us 5464459x 1995 vanbuskirk - chevron type mist eliminator and system

7/22/2019 US 5464459x 1995 VANBUSKIRK - Chevron Type Mist Eliminator and System

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United States Patent [19JVanBuskirk et al.[54] CHEVRON TYPE MIST ELIMINATOR AND

SYSTEM[75] Inventors: Gregory K. VanBuskirk Wichita,Kans.; Chang-Li Hsieh Carlisle,Mass.; Kenneth J McNulty Atkinson,

N.H.; Oie V Hansen Wichita, Kans.[73] Assignee: Koch Engineering Company Inc.,

Wichita, Kans.[21] Appl. No.: 254 373[22] Filed: Jun. 6 1994[51] Int Cl.6 . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . BOlD 45/08[52] U.S. CI . .......................... 55/257.2; 55/257.3; 55/440;

55/443[58] Field o Search .................................... 55/257.2, 440,

[56]

3,748,8323,757,4984,157,2504,557,7404,601,731

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55/442, 443, 257.3, 257.5References Cited

U.S. PATENT DOCUMENTS7 1973 Furlong et al. .......... ............ .. 55/257 2911973 Hurlbut et al. ........................... 55/440611979 Regehr et al ..................... 55/257.3 X12/1985 Smith ........................................ 55/4407/1986 Michelson ............................. 55/440 X

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ll US005464459A[11] Patent Number:[45] Date o Patent:

5 464 459Nov. 7 1995

4,968,328 1111990 Duke ..................................... 55/440 X4,975,101 1211990 Swanborn ................................. 55/4405,203,894 4/1993 Chowaniec ................................ 55/4405,268,011 1211993 Wurz ...................................... 55/257.25,269,823 12/1993 Wurz 55/443 XOTHER PUBLICATIONS

Munters Corporation, 8800 CM/1193/2000 , 8800 Series,Vertical Flow Mist Eliminators 1993.Primary Examiner-Richard L. ChiesaAttorney Agent r Firm Richard P Crowley[57] ABSTRACTA mist eliminator for removing liquid droplets from a gasstream, which includes a plurality of impingement bailles,the bailles having a profile including a short inlet section, alower angled section, a short interconnecting section, anupper angled section, and a short outlet section, the length ofthe lower angled section longer than the upper angledsection, the upper angled section having a greater angularinclination than the lower angled section, thereby providingfor a mist eliminator for use in a gas.-liquid contact columnof higher gas throughput, low pressure drop, moderateremoval efficiency, and low manufacturing cost, which iseasily cleaned, and particularly adapted for wet scrubbingpro cesses.

13 Claims 1 Drawing Sheet

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U.S. Patent Nov. 7 1995 5 464 459

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5 464 459CHEVRON TYPE MIST ELIMINATOR AND

SYSTEM

BACKGROUND OF THE INVENTIONMist eliminators are typically employed to remove liquidmist or liquid particles from agas stream in which liquid hasbeen suspended or entrained. Mist eliminators may be

employed in a wide variety of devices where there aregas-liquid contacts and are particularly used for the cleaningof waste or flue gas streams in a wet scrubber or otherapplications. In such processes, mist eliminator devices areprovided in one or more layers across a gas-liquid contactingcolumn or duct to remove the mist from the gas to providea mist-lean gas stream from a mist-rich gas stream.

Mist eliminators may comprise a wide variety of differentstructures; however, one very popular type of mist eliminator comprises a baffle-type or chevron-type mist eliminatorwhich is arranged in one or more layers and provides for azigzag or a tortuous ftow path through the generally parallel,spaced-apart, mist eliminator baffles, with the baffles generally having an upstream and a downstream edge andarranged horizontally within the gas-liquid column or chamber, although they may assume other sloped positions, and

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2which mist eliminator comprises a plurality of generallyspaced-apart, generally aligned, parallel impingement typebaffles or blades, which normally extend generally across thecross sectional area of the liquid rich gas stream ftow area toform at least one layer therein and to provide between therespective pairs of impinging baffles a non-linear or tortuousgas ftow path for the liquid-rich gas stream passing therebetween. A mist eliminator impingement blade includes ashort, straight, axially aligned inlet section having a lowerleader edge, and a lower angled section, a short, straight,axially aligned interconnecting section, an upper angledsection, and a short, straight, axially aligned outlet sectionhaving an outlet edge. The mist eliminator blade includes anupper angled section having a greater angular inclinationfrom the axis of the device than the lower angled section. For5 example, the inclined angle of the lower section is about 30from the vertical axis, while the inclined angle of the uppersection is about 45, (e.g. +5 ) from the vertical axis,whereby the lower angled section provides improved drainage of collected liquid from the liquid-rich gas stream, and20 the connecting section provides reduced pressure drop without substantial re-entrainment of the collected liquid.

