U.S. patent application number 10/611429 was filed with the patent office on 2004-04-01 for solvent pulping of biomass.
This patent application is currently assigned to ANDRITZ INC.. Invention is credited to Greenwood, Brian, Phillips, Joseph R., Pschorn, Thomas, Stromberg, Bertil C..
Application Number | 20040060673 10/611429 |
Document ID | / |
Family ID | 30119124 |
Filed Date | 2004-04-01 |
United States Patent
Application |
20040060673 |
Kind Code |
A1 |
Phillips, Joseph R. ; et
al. |
April 1, 2004 |
Solvent pulping of biomass
Abstract
An apparatus and process for solvent pulping of
cellulose-containing biomass utilizes at least one steaming vessel,
a plug screw feeder or compression screw device, at least one
super-atmospheric impregnation vessel, a solvent delignification
reactor capable of operating at a pressure of 350 psig or more, and
a solvent containing line for introducing solvent-containing liquor
at the plug screw feeder outlet or compression screw device outlet.
The process and system can also include at least one series
connected pressure diffuser and optionally a retention tube
downstream of each pressure diffuser to provide sufficient
retention time to substantially preclude re-deposition of lignin on
the cellulose fibers of the biomass, a blow tank connected to the
last of the pressure diffusers and retention tubes, and vessels for
multistage alcohol washing. The method steams the biomass and
impregnates it with solvent to produce an aqueous slurry of biomass
and solvent, delignifies the particulate biomass in the slurry,
removes solvent while continuing delignification of the biomass in
the slurry and while substantially precluding re-deposition of
lignin on the cellulose of the biomass, reduces the pressure of the
slurry; and then washes the slurry.
Inventors: |
Phillips, Joseph R.;
(Queensbury, NY) ; Greenwood, Brian; (Cummings,
GA) ; Stromberg, Bertil C.; (Bolton Landing, NY)
; Pschorn, Thomas; (Lennoxville, CA) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
1100 N GLEBE ROAD
8TH FLOOR
ARLINGTON
VA
22201-4714
US
|
Assignee: |
ANDRITZ INC.
Glens Falls
NY
|
Family ID: |
30119124 |
Appl. No.: |
10/611429 |
Filed: |
December 9, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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|
60392969 |
Jul 2, 2002 |
|
|
|
60406298 |
Aug 28, 2002 |
|
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60409573 |
Sep 11, 2002 |
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Current U.S.
Class: |
162/22 ; 162/238;
162/246; 162/37; 162/39; 162/52; 162/60; 162/61; 162/68;
162/82 |
Current CPC
Class: |
D21C 3/24 20130101; D21C
3/20 20130101 |
Class at
Publication: |
162/022 ;
162/052; 162/037; 162/039; 162/060; 162/061; 162/082; 162/068;
162/238; 162/246 |
International
Class: |
D21B 001/36; D21C
007/06; D21C 007/08; D21C 009/02; D21C 007/12; D21C 003/02 |
Claims
1. A method of solvent pulping cellulose-containing biomass
comprising substantially continuously and sequentially: a)
gradually stepping up the pressure and temperature of particulate,
crushed or shredded biomass from substantially atmospheric and
ambient to above about 350 psig and above kraft cooking
temperature, in a plurality of different stages of increasing
pressure and temperature; b) delignifying the particulate biomass
in an aqueous slurry of solvent at a pressure above about 350 psig
and a temperature above kraft cooking temperature; c)
simultaneously removing solvent while continuing delignification of
the biomass in the slurry, at a pressure above about 350 psig and
at a temperature above about 140 deg. C., preferably above about
180 deg. C.; d) substantially instantaneously greatly reducing the
pressure of the slurry; and then e) washing the slurry.
2. A method as recited in claim 1 wherein d) produces flashed
solvent, and further comprising f) condensing and reusing the
flashed solvent.
3. A method as recited in any preceding claim wherein c) is
practiced in at least one pressure diffuser, which is arranged in
series when there are more than one pressure diffuser.
4. A method as recited in any preceding claim further comprising g)
providing blow-back protection, upon upset conditions, in the
process prior to or intermediate within a).
5. A method as recited in claim 4 wherein g) is practiced by
providing a valve capable of withstanding the highest pressure
encountered during the practice of a)-e).
6. A method as recited in claim 5 wherein g) is practiced at a
location wherein the pressure on one operative side of the valve is
at substantially atmospheric pressure.
7. A method as recited in any preceding claim wherein b) and c) are
practiced at a temperature between about 180-210 degrees C., and a
pressure of between about 350-500 psig.
8. A method as recited in claim 1 wherein the solvent comprises
ethanol as the primary active constituent.
9. A method as recited in claim 1 wherein c) is practiced to
substantially preclude re-deposition of lignin on the cellulose of
the biomass.
10. A method as recited in claim 1 wherein solvent-containing
liquor used in b) and c) includes liquor removed from the slurry in
a subsequent stage, the removed liquor maintained under
substantially the same pressure as in the practice of b) and
c).
11. A method as recited in claim 1 wherein the biomass comprises
corn stovers.
12. A solvent pulping system for a cellulose containing biomass,
comprising: a) at least one steaming vessel having a first outlet;
b) at least one impregnation vessel operatively connected to the
first outlet, and having a second outlet; c) a blow-back
preventing, upon upset conditions, device; d) a solvent
delignification reactor operatively connected to b) and capable of
operating at a pressure of 350 psig or more; and wherein c) is
capable of withstanding the operating pressure of d).
13. A system as recited in claim 12 wherein d) has a third outlet,
and further comprising at least one pressure diffuser operatively
connected to the third outlet.
14. A system as recited in claim 12 further comprising an indirect
heater for heating solvent supplied to b).
15. A system as recited in claim 12 further comprising a blow tank
operatively connected to the last of the pressure diffusers
16. A system as recited in claim 15 further comprising a relief
condenser operatively connected to a gaseous relief from the blow
tank.
17. A system as recited in claim 12 wherein d) comprises an upflow
or vapor phase reactor.
18. A system as recited in claim 12 wherein b) includes a plug
screw feeder or compression screw device.
19. A system as recited in claim 12 wherein the system comprises a
plurality of vessels which incrementally raise the pressure of the
biomass.
20. A system as recited in claim 12 further comprising a plurality
of filtrate tanks maintained at substantially the same operating
pressure as d).
21. A system as recited in claim 12 and substantially devoid of a
filtrate tank.
22. A system as recited in claim 12 further comprising a nitrogen
purge for d).
23. A system as recited in claim 12 further comprising a nitrogen
pressure control device.
24. A system as recited in claim 12 further comprising an
extraction screen adjacent the third outlet.
25. A system as recited in claim 12 wherein c) comprises a rotary
valve capable of withstanding a pressure differential of between
about 350-500 psig.
26. A system as recited in claim 25 wherein c) is capable of
withstanding a pressure differential of about 450 psig.
27. A solvent pulping system for a cellulose containing biomass,
comprising: a) at least one steaming vessel having a first outlet;
b) at least one super-atmospheric impregnation vessel operatively
connected to the first outlet, and having a second outlet; c) a
solvent delignification reactor operatively connected to b) and
capable of operating at a pressure of 350 psig or more, and having
a third outlet; and d) a plurality of series connected pressure
diffusers operatively connected to the third outlet and operating
at 350 psig or more, and optionally a retention tube downstream of
each pressure diffuser to provide sufficient retention time to
substantially preclude re-deposition of lignin on the cellulose
fibers of the biomass.
