Abstract:
This invention relates to a series of treatments, both physical and chemical, to plant biomass resulting in the production of ethanol, lignin, and a high protein animal feed supplement. In plants having a high silica content, a fourth product is obtained, silica/caustic oxide (silicates solution, waterglass.) Both the 5-Carbon and 6-Carbon sugars are fermented to ethanol using an existing closed-loop fermentation system employing a genetically engineered thermophilic bacteria developed by Agrol, Ltd. The lignin and absolute ethanol are mixed producing a high energy fuel.

Description:
This application is a continuation in part of application Ser. No. 08/460,493, filed Jul. 13, 1995, now abandoned. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to a method for producing lignin fuel (a mixture of lignin and ethyl alcohol), silica/sodium oxide, cellulose, and other cellulose derivatives from plant biomass. 
     BACKGROUND OF THE INVENTION 
     Description or Prior Art 
     The production of ethyl alcohol (ethanol) from 5-carbon and 6-carbon sugars has recently focused on the development of genetically engineered organisms. Prior to the work done in genetic engineering, considerable work was done with organisms, extraction of hydrolytic enzymes for cellulose and hemicellulose. B. S. Montencourt and D. E. Eveleigh, 1978, discussed producing fuels from plant biomass. 
     Delignification was done by Wilkes, et al., 1983, using chlorine dioxide/acetic acid solution. 
     Kubat et at., U.S. Pat. No. 4,797,135 describes a method of treating plant biomass with a weak caustic solution to produce a highly comminuted flour of wood and other vegetable biomass suitable for the use as fuel. 
     Many pretreatment technologies for the conversion of plant biomass, generally agricultural by-products (residues), have been developed in the past. The following institutions have provided work in plant biomass to fuels: 
     The U.S. Army Natick Development Command, 
     The University of California, Berkeley, Department of Engineering, 
     The Lawrence Berkeley Laboratory, and 
     The Indiana Institute of Technology (Spano, et al.) 
     The U.S. Pat. No. 4,399,009 (Haag, 1981) claims the conversion of biological materials to liquid fuels. This patent uses zeolite catalysts to convert plant hydrocarbons with a molecular weight of over 150 into lower molecular weight entities for use as a liquid fuel. 
     A gasoline fuel extender (methyltetrahydrofuran, MTHF) has been derived from plant biomass. MTHF, up to 10%, has been added to gasoline as a replacement for tetraethyl lead. 
     Generally, the production of alternative fuels have centered around aromatic compounds and are therefore relatively expensive. 
     A fuel derived from a mixture of ethyl alcohol (ethanol) and a lignin extract using a strong caustic solvent is an economically viable engine fuel. 
     REFERENCES CITED 
     The references cited within the text are incorporated by reference to the extent they supplement, explain, provide background for, or teach methodology, techniques, and compositions employed herein. 
     Haag, W. O., Rodewald, P. G. and Weisz, P. B., U.S. Pat. No. 4,300,009, Nov. 10, 1981. A method of converting biological materials to liquid fuels. 
     Montencourt, B. S. and Eveleigh, D. E., Proceedings of Second Annual Symposium on Fuels from Biomass, Vol. II, p 613, Rensseleaer. Described strains of bacteria and fungi having cellulose hydrolyric capabilities 
     Humphrey, A. E. and E. J. Nolan, Preport to the Office of Technology Assessment, Biological Production of Liquid Fuels and Chemical Feedstocks, Govt. Printing Office, #052-003-00706. An economic evaluation of the Raphael Datzen Associates of the Gulf/Arkansas process. 
     Wang, D. I. C., C. L. Coaney, A. L. Demain, R. F. Gomez, and A. J. Sinskey, &#34;Degradation of Cellulosic Biomass and its Subsequent Utilization for the Production of Chemical Feedstocks,&#34;, September, 1979. Studies done at M.I.T. on packed fixed bed cellulose conversions. 
