US2242294A - Gas washing means and method - Google Patents

Description

Ma 20', 1941. Fox Em 2,242,294

GAS WASHING MEANS AND METHOD Filed May 16, 1938 5- Sheets-Sheet 1 May 20, 1941. I G j..-ox Em 2,242,294

GAS WASHING MEANS AND METHOD Filed May 16, 1938 J 5 Sheets-Sheet 2 vENToRls Gordon fix B 3? Alfred J. Ebn er w, Owen R.Rice MvMWmM May 20, 1941. G. FOX Em 2,242,294

GAS WASHING MEANS AND METHOD Filed May 16, 1938 w v SSheets-ShetB Fig. 5

ENTORS Gordo Fox BY I Alfre J.Eb ner- May 20, 1941. 6. FOX EI'AL GAS WASHING MEANS AND METHOD Filed May 16. 1938 s pa 4 W m m m v mm 1 a Mo .m MN s 5 9 %0 m 02 1941- 6. FOX ETA L I 2,242,294

GAS WASHING BANS AND METHOD Filed lay 16, 1938 5 Sheets-Sheet 5 Gas enters from dry dust catcher superheazea' to 550 E, containing about 50 grains per cubic foot moisture. (D'ewpoint #55) G as [says 3 evaporaior st ago Com. az'nz'ng Gas leaves conabouz 50 grains per cuser stage at bZc fool molsiure, wifh a abour 757: containdewpolnt of 155%; bui {hi [n9 about grains 9 may not be aqiuraper cubic fooi teofl lie. may be super. moisfure. I heaied 0 a higher femperaure such as 160-2007? /2v' "0 Figures are opproximae. If gas I]? i'emperaur-e [5 Q 99 much higher, such L2 as eoo-aoo'fi, he 2 amounz 0/ moisgao I tureevaporazea' b. 70 [a greoer and If, I I acwpoinf of 90: -60 leaving evapora- 2 I for szago is high- I 350 8/; hence empero- I I fur-e of flu: gas is 40 higher. Also fem- If I ,oeraz are ofrecz'n E cu/aalng Wafer is "Q I 7 higher. Q 7 I I II I M Y I I T 0 2o 40 6o m0 M0160 /80 WATER 7ZMPEPA7'UPE- Deana-s Home F11 15 2 I INVE 0R8 60RDON rox ALFRED JEBNER 0w5- R.'RICE Patented May 20, 1941 2,24 2,294 GAS WASHlNG MEANS AND METHOD Gordon I Fox,

Chicago, 111.,

Alfred J. Ebner, and Owen It. Rice, assignors to Freyn Engineering Company, Chicago, 111., a corporation of Maine Application May 16, 1938, Serial No. 208,208

15 Claims.

The present invention relates to gas Washing means and methods.

The present application is a continuation as to' common subject matter of the application, Serial No. 25,270, filed on June 6, 1935, by the same applicants, entitled Gas cleaning means and methods, which case was later abandoned.

More particularly the present invention relates to means for removing dust and other solid matter from combustible gas' such as that discharged from blast furnaces. It is common practice to scrub such gas by impingement with water sprays or by impingement of the dirty gas against. wetted baffles or hurdles to which a portion of the dirt .adheres because of the wetted condition of such bafiles. The effect of centrifugal force has also been utilized according to prior practice in depositing out those dust particles which are heavier than air. Other principles have been and are being utilized for clean- In addition to the dirt in the gas delivered from the dust catcher, a certain amount of moisture is contained in the gas, which, 'however, is in superheated condition. It is proposed to utilize the high temperature of the raw gas and the moisture content thereof in practicing the present invention.

An object of the present invention is'to clean gas thoroughly in a device having .no internal moving parts and with a minimum loss of gas pressure.

A further object is to provide gas cleanin means involving the use of water which will permit the recirculation of a considerable proportion of the water, thereby saving water cost, and also saving in -the size of the necessary clarifier for the discharge water, which clarifier is necess'ary in many localities.

A further object is to provide a gas cleaning system involving the useof water in whichthe amount. of water taken into the system and discharged therefrorn' is minimized without building up deposited matter or clogging the system.

A further object is to provide a cleaning system which will efiicientlyutilize the heat content of the gas to be cleaned, to the end that the very fine particles which are, most diflicult to entrap will be so conditioned that they will be separated from the gas before the gas is discharged from the system.

A further object is to provide a system involving means for providing a preliminary wet scrubbing, increasing the moisture content of the gas, cooling the gas and condensing-moisture contained therein to properly condition the fine dust particles, and the final separating of the fine dust particles, all in a relatively simple construction which is low in both manufacturing cost and operating cost.

A further object is to provide a gas cleaning system utilizing the relatively low surface tension of hot water in a stage of the cleaning apparatus which depends upon contact with wetted surfaces and upon impact between the dust 'particles and the water drops.

A further object is to provide a gas washing means whichwill utilize efficiently the sensible orate water and increase the moisture content of the gas as a preliminary to a condensingstage.

A further object is'to provide gas cleaning means which may utilize the sensible heat in the incoming gas at temperatures below the boiling point of water but above the dew point of the gas for preheating the make-up water used in the gas cleaning means.

A further objectis to provide gas cleaning means which will substantially reduce fuel costs or power costs from those of systems as now known and used.

A further object is to provide .gas cleaning means in which the heat of the gas to be cleaned is utilized for efficiently conditioning the dust particles in the gas whereby even the finest of these dust particles may be removed before the gas is discharged from the cleaning means.

A further object is to provide gas cleaning means which will deliver gas which is not only during the coarse cleaning that the water used.

in the fine cleaning may be discharged direct to the sewer without objection .due to excessive dirt content. v

A further object is to provide gas cleaning means which will clean large volumes of gas'at high. velocity in a minimum of apparatus area.

A further object is to provide an' improved method and means for conditioningjthe gas by increasing the eifective weight of the dust particles therein as a preliminary to separation of ,said dust particles out of the gas by centrifugal vA. further object is to provide gas cleaning means well adapted to meet the needs of mercial operation.

com-

Further objects will appear as the description proceeds.

