U.S. patent application number 09/883380 was filed with the patent office on 2001-10-18 for apparatus and process for removing fine impurities from a fibrous suspension.
This patent application is currently assigned to VOITH SULZER PAPIERTECHNIK PATENT GmbH. Invention is credited to Kemper, Martin, Wiese, Horst.
Application Number | 20010030030 09/883380 |
Document ID | / |
Family ID | 26043296 |
Filed Date | 2001-10-18 |
United States Patent
Application |
20010030030 |
Kind Code |
A1 |
Kemper, Martin ; et
al. |
October 18, 2001 |
Apparatus and process for removing fine impurities from a fibrous
suspension
Abstract
Process and apparatus for removing fine impurities from a
fibrous suspension. The process and apparatus each provide for
conveying the fibrous suspension to at least one sorting device,
separating the fibrous suspension using the at least one sorting
device into an accepts portion and a rejects portion, finishing at
least some of the accepts portion leaving the at least one sorting
device using a finishing device, separating at least some portion
of the rejects portion leaving the at least one sorting device
using at least one last sorting device into an accepts portion and
an rejects portion, separating at least some portion of the accepts
portion leaving the at least one last sorting device into an
accepts portion and a rejects portion using a flotation device, and
finishing at least some portion of the accepts portion leaving the
flotation device using the finishing device.
Inventors: |
Kemper, Martin; (Weingarten,
DE) ; Wiese, Horst; (Schongau, DE) |
Correspondence
Address: |
GREENBLUM & BERNSTEIN, P.L.C.
1941 ROLAND CLARKE PLACE
RESTON
VA
20191
US
|
Assignee: |
VOITH SULZER PAPIERTECHNIK PATENT
GmbH
Heidenheim
DE
|
Family ID: |
26043296 |
Appl. No.: |
09/883380 |
Filed: |
June 19, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09883380 |
Jun 19, 2001 |
|
|
|
09236235 |
Jan 22, 1999 |
|
|
|
6277239 |
|
|
|
|
Current U.S.
Class: |
162/55 ;
162/4 |
Current CPC
Class: |
D21F 1/70 20130101; Y02W
30/64 20150501; Y10S 210/928 20130101; D21B 1/32 20130101; Y02W
30/646 20150501; D21D 5/02 20130101 |
Class at
Publication: |
162/55 ;
162/4 |
International
Class: |
D21B 001/08; D21B
001/32; D21C 005/02; D21C 009/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 23, 1998 |
DE |
198 02 494.0 |
Feb 18, 1998 |
DE |
198 06 732.1 |
Claims
What is claimed is:
1. A process for removing fine impurities from a fibrous
suspension, comprising: conveying the fibrous suspension to at
least one sorting device; separating the fibrous suspension using
the at least one sorting device into an accepts portion and a
rejects portion; finishing at least some of the accepts portion
leaving the at least one sorting device using a finishing device;
separating at least some portion of the rejects portion leaving the
at least one sorting device using at least one last sorting device
into an accepts portion and an rejects portion; separating at least
some portion of the accepts portion leaving the at least one last
sorting device into an accepts portion and a rejects portion using
a flotation device; and finishing at least some portion of the
accepts portion leaving the flotation device using the finishing
device.
2. The process of claim 1, further comprising at least one
intermediate sorting device arranged between the at least one
sorting device and the at least one last sorting device, wherein
the process further comprises: separating at least some of the
rejects portion leaving the at least one sorting device using the
at least one intermediate sorting device into an accepts portion
and a rejects portion; and finishing at least some of the accepts
portion leaving the at least one intermediate sorting device using
the finishing device.
3. The process of claim 2, further comprising conveying at least
some of the rejects portion leaving the at least one intermediate
sorting device to the at least one last sorting device.
4. The process of claim 1, further comprising at least one
intermediate sorting device arranged between the at least one
sorting device and the at least one last sorting device and an
additional flotation device, wherein the process further comprises:
separating at least some of the rejects portion leaving the at
least one sorting device using the at least one intermediate
sorting device into an accepts portion and a rejects portion;
separating at least some of the accepts portion leaving the at
least one intermediate sorting device using the additional
flotation device into an accepts portion and a rejects portion; and
finishing at least some of the accepts portion leaving the
additional flotation device using the finishing device.
5. The process of claim 4, further comprising conveying at least
some of the rejects portion leaving the at least one intermediate
sorting device to the at least one last sorting device.
6. The process of claim 1, further comprising at least a first and
a second intermediate sorting device arranged between the at least
one sorting device and the at least one last sorting device,
wherein the process further comprises: separating at least some of
the rejects portion leaving the at least one sorting device using
the first intermediate sorting device into an accepts portion and a
rejects portion; separating at least some of the accepts portion
leaving the first intermediate sorting device using the second
intermediate sorting device into an accepts portion and a rejects
portion; and finishing at least some of the accepts portion leaving
the second intermediate sorting device using the finishing
device.
7. The process of claim 6, further comprising conveying at least
some of the rejects portion leaving each of the first and second
intermediate sorting devices to the at least one last sorting
device.
