Note: Descriptions are shown in the official language in which they were submitted.
1
PRODUCTION OF DIESEL FROM CELLULOSIC BIOMASS
TECHNICAL FIELD
The technical field generally relates to the production of hydrocarbon fuel
from biomass,
and more particularly to the production of a hydrocarbon product, such as
diesel, from
cellulosic biomass.
BACKGROUND
The conversion of biomass, particularly cellulosic and woody biomass, to
various forms
of liquid fuel has been achieved via various conventional pathways. Pyrolysis,
gasification, catalytic conversion and fermentation are some leading pathway
platforms
that have been developed. One challenge has been to evolve and encapsulate
those
pathways into long-term viable businesses. Consequently, the development of
the next-
generation biofuels industry has been relatively limited.
Another challenge is that the overall economic viability of various known
technology
platforms is a function of many other business and economic dynamics. The
history of
biofuel development is littered with examples of technology pathways that were
pursued
for certain technical merits, but key business dynamics, such as a long-term
sustainable
source of raw materials at assumed prices, were not properly accounted for.
Indeed, there are a number of challenges with respect to identifying and
implementing
reliable and efficient technologies for the conversion of biomass into liquid
fuel.
SUMMARY
In some implementations, there is provided a process for producing diesel from
biomass,
comprising: supplying cellulosic biomass to a solubilization unit to form an
organic slurry
comprising solubilized carbonaceous material, wherein the cellulosic biomass
is supplied
in particulate form via a plug screw feeder into the solubilization unit;
supplying the
organic slurry to a depolymerization unit to depolymerize carbonaceous
polymers
contained in the organic slurry and produce a treated hydrocarbon stream;
supplying the
treated hydrocarbon stream to a phase separator to produce at least an upper
gaseous
hydrocarbon stream and a bottom slurry phase; and supplying the gaseous
hydrocarbon
stream to a purification unit to produce a diesel stream.
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In some implementations, the cellulosic biomass comprises sawdust from wood
processing. In some implementations, the cellulosic biomass supplied to the
solubilization unit has particle sizes of at most 3 mm. The cellulosic biomass
supplied to
the solubilization unit can have particle sizes between 1 mm and 3 mm. The
cellulosic
biomass can be subjected to pre-grinding to obtain the particle sizes.
In some implementations, the cellulosic biomass is subjected to pre-drying so
as to have
a moisture content of about 5 wt% to about 15 wt prior to supply into the
solubilization
unit.
In some implementations, the cellulosic biomass is supplied into the
solubilization unit
below a liquid level of the organic slurry therein. In some implementations,
the
solubilization unit comprises an internal mixer operable to mix the organic
slurry and
promote solubilization.
In some implementations, the process further comprises recycling a portion of
the
bottom slurry phase back into the depolymerization unit.
In some implementations, the process further comprises supplying at least a
portion of
the bottom slurry phase from the phase separator to a residuals treatment unit
to
produce a recovered hydrocarbon gas and a solids enriched bottom fraction;
condensing
the recovered hydrocarbon gas to produce a recovered hydrocarbon liquid;
recycling at
least a portion of the recovered hydrocarbon liquid back into the
solubilization unit to
form part of the organic slurry.
In some implementations, there is provided a process for producing diesel from
biomass,
comprising: supplying cellulosic biomass to a solubilization unit to form an
organic slurry
comprising solubilized carbonaceous material, wherein the cellulosic biomass
is supplied
in particulate form below a liquid level of the organic slurry in the
solubilization unit;
supplying the organic slurry to a depolymerization unit to depolymerize
carbonaceous
polymers contained in the organic slurry and produce a treated hydrocarbon
stream;
supplying the treated hydrocarbon stream to a phase separator to produce at
least an
upper gaseous hydrocarbon stream and a bottom slurry phase; recycling a
portion of the
bottom slurry phase back into the depolymerization unit; and purifying the
gaseous
hydrocarbon stream to produce a diesel stream.
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In some implementations, process for producing diesel from biomass,
comprising:
supplying cellulosic biomass to a solubilization unit to form an organic
slurry comprising
solubilized carbonaceous material, wherein the solubilization unit is operated
at a
solubilization temperature between 160 C and about 200 C, for example;
supplying the
organic slurry to a depolymerization unit to depolymerize carbonaceous
polymers
contained in the organic slurry and produce a treated hydrocarbon stream,
wherein the
depolymerization unit is operated at a depolymerization temperature above that
of the
solubilization unit, for example between 260 C and about 300 C; operating a
fluid
transfer system to supply the organic from the solubilization unit to the
depolymerization
unit such that back-flow and back-heating from the depolymerization unit
toward the
solubilization unit are inhibited; supplying the treated hydrocarbon stream to
a phase
separator to produce at least an upper gaseous hydrocarbon stream and a bottom
slurry
phase; and purifying the gaseous hydrocarbon stream to produce a diesel
stream.
In some implementations, the fluid transfer system comprising an outlet line
for
withdrawing the organic slurry from the solubilization unit, at least one pump
coupled to
the outlet line for receiving the organic slurry therefrom and pumping the
organic slurry
downstream, and a downstream line coupled to the pump for receiving the
organic slurry
therefrom and supplying the organic slurry into the depolymerization unit.
In some implementations, the process includes measuring at least one process
variable,
and adjusting the pump based on the measured process variable.
In some implementations, a slurry temperature of the organic slurry is
measured in the
solubilization unit, the outlet line and/or the downstream line, and the pump
is controlled
to regulate transfer of the organic slurry in order to maintain the slurry
temperature below
a pre-determined threshold.
In some implementations, the pump is controlled to increase the flow rate of
the organic
slurry from the solubilization unit to the depolymerization unit in response
to a measured
back-heating of the organic slurry upstream of the depolymerization unit.
In some implementations, the pump is controlled to increase the flow rate of
the organic
slurry from the solubilization unit to the depolymerization unit in response
to a measured
viscosity reduction of the organic slurry upstream of the depolymerization
unit.
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In some implementations, the process includes recycling a portion of the
bottom slurry
phase back into the depolymerization unit. In some implementations, the
recycled
portion of the bottom slurry phase is fed back into the downstream line
upstream of the
depolymerization unit.
In some implementations, process for producing diesel from biomass,
comprising:
supplying cellulosic biomass to a solubilization unit to form an organic
slurry comprising
solubilized carbonaceous material; supplying the organic slurry to a
depolymerization
unit to depolymerize carbonaceous polymers contained in the organic slurry and
produce a treated hydrocarbon stream; supplying the treated hydrocarbon stream
to a
phase separator to produce at least an upper gaseous hydrocarbon stream and a
bottom slurry phase comprising liquid hydrocarbons and solid particulate
material;
withdrawing an underflow stream comprising the bottom slurry phase from the
phase
separator; recirculating at least a portion of the underflow stream as a
recirculated
stream back into the phase separator to provide agitation of the bottom slurry
phase
within the phase separator to inhibit deposition on the inner walls of the
phase separator;
and purifying the gaseous hydrocarbon stream to produce a diesel stream.
In some implementations, the recirculating comprises pumping the recirculated
stream
back into the phase separator below a liquid level therein. In some
implementations, the
recirculating comprises feeding the recirculated stream back into the phase
separator via
a single inlet. In some implementations, the recirculating comprises feeding
the
recirculated stream back into the phase separator via at least two inlets. In
some
implementations, the at least two inlets are each located at different heights
of the phase
separator. In some implementations, the at least two inlets are each located
at different
locations around the periphery of the phase separator.
In some implementations, a first portion of the underflow stream is
recirculated as the
recirculated stream, and a second portion of the underflow stream is supplied
to a
downstream unit. In some implementations, the second portion of the underflow
stream
is supplied to a residuals treatment unit to produce a recovered hydrocarbon
gas and a
solids enriched bottom fraction.
