GB2187656A - Fabric filter systems - Google Patents

Abstract

A system for filtering hot flue gas comprises two parallel rows of filter chambers 2, only one of which is shown, connected to common inlet manifold 4 and outlet manifold 16 which extend between the two rows. The filter bags in each chamber in turn are cleaned by reverse flow of filtered gas, which is drawn from manifold 16 through duct 76 to a fan (not shown) and returned through duct 78 to a reverse flow manifold 18, which extends between the two rows of chambers. To minimise heat loss and thereby prevent condensation, at least duct 78, and preferably both of ducts 76,78, is located inside the outer housing between the two rows. The ducts may share walls with each other, with adjacent filter chambers and with the housing. The housing wall may be insulated. <IMAGE>

Description

SPECIFICATION Fabric filter systems The present invention relates generallyto an apparatus forfiltering solids from a particulate-laden stream of gas, and more particularly, to improvements in the reverse gas fabric filter cleaning system of an apparatusforfiltering solids from a particulate-laden stream of gas.

Bag houses are generally employed to separate particulate matter from gas streams, for example, to separate fly ash and other undesirable particulate matter from a boiler flue gas stream, by fabric filtration with fabricfilter means generally known as bag filters. Fabric filtration with fabric filter means is not limited to air pollution control, but may also be employed in resource recovery applications where it is an object to recover particulate matterfrom a gas stream.

The filtration ofthe particulate matterfrom particulate-laden gas is carried out in filter houses, known in the trade as baghouses,which include a plurality of fabric bag filters suspended, generally, open-end down, within a plurality of compartments within the baghouse. Particulate-laden gas, such as flue gas containing fly ash particles resulting from the burning of coal, is directed upwardly into each of the bags within a given compartment, such that particulate matter collects inside the bags as a filter cake. Gas is forced to flow through the compartment by either a blowerfan or a suction fan, and accordingly, there is a pressure drop across the filters depending upon their resistance to gas flow.

As a filter cake accumulates on the bag surfaces, gas flow resistance increases, thereby decreasing gas flow and increasing pressure drop which must then be overcome by the fan. In order to decrease gas flow resistance and thereby increasesgas flow and decrease pressure drop, the bag filters orfabricfilter means are periodically cleaned to remove the accumulated filter cake.

As used herein, a baghouse or "fabricfilter system", has at least two rows of compartments constructed in such a way that one row of compartments is opposite or spaced apart from a second row of compartments and connected to each other by ductwork common to both rows of compartments. Each baghouse has a plurality of "compartments", for example, six compartments in each rowofcompartments. Each "compartment" is an independent structure and is normally separated from othercompartmentswithin the same individual row of compartments by walls, and iscontrollably separated from common inlet and outlet gas ducts by dampers orappropriatevalves. Each compartment includes multiple bags, typically arranged in rows and columns.Two rows of compartments, each row generally including a plurality of compartments with a pluralityoffabric filter means in each compartment, as well as inlet and outlet gas ducts common to both rows of compartments and a reverse gasfabricfilter cleaning system common to both rows of compartments ofthe present invention, are referred to herein as a fabric filter system.

Typical baghouses or fabric filter systems having two rows of compartments and the components thereof are well-known in the prior art. By way of example, bag filter cleaning devices having two rows of compartments and the components thereof are described in U.S. Patent No.3,945,400, U.S. Patent No.3,898,062, and U.S. Patent No.4,523,931. As will be seen from the foregoing references, there are many variations in components and structures for fabric filter cleaning systems.

As noted above, as thefabricfilter system removes particulates from gas, a dust cake develops on the surface of the filter, and it is necessary to clean the filter periodically to removethedustcake. Many methods have been suggested in the priorartforthe cleaning of the fabric filter means. One of the most frequently used cleaning methods for cleaning fabric filter means in bag houses has been carried out by reversing the direction of airflow through the filter elements.This is known as the reverse gas or reverse air cleaning system, and periodically, normal flow of dirty gas through the baghouse is interrupted, and clean gas isforced intothe baghouse to flow in a reverse direction through the filter bags in a selected compartment or compartments to dislodge the accumulated dust as described in U.S. Patent Nos.

4,507,130 and 3,898,062. The gas used for the bag-cleaning operation is usually referred to as "reverse gas" even though such gas could be atmospheric air. After the bags are thus cleaned, the flow of reverse gas is discontinued, and the compartment is put back on stream in the filtering mode of operation. In the multiple-compartment baghouse installation, continuous operation ofthe gas cleaning system is maintained by cleaning the compartments one by one while the dirty gas flows through the remaining on-line compartments. In orderto accomplish this mode of cleaning, a separate manifold system must be provided to supply reverse gas to the individual compartments ofthe baghouse.Valving arrangements must be provided to isolate each compartment from the dirty gas flow system and to connect them to the reverse gas duct. In all priorartfabricfiltersystemsofthe type having at least two spaced-apart rows of vertically oriented bag houses, the reverse gas is derived from a source through external ductwork, that is, ductwork located outside the walls of the baghouses and/or the fabric filter system, connected from the clean gas outlet manifold common to the two rows of baghouses down to grade elevation to the reverse gas fan and then back up to the top of the two rows of baghouses to the reverse gas manifold common to, that is, serving the two rows of baghouses.This external ductwork may consist of as much as 160 feet of insulated ductwork depending on the height of the total system, a typical large scale baghouse being about 80 feet high from grade level tothetopofthebaghouse.Thislargeamountof external ductwork is expensive, requiring large amounts of support steel ductwork, insulation and lagging, and therefore requires a large amount of real estate for the total flange-to-flange fabricfilter system and increases the risk of large amounts of heat loss. When heat loss occurs, condensation of thevapors in the flue gas can occur, andthe condensation of the vapors can extend into the compartments and the filter bags during cleaning.

