JP4117566B2 - Bug filter and its operation method - Google Patents

Description

  The present invention relates to a bag filter and an operation method thereof, and more particularly, a bag filter that collects particles such as dust contained in exhaust gas generated from a waste incinerator, an industrial waste incinerator, or a power plant with a filter cloth, and an operation thereof. Regarding the method.

  In dust incinerators, industrial waste incinerators, power plants, etc., dust collectors are installed to remove dust in the generated exhaust gas.

  As dust collectors, there are electrostatic dust collectors that generate static electricity and collect dust, and bag filters that collect dust by passing exhaust gas through a filter cloth. These are selected according to the type and scale of exhaust gas to be treated. The An electric dust collector is used for large-capacity exhaust gas processing such as a power plant because the exhaust gas pressure loss is low and maintenance is easy. On the other hand, bag filters are often used for exhaust gas treatment in incinerators because they have high dust collection efficiency and are suitable for removing fine particles. In recent years, especially in overseas plants, bug filters are increasingly applied to exhaust gas treatment for large capacity due to cost advantages.

  Conventionally, a bag filter arranges a plurality of filter cloths in parallel, and allows combustion exhaust gas to pass through these filter cloths. Dust contained in the combustion exhaust gas is collected by a plurality of filter cloths and deposited on the filter cloths. The accumulated dust is periodically wiped off by the compressed air supplied from the backwash device.

  A pulse jet type device known as a backwash device is provided with a venturi tube and a nozzle at the end of a filter cloth, and by injecting compressed air into the bag filter at regular intervals from this nozzle. The bag filter is deformed, and dust accumulated by the shearing force due to the deformation is removed.

Conventionally, the pulse jet type backwash device has a timer control type that injects compressed air at regular time intervals by timer control, and, as in Patent Document 1, the pressure between the inlet flue pressure and the outlet flue pressure. There has been proposed a backwash device that measures a differential pressure and controls a drop-off force by compressed air under a condition corresponding to the differential pressure.
JP 2001-17813 A

  However, with a timer-controlled backwash device that injects compressed air at regular time intervals, even if the dust concentration is high, the dust can be efficiently removed because the dust is discharged at a constant time regardless of the load of the bag filter. There was a problem that it could not be done. Therefore, the timer-controlled backwash device has a problem that the operation of a previous process such as an incinerator must be controlled.

  Moreover, in the backwashing device controlled by the differential pressure as in Patent Document 1, since it is not possible to cope with a sudden change in the dust concentration, not only the dust cannot be effectively removed, but also the dust concentration is reduced. There was a problem that the bag filter was damaged by the corresponding drop-off force (impact). Furthermore, since the load on the dust collector increases due to fluctuations in the amount of exhaust gas and the differential pressure rises once, the dust adheres to the filter cloth, so even if the number of times of compressed air injection is increased, the dust can be efficiently removed. It becomes difficult and the burden on each device of the bag filter increases, so there is a disadvantage that stable dust collection cannot be performed.

  The present invention has been made in view of such circumstances, and can cope with a load due to fluctuations in the amount of processing gas, can suppress a sudden increase in differential pressure, and perform a backwash operation under appropriate discharge conditions. An object of the present invention is to provide a bug filter and a method for operating the same.

In order to achieve the above object, the first aspect of the present invention collects dust in the exhaust gas by the filter cloth by passing the exhaust gas from the inlet flue through the filter cloth and the exhaust gas in which the dust is collected. A bag filter for exhausting from an exit flue, the bag filter having backwashing means for removing dust adhering to the filter cloth with compressed air, the dust concentration in the exhaust gas in the entrance flue at a predetermined time interval Concentration measuring means for measuring, and control means for controlling the air pressure and / or injection interval of the compressed air by the backwashing means based on the dust concentration measured by the density measuring means, the control means comprising the concentration measurement Prediction means for predicting a differential pressure between the pressure on the inlet flue side and the pressure on the outlet flue side based on the dust concentration measured by the means, and the prediction means Based on the predicted differential pressure and controls the air pressure and / or injection interval of the compressed air by said backwash means.