In some implementations, the recirculating is controlled to vary a
recirculation flow rate in
response to a measured process variable. The recirculating can be operated
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continuously or periodically. In some implementations, the recirculating is
performed
such that the recirculated stream is fed into the bottom slurry phase at a
fixed located
and feed direction.
In some implementations, there is provided a process for producing diesel from
biomass,
comprising: supplying cellulosic biomass to a solubilization unit to form an
organic slurry
comprising solubilized carbonaceous material; supplying the organic slurry to
a
depolymerization unit to depolymerize carbonaceous polymers contained in the
organic
slurry and produce a treated hydrocarbon stream; supplying the treated
hydrocarbon
stream to a phase separator to produce at least an upper gaseous hydrocarbon
stream
and a bottom slurry phase comprising liquid hydrocarbons and solid particulate
material;
supplying the gaseous hydrocarbon stream to a purification unit to produce a
diesel
stream; supplying at least a portion of the bottom slurry phase to a residuals
treatment
unit to produce a recovered hydrocarbon stream and a solids enriched bottom
fraction;
and recycling the recovered hydrocarbon stream back into the solubilization
unit to form
part of the organic slurry.
In some implementations, the recovered hydrocarbon stream withdrawn from the
residuals treatment unit is a recovered hydrocarbon gas, and the process
further
comprises condensing the recovered hydrocarbon gas to produce a recovered
hydrocarbon liquid; and recycling the recovered hydrocarbon liquid back into
the
solubilization unit to form part of the organic slurry.
In some implementations, the recovered hydrocarbon liquid is fed into the
solubilization
unit below a liquid level therein. In some implementations, the recovered
hydrocarbon
liquid is fed into the solubilization unit below a biomass feed inlet thereto.
In some
implementations, the recovered hydrocarbon liquid is supplied to a feed tank,
and then
pumped from the feed tank into to the solubilization unit.
In some implementations, supply of the recovered hydrocarbon liquid is
controlled based
on a measure process variable of the solubilization unit. In some
implementations, the
measured process variable comprises slurry temperature of the organic slurry
in the
solubilization unit, and the supply of the recovered hydrocarbon liquid is
controlled in
accordance with the slurry temperature. In some implementations, the measured
process variable comprises torque of a mixer deployed in the solubilization
unit to mix
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the organic slurry, and the supply of the recovered hydrocarbon liquid is
controlled in
accordance with the mixer torque. In some implementations, supply of the
recovered
hydrocarbon liquid is increased in response to the measure toque exceeding a
pre-
determined threshold value. In some implementations, supply of the recovered
hydrocarbon liquid is controlled to maintain a generally constant viscosity
and/or torque
in the solubilization unit.
In some implementations, the residuals treatment unit comprises a kiln or
furnace
operated at temperatures between 400 C and 450 C.
It should be noted that various features (such as operating parameters,
chemical
addition, process configuration, and so on) can be used in the above-mentioned
implementations of the processes, and some of such features are further
described
herein. Other carbonaceous feedstocks can be used instead of biomass, and
various
alternative process configurations can also be used. It should also be noted
that
intervening unit operations can be conducted in between two unit operations
mentioned
above (e.g., in between solubilization and depolymerization there can be a
heating step,
in between phase separation and purification there can be various other
cooling and
separating steps, and so on). In addition, systems can also be provided to
implement the
processes described herein, and may include a solubilization unit, a
depolymerization
unit, a phase separator, a purification unit, a residuals treatment unit, as
well as various
other components for interconnecting and managing the units and for
facilitating the
overall operation.
In some implementations, there is provided a process for producing synthetic
diesel from
biomass, comprising: supplying cellulosic biomass, lime and a catalyst to a
depolymerization reactor to form an organic slurry; circulating the organic
slurry through
the depolymerization reactor via a plurality of friction turbines that each
remove a slurry
stream from the depolymerization reactor, impart shear energy under vacuum
conditions
to the slurry stream, and return the slurry stream back into the
depolymerization reactor,
thereby depolymerizing carbonaceous polymers contained in the organic slurry
and
producing a treated hydrocarbon fluid and sludge; supplying the treated
hydrocarbon
fluid to a cooler to produce at least a hydrocarbon stream and a gas stream
comprising
CO2 and water; subjecting the hydrocarbon stream to distillation to produce
raw diesel
and a bottom fraction; supplying the bottom fraction back into the
depolymerization
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reactor; removing the sludge from the depolymerization reactor and subjecting
the
sludge to solids separation to produce ash and recovered hydrocarbons;
recycling the
recovered hydrocarbons back into the depolymerization reactor; and subjecting
the raw
diesel to purification to produce the synthetic diesel.
In some implementations, the process further includes a preparation step for
preparing
the cellulosic biomass to supplied into the depolymerization reactor, the
preparation step
comprising grinding and drying. The grinding can be performed to produce
particulate
biomass having a particle size of 3mm or below. The drying can be performed so
that
the cellulosic biomass has a moisture content of at most 15 wt%.
In some implementations, the supplying of the cellulosic biomass is performed
using a
feed screw, which can be a plug screw feeder. The plug screw feeder can be
configured
to supply the cellulosic biomass below a liquid level in the depolymerization
reactor.
In some implementations, the friction turbines are operated to heat the
organic slurry to
a temperature between 310 C and 330 C. Other temperature ranges are also
possible
(e.g., 280 C to 340 C, 290 C to 335 C, 315 C to 325 C or about 32000). The
organic
slurry can be circulated to have a residence time of between 30 seconds and 2
minutes
in the depolymerization reactor. The residence time can be provided depending
on other
factors, such as the temperature, composition, pressure and other operating
conditions
of the stage.
In some implementations, the cooler is a spray cooler, although other types of
cooler
equipment or similar units can be used. The gas stream can also be fed to an
additional
cooler to separate the water from the CO2.
In some implementations, the distillation further produces a light fraction.
It is noted that
the distillation can also produce multiple fractions that are each supplied
for further
processing, reuse, or storage, as desired.
In some implementations, the purification comprises filtration or polishing or
a
combination thereof. The purification can be performed to remove odors and/or
colors
from the raw diesel. ,
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In some implementations, subjecting the sludge to the solids separation
comprises a
thermal sludge treatment, or pressure-based sludge treatment operated at
vacuum
pressures.
In some implementations, with respect to the depolymerization stage, the
plurality of
friction turbines comprises at least three friction turbines or preferably
four turbines. The
friction turbines can be controlled using a frequency drive to control a
rotation speed
thereof, and can be operated to provide vacuum pressure conditions of about
0.4 bar to
about 0.6 bar.
In other implementations, there is a process for producing synthetic diesel
from biomass,
comprising: supplying cellulosic biomass and an organic oil to a
depolymerization reactor
to form an organic slurry; circulating the organic slurry through the
depolymerization
reactor via a plurality of friction turbines that each removes a slurry stream
from the
depolymerization reactor, imparts shear energy under vacuum conditions to the
slurry
stream, and returns the slurry stream back into the depolymerization reactor,
thereby
depolymerizing carbonaceous polymers contained in the organic slurry and
producing a
treated hydrocarbon fluid and sludge, the friction turbines being arranged at
different
heights and locations around a perimeter of the depolymerization reactor;
removing the
treated hydrocarbon fluid from the depolymerization reactor; and processing
the treated
hydrocarbon fluid into multiple components including synthetic diesel.
In some implementations, there is a process for producing synthetic diesel
from biomass,
comprising: supplying cellulosic biomass for solubilization and
depolymerization into a
reactor system to form an organic slurry; circulating the organic slurry
through the reactor
system via a friction turbine that removes a slurry stream from the reactor
system, imparts
shear energy under vacuum conditions to the slurry stream, and returns the
slurry stream
back into the reactor system, thereby depolymerizing carbonaceous polymers
contained
in the organic slurry and producing a treated hydrocarbon fluid and sludge;
removing the
treated hydrocarbon fluid from the depolymerization reactor; and processing
the treated
hydrocarbon fluid into multiple components including synthetic diesel. The
reactor system
can include a single stage reactor, or two stages for solubilization and
depolymerization
respectively.
