Note: Descriptions are shown in the official language in which they were submitted.
1
CHIP BIN ASSEMBLY INCLUDING A HOLLOVII TRANSITION WITH ONE
DIMENSIONAL CONVERGENCE ANID SIDE RELIEF
BACKGROUND AND SUMMARY OF THE INVENTION
In the production of chemical cellulose pulp (e. g. paper pulp) it is
highly desirable to obtain uniformity of treatment. One important way that
this uniformity is typically achieved or approached is to provide uniform
impregnation of the cooking liquor (e. g. white liquor) into the comminuted
cellulosic raw material (typically wood chips). In order for there to be
uniform impregnation the air must be removed from the chips, and this is
typically done by steaming.
In approximately the 1970s, it became common to at least initiate
steaming of the chips at an early stage in their treatment by supplying
steam to a conventional vertical vessel known as a "chip bin". In most
systems, chips were fed into the top of the chip bin, e. g. through an air
lock, where they were subjected to steam before moving downwardly
through the bin into a chip meter, and then a low pressure feeder,
subsequently to a horizontal steaming vessel 'where the removal of air in
the chips with steam was completed, and then either a feed mechanism
on top of a batch digester, or more commonly to a high pressure feeder for
a continuous digester. In addition to providing a volume for initial
steaming, the chip bin provides a storage volume sufficient to insure
supply of the continuous digester, andlor like components, on a regular
basis even though the chips are not continuou ly fed from a chip heap or
pile to the pulping system. This is especially important in winter weather
conditions in cold climates, where many pulp mills are located, because
of interruptions in an ability to continuously feed chips from a heap or pile
to the pulping system due to freezing of the chips in the pile, or other
weather related disruptions. Numerous problems of channeling or "rat-
holing" are caused by inhomogeneous chip feed. Frozen chips have
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2
different flow properties than normal chips, wet different than dry, and
sawdust and pin chips different than whole chips.
It has long been known that when wood chips (and like
comminuted cellulosic material) funnel downwardly in a chip bin, or
similar vessel, to a discharge having a smaller cross-sectional area than
the area of the vessel (chip bin) itself there is a tendency for the chips to
hang-up or bridge. Also some areas allow channelling of the chips to the
discharge, while in other areas the chips move little. This is a significant
problem because it can interrupt the continuity of supply and thereby
defeat a major purpose of a chip bin. Therefore since at least as early as
the 1970s conventional chip bins have often included a vibratory discharge
mechanism which continuously or periodically shakes the discharge,
minimizing bridging and the possibility of plugging, and promoting uniform
flow of chips through all portions of the chip loin. One such conventional
vibratory discharge is shown in U. S. Patent 4,124,440 and Canadian
Patent 1,146,788, both of which also show conventional mechanisms for
steaming the chips while in the chip bin.
While vibratory discharges for chip ibins have long been the
commercially preferred way of preventing bridging, and have long worked
well, as the size of pulping systems -- and therE;fore the size of the chip
bin
associated therewith -- has increased in the 1980s and 1990s, there have
been increasing practical operational difficulties. In fact for chip bins
having a maximum diameter of over about twelve feet (and certainly over
fourteen feet) problems in plugging, bridging, and channeling have
increased (especially for some woods, such as cedar), as have
maintenance and reliability problems associated with the vibratory
discharges. Some of these problems can be greatly alleviated or solved by
using conical inserts for the chip bin as shown in copending U. S. patent
5,454,490, however even with the system and method described therein
maintenance and reliability problems of a vibratory discharge, or other
problems, may still occur for chip bins having a maximum diameter of
about twelve feet or more.
a
3
According to the present invention, a method and apparatus are
provided which specifically address the problems of reliability and
maintenance of conventional vibratory discharges, and the problems of
chip bin pluggage, bridging andlor channelling. While the invention is
primarily directed to chip bins having a maximum diameter of about twelve
feet or more, many aspects thereof are appropriate for bins in general, and
of almost any size. The invention utilizes mass flow (as contrasted with the
"funnel flow" of co-pending U. S. patent 5,4541,490 in the chip bin, which
has significant benefits in promoting uniform steaming, and in minimizing
channeling.
According to the invention, the vibratory discharge is replaced with a
simpler, less troublesome, more easily maintained structure while not
only not sacrificing discharge efficiency and the ability to steam the chips,
but actually enhancing them. Also, in some of the embodiments of the
invention, the chip meter -- a conventional and necessary piece of
equipment associated with most chip bins for continuous digester
systems -- can be eliminated without elimination of its metering function,
thereby resulting in the potential for equipment and maintenance savings
for the chip feeding system as a whole.
According to the general method of the present invention,
comminuted cellulosic material is fed to a digester using a vertical open
interior chip bin having a top and bottom, arid a maximum diameter of
about twelve feet or more (e.g. fourteen feet or more), and a discharge
operatively connected to a digester. The discharge has a cross-sectional
area much less than half of the cross-sectional area of the chip bin (e.g.
less than one-tenth). The method comprises the steps of: (a) Feeding the
comminuted cellulosic material into the top of the chip bin, to flow,
downwardly in a column in the chip bin toward the bottom. (b) Causing the
comminuted cellulosic material to move into a gradually restricting open
flow path in the open interior of the chip bin having a cross-sectional area
less than half of the area at the maximum diameter of chip bin. (c) Without
vibrating the chip bin or the chip bin discharge, causing a substantially
uniform flow of comminuted cellulosic material in the gradually restricting
open flow path, substantially without briclging or hangups of the
comminuted cellulosic material in the flow path. (d) Steaming the
cornminuted cellulosic material while in the chip bin. And, (e) discharging
the comminuted cellulosic material from the chip bin discharge and
feeding it to the digester.
