WO2010075405A1

WO2010075405A1 - Modification of biomass for efficient conversion to fuels

Info

Publication number: WO2010075405A1
Application number: PCT/US2009/069232
Authority: WO
Inventors: Michael Brady; Dennis Stamires; Paul O'connor
Original assignee: Kior Inc.
Priority date: 2008-12-23
Filing date: 2009-12-22
Publication date: 2010-07-01
Also published as: DK2367974T3; EP2367974B1; BRPI0922925A2; CA2744747A1; US20110256615A1; NO2367974T3; CA2744747C; CN102264979A; EP2367974A1; US8500910B2; CN102264979B; WO2010075405A8; EP2367974A4

Abstract

A process is disclosed for preparing biomass particles for thermolytic or enzymatic conversion whereby the biomass particles having a moisture content of at least 20% are subjected to flash heating. The flash heating may be preceded by one or more adsorption/desorption cycles with water or steam. A swelling aid may be added during the adsorption part of an adsorption/desorption cycle.

Description

MODIFICATION OF BIOMASS FOR EFFICIENT CONVERSION TO FUELS

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The invention relates generally to a process for making biomass materia!, in particular lignoeellulαsie biomass material, more accessible to subsequent chemical or enzymatic treatment

2. Description of the Related Art

[0002] World energy demand is projected to increase substantially άwε to: increase in population growth; improvement of the standard of living in underdeveloped countries; and due to depletion of the reserves of fossil fuels.

[0003] Now, generally recognized by major countries, global climatic changes caused by increasing emissions of greenhouse gases, in particular COj require that newly developed energy sources musi be environmentally compatible and sustainable. Therefore, greener sources of energy are needed to replace or reduce the consumption of fossil fuels. Biomass is a source of a sustainable and renewable fuel, with potentially a net zero greenhouse gas impact.

[0004] To be usable as a fiiel biomass needs to be converted. Biomass conversion technologies include biological processes, such as anaerobic or aerobic digestion fermentation, and thermal conversion processes, such as direct combustion for heating and generating electricity., gasification for producing syngas, and pyrolysis for producing bio-oils for use as fuels and as a feedstock for producing chemicals.

[0005] The thermal conversion processes also include hydrothermal processes, wherein biomass is treated in slurry form in autoclaves at temperatures above 200 °C and under autogenous pressures.

[0006] Pyrolysis processes have high potential for large scale commercialization as they provide flexibility in varying process conditions, such as heating rate, temperature, pressure, contact time, atmosphere, etc., to optimize yields of liquids (oil), gas and char. Of particular interest is fast (or flash) pyrolysis, designed to convert the biomass to maximum amounts of oil, employing a very low residence time, a very high heating rate and temperatures close to 500 ºC.

[0007] The oil produced in biomass pyrolysis has a high energy density that can be directly used in combustion or refined to fuels and specialty chemicals.

[0008] However, the pyrolysis derived bio-oils., because of their high oxygen contents, high viscosity, acidity, collusiveness and low stability, have limited direct, applications as fuels. Intensive research is being carried out to upgrade the quality of said bio-oils to products that are comparable to conventional fuels in composition, chemical and physical properties.

[0009] The pretreatrnent processes of biomass before pyrolysis offer possible solutions in biomass modification that will allow the pyrolysis process to be conducted at less severe conditions (i.e., lower temperatures, shorter contact times), and more efficiently to the extent that more oil is produced and of better quality.

[0010] Biomass conversion in large commercial plants is now carried out to produce ethanol, primarily using as feeds renewable sources such as corn, sugar cane, and cereal grains. Because the cost of these raw materials represents roughly one-half of the total cost of the process to produce the ethanol , it is of paramount interest to use cheaper biomass raw materials for conversion to ethanol. Furthermore, it is important to utilize other biomass sources other than grains in order to minimize the impact on food prices.

[0011] Consequently, less costly iignocellulosic biomass materials derived from agricultural and forestry residues are very attractive for use as sources to be converted to ethanoi or other fuels.

[0012] Ethanol has been produced from expensive raw materials, i.e., sugar cane, corn, starches, grains, cereals. However, there is need to use less expensive materials such as non-food lignocellυlosic materials including grasses, municipal solid waste (MSW), wood wastes, forestry- and agricultural wastes. However, the technologies known fox handling the conversion of such raw materials efficiently to ethanol are limited, and different from those used commercially to convert the sugar cane, corn, mains and cereals. [0013] Therefore, the objective of tins im enύon is to develop economically feasible and environmentally friendly processes that will allow an efficient conversion of the non-food cellulosic raw materials to ethanol.

[0014] In general although there are potentially many processes that can technically meet the conversion requirements, to be successful a process must also meet the economic and environmental requirements.

[0015] The use of ethanol in automobile fuels not only reduces the need for petroleum (crude oil), but also substantially reduces the carbon dioxide car-exhaust emissions

[0016] Commercial large scale operations involving the production of ethanol from cellulosic biomass use biological oi non-biological processes to depolymerize (break down) the cellulose The most commonly used biological piocesses use enzymes. whereas the non-biological processes use an acid-hydrolysis to com en the cellulose to sugars, mostly using dilute or concentrated sulphuric acid. These processes are considered as a pretreatment of the biomass in the overall bioconversion processes, which are followed by fermentation and distillation.

