GB1566718A

GB1566718A - Device for separating a liquid mist from a gas

Info

Publication number: GB1566718A
Application number: GB41584/76A
Authority: GB
Original assignee: American Air Filter Co Inc
Current assignee: American Air Filter Co Inc
Priority date: 1975-10-29
Filing date: 1976-10-06
Publication date: 1980-05-08
Also published as: JPS5255063A; ES456711A1; FR2329327B1; BR7607160A; NL7610412A; FR2329327A1; AR210763A1; CA1065771A; AU1646876A; YU263676A; ZA764472B; DE2647374A1; FI762956A; DK487376A; NO762817L; IT1076931B; BE845955A; ES451328A1; DD127721A5

Description

(54) DEVICE FOR SEPARATING A LIQUID MIST FROM A GAS (71) We, AMERICAN AIR FILTER COM- PANY, INC., a corporation organised under the laws of Delaware, United States of America, of 215 Central Avenue, Louisville, Kentucky 40201, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a device for the removal of a liquid mist from a gas stream and gas separation apparatus which comprises means for scrubbing the gas with liquid and includes the said device.

Various types of gas separation apparatus are known which use a scrubbing liquid to separate impurities from a gas stream and as a result, a certain amount of the scrubbing liquid becomes entrained in the form of a mist in the separated gas stream. This scrubbing liquid must be eliminated from the gas stream before the gas stream is discharged to equipment located downstream of the separation apparatus or discharged to the atmosphere because it may damage the downstream equipment or pollute the atmosphere.

One type of known mist eliminator is formed by a plurality of aligned narrowly spaced apart chevron-shaped baffles with correspondingly parallel chevron-shaped narrow passages therebetween. Because of the shape of the baffles, this type of mist eliminator baffle is commonly called a chevron eliminator in the industry. Chevron eliminators function satisfactorily in applications wherein the pressure drop across the eliminators is relatively low. However, these chevron eliminators have a propensity to become clogged with mud consisting of a residue of particulate matter in the gas stream and the scrubbing liquid in applications wherein the pressure drop across the eliminators is relatively high. As the mud builds up in the narrow passages of the chevron eliminator, the mist eliminating efficiency decreases.

When the efficiency drops to an unacceptable level, the chevron mist eliminator baffles must be cleaned.

One way to clean these chevron eliminator baffles is to shut down the entire separation apparatus and physically remove the chevron baffles for washing. This procedure is obviously costly because of the cost of down time of the separation apparatus and further the cost of labour to remove, clean and replace the chevron baffles.

Alternatively, the chevron baffles can be cleaned while remaining installed. This becomes necessary in very large capacity separator installations because the mist eliminating capacity of the chevron mist eliminator is a direct function of its physical size. In large capacity separator installations, therefore, the chevron eliminators reach a size which makes it impractical if not impossible to remove them. However, cleaning the chevron eliminator baffles while installed in a separator apparatus has drawbacks. One way to clean the baffles requires that the separator apparatus be shut down so that workmen may physically enter the separator to manually clean the mud from the chevron baffles. Another way often employed is to place nozzles adjacent to and downstream from the chevron eliminator which nozzles periodically inject high energy cleaning fluid into the passages between the chevron baffles.

This can be done without shutting down the separator apparatus. The drawback, of course, is that the mud cleaned from the chevron baffles is re-entrained in the clean gas stream downstream of the chevron baffles, thus recontaminating the cleaned gas stream.

Examples of chevron mist eliminator baffles used in gas separator apparatus are shown in U.S. Patent No. 3,334,471, issued on August 8, 1967 to Robert A. Herron, and U.S. Patent No. 3,624,696, issued on November 30, 1971 to Irving Cohen and Harold J. Byrne.

Another type of known mist eliminator is formed by a series of staggered gas stream deflecting baffles forming a gas stream path.

As the gas stream carrying a liquid mist traverses the path, it impacts the baffles, thus depositing the liquid mist on one of the faces of the baffles. In addition, these baffles change the direction of flow of the gas stream imparting an angular acceleration to the mist carrying gas stream to centrifugalize residue liquid mist from the gas stream.

Such mist eliminator devices use planar baffles projecting into the gas stream at an obtuse angle relative to the general direction of the gas stream. This type of eliminator functions well in applications wherein a relatively medium pressure drop exists across the eliminator baffles. However, a mud consisting of separated particulate matter and separated liquid tends to build up on the baffles and after a while the eliminator does not eliminate enough of the liquid mist from the gas stream with the result that the gas stream exiting from the eliminator device is still wet when a medium wet gas stream is fed into it. When the gas stream impacts the planar baffles, the liquid mist is deposited on the impacted face of the baffle and the gas stream is turned in the direction of the obtuse angle, thus imparting a small angular acceleration to the gas stream.

