Flue Gas Cleaning System

Abstract

This application relates to a system or method for removing solid particles and / or gaseous constituents from flue gas, the system comprising: two or more filter chambers (10) with a plurality of filter bags, each filter bag having a filter surface through which particles are separated from the flue gas flow passing therethrough; at least one header tank with cleaning air at a controlled pressure, the header tank connected to a cleaning air supply source and in fluid communication with at least one flow valve; and a first controller configured to control the opening and closing of the flow valves in response to data input indicating that the differential pressure across all filter chambers of the system has reached a predetermined set value. The system uses the first or second controller to control the residence time of the flue gas by adjusting: i. the pressure of the cleaning air in the header tank based on a measured time between two successive pulses to maintain a constant average residence time of the flue gas in all filter chambers; and / or ii. the frequency of individual cleaning of each filter chamber based on measurements of the differential pressure and gas flow rate per chamber to balance the residence time of the flue gas in all filter chambers in the filter system.

Description

[Technical Field]

[0001] SUMMARY OF THE INVENTION The present application relates to a system and method for removing solid particulates and / or gaseous constituents from flue gas using a fabric scrubbing filter. [Background technology]

[0002] Fabric filter systems, also known as baghouses, are air pollution control devices that remove particles and gaseous components from air or gas emitted from industrial plants, such as incineration plants, power plants, and food processing plants. A typical fabric filter system consists of one or more chambers, each containing an array of filters, commonly called filter bags (or simply "bags"), which act as a filter medium. Particle-laden gas or air enters the fabric filter and is sucked through either the inner or outer bag, depending on the cleaning method. Dust accumulates and forms a layer known as a filter cake. The filter cake itself acts as a filter element, and the particles that make up the filter cake capture the incoming fine particles from the gas, which are then released into the environment. In so-called dry flue gas cleaning systems, absorbents, such as hydrated lime or sodium bicarbonate, are used in the filter cake to absorb acidic gas components, such as SO2 and HCl, present in the flue gas.

[0003] The buildup of filter cake on the filter fabric makes it difficult for air and gas to move through the filter, and at some point the filter's ability to continue filtering particles is reduced. Therefore, fabric filters need to be cleaned by removing at least some of the filter cake. There are various cleaning methods that can be applied for this purpose, the most common being mechanical shakers, countercurrent air, and pulse jets.

[0004] Cleaning can be done "off-line" or "on-line."

[0005] Offline cleaning typically requires the presence of multiple filter chambers to allow for chamber-by-chamber cleaning. When a filter chamber requires cleaning, it is isolated from the main airflow. Such an offline cleaning system is disclosed in U.S. Patent No. 5,623,399, which relates to a method for cleaning a multi-chamber fabric filter device, particularly fabric filters housed in various filter chambers of a dust collector. The filter chambers are cleaned in a fixed sequence: when the pressure differential of the dust collector reaches an upper limit, one of the filter chambers is isolated and the filter element housed therein is cleaned, after which the isolated chamber is returned to service. When the pressure differential of the dust collector next reaches an upper limit, another of the filter chambers is isolated and cleaned. This allows for continuous operation of the dust collector and allows the pressure differential of the dust collector to be maintained within a relatively narrow range. One major drawback of offline cleaning is that it typically involves the removal of the entire filter cake of the chamber, which has been shown to result in a loss of flow resistance and insufficient absorption of particulates and / or acid gas components over an extended period of time.

[0006] An online cleaning system does not require isolation of the filter chamber requiring cleaning. The present invention relates to online cleaning. In particular, the present application relates to a pulse jet filter system that uses pulses of high-pressure air to remove filter cake buildup on a filter fabric. During operation, these pulses or blasts of pressurized air initially dynamically expand the filter fabric, which is typically disposed on a cage or frame, thereby disrupting the particle layer and separating it from the filter fabric. The separated particulates are typically collected in a hopper at the lower end of the baghouse. Such online systems are well known in the art. An example of this general type of filter system is disclosed in U.S. Patent No. 5,627,999 to Colley et al.

[0007] While it is well established in the art how filter fabrics are cleaned by pulse jets, there is no consensus on how best to determine when a particular filter or row of filters should be cleaned, or in other words, how to determine the optimal time between subsequent operations of a pulse jet cleaning system to clean the filters (which is typically done row by row).