[0017] in the prior art we find descriptions of other kinds of pretreatments such as steam-ex plosion, which is followed b\ en/ymatic hydrolysis, fei mentation and distillation in the production of ethanol (see CE Wyman et al, Btoresource Technology 96 (2005) 1959- 1966).

[0018] Since the presently known processes for conversion of the lignocellulosic biomass (derhed from agricultural and forestry residues) are moie expensive than the processes used now commercially to produce ethanol from grains and cereals, there is a strong interest in developing new or improved processes that will allow a more cost- effective and environmentally acceptable manner of converting lignocellulosic biomass (from residues derived from agriculture and forestry materials) to ethanol.

[0019] In general lignocellulosic biomass from such residues consists mainly of three components; cellulose, hemicellulose and lignin. The cellulose component is a polymer of glucose, formed in long strand units, associated with the hemiceiiulose component layer and both tthe crystalline cellulose and hemicellulose) are encapsulated by the lignin

[0020] In ethanol production of the biocon\ersion processes, the cellulose and hemiccllulose are coin cited to sugars, such as glucose and xylose, followed by fermentation. Ligmn is a 3-dimensional branched pυiyaromatic matrix acting as a sheath (like a protecthe coating) to the cellulose and hemicellulose components of the biomass.

[0021] As a result due to the difference in the bonding of the components, the high crystallinit> of cellulose and due to the protective sheath of the lignin, the penetration, interaction reaction of the acids and or the enzymes is highly impeded by the restricted access to the bulk of the biomass panicles. 1 his problem is much less present when cereal grains are piocessed to produce ethanol.

[0022] However, foi biomass from non-ceieal giain sυuices, the ligmn present tesists the etvs me attack and hence lower yields aie obtained. To at least partly overcome this problem, pretrcarment of the biomass is necessan prior to subjecting the biomass to enzymatic hydrolysis (see N. Mosier et al,. Bioresource Technology 96 (2005), 673-680).

[0023] Since the major cost of the overall conversion process is due to the biomass feed and enzymes u is necessary to mmimi/e the use of enzymes and obtain the maximum conversion of the carbohydrates to ethanol

[0024] Lignoccllulosic biomass as a feedstock presents a large spectrum of compositions The interactions between composition, structuie and chemistry within the lignoceliuiosic material iesult in complex heterogeneous behavior towards the various preireatmeiu methods, and \n variations of reactiv ity twards enzymatic digestibility Specifically, the presence of three major components, that is . crystalline cellulose, hcmiceilulosc and Iignin, as well as their association in forming special composites, like the sheathing of cellulose by Iignin, hydrogen bonding between the components, etc.. contribute to the recalcitrant behavior of the raw lignoceliuiosic biomass . [0025] To improve the reactivity of the raw biomass towards enzymatic digestion., several pretreatment technologies have been developed, aimed at eliminating the physico-chemical and mechanical banter characteristics of the raw lignocelluiosic biomass in order to enhance the penetration of enzymes into the bulk of the individual biomass particles to cause digestion and hydrolysis.

[0026] These pretreatment processes, known to the prior art, involve chemical, biological, physical/mechanical and combinations thereof.

[0027] For a pretreatment process to be effective for large-scale commercial operations, to be cost effective and environmentally acceptable, it should not require use of very small biomass panicles, should preserve the hemicellulose, use a minimum amount of disposable materials, operate with low energy and labor requirements, minimize the formation of byproducts and degradation of products, utilize low-cost chemicals, and be capable of recycling the chemicals used in the process. Further, such pretreatmeni processes should require low-cost equipment, with low maintenance and operating costs.

[0028] For these reasons, a considerable amount of R&D work has been devoted during the last few years for developing means to pretreat the lignocellulosie biomass in such ways that the accessible bulk surface area increases, so that the raw biomass becomes more reactive to the enzymes, and more effective in producing mono- and oligosaccharides, which will allow an increase in the biomass ethanol conversion.

[0029] The most popular processes are acid and enzymatic hydrolysis processes, which are used mostly to convert the cellulose and hemicellulose to glucose.

[0030] In the prior art there are several versions of the original acid hydrolysis process. These involve either very concentrated acids or dilute acids in one or two step treatments, and combinations of acid treatment with steam treatments, such as steam-explosion.

[0031] Overall, the pretreatment processes utilizing acids, such as sulphuric acid, require specially constructed plant equipment that must be resistant to acid corrosion. Additionally, the use of acid requires neutralization by a low-cost base such as sodium hydroxide or calcium hydroxide, and the salts formed thereby must be filtered and washed from the hiomass This creates large wasste streams that require disposal and lead to additional costs Further, for the use of highly eoneenUated acids, the process requites an adduiona! evaporator io produce/recycle the highly concentrated acid, and to handle largo quantities of water used in the prcfreatment and recovery.

