U.S. patent application number 10/042718 was filed with the patent office on 2003-06-19 for system and method for improving the movement and discharge of material from vessels.
Invention is credited to Marcoccia, Bruno S., Prough, James Robert, Torregrossa, Louis O..
Application Number | 20030111200 10/042718 |
Document ID | / |
Family ID | 23197760 |
Filed Date | 2003-06-19 |
United States Patent
Application |
20030111200 |
Kind Code |
A1 |
Prough, James Robert ; et
al. |
June 19, 2003 |
System and method for improving the movement and discharge of
material from vessels
Abstract
Systems, methods, and vessels for reducing the stagnation and
non-uniform flow or treatment of solid materials and slurries in
vessels. The non-uniform flow or treatment that may characterize
the storage or treatment of solid materials in process industries
is minimized or eliminated by the introduction of liquid to the
bottom heads of the vessels, in particular, the introduction of
liquids in regions in the bottom heads where friction and
compression cause stagnation in the flow of material. The liquid
may be introduced by means of one or more nozzles, for example, one
or more evenly-spaced nozzles, and the flow of liquid to each
nozzle may be individually controlled. Though the systems, methods,
and vessels disclosed may be used in the processing of cellulose
materials, aspects of the present invention may be used in any
process or materials handling industry application where solid
materials or slurries are handled in vessels.
Inventors: |
Prough, James Robert;
(Saratoga, NY) ; Marcoccia, Bruno S.; (Peachtree
City, GA) ; Torregrossa, Louis O.; (Queensbury,
NY) |
Correspondence
Address: |
John Pietrangelo, Patent Agent
Heslin Rothenberg Farley & Mesiti P.C.
5 Columbia Circle
Albany
NY
12203
US
|
Family ID: |
23197760 |
Appl. No.: |
10/042718 |
Filed: |
July 16, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60309332 |
Aug 2, 2001 |
|
|
|
Current U.S.
Class: |
162/233 ;
162/237; 162/246; 422/129; 68/181R; 8/156 |
Current CPC
Class: |
D21C 7/14 20130101; D21C
7/06 20130101 |
Class at
Publication: |
162/233 ;
162/237; 162/246; 8/156; 422/129; 68/181.00R |
International
Class: |
D21C 007/06; D21C
007/08 |
Claims
1. A system for improving the movement of material in a vessel, the
vessel having an inlet, an outlet, a cylindrical portion having an
outer dimension, and a converging transition between the
cylindrical portion and the outlet, the system comprising: means
for introducing at least some liquid to the converging transition
at a location having a diameter greater than about 75% of the outer
dimension of the cylindrical portion of the vessel.
2. The system as recited in claim 1, wherein the means for
introducing at least some liquid to the converging transition
comprises a diameter greater than about 90% of the outer dimension
of the cylindrical portion of the vessel.
3. The system as recited in claim 1 wherein the cylindrical vessel
comprises a circular cylindrical vessel.
4. The system as recited in claim 3, wherein the outer dimension of
the circular cylindrical vessel comprises an outer diameter.
5. The system as recited in claim 1, wherein the means for
introducing at least some liquid comprises at least one nozzle.
6. The system as recited in claim 5, wherein the means for
introducing at least some liquid comprises a plurality of
evenly-spaced nozzles.
7. The system as recited in claim 6, wherein the vessel comprises a
vessel having a longitudinal axis and wherein the plurality of
evenly-spaced nozzles are oriented parallel to the longitudinal
axis of the vessel.
8. The system as recited in claim 6, wherein the vessel comprises a
vessel having a longitudinal axis and wherein the plurality of
evenly-spaced nozzles are oriented at an angle .alpha. to the
longitudinal axis of the vessel.
9. The system as recited in claim 8, wherein the angle .alpha.
ranges from about 30 degrees to about 60 degrees.
10. The system as recited in claim 1, wherein the vessel further
comprises at least one set of dilution nozzles evenly-spaced about
the outlet at a first diameter, and wherein the means for
introducing at least some liquid to the converging transition is
positioned at a second diameter greater than the first
diameter.
11. The system as recited in claim 10, wherein the means for
introducing at least some liquid comprises a plurality of
evenly-spaced nozzles positioned at a second diameter greater than
the first diameter.
12. The system as recited in claim 1, wherein the vessel further
comprises at least one baffle plate positioned in the converging
transition, and wherein the means for introducing at least some
liquid to the converging transition is positioned between the at
least one baffle plate and the outlet.
13. The system as recited in claim 12, wherein the means for
introducing at least some liquid comprises a plurality of
evenly-spaced nozzles.
14. The system as method as recited in claim 1, wherein the
cylindrical vessel comprises one of a continuous digester, a batch
digester, a washing vessel, a bleaching vessel, a storage vessel,
and a retention vessel.
15. A method of treating particulate material in a cylindrical
vessel having an interior, an inlet into which particulate material
is introduced, and an outlet from which particulate material is
discharged, the method comprising: causing the particulate material
to flow in the vessel interior in a substantially vertical flow
path; causing at least some of the particulate material to flow in
a non-vertical flow path toward the outlet by providing a
converging transition to the outlet; and introducing a liquid to
the converging transition to reduce the resistance to flow of the
particulate material through the converging transition to the
outlet.
16. The method as recited in claim 15, wherein the vessel comprises
a vessel having an outer dimension and wherein introducing a liquid
to the converging transition comprises introducing a liquid to the
converging transition at a location having a diameter which is
greater than about 75% of the outer dimension of the vessel.
17. The method as recited in claim 16, wherein introducing a liquid
to the converging transition comprises introducing a liquid to the
converging transition at a location having a diameter which is
greater than about 90% of the outer dimension of the vessel.
18. The method as recited in claim 15, wherein providing a
converging transition comprises providing a dished head having a
knuckle, and wherein introducing a liquid to the converging
transition comprises introducing a liquid to the knuckle of the
dished head.
19. The method as recited in claim 15, wherein providing a
converging transition comprises providing a conical transition
having a first diameter and a second diameter smaller than the
first diameter.
