NREL Summary—CAFI/IFAFS Project
April 17, 2002
Major Points
1.
Corn stover dilute acid pretreatment work is continuing in Enzyme Sugar Platform
(ESP) Project and Advanced Pretreatment Project.
 1 ton/day Sunds hydrolyzer
 200 kg/day Sunds horizontal digester (integration with Pneumapress filter)
 4 L steam gun
 2 L Zipperclave reactor
 1 L Parr reactor
 Percolation/shrinking-bed flowthrough reactors
2.
Pretreatment reactor Material of Construction subcontract starting soon.
 Focus is on “alternate” pretreatments
3.
2010 process engineering design report is being issued soon.
 Serves as starting point for defining “advanced pretreatment” process
performance targets and economics
Details
1.
Corn Stover Dilute Acid Pretreatment
Initial batch of corn stover resulted in 70-80% xylose yield (mostly monomers), ~80%
ethanol yields from cellulose in SSF.
 Poster presentation 1-11 “Dilute Sulfuric Acid Pretreatment of Corn Stover in
a Pilot-Scale Reactor: Investigation of Yields, Kinetics, and Solids Enzymatic
Digestibilities”
Some variability noted in subsequent batches.
 Compositional variability—higher carbohydrate, less lignin
 Xylose yield variability—slightly higher
 SSF performance variability—significantly higher conversion of cellulose and
ethanol yield
Bringing horizontal digester on- line with corn stover.
 Some feeding difficulties encountered
Pneumapress pressure belt filter (3 ft2) arrived early April.
 Capable of hot separation (up to 160 C) and hot washing/dewatering using a variety
of wash/dewatering fluids (acid, alkali, neutral, solvent, steam, air)
 Initial hot separation shakedown expected in August
3 ft2 Pneumapress pressure belt filter for elevated temperature separation/washing.
Steam gun results on corn stover reported in Poster 1-24 “Effects of Temperature and
Moisture on Dilute-Acid Steam-Explosion Pretreatment of Corn Stover and Cellulase
Enzyme Digestibility.”
New bench-scale (2 L) high solids, batch stirred reactor with steam injection is now available
(Zipperclave, Autoclave Engineers).
 Rapid heat up, cool down (< 1 minute)
2 liter Zipperclave reactor with high solids agitation and steam injection.
2.
Pretreatment Reactor Materials of Construction Subcontract
Subcontract will be conducted by a major engineering firm; material of construction
evaluation will be sub-tiered to a well-know corrosion firm.
Focus will be on non-sulfuric acid processes.
 Other acids, water/steam, alkali)
We need to specify likely reaction conditions for various pretreatment processes.
 Catalyst concentration, temperature, solids loading, etc.
Initial tests for general corrosion for a selected number and type of alloys
Additional consideration to effect of erosion, scouring of passivation layer, etc. in high solids
reactors with moving biomass in continuous reactors.
3.
2010 Process Engineering Design Report
Design report establishes technical and economic targets for advanced case scenarios.
Dilute acid pretreatment performance and capital/operating cost assumptions serve as
baseline for comparison.
 Capital costs, operating costs, overall yields can be broken out, can be developed for
each pretreatment
 Cost areas can trade-off within a given pretreatment, goal is a lower overall cost
Advanced Pretreatment Project technology evaluation efforts (now through end 2002) need
to establish process performance/cost criteria.
 2010 Case general targets may be a good place to start
 Alternate pretreatments each need a similar table
Advanced Pretreatment Project not as concerned with current state of technical
demonstration.
 Potential to achieve advanced targets
 Likelihood/risk
 R&D costs to achieve commercial viability (compared to others)
 Co-products in a biorefinery scenario (adequate market size)
Process Area
Pretreatment
Conditioning
Enzyme Production
Saccharification and
Fermentation
Parameter
Type
Reactor Solids Concentration
Reactor Residence Time
Acid Concentration (w/v)
Temperature (C)
Xylan to Xylose Yield
Xylan to Oligomer Yield
Xylan to Furfural Yield
Xylan to Tar Yield
Unconverted Xylose
Cellulose to Glucose Yield
Metal
Corrosion Rate (mpy)
Type of Conditioning
S/L Separation
Purchase Price ($/gal ethanol)
Enzyme Loading (FPU/g cellulose)
Hydrolysis Residence Time
Hydrolysis Temperature (C)
Fermentation Residence Time
Fermentation Temperature (C)
Cellulose to Glucose Yield
Glucose to Ethanol Yield
Overall Cellulose to Ethanol Yield
ESP Case
Dilute Acid
30%
2 min
1.1%
190
85%
2.5%
5%
2.5%
5%
6%
Incoloy 825
18.0
Overlime
Yes
0.11
12
1.5 days
65
2 days
37
90%
92%
82.8%
2010 Case
Dilute Acid
30%
2 min
1.1%
190
90%
2.5%
5%
0%
2.5%
7%
Incoloy 825
18.0
Overlime
Yes
0.10
12
1.5 days
65
1.5 days
41
90%
95%
85.5%