[0032] The acid pretreatracnts of lignoceliulosic biomass feeds used to convert the cellulose and hemicelhtlose to fermentable sugars have important disadvantages in the form of high costs, low efficiencies, and environmental problems Specifically, the high acid concentration process has the additional disadvantages of coπosiυn of equipment and high cost waste stream disposal, whereas the dilute (low acid concentiation) process produces a low and slow conversion of the biomass to fermentable sugars, and deactiv ation of the process by binding some of the enzymes to lignin,

[0033] Pretreatments using steaming (steam-explosion) as such and combinations with acid treatments also have certain disadvantages Diuing steam-explosion pretreafments, the pentoses and bexoses produced fioin the huiiolysis of the cellulose material are further, to some extent, converted to undesirable by-products such as furfural, levuliinie and formic acids together with other products {see M M. Wo et al. Appl. Biochemistry and Biotechnology 77 ( 1999) 47-54).

[0034] in general, processes nnoKrng acid treatments and steam-explosion produce compounds such as aliphatic acids, phenolic and furan det natives These degradation products act as inhibitors in subsequent processes using en/ymes to convert the sugars to ethanoi (see V.S. Chang, et al , Appl Biochemistry and Biotechnolog> 84 (2000) 5-

37),

[0035] Further, although high seveiity steam explosion allows the enzymes to ieact moie effectnely, it does degrade the produced sugars and reduces the yields, as well as making the lignin less reactive I sing less sex eie steamtng-acid pretreaimems produces lowei glucose yields, since the en/ymes cannot react with the major pail of the ceilulosic material (see J. Soderstrom, et al , Biomass and Bioenergy 24 (2003). 475-4R6 ; U S Patent 4,8R0,47.Und U S Patent 6.692.S78 U S Patent Application

[0036] in the prior ail, there are other pretreatment processes described such as high pressure and temperatures in the range of 200ºC to 250°C pretreatments. These conditions require special high pressure equipment which is costly and difficult to operate on a large scale commercially. Additionally, the cooking of biomass at such high temperatures and pressures produces excessive amounts of aldehydes, which inhibit the digestion process of the enzymes with the biomass.

[0037] Other pretreatmems known in the prior art involve the use of .sodium hydroxide and calcium oxide/hydroxide in dilute slurry forms, or under pressure and in air or in oxygen atmospheres. This requires processing taking several hours or several days. Overall, the processing of slurries requires large volume equipment, washing and filtration steps. Additionally, processing with lime produces non- recoverable salts as being occluded in the bulk of the biomass.

[0038] Other pretreatment processes described in the prior art involve the use of ammonia in liquid or gaseous form to treat the biomass.

[0039] The Ammonia Fiber Explosion (AFEX) process involves pressurized absorption of ammonia by biomass. followed by low pressure desorption that explosively erupts the biomass lignocelUiJosic matrix. A similar process is the ammonia- freeze explosion pretreatment. These processes need specialized equipment to handle the biomass, which must be agitated while it is exposed to high pressure ammonia gas, and subsequently exposed to a low pressure/vacuum condition to desorb ammonia. The overall process requires special equipment to handle the high ammonia pressure and vacuum conditions as well as recover, recom press, and recycle the ammonia.

[0040] This process in small scale operations produces pretreated herbaceous and non-woody agricultural biomass materials that have good enzymatic conversion yields. With forestry-derived and other hard and woody (lignin-πch) biomass materials the ammonia pretreatment process lias not been successful. Moreover, the overall costs in equipment and process operation are substantially high. [0041 ] Enzymatic hydrolysis_* presents a promising process for large-scale operation , using lignoeeliulosk biomass. as it is not enetgy intensive, envitonmenlailly compatible and does not require the use of couosive chemicals.

[0042] The main disadvantage of this process has been the cost of producing the enzymes, although during the most recent years, u ith new improved processes, this cosi has been reduced (see V S. Chang et ai., Applied Biochemistry and Biotechnology 84 (2000) 5-37).

[0043] It can be concluded that there is need for developing pretreatinent processes that allow the maximum conversion of lignυecllulosic biomass to ethanol via high yield enzymatic hydrolysis,. without the use of corrosive chemicals, waste streams and specialty high-cost equipment.

[0044] Such processes will produce high vields of fermentable sugars from ligrtoeeilulosic feedstocks and in an emirυmnentaϊly acceptable manner and will be carried out commercially at comparable costs to the presently used petroleum-derived fuels, and can be used as replacements.

[0045] in general, any pretreatment of the lignoceHulosic biomass particles to enhance its conversion must at least increase the micro-and macro-accessibility to the bulk of the particles, allow ing penetration of the enzymes and chemicals The enzymatic degradation and digestion of celluiosic matetials constitutes the key process of the natural carbon cycle