20. The method as recited in claim 19, wherein introducing a liquid
to the converging transition comprises introducing a liquid to the
vicinity of the second diameter of the conical transition.
21. The method as recited in claim 15, wherein introducing a liquid
to the converging transition comprises introducing a liquid to a
plurality of nozzles positioned in the converging transition.
22. The method as recited in claim 21, wherein introducing liquid
to a plurality of nozzles comprises controlling the flow of liquid
through at least one of the plurality of nozzles.
23. The method of claim 15, wherein the particulate material
comprises a comminuted cellulosic fibrous material.
24. The method as recited in claim 15, wherein the cylindrical
vessel comprises one of a continuous digester, a batch digester, a
washing vessel, a bleaching vessel, a storage vessel, and a
retention vessel.
25. A digester for treating comminuted cellulosic fibrous material,
the digester comprising: an inlet for introducing comminuted
cellulosic fibrous material; a circular cylindrical portion having
an outer diameter; an outlet for discharging treated comminuted
cellulosic fibrous material; a converging transition between the
circular cylindrical portion and the outlet; and means for
introducing at least some liquid to the converging transition at a
location having a diameter greater than about 75% of the outer
diameter of the circular cylindrical portion of the digester.
26. The digester as recited in claim 25, wherein the means for
introducing at least some liquid to the converging transition has a
diameter greater than about 90% of the outer diameter of the
circular cylindrical portion of-the digester.
27. The digester as recited in claim 25, wherein the means for
introducing at least some liquid comprises a plurality of
evenly-spaced nozzles.
28. The digester as recited in claim 25, wherein the digester
further comprises at least one set of dilution nozzles
evenly-spaced about the outlet at a first diameter, and wherein the
means for introducing at least some liquid to the converging
transition is positioned at a second diameter greater than the
first diameter.
29. The digester as recited in claim 28, wherein the means for
introducing at least some liquid comprises a plurality of
evenly-spaced nozzles positioned at a second diameter.
30. The digester as recited in claim 25, wherein the digester
further comprises at least one baffle plate positioned in the
converging transition, and wherein the means for introducing at
least some liquid to the converging transition is positioned
between the at least one baffle plate and the outlet.
31. The digester as recited in claim 30, wherein the means for
introducing at least some liquid comprises a plurality of
evenly-spaced nozzles.
32. The digester as recited in claim 31, wherein the digester
comprises a digester having a longitudinal axis, and wherein the
plurality of evenly-spaced nozzles comprise a plurality of
evenly-spaced nozzles oriented parallel to the longitudinal axis of
the digester.
33. The digester as recited in claim 31, wherein the vessel
comprises a vessel having a longitudinal axis and wherein the
plurality of evenly-spaced nozzles comprise nozzles oriented at an
angle .alpha. to the longitudinal axis of the vessel.
34. The digester as recited in claim 33, wherein the angle .alpha.
comprises an angle which ranges from about 30 degrees to about 60
degrees.
35. A method of treating comminuted cellulosic fibrous material in
a digester, the digester having an interior, an inlet for
introducing comminuted cellulosic fibrous material, and an outlet
for discharging treated comminuted cellulosic fibrous material, the
method comprising: causing the comminuted cellulosic fibrous
material to flow in the digester interior in a substantially
vertical flow path; causing at least some of the comminuted
cellulosic fibrous material to flow in a non-vertical flow path
toward the outlet by providing a converging transition to the
outlet; and introducing a liquid to the converging transition to
reduce the resistance to flow of the comminuted cellulosic fibrous
material through the converging transition to the outlet.
36. The method as recited in claim 35, wherein the digester
comprises a vessel having an outer diameter and wherein introducing
a liquid to the converging transition comprises introducing a
liquid to the converging transition at a location having a diameter
greater than about 75% of the outer diameter of the vessel.
37. The method as recited in claim 36, wherein introducing a liquid
to the converging transition comprises introducing a liquid to the
converging transition at a location having a diameter greater than
about 90% of the outer diameter of the vessel.
38. The method as recited in claim 35, wherein providing a
converging transition comprises providing a conical transition
having a first diameter and a second diameter smaller than the
first diameter.
39. The method as recited in claim 38, wherein introducing a liquid
to the converging transition comprises introducing a liquid to the
vicinity of the second diameter of the conical transition.
40. The method as recited in claim 39, wherein introducing a liquid
to the converging transition comprises introducing a liquid to a
plurality of nozzles positioned in the converging transition.
41. The method as recited in claim 40, wherein introducing liquid
to a plurality of nozzles comprises controlling the flow of liquid
through at least one of the plurality of nozzles.
42. The method of claim 35, wherein the digester comprises one of a
continuous digester and a batch digester.
43. The method as recited in claim 35, wherein causing the
comminuted cellulosic fibrous material to flow in the digester
interior in a substantially vertical flow path comprises causing
the comminuted cellulosic fibrous material to flow in the digester
interior in a substantially vertical downward flow.
44. The method as recited in claim 35, further comprising forming a
zone of compression in the converging transition wherein the
particulate material is compressed and resistance to flow is
increased.
45. The method as recited in claim 44, wherein introducing a liquid
to the converging transition comprises introducing a liquid to the
zone of compression in the converging transition.
46. The method as recited in claim 15, further comprising forming a
zone of compression in the converging transition wherein the
particulate material is compressed and resistance to flow is
increased.
47. The method as recited in claim 46, wherein introducing a liquid
to the converging transition comprises introducing a liquid to the
zone of compression in the converging transition.
48. The system as recited in claim 1, wherein the means for
introducing at least some liquid comprises means for controlling
the flow of the at least some liquid.
49. The system as recited in claim 2, wherein the means for
introducing at least some liquid comprises means for controlling
the flow of the at least some liquid.
50. The system as recited in claim 5, wherein the means for
introducing at least some liquid comprises means for controlling
the flow of the at least some liquid to the at least one
nozzle.
