waste treatment facilities

Abstract

To provide a waste processing facility which enables improvement of durability of a heat exchanger.SOLUTION: A waste processing facility includes: an incinerator for incinerating waste; 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 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 a 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 in which the heat exchange gas flows from an exhaust gas passage in which the exhaust gas flows. The partition member 522 includes: a first partition member 522a formed of a first material; and a second partition member 522b formed of a second material having acid corrosion resistance higher than that of the first material. Further, the second partition member 522b is disposed at an area RS where a temperature of a heat transfer surface may become a sulfuric acid dew point or lower.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Among waste treatment facilities that incinerate and treat waste, there are facilities that are equipped with heat exchangers that exchange heat between exhaust gas and a heating 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 combustion gas supplied to the pressurized fluidized furnace with combustion exhaust gas discharged from the pressurized fluidized furnace, a dust collector for removing dust and other particles from 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 white smoke prevention air with the combustion exhaust gas supplied from the turbocharger, and an exhaust gas treatment device for removing impurities from 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 a white smoke prevention blower, thereby raising the temperature of the white smoke prevention air and lowering the temperature of the combustion exhaust gas.

[0004] 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 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 then led to the low-temperature heat exchanger. [Prior art documents] [Patent documents]

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

[0006] In heat exchangers that perform heat exchange between exhaust gas and a heat transfer medium, such as those 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 transfer 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 other substances contained in SOx in the exhaust gas condense and adhere to the heat transfer surface of the heat exchanger. When 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 materials with unstable properties, such as waste, contains various components, and condensates of various components adhere to the heat transfer surface, causing corrosion of the heat exchanger's heat transfer surface. 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.

[0007] For these reasons, it is desirable to improve the durability of heat exchangers. [Means for solving the problem]

[0008] The waste treatment facility according to the present invention is characterized by comprising: an incinerator for incinerating waste; a dust collector for collecting dust contained in exhaust gas discharged from the incinerator; a smoke scrubbing device that is provided downstream of the dust collector in the direction of flow of the exhaust gas and performs a smoke scrubbing process to purify the exhaust gas; and a low-temperature heat exchanger that is provided between the dust collector and the smoke scrubbing device and recovers heat from the exhaust gas by exchanging heat between the exhaust gas and a heat exchange gas, the low-temperature heat exchanger having a flat plate-shaped main surface. The heat exchange gas passage through which the heat exchange gas flows and the exhaust gas passage through which the exhaust gas flows are formed between the opposing partition members. The partition members include a first partition member made of a first material and a second partition member made of a second material having higher acid corrosion resistance than the first material. The second partition member is arranged in a region where the temperature of the heat transfer surface of the partition member can be equal to or lower than the sulfuric acid dew point. The first material is stainless steel, and the second material is one of pure titanium, a titanium alloy containing 50% by mass or more of titanium, and a nickel alloy containing 40% by mass or more of nickel. It is at that point.

[0009] According to this configuration, the plurality of partition members separating the heat exchange gas passage through which the heat exchange gas flows and the exhaust gas passage through which the exhaust gas flows include a first partition member made of a first material and a second partition member made of a second material having higher acid corrosion resistance than the first material. The second partition member is disposed in a region where the temperature of the heat transfer surface of the partition member may be below the sulfuric acid dew point. In other words, by disposing the second partition member made of the second material having high acid corrosion resistance in a region where the temperature of the heat transfer surface of the partition member may be below the sulfuric acid dew point, acid corrosion of the partition member can be suppressed, thereby increasing the durability of the partition member. Therefore, the durability of the low-temperature heat exchanger can be increased. Furthermore, although materials with high acid corrosion resistance are generally expensive, disposing the second partition member in a region where the temperature may be below the sulfuric acid dew point can reduce the cost of the low-temperature heat exchanger.

[0010] Furthermore, with this configuration, since the low-temperature heat exchanger is provided downstream of the dust collector in the direction of exhaust gas flow, it is possible to recover the thermal energy of lower-temperature exhaust gas. 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. Furthermore, according to this configuration, by using as the material (second material) of the second partition member any of pure titanium, a titanium alloy containing 50% or more by mass of titanium, and a nickel alloy containing 40% or more by mass of nickel, which have higher acid corrosion resistance than the material (first material) of the first partition member, stainless steel, acid corrosion of the partition member can be reliably suppressed.

