Note: Descriptions are shown in the official language in which they were submitted.
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TITLE
System Including A Combined Tangential Shear Homogenizing
and Flashing Apparatus Having Single Or Dual Effluent
Outlet(s) and Method For Flash Treating biomass Utilizing
The Same
FIELD OF THE INVENTION
The invention relates to a system and method for
destructuring cellulosic or lignocellulosic biomass that
includes a combined tangential shear Homogenizing and
Flashing apparatus that imposes tangential shear on the
biomass while it is simultaneously exposed to a flashing
operation.
CLAIM OF PRIORITY
This application claims priority from each of the
following United States Provisional Applications, each of
which is hereby incorporated by reference:
(I) Combined Tangential Shear Homogenizing and
Flashing Apparatus Having A Uniform Rotor/Stator Gap
Dimension, Application S.N. 61/724,581, filed 09 November
2012;
(II) Combined Tangential Shear Homogenizing and
Flashing Apparatus Having A Non-Uniform Rotor/Stator Gap
Dimension, Application S.N. 61/724,587, filed 09 November
2012;
(III) Combined Tangential Shear Homogenizing and
Flashing Apparatus Having Rotor/Stator Gap Dimension With
Uniform and Non-Uniform Regions, Application S.N.
61/724,590, filed 09 November 2012;
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(IV) Combined Tangential Shear Homogenizing and
Flashing Apparatus Having A Parameter Responsive Variable
Rotor/Stator Gap Dimension, Application S.N. 61/724,594,
filed 09 November 2012;
(V) Method For Flash Treating Biomass While
Simultaneously Undergoing Tangential Shear
Homogenization, Application S.N. 61/724,598, filed 09
November 2012;
(VI) Combined Tangential Shear Homogenizing and
Flashing Apparatus Having A Housing With A Single
Effluent Outlet, Application S.N. 61/724,602, filed 09
November 2012;
(VII) Combined Tangential Shear Homogenizing and
Flashing Apparatus Having A Housing With Dual Effluent
Outlets, Application S.N. 61/724,612, filed 09 November
2012; and
(VIII) System For Destructuring Biomass Including A
Combined Tangential Shear Homogenizing and Flashing
Apparatus, Application S.N. 61/724,620, filed 09 November
2012.
CROSS-REFERENCE TO RELATED APPLICATIONS
Subject matter disclosed herein is disclosed in the
following copending applications, all filed
contemporaneously herewith and all assigned to the
assignee of the present invention:
Combined Tangential Shear Homogenizing and Flashing
Apparatus Having A Uniform Rotor/Stator Gap Dimension,
Application S. N. 13/790,189, filed March 08, 2013;
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Combined Tangential Shear Homogenizing and Flashing
Apparatus Having A Non-Uniform Rotor/Stator Gap Dimension
and A Parameter Responsive To A Variable Rotor/Stator Gap
Dimension, Application S. N. 1213/790,223, filed March
08, 2013;
Combined Tangential Shear Homogenizing and Flashing
Apparatus Having Rotor/Stator Gap Dimension With Uniform
and Non-Uniform Regions, Application S. N. 13/790,170,
filed March 08, 2013; and
System Including A Combined Tangential Shear
Homogenizing and Flashing Apparatus Having Single Or Dual
Effluent Outlet(s) and Method For Flash Treating Biomass
Utilizing The Same, Application S. N. 13/790,208, filed
March 08, 2013.
BACKGROUND OF THE INVENTION
As the world's supply of crude oil is diminished
there is growing interest in converting biomass into
fuels and chemicals. Biomass is created through
photosynthesis (using energy from the sun) where carbon
dioxide is reduced and combined with water to form a wide
range of organic polymeric structures. Biomass can be
aquatic or terrestrial plants. Specific biomass sources
include macroalgae (kelp), microalgae, energy crops
(e.g., grasses, trees), crop residue (e.g., corn stover,
forestry byproducts), biomass processing byproducts
(e.g., bagasse, sawdust), as well as postconsumer
products derived from aquatic or terrestrial plants
(e.g., office paper, retail waste and municipal solid
waste).
To be useful for further biological or chemical
transformations the polymeric nature of biomass must be
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destructured. The first step of destructuring is
commonly referred to as pretreatment. There is a
universal need to efficiently destructure the biomass
with minimal time, investment and energy.
