Systems and methods for auto-thermal pressurized oxidative pyrolysis in constant-volume reactors

Abstract

A pressurized oxidative pyrolysis system comprising a vessel configured to contain a solid feedstock and a gas phase; a gas inlet in fluid communication with the vessel and configured to introduce an oxidizing gas into the vessel at an initial pressure; a heating assembly thermally coupled to the vessel and configured to raise a temperature of the solid feedstock while the vessel remains closed; and a product outlet configured to permit removal of a carbonaceous solid product from the vessel after heating, wherein an exothermic reaction between the oxidizing gas and the solid feedstock during heating supplies heat for conversion of the solid feedstock to the carbonaceous solid product.

Description

Attorney Docket No.: 3229-8 PCTSYSTEMS AND METHODS FOR AUTO-THERMAL PRESSURIZED OXIDATIVE PYROLYSIS IN CONSTANT- VOLUME REACTORSCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of and priority to U. S. Provisional Patent Application No. 63 / 737.522 filed on December 20. 2024. the entire contents of which are incorporated by reference herein.GOVERNMENT SUPPORT

[0002] This invention was made with government support under N00014-20- 1-2270 awarded by the Office of Naval Research. The government has certain rights in the invention. TECHNICAL FIELD

[0003] The subject matter of the present disclosure relates generally to systems and methods for pressurized oxidative pyrolysis in constant-volume reactor systems and, in particular, to systems and methods for rapid auto-thermal, low-temperature conversion of biomass, mixed solid wastes, plastics, and metal salt-containing feedstocks into biochar, molded biocarbon, and carbon-metal composite materials under controlled oxidizing conditions in a closed pressurized vessel.BACKGROUND

[0004] Current thermochemical conversion approaches for biomass, plastic waste, and metal salt precursors are frequently inadequate in their energy efficiency, product quality, and scalability. Conventional atmospheric pyrolysis is strongly endothermic and typically requires substantial external heat input, often supplied by fossil-derived fuels, in order to sustain elevated reaction temperatures. This dependence on external energy increases operating costs and limits opportunities to reduce overall carbon footprint. Standard pyrolysis and gasificationAttorney Docket No.: 3229-8 PCT processes also struggle to produce biochar and biocarbon materials with sufficient mechanical strength and controlled morphology to function as practical substitutes for petroleum coke in metallurgical and related applications. Co-pyrolysis of mixed feedstocks such as plastics and biomass introduces additional complications due to differing decomposition temperatures and reaction pathways, which can result in incomplete conversion, formation of undesirable byproducts, and non-uniform carbon materials. Moreover, while elevated pressures and controlled oxidizing conditions have been shown to offer advantages, existing high pressure systems generally rely on complex heat management strategies and are not optimized for rapid, auto-thermal operation or for handling heterogeneous, moisture-containing feedstocks.

[0005] Accordingly, there remains a need for systems and methods that employ pressurized oxidative pyrolysis in constant-volume reactor configurations to achieve rapid, auto-thermal conversion of biomass, mixed solid wastes, plastics, and metal salt impregnated precursors at comparatively low bulk temperatures. In particular, there is a need for reactor systems and operating methodologies that exploit controlled introduction of oxidizing gas at low equivalence ratios to supply process heat internally, minimize reliance on external heating, and maintain stable auto-thermal behavior. There is also a need for such systems to accommodate wet or heterogeneous feedstocks, generate high fixed carbon yields, and produce molded biocarbon, biochar, and carbon-metal composite materials with improved density, mechanical strength, and reactivity, suitable for use across applications including metallurgical reduction, energy storage, and advanced structural materials.Attorney Docket No.: 3229-8 PCTSUMMARY

[0006] In accordance with aspects of the disclosure, a pressurized oxidative pyrolysis system includes a vessel configured to contain a solid feedstock and a gas phase, a gas inlet in fluid communication with the vessel and configured to introduce an oxidizing gas into the vessel at an initial pressure, a heating assembly thermally coupled to the vessel and configured to raise a temperature of the solid feedstock while the vessel remains closed, and a product outlet configured to permit removal of a carbonaceous solid product from the vessel after heating. The system is configured such that an exothermic reaction between the oxidizing gas and the solid feedstock during heating supplies heat for conversion of the solid feedstock to the carbonaceous solid product.

[0007] In an aspect of the present disclosure, the vessel may be a closed constant-volume reactor vessel operated under constant- volume conditions.

[0008] In an aspect of the present disclosure, the oxidizing gas may include at least one of air, a mixture of oxygen and nitrogen, or CO2, and an equivalence ratio between the oxidizing gas and the solid feedstock may be between 0.03 and about 0.4.

[0009] In an aspect of the present disclosure, the heating assembly may be configured to rapidly raise a temperature at a surface of the solid feedstock to a temperature between about 300 °C and about 650 °C.

[0010] In an aspect of the present disclosure, the heating assembly may include a fluidized sand bath configured to at least partially immerse the vessel.

[0011] In an aspect of the present disclosure, the solid feedstock may include at least one of wood, cereal straw, polyolefins, rubber, paper, macro algae, biocarbons, herbaceous plants, or a combination thereof.Attorney Docket No.: 3229-8 PCT

[0012] In an aspect of the present disclosure, the solid feedstock may include a wet or saturated feedstock containing water.

[0013] In an aspect of the present disclosure, the solid feedstock may include a mixture of biomass and a synthetic polymer.

[0014] In an aspect of the present disclosure, the solid feedstock may include a biomass material containing at least one of a dissolved or dispersed metal salt, a transition metal, an alkali earth metal, or a rare earth metal, and the carbonaceous solid product may include a carbon-metal composite.

[0015] In an aspect of the present disclosure, the carbonaceous solid product may include a biochar configured for pelletization and calcination to form a shaped biocarbon product.

[0016] In accordance with aspects of the disclosure, a method for pressurized oxidative pyrolysis of a solid feedstock includes loading the solid feedstock into a vessel, introducing an oxidizing gas into the vessel to establish an initial pressure while maintaining the vessel closed, heating the vessel to trigger an auto-thermal exothermic reaction between the oxidizing gas and the solid feedstock, and increasing a temperature and a pressure in the vessel via the auto-thermal exothermic reaction to convert the solid feedstock to a carbonaceous solid product and a volume of product gases.

[0017] In an aspect of the present disclosure, the vessel may be a closed constant-volume reactor vessel operated under constant-volume conditions.

[0018] In an aspect of the present disclosure, the oxidizing gas may include at least one of air, a mixture of oxygen and nitrogen, or CO2, and an equivalence ratio between the oxidizing gas and the solid feedstock may be between about 0.03 and about 0.4Attorney Docket No.: 3229-8 PCT

[0019] In an aspect of the present disclosure, an initiation temperature for the auto-thermal exothermic reaction may be between about 140 °C and about 190 °C.

[0020] In an aspect of the present disclosure, the auto-thermal exothermic reaction may increase a bulk temperature in the vessel to a temperature between about 300 °C and about 650 °C and may increase an internal pressure in the vessel to about 2500 psi.

[0021] In an aspect of the present disclosure, the solid feedstock may include at least one of wood, cereal straw, polyolefins, rubber, paper, macro algae, biocarbons, herbaceous plants, or a combination thereof.

[0022] In an aspect of the present disclosure, the solid feedstock may include a wet or saturated feedstock containing water.

[0023] In an aspect of the present disclosure, the method may further include cooling the vessel after the auto-thermal exothermic reaction, removing the carbonaceous solid product as a biochar from the vessel, pelletizing the biochar, and calcining the pelletized biochar to form a shaped biocarbon product.

[0024] In an aspect of the present disclosure, the method may further include analyzing gas phase products produced during the pressurized oxidative pyrolysis using a gas analysis device fluidly connected to the vessel.

[0025] In accordance with aspects of the disclosure, a pressurized oxidative pyrolysis system for producing a shaped biocarbon product includes a hopper configured to receive a solid carbon-containing feedstock, a screw feed configured to convey the solid carbon- containing feedstock from the hopper, a rotating valve positioned downstream of the screw feed and upstream of a closed constant-volume reactor vessel and configured to admit the solid carbon-containing feedstock into an interior of the closed constant-volume reactorAttorney Docket No.: 3229-8 PCT vessel, the closed constant-volume reactor vessel configured to contain the solid carbon- containing feedstock and a gas phase, a gas inlet in fluid communication with the closed constant-volume reactor vessel including a pressurizing valve configured to charge the closed constant-volume reactor vessel with an oxidizing gas including air at a pressure between about 450 psi and about 2500 psi, a heating assembly thermally coupled to the closed constantvolume reactor vessel and configured to heat the closed constant-volume reactor vessel from an initiation temperature between about 140 °C and about 190 °C while the closed constantvolume reactor vessel is maintained closed, an ignition wire extending into the closed constant-volume reactor vessel and configured to initiate an exothermic reaction between the oxidizing gas and the solid carbon-containing feedstock, a pressure relief valve in fluid communication with the closed constant-volume reactor vessel and configured to vent gas from the closed constant-volume reactor vessel when an internal pressure exceeds a predetermined limit, a product outlet configured to discharge a carbonaceous solid product from the closed constant-volume reactor vessel, a grinder configured to grind the carbonaceous solid product, and a product extrusion area configured to receive the ground carbonaceous solid product from the grinder and to extrude the ground carbonaceous solid product into a shaped biocarbon product. During operation, the exothermic reaction between the oxidizing gas and the solid carbon-containing feedstock auto-thermally increases a temperature in the closed constant-volume reactor vessel to between about 300 °C and about 650 °C under constant volume conditions to form the carbonaceous solid product.

[0026] Further details and aspects of exemplary embodiments of the present disclosure are described in more detail below with reference to the appended figures.Attorney Docket No.: 3229-8 PCTBRIEF DESCRIPTION OF THE DRAWINGS

[0027] 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 embodiments, in which the principles of the present disclosure are utilized, and the accompanying drawings of which:

[0028] FIG. 1 is an illustration of a pressurized oxidative pyrolysis system, in accordance with aspects of the present disclosure;

[0029] FIG. 2 is an exemplary embodiment of the system of FIG. 1 , in accordance with aspects of the present disclosure;

[0030] FIG. 3 is an illustration of an exemplary flowchart of a method for pressurized oxidative pyrolysis of a solid feedstock, in accordance with aspects of the present disclosure;

[0031] FIGS. 4A and 4B are illustrations of representative temperature and pressure profiles during pressurized oxidative pyrolysis in the system of FIG. 1 at a higher external heating temperature, in accordance with aspects of the present disclosure;

[0032] FIGS. 5A-5F are illustrations of representative temperature and pressure profiles during pressurized oxidative pyrolysis in the system of FIG. 1 at a lower external heating temperature, in accordance with aspects of the present disclosure;

[0033] FIGS. 6A-6F are images of example solid products obtained after pressurized oxidative pyrolysis in the system of FIG. 1. in accordance with aspects of the present disclosure;

[0034] FIGS. 7A and 7B are illustrations of representative char yields and proximate analyses of solid products formed by pressurized oxidative pyrolysis in the system of FIG. 1, in accordance with aspects of the present disclosure;Attorney Docket No.: 3229-8 PCT

[0035] FIGS. 8A and 8B are illustrations of representative product gas compositions obtained from pressurized oxidative pyrolysis in the system of FIG. 1, in accordance with aspects of the present disclosure;

[0036] FIGS. 9 A and 9B are illustrations of thermo gravimetric behavior and mechanical properties of biocarbon materials derived from pressurized oxidative pyrolysis in the system of FIG. 1, in accordance with aspects of the present disclosure;

[0037] FIGS. 10A and 10B are illustrations of temperature and pressure profiles during pressurized oxidative pyrolysis in the system of FIG. 1 using air with and without dissolved iron salts in the feedstock, in accordance with aspects of the present disclosure;

