gas passage from an exhaust gas passage; and a cleaning device 53 which cleans the partition members 522 with cleaning fluid. The cleaning device 53 is configured so that a first cleaning unit 533a, having multiple nozzles 536 which supply the cleaning fluid to the partition members 522, and a second cleaning unit 533b, disposed at a position different from the first cleaning unit 533a, can adjust supply amounts separately.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a waste treatment facility and a waste treatment method. [Background technology]

[0002] 2. Description of the Related Art Among waste treatment facilities that incinerate waste, there are facilities that are equipped with a heat exchanger that exchanges heat between exhaust gas and a heat medium (see, for example, Patent Documents 1 and 2).

[0003] 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 gas 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.

[0004] The facility disclosed in Patent Document 2 includes 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 guided to the low-temperature heat exchanger. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-15485 A [Patent Document 2] Japanese Patent Application Publication No. 52-74133 Summary of the Invention [Problem to be solved by the invention]

[0006] In a heat exchanger that performs heat exchange 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 becomes lower than the sulfuric acid dew point. In the portion where the temperature of the heat transfer surface of the heat exchanger becomes lower than 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, exhaust gas generated when combusting a combustible material whose properties are unstable, such as waste, contains various components, so that condensates of various components adhere to the heat transfer surface, causing corrosion of the heat transfer surface of the heat exchanger. Such a phenomenon is likely to occur in a relatively low-temperature exhaust gas that flows downstream of the dust collector in the flow direction of the exhaust gas.

[0007] For these reasons, it is desirable to suppress corrosion of heat exchangers caused by exhaust gases generated by burning waste whose properties are unstable. [Means for solving the problem]

[0008] 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 exhaust gas discharged from the incinerator, a smoke scrubbing device provided downstream of the dust collector in the exhaust gas flow direction of the exhaust gas and 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 and 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 cleaning unit having a plurality of nozzles for supplying the cleaning liquid to the partition member, and the cleaning unit is configured such that a first cleaning unit and a second cleaning unit provided at a position different from the first cleaning unit can individually adjust the supply amount. the low-temperature heat exchanger includes a first heat exchange unit cleaned by the first cleaning unit, and a second heat exchange unit disposed downstream of the first heat exchange unit in the exhaust gas flow direction and cleaned by the second cleaning unit, and a first supply amount of the cleaning liquid supplied from the nozzle of the first cleaning unit to the partition member is different from a second supply amount of the cleaning liquid supplied from the nozzle of the second cleaning unit to the partition member, It's at the point.

[0009] According to this configuration, the condensate adhering to the partition member is removed by washing it with a washing 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.

[0010] As described above, the region where the sulfuric acid component contained in the exhaust gas generated by burning waste with unstable properties can be condensed below the sulfuric acid dew point varies depending on the environment, etc. According to this configuration, the first cleaning unit and the second cleaning unit can each adjust the supply amount individually. Therefore, the cleaning conditions of 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 of the heat transfer surface of the partition member can be made below the sulfuric acid dew point). This makes it possible to suppress acid corrosion of the partition member (low-temperature heat exchanger) caused by the exhaust gas generated by burning waste with unstable properties. Also, when 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, but according to this configuration, the cleaning conditions of the first cleaning unit and the second cleaning unit can be made different, so that the temperature drop of the heat transfer surface can be suppressed and the decrease in the heat recovery rate of the exhaust gas can be suppressed.

[0011] In addition, 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. 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. 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 the corrosion of the heat exchanger caused by the exhaust gas generated by burning waste with unstable properties, while suppressing the decrease in the heat recovery rate.

[0013] Also,According to this configuration, the second heat exchange unit to be cleaned by the second cleaning unit is disposed downstream in the exhaust gas flow direction where the temperature of the heat transfer surface of the partition member may become equal to or lower than the sulfuric acid dew point. Therefore, for example, by making the supply amount of cleaning liquid from the cleaning unit (e.g., the second cleaning unit) corresponding to the heat exchange unit (e.g., the second heat exchange unit) that includes many areas where the temperature may become equal to or lower than the sulfuric acid dew point larger than the supply amount from the other cleaning units (the first cleaning unit), it is possible to efficiently suppress acid corrosion of the partition member. In addition, according to this configuration, the supply amounts of the cleaning liquid to the first cleaning unit and the second cleaning unit are made different depending on the region where the temperature of the heat transfer surface of the partition member may become equal to or lower than the sulfuric acid dew point, thereby making it possible to suppress acid corrosion of the partition member.

[0014] As another feature, in the low-temperature heat exchanger, the second heat exchange unit may be provided below the first heat exchange unit.

