Claims
- 1. A method of treating a slurry of compressible comminuted cellulosic fibrous material, having a permeability that varies as it is compressed, in a non-circular cross-section annulus treatment zone, comprising:(a) introducing a flow of the slurry having a consistency of between about 8-15% into the treatment zone to form a bed of slurry having a first side and a second side, and a width; (b) passing the slurry through the substantially atmospheric pressure treatment zone; (c) in the treatment zone introducing a treatment liquid into the bed at the first side thereof so that the liquid passes from the first side through to the second side thereof; (d) removing at least some of the liquid from the second side of the bed; and wherein (a)-(d) are practiced so that the slurry has a consistency at all times throughout the treatment zone of between about 8-18%; and wherein (b) is practiced substantially without disrupting the flow of slurry.
- 2. A method as recited in claim 1 wherein (c) and (d) are not practiced at spaced locations as the slurry moves through the treatment zone.
- 3. A method as recited in claim 2 wherein said method further comprises increasing the width of the slurry bed at least about 5% at the spaced locations where (c) and (d) are not practiced, to allow said slurry to recover permeability.
- 4. A method as recited in claim 1 wherein (d) is practiced by passing the slurry into contact with a screen surface, liquid passing through the screen surface; and further comprising at spaced points in time moving the screen surface to substantially prevent plugging thereof by rotating the screen surface about an axis substantially parallel to the direction of slurry flow through the treatment zone of less than 30 degrees, or by vibrating or oscillating the screen surface in a direction substantially transverse to the direction of flow of slurry through the treatment zone.
- 5. A method as recited in claim 1 wherein (d) is practiced by passing the slurry into contact with a screen surface, liquid passing through the screen surface; and further comprising at spaced points in time moving the screen surface to substantially prevent plugging thereof.
- 6. A method as recited in claim 5 wherein moving the screen surface is practiced in a direction or manner distinct from the vertical.
- 7. A method of treating a slurry of compressible comminuted cellulosic fibrous material, having a permeability that varies as it is compressed, in a substantially annular, substantially atmospheric pressure, treatment zone, comprising:(a) introducing a flow of the slurry having a consistency of between about 8-15% into the treatment zone to form a bed of slurry having a first side and a second side, and a width; (b) passing the slurry through the substantially atmospheric pressure treatment zone; (c) in the treatment zone introducing a treatment liquid into the bed at the first side thereof so that the liquid passes from the first side through to the second side thereof; (d) removing at least some of the liquid from the second side of the bed; and practicing (a)-(d) so as to positively control in the treatment zone the pressure drop across the bed, the friction load, the consistency of the slurry, the inverse of permeability, and the inverse of bed strength, so as to limit the negative impact thereof upon treatment efficiency.
- 8. A method as recited in claim 7 wherein (d) is practiced by passing the slurry into contact with a screen surface, liquid passing through the screen surface; and further comprising at spaced points in time moving the screen surface to substantially lugging thereof.
- 9. A method: recited in claim 7 wherein (c) and (d) are not practiced at spaced locations as the slurry moves through the treatment zone.
- 10. A method as recited in claim 9 further comprising increasing the width of the slurry bed at least about 5% at the spaced locations where (c) and (d) are not to allow the slurry to recover permeability.
- 11. A method as recited in claim 7 wherein (d) is practiced by passing the slurry into contact with a screen surface, liquid passing through the screen surface; and further comprising at spaced points in time rotating the screen surface about an axis substantially parallel to the direction of slurry flow through the treatment zone of less than 30 degrees, to substantially prevent plugging thereof.
- 12. A diffusion assembly for treating a liquid slurry of comminuted cellulosic fibrous material each assembly comprising:a substantially upright vessel defined by a vessel wall, for at least a treatment portion thereof between an inlet and outlet for a liquid slurry having a consistency between about 8-18%, said treatment portion comprising a substantially atmospheric pressure non-circular cross-section annulus; at least one screen surface which removes some of the liquid of the comminuted cellulosic fibrous material slurry from the treatment portion of the vessel, but minimal solids slurried by the liquid, said screen surface substantially vertically elongated and comprising screening portions vertically spaced by non-screening portions; treatment liquid introducing means for introducing treatment liquid into the slurry in said vessel treatment portion; and means for positively controlling in said treatment portion the pressure drop, friction load, consistency of the slurry, the inverse of permeability, and the inverse of slurry bed strength, so as to limit the negative impact thereof upon treatment.
- 13. An assembly as recited in claim 12 further comprising treatment liquid introducing devices associated with said treatment portion which introduce liquid into said treatment portion including so that the permeability of the slurry in said treatment portion is a maximum of about 750 pounds per square foot per foot.
- 14. An assembly as recited in claim 13 wherein said screen surface comprises screening portions vertically spaced by non-screening portions; and wherein said vessel wall bulges our substantially at the location of said non-screening portions so as to provide a slurry width thereat at leapt 5% wider than at said screening portions associated therewith.
- 15. An assembly as recited in claim 12 wherein said vessel has a substantially race track shape in cross-section at said treatment portion.
- 16. An assembly as recited in claim 12 wherein said screen surface comprises screening portions vertically spaced by non-screening portions; and wherein said vessel wall bulges our substantially at the location of said non-screening portions so as to provide a slurry width thereat at least 5% wider than at said screening portions associated therewith.
- 17. An assembly as recited in claim 16 wherein said vessel has a substantially race track shape in cross-section at said treatment portion.
- 18. An assembly as recited in claim 16 wherein said screen surface comprises screening portions vertically spaced by non-screening portions; and wherein said vessel wall bulges our substantially at the location of said non-screening portions so as to provide a slurry width thereat at least 5% wider than at said screening portions associated therewith.
- 19. An assembly as recited in claim 12 further comprising means for occasionally moving said screen surface so as to minimize plugging thereof.
- 20. An assembly as recited in claim 12 further comprising means for occasionally moving said screen surface in a direction or manner distinct from the vertical so as to minimize plugging thereof.
CROSS-REFERENCE TO RELATED APPLICATION
This application is a division of Ser. No. 09/306,416, filed May 6, 1999, which in turn is based upon U.S. provisional application serial No. 60/084,666 filed May 7, 1998.
US Referenced Citations (8)
Provisional Applications (1)
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Number |
Date |
Country |
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60/084666 |
May 1998 |
US |