[0008] Some pulse-jet cleaning systems employ a scheduled cleaning protocol, simply activating the pulse-jet cleaning at preset intervals. Other systems use the differential pressure across the filter media in the baghouse or filter chamber to determine when to activate the pulse-jet cleaning. The more particles that accumulate on the filter media, the more difficult it becomes for air to pass through the particle layer (filter cake), resulting in a higher differential pressure across the filter media. As a result, systems have been developed that monitor the pressure drop across the fabric filter and implement a scheduled cleaning process whenever the pressure drop reaches a certain level.

[0009] Patent Document 3 discloses a bag filter pulse control system that includes a pressure measurement unit for measuring the pressure in the inlet duct, the pressure in the discharge duct, the pressure in each filter section, and the supply pressure. A controller is provided that performs pulse control based on the information measured by the pressure measurement unit. This allows the user to select and apply various operating modes.

[0010] Patent Document 4 discloses a method for controlling the cleaning of a multiple baghouse fabric filter system, particularly a reverse gas flow type. This system and method controls the cleaning of an industrial filter system. The cleaning cycles of the individual baghouses are staggered in a predetermined manner so that the peak resistance of each baghouse coincides with the low resistance of the other baghouses. Because the peak resistances are offset, the peak pressure drop is reduced.

[0011] Regardless of the cleaning frequency, pulse-jet cleaning typically cleans the filter thoroughly by applying a pressure wave strong enough to remove all dust particles from the filter cake, leaving a very small amount of cake remaining after the pulse, approaching zero. However, as previously mentioned, the filter cake also acts as a filter element, and some particulates are necessary on the filter media to capture incoming particulates and absorb gaseous components not captured by the bag itself. For example, in a dry flue gas cleaning system, filter bags with a thin residual cake thickness after cleaning absorb only a small amount of acid gases and offer almost no flow resistance, resulting in nearly zero residence time for flue gases. As a result, the total amount of acid gases passing through a bank of bags immediately after cleaning will be significantly higher than a bank of bags that has developed a thick filter cake since the previous cleaning. On the other hand, a thick filter cake also reduces filter performance. Therefore, the filter efficiency of the baghouse depends on the presence of an optimum dust layer on the filter cloth, but for the reasons mentioned above, pulse jet cleaning systems used in the art are characterized by a filter cake thickness that constantly fluctuates between a minimum thickness after a pulse and a maximum thickness just before the next cleaning pulse.

[0012] Furthermore, pulse jet cleaning systems known in the art typically operate at a constant air pressure to clean the filter rows. The primary drawback of systems using constant air pressure is that they tend to shorten the wear life of the filter fabric and often use excessive energy. This is because the greater the pulse pressure utilized, the greater the wear on the filter fabric. Therefore, when using constant air pressure, it is likely that the air pressure will be set too low, resulting in poor cleaning performance, or that the air pressure will be set higher than necessary to effectively clean the filter fabric, placing excessive stress on the filter media. Furthermore, in the latter case, the system is inefficient because it utilizes more energy than is necessary to accomplish the cleaning task.

[0013] Finally, multi-chamber bag filters typically have uneven gas and particle distribution within the chambers. This results in differences in cake formation rate, average cake thickness, and the velocity of gas passing through each individual filter cake in each chamber, i.e., residence time. Furthermore, the residence time of flue gas within the filter cake also varies depending on the filter bag or row of filter bags within a filter chamber. This difference in residence time is problematic because some components, particularly acid gas components, require a certain amount of time in contact with the absorbent material. If residence times vary across the filter row or filter chamber, overall adequate absorption of these substances cannot be guaranteed.

[0014] Therefore, a need exists for a baghouse pulse jet cleaning method or system that allows for optimal cleaning efficiency, reduces slip-through of components absorbed in the filter cake, and extends the wear life of the filter media. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] U.S. Patent No. 4,500,326 [Patent Document 2] U.S. Patent No. 3,726,066 [Patent Document 3] Korean Patent Publication No. 2019-0081124 [Patent Document 4] U.S. Patent No. 4,507,130 Summary of the Invention [Means for solving the problem]

[0016] This problem is solved by the system defined in claim 1 and the method defined in claim 12. Preferred embodiments follow from the dependent claims.

