National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, CO 80401-3393

A -- RESEARCH & DEVELOPMENT -- POTENTIAL SOURCES SOUGHT SOL SOLDW-130 DUE 010598 POC Deborah J. Bullard, Subcontract Administrator, 303-384-6876, Mail Stop #3511 WEB: Alternative Fuels Data Center, www.afdc.nrel.gov. E-MAIL: Acquisition Services/Biofuels, bullardd@nrel.gov. SOURCES SOUGHT -- "INVESTIGATION OF SOLID/LIQUID SEPARATION AND WASHING OF LIGNOCELLULOSIC BIOMASS FROM LIGNOCELLULOSIC BIOMASS-TO-ETHANOL PROCESSES" 1.0 INTRODUCTION. A) Lignocellulosic biomass composed primarily of cellulose (a polymer of glucose) and hemicellulose (a polymer of five- and six-carbon sugars) can be converted to ethanol by fermentation of these sugars after conversion to their monomeric form. This conversion is usually accomplished by a cooking process (usually in the presence of an acid) that hydrolyzes the polymers to monomers, or in the case of cellulose, an enzyme can be used to hydrolyze the cellulose to glucose. Both processes are being investigated by NREL. B) Good solid/liquid separations and recovery of dissolved wood sugars are key to many of the proposed conversion technologies. Applications include the recovery of hemicellulosic sugars from pretreated biomass, recovery of glucose after the hydrolysis of cellulose, an adequate dewatering of the solids. These are criticalareas for the technology for which very little information is available. 2.0 BACKGROUND. The following sections provide background on the solid/liquid separations steps being considered for lignocellulosic conversion processes. In all cases it is desired to have continuous or at least semi-continuous operation of the solid/liquid separation equipment. 2.1 TWO-STAGE DILUTE ACID CONVERSION PROCESS. Raw feedstock of 1-5 mm particle size is impregnated with sulfuric acid and cooked (1st stage) at conditions sufficient to hydrolyze most of the hemicellulosic polymers. The 1st state material (1st stage hydrolysate) exits the reactor and is flashed cooled to 100 degrees C. and will have a total solids concentration of 25%-35%. It is desired to recover as much of the sugars as possible from the 1st stage hydrolysate while minimizing the use of wash water. It is also desired to obtain a highly concentrated slurry because the material will be reimpregnated with sulfuric acid and cooked at conditions sufficient to hydrolyze the cellulose (2nd stage). Low moisture content is desired to reduce acid and steam use. The material from the 2nd stage hydrolysis (2nd stage hydrolysate) is also flashed cooled to 100 degrees C. and will have a total solids concentration of 25%-35%. It is also desired to recover as much of the sugars solubilized during the 2nd stage process while minimizing wash water and producing a highly concentrated slurry. Some reduction of particle size will occur during the 1st stage process, but the material is still relatively easy to separate and wash. Data generated by NREL and vendors on the 1st stage hydrolysate will be made available to the subcontractor. Material from the 2nd stage process will have undergone significant size reduction that is expected to make washing and separation more difficult. No data is currently available for this material. 2.2 ENZYMATIC CONVERSION PROCESS. A) Raw feedstock of 1-5 mm particle size is impregnated with sulfuric acid and cooked at conditions sufficient to hydrolyze most of the hemicellulosic polymers. This material (hydrolysate) exits the reactor and is flashed cooled to 100 degrees C. and will have a total solids concentration of 25%-35%. It will be similar to the 1st stage hydrolysate discussed above. It is desired to dewater this material as much as possible and obtain a highly clarified filtrate, but washing is not needed. The liquid will be treated to remove fermentation inhibitors and then recombined with the solids. B) The separated liquid is treated with lime to neutralize the sulfuric acid, which also produces gypsum as a by-product. It is desired to remove as much of precipitated gypsum from the liquid as possible. This separation may be difficult because of the colloidal nature of the precipitated gypsum and its low concentration. C) The recombined solid and liquid (after gypsum separation) stream is sent to a simultaneous saccharification and fermentation process in which the cellulose is hydrolyzed to glucose using engymes. Significant reduction in particlesize will occur similar to the 2nd state hydrolysate discussed above. This fermentation broth is sent to distillation to remove the ehtanol and it is desired to recover the solids in the slurry stream (bottoms) exiting from the bottom of the column (100 degrees C.). This material should be dewatered as much as possible and again washing is not needed. 