U.S. patent application number 16/097904 was filed with the patent office on 2019-05-16 for filter for extruder press.
The applicant listed for this patent is GREENFIELD SPECIALTY ALCOHOLS INC.. Invention is credited to Christopher Bruce BRADT.
Application Number | 20190143247 16/097904 |
Document ID | / |
Family ID | 60157674 |
Filed Date | 2019-05-16 |
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United States Patent
Application |
20190143247 |
Kind Code |
A1 |
BRADT; Christopher Bruce |
May 16, 2019 |
FILTER FOR EXTRUDER PRESS
Abstract
A solid/fluid separation module (300) and press comprises at
least one filter unit (301) for a solid/fluid separating press
having a barrel with a core opening (112) for at least one conveyor
screw. The filter unit includes a pair of end plates (321,322) and
a plurality of intermediate filter plates (314) placed one behind
the other and sealingly compressed into a plate stack (310) between
the end plates. Each intermediate plate (314) has at least one
drainage perforation (362) separate from the core opening, the core
opening and drainage perforation each extending from a front face
to a back face of the intermediate filter plate. In the filter
unit, all end plates and barrel plates are aligned such that the
core openings form the core passage of the filter block and such
that the drainage perforations form an internal fluid collection
chamber (338) within the filter unit.
Inventors: |
BRADT; Christopher Bruce;
(LaSalle, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GREENFIELD SPECIALTY ALCOHOLS INC. |
Toronto |
|
CA |
|
|
Family ID: |
60157674 |
Appl. No.: |
16/097904 |
Filed: |
April 26, 2017 |
PCT Filed: |
April 26, 2017 |
PCT NO: |
PCT/CA2017/050509 |
371 Date: |
October 31, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62330444 |
May 2, 2016 |
|
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|
Current U.S.
Class: |
210/231 |
Current CPC
Class: |
B01D 25/12 20130101;
B30B 9/16 20130101; B30B 9/12 20130101; B30B 9/124 20130101; B01D
25/325 20130101; B30B 9/262 20130101; B30B 9/26 20130101 |
International
Class: |
B01D 25/12 20060101
B01D025/12; B01D 25/32 20060101 B01D025/32; B30B 9/12 20060101
B30B009/12; B30B 9/16 20060101 B30B009/16; B30B 9/26 20060101
B30B009/26 |
Claims
1. A solid/fluid separation module for a solid/fluid separating
press, the press having a barrel with a core opening for containing
a solid/fluid mixture and housing at least one conveyor screw for
conveying the solid/fluid mixture, the barrel being divided into at
least two barrel modules respectively defining an axial portion of
the barrel, the solid/fluid separation module being constructed for
forming at least one of the barrel modules and comprising a pair of
mounting plates for connection to adjacent barrel modules and a
filter unit fastened between the mounting plates, the filter unit
formed by a plurality of barrel plates stacked one behind the other
and sealingly compressed into a plate stack between a pair of end
plates, each barrel plate having a front face and a back face and
each mounting plate, end plate and barrel plate having a core
opening equal in cross-section to the core passage; at least one
barrel plate adjacent one of the end plates being a perforated
barrel plate having a drainage perforation separate from the core
opening, the core opening and drainage perforation each extending
from the front face to the back face, all mounting plates, end
plates, barrel plates and perforated barrel plates in the
separation module being oriented for the core openings to align and
form the core passage of the filter unit and all perforated barrel
plates being further aligned for the drainage perforations to align
and form an internal fluid collection chamber within the filter
unit; at least one of the perforated barrel plates being
constructed as a filter plate including at least one filter passage
extending from the core opening to the drainage perforation; and at
least one of the end plates having an evacuation passage connected
at an input end with the collection chamber and at an output end
with an exterior of the filter unit for draining from the
collection chamber separated fluids that were separated from the
solid/fluid mixture through the filter passage.
2. The solid/fluid separation module of claim 1, wherein all barrel
plates are perforated barrel plates and each end plate has an
evacuation passage for the collection chamber to allow circulation
of the separated fluids in the collection chamber for reducing
deposits in the collection chamber.
3. The solid/fluid separation module of claim 1 or 2, wherein each
perforated barrel plate includes at least two Independent drainage
perforations for the formation of an equal number of internal
collection chambers within the plate stack and each filter plate
includes at least one filer passage for each drainage
perforation.
4. The solid/fluid separation module of claim 3, wherein each
filter plate includes at least two filter passages extending from
the core opening to each drainage perforation.
5. The solid/fluid separation module of any one of claims 1-4,
wherein all barrel plates are perforated barrel plates including a
number of drainage perforations distributed about the core opening
for the formation of an equal number of separate interior
collection chambers in the filter block.
6. The solid/fluid separation module of claim 5, wherein at least
one end plate includes a separate evacuation passage for each
interior collection chamber.
7. The solid/fluid separation module of claim 6, wherein each end
plate includes a separate evacuation passage for each interior
collection chamber to allow selected circulation of separated
fluids through each collection chamber to reduce deposits in the
collection chamber.
8. The solid/fluid separation module of claim 7, wherein each
filter plate includes at least one filter passage for each drainage
perforation.
9. The solid/fluid separation module of any one of claims 1-8,
wherein the filter passage is formed in a front face of the filter
plate.
10. The solid/fluid separation module of any one of claims 1-8,
connectable to a pressure input for selectively connecting the
output end of each evacuation passage to a source of backpressure
for reversing a flow of the separated fluids in the collection
chamber and the filter passage to backwash the filter passage.
11. The solid/fluid separation module of claim 10, wherein each
evacuation passage is individually connectable to the pressure
input.
12. The solid/fluid separation module of claim 11, wherein one, two
or more of the evacuation passages are simultaneously connectable
to the pressure input.
13. The solid/fluid separation module of any one of claims 1-12,
wherein the plate stack is divided into first and second plate
stack sections joined along a longitudinal plane of symmetry of the
core passage and sealably clamped together for defining the
longitudinal portion of the core passage, at least one of the plate
stack sections including a plurality of barrel plate sections
stacked one behind the other and sealingly compressed into a plate
stack section between the end plate sections
14. The solid/fluid separation module of claim 13, wherein the
filter block Includes a clamping structure for clamping together
the first and second plate stack sections along the plane of
symmetry.
15. The solid/fluid separation module of claim 13, wherein the
filter block further includes for each plate stack section a
stacking structure for aligning the barrel plate sections one
behind the other in the plate stack and compressing the barrel
plates into the plate stack for clamping together the barrel plate
sections in each plate stack section.
16. The solid/fluid separation module of claim 1, wherein the
filter passage is in the front and/or back surface.
17. The solid/fluid separation module of any one of claims 1-16,
for use with a separating press including two conveyor screws,
wherein the plane of symmetry of the core passage extends through a
longitudinal axis of each conveyor screw.
18. The solid/fluid separation module of claim 13, wherein the
first plate stack section includes only barrel plates and the
second plate stack section includes at least one filter plate.
19. The solid/fluid separation module of claim 17, wherein the
first plate stack section is replaced by a solid block.
20. The solid/fluid separation module of any one of claims 1-19,
wherein each filter plate has a preselected pore size and each
filter passage in the filter plate has cross-sectional area at the
inner edge corresponding to the preselected pore size.
21. The solid/fluid separation module of claim 12, wherein each
plate stack section has a preselected filter pore size and a
preselected porosity, each filter passage having an opening area at
the inner edge corresponding to the preselected pore size and each
filter plate having a filter plate porosity calculated from a total
surface of the core opening, the preselected pore size and the
number of filter passages, the plate stack section including a
number of filter plates at least equal to the ratio of preselected
porosity to plate porosity.
22. A solid/fluid separating press, comprising at least one
conveyor screw for conveying a solid/fluid mixture and a barrel
divided into at least two barrel modules respectively defining a
longitudinal portion of a core passage for housing the at least one
conveyor screw, at least one of the barrel modules constructed as a
solid/fluid separation module including a pair of mounting plates
for connection to adjacent barrel modules and a split filter unit
fastened between the mounting plates; the split filter unit
including a plurality of barrel plates stacked one behind the other
and sealingly compressed into a plate stack between a pair of end
plates, each barrel plate having a front face and a back face and
each mounting plate, end plate and barrel plate having a core
opening equal in cross-section to the core passage, each end plate
being divided along a plane of symmetry of the core passage into
first and second end plate sections and each barrel plate being
divided along the plane of symmetry into first and second split
plates; at least one split plate adjacent one of the end plate
sections being a perforated split plate having a drainage
perforation separate from the core opening, the drainage
perforation extending from the front face to the back face, a
stacking structure for aligning the first split plates into a first
plate stack and the second split plates into a second plate stack,
wherein the first and second split plates are stacked one behind
the other in the first and second plate stack and compressed
between the first and second end plate sections into first and
second filter blocks respectively; a clamping structure for
clamping the first and second filter blocks together along the
plane of symmetry to form the split filter unit; all mounting
plates, end plate sections, split plates and perforated split
plates in the separation module being oriented for the core
openings to align and form the core passage of the separation
module and all perforated split plates being further aligned for
the drainage perforations to align and form an internal fluid
collection chamber within the respective first or second filter
block; at least one of the perforated split plates being
constructed as a filter plate including at least one filter passage
extending from the core opening to the drainage perforation; and at
least one of the end plate sections having an evacuation passage
connected at an input end with the collection chamber and at an
output end with an exterior of the split filter unit for draining
from the collection chamber separated fluids that were separated
from the solid/fluid mixture through the filter passage.
23. The solid/fluid separating press of claim 22, wherein each
barrel module is a filter block.
24. The sold/fluid separating press of claim 22 or 23, wherein each
split filter unit has a preselected pore size and each filter
passage has an opening area at the inner edge corresponding to the
preselected pore size.
25. The solid/fluid separating press of claim 22, wherein each
filter block has a preselected porosity calculated from a total
surface of the portion of the core opening defined by the filter
block, divided by the preselected pore size and the number of
filter passages in the filter block.
26. The solid/fluid separating press of claim 22, wherein each
filter block has a different pore size and/or porosity.
27. Use of the solid/fluid separating press of any one of claims
22-26, for separating fluids from a solid/fluid containing
mixture.
28. The use of claim 27, wherein the solid/fluid mixture is a
biomass.
29. The use of claim 28, wherein the biomass is lignocellulosic
biomass.