[0017] Specifically, the present invention provides a system and method for removing particulate and / or gaseous components from flue gas using a fabric filter in a filter chamber, which maximizes absorption performance while reducing energy consumption and extending filter life. The system and method are further suitable for removing acidic gaseous components, such as SO2, from flue gas and minimizing gas slip of the acidic gaseous components.

[0018] Throughout this application, the following definitions apply: The term "flue gas" refers to any type of gas stream emitted from an industrial plant containing solid particles (e.g., dust or fly ash) and / or gaseous components that need to be removed before the flue gas is released into the environment. To remove these components, the flue gas passes through conventional or membrane filter elements, such as filter bags or filter cartridges, which may incorporate fixed or replaceable sorbents in the filter material or filtrate, i.e., in the filter cake accumulated upstream of the filter.

[0019] "Residence time" refers to the time required for gas to pass through the filter cake, which depends on the thickness of the filter cake and the velocity of the gas flow.

[0020] Cleaning systems used in accordance with the present invention typically include multiple filters (sometimes referred to as "filter bags," "filter cloths," or "filter media") arranged in a row. Typically, such systems include multiple cleaning chambers, each containing multiple rows of filters. Each filter is cleaned with a cleaning pulse, i.e., a boost of compressed air. Typically, the filter bags in a row are pulse cleaned simultaneously.

[0021] The term "cycle time" is used to describe the time required to pulse clean all of the filter bags in a filter system once.

[0022] Particles in the flue gas that cannot pass through the filter accumulate on the upstream filter surface. This mass of accumulated particles is called the filter cake. In pulse jet cleaning, the pulse strength can be set so that not all of the filter cake is removed by the pulse. In this case, the filter cake has a static and a dynamic part. That is, the static part remains on the filter bag after pulse cleaning, while the dynamic part is removed by pulse cleaning and accumulates in the time between two cleaning pulses.

[0023] According to the present invention, there is provided a flue gas scrubbing system for removing solid particles and / or gaseous constituents from flue gas, the system comprising: two or more filter chambers comprising a plurality of filter bags, each filter bag having a filter surface where particles are separated from a flue gas flow passing through the filter surface, and particles accumulate upstream of the filter surface to form a filter cake; at least one header tank provided with cleaning air at a controlled pressure, the header tank connected to a cleaning air supply source and in fluid communication with at least one flow valve, the opening of which causes pulses of cleaning air to flow through at least one pulse air pipe towards a group of filter bags in a particular filter chamber to remove particles from the filter surface; and a first controller configured to control the opening and closing of the flow valve in response to data input indicating that a differential pressure drop across all filter chambers of the filter system or across an individual filter chamber has reached a predetermined set value.

[0024] The opening of the flow valve thus triggers a cleaning pulse. Preferably, the flow valve is controlled in response to the sum of the differential pressures, ie the occurrence of a pressure drop in the differential pressure across all filter chambers.

[0025] An important element of the present invention is that the first or second controller is configured to control the residence time of the flue gas by adjusting: i. the pressure of the cleaning air in the header tank based on the measured time between two successive pulses to maintain a constant average residence time of the flue gas in the filter cake in all filter chambers; and / or ii. adjusting the individual cleaning frequency of each filter chamber based on the measured differential pressure and gas flow rate per chamber to balance the residence time of the flue gas in the filter cake in all filter chambers in the filter system.

[0026] Thus, the present invention identifies two aspects that make it possible to improve the cleaning efficiency or cleaning "performance" of flue gas cleaning systems in which cleaning can be carried out "online", i.e. during normal operation.

[0027] The first aspect is the regulation of the cleaning air pressure in the header tank, which depends on the time between two consecutive cleaning pulses (i.e., cleaning frequency). It is customary to initiate a cleaning pulse when the differential pressure across all filters in the filter chambers reaches a given set value. While prior art systems have proposed varying the pulse width to maintain a constant differential pressure, the system of the present invention aims to maintain a constant mean residence time of flue gas in all filter chambers, regardless of the set differential pressure, by adjusting the pressure of the cleaning air in the header tank. This approach is based on the finding that for a given total differential pressure set value that triggers the next pulse and a given particle concentration in the flue gas (i.e., upstream of the filter), there is a specific relationship between the cleaning air pressure and the cleaning frequency. Simply put, a high cleaning pressure removes all the filter cake from the filter bag, thereby leading to a high cleaning efficiency. After complete removal of the filter cake, it takes a long time for a new (total) filter cake to form, which creates a sufficiently high differential pressure to trigger the next cleaning pulse. Therefore, the cleaning frequency is low. On the other hand, at low cleaning pressures, not all of the filter cake is removed (i.e., there is residual filter cake on the filter after the pulse) and the differential pressure set point is reached in a shorter time, resulting in lower cleaning efficiency and higher cleaning frequency.