Sincethevapors in theflue gas are acidicin nature, condensation ofthe aqueous acid on the filter bags can cause rapid deterioration of the fabric of the bags and substantial reduction in the life ofthe bags plus an increase in filter cake resistance or pressure drop due to the absorption of the aqueous acid or moisture. The baghouse and manifold system of U.S. Patent No.3,898,062 is representative of such a system with external ductwork located outside the walls oftwo spaced-apart rows of verticallyorientedofvertically oriented bag houses and shows flanged ducts on the casing with external fans and arrows which are representative of interconnecting ductwork. The type of reverse gas or reverse air cleaning system in U.S. Patent No. 3,898,062 has all ofthe disadvantages discussed above.

Accordingly, is is the primary object of the present invention to provide an improved filter system for filtering the particulate matter from particulate-laden gas.

It is another object ofthe present invention to provide a filtering system having an improved cleaning system for cleaning filter media, such as, bags, used to filter particulate matterfrom particulate-laden gas.

Another object ofthe present invention is to provide a filter system having an improved cleaning system of the reverse gas-type wherein filter media, such as, bags, having particulate matter accumulated from particulate-laden gas are cleaned by a clean gas passing in a reverse direction through thefabricfiltermeans.

Still another object of the present invention is to provide an improved cleaning systemforcleaning fabric filters with reverse gas flow without heat loss in a filter system having filter media, such as, bags, used to filter particulate matterfrom a gas.

It is another object of the present invention to provide an improved cleaning system for cleaning fabric filters with reverse gas flow without condensation of vapors from flue gas in a filter system having filter media, such as, bags, used to filter particulate matterfrom a gas.

Still another object of the present invention isto provide a method of preventing the condensation of vapors from flue gas in a cleaning system ofthe reverse gas-type wherein filter media, such as, bags, having particulate matter accumulated from particulate-laden gas are cleaned by a cleaning gas passing in a reverse direction through the fabricfilter means.

Other objects and advantages will be apparent from the following description.

In accordance with the objects of the invention, there is provided a fabricfilter system comprising: (a) at least two spaced-apart rows offilter compartments; (b) a gas inlet manifold for supplying particulate-laden gas to the filter compartments by common ductwork between the rows of compartments; (c) filter means in the filter compartments for removing particulate matterfrom particulate-laden gas to provide filtered gas; (d) a filtered gas outlet manifold for removing filtered gas from the filter compartments by common ductwork between the rows of compartments; (e) a cleaning system to clean the filter means in the filter compartments, the cleaning system having a reverse gas manifold connected to the filter compartments by common ductwork between the rows of compartments; and (f) clean gas supply means connected to the reverse gas manifold by common ductwork between the rowsofcompartments.

In accordance with the present invention, it is critical that the ductwork connecting the clean gas supply means to the reverse gas manifold be positioned between the two spaced-apart rows of filter compartments and that it be internally mounted in the baghouse. lnthismanner,theductwork connecting the clean gas supply means to the reverse gas manifold located between the spaced-apart rows of filter compartments becomes an integral part of the baghouse. In preferred embodiments, the clean gas supply means provides filtered gas from the filtered gas outlet manifold, and all ora substantial portion ofthe ductwork connecting the filtered gas outlet manifold to the reverse gas manifold is mounted internally in the baghouse and is located between the rows of compartments.In preferred embodiments, the internally-mounted ductwork for supplying the filtered gas having heat retained therein as a gas for cleaning thefabricfilter means, such as fabric filter bags, in the filter compartments of the baghouse, is provided with insulation to prevent heat loss, especially in those areas which define the outer or external wall ofthe ductwork and which form the end wall of the baghouse.

The elements ofthefabricfiltersystem which are mounted internally in the baghouse between the rows of compartments in accordance with the present invention include ductwork connected from the filtered gas outlet manifold and/or ductwork connected to the reverse gas manifold. Thus, in preferred embodiments, the clean gas supply means connected to the reverse gas manifold by common ductwork between the rows of compartments supplies filtered gas from the filtered gas outlet manifold, the filtered gas having heat retained therein, to the reverse gas manifold. Generally, the clean gas supply means includes at least one reverse gas fan for circulating the filtered gas having heat retained therein from the filtered gas outlet manifold to the reverse gas manifold by the ductwork mounted internally within the baghouse between the rows of compartments. The heat in the filtered gas supplied from the filtered gas outlet manifold to the reverse gas manifold through common ductwork mounted internally in the baghouse between the rows of compartments by the clean gas supply means is heatwhich is derived from the particulate-laden gas being filtered by filter means the filter compartments and supplied thereto through a gas inlet manifold. Atypical source of heated, particulate-laden gas is flue gas from a boiler.

At least partofthe ductworkforming the clean gas supply means is located alongthe end wall ofthe baghouse and is mounted internally in the baghouse between the rows of compartments for supplying the filtered gas from the filter gas outlet manifold to the reverse gas manifold for cleaning the filter means in the filter compartments. This internally-mounted ductwork utilizes existing steel in the end or side walls ofthe baghouse as a wall of the ductwork. In certain embodiments ofthe present invention the end wall of the baghouse serves a dual purpose as both the baghouse end wall as well as one walls ofthe ductwork supplying the cleaning gas from the filtered gas outlet manifold to the reverse gas manifold.Since a major portion ofthe ductwork forming a partofthis invention and located internally in the baghouse between the rows of compartments, is common with the existing steel ofthe baghouse, that is, an end wall ofthe baghouse, steel costs are greatly reduced. In accordance with the present invention, at least one wall of the ductwork, and upto three walls of the ductwork which are located internally in the baghouse between the rows of compartments, for supplying cleaning gas from the filtered gas outlet manifold to the reverse gas manifold are already present in the baghouse as walls which provide this economic advantage.

