U.S. patent application number 14/021540 was filed with the patent office on 2014-03-13 for generating deoxygenated pyrolysis vapors.
This patent application is currently assigned to Phillips 66 Company. The applicant listed for this patent is Phillips 66 Company. Invention is credited to Johnathan T. Gorke, Mark A. Hughes, Samuel T. Jones, Martin L. Perkins, Natalie A. Rebacz, Richard D. Sadok, Tie-Pan Shi, Liang Zhang.
Application Number | 20140069010 14/021540 |
Document ID | / |
Family ID | 50231774 |
Filed Date | 2014-03-13 |
United States Patent
Application |
20140069010 |
Kind Code |
A1 |
Hughes; Mark A. ; et
al. |
March 13, 2014 |
GENERATING DEOXYGENATED PYROLYSIS VAPORS
Abstract
The present disclosure relates generally to novel biomass
pyrolysis processes and systems that decrease entrainment of char
and other contaminants with the pyrolysis vapors. In certain
embodiments, the present disclosure provides methods and systems to
prevent entrainment of particles of char and heat carrier with
pyrolysis vapors leaving a reactor, while allowing rapid upgrading
of the vapors by catalyst(s) that are held in a an upgrading
reactor and protected from contact with the char.
Inventors: |
Hughes; Mark A.; (Owasso,
OK) ; Shi; Tie-Pan; (Bartlesville, OK) ;
Sadok; Richard D.; (Bartlesville, OK) ; Jones; Samuel
T.; (Dewey, OK) ; Gorke; Johnathan T.;
(Owasso, OK) ; Rebacz; Natalie A.; (Bartlesville,
OK) ; Zhang; Liang; (Owasso, OK) ; Perkins;
Martin L.; (Dewey, OK) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Phillips 66 Company |
Houston |
TX |
US |
|
|
Assignee: |
Phillips 66 Company
Houston
TX
|
Family ID: |
50231774 |
Appl. No.: |
14/021540 |
Filed: |
September 9, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61699098 |
Sep 10, 2012 |
|
|
|
Current U.S.
Class: |
48/111 ;
48/209 |
Current CPC
Class: |
Y02E 50/10 20130101;
C10K 3/02 20130101; C10G 2300/1011 20130101; C10B 7/10 20130101;
Y02E 50/30 20130101; Y02E 50/32 20130101; Y02P 20/145 20151101;
C10B 53/02 20130101; C10G 3/42 20130101; Y02E 50/14 20130101; C10B
49/16 20130101; Y02P 30/20 20151101; C10G 2/32 20130101 |
Class at
Publication: |
48/111 ;
48/209 |
International
Class: |
C10K 3/02 20060101
C10K003/02 |
Claims
1. A process for the production and upgrading of a pyrolysis
product, comprising the steps of: (a) pyrolyzing a biomass
feedstock in a first reactor comprising at least one auger that
conveys the feedstock through the reactor from a first end towards
a second end, wherein said pyrolyzing forms primary pyrolysis
products comprising a primary gaseous product and char; (b) passing
the primary gaseous product through a first outlet at or near the
top of the first reactor and to a second reactor, wherein the
primary gaseous product passing through the first outlet entrains
less than 0.5 wt. % of the char produced by the pyrolyzing of step
(a); (c) contacting the primary gaseous product with an upgrading
catalyst; (d) removing the char from the first reactor via a second
outlet located at or near the bottom of the first reactor.
2. The process of claim 1, wherein the primary gaseous product
passes upward through a disengagement zone prior to leaving the
first reactor via the first outlet, wherein the terminal falling
velocity of entrained char and heat carrier particles becomes
greater than the upward local velocity of the primary gaseous
product in the disengagement zone, thereby causing at least 99.5
wt. % of the char and heat carrier particles to be retained in the
first reactor.
3. The process of claim 1, wherein the first outlet is located
closer to the second end of the first reactor relative to the
second outlet, thereby decreasing entrainment of char in the
primary gaseous product.
4. The process of claim 1, wherein the first outlet is located
closer to the first end of the first reactor relative to the second
outlet, thereby decreasing entrainment of char in the primary
gaseous product.