28. A system as recited in claim 27 further comprising a plug screw
feeder or compression screw device between a) and b); and further
comprising a solvent containing line for introducing
solvent-containing liquor at the plug screw feeder outlet or
compression screw device outlet.
29. A system as recited in claim 27 further comprising an indirect
heater for heating solvent supplied to b), a blow tank operatively
connected to the last of pressure diffusers, and a relief condenser
operatively connected to a gaseous relief from the blow tank.
30. A system as recited in claim 27 wherein c) comprises an upflow
or vapor phase reactor, and wherein b) includes a plug screw
feeder; and further comprising at least one super-atmospheric
steaming vessel operatively connected between a) and b).
31. A system as recited in claim 27 further comprising a plurality
of filtrate tanks maintained at substantially the same operating
pressure as c).
32. A solvent pulping system for a cellulose containing biomass,
comprising: a) at least one steaming vessel having a first outlet;
b) at least one super-atmospheric impregnation vessel operatively
connected to the first outlet, and having a second outlet; c) a
solvent delignification reactor operatively connected to b) and
capable of operating at a pressure of 350 psig or more, and having
a third outlet; and wherein b) includes a plug screw feeder and a
fluffer at its outlet; and further comprising a solvent containing
line for introducing solvent-containing liquor at the plug screw
feeder outlet or between the plug screw feeder and fluffer, or in
the fluffer.
33. A solvent pulping system for a cellulose containing biomass,
comprising: a) at least one super-atmospheric steaming vessel
having a first outlet; b) at least one super-atmospheric
impregnation vessel operatively connected to the first outlet, and
having a second outlet; c) a solvent delignification reactor
operatively connected to b) and capable of operating at a pressure
of 350 psig or more, and having a third outlet; and d) a plug screw
feeder or compression screw device between a) and b); and e) a
solvent containing line for introducing solvent-containing liquor
at the plug screw feeder outlet or compression screw device
outlet.
34. A system as recited in claim 33 further comprising at least one
series connected pressure diffuser operatively connected to the
third outlet and operating at 350 psig or more, and optionally a
retention tube downstream of each pressure diffuser to provide
sufficient retention time to substantially preclude re-deposition
of lignin on the cellulose fibers of the biomass.
35. A system as recited in claim 34 further comprising a blow tank
operatively connected to the last of pressure diffusers and
retention tubes.
36. A system as recited in claim 34 further comprising vessels for
multistage alcohol washing located downstream from the last of
pressure diffusers and retention tubes.
37. A system as recited in claim 33 further comprising an indirect
heater for heating solvent supplied to b).
38. A system as recited in claim 33 wherein c) is a downflow
reactor.
39. A system as recited in claim 33 further comprising a plug screw
feeder or compression screw device in advance of a).
40. A system as recited in claim 33 further comprising a blow-back
preventing, upon upset conditions, device that is capable of
withstanding the operating pressure of c) and is located in advance
of a).
41. A method of solvent pulping cellulose-containing biomass
comprising substantially continuously and sequentially: a) steaming
the biomass and impregnating it with solvent to produce an aqueous
slurry of biomass and solvent; b) delignifying the particulate
biomass in the slurry at a pressure above about 350 psig and a
temperature above about 140 degrees C., preferably above about 180
degrees C.; c) simultaneously removing solvent while continuing
delignification of the biomass in the slurry, at a pressure above
about 350 psig and a temperature above about 180 degrees C. in a
series of stages, and to substantially preclude re-deposition of
lignin on the cellulose of the biomass; d) substantially
instantaneously greatly reducing the pressure of the slurry; and
then e) washing the slurry.
42. A method as recited in claim 41 wherein during b), c) and e)
filtrate is removed and held in tanks and then redirected to a
stage other than that from which it was removed, and further
comprising maintaining the filtrate tanks and connected piping at
substantially the same pressure as b) is practiced.
43. A method as recited in claim 41 wherein d) produces flashed
solvent, and further comprising f) condensing and reusing the
flashed solvent; and further comprising g) providing blow-back
protection, upon upset conditions, in the process prior to or
intermediate within a), by providing a rotary valve capable of
withstanding the highest pressure encountered during the practice
of a)-e), and wherein g) is practiced at a location wherein the
pressure on one operative side of the rotary vale is at
substantially atmospheric pressure.
44. A method as recited in claim 41 further comprising indirectly
heating the solvent supplied for impregnating the biomass in a) to
a temperature above about 180 degrees C.
45. A method as recited in claim 41 further comprising retaining
the slurry after at least one pressure diffuser stage for a time
sufficient to substantially prevent re-deposition of lignin on the
cellulose fibers of the biomass.
46. A method as recited in claim 41 wherein the liquor to material
ratio during delignification is between about 5:1 and 9:1.
Description
BACKGROUND AND SUMMARY OF INVENTION
[0001] Solvent pulping is a well known, though heretofore
economically impractical, technique for producing cellulose pulp,
primarily from wood-based cellulose (although it has been known to
produce cellulose pulp by solvent pulping wheat straw and reed).
The term "solvent pulping" as used herein means pulping cellulose
material using organic cooking chemicals, such as (but not
restricted to) aliphatic alcohols (e.g., methanol, ethanol,
tert-butanol, and isopropanol) with or without a small amount of a
mineral or organic acid, carboxylic acids with or without hydrogen
peroxide, formic acid, sulfuric acid or other mineral acids, and/or
acetic acid (with the effective component of the cooking liquor
peracetic acid).
[0002] The economic problems associated with solvent pulping have
been the inability to recover a high enough percentage of the
cooking liquor effective component (e.g., alcohol), the increased
COD pollution as a result of the discharge of the unrecovered
cooking liquor effective component, the need for significant
amounts of purchased power for electricity or steam, and the need
to build-in high levels of safety into the process in view of the
volatility of the cooking liquor effective component. Also,
technical and/or market problems with lignin or other chemical
(such as furfural) recovery for sale (often necessary for there to
be any chance that solvent pulping will be economical) have been
common.
[0003] According to one aspect of the present invention, solvent
pulping is utilized in a manner that has a higher level of
probability of being economically practical than past attempts.
This higher probability results from a high level of recovery of
solvent, the use of cheap raw material, and the equipment and
process designs that are recognized and utilized according to the
invention. The equipment utilized is all commercially available and
of proven design, yet put together in a highly efficient and
effective manner. The cellulose fiber produced may be used for any
purpose that pulped wood fibers are typically used, such as pulp
manufacture, packaging materials, or dissolved pulp and other
materials (including lignin and furfural) may be recovered.
[0004] The raw material comprises cellulose-containing biomass, and
desirably biomass that would typically be a waste or minor use
product. The invention may use any known or subsequently developed
suitable cellulose-containing biomass including (without
limitation) kenaf, whole industrial hemp stalks, bamboo,
agricultural residues (the byproducts of annual food and fiber
production) such as the straw of various grains, cereal grasses
(such as corn), flax, cotton linters, bagasse (sugar cane pulp),
banana stalks, and pineapple residue. The biomass that is desirable
is a chopped, crushed or shredded version--e.g., to a maximum
particle dimension of about one inch. For some agricultural
residues such as corn stovers, it can be advantageous to discard
roots and kernels.