[0046] Overall, in view of the fast increasing prices of eellulosic biomass materials used in food products and now with limited availability there is an increasing need to develop cost effective processes that will enable to cornea, cost effectrveiy, biomass materials that are not used in food pioducts. foi ethano i production. As the most populai existing pretreatment process presently available are only suitable for applications using biomass feeds derixed from biomass mateπals that are used in food products, there is a much greater need to develop new pretreatment processes that are effective in improving the cthanol yields from processing less costly feeds such as the woody types, using smaller amounts of en/ymes and less costK plant equipment, chemicals and o\erali processing. [0047] In the prior ail, the term cellulases is used to describe a class of enzymes responsible tor the biodegradation natural process. Cellulases are mainly produced by bacteria and fungi. For the purpose of this discussion, it is noted thai the proteinic conveyors of the complex enzyme groups have molecular weights in the region of 30,000 to 100,000, and have globular shapes with hydrodyπamic diameters in the range of 3 to 4 nm. Therefore, the openings of the cannulae, pores, cavities and interfibrillar interstices, must be large enough to allow molecules, ions, compounds, and enzymes to penetrate in the bulk of biomass. For an efficient enzymatic digestion and conversion, the biomass particle should have the largest possible number of such openings with diameters at least 3 to 4 nm (H.A. Kzassig et al. in Polymer Monographs, ºCellulose", vol. 11 ( 1993) p 202).

[0048] This invention is based on optimizing and utilizing a very basic property of lignocellulosic materials (like woods) which is the swelling which is caused by organic and inorganic liquids like water. Although this property of woods is a disadvantage for applications In construction, boards or packaging, etc., to the contrary, the swelling properly of woods and other lignocellulosic materials is very useful for the enzymatic conversion of such lignocellulosic materials to etha.no i (Mentanis G., et al., Wood Sd. Technol. (1994), 28, 1 19-134. F.F. Wangaard, et al., Wood Sci. Technol. ( 1967) 1 ,253-277).

[0049] This invention involves optimizing the water swelling process to affect penetration in the intercrystaUine regions reached through pores and capillaries leading into the imerfibrillar spaces.

[0050] In particular, the objective of mis invention is to provide conditions and the materials that cause optimum swelling that increases the accessibility and reactivity. Such optimum swelling involves both intrafibriilar and intercrystaUine water penetration.

[0051 ] To increase the penetration of water to achieve maximum bulking or swelling, solutions of salts, acids, bases and organic water soluble compounds can be used, and preferably sahs or inorganic bases The paths that the water and solute moleeuies follow on then way mto the bulk of {he biomass invoke the existing sttuctui a! pores, capillaries and \oiώ> between fibtiliai elements

[0052] While watci molecules penetrate into the interior of the biomass, the\ are causing disruption of fibrillar associations and move into regions interlinking the crystallite ensembles forming the fibπls (A Stamm, Ind. Eng. Chcm Vol. 27, No 4 (1035) 401-406}

[0053] Deepet penetrations which reφiiie more severe process conditions and higher solute concentrations, involve the penetration of water molecules into the lattice structure of the crystallites, causing iupturc of the hydrogen bonded layers and creation of accessible and rcacm e internal surfaces The strong interaction of w atcr and, for example, a strong inorganic base with the biomass, results in the opening of the muaplanar and interplanar hydrogen bonded lmks that cause lattice transformation, which in turn allows solute molecules'ions to diffuse between lattice layers Usually, the swelling oi bulking of the lignocellulosic materials (i e , woody kinds) by liquids, causes corresponding changes in the dimensions of the wood particles However, the changes, if any in the dimensions of the particles do not necessarily reflect the amount of solvent sorbet! in the bulk of the particle This is due to existence of fine and coarse capillaues within the bulk structure, that attract ionic solvents (e g., water) to fill the available space without causing measurable changes in the dimensions of the lignocellulosic mass

[0054] The effectiveness of the sohent to cause swelling depends primarily on its basicity, hvdrogen bonding affinity and moleeuim bonding The swelling properties of lignoceHulosic materials (such as wood), and the ability of different chemicals to cause swelling has been studied for o\cr 70 vears (A. Stamm, Ind Eng (Them. vol. 27. No 4. 1934) Briefly, it has been shown that the extent of swelling and solvent sorption can be related to the hydrogen bonding affinity of the solvent.

[0055] A simple model of the mechanism of the swelling piocess of wood with water mxoiv cs the penetration of water molecules via capillaries into the bulk strucuiic, wherein the water molecules first interact w ith the hydiogen-bonded hvdroxyl groups of the lignocellulosic mass to form a transition-state, that is. an energeticaliy unstable stale, which dissociates to a water (or solvent) molecule ami becomes hydrogen-bonded to the iignoceilulosie mass. Thus, this mechanism is based on a chemically activated process following the Aπhenius equation, characteristic of classical chemical reactions involving an activation energy.

[0056] Accordingly, the rate and extent of swelling substantially increases with increasing temperature. The interaction of water with the biomass that causes bulking (swelling) and at the same time creates accessibility, can be increased by the presence in (he water of certain soluble salts, which cause substantially more swelling (A. Starmm, J rid. Kng. Chem. vol. 27, No. 4. 1934).

[0057] The "activity" of certain salts to increase swelling is in the following order: Cations: Anions:

[0058] However, there are exceptions to this order, depending on concentrations, temperature and kind of biomass used. In general, much more swelling occurs in alkaline solutions than in acidic solutions.

