JP2009178620A - Method of replacing filter cloth in bag filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of replacing a filter cloth in a bag filter capable of suitably forming a pre-coat layer. <P>SOLUTION: The method of replacing a filter cloth in a bag filter includes the process of removing an existing filter cloth to install a new one in its place, the process of depositing a powdery reaction assistant on the surface of the upstream side of the new filter cloth by generating an air flow flowing from the upstream side to the downstream side of the new filter cloth while feeding the powdery reaction assistant to the upstream side of the new filter cloth, the subsequent process of removing the excessive powdery reaction assistant deposited thereon by blowing air from the downstream side to the upstream side via the new filter cloth, the subsequent process of measuring a differential pressure therebetween by blowing air at a constant rate from the upstream side to the downstream side thereof, and the determining process of making a determination on whether to repeat or not to repeat the above process of depositing powdery reaction assistant up to the process of measuring the differential pressure from the result of the measurement carried out in the preceding process of measuring the differential pressure. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a bag filter filter replacement method, and more particularly, to a filter filter replacement method used for a bag filter provided to collect exhaust gas from a waste incinerator or the like.

  In a garbage incineration facility or the like, exhaust gas generated by combustion of waste or the like is rendered harmless by various treatments and exhausted to the outside. As one of the treatments for exhaust gas, there is a dust removal by a bag filter provided with a filter cloth. The filter cloth deteriorates with use time and is periodically replaced. For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2002-102631), Patent Document 2 (Japanese Patent Application Laid-Open No. Hei 6-47222), and Patent Document 3 (Japanese Patent Application Laid-Open No. 2002-143625) are related to bag filter replacement techniques. ).

The requirement for the bag filter includes prevention of clogging and breakage of the filter cloth. As a cause of clogging or breakage of the filter cloth, for example, slaked lime added to remove hydrogen chloride can be cited. Slaked lime is supplied upstream of the bag filter. When slaked lime reacts with hydrogen chloride contained in the exhaust gas, calcium chloride (CaCl ₂ ) is generated. This calcium chloride has deliquescence, absorbs moisture at a low temperature and enters a solution state, and wets the ash deposit layer. In this way, when calcium chloride trapped in the filter cloth of the bag filter is deliquescent, it becomes a factor that clogs the filter cloth and lowers the air permeability. In addition, after deliquescence, the deposited layer dries and solidifies on the filter cloth, which reduces the flexibility of the filter cloth, thereby causing damage to the filter cloth. Moreover, the calcium chloride produced | generated by reaction of hydrogen chloride and slaked lime may damage a filter cloth.

  In order to prevent clogging or breakage of the filter cloth, a precoat layer may be provided on the filter cloth surface. As such a technique, Patent Document 4 (Japanese Patent Publication No. 3-26095) is cited. By pre-coating the reaction aid powder, a dust accumulation layer is formed on the pre-coating layer, and the dust does not directly touch the filter cloth. Therefore, the filter cloth can be prevented from being clogged or damaged due to dust adhesion.

JP 2002-102631 A JP-A-6-47222 JP 2002-143625 A Japanese Examined Patent Publication No. 3-26095

  The precoat layer as described in Patent Document 4 is formed on the upstream surface of the filter cloth after attaching a new filter cloth. At this time, it is important that the precoat layer is appropriately formed. For example, if there is a thin part of the precoat layer on the surface of the filter cloth or a part where the precoat layer is not provided, the dust directly touches the filter cloth, and the precoat layer works well. May not be obtained.

  However, since a large number of filter cloths are provided in a garbage incinerator or the like, it is not easy to check whether or not the precoat layer is properly formed on all the filter cloths.

  Therefore, the objective of this invention is providing the filter cloth replacement | exchange method which can form a precoat layer appropriately.