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In some implementations, there is a process for producing synthetic diesel
from
biomass, comprising: supplying cellulosic biomass and an organic oil to a
depolymerization reactor to form an organic slurry; circulating the organic
slurry through
the depolymerization reactor via at least one friction turbine that removes a
slurry stream
from the depolymerization reactor, imparts shear energy under vacuum
conditions to the
slurry stream, and returns the slurry stream back into the depolymerization
reactor,
thereby depolymerizing carbonaceous polymers contained in the organic slurry
and
producing a treated hydrocarbon fluid and sludge; removing the treated
hydrocarbon
fluid from the depolymerization reactor; separating the treated hydrocarbon
fluid into
multiple fractions including raw diesel and a heavy hydrocarbon fraction;
supplying the
heavy hydrocarbon fraction back into the depolymerization reactor; removing
the sludge
from the depolymerization reactor and subjecting the sludge to solids
separation to
produce ash and recovered hydrocarbons; recycling the recovered hydrocarbons
back
into the depolymerization reactor; and subjecting the raw diesel to
purification to produce
the synthetic diesel.
It is also noted that the processes and systems described herein can be
adapted to add
one or more features that are described or illustrated herein.
In some implementations, there is provided a process for producing synthetic
diesel from
biomass, comprising: supplying cellulosic biomass, a pH control agent and a
catalyst to
a depolymerization reactor to form an organic slurry; circulating the organic
slurry
through the depolymerization reactor via a plurality of friction turbines that
each remove
a slurry stream from the depolymerization reactor, impart shear energy under
vacuum
conditions to the slurry stream, and return the slurry stream back into the
depolymerization reactor, thereby depolymerizing carbonaceous polymers
contained in
the organic slurry and producing a treated hydrocarbon fluid and sludge;
supplying the
treated hydrocarbon fluid to a cooler to produce at least a hydrocarbon stream
and a gas
stream comprising CO2; treating the hydrocarbon stream to produce raw diesel;
removing the sludge from the depolymerization reactor and subjecting the
sludge to
solids separation to produce ash and recovered hydrocarbons; recycling the
recovered
hydrocarbons back into the depolymerization reactor; and subjecting the raw
diesel to
purification to produce the synthetic diesel.
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BRIEF DESCRIPTION OF THE DRAWINGS
Fig 1 is a block diagram of a process for the conversion of biomass into
diesel fuel.
Fig 2 is another more detailed block diagram for an example process for the
conversion
of biomass into diesel fuel.
Fig 3 is a side view schematic of a solubilization unit.
Fig 4 is another block diagram of a process for the conversion of biomass into
diesel fuel.
DETAILED DESCRIPTION
Figs 1 to 4 show various example processes for the conversion of biomass into
diesel.
Certain features and aspects of the processes will be described in further
detail below.
Date Recue/Date Received 2020-08-26
10
Referring to Fig 1, which is a high-level diagram of an example process for
producing
diesel from biomass, there are several unit operations that facilitate the
conversion and
handling of various streams. In general, biomass 10 is first supplied to a
solubilization
unit 12 to produce a solubilized biomass containing stream 14 (also referred
to as a
hydrocarbon rich slurry or biomass slurry), which is then supplied to a
depolymerization
unit 16 to produce a diesel containing stream 18 (also referred to as output
hydrocarbon
stream) and a residue stream 20. The diesel containing stream 18 is supplied
to a
separator 22 to produce a raw diesel stream 24, which is then sent to a
purification unit
26 to produce a more refined diesel product 28.
In addition, the residue stream 20 from the depolymerization unit 16 can be
supplied to a
residuals treatment unit 30. Also, additional residues 32, such as viscous
sludges, which
may be generated in the purification unit 26 can also be supplied to the
residuals
treatment unit 30. Other residues 33 withdrawn from the separator 22 can also
be
supplied to the treatment unit 30. The residuals treatment unit 30 can be
operated to
produce a recovered organics stream 34, which can be fed back to the
depolymerization
unit 16 or sent to other processing units.
Furthermore, the separator 22 produces the raw diesel stream 24 in addition to
a water
stream 36 and an off-gas stream 38 that can be supplied to a generator unit 40
to
generate power 42 that is used in the system. The generator unit 40 can also
receive a
portion of raw and/or refined diesel as a diesel-based fuel stream 44 for
power
generation.
As will be explained in further detail below, there are various techniques for
conducting
the unit operations and handling the streams generated in the process.
Biomass and carbonaceous feedstock materials
The biomass that is converted into diesel can be from various sources. In some
implementations, the biomass is cellulosic biomass, and more particularly wood
biomass. The wood biomass can be or include a low-value woody biomass
material.
Prior to supplying raw biomass to the solubilization unit, the biomass can be
subjected to
various pre-treatments, such as drying and size-reduction, in order to
facilitate
subsequent processing. In some implementations, the biomass is prepared to
take the
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form of a fine particulate material (e.g., course wood flour), where the
particle sizes can
preferably be below about 3 mm, e.g., ranging between about 1 mm and about 3
mm.
Larger particles can be used, although solids and slurry handling issues are
reduced and
solubilization is enhanced with smaller sized particles. It was found, for
example, that
particles of about 5 mm were not as advantageous as particles ground to 3 mm
or
smaller. The raw biomass can be pre-dried and then subjected to grinding to
produce
the particulate cellulosic material that is supplied into the solubilization
unit.
Conversion of low-value woody biomass into high-value sustainable diesel
products
facilitates efficient use of such raw materials. The wood based material can
be obtained
from the forestry sector and its value chain participants, which are in need
throughout
many regions of Canada and elsewhere of a technology as described herein. The
processes and systems described herein can facilitate primary forestry
activities to be
more economic and for secondary activities to have a market for their
residuals.
The wood based biomass can include sawdust from wood processing, bark and
other
woody materials, residual streams from the forestry or pulp-and-paper
industries, and so
on. In addition, the biomass that is used as the feedstock can include various
cellulosic
sources, including fuel crops, agriculture residues, some municipal solid
waste materials,
and so on. It is also noted that various carbonaceous feedstocks and
combinations of
carbonaceous feedstocks can be used in processes and systems described herein,
and
while biomass derived sources are preferred it is also possible to use other
carbonaceous materials (e.g., materials that include carbon-based polymers
and/or
sugars) as feedstocks. In addition, the source of carbonaceous material can
change
over time, such that a first material or combination of materials can be used
during start-
up and ramp up stages, while a second material or combination of materials can
be used
during steady state operations, for example.
In terms of the pre-drying, in some implementations the biomass (e.g., wood
biomass) is
dried to a moisture content of at most about 15 wt%, for example, or between
about 5
wt% and about 15 wt%. The pre-drying can be performed in a dryer (D in Fig 2),
which
can be located on-site with the rest of the processing units, or can be
located at a
remote location (e.g., saw mill). Preferably, the wood is in the form of wood
chips or
smaller particulates when subjected to the pre-drying step, to accelerate and
enhance
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the drying step. The wood is preferably pre-dried prior to the size-reduction
step to
produce the particulate biomass that is fed into the solubilization unit.
In terms of the grinding of the biomass, in some implementations the biomass
is pre-
ground just before being fed into the solubilization unit in order to avoid
substantial
moisture reabsorption. For example, the dried biomass can be fed into a
grinding unit (G
in Fig 2), located proximate to a hopper or other feed unit into which the
ground
particulate biomass is supplied. From the feed unit, the ground particulate
biomass can
be fed directly into the solubilization unit. The grinder G can be operable
for variable size
reduction and/or variable grinding rates to handle different feed rate
demands, different
biomass types, and other variables. The grinding can be adapted to factors in
the
solubilization unit, e.g., finer grinding to promote faster or more complete
solubilization, if
needed at certain operating conditions.