5. A system for the production and upgrading of a pyrolysis
product, comprising a pyrolysis reactor adapted for pyrolyzing a
biomass feedstock to produce a primary gaseous product, wherein the
pyrolysis reactor comprises at least one auger, an inlet for a
biomass feedstock and an outlet, wherein the pyrolysis reactor
contains a solid particulate heat carrier and char, wherein the
reactor is adapted to provide a disengagement zone that is, in
turn, adapted to allow the terminal falling velocity of entrained
char and heat carrier particles to become greater than the upward
local velocity of the primary gaseous product in the disengagement
zone prior to leaving the first reactor via the outlet such that
the reactor retains at least 99.5 wt. % of the solid particulate
heat carrier and char in the pyrolysis reactor.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a non-provisional application which
claims benefit under 35 USC .sctn.119(e) and priority to U.S.
Provisional Application Ser. No. 61/699,098 filed Sep. 10, 2012,
entitled "Generating Deoxygenated Pyrolysis Vapors", which is
hereby incorporated by reference herein.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] None.
FIELD OF THE INVENTION
[0003] This invention relates to pyrolysis of organic matter into
useful chemical or fuel products.
BACKGROUND
[0004] The U.S. Renewable Fuel Standards (RFS) mandate will require
higher volumes of advanced biofuels to be produced in the near
future. One method being developed to meet this mandate is the fast
pyrolysis of biomass. Conventional biomass fast pyrolysis requires
rapid heating of biomass in the absence of oxygen. Products include
a solid carbonaceous char that contains the vast quantities of
metals (e.g. Na, K, and Mg) present in the biomass feedstock. The
products also include a highly oxygenated pyrolysis oil (or pyoil)
that is not practical for upgrading to a transportation fuel
because of thermal stability issues associated with highly reactive
oxygenated components. The remainder of the pyrolysis product is
classified as non-condensable gas. To generate a viable
transportation fuel, catalysts may be employed during the pyrolysis
process. Catalysts such as zeolites can deoxygenate the primary
products from pyrolysis to create an intermediate liquid that can
be upgraded to a fuel using conventional refining methodology.
Hydrogen may also be added to perform hydro-catalytic pyrolysis,
which improves the quality of the product by significantly lowering
the oxygen content, the acid content, etc. The use of hydrogen
increases the yield of pyrolysis oil by hydrogenating the primary
pyrolysis products, which removes oxygen as water instead of carbon
oxides. The relatively low oxygen content intermediate produced is
easily upgradable to bio-derived fuels.
[0005] Unfortunately, when employing this process, the catalysts
tend to rapidly deactivate when contacted by char fines composed of
carbon and metals. Additionally, the char fines are often carried
out of the pyrolyzer by entrainment with the pyrolysis vapor,
resulting in a liquid product containing solids and metals that can
negatively impact downstream processes.
[0006] There is a need to improve fast pyrolysis technology to
allow for rapid catalytic upgrading of primary pyrolysis products
into products that are fungible with current petroleum-derived
liquid hydrocarbon fuels, while preventing char and associated
catalyst poisons from contacting upgrading catalysts that convert
these primary products.
BRIEF SUMMARY OF THE DISCLOSURE
[0007] In certain embodiments of the present disclosure, there is
provided a process for the production and upgrading of a pyrolysis
product, comprising the steps of: (a) pyrolyzing a biomass
feedstock in a first reactor comprising at least one auger that
conveys the feedstock through the reactor from a first end towards
a second end, wherein the pyrolyzing forms primary pyrolysis
products comprising a primary gaseous product and char; (b) passing
the primary gaseous product through a first outlet at or near the
top of the first reactor and to a second reactor, where the upward
local velocity of the primary gaseous product prior to passing
through the first outlet is sufficient to entrain less than 0.5 wt.
% of the char produced by the pyrolyzing of step (a); (c)
contacting the primary gaseous product with an upgrading catalyst;
(d) removing the char from the first reactor via a second outlet
located at or near the bottom of the first reactor.
[0008] In certain embodiments of the present disclosure, the
primary gaseous product passes upward through a disengagement zone
prior to leaving the first reactor via the first outlet, where the
terminal falling velocity of entrained char and heat carrier
particles becomes greater than the upward local velocity of the
primary gaseous product in the disengagement zone, thereby causing
at least 99.5 wt. % of the char and heat carrier solid particles
produced by the process to be retained in the first reactor.
[0009] In certain embodiments, the first outlet is located closer
to the second end of the first reactor relative to the second
outlet, thereby decreasing entrainment of char in the primary
gaseous product. 4. In certain alternative embodiments, the first
outlet is located closer to the first end of the first reactor
relative to the second outlet, thereby decreasing entrainment of
char in the primary gaseous product.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] A more complete understanding of the present invention and
benefits thereof may be acquired by referring to the follow
description taken in conjunction with the accompanying drawings in
which:
[0011] FIG. 1 is a simplified diagram of the inventive process
depicting a pyrolysis reactor with a catalyst vessel to receive and
upgrade the vapors from the pyrolysis reactor.
