CA1125670A - Cleaning process control method for textile barrier filter material - Google Patents
Cleaning process control method for textile barrier filter materialInfo
- Publication number
- CA1125670A CA1125670A CA345,382A CA345382A CA1125670A CA 1125670 A CA1125670 A CA 1125670A CA 345382 A CA345382 A CA 345382A CA 1125670 A CA1125670 A CA 1125670A
- Authority
- CA
- Canada
- Prior art keywords
- cleaning
- filter
- gas
- filter material
- pulses
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
- B01D46/02—Particle separators, e.g. dust precipitators, having hollow filters made of flexible material
- B01D46/04—Cleaning filters
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
- B01D46/42—Auxiliary equipment or operation thereof
- B01D46/4227—Manipulating filters or filter elements, e.g. handles or extracting tools
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
- B01D46/42—Auxiliary equipment or operation thereof
- B01D46/44—Auxiliary equipment or operation thereof controlling filtration
- B01D46/446—Auxiliary equipment or operation thereof controlling filtration by pressure measuring
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
- B01D46/42—Auxiliary equipment or operation thereof
- B01D46/44—Auxiliary equipment or operation thereof controlling filtration
- B01D46/448—Auxiliary equipment or operation thereof controlling filtration by temperature measuring
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
- B01D46/66—Regeneration of the filtering material or filter elements inside the filter
- B01D46/70—Regeneration of the filtering material or filter elements inside the filter by acting counter-currently on the filtering surface, e.g. by flushing on the non-cake side of the filter
- B01D46/71—Regeneration of the filtering material or filter elements inside the filter by acting counter-currently on the filtering surface, e.g. by flushing on the non-cake side of the filter with pressurised gas, e.g. pulsed air
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
- B01D46/90—Devices for taking out of action one or more units of multi-unit filters, e.g. for regeneration or maintenance
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Filtering Of Dispersed Particles In Gases (AREA)
- Filtration Of Liquid (AREA)
- Cleaning Implements For Floors, Carpets, Furniture, Walls, And The Like (AREA)
Abstract
ABSTRACT
A method of controlling the cleaning process for the cleaning of textile barrier filters, for example bag filters, subse-quent to dust precipitation on the filter material. The cleaning is carried out with a cleaning system comprising means for distributing compressed air pulses to the filter bags. The gas flow often shows great variations in flow, temperature and dust content, thereby giving rise to problems in the control of the cleaning process in such a manner, that neither over-cleaning nor under-cleaning occurs. For the control, the filter load vf is measured which is the ratio of the gas flow (m3/s) and the filter area (m2), as well as the pressure drop Pf over the filter material. At applications with great temperature variations of the gas, also the absolute temperature T is measured. The measuring results are processed in an electronic unit for calculating the filter resistance S, which is the ration Pf/vf, possibly standardized to a reference temperature To by multiplication with the ratio (To/T).alpha., where .alpha. is a constant with the value 0.76 at gas temperatures below 200°C. Through the filter resistance S the cleaning process is controlled by acting upon the cleaning interval, the time interval between the cleaning pulses, the cleaning pressure of the cleaning pulse or the duration thereof.
A method of controlling the cleaning process for the cleaning of textile barrier filters, for example bag filters, subse-quent to dust precipitation on the filter material. The cleaning is carried out with a cleaning system comprising means for distributing compressed air pulses to the filter bags. The gas flow often shows great variations in flow, temperature and dust content, thereby giving rise to problems in the control of the cleaning process in such a manner, that neither over-cleaning nor under-cleaning occurs. For the control, the filter load vf is measured which is the ratio of the gas flow (m3/s) and the filter area (m2), as well as the pressure drop Pf over the filter material. At applications with great temperature variations of the gas, also the absolute temperature T is measured. The measuring results are processed in an electronic unit for calculating the filter resistance S, which is the ration Pf/vf, possibly standardized to a reference temperature To by multiplication with the ratio (To/T).alpha., where .alpha. is a constant with the value 0.76 at gas temperatures below 200°C. Through the filter resistance S the cleaning process is controlled by acting upon the cleaning interval, the time interval between the cleaning pulses, the cleaning pressure of the cleaning pulse or the duration thereof.
Description
~ ~567~
Cleaning process control method for textile barrier filter material This invention relates to a method of controlling the cleaning process of the filter material of textile barrier filters, preferably of the bag filter type, where the polluted gas is supplied to a filter chamber via a crude gas inlet and passes through the filter material mounted in the filter chamber and precipitates dust thereon, and is dischargèd from the filter chamber via a clean gas outlet, and the cleaning process is effected by exposing the filter material to a compressed air pulse from a cleaning system controlled by a control system.
In a conventional control system, the cleaning system oE a bag filter usually is controlled by the flange-to-flange press-ure drop of the installation. In said flange-to-flange pressure drop the inlet and outlet dampers as well as the duct losses are included. The cleaning is initiated when a limit value for the flange-to-flange pressure drop is achieved~ The cleaning interval, thus, depends on the dust concentration of the gas.
