U.S. patent application number 12/179499 was filed with the patent office on 2009-03-26 for biomass energy conversion apparatus and method.
Invention is credited to Arthur M. Shulenberger, Mark Wechsler.
Application Number | 20090077892 12/179499 |
Document ID | / |
Family ID | 40470206 |
Filed Date | 2009-03-26 |
United States Patent
Application |
20090077892 |
Kind Code |
A1 |
Shulenberger; Arthur M. ; et
al. |
March 26, 2009 |
BIOMASS ENERGY CONVERSION APPARATUS AND METHOD
Abstract
Method and apparatus are disclosed to utilize the energy in
biomass (waste agricultural products). The inventive method and
apparatus utilized heat and mass flow to efficiently generate a
variety of products from biomass. In various embodiment, the
invention may generate a liquid fuel (such as methanol or dimethyl
ether), pure liquid CO2 (intended for CO2 sequestration), a soil
enhancement product (intended to return to the agricultural site),
process heat, and/or electricity. In one embodiment, the process
requires no external energy inputs, and preserves a large
percentage (ie. >50%) of the energy contained in the biomass. In
another embodiment, the inventive method and apparatus can
selectively be operated to produce electricity and or liquid
fuels.
Inventors: |
Shulenberger; Arthur M.;
(Millbrae, CA) ; Wechsler; Mark; (San Mateo,
CA) |
Correspondence
Address: |
STEVEN VOSEN
1563 SOLANO AVENUE #206
BERKELEY
CA
94707
US
|
Family ID: |
40470206 |
Appl. No.: |
12/179499 |
Filed: |
July 24, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60952506 |
Jul 27, 2007 |
|
|
|
Current U.S.
Class: |
48/62R ;
48/197R |
Current CPC
Class: |
C10J 3/66 20130101; Y02E
50/18 20130101; C10L 5/44 20130101; C10J 2300/1671 20130101; Y02E
50/10 20130101; Y02E 20/185 20130101; Y02E 50/32 20130101; C10J
2300/1846 20130101; C10J 2300/1665 20130101; C10L 9/083 20130101;
C10J 2300/0916 20130101; C10J 2300/0903 20130101; Y02E 20/18
20130101; C10J 2300/0959 20130101; C10J 2300/1678 20130101; Y02E
50/15 20130101; C10J 3/00 20130101; Y02E 50/30 20130101 |
Class at
Publication: |
48/62.R ;
48/197.R |
International
Class: |
C10J 3/00 20060101
C10J003/00 |
Claims
1. A method of operating a biomass energy conversion system, said
method comprising: receiving a biomass; selectively generating
output from the biomass energy conversion system, where said output
is one or more of electric power or liquid fuel; and providing said
output.
2. The method of claim 1, where said biomass energy conversion
system includes a biomass gasification unit to accept a biomass and
produce a gas, an electric power generator and a fuel synthesis
reactor, and where said selectively generating includes selectively
providing said gas to said electric power generator or said fuel
synthesis reactor.
3. The method of claim 2, where said method includes exchanging
heat from said electric power generator to at least a portion of
said fuel synthesis reactor.
4. The method of claim 2, where said method further includes
generating products of biomass gasification by thermally reacting
said biomass.
5. The method of claim 4, where said generating further includes
pyrolyzing the biomass.
6. The method of claim 5, where said generating further includes
partially oxidizing the pyrolyzed biomass.
7. The method of claim 3, where said method further includes
exchanging heat from said electric power generator or said fuel
synthesis reactor to heat the biomass.
8. The method of claim 1, where said biomass is rice straw.
9. An apparatus for generating either electric power or liquid fuel
from a biomass, said apparatus comprising: a biomass gasification
unit to accept biomass and produce a gas stream; a generator to
produce electric power from said gas stream; a synthesis unit to
produce a liquid fuel from said gas stream; and one or more valves
to selectively provide said gas stream to one or more of said
generator or said synthesis unit, where said one or more valves
controls the amount of electric power and the amount of liquid fuel
provided from the biomass.
10. The apparatus of claim 9, further comprising a heat exchanger
to provide thermal energy from said generator to said synthesis
unit.
11. The apparatus of claim 9, where said gasification unit includes
a torrefaction unit, and where said apparatus further includes a
heat exchanger to provide thermal energy from said generator or
said synthesis unit to said torrefaction unit.
12. A method for utilizing biomass, said method comprising: a
torrefaction process; one or more additional processes; and
providing heat from at least one of said one or more additional
processes to said torrefaction process.
13. The method of claim 12, where said method produces a synthetic
fuel, and where said one or more additional process is a fuel
synthesis process.
14. An apparatus for utilizing a biomass comprising: an oxygen
separation unit to produce oxygen-enriched gases from air; a
partial oxidation unit to accept a biomass stream and said
oxygen-enriched gases; and a thermoelectric generator, where said
thermoelectric generator accepts heat from said partial oxidation
unit and provides electricity for at least partially operating said
oxygen separation unit.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/952,506, filed Jul. 27, 2007, the entire
contents of which are hereby incorporated by reference herein and
made part of this specification.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention generally relates to the utilization
of energy from biomass, and more particularly to a method and
system that is capable of converting crop residues into one or more
of a liquid fuel, electrical power or process heat.
[0004] 2. Discussion of the Background
[0005] The prospect of converting biomass in the form of
agricultural products and/or waste into fuels or energy is
appealing, and is seen as a possible route to energy independence.
Many such materials are considered to be waste or are disposed of
in a manner that poses environmental problems. One such practice is
the burning of agricultural waste, such as crop residues, in the
field. Since the waste generally contains minerals taken up from
the soil to the plant, this process is beneficial to the soil.