[0012] FIG. 2 is a simplified diagram of the inventive process
depicting a pyrolysis reactor with a catalyst vessel to receive and
upgrade the vapors from the pyrolysis reactor.
[0013] FIG. 3 is a simplified diagram of the inventive process
depicting a pyrolysis reactor with a catalyst vessel to receive and
upgrade the vapors from the pyrolysis reactor.
[0014] FIG. 4 is a graph depicting total ion count normalized to
gas flow rate versus residence time in a micropyrolyzer. Shorter
residence times give higher ion counts, which are only generated
from low molecular weight species (.about.200-300 molecular weight)
resulting from primary pyrolysis, and not from secondary pyrolysis
products.
[0015] FIG. 5 is a graph illustrating the relationship between
residence time and the pyrolysis products formed.
[0016] The invention is susceptible to various modifications and
alternative forms, specific embodiments thereof are shown by way of
example in the drawings. The drawings may not be to scale. It
should be understood that the drawings and their accompanying
detailed descriptions are not intended to limit the scope of the
invention to the particular form disclosed, but rather, the
intention is to cover all modifications, equivalents and
alternatives falling within the spirit and scope of the present
invention as defined by the appended claims.
DETAILED DESCRIPTION
[0017] In the processes and systems of the current invention, a
biomass feedstock is fed to a pyrolysis reactor for conversion into
a mixture comprising hydrocarbons that are fungible with
petroleum-derived fuels that may include, but are not limited to,
gasoline, jet-fuel, diesel and gasoil. The methods and systems
described herein protect and extend the lifespan of the downstream
upgrading catalyst(s) by preventing contact between the catalyst(s)
and the char generated during pyrolysis of the biomass feedstock,
while simultaneously minimizing the time between production of the
pyrolysis vapors and subsequent upgrading, thereby maximizing
upgradability of the vapors to a product that is fungible with
petroleum-derived transportation fuels, fuel component or mixtures
thereof.
[0018] The pyrolysis reactor preferably comprises at least one
auger that assists in rapidly and evenly distributing heat to the
feedstock, as well as helping to convey the feedstock through the
pyrolysis reactor. Oxygenated hydrocarbon vapors are produced in
the pyrolysis reactor, and these vapors are gravitationally
separated from char, heat carrier, and metals in a disengagement
zone while avoiding vapor condensation. The vapors are then rapidly
contacted with an upgrading catalyst in at least one upgrading
reactor comprising at least one upgrading catalyst for conversion
of the vapors into a hydrocarbon mixture fungible with current
petroleum-derived fuels. Residence time between production of
pyrolysis vapors (i.e., the primary gaseous product) and contact
with the one or more upgrading catalysts is minimized to prevent
secondary pyrolysis reactions that decrease upgradability of the
compounds that comprise the primary gaseous product.
[0019] The char created by the process described herein is conveyed
through the reactor along with heat carrier by the at least one
auger, then falls by force of gravity into a sealed char catch and
is eliminated from the reactor. The pyrolysis vapors are swept
through the pyrolysis reactor, out an outlet near the top of the
reactor and immediately into an upgrading vessel containing at
least one upgrading catalyst, which may hydrogenate and deoxygenate
the pyrolysis products. The vessel may be operated as a fixed bed,
fluid bed, or moving bed. Removing the char prior to contacting
pyrolysis products with catalyst prevents catalyst
fouling/poisoning. The products from the upgrading vessel are
condensed or further upgraded, thereby generating a viable
transportation fuel or refinable intermediate.
[0020] Examples of biomass feedstock used in the present invention
include, but are not limited to, oil-containing biomass, such as
jatropha plant, macroalgae or microalgae. Carbohydrate-based
biomass may also be used as feedstock, where carbohydrate-based
refers to biomass where at least a fraction of its composition is
made of carbohydrates. Carbohydrate-based biomasses are available
from a variety of sources including cellulosic biomass and algal
biomass. Specific examples of feedstock useful in the current
invention include, but are not limited to: sugars, carbohydrates,
fatty acids, proteins, oils, eucalyptus oil, forest residues, dead
trees, branches, leaves, tree stumps, yard clippings, wood chips,
wood fiber, sugar beets, miscanthus, switchgrass, hemp, corn, corn
fiber, poplar, willow, sorghum, sugarcane, palm oil, corn syrup,
algal cultures, bacterial cultures, fermentation cultures, paper
manufacturing waste, agricultural residues (e.g., corn stover,
wheat straw and sugarcane bagasse), dedicated energy crops (e.g.,
poplar trees, switchgrass, and miscanthus giganteus sugarcane)
sawmill and paper mill discards, food manufacturing waste, meat
processing waste, animal waste, biological waste and/or municipal
sewage.
