METHODS OF FORMING A BIOMASS FEEDSTOCK AND RELATED BIOMASS PARTICLES AND SYSTEMS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001]This application claims the benefit under 35 U.S.C. § 119 (e) of U.S. Provisional Patent Application Ser. No. 63/710,784, filed Oct. 23, 2024, the disclosure of which is hereby incorporated herein in its entirety by this reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002]This invention was made with government support under Contract No. DE-AC07-05-ID14517 awarded by the United States Department of Energy. The government has certain rights in the invention.

TECHNICAL FIELD

[0003]This disclosure relates generally to methods of forming a biomass feedstock and to biomass particles of a biomass feedstock. More specifically, the disclosure relates to methods of forming the biomass feedstock that result in increased flowability properties and biomass feedstocks that include biomass particles with increased flowability properties.

BACKGROUND

[0004]Rapid population growth and industrial expansion are increasing energy demands, while fossil fuel depletion and environmental concerns underscore the shift towards clean and environmentally benign energy alternatives. Biomass, as a carbon-neutral and widely available resource, may offer a reduced ecological footprint and flexibility in various thermochemical conversion pathways, including combustion, pyrolysis, gasification, hydrothermal carbonization, and liquefaction. Gasification emerges prominently in the context of addressing imminent global energy requisites. This thermochemical transformation mechanism is used to produce syngas, fuels, and/or chemically relevant feedstocks from biomass. Gasification is able to yield a cleaner gas relative to combustion and pyrolysis processes, and confers heightened energy recovery efficiency while affording a thermal capacity advantage. Further, gasification demonstrates insensitivity toward some types of biomass owing to its capacity for complete breakdown into syngas. This characteristic allows gasification to efficiently utilize a diverse range of biomass feedstocks, including woody biomass, agricultural residues, energy crops, and municipal solid waste, among others.

[0005]Gasification has been recognized as a promising method to convert biomass to products such as biofuels or hydrogen. Over the past few decades, several biomass gasification technologies have been developed, predominantly featuring fixed- or fluidized-bed reactor configurations. However, these configurations have several well-documented challenges, including problems feeding non-uniform and inhomogeneous biomass particles, poor carbon conversion resulting from relatively low bed temperatures, risk of fluidized bed agglomeration and collapse if the temperature becomes too high, and production of high concentrations of condensable polyaromatic “tars” that foul downstream systems and waste carbon that could otherwise be part of the product gas.

[0006]A small number of commercial biomass gasification systems are currently operational. Some of these systems utilize nitrogen-diluted product gas for heat generation or biopower production through reciprocating engines. R-GAS® gasification system is one such biomass gasification system and is capable of gasifying an array of carbon-rich feedstocks. However, deployment of the R-GAS® gasification system for biomass operation is challenging due to the requirement to match biomass attributes to reactor requirements. Compared to most entrained flow gasifiers utilizing dry feedstocks, the R-GASR gasification system features a relatively low residence time and necessitates comparatively small particle sizes to achieve carbon conversion.

BRIEF SUMMARY

[0007]Disclosed is a method of forming a biomass feedstock comprising comminuting biomass into biomass fragments, densifying the biomass fragments into biomass pellets, thermally treating the biomass pellets to form thermally treated biomass pellets, and reducing a particle size of the thermally treated biomass pellets to form biomass particles. The biomass particles exhibit substantially the same properties throughout a volume of the biomass particles.

[0008]Disclosed are biomass particles comprising non-fossil biological material exhibiting one or more of a linear dimension of from about 100 microns to about 300 microns and a density of greater than or equal to about 500 kg/m³. An interior portion of the biomass particles exhibits substantially the same one or more properties as an exterior portion of the biomass particles.

[0009]Disclosed is a biomass processing system that comprises a comminution apparatus configured to comminute biomass, a densification apparatus configured to densify the comminuted biomass, a thermal treatment apparatus configured to thermally degrade the densified comminuted biomass, and a size reduction apparatus configured to reduce a particle size of the thermally degraded densified biomass to a linear dimension of from about 100 microns to about 300 microns.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]For a detailed understanding of the disclosure, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements have generally been designated with like numerals, and wherein:

[0011]FIG. 1A illustrates a flow diagram of forming biomass particles in accordance with embodiments of the disclosure;

[0012]FIG. 1B illustrates a biomass processing system in accordance with embodiments of the disclosure;

[0013]FIG. 2A illustrates biomass particles in accordance with embodiments of the disclosure;

[0014]FIG. 2B illustrates a biomass particle in accordance with embodiments of the disclosure;

[0015]FIG. 3 illustrates a gasification reactor system in accordance with embodiments of the disclosure;

[0016]FIG. 4 is a graph of cumulative passing (%) as a function of size for miscanthus feedstock in accordance with embodiments of the disclosure;

[0017]FIG. 5 illustrates a flowsheet of a gasification system in accordance with embodiments of the disclosure;

[0018]FIG. 6 is a graph comparing sieve size against a percentage of each sample passing through the sieve in accordance with embodiments of the disclosure;

[0019]FIG. 7 is a graph that shows temporal trends for torrefied flow rate and the differential pressure between a feed hopper and a lock hopper in accordance with embodiments of the disclosure;

[0020]FIG. 8 illustrates the energy demands for a baseline pathway, a torrefaction pathway, and a steam explosion pathway in accordance with embodiments of the disclosure;

[0021]FIG. 9 is a graph that shows the results for Yield loci and Mohr's circle analysis in accordance with embodiments of the disclosure;

[0022]FIG. 10A is a graph that shows the aspect ratio of the raw and torrefied wood pellets after size reduction in accordance with embodiments of the disclosure;

[0023]FIG. 10B is a graph that shows the results of a sphericity analysis in accordance with embodiments of the disclosure; and

[0024]FIG. 10C is a graph that shows the results of a convexity analysis in accordance with embodiments of the disclosure.

DETAILED DESCRIPTION

[0025]Systems and methods for producing a biomass feedstock are disclosed. The methods include subjecting a biomass material to a series of mechanical and thermochemical acts that include deconstruction and thermal treatment acts. Through these operations, the biomass material is converted into the biomass feedstock including biomass particles, which exhibit reduced moisture content, increased energy density, and enhanced physical and flow properties compared to biomass feedstocks prepared by conventional processes. The processed biomass material may be used as a biomass feedstock for a gasifier. Deconstruction of the biomass material forms biomass fragments that are sufficiently small and/or sufficiently uniform to be efficiently densified. Densifying the biomass fragments forms uniform, compacted biomass pellets upon which consistent and controlled thermal treatment is conducted. Thermally treating the biomass pellets forms thermally treated biomass pellets that exhibit hydrophobic properties, increased friability, and a changed (e.g., an altered) chemical composition. The thermal treatment facilitates downstream size reduction and increased energy density of the biomass pellets. Reducing the size of the thermally treated biomass pellets after the thermal treatment yields biomass particles of a controlled size and density. The resulting biomass particles exhibit a higher bulk density, lower interparticle cohesion, and enhanced flowability under pressurized conditions than biomass feedstocks prepared by conventional processes. The biomass particles may also be formed by varying the sequence of deconstructing the biomass, densifying the biomass, and thermally treating the biomass. Forming the biomass feedstock by methods according to embodiments of the disclosure produces a more uniform and homogeneous feedstock in chemical composition, size, and density, which may be provided to the gasifier. The methods also convert hydrophilic biomass material to hydrophobic biomass particles. The systems and methods according to embodiments of the disclosure overcome existing challenges associated with conventional fibrous, heterogeneous, and moisture-rich biomass, enabling cost-effective and scalable gasification for producing syngas, fuels, and other high-value products.

[0026]In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which are illustrated embodiments of the disclosure. These embodiments are described in sufficient detail to enable those of ordinary skill in the art to practice the disclosure. It should be understood, however, that the detailed description, while indicating examples of embodiments of the disclosure, are given by way of illustration only and not by way of limitation. Accordingly, various substitutions, modifications, additions, rearrangements, or combinations thereof are within the scope of this disclosure.

[0027]Additionally, various aspects or features will be presented in terms of systems or devices that may include a number of components, modules, etc. It is to be understood and appreciated that the various systems and/or devices may include additional components, modules, etc., and/or may not include all of the components, modules, etc., discussed in connection with the drawings. Furthermore, all or a portion of any embodiment disclosed herein may be utilized with all or a portion of any other embodiment, unless stated otherwise. Accordingly, the disclosure is not limited to any embodiment illustrated in any one or more of the accompanying drawings.

