JP6846778B2 - Mercury removal device and method in exhaust gas - Google Patents

Description

The present invention relates to an exhaust gas treatment device using a waste incinerator exhaust gas treatment device and a waste incinerator exhaust gas treatment device, and relates to a technique for reliably removing mercury contained in the exhaust gas discharged from the incinerator.

Conventionally, when treating exhaust gas discharged from a waste incinerator, the temperature is first lowered to 200 ° C. or lower, and then acidic components such as soot, hydrogen chloride and sulfur oxides contained in the exhaust gas, and dioxins. And after removing harmful substances such as mercury, it is released into the atmosphere from the chimney.

As a technique for removing mercury contained in exhaust gas, a technique for adding activated carbon functioning as a mercury adsorbent into exhaust gas containing mercury as shown in Patent Document 1 is known (Patent Document 1). 1). Further, a technique for removing mercury by using a pre-coated type bag filter in which the surface of a filter cloth is coated with activated carbon in advance has been proposed (Patent Document 2).

Japanese Unexamined Patent Publication No. 2014-213308 Patent No. 6114438

According to the technique disclosed in Patent Document 1, activated carbon that functions as an adsorbent is put into exhaust gas containing mercury, and the activated carbon that has adsorbed mercury is collected by a filtration type dust collector such as a bag filter. Mercury contained in the exhaust gas can be removed. At this time, the amount of activated carbon consumed can be reduced by providing a mercury concentration detector on the downstream side of the filtration type dust collector and adding activated carbon into the exhaust gas only when the mercury concentration exceeds a predetermined value. it can. However, since the mercury concentration is detected on the downstream side of the filtration type dust collector and the activated carbon is charged on the upstream side of the filtration type dust collector based on the detection result, the concentration is detected and the activated carbon is charged. There was a problem that a time delay occurred during the period and it was not possible to cope with the sudden rise in mercury concentration. In addition, even if the mercury concentration temporarily rises, activated carbon is supplied, which causes wasteful introduction of activated carbon.

On the other hand, the technique disclosed in Patent Document 2 removes mercury by using a bag filter using a filter cloth precoated with activated carbon or an alkaline chemical, and does not add activated carbon into the exhaust gas. It is possible to remove mercury in the exhaust gas while suppressing the consumption of activated carbon. In addition, activated carbon fibers for removing mercury that cannot be completely removed by the filter cloth are provided on the downstream side of the filter cloth in the bag filter, and whether the exhaust gas after passing through the filter cloth circulates the activated carbon fibers. It is equipped with a switching valve that can switch between.

Then, when the mercury concentration measured on the downstream side of the bag filter exceeds a predetermined value, mercury is removed by both the precoated filter cloth and the activated carbon fiber by switching the switching valve to the side where the activated carbon fiber is distributed. It has a structure. Further, when the mercury concentration does not exceed the predetermined value measured on the downstream side of the bag filter, the switching valve is switched to the side where the activated carbon fiber does not flow, so that the mercury is removed only by the precoated filter cloth.

In the case of the technique disclosed in Patent Document 2, since the adsorbent such as activated carbon is only used for precoating the filter cloth and is not put into the exhaust gas, wasteful consumption of the adsorbent can be suppressed. .. However, as in the technique disclosed in Patent Document 1, there is a possibility that a time delay may occur due to the detection of the mercury concentration on the downstream side of the bag filter, and the switching of the flow path cannot catch up with the sudden rise in the mercury concentration. It is also expected that the regulation standard value will be temporarily exceeded. Further, if the switching valve is switched early, the activated carbon fibers are circulated even when it is not necessary, and there arises a problem that the time until the activated carbon fibers break through is shortened. Such problems also occur when the detected mercury concentration fluctuates up and down in a short period of time. That is, when the detected mercury concentration fluctuates up and down in a short period of time, the switching valve is operated every time the concentration exceeds a predetermined concentration for switching, which leads to the use of unnecessary activated carbon fibers.

The present invention has been made in view of such a problem, and has a contradictory effect of quickly and surely removing mercury in exhaust gas without excessively using a fibrous adsorbent such as activated carbon fiber. It is an object of the present invention to provide an exhaust gas treatment device and a method for a waste incinerator.

The present invention provides the following solutions.