Referring to the drawings- Figure 1 is a diagrammatic view illustrating one embodiment of-the present'invention;

fFigure 2 is a view, more-or less diagrammatic in its nature, showing a section of a tower washer forming part of the structure illustrated in Figure 1;

Figure 3 is a horizontal sectional view taken along the planes indicated by the arrows 3-4 of .Fl ure2:

Figure 4 is a horizontal sectional view taken along the plane indicated by the arrows 4-4 of Figure 2;

Figure 5 is a view, on an enlarged scale, of a condenser forming part of the structure illustrated inFigure 1; Figure 6 is a horizontal sectional view taken along the plane indicated by the arrows 8-4 of Figure 5;

which water sprays are supplied by the water pipe II. The bottom of the water tower i0 is provided with a seal for permitting the exit of dirty-water while preventing the escape of gas therethrough. It will be sufflcient to state that associated with said seal is the pipe 20, which, through the valve 2|, may discharge into a thickener or clariiier 22. The thickener or clarifier 22 need not be described in detail, inasmuch as devices suitable for the purpose are readily available in the market. It is suiilcient to state that said thickener or clarifier 22 has the function of separating dirt from the dirty water discharged through the pipe 20, relatively clear water being drawn off from the upper region of the device. Itwill be noted that the pipe II, which supplies thewater sprays I4'-l4,

is connected to the pipe 20, whereby dirty water 'from the bottom of the washer I0 is circulated through said pipe I! to said water sprays I 4. A pump 23 is included in the pipe Ii for the purpose of recirculating the dirty water. Connection between the pipe 20 and the pump 28 is controlled by the valve 24. for discharging the relatively clarified water from the thickener 22 into the reservoir 24, which pipe 25 may be controlled by means of the valve 21. A discharge pipe 28 controlled by the valve 28 may be connected tothe pipe 25 between the thickener 22 and the valve 21 for discharging the relatively clarified water from the thickener 22 direct to the sewer, if desired. The pipe I 8, which supplies the upper water sprays l1l| of the tower washer II, communicates with the reservoir 20, a pump 30 being provided for raising the water from the reservoir 26 to saidwater sprays l1-l'|. A valve II is illustrated for controlling the connection between the pump 30 and the sprays I'I-l'l.

A gas pipe 32 provides communication from the upper portion of the tower washer ill to the 'lower portion of the dondenser ll. As will be mentioned more particularly hereinafter, the

Figure 7 is a fragmentary view taken along the plane indicated by the arrows 1-1 of Figure 5;

- Figure 8 1s a diagrammatic view illustrating a a typical path of a dust particle in passing up through the condenser illustrated in Figure 5;

Figure 9 is a diagrammatic view illustrating another embodiment of the present invention;

Figure 10 is a sectional view taken along the plane indicated by the arrows iii-Iii of Figure 9; Figure 11 is a sectional view taken along the plane indicated by the arrows I |-i I of Figure 9; Figure 12 is a sectional view taken along the plane indicated bythe arrows i2--l2 of Figure 9; and y Figure 13 is a chart illustrating approximately the relationship between temperature and the moisture content of gas in the practice of the invention. 4

Referring first to Figure -1, the numeral It indicates a'tower washer and the numeral .ll; indicates a condenser. Dirty .gas is admitted to the towerwasher I 0 through the pipe l2. Said pipe l2 in blast furnace service will as a usual condenser H includes a number of vertically disposed plates, indicated as a whole in Figure 1 by the numeral 33. Disposed above these plates .33 are a plurality of water sprays 34-34 supplied by the water-pipe 35, which may be connected to a source of clean; cool water supply. Disposed above the water sprays 34-44 is a fine dust collector, indicated by the numeral 38. The fine dust collector chosen for illustration in Figures 1 to 8 embodies the principles disclosed in the patent to Bleibtreu and Eberlein No.

; 1,933,699, granted November '1, 1933. The nne proposition be connected to adust catcher (not shown). The numeral It indicates, generally,'astage of hurdles, to be referred to more particularly hereinafter. Above said hurdles are a pinrality of water sprays, indicated by the numerals i4-l4, which water sprays are supplied by the water pipe I5. Above the water sprays l4-l4 is a second stage of hurdles i6, and above said stage of hurdles l6 are the water sprays l'i-II,

dust collector I6 is supplied by a plurality of water sprays 31-41, which are supplied bythe water pipes 14- connected to the water pipe 35. "'I'he'fine dust-collector 34 may be described briefly as follows: Said dust collector It operates upon the principle of centrifugal action and provides a plurality of circuitous passages for the gases which have passed the sprays 34-44 Said dust collector It includes the tubular member Ila, which tubular member has located therein the dividing partition 24b positioned diagonally with reference to said tubular member "a. Said dividing partition 36b extends from a region adjacent to the bottom of the tubular member "won one side thereof to a region adjacent to the top of said tubular member on the other side thereof. 5 Said tubular member a is open at its bottom to the condenser means located therebelow and is open at its top to the pipe 44-. An annular plate 360 is disposed between the tubular member 360. and the wall of the condenser H. A similar an- A pipe 251s provided t at opening 36c and will have two substantially semicircular routes of travel to the opening 36f, which communicates with the outlet pipe 44. Disposed between the tubular member 36a and the wallof the condenser H are a plurality of arcuate walls 359, preferably disposed through the greater part of their length coaxially with the condenser tower H. The extremities of said arcuate walls 36g- 36g adjacent to the opening, 36e may be disposed along planes indicated by the numerals Nike-36h, which diverge outwardly with reference to the axis of the condenser II. The other end portions ofthe arcuate walls 36g36y may be given a sharper curvature than the other portions of said arcuate walls 369, and the extremities of said arcuate walls 36g--36g adjacent to the opening 36f may be located in planes indicated by the numerals 36a'-3B;i; which converge toward the outer wall of thecondenser II. The outermost arcuate walls Slip-36g adjacentto the wall of the condenser .l I may, at their extremities adjacent to the opening 36f, be joined together as indicated by the numeral 36k.