Step (e) may be practiced by feeding the material directly from the
discharge to a low pressure feeder and then ultimately to a digester, or
alternatively the material may be fed directly from the discharge to a chip
meter, and then ultimately to the digester. Steps (b) and (c) may be
practiced by causing the comminuted cellulos,ic material to flow into two
distinct volumes each comprising about half oif a main volume defined by
a substantially circular cross-section top and a substantially rectangular
cross-section bottom, and a larger cross-sectional area at the top thereof
than at the bottom thereof, and opposite non-vertical gradually tapering
sides, and causing the material to move from each distinct volume to the
discharge using oppositely rotating feed screws (or opposite handed feed
screws rotated by a common shaft), the discharge being located
approximately midway between the two distinct: volumes. Steps (b) and (c)
may be further practiced by causing the material to flow into distinct
volumes wherein the degree of taper of the opposite non-vertical gradually
tapering sides is about 20-35°. Alternatively, steps (b) and (c) may be
practiced by causing the comminuted cellulosic material to flow through a
transition having one dimensional convergence and side relief between a
first volume having a circular cross-section oif at least about twelve feet
and a discharge having a circular cross-section of much less than half of
the first volume.
Step (d) is typically practiced by adding steam to the distinct
volumes by introducing the steam into a substantially vertical chip bin wall
interruption in at least one non-vertical gradually tapering side of each of
the distinct volumes.
According to another aspect of the present invention a bin is
provided in general. While the bin has specific utility as a chip bin,
particularly for diameters of about twelve feE~t or more, it is useful for
I?
5
almost any size chip bin, and for other bin constructions in general.
According to this aspect of the invention the bin comprises: A hollow
substantially right circular cylindrical main body portion having a
substantially vertical central axis, a top and an open bottom. A top wall
closing off the top of the main body portion, and having means for
introducing particulate material into the hollow main body portion mounted
thereon. A hollow transition portion connectecl to the bottom of the main
body portion having a substantially circular cross-section open top and a
substantially rectangular cross-section open k>ottom, and a larger cross-
sectional area at the top thereof than at the bottom thereof, and opposite
non-vertical gradually tapering side walls. At least one feed screw
mounted adjacent the open bottom of the transiition portion, in a housing. A
discharge operatively connected to the feed screw housing. And, means
for rotating the at least one feed screw to move particulate material from
the bottom of the transition portion to the discharge.
The bin may further comprise means for introducing steam to the
hollow transition portion, the means comprising a steam conduit, and a
substantially vertical wall interruption of at least one of the non-vertical
gradually tapering side walls of the transition portion, the steam conduit
connected to the substantially vertical wall interruption. The non-vertical
gradually tapering side walls of the transition portion may each have a
degree of taper that is about 20-35° (typically about 25-30°)
with respect to
vertical, which is about 10-20° greater than the mass flow angle for
the
material handled (the mass flow angle for most chips is about 10-15°).
The at least one feed screw may comprise first and second feed
screws mounted at the bottom of the transition portion, a junction provided
between the screws, and each mounted for rotation about a common
generally horizontal axis; and the means for rotating the at least one feed
screw may comprise means for rotating the first and second screws about
the axis in different directions (or opposite handed feed screws rotated by
a common shaft). The structure also preferably includes a baffle disposed
within the transition portion above the screw junction; and, the discharge
may comprise a substantially right rectangular parallelepiped discharge
;;_~- ,,~
,..-
operatively mounted to the screws substantially at the screw junction and
remote from the transition portion, the discharge for receipt of particulate
solid material from both the screws.
Alternatively the discharge may be offset: from the main body portion
in which case the at least one screw comprises a single screw that
transports particulate material substantially horizontally in a single
direction from the transition portion to the offset discharge.
As another embodiment, the at least one screw comprises first and
second screws, one mounted above the other for rotation about parallel
axes, the first screw having a housing mounted to the transition portion
and having an outlet therefrom offset from the main body portion, and the
second screw having a housing with an inlet connected to the first screw
housing outlet, and having the discharge as. the outlet, the discharge
being substantially concentric with the main body portion. In this case the
means for rotating the at least one screw coimprises means for rotating
the first and second screws so that they transport particulate material in
opposite substantially horizontal directions.
According to yet another modification, the transition portion
comprises a first transition portion, and further comprises a second
hollow transition portion between the first transition portion and the at
least
one screw, the second transition comprising a hollow substantially right
triangular prism with an open top and open k>ottom and having a larger
cross-sectional area at the bottom than at the 1':op, and the cross-sectional
area of the top being approximately the same as the cross-sectional area
of the bottom of the first transition portion. 'The bottom of the second
transition portion has a length at least fiver times its width; and the
discharge from the screw trough is a rectangular in cross section, having
a diameter approximately equal to the width of the bottom of the second
transition portion, and is substantially concentric with the main body
portion.
According to a still further embodiment i:he at least one feed screw
comprises first and second feed screws mounted at the bottom of the
transition portion, a junction provided betwE:en the screws and each
13
mounted for rotation about a common generally horizontal axis. The
means for rotating the feed screw comprises means for rotating the first
and second screws about the axis in different directions. The discharge
from the screw trough may comprise a substantially right rectangular
parallelepiped discharge operatively mounted t.o the screw substantially at
the screw junction and remote from the transition portion, the discharge for
receipt of particulate solid material from both tlhe screws. An agitator may
also be provided at the screw junction, and a chip meter, operated by a
motor, may be connected to the discharge. A controller coordinates the
operation of the chip meter motor and the me<~ns for rotating the first and
second screws.
