US2766930A - Centrifugal separator - Google Patents

Description

Oct. 16, 1956 l.. scHMlr-:DEL 2,766,930

CENTRIFUGAL sEPARAToR Filed Deo. 1o. 1952 4 Sheets-Sheet 2 f z i d /aa M A A51? gti-5i f n 7 Il --r 271 T d W n 2.... "9. l l (Ah l 1 k L n K g-I 53\ l I I IV l m2 if; 1: "2

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Oct. 16, 1956 Filed Dec. l0. .1952

United States Patent() CENTRIFU GAL SEPARATOR Ludwig Schmiedel, Wunstorf-Hannover, Germany, as-

signer to Starcosa Maschinenund Apparatebau G. rn. b. H., Wunstorf-Hannover, Germany Application December 10, 19552, Serial No. 325,134 Claims priority, application Germany December 14, 1951 Claims. (Cl. 233-7) This invention relates to an improvement in centrifugal separators of the type having a horizontal shaft and a nonperforated centrifugal drum for discharge of the heavy solids or media at one end of the drum and discharge of the carrier liquid more or less freed from solids at the opposite end of the drum.

It is an object of the present invention to keep the liquid leaving the separator as much as possible free from solid matter.

Another object of the invention is to provide means for the separation of solids with high settling rate.

Still another object of the invention is to provide means permitting separation not only basing on the settling rate of the solids, but also to consider their settling power as will be hereinafter described in greater detail.

With these and further objects in view, the invention consists in the constructional and operational features, combination of elements and other details as hereinafter described and defined in the accompanying claims.

In order that those skilled in the art may understand howto use the invention and to achieve its various objects,

some embodiments and exemplifications of the invention have been illustrated in the accompanying drawings, m

which:

Fig. l is a horizontal axial section through a centrifugal separator at the inlet end of the drum and nozzle discharge for the less heavy solids in the vicinity of the liquid outlet,

Fig. 2 is a cross section of Fig. l,

Figs. 3 and 4 are axial sections showing two diiferent modifications of a centrifugal separator having the invention applied thereto, with discharge of the heavier solids over a forward annular edge,

Figs. 5 and 6 are axial sections of two different modifications according to the invention each with a second screw conveyor unit arranged within the outer discharge screw, and

Fig. 7 is an enlarged fragmentary sectional view of the screw conveyor means as per Figs. 5 and 6.

Similar reference numerals denote similar parts in the different views.

In order that the invention and its various aspects may be fully understood by those skilled in the art, I will at first describe the same in a general way.

To achieve the above mentioned object of keeping the liquid discharging from the centrifugal separator as much as possible free from any solids, there is provided a second discharging device in the vicinity of the liquid outlet.'

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The boundary or separating line between the two settling zones with different settling power of the solids depends upon the size of the particles and the specilic gravity of these solids. From this boundary onwards the heavier particles have to be conveyed to the forward outlets by the forward screw or the forward part of the screw conveyor, and behind this boundary the lighter solids have to be conveyed to the outlets in front of the liquid outlets by the rearward screw or the rearward part of the screw conveyor with opposite angle of pitch. In this case it is oftentimes useful to construct the outlet for the said lighter solids in the form of nozzles; the outlets for the heavier solids may also be nozzles.

Since the boundary for the division of the discharge screw into two oppositely operating portions is not fixed once and for all, it is contemplated according to a further feature of the present invention to adapt the separator to the varying requirements of the material to be handled by providing means permitting axial displacement of the boundary between one conveying direction and the opposite conveying direction of the discharge screw in relation to the centrifugal separator. This can be achieved by constructing the discharge screw conveyor of a plurality of single segments which are pivoted on their carrier body. The boundary line can thus be axially displaced by suitable turning of the segments. After the turning of the segments they have to be lixed. To this end, auxiliary pins may be provided.

In order to achieve the above mentioned object of centrifuging solids with a high settling rate, means are provided for discharging the heavier solids in the forward end of the drum over anannular edge which is higher than the liquid level in the drum which is defined by the discharge Weir, rather than through nozzles. In this case the discharge by the screw is independent of the density of the liquid which is fed, or independent of the solid content of the liquid, and the screw will discharge always only the solids fed for discharge, regardless of their quantity. In this case, always only a predetermined quantity of liquid. contained in the medium is discharged. At any rate, however, this amount of liquid will be smaller than in case of discharge of the solids through a nozzle. The use of nozzles for discharging the heavier solids isadvantageous if said solids are of a slimy or muddy condition and thus unsuitable for being seized and lifted by a screw conveyor.