[0028]In addition, the embodiments may be described in terms of a method that is depicted as method acts, a flowchart, a flow diagram, a schematic diagram, a block diagram, etc. Although the method may describe operational acts in a particular sequence, it is to be understood that some or all of such acts may be performed in a different sequence. In certain circumstances, the acts are performed concurrently with other acts.

[0029]As used herein, the singular forms following “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Therefore, the terms should generally be construed to mean “one or more” unless specified otherwise or clear from the context to be directed to a singular form.

[0030]The terms “have,” “may have,” “include,” and “may include” as used herein indicate the presence of corresponding features (for example, elements such as numerical values, functions, operations, or parts), and do not preclude the presence of additional features.

[0031]The terms “A or B,” “at least one of A and B,” “one or more of A and B,” or “A and/or B” as used herein include all possible combinations of items enumerated with them. For example, use of these terms, with A and B representing different items, means: (1) including at least one A; (2) including at least one B; or (3) including both at least one A and at least one B.

[0032]Terms such as “first,” “second,” and so forth are used herein to distinguish one component from another without limiting the components and do not necessarily reflect importance, quantity, or an order of use. Furthermore, a reference to first and second elements does not mean that only two elements may be employed there or that the first element must precede the second element in some manner. Also, unless stated otherwise, a set of elements may comprise one or more elements.

[0033]It will be understood that, when two or more elements are described as being “coupled,” “operatively coupled,” “in communication,” or “in operable communication” with or to each other, the connection or communication may be direct, or there may be an intervening element between the two or more elements. To the contrary, it will be understood that when two or more elements are described as being “directly” coupled with or to another element or in “direct communication” with or to another element, there is no intervening element between the first two or more elements.

[0034]Furthermore, “connections” or “communication” between elements may be, without limitation, wired, wireless, electrical, mechanical, optical, chemical, electrochemical, comparative, by sensing, or in any other way two or more elements interact, communicate, or acknowledge each other.

[0035]The expression “configured to” as used herein may be used interchangeably with “suitable for,” “having the capacity to,” “designed to,” “adapted to,” “made to,” or “capable of” according to a context. The term “configured” does not necessarily mean “specifically designed to” in a hardware level. Instead, the expression “apparatus configured to . . . ” may mean that the apparatus is “capable of . . . ” along with other devices or parts in a certain context.

[0036]As used herein, the term “substantially” in reference to a given parameter, property, or condition means and includes to a degree that one of ordinary skill in the art would understand that the given parameter, property, or condition is met with a degree of variance, such as within acceptable tolerances. By way of example, depending on the particular parameter, property, or condition that is substantially met, the parameter, property, or condition may be at least 90.0 percent met, at least 95.0 percent met, at least 99.0 percent met, at least 99.9 percent met, or even 100.0 percent met.

[0037]As used herein, “about” or “approximately” in reference to a numerical value for a particular parameter is inclusive of the numerical value and a degree of variance from the numerical value that one of ordinary skill in the art would understand is within acceptable tolerances for the particular parameter. For example, “about” or “approximately” in reference to a numerical value may include additional numerical values within a range of from 90.0 percent to 110.0 percent of the numerical value, such as within a range of from 95.0 percent to 105.0 percent of the numerical value, within a range of from 97.5 percent to 102.5 percent of the numerical value, within a range of from 99.0 percent to 101.0 percent of the numerical value, within a range of from 99.5 percent to 100.5 percent of the numerical value, or within a range of from 99.9 percent to 100.1 percent of the numerical value.

[0038]As used herein, the term “biomass” means and includes an organic biological material derived from living or recently living plants (e.g., non-fossil biological material). The biomass may include, but is not limited to, lignocellulosic biomass, which is composed of carbohydrate polymers (e.g., cellulose, hemicellulose) and an aromatic polymer (lignin). Lignocellulosic biomass may be broadly classified as herbaceous or woody. Herbaceous biomass includes, for example, corn stover (Zea mays L.), wheat straw, energy sorghum, miscanthus, and switch grass. Woody biomass includes, for example, pine, eucalyptus, hybrid poplar, Douglas fir, and oak. The biomass material used as a feedstock may include a combination of woody and herbaceous biomass (e.g., 50% woody biomass and 50% herbaceous biomass). The biomass material may also include municipal solid waste. The biomass material may be produced for the specific purpose of producing energy (e.g., through the methods disclosed herein) or may be a byproduct of other activities (e.g., food production). The biomass material may exhibit an initial moisture content of from about 5% by weight (wt %) to about 35 wt % water on a wet basis, from about 10 wt % to about 30 wt % water on a wet basis, or from about 15 wt % to about 25 wt % water on a wet basis. In addition to being fibrous, the biomass material is hydrophilic due to its moisture content. In some embodiments, the biomass material is corn stover. In other embodiments, the biomass material is Douglas fir.

[0039]The biomass material may be subjected to one or more mechanical acts (e.g., comminution, densification, pulverization) and thermal treatment acts (e.g., torrefaction, steam explosion) to produce the biomass feedstock including the biomass particles. The systems and methods for preparing the biomass feedstock decrease moisture content, decrease size, and produce the biomass particles having a more uniform chemical composition, a more uniform size, and a more uniform morphology. The chemical composition of the biomass particles may also be changed from the chemical composition of the biomass material.

[0040]A method 100 of forming the biomass feedstock that includes biomass particles according to embodiments of the disclosure is illustrated as a simplified process flow diagram in FIG. 1A. The illustrated method 100 is nonlimiting and some process acts may be omitted, depending on feedstocks available and outputs required. The method 100 may include comminuting biomass 102 into biomass fragments, densifying the biomass fragments 104 to form biomass pellets, thermally treating the biomass pellets 106 to form thermally treated biomass pellets, and reducing a particle size of the thermally treated biomass pellets 108 to form biomass particles. The resulting biomass particles are used as a biomass feedstock for a gasifier or other reactor. The method 100 according to embodiments of the disclosure may be characterized as a “high moisture” process because the biomass material subjected to the method 100 exhibits a relatively higher moisture content than that of conventional processes.

[0041]The method 100 includes comminuting (e.g., fragmenting) the biomass material in act 102. The biomass material may be comminuted 102 into biomass fragments by processing the biomass material into smaller pieces by one or more mechanical processes. The comminution may, for example, include milling, cutting, shearing, grinding, clipping, and/or screening, such that the biomass fragments passed to subsequently conducted process acts are sufficiently small and uniform to be densified and thermally treated. The biomass material may be comminuted into biomass fragments having a minimum linear dimension (e.g., a width, a diameter, etc.) of less than about ¼ inch (less than about 6.35 mm). The comminuting of the biomass material may occur in a mill or other apparatus configured to reduce the biomass material into smaller pieces. In some embodiments, the biomass material is comminuted using a hammer mill or a knife mill. The biomass material may optionally be heated before comminution to reduce its moisture content from the initial moisture content.

[0042]The method 100 may proceed by densifying the comminuted biomass (e.g., the biomass fragments) in act 104 to form biomass pellets. The densification forms uniform, compacted pellets upon which consistent and controlled thermal treatment is conducted. During the densification, the biomass fragments are subjected to high pressure, such as in a pellet mill, a briquette press, an agglomerator, a cuber, an extruder, or other apparatus. The high pressure may be used to compress and/or compact the biomass fragments obtained from act 102 into cohesive, densified biomass pellets. The biomass pellets may exhibit a density of from about 1000 kg/m³ to about 1500 kg/m³, such as from about 1100 kg/m³ to about 1400 kg/m³ or from about 1200 kg/m³ to about 1300 kg/m³.