[0015] According to this configuration, the cleaning liquid supplied to the partition member flows smoothly downward due to gravity, so that the cleaning liquid is prevented from absorbing heat from the partition member located below the partition member to which it is supplied. As a result, it is possible to prevent the temperature of the cleaning unit (cleaning liquid) from decreasing due to the cleaning liquid stagnation in the partition member, and to suppress a decrease in the heat recovery rate. In addition, since the cleaning liquid supplied to the first heat exchange unit flows into the second heat exchange unit, the cleaning liquid supplied to the first heat exchange unit can be used to clean the second heat exchange unit.

[0018] In another feature, the second supply rate may be greater than the first supply rate.

[0019] According to this configuration, the second supply amount by the second cleaning unit, which cleans the second heat exchange unit located downstream in the exhaust gas flow direction where the temperature of the heat transfer surface of the partition member may become below the sulfuric acid dew point compared to the first heat exchange unit, is greater than the first supply amount by the first cleaning unit, so that acid corrosion of the partition member can be more efficiently suppressed.

[0020] As another feature, each of the first supply amount and the second supply amount may be adjusted by changing at least one value of a jetting frequency of the nozzle, a jetting amount per jetting of the nozzle, and a jetting time per jetting of the nozzle.

[0021] According to this configuration, the supply amount can be adjusted by changing at least one of the nozzle spray frequency, the nozzle spray amount per nozzle, and the nozzle spray duration per nozzle. Therefore, the supply amount can be easily adjusted according to the region where the temperature of the heat transfer surface of the partition member may become lower than the sulfuric acid dew point.

[0022] In another aspect, the waste material may include an ammonia component.

[0023] According to this configuration, since the waste contains an ammonia component, it is possible to lower the sulfuric acid dew point, and to suppress corrosion of the partition member caused by the exhaust gas.

[0024] A feature of the waste treatment method according to the present invention is 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 of collecting dust contained in an exhaust gas discharged from the incinerator, a heat recovery step of recovering heat from the exhaust gas by performing heat exchange between the dust-collected exhaust gas and a heat exchange gas, and a smoke washing step of purifying the exhaust gas from which the heat has been recovered, the heat recovery step including a cleaning step of cleaning 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, by a cleaning device, and in the cleaning step, the partition members are cleaned in a state in which the supply amounts of a first cleaning unit included in the cleaning device and a second cleaning unit arranged at a position different from the first cleaning unit can be individually adjusted. The heat exchange in the heat recovery step includes heat exchange in a first heat exchange unit that is cleaned by the first cleaning unit, and heat exchange in a second heat exchange unit that is disposed downstream of the first heat exchange unit in a flow direction of exhaust gas and is cleaned by the second cleaning unit, and in the cleaning step, a first supply amount of cleaning liquid supplied from the first cleaning unit to the partition member and a second supply amount of cleaning liquid supplied from the second cleaning unit to the partition member are adjusted to be different from each other. The point is that

[0025] According to this method, it is possible to achieve the same effects as those achieved by the waste treatment facility described above.

[0026] In another aspect, the waste material may include an ammonia component.

[0027] According to this method, since the waste contains an ammonia component, it is possible to lower the sulfuric acid dew point and suppress acid corrosion of the partition member. [Brief description of the drawings]

[0028] [Figure 1] 1 is a schematic diagram of a waste treatment facility according to an embodiment; [Diagram 2] FIG. 2 is a schematic diagram showing a configuration of a white smoke prevention reserve heat exchanger according to the embodiment. [Diagram 3] 5A and 5B are diagrams illustrating configurations of a heat exchange section and a cleaning section according to the embodiment. [Figure 4] FIG. 4 is a perspective view showing a plate member according to the embodiment. [Diagram 5] FIG. 2 is a diagram showing a configuration of a cleaning unit according to the embodiment. [Figure 6] FIG. 2 is a block diagram showing a configuration of a white smoke prevention reserve heat exchanger according to the embodiment. [Figure 7] 5A to 5C are diagrams illustrating an erosion mechanism on a main surface of a plate member according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Hereinafter, an embodiment of a waste treatment facility and a waste treatment method including a white smoke prevention reserve 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.

[0030] [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.

[0031] 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 collector 40, the white smoke prevention reserve heat exchanger 50, the wet smoke scrubber 60, and a 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."

[0032] [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).

[0033] The combustion air supplying device 20 supplies the incinerator 10 with combustion air to be used when burning waste in the incinerator 10. The combustion air supplying 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 supplying device 20.

[0034] The combustion air supplying device 20 has a combustion air heat exchanger 21 and a turbocharger 22. The combustion air supplying device 20 may have a fluidized bed blower instead of the turbocharger 22.

[0035] 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.

[0036] 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 by the pressure and thermal energy of the air heated in 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 by utilizing 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.

[0037] The white smoke prevention main heat exchanger 30 is provided downstream of the combustion air supplying device 20 in the exhaust gas flow direction D1, and the white smoke prevention main heat exchanger 30 receives the exhaust gas after heat exchange in the combustion air supplying device 20. The white smoke prevention main heat exchanger 30 is a type of heat exchanger, and is a shell-and-tube heat exchanger or a plate heat exchanger.