[0005] Some of the possibly utilized equipment and process designs
according to the present invention include:
[0006] Using simple, but effective blow-back prevention upon upset
conditions;
[0007] Gradually stepping up the pressure and temperature in the
system and process from atmospheric and ambient to high levels
(e.g., to about 20-35 atmospheres, similar to U.S. Pat. No.
4,100,016, the entire content of which is hereby incorporated by
reference in its entirety, and preferably to about 350-500 psig,
and above-kraft temperatures, preferably between about 180-210
degrees C.) necessary to properly delignify the raw material;
[0008] Using simple, highly reliable, equipment to provide pressure
and temperature step-up, while performing different functions
(e.g., steaming and impregnation);
[0009] Indirectly heating the cooking liquor in order to maintain
precise control over the solvent to material ratio and to allow the
use of lower pressure steam;
[0010] Extending delignification from a pre-hydrolysis reactor to
one or more pressurized vessels while initiating washing and
substantially precluding re-deposition of lignin (that is
precipitating of the lignin back on the cellulose fibers);
[0011] Minimizing energy and liquor losses by controlled hot liquor
flashing;
[0012] Providing for proper nitrogen purging where necessary during
start-up or shut-down;
[0013] Providing flexibility in the type of pre-hydrolyzing reactor
utilized; and
[0014] Providing for uniform treatment of the material.
[0015] The method of the invention is preferably, although not
necessarily, practiced continuously.
[0016] In the following description, one embodiment of the method
and apparatus will be described with respect to delignification of
agricultural residues, e.g., straw of various grains, cereal
grasses (such as corn stovers), flax, cotton linters, bagasse
(sugar cane pulp), banana stalks, and pineapple residue, using
ethanol as the primary solvent (e.g., about 40-60% ethanol with
water (and dissolved solids), and possibly a catalytic amount of a
mineral (e.g., hydrochloric or sulfuric) or organic (e.g., formic
or acetic) acid). The pressures, temperatures, and other conditions
mentioned are particularly advantageous for this type of raw
material and solvent. However, it is to be understood that the
invention is not so limited, but rather may use any known or
subsequently developed solvent, and any suitable
cellulose-containing biomass including (without limitation) kenaf,
whole industrial hemp stalks, bamboo, agricultural residues (the
byproducts of annual food and fiber production) such as the straw
of various grains, cereal grasses (such as corn), flax, cotton
linters, bagasse (sugar cane pulp), banana stalks, and pineapple
residue.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIGS. 1A, 1B and 1C schematically show a biomass pulping
system having a vapor phase (downflow) prehydrolysis reactor.
[0018] FIG. 2 schematically shows a biomass pulping system having a
hydraulic (upflow) prehydrolysis reactor.
[0019] FIG. 3 shows an alternative portion of a biomass pulping
system.
[0020] FIG. 4 shows an alternative portion of a biomass pulping
system using a hydraulic (upflow) prehydrolysis reactor.
[0021] FIGS. 5, and 5A-5E show an alternative portion of a biomass
pulping system.
[0022] FIG. 6 shows a block diagram of a biomass pulping
system.
[0023] FIG. 7 shows a block diagram of a biomass pulping
system.
DETAILED DESCRIPTION OF INVENTION
[0024] FIGS. 1A, 1B and 1C schematically illustrate one exemplary
form (and variations) a system can take for practicing an
advantageous solvent pulping method according to the invention.
FIGS. 2, 1B and 1C schematically illustrate another exemplary form
(and variations) a system can take for practicing an advantageous
solvent pulping method according to the invention. FIGS. 3, 4, 6
and 7 illustrate other embodiments (for example, possible changes
to FIGS. 1A, 1B, 1C and 2, or separate systems) that may be
utilized according to the present invention. FIG. 5 schematically
illustrates another exemplary form a system can take for practicing
an advantageous solvent pulping method according to the
invention.
[0025] In FIGS. 1A, 1B, 1C, 2, 3, 4, 6 and 7, many of the
components are similar (e.g., components 23 and 94--plug or
compression screw feeders, components 24 and 98--steaming vessel or
inclined steaming vessel, components 25 and 102--plug or
compression screw feeders, components 28 and 104--inclined
impregnation screw conveyor) and have similar connections and
processing conditions.
[0026] Major preferred components of the inventive systems include
an ambient/atmospheric biomass feed 10, steaming (with pressure
step-up) equipment 11, a combined safety barrier and pressure
step-up device 12, impregnation, pressure step-up and charging
equipment 13, a prehydrolysis main reactor 14 (or downflow, upflow,
multistage or inclined reactor 105, or downflow reactor 107),
subsequent pressurized delignifying and wash-initiating (and
delignification-continuing) equipment 15, controlled solvent
heating equipment 16, and delignified cellulose pulp washing
equipment 17 (also referred to as solvent or alcohol washing system
or equipment--which comprises conventional equipment). Other types
of equipment and apparatus are utilized with these major components
to get desired results.
[0027] The drawings use conventional abbreviations and symbols. For
example, valves with a "PC" designation are pressure controlled,
those with an "LC" designation are level controlled, those with a
"TC" designation are temperature controlled, and those with an "FC"
designation are flow controlled. Similarly, sensors sense
temperature, level, and density, etc.
[0028] The biomass feed 10 may comprise a simple conveyor 20 that
deposits particulate agricultural residues (e.g., corn stovers
having a maximum particle dimension of about one inch, and a bulk
density of about 8-9 b d lbs./cu.ft.) into a conventional screw
feeder airlock 21. The particulate is at substantially ambient
temperature (e.g., 25 degrees C.) and atmospheric pressure until
fed by the feeder 21 to the presteaming bin 22. An airlock is
utilized to preclude ethanol vapors from exiting the bin 22.
[0029] The steaming equipment 11 includes the bin 22, the screw 23,
the equipment 12, and the horizontal steaming vessel 24. The
steaming that occurs in bin 22 and vessel 24 removes air from the
biomass, and may be practiced using low pressure steam (e.g., at
about 50 psig). The bin 22 is preferably a DIAMONDBACK.RTM. chip
bin sold by Andritz Inc. and disclosed in U.S. Pat. Nos. 6,325,888,
5,500,083 and 5,628,873, the entire contents of which are
incorporated herein by reference. DIAMONDBACK vessels have single
convergence and side relief. This structure has no or few moving
parts or flexible seals, making it particularly suitable for
keeping air out and preventing ethanol leakage. Alternatively, bin
90 (in FIG. 3) is preferably a live bottom chip bin, with
atmospheric feed of Hammermilled cellulose-containing biomass.
Steaming in bin 22 is substantially atmospheric and for about 10-30
minutes. Steaming in vessel 24 (or 98--inclined) is for a short
period of time and preferably super-atmospheric (e.g., about 2-50
psig, preferably about 10-15 psig), and the biomass is at about 100
degrees C. when it enters vessel 24. The steaming in vessel 24 may
take between about 30 seconds to about 5 minutes at about 2-50
psig, e.g., about 1 minute.