The dust collector 36, asindicated above, operates upon the principle of centrifugal force. To this end the velocity ofthe gases through the passages provided by th arcuate walls 36g should be decidedly greater than. the velocity of the gas vertically between the condensing plates til-|. Accordingly, the tubular member 36a has a decidedly smaller diameter than the diameter of the condenser portion of the condenser tower,

II. The surfaces of the arcuate walls 369 and other surfaces within the dust collector 36 which are contacted by the gases to be cleaned are preferably rubber-covered andmay be wetted by means of the sprays 31-31.- The gas which has passed upwardly between the condenser plates 5l-5I and has been subjected tothe fog developed between said plates will have the very fine dust particles therein wetted, so that in passing aroundthe dust collector 36 the wetted particles will, by reason of centrifugal force, be directed against the wetted rubber-coated surfaces of the dust collector 36. In other words, the gases en-, tering the tubular member 36a have been given a thorough preliminary wetting in the treatment before said gases have reached the tubular member 3611, and in their wetted condition are carried along curvilinear courses at decidedly higher velocities than were had in 'the passage up between the condenser plates -5I5| The gas stream within the dust collector 38 is deflected from straight-line movement and is carried along of the fact that the curved passages or laminations are relatively narrow in a radial direction,

the dust particles need travel only a relatively.

short distance radially of the apparatus before impinging upon. the dust collecting surfaces. The dust and water particles deposited upon said dust collecting surfaces and the water from the.

sprays 31-41 will drain through the opening 36c through the condenser tower H to the outlet 39. It may be mentioned at this point that rubber-is particularly well adapted for use in cleaning gas by the method of contact with wetted surfaces, for the reason that water exhibits surface aflinity for a rubber surface and spreads readily upon it, thus wetting it easily, positively and completely. Furthermore, rubber has the decided advantage, for the purposes'set forth, in

the fact that the dust particles removed from the gas do not set and cling to the rubber, but are readily washed oft by the water contained in the gas stream due to its preliminary wetting or by the flushing water applied directly to the. dust collecting surfaces.

The sprays 31 need be located only at points adjacent to the entrances of the channels be tween the arcuate walls 36g--36g, so that the dust collector 36 will .be effective not only in removing fine dust particles but water particles as well, delivering clean, dry gas.

The lower portion of the condenser II is provided with an outlet 39, which discharges the relatively clean water from the condenser Ii through the pipe 40. Said pipe 40 is connected through the pipe 4| to the reservoir 26, said pipe 4| being controlled by the valve 42. If preferred, water from the pipe 4| may be discharged to the sewer, such discharge being controlled by the valve 43.. The upper portion of the condenser Il' communicates with the clean gas pipe 44,

throughwhich the clean gas may be conducted to the point of utilization of such clean gas.

Referring to Figure 2, the washer I0 is of general cylindrical contour, and disposed in the lower region thereof adjacent to the inlet pipe I! isan apron 45 of arcuate form coaxially disposed with reference to the washer l0. Said apron 45 directs the gases entering through the inlet pipe [2 in a more or less circular path. Disposed above. the apron 45 is the annular member 46 disposed coaxially with the' washer l0 and spaced a short distance from the inner surface of the cylindrical wallof the washer l0. Said annular member decreases in diameter upwardly, and water from the pipe, I5 is admittedthrough the pipe 53 of the outer tapered surfaceof said annular member for providing an annular curtain of dripping or flowing water disposed around the inner surface of the washer l0. Disposed above the. an-

. nular member 46 is the bank or stage of baflies through a plurality of radially spaced curved water carried along in the gas stream or to the water from the water sprays 31-41. By reason As mentioned hereinabove,-

or hurdles l3 supported by the cross beams 41-41. Said baflles or hurdles consist of a series of cross bars 48, illustrated as being. of inverted teardrop conformation in cross-section. Above the series of cross bars 48 is a series of cross bars 49 of the same cross-sectional conformation. but disposed in right-angular relationship with the. cross bars 48. Three series ofthe cross bars 48-48 are illustrated, and be-. tween them are disposed two series of the cross I bars 49-49 arranged crosswise therewith. Disposed above the water sprays l-4l4 is the bank of baflles or hurdles [6. The bank of baflles or hurdles is'illustrated as being similar to. the 'bank 1 l3, but, if preferred, the baflles may be smaller and more closely bank It.

Reference may now be had to the condenser ll, certain details of which are shown in Figures 5, 6 and 7. Said condenser includes the cylindrical wall 50, which in addition to housing the condenser plates (to be referred to presently) also houses the dust catcher 36. Disposed crosswise of the condenser II are a pair of supporting bars 50a, which support a plurality of condenser plates |5l. Said condenser plates preferably take the form of corrugated sheets, illustrated on an enlarged scale in Figure 7. Said sheets are preferably disposed with the crests and troughs of the corrugations of each sheet disposed in registry with the crests and troughs of the other sheets. According to the illustration in Figure 5, the corrugated sheets spaced than is the case in 5|5l are divided into four different sections arranged side by side within the condenser II, and said four sections are supplied by'the four water sprays 34-34. Said water sprays may take the form of pipes arranged along chords of the condenser II and will be so perforated as to spray water downwardly. The upper extremities of the corrugated sheets 5l-5l may lie in a surface of substantially semi-cylindrical contour, a water spray 34 being disposed along the axis of each of said surfaces of cylindrical contour.

Disposed above the water sprays 34-44 is the fine dust collector 38 for entrapping the fine particles of dust which have traveled that far with the gas through the system. Said collector 36 has been described hereinabove.

The principles of the present invention asillustrated in Figures 1 to 8 inclusive may be described as follows:

For the purpose of illustration it may be considered that the gas entering through the inlet pipe l2 has a temperature of about 350 degrees F. This superheated gas may, for example, contain about 30 grains of moisture per cubic foot.

the wall of the chamber down which water is flowing from the annular member 46. In this stage'the gas is given a preliminary centrifugal separation and the gas is distributed to the hutdle stage In passing-upward through the first hurdle stage l3, said gas impinges on 'wetted surfaces.

It is also more or less immersed in spray and splash resulting from the passage of a considerable quantity of water downward through this ,sistance to the entry of dust particles into the water drops or upon the wet surfaces. The high temperature of the water at this stage is important. Under practical conditions. the copious evaporation referred to can resultif the water isexposed to the incoming hot gas in sprays and is extended on surfaces at such high temperature that most of the heat in the incoming gas is devoted to formation of water vapor and relatively little is devoted to heating the water up to the temperature at which that vapor formation takes place, and further if the temperature of the water approximates or exceeds the dew point of the gas as such gas leaves the initial cleaning and evaporating stage. a

Referring to Figure 13 (which illustrates approximately the conditions'existing with respect to an entering gas temperature of 350 degrees F.), copious evaporation could be said to occur at and above about degrees F. water temperature. Under certain conditions the water tem-. perature recirculated instage ll of tower lfi'may be at or near boiling temperature, in which case the temperature of the gas leaving said stage It may be approximately 220 degrees 1".