The liquid mist separated from the gas stream then runs off the baffle and falls down into a reservoir. However, when the liquid mist entrained in the gas stream impacts the planar baffle, there is only a small amount of kinetic energy transferred to the baffle from the liquid mist because the baffle is rigid and not an efficient energy absorber.

For this reason, the liquid mist has an inclination to bounce off the baffle or splash back into the gas stream whereupon it is reentrained in the gas stream. Additionally, because of the obtuse angle at which the planar baffles are disposed, the change in direction imparted to the gas stream, and thus the angular acceleration induced thereby is relatively small and as a result the centrifugalizing effect is correspondingly small.

An example of a gas separator using this t.ype of obtusely disposed planar baffle is shown in U.S. Patent No. 2,491,645, issued on December 20, 1949 to A. R. Clark and James C. Buck.

Other mist eliminator devices use planar baffles projecting into the gas stream at a right angle to the general direction of flow of the gas stream. This type of eliminator has a similar performance to the previously described type. In this case when the gas stream carrying the liquid mist impacts the planar baffles, the liquid mist is deposited on the impacted face of the baffle and the gas stream is turned in the direction of the right angle, thus imparting an angular acceleration to the gas stream. The liquid mist separated from the gas stream then runs off the baffle and falls down into a reservoir.

However, when the liquid mist entrained in the gas stream impacts the baffle, there is only a small amount of kinetic energy transferred to the baffle from the liquid mist because the baffle is rigid and not an efficient energy absorber. For this reason, the liquid mist has an inclination to bounce off the baffle or splash back into the air stream whereupon it is re-entrained in the gas stream. Additionally, although these baffles disposed at a right angle to the gas stream more radically change the direction of flow of the gas stream, and therefore impart a greater angular acceleration to the gas stream for a higher centrifugalizing effect than do the obtusely disposed planar baffles, in doing so the right angle planar baffles create large eddy currents at the impacted faces of the baffles which are counter productive to the job of eliminating liquid mist from the gas stream because these eddies pick up previously deposited liquid from the baffles re-entraining the liquid in the gas stream. An example of a gas separator using this type of right angle disposed planar baffle is shown in U.S. Patent No. 3,390,400, issued on January 25, 1968 to Nils Dock.

Still other mist eliminator devices use planar baffles projecting into the gas stream at an acute angle to the general direction of flow of the gas stream. This type of eliminator functions well at a slightly higher pressure drop across the baffles than do the previously mentioned eliminators. However, it is about equally susceptible to mud buildup and also emits a wet gas stream when fed with a medium wet gas stream. As with the obtusely disposed and right angle disposed baffles, when the gas stream carrying the liquid mist impacts the planar baffles, the liquid mist is deposited on the impacted surface of the baffle and the gas stream is turned in the direction of the acute angle, thus imparting an angular acceleration to the gas stream. The liquid mist separated from the gas stream then runs off the baffle and falls down into a reservoir. Similarly, when the liquid mist entrained in the gas stream impacts the baffle, there is only a small amount of kinetic energy transferred to the baffle from the liquid mist because the baffle is rigid and not an efficient energy absorber. For this reason, the liquid mist has an inclination to bounce off the baffle or splash back into the air stream whereupon it is re-entrained in the gas stream.

Further, while these acutely disposed baffles more radically change the direction of flow of the gas stream, and therefore impart a greater angular acceleration to the gas stream for a greater centrifugalizing effect than either the obtusely disposed and right angle disposed planar baffles, they also create larger eddy currents at the impact faces of the baffles. These eddies pick up previously deposited liquid from the baffles re-entraining the liquid in the gas stream. Examples of separator devices using these acutely disposed mist eliminator baffles are shown in U.S. Patent No. 2,379,795, issued on July 3, 1945 to Orrin E. Fenn; U.S. Patent No.

3,710,551, issued on January 6, 1973 to John R. Sved; and U.S. Patent No. 3,738,627, issued on June 12, 1973 to Ronald R.

Scotchmur.

To overcome some of the adverse side effects of planar baffles, such as the general inability to completely dry or eliminate sent a concave surface to the gas stream.

some mist eliminators use curved baffles which project into the gas stream and present a concave surface to the gas stream.

