Screen Basket Optimized For Removal Of Stickies From Adhesives-Contaminated Recyclable Fiber

• US 20120181237A1
• Filed: 01/12/2012
• Published: 07/19/2012
• Est. Priority Date: 01/13/2011
• Status: Active Grant

• Current Assignee: GPCP IP Holdings LLC
• Original Assignee: Georgia-Pacific Consumer Products LP (KOCH Industries Incorporated)
• Inventors: Winkler, Wayne F., Lucas, Bradley E.
• Granted Patent: US 8,534,468 B2
• Time in Patent Office: Days
• US Class Current: 210/773
• CPC Class Codes: B01D 2201/184 Special form, dimension of the openings, pores of the filtering elements
• CPC Class Codes: B01D 33/067 Construction of the filtering drums, e.g. mounting or sealing arrangements
• CPC Class Codes: B01D 33/11 arranged for outward flow filtration
• CPC Class Codes: B01D 33/275 using contiguous impervious surfaces
• CPC Class Codes: B01D 33/68 Retarding cake deposition on the filter during the filtration period, e.g. using stirrers
• CPC Class Codes: D21D 5/026 with rotating cleaning foils
• CPC Class Codes: D21D 5/16 Cylinders and plates for screens
• CPC Class Codes: Y02W 30/64 Paper recycling

Abstract

A screen structure which is unusually effective at removing stickies from recyclable fiber but is tolerant of substantial swings in throughput which result in variations in the flow velocity through the screen-slot velocity. One example of the screen structure is created by forming a very large number of similarly shaped vanes then locking them into a ring structure to form a cylindrical screen basket but equivalent surface configurations can also be formed into sheet stock.

Claims

1. A method for screening recycled pulp comprising the steps of:

fiberizing and suspending the pulp in an aqueous liquid;

pressurizing said aqueous liquid;

passing said aqueous liquid containing said fiberized and suspended pulp to one screen having;

a metallic screen basket for screening of stickies having a supply side surface approximating that of a right circular cylinder having an axis “

A”

, a circumference “

C” and

a diameter “

D”

, said surface comprising a plurality of sequences of facets, each sequence comprising a generally circumferentially extending facet, an upstream generally diametrally extending facet adjacent thereto, and a downstream generally diametrally extending facet adjacent thereto, each said generally circumferential facet being generally parallel to the axis “

A”

of the cylinder and having a leading edge and a trailing edge, each said leading edge and trailing edge as well as each said upstream generally diametrally extending facet and each said downstream generally diametrally extending facet being generally parallel to the axis “

A”

of the cylinder, each said leading edge being located upon a cylindrical surface S1, and each said trailing edge being located upon a cylindrical surface S2, the diametral difference “

δ

”

between the distance from the axis “

A”

to the cylindrical surface S1 and the diametral distance from the axis “

A”

to the cylindrical surface S2 being between about 0.4 mm to about 0.6 mm, the normal direction to the surface of each said generally circumferential facet in each sequence of facets having a component directed toward the adjacent trailing edge of an adjacent generally circumferential facet in an adjacent sequence of facets , the angle “

α

”

between the normal to each said generally circumferential facet and the diametral direction of said right circular cylinder being between about 80° and

76°

, the distance “

t”

from the leading edge to the trailing edge of each said generally circumferential facet being between about 2.3 mm and 2.5 mm, the upstream generally diametrally extending facet of each sequence adjoining the leading edge of a generally circumferential facet and the downstream generally diametrally extending facet of each sequence adjoining the trailing edge, the distance “

w”

between the upstream generally diametrally extending facet of each sequence and the downstream generally diametrally extending facet of the next adjacent sequence being between about 0.11 mm and 0.145 mm, a channel leading from the supply side to the accepts side of said screen being defined between the upstream generally diametrally extending facet of each sequence and the downstream generally diametrally extending facet of the next adjacent sequence;

a plurality of foils deployed adjacent said supply surface, each said foil being adapted to induce flow past said accepts surface of said screen basket and thereby periodically induce backflow through said channels against the pressure applied to said aqueous liquid, forward flow responsive to the pressure applied to said aqueous liquid occurring during periods between said periodic backflow;

conducting forward flow passing though said channels as an accepts flow to a papermaking operation;

passing rejects flow from said supply side of said screen basket to another screen; and

recycling accepts from said other screen back to the supply to said one stream.

2. The method of claim 1, wherein the screen basket is comprised of a plurality of metallic faceted vanes.

3. The method of claim 1, wherein the screen basket is formed from at least one unitary metallic sheet, each sheet having a plurality of trenches formed into its surfaces and a plurality of slits formed therethrough.

4. The method of claim 1 wherein the screen basket comprises stainless steel.

5. The method of any preceding claim wherein a corrosion resistant hardened surface is disposed upon the screen basket.

6. The method of claim 1 wherein the screen basket is plated with chromium.

7. The method of claim 6 wherein the screen basket bears a hard plating comprising a major proportion of chromium having hardness of at least about 65 on the Rockwell C scale in a thickness of at least 0.2 mils up to about 1.0 mils.