3.0 OBJECTIVE. The goal of this work is to identify equipment for solid/liquid separations for the various proposed process configurations. Information will be generated on solid/liquid separation performance and sugar recovery. Appropriate equipment will be identified for each of the separations along with equipment and operating costs, utilities requirements, number of units required to meet process flow rates and number of spares required. Equipment will be sized for 50 MM gal/y ethanol production facility using flow rates to be specified by NREL. 4.0 SCOPE OF WORK. This work is to be carried out by the Subcontractor using in-house equipment or at vendor laboratories if required. NREL will generate material for all testing needs using hardwood sawdust and will provide chemical analysis (solids concentration and liquid component concentrations) if needed to determine process performance. Analysis will be performed on both the filtrate and cake. 5.0 TASKS. 5.1 TEST PLAN. A. The Subcontractor will prepare a plan for conducting this work for the following separations discussed above: 1) Dilute acid process (1st stage) -- Establish sugar recovery as a function of wash water usage and extent of slurry dewatering for each proposed piece of equipment. (Subcontractor should review available data and determine what additional testing of data is required). 2. Dilute acid process (2nd stage) -- Establish sugar recovery as a function of wash water usage and extent of slurry dewatering for each proposed piece of equipment. 3. Enzyme process (hydrolysate) -- Establish extent of slurry dewatering and clarity of the filtrate for each proposed piece of equipment. 4. Enzyme process (gypsum separation) -- Establish recovery of precipitated gypsum for each proposed piece of equipment. 5. Enzyme process (bottoms) -- Establish extent of slurry dewatering for each proposed pIece of equipment. B. In addition, the Subcontractor will recommend the best equipment or equipment configuration for each separation specified above, along with information on equipment and operating cost, utilities requirements, number of units required to meet process flow rates and number of spares required for all equipment considered or tested during this subcontract. C. The feed material for separations 1 and 3 above are the same and testing required for separation 1 may provide the required data for separation 3. Similarly, the feed material for separations 2 and 5 will be assumed to be a same material for testing purposes (i.e., they have both undergone cellulose hydrolysis that significantly reduces particle size). However, small quantities of the two different materials could be supplied if required. D. The plan will include a description of proposed vendor testing or Subcontractor initiated testing, expected outcome or data to be produced during the test (i.e., data necessary to establish performance on large-scale equipment, for example, sugar recovery as a function of wash water usage), amount of material required for the test and schedule for completion of work in this subcontract. Information generated during the tests must be sufficient for identification of appropriate large-scale equipment and prediction of performance. E. Appropriate equipment to consider includes continuous counter-current extractors and centrifugal, vacuum, and pressure separation equipment preferably with counter-current washing if required. In some cases, multiple pieces of equipment may be required to achieve the separation requirements. 5.2 SOLID/LIQUID SEPARATION TESTS. Task 5.2 will begin after approval of the test plan by the Technical Monitor and will implement the work described in the test plan. This will include any Subcontractor initiated testing and vendor testing as appropriate to generate the data for the solid/liquid separtions discussed in Task 5.1. ANY ORGANIZATION WHICH MIGHT BE INTERESTED IN WORKING WITH NREL IN THIS EFFORT SHOULD MAIL OR FAX A LIST OF QUALIFICATIONS TO THE NATIONAL RENEWABLE ENERGY LABORATORY, ATTN: DEBORAH J. BULLARD, MS #3511, 1617 COLE BLVD., GOLDEN, CO 80401-3393. Fax #: 303-384-6877. TELEPHONE INQUIRIES WILL NOT BE ACCEPTED. The list of qualification should be responsive to the items listed above. THIS SYNOPSIS IS NOT A REQUEST FOR PROPOSAL.**** (0336)

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