When the mist carrying gas stream impacts the concave face of the baffle liquid mist is deposited on the impacted baffle face and the gas stream is turned in the direction of the concave face, thus imparting an angular acceleration to the gas stream for centrifugalizing residue liquid mist from the gas stream. The use of curved mist eliminating baffles overcomes to a great extent the problem of eddy currents caused by planar baffles. However, because the curved baffles are rigid, and therefore poor energy absorbers, some of the liquid mist impacting the baffles bounces off or splashes back into the air stream whereupon it is re-entrained.

Nevertheless a better mist eliminating action is accomplished than in the previously mentioned eliminator devices employing planar baffles. An example of a gas separator apparatus using a curved mist eliminating baffle is shown in U.S. Patent No. 3,876,399, issued on April 8, 1975 to Joseph P. Saponaro.

The present invention recognizes the drawbacks of the prior art mist eliminators and provides a solution which obviates the problems of mud build-up on the separator members, eddy currents created when the direction of the gas stream is changed and inefficiency due to liquid mist bounce-off or splash as a result of impaction. In addition, the present invention leads to a solution of the problem of high pressure drop across the eliminator baffle at high gas stream velocities encountered by the prior art devices.

Further, the solution presented by the present invention is straightforward, .inexpen- sive and practical to manufacture.

More particularly, the present invention provides a mist eliminator device for separating a liquid mist from a gas stream containing the liquid mist comprising a housing containing a chamber up which the gas stream passes, a plurality of curved, staggered baffles mounted within said chamber which are arranged so as to define a sinuous path along which the gas stream flows, which path imparts an angular acceleration to the gas stream, said path being configured such that the mist contained in the gas is centrifuged therefrom substantially throughout the sinuous path, and a sump formed in at least one of the baffles at a location along the sinuous path, said sump being arranged to collect and be filled with the liquid formed by centrifuging the mist from the gas stream and further arranged such that the gas stream impacts the pool of liquid within the sump as it follows the sinuous path.

Several advantageous embodiments of the present invention are illustrated by way of example in the accompanying drawings, wherein like numerals refer to like parts throughout the several views, and in which: Figure 1 is a longitudinal cross-sectional view of one preferred embodiment of a mist eliminator device of the present invention: Figure 2 is a cross-sectional view taken along line 2-2 in Figure 1: Figure 3 is a longitudinal cross-sectional view of another preferred embodiment of a mist eliminator device of the present invention: Figure 4 is a longitudinal cross-sectional view of another preferred embodiment of a mist eliminator device of the present invention; Figure 5 is a longitudinal cross-sectional view of a gas separator apparatus incorporating the mist eliminator device of Figure 1; and Figure 6 is a longitudinal cross-sectional view of another gas separator apparatus incorporating the mist eliminator device of Figure 1.

Figure 1 illustrates a liquid mist eliminator device comprising a plurality of staggered gas stream directing baffles 12, 14 and 16 which co-operate to define a sinuous path to be followed by a gas stream containing a liquid mist which is to be centrifugalized from the gas stream as it traverses the sinuous path. The staggered baffles 12, 14 and 16 are illustrated as being enclosed in and attached to the walls of a housing 18. The housing 18 has a gas stream inlet 20 located proximate the upstream end of the sinuous path and a gas stream outlet 22 located proximate the downstream end of the sinuous path. For the sake of clarity of understanding, the general direction of flow of the gas stream from the upstream end to the downstream end of the sinuous path is defined by the phantom line A-A.

With continued reference to Figure 1, because the incoming gas stream will first encounter the baffle 12 and then the adjacently disposed baffle 14 as the gas stream traverses the sinuous path, in relationship to each other the baffle 12 is an upstream baffle and the baffle 14 is a downstream baffle. The upstream baffle 12 and the adiacent staggered downstream baffle 14 are shown as being arcuately shaped and gene rally concavely facing each other and, thus, toward the sinuous path formed therebetween.

The upstream arcuate baffle 12 is illustrated as being attached at its upstream edge 24 to one wall of the housing 18 and has a liquid trapping flange 26 projecting generally inward from its downstream edge 28 into the gas stream advantageously at an angle of approximately 30 degrees to the vertical. While the upstream arcuate baffle 12 is illustrated as a segment having a constant radius extending through an arc of approximately 90 degrees, it could extend through an arc of greater or less than 90 degrees depending upon the extent to which it is desired to redirect the direction of flow of the gas stream. Further, the arcuate baffle 12 could follow a volute of changing radius instead of the illustrated segment having a constant radius.

