Saturday, May 26, 2007

Thermochemical Ethanol Via Lignocellulosic Biomass

Thermochemical Ethanol via Indirect Gasification and Mixed Alcohol Synthesis of Lignocellulosic Biomass

S. Phillips, A. Aden, J. Jechura, and D. Dayton
National Renewable Energy Laboratory
T. Eggeman
Neoterics International, Inc.

Golden, Colorado: National Renewable Energy Laboratory

NREL/TP-510-41168 | April 2007
1. Executive Summary
This work addresses a policy initiative by the Federal Administration to apply United States Department of Energy (DOE) research to broadening the country’s domestic production of economic, flexible, and secure sources of energy fuels. President Bush stated in his 2006 State of the Union Address: “America is addicted to oil.” To reduce the Nation’s future demand for oil, the President has proposed the Advanced Energy Initiative which outlines significant new investments and policies to change the way we fuel our vehicles and change the way we power our homes and businesses. The specific goal for biomass in the Advanced Energy Initiative is to foster the breakthrough technologies needed to make cellulosic ethanol cost-competitive with corn-based ethanol by 2012.

In previous biomass conversion design reports by the National Renewable Energy Laboratory (NREL), a benchmark for achieving production of ethanol from cellulosic feedstocks that would be “cost competitive with corn-ethanol” has been quantified as $1.07 per gallon ethanol minimum plant gate price. This process design and technoeconomic evaluation addresses the conversion of biomass to ethanol via thermochemical pathways that are expected to be demonstrated at the pilot-unit level by 2012. This assessment is unique in its attempt to match up:

***Currently established and published technology.
***Technology currently under development or shortly to be under development from DOE Office of Biomass Program funding.
***Biomass resource availability in the 2012 time frame consistent with the Billion Ton Vision study.

Indirect steam gasification was chosen as the technology around which this process was developed based upon previous technoeconomic studies for the production of methanol and hydrogen from biomass. The operations for ethanol production are very similar to those for methanol production (although the specific process configuration will be different). The general process areas include: feed preparation, gasification, gas cleanup and conditioning, and alcohol synthesis & purification.

The cost of ethanol as determined in this assessment was derived using technology that has been developed and demonstrated or is currently being developed as part of the OBP research program. Combined, all process, market, and financial targets in the design represent what must be achieved to obtain the reported $1.01 per gallon, showing that ethanol from a thermochemical conversion process has the possibility of being produced in a manner that is “cost competitive with corn-ethanol” by 2012. This analysis has demonstrated that forest resources can be converted to ethanol in a cost competitive manner. This allows for greater flexibility in converting biomass resources to make stated volume targets by 2030.

Table of Contents
1. Executive Summary ..... i
2. Introduction ..... 1
2.1. Analysis Approach ..... 6
2.2. Process Design Overview ...... 10
2.3. Feedstock and Plant Size ...... 12
3. Process Design ..... 14
3.1. Process Design Basis ..... 14
3.2. Feed Handling and Drying – Area 100 ..... 14
3.3. Gasification – Area 200 ..... 15
3.4. Gas Cleanup and Conditioning – Area 300 ...... 17
3.5. Alcohol Synthesis – Area 400 ...... 20
3.6. Alcohol Separation – Area 500 ..... 25
3.7. Steam System and Power Generation Area - 600 ..... 26
3.8. Cooling Water and Other Utilities – Area 700 ..... 28
3.9. Additional Design Information ..... 29
3.10. Pinch Analysis ..... 29
3.11. Energy Balance ..... 30
3.12. Water Issues ..... 34
4. Process Economics ..... 35
4.1. Capital Costs ..... 35
4.2. Operating Costs ..... 38
4.3. Value of Higher Alcohol Co-Products ..... 41
4.4. Minimum Ethanol Plant Gate Price ..... 42
5. Process Economics, Sensitivity Analyses, and Alternate Scenarios .....43
5.1. Financial Scenarios ...... 45
5.2. Feedstocks ...... 46
5.3. Thermal Conversion ...... 50
5.4. Clean-Up & Conditioning ...... 50
5.5. Fuels Synthesis ...... 50
5.6. Markets ..... 50
6. Conclusions ..... 51
7. Future Work ..... 51
8. References ..... 53

List of Figures
Figure 1. U.S. list prices for ethanol ..... 2
Figure 2. Estimated capital intensities for biomass-to-methanol processes ..... 5
Figure 3. Approach to process analysis ..... 6
Figure 4. Chemical Engineering Magazine’s plant cost indices ...... 9
Figure 5. Block flow diagram ...... 10
Figure 6. Expected availability of biomass ...... 13
Figure 7. Pinch analysis composite curve ...... 30
Figure 8. Cost contribution details from each process area ..... 43
Figure 9. Effect of cost year on MESP ..... 44
Figure 10. Results of sensitivity analyses ..... 45
Figure 11. Sensitivity analysis of biomass ash content ..... 47
Figure 12. Sensitivity analysis of biomass moisture content ..... 48
Figure 13. Sensitivity analysis of raw syngas diverted for heat and power due to biomass moisture content ..... 49

List of Tables
Table 1. Chemical Engineering Magazine’s Plant Cost Indices ..... 8
Table 2. Ultimate Analysis of Hybrid Poplar Feed ..... 13
Table 3. Gasifier Operating Parameters, Gas Compositions, and Efficiencies ..... 16
Table 4. Current and Target Design Performance of Tar Reformer ..... 17
Table 5. Target Design Tar Reformer Conditions and Outlet Gas Composition ..... 18
Table 6. Process Conditions for Mixed Alcohols Synthesis ..... 21
Table 7. System of Reactions for Mixed Alcohol Synthesis ..... 23
Table 8. Mixed Alcohol Reaction Performance Results ..... 23
Table 9. Mixed Alcohol Product Distributions ..... 24
Table 10. Plant Power Requirements ..... 27
Table 11. Utility and Miscellaneous Design Information. ..... 29
Table 12. Overall Energy Analysis (LHV basis) ...... 33
Table 13. Process Water Demands for Thermochemical Ethanol ..... 34
Table 14. General Cost Factors in Determining Total Installed Equipment Costs ..... 35
Table 15. Cost Factors for Indirect Costs ..... 36
Table 16. Feed Handling & Drying and Gasifier & Gas Clean Up Costs from the Literature Scaled to 2,000 tonne/day plant ..... 36
Table 17. System Design Information for Gasification References ..... 37
Table 18. Variable Operating Costs ..... 38
Table 19. Labor Costs ..... 39
Table 20. Other Fixed Costs ..... 40
Table 21. Salary Comparison ..... 41
Table 22. Economic Parameters ..... 42

Appendices
Appendix A: List of Acronyms
Appendix B: OBP Thermochemical Platform Research Targets
Appendix C: NREL Biorefinery Design Database Description and Summary
Appendix D: Individual Equipment Cost Summary
Appendix F: Discounted Cash Flow Rate of Return Summary
Appendix G: Process Parameters & Operation Summary
Appendix H: Process Flow Diagrams (PFDs)
Appendix I: Syngas and Char Correlations
Appendix J: Alcohol Synthesis Catalyst References
Appendix K: Alcohol Synthesis Kinetics

Full Text Available
[http://www.nrel.gov/docs/fy07osti/41168.pdf]

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