Furthermore, because a substantial amount of the ductwork of the present invention is completely internal to the casing or walls ofthe compartments and/oiendwallsofthe baghouse, insulation requirements are also reduced. The internal walls of the ductwork of the present invention, that is, those wallswhich areadjacentorwhichareformed bythe compartment walls and/or other internal elements of the baghouse, and accordingly are integral to the existing baghouse casing, eliminate major heat losses which are characteristic ofthe prior artfabric filter systems having externally-located ductwork, that is, the ductwork described above mounted on the external portions of the baghouse.By the present invention, flue gas condensation is prevented within theductworkwhichsuppliesthecleaninggastothe reverse gas manifold for cleaning the fabric filter means in the filter compartments. Thus, acid condensation and/orwatercondensation from the flue gas on the filter bags which causes irreversible damage to the filter bags and/orforms wet filter cakes which cannot be easily cleaned from the filter bags, is prevented by the fabric filter system and method of the present invention. Since filter bags are a substantial part ofthe cost of the fabricfilter system, an increase in the life of the filter bags can resultinsubstantialsavingsoverthe lifeofthefabric filter system.

Another major advantage of the fabricfilter system and method of the present invention is found in the savings in real estate required for the baghouse system. By mounting the ductwork for providing the cleaning gas, that is, the filtered gas, to the reverse gas manifold, internally in the baghouse between the rows of compartments, substantial savings in space are achieved over the system which utilize the externally-mounted ductwork for providing the cleaning gastothe reverse gas manifold.

As used herein, the phrase "common ductwork" refers to ductwork which serves two rows of compartments and which is located between the rows of compartments. The term "ductwork ofthe present invention " refers to ductwork which is internally mounted in the baghouse between the rows of compartments and provides cleaning gas to the reverse gas manifold. In the preferred embodiments ofthe present invention,the "ductwork ofthe present invention" is the ductwork providing the cleaning gas, that is, filtered gas having heat retained therein, from the filtered gas outlet manifold to a reverse gas fan, and ductwork connecting the reverse gas fan to the reverse gas manifold. The reverse gas fan is generally located at a position external the baghouse or beneath the baghouse structure at the elevation level ofthe baghouse.

While the novel features ofthe invention are set forth with particularity in the appended claims, the invention will be better understood and appreciated from the following detailed description taken in conjunction with the drawings, in which: Figure 1 is a side elevational view of a portion of a baghouse showing a prior art clean gas supply means having all ductwork external to the baghouse.

Figure2 is a side elevational view of a segment of a baghouse showing an embodiment ofthe clean gas supply means ofthe present invention.

Figure 3 is an end elevational view of a segment of a baghouse showing an alternative embodiment of the clean gas supply means of the present invention.

Figure 4 is a perspective and partially schematic viewofa baghouse having multiple compartments showing a typical cleaning system and ductwork associated with a clean gas supply means.

Figure 5is a side elevational view of a baghouse showing an alternative embodiment of the clean gas supply means ofthe present invention.

Figure 6 is an end elevational view of a segment of a baghouse showing an alternative embodiment of the clean gas supply means of the present invention.

Referring to the drawings, Figure 1 illustrates a section of a prior art baghouse installation having a row ofvertically oriented filter compartments 2.

Although it is not shown in the side elevational view, a typical baghouse installation has two rows of vertically oriented compartments 2 having a gas inlet manifold for supplying particulate-laden gas to the filter compartments by common ductwork between the rows of compartments; filter means in the filter compartments for removing particulate matterfrom particulate-laden gas to provide filtered gas; a filter gas outlet manifold for removing filtered gas from the filter compartments by common ductwork between the rows of compartments; a cleaning system to clean the filter meansinthefilter compartments, the cleaning system having a reverse gas manifold connected to thefilter compartments by common ductwork between the rows of compartments; and clean gas supply means as shown in Figure 1 connected to the reverse gas manifold (not shown) by ductwork 62 externally mounted on the end wall 60 of the baghouse. As shown in Figure 1, in the prior art systems, all ofthe associated ductwork and fans for supplying clean gas or filtered gas, that is, reverse gas, to the reverse gas manifold of a fabric filter system are externally mounted on the end ofthe baghouse external to the end wall ofthe baghouse.

As shown in Figure 1, a typical prior art clean gas supply means connected to the reverse gas manifold (notshown) has at least one reverseairfan 10 located at grade level 70 and mounted externally of the baghouse by appropriate steel mounting members, such as, horizontal support member74 andvertical support member 72. Reverse air fan 10 removesfiltered gas from a filtered gas outlet manifold (notshown) by ductwork 66 located externally of baghouse end wall 60.The filtered gas passes in the direction of arrow 68 in d uctwo rk 66 to the inlet of reverse airfan 10 and is circulated from the outlet of reverse airfan 10 in the direction of arrow 64 through ductwork 62 located externally of baghouse end wall 60 into the reverse gas manifold (not shown) which supplies the filtered gas to filter compartments 2 being cleaned. In the typical prior art system as shown, all of the ductwork associated with the clean gas supply means, namely, all reverse gas ductwork, is located external to the flange4o-flange bag house system.The prior art reverse gas fan or blower is typically located at ground level with associated ductwork connected from the bag house filtered gas outlet manifold down to the fan inlet, then from the fan discharge side up the full length of the bag house to the reverse gas manifoldflangelocatedatornearthetopofthe baghouse.

Figure 2 illustrates a section of a baghouse installation having a row of vertically oriented filter compartments 2 with a clean gas supply means mounted internallyinthe baghouse and having ductwork between the rows of compartments in accordance with the present invention. Although it is not shown in the side elevational view of Figure 2, the baghouse installation having the clean gas supply means mounted internally in the baghouse between the rows of compartments, must have at least two rows of vertically oriented compartments 2 having ductwork and other related devices positioned between the two rows.The clean gas supply means of the present invention connected to the reverse gas manifold (not shown in Figure 2) by ductwork 76 and 78 between the rows of compartments is used i n a typ in atypicalfabricfiltersystem having at least two spaced-apart rows offilter compartments; a gas inlet manifold for supplying particulate-laden gas to the filter compartments by common ductwork between the rows of compartments; filter means in the filter compartments for removing particulate matterfrom particulate-laden gasto provide filtered gas; a filtered gas outlet manifold for removing filtered gas from the filter compartments by common ductwork between the rows of compartments; and a cleaning system to clean the filter means in the filter com pa rtm ents, the cl ean i ng system having a reverse gas manifold connected to the filter compartments by common ductwork between the rows of compartments.