The invention according to the first feature is a bag filter having an inlet and an outlet for exhaust gas discharged from a waste incinerator, and captures soot and harmful components contained in the exhaust gas introduced from the inlet. A filter cloth, a fibrous adsorbent that is arranged on the downstream side of the filter cloth and further adsorbs harmful components from the exhaust gas that has passed through the filter cloth, and a short-circuit flow that guides the exhaust gas after passing through the fibrous adsorbent to the discharge port. A bug filter and a bug having a path, a detour flow path that guides the exhaust gas to the discharge port without passing through the fibrous adsorbent, and a flow path switching means for selectively switching between the short-circuit flow path and the detour flow path. A chemical supply device that is arranged on the upstream side of the filter and supplies a chemical and a mercury adsorbent for neutralizing the acidic component contained in the exhaust gas into the exhaust gas on the upstream side of the bag filter, and in the exhaust gas on the upstream side of the bag filter. It is provided with a mercury concentration detecting device for detecting the mercury concentration of the above and a control device for switching and controlling the flow path switching means based on the mercury concentration detected by the mercury concentration detecting device, and the control device performs an exhaust gas filtration operation. At the same time, the chemical and mercury adsorbent are supplied from the chemical supply device to perform a precoating treatment to form a reaction layer of a predetermined thickness, and the mercury concentration in the exhaust gas measured on the upstream side of the bag filter exceeds the predetermined value. When the state continues for a predetermined time and is on an upward trend, the flow path switching means is switched to the short-circuit flow path side to guide the exhaust gas after flowing through the filter cloth to the fibrous adsorbent. Provide an exhaust gas treatment device for a waste incinerator.

According to the invention according to the first feature, when the mercury concentration measured on the upstream side of the bag filter exceeds a predetermined value for a predetermined time and further increases, the fibrous adsorbent is used. By configuring it to be used, it is possible to reliably treat mercury while suppressing the breakage of the fibrous adsorbent caused by frequent use of the fibrous adsorbent.

The invention according to the second feature is an invention according to the first feature, further comprising a mercury concentration detecting device for detecting the mercury concentration in the exhaust gas on the downstream side of the bag filter, and the control device has flowed through the filter cloth. In the state where the later exhaust gas is guided to the fibrous adsorbent, and the mercury concentration in the exhaust gas measured on the downstream side of the bag filter does not fall below the predetermined value and elapses for a predetermined time or tends to increase. Provided an exhaust gas treatment device for supplying a mercury adsorbent from a drug supply device.

According to the invention according to the second feature, when the mercury concentration measured on the downstream side of the bag filter does not fall below the predetermined value and the predetermined time elapses or the mercury concentration tends to increase, the adsorbent is supplied from the drug supply device. When the mercury concentration does not decrease even if the fibrous adsorbent is used, the adsorbent can be directly supplied to the exhaust gas to quickly capture the mercury.

The invention according to the third feature is the invention according to the first or second feature, and provides an exhaust gas treatment apparatus using activated carbon as a mercury adsorbent.

According to the invention according to the third feature, effective treatment of mercury is possible by using a relatively easily available adsorbent.

The invention according to the fourth feature is an invention according to any one of the first to third features, which is a plurality of ceramic filters for sucking exhaust gas as a mercury concentration detecting device, and alternately backwashes. Provided is an exhaust gas treatment apparatus using a ceramic filter.

According to the invention according to the fourth feature, when a plurality of ceramic filters are used at the same time and backwashing is performed with pulse air in a timely manner, which occurs when the ceramic filters are operated one by one at the time of stopping when the ceramic filters are switched. It is possible to avoid the situation where the exhaust gas cannot be sucked due to the influence of the adhering dust, and to stably introduce and analyze the exhaust gas.

According to the present invention, it is possible to provide an exhaust gas treatment apparatus and method for a waste incinerator, which has the contradictory effects of quickly and surely removing mercury in exhaust gas without excessively using the fibrous adsorbent.

FIG. 1 is a schematic view showing a waste incinerator exhaust gas treatment apparatus according to the present embodiment. FIG. 2 is a diagram showing an internal configuration of the bug filter according to the present embodiment, showing a state in which the flow path switching valve is open. FIG. 3 is a diagram showing an internal configuration of the bug filter according to the present embodiment, and shows a state in which the flow path switching valve is closed. FIG. 4 is a schematic view showing the configuration of the mercury concentration detecting device according to the present embodiment. FIG. 5 is a diagram showing a flowchart for explaining an exhaust gas treatment method using the waste incinerator exhaust gas treatment device according to the present embodiment.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. It should be noted that this is only an example, and the technical scope of the present invention is not limited to this.

[Overall configuration of waste incinerator exhaust gas treatment device 1]
First, the overall configuration of the waste incinerator exhaust gas treatment device according to the present embodiment will be described with reference to FIG.