The downstream arcuate baffle 14 is illustrated as being attached to a wall of the housing 18 so as to face the upstream baffle 12 and as being a segment having a constant radius and extending through an arc of approximately 180 degrees. However, the downstream baffle 14 could extend through an arc greater or less than 180 degrees depending upon the extent to which it is desired to redirect the direction of flow of the gas stream. Further, the arcuate baffle 14 could follow a volute of changing radius instead of the illustrated segment having a constant radius. The downstream arcuate baffle 14 has a liquid trapping flange 30 projecting generally inwards from its downstream edge 32 into the gas stream at an angle of approximately 30 degrees to the vertical and a sump, generally denoted as the numeral 34, formed downstream of the upstream edge 36 of the baffle 14. The sump 34, which is for collecting a pool 35 of liquid centrifugalized from the gas stream, is preferably located immediately downstream of the upstream edge 36 of the baffle 14 behind a weir flange 38 which projects generally inwards into the gas stream from the upstream edge 36 of the baffle 14. It has been found in practice that a one and a half inch high weir plate works well. The sump 34 is oriented so that the gas stream containing the liquid mist redirected by the upstream baffle 12 impacts the liquid pool collected in the sump. To this end, the downstream edge 28 of the upstream baffle 12 and the upstream edge 36 of the downstream baffle 14 overlap each other by a predetermined distance in the general axial direction of the eliminator device and are spaced apart a predetermined distance in a direction transverse to the said axial direction.

With reference to Figure 2, the downstream arcuate baffle 14 extends completely across the housing 18 between opposite walls thereof and is attached at its opposite ends 40, 42 to the walls of the housing 18. Thus, in this illustrated embodiment the sump 34 is defined by the concave surface of the downstream arcuate baffle 14, the weir flange 38, and the walls of the housing 18 to which the downstream arcuate baffle 14 is attached.

It should be obvious, however, that in the event the downstream baffle 14 does not extend completely across the housing 18 so that the ends 40 and 42 of the baffle 14 terminate a distance from the walls of the housing, that closure plates (not shown) can be attached to the arcuate baffle 14 and weir flange 38 at the ends 40 and 42 of the baffle 14 to take the place of the walls of the housing 18 in defining the sump 34.

Returning to Figure 1, the downstream edge 28 of the upsteam baffle 12 and the upstream edge 36 of the downstream baffle 14 co-operate to form, in essence, a nozzle through which the gas stream flows. In practice, it has been observed that best results are obtained when the cross-sectional area of this nozzle is greater than the crosssectional area of the gas stream inlet 20.

Likewise, another nozzle is formed between the downstream edge 32 of the baffle 14 and the downstream edge 28 of the upstream baffle 12. It has also been observed that best results are obtained when the cross-sectional area of this other nozzle is greater than the cross-sectional area of the nozzle formed between the downstream edge 28 of baffle 12 and upstream edge 36 of baffle 14. These observed results have been attributed to the fact that this construction approximates a diverging nozzle which decreases the velocity of the gas stream moving through it and decreases the pressure drop.

The baffle 16 is disposed downstream of the arcuate baffle 14 and is illustrated as being planar. The planar baffle 16 is attached to the same wall of the housing 18 as is the upstream arcuate baffle 12 and upwardly extends advantageously into the gas stream at an obtuse angle of approximately 135 degrees to the vertical, thus forming an angle to the general direction of flow of the gas stream. The planar baffle 16 has a liquid trapping flange 44 projecting advantageously from its downstream edge 46 at an angle of approximately 30 degrees to the vertical.

While it is true that the planar baffle 16 will cause more eddy currents than would an arcuate baffle, the consequences of eddy currents at this. most downstream baffle 16 are minimal because in most applications virtually all of the liquid mist will have been removed from the gas stream before the gas stream reaches the baffle 14. The planar shape of this baffle 14 is merely a manufacturing expedient because a planar baffle is easier to make than is an arcuate baffle.

However, it is foreseeable that in some appli cations, it may be desirable to substitute an arcuately shaped baffle for the planar baffle 16.

In operation, a gas stream containing a liquid mist, indicated by the arrows "A" enters the mist eliminator device through the inlet 20 in a direction toward the upstream baffle 12. The air stream impacts the baffle 12 which causes the air stream to change its direction of flow. This change in flow direction imparts an angular acceleration to the gas stream centrifugalizing a portion of the liquid mist. An additional amount of liquid mist is separated out of the gas stream by impaction against the baffle 12. The liquid mist separated out of the gas stream by impaction and by centrifugalizing runs along the concave surface of the baffle 12 until it meets the liquid trapping flange 26. The liquid trapping flange 26 acts as a dam and collects the separated liquid into a mass.