The method is adapted well for processes where the operation conditions, i.e. the gas flow, gas temperature and dust con-centration substantially are constant.
At varying gas flow and dust concentration, however, the aforesaid control system has the tendency of being controlled to a great extent by the gas flow. From a technical aspect, such control is definitely unsuitable. The ~lange-to-flange pressuxe drop at each moment being proportional to the gas flow, the cleaning can be initiated by short-duration flow ' . ' ' '' :. ~
:
i7al increases without being conditioned by dust deposits on the bags. The result thereof is over-cleaning, i.e. the dust cake is destroyed, and the filter material is exposed to the gas flow. The emission of dust, as well as the bag wear and the residual resistance of the bag all increase, because the fine dust fraction can more easily penetrate through the exposed filter material.
Also the opposite operation case can occur, i.e. high dust concentration and low gas flow, which results in a ~onsiderable growth of the dust cake without initiating cleaning. The in-crease in dust deposit per se, thus, is not sufficient for achieving at the lower gas flow the limit value, at which the cleaning is initiated. When the gas flow increases, the cleaning is initiated immediately, but then the cleaning effect (pulse pressure) is not adapted to the stronger dust cake.
Consequently, several cleaning operations are required for cleaning the filter, implying higher bag wear and shorter life.
In extreme cases it may even occur, that the operating level o~ the installation is shifted to the upper working point with the higher pressure drop and the lower gas flow. The upper working point re~ers to the point of intersection between the installation curve and, respectively, fan curve of the system. When the installation includes a pulse-cleaned filter, the installation curve assumes the shape of an -obliquely upwardly directed parabola, the "tip" o~ which corresponds to the maximum possible filter flow. When the upper working point has been achie~ed, the installation must ; be started again in order to return to the lower working point ~^- J with the lower pressure drop and the higher load.
- ~
67~
It is also known to control the cleaning process of a bag filter by initiating the cleaning pulses at a predetermined time interval, which is adjusted so as to yield the necessary cleaning when operating at maximum load. In this case the control is effected by a timer arrangement. It is obvious when the load on the filter is below the ma~imum load, the system will request cleaning even when there is no cleaning demand. This results in high wear of the filter material and increase in dust emission.
The object of the present invention is to bring about an improved control system, in which the disadvantages of con-ventional methods are eliminated. This object is achieved by controlling the cleaning in response to changes in the ratio between the pressure drop acxoss the filter material and the flow through the material, or the fi:Lter resistance. The invention, thus, is based on the understanding that the cleaning system is to he controlled by the dust deposit on the filter material, usually the filter bags, so that irres-pective of variations in the gas flow and dust concentration cleaning always is initiated in response to the same dust deposit on the bags. A suitable method is defined at which the viscosity of the gas is taken into consideration. This is expedient in cases when the gas to be cleaned also shows temperature variations in addition to flow variations. The invention contemplates alternative methods of controlling the cleaning effect of the cleaning system by acting upon the para-meters which influence on the cleaning effect.
6~
The invention is described in greater detail hereafter, with reference to the accompanying drawing, which is a section through a filter installation.
In the drawing, 1 designates a filter housing with filter chambers 2 arranged therein, in which chambers cassettes 3 or packages comprising a plurality of rows of filter bags 4 are located. The polluted gas to be cleaned is supplied to the filter housing via a crude gas duct 5, and the cleaned gas is led away from the filter housing via a clean air duct 6.
Within the filter housing, the crude gas is passed via a duct 7 to the crude gas inlet 8 of the filter chamber and then penetrates through the filter bags 4 while precipitating dust on the surface of the filter material. The cleaned gas is discharged from the clean gas side of the filter chamber via a clean gas outlet 9 to an outlet duct 10 located in the filter houaing and connected to the clean gas duct 6. The filter shown comprises a plurality of filter chambers (not shown), which are connected to the common ducts 7 and 10.
Damper means 11 and 12 are provided to shut-off the filter chambers, if nècessary, for inspection, filter exchange and the like. For the latter purpose hoisting means 13 are used to lift a cassette out of the filter chamber. The right-hand filter chamber in the Figure is shut down by the damper means 12. The left-hand filter chamber is in operation, as is apparent from the position of the damper means 11. The gas flow is indicated by arrows showing the flow direction.
A cleaning device 14 is provided for cleaning the filter bags and comprises in the embodiment shown a pressure tank 15 for cleaning medium, i~e. compressed air, a valve 16 for the 7~
supply of cleaning medium to a distribution duct 17, which is provided with jets 18. The mode of operation and the design of the cleaning device shown in the Figure are not described in detail here, but are stated to be of the kind disclosed in U.S. Pat. No. 4,033,732. The cleaning is effected by a pressure pulse directed downward in the bag imparting to the filter material an acceleration and retardation movement, whereby the dust is detached from the filter material and is collected in the dust bin 19. This cleaning method is tested thoroughly, and great knowledge has been gained with respect to the parameters influencing the cleaning effect.
