U.S. patent application number 12/796428 was filed with the patent office on 2010-09-30 for systems and methods for cyclic operations in a fuel synthesis process.
This patent application is currently assigned to SUNDROP FUELS, INC.. Invention is credited to Courtland Hilton.
Application Number | 20100249251 12/796428 |
Document ID | / |
Family ID | 42736707 |
Filed Date | 2010-09-30 |
United States Patent
Application |
20100249251 |
Kind Code |
A1 |
Hilton; Courtland |
September 30, 2010 |
SYSTEMS AND METHODS FOR CYCLIC OPERATIONS IN A FUEL SYNTHESIS
PROCESS
Abstract
A method, apparatus, and system for a fuel synthesis system
including a multiple methanol reactor train, operated in parallel
from a common input of 1) synthesis gas from a solar driven
chemical reactor and 2) synthesis gas from a storage tank. In some
embodiments, the multiple methanol reactor trains are idled as
needed based on a variable amount of synthesis gas fed into the
process. Additionally, some embodiments may include a controller to
control operation of the multiple methanol trains by potentially
idling one or more of the methanol reactor trains, switching to an
operational state, or altering the output from the reactor trains,
based on the amount of synthesis gas being generated by the solar
driven chemical reactor, which is subject to marked variations in
volume of synthesis gas output based on a seasonal, diurnal and
weather effects.
Inventors: |
Hilton; Courtland;
(Broomfield, CO) |
Correspondence
Address: |
Rutan & Tucker, LLP.
611 ANTON BLVD, SUITE 1400
COSTA MESA
CA
92626
US
|
Assignee: |
SUNDROP FUELS, INC.
Louisville
CO
|
Family ID: |
42736707 |
Appl. No.: |
12/796428 |
Filed: |
June 8, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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61248282 |
Oct 2, 2009 |
|
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61185492 |
Jun 9, 2009 |
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Current U.S.
Class: |
518/702 ;
422/105 |
Current CPC
Class: |
C01B 3/22 20130101; C10G
2300/1025 20130101; C10J 3/506 20130101; C10J 2300/1621 20130101;
B01J 19/245 20130101; C10J 3/00 20130101; C10J 2200/09 20130101;
C10J 2200/15 20130101; C10J 3/60 20130101; C10J 3/62 20130101; C10L
2290/42 20130101; C10L 2290/547 20130101; F24S 20/20 20180501; Y02E
50/10 20130101; C10J 3/482 20130101; C10J 2300/0916 20130101; C10J
2300/1659 20130101; C10G 2300/1014 20130101; C10J 3/58 20130101;
C10J 3/84 20130101; C10J 2300/1223 20130101; Y02E 50/30 20130101;
C10J 2300/123 20130101; C10J 3/466 20130101; C10L 2290/04 20130101;
C10J 2300/0909 20130101; C10L 2290/50 20130101; B01J 19/0013
20130101; C01B 2203/0811 20130101; C10J 2300/1292 20130101; Y02B
40/18 20130101; C01B 3/384 20130101; C10J 3/54 20130101; C10J
2300/094 20130101; Y02P 30/20 20151101; Y02P 20/129 20151101; C10J
3/485 20130101; B01J 19/2445 20130101; C01B 3/34 20130101; C10J
2300/1693 20130101; Y02P 20/50 20151101; B01J 19/0033 20130101;
C01B 2203/1685 20130101; C01B 2203/84 20130101; C10G 3/00 20130101;
Y02P 20/145 20151101; C01B 2203/0216 20130101; C10J 2300/1861
20130101; Y02T 50/678 20130101; C10L 2290/28 20130101; C01B
2203/061 20130101; C07C 29/15 20130101; C10J 3/82 20130101; B01J
2219/00186 20130101; C01B 2203/1241 20130101; C10J 2300/0989
20130101; Y02P 20/133 20151101; C10L 2200/0492 20130101; C10L
2290/08 20130101; C10G 2300/807 20130101; C10J 3/56 20130101; C07C
29/1518 20130101; C10J 2300/1284 20130101; C10K 1/024 20130101;
C10G 2/32 20130101; C10J 2200/158 20130101; C10L 2290/06 20130101;
C10J 2300/0973 20130101; Y02E 10/40 20130101; C10G 2/30 20130101;
C10J 2300/0906 20130101; C10L 2290/52 20130101; C10J 2300/0993
20130101; C10L 1/04 20130101; B01J 2219/00117 20130101; C10J 3/723
20130101; C10L 2290/02 20130101; C10J 3/721 20130101; C10J
2300/0976 20130101; C01B 2203/0233 20130101; C10J 2300/1665
20130101; C10J 2300/1853 20130101; C07C 29/15 20130101; C07C 31/04
20130101; C07C 29/1518 20130101; C07C 31/04 20130101 |
Class at
Publication: |
518/702 ;
422/105 |
International
Class: |
B01J 19/00 20060101
B01J019/00; C07C 1/04 20060101 C07C001/04 |
Claims
1. A fuel synthesis system comprising: a multiple methanol reactor
train, operated in parallel from a supply input of 1) synthesis gas
from a solar driven chemical reactor and 2) synthesis gas from a
storage unit, or 3) a combination of both, wherein the multiple
methanol reactor trains are idled as needed based on a variable
amount of synthesis gas fed into the process; and a controller to
control operation of the multiple methanol trains by 1) idling one
or more of the methanol reactor trains, 2) altering an output
amount being generated by one or more of the methanol reactor
trains, 3) switching one or more of the methanol reactor trains to
an operational state and 4) any combination of the three, based on
an amount of synthesis gas being generated by the solar driven
chemical reactor, which is subject to marked variations in volume
of synthesis gas output based on seasonal, diurnal and weather
effects.
2. The fuel synthesis system of claim 1, wherein the multiple
methanol reactor trains are physically separate reactor trains,
wherein the physically separate reactor trains are in parallel, and
wherein the control system controls parameters including
temperature, pressure, and chemistry of the fuel synthesis system
during idle non-production periods of time so that the fuel
synthesis system may rapidly resume fuel production when a supply
of solar generated synthesis gas resumes in sufficient quantities
to perform fuel synthesis.
3. The fuel synthesis system of claim 1, wherein the multiple
methanol reactor trains comprise a common reactor with a manifold
that feeds multiple virtual reactor trains from the manifold; and
wherein the multiple methanol reactor trains are incased in the
shell of the common reactor.
4. The fuel synthesis system of claim 1, wherein the methanol
trains have an input coupled to receive synthesis gas from the
upstream solar driven chemical reactor, wherein the control system
controls parameters of a downstream fuel synthesis process to
account for the cyclic supply of solar generated synthesis gas as a
feed product, wherein the controller controls parameters including
temperature, pressure, and chemistry of the fuel synthesis system
during idle non-production periods of time so that the fuel
synthesis system may rapidly resume fuel production when the supply
of solar generated synthesis gas resumes in sufficient quantities
to perform fuel synthesis, and wherein the controller controls the
parameters during cyclic operation of the fuel synthesis including
cyclic operation of the methanol synthesis plant with little to no
additional loss in catalytic activity or throughput over the
plant's lifetime above expected losses from the catalyst aging and
participating in the catalytic activity, by protecting the
catalyst, through 1) keeping the synthesis gas and product methanol
gas at a certain temperature and pressure such that the gases
remain vaporized and do not condense on the catalyst, prolonging
the life of the catalyst and 2) maintaining a chemically reducing
atmosphere for the catalyst.
5. The fuel synthesis system of claim 1, wherein a reactor is a
shell and tube reactor and when the reactor train is idled, the
temporarily idled reactor is kept at or near the reaction
temperature with heat makeup as required to offset heat losses 1)
with heat from a boiling water heated from an external boiler and
2) with heat from the methanol synthesis reaction, or 3) any
combination of the two; and wherein the shells of each reactor
train are interconnected such that a hot working fluid removing the
exothermic heat from a train that is operating is circulated around
an idle train to keep the idle trains near reaction temperature and
the reactor uses layers of insulation around the methanol reactor
train to keep the plant near reaction temperature.
6. The fuel synthesis system of claim 1, wherein, when a reactor
train is idled, the temporarily idled reactor train is kept at or
near the reaction temperature with waste heat from other areas of
the plant including a quenching operation on the synthesis gas
coming out of the solar driven chemical reactor; and wherein the
waste heat is stored in a 1) a hot solid, heated liquid, or heated
vapor, where the waste heat is generated during the operation of
the solar driven reactor when sunset or weather events are not
blocking the Sun.
7. The fuel synthesis system of claim 1, wherein, before a reactor
train is idled the H2 content inside the methanol reactor is
boosted by adding synthesis gas with a higher ratio of H2:CO from
the solar driven reactor, or adding supplemental H2 from an H2
storage supply, to ensure that a reducing atmosphere is maintained
within the reactor.
8. The fuel synthesis system of claim 1, wherein the multiple
methanol reactors comprise at least two methanol reactors that are
operable at a percentage of maximum throughput such that the fuel
synthesis system has a dynamic operating range of at least 16 to
100 percent of capacity.
9. The fuel synthesis system of claim 1, wherein the control system
comprises control algorithms that control reactor operation, the
control algorithms specifically allowing rapid and efficient
reactor cycling by 1) using synthesis gas from the solar driven
chemical reactor, 2) synthesis gas from the storage unit, and 3)
recycling synthesis gas and methanol product gas from the outlet of
the reactor trains to keep at least one of the trains operating at
some percent of its maximum throughput; and wherein the control
system keeps an idle reactors at or near reaction temperature and
pressure during the daily operation.
10. The fuel synthesis system of claim 1, wherein the control
system controls compressors in the fuel synthesis system to assist
in controlling pressure in a cyclic operation, wherein the system
comprises at least three levels of compression, a low-pressure
level, of less than 500 PSIG in a synthesis gas clean up portion of
a system just prior to a CO2 remediation unit, a higher
intermediate pressure 500-1500 PSIG level for injecting cleaned up
solar generated synthesis gas from the solar driven chemical
reactor into an input into the methanol synthesis process, and a
third level of compression for pumping excess synthesis gas from
the solar chemical reactor into the storage unit at a pressure
greater than the intermediate pressure.
11. The fuel synthesis system of claim 10, wherein the storage unit
comprises at least one of a pipeline or other underground storage
structure.
12. The fuel synthesis system of claim 10, further comprising a
flywheel drive mechanism including a flywheel sized such that it
can store enough rotational energy to start a compressor and small
enough to be started and accelerated using less power than is
needed to start the compressor; a low power starting mechanism for
starting and then accelerating the flywheel, the low power starting
mechanism providing enough power to rotate the flywheel, but less
power than is needed to start the compressor, wherein the speed of
the flywheel builds over time as power is received from the low
power starting mechanism; and a mechanism to couple the fly wheel
to the compressor such that rotational energy from the fly wheel
can be transferred to the compressor to start the compressor.
13. A control system for a fuel synthesis system comprising control
algorithms on reactor operation, the control algorithms
specifically allowing rapid and efficient reactor cycling by 1)
using synthesis gas from a solar driven chemical reactor, 2)
synthesis gas from a storage unit, and 3) recycling synthesis gas
and methanol product gas from the outlet of the reactor trains to
keep at least one of the trains operating at some percent of its
maximum throughput; and wherein the control system keeps an idle
reactor at or near reaction temperature and with a pressure change
of no more than 30% during the idle periods.
14. The control system of claim 13, further comprising a system
that controls compressors in a fuel synthesis system to assist in
controlling pressure in the cyclic operations, wherein the system
comprises at least two levels of compression, a first pressure
750-1200 PSIG level for injecting cleaned up solar generated
synthesis gas into a common input into the methanol synthesis
process, and a second level of compression for pumping excess
synthesis gas from the solar chemical reactor into the storage
unit, where the high pressure is defined as being greater than the
second level of compression.