[0043]If the biomass fragments are densified using a pellet mill, the biomass fragments may be pressed through a die hole (i.e., an orifice) having a diameter from about 5 mm to about 10 mm, forming cylindrical biomass pellets having a diameter approximately equal to the diameter of the die hole. In some embodiments, the cylindrical biomass pellets have a diameter of from about 6 mm to about 8 mm. The biomass pellets may be formed continuously and, optionally, may be cut upon reaching a selected (e.g., desired) length. For example, the compacted biomass fragments may be cut when the biomass pellets exhibit a length of from about one time to about five times an average diameter of the biomass pellets. If, for example, the biomass pellets have a diameter of about 6 mm, the biomass pellets may have a length of from about 6 mm to about 30 mm. Alternatively, the biomass pellets may not be cut to a specific length but may remain continuous or may break into discrete lengths during or after densification. The biomass pellets may be formed in other cross-sectional shapes, such as having a triangular shape in cross-section, a square shape in cross-section, or a hexagonal shape in cross-section. Such biomass pellets may be formed by passing the biomass fragments through a correspondingly-shaped die hole (e.g., an orifice having a maximum dimension in a range from about 6 mm to about 8 mm). If the biomass fragments are densified using a briquette press, the biomass pellets may be formed by passing the biomass fragments between adjacent rollers of the briquette press. The rollers may have indentations corresponding to a shape of an exterior surface of the biomass pellets to be formed. As the biomass fragments are pressed by the rollers, the biomass fragments form cohesive biomass pellets (e.g., briquettes). In some embodiments, the biomass fragments are pressed, then cut into the biomass pellets, such as discrete cubes.

[0044]During the densification, the biomass fragments may be subjected to a pressure of from about 10 MPa to about 600 MPa, such as from about 30 MPa to about 400 MPa, from about 30 MPa to about 300 MPa, from about 40 MPa to about 400 MPa, from about 50 MPa to about 500 MPa, from about 50 MPa to about 350 MPa, from about 100 MPa to about 400 MPa, from about 150 MPa to about 400 MPa, or from about 200 MPa to about 400 MPa. In conjunction with the pressure, the temperature of the biomass fragments may also increase during densification. For example, a temperature of the pellet die may be from about 65° C. to about 95° C., such as from about 70° C. to about 90° C., from about 75° C. to about 85° C., from about 70° C. to about 85° C., or from about 80° C. to about 85° C. during the densification. Without being bound to any particular theory, the increased temperature within the pellet die may evaporate some of the water in the biomass fragments. When the pressure is released, the moisture content of the densified biomass may decrease depending on the amount of water evaporated from the biomass fragments. For example, the moisture content of the biomass pellets following densification may be from about 8 wt % to about 10 wt % lower than the moisture content of the biomass before densification (e.g., the initial moisture content). The decrease in the moisture content may be attributed to frictional heat developed during the densification and cooling, which may cause the densified biomass to lose surface moisture due to flash-evaporation after the pressure is released. The moisture loss during the densification may be beneficial in that the water acts as a lubricant as the biomass fragments pass through the die path. Furthermore, the water may help lower the temperature of (i.e., cool) the apparatus (e.g., the pellet mill) during densification, preventing the apparatus from overheating. Interstitial spaces between grains of the biomass fragments become filled due to changes in the morphology within the biomass fragments. Smoothing of the biomass fragments and changes in morphology during the densification increase flowability of the biomass particles that are ultimately formed.

[0045]The method 100 may proceed by thermally treating the biomass pellets in act 106 to form thermally treated biomass pellets. During thermal treatment, the biomass pellets may be heated to a target (e.g., a desired) temperature and the target temperature may be maintained for a specific period of time. The thermal treatment may cause depolymerization of polymers (e.g., carbohydrate polymers, aromatic polymers) in the biomass pellets, as well as dehydration. Thermally treating the biomass pellets also embrittles surface features, which results in the thermally treated biomass pellets exhibiting a smoother surface and more regular shape. Conducting the thermal treatment on the densified pellets may enable the biomass pellets to be substantially uniformly treated. In other words, substantially all of the volume of an individual biomass pellet may be thermally treated to a same or similar extent, such as in both a horizontal cross-section and in a vertical cross-section of the biomass pellets. The thermal treatment may result in the degradation (e.g., thermal degradation) of the organic biological material of the biomass pellets, in addition to the loss of water, which leads to a loss of dry solids in the thermally treated biomass pellets. For example, the thermally treated biomass pellets may exhibit from about 1% to about 30% dry loss of solids when compared to the biomass pellets, such as from about 3% to about 25% dry loss of solids or from about 5% to about 20% dry loss of solids. The densification and thermal treatment of the densified biomass pellets forms thermally treated biomass pellets that exhibit increased hydrophobicity, increased friability, and a changed (e.g., an altered) chemical composition, which facilitates downstream size reduction. The thermally treated biomass pellets are carbon-enriched and also exhibit enhanced flow characteristics.

[0046]The biomass pellets may be thermally treated using, for example, torrefaction, which is a thermochemical process conducted in an inert or reduced oxygen environment in which water and volatile compounds are released. The torrefaction is conducted in an environment with limited or no oxygen, such as in an environment with less than about 1% by volume of oxygen. As the torrefaction proceeds, the thermal degradation of the organic biological material and resulting release of volatile gases from the thermally treated biomass pellets may further decrease the oxygen present in the environment to less than about 0.1% by volume of oxygen. The torrefaction may be conducted in a reactor, such as in a rotary kiln, a rotating cone, a fluidized bed, a moving bed, a fixed bed, or an auger.

[0047]During torrefaction, at least some of the polymers (e.g., carbohydrate polymers, aromatic polymers) in the biomass pellets may be depolymerized and dehydrated. An initial stage of torrefaction may, for example, dehydrate sugars present in the biomass pellets, such as hemicellulose and pentose. Amorphous and crystalline cellulose content is also decreased. Following or in conjunction with the dehydration, the sugars may be at least partially reacted (e.g., cracked), generating lower molecular weight, oxygenated volatile organics, such as one or more of an alcohol, an aldehyde, a ketone, and combinations thereof. The sugars may be subjected to chain scission reactions or ring scission reactions. From the mass lost by the biomass pellets during torrefaction, from about 70 wt % to about 80 wt % is believed to be water obtained from dehydration reactions and the remaining from about 20 wt % to about 30 wt % is believed to be oxygenated volatile organic compounds obtained from chain scissions and/or ring scissions (i.e., lost dry-solids). The water, along with the oxygenated volatile organics, may be removed in a gas phase, such as by evaporation. Once the water and oxygenated volatile organics are removed, the biomass particles become enriched in the remaining biological material, such as cellulose and/or lignin, and exhibit a higher elemental carbon concentration and a lower oxygen and hydrogen concentration. The thermally treated biomass pellets form a char-like material.

[0048]Using higher temperatures and longer residence times during torrefaction may lead to more extensive thermal degradation of the biological materials in the biomass pellets (e.g., torrefied biomass pellets), particularly hemicellulose, and the formation of more brittle and more friable thermally treated biomass pellets. The torrefaction may be conducted, for example, at a temperature of from about 150° C. to about 350° C., such as from about 150° C. to about 250° C., from about 175° C. to about 325° C., from about 200° C. to about 300° C., from about 250° C. to about 300° C., or from about 300° C. to about 350° C. The torrefaction may be conducted over a time period of from about 10 minutes to about 2 hours, from about 20 minutes to about 1.5 hours, or from about 30 minutes to about 1 hour. The torrefaction temperature and residence time used may depend on the compositional profile (e.g., makeup) of the biomass material. In addition, the torrefaction temperature and residence time may be selected to achieve a desired dry solid loss within the range described above, ensuring substantially uniform thermal treatment of the biomass pellets.

[0049]Alternatively, the biomass pellets may be subjected to a steam explosion process, which utilizes high-pressure, saturated steam followed by a rapid decompression to thermally treat the biomass pellets. The steam explosion process disrupts the lignocellulosic structure of the biomass material. The biomass pellets may be subjected to a pressure of from about 1 MPa to about 3 MPa at a temperature of from about 160° C. to about 240° C. to form the biomass particles. After a predetermined residence period, the pressure is released to atmospheric level, forming steam explosion biomass pellets.

[0050]The biomass particles may be size reduced in act 108 to form biomass particles. The thermally treated biomass pellets may be pulverized, cut, sheared, ground, clipped, etc., to form the biomass particles at a sufficiently small size and/or sufficiently dense state to efficiently flow into a gasification reactor. In some embodiment, the thermally treated biomass pellets are pulverized using a hammer mill. The biomass particles may have a linear dimension (e.g., a width, a length, a diameter, etc.) ranging from about 50 microns to about 300 microns, from about 100 microns to about 300 microns, from about 100 microns to about 250 microns, from about 150 microns to about 250 microns, or from about 150 microns to about 200 microns. A bulk density of the biomass particles may range from about 450 kg/m³ to about 800 kg/m³, such as about 500 kg/m³ to about 600 kg/m³, from about 500 kg/m³ to about 700 kg/m³, or from about 500 kg/m³ to about 800 kg/m³. In some embodiments, the bulk density of the biomass particles is greater than or equal to about 500 kg/m³. In comparison, the bulk density before size reduction is from about 200 kg/m³ to about 400 kg/m³.