According to the invention, the cleaning system ls controlled as follows. The total pressure of the gas and the static pressure are measured by means of a probe 20 disposed in tha flue duct 5. The dynamic pressure of the gas and its variation with time can be recorded by the pressure transmitter 21. The dynamic pressure being a function of the gas flow, a measure of the gas flow VarlatiOn~ thus, is obtained, and with knowledge of the duct area in question and the total area of the filter material it is possible, by a suitable signal processing, to obtain the filter load Vf as the output signal from the pressure transmitter 21. The filter load, thus, can be defined as the ratio between the gas flow (m3/s) and the filter area (m2).
At normal applications Vf amounts to bekween 0.02 and 0.06 m/s.
, A pressure-sensing means 22 is provided in the crude gas side ~crude gas inlet 8) of the filter chamber, and the pressure sensed is transferred to a pressure transmitter 23. A second :
67~) pressure-sensing means 24 is provided at the clean gas outlet 9 of the filter chamber, and the pressure sensed also is transferred to the pressure transmitter 23, where the differ-ential pressure pf is formed and cons~itutes the output signal frcm said transmitter. The differential pressure pfr thus, is the pressure drop prevailing over the filter material. In usual applications, pf varies from 0.75 to 2.5 kPa. The output signals from the pressure transmitters 21 and 23, i.e. Vf and pf/ are passed to an electronic unit 25 for further processing.
According to the invention, here the filter resistance S is calculated which is defined as the ratio between the pressure drop ovex the filter material pf and the filter load Vf. Normal values of S are 15 to 50 kPa/(m/s). The output signal S from the electronic unit is passed to a limit value unit 26 where comparison is made with a nominal value So of the filter resistance. From said limit value unit a signal C for filter cleaning is emitted when the filter resistance S has reached the nominal value So which has been set. Said signal C is passed to a control electronic unit 29, which emits the signals required for the cleaning system 14 to carry out the cleaning.
A compressed air compressor is started, and an electro-mechanic valve is actuated which via a pilot valve opens the valve 16 and thereby initiates the cleaning process.
In a great number of process applications the temperature of the gas varies substantially with the time. Hereby also the viscosity of the gas is changed and thereby influences the pressure drop over the filter material without a change having taken place cf the dust cake precipitated on the fibre material.
As the basic idea of the invention implies that only the size o~6~7at of the dust deposit shall act upon the control of the cleaning system, the invention comprises an appropriate method of compen-sating for temperature variations, and therewith viscosity variations, of the gas the calculation of the filter resistance by standardizing the temperature relative to a reference temperature To~ This is achieved by a temperature-sensing member 27 which senses the temperature of the gas and via a transmitter 28 transmits the value of the absolute temperature T of the gas to the electronic unit 25. In calculations of the filter resistance S, the ratio pf/Vf is multiplied with (T~/T) a, where To is a reference temperature in K and T is the prevail~
ing temperature in K. ~ is a constant, which at temperatures below 200C assumes the value 0.76.
.
According to the invention, the cleaning process is controlled by acting on one of the parameters which influence the cleaning process, as set forth hereinafter. The method most obvious for utilizing the invention in practice is to control the cleaning effect by acting upon the cleaning interval or the time interval `
between the cleaning pulses.
It should be mentioned in this connection, that the cleaning of a cassette with filter bags normally is carried out in sequential cycles one row after the other, and that the term cleaning interval refers to the time which is required from commencing the cleaning of one of the filter rows in the cassette until all filter rows have been cleaned and the next cleaning cycle is commenced. A claaning cycle, thus, can imply a rapid cleaning throughout the filter package and, thus, the time until the next cleaning interval is controlled. In .:
the other case, the cleanings take place one row after the other and without interruption when the cassette has been cleaned throughout. In this case, instead, the time between the cleaning pulses is acted upon. ~hen a large amount of dust is precipitated on the filter material, cleaning will be iniiiated at short time intervals, and in the case of small amounts of precipitated dust the corresponding time intervals will be long. -As the cleaning effect depends on the pressure of the cleaning medium or cleaning pulse, so that a higher pressure yields a higher cleaning effect than a low pressure, according to an alternative method the pressure of the cleaning pulse can be acted upon for controlling the cleaning effect. In this case preferably the time interval bet.ween the pressure pulses is constant, and prior to ev~ry cleaning the system emits a signal, which acts upon the cleaning pressure so that the clean-ing pulse which is delivered is just as powerful as required or effecting the necessary cleaning~ ~he control of the pulse pressure can be carried out in different ways, for example by controlling the tank pressure, which will be obvious to the expert. According to a further alternative, the cleaning effect of the cleaning pulse can be controlled by acting upon its duration. When the pulse d~s interrupted early, a reduced cleaning effect is obtained compared with when the pulse is permitted to develop in its entirety. This can be achieved, purely practically, by varying the duration of the signal CO
The invention is described in greater detail by way of the ollowing example. The experiment was carried out in a bag filter installation where the gas from an electric arc . ' ' `. ' ` ` ' .
