CA1119776A - Method and apparatus for optimizing removal of acid gases - Google Patents
Method and apparatus for optimizing removal of acid gasesInfo
- Publication number
- CA1119776A CA1119776A CA000316591A CA316591A CA1119776A CA 1119776 A CA1119776 A CA 1119776A CA 000316591 A CA000316591 A CA 000316591A CA 316591 A CA316591 A CA 316591A CA 1119776 A CA1119776 A CA 1119776A
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- CA
- Canada
- Prior art keywords
- filter
- particulate material
- layer
- gas
- particulate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/46—Removing components of defined structure
- B01D53/48—Sulfur compounds
- B01D53/52—Hydrogen sulfide
- B01D53/526—Mixtures of hydrogen sulfide and carbon dioxide
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
- B01D46/02—Particle separators, e.g. dust precipitators, having hollow filters made of flexible material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D50/00—Combinations of methods or devices for separating particles from gases or vapours
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Health & Medical Sciences (AREA)
- Biomedical Technology (AREA)
- Environmental & Geological Engineering (AREA)
- Analytical Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Treating Waste Gases (AREA)
- Chimneys And Flues (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The treatment of gases before exhaust thereof into the atmosphere for removal of pollutants such as acid gases, wherein such gases are passed through a filter having a layer of particulate on the ingoing side of the filter surface for the removal of acid gases by absorption and/or reaction where-in the filtered gases are recirculated until the integrity of the layer of particulate material has been re-established and the removal efficiency for acid gases has been optimized.
The treatment of gases before exhaust thereof into the atmosphere for removal of pollutants such as acid gases, wherein such gases are passed through a filter having a layer of particulate on the ingoing side of the filter surface for the removal of acid gases by absorption and/or reaction where-in the filtered gases are recirculated until the integrity of the layer of particulate material has been re-established and the removal efficiency for acid gases has been optimized.
Description
7~6 This invention relates to the treatment of gases for the removal of acid gases before release of the gases into the atmosphere.
In the United States Patent No. 3,721l066 and United States Patent No. 3,808,774, description is made of the use of a mineral nahcolite as an absorbent and/or reactant for the removal of acid gases from a gaseous stream passed into contact therewith. For this purpose, the nahco].ite, in finely divided form, is deposited to provide a highly pervious layer on the ingoing side of a filter surface through which the gaseous system is drawn.
To form the layer of nahcolite on the ingoing side of the filter surface, use can be made of procedures described in the United States Pring patents No. 2,875,844, No. 2,875,847, and No. 2,919,174, wherein the finely divided absorbent or reactant particles are introduced for suspension into the gaseous stream drawn through the filter medium whereby removal of gaseous components is effected while the particulate material is in contact with the gaseous stream during suspension and whereby the par-ticulate material is carried by the gaseous stream for separation .
onto the ingoing side of the filter surface as the gaseous stream . passes therethrough. This forms a layer of particulate material on the ingoing side of the filter mediumO In this location, the particulate material is in a position to be engaged by the . through-going gaseous stream to effect removal of acid gases from -the gaseous stream as it passes through the deposited layer.
In United States Patents No. 3,808,774 and No. 3,721,066, .: description is made of the use of nepheline syenite as a reactant ' . ~J
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built up on the ingoing side of a filter surface for reaction to remove acid gases from gaseous streams passing therethrough. As described in the aforementioned patents, the activity of the nepheline syenite, in the removal of acid gases, is increased by wetting the nepheline syenite or by pre-exposure of the nepheline syenite to moisture or high humidity. For this purpose, the nepheline syenite is either wet before introduction to provide the layer on the ingoing side of the filter surface or else moisture is introduced into the gaseous stream in which the nepheline syenite is suspended for building up the layer of particulate material on the filter surface. In either event, additional equipment is required to achieve the desired wetting of the nepheline syenite, and until the desired amount of wetting has been achieved for optimum efficiency, a considerable amount of gas has been exhausted into the atmosphere which contains undesirable amounts of acid gas.
Further, it has been found that the removal of acid gases by either technique is not optimized until a layer of the desired thickness of the particulate material has been built up on the ingoing side of the filter surface and the particulate material in the layer has been actuated for optimum acid gas removal. Thus, penetration of the acid gases is highest when the filter surface ~` is ~eing brought back on-stream after cleaning and such penetration diminishes as the layer is built up to the desired thickness and defects in the filter layer are repaired and while the particulate ~ material in the layer is being treated to optimum removal i~ efficiency.
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~ 2-. , ' " ~' ~g776 This invention relates to an improvement in the method for reloading a filter surface for use in the removal of acid gases from a gaseous stream during a normal filter cycle in which the acid gases are removed by absorption or reaction during passage of the gaseous stream through a layer of particulate material built up on the ingoing side of a filter surface in which the layer of particulate material is periodically removed from the filter surface, the rebuilding of the layer of particulate material on the ingoing side of the filter surface after the spent layer has `:
` 10 been removed, comprising introducing the particulate treating material into a gaseous stream for suspension of the treating material therein, flowing the gaseous stream with the suspension of treating material through the filter surface for separation of ~;
the particulate treating material onto the ingoing side of the ; filter surface until a layer of the desired thickness has been built ~ up on the ingoing side of the filter surface, recirculating filtered ~ gas during buildup of the layer, continuing the recirculation a~ter the layer has been huilt up until the efficiency of the particulate material for removal of acid gases has been optimized and then : 20 discontinuing the recirculation of filtered gas.
~ This invention further relates to an apparatus for carrying : ~ .
" out the process of this invention comprising a filter housing subdivided into a plurality of filter sections each of which has an inlet plenum chamber into which the gases to be treated are introduced and a clean gas plenum chamber which receives the gases ` after treatment, a plurality of filter elements within each section . in which the ingoing sides of the filter elements communicate with -2a-.