     Wilkes, C. W., &#34;Process Development Studies on Bioconversion of Cellulose and Production of Ethanol&#34;, Univ. of California, Berkeley, LBL-6860. Use of high temperature ethanol for removal of lignin from plant biomass and the use of ballmilling for size reduction on newsprint. 
     Kubat et al., U.S. Pat. No. 4,797,135, Treatment of plant biomass with a caustic solution for the production fuel. 
     Bayer, Ernst, U.S. Pat. No. 5,114,541. A process of producing solid liquid and gaseous fuels from biomass using high temperature (200 degrees C. to 600 degrees C.) 
     OBJECT OF THE INVENTION 
     The object of this invention is to produce a continuos treatment of plant biomass using state-of-the-art counter-current extractors to extract salts, proteins and hemicellulose (first extractor); lignin and silica from the residue coming from the first extractor (second extractor); the separation of the lignin from the silicate using an ultrafiltration unit, in plants containing a high percentage of silica; the production of ethyl alcohol (ethanol) from the cellulose coming from the second extractor; and to produce a mixture of lignin and ethyl alcohol (ethanol) as a high energy fuel. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     This invention describes the technology for: 
     producing ethyl alcohol (ethanol); 
     a sulfur-free lignin powder; 
     in plants containing a high percentage of silica, a silicate solution known as silica/caustic oxide, waterglass, silicate, and; 
     a mixture of the sulfur-free lignin with ethanol producing a high energy fuel, and 
     a high protein animal food supplement from the fermentation stillage 
     The first step is size reduction of the plant material using an hammermill or ballmill to between 40 and 60 mesh, preferably 50 mesh. 
     The reduced size plant material is fed into a counter-current extractor. The solvent fed into the opposite end of the counter-current extractor has a pH of between 3.0 and 5.0, preferably pH of 4.0. The solvent temperature will be maintained between 40 and 60 degrees C., preferably 50 degrees C. The resident time of the solid biomass in the first counter-current extractor will be between 50 minutes and 70 minutes, preferably 60 minutes. The acids used to adjust to the solvent pH will be acetic, carbon dioxide (carbonic acid), hydrocholoric, phosphoric, or sulfuric, preferably carbonic acid. The solvent leaving the first counter-current extractor will contain xylose (and other 5-carbon &#34;plant&#34; sugars such as arabinose, and mannose), soluble salts generally found in plant material (calcium salts, sodium salts are examples), and soluble proteins and polypeptides found in plant biomass. This solvent stream is sent directly to a fermentation unit having organisms that convert the 5-Carbon sugars into ethyl alcohol (ethanol). 
     The solid material leaving the first counter-current extractor is fed directly into a second counter-current extractor after passing through a belt press filter. The total solids of the material entering the second counter-current extractor will be between 70% and 80%, preferably 75%. The solvent entering the opposite end of the counter-current extractor is a strong caustic solution either potassium hydroxide (KOH) or sodium hydroxide (NaOH), preferably NaOH, at a concentration of 5% to 50% solution by weight, preferably 50%. The temperature of the strong caustic solvent will be between 40 degrees C. and 60 degrees C., preferably 50 degrees C. The residence time of the solid material in the second counter-current extractor will be between 110 minutes and 130 minutes, preferably 120 minutes. This strong caustic solution dissolves the lignin, and, in the case of plant material contain a high percentage of silica, the silica is placed in solution as the caustic silicate. 
     The mixture of lignin and caustic silicate is fed to an ultrafiltration unit. This ultrafiltration unit has a polysulfone membrane which allows the caustic solution, or the caustic silicate solution, to pass through the membrane while retaining and concentrating the lignin. The lignin is concentrated to 38% to 42% total solid, preferably 40% total solid. 
