JP6903028B2 - Mercury concentration measuring device, exhaust gas treatment device and exhaust gas treatment method - Google Patents

Description

The present invention relates to a mercury concentration measuring device, an exhaust gas treatment device, and an exhaust gas treatment method.

When general waste such as municipal waste is incinerated, exhaust gas containing mercury may be generated. In this case, a mercury adsorbent is supplied to the exhaust gas in order to remove mercury in the exhaust gas. On the other hand, the mercury contained in the exhaust gas is mainly zero-valent atomic mercury (hereinafter referred to as "zero-valent mercury") and divalent mercury constituting a mercury compound such as mercury chloride (hereinafter referred to as "" It exists as "divalent mercury"). Conventionally, in the measurement of the concentration of mercury contained in exhaust gas, divalent mercury in the taken-in gas is reduced to zero-valent mercury, and zero-valent mercury contained in the reduced gas (hereinafter, zero-valent mercury originally contained in exhaust gas). , And the zero-valent mercury obtained by reducing divalent mercury is collectively referred to as "total mercury"), and the concentration is detected as the mercury concentration. However, since it takes a certain amount of time to reduce divalent mercury to zero-valent mercury, it is difficult to control the supply amount of the mercury adsorbent with good responsiveness. Therefore, Patent Document 1 proposes a detection device that detects the amount of zero-valent mercury contained in exhaust gas without reducing divalent mercury to zero-valent mercury.

International Publication No. 2016/136714

By the way, with the detection device of Patent Document 1, it is not possible to obtain an accurate mercury concentration, and it is difficult to appropriately control the supply amount of the mercury adsorbent (with less excess or deficiency).

The present invention has been made in view of the above problems, and an object of the present invention is to selectively measure the mercury concentration rapidly and accurately, and to appropriately control the supply amount of the mercury adsorbent. Is also aimed at.

The invention according to claim 1 is a mercury concentration measuring device for measuring the concentration of mercury contained in a gas, which is a first intake port attached to a gas flow path and a gas taken in by the first intake port. A reduction unit that reduces the divalent mercury contained in the mercury to zero-valent mercury, a second intake port attached to the gas flow path, and a concentration acquisition unit that acquires a measured value of mercury concentration based on the zero-valent mercury. It is provided with a switching unit for selectively flowing one of the gas that has passed through the reduction unit or the gas taken in by the second intake port into the concentration acquisition unit, and is taken in by the first intake port. gas flows constantly to the reduction unit, the switching unit, wherein an inlet to the concentration acquisition portion of the gas passing through the reduced section, you switch a discharge to a predetermined discharge position.

The invention according to claim 2 is the mercury concentration measuring apparatus according to claim 1, wherein the first intake port also serves as the second intake port, and the switching unit is the first. A first flow path that connects the intake port to the concentration acquisition unit via the reduction unit, and a second flow path that bypasses the reduction unit and connects the first intake port and the concentration acquisition unit. And a flow path switching unit that switches the path of the gas flowing into the concentration acquisition unit between the first flow path and the second flow path.

The invention according to claim 3 is an exhaust gas treatment device, which is an adsorbent supply unit that supplies a mercury adsorbent to the exhaust gas in a flue in which the exhaust gas flows from a source of the exhaust gas toward an outlet to the outside. The zero-valent mercury concentration in the exhaust gas is located between the adsorbent collecting portion that collects the mercury adsorbent in the flue and the source and the adsorbent collecting portion in the flue. At a position between the zero-valent mercury concentration measuring unit for measuring the amount of mercury and the source and the adsorbent collecting unit in the flue, the zero-valent mercury originally contained in the exhaust gas and the zero-valent mercury in the exhaust gas. The total mercury concentration measuring unit that measures the total concentration of zero-valent mercury obtained by reducing divalent mercury as the total mercury concentration, and the adsorbent supply unit controls the supply amount of the mercury adsorbent based on the zero-valent mercury concentration. In addition, in a predetermined case, the control unit is provided to switch the control of the supply amount of the mercury adsorbent from the control based on the zero-valent mercury concentration to the control based on the total mercury concentration.

The invention according to claim 4 is the exhaust gas treatment apparatus according to claim 3 , wherein the mercury concentration measurement according to claim 1 or 2 also serves as the zero-valent mercury concentration measuring unit and the total mercury concentration measuring unit. Equipped with a device.

The invention according to claim 5 is the exhaust gas treatment apparatus according to claim 3 or 4 , wherein the zero-valent mercury concentration becomes equal to or higher than a predetermined threshold in the control based on the zero-valent mercury concentration. After increasing the supply amount of the mercury adsorbent, the control of the supply amount of the mercury adsorbent is switched from the control based on the zero-valent mercury concentration to the control based on the total mercury concentration.

The invention according to claim 6 is the exhaust gas treatment apparatus according to any one of claims 3 to 5 , wherein when the zero-valent mercury concentration is lower than a predetermined threshold value, the adsorbent collecting unit. The recovered adsorbent is supplied to a position between the recovered adsorbent storage unit that stores the mercury adsorbent collected by the above-mentioned method and the adsorbent collecting portion in the flue. A recovery adsorbent supply unit is further provided, and the control unit controls the supply amount of the recovery adsorbent by the recovery adsorbent supply unit based on the zero-valent mercury concentration.

The invention according to claim 7 is the exhaust gas treatment apparatus according to any one of claims 3 to 6 , at a position between the adsorbent collecting portion and the discharging port in the flue. The downstream mercury concentration measuring unit for measuring the total concentration of the zero-valent mercury originally contained in the exhaust gas and the reduced zero-valent mercury in the exhaust gas as the downstream mercury concentration is further provided. When the downstream mercury concentration is equal to or higher than a predetermined threshold value, the control unit controls the supply amount of the mercury adsorbent at least from the control based on the zero-valent mercury concentration or the total mercury concentration. Switch to concentration-based control.