[0021] FIG. 1 depicts an exemplary embodiment for a system for
conducting pyrolysis of organic material or biomass to useful
chemical products or fuel products. A pyrolysis reactor 20
comprises an external housing 21, a heat carrier inlet 17 for a
heat carrier 15, an feedstock inlet 10 for a biomass feedstock 12
and one or more helical augers 22 that when driven by a motor 25 to
rotate about a longitudinal axis convey the biomass feedstock 12
along the length of the housing 21 from an inlet end 18 towards an
outlet end 28. Near the outlet end 28, the char falls into a char
catch 31 by gravitational force. The biomass feedstock 12 is heated
in the pyrolysis reactor 20 by at least one heating method that may
include a heating jacket 21, a heated auger 22, or via introduction
of a heat carrier 15 via a heat carrier inlet 17 proximal the inlet
end 18 of the auger reactor 20. The pyrolysis reactor 20 is
operated to exclude most oxygen or air by the introduction of a
sweep gas. In the embodiment shown in FIG. 1, the sweep gas 19
enters through sweep gas inlet 16, although the sweep gas may
alternatively enter the system via other points of entry, such as
the biomass feedstock inlet 10 or heat carrier inlet 17. As the
biomass feedstock 12 is rapidly heated, primary gaseous product 37
rise to the upper portion of the pyrolysis reactor 20 and are swept
toward the second reactor end 28, exiting through a first outlet
32.
[0022] Arranged within close proximity of the pyrolysis reactor
first outlet 28 is an upgrading reactor 40 containing at least one
bed of an active upgrading catalyst 42. In certain embodiments, the
pyrolysis reactor 20 is in direct contact with the upgrading
reactor 40 with minimal distance between the pyrolysis reactor 20
and the upgrading catalyst 42. In the embodiment depicted in FIG.
1, a distributor plate 52 is placed above the outlet 32 to assist
in retaining within the reactor 20 any residual particulates that
may be entrained in the primary gaseous product (pyrolysis vapors)
37 leaving the reactor 20 through outlet 32. Distributor plate 52
may also serve to evenly distribute gases within the upgrading
reactor 40, such as when the upgrading catalyst 42 contained within
comprises, for example, a fluidized bed (not depicted).
[0023] When the pyrolysis reactor described herein comprises an
auger, the reactor is more efficient in char removal than a
conventional fluidized bed reactor, which produces char fines by
attrition that elutriate into the vapor product stream. The
majority of char formed during pyrolysis is conveyed by the auger
22 along with heat carrier 15 towards the outlet end 28 of the
pyrolysis reactor 20. The majority of char and/or ash produced
during pyrolysis of the feedstock exits the pyrolysis reactor 20 by
force of gravity into char catch 31. Thus, the char is diverted
from entering the upgrading reactor 40 and coming in contact with
the upgrading catalyst bed 42, which dramatically enhances the
longevity of the upgrading catalyst(s) 42. As noted above, it is
common for the biomass feedstock 12 to include measurable amounts
of metals that act as poisons to desirable upgrading catalysts, and
we have found that this metal content becomes concentrated in the
char produced during pyrolysis. With the physical arrangement
described herein, catalyst that are more susceptible to poisoning
by metals may be used to upgrade the pyrolysis vapors, since the
impact of metal poisoning and coke formation is dramatically
reduced. In addition, the product leaving the upgrading bed is free
of solids and metals, thereby removing the need for subsequent
particle removal
[0024] The pyrolysis reactor preferably comprises at least one
auger and may take many forms. In one embodiment, a single rotating
auger transports sand, biomass and solid pyrolysis products through
an elongated, cylindrical reactor. In the embodiment depicted in
FIG. 1, two rotating augers 22 operate in parallel. The first
pyrolysis product exits through a first outlet 32 located on the
upper side of the auger pyrolyzer 20, preferably near the top of
the reactor to prevent solids from leaving the reactor via this
outlet. The outlet 32 conveys the primary gaseous product 37
immediately to contact an upgrading catalyst 42, which is
optionally contained within an upgrading reactor 40.