     The ultrafiltration unit is of a special design where the polysulfone membrane is cast on the outside of a hollow ceramic core. The membrane and ceramic core are placed in a pressure vessel where the feed solution lignin--caustic solution or lignin--caustic silicate in plants having a high silica content, is passed over the membrane/ceramic core at a pressure, varying between 150 psig to 300 psig depending on concentration of lignin at a flow rate of 5 to 6 gallons per minute, depending on concentration of lignin. The concentrated lignin is washed to pH 7.0 to 6.5 with a target pH of 6.7. The lignin is then dried, ground into a high surface area powder approaching the surface area of powdered charcoal and then mixed with absolute (200 proof) ethyl alcohol (ethanol). 
     The caustic silicate solution that has passed through the polysulfone membrane is sent to a bleeder system when a portion of the caustic silicate is fed back, along with a replacement volume of strong caustic solution. The bled portion of the caustic silicate solution is packaged for sale as the caustic silicate (waterglass). In plants not having a high silica content, the caustic solution is returned to the 2 nd  extractor. 
     The solid material (mostly cellulose) leaving the second counter-current extractor is sent to a continuous centrifuge equipped with water washing prior to entering the sacchrification and fermentation system. The sacchrification is done using both a weak solution of a mineral acid such as sulfuric or hydrochloric acid (pH 2 to 3 with pH 2.5 ideal) giving partial sacchrification. A hydrolytic sacchrification enzyme such as Rutgers University Rut-C-30 or other Trichoderma reesei (virde), preferably T. reesei (virde) is added to complete the conversion of the cellulose to its glucose monomers. 
     Fermentation of the 6-Carbon sugar (glucose) and the 5-Carbon sugars will be done using a genetically engineered bacteria, Bacillus stearothermophilus strain LLD-R This bacteria has been developed by Agrol, Ltd. (U.S. patent Ser. No. 51/82,199). The stillage from this bacterial fermentation process has been analyzed and show to be a high protein animal food supplement. 
     The &#34;beer&#34; leaving the fermentation unit has an ethyl alcohol (ethanol) concentration of between 3% and 5% with a target of 4%. This beer is sent to a distillation unit where the ethyl alcohol (ethanol) is distilled to 100% (200 proof). At this point the dried powdered lignin is mixed with the 200 proof ethyl alcohol (ethanol) producing the high energy fuel. The ratio of lignin to ethanol is between 3 parts ethanol to one part lignin and 3.8 parts of ethanol to 1 part lignin, preferably 3.5 parts ethanol to 1 part lignin. 
     The stillage produced by the Agrol, Ltd. bacteria has been analyzed and show to be a high protein animal food supplement. 
     Following is a mass flow for rice straw and/or rice hulls conversion using the technology outlined above: 
     Stream designations are 
     Stream #1--Ground rice straw (or other plant biomass) entering 1 st  counter-current extractor, 
     Stream #2--Mild acid solution entering opposite end of 1 st  extractor, 
     Stream #3--Solution of 5-Carbon sugars, soluble salts, proteins to fermentation unit, 
     Stream #4--Solid materials leaving 1 st  extractor and entering 2 nd  extractor, 
     Stream #5--Caustic solution and feedback solution from ultrafiltration unit entering 2 nd  extractor, 
     Stream #6--Cellulose entering hydrolysis/fermentation unit, 
     Stream #7--Solution of lignin--caustic solution entering ultrafiltration unit, 
     Stream #8--Caustic solution leaving ultrafiltration unit, 
     Stream #8a.--Feedback solution of caustic solution into 2 nd  extractor, 
     Stream #8b--Silicate solution output, 
     Stream #9--Lignin output, 
     Stream #10--Lignin wash water, 
     Stream #11--High protein animal food supplement, 
     Stream #12--Ethanol output. 
     First Extraction 
     Dry rice straw and/or rice hulls, after being crushed in a mill is contacted (Stream #1) with a dilute acid stream in a counter-current extractor. The dilute acid is kept at a temperature of 50 degrees C. and is kept in contact with the crushed rice straw and/or rice hulls for one to two hours, preferably one and one-half hours. The 5-carbon sugars derived from the hydrolyzing of the hemicellulose is extracted. The crushed rice straw and/or rice hulls are passed through a filter press with a resulting material being 75% total solid (Stream #4). The 5-carbon sugar stream is sent directly to the fermentation unit (Stream #3). 