[0038] 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.

[0039] 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 configured with a bag filter. However, the dust collector 40 is not limited to being configured with a bag filter, and may be configured with a ceramic filter or the like.

[0040] 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 is a plate type heat exchanger in this embodiment. As the white smoke prevention reserve heat exchanger 50 is a plate type heat exchanger, heat exchange is performed over a wide heat transfer surface.

[0041] 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."

[0042] The white smoke prevention reserve heat exchanger 50 heats white smoke prevention air (an example of heat exchange gas) by utilizing the thermal energy of the introduced exhaust gas. More specifically, 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 drops to 50 degrees or more and 150 degrees or less.

[0043] 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 (one 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).

[0044] [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".

[0045] The white smoke prevention air path R2 connects the blower B that sends out white smoke prevention air, the white smoke prevention spare heat exchanger 50, the white smoke prevention main heat exchanger 30, the power generation equipment 70, and a chimney (not shown).

[0046] The white smoke prevention reserve heat exchanger 50 is provided downstream of the blower B in the air flow direction D2, and 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°C and 50°C. The temperature of the white smoke prevention air rises to between 50°C and 220°C by exchanging heat with the exhaust gas.

[0047] 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 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 more than the heat recovery amount of the white smoke prevention reserve heat exchanger 50 (for example, 1 to 5 times).

[0048] The power generation equipment 70 is provided downstream of the white smoke prevention main heat exchanger 30 in the air flow direction D2, and 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 utilizing the thermal energy of the white smoke prevention air that has been heated in the white smoke prevention main heat exchanger 30.

[0049] The power generation facility 70 includes a hot water boiler 71 , a circulation path 72 , and a power generation device 73 .

[0050] The hot water boiler 71 heats water by utilizing the thermal energy of the white smoke prevention air. The heated water (hot water) is introduced into the power generation device 73 via the circulation path 72.

[0051] 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 .

[0052] The power generation device 73 generates power using, as a heat source, water (hot water) introduced from the hot water boiler 71 via the circulation path 72. 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.

[0053] The white smoke prevention air from which thermal energy has been recovered in the hot water boiler 71 is introduced into the flue gas passage R1 downstream of the wet smoke scrubbing device 60, and merges with the flue gas discharged from the wet smoke scrubbing device 60. The temperature of the white smoke prevention air merged with the flue gas is 100°C or higher and 200°C or lower.

[0054] The flue gas discharged from the wet smoke scrubbing unit 60 is heated by merging with the white smoke prevention air. The flue gas heated by the white smoke prevention air is discharged into the atmosphere from a chimney (not shown). As described above, the flue 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 unit 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 flue gas before being discharged from the chimney and the increased temperature of the flue gas prevent the flue gas discharged from the chimney from turning into white smoke.

[0055] [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 contained in the housing 51.

[0056] [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. In this embodiment, the heat exchange section 52 includes two heat exchange units 521, and the two heat exchange units 521 are arranged along the exhaust gas flow direction D1. Hereinafter, of the two heat exchange units 521, the heat exchange unit 521 on the upstream side of the exhaust gas flow direction D1 is referred to as the "first heat exchange unit 521a," and the heat exchange unit 521 on the downstream side is referred to as the "second heat exchange unit 521b." In this embodiment, the second heat exchange unit 521b is arranged below the first heat exchange unit 521a.

[0057] The white smoke prevention air flows from the outside of the white smoke prevention preliminary heat exchanger 50 through the second heat exchange unit 521b and the first heat exchange unit 521a in this order, and is discharged to the outside of the white smoke prevention preliminary heat exchanger 50. The second heat exchange unit 521b and the first heat exchange unit 521a are connected via, for example, a duct (not shown), and the white smoke prevention air flows from the second heat exchange unit 521b to the first heat exchange unit 521a via the duct (not shown).

[0058] The first heat exchange unit 521a and the second heat exchange unit 521b each include a plurality of plate members 522 (an example of a partition member). The plate members 522 included in the first heat exchange unit 521a and the second heat exchange unit 521b have substantially the same configuration. Therefore, hereinafter, the configuration of the plate members 522 of the heat exchange unit 521 will be described with reference to FIG. 3, taking the plate members 522 of the first heat exchange unit 521a as an example.

[0059] [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.

[0060] 3 and 4, the plate member 522 is flat and has a main surface 522s. The plate members 522 are spaced apart from each other 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.

[0061] 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 "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 will be referred to as "a pair of plate members 522t."

[0062] As shown in FIG. 3, the heat exchange air passage R52 is formed between the heat exchange exhaust gas passages R51 adjacent to each other. 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, facing the first joining plate 522A through the heat exchange air passage R52.

