U.S. patent application number 12/063757 was filed with the patent office on 2010-07-15 for method and system for hydrolytic saccharification of a cellulosic biomass.
This patent application is currently assigned to KAWASAKI PLANT SYSTEMS KABUSHIKI KAISHA. Invention is credited to Noriaki Izumi, Takeshi Nagahama.
Application Number | 20100175690 12/063757 |
Document ID | / |
Family ID | 39324537 |
Filed Date | 2010-07-15 |
United States Patent
Application |
20100175690 |
Kind Code |
A1 |
Nagahama; Takeshi ; et
al. |
July 15, 2010 |
Method and System for Hydrolytic Saccharification of a Cellulosic
Biomass
Abstract
A method and system for hydrolyzing cellulose and/or
hemicellulose contained in a biomass into monosaccharides and
oligosaccharides by using high-temperature and high-pressure water
in a subcritical condition is provided. In hydrolyzing cellulose or
hemicellulose into saccharides by using high-temperature and
high-pressure water in a subcritical condition, a large amount of
slurry is cooled into a condition below the subcritical condition
by subjecting the slurry contained in a pressure vessel under a
high-temperature and high-pressure condition to flash evaporation
in a pressure vessel charged with a slurry of a cellulosic biomass
and heated halfway. It is possible to prevent saccharides from
degrading into organic acids and to save energy by recovery of
thermal energy. The cellulosic biomass is charged into a
water-permeable vessel and then the water-permeable vessel is
encapsulated into the pressure vessel together with water.
Inventors: |
Nagahama; Takeshi; (Hyogo,
JP) ; Izumi; Noriaki; (Hyogo, JP) |
Correspondence
Address: |
MARSHALL, GERSTEIN & BORUN LLP
233 SOUTH WACKER DRIVE, 6300 WILLIS TOWER
CHICAGO
IL
60606-6357
US
|
Assignee: |
KAWASAKI PLANT SYSTEMS KABUSHIKI
KAISHA
Kobe-shi
JP
|
Family ID: |
39324537 |
Appl. No.: |
12/063757 |
Filed: |
October 23, 2007 |
PCT Filed: |
October 23, 2007 |
PCT NO: |
PCT/JP2007/070600 |
371 Date: |
February 1, 2010 |
Current U.S.
Class: |
127/37 ;
127/1 |
Current CPC
Class: |
Y02P 20/59 20151101;
C12P 2201/00 20130101; C07H 3/06 20130101; C13K 1/02 20130101; C07H
3/04 20130101; C08J 2301/00 20130101; C08J 3/00 20130101; C07H 3/02
20130101 |
Class at
Publication: |
127/37 ;
127/1 |
International
Class: |
C13K 1/02 20060101
C13K001/02; B01J 3/04 20060101 B01J003/04 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 26, 2006 |
JP |
2006-291194 |
Claims
1. A method of hydrolytic saccharification of a cellulosic biomass
with use of plural pressure vessels, the method comprising a
charging step, a heating-up step, a hydrolyzing step, a temperature
lowering step, and a discharging step, which are performed
sequentially by each of said pressure vessels, wherein: said
charging step is a step of charging a slurry prepared by grinding
said cellulosic biomass and then mixing said cellulosic biomass
thus ground with water into each of said pressure vessels; said
heating-up step is a step of hermetically closing the pressure
vessel and heating up said slurry; said hydrolyzing step is a step
of hydrolyzing cellulose and/or hemicellulose contained in said
cellulosic biomass into saccharides by an oxidative power of
high-temperature and high-pressure water; said temperature lowering
step is a step of flash-evaporating the high-temperature and
high-pressure slurry contained in the pressure vessel to lower the
temperature thereof; said discharging step is a step of removing
the slurry out of the pressure vessel; while any one of said plural
pressure vessels performs said charging step, any one of the other
pressure vessels performs said discharging step so as to allow heat
exchange to occur between the slurry to be charged into the
pressure vessel performing the charging step and the slurry to be
discharged from the pressure vessel performing said discharging
step; and while any one of said plural pressure vessels performs
said heating-up step, any one of the other pressure vessels
performs said temperature lowering step and allows heat recovery to
be made by supplying flash vapor discharged from the pressure
vessel performing the temperature lowering step to the pressure
vessel performing the heating-up step.
2. A method of hydrolytic saccharification of a cellulosic biomass
with use of plural pressure vessels, the method comprising a
charging step, a heating-up step, a hydrolyzing step, a temperature
lowering step, and a discharging step, which are performed
sequentially by each of said pressure vessels, wherein: said
charging step is a step of charging said cellulosic biomass into a
water-permeable vessel and then encapsulating said water-permeable
vessel and water into each of said pressure vessels; said
heating-up step is a step of hermetically closing the pressure
vessel and heating up said cellulosic biomass and water; said
hydrolyzing step is a step of hydrolyzing cellulose and/or
hemicellulose contained in said cellulosic biomass into saccharides
by an oxidative power of high-temperature and high-pressure water;
said temperature lowering step is a step of flash-evaporating
high-temperature and high-pressure water contained in the pressure
vessel to lower the temperature thereof; said discharging step is a
step of removing said water and said water-permeable vessel out of
said pressure vessel; while any one of said plural pressure vessels
performs said charging step, any one of the other pressure vessels
performs said discharging step no as to allow heat exchange to
occur between water to be charged into the pressure vessel
performing said charging step and high-temperature water to be
discharged from the pressure vessel performing said discharging
step; and while any one of said plural pressure vessels performs
said heating-up step, any one of the other pressure vessels
performs said temperature lowering step and allows heat recovery to
be made by supplying flash vapor discharged from the pressure
vessel performing said temperature lowering step to the pressure
vessel performing said heating-up step.
3. The method according to claim 1, wherein equal time is required
to complete respective of all the five steps and the number of the
pressure vessels used is a multiple of five.
4. The method according to claim 1, wherein: equal time is required
to complete respective of all the four steps other than said
hydrolyzing step; the time required to complete said hydrolyzing
step is n times (where n is a natural number) as long as the time
required to complete each of the other four steps; and the number
of the pressure vessels used is a multiple of (4+n).
5. The method according to claim 1, wherein said hydrolyzing step
is performed at a temperature of not lower than 140.degree. C. and
not higher than 180.degree. C. to hydrolyze hemicellulose into
saccharides.
6. The method according to claim 2, wherein said hydrolyzing step
is performed at a temperature of not lower than 140.degree. C. and
not higher than 180.degree. C. to hydrolyze hemicellulose into
saccharides.
7. The method according to claim 5, wherein: the slurry resulting
from said discharging step is subjected to solid-liquid separation;
a slurry comprising a solid content obtained after dissolution of
hydrolyzed hemicellulose in water is prepared; the slurry obtained
after the solid-liquid separation is subjected to said charging
step again; and said hydrolyzing step is performed at a temperature
of not lower than 240.degree. C. and not higher than 280.degree. C.
to hydrolyze cellulose into saccharides.
8. The method according to claim 6, wherein said water-permeable
vessel having been subjected to said discharging step is subjected
to said charging step again and said hydrolyzing step is performed
at a temperature of not lower than 240.degree. C. and not higher
than 280.degree. C. to hydrolyze cellulose into saccharides.
9. The method according to claim 1, wherein said hydrolyzing step
is performed at a temperature of not lower than 240.degree. C. and
not higher than 280.degree. C. to hydrolyze cellulose into
saccharides.
10. The method according to claim 1, wherein said charging step
includes addition of ethanol in an amount of not less than 2 mol %
and not more than 10 mol % to the raw slurry.
11. The method according to claim 2, wherein said charging step
includes addition of ethanol in an amount of not less than 2 mol %
and not more than 10 mol % to said water.
12. A method of hydrolytic saccharification of a cellulosic biomass
with use of plural pressure vessels, the method comprising a
discharging and charging step, a heating-up step, a hydrolyzing
step, and a temperature lowering step, which are performed
sequentially by each of said pressure vessels, wherein: said
discharging and charging step is a step of removing a slurry out of
each of said pressure vessels after said temperature lowering step
and charging a slurry prepared by grinding said cellulosic biomass
and mixing said cellulosic biomass thus ground with water into the
same pressure vessel; said heating-up step is a step of
hermetically closing the pressure vessel and heating up the
pressure vessel; said hydrolyzing step is a step of hydrolyzing
cellulose and/or hemicellulose contained in said cellulosic biomass
into saccharides by an oxidative power of high-temperature and
high-pressure water; said temperature lowering step is a step of
flash-evaporating the high-temperature and high-pressure slurry
contained in the pressure vessel to lower the temperature thereof;
and while any one of said plural pressure vessels performs said
heating-up step, any one of the other pressure vessels performs
said temperature lowering step and allows heat recovery to be made
by supplying flash vapor discharged from the pressure vessel
performing the temperature lowering step to the pressure vessel
performing the heating-up step.