[0051]After the size reduction, the biomass particles may be size separated (e.g., screened) to ensure that the biomass particles of the biomass feedstock have a linear dimension (e.g., a width, a diameter, etc.) of less than about 200 microns. The biomass particles according to embodiments of the disclosure also exhibit a smoother surface and more regular shape than processed biomass prepared by conventional processes. The resulting biomass particles exhibit are sufficiently sized to be introduced to and within the gasifier. Biomass particles of a larger dimension may be removed (e.g., screened out) and collected. The screened out biomass particles may optionally be recycled, with the larger dimension biomass particles further size reduced until the desired linear dimension is achieved. The biomass particles may be broken down to a size that passes through a screen (e.g., sieve) of the desired size. Alternatively, the screened out biomass particles may be removed from the process and discarded, or used in another process. The resulting biomass particles may be sufficiently small in size and exhibit an enhanced flow behavior that facilitates a stable and continuous flow of the biomass feedstock into the gasifier. The biomass particles exhibit an increased energy density compared to biomass prepared by conventional processes and, therefore, have improved fuel properties compared to the biomass material.

[0052]The process acts of method 100 may also be conducted in a different sequence than that illustrated in FIG. 1A to form the biomass particles. The sequence of comminuting the biomass 102, densifying the biomass 104, and thermally treating the biomass 106 may be conducted in different sequences. For instance, the method 100 may include comminuting the biomass 102, thermally treating the biomass 106, densifying the thermally treated biomass 104, and reducing a particle size of the thermally treated and densified biomass 108 to form the biomass particles. Alternatively, the method 100 may include thermally treating the biomass 106, comminuting the thermally treated biomass 102, densifying the thermally treated biomass 104, and reducing a particle size of the thermally treated and densified biomass 108 to form the biomass particles.

[0053]The resulting biomass particles obtained after conducting the torrefaction process (e.g., torrefied biomass particles) may exhibit enhanced flow characteristics when compared to the biomass particles obtained from other types of thermal treatment, such as the steam explosion process. For example, the torrefied biomass particles may exhibit a smaller particle size distribution, including a decreased overall fiber size due to a loss in structure from the dehydration and depolymerization of sugars during torrefaction. The decreased overall fiber size may lead to a higher bulk density. The torrefied biomass particles may also exhibit smoother and more uniform edges when compared to, for example, jagged and irregular edges and hair-like fibers of biomass particles obtained from steam explosion (e.g., steam explosion biomass particles). The torrefied biomass particles may also exhibit lower measured values for angle of repose, internal friction, and apparent cohesion than the steam explosion biomass particles. These characteristics may contribute to an enhanced flow behavior of the torrefied biomass particles that facilitates a stable and continuous flow of biomass feedstock into the gasifier.

[0054]While the steam explosion biomass particles exhibit improved flow characteristics compared to processed biomass produced by conventional processes, the torrefied biomass particles exhibit further improved properties. For example, the higher elemental carbon concentration and lower oxygen and hydrogen concentration of the torrefied biomass particles result in an increase in the higher heating value (HHV) of the torrefied biomass particles, meaning more usable energy is available per unit weight. Furthermore, the oxygenated volatile organics that are generated during torrefaction may be combusted (e.g., thermally oxidized) during the method 100 to produce supplemental thermal energy. Thus, while the biomass particles produced by other thermal treatment processes, such as the steam explosion biomass particles, may benefit from the consumption of supplemental external energy, the production of the torrefied biomass particles may produce, rather than consume, supplemental energy. The supplemental energy produced by the torrefaction may offset energy otherwise used, for example, for drying the biomass prior to the comminuting 102 and densifying 104 or for other process heating, which reduces the external energy demand of the method 100 and lowering overall associated operating costs.

[0055]The method 100 may be conducted in a biomass processing system 120, as shown in FIG. 1B, which includes a comminution apparatus 122, a densification apparatus 124, a thermal treatment apparatus 126, and a size reduction apparatus 128. The components of the biomass processing system 120 may be coupled by one or more pipes, lines, etc., which are not shown for simplicity and convenience. The biomass processing system 120 may also include additional components (e.g., pipelines, line filters, valves, temperature detectors, flow detectors, pressure detectors, and the like), which are not shown for simplicity and convenience. A biomass material may be introduced into and through the biomass processing system 120 to form the biomass particles from the biomass material. The biomass material may be introduced to the comminution apparatus 122, which is configured to comminute the biomass material into biomass fragments. The comminution apparatus 122 may be a mill, such as a hammer mill or a knife mill. The biomass fragments are introduced to the densification apparatus 124, which may be a pellet mill, a briquette press, an agglomerator, a cuber, or an extruder. The biomass fragments are densified into the biomass pellets, which are introduced to the thermal treatment apparatus 126. The thermal treatment apparatus 126 may be a torrefaction reactor or a steam reactor. The torrefaction reactor may include, but is not limited to, a rotary kiln, a rotating cone, a fluidized bed, a moving bed, a fixed bed, or an auger. The thermally treated biomass pellets are introduced to the size reduction apparatus 128, which may include, but is not limited to, a hammer mill. Following size reduction, the biomass particles may be recovered from the biomass processing system 120.

[0056]The systems and methods according to embodiments of the disclosure overcome challenges associated with fibrous, heterogeneous, and moisture-rich biomass, enabling cost-effective and scalable gasification for producing syngas, fuels, and other high-value products.

[0057]FIG. 2A illustrates biomass particles 202 obtained after conducting the method 100 and FIG. 2B illustrates a single biomass particle 202 obtained after conducting the method 100. Since the biomass pellets are substantially uniformly thermally treated, properties of the biomass particles 202 are substantially the same throughout their volume. For instance, the color, porosity, surface area (e.g., surface roughness), etc., of the biomass particles 202 may be substantially the same throughout their volume. In other words, properties of the biomass particles 202 do not vary along a horizontal cross-section or along a vertical cross-section. If, for example, the biomass particles 202 have a substantially cylindrical shape, as shown in FIG. 2B, an interior portion 204 and an exterior portion 206 of the biomass particles 202 may exhibit substantially the same properties. A boundary between the interior portion 204 and exterior portion 206 is illustrated for convenience in FIG. 2B by a dashed line. However, the dashed line is not a precise representation of the boundary between the interior portion 204 and exterior portion 206. For example, the biomass particles 202 according to embodiments of the disclosure may exhibit one or more of substantially the same color, substantially the same porosity, or substantially the same roughness in both the interior portion 204 and the exterior portion 206 as a result of being substantially uniformly thermally treated. In comparison, processed biomass formed by conventional processes may exhibit a different color, different porosity, or different roughness in both the interior portion 204 and the exterior portion 206.

[0058]FIG. 3 illustrates a gasification system 300 into which the biomass particles 202 are introduced to form a product stream 330. The gasification system 300 may be used to form syngas, hydrogen, other biofuels, or other high-value products. The biomass particles 202 may be formed according to embodiments of the method 100 and may function as a biomass feedstock 320 of the gasification system 300. The biomass feedstock 320 may be introduced and held in a first storage vessel 302 (e.g., a primary storage container), which provides the entry point for introducing the biomass feedstock 320 into the gasification system 300 from atmospheric conditions. From the first storage vessel 302, the biomass feedstock 320 is transported to a second storage vessel 304 (e.g., a secondary storage container), which serves as an intermediate storage vessel configured to hold a sufficient volume of the biomass particles 202 for the gasification system 300 to operate continuously. The second storage vessel 304 may also be sufficiently sized to prevent the second storage vessel 304 from experiencing detrimental fluctuation effects from in the delivery of the biomass feedstock 320 to the first storage vessel 302. The second storage vessel 304 may be maintained at or near atmospheric pressure and may be configured to include agitation or aeration to maintain flowability of the biomass particles 202. The biomass feedstock 320 is discharged from the second storage vessel 304 into a pressurization container 306, which transitions the biomass feedstock 320 from atmospheric pressure to an elevated pressure. The pressurization container 306 is cyclically charged and pressurized with an inert gas, such as nitrogen, to a desired operating pressure of a gasification reactor 310. Once pressurized, the biomass feedstock 320 is transported to a pressurized container 308, which operates at the desired pressure of the gasification reactor 310 and serves as the final pressurized staging vessel prior to introduction (e.g., injection) of the biomass particles 202 into the gasification reactor 310. The gasification reactor 310 may be an entrained flow gasifier. The pressurized biomass particles 202 are subsequently introduced through a delivery line to the gasification reactor 310. Transfer of the biomass particles 202 from one process unit to another in the gasification system 300 may be achieved through the use of a pneumatic transport line, for example.