30. A filter unit for use in a solid/fluid separating press having
a core passage for containing a pressurized solid/fluid mixture,
and housing at least one conveyor screw for conveying the
solid/fluid mixture, the barrel being divided into at least two
barrel modules respectively defining an axial portion of the
barrel, the solid/fluid separation module being constructed for
forming at least one of the barrel modules and including a pair of
mounting plates for connection to adjacent barrel modules and the
filter unit fastened between the mounting plates, the filter unit
comprising a plurality of barrel plates stacked one behind the
other and sealingly compressed into a plate stack between a pair of
end plates, each barrel plate having a front face and a back face
and each end plate and barrel plate having a core opening equal in
cross-section to the core passage of the separating press; at least
one barrel plate adjacent one of the end plates being a perforated
barrel plate having a drainage perforation separate from the core
opening, the core opening and drainage perforation each extending
from the front face to the back face, all end plates, barrel plates
and perforated barrel plates in the filter unit being oriented for
the core openings to align and form the core passage of the filter
unit and all perforated barrel plates being further aligned for the
drainage perforations to align and form an internal fluid
collection chamber within the filter unit; at least one of the
perforated barrel plates being constructed as a filter plate
including at least one filter passage extending from the core
opening to the drainage perforation; and at least one of the end
plates having an evacuation passage connected at an input end with
the collection chamber and at an output end with an exterior of the
filter unit for draining from the collection chamber separated
fluids that were separated from the solid/fluid mixture through the
filter passage.
31. The filter unit of claim 30, wherein al barrel plates are
perforated barrel plates and each end plate has an evacuation
passage for the collection chamber to allow circulation of the
separated fluids in the collection chamber for reducing deposits in
the collection chamber.
32. The filter unit of claim 30 or 31, wherein each perforated
barrel plate includes at least two independent drainage
perforations for the formation of an equal number of internal
collection chambers within the plate stack and each filter plate
includes at least one filter passage for each drainage
perforation.
33. The filter unit of claim 32, wherein each filter plate includes
at least two filter passages extending from the core opening to
each drainage perforation.
34. The filter unit of any one of claims 30-33, wherein all barrel
plates are perforated barrel plates including a number of drainage
perforations distributed about the core opening for the formation
of an equal number of separate interior collection chambers in the
filter block.
35. The filter unit of claim 34, wherein at least one end plate
includes a separate evacuation passage for each interior collection
chamber.
36. The filter unit of claim 35, wherein each end plate includes a
separate evacuation passage for each interior collection chamber to
allow selected circulation of separated fluids through each
collection chamber to reduce deposits in the collection
chamber.
37. The filter unit of claim 36, wherein each filter plate includes
at least one filter passage for each drainage perforation.
38. The filter unit of any one of claims 30-37, wherein the filter
passage is formed in a front face of the filter plate.
39. The filter unit of any one of claims 30-37, connectable to a
pressure input for selectively connecting the output end of each
evacuation passage to a source of backpressure for reversing a flow
of the separated fluids in the collection chamber and the filter
passage to backwash the filter passage.
40. The filter unit of claim 39, wherein each evacuation passage is
individually connectable to the pressure input.
41. The filter unit of claim 40, wherein one, two or more of the
evacuation passages are simultaneously connectable to the pressure
input.
42. The filter unit of any one of claims 30-41, wherein filter unit
is a split fitter unit divided into first and second filter blocks
joined along a longitudinal plane of symmetry of the core passage
and sealably clamped together for defining the longitudinal portion
of the core passage, at least one of the filter blocks being a
stacked filter block including a pair of end plate sections and a
plurality of barrel plate sections stacked one behind the other and
sealingly compressed into a plate stack section between the end
plate sections.
43. The filter unit of claim 42, further comprising a releasable
clamping structure for releasably clamping together the first and
second filter blocks along the plane of symmetry.
44. The filter unit of claim 42, wherein each stacked filter block
further includes a stacking structure for aligning the barrel plate
sections one behind the other in the plate stack section and for
releasably compressing the barrel plate sections into the plate
stack section.
45. The filter unit of claim 30, wherein the filter passage is in
the front and/or back surface.
46. The filter unit of any one of claims 30-45, for use with a
separating press including two conveyor screws, wherein the plane
of symmetry of the core passage extends through a longitudinal axis
of each conveyor screw.
47. The filter unit of claim 45, wherein the first plate stack
section includes only barrel plates and the second plate stack
section includes at least one filter plate.
48. The filter unit of claim 45, wherein the first plate stack
section is replaced by a solid block.
49. The filter unit of any one of claims 30-48, wherein each filter
plate has a preselected pore size and each filter passage in the
filter plate has cross-sectional area at the inner edge
corresponding to the preselected pore size.
50. The filter unit of claim 30, wherein each plate stack section
has a preselected filter pore size and a preselected porosity, each
filter passage having an opening area at the inner edge
corresponding to the preselected pore size and each filter plate
having a filter plate porosity calculated from a total surface of
the core opening, the preselected pore size and the number of
filter passages, the plate stack section including a number of
filter plates at least equal to the ratio of preselected porosity
to plate porosity.
Description
[0001] This application claims the benefit of priority from U.S.
Provisional Patent Application No. 62/330,444, filed May 2, 2016,
the entire contents of which are incorporated by reference.
FIELD OF THE INVENTION
[0002] The present disclosure is broadly concerned with solid/fluid
separation devices and methods for the separation of different
types of solid/fluid mixtures.
BACKGROUND OF THE INVENTION
[0003] Solid/fluid or solid/liquid separation is necessary in many
commercial processes, for example biomass processing, food
processing (oil extraction), reduction of waste stream volume in
wet extraction processes, dewatering processes, or suspended solids
removal.
[0004] Many biomass treatment processes generate a wet fiber slurry
from which dissolved compounds, gases and/or liquids must be
separated at various process steps to isolate a solids and/or
fibrous portion. Solid/fluid separation is generally done by
filtration and either in batch operation, with filter presses, or
continuously by way of rotary presses, such as screw presses.
[0005] Processes including the washing and subsequent concentration
of a solid/liquid slurry under pressure require solid/liquid
separation equipment able to operate under pressure, preferably
without clogging. For example, a key component of process
efficiency in the conditioning or pretreatment of lignocellulosic
biomass is the ability to wash and squeeze hydrolyzed
hemi-cellulose sugars, toxins, inhibitors and/or other extractives
from the solid biomass/cellulose fraction. It is difficult with
conventional equipment to effectively separate solids from liquid
under pressure and especially the high temperature and pressure
conditions required for cellulose pre-treatment.
[0006] During solid/fluid separation, the amount of liquid
remaining in the solid fraction is dependent on the amount of
separating pressure applied, the thickness of the solids cake, and
the porosity of the filter. The porosity of the filter is dependent
on the number and size of the filter pores. A reduction in
pressure, an increase in cake thickness, or a decrease in porosity
of the filter, will all result in a decrease in the degree of
liquid/sold separation and the ultimate degree of dryness of the
solids fraction.
[0007] For a particular solids cake thickness and filter porosity,
maximum separation is achieved at the highest separating pressure
possible. Moreover, for a particular solids cake thickness and
separating pressure, maximum separation is dependent solely on the
pore size of the filter.
[0008] High separating pressures unfortunately require strong
filter media, which are able to withstand the separating pressure
within the press, making control of the filtering process difficult
and the required equipment very costly. Filter media in
commercially available Modular Screw Devices (MSDs) are generally
in the form of perforated pressure jackets. The higher the
separating pressures used, the stronger (thicker) the filter media
(pressure jacket) need to be in order to withstand those pressures.
The thicker the pressure jacket, the longer the drainage
perforations, the higher the flow resistance through the
perforations and the higher the risk of clogging. In order to
achieve with high-pressure jackets (thick jackets) the same filter
flow-through capacity as with low-pressure jackets (thin jackets),
the number of perforations must be increased. However, increasing
the number of perforations weakens the pressure jacket, once again
reducing the pressure capacity of the filter unit.
[0009] Another approach to overcome the higher flow resistance
encountered with longer perforations is to increase the diameter of
the perforations. However, this will limit the capacity of the
filter to retain small solids, or may lead to increased clogging
problems. Thus, the acceptable pore size of the filter is limited
by the size of the fibers and particles to be retained in the
solids fraction. The clarity of the liquid fraction is limited
solely by the pore size of the filter media and pores that are too
large reduce the liquid/solid separation efficiency and potentially
lead to plugging of downstream equipment.
[0010] Over time, filter media tend to plug with suspended solids,
especially at elevated pressures. Thus, backwashing is generally
required to clear any blockage and restore the original production
rate of the filter. However, once a filter becomes plugged, it
takes a pressure higher than the operating pressure to backwash the
media. This can become problematic when working with filter media
operating at pressures above 1000 psig in a process that is to be
continuous to maximize the production rate, for example to obtain
high cellulose pre-treatment process efficiency. Thus, it would be
preferable to backwash prior to complete plugging of the filter.
However, most backwashing requires interruption of the filtering
operations, so that increased backwashing reduces the production
rate.
[0011] Conventional single, twin, or triple screw extruders do not
have the residence time necessary for pre-treatment of biomass, and
also do not have useful and efficient solid/fluid separating
devices for the pre-treatment of biomass, in particular
lignocellulosic biomass. U.S. Pat. Nos. 3,230,865 and 7,347,140
disclose screw presses having a perforated casing for solid/liquid
separation. Operating pressures of such a screw press are low, due
to the low strength of the perforated casing. U.S. Pat. No.
5,515,776 discloses a worm press having drainage perforations in
the press jacket, which increase in cross-sectional area in flow
direction of the drained liquid. U.S. Pat. No. 7,357,074 is
directed to a screw press with a conical dewatering housing with a
plurality of perforations for the drainage of water from bulk
solids compressed in the press. Again, a perforated casing or
jacket is used. As will be readily understood, the higher the
number of perforations in the housing, the lower the pressure
resistance of the housing. Moreover, drilling perforations in a
housing or press jacket is associated with serious challenges when
very small apertures are desired for the separation of fine
solids.
[0012] U.S. Pat. No. 8,746,138 discloses a solid/fluid separation
module with high porosity for use in a high internal pressure press
device for solid/fluid separation at elevated pressures. The filter
module includes filter packs respectively made of a pair of plates
that create a drainage system. A filter plate with cut through
slots creates flow channels for the liquid to be removed and a
backer plate creates a drainage passage for the liquid in the flow
channels. The backer plate provides the structural support for
containing the internal pressure of the solids in the press during
the squeezing action. The need for a backer plate for each filter
plate limits the filter porosity, since the axial length of the
module represented by the cumulative thickness of the backer plates
cannot be used for filtering. Moreover, the use of a filter slot in
combination with a drainage passage in the backer plate results in
a long, tortuous path of the separated fluids with elevated
backpressure and ample opportunity for fines accumulations in the
slot and/or the passage.
[0013] Published U.S. Application US 2015/0336031 discloses another
solid/fluid separation module with high porosity for use in
solid/fluid separation of a pressurized mass in screw type press
devices. The separation module includes a housing creating a
pressurizable fluid collection chamber and a barrel section having
an axial core opening for containing the pressurized mass under
pressure. The barrel section is mounted in the housing and includes
a filter block, which forms at least an axial portion of the
barrel. The filter block includes a plurality of stacked barrel
plates, each having an inner edge defining the core opening and an
outer edge in contact with the collection chamber. The barrel
plates are constructed as a filter plates having a recessed filter
passage extending from the inner edge to the outer edge for
draining fluid in the pressurized solid/fluid mixture from the core
opening to the collection chamber. This creates a relatively long
flow path in the filter passage. To address the elevated risk of
clogging associated with such a long filter passage, the filter
passage at the inner edge is provided with a deviation which
prevents fibrous particles from penetrating into the filter passage
to any significant extent. However, clogging of the filter passage
with fines is still possible and removal of such clogging may prove
challenging due to the long filter passage. Cleaning of a
permanently clogged filter block requires disassembly of the press
device and especially removal of the conveying elements of the
device.
