CN114364449B - Exhaust gas treatment device and exhaust gas treatment method - Google Patents
Exhaust gas treatment device and exhaust gas treatment method Download PDFInfo
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- CN114364449B CN114364449B CN202080061448.8A CN202080061448A CN114364449B CN 114364449 B CN114364449 B CN 114364449B CN 202080061448 A CN202080061448 A CN 202080061448A CN 114364449 B CN114364449 B CN 114364449B
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- 238000000034 method Methods 0.000 title claims description 14
- 229910052753 mercury Inorganic materials 0.000 claims abstract description 598
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 claims abstract description 595
- 239000003463 adsorbent Substances 0.000 claims abstract description 89
- 238000005259 measurement Methods 0.000 claims abstract description 75
- 238000011156 evaluation Methods 0.000 claims abstract description 32
- 230000001186 cumulative effect Effects 0.000 claims abstract description 25
- 238000011144 upstream manufacturing Methods 0.000 claims description 31
- 230000009467 reduction Effects 0.000 claims description 14
- 239000007789 gas Substances 0.000 description 153
- 239000002594 sorbent Substances 0.000 description 20
- 239000004744 fabric Substances 0.000 description 17
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 10
- 230000007423 decrease Effects 0.000 description 10
- 238000010586 diagram Methods 0.000 description 10
- 230000008859 change Effects 0.000 description 9
- 239000002699 waste material Substances 0.000 description 8
- 239000010881 fly ash Substances 0.000 description 7
- 238000009825 accumulation Methods 0.000 description 6
- 230000000875 corresponding effect Effects 0.000 description 6
- 239000000126 substance Substances 0.000 description 6
- 238000011001 backwashing Methods 0.000 description 5
- 230000001276 controlling effect Effects 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- TXKMVPPZCYKFAC-UHFFFAOYSA-N disulfur monoxide Inorganic materials O=S=S TXKMVPPZCYKFAC-UHFFFAOYSA-N 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- 239000003054 catalyst Substances 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- 239000002250 absorbent Substances 0.000 description 2
- 230000002745 absorbent Effects 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 150000002013 dioxins Chemical class 0.000 description 2
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 description 2
- 229910000041 hydrogen chloride Inorganic materials 0.000 description 2
- 230000006698 induction Effects 0.000 description 2
- 229940008718 metallic mercury Drugs 0.000 description 2
- 230000004044 response Effects 0.000 description 2
- 230000004043 responsiveness Effects 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 1
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 1
- 235000011116 calcium hydroxide Nutrition 0.000 description 1
- 239000000920 calcium hydroxide Substances 0.000 description 1
- RCTYPNKXASFOBE-UHFFFAOYSA-M chloromercury Chemical compound [Hg]Cl RCTYPNKXASFOBE-UHFFFAOYSA-M 0.000 description 1
- 239000000567 combustion gas Substances 0.000 description 1
- 230000002596 correlated effect Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 238000011033 desalting Methods 0.000 description 1
- 230000003009 desulfurizing effect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- PNDPGZBMCMUPRI-UHFFFAOYSA-N iodine Chemical compound II PNDPGZBMCMUPRI-UHFFFAOYSA-N 0.000 description 1
- 150000002731 mercury compounds Chemical class 0.000 description 1
- 238000010422 painting Methods 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- XTQHKBHJIVJGKJ-UHFFFAOYSA-N sulfur monoxide Chemical compound S=O XTQHKBHJIVJGKJ-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/46—Removing components of defined structure
- B01D53/64—Heavy metals or compounds thereof, e.g. mercury
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/81—Solid phase processes
- B01D53/83—Solid phase processes with moving reactants
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES
- F23J15/00—Arrangements of devices for treating smoke or fumes
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
- F27D17/00—Arrangements for using waste heat; Arrangements for using, or disposing of, waste gases
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
- F27D19/00—Arrangements of controlling devices
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
- F27D21/00—Arrangements of monitoring devices; Arrangements of safety devices
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- Health & Medical Sciences (AREA)
- Biomedical Technology (AREA)
- Analytical Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Treating Waste Gases (AREA)
- Waste-Gas Treatment And Other Accessory Devices For Furnaces (AREA)
- Chimneys And Flues (AREA)
Abstract
The adsorbent supply unit (41) supplies mercury adsorbent to the exhaust gas in the flue (3). The upstream-side mercury concentration meter (45) is capable of switching between a zero-valent mercury measurement state in which the zero-valent mercury concentration of the exhaust gas is measured and a full-valent mercury measurement state in which the full-valent mercury concentration of the exhaust gas is measured. A control unit (40) controls the amount of supply of the mercury adsorbent based on the zero-valent mercury concentration of the upstream-side mercury concentration meter in the zero-valent mercury measurement state, acquires an evaluation value indicating the cumulative amount of zero-valent mercury in the exhaust gas based on the zero-valent mercury concentration during a period in which the zero-valent mercury concentration is greater than a first threshold value, compares the evaluation value with a second threshold value when the zero-valent mercury concentration is equal to or less than the first threshold value after the period, and switches the upstream-side mercury concentration meter to the full-mercury measurement state when the evaluation value is greater than the second threshold value, and controls the amount of supply of the mercury adsorbent based on the full-valent mercury concentration.
Description
Technical Field
The present invention relates to an exhaust gas treatment device and an exhaust gas treatment method.
[ citation of related application ]
The present application claims the benefit of priority from japanese patent application JP2019-183519 filed on 10/4 of 2019, the entire disclosure of which is incorporated herein.
Background
When waste such as municipal waste is burned, exhaust gas containing mercury may be generated. In this case, in order to remove mercury in the exhaust gas, a mercury adsorbent is supplied to the exhaust gas. The supply amount of the mercury sorbent is controlled according to the mercury concentration. On the other hand, mercury contained in exhaust gas mainly exists as zero-valent atomic mercury (hereinafter referred to as "zero-valent mercury") and divalent mercury (hereinafter referred to as "divalent mercury") constituting mercury compounds such as mercury chloride. Conventionally, in measurement of the mercury concentration contained in exhaust gas, the total concentration of zero-valent mercury obtained by reducing divalent mercury in the taken-in exhaust gas to zero-valent mercury and zero-valent mercury originally contained in the exhaust gas (hereinafter, these zero-valent mercury are collectively referred to as "total mercury") is detected as the mercury concentration.