As shown in FIG. 1, the waste incinerator exhaust gas treatment device of the present embodiment includes a waste incinerator 1, a heat recovery device 2 composed of an exhaust heat recovery boiler and an economizer, a gas cooling device 3, a bag filter 4, and the like. The attracting ventilator 5, the chimney 6, the chemical supply device 7, the first mercury concentration detecting device 8a provided on the upstream side of the bag filter 4, and the second mercury concentration detecting device provided on the downstream side of the bag filter 4. It is composed of a mercury concentration detection device 8 composed of 8b and a control device 9.

The waste incinerator 1 incinerates atypical general waste, industrial waste, infectious medical waste, etc. in a package having a predetermined shape, and is a stoker type or fluid. Any type of incinerator such as layered type or vertical type is used.

The heat recovery device 2 recovers heat from the high-temperature exhaust gas generated when waste is incinerated in the waste incinerator 1, and is, for example, an exhaust heat recovery boiler equipped with an evaporator or an exhaust heat recovery boiler. It is composed of an economizer that heats water upstream.

The gas cooling device 3 is capable of supplying the temperature of the exhaust gas discharged from the waste incinerator 1 and the heat recovery device 2 to the bag filter 4, and is described in the "Guidelines for Prevention of Dioxins Generation Related to Waste Disposal". The temperature is reduced to about 200 ° C or less, and the type does not matter.

The bag filter 4 removes soot and harmful components contained in the exhaust gas by filtering the exhaust gas whose temperature has been reduced by the gas cooling device 3, and as shown in FIGS. 2 and 3, the soot and dust and the like are removed. It includes a filter cloth 41 for filtering harmful components, a fibrous adsorbent 42 for adsorbing harmful components, a filter cloth 41 and a casing 43 for accommodating the fibrous adsorbent 42. The details of the bug filter 4 will be described later.

The attractive ventilator 5 is a ventilator arranged downstream of the bug filter 4 and is for sucking the exhaust gas purified by the bug filter 4 and releasing the exhaust gas from the chimney 6 to the atmosphere.

The chemical supply device 7 uses an exhaust gas as an alkaline chemical for neutralizing acidic components such as hydrogen chloride and sulfur oxides contained in the exhaust gas, and a mercury adsorbent for adsorbing harmful substances contained in the exhaust gas. It is supplied to the inside and the bag filter 4, and is arranged on the upstream side of the bag filter 4, preferably in the flue between the gas cooling device 3 and the bag filter 4.

In this embodiment, slaked lime is used as the alkaline agent and activated carbon is used as the mercury adsorbent. In particular, by using activated carbon as the mercury adsorbent, it becomes possible to effectively treat mercury using a relatively easily available adsorbent. The types of chemicals and mercury adsorbents used are not limited to this.

The mercury concentration detecting device 8 is installed on the upstream side of the bag filter 4, particularly on the upstream side flue of the gas cooling device 3, and is configured to continuously detect the mercury concentration before being adsorbed by the adsorbent. A second mercury concentration detector 8a and a second mercury concentration detector installed on the downstream side of the bag filter 4 and configured to continuously detect the mercury concentration after being adsorbed by the adsorbent and the fibrous adsorbent 42. It is composed of 8b.

The control device 9 controls the power of a motor (not shown) so as to perform switching control of the flow path switching means 45 described later based on the mercury concentration detected by the first mercury concentration detecting device 8a. Further, the supply of the alkaline drug and the adsorbent from the drug supply device 7 is controlled based on the mercury concentration detected by the second mercury concentration detection device 8b. The switching control of the flow path switching means 45 and the supply control of the alkaline drug and the adsorbent from the drug supply device 7 will be described later.

[Bug filter 4]
Next, the bug filter 4 in the present embodiment will be described with reference to FIGS. 2 and 3. FIG. 2 is a diagram showing an internal configuration of the bug filter 4 according to the present embodiment, showing a state in which the flow path switching means 45 described later is open, and FIG. 3 shows the flow path switching means 45 closed. It shows the state of the bug.

The bag filter 4 purifies the exhaust gas cooled by the cooling device 3, and includes an exhaust gas introduction port 4a provided below, a filter cloth 41 for filtering soot and harmful components contained in the exhaust gas, and the like. It is composed of a fibrous adsorbent 42 that further adsorbs harmful components from the exhaust gas that has passed through the filter cloth 41, a casing 43 that houses the filter cloth 41 and the fibrous adsorbent 42, and an exhaust gas discharge port 4b provided above. ..

In the casing 43, a partition wall 43c that partitions the internal space of the casing 43 into an upper space 43a in which the fibrous adsorbent 42 is arranged and a lower space 43b in which the filter cloth 41 is arranged is installed. ..