[0011] As another feature, the second partition member may be disposed downstream of the first partition member in the exhaust gas flow direction.

[0012] The temperature of the exhaust gas decreases downstream in the exhaust gas flow direction, and the temperature of the partition member also decreases in proportion to the exhaust gas temperature. According to this configuration, the second partition member 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, thereby efficiently suppressing acid corrosion of the partition member.

[0015] In another feature, the waste material may contain an ammonia component.

[0016] 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. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic diagram of a waste treatment facility according to an embodiment. [Figure 2] FIG. 2 is a schematic diagram illustrating a configuration of a white smoke prevention preparatory heat exchanger according to the embodiment. [Figure 3] 3A and 3B are diagrams illustrating the configuration of a heat exchange unit and a cleaning unit according to the embodiment. [Figure 4] FIG. 2 is a perspective view showing a plate member according to the embodiment. [Figure 5] FIG. 2 is a diagram showing the configuration of a cleaning unit according to the embodiment. [Figure 6]FIG. 2 is a block diagram showing the configuration of a white smoke prevention pre-heat exchanger according to the embodiment. [Figure 7] FIG. 4 is a graph showing the sulfuric acid concentration of condensed liquid formed by condensing SOx components in exhaust gas relative to the temperature of the plate member according to the embodiment. [Figure 8] 3A to 3C are diagrams illustrating a schematic erosion mechanism on a main surface of a plate member according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of a waste treatment facility equipped with a white smoke prevention pre-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 within the scope of the present invention.

[0019] [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 collector 40, a white smoke prevention spare heat exchanger 50 (an example of a low-temperature heat exchanger), a wet smoke washing device 60, and a power generation facility 70.

[0020] The waste treatment facility 100 also includes an exhaust gas passage R1 through which exhaust gas generated when waste is burned in the incinerator 10 flows. The incinerator 10, combustion air supply device 20, white smoke prevention main heat exchanger 30, dust collector 40, white smoke prevention spare heat exchanger 50, wet smoke scrubber 60, and 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 will be referred to as the "exhaust gas flow direction D1."

[0021] [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 to 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).

[0022] The combustion air supply device 20 supplies combustion air to the incinerator 10, which 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 the exhaust gas discharged from the incinerator 10 is introduced into the combustion air supply device 20.

[0023] The combustion air supply device 20 has a combustion air heat exchanger 21 and a supercharger 22. The combustion air supply device 20 may have a fluidization blower instead of the supercharger 22.

[0024] 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 a turbocharger 22.

[0025] 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.

[0026] 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 white smoke prevention main heat exchanger 30 receives the exhaust gas after heat exchange in the combustion air supply 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-type heat exchanger.

[0027] The white smoke prevention main heat exchanger 30 is provided to prevent the flue 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 flue gas introduced from the combustion air supply device 20 and air (hereinafter referred to as "white smoke prevention air"). This cools the flue gas and heats the white smoke prevention air. The white smoke prevention air is introduced by being pushed out from a blower B which is also 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.

[0028] 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 that has undergone heat exchange in the white smoke prevention main heat exchanger 30 is introduced into the dust collector 40. The dust collector 40 captures dust contained in the exhaust gas. In this embodiment, the dust collector 40 is configured as a bag filter. However, the dust collector 40 is not limited to being configured as a bag filter, and may be configured as a ceramic filter or the like.

[0029] The white smoke prevention preliminary heat exchanger 50 is provided downstream of the dust collector 40 in the exhaust gas flow direction D1, and exhaust gas is introduced into the white smoke prevention preliminary heat exchanger 50 after dust has been collected by the dust collector 40. The white smoke prevention preliminary heat exchanger 50 is a type of heat exchanger, and in this embodiment is a plate-type heat exchanger. Because the white smoke prevention preliminary heat exchanger 50 is a plate-type heat exchanger, heat exchange takes place over a wide heat transfer surface.