However, burning these residues releases CO.sub.2 and pollutants
into the air, and is often prohibited. The term "crop residue" as
used herein refers, without limitation, to materials left in the
field after a crop has been harvested, or left after the processing
of the crop into a usable resource.
[0006] While there is great interest in using crop residue for
producing liquid fuels or power, there is as yet no generally
useful or economic means for doing so. One problem with utilizing
crop residue, is that the cellulosic materials in the residuals are
notoriously difficult to refine into fuels. Thus, for example, many
prior art reactors for converting biomass into fuels result in tar,
ash, and soot. Tar can negatively effect the performance of the
conversion and the reactors, and generally must be removed before
fuel synthesis. Ash may form slag in the reactor, and must be
purged and disposed of at temperatures below their melting point.
Soot reduces the quantity of any gases produced in the reactor. In
addition, other problems in converting biomass to fuels include the
high energy input needed to produce synthesis gas of sufficient
quality to be used for liquid fuel synthesis, and the high capital
cost associated with production of O.sub.2 gas, if it is to be used
in the process.
[0007] Thus there is a need in the art for a method and apparatus
that permits for the production of liquid fuels from crop residue.
Such a method and apparatus should be cost efficient, energy
efficient, and operable on a wide variety of feedstocks, including
but not limited to crop and crop residue. The method and apparatus
should also be exhibit of one or more of the following features:
the removal of trapped atmospheric gases from the feedstock prior
to processing; the separation of most or all of the carbon dioxide
that is not formed into a liquid fuel; the easy removal of tars or
other compounds from the apparatus; have low emissions of oxides of
nitrogen and sulfur compounds; the ability to provide one or more
of electric power, process heat, or liquid fuels; and utilize
energy efficiently within the process.
BRIEF SUMMARY OF THE INVENTION
[0008] In certain embodiments, the disadvantages of prior art are
overcome by a method or apparatus which may include one or more of
the following features: 1) gasifying the feedstock sequentially at
increasing temperatures; 2) forming process oxygen from ambient
air; 3) reacting the feedstock with oxygen; 4) providing heat for
feedstock gasification from a fuel synthesis process; 5) reacting
the gasified feedstock with water to produce a favorable
hydrogen-to-carbon monoxide ratio, and then removing the carbon
dioxide and excess water to produce a mixture useful for a
conversion to fuels; 6) combining the oxidizing gas with water
and/or recirculating evolved gasses to achieve the proper
stoichiometry for hydrogen rich synthesis gas; 7) producing an
oxygen rich gas using surplus thermal energy from partial
oxidation; 8) removing and sequestering or utilizing the carbon
dioxide from the biomass; 9) a flash cooling step to prevent soot
formation; 10) providing the heat required for air separation from
a gas cooling process; and an efficient and cost effective method
for disposal of agricultural waste.
[0009] In certain embodiments, a method is provided for operating a
biomass energy conversion system. The method includes receiving a
biomass, selectively generating output from the biomass energy
conversion system, where the output is one or more of electric
power or liquid fuel, and providing the output.
[0010] In certain other embodiments, an apparatus is provided for
generating either electric power or liquid fuel from a biomass. The
apparatus includes a biomass gasification unit to accept biomass
and produce a gas stream, a generator to produce electric power
from the gas stream, a synthesis unit to produce a liquid fuel from
the gas stream, and one or more valves to selectively provide said
gas stream to one or more of said generator or said synthesis unit.
The one or more valves control the amount of electric power and the
amount of liquid fuel provided from the biomass.
[0011] In certain embodiments, a method for utilizing biomass is
provided. The method includes a torrefaction process, one or more
additional processes, and providing heat from at least one of said
one or more additional processes to said torrefaction process.
[0012] In certain other embodiments, an apparatus is provided for
utilizing a biomass. The apparatus includes an oxygen separation
unit to produce oxygen-enriched gases from air; a partial oxidation
unit to accept a biomass stream and the oxygen-enriched gases; and
a thermoelectric generator. The thermoelectric generator accepts
heat from the partial oxidation unit and provides electricity for
at least partially operating the oxygen separation unit.
[0013] Certain other embodiments of a biomass to fuel conversion
system or process may include, but are not limited to, one or more
of the following: 1) the production of oxygen; 2) energy recovery
from the system to produce oxygen or nitrogen depleted air; 3) the
use of oxygen, or nitrogen depleted air as the oxidizer; 4) the
removal of trapped ambient nitrogen from the biomass; 5)
effectively remove tars and other buildup from the system; 6) a
system that facilitates sequestering or using the CO2 from the
biomass; 7) utilizing several conversion steps, some of which are
endothermic and some of which are exothermic, and efficiently using
energy by transferring heat from exothermic to endothermic process
steps; and 8) operating one of the conversion steps according to
the following competing reactions by recirculating gases and/or
adding water: a) C+CO.sub.2.fwdarw.2 CO; b)
C+H.sub.2O.fwdarw.CO+H.sub.2; c) C+2
H.sub.2O.fwdarw.CO.sub.2+2H.sub.2; d)
CO+H.sub.2O.fwdarw.CO.sub.2+H.sub.2; e)
CH.sub.4+2H.sub.2O.fwdarw.CO.sub.2+4H.sub.2; 9) prevention of soot
formation from the unwanted reverse reaction of 8a)
2CO.fwdarw.C+CO.sub.2.; 10) Mixing the oxidizer with steam and
introducing this mixture as the oxidizer with the benefit of
improved thermal uniformity in the partial oxidation reaction; 11)
Mixing the oxidizer with steam and recirculated expressed
hydrocarbon gasses, thus partially oxidizing these gases prior to
introduction to the gassifier, resulting in improved thermal
uniformity in the gassifier and improved synthesis gas composition;
or 12) utilizing the ash content of the gasified biomass product as
an inert, thermal transfer medium, and controlling the ash volume
in the gassifier.
