US2356497A

US2356497A - Apparatus for the continuous purification of suspensions or sludges, especially of fibrous pulp of the paper industry

Info

Publication number: US2356497A
Application number: US292382A
Authority: US
Inventors: Banning Helmuth
Original assignee: Individual
Current assignee: Individual
Priority date: 1938-09-01
Filing date: 1939-08-29
Publication date: 1944-08-22
Anticipated expiration: 1961-08-22
Also published as: NL58122C; DE717978C; CH223311A; FR861417A

Description

.Aug. 22, 1944. H. BANNING 2,356,497

APPARATUS FOR THE CONTINUOUS PURIFICATION OF SUSPENSION-S OR SLUDGES, ESPECIALLY OF FIBROUS PULP OF THE PAPER INDUSTRY Filed Aug.- 29, 1939 2 Sheets-Shet 1 flgfl 10 3 7% hie/Mar HELMU 7' H BflN/V/NG Aug. 22, 1944. H. BANNING 2,356,497

APPARATUS FOR THE CONTINUOUS PURIFICATION OF SUSPENSIONS OR SLUDGES, ESPECIALLY OF FIBROUS PULP OF THE PAPER INDUSTRY Filed Aug. 29, 1959 2 Sheets-Sheet 2 Fig.4 1

w Ham/7W a/z/v/w/va PatentedA'ug. 22, 1944 APPARATUS FOR THE CONTINUOUS PURIFI- I CATION F SUSPENSIONS 0R SLUDGES, ESPECIALLY OF FIBROUS PULP OF THE 7 PAPER INDUSTRY Helmuth Banning, Duren, Germany; vested in. the Alien Property Custodian Application August 29, 1939, Serial No. 292,38

- In Germany August 31, 1938 Claims. (Cl. 210-68) This invention relates to a method of, and apparatus for, the continuous purification of suspensions or sludges, especially of, fibrous pulps of the paper industry, by means of a'centrifugal apparatus having a fixed outer wall guiding the pulp. The invention aims at a centrifugal method which is not interrupted by a periodical emptying out of the heavy particles accumulated in the centrifugal spaces. p

In the case of the known types of centrifugal apparatus a compacted firm cushion of fibres is formed at the closed wall of the rotary centrifugal drum, and the heavy contaminations accumulate in and on that cushion. This is disadvantageous in that the centrifugal drum becomes after a certain period of operation, filled with these retained particles of dirt, whereupon the apparatus has to be stopped for cleaning purposes.

Centrifugal machines are also known which act as centrifugal sorting machines, the suspension of pulp being forced through a rapidly rotating perforated drum. In the case of these sorting machines, the contaminations are only sorted out according to the widths of the perforations of the perforated drum. Contamlnations are retained in front of the sieve (considered in the direction of the current) while the fine fibres pass through it. The disadvantage of these known machines is due to the fact that the sieves are .very liable to cloggin Centrifugal machines also acting as centrifugal sorting machines are also known, where the pulp and the contaminations of greater specific gravity pass through a rapidly rotating drum sieve to a chamber outside the drum. In such cases, the

I contaminations are mainly separated out by gravity in a casing which is conically widened in the direction towards the outlet. Thus, the outer chamber of the centrifugal machine contains the contaminations as well as the pulp to be purified,

the two being not spacially separated. The drum sieve only serves the purpose of retaining contaminations of greater dimensions. As the contaminations and the pulp to be purified are present sideby side, it cannot be avoided that contaminations getinto the outlet for the pulp to be purified.

In order to avoid these disadvantages, it is,

according to the invention, proposed to produce apertures in the drum to the outside.

passed through the interior of the drum in axial direction, and the contaminations of greater specific gravity'are allowed to pass through the In this connection it is convenient to keep in an axial movemeht the suspension which has passed to heavy con- .therefroni are, to a large extent, separated from each other in the process according to the invention, and in contradistinction to the known processes, a particularly effective separation of the pulp to be purified and of the contaminations is obtained in a continuous operation. The purified pulp may be passed on for further use without being subjectedto any further purifying opera-' tion. When purifying a suspension ofpaper pulp, the purified pulp may, for example, be passed on direct to the paper machine.

