AU2018229555B2

AU2018229555B2 - Centrifugal screening apparatus

Info

Publication number: AU2018229555B2
Application number: AU2018229555A
Authority: AU
Inventors: Jeremy HANHINIEMI; Paul Joseph Jerks; Robert Christopher Thorne
Original assignee: Weir Minerals Australia Ltd
Current assignee: Weir Minerals Australia Ltd
Priority date: 2017-10-13
Filing date: 2018-09-14
Publication date: 2024-07-25
Anticipated expiration: 2038-09-14
Also published as: CN209575878U; AU2018229555A1

Abstract

A centrifugal screening apparatus including : a housing; a screen assembly mounted for rotation about a rotation axis in the housing and including a base of spoke piece and a substantially frustoconical screen member having a screening surface located between an outer feed end and an inner discharge end of the screen member wherein the diameter of the outer feed end is less than the diameter of the inner discharge end, the screen member rotatably secured at the inner discharge end to the base of spoke piece, the base of spoke piece cooperating with the housing to substantially divide the housing into a first portion for receiving filtrate passing through the screen member and a second portion for receiving product passing through the base of spoke piece; a scroll assembly having a plurality of substantially helical scroll vanes and mounted for rotation within the screen member with an edge of each vane lying in close proximity to the screening surface; drive means selected to differentially drive the rotation of the screen assembly and the scroll assembly about the rotation axis; and an inlet for receiving material to be screened from a material supply conduit, the inlet adapted to convey the material to be screened to the outer feed end of the screen member. 19 125 T\4 1235 126 12 1266 124 FIG. 4

Description

19 1235 125

T\4

126

12

1266

124 FIG. 4

CENTRIFUGAL SCREENING APPARATUS

Technical Field

[0001] This disclosure relates in general to centrifugal screening apparatus and a screen

member for use with same

Background of the Disclosure

[0002] Pulverized coal is washed by forming a water slurry and dewatering the slurry by

passage through a fine coal centrifugal scroll screen machine. A typical machine includes a

housing, a screen assembly mounted for rotation on a horizontal axis in the housing and

comprising a base of spoke piece supporting the lower, wider end of a frustoconical screen

member, the base of spoke piece cooperating with a dividing wall in the housing to form

housing portions receiving filtrate passing through the screen member and product passing

through the base of spoke piece respectively.

[0003] The screened coal product is actively stripped from the screening surface of the screen

member by a scroll assembly of helical scroll vanes mounted for differential rotation within the

screen member, the edges of which scrape the deposited fine coal and urge it through apertures

in the base of spoke piece. The progress towards and through the base of spoke piece is also

facilitated by the angle of the screen member. A drive assembly generally comprising an electric

motor and gearbox differentially drives the rotation of the screen assembly and scroll assembly

mounted on concentric drive shafts. Incoming fine coal slurry is delivered into an inlet

assembly supported on said housing and fed into the narrow end of the screen member. The

inlet end is narrow in order to achieve the angle of the screen necessary to encourage the coal

progress towards the base of spoke piece.

[0004] Due to the abrasive nature of the coal water slurry, the screen member, scroll assembly

and base of spoke piece of a typical fine coal centrifuge require frequent replacement due to the

wear associated with the operation of the centrifuge. It is typical for a screen member to be

replaced every four to six weeks of operation.

[0005] It is desirable to provide a centrifugal screening apparatus and/or screen member which

addresses the operational wear issues outlined above and where replacement of the screen

member, base of spoke piece and/or scroll assembly is required less often.