[0030] A wide variety of different types of equipment may be
utilized for the pieces of equipment 23 (or 94) and 24 (or 98). In
one embodiment, device 23 (or 94) is a plug screw
feeder/compression screw device (for example, a MSD
Impressafiner.RTM. sold by Andritz Inc.), or a variable speed
metering screw. The rate set by 23 determines system retention
time, and is used to determine proper solvent usage, and proper
cooking temperature. The vessel 24 or 98 is preferably a
conventional horizontal or inclined steaming vessel (e.g., having a
screw conveyor), also available from Andritz Inc., preferably
utilizing medium pressure steam, e.g., about 250 psig).
[0031] The device 12 performs both a safety function and a feeding,
gradual pressure step-up function. The device 12 (and all equipment
downstream of it until the blow tank) is capable of withstanding
the maximum pressure that may exist in the biomass containing
portions of the system (e.g., in the reactor 14). The typical
pressure in reactor 14 is between about 350-500 psig or lower,
therefore the device 12 should be designed to withstand a pressure
of 550 psig or lower, which will prevent blowback in case of an
upset condition, and in general will preclude ethanol (or other
solvent material) from escaping back through the feed system. While
other devices can be utilized (including having the separate
functions the device 12 performs), the device 12 desirably
comprises a conventional Andritz rotary valve 96, only constructed
to withstand 550 psig or lower. Such a valve allows continuous
efficiently controlled feeding of biomass into the pressurized
components of the system without unduly compressing, fiberizing, or
damaging the material conveyed.
[0032] Downstream of the steaming vessel 24 (or 98) is device 25
(or 102), a plug/compression screw feeder (for example, a MSD
Impressafiner.RTM. sold by Andritz Inc.). The device 25 forms a
compressed plug capable of obtaining about a 200 psig pressure
increase. The plug so formed also provides an excellent vapor
barrier so that little or no material (e.g., ethanol) can pass back
through it. Any excess moisture in the biomass is squeezed out in
device 25 (or 102), and removed through a screen assembly 26 in the
bottom of the device 25. The consistency of the material discharged
from device 25 may be monitored using the drive motor load, with a
typical consistency between about 40-60% od. The pressure of the
material discharged from device 25 is preferably about 200 psig. A
conventional fluffer 27 is preferably provided at the discharge of
the device 25.
[0033] In alternative embodiments like FIGS. 3, 4 and 6, and
similar to the above, downstream of the vessel 98 is device 100, a
conventional screw feeder, then device 102, a compression screw
device (for example, a MSD Impressafiner.RTM. sold by Andritz
Inc.). The device 102 forms a compressed plug. The plug so formed
also provides an excellent vapor barrier so that little or no
ethanol can pass back through it. Any excess moisture in the
biomass may be squeezed out in device 102, and removed through a
screen assembly in the bottom of the device 102. The consistency of
the material discharged from device 102 may be monitored using the
drive motor load, with a typical consistency between about 40-60%
od. The pressure of the material discharged from device 102 may be
about 200 psig.
[0034] In the embodiments depicted in FIGS. 3, 4 and 6, the
material preferably passes to chip bin 90, optionally to a screw
conveyor 92, to a compression screw device 94, to a rotary valve
96, to an inclined steaming vessel 98, to an optional screw feeding
device 100, to another compression screw device 102 (with solvent
added at line 29 after the discharge from device 102), to an
inclined impregnation vessel 104, and (in FIG. 3) to an optional
fluffer (not shown) and to reactor 14, or (in FIG. 4) to an
optional chip tube 81, to a screw feeding device 82, and to the
bottom/inlet of reactor 80.
[0035] Preferably, there are at least two preheaters 30 and 37 in
the system. One preheater 30 preheats the solvent added to the feed
system. The other preheater 37 "tops off" the heat required to go
to the impregnation equipment 28 to the reactor 14 temperature, but
more importantly, provides additional heat to raise the temperature
of the pressed pulp and the liquor drained from the second plug
screw feeder 25 (or 102) up to the reactor temperature. This
temperature increase is required because the impregnation equipment
must operate at a lower pressure than the reactor because a single
stage plug screw feeder can only generate a pressure of about 200
psig, thereby limiting the allowable temperature in the
impregnation equipment to avoid flashing.
[0036] The impregnation equipment 13 of FIG. 1A includes an
inclined screw conveyor 28 (or 104 in FIGS. 3, 4 and 6). Cooking
liquor (e.g., preferably about 40-60% ethanol, most of the
remainder being water (and dissolved solids) with perhaps a small
amount of acid) is added to the biomass in or before device 28 (or
104). In some of the exemplary embodiments illustrated, the cooking
liquor in line 29 is indirectly heated by medium pressure steam in
the indirect heater 30 and then fed to the conventional fluffer 27
(or at the discharge of 102), which substantially uniformly mixes
the biomass and cooking liquor so that uniform impregnation occurs.
Medium pressure steam may be added directly to the device 28 (or
104) via line 31 as long as the amount of liquid that will result
from the steam is considered in determining the constituents of the
cooking liquor, and the proper liquor-material ratio. For the
process of the invention, it is desirable that the liquor-material
ratio be high, e.g., between about 5:1 to 9:1 (e.g., about 6:1). In
one embodiment, impregnation typically takes between about 30
seconds and 5 minutes (e.g., about 1 minute) at about 200 psig.
[0037] According to the embodiment depicted in FIG. 1A, from the
inclined screw feeder 28, the biomass passes to another plug screw
feeder 32 where the pressure is increased to digesting pressure.
For many solvent pulping operations, including with ethanol as the
primary cooking liquor, the pressure is preferably increased to
between 300-425 psig, more preferably about 350-400 psig. Passage
of the biomass through the plug screw feeder 32 in the presence of
cooking liquor greatly increases the penetration rate of the
solvent into the biomass due to the flexing and working of the
material in the presence of the active cooking chemical. Any
drainage from the feeder 32 passes through a screen, into line 33
and is returned to the system. A second fluffer 34 may be provided
at the discharge of the feeder 32, and the biomass is discharged by
fluffer 34 into the prehydrolysis reactor.
[0038] The controlled solvent heating equipment 16 is connected to
the line 33, and may include tank 35, pump 36, and indirect
continuous circulation heater 37. The recirculated liquid from line
33 is heated in heater 37 (e.g., to about 210 deg. C. if the
desired cooking temperature is about 200 deg. C.) and then re-mixed
with the biomass. The heated re-circulated cooking liquor may be
re-mixed by adding it in lines 38 to the feeder 32 just before and
at the second fluffer 34. This heating and re-mixing allows the
biomass to reach the final desired prehydrolysis temperature (e.g.
between about 180-210 deg. C). The system 16 achieves this
desirable result with the use of lower pressure steam (250-325
psig) than would be necessary if steam were directly added to the
biomass. That is, lower pressure steam than otherwise would be
necessary (the otherwise necessary steam would be at a pressure of
400-500 psig) may be used in the heater 37. For this reason, and to
keep excess water out of the system, the makeup cooking liquor
(typically ethanol), and, if required, water, are also preheated
(in indirect heater 30) before addition to the cooking
circulation.
[0039] According to an embodiment as depicted in FIG. 3, from the
inclined screw feeder 104, the biomass can be passed to an optional
fluffer 34 (like in FIG. 1A) at the discharge of the impregnation
device 104, and the biomass is then discharged to a conventional
reactor 105. For many solvent pulping operations, including with
ethanol as the primary cooking liquor, the pressure is increased to
between 300-425 psig, preferably about 350-400 psig. Any drainage
from feeder 100 may pass through a screen, into line 33 and can be
returned to the system.