In addition, japanese patent application laid-open No. 2004-354067 (document 1) discloses a mercury measuring device capable of separating zero-valent mercury (metallic mercury) and divalent mercury in a gas and continuously measuring the same. In this device, the first column and the second column are connected in parallel. In the first column, only the zero-valent mercury is sent to the mercury measurer by capturing the divalent mercury contained in the gas by the first fixed catalyst. In the second column, bivalent mercury in the gas is reduced to zero-valent mercury by a second fixed catalyst, and the reduced zero-valent mercury and zero-valent mercury pre-existing in the gas are sent to other mercury measuring devices as full mercury (total mercury). In the two mercury measuring devices, the zero-valent mercury concentration and the total mercury concentration are measured, and the divalent mercury concentration is obtained by subtracting the zero-valent mercury concentration from the total mercury concentration.
However, in the mercury measuring device of patent document 1, since two concentration acquiring units (mercury measuring instruments) are required, the manufacturing cost of the device increases. Therefore, it is considered that only one concentration acquisition section is used to switch between a zero-valent mercury measurement state in which the zero-valent mercury concentration is measured and a full-valent mercury measurement state in which the full-valent mercury concentration is measured. In such a mercury concentration meter, manufacturing costs can be reduced. On the other hand, in the exhaust gas generated by the incineration of waste or the like, the total mercury concentration may be increased for a long time after the zero-valent mercury concentration is decreased. In this case, in the exhaust gas treatment device using the mercury concentration meter described above, when the supply amount of the mercury sorbent is controlled in accordance with the zero-valent mercury concentration of the mercury concentration meter in the zero-valent mercury measurement state, the full mercury concentration cannot be measured. As a result, in the above case, the mercury concentration in the exhaust gas cannot be reduced appropriately.
Disclosure of Invention
First, the technical problem to be solved
The present invention relates to an exhaust gas treatment device, and an object thereof is to appropriately reduce the mercury concentration of an exhaust gas in the exhaust gas treatment device even when the total mercury concentration increases for a long period of time after the zero-valent mercury concentration in the exhaust gas decreases.
(II) technical scheme
An exhaust gas treatment device of the present invention comprises: an adsorbent supply unit that supplies a mercury adsorbent to an exhaust gas in a flue through which the exhaust gas flows; an adsorbent trap unit that traps the mercury adsorbent in the flue; a mercury concentration meter that is disposed on an upstream side of the adsorbent trap portion in the flue in the flow direction of the exhaust gas, and is capable of switching between a zero-valent mercury measurement state in which a zero-valent mercury concentration of the exhaust gas is measured, and a full-valent mercury measurement state in which a total concentration of zero-valent mercury obtained after reduction of divalent mercury in the exhaust gas and zero-valent mercury originally contained in the exhaust gas is measured as a full-valent mercury concentration; and a control unit that controls the amount of supply of the mercury adsorbent by the adsorbent supply unit based on the zero-valent mercury concentration of the mercury concentration meter in the zero-valent mercury measurement state, acquires an evaluation value indicating the cumulative amount of zero-valent mercury in the exhaust gas from the zero-valent mercury concentration during a period in which the zero-valent mercury concentration is greater than a first threshold value, compares the evaluation value with a second threshold value when the zero-valent mercury concentration is equal to or less than the first threshold value after the period, and switches the mercury concentration meter to the total mercury measurement state when the evaluation value is greater than the second threshold value, and controls the amount of supply of the mercury adsorbent based on the total mercury concentration.
According to the present invention, the mercury concentration of the exhaust gas can be appropriately reduced in the exhaust gas treatment device even in the case where the total mercury concentration increases for a long period of time after the zero-valent mercury concentration in the exhaust gas decreases.
Preferably, the control unit switches the mercury concentration meter in the total mercury measurement state to the zero-valent mercury measurement state, and controls the supply amount of the mercury sorbent in accordance with the zero-valent mercury concentration when the total mercury concentration is equal to or lower than a third threshold.
Preferably, the apparatus further includes a downstream mercury concentration meter that is disposed downstream of the adsorbent trap in the flow direction of the exhaust gas in the flue, and measures, as a downstream mercury concentration, a total concentration of zero-valent mercury obtained after reduction of divalent mercury in the exhaust gas and zero-valent mercury originally contained in the exhaust gas, and the control unit switches control of the supply amount of the mercury adsorbent from control according to the zero-valent mercury concentration or the total mercury concentration to control according to at least the downstream mercury concentration when the downstream mercury concentration is greater than a fourth threshold.
The present invention also relates to an exhaust gas treatment method in an exhaust gas treatment device. In the exhaust gas treatment method, the exhaust gas treatment device includes: an adsorbent supply unit that supplies a mercury adsorbent to an exhaust gas in a flue through which the exhaust gas flows; an adsorbent trap unit that traps the mercury adsorbent in the flue; and a mercury concentration meter that is disposed on an upstream side of the adsorbent trap portion in the flue in the flow direction of the exhaust gas, and is capable of switching between a zero-valent mercury measurement state in which the zero-valent mercury concentration of the exhaust gas is measured, and a full-valent mercury measurement state in which a total concentration of zero-valent mercury obtained after reduction of divalent mercury in the exhaust gas and zero-valent mercury originally contained in the exhaust gas is measured as a full-valent mercury concentration. The exhaust gas treatment method includes the steps of: controlling a supply amount of the mercury adsorbent of the adsorbent supply portion according to the zero-valent mercury concentration of the mercury concentration meter in the zero-valent mercury measurement state; acquiring an evaluation value representing a cumulative amount of zero-valent mercury in the exhaust gas according to the zero-valent mercury concentration during a period in which the zero-valent mercury concentration is greater than a first threshold value; and comparing the evaluation value with a second threshold value when the zero-valent mercury concentration is equal to or lower than the first threshold value after the period, and switching the mercury concentration meter to the total mercury measurement state when the evaluation value is greater than the second threshold value, and controlling the supply amount of the mercury adsorbent according to the total mercury concentration.
The above objects, as well as additional objects, features, aspects and advantages of the present invention will become apparent from the following detailed description of the present invention, which proceeds with reference to the accompanying drawings.
Drawings
Fig. 1 is a diagram showing a structure of an incinerator.
Fig. 2 is a diagram showing the structure of the upstream mercury concentration meter.
Fig. 3 is a diagram showing an upstream-side mercury concentration meter in a zero-valent mercury measurement state.
