WO2007079220A2

WO2007079220A2 - Gas phase particulate filter house

Info

Publication number: WO2007079220A2
Application number: PCT/US2006/049569
Authority: WO
Inventors: Calvin E. Phelps
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-12-30
Filing date: 2006-12-29
Publication date: 2007-07-12
Anticipated expiration: 2008-06-30
Also published as: WO2007079220A3

Abstract

An array of filters (53, 54, 73) installed within an enclosure, shell, or housing (40) into which a gas phase stream containing small concentrations of solids or particulates is introduced for purposes of separating the solids from the gas (22). Solids separation is accomplished by dry filtration when the gas (22) is forced by pressure through filter openings that are smaller than the size of the particulates. The filters (53, 54, 73) are constructed with apertures of micron and nanometer dimensions.

Description

GAS PHASE PARTICULATE FILTER HOUSE

CROSS REFERENCE TO RELATED APPLICATIONS This application claims the benefit of the filing date of United States

Provisional Application for Patent Serial No. 60/755,254 filed December 30, 2005, which is fully incorporated herein by reference.

BACKGROUND

An apparatus for performing solid-gas phase separation in gas-based streams is provided.

Power and industrial plants produce flue gas during the combustion of fossil fuels that contain micron and nanometer sized flyash particles in a range of up to 100 microns, which must be separated from the gas for disposal, in order to reduce emissions into the atmosphere. The larger particles are removed in boiler equipment before introduction to highly efficient particulate separation apparatus. Conventional apparatus can collect particulates at 99+% efficiency (particulates entering minus particulates leaving divided by particulates entering multiplied by 100), primarily by the methods of electrostatic precipitation (ESP) or bag house (BH) filtration. Particulates can be expressed in weight flow per unit of time (for example, kilograms per hour or pounds per hour) or concentration per volume of flue gas (for example, grains per cubic meter or grains per cubic foot of flue gas, where 7000 grains is equivalent to one pound of weight and 15452 grains is equal to one kilogram). Typically, ESP and BH apparatus require that gas velocities be less than 300 feet per minute (fpm) (or 91.44 meters per minute (mpm)) to design for particulate collection efficiencies near 100%. Since flue gas normally flows in ducts from the boiler equipment to these apparatus in the velocity range of 3000-4000 feet per minute (or 914.4—1219.2 meters per minute), the ducts must be enlarged or split into two or more gas streams, and the apparatus must be necessarily large in plants with large flue gas volumes, in order to lower the flue gas velocities to less than 300 fpm (or 91.44 mpm).

One ESP or BH is typically installed into each of the split gas streams in order to design the apparatus and footprints within commercially available design ranges. Approximately 50% of the flyash flowing to these apparatus from the combustion of pulverized coal can be less than 10 microns in size. Particulates of less than 10 micron are normally referred to as nanometer sized particulates. The collection of nanometer sized particulates is accomplished less efficiently than micron size particulates.

Current EPA regulations control particulate matter with diameters of 10 micrometers or less (PMlO). The United States Environmental Protection Agency (EPA) has promulgated additional standards that will require efficient collection of fine particulate matter with diameter of 2.5 microns or less (PM2.5). The subject particulate filter house (PFH) is the only low cost alternative to an

ESP or BH that would provide a solution for both PMlO and PM2.5 particulate emission regulations.

The subject PFH would represent a significantly lower capital investment than an ESP or BH, and lower operating and maintenance costs. The PFH would have a smaller footprint, and smaller less complex connecting ductwork, and would efficiently collect particulates to meet current and pending EPA regulations. The PFH would provide significantly higher reliability factors and lower planned and forced outage rates for the unit. Lost generation capacity, or de-ratings, caused by stack discharge opacity limitations would be regained and fuel-purchasing flexibility would be increased. The PFH may also be used to collect particulates from other dry gas based streams.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a rigid frame electrostatic precipitator (ESP) apparatus.

FIG. 2 is a schematic representation of a pulsejet bag house (BH) apparatus.

FIG. 3 is a side elevational view of a two stage vertical panel particulate filter house

(PFH). FIG. 3-1 is a side elevational view of a two stage vertical panel particulate filter house

(PFH).

FIG. 3-2 is a side elevational view of a two stage horizontal panel particulate filter house (PFH). FIG. 3-3 is a cross sectional elevational view of a two stage horizontal panel filter house (PFH).

FIG. 3-4 is a schematic representation of a two stage FH filter bag.

FIG. 4 is a schematic horizontal cross sectional view of a single stage particulate filter house compartment.

FIG- 5 is a perspective view of a two stage particulate filter house with one front panel and the dust hoppers removed to show the internal equipment.

FIG. 6 is a front elevational view of a particulate filter house.

FIG. 7 is a plan view of the particulate filter house with a clean air plenum and tube sheet removed.

FIG. 8 is another plan view of a particulate filter house showing an optional filter bag cleaning, isolation, and leak detection systems.

FIG. 9 is a schematic representation of the air flow within a particulate filter house.

FIG. 10 is a close up view of the particulate filter house filter bag outlet nozzle depicting an optional method to pressurize and expand bags for cleaning.

DETAILED DESCRIPTION ESP Apparatus

A large commercial ESP 10 for cleaning large gas volumes in fossil fuel fired power plants or industrial plants is normally designed as shown in FIG 1. Gas flows horizontally through the ESP with the entrance 1.1 in the front of the housing (shell) 13 and the exit 12 in the rear of the housing 13. The bottom of the housing is equipped with multiple dust collection hoppers 14, which receive collected dust falling by gravity from the collection plates 15 during the cleaning cycle. The top of ESP housings contain high voltage alternating current electrical supply equipment 16 and rectifiers 18 to convert to direct current 19 for the electrodes 21 suspended vertically down into the gas stream.

In the case of positively charged particulates, the anode equipment may be arranged in geometric patterns of rows and lanes inside the gas stream and can be constructed by suspended wires with weights at the bottom to hold them in alignment, rigid electrodes, or rigid frames 21 to keep the wires in alignment as shown by FIG. 1. This process is normally referred to as providing a corona discharge, or electrical field through which the flue gas 22 and particles flow to impart charges to the particles. The collection plates 15 are suspended in geometric rows and lanes into the gas stream 22 to provide a designed gap on two sides of an anode 21 and are negatively charged to attract and collect the positively charged particles. An ESP has several stages of electrical fields in its front to rear direction by which different field intensities may be controlled to impart charges to the particles and improve collection efficiency, as the gas stream proceeds to the outlet ducts 24 and through the exit 12 as clean gas 28.

Dust cleaning intervals are scheduled to improve collection efficiency by minimizing the amount of re-entrained dust and can be accomplished with automatic vibrators or by rapping with automatic hammers to dislodge the caked dust on the collection plates. Hoppers 14 collect dust after rappers or vibrators 23 dislodge dust from the collection plates 15. Collected dust passes through air lock valves 25 to ash disposal 26. Flue gas velocities near the hoppers must be minimized to avoid re- entrainment of collected dust that has not been evacuated from the hoppers.