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the inlet plenum chamber and the outgoiny sides of the filter elements communicate with the clean gas plenum chamber and means for causing the gaseous stream to circulate through the sections from the inlet plenum chamber, through the filter elements, to the clean gas plenum chamber~ means for removing one section from the normal filter flow for cleaning the filter elements and for rebuilding the layer of particulate material on the filter elements including for each section means for introducing the particulate materia]. into the gas stream introduced into the inlet plenum chamber whereby the particulate material is carried by the gas stream to the ingoing side of the filter elements for separation thereon to form a layer of the particulate material on the ingoing side of the filter elements, a header common to the clean gas plenum chambers of the plurality of filter sections, and means for bleeding off a portion of the cleaned gas from the header for recirculation to the filter section for pre-treatment of the particulate material in the layer deposited on the ingoing side of the filter elements to optimize acid gas removal.
It is a purpose of this invention to pro~ide a method and apparatus for providing a layer of particulate absorbent and/or reactant for the removal of acid gases from a gas stream filtering therethrough, wherein the filtered gas is :
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not released into the atmosphere until the desired mass and integrity of the layer h~s been achieved and the particulate ~ material in the layer has been treated in a manner to tmprove .: its efficiency for acid gas removal.
5 . These and other objects and advantages of this inven- -tion will hereinafter appear and for purposes of illustration, -~ but not of limitation, embodiments of the invention are s~o~m in the accompanying drawings, in which:
Fig. 1 ~s a schematic flow diagram of a gas treating system in which the interior of the fil~er tubes represent the ingoing side of the filter surface and a shaker mechanism ~ is used to effect removal o~ the l~yer of particulate naterial , ~ for replacement with a fresh increment;
: Fig. 2 is a cross-section of the filter tube, sh.owing the layer of particulate material on tt~e ~ngoing side thereof and Fig. 3 is a fLow diagram illustrating a preferred .;~ practice of this invention. :~
Briefly described, the invention comprises removal ; 20 of the filter surface from the normal filter stream for remo~ -~
. val of the filter cake, and then reloading the filLer surface by introducing the particulate treating material for suspen-. sion in the gaseous stream, and circulati~ng the gaseous stream through the filter surface to build up t~e layer of particu-late material on the ingoing side as the gaseous stream filters therethrough until a layer of the desired thiclcness ~as been built up on the filter surface, recirculating the filtered gas :
during buildup of the layer of particulate material and after ; the layer has been built up until the removal ef~iciency of the particulate material has been optimized ~y pre-treatment in which use is made of the recirculating gas stream.
The invention will first be described as applied to ,he use of nahcolite, as representative of minerals or other particulate materials in which ac-tivation is increased when heated to elevated temperature. It will be apparent that the basic concept of this invention will have application also to the pre-treatment of nepheline syenite and similar minerals or , .
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other particulates that are increased in activity by pre-treatment to increase the temperature> moisture or other~7ise.
With nahcolite, utilization is made of the gas to be cleaned, or cleaned gas, as the carrier in which the nahcolite is suspended for transport to the filter surface ~Jhere the particulate material separates out on the ingoing side to form the layer as the gas filters therethrough. Such intro-duction of particulate material is cGntinued until a layer of the desired thickness has been built up on the filter surface with the continuous recycle of the filter gas. ~ecycle of filtered gas is continued after the introduction of particulate material has been terminated to supply the additional heat for ; raising the nahcolite to operating temperature for optimum ; removal of acid gases. Thereafter, the filter section can ~e returned to the normal filter cycle.
For this purpose, the hot gases issuing from the clean gas plenum chamber of the gas treating unit are recirculated ~;~ with means for introducing the particulate material into the recirculating gas stream whereby the particulate ma~erial is conveyed for deposition to form the treated layer on the-in-'i going side of the filter surface. When the particulate mater-~l ial has been introduced in an amount to build u~-a layer of i the desired thickness on the ingoing side of the filter sur-: face, the introduction o particulate material is discontin-ued while recirculation of the hot cleaned gas is continued ` until the layer of particulate ma~erial has been heated to elevated temperature for optimum utilization in the removal , of acid gases. Thereafter, recirculation oE cleaned gas is i~ discontinued and the unit is returned on~stream to form a ` ;-~ 30 part of the operating cycle for the processing of gases before ; exhaust into the atmospllere.
;, Referring now to the modification shown in Fig, 1, ; the numeral 10 indicates a gas treatment sectlon having a bottom wall 12 in the form of a cell plate which separates the section into an equalizing gas chamber 14 and a bag house 16. The equalizing chamber 14 comm~nicates directly with an .
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~, inlet plenum ch~mber 18 having an inlet 20 through which the gas to be treated is introduced into the section from a conduit 21.
A collecting hopper 22 communicates with the underside of the equalizing chamber 14. An outlet opening 24 and closure 26 are provided at the bottom of the hopper for the removal of solids collected in the hopper.
Each section of the plurality of sections making up the assembly is provided wi-th a plurality of filter tubes 28 formed of natural fibers, such as cotton and the like, and preferably of synthetic fibers, such as Nylon(a trade mark for a polyamide resin~, Dacron (a trade mark for a polyester resin), glass fibers and the like high temperature resistant fibers, woven or non-woven into a porous filter fabric. The upper ends of the ~ilter tubes .......... 28 are closed with a loop for suspension by angle rods 32 from shaker bars 34 which extend crosswise of the section. Means, such as a motor 36 and eccentric 36' are operatively connected to the . .
bars to impart a rocking mo~ement which causes the tubes to be whipped in a manner to loosen any accumulated layer 38 of ;` particulate material on the ingoing side of the filter surface.
~: 20 For a more detailed description of a suitable device operating on the shaker principle, reference can be made to United States Patent ` No. 2,879,863 and United States Patent No. 2,932,362. The lower ends of the filter tubes 28 are anchored by rings or collars 40 to ~ the cell plate 12 in communication with openings 40 extending - therethrough.