Fig. 4 is a diagram showing an upstream mercury concentration meter in a full mercury measurement state.
Fig. 5 is a graph showing changes in zero-valent mercury concentration and full mercury concentration.
Fig. 6 is a graph showing changes in zero-valent mercury concentration and full mercury concentration.
Fig. 7 is a diagram showing a flow of exhaust gas treatment in the exhaust gas treatment device.
Fig. 8 is a view showing another example of exhaust gas treatment in the exhaust gas treatment device.
Detailed Description
Fig. 1 is a diagram showing a structure of an incineration facility 1 according to an embodiment of the present invention. The incineration facility 1 is a facility for incinerating waste such as municipal waste. The incineration facility 1 includes an incinerator 21, a flue 3, an exhaust gas treatment device 4, and a stack 22. In the incinerator 21, combustion of waste and combustion of combustible gas generated from the waste are performed. The flue 3 is a gas flow path connecting the incinerator 21 and the chimney 22. In fig. 1, the flue 3 is indicated by a thick solid line. The exhaust gas treatment device 4 is provided in the flue 3. The duct 3 is further provided with an induction ventilator, not shown. By this induction ventilator, exhaust gas (combustion gas) generated in the incinerator 21 is discharged to the flue 3, and is guided to the stack 22 via the exhaust gas treatment device 4. In the incineration facility 1, exhaust gas generated by the incinerator 21 as a source is treated by the exhaust gas treatment device 4 while flowing from the incinerator 21 into the flue 3 toward the chimney 22. A denitration device or the like may be provided in the flue 3. In the following description, the interior of the chimney 22 is also considered as part of the flue 3.
The exhaust gas treatment device 4 includes a control unit 40, an adsorbent supply unit 41, a bag filter 42, an upstream mercury concentration meter 45, and a downstream mercury concentration meter 46. The control unit 40 is, for example, a computer provided with a CPU or the like, and is responsible for overall control of the exhaust gas treatment device 4. The control unit 40 may also serve as a control unit for the incineration plant 1. Bag filters 42 are provided on the flue 3. In the flue 3, an inlet of the upstream mercury concentration meter 45 and a supply port of the adsorbent supply unit 41 are provided on the upstream side (the incinerator 21 side) of the bag filter 42, and an inlet of the downstream mercury concentration meter 46 is provided on the downstream side (the chimney 22 side) of the bag filter 42. In fig. 1, an intake port of the downstream mercury concentration meter 46 is provided in the stack 22.
The upstream-side mercury concentration meter 45 measures the mercury concentration contained in the exhaust gas flowing in the flue 3. Details of the upstream mercury concentration meter 45 will be described later. The adsorbent supply unit 41 includes, for example, a desk feeder, and supplies (blows) a powdered mercury adsorbent to the exhaust gas flowing through the flue 3. The mercury sorbent is, for example, activated carbon. As the mercury adsorbent, an activated carbon having iodine, sulfur, or the like added to the surface of the activated carbon may be used. In the exhaust gas treatment device 4, an alkaline chemical supply unit that supplies an alkaline chemical to the exhaust gas may be provided upstream of the bag filter 42. The alkaline chemical is a chemical for desalting and desulfurizing, and is, for example, powdered slaked lime or the like.
The bag filter 42 is of a filtration type, and captures fly ash contained in the exhaust gas through a filter cloth. In addition, the mercury sorbent supplied from the sorbent supply section 41 is also captured by the filter cloth. The fly ash and mercury sorbent are deposited on the filter cloth. The bag filter 42 is an adsorbent trap portion that traps mercury adsorbent in the flue 3. In the bag filter 42, when the exhaust gas passes through the filter cloth, the mercury adsorbent deposited on the filter cloth adsorbs mercury contained in the exhaust gas. Adsorption of mercury in the mercury sorbent also occurs in the flue 3. The mercury adsorbent may further adsorb dioxins and the like contained in the exhaust gas. In addition, in the case of supplying the alkaline chemical described above, the alkaline chemical is also trapped by the filter cloth. The acid gas (hydrogen chloride, sulfur oxide, etc.) contained in the exhaust gas reacts with the basic agent on the filter cloth, thereby removing the acid gas from the exhaust gas.
In the bag filter 42, fly ash, mercury sorbent, and the like deposited on the filter cloth are swept off by a backwashing operation using compressed gas. In the backwashing operation, compressed gas is supplied to the filter cloth from the downstream side toward the upstream side in the flow direction of the exhaust gas (pulse injection). The compressed gas is, for example, compressed air. In the actual bag filter 42, a plurality of filter cloth groups are provided, and the above-described backwashing operation is performed for each filter cloth group. In a normal operation to be described later in the air discharge process, a backwash operation is sequentially performed on the plurality of filter cloth groups at a set cycle. Fly ash, mercury sorbent, etc. that have been swept off the filter cloth, that is, the collected matter collected by the bag filter 42, is discharged to a discharge processing unit, which is not shown. In the discharge processing section, the collected matter is subjected to a chelating process or the like as necessary.
Fig. 2 is a diagram showing the structure of the upstream mercury concentration meter 45. The upstream mercury concentration meter 45 includes a first inlet 51, a second inlet 52, a reduction unit 53, a concentration obtaining unit 54, and a switching unit 55. The switching unit 55 includes a first channel 551, a second channel 552, three-way valves 553 to 555, a first auxiliary channel 556, and a second auxiliary channel 557. The first inlet 51 and the second inlet 52 are mounted on the flue 3. The first inlet 51 is connected to the concentration obtaining portion 54 through a first channel 551. The second intake port 52 is connected to the concentration obtaining portion 54 through a second flow path 552. Specifically, in the vicinity of the concentration obtaining portion 54, the first channel 551 and the second channel 552 merge via the three-way valve 555 to form one channel. The concentration acquisition unit 54 acquires a measurement value of mercury concentration from zero-valent mercury (metallic mercury) by an ultraviolet absorption method or the like. The measured value of the mercury concentration is output to the control unit 40.
In the first flow path 551, a filter 591, a reduction portion 53, and a three-way valve 553 are provided in this order from the first intake port 51 toward the three-way valve 555. The filter 591 removes fly ash contained in the exhaust gas (sampling gas) taken in from the first intake port 51. The reduction portion 53 contains a reduction catalyst that reduces divalent mercury to zero-valent mercury. The reducing section 53 is heated to a predetermined temperature (for example, 350 to 400 ℃) by the heating section 531. A scrubber for removing hydrogen chloride or the like may be provided in the reduction unit 53. One end of the first auxiliary channel 556 is connected to the three-way valve 553. The other end of the first auxiliary flow channel 556 is connected to the flue 3 downstream of the first intake port 51. In the three-way valve 553, the path of the gas flowing in the first flow path 551 is switched between the flow path toward the three-way valve 555 and the first auxiliary flow path 556.