The invention according to claim 8 is a method for treating exhaust gas in an exhaust gas treatment device, wherein the exhaust gas treatment device uses the exhaust gas in a flue in which the exhaust gas flows from a source of the exhaust gas toward an outlet to the outside. Positions between the adsorbent supply unit that supplies the mercury adsorbent, the adsorbent collection unit that collects the mercury adsorbent in the flue, and the source and the adsorbent collection unit in the flue. At a position between the zero-valent mercury concentration measuring unit for measuring the zero-valent mercury concentration in the exhaust gas and the source and the adsorbent collecting unit in the flue, the exhaust gas is originally contained in the exhaust gas. The exhaust gas treatment method comprises a total mercury concentration measuring unit that measures the total concentration of zero-valent mercury and the reduced zero-valent mercury in the exhaust gas as the total mercury concentration, and the exhaust gas treatment method is the zero-valent mercury concentration. From the step of controlling the supply amount of the mercury adsorbent by the adsorbent supply unit and the control of the supply amount of the mercury adsorbent in a predetermined case from the control based on the zero-valent mercury concentration, all of the above. It includes a step of switching to control based on mercury concentration.

The invention according to claim 9 is the exhaust gas treatment method according to claim 8 , wherein the exhaust gas treatment device is located at a position between the adsorbent collecting portion and the discharge port in the flue. The exhaust gas is further provided with a downstream mercury concentration measuring unit that measures the total concentration of the zero-valent mercury originally contained in the exhaust gas and the reduced zero-valent mercury in the exhaust gas as the downstream mercury concentration. When the treatment method is such that the downstream mercury concentration is equal to or higher than a predetermined threshold value, the control of the supply amount of the mercury adsorbent is controlled from the control based on the zero-valent mercury concentration or the total mercury concentration to at least the downstream mercury. It further comprises a step of switching to concentration-based control.

In the inventions of claims 1 and 2 , rapid measurement of mercury concentration (measurement of zero-valent mercury concentration) and accurate measurement of mercury concentration (measurement of total mercury concentration) can be selectively performed.

In the inventions of claims 3 to 9 , the supply amount of the mercury adsorbent is controlled with good responsiveness based on the rapidly obtained zero-valent mercury concentration, and in a predetermined case, the mercury adsorbent is supplied based on the total mercury concentration. The amount can be controlled appropriately.

It is a figure which shows the structure of the incinerator. It is a figure which shows the structure of the mercury concentration measuring apparatus. It is a figure which shows the mercury concentration measuring apparatus at the time of measuring the zero-valent mercury concentration. It is a figure which shows the mercury concentration measuring apparatus at the time of measuring the total mercury concentration. It is a figure which shows the flow of the exhaust gas treatment in the exhaust gas treatment apparatus. It is a figure which shows another example of an exhaust gas treatment apparatus. It is a figure which shows another example of the mercury concentration measuring apparatus.

FIG. 1 is a diagram showing a configuration of an incinerator 1 according to an embodiment of the present invention. The incinerator 1 is an incinerator for incinerating waste such as municipal waste. The incinerator 1 includes an incinerator 21, a flue 3, an exhaust gas treatment device 4, and a chimney 22. In the incinerator 21, the waste is burned and the combustible gas generated from the waste is burned. The flue 3 is a gas flow path connecting the incinerator 21 and the chimney 22. The exhaust gas treatment device 4 is provided in the flue 3. The flue 3 is also provided with an induction ventilator (not shown). The exhaust gas (combustion gas) generated in the incinerator 21 is discharged to the flue 3 by the induced ventilator, and is guided to the chimney 22 via the exhaust gas treatment device 4. In the incinerator 1, the exhaust gas originating from the incinerator 21 flows through the flue 3 from the incinerator 21 toward the chimney 22, and the exhaust gas treatment device 4 performs a predetermined treatment on the exhaust gas. The chimney 22 includes an exhaust port that discharges exhaust gas to the atmosphere (outside). In FIG. 1, the flue 3 is shown by a thick solid line.

The exhaust gas treatment device 4 includes a control unit 40, an adsorbent supply unit 41, an alkaline chemical supply unit 42, a bag filter 43, a mercury concentration measuring device 45, a downstream mercury concentration measuring unit 46, and a hydrogen chloride concentration measurement. A unit 47 is provided. The control unit 40 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 incinerator 1. The bug filter 43 is provided in the flue 3. In the flue 3, the mercury concentration measuring device 45, the adsorbent supply unit 41 and the alkaline chemical supply unit 42 are connected to the upstream side (incinerator 21 side) of the bag filter 43, and the downstream side (chimney) of the bag filter 43. The downstream side mercury concentration measuring unit 46 and the hydrogen chloride concentration measuring unit 47 are connected to the 22 side). The flue 3 may also be provided with a denitration device or the like.

The mercury concentration measuring device 45 measures the mercury concentration contained in the exhaust gas flowing through the flue 3. Details of the configuration of the mercury concentration measuring device 45 will be described later. The adsorbent supply unit 41 supplies (blows) a powdery mercury adsorbent to the exhaust gas flowing through the flue 3. The mercury adsorbent is, for example, activated carbon. As the mercury adsorbent, for example, an impregnated activated carbon in which iodine or sulfur is impregnated on the surface of the activated carbon may be used. The alkaline chemical supply unit 42 supplies the alkaline chemical to the exhaust gas flowing through the flue 3. The alkaline agent is an agent for desalting and desulfurization, for example, powdered slaked lime (calcium hydroxide (Ca (OH) ₂ )). Other calcium-based agents (calcium-containing agents) such as dolomite hydroxide [Ca (OH) ₂ , Mg (OH) ₂ ] may be supplied to the exhaust gas as alkaline agents in place of or together with slaked lime. .. Sodium-based agents (sodium-containing agents) such as baking soda (NaHCO _{3) may be used in place of slaked lime.}

The bug filter 43 is a filtration type, and collects fly ash contained in the exhaust gas with a filter cloth. Further, the mercury adsorbent supplied by the adsorbent supply unit 41 and the slaked lime supplied by the alkaline agent supply unit 42 are also collected by the filter cloth. Fly ash, mercury adsorbent and slaked lime deposit on the filter cloth. Inside the bag filter 43, when the exhaust gas passes through the filter cloth, the mercury adsorbent adsorbs the mercury contained in the exhaust gas. Further, an acid gas (hydrogen chloride, sulfur oxide, etc.) contained in the exhaust gas reacts with slaked lime, and the acid gas is removed. The adsorption of mercury by the mercury adsorbent and the reaction between the acid gas and slaked lime also occur in the flue 3. The mercury adsorbent may further adsorb dioxins and the like contained in the exhaust gas.

