Solids-liquids separation device

A rotatable drum solids-liquids separation device having bailer scoop means forming a fluid-holding trough attached to and rotatable with the drum which is operable to pick-up fluid in an internal drum sump and during rotation to lift and transport the fluid to an outlet position higher in elevation than the sump level, normally at the centerline of the drum.

BACKGROUND OF THE INVENTION 
This invention concerns a solids-liquids separation apparatus including a 
rotable cylindrical drum where flow movement of process liquid is provided 
from a first level of fluid contained within the drum to a higher in 
elevation level outside the drum. The above function is provided by a 
series of internal bailers contained within the drum structure. 
FIELD OF INVENTION 
The present invention relates to a rotary liquids-solids separation drum 
device particularly to an apparatus for filtering solid particles from a 
liquid-solid slurry, including washers for pulp and paper stock pulps. The 
device provides for the movement of fluid from a sump at the bottom of the 
interior of the rotary drum to a site higher in elevation, namely to a 
centerline level without the use of pumps. 
DESCRIPTION OF PRIOR ART 
According to various processes well-known to the art and prior art 
apparatus, drum filters have been used for many years in which a filter 
fabric is conveyed about a perforated rotating drum and filtrate is 
extracted from a mat of slurried solid material on the fabric into the 
drum interior. A typical arrangement is seen in U.S. Pat. No. 2,745,712 
which provides for countercurrent washing of cooking liquor from paper 
pulp. Such patent shows wash liquor which has been sprayed on the exterior 
of the drum being conducted through the mat on the outside surface of the 
drum and through the apertures in the drum into the drum interior. To 
conserve the wash water being used for the washing cycle and to move the 
wash water to a preceding drum for countercurrent washing a gravity flow 
from the drum directly into a lower container by means of drop tubes 2, 4, 
6 and 8 is provided. FIG. 5 of the patent particularly shows the movement 
of the interior wash water into the lower tank. 
U.S. Pat. No. 4,160,297 shows a machine and process for washing paper pulp 
stock and similar free-filtering materials including a series of 
horizontally disposed wash drums, each mounted in a tank. Two endless 
filter belts are trained to pass over each of said drums and through 
liquid contained in each of the tanks. A mat of pulp is formed between 
endless filter belts and carried under each of the drums for washing 
therein. Wash liquor passes through the pulp mat as it travels under said 
drums thereby washing the pulp mat and the liquor passes from drum to drum 
by gravity flow. Thus in this type of device it is necessary to have the 
tanks stepped in elevation so that the materials from one tank flows into 
a lower tank. Likewise, it is necessary to have a mechanism for rising the 
liquid within the inside of the tank to a succeeding tank. This is 
accomplished by a series of siphon tubes which extend downwardly into the 
drum and terminate adjacent to cylindrical sidewalls thereof. A suitable 
primer means is also needed to provide initial suction to the siphon 
tubes. 
U.S. Pat. No. 4,324,116 shows a further mechanism for conducting wash water 
from the interior of the drum to another tank through which the drum 
passes. In this patent a series of radial extending filtrate conduits are 
disposed within the drum and in operation a rotary valve communicates with 
the conduits to permit liquid to flow through the apertures in the 
sidewall of the drum and then from the drum via a port 22. This port is 
connected to apply vacuum to the apertures and a pump is provided to move 
the recovered wash liquor to an upstream tank containing a second drum. As 
can be seen in each of these above patents, flow is either provided by 
gravity, by suction vacuum or by pumping to remove the fluid within the 
drum to a higher site outside the drum. 
SUMMARY 
The present invention is an improved, energy-conserving apparatus for 
transferring fluid from an interior sump in a drum-type filter or washer 
to another station in the flow path of the fluid slurry being treated 
wherein it is desired to move such fluid to a point higher in elevation 
than the sump level. The above function is performed by one or more fixed 
bailers fixed to rotate with the drum so as to pick up fluid from the drum 
sump and discharge the fluid at a higher elevation normally at the drum 
centerline so that the fluid can then flow by gravity to an upstream or 
downstream tank or other discharge point. The device acts to pick up fluid 
from the interior of the drum along the longitudinal length of the drum 
and move the picked-up fluid laterally along the axis of the drum, as the 
bailer pick-up means moves in its rotary cycle to a higher elevation and 
to a point of discharge of the fluid, whereby the fluid is caused to flow 
by gravity towards an outlet position adjacent the central axis of the 
drum. The device may also be employed to move fluid coming in one trunnion 
into the drum sump and then by the bailer action out the other trunnion.

DETAILED DESCRIPTION OF DRAWINGS 
A particular utilization of this invention is for pulp washer 
configurations which employ a wash liquor flow from a drum tank through a 
slurry mat on a drum to the interior of the drum with subsequent removal 
of the filtrate from the interior drum sump. In this invention this is 
done by means of interiorally placed bailers which convey fluid filtrate 
from the sump to an exit at the drum axis. The bailers rotate with the 
drum in a rotary cycle and in a first portion of the rotary cycle act to 
pick up fluid from the fluid sump within the drum and move it upwards to 
an elevation where it is dischargeable by gravity flow into an outlet 
contained at the rotation axis of the drum. This is illustrated clearly in 
relatively rudimentary terms in FIGS. 1-3. 