In the second flow path 552, a filter 592 and a three-way valve 554 are provided in this order from the second intake port 52 toward the three-way valve 555. The filter 592 removes fly ash contained in the exhaust gas taken in from the second intake port 52. One end of the second auxiliary flow path 557 is connected to the three-way valve 554. The other end of the second auxiliary flow path 557 is connected to the flue 3 downstream of the second intake port 52. In the three-way valve 554, the path of the gas flowing in the second flow path 552 is switched between the flow path toward the three-way valve 555 and the second auxiliary flow path 557.
In the upstream-side mercury concentration meter 45, measurement of the concentration of zero-valent mercury (hereinafter referred to as "zero-valent mercury concentration") contained in the exhaust gas flowing in the flue 3 and measurement of the total concentration of zero-valent mercury and divalent mercury (hereinafter referred to as "total mercury concentration") contained in the exhaust gas can be selectively performed. In other words, the zero-valent mercury measurement state in which the zero-valent mercury concentration is measured and the full-mercury measurement state in which the full-mercury concentration is measured can be switched. The zero-valent mercury measurement state and the full-valent mercury measurement state in the upstream mercury concentration meter 45 will be described below.
Fig. 3 is a diagram showing the upstream-side mercury concentration meter 45 in the zero-valent mercury measurement state, and fig. 4 is a diagram showing the upstream-side mercury concentration meter 45 in the total mercury measurement state. In fig. 3 and 4, the flow paths connected by the three-way valves 553 to 555 are shown by painting two of three triangles showing the three-way valves 553 to 555.
In the zero-valent mercury measurement state, as shown in fig. 3, the exhaust gas taken in from the first intake port 51 and flowing through the first flow path 551 is guided to the first auxiliary flow path 556 by the three-way valve 553, and returned to the flue 3. The exhaust gas taken in from the second intake port 52 and flowing through the second flow path 552 is guided to the three-way valve 555 side by the three-way valve 554, and further guided to the concentration obtaining portion 54 by the three-way valve 555. Thus, the concentration obtaining unit 54 obtains a measured value of the concentration of the zero-valent mercury originally contained in the exhaust gas (i.e., the zero-valent mercury concentration) without reducing the divalent mercury contained in the exhaust gas to the zero-valent mercury. Thus, in the zero-valent mercury measurement state, zero-valent mercury is detected, but bivalent mercury is not detected. Therefore, the time required for reducing the divalent mercury to zero-valent mercury can be omitted, thereby rapidly obtaining a measured value of mercury concentration.
In the all-mercury measurement state, as shown in fig. 4, the exhaust gas flowing in the second flow path 552 is guided to the second auxiliary flow path 557 through the three-way valve 554, and returned to the flue 3. The exhaust gas flowing through the first channel 551 is guided to the three-way valve 555 side by the three-way valve 553, and is further guided to the concentration obtaining portion 54 by the three-way valve 555. Thus, the concentration obtaining unit 54 obtains a measured value of the zero-valent mercury in the exhaust gas after the divalent mercury in the exhaust gas is reduced, and the total concentration of the zero-valent mercury originally contained in the exhaust gas (i.e., the total mercury concentration). In this way, in the total mercury measurement state, both zero-valent mercury and divalent mercury are detected, so that the measurement value of the mercury concentration can be accurately obtained.
As described above, the exhaust gas taken in through the first intake port 51 flows into the reduction portion 53 not only in the full mercury measurement state but also in the zero-valent mercury measurement state. That is, while the exhaust gas flows in the flue 3, the exhaust gas always flows into the reduction portion 53. Therefore, immediately after switching from the zero-valent mercury measurement state to the full mercury measurement state, the concentration acquisition portion 54 can stably acquire the measured value of the full mercury concentration. Similarly, the exhaust gas taken in through the second intake port 52 flows into the second flow path 552 not only in the zero-valent mercury measurement state but also in the full-valent mercury measurement state. Therefore, the second flow path 552 can be always warmed up by the exhaust gas, and the measured value of the zero-valent mercury concentration can be prevented or suppressed from becoming unstable immediately after the switching from the full-mercury measurement state to the zero-valent mercury measurement state.
The downstream-side mercury concentration meter 46 of fig. 1 measures the total mercury concentration in the exhaust gas, that is, the zero-valent mercury obtained after the divalent mercury in the exhaust gas is reduced, and the total concentration of the zero-valent mercury originally contained in the exhaust gas, on the downstream side of the bag filter 42. The downstream mercury concentration meter 46 has a structure in which, for example, the second flow path 552, the first auxiliary flow path 556, and the second auxiliary flow path 557 are omitted from the upstream mercury concentration meter 45 of fig. 2. The measured value of the downstream mercury concentration meter 46 is output to the control unit 40. As described above, in the example of fig. 1, the intake port of the downstream mercury concentration meter 46 is provided in the stack 22. In the following description, the total mercury concentration measured by the downstream-side mercury concentration meter 46 is referred to as "downstream-side mercury concentration".
Fig. 5 and 6 are graphs showing changes in the zero-valent mercury concentration and the full mercury concentration in the exhaust gas. Here, the mercury concentration of the exhaust gas at the upstream side of the bag filter 42 is measured using a mercury concentration meter for zero-valent mercury concentration measurement and a mercury concentration meter for total mercury concentration measurement, that is, two mercury concentration meters, instead of the upstream side mercury concentration meter 45. In fig. 5 and 6, the zero-valent mercury concentration is indicated by solid lines L1 and L3, and the full-valent mercury concentration is indicated by broken lines L2 and L4. In fig. 5, the concentration change for 4 hours is shown, and in fig. 6, the concentration change for 1 hour is shown.