The collected liquid continuously drains in solid streams, indicated by the arrows "B", downwardly into, for example, a reservoir 48 formed in the bottom of the housing 18 below the inlet 20. Because this separated liquid falls in the form of streams "B" of liquid rather than a mist or droplets, very little, if any, liquid is re-entrained in the gas stream "A".

The gas stream "A" next impinges upon the pool 35 of previously separated liquid collected in the sump 34 formed in the downstream baffle 14. Upon impact, the pool 35 absorbs the kinetic energy of a portion of the remaining liquid mist entrained in the gas stream, thus preventing the liquid mist from splashing off the downstream baffle 14 and into the gas stream and at the same time collects a portion of the liquid mist. As the pool 35 collects additional liquid, it overflows the weir flange 38 and falls in the form of solid streams, indicated by the arrows C", downwardly into the reservoir 48. Again, because this overflowing liquid falls in the form of coalesced liquid streams "C" rather than drops or mist, very little, if any, liquid is re-entrained in the gas stream "A". It should be noted that the surface of the pool 35 is at an angle to the horizontal plane because of the air stream flowing over it. This angle effectively in creases the surface area of the pool subjected to impact by the gas stream "A". Con currently, the downstream arcuate baffle 14 again smoothly changes the direction of flow of the gas stream thereby imparting an angular acceleration to the gas stream centrifugalizing most of the residue liquid mist from the gas stream. The residue liquid mist thus centrifugalized flows along the concave surface of the arcuate baffle 14 under the influence of the gas stream until it meets the liquid trapping flange 30. The liquid trap ping flange 30 acts as a dam and collects the separated residue liquid mist into a mass.

The collected residue liquid continuously drains in solid streams, indicated by arrows "D" downwardly into the reservoir 48. Because this separated liquid falls in the form of coalesced streams "D" rather than a mist or droplets, very little, if any, liquid is reentrained in the gas stream "A".

After leaving the area of the downstream edge 32 of the arcuate baffle 14, the gas stream "A" next impinges on the planar surface of the planar baffle 16 whereupon the gas stream is again caused to change direction to flow in the direction of the baffle 16 thereby imparting an angular acceleration to the gas stream centrifugalizing residual liquid mist from the gas stream. Some residual liquid mist is also separated from the gas stream by impaction against the baffle 16. The separated-out liquid mist flows along the planar baffle 16 until it meets the liquid trapping flange 44. The liquid trapping flange 44 acts as a dam and collects the separated liquid mist into a mass. The collected liquid continuously drains in coalesced streams, indicated by arrows "E", downwardly into the reservoir 48. As previously mentioned, because the liquid falls in the form of coalesced streams "E" rather than a mist or droplets, very little, if any, liquid is reentrained in the gas stream "A".

Upon leaving the downstream edge 46 of the baffle 16, the now mist-free gas stream flows out of the mist separator device through the outlet 22.

Accumulated liquid can be drained from the reservoir 48 through a conveniently located drain 50.

The flow of gas through the unit can be induced either by a fan (not shown) located upstream of the inlet 20, or, more conventionally, by a fan (not shown) located downstream of the outlet 22.

Now referring to Figure 3, there is illustrated another advantageous embodiment of a mist eliminator device of the present invention which is identical in every respect to the mist eliminator device of Figure 1 except for the relative dispositions of the downstream edge of the first upstream baffle and the upstream edge 36 of the second downstream baffle. In the mist eliminator device of Figure 3, the downstream edge 28 of the upstream arcuate baffle 12 and the upstream edge 36 of the immediately adiacent staggered downstream baffle 14 overlap in the general axial direction of the eliminator and lie in the same axial plane. This configuration has utility in applications wherein the velocity of the gas stream may be too low to propel the gas stream across the space between the downstream edge of the upstream baffle and the upstream edge of the downstream baffle of the mist eliminator device of Figure 1 and follow the sinuous path without dissipating somewhat before impacting the pool collected in the sump. The nozzle in the embodiment of Figure 3 formed between the downstream edge 28 of the upstream arcuate baffle 12 and the aligned upstream edge 36 of the downstream baffle 14 guides the gas stream to a point closer to the pool 35 than does the configuration of Figure 1, thus preventing dissipation of the gas stream.