[0040] According to the exemplary reactor feed system of FIG. 3
from bin 90 to feeder/conveyor 104 (read in conjunction with FIG.
1A and as an alternative to the reactor feed system from bin 22 to
feeder 32 in FIG. 1A), the controlled solvent heating equipment 16
is optionally not used (including recirculation line 33 to line
38). In the exemplary embodiment of FIG. 3, the reactor 105 can be
one of many commercially available reactors with associated
equipment, e.g., an upflow, downflow, multi-stage or inclined
reactor with associated equipment that is commonly known and
commercially available.
[0041] In the embodiment illustrated in FIG. 1A, the continuous
prehydrolysis reactor 14 is a vapor phase continuous downflow
ethanol-biomass reactor (digester). The reactor 14 includes a
substantially vertical vessel shell 39 having an inlet 40 at or
adjacent the top thereof and preferably directly connected to the
outlet from the second fluffer 34, and an outlet 41 at or adjacent
the bottom thereof. A vapor phase 42 is maintained at the top
portion of the reactor 14 as seen in FIG. 1A, and typically some
biomass--shown schematically at 43--is in a generally conically
shaped pile in the vapor phase 42. A gamma gauge, or the like,
senses and assists in controlling biomass level, while a dp cell,
or the like, senses and assists in controlling liquid level.
Off-gases are vented by the conventional vent 44. For start-up and
other conditions requiring safety procedures, a nitrogen purge is
provided for the vessel 39, as indicated schematically by line 45
and the associated pressure controlled valve illustrated in FIG.
1A. Additionally, this control scheme may be used to control an
"overpressure" situation under normal operations.
[0042] The cooking liquor (ethanol) and biomass move downwardly
substantially concurrently in the vessel 39, and some
delignification of the biomass occurs. While alkaline
delignification can be practiced, preferably the pH in the vessel
39 is about 4-5, and the consistency within the vessel is between
about 10-30% solids at the beginning of the process and 5-20%
solids at the finish. Somewhat spent cooking liquor is extracted by
extraction screen 46 just above outlet 41, and part of the
extracted liquor is passed in line 47 to the flash tank 48 (FIG.
1B), while another portion 47' is recirculated via line 49 to the
indirect heater 37. Some of the liquid from the pressurized
filtrate tank 63 can be flashed for ethanol recovery, as by passing
it in line 49' and combining it with line 47, to pass to flash tank
48. A conventional rotating scraper 50 is preferably provided at or
adjacent the outlet 41 of vessel 39 to prevent pluggage of the
vessel 39, and to help provide substantially uniform movement of
biomass through the reactor 14.
[0043] Unlike a conventional kraft continuous digester, the reactor
14 provides no countercurrent wash within the vessel 39 because the
biomass material (and particularly for corn stovers) is not
reliably permeable enough. Rather washing, and further
delignification, are provided in subsequent vessels. In the
preferred embodiment illustrated in FIGS. 1A and 1B, external
wash-initiating and delignification-continuing equipment 15 is
provided in the form of first and second series-connected
conventional pressure diffusers 51, 52; respectively. This allows
ethanol extraction to occur in stages, with successively cleaner
solvent, while the pressure diffusers 51, 52 are part of a modified
cooking system in much the same way that a digester wash zone is
part of a modified cooking system in a continuous kraft digester.
The pressure diffusers 51, 52 (and optionally 64) are preferably
conventional pressure diffusers available from Andritz, but are
designed to withstand pressures of 500 psig, or even higher, and at
least 450 psig for purposes of the present invention.
[0044] The wash/delignification liquor (diluted ethanol) in the
first diffuser 51 is added in line 53, from the filtrate tank 54
connected to the liquid discharge 55 from the second diffuser 52.
For the second diffuser 52, however, the wash/delignification
liquor introduced at 56 will be cleaner, not only including
filtrate from the filtrate tank 57 from the external wash system
17, but also fresh ethanol from line 58 from the solvent recovery
tank 59. The liquor added at 56 is heated in indirect heater 60 to
approximately the same temperature as in the main reactor 14 (e.g.,
about 180-210 degrees C., but perhaps between 100-200 degrees
C.).
[0045] Desirably, first and second retention tubes 61, 62,
respectively, are provided after each of the diffusers 51, 52. The
retention tubes 61, 62 let freshly extracted lignin diffuse out of
the biomass fibers after each diffuser 51, 52, and before the
subsequent treatment stage, greatly reducing lignin
reprecipitation. The volume of the tubes 61, 62 (given a
substantially constant material flow rate through the system) will
determine the retention time, preferably between about 1-10 minutes
(e.g., about 5 minutes) for corn stovers.
[0046] The use of pressure diffusers 51, 52 allows the process to
be continuously (without reduction) operated at very high
temperature and pressure without disadvantage. By maintaining high
super-atmospheric pressure and elevated temperature, it is possible
to keep ethanol vapors contained in a manner that cannot be
obtained with other conventional washing equipment. Also, filtrate
tanks (e.g., 54, 57, 63) between stages can be fully pressurized
(e.g., between about 350-425 psig) so as to prevent hot liquor from
flashing between stages, and to reduce or minimize pumping power
and difficulty. Pressurized filtrate tanks are possible because of
the use of the pressure diffusers 51, 52 and 64 (for the washing
equipment 17, 17' or 17a). It may be possible to operate the
desired process without the filtration tanks.
[0047] After the second retention tube 62, the pulp is discharged
to a conventional blow tank 65 (FIGS. 1B, 1C and 6); that is, the
pressure of the pulp is substantially instantaneously greatly
reduced (perhaps even to about atmospheric) while hot liquids
flash. It may be possible to operate the blow tank at about 15 psig
as well as to operate with an MC.RTM. pump at the discharge of the
tank. An MC.RTM. pump 72, available from Andritz Inc. or other
suitable pump for pumping a slurry with a large percentage of
solids, may be used to pump the pulp to the system 17, 17' or 17a.
In blow tank 65, a portion of the ethanol is flashed into a relief
condenser 66 (while simultaneously preheating process water, e.g.,
for making cooking liquor or steam), and then recycled via line 67
for reuse (e.g., at the impregnation stage). By this point, the
amount of lignin has been significantly reduced so that it will not
precipitate onto the cellulose fibers even though the concentration
of ethanol and the temperature have dropped significantly, and the
pH has decreased, as a result of flashing and washing.
[0048] The third pressure diffuser 64, in system 17, washes the
pulp and facilitates ethanol (or other solvent) recovery. The
diffuser 64 is designed to reduce the amount of ethanol left in the
pulp after flashing by about 90%. The removed ethanol is circulated
in line 68 to the filtrate tank 57, to be used as
wash/delignification liquor for the second diffuser 52. The wash
liquor for diffuser 64 preferably comprises substantially clean
water, introduced at 69. The extracted pulp in line 70 may be sent
to storage, or immediately bleached or otherwise treated, and
ultimately may be used for making any products that pulped wood
fibers (or, depending upon the biomass source, other cellulose
pulp) are typically good for manufacturing.
[0049] Instead of a single pressure diffuser 64, washing in stage
17 may be accomplished using a plurality of pressure diffusers, or
four or more stages of other conventional types of washers, or
combinations thereof depending on the degree of solvent recovery
desired and the level of loss than can be allowed. As shown in FIG.