[0038] FIGS. 11A and 11B are illustrations of temperature and pressure profiles during pressurized oxidative pyrolysis in the system of FIG. 1 comparing different dissolved metal salts in the feedstock, in accordance with aspects of the present disclosure;

[0039] FIG. 12 is an illustration of X-ray diffraction patterns of carbon-metal composite biocarbon materials produced by pressurized oxidative pyrolysis in the system of FIG. 1, in accordance with aspects of the present disclosure; and

[0040] FIG. 13 is a block diagram of a controller configured for use with the system of FIG. 1 , in accordance with aspects of the present disclosure.DETAILED DESCRIPTION

[0041] The present disclosure relates generally to systems and methods for pressurized oxidative pyrolysis in constant-volume reactor configurations and, in particular, to systems and methods for performing rapid auto-thermal, low-temperature conversion of diverse solid carbon-containing feedstocks, including biomass, plastics, mixed solid wastes, biocarbons,Attorney Docket No.: 3229-8 PCT graphite, and metal salt impregnated precursors, into biochar, molded biocarbon, and carbon- metal composite materials using low-cost oxidizing gases, minimal external heat input, and simple reactor platforms that can operate under constant-volume, high-pressure conditions without prior drying of the feedstock. The reactor platforms can further include one or more devices configured to accommodate transient overpressure events while preserving the constant-volume configuration during normal operation, such as one or more pressure relief valves, rupture disks, burst disks, and / or fast-acting vent valves, optionally in fluid communication with a containment volume or blowdown vessel. The present disclosure offers the benefit of achieving onset of auto-thermal conversion at unexpectedly low initiation temperatures for pressurized, oxygen-limited processing of diverse solid feedstocks, including wet feedstocks, for example initiation temperatures on the order of about 140 °C to about 190 °C, while still permitting rapid conversion to the carbonaceous solid products under closed, high-pressure, constant-volume conditions with minimal external heat input.

[0042] Although the present disclosure will be described in terms of specific 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.

[0043] For the purpose of promoting an understanding of the principles of the present disclosure, reference will now be made to exemplary embodiments 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 occurAttorney Docket No.: 3229-8 PCT to one skilled in the relevant art and having possession of this disclosure, are to be considered within the scope of the present disclosure.

[0044] Referring to FIGS. 1 and 2, a pressurized oxidative pyrolysis system 10 for autothermal conversion of solid carbon-containing materials is shown. The pressurized oxidative pyrolysis system 10 is configured to transform a solid feedstock 3 into a carbonaceous solid product 5 under pressurized, closed, constant- volume conditions, with heat supplied primarily by an exothermic reaction between the solid feedstock 3 and an oxidizing gas 4 at substoichiometric conditions. In certain embodiments, the pressurized oxidative pyrolysis system 10 is configured to maintain the vessel 12 at a high operating pressure during the autothermal exothermic event, for example by using a pressure relief valve 34 set to vent above a predetermined upper pressure limit (e.g., about 1500 psi to about 2500 psi or as high as about 5000 psi) while otherwise preserving closed, constant-volume operation below the limit. Although the limitation on pressure is dictated by the reactor rating, the pressurized oxidative pyrolysis system 10 may be used to achieve much higher pressure with high ER, high oxygen concentration, smaller particle sizes, and use of CO2 as an inert diluent.

[0045] The pressurized oxidative pyrolysis system 10 includes a vessel 12 configured to contain the solid feedstock 3 and a gas phase, a gas inlet 14 in fluid communication with the vessel 12 and configured for charging the oxidizing gas 4 to a selected initial pressure, a heating assembly 16 thermally coupled to the vessel 12 and configured to raise the temperature of the solid feedstock 3 to an initiation temperature, and a product outlet 18 configured to discharge the carbonaceous solid product 5 from the vessel 12 after completion of an auto-thermal exothermic event. In certain embodiments, the pressurized oxidative pyrolysis system 10 further includes a fluidized sand bath 20 (FIG. 2) surrounding at least aAttorney Docket No.: 3229-8 PCT portion of the vessel 12 to provide a uniform external heating environment, a gas analysis device 22 fluidly connected to the vessel 12 for characterization of gas phase products, a hopper 24 configured to receive and stage the solid feedstock 3, a screw feed 26 configured to convey the solid feedstock 3 from the hopper 24, and a rotating valve 28 positioned between the screw feed 26 and the vessel 12 and configured to admit the solid feedstock 3 into an interior of the vessel 12 while maintaining separation between an upstream ambient region and a downstream pressurizable region. In certain embodiments, the gas analysis device 22 is fluidly coupled to the vessel 12 via a sampling line that branches from, or is otherwise in fluid communication with, a gas exhaust path associated with the product outlet 18, such that gas phase products can be sampled without requiring a dedicated vent line. In embodiments, a volume of gas products discharged from the vessel 12 following completion of the autothermal exothermic event are routed to one or more downstream vessels 12 arranged in series and, after addition of an amount of oxidizing gas 4 to establish a desired oxygen concentration, are used at least in part to pressurize the downstream vessel 12 for a subsequent pressurized oxidative pyrolysis cycle.

[0046] The pressurized oxidative pyrolysis system 10 may further include a pressurizing valve 30 associated with the gas inlet 14 and configured to control charging of the oxidizing gas 4, a heat source 32 (e.g., an ignition wire) extending into the vessel 12 and configured to initiate or assist initiation of the exothermic reaction between the oxidizing gas 4 and the solid feedstock 3, and the pressure relief valve 34 in fluid communication with the vessel 12 and configured to vent gas from the vessel 12 when an internal pressure exceeds a predetermined limit. Downstream of the vessel 12, the pressurized oxidative pyrolysis system 10 may include a grinder 36 configured to grind the carbonaceous solid product 5 discharged through theAttorney Docket No.: 3229-8 PCT product outlet 18 and a product extrusion area 38 configured to receive the ground carbonaceous solid product 5 and to extrude the ground carbonaceous solid product 5 into a shaped biocarbon product 6. After the solid feedstock 3 is admitted into the vessel 12, the rotating valve 28 is closed to isolate the hopper 24 and screw feed 26 from the pressurizable region, and the oxidizing gas 4 is introduced into the vessel 12 through the gas inlet 14 by operation of the pressurizing valve 30 to pressurize the vessel 12 without pressurizing the hopper 24, such that the vessel 12 is filled, isolated, pressurized, and reacted in a batch cycle and then depressurized and emptied by opening the product outlet 18 before repeating the cycle. The pressurized oxidative pyrolysis system 10 can be implemented as a laboratory scale unit, a pilot plant module, or an industrial unit, and can operate in batch, semi batch, or semi continuous modes for processing of a wide range of solid feedstock 3 formulations, including biomass, plastics, and mixed waste streams that may be dry, moist, or saturated.

[0047] The vessel 12 provides the primary reaction volume in which pressurized oxidative pyrolysis occurs. The vessel 12 is configured as a pressure resistant enclosure that defines an interior volume suitable for containing the solid feedstock 3 and the oxidizing gas 4 under elevated temperature and pressure. In certain embodiments, the vessel 12 is a closed constantvolume reactor vessel that maintains a substantially fixed internal free volume during pressurization, heating, and reaction, so that changes in temperature and gas composition directly translate into corresponding changes in internal pressure. The vessel 12 may be cylindrical, spherical, or another compact geometry selected to distribute mechanical stress under high internal pressure and repeated thermal cycling. In many laboratory and pilot embodiments, the vessel 12 is a thick-walled cylindrical bomb with threaded or flanged closures at one or both ends, with seals selected to withstand multiple pressurization andAttorney Docket No.: 3229-8 PCT depressurization cycles without loss of containment. The vessel 12 may be oriented vertically, horizontally, or at an angle relative to the fluidized sand bath 20 or other heating environment, provided that the interior volume remains completely closed during the pressurized oxidative pyrolysis event.

[0048] The vessel 12 may be fabricated from high strength metallic materials such as stainless steels or nickel based alloys selected to tolerate repeated exposure to initiation temperatures between about 140 °C and about 190 °C and peak bulk temperatures between about 300 °C and about 650 °C, as well as internal pressures up to about 2500 psi in representative small scale systems. In certain embodiments, the pressurized oxidative pyrolysis system 10 is configured for operation at pressures greater than about 2500 psi, and peak pressure during the auto-thermal exothermic event can increase with increased oxygen concentration in the oxidizing gas 4, increased equivalence ratio, reduced particle size of the solid feedstock 3, use of CO2 as an inert or diluent gas in the gas phase, and impregnation of the solid feedstock 3 with metal salts or other metal containing additives.

[0049] In some embodiments, the vessel 12 may have an internal volume in a range from a few cubic centimeters to several liters to accommodate different batch sizes of the solid feedstock 3. Wall thickness, closure design, and seal configurations for the vessel 12 may follow conventional pressure vessel design practice for the intended design pressure and temperature, and may include metal to metal seals, high temperature gasket materials, or combinations thereof to maintain leak tight operation during the closed constant-volume portion of the cycle. In certain embodiments, an interior surface of the vessel 12 includes a refractory lining or refractory coating configured to reduce heat flux to the metallic wall and to mitigate thermal gradients and heat stress in the vessel 12 during the auto-thermalAttorney Docket No.: 3229-8 PCT exothermic event. The refractory lining or refractory coating may include a ceramic material, a ceramic composite, or a sprayed refractory material.

[0050] The vessel 12 is configured internally to receive the solid feedstock 3 as a packed bed, a loose charge, or a layered charge, with the amount of solid feedstock 3 selected so that a portion of the interior volume remains as a gas phase headspace for the oxidizing gas 4. In some embodiments, the vessel 12 is loaded so that the solid feedstock 3 occupies between about 10 percent and about 90 percent of the internal volume, thereby providing sufficient void space for gas flow, heat transfer, and pressure rise during the auto-thermal exothermic reaction. Internal surfaces of the vessel 12 may be smooth to facilitate discharge of the carbonaceous solid product 5 after reaction and cooling, or may include shallow features, shoulders, or transitions that assist in distributing the solid feedstock 3 during loading and reduce the formation of voids or bridging in the bed of the solid feedstock 3. In certain embodiments, the vessel 12 includes one or more internal thermocouples or thermowells that extend into the interior to allow direct measurement of internal temperatures during pressurization, heating, and reaction. The vessel 12 may include one or more ports that accommodate the gas inlet 14, the product outlet 18, the heat source 32, the pressure relief valve 34, and connections to the gas analysis device 22, with each port sealed so that the interior remains closed during the pressurized oxidative pyrolysis reaction.

[0051] In some embodiments, the vessel 12 is configured to be at least partially immersed in the fluidized sand bath 20 for uniform external heating along a substantial portion of its length, while in other embodiments only a selected axial region of the vessel 12 is immersed to create a controlled axial temperature profile. The exterior of the vessel 12 may further include lifting features, mounting brackets, or support structures that position the vessel 12Attorney Docket No.: 3229-8 PCT consistently within the heating assembly 16 and allow repeated insertion and removal between cycles without disturbing the internal configuration of the solid feedstock 3 and the oxidizing gas 4.

[0052] The gas inlet 14 is in fluid communication with the vessel 12 and is configured to introduce the oxidizing gas 4 into the interior of the vessel 12 while the vessel 12 is closed and configured for pressurization. The gas inlet 14 may include tubing, fittings, and ports constructed of metals compatible with the oxidizing gas 4 and the expected pressure and temperature ranges of the vessel 12, such as stainless steel or nickel-based alloys. The gas inlet 14 may be connected to a compressed gas source, for example a compressed air cylinder, a bank of air cylinders, a compressor feeding a storage receiver, or a manifold supplying controlled blends of oxygen and nitrogen, or CO2.