Older electrostatic precipitators were designed with about 200 square feet of collecting surface per 1000 cubic feet of gas (SCA) (or 60.96 square meters of collecting surface per 304.8 cubic meters of gas (SCM)) whereas current designs are normally equipped with a minimum of 400 SCA (or 121.92 SCM), which doubles the footprint area needed to install an ESP. Nano particles are more difficult to collect in an ESP and require lower gas velocities and extra electrical fields of anodes and cathodes, which further increase footprint areas.

An ESP is sensitive to changes in coal types, which reduces fuel flexibility. Using lower sulfur fossil fuels is desired to avoid installation of sulfur dioxide (SO₂) scrubbing equipment to meet EPA emission limits. Using lower sulfur fuel may require that flue gas conditioning be used to reduce flyash resistivity, which enables electrical charging of the particles for collection on the oppositely charged collection plates. Many plant installations are load limited to avoid exceeding EPA emission limits. BH Apparatus

A BH designed to filter large gas volumes from power plant or industrial plants is equipped with several thousand bags constructed from porous materials through which the gas passes, which separate the particulates from the flue gas. The bag fabric can be of membrane materials, woven or felted cotton, synthetic, or glass- fiber material in either a tube or envelope shape. A pulsejet type bag house (BH) 30 is depicted in FIG. 2 designed with unfiltered gas 22 on the outside of the bags, which is the most common type of large-scale installation. The open ends of the bags 33 are connected to matched openings on an upper tube sheet 35 through which the clean gas 28 flows above the tube sheet. Unfiltered flue gas 22 enters the inlet 31 at the front of the BH near the bottom above the dust collection hoppers 34 and flows vertically upwards parallel to the axis of the bags 33. The porous bags 33 filter the flue gas 22 and the clean gas 28 flows vertically upwards inside each bag, through the tube sheet 35 to the top plenum 36 above the tube sheet, and through the exit 32 at the back of the BH. A few thousand small vertically inclined bags 33 are suspended in equidistant rows and lanes from an overhead tube sheet 35. This construction provides a seal between the clean gas 28 on the inside of the bags 33 and above the tube sheet 35, and the unfiltered gas 22 below the tube sheet 35 and on the outside of the bags 33. The collected dust is filtered out and collects in cakes on the outside of the bags. The filtering material surface for a pulsejet BH is normally designed at an upper limit of 6 cubic feet of air per minute per square foot of filtering material (A/C = 6) (or 1.83 m³ per min. per 0.3048 m²).

The cleaning cycle for some of these type bag houses require that a section be taken out of service by isolating it with isolation dampers. Then, rapid jet pulses of compressed air are blown into each bag 33 to expand them and dislodge the caked dust so that it falls by gravity into the dust hoppers 34 at the bottom of the BH. Dust may pass through air lock valves 25 to ash disposal 26. This type cleaning requires that the BH be oversized so that full load operation can continue during a cleaning cycle. Some of the pulsejet type bag houses are designed for cleaning without an isolated section. These are cleaned with jet pulses in selected patterns of bags during a cycle to minimize dust re-entrainment.

Maintenance of the bags is an ongoing problem, primarily because of their construction and methods of removing the dust. Bag leaks are difficult to locate because of lack of access and the large number of bags involved. Each bag includes an internal metal wire cage for bag support and alignment of the bags into equidistant rows and lanes to minimize adjacent bag interferences. Erosion damage occurs from internal fabric and cage rubbing, bag to bag rubbing, and by external particulate impingement at velocities that can exceed 300 fpm (or 91.44 mpm). Fabric fatigue bag failures are caused by the method of cleaning, which is performed by bag expansion and contraction. In order to obtain government permitting for continued operation or to avoid load limitations at plants with boiler units equipped with electrostatic precipitators or bag houses that cannot meet particulate emission limits, these apparatus must be modified or demolished and replaced with current larger designs. Often, space is unavailable for this apparatus, . which requires larger footprints. Sometimes modifications entail construction of side streams for installation of up-to-date apparatus so that the combined stream can meet emission limits. These modifications are costly, requiring more ducts and numbers of apparatus, larger footprints, and large booster fans. Use of an ESP or BH to correct current deficiencies on PMlO regulations or to design for PM2.5 regulations economically is currently believed within the industry to require a hybrid ESP-BH combination (AHPC), which would represent a significantly greater capital investment for the owner as compared to a PFH. The AHPC would have increased operating and maintenance costs and have a larger footprint, which would require that installation space be available. The AHPC is designed with two integral stages of collection with the first stage containing an ESP having a lower than normal SCA of about 100 to 200 and the second stage containing a pulsejet bag house with about 25-65% of the normally required number of bags. The APPC integrates the best features from the ESP and BH apparatus with the ESP better at collecting larger particulates and the BH better at collecting smaller particulates. Filter bags for the AHPC are manufactured with membrane materials laminated to a felted or fabric backing. Since these filters are designed to collect nano particulates and to collect from 10 to 15% of the incoming dust, the accumulated dust layer occurs at a slower rate, as does the corresponding pressure loss from this dust layer. The filter bags are designed to A/C ratios in the range of 12 to 24 corresponding with the number of filter bags to be installed. This increase in A/C ratios from normal design parameters of about 6 for a pulse jet BH is possible because the conflicting parameters that occur in single stage collection were separated by the two stages of collection with the ESP stage collecting about 85-90% of the incoming dust as larger particles. However, the AHPC brings the same problems as currently experienced with the individual ESP and BH apparatus.

The apparatus described herein will provide gas phase-particulate filter houses (PFH) able to collect micro and nano sized particulates from gas phase streams at nearly 100% efficiency with entering gas velocities up to 4000 feet per minute (or 1219.2 meters per minute), or as limited by particulate erosion of the construction materials. Therefore, the number of filter house apparatus and the size of their footprints required are less than those required by conventional ESP or BH particulate control apparatus. This subject PFH may modify or replace existing ESP and BH equipment that is operating at marginal performance and may also address the PM2.5 regulations for collecting fine particulate matter.

When considering an application for a coal fired boiler unit that is generating steam to produce 600 megawatts of electricity per hour, the PFH footprint would be about one-half of that required for a BH and about one-third of that required for an ESP for applications to meet PMlO regulations. Additionally, since the PFH would accept flue gas at velocities up to the material particulate erosion limits of about 3600 fpm (1097.28 mpm), the PFH connecting ductwork is considerably smaller and less complex. The associated reduction in ductwork by installing one (1) PFH in lieu of two (2) bag houses or three (3) electrostatic precipitators provides a significant advantage over the BH or ESP. Furthermore, because of the PFH unique design features, equal flow distribution at low velocities can be delivered to the particulate collecting equipment without the necessity of physical or CFD flow modeling studies, which is normally required to specify the installation of flow or mixing devices to reduce pressure loss, and improve flow distribution and collection efficiency.