[0014] Advantages over the prior art may include, but are not
limited to: a) integration of oxygen production from air with the
system; 2) providing for carbon dioxide sequestration; 3)
eliminating nitrogen and/or argon contamination from the system; 4)
incorporation of a cleaning cycle; 5) providing a smaller scale
process with good efficiency and economics; 6) increasing the
carbon conversion efficiency and fuel output by effectively using
heat generated in the process; 7) lowering the temperature required
to achieve proper synthesis gas composition; 8) provide for
opportunistic electrical generation; 9) provide process heat for
general use, for instance in HVAC systems; 10) reducing the
operating and maintenance costs; and 11) increasing the amount of
biomass that may be processed and/or reducing the processing
time.
[0015] In certain embodiments, the fuel produced is methanol. The
methanol can be used, for example, as a transportation fuel or in
hydrocarbon processing. The carbon dioxide from the system may be
used to enhance oil recover or otherwise be sequestered or
utilized
[0016] In certain other embodiments, the fuel produced is DME
(dimethylether). The DME can be used, for example, as a
transportation fuel or as a propellant. The carbon dioxide from the
system may be used to enhance oil recover or otherwise be
sequestered or utilized
[0017] In certain embodiments, the fuel is produced in conjunction
with electricity. For instance, when fuel demand is low,
electricity can be produced and sold. Alternatively, when consumer
electricity demand is high, electrical production may have higher
value. A real time electro-mechanical system to monitor and
configure the optimum product mix reduces operating labor while
optimizing the economic value. The carbon dioxide from the system
may be used to enhance oil recover or otherwise be sequestered or
utilized. In one embodiment, the relative output levels of fuel and
electricity is monitored and the system is automatically configured
to match the application needs.
[0018] These features together with the various ancillary
provisions and features which will become apparent to those skilled
in the art from the following detailed description, are attained by
the method or apparatus of the present invention, preferred
embodiments thereof being shown with reference to the accompanying
drawings, by way of example only, wherein:
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0019] FIG. 1 is a schematic diagram of the interaction of
agriculture with the environment;
[0020] FIG. 2 is a schematic of a first embodiment biomass energy
conversion apparatus;
[0021] FIG. 3 is a schematic of a first embodiment of a process for
a biomass energy conversion apparatus;
[0022] FIG. 4 is a schematic of a second embodiment of a process
for a biomass energy conversion apparatus;
[0023] FIG. 5 is a schematic of a third embodiment of a process for
a biomass energy conversion apparatus;
[0024] FIG. 6 is a graph showing results of calculations of the
process of FIG. 5 at a constant pressure and variable partial
oxidation process temperature;
[0025] FIG. 7 is a schematic of a fourth embodiment of a process
for a biomass energy conversion apparatus;
[0026] FIG. 8 is a graph showing results of calculations of the
process of FIG. 7 at a constant pressure and variable partial
oxidation process temperature; and
[0027] FIG. 9 is a schematic of a fifth embodiment of a process for
a biomass energy conversion apparatus.
[0028] Reference symbols are used in the Figures to indicate
certain components, aspects or features shown therein, with
reference symbols common to more than one Figure indicating like
components, aspects or features shown therein.
DETAILED DESCRIPTION OF THE INVENTION
[0029] The present invention may be understood from a systems
approach to agriculture, and in particular to FIG. 1, which is a
schematic diagram showing the interaction of a prior art
agricultural system 100 with the environment. Plants within system
100 utilize CO.sub.2 from the air and nutrients from the soil,
water from the environment and energy from the sun to produce
O.sub.2, crops, and non-crop residue. A simplified overall chemical
balance may be written as:
6CO.sub.2(gas)+12H.sub.2O.sub.(liquid)+photons.fwdarw.C.sub.6H.sub.12O.s-
ub.6(aqueous)+6O.sub.2(gas)+6H.sub.2O.sub.(liquid)
The crop residue includes carbon compounds such as cellulose,
hemicellulose, and lignin. Rice straw, for example, has a
stoichiometry of CH.sub.1.77 O.sub.0.72. The crop residue typically
has little or no nutritional value, and is either is burnt to
fertilize the soil or is disposed of. Examples are presented herein
with a crop residue of rice straw. These examples are for
illustrative purposes only, and are not meant to be limiting of the
scope of the present invention.
[0030] FIG. 2 is a schematic of a first embodiment biomass energy
conversion apparatus 200. Apparatus 200 includes an oxygen
production unit 210 and a thermochemical conversion unit 220. Also
shown in FIG. 2 is the flow of air, water, and crop residue into
apparatus 200, and the flow of nitrogen, argon, a fuel, carbon
dioxide, and fertilizer from apparatus 200. Although FIG. 2 shows
oxygen production unit 210 and thermochemical conversion unit 220,
in certain embodiments, portions of the units are integrated or
shared.
[0031] Biomass energy conversion apparatus 200 may work in
conjunction with prior art agricultural process 100 to convert
agricultural crop residue into useful products including, but not
limited to, one or more of a fuel, electric power, fertilizer, or
process heat. The fuel may be, for example and without limitation,
a liquid fuel, such as methanol or dimethyl ether. In addition,
apparatus 200 may also produce concentrated streams of nitrogen
and/or carbon dioxide, which may be used for industrial purposes
or, in the case of carbon dioxide, sequestered to remove it from
the environment.