[0063] 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 when viewed from a direction perpendicular to the main surface 522s of the plate member 522. 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.

[0064] The plate member 522 may be made of a material selected from pure titanium, titanium alloy, stainless steel, nickel alloy, and the like. 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 (ALLOY22, ALLOY C-276), Inconel (registered trademark) (Inconel 600, Inconel 625, Inconel 718), and the like. Nickel alloys are suitable as materials for the plate member 522 because of their excellent resistance to acid corrosion.

[0065] [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, making it possible to suppress acid corrosion of the plate member 522.

[0066] 5, the cleaning section 53 includes a first tank 531, a cleaning liquid supply section 532, and a cleaning unit 533. In this embodiment, as shown in Fig. 2, the cleaning unit 533 includes a first cleaning unit 533a and a second cleaning unit 533b provided at a position different from that of the first cleaning unit 533a. The first cleaning unit 533a is provided corresponding to the first heat exchange unit 521a, and the second cleaning unit 533b is provided corresponding to the second heat exchange unit 521b.

[0067] 5, the cleaning liquid L1 is stored in the first tank 531. The first tank 531 is provided outside the housing 51 (see FIG. 2).

[0068] 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 units 533 (each of the first cleaning unit 533a and the second cleaning unit 533b), and the cleaning liquid L1 flowing through the cleaning liquid supply path 532b is supplied to the cleaning units 533 (each of the first cleaning unit 533a and the second cleaning unit 533b).

[0069] Each of the first cleaning unit 533a and the second cleaning unit 533b 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.

[0070] The nozzle pipe 535 is connected to a cleaning liquid supply path 532b via a control valve 537, and the cleaning liquid L1 is supplied from the cleaning liquid supply path 532b.

[0071] 2, each of the first cleaning unit 533a and the second cleaning unit 533b includes a plurality of nozzle pipes 535, which are arranged side by side in a direction perpendicular to the exhaust gas flow direction D1 on an imaginary plane parallel to a main surface 522s of the plate member 522. In this embodiment, each of the first cleaning unit 533a and the second cleaning unit 533b includes two nozzle pipes 535, which are connected to one control valve 537.

[0072] 3, the nozzle pipe 535 extends in a direction perpendicular to the main surface 522s of the plate member 522, and a plurality of nozzles 536 are provided along the extending direction. Note that FIG. 3 illustrates one of the two nozzle pipes 535 connected to one control valve 537.

[0073] 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.

[0074] 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 the 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 capable of adjusting the valve opening 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. As shown in FIG. 5, the control valve 537 is provided in each of the nozzle pipe 535 of the first cleaning unit 533a and the nozzle pipe 535 of the second cleaning unit 533b. The first cleaning unit 533a and the second cleaning unit 533b are configured to be able to individually adjust the supply amount by controlling the opening degree, etc. of each control valve 537.

[0075] 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 spray amount (L / piece) of cleaning liquid L1 sprayed from one nozzle 536 at a time, 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.

[0076] The supply amount is set based on, for example, the total area (hereinafter referred to as "total sulfuric acid condensation area") of the plate member 522 included in the sulfuric acid condensation area of ​​the heat exchanger 52 (area where the temperature of the heat transfer surface of the plate member 522 can be equal to or lower than 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 a 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. 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 the waste, compared to the exhaust gas generated by burning fossil fuels such as coal, and it is not easy to estimate the total sulfuric acid condensation area of ​​the plate member 522. For this reason, an experimental heat exchanger may be provided 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 related in advance based on, for example, the experimental results using the experimental heat exchanger, the results obtained by trial operation, etc.

[0077] In this embodiment, a different supply amount is set for each cleaning unit 533 (first cleaning unit 533a and second cleaning unit 533b) (see FIG. 2). That is, the supply amount can be made different according to the region where the temperature of the heat transfer surface of the plate member 522 may become equal to or lower than the sulfuric acid dew point (where condensate is likely to adhere to the plate member 522).

[0078] Specifically, 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 in this embodiment, the second supply amount is set to be larger than the first supply amount. This makes it possible to more efficiently suppress acid corrosion of the plate member 522.

[0079] As described with reference to FIG. 2, 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. That is, the second cleaning unit 533b is disposed downstream of the first cleaning unit 533a in the exhaust gas flow direction D1. The temperature of the exhaust gas decreases toward the downstream side in the exhaust gas flow direction D1, and the temperature of the heat transfer surface (main surface 522s) of the plate member 522 can become equal to or lower than the sulfuric acid dew point. That is, the total sulfuric acid condensation area of ​​the plate member 522 (second plate member 522b) included in the second heat exchange unit 521b is larger than the total sulfuric acid condensation area of ​​the plate member 522 (first plate member 522a) included in the first heat exchange unit 521a. Therefore, by making the second supply amount greater than the first supply amount, acid corrosion of the plate member 522 can be efficiently suppressed.