13. A method of hydrolytic saccharification of a cellulosic biomass
with use of plural pressure vessels, the method comprising a
discharging and charging step, a heating-up step, a hydrolyzing
step, and a temperature lowering step, which are performed
sequentially by each of said pressure vessels, wherein: said
discharging and charging step is a step of removing a cellulosic
biomass residue out of each of said pressure vessels after said
temperature lowering step and encapsulating water and a
water-permeable vessel charged with said cellulosic biomass into
the same pressure vessel; said heating-up step is a step of
hermetically closing the pressure vessel and heating up the
pressure vessel; said hydrolyzing step is a step of hydrolyzing
cellulose and/or hemicellulose contained in said cellulosic biomass
into saccharides by an oxidative power of high-temperature and
high-pressure water; said temperature lowering step is a step of
flash-evaporating high-temperature and high-pressure water
contained in the pressure vessel to lower the temperature thereof;
and while any one of said plural pressure vessels performs said
heating-up step, any one of the other pressure vessels performs
said temperature lowering step and allows heat recovery to be made
by supplying flash vapor discharged from the pressure vessel
performing said temperature lowering step to the pressure vessel
performing said heating-up step.
14. The method according to claim 12, wherein equal time is
required to complete respective of all the four steps and the
number of the pressure vessels used is a multiple of four.
15. The method according to claim 12, wherein: equal time is
required to complete respective of all the three steps other than
said hydrolyzing step; the time required to complete said
hydrolyzing step is n times (where n is a natural number) as long
as the time required to complete each of the other three steps; and
the number of the pressure vessels used is a multiple of (3+n).
16. The method according to claim 12, wherein said hydrolyzing step
is performed at a temperature of not lower than 140.degree. C. and
not higher than 180.degree. C. to hydrolyze hemicellulose into
saccharides.
17. The method according to claim 13, wherein said hydrolyzing step
is performed at a temperature of not lower than 140.degree. C. and
not higher than 180.degree. C. to hydrolyze hemicellulose into
saccharides.
18. The method according to claim 16, wherein: the slurry resulting
from said discharging and charging step is subjected to
solid-liquid separation; a slurry comprising a solid content
obtained after dissolution of hydrolyzed hemicellulose in water is
prepared; the slurry obtained after the solid-liquid separation is
subjected to said discharging and charging step again; and said
hydrolyzing step is performed at a temperature of not lower than
240.degree. C. and not higher than 280.degree. C. to hydrolyze
cellulose into saccharides.
19. The method according to claim 17, wherein said water-permeable
vessel having been subjected to said discharging step is subjected
to said charging step and said hydrolyzing step is performed at a
temperature of not lower than 240.degree. C. and not higher than
280.degree. C. to hydrolyze cellulose into saccharides.
20. The method according to claim 12, wherein said hydrolyzing step
is performed at a temperature of not lower than 240.degree. C. and
not higher than 280.degree. C. to hydrolyze cellulose into
saccharides.
21. The method according to claim 12, wherein said discharging and
charging step includes addition of ethanol in an amount of not less
than 2 mol % and not more than 10 mol % to the raw slurry.
22. The method according to claim 13, wherein said discharging and
charging step includes addition of ethanol in an amount of not less
than 2 mol % and not more than 10 mol % to water to be encapsulated
into the pressure vessel.
23. A system for hydrolytic saccharification of a cellulosic
biomass, comprising plural pressure vessels each configured to
perform sequential steps including: a charging step of charging a
slurry prepared by grinding said cellulosic biomass and then mixing
said cellulosic biomass thus ground with water into the pressure
vessel; a heating-up step of hermetically closing the pressure
vessel and heating up the pressure vessel; a hydrolyzing step of
hydrolyzing cellulose and/or hemicellulose contained in said
cellulosic biomass into saccharides by an oxidative power of
high-temperature and high-pressure water; a temperature lowering
step of flash-evaporating the high-temperature and high-pressure
slurry contained in the pressure vessel to lower the temperature
thereof; and a discharging step of removing the slurry out of the
pressure vessel, wherein: while any one of said plural pressure
vessels performs said charging step, any one of the other pressure
vessels performs said discharging step no as to allow heat exchange
to occur between the slurry to be charged into the pressure vessel
performing said charging step and the slurry to be discharged from
the pressure vessel performing said discharging step; and while any
one of said plural pressure vessels performs said heating-up step,
any one of the other pressure vessels performs said temperature
lowering step and allows heat recovery to be made by supplying
flash vapor discharged from the pressure vessel performing said
temperature lowering step to the pressure vessel performing said
heating-up step.
24. A system for hydrolytic saccharification of a cellulosic
biomass, comprising plural pressure vessels each configured to
perform sequential steps including: a charging step of
encapsulating water and a water-permeable vessel charged with said
cellulosic biomass into the pressure vessel; a heating-up step of
hermetically closing the pressure vessel and heating up the
pressure vessel; a hydrolyzing step of hydrolyzing cellulose and/or
hemicellulose contained in said cellulosic biomass into saccharides
by an oxidative power of high-temperature and high-pressure water;
a temperature lowering step of flash-evaporating high-temperature
and high-pressure water contained in the pressure vessel to lower
the temperature thereof; and a discharging step of removing a
residue of said cellulosic biomass out of the pressure vessel,
wherein: while any one of said plural pressure vessels performs
said charging step, any one of the other pressure vessels performs
said discharging step so as to allow heat exchange to occur between
water to be charged into the pressure vessel performing said
charging step and high-temperature water to be discharged from the
pressure vessel performing said discharging step; and while any one
of said plural pressure vessels performs said heating-up step, any
one of the other pressure vessels performs said temperature
lowering step and allows heat recovery to be made by supplying
flash vapor discharged from the pressure vessel performing said
temperature lowering step to the pressure vessel performing said
heating-up step.
25. The system according to claim 23, wherein equal time is
required to complete respective of all the five steps and the
number of the pressure vessels used is a multiple of five.
26. The system according to claim 23, wherein: equal time is
required to complete respective of all the four steps other than
said hydrolyzing step; the time required to complete said
hydrolyzing step is n times (where n is a natural number) as long
as the time required to complete each of the other four steps; and
the number of the pressure vessels used is a multiple of (4+n).
27. A system for hydrolytic saccharification of a cellulosic
biomass, comprising plural pressure vessels each configured to
perform sequential steps including: a discharging and charging step
of removing a slurry out of the pressure vessel after a temperature
lowering step and charging a slurry prepared by grinding said
cellulosic biomass and then mixing said cellulosic biomass thus
ground with water into the same pressure vessel; a heating-up step
of hermetically closing the pressure vessel and heating up the
pressure vessel; a hydrolyzing step of hydrolyzing cellulose and/or
hemicellulose contained in said biomass into saccharides by an
oxidative power of high-temperature and high-pressure water; and
the temperature lowering step of flash-evaporating the
high-temperature and high-pressure slurry contained in the pressure
vessel to lower the temperature thereof, wherein while any one of
said plural pressure vessels performs said heating-up step, any one
of the other pressure vessels performs said temperature lowering
step and allows heat recovery to be made by supplying flash vapor
discharged from the pressure vessel performing said temperature
lowering step to the pressure vessel performing said heating-up
step.
28. A system for hydrolytic saccharification of a cellulosic
biomass, comprising plural pressure vessels each configured to
perform sequential steps including: a discharging and charging step
of removing a cellulosic biomass residue out of the pressure vessel
after a temperature lowering step and encapsulating water and a
water-permeable vessel charged with said cellulosic biomass into
the pressure vessel; a heating-up step of hermetically closing the
pressure vessel and heating up the pressure vessel; a hydrolyzing
step of hydrolyzing cellulose and/or hemicellulose contained in
said cellulosic biomass into saccharides by an oxidative power of
high-temperature and high-pressure water; and the temperature
lowering step of flash-evaporating high-temperature and
high-pressure water contained in the pressure vessel to lower the
temperature thereof, wherein while any one of said plural pressure
vessels performs said heating-up step, any one of the other
pressure vessels performs said temperature lowering step and allows
heat recovery to be made by supplying flash vapor discharged from
the pressure vessel performing said temperature lowering step to
the pressure vessel performing said heating-up step.
29. The system according to claim 27, wherein equal time is
required to complete respective of all the four steps and the
number of the pressure vessels used is a multiple of four.
30. The system according to claim 27, wherein: equal time is
required to complete respective of all the three steps other than
said hydrolyzing step; the time required to complete said
hydrolyzing step is n times (where n is a natural number) as long
as the time required to complete each of the other three steps; and
the number of the pressure vessels used is a multiple of (3+n).
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a hydrolyzing method and
system for efficiently producing saccharides from biomasses,
particularly cellulosic biomasses, used as raw materials.
[0003] 2. Description of the Related Art
[0004] As part of biomass energy utilization, attempts have been
made to obtain ethanol (bioethanol) by hydrolyzing cellulose or
hemicellulose, which are major constituents of plants. Ethanol thus
obtained is planned to be utilized as a fuel to be mixed into an
automotive fuel or as an alternative fuel for gasoline.