The portion of the bag house 16 outside of the filter ~ tube constitutes the clean gas plenum chamber 44 having an outlet : ~5~
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opening 46 leading into conduit 48. The latter communicates with an exhaust fan 50, in normal filter flow, for causing the gas to be drawn into the section, through the filter tubes and into the clean gas plenum chamber. It will be understood that the exhaust fan or blower may be located other than in the conduit 48, it being desirable to locate the blower for inducing subatmospheric conditions within the clean air plenum chamber for circulation of the gases in the desired direction through the gas treating unit.
In Figure 1, illustration is made of a single treating , .
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section. It will be understood that the system is preferably formed of two or more such sections, eacll of which is se~ar-ately fed with the gas to be treated from a common header but wit-h the clean gas plenum chanbers interconnected for exhaust by a single unit. Thus one section can be cut off from the normal flow of gases to be treated while the other sections remain on stream.
In accordance with the practi.ce of this invention, a bypass in the form of a conduit 52 communicates the outle~
conduit 48 with the inlet conduit 21, with the by~ass being located beyond the blower. Blocking means, such as a damper -54, is mounted for rocking movement about a pivot 56 between open position, shown in solid lines in Fig. 1, and closed posi-tion, shown ~n broken lines i~ Fig. 1. In the open position, the damper 54 shuts off the bypass and leaves ~he condui~ 48 open for exhaust of the cleaned gas into the atmosphere. In closed position, the passage to the atmos~here is blocked by damper 54 while the bypass is open to enable the hot cleaned ` gases from the conduit 48 to pass :through the bypass and into the conduit 21.
' A blocking means, in the form of a damper plate 58, ;~
; is also provided at the juncture of the bypass w~th th~ con-duit 21 with means for actuation to block off the bypass when in open position and to open the bypass and block off the con-~ 25 duit 21 when in closed position.
: ~ A storage bin or hopper 60 containing nahcolite 62 -in finely divided form is provided with an outlet 64 communi-cating with the conduit 21 between the inlet 20 and the by-pass 52. A valve means of conventional construction is pro-; 30 vided at the outlet for controlling the flow of nahcolite from the hopper into the conduit.
In a normal cycle of operation, the filter tubes 28 are lined internally with a removable layer 66 of nahcolite.
With the dam~ers 54 and 5g in open position, gas to be treated is dra~7n through conduit 21, into the inlet plenum chamber 18, through the equalizing cham~er 14 and into the open ends of the filter tubes 28. ~s the gas is drawn through :~
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the filter tubes from the inside to the outside, acid gases are extracted by the nahcolite and particulate matter, if any, is filtered out so that cleaned gas passes through the filter tubes into ~he clean gas plenum chamber from which it is drawn by the blower 50 through the conduit 48 for release into the atmosphere. The gases treated are usually the effluent gases from a power plant or other exhaust from the burning of fossil or gaseous fuel wherein the effluent gases are at a sufficiently high temperature to maintain nahcolite at efficient operating lQ temperature such as within the range of 180Q-550F.
~en the ability of the nahcolite to remove acid gases from the gaseous stream passing into contact therewith has become substantially exhausted, such as after 20-60 minutes of operation, or when the pressure drop across the filter ele-ment becomes excessive because of the buildup o~ the filter cakeJ the section is relegated to a cleaning cycle in which ` the bags are shaken to loosen the layer of particulate material ~ `
on the ingoing side of the filter surface. The loosened parti-culate material falls gravitationally into the hopper ~or removal from the system.
During the cleaning cycle, gas flow is discontinued by closure of damper 58 in the line 21 leading to the section ; to be cleaned, while dampers S~ remain open to permit the flow of gas to be cleaned to each o~ the other sections.
Before the cleaned section îs returned on streamJ a ~- layer of nahcolite is reformed on the ingoing side of the fil-ter tubes. In accordance wi.th the p-f actice of this invention, this is accomplished by closing the damper 54 whereby clean hot gas from the other sections is combined with the cleaned gas recirculating in one section for passage through the by~ ;~
pass 52, the passage 21, and lnto theinlet 20 and cham~ers18 and 14 and then through the filter tubes. The gate valve 64 is opened for introduction o nahcolite which becomes suspended in the gas stream passing through conduit 21 and from which it is separated to reEorm the layer of nahcolite on the in-golng side of the filter tubes as the gases filter there-through. When a layer of the desired thickness has been built ~
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: up on the ingoing side of the filter tubes, the valve 64 is closed while recirculation o the hot cleaned gases is con-:`: tinued until the temperature of the nahcolite in ~he built up layer has been raised to the desired ~emperatur~ for efi-~ 5 cient and effective removal of acid gases, such as to a tem-,~'' perature within the range of 180-550F.
Such additional heating by the recirculated hot :` cleaned gas will often take 5-15 minutes after the layer has '` been deposited thereby to provide for a reloading cycle of ~'~ 10 about 10-15 minutes in total. Thereafter the section can be :~ returned on stream by opening the dampers 5~,and 58.
.," A multiple filter section of the ~ype preferred is ~: . illustrated in Fig. 3 wherein the filter elements are arranged '~ ' in separate compartments A, B, C and D. Each c.ompartment has , '~
,'~ 15 its own damper 58a for controlling normal filter flow from -' header 70 into the compartment and each compartment also'has ~ its own da,mper 58b for controlling flow of bypassed gas from .,, header 82 which communicates with chamber 78 into which by-.~ passed gas is circulated by bypass line 76. Nahcolite is "'~, 20 introduced into chamber 78 from hopper ~0. The exhaust from , ~:
each of the compartments is combined-in header 48a for exhaust ~.