[0059]The first storage vessel 302, second storage vessel 304, pressurization container 306, and pressurized container 308, in combination, provide a staged pressurization and delivery gasification system 300 that enables consistent, flowable, and pressurized introduction of the biomass particles 202 into the gasification reactor under controlled operating conditions. The first storage vessel 302, second storage vessel 304, pressurization container 306, and pressurized container 308 are coupled together such that the biomass feedstock 320 is transported between the components of the gasification system 300. The gasification system 300 includes additional components (e.g., pipelines, line filters, valves, temperature detectors, flow detectors, pressure detectors, and the like) for pressurized transport and introduction of the biomass feedstock 320 into the gasification reactor 310, which are not illustrated herein for simplicity and convenience. The size and density of the biomass particles 202 formed according to embodiments of the disclosure enables enhanced flow properties as the biomass particles 202 are transported into and through the gasification system 300.

[0060]The following examples serve to explain embodiments of the disclosure in more detail. These examples are not to be construed as being exhaustive or exclusive as to the scope of the disclosure.

EXAMPLES

Materials

[0061]Corn stover (Zea mays L.) was obtained from Ekamor Resource Corporation, Cookeville, TN as baled (round, 4 feet diameter) from standard agricultural equipment. The moisture content of the raw corn stover was 11.86±4.61 wt %. The moisture content of the raw corn stover was determined in accordance with American Society for Testing and Materials (ASTM) standard method E1756. Corn stover samples were placed in an oven for 24 hours at 105° C. After the drying period, samples were removed, allowed to cool, and weighed. The moisture content was calculated as the difference between the initial and final mass, divided by the initial mass. The bale was deconstructed using a customized in-feed system (Warren & Baerg Manufacturing) that uses non-destructive rotors to loosen the bale flakes, followed by grinding to less than ¼ inch particles using a hammermill (Bliss Industries, Eliminator E-4424-TF). The ground corn stover was then densified to ¼ inch pellets using B35A-75 Bliss Pioneer Pellet Mill (Ponca City, OK). Densification was conducted for feeding into a torrefaction oven and for ensuring uniform treatment. A fraction of the deconstructed bale corn stover was ground to less than 2 mm particle using the Bliss Hammermill, which was also used for a steam explosion process. Pulverization of the feedstock following preprocessing is described below.

[0062]A woody feedstock, Douglas Fir (Pseudotsuga menziesii) feedstock, was also used and was sourced in a ¼ inch pellet format from OR, USA. As received pellets were also used for a torrefaction process.

[0063]A miscanthus feedstock was also used and subjected to torrefaction and subsequent pulverization. The miscanthus feedstock included both a loose form and pellets.

Methods

Torrefaction

[0064]Corn stover pellets were torrefied in a pilot scale rotary kiln located at Natural Resources Research Institute, Coleraine, MN. The torrefaction was conducted at 245±10° C. kiln temperature for a 30 min holding time. The pellets were uniformly heated across the cross-section. In addition, the carbon content of both the inside and the outside of a few random pellets was characterized, with the inside of the pellet defined as the inner half, while the outer half was considered the outside (see FIG. 2B). The analysis showed that the relative mean absolute difference in carbon content between the inside and outside of the pellets was 2.1% on average and spanned from 0.5% to 4.2%. The overall solid mass yield was 84.2±3.7 wt %.

[0065]The influence of torrefaction temperature on the granular properties of the biomass feedstock was also investigated. To achieve this, the woody feedstock was torrefied in a LECO Thermogravimetric Analyzer (TGA) 701 (St. Joseph, MI). The torrefaction was conducted at temperatures of 250° C., 275° C., and 300° C. for a duration of 15 minutes under an inert atmosphere. The resulting mass yields were 74.5±0.8 wt % at 250° C., 54.1±1.0 wt % at 275° C., and 44.3±0.4 wt % at 300° C. The torrefied wood samples were denoted as “Wood_TX,” where X represents the torrefaction temperature.

[0066]Torrefaction played an important role in the physical and chemical properties of the biomass. The torrefaction temperature and residence time are paramount in determining these characteristics of the resultant material. Increased torrefaction temperatures led to more extensive thermal degradation of the biomass components, particularly hemicellulose, and the formation of a more brittle and friable material. Increased residence time allowed for the progression of the thermal reactions to a point where the biomass achieved a uniform consistency and particle size distribution upon subsequent grinding. These alterations are important for ensuring a stable and continuous flow of feedstock into the gasification reactor. The torrefied biomass with optimal flow characteristics exhibited improved bulk density, reduced fibrousness, and enhanced grinding efficiency, leading to a more controlled and efficient material handling experience downstream in the gasification operation.

[0067]Torrefaction of the miscanthus feedstock was conducted under conditions of 260° C. with a residence time of 30 minutes for both feedstock types (loose form and pellets), followed by a pulverization process. Table 1 presents the characteristics of the pulverized materials

[0068]The particle size distribution of the torrefied and pulverized miscanthus is shown in FIG. 4. While the particle size distributions of both materials exhibited similarities, there was a significant divergence in their densities. Given that density is an important parameter alongside particle size for successful flow through an ultra dense phase (UDP) line and flow into a pressurized gasifier system, the results indicate that the densification act is important to the overall processing pathway. Therefore, both torrefaction and pelletization (i.e., a combination of size, shape features, and bulk/packing density) were found to contribute to the overall process of forming the biomass particles.

Steam Explosion

[0069]Steam explosion modified the structural integrity of lignocellulosic biomass. The process involved subjecting the biomass to high-pressure saturated steam, at a temperature between 160° C. to 260° C., for a short duration before the pressure is abruptly reduced. The rapid decompression caused the steam to flash-evaporate, leading to an expansion of water within the biomass fibers. The mechanical forces generated by the expansion disrupt the plant cell walls and make the structure more brittle. The steam explosion was conducted in a custom-made pressure vessel (Southern Fabrication Works, Burley, ID) into which 2 mm ground corn stover was introduced. The experiment was conducted at a steam pressure of 150 psi steam pressure and a residence time of 20 min. The steam exploded sample was air dried prior to further processing and characterization.

Size Reduction of Thermally Treated Materials

[0070]The torrefied corn stover pellets were pulverized using a H28 pilot scale Schutte Buffalo Hammer Mill (Buffalo, NY) with a 20-mesh (841 μm) screen. The pulverized material was sieved through a 40-mesh (400 μm) oscillating sieve deck (Forest Concepts, Auburn, WA) to impart some control toward a smaller nominal particle size of 200 μm. Pulverized material with a particle size greater than 400 μm obtained from the system was recycled back to the hammer mill. The recycling of pulverized material with a particle size greater than 400 μm was continued until greater than 95% of the initial material (the pulverized, torrefied corn stover pellets) passed through the 400 μm screen. A similar method was used to pulverize the steam exploded corn stover. Both the torrefied sample and the steam exploded sample, used two recycles for the greater than 400 μm particles to pass more than 95% of the whole sample through the 400 μm screen. The respective recycle amounts for the two recycles for the torrefied samples were 15% and 7%, respectively, to achieve the greater than 95% metric, and the respective recycle amounts for the two recycles for the steam exploded sample was 25% and 12%, respectively. Extrapolating these numbers to consider a continuous process that includes recycling, the material hold-up inside the mill may be estimated at 1.28 kg/kg-feed for the torrefied feedstock while the steam exploded sample resulted in a 1.59 kg/kg-feed hold-up.

Physical Characterization

[0071]Particle size distribution (PSD) assessment was conducted on a Ro-Tap separator (WS Tyler Model RX-29) in accordance with the protocol outlined in the American Society of Agricultural and Biological Engineers (ASABE) standard method S319.3. A set of wire-mesh sieves were used to separate particles based on the physical opening size in the mesh while the devices agitate the bulk material. The sample was introduced into the uppermost (largest opening) sieve, subsequently positioned within the Ro-Tap apparatus and operated for a duration of 10 minutes. After this, the sample was analytically collected, and the mass retained on each individual sieve was recorded to the nearest 0.01 g. This yielded the proportional quantity of the sample retained/passing each successive sieve and, therefore, a discretized distribution of particle sizes. By leveraging these measured masses, cumulative distributions of particle passage were derived.