7, one set of pressure diffuser 51 and retention tube 61 is used
before the blow tank 65 followed by the vessels for multistage
alcohol (solvent) washing 17a (which are conventional washing
equipment and associated piping).
[0050] The unique system and embodiments of the subject invention
allow highly beneficial recirculation of solvent, allows the use of
lower pressure steam, reduces water entering the system that keeps
the evaporation needs of the final product lower and that results
in the need for less solvent to maintain proper solvent
concentration.
[0051] As noted above, FIG. 2 illustrates another embodiment that
may be utilized according to the present invention. In FIG. 2, all
of the components are preferably similar to those in FIG. 1A (and
designated by the same reference numerals); except that an upflow
hydraulic prehydrolysis reactor 80 is used.
[0052] As also noted above, FIG. 4 illustrates another embodiment
that may be utilized according to the present invention. In FIG. 4,
most of the components are preferably substantially the same as in
FIGS. 1 and 2 (components 23 and 94, components 24 and 98,
components 34 and 100, components 25 and 102, components 28 and
104) and have similar connections, except the different sequence of
the components and the use of a live bottom buffer bin 90 instead
of bin 22. For the system depicted in FIG. 4, the operation is
similar to that described above for FIG. 3, except an upflow,
hydraulic prehydrolysis reactor 80 and optional components (81 and
82) are used, similar to the system depicted in FIG. 2.
[0053] As is conventional for upflow reactors, a "chip tube"
(available from Andritz Inc.) 81 can receive the slurry of biomass
and cooking liquor that is to be introduced into the reactor 80. In
this case, the slurry can originate from a second, optional fluffer
34, as in FIG. 2. A screw feeder 82 may be used to transport the
ethanol-biomass slurry from the chip tube 81 to the inlet 83 of the
reactor 80 to flow upwardly in the hydraulic reactor 80. The
extraction screen 46 is adjacent the outlet 84 of the reactor 80,
near the top thereof, as is the scraper 50.
[0054] As further noted above, FIG. 6 illustrates another
embodiment that may be utilized according to the present invention.
FIG. 7 illustrates another embodiment that may be utilized
according to the present invention. In FIGS. 6 and 7, all of the
components are preferably similar to those in FIGS. 1A and 3 (and
designated by the same reference numerals), including the use of a
downflow reactor. Hammermilled cellulose-containing biomass
material passes (via atmospheric feed) to chip bin 90, optionally
to a screw conveyor 92, to a compression screw device 94 (e.g., a
MSD Impressafiner.RTM. available from Andritz Inc.), to a valve 96,
to an inclined steaming vessel 98 (utilizing medium pressure steam,
e.g., at about 250 psig), to an optional screw feeding device 100,
to another compression screw device 102 (e.g., a MSD
Impressafiner.RTM. available from Andritz Inc.), with solvent
(e.g., ethanol) added at line 29 after the discharge from device
102 (e.g., at the outlet of device 102--meaning at the outlet per
se or near the actual outlet and before the impregnation vessel
104), to an inclined impregnation vessel (screw conveyor) 104, to a
conventional downflow reactor 107 (like reactor 14 in FIG. 1A), to
a pressure diffuser 51 (at full reactor temperature and pressure,
e.g., about 180 to 210 degrees C. and about 350 to 500 psig), to a
retention tube 61 (for additional reaction time), to a pressure
diffuser 52 (at full reactor temperature and pressure, e.g., about
180 to 210 degrees C. and about 350 to 500 psig), to a retention
tube 62 (for additional reaction time), to a conventional blow tank
65 (with an optional scraper), for example, at atmospheric pressure
and at a boiling point of about 75 to 100 degrees C. (when using
ethanol, because the boiling point of ethanol and water), to a pump
72 (e.g., an MC.RTM. Pump available from Andritz Inc.), to
conventional vessels for multistage alcohol washing system 17a.
Unlike FIG. 6 (which discloses at least two sets of pressure
diffusers and retention tubes--and more of which can be utilized),
FIG. 7 only shows one set of a pressure diffuser and a retention
tube.
[0055] In this embodiment of the invention, like the other
embodiments, the compression screw feeders 94 and 102 form a plug
of material at discharge to effectively block or hinder the back
passage of solvent or solvent exhaust. In another aspect of the
invention, the retention tubes 61 and 62, at least one of which is
utilized in the systems, processes and methods of the invention, in
conjunction with the pressure diffusers 51 and 52, at least one of
which is utilized in the systems, processes and methods of the
invention, greatly assist with the final stages of cooking and the
initial stages of washing of the material. This assists in allowing
the use of a smaller reactor/digester 107 (or 105 in FIG. 3), i.e.,
the bottom half of a digester is not necessary for washing due to
the washing capabilities of the pressure diffuser(s) and retention
tube(s). In this regard, a retention tube is a wide space in the
processing line where lignin continues to dissolve.
[0056] FIG. 5 illustrates an additional embodiment that may be
utilized according to the present invention. This embodiment is
particularly useful for low production rate cases, but could be
used for a wide range of production rates. While a system using two
screw conveyors is described, it should be noted that any number of
screw conveyors could be used.
[0057] The embodiment illustrated in FIG. 5 relates to the feed
system, which may be operated in a continuous manner. Biomass is
fed to a bin, such as a live bottom bin 200. This bin may be over
sized to allow for up to 8 hours of retention time. The bin also
may be large enough to allow for the immediate condensation of any
ethanol or other solvent used in the pulping, if such solvent
should back into the bin from the downstream equipment, rather than
releasing the solvent to the atmosphere. Preferably, two
independently operated metering screws 201, 202 equipped with
variable speed drives may be located in the bottom of the live
bottom bin to remove the biomass from the bin in a controlled
fashion at a specified rate. Only one metering screw may be turning
at any given time.
[0058] Material from each metering screw 201, 202 may be discharged
into a separate screw conveyor 204 (SC#1), 205 (SC#2) which
functions as a biomass pretreatment vessel. Preferably, the system
may contain two such vessels, one for each metering screw 201, 202,
and they may be operated in parallel with the operating cycles
offset in time. Each screw conveyor 204, 205 may be equipped with
inlet and outlet isolation valves, a variable speed drive and
revolution counter, inlet distribution headers for the addition of
steam, solvent, and inert purge gas, a vent header for the
collection and removal of purged air and other gases, and
temperature and pressure measurement instrumentation. The screw
conveyors 204, 205 may be operated on alternating cycles such that
one conveyor is always emptying pretreated biomass, at the desired
production rate, into a feed chute 210 located above an inclined
impregnation vessel (IV) 214. A mixer 212 may be located between
the feed chute 210 and the IV 214. From the feed chute forward, the
system may be operated in a continuous manner at a uniform
production rate. The conveyor(s) which is not conveying biomass
material into the feed chute may be utilized in a batch mode to
carry out the other required pretreatment operations, as detailed
in the table below. These operations may include uniformly filling
and isolating the conveyor, steam purging the biomass in the
conveyor to remove all air, heating the biomass to the desired
pretreatment temperature, impregnating the biomass with the desired
amount and concentration of water-solvent mixture preheated to the
desired pretreatment temperature, pressurizing the conveyor with N2
(232) or other inert gas up to the feed chute pressure and opening
the discharge valve 220, 221 between the conveyor 204, 205 and the
feed chute 210, isolating the conveyor 204, 205 after the biomass
has been conveyed into the feed chute 210, depressurizing the
conveyor 204, 205 by venting it to a condenser 208, and steam
purging the conveyor 204, 205 to remove any residual solvent
vapors.
