PROCESS AND SYSTEM FOR MOBILE PYROLYSIS OF BIOMASS FOR BIOCHAR PRODUCTION

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The application claims priority to and incorporates by reference U.S. provisional application 63/969,242 filed on Sep. 18, 2024.

FIELD

The present invention relates generally to a method and apparatus for the continuous production of carbonaceous pyrolysis products. More particularly, the present invention relates to a method and apparatus for the mobile production of biochar from agricultural residues.

BACKGROUND

Biochar is a solid carbon product produced from the pyrolysis of biomass used as a soil amendment and carbon removal medium. Pyrolysis is the chemical transformation or decomposition of chemical compounds caused by heat. It occurs spontaneously at temperatures in the range of 300° to 800° C. and produces certain by-products such as carbonized biomass, combustible gaseous and volatile organic compounds (VOC's) known as tars. Biochar can be produced from a range of biomass materials including wood, tree bark, vegetable biomass, paper and cardboard waste, food waste, and agricultural residues. While agricultural residues are abundant and low cost, difficulty in collection, transport, and conversion have limited their use as a biochar feedstock.

Pyrolysis has been used as a method for producing carbonized materials for centuries. The pyrolysis process typically occurs in a stationary kiln or in a retort. A kiln is a thermally insulated chamber in which the oxygen available for combustion is restricted. A retort utilizes an outer space where pyrolysis products or other fuels are burned to provide energy to a central space where biomass is pyrolyzed without oxygen. Batch kilns and retorts are simple to construct but require loading and unloading between production cycles and are time intensive to produce char. Stationary production methods are also limited in which feedstocks can be used and require transportation of feedstocks and product biochar. Moreover, without adequate flaring or burn-off of gaseous by-products, these methods can produce a large amount of air pollutants.

The thermochemical pathways to producing biochar are fast pyrolysis and slow pyrolysis. Many other methods, such as microwave pyrolysis and vacuum pyrolysis, exist but are not directly relevant to this application. The focus of most industrial biomass pyrolysis operations has been to produce pyrolysis gases and/or oils with charcoal as a byproduct. Both fast and slow pyrolysis require an oxygen free environment, requiring the process to be carried out in a closed reactor. When the reactor fills with pyrolysis gases which result from thermal decomposition of biomass (primarily H2, CO, CO₂ and CH₄) a significant explosion hazard is created which demands a higher engineering and production cost to ensure the safety of personnel working with the equipment. In addition, one of the primary by-products of pyrolysis is an oil composed of various compounds including high percentages of oxygenated hydrocarbons and poly-nuclear aromatics. These oils are hazardous to tissues and the environment and are a substantial environmental hazard.

Examples of apparatus for producing charcoal are numerous. A historical example is U.S. Pat. No. 757,939 issued Apr. 19, 1904, to Mackie for “Apparatus for the distillation of Wood.” The apparatus described is an inclined retort contained within a kiln and adapted for pyrolysis of wood. The retort includes a drainpipe at one end thereof for collecting the pyrolysis by-products and condensing them in a suitable collector. As can be seen from the configuration of the system, it is a batch-type operation which requires loading, sealing, heating, unsealing, and unloading the retort-a very time-consuming process.

A more recent example, U.S. Pat. No. 6,790,317 issued Sep. 14, 2004, to Anatal for “Process for Flash Carbonization of Biomass.” Anatal discloses a process for the low energy input pyrolytic conversion of biomass in an atmosphere of pressurized air. Again, the process is not continuous, and moreover, the process disclosed by Anatal produces a product charcoal that has a higher content of volatiles than a biochar produced at atmospheric pressure.

Air quality is also a primary concern. The pyrolysis process produces a large mass of gases that can be considered air pollutants, specifically CO, CH₄ and higher hydrocarbons. If these gases are not properly combusted, they can present a significant air quality and greenhouse gas risk. Many gasification and pyrolysis units are operated either at such a small scale (camp stoves, two-barrel retort) that production of a substantial amount of char for a commercial user is impractical or at such a large scale that feedstocks must be transported over substantial distances to the processing facility. At the end of the production cycle, the carbonized material must also be transported to the end use site. In such cases, the materials transportation costs quickly become prohibitively expensive, or the CO₂ emissions of transportation become larger than the carbon removed by the product.

To address costs of biomass transportation, U.S. Pat. No. 9,505,984B2 issued May 5, 2011, describes a process for producing pyrolytic carbons using partial oxidation of pyrolysis gases in situ to provide energy. The patent describes a mobile unit which operates in a stationary configuration and was targeted at processing wood wastes from forestry operations.

In view of the foregoing, it is apparent that a need exists for a process and apparatus which is capable of safely, economically, and continuously producing carbonaceous and gaseous pyrolysis by-products for soil amendment, from a wide variety of agricultural feedstocks and which operate both in stationary, edge-of-field and in-field, on-the-fly modes. U.S. Pat. No. 11,465,948B2, issued Jul. 21, 2021, describes a system for mobile, in field biochar production. This application builds on the foundation of U.S. Pat. No. 11,465,948B2 with several significant improvements in process and method.

SUMMARY

A system and method of biomass pyrolysis for biochar production. A mobile pyrolysis and oxidizer apparatus is moved through a field of biomass. The mobile apparatus includes a first reactor and a second reactor. The first reactor is coupled to the second reactor via a syngas channel. The first reactor is heated to a first temperature, at least in part, using a syngas via the syngas channel. The second reactor is heated to a second temperature, at least in part, using the syngas via the syngas channel. In some modes of operation, wherein the second temperature is a temperature that is a higher temperature than the first temperature. Collected biomass is conveyed as feedstock through the first reactor and then through the second reactor. The feedstock is torrefied via first rector, and a portion of the feedstock is pyrolyzed via the second reactor.