Summary

[0006] According to one aspect, there is provided a centrifugal screening apparatus including:

a housing;

a screen assembly mounted for rotation about a rotation axis in the housing and

including a base of spoke piece and a substantially frustoconical screen member having a

screening surface located between an outer feed end and an inner discharge end of the screen

member wherein the diameter of the outer feed end is less than the diameter of the inner

discharge end, the screen member rotatably secured at the inner discharge end to the base of

spoke piece, the base of spoke piece cooperating with the housing to substantially divide the

housing into a first portion for receiving filtrate passing through the screen member and a

second portion for receiving product passing through the base of spoke piece;

a scroll assembly having a plurality of substantially helical scroll vanes and mounted

for rotation within the screen member with an edge of each vane lying in close proximity to the

screening surface; drive means selected to differentially drive the rotation of the screen assembly and the scroll assembly about the rotation axis; and an inlet for receiving material to be screened from a material supply conduit, the inlet adapted to convey the material to be screened to the outer feed end of the screen member wherein the diameter of the inner discharge end of the screen member is sized to provide a centripetal acceleration to the material to be screened of about 1Og m/s 2 to about 130g m/s 2 in use, wherein g is the Earth's gravitation of 9.8 m/s2

.

[0007] According to another aspect there is provided a centrifugal screening apparatus

including:

a housing;

a screen assembly mounted for rotation about a rotation axis in the housing and including a base

of spoke piece and a substantially frustoconical screen member having a screening surface

located between an outer feed end and an inner discharge end of the screen member wherein

the diameter of the outer feed end is less than the diameter of the inner discharge end, the screen

member rotatably secured at the inner discharge end to the base of spoke piece, the base of

spoke piece cooperating with the housing to substantially divide the housing into a first portion

for receiving filtrate passing through the screen member and a second portion for receiving

product passing through the base of spoke piece;

a scroll assembly having a plurality of substantially helical scroll vanes and mounted for

rotation within the screen member with an edge of each vane lying in close proximity to the

screening surface;

drive means selected to differentially drive the rotation of the screen assembly and the scroll

assembly about the rotation axis; and an inlet for receiving material to be screened from a material supply conduit, the inlet adapted to convey the material to be screened to the outer feed end of the screen member wherein the diameter of the inner discharge end of the screen member is sized from about 1.4 m to about

2.3 m and in use the screen assembly is rotated at a speed of between about 300 revolutions per

minute to about 400 revolutions per minute.

[0008] According to another aspect there is provided a method of operating a centrifugal

screening apparatus to reduce abrasive wear wherein the centrifugal screen apparatus includes:

a housing;

product passing through the base of spoke piece;

screening surface;

assembly about the rotation axis; and,

an inlet for receiving material to be screened from a material supply conduit, the inlet adapted

to convey the material to be screened to the outer feed end of the screen member, wherein the method includes operating the centrifugal screening apparatus to drive the rotation of the screen assembly at a speed of between about 300 revolutions per minute to about 400 revolutions per minute.

[0009] In certain embodiments the screen assembly is rotated at a speed of between about 300

revolutions per minute to about 400 revolutions per minute when in use.

[0010] In certain embodiments the diameter of the inner discharge end of the screen member is

from about 1.4 m to about 2.3 m.

[0011] In certain embodiments the diameter of the inner discharge end of the screen member is

from about 1.5 m to about 2.0 m.

[0012] In certain embodiments the screen assembly is rotated at a speed of about 320 to about

380 revolutions per minute when in use.

[0013] In certain embodiments the diameter of the inner discharge end of the screen member is

from about 2 m to about 2.3 m when the screen assembly is rotated at a speed of about 300 to

about 330 revolutions per minute.

[0014] In certain embodiments the diameter of the inner discharge end of the screen member is

from about 1.6 m to about 2.2 m when the screen assembly is rotated at a speed of about 310 to

about 380 revolutions per minute.

[0015] In certain embodiments the diameter of the inner discharge end of the screen member is

from about 1.5 m to about 1.7 m when the screen assembly is rotated at a speed of about 350

to about 380 revolutions per minute.

[0016] In certain embodiments the diameter of the inner discharge end of the screen member is

from about 1.4 m to about 1.5 m when the screen assembly is rotated at a speed of about 360

to about 390 revolutions per minute.