According to another aspect of the present invention a chip bin
assembly is provided comprising the following elements: A hollow
substantially right circular cylindrical main body portion having a
substantially vertical central axis, a top and a bottom, and having a first
diameter. A top wall closing off the top of the main body portion, and having
means for introducing wood chips into the hollow main body portion
mounted thereon. A hollow substantially right, rectangular parallelepiped
discharge having a second diameter with is less than one half of the first
diameter. A hollow transition portion disposed between the main body
portion and the discharge having one dimensional convergence and side
relief. Means for introducing steam to the hollow interior of the bin. And,
means for connecting, the discharge to a digester.
The assembly may also comprise first and second feed screws
mounted adjacent the bottom of the transition portion, a junction provided
between the screws, and each mounted for rotation about a common
generally horizontal axis; and means for rotating the screws about the axis
in different directions (or opposite handed feed screws rotated by a
common shaft) to move wood chips from the transition portion to the
discharge conduit. Alternatively the transition portion may include at least
one substantially planar non-vertical wall portion; and the means for
introducing steam into the bin preferably introduces steam into the
transition portion, and comprises a steam conduit, and a substantially
vertical wall interruption of the substantially planar non-vertical wall
portion
of the transition portion, the steam conduit connected to the substantially
vertical wall interruption.
In the most preferred embodiment of the present invention, a chip
bin assembly is provided which takes the place of conventional chip bins,
and which feeds down to a circular cross :>ection discharge which is
typically connected to a conventional chip meter or low pressure feeder,
ultimately being connected to a high pressurf: feeder which feeds chips
under pressure to the top of a substantially vertical continuous digester.
The preferred chip bin assembly comprises the following components: A
hollow substantially right circular cylindrical main body having a
substantially vertical central axis, a top and a~ bottom, and having a first
diameter. A top wall closing off the top of the main body, and having an
inlet for introducing wood chips into the hollow main body. A non-vibrating
discharge operatively connected to the bottom of the main body. A hollow
transition disposed between the discharge and the main body, the hollow
transition comprising: a first, uppermost, portion having a generally right
rectangular parallelepiped configuration including opposite side faces
having generally triangular shapes, and providing one dimensional
convergence and side relief; a second portion tapering from a generally
rectangular parallelepiped configuration at a.n upper part thereof to a
generally circular configuration at a lower part i:hereof and having opposite
side faces having generally triangular shapes which align with the first
portion generally triangular shapes to defiine substantially diamond
shaped wall portions; a third portion substantially the same as the first
portion, only smaller, and connected to the second portion lower part; and
a fourth, lowermost, portion substantially the game as the second portion
only smaller, and connected to the third portion in the same manner as the
second portion is connected to the first portion, and connected to the
discharge. And means for introducing steam into at least one of the main
body and the hollow transition to steam wood .chips therein.
The means for introducing steam preferably includes means for
introducing steam into the least one of the generally triangular shapes of
J)
9
the side faces of the second portion of the hollow transition, and preferably
into both side faces. Also, steam is also preferably introduced into the
main body. At least one air blaster is prefer<~bly mounted to the hollow
transition -- such as first and second air blasters mounted to each of the
first and third portions of the hollow transition on opposite sides of the
first
and third portions spaced from the faces having generally triangular
shapes -- to break up hung-up wood chips in the transition.
The main body may include at least one conical ring insert for
relieving compaction pressure on chips in the main body, such as
disclosed in copending U S patent 5,454,49~D. As indicated above, the
discharge is preferably circular in cross section, having a second diameter
which is about 1/3 or less of the first diameter (e.g. the first diameter is
15
feet, the second diameter is about 4 feet). The lower part of the second
portion of the hollow transition is also preferak>ly circular in cross
section,
having a third diameter, the third diameter being at least 50% greater than
the second diameter and at least 30% less tlhan the first diameter. The
discharge is typically operatively connected to the high pressure feeder
(e.g. through a chip meter andlor low pressure. feeder), and to a
continuous digester.
According to another aspect of the present invention a system for
making chemical pulp from wood chips is provided comprising the
following components: A substantially vertical continuous digester having
a top and a bottom, and an inlet adjacent said top. A high pressure feeder
for feeding wood chips to the continuous diges>ter inlet. And a chip bin for
supplying wood chips to the high pressure feeder, the chip bin
comprising: a hollow substantially right circular cylindrical main body
having a substantially vertical central axis, a top and a bottom, and having
a first diameter; a top wall closing off the top of said main body, and having
an inlet for introducing wood chips into the hollow main body; a non-
vibrating discharge operatively connected to said bottom of the main body;
a hollow transition disposed, between the discharge and the main body,
the hollow transition comprising: a first, uppermost, portion having a
generally right rectangular parallelepiped configuration including opposite
10
side faces having generally triangular shapes, and providing one
dimensional convergence and side relief; a second portion tapering from
a generally rectangular parallelepiped configuration at an upper part,
thereof to a generally circular configuration at a lower part thereof and
having opposite side faces having generally triangular shapes which align
with the first portion generally triangular shapes to define substantially
diamond shaped wall portions; a third portion substantially the same as
the first portion, only smaller, and connected i:o the second portion lower
part; and a fourth, lowermost, portion substantially the same as the
second portion only smaller, and connected to the third portion in the
same manner as the second portion is connected to said first portion, and
connected to the discharge.