The appended claims may serve as a summary of this application.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an embodiment of a forage harvester, tractor and pyrolysis and oxidizer apparatus.

FIGS. 2A-2B are diagrams illustrating a process according to some embodiments.

FIGS. 3A-3B are diagrams illustrating a multi-stage control process according to some embodiments.

FIG. 4 is a diagram illustrating a method according to some embodiments.

DETAILED DESCRIPTION OF THE DRAWINGS

In this specification, reference is made in detail to specific embodiments of the invention. Some of the embodiments or their aspects are illustrated in the drawings.

For clarity in explanation, the invention has been described with reference to specific embodiments, however it should be understood that the invention is not limited to the described embodiments. On the contrary, the invention covers alternatives, modifications, and their equivalents as may be included within its scope as defined by any patent claims. The following embodiments of the invention are set forth without any loss of generality to, and without imposing limitations on, the claimed invention. In the following description, specific details are set forth in order to provide a thorough understanding of the present invention. The present invention may be practiced without some or all of these specific details. In addition, well-known features may not have been described in detail to avoid unnecessarily obscuring the invention.

In addition, it should be understood that steps of the exemplary methods set forth in this exemplary patent can be performed in different orders than the order presented in this specification. Furthermore, some steps of the exemplary methods may be performed in parallel rather than being performed sequentially. Also, the steps of the exemplary methods may be performed in a network environment in which some steps are performed by different computers in the networked environment.

The system described herein is a process and the accompanying equipment for the thermal conversion of in-field agricultural residues into biochar for direct application for use as a soil amendment and carbon removal medium.

FIG. 1 is a diagram illustrating an embodiment of a forage harvester, tractor and pyrolysis and oxidizer apparatus. The system, as shown in FIG. 1 comprises three components: the Prime Mover (101) is a tractor which supplies locomotive power and control as well as hydraulic and mechanical power to other systems, the Forage Harvester (102) collects the in-field biomass and conveys it to the Pyrolysis Trailer (103) which converts harvested residues into biochar, quenches and deploys produced biochar, and cleanly combusts produced pyrolysis gases. The figure shown is one example of multiple potential embodiments in which the elements of power, harvesting, and conversion utilize three separate modules. Embodiments in which elements are combined into two or one modules are also considered in this invention.

FIGS. 2A-2B are diagrams illustrating a process performed by the system according to some embodiments. The process works as follows: The system, shown in FIGS. 2A-2B, is moved through an agricultural field (such as corn field, rice field, sorghum field, or other row crop field), driven and powered by a Prime Mover (201) which supplies mechanical, hydraulic, and electrical power as well as control. Biomass residues (203) are collected by the Forage Harvester (205) which chops and sizes incoming biomass to a target size. Sized biomass is conveyed pneumatically through a Capacitive Flowmeter (207) to an Impact Plate Flowmeter (209) before collection in the Input Hopper (211). Measurements from the Capacitive Flowmeter (207) and Impact Plate Flowmeter (209) are compared to provide information on incoming feedstock moisture content and other properties.

Feedstock from the Input Hopper (211) is conveyed through the Input Airlock (213) into Reactor 1 (215). Reactor 1 is heated through a combination of the Reactor 1 Burner (217), recirculated pyrolysis gases (219), and Air Injection (221) which react with produced and recycled pyrolysis gases in a partial oxidation reaction. In practice, a burner may be used to externally oxidize recycled pyrolysis gases, outside of reactor 1. Biomass and gases move through Reactor 1 (215) in a co-current configuration. As the biomass moves through Reactor 1 (215), via two auger screws the biomass material experiences a torrefaction process at reactor temperatures between 200-400° C., reaching temperatures between 100-400° C. Pyrolysis gases, or Reactor 1 Syngas (223), produced in Reactor 1 (215) are removed via suction from the Syngas Blower (225) and mixed with Reactor 2 Syngas (227). Torrefied material is gravity fed into Reactor 2 (231).

Reactor 2 (231) is heated through a combination of the Reactor 2 Burner (233), recirculated pyrolysis gases (219), and Air Injection (235) which reacts with produced pyrolysis gases in a partial oxidation reaction. Torrefied biomass and gases move through Reactor 1 (215) in a counter-current configuration. As the torrefied biomass moves though Reactor 2 (215), via two auger screws the biomass material is pyrolyzed at reactor temperatures between 500-800° C., reaching material temperatures between 400-600° C. Pyrolyzed biochar exits Reactor 2 (231) through the Outlet Airlock (237) into the Quencher (239) where it is cooled with Water (241) before weight measurement at an outlet Load Cell (243) and discharge to a Spreader (245). Reactor 2 Syngas (227), produced in Reactor 2 (231) is removed via suction from the Syngas Blower (225) and mixed with Reactor 1 Syngas (223) to form a Combined Syngas Stream (229).

The Combined Syngas Stream (229) is motivated to a Cyclone (247), where larger particles are removed and then to a Thermal Oxidizer (249) to cleanly combust all pyrolysis products. Entrained char from the syngas is removed by the Cyclone (247) through the Cyclone Airlock (251) and quenched with water (241) before being disposed to the ground directly or through a spreader or mixer.