In the bag filter 43, fly ash and the like (including mercury adsorbent, slaked lime, and a reaction product of slaked lime and acid gas) deposited on the filter cloth are removed by a backwashing operation using a compressed gas. In the backwash operation, compressed gas (pulse jet) is supplied to the filter cloth from the downstream side to the upstream side in the flow direction of the exhaust gas. The compressed gas is, for example, compressed air. Fly ash and the like that have been wiped off from the filter cloth, that is, the collected material by the bag filter 43, is discharged to a discharge processing unit (not shown). In the discharge treatment section, the collected material is subjected to chelation treatment or the like as necessary. As described above, since the collected material contains a mercury adsorbent, the bag filter 43 can be regarded as an adsorbent collecting unit that collects the mercury adsorbent.

FIG. 2 is a diagram showing the configuration of the mercury concentration measuring device 45. The mercury concentration measuring device 45 includes a first intake port 51, a second intake port 52, a reduction unit 53, a concentration acquisition unit 54, and a switching unit 55. The switching unit 55 includes a first flow path 551, a second flow path 552, three three-way valves 553 to 555, a first auxiliary flow path 556, and a second auxiliary flow path 557. The first intake port 51 and the second intake port 52 are attached to the flue 3. The first intake port 51 is connected to the concentration acquisition unit 54 by the first flow path 551. The second intake port 52 is connected to the concentration acquisition unit 54 by the second flow path 552. Specifically, in the vicinity of the concentration acquisition unit 54, the first flow path 551 and the second flow path 552 merge via the three-way valve 555 to form one flow path. The concentration acquisition unit 54 acquires a measured value of mercury concentration based on 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 section 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 unit 53 includes a reduction catalyst that reduces divalent mercury to zero-valent mercury. The reduction unit 53 is constantly heated to a predetermined temperature (for example, 350 to 400 ° C.) by the heating unit 531. The reducing unit 53 may be provided with a scrubber for removing hydrogen chloride and the like. One end of the first auxiliary flow path 556 is connected to the three-way valve 553. The other end of the first auxiliary flow path 556 is connected to the flue 3 on the downstream side of the first intake port 51. In the three-way valve 553, the path of the gas flowing through 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, the filter 592 and the 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 on the downstream side of the second intake port 52. In the three-way valve 554, the path of the gas flowing through the second flow path 552 is switched between the flow path toward the three-way valve 555 and the second auxiliary flow path 557.

The mercury concentration measuring device 45 measures the concentration of zero-valent mercury contained in the exhaust gas flowing through the flue 3 (hereinafter referred to as “zero-valent mercury concentration”), and measures the zero-valent mercury and divalent mercury contained in the exhaust gas. It is possible to selectively measure the total concentration (hereinafter referred to as "total mercury concentration"). FIG. 3 is a diagram showing a mercury concentration measuring device 45 at the time of measuring the zero-valent mercury concentration, and FIG. 4 is a diagram showing a mercury concentration measuring device 45 at the time of measuring the total mercury concentration. In FIGS. 3 and 4, two of the three triangles indicating the three-way valves 553 to 555 are filled to show the flow path connected by the three-way valves 553 to 555.

In the measurement of the zero-valent mercury concentration, 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 smoke. Return to road 3. Further, 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 acquisition unit 54 by the three-way valve 555. As a result, the concentration acquisition unit 54 measures the mercury concentration (that is, zero valence) based on the amount of zero-valent mercury originally contained in the exhaust gas without reducing the divalent mercury contained in the exhaust gas to zero-valent mercury. Mercury concentration) is acquired. As described above, in the measurement of the zero-valent mercury concentration, the zero-valent mercury is detected, but the divalent mercury is not detected. Therefore, it is possible to quickly obtain the measured value of the mercury concentration by omitting the time required for reducing the divalent mercury to the zero-valent mercury.

In the measurement of the total mercury concentration, as shown in FIG. 4, the exhaust gas flowing through the second flow path 552 is guided to the second auxiliary flow path 557 by the three-way valve 554 and returned to the flue 3. Further, the exhaust gas flowing through the first flow path 551 is guided to the three-way valve 555 side by the three-way valve 555, and further guided to the concentration acquisition unit 54 by the three-way valve 555. As a result, the concentration acquisition unit 54 measures the mercury concentration (that is, total mercury) based on the total amount of the zero-valent mercury originally contained in the exhaust gas and the reduced zero-valent mercury in the exhaust gas. Concentration) is obtained. As described above, in the measurement of the total mercury concentration, both zero-valent mercury and divalent mercury are detected, so that the measured value of the mercury concentration can be accurately obtained.

As described above, the exhaust gas taken in by the first intake port 51 flows into the reduction unit 53 not only when measuring the total mercury concentration but also when measuring the zero-valent mercury concentration. That is, while the exhaust gas flows through the flue 3, the exhaust gas always flows into the reduction unit 53. Therefore, immediately after switching from the measurement of the zero-valent mercury concentration to the measurement of the total mercury concentration, the concentration acquisition unit 54 can stably acquire the measured value of the total mercury concentration. Similarly, the exhaust gas taken in by the second intake port 52 flows into the second flow path 552 not only when measuring the zero-valent mercury concentration but also when measuring the total mercury concentration. Therefore, the second flow path 552 can be constantly warmed by the exhaust gas, and it is possible to prevent the measured value of the zero-valent mercury concentration from becoming unstable immediately after switching from the measurement of the total mercury concentration to the measurement of the zero-valent mercury concentration. It is suppressed.