The filter cloth 41 captures soot and harmful components contained in the exhaust gas introduced into the lower space 43b of the casing 43, and is made of woven cloth or non-woven fabric and has one end opened and the other end closed. Is formed as an aggregate of. Each tubular body is arranged so that the end portion at which the opening is formed penetrates the opening formed at the partition wall 43c.

In the present embodiment, the tubular body having the lower end closed and the upper end opened is arranged in a plurality of openings provided in the width direction and the depth direction of the partition wall 43c, so that the exhaust gas flowing in from below It forms a filter cloth 41 capable of catching soot and dust.

That is, the exhaust gas introduced into the lower space 43b of the casing 43 and flowing from the lower side to the upper side passes through the filter cloth 41 whose lower end is closed and flows into the upper space 43a through the opening at the upper end. Then, when passing through the filter cloth 41, soot and dust contained in the exhaust gas are removed, and the exhaust gas becomes purified and flows into the upper space 43a.

As will be described later, the surface of the filter cloth 41 of the bag filter 4 according to the present embodiment is precoated with an alkaline agent and an adsorbent, so that in addition to the filtering effect of soot and dust, hydrogen chloride, sulfur oxides, etc. And harmful components such as mercury can be effectively purified and adsorbed.

Examples of the fibrous adsorbent 42 that adsorbs mercury include activated carbon fibers and those called Activated Carbon Fibers (ACF). ACF has an excellent function of adsorbing and removing harmful components such as nitrogen oxides, dioxins, polychlorinated biphenyls (PCBs), mercury and odors contained in exhaust gas.

The fibrous adsorbent 42 is preferably impregnated with a chemical effective for adsorbing mercury in order to enhance the ability to adsorb mercury.

The fibrous adsorbent 42 is installed in the upper space 43a of the casing 43 so as to partition the upper space 43a from the upstream side and the downstream side in the exhaust gas distribution direction.

That is, the fibrous adsorbent 42 of the bug filter 4 according to the present embodiment is configured by arranging a plurality of filter members side by side on substantially the same plane, and the upper space 43a is the fibrous adsorbent 42. It is divided into a part located above and a part located below. At that time, the filter members constituting the fibrous adsorbent 42 are arranged side by side in the width direction and the depth direction on the support frame 42s arranged at a predetermined height.

An exhaust gas discharge flow path 44 is connected to the upper space 43a of the casing, and the discharge flow path 44 is located above by a partition plate 44c arranged at a predetermined height to provide a fibrous adsorbent 42. It is divided into a short-circuit flow path 44a through which the exhaust gas after flowing through flows, and a bypass flow path 44b located below and discharging the exhaust gas without flowing through the fibrous adsorbent 42.

That is, as described above, the upper space 43a of the casing is divided into the upstream side and the downstream side in the exhaust gas flow direction by the fibrous adsorbent 42, but the short-circuit flow path 44a communicates with the space on the downstream side of the fibrous adsorbent 42. The detour flow path 44b communicates with the space on the upstream side of the fibrous adsorbent 42.

In the discharge flow path 44, a short-circuit flow path 44a through which the exhaust gas after passing through the fibrous adsorbent 42 flows and a detour flow path 44b through which the exhaust gas that does not pass through the fibrous adsorbent 42 flows are selectively distributed. The flow path switching means 45 is provided.

In the present embodiment, the flow path switching means 45 is composed of a flow path on-off valve installed in the bypass flow path 44b, and the bypass flow path 44b is powered by a motor (not shown) in accordance with a command from the control device 9. It is configured so that it can be switched between open and closed.

That is, as shown in FIG. 3, when the bypass flow path 44b is closed by operating the flow path switching means 45, the exhaust gas flowing into the upper space 43b is purified by flowing through the fibrous adsorbent 42. , Is discharged from the exhaust gas discharge port 4b via the short-circuit flow path 44a.

On the other hand, as shown in FIG. 2, when the bypass flow path 44b is opened by operating the flow path switching means 45, the ventilation resistance of the fibrous adsorbent 42 causes the flow path switching means 45 and the bypass flow path 44b to be ventilated. Since it is larger than the resistance, the exhaust gas flowing into the upper space 43a bypasses the fibrous adsorbent 42, passes through the flow path switching means 45 and the bypass flow path 44b, and is discharged from the exhaust gas discharge port 4b.

In the present embodiment, the support frame 42s on which the fibrous adsorbent 42 is installed and the partition plate 44c are arranged on substantially the same plane as separate members, but the support frame 42s and the partition plate 44c are the same. It may be configured as a member.

[Mercury concentration detector 8]
Next, the mercury concentration detecting device 8 according to the present embodiment will be described with reference to FIG.