The Thermal Oxidizer (249) combusts pyrolysis gases in the Combined Syngas Stream (229) using air from the Air Blower (251) and ignition from the Thermal Oxidizer Burner (257). The Thermal Oxidizer Burner may be any burner capable of initiating combustion in the Thermal Oxidizer (249), but practically a multi-fuel, modulating burner is the ideal choice.

The control methodology, which is key to the operation of the invention, consists of a series of feedback loops and predictive control algorithms which control reaction conditions based on sensor data and prior run data. The system described herein is thermally self-sustaining, utilizing the chemical energy from oxidation of pyrolysis gases to drive the process through partial oxidation. In order to start the system, external energy is required, creating a need for multiple, distinct control conditions. Separating process stages into multiple distinct conditions allows for fine tuning of control based on the specific thermochemical reactions occurring at each stage. At minimum, four control stages are described, although the process may be divided into eight or more distinct control stages. The minimum four stages are Preheat, Transition, Autothermal, and Shutdown.

Preheat operation describes a condition where a cold system is brought up to reaction temperatures. This is accomplished using external energy from external fuels such as propane, diesel, biodiesel, charcoal, natural gas, electric heating, or others. Biomass feedstock will be fed at a low rate. The goal of this stage is to heat the reactor to temperatures which will initiate thermal decomposition of the feedstock, priority is not on product char quality or yield. This stage continues until the system reaches target temperatures.

Transition operation describes a condition where the system transitions off of external fuels in order to operate in a thermally self-sustaining modality. A secondary goal is to reduce the total air added to the process. Added air supplies energy through oxidation of process gases but should be minimized to preserve solid carbon yields. The transition is described as a gradual shift, where external fuels are first modulated down so that all of the process energy is derived from incoming biomass feedstock and then where air into the system is balanced to maintain efficiency.

Autothermal operation describes the standard operating condition of the system, where the goal is to maintain reactor conditions as biomass is pyrolyzed. The goal of the control system in this stage is to maintain balanced control and adjust for variations in conditions from input variations. This stage can be enhanced using predictive control algorithms to proactively adjust reactor heating rates based on measured variations in input feed rate, moisture, and composition.

Shutdown operation describes the process of safely evacuating biomass, char, and gases from the reactors and cooling the combustible gas concentration and temperature in the reactor to a safe level. system in a manner which is safe for both operators and equipment.

FIGS. 3A-3B are diagrams illustrating a multi-stage control process according to some embodiments. To start the process and bring reactors up to temperatures required for pyrolysis Stage 1: Preheat is used. In Stage 1: Preheat, burners in Reactors 1 and 2 as well as the Thermal Oxidizer (217, 233, and 257) are activated using an external fuel such as natural gas, propane, vegetable oil, or biodiesel. Fresh air supply (259) is off or idling and the Syngas Blower (225) is set to a low speed, such as 250 rpm. Feedstock is introduced into the reactors to begin pyrolysis and to supply reactor energy. Target temperatures are monitored at thermocouples in Reactor 1 and Reactor 2, as well as the syngas streams and Thermal Oxidizer. Stage 1: Preheat is maintained until temperature sensors surpass threshold values (>200° C. bed temperature and >600° C. gas temperature). At this point, the system moves into Stage 2 Lean Burn.

In Stage 2: Lean Burn, the system continues to heat towards pyrolysis conditions using biomass as an added fuel source to achieve higher temperatures. The fresh air supply (221 and 235) is used at a low speed based off of thermocouple readings in the reactors targeted at 400° C. The Syngas Blower (225) is set to maintain a vacuum between 0.05 and 0.25 in H2O at the material inlet, modulated by a control loop. Feedstock from the Input Hopper (211) is conveyed through the Input Airlock (213) into Reactor 1 (215) at increasing rates based on Reactor 2 temperatures, measured by thermocouples. Target temperatures are monitored at thermocouples in Reactor 2, as well as the syngas streams and Thermal Oxidizer. Additionally, lambda (λ) sensors which measure the reducing potential of the gas stream are used to determine the combustibility of the gasses in the gas path and the reactors. Stage 2: Lean Burn is maintained until λ sensors in Reactor 2 fall below threshold values of 1.0. At this point, the system moves into Stage 3: Exhaust Recycle Transition.

In Stage 3: Exhaust Recycle Transition, the system transitions to recycle produced pyrolysis gases to displace the air in Reactor 1, creating a more inert or fuel rich environment. Burners in Reactor 2 as well as the Thermal Oxidizer (233, and 257) continue to fire. Recycled pyrolysis gases (219) are introduced to the reactors to supply energy and the fresh air supply (221 and 235) is used at an increasing speed based off of thermocouple readings in the reactors. The Syngas Blower (225) continues to maintain a 0.05-0.25 in H2O vacuum at the material inlet, modulated by a control loop. Feedstock from the Input Hopper (211) is conveyed through the Input Airlock (213) into Reactor 1 (215) at increasing rates based on Reactor 1 temperatures, measured by thermocouples. Target temperatures are monitored at thermocouples in Reactor 1 and Reactor 2, as well as the syngas streams and Thermal Oxidizer. Additionally, lambda (λ) sensors which measure the reducing potential of the gas stream are used to determine the pyrolysis gas composition. Stage 3: Exhaust Recycle Transition is maintained until all temperatures and λ sensors in both reactors and the thermal oxidizer surpass threshold values. At this point, the system moves into Stage 4: Transition to Rich. In practice, stages 2 and stage 3 may be combined.

In Stage 4: Transition to Rich, the system maintains reactor temperatures while balancing the oxygen in the system with the target of receiving the lowest oxidation which will provide the necessary heat for the reaction. In this stage, feed rates are increased to 100% or the target condition, and pyrolysis gas recirculation and air injection are balanced to maintain target temperatures, pressures, and λ values.