[0005] Major constituents of plants include cellulose (a polymer of
glucose, which is a C6 saccharide comprising six carbon atoms),
hemicellulose (a polymer of a C5 saccharide comprising five carbon
atoms and a C6 saccharide), lignin, starch, and the like. Ethanol
is produced from saccharides, such as a C5 saccharide, C6
saccharide, and oligosaccharide which is a complex of these
saccharides, used as raw materials, by the fermentation action of
yeast fungi or the like.
[0006] Three methods of hydrolyzing a cellulosic biomass comprising
cellulose, hemicellulose or the like into saccharides are about to
be utilized industrially, which include: 1) a method of hydrolyzing
such a biomass by the oxidative power of a strong acid, such as
sulfuric acid; 2) a method of hydrolyzing such a biomass by yeast;
and 3) a method utilizing the oxidative power of supercritical
water, subcritical water or the like. However, the hydrolytic
method 1) using the acid indispensably requires a treatment for
neutralizing the added acid after hydrolysis of cellulose or
hemicellulose into saccharides and before fermentation of the
saccharides into ethanol because the added acid acts as an
inhibitor against the fermentation by yeast or the like. The cost
of such a treatment makes it difficult to put this method into
practice in view of the economical aspect.
[0007] The outlook for industrial-scale realization of the
hydrolyzing method 2) using yeast is still vague in view of the
cost efficiency because an effective yeast for the method 2) has
not been found yet and, if found, such a yeast is expected to incur
a high production cost thereof, though the method 2) can be
realized by a normal-temperature and normal-pressure process.
[0008] As the method 3) of hydrolyzing cellulose or the like into
saccharides by using supercritical or subcritical water, patent
document 1 has disclosed a method of producing water-insoluble
polysaccharides, which is characterized by hydrolysis of cellulosic
powder by bringing the powder into contact with pressurized hot
water at 240 to 340.degree. C. Patent document 2 has disclosed a
method including: hydrolyzing biomass chips with hot water
pressurized to a saturated vapor pressure or more at 140 to
230.degree. C. for a predetermined time period to extract
hemicellulose; and then conducting hydrolysis using pressurized hot
water heated to a temperature not less than the cellulose
hydrolyzing temperature to extract cellulose. Patent document 3 has
disclosed a method of producing glucose and/or water-soluble
cello-oligosaccharide, which is characterized in that cellulose
having a mean polymerization degree of not less than 100 is
hydrolyzed by the steps of: bringing the cellulose into contact
with supercritical or subcritical water at a temperature of not
lower than 250.degree. C. and not higher than 450.degree. C. and a
pressure of not less than 15 Mpa and not more than 450 MPa for a
time period of not less than 0.01 seconds and not more than 5
seconds; cooling the cellulose; and then bringing the cellulose
into contact with subcritical water at a temperature of not lower
than 250.degree. C. and not higher than 350.degree. C. and a
pressure of not less than 15 Mpa and not more than 450 MPa for a
time period of not less than 1 seconds and not more than 10
minutes.
[0009] On the other hand, patent document 4 has disclosed a method
of treating a biomass-type waste, which includes: placing a subject
for treatment containing a solvent comprising low-molecular-weight
alcohol as a major component and the biomass-type waste into a
closed vessel; and treating the subject by pressurizing and heating
the interior of the closed vessel on that the low-molecular-weight
alcohol reaches its supercritical condition. Also, patent document
5 has disclosed a method of hydrolyzing and liquefying a biomass,
which includes treating a cellulosic biomass by using a mixed
solvent prepared by adding 5-20% by volume of water to a C1 to C8
aliphatic alcohol under the supercritical or subcritical condition
of the alcohol.
[0010] Patent document 1: Japanese Patent Provisional Publication
No. 2000-186102
[0011] Patent document 2: Japanese Patent Provisional Publication
No. 2002-59118
[0012] Patent document 3: Japanese Patent Provisional Publication
No. 2003-212888
[0013] Patent document 4: Japanese Patent Provisional Publication
No. 2001-170601
[0014] Patent document 5: Japanese Patent Provisional Publication
No. 2005-296906
[0015] As compared with the hydrolytic method using a strong acid,
the method of hydrolytic saccharification of cellulose and
hemicellulose as major constituents of a biomass by using
high-temperature and high-pressure supercritical or subcritical
water requires a lower processing cost and is amore environment
friendly because this method does not require any acid neutralizing
treatment. However, this method has a drawback that without cooling
immediately after the completion of hydrolysis, saccharides
produced thus far would degrade into organic acids or the like
because the use of supercritical or subcritical water causes
cellulose and hemicellulose to hydrolyze into saccharides
completely in several seconds to several minutes by its strong
oxidative power.
[0016] With a laboratory-scale small system for hydrolysis, it
seems that such degradation can be prevented by rapidly cooling
supercritical or subcritical water in the heating vessel. With an
industrial-scale hydrolysis system, however, it is very difficult
to cool a large amount of supercritical or subcritical water in a
short time. For this reason, the cellulosic biomass hydrolysing
method using high-temperature and high-pressure supercritical or
subcritical water, when applied to a plant-scale system, will give
a low yield of saccharides, which forms one of the factors that
prevent this method from being put to practice.
[0017] In using a large amount of supercritical or subcritical
water, the slurry has to be heated with a large amount of energy,
which forms a factor raising the processing cost. The cellulosic
biomass hydrolyzing method, which subjects a slurry containing
alcohol or the like as a solvent to hydrolysis under a
supercritical or subcritical condition, requires a very high vapor
pressure, hence, requires a larger amount of energy and has to use
a system having a high pressure resistance.
[0018] It is an object of the present invention to provide a method
and system for hydrolyzing cellulose and/or hemicellulose contained
in a biomass into monosaccharides and oligosaccharides (hereinafter
will be referred to as "saccharides") by using high-temperature and
high-pressure water in a subcritical condition, which method and
system is excellent in thermal efficiency and yields of
saccharides.
SUMMARY OF THE INVENTION
[0019] The inventor of the present invention has found out that in
hydrolyzing cellulose or hemicellulose into saccharides by using
high-temperature and high-pressure water in a subcritical condition
it is possible to cool a large amount of slurry to a temperature
not higher than the cellulose hydrolyzing temperature thereby
preventing saccharides from degrading into organic acids or the
like as well as to save energy by recovery of thermal energy, by
subjecting the slurry contained in a pressure vessel under a
high-temperature and high-pressure condition to flash evaporation
in a pressure vessel that is charged with a slurry of a cellulosic
biomass and heated halfway. Thus, the present invention has been
accomplished.
[0020] Specifically, the present invention is directed to a method
of hydrolytic saccharification of a cellulosic biomass with use of
plural pressure vessels, the method comprising a charging step, a
heating-up step, a hydrolyzing step, a temperature lowering step,
and a discharging step, which are performed sequentially by each of
the pressure vessels, wherein:
[0021] the charging step is a step of charging a slurry prepared by
grinding the cellulosic biomass and then mixing the cellulosic
biomass thus ground with water (hereinafter will be referred to as
"slurry") into each of the pressure vessels;
[0022] the heating-up step is a step of hermetically closing the
pressure vessel and heating up the slurry;
[0023] the hydrolyzing step is a step of hydrolyzing cellulose
and/or hemicellulose contained in the cellulosic biomass into
saccharides by an oxidative power of high-temperature and
high-pressure water;
[0024] the temperature lowering step is a step of flash-evaporating
the high-temperature and high-pressure slurry contained in the
pressure vessel to flash evaporation to lower the temperature
thereof;
[0025] the discharging step is a step of removing the slurry out of
the pressure vessel;
[0026] while any one of the plural pressure vessels performs the
charging step, any one of the other pressure vessels performs the
discharging step so as to allow heat exchange to occur between the
slurry to be charged into the pressure vessel performing the
charging step and the slurry to be discharged from the pressure
vessel performing the discharging step; and
[0027] while any one of the plural pressure vessels performs the
heating-up step, any one of the other pressure vessels performs the
temperature lowering step and allows heat recovery to be made by
supplying flash vapor discharged from the pressure vessel
performing the temperature lowering step to the pressure vessel
performing the heating-up step (claim 1).
[0028] The present invention is also directed to a system for
hydrolytic saccharification of a cellulosic biomass, comprising
plural pressure vessels each configured to perform sequential steps
including:
[0029] a charging step of charging a slurry prepared by grinding
the cellulosic biomass and then mixing the cellulosic biomass thus
ground with water into the pressure vessel;
[0030] a heating-up step of hermetically closing the pressure
vessel and heating up the pressure vessel;
[0031] a hydrolyzing step of hydrolyzing cellulose and/or
hemicellulose contained in the cellulosic biomass into saccharides
by an oxidative power of high-temperature and high-pressure
water;
[0032] a temperature lowering step of flash-evaporating the
high-temperature and high-pressure slurry contained in the pressure
vessel to lower the temperature thereof; and
[0033] a discharging step of removing the slurry out of the
pressure vessel, wherein:
[0034] while any one of the plural pressure vessels performs the
charging step, any one of the other pressure vessels performs the
discharging step so as to allow heat exchange to occur between the
slurry to be charged into the pressure vessel performing the
charging step and the slurry to be discharged from the pressure
vessel performing the discharging step; and
[0035] while any one of the plural pressure vessels performs the
heating-up step, any one of the other pressure vessels performs the
temperature lowering step and allows heat recovery to be made by
supplying flash vapor discharged from the pressure vessel
performing the temperature lowering step to the pressure vessel
performing the heating-up step (claim 23).