[0017] In certain embodiments the screening surface located between the outer feed end and an

inner discharge end of the screen member is orientated at an angle of about 20 from the rotation

axis.

[0018] According to another aspect there is provided a centrifugal screening apparatus

including:

a housing;

a screen assembly mounted for rotation about a rotation axis in the housing and

discharge end, the screen member releasably secured at the inner discharge end to the base of

spoke piece, the screen member cooperating with the housing to substantially divide the housing

into a first portion for receiving filtrate passing through the screen member and a second portion

for receiving product passing from the inner discharge end of the screen assembly;

screening surface;

drive means selected to differentially drive the rotation of the screen assembly and

the scroll assembly about the rotation axis; and an inlet for receiving material to be screened from a material supply conduit, the inlet adapted to convey the material to be screened to the outer feed end of the screen member.

[0019] In certain embodiments the screen member includes a fastening portion at the inner

discharge end for releasably securing the inner discharge end to the base of spoke piece.

[0020] In certain embodiments the screen member includes an outlet region for delivering

product to the second portion of the housing. In one form the outlet region is located between

the fastening portion and the screening surface of the screen member.

[0021] In certain embodiments the fastening portion is integral with the outer peripheral

diameter of the inner discharge end of the screen member.

[0022] In certain embodiments the outlet region includes a plurality of discreet passageways

spaced around the periphery of the inner discharge end, the discreet passageways divided by

dividing portions located between adjacent passageways.

[0023] In certain embodiments the rotation axis is substantially horizontal.

[0024] According to another aspect there is provided a frustoconical screen member for use

with a centrifugal screening apparatus, the screen member including a screening surface located

between an outer feed end and an inner discharge end of the screen member wherein the

diameter of the outer feed end is less than the diameter of the inner discharge end and wherein

the diameter of the inner discharge end of the is sized to provide a centripetal acceleration to

the material to be screened of about 120g m/s 2 when the screen member is rotated at a speed of

between about 300 revolutions per minute to about 400 revolutions per minute, wherein g is the

Earth's gravitation of 9.8 m/s2 .

[0025] According to another aspect there is provided a frustoconical screen member for use

the diameter of the inner discharge end is from about 1.4 m to about 2.3 m.

[0026] In certain embodiments the diameter of the inner discharge end is from about 1.5 m to

about 2.0 m.

[0027] According to another aspect there is provided a frustoconical screen member for use

the screen member includes a fastening portion at the inner discharge end and an outlet region

for delivering product wherein the outlet region is located between the fastening portion and

the screening surface of the screen member.

[0028] According to another aspect there is provided A centrifugal screening apparatus

including: a housing; a screen assembly mounted for rotation about a rotation axis in the

housing and including a base of spoke piece and a substantially frustoconical screen member

having a screening surface located between an outer feed end and an inner discharge end of the

screen member wherein the diameter of the outer feed end is less than the diameter of the inner

discharge end, the screen member including a fastening portion at the inner discharge end for

releasably securing the screen member to the base of spoke piece, the screen member

cooperating with the housing to substantially divide the housing into a first portion for receiving

filtrate passing through the screen member and a second portion for receiving product passing

from the inner discharge end of the screen assembly; a scroll assembly having a plurality of substantially helical scroll vanes and mounted for rotation within the screen member with an edge of each vane lying in close proximity to the screening surface; drive means selected to differentially drive the rotation of the screen assembly and the scroll assembly about the rotation axis; and an inlet for receiving material to be screened from a material supply conduit, the inlet adapted to convey the material to be screened to the outer feed end of the screen member and wherein the screen member includes an outlet region located between the fastening portion and the screening surface of the screen member for delivering product to the second portion of the housing.