In Stage 5: First Stage Partial Oxidation (Pox), the system operates on produced pyrolysis gases without the use of external fuels. Burners may continue to fire utilizing pyrolysis gases, be used to supply fresh air, or be turned off entirely. Recycled pyrolysis gases (219) are introduced to the reactors to supply energy and the fresh air supply (221 and 235) may be used based off of thermocouple readings in the reactors. In practice, necessary air may be supplied by draft air through airlocks and seals drawn by vacuum or positive displacement in the reactor. The Syngas Blower (225) continues to maintain a 0.05-0.25 in H2O vacuum at the material inlet, modulated by a control feedback loop. Target temperatures are monitored at thermocouples in Reactor 1 and Reactor 2, as well as the syngas streams and Thermal Oxidizer, with the goal of maintaining uniform temperatures while reducing oxidation of pyrolysis gasses. In this stage, λ sensors at the reactor burners will read lean (>1.2) while all other λ sensors read rich (<0.8). Stage 5: First Stage Partial Oxidation (Pox) is maintained until burner λ sensors in both reactors begin to read rich and the material inlet to Reactor 2 increases above 160° C. At this point, the system moves into Stage 6: Second Stage Partial Oxidation (Pox).

In Stage 6: Second Stage Partial Oxidation (Pox), the system reduces the oxidation of pyrolysis gases through increases of gas recycle and reduction of air introduction to the reactors or increasing the feed-rate. Reducing oxygen input at given feed-rate increases the yield of solid carbon, moderates reactor temperatures, and provides for cleaner emissions and more energy efficient operation. In this stage, λ sensors at the reactor burners will read neutral to rich (<1.0) while all other λ sensors read rich (<0.8). The temperature of the material inlet to Reactor 2 increases to >220° C. At this point, the system moves into Stage 6: Full Autothermal.

In practice, stages 3 through 6 may be combined although there is utility to separating them into distinct steps as described above.

In Stage 7: Full Autothermal. Once the autothermal condition is achieved a PID controller starts by monitoring temperature, pressure and oxygen at both reactors and sending a feedback signal to control different actuators:

The syngas suction blower (225) receives a signal from the pressure sensors to have a negative pressure at both reactors (215 & 231).

The control valves (253 & 255) from syngas blower receive a feedback signal from the oxygen, temperature, and pressure sensors to recirculate the appropriate amount of syngas back to the reactor to keep a set temperature at various stages of the process (FIG. 3).

The air injectors (221 & 235) receive feedback from the oxygen, temperature, and pressure sensors to push a certain volume of air into the system to cause combustion to raise the temperature at the reactor.

Additionally, as part of the system a thermal oxidizer is used to eliminate all the VOC's released to the environment from the disposal syngas. This thermal oxidizer is also controlled by a PID controller with the following parameters:

The Thermal Oxidizer burner (257) is controlled by receiving a feedback signal from the temperature and the oxygen sensor at the stack of the oxidizer (261).

The air blower (259) is controlled by the same sensors as the burner but is used in an emergency to cool down the thermal oxidizer (249).

In Stage 8: Cool Down, the system is brought from operational conditions to a cool condition safely. In this stage feed is stopped and biomass and char are removed from the reactor. Air injection and recirculation are stopped to reduce heat generation and to prevent sudden ignition events from rapidly changing gas composition. Syngas Blower speed is reduced in response to lower gas production and recirculation.

At any point, if target values fall below critical values, the system will automatically change into an appropriate control setting to maintain reactor temperatures and ensure high quality char outputs.

Example Embodiments

An embodiment of the invention is a system for the mobile, in-field pyrolytic conversion of agricultural, biomass residues into biomass charcoal (Biochar) for application to the field in which the residues were harvested.

Another embodiment of the invention is a system for the automated control of the reactor including measurement of mass flow rates, material compositions, moisture levels, temperatures, pressures, gas compositions, and other variables and control of trailer speed, motor speeds, heating and cooling rates, and other control setpoints.

Another embodiment of the invention is a system which utilized in-situ, partial oxidation of evolved pyrolysis gases to provide the heat energy for the process. The partial oxidation process adds a fraction of the air or oxygen required for stoichiometric combustion, resulting in a release of heat energy, an increase in temperatures, and a by-product pyrolysis gas which still has significant chemical energy for combustion.

The system and method of operation offer the ability to produce high-quality biochar as defined by containing at least 60% total carbon by mass and having an atomic Hydrogen to Carbon ratio of less than 0.4, through innovative control architecture that allows for tighter process control and proactive system adjustments.

Another embodiment of the invention is a high volumetric efficiency and low residence time of material in the system, allowing for a high reactor throughput in a platform which can fit on a trailer and be towed by a common agricultural tractor.

Another embodiment of the invention is a means of disposing of agricultural wastes which provides for clean and controlled air emissions when compared to open burning of fields or the decay of biomass through decomposition.

Another embodiment of the invention is the ability to agricultural residues which have been an obstacle for other pyrolysis and biochar production systems.

Another embodiment of the invention is a control system which utilizes multiple distinct loops and methodologies determined by process temperatures, pressures, and gas compositions as measured by on-board sensors. By dividing system operation into multiple distinct stages at a high resolution, operational efficiencies are significantly increased.

Another embodiment of the invention is a means for measuring both the mass and moisture of incoming feedstock in order to proactively adjust reactor conditions to maintain consistent temperatures and product char properties.