[0072]The determination of bulk densities (both in the loose and tapped states) of the samples were accomplished using a modified adaptation of the ASABE standard methodology S269.4. The sample was introduced into a cylindrical receptacle with a diameter of 195 mm. This was achieved by pouring the specimen from an elevation of 0.6 m above the upper rim of the receptacle until the material's height reached approximately 90% of the receptacle's diameter. The “loose bulk density” was computed by dividing the mass of the sample by the volume it occupied. The volume was deduced from an average of no less than four height measurements taken around the outer perimeter of the receptacle.

[0073]For the determination of “tapped bulk density,” the receptacle containing the sample was subjected to five drops from a height of 0.15 m onto a rigid surface, as stipulated by the ASABE standard procedure. Subsequently, the tapped bulk density was assessed using the same protocol as in determination of loose bulk density.

Chemical Characterization

[0074]The analysis was conducted using an Elementar Vario EL cube instrument (Ronkonhoma, NY) in accordance with ASTM standard method D 3176-09. Calibration was achieved using a certified Alfalfa standard. The sample underwent combustion at 1150° C. in the presence of ultra-high purity (UHP) oxygen at a flowrate of 38 mL/min, accompanied by a carrier gas (UHP helium) at 230 mL/min. The resultant combusted gas was subjected to analysis utilizing a thermal conductivity detector (TCD) for elemental carbon, hydrogen, and nitrogen determination. Sulfur content was measured using an infrared (IR) detector. Oxygen content was determined via the difference method, a widely employed approach.

[0075]Proximate analysis was conducted using a LECO TGA 701 (St. Joseph, MI) following ASTM D 7582 guidelines. The sample underwent controlled heating from ambient temperature to 107° C. at a rate of 6° C./min, maintained until a stable mass was attained, with mass loss representing moisture content. Subsequent heating to 950° C. at 50° C./min, held isothermally for 9 minutes, assured complete volatile matter (VM) elimination. Inert UHP grade nitrogen at 10 L/min maintained the atmosphere. After cooling to 600° C., oxygen (3.5 L/min) replaced nitrogen for sample combustion. Temperature was then ramped to 750° C. at 13° C./min, sustained until consistent mass was achieved, and the remaining mass was used to define the ash content. Fixed carbon (FC) was deduced by subtracting volatile matter and ash percentages from 100%.

[0076]The higher heating value (HHV) was assessed in accordance with ASTM method D 5865, employing a LECO AC600 (St. Joseph, MI) isoperibolic system. The sample underwent combustion using ultra-high purity (UHP) grade oxygen at 450 psi, and all ensuing computations followed the guidelines stipulated in method D 5865. Furthermore, the elemental ash compositions of the aforementioned specimens were assessed utilizing inductively coupled plasma atomic emission spectroscopy (ICPAES) in oxide forms, encompassing SiO₂, Na₂O, MgO, K₂O, SO₃, CaO, P₂O₅, Al₂O₃, and Fe₂O₃, following ASTM method D3682 guidelines.

Mechanical Characterization

[0077]The experimental determination of the angle of repose involved the use of a bottomless (lifting) cylinder. A hollow polycarbonate cylinder with dimensions 7.5 cm in internal diameter and 38 cm in length was employed, along with a smooth stainless-steel surface serving as a base. Graduations were made along the four principal directions from the cylinder's center to monitor the onset and dimensions of the resulting pile base. In a standard test, the cylinder was positioned vertically at the center of the stainless-steel surface. The cylinder was filled with a sample to a height of 30 cm, leaving approximately 8 cm of vacant space between the top of the sample and the cylinder's upper edge to mitigate end effects. The cylinder was then manually lifted at a deliberate pullout speed of approximately 1.5 m/min. Upon release from the cylinder, the material formed a pile. The static angle of repose was determined by measuring the pile's height (h) and the radius (r, calculated as the average of readings along the four principal directions). This information was utilized to compute the angle using the arctangent function (tan⁻¹(h/r)). To account for potential variations in both the samples and measurements, the angle of repose was measured at least 5 times for each sample.

[0078]An automated Schulze ring shear tester (Dietmar Schulze Schüttgutmesstechnik, Wolfenbüttel, Germany) was used to quantify the shear strength of materials, utilizing a size M shear cell (outer diameter: 20 cm, inner diameter: 10 cm) following ASTM D6773-08 guidelines. The experiment was conducted at a pre-shear consolidation stress of 10 kPa. The material depth was 40 mm, providing a test volume of approximately 900 mL, while the rotational speed was 0.02 rad/min, enabling quasi-static yielding measurements.

[0079]An MRC 102 Anton Parr powder rheometer (Torrance, CA) was used to obtain shear properties of the different samples. This instrument worked very similar to the larger Schulze ring shear tester described above. Material was loaded in an annular ring (outer diameter: 4.5 cm, inner diameter: 1.9 cm) and normal force applied to the sample at 10 kpa (pre-shear stress). During the test, the annular ring rotated, which allowed shear stresses to be measured at different normal stress conditions. The measurement method was set up to record shear stress at 1, 2.5, 5, and 7.5 kPa normal stress, after every pre-shear step. The measurement results helped construct yield loci and Mohr's circles for subsequent shear and flow properties analysis.

[0080]The shear properties were also measured using FT4 powder rheometer (Norcross, GA) to validate the measurement techniques. Tests were conducted in a 25 mm diameter 10 mL volume spilt vessel. Applied normal stresses were 3 kPa and 9 kPa, where 9 kPa was very close to the applied stress in the Schulze tester and 3 kPa was lower to understand the effect of initial stress on shear properties.

[0081]Particle shape distributions were obtained with a L02 QicPic size analyzer (Sympatec GmbH, Germany). For this analysis, the particles were slowly fed past a highspeed camera, where images of the falling particles were collected at 80 Hz to ensure each particle was captured, at most, once. The image set then went through filtering and binarization to obtain particle bounding silhouettes, on which various image-based measurements were extracted. For these results, the characteristic particle dimension of the minimum Feret diameter (minimum distance measured orthogonal to two parallel bounding lines) was assumed. The aspect ratio and sphericity distributions were calculated as:

$\begin{array}{cc}\mathrm{Aspect}\mathrm{ratio}=\frac{\mathrm{Minimum}\mathrm{Feret}\mathrm{diameter}}{\mathrm{Maximum}\mathrm{Feret}\mathrm{diameter}}& \left(1\right)\end{array}$$\begin{array}{cc}\mathrm{Sphericity}=\frac{2\times \sqrt{\pi \times \mathrm{Surface}\mathrm{area}}}{\mathrm{Perimeter}}& \left(2\right)\end{array}$

Flow Tests in Entrained Flow Gasifier

[0082]The feedstock flowability tests were performed using an R-GAS® gasification unit. R-GAS® is a highly compact entrained flow gasification technology that includes UDP flow combined with flow splitting mechanisms, injectors demonstrating high mixing efficiency, reactor cooling through high heat flux employing a water-cooled refractory-free liner, and rapid quench techniques. The injector and liner cooling technologies were derived from proven design principles in rocket engines. Their development substantiated the application of these principles to solid feedstocks. The UDP flow approach significantly reduced the need for parasitic transport gas volume in proportion to the feedstock, leading to an intimate contact between feed particles and driving flow dynamics via particle-to-particle interactions rather than gas flow. This achievement permitted uniform flow distribution to R-GAS®'s multiple injector elements by eliminating flow striation caused by variations in feed/transport gas densities in regions characterized by pronounced curvature.

[0083]FIG. 5 represents a flowsheet of a gasification system 400 that includes an access hopper 402, an atmospheric pressure bin 404, a feed hopper 408, and a lock hopper 406. A known quantity of biomass feedstock 320 was loaded into the access hopper 402 (e.g., first storage vessel 302) and then into the atmospheric pressure bin 404 (e.g., second storage vessel 304 in FIG. 3) via cyclone air. The biomass feedstock 320 was then transferred to feed hopper 408 (e.g., pressurized container 308) via the lock hopper 406 (e.g., pressurization container 306 in FIG. 3) at atmospheric pressure by gravity flow. The lock hopper 406 was pressurized to 365 psig and then the feed hopper was pressurized to the target pressure without compacting the biomass feedstock and the pressure was recorded. The biomass feedstock in the feed hopper 408 was aerated using pulsating gas to avoid consolidation. The biomass feedstock was then recirculated to feed hopper 408 which worked as a simulated pressurized gasifier through the UDP line 410. The pressure of the feed hopper 408 did not exceed 585 psig, which was the available maximum pressure of nitrogen. After completion of each test, a back pulse filter was checked to make sure no material accumulated. Testing was repeated for each feedstock to ensure the biomass feedstocks consistently flowed at operating conditions and to verify the mass flow rate of material at set differential pressure.