[0029] According to another aspect, there is provided a frustoconical screen member for use

with a centrifugal screening apparatus for separating material to be screened into filtrate and

product, the screen member including a screening surface located between an outer feed end

and an inner discharge end of the screen member, wherein the screening surface allows filtrate

to pass therethrough, wherein the diameter of the outer feed end is less than the diameter of the

inner discharge end and wherein the screen member includes a fastening portion at the inner

discharge end for securing the screen member to a base of spoke piece when assembled as part

of the centrifugal screening apparatus, and, an outlet region for delivering product wherein the

outlet region is located between the fastening portion and the screening surface of the screen

member and wherein the outlet region includes a plurality of discreet passageways spaced

around the periphery of the inner discharge end, the discreet passageways divided by dividing

portions located between adjacent passageways.

[0030] Other aspects, features, and advantages will become apparent from the following

detailed description when taken in conjunction with the accompanying drawings, which are a

part of this disclosure and which illustrate, by way of example, principles of the inventions

disclosed.

Description of the Figures

[0031] The accompanying drawings facilitate an understanding of the various embodiments.

[0032] FIG. 1 is a vertical section through a centrifugal screening apparatus in accordance

with this disclosure;

[0033] FIG. 2 is a cut-away isometric view of the apparatus of FIG. 1;

[0034] FIG. 3 is a cut-away, isometric wire frame view of the apparatus of FIG. 1, showing

product and effluent flow;

[0035] FIG. 4 is a perspective view of a screen member in accordance with this disclosure;

[0036] FIG. 5 is a side elevation view of the screen member of FIG 4;

[0037] FIG. 6 is a detail view showing product flow of G shown in FIG 5;

[0038] FIG. 7 is a vertical section through a centrifugal screening apparatus showing product

flow in accordance with this disclosure with detailed section; and,

[0039] FIG.8 is an exploded assembly view of a centrifugal screening apparatus in accordance

with this disclosure.

Detailed Description

[0040] In the FIGS. 1 to 3 there is provided generally a centrifugal screening apparatus

including an inner "dry side" housing portion 10 and an outer "wet side" housing portion 11.

A screen assembly 12 is mounted for rotation in the wet side housing portion 11 and includes a

base of spoke piece 13 and a frustoconical screen member 14 having a wedge-wire formed inner

screening surface 15 and removably secured by its base to the base of spoke piece 13. In this

embodiment, the base of spoke piece 13 cooperates with the housing 10 to substantially divide the housing 10, into the wet side housing portion 11 receiving filtrate passing through the screen member 14 to an effluent chamber 16 and the dry side housing portion 12 receiving product passing through the base of spoke piece 13 to a product delivery chamber 17. The filtrate or effluent chamber 16 is integrally formed with the outer wet side housing portion 11.

[0041] A scroll assembly 20 is mounted within the housing 11 and has a plurality of

substantially helical scroll vanes 21 supported on a conical liner 22 fabricated to a drive plate

23. The drive plate 23 has a hub 24 secured to an inner drive shaft 25 whereby the scroll

assembly 20 is mounted for rotation within the screen member 14 with an edge of each said

vane 21 lying in selected proximity to the screening surface 15. The inner drive shaft 25 forms

part of a drive assembly including an outer shaft 26 mounting the base of spoke piece 13 by a

drive cone 27, the inner 25 and outer 26 drive shafts being differentially driven to rotate the

screen assembly 12 and the scroll assembly 20 about the machine axis at different speeds in

use.

[0042] An inlet assembly 30 is supported on the wet side housing portion 11 and includes an

inlet body 31 defining a substantially annular inlet space 32 with an axial occluding plug portion

33, the annular inlet space 32 being substantially coaxial with and opening in to an open apical

end 34 of the screen member 14. A material supply conduit 35 delivers the material to be

screened under gravity head to the annular inlet space 32, the material supply conduit 35 being

aligned in a tangent to the annular inlet space 32 to deliver said material to the screening surface

15 substantially in the direction of rotation of the screen assembly 12, as shown in the flow path

36 of FIG. 3.

[0043] The inlet body 31 includes an integral spigot 37 connected to the supply conduit 35 via

sleeve coupling 40, permitting decoupling of the inlet assembly 30 from the supply conduit 35

for maintenance.