Further, in order to achieve the above object, the invention according to claim 2 allows dust in the exhaust gas to be collected by the filter cloth by passing the exhaust gas from the inlet flue through the filter cloth. A bag filter for exhausting exhaust gas from an outlet flue, wherein the dust in the exhaust flue in the inlet flue is a bag filter operating method in which dust adhered to the filter cloth is removed by compressed air supplied from backwashing means. Concentration is measured at predetermined time intervals by the concentration measuring means, and based on a plurality of dust concentrations measured by the concentration measuring means, a differential pressure between the pressure on the inlet flue side and the pressure on the outlet flue side is predicted. The dust is removed by controlling the air pressure and / or the injection interval of the compressed air by the backwashing unit based on the predicted differential pressure.

  According to the present invention, in the bag filter, exhaust gas from the inlet flue is passed through the filter cloth, dust in the exhaust gas is collected by the filter cloth, and exhaust gas in which the dust is collected is exhausted from the outlet flue. By doing so, the dust in the exhaust gas is removed. If the exhaust gas is collected continuously by the bag filter, dust accumulates on the surface of the filter cloth and the dust collection capability decreases. Therefore, backwashing means is installed in the bag filter and compressed by the backwashing means. It is necessary to periodically perform backwashing to remove dust accumulated on the surface of the filter cloth by air.

  The backwashing of the bag filter of the present invention is performed by measuring the dust concentration in the exhaust gas passing by the concentration measuring means provided in the inlet flue of the bag filter at predetermined time intervals, and performing backwashing based on the measured dust concentration. The control means controls the air pressure and the injection interval of the compressed air in the washing means. As a result, backwashing with compressed air can always be performed in advance at an appropriate air pressure and / or injection interval in accordance with changes in dust concentration in the exhaust gas flowing into the bag filter. Can be removed efficiently. As a result, it is possible to maintain a stable dust collection capability in the bag filter, and it is possible to prevent the life of the bag filter from being reduced due to an excessive number of times and pressure in backwashing.

According to claim 1 and 2, in the bag filter, in the control means, the pressure difference between the inlet flue side and the outlet flue side is calculated by the predicting means from the respective dust concentrations in the exhaust gas measured a plurality of times by the concentration measuring means. The air pressure and / or the injection interval of the compressed air is controlled based on the predicted differential pressure. That is, a differential pressure generated in the future is predicted from a plurality of dust concentrations measured by the control means, and the backwashing means is controlled so that the actual differential pressure does not become the differential pressure predicted by the prediction means. The dust accumulated on the surface was removed. As a result, backwashing with compressed air is performed at the minimum necessary pressure and injection interval, and a stable differential pressure can be maintained with respect to the bag filter, so that stable dust collection in the bag filter is efficiently performed. In addition, it is possible to prevent a decrease in the life of the filter cloth.

  As described above, according to the bag filter and the operation method thereof according to the present invention, the process pressure is controlled because the air pressure and / or the injection interval of the compressed air is controlled based on the measured dust concentration in the exhaust gas. Backwashing can be performed that can cope with a load due to fluctuations in the amount and suppress a sudden increase in differential pressure. Thereby, in the bag filter, it is possible to efficiently collect the stable exhaust gas and to prevent the life of the filter cloth from being reduced.

  Hereinafter, a preferred embodiment of a bag filter and an operation method thereof according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a configuration diagram of a bag filter 10 which is an embodiment suitably using the bag filter and its operating method of the present invention.

  As shown in the figure, the bag filter 10 includes a casing 12 mainly formed in a hopper shape, an inlet flue 14 installed on the lower side surface of the casing 12, and an outlet flue 16 installed on the upper side surface of the casing 12. And. The outlet flue 16 is provided with a fan (not shown), and the exhaust gas is introduced into the casing 12 from the inlet flue 14 by the driving of the fan and is discharged from the outlet flue 16.