The downstream mercury concentration measuring unit 46 in FIG. 1 measures the total concentration of 0-valent mercury and divalent mercury in the exhaust gas, that is, the total mercury concentration on the downstream side of the bag filter 43. The downstream mercury concentration measuring unit 46 has, for example, in the mercury concentration measuring device 45 of FIG. 2, a configuration in which the second flow path 552, the first auxiliary flow path 556, and the second auxiliary flow path 557 are omitted. The value measured by the downstream mercury concentration measuring unit 46 is output to the control unit 40. The intake port of the downstream mercury concentration measuring unit 46 is provided in, for example, the chimney 22. In the flue 3, intake ports of the downstream mercury concentration measuring unit 46 may be provided at a plurality of positions between the bag filter 43 and the chimney 22, and the total mercury concentration at each position may be measured. In the following description, the total mercury concentration measured by the downstream mercury concentration measuring unit 46 is referred to as "downstream mercury concentration", and when simply referred to as "total mercury concentration", the mercury concentration measuring device 45 arranged on the upstream side It shall mean the total mercury concentration measured by.

The hydrogen chloride concentration measuring unit 47 measures the hydrogen chloride concentration in the exhaust gas on the downstream side of the bag filter 43. For the measurement of hydrogen chloride concentration, for example, laser light or the like is used. The measured value of the hydrogen chloride concentration is output to the control unit 40. Here, it is known that hydrogen chloride in the exhaust gas promotes mercury adsorption by activated carbon. Therefore, when activated carbon is used as the mercury adsorbent, the amount of slaked lime supplied is based on the hydrogen chloride concentration within the range where the hydrogen chloride concentration in the exhaust gas does not drop below a predetermined value in order to properly adsorb mercury with the activated carbon. It is preferable that the control (increase / decrease) is performed.

FIG. 5 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 for reducing the mercury concentration contained in the exhaust gas by controlling the supply amount of the mercury adsorbent by the adsorbent supply unit 41. In the actual exhaust gas treatment device 4, the control of the supply amount of slaked lime by the alkaline chemical supply unit 42 is also performed in parallel with the control of the supply amount of the mercury adsorbent. In exhaust gas treatment, as a general rule, the mercury concentration (zero-valent mercury concentration or total mercury concentration) is measured by the mercury concentration measuring device 45, the downstream mercury concentration is measured by the downstream mercury concentration measuring unit 46, and the hydrogen chloride concentration measuring unit. The measurement of the hydrogen chloride concentration according to 47 is continuously performed.

In the normal state of the exhaust gas treatment device 4, the zero-valent mercury concentration is measured by the mercury concentration measuring device 45, and the control unit 40 measures mercury by the adsorbent supply unit 41 based on (measured value) of the zero-valent mercury concentration. The amount of adsorbent supplied is controlled. For example, when the zero-valent mercury concentration is relatively high, the supply amount of the mercury adsorbent is increased, and when the zero-valent mercury concentration is relatively low, the supply amount of the mercury adsorbent is decreased. When the mercury adsorbent is activated carbon, the activated carbon also adsorbs dioxin. Therefore, it is preferable that a predetermined amount or more of the mercury adsorbent is constantly supplied to the flue 3 while the exhaust gas flows through the flue 3.

Here, the adsorption of mercury by the mercury adsorbent mainly occurs in the bag filter 43. Further, in the control based on the zero-valent mercury concentration, the downstream mercury concentration obtained on the downstream side of the bag filter 43 is not used, but the zero-valent mercury concentration obtained on the upstream side of the bag filter 43 is used. Therefore, it can be said that the control based on the zero-valent mercury concentration is feedforward control (FF control). The same applies to the control based on the total mercury concentration described later.

As described above, in the measurement of the zero-valent mercury concentration, there is no time lag due to the reduction of divalent mercury. As a result, in the control based on the zero-valent mercury concentration, the supply amount of the mercury adsorbent can be quickly responded to the change in the zero-valent mercury concentration in the exhaust gas flowing in the vicinity of the second intake port 52, that is, with good responsiveness. It becomes possible to control. In the control unit 40, the zero-valent mercury concentration used for control may be a moving average over a certain period of time (the same applies to the total mercury concentration and the downstream mercury concentration).

When the zero-valent mercury concentration exceeds a predetermined first threshold due to incineration of waste containing a large amount of mercury, the control unit 40 satisfies the condition for switching from the measurement of the zero-valent mercury concentration to the measurement of the total mercury concentration. The determination is made (step S11), and the mercury concentration measuring device 45 switches to the measurement of the total mercury concentration. As a result, in the control unit 40, the control of the supply amount of the mercury adsorbent is switched from the control based on the zero-valent mercury concentration to the control based on the total mercury concentration (step S12). At this time, the supply amount of the mercury adsorbent is increased to some extent as the zero-valent mercury concentration increases. Therefore, the switch from the control based on the zero-valent mercury concentration to the control based on the total mercury concentration is performed after increasing the supply amount of the mercury adsorbent in the control based on the zero-valent mercury concentration.

The switching from the measurement of the zero-valent mercury concentration to the measurement of the total mercury concentration may be performed based on other switching conditions. For example, after the zero-valent mercury concentration becomes equal to or higher than the first threshold value, the current zero-valent mercury concentration and the immediately preceding zero-valent mercury concentration (each may be a moving average; the same applies hereinafter) are compared. Then, when the current zero-valent mercury concentration is lower than the immediately preceding zero-valent mercury concentration, that is, when the zero-valent mercury concentration is decreasing, it is determined that the switching condition is satisfied. Further, when the zero-valent mercury concentration becomes equal to or higher than the first threshold value, the supply amount of the mercury adsorbent is increased to some extent, and then the zero-valent mercury concentration decreases to be equal to or lower than the predetermined threshold value, the switching condition is satisfied. It may be determined.

In the control based on the total mercury concentration, the supply amount of the mercury adsorbent is increased when the total mercury concentration is relatively high, and the supply amount of the mercury adsorbent is decreased when the total mercury concentration is relatively low. As described above, since accurate mercury concentration can be obtained by measuring the total mercury concentration, it is possible to appropriately control the supply amount of the mercury adsorbent (with less excess or deficiency) by controlling based on the total mercury concentration. It becomes. When measuring the total mercury concentration, the mercury concentration in the exhaust gas is high, and a relatively large amount of mercury adsorbent is required. By setting the supply amount of the mercury adsorbent to an appropriate amount based on the total mercury concentration, the mercury adsorbent can be used efficiently.