In the embodiment of the present invention as shown in Figure 2, the entire clean gas supply means including reverse gas fan 10, ductwork76 on the filtered gas manifold side of reverse gas fan 10 and ductwork 78 on reverse gas manifold side of reverse gasfan 10, is included within the confines and/or walls of the bag house. As shown in Figure 2, ductwork 78 on reverse gas manifold side of reverse gas fan 10 is connected to the reverse gas manifold (notshown) and is internally mounted within the baghouse. One sidewall oftheductwork78is defined by baghouse end wall 60.Ductwork 78 which is internally mounted in the baghouse, is positioned between two rows of vertically oriented compartments 2, and in the embodiment shown, shares a common side wall with ductwork 76 from the point where ductwork 76 is connected to the filtered gas outlet manifold to the pointwhere ductwork 76 assumes a non-vertical direction and connects to the inlet side of reverse gas fan 10.

Ductwork 76 on the filtered gas manifold side of reverse fan 10 connects to the filtered gas manifold (not shown) and is also internally mounted in the bag house between two rows offilter compartments 2. Aside wall of ductwork 76 also is defined by baghouse end wall 60, and as indicated above, shares a side wall with ductwork 78 from the point where the discharge side of reverse gas fan 10 runs vertical with ductwork 76.In the embodiment shown in Figure 2, ductwork 76 and ductwork 78 are shown as rectangular ducts, however, the ductwork ofthe present invention, that is, the ductwork connected with the clean gas supply means mounted internally in the bag house between the rows of compartments may assume other cross-sectional configurations, such as those which are circular in cross section, and the like. In Figure 2, reverse gas fan lOis shown inthe lower portions ofthe baghouse and is located between the two rows of compartments in the area of hoppers 8. Thus, reverse gas fan 10 in Figure 2 is located between two rows of hoppers 8.Particulate matter in the dirtygas orparticulate-laden gasfalls into hoppers 8 after it is filtered by the filter means in the filter compartments. In certain embodiments of the present invention as discussed in greater detail below, reverse gas fan 10 and/or sections of ductwork 76 and ductwork 78 where such sections join the inlet side and discharge side respectively of reverse gas fan 10 can be located in various positions both inside the end wall ofthe baghouse and outside the end wall of the baghouse, as long as at least a segment of ductwork 78 on the reverse gas manifold side of reverse gas fan 10 is mounted internally in the baghouse, that is, inside baghouse end wall 60, between two rows of vertically oriented compartments 2.

The elevational view of the end of a segment of a bag house as shown in Figure 3 illustrated an embodimentofthepresentinvention referredtoas the "horseshoe" design having two reverse gas fans 10 and 10'. In this embodiment,the second reverse gas fan loins held in reverse in case of failure, shut down or maintenance of first reverse gas fan 10. As seen in the drawing, ductwork 76 on the filtered gas manifold side of reverse gas fan 10 and 10' is a common sourceoffiltered gasforthe gas inlet of both reverse gas fans 10 and 10'. The discharge side of reverse gas fans 10 and 10' both connectto ductwork 78 on the reverse gas manifold side of reverse gas fans 10 and 10'.

It can be seen in the embodiment of Figure 3that ductwork 78 is connected from reverse gas fans 10 and 10' to reverse gas manifold 18. Ductwork 76 connects the filtered gas manifold to the inlets of reverse gas fans 10 and 10'. It can be easily seen by one skilled in the artthata single reverse gas fan 10 can be provided between hoppers 8 instead ofthe dual reverse gas fans 10 and 10' as shown. Thefans are normally positioned at grade level 70. Horizontal support members 74 and vertical support members 72 are also shown in Figure 3. It can also be seen from the embodiment illustrated in Figu re 3 that the ductwork 76 and 78 located between two rows of filter compartments 2 share a common inner wall 86.

Furthermore, from the embodiment shown in Figure 3, it can be seen that one of the walls of ductwork78 is defined by wall 84 of compartment 2 and a wall of ductwork 76 is defined by a wall 82 of filter compartment 2 located on the other side of the baghouse.

Figure 4 illustrates one side of a baghouse installation having a row ofverticallyorientedfilter compartments 2 along with the associated supply and exhaust ductwork common to thefilter compartments. Although it is not shown in the perspective view of Figure 4 in order to more easily illustrate the present invention, a second row of vertically oriented compartments is connected to the associated ductwork in such a mannerthatthe associated ductwork is positioned between the two rows of compartments, and the associated ductwork provides common supply and exhaust gas streams forthetwo rows of vertically oriented compartments.

As shown in Figure 4, dirty gas from a source (not shown), for example, from a coal fired power plant, flows through dirty gas inlet manifold 4 in the direction of arrow 12 into compartments 2. The particulate-laden gas (dirty gas) passes through gas inlet damper opening 6' into hopper 8 of compartments 2. Each compartment 2 has at least one such gas inlet damper opening 6, generally designated as a gas inlet damper opening which also serves as a cleaning gas outlet during the cleaning cycle. The flow ofgas in gas inletdamperopening 6 as illustrated in Figure 4, shows the flow path during the cleaning cycle ratherthan the filtering cycle, thus the arrows from gas inlet damper opening 6show cleaning gas exiting hopper 8 through gas inlet damper opening 6 into dirty gas inlet manifold 4.The dark arrows in Figure 1 indicate the flow path during cleaning.