When considering pending PM2.5 regulations, the relative footprint advantage of a PFH would significantly increase. The PFH would not need to increase in size to meet PM2.5, whereas, the ESP and BH sizes would have to increase significantly to meet these regulations on a continuous basis. Moreover, unique features of the PFH can distribute the gas and dust evenly to the PFH filters at velocities less than 150 φm (or 45.72 mpm) to cause collection of a balanced dust cake layer over the surface of the filters, which improves efficiency and provides other advantages over a BH, such as: 1) preventing damage to the filtering materials, as would be caused by uneven dust weights, extending material life and preserving aperture designs; 2) allowing operation at a lower filter differential pressure between cleanings; 3) the lower dust impact velocities would not alter the filter apertures and blinding would not occur to cause greater pressure losses; 4) by contrast, uneven dust cake distributions as experienced in a BH cause the flue gas to redistribute to another filtering area containing less cake, which would cause higher local velocities and damage to the filter materials; 5) since the PFH first stage panel filters can collect up to 90% of the incoming dust, the second stage filter bags can be designed for higher A/C ratios, resulting in significantly less filtering surface.

Further, the reliability of the PFH would be improved over a BH by these other unique mechanics, such as the PFH cleaning equipment would not inherently cause damage to filter materials, as currently experienced on a BH, in which the filter bags are sometimes overstressed to loosen the dust cake layer. In addition, the PFH cleaning equipment would not overstress the filter material by expanding or bending it excessively, which promotes blinding of the apertures. During a pulse-jet BH cleaning cycle, high-pressure air quickly expands the bags to loosen the dust cakes, but then as rapidly, the re-entrained dust is drawn into the apertures as normal circulation restarts, which entraps dust as the bags deflate. This cleaning action also causes loss in collection efficiency as dust is caused to exit the apparatus.

The PFH includes mechanics to locate a leaking filter during operation and then isolate it so that operation can continue to maximum rating. Also, the cleaning mechanics would isolate small groups of filters for cleaning, which minimizes re- entrainment of dust during the cleaning cycle so that the same dust is not continuously recollected, which extends filtering life. Additionally, the PFH can include structural support features to prevent filter material damage from overstressing due to dust layer dead weights. Furthermore, the PFH filtering materials would have significantly less dust to collect than a BH since most of the dust is removed before reaching the filters. In addition, the PFH would have significantly less dust re-entrainment from the hoppers and during the cleaning cycle so that recollection is minimized. Another mechanic that improves reliability over a BH is that the PFH controls the influent to evenly distribute it to the filtering equipment at less than 150 feet per minute (fpm) (or 45.72 mpm) unbalanced face velocity. By comparison, velocities of influent introduced into current ESP and BH collecting equipment would be limited to an average velocity of 300 fpm (91.44 mpm). However, when considering the inherent flow unbalances experienced in an ESP or BH, the unbalanced velocities would considerably exceed 300 fpm (91.44 mpm). To design an ESP or BH to meet PMlO and PM2.5 regulations, gas and dust velocities and flow unbalances to the collecting equipment must be significantly reduced, which would cause larger footprint sizes and costs. Lastly, the PFH is not dependent on gas conditioning as normally required in an ESP or AHPC apparatus to meet fuel flexibility requirements and collection efficiency.

In the subject PFH apparatus, an array of filters is disposed within an enclosure, shell, or housing into which is introduced a gas phase stream containing small concentrations of solids or particulates, for the purpose of separating the solids from the gas. Solids separation is accomplished by dry filtration when the gas is forced by pressure through filter openings that are smaller than the size of the particulates. The filters are constructed with apertures in micron and nano dimensions. The present apparatus may be installed in fossil fuel fired power plants or industrial plants, or in any other type of plant requiring separation of solids from a gas-based stream. This apparatus may be retrofitted into the existing spaces of prior art apparatus, or within their existing modified housings to meet particulate emission limits and regain lost generation capabilities. The footprint of this apparatus can be more than 50% smaller than prior art apparatus and the connecting ductwork can be proportionately smaller and less complex as shown in the Example Calculations Tables below. This apparatus may be used alone to meet EPA particulate emission limits, or parts of this apparatus may be retrofitted to integrate with prior art apparatus to meet EPA particulate emission limits. FIG. 3 shows a two stage vertical panel Particulate Filter House (PFH) 40 equipped with multiple first and second stage chambers arranged side by side in alternating patterns, so that one side of a first stage chamber is immediately adjacent to one side of a second stage chamber. The gas-based stream can enter the PFH through an inlet duct 41 in the front or rear, or both front and rear of the housing 43. Conventional materials may be used in this PFH configuration, such as porous filters made of cloth, metal, polymer composites, vegetable materials, membranes, substrates, or ceramics. The arrangement of the PFH chamber and its details are heretofore unknown, however.

FIG. 3 shows dirty, or unfiltered flue gas 22 depicted by shaded fill arrows, and clean gas 28 depicted by white filled arrows. Unfiltered or dirty gas 22 may enter the inlet duct 41 in the front housing and flow horizontally into multiple parallel first stage chambers 51, which are individually enclosed and alternately spaced. Each first stage chamber 51 may be open in the front for the gas entrance, enclosed on both sides by standard perforated plates 53, enclosed on the top by a solid tube sheet or seal plate 55, enclosed on the back by an end plate, and enclosed on the bottom by closed, gas tight shut-off dampers 56 to be used during the cleaning cycle. This construction provides that the gas exits the first stage through the perforated plate openings on the sides and flows to the second stage 52. The second stage 52 may comprise multiple chambers, each enclosed by filter material 54 on both sides through which the gas enters the chamber. The remaining second stage enclosure may comprise end plates on the front and rear, a bottom plate, and an open connection on the top that is seal connected to matched openings on the tube sheet or seal plate 55, through which the clean gas 28 may exit to the clean gas plenum 58. This construction provides a seal between the clean gas on the inside of the second stage chambers 52 and above the tube sheet 55, and the dirty or unfiltered gas 22 below the tube sheet 55 and on the outside of the second stage chambers 52. The clean gas 28 may flow vertically upward through the second stage compartments and tube sheet 55, and exit the clean gas plenum 58 through the rear connection. The closed gas tight shut-off dampers 56 shown below the second stage 52 may be used in part of the cleaning cycle, when the dust cakes are dislodged from the outside of the filter material.

Fig. 3-1 provides a cross sectional view A-A from Fig. 3, and is a cross sectional view rearward across the height and width of the PFH through the first stage chambers and centerlines of second stage chambers 52. The dirty or unfiltered flue gas 22, such as from boiler equipment, may enter the front of the PFH horizontally and flow to the inlets 41 of the first stage chambers. The unfiltered flue gas 22 may flow horizontally in first stage lanes toward the rear and exit the first stage chambers 51 through the first stage perforated plate 53 openings on the sides, which shield the second stage filter panel 54 from higher velocity gas and particulates. The first stage perforated plate openings may be on the order of about 2.5 μm to about lOμm.