  A partition plate 18 is horizontally disposed inside the casing 12, and the partition plate 18 partitions the interior of the casing 12 into an inlet flue side casing 12a and an outlet flue side casing 12b. A number of holes 20, 20... Are formed in the partition plate 18 so as to be aligned vertically and horizontally, and filter cloths 22, 22.

  The filter cloth 22 is formed by forming a porous cloth, felt, or the like into a cylindrical shape, and its lower end is closed. The filter cloth 22 is attached so that the opened upper end faces the hole 20 formed in the partition plate 18. Thereby, after the exhaust gas introduced into the inlet flue side casing 12a from the inlet flue 14 enters the inside from the outside of the filter cloth 22, the exhaust flue passes through the hole 20 and passes through the outlet flue side casing 12b. 16 is exhausted. At that time, since dust floating in the exhaust gas is collected by the filter cloth 22, clean gas is exhausted from the outlet flue 16.

  A backwash device 30 is provided above the bag filter 10. The backwash device 30 mainly includes a pulse pipe 32 that is a backwash means, a compressed air tank 34, a compression regulator 36 and a diaphragm valve 38 that are adjustment means, and a control unit 40 that is a control means. .

  The pulse pipe 32 is installed in the outlet flue-side casing 12b, and nozzles 42, 42,... Are disposed above the holes 20, 20, and connected to a compressed air tank 34 that stores and supplies compressed air. ing. The pulse pipe 32 is provided with a compression adjuster 36 for adjusting the air pressure of the compressed air and a diaphragm valve 38 for adjusting the injection interval of the compressed air. Therefore, by adjusting the compression regulator 36 and the diaphragm valve 38, the compressed air supplied from the compressed air tank 34 to the pulse pipe 32 is filtered from the nozzles 42, 42,... With the air pressure and the injection interval adjusted. Sprayed to the inner surface of the fabric 22.

  FIG. 2 is a schematic diagram showing the positional relationship between the filter cloth 22 and the nozzle 42 in the bag filter 10.

  The filter cloth 22 is attached so as to face the hole 20 formed in the partition plate 18, and a venturi pipe 44 is installed inside the opening of the filter cloth 22. As shown in FIG. 2, the venturi tube 44 has a shape in which the lower part is narrowed, and the inner diameter of the lower part is formed, for example, approximately half of the inner diameter of the filter cloth 22. Therefore, the compressed air injected from the nozzle 42 via the pulse pipe 32 is blown to the opening of the filter cloth 22. At this time, since the compressed air is efficiently supplied to the inside of the filter cloth 22 via the venturi pipe 44, the shape of the filter cloth 22 is deformed, and the dust accumulated on the outer surface of the filter cloth 22 by the shearing force generated by the deformation. Will be dismissed.

  As shown in FIG. 1, the bag filter 10 includes a dust concentration meter 46 that is a dust concentration measuring means in the vicinity of the inlet flue 14, and a differential pressure gauge that is a differential pressure measuring means in the vicinity of the casing 12. 48 is arranged. The dust concentration meter 46 measures the dust concentration in the exhaust gas passing through the inlet flue 14, and the differential pressure meter 48 measures the pressure in the inlet flue side casing 12a and the pressure in the outlet flue side casing 12b. . The dust concentration meter 46 and the differential pressure gauge 48 are connected to a control unit 40 that is a control unit and a prediction unit, and the measurement values measured by the dust concentration meter 46 and the differential pressure meter 48 are transmitted to the control unit 40.

  The control unit 40 controls the adjustment of the compressed air by the compression adjuster 36 and the diaphragm valve 38 to be connected based on each received measurement value and compared with a set predetermined value.

  Next, the operation of the bag filter of the present invention and its operation method will be described using the bag filter 10 according to the embodiment described above.