[0080] In this embodiment, the second cleaning unit 533b (second heat exchange unit 521b) is provided below the first cleaning unit 533a (first heat exchange unit 521a). This allows the sprayed cleaning liquid L1 to flow smoothly downward due to gravity, and prevents the cleaning liquid L1 from taking heat from the plate member 522 located below. As a result, it is possible to prevent the cleaning unit 533 (cleaning liquid L1) from being cooled due to the cleaning liquid L1 staying on the plate member 522, and to suppress a decrease in the heat recovery rate of the exhaust gas. In addition, since the cleaning liquid L1 supplied to the first heat exchange unit 521a flows into the second heat exchange unit 521b, the cleaning liquid L1 supplied to the first heat exchange unit 521a can be used to clean the second heat exchange unit 521b.

[0081] The ejection conditions (cleaning conditions) of the ejection frequency, the ejection amount, and the ejection time are set so as to obtain a set supply amount. In this embodiment, the ejection frequency of the second nozzle 536b ejecting the cleaning liquid L1 is set to be higher than the ejection frequency of the first nozzle 536a ejecting the cleaning liquid L1, so that the second supply amount is set to be higher than the first supply amount. The ejection amount of the second nozzle 536b may be set to be higher than the ejection amount of the first nozzle 536a, so that the second supply amount is higher than the first supply amount, or the ejection time of the second nozzle 536b may be set to be longer than the ejection time of the first nozzle 536a, so that the second supply amount is higher than the first supply amount. The supply amount may be set by combining at least two of the ejection frequency, the ejection amount, and the ejection time. That is, the supply amount is adjusted by changing at least one value of the ejection frequency of the nozzle 536, the ejection amount per one, and the ejection time per one. This makes it possible to easily adjust the supply amount depending on the region where the temperature of the heat transfer surface (main surface 522s) of the plate member 522 can become equal to or lower than the sulfuric acid dew point.

[0082] The injection conditions (supply amount) may be predetermined constant conditions, but may also be set by a control device 55 further provided in the white smoke prevention preliminary heat exchanger 50, as shown in FIG.

[0083] 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.

[0084] 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 introduction 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 introduction 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. In this embodiment, the flow rate of the exhaust gas, the introduction temperature of the exhaust gas, the exhaust temperature of the exhaust gas, the introduction temperature of the white smoke prevention air, the exhaust temperature of the white smoke prevention air, and the flow rate of the white smoke prevention air are each actually measured values. However, at least one of the flow rate of the exhaust gas, the inlet temperature of the exhaust gas, the exhaust temperature of the exhaust gas, the inlet temperature of the white smoke prevention air, the outlet temperature of the white smoke prevention air, and the flow rate of the white smoke prevention air is an actual measurement value, and the other temperatures or flow rates may be approximate values ​​obtained based on experimental results, etc. This makes it possible to reduce the cost of the waste treatment facility 100.

[0085] The temperature of the exhaust gas and the temperature of the white smoke prevention air are acquired based on information output from a temperature sensor S further provided in the white smoke prevention preliminary heat exchanger 50. The temperature sensor S is, for example, a thermocouple, a resistance temperature detector, etc. The temperature sensor S acquires the temperature of the measurement object and outputs information indicating the temperature.

[0086] 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 an inlet 50a through which exhaust gas is introduced as shown in Fig. 2, 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 an outlet 50b through which exhaust gas is discharged, the third temperature sensor S3 is inserted into a duct connected to an inlet 50c through which white smoke prevention air is introduced, and the fourth temperature sensor S4 is inserted into a duct connected to an outlet 50d through which white smoke prevention air is discharged, and measures the center of the exhaust gas flow in those ducts.

[0087] The flow rates of the exhaust gas and the white smoke prevention air are acquired 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 an inlet 50a through which the exhaust gas is introduced. The second flow meter F2 is provided, for example, inside a duct connected to an 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.

[0088] The temperature acquisition unit 551 shown in Fig. 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 inlet temperature of the exhaust gas is 200 degrees, the exhaust gas discharge temperature is 100 degrees, the inlet temperature of the white smoke prevention air is 20 degrees, and the discharge temperature of the white smoke prevention air is 125 degrees, the temperature acquisition unit 551 estimates that the temperature of the plate member 522 changes approximately linearly in the range from 160 degrees to 60 degrees along the flow direction of the exhaust gas, taking into account the amount of heat transfer, and calculates the plate temperature.

[0089] The supply amount setting unit 552 sets the supply amount of the 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 ​​each plate of the first heat exchange unit 521a and the second heat exchange unit 521b. Note that association information between the total sulfuric acid condensation area and the supply amount is stored in advance in a memory area of ​​the control device 55. The supply amount setting unit 552 sets the supply amount of the 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.