' , `
, 67~
g furnace was cleaned. In these installations the gas flow, and also the temperature, vary substantially in operation. The flow through the filter varied between 300,000 Nm3/h and 440,000 Nm3/h, and the temperature varied between 2~C and 100C. The filter installation comprised four sections with 336 bags each, and each bag had the length 5 m and the diameter 0.127 m. The total filter area amounted to 2688 m2. Compared with convent-ional operation, the method of operation according to the in-vention resulted in that the mean cleaning interval increased by 33%, from 1.25 to 1.65 minutes. In the case when also the temperature variation of the gas was taken into consideration, the cleaning interval increased additionally from 1.65 to 1.85 minutes.
`~ The advantages gained by utilizing the invention over the conventional prior art can be summarized as follows~ The cleaning of the filter bags always takes place in response to a certain dust deposit on the bags, thereby preventing over-cleaning and inc~eased bag wear. The bags hereby have a longer life. The total emission for the filter installation is decreased, because no bags are over-cleaned and there always remains a dust cake on the filter material. Hereby also deep penetration of fine dust into the filter material is prevented which yields a lower residual resistance and thereby a lower mean pressure drop over the ~ilter bags.
This implies a substantial energy saving in the form of reduced fan work. The reduced number of cleanings, further, implies a decrease in the energ~ consumption ~or the cleaning ;s~stem proper.
' ,, -. .
.~
Cleaning process control method for textile barrier filter material This invention relates to a method of controlling the cleaning process of the filter material of textile barrier filters, preferably of the bag filter type, where the polluted gas is supplied to a filter chamber via a crude gas inlet and passes through the filter material mounted in the filter chamber and precipitates dust thereon, and is dischargèd from the filter chamber via a clean gas outlet, and the cleaning process is effected by exposing the filter material to a compressed air pulse from a cleaning system controlled by a control system.
In a conventional control system, the cleaning system oE a bag filter usually is controlled by the flange-to-flange press-ure drop of the installation. In said flange-to-flange pressure drop the inlet and outlet dampers as well as the duct losses are included. The cleaning is initiated when a limit value for the flange-to-flange pressure drop is achieved~ The cleaning interval, thus, depends on the dust concentration of the gas.
The method is adapted well for processes where the operation conditions, i.e. the gas flow, gas temperature and dust con-centration substantially are constant.
At varying gas flow and dust concentration, however, the aforesaid control system has the tendency of being controlled to a great extent by the gas flow. From a technical aspect, such control is definitely unsuitable. The ~lange-to-flange pressuxe drop at each moment being proportional to the gas flow, the cleaning can be initiated by short-duration flow ' . ' ' '' :. ~
:
i7al increases without being conditioned by dust deposits on the bags. The result thereof is over-cleaning, i.e. the dust cake is destroyed, and the filter material is exposed to the gas flow. The emission of dust, as well as the bag wear and the residual resistance of the bag all increase, because the fine dust fraction can more easily penetrate through the exposed filter material.
Also the opposite operation case can occur, i.e. high dust concentration and low gas flow, which results in a ~onsiderable growth of the dust cake without initiating cleaning. The in-crease in dust deposit per se, thus, is not sufficient for achieving at the lower gas flow the limit value, at which the cleaning is initiated. When the gas flow increases, the cleaning is initiated immediately, but then the cleaning effect (pulse pressure) is not adapted to the stronger dust cake.
Consequently, several cleaning operations are required for cleaning the filter, implying higher bag wear and shorter life.
In extreme cases it may even occur, that the operating level o~ the installation is shifted to the upper working point with the higher pressure drop and the lower gas flow. The upper working point re~ers to the point of intersection between the installation curve and, respectively, fan curve of the system. When the installation includes a pulse-cleaned filter, the installation curve assumes the shape of an -obliquely upwardly directed parabola, the "tip" o~ which corresponds to the maximum possible filter flow. When the upper working point has been achie~ed, the installation must ; be started again in order to return to the lower working point ~^- J with the lower pressure drop and the higher load.
- ~
67~
It is also known to control the cleaning process of a bag filter by initiating the cleaning pulses at a predetermined time interval, which is adjusted so as to yield the necessary cleaning when operating at maximum load. In this case the control is effected by a timer arrangement. It is obvious when the load on the filter is below the ma~imum load, the system will request cleaning even when there is no cleaning demand. This results in high wear of the filter material and increase in dust emission.