[0036] In the method and system for hydrolytic saccharification of
a cellulosic biomass according to the present invention, five
process steps are performed in each of the plural pressure vessels.
By connecting the pressure vessel at the temperature lowering step
to another pressure vessel at the heating-up step, the slurry in
the pressure vessel at the temperature lowering step can be rapidly
cooled by flash evaporation. At the same time, the slurry in the
pressure vessel performing the heating-up step can be heated by
high-temperature flash vapor, whereby the energy required to heat
the slurry can be saved.
[0037] By reducing the internal pressure of the pressure vessel
from the gas phase portion, there is no danger that the dissolved
components and solid contents of the slurry move to clog the nozzle
and piping for passage of flash vapor. Further, there is no need to
provide a special temperature controller or the like. In supplying
the preheated side (i.e., the pressure vessel at the heating-up
step) with flash vapor, the preheating of the slurry becomes more
effective by supplying flash vapor into the slurry.
[0038] The method and system for hydrolytic saccharification of a
cellulosic biomass according to the present invention allows heat
exchange to occur between the slurry to be discharged (drained)
from the pressure vessel at the discharging step and the slurry to
be charged into another pressure vessel at the charging step,
thereby making it possible to further save the energy required to
heat the slurry.
[0039] The present invention is also directed to a method of
hydrolytic saccharification of a cellulosic biomass with use of
plural pressure vessels, the method comprising a charging step, a
heating-up step, a hydrolyzing step, a temperature lowering step,
and a discharging step, which are performed sequentially by each of
the pressure vessels, wherein:
[0040] the charging step is a step of charging the cellulosic
biomass into a water-permeable vessel and then encapsulating the
water-permeable vessel and water into each of the pressure
vessels;
[0041] the heating-up step is a step of hermetically closing the
pressure vessel and heating up the cellulosic biomass and
water;
[0042] the hydrolyzing step is a step of hydrolyzing cellulose
and/or hemicellulose contained in the cellulosic biomass into
saccharides by an oxidative power of high-temperature and
high-pressure water;
[0043] the temperature lowering step is a step of flash-evaporating
high-temperature and high-pressure water contained in the pressure
vessel to lower the temperature thereof;
[0044] the discharging step is a step of removing the water and the
water-permeable vessel out of the pressure vessel;
[0045] while any one of the plural pressure vessels performs the
charging step, any one of the other pressure vessels performs the
discharging step so as to allow heat exchange to occur between
water to be charged into the pressure vessel performing the
charging step and high-temperature water to be discharged from the
pressure vessel performing the discharging step; and
[0046] while any one of the plural pressure vessels performs the
heating-up step, any one of the other pressure vessels performs the
temperature lowering step and allows heat recovery to be made by
supplying flash vapor discharged from the pressure vessel
performing the temperature lowering step to the pressure vessel
performing the heating-up step (claim 2).
[0047] The present invention is also directed to a system for
hydrolytic saccharification of a cellulosic biomass, comprising
plural pressure vessels each configured to perform sequential steps
including:
[0048] a charging step of encapsulating water and a water-permeable
vessel charged with the cellulosic biomass into the pressure
vessel;
[0049] a heating-up step of hermetically closing the pressure
vessel and heating up the pressure vessel;
[0050] a hydrolyzing step of hydrolyzing cellulose and/or
hemicellulose contained in the cellulosic biomass into saccharides
by an oxidative power of high-temperature and high-pressure
water;
[0051] a temperature lowering step of flash-evaporating
high-temperature and high-pressure water contained in the pressure
vessel to lower the temperature thereof; and
[0052] a discharging step of removing a residue of the cellulosic
biomass out of the pressure vessel, wherein:
[0053] while any one of the plural pressure vessels performs the
charging step, any one of the other pressure vessels performs the
discharging step so as to allow heat exchange to occur between
water to be charged into the pressure vessel performing the
charging step and high-temperature water to be discharged from the
pressure vessel performing the discharging step; and
[0054] while any one of the plural pressure vessels performs the
heating-up step, any one of the other pressure vessels performs the
temperature lowering step and allows heat recovery to be made by
supplying flash vapor discharged from the pressure vessel
performing the temperature lowering step to the pressure vessel
performing the heating-up step (claim 24).
[0055] In hydrolyzing cellulose or hemicellulose into saccharides
by using high-temperature and high-pressure water in a subcritical
condition, the cellulosic biomass is charged into the
water-permeable vessel having perforations, apertures or the like
for allowing water to move from the exterior to the interior of the
water-permeable vessel and vice versa and then the water-permeable
vessel and water are encapsulated into each pressure vessel
(compressive and dense encapsulation). By so doing, the vessels and
associated piping can be prevented from being contaminated with
fine residue of slurry.
[0056] In cases where equal time is required to complete respective
of all the aforementioned five steps, the number of the pressure
vessels used is preferably a multiple of five (claims 3 and 25).
With this feature, the sequential steps can be performed smoothly
while performing heat recovery twice.
[0057] In cases where equal time is required to complete respective
of all the four steps other than the hydrolyzing step and the time
required to complete the hydrolyzing step is n times (where n is a
natural number) as long as the time required to complete respective
of all the other four steps, the number of the pressure vessels
used is preferably a multiple of (4+n) (claims 4 and 26). Where the
time required to complete the hydrolyzing step is n times as long
as that required to complete any other step, the number of pressure
vessels to perform the hydrolyzing step is preferably n times as
large as the number of pressure vessels to perform the other steps.
With this feature, the sequential steps can be performed smoothly
while performing heat recovery twice.
[0058] When the hydrolyzing step is performed at a temperature of
not lower than 140.degree. C. and not higher than 180.degree. C.,
hemicellulose can be hydrolyzed into saccharides (mainly including
C5 monosaccharides) (claims 5 and 6). A biomass containing a large
amount of hemicellulose is preferably processed under relatively
moderate conditions because high-temperature processing causes C5
monosaccharides and the like to degrade into organic acids and the
like.
[0059] Thereafter, the slurry resulting from the discharging step
is subjected to solid-liquid separation; a solid content produced
after elution of hydrolyzed hemicellulose to the solvent side is
separated out for use as afresh raw slurry; the raw slurry is
subjected to the charging step again; and the hydrolyzing step is
performed at a temperature of not lower than 240.degree. C. and not
higher than 280.degree. C. By so doing, cellulose can be hydrolyzed
into saccharides (mainly including C6 monosaccharides) (claim
7).
[0060] Alternatively, by subjecting the water-permeable vessel
having been subjected to the discharge step to the charging step
again and performing the hydrolyzing step at a temperature of not
lower than 240.degree. C. and not higher than 280.degree. C., it is
possible to hydrolyze cellulose into saccharides (claim 8).
[0061] Hemicellulose contained in the biomass is first hydrolyzed
into saccharides at a temperature of not lower than 140.degree. C.
and not higher than 180.degree. C. and then the biomass is
subjected to solid-liquid separation. By so doing, cellulose can be
separated out as a solid. A slurry comprising the cellulose thus
obtained is subjected to the charging step and then to the
hydrolyzing step at a temperature of not lower than 240.degree. C.
and not higher than 280.degree. C. By so doing, the cellulose can
be hydrolyzed into saccharides. This process is effective for a
biomass containing cellulose and hemicellulose in substantially
equal amounts.
[0062] When the hydrolyzing step is performed at a temperature of
not lower than 240.degree. C. and not higher than 280.degree. C.,
cellulose can be hydrolyzed into saccharides (mainly including C6
monosaccharides) (claim 9). In the case of a biomass having a high
cellulose content, a process for hydrolyzing only cellulose into
saccharides at a relatively high temperature is more effective
because the necessity to take degradation of hemicellulose into
consideration is low.
[0063] Preferably, the charging step includes addition of ethanol
in an amount of not less than 2 mol % and not more than 10 mol % to
the raw slurry or to water to be encapsulated in the pressure
vessel step (claims 10 and 11). The addition of a small amount of
ethanol to the raw slurry causes the reaction rate of hydrolysis of
cellulose and/or hemicellulose into saccharides by subcritical
water to be lowered. Thus, the cellulose and/or hemicellulose
hydrolysis time in the hydrolyzing step can be adjusted so as to
facilitate inhibition of degradation into organic acids and the
like, thereby raising the yield.