In the apparatus for carrying out the process according to the invention, the sludge or'pulp suspension to be purified is introduced near the shaft into a fixed centrifugal casing which is closed on all sides. A drum perforated'in some places rotates with high speed inside the centrifugal casing, imparts rotation to the pulp and divides the centrifugal space into two separate centrifugal zones. The suspension tobe purified enters the inner centrifugal zone through an aperture in the end wall of the casing and leaves it, purified, at the other end. The contaminations pass through the apertures in the centrifugal drum and collect in a suspension of pulp at the wall of the outer casing, which suspension is also subjected to the centrifugal effect and becomes more and more dense towards the outer side. The contaminations are directly withdrawn from the outer centrifugal zone either'continuously or periodically.

Sedimentation along the drum in the inner centrifugal zone may, in the case of the apparatus according to the invention, be repeatedly interrupted by substantially'radial surfaces which deflect the current of pulp either towards the I inside or towards the outside, thereby facilitating the separation of the contaminations. The contaminations are.retained by the surfaces, in

front of which the passage apertures in the drum are preferably arranged. The contaminations pass through these apertures into the outer zone. Sedimentation in the outer zone may also be effected in separate steps, the heavy substances being collected at the wall of the centrifugal body, perhaps by ribs or shoulders, from where they are led off separately. l

' The whole length of the two centrifugal zones -is fully utilized for purifying, the pulp in the inner zone being quickly accelerated tothe rotational speed of the drum by means such as a pump, and, after purification, being removed from the centrifugal machine at once. As a further modification of the centrifugal machine,.

the outer wall thereof may, for example, be given a special conical shape so as to increase the percentage of contaminations in the pulp at the point of withdrawal. Similarly, a definite control of the centrifuging and of the sedimenting operations and of the withdrawal of the contaminations may be effected by p oviding inside the centrifugal space a circuit from the inner to the outer zone and back to the inlet side.

In the drawings, a number of embodiments of apparatus according to the invention are diagrammatically shown by way of example.

Fig. 1 is a vertical, longitudinal section of a centrifugal machine,

Figs. 2 and 3 are side views of centrifugal machines having modified casings.

Figs. 4 and 5 are vertical,longitudinal sections of centrifugal machines with different means for guiding the pulp,

. Fig.6 is a vertical, longitudinal section of a. different embodiment of a centrifugal machine, Fig. '7 is a cross-section of a centrifugal drum,

and l Fig. 8 is a view of an end face of a centrifugal drum.

The centrifugal machine consists, for example, of a cylindrical casing l, at one end face 2 of which the suspension is admitted through a curved tube fitting 3. The suspension leaves through the curved tube fitting 5 at the opposite end wall 4. The centrifugal shaft 6 is situated inside the casing, has its bearings outside there- I of, and is rapidly rotated by means of a suitable drive. Inside the fixed centrifugal casing, the

shaft carries the frusto-conical body 1. Radial arms 8, mounted on the body 1, carrythe perforated centrifugal drum 9. For the purpose of accelerating the pulp admitted through the tube fitting 3, the arms at the front end of the body I may be shaped to form vanes 10.

Fitted to the outer wall of the casing is a tube l i for the withdrawal of the suspension accumulated'inside the wall, which suspension contains the particles of dirt. Withdrawal can either be effected continuously in small quantities, or the aperture is opened periodically as soon as considerable quantities of dirt have accumulated inside the outer wall. a