vertical positions. 25

The mist eliminator includes an interconnecting straightline section which has a length ranging from about 5 to 55of the length of the lower angular section of the misteliminator, wherein the upper angular section has a length ofless than generally 80 , for example, 60 , of the length ofthe lower angular section, and wherein the impingementbaffles of the mist eliminator are generally spaced apart in

These baffle-type mist eliminators are designed so that theliquid droplets may be collected and not re-entrained duringthe passage through the mist eliminator, so that the design ofthe proper mist eliminator is a function of a number of 30variables, such as, but not limited to, the design and geometry of the gas ftow path through the mist eliminator, thenature of the gas stream, temperatures, velocities andamount and droplet size of the liquid.

one or more layers of about 0.5 to 5 inches, for example, andpreferably from about 1Yi to 21 2 inches, for example, in awet scrubbing process. Mist eliminators of the inventiongenerally have a straight inlet and a straight outlet. Theinterconnecting sections and outlet preferably are about the35 same length, and preferably are aligned with the axis of thecolumn. Mist eliminators of the invention are employed inone or two or more layers, generally extending horizontallysubstantially across the cross-section of a gas-liquid column,

One illustrated example of a chevron-type mist eliminatorand method is described, for example, in U.S. Pat. No.4,601,731, issued Jul. 22, 1986. This mist eliminator, asdescribed, is employed in a gas-liquid column with a layercomposed of a plurality of parallel, spaced-apart serpentinebaffles, extending across the upwardly ftowing gas path, 40defining therebetween a plurality of tortuous gas ftow paths.The baffles are presented substantially angularly to the axis

such as a wet scrubbing process column or the like.While the various sections of the mist eliminator of theinvention may vary in length, the five section mist eliminator

of the invention, in one preferred embodiment, should bespaced apart from 0.5 to 3 inches, have an inlet length of 4to 1 inch, a lower angular section length of 3 to 8 inches, anof the column and have surfaces for the impingement of theupwardly ftowing mist-rich gas stream to provide for liquidcollection, and includes downwardly projecting drainagepoints on the leading edge of the baffles to promote the rapiddrainage of the baffles. The chevron-type baffles employedprovide for a change in direction of the gas fiow path at anangle of about 45, generally at least four times in each misteliminator layer.

t is desirable to provide for a new and improved chevronor baffle-type mist eliminator-system containing such misteliminators and a method of removing liquids in gas-richstreams, particularly where higher gas throughputs aredesired to pass through the mist-eliminator device beforecollected liquid is re-entrained in the gas stream, such as, butnot limited to, wet scrubbing process towers of large diam-eter.

SUMMARY OF TH INVENTIONThe invention relates to a baffle-type mist eliminator andsystem containing one or more layers of baffle-type misteliminators, and a method for removing liquid mist or liquiddroplets from a gas stream.The invention is directed to a mist eliminator device forremoving liquid droplets from a liquid-rich gas stream, and

45 interconnecting section length of 1 to l 1 2 inches, an upperangle section length of 3 to 4 inches, and a straight outletsection of 1 to l 1 2 inches. The mist eliminator so designedprovides for high re-entrainment velocity, that is, a reentrainment velocity of greater than about 19-20 feet per5 second, and provides for a low pressure drop in comparisonto a similar baffle-type arrangement with the same performance efficiency.