Another embodiment of the invention is a means for measuring both the mass and moisture of outgoing biochar in order to accurately measure the carbon delivered to fields and the atmospheric carbon dioxide removal through biochar conversion.

Another embodiment of the invention is the use of rotary airlocks which use dual rotor configuration to lower the profile of the airlocks and the reactor in total. These airlocks may use an energized seal constructed from a spring steel or high temperature silicone in order to accommodate for thermal expansion and provide good sealing at a wide range of temperatures.

Another embodiment of the invention is the use of a compaction system to provide air locking and atmospheric control by utilizing screws with increasing pitch to compact incoming material and outgoing carbon.

Another embodiment of the invention is a two-stage pyrolysis reactor in which the pyrolysis reaction is divided into a low temperature reaction at drying and torrefaction temperatures and a second stage reactor whip operates at higher, pyrolysis temperatures.

Another embodiment of the invention is a concurrent pyrolysis reactor in the first reactor stage in which the flow of solids and gases is in the same direction which allows for a high temperature differential between incoming biomass and the gas phase to provide high heating rates which stabilize as the material reaches target temperatures.

Another embodiment of the invention is a countercurrent pyrolysis reactor in the second reactor stage in which the flow of solids and gases is in opposition which allows for a consistent temperature differential between carbonizing material and the gas phase to provide heating to high pyrolysis temperatures which will also circulate evolved compounds such as polycyclic aromatic hydrocarbons (PAHs) to maximize residence time for increased destruction efficiencies and lower PAH in the final product material.

Another embodiment of the invention is the re-circulation of partially oxidized process gas evolved from pyrolysis gas to provide heat to the reactors in regions in which the rate of evolution of pyrolysis gases from volatilization of biomass is lower, either because the feedstock material is cooler than peak volatilization temperatures or because the biomass has been effectively carbonized.

Another embodiment of the invention is the use of “distributed air introduction, either through negative pressure or positive pressure, which distributes air into the reactors for better control and temperature moderation, as well as giving the ability to fine tune heat in the reactors.

Another embodiment of the invention is the use of “Air Multipliers” Which utilize a stream of high-pressure, low-volume air to motivate a low-pressure, high-volume stream of air without moving parts.

Another embodiment of the invention is the use of two screw conveyors which rotate in opposite directions, and which overlap and are timed so as not to collide with one another while increasing the mixing of solid material in the reactors.

Another embodiment of the invention is the use of screw conveyors with a pitch which is variable along the length of the reactor such that the flow of material in the reactor is slowed as volume is lost to pyrolysis, maintaining a consistent fill level, and increasing the residence time of material in the reactors. These screws may be tuned to specific feedstock compositions and replaced for changing feedstocks.

Another embodiment of the invention is the use of a cyclone in a horizontal configuration to separate entrained particulate matter from the gas stream in order to provide low particulate emissions.

Another embodiment of the invention is the use of a controlled burner system to completely combust produced pyrolysis gases and minimize the emission of pollutants such as methane, volatile hydrocarbons, carbon monoxide, and nitrogen oxides.

Another embodiment of the invention is a system which utilizes machine learning algorithms to determine setpoints for reactor conditions based on collected data for feedstock types, locations, and weather conditions.

One aspect of the system is a system mobile, in-field pyrolytic conversion of agricultural, biomass residues into biomass charcoal (Biochar) for application to the field in which the residues were harvested. The system is designed to be pulled behind a tractor with forage head or a forage harvester with wide fixability of integration with common agricultural equipment. The system allows for the conversion of agricultural residues into biochar without the need for collection or transport of biomass or the shipping and distribution of product char. The removal of these transportation costs are significant reductions in cost and carbon emissions in biochar utilization which allows for lower cost implementation of biochar as a soil amendment and higher efficiency carbon removal through biochar as a carbon storage medium. A further advantage of the mobile, in-field system is that mineral nutrients such as potassium and phosphorous which are used to grow crops are maintained in the field in the biochar product, reducing the need for the use of those elements by farmers.

Another aspect of the invention is a system the automated control of the reactor, which includes high resolution measurement of mass flow rates, material compositions, moisture levels, temperatures, pressures, gas compositions, and other variables and control of trailer speed, motor speeds, heating and cooling rates, and other control setpoints. This automated control allows for rapid changes of set points to fluctuations of operating conditions which are endemic of a mobile, in-field system. Another advantage of this invention is the ability to provide live calculation of the carbon intensity of biochar production, allowing for active optimization of carbon removal as well as high-resolution measurement, reporting, and verification (MRV) of carbon removal. Standardized automation and monitoring architecture allows for fleet wide MRV management facilitating carbon removal value to be integrated across individual machines, operating in different settings.

Another aspect of the invention is the use of in-situ, partial oxidation of evolved pyrolysis gases to provide the heat energy for the process. The partial oxidation process uses a fraction of the air or oxygen required for stoichiometric combustion, resulting in a release of heat energy, an increase in temperatures, and a by-product pyrolysis gas which still has significant chemical energy for combustion. An advantage of this system is high efficiency of biomass heating through direct heating in the reactor as opposed to through-wall heating. Another advantage is the use of chemical energy of the feedstock biomass which eliminates the need for external fuels. In a mobile system, reduced use of external fuels reduced the frequency of stops needed for refueling.

Another aspect of the invention is the ability to produce high-quality biochar as defined by containing at least 60% total carbon by mass and having an atomic Hydrogen to Carbon ratio of less than 0.4, through innovative, high resolution, control architecture that allows for tighter process control and proactive system adjustments. The ability to use this control system for active MRV estimation allows the system to maintain a high-quality biochar product while reducing the production of under-spec material.