Extensive work has focused on improving
pretreatment. Various chemical pretreatment methods are
known, including treatments with acids or bases,
introducing solvents, water, enzymes, recycled
destructuring reaction products, and chemical or
biological agents or catalysts to promote
depolymerization.
Such chemical pretreatment methods may be used in
combination with mechanical pretreatment techniques that
impose physical deformations on the biomass. These
mechanical pretreatment techniques involve the use of
apparatus that subject biomass at elevated temperatures
and pressures to operations such as mixing, grinding
and/or milling. These activities facilitate size
reduction and/or the destructuring of the biomass. Under
these pretreatment conditions the state of the biomass
may be altered to the extent that portions of the biomass
dissolve, liquify and/or melt. The state of the
pretreated biomass ranges from solids, to compressible
solids, to molten material and liquids or mixtures
thereof.
It has been recognized that improved destructuring
may be achieved by rapidly transitioning the biomass to
lower pressure with a resulting flash and cooling of the
biomass due to latent heat of vaporization of the flashed
components. This state change may be referred to as
flashing or steam explosion. The process may be
complemented with additional steam in a jet cooker. The
increased shear in the high velocity two-phase flow
introduces gradients that disrupt some of the biomass
structure. In general shear fields are in the flow
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direction, although turbulence may exist. The magnitude
of the shear is dependent on the combination of the flow
properties of the pretreated materials and the change in
state for the apparatus (i.e., temperature and pressure).
Thus, the shear is difficult to control independently of
the biomass fluid properties.
It has been attempted to adjust the flashing
operation with varying cross section in the flash device.
Unfortunately, the flashing operation can be compromised
by variations in the quality of the pretreated biomass
flow characteristics and particulate size resulting in
erratic performance or pluggage in the flash device. The
pretreated biomass quality is a function of the
variability of the biomass feed material (inherent
genetics of the biomass, agronometry conditions, harvest,
and storage conditions) and how the varying structure and
composition of the biomass is transformed by the
pretreatment activities.
In moving this pretreated biomass material from one
vessel to another for treatments or subjecting the
material to a flashing operation the variability of
viscosity, solids content, and particle size may
challenge proper operation of typical types of valves,
nozzles, and metering devices and may result in erratic
performance, instability, or pluggage.
For example, U.S. Published Application 2008/0277082
discloses a system with a flash across a valve. If the
pretreated material flowing through the valve has
variable flow characteristics the valve may plug.
Similarly, in U.S. Published Application 2010/0317053 the
plunger associated with the valve may not seal properly
due to variations in the quality of the pretreated
biomass and/or the presences of solids.
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In view of the foregoing it is believed that there
remains a need for an apparatus, method and system
through which pretreated biomass can pass to achieve a
flash operation while maintaining stable operation with
minimal pluggage and the ability to subject the flashing
biomass to shear forces independent of the flow
properties of the pretreated biomass.
SUMMARY OF THE INVENTION
The present invention relates to a method, apparatus
and system for destructuring pretreated biomass at above
atmospheric pressure and at an elevated temperature by
discharge of the same into a reduced pressure zone (a
flashing operation) defined within the housing of a
combined tangential shear homogenizing and flashing
apparatus that includes a stator and a relatively movable
rotor. While the material is being subjected to flashing
a tangential shearing force is imposed on the material by
the action of the relatively moving rotor and stator.
Introducing an independent tangential shear in a rotating
device during the flashing operation homogenizes the
volume of pretreated biomass. The apparatus provides
inherently more stable performance due to the ability of
the rotation to shear particles to a more acceptable size
while systematically sweeping potential particle
accumulations away from the flashing zone of the device.
In other aspects the invention is directed to a
combined tangential shear homogenizing and flashing
apparatus having various configurations of rotor and
stator that results in different axial dimensions being
defined therebetween the rotor and stator.
In yet another aspect the gap defined between the
rotor and stator and/or the rotational speed of the rotor
is/are varied in accordance measured parameters of the
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pretreated biomass, such as pressure, temperature,
particle size and/or material composition.