  In the following, means for solving the problem will be described using reference numerals with parentheses used in [Best Mode for Carrying Out the Invention]. These symbols are added to clarify the correspondence between the description of [Claims] and the description of [Best Mode for Carrying Out the Invention], and [Claims] It should not be used for the interpretation of the technical scope of the invention described in.

The filter cloth exchange method according to the present invention is a process of removing an old filter cloth and attaching a new filter cloth (10) (step S10), while supplying reaction aid powder to the upstream side of the new filter cloth (10), The process of depositing the reaction aid powder on the upstream surface of the new filter cloth (10) by blowing air from the upstream side of the new filter cloth (10) to the downstream side (step S20) and the process of depositing (S20) Later, the air is blown from the downstream side to the upstream side through the new filter cloth (10) to remove the excessively deposited reaction aid powder (step S30), and after the removal step (S30), upstream Based on the measurement results in the step of measuring the differential pressure between the upstream side and the downstream side (step S40) and the step of measuring the differential pressure (S40) while blowing air at a constant air volume from the side to the downstream side. Measure the differential pressure from the step (S20) ; And a step (step S50) to determine whether to repeat the processing up to step (S40) for.
Immediately after the step (S20) of depositing the reaction aid powder, the reaction aid powder is excessively deposited on the surface of the filter cloth. When the removing step (S30) is performed, the excessively deposited reaction aid powder is removed, and only the fixing layer remains. This fixing layer is a layer that does not easily fall off. By measuring the differential pressure in the step of measuring the differential pressure (step S40), the state of the fixing layer can be known. That is, it can be seen that the fixing layer is dense when the differential pressure is large, and the fixing layer is sparse when the differential pressure is small. In the determining step (S50), if the differential pressure is small, it is determined that the fixing layer is not sufficiently formed, and the deposition of the reaction aid powder is repeated. Thereby, the fixing layer can be finally formed sufficiently densely, and a precoat layer made of the reaction aid powder can be formed in an appropriate state.

  The filter cloth replacement method preferably further includes a final pre-coating step (S60) that is performed when it is determined that the processing is not repeated in the determining step (S50). The processing in the final pre-coating step (S60) is the same as the depositing step (S20).

  The step of determining (S50) determines to repeat the process when the measurement result in the step of measuring the differential pressure (S40) is lower than a predetermined target differential pressure, and the process is performed when the measured pressure is equal to or greater than the target differential pressure. It is preferable that the process of not repeating is included.

  The target differential pressure is not less than 2 times and not more than 5 times the initial differential pressure, which is the differential pressure between the upstream side and the downstream side in a state where the deposition step (S20) has never been performed. It is preferable.

  The new filter cloth (10) is preferably a double-woven, twill-woven or plain-woven glass fiber, or a felt made of glass and PTFE (polytetrafluoroethylene).

  The reaction auxiliary powder is preferably one or a mixture of two or more selected from powders of zeolite, diatomaceous earth, pearlite and the like, and more preferably contains diatomaceous earth.

  In the attaching step (S10), the new filter cloth (10) is preferably attached in the middle of the path for exhausting the exhaust gas from the waste incinerator (1) to the outside.

  ADVANTAGE OF THE INVENTION According to this invention, the filter cloth replacement | exchange method which can form a precoat layer appropriately is provided.

  Embodiments of a filter cloth replacement method according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram illustrating a waste incineration facility to which the filter cloth replacement method of the present embodiment is applied.

  As shown in FIG. 1, the waste incineration facility includes a waste incinerator 1, a temperature reducing tower 2, a bag filter 3, an induction fan 4, a downstream device (not shown), and a reaction aid supply. A silo 6 and a chemical silo 12 for supplying slaked lime and the like are provided. In the waste incinerator 1, waste is burned and exhaust gas is generated. The generated exhaust gas is sent to the downstream side by the airflow generated by the induction fan 4. Specifically, after being cooled by a boiler (not shown) or the temperature reducing tower 2, it is sent to the bag filter 3 through the bag filter inlet duct 7. The bag filter 3 captures dust in the exhaust gas. The exhaust gas that has passed through the bag filter 3 is sent to the induction fan 4 through the bag filter outlet duct 9. The downstream device includes, for example, a catalyst denitration device, a wet exhaust gas cleaning device, and the like. The exhaust gas is detoxified by the downstream device and then exhausted from the chimney 5 to the outside.