The control unit 40 compares the current total mercury concentration with the immediately preceding total mercury concentration. As described above, each of the current total mercury concentration and the immediately preceding total mercury concentration may be calculated as a moving average. When the current total mercury concentration is equal to or higher than the immediately preceding total mercury concentration (step S13), the control based on the total mercury concentration is continued. When the current total mercury concentration is lower than the immediately preceding total mercury concentration, it is determined that the total mercury concentration is decreasing (step S13). When the current total mercury concentration is continuously lower than the immediately preceding total mercury concentration for a certain period of time, it may be determined that the total mercury concentration is decreasing.

When the total mercury concentration is decreasing, the downstream mercury concentration is compared with a predetermined second threshold. Here, in the control based on the zero-valent mercury concentration and the control based on the total mercury concentration, the downstream mercury concentration is usually kept low by the supply of the mercury adsorbent. When the downstream mercury concentration is lower than the second threshold value, that is, when the downstream mercury concentration is kept low (step S14), the mercury concentration measuring device 45 measures the total mercury concentration and determines that the zero-valent mercury. Switch to concentration measurement. As a result, 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 zero-valent mercury concentration, and is returned to the control in the normal state (step S17). In this case, the feedforward control is maintained without switching to the feedback control described later.

On the other hand, when the mercury adsorbent existing in the flue 3 contains a large amount of mercury, such as on the filter cloth of the bag filter 43, and the mercury is desorbed from the mercury adsorbent (the mercury adsorbent is broken). For example, in the comparison between the downstream mercury concentration and the second threshold, the downstream mercury concentration becomes equal to or higher than the second threshold (step S14). In this case, 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 mercury concentration (step S15). In the control based on the downstream mercury concentration, the supply amount of the mercury adsorbent is increased when the downstream mercury concentration is relatively high, and the supply amount of the mercury adsorbent is decreased when the downstream mercury concentration is relatively low. To.

In the control based on the downstream mercury concentration, the zero-valent mercury concentration or the total mercury concentration obtained on the upstream side of the bag filter 43 is not used, but the downstream mercury concentration obtained on the downstream side of the bag filter 43 is used. Therefore, it can be said that the control based on the downstream mercury concentration is feedback control (FB control). Control based on the mercury concentration on the downstream side makes it possible to more reliably reduce the mercury concentration of the exhaust gas discharged to the atmosphere. In addition, with the switch to the control based on the downstream mercury concentration, the mercury concentration measuring device 45 may switch from the measurement of the total mercury concentration to the measurement of the zero-valent mercury concentration.

Switching from feed-forward control using the mercury concentration on the upstream side (zero-valent mercury concentration or total mercury concentration) of the bag filter 43 to feedback control using the mercury concentration on the downstream side (downstream mercury concentration) is performed by the operator. May be done manually by. For example, in the case of control based on the total mercury concentration, when the total mercury concentration decreases and the downstream mercury concentration is equal to or higher than the second threshold value (steps S13 and S14), the control unit 40 performs feedback control. A notification prompting the switch is given to the operator. The notification prompting the switching is performed, for example, by displaying on a display, outputting a voice, or the like. The exhaust gas treatment device 4 is provided with a changeover switch for instructing switching from feedforward control to feedback control, and the operator operates the changeover switch in response to a notification prompting the changeover to provide feedback from the feedforward control. Switching to control is performed (step S15).

In the control based on the downstream mercury concentration, the mercury concentration (zero-valent mercury concentration or total mercury concentration) obtained by the mercury concentration measuring device 45 may be used. That is, in step S15, the feedforward control may be switched to the control in which the feedforward control and the feedback control are used together. Switching to control using both may be performed manually.

In the control unit 40, the downstream mercury concentration is compared with a predetermined third threshold value. The third threshold value may be the same as the second threshold value. When the downstream mercury concentration is equal to or higher than the third threshold value (step S16), the control of the supply amount of the mercury adsorbent based on the downstream mercury concentration is continued. When the downstream mercury concentration becomes lower than the third threshold value (step S16), it is considered that the desorption of mercury from the mercury adsorbent is suppressed. In this case, the control of the supply amount of the mercury adsorbent is switched from the control based on the downstream mercury concentration to the control based on the zero-valent mercury concentration (step S17). That is, the control returns to the normal state of the exhaust gas treatment device 4. Comparing the current downstream mercury concentration with the immediately preceding downstream mercury concentration, when the downstream mercury concentration is decreasing, the control of the supply amount of the mercury adsorbent is based on the zero-valent mercury concentration. May be returned to. In the exhaust gas treatment device 4, the treatment of FIG. 5 is continuously performed while the exhaust gas is flowing through the flue 3.

As described above, in the mercury concentration measuring device 45, the first intake port 51 and the second intake port 52 are attached to the flue 3. Further, the divalent mercury contained in the exhaust gas taken in by the first intake port 51 is reduced to 0-valent mercury by the reducing unit 53. Then, one of the exhaust gas that has passed through the reduction unit 53 or the exhaust gas that has been taken in by the second intake port 52 is selectively flowed into the concentration acquisition unit 54 by the switching unit 55. Thereby, rapid measurement of mercury concentration (measurement of zero-valent mercury concentration) and accurate measurement of mercury concentration (measurement of total mercury concentration) can be selectively performed. Further, the exhaust gas taken in by the first intake port 51 constantly flows into the reduction section 53, and the switching section 55 causes the exhaust gas that has passed through the reduction section 53 to flow into the concentration acquisition section 54 and the flue, which is the discharge position. The discharge to 3 can be switched. As a result, the measured value of the total mercury concentration can be obtained immediately after switching from the measurement of the zero-valent mercury concentration to the measurement of the total mercury concentration.