It is the primary object of the present invention to provide for the
effective feeding of particulate material, such as wood chips, downwardly
in a bin without the necessity of a vibratory discharge, even where the
diameter of the bin is twelve feet or more. This and other objects of the
invention will become clear from an inspection of the detailed description
of the invention and from the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 is a schematic side view of a chip bin according to the
present invention in association with conventional other equipment for the
production of chemical pulp;
FIGURE 2 is a schematic front view, with some portions cut away for
clarity of illustration of the internal components, of one embodiment that
the chip bin of FIGURE 1 can take;
FIGURE 3 is a side view, with the scrE:w motor and end housing
removed for clarity of illustration, of the chip bin embodiment of FIGURE 2;
FIGURE 4 is a top plan view of the transition portion of the chip bin
of FIGURES 2 and 3;
11
FIGURE 5 is a side detail cross-sectional view schematically
illustrating the manner in which steam can be, introduced into the
transition portion of the chip bin of FIGURES 2 through 4;
FIGURES 6 and 7 are views like that of (FIGURES 2 and 3 only for a
second embodiment of a chip bin according to the invention;
FIGURES 8 and 9 are views like those of FIGURES 2 and 3 for a
third embodiment of a chip bin according to the present invention;
FIGURE 10 is a detail front view, with portions cut away to illustrate
internal components, of a modified form of the transition and screw
components only of the embodiment of FIGURE=S 2 and 3;
FIGURES 11 and 12 are views like those of FIGURES 2 and 3, but
for only the transition and screw component portions, of a further
modification of the chip bin embodiment of FIGIJRES 2 and 3;
FIGURE 13 is a top plan view of the transition and like, portions of
the embodiment of FIGURES 11 and 12;
FIGURES 14 and 15 are views like those of FIGURES 2 and 3 for yet
another modification of the transition, screw feed, and like components, of
a chip bin according to the invention;
FIGURES 16 and 17 are views like those of FIGURES 6 and 7 only
for the transition and screw feed portions only, of yet another embodiment
according to the present invention, the plan view of the structures of
FIGURES 16 and 17 being essentially the same as the plan view of
FIGURE 13;
FIGURE 18 is a side view, partly in cross section and partly in
elevation, of another embodiment of a chip bin assembly according to the
invention and showing schematically connected up to a low pressure
feeder and a digester;
FIGURE 19 is a bottom plan view of they chip assembly in FIGURE
18;
FIGURE 20 is a detailed side cross sectional view showing an
exemplary nozzle connection to the transition for mounting of an air blaster
in the vessel of FIGURES 18 and 19; and
12
FIGURE 21 is a side view of a modified form of the hollow transition
of the assembly of FIGURES 18 and 19.
DETAILED DESCRIPTION OF THE DRAWINGS
FIGURE 1 schematically illustrates a chip bin 10 according to the
present invention, having a closed top 11 with a conventional inlet 12 in the
top thereof for the introduction of wood chips or other comminuted
cellulosic material. As is conventional an air lock 13 is preferably
connected to the inlet 12, and a vent pipe 14 is next to the inlet 12. Chips
are introduced through the air lock 13 in the conduit 12 through the top 11
of the chip bin 10, as indicated schematically by arrow 15. The chip bin 10
also has other conventional vents, reliefs, and the like associated
therewith, and also typically has an internal level sensing mechanism,
such as a conventional gamma source level control illustrated
schematically by reference numeral 17 in FIGURE 1.
Steam is supplied to the chip bin 10 to start steaming of the chips
within it. The steam is typically low pressurE; steam, such as provided
through lines 18 and 19 from conventional sources within the pulp mill.
Line 18, in the exemplary embodiment illustrated, is shown connected to
the main body portion of the chip bin 10, while line 19 is operatively
connected to a lower portion thereof. The mechanisms for control of the
steam addition to the chip bin, and for sensing and control of the level of
chips within the bin 10, the control of air lock 13, and the control of
various
vents associated therewith, are conventional.
The chip bin 10 is a vertical vessel with a discharge at the bottom
thereof typically connected to a chip meter 21. 'The chip meter 21 is shown
illustrated in dotted line in FIGURE 1 since it is not necessary in all
embodiments of the chip bin according to they invention. In some of the
embodiments of the chip bin according to the invention metering action is
inherently provided by components of the chip bin which take the place of a
conventional vibratory discharge (such as shown in U.S. patent
4,124,440). Below the chip bin 10, and below the chip meter 21 if provided,
a
13
is a low pressure feeder 22 which feeds the chips after initial steaming
from the chip bin 10 into a conventional horizontal steaming vessel 23.
The vessel 23 typically has a vent conduit 24, and a header 25 connected
to the low pressure steam source 19 for the introduction of steam, and a
chips outlet 26. An internal screw is typicall~~ provided in the steaming
vessel 23. From the outlet 26 the steamed chips are then fed -- as
illustrated schematically at 27 in FIGURE 1 -~- to a high pressure feeder
and continuous digester, or to a feed meclhanism on top of a batch
digester, or the like, through various conventiional treatment andlor feed
mechanisms.
FIGURES 2 through 17 illustrate various embodiments and details
of the chip bin 10 of FIGURE 1. However all of the accessories such as an
air lock, vent pipes, steam conduits, etc. <~re not shown associated
therewith, but would of course commonly be provided. While the chip bin
10 according to the present invention typically has a maximum diameter of
twelve feet or more (typically fourteen feet or more), which is where
significant problems occur in conventional systems having vibratory
discharges, there are many aspects of the invE:ntion that are applicable to
chip bins of any size, and some aspects of the invention applicable to bins
in general. In all the embodiments, the internal conical-insert bin,
construction of co-pending application serial no. 081130,525 may be
utilized.