[0014] Published U.S. Application US 2015/0343350 discloses a
further solid/fluid separation module for use in screw type press
devices. The module can be incorporated as a barrel module into a
modular screw device or a screw extruder and includes a split
filter unit allowing for assembly or removal of the filter unit
without removal of the screw or extruder screw. The split filter
unit includes first and second filter blocks joinable along a
longitudinal plane of symmetry of the core passage. The filter
blocks are mounted in a sealed housing so that the housing and
joined filter sections together define a longitudinal portion of
the core passage. The filter blocks including a plurality of barrel
plates having an inner edge located at the core opening and an
outer edge for contact with a fluid collection chamber formed by
the housing. The barrel plates are constructed as filter plates and
include a filter passage extending from the inner edge to the outer
edge for filtering of the pressurized mass at the inner edge and
draining of the separated fluid into the collection chamber at the
outer edge. Fluid separated from the pressurized mass by the filter
block through the filter passage is collected in the collection
chamber from which it is then drained. Clogging of the filter
passage with particulates occurs due to the long filter passage
extending from the core opening to the outside of the filter block.
The length of the filter passage also makes, removal of such
dogging challenging and backwashing is difficult due to significant
backpressure. Moreover, backwashing of a clogged filter block
requires the draining of the separated fluids from the collection
chamber, supplying backwashing fluid into the chamber and removing
the backwashing fluid upon completion of the backwash cycle. This
creates significant down time and cost.
SUMMARY OF THE INVENTION
[0015] It is an object of the present invention to obviate or
mitigate at least one disadvantage of previous solid/liquid
separation devices and processes.
[0016] In order to improve the operation and maintenance of a
solid/fluid separation device, the invention provides a filter unit
for a solid/fluid separating press having a barrel with a core
opening for containing a solid/fluid mixture and housing at least
one conveyor screw for conveying the solid/fluid mixture, the
barrel being divided into at least two barrel modules respectively
defining an axial portion of the barrel. The filter unit forms at
least one of the barrel modules and includes a filter block with an
internal fluid collection chamber, rather than an external
collection chamber. By providing an internal collection chamber,
the distance between the core opening and the collection chamber,
and thus the distance and fluids separated from the mixture in the
core opening must travel in a filter passage is reduced, which
reduces backpressure and fines accumulations and facilitates
backwashing.
[0017] In one embodiment, the filter unit includes a pair of end
plates for connection to adjacent barrel modules and a barrel
section formed by a plurality of barrel plates stacked one behind
the other and sealingly compressed into a plate stack between the
end plates. Each of the end plates and barrel plates has a core
opening equal in cross-section to the core passage. Each barrel
plate has a front face, a back face, and a drainage perforation
separate from the core opening. The core opening and drainage
perforation each extend from the front face to the back face. In
the filter unit, all end plates and barrel plates are aligned such
that the core openings form the core passage of the filter block.
Moreover, the barrel plates are aligned such that the drainage
perforations form an internal fluid collection chamber within the
filter unit. At least one of the barrel plates is constructed as a
filter plate including at least one filter passage extending from
the core opening to the drainage perforation and at least one of
the end plates has an evacuation passage connected at an input end
with the collection chamber and at an output end with an exterior
of the filter block for draining from the collection chamber
separated fluids that were separated from the solid/fluid mixture
through the filter passage.
[0018] In another embodiment, each end plate has an evacuation
passage for the collection chamber. By providing an evacuation
passages at both ends of the collection chamber, separated fluids
in the collection chamber can be circulated through the collection
chamber for reducing the accumulation of fines deposits, or
resinous deposits, for example lignin, in the collection
chamber.
[0019] In a further embodiment, each barrel plate includes at least
two separate drainage perforations for the formation of an equal
number of internal collection chambers within the plate stack and
at least one filter passage for each drainage perforation.
[0020] In yet another embodiment, each filter plate includes at
least two filter passages extending from the core opening to each
drainage perforation.
[0021] In still another embodiment, each barrel plate includes a
number of separate drainage perforations distributed about the core
opening for the formation of an equal number of separate interior
collection chambers in the filter block. One or more filter
passages can be provided for each drainage perforation.
[0022] In yet a further embodiment, at least one end plate includes
a separate evacuation passage for each interior collection chamber.
In still a further embodiment, both end plates include a separate
evacuation passage for each collection chamber to allow for
circulation of separated fluids through each collection chamber
independently and to allow for backwashing of each collection
chamber independently.
[0023] The filter passage may be a slit cut through the filter
plate, a recess provided in the front face of the filter plate, a
recess provided in the back face of the filter plate, or a pair of
recess provided in the front and back faces respectively.
[0024] In still a further embodiment, the filter unit is
connectable to a pressure input for selectively connecting the
output end of each evacuation passage to a source of backpressure
for generating a reverse flow of the separated fluids, or a
backwashing fluid, in the collection chamber and the filter passage
for backwashing of at least the filter passage.
[0025] Where separate evacuation passages are provided for the
collection chambers in the filter unit, each evacuation passage may
be individually connectable to the pressure input. One, two or more
of the evacuation passages may be simultaneously connectable to the
pressure input.
[0026] By providing each filter plate with a drainage perforation
located within the confines of the filter plate and separate from
the core opening, the distance of travel of filtered fluid within
the filter passage is shortened and the need for a pressurizable
collection chamber about the plate stack is obviated. By aligning
the drainage perforations in adjacent filter plates, a fluid
collection conduit is formed that principally functions like an
internal fluid collection chamber located fully within the plate
stack and closed by the end plates. This simplifies construction of
the separation device. Moreover, a pressure input may be provided
for generating a backpressure in the separated fluids in the
conduit. That backpressure can be used to generate a reverse flow
of the separated fluids in the collection conduit and the filter
passages to achieve a backwashing of the filter passages connected
to the collection conduit. This obviates the need for first
draining the separated fluids and the need for using a separate
backwashing fluid. Moreover, by simply applying a backpressure to
the separated fluids in the collection conduit, backwashing can be
carried out repeatedly and/or periodically to not only remove, but
prevent, dogging. In addition, by providing the collection conduit
within the filter stack, thereby allowing the direct application of
backpressure, periodic backwashing can be carried out during
operation and without interruption of the treatment of the
pressurized mass. The end plates may be provided with an evacuation
passage for each collection chamber to allow individual backwashing
of each collection chamber and the respectively connected filter
passages. If one or only a few collection chambers are backwashed
at any given time, the backwashing and separating processes can be
operated simultaneously, thereby providing for continuous operation
of the filter press and significantly reducing down times.
[0027] Although two or more filter passages can be connected to the
same drainage perforation, in one embodiment of the invention each
filter passage is connected to an individual drainage perforation.
In a further embodiment, each filter plate includes multiple filter
passages in the front face and one drainage perforation for each
filter passage, so that the plate stack includes a number of
collection conduits equal to the number of filter passages in each
filter plate. In another embodiment, the cross-sectional area of
the drainage perforation is always a multiple of the
cross-sectional area of the filter passage. In a further
embodiment, the cross-sectional area of each collection conduit
formed in the plate stack is equal to or larger than a cumulative
cross-sectional area of all filter passages connected thereto.
[0028] In still a further embodiment, a large number, or the
majority, of the barrel plates in at least one of the filter blocks
are constructed as a filter plate. To achieve the highest possible
porosity, each barrel plate may be constructed as a filter plate.
Moreover, each filter plate may include multiple filter passages.
The number of filter passages in each filter plate may be chosen to
maximize porosity without compromising filter plate or filter block
integrity.
[0029] The separation module of the invention may be used, for
example, in a large bore screw extruder for compressing the
solid/fluid mixture at pressures above 300 psig.
[0030] To achieve improved operating flexibility at reduced
maintenance cost, the solid/fluid separation module of the
invention in still another embodiment requires only the stopping of
the screw rotation for replacement of the filter stack without any
disassembly of any part other than the separation module. This is
achieved by a split filter unit including first and second filter
block sections sealably joinable along a longitudinal plane to
define the core passage of the extruder screw. The filter block
sections are preferably sealably joinable along a plane of symmetry
of the core passage so that the joined filter block sections
together define the longitudinal portion of the core passage.
[0031] In one embodiment, at least one of the filter block sections
is a stacked filter block including a plurality of stacked barrel
plate sections sealingly compressed one behind the other into a
plate section stack between a pair of end plate sections. Each
barrel plate section has flat front and back surfaces, an inner
edge located at the core opening and an outer edge. At least one
barrel plate section adjacent one of the end plates is a perforated
barrel plate section having a drainage perforation separate from
the core opening, the core opening and drainage perforation each
extending from the front face to the back face, and all end plate
sections, barrel plate sections and perforated barrel plate
sections in the split filter unit being oriented for the core
openings to align and form the core passage of the filter block and
al perforated barrel plate sections being aligned for the drainage
perforations to align and form an internal fluid collection chamber
within the filter block. At least one of the perforated barrel
plate sections is constructed as a filter plate section including
at least one filter passage extending from the core opening to the
drainage perforation. The drainage perforation extends completely
through the filter plate section from the front face to the back
face. In the filter block, the drainage perforations in mutually
contacting filter plate sections are aligned to form an internal
fluid collection chamber extending through the stacked filter plate
sections for collecting fluids drained from the respectively
connected filter passages. In the filter block, at least one of the
end plate sections has a compression face in contact with one of
the filter plate sections, the compression face having a drainage
passage fluidly connected at an input end with the drainage
perforation of the adjacent filter plate section. This allows fluid
to drain from the collection conduit extending from the drainage
perforation. At an output end, the drainage passage opens to an
exterior of the plate section stack, which allows fluids
accumulating in the drainage passage and the collection conduit to
be drained to the exterior of the separation module.
[0032] In a variant embodiment, the separation module includes a
split filter unit made of a stack of barrel plates which each have
a central bore for receiving the extruder screw and are each split
into first and second barrel plate sections along a separation
plane extending across a line of symmetry of the central bore. When
the barrel plate sections are stacked, the division of the barrel
plates into the first and second barrel plate sections leads to a
division of the filter unit along the separation plane into first
and second filter blocks or filter halves, which can be placed
about the conveyor screw. The end plates may be whole or split and
either remain installed about the conveyor screw when whole, or are
integrated with the filter block when split. Preferably, each
filter block of the split filter unit includes pair of end plate
sections.