     Units included: hammer/ball mill, counter-current extractor, belt-press filter 
     Second Extraction 
     Wet straw is contacted with a high concentration of a caustic (40% to 60%, 50% preferred) solution at 50 degrees C. along with recycle (Stream #8b) containing the caustic silicate solution. Silica and lignin are solubilized; the silica combines with the caustic to form a silica/caustic oxide in a 1:1 ratio complex. The wet rice straw and/or rice hulls is centrifuged to 75% to 80% total solid, preferably to 77% total solid (Steam #6); The solid cellulose resulting from the extraction above is sent to Ethyl alcohol (ethanol) production (Stream #7). 
     Units included: counter-current extractor, centrifuge 
     Lignin Recovery 
     Lignin and the caustic silicate in solution are passed through an ultrafiltration unit. In stages, Lignin is isolated and concentrated, then washed to near neutrality (Stream #10) to recover the caustic/caustic oxide in solution. The caustic/caustic oxide solution is recycled in a 85:15 product/recycle ratio (Stream #8A/8B). Lignin emerges as 65% total solid in water (Stream #9); Caustic/caustic oxide obtained as 50 mass % solution (Stream #8B). 
     Units included: Ultrafiltration unit(s), washing centrifuge 
     Ethyl Alcohol (Ethanol) Production and Isolation 
     Wet rice straw and/or rice hulls from the second extraction system (Stream #6) as well as filtrate from First Extraction (Stream #3) are fermented. Ethyl alcohol (ethanol) is purified to 100% (200 proof). Carbon dioxide and stillage from the fermentation process and water are removed (Stream #12). 
     Units included: Fermentor, Distillation unit 
     Energy Requirements for Rice Straw/Rice Hulls Conversion 
     Basis: 1 ton rice straw and/or rice hulls/hr. 
     Primary Energy Costs 
     Heating of solutions in both Extractor #1 and Extractor #2 is calculated at 317,000 BTU for Extractor #1, 185,000 BTU Extractor #2, and 2,000,000 BTU distillation for a total heat energy of 2,502,000 BTU/hr. 
     Secondary Energy Costs 
     Mechanical energy units for the Mill (102,000 BTU), Extractor #1 (25,500 BTU), Belt-Press Filter (51,000 BTU), Extractor #2 (51,000 BTU), Centrifuge (77,000 BTU), and Ultrafiltration (128,000 BTU) for a total mechanical energy of 435,000 BTU/hr. 
     Total Energy Costs 
     2,937,000 BTU/hr 
     Mass Flow (Mass in lbs/hr) 
     Water 
     Stream #1, 39.74 lbs.; Stream #2, 5,961 lbs; Stream #3, 5,599 lbs; Stream #4, 421.9 lbs; Stream #5, 421.9 lbs; Stream #6, 231.6 lbs; Stream #7, 699.7 lbs; Stream 8a, 89.9 lbs; Stream #8b 509.5 lbs; Stream #9, 536.9 lbs; Stream #10 436.6 lbs; 
     Soluble Components 
     Caustic 
     Streams #1 through #4, 0.0 lbs; Stream #5, 266.9 lbs; Stream #6, 8.1 lbs; Stream #7, 304.6 lbs; Stream #8, 304.6 lbs; Stream 8A, 45.7 lbs; Stream 8B, 258.9 lbs; Streams #9, #10, #11 and #12, 0.0 lbs; 
     Silica(Silica/Caustic oxide) 
     Streams #1 through #4, 0.0 lbs; Stream #5, 255.9 lbs; Stream #6, 8.1 lbs; Stream #7, 304.6 lbs; Stream #8, 304.6 lbs; Stream #8a, 45.7 lbs; Stream #8b, 258.9 lbs; Stream #9 and #10, 0.0 lbs. 