[0028] In view of the above, the system of the present invention uses a controller designed to adjust the pressure of the cleaning air in the cleaning tank until the time between two cleaning pulses reaches a predetermined set value. This ensures that the average time (i.e., residence time) that the flue gas spends in a particular filter cake during each cleaning cycle (each filter bag is cleaned once) is constant. Pulse width adjustment is not required (although it can be done if necessary). This avoids the aforementioned drawbacks of pulse jet cleaning systems that operate at a constant air pressure to clean the filter rows.

[0029] To improve the quality of control, the pressure of the scrubbing air in the header tank is preferably adjusted further depending on the measured particle concentration in the flue gas and / or the estimated bulk density of the filter cake, which can be estimated from a sample of the filter cake taken from the hopper (i.e., where the exfoliated particles are collected).

[0030] The second aspect is to adjust the individual cleaning frequency of each filter chamber depending on the measured differential pressure and gas flow rate for each filter chamber. It has been found that the ratio of the measured differential pressure to the measured gas flow rate for a particular filter chamber is an indirect indicator of the particle concentration in the flue gas ("flue gas load"). Based on this and the further finding that the rate of filter cake formation increases with the flow rate of flue gas through the filter chamber and the particle concentration in the flue gas, the cleaning frequency can be adjusted so that chambers with faster cake formation are cleaned more frequently than chambers with slower cake formation. The average residence time and cleaning frequency are inversely related to each other. Therefore, by controlling the cleaning frequency of each individual chamber, the average residence time of the flue gas in the filter cake of each chamber can also be controlled. This allows the residence time of the flue gas to be balanced across all filter chambers, reducing the difference in residence time between two filter chambers. This allows the cleaning performance of each cleaning chamber to be optimized. In particular, in dry or semi-dry gas scrubbing systems, where an absorbent is injected into the flue gas upstream of the filter to absorb acid gas components, a balanced residence time avoids chambers with low absorption rates, thereby improving the overall acid absorption rate.

[0031] Preferably, both the pressure of the cleaning air in the header tank and the frequency of cleaning of each filter chamber are controlled to provide optimum residence time, and therefore optimum cleaning efficiency and maximum absorption efficiency.

[0032] To regulate the pressure of the cleaning air in the header tank, the controller preferably controls the opening and closing of at least one pressure control valve. A preferred type of pressure control valve is a proportional pressure control valve operated by adjusting the pressure set point of the valve, preferably one that is continuously adjusted.

[0033] Therefore, the pressure of the cleaning air in the header tank can be adjusted independently of the overall differential pressure.

[0034] The system of the present invention is particularly suited for removing particulates and acidic gaseous components from flue gas. Therefore, it is preferably a dry or semi-dry gas scrubbing system, in which an absorbent is injected into the flue gas upstream of the filter to absorb the acidic gaseous components. The absorbent is capable of absorbing acidic gaseous components, such as SO2 and HCl, under the operating conditions of the filter system employed. Preferred absorbents are hydrated lime and sodium bicarbonate. After the scrubbing pulse, the dynamic filter cake containing the absorbent can be recycled. Notably, the residual (static) filter cake generally contains little absorbent and is therefore largely inactive with respect to acidic gas absorption.

[0035] To regulate the individual cleaning frequency of each filter chamber, knowledge of the differential pressure and gas flow rate per chamber is required. Regarding the latter, prior art systems typically use a single flow measurement device that measures the sum of all chamber flows. It is often assumed that higher differential pressures across the chamber tubesheets are caused by higher gas flow rates through the chambers.