15. The control system of claim 13, wherein the system controls
operation of multiple methanol trains by 1) idling one or more of
the methanol reactor trains and/or 2) reducing an output amount
being generated by one or more of the methanol reactor trains based
on the amount of synthesis gas being generated by the solar driven
chemical reactor, which is subject to marked variations in volume
of synthesis gas output based on a seasonal, diurnal and weather
effects; and wherein the multiple methanol reactor trains are idled
or set at a reduced output as needed based on a variable amount of
synthesis gas fed into the process.
16. The control system of claim 13, wherein the control system
controls parameters including temperature, pressure, and chemistry
of a fuel synthesis system during idle non-production periods of
time so that the fuel synthesis system may rapidly resume fuel
production when the supply of solar generated synthesis gas resumes
in sufficient quantities to perform fuel synthesis.
17. The control system of claim 13, wherein the control system
controls parameters including temperature, pressure, and chemistry
of a fuel synthesis system during cyclic operation of the fuel
synthesis including cyclic operation of the methanol synthesis
plant with little to expected typical loss in catalytic activity or
throughput over the plant's lifetime allowing for the protection of
the catalyst, by keeping the synthesis gas and product methanol gas
at a certain temperature and pressure such that the gases remain
vaporized and do not condense on the catalyst, prolonging the life
of the catalyst.
18. The control system of claim 13, wherein the control system
controls a temperature of a reactor train when the reactor train is
temporarily idled, such that the idled reactor is kept at or near a
reaction temperature with heat makeup as required to offset heat
losses with one or more of 1) heat from boiling water heated from
an external boiler, 2) heat from the methanol synthesis reaction
from another methanol reactor that is operating, 3) an internal
electric heater or a combination of all three, where the operation
of the external boiler controlled by the control system.
19. The control system of claim 13, wherein the control system
controls a temperature of a reactor train when the reactor train is
temporarily idled, such that the idled reactor is kept at or near a
reaction temperature with waste heat from other areas of the plant
including the quenching operation on the synthesis gas coming out
of the solar driven chemical reactor.
20. A method for an integrated solar driven chemical plant,
comprising: conducting a chemical reaction in a solar driven
chemical reactor having multiple reactor tubes using concentrated
solar energy to drive the conversion of the chemical reactant,
wherein an endothermic chemical reaction conducted in the reactor
tubes includes one or more of the following: biomass gasification,
steam methane reforming, methane cracking, using solar thermal
energy coming from a concentrated solar energy field; supplying the
products from the chemical reaction for a catalytic conversion of
the products from the solar driven chemical reaction into a
hydrocarbon fuel or other chemical in a chemical synthesis plant;
where an operation of the chemical synthesis plant is dependent
upon an amount of product generated in the solar driven chemical
reactor; and a control system for the chemical synthesis plant is
configured to send control signals to and receiving feedback from a
control system for the chemical reactor, and the control system for
the chemical reactor at least indicates the amount of product being
generated in the solar driven chemical reactor.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of both U.S. Provisional
Patent Application Ser. No. 61/248,282, filed Oct. 2, 2009 and
entitled "VARIOUS METHODS AND APPARATUSES FOR SUN DRIVEN
PROCESSES," and U.S. Provisional Patent Application Ser. No
61/185,492, entitled "VARIOUS METHODS AND APPARATUSES FOR
SOLAR-THERMAL GASIFICATION OF BIOMASS TO PRODUCE SYNTHESIS GAS"
filed Jun. 9, 2009.
NOTICE OF COPYRIGHT
[0002] A portion of the disclosure of this patent document contains
material that is subject to copyright protection. The copyright
owner has no objection to the facsimile reproduction by anyone of
the software engine and its modules, as it appears in the Patent
and Trademark Office Patent file or records, but otherwise reserves
all copyright rights whatsoever.
FIELD OF THE INVENTION
[0003] Embodiments of the invention generally relate to systems,
methods, and apparatus for refining biomass and other materials.
More particularly, an aspect of an embodiment of the invention
relates to solar-driven systems, methods, and apparatus for
refining biomass and other materials.
BACKGROUND OF THE INVENTION
[0004] Biomass gasification is an endothermic process; energy must
be put into the process to drive it forward. Typically, this is
performed by partially oxidizing (burning) the biomass itself.
Between 30% and 40% of the biomass must be consumed to drive the
process, and at the temperatures which the process is generally
limited to (for efficiency reasons), conversion is typically
limited, giving still lower yields. In contrast, the proposed
solar-driven biorefinery uses an external source of energy (solar)
to provide the energy required for reaction, so none of the biomass
needs to be consumed to achieve the conversion. This can result in
significantly higher yields of gallons of gasoline per biomass ton
than previous technologies, as the energy source being used to
drive the conversion is renewable and carbon free. In addition,
chemical reactors are generally engineered to operate at constant
conditions around the clock.
SUMMARY OF THE INVENTION
[0005] Some embodiments relate to a solar-driven chemical plant,
including a solar thermal receiver having a cavity with an inner
wall, where the solar thermal receiver can be aligned to absorb
concentrated solar energy from one or more of 1) an array of
heliostats, 2) solar concentrating dishes, and 3) any combination
of the two.
[0006] In some embodiments, a fuel synthesis system including a
multiple methanol reactor train, operated in parallel from a common
input of 1) synthesis gas from a solar driven chemical reactor and
2) synthesis gas from a storage tank. Some embodiments may include
a controller to control operation of the multiple methanol trains
by potentially idling one or more of the methanol reactor trains or
reducing output of the trains based on a lower amount of synthesis
gas being generated by the solar driven chemical reactor, or
switching an idle train to an operational state or increasing
output of a train when the amount of syngas gas is higher, both of
which are subject to marked variations in volume of synthesis gas
output based on a seasonal, diurnal and weather effects.
Additionally, in some embodiments the multiple methanol reactor
trains are idled as needed based on a variable amount of synthesis
gas fed into the process.
[0007] In some embodiments, a fuel synthesis system can include
control algorithms on reactor operation. The control algorithms may
specifically allow rapid and efficient reactor cycling. This can be
by using synthesis gas from a solar driven chemical reactor.
Additionally, synthesis gas from a storage tank may provide for
rapid and efficient reactor cycling, e.g., by maintaining reactor
temperature. Recycling synthesis gas and methanol product gas from
the outlet of the reactor trains can also be used to keep at least
one of the trains operating at some percent of its maximum
throughput.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The drawings refer to embodiments of the invention in
which:
[0009] FIG. 1 illustrates a block diagram of an embodiment of an
example process flow in accordance with the systems and methods
described herein;
[0010] FIG. 2A illustrates a diagram of an embodiment of a solar
chemical reactor in accordance with the systems and methods
described herein;
[0011] FIG. 2B illustrates a diagram of an embodiment of methanol
reactor train;
[0012] FIG. 3 illustrates a diagram of an embodiment of a quenching
via an injection cooling medium into reaction products, gas clean
up, and ash removal system;
[0013] FIG. 4 illustrates a diagram of an embodiment of an example
quenching, gas clean up, and ash removal system; and
[0014] FIG. 5 illustrates a diagram of an embodiment of a multiple
level compressor system strategy.
[0015] While the invention is subject to various modifications and
alternative forms, specific embodiments thereof have been shown by
way of example in the drawings and will herein be described in
detail. The invention should be understood to not be limited to the
particular forms disclosed, but on the contrary, the intention is
to cover all modifications, equivalents, and alternatives falling
within the spirit and scope of the invention.
DETAILED DISCUSSION
[0016] In the following description, numerous specific details are
set forth, such as examples of specific data signals, named
components, connections, number of reactor tubes, etc., in order to
provide a thorough understanding of the present invention. It will
be apparent, however, to one of ordinary skill in the art that the
present invention may be practiced without these specific details.
In other instances, well known components or methods have not been
described in detail but rather in a block diagram in order to avoid
unnecessarily obscuring the present invention. Further, specific
numeric references such as first reactor tube, may be made.
However, the specific numeric reference should not be interpreted
as a literal sequential order but rather interpreted that the first
reactor tube is different from a second reactor tube. Thus, the
specific details set forth are merely exemplary. The specific
details may be varied from and still be contemplated to be within
the spirit and scope of the present invention. The term coupled is
defined as meaning connected either directly to the component or
indirectly to the component through another component.
[0017] Some embodiments relate to a solar-driven fuel synthesis
system configured for cyclic operations in a fuel synthesis
process. In some embodiments, a fuel synthesis system including a
multiple methanol reactor train, operated in parallel from a common
input of 1) synthesis gas from a solar driven chemical reactor and
2) synthesis gas from a storage tank. Some embodiments may include
a controller to control operation of the multiple methanol trains
by potentially idling one or more of the methanol reactor trains
based on theamount of synthesis gas being generated by the solar
driven chemical reactor, which is subject to marked variations in
volume of synthesis gas output based on a seasonal, diurnal and
weather effects. Additionally, in some embodiments the multiple
methanol reactor trains are idled as needed based on a variable
amount of synthesis gas fed into the process.
[0018] In some embodiments, a fuel synthesis system can include
control algorithms on reactor operation. The control algorithms may
specifically allow rapid and efficient reactor cycling. This can be
by using synthesis gas from a solar driven chemical reactor.
Additionally, synthesis gas from a storage tank may provide for
rapid and efficient reactor cycling, e.g., by maintaining reactor
temperature. Recycling synthesis gas and methanol product gas from
the outlet of the reactor trains can also be used to keep at least
one of the trains operating at some percent of its maximum
throughput.
[0019] Although some embodiments apply to a wide variety of
chemical reactors, for brevity and clarity this discussion focuses
on the synthesis of methanol from synthesis gas. It will be
understood by those of skill in the art that the systems and
methods described herein might be applied to other chemical
reactors.
[0020] FIG. 1 illustrates a block diagram of an example process
flow. Some embodiments encompass a solar-driven-biomass
gasification to liquid fuel/electrical process. The process might
also include generation, chemical processing, or bio-char, for
solar generated synthesis gas derivative product or other similar
technical process. In a specific example implementation the process
described is a solar-driven-biomass gasification to `green` liquid
fuel process. In an embodiment, this process includes one or more
of the following process steps.
[0021] The integrated chemical plant includes several process steps
including a grinding system 100 for making biomass particles and
other chemical feed preparation process that is run on an as-needed
basis, a chemical reactant feed system 104 that supplies chemical
reactant, including the biomass particles, when the solar driven
chemical reactor is at at least its minimum operating temperature,
a solar concentrating field process 110 that is stowed when not in
use and aligned to focus the concentrated solar energy at the solar
driven chemical reactor 106 at least near sunrise. This near
sunrise could be roughly within 90 minutes of Sunrise depending on
time of year and current weather conditions. The solar driven
chemical reactor process 106 is kept at or near operating
temperature during off production hours, a compressor process 114
that switches levels of compression between compressing and idling
twenty four hours a day, a synthesis gas clean-up process 108, an
intermediate chemical generation process 116 such as methanol
synthesis, and a final stage chemical process 124 such as
generation of a liquid hydrocarbon fuel process such as methanol to
gasoline.
[0022] Some process steps may be started in parallel with other
process steps, while others may run continuously and just change
states from idle to operational.
[0023] Biomass grinding or densification, transport and offload 100
may be part of the overall process. Bales of the biomass can be
compressed and densified by a compactor to facilitate transport to
on-site via the densification achieved by the double
compression.