The object of the present invention is to bring about an improved control system, in which the disadvantages of con-ventional methods are eliminated. This object is achieved by controlling the cleaning in response to changes in the ratio between the pressure drop acxoss the filter material and the flow through the material, or the fi:Lter resistance. The invention, thus, is based on the understanding that the cleaning system is to he controlled by the dust deposit on the filter material, usually the filter bags, so that irres-pective of variations in the gas flow and dust concentration cleaning always is initiated in response to the same dust deposit on the bags. A suitable method is defined at which the viscosity of the gas is taken into consideration. This is expedient in cases when the gas to be cleaned also shows temperature variations in addition to flow variations. The invention contemplates alternative methods of controlling the cleaning effect of the cleaning system by acting upon the para-meters which influence on the cleaning effect.
6~
The invention is described in greater detail hereafter, with reference to the accompanying drawing, which is a section through a filter installation.
In the drawing, 1 designates a filter housing with filter chambers 2 arranged therein, in which chambers cassettes 3 or packages comprising a plurality of rows of filter bags 4 are located. The polluted gas to be cleaned is supplied to the filter housing via a crude gas duct 5, and the cleaned gas is led away from the filter housing via a clean air duct 6.
Within the filter housing, the crude gas is passed via a duct 7 to the crude gas inlet 8 of the filter chamber and then penetrates through the filter bags 4 while precipitating dust on the surface of the filter material. The cleaned gas is discharged from the clean gas side of the filter chamber via a clean gas outlet 9 to an outlet duct 10 located in the filter houaing and connected to the clean gas duct 6. The filter shown comprises a plurality of filter chambers (not shown), which are connected to the common ducts 7 and 10.
Damper means 11 and 12 are provided to shut-off the filter chambers, if nècessary, for inspection, filter exchange and the like. For the latter purpose hoisting means 13 are used to lift a cassette out of the filter chamber. The right-hand filter chamber in the Figure is shut down by the damper means 12. The left-hand filter chamber is in operation, as is apparent from the position of the damper means 11. The gas flow is indicated by arrows showing the flow direction.
A cleaning device 14 is provided for cleaning the filter bags and comprises in the embodiment shown a pressure tank 15 for cleaning medium, i~e. compressed air, a valve 16 for the 7~
supply of cleaning medium to a distribution duct 17, which is provided with jets 18. The mode of operation and the design of the cleaning device shown in the Figure are not described in detail here, but are stated to be of the kind disclosed in U.S. Pat. No. 4,033,732. The cleaning is effected by a pressure pulse directed downward in the bag imparting to the filter material an acceleration and retardation movement, whereby the dust is detached from the filter material and is collected in the dust bin 19. This cleaning method is tested thoroughly, and great knowledge has been gained with respect to the parameters influencing the cleaning effect.
According to the invention, the cleaning system ls controlled as follows. The total pressure of the gas and the static pressure are measured by means of a probe 20 disposed in tha flue duct 5. The dynamic pressure of the gas and its variation with time can be recorded by the pressure transmitter 21. The dynamic pressure being a function of the gas flow, a measure of the gas flow VarlatiOn~ thus, is obtained, and with knowledge of the duct area in question and the total area of the filter material it is possible, by a suitable signal processing, to obtain the filter load Vf as the output signal from the pressure transmitter 21. The filter load, thus, can be defined as the ratio between the gas flow (m3/s) and the filter area (m2).
At normal applications Vf amounts to bekween 0.02 and 0.06 m/s.
, A pressure-sensing means 22 is provided in the crude gas side ~crude gas inlet 8) of the filter chamber, and the pressure sensed is transferred to a pressure transmitter 23. A second :
67~) pressure-sensing means 24 is provided at the clean gas outlet 9 of the filter chamber, and the pressure sensed also is transferred to the pressure transmitter 23, where the differ-ential pressure pf is formed and cons~itutes the output signal frcm said transmitter. The differential pressure pfr thus, is the pressure drop prevailing over the filter material. In usual applications, pf varies from 0.75 to 2.5 kPa. The output signals from the pressure transmitters 21 and 23, i.e. Vf and pf/ are passed to an electronic unit 25 for further processing.
According to the invention, here the filter resistance S is calculated which is defined as the ratio between the pressure drop ovex the filter material pf and the filter load Vf. Normal values of S are 15 to 50 kPa/(m/s). The output signal S from the electronic unit is passed to a limit value unit 26 where comparison is made with a nominal value So of the filter resistance. From said limit value unit a signal C for filter cleaning is emitted when the filter resistance S has reached the nominal value So which has been set. Said signal C is passed to a control electronic unit 29, which emits the signals required for the cleaning system 14 to carry out the cleaning.
A compressed air compressor is started, and an electro-mechanic valve is actuated which via a pilot valve opens the valve 16 and thereby initiates the cleaning process.
In a great number of process applications the temperature of the gas varies substantially with the time. Hereby also the viscosity of the gas is changed and thereby influences the pressure drop over the filter material without a change having taken place cf the dust cake precipitated on the fibre material.