8. The process of claim 1, further comprising an additional sorting
device arranged after the at least one last sorting device, wherein
the process further comprises: separating at least some of the
rejects portion leaving the at least one last sorting device using
the at least one additional sorting device into an accepts portion
and a rejects portion; and conveying at least some of the accepts
portion leaving the additional sorting device to the at least one
last sorting device.
9. The process of claim 1, further comprising a first and a second
intermediate sorting device arranged between the at least one
sorting device and the at least one last sorting device and further
comprising an additional sorting device arranged after the at least
one last sorting device, wherein the process further comprises:
separating at least some of the rejects portion leaving the at
least one sorting device using the first intermediate sorting
device into an accepts portion and a rejects portion; separating at
least some of the accepts portion leaving the first intermediate
sorting device using the second intermediate sorting device into an
accepts portion and a rejects portion; separating at least some of
the rejects portion leaving the at least one last sorting device
using the additional sorting device into an accepts portion and a
rejects portion; and finishing at least some of the accepts portion
leaving the second intermediate sorting device using the finishing
device.
10. The process of claim 9, further comprising conveying at least
some of the accepts portion leaving the additional sorting device
to the flotation device.
11. The process of claim 10, further comprising conveying at least
some of the rejects portion leaving each of the first and second
intermediate sorting devices to the at least one last sorting
device.
12. The process of claim 1, wherein before the conveying of the
fibrous suspension to at least one sorting device, the process
comprises subjecting the fibrous suspension to at least one of
dissolution and pre-purification.
13. The process of claim 12, wherein before the conveying of the
fibrous suspension to at least one sorting device, the process
comprises subjecting the fibrous suspension to each of dissolution
and pre-purification.
14. The process of claim 12, further comprising removing ink
particles during pre-purification.
15. The process of claim 14, wherein the ink particles are removed
by flotation during pre-purification.
16. The process of claim 1, wherein the flotation device performs a
flotation separation without chemicals.
17. The process of claim 16, wherein the flotation device performs
a flotation separation without chemicals used to remove inks.
18. The process of claim 16, wherein the flotation device performs
a flotation separation without flotation chemicals.
19. The process of claim 1, wherein at least one of the at least
one sorting device and the at least one last sorting device
comprises a pressure sorter.
20. The process of claim 19, wherein the pressure sorter is
equipped with at least one wire.
21. The process of claim 20, wherein the at least one wire has
openings.
22. The process of claim 21, wherein the openings comprise slits
having a width of between about 0.08 and 0.5 mm.
23. The process of claim 21, wherein the openings comprise holes
having a diameter of between about 0.8 and 3 mm.
24. The process of claim 1, wherein a dry matter content of the
fibrous suspension before entering the at least one sorting device
is between about 0.6 and 2.5%.
25. The process of claim 1, wherein a dry matter content of the
fibrous suspension before entering the at least one sorting device
is between about 2 and 4%.
26. The process of claim 1, wherein the flotation device comprises
a selectively functioning flotation cell.
27. The process of claim 1, wherein the fibrous material suspension
comprises adhesive particles.
28. The process of claim 1, further comprising chemically treating
the fibrous material suspension in order to increase a surface
activity of interfering materials, the chemical treatment occurring
prior to the flotation device.
29. The process of claim 1, wherein before the conveying of the
fibrous suspension to at least one sorting device, the process
comprises subjecting the fibrous suspension to dispersion, and
further comprising transmitting a specific work of at least 20
kWh/to to the fibrous suspension during the dispersion.
30. An apparatus for removing fine impurities from a fibrous
suspension, comprising: at least one sorting device arranged to
receive the fibrous suspension; the least one sorting device
separating the fibrous suspension into an accepts portion and a
rejects portion; a finishing device for finishing at least some of
the accepts portion leaving the at least one sorting device; at
least one last sorting device for separating at least some portion
of the rejects portion leaving the at least one sorting device into
an accepts portion and an rejects portion; and a flotation device
for separating at least some portion of the accepts portion leaving
the at least one last sorting device into an accepts portion and a
rejects portion, wherein at least some portion of the accepts
portion leaving the flotation device is subjected to finishing
using the finishing device.
31. The apparatus of claim 30, further comprising at least one
intermediate sorting device arranged between the at least one
sorting device and the at least one last sorting device, wherein at
least some of the rejects portion leaving the at least one sorting
device is separated using the at least one intermediate sorting
device into an accepts portion and a rejects portion, and wherein
at least some of the accepts portion leaving the at least one
intermediate sorting device is subjected to finishing using the
finishing device.
32. The apparatus of claim 31, wherein at least some of the rejects
portion leaving the at least one intermediate sorting device are
conveyed to the at least one last sorting device.
33. The apparatus of claim 30, further comprising at least one
intermediate sorting device arranged between the at least one
sorting device and the at least one last sorting device and an
additional flotation device, wherein at least some of the rejects
portion leaving the at least one sorting device is separated using
the at least one intermediate sorting device into an accepts
portion and a rejects portion, wherein at least some of the accepts
portion leaving the at least one intermediate sorting device is
separated using the additional flotation device into an accepts
portion and a rejects portion, and wherein at least some of the
accepts portion leaving the additional flotation device is
subjected to finishing using the finishing device.
34. The apparatus of claim 33, wherein at least some of the rejects
portion leaving the at least one intermediate sorting device are
conveyed to the at least one last sorting device.