The body 1 forces the admitted pulp, which moves along the shaft, to flow radially, whereby it enters the zone of influence of the rotating centrifugal drum 9 and is also rotated. The current of pulp following body I forces said pulp along the drum having a perforated wall, so that the pulp fills the entire internal space-of the closed casing l of'the centrifugal machine. While the pulp passes through the centrifugal zone along thecylindrical wall of the drum which may, for example-, be perforated, an increase in the density of the suspension occurs in the direction towards the outer wall of the casing, but this increase is limited because of the setting up in the space between drum and casing of eddy currents near the fixed wall prevents further densification. The heavy contaminations contained in the current of pulp are caused to pass through the apertures in the wall of the drum and collect in the suspension contained between the fixed wall and the rotating wall of the drum. The purified pulp on the other hand, flow's along the inner wall of the perforated drum to the other end of the closed casing and leaves through an opening 9-5 in the end wall 9--a.

It is advantageous to accelerate the admitted pulp initially, by a radial system of vanes H), to

the circumferential speed of the rotating perforated drum, or nearly to that speed. This imparts to the pulp the required circumferential speed already at the front end of the rotating drum, so that the whole length of the latter may 'be utilized for the separation of the heavy particles. The fixed casing may be so constructed that the dirt separated out collects mostly in the vicinity of the connecting fittings of the pipe ll. According to Fig. 2, the outer shell of the casing 3| is constructed conically, and the tube H is connected at a point where the diameter of the cone is the greatest, and where the particles of dirt mainly collect. The perforated drum 39 may also be constructed conically.

As shown in Fig. 3, it is advantageous to have the outer wall of the casing widening in the direction towards the inlet and not in the direction towards the outlet, in order to keep the collecting point of the dirt as far as possible from the outlet 5 for the purified pulp.

Fig. 3 shows a centrifugal machine of this type having an outer shell 32 set oil in steps. Tubes I I are connected to each end of a step. Instead of a cylindrical outer shell, an outer shell having conical steps of any other type may also be employed (Fig. 5). A further improvement in the purifying process is obtained by arranging annular shoulders I2 inside the rotating drum 38, or of rings I 4 inside the fixed outer shell I, as is shown in Fig. 4. There, the body 31 carries rings l3, and the rotating drum 38 carries annular shoulders l2 projecting towards the inside, the pulp being alternatingly deflected to the inside and to the outside 'by the .edges of these parts. The pulp flowing along is dammed up or obstructed by these shoulders I2 and rings I3, whereby a slower fiow'of the pulp is caused in these places and also eddying currents at the edges of the shoulders I2 and the rings l3. This favours a deposition of the-dirt in front of the shoulders l2 and the passing thereof through the holes in the drum.

The shoulders I! are conveniently arranged to widen conically in the directionof the axial flow, so that heavy particles may deposit behindthe shoulders, being separated out of the pulp passing over the edges of the shoulders.

It is also advantageous to sub-divide the outer centrifugal zone by annular rings I, in order to prevent a movement of the dirt along the outer wall towards the outlet of the purified pulp. The largest dirt particleswill deposit in the first section of the outer centrifugal zone, and comparatively small proportions of dirt will be washed through the pipes II of the sections gradually nearing the outlet. The provision of the shoulders I2 and rings l4 results in that the dirt is thrown back into the preceding'zone in which it was separated out, so that dirt, once it has been separated out, can no longer reach the outlet end of the centrifugal machine.

According to Fig. the portions of the fixed casing 33 form conical sub-divisions. In order to obtain the advantages described above, the cones forming the casing widen in the direction towards the outlet for the purified pulp and are connected with the adjoining conicalportion by radially disposed surfaces. The tubes It are attached at the bottom of the centrifugal machine in front of the respective 'radial surfaces. Radial ribs [5 are conveniently provided on the outer shell of the centrifugal drum-3E, deflecting towards the outer wall the heavy particles separated out in the outer zone.

According to Fig. 5, the inlet side of the drum 35 is constructed as a rotor 34 of a pump. A different system of guiding the pulp in the inner zone of the centrifugal drum 36 is-obtained by an alte'rnating arrangement of radial partition walls I6 between the drum 36 and the body 35. Openings I! are provided in the partition walls and are alternatingly disposed near the drum and-near the body, or half way between the two, whereby passages for the pulp are formed at different distances from the axis of rotation. This results in that even the finest contaminations are separated out, the specific gravity of which approximates that of the pulp fibres.