As the basic idea of the invention implies that only the size o~6~7at of the dust deposit shall act upon the control of the cleaning system, the invention comprises an appropriate method of compen-sating for temperature variations, and therewith viscosity variations, of the gas the calculation of the filter resistance by standardizing the temperature relative to a reference temperature To~ This is achieved by a temperature-sensing member 27 which senses the temperature of the gas and via a transmitter 28 transmits the value of the absolute temperature T of the gas to the electronic unit 25. In calculations of the filter resistance S, the ratio pf/Vf is multiplied with (T~/T) a, where To is a reference temperature in K and T is the prevail~
ing temperature in K. ~ is a constant, which at temperatures below 200C assumes the value 0.76.
.
According to the invention, the cleaning process is controlled by acting on one of the parameters which influence the cleaning process, as set forth hereinafter. The method most obvious for utilizing the invention in practice is to control the cleaning effect by acting upon the cleaning interval or the time interval `
between the cleaning pulses.
It should be mentioned in this connection, that the cleaning of a cassette with filter bags normally is carried out in sequential cycles one row after the other, and that the term cleaning interval refers to the time which is required from commencing the cleaning of one of the filter rows in the cassette until all filter rows have been cleaned and the next cleaning cycle is commenced. A claaning cycle, thus, can imply a rapid cleaning throughout the filter package and, thus, the time until the next cleaning interval is controlled. In .:
the other case, the cleanings take place one row after the other and without interruption when the cassette has been cleaned throughout. In this case, instead, the time between the cleaning pulses is acted upon. ~hen a large amount of dust is precipitated on the filter material, cleaning will be iniiiated at short time intervals, and in the case of small amounts of precipitated dust the corresponding time intervals will be long. -As the cleaning effect depends on the pressure of the cleaning medium or cleaning pulse, so that a higher pressure yields a higher cleaning effect than a low pressure, according to an alternative method the pressure of the cleaning pulse can be acted upon for controlling the cleaning effect. In this case preferably the time interval bet.ween the pressure pulses is constant, and prior to ev~ry cleaning the system emits a signal, which acts upon the cleaning pressure so that the clean-ing pulse which is delivered is just as powerful as required or effecting the necessary cleaning~ ~he control of the pulse pressure can be carried out in different ways, for example by controlling the tank pressure, which will be obvious to the expert. According to a further alternative, the cleaning effect of the cleaning pulse can be controlled by acting upon its duration. When the pulse d~s interrupted early, a reduced cleaning effect is obtained compared with when the pulse is permitted to develop in its entirety. This can be achieved, purely practically, by varying the duration of the signal CO
The invention is described in greater detail by way of the ollowing example. The experiment was carried out in a bag filter installation where the gas from an electric arc . ' ' `. ' ` ` ' .
' , `
, 67~
g furnace was cleaned. In these installations the gas flow, and also the temperature, vary substantially in operation. The flow through the filter varied between 300,000 Nm3/h and 440,000 Nm3/h, and the temperature varied between 2~C and 100C. The filter installation comprised four sections with 336 bags each, and each bag had the length 5 m and the diameter 0.127 m. The total filter area amounted to 2688 m2. Compared with convent-ional operation, the method of operation according to the in-vention resulted in that the mean cleaning interval increased by 33%, from 1.25 to 1.65 minutes. In the case when also the temperature variation of the gas was taken into consideration, the cleaning interval increased additionally from 1.65 to 1.85 minutes.
`~ The advantages gained by utilizing the invention over the conventional prior art can be summarized as follows~ The cleaning of the filter bags always takes place in response to a certain dust deposit on the bags, thereby preventing over-cleaning and inc~eased bag wear. The bags hereby have a longer life. The total emission for the filter installation is decreased, because no bags are over-cleaned and there always remains a dust cake on the filter material. Hereby also deep penetration of fine dust into the filter material is prevented which yields a lower residual resistance and thereby a lower mean pressure drop over the ~ilter bags.
This implies a substantial energy saving in the form of reduced fan work. The reduced number of cleanings, further, implies a decrease in the energ~ consumption ~or the cleaning ;s~stem proper.
' ,, -. .
.~
Claims (8)
1. A method of controlling the cleaning process for the cleaning of the filter material in textile barrier filters where the polluted gas is supplied to a filter chamber via a crude gas inlet and passes through the filter material mounted in the filter chamber and precipitates dust thereon, and is discharged from the filter chamber via a clean gas outlet, and the cleaning process is effected by exposing the filter material to compressed air pulses from a cleaning system controlled by a control system, comprising the steps of measuring the pressure drop Pf over the filter material, measuring the gas flow to determine the filter load vf, which is the ratio between the gas flow and the filter area, computing the filter resistance S, which is the ratio between Pf and vf, and comparing S with a nominal value So of filter resistance, and in response to deviation of S from So, emitting a control signal for controlling the operation of the cleaning system on the filter material.