In still other aspects the housing of the combined
tangential shear homogenizing and flashing apparatus is
provided with one or more outlet ports that direct
communicate with a downstream process utility.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be more fully understood from the
following detailed description, taken in connection with
the accompanying drawings, which form a part of this
application and in which:
Figure 1 is a highly stylized schematic
representation of a system for implementing a method for
destructuring biomass that includes a combined tangential
shear homogenizing and flashing apparatus in which a gap
of uniform axial dimension is defined between the rotor
and stator elements of the apparatus, all in accordance
with various aspects of the present invention;
Figure 2 is a highly stylized schematic
representation of an alternate implementation of an
embodiment of a combined tangential shear homogenizing
and flashing apparatus in which a gap of uniform axial
dimension is defined between the rotor and stator
elements of the apparatus;
Figures 3 and 4 are highly stylized schematic
representations of alternate implementations of an
embodiment of a combined tangential shear homogenizing
and flashing apparatus in which a gap of non-uniform
dimension is defined between the rotor and stator
elements of the apparatus;
Figure 5 is a highly stylized schematic
representation of yet another alternate embodiment of a
combined tangential shear homogenizing and flashing
apparatus in which a gap defined between the rotor and
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stator elements of the apparatus has regions that exhibit
uniform and non-uniform axial dimensions;
Figure 6 is highly stylized schematic representation
of a modification useful with any of the embodiments
shown in Figures 1 through 5 wherein a flow diverter is
disposed in the entrance region of the mixing zone; and
Figure 7 is highly stylized schematic representation
of another modification useful with any of the
embodiments shown in Figures 1 through 5 wherein the
rotor and stator are provided with cylindrical portions
that align to define an annular milling region in the
entrance region of the mixing zone.
DETAILED DESCRIPTION
Throughout the following detailed description
similar reference characters refer to similar elements in
all figures of the drawings.
Figure 1 is a highly stylized schematic illustration
of a system generally indicated by reference character 10
for implementing a method for destructuring biomass, both
in accordance with various aspects of the present
invention.
The system 10 includes a pretreatment device 12
operative to pretreat one or more stream(s) 14 of raw
cellulosic feedstock with processing aids such as water,
solvents, compatabolizing agents, acids, bases and/or
catalyst in preparation for destructuring and other
further operations. Any suitable pretreatment operation
on the biomass may be performed within the pretreatment
device 12, as, for example, agitating, washing,
pressurizing and/or heating the biomass to a
predetermined elevated temperature. Pretreated material
from the source 12 is conducted through a feed line 16 to
a combined tangential shear homogenizing and flashing
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apparatus 20 also in accordance with the present
invention.
The combined tangential shear homogenizing and
flashing apparatus 20 itself comprises a housing 20H
having an inlet port and channel 201 and at least a first
effluent output port 20E1. However, it lies within the
contemplation of the present invention to provide a
separate second output port 20E2 for the housing 20H. A
stator 20F and a rotor 20R are disposed within the
housing 20H in confrontational orientation with respect
to each other. In the arrangement illustrated in Figure
1 the rotor and stator are parallel to each other and are
oriented substantially perpendicular to the axis 20A.
The stator 20F is secured in a fixed disposition at
any convenient location within the housing. The rotor
20R is mounted on a shaft 20S for relative rotation with
respect to the stator. Motive force for the rotor 20R is
provided by a drive motor 20M connected to the shaft 20S.
The shaft 20S aligns with the axis 20A of the apparatus
20.
The stator 20S and the rotor 20R cooperate to define
a mixing zone 20Z therebetween. The inlet channel 201 is
connectible to the feed line 16 and serves to conduct
pressurized biomass material from the pretreatment device
12 into the entrance region 20N of the mixing zone 20Z
located in the vicinity of the axis 20A. The exit 20T of
the mixing zone 20Z is disposed at the radially outer
edge of the rotor 20R and communicates with the interior
of the housing 20H and thus, with the first effluent
output port 20E1 and the second output port 20E2 , if
present.
In a typical arrangement as illustrated in Figure 1
the rotor and the stator are each substantially disk-
shaped members. However, it should be understood that
the rotor and stator can have any convenient three-
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dimensional configuration, peripheral shape and size.