[0036] However, this assumption is only true if the particle distribution is balanced and all chambers receive the same amount of particles at the chamber inlet. Furthermore, this only applies if filter cleaning is performed at the same frequency for all chambers. To improve the accuracy of gas flow measurement, in the system of the present invention, each chamber preferably includes a chamber outlet connected to the clean gas duct, and a gas flow measurement device is installed downstream of each chamber outlet.

[0037] Preferably, each gas flow measurement device is located in a separate outlet flow path section fluidly connecting the chamber outlet of the associated filter chamber with the clean gas duct, thereby further improving even distribution of gas from a particular filter chamber to the inlet of the associated gas flow measurement device.

[0038] Once the gas flow rates for each chamber are measured individually, there is no advantage to keeping the gas flows from the chamber outlets separate, so it is preferred that the individual outlet flow path sections of all filter chambers join into a common clean gas duct downstream of the gas flow measurement device.

[0039] Considering that the velocity of the gas at the chamber outlet may vary significantly, the gas flow measurement device is preferably arranged for integral gas flow measurement. Preferably, the gas flow measurement device is a Venturi flow meter.

[0040] In addition to the systems described above, the present invention also provides a method for removing solid particles and / or gaseous constituents from flue gas, the method comprising the steps of: a) providing a filter system according to any one of the preceding claims, the system comprising: two or more filter chambers each comprising a plurality of filter bags, each filter bag having a filter surface at which particles are separated from a flue gas flow passing over said filter surface; and at least one header tank provided with cleaning air at a controlled pressure, the header tank connected to a cleaning air supply source and in fluid communication with at least one flow valve, the opening of which causes pulses of cleaning air to flow through the at least one pulse air tube towards the filter bags and remove particles from the filter surface. a header tank configured to remove air from the header tank; at least one pressure control valve configured to control the pressure of air in the header tank; a first controller configured to control the opening and closing of the flow valves in response to a data input indicating that the differential pressure drop across the filter bags has reached a given set value; and means for measuring the cleaning pulse frequency, and / or means for measuring the differential pressure and gas flow rate for each filter chamber; and b) determining particle concentration in the flue gas and measuring the cleaning pulse frequency; and / or measuring the differential pressure and gas flow rate per chamber.

[0041] The method further comprises the step of: c) using the first controller or the second controller, adjusting the pressure of the cleaning air in the header tank based on the measured cleaning pulse frequency to maintain a constant average residence time of the flue gas in all filter chambers; and / or adjusting the cleaning frequency for each filter chamber based on measurements of the differential pressure and gas flow rate per filter chamber to balance the residence time of the flue gas in all filter chambers in the filter system.

[0042] The pressure of the cleaning air in the header tank is preferably adjusted further depending on the measured particle concentration in the flue gas and / or the estimated bulk density of the filter cake, thereby improving the control of the cleaning air pressure.

[0043] The method of the present invention is preferably used in dry flue gas scrubbing systems for removing particulate and acid gas components from flue gases.

[0044] To enable highly accurate gas flow measurements, the gas flow rate for each filter chamber is preferably measured using a respective gas flow measuring device, preferably a Venturi flow meter, located downstream of the outlet of that chamber, i.e., there are preferably an equal number of filter chambers and gas flow measuring devices.

[0045] The preferred features of the individual gas flow measurements are described in further detail in connection with the accompanying figures. [Brief explanation of the drawings]

[0046] [Figure 1A] FIG. 1A illustrates a portion of an embodiment of a filter system according to the present invention, including six filter chambers arranged in two filter rows, each filter chamber having a chamber outlet connected to a respective flow measurement device. [Figure 1B] FIG. 1B shows a cross section through the chamber outlet and a row of gas flow measurement devices of the system of FIG. 1A. [Figure 1C] FIG. 1C is a perspective view of the two rows of chamber outlets and associated gas flow measurement devices of FIG. 1A. DETAILED DESCRIPTION OF THE INVENTION

[0047] FIG. 1A illustrates a portion of a flue gas scrubbing system according to an embodiment of the present invention. In the illustrated example, the system includes six filter chambers 10 within respective tubular housings 12 having a rectangular cross-section main upper section 14 and a tapered lower collection section 16 ("hopper") for collecting particles filtered from the flue gas. Internally, each filter chamber contains multiple rows of filter bags (the interior of the filter chambers is not shown). The illustrated system is designed for dry flue gas scrubbing, in which an absorbent, such as hydrated lime or sodium bicarbonate, is injected into the flue gas upstream of the filter to absorb acid gas components from the flue gas. Injection of the absorbent occurs through a gas duct-shaped reactor 17 in the illustrated embodiment. However, other reactor shapes and designs are naturally possible.