2. A method as defined in claim 1, including the step of measuring the absolute temperature T of the gas in relation to reference Temperature To, and correcting the measurement of the filter resistance S in response to any viscosity change of the gas.
3. A method as defined in claim 2, wherein the control system provides the correction by multiplying the ratio Pf/vf by (To/T).alpha., where T and To are temperatures in °K. and is a constant which at temperatures below 200°C assumes the value 0.76.
4. A method according to claim 1 wherein the signal from the control system varies the pressure of the clean-ing pulses.
5. A method according to claim 1 wherein the signal from the control system varies the duration of the clean-ing pulses.
6. A method according to claim 1 wherein the cleaning process is operated in sequential cycles initiated at set time intervals and the control signal varies the set time intervals.
7. A method according to claim 6 wherein each of the cleaning cycles comprises a series of pulses and the in-tervals are controlled by varying the time between the completion of the series and the start of the next cycle.
8. A method according to claim 6 wherein each of the cleaning cycles comprises a series of pulses and the in-tervals are controlled by varying the time between pulses.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE7901181A SE7901181L (en) | 1979-02-12 | 1979-02-12 | SET TO CONTROL THE CLEANING PROCESS BY CLEANING THE FILTER MATERIAL BY TEXTILE LOCK FILTER |
| SE7901181-3 | 1979-02-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1125670A true CA1125670A (en) | 1982-06-15 |
Family
ID=20337254
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA345,382A Expired CA1125670A (en) | 1979-02-12 | 1980-02-11 | Cleaning process control method for textile barrier filter material |
Country Status (17)
| Country | Link |
|---|---|
| EP (1) | EP0015409B1 (en) |
| JP (1) | JPS5825489B2 (en) |
| AR (1) | AR225914A1 (en) |
| AT (1) | ATE1695T1 (en) |
| AU (1) | AU535897B2 (en) |
| BR (1) | BR8000747A (en) |
| CA (1) | CA1125670A (en) |
| DE (1) | DE3060983D1 (en) |
| ES (1) | ES488470A0 (en) |
| FI (1) | FI64747C (en) |
| GR (1) | GR73136B (en) |
| IN (1) | IN152147B (en) |
| MX (1) | MX155944A (en) |
| NO (1) | NO149762C (en) |
| NZ (1) | NZ192835A (en) |
| SE (1) | SE7901181L (en) |
| YU (1) | YU40590B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US11274235B2 (en) | 2015-04-24 | 2022-03-15 | 3M Innovative Properties Company | Acrylic adhesive compositions and acrylic adhesive tapes which enable clean removal from delicate surfaces |
Families Citing this family (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5730520A (en) * | 1980-07-31 | 1982-02-18 | Amano Corp | Pulse jet type filter dust remover for dust collector |
| DE3308085A1 (en) * | 1983-03-08 | 1984-09-20 | Straub, Hartwig, 6965 Ahorn | Process and apparatus for cleaning filter inserts |
| DE3336487C2 (en) * | 1983-10-07 | 1986-07-03 | Hölter, Heinz, Dipl.-Ing., 4390 Gladbeck | Method and device for monitoring the function of a controlled filter cleaning system |
| DE3520413A1 (en) * | 1985-06-07 | 1986-12-11 | Daimler-Benz Ag, 7000 Stuttgart | AIR FILTER DEVICE ARRANGED IN THE AIR FLOW OF A HEATING OR AIR CONDITIONING DEVICE OF A MOTOR VEHICLE |
| JPS6364884U (en) * | 1986-10-18 | 1988-04-28 | ||
| US4719791A (en) * | 1986-12-05 | 1988-01-19 | Ets, Inc. | Individual filter bag monitoring system for baghouses |
| WO1988007648A1 (en) * | 1987-03-23 | 1988-10-06 | Westinghouse Electric Corporation | Method and apparatus of cleaning toxic substances from the exhaust of an incinerator burning-municipal solid waste |
| DE3718846A1 (en) * | 1987-03-30 | 1988-10-13 | Steinmueller Gmbh L & C | METHOD FOR DUST-DUSTING A DUST-CONTAINING GAS BY MEANS OF THE GAS TRANSFERABLE FILTER ELEMENTS |
| DE29512238U1 (en) * | 1995-07-28 | 1995-10-12 | Siemens AG, 80333 München | Emission control system |