Fig. 6 shows a construction of the casing 33 having a helical inlet F8 for the pulp and a helical outlet l9 for the pulp. This permits a utilisation of the kinetic energy of the pulp as admitted, in.

order to impart a rotary movement to the admitted pulp, whereby a saving in energy is obtained. Constructing the outlet portion spirally permits achieving a higher outlet pressure. In the case of this embodiment, the casing 33 is, for example, conically widened in the direction towards tneinlet, slightly first and more later, whereby an annular pocket 20 is formed from which the dirty pulp is withdrawn. A conical tube 2! surrounding the shaft is provided for'the retention of the light constituents. That tube receives the light contaminations which, in view of the centrifugal force, move towards the shaft, so that they may be withdrawn throughthe pipe 22.

The construction of the rotary perforated drum 29 may also vary, depending on the type of suspension to be purified. For the separation of finer contaminations it is sufficient to use a shell perfo rated by fine holes, while larger perforations are provided forthe purification of pulp having coarser contaminations.

A convenient embodimentof a centrifugal drum is shown in Fig. 7. Rings 24 serving for the retention of the contaminations of the suspension carry ribs 25 which extend axially and leave between each other slots through which the heavy particles pass.

An undesirable passage of pulp from the outer to the inner centrifugal zone, particularly at the outlet end of the-rotating drum 29 is prevented by providing the rotating drum 29 at its ends with annular rings 26 which are closely adjacent to inwardly extended flanges 33a of the casing 33.

Channels ,2! (Fig. 8) are provided in the outer surfaces of the annular rings 26, or corresponding ribs are attached thereto, their direction being approximately radial. By means of a suitable width of these rings, it is possible to produce a suitable current between the flanges 33-a of the casing 33 and the rotating annular rings 26, which tinuously withdrawn from the outer part of the casing and supplied back to the inlet. In this connection it is'convenient to withdraw that quantity of pulp not at the outer circumference of the casing, where the greatest proportcn of dirt collects, but at a point somewhat nearer to the axis. What I claim as new and desire to secure by Letters Patent is:

1. An apparatus for the continuous purifica tion of suspensions or sludges particularly of fibrous pulp as used in the paper industry, which contain contaminations'of higher specific gravity, comprising a fixed casing, an enclosed drum having inlet and discharge openings at its ends, respectively, and aperture only on its cylindrical face, rotatably arranged in said casing, said drum being provided with inwardly and outwardly extending radial annular members forming communicating annular compartments adjacent the cylindrical wall of said drum, said apertures being of a size exceeding that of the contaminations, inlet means for unobstructedly admitting the suspension and the contaminations into the interior of the drum. outlet means for dischargingthe purified suspension from the interior of the drum at the end of the drum, said outlet being restricted to cause a higher density of pulp in the space between said drum and casing and an accumulation of said contaminations in said space, an additional outlet for purified suspensions concentric with said drum and of such dia-meter that said suspensions flow freely therethrough in a substantially axial direction, and means for the rapid rotation of the drum to cause contaminations of higher specific gravity to pass out through said apertures.