FIG. 1 shows the initial part of the pick-up cycle wherein a bailer 10 
having a lip portion 11 functions to pick up fluid within the sump and 
convey it upwardly in a fluid holding trough 14 formed by the lip portion 
and a longitudinal-extending baffle 12. The bailer 10 is rotated in the 
clockwise position about the rotation axis at a fluid outlet 13. 
FIG. 2 shows the rotation after approximately 45.degree. travel from the 
initial pick up. At this point, the tip edge of the lip 11 and the 
adjacent surface of baffle 12 forming the trough 14 is in a horizontal 
plane and the slope of the baffle allows fluid to flow down the surface of 
baffle 12 into outlet 13. By the time the pick-up lip 11 has reached a top 
vertical position as shown in FIG. 3, discharge of all fluid from the 
trough 14 has been accomplished and the bailer is ready to make another 
half revolution and to again pick up and hold fluid from the sump when it 
has reached the approximate so-called six o'clock position in its rotary 
movement. The tip edge of the pick-up means 11 will intersect the fluid 
upper surface in the sump before that position and will scoop the fluid 
into the trough as it revolves around the bottom part of the rotary cycle. 
FIG. 1 actually illustrates the cycle as it is leaving the sump with the 
scooped-up fluid within trough 14. 
FIG. 4 illustrates application of the invention to a paper pulp washer. A 
washer such as typically shown in U.S. Pat. Nos. 4,160,297 and 4,324,116 
illustrates countercurrent washing through the utilization of multiple 
drums and tanks in the pulp washer. FIG. 4 is a partial illustration of a 
co-current version of an overall pulp washing system. Drums 20 and 21 
rotate within fluid tanks 22 and 23. A pair of bailers 24 and 25 are shown 
in drum 20 only for illustration purposes. Normally, four bailers will be 
contained in each drum, one in each quadrant, so that the various 
functions of the bailing device will be simultaneously performed during 
the entire rotary cycle. Bailers 24 and 25 have bailer pick-up means 26 
and 27 extending generally at right angles to the radially extending 
baffles 28 and 29. The pick-up means are attached to a series of conical 
or pyramidal baffles which together form troughs which hold the scooped up 
fluid from sump 32. Sump 32 is at the situs A of the fluid which is 
desired to be moved to a higher elevation point. As the drum and its 
attached bailers are rotated clockwise, the combination of the bailer 
pick-up and the baffles scoop up a volume of sump fluid into the trough 
and transport it to a higher elevation along the rotary cycle. When the 
bailer 25, for example, reaches the position illustrated by the dotted 
lines at 42, the trough is at such an angle so as to allow fluid contained 
in the trough, formed by the bailer pick-up means and the baffle, to flow 
by gravity down the baffle towards its apex and length-wise of the drum to 
an outlet 30 contained in the drum trunnion 31. Fluid which has been 
raised from situs A flows into the outlet 30 where it is transported by 
gravity through line 40 to situs B typically the sump 41 of tank 23 
through which the other drum 21 rotates. Situs B is at an elevation above 
situs A but below the elevation of the outlet 30 of such tank 22. Filter 
belt 35 is pulled through the total system by the rotary motion of the 
various drums 21 and 22. Illustrated also is top drum 36 which acts as a 
spray wash drum. Suitable sprays 37 spray wash fluid on the filter belt 
and its mat of paper or other fibers so that the paper stock may be washed 
clean of digestor chemicals, for example. Wash water flow 38 from drum 36 
may fall by gravity onto incline flowdeck 39 and become part of the fluid 
in sump 41 within tank 23. 
FIG. 5 shows a cross-sectional view of a drum filter including this 
invention. Drum 50 contains a cylindrical surface 51 which is apertured so 
as to allow passage of filterable liquid or filtrate through the 
apertures. Drum ends 52 generally seal the interior of the drum. Centrally 
of the drum ends at the axis of the drum are trunnions 53 which rotate in 
suitable trunnion bearings and allow passage of fluid collected in the 
interior of the drum to an exterior point. Baffles 54 are provided within 
the drum and are connected to a framework fixedly connected to the drum 
interior. This framework comprises a first pair of support rings 60 
situated at the extremeties of the drum, a second pair of support rings 61 
at a midpoint between the central part of the drum and each drum end and a 
central support ring 62 for supporting a series of baffles which form the 
fluid-conducting troughs of this invention. Baffles 54 are shown as 
forming a pair of pyramidal members having abutting base portions at the 
central portion of the drum at ring 62 at the lateral midpoint of the 
drum. The apices of the pyramidal baffles extend towards the drum ends of 
the drum 50 and are in flow communication with a circle sector outlet 63 
contained in hub 53. The truncated apex of each of these pyramidal members 
terminates at a point 59 within the trunnion 53. 