8. A metallic screen basket for screening of stickies containing recycled fibers, having a supply side surface approximating that of a right circular cylinder having an axis “

A”

, a circumference “

C” and

a diameter “

D”

, said surface comprising a plurality of sequences of facets, each sequence comprising a generally circumferentially extending facet, an upstream generally diametrally extending facet adjacent thereto, and a downstream generally diametrally extending facet adjacent thereto, each said generally circumferential facet being generally parallel to the axis “

A”

of the cylinder and having a leading edge and a trailing edge, each said leading edge and trailing edge as well as each said upstream generally diametrally extending facet and each said downstream generally diametrally extending facet being generally parallel to the axis “

A”

of the cylinder, each said leading edge being located upon a cylindrical surface S1, and each said trailing edge being located upon a cylindrical surface S2, the diametral difference “

d”

between the distance from the axis “

A”

to the cylindrical surface S1 and the diametral distance from the axis “

A”

to the cylindrical surface S2 being between about 0.35 mm to about 0.60 mm, the normal direction to the surface of each said generally circumferential facet in each sequence of facets having a component directed toward the adjacent trailing edge of an adjacent generally circumferential facet in an adjacent sequence of facets , the angle “

a”

between the normal to each said generally circumferential facet and the diametral direction of said right circular cylinder being between about 80° and

76°

, the distance “

t”

from the leading edge to the trailing edge of each said generally circumferential facet being between about 2.30 mm and 2.5 mm, the upstream generally diametrally extending facet of each sequence adjoining the leading edge of a generally circumferential facet and the downstream generally diametrally extending facet of each sequence adjoining the trailing edge, the distance between the upstream generally diametrally extending facet of each sequence and the downstream generally diametrally extending facet of the next adjacent sequence being between about 0.11 mm and 0.145 mm, a channel leading from the supply side to the accepts side of said screen being defined between the upstream generally diametrally extending facet of each sequence and the downstream generally diametrally extending facet of the next adjacent sequence.

9. The metallic screen basket of claim 8, wherein the screen basket is comprised of a plurality of metallic faceted vanes.

10. The metallic screen basket of claim 8, wherein the screen basket is formed from at least one unitary metallic sheet, each sheet having a plurality of trenches formed into its surfaces and a plurality of slits formed therethrough.

11. The metallic screen basket of any of claims 8 to 10 wherein the screen basket comprises stainless steel.

12. The metallic screen basket of any of claims 8 to 10 wherein a corrosion resistant hardened surface is disposed upon the screen basket.

13. The metallic screen basket of claim 8 wherein the screen basket is plated with chromium.

14. The metallic screen basket of claim 13 wherein the screen basket bears a hard plating comprising a major proportion of chromium having hardness of at least about 65 on the Rockwell C scale in a thickness of at least 0.2 mils up to about 1.0 mils.

15. An improved screen for separating a supply stream comprising an aqueous dispersion of papermaking fibers contaminated with adhesives into an accepts stream enriched in fibers and depleted in adhesive relative to said supply stream and a rejects stream enriched in adhesive and depleted in fiber relative to said supply stream, said screen comprising:

a housing;

a generally cylindrical screen basket disposed within said housing, defining an accepts region exterior to said screen basket;

a supply duct issuing into said screen basket within said housing;

an accepts duct leading from accepts region in said housing; and

a rejects duct adapted to receive aqueous dispersion not passing through said screen basket;

wherein the improvement comprises;

said screen basket comprising a plurality of metallic faceted vanes defining an interior supply side surface approximating that of a right circular cylinder having an axis “

A”

, a circumference “

C” and

a diameter “

D”

, each vane having formed therein;

a generally circumferentially extending facet, an upstream generally diametrally extending facet adjacent thereto, and a downstream generally diametrally extending facet adjacent thereto, each said generally circumferential facet being generally parallel to the axis “

A”

of the cylinder and having a leading edge and a trailing edge, each said leading edge and trailing edge as well as each said upstream generally diametrally extending facet and each said downstream generally diametrally extending facet being generally parallel to the axis “

A”

of the cylinder, each said leading edge being located upon an imaginary cylindrical surface S1 generally coaxial with said screen basket, and each said trailing edge being located upon another imaginary cylindrical surface S2 generally coaxial with said screen basket, the diametral difference “

d”

between the distance from the axis “

A”

to the cylindrical surface S1 and the diametral distance from the axis “

A”

to the cylindrical surface S2 being between about 0.35 mm to about 0.60 mm, the normal direction to the surface of each said generally circumferential facet on each vane having a component directed toward the adjacent trailing edge of an adjacent generally circumferential facet in an adjacent vane , the angle “

a”

between the normal to each said generally circumferential facet and the diametral direction of said right circular cylinder being between about 80° and

76°

, the distance “

t”

from the leading edge to the trailing edge of each said generally circumferential facet being between about 2.30 mm and 2.5 mm, the upstream generally diametrally extending facet of each vane adjoining the leading edge of a generally circumferential facet and the downstream generally diametrally extending facet of each vane adjoining the trailing edge, the distance between the upstream generally diametrally extending facet of each vane and the downstream generally diametrally extending facet of the next adjacent vane being between about 0.11 mm and 0.145 mm, a relieved channel leading from the supply side to the accepts side of said screen being defined between the upstream generally diametrally extending facet of each vane and the downstream generally diametrally extending facet of the next adjacent vane.

16. The improved screen of claim 15, wherein the screen is comprised of a plurality of metallic faceted vanes.

17. The improved screen of claim 15, wherein the screen is formed from at least one unitary metallic sheet, each sheet having a plurality of trenches formed into its surfaces and a plurality of slits formed therethrough.

18. The improved screen of any of claims 15 to 17 wherein the screen comprises stainless steel.

19. The improved screen of any of claims 15 to 17 wherein a corrosion resistant hardened surface is disposed upon the screen.

20. The improved screen of any of claims 15 to 17 wherein the screen is plated with chromium.

21. The improved screen of claim 15 wherein the screen bears a hard plating comprising a major proportion of chromium having hardness of at least about 65 on the Rockwell C scale in a thickness of at least 0.2 mils up to about 1.0 mils.