As shown in FIG. 4, the mercury concentration detecting device 8 in the present embodiment has a plurality of ceramic filters 81a and 81b whose tips protrude into the flue and samples exhaust gas, and exhaust gas that measures the mercury concentration in the supplied exhaust gas. Exhaust gas supply pipes 83a, 83b, exhaust gas supply pipes 83a, 83b, which are connected to the analyzer 82, the ceramic filters 81a, 81b, and the exhaust gas analyzer 82, and supply the exhaust gas introduced from the ceramic filters 81a, 81b to the exhaust gas analyzer 82, Exhaust gas electromagnetic valves 84a and 84b arranged in 83b and controlling the flow of exhaust gas by opening / closing operation, compressed air supply source 85, and compressed air supply pipe for guiding compressed air supplied from compressed air supply source 85 to a ceramic filter. It is composed of 86a and 86b and compressed air electromagnetic valves 87a and 87b which are arranged in compressed air supply pipes 86a and 86b and control the flow of compressed air by opening and closing operations.

In the mercury concentration detecting device 8 having such a configuration, all the exhaust gas solenoid valves 84a and 84b are opened and all the compressed air solenoid valves 87a and 87b are closed during normal operation, so that all the ceramics are used. Exhaust gas is sampled from the filters 81a and 81b and introduced into the exhaust gas analyzer 82 via the exhaust gas supply pipes 83a and 83b to measure the mercury concentration in the exhaust gas.

Then, in a timely manner, one of the exhaust gas solenoid valves 84a and 84b is closed and the other compressed air solenoid valves 87a and 87b are opened, and pulse air is supplied from either the compressed air supply source 85 or the compressed air supply pipes 86a or 86b. Is supplied to backwash the dust adhering to one surface of the ceramic filters 81a and 81b to prevent clogging of the ceramic filters 81a and 81b. Backwashing of such ceramic filters is performed alternately.

In this way, by using multiple ceramic filters at the same time and alternately backwashing with pulsed air, the exhaust gas is affected by the dust adhering at the time of stopping when switching, which occurs when the ceramic filters are operated one by one. It is possible to avoid the situation where the ceramics cannot be sucked and to perform stable introduction and analysis of exhaust gas.

[Exhaust gas treatment method using the waste incinerator exhaust gas treatment device 1]
Next, the exhaust gas treatment method using the waste incinerator exhaust gas treatment device 1 according to the present embodiment will be described with reference to FIG.

[Step S100: Precoat of filter cloth 41]
First, during the operation of the waste incinerator, the surface of the filter cloth 41 of the bag filter 4 is supplied from the chemical supply device 7 to the bag filter 4 via the flue gas stack for a predetermined time. Is precoated to form a reaction layer of a drug and an adsorbent having a predetermined thickness (step S100).

[Steps S110 to S120: Purification of exhaust gas by filter cloth 41]
When the precoating treatment in step S100 is completed, the exhaust gas treatment with the precoated filter cloth 41 is carried out (step S110).

At this time, as shown in FIG. 2, the flow path switching means 45 is set to face the opening direction, and the exhaust gas purified by the filter cloth 41 passes through the detour flow path 44b without passing through the fibrous adsorbent 42. Then, it is discharged from the discharge port 4b.

At the same time, the control device 9 continues a state in which the first mercury concentration, which is the mercury concentration upstream of the bag filter 4, exceeds a predetermined value, as measured by the first mercury concentration detecting means 8a, for a predetermined time, and further. A process of determining whether or not there is an upward trend (condition 1) is executed (step S120).

The passage of a predetermined time is timed and determined by a timer (not shown). Whether or not the first mercury concentration is on the rise is determined based on the time change of the mercury concentration, which is calculated based on the mercury concentration measured by the first mercury concentration detecting means 8a and the time measured by the timer. Will be done.

In step S120, if the state in which the first mercury concentration exceeds a predetermined value continues for a predetermined time and is not in a situation where the concentration is on an upward trend, that is, if it is determined to be N in step S120, the process returns to step S110. Continue to purify the exhaust gas using only the pre-coated filter cloth 41.

When it was determined to be N in step S120, the mercury concentration on the upstream side of the bag filter 4 was lower than the predetermined value, the elapsed time from exceeding the predetermined value was short, or the elapsed time was long. However, since the mercury concentration does not tend to increase, purification with only the filter cloth 41 is sufficient. In particular, in step S100, since the precoating treatment for forming the reaction layer of the adsorbent having a predetermined thickness is performed on the surface of the filter cloth 41, the adsorption capacity on the surface of the filter cloth 41 is improved, and the required adsorption capacity is obtained. It will be possible to demonstrate.