Another aspect of the invention is a high volumetric efficiency and low residence time of material in the system, allowing for a high reactor throughput in a platform which can fit on a trailer and be towed by a common agricultural tractor. This also allows for a significantly higher throughput for comparable capital cost which results in a product biochar (and unit of sequestered carbon) at a lower cost.

Another aspect of the invention is a means of disposing of agricultural wastes which provides for clean and controlled air emissions when compared to open burning of fields or the decay of biomass through decomposition. Decomposing agricultural residues and open field burning of residues are both significant sources of greenhouse gases and air pollutants. The invention described captures a significant portion of the carbon of agricultural residues which avoids CO₂ emissions and the use of an enclosed, controlled combustion chamber for destroying waste gases creates a clean, controlled exhaust stream.

Another aspect of the invention is the ability to utilize agricultural residues which have been an obstacle for other pyrolysis and biochar production systems. Biomass sources including corn stover, rice straw, and sugarcane bagasse are difficult to handle, transport, and process in conventional pyrolysis equipment. An advantage of this invention is a system which can process these waste materials into a valuable product.

Another aspect of the invention is a control system which utilizes multiple distinct loops and methodologies determined by process temperatures, pressures, and gas compositions as measured by on-board sensors. By dividing system operation into multiple distinct stages at a high resolution, control parameters can be tuned to recognizer and adjust for multiple distinct reactor conditions.

Another aspect of the invention is a means for measuring both the mass and moisture of incoming feedstock in order to proactively adjust reactor conditions to maintain consistent temperatures and product char properties. This is advantageous overusing in-reactor sensors solely to control the pyrolysis reaction because it provides for proactive control to ensure the pyrolysis reaction does not leave target ranges, preventing the production of off-spec material.

Another aspect of the invention is a means for measuring both the mass and moisture of outgoing biochar in order to accurately measure the carbon delivered to fields and the atmospheric carbon dioxide sequestered through biochar conversion. This is advantageous over measuring mass alone since biochar can be quenched to prevent burning and improve soil integration while maintaining a record of carbon produced and applied.

Another aspect of the invention is the use of rotary airlocks which use dual rotor configuration to lower the profile of the airlocks and the reactor in total. These airlocks may use an energized seal constructed from a spring steel or high temperature silicone in order to accommodate for thermal expansion and provide good sealing at a wide range of temperatures. Conventional airlocks are limited by physical size, having height to width ratio of greater than 1:1, which increases the height of a mobile system beyond what can be transported over roadways. Additionally, conventional airlocks are designed to operate at a narrow temperature range and will jam at higher temperatures and allow bypass air at lower temperatures. An advantage of the invention is that the dual rotor airlocks have an aspect ratio less than 1:1 and the use of energized seals allow for use at a wide range of temperatures.

Another aspect of the invention is the use of a compaction system to provide air locking and atmospheric control by utilizing screws with increasing pitch to compact incoming material and outgoing carbon. The compaction system offers several advantages, firstly the densification of incoming biomass which increases the volumetric efficiency of the reactor and thermal conductivity of the bulk feedstock. Another advantage is the air locking which can be improved over rotary vein and double-dump airlocks.

Another aspect of the invention is a two-stage pyrolysis reactor in which the pyrolysis reaction is divided into a low temperature reaction at drying and torrefaction temperatures and a second stage reactor whip operates at higher, pyrolysis temperatures. The separation of the reactor into multiple stages allows for improved control of reactor temperatures and atmosphere to separate distinct stages of the thermal decomposition of biomass.

Another aspect of the invention is a concurrent reactor in the first reactor stage in which the flow of solids and gases is in the same direction which allows for an elevated temperature differential between incoming biomass and the gas phase to provide high heating rates which stabilize as the material reaches target temperatures. This is advantageous over a counter current flow for torrefaction and drying which applies the highest gas heat to dry material, which can cause over-heating. Another advantage over counter current drying is the tendency of countercurrent drying to recondense water and aqueous species back onto cooler, incoming feedstock.

Another aspect of the invention is a countercurrent pyrolysis reactor in the second reactor stage in which the flow of solids and gases is in opposition which allows for a consistent temperature differential between carbonizing material and the gas phase to provide heating to high pyrolysis temperatures which will also circulate evolved compounds such as polycyclic aromatic hydrocarbons (PAHs) to maximize residence time for increased destruction efficiencies and lower PAH in the final product material. This is advantageous over a concurrent flow for pyrolysis and in which the peak heating differential is applied to incoming material, limiting the maximum temperature material may reach. Another advantage over concurrent flow for pyrolysis is ability to recondense volatile carbon species into cooler incoming material, allowing for longer residence time to allow for secondary pyrolysis reactions to destroy PAHs and other hydrocarbons.

Another aspect of the invention is the re-circulation of pyrolysis gas provide heat to the reactors in regions in which the rate of evolution of pyrolysis gases from volatilization of biomass is lower, either because the feedstock material is cooler than peak volatilization temperatures or because the biomass has been effectively carbonized. This gives a significant advantage in both reducing or eliminating the need for external fuels and in providing a heat source early in the reactor to accelerate thermal decomposition.

Another aspect of the invention is the use of distributed air introduction, which is advantageous over single point air introduction because it allows for the fine tuning of the process reaction across the reactor length. Adding all of the reaction air at a single point centralizes the reaction, creating a single hot zone and making heat distribution difficult. Multipoint injection allows for fine tuning heat through the reactor and results in lower overall air use for higher yields and more efficient operation.