[0030] The white smoke prevention reserve heat exchanger 50 is provided to prevent the exhaust gas discharged from the chimney from cooling 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 referred to as the "low-temperature heat exchanger," and the white smoke prevention main heat exchanger 30 is sometimes referred to as the "high-temperature heat exchanger."

[0031] The white smoke prevention preheat exchanger 50 heats white smoke prevention air (an example of heat exchange gas) by utilizing the thermal energy of the introduced exhaust gas. Specifically, the white smoke prevention preheat exchanger 50 exchanges heat between the exhaust gas introduced from the dust collector 40, i.e., the exhaust gas after dust removal, 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. The temperature of the exhaust gas introduced into the white smoke prevention preheat exchanger 50 is between 160°C and 250°C. By performing heat exchange in the white smoke prevention preheat exchanger 50, the temperature of the exhaust gas drops to between 50°C and 150°C.

[0032] The wet smoke scrubbing device 60 is provided downstream of the white smoke prevention preliminary heat exchanger 50 in the flue gas flow direction D1, and the flue gas that has undergone heat exchange in the white smoke prevention preliminary 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 flue gas. In this embodiment, the wet smoke scrubbing device 60 purifies the flue gas through the wet smoke scrubbing process and removes moisture from the flue gas through dehumidification and cooling. Circulating water containing a chemical agent is used to purify the flue gas. Cooling water is used to dehumidify and cool the flue gas. The amount of flue gas is reduced by removing moisture from the flue gas through dehumidification and cooling. The purified flue gas flows toward a chimney (not shown).

[0033] [White smoke prevention air path] The waste treatment facility 100 further includes a white smoke prevention air path R2 through which white smoke prevention air flows. Hereinafter, the flow direction of the white smoke prevention air flowing through the white smoke prevention air path R2 will be referred to as "air flow direction D2".

[0034] The white smoke prevention air path R2 connects the blower B that sends out white smoke prevention air, the white smoke prevention auxiliary heat exchanger 50, the white smoke prevention main heat exchanger 30, the power generation equipment 70, and a chimney (not shown).

[0035] The white smoke prevention pre-heat exchanger 50 is located 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 pre-heat exchanger 50. The temperature of the white smoke prevention air introduced into the white smoke prevention pre-heat exchanger 50 is the same as the outside air temperature, and is between 0 and 50°C. The temperature of the white smoke prevention air rises to between 50 and 220°C by exchanging heat with the exhaust gas.

[0036] The white smoke prevention main heat exchanger 30 is located downstream of the white smoke prevention backup heat exchanger 50 in the air flow direction D2, and white smoke prevention air is introduced into the white smoke prevention main heat exchanger 30 after heat exchange in the white smoke prevention backup heat exchanger 50. The temperature of the white smoke prevention air introduced into the white smoke prevention main heat exchanger 30 is between 50°C and 220°C (for example, around 125°C). The temperature of the white smoke prevention air increases to between 220°C and 550°C by heat exchange in the white smoke prevention main heat exchanger 30. The heat recovery capacity of the white smoke prevention main heat exchanger 30 is preferably configured to be equal to or greater than the heat recovery capacity of the white smoke prevention backup heat exchanger 50 (for example, between 1 and 5 times).

[0037] 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.

[0038] The power generation facility 70 includes a hot water boiler 71 , a circulation path 72 , and a power generation device 73 .

[0039] 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 a circulation path 72.

[0040] 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 .

[0041] 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.

[0042] 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 between 100°C and 200°C.

[0043] 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 in stages by the white smoke prevention main heat exchanger 30 and the white smoke prevention reserve heat exchanger 50, and is finally cooled in the wet smoke scrubbing unit 60. After being cooled, the flue gas is heated by the white smoke prevention air that has passed through the power generation facility 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 from turning into white smoke when discharged from the chimney.

[0044] [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 housed in the housing 51.

[0045] [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 in the exhaust gas flow direction D1 will be referred to as the "first heat exchange unit 521a," and the heat exchange unit 521 on the downstream side will be 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.

[0046] The white smoke prevention air flows from outside 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 then 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).

[0047] 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).