The perforated plates 53 can considerably reduce the first stage chamber exit gas velocity because their combined open areas can be 50 times, or more, greater than the chamber inlet area as shown in the Example Calculations Tables below. Because of this magnitude of reduction in flue gas 22 and particulate velocities, the larger particles will separate from the gas and fall by gravity to the top of the closed dampers 56 below.

The perforated plates 53 also provide nearly equal gas and particulate distribution to the second stage inlet filter panel 54 because of the equal distribution of the open area holes. This equal distribution improves cloth surface effectiveness when compared to prior art bag houses. Particulates are collected on the outside of the second stage filter panel 54 and the clean gas 28 flows through the filter panel 54, which is constructed with apertures in nano dimensions such as an average diameter of about 50 nm to about 5μm, preferably 50nm to about 2.5 μm. The filter panels 54 may be constructed from known fabric materials as discussed above, and may use the pleated designs conventionally used in bag houses. Framing materials for second stage chambers may comprise materials known in the prior art, such as but not limited to plastics or corrosion resistant metals. The clean gas 28 may flow vertically upwards in the second stage chambers

52, and exit through the top connection and tube sheet 55, flow into the clean gas plenum 58 and exit the PFH through its rear outlet 42.

Fig. 3-2 shows an alternate two stage horizontal particulate filter house PFH 50 arrangement with both the dirty (un filtered) flue gas 22 and clean gas 28 flowing horizontally through the PFH with the inlet 41 at the front of the housing 43 and the outlet 42 at the back of the housing, similar to an ESP arrangement. This arrangement uses a vertical tube sheet 55 on the outlet 42, to match the second stage chamber 52 outlet chamber connections. This arrangement need not incorporate an overhead clean gas plenum 58. The gap between the tube sheet 55 and second stage outlet rim 57 may include a gasket 59, with a force exerted to squeeze the gasket between these two surfaces to ensure sealing. The force may be applied by bolts around the perimeter of the outlet rim 57 threaded into the tube sheet 55, or by adjustment bolts providing tension from the opposite end of the chambers. Other known sealing methods may be used. This arrangement is suitable for retrofitting an existing ESP installation.

Fig. 3-3 shows cross sectional view Al-Al taken from Fig. 3-2, showing a horizontal cross sectional view upwards across the length and width of the PFH 50 through the first stage and centerlines of second stage compartments. The horizontal second stage construction is shown to be similar to the vertically arranged second stage compartments shown in Fig. 3-1. hi certain embodiments, the horizontal compartments in any particular lane do not have spaces between immediately adjacent compartments, because dust can accumulate on the outside tops of the compartments.

Dirty flue gas 22 enters the front of the first stage inlet 41, flowing horizontally into the lanes of the first stage chamber 51, passing through the first stage outlet, that is, the perforated plate 53 sides, to the second stage filter panels 54. Clean gas flows through the second stage filter panels 54, flows horizontally through the tube sheet 55 to the outlet 42 connection on the back of the PFH.

Collected dust re-entrainment is minimized in the second stage during the cleaning cycle with the subject apparatus because of the very low gas velocities. In the case of known bag houses that are cleaned without isolating a particular section for cleaning; dust re-entrainment is a problem since the direction of gas flow opposes the downward falling direction of the collected dust. The subject PFH arrangement avoids re-entrained dust problems. The dampers 56 on the PFH may also eliminate dust re-entrainment problems from the hoppers 44 that are experienced on known apparatus. The bottom dampers 56 may be opened one stage at a time to prevent gas bypassing from the first to the second stage, and to dump the dust into the hoppers 44 without causing dust re-entrainment. After dumping the dust, the dampers are re- closed. Dust may be evacuated from the hoppers using rotary or slide gate air lock type valves 45 to avoid air in-leakage or gas-dust out-leakage.

An alternate method to construct a Particulate Filter House without dampers includes using a greater number of dust hoppers, which are dedicated to either the first stage or the second stage, with plate gas tight seals between the first and second stages. Gas flowing into the first stage at a velocity of 1000 fpm (304.8 mpm) can exit this stage at 20 fpm (6.096mpm) velocity through the perforated plate openings as shown by the Example Calculations Tables, using 50% open area perforated plates. The PFH first stage arrangement provides a much larger exit area through the open areas of the perforated plates along the sides of the chamber than does the inlet area of the chamber at the front of the housing. Perforated plates may be selected with other open areas to suit the desired design conditions. For example, but not for limitation, referring to the Example Calculations using a front inlet arrangement, one first stage chamber inlet dimensions could be reasonably assumed to be 40 feet in height by 1 foot in width (12.192 meters in height by .3048 meters in width), or have a 40 square feet inlet area (12.192 square meters). The perforated plate sides of the first stage chamber could be reasonably assumed to be 40 feet (12.192 meters) in height by 50 feet (15.24 meters) in length. The total exit area of both sides constructed of 50% open perforated plate would be 2000 square feet (609.6 square meters). The ratio of chamber inlet area to exit area is 1/50, which results in an exit velocity of 20 fpm (6.096mpm) (1000 fpm (304.8 mpm) inlet velocity multiplied by the 1/50 ratio).

The filter chambers can be top or bottom supported, or both top and bottom supported, if necessary, with provisions for differential expansion from top to bottom. The filters may be constructed from available pleated fabric materials. The filters may be seal connected to a rigid support frame, to construct compartments.

Another method by which to construct the second stage of a two stage PFH is shown by Fig. 3-4, which shows a filter bag 60 design for the second stage filter panel 54. The bags may connect to the tube sheet 55 in a known manner, but the bags may be aligned in closely spaced rows, forming lanes similar to the panel filter lanes shown in Fig. 3-1. The PFH bag diameters and lengths can be extended beyond prior art dimensions by constructing the bags in multiple segments 61, 62 connected by expansion joints 63, such as a bellows type, for example but not for limitation. Figure 3-4 shows a two-segment bag with an upper bag segment 61, and with the lower bag segment 62 top supported on shelf brackets 64 that are affixed to the second stage framing structure (not shown) for load transfer. External doughnut rings 65a, 65b may be included as part of the bag design to maintain shape and to provide support. A protective boot 66 may be installed over this area as shown to avoid- accumulation of dust, and to allow the dust cake to fall into the dust hoppers below. Arrows 68 in Fig. 3-4 represent the dead weight of the bag and any associated dust cake. Structural guides can be installed from the second stage framing to maintain bag alignment. A bag protector 69 may also provide additional protection. Cleaning methods can include pulsejet, sonic horns, vibrators, rappers or other known means.

