The National Renewable Energy Laboratory (NREL) has undertaken a complete review and update of the process design and economic model for the biomass-to-ethanol enzymatic based process. The process design includes the core technologies being researched by the U.S. Department of Energy (DOE): prehydrolysis, simultaneous saccharification and co-fermentation, and cellulase enzyme production. In addition, all ancillary areas--feed handling, product recovery and purification, wastewater treatment lignin burner and boiler--turbogenerator, and utilities--are included. NREL engaged Delta-T Corporation to assist in the process design evaluation, equipment costing, and overall plant integration. The process design and costing for the lignin burner and boiler turbogenerator has been reviewed by Reaction Engineering Inc. and the wastewater treatment by Merrick and Company. An overview of both reviews is included here. The purpose of this update was to ensure that the process design and equipment costs were reasonable and consistent with good engineering practice for plants of this type using available technical data. This work has resulted in an economic model that can be used to predict the cost of producing ethanol from cellulosic biomass using this technology if a plant were to be built in the next few years. The model was also extended using technology improvements that are expected to be developed based on the current DOE research plan. Future process designs and cost estimates are given for the years 2005, 2010, and 2015.

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Lignocellulosic Biomass to Ethanol Process Design and Economics Utilizing Co-Current Dilute Acid Prehydrolysis and Enzymatic Hydrolysis Current and Futuristic Scenarios

New experimental results are presented for the solubility of carbon dioxide in the ionic liquid 1-N-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) for temperatures from (293 to 393) K and pressures up to about 9.7 MPa. Solubility pressures are correlated by means of the extended Henry's law.

Solubility of CO2 in the Ionic Liquid [bmim][PF6]

Experimental results for the solubility of the single gases carbon dioxide and hydrogen sulfide in aqueous solutions of 2,2‘-methyliminodiethanol (N-methyldiethanolamine (MDEA)) at temperatures between 313 and 413 K and total pressures up to 5 MPa are reported. A model taking into account chemical reactions as well as physical interactions is used to correlate the new data. The correlation is also used to compare the new experimental data with literature data.

Solubility of single gases carbon dioxide and hydrogen sulfide in aqueous solutions of N-methyldiethanolamine in the temperature range 313--413 K at pressures up to 5 MPa

Online NMR spectroscopic study of species distribution in MEA-H2O-CO2 and DEA-H2O-CO2

As part of an ongoing project dealing with the measurement and correlation of phase equilibria in aqueous solutions containing a weak base like ammonia and acid gases like carbon dioxide, sulfur dioxide and hydrogen cyanide, the solubility of carbon dioxide was measured in aqueous solutions containing the single salts sodium sulfate and ammonium sulfate as well as in a solution containing both salts. The temperature ranged from 313.15 K to 433.15 K and pressures up to 10 MPa. Pitzer's semiempirical model is used to correlate the new data. From the results for the solubility of carbon dioxide in the single salt aqueous solutions, interaction parameters were determined. With these parameters the solubility of carbon dioxide in an aqueous mixture containing both salts is predicted quantitatively.

An Experimental and Theoretical Investigation on the Solubility of Carbon Dioxide in Aqueous Solutions of Strong Electrolytes

Expressions for predicting pure-component and cross second virial coefficients for simple and complex systems have been developed from the bound-pair formalism of Stogryn and Hirschfelder. For pure components, the generalized correlation requires the critical temperature and pressure, Thompson's mean radius of gyration or the parachor, dipole moment, and, if appropriate, a parameter to describe chemical association which depends only in the type of group (hydroxyl, amine, ester, carboxylic acid, etc.). Mixing rules have been developed for predicting cross coefficients and solvation effects can be accounted for in a similar manner to association. Agreement with experimental data on 39 nonpolar and 102 polar and associating compounds, 119 mixed nonpolar systems, and 73 mixed systems involving polar compounds, is comparable to or better than that of several other correlations including those which require data to obtain parameters. The method should be most accurate for systems of complex molecules where no data are available In order to accurately predict phase equilibria involving the vapor phase at pressures above atmospheric, deviations from the perfect-gas law usually need to be taken into account (Prausnitz, 1969; Nagata and Yasuda, 1974). The vinal equation terminated at the second coefficient is a simple but accurate method for conditions up to a density of about one-half the critical and has been employed in completely developed methods for predicting vapor-liquid equilibria such as Prausnitz et al. (1967). Several analytical methods for predicting values for the second virial coefficient have been developed (Black, 1958; O'Connell and Prausnitz, 1967; Kreglewski, 1969; Nothnagel et al., 1973; Tsonopoulos, 1974), but except for the last, all suffer from the disadvantage of often requiring one or more parameters that must be obtained from data, or the results are too inaccurate to be acceptable. This work develops an accurate method for predicting second virial coefficients using only critical properties and molecular parameters. all of which may usually be estimated from molecular structure to the required accuracy. From extensive comparisons with pure component and cross vinal coefficient data, the present method appears to be more consistently accurate than any other purely predictive method. In addition, for strongly associating substances, the method predicts association effects at higher densities in a realistic fashion (Nothnagel et al., 1973) using a parameter which depends only on the group interaction.

John P. O'Connell

Papers

A Generalized Method for Predicting Second Virial Coefficients

Some Generalizations about Processes to Absorb Gases and Mercaptans