[0048] [Plate member] 3 , the plate member 522 separates the white smoke prevention preliminary heat exchanger 50 into 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. A plurality of heat exchange exhaust gas passages R51 and a plurality of heat exchange air passages R52 are formed in parallel within the white smoke prevention preliminary heat exchanger 50, and the heat exchange exhaust gas passages R51 and the heat exchange air passages R52 are arranged alternately. The heat exchange exhaust gas passage R51 is the exhaust gas passage R1 within the white smoke prevention preliminary heat exchanger 50, and the heat exchange air passage R52 is the white smoke prevention air passage R2 within the white smoke prevention preliminary heat exchanger 50.

[0049] 3 and 4, the plate member 522 is flat and has a main surface 522s. The 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 minute irregularities such as grooves or protrusions may be formed on at least one side of the main surfaces 522s.

[0050] 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 with the heat exchange exhaust gas passage R51 therebetween will be referred to as "a pair of plate members 522t."

[0051] As shown in FIG. 3, the heat exchange air passage R52 is formed between adjacent heat exchange exhaust gas passages R51. As shown in FIG. 4, the heat exchange air passage R52 is formed by joining second ends 522f of a first joining plate 522A and a second joining plate 522B of an adjacent pair of plate members 522t. The second end 522f is an end of the plate member 522 in a direction perpendicular to the first end 522e and is formed between adjacent first end portions 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 across the heat exchange air passage R52.

[0052] The heat exchange exhaust gas passage R51 and the heat exchange air passage R52 overlap with each other across 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.

[0053] [Cleaning section] 3, the cleaning unit 53 cleans the plate member 522 with cleaning liquid L1. The cleaning liquid L1 is a liquid for removing deposits (condensate) adhering to the plate member 522, and in this embodiment is water (tap water, industrial water, sand filtered water, treated sewage water, etc.). The cleaning liquid L1 may also be an alkaline aqueous solution containing sodium hydroxide or the like.

[0054] When the temperature of the heat transfer surface (main surface 522s) of the plate member 522 drops due to the heat recovery of the exhaust gas, components contained in the exhaust gas condense and adhere to the plate member 522. In this embodiment, the cleaning unit 53 cleans the plate member 522 at predetermined intervals (preset frequency). This removes deposits adhered to the plate member 522, making it possible to suppress acid corrosion of the plate member 522. Furthermore, because the cleaning unit 53 is incorporated into the waste treatment facility 100, it becomes possible to clean the plate member 522 to which condensed matter has adhered during operation, making it possible to prevent the condensed matter from continuing to adhere 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.

[0055] 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 .

[0056] The cleaning liquid L1 is stored in the first tank 531. The first tank 531 is provided outside the housing 51 (see FIG. 2).

[0057] 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 receives the cleaning liquid L1 transferred by the first pump 532a. 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.

[0058] 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.

[0059] The nozzle pipe 535 is connected to the cleaning liquid supply path 532b via a control valve 537, and the cleaning liquid L1 is supplied from the cleaning liquid supply path 532b.

[0060] 2, the cleaning unit 533 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 the main surface 522s of the plate member 522. In this embodiment, the cleaning unit 533 includes two nozzle pipes 535, and the two nozzle pipes 535 are connected to one control valve 537.

[0061] 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 two nozzle pipes 535 connected to one control valve 537.

[0062] 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.

[0063] 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 degree between fully open and fully closed, and a solenoid valve that switches ON (fully open) / OFF (fully closed) by timer operation.

[0064] Here, the supply amount refers to the amount of cleaning liquid L1 supplied to a heat exchange unit 521 per unit time (e.g., 24 hours) from a plurality of nozzles 536 constituting a 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·pieces) by the spray time (min) of one nozzle 536. Spray conditions such as the spray frequency, spray amount, and spray time are set by a control device 55 further provided in the white smoke prevention preliminary heat exchanger 50, as shown in FIG. 6.

[0065] The control device 55 controls the operation of the cleaning unit 53 (control valve 537). The control device 55 is configured, for example, as part of a programmable logic controller (sequencer) or a distributed control system (DCS). Alternatively, the control device 55 may be configured as a hardware timer that measures time such as cleaning time. The control device 55 may include a processor such as a central processing unit (CPU) and a storage area configured as 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 storage area.