[0024] A grinding system 100 couples through storage 102 to the
entrained-flow biomass feed system 104. A conveyer brings the
biomass to the grinding system that grinds biomass into particles
via a mechanical cutting device cooperating with a set of filters
with specific sized holes in the filters. The grinding system
generates particles that have an average smallest dimension size
between 200 microns (um) and 2000 um in diameter, such to fit
through the holes in the filters, with a general range of between
500 um and 1000 um, and then the particles are loaded into a feed
vessel such as a lock hopper system with a standard belt or
pneumatic conveyer. The biomass may be in an embodiment non-food
stock biomass. In other cases, food stock biomass or a combination
of the two might also be processed.
[0025] Two or more feed line supply the particles of biomass having
an average smallest dimension size between 50 microns (um) and 2000
um to the chemical reactor. An entrained gas biomass feed system
uses an entrainment carrier gas to move a variety of biomass
sources fed as particles into the solar driven chemical
reactor.
[0026] A solar receiver and gasifier 106 may be used to break down
the biomass. An example biomass gasifier design and operation can
include a solar chemical reactor and solar receiver to generate
components of synthesis gas. The feed-forward portion and the
feedback portion of the control system adapts the operation of the
reactor to both long and short term disturbances in available solar
energy. Various solar concentrator field designs to drive the
biomass gasifier can be used. Some example systems may include a
solar concentrator, focused mirror array, etc. to drive biomass
gasifier 110.
[0027] Quenching, gas clean up, and ash removal from biomass
gasifier 108 occur to make the produced synthesis gas useable for
the next process step. Some gasses generated in the chemical
reactor may be a waste product, while other gasses can be
compressed 114 prior to storage 118 or sent directly for methanol
synthesis 116. Methanol may then be stored 120 for later methanol
to gasoline conversion 122.
[0028] A storage capacity of the synthesis gas and idling of the
methanol trains is created to decouple a response rate of the
methanol synthesis plant from the response rate of the solar driven
chemical reactor. The storage capacity and idling processes
established for the integrated solar driven chemical plant also
decouples a direct production rate of the synthesis gas generated
in the solar driven chemical reactor from the supply requirements
of the methanol synthesis plant.
[0029] An on-site fuel synthesis reactor that is geographically
located on the same site as the chemical reactor and integrated to
receive the hydrogen and carbon monoxide products from the
gasification reaction can be used in some embodiments.
Additionally, the on-site fuel synthesis reactor has an input to
receive the hydrogen and carbon monoxide products and use them in a
hydrocarbon fuel synthesis process to create a liquid hydrocarbon
fuel. The on-site fuel synthesis reactor may be connected to the
rest of the plant facility by a pipeline that is generally less
than 15 miles in distance. The on-site fuel synthesis reactor may
supply various feedback parameters and other request to the control
system. For example, the on-site fuel synthesis reactor can request
the control system to alter the H2 to CO ratio of the synthesis gas
coming out of the quenching and gas clean up portion of the plant
and the control system will do so.
[0030] In various embodiments, synthesis gas may be fed to another
technical application.
[0031] For example, some embodiments may use a series of
compressors to provide compression 114. Such a system might include
at least three levels of compression. In some embodiments, a first
low-pressure stage, of less than 500 PSIG may be located in a
synthesis gas clean up portion of a system just prior to an amine
step. Other embodiments may include a low-pressure level that is
less than 500, 250, or 100 PSIG, for example, depending on the
specific embodiment. An intermediate pressure 500-1500 PSIG level
for injecting cleaned up solar generated synthesis gas into a
common input into the methanol process may be located and a third
stage level for pumping excess synthesis gas from the solar
chemical reactor into a high pressure 2000-3000 PSIG storage
tank.
[0032] In some embodiments, the synthesis gas exits the storage
vessels 118 or the synthesis gas compressor 114 to enter the
methanol synthesis unit 116. The unit 116 may comprise standard
shell and tube Lurgi style methanol reactors. This is a well-known
process and is operated on very large scales (millions of gallons
of methanol per year) worldwide. The process operates at a 4:1
recycle ratio and converts 96% of the synthesis gas to methanol. In
an embodiment, the process operates at another example 7.5:1
recycle ratio and conversion of 95% of the synthesis gas to
methanol. The raw methanol is distilled from the entrained water
product and fed to a standard methanol-to-gasoline (MTG) unit,
where the methanol is converted to gasoline and LPG.
[0033] In various embodiments, synthesis gas may be feed to another
technical application. Examples include a synthesis gas to other
chemical conversion process. The other chemical of chemicals
produced can include liquefied fuels such as
transportation-liquefied fuels. Some transportation-liquefied fuels
include jet fuel, DME, gasoline, diesel, and mixed alcohol,
bio-char with a high sequestered amount of carbon; chemical
production, electricity generation, synthetic natural gas
production, heating oil generation, and other similar synthesis gas
based technical applications. In an example hydrocarbon based fuel,
e.g., methanol, 116 may be formed from synthesis gas. The methanol
may be further converted to gasoline or other fuels 122 and various
products may be separated out from the gasoline 124 or synthesis
gas. These products, e.g., gasoline, may then be stored for later
use as an energy source.
[0034] In starting large motor(s) such as those involved with the
compression of gases in a synthesis plant, large electrical demands
are placed on the electrical power grid. Such demand is not only
costly but can also exceed the infrastructure capacity to deliver
the needed power. If these large motors for, say, compressors, are
idled frequently, say in a diurnal fashion, such costs or
limitations may prevent the diurnal cycling. Accordingly, some
embodiments may couple the stored angular momentum of a flywheel to
the motor to provide the majority of motive force required for
motor starting.
[0035] A flywheel drive mechanism may be used to start the
compressors. The flywheel drive mechanism may including a flywheel
sized such that it can store enough rotational energy to start a
compressor and small enough to be started using less power than is
needed to start the compressor. A low power starting mechanism may
be used to starting the flywheel. The low power starting mechanism
can provide enough power to rotate the flywheel, but less power
than is needed to start the compressor. Using a flywheel to start
the compressor can decrease or eliminate surges in electrical power
that might otherwise be needed to start a compressor because the
speed of the flywheel builds over time as power is received from
the low power starting mechanism. Additionally, a mechanism to
couple the fly wheel to the compressor is used so that rotational
energy from the fly wheel can be transferred to the compressor to
start the compressor. Although discussed in the context of
electrical load, a flywheel might be applied to assisting with
other motive force replacement, like a steam drive etc.
[0036] Accordingly, some embodiments might start large motors
without high electrical demand, start large motors without high
stress on motor windings etc., and allow cycling of motors in
situations where recirculation of compressor feed/effluent is not a
viable solution. Such a system may provide for lower power charges
and longer motor life in the face of many starts and stops.
[0037] In some embodiments, motors are coupled to the rotational
energy of a flywheel. Coupling can be in various ways, e.g.,
mechanically direct through a clutch, via hydraulics where the
flywheel supplies the power to the hydraulic pump, etc. When the
motor is started the power brought to bear on the motor shaft can
be from the storage energy of a flywheel. Additionally, the motor
can be started in a variety of modes. For example, a hybrid mode
where both electricity and flywheel energy is simultaneously
applied, a sequential mode, e.g., flywheel energy is applied and
then transitioned to electrical energy, etc.
[0038] Additionally, in some embodiments, flywheel energy can be
accumulated in various ways. For example, slowly over time from a
smaller motor that does not place large demands on the
infrastructure, or flywheel energy can be added from the motor
itself as operates and/or as it shuts down during the idle
process.
[0039] FIG. 2A illustrates a diagram of an embodiment of a solar
gasifier (reactors) 200 in accordance with the systems and methods
described herein. As illustrated in FIG. 2, the reactor 200 can
take in biomass particles in a carrier gas stream 210 and output
synthesis gas 212.
[0040] The reactor 200 can receive solar energy 202 through a
window or aperture. This solar energy 202 may be used to heat a
solar heated reactor chamber 206 that can be located within a
receiver cavity. This reactor chamber can included reactor tubes
that contain biomass particles as the particles follow through the
reactor. The biomass particles may be heated to a temperature such
that they react inside the tubes. After biomass particles react
within the tubes of the reactor chamber 206 the reaction products
can be quenched 208 to prevent back reaction.
[0041] In some embodiments, a fuel synthesis system can include a
multiple methanol reactor train 214. The multiple methanol reactor
train 214 may be operated in parallel from a common input of 1)
synthesis gas from the solar driven chemical reactor 200 and 2)
synthesis gas from a storage tank. The synthesis gas from the
storage tank can allow the methanol reactor train 214 to continue
operation when the supply of synthesis gas from the solar driven
chemical reactor 200 is low. Additionally, the storage tanks may
include at least one of a tank, a pipeline, or an underground
structure. Underground geologic formations can include salt domes,
injection wells, etc.
[0042] In some embodiments, multiple methanol reactor trains 214
are physically separate reactor trains. The physically separate
reactor trains can be in parallel with each other. In other
embodiments, the multiple methanol reactor trains 214 include a
common reactor with a manifold that feeds multiple virtual reactor
trains from that manifold. For example, the multiple methanol
reactor trains 214 may be incased in the shell of the common
reactor. In some embodiments, the methanol reactors can be a shell
and tube reactor.
[0043] When the reactor train 214 is temporarily idled it may be
kept at or near the reaction temperature with heat makeup as
required to offset heat losses. This heat may be provided by one or
more of 1) heat from boiling water heated from an external boiler,
2) heat from the methanol synthesis reaction from another methanol
reactor that is operating, 3) an internal electric heater, 4) other
sources, or any combination of the four.
[0044] In some embodiments, the reactor 214 can be a shell and tube
reactor. In such a system, the shells of each reactor train may be
interconnected. By interconnecting the shells, a hot working fluid
can be used to remove the exothermic heat from a train that is
operating and to circulate the fluid around idle trains to keep the
idle trains near reaction temperature and the reactor uses layers
of insulation around the methanol reactor train to keep the plant
near reaction temperature. Also, each of the reactor trains may
share a common shell that may be heated similar to above.
[0045] A temporarily idled reactor might also be kept at or near
the reaction temperature with waste heat from other areas of the
plant. For example, waste heat from the quenching operation on the
synthesis gas coming out of the solar driven chemical reactor might
be used. The waste heat may be stored in a solid whether a
monolithic block including rock or carbon or a composite like
concrete; pieces of solid including gravel; molten solids including
a salt or blend of salts; heated liquids; or heated pressurized
vapor, such as steam; or combinations of the above. This waste heat
is provided during the operation of the solar driven reactor. When
the weather events are not blocking the sun, the sun may provide
massive amounts of excess heat, which exist in the synthesis gas
gas products coming out of that chemical reactor and need to be
rapidly quenched, generally within 0.1 to 10 seconds. This waste
heat can be captured during the quench and may be stored in a
variety of ways including those listed above in this paragraph and
used later as a heat source when the weather conditions cause the
synthesis gas supply to go low. When the synthesis gas supply is
low, the heat from the thermal storage may be used to heat the idle
methanol reactors.
[0046] In some embodiments, before a reactor train 214 goes idled,
the H2 content inside the methanol reactor may be boosted by adding
synthesis gas with a higher ratio of H2:CO from the solar driven
reactor or adding supplemental H2 from an H2 storage supply. The H2
concentration in the idled reactor(s) may be adjusted at this
point, if required, to ensure that a reducing atmosphere is
maintained within the reactor. This atmosphere allows the cyclic
operation of the methanol synthesis plant with little to no
additional loss in heterogeneous catalytic activity or throughput
over the plant's lifetime other than through aging and the
catalytic activity itself.
