Process for biocarbon production with high compressive strength for use in metallurgic applications

Abstract

A method for making transient plastic phase biochar from various biomass feedstocks includes receiving a biomass feedstock at a pyrolysis chamber, providing an inert gas or air environment to the pyrolysis chamber, and pyrolyzing the biomass feedstock in the pyrolysis chamber at a pressure above 1500 psi and a temperature range of 290 - 350 °C to generate the transient plastic phase biochar. The method may further include making a transient plastic phase biocarbon by grinding the transient plastic phase biochar into a powder, compressing the powder into a pellet, and devolatilized the pellet in an inert environment at atmospheric pressure at a temperature range of 300 - 1200 °C for 1 hour at a heating rate of 3-10 °C / min produce transient plastic phase biocarbon.

Description

PROCESS FOR BIOCARBON PRODUCTION WITH HIGH COMPRESSIVE STRENGTH FOR USE IN METALLURGIC APPLICATIONSCROSS-REFERENCE TO RELATED APPLICATION AND CLAIM OF PRIORITYThis application claims the benefit of, and priority to, U.S. Provisional Patent Application No. 63 / 453,556 filed on March 21, 2023, the entire contents of which are hereby incorporated herein by reference.GOVERNMENT SUPPORT

[0001] This invention was made with government support under N00014-17-1-2206, N00014- 19- 1-2159, N00014-18-1-2127, and N00014-20- 1-2270 awarded by the Office of Naval Research. The government has certain rights in the invention.TECHNICAL FIELD

[0002] The present disclosure relates generally to the field of biocarbon, specifically to a method of producing transient plastic phase biochar (TPPB).BACKGROUND

[0003] Woody biomass may be thermochemically converted into engineered carbon materials to displace those currently produced from fossil resources to facilitate reducing greenhouse gas emissions. Industrial carbon materials produced include coal tar pitch, carbon black, graphite, and calcined coke, which may be used in electrode materials (aluminum manufacturing), metallurgic reductants (e.g., Mn), carbon binders, batteryanodes, filler for tires, and ink components. Engineered carbon materials such as electrodes for the metallurgic industry and anodes for lithium-ion batteries generally require a fixed carbon content greater than 90%, high crystallinity, low surface area, high compressive strength of 40-50 MPa, true density greater than 2.05 g / cc, low ash content and low coefficients of thermal expansion.

[0004] Fast pyrolysis may be utilized to convert solid biomass into a bio-oil which may be further fractionated and used as a green-binder and / or as carbonization feedstock and may improve material properties, but the process requires multiple unit operations to thermochemically fractionate biomass components, reformulate to obtain desired mixtures, and carbonize to obtain the final product.SUMMARY

[0005] The present disclosure relates generally to the field of biocarbon. More specifically, an aspect of the present disclosure provides systems and methods for making transient plastic phase biochar, which serves as an improved biobased feedstock for producing biocarbon. An aspect of the present disclosure provides a method for making transient plastic phase biochar from various biomass feedstocks. The method includes receiving a biomass feedstock at a pyrolysis chamber, providing an inert gas or air to the pyrolysis chamber, and pyrolyzing the biomass feedstock in the pyrolysis chamber at a pressure above 1500 psi and a temperature range of 290 - 350 °C to generate the transient plastic phase biochar.

[0006] In an aspect of the present disclosure, the method further includes grinding the transient plastic phase biochar into a powder, compressing the powder into a pellets, and devolatilizing the pellet in an inert environment at atmospheric pressure at a temperatureranging from 300- 1200 °C for 1 hour at a heating rate of 3-10 °C / min to produce transient plastic phase biocarbon.

[0007] In another aspect of the present disclosure, a duration of the pyrolysis is 1 hour.

[0008] In an aspect of the present disclosure, the inert gas is nitrogen.

[0009] In an aspect of the present disclosure, the biomass feedstock is hard-wood or soft wood, including one or more of birch stem wood, oak, spruce, eucalyptus, cellulose, or rice straw.

[0010] In accordance with further aspects of the present disclosure, the biomass feedstock moisture content between 8-100%.

[0011] In an aspect of the present disclosure, the biomass feedstock has particles with a size of 0.2-4 mm.

[0012] In another aspect of the present disclosure, the biomass feedstock is not ground or dried prior to being received at the pyrolysis chamber.

[0013] In aspects, transient plastic phase biocarbon is made by receiving a biomass feedstock at a pyrolysis chamber, providing an inert gas or air atmosphere to the pyrolysis chamber, and pyrolyzing the biomass feedstock in the pyrolysis chamber at a pressure above 1500 psi and a temperature range of 290 - 350 °C to generate transient plastic phase biochar. The method further includes grinding the transient plastic phase biochar into a powder, compressing the powder into a pellet, and devolatilizing the pellet in an inert environment at atmospheric pressure at a temperature ranging from 300 °C to 1200 °C for 1 hour at a heating rate of 3-10 °C / min. Depending on the desired degree of carbonization required.

[0014] In an aspect of the present disclosure, the transient plastic phase biocarbon has a tensile strength ranging from 10 to 45 MPa.

[0015] In another aspect of the present disclosure, the transient plastic phase biochar has a compressive strength greater than 150 MPa.

[0016] In yet another aspect of the present disclosure, the transient plastic phase biochar has a fixed carbon content greater than 90%.

[0017] In accordance with further aspects of the present disclosure, the transient plastic phase biochar has a true density greater than 2. Ig / ml.

[0018] In an aspect of the present disclosure, the transient plastic phase biocarbon is used for metallurgical reductants, binders, electrodes, or high value specialty materials.