[0003] Certain salts (like concentrated ZnCl;) used in hot solutions to cause swelling, react much further by splitting fibrillar aggregates and even dissolving parts of the biomass (Penn. W.S. (1949) Elec. Maimf. 5, (1), 8).

[0003] Bases, both organic and inorganic, have much more of an affinity to interact with biomass materials. According to one theory, celluiosic materials can be considered to exhibit chemical properties similar to mono-basic acids, which can be neutralized by contacting the biomass with strong bases,

[0003] In general, the affinity of certain bases to cause swelling for celluiosic materials can classified in the following order:

(See K. E. Cabradilla and S. H. Zeromiaπ, 'Influence of Crystallinity on the Thermal Properties" in Thermal Uses and Properties of Carbohydrates and Lignins, Academic Press ( 1976)).

[0062] Briefly, and for the purpose of this invention, the action of water or other polar solvents and when enhanced by soluble salts bases or acids, but preferably with strong bases, and conducted at optimum temperature, concentration and pll result, to different extents, in the following:

• Rupture of hydrogen bonds thai hold together fibril aggregates, thereby creating more reactive bulk surface areas.

• Breaking of intrapianar and interplanar hydrogen bonds, allowing different biomass components to move, dissolve or rearrange as well as allow the soluble (salt) ions to penetrate to the interior of the biomass;.

[0063] As a result of these chemical interactions, the balk is transformed to a sponge-like structure. The swelling enlarges the pores and capillaries with exits to the surface, as well as opening of interfibrillar spaces, such that the biomass becomes accessible for reactions with chemical compounds, salt, acids, bases, as well as enzymes.

[0064] Biomass swollen with polar liquids like water, when it is subsequently dried at relatively low temperatures (at. 8G-H)OºC), does not allow all liquid present in the swollen regions to escape. This entrapment of the swelling agents and/or present solutes, like salts, is accompanied by some shrinkage of the biomass panicles. Consequently, the swelling process followed with a drying step to entrap (encapsulate) chemical compounds, which may form inclusion complexes within the pores, voids, capillaries, interfibrillar interstices, provides means to activate the biomass in a way that the biomass becomes more reactive in the enzymatic conversion, as well as to thermal and hydrotherma! conversion for the production of fuels.

[0065] In general lignocellnlosic biomass, depending on its origin, contains, besides cellulose, hemicellulose and lignin, other components such as resins, tannins, terpenes, fats, etc. These materials are referred to as "extractives," as they can be removed by (organic) solvents, such as alcohols. Additionally, the lignocellulosic biomass, depending on its kind and origin, contain a variety of metals. Mild treatments, like hot water (60-9OºC) can remove most of these "extractives" without altering the cellulosic components of the biomass. In genera!, the removal of "extractives" results in increasing the rate of diffusion of the solvent and solutes into the biomass, while increasing the size of the capillaries, disrupting the cell wall structure, and decreasing the network of secondary hydrogen bonds. Thus, the interna! structure of the cell wall loses stability and increases the reactivity of the exposed surfaces towards the sol vent/solute molecules. Therefore, removal of the "extractives" increases the rate of swelling, and its amount (G. Mantanis et al., Holzforschung, 49 (1995) 2.W-248; WO 00/74909 A l).

[0066] Lignocellulosic biomass, besides the organic extractive components., contains also inorganic extractives. About 20 kinds of metals have been identified in various kinds of iignoceliulosic biomass, which vary not only with the kind of biomass. but also with its origin.

[0067] In general depending on the source of the biomass, its history of growth, location, etc., about 20 inorganic species have been found to be present in different kinds of biomass, with the most abundant being Na. K, Ca, Mg, S, Si₅ Fe₅ Mn, AK P. hi some biomass sources, the total concentration of inorganic species can reach 25% based on dry weight of the biomass.

[0068] Thus, there is a particular need for processes that prepare non-food biomass materials, in particular Iignocellulosic biomass materials, for subsequent enzymatic or chemical conversion to liquid fuels.

BRIEF SUMMARY OF THE INVENTION

[0069] The present invention addresses these problems by providing a process for opening up the structure of a biomass material, said process comprising the steps of:

( i) providing biomass particles having a moisture content of at least 20 wt.%

(ii) subjecting the biomass panicles to flash heating.

[0070] Optionally the biomass panicles are subjected to a pretreatment step. The process including the optional pretreaiment step can be exemplified as follows: in the first step of the process Iignocellulosic biomass in the form of powder, chips, granules, etc., is treated in a kneader at a temperatures near 100ºC, in the presence of water or in an aqueous solution of a salt, an acid, or a base solution, such that sufficient water or aqueous solution is sorbed by the biomass. [0071 ] After this pretreafment. the biomass with the scvtbed water can be processed in an extruder or filter ptess wherein water is squeezed out Optionalh the biomass coming out of the extruder or filter press can be returned to the kneader for another cycle of water sorption and then again passed through the extruder or filter press. The water squeezed out from the extruder or filter press contains the extractives which are both organic and inorganic.

[0003] Another option involves the removal of some of the extracth es in one or more "sorption-tlesorption" cycles, aαd finally in the final sorption cycle to use water soluble inorganic additives such as salts, acids or bases which may enhance subsequent conversion processes to pioduce bio-oils, syngases, or ethanol.