In the control unit 40 of the exhaust gas treatment device 4, the supply amount of the mercury adsorbent by the adsorbent supply unit 41 is controlled based on the zero-valent mercury concentration, and in a predetermined case, the supply amount of the mercury adsorbent is controlled. The control is switched from the control based on the zero-valent mercury concentration to the control based on the total mercury concentration. As a result, the supply amount of the mercury adsorbent is responsively controlled based on the rapidly obtained zero-valent mercury concentration, and the supply amount of the mercury adsorbent is appropriately controlled based on the total mercury concentration in a predetermined case. Can be controlled (less shortage). Further, when the downstream mercury concentration is equal to or higher than a predetermined 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 mercury concentration. As a result, the mercury concentration of the exhaust gas discharged to the atmosphere can be more reliably lowered.

FIG. 6 is a diagram showing another example of the exhaust gas treatment device. In the exhaust gas treatment device 4a of FIG. 6, a collected material distribution section 441, a recovery ash storage section 442, a recovery ash supply section 443, and an emission treatment section 444 are added to the exhaust gas treatment device 4 of FIG. Other configurations are the same as in FIG. 1, and the same configurations are designated by the same reference numerals. Note that in FIG. 6, the control unit 40 is not shown.

As described above, in the bag filter 43, the collected material deposited on the filter cloth is wiped off by the backwashing operation. The collected material distribution unit 441 distributes the collected material discharged from the bug filter 43 to the collected ash storage unit 442 and the discharge processing unit 444. In the discharge processing unit 444, the collected material is subjected to a chelate treatment or the like as necessary, and then the collected material is discarded. The recovered ash storage unit 442 stores the collected material supplied by the collected material distribution unit 441 as recovered ash. The recovered ash supply unit 443 supplies the recovered ash to a position upstream of the bag filter 43 in the flue 3. Since the recovered ash contains a mercury adsorbent, the recovered ash can be regarded as a recovered adsorbent. The recovered ash storage section 442 and the recovered ash supply section 443 are a recovery adsorbent storage section and a recovery adsorbent supply section, respectively.

In the exhaust gas treatment device 4a of FIG. 6, when the zero-valent mercury concentration is lower than a predetermined threshold value, the collected material collected by the bag filter 43 is stored as recovered ash. For example, when the threshold value is the same as the first threshold value described above, the zero-valent mercury concentration is lower than the first threshold value, and when the control unit 40 performs control based on the zero-valent mercury concentration, The collected material distribution unit 441 supplies the collected material from the bag filter 43 to the collected ash storage unit 442. Therefore, the mercury adsorbent having a relatively small amount of mercury adsorbed is stored as recovered ash in the recovered ash storage unit 442. On the other hand, when the zero-valent mercury concentration is equal to or higher than the first threshold value, the collected material distribution unit 441 supplies the collected material from the bag filter 43 to the discharge processing unit 444. Therefore, a mercury adsorbent having a relatively large amount of mercury adsorbed is not included in the recovered ash.

In the distribution of the collected material in the collected material distribution unit 441, the downstream mercury concentration may be referred to. As described above, when the mercury concentration on the downstream side is high, it is considered that the mercury adsorbent existing on the filter cloth of the bag filter 43 contains a large amount of mercury, and the mercury is desorbed from the mercury adsorbent. .. Therefore, even when the zero-valent mercury concentration is lower than a predetermined threshold value, when the downstream mercury concentration is, for example, the second threshold value or more, the collected material from the bag filter 43 is sent to the discharge processing unit 444. It is preferable to be supplied.

In the control of the normal state in the exhaust gas treatment device 4a, the supply amount of the recovered ash by the recovered ash supply unit 443 is controlled based on the zero-valent mercury concentration in the same manner as the supply amount of the mercury adsorbent by the adsorbent supply unit 41. You may. Therefore, when the zero-valent mercury concentration is relatively high, the supply amount of recovered ash may be increased, and when the zero-valent mercury concentration is relatively low, the supply amount of recovered ash may be decreased. Further, in a predetermined case, the supply amount of the recovered ash may be reduced in order to preferentially supply the new mercury adsorbent from the adsorbent supply unit 41. In the control based on the total mercury concentration and the control based on the downstream mercury concentration, the supply amount of the recovered ash may be increased or decreased in the same manner as the supply amount of the mercury adsorbent, and is newly added from the adsorbent supply unit 41. The supply of recovered ash may be reduced in order to preferentially supply the mercury adsorbent.

As described above, in the exhaust gas treatment device 4a of FIG. 6, when the zero-valent mercury concentration is lower than a predetermined threshold value, the collected material containing the mercury adsorbent collected by the bag filter 43 is stored as recovered ash. Will be done. Then, the amount of the recovered ash supplied to the flue 3 by the recovered ash supply unit 443 may be controlled based on the zero-valent mercury concentration. As a result, mercury in the exhaust gas can be removed while reducing the consumption of the mercury adsorbent in the adsorbent supply unit 41.

In the exhaust gas treatment device 4a, another bug filter may be arranged between the incinerator 21 of FIG. 6 and the adsorbent supply unit 41. In this case, the fly ash contained in the exhaust gas is collected by the other bug filter, and the mercury adsorbent supplied to the flue 3 by the adsorbent supply unit 41 is mainly collected by the bag filter 43. Further, in the exhaust gas treatment device 4a of FIG. 6, the same combination as the bug filter 43, the adsorbent supply unit 41, the collected material distribution unit 441, the recovered ash storage unit 442, and the recovered ash supply unit 443 is a bug in the flue 3. It may be added between the filter 43 and the chimney 22.

FIG. 7 is a diagram showing another example of the mercury concentration measuring device. In the mercury concentration measuring device 45a of FIG. 7, the second intake port 52 in the mercury concentration measuring device 45 of FIG. 2 is omitted, and the configuration of the switching unit 56 is different. Other configurations are the same as those of the mercury concentration measuring device 45 of FIG. 2, and the same configurations are designated by the same reference numerals.

The switching unit 56 includes a first flow path 561, a second flow path 562, and two three-way valves 563 and 564. The first flow path 561 connects the first intake port 51 and the concentration acquisition unit 54. In the first flow path 561, a filter 591, a three-way valve 563, a reduction section 53, and a three-way valve 564 are provided in this order from the first intake port 51 toward the concentration acquisition section 54. The configuration of the filter 591 and the reducing unit 53 is the same as described above.