51. The system as recited in claim 10, wherein the means for
introducing at least some liquid to the converging transition at a
second diameter comprises means for controlling the flow of the at
least some liquid.
52. The method as recited in claim 19, wherein introducing a liquid
to the converging transition comprises introducing a liquid to the
vicinity of the first diameter of the conical transition.
53. The method as recited in claim 20, wherein introducing a liquid
to the converging transition further comprises introducing a liquid
to the vicinity of the first diameter of the conical
transition.
54. The digester as recited in claim 25, wherein the means for
introducing at least some liquid comprises means for controlling
the flow of the at least some liquid.
55. The digester as recited in claim 27, wherein the means for
introducing at least some liquid comprises means for controlling
the flow of the at least some liquid to the plurality of
evenly-spaced nozzles.
56. The system as recited in claim 1, wherein the converging
transition comprises an outer surface and wherein the means for
introducing at least some liquid comprises means for introducing at
least some liquid having a location wherein a line drawn tangent to
the outer surface at the location defines an angle .phi. with the
horizontal.
57. The system as recited in claim 56, wherein the angle .phi.
comprises an angle ranging from about 45 degrees to about 75
degrees.
58. The method as recited in claim 15, wherein the converging
transition comprises an outer surface and wherein introducing a
liquid to the converging transition comprises introducing the
liquid at a location wherein a line drawn tangent to the outer
surface at the location defines an angle .phi. with the
horizontal.
59. The method as system as recited in claim 58, wherein the angle
.phi. comprises an angle ranging from about 45 degrees to about 75
degrees.
60. The digester as recited in claim 25, wherein the converging
transition comprises an outer surface and wherein the means for
introducing at least some liquid comprises means for introducing at
least some liquid having a location wherein a line drawn tangent to
the outer surface at the location defines an angle .phi. with the
horizontal.
61. The digester as recited in claim 60, wherein the angle .phi.
comprises an angle ranging from about 45 degrees to about 75
degrees.
62. The method as recited in claim 35, wherein the converging
transition comprises an outer surface and wherein introducing a
liquid to the converging transition comprises introducing the
liquid at a location wherein a line drawn tangent to the outer
surface at the location defines an angle .phi. with the
horizontal.
63. The method as system as recited in claim 62, wherein the angle
.phi. comprises an angle ranging from about 45 degrees to about 75
degrees.
Description
REFERENCE TO RELATED APPLICATIONS
[0001] This application draws priority from U.S. Provisional Patent
application No. 60/309,332 filed on Aug. 2, 2001 (attorney ref.
2065.005 P). The disclosure of this Provisional Patent Application
is incorporated by reference herein in its entirety.
TECHNICAL FIELD
[0002] This invention relates generally to systems and methods for
improving the movement of solid materials in vessels and the
discharge of solid materials from vessels. Specifically, the
present invention provides systems and methods for improving the
movement and discharge of comminuted cellulosic fibrous material in
treatment vessels, for example, in the pulping process.
BACKGROUND OF THE INVENTION
[0003] In many process industries, cylindrical vessels are used to
store or treat the materials processed. For example, in the Pulp
and Paper Industry, solid materials are handled and treated in
assorted vessels. These materials typically include softwood or
hardwood chips, recycled papers, and cellulose pulp, among other
types of materials. Often, the movement of solid materials in
treatment and storage vessels or the discharge of the solid
materials from treatment or storage vessels is critical to the
effectiveness and efficiency of the process being performed. For
example, in vessels where treatment or retention time or uniformity
of treatment chemical concentration can affect the quality of the
product produced, discontinuous, interrupted, or non-uniform
movement or discharge of the material from the vessels can
dramatically adversely effect the quality of the product produced.
The adverse effects upon the quality of the product can be the
result of either non-uniform flow of material, non-uniform flow of
treatment fluids, non-uniform temperature distribution, non-uniform
treatment chemical concentrations, or combinations thereof.
[0004] For example, in the Chemical Pulping Industry, comminuted
fibrous materials, such as softwood or hardwood chips, are treated
with treatment chemicals at time, temperature, and pressure. In the
processing of wood chips, the non-uniform movement of wood chips
and treatment liquids, for example, kraft treatment liquor, can
significantly affect the time, temperature, and chemical
concentrations at which chips are treated. Specifically, the
quality of the pulp produced, for example, the pulp's cooking
uniformity, strength characteristics, and brightness, among other
things, can be adversely affected by the non-uniform movement of
the chips or the treatment liquid during treatment.
[0005] Though common to many process and material handling
industries, in the Pulping Industry, treatment of wood chips, and
other forms of comminuted cellulosic fibrous material, is typically
performed in tall cylindrical vessels or reactors, and the like,
for example, one typical reactor vessel used in the art is referred
to as a "digester". Typically, wood chips are introduced at an
inlet at the top of these vessels and as the chips proceed
downward, typically under the force of gravity, the chips are
treated with cooking chemical, for example, kraft white or black
liquor, as liquid streams containing the cooking chemical are
introduced and removed from the chips as they proceed downward.
Typically, the movement of treatment liquids relative to the wood
chips, for example, laterally or vertically between the interstices
of the wood chips, is often critical to the uniform distribution of
cooking chemical and temperature during the treatment process--a
process referred to in the art as "cooking". Non-uniformities in
temperature or chemical distribution in the vertical treatment
vessel can result in non-uniformly-cooked chips, for example,
over-cooked or under-cooked chips, which can affect the efficiency
of the cooking process, for example, the degree of delignification,
or the efficient use of cooking chemical, or the quality of the
product produced, among other things, or a combination thereof.
