US2183142A - Method of cleaning wool - Google Patents

Description

Dec. 12 1939. F. H. MACKENZIE METHOD 0F CLEANING WQOL Filed Sept. 14, 1956 2 Sheets-Sheet 1 [l Nvl-:N oR

BY f/ Dec..l2, 1939i. l F. H. MAcKENzlE METHOD 0F CLEANING wooL Filed sept. 14, 1936 2 Sheets-Sheet 2v Patented Dec. 12,'19'39 UNITED STATES lParra-rrr omer.

2,183,142 METHOD F CLEANING W001i; Franklin H. Maokenzi Bywood, Pa., assigner to American Chemical Paint Company,

Ambler, Pa., a corporation of Delaware Applmanon'sepmber 14, 1936, serial No. 100,591; y

1o claims. (ci. s-isail This invention -relates to the art of cleaning wool, especially raw wool, and the principal object of the invention is to provide a`method of,v

as well as suitable .means for, cleaning wool with 5 lmaximum economy in consumption of chemicals, water, and heatjand with maximum uniformity in the color, feel", grease content and tensile strength of the .resulting product.

Another important object of the invention is to provide a wool cleaning system in which shutdowns for repair, replacement or renewal of solution are entirely eliminated. In other words, it is an object of my invention to provide a wool cleaning system .which is capable of substantially contlnuous'operation.'

More specifically statedVit is an object oflthe invention to maintain the scouring solution in the scouring bowl of accumulations of dirt and grease by providing a system for cleaning the solution by means of which the dirt and-grease are largely separated therefrom and segregated in certain parts ofthe apparatusl into which the wool does not enter.

Another object of the invention is the provision of a process by means of which it is possible to effect perfect cleaning of the wool without the necessity of adding soap or other soap-like materialV toA the scouring solution, as well as to markedly reduce the consumption of alkaline detergent heretofore commonly employed in the scouring process. 1

A .still further object of the invention is to segregate, in easily purified form, the wool grease removed from thc-wool.

The invention also makes possible the attainment of a greatly simplified method .of controlling the cleaning process and one in which the control may be placed under conventional electrical apparatus and made almost'entirely o automatic as well as highly sclentlc in character.

f Still another object of the invention is to pracy tically eliminate stream pollution ,with grease,

since grease recovery with my process is very high. f

Apparatus suitable for use in connection with my improved wool cleaning method or system is illustrated in -the accompanying drawings wherein:

Figure 1 is a purely diagrammatic representation illustrating the iiow ofthe solution, but in no way showing the mechanism for handling the wool, which mechanism in and of itself forms no part .of the present invention and may be or bowls as free as possible` *It should be noted, however, that the wool Apasses through the apparatus in a direction from left to right, and

Figure 2 is a similar diagram illustrating some slight modifications which are particularly useful in handling wools which are unusually high in grease content.

f The wool is first washed or desuinted in what I have termed a desuinting bowl l. `This first treatment is adapted to remove water soluble m matter, suspensible colloidal matter and the loose solid dirt which comprises the greater part of such solid dirt present in the wool. For this. purpose plain cold water may be employed, but for the sake of economy, as will appear below, I 15 use in part, at least, water from the stagegwhere N the wool is flnally'rinsed.

" This preliminary washing or desuinting treatment may be performed in one or more stages, althoughl in the present disclosure I have illus- 20 trated but one stage, as this will be suflicient to illustrate the principles involved. However, in case more than one such preliminary stage is employed, I might mention that- Ihave found it most economical and efcient to supply water from the final wool rinse to the first stage and fresh water to the last stage, the overflow and the squeezed out water from which last stage are passed to the immediately preceding stage, and so forth. so After -this vpreliminary washing or desuinting' treatment, the wool is treated or scoured in the scouring bowls 2 and 3 with one or more solutions adapted to remove grease and residual dirt. -If desired, only one scouring bowl may -be em-v ployed, but I prefer to use two or more, in which event the several bowls should be interconnected as by a pipe 4 inorder to maintain the same .liq'uid level in each.

Following the scouring o peration, the wool is '40 rinsed in the rinsing bowl 5.

Each of the bowls I, 2, 3 and 5 is preferably provided with a conical bottom construction forming sumps 6 over which are placed suitable perforated bronze plates 1 along which the wool 45 is moved by mechanical rakes familiar to those skilled in this art.