Material Characteristics Results

Physical Properties

[0084]The physical characteristics of the torrefied corn stover (TCS) and steam exploded corn stover (SECS) were investigated with regard to parameters such as moisture content, bulk densities, and PSD, as detailed in Table 2 below and depicted in FIG. 6. FIG. 6 is a graph comparing the sieve size against the percent of each sample passing through the sieve. While both TCS and SECS exhibited diminished moisture content in comparison to raw corn stover, TCS demonstrated the lowest moisture content, measuring 1.02±0.02 wt %, while SECS displayed 4.4±0.03 wt %. This divergence could arise from the drying phase during torrefaction which does not exist in the steam explosion. In both the torrefaction and steam explosion, low moisture content is used for fuel production and for effective thermochemical conversion downstream. The thermal treatments modified the original biomass fibers, making them more resistant to moisture uptake both in magnitude and in uptake rate.

[0085]The bulk densities (both in loose and tapped conditions) of TCS exceeded those of SECS. For example, the loose and tapped densities of TCS were 495.24±18.69 kg/m³ and 591.59±7.09 kg/m³, respectively, while the loose and tapped densities were 234.67=1.86 kg/m³ and 280.06±6.46 kg/m³, respectively, for the SECS. As FIG. 6 illustrates, the particle size distribution of TCS exhibited finer characteristics relative to SECS. For instance, the D₅₀ for TCS was recorded as 156±11 μm, whereas SECS registered 268±15 μm. This was further observed for the larger particle sizes, where the top size for TCS was approaching around 400 μm while comparatively the SECS exhibited a plateau behavior around 500-600 μm. This discrepancy might be attributed to torrefaction rendering the biomass structurally more susceptible by eliminating sugar derivatives, a contrast to steam explosion treatment. This loss in structure and decrease in overall large fiber sizes further explain why the TCS had a comparatively higher bulk density. In addition, because the TCS was also densified prior to treatment, much of the original fibrous nature was destroyed in comparison to the SECS and the original sample.

Chemical Properties

[0086]The chemical attributes of torrefied and steam exploded samples, along with raw (e.g., untreated) corn stover (CS), were examined through ultimate and proximate analyses, as well as HHV, as indicated in Table 3 below. Hydrogen, carbon, and oxygen content was determined, as well as volatile compounds (VM), fixed carbon (FC), and ash. The ultimate analysis revealed an approximately 3% elevation in elemental carbon content for the TCS in contrast to raw CS, while the alteration in SECS was statistically insignificant. Similarly, hydrogen and oxygen levels in the TCS experienced respective reductions of about 1% and 4% compared to raw CS, whereas SECS showed negligible changes. In line with the mild thermal torrefaction process, the biomass predominantly underwent dehydration reactions leading to substantial oxygen reduction and marginal hydrogen decrease, corroborating findings in this study.

[0087]Proximate analysis indicated a decline of approximately 9% in volatile matter and corresponding increases of around 6% in fixed carbon and 3% in ash content for the TCS relative to raw CS. Notably, TCS demonstrated an increased HHV of approximately 1.2 MJ/kg compared to raw CS which is aligned with previous findings. Conversely, there were no statistically significant variations observed in the proximate analysis and HHV for the SECS sample, consistent with outcomes from the ultimate analysis. Although the improvement of calorific value and fixed carbon was not significant, incorporating these preprocessing methods, specifically torrefaction, into biomass preparation prior to gasification enhanced feedstock uniformity and reduced particle size, leading to lower grinding energy requirements. These processes also impart hydrophobic properties to the biomass, mitigating challenges associated with moisture content during gasification.

[0088]Table 4 presents the comprehensive elemental ash analysis, indicating the proportion of inorganic constituents post complete oxidation. Notably, Si content was dominant across all examined samples, constituting 71.1% in raw CS. The Si concentration diminished in TCS, while remaining relatively constant in SECS. Similarly, Na exhibited a reduction subsequent to torrefaction, retaining consistent levels post steam explosion. In contrast, the elements Al, Ca, Mg, and K experienced notable increases after torrefaction treatment, with their levels remaining mostly consistent following steam explosion. These trends are expected due to the nature of intrinsic and exogenous inorganics that are prevalent in corn stover and biomass more generally. SiO₂ is primarily present as exogenous material from soil that is either captured/adhered to corn stover/biomass during harvest and collection. Through additional processing stages (milling, pelleting, through the tumbling action of the rotary drum style torrefier, etc.) more and more of this loose soil is dislodged from the sample and is removed as particulates. Similar to the analyses above and because the inorganic speciation is a summative measure, some of the relative increases in inorganics are expected, especially the physiologically necessary minerals needed during plant growth, such as Ca, Mg, and K. Typically Al, Fe, and Ti are also associated with exogenous contaminants, depending on the local soil chemistry. A subset of elements including P, S, and Cl exhibited an ascending trajectory subsequent to torrefaction, while displaying a converse decreasing trend after steam explosion, where the liquid processing could have removed some extractives, and amino acid barring proteins, etc., to account for this shift.

Mechanical Properties

[0089]The mechanical properties for the TCS and SECS samples are summarized in Table 5 below. As illustrated by the measured values, the TCS exhibited preferential flow characteristics compared to the SECS. For the angle of repose, the internal friction (and effective friction not tabulated), and the apparent cohesion as measured in the Shulze ring shear tester, the TCS had lower measured values. The angle of repose is an aggregated measurement of flow performance under simple gravitational flow. This measurement was found to be largely dependent on the overall particle size and morphology, in addition to the effective rolling resistances. This has been shown, in turn, to be largely based on the overall surface roughness/character as well as the size and relative aspect ratio of the particles, where size, aspect ratio, moisture and roughness all have positive correlations with the angle of repose. As illustrated in FIG. 6, the TCS has a slightly smaller particle size which potentially contributed to the smaller angle of repose. As previously reported, there is a correlation between the angle of repose and powder flowability, indicating that an angle of repose ranging from 31° to 35° is associated with good flowability, which is consistent with the findings for TCS in this study. Conversely, an angle of repose between 36° and 40° corresponds to fair flowability, as observed in the SECS analyzed herein. However, the flowability may also be influenced by other factors related to surface morphology. Further to evaluate this morphology, when looking at micrographs (not shown) of TCS and SECS, the SECS particles were alongside many hair-like fibers and have jagged and irregular edges where the particles fractured across the direction of the vascular bundles. In comparison, the TCS particles had much smoother, more uniform edges and fracture patterns. Further the hair-like fibers and surface features/asperities did not appear in the images for the torrefied samples. The morphological differences are hypothesized to contribute to both the decrease in apparent bulk cohesion as well as the internal friction. Although these measurements are limited in their application to low-stress or stress-free conditions, the isotropic gas pressure present during successful operation of the UPD flow into a gasifier could provide a similarly suitable flow condition.

Flow Performance of the Processed Materials

[0090]Flow performance studies were conducted for the TCS sample. First, flow performance studies were based on a feeding test of TCS through an existing ⅜ inch UDP. However, while using the ⅜ inch UDP, most of the feeding test attempts were unsuccessful due to plugging. Hence, the UDP line was replaced with a bigger line (½ inch diameter), which corresponds to an increase in the tube cross-sectional area of about 100%. With the bigger line, the TCS flowed successfully and reliably through the R-GAS® pilot feed systems and the ½ inch UDP line while achieving the target pressure, transport gas, and flowrate. FIG. 7 shows temporal trends for the torrefied flow rate and the differential pressure (DP) between feed hopper 408 and lock hopper 406 of three successful back-to-back feed tests, noting that a relatively small pressure difference between the measurements and consistency of the measured value are indicators of preferred, stable operation. The SECS was not tested for flow performance.

Energy Consumption During Feedstock Preprocessing

[0091]The pulverization energy of torrefied and steam exploded CS was determined by analyzing the data logged (greater than 2 Hz) in a variable frequency drive (VFD). A baseline was established by operating the mill with an empty chamber prior to running it with samples, as well as the apparent asymptotic behavior after the mill chamber is charged with material and subsequently emptied to a minimum amount of feedstock hold-up. The energy consumption during the no-load condition was factored into the calculation of pulverization energy for each sample.