Because of the fact that the water in this stage is of high temperature, most of the heat in the gas is available to cause evaporation, and a large amount of evaporation takes place. The heat for this evaporation is supplied by the incoming gas,'this is-the sensible heat of the gas and the superheat of its contained water vapor. In this stage the incominggas is cooled from its incoming temperature of-'-say 350 degrees F. to a temperature which may be about 200 degrees F. The heat thus delivered by the gas is sufficient to raise and to maintain the temperature of all the water in this stage at. a suiliciently high point to evaporate about l0 to 20 grains of additional moisture per cubic foot of gas. Therefore, the gas leaving this. stage may be at about 200 degrees F. and may contain about 30 plus 13, or 43 grains of moisture per cubic foot, standard conditions.

Because of the considerable quantities of dirt involved in this stage of gas cleaning, it is necessary that a large amount of flushingwater be used.- As has been stated above, the water should be at'hlgh temperature. To meet this requirement the present invention contemplates the recirculation of the wash water in the first clog with dirt. To prevent such concentration the present invention contemplates the recirculation of only a portion of the water from the bottom of the washer ill. According to practice which is at present preferred, one-fifth to onetenth of-the discharge from the bottom of the washer II is delivered to the thickener or clarifler 22. This fraction of the water required in the washer I0 is made up by relatively clear water drawn from the reservoir 28. The practice as at present preferred results in a concentration in the first stage of cleaning in the washer ID of about 1400 grainsper gallon. This concentration is not sufllcient to cause difliculty in pumpage or in the spray nozzles I4-l4 provided the spraynozzles |4.-l4 are relatively coarse. The spray delivered by the nozzles 14- need not be very fine. Of course, the concentration of the dirty water within the stage II of the washer l0 may be chosen as desired, the degree of concentration being controllable by proportioning the flow of discharge from the washer ill to the thickener 22 and then back through the pipe l to the spray nozzles.l4-l 4.

The question may arise as to why water delivered through the pipe ii to the spray nozzles l4 may notbe water which has been clarified in the thickener 22. In the first place it is' necessary, to obtain proper settling, that the water remain in the thickener for a considerable number of hours, in which period of time it would lose much of its heat. In this stage of the cleaning the water should be maintained at high temperature, so that the advantages of low surface tension and maximum extent of evaporation may be utilized. In the second place it is preferable to discharge an efiiuent of relatively high concentration to the thickener 22 for the purpose of conserving space and cost of said thickener. The size 'of the thickener depends largely upon the quantity of liquid and is notzgreatly-infiuenced by the percentage of dirt in the eifiuent In making up the one-fifth to one-tenth (which fractions were taken by way of example) of the eflluent from the washer l0, itis not desirable to use ordinary cold water since the temperature of the water in the first hurdle stage [3 would be reduced and much of the sensible heat in the gas would be utilized in bringing up the temperature of the water in this stage. This would hinder evaporation in this stage and would hold down the moisture content in the gas delivered from this stage.

As indicated above, it is desirable to use only a minimum of the sensible heat in the gas above 200 degrees F. in heating the water in the hurdle stage l3. This is desirable in order that a maximum of the heat in the gas may be available for evaporation. There is, however, less objection to the use of the sensible heat below 200 degrees F. in the gas for preheating water, since this heat is less effective to cause evaporation. To this end the second stage of hurdles I6 is disposed above the water sprays l4-l4. This second stage of hurdles serves 'a triple purpose. First, it constitutes a stage of impingement cleaning for the gas for removing particles of dust which have escaped the hurdles in the first stage. Second, the gas in the second stage of hurdles, in giving up sensible heat to the water in said second stage, acts as a preheater ofthe makeup water delivered to the first stage l3. Third, the second stage of hurdles [6 serves to partially cool the gas.

In the second stage of hurdles IS the individual hurdles will be smaller and more closely spaced than in the first stage of hurdles l3. Because the-gas is now relatively clean, and because the amount of dirt deposited in stage 16 is relatively small, a relatively small amount of water will sufilce. This amount of water can be regulated to that required as make-up for the first stage.

Since this make-up water is of relatively small amount and since it will be relatively clean water, it can be' pumped without excessive cost to a relatively high pressure and be delivered through relatively small spray nozzles. It is preferred to have this pressure at least twice as high as the pressure of the sprays in the first stage. This practice will result in even distribution of this relatively small amount of water over the hurdles in the second stage of hurdles Hi. It will also present more surfaces to have intimate contact with the gas and will serve to give extra cleaning and wetting of. the gas. The gas leaving the second stage of hurdles IE will have its dirt content very considerably reduced relative to the gas leaving the first stage of hurdles l3.

- It might seem that the intermingling of warm gas with the relatively cool water from the water jets "-41 would cause condensation to take place in the second stage of hurdles l6. Extensive condensation will not occur at this stage, for

the following reasons: According to the example given above, the gas'entering the second stage IB of hurdles contains about to 45 grains per cubic foot of moisture. The dew point of such gas is about 125 to 130 degrees F. At higher temperatures this gas is superheated. Condensation will not take place until the gas reaches its dew point. It is possible and practicable to control the quantity or the temperature, or-both, of' the water supply to this stage in such manner as to control the temperature of the gas leaving the stage. This control is had by drawing water from the reservoir 26, which water in service will .be considerably above atmospheric temperatures.

In practice the temperature of the water delivered from the reservoir 26 will be about 130 degrees F'., and in a tower washer having 60,000

' cubic feet per minute capacity the water delivered from the reservoir 26 and the spray nozzles I'I-|1'will be about 200 gallons per minute. The gas will leave the tower 10 at about to degrees F., only slightly superheated, and

containing about 43 grains of moisture per cubic foot.

Another factor diminishing condensation in this stage is the element of time. If the gas should reach or fall below its dew point in passing through this stage, only a brief time will elapse during which condensation will occur; During this brief interval the gas will be leaving this stage and passing to the next succeeding stage. I p

The moisture laden gas delivered by the washer [0 passes to the base of the condenser tower II. The wet gas passes upwardly between the plurality of corrugatedplates 5l5l. Water from the water sprays 34-34 flows down these surfaces from above. This water comes from a source of clean water supply and will be relatively cool. Accordingly, the surfaces of the corrugated plates 5l5| are cooled. The gas .condensation causes a fog to be formed inthe condenser lanes between the corrugated plates 5l5l. In condensing, some of the moisture will form directly on the cool walls, but most of it will form in the space within the gas lanes between the plates 5|-5l. In these lanes there will be relatively few drops of water originating from sprays 34-34 since the effect of the rising gas will be to buoy up the water drops and drift them to thecorrugated plates 5|5l. The action referred to is illustrated in Figure 8, in

which the numerals 5252 indicate thin streams of water flowing down the corrugated plates til-5|. The course of a dust particle or water drop from midstream between neighboring plates Sl-il to a curtain ofwater 52 is illustrated in that figure. The velocity of flow through the lanes between the plates 5I-5I will in practice not be high. As an example, it may be stated that the flow of gas will be approximately 5 to 10 feet per second. This velocity will not be sufflcient to blow the water off the plates il-Sl, and the quantity of water will be such as to'cause only thin streams to flow down the plates. Such streams are not easily blown off the surfaces. Because of the moderate velocity, the gas will not be highly turbulent, producing the result that heat transfer from the gas to the water streams is least by contact and mostly by radiation. Th flow of gas will be placid.

