Filter cloth regeneration method and filter cloth regeneration system

Abstract

To provide a filter cloth regeneration method and a filter cloth regeneration system capable of continuously using filter cloth without replacing it by reducing harmful substances adsorbed and stored on the filter cloth.SOLUTION: In a bag filter 11 equipped with filter cloth 11b and used in processing of waste gas generated from a waste incinerator 5, this filter cloth regeneration method for reducing harmful substances adsorbed and stored on the filter cloth 11b comprises: an elimination step of eliminating the harmful substances from the filter cloth 11b by heating air on the downstream side of the bag filter 11 to a temperature higher than an operation temperature of the bag filter 11 during incineration disposal to supply and circulate the air on the upstream side of the bag filter 11 while the incinerator is stopped; and a readsorption step of adsorbing the harmful substances eliminated in the elimination step on an active carbon coating layer 18c.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and system for regenerating a filter cloth. [Background technology]

[0002] The exhaust gas generated when waste is burned in an incinerator is sent to a boiler or economizer for heat recovery. After heat recovery, the exhaust gas is sent to a filter-type dust collector (also called a bag filter) and then discharged to the outside through a chimney by an induced draft fan (see, for example, Patent Document 1 below).

[0003] A bag filter is a device that has multiple filter cloths installed inside it and collects dust generated by incinerators, including soot and dust, hydrated lime and its reaction products for removing acid gases, and activated carbon for removing dioxins.A bag filter has a fixed layer called a primary adhesion layer formed on the filter cloth that remains even after the dust has been brushed off, and this fixed layer collects dust with high efficiency.

[0004] On the other hand, most dioxins are adsorbed onto activated carbon, etc., and collected together with dust in the fixed layer on the filter cloth, where they are brushed off and discharged outside the system, but some dioxins are adsorbed and accumulated in the fixed layer on the filter cloth. In particular, when disaster waste is received, combustion tends to become unstable, and if this continues for a long period of time, high concentrations of dioxins may accumulate in the fixed layer on the filter cloth. When this happens, the dioxin concentration in the exhaust gas downstream of the bag filter tends to increase.

[0005] Normally, the lifespan of a filter cloth is determined by clogging of the filter cloth (reduced breathability), weakening of its strength, or localized wear and holes caused by dust being brushed off. However, if the filter cloth needs to be replaced earlier than planned due to the above-mentioned events, this will lead to increased maintenance costs. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6935885 Summary of the Invention [Problem to be solved by the invention]

[0007] The present disclosure aims to provide a method and system for regenerating a filter cloth that reduces harmful substances adsorbed and accumulated on the filter cloth, thereby enabling the filter cloth to be used continuously without replacement. [Means for solving the problem]

[0008] The filter cloth regeneration method of the present disclosure is used to treat exhaust gas generated from a waste incinerator, and is a filter cloth regeneration method for reducing harmful substances adsorbed and accumulated on the filter cloth in a filter-type dust collector equipped with the filter cloth, a desorption process in which, during shutdown, the air downstream of the filter-type dust collector is heated to a temperature higher than the operating temperature of the filter-type dust collector during incineration treatment, and is supplied to the upstream side of the filter-type dust collector and circulated to desorb the harmful substances from the filter cloth; The method may further include a re-adsorption step of adsorbing the hazardous substances desorbed in the desorption step onto an adsorbent.

[0009] The operating temperature of the filter dust collector during incineration treatment is about 150 to 200° C., and may be, for example, about 160° C. When the operating temperature of the filter dust collector is 160° C., air may be heated to, for example, about 180° C. and circulated.

[0010] In the filter cloth regeneration method of the present disclosure, the adsorbent may be an activated carbon coating layer formed on the filter cloth by supplying activated carbon to the upstream side of the filter-type dust collector when the furnace is shut down prior to the desorption step.

[0011] The method for regenerating a filter cloth according to the present disclosure may include a step of brushing off dust on the filter cloth before forming the activated carbon coating layer.