Another aspect of the invention is the use of “Air Multipliers” Which utilize a stream of high-pressure, low-volume air to motivate a low-pressure, high-volume stream of air without moving parts. This is an advantage of air motivation using blowers or other systems with moving parts which are subject to jamming, overheating, and clogging with incoming material.

Another aspect of the invention is the use of two screw conveyors which rotate in opposite directions, and which overlap and are timed so as not to collide with one another while increasing the mixing of solid material in the reactors. An advantage to increasing mixing is an increase in process efficiency and uniformity, which reduces the time necessary to process material and the carbon yield of the system.

Another aspect of the invention is the use of screw conveyors with a pitch which is variable along the length of the reactor such that the flow of material in the reactor is slowed as volume is lost to pyrolysis, maintaining a consistent fill level, and increasing the residence time of material in the reactors. These screws may be tuned to specific feedstock compositions and replaced for changing feedstocks. Screw conveyors with a constant pitch will have a constant linear speed of material and a decreasing reactor fill volume as material decomposes. The longer residence time and consistent fill volume provides improved spatial reactor efficiency and process efficiency.

Another aspect of the invention is the use of a cyclone in a horizontal configuration to separate entrained particulate matter from the gas stream in order to provide low particulate emissions. The use of a cyclone is advantageous over cyclone-free operation for multiple reasons. Firstly, the cyclone collects a carbon product which would be lost to combustion. Secondly, the use of a cyclone to collect particulates reduces air emissions. Third, the cyclone being placed before the suction blower reduced abrasive carbon impingement on the blower which would reduce the blower's service life. The horizontal cyclone reduced the height of the system, which is a benefit to the system mobility.

Another aspect of the invention is the use of a controlled burner system to completely combust produced pyrolysis gases and minimize the emission of pollutants such as methane, volatile hydrocarbons, carbon monoxide, and nitrogen oxides. An advantage of a con trolled burner with active sensing of combustion temperature and gas composition allows for algorithmic control to rapidly respond to changing conditions. A further advantage is the ability of a controlled combustion system in conjunction with input biomass monitoring allows for proactive control of combustion conditions to anticipate changes based on incoming biomass and other process conditions.

Another aspect of the invention is a system which utilizes machine learning algorithms to determine setpoints for reactor conditions based on collected data for feedstock types, locations, and weather conditions. The advantage of this aspect of the invention is that it allows for a higher degree of control to accommodate the many changes between feedstocks, weather conditions, localities, and other field conditions which will impact a mobile, in-field system.

FIG. 4 is a diagram illustrating a method 400 according to some embodiments. In step 410, a mobile pyrolysis and oxidizer apparatus is maneuvered through a field of biomass. In some embodiments, the mobile apparatus includes a first reactor with a reactor chamber, a plurality of air injectors, and a reactor burner. The mobile apparatus also includes a second reactor with a reactor chamber, a plurality of air injectors, and a reactor burner. In some embodiments, first reactor is coupled to the second reactor via a syngas channel (such as tubing or piping).

In step 420, the biomass from the field is harvested or collected and is fed into the mobile apparatus as feedstock.

In step 430, the biomass is processed through a first reactor where the collected biomass is heated to cause torrefaction of the biomass. In some embodiments, the first reactor is heated to a first temperature, at least in part, using a syngas via the syngas channel.

In step 440, the torrefied biomass is then processed through a second reactor where the torrefied biomass is heated to cause pyrolysis of the torrefied biomass. In some embodiments, the second reactor is heated to a second temperature, at least in part, using the syngas via the syngas channel. The second temperature is a temperature that is a higher temperature than the first temperature. In some embodiments, the first temperature ranges from between 200-400° C., and the second temperature ranges between 500-800° C.

In some embodiments, a portion of the biomass is torrefied via the heat applied to the feedstock while being conveyed through the first rector chamber, and a portion of the torrefied biomass is pyrolyzed while being conveyed through the second rector chamber.

In step 450, the pyrolyzed biomass is passed from the second reactor to a quencher to cool the heated pyrolyzed biomass. In some embodiments, the mobile apparatus includes a quencher with a water supply container that holds water, and a quencher chamber to quench (i.e., cool with the water) the heated biomass.

In step 460, the processed biomass is then output from the mobile apparatus. The method 400 may be continuously performed while the mobile apparatus maneuvers through a field of biomass.

It will be appreciated that the present disclosure may include any one and up to all of the following examples.

Example 1. A method of biomass pyrolysis for biochar production comprising the operations of: maneuvering a mobile pyrolysis and oxidizer apparatus through a field of biomass, the mobile apparatus comprising: a first reactor, comprising: a first reactor chamber; a first plurality of air injectors; and a first reactor burner; a second reactor, comprising: a second reactor chamber; a second plurality of air injectors; and a second reactor burner, wherein the first reactor is coupled to the second reactor via a syngas channel; and a quencher comprising: a water supply container; and a quencher chamber; heating the first reactor to a first temperature, at least in part, using a syngas via the syngas channel; heating the second reactor to a second temperature, at least in part, using the syngas via the syngas channel, wherein the second temperature is a temperature that is a higher temperature than the first temperature; collecting the biomass as a feedstock and feeding the feedstock into the apparatus; conveying the feedstock through the first reactor chamber; conveying the feedstock through the second reactor chamber; and conveying the feedstock through the quencher chamber, wherein the feedstock material is cooled to a lower temperature than the second temperature.

Example 2. The method of Example 1, wherein the first temperature ranges from between 200-400° C., and the second temperature ranges between 500-800° C.