[Steps S130 to S140: Purification of exhaust gas by filter cloth 41 and fibrous adsorbent 42]
On the other hand, in step S120, when the state in which the first mercury concentration exceeds a predetermined value continues for a predetermined time and is on an upward trend, that is, when it is determined to be Y in step S120, the process proceeds to step S130. In addition to purification with the pre-coated filter cloth 41, purification with the fibrous adsorbent 42 is performed (step S130).

That is, in step S130, as shown in FIG. 3, the flow path switching means 45 is switched in the closing direction to change the path through which the exhaust gas flows, and the exhaust gas purified by the filter cloth 41 is the fibrous adsorbent 42. Through. Therefore, the mercury remaining in the exhaust gas is adsorbed when passing through the fibrous adsorbent 42, and the exhaust gas purified in two steps by the filter cloth 41 and the fibrous adsorbent 42 passes through the short-circuit flow path 44a to the discharge port 4b. Exhaust from.

That is, if the mercury concentration before purification exceeds a predetermined value, there is a possibility that mercury in the exhaust gas cannot be sufficiently adsorbed only by purification with the filter cloth 41. Therefore, in order to strengthen the purification, mercury is surely adsorbed by using the fibrous adsorbent 42 in addition to the filter cloth 41.

By the way, if the condition for using the fibrous adsorbent 42 is only that the mercury concentration exceeds a predetermined value, so-called hunting in which the use and non-use of the fibrous adsorbent 42 are frequently switched in the vicinity of the predetermined value. The phenomenon occurs. Further, since the path is changed to the short-circuited flow path 44a early, there is a problem that the time for the exhaust gas to pass through the fibrous adsorbent 42 becomes long and the time until the fibrous adsorbent breaks is shortened. Occurs.

Therefore, in the present invention, the condition for using the fibrous adsorbent 42 is not simply that the mercury concentration exceeds a predetermined value, but the state in which the mercury concentration exceeds a predetermined value continues for a predetermined time, and further. The condition for using the fibrous adsorbent 42 is that the fibrous adsorbent 42 is on the rise. By doing so, it is possible to surely reduce the mercury concentration while preventing the hunting phenomenon.

At this time, the fiber is not simply added as a condition for using the fibrous adsorbent 42 that the mercury concentration exceeds a predetermined value for a predetermined time, but as a condition that the mercury concentration tends to increase further. It prevents the time until the state adsorbent breaks is shortened, and enables economical operation. This is because the first mercury concentration measured by the first mercury concentration detecting means 8a indicates the concentration of mercury contained in the exhaust gas before the purification treatment, so that the time change of the first mercury concentration is thereafter. It is an important factor in determining the degree of exhaust gas treatment applied to the mercury. That is, if the time change of the first mercury concentration tends to decrease or is substantially flat, the filter cloth 41 is precoated without any special treatment thereafter. It is possible to reduce the concentration to a specified value or less by a normal treatment using only the filter cloth 41. If the fibrous adsorbent 42 is used in such a case, the time until the fibrous adsorbent breaks is shortened.

Therefore, in the present embodiment, the mercury concentration measured on the upstream side of the bug filter 4 continues to exceed a predetermined value for a predetermined time, and is frequently increased on condition that the mercury concentration tends to increase further. While suppressing the breakage of the fibrous adsorbent caused by using the fibrous adsorbent 42, it is possible to reliably treat mercury.

Returning to FIG. 5, in step S130, the exhaust gas was purified by the filter cloth 41 and the fibrous adsorbent 42, and at the same time, did the control device 9 elapse a certain time after the concentration of the first mercury was lower than the predetermined concentration? The process of determining whether (condition 2) is executed (step S140).

When the first mercury concentration falls below the predetermined concentration and a certain time elapses, that is, when Y is determined in step S140, the process returns to step S110, and as shown in FIG. 2, the flow path switching means 45 is opened. The exhaust gas purified by the filter cloth 41 passes through the detour flow path 44b without passing through the fibrous adsorbent 42, and is controlled to be discharged from the discharge port 4b.

That is, when it is determined to be Y in step S140, it is determined that it is not necessary to use the fibrous adsorbent 42, and purification is performed using only the precoated filter cloth 41.

[Steps S150 to S160: Purification of exhaust gas by supplying an adsorbent]
On the other hand, when N is determined in step S140, the process proceeds to step S150, and the secondary mercury concentration measured by the secondary mercury concentration detecting means 8b installed on the downstream side of the bug filter 4 does not fall below a predetermined value. A process of determining whether a predetermined time has elapsed or whether or not the predetermined time has elapsed (condition 3) is executed (step S150).

