Profile bar screen for digester vessels

Patent metadata

Field	Value
Publication number	US-10087579-B2
Application number	US-201515507813-A
Country	US
Kind code	B2
Filing date	Aug 27, 2015
Priority date	Sep 1, 2014
Publication date	Oct 2, 2018
Grant date	Oct 2, 2018

Abstract

The invention relates to an improved profile bar screen for draining treatment liquor from a suspension of comminuted cellulose material and treatment liquor in an essentially cylindrical digester vessel. According to the invention is a profile bar screen designed with horizontal support arches 11 with integrated support shoulders 12 only at the outer ends of the support arch which support shoulders rest against the inside of the vessel wall 1 . The invention combines the techniques from self-supporting screens with support members of weaker screen designs, avoiding need to make any additional welds in the classified pressure vessel wall of the digester. Installation of new screens in compartments previously equipped with blind plates in checkered screen rows may be done quickly and at less costs during shorter down time of digester.

First claim

The invention claimed is:

1. A profile bar screen for draining treatment liquor from a suspension of comminuted cellulose material and treatment liquor in an essentially cylindrical digester vessel having an outer wall, said profile bar screen being arranged inside the outer wall of the cylindrical digester vessel thereby forming a withdrawal chamber between the outer wall of the digester vessel and the profile bar screen, the profile bar screen comprising:
vertical profile bar elements facing the suspension of comminuted cellulose material, said vertical profile bar elements arranged in parallel to each other and forming a withdrawal slot for treatment liquor between neighboring ones of said vertical profile bar elements; and
a plurality of horizontal support arches having vertical mounting slots for mounting said vertical profile bar elements in said mounting slots, the plurality of horizontal support arches having integrated support shoulders resting against the inside of the outer wall of the cylindrical digester vessel, each of said plurality of horizontal support arches having only two of said integrated support shoulders located at each respective end of each of said plurality of support arches whereby the plurality of horizontal support arches between said integrated support shoulders is located at a distance from the outer wall of the cylindrical digester vessel, enabling a free unobstructed flow of withdrawn cooking liquor between said outer wall of said cylindrical digester vessel and said plurality of horizontal support arches and between said two integrated support shoulders in each of said plurality of horizontal support arches.

2. The profile bar screen as claimed in claim 1 , wherein each of said plurality of horizontal support arches including the two integrated support shoulders comprises a single piece made from a metal plate with a thickness in the range of from 12- to 18 mm.

3. The profile bar screen as claimed in claim 2 , including a support bar for said outer wall of the cylindrical digester vessel and an L-shaped frame with a first leg and a second leg arranged orthogonally towards each other attached to the plurality of horizontal support arches and having an inwardly facing side and an outwardly facing side, with the first leg attached to the plurality of horizontal support arches, and oriented in the radial direction of the cylindrical digester vessel and the second leg oriented in the circumferential direction of the cylindrical digester vessel, and with the inwardly facing side of the second leg being flush with the surface of the vertical profile bar elements facing the suspension of comminuted cellulose material kept inside the digester and the outwardly facing side of the second leg abutting the support bar finding final load support in the outer wall of the cylindrical digester vessel.

4. The profile bar screen as claimed in claim 3 , wherein said plurality of horizontal support arches include expansion slots having an open end facing towards the interior of the cylindrical digester vessel and a closed end in the area of one of said integral support shoulders, thereby allowing for a flexibility of the plurality of horizontal support arches such that said integrated support shoulders may rest against the outer wall of the cylindrical digester vessel despite any local deviations from a perfect cylindrical shape of the outer wall of the cylindrical digester vessel.

5. The profile bar screen as claimed in claim 2 , wherein the length of the plurality of horizontal support arches in the circumferential direction of the cylindrical digester vessel of the screen is in the range of from 200- to 600 mm.

6. The profile bar screen as claimed in claim 5 , wherein the length of the plurality of support shoulders in the circumferential direction of the cylindrical digester vessel is in the range from 20- to 60 mm, and is less than 10% in relation to the length of the plurality of horizontal support arches, thereby providing a large unhindered withdrawal flow channel between said integrated support shoulders providing less exposure for sedimentation to build up.

7. The profile bar screen as claimed in claim 6 , wherein the length of the plurality of horizontal support arches is about 40 mm.

8. The profile bar screen as claimed in claim 6 , wherein the plurality of horizontal support arches are produced from a simple piece of sheet metal.

9. The profile bar screen as claimed in claim 5 , including a plurality of support members welded to a part of said outer wall of said cylindrical digester vessel by means of fillet welds, and wherein the integrated support shoulders includes an outer edge closest to outer wall of the cylindrical digester vessel and a closest one of said support members includes a large radius that provides clearance to any of said fillet welds, said large radius exceeding 10 mm.

10. The profile bar screen as claimed in claim 9 , including a plurality of support members welded to a part of said outer wall of said cylindrical digester vessel, wherein the integrated support shoulders include an inner edge closest to the large unencumbered withdrawal flow channel and furthest away from a closest one of said plurality of support members includes a smaller radius exceeding 3 mm, no larger than said large radius.

11. The profile bar screen as claimed in claim 2 , wherein the plurality of horizontal support arches have a thickness of about 15 mm.

12. The profile bar screen as claimed in claim 2 , wherein said plurality of horizontal support arches are cut from said single piece by means of water jet or a laser.

Assignees

• Valmet Oy

Inventors

• Ottosson Per-Anders
• Söderman Jerk

Classifications

• D21C7/14 Primary

  Means for circulating the lye · CPC title

• D21C7/00 Primary

  Digesters · CPC title

• D21C7/08 Primary

  Discharge devices · CPC title