[0090] Moreover, 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, when the temperature drop of the plate member 522 caused by one jetting from the nozzle 536 is equal to or higher than the first temperature drop threshold set in advance, the supply amount is set to a value smaller than the set supply amount (the supply amount is reduced). On the other hand, when the temperature drop of the plate member 522 caused by one jetting from the nozzle 536 is equal to or higher than the second temperature drop threshold set in advance 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, when the temperature drop of the plate member 522 caused by one jetting from the nozzle 536 is lower than the second temperature drop threshold set in advance, the supply amount is set to a value larger than the set supply amount (the supply amount is increased). Note that the first temperature drop threshold is a value larger than the second temperature drop threshold. Moreover, information indicating the first temperature drop threshold and information indicating the second temperature drop threshold are stored in advance in a storage area of ​​the control device 55.

[0091] The condition setting unit 553 sets the jetting conditions (ejection amount, jetting time, and jetting frequency) of the nozzles 536 so that a set supply amount of cleaning liquid L1 is supplied to the plate member 522. In this embodiment, the condition setting unit 553 sets the jetting conditions of the first cleaning unit 533a and the second cleaning unit 533b so that the second supply amount is greater than the first supply amount. Note that the jetting conditions of each of the multiple nozzles 536 constituting a single cleaning unit 533 are the same.

[0092] The cleaning control unit 554 controls the operation of the control valve 537. More specifically, the cleaning control unit 554 controls the operation of the control valve 537 (for example, the timer operation of the solenoid valve) so as to achieve the injection frequency, injection time, and injection amount set by the condition setting unit 553. In this embodiment, the cleaning control unit 554 can individually control the control valves 537 of the first heat exchange unit 521a and the second heat exchange unit 521b. 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.

[0093] [Effects of the embodiment] As described above, according to this embodiment, the white smoke prevention reserve heat exchanger 50 is provided downstream of the dust collector 40 in the exhaust gas flow direction D1, so that it is possible to recover thermal energy from lower temperature exhaust gas. This allows the heat of the exhaust gas to be recovered without waste, and improves the heat recovery rate of the exhaust gas. 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.

[0094] 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 (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 lower than 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.

[0095] In addition, the region RS where the sulfuric acid component contained in the exhaust gas generated by burning waste with unstable properties can be condensed below the sulfuric acid dew point varies depending on the environment, etc., but according to this embodiment, the spraying conditions (cleaning conditions) of the first cleaning unit 533a and the second cleaning unit 533b can be made different depending on the region where the condensate is likely to adhere (the temperature of the main surface 522s of the plate member 522 can be made below the sulfuric acid dew point). This makes it possible to suppress acid corrosion of the plate member 522. Also, when the amount of the cleaning liquid L1 is increased, the temperature of the heat transfer surface (main surface 522s) of the plate member 522 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, but according to this embodiment, the spraying conditions (cleaning conditions) of the first cleaning unit 533a and the second cleaning unit 533b can be made different, so that the temperature drop of the heat transfer surface can be suppressed and the decrease in the heat recovery rate of the exhaust gas can be suppressed. Therefore, it is possible to suppress corrosion of the heat exchanger caused by exhaust gas generated by burning waste with unstable properties, while suppressing a decrease in the heat recovery rate.

[0096] In addition, in the case where the waste is ammonia-containing waste such as dehydrated sludge obtained by dehydrating sewage sludge, NH 3 As shown in FIG. 7, the ammonia derived from the waste is still present without adding any ammonia (ammonia), and the SOx and NH 3 and SOx react with NH 4 ) 2 SO 4 (ammonium sulfate). HCl (hydrochloric acid) in the exhaust gas is converted to NH 3 reacts with NH 4Cl (ammonium chloride). FIG. 7 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 cleaned. The vertical axis in FIG. 7 shows the temperature of the main surface 522s (heat transfer surface) of the plate member 522, and the horizontal axis shows the relative amount of products generated near the main surface 522s of the plate member 522. The vertical axis shows lower temperatures. Also, from the left in FIG. 7, black ink hatching shows Fe 2 O 3 (iron(III) oxide), and the upward-sloping hatching indicates the relative amount of NH 4 The upward-sloping hatching indicates the relative amount of (NH 4 ) 2 SO 4 The lighter shaded areas indicate the relative amount of H 2 As shown in FIG. 7, the relative amounts of Fe and O are 2 O 3 , (NH 4 ) 2 SO 4 Compared with sulfuric acid, the plate member 522 is less susceptible to acid corrosion in the presence of water, and has the effect of reducing the sulfuric acid concentration, thereby improving the durability of the plate member 522. In particular, below the sulfuric acid dew point Ts, condensation of sulfuric acid begins, and NH 3 It reacts with (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 water condensation is small and the sulfuric acid concentration is likely to increase, (NH 4 ) 2 SO 4 The generation of NH becomes dominant, and it becomes possible to reduce 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. 4 Cl dissolves in water, causing the pH to increase, but NH 4 In addition, when the plate member 522 is not washed with the cleaning liquid L1, the adhesion of the Cl aqueous solution can be prevented. 2 O3 It was also confirmed that solid matter mainly composed of was attached over the entire main surface 522s of the plate member 522, so cleaning with the cleaning liquid L1 was also effective in preventing rust.