[0006] In vertical treatment vessels, the uniformity of temperature
and chemical distribution are also affected by the compression
within the column of material, often referred to as the "chip
column". As the material proceeds through the vessel, typically
downward from the inlet to the outlet, the weight of the material
and liquid above the material increases wherein the material near
the bottom of the vessel is more compressed than the material at
the top of the vessel. This compression within the chip column can
interfere with movement of treatment liquids in the chip column by,
among other things, compressing the chips and reducing the
interstitial spaces between chips and thus reducing the pathways
for liquid movement. Compression in the chip column further
exacerbates non-uniform liquid movement when the material being
handled is a flexible or pliable material, such as wood chips,
which deform under the force of compression and further limit the
size of potential liquid pathways. In downward-flowing treatment
vessels, having outlets at the bottom, this compression is highest
in the discharge zone of vertical vessels. Thus, there is a need in
the art to minimize or reduce non-uniform treatment in vessels due
to material compression.
[0007] Discharge zones of treatment vessels in the Pulping Industry
typically include some form of converging transition, for example,
a transition from a vertical vessel wall at one diameter to a
centrally-located discharge having a second diameter, smaller than
the vessel diameter. This converging transition typically causes
the path of material flow to change from an essentially vertical
direction to a somewhat horizontal direction. This convergence
provides additional material compression which can further limit
the flow of treatment liquid though the material. This convergence
can also provide an obstruction to the uniform flow of material,
which again, can affect the uniformity of treatment of the
material. Thus, there is a need in the art to provide treatment
vessels and treatment methods that reduce or minimize non-uniform
treatment due to convergent flow in the outlets of treatment
vessels.
[0008] In vertical cylindrical vessels, the uniformity of the
movement of material, for example, from an inlet at the top to an
outlet at the bottom, can be significantly affected by the
uniformity of the discharge at the bottom of the vertical vessel.
Discharge zones in vessels used in the Pulping Industry often
include an agitating device, for example, a rotating agitator, to
assist in promoting discharge of the material out of the outlet.
Since the flow of material out the bottom of a vessel can affect
the movement of the material above the outlet of the vessel, a
non-uniform discharge of material out the bottom of the vessel can
interfere with the desired uniform movement and treatment in the
vessel above. Thus, there is also a need in the art to provide
systems and methods for improving the uniformity of discharge of
solid material from vessels.
SUMMARY OF THE INVENTION
[0009] The present invention provides methods and systems which
address many of the limitations of the prior art methods and
systems. One aspect of the invention is a system for improving the
movement of solid material in a cylindrical vessel, the vessel
having an inlet, an outlet, a cylindrical portion having an outer
dimension, and a converging transition between the cylindrical
portion and the outlet, the system comprising means for introducing
at least some liquid to the converging transition at a location
having a diameter greater than about 75% of the outer dimension of
the cylindrical portion of the vessel. In one aspect of the
invention, the means for introducing at least some liquid to the
converging transition has a diameter greater than about 90% of the
outer dimension of the cylindrical portion of the vessel. In
another aspect of the invention, the means for introducing at least
some liquid comprises at least one nozzle, for example, a plurality
of evenly-spaced nozzles. According to another aspect of the
invention, the vessel further comprises at least one set of
dilution nozzles evenly-spaced about the outlet at a first
diameter, and wherein the means for introducing at least some
liquid to the converging transition is positioned at a second
diameter greater than the first diameter. In another aspect of the
invention, the vessel further comprises at least one baffle plate
(also known as a "slide plate") positioned in the converging
transition, and wherein the means for introducing at least some
liquid to the converging transition is positioned between the at
least one baffle plate and the outlet.
[0010] Another aspect of the invention is a method of treating
particulate material in a cylindrical vessel having an interior, an
inlet into which particulate material is introduced, and an outlet
from which particulate material is discharged, the method
comprising: causing the particulate material to flow in the vessel
interior in a substantially vertical flow path; causing at least
some of the particulate material to flow in a non-vertical flow
path toward the outlet by providing a converging transition to the
outlet; and introducing a liquid to the converging transition to
reduce the resistance to flow of the particulate material through
the converging transition to the outlet. In one aspect of the
invention, the vessel comprises a vessel having an outer dimension
and wherein introducing a liquid to the converging transition
comprises introducing a liquid to the converging transition at a
location having a diameter greater than about 75% of the outer
dimension of the vessel, or greater than about 90% of the outer
dimension of the vessel. In one aspect of the invention, providing
a converging transition comprises providing a conical transition
having a first diameter and a second diameter smaller than the
first diameter. In another aspect of the invention, introducing a
liquid to the converging transition comprises introducing a liquid
to the vicinity of the second diameter of the conical transition.
Another aspect of the invention further comprises forming a zone of
compression in the converging transition wherein the particulate
material is compressed and resistance to flow is increased. In one
aspect of the invention, introducing a liquid to the converging
transition comprises introducing a liquid to the zone of
compression.
[0011] Another aspect of the present invention is a digester for
treating comminuted cellulosic fibrous material, the digester
comprising: an inlet for introducing comminuted cellulosic fibrous
material; a circular cylindrical portion having an outer diameter;
an outlet for discharging treated comminuted cellulosic fibrous
material; a converging transition between the circular cylindrical
portion and the outlet; and means for introducing at least some
liquid to the converging transition at a location having a diameter
greater than about 75% of the outer diameter of the circular
cylindrical portion of the digester. In one aspect of the
invention, the means for introducing at least some liquid to the
converging transition has a diameter greater than about 90% of the
outer diameter of the circular cylindrical portion of the digester.
In one aspect of the invention, the means for introducing at least
some liquid comprises a plurality of evenly-spaced nozzles. In
another aspect of the invention, the digester further comprises at
least one set of dilution nozzles evenly-spaced about the outlet at
a first diameter, and wherein the means for introducing at least
some liquid to the converging transition is positioned at a second
diameter greater than the first diameter. In another aspect of the
invention, the digester further comprises at least one baffle plate
positioned in the converging transition, and wherein the means for
introducing at least some liquid to the converging transition is
positioned between the at least one baffle plate and the
outlet.