[0033] In either embodiment, each filter block also includes a
stacking structure for aligning the stacked plate sections and for
combining them into the filter block. The separation module further
includes a clamping structure for clamping the first and second
filter blocks about the conveyor screw to form a clamped split
filter block enclosing the extruder screw and sealing the core
opening along the separation plane. At least one of the stacked
barrel plate sections is constructed as a filter plate section
defining a filter passage for liquid to drain away from the central
bore.
[0034] For removal of the split filter unit from the extruder, the
clamping structure is opened and one or both of the filter block
sections removed from the extruder. By incorporating the separated
fluid collecting structure within the filter block section, the
housing for the split filter unit is obviated. Assembly and
disassembly of the split filter unit is thereby much simplified and
maintenance downtimes are reduced. The installation of replacement
filter blocks, different filter blocks, or the same filter blocks
after cleaning, is then achieved in reverse order. A seal is
preferably inserted between the first and second filter block
sections in the separation plane for improved sealing of the
central bore and split seals are preferably provided between the
filter blocks and adjacent barrel modules.
[0035] The filter passages can be formed directly in the filter
plate by cutting filter slots into the filter plate, or by simply
recessing a fluid passage into either one or both surfaces of the
filter plate. This can be achieved much more easily than the
conventional approach of drilling holes in a pressure jacket. For
example, a recessed filter passage can be produced by etching the
filter passage into the filter plate surface. By only recessing the
filter passage into a surface of the filter plate, the overall
integrity of the filter plate is affected less than in filter
plates having cut through filter slots. Using recessed passages
allows for the creation of much smaller filter pores by using very
narrow and shallow passages. For example, by cutting a filter
passage of 0.01 inch width and 0.001 inch depth into the filter
plate, a pore size of only 0.00001 square inch can be achieved
(smallest depth of passage*smallest width of passage).
[0036] In one aspect, the invention provides a filter unit for a
solid/fluid separating press with at least one conveyor screw for
conveying a solid/fluid mixture, the press having a barrel divided
Into at least two barrel modules respectively defining a
longitudinal portion of a core passage for housing the at least one
conveyor screw. At least one of the barrel modules is a filter unit
including first and second filter blocks joinable along a
longitudinal plane of symmetry of the core passage for defining the
core passage when joined along the plane of symmetry. The filter
blocks are sealably joined for together defining the longitudinal
portion of the core passage. At least one of the filter blocks is a
stacked block including a plurality of the barrel plate sections,
while the other block may be a solid block.
[0037] Each filter plate section can have a preselected pore size,
whereby each filter passage has an opening area at the inner edge
corresponding to the preselected pore size. Moreover, each filter
block may have a preselected filter pore size and a preselected
porosity, whereby each filter passage has an opening area at the
inner edge corresponding to the preselected pore size, each filter
plate section having a plate porosity calculated from a total
surface of the core opening, the preselected pore size and the
number of filter passages. The porosity of the filter block is then
calculate as the sum of the plate porosities of all filter plate
sections in the stack.
[0038] In yet another aspect, the invention provides a sold/fluid
separating press including at least one conveyor screw for
conveying a solid/fluid containing mixture and a barrel defining a
core passage for the at least one extruder screw, the core passage
having a longitudinal axis for each extruder screw, the barrel
including at least two barrel modules, all of which are solid/fluid
separating modules in accordance with the invention. In another
embodiment, each solid/fluid separating module has a preselected
pore size and each filter passage has an opening area at the inner
edge corresponding to the preselected pore size. The filter module
may have a preselected porosity calculated from a total surface of
the core opening divided by the preselected pore size and the
number of filter passages in the filter blocks.
[0039] In still another aspect, the invention provides a use of the
solid/fluid separating press in accordance of the invention for
separating fluids from a solid/fluid containing mixture, for
example biomass, such as lignocellulosic biomass.
[0040] The separation module in accordance with the invention in
one embodiment includes a filter unit having a porosity of 5% to
20% (total pore area relative to the total filter surface) and is
constructed to withstand operating pressures of 300 psig to 10,000
psig, at a filter porosity of 5 to 20%, or 11 to 20%. Each filter
plate may include a plurality of filter passages with a pore size
of 0.0005 to 0.00001 square inch.
[0041] In another embodiment, the filter unit includes filter
plates, or filter plate sections with filter passages having a pore
size of 0.00001 square inch for the separation of fine solids, a
porosity of 5.7% and a pressure resistance of 2,500 psig. In still
another embodiment, the filter unit includes pores having a pore
size of 0.0005 square inch and a porosity of 20% and a pressure
resistance of 5.000 psig. In a further embodiment, the filter unit
includes pores of a pore size of 0.00005 square inch and a porosity
of 11.4%. In still a further embodiment, the filter unit includes
pores having a pore size of 0.00001 square inch and a porosity of
20%.
[0042] In the filter unit in accordance with the invention, the
pore size can be controlled by varying either one or both of the
width and depth of the filter passages. To maintain maximum filter
plate integrity, the depth of the filter passage can be maintained
as small as possible and pore size controlled by varying the filter
passage width. The width of the filter passages may vary from 0.1
inch to 0.01 inch and the depth of the filter passages may vary
from 0.001 inch to 0.015 inch. The filter passages in a filter
plate may all have the same pore size, or may have different pore
sizes.
[0043] In the solid/fluid separation press in accordance with the
invention, the separation module is mounted to the barrel of the
press and the core opening is sized to fittingly receive a
longitudinal portion of the extruder screw, or screws, of the
press. The conveyor screw has sufficiently close tolerances to the
central bore of the clamped filter block for generating a
significant separating pressure. This provides a solid/fluid
separation device, which allows for the separation of solid and
liquid portions of a solid/fluid mixture in a high pressure and
high temperature environment.
[0044] In a further embodiment of the sold/fluid separation press,
the press includes twin, intermeshing conveyor screws, the
separation module is mounted to the barrel of the twin screw press
and the central bore is sized to fittingly receive a portion of the
intermeshing conveyor screws.
[0045] Other aspects and features of the present disclosure will
become apparent to those ordinarily skilled in the art upon review
of the following description of specific embodiments in conjunction
with the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0046] For a better understanding of the embodiments described
herein, and to show more dearly how they may be carried into
effect, reference will now be made, by way of example only, to the
accompanying drawings which show the exemplary embodiments and in
which:
[0047] FIG. 1 is a partially schematic side elevational view of an
exemplary solid/fluid separating press including a pair of
separation modules in accordance with the invention;
[0048] FIG. 2 is a vertical sectional view of an exemplary press as
shown in of FIG. 1, but including only one separation module, for
reasons of simplicity;
[0049] FIG. 3a is a perspective view of an exemplary, tapered twin
extrusion screw set, which may be used in the exemplary embodiment
of FIG. 1;
[0050] FIG. 3b is a plan view of an exemplary, non-tapered twin
extrusion screw set, which may be used in the exemplary embodiment
of FIG. 1 together with a cylindrical barrel (not shown);
[0051] FIG. 4a schematically illustrates an embodiment of a filter
unit in accordance with the invention in axially exploded view;
[0052] FIG. 4b schematically illustrates an embodiment of a split
filter unit in accordance with the invention in axially exploded
view;
[0053] FIG. 5 illustrates the split filter unit of FIG. 4a in
vertically exploded view;
[0054] FIG. 6 illustrates a perspective end view of the split
filter unit of the separation module of FIGS. 4a and 5;
[0055] FIG. 7 is a perspective view of a lower filter block of the
split filter unit of FIG. 6;
[0056] FIG. 8 is a perspective view of an upper filter block of the
split filter unit of FIG. 6;
[0057] FIG. 9 illustrates the lower filter plate stack of FIG. 7 in
exploded view;
[0058] FIG. 10a is an axial plan view of an exemplary filter plate
for inclusion in the filter plate stack of the filter unit of FIG.
4a;
[0059] FIG. 10b is an axial plan view of an exemplary split filter
plate for inclusion in the upper or lower filter plate stack of
FIG. 7 or 8;
[0060] FIG. 11 is a perspective view of an optional compression
plate as shown in the exploded filter plate stack of FIG. 9;
[0061] FIG. 12 is a perspective view of an end plate section seen
from the plate stack side;
[0062] FIG. 13 is a perspective view of an end plate section seen
from the mounting plate side;
[0063] FIG. 14 is a top plan view of the end plate section of FIGS.
11 and 12;
[0064] FIG. 15 is a cross-section through the end plate section of
FIGS. 11 and 12;
[0065] FIG. 16 is an enlargement of portion A of FIG. 10a or
10b;
[0066] FIG. 17 is a variant of the enlargement of FIG. 16;
[0067] FIG. 18 is an enlargement of the intake end of an exemplary
filter passage;
[0068] FIGS. 19A to 19E are variants of the intake end of FIG.
18;
[0069] FIG. 20 is a cross-sections through the filter unit of FIG.
4B;
[0070] FIG. 21 is illustrates another embodiment of a solid/fluid
separation module in exploded view;
[0071] FIG. 22 shows a vertical cross-section through the
solid/fluid separation module of FIG. 21;
[0072] FIG. 23 is a partial cut-away view of the solid/fluid
separation module of FIG. 21; and
[0073] FIG. 24 is a perspective view of an exemplary split filter
unit of the embodiment of FIG. 21.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0074] It will be appreciated that for simplicity and clarity of
illustration, where considered appropriate, reference numerals may
be repeated among the figures to indicate corresponding or
analogous elements or steps. In addition, numerous specific details
are set forth in order to provide a thorough understanding of the
exemplary embodiments described herein. However, it will be
understood by those of ordinary skill in the art that the
embodiments described herein may be practiced without these
specific details. In other instances, well-known methods,
procedures and components have not been described in detail so as
not to obscure the embodiments described herein. Furthermore, this
description is not to be considered as limiting the scope of the
embodiments described herein in any way, but rather as merely
describing the implementation of the various embodiments described
herein.
[0075] The solid/fluid separation module of the invention is
intended for use with a single screw, twin screw or multi-screw
solid/fluid separation press, for example a twin screw extruder
assembly having parallel or non-parallel screws with the flighting
of the screws intercalated or intermeshed at least along a part of
the length of the extruder barrel to define close-clearance spaces
between the screws and between each screw and the barrel. However,
the solid/fluid separation module of the invention can also be used
with screw extruders having more than two conveyor screws.
[0076] In prior filter or solid/fluid separation devices for use
with MSDs or extruders, the integrity of the filtering jacket under
pressure is dependent on jacket thickness and porosity. Filter
capacity is dependent on Jacket porosity. However, the higher the
jacket porosity the lower the pressure resistance of the filter
jacket. Efforts to address this problem by building the filter
jacket from stacked filter plates as disclosed in U.S. Pat. No.