Each bowl is. provided with an inclinedl plate 8 leading tothe squeeze rolls 9 into which latter the wool is pushed by rapidly oscillating rakes 50 called crabs, as is well understood byjthose familiar with this art. Beneath each set -of squeeze rolls is a hopper l0 into which falls the' wrung-out solution and any overow from the bowl. In the preliminary desuinting bowl i and in the rinsing bowl 5 the wool may be given a spray of fresh water just before entering the squeeze rollsby means of a perforated pipe II. The sumps 6 at the bottoms of these bowls are provided at their lowest points with suitable plug valves I2 which may be opened to permit discharge to waste through pipes I2a when desired for purposes of cleaning.

Water for the preliminary washing or desuinting operation may be introduced into the bowl I through a suitable connection as indicated by the arrow I3, and fresh water for rinsing the wool in the rinsing bowl 5 may be added through a suitable connection as indicated by the arrow I4. The water from the hopper ID of the rinsing bowl 5 is withdrawn through the pipe I5 and delivered by means of a pump I6 to the head end of the preliminary washing or desuinting bowl I, as clearly shown in the drawings.

In Figure 1 the solution which overflows into the hoppers I 0 of the scouring bowls 2 and 3 or which is wrung out by the squeeze rolls, is delivered to the heads of the bows by pumps I1 through suitable piping I8, as clearly shown in the drawings. y

'Ihe solutions in the scouring bowls 2 and 3 generally contain a mild alkaline detergent salt such as'soda ash, and a soap or soap-like substance as their cleansing agents. The alkaline detergent is preferably introduced as a solution through the connections indicated by the arrows I9. During use these solutions accumulate grease and dirt from the wool, and theA alkaline de tergent salt is consumed by reaction with fatty acids in the grease, and in the conventional method of cleaning wool the solution rapidly becomes unt for use so that in spite of frequent partial drainage of the solution, dilution with water, and restoration of soap and alkali, it must sooner or later be discarded entirely. This, of course, is extremely wasteful and inefi'icient and has evolved more or less frequent shut-downs, which objections the present invention overcomes.

The bottoms of the sumps 6 of the scouring bowls 2 and 3 are connected by means of suitable pipes 20 and 2l to the pipe 22, which latter de^ livers, as indicated by the arrows, to a woolscreen 23 located above a settling tank 24. A powerful pump 25 capable of withdrawing the sludge from the bowls 2 and 3 at extremely high speed is introduced into the pipe 22 so that the sumps of these bowls can be cleaned with great rapidity. By this means their content of deposited or settled dirt is readily withdrawn along with a portion of the solution so as to maintain the solution in the scouring bowlsvin a comparatively clean condition. The pump 25 may be operated continuously or intermittently as may be necessary, although I prefer to run it at intervals and at high speed so as to rapidly and effectively clean out the sumps. In this way the solution is continually being withdrawn for the purpose of cleaning it as will appear below.

The settling tank 24 is provided with heating coils 26 as well as with conical or pyramidal bottoms 2l forming collecting sumps from which the settled dirt may be withdrawn to waste through the pipes 28 under the control of suitable valves From the settling tank 24 I prefer to withdraw or overflow the solution into another settling tank 30 also provided with sumps 3| having discharge to waste through the pipes 32 under the control of valves 33.

centrifuge 4I for a The settling tank 24 is provided with an upwardly extending bame 34 over which the solution passes on its way to the outlet 35, the baille 34 serving as an aid in effecting quiet separation of the settleable dirt.

The settling tank 30 is similarly provided with heating coils 26 and with a downwardly extending baffle 36 under which the solution must pass on its way to the outlet 31, the baille serving to separate and segregate in the right-hand compartment of the tank any creamed grease. By thus trapping the creamed" grease in the righthand compartment of the tank it is prevented from reaching the outlet 31.

Preferred operation, however, contemplates that the solution in tank 30 pass by way of the skimming launder 38, pipe 39 and pump 40 into purpose which will be described below.

It is obvious that by means of the settling tanks 24 and 30 the contaminated solution is subjected to a field of gravitational force and in this field the major portion of the settleable dirt, solids, etc. is collected in the sumps 21 and 3| from which, as stated, it can be discharged to waste. The volume lost by such discharge can then be replaced by fresh water through the connection 42.