[0025] The temperature within the pyrolysis reactor may be
maintained via one or more of several mechanisms, such as heating
of the reactor walls, heating of the at least one auger, microwave
or inductive heating, addition of a heated sweep gas, and addition
a of a solid particulate that has been pre-heated to a temperature
of at least 900.degree. F. (482.degree. C.). Regardless of the
heating mechanism utilized, preferably the pyrolysis reactor is
maintained at a temperature of at least 600.degree. F. (315.degree.
C.).
[0026] To reduce particle entrainment leading to heat carrier
exiting the reactor via outlet 32, the median heat carrier particle
size is greater than about 100 microns, and preferably greater than
about 250 microns. For similar reasons, the bulk density of the
heat carrier particles is at least 500 kg/m.sup.3, and preferably
greater than about 1,000 kg/m.sup.3.
[0027] Conventional pyrolysis methods and systems have suffered
from either 1) char carry over in the pyrolysis vapors, which leads
to upgrading catalyst deactivation, or 2) use of mechanical
separation devices to remove char from pyrolysis vapors, which
results in an undesirable delay prior to catalytic upgrading. This
delay can allow secondary pyrolysis reactions to occur that produce
products comprising 16 or more carbons that are difficult to
upgrade into a bio-derived fuel. Again referring to the embodiment
depicted in FIG. 1, a "disengagement zone" 45 is located proximal
to the outlet end 28 of the pyrolysis reactor, and near the first
outlet 32. This zone is designed to provide a space where the
upward local velocity of the primary gaseous product 37 prior to
passing through the first outlet 32 is sufficient to entrain less
than 0.5% (by wt.) of the char produced by the pyrolysis of the
biomass feedstock. In certain embodiments, the upward local
velocity of the primary gaseous product 37 prior to passing through
the first outlet 32 is sufficient to entrain less than 0.1% (by
wt.) of the char produced by the pyrolysis of the biomass
feedstock. Achieving this low percentage of char carryover requires
designing the height and diameter of the disengagement zone 45 to
allow the terminal falling velocity of the char and heat carrier
particles to exceed the upward local velocity of the primary
gaseous product 37 exiting the first outlet 32. This results in
nearly all char particles being retained in the pyrolysis reactor,
thereby preventing these particles from contacting the upgrading
catalyst.
[0028] FIG. 2 depicts an alternative embodiment, wherein the
disengagement zone 45 may be smaller (or not present) and residual
char particles may be instead be removed by passing the primary
gaseous product 37 through an upgrading reactor 40 comprising a
fluidized bed. In yet another embodiment depicted in FIG. 3, the
primary gaseous product 37 may raise through a reactor 55
comprising a moving bed granular filter that additionally comprises
an initial upgrading catalyst 60. Optionally, the catalyst may
migrate downward in counter-current flow against the rising gases,
and char 31 and spent catalyst 62 would leave out the bottom of the
reactor 20.
[0029] In certain embodiments, a sweep gas is employed that may
comprise one or more of many gases that are either inert or
reactive. For example, the sweep gas may comprise gases such as
nitrogen, helium, argon, hydrogen, methane and mixtures thereof. If
the sweep gas comprises a reactive gas, the reactive gas may
optionally react with the biomass during pyrolysis, may serve as a
reactant when the pyrolysis products are upgraded by contacting the
upgrading catalyst(s), or both. The sweep gas may be injected into
the system at more than one point, or injected simultaneously at
multiple points. One point may comprise combining the sweep gas
with the feedstock prior to entering the pyrolysis reactor, while
another may comprise injecting sweep gas directly into the
pyrolysis reactor proximal to the biomass feedstock inlet. A third
point may comprise injecting the sweep gas proximal to the first
outlet of the pyrolysis reactor. This may be preferable if the
sweep gas is to be used as a reactant during upgrading of the
primary gaseous product.
[0030] In certain embodiments, a gas may be injected just upstream
of the pyrolysis reactor first outlet in order to 1) assist in
preventing entrained char and heat carrier particles from leaving
the pyrolysis reactor, 2) quench the primary gaseous product to a
lower temperature, 3) heat the primary gaseous product to a higher
temperature, or combinations thereof. In embodiments where the
sweep gas serves to quench the primary gaseous product, such
quenching may prevent coking. Embodiments where the sweep gas
serves to heat the primary gaseous product may prevent formation of
char and secondary pyrolysis reactions that may reduce the
subsequent upgradability of the primary gaseous product to a
bio-derived fuel. However, quenching is limited such that the
quenched primary gaseous product does not condense prior to
contacting the upgrading catalyst(s). Typically, this requires that
the quenched primary gaseous product still maintains a temperature
of at least 250.degree. C. to prevent condensation.