As mentioned above, it is also intended according to the present invention to consider the settling power of the solids. The following example will explain this term:

If a suspension consisting of water and starch with a predetermined solid content, is introduced into a show vessel of about 300 mms. height and 40 mms. inner width, and the starch is allowed to settle, the starch will settle on the bottom of the show vessel after a predetermined time in a predetermined height, while the liquid above the starch is clear. Experience has shown that the starch settles in the show vessel with a moisture of about 50 to 55%. If maize gluten is stirred into a suspension with the same quantity by weight of water and allowed to settle, the maize gluten will settle almost within the same time; however, the height of the layer is a multiple of that of the starch. For instance, if the starch layer has a height of l0 mms., the settled layer of maize gluten will have a height of about 60 mms. This is due to the fact that the maize gluten is not granular like the starch, but ilaky and that it will never condense to the same extent as starch. Settled maize gluten has a moisture content of about water. Accordingly the settling power of maize gluten is much worse, in fact, 6 times worse than that of starch.

rator according yto the invention has'been described in detail with reference to Fig. l, it will be sufficient to dscuss only the modified features with reference to Figs. 3 and 4.

The ange 1 of the truncated cone body m1 is formed with outlets 10 leading into a surrounding casing j with outlet 17. The openings 10 are the Vdirect continuation of the left hand opening of the forward conical part 3 of the centrifugal drum, in such a way that an annular edge 2 is formed which as shown in Figs. 3 and 4, is located at a higher level than the level of the liquid defined by the weir 7 during the centrifuging. 'Ihe liquid moves within the drum in the direction of the arrow a, Fig. 4.

While the drum according to Fig. 3 consists of two parts 3 and 4, which are interconnected by flanges and screw means (not shown) the .drum t of the centrifugal separator as per Fig. 4 is of truncated conical section, the heavier solids being discharged through the narrow part of the truncated cone and the openings 10 disposed in this part while the Weir 7 is located at the wide end of the drum t. In both cases the right hand part 16 of the screw conveys settled material to the nozzles 30 located at some distance before the Weir 7 and leading to the discharge 3l. The continuous conical enlargement of the drum t as per Fig. 4 as distinguished from the construction of the drum part 4 as per Fig. 4 serves the following purpose.

Where the lighter solid constituents have a very small settling rate, the rate of flow of the suspension has to be kept as low as possible in order that the solid constituents have sufficient time to settle. This requirement is met by the construction as per Fig. 4. Owing to the growing cross section of the flow bed in the direction of arrow a the rate of ow is gradually decreasing so that the light solids are allowed to settle. Preferably, provision for axial shifting of the boundary between the two parts of the discharging screw is made in the modifications as per Figs. 3 and 4 in the same way as described with reference to Figs. l and 2.

The centrifugal separator as per Fig. 5 is constructed on principle in the same way as that shown in Fig. 1, while the centrifugal separator as per Fig. 6 corresponds to that of Fig. 3. In both embodiments as per Figs. 5 and 6 it has been taken into account that a mud layer may form above the solid material of a higher settling power. In both cases, Figs. 5 and 6, a second screw is arranged within the screw serving to discharge the material deposited on the wall of the drum; again, said. second screw may consist of a few threads only. It is displaced relatively to the real discharge screw means towards the interior. in the embodiment as per Fig. 5 the solids of higher specific gravity are conveyed by the screw portion 15 to the forward set of nozzles 20 and the ysolids of lower specific gravity are conveyed to the set of nozzles 30 through the screw portion 16, while in the embodiment of Fig. 6 the forward set of nozzles is substituted by an annular edge 2.

In both cases a second screw 33 is provided within the screw 1S, i6. It need not extend over the entire length of the drum and in the exemplications as per Figs. 5 and 6 is provided substantially in the forward part of the drum, i. e., more towards the inlet side. The fillets of the screw 33 are located so as to dip into the mud layer. The outer edges of the inner screw 33 are disposed within the inner edges of the strips making up the outer worm and have an oppositely directed pitch. Therefore, the forward part 15 of the outer screw Fig. 5 conveys the material to the set of nozzles 20 and in Fig. 6 to the annular edge 2, i. e., in the direction of arrow X, while the inner screw conveys the material in the direction of arrow Y to the opposite side. This will be seen more clearly from Figure 7. Since the inner screw 33 consists of a strip, a free space is left in its interior for unhampered ow of liquid.