8,746,138, published U.S. Application US 2015/0336031 and published
U.S. Application US 2015/0343350 have resulted in improved filter
integrity, but are still subject to clogging caused by fine
particulates accumulating and eventually blocking the individual
filter passages. The inventors have now surprisingly discovered
that the degree and speed of dogging is more closely linked with
the length of the filter passage than the width of the filter
passage. That means filter passages which widen from the core
opening to the outside of the filter unit become dogged as often as
filter passages of constant cross-section, while a direct
relationship exists between the length of a filter passage and the
risk of clogging. However, short filter passages require filter
jackets of small thickness or filter plates having a narrow annulus
surrounding the core opening and those jackets and filter plates
are undesirable because of their low pressure resistance. Thus, a
solution was required for the problem of providing short filter
passages in thick filter jackets or filter stacks for screw
conveyors operating at elevated pressures.
[0077] The inventors have now found a solution which effectively
reduces the length of the filter passages in a stacked filter unit
without significantly reducing the pressure resistance of the plate
stack due to a wide, continuous annulus remaining in each filter
plate, which annulus provides the plate with its pressure
resistance. This is achieved by using a transverse drainage
perforation that extends through the filter plate separate from the
core opening. The drainage perforation is used together with a
filter passage which extends from the core opening to the drainage
perforation. The drainage perforation is located within the filter
plate, between the inner and outer edges of the filter plate so
that the filter plate includes a continuous annulus radially
outward from the perforation. The perforation is preferably closer
to the inner edge than to the outer edge to minimize the length of
the filter passage. In the filter stack, the drainage perforations
of adjacent filter plates are aligned to form a drainage conduit,
which drainage conduit is connected at the end plates to the
outside of the stack. By providing the transverse perforation
within the filter plate and close to the core opening, the
operational thickness of the filter plate as far as the filtering
operation is concerned (filter thickness) is much reduced, while
the operational thickness of the filter plate as far as the
pressure resistance is concerned (overall thickness) remains the
same. Moreover, the need for an external, sealed fluid collection
chamber surrounding the stack of filter plates, as disclosed in the
known stacked filter units mentioned above is obviated, since
replaced by the internal collection chamber. In addition, the use
of the transverse perforation within the filter plate for the first
time allows for the selection of an overall thickness of the filter
plate independent from the length of the filter passage and the
inner diameter of the external collection chamber.
[0078] The perforation in the filter plate may have a cross-section
at least as large as the cross-section of the filter passage
connected thereto. Preferably the perforation has a cross-section
at least twice the cross-section of the filter passage connected
thereto. In one embodiment, two filter passages are connected to
each perforation. Preferably, the cross-section of the perforation
is at least twice the cumulative cross-section of al filter
passages connected thereto. In another embodiment, more than two
filter passages are connected to each drainage perforation. If
maximum drainage capacity is desired, a drainage perforation may be
provided for each filter passage.
[0079] The filter unit may be constructed as a single block filter
unit or as a split filter unit for a solid/fluid separating device,
or a solid/fluid separating screw press, or a modular screw device.
The single block filter unit or split filter unit can be installed
into and/or removed from the solid/fluid separating device or press
without requiring disassembly of the separating device, any
assembly or disassembly being limited to the split filter unit of
the separating module. In particular, the split filter unit of the
invention can be installed or removed from the separating module
without removal of the conveyor screw from the screw press.
[0080] In addition to this advantage, the solid/fluid separating
module of the invention can include a filter unit able to handle
very high pressures (up to 20,000 psig). Some or all of the barrel
plates in the stacked filter unit can be constructed as filter
plates to create a filter plate stack able to generate solids
levels from 50-90%. The filter plate stack can provide the further
advantage of a very small pore size filter, so that a liquid
portion extracted with this filter can contain little suspended
solids. The combination of a high pressure filter unit in
accordance with the invention with a twin-screw extruder press can
result in a solid/liquid separation device capable of developing
virtually dry cake of a solids level above 80%. A twin conveyor
screw press in accordance with the invention and including a filter
unit in accordance with the invention can process a solid/fluid
mixture in a thin layer at pressures exceeding 300 psi while at the
same time allowing trapped liquid and water a path to migrate out
of the mixture through the filter unit.
[0081] Using a screw press or extruder press with a filter unit in
accordance with the invention, one can apply significant shear
forces/stresses to a solid/fluid mixture, which forces are applied
in a thin cake to free up liquid to migrate out through the filter
unit. More importantly, using an internal fluid collection chamber
within the filter block simplifies the filter unit in accordance
with the invention and reduces the length of the individual filter
passages, which may reduce the risk of clogging, reduce back
pressure and facilitate backwashing.
[0082] Turning now to the drawings, FIG. 1 schematically
illustrates an exemplary solid fluid separating apparatus 100 in
accordance with the invention. The apparatus includes a twin-screw
extruder with a barrel 216 divided into barrel modules 212 and
separation modules 600 including filter units 300. The extruder is
driven by a motor 226 through an intermediate gear box drive 224,
both the motor and gear box being conventional components. Although
the separation modules 600 in the illustrated exemplary embodiment
are shown to have a larger axial length than the barrel modules
212, in another embodiment, the axial length of the separation
modules 600 can be adjusted to be identical to that of the barrel
modules 212, to allow for swapping of the barrel modules with the
separation modules and vice versa. The separation modules 600 in
accordance with the invention, will be described in more detail in
the following.
[0083] FIG. 2 illustrates a simplified exemplary embodiment of the
apparatus 100 shown in FIG. 1, including only a single separating
module 600. As is apparent from FIG. 2, the apparatus 100 broadly
includes a sectionalized barrel 216 with an outlet 220 and a
specialized twin screw assembly 222 within the barrel 216; the
assembly 222 is coupled via the gear box drive 224 to the motor 226
(see FIG. 1). The barrel 216 in the simplified exemplary embodiment
illustrated is made up of two end-to-end interconnected tubular
barrel modules 228, 230, and a separating module 600. Each barrel
module is provided with an external jacket 234, 236, to allow
circulation of cooling or heating media for temperature control of
the extruder device. The separating module 600 includes internal
collection chambers 338,339. The separating module 600 may include
a die 240. The die includes a central opening, the width of which
is selected to produce the desired back pressure in the barrel 216
and the separating module 600. Other means for generating a
backpressure at the separation module can also be used. The
pressure in the barrel 216 and the separating module 600 can also
be controlled by the fit between the screws 250,252 and the barrel
216 and the rotational speed of the screws 250, 252. Each of the
modules 228, 230 also includes an internal sleeve 242, 244 which
defines a continuous screw assembly-receiving opening or core
passage 248 within the barrel. This core passage 248 can be tapered
as shown in FIG. 2, or cylindrical (when cylindrical screws are
used) and has a generally "figure eight" shape in order to
accommodate the dual screw assembly 222. In the illustrated
exemplary embodiment, the core opening 248 is widest at the rear
end of barrel module 228 and progressively and uniformly tapers to
the end of the apparatus at the outlet 220 of the barrel 216. It
will be observed that the assembly 222 also presents material
backflow passageways 280 and kneading zones 282 between the screws
250, 252.
[0084] The screw assembly 222 includes first and second elongated
screws 250, 252 which are in side-by-side relationship as best seen
in FIG. 3a. If a non-tapered barrel of constant cross-section is
used (not shown), a pair of straight or cylindrical screws as shown
in FIG. 3b can be used as screws 250 and 252. As shown in FIG. 2,
each of the screws 250, 252 includes an elongated central shaft
254, 256 as well as outwardly extending helical flighting 258, 260.
In the tapered screws as shown in FIGS. 2 and 3a, the shafts 254,
256 each have an outer surface which is progressively and uniformly
tapered through a first taper angle from points 262, 264 proximal
to the rear ends of the corresponding shafts 254, 256, to forward
points 266, 268 adjacent the forward ends of the shafts. This taper
angle generally varies from about 0.5-5.degree., and more
preferably from about 1-2.2.degree.. The illustrated embodiment has
a taper angle of 1.3424.degree..
[0085] The flighting 258, 260 (in the embodiment illustrated double
flights are used, but single or multiple flights are also a
possibility) extends essentially the full length of the shafts 252,
254 between points 262, 266 and 264, 268. Thus, the flighting 258,
260 proceeds from a rear end adjacent the point 262, 264 in a
continuous fashion to the forward point 266, 268. In addition, the
flighting presents an outer surface 270, 272 on each of the screws
250, 252. The geometry of the flighting 258, 260 is such that the
flight depth progressively and uniformly decreases as the fighting
proceeds from the rear end to the front end of the screws 250, 252.
Consequently, the outer surfaces 270, 272 of the flighting 258, 260
also taper from rear to front in a progressive and uniform fashion.
The second angle of taper of the lighting depth and the outer
fighting surfaces can range from 2-6.degree. and in the illustrated
embodiment is 3.304.degree..
[0086] Finally, the fighting 258, 260 can be designed so that the
width of the flighting outer surfaces 270, 272 increases in a
progressive and uniform fashion from the rear end of the screws to
the front ends thereof. This configuration is best illustrated in
FIGS. 2 and 3a, where it will be seen that the width is relatively
small at the rear ends of the screws 250, 252, but increases to a
wider width at the forward ends of the screws. As indicated
previously however, the width may be constant throughout the length
of the screws, or could narrow from the rearward ends to the
forward ends thereof.
[0087] The screws 250, 252 can be oriented parallel, when
cylindrical screws are used, or can be oriented so that their
respective center axes are at a converging angle relative to each
other, with an included angle that may range from about
1-8.degree..
[0088] During operation, the mixture to be separated is passed into
and through the extruder device 300. The screw assembly 222 is
rotated so as to co-rotate the screws 250, 252, usually at a speed
of from about 20-1,200 rpm. Pressures within the extruder are
usually at a maximum just adjacent the outlet die, and usually
range from about 300-20,000 psig, more preferably from about
1,000-10,000 psig. Maximum temperatures within the extruder
normally range from about 40-500.degree. C.
[0089] Extrusion conditions are created within the device 300 so
that the product emerging from the extruder barrel usually has a
higher solids content than the product fed into the extruder. The
preferred solids content to be achieved in biofuel production from
lignocellulosic biomass to be achieved with the separation device
of this disclosure is above 50%.
[0090] During passage of the extrudable mixture through the barrel
216, the screw assembly 222 acts on the mixture to create, together
with the endmost die 240, the desired pressure for separation. It
has been found that a wide variety of solid/liquid mixtures may be
separated using the equipment of the invention; simply by changing
the rotational speed of the screw assembly 222 and, as necessary,
temperature conditions within the barrel, which means merely by
changing the operational characteristics of the apparatus.
[0091] An exemplary embodiment of a solid/fluid separation module
300 in accordance with the invention is shown in FIGS. 4A, 4B, 5
and 6, while parts of the module will be discussed with reference
to FIGS. 7 to 20. The exemplary module is capable of withstanding
very high internal pressure forces (up to 20,000 psig) due to the
use of internal fluid collection chambers.