[0032] In one embodiment, one or more components of air are
separated within oxygen production unit 210. Thus, for example,
unit 210 accepts air from the environment and generates oxygen, or
alternatively oxygen-enriched air, for use as an oxidizer in
thermochemical conversion unit 220. The nitrogen may be a waste
stream of unit 210 or, alternatively, some or all of the nitrogen
may be provided to unit 220 for inclusion in a fertilizer.
[0033] Thermochemical conversion unit 220 accepts oxygen from unit
210, water, and crop residue (such as crop residue from prior art
agricultural process 100) and produces three streams: a fuel,
carbon dioxide, and fertilizer, which includes minerals from the
crop residue. It is preferred, though not necessary, for the fuel
to be transportable in a liquid state--that is it is predominantly
liquid at ambient conditions or under easily achievable elevated
pressures and/or reduced temperatures. In another embodiment, some
or all of the fuel is consumed within unit 220 to generate electric
power.
[0034] In one embodiment, oxygen production unit 210 and
thermochemical conversion unit 220 are integrated, so that heat
and/or work from thermochemical conversion process 220 drives some
or all of the oxygen production unit 210. In another embodiment,
grid electricity is used to power oxygen production unit 210 and
thermochemical conversion unit 220 generates electricity which is
returned to the electric grid. Alternatively, biomass energy
conversion apparatus 200 operates independent of the electric
grid.
[0035] In one embodiment, apparatus 200 converts crop residue,
including but not limited to rice straw, to methanol or dimethyl
ether, pure liquid CO.sub.2, and a soil enhancement product formed
by ash from the conversion process. In another embodiment,
apparatus 200 requires no external energy inputs, and preserves a
large percentage (i.e. .about.50%) of the energy contained in the
biomass.
[0036] As an example of fuel synthesis reactions which may take
place as part of thermochemical conversion unit 220, the overall
reaction for the synthesis of methanol from glucose is the
exothermic reaction:
C.sub.6H.sub.12O.sub.6(solid)+3/2O.sub.2(gas).fwdarw.3CH.sub.3OH.sub.(li-
quid)+3 CO.sub.2(gas); .DELTA.H=-634.12 MJ/Kmol.
In this reaction, 50% of the carbon is converted to methanol.
Approximately 78% of the energy content is retained in the methanol
since the heat of combustion of glucose, given by
C.sub.6H.sub.12O.sub.6(solid)+6O.sub.2(gas).fwdarw.6CO.sub.2(gas))+6H.su-
b.2O.sub.(liquid).DELTA.H=-2,813.52 MJ/Kmol,
is approximately 78% of the the heat of combustion of methanol:
3CH.sub.3OH.sub.(liquid)+9/2O.sub.2(gas).fwdarw.3CO.sub.2(gas)+6H.sub.2O-
.sub.(liquid).DELTA.H=-2,179.4 MJ/Kmol
In addition, the partial oxidation of the glucose can provides the
energy to drive the conversion process.
[0037] For rice straw, the overall reaction is similar, but
involves many sequential intermediate reactions. A chemical
description of rice straw follows, and a process to economically
convert rice straw to methanol and CO.sub.2 will be described.
Ideally this equipment will be located close (<30 miles) to the
rice fields, to minimize transportation costs and losses.
[0038] Rice straw is a combination of cellulose, hemicellulose and
lignin and mineral compounds (ash). As an example, 1 tonne of dry
rice straw includes 70% hydrocarbons and 20% ash and 10% water.
Thus a tonne of dry, ash free rice straw contains 28 kmol of
elemental carbon. More specifically, the stoichiometry and mass
fraction of ash free rice straw is given in Table I, and the energy
content is calculated in Table II. The stoichiometry of rice straw
may be represented as CH.sub.1.77O.sub.0.72(solid), and the energy
content is 15.413 kJ/g.
TABLE-US-00001 TABLE I Composition of Rice Straw Fraction Dry
Compound stoichiometry C H O N Mass Cellulose 6 12 5 0 37%
Hemi-cellulose 5 10 5 0 24% Lignin 10 12 3 0 14% Protein (less S,
P) 11 18 4 3 5% Approximate error 1 -4 0 0 1%
TABLE-US-00002 TABLE II Energy Content of Rice Straw Energy (HHV)
Value Calculation C 0.3968 .times. 34.91 = 13.854 H 0.0497 .times.
117.83 = 5.857 O 0.3578 .times. -10.34 = -3.700 S 0.0040 .times.
10.05 = 0.040 N 0.1600 .times. -1.51 = -0.242 ash 0.1878 .times.
-2.11 = -0.396 15.413 kJ/g
[0039] FIG. 3 is a schematic of a first embodiment of a process 300
for a biomass energy conversion apparatus which may be, for example
and without limitation, biomass energy conversion apparatus 200.
Process 300 shows the energy and mass flow and includes an oxygen
separation process 310 and a thermochemical conversion process 320.
As described in further detail subsequently, process 320 converts
biomass into a gas mixture of H.sub.2 and CO having a molar ratio
of 2:1 such that the methanol synthesis process 327 can generate
methanol (CH.sub.3OH).
[0040] Thermochemical conversion process 320 includes a biomass
preparation process 321, a torrefaction process 322, a pyrolysis
process 323, a partial oxidation process 324, a water shift process
325, a carbon dioxide removal process 326, and a methanol synthesis
process 327. One or more of processes 310, 321, 322, 323, 324, 325,
326, and 327 may be carried in one or more individual apparatus,
and/or one or more individual apparatus may carry out one or more
of the processes. In one embodiment oxygen separation process 310
is carried out by oxygen separation unit 210 and thermochemical
conversion process 320 is carried out by thermochemical conversion
unit 220.
[0041] An indication of representative, though not limiting,
materials flowing into and out of 310, 321, 322, 323, 324, 325,
326, and 327 are indicated in FIG. 3. The materials indicated are
illustrative for biomass, and other components may be present.