~ into the atmosphere by exhauster 50 or for recycle through ~y- ~`
,' pass 76, as heretofore described. In this instance, the ::' exhauster 90 in the bypass 76 draws off enough of the cleaned -, 25 gas from the header 48a to handle one compartment. ';
~hen damper 52a is open, damper 58b to the same com-.~ partment is closed to enable normal flow of gas to be cleaned ~' to the compartment. I~hen damper 58a îs closed then damper 58b ~ to the same compartment is open.to shut off normal filter flow ,~ 30 and for enabling passage of bypass gas from the header 82 into ,.
the compartment. :
It will be apparent that the system described pro-vides for reloading and heating of the nahcolite, withou.t the : need for additional equipment or space and that deposition of nahcolite to orm the operative layer is effected with clean gas as it is generated during operation of the equipmen~. More importantly, the heat used to raise the temperature of the .
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7~6 nahcolite to a level for most efficient removal of acid gases represents residual heat in the recirculating cleaned gas that would otherwise be wasted into the atmosphere. In a four sec-tion system, operating on a one hour cycle, it will be appar-ent that three sections can be "on stream" while one section is in the cleaning and regenerating cycle using the clean hot gases - from the sec~ions that are on stream.
~hen use is made of nepheline syenite as the ~ar~icu~
late material, the same concepts can be employed or pre-treat-ment of the particulate material to increase the moisture con-~' tent. Thus the buildup of the layer of nepheline syenite on the ingoing side of the filter surface can be achieved in the same manner as described for nahcolite. ~lowever, instead of merely recirculating the gases passing through the filter sur-face, means are provided for introducing moisture into the ~ gas stream to increase the moisture content of the recircu-'~! lated gases whereby the moisture content of the nepheline sye-nite in the already deposited layer is also increased. I~hen ; the desired amount of moisture-content has been achieved for optimum removal of acid gases by the nepheline syenite in the , deposited layer, the recycle o clean gas can be discontinued and the filter section returned to the normal filter cycle.
For this purpose, means would be provided for intro-ducing moisture, as by spraying, into line 21. Such introduc- ;`
tion of moisture would be carried ou~ while ~he particulate material is introduced for suspension into the gas stream to be treated or recycled gas, and into the recycled gas after the in~roduction of particulate ~aterial has been discontin-ued.
Similarly, in the modification shown in Fig. 3, the moisture would be introduced as by means of a spray ~6 into the chamber 78 or else in lines 76 or ~2, during the intro-duction of particulate material for suspension in the recycled clean gas stream and af-terwards, until the moisture content of the nepheLine syenite in the deposited layer has been raised to the desired level. Thereafter the filter section woula - e returned on stream.
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It will be understood that the concepts of this inven-ion will have application to the pre-treatment of other mater-'' 21s used in the removal of contaminated gases wherei.n the re~oval efficiency of the material is increased by reaction .,ith elements capable of being carried by recirculated gases before release of the gases into the atmosphere. Such other materials can be represented by absorbents such as activa~ed carbon and/or reactants such as sodium aluminate or other base materials as described in the aforementioned Pring patents.
1~ It will be understood that changes may be made in the details of construction, arrangement and operation without departin-g from the spirit of the invention, especially as defined in the folloT~Jing claims.
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In the United States Patent No. 3,721l066 and United States Patent No. 3,808,774, description is made of the use of a mineral nahcolite as an absorbent and/or reactant for the removal of acid gases from a gaseous stream passed into contact therewith. For this purpose, the nahco].ite, in finely divided form, is deposited to provide a highly pervious layer on the ingoing side of a filter surface through which the gaseous system is drawn.
To form the layer of nahcolite on the ingoing side of the filter surface, use can be made of procedures described in the United States Pring patents No. 2,875,844, No. 2,875,847, and No. 2,919,174, wherein the finely divided absorbent or reactant particles are introduced for suspension into the gaseous stream drawn through the filter medium whereby removal of gaseous components is effected while the particulate material is in contact with the gaseous stream during suspension and whereby the par-ticulate material is carried by the gaseous stream for separation .
onto the ingoing side of the filter surface as the gaseous stream . passes therethrough. This forms a layer of particulate material on the ingoing side of the filter mediumO In this location, the particulate material is in a position to be engaged by the . through-going gaseous stream to effect removal of acid gases from -the gaseous stream as it passes through the deposited layer.
In United States Patents No. 3,808,774 and No. 3,721,066, .: description is made of the use of nepheline syenite as a reactant ' . ~J
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built up on the ingoing side of a filter surface for reaction to remove acid gases from gaseous streams passing therethrough. As described in the aforementioned patents, the activity of the nepheline syenite, in the removal of acid gases, is increased by wetting the nepheline syenite or by pre-exposure of the nepheline syenite to moisture or high humidity. For this purpose, the nepheline syenite is either wet before introduction to provide the layer on the ingoing side of the filter surface or else moisture is introduced into the gaseous stream in which the nepheline syenite is suspended for building up the layer of particulate material on the filter surface. In either event, additional equipment is required to achieve the desired wetting of the nepheline syenite, and until the desired amount of wetting has been achieved for optimum efficiency, a considerable amount of gas has been exhausted into the atmosphere which contains undesirable amounts of acid gas.
Further, it has been found that the removal of acid gases by either technique is not optimized until a layer of the desired thickness of the particulate material has been built up on the ingoing side of the filter surface and the particulate material in the layer has been actuated for optimum acid gas removal. Thus, penetration of the acid gases is highest when the filter surface ~` is ~eing brought back on-stream after cleaning and such penetration diminishes as the layer is built up to the desired thickness and defects in the filter layer are repaired and while the particulate ~ material in the layer is being treated to optimum removal i~ efficiency.