FIG. 4 shows a single stage compartment design 70, multiples of which are used for installation in a single stage PFH. The single stage PFH may be substantially arranged as shown in FIG. 3, but without the second stage compartments. The single stage PFH arranges single stage compartments side to side in centerline dimensions to provide lanes between them for the dirty (unfiltered) gas inlets and lane flow. The dirty gas 22 enters the PFH at the front connection and' flows horizontally into the lanes created by single stage filter panels 71, towards the rear on both sides of each single stage compartment. The gas is filtered by the single stage filter panels 71.

FIG. 4 is a horizontal cross sectional view of one single stage compartment, with clean gas flowing vertically upwards (out of the plane of the paper) after filtration by the materials on the sides of the compartment, to the tube sheet or panel plate connection 72. A separate second stage is not required in this PFH because it is incorporated in of the construction of the first stage. The single stage filter material in the panels 71 distributes and filters the gas in one stage. Shielding is not required to prevent erosive damage to the filter material, since it may be made from durable materials, such as but not limited to stainless steels or ceramics. The pleated or bellows type filter construction provides self-shielding to allow dust cake collection.

The dirty flue gas 22 is filtered through the filter materials on the sides of the compartments and the clean gas flows vertically upwards inside the compartments, through the tube sheet or panel plate 72 to the top clean gas plenum (not shown), and exits through the outlet connection. The filter material may be corrosion resistant metal or ceramic plate, which is nano drilled. Flat metal plate can be drilled first, and then bent into pleated or bellow type configurations to increase the amount of filter plate open area, as compared to a flat plate area having the same overall side dimensions. The ceramic plate can be formed into these configurations during manufacturing and then drilled.

Illustrative technologies to economically drill large nano-perforated plates include electron beam drilling equipment which can drill thousands of nano apertures simultaneously down to an average diameter of about 50nm. Other types of materials available for nano filters include woven metal wire mesh screens and other durable materials, such as but not limited to Fiberglass or ceramic fibers woven into screens, having apertures on the order of 50 ran to lOμm, depending on whether the filter material are to be used for first stage or second stage filtration. Use of woven materials may require additional frame working to shape the compartments into the bellows design. Otherwise, flat filter shapes may be used. The single stage PFH compartments may be enclosed at the bottoms by a plate(s) and do not require dampers as shown by FIG. 3 for isolation of compartments or for the cleaning cycle.

FIG. 5 provides an overall prospective of the PFH 40 with the dust hoppers 34 and a front panel plate 72 omitted to show the inside features. The PFH 40 of this embodiment is arranged in two series gas passes, or two stages. Both stages are constructed with multiple rectangular chambers that are arranged side by side in alternating patterns so that each side of a first stage chamber 51 adjoins one side of adjacent second stage chambers 52.

The flue gas 22 enters the front of the PFH 40 into the first stage chamber 51 flowing horizontally through multiple parallel lanes, or channels. The other boundaries of the first stage chamber 51 with the sides enclosed by perforated plates, the top by the tube sheet 74, the back by plate work, and the bottom by a combination of plate work, perforated plates 53 and dust hoppers 34, as shown in FIG. 6. The first stage chamber 51 boundaries are sealed from the second stage chamber 52 boundaries, so that the flue gas 22 must exit the first stage chamber 51 through the perforated plates 53 on the sides. Attached to the backside of the perforated plates 53 are filter panels 76 arranged from top to bottom in elongated semi-circular shapes to increase filtering surface collection area. The filter panels 16 are shown more clearly in FIG. 7. The filter panels 76 may be made from existing materials and designs with micro apertures on the order of 2.5μm to 10 μm, such as, for example, but not limitation, woven metal wire or fabrics, membranes, metal or fabric substrates, and the like. The filter panels 76 may be designed to balance the flow through the first stage chamber 51 and second stage chamber 52 by having open areas on the order of approximately 10 to 25%, which produces a pressure drop to induce balanced flow through the complete PFH 40. The micron size dust particles are filtered from the gas by the filter panel 76 so that it collects on the inside of the filter panel 76 in dust cakes, which are loosened during the cleaning cycle by air horns, vibrators, rappers, detonation devices, or other type cleaning apparatus. The dust cakes fall to the first stage dust hoppers 78 below for disposal. The filter panel apertures can be designed for 2.5 to 10 micron sized particulate, or a similar size to collect the required amount of dust from the flue gas before flowing to the second stage. The PFH 40 can be designed for high first stage collection capabilities of up to 90% or higher, so that the amount of collecting surface in the second stage can be minimized, which would allow a higher designed air to cloth ratio (A/C). The dust and gas continues to the second stage at optimized flow distributions at velocities less than 150 fpm (45.72 mpm). The first stage chamber 51 can evenly distribute the gas and dust to the second stage chambers 52 between the rows of filter bags, best shown by FIG. 7. The second stage filter material 73 such as a panel, are arranged in geometric configurations so that lanes are provided between the rows from side to side of the PFH 40 for the evenly distributed gas and dust to flow at unbalanced velocities of less than 150 fpm (45.72 mpm). The dirty gas 82 is filtered through the nano apertures, on the order of 50 run to 5 μm, in some embodiments 50nm to 2.5 μm, of the second stage filter material 73 so that the dust collects in layers or cakes on the outside of the bags. In certain embodiments, most apertures in any given filter material or filter panel will have a diameter in a relatively narrow size range. The dust cakes are loosened during the cleaning cycle and fall to the second stage dust hoppers 80 below. The clean gas 28 flows upwards inside the bags through the tube sheet 74 to the clean gas plenum 58. The clean gas 28 may exit the clean gas plenum 58 in any desired direction.

The second stage chamber 52 may share sides with the first stage outlet sides, the top by the tube sheet 74, the front and back by plate work, and the bottom by dust hoppers 34. Large diameter filter material 73 extend from the tube sheet 74 down to the hopper area to facilitate the installation of a large area filtering surface in a compact footprint. The tube sheet 74 top may support the filter material 73, which may also be bottom supported and may be also intermediately supported, such as by a structure suspended from the tube sheet 74, which in certain embodiments has an expansion coefficient similar to the filtering material to maintain the design integrity of the filtering material. These features shield the filtering materials from high velocity flue gas and debris and evenly distribute the dust and gas to the bags at low velocities. These features permit an even distribution of dust cake to collect on the second stage filter material 73, which prevents damage to the materials caused by uneven dust dead weights, preserves the apertures for fine particulate filtering, and allows the filters to operate at a lower differential pressure between cleanings as compared to a BH.

The arrangement of the flow channels exiting the first stage chamber 51 and entering the second stage chamber 52 provides a much greater flow area than the inlet flow area of the first stage chambers at the front of the PFH 40. For example, assuming one first stage chamber with inlet dimensions of 40 feet (12.192 meters) in height by 2 feet (.6096 meters) in width, the inlet area would be 80 square feet (24.384 square meters). Then, assuming one first stage outlet side dimensions of 40 feet (12.192 meters) in height by 50 feet (15.24 meters) in length, the total exit area would be 4000 square feet (1219.2 square meters) for both sides. The ratio of PFH inlet area to second stage inlet area would be 1:50, so that flue gas entering the first stage at a velocity of 3600 fpm (1097.28 mpm) would enter the second stage at 72 fpm (21.5 mpm) with unobstructed flow paths.