I should like to call attention to the fact that although I have shown and prefer to use two in dependent gravitational separating or settling tanks, yet it is quite possible to combine these tanks into one, just so long as they are of proper size and arranged in a manner suitable for effecting the desired separation of solids as well as of creamed grease.

In the centrifuge 4I the already partly purified solution is still further purified by means of a centrifugal field of force, the centrifuge being arranged so that the finally puried solution can be withdrawn through the pipe 43 by means of pump 44 and delivered to scouring bowls 2 and 3 through the connections 45 and 46. 'I'he grease can be segregated and withdrawn through the pipe 46a and the sludge and other more solid solution thereto is cut oft' and water may be introduced through the pipe- 52 to the pipe 43 as shown and upon such occasions the flow from the centrifuge is closed by means of a suitable valve 53.

A sumary of the operation and the advantages which flow therefrom will now be given.

The preliminary washing or desuinting operation which is given in the bowl I very greatly reduces the rate of contamination of the scouring solutions in bowls 2 and 3 because this preliminary treatment serves to remove much of the solid impurities and prevents excessive accumulation of solubles or colloidally suspensible impurities in the bowls 2 and 3, which impurities have the property of destroying the detergent power of the soap and which cannot be removed by sedimentation in the elds of gravitational and centrifugal force to which the solution is later subjected. Moreover, this vpreliminary washing or desuinting treatment reduces the load on the solution purifying apparatus and helps to make possible very economical operation of the system as a whole. Furthermore, the removal of practically all of the soluble material from the wool at this preliminary point makes possible a greatly facilitated control of the concentrations of the scouring solutions by electrical conductirnetricl methods such, for example, as are disclosed in my copending applications, Serial Nos. 1,588 led January 12, 1935 (Patent Number 2,068,498, patented January 19, 193'?) and 9,519 flled March 5, 1935 (Patent Number 2,068,499, patented January `19, 1937). The methods of procedure disclosed in those applications are equally applicablehere, but certain improvements and short cuts are made possible by the present invention. The former of these two applications relates particularly to a method of testing and restoring the effectiveness of de'- tergent baths and makes use of three criteria to that end, namely, the electrical conductivity, the foam life and the sediment content of the solution under treatment.

improved apparatus for measuring the concentration of solutions, which apparatus is suitable for use in measuring the concentrations of the solutions in all of the bowls of the present disclosure. l

In the present improvement the scouring liquor is continually circulated through the purifying portion of the apparatus andafter purification 'is returned to the scouring bowls where there is added only suicient alkaline detergent salt to replace that consumed in the cleaning process or lost by withdrawal of the sediment and sludge. Furthermore, since suicient soap to replace all soap lost from the system either in the wool or in the discarded solid sludge is formed by the reaction of the detergent salt with the fatty acid in the wool, no soap need be added lexcept when making up fresh solutions after a shut-down or when rst 'starting the equipment into operation, such addition being discontinued when the rate of soap formation has become at least equal to'the rate of soap consumption. Under the conditions of the present invention it is 'only necessary to determine the quantity of v alkali which should be added in order to keep the solution in perfect condition and this can best be accomplished by means of a coordinated system of control by electrical conductivity.

lIn the scouring'operation in bowls 2 and .3`

the temperature of the solution is generally in the neighborhood of to 140 F. but in the settling tanks 24 and 30 I prefer to raise this tempera/ture by means of the heating coils 26 to a temperature. anywhere from to 190 F.

' This temperature plus vthe lack of agitation in -of the solid dirt and allow a. small proportion of 'the 'grease to rise to the surface, but in order to permit of continuous reuse of the solution it is generally desirable to effect a more complete The second ofthe twoapplications mentioned relates specifically to an removal by means of the centrifugal apparatus already described. The centrifuge may be operated continuously, although not necessarily so,

and especially where the grease content of the wool is low the centrifuge need be operated for only a small part of the time. For example, I have found that with certain wools where the apparatus is to remain in operation for three shifts of 8 hours each, intensive operation of the centrifuge for one eight-hour cycle per day may serve to keep the grease-and sediment content of the scouring solution at all times below objectionable limits.