[0066] [Plate member material] 2, the heat exchange section 52 includes a region RS 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 Ts. In this embodiment, the region RS is located within the second heat exchange unit 521b, which is arranged downstream of the first heat exchange unit 521a in the exhaust gas flow direction D1.

[0067] Region RS is a 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 Ts (see FIG. 7). FIG. 7 is a diagram schematically showing the sulfuric acid concentration C of the condensate formed by condensing the SOx components in the exhaust gas versus the temperature of the plate member 522. The vertical axis in FIG. 7 represents the temperature of the heat transfer surface (main surface 522s) of the plate member 522, and the curve represents the sulfuric acid concentration C of the condensate formed by condensing the SOx components in the exhaust gas.

[0068] The sulfuric acid dew point Ts varies depending on the concentrations of sulfuric acid and water contained in the exhaust gas, but is, for example, 130 to 150 degrees.

[0069] As shown in FIG. 7, in the region RS, the sulfuric acid concentration C of the condensed liquid decreases as the temperature of the heat transfer surface of the plate member 522 decreases.

[0070] 7, the lower the sulfuric acid concentration C of the condensate, the less likely the condensate (condensate) will adhere to the plate member 522, and the less acid corrosion of the plate member 522 will occur. However, the higher the sulfuric acid concentration C of the condensate, the more likely the condensate (condensate) will adhere to the plate member 522, and the more likely acid corrosion of the plate member 522 will occur. For this reason, in this embodiment, a material (second material) that is more resistant to acid corrosion than the material (first material) of the plate members 522 that are arranged outside the region RS (plate members 522 that are arranged in the first heat exchange unit 521a where the region RS is not located) is selected as the material. This makes it possible to suppress acid corrosion of the plate members 522. Hereinafter, the plate member 522 made of the first material will be referred to as the "first plate member 522a" (an example of the first partition member), and the plate member 522 made of the second material will be referred to as the "second plate member 522b" (an example of the second partition member).

[0071] The plate member 522 can be made of, for example, pure titanium, a titanium alloy, stainless steel, or a nickel alloy. In this embodiment, stainless steel is selected as the first material, and a nickel alloy is selected as the second material. Examples of stainless steel include austenitic stainless steel such as SUS316 (10-18 mass% nickel, 16-18 mass% chromium, 2-3 mass% molybdenum, balance iron) and SUS304 (8-10.5 mass% nickel, 18-20 mass% chromium, balance iron). Note that pure titanium or a titanium alloy containing 50 mass% titanium, other than a nickel alloy, may also be selected as the second material.

[0072] Examples of nickel alloys include Hastelloy (registered trademark), ALLOY, Inconel (registered trademark), etc. Examples of Hastelloy include Hastelloy C-22 (3 mass% iron, 56 mass% nickel, 22 mass% chromium, 13 mass% molybdenum, 3 mass% tungsten), Hastelloy C-276 (5 mass% iron, 57 mass% nickel, 16 mass% chromium, 16 mass% molybdenum, 4 mass% tungsten), other Hastelloys, etc. Other Hastelloys include Hastelloys containing 43 to 71 mass% nickel, such as Hastelloy C-4 (nickel 65 mass%, chromium 16 mass%, molybdenum 16 mass%), Hastelloy C-22HS (nickel 61 mass%, chromium 21 mass%, molybdenum 17 mass%), Hastelloy C-2000 (nickel 59 mass%, chromium 23 mass%, molybdenum 16 mass%, copper 1.6 mass%), and Hastelloy HYBRID-BC1 (nickel 62 mass%, chromium 15 mass%, molybdenum 22 mass%, manganese 0.25 mass%).

[0073] Examples of ALLOY include ALLOY22 (2 to 6 mass% iron, approximately 56 mass% nickel, 20 to 22.5 mass% chromium, 12.5 to 14.5 mass% molybdenum, and 2.5 to 3.5 mass% tungsten) and ALLOY C-276 (4 to 7 mass% iron, approximately 57 mass% nickel, 14.5 to 16.5 mass% chromium, 15 to 17 mass% molybdenum, and 3 to 4.5 mass% tungsten).