Turning now to Figure 4, there is illustrated another advantageous embodiment of a mist eliminator of the present invention which is identical in every respect to the mist eliminator device of Figure 1 except for the relative dispositions of the downstream edge of the upstream arcuate baffle 12 and upstream edge of the downstream baffle 14.

In the mist eliminator device of Figure 4, the downstream edge 28 of the upstream arcuate baffle 12 and the upstream edge 36 of the downstream baffle 14 overlap each other by predetermined distances in both the general axial direction of the eliminator device and in a direction transverse to the said axial direction. This configuration also has utility in applications wherein the velocity of the gas stream may be too low to propel the gas stream across the space between the downstream edge of baffle 12 and upstream edge of baffle 14 of the mist eliminator device shown in Figures 1 and 3 and follow the sinuous path without dissipating somewhat before impacting the pool collected in the sump. The nozzle in the embodiment of Figure 4 formed between the overlapping downstream edge 28 and upstream edge 36 guides the gas stream into the downstream arcuate baffle 14 to a point immediately over the surface of the pool 35, thus preventing dissipation of the gas stream.

The mist eliminator device of the present invention can be used to eliminate a liquid mist from a gas stream emanating from virtually any source.

For example, the mist eliminator device of the present invention can be used in place of the chevron mist eliminator baffles used in the devices disclosed of U.S. Patent Nos.

3,334,471 and 3,624,696. Likewise, the mist eliminator device of the present invention can be used in the devices disclosed in U.S.

Patent Nos. 2,373,330; 2,379,795; 2,491,645; 3,018,847; 3,390,400; 3,876,399; 3,710.551 and 3,738,627 in place of the mist eliminators disclosed therein.

Figure 5 illustrates a gas separator apparatus 52 comprising the mist eliminator device of Figure 1 of the present invention located downstream of an impurity remov ing means, generally denoted as the numeral 54, which removes impurities entrained in a gas stream by contacting these impurities with a scrubbing liquid.

gas gas separator apparatus 52 is illus- trated as comprising a housing 118, enclosing both the mist eliminator components and the impurity removing means 54. The housing 118 defines a dirty gas inlet chamber 56 having a dirty gas inlet 48 and a scrubbing liquid reservoir 148.

The impurity removing means 54 is in the form of a stationary impeller section which comprises a generally S-shaped gas stream directing wall 62 and an arcuate gas stream directing wall 64 spaced from the S-shaped wall 62 to define a diverging S-shaped gas stream passage therebetween which S-shaped passage provides gas stream communication between the dirty gas inlet chamber 56 and mist eliminating means. The lower edge of the arcuate wall 64 extends downwardly into the reservoir 148 below the level of the scrubbing liquid contained therein when a dirt a gas stream by contacting these impurities with a scrubbing liquid.

The impurity removing means 154 comprises a flow through housing 156 having a dirty gas inlet 158 at one end and a clean gas outlet 160 at the other end. The clean gas outlet 160 is in fluid communication with the gas stream inlet 20 of the mist eliminator by means of, for example, duct 162.

A dirty gas stream enters the housing 156 and passes through a first restraining grid 164 extending across one extremity of the housing 156. The dirty gas stream then passes into contact zone 166 where it contacts elements 168, which advantageously are substantially spherical in shape. The spherical elements 168 are coated with a thin film of scrubbing liquid from treating fluid inlets or nozzles 170, 172. Upon contacting the spherical elements 168, the dirty gas is cleaned since the thin film of scrubbing liquid coating thereon either causes particulate matter to adhere thereto, or, alternatively, chemically reacts with the impurities in the gas stream. The spherical elements 168 are buoyed upwardly toward a second restraining grid 174 which is positioned to direct the clean gas stream out of the contact zone 166. The spherical elements 168 fall by gravity into element treating zone 176 which is formed by baffle means 178 dividing a portion of the housing 156 between the first and second restraining grids into the contact zone 166 and the element treating zone 176 for recirculation back into the contact zone 166. The substantially spherical elements 168 continue to fall downwardly in the element treating zone 176 past the scrubbing fluid inlet 170, which is emitting a scrubbing liquid, until they reach the lower portion of the zone 176. At the lower portion of the element treating zone 176, there exists an exit aperture 180. Directly below exit aperture 180 is the first restraining grid 164 having integral therewith a fluid impervious portion 182. The fluid impervious portion 182 prevents the dirty gas stream from overcoming the force exerted by the scrubbing liquid from fluid inlet 170 on the spherical elements 168, and forcing them upwardly in the element treating zone 176.