I wish to direct attention to the fact that successful operation of the centrifugal machine without too frequent shut-downs for inspection and minor `repairs depends on sending into it liquids whose content in abrasive dirt is not too high. In practice, thereforewit is notsfeasible to circulate the liquors from the sumps of the scouring tanks directly into the centrifugal machine,

since at this time they contain comparatively large quantities-of gritty solids which are too erosive in their eiect upon the valvesand valve seats. However, with the settling before cen'' .trifuging in the gravitational field described it is necessary to renew the valves and the valve seats only very occasionally and this occasional renewal is not particularly expensive or laborious.

not from a high-grease location, since the grease is segregated in one portion of the tank 30 by means of the baiile'3'6 and withdrawal of the solution takes place from another portion through the outlet 3l.

After treatment-with the scouring liquor the wool is rinsed With fresh, constantly running water in one or more rinsing bowls, the flow of vater in these rinsing tanks being so controlled as' to keep the content in scouring solution brought in with the wool at a very low value below a predetermined maximum. The rinsed wool, after passing through the final squeeze rolls 9, is ready for bluing, bleaching, drying or any subsequent desired treatment. I

The use o-f rinse water from the bowl 5 in the desuinting bowl l serves to conserve water and the circulation in each of the bowls I, 2, 3 and 5 from the head end to the discharge'end is facilitated by means of the arrangement whereby any solutions entering the several bowls are introduced at the head end and withdrawn from the opposite end. e

It will thus be seen that my invention makes it possible to completelyerecover the usefulconstitu# ents of the scouring solutions and that no soap or other soap-like substance need be added after a new scouring solution has been in operation for out the bowlsare extremely infrequent and ac--- 75 cumulation of soap destroying colloidal matter in the scouring solution is avoided, which latter advantage, together with the continuous removal of the accumulated grease, permits indefinite 5 use of the scouring solution without the deliberate wastage of any part thereof except for the small amount necessary to carry away the sludge deposited in the tanks.

By my improvements, also, a wool-cleaning process becomes susceptible of accurate and scientific control by means of simple conductimetric measurements and thiscontrol may easily be made automatic by means of well understood devices for translating conductimetric readings,

5 liquid levels, etc., into appropriate mechanical action or chemical addition.

Finally I have found that my improvements make possible a great enhancement in the quality and uniformity of the washed wool.

I should like to point out that when starting a system in accordance with the present invention I prefer to control additions of alkaline detergent salt and soap in accordance with the process of my earlier application No. 1,588 above 25 referred to, because at this time, namely, at start,

the rate of formation of soap is not sufficient to maintain the required foam life. However, after a certain interval itwill be found that the foam life no longer falls with time so that the addi- 30 tion of soap or other soap-like substance may then be discontinued. A further building up of soap in the solution will then do no harm unless the soap content should rise to an extent sufficient to cause slippage of the squeeze rolls, but this is of rather infrequent occurrence and can be corrected by increasing the rate of circulation through the purifying system to decrease the time the grease is in contact with the solution or by lowering the temperature of the scouring in this art.

During this time of preliminary stabilization the alkalinity of the solution may be controlled also in accordance with the method disclosed in application Serial No. 1,588. The quantity vof solid suspended matter in the scouring bowls, however, need not be determined because these solids are being continuously and automatically transferred to the purication system, although it is convenient at this time to test the solutions in the settling tanks for their rate of accumulation of settleable solids because by so doing it is possible to determine the proper intervals at which to drain the sludge from the sumps of the settling tanks.

In operating the system the pump 44, of course, is run continuously so that the level in the bowls 2 and 3 is gradually and constantly rising. If desired, this rise can conveniently be made to time the cycles of operation of the withdrawing pump 25. For example, a oat controlled switch in either bowl 2 or 3 may be arranged to turn on the electric motor of pump when the solution rises to a certain predetermined level and shut it off again when the solution falls to a certain predetermined low level. The frequency of this operation is thus in proportion to the rate at which solution is added to the bowls from the purifying system and this latter is easily under the direct control of the operator.

The volume lost by withdrawals from the settling tanks 24 and 30, as described, is replaced with water and this replacement likewise is best made automatic under the control of a suitable float operated valve in the settling tank 24.

solution or by other means obvious to one skilledA aisance obviously it wai ocaslonany be to allow the sludge accumulated in the sumps 8 of the desuinting bowl l to run to waste by opening the plug valves i2 and additions of water from the rinsing bowl or fresh water to the desuinting bowl will necessitate running an equal volume of used desuinting water to waste as just described. Furthermore, the squeezings from the wool desuinted in bowl I are likewise run. to waste through the pipe 54.