[0053] The pressurizing valve 30 is associated with the gas inlet 14 and regulates flow of the oxidizing gas 4 into the vessel 12. The pressurizing valve 30 may be a manual needle valve, a ball valve, a high-pressure solenoid valve, or another shutoff device configured to handle the target pressure range. In operation, the pressurizing valve 30 is opened to admit the oxidizing gas 4 until an initial pressure within the vessel 12 has been established, after which the pressurizing valve 30 is closed to isolate the interior of the vessel 12 from the external gas source during the pressurized oxidative pyrolysis event. In certain embodiments, the oxidizing gas 4 is air, which provides oxygen and nitrogen, or CO2 in proportions consistent with ambient air and allows convenient operation with commercially available air supplies. In other embodiments, the oxidizing gas 4 is a controlled mixture of oxygen and nitrogen, or CO2, for example a mixture with an oxygen mole fraction near that of air, slightly enriched oxygen mixtures to promote more vigorous auto-thermal behavior, or slightlyAttorney Docket No.: 3229-8 PCT oxygen lean mixtures to moderate the exothermic reaction, with the composition selected to maintain substoichiometric conditions.

[0054] The gas inlet 14 and the pressurizing valve 30 are configured so that an operator or a controller 300 (FIG. 13) can select an initial pressure for the oxidizing gas 4, such as between about 450 psi and about 2500 psi for a given vessel 12 volume and a given mass of the solid feedstock 3, while also limiting the total oxygen charged so that the equivalence ratio between the oxidizing gas 4 and the solid feedstock 3 remains less than about 0.1 or, alternatively, between about 0.03 and about 0.4. In some embodiments, the gas inlet 14 may include one or more pressure sensors, gauges, or transducers that register internal pressure in the vessel 12 during pressurization, heating, and reaction and provide feedback to the operator or controller for process monitoring and safety, although pressure sensing hardware is not required to define the structural configuration of the gas inlet 14 and the pressurizing valve 30.

[0055] The heating assembly 16 is thermally coupled to the vessel 12 and is configured to raise the temperature of the solid feedstock 3 while the vessel 12 remains closed. The heating assembly 16 may include electrical resistance heaters, a furnace, or other external heating devices that transfer heat to an exterior surface of the vessel 12 by conduction, convection, and / or radiation. In laboratory embodiments, the heating assembly 16 includes the fluidized sand bath 20, as depicted in FIG. 2. The fluidized sand bath 20 is a vessel containing a bed of granular material, such as silica sand, alumina beads, or other refractory particles, through which a fluidizing gas is passed to suspend and mix the particles and to produce a well stirred thermal medium. One or more heaters associated with the fluidized sand bath 20 raise the temperature of the bed to a selected setpoint, for example in the range of about 140 °C to about 190 °C during a preheating phase. The fluidizing gas for the fluidized sand bath 20 mayAttorney Docket No.: 3229-8 PCT include air, nitrogen, or another gas suitable for stable fluidization and heat transfer, with flow rates adjusted so that the granular material is fully fluidized without elutriation loss. The vessel 12 is positioned so that at least a portion of the vessel 12 is immersed in the fluidized bed, which provides highly uniform thermal contact around the circumference and along the length of the vessel 12, thereby reducing temperature gradients within the solid feedstock 3 and the oxidizing gas 4. In some embodiments, the heating assembly 16 includes insulation around the fluidized sand bath 20 and around the vessel 12 to limit heat loss to the surroundings and to promote reproducible thermal ramp profiles between batches. The heating assembly 16 is configured so that the vessel 12 and the solid feedstock 3 are brought to an initiation temperature at which the reaction between the oxidizing gas 4 and the solid feedstock 3 begins to accelerate, and the heating assembly 16 may also be operated to maintain or adjust the external temperature during the auto-thermal exothermic event if desired for specific process profiles.

[0056] In certain embodiments, the heating assembly 16 is configured so that the bulk temperature of the solid feedstock 3 and the oxidizing gas 4 in the vessel 12 is raised from ambient temperature to an initiation temperature between about 140 °C and about 190 °C, after which the exothermic reaction between the oxidizing gas 4 and the solid feedstock 3 increases the temperature further to a maximum temperature between about 300 °C and about 650 °C without additional external heat input. The thermal response during this exothermic period may be monitored by thermocouples associated with the vessel 12, and the heating assembly 16 may be operated in a hold mode, a reduced power mode, or a full off mode during the peak of the exothermic event depending on desired control of the temperature trajectory. In some embodiments, the heating assembly 16 is used to hold the vessel 12 at an elevatedAttorney Docket No.: 3229-8 PCT temperature for a period after the exothermic event to promote completion of devolatilization or to stabilize the structure of the carbonaceous solid product 5, while in other embodiments the heating assembly 16 is turned off or withdrawn to allow the vessel 12 to cool at a natural or accelerated rate. In embodiments, prior to onset of the auto-thermal exothermic reaction, the heating assembly 16 is further configured to raise a temperature at an exterior surface of the vessel 12 and. by heat transfer, a temperature at or near an outer region or surface of the solid feedstock 3 to a temperature between about 300 °C and about 650 °C, while a bulk temperature of the solid feedstock 3 and the oxidizing gas 4 is raised to the initiation temperature.

[0057] The solid feedstock 3 is the solid carbon-containing material introduced into the vessel 12 for conversion to the carbonaceous solid product 5. The solid feedstock 3 may take a variety of forms, including both single component and mixed materials. In some embodiments, the solid feedstock 3 includes biomass materials such as wood, rice straw, herbaceous plants, or macro algae. The wood may be in the form of chips, pellets, sawdust, shavings, or densified blocks, and may be derived from softwoods, hardwoods, or mixtures thereof. Cereal straw (e.g., rice or wheat) may be chopped or shredded to lengths suitable for packing within the vessel 12, and macro algae and / or biosolids may be provided as dried or partially dried biomass fragments. The density of the solid feedstock 3 may vary from low density fibrous materials, such as straw and macro algae, to higher density pellets and briquettes formed from wood or blended biomass. In other embodiments, the solid feedstock 3 includes synthetic polymers such as polyolefins, rubber, carbon (e.g., petroleum or biobased), or paper-based materials, including cardboard, newsprint, office paper, or mixedAttorney Docket No.: 3229-8 PCT paper fractions derived from waste streams. The solid feedstock 3 may be present as granules, flakes, chopped fragments, or compacted pieces.

[0058] In certain embodiments, the solid feedstock 3 is a heterogeneous mixture of biomass and synthetic polymers, such as mixtures of spruce pellets and polyolefins flakes, mixtures of wood and rubber particles, mixtures of paper products and plastics, or standardized mixed waste blends that emulate components of municipal solid waste. Such blended solid feedstock 3 formulations may include, for example, combinations of food like materials, plastic trays, polystyrene fragments, rubber, wood, and added water in proportions selected to reproduce realistic waste processing conditions. The solid feedstock 3 may be formulated so that individual components are uniformly distributed or layered within the vessel 12, depending on the desired contact patterns and heat transfer characteristics during pressurized oxidative pyrolysis.

[0059] The solid feedstock 3 can be dry, moist, wet, or saturated. In certain embodiments, the solid feedstock 3 is a wet or saturated feedstock containing water that has not been removed prior to operation of the pressurized oxidative pyrolysis system 10. For example, wood chips, sawdust, pellets, or straw may be fully saturated with water so that capillaries and pores contain liquid water at the time of loading into the vessel 12. Macro algae or other aquatic biomass may be processed in a partially dewatered or fully saturated state. The solid feedstock 3 may also include intentionally added water beyond that intrinsically present in the biomass or waste material, so that the overall water content reflects realistic wet waste conditions. Moisture levels may therefore range from essentially oven dry solids to materials saturated with free water, with the mass of water selected in combination with the mass of dry solid to achieve desired temperature and pressure trajectories during the auto-thermal reaction.Attorney Docket No.: 3229-8 PCTThe ability of the pressurized oxidative pyrolysis system 10 to process saturated solid feedstock 3 without a dedicated pre drying step is beneficial, as the exothermic reaction between the oxidizing gas 4 and the solid feedstock 3 provides sufficient heat to heat the wet solid feedstock 3, heat the gas phase, drive pyrolytic conversion under constant-volume conditions, and remove at least a portion of the water from the solid feedstock 3 during the auto-thermal exothermic event. In certain embodiments, the resulting carbonaceous solid product 5 retains substantially less water than the initial solid feedstock 3, so that subsequent water removal from the carbonaceous solid product 5 is significantly easier and less energy intensive than pre drying the saturated solid feedstock 3 prior to conversion. Accordingly, the pressurized oxidative pyrolysis system 10 can handle feedstocks that would otherwise require energy intensive drying before conventional thermal processing.

[0060] In additional embodiments, the solid feedstock 3 includes biomass that has been treated with aqueous solutions of metal salts to introduce metal species into the structure of the resulting carbonaceous solid product 5. For example, spruce wood, other wood species, agricultural residues, or similar porous biomass materials may be soaked in solutions containing iron nitrate, nickel nitrate, cobalt nitrate, copper nitrate, or combinations of such metal salts, optionally at different concentrations and immersion times to adjust loading levels, then drained and used as the solid feedstock 3 without complete removal of the impregnating solution. The impregnated biomass may be used in a moist state or may be partially dried, with residual solution remaining within pores and cell walls. Under pressurized oxidative pyrolysis conditions, the resulting carbonaceous solid product 5 may include a carbon metal composite in which metal oxides, mixed metal oxides, or reduced metal phases are dispersed within the carbon matrix at microscopic and mesoscopic length scales. TheAttorney Docket No.: 3229-8 PCT distribution, oxidation state, and phase composition of the metals within the carbonaceous solid product 5 can be influenced by the identity of the metal salts, the impregnation procedure, and the pressurized oxidative pyrolysis conditions. The solid feedstock 3 may therefore be selected and prepared to generate carbonaceous solid product 5 with tailored catalytic, electrochemical, or metallurgical properties, including enhanced reactivity for gasification, catalytic activity for downstream chemical transformations, or mechanical and thermal properties suitable for use as a molded biocarbon precursor in metallurgical applications.

[0061] The hopper 24 is configured to receive the solid feedstock 3 upstream of the vessel 12 and to stage the solid feedstock 3 for controlled delivery into the screw feed 26. The hopper 24 may be a gravity fed bin, chute, or funnel that holds a batch of the solid feedstock 3 and directs it downward toward the screw feed 26 under the influence of gravity. The hopper 24 may have a rectangular, cylindrical, conical, or pyramidal shape, or combinations of these shapes, with sidewalls and an outlet geometry selected to promote consistent flow of the solid feedstock 3. In certain embodiments, the hopper 24 is sized according to the capacity of the vessel 12 and the desired batch size, so that a single filling of the hopper 24 supplies one or more charges of the solid feedstock 3 to the vessel 12. Internal surfaces of the hopper 24 may be smooth, coated, or polished to reduce friction and to promote flow of irregular particles, fibrous biomass, pellets, and mixtures of biomass and plastic without bridging or hanging up. In some embodiments, the hopper 24 includes features such as sloped walls, rounded corners, or flow directing baffles that guide the solid feedstock 3 toward the inlet of the screw feed 26. The hopper 24 may be constructed from metals such as stainless steel or from other structurally suitable materials compatible with the solid feedstock 3 and with typicalAttorney Docket No.: 3229-8 PCT environmental conditions near the pressurized oxidative pyrolysis system 10. In some embodiments, the hopper 24 includes level indicators, simple mechanical sight windows, or transparent sections that allow an operator to verify the amount of the solid feedstock 3 available for loading and to monitor depletion during operation. The hopper 24 may be mounted on a frame or support structure that positions the outlet of the hopper 24 at an elevation and alignment appropriate for reliable delivery of the solid feedstock 3 into the screw feed 26 while maintaining clearance above the vessel 12 and associated components of the pressurized oxidative pyrolysis system 10.