FIG. 9 is a schematic representation of the first and second stage flow paths of air and dust within the two stage PFH 40. Flue gas 22 enters the PFH 40, flowing at a velocity, for example, up to 3600 fpm (1097.28 mpm) in certain embodiments, and directed towards the first stage inlet perforated plate 53, wherein the flue gas 22 passes through the perforated plate 53. The perforated plates which form the sides of the first stage permit significantly higher apparatus entrance velocities, and shield the filtering material to prevent particulate erosion damage. The unfludized dust is filtered by the perforated plate 53 and then falls (depicted by arrow 88) to the first stage dust hoppers 78. Then the once filtered gas 86 passes through the first stage filter panels 76. As with the unfluidized dust from the perforated plate 53, dust cake (depicted by arrow 90) from the first stage filter panel 76 falls into the first stage dust hoppers 78. From there, the first stage filtered gas 92, which still contains fine dust particles, is evenly distributed in flowing lanes (depicted by gas streams 94), in certain embodiments at a maximum velocity of 150 fpm (45.72 mpm) to the second stage filter material 73. The gas then is filtered by the second stage filter material 73. Loosened dust cake (depicted by arrow 96) collected on the outside of the second stage filter material 73 falls by gravity to the second stage dust hoppers 80. Accordingly, the clean gas 98 flows in second stage compartment 97 which is inside the second stage filter material 73 into the clean gas plenum 58 and out of the PFH 40.

The cleaning equipment shown in FIG. 10 is designed to provide reverse clean gas flow to individual bags or groups of bags through the connections on top of the bags, wherein the clean gas 28 is introduced by a nozzle 84 at a downward angle and tangentially to induce a downward vortex 100 inside the second stage filter material 73. A reverse air fan takes clean gas 28 from the common outlet plenum 89 and discharges it to second stage filter material 73 by damper selection to provide high volume, low pressure air to the inside of the second stage filter material 73, which slightly expands them, and isolates them to take them out of service. Air horns, rappers, vibrators, or detonation devices may then be used to loosen the dust cake so that it falls down to the second stage hoppers. The cleaning mechanics helps prevent damage to the filtering material and minimizes re-entrainment of the dust for recollection. Isolation of groups of bags and then individual bag isolation will enable location of a leak, which is a significant contribution to operation and maintenance. Long-term operation with one or more bags isolated and out of service may be accomplished with a smaller isolation fan. The cleaning mechanics helps preserve the filtering material aperture integrity.

For example, as shown in FIG. 8, the second stage filter material 73 may have bag nozzles 84 disposed proximate to the tube sheet 55, wherein the nozzle 84 may provide clean gas 28 in a reverse direction from which the flue gas 22 travels during normal operation. There is a nozzle 84 for each second stage filter bag and each nozzle 84 is connected in series to the other nozzles 84 for each second stage filter bag group. The second stage filter bag group is then associated with a pressurization damper within the first stage chamber 51. Conventional cleaning methods may also be used. In addition, filtering material failures or other leaks can be more easily detected than prior art because of its construction with only a few filtering compartments and bags. Moreover, the dust cleaning cycles can be conducted with significantly less re- entrainment from the filters since the flue gas flow does not oppose the direction of falling dust flow, and because of the low gas velocities.

Benefits of Two-Stage Filtration

It is known within the industry that collection of nanometer sized particulates from flue gas of less than 2.5-micron size is significantly more difficult and more costly than collection of larger particulates when using state of the art ESP or BH apparatus. The BH is designed with a single stage of filtration, inherently making this apparatus uneconomical. The process of collecting a wide range of particulate sizes and nearly 100% of the incoming dust in one stage requires that the filtering bags be designed for a low A/C ratio to integrate the designed pressure loss with cleaning frequencies. • Since BH filtering materials are designed with apertures that must be partially bridged by dust to provide smaller apertures to filter the smaller particles, collection efficiency is reduced after each cleaning. Because of the inherently unbalanced flow conditions in a BH, an uneven dust cake layer accumulates on the filters. The cleaning energy required to loosen the uneven accumulated dust cake layer from the filters also loosens the residual layer required for small particle filtering. A significant amount of dust dispersed during the cleaning cycle does not drop to the collection hoppers and is re-collected by the filters. Some estimates on recollection of dust ranges as high as 40%, which causes the cleaning cycle frequency to increase with corresponding intervals of lower average BH collection efficiency and higher average pressure losses. These conflicting parameters of A/C ratio, efficiency, pressure loss, and cleaning frequency are difficult to coordinate in one stage of filtration. A PFH with two stages of filtration provides greater flexibility than state of the art apparatus. The first stage filter panels can collect 2.5 microns size particles or greater and the second stage filter bags can collect particles of less than 2.5 micron size. The 2.5-micron split for collection between the first and second stage can differ as desired, and will be based on the actual gas and dust conditions. Because of the arrangement of the PFH flow channels and the design of the micron filter panels with about 10 to 15% open area, flow balancing of gas and dust at low velocities to both the first and second stage filters is inherently controlled by first stage filter pressure loss. The first stage filter panels collect up to 90% or more of the incoming particles and evenly distribute the remaining dust to the second stage filters. These PFH features can minimize pressure loss, preserve the filter apertures, optimize collection efficiency, and optimize footprint size reduction. First stage cleaning frequency is not related to PFH collection efficiency and is only based on controlling first stage pressure loss. As a result, the first stage filters can be designed for higher A/C ratios with cleaning frequencies based on the amount of accumulated dust cake and its associated pressure loss. For purposes of footprint comparison to a BH and ESP, an A/C ratio of IS is used in the example calculations for the PFH filter panels to compare footprint sizes. The first stage filters may be cleaned by conventional apparatus as discussed above. The second stage filters may comprise of a second set of filter panels or filter bags with nanometer sized apertures. In the case of filter bags, cleaning methods can include a low pressure-high volume reverse clean gas system which introduces clean gas to the inside of the bags for gentle expansion of the bags, followed by use of rappers, vibrators, sonic horns, or detonation cleaning devices to loosened the dust cake. Since the reverse clean gas system isolates the bags and removes them from service when cleaning, dispersion and recollection is significantly less than experienced in a BH. Because of this cleaning method, and since the second stage filters only collect small particles comprising about 10% of the PFH incoming dust that is evenly distributed to its surface, the A/C ratio can be greater than 6 fpm (1.83 mpm) and can approach 24 fpm (7.32 mpm). The second stage filters may be manufactured from known materials with nanometer sized apertures, which are preserved by the PFH design features so that high collection efficiency is continuous and not dependent on residual dust layer or the cleaning method or its frequency. The lessened frequency of cleanings will be based on control of accumulated dust pressure drop. For purposes of comparing a PFH to the footprints of an ESP and BH, an A/C ratio of 9 is used for the second stage bags in the example calculations to compare footprint sizes.