[0074] Examples of Inconel include Inconel 600 (6 to 10 mass% iron, 72 mass% nickel, 14 to 17 mass% chromium), Inconel 625 (58 mass% nickel, 20 to 23 mass% chromium, 8 to 10 mass% molybdenum, 3.15 to 4.15 mass% niobium), and Inconel 718 (a small amount of iron, 50 to 55 mass% nickel, 17 to 21 mass% chromium, 2.8 to 3.3 mass% molybdenum, 4.75 to 5.5 mass% niobium, 0.65 to 1.15 mass% titanium, and 0.2 to 0.8 mass% aluminum).

[0075] That is, the second material contains 40% to 75% by mass of nickel as the main component, more than 0 and 25% or less by mass of chromium as an essential component, and the remainder contains molybdenum, iron, tungsten, copper, manganese, niobium, titanium, aluminum, impurities, etc.

[0076] As described above, in this embodiment, the region RS where the temperature of the heat transfer surface (main surface 522s) of the plate member 522 can be equal to or lower than the sulfuric acid dew point Ts is a region within the second heat exchange unit 521b. Therefore, in this embodiment, the second heat exchange unit 521b is provided with a second plate member 522b made of a second material, and the first heat exchange unit 521a is provided with a first plate member 522a made of a first material. That is, the plate member 522 includes a first plate member 522a made of a first material and a second plate member 522b made of a second material having higher acid corrosion resistance than the first material, and the second plate member 522b is disposed downstream of the first plate member 522a in the exhaust gas flow direction D1. By using the second material having high acid corrosion resistance for the plate member 522 that constitutes the heat exchange section 52, the plate member 522 disposed downstream in the exhaust gas flow direction D1 can be efficiently suppressed from acid corrosion.

[0077] The concentration of sulfuric acid components (sulfur trioxide) contained in exhaust gas generated by burning coal (fossil fuel), such as in a coal-fired 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 generated by burning fossil fuels, and the effects of acid corrosion have traditionally been less of a problem in heat exchangers installed in waste treatment facilities than in the case of fossil fuels. However, in this embodiment, the presence of region RS in the white smoke prevention reserve heat exchanger 50 has been identified, and by placing a plate member 522 made of a material with high acid corrosion resistance in region RS, it has become possible to increase the durability of the heat exchanger even when it is installed in a low temperature range.

[0078] Furthermore, the sulfur content of exhaust gases generated by burning fossil fuels is somewhat fixed for each type of coal, making it easy to estimate the concentration of sulfur trioxide in the exhaust gases. However, the properties of waste are unstable, making it difficult to estimate the concentration of sulfur trioxide in the exhaust gases generated by burning waste. Therefore, the region RS may be determined based on the results of an experiment in which an experimental heat exchanger is installed in an existing waste treatment facility.

[0079] For example, an experimental heat exchanger may be installed in an existing waste treatment facility that does not have a white smoke prevention preheat exchanger. The degree of corrosion of a test piece placed in the experimental heat exchanger may be determined, and the region of the actual facility corresponding to the region of high corrosion on the test piece may be determined as the region RS. The degree of corrosion of the test piece may be determined by measuring the thickness of the test piece without contact, or by removing the test piece through an inspection hatch provided in the experimental heat exchanger and measuring the thickness of the test piece. By placing the second plate member 522b in the region RS determined by experiment, corrosion of the plate member 522 can be more reliably suppressed, thereby improving the durability of the white smoke prevention preheat exchanger 50. The experimental heat exchanger is installed between the dust collector and wet smoke scrubber of the existing waste treatment facility in the direction of exhaust gas flow.

[0080] [Effects of the embodiment] As described above, according to this embodiment, the white smoke prevention preheat exchanger 50 is provided downstream of the dust collector 40 in the exhaust gas flow direction D1, making it possible to recover thermal energy from lower-temperature exhaust gas. This allows the heat of the exhaust gas to be recovered without waste, improving the heat recovery rate of the exhaust gas. Moreover, because the white smoke prevention preheat exchanger 50 performs gas-to-gas heat exchange between the exhaust gas and the white smoke prevention air via the plate member 522, the temperature of the clean white smoke prevention air can be increased, making it possible to use it for various purposes, such as power generation.