[0064] The present invention is also directed to a method of
hydrolytic saccharification of a cellulosic biomass with use of
plural pressure vessels, the method comprising a discharging and
charging step, a heating-up step, a hydrolyzing step, and a
temperature lowering step, which are performed sequentially by each
of the pressure vessels, wherein:
[0065] the discharging and charging step is a step of removing a
slurry out of each of the pressure vessel after the temperature
lowering step and charging a slurry prepared by grinding the
cellulosic biomass and mixing the cellulosic biomass thus ground
with water into the same pressure vessel;
[0066] the heating-up step is a step of hermetically closing the
pressure vessel and heating up the pressure vessel;
[0067] the hydrolyzing step is a step of hydrolyzing cellulose
and/or hemicellulose contained in the cellulosic biomass into
saccharides by an oxidative power of high-temperature and
high-pressure water;
[0068] the temperature lowering step is a step of flash-evaporating
the high-temperature and high-pressure slurry contained in the
pressure vessel to lower the temperature thereof; and
[0069] while any one of the plural pressure vessels performs the
heating-up step, any one of the other pressure vessels performs the
temperature lowering step and allows heat recovery to be made by
supplying flash vapor discharged from the pressure vessel
performing the temperature lowering step to the pressure vessel
performing the heating-up step (claim 12).
[0070] The present invention is also directed to a system for
hydrolytic saccharification of a cellulosic biomass, comprising
plural pressure vessels each configured to perform sequential steps
including:
[0071] a discharging and charging step of removing a
high-temperature slurry out of the pressure vessel after a
temperature lowering step and charging a slurry prepared by
grinding the cellulosic biomass and then mixing the cellulosic
biomass thus ground with water into the same pressure vessel;
[0072] a heating-up step of hermetically closing the pressure
vessel and heating up the pressure vessel;
[0073] a hydrolyzing step of hydrolyzing cellulose and/or
hemicellulose contained in the cellulosic biomass into saccharides
by an oxidative power of high-temperature and high-pressure water;
and
[0074] the temperature lowering step of flash-evaporating the
high-temperature and high-pressure slurry contained in the pressure
vessel to lower the temperature thereof, wherein
[0075] while any one of the plural pressure vessels performs the
heating-up step, any one of the other pressure vessels performs the
temperature lowering step and allows heat recovery to be made by
supplying flash vapor discharged from the pressure vessel
performing the temperature lowering step to the pressure vessel
performing the heating-up step (claim 27).
[0076] The present invention is also directed to a method of
hydrolytic saccharification of a cellulosic biomass with use of
plural pressure vessels, the method comprising a discharging and
charging step, a heating-up step, a hydrolyzing step, and a
temperature lowering step, which are performed sequentially by each
of the pressure vessels, wherein:
[0077] the discharging and charging step is a step of removing a
cellulosic biomass residue out of each of the pressure vessels
after the temperature lowering step and encapsulating water and a
water-permeable vessel charged with the cellulosic biomass into the
same pressure vessel;
[0078] the heating-up step is a step of hermetically closing the
pressure vessel and heating up the pressure vessel;
[0079] the hydrolyzing step is a step of hydrolyzing cellulose
and/or hemicellulose contained in the biomass into saccharides by
an oxidative power of high-temperature and high-pressure water;
[0080] the temperature lowering step is a step of flash-evaporating
high-temperature and high-pressure water contained in the pressure
vessel to lower the temperature thereof; and
[0081] while any one of the plural pressure vessels performs the
heating-up step, any one of the other pressure vessels performs the
temperature lowering step and allows heat recovery to be made by
supplying flash vapor discharged from the pressure vessel
performing the temperature lowering step to the pressure vessel
performing the heating-up step (claim 13).
[0082] The present invention is also directed to a system for
hydrolytic saccharification of a cellulosic biomass, comprising
plural pressure vessels each configured to perform sequential steps
including:
[0083] a discharging and charging step of removing a cellulosic
biomass residue out of the pressure vessel after a temperature
lowering step and encapsulating water and a water-permeable vessel
charged with the cellulosic biomass into the pressure vessel;
[0084] a heating-up step of hermetically closing the pressure
vessel and heating up the pressure vessel;
[0085] a hydrolyzing step of hydrolyzing cellulose and/or
hemicellulose contained in the cellulosic biomass into saccharides
by an oxidative power of high-temperature and high-pressure water;
and
[0086] the temperature lowering step of flash-evaporating
high-temperature and high-pressure water contained in the pressure
vessel to lower the temperature thereof, wherein
[0087] while any one of the plural pressure vessels performs the
heating-up step, any one of the other pressure vessels performs the
temperature lowering step and allows heat recovery to be made by
supplying flash vapor discharged from the pressure vessel
performing the temperature lowering step to the pressure vessel
performing the heating-up step (claim 28).
[0088] By thus performing the discharging step and the charging
step in one pressure vessel, it is possible to reduce the total
number of process steps to four and the total number of pressure
vessels used to four (or a multiple of four) and shorten the
processing time. For this reason, this method and system has the
advantage of improving the production capacity. With the hydrolytic
saccharification method and system having four steps in total
according to the present invention, heat exchange between the
high-temperature slurry to be discharged from each vessel and the
slurry (raw slurry) to be charged into the same pressure vessel is
possible in the discharging and charging step.
[0089] Similarly, with the hydrolytic saccharification method and
system having four process steps in total according to the present
invention, heat exchange between high-temperature water be
discharged from each vessel and water to be charged into the same
pressure vessel is possible in the discharging and charging
step.
[0090] In cases where equal time is required to complete respective
of all the aforementioned four steps, the number of pressure
vessels used is preferably a multiple of four (claims 14 and 29).
With this feature, the sequential steps can be performed smoothly
while performing heat recovery twice.
[0091] In cases where equal time is required to complete respective
of all the three steps other than the hydrolyzing step and the time
required to complete the hydrolyzing step is n times (where n is a
natural number) as long as the time required to complete each of
the other three steps, the number of pressure vessels used is
preferably a multiple of (3+n) (claims 15 and 30). In cases where
the time required to complete the hydrolyzing step is n times as
long as that required to complete any other step, the number of
pressure vessels to perform the hydrolyzing step is preferably n
times as large as the number of pressure vessels to perform the
other steps. With this feature, the sequential steps can be
performed smoothly while performing heat recovery twice.
[0092] When the hydrolyzing step is performed at a temperature of
not lower than 140.degree. C. and not higher than 180.degree. C.,
the hydrolytic saccharification method including four process steps
in total is also capable of hydrolyzing hemicellulose into
saccharides (mainly including C5 monosaccharides) (claims 16 and
17).
[0093] The slurry resulting from the discharging and charging step
is subjected to solid-liquid separation; a solid content produced
after elution of hydrolyzed hemicellulose to the solvent side is
separated out for use as a fresh raw slurry; the raw slurry is
charged into the same pressure vessel again in the discharging and
charging step; and the hydrolyzing step is performed at a
temperature of not lower than 240.degree. C. and not higher than
280.degree. C. By so doing, cellulose can be hydrolyzed into
saccharides (mainly including C6 monosaccharides) (claim 18).
[0094] Alternatively, by subjecting the water-permeable vessel
having been subjected to the discharge step to the charging step
again and performing the hydrolyzing step at a temperature of not
lower than 240.degree. C. and not higher than 280.degree. C., it is
possible to hydrolyze cellulose into saccharides (claim 19).
[0095] When the hydrolyzing step is performed at a temperature of
not lower than 240.degree. C. and not higher than 280.degree. C.,
cellulose can be hydrolyzed into saccharides (mainly including C6
monosaccharides) (claim 20).
[0096] Preferably, the discharging and charging step includes
addition of ethanol in an amount of not less than 2 mol % and not
more than 10 mol % to the raw slurry or to water to be encapsulated
into each pressure vessel (claims 21 and 22). The reasons that the
aforementioned temperature conditions and the addition of ethanol
are preferable are as stated above for the charging step of the
hydrolytic saccharification method including five process steps in
total.
[0097] Ethanol added to the raw slurry is mostly transferred to
flash vapor in the temperature lowering step and then collected
into the slurry in another pressure vessel performing the
heating-up step. The aqueous solution containing saccharides, which
is removed out of each pressure vessel by the discharging step, is
subjected to ethanol fermentation and thereby converted to
bioethanol. If ethanol remains in the initial phase of ethanol
fermentation, fermentation by yeast is inhibited by such residual
ethanol. The inventions according to claims 10, 11, 21 and 22 have
the feature that ethanol fermentation is difficult to inhibit
because the method can reduce the amount of ethanol in the slurry
containing cellulose and/or hemicellulose which is obtained after
the discharging step while keeping a desired ethanol concentration
in the hydrolyzing step.
[0098] As disclosed in patent document 4 or 5, when the medium
comprising alcohol or the like as a major component is brought into
its subcritical condition, the internal pressure of the pressure
vessel becomes as high as or higher than 12 MPa at 280.degree. C.
for example. With the invention according to claim 7, in contrast,
the internal pressure of the pressure vessel reaches no more than
about 7.5 to about 9.7 MPa at 280.degree. C., which the same
temperature. Thus, the method according to this invention is
capable of saving the pressurizing energy while allowing the
pressure resistance of the pressure vessel to lower, thereby
offering an economical merit.