[0019] In aspects, a system for making transient plastic phase biochar from various biomass feedstocks is described. The system includes a biomass feedstock, a pyrolysis chamber, and a heat source. The biomass feedstock is pyrolyzed in the pyrolysis chamber at a pressure above 1500 psi and a temperature range of 290 ’ 350 °C to generate the transient plastic phase biochar.

[0020] In an aspect of the present disclosure, the system further includes a grinder, a compressing apparatus, and a devolatilization apparatus. The grinder grinds the transient plastic phase biochar into a powder. The compressing apparatus compresses the powder into a pellet. The devolatilization apparatus devolatilizes the pellet in an inert environment at atmospheric pressure at a temperature range of 300 - 1200 °C for 1 hour at a heating rate of 3-10 °C / min to produce transient plastic phase biocarbon.

[0021] Further details and aspects of the present disclosure are described in more detail below with reference to the appended drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0022] A better understanding of the features and advantages of the present disclosure will be obtained by reference to the following detailed description that sets forth illustrative aspects, in which the principles of the present disclosure are utilized, and the accompanying drawings of which:

[0023] FIG. 1 illustrates an example system that can be utilized to produce biocarbon with high compressive strength, in accordance with aspects of the disclosure;

[0024] FIG. 2 illustrates a wall heated tube bomb reactor system in accordance with aspects of the disclosure;

[0025] FIG. 3A illustrates results from 1-2 mm birch particles following constant pressure carbonization experiments at 320 °C for 30 min.;

[0026] FIG 3B illustrates solid yield and fixed carbon content as a function of pressure;

[0027] FIG. 3C illustrates heating profiles from constant pressure pyrolysis with 1-2 mm birch particles reacted at 320 °C for 30 min. in accordance with aspects of the present disclosure;

[0028] FIG. 4A shows compressibility profiles of two size classes of TPPB and NTPPB powders formed into 6 mm pellets across a range of piston loading pressures;

[0029] FIG. 4B illustrates compaction profiles of two size classes of TPPB and NTPPB powders formed into 6 mm pellets;

[0030] FIG. 4C illustrates tabletability profiles of two size classes of TPPB and NTPPB powders formed into 6 mm pellets across a range of piston loading pressures in accordance with aspects of the present disclosure;

[0031] FIG. 5 illustrates the change in volume after 128 hours at room temperature asa function of compression pressure for TPPB and NTPPB pellets produced in accordance with aspects of the disclosure;

[0032] FIG. 6 illustrates a plot of pellet tensile moduli as a function of pellet-forming pressure for pellets produced in accordance with aspects of the disclosure; and

[0033] FIG. 7 illustrates a plot of pellet tensile strength as a function of calcination temperature for pellets produced in accordance with aspects of the disclosure.DETAILED DESCRIPTION

[0034] The present disclosure relates generally to the field of biocarbon and biochar. More specifically, an aspect of the present disclosure provides systems and methods for producing transient plastic phase biochar (TPPB).

[0035] Aspects of the present disclosure are described in detail with reference to the drawings wherein reference numerals identify similar or identical elements.

[0036] Although the present disclosure will be described in terms of specific aspects and examples, it will be readily apparent to those skilled in this art that various modifications, rearrangements, and substitutions may be made without departing from the spirit of the present disclosure. The scope of the present disclosure is defined by the claims appended hereto.

[0037] For the purpose of promoting an understanding of the principles of the present disclosure, reference will now be made to exemplary aspects illustrated in the drawings, and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the present disclosure is thereby intended. Any alterations and further modifications of the novel features illustrated herein, and any additional applications of the principles of the present disclosure as illustrated herein, which would occur to one skilled in therelevant art and having possession of this disclosure, are to be considered within the scope of the present disclosure.

[0038] FIG. 1 illustrates an example system that can be utilized to produce biocarbon with high compressive strength, arranged in accordance with at least some embodiments presented herein. As discussed in more detail below biocarbon with high compressive strength may be effective in metallurgic applications.

[0039] System 100 may include a biomass feedstock 10, a pyrolysis chamber 20, and a heat source 30. In some examples system 100 may further include an inert gas feed 40. Inert gas feed 40 may be a nitrogen gas feed and may provide an inert nitrogen gas environment to pyrolysis chamber 20. Heat source 30 may provide heat to pyrolysis chamber 20 to moderate a temperature within pyrolysis chamber to a desired temperature, e.g., to a desired temperature up to 350° C. Pyrolysis chamber 20 may operate at any suitable pressure for pyrolysis to occur, in aspects, at a pressure of 1500 psi or higher. Biomass feedstock 10 may be received at pyrolysis chamber 20. Biomass feedstock 10 may be pyrolyzed within pyrolysis chamber 20 at a pressure greater than 1500 psi and at a temperature less than 350° C and may generate a transient plastic phase (TPP) biochar 50. Biomass feedstock 10 may be pyrolyzed within pyrolysis chamber 20 in an air atmosphere or in a nitrogen gas environment.

[0040] Biomass feedstock 10 may include woody biomass such as hard-wood or soft wood, including birch stem wood, oak, spruce, eucalyptus, cellulose, and / or rice straw. Biomass feedstock 10 may include biomass particles with a size of less than 0.2 to 4 mm with a moisture content of 8-100%. In some embodiments, biomass feedstock 10 is not ground or dried prior to being received at pyrolysis chamber 20. In some embodiments,moisture may be added to pyrolysis chamber 20 when biomass feedstock 10 includes spruce, eucalyptus, cellulose, and / or rice straw. In some embodiments, moisture may not be added to pyrolysis chamber 20 when biomass feedstock 10 includes birch and / or oak. In some embodiments, biomass feedstock 10 with larger particles and higher moisture content may perform better for the formation of TPP biochar (TPPB) 50.