The fog formed in the lanes between the corrugated plates 5|5l will use the dust particles as nuclei. Since all 01 the larger dust particles be coated with moisture. Some of these moist particles will adhere together, forming droplets and drops, and will attach to the condensing surfaces of the plates 5|5|. Some of the wetted particles will be so small and light in weight that they will be carried up and out of the condenser stage into the sprays 34 and into the fine dust catcher 35.

As indicated above, the water supplied to the condenser plates 5i--5l will be relatively cold, that isnear atmospheric temperature, For this reason it will be possible to reduce the temperature of the gas emerging from between the condenser plates 5l-5l to nearly the temperature of the incoming water, inasmuch as the water and the gas are flowing in opposite directions. A substantial temperature diflerence will exist between the water and the gas throughout the condensing stage. Such a substantial tempera,- ture difierence is conducive to substantial reduction of the area of the necessary condensing surface. By way of example, it may be stated that in the condensing stage thegas is cooled from 140 degrees F. to 80 degrees F. (assuming water at 70 degrees F.). Even with this moderate range-of cooling, considerable surface is required. a

If the gas were to enter at 200 degrees F., a much greater amount of cooling and condensing surface would be required. Thus it is evident why the pre-cooling in the second hurdle stage IB and the fine spray in the tower washer l effects substantial economy in the condensing surface required in the tower H, where intimate intermingling of the gas and the water drops must be avoided in order that the dust particles alone may serve as nuclei for moisture condensation.

The function of the condenser H may be described in other language, as follows: As previously indicated, the gas, as it passes through the upper stage of hurdles IS in the washer i0, is cooled to a point approximating the dew point. It therefore enters the condenser H in saturated or in only slightly superheated condition. When the gas passes upward between the condenser plates i5l it is further cooled. This cooling is gradual. It is automatically caused tobe gradual, because the counter-current flow of water and gas tends to maintain approximately a constant temperature difference between the gas and the condenser walls from bottom to top. In other'words, the tendency is to distribute the cooling effect.

have already been removed by impingement in It is well known that when a gas or fluid passes through a narrow channel, the fluid adjacent to the sides of. the channel travels more slowly because of the wall friction, and the fluid in the middle tends to travel more rapidly. Thus a particle in the gas entering the narrow channels between condenser plates 5 I-il tends initially to travel up the middle of said channels. As the stream is held back on the sides, the fluid in the middle of the channel tends to move toward the side of the channel. Eventually it reaches the side of the channel, where a little eddying may occur (see Figure 8) As the particle referred to passes up the middle of the channel it is cooled by radiation of its .heat to the cooled condenser walls and by some mixture with cooler gas along the sides. As the gas cools, some of this moisture condenses. Dust particles in the middle of the stream serve as nuclei for the condensation 01' such moisture, the result being that these dust particles are wetted. As the wetted dust nuclei pass upward, they tend to gather more moisture due to further condensation and due to contact with other wetted dust nuclei.

As a result of the forward and gradual sidewise movement of the dust nuclei in the narrow channel, the wetted dust nuclei and the droplets of moisture tend to be carried toward the condenser. plates 5|--5I, where they contact the water flowingdown these plates and are caught and flushed by said water.

Thus by a combination of counter-flow and passage of thegas upward in narrow channels between surfaces carrying cooling water, the gas is first cooled out of contact with the cooling surfaces in such manner as to cause deposition. In this manner most of the moisture initially in the gas is caused to condense and attach itself to dry dust particles. The droplets of moisture are caused to be deposited out of the gas stream soon after their ormation, so that they do not long continue to ow and to steal the moisture which is needed to be condensed on dry particles in the condenser. If the gas velocity through the condenser II were too great, there would be too much turbulence in the narrow channels between the plates til-5| and the gas would not be cooled before contacting said plates. Too much of the condensation would, under these conditions, take place on the wetted plates and too little would take place in the gas lanes between the plates. 0n the other hand, if the gas velocity through the condenser be too low, or if the plates be spaced too far apart, the gas would be too Stratified. Under the latter conditions, some of the gas would flow through the entire length of the condenser in the middle strata and the droplets would not be deposited out of the gas stream. They will tend to grow into large drops, robbing the dust particles of the necessary moisture. Therefore, the flow of gas should be regulated to the spacing between the condenser plates 5i5l. As indicated above, in a condenser having a capacity of 60,000 cubic feet of gas per water sprays also serve to give the gas a further cooling. They also serve to catch some of the particles which have escaped thus far in the cleaning system. In other words, the condenser plates and the water from the water sprays 34 catch some of the finer .dust particles which,

had remained unwetted in the prior stages of the cleaning operation. These finer particles will be separated out in the condenser stage and will be discharged through the bottom of the condenser II.

The gas, after passing the water sprays 34-34, still must pass through the centrifugal. dust collector 36. This centrifugal collector functions very effectively because the smallest dirt particles have been wetted muchv more completely than is possible in certain types of .tower washer heretofore known and used, and, furthermore, the velocity of gas flow therethrough is decidedly greater than up between the condenser plates iii-5|. The thorough wetting to which the very fine dust particles of the gas have been subjected has added greatly to the weight of these particles and they are therefore particularly susceptible to centrifugal separation and deposition upon the curved rubber water-wetted surfaces of the centrifugal trap. Moreover, since the particles have been pre-conditioned by wetting, they will attach themselves to the water on the water-wetted rubber surfaces 'referred'to very readily, and will thus deposit a gradual drift down these surfaces.