[0044] The annular inlet space 32 and spigot 37 are lined with a wear resistant tiles 41 formed

of sintered alumina. The inlet body 31 is fabricated from steel. The wear resistant tiles 41 are

bonded to the steel with epoxy based adhesive grouting composition.

[0045] The inlet assembly 30 is hinged to the wet side housing portion 11. The inlet assembly

30 extends an outer cylindrical wall portion 42 into the wet side housing portion 11 to confine

the feed to an annular space 43 defined by the screening surface 15 and the scroll vanes 21.

The hinge arrangement (not shown) hinging the inlet assembly 30 to the wet side housing

portion 11 is positioned and configured to allow the inlet assembly 30, including the wall

portion 42 extending into the housing portion 11, to clear the housing portion 11 to enable

maintenance access. The inlet assembly 30 is sealed to the housing portion 11 by a gasketed

flange 44 compressed to the housing portion 11 closure bolts installed through holes 45.

[0046] The fixed, inner portion dry side housing portion 10 is associated with and supports the

drive means and the outer, wet side housing portion 11 associated with the inlet assembly 30

each have complementary peripheral mating flanges 46, 47 secured with selectively releasable

fixing means 50. The housing portions 10, 11 are selectively separable substantially in the

plane of the join between the base of spoke piece 13 and the screen member 14.

[0047] The housing portions 10, 11 are hinged together about a substantially vertical hinge (not

shown) to provide access to the wet side components for ground-level maintenance. The hinge

portions are geometrically selected to cooperate with the hinged inlet assembly 30 as described

above to allow the assembly of the outer housing portion 11 and inlet assembly 30 to be opened

with ample clearance of the wet-end parts, to provide maintenance access to the entire wet side

of the apparatus. In the aggressive environment anticipated for screen machines, the hinge

portion or portions are lubricated by a positive pressure lubricator (not shown), in this

embodiment comprising a grease reservoir pressurized by a spring loaded piston and having a delivery outlet spigot screwed into the bore of each hinge to lubricate the pin-to-bore surfaces thereof.

[0048] The drive for the respective shafts 25, 26 includes a motor driven transmission belt 66

driving a power-dividing gearbox 67 providing the differential drive through the concentric

shafts 25, 26.

[0049] The frustoconical screen member 14 of the screen assembly 13 includes a narrow outer

feed end 18 and a larger inner discharge end 19. It was found that when the screen member was

sized to provide a centripetal acceleration to the material to be screened of about 11Og m/s2 to

about 130g m/s 2, and preferably about 120g m/s 2, wherein g is the Earth's gravitation of 9.8

m/s2 and the speed at which the screen member 14 is rotated is set between about 300 to about

400 revolutions per minute, then the rate of wear on the screen member was significantly

reduced. Indeed, it was found that during typical operation of the centrifugal screen apparatus

so configured, that the screen member 14 did not need to be replaced for at least 10 weeks after

continuous operation dewatering fine coal slurry, and in many instances for at least 12 weeks.

[0050] In a preferred embodiment, it was found that when the diameter of the inner discharge

end 19 of the screen member 14 is sized from about 1.4 m to about 2.3 m, and more preferably

from about 1.5 m to about 2.0 m, and the speed at which the screen member 14 is rotated is set

to about 300 to about 400 revolutions per minute, and more preferably from 350 to about 380

revolutions per minute, then the wear on the screen member was significantly reduced during

operation of the centrifugal screening apparatus when dewatering fine coal slurry. Furthermore,

it was also found that wear on the scroll assembly 20 and base of spoke piece 13 was also

significantly reduced.

[0051] By significantly reducing the amount of wear on the screen member 14, scroll assembly

20, and base of spoke piece 13 during the operation of the centrifugal screening apparatus, the working life of these components is increased which provides that maintenance time when the centrifugal screening apparatus is offline is significantly reduced leading to increased operational efficiency.