EXAMPLE CALCULATIONS

FOOTPRINT COMPARISON OF FILTER HOUSE TO PULSEJET BH AND ESP

Table 1

Assumptions for flue gas parameters to equipment: Flue Gas Flow, W₈ = 5,000,000 pound per hour (lb/hr) Gas Temperature in Fahrenheit Scale, T_g = 325⁰F Gas Pressure = -10 inches water gage (iwg) Atmospheric Pressure = Standard 29.92 inches of mercury ("Hg) = 407 iwg

Standard flue gas density, p_s = 0.072 pounds per cubic feet (lb/ft³) at 7O⁰F & 29.92 "Hg Conversion Factors:

Absolute Temperature Scale, ⁰F = 46O⁰R (Rankine) + ⁰F, where 0 ⁰R = - 46O ⁰F

Calculate corrected actual density, p_a: pa = (ps) multiplied by (absolute temperature correction) multiplied by

(gas pressure correction with respect to standard atmospheric pressure) P_a = (0.072) [(460 + 70)/(460 + 325)] [(407 -10)/407] = 0.0474 lb/ft³

Calculate actual cubic feet per minute gas flow, ACFM: ACFM = (W_g) multiplied by (l/p_a) multiplied by (1 hour/60 minutes)

ACFM = (5,000,000) (1/0.0474) (1/60) = 1,758,100

Table 2 BH Design Parameters and Calculations:

A/C = 6 Maximum can velocity, V_c = 300 fpm

Pleated bags: 6" diameter (d) by 20' length (L), circumference, c = πd = 1.57', effectiveness = 2

Pleated bag surface area, A_Pb = 2 (200 % effectiveness) multiplied by^' c multiplied by L A_pb = 2 (c) (L) - 2 (1.57') (20') = 62.8 ft² Ft² of fabric, A_f= ACFM of gas divided by 6 A/C ratio A_f= 1,758,100/6 = 293,000 ft² Number of bags, Nb = Af divided by A_Pb

N_b = 293,000/62.8 = 4,666

Can gas free flow area, A₀ = ACFM of gas divided by can velocity of 300 fpm Acf - 1 ,758,000/300 = 5,860 ft² of gas free flow area

Obstructed free flow area by bottom of bags, A₀ = 4,666 bags multiplied by area of one bag closed end

A₀ = (4,666) [( π) (0.5')²]/4 = 916 ft² Can plan area, A_cP = A_cf + A₀

A_cp = A_cf + A₀ = 5,860 + 916 = 6,776 ft²

Assume two (2) bag houses are required because of large footprint area: Can plan area per BH, A_cP/ number of BHs = A_cp divided by 2

Aep/BH = A_cp/2 = 6,776/2 = 3,388 ft²

Assume width by depth of can area = 70' X 50' = 3500 ft², which is greater than 3,388 ft² Assume height = 45'

Therefore, two (2) Bag Houses are required for the assumed parameters and flue gas conditions: Each footprint is 70' X 50'

Height = 45', excluding hoppers and top clean gas outlet plenum.

Table 3

ESP calculations for the assumed flue gas conditions: Assume ESP footprint and height are equal to two bag houses:

Width = 70' X 2 = 140' Height = 45' Depth = 50'

ACFM = 1,758,000

Calculate inlet velocity, V_espi : Total inlet area, A _espi= 2 multiplied by width multiplied by height

Aespi= (2) (7O')(45') = 6,300 ft²

V_espi = ACFM divided by A_∞p, = 1,758,100 ft³/6,300 ft² = 279 fpm (without considering obstructions in the gas stream) Normally, 300 fpm is maximum velocity entering ESP; therefore, the inlet openings are within design range.

Calculate SCA:

Assume collection plates = 18" centerlines parallel to gas flow or 9" gap on both sides of charging electrodes.

Number plates, N_espp = width divided by 1.5' centers N_espp = 140/1.5 = 93 plates

SCA = (1000) (Ne_spp) (2 flat plate sides) (width) (height) divided by ACFM

SCA = (93) (2) (45) (5O)(IOOO)/ 1,758,000 ft³ = 238 ft²/1000 ft³ Normally SCA = 400

Therefore. 400 SCA/ 238 SCA = 1.68 more SCA required to design the collection plates for an SCA= 400. Rounding off to the nearest 0.5 or one BH footprint, the ESP footprint is approximately 1.5 times the BH footprint.

Table 4

PFH calculations for the assumed flue gas conditions: Assume PFH footprint and height are equal to one of the two bag houses:

Width = 70', Height = 45', and Depth = 50'

Filter area of first stage panels based on A/C ratio = 18 fpm: AFH_f= 1,758,100/18 = 97,672 ft²

Assuming that the first stage panels are flat and manufactured from known cartridge type fabric materials, one first stage compartmentside areas, AFHfp = 2 sides multiplied by height multiplied by depth multiplied by 2 (200% pleated cloth area effectiveness) AFH_fp = 2 (45 ') (50') (2) = 9000 ft²

Number first stage compartments, NFH_C = fabric panel cloth area divided by two fabric panel side areas

NFH_c = AFH_f/ AFHφ = 97,672 ft²/9000 ft² = 10.85 Since the number of first stage compartments can be reduced by using non-flat filter panels, manufactured from woven wire or other materials. Recalculate the number of compartments using a U-shaped filter panel, spaced at 14" (1.167') centerlines from front to rear of PFH, wherein the leg of the "U" measures 18 inches and the diameter of the curved portion is 12 inches (radius is six inches):

Area of one first stage compartment filter panel sides, AFH_f = 2 sides multiplied by area of one filter panel multiplied by number of filter panels: Inside surface area of one filter panel, FP₃ = The quantity of [(π) times radius (R) plus length of 2 Legs] times the height = [(π) (0.5') + (3')] (45') = 205.7 ft² Number of panels in depth, FP_d = Depth divided by centerline spacing = 5071.167' = 43

AFH_f = 2 (FP₈) (FP_d) =2 (205.7) (43) = 17,690 ft² Number of Compartments, NFH_C = AFH_fp / AFH_f = 97,672 / 17,690 = 5.5

(use 5) Filter area of second stage membrane bags based on AJC ratio = 9 fpm:

AFH₅= 1,758,100/9 = 195,345 ft²

Area of one filter bag:

Assume bags = 12" diameter (d) by 45 feet in length (L).