[0012] Another aspect of the invention is a method of treating
comminuted cellulosic fibrous material in a digester, the digester
having an interior, an inlet for introducing comminuted cellulosic
fibrous material, and an outlet for discharging treated comminuted
cellulosic fibrous material, the method comprising: causing the
comminuted cellulosic fibrous material to flow in the digester
interior in a substantially vertical flow path; causing at least
some of the comminuted cellulosic fibrous material to flow in a
non-vertical flow path toward the outlet by providing a converging
transition to the outlet; and introducing a liquid to the
converging transition to reduce the resistance to flow of the
comminuted cellulosic fibrous material through the converging
transition to the outlet. In one aspect of the invention, the
digester comprises a vessel having an outer diameter and wherein
introducing a liquid to the converging transition comprises
introducing a liquid to the converging transition at a location
having a diameter which is greater than about 75% of the outer
diameter of the vessel. In another aspect of the invention,
introducing a liquid to the converging transition comprises
introducing a liquid to the converging transition at a location
having a diameter which is greater than about 90% of the outer
diameter of the vessel. In another aspect of the invention,
providing a converging transition comprises providing a conical
transition having a first diameter and a second diameter smaller
than the first diameter. In another aspect of the invention,
introducing a liquid to the converging transition comprises
introducing a liquid to a plurality of nozzles positioned in the
converging transition. Another aspect of the invention further
comprises forming a zone of compression in the converging
transition wherein the comminuted cellulosic fibrous material is
compressed and resistance to flow is increased. In one aspect of
the invention, introducing a liquid to the converging transition
comprises introducing a liquid to the zone of compression.
[0013] These and other embodiments and aspects of the present
invention will become more apparent upon review of the attached
drawings, description below, and attached claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The subject matter which is regarded as the invention is
particularly pointed out and distinctly claimed in the concluding
portion of the specification. The invention, however, both as to
organization and method of practice, together with further objects
and advantages thereof, may best be understood by reference to the
following detailed descriptions of the preferred embodiments and
the accompanying drawings in which:
[0015] FIG. 1 is an elevation view in cross-section of a comminuted
fibrous material treatment vessel according to the prior art.
[0016] FIG. 2 is an elevation view of the bottom section of a
comminuted fibrous material treatment vessel similar to the view
shown in FIG. 1 but illustrating one aspect of the present
invention.
[0017] FIG. 3 is a detailed view of one aspect of the invention
shown in FIG. 2.
DETAILED DESCRIPTION OF SOME ASPECTS OF THE INVENTION
[0018] FIG. 1 illustrates a cross-sectional view of two
representative portions of a cylindrical treatment vessel 10, for
example, a cylindrical pulping vessel, or digester, typically used
in the Pulping Industry. In particular, vessel 10 of FIG. 1
illustrates a typical continuous chemical pulping digester, that
is, a treatment vessel which operates essentially continuously with
wood chips continuously introduced at the top and pulp discharged
at the bottom. FIG. 1 illustrates the upper section 12 having an
inlet 14 and an upper head 15 and a bottom section 16 having a
bottom head 17 and a discharge 18. Vessel 10 typically includes a
cylindrical section 19 between the upper head 15 and the bottom
head 17. The diameter of cylindrical section 19 may typically vary,
for example, the diameter of section 19 may increase in a step-wise
fashion along the length of vessel 10.
[0019] According to conventional practice, a slurry of comminuted
fibrous material 20, for example, a slurry of wood chips in
treatment chemical, is typically introduced to inlet 14 and passes
downward in vessel 10 as indicated by arrows 22. The treatment in
vessel 10 may be under temperature and pressure, for example, at a
temperature over 100 degrees C. (212 degrees F.) and at a pressure
greater than 5 bar (72.5 psig). The treatment time in vessel 10 may
range from 1 to 6 hours and will typically dictate the height of
vessel 10. Typically, prior art treatment vessels may range from 50
feet in height to over 250 feet in height depending upon the
desired treatment time and production rate. The production rate
desired also typically dictates the maximum diameter of vessel 10,
which may range from about 12 feet to about 35 feet.
[0020] In a typical prior art treatment vessel 10, after being
introduced to inlet section 12 and passing through and being
treated in cylindrical section 19, the slurry of comminuted fibrous
material enters the bottom section 16 as indicated by arrows 24.
The slurry may be further treated with treatment liquid, as
indicated, for example, by arrows 26, and the slurry is ultimately
discharged out of outlet 18. The discharge of treated material out
of outlet 18 is typically aided by a rotating discharge device 28.
One typical discharge-device includes a central deflection cone 30
and two or more agitating arms 32 having paddles 34, though other
types of discharge devices may be used. Discharge device 28 is
typically driven by a drive train, for example, an electric motor
and gear box, not shown.
[0021] As is typical in the art, the discharge of treated material
may be aided by the addition of dilution liquid, in particular,
cooling dilution liquid, introduced to lower head 17 via two or
more nozzles 36. Nozzles 36 are typically uniformly spaced about
the central discharge 18 and introduce dilution liquid, for
example, filtrate from a downstream pulp washer, to dilute the
slurry of material in the vicinity of outlet 18. The dilution of
the slurry, or the reduction in the slurry consistency, allows the
material to be more readily discharged, for example, by means of
discharge device 28. However, conventional nozzles 36 are typically
located to aid discharge from outlet 18, and, the inventors
believe, are therefore located too distant from the region of
compression to provide any significant impact upon the flow of
material in those compressed regions. The dilution introduced by
nozzles 36 also typically cools the slurry which, among other
things, reduces the temperature of the slurry in preparation for
further treatment, for example, pulp washing.
[0022] As is also typical in the prior art, dilution liquid may
also be introduced via nozzles 38 located in the bottom of
cylindrical section 19 above the bottom head 17. The dilution
introduced via nozzles 38 may also reduce the consistency of the
slurry and cool the slurry prior to discharge. However, the liquid
introduced via nozzles 38 may also pass upward as indicated by
arrows 26 to cool or treat the slurry passing downward as indicated
by arrows 24.
[0023] The mode of slurry flow and dilution introduction
illustrated in FIG. 1 is common to most, if not all, of the
hundreds of continuous digesters in operation throughout the world.