35. The apparatus of claim 30, further comprising at least a first
and a second intermediate sorting device arranged between the at
least one sorting device and the at least one last sorting device,
wherein at least some of the rejects portion leaving the at least
one sorting device is separated using the first intermediate
sorting device into an accepts portion and a rejects portion,
wherein at least some of the accepts portion leaving the first
intermediate sorting device is separated using the second
intermediate sorting device into an accepts portion and a rejects
portion, and wherein at least some of the accepts portion leaving
the second intermediate sorting device is subjected to finishing
using the finishing device.
36. The apparatus of claim 35, wherein at least some of the rejects
portion leaving each of the first and second intermediate sorting
devices is conveyed to the at least one last sorting device.
37. The apparatus of claim 30, further comprising an additional
sorting device arranged after the at least one last sorting device,
wherein at least some of the rejects portion leaving the at least
one last sorting device is separates using the at least one
additional sorting device into an accepts portion and a rejects
portion, and wherein at least some of the accepts portion leaving
the additional sorting device is conveyed to the at least one last
sorting device.
38. The apparatus of claim 30, further comprising a first and a
second intermediate sorting device arranged between the at least
one sorting device and the at least one last sorting device and
further comprising an additional sorting device arranged after the
at least one last sorting device, wherein at least some of the
rejects portion leaving the at least one sorting device is
separated using the first intermediate sorting device into an
accepts portion and a rejects portion, wherein at least some of the
accepts portion leaving the first intermediate sorting device is
separated using the second intermediate sorting device into an
accepts portion and a rejects portion, wherein at least some of the
rejects portion leaving the at least one last sorting device is
separated using the additional sorting device into an accepts
portion and a rejects portion, and wherein at least some of the
accepts portion leaving the second intermediate sorting device is
subjected to finishing using the finishing device.
39. The apparatus of claim 38, wherein at least some of the accepts
portion leaving the additional sorting device is conveyed to the
flotation device.
40. The apparatus of claim 39, wherein at least some of the rejects
portion leaving each of the first and second intermediate sorting
devices is conveyed to the at least one last sorting device.
41. The apparatus of claim 30, wherein before the fibrous
suspension is conveyed to at least one sorting device, the fibrous
suspension is subjected to at least one of dissolution in a
dissolution device and pre-purification in a pre-purification
device.
42. The apparatus of claim 41, wherein before the fibrous
suspension is conveyed to at least one sorting device, the fibrous
material suspension is subjected to each of dissolution and
pre-purification.
43. The apparatus of claim 42, wherein ink particles are removed
during pre-purification.
44. The apparatus of claim 43, wherein the ink particles are
removed by flotation during pre-purification.
45. The apparatus of claim 30, wherein the flotation device
performs a flotation separation without chemicals.
46. The apparatus of claim 45, wherein the flotation device
performs a flotation separation without chemicals used to remove
inks.
47. The apparatus of claim 45, wherein the flotation device
performs a flotation separation without flotation chemicals.
48. The apparatus of claim 30, wherein at least one of the at least
one sorting device and the at least one last sorting device
comprises a pressure sorter.
49. The apparatus of claim 48, wherein the pressure sorter is
equipped with at least one wire.
50. The apparatus of claim 49, wherein the at least one wire has
openings.
51. The apparatus of claim 50, wherein the openings comprise slits
having a width of between about 0.08 and 0.5 mm.
52. The apparatus of claim 50, wherein the openings comprise holes
having a diameter of between about 0.8 and 3 mm.
53. The apparatus of claim 30, wherein a dry matter content of the
fibrous suspension before entering the at least one sorting device
is between about 0.6 and 2.5%.
54. The apparatus of claim 30, wherein a dry matter content of the
fibrous suspension before entering the at least one sorting device
is between about 2 and 4%.
55. The apparatus of claim 30, wherein the flotation device
comprises a selectively functioning flotation cell.
56. The apparatus of claim 30, wherein the fibrous material
suspension comprises adhesive particles.
57. The apparatus of claim 30, wherein the fibrous material
suspension is chemically treated in order to increase a surface
activity of interfering materials, the chemical treatment occurring
prior to the flotation device.
58. The apparatus of claim 30, wherein before the fibrous
suspension is conveyed to at least one sorting device, the fibrous
suspension is subjected to dispersion, and wherein a specific work
of at least 20 kWh/to is transmitted to the fibrous suspension
during the dispersion.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of U.S.
application Ser. No. 09/236,235, filed Jan. 22, 1999, the
disclosure of which is expressly incorporated by reference herein
in its entirety. The present application also claims priority under
35 U.S.C..sctn. 119 of German Patent Application No. 198 02 494.0,
filed on Jan. 23, 1998, and German Patent Application No. 198 06
732.1, filed on Feb. 18, 1998, the disclosures of which are
expressly incorporated by reference herein in their entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to an apparatus and process for
removing impurities, and more particularly, to an apparatus and
process for removing fine impurities from a fibrous suspension.
[0004] 2. Discussion of Background Information
[0005] Fibrous suspensions, particularly those obtained from
recycled paper which are intended for paper production, contain
undesirable attendant materials, also referred to as "interfering
materials," which must be removed in the preparation system. The
removal of these interfering materials is generally performed in
various steps since a fibrous suspension purification in a single
process step is rarely successful.