Each compartment 2 is of conventional internal construction and is not described herein. It is well known in the artthatthe particulate-laden gas or dirty gas flows up into the fabric filter means, generally described as filter bags 50 and through the fabric to be cleaned thereby. Conventional filter bags are illustrated and described in U.S. Patent No.

3,955,947. Some of the particulate matter in the dirty gas or particulate-laden gas falls into hoppers 8 and is removed therefrom by a suitable dust-removal system (not shown). The bulk of the particulate matter from the particulate-laden gas becomes lodged upon and within the surface of the filter bags or in the interstices ofthe fabric. During a filtration cycle in a compartment, cleaned (filtered) gas flows from the upper end of the compartment 2 into a cleaned or filtered gas outlet manifold 16 connected to compartment 2 by one or more gas outlets or gas outlet ducts.The cleaned gas flows from the clean gas outlet manifold 16 and eventual Iy i nto the atmosphere, or it may be used for various purposes, for example, as cleaning orfilteredgasforusein reverse gas manifold 18, the cleaning system and clean gas supply means of the present invention. As shown in Figure 4, cleaned or filtered gas flows in the direction of arrow 14 in filtered or clean gas manifold 16.

A blower (notshown) may be used to propel the particulate-laden gas through the filter system, and the pressure side of a suitable blower may be used to propel the particulate-laden gas into gas inlet manifold 4, or the suction side of a suitable blower may be usedto drawthe gasthrough the system on the cleaned orfiltered gas side ofthefiltersystem in the direction of arrow 14 at clean gas outlet manifold 16. Clean gas manifold 16 delivers cleaned (filtered) gas from compartments 2, and in the present invention clean gas outlet manifold 16 is connected to reverse gas manifold 18 by a clean gas supply meansthroughductwork76and78.Thecleanedor filtered gas is used as cleaning gas in the reverse gas manifold to assist in cleaning the fabric filter means.

Reverse gas manifold 18 is connected to ductwork 78, a reverse gas fan (not shown in Figure 4) and ductwork76to provide filtered gas from clean gas outlet manifold 16 as a source of cleaning gasfor cleaning fabric filter means 50. The filtered gas is supplied for the cleaning system to the reverse gas manifold by using a blower designated herein as a reverse airfan (not shown,) which provides the filtered gas for the cleaning system.As shown in Figure 4 the clean gas supply means shown at the end ofthe baghouse having the dirty gas inlet 12, is internally mounted in the baghouse between two rows ofvertically-oriented compartments 2 (although one of the rows of vertically-oriented compartments 2 has been omitted from the illustration of Figure 4for ease of viewing the present invention). Filtered gas flowing in the direction of arrow 68 is removed from clean gas outlet manifold 1 6through ductwork 76. Ductwork 76 is connected to a blower generally designated as a reverse gas fan (not shown), the outlet of which is connected to ductwork 78 to provide filtered gas flowing in the direction of arrow 64to reverse gas manifold 18. As shown in the embodiment in Figure4,poppetvalves 24 are in an open position and permit the flow of the filtered gas (cleaning gas) into compartment 2 undergoing cleaning. The flow ofthe cleaning gas from reverse gas manifold 18 into compartment 2 is shown by solid-colored arrow 20. The cleaning gas passes in a reverse direction,that is, a reverse direction relative to the direction of the particulate-laden gas being filtered, through filter bags 50 and flows in the reverse direction into hopper 8 in the direction of solid-colored arrow 92 and from hopper8 into dirty gas inlet manifold 4 through open gas inlet damper opening 6 in the direction ofthe solid-colored arrows 94to be redistributed to the one-line compartments.When poppet valves 24 are in the closed position, such as illustrated by the closed poppet valves 30 which control the passage of the filtered gas for compartment 2 (not shown) on the side ofthe bag house opposite the compartment 2 shown with open poppet valves 24, the flow offiltered gas provided from reverse gas manifold 18 to compartment 2 in accordance with the present invention, ceases. At that point in time, compartment 2 is ready for the filtration cycle.

The clean gas supply means connected to the reverse gas manifold by ductwork between the rows of compartments of the present invention may be used in anytype of baghouse installation comprising two rows ofvertically oriented compartments having ductwork and other related devices positioned between the two rows, including those baghouse installations having the dirty gas inlet on one end ofthe baghouse and a clean gas outlet on the other end ofthe bag house as illustrated in Figure 6 below, as well asthe preferred embodiment wherein the bag house installation has the dirty gas inlet and the clean gas outlet on the same end ofthe baghouse as illustrated in Figures4and 5. In one embodimentthe dirty gas inlet is on the end of the baghouse having the clean gas supply means and the clean gas outlet is on the other end ofthe baghouse. It is difficult to accommodate this arrangement in a baghouse having the ductwork of the present invention because it is difficult to build the clean gas supply means on the end ofthe baghousehavingthedirtygasinletductduetothe large area requiredforthe dirty gas inletinthe end of the baghouse.Thus, although it is possible to build the clean gas supply means ofthe present invention on the end ofthe baghouse having the dirty gas inlet, it is generally necessary to sacrifice dirty gas inlet capacity to accommodate the internally mounted ductwork of the present invention.

Figure 5 shows a baghouse installation ofthe present invention having dirty gas flowing in the direction of arrow 12 into dirty gas inlet manifold 4 and clean gas flowing in the direction of arrow 14 from cleaned gas outlet manifold 16, both of which are located on the same end of the baghouse. The clean gas supply means connected to the reverse gas manifold by ductwork between the rows of compartments is shown on the end ofthe baghouse having baghouse end wall 60 opposite the end ofthe baghouse having the dirty gas inletandtheclean gas outlet. A cutaway portion of compartment 2 shows vertically-orientedfilter means 50 in the filter compartment 2 for removing particulate matterfrom particulate-laden gas to provide filtered gas.Figure5 also illustrates the embodiment ofthe present invention where ductwork 78 on the reverse gas manifold side of reverse gas fan 10 is mounted internally in the baghouse between two rows of compartmentswhileductwork76onthefilteredgas manifoldsideofreversegasfan 10 is mounted externally to the baghouse. Filtered gas is removed from the filtered or cleaned gas outlet manifold 16 through ductwork 76 in the direction of arrow 68 through reverse gas fan 10, and ductwork78 in the direction of arrow 64 into reverse gas manifold 18 where its flow is controlled into compartments 2 by appropriate control means 24, such as poppet valve 24. Ductwork 78 in the embodiment shown in Figure 5 has an outerwall defined by baghouse end wall 60.