[0092] As can be seen from FIG. 4A, showing a first embodiment of
the separation module 600, the module includes the mounting plates
630, 632 for connection to adjacent barrel blocks 500, 520 with
bolts 129 and a block filter unit 301 with front and back end
plates 321, 322 and intermediate filter plates 314 (see FIG. 10A)
stacked between the end plates and compressed therebetween into a
filter plate stack 310 by alignment bolts 316. The filler unit 300
is clamped between the mounting plates 630, 632 by connecting rods
640. The mounting plates 630, 632, end plates 321, 322 and filter
plates 314 each have a core opening 112 and all plates are aligned
in the block filter unit 301 to define the core passage 248 (see
FIG. 2). Both end plates 321, 322 include a seal groove 390 for
receiving part of the seal 652 inserted between the mounting plate
and end plate at each end of the block filter unit 301. The seal
652, preferably an O-ring, is compressed when the separation module
600 is clamped together by the connecting rods 640 to seal about
the core opening 112. The separation module 600 of FIG. 4A is
removed from the separation apparatus 100 by disassembling the
extruder barrel 212 (see FIG. 1).
[0093] As can be seen from FIG. 4B, showing a second embodiment of
the separation module 600, the module includes the mounting plates
630, 632 for connection to adjacent barrel blocks 500, 520 with
bolts 129 and a split block filter unit. 300. When comparing the
block filter unit 301 and the split block filter unit 300, it is
apparent that the split block filter unit 300 is split into upper
and lower (or first and second) filter blocks 302, 304,
respectively constructed in the illustrated exemplary embodiment as
plate packs 310 and 320. Moreover, the end plates 305, 306 are
split into front end plate sections 311, 321 and back end plate
sections 312, 322 (see FIGS. 8 and 9). In addition, the filter
plates 314 are split into upper and lower split plate sections
314a. The split block filter unit 300 is clamped between the
mounting plates 630, 632 by connecting rods 640. The filter blocks
302, 304 are joined along a plane of symmetry of the core passage
248 (see FIG. 2) and clamped together by a clamping structure to
form a clamped block 355. The clamping structure includes upper and
lower clamping arrangements 340 and 330 to form the split block
filter unit 300. All split end plates 311, 321, 312, 322 include a
seal groove 390 for receiving part of the seal 652 inserted between
the mounting plate and end plate at each end of the block filter
unit 301. The seal 652, preferably an O-ring, is compressed when
the separation module 600 is clamped together by the connecting
rods 640 to seal about the core opening 112. In accordance with a
key aspect of this second embodiment, the split block filter unit
300 can be installed into and disassembled from between the
mounting plates 630, 632 while the mounting plates are integrated
into the extruder barrel 212 (FIG. 1) and while an extruder screw
extends, or extruder screws extend, through the extruder barrel.
This is best understood from FIG. 5.
[0094] For removal of the split block filter unit 300, the
connecting rods 640 are removed to provide access to the split
block filter unit 300 and to loosen the connection between the
mounting plates and the split block filter unit 300. Then, the
upper and lower clamping arrangements 340 and 330 are loosened and
the bottom clamping arrangement is disconnected from the connecting
rods 347. Once disconnected, the bottom clamping arrangement 330
will fall down together with the lower filter block 304, here the
plate pack 320. The upper clamping arrangement 340, the upper
filter block 302, here the plate pack 310, and connecting rods 347
remain seated between the mounting plates 630, 632, supported by
the extruder screws (not shown). Removal of the upper clamping
arrangement 340 and the connecting rods 347 upward from between the
mounting plates 630, 632 will allow access to the upper filter
block 302, here the plate pack 310, which can then also be removed.
The upper and lower filter blocks 302, 304 in the form of plate
packs 310, 320 can then be disassembled, cleaned, reassembled and
reinstalled, or simply replaced. Assembly of the split block filter
unit 300 about the extruder screws and in between the mounting
plates 630, 632 will occur in reverse order, starting with the
upper filter block 302. During assembly, a pair of seals 350 is
positioned between the filter blocks 302, 304 for sealing of the
filter blocks about the extruder screws to seal the core
passage.
[0095] The upper and lower filter blocks 302, 304 can each
independently be a solid block, a solid block with drilled
filtering passages, or a stacked block as discussed in more detail
below in relation to FIGS. 7-9, as long as at least one of the
filter blocks includes at least one filtering passage. In the
exemplary embodiment illustrated in FIGS. 5-9, both filter blocks
302, 304 are stacked blocks 310, 320, as will be discussed in more
detail below.
[0096] The upper and lower clamping arrangements 340, 330 of the
clamping structure as illustrated in detail in FIGS. 5 and 6, each
include two or more parallel clamping bars 344, 334, which are
spaced apart to allow the passage therebetween of fluids separated
by the split block filter unit 300. The clamping bars 344, 334 are
maintained in a fixed, spaced apart relationship by bridging bars
342, 332 to which the clamping bars are bolted by bolts 348, 338
(FIG. 6) and which rest against a pair of lateral clamping
shoulders of the stacked blocks formed by the clamping edges 323b
(FIG. 10B) of the barrel plates and end plates in the stacked
block. The upper and lower clamping arrangements 340, 330 are
connected with one another about the extruder screws and filter
blocks 302, 304 to allow for the clamping of the filter blocks
against one another, thereby sealing the filter blocks about the
extruder screws. The upper and lower clamping arrangements 340, 330
are connected by way of connecting rods 347 which extend past the
filter blocks 302, 304. The upper and lower clamping bars 344, 334
are bolted to the connecting rods by bolts 346, 336. The assembly
of the upper and lower clamping arrangements 340, 330 as described
includes separate clamping bars 344, 334 and bridging bars 342,
332. This construction provides a modular approach, allowing
longitudinal elongation or shortening of the clamping arrangements
by simply adding or removing clamping bars and using longer or
shorter bridging bars. In the alternative, the upper and lower
clamping arrangements 340, 330 can respectively made in one
piece.
[0097] The embodiment of FIGS. 4a-6 can be used with extruders of
smaller barrel diameter in which one can physically slide the
barrel sections apart and tighten them back together. In larger
diameter extruders, for example 3 inch or larger, the barrel
sections are fixed in place and moving them apart is physically
impossible so that another manner of incorporating the split filter
unit into the barrel must be found. An exemplary separation module
200e for use in such extruders is illustrated in FIGS. 21-24. As
can be seen from FIG. 21, the separation module 200a includes a
frame 100, a split block filter unit 300 essentially identical with
the split block filter unit 300 of FIGS. 4a-6 and a sealing
arrangement 400 for sealably fastening the split filter block 300
in the frame 100 about the conveyor screws (not shown). The frame
100 is sized and constructed to form a barrel section for the large
diameter extruder and is fixed in place together with the other
barrel sections of the extruder. For that purpose, the frame 100
includes left and right side walls 101, 102, front and back walls
103, 104. The walls 101-104 form a rectangular box which is
integratable into the barrel of the large diameter extruder through
bolts (not shown) engaging threaded blind bores 108 in the front
and rear edges of the side walls 101, 102 and in the front and rear
walls 103, 104. The frame may include lids 105, 106 to close off
the frame and convert it into a housing for added protection of the
filter unit 300. Those lids may be hingedly or otherwise attached
to one of the walls 101, 102, 103, 104 of the frame to reduce the
risk of the lids being misplaced during assembly or disassembly of
the filter unit 300. Front and rear walls 103, 104 include a core
opening 112 for accommodating the extruder screws (not shown) of
the large diameter extruder. The filter blocks 302a. 304a are
Joined along a plane of symmetry of the core opening 112 and
clamped together by a clamping structure to form a clamped block
355. The clamping structure includes upper and lower clamping
arrangements 340 and 330 to form the split block filter unit 300.
Since the barrel sections in the large diameter extruder cannot be
moved apart, the split block filter unit 300 can be installed into
and disassembled from the frame 100 while the frame remains
integrated into the extruder barrel 21 (FIG. 1) and while an
extruder screw extends, or extruder screws extend, through the
extruder barrel. This is best understood from FIGS. 22-24.
[0098] Referring to FIGS. 21 to 24, the locking arrangement 400
functions to lock the filter unit 300 in the frame 100 between the
front and back walls 101, 102 and seal the throughgoing core
passage 112 within the filter unit 300. The locking arrangement 400
includes an externally threaded cylindrical base sleeve 406
attached to, or integrated into, one of the front and back walls
101, 102 in concentric alignment with the core passage 112, a
threaded cap nut 404 threadedly engageable with the base sleeve, a
circular seal 402 for placement between the cap nut 404 and the
clamped block 355 and a flat seal 405 for placement between the
clamped block 355 and the other of the front and back walls 101,
102 to which the base sleeve 406 is not attached. Threading of the
cap nut 404 onto the base sleeve 406 increases the spacing between
the cap nut and the opposing end wall of the housing 100, while
unthreading decreases this spacing. Thus, the cap nut 404 is fully
threaded onto the base sleeve 406 for installation and removal of
the clamped block 355 of the filter unit 300. For sealing of the
filter unit 300 in the frame, the cap nut 404 is unthreaded until
the clamped block is tightly pressed between the cap nut 404 and
the opposing end wall of the frame (see FIGS. 22 and 23). Although
the use of a rotatable locking arrangement as illustrated in FIGS.
21 to 24 provides for an easy locking in and unlocking of the
clamped block from the frame, any other locking structure useful
for reliably locking the clamped block in the frame while sealing
the core passage can be used. For example, a pair of opposing
wedges (not illustrated) with an opening or slot for accommodating
the core opening may be used, in place of the base sleeve 406 and
cap nut 404, to wedge the clamped block in the frame. One of the
wedges can be attached to, or integrated into one of the front and
back walls 101, 102 for ease of locking and unlocking.
[0099] For removal of the split block filter unit 300, upper and
lower lids 105, 108 of frame 100 (if included) are removed to
provide access to the split block filter unit 300. The filter unit
sealing arrangement 400 (FIGS. 22-24) is loosened to unlock the
filter unit 300 in the frame. Then, the upper and lower clamping
arrangements 340 and 330 are loosened and the bottom clamping
arrangement is disconnected from the connecting rods 347. Once
disconnected, the bottom clamping arrangement 330 will fall out of
the frame 100 together with the lower filter block 304, here the
plate pack 320. The upper clamping arrangement 340, the upper
filter block 302, here the plate peck 310, and connecting rods 347
remain seated in the frame, supported by the extruder screws (not
shown). Removal of the upper clamping arrangement 340 and the
connecting rods 347 upward from the frame 100 will allow access to
the upper filter block 302, here the plate pack 310, which can then
also be removed from the frame. The upper and lower filter blocks
302, 304 in the form of plate packs 310, 320 can then be
disassembled, cleaned, reassembled and reinstalled, or simply
replaced. Assembly of the filter unit 300 about the extruder screws
and in the frame 100 will occur in reverse order, starting with the
upper filter block 302. During assembly, a pair of seals 350 is
positioned between the filter blocks 302, 304 for sealing of the
filter blocks about the extruder screws to seal the core passage
112 from the collection chamber 110.