[0062] The screw feed 26 is configured to convey the solid feedstock 3 from the hopper 24 toward the rotating valve 28 in a controlled and repeatable manner. The screw feed 26 may include an auger or screw housed within a tubular casing, with the screw driven by a motor through a direct drive or a gear reduction assembly to move the solid feedstock 3 at a controlled rate. The screw feed 26 receives the solid feedstock 3 discharged from the hopper 24 and advances the solid feedstock 3 along the axis of the screw toward the rotating valve 28. The screw feed 26 may operate at ambient pressure on the upstream side and may terminate in close proximity to, or in a mating interface with, the rotating valve 28, which separates the ambient region from the pressurizable region associated with the vessel 12. The length, diameter, and pitch of the screw within the screw feed 26 may be selected according to the particle size, density, and flow characteristics of the solid feedstock 3, and may be chosen to minimize void formation and to promote uniform volumetric delivery. In some embodiments, the screw feed 26 includes a single helical screw, while in other embodiments the screw feed 26 includes twin screws arranged to intermesh and provide improved conveying of irregular or fibrous components of the solid feedstock 3.Attorney Docket No.: 3229-8 PCT

[0063] The tubular casing of the screw feed 26 may be cylindrical or slightly tapered and may be fabricated from metals such as stainless steel or other materials compatible with the solid feedstock 3 and the surrounding environment. The screw feed 26 may include seals, bearings, and end supports that maintain alignment of the screw and contain dust or fines generated during conveying. In certain embodiments, the screw feed 26 is oriented horizontally, while in other embodiments the screw feed 26 is inclined or vertically oriented to accommodate plant layout or to optimize gravity assistance. The rotational speed of the screw in the screw feed 26 may be adjustable, for example through motor speed control, to allow adjustment of the mass flow rate of the solid feedstock 3 delivered to the rotating valve 28. The screw feed 26 may therefore be configured to deliver a desired mass per unit time of the solid feedstock 3 to the rotating valve 28, based on the bulk density of the solid feedstock 3 and the volumetric displacement per revolution of the screw.

[0064] The rotating valve 28 is positioned downstream of the screw feed 26 and upstream of the vessel 12 and is configured to admit the solid feedstock 3 into the interior of the vessel 12 while limiting gas communication between the vessel 12 and upstream feed handling hardware. The rotating valve 28 establishes a mechanical interface between an upstream region that operates near ambient pressure during loading and a downstream region that is configured to be sealed and pressurized as part of the pressurized oxidative pyrolysis cycle. The rotating valve 28 may be a rotary airlock type valve that includes a rotor with one or more pockets or cavities, housed in a closely fitting valve body. During operation, the pockets of the rotating valve 28 intermittently fill with the solid feedstock 3 discharged from the screw feed 26 at a first rotational position and release the solid feedstock 3 into an opening leading to the vessel 12 at a second rotational position. The rotation of the rotor in the rotating valveAttorney Docket No.: 3229-8 PCT28 thus meters the solid feedstock 3 into the vessel 12 in discrete increments while reducing direct open flow paths for gas between the interior of the vessel 12 and the upstream side of the pressurized oxidative pyrolysis system 10.

[0065] The body of the rotating valve 28 may be fabricated from metal, such as stainless steel, with an internal bore that closely conforms to the outer profile of the rotor. The rotor of the rotating valve 28 may include multiple radially oriented vanes that define the pockets, with tips that are sized to minimize clearances and reduce leakage of gas. Shaft seals and bearings associated with the rotor support rotation while maintaining acceptable sealing between the interior of the rotating valve 28 and the surrounding environment. The geometry of the pockets, the number of pockets, and the rotational speed of the rotor in the rotating valve 28 may be selected to coordinate with the delivery rate of the screw feed 26 and the batch size of the vessel 12. In some embodiments, the rotating valve 28 is operated intermittently, with rotation occurring during a loading phase when the vessel 12 is at or near atmospheric pressure. Once the vessel 12 has been charged with the desired amount of the solid feedstock 3, the rotating valve 28 may be stopped with the pockets oriented so that no pocket directly connects the upstream and downstream openings, and the vessel 12 is then sealed and brought to pressure using the gas inlet 14 and the pressurizing valve 30. During pressurization and heating of the vessel 12, the downstream side of the rotating valve 28 remains static, and pressure within the vessel 12 is contained by the seals and structure of the vessel 12 and associated closures rather than by the rotating valve 28.

[0066] The heat source 32 extends into the vessel 12 and is configured to initiate or assist initiation of the exothermic reaction between the oxidizing gas 4 and the solid feedstock 3. The heat source 32 may be made of a resistive metal such as nichrome, Kanthal®, or anotherAttorney Docket No.: 3229-8 PCT high temperature alloy that can withstand repeated electrical heating cycles in the reactive atmosphere within the vessel 12. The heat source 32 may be routed through an insulated electrical feedthrough in a wall or closure of the vessel 12 so that electrical connections remain outside the pressurized region while a central active portion of the heat source 32 is exposed within the interior volume of the vessel 12. In certain embodiments, the heat source 32 is positioned so that the central active portion lies within or adjacent to the bed of the solid feedstock 3, for example near the center of the charge of the solid feedstock 3 or in a region where gas and solid contact is expected to be representative of the bulk of the solid feedstock 3.

[0067] The heat source 32 may be supported by ceramic spacers, insulating sleeves, or other nonconductive supports that maintain its position while minimizing conduction of heat to the vessel 12 wall. During heating, the heat source 32 can be energized briefly by an external power supply to produce a localized region of elevated temperature within the solid feedstock 3 and the oxidizing gas 4, which can ignite or assist ignition of the exothermic reaction between the oxidizing gas 4 and the solid feedstock 3. The duration and magnitude of the electrical pulse applied to the heat source 32 may be selected so that the heat source 32 attains a temperature above the expected ignition threshold of the solid feedstock 3 under the prevailing pressure and gas composition conditions. In some embodiments, the heating assembly 16 and the fluidized sand bath 20 bring the vessel 12 and the solid feedstock 3 to the initiation temperature without use of the heat source 32, so that auto-thermal ignition occurs as the bulk temperature enters the range between about 140 °C and about 190 °C. In other embodiments, particularly when the solid feedstock 3 is highly saturated with water or includes components that are more difficult to ignite, the heat source 32 provides a reliableAttorney Docket No.: 3229-8 PCT way to trigger the exothermic reaction at a defined point in the heating cycle, thereby improving repeatability of the pressurized oxidative pyrolysis process in the vessel 12.

[0068] The pressure relief valve 34 is in fluid communication with the vessel 12 and is configured to vent gas from the vessel 12 when internal pressure exceeds a predetermined limit. The pressure relief valve 34 provides a safety path for gas discharge in the event that the pressure generated during pressurized oxidative pyrolysis rises above the intended operating range. The pressure relief valve 34 may be connected to a port near the top or side of the vessel 12 so that gas accumulating in the headspace above the solid feedstock 3 can be released preferentially. The pressure relief valve 34 may be a spring-loaded relief valve, a rupture disk, or a combination of a spring loaded relief valve and a rupture disk arranged in series or parallel, with the specific configuration selected based on system size, regulatory requirements, and desired redundancy.

[0069] In some embodiments, the pressure relief valve 34 is a spring-loaded relief valve with an adjustable or fixed setpoint pressure, where a spring and disc assembly remains closed during normal operation and opens when the internal pressure of the vessel 12 exceeds the setpoint. In other embodiments, the pressure relief valve 34 includes a rupture disk that is designed to burst at a defined pressure, providing a non-reclosing safety vent. A combination of a rupture disk upstream of a spring-loaded relief valve may be used to protect the spring- loaded relief valve from the process environment while providing a secondary resealing function. The pressure relief valve 34 is selected to open or actuate at a pressure that is below the maximum design pressure of the vessel 12 yet higher than the anticipated peak pressure during normal operation for the selected solid feedstock 3, oxidizing gas 4 charge, and heating profile. In the event that an abnormal reaction condition, such as an unexpected runawayAttorney Docket No.: 3229-8 PCT exothermic event or an error in gas charging, causes pressure in the vessel 12 to exceed this threshold, the pressure relief valve 34 allows gas to escape, preventing damage to the vessel 12 and associated components of the pressurized oxidative pyrolysis system 10. The vented gas may be directed to a safe discharge location, such as a vent stack, flare, or scrubber, or may be routed to a capture system for sampling or environmental control, depending on the installation and scale of the pressurized oxidative pyrolysis system 10.

[0070] The product outlet 18 is configured to permit removal of the carbonaceous solid product 5 from the vessel 12 after heating and after the exothermic reaction has completed and the vessel 12 has been depressurized to a safe pressure. The product outlet 18 may be located at a lower region of the vessel 12 so that the carbonaceous solid product 5 can be discharged by gravity, or may be located at a sidewall position with internal geometry that guides the carbonaceous solid product 5 toward the opening. In basic batch embodiments, the product outlet 18 may be a removable bottom cap, a threaded plug, or an access door that seals the vessel 12 during pressurization and heating and that, when opened after cooling and depressurization, allows the carbonaceous solid product 5 to fall by gravity into a collection receptacle. Sealing elements associated with the product outlet 18, such as metal-to-metal seats or high temperature gasket materials, may be selected to maintain leak tight closure of the vessel 12 during the pressurized oxidative pyrolysis cycle. In configurations that incorporate the grinder 36 and the product extrusion area 38. the product outlet 18 may discharge the carbonaceous solid product 5 directly into an inlet of the grinder 36, for example through a short chute or transition piece aligned with the grinding chamber. The product outlet 18 may include internal features that promote complete discharge of the carbonaceous solid product 5, such as conical transitions, tapered sections, or inclined surfaces that reduceAttorney Docket No.: 3229-8 PCT stagnant zones and prevent accumulation of the carbonaceous solid product 5 within the vessel 12. In some embodiments, the product outlet 18 may include a slide gate, hinged door, or similar closure mechanism that can be opened and closed in a controlled manner to regulate the flow of the carbonaceous solid product 5 from the vessel 12 to downstream handling equipment, while in other embodiments the product outlet 18 is opened fully at the end of each batch to allow the entire charge of the carbonaceous solid product 5 to be discharged before reloading the vessel 12 with fresh solid feedstock 3.

[0071] The grinder 36 is configured to grind the carbonaceous solid product 5 into a more uniform and smaller particle size suitable for subsequent pelletization, extrusion, or other forming operations. The grinder 36 may be located directly beneath the product outlet 18 so that the carbonaceous solid product 5 discharged from the vessel 12 falls by gravity into an inlet of the grinder 36, or the grinder 36 may receive the carbonaceous solid product 5 via a short chute, transition piece, or enclosed conveyance that maintains containment of dust and fines. The grinder 36 may be a hammer mill, a roll crusher, a jaw crusher, a pin mill, or another type of comminution device suitable for brittle char materials produced by pressurized oxidative pyrolysis. Internal components of the grinder 36 that contact the carbonaceous solid product 5 may be fabricated from steels, wear resistant alloys, or other materials selected to tolerate abrasion while avoiding undue contamination of the carbonaceous solid product 5. The grinder 36 receives the carbonaceous solid product 5 from the product outlet 18 and reduces the particle size to a distribution that improves flowability, mixing, and packing in downstream forming processes in the product extrusion area 38. In some embodiments, the grinder 36 is configured to produce ground carbonaceous solid product 5 with a characteristic particle size in the millimeter or sub millimeter range, with the degree of grinding adjustedAttorney Docket No.: 3229-8 PCT through screen selection, rotor speed, or roll spacing to suit specific shaped biocarbon product 6 geometries. The ground output of the grinder 36 is directed to the product extrusion area 38 by gravity, mechanical conveyors, or simple chutes.