One bag filtering surface, FH_b ⁼ π times d times L times 2 (200% pleated cloth area effectiveness) = (π) (1 ') (45') (2) = 282.7 ft²

Number of bags, FH_bags = AFH₅/ FH_b = 691

Number of bags in depth, assuming that front to rear centerlines = 20" (1.67'), including 8" lanes between each row of bags:

Number of bags in depth, N_d = 5071.67' = 30

Number of bags in width = FH_bags / N_d =691/30 = 23 (use 24)

Width taken by bags at 16" centerlines = 24 times 1.33 = 32'

Width taken by filter panels = (24") (10) = 20' Width remaining for first stage compartment flow channels = 70' - 32' -

20' = 18'

Width of each first stage flow channel = 18' divided by number of channels = 18 / 5 = 3.6' each (use 3' to allow for clearances/obstructions)

First Stage Inlet Area, A_sl = number of compartments multiplied by height and width of one compartment.

A₅, -(5) (45') (3^s) = 675 ft² First Stage Inlet Velocity, V₈₁ = ACFM divided by A_si

V_si = 1,758,100 ft³/675 ft² = 2605 fpm

This is a conservatively sized PFH to demonstrate that for the given filtering conditions, one PFH is required with an equivalent footprint of 50% of that required for a BH and 33% of that required for an ESP. These calculations do not consider the pending PM2.5 requirements for the BH or the ESP, which will give the PFH an even greater footprint advantage.

Apparatus designed with a PFH first stage only using standard perforated plates are suitable for dust collection purposes where the plant is interested in collection of only the larger particles. The single stage PFH with nano-drilled bellow plate configurations offers a very favorable economic design, as shown in FIG. 4, and would significantly reduce particulate collection operating and maintenance costs. Cleaning equipment is simplified and reduces capital costs. Ductwork is simplified and reduces capital costs. The PFH apparatus can be retrofitted into the spaces of existing plants to economically regain lost generation capacity, while meeting EPA emission limits.

Although the invention has been described in detail through the above detailed description and the preceding examples, these examples are for the purpose of illustration only and it is understood that variations and modifications can be made by one skilled in the art without departing from the spirit and the scope of the invention. It should be understood that the embodiments described above are not only in the alternative, but can be combined.

Claims

I Claim:

1. A particulate filter house for separating solid particulates from a gas stream having a plurality of chambers comprising at least one ϋlter panel having a plurality of apertures with an average diameter of about 50 nanometers to about 10 microns, wherein the chambers are arranged so that particulate laden gas is distributed between the chambers for filtration by the at least one filter panel, such that filtered gas flows into chambers and is channeled to an outlet.

2. The particulate filter house of claim 1 wherein the at least one filter panel is pleated or bellowed in configuration to increase surface area of the panel as compared to a flat plate area having the same overall side dimensions.

3. The particulate filter house of claim 1 wherein the chambers are arranged so that particulate laden gas is evenly distributed between the chambers for filtration by the at least one filter panel, such that filtered gas flows into the chambers and exits by being channeled evenly to a succeeding stage of filtration.

4. The particulate filter house of claim 1 or 2 wherein the at least one filter panel comprises at least one of woven metal wire or fabric, metal or ceramic plates, polymer composites, vegetable materials, membrane materials, woven or felted cotton, or synthetic fiber, glass fiber, or ceramic fiber woven into cloth or screens.

5. A multistage particulate filter house for separating solid particulates from a gas stream having multiple first stage chambers and second stage chambers, such that one side of a first stage chamber is adjacent to one side of a second stage chamber; wherein particulate laden gas can flow into the first stage chambers having at least one filter panel, optionally shielded by a perforated plate, wherein the at least one filter panel has apertures with an average diameter of about 2.5 microns to about 10 microns, and wherein partially filtered gas can flow out of the first stage chambers and into the second stage chambers; wherein the second stage chambers contain an array of multiple second stage compartments, wherein the second stage compartments are at least partially enclosed by a second stage filter material having a plurality of apertures with an average diameter of about 50 nanometers to about 5 microns, optionally about 50 nanometers to about 2.5 microns, wherein the partially filtered gas flowing into the second stage chambers is distributed to the second stage filter material and is filtered by the second stage filter material such that filtered gas flows into the second stage compartments and is channeled to an outlet.

6. The multistage particulate filter house of claim 5, wherein the first stage chambers are partially enclosed by a tube sheet or seal plate, and wherein the second stage compartments communicate with an opening in the tube sheet or seal plate, through which opening the filtered gas is channeled to the outlet, optionally via a clean gas compartment or plenum.

7. The multistage particulate filter house of claim 5, wherein the ratio of the at least one filter panel and optional perforated plate open area of the first stage chambers outlet to the first stage chambers inlet open area is at least 50:1.

8. The multistage particulate filter house of claim 5, capable of accepting particulate laden gas at velocities up to about 3600 feet per minute (1097.28 meters per minute) at the first stage chamber inlet and distributing the partially filtered gas to the second stage chamber filter material at velocities less than about 150 feet per minute (45.72 meters per minute).

9. The multistage particulate filter house of claim 5 wherein the at least one filter panel and optional perforated plate of the first stage chambers outlet have an open area of about 10% to about 25%, based on total area of the filter panel and the perforated plate.

10. The multistage particulate filter house of claim 5, wherein gas tight shut-off dampers are disposed below the first stage chambers and the second stage chambers to collect particulate that is filtered from the particulate laden gas by the at least one filter panel and optional perforated plate, and from the partially filtered gas by the second stage filter material for disposal into dust hoppers.

11. The multistage particulate filter house of claim 5, wherein segregated first stage dust hoppers and second stage dust hoppers without dampers are disposed below the first stage chambers and the second stage chambers respectively, to collect particulate that is filtered from the particulate laden gas by the at least one filter panel and optional perforated plate, and from the partially filtered gas by the second stage filter material.

12. The multistage particulate filter house of claim 5, wherein a nozzle is disposed at the outlet of the second stage compartments, and wherein the nozzle is capable of providing clean gas at a downward angle and tangentially to the compartment outlet, and inducing a downward air vortex within the second stage compartments to provide a reverse clean gas flow to assist in cleaning the second stage filter material.

13. The multistage particulate filter house of claim 12, wherein ducts for introducing a reverse flow of clean gas and isolation dampers are associated with individual or groups of second stage compartments for at least one of cleaning, or detection and isolation of leakage.

14. The multistage particulate filter house of claim 5, wherein the filter material of the second stage compartments is supported at the second stage compartment top and bottom, and optionally additionally between the top and the bottom.

15. The multistage particulate filter house of claim 5, wherein the filter materials comprise at least one of woven metal wire or fabric, metal or ceramic plates, polymer composites, vegetable materials, membrane materials, woven or felted cotton, or synthetic fiber, glass fiber, or ceramic fiber woven into cloth or screens.

16. The multistage particulate filter house of claim 5 wherein the first stage chambers are capable of removing about 90% of the incoming particulate and wherein the at least one filter panel of the first stage chambers has an A/C ratio higher than 6.

17. The multistage particulate filter house of claim 5 wherein the second stage chambers receive about 10% of the particulate entering the particulate filter house, and wherein the second stage filter material has an A/C ratio greater than 6.