     Silica/Caustic oxide 
     Streams #1 through Stream #6, 0.0 lbs; Stream #7 and #8, 294.8 lbs; Stream #8a, 45.7 lbs; Stream #8b, 258.9 lbs; Streams #9 and #10, 0.0 lbs. 
     Lignin (in solution) 
     Streams #1 though #6, 0.0 lbs; Stream #7, 289.1 lbs; Streams #8a through Stream #10, 0.0 lbs. 
     TOTAL SOLUTION 
     Stream #1, 39.7 lbs; Stream #2, 5,961 lbs; Stream #3, 5,599.2 lbs; Stream #4, 401.5 lbs; Stream #5, 688.8 lbs; Stream #6, 221.6 lbs; Stream #7, 1,588.2 lbs; Stream #8, 1,198.8 lbs; Stream #8a, 179.8 lbs; Stream #8b, 1,018.9 lbs; Stream #9, 536.9 lbs; Stream #10, 436.6 lbs. 
     Insoluble Components 
     Cellulose 
     Stream #1, 635.8 lbs; Streams #2 and #3, 0.0 lbs; Stream #4, 635.8 lbs; Stream #5, 0.0 lbs; Stream #6, 635.8 lbs; Stream #7 through #10, 0.0 lbs. 
     Hemicellulose 
     Stream #1, 616.0 lbs; Stream #2, 0.0 lbs; Stream #3, 603.7 lbs; Stream #4, 12.3 lbs; Stream #5, 0.0 lbs; Stream #6, 12.3 lbs; Streams #7 through #10, 0.0 lbs; 
     Lignin 
     Stream #1, 298.1 lbs; Stream #2 and #3, 0.0 lbs; Stream #4, 298.1 lbs; Stream #5, 0.0 lbs; Stream #6, 8.9 lbs; Streams #7 through #8b, 0.0 lbs; Stream #9, 289.1 Stream #10, 0.0 lbs. 
     Silica 
     Stream #1, 258.3 lbs; Streams #2 and #3, 0.0 lbs; Stream #4, 258.3 lbs; Streams #5, 0.0 lbs; Stream #6, 7.8 lbs; Streams #7 through #10, 0.0 lbs. 
     Proteins 
     Stream #1, 99.4 lbs; Stream #2, 0.0 lbs; Stream #3, 99.4 lbs; Streams #4 through #10, 0.0 lbs. 
     Ash (less Silica) 
     Stream #1, 39.7 lbs; Stream #2, 0.0 lbs; Stream #3, 39.7 lbs; Streams #4 through #10, 0.0 lbs. 
     TOTAL SOLIDS 
     Stream #1, 1,947.3 lbs; Stream #2, 0.0 lbs; Stream #3, 742.7 lbs; Stream #4, 1,204.5 lbs; Stream #5, 0.0 lbs; Stream #6, 664.9 lbs; Streams #7 through #8b, 0.0 lbs; Stream #9, 289.1 lbs; Stream #10, 0.0 lbs. 
     TOTAL MASS 
     Stream #1, 1,987 lbs; Stream #2, 5,961 lbs; Stream #3, 6,342 lbs; Stream #4, 1,606 lbs; Stream #5, 688.8 lbs; Stream #6, 886.5 lbs; Stream #7, 1,588.2 lbs; Stream #8, 1,194.8 lbs; Stream #8a, 179.8 lbs; Stream #8b, 1,018.9 lbs; Stream #9, 826 lbs; Stream #10, 436.6 lbs. 
     PERCENT TOTAL SOLIDS 
     Stream #1, 98%, Stream #2, 0%, Stream #3, 12%; Stream #4, 75%; Stream #5, 0%; Stream #6, 75%; Stream #7 through #8b, 0%; Stream #9, 35%; Stream #10, 0%. 
     Note #1 There is a loss of 13 lbs in the milling process. 
     Note #2 344.4 lbs of the caustic solution forms the caustic oxide.