[0031] The volumetric flow rate, or "standard gas hourly space
velocity" (SGHSV) of the sweep gas is adjusted to minimize the time
between pyrolysis and catalytic upgrading, such that the upgrading
catalyst (or optionally, catalysts) contacts primary products of
pyrolysis and not secondary pyrolysis products that comprise 16 or
more carbons and are more difficult to upgrade to a bio-derived
fuel. Volumetric flow rate for a given embodiment depends upon
factors including, but not limited to, the volume of the pyrolysis
reactor, the temperature and pressure at which the pyrolysis
reactor is maintained, the feed rate of the biomass feedstock to
the pyrolysis reactor, and the type of feedstock utilized. A paper
by J. N. Brown, et al. provides one example of how these variables
can be adjusted to determine an optimal volumetric flow rate for a
desired pyrolysis outcome, including, for example, the pyrolysis
liquid to pygas ratio, and the relative percentage of the feedstock
converted to char.
[0032] The pressure maintained within the pyrolysis reactor is
generally within a range of about 0 psig to 3000 psig. Preferably,
the pyrolysis reactor is maintained at a pressure in the range of
100 psig to 500 psig to increase throughput of biomass feedstock,
and in certain embodiments, facilitate catalytic upgrading of the
primary gaseous product.
[0033] The primary gaseous product is driven by the sweep gas (or
optionally, a pressure differential) from the pyrolysis reactor via
the first outlet and enters an upgrading reactor and contacts an
upgrading catalyst. Minimizing residence time of the primary
gaseous product in the pyrolysis reactor is important for
maximizing the percentage of primary gaseous product that is
successfully upgraded to a bio-derived fuel. Conditions of
temperature and pressure, as well as reactor dimensions are chosen
to assure a residence time of the primary gaseous product in the
pyrolysis reactor that is less than 5 seconds, preferably less than
3 seconds, more preferably less than 1 second, even more preferably
less than 0.3 second and most preferably less than 0.1 second.
[0034] Minimizing residence time of the primary gaseous product in
the pyrolysis reactor prevents the occurrence of secondary
pyrolysis reactions that form larger oxygenated species comprising
16 or more carbon atoms. These larger oxygenated species are likely
to form coke, which is extremely detrimental to the process by
fouling process equipment and heat carrier. Additionally, diversion
of the primary gaseous product into secondary pyrolysis reactions
decreases the conversion efficiency of the feedstock into smaller
species that are more easily upgraded into a bio-derived fuel.
[0035] The physical distance between the pyrolyzer and the
upgrading catalyst(s) contained within the upgrading reactor may
vary, but is preferably minimized, taking into consideration the
space velocity of the primary gaseous product (optionally in a
mixture with a sweep gas) out of the pyrolysis reactor. Minimizing
this distance assists in decreasing the time between production of
the primary gaseous product and subsequent contacting with one or
more upgrading catalyst(s). Through optimizing the variables of
distance and space velocity, the current invention assures that the
upgrading catalyst sees primary products from pyrolysis and not
secondary products created by reactions occurring after pyrolysis.
Generally, the distance between the pyrolyzer and the upgrading
catalyst(s) is less than 4 ft. More preferably, this distance is
less than 1 ft., and most preferably, less than 6 inches.
[0036] Referring to FIG. 4, we have found that reducing the total
distance primary pyrolysis vapor must travel results in a decreased
vapor residence time. Decreased residence time decreases the amount
of time available for secondary pyrolysis reactions to occur. These
reactions result in higher molecular weight species that can be
difficult to upgrade. FIG. 4 illustrates the importance of
minimizing residence time based on experiments in a micropyrolyzer.
In those experiments, the sweep gas flow rate was adjusted to
affect the overall gas residence time. Pyrolysis vapors
(475.degree. C., 1.5 mg red oak) and sweep gas (He) were sent from
the pyrolyzer into a 4-mm I.D..times.8 mm inlet liner, after which
they entered a capillary column and were quenched with cold
nitrogen to prevent further reaction. The total ion count was
measured and normalized to the mass of sample and gas flow rate to
eliminate the effect of sample dilution on the ion count.
[0037] Decreasing residence time is generally performed by
increasing the sweep gas flow. However, increasing this flow can
introduce significant particle entrainment that can be detrimental
to pyrolysis vapor upgrading An example of this entrainment is
shown in Table I, which shows the metal content of collected
pyrolysis oil, and thus pyrolysis vapors, increases with increasing
sweep rate.