Solubilization
Referring to Fig 2, the solubilization unit 12 receives the biomass feed
material 10, which
has preferably been pre-treated so as to have a moisture content of about 5
wt% to
about 15 wt%, and a size of about 1 mm to about 3 mm. The solubilization unit
12
preferably comprises a solubilization vessel 46 that can be configured as a
mixing
reactor having a mixing element 47 extending into the reaction chamber. The
mixing
element 47 can include an impeller-type mixer or another type of reactor
mixer.
The solubilization unit 12 also receives an organic liquid into which the
biomass
dissolves, and chemical agents to enhance the process. The organic liquid can
be a
medium or high-temperature carrier oil 48. The carrier oil 48 used in the
process can be
a high-performance mineral oil with a boiling temperature above about 370 C.
In some
implementations, the carrier oil 48 can be used to help dissolve the biomass
and create
the hydrocarbon rich slurry. The carrier oil 48 can be used primarily or
exclusively at
start-up, and it can be re-circulated throughout the system such that, over
time, it is
gradually displaced by a recycled heavier oil fraction produced by the
process, while it is
in part broken into diesel and in part ends with the heavy bottom residue in
the phase
separator. In some implementations, the process does not require constant
addition of
the carrier oil 48 and can be mainly used during start-up situations. However,
carrier oil
48 can be used as a top-up fluid if necessary. The carrier oil 48 can be added
via a
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distinct line into the solubilization vessel 46 or the same line as the
recycled heavier oil
stream.
Regarding the chemical agents, a catalyst 50 and a pH control agent 52 can be
added to
provide appropriate conditions for dissolution and depolymerization. The pH
control
agent 52, such as lime, can be added to support the solubilizing process into
the organic
liquid. Lime can be used to control the pH of the process mixture to about 8.5
to about
9.5, or about 9, as this pH level favors the depolymerization of biomass to
linear and
saturated hydrocarbons as well as to precipitate any metals and sulphur found
in the
process medium. Lime can be added to the system at about 1.5% to about 4%
(w/w)
based on the biomass input, for example. The pH control agent 52 can also be
added
into the solubilization vessel 46 and/or at other locations in the process.
The catalyst 50, which can be a sodium-aluminum silicate type catalyst, can be
added
for lowering the activation energy of depolymerization and allows for the
depolymerization of biomass at lower temperatures. Catalyst 50 can be added to
the
system at 0.25% to 3% (w/w) based on the biomass input, for example. Catalyst
can be
added at various locations in the process, such as directly into the
solubilization vessel
46, in-line in between the solubilization vessel 46 and the depolymerization
unit 16 or the
separator 22, into the recycle line that feeds into the solubilization vessel
46 or an
upstream tank or mixer, and/or directly into the separator 22, for example.
Preferably,
the catalyst is added into the solubilization vessel 46 to enable it to begin
reactions early
on in the process and to enhance mixing with the slurry. In addition, both
lime 52 and
catalyst 50 can contribute to the formation of hydrogen radicals from the
biomass, which
are suitable for making saturated hydrocarbons through molecular recombination
and
positively influence the stability of the diesel product.
It should be noted here that the catalyst 50 and the pH control agent 52, as
well as other
chemical agents, can be added in various ways and at various stages of the
overall
process. In one implementation, the catalyst 50 and the pH control agent 52
are both
added into the solubilization vessel 46 such that the resulting mixture in the
solubilization
vessel 46 includes the biomass, the organic liquid, the catalyst 50 and the pH
control
agent 52. Alternatively, in some other implementations, the catalyst 50 may be
added
into the solubilized biomass containing stream 14 that is withdrawn from the
solubilization vessel 46, prior to introduction into the depolymerization unit
16. The
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chemical agents can also be added in various forms (e.g., solid, dispersed in
carrier
fluid, and so on).
In some implementations, the solubilization vessel 46 enables mixing of the
contents
while being kept under temperature and pressure conditions that favour
evaporation of
water, solubilization of the biomass into the organic liquid, and efficient
operation and
energy use. The solubilization vessel 46 can be operated at temperatures
between, for
example, about 160 C and about 200 C, about 170 C and about 190 C, about 175 C
and about 185 C, or about 180 C, or another temperature that is provided based
on the
operating pressures. The pressure in the solubilization vessel 46 can be
above, at or
below atmospheric pressure. In one example, the solubilization vessel 46 is
operated at
vacuum pressure conditions. The temperature and pressure conditions can also
be
provided to facilitate extraction and vaporization of existing moisture out of
the biomass
and for the creation of the hydrocarbon rich slurry (also referred to as the
solubilized
biomass containing stream). Water is released from the input biomass quickly,
which is
facilitated be mixing the contents of the vessel 46, and the water vapour is
recovered via
a condenser column 54 mounted on top of the solubilization vessel 46. Water
can then
be collected in a recovery tank 55, preferably after being cooled. In some
implementations, the residence time in the solubilization vessel 46 is between
about 30
minutes and about 45 minutes. It is also noted that some water remains in the
biomass
slurry 14 that is withdrawn from the solubilization unit 12, and is involved
in subsequent
reactions.
Referring to Figs 2 and 3, the solubilization unit 12 includes a biomass feed
system 56
that can advantageously include a feed screw for feeding the particulate
biomass into
the solubilization vessel 46. The feed screw 56 can have various constructions
and
arrangements. For example, the feed screw 56 can be arranged at an oblique
downward
angle, and its downstream end can be fluidly coupled to the reaction chamber
via the
lower part of a side wall of the solubilization vessel 46.
In some implementations, the biomass feed system (e.g., feed screw 56) is
arranged to
feed the biomass below the liquid level of the organic liquid in the
solubilization vessel
46, which can facilitate effective mixing, reduce accumulation of biomass
(e.g., at the top
of the vessel), and reduce entrainment of biomass as a fine dust via overhead
systems
or vacuum line when vacuum pressures are implemented, thereby inhibiting
solids
CA 3010168 2019-11-21
15
plugging of column/condenser trays over time. Feeding the particulate biomass
into the
solubilization vessel 46 underneath the liquid level in the vessel is
preferably done by
using a plug feed screw, which compresses the particulate biomass in a short
path and
pushes it into the vessel where it is dissolved. This biomass feeding
arrangement can
also enhance safety by compressing air out of the biomass material, which
prevents
potential issues when the biomass input touches the hot organic liquid in the
vessel. This
biomass feeding arrangement also reduces or eliminates issues with fine
biomass dust
going into the overhead column, since the mixing action in the vessel enables
the
biomass to be quickly dissolved/dispersed into the hot oil and substantially
prevents
anything except water vapour and light hydrocarbon vapours to travel out of
the liquid
medium.
Thus, in some implementations, the biomass feeding system is configured and
operated
to receive an air-containing particular biomass material, and compress air out
of the
biomass material during feeding so that the compressed biomass fed into the
reactor is
depleted in air upon contact with the hot organic liquid. Preferably, the
biomass feeding
system is arranged to feed the preferably compressed biomass into the
solubilization
vessel 46 below the liquid level. Such feeding features are preferably enabled
by using a
feed screw, although other configurations and systems are also possible.