[0073] One or more of the "sorption-desorption" cycles may be conducted using an alkaline water solution such as sodium hydroxide, or using an acidic vsater solutions such as sulfuric, nitric or hydrochloric acids that enhance the temoval of metals from biomass and also hydrolysis of the components, ail resulting in creating larger internal surface area and volume, making the biomass more accessible to enzyme digestion or to chemical reactions.

[0003] The second step of the process causes an instant sorbcd water flash- vaporization, which results in rapid vapor pressure increase that bursts and ruptures the compacted fiber structure of the biomass particle, thus creating larger voids, internal v olume and surface area as well as destroying hydrogen bonding between indiv idual components, thus exposing them to external chemical reactions, which include cn/yrmuic digestion and hydrolysis and reactions with acids and bases

[0003] It is advantageous to combine the flash vaporization with a precipitous pressure reduction, so as to further increase the explosive forces exerted on the biomass statctuie. Such a pressure drop may be effected by opening a valve to a vacuum source Conveninently, the vacuum source may compπse a buffer vessel having a large volume, so that the vacuum source can cope with the sudden supply of gases and vapors The vessel containing the biomass material may be provided with a gas solid scparator, such as a cyclone, to prevent the particulate material from being sucked into the vacuum source. [0076] An alternate way of effecting a precipitous pressure drop makes use of the Bernoulli effect. The biomass materia! is taken up by a lift gas, and transported at a high rate of flow through a tube system. The tube system is provided with a restriction having a significantly smaller diameter than the upstream and downstream portions of the tube system. As the lift gas is being forced through the restriction, the flow rate accelerates, and the pressure drops.

[0077] Additionally, the modified biomass produced in the second step is more reactive towards hydrothermal and thermoconversions. such as pyroijsis, gasification and combustion, in particular, in pyrol ytic reactions, the so modified biomass, due to its larger bulk porosity, allows the formed gases and condensable vapors (oils) to escape faster and with a smaller amount of bulk entrapment; thus higher yields of oils and gases can be produced in commercial pyrolysis and gasification operation, with minimum amounts of residues (chars).

[0078] There are cases in pyroKsis and gasification of biomass conversion wherein the addition of inorganic additives enhances some of the product yields and the selectively. For example, lime added to biomass enhances the gasification process. In such processes lime has been physically mixed with the biomass feaό. 1 iowever, the effect of the lime can be further enhanced using the process of this invention that allows the lime to be "in-planted" in the bulk of the biomass particle. For example, in the first step of the process of this invention, lime, or other inorganic salts, such salts of the alkaline or alkaline earth metals, are introduced in the water used to be sorbed by the biomass during kneading. Subsequently, the biomass. hav ing sorbed the water solution containing the metal salt(s). is processed in the second step of this invention wherein the Hash (rapid) sorbed water vaporization allows the water vapor (steam) to escape while it ruptures the bulk of the biomass particle and at the same time while it vaporizes, deposits uniformly the metals on the internal surface of the particles. Therefore, the mctal(s) in the product of the second step are uniformly distributed within the bulk and are in close contact with the three biomass components, i.e., the lignin, hemicelluiose and cellulose. Thus, all three components are present in a highly porous composite with increased accessibility to penetration of chemicals from outside environments into the interior of the particle, as well as hav ing larger exit channeis, voids, etc., that allow a faster and unhindered diffusion and exit of vapors / gases liquids produced in the bulk, as, for example, in pvrolysis and gasification biomass conversion processes.

[0079] In another embodiment, the swollen biomass containing water or a solution, is coated with an inorganic materia! such as a catalyst, and subsequently is dried to fix tiie inorganic coating onto the biomass particle. This process is followed by heating the dried / coated biomass particles by a rapid flash heating technique described in this invention to cause the internal vapors .^' gases to explode.

DETAILED DESCRIPTION OF THE INVENTION

[0080] We have discos ered that when the swollen biomass particles prepared as described above are exposed to sudden rapid heating, or flash -heating, the sorbed watei in the bulk of the biomass undergoes sudden \aρori/aiion that iesuhs in tapidiv increasing the iiuernal vapor pressure, theieby causing structuuii disruption in the bulk of the particle Tins "in-situ" high pressoie steam formation in the process of rupturing the compact arrangement of the fibrils also reduces the hydrogen bonding in regions of component interactions, therein- creating more internal surface area, larger pores and channels and increased accessibility to the interior of the biomass particle. Therefore, the increase of the internal openings and of the accessibility results in transforming the biomass material to a more porous and reacm e form, ailo\s ing the enzymes to enter the bulk of the mass of the paiticle and hence produce higher yields of en/yraadc conversion to sugars and eihanol.

[0081] Suitable plant equipment to conduct the process, is a\ ailable commercially for large scale operations, and this includes such equipment as Hash dryers. AO- heateis. microwave o\ens. tornado/eye lone-type high temperature dners. etc.

The Process

[0082] The preferred process of the invention, including the optional pretrcatment step, w ill be described as a "'two-step process.

The First Step.