[0006] Wet straining processes have turned out to be particularly
effective for the removal of fine impurities. In such processes,
the suspension is conveyed into a straining device and is divided
into at least two portions, an "accepts" portion, i.e., the
materials that have passed the wire, and a "rejects" portion, i.e.,
the materials rejected due to their size. Generally, in the
parlance of paper makers, such wet straining processes are known as
"sorting." It is also known to subject the rejected materials,
i.e., the rejects portion, to one or more additional subsequent
straining steps. This process is known as "multistep sorting."
Multistep sorting can be carried out at various points of the paper
stock preparation. Generally, the later the sorting occurs during
the process, the finer the wire openings that can be used in the
process. Examples of multistep wet straining are demonstrated in
the scientific paper "Sortierung von Altpapierstoff zur Herstellung
von graphischen Papieren" [Sorting of Recycled Paper Stock for the
Manufacturing of Graphic Papers] by R. Rienecker from the
Wochenblatt fur Papierfabrikation [Weekly for Paper Making] No.
23/24, 1997, pp. 1149 to 1159.
[0007] Although a large number of different systems are already
known and used for purifying paper stock suspensions, these systems
are often unsuccessful in removing all interfering impurities from
the suspension. In particular, very fine, adhesive impurities,
which often cause great difficulties in the production of paper,
even in small quantities, can only be removed at great expense, if
at all.
SUMMARY OF THE INVENTION
[0008] The present invention provides an apparatus and process for
removing fine impurities from a fibrous suspension. The apparatus
comprises a dissolution device, a pre-purification device, a wet
straining device, and a flotation device. The wet straining device
comprises at least two sorting devices installed in sequence, each
sorting device having a wire for separating the fibrous suspension
into an "accepts" portion and a "rejects" portion. The flotation
device is adapted to purify the "accepts" portion of at least one
sorting device, and further separates the fibrous suspension into
an "accepts" portion and a "rejects" portion.
[0009] The flotation device may be further adapted to purify the
"accepts" portion of the last of the at least two sorting devices.
Additionally, the flotation device may be adapted to receive the
"accepts" portions of the last two of the at least two sorting
devices.
[0010] The apparatus may also comprise a finishing device adapted
to receive at least one "accepts" portion of the wet straining
device. Furthermore, the apparatus may be adapted to receive at
least one "accepts" portion of the flotation device.
[0011] The pre-purification device may be adapted to remove ink
particles, and may remove these ink particles by flotation
[0012] Additionally, the sorting devices of the wet straining
device may be embodied as closed pressure sorters. The pressure
sorters may each be equipped with wires having free wire openings,
the free wire openings having slits with a width of between about
0.08 and 0.5 mm. Alternatively, the free wire openings may be holes
with a diameter of between about 0.8 and 3 mm.
[0013] The flotation device may additionally comprise a selectively
functioning flotation cell.
[0014] The process for removing fine impurities from a fibrous
suspension comprises the steps of subjecting the fibrous suspension
to a dissolution process, subjecting the fibrous suspension to a
pre-purification process, and purifying the fibrous suspension in a
wet straining process. At the wet straining process, at least two
sorting devices are installed in sequence, each sorting device
having a wire for separating the fibrous suspension into an
"accepts" portion and a "rejects" portion. The wet straining
process comprises introducing a "rejects" portion rejected at the
wire of a preceding sorting device into the subsequent sorting
device until a last subsequent sorting device has been reached,
conveying the "rejects" portion out of the process, and conveying
the "accepts" portion to a flotation process. The "accepts" portion
is purified by at least one flotation process, which further
separates the fibrous suspension into an "accepts" portion and a
"rejects" portion, the "rejects" portion containing a majority of
the impurities of the fibrous suspension, and the "accepts" portion
containing a majority of the fibers of the fibrous suspension.
[0015] The "accepts" portions of the sorting devices may contain
the highest percentage of interfering materials that can be floated
and may be purified in the flotation process.
[0016] Additionally, the "accepts" portion of the last subsequent
sorting device may be purified in the flotation process.
Alternatively, the "accepts" portions of the last two steps of the
wet straining process may be supplied to the flotation step
process.
[0017] The "accepts" portions of the wet straining process that are
not purified in the flotation process may also be combined and
supplied directly to a finishing process. Also, the "accepts"
portion of the flotation process may be supplied to the remaining
"accepts" portions of the wet straining process.
[0018] The pre-purification process may remove ink particles, and
may remove these ink particles by flotation
[0019] The sorting devices of the wet straining process may be
closed pressure sorters. These pressure sorters may be equipped
with wires having free wire openings having slits with a width of
between about 0.08 and 0.5 mm. Alternatively, the free wire
openings may be holes with a diameter of between about 0.8 and 3
mm.
[0020] At the beginning of the wet straining process, the dry
matter content of the fibrous suspension may be set to a value of
between about 0.6 and 2.5%, or alternatively, may be set to a value
of between about 2 and 4%.
[0021] The flotation step may be performed in a selectively
functioning flotation cell.
[0022] The suspension to be purified may further contain adhesive
particles.