2. Apparatus according to claim 1, where the widths of the inlet means are smaller than those of the outlet means.

3. Apparatus according to claim 1, having the outlet opening disposed centrally, relatively to the axis of the drum, in the casing, and havin an outlet opening of a diameter which is smaller than that of the drum. 4. Apparatus according to claim 1, where the ends of the drum have inwardly projecting rims. 5. Apparatus for the continuous purification of suspensions or sludges, especially of the fibrous pulp as used in the paper industry, which contain contaminations of higher specific gravity, comprising a fi;-.ed casing, an enclosed drum having inlet and discharge openings at its ends, respectively, and apertures only on its cylindrical face, rotatably arranged in the casing, said drum being provided with inwardly and outwardly extending radial annular members forming communicating annular compartments adjacent the cylindrical wall of said drum, said apertures being of asize exceeding that of the contaminations, inlet means for admitting the suspension and the contaminations into the interior of the drum, outlet means for unobstructe dly discharging the purified suspension from the interior of the drum at one end of the drum, said outlet being restricted to cause a higher density of pulp in the ,space between said drum and casing and an accumula-' tion of said contaminations in said space, an additional outlet for purified suspensions concentric with said drum and of such diameter that said suspensions flow freely therethrough in a substantially axial direction, means for the rapid rotation of the drum to cause contaminations of higher specific gravity to pass out through mid apertures, means arranged on the driving shaft inside the drum and adapted to guide the admitted suspension radially towards the wall of the drum and then axially to the end of the drum, and means for accelerating the "radially moving suspension to the circumferential speed of the drum. 6. Apparatus according to claim- 5, where the means arranged on the shaft of the dr'urn inside the drum consist of a displacement body: 7. Apparatus according'to claim 5, characterized by pump vanes arranged on the shaft ,of the 8. Apparatus for the continuous purification of suspensions or sludges, especially of the fibrous pulp as used in the paper industry, which contain contaminations of higher specific gravity, comprising a fixed casing, an enclosed drum having inlet and discharge openings at its ends, respectively, and apertures only in its cylindrical face, rotatably arranged in said casing, said drum being provided with inwardly and outwardly extending radial annular members forming communicating annular compartments adjacent the cylindrical wall of said drum, said apertures being of a size exceeding that of the contaminatio-ns, inlet means for admitting the suspension and the contaminations into the interior of the drum, outletmeans for unobstructedly discharging the purified suspension from the interior of the drum at the end of the drum, means for the rapid rotation of the drum to cause contaminations of higher Specific gravity to pass out through said apertures, deflecting surfaces arranged'inside'the drum, the interior of said drumbeing divided into a plurality of annular chambers, each adapted to deflect in a radial direction the flow which is substantially axial.

the said deflecting surfaces consist ofj'transverse walls alternatingly arranged on the shaft of the drum and on the wall of the drum.

12. Apparatus for the continuous purification of suspensions or sludges, especially of the fibrous pulps as used in the paper industry, which contain contaminations of higher specific gravity, comprising a fixed casing, a drum rotatably ar-- ranged in the casing, said drum being provided with inwardly and outwardly extendin radial anthe drum at the end of the drum, means "for the rapid rotation of the drum to cause contaminations of higher specific gravity to pass out through said apertures, and deflecting surfaces in the space between the outer wall of the drum and the fixed casing, the interior of said. drum being divided into a plurality of annular chambers, each adapted to deflect in a radial direction the flow which is'substantiallyaxial.

13. Apparatus according to claim 12, where the said deflecting surfaces consist of transverse walls alternatingly arranged on the outer-side of, the drill]! and on the inner wall of the casing.

' 14.: Apparatus for the continuous purification 1 comprising a fixed casing, a drum rotatably arnular members forming communicating annular compartments adjacent thecylindrical wall of said drum, said wall of the drum having aperture of a size exceeding that of the contaminations, inlet means for admitting the suspension and the contaminations into the interior of the drum, outlet means for unobstructedly discharg-v ranged in said casing, said drum being provided with inwardly and outwardly extending radial-annular members forming communicating annular compartments adjacent the :cylindrical wall of said drum, said wall having apertures of a size exceeding that of the contaminations, inlet means for admitting the suspension into the interior of the drum, means'for unobstructedly discharging the purified suspension from the interior of the drum at the end of the drum, means for the rapid rotation of the drum to cause contamination of higher specific gravity to pass out through said apertures, deflecting surfaces in the space between the outer wall of the drum and the, fixed casing, the interior of said drum being divided into a plurality of annularchambers, each adapted to deflect in a radial direction the flow which is substantially axial, and outlet apertures in the wall of the casing disposed in front of the deflecting surfaces.