[0083] In the first step the biomass. in powder, granules, chips, or in any other particulate form, is treated in a mechanical mixer such as a kneader, mix-mulier or ball-mil!, in the presence of water to cause the water sorption by the biomass. Treatements using a kneader or a mix muller are preferred m this invention, at. both kinds of mixing machines have capabilities to heat the biomass while it is soibing the water

[0084] As the sorption rate and sorption capacity of the different kinds of biomass vary, the sorption conditions need to be adjusted to achieve the optimum of water sorption Theerefore, residence, time and temperature can be different depending on the vsatet sorbing properties of the treated bioinass. To aid the sorption m terms of rate and capacity, sorption aids oi swelling aids nun- be added to the water or to the biomass while it is treated in the mixing de\ice.

[0085] A preferred sorption additi\e is an inorganic base, such as. but not limited to, a hydroxide, carbonate or hydroxyl carbonate of the alkaline and alkaline earth metals.

[0086] The swelling aid can comprise at least one cation from the group consisting of K NH ₄, Na Ba. Mn. Mg: Ca. Li: Zn. AI The swelling aid can also comprise at least one anion from the group consisting of C1O3; SO4; SO3, NO3: Ci; Br, CIO4, 1. CNS, ΪISO4. OH: HCO3. ΪISO3. (OH)COX and aluminate

[0003] For certain biomass materials containing relatively high concentrations of indigenous metals which adversely affect the enzj matic digestion <' h>drol>sjs processes, the first step of this invention is used to extract most of the metals from the biomass feed

[0088] Operating in this mode, the sorption of the first step \s conducted without addition of metal salts. Howevet, if needed to enhance the metal extraction, the pH of the water can be increased above 7 by the addition of a base, preferably ammonium hydroxide or urea The biomass can be tieated. for example, m a kneader at temperatures from ambient to the boiling point of water

[0089] The biomass having sorbed the water from the kneader is contimioush dά to an extruder, centrifuge or to a filter press, where part of the sorbed water is squeezed out of the biomass. This squeezed-out water contains portions of the extracted metals The biomass from the fust metal extinction, coming out from the extrudei or filter press, can be returned into the kneader. where more watei is added ibi another cycle of .sorption to remove more metals, so the cycle is repeated.

[0090] hi another variation of the operation of the first step, the first sorption step is conducted at pH above 7. and m the following step(s) the water sorption is done at pH below 7

[0091] I Therefore, low-cost liguocellulosic materials which contain organic extractives (resins, oil, tannins) as well as inorganic extraction (metal salts), can be used in the process of this invention [0092] In order io remove ftom the biomass both the organic and inorganic extractives, which all inhibit the enzymatic digestion / hydrolysis to form the sugars and the eth.an.oi. the first/second cycles tn sorption of water in the kneader can be done at an alkaline pH that enhances the removal of the organic extractives, and followed by the third /fourth sorption step which can be done at an acidic pH to enhance the removal of metal extractives. It is possible to employ a pH-Cycle-Swing between alternating acid base pHs. Obviously, the order and number of cycles can be varied , and is done in a way to optimize the conditions to achieve the le\els of metals acceptable to be present in the feed before the enzymatic conversion step.

[0093] The essence of the piocess conducted in this first step, that is. the sorption of water follow ed by "forced" desorption. all involving water in the liquid phase, can be em isioned as a kind of ºChimie- Douce" where the water enters the pores, cavities, capillaries of the biomass particles, dissolving some of the water-soluble extractiv es and subsequently is squeezed out of the biomass particles, carrying in it the soluble extracth es. Said procedure can be repeated in order to achieve the degree of extractive removal desired.

[0094] Further, while this " Chimic~Douce" procedure operates and is removing extractives from the surface and bulk of biomass panicles. at the same time this ("cleansing" ) procedure creates more surface area, opens pores, channels, and overall increases the susceptibility of the biomass particles of enzyme digestion, chemical reactions, and so on.

[0095] Another variation of the mode of operation of the first step of this invention involves the use of a kneader or other mixing device which has an enclosed chamber, allowing it to heat the biomass at temperatures abov e 100ºC while the steam generated is kept within the kneader chamber.

[0096] Therefore, in the first siep we perform a bulk-cleansing via the ºChimie- Douce- procedure, while at the same time more porosity and interna! surface area is created. The Second Step

[0097] in this step of the process, more internal surface area, larger pores, channels, voids, cannuiae and openings to the bulk of the biomass particles are created, thus making the particle more accessible to enzymatic digestion, hydrolysis and to chemical reactions.

[0098] Specifically this step of the overall process involves heating the sorbed water present into the biomass particles rapidly to cause an in-situ flash heating (ie... vaporization) of the sorbed water that, creates an instant internal high pressure that bursts (ruptures) apart the compact lignocellulosic particle structure, thus creating a large number and bigger openings to the bulk of the biomass particle,

[0099] The flash heating can comprise increasing the temperature from 90 ºC or below, preferably 80 ºC or below, to i 10 ºC or above, preferably 120 ºC or above, in less than 30 seconds, preferably less than 10 seconds.