[0047] A multiple methanol reactor 214 system can include, for
example, at least two methanol reactors that are operable at a
percentage of maximum throughput such that the fuel synthesis
system has a dynamic range of at least 16 to 100 percent. This
gives the plant at least a 5:1 dynamic range when the reactors are
equally sized and each capable of 50% individual turn down. In
additional embodiments, the multiple methanol reactor 214 system
can include at least two methanol reactors that are operable at a
percentage of maximum throughput such that the fuel synthesis
system has a desired dynamic range. The methanol reactors may be
equally sized reactors each of equal 50% turn down or the
individual reactors may have different capacities and varying turn
down percentage from for example 100 to 1, and 100 to 20. In short,
most process will not run with 100% turn down. Typically there is
no motivation to pay the extra to have high turndown as process is
designed to run at steady state near capacity. This integrated
plant's design however, requires frequent change in output. This
increased dynamic operating range costs significant money and thus
is not an obvious alternative for a non-cycling process. Increased
dynamic operating range can require, for example, extra compressors
(of small size) etc. to operate in parallel with a normal
compressor suite. Many processes with non-desired parallel
reactions may have to operate at a given gas velocity so that there
is not time for the undesired reaction to occur. To turn such a
reactor down near 100% enhances side reaction activity and lowers
or ruins the quality of product.
[0048] FIG. 2B illustrates a diagram of an embodiment of a methanol
reactor train 250. The methanol reactor train 250 is for the cyclic
operation of the fuel synthesis section downstream of solar
synthesis gas production. Chemical reactors and their processes are
traditionally engineered to operate at constant conditions 24 hours
per day, 7 days per week. In applications such as the solar
generation of synthesis gas, however, marked variations in
synthesis gas output on a seasonal, diurnal and weather modulated
basis can occur. Processes, such as the example application, that
are downstream of the solar generation of synthesis gas can be
engineered to operate in this highly variable environment.
[0049] For example, a downstream fuel synthesis process can have
its parameters controlled to account for the cyclic supply of solar
generated synthesis gas as a feed product. Thus, the parameters
such as temperature, pressure, and chemistry of the fuel synthesis
plant can be controlled during idle non-production periods of time
so that the fuel synthesis plant may rapidly resume to fuel product
when the supply of solar generated synthesis gas resumes in
sufficient quantities.
[0050] In some examples, cyclic operation of chemical reactors 254
may be subject to highly variable feedstock flows. Additionally, a
solar driven plant may generally provide cyclic operation of the
fuel synthesis process due to the cyclic nature of the availability
of sunshine. The synthesis gas flow to the synthesis process may be
discontinued at the end of each solar day or from time to time
during the day or night. The H2 concentration in the idled
reactor(s) can be adjusted at this point, if required, e.g., to
ensure that a reducing atmosphere is maintained within the
reactor(s). This atmosphere can allow the cyclic operation of the
methanol synthesis plant with little to no loss in heterogeneous
catalytic activity or throughput over the plant's lifetime, for
example, when a conventional catalyst is used in fuel
synthesis.
[0051] The temporarily idled reactor(s) can be kept at or near the
reaction temperature with heat makeup as required to offset heat
losses. An example embodiment of this is the use of boiling water
in, for example, shell and tube reactors that can be heated from an
external boiler. Additionally, the temporarily idled reactor(s) can
be kept at or near the reaction pressure, such as within 70% of
operating reaction pressure or greater. Temperature and pressure
conditions may be specified not only to allow the rapid restart of
the reactor trains but also to assure that products or phases that
can damage equipment, product quality, catalysts, etc. do not form.
One example system can use a boiling water shell reactor or
mini-reactor with high heat removal capability to keep synthesis
system warm. The reactors can be isothermal boiling water shell and
tube reactors with the catalyst packed in the tubes. Additionally,
the fuel synthesis reactor shell can be well insulated. This
configuration can allow a fuel synthesis reactor to be maintained
at a warm idle and restarted with little consequence. Additionally,
pumps and compressors may be kept in re-circulation mode or may
also be idled and the fuel synthesis reactor restart occurs when
synthesis gas is again made available to the reactor.
[0052] In some applications, such as the solar generation of
synthesis gas, marked variations in feedstock availability, on at
least a diurnal basis, occur. Such variability may normally be
handled through feedstock storage so that a steady rate of
feedstock can be supplied to the chemical reactor. In some cases,
the cost or other problems of storage can leave no alternative but
to operate the chemical reactor on a cyclic basis.
[0053] Commercial methanol reactors are designed with the goal of
steady state operation 24 hours a day, 7 days a week. Unlike
commercial methanol reactors, some embodiments described herein may
be designed for cyclic operation. For example, some embodiments may
be designed for diurnal operation to allow for the production of
liquid fuels in solar feedstock production environments. Some
systems may operate chemical reactors in a non-batch cyclical
environment. Additionally, the example systems may idle and restart
reactors routinely and in a timely fashion and avoid the costs of
extensive feedstock storage.
[0054] Reactor construction may be tailored to specifically allow
rapid and efficient reactor cycling. Reactors and perhaps process
piping and equipment can be insulated and supplied with a means of
maintaining temperature and pressure. For example, a small boiler
or resistance heaters can provide in the boiling water shell of
tubular reactor(s) to maintain temperature. Insulation is not
required but can lower the energy costs of maintaining process
temperature during times when the reactor is not actively
processing.
[0055] Reactor operation and control algorithms may specifically
allow rapid and efficient reactor cycling. Additionally, reactor
and pump control algorithms can allow very broad dynamic range of
operations. When feedstock availability decreases beyond the
dynamic range of the reactor(s), each reactor can be warm idled by
shutting off feedstock flow and, if desired, recycle flow.
Accordingly, the reactor can be maintained at or near reaction
temperature and pressure and if required, hydrogen can be injected
to assure the gas environment remains reducing.
[0056] When feedstock is available, it can be mixed with the
recycle stream, if any, and feed into the reactor that is already
hot and at pressure. Additionally, the feed stream can be
preheated. In some embodiments, when using a boiling water shell
and tube reactor, there can be enough thermal mass in the reactor
to heat to keep the reaction zones hot enough for reaction to
begin. In the methanol case, which is exothermic, heat can be
available as a reaction by-product.
[0057] Some embodiments can provide a wide dynamic range for
chemical reactor use in solar bio-refineries. Chemical reactors
being fed by feedstocks of cyclic availability (e.g., diurnal with
cloud events) can require a wide dynamic range to continue
production under a wide variety of feedstock flow rate conditions.
Three ways to handle a variable amount of solar generated synthesis
gas being supplied as an input might be used. These ways include
(1) use of a number of parallel fuel synthesis reactors, (2) use of
storage tanks to store and supplement the supply of solar generated
synthesis gas, and (3) a hybrid of both parallel trains and a
limited amount of storage mechanisms of supplemental synthesis
gas.
[0058] Normally designed reactors are designed to generally run
24-7 at a single point and often have dynamic ranges allowing
operation from 100% to 50%. In an example solar reactor situation a
dynamic range from 100%-17% could be needed. To achieve this, a
suite of parallel reactors 254 may be treated, from an overall
control perspective, as a single reactor. Integrated local reactor
controllers vary each reactors performance to achieve the required
overall product quality and output. For example, three equal sized
reactors, each with a design turndown of 50%, can achieve a
turndown (as a set) of below 17%. Of course, depending on the size
of the individual reactors and their individual turndown ability,
the number of reactors needed to meet a specific wide dynamic range
requirement will vary anywhere from one reactor to many.
[0059] In some embodiments, each reactor in the train may be of the
same capacity or of different size capacities. The turn down range
of the overall set may be from 100-1% depending on the number of
parallel reactors used. Accordingly, systems may turn the operation
of the parallel reactors up, down, on, and off to track and balance
the variable amount of synthesis gas being supplied, controlling
the variability seen by each reactor to be within its dynamic
range, to keep the system operating during the cyclic ups and down
of the supplied synthesis gas. Further, portions of the reactor
suite may be shut down completely during certain times if
required.
[0060] These wide dynamic range suites may include of multiple
reactors, reactor(s) with multiple internal feed structures that
can be modulated, or both. Thus, multiple trains to start up and
shutdown to respond to the potentially dynamic nature of the amount
of synthesis gas feed or a single train with multiple internal
manifolds feeding different capacity zones within the single
reactor may be used.
[0061] Re-circulated end-product gas and/or tail gas fed back to
the supply input flow strategies may also be applied to assure a
smooth controlled response to variability. When operating during a
time of rapid decrease in solar generated syngas, a portion of the
output product gas (methanol) and other tail gases (CO2 and
methane) these products may be recycled back into the synthesis gas
feed into the parallel reactor trains. This control technique
allows for the hardware of the fuel synthesis reactor plant to more
gradually change up and down than the supplied solar generated
synthesis gas. The supplemental re-circulated output product gas
(e.g. methanol) and other tail gases (e.g. CO2 and Methane)
increases or decreases to make up for the swing in the supplied
solar generated synthesis gas and thereby contributes to the more
stable operation of the fuel synthesis plant.
[0062] Accordingly, some embodiments may use established fuel
synthesis techniques adapted for a variable amount of synthesis gas
fed into the process. High-pressure synthesis gas storage and
parallel trains of methanol reactors that maintain near or close to
full reaction temperature and pressure 24-7 even when no synthesis
gas is flowing to one or more of the parallel trains may be used. A
control system operating the suite of parallel reactors 254 may be
designed to tolerate transient flow of synthesis gas operation. The
control system of the process for transient synthesis gas feed can
dictate the extent of such synthesis gas storage capacity and when
it will be saved or used, how many trains will be in operation,
amount of recirculation of output gases back into the input feed,
rate at which each train is operating at, and other similar plant
parameters.
[0063] The control system and hardware designs can provide the
ability to perform routine cycling, due to the diurnal solar energy
source, of the rates of production in the methanol synthesis plant.
The synthesis gas can be stored directly in gaseous form or in
other phases via changes in temperature, pressure, chemical
reaction, absorption, etc. The solar generated synthesis gas from
the chemical reactor is compressed and fed either into a storage
system or directly into the methanol synthesis unit, depending on
the process needs at the time of production.
[0064] Solar produced, renewable, synthesis gas may be stored for
multiple uses within the solar biorefinery. For example, stored
synthesis gas may be combined 252 with clean synthesis gas from a
solar reactor for conversion to methanol. Use may occur during
start-up, during cloud events, during the night, during times of
over production or at other times. A few examples include using the
stored gas to feed or stabilize feed flow rates to compressors
during start-up or short-term cloud events and using the stored gas
to capacity buffer the amine unit or other unit operations during
cloud events. The stored synthesis gas may also feed the methanol
synthesis reactor trains during start-up, cloud events, and during
the night. Synthesis gas may be stored as a compressed gas or
absorbed into a solid, or in a liquid form.
[0065] The methanol synthesis reactors 254 can be standard boiling
water shell packed tube (Lurgi style) reactors, using a
Cu/ZnO/Al203 catalyst. The exothermic heat of reaction can be
removed by boiling water on the shell side of the reactor. The
product methanol then passes through a heat exchanger to preheat
the feed stream and two additional heat exchangers in order to
bring the temperature to an appropriate level for separations
(66.degree. C.). The product stream then enters a flash drum, where
the un-reacted synthesis gas can be separated from the raw methanol
and water products. Some of the un-reacted synthesis gas is purged
(as it contains some inert CO2 not removed by the amine system,
which would build up in the system) and it can be recompressed by a
bank of three recycle compressors (again, for turndown reasons),
after which it rejoins the feed stream from the solar process or
the synthesis gas storage area.