The mist eliminator of the invention provides for substantially straight, linear segments that are comprised of the55 blade or baffle profile in combination with a relatively smallinclination from the vertical for the inlet pass and a relativelylarger inclination from the vertical of the outlet pass; that is,between the inlet and the outlet straight linear segments.(The combination of the impingement baffleor blade profile60 in the mist eliminator and the resulting tortuous ftow channeldeveloped by the overlap of the successive blade profilepermits a higher gas throughput before collected liquidmoisture is re-entrained in the gas stream). The profile of themist eliminator of the invention provides for a steeper inlet65 pass which causes better drainage of collected liquid fromthe surface of the baffle, also the employment of a verticalfiat linear segment between the pair of inclined, angular


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impinging bailles of the mist eliminator greatly reduces thepressure drop relative to any type of chevron-type misteliminator without such single vertically extending segments. The mist eliminator of the invention as employedoffers high capacity, low pressure drop and moderate mist 5removal efficiency. The open, less complicated impingementbaille profile provides for the easy cleaning of the misteliminator in use and is particularly desirable for wet scrubbing processes. As desired and preferably, the lower leadingedge of the straight line inlet section may be serrated or 10otherwise treated or notched to provide for improved drainage of the collected liquid from the lower leading edge. Ithas been found that there is a relationship between theoverlap of the inlet section with the adjacent interconnectingsection which is important to capacity and the outlet section 15and the adjacent interconnecting section which is also, butless, important to the capacity of the mist eliminator. Thebailles are arranged in a selected preferred overlap relationship. f a plane is drawn from the straight inlet section of onebaille, it will intersect both angled upper and lower sections 20of the next spaced-apart baille.

4ammonium sulfate, or other reagents, with nozzles 24 isused to scrub the upwardly flowing flue gas, to removcsulfur dioxide or other gaseous contaminants from the fluegas.

FIG. 2 is an enlarged perspective view illustration of apair of aligned, spaced-apart mist eliminator blades 50 uscdin FIG. 1 with each of the mist eliminators 50 having astraight baille inlet section 52 having a leading edgc whichmay have drainage teeth 56 to promote liquid drainage ofcollected liquid.

The mist eliminator 50 includes an elongated, Jower(angularly inclined by 30 from the vertical axis of thecolumn 10 baille section 58, a short, straight, axiallypositioned interconnecting baille section 60, an upper angular (inclined by 45 from the vertical axis of the column 10)baille section 62, which section 60 is shorter in length thanlower section 58 and an upper, straight outlet baille section64 which, as illustrated, is about the same length as the inletsection 52. The lower section, with its Jower inclined angle,permits the removal of large liquid (water) droplcts in theupwardly flowing scrubbed flue gas stream, while the inter-connecting section 60 promotes a Jow or reduced pressuredrop, while the upper, more inclined section 62 promotes theremoval by impaction of finer sized liquid mist particles.

The distance between this inlet plane and the plane of thestraight, interconnecting section of the spaced-apart adjacentbaille is a measure of baille inlet overlap. It is preferred thatthe baille be positioned with a spacing of baille inlet overlapof between 10 and 50 of the distance between the respective planes.

Also, it is preferred that the baille outlet overlap bepositioned between about 10 and 150 of the distancebetween the outlet plane and the plane of the interconnectingsection of the spaced-apart adjacent baille.

25 The parallel, spaced-apart pair of mist eliminators 50 asillustrated, provides a tortuous flue gas flow path betwecnthe blades for impingement of the mist-liquid droplet richflue gas against the baille sections of the mist eliminator.

The invention will be described for the purposes ofillustration only in connection with certain illustratedembodiments; however, it is recognized that various 35improvements, additions, modifications and changes may bemade to the illustrated embodiments, ail falling within thespirit and scope of the invention.

The simpler profile design permits high gas throughput,3 easy manufacture, and permits easy cleaning of the misteliminator. The combination of its natural featurcs providcfor high capacity, low pressure drop, and good efficiency inmist removal.

BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is an illustrated schematic drawing of a wetscrubber column showing a cross section of the mist eliminator of the invention.

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FIG. 2 is an enlarged perspective view of a pair of bladesof the mist eliminators shown in FIG. 1 45

DESCRIPTION OF THE PREFERREDEMBODIMENTSFIG. 1 is a schematic, sectional illustration of a mist 5eliminator system 10 employed in a wet scrubbing processin a column 12 having an inlet 14 for the introduction of aflue gas containing, for example, sulfur dioxide to bescrubbed, and an outlet 16 for the removal of a mist-leancleaned or scrubbed flue gas. The column 16 includes a fist 55stage layer 20 of a plurality of impingement bailles 50 (seeFIG. 2 and a vertical, spaced-apart second stage layer 18 ofa plurality of impingement bailles 50. The layers 18 nd 20are illustrated as the same as in a preferred embodiment;however, it is recognized that the first or second stage layers 60