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~ 2-. , ' " ~' ~g776 This invention relates to an improvement in the method for reloading a filter surface for use in the removal of acid gases from a gaseous stream during a normal filter cycle in which the acid gases are removed by absorption or reaction during passage of the gaseous stream through a layer of particulate material built up on the ingoing side of a filter surface in which the layer of particulate material is periodically removed from the filter surface, the rebuilding of the layer of particulate material on the ingoing side of the filter surface after the spent layer has `:
` 10 been removed, comprising introducing the particulate treating material into a gaseous stream for suspension of the treating material therein, flowing the gaseous stream with the suspension of treating material through the filter surface for separation of ~;
the particulate treating material onto the ingoing side of the ; filter surface until a layer of the desired thickness has been built ~ up on the ingoing side of the filter surface, recirculating filtered ~ gas during buildup of the layer, continuing the recirculation a~ter the layer has been huilt up until the efficiency of the particulate material for removal of acid gases has been optimized and then : 20 discontinuing the recirculation of filtered gas.
~ This invention further relates to an apparatus for carrying : ~ .
" out the process of this invention comprising a filter housing subdivided into a plurality of filter sections each of which has an inlet plenum chamber into which the gases to be treated are introduced and a clean gas plenum chamber which receives the gases ` after treatment, a plurality of filter elements within each section . in which the ingoing sides of the filter elements communicate with -2a-.
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the inlet plenum chamber and the outgoiny sides of the filter elements communicate with the clean gas plenum chamber and means for causing the gaseous stream to circulate through the sections from the inlet plenum chamber, through the filter elements, to the clean gas plenum chamber~ means for removing one section from the normal filter flow for cleaning the filter elements and for rebuilding the layer of particulate material on the filter elements including for each section means for introducing the particulate materia]. into the gas stream introduced into the inlet plenum chamber whereby the particulate material is carried by the gas stream to the ingoing side of the filter elements for separation thereon to form a layer of the particulate material on the ingoing side of the filter elements, a header common to the clean gas plenum chambers of the plurality of filter sections, and means for bleeding off a portion of the cleaned gas from the header for recirculation to the filter section for pre-treatment of the particulate material in the layer deposited on the ingoing side of the filter elements to optimize acid gas removal.
It is a purpose of this invention to pro~ide a method and apparatus for providing a layer of particulate absorbent and/or reactant for the removal of acid gases from a gas stream filtering therethrough, wherein the filtered gas is :
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not released into the atmosphere until the desired mass and integrity of the layer h~s been achieved and the particulate ~ material in the layer has been treated in a manner to tmprove .: its efficiency for acid gas removal.
5 . These and other objects and advantages of this inven- -tion will hereinafter appear and for purposes of illustration, -~ but not of limitation, embodiments of the invention are s~o~m in the accompanying drawings, in which:
Fig. 1 ~s a schematic flow diagram of a gas treating system in which the interior of the fil~er tubes represent the ingoing side of the filter surface and a shaker mechanism ~ is used to effect removal o~ the l~yer of particulate naterial , ~ for replacement with a fresh increment;
: Fig. 2 is a cross-section of the filter tube, sh.owing the layer of particulate material on tt~e ~ngoing side thereof and Fig. 3 is a fLow diagram illustrating a preferred .;~ practice of this invention. :~
Briefly described, the invention comprises removal ; 20 of the filter surface from the normal filter stream for remo~ -~
. val of the filter cake, and then reloading the filLer surface by introducing the particulate treating material for suspen-. sion in the gaseous stream, and circulati~ng the gaseous stream through the filter surface to build up t~e layer of particu-late material on the ingoing side as the gaseous stream filters therethrough until a layer of the desired thiclcness ~as been built up on the filter surface, recirculating the filtered gas :
during buildup of the layer of particulate material and after ; the layer has been built up until the removal ef~iciency of the particulate material has been optimized ~y pre-treatment in which use is made of the recirculating gas stream.
The invention will first be described as applied to ,he use of nahcolite, as representative of minerals or other particulate materials in which ac-tivation is increased when heated to elevated temperature. It will be apparent that the basic concept of this invention will have application also to the pre-treatment of nepheline syenite and similar minerals or , .
~ 7 ~
other particulates that are increased in activity by pre-treatment to increase the temperature> moisture or other~7ise.
With nahcolite, utilization is made of the gas to be cleaned, or cleaned gas, as the carrier in which the nahcolite is suspended for transport to the filter surface ~Jhere the particulate material separates out on the ingoing side to form the layer as the gas filters therethrough. Such intro-duction of particulate material is cGntinued until a layer of the desired thickness has been built up on the filter surface with the continuous recycle of the filter gas. ~ecycle of filtered gas is continued after the introduction of particulate material has been terminated to supply the additional heat for ; raising the nahcolite to operating temperature for optimum ; removal of acid gases. Thereafter, the filter section can ~e returned to the normal filter cycle.
For this purpose, the hot gases issuing from the clean gas plenum chamber of the gas treating unit are recirculated ~;~ with means for introducing the particulate material into the recirculating gas stream whereby the particulate ma~erial is conveyed for deposition to form the treated layer on the-in-'i going side of the filter surface. When the particulate mater-~l ial has been introduced in an amount to build u~-a layer of i the desired thickness on the ingoing side of the filter sur-: face, the introduction o particulate material is discontin-ued while recirculation of the hot cleaned gas is continued ` until the layer of particulate ma~erial has been heated to elevated temperature for optimum utilization in the removal , of acid gases. Thereafter, recirculation oE cleaned gas is i~ discontinued and the unit is returned on~stream to form a ` ;-~ 30 part of the operating cycle for the processing of gases before ; exhaust into the atmospllere.
;, Referring now to the modification shown in Fig, 1, ; the numeral 10 indicates a gas treatment sectlon having a bottom wall 12 in the form of a cell plate which separates the section into an equalizing gas chamber 14 and a bag house 16. The equalizing chamber 14 comm~nicates directly with an .
.
~, inlet plenum ch~mber 18 having an inlet 20 through which the gas to be treated is introduced into the section from a conduit 21.
A collecting hopper 22 communicates with the underside of the equalizing chamber 14. An outlet opening 24 and closure 26 are provided at the bottom of the hopper for the removal of solids collected in the hopper.