[0097] [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).

[0098] (1) In the present embodiment, the white smoke prevention reserve heat exchanger 50 is a cross-flow plate-type heat exchanger, but the white smoke prevention reserve heat exchanger 50 may be a counterflow, parallel flow, or other plate-type heat exchanger. Furthermore, 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 directions of the exhaust gas and the white smoke prevention air in the white smoke prevention preliminary heat exchanger 50 can be changed as appropriate.

[0099] (2) In the present embodiment, the case where there is one white smoke prevention main heat exchanger 30 has been described. However, there may be a plurality of white smoke prevention main heat exchangers 30.

[0100] (3) In the present embodiment, an example has been described in which the white smoke prevention main heat exchanger 30 and the white smoke prevention reserve heat exchanger 50 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.

[0101] (4) In the present embodiment, the dust collecting device 40 is provided downstream of the white smoke prevention main heat exchanger 30 in the exhaust gas flow direction D1. However, the dust collecting device 40 may be provided upstream of the white smoke prevention main heat exchanger 30 in the exhaust gas flow direction D1.

[0102] (5) In this embodiment, the power generation equipment 70 has a hot water boiler 71, a circulation path 72, and a power generation device 73. However, the power generation equipment 70 may also be composed of a steam boiler, a water supply pump, a water supply tank, etc.

[0103] (6) In this embodiment, the second heat exchange unit 521b is provided below the first heat exchange unit 521a, but the second heat exchange unit 521b does not have to be provided below the first heat exchange unit 521a as long as it is downstream of the first heat exchange unit 521a in the exhaust gas flow direction D1, and may be provided in parallel to the first heat exchange unit 521a or above the first heat exchange unit 521a.

[0104] (7) In the present embodiment, the case where there are two heat exchange units 521 has been described, but there may be one heat exchange unit 521, or three or more heat exchange units. When there are three or more heat exchange units 521, the combination of the number of first heat exchange units 521a and the number of second heat exchange units 521b is set arbitrarily. In addition, the cleaning units 533 are provided according to the number of heat exchange units 521.

[0105] (8) The number of nozzle pipes 535 included in the cleaning unit 533 can be changed arbitrarily. In addition, the number of nozzles 536 provided in the nozzle pipes 535 can also be changed arbitrarily. In addition, the number of nozzle pipes 535 connected to one control valve 537 can also be changed arbitrarily.

[0106] (9) In the present embodiment, the cleaning section 53 includes the first tank 531, but the cleaning section 53 may omit the first tank 531. In this case, the nozzle 536 is supplied with clean water, industrial water, sand filtered water, treated sewage water, or the like. In addition, the control valve 537 is a combination of a manual valve and an electromagnetic valve, but the control valve 537 may be any valve capable of controlling the valve opening. In addition, in the present embodiment, the first pump 532a is a pump common to the first cleaning unit 533a and the second cleaning unit 533b, but the first cleaning unit 533a and the second cleaning unit 533b may each have a pump capable of being controlled individually.

[0107] (10) In the present embodiment, the case has been described where the jetting conditions (cleaning conditions) of the nozzle 536 are set by the control device 55, but the jetting conditions may be set manually. For example, in periodic inspections that are performed periodically, such as every year or every six months, an engineer may set the jetting conditions of the nozzle 536 based on the degree of progress of corrosion of the plate member 522, etc. Note that the jetting conditions are not limited to being set by an engineer, and may be set by an operator, a worker, or the like.

[0108] (11) In this embodiment, the temperature acquisition unit 551 acquires the plate temperature based on the introduction 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 introduction 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. The temperature acquisition unit 551 may acquire the plate temperature based on at least one of the introduction temperature of the exhaust gas, the exhaust temperature of the exhaust gas, the introduction 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. Also, for example, the white smoke prevention preliminary heat exchanger 50 may further include a temperature sensor for acquiring the temperature of the plate member 522, and the temperature acquisition unit 551 may acquire the temperature (representative value) of a plate member 522 preset from among the plurality of plate members 522 as the plate temperature. The temperature sensor may acquire the temperature (representative value) of each of the plurality of plate members 522 that constitute the heat exchange unit 521 (each of the first heat exchange unit 521a and the second heat exchange unit 521b). Furthermore, the white smoke prevention preliminary heat exchanger 50 may include, for example, a plurality of temperature sensors for acquiring the temperature of the plate member 522, and the temperature acquisition unit 551 may acquire the maximum value, the minimum value, or the average value of the temperatures of the plurality of plate members 522 acquired by the plurality of temperature sensors as the plate temperature. The plurality of temperature sensors may be provided on one plate member 522, or may be provided distributed among the plurality of plate members 522. The greater the number of temperature sensors provided on one plate member 522, the higher the accuracy.