Referring to Figs 2 and 3, the hydrocarbon rich slurry 14 is transferred from
the
solubilization unit 12 to the depolymerization unit 16. This fluid transfer
can involve
certain challenges. For example, in a continuous system in which the transfer
line is in
fluid communication between the solubilization unit 12 and the
depolymerization unit 16,
there can be certain backflow and back-heating issues. In particular, the
hydrocarbon
rich slurry 14 from the solubilization unit 12 is thicker (higher viscosity)
and cooler
compared to the mixture in the depolymerization unit 16, which is operated at
higher
temperatures (e.g., about 260 C to about 300 C). The temperature difference
between
the two units 12, 16 can be, for example, between about 80 C to about 120 C,
which can
result in a notable viscosity difference. Under a gravity-based slurry
transfer mechanism,
backflow and/or back-heating can occur and can result in process upsets and
process
control difficulties. Thicker and cooler slurry from the solubilization unit
12 transfers into
the depolymerization unit 16 as long as the level differential favors the
solubilization unit
12, which presents process limitations. For instance, there could be backflow
of material
from the depolymerization unit 16 into the solubilization unit 12 as the
hotter and less
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viscous slurry can have a greater tendency of flowing back. Such backflow and
other
heat transfer mechanisms can slowly increase the temperature in the
solubilization unit
12. Even though biomass is fed to it at ambient temperatures, which cools the
medium in
the vessel 46, there is a risk that the comfortable or optimal process
temperature levels
in the solubilization unit 12 can be exceeded over time (e.g., exceeding
20000). In
addition, if the level differential between the two units 12, 16 is lost
(which can be
detected by the level measurement device 57), the gravity flow ceases and this
overall
operating method can be challenging to maintain. It can also be said that when
the
temperature differential between the two units 12, 16 is lost, reversible flow
would be
stopped.
In order to advantageously transfer slurry 14 from the solubilization unit 12
to the
depolymerization unit 16, various systems can be implemented. For example, a
slurry
transfer device 58 can be provided and operated to ensure downstream slurry
transport
such that backflow and back-heating issues are mitigated or eliminated. In one
implementation, the slurry transfer device 58 includes a pump that is
configured and
operated to displace the process mixture from the solubilization unit 12 to
the
depolymerization unit 16 by force. This enhances the stability of the system
from the
process conditions point of view.
Various different transfer system configurations incorporating piping, at
least one pump,
and other optional units, can be used. For example, referring to Fig 3, the
transfer
system between the solubilization unit 12 to the depolymerization unit 16 can
include an
upstream pipe section coupled to a pump which is coupled to a downstream pipe
section
that, in turn, is in fluid communication with an inlet of the depolymerization
unit 16.
Various different types of pumps can be used, e.g., rotary pump, Lobe pump, or
other
pumps particularly those suited for slurry transport.
Furthermore, referring to Fig 3, the transfer system between the
solubilization unit 12 to
the depolymerization unit 16 can include a control system 60 for controlling
the pump 58
in accordance with measured characteristics (e.g., temperature and/or
viscosity) of the
slurry 14 at one or more locations (e.g., upstream or downstream of the pump,
proximate
or remote from either unit 12, 16). The control system 60 can also be used to
control
valves 64 and other features of the process. For instance, a temperature probe
can be
deployed to measure the temperature of the slurry stream 14, and the pump 58
can be
CA 3010168 2018-07-03
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operated accordingly. In addition, there may be a bypass line 62 and valves 64
that can
be controlled so that the pump 58 is engaged when needed (e.g., when backflow
or
back-heating is detected or exceeds a threshold value). The control system 60
can also
be coupled to the solubilization unit 12 and/or the depolymerization unit 16
to control the
temperature conditions therein in response to characteristics of the slurry.
Referring to Fig 2, there can be multiple outlet slurry lines (which can be
seen as
characters 14 and 14', for example) from the solubilization unit 12. At least
one of the
slurry lines can be coupled to the slurry transfer device 58 (14 in Fig 2)
while the other
slurry line can be arranged for gravity-based transfer (14' in Fig 2). A
control unit can be
configured and used so that the slurry is transported via one or both of the
lines 14, 14'
depending on operating parameters.
Still referring to Fig 2, it is noted that the slurry 14 can be fed directly
from the
solubilization unit 12 to the depolymerization unit 16 (e.g., via the slurry
transport
device 58, see line 14 of Fig 2) or the slurry can be fed into the separator
22 and a slurry
recycle stream 66 can be withdrawn from the separator 22 and fed into the
depolymerization unit 16. It is also noted that both can be implemented
(simultaneously
or alternately), as illustrated in Fig 2, where the slurry recycle stream 66
is first combined
with the slurry stream 14 and then fed into the depolymerization unit 16.
It is also noted that other lines can be provided, such as a dump line 68 that
supplies the
slurry 14 into a storage tank 70, which may be done during process upset
conditions, off-
spec slurry conditions, emergency circumstances, and so on. A reintroduction
line 72
can be used to reintroduce fluids in the storage tank 70 back into the feed
sent to the
depolymerization unit 16 (as illustrated) or back into the solubilization unit
12 (not
illustrated here).
Turning to Fig 3, the solubilization vessel 46 can be equipped with a cooling
system 74
such as a jacket 76 coupled to cooling fluid 78 or other means for cooling and
facilitating
temperature control. The cooling fluid can flow through a heat exchanger 80.
In addition,
a temperature control system 82 can be provided to control the temperature in
the vessel
46. The temperature control system 82 can be coupled to one or more
temperature
sensors 84, and to process control points to regulate the feed of biomass,
recycled
organic liquid, outlet slurry, and cooling fluid. The cooling system 74 can be
part
CA 3010168 2019-11-21
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of an integrated heat exchange loop for controlling temperatures in various
units of the
overall process.
Depolymerization
Referring to Fig 2, the hydrocarbon rich slurry 14 is supplied into the
depolymerization
unit 16 to enable advancement of depolymerization reactions.
= The depolymerization unit 16 can have various designs and features. The
depolymerization unit 16 can be provided to perform what is generally known in
the
industry as "catalytic pressureless depolymerization" (CPD) although other
catalytic
depolymerization methods can also be used.
In some cases, the depolymerization unit 16 can include a friction turbine,
which can
provide the primary heat source for the depolymerization reactions. It is
nevertheless
noted that upstream heat exchangers and/or in situ heating with heating
devices can be
provided. In friction turbine cases, the rotation speed, controlled by a
frequency drive,
creates vacuum conditions where the depolymerization reactions are occurring.
In other
reactor designs, the temperature and pressure conditions can be provided by
other
means. The temperature of the rich hydrocarbon slurry 14 can be increased to
approximately 260-300 C by re-circulation through the friction turbine, at
which point the
long polymers of cellulose, hemicellulose and lignin, as the main constituents
of the
biomass, are broken down into alkanes, saturated and short-chain hydrocarbons.
The
exact mechanisms of depolymerization depend on the specific feedstock
composition
and process conditions, and can be determined by operating experience. In
terms of the
biomass constituents, hemicellulose is first converted into diesel range
alkanes, followed
by the conversion of cellulose and lignin. The residence time in the friction
turbine
reactor (e.g., 16 in Fig 2) can be between one to a few seconds. For other
reactor
designs, the residence time can be longer. The mixture of newly generated
diesel, in
gaseous form, along with carbon dioxide and other liquids leave the turbine 16
and enter
a top section of the phase separator 22. Driving oxygen out from the biomass
compounds during the molecular recombination in the process generates some
carbon
dioxide. By driving oxygen out via the carbon dioxide stream, the diesel range
compounds are left without oxygen (or highly depleted in oxygen), which
facilitates high
CA 3010168 2018-07-03
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product stability. It is again noted that various other reactor designs can be
used instead
of a friction turbine to effect depolymerization.
Referring still to Fig 2, in this optional process configuration, the feed to
the
depolymerization unit 16 includes the slurry 14 as well as a recycle stream 66
from the
slurry phase at the bottom of the separator 22. The output hydrocarbon stream
18 from
the depolymerization unit 16 is thus a complex mixture of hydrocarbons and
other
compounds that will be separated upon entry into the separator 22. The
separator 22 is
operated so that the desired hydrocarbon products (e.g., diesel) are gaseous
at the
process conditions of the separator 22, and are thus recuperated via the
overhead
system 86 as a raw hydrocarbon product stream 88. Meanwhile, the components of
the
output hydrocarbon stream 18 from the depolymerization unit 16 that are liquid
at the
process conditions of the separator 22 separate with the bottom fraction and
can be
recirculated back into the depolymerization unit 16 for further
depolymerization
reactions. It is noted that this depolymerization-separation dual unit
configuration with
recirculation of slurry from the separator is one preferred configuration, and
that various
other Process configurations can be used with or without recirculation
depending on the
conditions and the equipment that is used.