In preferred embodiments of the present invention, means are provided for continuously passing the filtered gas from the filtered gas outlet manifold through the internally mounted ductwork as well as any externally mounted ductwork connecting the filtered gas outlet manifold to the reverse gas manifold and into the filter compartments to maintain the temperature ofthe ductworkandthefabricfiltermeansatthe temperature ofthefiltered gas. This positive and continuous flow of filtered gas through the cleaning system by the cleaned gas supply means connected to the reverse gas manifold by ductwork mounted internally in the baghouse between the rows of compartments is generally achieved by providing means for continuously passing the gas in the reverse gas manifold 18 into cleaned gas outlet manifold 16.As shown in Figure 5, poppet valve 96 provides an opening from reverse gas manifold 18 to cleaned gas outlet manifold 16. Thus, when none of the filtered gas passing through the clean gas supply means and into the reverse gas manifold is passing into any of the compartments 2, poppet valve 96 or other suitable valving means is opened so that reverse gas fan 10 can continuously provide the filtered gas having heat retained therein through the clean gas supply means. In this manner, the entire cleaning system, including the clean gas supply means is provided with filtered gas having heat retained therein to maintain the temperature of all of the ductwork and other elements associated therewith atthetemperature ofthefiltered gas, and generally between about 30"C to about800 C.

The elevational view of the end of a segment of a baghouse as shown in Figure 6 illustrates an embodiment of the present invention wherein clean gas outlet manifold 16 delivers cleaned (filtered) gas from compartments 2 to the exterior of the baghouse. Thus, Fig u re 6 shows the end of a baghouse installation having the clean gas outlet on the opposite end of the baghousefrom the dirty gas inlet, and the clean gas outlet is on the same end of the baghouse as the clean gas supply means. In Figure 6, ductwork76 ofthe clean gas supplymeans receives filtered gas from clean gas outlet manifold 16, and the filtered gas passes through ductwork 76 in the direction of arrow 68to reverse gas fan 10 where it is directed from the outlet of the reverse gas fan in the direction of arrow 64through ductwork 78 which connects reverse gas fan 10 to reverse gas manifold 18. Thecleaning gas orfiltered gas directed in this mannerbythe clean gassupply means is utilized in reverse gas manifold 18 to selectively clean filter bags 50 in compartments 2 as it passes from reverse gas manifold 18through poppetvalves 24.

Although the interior of compartments 2 has not been described with any detail above, normally, the interior of the compartment 2 is conventional and contains multiple fabric means, such as filter bags, as shown in U.S. Patent 3,955,947. In various embodiments of the present invention, it also possible to incorporate other ducts and controls as desired. Any conventional poppet damper means as well as other conventional dampers and/or valves, andthe like, may be used in controlling gasfiowand in communicating from duct to duct and compartmentto duct. All poppet damper means and other elements of the system can be controlled manually and/or automatically as desired. Poppet damper means are described in U.S. Patent No.

4,360,370. Although poppet damper means are the preferred devices for controlling gas flow in the gas inlets and gas outlets, otherwell-known means,such as, butterfly valves and louvers, may be used in place of poppet damper means for selectively blocking gas inlets and outlets.

Generally, the particulate-laden gas entering the bag house is derived from a heated source wherein the particulate-laden gas contains substantial amounts of heat. The heated, particulate-laden gas mayrangefrom ambienttemperatureuptoabout 1 500#C. After the heated, particulate-laden gas has been filtered in the bag house filter system, the cleaned orfiltered gas has heat retained therein.In most cases, the cleaned orfiltered gas has a temperature of about 30 C to a temperature of about 800 C. By passing the filtered gas having heat retained therein through the clean gas supply means connected to the reverse gas manifold by ductwork mounted internally in the bag house between the rows of compartments, it is possible to preventthe condensation of va pors from fluegas in the cleaning system ofthe present invention.

In accordance with the present invention, there is provided a method of preventing the condensation of vapors from flue gas in a cleaning system ofthe reverse gas type in a baghouse filter system having a plurality offilter compartments arranged in two spaced-apart rows, each filter compartment having a gas inlet for receiving heated particulate-laden gas from a gas inlet manifold mounted internally in the baghouse between the rows of compartments, the gas inlet manifold being connected to a source of heated, particulate-laden gas; a filtered gas outlet for delivering filtered gas having heat retained therein from the filter compartment to a filtered gas outlet manifold mounted internally in the baghouse between the rows of compartments, the gas outlet manifold being connected to a baghouse clean gas outlet; fabric filter means between the gas inlet and the gas outlet of each filter compartment; a cleaning system to clean the fabric filter means with filtered gas from the filtered gas outlet manifold, the filtered gas having heat retained therein; and meansfor selectively cleaning the fabricfilter means of at least one filter compartment, comprising: (a) internally mounting between the two rows of filter compartments in the bag house the ductwork connecting the filtered gas outlet manifold to the reverse gas manifold through a reverse gasfan, the outer wall ofthe ductwork being defined by the end wall ofthe baghouse; (b) insulating the outerwall of the ductwork defined by the end wall of the bag house to prevent heat loss; and (c) passing the filtered gas having heat retained therein through the internally mounted ductwork connecting thefiltered gas outlet manifold tothe reverse gas manifold and into thefilter compartments to clean the fabricfilter means whereby heat is retained in the reverse gas and prevents condensation of the flue gas in the internally mounted ductwork and on the fabricfilter bags in thefilter compartment.