The scrubbing liquid from fluid inlet 170 cleans the spherical elements 168 leaving them coated with a thin film of the scrubbing liquid, and recirculates them again into the dirty gas stream. The scrubbing liquid inlet 170 as well as the scrubbing liquid from nozzle 172 drains downwardly and is collected in reservoir 184 of the housing 156, from which it may be withdrawn through drain 186.

The scrubbing liquid emitting from nozzle 172 may be a different liquid than that emitting from inlet 170. For example, in the removal of sulphur dioxide, it may be desirable to formulate a liquid to be introduced through nozzle 172 which contains a high concentration of calcium carbonate, with a view toward reacting the calcium carbonate chemically with the SO of the dirty gas to form calcium sulphate. The calcium sulphate is a solid which can be flushed from the spherical elements 168 by a spray of water from treating fluid inlet 170. The impurity removing means 154 is more fully described in U.S. Patent No. 3,810,348, issued on May 14, 1974 to Thomas W. Byers et al.

The cleaned gas stream exiting the contact zone 166 through the restraining grid 174 has an entrained mist of scrubbing liquid. The cleaned gas stream with the entrained mist of scrubbing liquid exits the housing 156 via outlet 160 and flows through the duct 162 and into the inlet 20 of the mist eliminator device as indicated by arrows "A". The process of mist elimination then follows as described in relationship to Figure 1 and a cleaned gas stream exits from the mist eliminator through outlet 22.

WHAT WE CLAIM IS:- 1. A mist eliminator device for separating a liquid from a mist-containing stream of gas comprising a housing containing a chamber up which the gas stream passes, a plurality of curved, staggered baffles mounted within said chamber which are arranged so as to define a sinuous path along which the gas stream flows, which path imparts an angular acceleration to the gas stream, said path being configured such that the mist contained in the gas is centrifuged therefrom substantially throughout the sinuous path, and a sump formed in at least one of the baffles at a location along the sinous path, said sump being arranged to collect and be filled with the liquid formed by centrifuging the mist from the gas stream and further arranged such that the gas stream impacts the pool of liquid within the sump as it follows the sinuous path.

2. A mist eliminator device wherein the sump is defined in part by a weir flange formed on the appropriate baffle at its upstream edge.

3. A mist eliminator device according to Claim 2 wherein the flange is one and a half inches high.

4. A mist eliminator device according to any preceding claim wherein the housing contains a baffle effectively immediately upstream of the baffle containing the sump which has a liquid trapping flange projecting substantially downwards from its downstream edge.

5. A mist eliminator device according to Claim 4 wherein the said baffle containing the sump has a liquid trapping flange projecting substantially downwards from its downstream edge.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

a gas stream by contacting these impurities with a scrubbing liquid.

The impurity removing means 154 comprises a flow through housing 156 having a dirty gas inlet 158 at one end and a clean gas outlet 160 at the other end. The clean gas outlet 160 is in fluid communication with the gas stream inlet 20 of the mist eliminator by means of, for example, duct 162.

A dirty gas stream enters the housing 156 and passes through a first restraining grid 164 extending across one extremity of the housing 156. The dirty gas stream then passes into contact zone 166 where it contacts elements 168, which advantageously are substantially spherical in shape. The spherical elements 168 are coated with a thin film of scrubbing liquid from treating fluid inlets or nozzles 170, 172. Upon contacting the spherical elements 168, the dirty gas is cleaned since the thin film of scrubbing liquid coating thereon either causes particulate matter to adhere thereto, or, alternatively, chemically reacts with the impurities in the gas stream. The spherical elements 168 are buoyed upwardly toward a second restraining grid 174 which is positioned to direct the clean gas stream out of the contact zone 166. The spherical elements 168 fall by gravity into element treating zone 176 which is formed by baffle means 178 dividing a portion of the housing 156 between the first and second restraining grids into the contact zone 166 and the element treating zone 176 for recirculation back into the contact zone 166. The substantially spherical elements 168 continue to fall downwardly in the element treating zone 176 past the scrubbing fluid inlet 170, which is emitting a scrubbing liquid, until they reach the lower portion of the zone 176. At the lower portion of the element treating zone 176, there exists an exit aperture 180. Directly below exit aperture 180 is the first restraining grid 164 having integral therewith a fluid impervious portion 182. The fluid impervious portion 182 prevents the dirty gas stream from overcoming the force exerted by the scrubbing liquid from fluid inlet 170 on the spherical elements 168, and forcing them upwardly in the element treating zone 176.