Inasmuch as the water discharged from the condenser tower I I has been subjected to gas out of which the heavier particles have already been removed, said discharge water will compare favorably with the efliuent from the thickener 22 and may be passed directly to the sewer. In order -to economize water, a portion of the relatively clear eilluent from the condenser H may.

be delivered to the reservoir 26 for delivery to the top sprays ll-Il of the tower washer I0. To this end a certain proportion of the eilluent from the condenser ll at say about 110 degrees F. will be mixed with the eflluent from the thickener 22 at about 150 to 160 degrees F. By controlling the ratio of the amount of water from the condenser I l with that discharged from the thickener 22, the temperature of the water delivered to the upper sprays ll of the tower washer I!) may be controlled.

Referring now to the structure illustrated in Figures 9, 10, 11 and 12, a modified meansgis' illustrated for supplying evaporated moisture to the gas to be cleaned and a modified means is illustrated for producing the preferential deposition of the resulting fog upon the dust particles as nuclei. I

According to the disclosure of Figures 9 to 12' inclusive, a vertical casing 60 is provided which may be cylindrical in cross section. Said casing 68 has the conical bottom 6|, which at the lower extremity thereof is provided with the outlet assembly 62 for permitting the drawing off of the water from said lower extremity while providing a gas seal. Said cylindrical casing is pr'ovided near the bottom thereof with the gas inlet 63, which will admit hot dirty gases, which gases will in practice be well above the boiling point of water.

Disposed within the casing 68 are a plurality of hurdles 64-64, which may be of the inverted teardrop conformation above described in connection with Figure 2. Said hurdles may as described in connection with said Figure 2, take the form of bars, certain groups of said bars being arranged crosswise with respect to other groups. Disposed above the hurdles 64 are a. plurality of casing 68.

'garted bars arranged in groups,

freshwater supply pipe nected to any preferred service main. Said fresh spray nozzles 65-65 spaced around the periphery of the casing 68. Said spray nozzles 65-65 are connected to the ring pipe 66, which encircles the Said ring pipe 66 is connected through the pipe 61 to the pump be located adjacent to the bottom of the apparatus for convenience in servicing. Said pump 68 is' connected through the pipe 69 with the lower region of the truncatedbottom 6| of the casing 68. It will be understood that hot dirty water from the bottom of the casing 60 will be recirculated by the pump 68 through the spray nozzles 65-65 onto .the,hu'rdles 64, part of the dirty water being-discharged and a controlled amount of fresh make-up water being added, as will be described presently.

In the embodiment of the invention illustrated in Figures 9 to 12 inclusive, a plurality of baffles 10-18 are provided, which are arranged in echelon with reference to one another in a manner to permit the upward flow of gases around said baffles but to divert water falling upon said baflles from above. Said baffies 18-10 have inclined tops whereby to divert water from above downwardly toward the peripheral trough 12.

Connecting with the lower portion of said trough 12 are a plurality of U-connections 13-13 from which pipes I4 may conduct water from said trough 12 to the sewer or other desired place.

Disposed above the baflles Ill-I8 are the hurd1es15-I5,'which hurdles may take the form of inverted teardrops and may comprise elonthe axes of the bars of certain of said groups being disposed crosswise with reference', to the axes of bars of other groups.

Disposed above the g lhurdles 15-15 are aplurality of spray nozzles-16, which may be disposed in spaced relationship around the periphery of the casing 60. Said spray nozzles 16 are conwhich encircles the eas- 11 isconnected to the 18, which may be connected to the ring pipe TI ing 60. Said ring pipe water supply pipe I8 is also connected through the pipe 19 and the valve 80 to the pipe 69, wherethe operator a controlled amount of fresh water may be mixed with the dirty water drawn from the bottom of the casing 60 and delivered through the recirculating pipe 61.

The sprays delivered by the preferably have such overlapping relationship that they will more or less uniformly cover the hurdles 15. Referring to Figure 11, the diagrams indicated by the broken lines 8| indicate how the sprays in relatively fine condition shower by at the option of said hurdles 15-15.

Disposed above the spray nozzles 16-16'are the horizontally directed spray nozzles 82-82, which are also disposed in spaced peripheral relationship with the wall of the casing 60.- Said spray nozzles 82-82 are connected through the ring pipe 11 and are intended to direct intense, substantially horizontal sprays toward the axis of the chamber 68. Valves 83 and 84 control the flow of water to the spray nozzles 16 and 82. The sprays from nozzles 16 and 82 are relatively fine sprays resulting from the use of relatively fine nozzles.- The fresh, clean water of this stage is delivered to these nozzles at a higher pressure than that of the dirty recirculated water delivered to coarse nozzles 65. Preferably the fine sprays from nozzles I6 and 82 are at a pressure at least twice as high as the pressure-of the coarse 68, which in practice will,

spray nozzles 16-16' 2 passed through the plenum chamber 85.

Figures 9m 12 inclusive contemplates a plenum chamber above the horizontally directed spray nozzles 82-82. As will be pointed out hereinafter, the plenum chamber has the function of allowing the fog to condense preferentially upon the dust particles in the gas being cleaned, there being no fixed surfaces in said plenum chamber. The plenum chamber referred to is indicated by the numeral 85.