[0041] TPPB biochar 50 may have enhanced plasticity and may be ideally suited for pressure molding or extrusion. In some examples, TPPB biochar 50 may be mixed with other materials such as pet-coke and zeolite materials to serve as a platform to produce composite materials. After cooling, the recovered TPP solid biochar 50 may be ground into a fine powder 55. Powder 55 may be pressure molded, extruded, or compressed into a specific geometry such as pellet 60. Pellets 60 may be calcined (N2) in a devolatilization apparatus 90. Devolatilization apparatus 90 may devolatilize or perform a calcination of pellet 60 resulting in pellet 65. Devolatilization apparatus 90 may devolatilize pellet 60 in an inert environment at atmospheric pressure at a temperature ranging from 300 to 1200 °C for 1 hour at a heating rate of 3-10 °C / min resulting in transient plastic phase biocarbon (TPPC) pellets 65.

[0042] To demonstrate the utility of TPP biochar 50 compared to standard materials, pellets 65 and pellets from standard pyrolysis (SP) biocarbons from various feedstocks (birch, spruce, rice straw) were produced in parallel while holding all variables constant including particle size, temperature, and pellet formation conditions. The tensile strengths of devolatilized TPP pellets 60 consistently showed tensile strength improvement between 4-10x’s higher than the standard pyrolysis precursor pellets. Additional moisture and reduced reaction time during the biochar formation reaction in pyrolysis chamber 20 maylead to further improvements in mechanical properties. In addition to higher compressive strength calcined TPP pellet 60 has a smooth surface compared to the devolatilized standard pyrolysis pellet and may have additional benefits related to CO2 reactivity, and friability.

[0043] TPP solid biochar 55 intermediate product may be compressed by a compressing apparatus 80 into a pellet 60 with less elasticity than materials that have not undergone a molten phase and during pelletization. The reduced elasticity may enable greater bonding between particles and upon devolatilization, the particles may aggregate to form coherent structures.

[0044] Grinding the TPP biochar 50 into a fine powder 55 prior to pelletization and calcination may increase tensile and compressive strength with a tensile strength measured ranging from 10 to 50 MPa and compressive strength greater than 100 MPa. A grinder 70 such as a cryomill may be used for grinding, but other methods to produce a fine powder 55 may be applicable.

[0045] The use of system 100 to produce devolatilized TPP biocarbon 50 does not require biomass feedstock 10 to be ground into a fine powder prior to the initial TPP pyrolysis reaction and also does not require that biomass feedstock 10 be dried prior to the initial TPP pyrolysis reaction, thus reducing the required processing steps.

[0046] TPP solid biochar 50 may grind easily compared to the parent biomass of biomass feedstock 10 and therefore conducting the initial TPP pyrolysis reaction prior to size reduction may reduce the required input energy for system 100.

[0047] Powder 55 may be formed into customized shapes prior to a secondary heat treatment and may retain the customized shape as a final hardened biocarbon. Casted ormolded powder shapes, once hardened, can be used in a variety of applications and industries, including but not limited to body armor, skid plates, molds, or electrodes.

[0048] Pyrolysis at pyrolysis chamber 20 may require less than 1 hour to complete. TPP biochar (TPPB) 50 may be utilized as a binder by producing mixtures of TPPB and petcoke and in experiments, good performance was achieved with 50% TPPB / 50% petcoke mixtures. These mixtures were produced by grinding the materials together with a cryomill 70.

[0049] System 100 may be used to perform a unique processing sequence to generate biocarbon pellets 65 with improved mechanical properties compared to biobased carbon produced via conventional routes. Biocarbon 65 may have tensile strength greater than 40 MPa and compressive strength greater than 100 MPa, a fixed carbon content greater than 90%, and a true density greater than 2.1g / ml. The properties of biocarbon 65 may be suitable for metallurgical processes including metallurgical reductants, binders, electrodes, or high value specialty materials. Strength properties of biocarbon 65 may be superior to a biobased carbon material with or without a binder addition and may be comparable to mechanical properties of glassy carbons.

[0050] The elasticity, plasticity, fracture strength, and ductility of powder 55 compressed into pellets 60 was studied using a universal tester, die, micrometer, balance, and helium pycnometer. As powder 55 was compressed into pellet 60, individual particles may fracture and deform reducing a pore space between and within the particles. A solid fraction (the ratio of apparent density to true density (equation 1)) and porosity (equation 2) of pellets 60 may provide insight into differences between materials. If sufficient compressive force was applied to remove all void space, the apparent density would equal the true density. A solid fraction greater than 1 may be realized if the compressive load isSieat enough to compress the solid material itself. After the compressive load is released, pellet 60 may expand in volume. The extent to which the material of pellet 60 expands may reflect the material elasticity. The extent to which powder 55 may form a stable pellet60 may be related to the extent to which the material undergoes plastic deformation under a compressive load. Materials that deform elastically do not form stable pellets.id Fra cti onr Waals and London dispersion forces between particle surfaces are responsible for intra-pellet cohesion and decrease rapidly with distance (inverse of distance to the sixth power). The overall total strength of pellet 60 may be the product of bonding strength and bonding area. The strength of pellet 60 may increase when powder 55 undergoes fracture and plastic deformation by developing more bonding area, or contact surfaces between particles, within pellet 60. Once formed the overall strength of pellet 60 may be determined by breaking pellet 60. Diametric compression (force applied on the diameter of pellet 60) may be used to break pellet 60 and the measured a maximum force(Fmax) which may be used to calculate the tensile strength using (equation 3). A compressive strength may be determined by loading pellet 60 on a cylindrical axis and may be calculated from a measured maximum force (Fmax) using (equation 4).Where D is the pellet diameter, H is the pellet height (axial length), and r is the pellet radius.