Each section of the plurality of sections making up the assembly is provided wi-th a plurality of filter tubes 28 formed of natural fibers, such as cotton and the like, and preferably of synthetic fibers, such as Nylon(a trade mark for a polyamide resin~, Dacron (a trade mark for a polyester resin), glass fibers and the like high temperature resistant fibers, woven or non-woven into a porous filter fabric. The upper ends of the ~ilter tubes .......... 28 are closed with a loop for suspension by angle rods 32 from shaker bars 34 which extend crosswise of the section. Means, such as a motor 36 and eccentric 36' are operatively connected to the . .
bars to impart a rocking mo~ement which causes the tubes to be whipped in a manner to loosen any accumulated layer 38 of ;` particulate material on the ingoing side of the filter surface.
~: 20 For a more detailed description of a suitable device operating on the shaker principle, reference can be made to United States Patent ` No. 2,879,863 and United States Patent No. 2,932,362. The lower ends of the filter tubes 28 are anchored by rings or collars 40 to ~ the cell plate 12 in communication with openings 40 extending - therethrough.
The portion of the bag house 16 outside of the filter ~ tube constitutes the clean gas plenum chamber 44 having an outlet : ~5~
'" , -.
opening 46 leading into conduit 48. The latter communicates with an exhaust fan 50, in normal filter flow, for causing the gas to be drawn into the section, through the filter tubes and into the clean gas plenum chamber. It will be understood that the exhaust fan or blower may be located other than in the conduit 48, it being desirable to locate the blower for inducing subatmospheric conditions within the clean air plenum chamber for circulation of the gases in the desired direction through the gas treating unit.
In Figure 1, illustration is made of a single treating , .
, .
.
~, ,:
.
; -5a-: .t.
...~,~
: .
: :. ~ .: :
section. It will be understood that the system is preferably formed of two or more such sections, eacll of which is se~ar-ately fed with the gas to be treated from a common header but wit-h the clean gas plenum chanbers interconnected for exhaust by a single unit. Thus one section can be cut off from the normal flow of gases to be treated while the other sections remain on stream.
In accordance with the practi.ce of this invention, a bypass in the form of a conduit 52 communicates the outle~
conduit 48 with the inlet conduit 21, with the by~ass being located beyond the blower. Blocking means, such as a damper -54, is mounted for rocking movement about a pivot 56 between open position, shown in solid lines in Fig. 1, and closed posi-tion, shown ~n broken lines i~ Fig. 1. In the open position, the damper 54 shuts off the bypass and leaves ~he condui~ 48 open for exhaust of the cleaned gas into the atmosphere. In closed position, the passage to the atmos~here is blocked by damper 54 while the bypass is open to enable the hot cleaned ` gases from the conduit 48 to pass :through the bypass and into the conduit 21.
' A blocking means, in the form of a damper plate 58, ;~
; is also provided at the juncture of the bypass w~th th~ con-duit 21 with means for actuation to block off the bypass when in open position and to open the bypass and block off the con-~ 25 duit 21 when in closed position.
: ~ A storage bin or hopper 60 containing nahcolite 62 -in finely divided form is provided with an outlet 64 communi-cating with the conduit 21 between the inlet 20 and the by-pass 52. A valve means of conventional construction is pro-; 30 vided at the outlet for controlling the flow of nahcolite from the hopper into the conduit.
In a normal cycle of operation, the filter tubes 28 are lined internally with a removable layer 66 of nahcolite.
With the dam~ers 54 and 5g in open position, gas to be treated is dra~7n through conduit 21, into the inlet plenum chamber 18, through the equalizing cham~er 14 and into the open ends of the filter tubes 28. ~s the gas is drawn through :~
' ~, .
,,,:
'7~
the filter tubes from the inside to the outside, acid gases are extracted by the nahcolite and particulate matter, if any, is filtered out so that cleaned gas passes through the filter tubes into ~he clean gas plenum chamber from which it is drawn by the blower 50 through the conduit 48 for release into the atmosphere. The gases treated are usually the effluent gases from a power plant or other exhaust from the burning of fossil or gaseous fuel wherein the effluent gases are at a sufficiently high temperature to maintain nahcolite at efficient operating lQ temperature such as within the range of 180Q-550F.
~en the ability of the nahcolite to remove acid gases from the gaseous stream passing into contact therewith has become substantially exhausted, such as after 20-60 minutes of operation, or when the pressure drop across the filter ele-ment becomes excessive because of the buildup o~ the filter cakeJ the section is relegated to a cleaning cycle in which ` the bags are shaken to loosen the layer of particulate material ~ `
on the ingoing side of the filter surface. The loosened parti-culate material falls gravitationally into the hopper ~or removal from the system.
During the cleaning cycle, gas flow is discontinued by closure of damper 58 in the line 21 leading to the section ; to be cleaned, while dampers S~ remain open to permit the flow of gas to be cleaned to each o~ the other sections.
Before the cleaned section îs returned on streamJ a ~- layer of nahcolite is reformed on the ingoing side of the fil-ter tubes. In accordance wi.th the p-f actice of this invention, this is accomplished by closing the damper 54 whereby clean hot gas from the other sections is combined with the cleaned gas recirculating in one section for passage through the by~ ;~
pass 52, the passage 21, and lnto theinlet 20 and cham~ers18 and 14 and then through the filter tubes. The gate valve 64 is opened for introduction o nahcolite which becomes suspended in the gas stream passing through conduit 21 and from which it is separated to reEorm the layer of nahcolite on the in-golng side of the filter tubes as the gases filter there-through. When a layer of the desired thickness has been built ~
, :1.
.. ~ , . . .
~ 1.197~7G
.
: up on the ingoing side of the filter tubes, the valve 64 is closed while recirculation o the hot cleaned gases is con-:`: tinued until the temperature of the nahcolite in ~he built up layer has been raised to the desired ~emperatur~ for efi-~ 5 cient and effective removal of acid gases, such as to a tem-,~'' perature within the range of 180-550F.