The top portion of the casing 60 may be conical in form, as indicated by the numeral 86, and at the top of said'co'nical portion 86 there maybe provided the centrifugal fine dust collector 31. The particular fine dust collector chosen for illustration in Figures 9 to 12 embodies the structure'illustrated and described in the application of John C. Hayes, Serial No. 60,948, filed January 27, 1936. Said fine dust collector 81 may be supplied with water from-'aplurality of spray nozzles (not illustrated). Said fine dust collector may be described briefly as follows: Said dust collector 81 operates on the principle of centrifugal actionand provides a plurality of circuitous passageways for the gases which have Said dust collector 81 includes the tubular member 81a, which rtubular member has located therein the dividing partition 81b positioned diagonally with reference to said tubular member 81a. Said dividing partition 81b extends from a region adjacent to the bottom of the tubular member 81a on one side thereof to a region adjacent to the top of said tubular member at the other side thereof. Said tubular member 81a .is open at its bottom to the plenum chamber 85 and is open at its top to the gas outlet 88. A plate 810 in the form of a section of an annulus is disposed between the tubular member 81a at the bottom thereof and the outer peripheral wall of said fine dust collector. An annular plate 81d is located at the top of the tubular member 81a. and extends from said tubular member 81a to the outer peripheral wall of the fine dust collector. The tubular member 81a is provided with the opening 81e and with a corresponding opening 81 diametrically opposite to the opening 816. Said openings 81c and 81 extend preferably throughout the length of the tubular member 81a between the plates 81c and 81d. The section of the annulus 810 is provided with an opening corresponding in size and location to the opening We. The boundaries of said opening in the plate 810 are indicated by the lines flit-81h. It will be disposed along planes indicated by the lines flit-81h, which diverge outwardly with reference to-the axis of the dust collector 81. The other end portions of the arcuate walls 8111-410 may be given a sharper curvature than the other portions of said arcuate walls 810-810, and the extremity of said arcuate walls 810-810 adjacent to the openings 81 may be located in planes indicated by the numerals 81i-817, which converge toward the outer wall of the dust collector 81. The dust collector 81, as indicated above, operates upon the principle of centrifugal force. To this end the velocity of the gases through the Passages provided by the arcuate walls 810-41 of the plenum chamber 85, and the total -crossbe obvious that gas entering the tubular member 81a. will travel through the opening 81c and through the opening, just referred to, in the plate 81a, and will have two substantially semi-circular routes of travel to the opening 81 which communicates with the gas outlet 88. Disposed between the tubular member 81a and the outer wall of the dust collector are a. plurality of arcuate sectional area of the passages provided by the walls fizz-81a will be sufhcienltly restricted to insure, the gas velocity referred to. The surfaces of the arcuate walls 810 and other surfaces of the dust collector 81 which are contacted by the gases to'be cleaned are preferably rubber-covered and may be wetted by sprays (not illustrated). The gas which has passed upwardly through the plenum chamber 81 will, as discussed brieiiv hereinafter, have the very fine dust particles therein wetted, so that in passing around the dust collector 81 the wetted particles will, by reason of centrifugal force, be directed against the wetted rubber-coated surfaces of the dust collector 81. In other words, the gases entering the tubular member 81a have been given a thorough preliminary wetting in the treatment before said gases have reached the tubular member 81a, and

in their wetted condition are carried along the curvilinear courses at decidedly higher velocities than were had in the plenum chamber 85 below said tubular member 81a. The gas stream within the dust collector 81 is deflected from straightline movement and is carried along through a plurality of radially spaced curved courses, or laminations, with the effect that the dust particles remaining in the gas are disposed upon the curved partitions or upon the wall of the dust collector;

Those details of construction illustrated in Figures 9 to 12, inclusive, which relate to the bailies 1010 for diverting water away from the hurdles 646l in the lower part of the casing 60 form no part of the present invention, but constitute the invention of Owen R. Rice and Wilfred 'C. Schofield described and claimed in their apover the hurdles 64-44 by the spray nozzles walls 810, preferably disposed throughout the,

greater part of their length coaxially with the dust collector 81. The extremities of said arcuarte walls 81g-81g adjacent to the opening 81c may available.

wherein some of the heat remaining in the gas after it has left the initial cleaning and evaporating stage is delivered to the make-up water before such water enters the hot mixing stage; or this method may be employed in combination with another source of preheat such as exhaust steam from turbines driving the pumps. The coarser dust particles will be removed in passing up through the region of the hurdles "-64, and the gas will have a large amount of evaporated moisture added thereto, as discussed in detail in connection with Figures 1 to 8 inclusive.' The gas carrying the evaporated moisture will pass upwardly around the bailles ll-ll through the hurdles 15. The bank of hurdles 15 will be relatively shallow, and a controlled quantity of water spray is imposed thereupon from the spray nozzles 16-16 and 82-82. The gaspassing upwardly around the hurdles 15-15 is cooled to a temperature not substantially below the dew point of said gas, that is-said gas is cooled to a temperature not substantially below the temperature at which water vapor in the gas tends to condense. After passing the hurdles IF-I5, the gas passes through the short zone of intense horizontally directed water sprays. The time that is takes for the gas to travel through this latter zone of sprays is very brief. However, the ,efiective heat transfer surface represented by the hurdles l6. and this intense horizontal spray zone is so great that the desired cooling of the gas to a temperature below dew point, depending upon the temperature of the available water, will be accomplished.

Obviously, the evaporate/i moisture in the gas will not condehse until the gas is cooled to or below its dew point. There is a certain time lag between the cooling of the gas and the condenscopious evaporation, and impinging said gas against fixed dust collecting surfaces wetted with said water to increase the moisture content of said gas and thereafter exposing said gas in a placid flow in a vertical direction tov extend smooth surfaces wetted with cooler water to cause condensation from said gas.

2. I-'he method of scrubbing blast furnacegas' which consists of mixing water. with said gas,

which water is at a temperature to produce copi ous evaporation, and impinging said gas against fixed dust collecting surfaces wetted with said ingof the water vapor. While the gas is passing through the plenum chamber 85, the tempera-- ture of which is governed in part by the sprays 8282, condensation proceeds as a result of. the

cooling that has been secured during the passage of the gas through the intense brief zone of horizontal sprays directed by the spraynomlos 82. There are no fixed surfaces in this plenum chamber 85 and consequently the flow of gas therethrough is placid. Condensation can take place only upon the dust particles in the gas. The condensing water vapor seeks objects 'or surfaces upon which to nucleate itself in condensing. The dust particles provide these objects and surfaces.

As indicated above, the wetted' dust particles which have passed through theplenum chamber 85 are removed from-the gas in the dust collector 'The means. defining the circuitous or curvilinear passageways in the fine dust collectors and I1 have the advantage that they utilize bothcentrifugal action and turbulence of the gas in their functions. It will be understood, of course, that water to remove certain of the dustparticles in said gas and to increase the moisture content of said gas, recirculating a portion of said water at a temperature sufficient to produce copious evaporation in the gas scrubbing operation, discharging the remainder of said water and exposing said gas in a placid flow in a vertical direction to extended smooth surfaces wetted with cooler water to cause condensation from said gas.

3. The method ofscrubbing blast furnace gas having a temperature above the boiling point of water which consists in mixing water with said gas to remove-the coarse dust particles therefrom and to increase the moisture content thereof, recirculating a fraction of said water directly to said scrubbing operation, discharging the re-' maining fraction of said water, supplying make-up water to said gas after said gas has left said-water mixing ,step and delivering said make-up water to said water mixing step, said make-up water being added in a quantity and at a temperature to reduce the temperature of 7 said gas and impinging said-gas against fixed dust collecting surfaces wetted with said water to remove the coarser particles of dust therefrom for initial-cleaning and to increase the moisture content of said gas, recirculating a portion of said water, clarifying the remaining portion of said water, applyingsaid clarified water'to said gas after said gas has been subjected to said initial cleaning, the temperature of said clarified water being 'chosen. 'of a value to reduce the temperatureof said gas substantially to its dew point, and subjecting said gas further to a condensing. action whereby to produce a fogadapted to adhere to the smaller dust particles in said gas.