[0052] In addition, scheduled maintenance work for coal processing plants , often referred to

as 'change outs', are typically scheduled every 10 or 12 weeks. As such, another significant

advantage of sizing the screen member and operating the centrifugal screening apparatus as

above described, is that the replacement of a screen member 14 due to wear coincides with the

scheduled maintenance schedule for the coal processing plant.

[0053] Referring to FIGS. 4 to 6 there is shown an alternative embodiment of the screen

member 14 which includes an outlet region 123 that consists of passageways 125 where

material to be screened may exit and pass to the housing second portion 121 or'dry side'housing

portion from the inner discharge end 19 of the screen member 14. This arrangement is an

alternative embodiment as shown in FIGS. 1 to 3 where the coal exists the dewatering part of

the centrifugal screening apparatus by passing through outlets in the base of spoke piece 13 and

then into the dry side housing portion 10.

[0054] The outlet region of the screen member 14 includes a plurality of discreet passageways

125 that are equally spaced around the circumference of the outlet region 123 on the inner

discharge end 19 of the screen member 14. Each of the discreet passageways is in the form of

an opening that is defined by dividing portions 126, an outer peripheral band 124 and a top wall

128 integral with the structure of the screen member 14. FIG. 6 provides an indication of the

flow path of material to be screened, such as the fine coal solids, as it travels through the

centrifugal separator between the scroll assembly 20 and the screen member 14 in this

embodiment. As can be seen, the material particles (shown by the arrow) travel towards the inner discharge end 19 of the screen member 14 where they exit the screen member via the plurality of discreet passageways 125 spaced around the outlet region 123.

[0055] Referring to FIGS. 7 and 8 the screen member 14 includes a flange 127 that cooperates

with dividing portion 129 to define the housing second portion 121, or'dry side'housing portion

which is divided from the housing first portion 120, or'wet side'. The flange 127 is located prior

to the outlet region 123 along the length of the screen member 14 when moving from the outer

feed end 18 to the inner discharge end 19. This provides that the outlet region 123 of the screen

member is located within the housing second portion 121 such that the material to be screened

travelling through the centrifugal screening apparatus exists directly into the housing second

portion 121 via the outlet region 123 of the screen member 14.

[0056] In this embodiment, the base of spoke piece 13 does not include any outlets located

within its form and instead the material to be screened passes through the outlet region 123

located in the screen member 14 and into the housing second portion 121.

[0057] In an embodiment the outlet region 123, including the dividing portions 126, peripheral

band 124 and top wall 128 may be comprised of a composite materials to address the competing

material properties of tensile strength, toughness, corrosion resistance, and hardness which are

required at this hard wearing location of the screen member 14. Such a composite material may

comprise layering of one or more hard wearing materials bonded to tension carrying substrate.

This allows for a flexible connection in the axial shaft direction when assembled within the

centrifugal screening apparatus, ensuring that no tension or bending loads are transferred into

the hard wearing material and are instead taken by the tension carrying substrate.

[0058] In another embodiment the screen member may include an integrated wear plate either

attached to or integral with the periphery band member124. The integrated wear plate covers

the base of spoke piece 13 which provides that the wear plate is exposed to the product flow of the material to be screened and thereby shielding the base of spoke piece from wear during operation.

[0059] By providing the outlet region 123 in the screen member 14 rather than in the base of

spoke piece 13, wear impacting on the base of spoke piece is significantly reduced to the point

where it does not require frequent replacement during typical operation of the centrifugal

screening apparatus.

[0060] In the foregoing description of certain embodiments, specific terminology has been

resorted to for the sake of clarity. However, the disclosure is not intended to be limited to the

specific terms so selected, and it is to be understood that each specific term includes other

technical equivalents which operate in a similar manner to accomplish a similar technical

purpose. Terms such as "left" and right", "front" and "rear", "above" and "below" and the like

are used as words of convenience to provide reference points and are not to be construed as

limiting terms.