[0012] The adsorbent may contain an adsorbent capable of adsorbing harmful substances, such as activated carbon, zeolite, or activated clay.

[0013] In the method for regenerating a filter cloth according to the present disclosure, the harmful substances may be adsorbed and accumulated in a primary adhesion layer formed on the filter cloth.

[0014] In the method for regenerating a filter cloth of the present disclosure, the harmful substances may be dioxins or mercury.

[0015] The method for regenerating a filter cloth according to the present disclosure may include a discharge step of brushing off the activated carbon coating layer that has adsorbed the harmful substances from the filter cloth and discharging it outside the system.

[0016] The filter cloth regeneration system of the present disclosure is used to treat exhaust gas generated from a waste incinerator, and is a filter cloth regeneration system that reduces harmful substances adsorbed and accumulated on the filter cloth in a filtration type dust collector equipped with a filter cloth, a warm air circulation line that heats the air downstream of the filter-type dust collector to a temperature higher than the operating temperature of the filter-type dust collector during incineration treatment and supplies it to the upstream side of the filter-type dust collector and circulates it, thereby desorbing the harmful substances from the filter cloth; and and an adsorbent for adsorbing the desorbed harmful substances.

[0017] The hot air circulation line may have one end connected to a duct downstream of the filter-type dust collector and the other end connected to a duct upstream of the filter-type dust collector.

[0018] The hot air circulation line may include a hot air circulation fan that draws in air downstream of the filter-type dust collector, and a hot air generating means that heats the air drawn in by the hot air circulation fan.

[0019] The hot air means may be disposed downstream of the hot air circulation fan, or may be disposed upstream of the hot air circulation fan.

[0020] In the filter cloth regeneration system of the present disclosure, the adsorbent may be an activated carbon coating layer formed on the filter cloth by supplying activated carbon to the upstream side of the filter dust collector when the furnace is shut down.

[0021] In the filter cloth regeneration system of the present disclosure, the adsorbent may be an activated carbon filter or an activated carbon packed bed disposed on the hot air circulation line.

[0022] According to the filter cloth regeneration method and filter cloth regeneration system disclosed herein, harmful substances adsorbed and accumulated on the filter cloth can be reduced, so that the filter cloth can be used continuously without replacement. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a diagram showing the configuration of a waste incineration facility according to an embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged cross-sectional view of region II in FIG. [Figure 3] Cross-sectional view of filter cloth to explain how to regenerate the filter cloth [Figure 4] Cross-sectional view of filter cloth to explain how to regenerate the filter cloth [Figure 5] Cross-sectional view of filter cloth to explain how to regenerate the filter cloth [Figure 6] Cross-sectional view of filter cloth to explain how to regenerate the filter cloth [Figure 7] FIG. 10 is a diagram showing the configuration of a waste incineration facility according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0024] An embodiment of the present invention will be described below. The embodiment described below is an example of the present invention. The present invention is not limited to the following embodiment, and includes various modified forms that are implemented within the scope of the present invention. Note that not all of the configurations described below are necessarily essential configurations of the present invention.

[0025] FIG. 1 shows an example of the configuration of a waste incineration facility. The waste incineration facility 1 includes a hopper 2 into which waste is fed, and a stoker 3 to which the waste fed into the hopper 2 is fed by a dust feeder 4. The stoker 3 is an example of a combustion device, and other types of combustion devices may be used. The stoker 3 is driven to move back and forth to feed the waste to a waste incinerator 5. The waste incinerator 5 includes a primary combustion chamber 5a provided above the stoker 3, a secondary combustion chamber 5b further above that, an ash outlet 5c for discharging incineration ash, and an exhaust gas outlet 5d for discharging exhaust gas from within the furnace.