  The amount and dust concentration of the exhaust gas supplied to the bag filter 10 varies depending on the state of the previous process. Therefore, when the amount of exhaust gas to be processed and the dust concentration are rapidly increased and the load on the bag filter 10 is rapidly increased, the dust rapidly accumulated on the filter cloths 22, 22. In addition, the dust accumulated on the filter cloths 22, 22...

  As a countermeasure, if the number of times of compressed air to be injected and the pressure are increased, dust accumulated on the filter cloths 22, 22... Can be reliably shaken off. However, if the backwashing apparatus 30 injects compressed air at an excessive injection interval or air pressure, the filter cloths 22, 22 ... are damaged by the impact, and the life of the filter cloths 22, 22 ... is reduced. Problems occur.

  Therefore, in the present invention, the dust concentration in the exhaust gas measured by the dust concentration meter 46 installed in the inlet flue 14, the inlet flue side casing 12a and the outlet flue side casing 12b measured by the differential pressure gauge 48, Based on the differential pressure, the control unit 40 controls the number and pressure of compressed air injected from the nozzles 42, 42,.

  FIG. 3 is a first graph showing the differential pressure generated in the filter cloths 22, 22... With respect to the operation time of the bag filter 10.

When the current differential pressure measured by the differential pressure gauge 48 is point A and the amount of exhaust gas and the dust concentration are constant, the differential pressure generated in the filter cloths 22, 22... Increases with the slope indicated by the solid line B. To do.
The control unit 40 calculates the predicted differential pressure generated in the filter cloths 22, 22,... From the value of the dust concentration measured by the dust concentration meter 46, and the differential pressure changes with the inclination indicated by the broken line C. In that case, the control unit 40 controls the adjustment of the compressed air in the compression adjuster 36 and the diaphragm valve 38 so as to be the same as the inclination of the solid line A, and is injected onto the filter cloths 22, 22. Increase the pressure and time of compressed air. On the other hand, when the control unit 40 predicts that the differential pressure changes with the slope indicated by the broken line C ′ from the dust concentration of the exhaust gas measured by the dust concentration meter 46, the control unit 40 applies the filter cloths 22, 22. The pressure and time of the compressed air to be injected are reduced, and the adjustment of the compressed air in the compression adjuster 36 and the diaphragm valve 38 is controlled so as to be the same as the slope of the solid line A. For example, if the compressed air that is injected when indicated by the solid line B is injected at an interval of 30 minutes at a pressure of 0.5 MPa, and the differential pressure predicted from the dust concentration shows the slope of the broken line C, the compressed air Air is injected at intervals of 20 minutes at a pressure of 0.6 MPa.

  FIG. 4 is a second graph showing the differential pressure generated in the filter cloths 22, 22... With respect to a certain operation time of the bag filter 10 and each reference line in the differential pressure.

  When the current differential pressure measured by the differential pressure gauge 48 is a point X, the differential pressure predicted from the dust concentration measured by the dust concentration meter 46 is calculated by the control unit 40. When the estimated differential pressure exceeds the range of each allowable line Y, Y indicated by the broken line, the control unit 40 controls the adjustment of the compressed air in the compression adjuster 36 and the diaphragm valve 38 and is set in advance. Compressed air is injected with pressure and time. For example, when the compressed air injected by normal discharge is injected at an interval of 30 minutes at a pressure of 0.5 MPa, and the differential pressure of the allowable line Y is set at 2 KPa, the difference predicted from the dust concentration When the pressure exceeds Y, the compressed air is injected at an interval of 20 minutes at a pressure of 0.6 MPa. When the pressure is below Y, the compressed air is injected at an interval of 40 minutes at a pressure of 0.4 MPa.