[0061] In this specification, the word "comprising" is to be understood in its "open" sense,

that is, in the sense of "including", and thus not limited to its "closed" sense, that is the sense

of "consisting only of'. A corresponding meaning is to be attributed to the corresponding words

"comprise", "comprised" and "comprises" where they appear.

[0062] In addition, the foregoing describes only some embodiments of the invention(s), and

alterations, modifications, additions and/or changes can be made thereto without departing from

the scope and spirit of the disclosed embodiments, the embodiments being illustrative and not

restrictive.

[0063] Furthermore, invention(s) have described in connection with what are presently

considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention(s). Also, the various embodiments described above may be implemented in conjunction with other embodiments, e.g., aspects of one embodiment may be combined with aspects of another embodiment to realize yet other embodiments. Further, each independent feature or component of any given assembly may constitute an additional embodiment.

List of Parts

dry side housing portion 11 outer wet side housing portion 12 screen assembly 13 base of spoke piece 14 frusto conical screen member inner screening surface 16 effluent chamber 17 product delivery chamber

18 outer feed end 19 inner discharge end D diameter of inner discharge end X axis of rotation

scroll assembly 21 vertical scroll vanes 22 conical liner 23 drive plate 24 hub inner drive shaft 26 outer shaft 27 drive cone

inlet assembly 31 inlet body 32 annular inlet space 33 plug portion 34 apical end material supply conduit 36 flow pattern 37 spigot

coupling 41 inner resistant tiles 42 outer cylindrical wall portion 43 annular space 44 gasketed flange holes 46 flange 47 flange

fixing means 51 key slots 52 blind stud 53 stud holes 54 nut washer 56 slot holes

57 weld

sealing flange portion 61 polyurethane resistant retainer 62 cylindrical side wall 63 end wall 64 aperture side surface 66 transmission belt 67 gearbox

lubrication system 71 impeller pump 72 reservoir 73 cartridges 74 selector assembly return line 76 supply liner 77 changeover valve

100 cap 102 monorail 110 inner conical wall portion 111 enclosed annulus

120 housing first portion 121 housing second portion 122 fastening portion 123 outlet region 124 periphery 125 passageways 126 dividing portions 127 flange 128 top wall 129 dividing portion

Claims

The claims defining the invention are as follows:

1. A centrifugal screening apparatus including:

a housing;

a screen assembly mounted for rotation about a rotation axis in the housing and

from the inner discharge end of the screen assembly;

screening surface;

drive means selected to differentially drive the rotation of the screen assembly and the

scroll assembly about the rotation axis; and

to convey the material to be screened to the outer feed end of the screen member and wherein

the screen member includes an outlet region located between the fastening portion and the

screening surface of the screen member for delivering product to the second portion of the

housing.

2. The centrifugal screening apparatus according to claim 1 wherein the fastening portion

is integral with a periphery of the inner discharge end of the screen member.

3. The centrifugal screening apparatus according to claim 1 or claim 2 wherein the outlet

region includes a plurality of discreet passageways spaced around the periphery of the inner

discharge end, the discreet passageways divided by dividing portions located between adjacent

passageways.

4. The centrifugal screening apparatus according to any one of claims 1 to 3 wherein said

rotation axis is substantially horizontal.

5. A frustoconical screen member for use with a centrifugal screening apparatus for

separating material to be screened into filtrate and product, the screen member including a

member, wherein the screening surface allows filtrate to pass therethrough, wherein the

the screen member includes a fastening portion at the inner discharge end for securing the screen

member to a base of spoke piece when assembled as part of the centrifugal screening apparatus,

and, an outlet region for delivering product wherein the outlet region is located between the

fastening portion and the screening surface of the screen member and wherein the outlet region

includes a plurality of discreet passageways spaced around the periphery of the inner discharge

end, the discreet passageways divided by dividing portions located between adjacent

passageways.