[0099] The foregoing and other objects, features and attendant
advantages of the present invention will become more apparent from
the reading of the following detailed description of the invention
in conjunction with the accompanying drawings.
ADVANTAGE OF THE INVENTION
[0100] According to the present invention, cellulose and/or
hemicellulose contained in a cellulosic biomass can be hydrolyzed
into saccharides in a high yield at a low cost with use of plural
pressure vessels. Also, the present invention can save the required
calorie by about 60% and hence has a very excellent economical
merit because waste heat can be easily recovered from a pressure
vessel performing another step and utilized for preheating to a
suitable temperature for hydrolytic saccharification reaction.
[0101] By charging a cellulosic biomass into the water-permeable
vessel and encapsulating the water-permeable vessel and water into
each pressure vessel, it is possible to prevent piping and the like
from being stained as well as to improve the operating efficiency
further.
BRIEF DESCRIPTION OF THE DRAWINGS
[0102] FIG. 1 is a chart illustrating a procedure for operating a
hydrolytic saccharification system according to embodiment 1;
[0103] FIG. 2 is a time schedule chart for operating the hydrolytic
saccharification system of embodiment 1 as a sequencing batch
system;
[0104] FIG. 3 is a time schedule chart for operating a hydrolytic
saccharification system of embodiment 2 as a sequencing batch
system;
[0105] FIG. 4 is a graph plotting the relationship between the
reaction time of hydrolytic saccharification of a biomass and the
yield of saccharides (%);
[0106] FIG. 5 is a time schedule chart for operating a hydrolytic
saccharification system of embodiment 3 as a sequencing batch
system; and
[0107] FIG. 6 is a view illustrating an example in which dried
bagasse is compressively and densely charged into a water-permeable
vessel according to embodiment 4.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0108] Hereinafter, embodiments of the present invention will be
described with appropriate reference to the drawings. It is to be
noted that the present invention is not limited to the embodiments
described below.
Embodiment 1
[0109] Referring to FIG. 1, description will be made of a procedure
for operating a hydrolytic saccharification system configured to
perform five process steps in total and use five pressure vessels
according to embodiment 1.
[0110] First, a cellulosic biomass (for example, a vegetation
biomass comprising bagasse, sugar beet residue, straws or the like)
is ground to sizes of not more than several millimeters and then
mixed with water or a dilute ethanol aqueous solution (2 to 10 mol
%) to prepare a slurry having a solid matter concentration of about
30%. The slurry thus obtained (raw slurry) is charged into pressure
vessel No. 1, as shown in FIG. 1(a) (charging step). Since there is
no thermal energy released from any other pressure vessel at the
time the hydrolytic saccharification system starts operating, the
raw slurry cannot be preheated by heat exchange.
[0111] Pressure vessels Nos. 1 to 5 each repeatedly perform the
sequence of process steps: charging step.fwdarw.heating-up
step.fwdarw.hydrolyzing step.fwdarw.temperature lowering
step.fwdarw.discharging step, and four pressure vessels Nos. 2 to 5
each operate with a time lag corresponding to one process step. In
the case of FIGS. 1(a) to 1(e), when pressure vessel No. 1 is at
the charging step, pressure vessels Nos. 2 to 5 are at the
discharging step, temperature lowering step, hydrolyzing step and
heating-up step, respectively.
[0112] In FIGS. 1(a) to 1(e), the terms "preheat and charge",
"preheat and heat-up", "heat-up", "flash" and "drainage" represent
the charging step, heating-up step, hydrolyzing step, temperature
lowering step and discharging step, respectively.
[0113] In cases where the hydrolytic saccharification system is
already in operation and the second or later charging step is to be
performed by pressure vessel No. 1, heat exchange is allowed to
occur between a slurry (containing saccharides) to be discharged
(or drained) from pressure vessel No. 2 at the discharge step and
the raw slurry to be charged into pressure vessel No. 1, thereby
preheating the raw slurry.
[0114] Subsequently, pressure vessel No. 1 is closed hermetically
(heating-up step). At that time pressure vessel No. 4 is at the
temperature lowering step as shown in FIG. 1(b). For this reason,
high-temperature gas present in an upper portion of pressure vessel
No. 4 is supplied as flash vapor to pressure vessel No. 1 in order
to recover heat. (As described above, flash vapor is preferably
supplied into the aqueous solution contained in the pressure
vessel.) As a result, the temperature of the slurry contained in
pressure vessel No. 1 is raised further, whereby the energy
required to bring the slurry into its subcritical condition can be
saved.
[0115] Subsequently, the interior of pressure vessel No. 1 is
heated using a heat source, such as high-temperature steam, to
bring the slurry into its subcritical condition, as shown in FIG.
1(c) (hydrolyzing step). Preferably, ethanol is previously added to
the raw slurry to a concentration of not less than 2 mol % and not
more than 10 mol %. The addition of ethanol allows the hydrolysis
reaction rate to be lowered, thereby making it easy to control the
hydrolysis reaction of cellulose or hemicellulose in the
hydrolyzing step.
[0116] The "hydrolyzing step", as used in the present invention, is
meant to include not only the time during which the slurry is in
the subcritical condition but also the time required to heat the
slurry having been raised in temperature by the heating-up step
until the slurry is brought into the subcritical condition.
[0117] If ethanol is added to the raw slurry to a concentration of
more than 10 mol %, the hydrolysis time becomes longer than
necessary while at the same time the pressure vessel needs to have
a higher pressure resistance. In addition, the slurry discharged
(or drained) by the discharging step contains a high concentration
of residual ethanol. For these reasons, the addition of too much
ethanol impairs the practical value of the invention.
[0118] Subsequently, pressure vessel No. 1 having passed a proper
hydrolysis time is connected to pressure vessel No. 3 at the
preheating step in order to supply, as flash vapor, the
high-temperature slurry present in a lower portion of pressure
vessel No. 1 into pressure vessel No. 3, as shown in FIG. 1(d). By
so doing, the interior of pressure vessel No. 1 is rapidly cooled
to a temperature below the hydrolytic saccharification temperature,
thereby making it possible to stop degradation reaction of
saccharides into organic acids or the like. At the same time, the
temperature of the slurry in pressure vessel No. 3 is raised.
[0119] In order for hemicellulose contained in the biomass to be
hydrolytically saccharificated in the hydrolyzing step, the
temperature of the slurry is adjusted to within the temperature
range of from 140.degree. C. to 180.degree. C. which allows only
hemicellulose to be hydrolytically saccharificated, without being
raised to within the temperature range (240.degree. C. to
280.degree. C.) which allows cellulose to be hydrolytically
saccharificated. On the other hand, in order for cellulose
contained in the biomass to be hydrolytically saccharificated, the
temperature of the slurry is raised to within the temperature range
(240.degree. C. to 280.degree. C.) which allows cellulose to be
hydrolytically saccharificated.
[0120] Subsequently, pressure vessel No. 1 of which the temperature
has lowered and of which the pressure has lowered to a normal
pressure or a pressure close to the normal pressure is opened and
the slurry containing saccharides is discharged (or drained)
therefrom, as shown in FIG. 1(e) (discharging step). In the case of
the slurry having been subjected to a temperature of from
240.degree. C. to 280.degree. C. in the hydrolyzing step, the
temperature of the slurry in the discharging step is about
110.degree. C. to about 150.degree. C. For this reason, heat
exchange is allowed to occur between the slurry in pressure vessel
No. 1 at the discharging step and the slurry to be charged into
pressure vessel No. 5. By so doing, it is possible to preheat the
slurry to be charged into pressure vessel No. 5 as well as to cool
the slurry to be removed out of pressure vessel No. 1.
[0121] While description has been made mainly of the operating
procedure for pressure vessel No. 1 with reference to FIGS. 1(a) to
1(e), pressure vessels Nos. 2 to 5 are each operated according to
the same procedure. With respect to the pressure vessels other than
pressure vessel No. 1, the waste heat recovery (i.e., heat
exchange) operations using flash vapor and high-temperature slurry
are partly omitted from FIGS. 1(a) to (e). However, it is needless
to say that waste heat recovery (i.e., heat exchange) is performed
for each of these pressure vessels in the same manner as for
pressure vessel No. 1.
[0122] Saccharides and residual solid content coexist in the slurry
discharged (or drained) by the discharging step and cooled by heat
exchange. Where the hydrolyzing step temperature is within the
range of from 140.degree. C. to 180.degree. C., the residual solid
content comprises cellulose and lignin as major components. Where
the hydrolyzing step temperature is within the range of from
240.degree. C. to 280.degree. C., the residual solid content
comprises lignin as a major component.