FIGURES 2 through 5 illustrate one embodiment of a chip bin
according to the invention which may be referred to as a "chisel design". In
this embodiment, as in all embodiments of the chip bin according to the
invention, the vibratory discharge conventional in prior art chip bins has
been eliminated. In the FIGURES 2 through .5 embodiment components
comparable to those in FIGURE 1 are shown by the same reference
numeral only preceded by a "1".
The chip bin 110 includes a hollow substantially right circular
cylindrical main body portion 30 having a substantially vertical central axis,
a top 111, and an open bottom 29. It has a maximum (and preferably
substantially uniform) internal diameter 31, which typically is twelve feet or
d)
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14
more (e.g. fourteen feet or more, for example sixteen feet). The top 111 is
defined by a top wall which has the conduit 112 (connected to the
conventional air lock, etc., not shown in FIGURES 2 through 5) which
comprises means for introducing particulate material, typically wood chips
or other comminuted cellulosic fibrous material, into the main body portion
30. A steam introduction header 32, which introduces steam at a plurality
of points around the circumference of the main body 30, may be provided
as the sole, or as one of several, mechanismis for steaming chips within
the bin 110.
The bin 110 also comprises a hollow tr<~nsition portion 33 having a
substantially circular cross-section open top 34 and a substantially
rectangular cross-section open bottom 35 (sere FIGURE 4 in particular).
The transition portion 33 top 34 -- which is continuous with the bottom 29
of the main body portion 30 -- has opposite side non-vertical gradually
tapering side walls 36. The side walls 36 makE: an angle 37 (see FIGURE
3) with respect to the vertical, which angle 37 is typically about 20-
35°, and
preferably about 25-30°, but will vary depending upon the particular
material handled by the bin 110 (e.g. the particular species of wood chips
commonly used). So that a smooth geomeitric transition between the
circular configuration of the main body portion 30 and the substantially
rectangular bottom 35 of the transition 33 is provided, the ends 38 of the
transition 33 are continuously curved surfaces, as indicated by the
shading in FIGURES 2 and 3, and as also seen in FIGURE 4. Typically, the
main body portion 30 is welded to the transition portion 33 to provide a
continuous fluid-tight wall so that steam introduced into the hollow interior
of the portions 30, 33 cannot escape, except through designed vents. Note
that the transition 33 has a height 39 which is typically less than the
diameter 31 (e.g. in one embodiment for a diameter 31 of sixteen feet the
height 39 would be about twelve feet).
In the FIGURE 2 embodiment a baffle 40 is illustrated within the
transition 33 for causing the chips flowing downwardly from the main body
portion 30 to flow into two different volumes on opposite sides thereof. For
clarity of illustration of the other components t:he baffle 40 is not seen in
15
FIGURE 4, but spans the entire volume between the non-vertical gradually
tapering side walls 36, and makes an angle with respect to the vertical
approximately the same as the angle 37.
Located adjacent the open bottom 35 of the transition 33,
therebelow, is at least one feed screw mounted in a housing which is
connected to the bottom 35. In the embodiment of FIGURES 2 and 3, two
feed screws 41, 42 are provided mounted on separate shafts 43, 44 driven
by motors 45, 46 respectively, and with a junction 47 therebetween. The
details of the bearings, etc. for mounting i:he shafts 43, 45 are not
illustrated, nor are the details of the feed screws 41, 42. The feed screws
41, 42 are conventional per se, and may be single screws, multiple
screws, or any suitable conventional type. The motors 45, 46 rotate the
screws 41, 42 in opposite directions, so that the screws feed the chips
toward the middle (below the baffle 40), typical screw speeds being about
10-100 rpm. Alternatively and just as preferred (though not shown in the
drawings) the first and second feed screws 4f , 42 may be different hand
(right and left) screws on a common shaft (43) rotated by a common motor
(45). In both cases the screws are "oppositely directed".
The housing for the screws 41, 42 preferably has substantially the
same width as the width of the open bottom 35 of the transition 33.
Operatively connected to the feed screw housing remote from the
transition 33 (typically on the opposite side thereof) is the discharge 49.
The discharge 49 typically comprises a hollow substantially right
rectangular parallelepiped conduit, connection, or transition, centrally
located just below the junction 47, and having a diameter 50 which is
approximately the same as the width of the housing for the screws 41, 42
(essentially the same as the screw 41, 42 diameters). In order for
maximum feeding efficiency to exist, associatE:d with the "chisel" shaped
transition 33, the length of each screw 41, 42 should be at least about 2.5
times the diameter of the screws, and these dimensions will be taken into
account when designing the diameter 50, the screws 41, 42, etc.
As seen in FIGURES 2 and 3, the discharge 49 may be connected
directly to a conventional low pressure feeder 122 (that is a chip meter is
16
not necessary), and in fact the discharge 49 may comprise the inlet
connection to the low pressure feeder 122. Since the screws 41, 42
provide a metering action (which is controlled by controlling the speed of
rotation thereof by controlling the motors 45, 46) the typically necessary
chip meter (21 in FIGURE 1) can be eliminated.
Instead of screws other equivalent metering and transporting
elements may be used, e.g. star feeders.
Instead, or in addition to, introducing steam into the chip bin 110
using the steam introduction header 32, steam may be introduced into the
transition 33. The preferred manner in which this is done is illustrated in
FIGURE 5. Steam introduction is not effective in inwardly angled walls
such as the gradually tapering side walls 36 of the transition 33 since the
steam ports would have a tendency to clog. However this problem is
alleviated according to the present invention, a:> illustrated in FIGURE 5, by
providing a substantially vertical wall interruption 53 of at least one of the
non-vertical gradually tapering side walls 36 (and preferably at multiple
locations along each of the walls 36). A scream conduit 54, such as
connected to a steam header 55 supplied with low pressure steam,
penetrates the transition 33 at the substantially vertical wall interruption
53,
the interruption 53 being a minor discontinuity in the slope of the wall 36.