I should like to point out that during normal operation of my process I prefer to replace all loss of water from the scouring system or from the puriiication system either by evaporation, or with the solid sludge which is regularly drained from the sumps, or by any other means, solely by additions in the gravitational :Geld through the pipe 42. This assists the operation of the process as a whole by accelerating the rate of settling in the gravitational field as well as the rate of separation in the centrifugal field.

In Figure 2 the principle of operation is essentially the same. The arrangement shown, however, s particularly designed for the handling of wools which are very high in grease content. especially where the securing bowls are of rather small volumetric capacity. In situations of this kind the grease content of the scouring liquor in bowl 2 may rise to such a high value that om creaming of the grease occurs in this To eliminate this grease without draining the bowl the squeezings from the squeeze rolls 8 of the bowl 2 are carried from the hopper I0 by way of the pump 55 and pipe 56 directly to the settling tank 24 through the wool-screen 23 as shown by the arrows.

When operating in this way the solution wrung out in the bowl 2 is not returned to the head of the bowl to maintain the circulation of the solu.- tion and thus prevent piling up of the wool as in the case of the diagram of Figure 1. Instead, the squeezings from the succeeding scouring bowl 3 are returned by way of the pump 51 and pipe 58 to the head of the bowl 2 as shown, in order to cause the necessary circulation. In this case the purified liquor from the centrifuge 4| is returned in its entirety to the head of bowl 3 by Way of the pump 59 and pipe 60, thus acting to circulate the solution in bowl 3.

The removal of sludge from the sumps of bowls 2 and 3 is accomplished as before, by the operation of pump 25 preferably under the control of a switching mechanism operated by change of .level in the bowls 2 or 3. Solution drawn from the settling tank 30 from beyond the grease retaining baie 36 is continuously added to both of the scouring bowls 2 and 3 by means of pipe 6I and pump 62. By varying the quantity of solution pumped by the pump 62, the rate of increase in the level of the solution in the bowls 2 and 3 and hence the frequency of operation of the pump 25 may be varied at the will of the operator.

'I'he solution pumped by pump B2 may be conveniently added to the bowls 2 and 3 through tunnels 63 through which may also be added the alkaline detergent chemical, etc. in the form of solution as required. In other respects the system of this figure operates in exactly the same way as the system of Figure 1, although in the arrangement of Figure 2 the scouring solution is withdrawn to the purication system not only through the sumps of the scouring bowls 2 and 3 but also from the hopper l0 of the scouring bowl 2. Moreover. the solution is returned to the bowls 2 and 3 from the purification system in two different ways; first, the portion which has been subjected both to the gravitational and to the centrifugal elds of force returns to the head of bowl 34 and. second, another portion which has 'been subjected only to the gravitational eld of force returns, under baille 36, to the funnels 63 of both of the bowls 2 and 3.

As stated, this arrangement makes possible a reduction in the volumes of bowls 2 and 3' to a minimum without interfering with the ability of the scouring system as a whole to wash wool which is exceptionally high in grease content.

I should like to call attention to the fact that inasmuch as the scouring operation in bowls 2 and 3 is generally conducted at a temperature in the neighborhood of 120 F. to 140 F., while I prefer a temperature anywhere from 1 50" F. to 190 F.vin the settling tanks 24 and 30, it may sometimes be necessary to cool the solution before returning it to the scouring bowls. This is especially true in thearrangement of Figure 2 where solution is regularly returned from the settling Atanks directly to the scouring bowls through the pipe 6l and pump 62.

In some installations it may not be necessary to cool the solution after it leaves the purifying system and before it is returned to the scouring system because the drop in temperature may be quite suiiicient to bring the solution down to the desired temperature for the scouring bowls, but therewill be occasions when this is not so, in which event, as stated, suitable cooling apparatus should be installed, such, for example, as a double pipe heat exchanger 64. The pipe 6| carrying the purified solution from tank 30 to tanks 2 and 3 may be arranged so as to be the inner pipe of such a heat exchanger and cooling water may be vsupplied to the outer pipe through the connection 65.

Where cooling apparatus of this nature is employed, I prefer to utilize the cooling water coming in through the pipe 65 in the rinsing bowl 5 and to this end a suitable connection 66 is provided between the heater 64 and the bowl 5.