Regarding the depolymerization unit 16, while a friction turbine or vacuum
pump can be
optional equipment that can be used, various other CPD reactors or other types
of
depolymerization reactors can be used in the process. Preferably, the
depolymerization
unit 16 is configured to employ high-intensity conditions at relatively short
residence
times, and can be included in a loop with the phase separator 22, which will
be
described in further details below. The operating conditions in the
depolymerization unit
16 are preferably provided so that the output stream is a mixture of gas-phase
hydrocarbons, light liquid-phase hydrocarbons, heavy liquid-phase
hydrocarbons, small
amounts of water, and some particulate solids (organic and inorganic), so that
this
mixture can then be separated into gas and liquid/slurry phases in the
separator 22 and
the liquid/slurry phase can then be reintroduced into the depolymerization
unit 16. This
loop-type configuration is a preferred method of depolymerization and
separation of the
desired product components. However, it should be noted that, in some
implementations, other configurations can be used to produce desired
hydrocarbon
components.
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Phase separation
As mentioned above, the main output stream 18 produced by the depolymerization
unit
16 is a mixture of gases and light and heavy liquids. Preferably, the
depolymerization
unit 16 has a single output stream 18, although ills possible that the
depolymerization
unit could have multiple outlet. The hydrocarbon stream 18 is fed into the
phase
separator 22. The gaseous compounds (e.g., diesel and carbon dioxide) leave
the phase
separator 22 through a distillation column 90 mounted on top of the phase
separator
vessel 22, then immediately after being condensed and discharged out of the
process. In
particular, the gaseous overhead stream 88 is fed to a quencher 92, to produce
a
quenched stream 94 that is supplied to an oil-water separator 96. The water 98
is
separated, cooled in a water cooler 100, and then sent to a holding tank 102.
The liquid
hydrocarbon stream 104 is separated, fed through a hydrocarbon cooler 106 and
then
into a hydrocarbon holding tank 108, after which it is sent via a hydrocarbon
pump 110
to the purification unit 26.
In some implementations, the purification unit 26 includes a distillation
vessel that
produces at least a purified upper hydrocarbon fraction 112 and a bottom
fraction 114.
The distillation vessel can be operated in batch mode, such that a proportion
of
hydrocarbons are fed from the holding tank 108 .into the distillation vessel
which is then
operated until the top and bottom fractions are produced. In some
implementations, the
distillation vessel can produce two, three or more cuts and/or can be operated
in
continuous mode. As shown in Fig 2, the upper hydrocarbon fraction 112 can be
supplied to a product cooler 116 and then to a product tank 118, from which
the
hydrocarbon can be transported for final storage, pipelining, and the like, as
the final
diesel product 28. More regarding the purification unit 26 will be discussed
further below.
In terms of process operating conditions in the separator 22, the process
temperatures
in the phase separator can be approximately 280 C, and can be controlled by a
cooling
loop to maintain optimal diesel yield. Residence time in the phase separator
22 can be
set at between 30 and 60 minutes. It is noted in this regard that the
separator 22
operating conditions can be paired and coordinated with the desired phase
separation
(i.e., depending on the desired gaseous hydrocarbon components that are to be
removed) and with the operation of the depolymerization unit 16 when recycling
of the
liquid phase back to depolymerization is envisioned as part of the process. In
some
CA 3010168 2018-07-03
21
advantageous setups, there are no heat exchangers between the separator 22 and
the
depolymerization unit 16, and the units are operated at generally similar
temperatures.
Alternatively, in some cases, it may be desirable to have heat exchangers
(e.g., heater
and cooler) in between the two vessels, for example when higher temperatures
are
desirable for depolymerization and lower temperatures are desirable for the
target phase
separation, or vice versa.
In the phase separator 22, the heavier liquid fraction moves towards the
bottom of the
phase separator where it is redirected into the depolymerization unit 16 again
for more
diesel production until eventually a heavy residue mixed with ash and catalyst
settles to
the bottom of the separator 22. To avoid accumulation of heavy oil and
ash/catalyst
particulates, the separator residue 33 can be frequently discharged into the
residuals
treatment unit 30 (which can also be called an ash treatment unit) for
catalyst and oil
recovery, which will be discussed further below.
Referring to Fig 2, a separator underflow stream 120 can be withdrawn from the
bottom
of the separator 22 and can then be used in various ways. In some
implementations, as
illustrated, at least a portion of the separator underflow stream 120 can be
returned as a
recirculation stream 122 back into the vessel. Since the bottom fraction in
the separator
22 is a slurry that includes small particulate material of various
compositions suspended
in an organic phase, solids can tend to deposit on the inner wall surfaces of
the
separator 22. Such deposition can be exacerbated due to the relatively high
viscosity
and solids rich medium in the lower part of the separator 22, which can cause
stagnation
which can, in turn, promote deposition or agglomeration and, in some cases,
plugging of
lines. Thus, mixing in the bottom fraction of the separator 22 can keep the
particulate
solids in suspension, promote the solids flow with the organic phase back into
the
depolymerization unit 16 as the slurry recycle stream 66, and reduce
deposition and
plugging.
In some implementations, the recirculation stream 122 can be used to induce
mixing
sufficient to inhibit deposition and plugging. Thus, the solids rich slurry at
the bottom of
the separator 22 is withdrawn and recirculated back into the slurry phase in
the
separator 22. A recirculation pump 124 can be used to recirculate the slurry,
and there
may be one or multiple recirculation inlet lines 126a, 126b back into the
separator 22. In
addition, by withdrawing and recirculating the bottoms of the separator, the
heavier
CA 3010168 2018-07-03
22
organic compounds can also be reintroduced into the bulk of the bottom
fraction of the
separator, so that they can be recycled back into the depolymerization unit
16. Thus, the
recirculation enables mixing, inhibits deposition and pugging, and facilitates
further
processing of the heavy bottom components to depolymerize and extract
remaining oil.
Fig 2 also shows that the recirculation system can send back a recirculated
portion (e.g.
stream 122) of the separator underflow stream 120, while a remaining portion
can be
supplied to another unit, which may be downstream, such as the residue
treatment unit
30. It should be noted that various proportions of streams 122 and 33 can be
envisioned.
In addition, the recirculation can be done in various ways and can include one
or multiple
recirculation lines configured to return material back into the separator 22.
In Fig 2, two
recirculation inlet lines 126a, 126b are illustrated one above the other on
the same side
of the separator 22, although various other arrangements are possible. For
instance, two
recirculation inlet lines can be provided at different heights and/or at
different locations
around the separator 22. The recirculation inlet lines can be positioned and
operated so
that mixing occurs at desired locations of the bottom liquid fraction of the
separator 22.
For example, the recirculation inlet lines can be provided in sufficient
number and
orientation so that substantially all of the inner wall surfaces of the
separator 22 that are
susceptible to fouling can be proximate to agitated fluid. The recirculation
inlet lines can
also be in fixed positions or can be displaceable to provide variations in
terms of the
direction of the inlet flow. In addition, the recirculation inlet lines can be
controlled to
have the same or different flow rates entering the separator 22, as well as at
different
times. Valves and controls can be provided on the recirculation inlet lines to
vary the flow
rates, for example. The recirculation inlet lines (e.g., flow rate, direction,
etc.) can be
controlled actively in response to measured variables, or they can be run in a
relatively
constant manner (automatically or manually). It is also noted that the
recirculation inlet
lines can be operated to continuously supply material into the separator 22,
or
periodically supply such material (e.g., operated in on/off modes, where the
on-mode
can be a fixed or variable flow rate).
The recirculation system provided for the separator 22 facilitates preventing
fouling of
the vessel while allowing for both discharge of the heavy solids stream from
the bottom
of the separator and frequent transfer to the residue treatment unit 30.