The arrangement of FIGURE 5 is provided in each of the subsequent
embodiments of chip bins according to the invention, but will not be shown
or described in detail with respect to the other .embodiments.
FIGURES 6 and 7 illustrate another embodiment of chop bin
according to the invention. Components in the FIGURES 6 and 7
embodiment comparable to those in the FIGURES 1 through 5
embodiments are shown by the same two digit reference numeral only
preceded by a "2".
In the FIGURES 6 and 7 embodiment, the hollow substantially right
circular cylindrical main body portion 230 is the same as the main body
portion 30 in the FIGURES 2 through 5 embodiment, as are the screws
241, 242, and associated components at the bottom of the chip bin 210 to
their counterparts. The difference between the FIGURES 6 and 7
1
17
embodiment and the FIGURES 2 and 3 embodiment is the nature of the
transition 233.
The transition 233 of FIGURES 6 and 7 incorporates the basic
design features of U.S. patent 4,958,741 which is supplied commercially
under the trademark "Diamond Back Hopper" by J.R. Johanson, Inc. of
San Luis Obispo, California. The hollow transition portion 233 has one
dimensional convergence and side relief, provided by triangular shaped
substantially flat side panels 58 connected together by curved end wall
portions 59, the portions 58 making an angle 237 comparable to the angle
37 in the FIGURES 2 and 3 embodiment (e.g. about 20-35°). In the
FIGURES 6 and 7 embodiment a second hollow transition 61, having
generally the configuration of a rectangular parallelepiped (with rounded
ends) has flat triangular, substantially vertical side panels 62 on each side
thereof, and rounded end portions 64, and leads the chips from the
transition 233 to the screws 241, 242, in two separate flow paths, with the
one dimensional convergence and side relief of each minimizing the
possibility of hangup (bridging). Expansion joints 63 preferably mount
each of the sides of second transition 61 defining different flow paths to
the housing for screws 241, 242.
In the FIGURES 8 and 9 embodiment, components comparable to
those in the FIGURES 1 through 7 embodiments are shown by the same
two digit reference numeral only preceded by a "3". For the chip bin 310 of
FIGURES 8 and 9, no screws 41, 42, 241, 242 .are provided, and rather the
metering function they provide is instead supplied by the conventional chip
meter 321. In the FIGURES 8 and 9 embodiment again one dimensional
convergence and side relief is provided, in this case using components
having the same basic configuration as thosE~ illustrated in FIGURES 1
and 2 in U.S. patent 4,958,741. While the transition 333 is substantially the
same as the transition 233, the transition 3Ei1 is different, having the
triangular side walls 68 which are substantially flat, and connected
together by the curved end portions 69, providing the smooth transition
from the substantially rectangular bottom of the transition 333 to the
7)
18
circular discharge 349, having a configuration similar to that of a truncated
right triangular prism.
In the construction of the FIGURES 2 through 5 embodiment, some
time there are restrictions on the sizes of components that are too
restrictive for some installations. The necessary dimensional relationship
that provides such restrictions is -- as earlier indicated the necessity of
having the length of the outlet of the transition at least about 2.5 times the
outlet width for proper feeding. In the embodiiment of FIGURE 10 this is
accommodated by providing a single screw 71 in a screw housing 70
mounted to the substantially rectangular open bottom 35 of the transition
33, the screw 71 driven by the motor 72 and moving the chips in the
direction of the arrow illustrated in FIGURE 10 to an outlet 73 that is offset
with respect to the main body portion 30 (and transition 33). A conduit 74
may be provided in the housing 70 at the end thereof remote from the
outlet 33 to act as a vent, or to allow steam for steaming the chips to be
introduced thereat.
Under some circumstances, it is possik>le to provide the outlet 73
as the direct connection to a low pressure feeder, or the rest of the
digester system 27 (from FIGURE 1), however in many situations it is
more desirable to have the ultimate discharge from the chip bin to be
concentric with the vertical axis of the main body portion 30. In order to
accommodate this, a second screw 76 in screw housing 75, located
below the first screw 71 and first screw housing 70, and illustrated in
dotted line in FIGURE 10, is provided. The screw 76, driven by motor 77,
moves the chips from the conduit 73 back toward the center of the chip bin
110 to the substantially right rectangular parallelepiped discharge 49
which is concentric with the main body portion 30. The screws 71, 76
preferably rotate about parallel axes in a common substantially vertical
plane.
The embodiment of FIGURES 11 throu~~h 12 deals with the same
dimensional problem that the FIGURE 10 embodiment deals with only in a
different way. In the FIGURES 11 through 12 embodiment, a second
hollow transition portion 80 is provided between the first transition portion
_..
r<. _.
19 ,
33 and the at least one screw (screws 41, 42 in FIGURES 11 through 13).
The second hollow transition 80 has a cross-sectional configuration
substantially the same as a race course oval with substantially vertical
side walls 81 but with the end walls 82 thereof slightly curved, and with a
baffle 83 located in the center bottom portion thereof above the junction 47.
The open top 84, which has the same cross-sectional area as the open
bottom 35 of the first transition 33, is smaller than the cross-sectional area
of the open bottom 85, both the top 84 and bottom 85 being substantially
oval (as seen in FIGURE 13). FIGURE 13 illustrates the dimensional
relationship that is highly desirable, namely the width W of the bottom
35/top 84 (which is essentially the same as they diameter of the screws 41,
42) requires an outlet length (for each screw 41, 42) greater than about 2.5
W.