[0023] Before the flotation step, the suspension may be subjected
to a chemical treatment in which surface activity of the
interfering materials is increased.
[0024] The fibrous suspension may be dispersed before the flotation
process or alternatively, before the wet straining process. A
specific work of at least 20 kWh/to may be transmitted to the
fibrous suspension during the dispersion of the fibrous
suspension.
[0025] The invention also provides for a process for removing fine
impurities from a fibrous suspension, comprising conveying the
fibrous suspension to at least one sorting device, separating the
fibrous suspension using the at least one sorting device into an
accepts portion and a rejects portion, finishing at least some of
the accepts portion leaving the at least one sorting device using a
finishing device, separating at least some portion of the rejects
portion leaving the at least one sorting device using at least one
last sorting device into an accepts portion and an rejects portion,
separating at least some portion of the accepts portion leaving the
at least one last sorting device into an accepts portion and a
rejects portion using a flotation device, and finishing at least
some portion of the accepts portion leaving the flotation device
using the finishing device.
[0026] At least one intermediate sorting device may be arranged
between the at least one sorting device and the at least one last
sorting device, and the process may further comprise separating at
least some of the rejects portion leaving the at least one sorting
device using the at least one intermediate sorting device into an
accepts portion and a rejects portion, and finishing at least some
of the accepts portion leaving the at least one intermediate
sorting device using the finishing device. The process may further
comprise conveying at least some of the rejects portion leaving the
at least one intermediate sorting device to the at least one last
sorting device.
[0027] At least one intermediate sorting device may be arranged
between the at least one sorting device and the at least one last
sorting device and an additional flotation device, and the process
may further comprise separating at least some of the rejects
portion leaving the at least one sorting device using the at least
one intermediate sorting device into an accepts portion and a
rejects portion, separating at least some of the accepts portion
leaving the at least one intermediate sorting device using the
additional flotation device into an accepts portion and a rejects
portion, and finishing at least some of the accepts portion leaving
the additional flotation device using the finishing device. The
process may further comprise conveying at least some of the rejects
portion leaving the at least one intermediate sorting device to the
at least one last sorting device.
[0028] At least a first and a second intermediate sorting device
may be arranged between the at least one sorting device and the at
least one last sorting device, and the process may further comprise
separating at least some of the rejects portion leaving the at
least one sorting device using the first intermediate sorting
device into an accepts portion and a rejects portion, separating at
least some of the accepts portion leaving the first intermediate
sorting device using the second intermediate sorting device into an
accepts portion and a rejects portion, and finishing at least some
of the accepts portion leaving the second intermediate sorting
device using the finishing device. The process may further comprise
conveying at least some of the rejects portion leaving each of the
first and second intermediate sorting devices to the at least one
last sorting device.
[0029] An additional sorting device may be arranged after the at
least one last sorting device, and the process may further comprise
separating at least some of the rejects portion leaving the at
least one last sorting device using the at least one additional
sorting device into an accepts portion and a rejects portion, and
conveying at least some of the accepts portion leaving the
additional sorting device to the at least one last sorting
device.
[0030] A first and a second intermediate sorting device may be
arranged between the at least one sorting device and the at least
one last sorting device and further comprising an additional
sorting device arranged after the at least one last sorting device,
and the process may further comprise separating at least some of
the rejects portion leaving the at least one sorting device using
the first intermediate sorting device into an accepts portion and a
rejects portion, separating at least some of the accepts portion
leaving the first intermediate sorting device using the second
intermediate sorting device into an accepts portion and a rejects
portion, separating at least some of the rejects portion leaving
the at least one last sorting device using the additional sorting
device into an accepts portion and a rejects portion, and finishing
at least some of the accepts portion leaving the second
intermediate sorting device using the finishing device. The process
may further comprise conveying at least some of the accepts portion
leaving the additional sorting device to the flotation device. The
process may further comprise conveying at least some of the rejects
portion leaving each of the first and second intermediate sorting
devices to the at least one last sorting device.
[0031] Before the conveying of the fibrous suspension to at least
one sorting device, the process may comprise subjecting the fibrous
suspension to at least one of dissolution and pre-purification.
Before the conveying of the fibrous suspension to at least one
sorting device, the process may comprise subjecting the fibrous
suspension to each of dissolution and pre-purification.
[0032] The process may further comprise removing ink particles
during pre-purification. The ink particles may be removed by
flotation during pre-purification. The flotation device may perform
a flotation separation without chemicals. The flotation device may
perform a flotation separation without chemicals used to remove
inks. The flotation device may perform a flotation separation
without flotation chemicals. At least one of the at least one
sorting device and the at least one last sorting device may
comprise a pressure sorter. The pressure sorter may be equipped
with at least one wire. The at least one wire may have openings.
The openings may comprise slits having a width of between about
0.08 and 0.5 mm. The openings may comprise holes having a diameter
of between about 0.8 and 3 mm. A dry matter content of the fibrous
suspension before entering the at least one sorting device may be
between about 0.6 and 2.5%. A dry matter content of the fibrous
suspension before entering the at least one sorting device may be
between about 2 and 4%. The flotation device may comprise a
selectively functioning flotation cell. The fibrous material
suspension may comprise adhesive particles.