CA 3010168 2018-07-03
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It is also noted that the pump 124 can be operated periodically so that when
not
operating the solids and heavy liquids drop down to the bottom of the
separator, and
when turned on the heavy solids rich bottom phase is evacuated from the
separator 22
and can be sent to the ash plant 30, the recirculation system, or a
combination thereof.
Purification
In some implementations, the purification unit 26 includes a distillation
vessel that
produces at least a purified upper hydrocarbon fraction 112 and a bottom
fraction 114.
The distillation vessel can be operated in batch mode, such that a proportion
of
hydrocarbons are fed from the holding tank 108 into the distillation vessel
which is then
operated until the top and bottom fractions are produced. In some
implementations, the
distillation vessel can produce multiple cuts and/or can be operated in
continuous mode.
Referring to Fig 2, the bottom fraction 114 can be fed to a tank, which can be
the same
storage tank 70 that is used periodically for holding slurry, as discussed
above. The tank
70 can have a discharge 71 from which undesirable material is drained, e.g.,
for
disposal, rather than being recycled back into the process. As illustrated,
various
bottom/underflow streams can be supplied to the storage tank 70, which can be
done
during upset conditions or at other times.
The upper hydrocarbon fraction 112 is supplied to a product cooler 116 and
then to a
product tank 118, from which the hydrocarbon can be transported for final
storage,
pipelining, and the like, as the final hydrocarbon (e.g., diesel) product 28.
In some
implementations, this hydrocarbon stream 28 is a final product, such as diesel
fuel, that
can be sold to market. However, it should also be noted that the hydrocarbon
stream
could be an intermediate that can be subjected to further upgrading,
separation,
conversion or reaction to produce other final products. Depending on the
purification unit
26 that is used, the resulting upper hydrocarbon fraction 112 or other
fractions (e.g., a
middle fraction) that may be withdrawn from the purification unit 26 may have
different
compositions and properties and may, in some cases, benefit from further
processing.
Nevertheless, it is preferable that the purification unit 26 consist of a
single separation
vessel, such as a distillation tower, that produces the upper hydrocarbon
fraction 112
that can simply be cooled and transported for final storage, pipelining or
sale as a
product.
CA 3010168 2018-07-03
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It is also noted that the overall purification stage can include not only
distillation but also
various polishing or filtering steps, for instance to ensure no fine char
particulates end up
in the product storage. Other purification and/or separation steps can be
implemented
prior to the distillation step. In addition, prior to distillation, there may
be a pre-heating
step (not illustrated) that can be implemented in various ways depending on
the setup
and operation of the distillation tower.
Thus, in some implementations, when raw diesel is made from the
depolymerization-
separation loop, its quality can be improved by secondary distillation 26. Raw
diesel
(e.g., stream 88) can have some traces of water and other impurities and
traditionally
benefits from thermal treatment to improve quality parameters. This
purification step can
be operated as independent from the rest of the process setup, functioning on
a batch
basis where a volume of raw diesel is transferred into the purification unit
26 and purified
by first taking out petroleum light ends (e.g., at around 175 C), then
distilling the
remaining volume (e.g., at around 300-320 C). The secondary distillation
output can be
referred to as finished diesel.
Residuals and ash processing
The residuals treatment unit 30 (which can also be referred to as an ash
plant) facilitates
recovery of heavier phase organics for supply back into the process, thereby
enhancing
overall recovery of hydrocarbons as valuable products and also reducing waste
generation. The ash plant can also facilitate recovery of catalyst for reuse
in the process.
The ash plant further enables drying of inorganic materials (e.g., ash from
wood) for
reuse or disposal in dry form.
The ash plant is, however, an optional unit in the overall process. For
example, in some
scenarios, the bottom fraction from the separator (e.g., stream 33) could be
sold as an
industrial fuel material in which case no ash plant would be used in the
overall process.
The phase separator can produce bottom residue that is a high energy value
stream,
similar to Bunker C, and as such can be utilized in boilers and furnaces/kilns
burning
heavy oils for heat.
Preferably, the process includes recovery of the organics in stream 33 by
putting them
back into the process for additional diesel production. The ash plant can be a
kiln-like
device that operates in a range of 400-450 C, where a heavy oil-containing
steam is
CA 3010168 2018-07-03
25
exposed to the high temperature, allowing organics to evaporate from the
ash/catalyst
mixture and solids to be dried before discharge and final disposal. Thus, at
least a
portion of the separator bottoms stream 33 is sent to the ash plant 30, which
generates a
gaseous hydrocarbon stream (which also can be called a recovered hydrocarbons
stream 34) and a solids enriched stream 128. The gaseous hydrocarbon stream 34
can
then be condensed in a condenser 130 to produce a recovered hydrocarbon liquid
132
which can be fed to a holding tank 134. The recovered hydrocarbon liquid 132
can then
be recycled back into the process.
In some implementations, the recovered hydrocarbon liquid 132 can be held in a
feed
tank 136 and fed back into the solubilization vessel 46. As noted above, the
recovered
hydrocarbon liquid 132 gradually takes the place of the organic carrier fluid
used at the
beginning of the process. The recovered hydrocarbon liquid 132 can be provided
for
dilution of the biomass and can be dosed based on one or more measured
variables in
the solubilization unit 12. For example, the torque of the mixer 47 can be
measured and
the amount of recovered hydrocarbon liquid 132 fed into the solubilization
vessel 46 can
be based on the torque, such that higher torque indicates too much biomass and
thus
more recovered hydrocarbon liquid 132 is supplied into the vessel 46. Various
valves
138 and a feed pump 140 can be provided to supply the recovered hydrocarbon
liquid
132 from the feed tank 136 into the solubilization vessel 46. The flow rate of
the
recovered hydrocarbon liquid 132 into the solubilization vessel 46 can also be
based on
other factors, such as the flow rate of the biomass feedstock, operation of
the feed screw
(e.g., rotation speed), temperature or viscosity measurements of the slurry in
the vessel
46, dissolution rate of the biomass, and so on. If the biomass dissolution
rate is lower
than desired, additional recovered hydrocarbon liquid can be added to dilute
the mixture
and thus promote solubilization. In some implementations, the recovered
hydrocarbon
liquid 132 is recycled for use as a top-up organic liquid in the
solubilization unit 12 in
combination with another organic liquid (e.g., carrier liquid).
It should be noted that the recovered hydrocarbon liquid 132 can be supplied
to other
units of the process as well, depending on the setup of the process. For
example, in
some implementations, a portion of the recovered hydrocarbon liquid 132 can be
supplied into the depolymerization unit 16, the phase separator 22, and/or the
feed lines
thereto.
CA 3010168 2018-07-03
26
Hydrocarbon products
In the preferred implementation, at least a diesel product is produced as the
final output
of the process. As explained above, depending on the operation of the various
units,
other hydrocarbon cuts, intermediates and/or products can be produced for
sale.
On the downstream side of the technology, production of the hydrocarbon
product (e.g.,
diesel) can help meet growing market demand for cellulosic feedstock based
sources of
renewable or clean fuels. Both legislation and evolving end-user sentiment
about climate
change and the environmental footprint of their activities are contributing to
this demand.
To date, many varying pathways have been developed or are being developed to
try to
address the same opportunity. However, challenges with economics and quality
have
led to limited success. Processes described herein facilitate distinct
advantages over
existing processes, such as lower capital cost, low supply chain cost and drop-
in or high-
blend wall product quality.
It should also be noted that by-products can also be produced by various units
in the
process, e.g., bottom streams that have high energy content and can be sold as
fuels or
intermediates for upgrading, various distillation cuts, and so on.