[0066] If this design has enough storage to store an entire year's
production of synthesis gas, a synthesis plant could be operated
similarly to current methanol synthesis operations. Due to the high
cost of compressed gas storage, this is generally not an option for
the design of some of the embodiments of this solar thermal
biorefinery. Similarly, if the methanol plant was of inconsequent
cost and had the same dynamic range as the gasifier, the entire
plant could be built to the maximum throughput (as determined by
solar energy availability) and no storage would be needed at all.
Yet this is generally not the case for either.
[0067] As a result, the configuration used in some embodiments is a
balance between the cost of excess methanol synthesis capacity and
the cost of gas storage. In one example, a storage implementation
may maintain production at summer operational capacity for
approximately 12 hours. The plant could then run 24-7 during the
summer months. In the winter, the storage could be filled over
several days time and then the synthesis operation taken out of
idle to run for an uninterrupted length of time before returning to
idle and extended storage filling.
[0068] The synthesis gas produced by the solar process is
principally comprised of hydrogen, carbon monoxide, and some
(.about.5%) carbon dioxide and water. To avoid corrosion problems
in a metal storage container, this gas should be dry or the storage
container should be coated or protected . Many options exist for
synthesis gas storage. For example, a pipeline can be used as a
very effective storage container for synthesis gas.
[0069] There are three areas of general concern when storing
synthesis gas in a pipeline or vessel: hydrogen embrittlement, CO
stress corrosion cracking and formation of iron carbonyl, the
presence of moisture, which with the carbon dioxide present in the
gas can form an acidic environment. At the specified process
conditions and using carbon steel pipe, hydrogen embrittlement is
not a pipeline failure risk. CO effects can be mitigated via a
plastic liner, which is formed in-situ in the pipeline as it is
laid. Even without the liner CO stress cracking effects can also be
mitigated by drying of the gas stream. In addition, our synthesis
gas storage temperature is low, (about 32.degree. C. with a short
term maximum of about 55.degree. C., well below the 200.degree. C.
temperature for maximum carbonyl formation. Even without a liner,
carbonyl formation rates are low enough that pipeline lifetime may
not be compromised. Catalyst risk can be mitigated by a polishing
bed. The pipeline may generally need to be protected from carbonic
acids.
[0070] For example, in a particular embodiment a pipeline might be
used for storage. At the pressures and temperatures generally used
in some embodiments, dry synthesis gas can be stored in carbon
steel pipes, using, for example, technology developed for natural
gas pipelines. In one example, the pipeline is 24 inches in
diameter and about 16 miles long and is buried around the perimeter
of the solar field. The synthesis gas is pressurized to a maximum
Psig, for example, of 3000 PSIG. In the absence of water, the
carbon dioxide component can be stored safely in these vessels.
Liquid carbonyls that may form during storage may be eliminated
with appropriate liquid traps before the gas is sent to the
synthesis side of the plant.
[0071] The pipeline may also be made from plastics, composites, or
laminates. Additionally, the pipeline may be below ground or above
ground or both. The pipeline can be used as the storage mechanism.
Additionally, absorbents such as a hydride for H2 and another
absorbent for CO may be place in the storage mechanism/pipeline may
provide the same or an even greater amount of storage capacity of
the synthesis gas while being stored at a lower pressure.
[0072] In some embodiments, the synthesis gas can be stored at 3000
psig and can be delivered to the methanol synthesis process at 1200
psig. The actual maximum storage pressure will be an economic
optimization that accounts for the reactor pressure, compression
costs, storage costs, operational demands, etc. Synthesis gas can
leave the storage tanks through an expander and heat exchanger, or
the direct synthesis gas compressor as described below and may be
mixed with recycled synthesis gas from the methanol process. The
synthesis reactor can operate with no recycle as a single pass
reactor or can operate with a variety of recycle ratios with a
preferred range being 3:1-5:1 Additionally, the blended stream can
be preheated with the waste heat from the methanol reactor product
stream and is fed to a bank of one or more methanol synthesis
reactors in parallel. The parallel ganging of methanol reactors may
allow for the dynamic range required to operate with a feed from a
solar process that essentially shuts down daily. Creating storage
capacity of the synthesis gas and idling of the methanol trains may
be used to decouple a response rate of the methanol synthesis plant
from the response rate of the solar driven chemical reactor. The
storage capacity and idling processes can be established for the
integrated solar driven chemical plant to decouple a direct
production rate of the synthesis gas generated in the solar driven
chemical reactor from the supply requirements of the methanol
synthesis plant. For example, solar produced, renewable, synthesis
gas may be stored for multiple uses within the solar biorefinery.
The stored gas is used to feed compressors during start-up, to
buffer the gas clean up units during cloud events, and to feed the
methanol synthesis reactor trains during start-up, cloud events,
and during the night. The synthesis gas is stored within a pipeline
in a fashion and utilizing technology very similar to that used by
natural gas pipelines
[0073] In some embodiments, the methanol synthesis unit can be
designed to handle 53% of the peak synthesis gas output from the
solar reactor for the proposed site. An example plant, with
appropriately sized storage, might run at near full capacity 24
hours per day during the summer months, utilizing daytime filled
storage as necessary. The rest of the year the plant may respond to
seasonal variations by tuning its production and storage rates to
provide storage that allows for 24-hour operation at reduced
throughput. There may still be weather events of extended length
that can require the warm idling of the methanol synthesis unit,
and these can be managed through intelligent design of controls and
reactor systems.
[0074] In one example, the methanol synthesis process can contain
three reactor trains 254 that can operate in controlled
synchronicity to provide the required dynamic range, including the
capability to perform warm idles. Integrated control systems allow
all portions of the plant to maintain high quality product output
in the face of both expected and unexpected variations in solar
energy. Process disruptions can be classified into three
categories, each with its own control strategy: short-term
fluctuation, nightfall, and large and extended change (including
seasonal variation).
[0075] In the event of a short-term fluctuation, e.g., a variation
or interruption in synthesis gas supply of several hours or less,
synthesis gas may be supplied from storage and/or the methanol
reactors are allowed to move within their dynamic range of stable
operation.
[0076] When nightfall occurs, the methanol unit continues at
constant operation at the output level selected by the control
system, which can be based on the available storage and the season.
In the summer, this can be at near 100% of design capacity, driven
by long days and short nights. During the winter, throughput will
generally be much lower to maintain steady operation over the
course of the long night. Alternatively, during winter or low
productivity times the storage can be filled to maximum and then
feed to the synthesis operation at a rate that allows the synthesis
operation to run at a steady rate for as long as possible before
being re-idled and the storage cycle repeated.
[0077] In one embodiment, with adequate syngas storage, a reactor
or suite of reactors may be operated within a narrow dynamic range.
The output from the solar gasifier is initially routed straight to
storage. For example, in the early morning hours when syngas flow
rates may be below the desired operational point of the reactor or
reactor suite, the low volume flow would be routed straight to
storage. After the storage reaches an appropriate level flow from
the storage and/or gasifier is directed to the synthesis reactor
which comes out of idle and operates at the desired operational
point without going through a wide dynamic range operational
ramp.
[0078] If a large and extended change in synthesis gas availability
occurs, e.g. from extended weather or an unexpected shortage of
stored synthesis gas, the control system directs a more pronounced
response directing the reactor/s to their maximum combined
turndown. In the case of three equal sized reactors, each with 50%
turndown capability, that would be a combined system turn down to
one sixth of maximum capacity. The control system determines,
within stable operational limits, how to direct the parallel
reactor trains to smoothly move to any output capacity within the
wide dynamic range of the system. Consider, for example, a
situation in which the entire system needs to run at 25% of design
capacity. Two reactors would be warm idled and the remaining
reactor would run at 75% of its capacity.
[0079] In one embodiment, the warm idle process can include using
reactors that are isothermal boiling water shell and tube reactors
with the catalyst packed in the tubes. The reactor shell can be
well insulated. This configuration may help in maintaining a
reactor at a warm idle and provide for rapid restarts. When the
control system or plant operator commands a warm idle of a specific
reactor in a methanol synthesis train, all reactor product effluent
flow can be halted. This can be simultaneously accompanied with or
followed by halting the reactor feed. The recycle flow may continue
or may be idled. The reaction of internal gas may then proceed to
equilibrium where it remains indefinitely.
[0080] The majority of this equilibrium composition is un-reacted
hydrogen, which keeps the catalyst under a reducing atmosphere.
There may be a decrease in pressure due to the consumption of a
portion of the reactants. An externally fueled package boiler may
be used to maintain the temperature of the liquid water that is
bathing the reactor tubes, maintaining the catalyst at a process
temperature that assures no condensation of products and will keep
it in a condition to immediately respond to the restoration of
fresh synthesis gas feed. Other portions of the reactor train, such
as the insulated steam drum and the recycle pumps and line, may
also be kept at temperature by the external boiler. The external
boiler might be fueled with a variety of fuels including, for
example, LPG, methanol, electricity, stored syngas, or natural gas.
When it becomes time to bring the reactor out of the idle state,
feed flow can be started at the lowest stable rate. If the recycle
was not flowing during idle, the feed flow can be accompanied by or
followed by the start of the recycle stream. The thermal mass of
the reactor may heat enough of the incoming gas to initiate
catalytic action, which accelerates the heating of the incoming
recycle steam followed by external heating of the feed gas by the
reactor effluent as the reactor returns to its operating
condition.
[0081] In some embodiments, raw methanol, which includes 3-20%
water, can be stored in, e.g., a 150,000-gallon tank that feeds the
MTG gasoline conversion process. This liquid feed can decouple the
MTG process from any of the cyclic solar process demands. The total
storage capacity for a commercial plant can be sized based on
feeder plant reliability and stability as well as down steam fuel
transportation services. The storage size may be sized to allow the
MTG plant to operate independently for whatever length of time is
desired.
[0082] The storage tanks can follow standard industrial practices
as to materials and construction. Each tank might reside above
ground and sit within a lipped concrete apron that provides for
capture and holding of unexpected spills or tank leaks allowing
safe and environmentally appropriate mitigation to occur.
Additionally, embodiments that convert the methanol to gasoline
might also include a methanol-to-gasoline unit to convert the
methanol to gasoline.
[0083] In some embodiments, a control system for the chemical
reactor sends control signals to and receives feedback from a
control system for the methanol synthesis plant. For example, some
embodiments may use a control signal from the methanol plant just
prior to idling a train is sent to the control system for the
synthesis gas chemical reactor to boost the H2:CO molarity ratio.
This can allow for time to alter synthesis gas composition
including H2:CO ratio for methanol synthesis.
[0084] FIG. 3 illustrates a diagram of an embodiment of a quenching
via an injection of cooling medium into the reaction products, gas
clean up, and particle and ash removal system 316. Direct quenching
methods of cooling the hot reaction products via for example direct
spraying of cooling mediums into the stream carrying the hot
reaction products causing the cooling of the hot reaction products
are discussed in FIG. 3. Other example methods such as annular
quenching methods of cooling the pipe carrying the hot reaction
product from the solar driven reactor via heat transfer through the
pipe are discussed, for example in FIG. 4. Features described in
one embodiment may be used in another embodiment.
[0085] The solar-driven chemical plant may directly cool the
reaction products from the effluent stream out of the solar driven
reactor. One or more spray nozzles in the quench zone 302 spray a
cooling fluid directly into the reaction product stream from the
solar driven chemical reactor. In an embodiment where the cooling
fluid is a liquid, the direct spraying of a liquid cooling fluid
into the stream carrying the hot reaction products causes the
liquid cooling fluid to vaporize into a gas. The liquid cooling
fluid, such as water, becomes a superheated vapor, such as
superheated steam, extracting the energy from the hot reaction
products.