TABLE-US-00001 TABLE I Metal content in collected heavy pyrolysis
oil at different sweep gas (hydrogen) flow rates. Si is present in
the heat carrier (sand), while K and Ca are present in char. The
metal content was determined by X-Ray analysis (KARNAK). Sweep Flow
(sL/min) Si in pyoil (ppm) K in pyoil (ppm) Ca in pyoil (ppm) 5 460
40 <5 50 755 75 45 100 2000 260 120
[0038] The increase is due to additional particle entrainment in
the pyrolysis vapors. Furthermore, in the experiment, the pyrolysis
vapors passed through a cyclone prior to collection, indicating
that fine heat carrier particles were not collected by the cyclone,
or the efficiency of their collection decreased as sweep flow
increased. The present inventive disclosure does not employ a
conventional cyclone, thus further reducing residence time by
removing additional piping and a reactor vessel, and can be readily
tailored to remove smaller particles while still maintaining short
residence times.
[0039] Optionally, the disengagement zone between the pyrolyzer and
the upgrading catalyst may include additional features to limit
reactivity of the primary gaseous product prior to contact with the
upgrading catalyst(s). These may include (but are not limited to)
temperature control, introduction of a gas or fluid to quench the
primary gaseous product (as mentioned previously), flow control
through judicious choices in geometry (preferably, a geometry
minimizing bends and small orifices to decrease the potential for
vapor condensation, the presence of a pre-catalyst (such as zeolite
monolith, or any of the above-mentioned upgrading catalysts) at the
interface between reactors.
[0040] In some embodiments, a catalyst monolith may be utilized as
a pre-catalyst bed, or guard bed, while in other embodiments, the
pre-catalyst may comprise a fluidized bed of catalyst integrated
with the distributor assembly to control reactivity in this region.
The fluidized bed of catalyst may additionally function as a moving
bed filter to remove residual particulates. Such methods may be as
described in U.S. Pat. No. 8,268,271, which is hereby incorporated
by reference.
[0041] The at least one upgrading bed may utilize any type of
reactor configuration including, but not limited to, a fixed bed, a
bubbling bed, a circulating bed, a moving bed, a counter current
reactor or combinations of one or more of these configurations. The
catalyst may be periodically removed from the upgrading reactor and
passed through a regenerator for de-coking as needed, then returned
to the pyrolysis reactor. Optionally, fresh catalyst may be added
on a periodic or continuous basis to the pyrolysis reactor to
account for catalyst attrition. In certain embodiments, there may
be no means of introducing fresh catalyst.
[0042] Examples of some upgrading catalysts and typical reaction
conditions are disclosed in U.S. patent application Ser. No.
13/416,533, although any catalyst known to catalyze the conversion
of primary gaseous product to a bio-derived fuel may be utilized.
The catalyst may include, but is not limited to zeolites, metal
modified zeolites, and other modified zeolites. Other catalysts may
include forms of alumina, silica-alumina, and silica, unmodified or
modified with various metals, not limited but including, Nickel,
Cobalt, Molybdenum, Tungsten, Cerium, Praseodymium, Iron, Platinum,
Palladium, Ruthenium and Copper or mixtures thereof. Still other
catalysts may include unsupported metals, supported or unsupported
metal oxides or metal phosphides, and mixtures thereof. Catalyst
types include deoxygenation catalysts, hydrogenation catalysts,
hydrotreating catalysts, hydrocracking catalysts, water-gas-shift
catalysts and condensation catalysts. Catalysts may be sulfided or
un-sulfided. In certain embodiments, each catalyst bed may comprise
mixtures of one or more catalysts of the types described above.
Optionally, multiple catalyst beds may be placed within a single
reactor, or multiple catalyst beds may be placed in different
reactors to facilitate different reaction conditions. When multiple
reactors are utilized, they may be arranged to either in parallel
or series.
[0043] If multiple upgrading reactors are utilized, different
conditions may be maintained in each reactor in order to facilitate
a given catalytic reaction. To facilitate flow of the vapors
through multiple reactors, a pressure differential may be
maintained wherein the pressure in each successive reactor
progressively decreases.
[0044] The residence time of the pyrolysis vapors in each upgrading
reactor generally ranges from 0.01 sec to 1000 sec. preferably, the
residence time is in a range from 0.05 sec to 400 secs. More
preferably, the residence time is in a range from 0.1 sec to 200
sec. Most preferably, the residence time is in a range from 0.1 sec
to 100 sec.