[0042] Also shown of representative, though not limiting, energy or
power flows are several additional arrows in FIG. 3. The flow of
heat from methanol synthesis process 327 into torrefaction process
322 is indicated as Q1, and the flow of heat from partial oxidation
process 324 into a pyrolysis process 323 is indicated as Q2. It is
understood that there may be other heat flows into and out of the
various processes in addition to Q1 and Q2, which are shown for the
purposes of discussion of several aspects of the present
invention.
[0043] Typically, processes 310, 321, 322, 323, and 326 are
endothermic (requiring the input of energy to operate), and
processes 324 and 325 are exothermic (generating excess heat). FIG.
3, 4, 5, 7, and 9, which each show processes, do not explicitly
show all of the energy balances for each process. In general, the
present invention includes the exchange of thermal or electric
power between components to maximize the thermal efficiency of the
overall process.
[0044] Biomass preparation process 321 prepares the biomass by
drying and/or compressing the biomass prior to thermal conversion.
In the embodiment in FIG. 3, biomass is heated and compressed in
biomass preparation process 321, converting biomass to compressed
biomass, at a low or slightly elevated temperature, T0. Compression
reduces the volume of biomass and squeezes out any trapped
air--specifically nitrogen gas which may interfere with process
320. In one embodiment, temperature T0, is greater than the ambient
temperature. In another embodiment, temperature T0 is greater than
100.degree. C., or is approximately 150.degree. C. The elevated
temperature evaporates the water, drying the biomass. The apparatus
to carry out biomass preparation process 321 may include devices
commonly used for solid handling applications in the food
processing industry, or specialty devices developed for biomass
power applications.
[0045] The compressed biomass undergoes torrefaction in
torrefaction process 322 at low temperature, T1. In one embodiment,
the equipment to operate torrefaction process 322 may be insulated
pipe, or an insulated pipe with an internal auger to move material.
The output of the torrefaction process 322 includes, in one
embodiment, the torrefaction products of biomass, which may include
torrefaction products of hemicellulose such as CO.sub.2, H.sub.2O
and acetic acid, and de-polymerized solids such as cellulose and
lignin, with some solids remaining. In one embodiment, T1 is
between 200.degree. C. and 300.degree. C. In another embodiment, T1
is approximately 230.degree. C. In another embodiment, the
temperature T1 is maintained by heat transfer Q1 from methanol
synthesis process 327, which, as described subsequently, may
operate at a higher temperature T5.
[0046] The gas and solid products from torrefaction process 322
then undergo pyrolysis in pyrolysis process 324 at a temperature
T2, which is greater than temperature T1. In one embodiment, during
pyrolysis, de-polymerized cellulose and lignin are converted in
torrefaction process 322 to C(s), CO, CO.sub.2, H.sub.2O, and
hydrocarbon gases. In one embodiment, the temperature T1 is between
approximately 400.degree. C. and approximately 750.degree. C. In
another embodiment, the temperature T2 is maintained by heat
transfer Q2 from partial oxidation process 324, which, as described
subsequently, may operate at a higher temperature T3. In one
embodiment, the equipment to operate the pyrolysis process 324 may
be an insulated pipe with provision for gas exchange and
counterflow.
[0047] In oxygen separation process 310, air is separated into an
oxygen fraction and an oxygen-depleted air fraction. In one
embodiment, the energy for process 310 (not shown in FIG. 3) is
obtained from exothermic reactions occurring in process 320, such
as from the partial oxidation process 324. In another embodiment,
an apparatus for carrying out oxygen separation process 310 may
include cryogenic equipment, such as the Apsen 1000 manufactured by
Cosmodyne, Inc. (Seal Beach, Calif.). In yet another embodiment,
the oxygen separation process 310 may be accomplished by using a
PSA (Pressure Swing Absorption) or VPSA (Vacuum Pressure Swing
Absorption) plant, such as manufactured by Universal Industrial
Gasses, Inc.
[0048] In partial oxidation process 324, the oxygen and the gas and
solid products from pyrolysis process 323 are partially oxidized,
producing ash and CO.sub.2, CO, H.sub.2O, and H.sub.2. The ash is
removed, producing a stream of CO.sub.2, CO, H.sub.2O, and H.sub.2.
The ash includes mineral content, as such may be useful for
treating soil. In one embodiment, the equipment that operates
partial oxidation process 324 may include a furnace, such as
furnaces routinely manufactured for the coal power industry.
[0049] Water shift process 325 accepts gases from partial oxidation
process 324 and water, and operates at a temperature T4. The water
shift reaction is a well-known reaction that converts carbon
monoxide and water to carbon dioxide and hydrogen through the
reaction: CO+H.sub.2O.fwdarw.CO.sub.2+H.sub.2. Preferably, the
amount of water added to the water shift process 325 is sufficient
to result in a H.sub.2:CO ratio of 2:1, which is an advantageous
proportion for use in methanol synthesis process 327. Specifically,
the amount of H.sub.2O added is selected to shift some of the CO to
H.sub.2, and give the 2:1 ratio of H.sub.2 to CO.
[0050] In CO2 removal process 326, gases from water shift process
325 are compressed to a pressure of 50 bars, which liquefies the
CO.sub.2 for easy separation from the remaining H.sub.2 and CO. In
one embodiment, the energy required to operate CO2 removal process
326 is obtained from the exothermic partial oxidation process 324.
The CO.sub.2 thus removed may be used commercially or used to
enhance oil recovery or otherwise sequestered. In one embodiment,
the equipment to operate the CO2 removal process 326 may include a
condenser and compressor.