  The filter cloth replacement method of the present embodiment is applied to replacement of the filter cloth attached in the bag filter 3 described above. Hereinafter, the bug filter 3 will be described.

The bag filter 3 has a room connected to the bag filter inlet duct 7 and the bag filter outlet duct 9, and the room is divided into a dirty chamber 34 on the upstream side and a clean chamber 33 on the downstream side by a thimble plate 31. It is divided. The dirty chamber 34 is connected to the bag filter inlet duct 7, and the clean chamber 33 is connected to the bag filter outlet duct 9. The thimble plate 31 is provided with a plurality of openings for hanging the filter cloth 10. From each opening, the filter cloth 10 is suspended toward the dirty chamber 34 side.
The filter cloth 10 has a bag shape, and the opening portion of the filter cloth substantially coincides with the opening portion of the thimble plate 31. Although not shown, a cage for maintaining the shape of the filter cloth is inserted into the filter cloth. As the filter cloth, for example, double woven, twill, plain woven glass fibers, felt made of glass and PTFE, or the like is used.

  With such a configuration, in the bag filter 3, exhaust gas is introduced into the dirty chamber 34 from the bag filter inlet duct 7 during normal use. The exhaust gas introduced into the dirty chamber 34 passes through the filter cloth, and dust is removed. Then, the exhaust gas is sent to the clean chamber 33 and exhausted from the bag filter outlet duct 9 to the outside of the bag filter 3.

  In the clean chamber 33, backwash nozzles 32 are attached to the filter cloths 10. Although not shown, the backwash nozzle 32 is connected to an air compressor via a pipe. The airflow passing through the filter cloth 10 is ejected from the clean chamber 33 side toward the dirty chamber 34 side. The backwash nozzle 32 is for removing dust accumulated on the filter cloth 10.

  A differential pressure gauge 35 is further attached to the bag filter 3. The differential pressure gauge 35 is provided so as to measure the differential pressure between the dirty chamber 34 and the clean chamber 33. The differential pressure gauge 35 is, for example, a manometer.

  In FIG. 1, only one room is shown in the bag filter 3. However, the inside of the bag filter 3 may be divided into a plurality of rooms, and each of the plurality of rooms may be divided into a dirty room 34 and a clean room 33.

  The reaction aid supplied from the reaction aid supply silo 6 is deposited on the filter cloth 10 in the bag filter 3. Below, the reaction adjuvant supply silo 6 is demonstrated.

  The reaction aid supply silo 6 is connected to the bag filter inlet duct 7 through the powder transport pipe 8 and supplies the powdery reaction aid to the bag filter inlet duct 7. The reaction aid is supplied for the purpose of preventing clogging and breakage of the filter cloth. As the reaction aid, those having a small bulk density, good air permeability, and not sticky even after inhalation are preferably used. Specifically, one or a mixture of two or more selected from powders such as zeolite, diatomaceous earth, and pearlite is preferably used, and diatomaceous earth is more preferably used. By supplying such a reaction aid, dust is deposited on the filter cloth together with the reaction aid in the bag filter 3. The dust deposited with the reaction aid can be easily removed from the filter cloth together with the reaction aid, and the filter cloth surface can be kept clean.