[0045] The temperature maintained within each upgrading reactor is
generally in the range from 72.degree. F. to 1500.degree. F.
Preferably, the temperature is in the range from 100.degree. F. to
1000.degree. F., although if multiple upgrading reactors are used,
each may be maintained at a different temperature within this
range.
[0046] Certain upgrading reactions are advantageously conducted at
a pressure that is greater than atmospheric pressure. The pressure
that is maintained in the one or more upgrading reactors may range
from 0-3000 psig, although a preferred pressure range is zero to
1000 psig. In certain embodiments, the pressure may range from 10
to 800 psig, from 20 to 650 psig, from 100 to 500 psig. An
exemplary pressure might be 400 psig.
[0047] The flow of gas and vapors within each upgrading reactor is
preferably upward, although downward or lateral gas flow may also
be utilized. Upon exiting the final upgrading reactor, the upgraded
gas and/or vapors are directed to a condensation system that
functions to reduce the temperature of upgraded product vapors to a
temperature that is at or below the dew point for at least one
component. Typically, the conditions utilized do not result in the
condensation of methane, but preferably will condense C4+
hydrocarbons. Hydrogen may be separated from the non-condensed gas
by a variety of conventional methods and recycled as the sweep gas.
In certain embodiments, the recycled hydrogen may be added directly
into, or just upstream from, an upgrading reactor to facilitate one
or more upgrading reactions. Alternatively, the entirety, or some
fraction, of the bulk non-condensable gas is used for the same
purpose. In another embodiment, the entirety, or some fraction, of
the bulk of the non-condensable gas is sent to a combustor or
hydrogen generation unit (e.g., a reformer) to generate either heat
or hydrogen, respectively. The resulting heat or hydrogen may then
be partially or entirely recycled back to the process.
[0048] The following examples of certain embodiments of the
invention are given. Each example is provided by way of explanation
of the invention, one of many embodiments of the invention.
[0049] The following examples are intended to be illustrative of
specific embodiments and should not be interpreted to limit, or
define, the scope of the invention in any way.
Example 1
[0050] FIG. 5 graphically depicts the relationship between
residence time of the pyrolysis vapors in the pyrolysis reactor
versus pyrolysis product size distribution (quantified as carbon
number of the product). Product size distribution was first
quantified at 0.3 seconds of residence time (white bars), then at 3
seconds of residence time (grey bars) in a 100 micron capillary
maintained at pyrolysis temperatures (610.degree. F.). At 3 seconds
of vapor residence time, the proportion of C16+ species increased
versus the relative abundance of levoglucosan, a key six carbon
primary pyrolysis product. Furthermore, the proportion of
phenolics, furans, and other carbohydrates/sugars comprising less
than 16 carbon atoms decreased at the longer residence times, which
was likely due to oligomerization of these primary compounds to
heavier compounds of 16 carbons or greater, which are difficult to
upgrade to fuel-range hydrocarbons.
DEFINITIONS
[0051] As used herein, the term "entrainment" is defined as
transport of a solid particle by a gas stream. Entrainment of a
given solid particle typically occurs when the local velocity of a
gas stream exceeds the terminal falling velocity of the
particle.
[0052] As used herein, the term "standard gas hourly space
velocity" or "SGHSV" refers to the gas hourly space velocity of a
gas stream measured at standard conditions.
[0053] In closing, it should be noted that the discussion of any
reference is not an admission that it is prior art to the present
disclosure, in particular, any reference that may have a
publication date after the priority date of this application. At
the same time, each and every claim below is hereby incorporated
into this detailed description or specification as an additional
embodiment of the present invention.
[0054] Although the systems and processes described herein have
been described in detail, it should be understood that various
changes, substitutions, and alterations can be made without
departing from the spirit and scope of the invention as defined by
the following claims. Those skilled in the art may be able to study
the preferred embodiments and identify other ways to practice the
invention that are not exactly as described herein. It is the
intent of the inventors that variations and equivalents of the
invention are within the scope of the claims while the description,
abstract and drawings are not to be used to limit the scope of the
invention. The invention is specifically intended to be as broad as
the claims below and their equivalents.
REFERENCES
[0055] All of the references cited herein are expressly
incorporated by reference. The discussion of any reference is not
an admission that it is prior art to the present invention,
especially any reference that may have a publication data after the
priority date of this application. Incorporated references are
listed again here for convenience: [0056] 1. Brown, J. N., et al.
"Process Optimization of an Auger Pyrolyzer with Heat Carrier Using
Response Surface Methodology." Biores. Tech. 103:405-4141
(2012).
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