[0052] Several important relationships may be used to compare pellets 60 from different materials including: the compressibility profile (solid fraction vs compressionpressure) which reflects the degree to which particles fracture and undergo plastic deformation, the compactability profile (tensile strength vs solid fraction) which reflects the relative strength holding individual particles together; the tabletability profile (tensile strength vs compression pressure) which reflects the overall suitability of the material to form pellets 60; and the tensile modulus which provides a measure of pellet 60 ductility.

[0053] ExamplesSample Preparation: Norwegian birch stem wood chips were ground into <2 mm and <4 mm size fractions using a rotary knife mill (Fritsch Pulverisette 19, Idar-Oberstein, Germany), and size fractionated using a sieve shaker (Rotap RX-29, WS Tyler, Mentor, OH) for 5 minute intervals. Material moisture content was determined by drying overnight at 105 °C or until constant weight. To produce test samples with moisture content greater than the equilibrium value of the parent birch (-10% wet basis), the prescribed amount of water and parent birch were added to an empty reactor, sealed, and allowed to equilibrate overnight (or longer as required). A fine powder sample was prepared by further grinding a 1-2 mm size fraction in a Retsch ZM 200 Ultra Centrifugal Mill to pass a 0.2 mm screen.

[0054] Biomass Pyrolysis: All pressurized pyrolysis tests were run using a wall heated tube bomb (WHTB) reactor system as illustrated in FIG. 2. The reactor may include a back pressure regulator (Swagelok 316 SS KPB series (0-20.7 MPa) with PEEK seats and 0.06 Cv) to allow for both constant volume and constant pressure reaction conditions.

[0055] An aluminum shroud may be added to cover a top of the reactor to minimize heat and alundum loss from the sand bath. Experiments utilized (1) a “double” reactor comprising two 25 mm paired WHTBs, (2) a “small” 12.5 mm single WHTB, and (3) a 12.5 mm, “partitioned” WHTB that used a screen to separate the reactor volume into two sub-volumes.The latter was used to verify whether the biomass feedstock had experienced a molten phase.After loading with biomass, the reactors were weighed, leak checked, purged, and pressurized using industrial nitrogen from a compressed gas cylinder. For each test, the reactors were immersed in a temperature-controlled sand bath for 30 min, with the starting time defined by the reactor making contact with the hot sand bath surface. The system pressure for constant pressure pyrolysis was initially set using a N2 compressed gas cylinder to 10-20% above the desired pressure with the back pressure regulator (BPR) adjusted to 20.7 MPa. With the discharge from the BPR connected to a dry gas meter the BPR setpoint was reduced until flow was observed at the dry gas meter. The dry gas meter was then removed from the system and the pressure adjusted to the setpoint using the BPR. When the test was completed, the reactors were cooled to room temperature, depressurized, and weighed, and their contents quantitatively recovered.

[0056] Constant pressure WHTB tests were conducted to determine the role of pressure on the formation of TPPB. All constant pressure reactor tests were pressurized to the prescribed set point prior to being immersed in the sand bath. Gas was released through the back pressure valve as the system heated after immersion. This transient heating period produced a -15% overshoot above the set point pressure while the system came to steady state. A summary of constant pressure tests (CP Series) to determine the effect of pressure on TPPB formation is shown in Table 1. Tests with reactor pressures of 0, 0.69, 4.5 and 6.9 MPa were conducted at a temperature of 320 °C. These tests used the double reactor system with a three-point internal thermocouple. An average of the three temperatures is reported. All reactors were fully loaded with 1-2 mm birch particles (-28 g total) to replicate solid feedstock conditions across the test series. Two additional tests were conducted to compare the effect of feedstock particle size.The fine powder material (< 0.2 mm) tests shown as IDs 10 and 11 in Table 1 were conducted as 0.69 and 12.4 MPa constant-pressure counter parts to IDs 2, 5, and 6.

[0057] Melt Test series shown in Table 1 used the sectioned WHTB with the upper section of the reactor loaded with ~2.5 g of birch wood (2-4 mm) and the bottom section empty. The volume of the upper section was 70% of the total and the remaining 30% below the 1 mm screen. Under constant pressure (12.4 MPa) test conditions, generated gases would flow upwards out of the reactor and through the back pressure regulator. The material found in the bottom section of the reactor would have passed through the 1 mm screen separating the two reactor sections, indicating that a molten phase had occurred. This test also verified that TPPB formation was not inhibited by a large void volume in the reactor.

[0058] Additional experiments were conducted to augment the constant pressure series and better understand the effect of temperature on TPPB formation. To this end, Tests 4 and 8 in Table 1 were conducted at the same constant pressure condition but at 320 and 420 °C, respectively. An additional experiment was conducted to seek a lower temperature boundary for TPPB formation using a pressure that formed TPPB at 320°C and 30 minutes reaction time.Test 9 was conducted at 275 °C based on the results obtained from Test 6.Table 1: Experiment list for constant pressure reactions* All reaction times were 30 minvtes.