[0059] The entire operating cycle for one conveyor may take
approximately 70 minutes, and may consist of 8 individual steps, as
follows:
[0060] Step 1(.about.5 minutes): The screw conveyor (SC) inlet
valve 203, 233 is opened and the metering screw 201, 202 and SC's
204, 205 are started in order to transfer biomass from the live
bottom bin 200 into the screw conveyor 204, 205. The screw conveyor
rpm rate is set so as to have the biomass distributed along the
entire length of the conveyor 204, 205 in the allotted fill time. A
conveyor shaft revolution counter is used to determine when the
biomass material has moved along the SC 204, 205 to the discharge
point 206, 207. The metering screw speed is set to fill the SC 204,
205 to the desired level along its length, and is ratioed to the
desired production rate and the SC conveyor speed. At the end of
step 1, the SC 204, 205 and metering screw 201, 202 are stopped and
the inlet valve 203, 233 to the SC 204, 205 is closed, isolating
the SC 204, 205 from the metering screw 201, 202 and the live
bottom bin 200.
[0061] Step 2 (.about.5 minutes): When the SC 204, 205 is isolated,
low pressure steam (about 5-30 psig) is used to purge any air in
the biomass material through a vent line to a relief condenser
208.
[0062] Step 3 (.about.5 minutes): After purging the air from the
system, the relief valve 238, 240 is closed. Steam continues to be
added to the SC 204, 205 until the system is up to the desired
preimpregnation temperature, approximately 280-300 degrees F. At
this point, the hydrolysis reactions between the solvent and
biomass are still very slow, so the retention time in the SC 204,
205, which will vary between material located near the inlet and
the outlet of the SC when the material is conveyed out of the SC
204, 205, does not adversely affect the uniformity of treatment.
The steam (230) used in this step is preferably about 75-150 psig
steam.
[0063] Step 4 (.about.5 minutes): Preheated water and solvent
mixture is added to the SC 204, 205 through a spray header 216, 217
along the top of the SC to preimpregnate the biomass prior to
pressurization with N2 (232) or other inert gas (next step). The
amount of each liquid is adjusted for the desired liquid to biomass
ratio, the initial biomass moisture, the steam condensed in the SC
204, 205, and the anticipated condensation of steam and ethanol
vapor to be later added in the impregnation vessel to bring the
biomass up to the desired final reaction temperature prior to
entering the reactor.
[0064] Step 5 (.about.5 minutes): Next, the SC 204, 205 is brought
up to the IV feed chute pressure by adding a pressurized inert gas
such as N2 232. The pressure is monitored in the SC 204, 205, and
the final pressure is adjusted using a DP cell to measure the
differential pressure between the SC 204, 205 and the feed chute
210 to ensure close control before opening the SC discharge valve
220, 221.
[0065] Step 6 (.about.35 minutes): When the SC 204, 205 and IV feed
chute 210 pressures are equal, the SC discharge valve 220, 221 is
opened. When the other screw conveyor (SC #2) 205 has finished
transferring its supply of biomass to the IV feed chute 210, the
SC(SC#1) 204 is started and set at the desired production rate. The
biomass is then steadily transferred into the IV feed chute 210
until SC #1 204 is empty, at which time SC #2 205 will again be
ready to transfer material into the feed chute 210. As a result,
the IV feed chute 210 receives a steady and continuous influx of
material throughout the entire cycle, even though the SCs 204, 205
may be operated in a semi-continuous manner. This enables the rest
of the system to also operate in a stable, continuous manner.
During step 6, a small amount of N2, or other inert gas, purge may
be added to the inlet end of the SC 204, 205. This keeps hot vapors
from diffusing back into the SC 204, 205 and prematurely heating
the biomass and solvent near the inlet of the SC, resulting in
uneven treatment of the biomass.
[0066] Step 7 (.about.5 minutes): After all of the biomass in SC #1
204 has been transferred into the IV feed chute 210, the SC
discharge valve 220 is closed, isolating the SC #1 204 from the
feed chute 210. Both the total SC revolutions and the drive
amperage may be used to monitor the material transfer completion. A
gamma gauge at the transfer point into the feed chute can also
serve as a backup control method. The N2, or other inert gas, purge
is also closed at this time. After the SC 204, 205 is isolated, the
relief valve 238, 240 to the condenser 208 is opened and the
pressure is relieved down to .about.0 psig.
[0067] Step 8 (.about.5 minutes): After the SC pressure has dropped
close to 0 psig, the SC 204, 205 is purged with low pressure steam
to the condenser to remove any traces of residual solvent before
opening the SC inlet valve 203, 233 and exposing the metering screw
201, 202 and live bottom bin 200 to the vapors remaining in the SC.
If desired, a brief water wash or N2 (or other inert gas) purge can
also be inserted in the cycle at this point to cool the SC, but
normally this will not be necessary.
[0068] At the end of step 8, all steam, water, and N2 (or other
inert gas) purges are shut off and the relief valve 238, 240 to the
condenser 208 is closed. The SC pressure is checked and the DP
between the SC 204, 205 and the metering screw 201, 202 is
preferably at zero. The inlet valve 203, 233 may then be opened to
begin another cycle.
[0069] The following Table 1 illustrates the timing of the
interconnected operating cycles of SC #1 and SC #2.
1TABLE 1 Continuous feed system pretreatment screw conveyor cycle
#1 Screw Conveyor (SC) Cycle Schedule #2 Screw Conveyor SC Cycle
Schedule Step Start Time. Step # Step # minutes (#1 SC) Action
Purpose of step (sc #1) (#2 SC) Action Cycle as shown starts at the
beginning of step 1 for SC #1. SC #2 is already into step 6,
feeding biomass from SC #2 into the impregnation vessel feed chute.