The surfaces of the rotor and stator can be smooth or
patterned with groves or elevated sections so as to
facilitate particle size reduction. The various
structural elements of the apparatus 20 may be
manufactured of any suitable materials of construction.
The rotor, stator, housing may be preferably made from
stainless steel. Various alternative structural
configurations of the rotor 20R and stator 20S and the
resulting modifications to the configuration of the
mixing zone 20Z are discussed herein.
As will be described the apparatus 20 assists in the
destructuring process by homogenizing the pretreated
biomass while simultaneously causing a partial phase
separation of the homogenized biomass into vapor and
liquid phases. The distinct liquid and vapor phases so
produced may be conducted singly or together directly to
a processing utility 28 disposed downstream of the
apparatus 20. If only a single effluent output port 20E1
is provided both the liquid and vapor phases resulting
from the homogenization and flash of the biomass are
conveyed through a first conduit 22 to the utility 28.
If the housing 20H is provided with a second output port
20E2 the vapor phase is carried via the conduit 24 to the
utility 28 and the liquid phase is conducted separately
to the utility 28 through the first conduit 22.
Representative of the various processing devices that may
be used for the utility 28 include an agitating vessel
for further destructuring.
However, it should be appreciated that flashed vapor
of the biomass leaving the housing through the second
outlet port 20E2 may require different processing.
Accordingly, the conduit 24 may be connected to an
alternative processing utility 28A in which the vapor
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phase may be isolated for recycling and re-use or refined
for various applications.
In a system in accordance with the present invention
the conduits 22, 24 provide direct, uninterrupted fluid
communication between the respective outlet ports 20E1,
20E2 and the particular utility(ies) 28, 28A to which
they are connected. As used in this application the term
"direct", "directly" (or like terms) means that
effluent(s) from the mixing zone 20Z is(are) conducted to
their respective destination(s) without any impediment to
fluid communication and without the need to pass through
a separate intermediate device (such as a discrete flash
or metering device).
The dimension of the mixing zone 20Z may be measured
in a direction parallel to the axis 20A and is determined
by the magnitude of the axial gap 20G between the rotor
20R and the stator 20F. Since in Figure 1 the rotor and
stator are arranged parallel to each other and are
situated substantially perpendicular to the axis 20A, the
gap 20G, and thus the axial dimension of the mixing zone,
is uniform across the across the full radial extent of
the mixing zone 20Z. It should be noted that if the
confronting surfaces of the rotor and/or stator in any
embodiment of the invention are patterned with grooves
and/or elevated sections to facilitate homogenization the
axial dimension of the gap between the rotor and the
stator is defined as the underlying surface should the
grooves and elevated sections be eliminated.
The dimension of the gap 20G may be adjusted by
relocating the rotor with respect to the stator.
Suitable expedients for manually adjusting the axial
dimension of the gap prior to operation include shims,
threaded shaft components, and hydraulic positioning
devices. However, in the preferred case the dimension of
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the gap is automatically adjusted during operation by a
gap adjustment control system 34 to be described.
The axial dimension of the gap is initially sized to
a predetermined value based upon the particular pressure,
temperature and nature of the biomass to be destructured.
This initial sizing of the gap sets the predetermined
appropriate initial axial dimension of the mixing zone
20Z. A predetermined volume of biomass having a
predetermined pressure and temperature is introduced into
the mixing zone 20Z through the inlet port 201.
In operation, various properties of the pretreated
biomass influent into the entrance 20N of the mixing zone
20Z are monitored by a sensor network generally indicated
by reference numeral 30. The sensor 30 may include one
or more sensing devices operative to monitor parameters
such as pressure, temperature, particle size and/or
composition (e.g., nature) of the pretreated influent
biomass.
The flow of the pretreated biomass in a
substantially radially outward direction through the
mixing zone 20Z is controlled by the pressure difference
between the entrance 20N and exit 20T. As the pretreated
biomass flows radially outwardly through the mixing zone
20Z it undergoes a pressure drop. The pressure gradient
vector, indicative of the change in pressure through the
mixing zone, is indicated in the drawing by the vector P.