By the measurement using the two mercury concentrators described above, it was confirmed that the change in the zero-valent mercury concentration and the full mercury concentration was classified into the first mode and the second mode. In the first mode, as shown in fig. 5, after the sharp convex portion P1 is detected in the line L1 of zero-valent mercury concentration, the wide convex portion P2 is detected in the line L2 of full mercury concentration. In the second mode, as shown in fig. 6, after the sharp convex portion P3 is detected in the line L3 of zero-valent mercury concentration, a wide convex portion such as the convex portion P2 of fig. 5 is not detected in the line L4 of full mercury concentration. As described later, when the cumulative amount of zero-valent mercury is calculated for the protruding portions P1 and P3 from the zero-valent mercury concentration, period, and the like corresponding to the height and width of the protruding portions, the cumulative amount of zero-valent mercury corresponding to the protruding portion P1 in the first mode is sufficiently larger than the cumulative amount of zero-valent mercury corresponding to the protruding portion P3 in the second mode. The calculation of the cumulative amount of zero-valent mercury will be described later. As described above, the scale of the horizontal axis in fig. 5 and 6 is different.
As described later, at the time of normal operation in the exhaust gas treatment, the supply amount of the mercury adsorbent in the adsorbent supply unit 41 is controlled based on the zero-valent mercury concentration. That is, the supply amount of the mercury adsorbent increases when the zero-valent mercury concentration is high, and decreases when the zero-valent mercury concentration is low. Accordingly, in both the first mode and the second mode, the supply amount of the mercury sorbent increases correspondingly to the convex portions P1 and P3 having the sharp zero-valent mercury concentration, and when the zero-valent mercury concentration decreases, the supply amount of the mercury sorbent decreases.
At this time, in the second mode shown in fig. 6, since the total mercury concentration becomes smaller after the zero-valent mercury concentration becomes smaller, the mercury concentration of the exhaust gas passing through the bag filter 42 can be appropriately reduced without increasing the supply amount of the mercury absorbent. In contrast, in the first mode shown in fig. 5, the total mercury concentration increases for a long period of time after the zero-valent mercury concentration decreases, and therefore, the mercury concentration of the exhaust gas passing through the bag filter 42 cannot be reduced appropriately without increasing the supply amount of the mercury absorbent. In addition, as described above, in the actual exhaust gas treatment device 4, since the zero-valent mercury measurement state and the full mercury measurement state are switched in the upstream-side mercury concentration meter 45, when the supply amount of the mercury adsorbent is controlled in accordance with the zero-valent mercury concentration of the upstream-side mercury concentration meter 45 in the zero-valent mercury measurement state, the full mercury concentration cannot be measured. Therefore, the detection of the first mode cannot be performed by measuring the total mercury concentration. The exhaust gas treatment in the exhaust gas treatment device 4 that can appropriately reduce the mercury concentration of the exhaust gas in both the first mode and the second mode will be described below.
Fig. 7 is a diagram showing a flow of exhaust gas treatment in the exhaust gas treatment device 4. The exhaust gas treatment in the following description is a treatment of controlling the supply amount of the mercury adsorbent in the adsorbent supply unit 41 to reduce the mercury concentration in the exhaust gas. In the exhaust gas treatment device 4, measurement of the mercury concentration (zero-valent mercury concentration or total mercury concentration) by the upstream-side mercury concentration meter 45 and measurement of the downstream-side mercury concentration by the downstream-side mercury concentration meter 46 are continued in principle. In fig. 7, control using only the upstream side mercury concentration meter 45 is shown, and control using the upstream side mercury concentration meter 45 and the downstream side mercury concentration meter 46 will be described later. Hereinafter, in the case of simply referred to as "total mercury concentration", it means the total mercury concentration measured by the upstream-side mercury concentration meter 45.
At the time of normal operation in the exhaust gas treatment, the zero-valent mercury concentration is measured by the upstream-side mercury concentration meter 45 in the zero-valent mercury measurement state, and the control unit 40 controls the supply amount of the mercury adsorbent to the adsorbent supply unit 41 based on (the measured value of) the zero-valent mercury concentration (see step S18 described later). In the following description, the control of the supply amount of the mercury sorbent based on the zero-valent mercury concentration is simply referred to as "control based on the zero-valent mercury concentration" (the same applies to control based on the total mercury concentration and control based on the downstream-side mercury concentration, which will be described later). In the control based on the zero-valent mercury concentration, for example, in the case where the zero-valent mercury concentration is high, the supply amount of the mercury adsorbent increases, and in the case where the zero-valent mercury concentration is low, the supply amount of the mercury adsorbent decreases. In addition, in the case where the mercury adsorbent is activated carbon, since the activated carbon also adsorbs dioxins, it is preferable that a predetermined amount or more of mercury adsorbent is always supplied to the flue 3 while the exhaust gas flows through the flue 3.
Here, the adsorption of mercury by the mercury sorbent occurs mainly in the bag filter 42. In the control based on the zero-valent mercury concentration, the zero-valent mercury concentration obtained on the upstream side of the bag filter 42 is used instead of the downstream-side mercury concentration obtained on the downstream side of the bag filter 42. Therefore, it can be said that the control based on the zero-valent mercury concentration is feed-forward control (FF control). The same applies to the control based on the total mercury concentration described later.
As described above, in the zero-valent mercury measurement state, no time lag caused by the reduction of divalent mercury occurs. Thus, in the control based on the zero-valent mercury concentration, the change in the zero-valent mercury concentration in the exhaust gas flowing in the vicinity of the second intake port 52 can be promptly handled, that is, the supply amount of the mercury adsorbent can be controlled with good responsiveness. The zero-valent mercury concentration used for control in the control unit 40 may be a moving average or the like over a predetermined period of time (the same applies to the total mercury concentration and the downstream mercury concentration).
In parallel with the control based on the zero-valent mercury concentration, the control unit 40 compares the zero-valent mercury concentration with a predetermined first threshold value. The first threshold is, for example, 10 to 50. Mu.g/m 3 N (12% in oxygen). When the zero-valent mercury concentration is greater than the first threshold value due to incineration or the like of the waste containing much mercury (step S11), accumulation of the amount of zero-valent mercury in the exhaust gas is started (step S12). Accumulation of the amount of zero-valent mercury, e.g. at regular intervals ΔH [ H ]]Is carried out. The control unit 40 always inputs the value A [ mu ] g/m of zero-valent mercury concentration 3 N]Flow rate B m of exhaust gas 3 N/h]In the accumulation of the amount of zero-valent mercury, the accumulation amount of zero-valent mercury from the start of the accumulation to the present is obtained by Σ (a×b×Δh). The cumulative amount of zero-valent mercury is an evaluation value used in the determination described later. The accumulation of the amount of zero-valent mercury is performed in parallel with the control based on the zero-valent mercury concentration.