[0072] The product extrusion area 38 is configured to receive the ground carbonaceous solid product 5 from the grinder 36 and to extrude the ground carbonaceous solid product 5 into a shaped biocarbon product 6. The product extrusion area 38 may include mixing hardware such as a paddle mixer, a ribbon blender, or the feed section of an extruder that combines the ground carbonaceous solid product 5 with optional binders, moisture adjusters, or additives to form a cohesive mixture suitable for forming. Binders may include, for example, starches, lignin rich residues, or other carbonaceous binders compatible with subsequent calcination, while water or other volatile liquids may be added to adjust plasticity. The product extrusion area 38 may further include an extruder or press, such as a single screw extruder, a twin-screw extruder, a piston press, or a roll press, that forces the mixture through a die to form pellets, rods, briquettes, blocks, or other shapes that define the shaped biocarbon product 6. Die geometry, extrusion pressure, and throughput in the product extrusion area 38 may be selected according to the desired dimensions, density, and mechanical properties of the shaped biocarbon product 6. In some embodiments, the shaped biocarbon product 6 emerging from the product extrusion area 38 is then subjected to a separate calcination step in a furnace, under inert gas such as nitrogen or argon, at elevated temperatures such as between about 750 and aboutl 500 °C, to adjust porosity, strength, and reactivity. The shaped biocarbon product 6 produced in this manner can be used as a molded biocarbon in metallurgical and energy applications, including as a partial or full replacement for metallurgical coke or as a reactive carbon source in other high temperature processes.Attorney Docket No.: 3229-8 PCT

[0073] The carbonaceous solid product 5 produced in the vessel 12 under pressurized oxidative pyrolysis conditions is generally a biochar when the solid feedstock 3 is biomass. The carbonaceous solid product 5 exhibits increased fixed carbon content and reduced volatile matter compared to the original solid feedstock 3, with the degree of carbonization influenced by the maximum temperature reached and the duration of the exothermic event. The carbonaceous solid product 5 may retain recognizable macro structure of the original solid feedstock 3, such as pellet or chip geometry, while developing internal porosity and a more graphitic or disordered carbon micro structure. When the solid feedstock 3 contains dissolved or dispersed metal salts, the carbonaceous solid product 5 is a carbon metal composite with metal containing phases supported on or within the carbon matrix, which may include metal oxides, mixed oxides, or reduced metals depending on the pressurized oxidative pyrolysis conditions. The carbonaceous solid product 5 is structurally suited for subsequent grinding in the grinder 36 and formation into the shaped biocarbon product 6 in the product extrusion area 38. In certain embodiments, the carbonaceous solid product 5 is explicitly configured as a biochar intended for pelletization and calcination to form the shaped biocarbon product 6, which may serve as a drop in or partial replacement for traditional metallurgical coke in blast furnaces, foundries, or other high temperature reactors, or as a functional carbon material in energy storage and environmental applications.

[0074] The gas analysis device 22 is fluidly connected to the vessel 12 and is configured to analyze gas phase products produced during pressurized oxidative pyrolysis. The gas analysis device 22 may be a gas chromatograph, such as a micro gas chromatograph, equipped with appropriate columns and detectors to quantify species such as hydrogen, nitrogen, oxygen, carbon monoxide, carbon dioxide, methane, and light hydrocarbons present in theAttorney Docket No.: 3229-8 PCT gas phase. The gas analysis device 22 may be connected to the vessel 12 through sampling lines and valves that allow a portion of the gas phase from the headspace of the vessel 12 to be withdrawn after completion of the auto-thermal exothermic reaction and after cooling to a suitable sampling temperature. In some embodiments, the gas analysis device 22 includes thermal conductivity detectors, flame ionization detectors, or other detectors commonly used in gas chromatography. One or more valves can be opened to allow a sample of the gas phase from the vessel 12 to be drawn into the gas analysis device 22 either by pressure driven flow or by a sampling pump.

[0075] Referring to FIG. 3, a flowchart of a method 200 for pressurized oxidative pyrolysis of the solid feedstock 3 using the vessel 12 of the pressurized oxidative pyrolysis system 10 is shown. The method 200 provides a sequence of operations in which the solid feedstock 3 is loaded into the vessel 12, the oxidizing gas 4 is introduced to a controlled initial pressure, the vessel 12 is heated until an auto-thermal exothermic reaction between the solid feedstock 3 and the oxidizing gas 4 is triggered, and the resulting increase in temperature and pressure under constant-volume conditions converts the solid feedstock 3 into the carbonaceous solid product 5. The method 200 can be implemented in batch laboratory bomb reactors, pilot reactors, or larger industrial vessels 12, provided that pressure containment and thermal control consistent with the described conditions are maintained.

[0076] At block 202, the method 200 includes loading the solid feedstock 3 into the vessel 12. The solid feedstock 3 may be introduced directly into the vessel 12 by opening a removable head or access port and pouring, scooping, or otherwise charging a measured quantity of the solid feedstock 3 into an internal cavity of the vessel 12. In other embodiments of the method 200, the solid feedstock 3 is prepared upstream and delivered via the hopperAttorney Docket No.: 3229-8 PCT24, the screw feed 26, and the rotating valve 28 that together meter the solid feedstock 3 into the interior of the vessel 12 while limiting communication between ambient conditions and the pressurizable volume of the vessel 12. The solid feedstock 3 can be arranged as a loose packed bed, a layered bed, or compacted segments, with bulk density tailored to the size of the vessel 12 and the desired conversion behavior. At block 202, the mass of the solid feedstock 3 is typically recorded so that the subsequent charge of oxidizing gas 4 can be selected to achieve a predetermined equivalence ratio and so that mass yields of the carbonaceous solid product 5 can be calculated. The solid feedstock 3 may be selected from biomass materials such as wood chips, cereal straw, and macro algae, plastics such as polyolefins and rubber, cellulosic materials such as paper, or combinations thereof, including mixtures of biomass and synthetic polymers.

[0077] At block 204, the method 200 includes introducing the oxidizing gas 4 into the vessel 12 to establish an initial pressure while maintaining the vessel 12 closed. After the solid feedstock 3 is loaded and the vessel 12 is sealed, the oxidizing gas 4 is supplied through the gas inlet 14 under regulation of the pressurizing valve 30. As the oxidizing gas 4 flows into the interior of the vessel 12, the internal pressure increases, and the rate of introduction is controlled so that the vessel 12 is not subjected to undue pressure shock. The oxidizing gas 4 fills the void spaces around the solid feedstock 3 and the headspace within the vessel 12, thereby forming a gas phase in contact with the solid feedstock 3. At block 204, pressure is monitored continuously using one or more pressure indicators attached to the vessel 12, and when the desired initial pressure is reached, the pressurizing valve 30 is closed to isolate the vessel 12. The method 200 relies on maintaining the vessel 12 in a closed state during subsequent heating such that the internal gas volume remains substantially constant and theAttorney Docket No.: 3229-8 PCT pressure rise that follows is a direct consequence of the auto-thermal exothermic reaction between the oxidizing gas 4 and the solid feedstock 3.

[0078] At block 206, the method 200 includes heating the vessel 12 to trigger an autothermal exothermic reaction between the oxidizing gas 4 and the solid feedstock 3. Heat is applied externally to the vessel 12 via the heating assembly 16. In some embodiments of the method 200. the vessel 12 is partially or fully immersed within the fluidized sand bath 20 (FIG. 2) in which heated granular media such as silica sand or alumina beads transfer heat uniformly to the outer surface of the vessel 12. In other embodiments, the vessel 12 is wrapped with electrical band heaters, placed within a resistance-heated furnace, or surrounded by a heated jacket. The heating assembly 16 brings the contents of the vessel 12 from ambient temperature to an initiation temperature in a controlled manner, with temperature monitored at one or more locations on or within the vessel 12. When the internal temperature of the vessel 12 reaches a temperature window conducive to rapid oxidation of the solid feedstock 3 by the oxidizing gas 4, the exothermic reaction accelerates and transitions into an autothermal regime in which heat generated by the reaction itself sustains and increases the temperature without additional or with reduced input from the heating assembly 16. In some embodiments of the method 200, the heat source 32 extending into the vessel 12 is momentarily energized to create a local hot zone that assists ignition of the solid feedstock 3, particularly when the solid feedstock 3 is highly moist or otherwise resistant to ignition.

[0079] At block 208, the method 200 includes increasing a temperature and a pressure in the vessel 12 via the auto-thermal exothermic reaction under constant-volume conditions to convert the solid feedstock 3 to the carbonaceous solid product 5. Once the exothermic reaction between the oxidizing gas 4 and the solid feedstock 3 is initiated at the conditionsAttorney Docket No.: 3229-8 PCT achieved in block 206, the reaction proceeds rapidly, generating heat and forming gaseous products that increase the temperature and pressure within the sealed vessel 12. Because the internal volume of the vessel 12 is essentially fixed, the pressure rise is determined by the quantity of oxidizing gas 4 present, the extent of gas generation, and the temperature increase. The method 200 allows the temperature within the vessel 12 to rise from the initiation regime to peak temperatures in the range of a few hundred degrees Celsius while maintaining the vessel 12 closed, and the internal pressure may reach levels approaching or around 2500 psi for laboratory scale vessels 12. During this auto-thermal period, the solid feedstock 3 is transformed into the carbonaceous solid product 5 as volatile components are driven off or oxidized and a carbon-rich solid matrix remains. After the auto-thermal event subsides, the heating assembly 16 can be de-energized or set to a lower holding temperature, and the vessel 12 is allowed to cool under controlled conditions so that the carbonaceous solid product 5 can be safely removed during subsequent handling steps.

[0080] In embodiments, the method 200 may further include configuring the vessel 12 as a closed constant-volume reactor vessel that is designed to maintain a substantially fixed internal free volume during blocks 202, 204, 206, and 208. The vessel 12 may be constructed with sufficiently rigid walls and closures, such as thick-walled cylindrical shells with hemispherical end caps, so that elastic deformation under pressure is minimal and has negligible effect on the volume. The selection of materials and wall thicknesses for the vessel 12 may follow pressure vessel design codes for anticipated maximum pressures, thereby ensuring that the constant-volume assumption used in analyzing temperature and pressure changes during the auto-thermal exothermic reaction is valid.Attorney Docket No.: 3229-8 PCT

[0081] In embodiments, the method 200 may further include selecting the oxidizing gas 4 from air or from mixtures of oxygen and nitrogen, or CO2, and controlling the mass of oxidizing gas 4 introduced at block 204 relative to the mass of the solid feedstock 3 loaded at block 202 so that an equivalence ratio less than about 0.1 is maintained. For example, the mass of oxygen added with the oxidizing gas 4 may be chosen to provide between about 2 percent and about 8 percent of the stoichiometric oxygen required to completely combust the solid feedstock 3 to carbon dioxide and water. This limitation on equivalence ratio ensures that the method 200 yields the carbonaceous solid product 5 with high fixed carbon content instead of complete combustion to gas and ash.

[0082] In embodiments, the method 200 may further include controlling the heating at block 206 so that the initiation temperature within the vessel 12 lies between about 140 °C and about 190 °C. Temperature sensors in thermal contact with the vessel 12 or located within the interior of the vessel 12 may be used to detect when this initiation temperature range is reached. The heating assembly 16 may be programmed to follow a specified ramp rate, such as between about 1 °C per minute and about 10 °C per minute, to reduce the risk of overshooting the initiation temperature and permit reproducible ignition behavior of the solid feedstock 3.

[0083] In embodiments, the method 200 may further include allowing the auto-thermal exothermic reaction in block 208 to increase a bulk temperature in the vessel 12 to a temperature between about 300 °C and about 650 °C and to increase an internal pressure in the vessel 12 to about 2500 psi, depending on the volume of the vessel 12, the mass and composition of the solid feedstock 3, and the quantity of oxidizing gas 4 charged at block 204. The resulting pressure profile as a function of time may exhibit a sharp peak correspondingAttorney Docket No.: 3229-8 PCT to the exothermic event, and the temperature profile may show a rapid rise followed by gradual cooling. These profiles can be used to characterize the reactivity of different types of solid feedstock 3.