Simultaneously with the flow of pretreated biomass
through the mixing zone 20Z the motor 20M rotates the
rotor 20R with respect to the stator 20F. The relative
rotational movement between the rotor and stator
generates a circumferentially directed shear field within
the mixing zone 20Z. The shear field imparts a
tangential shear force to the volume of pretreated
biomass flowing through the mixing zone 20Z. The
direction of the tangential shear force is indicated in
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the drawing by the vector S. The tangential shear force
homogenizes the pretreated biomass while the pressure
difference across the mixing zone causes a partial phase
separation of the homogenized biomass into vapor and
liquid phases. Depending upon the particular structure
of the rotor and stator the phase separation may occur
within the radial extent of the mixing zone or within a
predetermined close distance from the exit 201 thereof.
In the case illustrated in Figure 1 the partial phase
separation occurs within the mixing zone.
In accordance with this invention selection of the
predetermined initial size of the gap 20G coupled with
the pressure differential and temperature of the biomass
cause a partial phase separation of the homogenized
pretreated biomass into vapor and liquid phases such that
the biomass undergoes at least a three-fold total
volumetric increase and a weight transition to a vapor
state of at least one percent (1%).
Introducing an independent tangential shear force S
in a rotating device during the flashing operation
provides inherently more stable performance due to the
ability of the rotation to homogenize particles to a more
acceptable size while systematically sweeping potential
particle accumulations away from the flashing zone of the
device.
Due to the inherent inconsistencies of biomass
composition and the manner in which various pretreatment
operations impact these inconsistencies the resulting
pretreated biomass in the flow line 16 may contain
significant variations in fluid properties as well as
size of discrete particles.
Accordingly, as a further aspect of the present
invention the gap adjustment control system 34 enables
the apparatus 20 and a system 10 incorporating the same
to adapt automatically to adjust the gap 20G between the
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rotor and the stator and to compensate for such
variations in pretreated biomass composition, flow
properties and particulate size. This ability to vary
the gap 20G allows the apparatus 20 also to function as a
metering device.
In addition to the sensor 30 the gap adjustment
control system 34 includes a programmable controller
device 34C that is responsive to the signals from the
sensor network 30 to vary the gap dimension 20G and thus,
the axial dimension of the mixing zone 20Z, in accordance
with one or more of the various sensed parameters of the
influent pretreated biomass. The gap adjustment control
system 34 may further include actuator 36 operatively
connected to the motor 20M to physically effect
adjustments to the gap dimension. The actuator 36
responds to a control signal from the control system 34
carried on a line 34A to move the motor and the rotor
connected thereto as a unit toward and away from the
stator thus to vary the gap dimension of the mixing zone
based upon various measured parameters of the influent
pretreated biomass. Thus, for example, the pressure of
the biomass feed through the mixing zone 20Z may be
maintained constant or varied in any predetermined way.
Additionally or alternatively, for example, the gap
dimension may be varied in a time-controlled manner to
expel troublesome particles. It should be understood
that various other expedients may be used to effect
modification of the gap dimension, and that such other
expedients are to be construed as lying within the
contemplation of the present invention. For example, the
gap dimension may be altered by displacing the stator
within the housing relative to the rotor.
Alternatively or additionally, a signal from the
control system 34 carried on a line 34B may be applied as
a motor control signal to vary the rotational speed of
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the rotor 20M. Changing the rotational speed of the
rotor facilitates particle size reduction.
As mentioned earlier, in the arrangement shown in
Figure 1 the rotor and stator are each substantially
disk-shaped members that are mounted parallel to each
other and substantially perpendicular to the axis 20A
such that the gap 20G is uniform across the entire radial
extent of the mixing zone 20Z. Figure 2 illustrates an
alternate implementation of an apparatus 20 having a
uniform axial dimension across the mixing zone but in
which the rotor and stator are frustoconically shaped to
facilitate material flow. Similar to the situation in
Figure 1, with the arrangement shown in Figure 2 the
flash occurs within the radial extent of the mixing zone.
The location of the flash can be adjusted by
appropriate adjustment of the geometry of the rotor
and/or stator. Figures 3 and 4 illustrate two forms of
an alternate embodiment of the apparatus 20 in which the
mixing zone 20Z defined by the gap 20G between the rotor
and stator has a non-uniform dimension. In these Figures
the largest axial dimension 20GL of the gap, and thus of
the mixing zone, is located in the vicinity of the
entrance 20N.