When the zero-valent mercury concentration is equal to or lower than the first threshold value (step S13), the evaluation value is compared with a predetermined second threshold value. Typically, the evaluation value is the cumulative amount of zero-valent mercury itself, and as described above, the cumulative period is a period from when the zero-valent mercury concentration is greater than the first threshold value to immediately before the zero-valent mercury concentration becomes equal to or less than the first threshold value, that is, a period in which the zero-valent mercury concentration is greater than the first threshold value. When the garbage disposal amount is 100 t/day, the second threshold is, for example, 0.5 to 2g. The second threshold value is changed in proportion to the garbage disposal amount of the incineration apparatus. The evaluation value may be a value other than the cumulative amount of zero-valent mercury in the entire period, or may be a cumulative amount in a part of the period if it is possible to determine which of the first mode and the second mode the change in the zero-valent mercury concentration indicates, as will be described later. The evaluation value may be another value correlated with the cumulative amount of zero-valent mercury. In this way, the evaluation value may be a value indicating the cumulative amount of zero-valent mercury in the exhaust gas in the cumulative period including at least a part of the period in which the zero-valent mercury concentration is greater than the first threshold value. In the following description, the evaluation value is the cumulative amount of zero-valent mercury in the entire period.
When the evaluation value (here, the cumulative amount of zero-valent mercury) is equal to or less than the second threshold value (step S14), the cumulative amount of zero-valent mercury is returned to 0, and reset is performed (step S15). In addition, returning to step S11, the zero-valent mercury concentration is compared with a first threshold. In this case, since the zero-valent mercury concentration is equal to or lower than the first threshold value, the supply amount of the mercury sorbent is relatively small. As described later, the second threshold value is used to determine whether a change in the zero-valent mercury concentration at which the evaluation value is obtained indicates the first mode or the second mode, and when the evaluation value is equal to or lower than the second threshold value, it is estimated that the change in the zero-valent mercury concentration indicates the second mode. In the second mode, as shown in fig. 6, the zero-valent mercury concentration becomes smaller, and the full mercury concentration becomes smaller. Therefore, even if the control based on the zero-valent mercury concentration is continued, the mercury concentration of the exhaust gas can be appropriately reduced.
On the other hand, when the evaluation value is greater than the second threshold value (step S14), the upstream-side mercury concentration meter 45 is switched to the full mercury measurement state. Thereby, the control of the supply amount of the mercury sorbent is switched from the control based on the zero-valent mercury concentration to the control based on the full mercury concentration (step S16). In the control based on the total mercury concentration, the supply amount of the mercury sorbent is controlled in accordance with the total mercury concentration. Therefore, the supply amount of the mercury adsorbent increases when the total mercury concentration is high, and decreases when the total mercury concentration is low.
As described above, the cumulative amount of zero-valent mercury corresponding to the convex portion P1 in the first mode is sufficiently larger than the cumulative amount of zero-valent mercury corresponding to the convex portion P3 in the second mode. In the exhaust gas treatment device 4, a second threshold value for determining whether a change in the zero-valent mercury concentration at which the evaluation value is obtained indicates the first mode or the second mode is set in advance by comparison with an evaluation value indicating the cumulative amount of zero-valent mercury. When the evaluation value is greater than the second threshold value, it is presumed that the change in the zero-valent mercury concentration indicates the first mode. In the first mode, as shown in fig. 5, the zero-valent mercury concentration is reduced and then the total mercury concentration is increased for a long period of time, but in the exhaust gas treatment device 4, the mercury concentration in the exhaust gas can be appropriately reduced by controlling the supply amount of the mercury adsorbent in accordance with the total mercury concentration. In addition, since a correct mercury concentration can be obtained in the total mercury measurement state, the amount of supply of the mercury adsorbent can be controlled and the excess or deficiency can be reduced in the control based on the total mercury concentration.
In parallel with the control based on the total mercury concentration, the control unit 40 compares the total mercury concentration with a predetermined third threshold value. The third threshold is, for example, 50 to 200. Mu.g/m 3 N (12% in oxygen). Typically, the third threshold is greater than the first threshold. If the total mercury concentration is greater than the third threshold (step S17), control based on the total mercury concentration is continued. When the total mercury concentration is equal to or lower than the third threshold value (step S17), the upstream-side mercury concentration meter 45 is switched from the total mercury measurement state to the zero-valent mercury measurement state. Thereby, the control of the supply amount of the mercury sorbent is switched from the control based on the total mercury concentration to the control based on the zero-valent mercury concentration, and the control returns to the normal time (step S18).
At this time, since the mercury adsorbent on the filter cloth adsorbs a large amount of mercury in the bag filter 42, the backwashing operation is preferably performed at a period shorter than the normal set period. This can suppress the mercury from escaping from the mercury adsorbent on the filter cloth and increase the downstream mercury concentration. Further, the mercury concentration (total mercury concentration) on the upstream side of the bag filter 42 is reduced, and thus, the exhaust gas having a high mercury concentration is suppressed from increasing in the downstream side mercury concentration due to the filter cloth on which the mercury adsorbent is not deposited by the backwashing operation.
In the control unit 40, the cumulative amount of zero-valent mercury is reset (step S15). Then, returning to step S11, the zero-valent mercury concentration is compared with a first threshold. In the exhaust gas treatment device 4, the process of fig. 7 is continued while the exhaust gas flows through the flue 3.
As described above, in the upstream mercury concentration meter 45 of the exhaust gas treatment device 4, the zero-valent mercury measurement state and the full-valent mercury measurement state can be switched. Thus, the zero-valent mercury concentration and the full mercury concentration can be selectively measured using one concentration obtaining portion 54, and the manufacturing cost of the upstream-side mercury concentration meter 45 can be reduced. In the exhaust gas treatment by the exhaust gas treatment device 4, in general, the supply amount of the mercury adsorbent is controlled according to the zero-valent mercury concentration of the upstream-side mercury concentration meter 45 in the zero-valent mercury measurement state. In addition, during a period in which the zero-valent mercury concentration is greater than the first threshold value, an evaluation value representing the cumulative amount of zero-valent mercury in the exhaust gas is acquired based on the zero-valent mercury concentration. After this period, when the zero-valent mercury concentration is equal to or lower than the first threshold value, the evaluation value and the second threshold value are compared. When the evaluation value is greater than the second threshold value, the upstream mercury concentration meter 45 is switched to the full mercury measurement state, and the supply amount of the mercury adsorbent is controlled based on the full mercury concentration. Thus, even when the total mercury concentration increases for a long period of time after the zero-valent mercury concentration in the exhaust gas decreases (see the first mode of fig. 5), the mercury concentration in the exhaust gas can be appropriately reduced in the exhaust gas treatment device 4.