When the secondary mercury concentration measured by the secondary mercury concentration detecting means 8b does not fall below the predetermined value and the predetermined time elapses or tends to increase, that is, when it is determined to be Y in step S150. Proceeding to step S160, the control device 9 executes a process of supplying the adsorbent from the drug supply device 7 (step S160).

That is, if the concentration of mercury contained in the exhaust gas after purification does not decrease even if the fibrous adsorbent 42 is used, the purification is further strengthened by directly supplying the adsorbent into the exhaust gas. It is possible to realize stepwise purification.

In step S150, in the situation where the predetermined time elapses or the concentration tends to increase without the secondary mercury concentration falling below the predetermined value, even if the filter cloth 41 and the fibrous adsorbent 42 are used for double purification. Since it is the case that the mercury concentration after purification does not decrease or increases, it is judged that it is necessary to further strengthen the adsorption. Therefore, in the present embodiment, in such a case, the mercury concentration is rapidly reduced by directly supplying the adsorbent into the exhaust gas from the drug supply device 7 provided upstream of the bug filter 4.

On the other hand, when the secondary mercury concentration measured by the secondary mercury concentration detecting means 8b decreases or tends to decrease to a predetermined value or less before the predetermined time elapses, that is, it is determined to be N in step S150. If so, the process returns to step S130 and the purification of the exhaust gas using the filter cloth 41 and the fibrous adsorbent 42 is continued.

That is, in step S150, the situation where the secondary mercury concentration decreases or tends to decrease to a predetermined value or less before the predetermined time elapses is caused by double purification by the filter cloth 41 and the fibrous adsorbent 42. Since it can be determined that mercury can be effectively adsorbed, the required adsorption capacity can be secured by continuing the purification with the filter cloth 41 and the fibrous adsorbent 42 as it is.

By the way, when it is determined to be Y in step S150 and the exhaust gas is purified by supplying the adsorbent in addition to the filter cloth 41 and the fibrous adsorbent 42 in step S160, the control device 9 has the predetermined secondary mercury concentration. A process of determining whether or not a certain time has elapsed below the value (condition 4) is executed (step S170).

When the secondary mercury concentration is below the predetermined value and a certain period of time has not elapsed, that is, when it is determined to be N in step S170, it is determined that purification by direct supply of the adsorbent is still necessary. Therefore, the process returns to step S160, and the supply of the adsorbent from the drug supply device 7 is continued.

On the other hand, when the secondary mercury concentration falls below the predetermined value and a certain period of time elapses, that is, when Y is determined in step S170, it is determined that purification by directly supplying the adsorbent is no longer necessary. , Step S180, the control device 9 stops the supply of the adsorbent from the drug supply device 7, and then returns to step S130 to continue purifying the exhaust gas using the filter cloth 41 and the fibrous adsorbent 42.

By repeating such treatment, mercury in the exhaust gas can be stably treated. Further, by performing the precoating treatment again as necessary, it is possible to suppress a decrease in the adsorption capacity on the surface of the filter cloth 41.

In particular, by configuring the fibrous adsorbent 42 to be used when the mercury concentration measured on the upstream side of the bag filter 4 exceeds a predetermined value for a predetermined time and further increases. It is possible to reliably treat mercury while suppressing the breakage of the fibrous adsorbent caused by the frequent use of the fibrous adsorbent 42.

Further, when the mercury concentration measured on the downstream side of the bag filter 4 does not fall below the predetermined value and the predetermined time elapses or the mercury concentration tends to increase, the adsorbent is supplied from the drug supply device 7. Therefore, when the mercury concentration does not decrease even if the fibrous adsorbent 42 is used, the adsorbent can be directly supplied to the exhaust gas to quickly capture the mercury.

In addition, the following effects can be obtained as incidental effects of the present invention.

In general, although it is not possible to continuously measure the concentration of dioxin itself, the fibrous adsorbent used as a mercury adsorbent also has the effect of adsorbing dioxin, so monoxide is an indicator of the concentration of dioxin. To reduce the concentration of dioxin by measuring the carbon (CO) concentration or the total hydrocarbon (THC) concentration and controlling the exhaust gas to flow through the fibrous adsorbent when these concentrations exceed a predetermined value. Can be done.

By continuously measuring the mercury concentration at the upstream position of the bag filter, the amount of the adsorbent required for precoating can be controlled to an appropriate amount, and the use of wasteful adsorbent can be reduced.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments described above. In addition, the effects described in the embodiments of the present invention merely list the most preferable effects arising from the present invention, and the effects according to the present invention are limited to those described in the embodiments of the present invention. is not it.