It is not always necessary to construct the inner screw 33 in the form of a complete screw from the start to the end. In many instances it'will be sufficient to provide single strip-shaped screw segments. Owing tothe oblique arrangement of these segments the liquid is forcibly moved, as by a paddle, i. e. in the direction of arrow Y. The deposited mud is thus conveyed to the outlet end and discharged through the nozzles 30 in Figs. 4 and 5, while the liquid flows off over the Weir 7.

While the invention has been described in detail with respect to certain now preferred examples and embodiments of the invention it will be understood by those skilled in the art after understanding the invention that various changes and modifications may be made without departing from the spirit and scope of the invention and it is intended, therefore, to cover all such changes and modifications in the appended claims.

l claim:

l. A centrifugal separator comprising a horizontal shaft, a non-perforated centrifugal drum mounted thereon, forward outlet means for the heavier solids at one end of the drum, rearward outlet means at the opposite end of the drum for the carrier liquid at least partly freed from solids, outlet means for lighter solids in the vicinity of the liquid outlet means, and a rotatable conveyor screw including two parts lying one after the other and constituting oppositely directed helices, in such a way that the forward part of the screw is adapted to convey the heavier solids against direction of the liquid ow to the forward outlet means while the rearward part of the screw is adapted to convey the lighter solids to the rearward outlet means.

2. A centrifugal separator comprising Ia horizontal shaft, a non-perforated centrifugal drum mounted thereon, forward outlet means for the heavier solids at one end of the drum, rearward outlet means at the opposite end of the drum for the carrier liquid lat least partly freed from solids, nozzles for discharging the lighter solids in the vicinity of the liquid outlet means, and a rotary screw conveyor including two parts of opposite pitch angle lying one after the other, in such a way that the forward part of the screw is adapted to convey the heavier solids against direction of the liquid ilow to the forward outlet means while the rearward part of the screw is adapted to convey the lighter solids to the rearward outlet means.

3.V A centrifugal separator comprising a horizontal shaft, a non-perforated centrifugal drum mounted thereon, nozzles for the discharge of the heavier solids at one end of the drum, rearward outlet means at the opposite end of the drum for the carrier liquid at least partly freed from solids, nozzles for discharging the lighter solids in the vicinity of the liquid outlet means, and a rotary screw conveyor including two parts of opposite pitch angle lying one after the other, in such a way that the forward part of the screw is adapted to convey the heavier solids against direction of the liquid iiow to the forward outlet means While the rearward part of the screw is adapted to convey the lighter solids to the rearward outlet means.

4. A centrifugal separator comprising a horizontal shaft, a non-perforated centrifugal drum mounted thereon, a weir disposed at one end of the drum for the flow thereover of the carrier liquid at least partly freed from solids, an annular edge member located nearer to the axis of rotation of the drum than the overflow Weir, for discharging the heavier solids at the opposite end of the drum, outlet means for the lighter solids in the vicinity of the liquid outlet means, and a rotary screw conveyor including two parts of opposite pitch angle lying one after the other, in such a way that the forward part of the screw is adapted to convey the heavier solids against direction of the liquid flow to the forward outlet means while the rearward part of the screw is adapted to convey the lighter solids to the rearward outlet means.

5. A centrifugal separator comprising a horizontal shaft, a non-perforated centrifugal drum mounted thereon, forward outlet means for the heavier solids at one end of y theV drum, vrearward outlet arenoso the drum for-thecarrierliquid at least partly'freed from s'olidsyaweir disposed at4 one end of the'drum for thelliow thereovenof tthe carrier liquid at least partly freed-from solids, andra rotary screw conveyor including-two' parts of 'Yoppositepitehiangleyin such away that'the forward part of the screwis' adapted to convey the heavier'solids Vagainst direction of Yth'eliquid 'ow to the'forward outlet means while the rearward part ofthe screw is adapted to convey the'lighter'solids to the rearward' outlet means, said screw conveyor vincluding ymeans for axially displacing the on, forward outlet means for the heavier solids at one end .of the drum, rearward outlet means at the Vopposite end of the drum for the carrier liquid'at least partly freed kvicinityof the liquid, outlet means, and a rotary screw conveyor including two parts of opposite pitch angle,' in

Y such a wayithat the forward part'of the screwgis adapted to convey the heavier-solids against direction of the liquid Y ow to the forward outlet means while the rearward Ypart of the screw is adapted to convey the lighter solids'to the rearward outlet means, said screw conveyor including segments which can be adjusted to opposite pitch angles for axially displacing the boundary line between the two parts with opposite direction of conveying.