  FIG. 2A is a schematic view showing an example of the reaction aid supply silo 6. The reaction aid supply silo 6 in the example shown in FIG. 2A includes a quantitative supply device 61, a supply plate 63, and a blower 64. The blower 64 is connected to the bag filter inlet duct 7 via the powder transport pipe 8. The blower 64 generates an airflow that flows in the powder transport pipe 8 toward the bag filter inlet duct 7 side. In the reaction aid supply silo 6, the reaction aid is sent from the fixed amount feeder 61 to the supply plate 63. FIG. 2B is a diagram showing a positional relationship among the quantitative feeder 61, the supply plate 63, and the powder transport pipe 8. The supply plate 63 has an annular shape, and a part thereof is disposed in the lower part of the fixed amount feeder 61 and the other part is disposed in the powder transport pipe 8. The supply plate 63 is divided into a plurality of open upper squares. The supply plate 63 is rotated by a rotation mechanism (not shown). With such a configuration, the reaction aid is supplied from the quantitative supply device 61 to each of the plurality of masses of the supply plate 63. Each mass supplied with the reaction aid is arranged in the powder transport pipe 8 by the rotation of the supply plate 63. The reaction aid is wound up in the air flow by the blower 64 in the powder transport pipe 8 and introduced into the bag filter inlet duct 7 side.

  If the reaction aid supply silo 6 of the example shown in FIGS. 2A and 2B is used, the powdery reaction aid can be uniformly supplied to the bag filter inlet duct 7. Further, the supply amount of the reaction aid can be accurately controlled by controlling the rotation speed of the supply plate 63 and the like.

  The chemical silo 12 is for supplying slaked lime to remove hydrogen chloride and the like. As the chemical silo 12, one having the same configuration as the reaction aid supply silo 6 can be used.

  In the above-described waste incineration facility, the filter cloth 10 in the bag filter 3 deteriorates with the use time. Therefore, the filter cloth 10 needs to be replaced periodically. Below, the filter cloth replacement | exchange method which concerns on this embodiment is demonstrated. FIG. 3 is a flowchart showing a filter cloth replacement method.

Step S10: Attaching the filter cloth 10 First, the old filter cloth is removed from the bag filter 3, and a new filter cloth 10 is attached to the bag filter 3.

Step S20: Pre-Coating Next, a reaction aid is pre-coated on the surface of a new filter cloth 10 to form a pre-coating layer 11. Specifically, first, the induction ventilator 4 is driven to generate an airflow having a constant air volume that passes through the bag filter 3. When the flow velocity of the airflow is stabilized, the reaction aid supply silo 6 is operated to supply the reaction aid to the bag filter inlet duct 7. The reaction aid is preferably supplied in a constant amount per unit time. The reaction aid supplied to the bag filter inlet duct 7 is guided into the bag filter 3 and captured by the newly attached filter cloth 10. Thereby, the layer (precoat layer) in which the reaction aid is deposited is formed on the filter cloth 10. Here, during the supply of the reaction aid, the differential pressure ΔP between the dirty chamber 34 and the clean chamber 33 is measured by the differential pressure gauge 35. As the precoat layer 11 is formed on the filter cloth, the differential pressure ΔP increases. FIG. 4 is a graph showing the relationship between time and differential pressure ΔP. In this graph, the supply of the reaction aid is started at time t1 (differential pressure ΔP = P1). Further, the differential pressure ΔP increases with the passage of time. When the differential pressure ΔP reaches a predetermined intermediate target differential pressure, the supply of the reaction aid is stopped. For example, the intermediate target differential pressure is set to a value that is larger by a certain value (for example, 15 to ₂₀ mmH ₂ O) than the differential pressure before the processing in step S20. In the example of FIG. 4, the intermediate target differential pressure is set to P5, and the supply of the reaction aid is stopped at time t2.