In the structure shown in Figure 3 one (or both) of
the rotor and/or stator is(are) frustoconically shaped
members that are inclined with respect to the axis 20A
such that the members taper uniformly toward each other
at positions radially outwardly from the axis 20A. As a
result of this structure the smallest axial gap dimension
20G occurs near the exit 201 at the radially outer edge
of the mixing zone 20Z. The smallest axial gap dimension
20G presents a restriction to the substantially radially
outwardly flow of biomass. In this form of the invention
the partial phase separation occurs just past the
radially outer edge.
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The arrangement shown in Figure 4 illustrates an
construction in which the smallest axial gap dimension
20G, and thus the restriction to biomass flow, occurs at
a selected location radially inwardly from the exit 20T
of the mixing zone 20Z. In the arrangement shown in
Figure 4 the flow restriction should be not more than
one-third of the radial distance of the mixing zone
inwardly from the exit of the mixing zone. In Figure 4
the restriction is defined by a constrictive feature 20K
that is formed in the stator 20F. The partial phase
separation occurs within the mixing zone in the vicinity
of the feature 20K. It should be understood that an
analogous feature may alternatively or additionally be
provided on the rotor 20R.
Figure 5 illustrates another alternate embodiment of
the apparatus 20. In this embodiment the rotor and the
stator are configured to present a hybrid structure
having a variety of gap configurations. A radially inner
region 20G1 includes sections 20Gu and 2OGN having uniform
20Gu and non-uniform 2OGN axial dimensions, respectively.
If desired, the section 20Gu of uniform dimension in the
radially inner region 20G1 may be omitted.
Alternatively, any convenient number of additional
uniform and non-uniform sections may be provided in the
radially inner region 20G1 if desired.
A radially outer region 20Gm has a uniform axial gap
dimension and defines the smallest axial dimension 20Gs
of the gap. The confronting surfaces of the rotor and
stator in this region 20Gv cooperate to function as a
metering device. The metering action provided by these
surfaces regulates the exit pressure and provides
improved pressure stability when compared to the
structure of Figure 4 where the smallest axial dimension
20G is a point contact.
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Figures 6 and 7 illustrate two additional structural
details that may be used with any of the rotor/stator
arrangements illustrated in Figures 1 through 5.
In Figure 6 a flow diverter 20L is positioned
between the rotor 20R and the stator 20F at a
predetermined location near the entrance 20N of the
mixing zone. The flow diverter 20L serves to streamline
influent flow and avoid dead zones or abrupt direction
changes that may lead to pockets of stagnant material.
The flow diverter 20L may be mounted at any convenient
location on either the rotor or the stator.
Figure 7 illustrates an arrangement in which the
apparatus is provided with a milling device disposed
upstream of the entrance 20N of the mixing zone 20Z. The
stator 20F has a substantially cylindrical portion 20C
having a predetermined axial dimension formed thereon.
Correspondingly, a substantially cylindrical barrel 20B
mounted to the rotor 20R. The barrel 20B has a
predetermined axial dimension. The barrel 20B extends
axially from the rotor 20R into concentric nested
relationship with the cylindrical portion 20C of the
stator.
The barrel and the cylindrical portion of the stator
cooperate to define an axially extending milling zone 38
disposed between the rotor and the stator. The axial
dimension of the milling zone 38 is determined by the
extent of axial overlap between the barrel 20B and the
cylindrical portion 20C.
Any of a variety of mixing enhancers 38E may be may
be incorporated on the barrel 20B and/or the walls of the
cylinder 20C. In Figure 7 the mixing enhancers 38E are
shown in the form of pins. However, it is understood
that other suitable forms of mixing enhancers, such as
Maddock straight, Maddock tapered, pineapple, or gear may
be used. Drawings of such mixing enhancers are shown in
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Perry's Chemical Engineering Handbook, Seventh Edition,
Figure 18-48.
Yet further, if desired, a flow 20L diverter may be
mounted at the upstream end of the barrel 20B.
-o-O-o-
Those skilled in the art, having the benefit of the
teachings of the present invention, may impart
modifications thereto. Such modifications are to be
construed as lying within the scope of the present
invention, as defined by the appended claims.
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