'I'he degree to which it will be necessary to cool the solution returning through the pipe 6I will depend, of course, upon quite a number of factors, such, for example, as the distance between the settling tank 30 and the scouring bowls 2 and 3. Furthermore, the amount of cooling water which may be necessary will vary and it will be obvious that more or less rinsing water may be supplied thru the connection I4 as may be necessary in relation to thequantity of coolingwater coming in through the pipe 66.

In some installations practically all of the rinse water may come in as cooling water from the cooler 64 without heating the rinse water above approximately 115 F'., which would not be too high 'for satisfactory operation of the'system.

The arrangement shownis capable of very flexible operation so as to meet the requirements of individual installations so that I am always enabled to maintain inl the scouring bowls the temperature which I prefer, namely, a temperature in the'neighborhood of 120 F. to 140 F.

The arrangements of apparatus described above and illustrated in Figures 1 and 2 are given only by way of illustration; variations'from the exact arrangements described may be incor-A porated without ldeparting from the spirit 'of the invention.

For instance, in the arrangement of Figure2,

I6 if the capacity of the centrifuge is sufficient, it

' scouring stage;

will not be necessary to return any of the solution to the bowls directly from the settling tanks of the purification system. In this case pipe 6| and pump 62 may be omitted, and heat exchanger 65 may be inserted in the return line which comes from the centrifuge. Pipe 6l containing a valve, similar to pipe 31 and valve 52 of Figure 1, whereby purified solution may pass directly from settling tank 30 to pump 59 at periods during which the centrifuge is being cleaned or is not in operation for any other reason.

These and other variations, which will be 0bvious to one skilled in the art, may be made in the arrangement of apparatus within the scope of the appended claims. i

I claim:

1. The substantially continuously operable method of cleaning wool which comprises preliminarily washing it with water; then scouring with a detergent solution followed by rinsing with water; continually withdrawing a portion of the scouring solution containing substantially all of the settled dirt; heatingthe withdrawn solution to a temperature substantially above scouring temperature; subjecting the withdrawn solution to a field of gravitational force to segregate itinto layers of grease, purified solution and sludge; withdrawing purified solution while restraining the grease; discharging the sludge; and returning the withdrawn purified solution to the scouring stage.

2. The method of claim 1 wherein water from the rinsing stage is used in the preliminary washing stage.

`may then be replaced by a short by-pass pipe 3. The method of claim 1 wherein water lost l prises preliminarily washing it with water; then scouring with a detergent solution followed by rinsing with water; continually withdrawing a portion of the scouring solution containing substantially allof the settled dirt; separate grease and solids from said withdrawn solution to leave vpurified detergent solution; heating the scouring solution while separating the grease and the solids therefrom; water cooling the solution after separation; returning the purified solution to the and delivering cooling water from the cooling stage to the rinsing stage.

7. The substantially continuously operable method of` cleaning wool which comprises preliminarily washing it with water; then scouring with a detergent solution followed by rinsing with water; continually withdrawing a portion of the scouring solution containing substantially all of the settled dirt; subjecting 'the withdrawn solution to -a field of gravitational force to segregate vit into layers .of grease, purified solution and drawn purified solutionis cooled' with water prior to its return to the scouring stage and `wherein cooling water from the cooling stage is delivered to the rinsing stage.

9. The substantially continuously operable method oi' cleaning wool which comprises preliminarily washing it with water; then scouring with an alkali detergent solution followed by rinsing with water; continually withdrawing a portion of the scouring solution containing substantially all of the settled dirt; heating the withdrawn solution to al temperature substantially above scouring temperature; subjecting the withdrawn solution to a iield of gravitational force; discharging the settled dirt from said eld of gravitational force; withdrawing solution of high grease concentration from said gravitational field and delivering it to a ileld of centrifugal torce to segregate it into strata of grease, sludge and puriiied solution; and returning puriiied solution to the scouring stage.

10. The substantially continuously operable method of cleaning wool which comprises preliminarily washing it with water; then scouring with an alkali detergent solution followed by rinsing with water; continually withdrawing a portion of the scouring solution containing substantially all of the settled dirt; heating the withdrawn solution to a 4temperature substantially above scouring temperature; separating grease and solids from said heated withdrawn solutionl to leave puriiled detergent solution; and returning purified detergent solution to the scouring stage.

FRANKLINH. MACKENZIE.

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