  FIG. 5A is an explanatory diagram showing the precoat layer 11 deposited in step S20. The precoat layer 11 can be divided into a portion deposited on the surface of the filter cloth 10 (hereinafter referred to as a fixing layer 11-1) and a portion deposited on the fixing layer 11-1 (hereinafter referred to as an excess layer 11-2). . FIG. 5B is an explanatory diagram for explaining the state of the fixing layer 11-1. The reaction aids are deposited so as to be sandwiched between gaps of the filter cloth 10 woven in a mesh shape. Therefore, the fixing layer 11-1 does not easily fall off the filter cloth 10. On the other hand, the surplus layer 11-2 is not directly captured by the filter cloth 10, but easily drops off when vibration is applied to the filter cloth 10. In order to prevent clogging and damage of the filter cloth 10, it is important that the fixing layer 11-1 is appropriately formed. However, after step S20 is performed only once, the fixing layer 11-1 may be formed in a sparse state, and the surplus layer 11-2 may be formed thereon. Even if the supply of the reaction aid is continued in this state, only the thickness of the surplus layer 11-2 increases, and the density of the fixing layer 11-1 does not change. Therefore, the process after the next step S30 is executed.

Step S30: Backwashing After step S20, a backwashing process is performed, and the surplus layer 11-2 is removed. Specifically, an air flow is injected from the nozzle 32 into the filter cloth 10 to generate an air flow passing through the filter cloth 10 from the clean chamber 33 side to the dirty chamber 34 side. As a result, the surplus layer 11-2 is removed, and only the fixing layer 11-1 is formed on the surface of the filter cloth 10.

Step S40: Differential Pressure Measurement After the backwashing in step S30 is completed, the differential pressure ΔP is measured in a state where a constant amount of airflow is flowing from the dirty chamber 34 side to the clean chamber 33 side. In the example shown in FIG. 4, backwashing is performed at time t2, and the differential pressure ΔP after backwashing is P2.

Steps S50 to 60: Determination of differential pressure and execution of final precoat Next, based on the measurement result in step S40, it is determined whether to repeat the processing from steps S20 to S40 again or to perform the final precoat. Specifically, the differential pressure ΔP after backwashing measured in S40 is compared with a predetermined target differential pressure Ptarget. If the differential pressure in S40 is lower than the target differential pressure Ptarget, it is determined that the fixing layer 11-1 is not formed sufficiently dense, and the processing from steps S20 to S40 is repeated again. On the other hand, if the differential pressure in S40 is equal to or higher than the target differential pressure Ptarget, it is determined that the fixing layer 11-1 is sufficiently dense and the process of the next step S60 is performed.
In step S60, final pre-coating is performed under the same conditions as in step S20. The pre-coating is finished at the stage when the final differential pressure P6 is set in advance, and the processing after the back washing in step S30 is not performed and the actual operation is prepared.

  In the example shown in FIG. 4, the differential pressure P2 after backwashing at time t2 is lower than the target differential pressure Ptarget. Therefore, the second processing from Step S20 to Step S40 is executed. Further, the differential pressure after backwashing in the second step S40 (the differential pressure P3 at time t3) is still lower than the target differential pressure Ptarget. Accordingly, the third processing from Step S20 to Step S40 is executed. The differential pressure after backwashing (the differential pressure P4 at time t4) in the third step S40 is equal to or higher than the target differential pressure Ptarget. Therefore, the final precoat (step S60) is performed after time t4. At time t5 in step S60, the final differential pressure P6 is reached, and the process is terminated.

The value of the target differential pressure Ptarget used in step S50 is 2 times or more and 5 times or less with respect to the initial differential pressure (P1 in the example of FIG. 4) that is the differential pressure before the first precoat. preferable. When the target differential pressure Ptarget is smaller than twice the initial differential pressure, the fixing layer 11-1 tends not to be formed sufficiently densely. On the other hand, when the target differential pressure Ptarget is larger than five times the initial differential pressure, the number of processes required until the differential pressure after backwash becomes equal to or higher than the target differential pressure Ptarget is too long, and the processing time is long. Easy to be.
More preferably, if the initial differential pressure was 10mmH ₂ O~15mmH ₂ O, it is within the target differential pressure Ptarget of 30~35mmH ₂ O.