[0059] A summary of constant volume tests is shown in Table 2. Tests were all conducted at 320 °C across a range of initial reactor nitrogen pressures from 0 to 2.0 MPa. All reaction times were 30 minutes.Table 2: Experiments for constant wofume reaction series. Ail reaction times were 30 minutes.Biochar pellets 60 (6 mm diameter) were formed from 0.5 to 1.0 mm particles under 168 MPa pressure. After weighing, pellets 60 were devolatilized in a 25 mm quartz tube furnace at a rate of 1 °C / min to 900 °C, held for 1 hr., then passively cooled. 1.6 L / min of nitrogen (Matheson Tri-Gas, Ultra-High Purity, 99.999% purity) was flowed through a trap (Restek, RES-20601) rated to remove oxygen below 20 ppb and then purged the quartz tube. Following devolatilization, the mass of the resulting pellets 65 was determined and the dimensions measured using a micrometer (Mintoya Corp., Model CD-6”C, +5 pm). Moisture content, volatile matter, fixed carbon, and ash of the biochar produced from the WHTB reactor were determined using a LECO TGA801 System with operating conditions as specified by the manufacturer for proximate analysis. All samples were run in triplicate with ~1 g of sample used for each replicate. The LECO TGA801 program is provided below.Leco 801 proximate analysis program:(A) moisture content determination:(1) heat the crucibles without lids under nitrogen atmosphere (flow = 10.0 L / min) from25.0°C to 105.0 °C at 6 °C / min(2) hold at 105.0 °C for 15 min(3) repeatedly weigh the crucibles until reaching constancy (i.e., mass change between successive measurements is < 0.5 mg)(B) volatile matter content determination:(1) place lids on the crucibles(2) heat the crucibles with lids under nitrogen atmosphere (flow = 10.0 L / min) from 105.0°C to 950.0 °C at 45 °C / min(3) hold at 950.0 °C for 7 min(4) weigh the crucibles(C) ash content determination:(1) cool the system from 950°C to 450 °C and remove the crucible lids(2) heat the system under oxygen atmosphere (flow = 3.5 L / min) to 600 °C , and then ramp from 600 °C to 750°C at 3 °C / min(3) hold at 750.0 °C for 75min(4) repeatedly weigh the crucibles until reaching constancy (i.e., mass change between successive measurements is < 0.5 mg)

[0060] Biochar powder 55 compaction experiments were conducted using a universal tester, (Shimadzu, model AGS-X) equipped with a 5 kN load cell (+1% from 10-5000 N) with Trapezium software (version 1.5.6) and a 6 mm diameter die (Precision Elements Ltd, Traverse City, MI) made from D2 tool steel. Pellets 60 were formed in the die using a piston travel speed of 10 mm / min to reach the target maximum force and then held for 120 sec. The measurement start point in the compression program was defined at a force of 20N. The piston travel distance, the height of pellet 60 at the end of the compression stroke(under load in the die), and the height and diameter of pellet 60 after removal from the die and immediately before tensile strength determination were recorded for each sample. Tensile strength was determined using diametric compression of cylindrical pellets 60 with a piston travel speed of 1 mm / min, and calculated using equation (5), where F is the measured force and Do is the initial diameter.

[0061] The tensile modulus, E, was determined using the max slope function and a 250- point fit in the Trapezium software. The force-displacement slope (N / mm) obtained in Trapezium was converted into stress vs strain (N / mm2= MPa) using equations (5), (6) and (7).

[0062] The thermal expansion of the TPPB and NTPPB (non-transient plastic phase biochar) pellets was determined by placing pellets into a furnace (air) at 100, 150, 200 °C for 1 hour and measuring the diameter and radius using a micrometer.

[0063] SEM micrographs were obtained using a JOEL JSM 5900LV SEM with a working distance of 18 mm with corresponding voltage of 15 kV and spot size of 24.

[0064] NMR spectra of TPPB samples were acquired at the Chemical Instrumentation Facility at Iowa State University using a Bruker Avance 400 under a 9.6 T field corresponding to Lamor frequencies for 1H of 400.13 MHz and 100.62 MHz for 13C. A 4 mm three channel probe was run in double resonance mode with a MAS frequency of 14 kHz using 62.5 kHz TPPM 1H decoupling. Cross polarized spectra were acquired using50 kHz power on 13C with a 1H sideband match condition with a cross polarization period of 5 ms. Direct polarized (DP) spectra were acquired with a recycle delay of 50 s and 3 k scans.

[0065] Thermogravimetric analysis (TGA) was performed using a TA Instruments TGA 5500 under a 50 ml / min flow of ultra-high purity N2. The heating program ramped 10 °C / min to 110 °C with a 30-minute hold to evaporate all residual moisture followed by a 10 °C / min ramp to 1100 °C.

[0066] The results of the tests summarized in Tables 1 and 2 are described below.

[0067] Influence of pressure on TPPB formation - Experiments 1 - 5 and 10 / 11 in Table 1.Figure 3 A shows results from 1-2 mm birch particles following constant pressure carbonization experiments at 320 °C for 30 min.; Figure 3B shows solid yield and fixed carbon content as a function of pressure; and Figure 3C shows heating profiles from constant pressure pyrolysis with 1-2 mm birch particles reacted at 320 °C for 30 min. As shown in Figure 3A, no TPPB formation was observed under pressures of 0, 0.69, and 4.48 MPa, minor TPPB formation was observed at 6.89 MPa, and complete TPPB formation occurred at 10.3 MPa. As shown in Figure 3B, minimal differences in solid and fixed carbon content were observed as a function of pressure, despite drastic changes in the material morphology. TPPB did not result from secondary char formation around individual primary biochar particles as differences in the solid yield and potentially fixed carbon content were not observed. Particles in a size range of 1-2 mm were selected for two reasons. First, larger particles have a larger void space than a fine powder, and the formation of TPPB would be much more apparent. Second, pyrolysis reactions under constant pressure conditions release gas from the system upon heating in the sand bath. Effectively this outgassing would not be favorable for TPPB to form if the primarymechanism was secondary charcoal formation. The temperature profiles for each of the test conditions are shown in Figure 3C. Lower reactor pressures display a prominent endotherm occurring near the corresponding boiling point of water (dashed horizontal line). Under conditions that formed TPPB, the temperature profile steepens at -210 °C where the profiles of the three highest pressure experiments diverge. Additionally, the boiling point of water at 6.9 MPa is 275 °C, and therefore if TPPB formation is water mediated melting, the temperature expected for this to occur would be > 275 °C. Results from tests run with a fine powder were consistent with respect to TPPB formation.