| AT403256B (en) * | 1996-07-31 | 1997-12-29 | Scheuch Alois Gmbh | Method for controlling the cleaning of filters |
| JP2007268465A (en) * | 2006-03-31 | 2007-10-18 | Nippon Steel Engineering Co Ltd | Apparatus and method of controlling filter type dust collector |
| FR2908326B1 (en) * | 2006-11-10 | 2009-01-09 | Lab Sa Sa | METHOD FOR MANAGING THE CLEANING OF A SLEEVE FILTER |
| CN103599667A (en) * | 2013-12-09 | 2014-02-26 | 昆山亿诚化工容器有限公司 | Dust removing net for off-gas purifying equipment |
| CN104056503B (en) * | 2014-06-11 | 2015-10-28 | 常熟市上海飞奥压力容器制造有限公司 | Multipurpose horizontal natural gas separator-filter |
| CN111841183B (en) * | 2020-08-06 | 2021-08-03 | 南京溧水高新产业股权投资有限公司 | Filter processing device of textile equipment |
| DE102022133549A1 (en) * | 2022-12-15 | 2024-06-20 | Hengst Se | Control system for an extraction system |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB812244A (en) * | 1956-07-09 | 1959-04-22 | Metals Disintegrating Co | A gas filtering apparatus |
| DE1507768A1 (en) * | 1966-04-23 | 1969-07-31 | Alpine Ag | Air volume control through filter |
| DE1507843A1 (en) * | 1966-08-11 | 1969-12-18 | Rheinische Kalksteinwerke | Filter system for separating dust from gases |
| CH543295A (en) * | 1970-08-28 | 1973-10-31 | Buehler Ag Geb | Pressure control system - for a pneumatic dedusting plant |
| CH527635A (en) * | 1970-08-28 | 1972-09-15 | Buehler Ag Geb | Pneumatic dedusting system |
| US3948623A (en) * | 1972-08-29 | 1976-04-06 | Chevron Research Company | Anhydride separation |
| DE2606146A1 (en) * | 1976-02-17 | 1977-08-25 | Wibau Gmbh | METHOD FOR CLEANING DUST-LOADED SURFACES FROM BAG AND AREA FILTERS |
-
1979
- 1979-02-12 SE SE7901181A patent/SE7901181L/en unknown
-
1980
- 1980-01-29 AU AU55003/80A patent/AU535897B2/en not_active Ceased
- 1980-02-04 FI FI800324A patent/FI64747C/en not_active IP Right Cessation
- 1980-02-07 JP JP55014268A patent/JPS5825489B2/en not_active Expired
- 1980-02-07 BR BR8000747A patent/BR8000747A/en not_active IP Right Cessation
- 1980-02-08 NZ NZ192835A patent/NZ192835A/en unknown
- 1980-02-11 GR GR61185A patent/GR73136B/el unknown
- 1980-02-11 DE DE8080100691T patent/DE3060983D1/en not_active Expired
- 1980-02-11 ES ES488470A patent/ES488470A0/en active Granted
- 1980-02-11 EP EP80100691A patent/EP0015409B1/en not_active Expired
- 1980-02-11 YU YU358/80A patent/YU40590B/en unknown
- 1980-02-11 CA CA345,382A patent/CA1125670A/en not_active Expired
- 1980-02-11 NO NO800349A patent/NO149762C/en unknown
- 1980-02-11 AT AT80100691T patent/ATE1695T1/en not_active IP Right Cessation
- 1980-02-11 MX MX181143A patent/MX155944A/en unknown
- 1980-02-11 AR AR279929A patent/AR225914A1/en active
- 1980-02-12 IN IN161/CAL/80A patent/IN152147B/en unknown
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US11274235B2 (en) | 2015-04-24 | 2022-03-15 | 3M Innovative Properties Company | Acrylic adhesive compositions and acrylic adhesive tapes which enable clean removal from delicate surfaces |
Also Published As
| Publication number | Publication date |
|---|---|
| GR73136B (en) | 1984-02-07 |
| ATE1695T1 (en) | 1982-11-15 |
| AU5500380A (en) | 1980-08-21 |
| NO149762B (en) | 1984-03-12 |
| JPS55106513A (en) | 1980-08-15 |
| IN152147B (en) | 1983-10-29 |
| NZ192835A (en) | 1984-07-06 |
| FI800324A (en) | 1980-08-13 |
| ES8101399A1 (en) | 1980-12-16 |
| YU35880A (en) | 1982-10-31 |
| FI64747B (en) | 1983-09-30 |
| FI64747C (en) | 1984-01-10 |
| EP0015409A1 (en) | 1980-09-17 |
| SE7901181A0 (en) | 1980-08-13 |
| DE3060983D1 (en) | 1982-12-02 |
| ES488470A0 (en) | 1980-12-16 |
| SE7901181L (en) | 1980-08-13 |
| YU40590B (en) | 1986-02-28 |
| BR8000747A (en) | 1980-10-21 |
| EP0015409B1 (en) | 1982-10-27 |
| AR225914A1 (en) | 1982-05-14 |
| JPS5825489B2 (en) | 1983-05-27 |
| NO800349L (en) | 1980-08-13 |
| NO149762C (en) | 1984-06-20 |
| MX155944A (en) | 1988-05-27 |
| AU535897B2 (en) | 1984-04-12 |
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