The second flow path 562 connects the three-way valve 563 and the three-way valve 564 without passing through the reduction section 53. Here, the flow path between the first intake port 51 and the three-way valve 563 and the flow path between the three-way valve 564 and the concentration acquisition unit 54 are formed by the first flow path 561 and the second flow path 562. It is considered to be shared. Therefore, the first flow path 561 is connected to the concentration acquisition unit 54 from the first intake port 51 via the reduction unit 53, and the second flow path 562 bypasses the reduction unit 53 and is the first. The intake port 51 and the concentration acquisition unit 54 are connected. Further, the three-way valves 563 and 564 operate as a flow path switching unit that switches the path of the gas flowing into the concentration acquisition unit 54 between the first flow path 561 and the second flow path 562.

In the measurement of the total mercury concentration, the exhaust gas taken in by the first intake port 51 is guided to the reduction section 53 by the three-way valve 563, and further guided to the concentration acquisition section 54 by the three-way valve 564. As a result, the concentration acquisition unit 54 acquires the total mercury concentration. In the measurement of the zero-valent mercury concentration, the exhaust gas taken in by the first intake port 51 is guided to the second flow path 562 by the three-way valve 563, and further guided to the concentration acquisition unit 54 by the three-way valve 564. As a result, the exhaust gas taken in by the first intake port 51 is guided to the concentration acquisition unit 54 without passing through the reduction unit 53, and the zero-valent mercury concentration is acquired by the concentration acquisition unit 54.

As described above, in the mercury concentration measuring device 45 of FIG. 2, when measuring the zero-valent mercury concentration, the exhaust gas taken in by the second intake port 52 does not pass through the reducing unit 53 and is a concentration acquisition unit. Guided to 54. Therefore, in the mercury concentration measuring device 45a of FIG. 7, it can be said that the first intake port 51 also serves as the second intake port 52. In the mercury concentration measuring device 45a using only one intake port 51, even if it is difficult to install a plurality of intake ports in the flue 3, the measurement of the zero-valent mercury concentration and the measurement of the total mercury concentration are selectively performed. Can be done. The mercury concentration measuring device 45a may adopt a configuration in which the gas taken in by the first intake port 51 always flows into the reducing unit 53.

The mercury concentration measuring devices 45, 45a and the exhaust gas treatment devices 4, 4a can be variously modified.

In the exhaust gas treatment devices 4 and 4a, a zero-valent mercury concentration measuring unit for measuring the zero-valent mercury concentration in the exhaust gas and a total mercury concentration measuring unit for measuring the total mercury concentration in the exhaust gas may be separately provided. In this case, these two measuring units are arranged between the incinerator 21 and the bag filter 43 in the flue 3, and both the zero-valent mercury concentration and the total mercury concentration are constantly measured. In the control unit 40, the supply amount of the mercury adsorbent by the adsorbent supply unit 41 is responsively controlled based on the zero-valent mercury concentration in a normal state, and in a predetermined case, the mercury adsorbent is based on the total mercury concentration. Supply amount is properly controlled. On the other hand, when the mercury concentration measuring devices 45 and 45a of FIGS. 2 and 7 that also serve as the zero-valent mercury concentration measuring unit and the total mercury concentration measuring unit are used, the configuration of the exhaust gas treatment devices 4 and 4a can be simplified. it can. Depending on the design of the exhaust gas treatment devices 4, 4a, the mercury concentration measuring devices 45, 45a may be used in the downstream mercury concentration measuring unit 46.

In the above embodiment, the control based on the total mercury concentration is switched to the control based on the downstream mercury concentration, but when the downstream mercury concentration becomes equal to or higher than the second threshold value during the control based on the zero-valent mercury concentration, mercury Control of the supply amount of the adsorbent may be switched to control based on the downstream mercury concentration. Further, as described above, the zero-valent mercury concentration or the total mercury concentration may be referred to in the control based on the downstream mercury concentration. As described above, in the exhaust gas treatment devices 4 and 4a, when the downstream mercury concentration is equal to or higher than a predetermined threshold (preferably, the zero-valent mercury concentration and the total mercury concentration are equal to or lower than the predetermined threshold and the downstream side is downstream. When the mercury concentration is equal to or higher than a predetermined threshold value), the control of the supply amount of the mercury adsorbent may be 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 mercury concentration. This makes it possible to more reliably reduce the mercury concentration of the exhaust gas discharged to the atmosphere.

The adsorbent supply unit 41 may be provided in the flue 3 on the upstream side of the adsorbent collection unit (bug filter 43), that is, at any position between the incinerator 21 and the adsorbent collection unit. Good. The same applies to the recovered adsorbent supply unit (recovered ash supply unit 443), the zero-valent mercury concentration measuring unit, and the total mercury concentration measuring unit (mercury concentration measuring devices 45, 45a). Further, the downstream mercury concentration measuring unit 46 may be provided at any position between the adsorbent collecting unit and the discharge port of the chimney 22 in the flue 3.

The exhaust gas treatment devices 4 and 4a may be used in facilities other than the incinerator facility 1, and depending on the facilities and the like provided with the exhaust gas treatment devices 4 and 4a, the supply of slaked lime and the control based on the mercury concentration on the downstream side are omitted. May be good. Further, the mercury concentration measuring devices 45 and 45a may be used in addition to the exhaust gas treatment devices 4 and 4a, and in this case, the mercury concentration contained in the gas other than the exhaust gas may be measured.

The above-described embodiment and the configurations in each modification may be appropriately combined as long as they do not conflict with each other.

