Systems, methods, and techniques for co 2 capture and high-purity syngas generation

Abstract

Exemplary systems and methods process tail gas streams. Exemplary reactor systems may include a countercurrent reactor and a co-current reactor. Alternatively, exemplary reactor systems may include a first countercurrent reactor and a second countercurrent reactor. Exemplary reactor systems may further include a combustor reactor and a separation unit. Exemplary methods may include receiving oxygen carrier solids and tail gases, generating lower oxidation state oxygen carrier solids, collecting a first gas stream, providing a carbonaceous feedstock and a gaseous stream, and collecting a second gas stream. The first gas stream may include at least 90 volume percent (vol%) carbon dioxide (CO2). The second gas stream may include carbon monoxide (CO) and hydrogen (H2).

Description

SYSTEMS, METHODS, AND TECHNIQUES FOR CO2CAPTURE AND HIGH-PURITYSYNGAS GENERATIONCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 578,307 filed on August 23, 2023, and U.S. Provisional Patent Application No. 63 / 600,268 filed on November 17, 2023, the entire contents both of which are incorporated herein by reference.TECHNICAL FIELD

[0002] The present disclosure relates to systems, methods, and techniques for processing tail gas streams. Exemplary systems and methods may recover energy from a tail gas stream, generate carbon dioxide (CO2), and / or generate a high purity syngas stream.INTRODUCTION

[0003] Syngas, a mixture of hydrogen and carbon monoxide, is a platform chemical used in a variety of industries for multiple applications such as hydrogen, methanol, liquid fuels, and steel production, to name a few. In many of these downstream applications, a stream of waste gas or tail gases is generated, which is either flared or used for capturing carbon dioxide (CO2). In these applications, an acid gas removal unit is typically used for carbon capture, which is highly energy intensive and, therefore, decreases the efficiency of the entire plant.

[0004] Exemplary systems contemplated herein relate to chemical looping, which is based on redox reactions occurring in oxygen carrier solids. Typically, exemplary oxygen carrier solids are transient metal oxide materials that can exist in multiple oxidation states and thus can undergo multiple redox reactions.

[0005] The selectivity of an oxygen carrier particle towards the formation of full oxidation products (carbon dioxide (CO2) and water (H2O)) versus the formation of partial oxidation products (hydrogen (H2) and carbon monoxide (CO)) is dependent on the oxidation power of the oxygen carrier particle. The stronger the oxidation power, the higher the tendency of the formation of the full oxidation products. The oxidation power is governed by the thermodynamic Gibbs free energy of the reduction reaction. For example, calcium ferrite (Ca2Fe20s)-based oxygen carrier particles are a weaker oxidant as compared to iron oxide (Fe2O3)-based oxygen carrier particles.Accordingly, calcium ferrite is preferred for syngas production, whereas iron oxide is preferred for complete oxidation applications.

[0006] Similarly, an oxygen carrier particle that exists in multiple oxidation states may have different oxidation powers in different states. For example, iron (III) oxide (Fe2O3) has higher oxidation power than iron (II, III) oxide (FesCh), which in turn has higher oxidation power than iron (II) oxide (FeO). Therefore, a higher oxidation state of the oxygen carrier particle is preferred to be in contact with the outlet product if full combustion is desired, whereas a reduced oxidation state of the oxygen carrier particle is preferred to be in contact with the outlet product if partial combustion is desired. As a result, a countercurrent moving bed allows for full combustion products, whereas a co-current moving bed works with partial oxidation products.SUMMARY

[0007] In one aspect, a reactor system comprising a countercurrent reactor and a co-current reactor is disclosed. The reactor system may comprise a countercurrent reactor comprising: a first solids inlet adjacent a top portion of the countercurrent reactor, the first solids inlet configured to receive oxygen carrier solids having multiple oxidation states; a first solids outlet adjacent a bottom portion of the countercurrent reactor; a tail gas inlet adjacent the bottom portion of the countercurrent reactor, the tail gas inlet being in fluid communication with a first process element; and a carbon dioxide (CO2) gas outlet adjacent the top portion of the countercurrent reactor; a cocurrent reactor comprising: a second solids inlet adjacent a top portion of the co-current reactor, the second solids inlet being in fluid communication with the first solids outlet; a second solids outlet adjacent a bottom portion of the co-current reactor; a carbonaceous feedstock inlet adjacent the top portion of the co-current reactor, the carbonaceous feedstock inlet being in communication with a carbonaceous feedstock source; a steam inlet adjacent the top portion of the co-current reactor, the steam inlet being in fluid communication with a steam source; and a syngas outlet adjacent the bottom portion of the co-current reactor, the syngas outlet being in fluid communication with a second process element; a combustor reactor comprising: a third solids inlet in fluid communication with the second solids outlet; an air inlet in fluid communication with an air source; and a third solids outlet in fluid communication with a riser; and a separation unit configured to separate solids from depleted air, the separation unit comprising: a fourth solids inlet in fluid communication with the riser; an air outlet; and a fourth solids outlet in fluidcommunication with the first solids inlet. The second process element may be the same as the first process element.