[0109] (12) 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.

[0110] (13) In the present embodiment, the flat plate member 522 is used as an example of the partition member. However, instead of the flat plate member 522, a plate member having a curved portion, such as a plate member that is curved in an uneven shape, may be used.

[0111] (14) In the present embodiment, the pair of plate members 522t are provided in parallel with a space between them so that the opposing main surfaces 522s are parallel to each other, but the opposing main surfaces 522s of the pair of plate members 522 may be provided at an incline so as to approach each other toward the downstream side in the exhaust gas flow direction D1. This allows, for example, the cleaning liquid L1 to accumulate 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.

[0112] (15) In the present embodiment, the supply rate setting unit 552 adjusts the supply rate. However, the supply rate setting unit 552 does not have to adjust the supply rate.

[0113] (16) In the present embodiment, the first supply amount is set to be greater than the second supply amount. However, the second supply amount may be equal to the first supply amount, or the second supply amount may be set to be greater than the first supply amount. For example, the deposit of exhaust gas generated by burning sewage sludge among waste materials is mainly ammonium sulfate, which is less soluble in water than the deposit of 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, in the case where the second heat exchange unit 521b is disposed below the first heat exchange unit 521a, the cleaning liquid L1 supplied from the first cleaning unit 533a to the first heat exchange unit 521a flows into the second heat exchange unit 521b, so that the second supply amount of the cleaning liquid L1 supplied from the second cleaning unit 533b can be reduced. As a result, the second supply amount can be made smaller than the first supply amount. [Industrial Applicability]

[0114] INDUSTRIAL APPLICABILITY The present invention can be used in a waste treatment facility and a waste treatment method. [Explanation of symbols]

[0115] 10: Incinerator 40: Dust collector 50: White smoke prevention spare heat exchanger (low temperature heat exchanger) 53: Cleaning section (cleaning device) 536: Nozzle 60: Smoke cleaning device (wet type smoke cleaning device) 100: Waste treatment facilities 521a: First heat exchange unit 521b: Second heat exchange unit 522: Plate member (partition member) 533: Cleaning unit 533a: First cleaning unit 533b: Second cleaning unit D1: Exhaust gas flow direction L1: cleaning solution R51: Heat exchange exhaust gas passage (exhaust gas passage) R52: Heat exchange air passage (heat exchange gas passage)

Claims

1. 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 comprises: 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; A cleaning device that cleans the partition member with a cleaning liquid, the cleaning device includes a cleaning unit having a plurality of nozzles that supply the cleaning liquid to the partition member; the cleaning unit is configured such that a first cleaning unit and a second cleaning unit disposed at a position different from that of the first cleaning unit are capable of individually adjusting a supply amount of the cleaning agent; the low-temperature heat exchanger includes a first heat exchange unit that is cleaned by the first cleaning unit, and a second heat exchange unit that is disposed downstream of the first heat exchange unit in the exhaust gas flow direction and that is cleaned by the second cleaning unit, A waste treatment facility, wherein a first supply amount of the cleaning liquid supplied from the nozzle of the first cleaning unit to the partition member is different from a second supply amount of the cleaning liquid supplied from the nozzle of the second cleaning unit to the partition member.

2. The waste treatment facility according to claim 1 , wherein in the low-temperature heat exchanger, the second heat exchange unit is provided below the first heat exchange unit.

3. The waste treatment facility according to claim 1 , wherein the second supply rate is greater than the first supply rate.

4. 4. The waste treatment facility according to claim 3, wherein each of the first supply amount and the second supply amount is adjusted by changing at least one value of a spray frequency of the nozzle, a spray amount per spray of the nozzle, and a spray time per spray of the nozzle.

5. The waste treatment facility according to claim 1 , wherein the waste contains an ammonia component.

6. 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; In the cleaning step, the partition member is cleaned in a state in which a first cleaning unit included in the cleaning device and a second cleaning unit disposed at a position different from the first cleaning unit are capable of individually adjusting supply amounts of the cleaning agent, the heat exchange in the heat recovery step includes heat exchange in a first heat exchange unit that is cleaned by the first cleaning unit, and heat exchange in a second heat exchange unit that is disposed downstream of the first heat exchange unit in a flow direction of the exhaust gas and that is cleaned by the second cleaning unit; a first supply amount of the cleaning liquid supplied from the first cleaning unit to the partition member and a second supply amount of the cleaning liquid supplied from the second cleaning unit to the partition member are adjusted to be different from each other in the cleaning step.

7. 7. The method for treating waste according to claim 6, wherein the waste contains an ammonia component.

Images