In the FIGURES 11 through 13 embocliment, the discharge 49 is
substantially concentric with the main body portion 30 yet the desired
dimensional relationship Wlgreater than 2.5 W, is readily achieved. The
baffle 83 divides the flow of chips into two different volumes, and prevents
short circuiting of the chips directly to the discharge 49.
FIGURES 14 and 15 show an embodiment similar to that in
FIGURES 2 and 3 only without a baffle. Since the central discharge 49
could be prone to short circuiting, a conventional chip meter 121 is
included in this embodiment, run by a motor Et6, even though the screws
41, 42 are provided. With such an arrangemeint it is necessary to control
the speeds of the motors 45, 46 (or a single motor taking the place of
motors 45, 46), 86 to prevent starvation of the chip meter 121, as by using
the controller 87. Also in this embodiment there is the possibility of chip
hangup at the junction between the screws 4'1, 42, and to eliminate this
possibility it is desirable to provide the agitatoir 88, driven by a motor 89,
located at the junction between the screws 41, 42. Thus in this
embodiment the screws 41, 42 do not provide a metering function (as they
do, for example, in the FIGURES 2 and 3 embodiment), but rather only a
transporting function, facilitated by the agitator 88.
I)
20 .~._
In the FIGURES 16 and 17 embodiment'., the same advantages with
respect to the lengthldiameter ratio of the screws 241, 242 as are obtained
in the FIGURES 11 through 13 embodiment for the "chisel" bin design are
obtained for the "Diamond Back"~ design of FIGURES 6 and 7. That is
below the transition 233 instead of the substantially rectangular
parallelepiped transition 61 a truncated substaintially right triangular prism
(with rounded ends, simulating a race tack oval) transition 90 is provided,
having substantially vertical planar side platen 91, and the rounded ends
92. A baffle 93 is mounted within the transition 90 above the junction 247
for the screws 241, 242 to divide the chips flow into two different volumes.
The second transition 90 has a substantially rE:ctangular shaped open top
94 and a substantially rectangular shaped open bottom 95, the area of the
open top 94 being significantly less than the arE~a of the open bottom 95.
While the chip bins according to the invention can be used as bins
per se rather than exclusively in chemical pulping systems, they are
particularly suitable for use with a method of feeding comminuted
cellulose material to a digester and where they have a maximum diameter
of about twelve feet or more, and with a discharge which is operatively
connected to a digester and has a cross-sectional area less than half of
the cross-sectional area of the chip bin. With respect to the FIGURES 2
and 3 embodiment in particular, the comminuted cellulose material is fed
into the top of the chip bin 110 through the concluit 112, to flow downwardly
in a column in the chip bin 110 toward the bottom (where the discharge 49
is located). The comminuted cellulose material is caused to move in a
gradually restricting open flow path in the interior of the chip bin until the
open flow path has a cross-sectional area (in the transition 33) less than
half of the cross-sectional area at the maximum diameter portion (30) of
the chip bin 110. Then without vibrating they chip bin or the chip bin
discharge, a substantially uniform flow of 1'he comminuted cellulose
material is provided in the gradually restricting open flow path,
substantially without bridging of the cellulose material. While in the bin,
and typically also while in the gradually restricting open flow path, the
comminuted cellulosic material is steamed, as by introducing steam at 32
~.
21
and 55 (see FIGURES 2 and 5), and subsequently the partially steamed
comminuted cellulosic material is discharged from the bottom of the
transition 33, metered by the screws 41, 42, into the discharge 49. From
the discharge 49 the cellulose material is fed to the digester (27 in FIG. 1),
as through the low pressure feeder 122 and the other conventional
components illustrated in FIGURE 1.
The embodiment illustrated in FIGURES 18 through 20 is a
preferred embodiment for use in place of conventional chip bin
assemblies. The chip bin assembly illustrated in FIGURES 18 and 19 is
shown generally by reference numeral 40~D, and includes a hollow
substantially right circular cylindrical main body 401 having a substantially
vertical center axis 402, a top (see 403 in FIGURE 18), a bottom 404, and a
first diameter 405. Typically the diameter 405 is greater than 12 feet, e.g.
about 15 feet. An inspection portal 406 may be provided too. The top is
defined by a top wall 403 which closes off the main body 401, and
includes an inlet 407 for introducing wood chips (or like comminuted
cellulosic fibrous material) into the hollow main body 401. A non-vibrating
discharge 408 is operatively connected to the bottom 404 of the main body
401, through the hollow transition 410. In ithe preferred embodiment
illustrated in FIGURES 18 and 19 the discharge 408 is circular in cross
section, having a second diameter 411 which is typically much less than --
e.g. about 1I3 or less -- than the first diameter 405. For example, the
diameter 411 (see FIGURE 19 may be about 4 feet when the first diameter
is about 15 feet).
The discharge 408 is a combination ex~>ansion joint and transition.
As an expansion joint it accommodates tlhermal expansion in the
assembly 400, and between assembly 400 and adjoining assemblies
(e.g, pipes, chip meters, feeders, etc.).
The discharge 408 is operatively connected to a continuous
digester, typically through a high pressure feeder 413. Also, a chip meter
414, and associated other conventional components such as a low
pressure feeder 412, a horizontal steaming vessel (not shown), and chip
chute are provided for supplying wood chips to the low pressure
v
2
circulation of the high pressure feeder 413. As is conventional, high
pressure pump 416 displaces the chips from the high pressure feeder
413 and feeds them to the top of a continuous digester. Alternatively, the
low pressure feeder 412 and associated steaming vessel and chip chute
may be replaced by a slurry pump (not shown) connected directly to the
high pressure feeder 413. In this case high pressure feeder exhaust is
connected to line 437.