[0092]Specific energy consumption during milling was computed relative to the mass of the sample introduced to the mill. This measurement represented the average energy consumption for a theoretical instantaneous input of material to the mill. It is important to note that the continuous milling power draw differs from these outcomes due to varying throughput rates and electrical efficiencies, etc., during consistent feeding to the mill. Nevertheless, the provided measurements reflected a singular pass of the mill, discharging material through a 20 mesh (841 μm) retention screen, and were used to qualitatively compare the energy consumption during milling in the absence of requiring precision feeding equipment and other uncontrolled factors. In the context of the production scenario described above, the measurements were adjusted based on the relative recycle ratio (1.28 kg/kg-feed for the torrefied feedstock, 1.59 kg/kg-feed for steam exploded, and 1.75 kg/kg-feed for raw CS) to ensure all material met the targeted particle size specification for entrained flow gasification.

[0093]FIG. 8 illustrates the energy demand during each phase. As depicted in FIG. 8, the torrefaction process yields surplus energy through the thermal oxidation of volatiles extracted during torrefaction. This energy surpassed that required for other procedures such as densification, pulverization, and comminution, assuming thermal energy is harnessed effectively. Conversely, the steam explosion pathway needed supplementary external energy, as indicated in FIG. 8 for the steam explosion route. It is noteworthy that the steam-exploded sample exhibited higher energy requirements for pulverization of 95% of the material in comparison to the torrefied sample, despite steam explosion using an initially ground sample (less than 2 mm, D₅₀: 630 μm). In contrast, the torrefied sample was in pellet form, but the torrefaction facilitated the degradation of biopolymer structures, particularly hemicellulose sugar derivatives, weakening the material's composition and necessitating reduced energy for pulverization. This finding aligns with previous findings, which emphasized that torrefaction facilitated easier grinding and reduced energy inputs compared to other preprocessing methods. The energy consumption associated with the pulverization of raw CS pellets was the most substantial when compared to the three evaluated methodologies, as indicated by FIG. 8 for the baseline.

Effect of Torrefaction Temperature of Granular Properties

[0094]The favorable impact of torrefaction on the production of uniform granular material suitable for UDP feeding systems was observed at various temperatures (250° C., 275° C., 300° C.). Consequently, the elucidation of the influence of torrefaction severity on granular properties was investigated. Yield loci and Mohr's circle analyses were conducted on raw and torrefied, pelletized pine wood specimens. FIG. 9 is a graph showing the results for yield loci and Mohr's circle analysis for raw and torrefied pelletized pine wood at 10 kPa pre-shear. Clear distinctions were observed between the raw pelletized feedstock alone and the torrefied material, with discernible trends correlating with torrefaction severity. Notably, effective bulk cohesion and internal friction exhibited significant reductions in the torrefied material, suggesting a propensity for preferential behavior in unconfined flow fields, particularly under more severe reaction conditions as shown in Table 6. These alterations were accompanied by modifications in particle size, shape, and packing densities. Moreover, a decrease in unconfined yield stress, internal friction, and cohesion with increasing torrefaction severity was observed.

[0095]For instance, torrefied wood at 300° C. compared to raw wood, the unconfined yield stress decreased from 3.36 kPa to 0.56 kPa, the angle of internal friction decreased from 44.2° to 41.04°, while cohesion decreased from 0.71 kPa to 0.13 kPa. Collectively, these favorable adjustments culminated in enhanced flowability. These measurements compared to the steam exploded samples (as seen in Table 5) are also supported by the observations discussed above in feed testing in the pilot-scale conversion plant.

[0096]FIG. 10A presents the aspect ratio of the raw and torrefied wood pellets after size reduction. The aspect ratio relates a characteristic length to a characteristic diameter, or a relative particle length. In this case, a measure of 1 indicate an equally dimensioned diameter and length while lower values indicate increasing fiber lengths. The volume-based distribution is based on a spherical volume model utilizing the EQPC as a characteristic diameter. The raw pellets have the widest distribution of aspect ratios, while also having the longest relative fiber length. This is believed to lead to flow instability and flow upsets and is likely linked to the high effective cohesion and internal friction presented earlier. The opposite is true for the most severe torrefaction treatment and likely contributed to the improved flow character, with the most severe torrefaction treatment samples having the narrowest distribution of fiber length and relatively shortest fibers. The aspect ratio of particles significantly impacted their flow behavior. Particles with higher aspect ratios, such as elongated or needle-like shapes, tended to interlock more easily and exhibit higher frictional forces, which can impede flow. In contrast, particles with lower aspect ratios, such as the biomass particles according to embodiments of the disclosure, which are more spherical, demonstrated superior flow properties due to reduced interparticle friction and less mechanical interlocking.

[0097]FIG. 10B shows the results of a sphericity analysis which relates particles cross-sectional area to the perimeter and estimates an index to approximate how close a particle is to being approximately spherical, where a perfect sphere would have a value of 1. In general, spheres would represent smoother, more regularly shaped/dimensioned particles that would tend to have more consistent granular flow behavior with less forces. For example, geomechanics and soil physics have long established roughness factors into correlations (negative correlation) for flow performance and static/dynamic stress mechanics. It was directly observed that the raw material sphericity is distinctly offset from that of the clustered torrefied samples. Non-spherical particles introduced additional complexities to flow behavior due to rotational interactions and anisotropic collision dynamics. The morphology of particles played a crucial role in determining flow behavior. Spherical particles demonstrated superior flow properties compared to irregularly shaped particles, which can interlock and impede flow due to mechanical interlocking and frictional forces. The effect of particle shape descriptors, such as surface area to cross-sectional area ratio, on bulk cohesion and unconfined yield strength was consistent with previous findings.

[0098]FIG. 10C shows the results of a convexity analysis. The convexity relates the measured particle area to that of the convex hull area where convex shape intrusions are smoothed/included. A value of 1 indicates no convex intrusions into the particle area, or a more continuous exterior area projection. Similar to the sphericity, it was observed that the raw material had the most convex/angular (lowest convexity value) particles that would lead to higher particle-particle friction and higher yielding forces. Surface characteristics, including roughness, had a profound impact on flow behavior. Rougher surfaces increased friction, reducing flowability, while surface treatments enhanced flow performance by modifying these characteristics, such as by smoother surfaces or surfaces treated to reduce roughness increasing the flowability of particulate materials.

[0099]Furthermore, bulk density measurements illustrated an increase in density for low-temperature (225° C.) torrefied wood due to particle size and shape regularity, leading to denser packing. However, with increasing torrefaction severity, bulk density and particle envelope densities exhibited a decreasing trend. For instance, densities were measured as 468±13 and 440±10 kg/m³ for Wood_T275 and Wood_T300, respectively.

[0100]It was determined that preprocessing techniques that alter the chemical and mechanical attributes of biomass enhance the suitability of biomass for use as a feedstock in a gasification process. The preprocessing, particularly densification followed by torrefaction, not only reduced the grinding energy used for the preprocessing but also induced favorable alterations in granular properties. The deformation in cellular structure as well as collapse of particle macro/micro pores during densification weakened the fiber structure of the particles, which gives the cellular structure flexibility and survival traits required to exist in natural elements and weather. It was observed that well-formed torrefied pellets will not size reduce to long aspect-ratio fibers as not densified material due to the embrittlement of the macro fiber strength properties, whereas the steam exploded sample showed long fibrous structure. Torrefaction facilitated the production of uniform granular material, enhanced flowability, and reduced mechanical energy requirements for biomass processing. Moreover, torrefaction-induced alterations in biomass properties, such as decreased cohesion and internal friction, coupled with modifications in particle size, shape, and packing densities, demonstrated the potential to streamline gasification processes using torrefaction. Torrefaction of biomass is, therefore, a promising avenue for overcoming challenges associated with biomass variability and moisture content, enabling more efficient and sustainable energy conversion. The integration of torrefaction into biomass preprocessing advances the viability and scalability of biomass gasification processes.

[0101]The embodiments of the disclosure described above and illustrated in the accompanying drawings do not limit the scope of the disclosure, which is encompassed by the scope of the appended claims and their legal equivalents. Any equivalent embodiments are within the scope of this disclosure. Indeed, various modifications of the disclosure, in addition to those shown and described herein, such as alternate useful combinations of the elements described, will become apparent to those skilled in the art from the description. Such modifications and embodiments also fall within the scope of the appended claims and equivalents.