[0081] Furthermore, the plurality of plate members 522 separating the heat exchange air passage R52 through which the white smoke prevention air flows and the heat exchange exhaust gas passage R51 through which the exhaust gas flows include first plate members 522a made of a first material and second plate members 522b made of a second material having higher acid corrosion resistance than the first material, and the second plate members 522b are arranged in a region RS where the temperature of the heat transfer surface of the plate members 522 may be equal to or lower than the sulfuric acid dew point Ts. That is, the second plate members 522b made of the second material having high acid corrosion resistance are arranged in the region RS where the temperature of the heat transfer surface of the plate members 522 may be equal to or lower than the sulfuric acid dew point Ts. This suppresses acid corrosion of the plate members 522 and improves the durability of the plate members 522. This improves the durability of the white smoke prevention reserve heat exchanger 50. Furthermore, although materials with high acid corrosion resistance are generally expensive, arranging the second plate members 522b in the region RS where the temperature may be equal to or lower than the sulfuric acid dew point reduces the cost of the low-temperature heat exchanger.

[0082] Furthermore, when the waste is ammonia-containing waste, such as dehydrated sludge obtained by dehydrating sewage sludge, ammonia derived from the waste remains present in the exhaust gas flowing through the white smoke prevention preheat exchanger 50 without adding NH3 (ammonia). As shown in FIG. 8, SOx in the exhaust gas reacts with NH3 on the main surface 522s (heat transfer surface) of the plate member 522 and in its vicinity, converting SOx to (NH4)2SO4 (ammonium sulfate), which is relatively less corrosive than SOx. Furthermore, HCl (hydrochloric acid) in the exhaust gas reacts with NH3 to convert to NH4Cl (ammonium chloride). FIG. 8 is a schematic diagram illustrating the erosion mechanism when the main surface 522s (heat transfer surface) of the plate member 522 is not cleaned. The vertical axis in FIG. 8 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. Note that the temperature decreases toward the bottom of the vertical axis. In addition, from left to right in Figure 8, the black hatching indicates the relative amount of Fe2O3 (iron(III) oxide), the left-leaning hatching indicates the relative amount of NH4Cl, the right-leaning hatching indicates the relative amount of (NH4)2SO4, and the light-black hatching indicates the relative amount of HO. As shown in Figure 8, 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 sulfuric acid concentration, thereby improving the durability of the plate member 522. In particular, it has been discovered that below the sulfuric acid dew point Ts, sulfuric acid begins to condense and reacts with NH3 depending on the amount of condensed water to form (NH4)2SO4. Based on these findings, when the waste is ammonia-containing waste such as sewage sludge, the production of (NH4)2SO4 instead of sulfuric acid becomes dominant, even near the sulfuric acid dew point Ts where the amount of condensed water is small and the sulfuric acid concentration tends to increase, making it possible to reduce the sulfuric acid concentration below the sulfuric acid dew point Ts. As a result, cleaning with the cleaning liquid L1 sprayed from the nozzle 536 described above can suppress acid corrosion of the plate member 522. Furthermore, although NH4Cl dissolves in water and the pH becomes high, cleaning with the cleaning liquid L1 sprayed from the nozzle 536 can prevent adhesion of the NH4Cl aqueous solution.It has also been confirmed that if the plate member 522 is not washed with the cleaning liquid L1, solid substances mainly composed of Fe2O3 adhere to the entire main surface 522s of the plate member 522, and therefore, cleaning with the cleaning liquid L1 is also effective in preventing rust.

[0083] [Another embodiment] The present invention may be configured as follows in addition to 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).

[0084] (1) In the present embodiment, the white smoke prevention preheat exchanger 50 is a cross-flow plate-type heat exchanger. However, the white smoke prevention preheat 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 ) of the white smoke prevention preheat exchanger 50 are not limited to those described in the embodiment and can be modified as appropriate. In this case, the flow directions of the exhaust gas and white smoke prevention air in the white smoke prevention preheat exchanger 50 can be modified as appropriate.

[0085] (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.