[0123] After the residual solid content of the slurry has been
removed away by solid-liquid separation, the resulting liquid is
subjected to ethanol fermentation utilizing the fermentation action
and the like of yeast, thus giving bioethanol. Since such an
ethanol fermentation technique is well-known, description thereof
is omitted herein. Saccharides obtained by the present invention
can be converted to bioethanol by a known fermentation process
other than yeast fermentation.
[0124] Referring to FIG. 2, description will be made of a time
schedule for operating the hydrolytic saccharification system using
the five pressure vessels shown in FIGS. 1(a) to 1(b) as a
sequencing batch system. In FIG. 2, the time required to complete
each process step is five minutes.
[0125] Initially, pressure vessel No. 1 performs the charging step
and, subsequently, pressure vessels Nos. 2 to 5 perform the
charging step sequentially with a time lag of five minutes from one
pressure vessel to the next one. Each pressure vessel repeats the
five sequential steps:
[C].fwdarw.[PH].fwdarw.[GL].fwdarw.[F].fwdarw.[DC] and,
accordingly, one cycle of the hydrolytic saccharification process
for a cellulosic biomass is 5 min.times.5 steps=25 minutes.
Pressure vessels Nos. 1 to 5 perform this cycle sequentially with a
time lag of five minutes from one pressure vessel to the next
one.
[0126] Flashing vapor contained in pressure vessel No. 1 at the
temperature lowering step is supplied to pressure vessel No. 2 at
the heating-up step, thus making heat recovery. Likewise, flashing
vapor contained in each of pressure vessels Nos. 2 to 5 at the
temperature lowering step is supplied to a respective one of
pressure vessels Nos. 3, 4, 5 and 1, thus making heat recovery.
[0127] The slurry to be discharged (or drained) from pressure
vessel No. 1 at the discharging step exchanges heat with the slurry
to be charged into pressure vessel No. 5 at the charging step.
Likewise, the high-temperature slurry contained in each of pressure
vessels Nos. 2 to 5 at the discharge step exchanges heat with the
slurry to be charged into a respective one of pressure vessels Nos.
1 to 4 at the charging step.
[0128] Such a sequencing batch system makes it possible to
hydrolytically saccharificate a biomass in a short time with the
required energy saved.
Embodiment 2
[0129] Referring to FIG. 3, description will be made of a time
schedule for operating a hydrolytic saccharification system as a
sequencing batch system, the hydrolytic saccharification system
being configured to perform four steps in total and use four
pressure vessels each configured to perform the discharging step
and the charging step in parallel as a discharging and charging
step in a steady operation. In FIG. 3, the time required to
complete each step is five minutes.
[0130] Initially, pressure vessel No. 1 performs the first charging
step Co and, subsequently, pressure vessels Nos. 2 to 4 perform the
first charging step Co sequentially with a time lag of five minutes
from one pressure vessel to the next one. When the system starts
operating, the system performs the same charging step as does the
hydrolytic saccharification system shown in FIG. 1. For this
reason, the discharging and charging step performed first is
referred to as "first charging step Co" in FIG. 3. In steady
operation, each pressure vessel repeats the four sequential steps:
[C].fwdarw.[PH].fwdarw.[GL].fwdarw.[F] and, accordingly, one cycle
of the hydrolytic saccharification process for a cellulosic biomass
is 5 min.times.4 steps=25 minutes. Pressure vessels Nos. 1 to 4
perform this cycle sequentially with a time lag of five minutes
from one pressure vessel to the next one.
[0131] Flashing vapor contained in pressure vessel No. 1 at the
temperature lowering step is supplied to pressure vessel No. 2 at
the heating-up step, thus making heat recovery. Likewise, flashing
vapor contained in each of pressure vessels Nos. 2 to 4 at the
temperature lowering step is supplied to a respective one of
pressure vessels Nos. 3 to 5 at the heating-up step, thus making
heat recovery.
[0132] The slurry is removed out of pressure vessel No. 1 at the
discharging and charging step after the temperature lowering step
and then a raw slurry is charged into the same pressure vessel.
That is, pressure vessel No. 1 having completed the temperature
lowering step performs the discharging step and the charging step
in parallel. When the temperature of the slurry to be discharged is
sufficiently high, heat exchange with the raw slurry to be charged
may be made.
[0133] In terminating the operation, pressure vessel No. 1 having
completed the last temperature lowering step performs the last
discharging step Cx and, subsequently, pressure vessels Nos. 2 to 4
perform the last discharging step Cx sequentially with a time lag
of five minutes from one pressure vessel to the next one. In
terminating the operation of the system, the system performs the
same discharging step as does the hydrolytic saccharification
system shown in FIG. 1. For this reason, the discharging and
charging step performed last is referred to as "the last
discharging step Cx" in FIG. 3.
[0134] This sequencing batch system is capable of achieving
continuous hydrolytic saccharification in a shorter time with fewer
pressure vessels than the hydrolytic saccharification system shown
in FIGS. 1 and 2.
Effect of the Addition of Ethanol in the Hydrolyzing Step
[0135] Effect of the addition of ethanol on hydrolytic
saccharification of reagent cellulose under the subcritical
condition was studied with the reagent cellulose used as a biomass.
FIG. 4 shows the result of an experiment in which pure water and 5
wt % (2 mol %) ethanol aqueous solution, which were at the same
temperature of 280.degree. C., were each passed through the
above-noted cellulose.
[0136] FIG. 4 shows the relationship between the reaction time and
the yield of saccharides (%). The addition of ethanol was found to
have substantially no effect on the maximum yield of saccharides.
With respect to the saccharide production rate and the hydrolysis
rate, however, they were apparently lowered by the addition of
ethanol. For example, the time required to reach the maximum yield
was increased about three times (0.7 min.fwdarw.2.0 min) by the
addition of ethanol.
[0137] It is difficult for an industrial-scale system to control
the reaction time under the subcritical condition to the second.
For this reason, the addition of ethanol to a raw slurry was
confirmed effective in raising the yield of saccharides.
Embodiment 3
[0138] Referring to FIG. 5, description will be made of a time
schedule for operating a hydrolytic saccharification system as a
sequencing batch system, the hydrolytic saccharification system
being configured to perform five steps in total and use eight
pressure vessels. This system is adapted to cases where a
cellulosic biomass is difficult to hydrolytically saccharificate
under the subcritical condition and, hence, the hydrolyzing step
cannot but be performed for a longer time than the other four
steps. In FIG. 5, the time required to complete the hydrolyzing
step is 20 minutes and that required to complete any other step is
five minutes.
[0139] Initially, pressure vessel No. 1 performs the charging step
and, subsequently, pressure vessels Nos. 2 to 8 perform the
charging step sequentially with a time lag of five minutes from one
pressure vessel to the next one. Each pressure vessel repeats the
five sequential steps:
[C].fwdarw.[PH].fwdarw.[GL].fwdarw.[F].fwdarw.[DC]. Here, the time
required to complete the step of hydrolyzing a cellulosic biomass
into saccharides is 20 minutes and, accordingly, one cycle of the
hydrolytic saccharification process is (5 min.times.4 steps)+(20
min.times.1 step)=40 minutes. Pressure vessels Nos. 1 to 8 perform
this cycle sequentially with a time lag of five minutes from one
pressure vessel to the next one.
[0140] With the sequencing batch system shown in FIG. 5, the time
required to complete the hydrolyzing step is four times as long as
that required to complete any other process step. Therefore, if
five pressure vessels, the number of which corresponds to the five
process steps, are used, the thermal energy of flash vapor and that
of high-temperature slurry cannot be recovered unless each of the
process steps other than the hydrolyzing step takes 20 minutes as
does the hydrolyzing step. For this reason, the processing time
would be very long. In view of such an inconvenience, the
hydrolytic saccharification system according to the present
embodiment uses eight pressure vessels to realize effective heat
recovery while taking five minutes for any other process step than
the hydrolyzing step as does the foregoing system and 20 minutes
for the hydrolyzing step.
[0141] When pressure vessel No. 1 is at the temperature lowering
step, flashing vapor contained in pressure vessel No. 1 is supplied
to pressure vessel No. 6 at the heating-up step. Likewise, flashing
vapor contained in each of pressure vessels Nos. 2 to 8 at the
temperature lowering step is supplied to a respective one of
pressure vessels Nos. 7, 8, 1, 2, 3, 4 and 5, thus making heat
recovery.
[0142] The high-temperature slurry to be discharged (or drained)
from pressure vessel No. 1 at the discharging step exchanges heat
with the slurry to be charged into pressure vessel No. 8 at the
charging step. Likewise, the high-temperature slurry to be
discharged from each of pressure vessels Nos. 2 to 8 at the
discharge step exchanges heat with the slurry to be charged into a
respective one of pressure vessels Nos. 1 to 7.
[0143] In cases where equal time is required to complete respective
of the four steps other than the hydrolyzing step and the time
required to complete the hydrolyzing step is n times (where n is a
natural number; n is four in this example) as long as the time
required to complete each of the other four steps, the number of
pressure vessels used is preferably a multiple of (4+n). The system
thus arranged a sequencing batch system is capable of achieving
continuous hydrolytic saccharification of a cellulosic biomass in a
short time with the required energy saved, like embodiment 1.