However, the inventors have discovered that this mode of operating
a treatment vessel, in particular, this mode of introducing
dilution liquid to the bottom head of the treatment vessel, does
not promote uniform movement of slurry and thus does not promote
the uniform treatment of the solid material contained in the
slurry. For instance, conventional digester operation may exhibit
non-uniform movement of slurry and liquid in the vicinity of bottom
head 17. For example, prior art continuous digester operation may
be characterized by temperature gradients about bottom head 17 and
non-uniform flows in nozzles 36 and 38 (for example, as indicated
by surface temperature differences of individual nozzles).
[0024] Though the actual cause of these temperature gradients and
the consequent non-uniform flows with which the temperature
gradients are associated is unclear the inventors theorize that the
non-uniformities may be caused by the combined effects of the
resistance to flow provided by the converging flow path of bottom
head 17 and compression of the slurry due to the weight of the chip
column above. The inventors suggest that the resistance to flow may
be a function of the friction properties between the material being
treated (that is, the treated wood chips) in the slurry and the
internal surface of bottom head 17. For example, when the resisting
force of friction exceeds the motive force of the down-flowing chip
mass, the flow of slurry may decrease and the slurry may become
compressed. This compression of the slurry may cause the slurry to
thicken or dewater which can further increase the friction of the
slurry against bottom head 17 and further exacerbate an undesirable
flow condition.
[0025] According to one aspect of the invention, the resistance to
slurry flow is reduced or minimized by introducing liquid to the
slurry in the vicinity of bottom head 17, for example, in addition
to the dilution introduced via nozzles 36. The inventors surmise
that the diluting effect of the liquid reduces the restriction to
flow by either reducing the consistency of the slurry or reducing
the friction between the wall and slurry, or a combination of both.
According to one aspect of the invention, dilution is introduced
anywhere in bottom head 17 where regions of compression and flow
resistance can hamper the flow of slurry. In another aspect of the
invention, dilution is introduced at a location where the shape of
head 17 imposes a change in flow path of the slurry from an
essentially vertical path to a non-vertical path. In another aspect
of the invention, dilution is introduced to bottom head 17 in the
vicinity of the corner or knuckle of bottom head 17.
[0026] According to another aspect of the invention, one or more
baffle plates may be introduced to the converging transition. For
example, a continues ring of one or more plates may be provided in
the transition zone of the converging bottom head 17 to promote
movement of slurry toward outlet 18 and minimize stagnation of
slurry in the corner or "knuckle" of bottom head 17. These baffle
plates, sometimes referred to as "slide plates", can be used with
or without the dilution nozzles discussed above.
[0027] One aspect of the present invention which address this and
other disadvantages of the prior art is illustrated in FIG. 2.
Though the discussion of the aspect of the invention shown in FIG.
2 describes the present invention with respect to its application
to the operation of a continuous chemical pulping digester, it will
be apparent to those of skill in the art that the present invention
may be applied to any vessel, in and out of the Pulp and Paper
Industry, which handles solid materials or slurries of solid
materials, which includes, but is not limited to, storage vessels,
retention vessels, treatment vessels (for example, washing and
bleaching vessels), among others.
[0028] FIG. 2 illustrates a cross-section view of vessel 50
incorporating one or more aspects of the present invention. FIG. 2
illustrates a bottom section 52 of vessel 50 that is very similar
to bottom section 16 of vessel 10 shown in FIG. 1. Vessel 50
typically includes a top section 12 as shown in FIG. 1, but the top
section of vessel 50 is omitted for clarity of illustration. The
features of FIG. 2 which are essentially identical to the features
of FIG. 1 are identified in FIG. 2 by the same reference numbers
used in FIG. 1. Similar to vessel 10 in FIG. 1, vessel 50 in FIG. 2
includes a cylindrical vessel section 19, a bottom head 17, a
discharge 18, and a rotating discharge device 28, and may include
dilution nozzles 36 in the bottom head and dilution nozzles 38
above the bottom head.
[0029] According to one aspect of the invention, as shown in FIG.
2, dilution liquid is introduced to bottom head 17 via one or more
nozzles 54. Nozzles 54 are typically positioned at a radial
position closer to the outside diameter of vessel 50 than to outlet
18. For example, nozzles 54 may be positioned at a radial distance
that is at least about 75% of the outer radius of vessel 50, for
instance, at least about 75% of the outer radius of bottom head 17.
In addition, a plurality of nozzles 54 may be uniformly located on
a diameter that is at least about 75% of the outer diameter of
vessel 50. In one aspect of the invention, the radial distance (or
common diameter) of the position of one or more nozzles 54 is at
least 90% of the outer radius (or diameter) of vessel 50 (or 90% of
the outer radius of bottom head 17). Nozzles 54 may comprise
conduits or pipe having nominal diameters ranging from about
one-half inch to about 5 inches. In one aspect of the invention, as
shown in FIG. 2, nozzles 54 may comprise 1-inch to 2-inch pipe. In
one aspect of the invention, nozzles 54 are provided to a vessel
having one or more existing nozzles 36 (that is, one or "bottom
dilution nozzles" as they are known in the art). When nozzles 36
are present, nozzles 54 may be positioned in bottom head 17 at a
radial distance beyond nozzles 36. Also, in one aspect of the
invention, when both nozzles 36 and 54 are provided, the location
of nozzles 54 may be staggered, or positioned circumferentially
between, nozzles 36.
[0030] In one aspect of the invention, at least one nozzle 54 may
be positioned in bottom head 17 where the slurry within bottom head
17 undergoes increased compression. In one aspect of the invention,
at least one nozzle 54 may be positioned in bottom head 17 where
movement of the slurry within bottom head 17 is hindered or
stagnated, for example, due to compression or frictional forces
within bottom head 17. For example, in one aspect of the invention,
for a flanged and dished bottom head 17 having an outer diameter of
about 20 feet (that is, having an outer radius of about 10 feet),
one or more nozzles 54 may be uniformly positioned at a radius of
about 9 feet 6 inches.