0 1 open SC #1 inlet vatve load screw conveyor 6 continue feeding
biomass from SC #2 into start metering screw #1 from live bottom
bin with biomass IV feed chute start screw conveyor #1 for
pretreatment fill SC with biomass to desire level for length of
screw conveyor 5 2 stop metering screw #1 from l.b. bin at purge
air from biomass 6 continue feeding biomass from SC #2 into
calculated SC #1 fill time. stop screw and SC IV feed chute
conveyor #1 and close SC #1 intel valve open SC #1 relief valve to
condenser open purge steam valve partway on manual control, purge
air from SC #1 10 3 put purge relief valve and Inlet steam valve on
brIng biomass up to 6 continue feeding biomass from SC #2 into
temperature control set both on automatic to pretreatment
temperature IV feed chute target -300 degF irm SC #1 strut purge
relief valve when reach -300 deg F. leave inlet steam on automatIc
control set at -300 deg. F. 15 4 Add calculated amount of -300
degree preheated add solvent to 6 continue feeding biomass from SC
#2 into solvent/water mixture to SC #1 biomass for IV feed chute
through spray header preimpregnation 20 5 Open N2 pressurization
valve to SC #1 equalize SC #1 and 6 continue feeding biomass from
SC #2 into Set on DP control between SC #1 and feed IV feed chute
pressures IV feed chute chute. Pressurize SC #1 to IV feed chute
for transfer of biomass pressure (reactor pressure) with N2. from
SC to IV 25 6 Open SC #1 discharge valve 1. keop biomass from 7 SC
#2 is empty of biomass Set N2 valve to prurge flow control
prematurely ovenheating Close SC #2 discharge valve and N2 purge
Start SC #1 and begin feeding biomass 2. begin feeding biomass
valve open SC #2 relief valve to condenser from SC #1 into IV teen
chute a from SC #1 to IV feed relieve SC #2 pressure down to 0 psig
predetermined production rate by setting chute SC #1 rpm at target
rate. 30 6 continue feeding biomass from SC #1 into continuously
feed 8 Open steam purge valve to preset purge IV feed chute biomass
at desired rate to remove any traces of ethanol in production rate
SC#2. into IV 35 6 continue feeding biomass from SC #1 into
continuously feed 1 close steam purge valve and open SC #2 IV feed
chute biomass at desired inlet valve start metering screw #2 from
productiorm rate live bottom bin at desired SC fill rate start into
IV screw conveyor #2 at desired rate fill SC#2 with biomass to
desired level for length of screw conveyor 40 6 continue feeding
biomass from SC #1 into continuously feed 2 stop metering screw #2
from l.b. bin at IV feed chute biomass at desired calculated SC #2
fill time. production rate stop screw conveyor #2 and close SC into
IV #2 inlet valve open SC #2 relief valve to condenser open purge
steam valve partway on manual control, purge air from Sc #2 45 6
continue feeding biomass from SC #1 into continuously feed 3 put
purge relief valve and inlet steam IV feed chute biomass at desired
valve on temperature control production rate set both on automatic
to target -300 info IV deg F. in SC #2 shut purge relief valve when
reach -300 deg F. leave inlet steam on 50 6 continue feeding
biomass from SC #1 into continuously feed 4 automatic control set
at -300 deg. F. Add IV feed chute biomass at desired calculated
amount of -300 degree production rate preheated solvent/water
mixture into IV to SC #2 through spray treader 55 6 continnie
feeding biomass from SC #1 into continuously feed 5 Open N2
pressurization valve to SC #2 IV feed chute biomass at desired Set
on DP control between Sc #2 and production rate feed chute.
Pressurize SC #2 to IV feed into IV chute pressure (reactor
pressure) with Na. 60 7 SC #1 is empty at biomass isolate and 6
Open SC #2 discharge valve Close SC #1 discharge valve and N2 purge
valve depressurize Set N2 valve to purge flow control open SC #1
relief valve to condenser Sc #1 Start SC #2 and begin feeding
biomass relieve SC #1 pressure down to 0 psig from SC #2 into IV
feed chute at predetermined production rate by setting SC #2 rpm at
target rate. 65 8 Open steam purge valve to preset purge rate to
purge any residual 6 continue feeding biomass from SC #2 into
remove any traces of ethanol in SC #1 solvent from Sc #1 IV feed
chute before opening inlet valve 70 1 Close steam purge valve begin
cycle again 6 continue feeding biomass from Open SC #1 biamass
Inlet valve Sc #2 into IV feed chute start metering screw #1 at
predetermined fill rate start SC #1 at predetenmined fill rate
REPEAT CYClE
[0070] After the biomass material is transferred into the IV chip
chute 210, it moves down into the impregnation vessel (IV) 214,
which preferably consists of an inclined screw conveyor equipped
with the appropriate headers and control instrumentation.
Preferably, the biomass enters the lower end of the unit and is
transferred upward through the IV 214 by the action of an inclined
conveyor screw. Any free liquid with the biomass maintains a liquid
level set by the elevation of the overflow into the main reactor
250. The retention time in the IV 214 is about 5 minutes.
[0071] In the IV 214, the temperature of the biomass and
solvent/water mixture is increased to about 380-400.degree. F. This
temperature increase is achieved by introducing a mixture of steam
at about 450 psig and solvent (at a pressure of about 450 psig). A
solvent boiler 252 is used to obtain the mixture of solvent and
steam needed to increase the temperature of the biomass and
solvent/water mixture in the impregnation vessel 214 to about
400.degree. F. Temperature control at the impregnation vessel 214
may be used to control the quantity of steam/solvent mixture from
the boiler to the impregnation vessel.
[0072] The amount of solvent and steam used for heating in the IV
214 preferably supplements the solvent introduced into the
impregnation vessel from the SC 204, 205 and results in the total
solvent required for the reaction. All solvent and steam needed for
the reaction is preferably added prior to the biomass being fed to
the reactor 250. The reactor 250 and downstream equipment used for
this process may be the same as that in FIGS. 1A and 1B or FIG.
2.
[0073] In a commercial size installation, it may be preferable or
necessary to use an inert gas circulation/recovery system.
[0074] The description given above is based on a preferred system
using two parallel screw conveyors for pretreatment vessels. Two is
the minimum number of SCs for this type of system, but more may be
used if desired. Reasons for using 3 or more SCs in the feed system
include possible mechanical design limitations for very large SCs,
cost tradeoffs between a small number of large vessels versus a
larger number of smaller vessels, and the advantage of being able
to take one SC off line for maintenance without interrupting the
operation. The basic rule is still the same: that one SC must be
steadily discharging material into the IV feed chute at all times.
Thus for step 6 above, with 2 SCs, step 6 takes {fraction (1/26)}
of the total cycle time, for 3 SCs 1/3 of the cycle time, and for n
SCs 1/n of the cycle time. Except for step 6, the cycle can be
interrupted and held at any point if extra time is available, as
for example at reduced production rates.
[0075] It is also possible to use other configurations for the
pretreatment vessels rather than screw conveyors. Drag chain
systems or even vertical gravity flow vessels can also be used.
[0076] The main reactor can also be any of these types of
configurations. It is not necessary for the reactor to be a
vertical unit. It may be an inclined or horizontal unit, equipped
with either a conveyor screw or drag chain conveyor.
[0077] The impregnation vessel (IV) may also be either horizontal
or inclined, and equipped with either a conveyor screw or drag
chain conveyor.
[0078] Conventional or subsequently-developed techniques will be
utilized to recover lignin, furfural, and other saleable
commodities, from various streams from the processes described
above and illustrated in FIGS. 1A, 1B, 2, 3, 4, 5, 5A-5E and 6.
[0079] The equipment utilized in the systems, processes and methods
of the invention can be made of any material that will stand up to
the chemicals and conditions described. Preferably, the wetted
components are made of 316L stainless steel, or Hastalloy C, or
higher metallurgies, depending on the temperature and pH used in
any particular application. Generally speaking, lower pH's and
higher temperatures will require more corrosion resistant
metallurgies.
[0080] The invention is not to be limited except by the prior art.
All ranges include each specific range within a broad range (e.g.,
180-210 deg. C. means 181-209 deg., 199-201 deg., 190-200 deg., and
all other narrower ranges within the broad range). Recognized
equivalents may be used where appropriate. Other conventional
conditions and procedures may be used for the solvent pulping and
recovery of materials too, such as shown in U.S. Pat. Nos.
6,364,999, 5,865,948, 5,788,812, 5,681,427, 4,941,944, 4,764,996,
4,100,016, 3,585,104, and 1,856,567, the disclosures of which are
hereby incorporated by reference herein.
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