[0026] The waste incineration facility 1 also includes a boiler 6 connected to the waste incinerator 5, and an economizer 7 connected to the boiler 6. Exhaust gas generated when waste is burned in the waste incinerator 5 is sent to the boiler 6 and the economizer 7 for heat recovery. The exhaust gas contains soot, dust, and heavy metals, as well as acidic gases such as SOx, and harmful substances such as dioxins and mercury, so the exhaust gas after heat recovery is sent to exhaust gas treatment equipment 8 and then discharged to the outside via a chimney 10 by an induced draft fan 9.

[0027] The exhaust gas treatment facility 8 includes a bag filter 11, an activated carbon supply device 12, and a hot air circulation line 13. The economizer 7 and the bag filter 11 are connected by a duct 14, and the bag filter 11 and the induced draft fan 9 are connected by a duct 15.

[0028] The exhaust gas treatment facility 8 may also include a slaked lime supplying device (not shown). The slaked lime supplying device supplies slaked lime into the duct 14 as an acid gas removing agent for removing acid gases such as SOx.

[0029] The waste incineration facility 1 also includes a control device (not shown) for controlling each part. The control device is a computer equipped with a processor such as a CPU and an MPU, memories such as a ROM and a RAM, various interfaces, etc. The processor executes a program stored in the memory, and the software and hardware work together to realize each part of the control device.

[0030] The bag filter 11 is a filter-type dust collector that filters dust-containing exhaust gas through a number of installed bag-shaped filters made of cloth or nonwoven fabric. The bag filter 11 is configured by incorporating a number of filter cloths 11b inside a casing 11a. The dust, i.e., fly ash, collected by the bag filter 11 is sequentially discharged via a screw conveyor, rotary valve, or the like (not shown) and transported to fly ash treatment equipment 16.

[0031] The interior of the casing 11a is divided into upper and lower sections by a plate 11c, and the interior of the casing 11a is partitioned into a pre-filtration exhaust gas chamber 11d below the plate 11c and a post-filtration exhaust gas chamber 11e above the plate 11c. The pre-filtration exhaust gas chamber 11d is connected to a duct 14, and the post-filtration exhaust gas chamber 11e is connected to a duct 15. The ducts 14 and 15 are equipped with valves 14a and 15a that open and close the ducts 14 and 15, respectively. The valves 14a and 15a may be opened and closed in response to control signals from a control device. The plate 11c is provided with a plurality of openings for suspending the filter cloth 11b, and the filter cloth 11b is suspended from each opening so as to be disposed within the pre-filtration exhaust gas chamber 11d.

[0032] The filter cloth 11b is a cylindrical bag with its closed lower end inserted into the pre-filtration exhaust gas chamber 11d and its open upper end facing the post-filtration exhaust gas chamber 11e. An aggregate (not shown) is incorporated inside the filter cloth 11b to maintain its cylindrical shape. Suitable materials for the filter cloth 11b include woven fabrics such as double weave, twill weave, and plain weave made of glass fiber or PTFE fiber, and felt.

[0033] The activated carbon supply device 12 may include an activated carbon tank 12a that stores activated carbon as an adsorbent for adsorbing harmful substances such as dioxins and mercury, a feeder 12b that discharges the activated carbon stored in the activated carbon tank 12a, and an activated carbon supply pipe 12c that connects the feeder 12b to the duct 14 to guide the activated carbon discharged from the feeder 12b to the duct 14. The activated carbon supply device 12 is configured such that the feeder 12b discharges the activated carbon stored in the activated carbon tank 12a based on a predetermined control signal from the control device, and the discharged activated carbon is supplied into the duct 14 via the activated carbon supply pipe 12c. The activated carbon supplied into the duct 14 is pneumatically transported by the exhaust gas flowing through the duct 14 and blown into the bag filter 11.

[0034] The hot air circulation line 13 is provided with a circulation gas path 13a that branches off from a duct 15 downstream of the bag filter 11 and returns to a duct 14 upstream of the bag filter 11. One end of the hot air circulation line 13 is connected to the duct 15 upstream of a valve 15a, and the other end is connected to the duct 14 downstream of a valve 14a.