' 5. The method of scrubbing blast furnace gas V of a temperature above the boiling point of water which comprises mixing hot water with these passageways may be straight, if preferred,

turbulence'alone'being relied upon to bring the dust particles into contact with the wetted walls defining said passageways.

Though certain preferred embodiments of the v present invention have been described in detail,

many modifications will occur to those skilled in the art. It isintended to cover all such modifications that fall within the scope of the appended fclaims. I I what is claimed is-- l. The method of scrubbing blast furnace gas which consists of mixing such gas with water,

which water is at a temperature to produce gas after said gas to remove the coarser particles of dust therefrom for initial cleaning and to increase the moisture content thereof,' recirculating directly a por'tion of said water through said initial cleaning operation, applying other water to said it has been subjected to said initial cleaning operation, the temperature of said other water being chosen of a value to reduce the gas substantially to its dew point, and subjecting said gasfurther to a condensing action by passingit through channels bounded by water wetted surfaces whereby to produce a fog adapted to adhere to the smaller dust'particles in the gas. 6. In gas cleaning means, in combination, a gas washing tower, hurdles therein, meansfor subjecting hot dirty gas to a recirculation'of hot dirty water to increase the moisture content of said gas, means for cooling said gas to about its dew point after said gas has been subjected to said hot dirty water, and condenser means for treating said cooled gas, said condenser means having vertical water-wetted surfaces for condensing said cooled gas.

7. In gas cleaning means, in combination, a gas washer including hurdles, means for admitting gas into the region of said hurdles, means for recirculating hot'water inthe form of spray in contact with said gas through the region of said hurdles, means for cooling the gas after it has passed said hurdles to about the, dew point of said gas, condenser means for treating said cooled gas, said condenser means including means providing a plurality of vertically disposed lanes, and water delivery means for bounding said lanes with streams of water.

8. In gas cleaning means, in combination, a

gas washer including hurdles, means for admitting gas into the region ,of said hurdles, means and cooling to approximately its dew point, a condenser tower including a shell and vertically disposed surfaces disposed in generally parallel relationship with one another within said shell, means for directing said cooled gas upwardly between said surfaces, and water delivery means for directing streams of water down along said surfaces, said shell having also disposed therein a centrifugal dust catcher disposed above said plates, said centrifugal'dust catcher having restricted passageways for speeding up the flow of gases therethrough relative to the speed of gases fied ,in contact with water which water is at a for recirculating hot water in the form of spray in contact with said gas through the region of said hurdles, means for cooling the gas after it has passed said hurdles to about the dew point of said gas, condenser means for treating said cooled gas, said condenser means including means providing a plurality of vertically disposed. lanes, and water delivery means for bounding said lanes with-streams of .water, said water delivery means being so disposed that said streams of water flow oppositely to the flow of gas through said lanes.

9. In a gas cleaning system,.in combination, a two-stage gas washer including a first stage of hurdles and a second stage of hurdles, means for delivering hot dirty gas below said first stage of hurdles, water sprays above said first stage of hurdles, means for' recirculating water from the bottom of said gas washer to said water sprays, upper water sprays, and means for delivering water to said upper water spray-s, said upper water I temperature to produce copious evaporation, the gas is next further cleaned and cooled to approximately its dew point by contact with water at a lower temperature, the gas in non-turbulent condition is next further cooled below its dew point and then passed through water sprays, and, the gas is then passed through a separating action to remove therefrom small wetted dust particles and water drops, the gas in said separating action being speeded up relative to its speed while being cooled in non-turbulent condition below its dew point.

-13. The method of cleaning blast furnace gas which consists-of mixing said gas intimately with hot water to remove the coarser dust.particles and to increase'the moisture content of the gas, recirculating directly the major portion of said hot water to said mixing stage, subjecting said gas in non-turbulent condition to thermal communication with colder water to create a fog adapted to adhere to the finer dust particles, and passing the gas through separating action to remove therefrom wetted dust particles, and water drops, the gasv in said separating action being speeded up relative to its speedwhile being cooled in non-turbulent condition below its dew point.

hurdles and a secondstage of hurdles, means for delivering hot dirty gas below said first stage of hurdles, water sprays above said first stage of sprays being positioned to direct water upon said second stage of hurdles, said second stage of hurdles being so positioned relative to said first stage of hurdles that water will flow, from said second stage of hurdles down over said first stage of hurdles, a condenser, means for conducting gas from above said second stage of hurdles to the bottom of said condenser, means for directing water in streams defining paths for the upward flow of gas through said condenser, and meansfor conducting water from the bottom of said condenser.

11. In gas cleaning means, in combination, means for increasing the moisture content of gas 14. The method of cleaning blast furnace gas which consists, in one stage, in removing the coarser dust particles in contact with water at a temperature to produce copious evaporation to increase the moisture content of the gas, recirculating the major portion of this water and discharging a minor portion thereof, and in a subsequent stage subjecting the gas to contact with make-up water to elevate the temperature of said make-up water while cooling the gas to approxivmate'ly its dew point, said make-up water being delivered by gravity from said subsequent stage to said first-mentioned stage.

15. The method of cleaning blast furnace gas having a temperature above the boiling point of water, which consists in partially cleaning and humidfying the gas by contact with hot water, the major part of which is recirculated and the minor part of which is withdrawn, and thereafter causing said gas to pass in a placid flow through a region wherein it is subjected to thermal communication with colder water to create a fog adapted to adhere to the finer dust particles and then passing the gas at increased velocity through restricted passageways between plates whereby to remove the water drops and wetted dust particles from the gas stream.

' GORDON FOX.

ALFRED J. EBNER. OWEN R- RICE.

for the patent number "2,207,771" read 2,20h.,T7l--; page 9, first column,

CERTI'FICAI'E 0F CORRECTION.

Patent No. 2,2h2,29h. V May '20, 19!;1.

. GORDON Fox, ET AL.

Itis hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page}, first column, line 6, for the word "through" read -throughout--; page second column, line 25, for "this" read --that-; page 8, second column, line 57,

line27, for "is" read --it-.-; and second column, line 5, for "extend" read --ektended and that the said Letters Patent should be read with this correction therein that the same may conform to the recordof the case in the Patent office. 7

Signed and sealed this 2mm day of June A. D. 191 1.

Henry Van Arsdale (Seal) I Acting Commissioner of Patents.

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