FIG. 6 is a view taken at the centerline of the drum 50 and shows the 
"swastika"-like pickup means 55, 56, 57 and 58 extending around the inner 
periphery of the cylindrical wall 51 of the drum 50. Pickup lips 55-58 
form with the section walls and baffles 54 a longitudinally-extending 
trough or overall baffle means having a minimum depth at the midpoint of 
the drum and a maximum depth adjacent the drum outlet at point 59. Section 
walls 67 give structural integrity and stiffness to the drum as well as 
providing the sides of the formed trough. Lips 55-58 run generally 
parallel to the inner periphery of the drum 50 while the surface of the 
baffles extend inwardly as the baffle progresses from its basepoint to the 
end of the drum. Section walls 67 form the sides of the trough. Thus, all 
fluid that is picked up by the pickup means flows outwardly towards the 
ends of the drums to the circle sector 63 contained in trunnions 53. 
Baffles 54 forming the bottom of the trough may also be made from two 
conical members with abutting bases at the midpoint of the drum length 
with their open apices ending in the trunnions or may be in the form of 
one cone or pyramid extending the whole length of the drum. In the latter 
case, outward flow of fluid will occur at one end of the drum only. 
FIG. 7 shows a detail of the center ring and the welding of the respective 
bases of each of the pyramidal sections to that ring. Ring 62 comprises a 
first ring section 64 and a second ring section 66 joined by a peripheral 
weld 65. Ring 62 is attached both to the walls of the pyramidal baffle and 
to the inner peripheral wall of the cylindrical wall section 51 of drum 
50. 
FIG. 8 shows a view of the drum of FIG. 5 taken on the lines 8--8. The 
framework on which the pickup scoop means 55-58 is mounted comprises a 
spider 76 connected to a support ring 75 which is connected to a surface 
of trunnion 53 and welded to the inner periphery of the cylindrical drum 
surface 51. 
FIG. 9 is a partial view of the support and outlet structure for the 
trunnion of a typical drum filter incorporating this invention. Trunnion 
53 is supported on a trunnion bearing 70 which is supported by a trunnion 
support 71. Trunnion bearing is provided between the end wall 74 and the 
tank or vat 77 in which the drum 50 rotates and the trunnion end. A 
suitable stuffing box 73 is provided around the periphery of the trunnion 
53 where it passes through the aperture 78 contained in tank end 74. 
Extending outwardly from the end of trunnion 53 is an outlet box 72 which 
receives the filtrate from the interior of the drum which is conveyed to 
it through the bailer means. No seal is needed at the point of entrance of 
the trunnion into outlet box 72 unlike prior art devices. Fluid picked up 
by lips 55-58 flow into trough 14 and are conveyed down the slope of 
baffles 54 towards the apex of the conical or pyramid members forming the 
baffle structure. Filtrate 68 thus flows towards that apex and is 
discharged into outlet box 72 and falls by gravity downwardly through pipe 
40 to any appropriate site. 
FIG. 10 shows a gravity decker or thickener used in the pulp and paper 
industry or in other industries where thickening of slurries are desired. 
Appropriate feed is fed into an inlet 81 in a semicylindrical tank 82 
containing a rotary drum 83. Filtrate from the liquid solid slurry 
contained between the drum and the tank flows through the perforated drum 
surface and forms inner sump 89. Bailer pickup means 88 scoops up the 
fluid filtrate within the drum and picks up a volume 90 of such fluid and 
conveys it upwardly to a discharge point at a portion of the rotary cycle 
above the horizontal. Filtrate is shown at 91 flowing into outlet 30. A 
mat is shown formed on the surface of the drum 83 which is transferred to 
couch roll 85. A doctor blade 86 scrapes off the fibrous mat from roll 85 
and the desired product 87 is transferred to further operations. Filtrate 
91 is removed through outlet port 30 as shown in FIG. 9, for example. 
FIG. 11 shows a gravity filter 92 which also may use the present invention. 
In this embodiment, feed is transferred by inlet 81 to tank 82 in which a 
drum 83 rotates. A portion of the liquid contained in the liquid-slurry 
within the space between the tank 82 and drum 83 is conducted by vacuum or 
hydrostatic head into an interior portion of drum 83 forming a filtrate 
volume in sump 89. Pickup means 88 scoops up the filtrate liquid in the 
sump in its particular quadrant and moves a volume 90 of that sump fluid 
around with tank 82 to and above the horizontal position of the pickup 
means to a point which it can be discharged as at 91 into the outlet port. 
As the filtrate is removed from the tank, other filtrate comes into the 
succeeding quadrants and the material in the space between the tank 82 and 
drum 83 increases in percent solids. Thickened slurry exits the tank 82 by 
outlet 94. For example, this particular modification may be used as a 
black liquor filter for removing fiber from black liquor prior to its 
evaporation. 
It is also contemplated that the bailer of this invention may be just one 
segment of a quadrant in which a triangular baffle or floor is provided 
between two radial walls extending from the axis of a drum to the drum 
outer cylindrical surface over a desired length of drum. A scoop lip picks 
up filtrate in a trough formed by the baffle, the radial walls and end 
walls of the drum. The apex of the baffle leads into a drain tube at the 
drum trunnion for discharge of the filtrate.