[00100] During the process of the particle bulk rupture and volume expansion, some hydrogen bonding between the components (i.e., cellulose, hemicellulose and lignin) is destroyed and possibly some rearrangement takes place as the lignin, under such severe hydrothermal conditions developed instantly in the bulk of the panicle, becomes plastic and can rearrange its crystal lographic location and its association with the cellulose and hemicellulose components. Accordingly, lignin renders itself to be accessible to chemical reactions and becomes easier to be removed by subsequent chemical treatments like, for example, acid leaching of the said treated biomass, to produce delignified celluiosic biomass materials.

[00101] Further, the biomass product obtained in this second step of the overall process can be recycled to the iϊrst step of the process wherein more indigenous metals can be removed and/or chemical catalysts additives, incorporated into the biomass particle.

[00102] Using the product of the second step of the overall process, which has more accessibility to the bulk of the biomass particles, recycled to the first step of the process, the water sorption is further facilitated and the removal or addition of chemical compounds into the bulk of the biomass particles is further enhanced. [0003] Heating systems that can provide rapid heating in large scale commercial opeicttiυns include flash dryers, microwave heating ovens, AC-heaters, tornado-type fluidized bed healers, and so on. The dielectric heating is used commercialh by radio frequency (Rf) heaters operating below 100 MHz. and microwa\e heating equipment opciaϋng ai frequencies above 500 MHz The biυmass particles containing the sorbed water (being in swollen state) need to be rapidly heated to cause the instant sorbed water vaporization: however, the temperature and the heating time must be chosen so that the biυmass itself does, not start to become carbonized, or undergo oxidatise surface reactions. The steam produced in the second step of the process can be condensed and the water recycled back \o the first step of the process; otherwise, the steam can be used to provide heat to the fiisi step of the piocess.

[00104] Thus, the invention has been described by reference to certain embodiments discussed abo\e. It will be recognized that these embodiments are susceptible to various modifications and alternative forms well known to those of skill in the an. jooto?! Many modifications in addition to those described above may be made to the structures and techniques described herein without departing from the spirit and scope of the invention. Accotdingly, although specific embodiments have been described, these are examples only and are not limiting upon the scope of the invention.

Claims

WHAl IS CLAIMED IS:

1. A process for preparing biomass panicles for thermolytic or enzymatic conversion, said ptocess composing the steps of:

[1] providing biomass panicles having a moisture content of at least 20

Wt ^%

[11] subjecting the biomass particles to flash heating.

2. The process of claim I wherein the moisture content of the biomass panicles resulting from step (i) is at least 30 wt.% preferably at least 35 wt % .

3. The process of claim I or 2 wherein step (i) comprises contacting biomass panicles w ith water or steam.

4. The process of claim 3 wherein step (i) comprises mechanical treatment.

5. The process of claim 4 wherein the mechanical treatment is carried out in a krteader. an exlrudei, a mi.ver-extnider, a mix-muliet. a baii mill, or a combination thereof.

6. The process of claim 3 wherein step (i) further comprises contacting the biomass particles with a swelling aid.

7. The process of claim 6 wherein the swelling aid is selected from water soluble bases, water soluble acids, water soluble salts, and mixtures thereof.

8. The process of claim 7 wherein the swelling aid comprises at least one cation from the group consisting of K. NH₄, Na; Ba; Mn; Mg; Ca, Li; Zn, Al

9. The process of claim 7 or S wherein the swelling aid comprises at least one anion from the group consisting of CIO3; SO4: SO3; NO3: Ck Br; CIO4; I; CNS; HSO4; OH: MCO3; HSO3; (0HXO3; and aluminate.

10 The process of any one of the preceding claims wherein the Ωash heating is carried out with radio frequency energy or microwave energy.

1 1. The process of any of the preceding claims wherein the Hash heating comprises increasing the temperature from 90 ºC or below, preferably SO ºC or below, to 1 10 ºC or above, preferably 120 ºC or above, in less than 30 seconds, preferably less than 10 seconds.

12. The process of any one of the preceding claims wherein the flash heating is followed by a pressure drop.

13. The process of any one of the preceding claims wherein step (i) is preceded by at least one absorption, desorption cycle wherein a liquid comprising water is absorbed into and desorbed from ^aid biomass particles.

14 The process of claim i J wherein extractives are removed from the biomass particles in the at least one absorption desorption cycle.

15. The process of claim 13 or 14 wherein the desorption part of the absorption/desorption cycle comprises squeezing water from the biomass particles in an extruder, centrifuge or a filter press.

16. The process of any one of claims 13-15 wherein the at least one absorplion/desorptioπ cycle comprises a pH cycle swing.

17. The process of any one of the preceding claims wherein the biomass material is a ceiiuiosic biomass material.

18. The process of claim 17 wherein the cellulosic biomass material is selected from the group consisting of wood, grass, straw, bagasse, com husks, citrus peels, algae and mixtures .hereof.

19. The process of any of the preceding claims wherein said thermolytic conversion is selected from the group consisting of: gasification, combustion, pyroiysis. liquefaction, hydrothermal conversion, and combinations thereof.

20. The process of claim 19 wherein said thermal conversion is also in the presence of a caιalyst.