15. Apparatus forthe. continuous purification of suspensions or sludges, especially of fibrous pulps as used in the paper industry, which contain contaminations of; higherspecific gravity,

comprising a fixed casing, a drum rotatably arranged insaid casing, said drum having a smaller diameter than the casing and apertures of a size exceeding that of the contamination, inlet means for admitting the suspension into the interior of the drum, outlet means, for unobstructedly discharging the purified suspension from the interior of the drum at the endof the drum, means for the rapid rotation of s the drum to cause con- -taminations of higher specific gravity to pass out through said apertures, deflecting surfaces in the space between the outer wall of the drum and the fixed casing, the interior of said drum being divided into a plurality-of annular chambers, each suspensions or sludges, especially of the fibrous pulps as used in the paper industry, which contain co'ntaminations of higher specific gravity, comprising a fixed casing, a drum rotatably arranged in the casing, said drum being provided with inwardly and outwardly extending radial annular members formingcommunicating annular compartments adjacent the cylindrical wall of ing the purified suspension from the interior'of (5 said drum; said wall of the drum having aperturesof a size exceeding that'of the contaminations, 'inl'et means for admitting the suspension and the contaminations into the interior of the drum, outlet means for unobstructedly discharg,

ingthe purifiedsuspension from the interior of the drum at the end of the drum, means for the rapid rotation of the drum to cause contaminations of higher specific gravity to pass out through said apertures, and means constituting part of 17. Apparatus for the continuous purification of suspensions or sludges,'especially of the fibrous pulps as used in the paper industry, which contain contaminations of higher specific gravity, consisting of a fixed casing, a drum rotatably arranged in said casing, said drum having a diameter smaller than that of the casing and apertures of a size exceeding that of the contaminations, inlet means for admittin the suspension and the contaminations into the interior of the. drum, outlet mean for unobstructedly discharging the purified suspension from the interior of the drum at the end of the drum, means for the rapid rotation of the drum to cause contaminations of higher specific gravity to pass out through said apertures, and a tube co-axially arranged at the end of the drum and adapted to remove contaminations of lower specific gravity, said tube having a smaller diameter than the outlet aperture of the drum.

18. Apparatus for the continuous purification of suspensions or sludges, especially of the fibrous pulps as used in the paper industry, which contain contaminations of a higher specific gravity, comprising a fixed casing, a drum rotatably arranged in said casing, said drum being provided with inwardly and outwardly extending radial annular members forming communicating annular compartments adjacent the cylindrical wall of said drum, said wall having apertures of asize exceeding that of the contaminations, inlet means for admitting the suspension and the contaminations into the interior of the drum, outlet means for unobstructedly discharging the puriefied suspension from the interior of the drum at the end of the drum, and means for the rapid rotation of the drum to cause contaminations of higher specific gravity to pass out through said apertures, said inlet means and outlet means having approximately radial ribs.

19. Apparatus for the continuous purification v of suspensions or sludges, especially of the fibrous pulps as used in the paper industry, which contain contaminations of a higher specific gravity, comprising a fixed casing, a drum rotatably arranged in said casing, said drum being provided with inwardly and outwardly extending radial annular'members forming communicating annula r compartments adjacent the cylindrical wall of said drum, said wall being provided with apertures, inlet means for admitting the suspension and the contaminations into the interior of the drum, outlet means for unobstructedly discharging the purified suspension from the interior of the drum at the end of the drum, and means for the rapid rotation of the drum to cause contaminations of higher specific gravity to pas:- ut through said apertures, the ends of the drum hav ing inwardly projecting edges provided with ribs and grooves.

r 20. Apparatus according to claim 8, where the wall of the drum is divided after the deflecting surfaces, considered in the direction of flow, into a series of conical surfaces, openings being provided in the wall of the drum in front of the defleeting surfaces considered in the direction of fiow.

HELMUTH BANNING.