[0086] A control system can control one or more of the following
plant parameters to ensure the temperature is at or below the
desired cooled temperature, for example, 400 C, when leaving the
quench zone 302. For example, the control system may control 1)
changes a flow rate of a cooling medium being sprayed into the hot
reaction products. Additionally, the control system may 2) provide
feedback to change the flow rate of biomass into the solar driven
chemical reactor. Additionally, the control system may 3) direct
the concentrating field to change an amount of concentrated solar
energy being directed at the aperture of solar thermal receiver.
The control system may command a combination of some or all of the
above.
[0087] Thus, the quench zone 302 may form near an exit of a
gasification reaction zone in the reactor tubes of the chemical
reactor and cool the effluent while not cracking or not thermally
affecting the reactor tubes. Two or more of the multiple reactor
tubes may form into a group at the exit. The group may combine
their reaction products and un-reacted particles from the biomass
gasification into a larger tube per group that forms a portion of
the quench zone 302 or all of the tubes may supply the reaction
products into a common manifold that forms a portion of the quench
zone 302.
[0088] The one or more sprayers such as nozzles, valves etc.,
inside the quench zone 302 inject the cooling fluid directly into
the reaction product synthesis gas stream to make the temperature
transition from the at least 1000 degree C. to 800 degrees C. or
less within the 0.1- 10 seconds to prevent metal dusting corrosion
of the pipe walls.
[0089] A particle filter removal component 316 downstream of the
quench zone 302 removes ash and other particles from the
superheated gas and hot reaction products supplied from the quench
zone 302. The particle filter removal component 316 can remove
moisture as well as chemicals that may be harmful to the Rankine
cycle engine. The hot reaction products and superheated gas can
used as a medium to drive a Rankine cycle engine, such as a
turbine, to draw the energy from the super heated vapor form of the
cooling medium and hot reaction products. The Rankine cycle engine
has an input to receive the hot reaction products and superheated
gas. The super heated vapor form of the cooling medium and the hot
reaction products after transferring their energy through the
Rankine cycle change to a saturated vapor heavy in moisture
content. The Rankine cycle engine may be inline with the process
flow of the gas stream to directly receive the hot reaction
products and superheated gas as the medium that drive the engine. A
heat exchanger may also be inline with the process flow of the gas
stream to directly receive the hot reaction products and
superheated gas as the medium exact the energy from the gas stream
and the hot effluent medium leaving the inline heat exchanger would
drive the Rankine cycle engine.
[0090] Thus, the super heated vapor form of the cooling medium and
hot reaction products after transferring their energy change states
to a saturated vapor heavy in liquid. The saturated vapor flows
through one or more knock out drums 312, 314 to dry the vapor,
which then can run an organic turbine or transfer its energy via a
steam condensing heat exchanger 304. Thus, the knockout drums 312,
314 located downstream of the Rankine engine remove entrained water
or other moisture from the synthesis gas stream supplied from the
quench zone 302. Additional heat exchangers 308, 328 may also
further cool the vapor.
[0091] In one embodiment, a solar-driven chemical reactor system
includes a sulfur remediation unit 310 downstream of the quench
zone 302. The sulfur remediation unit 310 can reduce an amount of
sulfur present in a synthesis gas stream. Such a remediation unit
310 may reduce an amount of sulfur in a synthesis gas stream,
containing at least the carbon monoxide and hydrogen molecules,
from the gasification reaction down to a level below 50 ppb of
sulfur in the synthesis gas stream.
[0092] A CO2 removal unit 318 sits behind the knockout drum and
removes CO2 from the synthesis gas stream supplied from the quench
zone 302. The CO2 content of the synthesis gas stream is reduced by
the CO2 removal unit 318 to CO2 to less than 15% and a preferred
range of 2-7% of the synthesis gas stream. Also, a sulfur
remediation unit 310 can be located downstream of the quench zone
302 to reduce an amount of hydrogen sulfide present in a synthesis
gas stream. The synthesis gas stream may contain at least the
carbon monoxide and hydrogen molecules from the gasification
reaction down to a level equal to or below 100 ppb and preferably
50 ppb of sulfur. Additionally, an amine or other
absorption/desorption like unit may remove both sulfur and CO2.
However, if the sulfur levels are below the threshold due to sulfur
removal via metal oxide particles being present in the reactor
chemical reactor and/or quenching process, then an amine or other
absorption/desorption like unit to remove both CO2 and sulfur might
be replaced with just a CO2 filter.
[0093] In an embodiment, the sulfur remediation component 310
reduces an amount of sulfur present in a synthesis gas stream down
to a level equal to or below 100 ppm. The sulfur remediation
component 310 may be located after the rapid quench zone 302 and
the particle filter removal component but before the CO2 removal
unit.
[0094] The synthesis gas coming to the compressors for storage or
the methanol plant supply is high quality synthesis gas. The
greater than 1000 degree C. temperature of the reaction products
from the chemical reactor is a high enough temperature for the
greater than 90 percent conversion of the biomass particles to
product gases and eliminates tar products to less than 200 mg/m 3
and preferably less than 50 mg/m 3. Also this renewable synthesis
gas is an unusually clean because the sulfur level is controlled,
CO2 removal occurs in the CO2 removal unit, water and other
moisture removal occurs in the knockout drums, and particle filter
removal occurs in the particle filter removal component.
[0095] In an embodiment, the synthesis gas can have total tar
concentrations below 200 mg Nm-3, catalyst poison concentrations
below 100 ppb for H2S, HCl, and NH3, and have a H2:CO ratio within
the example range 2.3 to 2.7. These compositional concentration
measurements can be taken periodically during gasifier operation
through FTIR spectroscopy and gas chromatography periodically and
measured with other detectors on a steady state basis. These
parameters may be fed to the control system to ensure that
synthesis gas composition does not vary (+/-10%) from the desired
composition, as well as to verify that catalyst poison
concentrations are not above deactivation thresholds for the
methanol synthesis catalyst. Ash measurements can be made one or
more times daily and mass balances can be performed to ensure that
overall biomass conversion remains above threshold targets and that
alkali deposits are not being formed on the inside of the
reactor.
[0096] The injection of the cooling fluid in the quench zone 302
may be controlled to also alter the chemical composition of the gas
stream necessary to achieve the proper H2 to CO ratio of synthesis
gas composition necessary for fuel synthesis, such as a 2:1 to
2.7:1 H2 to CO ratio. The controlled reactions may include one or
more of the following example reactions.
[0097] 1 ) Water injects and mixes with the reaction product
synthesis gas stream in order for an exothermic water gas-shift
reaction to occur (CO+H2O.fwdarw.CO2+H2+energy) for increasing
hydrogen and decreasing carbon monoxide.
[0098] 2) Carbon dioxide is supplied with the natural gas
entrainment gas, and/or generated in the biomass gasification
reaction and becomes part of the reaction product synthesis gas
stream in order for decreasing hydrogen and increasing carbon
monoxide in an endothermic reverse water-gas shift reaction to
occur (CO2+H2+energy.fwdarw.CO+H2O).
[0099] 3) Methane, and low temperature water injects and mixes with
the reaction product synthesis gas stream in the presence of a
catalyst to drive the endothermic steam reformation of methane to
occur (CH4+H2O+energy.fwdarw.3H2+CO) for increasing an amount of
hydrogen relative to the carbon monoxide.
[0100] In some embodiments, the methanol trains have an input
coupled to receive synthesis gas from an upstream solar driven
chemical reactor. Additionally, a downstream fuel synthesis process
can have its parameters controlled by the control system to account
for the cyclic supply of solar generated synthesis gas as a feed
product. For example, the controller may control parameters such as
temperature, pressure, and chemistry of the fuel synthesis system
during idle non-production periods of time so that the fuel
synthesis system may rapidly resume when the supply of solar
generated synthesis gas resumes in sufficient quantities to perform
fuel synthesis. For example, the fuel synthesis system may resume
fuel synthesis within from 2 to 120 seconds and preferably within
10 seconds. In slower responding systems, the, the fuel synthesis
system may resume fuel synthesis within from 10 minutes and 60
minutes depending upon how long the train has been idling and/or if
all of the trains have been idling and now one or more are coming
back to an operational state.
[0101] FIG. 4 illustrates a diagram of an embodiment of a
quenching, gas clean up, and ash removal system 400. A solar-driven
chemical reactor system may include a solar thermal receiver
aligned to absorb concentrated solar energy from one or more solar
energy concentrating fields including 1) an array of heliostats, 2)
solar concentrating dishes, and 3) any combination of the two.
[0102] An embodiment can include a solar driven chemical reactor
that has multiple reactor tubes located inside the solar thermal
receiver. In the multiple reactor tubes, particles of biomass may
be gasified in the presence of a carrier gas in a gasification
reaction. The gasification can produce reaction products that
include hydrogen and carbon monoxide gas having an exit temperature
from the tubes exceeding 1000 degrees C.
[0103] An embodiment may include one of 1) one or more apertures
open to an atmosphere of the Earth or 2) one or more windows. The
apertures or windows may be configured to pass the concentrated
solar energy from the solar energy concentrating fields into the
solar thermal receiver. The energy can impinge on the multiple
reactor tubes and cavity walls of the receiver. Additionally, the
reactor tubes serve the dual functions of 1) segregating the
biomass gasification reaction environment from the atmosphere of
the receiver and 2) transferring energy by solar radiation
absorption and heat radiation, convection, and conduction to the
reacting particles. This energy may drive the endothermic
gasification reaction of the particles of biomass flowing through
the reactor tubes.
[0104] In an embodiment, a quench zone 402 immediately downstream
of an exit of the chemical reactor may be used to immediately
quench via rapid cooling of at least the hydrogen and carbon
monoxide reaction products. The cooling might occur within 0.1-10
seconds of exiting the chemical reactor. Cooling to a temperature
of 800 degrees C. or less is possible. 800 degrees C. is below a
level to prevent metal dusting of some alloys if not cooled by the
immediate quench. Additionally, the quench may prevent coalescence
of ash remnants of the biomass particles.
[0105] An embodiment includes an exit of a gasification reaction
zone in the reactor tubes of the chemical reactor. At the exit, the
reaction products and un-reacted particles from the biomass
gasification in the multiple tubes may be joined into several large
tubes that form a portion of the quench zone 402. Additionally, a
heat exchanger 404 can also form a part of the quench zone 402. A
cooling fluid such as water/steam may be passed on an inside
through heat exchanging tubes in the annular region of the quench
zone 402 to cool the reaction product synthesis gas stream on the
outside of the heat exchanging tubes. The cooling fluid may also be
used to recuperate waste heat from the reaction product synthesis
gas stream.
[0106] Additionally, in some embodiments, the reactor tubes that
come out of the gasification reaction zone may be jacketed and make
a temperature transition from the at least 1000 degree C. to less
than 400 degrees C. A cooling fluid, such as water/steam, may be
passed through the jacket to cool the tubes containing the reaction
product synthesis gas stream making the temperature transition. In
another embodiment, a quench zone 402 design may include dumping
the reaction products from some or all the reactor tubes into a
manifold and then into central single tube.
[0107] In an embodiment, a solar-driven bio-refinery may include an
exit of a gasification reaction zone in the reactor tubes of the
chemical reactor. The exit the reaction products and un-reacted
particles from the biomass gasification in the multiple tubes can
be dumped into a manifold and then into one or more synthesis gas
tubes containing the reaction product synthesis gas stream of
reaction products and un-reacted particles.