When the total mercury concentration is equal to or lower than the third threshold value, the upstream mercury concentration meter 45 in the total mercury measurement state is switched to the zero-valent mercury measurement state, and the supply amount of the mercury adsorbent is controlled in accordance with the zero-valent mercury concentration. Thus, after the total mercury concentration is reduced, the control is returned to the control based on the zero-valent mercury concentration, and the supply amount of the mercury adsorbent can be controlled with good responsiveness.
Next, control using the upstream side mercury concentration meter 45 and the downstream side mercury concentration meter 46 will be described. Fig. 8 is a view showing another example of the exhaust gas treatment in the exhaust gas treatment device 4. Steps S19 to S21 in fig. 8 are the processing performed between step S17 and step S18 in fig. 7. The following describes a process after the control of the supply amount of the mercury sorbent in step S16 is switched from the control based on the zero-valent mercury concentration to the control based on the total mercury concentration.
In parallel with the control based on the total mercury concentration, the control unit 40 compares the total mercury concentration with a third threshold value. When the total mercury concentration is equal to or lower than the third threshold value (step S17), the downstream-side mercury concentration obtained by the downstream-side mercury concentration meter 46 is compared with a predetermined fourth threshold value. The fourth threshold is, for example, 20 to 50. Mu.g/m 3 N (12% in oxygen). Here, in the control based on the zero-valent mercury concentration and the control based on the total mercury concentration, the downstream-side mercury concentration is generally kept low by the supply of the mercury adsorbent. When the downstream-side mercury concentration is equal to or lower than the fourth threshold value, that is, when the downstream-side mercury concentration is kept low (step S19), the upstream-side mercury concentration meter 45 is switched from the full mercury measurement state to the zero-valent mercury measurement state. Thereby, the control of the supply amount of the mercury sorbent is switched from the control based on the total mercury concentration to the control based on the zero-valent mercury concentration, and the control returns to the normal time (step S18). In addition, as in the process of fig. 7, when the total mercury concentration is equal to or lower than the third threshold value in step S17, the bag filter 42 may be backwashed at a shorter period than the normal setting period.
On the other hand, the mercury adsorbent on the filter cloth of the bag filter 42 contains a large amount of mercury, and when the mercury is released from the mercury adsorbent, the downstream-side mercury concentration is greater than the fourth threshold value in comparison with the fourth threshold value (step S19). In this case, in the control unit 40, the control of the supply amount of the mercury adsorbent is switched from the control based on the total mercury concentration to the control based on the downstream-side mercury concentration (step S20). In the control based on the downstream-side mercury concentration, the supply amount of the mercury adsorbent increases when the downstream-side mercury concentration is high, and decreases when the downstream-side mercury concentration is low.
In the control based on the downstream-side mercury concentration, the zero-valent mercury concentration or the full mercury concentration obtained on the upstream side than the bag filter 42 is not used, but the downstream-side mercury concentration obtained on the downstream side than the bag filter 42 is used. Therefore, it can be said that the control based on the downstream-side mercury concentration is feedback control (FB control). By controlling the downstream-side mercury concentration, the mercury concentration of the exhaust gas discharged to the atmosphere can be more reliably reduced. In addition, the upstream-side mercury concentration meter 45 may be switched from the full mercury measurement state to the zero-valent mercury measurement state in response to switching to control based on the downstream-side mercury concentration.
The switching from the feed-forward control of the mercury concentration (zero-valent mercury concentration or full mercury concentration) on the upstream side using the bag filter 42 to the feedback control of the mercury concentration (downstream side mercury concentration) on the downstream side using the same may also be performed manually by the operator. For example, when the total mercury concentration is equal to or lower than the third threshold value and the downstream mercury concentration is higher than the fourth threshold value during the control based on the total mercury concentration (steps S17 and S19), the control unit 40 notifies the operator to prompt the switching to the feedback control. The notification of the presentation switching is performed by, for example, display on a display, output of sound, or the like. The exhaust gas treatment device 4 is provided with a changeover switch for instructing changeover from the feedforward control to the feedback control, and the operator operates the changeover switch in response to the notification of the instruction of changeover, thereby performing changeover from the feedforward control to the feedback control (step S20).
In the control based on the downstream-side mercury concentration, the mercury concentration (zero-valent mercury concentration or full mercury concentration) obtained by the upstream-side mercury concentration meter 45 may also be used. That is, in step S20, the control may be switched from the feedforward control to the control using both the feedforward control and the feedback control. The switching to control using both can also be performed manually.
In the control unit 40, the downstream-side mercury concentration is compared with a predetermined fifth threshold value. The fifth threshold is, for example, 20 to 50. Mu.g/m 3 N (12% in oxygen). The fifth threshold may be the same as the fourth threshold. If the downstream-side mercury concentration is greater than the fifth threshold (step S21), control of the supply amount of the mercury adsorbent based on the downstream-side mercury concentration is continued. When the downstream-side mercury concentration is equal to or lower than the fifth threshold value (step S21), the control of the supply amount of the mercury adsorbent is switched from the control based on the downstream-side mercury concentration to the control based on the zero-valent mercury concentration (step S18). That is, the control is returned to the normal time in the exhaust gas treatment device 4.
As described above, in the exhaust gas treatment of fig. 8, when the downstream-side mercury concentration is greater than the fourth threshold value, the control unit 40 switches the control of the supply amount of the mercury adsorbent from the control based on the total mercury concentration to the control based on the downstream-side mercury concentration. This can reduce the mercury concentration in the exhaust gas discharged to the atmosphere more reliably.