[0033] The process may further comprise chemically treating the
fibrous material suspension in order to increase a surface activity
of interfering materials, the chemical treatment occurring prior to
the flotation device. Before the conveying of the fibrous
suspension to at least one sorting device, the process may comprise
subjecting the fibrous suspension to dispersion, and further
comprising transmitting a specific work of at least 20 kWh/to to
the fibrous suspension during the dispersion.
[0034] The invention further provides for an apparatus for removing
fine impurities from a fibrous suspension, comprising at least one
sorting device arranged to receive the fibrous suspension, the
least one sorting device separates the fibrous suspension into an
accepts portion and a rejects portion, a finishing device for
finishing at least some of the accepts portion leaving the at least
one sorting device, at least one last sorting device for separating
at least some portion of the rejects portion leaving the at least
one sorting device into an accepts portion and an rejects portion,
and a flotation device for separating at least some portion of the
accepts portion leaving the at least one last sorting device into
an accepts portion and a rejects portion, wherein at least some
portion of the accepts portion leaving the flotation device is
subjected to finishing using the finishing device.
[0035] The apparatus may further comprise at least one intermediate
sorting device arranged between the at least one sorting device and
the at least one last sorting device, wherein at least some of the
rejects portion leaving the at least one sorting device is
separated using the at least one intermediate sorting device into
an accepts portion and a rejects portion, and wherein at least some
of the accepts portion leaving the at least one intermediate
sorting device is subjected to finishing using the finishing
device. At least some of the rejects portion leaving the at least
one intermediate sorting device may be conveyed to the at least one
last sorting device.
[0036] The apparatus may further comprise at least one intermediate
sorting device arranged between the at least one sorting device and
the at least one last sorting device and an additional flotation
device, wherein at least some of the rejects portion leaving the at
least one sorting device is separated using the at least one
intermediate sorting device into an accepts portion and a rejects
portion, wherein at least some of the accepts portion leaving the
at least one intermediate sorting device is separated using the
additional flotation device into an accepts portion and a rejects
portion, and wherein at least some of the accepts portion leaving
the additional flotation device is subjected to finishing using the
finishing device. At least one of the rejects portion leaving the
at least one intermediate sorting device may be conveyed to the at
least one last sorting device.
[0037] The apparatus may further comprise at least a first and a
second intermediate sorting device arranged between the at least
one sorting device and the at least one last sorting device,
wherein at least some of the rejects portion leaving the at least
one sorting device is separated using the first intermediate
sorting device into an accepts portion and a rejects portion,
wherein at least some of the accepts portion leaving the first
intermediate sorting device is separated using the second
intermediate sorting device into an accepts portion and a rejects
portion, and wherein at least some of the accepts portion leaving
the second intermediate sorting device is subjected to finishing
using the finishing device. At least some of the rejects portion
leaving each of the first and second intermediate sorting devices
may be conveyed to the at least one last sorting device.
[0038] The apparatus may further comprise an additional sorting
device arranged after the at least one last sorting device, wherein
at least some of the rejects portion leaving the at least one last
sorting device is separates using the at least one additional
sorting device into an accepts portion and a rejects portion, and
wherein at least some of the accepts portion leaving the additional
sorting device is conveyed to the at least one last sorting
device.
[0039] The apparatus may further comprise a first and a second
intermediate sorting device arranged between the at least one
sorting device and the at least one last sorting device and further
comprising an additional sorting device arranged after the at least
one last sorting device, wherein at least some of the rejects
portion leaving the at least one sorting device is separated using
the first intermediate sorting device into an accepts portion and a
rejects portion, wherein at least some of the accepts portion
leaving the first intermediate sorting device is separated using
the second intermediate sorting device into an accepts portion and
a rejects portion, wherein at least some of the rejects portion
leaving the at least one last sorting device is separated using the
additional sorting device into an accepts portion and a rejects
portion, and wherein at least some of the accepts portion leaving
the second intermediate sorting device is subjected to finishing
using the finishing device. At least some of the accepts portion
leaving the additional sorting device may be conveyed to the
flotation device. At least some of the rejects portion leaving each
of the first and second intermediate sorting devices may be
conveyed to the at least one last sorting device.
[0040] Before the fibrous suspension is conveyed to at least one
sorting device, the fibrous suspension may be subjected to at least
one of dissolution in a dissolution device and pre-purification in
a pre-purification device. Before the fibrous suspension is
conveyed to at least one sorting device, the fibrous material
suspension may be subjected to each of dissolution and
pre-purification.
[0041] Ink particles may be removed during pre-purification. The
ink particles may be removed by flotation during pre-purification.
The flotation device may perform a flotation separation without
chemicals. The flotation device may perform a flotation separation
without chemicals used to remove inks. The flotation device may
perform a flotation separation without flotation chemicals. At
least one of the at least one sorting device and the at least one
last sorting device may comprise a pressure sorter. The pressure
sorter may be equipped with at least one wire. The at least one
wire may have openings. The openings may comprise slits having a
width of between about 0.08 and 0.5 mm. The openings may comprise
holes having a diameter of between about 0.8 and 3 mm. A dry matter
content of the fibrous suspension before entering the at least one
sorting device may be between about 0.6 and 2.5%. A dry matter
content of the fibrous suspension before entering the at least one
sorting device may be between about 2 and 4%. The flotation device
may comprise a selectively functioning flotation cell. The fibrous
material suspension may comprise adhesive particles. The fibrous
material suspension may be chemically treated in order to increase
a surface activity of interfering materials, the chemical treatment
occurring prior to the flotation device. Before the fibrous
suspension is conveyed to at least one sorting device, the fibrous
suspension may be subjected to dispersion, and wherein a specific
work of at least 20 kWh/to is transmitted to the fibrous suspension
during the dispersion.