[0086] (3) In the present embodiment, the white smoke prevention main heat exchanger 30 and the white smoke prevention backup heat exchanger 50 are configured to heat the white smoke prevention air in order to prevent white smoke. However, the white smoke prevention main heat exchanger 30 and the white smoke prevention backup heat exchanger 50 may be heat exchangers that are simply provided to recover heat from exhaust gas.

[0087] (4) In the present embodiment, the dust collector 40 is provided downstream of the white smoke prevention main heat exchanger 30 in the exhaust gas flow direction D1. However, the dust collector 40 may be provided upstream of the white smoke prevention main heat exchanger 30 in the exhaust gas flow direction D1.

[0088] (5) In this embodiment, the second heat exchange unit 521b is arranged below the first heat exchange unit 521a, but the second heat exchange unit 521b does not have to be arranged 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 arranged parallel to the first heat exchange unit 521a or above the first heat exchange unit 521a.

[0089] (6) In the present embodiment, the case where there are two heat exchange units 521 has been described, but there may be one or three or more heat exchange units 521. 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 can be set arbitrarily.

[0090] (7) In this embodiment, the second plate member 522b made of the second material is disposed in the second heat exchange unit 521b. However, the second plate member 522b may be disposed in the region RS where the temperature of the main surface 522s of the plate member 522 can be equal to or lower than the sulfuric acid dew point Ts. For example, the second plate member 522b may be a plate member 522 disposed in part of the second heat exchange unit 521b. Alternatively, the second plate member 522b may be a plate member 522 disposed in part of the first heat exchange unit 521a and all of the second heat exchange unit 521b, or may be a plate member 522 disposed in only part of the first heat exchange unit 521a.

[0091] (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 on 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.

[0092] (9) In the present embodiment, the cleaning unit 53 includes the first tank 531. However, the cleaning unit 53 may omit the first tank 531. In this case, tap water, industrial water, sand-filtered water, treated sewage 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 opening degree can be controlled.

[0093] (10) In the present embodiment, the case where the spray conditions (cleaning conditions) of the nozzle 536 are set by the control device 55 has been described. However, the spray conditions may be set manually. For example, in periodic inspections that are carried out 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. Note that the spray conditions may not be set by an engineer, but may also be set by an operator, a worker, or the like.

[0094] (11) In the present embodiment, the cleaning unit 53 sprays the cleaning liquid L1 from the multiple nozzles 536 to clean the plate member 522 with the cleaning liquid L1, 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 holes provided in a pipe.

[0095] (12) In this embodiment, a 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.

[0096] (13) In the present 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, but the opposing main surfaces 522s of the pair of plate members 522 may be inclined so that they approach each other toward the downstream side in the exhaust gas flow direction D1. This allows, for example, the cleaning liquid L1 to stagnate 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.

[0097] (14) 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. [Industrial Applicability]

[0098] The present invention can be used in waste treatment facilities. [Explanation of symbols]

[0099] 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 facilities 522: Plate member (partition member) 522a: First plate member (first partition member) 522b: Second plate member (second partition member) D1: Exhaust gas flow direction R51: Heat exchange exhaust gas passage (exhaust gas passage) R52: Heat exchange air passage (heat exchange gas passage) RS: Area where the temperature may be above the sulfuric acid dew point Ts: Sulfuric acid dew point

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 the exhaust gas 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, which recovers 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 each having a flat main surface, The plurality of partition members are spaced apart and arranged such that the main surfaces are parallel to each other, a heat exchange gas passage through which the heat exchange gas flows and an exhaust gas passage through which the exhaust gas flows are formed between the opposing partition members, the partition member includes a first partition member made of a first material and a second partition member made of a second material having higher acid corrosion resistance than the first material; the second partition member is disposed in a region where the temperature of the heat transfer surface of the partition member can be equal to or lower than the sulfuric acid dew point; the first material is stainless steel; The second material is one of pure titanium, a titanium alloy containing 50% by mass or more of titanium, and a nickel alloy containing 40% by mass or more of nickel.

2. The waste treatment facility according to claim 1 , wherein the second partition member is disposed downstream of the first partition member in the exhaust gas flow direction.

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

Images