A bar screen is primarily intended for use in draining liquid from wood chips and pulp without blocking the bar screen. The area of use is especially a process area, in which cooking and circulation liquid is removed from a pressure vessel when making chemical pulp and paper pulp by continuous method. This type of bar screen is characterized in that behind the filtering gap of the screen bars, there is a flow space in which the liquid flows towards a discharge outlet. By adjusting the flow space, a flow rate of liquid which stops blocking due to accumulation is maintained in the background. The sturdiness of the screen structure is improved by adjustable support taps.
1. A bar screen for draining liquid from chips in a pulp processor, the bar screen comprising:
a frame and plural screen bars fastened substantially parallel to the frame at their opposite ends in such a manner that a filtering gap is formed between adjacent ones of the screen bars, each of the screen bars having essentially parallel end faces having a length of 0-40 mm, the end faces being connected by rounded parts;
the gap between the adjacent ones of the screen bars being divided in two adjacent parts, a front part with a narrowing round-edged cone shape and a back part with a widening round-edged cone shape, the back part providing a channel for a flow of extracted liquid;
a filtrate chamber in fluid communication with the back part for extraction of the liquid therefrom; and
a saddle support between opposite ends of the screen bars supporting at least one of the screen bars, wherein at the gap in the saddle support, a space is provided separate from the back part to prevent a decrease in surface area of the filtrate chamber at the saddle support.
2. The bar screen of claim 1 , wherein the screen bars are rotatable around their longitudinal axes.
3. The bar screen of claim 1 , wherein the screen bars have a surface Ra of 0.6 to 0.8.
4. The bar screen of claim 1 , wherein the end faces have a length greater than 0 mm.
5. A bar screen for draining liquid from chips in a pulp processor, the bar screen comprising:
a frame and plural screen bars fastened substantially parallel to the frame at their opposite ends in such a manner that a filtering gap is formed between adjacent ones of the screen bars, each of the screen bars having essentially parallel end faces having a length of 0-40 mm, the end faces being connected by rounded parts;
the gap between the adjacent ones of the screen bars being divided in two adjacent parts, a front part with a narrowing round-edged cone shape and a back part with a widening round-edged cone shape, the back part providing a channel for a flow of extracted liquid; and
a wall adjacent to said screen bars, the wall being movable relative to the end faces at the back part so as to define a depth of a flow space for the extracted liquid.
6. The bar screen of claim 5 , wherein the screen bars are rotatable around their longitudinal axes.
7. The bar screen of claim 5 , wherein the screen bars have a surface Ra of 0.6 to 0.8.
8. The bar screen of claim 5 , wherein the end faces have a length of greater than 0 mm.
9. A bar screen for draining liquid from chips in a pulp processor, the bar screen comprising:
a frame and plural screen bars fastened substantially parallel to the frame at their opposite ends in such a manner that a filtering gap is formed between adjacent ones of the screen bars, each of the screen bars having essentially parallel end faces having a length of 0-40 mm, the end faces being connected by rounded parts,
the screen bars being rotatable around their longitudinal axes.
10. The bar screen of claim 9 , wherein the screen bars have a surface Ra of 0.6 to 0.8.
11. A bar screen for draining liquid from chips in a pulp processor, the bar screen comprising:
a frame and plural screen bars fastened substantially parallel to the frame at their opposite ends in such a manner that a filtering gap is formed between adjacent ones of the screen bars, each of the screen bars having essentially parallel end faces having a length of 0-40 mm, the end faces being connected by rounded parts,
the screen bars having a surface Ra of 0.6 to 0.8.
12. The bar screen of claim 11 , wherein the screen bars are coated with a fluoroplastic.
13. The bar screen of claim 11 , further comprising at least one saddle support between opposite ends of the screen bars.
14. The bar screen of claim 11 , wherein the end faces have a length of greater than 0 mm.
15. A bar screen for draining liquid from chips in a pulp processor, the bar screen comprising:
a frame and plural rounded screen bars fastened substantially parallel to the frame at their opposite ends in such a manner that a filtering gap is formed between adjacent ones of the screen bars;
the gap between the adjacent ones of the screen bars being divided in two adjacent parts, a front part with a narrowing round-edged cone shape and a back part with a widening round-edged cone shape, the back part providing a channel for a flow of extracted liquid;
each of the screen bars having a diameter of 4 to 40 mm; and
each gap being 2 to 15 mm wide.
16. The bar screen of claim 15 , wherein each of the screen bars has a diameter of 10 to 20 mm and each gap is 3 to 8 mm wide.
17. The bar screen of claim 15 , wherein each of the screen bars is symmetric.
18. The bar screen of claim 15 , wherein each of the screen bars has essentially parallel end faces having a length of 0-40 mm, the end faces being connected by rounded parts.
19. The bar screen of claim 18 , wherein the end faces have a length greater than zero.
20. The bar screen of claim 15 , wherein the gap is from D/4 to D/3.8, where D is a diameter of the screen bars.
21. The bar screen of claim 15 , wherein a joint of an end of the screen bars is arranged to allow a rotation of the screen bars around their longitudinal axes.
22. The bar screen of claim 15 , wherein the screen bars are surface-ground to a value Ra=0.6 to 0.8.
23. The bar screen of claim 15 , wherein the screen bars are electro-polished or coated with a low-friction agent.
24. The bar screen of claim 15 , further comprising a cleaner for mechanically cleaning the gap.
25. A bar screen for draining liquid from chips in a pulp processor, the bar screen comprising:
a frame and plural screen bars fastened substantially parallel to the frame at their opposite ends in such a manner that a filtering gap is formed between adjacent ones of the screen bars, each of the screen bars having essentially parallel end faces having a length of greater than 0 mm and no more than 40 mm, the end faces being connected by rounded parts; and
the gap between the adjacent ones of the screen bars being divided in two adjacent parts, a front part with a narrowing round-edged cone shape and a back part with a widening round-edged cone shape, the back part providing a channel for a flow of extracted liquid.
26. The bar screen of claim 25 , wherein the end faces have a length of 20 mm.