[0042] Other exemplary embodiments and advantages of the present
invention may be ascertained by reviewing the present disclosure
and the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] The present invention is further described in the detailed
description which follows, in reference to the noted plurality of
drawings by way of non-limiting examples of certain embodiments of
the present invention, in which like numerals represent like
elements throughout the several views of the drawings, and
wherein:
[0044] FIG. 1 shows a basic process schematic for carrying out the
process according to an embodiment of the present invention;
[0045] FIG. 2 shows a basic process schematic for carrying out the
process according to a second embodiment of the present
invention;
[0046] FIG. 3 shows a basic process schematic for carrying out the
process according to a third embodiment of the present
invention;
[0047] FIG. 4 shows a basic process schematic for carrying out the
process according to a fourth embodiment of the present
invention;
[0048] FIG. 5 shows a basic process schematic for carrying out the
process according to a fifth embodiment of the present
invention;
[0049] FIG. 6 shows a basic process schematic for carrying out the
process according to a sixth embodiment of the present invention;
and
[0050] FIG. 7 shows a basic process schematic for carrying out the
process according to a seventh embodiment of the present
invention.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0051] The particulars shown herein are by way of example and for
purposes of illustrative discussion of the embodiments of the
present invention only and are presented in the cause of providing
what is believed to be the most useful and readily understood
description of the principles and conceptual aspects of the present
invention. In this regard, no attempt is made to show structural
details of the present invention in more detail than is necessary
for the fundamental understanding of the present invention, the
description taken with the drawings making apparent to those
skilled in the art how the several forms of the present invention
may be embodied in practice.
[0052] In multistep wet straining, rejects of a sorting step are
introduced into a subsequent sorting step. The accepted stock
quality differs depending on whether the step is the first, second,
or a subsequent step. The content of the interfering materials of
the accepted stock generally increases from step to step. A certain
amount of interfering materials to be sorted will invariably get
into the accepted stock, even if this amount is small. The accepted
stock of the last step has the highest comparative percentage of
interfering materials because of the increase in the dirt content
from step to step, especially with interfering materials that are
very fine or are not very dimensionally stable. These interfering
materials can easily get into the accepted stock during the wet
straining process. In particular instances, the content of the
interfering materials can also be the highest in the accepted stock
of the sorting device that does not belong to the last step.
[0053] The "accepts" quantity decreases from step to step and the
percentage of interfering materials increases. Fine interfering
materials can be separated out effectively by a flotation process
provided that the materials are hydrophobic. These materials
include adhesives (also called "stickies"). The present invention
economically removes much of this fine interfering material.
[0054] The present invention uses a flotation process, which
functions selectively, i.e., it leaves the hydrophilic fibers in
the accepted stock and concentrates on only the interfering
materials in the flotation foam. Selective flotation processes of
this kind are widely known in the art and are, therefore, not
explained in detail. The suspension is prepared before the actual
flotation so that as great as possible a percentage of the
interfering materials contained therein can be floated. The
preparation of the suspension can be executed either mechanically
or chemically. For example chemical means may be used to increase
the surface activity of the materials to be floated out, in order
to intensify their hydrophobic nature.
[0055] Referring to the drawings wherein like numerals represent
like elements, FIG. 1 shows the division of the process into the
individual steps: dissolution 1 (by a dissolution device),
pre-purification 2 (by a pre-purification device), wet straining 3
(by a wet straining device), flotation 4 (by a flotation device),
and finishing 5 (by a finishing device). In dissolution 1, paper
stock to be processed is mixed with water and broken down to the
point that a pumpable suspension is produced. This suspension may
also be speck-free. Pre-purification 2 is also carried out early in
the process, e.g., with the aid of hydrocyclones or junk sorters.
Removal of printing inks, known as de-inking, can also be carried
out at the pre-purification step 2. The dissolution 1 can also be
continuously performed at the de-inking process. The suspension can
be deflaked or dispersed and thus prepared for the wet straining
process 3. During dispersion, a specific work of at least 20 kWh/to
is transmitted to the fibrous suspension. The dissolution 1 and
pre-purification 2 processes are usually not separate and discrete,
as shown in the Figures, but take place in partial steps and in an
alternating manner.
[0056] After execution of these dissolution 1 and pre-purification
2 steps, the suspension S travels into the multistep wet straining
device 3. In the example shown, the wet straining device 3 includes
a respective first sorting device 7, a second sorting device 7' and
a third sorting device 7". At least one wire is disposed in each of
the sorting devices 7, 7', 7", which divides the incoming
suspension S into an "accepts" portion 9, 9', or 9" and a "rejects"
portion 8, 8', or 8". Each sorting device 7, 7', 7" performs a
respective first, second and last sorting step 6. The sorting
devices 7, 7', 7" are connected so that the subsequent step
respectively receives the "rejects" portion of the preceding step.