[0100] The lower and upper stacked blocks 310, 320 as illustrated
in separation in FIGS. 7, 8 and 9, are assembled from barrel plate
sections 314a, end plate sections and a stacking structure. The end
plate sections include front end plate sections 311, 321 and back
end plate sections 312, 322. The stacking structure includes
alignment rods 317 (FIG. 9) and alignment bolts 316. The barrel
plate sections 314a are preferably mirror image to one another
along the plane of symmetry, so that a single type of barrel plate
section 314a (see FIG. 10B) can be used for either stacked block.
The barrel plate sections 314a include alignment bores 325 for the
alignment rods 317 as shown in FIG. 9, which shows the lower filter
block 304 in exploded view. In the exemplary embodiment of a lower
stacked block 310 as shown in FIG. 9, a plurality of barrel plate
sections 314a are compressed between front and back end plate
sections 321, 322 having the same basic overall outline as the
barrel plate sections 314a but being much thicker for even
compression of the plate pack. The front and back end plate
sections 321, 322 include the same alignment bores 325 as the
barrel plate sections 314a and recesses 318 for the bolts 316. The
alignment rods 317 in combination with clamping bolts 316 recessed
into the front and back end plate sections 321, 322 are used to
clamp the plate pack between the end plates 321, 322 to seal the
barrel plate sections 314a together and form the lower stacked
block 310. The upper stacked block 320 is assembled in an identical
manner using barrel plate sections 314a, front and back end plate
sections 311, 312 (which can be identical to back and front end
sections 322, 321 respectively), the alignment rods 317 and
alignment bolts 316, whereby the end plate sections 311, 321, can
be shaped mirror image to the end plate sections 321, 322.
[0101] Other arrangements for holding the barrel plates aligned and
compressed in a plate stack can also be used. The alignment
structure can also be integrated with the associated clamping
arrangement (not shown) to allow handling of the upper and lower
filter blocks 310, 320 together with the respectively associated
clamping arrangement. One or more of the barrel plate sections 314a
in the upper and lower stacked blocks 320, 310 can be constructed
as a filter plate. The detailed construction of such a filter plate
will be discussed in more detail below in reference to FIGS. 10A
and 10B.
[0102] As illustrated in FIGS. 4, 5 and 7-9, the split block filter
unit 300 includes barrel plate sections 314a which, when stacked
and clamped in the split block filter unit 300, define a portion of
the core passage 248 extending through the barrel 212 of the
separating apparatus 100 (see FIG. 2). The core passage 248 has
one, two or more longitudinal axes, equal in number to the number
of extruder screws housed in the core passage.
[0103] The block filter unit 301 is made of stacked barrel plates
in an manner similar to that disclosed in U.S. Application US
2012/0118517. In the block filter unit 301, the barrel plates 314
are continuous about the core opening (see FIG. 10A) and therefore
cannot be removed from about the conveyor screw, but must be pulled
off the conveyor screw, or disassembled from the filter press until
the conveyor screw has been removed. To enable removal of the
stacked barrel plates from the filter press without removal of the
extruder screws, the split block filter unit 300 is used. The split
block filter unit 300 is achieved by splitting the full barrel
plates 314 into first and second halves along a plane of symmetry
extending through each longitudinal axis of the core opening 112,
or by building separate split block halves from barrel plate
sections designed to form half of the core opening. The latter
approach is more advantageous, since it allows for the
simplification of the barrel plate sections and the stacked block
structure, as will be discussed below. The barrel plates can be
divided along the plane of symmetry 117 of the core opening 112,
which plane extends through the two longitudinal axes 113, 115 into
upper split plates 314 and lower split plates 324 (FIG. 6).
Alternatively, rather than splitting full plates, separate upper
and lower barrel plate sections can be separately produced, which
barrel plate sections can be different in design, or of mirror
image design as shown in FIGS. 7, 8 and 9. Making the upper and
lower barrel plate sections 314a of mirror image design makes is
possible to use a single type of universal filter plate 370 as
shown in FIG. 10B, which can be used for both the upper and lower
barrel plate packs 310, 320.
[0104] The single design, universal barrel plate 370 includes a
body 371 with flat front and rear faces, an inner edge 328
extending between the front and rear surfaces, an outer edge 329
extending between the front and rear surfaces and lateral tabs 323.
The inner edge 328 defines exactly one half of the central core
opening 112 located to one side of the plane of symmetry 117. The
outer edge 329 is convexly curved to maintain a minimum body width
between the inner and outer edges 328, 329. The lateral tabs 323
are provided for clamping of the universal barrel plate 370, when
part of a stacked block, along the plane of symmetry 117 against
the stacked barrel plates of a like stacked block. The universal
barrel plates 370 when stacked in a stacked block each include a
sealing edge 323a extending in the plane of symmetry 117 for
engagement with the sealing edge of a like universal barrel plate
370 placed in mirror image on the opposite side of the plane of
symmetry. The lateral tabs 323 each further include a clamping edge
323b extending parallel to the sealing edge 323a for engagement by
one of the bridging bars 342, 332 (FIG. 6). The clamping edges 323b
of the barrel plates 370 in a plate stack together form a clamping
shoulder for engagement by one of the bridging bars 342, 332 of the
upper and lower clamping arrangements 340, 330 respectively. The
universal barrel plate 370 includes alignment bores 325 for
receiving the alignment rods 317 as shown in FIG. 9. In the
exemplary embodiment shown in FIG. 9, a plurality of universal
barrel plates 370 is compressed into the lower stacked block 310
(the upper stacked block 320 being identical and simply used upside
down) by the front and back end plate sections 321, 322. The
alignment rods 317 in combination with clamping bolts 316 are used
to clamp the plate pack between the end plates to seal the barrel
plates 370 together and form the stacked block 310, 320.
[0105] In order to achieve a separation of fluids from a
pressurized fluid/solids mixture in the core opening 112, one or
more of the universal barrel plates 370 in the stacked block 310,
320 can be constructed as a universal filter plate 372 including
one or more filter passages 360 which each define a fluid passage
in the filter plate 372 extending away from the inner edge 328. The
universal filter plate 372 further includes one or more drainage
perforations 362 which are located within body 371, between the
inner and outer edges 328, 329 and extend completely through body
371 from one face to the other. Each filter passage 360 extends all
the way from the inner edge 328 to one of the drainage perforations
362. The filter passages 360 can be provided by cutting, scoring,
etching or bending of the barrel plate sections 314a. Thus, the
filter passage may be a sit cut completely through the universal
filter plate 372 (not shown), a deformation of the body 371, or a
scored or etched recess in one of the faces of the body 371. The
exact manner in which the passage is created will not be further
discussed herein, since not of particular significance to the
present invention. Filter passages acid etched into a face of the
filter plate 372 have proven advantageous, since acid etching
allows for the manufacture of filter passages of much smaller
cross-section than scored or cut through passages. If the filter
passage 360 extends from the inner edge 328 to the drainage
perforation 362 in the front surface of the filter plate, only one
type of filter plate is needed, since when this filter plate is
stacked one behind the other with other like filter plates, the
back surface of one filter plate will always function as a cover
for the filter passage 360 in the like filter plate immediately
behind.
[0106] In one embodiment, each barrel plate 314, barrel plate
section 314a, or universal barrel plate 370, is constructed as a
filter plate to simplify the filter unit design and to maximize the
filtering capacity of the filter unit. To maximize the porosity of
a stacked block, each filter plate includes the maximum number of
filter passages 360 and drainage perforations 362 which can be
included in the filter plate without harming the structural
integrity and pressure retention capacity of the filter plate and
of the stacked block in which it is included. To reduce
manufacturing cost and facilitate assembly, all barrel plates used
in the split block filter unit 300 a universal filter plates 372 of
identical construction.
[0107] The number of barrel plates included in the separating
module 600 can be adjusted according to the plate thickness and the
desired filter porosity. In the illustrated embodiment of FIGS. 5
and 6, each stacked block 310, 320 included 300 universal filter
plates 372 in a stack of 6 inch length, each plate being 0.020 inch
thick, having 56 filter channels at a width of 0.04'' and a depth
of 0.005'' and having an overall open area of 3.36 square inches.
With the illustrated embodiment, a biomass of 30% dry matter
content was squeezed and dried to a 48% dry matter content at
barrel pressures of about 300 psig. In another embodiment, each
stacked block 310, 320 may include 200 universal filter plates 372
per inch of stacked length, each plate being 0.005 inch thick and
having an overall open area of 0.864 square inches. With that
embodiment, a dry matter content of 72% may be achieved at barrel
pressures of about 600 psig. On a continuous basis, 100 g of
biomass containing 40 g of solids and 60 g of water can be squeezed
out in the filter module 300 using 600 psig internal force at a
temperature of 100 C to obtain a dry biomass discharge (solids
portion of the liquid/solid biomass) containing 39 g of suspended
solids and 15 g of water. The filtrate obtained will contain about
95 g of water, which will be relatively clean and contain only a
small amount (about 19 g) of suspended solids with a mean particle
size equal to the pore size of the filter passages 360.
[0108] In the illustrated embodiment of the universal filter plate
372 of FIG. 10B, the filter passages 360 are in the form of a
recess cut to a depth, which is only a fraction of the filter plate
thickness, to minimize the effect of the recess on the structural
integrity of the plate and to prevent warping or buckling of the
plate during installation or operation as much as possible.
Preferably, the recess has a depth, which is at most 1/3 of the
plate thickness, more preferably 1/5 of the plate thickness, most
preferably at most 1/10 of the plate thickness. Very small filter
pores can be achieved in this manner by using very thin filter
plates and very shallow recesses. For example, by cutting filter
passages 360 of 0.05 inch width and 0.001 inch depth into the
filter plate 372, a pore size of only 0.00005 square inch can be
achieved. For even finer filtering, filter passages of 0.01 inch
width can be used. The filter passage 360 can be produced, for
example, by laser cutting or acid etching. In the illustrated
exemplary embodiment, the filter plates 372 were made of 316
Stainless Steel and the passages 360 were cut by acid etching. A
conventional photo lithography process can be used to define on the
filter plate 372 the shape and pattern of the passages to be cut.
The design, location and orientation of the passages 360 is
preferably chosen to be mirror image to a center line of the filter
plate 372 in order to allow use of the filter plates in a back to
front or back to back stacking orientation. In the back to front
orientation, the passages 360 are covered by the back face of the
adjacent filter plate 372 and in the back to back orientation the
filter plates 372 are stacked in pairs so that the filter passages
of both plates in the pair line up with one another, resulting in
double the filter pore size, at the same porosity.
[0109] FIGS. 9 and 11 illustrate an optional compression plate
314b, which may be included in the plate stacks 310, 320 if very
thin universal filter plates 372 are used and the drainage passage
363 in the end plate sections connects to multiple, or all
collection chambers 338. The compression plate 314b is used to
avoid deformation into the drainage passage 363 of the universal
filter plate 372 adjacent the end plate section.