In the exhaust gas treatment of fig. 8, the control based on the total mercury concentration is switched from the control based on the downstream-side mercury concentration, but in the case where the downstream-side mercury concentration is greater than the fourth threshold value in the control based on the zero-valent mercury concentration or the total mercury concentration, the control of the supply amount of the mercury adsorbent may be switched to the control based on the downstream-side mercury concentration. In addition, as described above, in the control based on the downstream-side mercury concentration, not only the downstream-side mercury concentration but also the zero-valent mercury concentration or the full mercury concentration may be used. As described above, in the exhaust gas treatment device 4, preferably, when the downstream-side mercury concentration is higher than the fourth threshold value (for example, when the zero-valent mercury concentration and the total mercury concentration are equal to or lower than a predetermined threshold value and the downstream-side mercury concentration is higher than the fourth threshold value), the control of the supply amount of the mercury adsorbent is switched from the control based on the zero-valent mercury concentration or the total mercury concentration to the control based on at least the downstream-side mercury concentration. This can reduce the mercury concentration in the exhaust gas discharged to the atmosphere more reliably.
Various modifications can be made to the exhaust gas treatment device 4.
In the exhaust gas treatment device 4 of fig. 1, another bag filter may be disposed between the incinerator 21 and the adsorbent supply unit 41. In this case, fly ash contained in the exhaust gas is captured by the other bag filter, and the mercury adsorbent (in the case where the alkaline agent is also supplied, the mercury adsorbent and the alkaline agent) supplied from the adsorbent supply unit 41 to the flue 3 is mainly captured in the bag filter 42.
In the flue 3, the inlet of the upstream mercury concentration meter 45 may be disposed at an arbitrary position on the upstream side in the flow direction of the exhaust gas with respect to the bag filter 42. The intake port of the downstream mercury concentration meter 46 may be disposed at any position downstream of the bag filter 42 in the exhaust gas flow direction.
The exhaust gas treatment device 4 may be used in a device other than the incineration device 1.
The above-described embodiments and the configurations in the respective modifications can be appropriately combined without contradiction. In addition, the numerical value herein is a limit value corresponding to japan, and in the case of application to other countries, it is necessary to correspond to the limit value of that country.
Although the invention has been described in detail, the foregoing description is by way of illustration and not limitation. Accordingly, various modifications may be made without departing from the scope of the invention.
Reference numerals
3. Flue duct
4. Exhaust gas treatment device
40. Control unit
41. Adsorbent supply unit
42. Bag filter
45. Upstream mercury concentration meter
46. Downstream mercury concentration meter
S11-S21.
Claims (4)
1. An exhaust gas treatment device is provided with:
an adsorbent supply unit that supplies a mercury adsorbent to an exhaust gas in a flue through which the exhaust gas flows;
an adsorbent trap unit that traps the mercury adsorbent in the flue;
a mercury concentration meter that is disposed on an upstream side of the adsorbent trap portion in the flue in the flow direction of the exhaust gas, and is capable of switching between a zero-valent mercury measurement state in which a zero-valent mercury concentration of the exhaust gas is measured, and a full-valent mercury measurement state in which a total concentration of zero-valent mercury obtained after reduction of divalent mercury in the exhaust gas and zero-valent mercury originally contained in the exhaust gas is measured as a full-valent mercury concentration; and
a control unit that controls the amount of supply of the mercury adsorbent by the adsorbent supply unit based on the zero-valent mercury concentration of the mercury concentration meter in the zero-valent mercury measurement state, obtains an evaluation value indicating the cumulative amount of zero-valent mercury in the exhaust gas from the zero-valent mercury concentration during a period in which the zero-valent mercury concentration is greater than a first threshold value, compares the evaluation value with a second threshold value when the zero-valent mercury concentration is equal to or less than the first threshold value after the period, and switches the mercury concentration meter to the total mercury measurement state when the evaluation value is greater than the second threshold value, and controls the amount of supply of the mercury adsorbent based on the total mercury concentration.
2. The exhaust gas treatment device according to claim 1, wherein,
when the total mercury concentration is equal to or lower than a third threshold value, the control unit switches the mercury concentration meter in the total mercury measurement state to the zero-valent mercury measurement state, and controls the supply amount of the mercury adsorbent in accordance with the zero-valent mercury concentration.
3. The exhaust gas treatment device according to claim 1 or 2, characterized in that,
further provided with a downstream mercury concentration meter disposed downstream of the adsorbent trap in the flue in the flow direction of the exhaust gas, for measuring, as a downstream mercury concentration, a total concentration of zero-valent mercury obtained after reduction of divalent mercury in the exhaust gas and zero-valent mercury originally contained in the exhaust gas,
the control unit switches control of the supply amount of the mercury adsorbent from control according to the zero-valent mercury concentration or the total mercury concentration to control according to at least the downstream-side mercury concentration when the downstream-side mercury concentration is greater than a fourth threshold.
4. An exhaust gas treatment method in an exhaust gas treatment device, the exhaust gas treatment device comprising:
an adsorbent supply unit that supplies a mercury adsorbent to an exhaust gas in a flue through which the exhaust gas flows;
an adsorbent trap unit that traps the mercury adsorbent in the flue; and
a mercury concentration meter that is disposed upstream of the adsorbent trap in the flue in the flow direction of the exhaust gas, and is capable of switching between a zero-valent mercury measurement state in which the zero-valent mercury concentration of the exhaust gas is measured, and a total concentration of zero-valent mercury that is obtained after reduction of divalent mercury in the exhaust gas and zero-valent mercury that is originally contained in the exhaust gas is measured as a total mercury concentration,
the exhaust gas treatment method includes the steps of:
controlling a supply amount of the mercury adsorbent of the adsorbent supply portion according to the zero-valent mercury concentration of the mercury concentration meter in the zero-valent mercury measurement state;
acquiring an evaluation value representing a cumulative amount of zero-valent mercury in the exhaust gas according to the zero-valent mercury concentration during a period in which the zero-valent mercury concentration is greater than a first threshold value; and
and comparing the evaluation value with a second threshold value when the zero-valent mercury concentration is equal to or lower than the first threshold value after the period, and switching the mercury concentration meter to the total mercury measurement state when the evaluation value is greater than the second threshold value, and controlling the supply amount of the mercury adsorbent according to the total mercury concentration.
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| JP2019183519A JP7203711B2 (en) | 2019-10-04 | 2019-10-04 | Exhaust gas treatment device and exhaust gas treatment method |
| PCT/JP2020/032450 WO2021065267A1 (en) | 2019-10-04 | 2020-08-27 | Exhaust gas treatment apparatus and exhaust gas treatment method |
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| CN114364449A (en) | 2022-04-15 |
| JP2021058827A (en) | 2021-04-15 |
| WO2021065267A1 (en) | 2021-04-08 |
| JP7203711B2 (en) | 2023-01-13 |
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