[0035] The hot air circulation line 13 includes a hot air circulation fan 13b that draws air downstream of the bag filter 11 and a hot air generator 13c that heats the air drawn by the hot air circulation fan 13b. The hot air circulation fan 13b and the hot air generator 13c are arranged in this order, for example, from upstream to downstream, in the circulating gas path 13a. The hot air circulation fan 13b draws air from the duct 15 into the circulating gas path 13a. The hot air generator 13c is composed of, for example, various heaters. In this embodiment, the hot air generator 13c is provided downstream of the hot air circulation fan 13b, but it can also be provided upstream of the hot air circulation fan 13b. The circulating gas path 13a includes valves 13d and 13e that open and close the circulating gas path 13a. The valves 13d and 13e may be opened and closed in response to control signals from a control device. Valve 13d is disposed upstream of hot air circulation fan 13b and hot air generating means 13c, and valve 13e is disposed downstream of hot air circulation fan 13b and hot air generating means 13c. Valves 13d and 13e are closed when waste incinerator 5 is in operation.

[0036] The bag filter 11 is also provided with a dust removal device 17. The dust removal device 17 may include an air compressor 17a, a main supply pipe 17b through which compressed air from the air compressor 17a flows, branch supply pipes 17c branching from the main supply pipe 17b and leading to each group of filter cloths 11b, and a valve 17d for opening and closing the branch supply pipe 17c. When the valve 17d is opened in response to an open command signal from the control device, the dust removal device 17 is configured so that compressed air from the air compressor 17a is injected onto the inner surface of the filter cloth 11b via the main supply pipe 17b and the branch supply pipe 17c, and the compressed air passes from the inner periphery to the outer periphery of the filter cloth 11b, thereby blowing away dust and other particles adhering to and accumulating on the outer surface of the filter cloth 11b.

[0037] Figure 2 is an enlarged cross-sectional view of region II in Figure 1. As shown in Figure 2, in bag filter 11, primary adhesion layer 18a is formed on filter cloth 11b, which remains even after dust has been brushed off. Bag filter 11 collects dust with high efficiency using primary adhesion layer 18a.

[0038] Most of the dioxins 18d are adsorbed onto the activated carbon supplied by the activated carbon supply device 12, and the activated carbon that has adsorbed the dioxins 18d is collected on the primary adhesion layer 18a as a dust layer 18b together with other soot and dust. The dust on the filter cloth 11b is appropriately brushed off by the brushing device 17, but even after the dust is brushed off, the primary adhesion layer 18a remains and only the dust layer 18b is brushed off. Therefore, most of the dioxins 18d are discharged to the outside of the system as the dust layer 18b.

[0039] However, some dioxins 18d are adsorbed and accumulated in the primary adhesion layer 18a. In particular, when disaster waste or the like is received, combustion tends to become unstable, and if this continues for a long period of time, high concentrations of dioxins 18d may accumulate in the primary adhesion layer 18a. When this occurs, dioxins 18d that have been detached from the primary adhesion layer 18a pass through the filter cloth 11b, and the dioxin concentration in the exhaust gas downstream of the bag filter 11 tends to increase. Conventionally, in order to eliminate the risk of high concentrations of dioxins 18d accumulating in the primary adhesion layer 18a and increasing the dioxin concentration in the exhaust gas downstream of the bag filter 11, it was necessary to replace the filter cloth 11b.

[0040] According to the regeneration method and regeneration system for filter cloth 11b of this embodiment, it is possible to reduce the dioxins 18d adsorbed and accumulated on filter cloth 11b, specifically in primary adhesion layer 18a, and therefore filter cloth 11b can be continuously used without replacement, i.e., filter cloth 11b can be regenerated. The regeneration system for filter cloth 11b and the regeneration method for filter cloth 11b will be described in detail below.