[0068] TPPB solids 50 produced by a partitioned reactor (Table 1, test 6) may have undergone a morphology transformation as 62% of the dry product mass was recovered below the 1 mm screen and the remaining 38% above. The screen was plugged with material with the same morphology as the contents of the lower reactor. Moreover, the material that did not pass through the 1 mm screen was accumulated as a solid chunk piled atop the screen. The biomass feedstock may have passed through a molten phase during the course of the reaction to produce this product location and form. An additional experiment was run under NTPPB formation conditions (0.69 MPa, 320 °C, 30 min) and resulted in biochar 50 which retained the parent particle morphology and 100% of the solid product mass was recovered from above the screen.

[0069] Results from Table 1, test 8 conditions produced a biochar product 50 that showed only partial TPPB formation, comparable to the product 50 from test 4. Tests 4 and 5 as a pair demonstrate that increased pressure can shift biochar 50 characteristics from a partial TPPB product to a fully agglomerated TPPB product. Test 4 and 8 as a pair demonstrate that an increase in temperature of 100 °C does not produce a comparable effect on biochar product 50 characteristics. Taken together, this suggests that a minimumpressure may assist in TPPB formation, which may likely be related to the boiling point of water.

[0070] The experiments also identified a minimum temperature suitable for TPPB formation. A minimum temperature of greater than 275 °C can be inferred from the constant pressure experiment results. Test 9 temperature, 270 °C, corresponds to the boiling point of water at 6.89 MPa. Under these conditions TPPB formation was not observed, suggesting a minimum temperature greater than 275 °C may assist in TPPB formation with a 30 min reaction time. These results corroborate the conclusions drawn from the water-boiling point curves and TPP formation from the constant pressure series. Taken together, it appears that the reactions responsible for TPPB formation have an activation energy threshold above 275 °C for the range of test parameters summarized in Table 1.

[0071] TPPB formation was initially observed from constant volume reactor conditions which resulted in elevated pressures. The role of pressure is more complicated to investigate since pressure changes with temperature as the reaction proceeds. Results from constant volume experiments show that initial pressures of 1.1 and 2.0 MPa lead to TPPB formation, whereas initial gage pressures of 0 and 0.56 MPa did not lead to TPPB formation. The temperature pressure profiles from the constant volume experiments supported the conclusions from the constant pressure experiments.

[0072] Solid state13C NMR quantitatively identifies functional groups present in samples. Analysis of chars and humic materials may be difficult due to numerous overlapping aromatic peaks being present. Advanced NMR techniques have improved the understanding of average chemical structures present in low temperature char materials. To compare functional groups of TPPB and NTPPB, semi-quantitative13C cross -polarized spectra were obtained using a longcross polarized spin transfer time (5 ms). Spectra show no detectable differences in the prominent peak locations, and the relative intensity of major peaks demonstrating that the two materials have minimal differences in average chemical structures. Both spectra lack residual intensity characteristic of alkyl OCH groups present as carbohydrates in the parent biomass, indicating that both materials have been significantly transformed. Both spectra are dominated by sp2hybridized carbon in the form of furanic and phenolic species that contain a large fraction of O-CH3 groups. Both spectra exhibit a large aromatic peak area that reflects a mixture of lignin and furanic products, and the characteristic Caromatic-0 one (150-165 ppm) and two bonds (100-110 ppm) from oxygen. The alkyl region of the spectra has a sharp OCH3 peak at 55 ppm corresponding to methoxy groups present on lignin. A sharp CH2 peak at 30 ppm and ketone at 205 ppm reflect levulinic acid. CH3-COO groups cause a sharp CH3 peak at 21 ppm characteristic of acetic acid and / or acetate. These results show that the materials are not drastically different despite the huge difference in morphology.

[0073] Compressibility profiles of TPPB and NTPPB using small (0.075-0.15 mm) and large (0.5-1 mm) particle size fractions show the two materials behave drastically different (Figure 6A). The TPPB solid fraction at 166 MPa approaches nearly 80% compared to the NTPPB which is below 60%. The difference in the response is greater at 53 MPa with solid fractions of TPPB being 68% and NTPPB being 42%. Differences are also reflected by the minimum pressure used to form a stable pellet, with TPPB forming a stable pellet with as little as 8.8 MPa pressure, compared to 53 MPa required for the NTPPB material. The compressibility profiles of the two TPPB particle size classes are identical, whereas the NTPP values differ by ~3% (absolute) with the smaller size class having a higher solid fraction. These differences indicate that the TPPB material undergoes plastic deformationand / or fracture to a far greater extent than NTPPB. This mechanical response would be consistent with TPPB having undergone a molten phase, which would result in a breakdown of the macromolecular structure of the parent material.