[0031] In one aspect of the invention, the flow of liquid to
nozzles 54 is controlled, for example, by means of one or more flow
controlling devices 56. Flow control devices 56 may be one or more
valves (for example, a ball, gate, or other type valve) or other
type flow control device. Flow control devices 56 may be manual or
automated flow control devices, for example, hand-operated valves
or automated valves having valve controllers. In another aspect of
the invention, the flow of liquid to one or more nozzles 54 may be
monitored by means of a flow monitoring device 58, for example, a
flow meter of conventional type. According to one aspect of the
invention, the flow of liquid to one or more nozzles 54 may be
controlled by a single flow control device (for example, a flow
control valve) for directing liquid to one or more nozzles 54. In
this aspect of the invention, by controlling the rate of flow of
liquid to each nozzle 54, plugging of individual nozzles 54 may be
minimized or prevented. In another aspect of the invention, the
flow of liquid to one or more nozzles 54 may be controlled by
individual flow control device 56 associated with each of the one
or more nozzles 54. In one aspect of the invention, the flow of
liquid to each of the one or more nozzles 54 may be monitored and
controlled by means of an automated flow control device and a flow
monitoring device, for example, an automated flow control valve
having a closed-loop automated valve controller which operates in
response to a flow signal provided by the flow monitoring device.
The control of the flow control device may also be regulated by a
pressure sensor associated with the pressure in vessel 50 or to the
pressure in a conduit leading to vessel 50. The flow control
arrangement may include an automated controller having an algorithm
for controlling the flow to one or more nozzles 54 in response to
one or more operator-defined criteria, for example, liquid flow
rate, difference in two liquid flow rates, production rate, slurry
temperature, or vessel pressure, among other things.
[0032] The liquid provided to nozzles 54 may be obtained from any
convenient source. For example, the liquid introduced to nozzles 54
may comprise water (essentially clean or otherwise), cooking liquor
(including kraft white liquor or soda cooking liquor), spent
cooking liquor, washing or bleaching filtrate, filtrate from the
paper machines (for example, white water), evaporator condensate,
flashed cooking liquor condensate, or other chemicals (such as
sodium hydroxide) or additives (such as anthraquinone, polysulfide,
or their equivalents or derivatives) which can be used to treat the
comminuted fibrous material in the slurry in addition to promoting
uniform movement of the slurry.
[0033] According to another aspect of the invention, as shown in
FIG. 2 in phantom, one or more baffle plates 60 may be positioned
in bottom head 17 to promote the movement of the slurry toward
outlet 18. In one aspect of the invention, baffle plates (sometimes
referred to as "slide plates") may comprise one or more plates
assembled to provide an annular surface encircling the inside of
bottom head 17. Plates 60 may be planer or flat plates, but also
may comprise at least some curvature to facilitate conforming to
bottom head 17 during installation. Plates 60 may also be
non-planar, for example, the shape of plates 60 may be fashioned to
optimize directing the slurry to outlet 18 while minimizing
localized compression of the slurry adjacent to plate 60. Plates 60
may comprise materials or surfaces providing reduced friction to
the slurry of material passing over them. For example, plates 60
may be steel plates, stainless steel plates (for example, 304 or
316 stainless steel plates) or other materials providing reduced
friction. Plates 60 may be treated, for example, polished or
coated, to reduce friction, for example, coated with a material
containing a low-friction material, such as polytetrafluoroethylene
(such as Dupont's Teflon.RTM. polytetrafluoroethylene or its
equivalent). Plates 60 may be mounted to bottom head 17 by
conventional means, for example, via welding or mechanical
fastening, and may include one or more support or gusset plates
(not shown) as required for proper installation and structural
integrity. Plates 60 may have a thickness of between about 0.125
inches to about 1.00 inches. In one aspect of the invention, plates
60 may have a thickness of between about 0.25 and about 0.50
inches.
[0034] FIG. 3 illustrates a detailed view of a cross-section of
bottom head 17 in the vicinity of a nozzle 54 as shown in FIG. 2.
FIG. 3 illustrates a section of cylindrical section 19, a section
of bottom head 17, a representative nozzle 36, and a representative
nozzle 54, according to one aspect of the invention, and baffle
plate 60 (shown in phantom), according to another aspect of the
invention. As shown in FIG. 3, according to one aspect of the
invention, the axis 64 of nozzle 54 may be oriented at an angle
relative to the outer surface of bottom head 17 or to the axis 62
of vessel 50. In one aspect of the invention, axis 64 of one or
more nozzles 54 may make an angle .alpha. with axis 62 of vessel
50. In one aspect of the invention, the angle .alpha. may be about
0 degrees, that is, the axis of nozzle 54 is essentially parallel
to axis 62. In one aspect of the invention the angle .alpha. may be
greater than 0 degrees, for example, between about 5 degrees and
about 90 degrees. In another aspect of the invention, the axis 64
of valve 54 may be perpendicular to the outer surface of bottom
head 17.
[0035] According to one aspect of the invention, liquid may be
introduced to bottom head 17 via one or more nozzles 58 (shown in
phantom in FIG. 3) instead of to nozzles 54. Nozzles 58 may be
located in the curved section of bottom head 17 (for example, in
the "knuckle" of bottom head 17). Nozzles 58 may be located with
respect to the horizontal (as indicated by line 74), for example,
by an angle .gamma.. The angle .gamma. may be an angle between
about 15 degrees and about 75 degrees, and In one aspect of the
invention, the angle .gamma. may be between about 30 degrees and
about 60 degrees.
[0036] As shown in FIG. 3, baffle plate 60 may comprise a conical
baffle plate and may have a first, inside diameter 66 and a second,
outside diameter 68. Inside diameter 66 may be at least as great as
the diameter of outlet 18, and may be greater than the diameter of
the position of nozzles 36 or greater than the diameter of the
position of nozzles 54. Outer diameter 68 may be about equal to the
inside diameter of bottom head 17. Baffle plate 60 may also be
oriented at any desired angle of inclination. In one aspect of the
invention, plate 60 is oriented at an angle .beta. to the
horizontal, for example, as illustrated by line 70. In one aspect
of the invention, the angle .beta. comprises an angle between about
15 degrees and about 75 degrees. In another aspect of the invention
the angle .beta. comprises an angle between about 30 degrees and
about 60 degrees. For example, in the aspect of the invention shown
in FIG. 3, the angle .beta. comprises an angle of about 45 degrees
with the horizontal.