[0110] As illustrated in FIGS. 12 to 15, illustrating one
embodiment of a universal end plate 327 includes the alignment
bores 325, an inner edge 328 which defines part of the core opening
112 in the plate stack 310, 320 and an outer edge accessible when
the end plate is incorporated into the separation module 600. On a
face directed towards the filter plates, the universal end plate
327 includes the drainage passage 363 which is aligned with the
drainage perforations 362 in the filter plates to allow draining of
the collection chambers 338 formed by the drainage perforations in
the plate stacks. The drainage passage has an outlet 364 on the
outer edge. On a face directed towards the mounting plates in the
separation module 600, the universal end plate 327 has a seal
groove 390 for receiving part of the seal positioned between the
filter unit 301, 300 and the mounting plates 630, 632 in the
separation module 600.
[0111] The separation of liquid from an extrudable mixture
including fibrous solids creates particular challenges for the
filter construction. The fibers may enter Into and align in
parallel in the filter passages 360, causing a tight plug in the
passage which not only reduces or prevents the passage of fluid,
but may be very difficult, if not impossible, to remove by
backwashing. This problem forms the basis of the embodiments of a
fitter passage 360 in accordance with the invention as illustrated
in FIGS. 16 to 19E. To address the problem, the filter passages 360
may include a directional deflection 800, as illustrated in FIGS.
16 to 19E, at any point along their length to block any straight
line path through the passage. This may be achieved with providing
a S-shaped, or Z-shaped curve in the longitudinal extent of the
passage or by including a fork or split in the passage, for
example, T-shaped, V-shaped, Y-shaped or U-shaped splits. An
exemplary deflection in the form of a U-shaped split is shown in
FIGS. 16 to 19E. It is the purpose of the directional deflection
800 to impede a straight line passage through the filter passage
360, or a straight passage of a linear fiber. Thus, any directional
deflection 800 in the filter passage 360 which is sufficient to
block a straight line pass through the filter passage 360 can be
used, irrespective of the shape of the deflection, or the location
of the deflection along the longitudinal extent of the filter
passage 360. In the embodiment illustrated in FIGS. 17 to 19E, the
deflection 800 is advantageously located at the end of the passage
380 at the inner edge 328. In the U-shaped deflection 800
illustrated in FIGS. 16 to 19E, the filter passage 360 includes a
recess 832 of a width of A, etched into the front surface 319 of
the filter plate 372. The U-shaped split is created by branching
the recess 832 into a pair of opposing branches 820 by curving the
recess 832 in opposite directions at a radius equal to the width of
the recess, in the illustrated embodiment a radius of 0.001 inches
(1 micron). The branches 820 are then curved back to the original
direction of the recess at the same radius, to create the U-shaped
split. The portion of the front face 319 located between the inner
edge 328 and the branches 820 creates a bumper 810 which blocks the
straight line passage through the filter passage 360.
[0112] As illustrated in FIG. 18, short fibers 850, those having a
length shorter than the width of the filter passage 360, may be
able to pass the deflection 800, but are less likely to accumulate
in and block the passage 360, since they are not long enough to jam
in the passage. On the other hand, long fibers 860, those having a
length greater than the width of the passage 360 will most likely
jam in the deflection 800. Long fibers 860 that jam in the
deflection 800, will jam at different depths and angles in the
deflection 800, depending on the overall length of the long fibers
860. This results in a non-parallel, generally random orientation
of the jammed fibers 860, similar to a random logjam in a tight
turn of a river. This generally non-parallel orientation of the
jammed fibers 860 prevents a complete plugging of the filter
passage 360 at the deflection. At the same time, the fiber jam may
create an additional filter layer, aiding in the retaining of
superfine solids that would normally pass through the filter
passage 360.
[0113] FIGS. 19A to 19E schematically illustrate other types of
deflections in the filter passage 360, such as Y-shaped, V-shaped,
T-shaped, S-shaped and Z-shaped deflections. The filtering passages
360 in the exemplary embodiments of FIGS. 16-19E may widen away
from the deflection, for example from the deflection 800 to the
drainage perforation.
[0114] A cross section through a split block filter unit 300 in
accordance with the invention is illustrated in FIG. 20. As is
apparent from FIG. 20, the end plate sections 311, 321, 312, 322,
and universal barrel plates 370 are all aligned so that the core
openings 112 align to form the core passage for receiving the
conveyor screws. Moreover, the barrel plates which are constructed
as universal filter plates 372 are stacked together against one of
the end plates and aligned so that their drainage perforations 362
align to form collection chambers 338 that extend parallel to the
axis of the core passage. Moreover, at least one of the end plate
sections in each plate stack 310, 320 includes a drainage passage
363 connecting the collection chambers 338 with an exterior of the
filter unit, for drainage from the collection chambers 338 of fluid
separated through the filter passages 360. A separate drainage
passage 363 may be provided for each collection chamber 338, or the
drainage passage 363 can connect two or more collection chambers
338. When both end plate sections of a plate stack are provided
with drainage passages 363, separated fluid can be circulated
through the collection chambers in the plate stack to reduce the
risk of fines accumulation. The outlet end 364 of the drainage
passage 383 can be connected to source of pressurized backwash
fluid, for example steam, for backwashing of the respectively
connected collection chambers 338 and filter passages 360.
[0115] The principle construction of assembling a portion of the
barrel from stacked identical barrel plates, which may be
constructed as filter plates, allows for significant design
variability and even enables the variation of the filtering or
separation capacity and behavior of an extruder press by not only
varying the filtering capacity of individual separating modules
600, but by converting separating modules 800 into barrel modules
212 by simply replacing the stacked blocks 310, 320 including one
or more filtering plates with stacked blocks including only barrel
plates and no filter plates, or even blocks of overall solid
construction. In one possible embodiment, the complete barrel is
constructed using separating modules, some of which have been
converted to barrel modules 212 by replacement of the filter plates
in the stacked blocks 310, 320 with barrel plates, in another
embodiment, each separating module includes a solid filter block
and a stacked filter block, whereby the solid block forms the upper
filter block of the filter unit and the stacked block forms the
lower filter block. It is a significant advantage of an arrangement
in which each barrel module is a separating module in accordance
with the invention that any part of the barrel can be used as a
barrel section or as a filter unit and can be converted from one to
the other without requiring disassembly of the barrel, by simply
exchanging the filter blocks. Each of the filter blocks along the
barrel can be a solid filter blocks, or a stacked block with a
particularly selected porosity. Separation modules in which the
upper and lower filter blocks are both solid blocks or stacked
blocks devoid of any filter passage then function as a regular
barrel module 212. Moreover, it is another significant advantage of
such an arrangement that a blockage in any part of the barrel,
whether in a separating/filtering region or not, can be cleared,
without the need for disassembly of the extruder press or removal
of the conveyor screws, by simply replacing the dogged filter block
with a clean like filter block and/or removing the compacted solids
surrounding the conveyor screws and blocking the core passage
112.
[0116] Overall, with higher pressure capability, either more liquid
can be squeezed from the solids or, for the same material dryness,
a higher production rate can be achieved per unit filtration area.
The quality of filtration (solids capture) can be controlled
depending on plate configurations and thicknesses. The
filtration/pressure rating/capital cost can be optimized depending
on the filtration requirements of the particular biomass. The plate
configurations can be installed in an extruder (single, twin or
triple screws) to develop high pressure, high throughput,
continuous separation. The solid/fluid separation module can be
constructed with sufficiently tight spacing between the conveyor
screws themselves and between the conveyor screws and the inner
edge to achieve a self-cleaning effect (for twin and triple screws)
by a wiping action of the screws and by an cross axial flow
pattern. The filtration area is flexible depending on process
requirements as the length of plate pack can be easily custom fit
for the particular requirements. The module can be used to wash
solids in a co current or counter current configuration in single
or multiple stages in one machine reducing capital cost and energy
requirements. The pressure of the liquid filtrate can be controlled
from vacuum conditions to even higher than the filter block
internal pressure (2,000 to 3,000 psig), if required. This provides
great process flexibility for further separations in the liquid
stream (example super critical CO2 under high pressure, ammonia
liquid used for washing under high pressure, or release of VOC and
ammonia gases in the liquid filtrate chamber using vacuum).
[0117] In the exemplary solid/fluid separation device described,
the screw elements that transfer the material internally in the
separation device have very close tolerances to the internal
surface of the filter block and continually scrape the material
away from the filter surface. In the event that a small amount of
fibers became trapped on the surface of the filter, they will be
sheared by the extruder elements into smaller pieces and ultimately
pass through the filter and out with the liquid stream. The high
back pressure capability of the internal fluid collection chambers
(higher than Internal filter block pressure) can be used to back
flush the filter during operation in case of plugging or scaling of
the filter, minimizing down time. Of course, any plugging which
cannot be cleared by backwashing can be removed by disassembly of
only the filter unit 300 which is plugged, without removal of the
whole separation module 600 from the separating apparatus 100 or
removal of the extruder screws.
[0118] It will be readily understood that the solid/fluid
separation module in accordance with the invention can be used in
many different applications to separate solid/fluid portions of a
solid/fluid mixture.
[0119] Different filter modules 600 have been made and tested. The
pressure rating of the filter plates was somewhat independent of
the filter porosity, the number and size of filter passages, and
the number of drainage perforations. By moving the collection
passages into the filter block, al filter plates include a
continuous annulus which has the full plate thickness and is
centered about the core opening. It is this annulus which provides
the filter plates with their pressure resistance. Any differences
in filter plate design, other than plate thickness, are found
between the inner edge at the core opening and the annulus. Thus,
the area of the annulus is fairly consistent for different filter
plate designs, which is the reason for small variations in pressure
resistance observed between filter modules of different design. One
filter plate design tested had a thickness of 0.020'', a filter
passage width of 0.04''. Different filter passage depths of
0.005'', 0.010'', 0.0075'' and 0.015'' were tested.
[0120] The total number of filter plates can vary depending on the
type of solid/fluid mixture to be separated, for example biomass,
and influences the overall filter area. For the same liquid
separation conditions, more plates/more surface area is required
for smaller pores. The size of the filter pores controls the amount
of solids which pass to the liquid portion. Each solid/fluid
mixture may require a certain pore size to achieve an optimal
solids capture (amount of suspended solids in liquid filtrate). By
using separation modules in accordance with the invention, the
porosity, pore size and total filter area of the solid/fluid
separation device can be varied and adjusted without disassembly of
the device or removal of the conveyor screws, making it possible to
adjust the separating properties of the separating device `on the
fly`.
[0121] Although this disclosure has described and illustrated by
way of certain embodiments, it is also to be understood that the
system, apparatus and method described is not restricted to these
particular embodiments. Rather, it is understood that all
embodiments, which are functional or mechanical equivalents of the
specific embodiments and features that have been described and
illustrated herein are included. It will be understood that,
although various features have been described with respect to one
or another of the embodiments, the various features and embodiments
may be combined or used in conjunction with other features and
embodiments as described and illustrated herein.
* * * * *