[0051] Lastly, methanol synthesis process 327 accepts material from
CO2 removal process 326 and produces methanol. Specifically,
H.sub.2 and CO undergo conversion to methanol at a temperature T5
according to the reaction:
CO.sub.(gas)+2H.sub.2(gas).fwdarw.CH.sub.3OH.sub.(liquid).
[0052] In certain embodiments, the energy required to drive the
endothermic processes (torrefaction process 322, pyrolysis process
323, Biomass preparation process 321, and oxygen separation process
310) may be obtained from the exothermic processes (partial
oxidation process 324 and methanol synthesis process 327). In the
previous discussion, energy from methanol synthesis process 327 is
sufficient to operate torrefaction process 322, and energy from
partial oxidation process 324 is sufficient to operate the
pyrolysis process 323, the oxygen separation process 310, and the
carbon dioxide removal process 326.
[0053] From an energy and mass balance of the system of FIG. 3, and
it has been determined that process 300 achieves: 1) a 50% carbon
to methanol conversion; 2) a 50% carbon to CO.sub.2 conversion; 3)
retention of 75% of the original biomass energy content in the
methanol; and 4) the production of 565 liters of methanol for each
dry tonne of rice straw.
[0054] FIG. 4 is a schematic of a second embodiment of a process
400 for a biomass energy conversion apparatus which may be, for
example and without limitation, biomass energy conversion apparatus
200. Process 400 is generally similar to process 300, except as
explicitly discussed below.
[0055] In process 400, oxygen from oxygen separation process 310 is
provided to partial oxidation process 324 and a pyrolysis process
423. The energy to drive the pyrolysis reactions in pyrolysis
process 323, which was, for example supplied by Q2 in processes
300, is supplied by exothermic reactions between oxygen and the
other gases entering the pyrolysis. Thus, for example, the
equipment to carry out pyrolysis process 432 includes a burner to
combust oxygen to increase the temperature of the pyrolysis process
to a value of T2.
[0056] Also in process 400, heat in the amount of Q3 is provided
from partial oxidation process 324 to a thermal electric generator
401, which powers oxygen separation process 310. Some of the power
from the thermal electric generator 401 may alternatively be
provided to biomass preparation process 321.
[0057] FIG. 5 is a schematic of a third embodiment of a process 500
for a biomass energy conversion apparatus which may be, for example
and without limitation, biomass energy conversion apparatus 200.
Process 500 is generally similar to processes 300 and/or 400, and
includes a thermochemical conversion process 520 which is generally
similar to processes 320, except as explicitly discussed below.
Specifically, process 500 has components that may be configured to
achieve different outputs from a biomass stream and in which
electricity is chosen as the primary output.
[0058] Process 520 includes an electric generator 501, heat
exchange processes 503 and 505, a condenser process 507 and a
compression process 509. Process 520 converts biomass into
electricity in electric generator 501, which requires an energy
rich stream that does not have to have the specific concentrations
required of a fuel synthesis reaction. Process 520 therefore does
not require a water shift process to obtain specific molar ratios,
as does methanol synthesis process 327
[0059] The input biomass flow is indicated in FIG. 5 as M.sub.1,
the prepared biomass as M.sub.2, the torrifacted biomass as
M'.sub.1, the partially oxidized gases as M.sub.3, the electric
generator effluent as M.sub.4. The heat flow from heat exchange
processes 505 to biomass preparation process 321 is Q'1, the heat
flow from heat exchange processes 505 to compression process 509 is
Q4, and the external power into biomass preparation process is
E.sub.1e. The heat flow from heat exchange processes 503 to
torrefaction process 322 is Q1. Electric generator 501 provides
electric power E.sub.3e to the oxygen separation process 310 and
E.sub.e as electric power production of process 500.
[0060] Oxygen is separated from air in oxygen separation process
310. In one embodiment, the separation is cryogenic, and the energy
to run process 310 is obtained from electric power provided by
electric generator 501. One example of such cryogenic equipment is
the Apsen 1000 manufactured by Cosmodyne, Inc (Seal Beach, Calif.).
The cryogenically produced oxygen and oxygen-depleted air are
obtained at high pressure, and energy can be recovered from these
streams in a turbine (not shown). This energy can be used, for
instance, to cool the cold side of the electric generator 501. In a
second embodiment, the energy required for selectively removing
nitrogen from air, producing a gas essentially comprised of 95%
O.sub.2 and 5% Ar, at low pressure, is obtained from the electric
generator 501. One example of a low-pressure system is a PSA
(Pressure Swing Absorption) or VPSA (Vacuum Pressure Swing
Absorption) plant, such as manufactured by Universal Industrial
Gases, Inc. (Easton, Pa.).
[0061] The gases from partial oxidation process 324 are sent to the
electric generator 501. In one embodiment, electric generator 501
operates according to an IGCC process (Chevron Corp, San Ramon,
Calif.), and can provide very high efficiency (ie. 50%). In another
embodiment, electric generator 501 is a steam generator, with the
steam being heated by combustion of the partially oxidized gases.
Electric generators are commonly available and the technology
choice will be determined by the scale of the overall system. In
either case, flue gases (stream M.sub.4 in FIG. 5) will be
generated by electric generator 501. The flue gases are then
preferably cooled in heat exchange processes 503 and 505 and
condenser process 507 and compressed compression process 509 to
remove liquid CO.sub.2 at a pressure of 10 bars, which liquefies
the H.sub.2O for easy separation from the remaining CO.sub.2. In
one embodiment, the energy required to operate the processes 507
and 509 is obtained from the electric generator 501. The CO.sub.2
may be used commercially or used to enhance oil recovery or
otherwise sequestered.