Such additional heating by the recirculated hot :` cleaned gas will often take 5-15 minutes after the layer has '` been deposited thereby to provide for a reloading cycle of ~'~ 10 about 10-15 minutes in total. Thereafter the section can be :~ returned on stream by opening the dampers 5~,and 58.
.," A multiple filter section of the ~ype preferred is ~: . illustrated in Fig. 3 wherein the filter elements are arranged '~ ' in separate compartments A, B, C and D. Each c.ompartment has , '~
,'~ 15 its own damper 58a for controlling normal filter flow from -' header 70 into the compartment and each compartment also'has ~ its own da,mper 58b for controlling flow of bypassed gas from .,, header 82 which communicates with chamber 78 into which by-.~ passed gas is circulated by bypass line 76. Nahcolite is "'~, 20 introduced into chamber 78 from hopper ~0. The exhaust from , ~:
each of the compartments is combined-in header 48a for exhaust ~.
~ into the atmosphere by exhauster 50 or for recycle through ~y- ~`
,' pass 76, as heretofore described. In this instance, the ::' exhauster 90 in the bypass 76 draws off enough of the cleaned -, 25 gas from the header 48a to handle one compartment. ';
~hen damper 52a is open, damper 58b to the same com-.~ partment is closed to enable normal flow of gas to be cleaned ~' to the compartment. I~hen damper 58a îs closed then damper 58b ~ to the same compartment is open.to shut off normal filter flow ,~ 30 and for enabling passage of bypass gas from the header 82 into ,.
the compartment. :
It will be apparent that the system described pro-vides for reloading and heating of the nahcolite, withou.t the : need for additional equipment or space and that deposition of nahcolite to orm the operative layer is effected with clean gas as it is generated during operation of the equipmen~. More importantly, the heat used to raise the temperature of the .
" ~ ' ' ' ~ ` ' ' . ' " '' ' -., :,.~ .
, ' , ' : ' -:
.
7~6 nahcolite to a level for most efficient removal of acid gases represents residual heat in the recirculating cleaned gas that would otherwise be wasted into the atmosphere. In a four sec-tion system, operating on a one hour cycle, it will be appar-ent that three sections can be "on stream" while one section is in the cleaning and regenerating cycle using the clean hot gases - from the sec~ions that are on stream.
~hen use is made of nepheline syenite as the ~ar~icu~
late material, the same concepts can be employed or pre-treat-ment of the particulate material to increase the moisture con-~' tent. Thus the buildup of the layer of nepheline syenite on the ingoing side of the filter surface can be achieved in the same manner as described for nahcolite. ~lowever, instead of merely recirculating the gases passing through the filter sur-face, means are provided for introducing moisture into the ~ gas stream to increase the moisture content of the recircu-'~! lated gases whereby the moisture content of the nepheline sye-nite in the already deposited layer is also increased. I~hen ; the desired amount of moisture-content has been achieved for optimum removal of acid gases by the nepheline syenite in the , deposited layer, the recycle o clean gas can be discontinued and the filter section returned to the normal filter cycle.
For this purpose, means would be provided for intro-ducing moisture, as by spraying, into line 21. Such introduc- ;`
tion of moisture would be carried ou~ while ~he particulate material is introduced for suspension into the gas stream to be treated or recycled gas, and into the recycled gas after the in~roduction of particulate ~aterial has been discontin-ued.
Similarly, in the modification shown in Fig. 3, the moisture would be introduced as by means of a spray ~6 into the chamber 78 or else in lines 76 or ~2, during the intro-duction of particulate material for suspension in the recycled clean gas stream and af-terwards, until the moisture content of the nepheLine syenite in the deposited layer has been raised to the desired level. Thereafter the filter section woula - e returned on stream.
;
. . .
...... ~:, . :
: . . . .
. . .
. . .
7~;
It will be understood that the concepts of this inven-ion will have application to the pre-treatment of other mater-'' 21s used in the removal of contaminated gases wherei.n the re~oval efficiency of the material is increased by reaction .,ith elements capable of being carried by recirculated gases before release of the gases into the atmosphere. Such other materials can be represented by absorbents such as activa~ed carbon and/or reactants such as sodium aluminate or other base materials as described in the aforementioned Pring patents.
1~ It will be understood that changes may be made in the details of construction, arrangement and operation without departin-g from the spirit of the invention, especially as defined in the folloT~Jing claims.
,, . ' ' - ' :
, :
,, . , . : .
Claims (13)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In the method for reloading a filter surface for use in the removal of acid gases from a gaseous stream during a normal filter cycle in which the acid gases are removed by absorption or reaction during passage of the gaseous stream through a layer of particulate material built up on the ingoing side of a filter surface in which the layer of particulate material is periodically removed from the filter surface, the rebuilding of the layer of particulate material on the ingoing side of the filter surface after the spent layer has been removed, comprising introducing the particulate treating mater-ial into a gaseous stream for suspension of the treating material therein, flowing the gaseous stream with the suspension of treating material through the filter surface for separation of the particulate treating material onto the ingoing side of the filter surface until a layer of the desired thickness has been built up on the ingoing side of the filter surface, recirculating filtered gas during buildup of the layer, continuing the recirculation after the layer has been built up until the efficiency of the particulate material for removal of acid gases has been optimized and then discontinuing the recir-culation of filtered gas.
2. The method as claimed in claim 1 in which the particulate mat-erial is introduced into the gaseous stream for transport thereby until the desired amount of particulate material has been collected on the filter sur-face, and discontinuing the introduction of particulate material while contin-uing the recirculation of filtered gas to effect the desired pretreatment of the particulate material in the layer.
3. The method as claimed in claim 1 in which the particulate mat-erial is introduced directly into a stream of recirculated filtered gas.
4. The method as claimed in Claim 1 in which the particulate treating material is of the type in which the efficiency for removal of acid gases is increased when the particulate material is at elevated temperature, and in which the gas to be cleaned is at a temperature sufficient to heat the particulate material to a temperature for optimizing removal efficiency.