[0048] At predetermined time intervals, the upstream face of the cleaning bags is cleaned by pulses of compressed cleaning air to remove accumulated particles (filter cake). The cleaning air is released at a determined pressure from a header tank and supplied to all or a group (e.g., a row) of filter bags in a particular filter chamber via a pulse air line. The filter bags, header tank, and pulse air line are not shown. These components of a pulse jet filter cleaning system are well known in the art and are described, for example, in U.S. Patent No. 5,649,997.

[0049] Particulate matter separated from the filter surface by the pulse is collected in the collection section 16 for subsequent removal. If a sorbent is used to absorb gaseous components from the flue gas, the sorbent accumulates in a filter cake. Typically, at least a portion of the sorbent-containing filter cake separated from the filter surface and collected in the collection section is recycled. In the illustrated embodiment, the sorbent-containing filter cake material is reinjected through a reactor 17. Each filter chamber has a chamber inlet 18 fluidly connected to a flue gas supply duct 20 for supplying flue gas containing solid particles and acidic gaseous components requiring removal. Only one flue gas supply duct is visible in FIG. 1A. Each filter chamber 10 further includes a respective chamber outlet 22 for discharging the cleaned flue gas after passing through the filter bag within the filter chamber. Each chamber outlet 22 is fluidly connected to an associated individual outlet flow path section 24, which includes a respective flow measurement device 26 for measuring the integral gas flow rate of the associated filter chamber. The separate outlet flow path sections 24 of all filter chambers 10 merge further downstream into a common clean gas duct 28. Installing individual flow measurement devices 26 for each filter chamber 10 and locating them in their respective flow path sections 24 ensures uniform gas distribution from a particular filter chamber to the inlet of the associated flow measurement device. This allows for accurate measurement of gas flow from each individual filter chamber. The flow measurement device can be a Venturi flow meter or an array of instruments (such as a Pitot or Prandtl tube) that measure the dynamic pressure of the gas flow. The integral measurement provides a stable and accurate flow rate regardless of fluctuating gas flow velocity profiles.

[0050] The system further includes a controller (not shown) for adjusting the cleaning frequency of each filter chamber based on measurements of the individual differential pressure and gas flow rate through each filter chamber. More specifically, the measured differential pressure per chamber and the measured individual chamber flow rates are used as data inputs for the controller to adjust the cleaning frequency of each filter chamber with the goal of maintaining a constant residence time in each chamber.

[0051] FIG. 1B shows a separated cross-section through the chamber outlet 22 of the system of FIG. 1A and the row of gas flow measurement devices 26. Here, it is clearly shown that each filter chamber outlet 22 is fluidly connected to an independent individual outlet flow path section 24 that includes its respective gas flow measurement device 26. Further downstream, it is shown that all of the outlet individual flow path sections come together and merge into a common clean gas duct 28. In the illustrated embodiment, three filter chambers are arranged in a row, and the outlet flow path sections 24 of these three filter chambers extend parallel to each other and at a distance in the vertical direction before merging into the common clean gas duct 28.

[0052] FIG. 1C shows a perspective view of two rows of chamber outlets 22, the associated individual outlet flow path sections 24, and the associated gas measurement devices 26 separated from each other. The individual outlet flow path sections 24 of all six filter chambers merge into a common clean gas duct 28.