[0084] In embodiments, the method 200 may further include selecting the solid feedstock 3 at block 202 from at least one of wood, cereal straw, polyolefins, rubber, paper, macro algae, or combinations thereof. Different solid feedstock 3 may be tested under otherwise comparable conditions. In addition, the method 200 may be implemented with solid feedstock 3 that includes mixtures of biomass and synthetic polymers, such as combinations of wood chips and polyolefins flakes, thereby modeling mixed waste streams.

[0085] In embodiments, the method 200 may further include loading at block 202 a solid feedstock 3 that includes a wet or saturated solid feedstock 3 containing water. The moisture content of the solid feedstock 3 may range from mildly moist materials with a few percent water up to fully saturated materials containing free water in pores and on surfaces. The method 200 allows the auto-thermal exothermic reaction to proceed without prior drying of such wet solid feedstock 3, demonstrating that the heat generated by reaction with the oxidizing gas 4 is sufficient to drive conversion to the carbonaceous solid product 5 while water is retained primarily in a condensed phase during at least a portion of the process, thereby avoiding the energetic cost associated with evaporating the majority of the water before conversion.

[0086] In embodiments, the method 200 may further include, after block 208, cooling the vessel 12 once the auto-thermal exothermic reaction has subsided, removing the carbonaceous solid product 5 from the vessel 12 as a biochar, pelletizing the biochar, and calcining the pelletized biochar to form shaped biocarbon product 6. Cooling of the vessel 12 may beAttorney Docket No.: 3229-8 PCT achieved by turning off or reducing the output of the heating assembly 16 and allowing natural convection to remove heat, or by applying forced air or liquid cooling to the exterior of the vessel 12. Once the vessel 12 has reached a safe temperature and pressure, the vessel 12 is opened or the product outlet 18 is actuated to discharge the carbonaceous solid product 5. The carbonaceous solid product 5 may then be ground using the grinder 36 to reduce particle size and improve packing behavior. The ground carbonaceous solid product 5 can be pelletized using the product extrusion area 38, for example by mixing with a binder and pressing or extruding through dies to form pellets, briquettes, or other shapes. These shaped bodies may then be calcined in a furnace under controlled atmospheres to further remove volatiles and enhance strength, thereby forming shaped biocarbon product 6 suitable for use in metallurgical and other high-temperature applications.

[0087] In embodiments, the method 200 may further include analyzing gas-phase products produced during the pressurized oxidative pyrolysis using the gas analysis device 22 fluidly connected to the vessel 12. After the vessel 12 has cooled to a suitable sampling temperature following block 208, the gas analysis device 22 may be connected via valves and sampling lines to the headspace of the vessel 12 to withdraw a representative gas sample. The gas analysis device 22 may be configured as a gas chromatograph with columns for separation of hydrogen, nitrogen, oxygen, carbon monoxide, carbon dioxide, and light hydrocarbons, and with detectors such as thermal conductivity detectors and flame ionization detectors. Data obtained from the gas analysis device 22 can be used to quantify yields of gaseous products and to assess the efficiency and selectivity of the method 200 for different solid feedstock 3 and oxidizing gas 4 conditions, and, in certain embodiments, the gaseous products are routed for beneficial use, including directing at least a portion of the gaseous products to pressurizeAttorney Docket No.: 3229-8 PCT a second vessel 12 arranged in series with the vessel 12 and / or directing at least a portion of the gaseous products to an engine or generator set to produce electrical power.

[0088] In certain embodiments, the pressurized oxidative pyrolysis system 10 and the method 200 are further used to produce an activated biocarbon or activated biochar by controlled pressurized oxidative pyrolysis conditions that increase internal porosity and surface area of the carbonaceous solid product 5. Activation can be achieved during the autothermal event or during a subsequent treatment step by selecting the oxidizing gas 4 composition, initial pressure, and equivalence ratio to promote partial oxidation and pore formation in the carbonaceous solid product 5 while maintaining the carbonaceous solid product 5 as a solid phase. This activation approach can be performed at comparatively low initiation temperatures and over short time intervals relative to conventional activation techniques, and can yield carbonaceous solid products 5 suitable for adsorption and related uses, including filtration, contaminant capture, gas separation, and electrochemical applications.

[0089] Referring to FIGS. 4A-9B, representative operating profiles and product properties obtained using the pressurized oxidative pyrolysis system 10 are shown for a range of solid feedstock 3 types, oxidizing gas 4 loadings, moisture levels, and fluidized sand bath 20 temperatures. In one set of representative conditions, the fluidized sand bath 20 is set to a relatively high external temperature of about 320 °C and the vessel 12 is charged with birch wood particles as the solid feedstock 3 (FIGS. 4A and 4B). When the oxidizing gas 4 is air at low oxygen equivalence ratio, the temperature and pressure histories inside the vessel 12 resemble those obtained with nitrogen alone, with gradual pressurization and heating largely governed by external heat from the fluidized sand bath 20. As the oxygen equivalence ratioAttorney Docket No.: 3229-8 PCT of the oxidizing gas 4 is increased, small pressure spikes appear, and at higher oxygen equivalence ratios pronounced auto-thermal events are observed in which the pressure in the vessel 12 rises from a few megapascals to values on the order of 6 to more than 10 megapascals in a time window of a few seconds, accompanied by rapid internal temperature increases. Further increases in the total initial pressure of the oxidizing gas 4, for example by adding nitrogen while maintaining the same oxygen equivalence ratio, sharpen these pressure spikes and demonstrate that elevated pressure in combination with sufficient oxygen loading promotes strong auto-thermal behavior. When the solid feedstock 3 is fully saturated with water at these higher sand bath 20 temperatures, the rate and magnitude of the pressure increase are moderated by the added thermal mass and phase change of water, although the pressurized oxidative pyrolysis system 10 still converts the solid feedstock 3 to a carbonaceous solid product 5 without a separate drying step.

[0090] Char yields and gas compositions measured under these higher sand bath 20 temperature conditions show that the carbonaceous solid product 5 typically has char yields in the range of roughly 40 to 55 percent on a dry basis, with volatile contents around 47 to 53 percent and fixed carbon contents around 46 to 50 percent. Fixed carbon yields are generally in the range of about 19 to about 27 percent. The gas analysis device 22 detects that nearly all of the oxygen in the oxidizing gas 4 is consumed, with the product gas dominated by carbon dioxide, substantial fractions of carbon monoxide, and smaller fractions of methane, together with nitrogen. Conditions that produce more rapid pressure and temperature excursions tend to yield higher carbon monoxide and methane fractions, while conditions with wetter solid feedstock 3 produce gas streams richer in carbon dioxide and lower in carbon monoxide. These observations indicate that both the intensity of the auto-thermal event and the moistureAttorney Docket No.: 3229-8 PCT content of the solid feedstock 3 influence the balance between partial oxidation, complete oxidation, and devolatilization pathways.

[0091] As depicted generally in FIGS. 5A-6F, in a second set of representative conditions, the fluidized sand bath 20 temperature is reduced to about 200 °C to more clearly identify oxidative onset behavior. For a range of wood species as the solid feedstock 3 and an oxidizing gas 4 mixture that includes oxygen and nitrogen at elevated initial pressure, the internal temperature in the vessel 12 rises gradually toward the sand bath 20 temperature and then exhibits a distinct onset of auto-thermal pressurized oxidative pyrolysis when the internal temperature reaches a threshold between about 165 °C and about 195 °C. At this onset, pressure in the vessel 12 rapidly increases to values on the order of 9 to 11 megapascals, and internal temperatures rise to peak values modestly above the sand bath 20 setpoint, typically between about 255 °C and about 270 °C under these conditions. Visual examination of the resulting carbonaceous solid product 5 shows that material near the bottom of the vessel 12 is more thoroughly carbonized, often exhibiting evidence of a transient plastic phase, while material near the top may remain partially carbonized. Adjusting the fill level of the vessel 12 so that the same oxygen charge corresponds to a higher equivalence ratio yields more extensively carbonized and more homogeneous carbonaceous solid product 5, consistent with more complete oxidative transformation of a smaller mass of solid feedstock 3.

[0092] Char yields at these lower sand bath 20 temperatures generally fall in the range of about 40 to about 60 percent, with volatile contents in the range of about 48 to about 60 percent and fixed carbon contents around 39 to 43 percent for fully loaded vessels. Reducing the mass of solid feedstock 3 for a given charge of oxidizing gas 4 lowers the char yield and increases the fixed carbon fraction, reflecting more extensive carbonization at higher oxygenAttorney Docket No.: 3229-8 PCT equivalence ratio. Adding moderate amounts of water to the solid feedstock 3 tends to increase char yield but reduce the fixed carbon fraction of the carbonaceous solid product 5, consistent with a portion of the exothermic energy being diverted to heat water and with less complete carbonization of the solid feedstock 3. Across these conditions, the fixed carbon yield remains relatively robust and demonstrates that the pressurized oxidative pyrolysis system 10 can generate substantial fixed carbon content even when operated at sand bath 20 temperatures near 200 °C.

[0093] In FIGS. 7A-8B, a third group of representative operating regimes focuses on the influence of oxygen partial pressure and feedstock moisture content in the pressurized oxidative pyrolysis system 10, again with eucalyptus wood as the solid feedstock 3 and the fluidized sand bath 20 set near 200 °C. At moderate oxygen partial pressure, internal temperatures rise above the sand bath 20 temperature and pressures increase modestly, indicating net exothermic behavior without a severe runaway event. As the oxygen partial pressure is increased while maintaining similar total pressure, the pressurized oxidative pyrolysis system 10 exhibits very rapid pressure and temperature spikes once the threshold onset temperature is reached, with maximum internal temperatures that can exceed 350 °C to 400 °C and pressures on the order of 14 megapascals in a matter of seconds. Under these high oxygen partial pressure conditions with low to moderate moisture content, the carbonaceous solid product 5 is highly carbonized and visually homogeneous, and large portions of the bed show evidence of transient plastic phase transition that is beneficial for downstream densification into the shaped biocarbon product 6. When significant amounts of water, for example 20 to 40 weight percent, are added to the solid feedstock 3 at similar oxygen loading, the pressurized oxidative pyrolysis system 10 still exhibits rapid onset behavior, but the peakAttorney Docket No.: 3229-8 PCT temperatures and pressures are reduced and the onset temperature shifts upward relative to the sand bath 20 temperature. The additional water moderates the exotherm, increases the char yield, and produces carbonaceous solid product 5 with higher volatile content and lower fixed carbon fraction, which is reflected in thermogravimetric analysis as increased mass loss in the 300 °C to 400 °C range.

[0094] Gas analyses under these oxygen and moisture variation conditions show that residual oxygen in the product gas remains low across a broad range of cases, confirming that the oxidizing gas 4 continues to be consumed efficiently. Carbon dioxide, carbon monoxide, and methane dominate the gas phase, with carbon monoxide and methane fractions generally increasing with higher oxygen loading and decreasing with higher moisture content in favor of carbon dioxide. The combined carbon monoxide and methane fractions in drier cases can approach levels that make energy recovery from the gas phase attractive at scale. Comparisons between measured pressure temperature trajectories and ideal gas predictions demonstrate that once the pressurized oxidative pyrolysis system 10 passes the oxidative onset threshold, pressure rises much faster than would be expected from heating alone, indicating rapid gas generation within the vessel 12 as the solid feedstock 3 reacts. Immediately following the pressure peak, pressure declines while internal temperature continues to rise, consistent with continued heat release accompanied by consumption of gaseous oxidant, dissolution of gas into pores, and redistribution of gas within the carbonaceous solid product 5.