In the present invention, the "rejects" portions 8, 8', or 8" may
vary in magnitude from each other.
[0057] The wet straining process 3 shown in FIG. 1 has three steps.
The "accepts" portion 9" of the last step 6 is treated in by a
flotation device 4 in a flotation step, for which a flotation cell
12 is used. The fine interfering materials are removed as
completely as possible in the "rejects" portion 11, and the
purified fibrous suspension travels as an "accepts" portion 10,
together with the remaining "accepts" portions 9, 9', into the
finishing device 5 of the finishing step.
[0058] While FIG. 1 shows a three step wet straining 3, it is
readily appreciable by those skilled in the art that more or fewer
than three wet straining steps may be used in alternative
embodiments. FIG. 2 shows a two-step wet straining process 3. The
number of wet straining steps 3 used in the invention depends on
individual specific conditions and requirements, and the needs of
the user.
[0059] As shown in FIG. 3, the sorting device 7' of the
wet-straining step 3 may also be combined with a flotation step 4.
Thus, the wet straining process 3 can be made more efficient when
excessive interfering material quantities are already contained by
the sorting device 7' of the wet-straining step 3. In certain
instances, a last step 6 is performed at the sorting device 7"
(e.g., by means of very fine wire openings) so that few interfering
materials get into the "accepts" portion at this step.
Additionally, the flotation of the "accepts" portion of the sorting
device 7' of the wet-straining step 3 alone may suffice.
[0060] The "accepts" portion 9' of the sorting device 7' (i.e., the
second step), together with the "accepts" portion 9" of the sorting
device 7" (i.e., at the last step 6), could also be introduced into
a single flotation cell 12 in alternative embodiments.
[0061] In the embodiment shown in FIG. 4, the accepted stock of the
sorting device 7' (i.e., the second step) is improved. Two sorting
devices 7' are connected in series with respect to the accepted
stock and the combined "rejects" 8" are supplied into the sorting
device 7" of the last step 6. The "accepts" portion 9' of the
second step is then combined with the "accepts" portion 9 from the
first step.
[0062] FIG. 5 shows a variant of multistep wet straining 3. In this
variant, the "rejects" 8" from the last step 6 are introduced into
an additional sorting device 13. An "accepts" portion 15 of this
additional sorting device 13 is returned and travels into the
sorting device 7", together with the "rejects" portion 8 of the
first step, into the sorting device 7" of the last step 6. The
"rejects" portion 14 of the sorting device 13 is conveyed out of
the system.
[0063] Referring to FIG. 6, the "accepts" portions 9" of last two
steps 6 and 6' are purified in the flotation step 4. Step 6' is
performed at an intermediate sorting device 7"'. The embodiment of
FIG. 6 is useful in that oftentimes, there are impurities in the
"accepts" portion of the second sorting device 7'. There is thus an
additional opportunity for the removal of impurities after the
suspension leaves the second sorting device 7'. The sorting devices
7' of the second step can be operated at a higher flow rate since
the suspension S is further purified further as an "accepts"
portion. As a result, the last sorting device 7" is smaller or it
can be operated more effectively.
[0064] FIG. 7 shows an additional embodiment of the
pre-purification device 2. A majority of ink particles are removed
from the fibrous suspension, e.g., by means of flotation. The
process according to the invention leads to an improvement in stock
quality. The flotation step 4 is particularly effective if it can
be exclusively tailored to those interfering materials that can be
floated, such as adhesive and hot-melting interfering materials,
known as "stickies," which, unlike inks, can often be easily
removed and with fewer chemicals. The flotation 4 step is
especially useful if inks need not be entirely removed, e.g. raw
materials for packaging papers.
[0065] The sorting devices 7, 7', 7" are influenced by stock
density and the size of the sorting device wire openings. Fibrous
suspensions are often sorted in a preparation system, e.g., with
stock densities of approximately 2 to 4% and perforated wires of
approximately 2 mm. Furthermore, suspensions are also sorted at
other locations with slits that have a width of approximately 0.2
mm and stock densities under about 1%. The process according to the
invention can be used for both above examples, wherein results
often differ. In sorters with slits of approximately 0.2 mm in
width, stock densities of around 2 to 3% are still possible. These
densities lead to a relatively large mass throughput with a
favorable sorting quality and, therefore, lead to optimal and
economical operation. However, as problems often arise with
adhesive interfering materials ("stickies"), the process according
to the invention is particularly useful.
[0066] It is noted that the foregoing examples have been provided
merely for the purpose of explanation and are in no way to be
construed as limiting of the present invention. While the present
invention has been described with reference to certain embodiments,
it is understood that the words which have been used herein are
words of description and illustration, rather than words of
limitation. Changes may be made, within the purview of the appended
claims, as presently stated and as amended, without departing from
the scope and spirit of the present invention in its aspects.
Although the present invention has been described herein with
reference to particular means, materials and embodiments, the
present invention is not intended to be limited to the particulars
disclosed herein; rather, the present invention extends to all
functionally equivalent structures, methods and uses, such as are
within the scope of the appended claims.
* * * * *