5, The method as claimed in Claim 4 in which the particulate material is nahcolite and in which the filtered gases at elevated temperature are recycled to heat the deposited layer of nahcolite to elevated temperature.
6. The method as claimed in Claim 5 in which the nahcolite is heated by the recirculating gases to a tempera-ture within the range of 180°-550°F.
7. The method as claimed in Claim 1 in which the particulate teeating material is of the type in which the efficiency for the removal of acid gases is increased when the particulate material has been pre-treated with moisture, the steps of introducing moisture into the recycled gaseous stream for pre-treatment of the layer of particulate material after it has been deposited on the filter surface.
8. The method as claimed in Claim 7 in which the particulate material is nepheline syenite.
9. Apparatus for carrying out the process of Claim 1 comprising a filter housing subdivided into a plurality of filter sections each of which has an inlet plenum chamber into which the gases to be treated are introduced and a clean gas plenum chamber which receives the gases after treatment, a plurality of filter elements within each section in which the ingoing sides of the filter elements communicate with the in-let plenum chamber and the outgoing sides of the filter ele-ments communicate with the clean gas plenum chamber and means for causing the gaseous stream to circulate through the sec-tions from the inlet plenum chamber, through the filter ele-ments, to the clean gas plenum chamber, means for removing one section from the normal filter flow for cleaning the filter elements and for rebuilding the layer of particulate material on the filter elements including for each section means for introducing the particulate material into the gas stream introduced into the inlet plenum chamber whereby the parti-culate material is carried by the gas stream to the ingoing side of the filter elements for separation thereon to form a layer of the particulate material on the ingoing side of the filter elements, a header common to the clean gas plenum chambers of the plurality of filter sections, and means for bleeding off a portion of the cleaned gas from the header for recirculation to the filter section for pre-treatment of the particulate material in the layer deposited on the ingoing side of the filter elements to optimize acid gas removal.
10. Apparatus as claimed in Claim 9 in which, when the particulate material is of the type in which the activity for removal of acid gases is optimized when pre-heated to elevated temperature, the gaseous stream comprises a hot gas stream, which includes means for controlling the recirculation of the cleaned gas from the clean gas plenum chamber to the inlet plenum chamber and in which such means permits recirculation after introduction of the particulate material has been discontinued to heat up the deposited layer of particulate material collected on the ingoing side of the filter elements, and which includes means for discontinuing recirculation and returning the apparatus to normal filter flow when the built up layer of particulate material has attained the desired temperature.
11. Apparatus as claimed in Claim 10 in which the particulate treating material is nahcolite.
12. Apparatus as claimed in Claim 9 in which, when the particulate material is of the type in which the efficiency for the removal of acid gases is increased when the particulate material has been pre-treated with moisture, the apparatus includes means for introduction of moisture into the recircu-lating gas stream.
13. Apparatus as claimed in Claim 12 in which the particulate material is nepheline syenite.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US85303077A | 1977-11-21 | 1977-11-21 | |
| US853,030 | 1977-11-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1119776A true CA1119776A (en) | 1982-03-16 |
Family
ID=25314840
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000316591A Expired CA1119776A (en) | 1977-11-21 | 1978-11-21 | Method and apparatus for optimizing removal of acid gases |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS5479163A (en) |
| AU (1) | AU518988B2 (en) |
| CA (1) | CA1119776A (en) |
| GB (1) | GB2008969B (en) |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3011177A1 (en) * | 1980-03-22 | 1981-10-08 | Heinz Ing.(grad.) 4390 Gladbeck Hölter | Waste gas chemisorbent materials dried in branch circuit - before return to main flow leading to filter |
| DE3020049A1 (en) * | 1980-05-24 | 1981-12-10 | Heinz Ing.(grad.) 4390 Gladbeck Hölter | Chemisorption filter for gas purificn. - has small area being cleaned, giving large available area for reaction |
| US5298162A (en) * | 1986-04-29 | 1994-03-29 | Kurt W. Niederer | Multi-stage fluid filter |
| BE1003446A4 (en) * | 1989-10-09 | 1992-03-24 | Wulbrecht Hendrik | Smoke filter speed retardant reiniginsinstallatie room and for the filter cloth. |
| ITMI20022732A1 (en) * | 2002-12-20 | 2004-06-21 | Voest Alpine Impianti S R L | SYSTEM FOR SEPARATING DUST PRESENT IN A SMOKE OF |
| ITUB20154809A1 (en) * | 2015-10-15 | 2016-01-16 | Domenico Tanfoglio | BIOGAS PURIFIER |
| SE541920C2 (en) * | 2017-10-01 | 2020-01-07 | Absolent Ab | Filter system with a layer comprising active carbon containing permeable bags |
| CN110038355B (en) * | 2019-05-10 | 2023-09-08 | 潍坊智滤环保科技有限公司 | Air purifying device, system and application |
| CN112717575B (en) * | 2020-12-08 | 2023-07-04 | 内蒙古万众炜业科技环保股份公司 | Tail gas treatment device and process for generating power by using raw gas |
| CN115105902B (en) * | 2022-08-29 | 2022-11-15 | 启东凯顺机械制造有限公司 | Early warning method for replacement time of filter bag for filtering industrial dust |
-
1978
- 1978-11-17 GB GB7845041A patent/GB2008969B/en not_active Expired
- 1978-11-20 AU AU41707/78A patent/AU518988B2/en not_active Expired
- 1978-11-21 CA CA000316591A patent/CA1119776A/en not_active Expired
- 1978-11-21 JP JP14292878A patent/JPS5479163A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| GB2008969A (en) | 1979-06-13 |
| AU4170778A (en) | 1979-05-31 |
| AU518988B2 (en) | 1981-10-29 |
| GB2008969B (en) | 1982-06-23 |
| JPS5479163A (en) | 1979-06-23 |
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