Further, the above-described embodiment has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to the one including all the described configurations. Further, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. .. In addition, other configurations may be added, deleted, or replaced with respect to a part of the configurations of each embodiment.

The exhaust gas treatment method using the waste incinerator exhaust gas treatment device of the present invention can be applied to an industrial waste incineration facility or the like that may treat mercury-containing waste.

1 Waste incinerator 2 Heat recovery device 3 Gas cooling device 4 Bug filter 4a Exhaust gas introduction port 4b Exhaust gas discharge port 41 Filter cloth 42 Fibrous adsorbent 43 Casing 43a Upper space 43b Lower space 43c Partition wall 44 Discharge flow path 44a Short circuit flow path 44b Bypass flow path 44c Partition plate 45 Flow path switching means 5 Induction ventilator 6 Chimney 7 Chemical supply device 8 Mercury concentration detection device 8a First mercury concentration detection device 8b Second mercury concentration detection device 9 Control device

Claims (5)

A bag filter having an introduction port and an exhaust port for exhaust gas discharged from a waste incinerator, and a filter cloth for capturing soot and harmful components contained in the exhaust gas introduced from the introduction port, and a filter cloth of the filter cloth. A fibrous adsorbent that is arranged on the downstream side and further adsorbs harmful components from the exhaust gas that has passed through the filter cloth, a short-circuit flow path that guides the exhaust gas that has passed through the fibrous adsorbent to the discharge port, and the above. A bag filter including a detour flow path that guides the exhaust gas to the discharge port without passing through the fibrous adsorbent, and a flow path switching means for selectively switching between the short-circuit flow path and the detour flow path.
A drug supply device disposed on the upstream side of the bag filter and supplying a drug and a mercury adsorbent for neutralizing an acidic component contained in the exhaust gas to the exhaust gas and the bag filter.
A mercury concentration detector for detecting the mercury concentration in the exhaust gas on the upstream side of the drug supply device,
A control device for switching and controlling the flow path switching means based on the mercury concentration detected by the mercury concentration detecting device is provided.
When the exhaust gas is filtered, the control device supplies the drug and the mercury adsorbent from the drug supply device to perform a precoating process to form a reaction layer having a predetermined thickness, and on the upstream side of the bag filter. When the measured mercury concentration in the exhaust gas continues to exceed a predetermined value for a predetermined time and tends to increase further, the flow path switching means is switched to the short-circuit flow path side to flow through the filter cloth. The exhaust gas after the above is guided to the fibrous adsorbent.
Exhaust gas treatment equipment for waste incinerators. A mercury concentration detecting device for detecting the mercury concentration in the exhaust gas on the downstream side of the bug filter is further provided.
In the control device, the mercury concentration in the exhaust gas measured on the downstream side of the bag filter does not fall below a predetermined value in a state where the exhaust gas after flowing through the filter cloth is guided to the fibrous adsorbent. When a predetermined time elapses or the tendency is increasing, the mercury adsorbent is supplied from the drug supply device.
The waste incinerator exhaust gas treatment device according to claim 1. Activated carbon is used as the mercury adsorbent.
The waste incinerator exhaust gas treatment apparatus according to claim 1 or 2. As the mercury concentration detecting device, a plurality of ceramic filters that suck exhaust gas and that alternately perform backwashing are used.
The waste incinerator exhaust gas treatment apparatus according to claims 1 to 3. A bag filter having an introduction port and an exhaust port for exhaust gas discharged from a waste incinerator, and a filter cloth for capturing soot and harmful components contained in the exhaust gas introduced from the introduction port, and the filter cloth A fibrous adsorbent that is arranged on the downstream side and further adsorbs harmful components from the exhaust gas that has passed through the filter cloth, a short-circuit flow path that guides the exhaust gas that has passed through the fibrous adsorbent to the discharge port, and the above. A bag filter provided with a detour flow path that guides the exhaust gas to the discharge port without passing through the fibrous adsorbent and a flow path switching means for selectively switching between the short-circuit flow path and the detour flow path was used. It is a waste incinerator exhaust gas treatment method.
The filter cloth is precoated by supplying a chemical that neutralizes the acidic component contained in the exhaust gas and a mercury adsorbent to form a reaction layer having a predetermined thickness, and the exhaust gas is filtered and the exhaust gas is filtered. When the mercury concentration in the exhaust gas measured on the upstream side of the position where the drug and the mercury adsorbent are supplied continues to exceed a predetermined value for a predetermined time and tends to increase further, after flowing through the filter cloth. Controls to guide the exhaust gas from the above to the fibrous adsorbent.
A waste incinerator exhaust gas treatment method characterized by this.

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