Claims

1. 1. A flue gas scrubbing system for removing solid particles and / or gaseous constituents from a flue gas, comprising: Two or more filter chambers (10) comprising a plurality of filter bags, Each filter bag has a filter chamber (10) having a filter surface where particles are separated from the flue gas flow passing through the filter surface, and particles accumulate upstream of the filter surface to form a filter cake; at least one header tank containing cleaning air at a controlled pressure, said header tank connected to a cleaning air source and in fluid communication with at least one flow valve, the opening of which causes pulses of cleaning air to flow through at least one pulse air tube toward a group of filter bags in a particular filter chamber to remove particles from the filter surfaces; a first controller configured to control the opening and closing of the flow valves in response to a data input indicating that a differential pressure across all filter chambers of the system has reached a predetermined set point; A flue gas scrubbing system comprising: The first controller or the second controller may perform the following adjustments: i. the pressure of the cleaning air in the header tank based on the measured time between two successive pulses to maintain a constant mean residence time of the flue gas in the filter cake in all filter chambers; and / or ii. Individual cleaning frequencies for each filter chamber based on chamber-to-chamber differential pressure and gas flow measurements to balance the residence time of the flue gas in the filter cake for all filter chambers in the filter system. a control system for controlling the residence time of the flue gas by adjusting the

2. 2. The system of claim 1, wherein the controller is operable to adjust both the pressure of the cleaning air in the header tank and the cleaning frequency for each filter chamber.

3. 3. The system according to claim 1, wherein the controller is a PID controller.

4. 4. The system according to claim 1, wherein the pressure of the cleaning air in the header tank is regulated by opening and closing at least one pressure control valve controlled by the controller.

5. 5. A system according to claim 4, characterized in that the pressure control valve is a proportional pressure control valve which operates by adjusting, preferably continuously, the pressure set point of the valve.

6. 6. A system according to claim 1, wherein the pressure of the cleaning air in the header tank is regulated independently of the overall differential pressure.

7. 7. The system according to claim 1, wherein the pressure of the scrubbing air in the header tank is further adjusted depending on the measured particle concentration in the flue gas and / or the estimated filter cake bulk density.

8. 8. The system according to claim 1, wherein each filter chamber (10) comprises a chamber outlet (22) connected to a clean gas duct, and wherein a gas flow measuring device (26) is installed downstream of each chamber outlet (22).

9. 9. The system of claim 8, wherein each gas flow measurement device (26) is installed in a separate outlet flow path section (24) fluidly connecting the chamber outlet (22) of an associated filter chamber (10) with the clean gas duct.

10. 10. The system of claim 9, wherein the individual outlet flow passage sections (24) of all filter chambers (10) merge into a common clean gas duct (28).

11. A system according to any one of claims 8 to 10, characterized in that the gas flow measurement device (26) is provided for integral gas flow measurement and is preferably a Venturi flow meter.

12. 1. A method for removing solid particles and gaseous components from a flue gas, comprising: a) providing a filter system according to any one of claims 1 to 11, said system comprising: two or more filter chambers (10) each comprising a plurality of filter bags, each filter bag having a filter surface by which particles are separated from a flue gas flow passing through said filter surface; at least one header tank containing controlled pressure cleaning air; a header tank connected to a cleaning air supply and in fluid communication with at least one flow valve, the opening of which causes pulses of cleaning air to flow through at least one pulse air tube toward all or a group of filter bags in a particular filter chamber to remove particles from the filter faces; at least one pressure control valve configured to control the pressure of the air in the header tank; a first controller configured to control the opening and closing of the flow valves in response to a data input indicating that a differential pressure across all filter chambers in the filter system has reached a predetermined setpoint; means for measuring the frequency of said cleaning pulses and / or means for measuring the differential pressure and gas flow rate for each filter chamber; Providing a system according to any one of claims 1 to 11, the system comprising: b) determining the particle concentration in the flue gas and measuring the time between two successive pulses; and / or measuring the differential pressure and gas flow rate per chamber; c) using the first controller or the second controller, adjusting the pressure of the cleaning air in the header tank based on the measured cleaning pulse frequency to maintain a constant mean residence time of the flue gas in all filter chambers; and / or based on differential pressure and gas flow measurements from filter chamber to filter chamber to balance the residence time of the flue gas in all filter chambers in the filter system. adjusting the cleaning frequency for each filter chamber; A method comprising:

13. 13. The method of claim 12 for use in a dry flue gas scrubbing system for removing particulates and acid gaseous constituents from said flue gas.

14. 14. The method of claim 13, wherein an absorbent is injected into the flue gas upstream of the filter to absorb acid gaseous components.

15. 15. The method according to any one of claims 12 to 14, characterized in that the gas flow rate per filter chamber is measured using a respective gas flow measuring device (26), preferably a Venturi flow meter, installed downstream of the associated chamber outlet (22).

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