[0074] Figure 4A illustrates compressibility profiles of two size classes of TPPB and NTPPB powders formed into 6 mm pellets across a range of piston loading pressures. Figure 4B illustrates compaction profiles of two size classes of TPPB and NTPPB powders formed into 6 mm pellets. Figure 4C illustrates tabletability profiles of two size classes of TPPB and NTPPB powders formed into 6 mm pellets across a range of piston loading pressures. In Figure 4C the dotted line represents highest value for bio-oil (30 wt%) - biochar (70 wt%) pellet pressed at 60 °C. The compactability profiles for TPPB and NTPPB pellets from the same two particle size fractions are shown in Figure 4B. These plots show that their maximum tensile strengths (0.5 to 0.6 MPa) are comparable at their highest solid fractions. At 0.55 to 0.6 solid fractions, NTPPB has an order of magnitude higher tensile strength. This behavior would be consistent with TPPB having a greater inter-particle bonding area, but lower bonding strength and NTPPB having greater bonding strength and lower bonding area. This would be consistent with NTPPB material retaining its structural integrity, and the associated strength. The tabletability profiles for TPPB and NTPPB pellets from the same two particle size fractions are shown in Figure 4C. TPPB pellets exhibit greater tensile strength than NTPPB pellets at low pressures and asymptotically approach a common 0.5 to 0.6 MPa range at compression pressures of 168 MPa reflecting the increased bonding area between particles. The NTPPB pellet profiles exhibit a linear increase in tensile strength with increasing pressure from 53 and 168 MPa. This reflects how NTPPB is resistant to plastic deformation and fracture compared to TPPB, allowing for additional bonding area to develop with higher pressures.

[0075] Data from the compressibility, compactability, and tabletability profiles suggests that NTPPB is more resistant to fracture and plastic deformation when compared to TPPB which may be apparent from the greater volume expansion of pellets after compressive loads are removed. The change in volume after 128 hours at room temperature are shown in Figure 5 as a function of compression pressure for TPPB and NTPPB pellets. These data show that at all pressures the NTPPB expands to a far greater extent than the TPPB materials. At 168 MPa the TPPB and NTPPB materials expanded 4% and 15%, respectively, representing nearly 4 fold greater volume expansion. This large difference in elasticity between the TPPB and NTPPB materials is consistent with the compressibility, compactability, and tabletability profiles.

[0076] Figure 6 illustrates a plot of pellet tensile moduli as a function of pellet-forming pressure. At 168 MPa compression pressure TPPB has a tensile modulus of around 50 MPa compared to NTPPB at ~20 MPa. Additionally, the response of tensile modulus vs compression pressure shows TPPB has a slope nearly twice that of NTPPB. These data show that the pellets formed from TPPB are much less ductile compared to NTPPB. Calcined (N2) and un-calcined TPPB and NTPPB pellets produced from <0.2 mm birch particles exhibited reduced mechanical strength compared to their 1 to 2 mm counterparts. Calcining by devolatilization apparatus 90 may produce TPPC pellets 65 with increased the tensile strength of the <0.2 mm and 1-2 mm size class TPPB pellets 60 by factors of ~ 6 and 9, respectively. As shown in Figure 6 the greater elasticity of NTPPB material pellets observed at room temperature was amplified when heated. After 1 hr. at 200 °C the NTPPB pellet expanded by 11.5% compared to 2.5% for the TPPB pellet 60. These data suggest that the TPPB pellets 60 would be more apt to maintain mechanical integrity followingheating compared to the NTPPB pellets. Reduced thermal expansion may allow for greater intraparticle contacts to be retained and allow for formation of covalent bonds between particles to form a strong contiguous solid.

[0077] As a result of having undergone a molten phase, TPPB pellets 60 may have a much higher solid fraction and much lower elasticity and thermal expansion. Upon further heating to convert TPPB into biocarbon TPPC, there may be greater intra particle contact, leading to greater covalent bond formation between particles resulting in a material with greater mechanical strength compared to the NTPPB material. TPPB pellets 60 and NTPPB (0.5-1 mm particles) pellets were devolatilized by heating to 900 °C. Pellets 60 produced from TPPB and NTPPB (0.5-1 mm particles) were calcined (N2) at 900 °C. The calcination (N2) temperature is near the “fixed carbon” temperature (950 °C) used in proximate analysis to measure the fixed carbon content. After calcination, pellets 65 may contain predominantly fixed carbon and low levels of ash. Differences in the mechanical properties of TPPB pellets 60 and NTPPB pellets carried over to the TPPC pellets 65 and NTPPC pellets and were amplified (Table 3). The density of the TPPC pellets 65 are nearly double that of NTPPC pellets, with tensile and compressive strengths that are nearly ten-fold greater. The compressive strength reported for the TPPC (17 MPa) is comparable to values reported for materials produced with bio-oil / pitch binders (22-36 MPa), biomass / steam exploded wood pellets (5.5-16.7 MPa), coal tar pitch binders (14-35 MPa), and a commercial “Formcoke” process (28-55 MPa). These unoptimized results compared with those from competing applications and market products indicate that TPP material has potential to unlock new biochar applications. These results verify that the molten phase breakdown of macromolecular structure results in a carbon enriched material with drastically improved mechanical properties compared to conventional biochar anddemonstrate an innovative approach for engineering biocarbon properties.

[0078] Table 3: Comparison of devolatilized TPPC and NTPPC pellets.

[0079] FIG. 7 illustrates a plot of pellet tensile strength as a function of calcination temperature for pellets produced in accordance with aspects of the disclosure. As shown in FIG. 7, the calcination temperature range may be broad and may depend on the application for the material produced. FIG. 7 also shows that calcination temperatures at 300 °C produced strong materials 16 MPa tensile strength.

[0080] A process in accordance with the present disclosure may form TPPB without requiring drying or size reduction of the biomass prior to pyrolysis resulting in a reduction in unit operations and significant energy savings. A system in accordance with the present disclosure may keep water in the condensed phase and avoid the energy penalty associated with the latent heat of vaporization. A system in accordance with the present disclosure may produce a material which does not require a binder to form a strong pellet reducing input cost and the number of unit operations.

[0081] Certain aspects of the present disclosure may include some, all, or none of theabove advantages and / or one or more other advantages readily apparent to those skilled in the art from the drawings, descriptions, and claims included herein. Moreover, while specific advantages have been enumerated above, the various aspects of the present disclosure may include all, some, or none of the enumerated advantages and / or other advantages not specifically enumerated above.