3 Flue 4, 4a Exhaust treatment device 21 Incinerator 22 Chimney 40 Control unit 41 Adsorbent supply unit 43 Bug filter 45, 45a Mercury concentration measuring device 46 Downstream mercury concentration measuring unit 51 1st intake 52 2nd intake Mouth 53 Reduction unit 54 Concentration acquisition unit 55,56 Switching unit 442 Recovery ash storage section 443 Recovery ash supply section 551,561 First flow path 552,562 Second flow path 553 to 555,563,564 Three-way valve S11 to S17 Step

Claims (9)

A mercury concentration measuring device that measures the concentration of mercury contained in gas.
The first intake port attached to the gas flow path and
A reducing unit that reduces divalent mercury contained in the gas taken in by the first intake port to zero-valent mercury,
A second intake port attached to the gas flow path and
A concentration acquisition unit that acquires a measured value of mercury concentration based on zero-valent mercury,
A switching unit that selectively causes one of the gas that has passed through the reduction unit and the gas that has been taken in by the second intake port to flow into the concentration acquisition unit.
Equipped with a,
The gas taken in at the first intake port constantly flows into the reducing part, and
The switching unit, the inflow to the concentration acquisition portion of the gas passing through the reduced portion, the discharge mercury concentration measuring device according to claim to switch between a to a predetermined discharge position. The mercury concentration measuring device according to claim 1.
The first intake port also serves as the second intake port.
The switching unit
A first flow path connecting from the first intake port to the concentration acquisition unit via the reduction unit, and
A second flow path that bypasses the reduction section and connects the first intake port and the concentration acquisition section.
A flow path switching unit that switches the path of the gas flowing into the concentration acquisition unit between the first flow path and the second flow path,
A mercury concentration measuring device comprising. It is an exhaust gas treatment device
In the flue where the exhaust gas flows from the source of the exhaust gas to the exhaust port to the outside, the adsorbent supply unit that supplies the mercury adsorbent to the exhaust gas and the adsorbent supply unit.
An adsorbent collecting unit that collects the mercury adsorbent in the flue,
A zero-valent mercury concentration measuring unit that measures the zero-valent mercury concentration in the exhaust gas at a position between the source and the adsorbent collecting unit in the flue.
At a position between the source and the adsorbent collecting portion in the flue, the zero-valent mercury originally contained in the exhaust gas and the zero-valent mercury obtained by reducing the divalent mercury in the exhaust gas A total mercury concentration measuring unit that measures the total concentration as the total mercury concentration,
The supply amount of the mercury adsorbent by the adsorbent supply unit is controlled based on the zero-valent mercury concentration, and the control of the supply amount of the mercury adsorbent is controlled based on the zero-valent mercury concentration in a predetermined case. To the control unit that switches to control based on the total mercury concentration,
An exhaust gas treatment device characterized by being equipped with. The exhaust gas treatment apparatus according to claim 3.
The exhaust gas treatment apparatus according to claim 1 or 2 , further comprising the zero-valent mercury concentration measuring unit and the total mercury concentration measuring unit. The exhaust gas treatment apparatus according to claim 3 or 4.
In the control based on the zero-valent mercury concentration, the control unit controls the supply amount of the mercury adsorbent after the zero-valent mercury concentration becomes equal to or higher than a predetermined threshold value and the supply amount of the mercury adsorbent is increased. An exhaust gas treatment apparatus characterized by switching from the control based on the zero-valent mercury concentration to the control based on the total mercury concentration. The exhaust gas treatment apparatus according to any one of claims 3 to 5.
When the zero-valent mercury concentration is lower than a predetermined threshold value, a recovery adsorbent storage unit that stores the mercury adsorbent collected by the adsorbent collection unit as a recovery adsorbent, and a recovery adsorbent storage unit.
A recovery adsorbent supply unit that supplies the recovery adsorbent to a position between the source and the adsorbent collection unit in the flue.
With more
An exhaust gas treatment apparatus characterized in that the control unit controls the supply amount of the recovered adsorbent by the recovered adsorbent supply unit based on the zero-valent mercury concentration. The exhaust gas treatment apparatus according to any one of claims 3 to 6.
At a position between the adsorbent collecting portion and the exhaust port in the flue, the zero-valent mercury originally contained in the exhaust gas and the zero-valent mercury obtained by reducing the divalent mercury in the exhaust gas. Further equipped with a downstream mercury concentration measuring unit that measures the total concentration as the downstream mercury concentration,
When the downstream mercury concentration is equal to or higher than a predetermined threshold value, the control unit controls the supply amount of the mercury adsorbent at least on the downstream side from the control based on the zero-valent mercury concentration or the total mercury concentration. An exhaust gas treatment device characterized in that it can be switched to control based on mercury concentration. This is an exhaust gas treatment method for exhaust gas treatment equipment.
The exhaust gas treatment device
In the flue where the exhaust gas flows from the source of the exhaust gas to the exhaust port to the outside, the adsorbent supply unit that supplies the mercury adsorbent to the exhaust gas and the adsorbent supply unit.
An adsorbent collecting unit that collects the mercury adsorbent in the flue,
A zero-valent mercury concentration measuring unit that measures the zero-valent mercury concentration in the exhaust gas at a position between the source and the adsorbent collecting unit in the flue.
At a position between the source and the adsorbent collecting portion in the flue, the zero-valent mercury originally contained in the exhaust gas and the zero-valent mercury obtained by reducing the divalent mercury in the exhaust gas A total mercury concentration measuring unit that measures the total concentration as the total mercury concentration,
With
The exhaust gas treatment method
A step of controlling the supply amount of the mercury adsorbent by the adsorbent supply unit based on the zero-valent mercury concentration, and a step of controlling the supply amount of the mercury adsorbent.
In a predetermined case, the step of switching the control of the supply amount of the mercury adsorbent from the control based on the zero-valent mercury concentration to the control based on the total mercury concentration, and
An exhaust gas treatment method characterized by comprising. The exhaust gas treatment method according to claim 8.
The exhaust gas treatment device
At a position between the adsorbent collecting portion and the exhaust port in the flue, the zero-valent mercury originally contained in the exhaust gas and the zero-valent mercury obtained by reducing the divalent mercury in the exhaust gas. Further equipped with a downstream mercury concentration measuring unit that measures the total concentration as the downstream mercury concentration,
The exhaust gas treatment method
When the downstream mercury concentration is equal to or higher than a predetermined threshold, the control of the supply amount of the mercury adsorbent is controlled from the control based on the zero-valent mercury concentration or the total mercury concentration to at least the control based on the downstream mercury concentration. An exhaust gas treatment method characterized by further including a process of switching to.

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