[0037] In one aspect of the invention, plates 60 may be used in
conjunction with nozzles 54, but in another aspect of the
invention, plates 60 may be used alone without the presence of
nozzles 54. In one aspect of the invention, nozzles 54 may be used
without the presence of plates 60. In one aspect of the invention,
when plates 60 are used with nozzles 54, nozzles 54 may be
positioned within the inside diameter 66 of plates 60. According to
this aspect of the invention, nozzles 54 may introduce liquid to
the slurry as the slurry leaves contact with plates 60, for
example, within 6 inches of the inside diameter 66 of plates 60. In
one aspect of the invention, liquid may be introduced in the
vicinity of the first diameter 68 of plates 60 or in the vicinity
of the second diameter 66 of plates 60 or in the vicinity of both
diameters 66 and 68.
[0038] In another aspect of the invention, one or more nozzles 58
may extend through bottom head 17 to one or more apertures or
perforations in plates 60. In one aspect of the invention, each
extended nozzle provides liquid to an individual aperture or
perforation in plates 60. These extended nozzles, or simply pipes
or conduits, may provide dilution to the surface of 60 or to the
slurry passing the surface of plate 60. The one or more apertures
or perforations in plate 60 may be a plurality of circular holes or
slots, for example, annular slots. In one aspect of the invention,
the one or more apertures or perforations may be positioned at
about the inner diameter 66 of plates 60.
[0039] In another aspect of the invention, some liquid may be
provided to bottom head 17 via one or more nozzles 58 positioned in
bottom head 17 as a function of the angle of a line drawn tangent
to bottom head 17. As shown in FIG. 3, one or more nozzles 58 may
be positioned in bottom head 17 at a position wherein a tangent
line 76 (shown in phantom) forms an angle .phi. with the
horizontal, for example, as indicated by line 78. In one aspect of
the invention, the angle .phi. may range from about 45 degrees to
about 75 degrees. In another aspect of the invention, the angle
.phi. may range from about 55 degrees to about 65 degrees, for
example, in FIG. 3, the angle .phi. comprises an angle of about 60
degrees.
[0040] Pulp mill trials of one aspect of the invention as applied
to continuous digesters dramatically illustrated the benefits of
one aspect of the present invention compared to the prior art. The
continuous digester used in the trial was one having an
"extraction", or liquor removal, from a set of annular screens (or
"extraction screens") positioned above the outlet head of the
digester, for example, positioned in cylindrical section 19 in FIG.
1. One indication of non-uniform movement (also known as
"channeling"), and corresponding non-uniform treatment, in the
outlet section of such a digester is a limitation in the flow of
liquid out of the extraction screens and temperature gradients in
the bottom of the digester. For example, non-uniform movement of
slurry in the outlet section of a digester can result in stagnated
flow in the regions near the extraction screens which can cause the
extraction screens to plug with cellulose material and hinder
liquid removal. In the mill trials, a digester was operated in the
prior art mode with liquor introduced to the conventional side
dilution nozzles (that is, nozzles 38 in FIGS. 1, and 2). Under
such conventional conditions, the flow of liquid out of the
extraction screen was limited to only about 40 GPM; no further flow
could be obtained. In addition, marked temperature gradients were
present in the outlet section of the digester, further indicating a
non-uniform flow condition. However, when dilution liquid was
introduced to four evenly-spaced dilution nozzles according to the
present invention (that is, via four nozzles 54 shown in FIG. 2),
the operators were able to increase the extraction flow from the
extraction screens to 200 GPM, that is, a 500% increase compared to
prior art operation. (The flow was limited to 200 GPM by other
factors unrelated to the present invention and may have increased
even further when employing one aspect of the present invention.)
Using this aspect of the present invention, the operators were also
able to reduce temperature gradients in the outlet zone. The
increased extraction flow and reduced temperature gradients were
attributed to the reduction or elimination of stagnant flow in the
bottom head which resulted in a reduction or elimination of
stagnant flow in the vicinity of the extraction screens, which this
aspect of the invention provided.
[0041] Though the aspects of the invention described and
illustrated with respect to FIGS. 1 through 3 may apply to
digesters, for example, continuous digesters, those of skill in the
art will recognize that the present invention is applicable to many
different kinds of treatment vessels used in the Pulp and Paper
Industry, and used outside the Pulp and Paper Industry, which
handle solid materials or slurries of solid materials. For example,
within the Pulp and Paper Industry, the present invention may be
used in pulping vessels or reactors, washing vessels, bleaching
vessels, pulp or chip storage or retention vessels or bins, among
other vessels. Outside the Pulp and Paper Industry, the present
invention may be used in any application which handles solid
materials or slurries of solid materials, for example, in the
materials handling industry, chemical industry, mining industry,
food processing industry, and the like.
[0042] As such, the present invention, may be applied to any type
of vessel under any types of temperature and pressures. For
example, vessel 50 may treat or retain solid material at ambient
temperature or at elevated temperature, for example, at a
temperature ranging from about 10 degrees C. (50 degrees F.) to
about 200 degrees C. (392 degrees F.). Similarly, vessel 50 may be
pressurized or unpressurized. In one aspect of the invention,
vessel 50 is operated at ambient pressure. In another aspect of the
invention, vessel 50 may be operated at subatmospheric pressure or
superatmospheric pressure, for example, at a pressure between about
5 bar gage (72.5 psig) to about 15 bar gage (217.5 psig).
[0043] While the invention has been particularly shown and
described with reference to preferred embodiment, it will be
understood by those skilled in the art that various changes in form
and details may be made to the invention without departing from the
spirit and scope of the invention described in the following
claims.
* * * * *