[0108] One or more injection pipes in the quench zone 402 can be
located near the exit of the gasification reaction zone of the
reactor tubes. In the quench zone 402 low temperature water (H2O),
methane (CH4) with low temperature water and oxygen, and/or low
temperature methanol (CH3OH) can be injected into the synthesis gas
tubes and/or manifold. This can simultaneously 1) rapidly cool the
reaction product synthesis gas stream from the at least 1000 degree
C. to less than 800 degrees C. and 2) provide chemical compounds
necessary to achieve a proper H2 to CO ratio of synthesis gas
necessary for fuel synthesis. Additionally, the energy to cause the
endothermic reactions may come from heat contained in the reaction
product synthesis gas stream.
[0109] In some embodiments, a ratio from 2:1 to 2.7:1 H2 to CO may
be desired. Various chemical compounds might be used to achieve the
proper H2 to CO ratio of synthesis gas composition necessary for
fuel synthesis. For example, water might be supplied and mixed with
the hydrogen, carbon monoxide, and carbon dioxide in the reaction
product synthesis gas stream. Using water with the hydrogen, carbon
monoxide, and carbon dioxide may provide at least one of A) an
exothermic water gas-shift reaction to occur
(CO+H2O.fwdarw.CO2+H2+energy) for increasing hydrogen and
decreasing carbon monoxide, and B) an endothermic reverse water-gas
shift reaction to occur (CO2+H2+energy.fwdarw.CO+H2O) for
increasing carbon monoxide and decreasing hydrogen. In another
example, methane, low temperature water, and oxygen supplied and
mixed with the reaction product synthesis gas stream may be used to
drive the endothermic steam reformation of methane to occur
(4CH4+O2+2H2O+energy.fwdarw.10H2+4CO). This can increase an amount
of hydrogen relative to the carbon monoxide. Additionally, with
either of the above H2 to CO ratio shifting reactions, later
injecting low temperature methanol to further cool the synthesis
gas and other reaction products traveling in the quench zone.
[0110] In one embodiment, after the reactor, the quench zone 402
injects via spraying water to obtain water gas shift stages (steam
reformation) to increase CO production and for quenching between
the temperature ranges of 450 C.-750 C. The process may cause both
cooling and create the synthesis gas in the proper H2:CO ratio at
the same time. In addition, the process may also feed biomass
particles with steam and perform a water gas shift during the
gasification reaction to obtain a 2:1 to 2.7:1 H2 to CO ratio
and/or feed biomass particles with methane and perform steam
reformation to obtain the 2:1 H2 to CO ratio.
[0111] The exothermic water-gas shift reaction (WGS Reaction) is a
chemical reaction in which carbon monoxide reacts with water vapor
to form carbon dioxide and hydrogen: CO+H2O.fwdarw.CO2+H2. The
endothermic RWGS produces the resultant H2+CO molecules for the
synthesis gas. (CO2+H2.fwdarw.CO+H2O) In another variant of the
reverse water gas shift reaction, the chemical formula may be
represented as (2 CO2+3 H2+energy--.fwdarw.2 CO+3 H2O). The RWGS
may occur in the presence of a catalyst such as a Nickel alloy,
Ni/Al2O3, etc. The exit synthesis gas from with the RWGS or WGS,
may then be immediately cooled/quenched in the quench zone to
stabilize or otherwise capture the 2:1 ratio of H2 to CO.
[0112] In one embodiment, the solar-driven chemical reactor system
may include a heat exchanger 404 forming part of the quench zone
402. One or more supply pipes may introduce a cooling medium with
the reaction products. The heat exchanger 404 may introduced a
cooled medium in one or more of a tail gas of N2, CO2, low
temperature synthesis gas recycled from a storage tank, or other
similar tail gas. Additionally, the reaction products may be cooled
rapidly down to at least to 400 degrees C. to prevent metal dusting
in almost all alloys. Rapid quenching in the quench zone 402 may
also prevents abrasive carbon formation. The reaction products may
be cooled rapidly down to at least to 500 degrees C. to prevent
metal dusting in most alloys.
[0113] In some embodiments, a solar-driven chemical reactor system
may include a Brayton engine to generate to electricity. In such a
system, the quench zone 402 can have a cooling medium fed through a
heat exchanger 404 to quench and cool the reaction products exiting
the reactor. The heated cooling medium leaving the heat exchanger
404 uses recouped waste heat from the quench process to drive the
Brayton engine to generate to the electricity 406. Additional heat
exchangers 408 might also be used to provide additional cooling or
drive the Brayton engine to generate to the electricity.
Recuperated heat in a Brayton cycle engine may generate electrical
power. For example, such an engine could run on air, other gases,
or supercritical CO2, heated using waste heat, for example.
[0114] In an embodiment, a solar-driven chemical reactor system can
include one or more cooling jackets. The reactor tubes that contain
synthesis gas and other reaction products may be made of high
temperature material. The reaction products contained in the
reactor tubes may make an initial transition in the quench zone 402
to a high temperature alloy, e.g., inconnel or similar alloy.
[0115] Once the temperature of the synthesis gas and other reaction
products is low enough, the tubes carrying the synthesis gas can
make a final transition to a low temperature material, such as
stainless steel thru to carbon steel, etc. A cooling jacket can
cover at least a portion of the reactor tubes, which aids in the
quench and also allows the use of lower temperature tolerant
transition materials to carry the synthesis gas and reaction
products downstream of the chemical reactor in the quench zone
402.
[0116] An embodiment of the solar-driven chemical reactor system
includes a pneumatic biomass feed system to feed the particles of
biomass in a CO2 gas or steam carrier gas to the reactor tubes of
the solar driven chemical reactor. A heat exchanger 404 in the
quench zone 402 may be used to quench and cool the reaction
products exiting the reactor tubes. Additionally, the heat
exchanger 404 can be fed with a cooling medium. The cooling medium
can carry waste heat away from the quenching exits the heat
exchanger 404.
[0117] A counter flow heat exchange may be used to receive the
cooling medium. Waste heat carried away by this cooling medium
might be used to pre-heated the biomass particles are up to a
maximum temperature of 400 degrees C. prior to entry into the
chemical reactor by the carrier gas. For example, the carrier gas
can be heated by the cooling medium carrying the waste heat of the
reaction products in the counter flow heat exchanger.
[0118] In an embodiment, the solar-driven chemical reactor system
includes a pneumatic biomass feed system to grind and pulverize
biomass to a particle size controlled to an average smallest
dimension size between 50 microns (um) and 2000 um. These particles
may have a general range of between 200 um and 1000 um.
Additionally, the pneumatic biomass feed system may supply a
variety of non-food stock biomass sources fed as particles into the
solar driven chemical reactor. The variety of non-food stock
biomass sources can include three or more types of biomass that can
be fed, individually or in combinational mixtures. Some examples of
non-food stock biomass sources include rice straw, corn stover,
switch grass, non-food wheat straw, miscanthus, orchard wastes,
forest thinnings, forestry wastes, energy crops, source separated
green wastes and other similar biomass sources. The biomass sources
can be in a raw state or in a partially torrified state, as long as
a few parameters, including particle size of the non-food stock
biomass and operating temperature range of the reactor tubes are
controlled including.
[0119] In one embodiment, a feed-forward and feedback control
system can be configured to manage predicted changes in available
solar energy as well as actual measured stochastic changes in
available solar energy. The control system balances the
gasification reaction between biomass feed rate and an amount of
concentrated solar energy directed at the apertures or windows of
the solar thermal receiver to the control temperature of the
chemical reaction.
[0120] A control system can be used to balance operations of the
reactors within the reactor suite to achieve a smoothly varying and
wide dynamic range to accommodate seasonal and diurnal variations
in feedstock availability. Reactors may be warm idled and/or
restarted frequently and a multifaceted control system may be used
to more quickly stabilize the output of a restarted reactor.
[0121] The system may control the temperature to keep the reaction
temperature high enough for greater than 90 percent conversion of
the biomass to product gases. The system may also control the
temperature to provide for elimination of tar products to less than
200 mg/m 3 and preferably less than 50 mg/m 3. Additionally, the
temperature may also be controlled to keep it at a low enough
reactor tube wall temperature to not structurally weaken the walls
or significantly reduce receiver efficiency. For example, a
temperature of less than 1600 degrees C. might be used.
[0122] In an embodiment, the solar thermal receiver may have an
indirect radiation driven geometry. For example, the indirect
radiation driven geometry may be in the form of an absorbing,
integrating cavity, of the solar thermal receiver. An inner wall of
the cavity and the reactor tubes exchange energy primarily by
radiation, not by convection or conduction. Exchanging energy
primarily by radiation may allow for the reactor tubes to achieve a
fairly uniform temperature profile even though the concentrated
solar energy is merely directly impinging on the reactor tubes from
one direction. Additionally, the radiation heat transfer from the
inner wall and the reactor tubes can be the primary source of
energy driving the gasification reaction in which the small biomass
particles act as millions of tiny absorbing surfaces of radiant
heat energy coming from the inner wall and the tubes.
[0123] In an embodiment, the solar driven chemical reactor can have
a downdraft geometry. Such a geometer has multiple reactor tubes in
a vertical orientation. These tubes are located inside the solar
thermal receiver. Additionally, the multiple reactor tubes in this
chemical reactor design increase available reactor surface area for
radiative exchange to the biomass particles as well as inter-tube
radiation exchange. The tubes may also function to isolate a
reacting environment inside the tubes from the cavity receiver
environment outside the tubes. In some embodiments, high heat
transfer rates of the walls and tubes allow the particles biomass
to achieve the high enough temperature necessary for substantial
tar destruction and complete gasification of greater than 90
percent of the biomass particles into reaction in a very short
residence time between a range of 0.01 and 5 seconds.
[0124] In an embodiment of a downdraft geometry, the biomass
particles fall through the downdraft reactor to substantially
eliminate an undesirable build-up of product on the tube walls in
the reaction zone. Buildup could lead to reduced heat transfer and
even clogging of the tube because of the pressure and gravity
pulling the particles through the reaction zone of the reactor
tube. Additionally, low surface area to volume ratios may provide
less surface area for the material to sticking. In some
embodiments, ash fusion and deposition may not be a problem due to
short residence time in some downdraft reactor systems.
[0125] In one embodiment, a solar-driven chemical reactor system
includes an ash and particle storage mechanism. In such a system,
un-reacted biomass particles and ash remnants of the biomass exit
the solar driven chemical reactor at the greater than 1000 degrees
C.
[0126] A separator may be configured to separate the particles and
ash remnants from the gas products of the reaction products into
the ash and particle storage mechanism. Some example systems may
store these un-reacted biomass particles and ash remnants to
extract their heat, This heat may be used to heat a working fluid,
gaseous, or solid medium that drives an electricity generation
apparatus or other apparatus used in doing heat based processes
such as thermodynamic work, preheating water, preheating gas
streams, etc.
[0127] In one embodiment, a solar-driven chemical reactor may
include a sulfur removal sorbent 410. The sulfur removal sorbent
410 may be present in the biomass gasification process or initially
introduced in the quench zone, to reduce an amount of sulfur
present in a synthesis gas stream exiting the quench zone.
[0128] In one embodiment, a series of sintered porous stainless
steel metal filters 412, 414 to remove particulates from the
synthesis gas stream exiting the quench zone may be used. The
particulates can be sent to an ash holding vessel. In such a vessel
the particulates can be staged for removal to be used as a soil
additive, as the particulates contain only biologically derived
materials and gypsum from the sulfur removal sorbent.
[0129] In one embodiment, a solar-driven chemical reactor system
includes a sulfur remediation unit 410 downstream of the quench
zone 402. The sulfur remediation unit 410 can reduce an amount of
sulfur present in a synthesis gas stream. Such a remediation unit
410 may reduce an amount of sulfur in a synthesis gas stream,
containing at least the carbon monoxide and hydrogen molecules,
from the gasification reaction down to a level below 50 ppb of
sulfur in the synthesis gas stream.