[0095] As shown in FIGS. 9 A and 9B, mechanical testing of pelletized and calcined shaped biocarbon product 6 formed from selected carbonaceous solid product 5 generated under these more strongly auto-thermal conditions shows that the shaped biocarbon product 6 exhibits tensile strengths in the tens of megapascals and apparent densities approaching orAttorney Docket No.: 3229-8 PCT exceeding one gram per cubic centimeter. Moisture addition during pressurized oxidative pyrolysis generally increases the strength and density of the shaped biocarbon product 6 up to a point, with very high moisture loadings sometimes reducing tensile strength while maintaining or slightly increasing density. The measured mechanical properties of the shaped biocarbon product 6 compare favorably with ranges reported for metallurgical and anode cokes, which indicates that the pressurized oxidative pyrolysis system 10 can generate molded biocarbon materials that are strong and dense enough for use as partial or full replacements for fossil derived reductants and anode materials in metallurgical and energy applications.

[0096] Referring now to FIGS. 10A-12, representative results are shown for pressurized oxidative pyrolysis conducted in the pressurized oxidative pyrolysis system 10 when the solid feedstock 3 includes biomass impregnated with dissolved metal salts. In one set of embodiments, spruce wood particles are used as the solid feedstock 3 and are either untreated or incipient wetness impregnated in aqueous solutions of iron, copper, or nickel salts to introduce controlled quantities of Fe2+, Cu2+, or Ni2into the pores and cell structure of the solid feedstock 3 before loading into the vessel 12. The oxidizing gas 4 is air at several initial pressures, for example about 3.1, about 4.1, and about 5.2 megapascals, and the fluidized sand bath 20 establishes a uniform external temperature as described above. Temperature-pressure profiles recorded inside the vessel 12 show that the presence and identity of the dissolved metal salt in the solid feedstock 3 strongly influence the onset temperature for auto-thermal pressurized oxidative pyrolysis, the magnitude of the pressure spike, and the balance between heat release and gas generation.

[0097] As depicted in FIGS. 10A and 10B, when the solid feedstock 3 contains about 1.25 weight percent iron (expressed as Fe2+on a dry biomass basis), the auto-thermal onsetAttorney Docket No.: 3229-8 PCT temperature for the exothermic reaction between the oxidizing gas 4 and the solid feedstock 3 is reduced by on the order of several tens of degrees Celsius relative to metal free spruce. Representative onset temperatures that are near about 195 °C for untreated spruce are reduced to values in the range of about 130 °C to about 175 °C when the same oxidizing gas 4 pressures are applied to iron impregnated solid feedstock 3. At the same time, the pressure rise associated with the auto-thermal event increases by roughly a factor of two across the air pressure range, with pressure increments that may grow from a few megapascals for untreated spruce to more than ten megapascals for iron impregnated spruce at the highest initial air pressure. These results indicate that iron in the solid feedstock 3 acts as a strong catalyst for pressurized oxidative pyrolysis, lowering the threshold temperature for onset while favoring more extensive gas generation under constant-volume conditions

[0098] Comparison of the peak pressure and maximum internal temperature suggests that conditions with higher pressure generation often display somewhat lower peak internal temperatures, which is consistent with a portion of the exothermic energy being consumed by endothermic volatile release and gas formation reactions, including thermal cracking pathways, rather than being directed solely into further heating of the vessel 12 contents.

[0099] FIGS. 10A-11B further illustrate that when the solid feedstock 3 contains other metal species at similar loadings, the behavior of the pressurized oxidative pyrolysis system 10 is metal specific. Copper addition at about 1.25 weight percent reduces the onset temperature relative to metal free spruce to values similar to those achieved with iron, indicating that copper also promotes earlier auto-thermal onset. However, the resulting pressure spike is lower than that observed for iron at the same air pressure, and the maximum internal temperature is higher, suggesting a different balance between gas formation and heatAttorney Docket No.: 3229-8 PCT retention in the vessel 12. In contrast, nickel addition at similar loading does not significantly reduce the onset temperature relative to untreated spruce and yields lower peak pressures and lower peak temperatures. In these nickel impregnated cases, the pressurized oxidative pyrolysis system 10 still consumes oxygen and converts the solid feedstock 3 to a carbonaceous solid product 5, but the reaction pathway appears less vigorous and less strongly auto-thermal.

[0100] Gas phase analyses for these metal modified conditions, summarized schematically in FIG. 11, show that the gas analysis device 22 detects product gases dominated by nitrogen and carbon dioxide, with measurable fractions of carbon monoxide and methane and low residual oxygen across metal free and metal containing cases. At a given air pressure, the introduction of about 1.25 weight percent iron into the solid feedstock 3 modestly increases the methane fraction and can increase carbon monoxide relative to metal free conditions, while maintaining significant carbon dioxide fractions, and increases the total product gas volume. Copper addition at similar loading yields gas streams with elevated methane and altered carbon dioxide and nitrogen fractions, while nickel addition tends to produce gas compositions with relatively lower carbon monoxide and methane and higher nitrogen fractions. Increasing the iron loading to higher values, for example around 2.5 weight percent, further increases methane generation and gas volume but begins to diminish the structural properties of the resulting shaped biocarbon product 6, as discussed below.

[0101] For metal free spruce under increasing initial air pressure, the shaped biocarbon product 6 exhibits biocarbon yields on the order of 50 to nearly 60 percent, apparent densities near about 0.95 to about 1.02 grams per cubic centimeter, and tensile strengths on the order of 13 to 16 megapascals, which already place the shaped biocarbon product 6 at or aboveAttorney Docket No.: 3229-8 PCT strength levels reported for some metallurgical cokes. Iron addition at about 1.25 weight percent maintains similar biocarbon yields and densities but reduces tensile strength to values in the mid-single digit to low double digit megapascal range under otherwise similar conditions, which indicates that although iron catalyzes pressurized oxidative pyrolysis and lowers onset temperature, it can lead to more friable shaped biocarbon product 6 in some regimes. Copper addition at about 1.25 weight percent at elevated initial air pressure generates a shaped biocarbon product 6 with both high yield and significantly enhanced density, for example apparent densities around or above 1.2 grams per cubic centimeter, and tensile strengths that can exceed 30 megapascals. This combination of high strength and high density indicates that copper containing carbonaceous solid product 5 can be transformed into shaped biocarbon product 6 with mechanical properties that are comparable to or better than some conventional baked fossil anode materials. Nickel containing samples at similar loading tend to show lower tensile strength and only modest density changes, and samples with higher iron loadings, for example about 2.5 weight percent, exhibit substantial reductions in density and tensile strength, suggesting that excessive iron can disrupt the carbon matrix and limit mechanical performance.

[0102] As shown in FIG. 12, structural characterization of the carbon metal composite carbonaceous solid product 5 formed from metal impregnated solid feedstock 3 shows that the metal is retained in reduced or carbide forms rather than as simple oxides. X-ray diffraction patterns reveal that iron impregnated cases yield carbonaceous solid product 5 in which the dominant iron phase is an orthorhombic iron carbide, sometimes referred to as cohenite, embedded within the carbon matrix. Nickel and copper impregnated cases yield carbonaceous solid product 5 where nickel and copper appear primarily as reduced metallicAttorney Docket No.: 3229-8 PCT phases. Oxide phases are not strongly evident in these diffraction patterns, which suggests that pressurized oxidative pyrolysis under the specified low equivalence ratio and high pressure conditions drives reduction and carbothermal reduction rather than stabilizing simple oxides. In copper containing cases, graphitic peaks are relatively weak, which indicates that the carbon matrix remains largely non graphitized under the tested conditions even when the shaped biocarbon product 6 exhibits high mechanical strength and density.

[0103] Taken together, the temperature pressure histories, gas composition data, mechanical property measurements, and phase analyses in FIGS. 10-12 show that incorporation of selected dissolved metal salts into the solid feedstock 3 provides an additional degree of control over pressurized oxidative pyrolysis in the pressurized oxidative pyrolysis system 10. Iron and copper in particular reduce the onset temperature for the auto-thermal reaction between the oxidizing gas 4 and the solid feedstock 3, increase pressure generation under constant-volume conditions, and generate carbon metal composite forms of the carbonaceous solid product 5 that can be processed into shaped biocarbon product 6 with tailored strength and density. By adjusting metal identity and loading, along with air pressure, equivalence ratio, and moisture content, an operator can tune both the thermochemical response of the vessel 12 and the microstructure and performance of the resulting biocarbon and carbon metal composite products.

[0104] Referring to FIG. 13, a controller 300 is configured to manage and coordinate operation of the pressurized oxidative pyrolysis system 10, including preparation and processing steps of method 200 as well as subsystems such as the vessel 12, the gas inlet 14 and associated pressurizing valve 30, the heating assembly 16 including any fluidized sand bath 20, the hopper 24, the screw feed 26, the rotating valve 28, the heat source 32, theAttorney Docket No.: 3229-8 PCT pressure relief valve 34, the product outlet 18, the grinder 36, the product extrusion area 38, and the gas analysis device 22. The controller 300 is provided to automate, supervise, and log the sequence of operations that transform the solid feedstock 3 into the carbonaceous solid product 5 under controlled pressurized oxidative pyrolysis conditions, and to enforce safety limits on temperature and pressure within the vessel 12.

[0105] The controller 300 includes a processor 320 operatively connected to a memory 330 and to storage 310. The memory 330 may include volatile memory elements, such as random access memory, and non-volatile memory elements, such as flash memory, magnetic disk, optical storage, or solid-state drives, and is configured to store computer-readable instructions, configuration parameters, and real-time operating data. The processor 320 may include one or more microprocessors, digital signal processors, central processing units, application-specific integrated circuits, or field-programmable gate arrays 350. In certain embodiments, the processor 320 and the memory 330 are integrated within a single embedded control module of the controller 300; in other embodiments, the memory 330 and the storage 310 are located on separate boards or devices electrically connected to the processor 320 by high-speed buses or cabling. The storage 310 may retain longer-term data such as historical temperature and pressure profiles, batch records, feedstock identifiers, calibration tables, process recipes, and maintenance logs associated with the pressurized oxidative pyrolysis system 10.

[0106] The controller 300 may further include a network interface 340 configured to provide wired or wireless communication between the pressurized oxidative pyrolysis system 10 and external devices. The network interface 340 can support Ethernet, industrial fieldbuses, serial links, or wireless standards. Through the network interface 340, the controller 300 mayAttorney Docket No.: 3229-8 PCT exchange data with local supervisory computers, distributed control modules in a plant-wide system, or remote servers used for monitoring, diagnostics, or data archiving. In some embodiments, the network interface 340 allows remote access to adjust process setpoints, download updated control algorithms to the memory 330, or retrieve historical data from the storage 310, subject to appropriate security and safety constraints.

[0107] The memory 330 stores instructions that, when executed by the processor 320, operate the controller 300 to coordinate and control the subsystems of the pressurized oxidative pyrolysis system 10. These instructions may implement a sequence that corresponds to method 200, including loading of the solid feedstock 3 into the vessel 12 at block 202, introduction of the oxidizing gas 4 through the gas inlet 14 at block 204, controlled heating of the vessel 12 by the heating assembly 16 at block 206, and monitoring of the auto-thermal exothermic reaction and the resulting increase in temperature and pressure at block 208. Control logic stored in the memory 330 may define process recipes specifying target initial pressures for the oxidizing gas 4, equivalence ratios relative to the solid feedstock 3, desired initiation temperature ranges, maximum allowable temperatures and pressures within the vessel 12, and timing for subsequent cooling, discharge, grinding, pelletizing, and calcination steps applied to the carbonaceous solid product 5.

[0108] In representative operation, the controller 300 receives sensor inputs from temperature and pressure devices associated with the vessel 12, from flow and pressure sensors associated with the gas inlet 14 and the pressurizing valve 30, and from position or speed feedback sensors associated with the hopper 24, the screw feed 26, the rotating valve 28, the grinder 36, and the product extrusion area 38. The processor 320 executes algorithms to interpret these sensor inputs and to generate control signals that actuate heating elementsAttorney Docket No.: 3229-8 PCT in the heating assembly 16, open or close the pressurizing valve 30, start or stop drive motors for the screw feed 26, adjust operating speeds for the grinder 36, and control forming operations in the product extrusion area 38. Through these actions, the controller 300 can regulate the rate of loading of the solid feedstock 3, the quantity and timing of introduction of the oxidizing gas 4, the thermal ramp to the initiation temperature, and the downstream handling of the carbonaceous solid product 5.