[0041] <Filter cloth regeneration system> The regeneration system for filter cloth 11b is used to treat exhaust gas generated from a waste incinerator 5 and reduces harmful substances adsorbed and accumulated on filter cloth 11b in a filter-type dust collector (in this embodiment, a bag filter) 11 equipped with filter cloth 11b. During furnace shutdown, air downstream of filter-type dust collector (in this embodiment, a bag filter) 11 is heated to a temperature higher than the operating temperature of filter-type dust collector (in this embodiment, a bag filter) 11 during incineration treatment, and the heated air is supplied to the upstream side of filter-type dust collector (in this embodiment, a bag filter) 11 for circulation, thereby desorbing harmful substances from filter cloth 11b. The regeneration system for filter cloth 11b may also include a hot air circulation line 13 that adsorbs the desorbed harmful substances (in this embodiment, an activated carbon coating layer described below) 18c. The regeneration system for filter cloth 11b may also include a brushing device 17 and a control device (not shown) that controls activated carbon supply device 12, hot air circulation line 13, and brushing device 17.

[0042] <How to regenerate filter cloth> [Shaking off process] First, when the waste incinerator 5 is shut down, the dust layer 18b is thoroughly brushed off by the brushing device 17. At this time, as described above, the primary adhesion layer 18a remains on the filter cloth 11b.

[0043] [Activated carbon coating layer formation process] Next, activated carbon is blown into the bag filter 11 by the activated carbon supply device 12, and as shown in FIG. 3, an activated carbon coating layer 18c is formed on the filter cloth 11b, specifically on the primary adhesion layer 18a.

[0044] [Desorption process] Next, as shown in Figure 4, during shutdown, the temperature of the hot air circulation line 13 is raised to above the operating temperature of the bag filter 11, thereby desorbing the dioxins 18d adsorbed to the primary adhesion layer 18a. "During shutdown" refers to a state in which the operation of the waste incinerator 5 is stopped. Before shutdown (when shutting down), the waste in the waste incinerator 5 is completely burned, and the exhaust gas in the bag filter 11 is replaced with air (atmospheric air). In this state, by closing valve 14a upstream of the bag filter 11 and valve 15a downstream of the bag filter 11, air is filled inside the bag filter 11. At this time, by opening valves 13d and 13e, the air in the bag filter 11 is circulated via the hot air circulation line 13.

[0045] Dioxins 18d are desorbed as the temperature rises, and desorption can be promoted by setting the temperature higher than the operating temperature of the bag filter 11 to which the dioxins 18d are adsorbed. The operating temperature of the bag filter 11 is approximately 150 to 200°C, and the bag filter 11 is often operated at, for example, approximately 160°C. For example, in a waste incineration facility 1 where the operating temperature of the bag filter 11 is 160°C, the temperature of the hot air circulating in the hot air circulation line 13 is raised to approximately 180°C. However, if the hot air circulating temperature is raised to 200°C or higher, there is a risk of resynthesis of dioxins 18d on the filter cloth 11b, so it is not preferable to raise the temperature to 200°C or higher.

[0046] [Re-adsorption process] Because the activated carbon coating layer 18c has a higher adsorption capacity for dioxins 18d than the primary attachment layer 18a, dioxins 18d are more easily adsorbed by the activated carbon coating layer 18c than by the primary attachment layer 18a. As a result, most of the dioxins 18d desorbed from the primary attachment layer 18a are transferred to the activated carbon coating layer 18c by the circulating air. As a result, as shown in Figure 5, the dioxins 18d desorbed in the desorption step can be adsorbed by the activated carbon coating layer 18c. At this time, in order to stably re-adsorb the dioxins 18d desorbed in the desorption step, it is preferable to lower the circulating hot air temperature back to the operating temperature of the bag filter 11.