By the foregoing method and apparatus, the ductwork from the filtered gas outlet manifold to the reverse gas fan can be maintained at the temperature of the filtered gas, and in preferred embodiments, at a temperature of about 300C to a temperature of about 800 C. Furthermore, the ductworkfrom the reverse gas fan to the reverse gas manifold can also be maintained at the temperature of the filtered gas, and in preferred embodiments, at a temperature of about 30 C to a temperature of about 800 C. Thus, when all or part of the ductwork connecting the filtered gas outlet manifold to the reverse gas manifold through a reverse gas fan is internally mounted between two rows offiltercompartments in the baghouse, and filtered gas having heat retained therein is passed through the ductwork at least part of which is internally mounted and connecting the filtered gas outlet manifold to the reverse gas manifold, the condensation of vapors from theflue gas is prevented in the cleaning system.

Furthermore, by the apparatus and method of the present invention, condensation of the flue gas is also prevented on the fabric filter bags in the filter compartment because the fabric filter means in the filter compartment is also maintained at the temperature of the filtered gas, and preferably at a temperature of about30 Cto a temperature of about 800 C, while the fabric filter means is being cleaned.

By insulating all or part ofthe ductworkand other elements of the clean gas supply means, such as the reverse gas fan, the prevention of heat loss is even further diminished. As indicated above, in preferred embodiments of the present invention, the filtered gas having heat retained therein is continuously passed through the ductwork connecting the filtered gas outlet manifold to the reverse gas manifold and into the filter compartments to maintain the temperature of the ductwork and the fabricfilter means at the temperature of the filtered gas.

By the apparatus and method of the present invention as set forth above, flue gas condensation can be prevented within the ductwork which supplies the cleaning gas to the reverse gas manifold for cleaning the fabric filter means in the filter compartments of a baghouse filter system having a reverse gas manifold from which the cleaning gas selectively passes into compartments to clean the fabricfilter means therein, and acid condensation and/or water condensation from the flue gas on the filter bags which causes irreversible damage to the filter bags and/orforms wet filter cakes which cannot be easily cleaned from the filter bags, is prevented.

Furthermore, by the apparatus ofthe present invention wherein the ductwork for providing the cleaning or filtered gas to the reverse gas manifold is mounted internally in the baghouse between the rows of compartments, substantial savings in space are achieved over the systems which utilize the externally-mounted ductwork for providing the cleaning gas to the reverse gas manifold.

Furthermore, substantial savings can also be realized from savings in the amount of insulation required to insulate ductwork, in the amount of ductwork and support steel and in foundation costs.

By the apparatus and method ofthe present invention, the overall size ofthe baghouse can be substantially reduced without reducing the capacity ofthe baghouse and/or any of its components in its capacity to remove particulate matterfrom particulate-laden gas.

While specific embodiments of the invention have illustrated and described herein, it is realized that numerous modifications and changes will occurto those skilled in the art. It is therefore to be understood thatthe appended claims are intended to coverall such modifications and changes as fall within the true spirit and scope of the invention.

Claims (26)

1. Afabricfiltersystem comprising: (a) at least two spaced-apart rows offilter compartments; (b) a gas inlet manifold for supplying particulate-laden gas to the filter compartments by common ductwork between the rows of compartments; (c) filter means in the filter compartments for removing particulate matterfrom particulate-laden gas to provide filtered gas; (d) a filtered gas outlet manifold for removing filtered gas from the filter compartments by common ductwork between the rows of compartments; (e) a cleaning system to clean the filter means in the filter compartments, the cleaning system having a reverse gas manifold connected to the filter compartments by common ductwork between the rows of compartments; and (f) clean gas supply means connected to the reverse gas manifold by common ductwork between the rows of compartments.

2. The fabricfilter system of Claim 1 wherein the clean gassuppiy means providesfilteredgasfrom the filtered gas outlet manifold to the reverse gas manifold by common ductwork between the rows of compartments.

3. The fabricfilter system of Claim 1 further comprises a reverse gas fan to provide clean gas to the reverse gas manifold.

4. The fabric filter system of Claim 3 wherein the reverse gas fan provides filtered gas to the reverse gas manifold by ductwork between the two rows of compartments from the filtered gas outlet manifold by ductwork between the two rows of compartments.

5. The fabric filter system of Claim 1 further comprising an end wall enclosing the fabricfilter system on the end having the clean gas supply means, the end wall defining the outerwall ofthe common ductwork connecting the clean gas supply means to the reverse gas manifold.

6. The fabric filter system of Claim 5 wherein the end wall of the fabricfilter system defining the common ductwork connecting the clean gas supply means to the reverse gas manifold is insulated to prevent heat loss.

7. The fabric filter system of Claim 1 further comprising an end wall enclosing thefabricfilter system on the end having the clean gas supply means, the end wall defining the outer wall ofthe common ductwork connecting the filtered gas outlet manifold to the clean gas supply means.

8. The fabric filter system of Claim 7 wherein the end wall of the fabricfilter system defining the common ductwork connecting the filtered gas outlet manifold to the clean gas supply means is insulated to prevent heat loss.

9. The fabric filter system of Claim 1 further comprising an end wall enclosing the fabricfilter system on the end having the clean gas supply means, the end wall defining the outer wall of the common ductwork connecting the clean gas supply means to the reverse gas manifold and further defining the outer wall of the common ductwork connecting the filtered gas outlet manifold to the clean gas supply means.

10. The filter system of Claim 9 wherein the end wall of the fabric filter system defining the common ductwork connecting the clean gas supply means to the reverse gas manifold and connecting the filtered gas outlet manifold to the clean gas supply means is insulated to prevent heat loss.