' 7. A centrifugal separator comprising a horizontal shaft, a non-perforated centrifugal drum mountedthereon, forward outlet means for the heavier solids at one end of the drum, rearward outlet means at the opposite end of the drum for the carrier liquid at least partly freed from solids, outlet means for the .lighter solids in the vicinity of the liquid outlet means, and a rotary screw conveyor including two parts of opposite .pitch angle, in such a way that the forward part of the-screw-is adapted to convey the'heavier solids against direction of the liquid ow to the forward outlet means while Ythe rearward'part of the screw is adapted to convey the. lighter solids tothe 'rearward outlet means, said screw conveyor including a l carrier drum and a Yscrew mounted on said carrierdrum and comprising segmentswhich are pivotally mounted on Vthe .carrier drum and can be fixedv atopposite pitehangles Y for axially displacing the boundary line between the two Y parts with opposite direction of conveying.

'78. .A centrifugal separator comprising a horizontal shaftJ-a non-perforated centrifugal Vdru'mmounted theres on, forward outlet meansfor the heavier solids at one end Vof the drum, rearward outlet means at the opposite end of the drum-for the carrier liquid at least partly freed from means at the-opposite'end of .from solids, outlet means .for the lighter solids in the solids,routlet means for lighter solids in the vicinityV of the liquidoutlet means, a first screw conveyor comprising two parts with oppositely directedfpiteh anglerlying oneV Yshaped screw threads.

flowgtoA theforward'outletmeans, whiley the-rearward'part of =the screw -is adapted -to 'convey vthe lighter Vsolids Vdeposited 'on `the Ainner Wall 'of the-'centrifugal drum to `the rearward outlet means, and a secondscrew conveyorcoaxi-ally-'disposedinthe annular space'within-therst screw conveyor and 'includingfa'VY conveyor.- screw in the form'of ahelicakstpleavirigfafree space for passageof liquid between-the innerfedges of the helicalstrip and -the shaft. -9."A- vcentrifugal lseparator 'comprising a horizontal shaft, a non-perforated. centrifugal vdrum mounted thereon,` forward'outlet'means foi-'theV heavier solids at one end of thefdrumrrearward outletm'eans at-th'e opposite end of Ythe'drnml forA Ythe carrier liquid at least 4partly freed from solids, 'outlet meanslforilighte'r solids in. the vicinity of Y theliqnidoutlet means, 'aifirst Vscrew conveyor comprising tn-'oapartswith oppositely directed Vpitch Vangle lying one after'thejother, whereby ithe forward part of thescrew is adaptedto convey"theheavier solidsr'deposited von the innerwall ofthefcentrifugal drum, against direction of the liquid Yhow, tothe forward outlet means, whileY the rearwardpartof the screw is ladapted to convey the lighter Y solids deposited on the inner wall of the centrifugal drum tothe rearward outlet means, and asecond screw conveyor coaxially dispose'd'in'the annular space within the rst'screw conveyor and including a conveyor VscrewV inY 'theform Vof ahelical strip leaving afree space for passage of the liquid outlet means, a first screw conveyor comprising tworpartsk with oppositely directed Vpitch angle.' lying Y one after the other, whereby the'forward part of the screw is adapted to convey the heavier solids deposited on the solids 'deposited on the inner wall of the centrifugal drum tosthe rearward outlet means, and `a second screw-conveyor coaxially disposed in the annular space withinthe Y.

rst screw conveyor and including a'conveyorY screw in the formof'a helical strip leaving a free space. for passage n of liquid between'the inner edges of the helical strip and few Vsegrnent- 1 the shaft, Vsaid helical Vstrip comprising a References'Cite'd inthe'riile of thispatent UNITED STATES-PATENTS 2,184,598 `Iahn Dec. 26, 1.7939 .2,528;974 Y ARitsch Nov. 7, 1950 VFOREIGN PATENTS Germany Nov. 13, 1937

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