[0047] [Discharge process] Finally, as shown in Fig. 6, the activated carbon coating layer 18c that has adsorbed dioxins 18d is brushed off from the filter cloth 11b by a brushing device 17 and discharged to the outside of the system. If the dioxin concentration in the brushed-off dust (activated carbon coating layer 18c) is higher than the landfill standard value, the dust may be introduced into the furnace after the next start-up of the waste incinerator 5, and the dioxins 18d in the dust may be decomposed and rendered harmless in the high-temperature furnace.

[0048] <Other embodiments> In the above embodiment, the harmful substance is dioxins 18d, but is not limited thereto. The harmful substance may also be mercury. Because activated carbon can also adsorb mercury, the regeneration method and regeneration system for the filter cloth 11b according to the above embodiment can reduce the amount of mercury adsorbed and accumulated on the filter cloth 11b.

[0049] In the above embodiment, the adsorbent that adsorbs harmful substances is the activated carbon coating layer 18c, but the regeneration method and system for the filter cloth 11b are not limited to this. The adsorbent may be an activated carbon filter 19 arranged on the hot air circulation line 13, as shown in Figure 7. Furthermore, instead of the activated carbon filter 19, a filter using an adsorbent other than activated carbon or an activated carbon packed bed may be used. [Explanation of symbols]

[0050] 1: Waste incineration facility 2: Hopper 3: Stalker 4: Dust feeder 5: Waste incinerator 5d: Exhaust gas outlet 6: Boiler 7: Economizer 8: Exhaust gas treatment equipment 9: Attractive fan 10: Chimney 11: Bag filter 11b: Filter cloth 12:Activated carbon supply device 13: Hot air circulation line 13a: Circulation gas route 13b: Warm air circulation fan 13c: Hot air generating means 16: Fly ash processing equipment 17: Brush-off device 18a: Primary attachment layer 18b: Dust layer 18c: Activated carbon coating layer 18d: Dioxins 19: Activated carbon filter

Claims

1. A method for regenerating a filter cloth in a filter-type dust collector used to treat exhaust gas generated from a waste incinerator and equipped with a filter cloth, which reduces harmful substances adsorbed and accumulated on the filter cloth, a desorption process in which, during shutdown, the air downstream of the filter-type dust collector is heated to a temperature higher than the operating temperature of the filter-type dust collector during incineration treatment, and is supplied to the upstream side of the filter-type dust collector and circulated to desorb the harmful substances from the filter cloth; a re-adsorption step of adsorbing the harmful substances desorbed in the desorption step onto an adsorbent.

2. 2. The method for regenerating a filter cloth according to claim 1, wherein the adsorbent is an activated carbon coating layer formed on the filter cloth by supplying activated carbon to the upstream side of the filter-type dust collector when the furnace is shut down prior to the desorption step.

3. 3. The method for regenerating a filter cloth according to claim 1, wherein the harmful substances are adsorbed and accumulated in a primary adhesion layer formed on the filter cloth.

4. 3. The method for regenerating a filter cloth according to claim 1, wherein the harmful substances are dioxins or mercury.

5. 3. The method for regenerating a filter cloth according to claim 2, further comprising a discharge step of brushing off the activated carbon coating layer that has adsorbed the harmful substances from the filter cloth and discharging the same outside the system.

6. A filter cloth regeneration system for reducing harmful substances adsorbed and accumulated on a filter cloth in a filter-type dust collector used to treat exhaust gas generated from a waste incinerator, comprising: a warm air circulation line that heats the air downstream of the filter-type dust collector to a temperature higher than the operating temperature of the filter-type dust collector during incineration treatment and supplies it to the upstream side of the filter-type dust collector and circulates it, thereby desorbing the harmful substances from the filter cloth; and and an adsorbent that adsorbs the desorbed harmful substances.

7. 7. The filter cloth regeneration system according to claim 6, wherein the adsorbent is an activated carbon coating layer formed on the filter cloth by supplying activated carbon to the upstream side of the filter dust collector when the furnace is shut down.

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