Example 3. The method of any one of Examples 1-2, further comprising: wherein the mobile apparatus further comprises a syngas blower; extracting from the first reactor, via a suction generated by the syngas blower, syngas that was produced in the first reactor; and inputting the extracted syngas from the first reactor to the second reactor chamber, thereby mixing resident syngas in the second reactor chamber with the extract syngas from the first reactor.

Example 4. The method of any one of Examples 1-3, further comprising: gravity feeding the feedstock from the first reactor to the second reactor.

Example 5. The method of any one of Examples 1-4, wherein a portion of the feedstock is torrefied via the heat applied to the feedstock while being conveyed through the first rector chamber, and a portion of the feedstock is pyrolyzed while being conveyed through the second rector chamber.

Example 6. The method of any one of Examples 1-5, further comprising: wherein the mobile apparatus further comprises a thermal oxidizer; extracting from the first reactor and/or the second reactor syngas that has biomass particles; combusting via the thermal oxidizer the biomass particles in the extracted syngas thereby producing char of the biomass particles; quenching the char with water; and disposing to a ground surface the quenched char.

Example 7. The method of any one of Examples 1-6, further comprising the operations of: monitoring via one or more temperature sensors, a temperature associated with the first reactor chamber; providing air or oxygen into the first reactor chamber via the first plurality of air injectors, and increasing the temperature associated with the first reactor chamber; monitoring via one or more other temperature sensors, a temperature associated with the second reactor chamber; and providing air or oxygen into the second reactor chamber via the second plurality of air injectors, and increasing the temperature associated with the second reactor chamber.

Example 8. The method of any one of Examples 1-7, further comprising the operations of: controlling the first reactor and the second rector in a plurality of stages, where the first temperature and the second temperature are changed according the predetermined parameters for a respective stage.

Example 9. The method of any one of Examples 1-8, wherein a first stage is a preheat stage wherein the first burner and the second burner are activated using an external fuel source; wherein the preheat stage is maintained until the first temperature reaches a first predetermined threshold temperature and the second temperature reaches a predetermined second threshold temperature.

Example 10. The method of any one of Examples 1-9, wherein in another stage, wherein in another stage, the mobile apparatus heats the first reactor chamber and the second reactor chamber via utilizing as a fuel source syngas that was generated by the mobile apparatus.

Example 11. A system for mobile pyrolysis of biomass for biochar production comprising: a mobile pyrolysis and oxidizer apparatus comprising: a first reactor, comprising: a first reactor chamber; a first air injector; and a first reactor burner; and a second reactor, comprising: a second reactor chamber; a second air injector; and a second reactor burner; and a quencher comprising: a water supply container; and a quencher chamber; wherein the first reactor is coupled to the second reactor via a syngas channel; wherein the first reactor heats to a first temperature, at least in part, using a syngas via the syngas channel; wherein the second reactor heats to a second temperature, at least in part, using the syngas via the syngas channel, wherein the second temperature is a temperature that is a higher temperature than the first temperature; wherein collected biomass is feedstock that is transferred through the first reactor chamber; and wherein the feedstock is transferred through the second reactor chamber; wherein feedstock transferred through the quencher chamber is cooled to a lower temperature than the second temperature.

Example 12. The system of Example 11, wherein the first temperature ranges from between 200-400° C., and the second temperature ranges between 500-800° C.

Example 13. The system of any one of Examples 11-12, further comprising: a syngas blower, wherein the syngas blower is configured to generate a suction that causes syngas produced in the first reactor to be extracted from the first reactor; and wherein extracted syngas from the first reactor is input into the second reactor chamber, thereby mixing resident syngas in the second reactor chamber with the extracted syngas from the first reactor.

Example 14. The system of any one of Examples 11-13, the feedstock is output from the first reactor into the second reactor.

Example 15. The system of any one of Examples 11-14, wherein a portion of the feedstock is torrefied via the heat applied to the feedstock while being conveyed through the first rector chamber, and a portion of the feedstock is pyrolyzed while being conveyed through the second rector chamber.

Example 16. The system of any one of Examples 11-15, further wherein the mobile apparatus further comprises a thermal oxidizer that combusts biomass particles in extracted syngas.

Example 17. The system of any one of Examples 11-16, further comprising: one or more temperature sensors that monitor a temperature associated with the first reactor chamber, wherein the first plurality of air injectors provide air or oxygen into the first reactor chamber to increase the temperature associated with the first reactor chamber; and one or more other temperature sensors that monitor a temperature associated with the second reactor chamber, wherein the second plurality of air injectors provide air or oxygen into the second reactor chamber to increase the temperature associated with the second reactor chamber.

Example 18. The system of any one of Examples 11-17, wherein the first reactor and second reactor are operable in a plurality of stages, where the first temperature and the second temperature are changed according to predetermined parameters for a respective stage.

Example 19. The system of any one of Examples 11-18 wherein a first stage is a preheat stage wherein the first burner and the second burner are activated using an external fuel source; wherein the preheat stage is maintained until the first temperature reaches a first predetermined threshold temperature and the second temperature reaches a predetermined second threshold temperature.

Example 20. The system of any one of Examples 11-19, wherein in another stage, wherein in another stage, the mobile apparatus heats the first reactor chamber and the second reactor chamber via utilizing as a fuel source syngas that was generated by the mobile apparatus.

In the foregoing disclosure, implementations of the disclosure have been described with reference to specific example implementations thereof. It will be evident that various modifications may be made thereto without departing from the broader spirit and scope of implementations of the disclosure as set forth in the following claims. The disclosure and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.