[0144] While embodiment 3 uses eight pressure vessels, the
hydrolytic saccharification system, when comprising two sequencing
bath systems, may use 16 pressure vessels in total. The hydrolytic
saccharification system configured to perform four process steps in
total may be operated in a similar manner as above.
Embodiment 4
[0145] With respect to the foregoing embodiments 1 to 3,
description has been directed to the cases where a cellulosic
biomass is ground and then mixed with water to prepare a slurry,
which is then charged into a pressure vessel in the charging step
or the discharging and charging step. In the charging step or the
discharging and charging step according to the present invention,
however, a cellulosic biomass need not necessarily be slurried.
Hydrolysis saccharification of a cellulosic biomass can be achieved
also by such a charging step or discharging and charging step which
includes: charging a cellulosic biomass, such as bagasse, into a
water-permeable vessel having perforations, apertures or the like
for allowing water to move from the exterior to the interior of the
water-permeable vessel and vice versa; and encapsulating the
water-permeable vessel and water into each pressure vessel
(compressive and dense encapsulation).
[0146] Though there is no limitation on the material of the
water-permeable vessel as long as the material can withstand
elevated temperatures in the pressure vessel, the material is
preferably stainless steel and a like material having a high
endurance. Also, there is no limitation on the shape of the
water-permeable vessel; for example, a rectangular-parallelepiped
shape, a cylindrical shape or the like may be appropriately
selected for the water-permeable vessel. However, the same shape as
the internal shape (cylindrical shape) of each pressure vessel is
preferable in view of its high volumetric efficiency. Any means for
ensuring the water-permeability may be employed without any
particular limitation as long as the water-permeable vessel allows
water to move from the exterior to the interior of the
water-permeable vessel and vice versa; for example, the
water-permeable vessel may be partially or entirely reticulated;
the water-permeable vessel may be formed with slits or circular
perforations; or the water-permeable vessel may have open top.
[0147] FIG. 6 illustrates an example in which dried bagasse as a
cellulosic biomas is charged into the water-permeable vessel. In
this figure, the water-permeable vessel to be charged with bagasse
has a cylindrical shape (with open top) having a bottom surface and
a peripheral surface, which are formed with multiple perforations.
In this case there is no need to grind the dried bagasse. The dried
bagasse may be used with its length left as it is or cut to an
appropriate length.
[0148] After charging, it is preferable to compress the dried
bagasse within the water-permeable vessel from above by means of a
pressing machine or the like. The dried baggase in a previously
compressed condition may be charged into the water-permeable
vessel. The dried bagasse, which has a bulk specific gravity of
about 5 to about 10 kg/m3 before compression, can be compressed to
a bulk specific gravity of not less than 50 kg/m3. The dried
bagasse in this compressed condition is encapsulated into each
pressure vessel and then water is poured into the pressure vessel
to capacity. By so doing, the interior of the pressure vessel has a
solid matter concentration of about several %, which is the same
level of solid matter concentration as the slurry. Therefore, the
pressure vessel has substantially the same volumetric efficiency as
with the dried bagasse in the form of slurry.
[0149] In compressing dried bagasse within the water-permeable
vessel, it is preferable that the water-permeable vessel is
compressively and densely charged with dried bagasse as much as
possible by repeating the introduction of dried bagasse into the
water-permeable vessel and the pressing operation. The pressing
operation may be performed only once as long as a sufficient amount
of dried bagasse can be compressively and densely charged into the
water-permeable vessel.
[0150] The bulk specific gravity of a cellulosic biomass, such as
dried baggase, is preferably adjusted to a value of not less than
50 kg/m3 and not more than 300 kg/m3, more preferably not less than
100 kg/m3 and not more than 200 kg/m3, before encapsulation into
the pressure vessel. If the bulk specific gravity of the cellulosic
biomass is too low, the solid matter concentration becomes lower
than that of the cellulosic biomass in the form of slurry, which
results in a lowered volumetric efficiency. On the other hand, if
the bulk specific gravity of the cellulosic biomass is too high, it
is difficult for water to penetrate into the cellulosic biomass
and, hence, the hydrolysis reaction of the cellulosic biomass
occurs with difficulty.
[0151] In slurrying a cellulosic biomass such as dried bagasse, the
energy required to pulverize the cellulosic biomass is about 0.5 to
2 kW per 1 kg of the raw material. Such a pulverizing operation is
eliminated in the present embodiment. Even if grinding is
necessary, pulverization is not required. The amount of work
required to pretreat the cellulosic biomass is reduced to 1/10 to
1/2.
[0152] In charging the cellulosic biomass in the form of slurry
into a pressure vessel, it is required that the solid matter
concentration be lowered or the cellulosic biomass be pulverized in
order to prevent the piping from being clogged. The cellulosic
biomass has a relatively high water content. For this reason, even
when the solid matter concentration of the slurry is about 10% with
the water content of the cellulosic biomass taken into
consideration, the flowability of the slurry is low. However, by
encapsulating the water-permeable vessel charged with the
cellulosic biomass into the pressure vessel together with water,
the solid matter concentration within the pressure vessel can be
made substantially equal to that of the slurry, as described
above.
[0153] With the cellulosic biomass in the form of slurry, solid
matter is sometimes deposited on the inner wall of the piping as
well as on the inner wall of the pressure vessel and remains
thereon as residual solid matter. Such residual solid matter not
only causes the volumetric efficiency of each of the piping and the
pressure vessel but also mixes, as reacted fine powder, into
unreacted slurry. Therefore, such residual solid matter causes the
frequency of cleaning to increase. However, such a problem will not
arise by virtue of the step of encapsulating the water-permeable
vessel charged with the cellulosic biomass into the pressure vessel
together with water, followed by heating because only water passes
through the piping with the cellulosic biomass left within the
water-permeable vessel.
[0154] Further, in cases where the cellulosic biomass is heated at
a temperature of not lower than 140.degree. C. and not higher than
180.degree. C. to hydrolyze hemicellulose into saccharides and then
the residual solid matter is heated at a temperature of not lower
than 240.degree. C. and not higher than 280.degree. C. to hydrolyze
cellulose into saccharides, it is required that the solid content
obtained after the hydrolysis of hemicellulose be separated out by
solid-liquid separation and then mixed with water again to form a
slurry when the charging step or the discharging and charging step
includes charging the cellulosic biomass in the form of slurry into
the pressure vessel. However, with the process of encapsulating the
water-permeable vessel charged with the cellulosic biomass into the
pressure vessel together with water and then heating the pressure
vessel, there are advantages that it is sufficient to discharge
water containing saccharides and that the water-permeable vessel
serves also as the means for solid-liquid separation. By collecting
water containing saccharides that remains together with the biomass
residue in the water-permeable vessel by washing the biomass
residue, it is possible to collect saccharides more
efficiently.
[0155] In cases where the water-permeable vessel charged with the
cellulosic biomass is encapsulated into the pressure vessel
together with water in the charging step or the discharging and
charging step, the discharging step or the discharging and charging
step includes: discharging high-temperature water containing
saccharides; removing the water-permeable vessel out of the
pressure vessel; and removing a solid residue (which is a residual
solid matter left after hydrolysis of cellulose and/or
hemicellulose contained in the cellulosic biomass and comprising
lignin and an ash content as major components), followed by
disposal.
[0156] Since this residue can be utilized as a fuel for heating the
interior of the pressure vessel, the present embodiment, according
to which the solid matter concentration within the pressure vessel
can be raised and, hence, the amount of residue removed out of the
pressure vessel can be increased, is capable of suppressing the
amount of fuel to be used, such as petrol.
[0157] In the temperature lowering step, high-temperature water
contained in the pressure vessel is flash-evaporated to exchange
heat with water to be charged into the pressure vessel performing
the charging step. Other features are similar to the corresponding
features of the method and system in which the cellulosic biomass
in the form of slurry is charged by the charging step or the
discharging and charging step.
[0158] For example, in the case of the charging step in which the
cellulosic biomass is charged into the water-permeable vessel and
then encapsulated into the pressure vessel together with water, the
"water and water-permeable vessel charged with the cellulosic
biomass" is equivalent to the "raw slurry" appearing in FIG. 1
illustrating the procedure for operating the hydrolytic
saccharification system of embodiment 1.
[0159] It will be apparent from the foregoing description that many
improvements and other embodiments of the present invention may
occur to those skilled in the art. Therefore, the foregoing
description should be construed as an illustration only and is
provided for the purpose of teaching the best mode for carrying out
the present invention to those skilled in the art. The details of
the structure and/or the function of the present invention can be
modified substantially without departing from the spirit of the
present invention.
INDUSTRIAL APPLICABILITY
[0160] The present invention is useful as a method and system for
hydrolyzing a cellulosic biomass into saccharides, to be applied in
industrial fields such as the bioindustry and energy industry.
* * * * *