[0130] In one embodiment, a dual stage cyclone filters can be
located before the sulfur remediation unit to allow un-reacted
biomass recycling with cyclone separation. A first heavy cyclone
stage can be constructed to remove heavy particles and a second
lighter cyclone stage can be constructed to remove lighter
particles consisting mainly of un-reacted biomass. The
substantially particle-free synthesis gas then passes into the
sulfur remediation unit.
[0131] In one embodiment, a solar-driven chemical reactor system
may include a synthesis gas stream including the carbon monoxide
and hydrogen molecules that come out from the quench zone 402. A
knockout drum may be located downstream of the quench zone. The
knockout drum may be used to remove entrained water from the
synthesis gas stream supplied from the quench zone.
[0132] A particle filter removal component 416 may be located
downstream of the quench zone 402 where ash and other particles are
removed from the synthesis gas stream supplied from the quench
zone. Additionally, a CO2 removal unit 418, such as an amine acid
gas removal unit, may sit behind the knockout drum. Such a CO2
removal unit 418 removes CO2 from the synthesis gas stream supplied
from the quench zone. For example, CO2 content of the synthesis gas
stream may be reduced by the CO2 removal unit to CO2 being less 5%
of the synthesis gas stream.
[0133] FIG. 5 illustrates a diagram of an embodiment of a multiple
stage compressor system. In such a system, a solar driven reactor
502 for synthesis gas can produce synthesis gas from bio-particles
using solar energy to break down the bio-particles. A compressor
set 504, 510, 512 pressurizes synthesis gas in different stages in
the plant. For example, some embodiments might include at least
three stages of compressors 504, 510, 512. A first low-pressure
stage 504 may be located in a synthesis gas clean up portion of a
system just prior to an amine step. The low-pressure stage may be
less than 750 PSIG. In other embodiments, the low-pressure stage
may be less than 250 PSIG. In still other embodiments, the
low-pressure stage may be less than 100 PSIG. The first compressor
504 feeds the synthesis gas stream to the COS cleanup 506 and CO2
and sulfur remediation units 508, such as an amine plant. The
pressure may be for example 100 PSIG.
[0134] A higher pressure 750-1200 PSIG stage 510 for injecting
cleaned up solar generated synthesis gas into a common input into
the methanol process may be located. The second compressor 510
directly feeds synthesis gas to a methanol synthesis unit and
brings the pressure to that required for methanol synthesis.
[0135] The third stage compressor 512 may be used for pumping
excess synthesis gas from the solar chemical reactor into a high
pressure 2000-3000 PSIG storage tank. Generally, the compressor
will re-circulate synthesis gas from the storage tank 516 as a way
to maintain an idle state but be ready to operate 24 hours a
day.
[0136] A synthesis gas storage unit 516 may exist to account for
diurnal events placed before a CO2 and sulfur removal plant 508.
The synthesis gas storage buffer 516 before the CO2 and sulfur
plant 508 allows for the CO2 and units to be significantly smaller
in size/capacity. For example, the synthesis gas storage unit 516
is sized to handle peak daytime synthesis gas flow for the location
of the system, whereas the CO2 and sulfur unit 508 removes CO2 and
sulfur to required levels for synthesis of methanol and may be
sized for 50-85% flow. The synthesis gas may be re-circulated
through these CO2 and sulfur remediation units 508 to place the
sulfur and CO2 levels in the synthesis gas into acceptable limits.
In an embodiment, the synthesis gas storage unit 516 is sized to
operate the methanol synthesis plant 514 for 1 hour at 100 percent
peak output without receiving supplemental synthesis gas coming out
of the solar driven chemical reactor 502.
[0137] The synthesis gas exits the storage vessels 516 or the
synthesis gas compressor 510 to enter the methanol synthesis unit
514. Methanol is a chemical with formula CH3OH (often abbreviated
MeOH). It is the simplest alcohol, and is a flammable fuel and can
be stored as a liquid at normal temperatures. In one example of
methanol synthesis, the Carbon monoxide, Carbon dioxide, and
hydrogen in synthesis gas react on a catalyst to produce methanol.
A widely used catalyst is a mixture of copper, zinc oxide, and
alumina. As an example, at 5-10 MPa (50-100 atm) and 250.degree.
C., it can catalyze the production of methanol from the carbon
oxides and hydrogen with high selectivity according to the overall
reaction:
CO+2 H.sub.2.fwdarw.CH.sub.3OH
[0138] The methanol synthesis consumes 2 moles of hydrogen gas for
every mole of carbon monoxide. One way of dealing with the excess
hydrogen if it exists is to inject carbon dioxide into the methanol
synthesis reactor, where it, too, reacts to form methanol according
to the overall equation:
CO.sub.2+3 H.sub.2.fwdarw.CH.sub.3OH+H.sub.2O
[0139] In an embodiment, the control system may supply synthesis
gas with higher amount of CO2 when the trains are running and no
idling is expected. However, the control system may supply
synthesis gas with lower amount of CO2 and H2 rich ratio when
idling of the methanol reactor plants is anticipated.
[0140] The methanol synthesis unit 514 may consist of standard
shell and tube Lurgi style methanol reactors. This is a well-known
process and is operated on very large scales (millions of gallons
of methanol per year) worldwide. However, this methanol synthesis
unit 514 may be operated on a cyclic basis. The methanol synthesis
process operates at an example 4:1 recycle ratio and converts 96%
of the synthesis gas to methanol. The raw methanol is distilled
from the entrained water product and fed to a standard
methanol-to-gasoline (MTG) unit, where an example 97% of the
methanol is converted to gasoline and LPG, with a ratio of 4.8
gallons of gasoline per gallon of LPG. The LPG and C-2 hydrocarbons
can be burned to preheat the recycle stream in the MTG plant and to
generate electricity to support plant operations. Additionally,
methanol may be stored in methanol storage 518 or re-circulated as
needed, for example, when idling.
[0141] As discussed above, multiple methanol reactor trains can be
operated in parallel from a common input of 1) synthesis gas from
either 1) a solar driven chemical reactor and 2) synthesis gas from
a storage tank or a combination of both. The fuel synthesis portion
of the control system controls the operation of the multiple trains
by potentially idling one or more of the methanol reactor trains
based on feedback from the amount of synthesis gas being generated
by the solar driven chemical reactor, which is subject to marked
variations in volume of synthesis gas output based on a seasonal,
diurnal and weather effects. Thus, the multiple methanol reactor
trains are individually controllable to be cycled between the idle
state and the operational state due to the variable amount of
synthesis gas being fed into the process from the solar driven
chemical reactor.
[0142] The downstream fuel synthesis process can have its
parameters controlled to account for the cyclic supply of solar
generated synthesis gas as a feed product. Thus, the methanol
synthesis control system may control parameters including
chemistry, temperature, and pressure of the methanol synthesis
plant during idle non-production periods of time so that the
methanol synthesis plant may rapidly resume to generating product
methanol when the supply of solar generated synthesis gas resumes
in sufficient quantities. Additionally, the methanol synthesis
control system may control parameters including chemistry,
temperature, and pressure of the methanol synthesis plant during
idle non-production periods of time so that the methanol synthesis
plant has little to no loss in catalytic activity or throughput
over the plant's lifetime. This allows for the protection of the
catalyst, as long as the synthesis gas and product methanol gas are
kept at a certain temperature and pressure, then the gases remains
vaporized and does not condense on the catalyst prolonging the life
of the catalyst.
[0143] As discussed, the multiple methanol reactor trains may be
operated in parallel from an input supplied with syngas from either
1) the solar driven chemical reactor 2) from a syngas storage unit,
or a combination of both. The operation of the multiple trains is
controlled by potentially 1) idling one or more of the methanol
reactor trains or 2) reducing the output of one or more of the
methanol reactor trains based on feedback from the amount of
synthesis gas being generated by the solar driven chemical reactor,
which is subject to marked variations in volume of syngas output
based on a seasonal, diurnal and weather effects. Thus, the
multiple methanol reactor trains are individually controllable to
be cycled between the idle state and some percentage of maximum
throughput in the operational state due to the variable amount of
syngas being fed into the process from the solar driven chemical
reactor.
[0144] In some embodiments, wide dynamic range compressor use in
solar bio-refineries can be used. A suite of compressors, with
their appropriate control system(s), can allow for flexible wide
range turn down. Compressors may use re-circulation and other
strategies as well as direct turndown to achieve a flexible suite
output. Additionally, compressors may be of various sizes and may
be organized in both a serial and parallel fashion to achieve the
compression pressure and volume required.
[0145] In some embodiments, a controller may be used to control
operation of the multiple methanol trains. For example, the control
system may potentially idle one or more of the methanol reactor
trains based on theamount of synthesis gas being generated by the
solar driven chemical reactor. The amount of synthesis gas being
generated is subject to marked variations in volume of synthesis
gas output based on a seasonal, diurnal and weather effects.
Accordingly, the multiple methanol reactor trains are idled as
needed based on a variable amount of synthesis gas fed into the
process.
[0146] In some embodiments, the controller may control various
parameters including temperature and pressure during cyclic
operation of the fuel synthesis system, including cyclic operation
of the methanol synthesis plant. This may provide for little to no
loss in catalytic activity or throughput over the plant's lifetime
allowing for the protection of the catalyst. For example, the
catalyst may be protected by keeping the synthesis gas and product
methanol gas at a certain temperature and pressure such that the
gases remain vaporized and does not condense on the catalyst,
prolonging the life of the catalyst.
[0147] In some embodiments, the control system comprises control
algorithms that control reactor operation. For example, the control
algorithms may allow rapid and efficient reactor cycling by using
synthesis gas from a solar driven chemical reactor. The control
algorithms may use synthesis gas from a storage tank to allow for
rapid and efficient reactor cycling. The control algorithms may
also use recycling synthesis gas and methanol product gas from the
outlet of the reactor trains to keep at least one of the trains
operating at some percent of its maximum throughput. Additionally,
the control system may also keep any idle reactors at or near
reaction temperature and pressure during the daily operation. The
compressor control system can also be designed for using different
types of compressors, operating compressors at potentially
different pressure, etc.
[0148] The control system may also control parameters including
temperature, pressure, and chemistry of a fuel synthesis system
during idle non-production periods of time so that the fuel
synthesis system may rapidly resume fuel product when the supply of
solar generated synthesis gas resumes in sufficient quantities to
perform fuel synthesis. Additionally, in some embodiments, the
control system may control compressors in a fuel synthesis system.
This can assist in controlling pressure in the cyclic
operations.
[0149] In some embodiments, the control system may control
temperature of a reactor train when the reactor train is
temporarily idled. This can be done so that an idled reactor is
kept at or near a reaction temperature with heat makeup as required
to offset heat losses. These losses might be offset using heat from
boiling water heated from an external boiler or with heat from the
methanol synthesis reaction.
[0150] In some embodiments, the control system controls a
temperature of a reactor train when the reactor train is
temporarily idled, such that the idled reactor is kept at or near a
reaction temperature with waste heat from other areas of the plant
including the quenching operation on the synthesis gas coming out
of the solar driven chemical reactor.
[0151] It will be understood by those of skill in the art that the
multiple parallel methanol reactor trains and the control system
described above is an example system. The systems and methods
described herein may also be applied to Fischer-Troupe processes,
solid chemistry approaches, etc. to, for example, provide for
cyclic operation. Accordingly, in other embodiments, Fischer-Troupe
processes, solid chemistry approaches, etc., may include multiple
parallel reactors and these reactors might be kept at or near
reaction temperature and pressure when idle to allow for a quicker
startup. Additionally, various storage devices might be used to
allow for recirculation of materials during idling periods.
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