Further, the value of the final differential pressure P6 used in step S60 is preferably set within a range of 3 to 5 times the initial differential pressure. When the final differential pressure is smaller than three times the initial differential pressure, the precoat layer 11 is not sufficiently formed finally, and the filter cloth 10 tends to be damaged or clogged during actual operation. On the other hand, if the final differential pressure is greater than five times the initial differential pressure, the processing time until the differential pressure is equal to or higher than the final differential pressure in step S60 tends to be long.
More _preferably, when was 10mmH ₂ O~15mmH 2 O, is within the final differential pressure 30~40mmH ₂ O.

  As described above, according to the present embodiment, it is determined whether to perform final precoating or to repeat the processing from precoating to backwashing based on the differential pressure after backwashing. By measuring the differential pressure after backwashing, it can be determined whether or not the fixing layer 11-1 is properly formed. At this time, it is only necessary to measure the differential pressure between the dirty chamber 34 side and the clean chamber 33 side, and the deposition state of the precoat layer 11 can be easily determined. Therefore, the precoat layer 11 can be formed in an appropriate state by a simple method.

It is a schematic block diagram which shows a garbage incineration facility. It is a schematic block diagram which shows the reaction auxiliary agent supply silo. It is a schematic block diagram which shows the reaction auxiliary agent supply silo. It is a flowchart which shows the filter cloth replacement | exchange method. It is a graph which shows the relationship between time and differential pressure. 1 is a schematic view showing a precoat layer 11. FIG. 1 is a schematic view showing a precoat layer 11. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Incinerator 2 Cooling tower 3 Bag filter 4 Attracting fan 5 Chimney 6 Reaction aid supply silo 7 Bag filter inlet duct 8 Powder transport pipe 9 Bag filter outlet duct 10 Filter cloth 11 Precoat layer 11-1 Fixing layer 11- 2 Surplus layer 12 Chemical silo 31 Thimble plate 32 Backwash nozzle 33 Clean room 34 Dirty room 35 Differential pressure gauge 62 Constant supply machine 63 Supply plate 64 Blower

Claims (6)

Removing old filter cloth and attaching new filter cloth;
While supplying the reaction aid powder to the upstream side of the new filter cloth, an air flow from the upstream side to the downstream side of the new filter cloth is generated, and the reaction aid powder is applied to the upstream surface of the new filter cloth. Depositing; and
After the step of depositing, a step of jetting gas so as to pass the new filter cloth from the downstream side to the upstream side to remove the excessively deposited reaction aid powder;
After the removing step, measuring the differential pressure between the upstream side and the downstream side while blowing with a constant air volume from the upstream side toward the downstream side;
Determining whether to repeat the process from the step of depositing to the step of measuring the differential pressure based on the measurement result in the step of measuring the differential pressure;
A filter cloth exchange method comprising: The filter cloth replacement method according to claim 1,
The determining step determines that the process is repeated when the measurement result in the step of measuring the differential pressure is lower than a predetermined target differential pressure, and does not repeat the process when the measurement result is equal to or higher than the target differential pressure. The filter cloth exchange method including the process of judging. The filter cloth replacement method according to claim 2,
The target differential pressure is not less than 2 times and not more than 5 times the initial differential pressure that is a differential pressure between the upstream side and the downstream side in a state where the deposition process has never been performed. How to change filter cloth. The filter cloth replacement method according to any one of claims 1 to 3,
Furthermore,
A final pre-coating step, which is performed when it is determined that the processing is not repeated in the step of determining,
Comprising
The process in the said last precoat process is the same filter cloth exchange method as the said process to deposit. The filter cloth replacement method according to any one of claims 1 to 4,
The new filter cloth is a filter cloth exchange method made of felt made of double woven, twill, plain woven glass fiber, glass and PTFE (polytetrafluoroethylene). The filter cloth replacement method according to any one of claims 1 to 5,
In the attaching step, the new filter cloth is attached in the middle of a route for exhausting exhaust gas from a waste incinerator to the outside.

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