[0062] In certain embodiments, the energy required to drive the
endothermic processes (torrefaction process 322, pyrolysis process
323, biomass preparation process 321, and oxygen separation process
310) may be obtained from the exothermic processes (partial
oxidation process 324 and methanol synthesis process 327). In the
previous discussion, energy from methanol synthesis process 327 is
sufficient to operate torrefaction process 322, and energy from
partial oxidation process 324 is sufficient to operate the
pyrolysis process 323, the oxygen separation process 310, and the
carbon dioxide removal process 326.
[0063] An energy and mass balance of the embodiment and
configuration of FIG. 5 has determined that process 500 achieves:
1) a 100% carbon to CO.sub.2 conversion; 2) conversion of 25% of
the original biomass energy content into electricity.
[0064] FIG. 6 is a graph 600 showing results of equilibrium
calculations corresponding to the process of FIG. 5. Specifically,
graph 600 shows species fractions exiting partial oxidation process
324 at various temperatures T3 from 0 C to 1000 C, while the
pressure is 1 bar.
[0065] Table III shows details of the results for the conversion of
biomass (the "Input Species") to gases exiting partial oxidation
process 324 at a temperature T3 of 800 C, which the approximate
temperature at which the gasses exiting partial oxidation process
324 contain no hydrocarbons.
TABLE-US-00003 TABLE III Partial Oxidation Process Gases for
Process 500 at a Partial Oxidation Temperature of 800 C. Temper.
Amount Amount Amount Latent H Total H .degree. C. kmol kg Nm.sup.3
MJ MJ INPUT SPECIES (1) Formula H2O (g) 120.000 1.110 19.997 24.879
3.57 -264.86 C6H10O4 (ADAg) 120.000 4.790 700.023 107.361 87.46
-4055.10 O2 (g) 25.000 9.580 306.549 218.339 0.00 0.00 OUTPUT
SPECIES (1) Formula H2O (g) 800.000 4.905 88.365 109.939 142.75
-1043.41 CO2 (g) 800.000 5.861 257.941 133.579 219.30 -2087.03 CO
(g) 800.000 22.803 638.721 519.708 550.35 -1970.32 H2 (g) 800.000
20.003 40.323 458.205 456.90 456.90 CH4 (g) 800.000 0.076 1.221
1.706 3.37 -2.31 Kmol kg Nm.sup.3 MJ MJ BALANCE: 38.168 0.002
872.557 1281.64 -327.21
[0066] FIG. 7 is a schematic of a fourth embodiment of a process
700 for a biomass energy conversion apparatus which may be, for
example and without limitation, biomass energy conversion apparatus
200. Process 700 is generally similar to processes 300, 400, and/or
500, and includes a thermochemical conversion process 720 which is
generally similar to processes 320, except as explicitly discussed
below.
[0067] Process 700 includes an oxidizer/steam mixing process 701, a
flash cooler process 703 and heater 705, condensing process 707 and
a first compression process 709 to remove carbon dioxide, a second
compression process 711, and an optional DME synthesis process
713.
[0068] Oxygen produced by the oxygen separation process 310 is
combined with a predetermined volume of steam in the oxidizer/steam
mixing process 701 and then provided to the partial oxidation
process 324. By combining H.sub.2O and O.sub.2 as an oxidizer, the
ratio of CO:H.sub.2 in the resulting synthesis gas can be optimized
for methanol synthesis stoichiometry, eliminating the need for a
water shift process as, for example, in process 300. Alternatively,
process 700 may be run with no or minimal water entering the
oxidizer mixing unit, and an water shift reaction processor such as
process 325. In either case, adding the H.sub.2O converts carbon
monoxide and water to carbon dioxide and hydrogen through the
reaction: CO+H.sub.2O.fwdarw.CO.sub.2+H.sub.2. Preferably, the
amount of water added to oxidizer/steam mixing processor 701 (water
shift process 325) is sufficient to result in a H.sub.2:CO ratio of
2:1, which will be needed in methanol synthesis process 327. In one
embodiment, steam is added at approximately 400-600.degree. C. This
steam is generated in the heater 705, which has an input of
recycled water, which is expressed and separated in the condensing
process 707, and is approximately the proper volume to achieve the
desired synthesis gas composition. The recycled H.sub.2O stream is
heated to produce steam by a counterflow heat exchanger coupling
the H.sub.2O stream to the POX output gas stream. It is important
that this heat exchange process cool the synthesis gas sufficiently
quickly to eliminate the formation of soot through the unwanted
reaction 2CO.fwdarw.C(s)+CO.sub.2.
[0069] The cooled gases from flash cooler 703 are then condensed
(phase separating the H.sub.2O) and compressed to 7-10 bars, which
liquefies the CO.sub.2 for easy separation from the remaining
H.sub.2 and CO. In one embodiment, the energy required to operate
condensing process 707 is obtained from the exothermic partial
oxidation process 324. In a second embodiment, the energy required
is supplied from grid electricity. The CO.sub.2 may be used
commercially or used to enhance oil recovery or otherwise
sequestered.
[0070] As an alternative embodiment, the methanol can be further
processed to DME in the optional DME synthesis process 713 to
provide a diesel alternative with a higher energy density than
methanol, and which may also be more appropriate for farming
equipment and trucking. This DME is produced according to the
reaction:
2CH3.sub.2OH.sub.(liquids).fwdarw.CH.sub.3OCH.sub.3(liquid)+H.sub.2O.sub-
.(liquid)
[0071] In one embodiment, the equipment to operate the DME
synthesis process 713 may be a DME Reactor, such as manufactured
for the coal-to-liquid industry.
[0072] Based on system simulations of the energy and mass balance
of the system of FIG. 7, it has been determined that process 700
achieves: 1) .about.50% carbon to methanol conversion; 2)
.about.50% carbon to CO2 conversion; 3) retention of 75% of the
original biomass energy content in the fuel; and 4) the production
of 565 liters of methanol for each dry tonne of rice straw.