11. The fabricfilter system of Claim 1 further comprising a reverse gas fan to provide cleaning gas to the reverse gas manifold from the filtered gas outlet manifold.

12. The fabricfilter system of Claim 11 wherein the reverse gas fans provide filtered gas to the reverse gas manifold through ductwork between the two rows of compartments from the filtered gas outlet manifold through ductwork between the two rows of compartments, the end wall enclosing the end of the fabric filter system defining the outerwall of the ductwork of the common ducts connecting the filtered gas outlet manifold to the clean gas supply means or connecting the clean gas supply means to the reverse gas manifold or both.

13. A baghouse filter system ofthetype having at least two spaced-apart rows offilter compartments, each filter compartment having agasinletfor receiving particulate-laden gas, a gas outlet for delivering filtered gas,fabricfilter means between the gas inlet and the gas outlet and meansfor selectively blocking the gas inlet of each compartment, comprising:: (a) a gas in let manifold mounted internally in the baghouse and connected to a source of particulate-laden gas and to the gas inlet of a plurality of the spaced-apart filter compartments by common ductwork between the rows of filter compartments; (b) a filtered gas outlet manifold connected to the gas outlet of a plurality offiltercompartments andto a bag house clean gas outlet for removing filtered gas from the filter compartments by common ductwork between the rows of compartments; (c) a cleaning system to clean the filter means in the filter compartments, the cleaning system having a reverse gas manifold mounted internally in the bag house and being connected to the filter compartments by common ductwork between the rows of compartments;; (d) meansforselectivelycleaningthefiltermeans in each filter compartment; and (e) a reverse gas fan to provide clean gas to the reverse gas manifold by common ductwork between the rows of compartments and mounted internally in the bag house, the clean gas being filtered gas derived from the filtered gas outlet manifold by ductwork connecting the filtered gas outlet manifold to the reverse gas fan, the ductwork from the filtered gas outlet manifold being mounted internally in the bag house between the two rows of compartments.

14. The baghouse filter system of Claim 13 further comprising an end wall enclosing one end of the baghouse,the end wall defining the outerwall of the common ductwork connecting the clean gas supply meanstothe reverse gas manifold or connecting the filtered gas outlet manifold to the clean gas supply means or both.

15. The fabric filter system of Claim i4wherein the end wall of the fabric filter system defining the common ductwork connecting the clean gas supply means to the reverse gas manifold or connecting the filtergasoutletmanifoldtotheclean gas supply means or both, is insulated to prevent heat loss.

16. The baghousefilter system of Claim 13 wherein the clean gas supply means comprises two reverse gas fans connected to the reverse gas manifold and to the filtered gas outlet manifold.

17. A method of preventing the condensation of vapors from flue gas in a cleaning system ofthe reverse gas type in a bag house filter system having a plurality of filter compartments arranged in two spaced-apart rows, each filter compartment having a gas inlet for receiving heated particulate-laden gas from a gas inlet manifold mounted internally in the baghouse between the rows of compartments, the gas inlet manifold being connected to a source of heated, particulate-laden gas; a filtered gas outletfor delivering filtered gas having heat retained therein from the filter compartment to a filtered gas outlet manifold mounted internally in the baghouse between the rowsofcompartments,thegasoutlet manifold being connected to a baghouse clean gas outlet; fabric filter means between the gas inlet and the gas outlet of each filter compartment; a cleaning system to clean the fabric filter means with filtered gas from the filtered gas outlet manifold, the filter means having heat retained therein; and means for selectively cleaning the fabric filter means of at least onefiltercompartment, comprising: (a) internally mounting between the two rows of filter compartments in the bag house the ductwork connecting the filtered gas outlet manifold to the reverse gas manifold through a reverse gas fan, the outerwall of the ductwork being defined by the end wall ofthe baghouse; (b) insulating the outerwall ofthe ductwork defined by the end wall of the bag house to prevent heat loss;; (c) passing the filtered gas having heat retained therein through the internally mounted ductwork connecting the filtered gas outlet manifold to the reverse gas manifold and into the filter compartmentstocleanthefabricfiltermeans whereby heat is retained in the reverse gas and prevents condensation of the flue gas in the internally mounted ductwork and on the fabricfilter bags in the filter compartment.

18. The method of Claim 17 wherein the ductwork from the filtered gas outlet manifold to the reverse gas fan is maintained at the temperature of the filtered gas.

19. ThemethodofClaim 18whereinthe ductwork connecting the filtered gas outlet manifold to the reverse gas fan is maintained at a temperature of about30 Cto a temperature of about800 C.

20. The method of Claim 17 wherein the ductwork from the reverse gas fan to the reverse gas manifold is maintained at the temperature ofthe filtered gas.

21. The method of Claim 20 wherein the ductwork connecting the reverse gas fan to the reverse gas manifold is maintained at a temperature of about 30 C to a temperature of about 800 C.

22. ThemethodofClaim 17whereinthefabric filter means in the filter compartment is maintained at the temperature of the filtered gas whilethefabric filter means are being cleaned.

23. The method of Claim 22 wherein the fabric filter means in the filter compartment is maintained at a temperature of about 30"C to a temperature of about 8000C while the fabricfilter means is being cleaned.

24. The method of Claim 17 further comprising insulating the ductwork and elements of the reverse gas fan to prevent heat loss.

25. The method of Claim 17 wherein the filtered gas having heat retained therein is continuously passed through the internally mounted ductwork connecting the filtered gas outlet manifold to the reverse gas manifold and into thefilter compartments to maintain the temperature ofthe ductwork and the fabric filter means at the temperature ofthefiltered gas.

26. The method of Claim 17 wherein the filtered gas having heat retained therein is continuously passed through the internally mounted ductwork connecting the filtered gas outlet manifold to the reverse gas manifold and into the filter compartments to maintain the temperature of the ductwork and the fabric filter means at about 30 C to about 800 C.