The scrubbing liquid from fluid inlet 170 cleans the spherical elements 168 leaving them coated with a thin film of the scrubbing liquid, and recirculates them again into the dirty gas stream. The scrubbing liquid inlet 170 as well as the scrubbing liquid from nozzle 172 drains downwardly and is collected in reservoir 184 of the housing 156, from which it may be withdrawn through drain 186.

The scrubbing liquid emitting from nozzle

172 may be a different liquid than that emitting from inlet 170. For example, in the removal of sulphur dioxide, it may be desirable to formulate a liquid to be introduced through nozzle 172 which contains a high concentration of calcium carbonate, with a view toward reacting the calcium carbonate chemically with the SO of the dirty gas to form calcium sulphate. The calcium sulphate is a solid which can be flushed from the spherical elements 168 by a spray of water from treating fluid inlet 170. The impurity removing means 154 is more fully described in U.S. Patent No. 3,810,348, issued on May 14, 1974 to Thomas W. Byers et al.

The cleaned gas stream exiting the contact zone 166 through the restraining grid 174 has an entrained mist of scrubbing liquid. The cleaned gas stream with the entrained mist of scrubbing liquid exits the housing 156 via outlet 160 and flows through the duct 162 and into the inlet 20 of the mist eliminator device as indicated by arrows "A". The process of mist elimination then follows as described in relationship to Figure 1 and a cleaned gas stream exits from the mist eliminator through outlet 22.

WHAT WE CLAIM IS:- 1. A mist eliminator device for separating a liquid from a mist-containing stream of gas comprising a housing containing a chamber up which the gas stream passes, a plurality of curved, staggered baffles mounted within said chamber which are arranged so as to define a sinuous path along which the gas stream flows, which path imparts an angular acceleration to the gas stream, said path being configured such that the mist contained in the gas is centrifuged therefrom substantially throughout the sinuous path, and a sump formed in at least one of the baffles at a location along the sinous path, said sump being arranged to collect and be filled with the liquid formed by centrifuging the mist from the gas stream and further arranged such that the gas stream impacts the pool of liquid within the sump as it follows the sinuous path.
2. A mist eliminator device wherein the sump is defined in part by a weir flange formed on the appropriate baffle at its upstream edge.
3. A mist eliminator device according to Claim 2 wherein the flange is one and a half inches high.
4. A mist eliminator device according to any preceding claim wherein the housing contains a baffle effectively immediately upstream of the baffle containing the sump which has a liquid trapping flange projecting substantially downwards from its downstream edge.
5. A mist eliminator device according to Claim 4 wherein the said baffle containing the sump has a liquid trapping flange projecting substantially downwards from its downstream edge.
6. A mist eliminator device according to

Claim 5 wherein said flanges formed on the downstream edges of the respective baffles are disposed at an angle of 30 to the vertical axis of the device.
7. A mist eliminator device according to any preceding claim wherein the sinuous path is defined by a pair of baffles generally oppositely disposed about a vertical axis, one of said baffles being also disposed generally upstream of the other relative to said path.
8. A mist eliminator device according to Claim 7 wherein in the horizontal direction a gap exists between the upstream edge of the relatively downstream baffle and the downstream edge of the said upstream baffle.
9. A mist eliminator device according to Claim 7 wherein the upstream edge of the relatively downstream baffle and the downstream edge of the said upstream baffle are contained in the same vertical plane.
10. A mist eliminator device according to Claim 7 wherein the upstream edge of the relatively downstream baffle and the downstream edge of the said upstream baffle overlap in the horizontal direction.
11. A mist eliminator device according to any preceding claim further comprising a planar baffle arranged at an angle downstream of said curved baffles whereby it is impinged by the said gas stream.
12. A mist eliminator device according to Claim 11 wherein the planar baffle is disposed at an angle of 45" to the vertical axis of the device.
13. A mist eliminator device according to Claim 11 or Claim 12 whtrein the planar baffle has a liquid trapping flange projecting into the sinuous path from the downstream edge thereof.
14. A mist eliminator device according to Claim 13 wherein the liquid trapping flange on the planar baffle is disposed at an angle of 30 to the vertical axis of the device.
15. A mist eliminator device substantially as described herein with reference to Figures 1, 2, 3 or 4 of the accompanying drawings.
16. A gas separation apparatus for separating impurities from a gas stream, the apparatus comprising means for contacting the impurities contained in the gas stream with a scrubbing liquid to separate the impurities from the gas stream, and a mist eliminator device according to any preceding claim.
17. A gas separation apparatus substantially as described herein with reference to Figure 5 or Figure 6 of the accompanying drawings.