[0073] FIG. 8 is a graph 800 showing results of equilibrium
calculations corresponding to the process of FIG. 7. Specifically,
graph 800 shows species fractions exiting partial oxidation process
324 at various temperatures T3 from 0 C to 1000 C, while the
pressure is 1 bar, including steam provided from oxidizer/steam
mixing process 701.
[0074] Table IV shows details of the results for the conversion of
biomass (the "Input Species") to gases exiting partial oxidation
process 324 at a temperature T3 of 800 C, which the approximate
temperature at which the gasses exiting partial oxidation process
324 contain no hydrocarbons.
TABLE-US-00004 TABLE IV Results for Process 700 at a partial
oxidation temperature of 800 C. Temper. Amount Amount Amount Latent
H Total H .degree. C. kmol kg Nm.sup.3 MJ MJ INPUT SPECIES (1)
Formula H2O (g) 500.000 34.051 613.436 763.205 578.36 -7656.05
C6H10O4 (ADAg) 120.000 4.790 700.023 107.361 87.46 -4055.10 O2 (g)
25.000 9.580 306.549 218.339 0.00 0.00 OUTPUT SPECIES (1) Formula
H2O (g) 800.000 29.000 522.441 649.994 843.96 -6168.98 CO2 (g)
800.000 14.700 646.944 335.031 550.04 -5234.48 CO (g) 800.000
14.000 392.146 319.077 337.89 -1209.69 H2 (g) 800.000 29.000 58.458
664.298 662.41 662.41 CH4 (g) 800.000 0.000 0.000 0.000 0.00 0.00
kmol kg Nm.sup.3 MJ MJ BALANCE: 38.279 -0.018 879.494 1728.48
-239.60
[0075] In certain embodiments, the components of the various
embodiments may be combined in a single device, and the selection
of components for operation may be selected for specific outputs.
Thus, for example, apparatus for carrying out process 500 provides
for the production of electricity, and apparatus for carrying out
process 300, 400, or 700 provides for the production of liquid
fuels. In this way, a plant may be operated to economic advantage,
such as by producing electricity at high electricity demand and
producing liquid fuels ad low electricity demand.
[0076] FIG. 9 is a schematic of a fifth embodiment of a process 900
for a biomass energy conversion apparatus which may be, for example
and without limitation, biomass energy conversion apparatus 200.
Process 900 is generally similar to processes 300, 400, 500 and/or
700, except as explicitly discussed below.
[0077] Process 900 includes a includes a thermochemical conversion
process 920 that further includes a biomass-to-gas generation
process 921, a fuel synthesis process 923, and an electric
generation process 925. Oxygen from oxygen separation process 310
and biomass are provided to biomass-generation process 921. The
flow of material from process 921 is then controlled by valves V1
and V2 to flow to one or more of fuel synthesis process 923 or
electric generation process 925. As shown in FIG. 9, heat Q from
electric generation process 925 may flow to fuel synthesis process
923. This heat flow may maintain the fuel synthesis components at a
temperature necessary to produce fuel the instant the flow diverts
gas through fuel synthesis process 923.
[0078] In one embodiment, biomass-generation process 921 includes
biomass preparation process 321, torrefaction process 322,
pyrolysis process 323, and partial oxidation process 324. In
another embodiment, biomass-generation process 921 includes thermal
generator process 401.
[0079] In one embodiment, fuel synthesis process 923 includes water
shift process 325, carbon dioxide removal process 326, methanol
synthesis process 327, as in FIG. 3, and optionally DMI synthesis
process 713. In another embodiment, fuel synthesis process 923
includes oxidizer/steam mixing process 701, flash cooler process
703 and heater 705, condensing process 707 and first compression
process 709, second compression process 711, and an optional DME
synthesis process 713, as in FIG. 7.
[0080] In one embodiment, electric generation process 925 includes
electric generator 501, heat exchange processes 503 and 505,
condenser process 507 and compression process 509 as in FIG. 5.
[0081] Reference throughout this specification to "one embodiment"
or "an embodiment" means that a particular feature, structure or
characteristic described in connection with the embodiment is
included in at least one embodiment of the present invention. Thus,
appearances of the phrases "in one embodiment" or "in an
embodiment" in various places throughout this specification are not
necessarily all referring to the same embodiment. Furthermore, the
particular features, structures or characteristics may be combined
in any suitable manner, as would be apparent to one of ordinary
skill in the art from this disclosure, in one or more
embodiments.
[0082] Similarly, it should be appreciated that in the above
description of exemplary embodiments of the invention, various
features of the invention are sometimes grouped together in a
single embodiment, figure, or description thereof for the purpose
of streamlining the disclosure and aiding in the understanding of
one or more of the various inventive aspects. This method of
disclosure, however, is not to be interpreted as reflecting an
intention that the claimed invention requires more features than
are expressly recited in each claim. Rather, as the following
claims reflect, inventive aspects lie in less than all features of
a single foregoing disclosed embodiment. Thus, the claims following
the Detailed Description are hereby expressly incorporated into
this Detailed Description, with each claim standing on its own as a
separate embodiment of this invention.
[0083] Thus, while there has been described what is believed to be
the preferred embodiments of the invention, those skilled in the
art will recognize that other and further modifications may be made
thereto without departing from the spirit of the invention, and it
is intended to claim all such changes and modifications as fall
within the scope of the invention. For example, any formulas given
above are merely representative of procedures that may be used.
Functionality may be added or deleted from the block diagrams and
operations may be interchanged among functional blocks. Steps may
be added or deleted to methods described within the scope of the
present invention.
* * * * *