The hollow transition 410 for the chip bin assembly 400 provides for
the optimum feeding of the chips while allowing steaming, during feeding,
and minimizing the chance for chip hangup even though the chips flow
path is greatly reduced in size (e.g. from a 15 foot diameter to a 4 foot
diameter). The preferred hollow transition 410 illustrated in FIGURES 18
and 19 comprises a double Diamondback~ type of configuration, sold by
J, R. Johanson, Inc. of San Luis Obispo, California, and as generally
disclosed in U.S. Patent 4,958,741.
The hollow transition 410 includes a first uppermost portion 418
having a generally right rectangular parallelepiped configuration (with
opposite end faces curved) and including opposite side faces having
generally triangular shapes 419, and providing one dimensional
convergence and side relief. A second portion .420 tapers from a generally
rectangular parallelepiped configuration at an upper part 421 thereof to a
generally circular configuration at the lower part 422 thereof. It also has
opposite side faces having, generally triangular shapes 423 which align
with the first portion 418 generally triangular shapes 419 to define
substantially diamond shaped wall portions, ass clearly seen in FIGURE
18.
While the lower part 422 of the second portion 420 may be
connected directly to the discharge 408, preferably the transition 410 also
includes a third portion 426 which is substani':ially the same as the first
portion 418 (including the generally triangulair shapes 427 on opposite
side faces), only smaller, and a fourth portion 429 substantially identical to
the second portion 420, only smaller, and including the generally
triangular shapes 430 which cooperate with the shapes 427 to define
23 "
substantially diamond shaped wall portions as also clearly seen in
FIGURE 18. When the third and fourth portions 426, 429 are utilized, the
lower part 422 of the second portion 420 has a third diameter which is
generally intermediate the first and second diameters, typically being at
least 50% greater than the second diameter and at least 30% less than
the first diameter. For example, where the first diameter is about 15 feet
and the second diameter is about 4 feet, the tlhird diameter -- indicated at
432 in FIGURE 19 -- is about 8 feet.
The chip bin assembly 400 also includes means for introducing
steam into at least one of the main body 401 and hollow transition 410 to
steam wood chips therein. Preferably steam is introduced into both. For
example, a conventional steam header assennbly 433 (see FIGURE 18)
introduces steam into one or more places along the main body 401, while
steam is introduced from source 434 into the hollow transition 410. In the
preferred embodiment illustrated in the dravuings, low pressure steam
from source 434 is introduced into the transition 410 utilizing conduits 435
provided in the faces 423 of the second portion 420. Also, steam relief 437
from the low pressure feeder 412 may be provided to one of the generally
triangular shapes 423, via conduit 438, as seen in both FIGURES 18 and
19. A wide variety of other mechanisms for iintroducing steam, utilizing
headers, branches, conduits, nozzles, or the positioned wherever desired,
may also be provided.
The main body 401 also may include conical ring inserts, such as
the conical insert 440 seen in FIGURE 18,. for relieving compaction
pressure on chips in the main body 401. Such conical insert rings 440 are
fully described in copending U. S. patent 5,454,490.
While the transition 410 is normally effective to prevent hangups,
because there is such a large diameter reduction from the main body 401
to the discharge 408, and because no vibratory action is provided at the
discharge 408 (or other components), it is preferred that some sort of
mechanism be utilized to break up hangups if they do occur. This is
preferably provided by utilizing one or more air blasters, such as shown
schematically at 442 in FIGURES 18 through 20, connected at the
24
appropriate places to the transition 410. Air' blasters are conventional
structures per se, which supply either high powered air, nitrogen or like
gas, for the purpose of dislodging trapped or hung-up solids (wood chips),
For example, the air blasters 442 may be of the conventional type
manufactured by Global Manufacturing, Inc. of I'~_ittle Rock, Arkansas.
In the preferred embodiment illustrated in FIGURES 18 through 20 it
will be seen that first and second air blasters (which may include first and
second connections to a common air blaster) are provided connected to
nozzles 443 on the end walls (generally perpendicular to the side faces
containing the generally triangular portions 4'19) of the first portion 418,
and nozzles 444 connected to the end walls ~of the third portion 426. As
seen most clearly in FIGURE 20, for one of the nozzles 443, preferably the
nozzle 443 is disposed at an angle 446 -- which is preferably about 45
degrees -- to the end wall of the portion 418, and is disposed within a
support ring 447 which extends outwardly from the portion 418. For
example, the dimension 448 may be about 6 inches, and the dimension
449 about one foot. The angled, downwardly directed, gas blasts provided
by the air blaster 442 when activated dislodge any chip hangups in the
transition 410. The air blasters 442 may be operated manually when the
hangup is noticed by an operator, or blasters 442 may be operated
automatically by sensing the flow rate through the discharge 408, or in
other desired manners. The blasters 442 may be mounted elsewhere in
the main section of the bin (i.e. not necessarily within support rings 447).
The shapes 419, 423, 427, 430 need not be truly triangular. The
term "generally triangular" as used in the presE:nt specification and claims
includes shapes such as those illustrated at 419' and 423' in FIGURE 21
(the reference numerals in FIGURE 21 are the same as those in FIGURE
18, only followed by a ""'), or other modification:. thereof.
While the invention has been herein shown and described in what
is presently conceived to be the most practical and preferred embodiment
thereof it will be apparent to those in ordinan~ skill in the art that many
modifications may be made thereof within the scope of the invention,
l~
25
which scope is to be accorded the broadest ini:erpretation of the appended
claims so as to encompass all equivalent structures and methods.