Further process implementations and features
Figs 1 and 2 illustrate one implementation of the process in which the
solubilization and
depolynnerization units are two separate vessels that are interconnected with
piping for
fluid transfer. However, as shown in Fig 4, the solubilization and
depolynnerization
operations can be conducted in a single stage within a reactor. In this case,
the reactor
can be integrated with upstream and downstream units and equipment as
described in
further detail below with reference to Fig 4, or could be integrated with
units in a similar
manner as illustrated in previous figures while adapting the piping and
operations for a
single stage configuration rather than a two stage configuration. In addition,
certain
features of the two example systems (with single stage and two stage) can be
combined
together for some implementations of the process.
Referring to Fig 4, the reactor is coupled to upstream biomass preparation and
downstream phase separation and residue treatment units. In the biomass
preparation
step, biomass or any carbonaceous feedstock can be ground to a particle size
of 3 mm
CA 3010168 2018-07-03
27
or less and dried to a maximum moisture content of 15 wt%., for example. The
ground
dried biomass can be premixed or otherwise combined with lime and catalyst.
Other
features of biomass preparation as described further above can also be applied
here.
The ground dried biomass is then fed, together with lime and catalyst,
directly into the
reactor (which can be referred to herein as a single stage reactor or a
depolymerization
reactor, for example) that is initially charged with a thermal carrier oil,
thereby creating a
hydrocarbon-rich slurry. The reactor is coupled to the feeder, which can be
the screw
feeder as described herein, to receive the biomass and other compounds. The
feed is
introduced below the liquid level in the reactor and the feeding can have one
or more
features as described above for the example with a standalone solubilization
unit.
Referring to Fig 4, the reactor is connected to at least one friction turbine,
preferably
multiple friction turbines that are operated in parallel as shown
schematically in Fig 4.
Depending on the sizing of the turbines and other operating parameters, the
number,
location and configuration of the turbines can be determined. In Fig 4, there
are four
friction turbines coupled to the lower section of the reactor. When multiple
friction
turbines are used, they can be located and arranged in different ways about
the reactor,
for example with turbines arranged at different heights and/or at different
locations
around the perimeter of the reactor. The withdrawn lines and return lines for
the
respective friction turbines can also be located at different heights and/or
locations about
the perimeter to provide desired fluid flow characteristics within the reactor
and to
process the material effectively.
Still referring to Fig 4, the hydrocarbon-rich slurry is continuously fed from
the reactor
into the turbines. Preferably, the friction turbines are the primary source of
heat and
mechanical energy (shear) inputs for the depolymerization reactions. The
turbines'
rotation speed, which can be controlled by a frequency drive, creates slight
vacuum
conditions (e.g., about 0.5 bar) where depolymerization reactions are
occurring. The
temperature of the hydrocarbon-rich slurry is increased to approximately 320 C
by re-
circulation through the reactor via the friction turbines. At this point, the
long polymers of
cellulose, hemicellulose and lignin present in biomass are broken down into
alkanes,
saturated and short-chain hydrocarbons. The residence time in the reactor can
be
between about 30 seconds and about 2 minutes, for example. Oxygen is removed
from
the biomass components during molecular recombination following
depolymerization
and carbon dioxide and water vapour are created.
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Still referring to Fig 4, the mixture of newly created diesel in gaseous form
along with
carbon dioxide and water vapor leaves the reactor and moves to a phase
separation
step. The diesel and other hydrocarbons are separated from water and carbon
dioxide
by condensation in a cooler (e.g., spray cooler).
Referring to Fig 4, diesel and other hydrocarbons exiting the cooler are then
separated
by distillation (e.g. fractional distillation) while the residual hydrocarbon
bottom fraction
can be sent back to the reactor for further processing. Water is then removed
from
carbon dioxide by additional condensation. The fractional distillation can
also be
integrated with other units as shown in Fig 2, for alternative implementations
of the
process.
Referring to Fig 4, the raw diesel exiting the fractional distillation unit
can then be
supplied to a purifier, which can include polishing and/or filtration, to
improve its color
and odor and to ensure that the properties of the final synthetic diesel
product fulfill the
standing quality specification. The purifier thus produces a synthetic diesel
stream that
can be pumped for storage.
Referring still to Fig 4, in the reactor, recycling of the bottom fraction
from the phase
separation step (e.g., distillation) and continuous feeding of biomass lead to
the
accumulation of a viscous sludge with high solid content in the bottom of the
reactor.
This sludge can be continuously removed and transferred to a residue treatment
unit via
a lobe pump for example. The residue separation unit (also referred to as a
solid
separation unit) can rely on a thermal or pressure-based process. If thermal
operation is
used, then the separation unit can be operating at around 450-500 C at which
organics
present in the sludge are vaporized and separated from the inorganics (ashes).
The
recovered organic vapours can be further condensed to give an oil stream,
which can be
sent back to the reactor and used to replace part of the required carrier oil,
as shown in
Fig 4. The thermal process can be supported by solvent extraction, in cases
where it is
justified, for better efficiency and/or avoidance of hydrocarbon phase
transformation.
Inorganics are left to dry and sent for final disposal. If a pressure-based
process is used,
it can operate at 100-150 psi, for example, where the hot sludge stream would
be
processed without going through a phase change. Filtration can separate most
of the oil,
which is sent back to the reactor as needed for carrier oil makeup, while
residual
separated solids are sent to final disposal.
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Furthermore, various piping and vessels can also be provided for start-up
purposes,
whereas once the process has been ramped up the process can be operated as
generally shown in Fig 4, where the process includes five main steps: biomass
preparation, depolymerization, phase separation, purification and residue
treatment. In
addition, various sampling locations can be provided and are beneficial to
allow for
sample taking from which properties of fluids and materials can be tested. It
should be
noted that process control can be implemented based on properties measured at
such
sample locations.
Additional comments on technology implementations
The conversion of biomass to liquid fuels can be achieved via many pathways.
Pyrolysis,
gasification, catalytic conversion and fermentation are some leading pathway
platforms
that are being developed today. It is challenging to compare the
competitiveness of
technology platforms in and of themselves, as the overall economic viability
is also a
function of many other business dynamics. As an example, pyrolysis or fast
pyrolysis
has proven a viable technical platform for the conversion of biomass to a
liquid fuel. Its
performance has a comparable yield, capital cost footprint and conversion cost
per unit
to the preferred catalytic depolymerization techniques described herein. A
disadvantage
of the pyrolysis methods is their lower product quality. Pyrolysis products,
often referred
to as bio-crude, require further upgrading to be integrated into end-use
applications. This
is disadvantageous because large-scale refining platforms may not wish to
integrate
small volumes of bio-crude with differing properties to their crude sources.
Gasification
followed by a Fischer-Tropsch (or similar proprietary) back-end has also been
demonstrated to convert biomass to liquid fuels. In this case the yield and
product quality
are comparable to the preferred catalytic depolymerization techniques
described herein;
however, they have higher cost per unit of output. As a result, these projects
pursue
large scales to improve this dynamic, which has resulted in challenges to run
scaled-up
gasification equipment consistently with a variable feedstock, such as
biomass. The
preferred catalytic depolymerization techniques described herein, which
include a
solubilization step followed by depolymerization below pyrolysis conditions
and then
phase separation and purification steps, facilitates superior product quality,
economic
feasibility on a distributed production footprint and access to sustainably
priced biomass.
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Thus, in some preferred implementations, the various innovative aspects
described
herein can be used with a catalytic depolymerization technology platform,
where the
biomass is solubilized and then subjected to catalytic depolymerization below
pyrolysis
conditions, followed by phase separation and then purification of the
separated diesel-
range hydrocarbon stream. Nevertheless, various innovative aspects described
herein
can also be used in connection with other technology platforms that include
unit
operations such as biomass solubilization, organic slurry transport between a
lower
temperature unit and a higher temperature unit, separation vessels or reactors
in which
the bottom fraction includes solid and heavy liquid components that may tend
to deposit
and plug equipment if not kept in suspension or agitated, and so on. In
addition, while
preferred implementations have been described in detail herein with respect to
producing a diesel product, various innovative aspects can also be used in
connection
with processes for producing other hydrocarbon products from biomass.
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