[0082] The aspects disclosed herein are examples of the disclosure and may be embodied in various forms. For instance, although certain aspects herein are described as separate aspects, each of the aspects herein may be combined with one or more of the other aspects herein. Specific structural and functional details disclosed herein are not to be interpreted as limiting, but as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present disclosure in virtually any appropriately detailed structure. Like reference numerals may refer to similar or identical elements throughout the description of the figures.

[0083] The phrases “in an aspect,” “in aspects,” “in various aspects,” “in some aspects,” or “in other aspects” may each refer to one or more of the same or different example Aspects provided in the present disclosure. A phrase in the form “A or B” means “(A), (B), or (A and B).” A phrase in the form “at least one of A, B, or C” means “(A); (B); (C); (A and B); (A and C); (B and C); or (A, B, and C).”

[0084] It should be understood that the foregoing description is only illustrative of the present disclosure. Various alternatives and modifications can be devised by those skilled in the art without departing from the disclosure. Accordingly, the present disclosure is intended to embrace all such alternatives, modifications, and variances. The aspects described with reference to the attached drawing figures are presented only to demonstrate certain examples of the disclosure. Other elements, steps, methods, and techniques that are insubstantially different from those describedabove and / or in the appended claims are also intended to be within the scope of the disclosure.

Claims

WHAT IS CLAIMED IS:

1. A method of making transient plastic phase biochar from a biomass feedstocks, the method comprising: receiving the biomass feedstock at a pyrolysis chamber; providing an inert gas or air to the pyrolysis chamber; and pyrolyzing the biomass feedstock in the pyrolysis chamber at a pressure above 1500 psi and a temperature range of 290 - 350 °C to generate the transient plastic phase biochar with enhanced plasticity ideally suited for pressure molding or extrusion.

2. The method of producing transient plastic phase biocarbon, comprising: grinding a transient plastic phase biochar in accordance with claim 1 into a powder; compressing the powder into a pellet; and devolatilized the pellet in an inert environment at atmospheric pressure at a temperature range of 300-1200 °C for 1 hour at a heating rate of 3-10 °C / min to produce transient plastic phase biocarbon.

3. The method of claim 1, wherein a duration of the pyrolyzing is under 1 hour.

4. The method of claim 1, wherein the inert gas provided is nitrogen.

5. The method of claim 1, wherein the biomass feedstock comprises one or more of birch stem wood, oak, spruce, eucalyptus, cellulose or rice straw.

6. The method of claim 1, wherein the biomass feedstock has a moisture content between 8-100%.

7. The method of claim 1 wherein the biomass feedstock has particles with a size of 0.2-4 mm.

8. The method of claim 1 , wherein the biomass feedstock is not ground or dried prior to being received at the pyrolysis chamber.

9. A transient plastic phase biocarbon made by the method of: receiving a biomass feedstock at a pyrolysis chamber; providing an inert gas or air atmosphere to the pyrolysis chamber; pyrolyzing the biomass feedstock in the pyrolysis chamber at a pressure above 1500 psi and a temperature below 350 °C to generate transient plastic phase biochar; grinding the transient plastic phase biochar into a powder; compressing or extruding the powder into a known geometry pellet; and calcining the pellet in an inert environment at atmospheric pressure at a temperature ranging from 300 - 1200 °C for 1 hour at a heating rate of 3-10 °C / min.

10. The transient plastic phase biocarbon of claim 9, wherein the transient plastic phase biocarbon has a tensile strength ranging from 10 to 45 MPa.

11. The transient plastic phase biocarbon of claim 9, wherein the transient plastic phase biocarbon has a compressive strength greater than 150 MPa.

12. The transient plastic phase biocarbon of claim 9, wherein the transient plastic phase biocarbon has a fixed carbon content greater than 90%.

13. The transient plastic phase biocarbon of claim 9, wherein the transient plastic phase biochar has a true density greater than 2.1g / ml.

14. The transient plastic phase biocarbon of claim 9, wherein the transient plastic phase biocarbon is used for metallurgical reductants, binders, electrodes, or high value specialty materials.

15. The transient plastic phase biocarbon of claim 9, wherein the biomass feedstock includes at least one of birch stem wood, oak, spruce, eucalyptus, cellulose, or rice straw, has a moisture content between 8-100%, and is not ground or dried prior to being received at the pyrolysis chamber.

16. A system for making transient plastic phase biochar from a biomass feedstock, the system comprising: a pyrolysis chamber configured to receive and pyrolyze a biomass feedstock; a heat source; andwherein the biomass feedstock is pyrolyzed in the pyrolysis chamber at a pressure above1500 psi and a temperature range of 290 - 350 °C to generate the transient plastic phase biochar.

17. The system of claim 16, further comprising: a grinder; a compressing apparatus; and a devolatilization apparatus, wherein the grinder grinds the transient plastic phase biochar into a powder, the compressing apparatus compresses the powder into a pellet, and the devolatilization apparatus devolatilizes the pellet in an inert environment at atmospheric pressure at a temperature range of 300-1200 °C for 1 hour at a heating rate of 3-10 °C / min to produce transient plastic phase biocarbon.

18. The system of claim 16, wherein the biomass feedstock includes at least one of birch stem wood, oak, spruce, eucalyptus, cellulose, or rice straw, has a moisture content between 8-100%, and is not ground or dried prior to being received at the pyrolysis chamber.

19. The system of claim 17, wherein the transient plastic phase biocarbon has a tensile strength greater than 40 MPa.

20. The system of claim 17, wherein the transient plastic phase biocarbon is used for metallurgical reductants, binders, electrodes, or high value specialty materials.

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