  In this way, based on the differential pressure between the inlet flue side casing 12a and the outlet flue side casing 12b at the present time, the filter cloths 22, 22 ... are predicted from the dust concentration in the exhaust gas introduced into the bag filter 10. The pressure difference is calculated in advance, and the compressed air pressure and the injection interval are adjusted in advance, so that even if the amount of exhaust gas to be treated or the dust concentration is changed suddenly, it accumulates in advance on the filter cloths 22, 22. Since the dust thus collected is backwashed with the minimum required air pressure and spray interval, it accumulates on the filter cloths 22, 22 ... without damaging the filter cloths 22, 22 ... due to excessive impact during backwashing. The dust that has been collected can be removed efficiently. Accordingly, it is possible to provide the bag filter 10 that can always stably collect dust with respect to the exhaust gas that is likely to fluctuate under the conditions of the previous process and can extend the life of the filter cloths 22, 22. it can.

  In the bag filter 10 described above, the number, shape, material, and the like of each device or member used are not particularly limited.

  In the bag filter 10, the fixed type venturi tubes 44, 44... Are installed inside the openings of the filter cloths 22, 22. If the movable venturi pipes 44, 44,... Are provided and installed only when it is necessary to wipe off, compressed air can be blown onto the filter cloths 22, 22 ... more efficiently.

  Moreover, in the bag filter 10, although comprised so that the dust in waste gas may be isolate | separated by the outer surface of filter cloth 22,22 ..., it does not specifically limit. The present invention can also be suitably used in a bag filter configured to separate dust from exhaust gas on the inner surfaces of the filter cloths 22, 22.

Configuration diagram of a bug filter according to an embodiment of the present invention The schematic diagram which showed arrangement | positioning of the filter cloth and nozzle in the bag filter which is embodiment of this invention The 1st graph which showed the differential pressure of an entrance flue and an exit flue with respect to operation time in the bag filter of the present invention The 2nd graph which showed the differential pressure of an entrance flue and an exit flue with respect to operation time in the bag filter of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Bag filter, 12 ... Casing, 12a ... Inlet flue side casing, 12b ... Outlet flue side casing, 14 ... Inlet flue, 16 ... Outlet flue, 18 ... Partition plate, 20 ... Hole, 22 ... Filter cloth , 30 ... Backwash device, 32 ... Pulse piping, 34 ... Compressed air tank, 36 ... Compression regulator, 38 ... Diaphragm valve, 40 ... Control part, 42 ... Nozzle, 44 ... Venturi tube, 46 ... Dust concentration meter, 48 ... Differential pressure gauge

Claims (2)

A bag filter that collects dust in the exhaust gas by the filter cloth by passing the exhaust gas from the inlet flue through the filter cloth and exhausts the exhaust gas in which the dust is collected from the outlet flue, In the bag filter with backwashing means to remove the adhered dust with compressed air,
Concentration measuring means for measuring the dust concentration in the exhaust gas in the inlet flue at predetermined time intervals, and controlling the air pressure and / or injection interval of the compressed air by the backwashing means based on the dust concentration measured by the concentration measuring means and control means for,
The control means includes prediction means for predicting a differential pressure between the pressure on the inlet flue side and the pressure on the outlet flue side based on the dust concentration measured by the concentration measurement means, and the prediction means The bag filter characterized by controlling the air pressure and / or the injection interval of the compressed air by the backwashing unit based on the predicted differential pressure . A bag filter that collects dust in the exhaust gas by the filter cloth by passing the exhaust gas from the inlet flue through the filter cloth and exhausts the exhaust gas in which the dust is collected from the outlet flue from the backwashing means In the operation method of the bag filter for removing dust adhering to the filter cloth by the supplied compressed air,
  The dust concentration in the exhaust gas in the inlet flue is measured at predetermined time intervals by the concentration measuring means, and the pressure on the inlet flue side and the outlet flue side are determined based on the plurality of dust concentrations measured by the concentration measuring means. A bag filter operating method characterized by predicting a differential pressure with respect to the pressure of the air and controlling the air pressure and / or the injection interval of the compressed air by the backwashing means based on the predicted differential pressure to remove dust .

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