18 and 20 or even other mist eliminator layers may be usedand be different, provided that at least one layer comprisesor includes the mist eliminator 50 of the invention. A waterwash system comprising pipes and spray nozzles 22 belowthe second stage layer 18 and above and below the first stage 65layer 20 is used to wash the mist eliminators 50. A reagentsolution or water slurry system such as of lime, limestone,

What is claimed is:1 A mist eliminator for removing liquid droplets from aliquid-rich gas stream, said mist eliminator comprising:a a plurality of spaced-apart, substantially aligned, substantially parallel, impingement bailles extending substantially across the cross-sectional area of an apparatusthrough which a liquid-rich gas stream is passing toform a layer and to provide a substantially tortuousflow path for the liquid-rich gas stream passing throughadjacent pairs of the impingement bailles of the misteliminator;b) each impingement baille having a short, straight,axially aligned inlet section with a lower leading cdgc,a lower angled section extending from the inlct section,a short, straight, axially aligned, intcrconnccting section extending from the lower anglcd section, an uppcrangled section extending from the interconnecting sec-tion, and a short, straight, axially aligned outlet sectionhaving an outlet leading edge with the lcngth of thelower angled section longer than the lcngth of the upper

angled section; andc the upper angled section having a greater angularinclination from the axis of the apparatus than the loweranglcd section, whereby the mist eliminator providcsfor improved drainage of collccted liquid from the misteliminator, and the interconnecting section providcs areduced pressure drop with a high liquid-gas streamthroughput.2. The mist eliminator of claim 1 wherein the lowcrsection has an inclined angle of about 30 from the axis ofthe apparatus.3. The apparatus of claim 1 wherein the upper section hasan inclined angle of about 45 from the axis of the apparatus.


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4 The mist eliminator of claim 1 wherein the lowersection has an inclined angle of about 30 from the axis ofthe apparatus and the upper section has an inclined angle ofabout 45 from the axis of the apparatus.

adjacent baffle.6

5 The mist eliminator of claim 1 wherein the intercon- 5necting section has a length of about 5 to 55 of the length

11 The mist eliminator of claim 1Wherein the baffles arepositioned apart in an overlap relationship a distance ofbetween 10 to 150 of the distance between the outletsection plane and the interconnecting section plane of thenext adjacent baffle.of the lower angular section.

6 The mist eliminator of claim 1 wherein the upperangular section has a length of less than about 80 of thelength of the lower angular section.

7 The mist eliminator of claim 1 wherein the misteliminator blades are spaced apart from about 0.5 to 5inches.8 The mist eliminator of claim 1 wherein the inlet, outletand interconnecting sections are ail about the same linearlength.9 The mist eliminator of claim 1 wherein the inlet sectionhas a length of 14 to 1 inch and the lower angular section hasa length of 3 to 8 inches, and the interconnecting section hasa length of 1 to l 1 2 inches, and the upper angular section hasa length of 3 to 4 inches, and the outlet section has a length

of to 1 i inches; and wherein the impingement baffles arespaced apart from about 1 to 3 inches.10 The mist eliminator of claim 1 wherein the baffles arepositioned apart in an overlap relationship a distance ofbetween about 10 to 50 of the distance between the inletsection plane and the intersecting section plane of the next

12 A gas-liquid column which includes an inlet for theintroduction of an upwardly flowing gas, an outlet in theupper section of the column for the removal of a mist-lean1 gas stream, at least one layer of mist eliminators of claim 1extending substantially across the cross section of the column and liquid means within the column to contact theupwardly moving gas stream and to provide a liquid-rich gas

5 stream and with the mist eliminators employed in a layerabove the upwardly flowing liquid-rich gas stream.13 The gas-liquid exchange column of claim 12 whichincludes first and second layers of a mist eliminator which

are spaced apart and extend substantially across the cross20 section area of the column which includes a liquid washsystem and g s flue inlet in the lower section of the columnfor the introduction of a flue-gas to be scrubbed in a liquidwash system which includes scrubbing agents to contact the

flue gas and an outlet in the upper section of the column for25 the removal of a mist-lean, clean flue gas.

us 5464459x 1995 vanbuskirk - chevron type mist eliminator and system

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