[0109] The controller 300 may be configured to monitor the temperature within or on the vessel 12 during heating and to detect when the initiation temperature associated with onset of the auto-thermal exothermic reaction has been reached. For example, the memory 330 may store threshold values for the initiation temperature, such as between about 140 °C and about 190 °C, and the processor 320 may compare measured temperatures to these thresholds to determine when to reduce or hold output from the heating assembly 16. In some embodiments, the controller 300 may also analyze the rate of change of pressure or temperature in the vessel 12 to recognize the beginning of the exothermic event, and may respond by preventing further increases in heater power, logging the time of onset, and verifying that the pressure remains within predefined safety limits as the auto-thermal exothermic reaction proceeds.

[0110] The controller 300 may also implement safety functions for the pressurized oxidative pyrolysis system 10. The memory 330 may store maximum allowable pressures and temperatures for safe operation of the vessel 12, and the processor 320 may continuously compare measured values against these limits. If a pressure near the design limit of the vessel 12 is detected, the controller 300 may automatically de-energize the heating assembly 16 and inhibit further introduction of the oxidizing gas 4 through the gas inlet 14 and the pressurizing valve 30. The controller 300 may also issue alarms or notifications via the network interfaceAttorney Docket No.: 3229-8 PCT340 or local user interfaces before, during, and after an auto-thermal exothermic event. While the pressure relief valve 34 may be a mechanical or passive safety component, the controller 300 can still monitor related pressure signals to verify that pressure is decreasing after activation of the pressure relief valve 34 or after completion of the auto-thermal reaction.

[0111] The processor 320 can execute algorithms for temperature and pressure control within the vessel 12, for flow and pressure management within the gas inlet 14, and for sequencing of material handling operations associated with the hopper 24, the screw feed 26, the rotating valve 28, the product outlet 18, the grinder 36, and the product extrusion area 38. For example, the controller 300 may start the screw feed 26 and the rotating valve 28 only when the vessel 12 is at atmospheric pressure and in a safe loading configuration, then close the rotating valve 28 and seal the vessel 12 prior to block 204. Similarly, once block 208 is complete and the vessel 12 has cooled to a prescribed temperature and been depressurized, the controller 300 may open or actuate the product outlet 18 and start the grinder 36 to process the carbonaceous solid product 5, followed by operation of the product extrusion area 38 to form shaped biocarbon products 6.

[0112] The controller 300 may also coordinate the gas analysis functions associated with the gas analysis device 22. After the auto-thermal exothermic reaction has completed and the vessel 12 has reached a temperature suitable for sampling, the controller 300 may open one or more valves connecting the vessel 12 to the gas analysis device 22, manage sampling timing, and log measured gas compositions. The processor 320 can associate gas composition data with specific runs, solid feedstock 3 types, oxidizing gas 4 parameters, temperature and pressure histories, and resulting properties of the carbonaceous solid product 5, all of which can be stored in the storage 310 for later analysis and quality control.Attorney Docket No.: 3229-8 PCT

[0113] The memory 330 may further store advanced data processing algorithms that, when executed by the processor 320, analyze trends in temperature, pressure, and gas composition over many cycles of method 200 to optimize performance of the pressurized oxidative pyrolysis system 10. For example, the controller 300 may adjust heating rates of the heating assembly 16 or target initiation temperatures to refine the extent of conversion of the solid feedstock 3 to the carbonaceous solid product 5. or to tailor the formation of biochar versus carbon-metal composite structures in the carbonaceous solid product 5. Historical data recorded in the storage 310 can be used to identify reproducibility and stability of operation, to schedule maintenance actions, and to document performance characteristics for different types of solid feedstock 3.

[0114] Through execution of instructions stored in the memory 330 by the processor 320, the controller 300 can also schedule repeated cycles of method 200. For batch operation, the controller 300 may wait for confirmation that the vessel 12 has been reloaded with the solid feedstock 3 at block 202, then automatically proceed through blocks 204, 206, and 208, followed by optional cooling, discharge, grinding, pelletizing, and calcination sequences. For semi-continuous embodiments, the controller 300 may implement a repeating pattern of loading and discharge with partial overlapping timelines, while maintaining strict adherence to safety and constant- volume requirements during each pressured oxidative pyrolysis event.

[0115] The network interface 340, under control of the processor 320 and instructions in the memory 330, may be used to transmit summary data, alarms, and status information to remote monitoring systems. Operators may use external systems to review real-time plots of vessel 12 temperature, vessel 12 pressure, heater output from the heating assembly 16, flow or state of the oxidizing gas 4 at the gas inlet 14 and the pressurizing valve 30, and materialAttorney Docket No.: 3229-8 PCT handling states at the hopper 24, the screw feed 26, the rotating valve 28, the product outlet 18, the grinder 36, and the product extrusion area 38. The storage 310 may archive full time series data and batch records over extended periods, providing a basis for long-term performance evaluation, process improvement, and regulatory or customer reporting.

[0116] Certain embodiments of the present disclosure may include some, all, or none of the above 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 embodiments of the present disclosure may include all, some, or none of the enumerated advantages and / or other advantages not specifically enumerated above.

[0117] The embodiments disclosed herein are examples of the disclosure and may be embodied in various forms. For instance, although certain embodiments herein are described as separate embodiments, each of the embodiments herein may be combined with one or more of the other embodiments 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.

[0118] The phrases “in an embodiment.” “in embodiments,” “in various embodiments,” “in some embodiments,” or “in other embodiments” may each refer to one or more of the same or different example embodiments 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).”Attorney Docket No.: 3229-8 PCT

[0119] 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 embodiments 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 described above and / or in the appended claims are also intended to be within the scope of the disclosure.

Claims

Attorney Docket No.: 3229-8 PCTWHAT IS CLAIMED IS:

1. A pressurized oxidative pyrolysis system comprising: a vessel configured to contain a solid feedstock and a gas phase; a gas inlet in fluid communication with the vessel and configured to introduce an oxidizing gas into the vessel at an initial pressure; a heating assembly thermally coupled to the vessel and configured to raise a temperature of the solid feedstock while the vessel remains closed; and a product outlet configured to permit removal of a carbonaceous solid product from the vessel after heating, wherein an exothermic reaction between the oxidizing gas and the solid feedstock during heating supplies heat for conversion of the solid feedstock to the carbonaceous solid product.

2. The system of claim 1, wherein the vessel is a closed constant- volume reactor vessel operated under constant-volume conditions.

3. The system of claim 1, wherein the oxidizing gas comprises at least one of air, a mixture of oxygen and nitrogen, or CO2, and wherein an equivalence ratio between the oxidizing gas and the solid feedstock is between about 0.03 and about 0.4.

4. The system of claim 1, wherein the heating assembly is configured to rapidly raise a temperature at a surface of the solid feedstock to a temperature between about 300 °C and about 650 °C.Attorney Docket No.: 3229-8 PCT5. The system of claim 1 , wherein the heating assembly comprises a fluidized sand bath configured to at least partially immerse the vessel.

6. The system of claim 1, wherein the solid feedstock comprises at least one of wood, cereal straw, polyolefins, rubber, paper, macro algae, biocarbons, herbaceous plants, or a combination thereof.

7. The system of claim 1, wherein the solid feedstock comprises a wet or saturated feedstock containing water.

8. The system of claim 1, wherein the solid feedstock comprises a mixture of biomass and a synthetic polymer.

9. The system of claim 1, wherein the solid feedstock comprises a biomass material containing at least one of a dissolved or dispersed metal salt, a transition metal, an alkali earth metal, or a rare earth metal, and wherein the carbonaceous solid product comprises a carbon-metal composite.

10. The system of claim 1, wherein the carbonaceous solid product comprises a biochar configured for pelletization and calcination to form a shaped biocarbon product.

11. A method for pressurized oxidative pyrolysis of a solid feedstock, comprising: loading the solid feedstock into a vessel; introducing an oxidizing gas into the vessel to establish an initial pressure while maintaining the vessel closed;Attorney Docket No.: 3229-8 PCT heating the vessel to trigger an auto-thermal exothermic reaction between the oxidizing gas and the solid feedstock; and increasing a temperature and a pressure in the vessel via the auto-thermal exothermic reaction to convert the solid feedstock to a carbonaceous solid product and a volume of product gases.

12. The method of claim 11, wherein the vessel is a closed constant- volume reactor vessel operated under constant-volume conditions.

13. The method of claim 11, wherein the oxidizing gas comprises at least one of air, a mixture of oxygen and nitrogen, or CO2, and wherein an equivalence ratio between the oxidizing gas and the solid feedstock is between about 0.03 and about 0.4.

14. The method of claim 11, wherein an initiation temperature is between about 140 °C and about 190 °C.

15. The method of claim 11, wherein the auto-thermal exothermic reaction increases a bulk temperature in the vessel to a temperature between about 300 °C and about 650 °C and increases an internal pressure in the vessel to about 2500 psi.

16. The method of claim 11, wherein the solid feedstock comprises at least one of wood, cereal straw, polyolefins, rubber, paper, macro algae, biocarbons, herbaceous plants, or a combination thereof.Attorney Docket No.: 3229-8 PCT17. The method of claim 11 , wherein the solid feedstock comprises a wet or saturated feedstock containing water.

18. The method of claim 11, further comprising: cooling the vessel after the auto-thermal exothermic reaction; removing the carbonaceous solid product as a biochar from the vessel; pelletizing the biochar; and calcining the pelletized biochar to form a shaped biocarbon product.

19. The method of claim 11, further comprising analyzing gas-phase products produced during the pressurized oxidative pyrolysis using a gas analysis device fluidly connected to the vessel.

20. A pressurized oxidative pyrolysis system for producing a shaped biocarbon product, comprising: a hopper configured to receive a solid carbon-containing feedstock; a screw feed configured to convey the solid carbon-containing feedstock from the hopper; a rotating valve positioned downstream of the screw feed and upstream of a closed constant-volume reactor vessel and configured to admit the solid carbon-containing feedstock into an interior of the closed constant- volume reactor vessel; the closed constant-volume reactor vessel configured to contain the solid carbon- containing feedstock and a gas phase; a gas inlet in fluid communication with the closed constant-volume reactor vessel comprising a pressurizing valve configured to charge the closed constant- volume reactor vesselAttorney Docket No.: 3229-8 PCT with an oxidizing gas comprising air at a pressure between about 450 psi and about 2500 psi; a heating assembly thermally coupled to the closed constant-volume reactor vessel and configured to heat the closed constant-volume reactor vessel from an initiation temperature between about 140 °C and about 190 °C while the closed constant-volume reactor vessel is maintained closed; an ignition wire extending into the closed constant-volume reactor vessel and configured to initiate an exothermic reaction between the oxidizing gas and the solid carbon-containing feedstock; a pressure relief valve in fluid communication with the closed constant-volume reactor vessel and configured to vent gas from the closed constant- volume reactor vessel when an internal pressure exceeds a predetermined limit; a product outlet configured to discharge a carbonaceous solid product from the closed constant- volume reactor vessel; a grinder configured to grind the carbonaceous solid product; and a product extrusion area configured to receive the ground carbonaceous solid product from the grinder and to extrude the ground carbonaceous solid product into a shaped biocarbon product, wherein, during operation, the exothermic reaction between the oxidizing gas and the solid carbon-containing feedstock auto-thermally increases a temperature in the closed constant-volume reactor vessel to between about 300 °C and about 650 °C under constant-volume conditions to form the carbonaceous solid product.

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