[0008] In another aspect, a method of operating a reactor system comprising a countercurrent reactor and a co-current reactor is disclosed is disclosed. The method may comprise receiving first oxidation state oxygen carrier solids at a first solids inlet of the countercurrent reactor, the first oxidation state oxygen carrier solids being oxygen carrier solids at a first oxidation state and having multiple oxidation states; receiving tail gases at a tail gas inlet of the countercurrent reactor whereby the first oxidation state oxygen carrier solids in the countercurrent reactor are reduced to generate first lower oxidation state oxygen carrier solids, the tail gases comprising at least one of: carbon monoxide (CO), carbon dioxide (CO2), hydrogen (H2), and methane (CH4); the tail gases being provided such that the tail gases flow in a countercurrent fashion relative to the first oxidation state oxygen carrier solids; collecting a first gas stream from an outlet of the countercurrent reactor, the first gas stream comprising at least 90 volume percent (vol%) carbon dioxide (CO2); providing the first lower oxidation state oxygen carrier solids from the countercurrent reactor to a second solids inlet of the co-current reactor; providing a carbonaceous feedstock and steam to the cocurrent reactor such that the carbonaceous feedstock, steam, and first lower oxidation state oxygen carrier solids are in co-current flow, whereupon the first lower oxidation state oxygen carrier solids are reduced, thereby generating second lower oxidation state oxygen carrier solids; collecting a second gas stream from an outlet of the co-current reactor, the second gas stream comprising carbon monoxide (CO) and hydrogen (H2); providing the second lower oxidation state oxygen carrier solids to a solids inlet of a combustor; providing air to the combustor, whereupon the second lower oxidation state oxygen carrier solids are oxidized, thereby regenerating the first oxidation state oxygen carrier solids, and generating depleted air; providing the first oxidation state oxygen carrier solids and the depleted air to a separation unit; collecting depleted air from the separation unit; and providing the first oxidation state oxygen carrier solids to the countercurrent reactor.

[0009] In another aspect, a reactor system comprising a first countercurrent reactor and a second countercurrent reactor is disclosed. The reactor system may comprise a first countercurrent reactor comprising: a first solids inlet adjacent a top portion of the first countercurrent reactor, the first solids inlet configured to receive oxygen carrier solids; a first solids outlet adjacent a bottom portion of the first countercurrent reactor; a tail gas inlet adjacent the bottom portion of the first countercurrent reactor, the tail gas inlet being in fluid communication with a first process element;a carbonaceous feedstock inlet adjacent the top portion of the first countercurrent reactor, the carbonaceous feedstock inlet being in fluid communication with a carbonaceous feedstock source; and a carbon dioxide (CO2) gas outlet adjacent the top portion of the first countercurrent reactor; a second countercurrent reactor comprising: a second solids inlet adjacent a top portion of the second countercurrent reactor, the second solids inlet being in fluid communication with the first solids outlet; a second solids outlet adjacent a bottom portion of the second countercurrent reactor; a gas inlet adjacent the bottom portion of the second countercurrent reactor, the gas inlet being in fluid communication with a gas source configured to provide a gaseous stream comprising steam and / or carbon dioxide (CO2); and a syngas outlet adjacent the top portion of the second countercurrent reactor, the syngas outlet being in fluid communication with a second process element; a combustor reactor comprising: a third solids inlet in fluid communication with the second solids outlet; an air inlet in fluid communication with an air source; and a third solids outlet in fluid communication with a riser; and a separation unit configured to separate solids from depleted air, the separation unit comprising: a fourth solids inlet in fluid communication with the riser; an air outlet; and a fourth solids outlet in fluid communication with the first solids inlet. The second process element may be the same as the first process element.

[0010] Before any embodiments of the disclosure are explained in detail, it is to be understood that the disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The disclosure is capable of other embodiments and of being practiced or of being carried out in various ways.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. l is a schematic depiction of a first exemplary reactor system.

[0012] FIG. 2 is a schematic depiction of a second exemplary reactor system.

[0013] FIG. 3 shows a flow diagram of the ASPEN model used to simulate example reactors.

[0014] FIG. 4 is a graph showing CO2 purity (by volume percent (vol%)) and oxygen carrier solids conversion (% by weight (wt%)) for a simulated countercurrent reactor (reducer 1).

[0015] FIG. 5 is a graph showing syngas purity (vol%) and oxygen carrier solids conversion (wt%) for a simulated co-current reactor (reducer 2).

[0016] FIG. 6 is a graph showing CO2 purity (vol%) over time (minutes) for an example countercurrent reactor (reducer 1) in an example bench-scale reactor system processing biomass.

[0017] FIG. 7 is a graph showing syngas purity (vol%) over time (minutes) from an example co-current reactor (reducer 2) in an example bench-scale reactor system processing biomass.DETAILED DESCRIPTION

[0018] Systems, methods, and techniques disclosed and contemplated herein relate to processing tail gas streams. Exemplary systems may be integrated into any downstream application that uses syngas and generates a tail gas stream. Exemplary systems may recover energy from the tail gas stream, generate a capture-ready stream of carbon dioxide (CO2) in certain conditions, and may also generate a high-purity syngas stream that can be used for the downstream application.

[0019] Exemplary systems may involve multiple moving bed reactors, either in a concurrent or countercurrent manner, to reduce oxygen carrier solids and oxidize the inlet carbonaceous feedstock. The inlet feedstock may be a tail gas stream from a downstream application. The inlet feedstock may be an inlet carbonaceous feedstock such as natural gas, biomass, or coal. Exemplary systems may also implement a fluidized bed reactor in fluid communication with the moving beds for the regeneration of the oxygen carrier solids in air / steam / CCh. The oxygen carrier solids may then be conveyed back to the moving bed using a riser.I. Definitions

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, the present document, including definitions, will control. Methods and materials are described below, although methods and materials similar or equivalent to those described herein can be used in practice or testing of the present disclosure. All publications, patent applications, patents and other references mentioned herein are incorporated by reference in their entirety. The materials, methods, and examples disclosed herein are illustrative only and not intended to be limiting.

[0021] The terms “comprise(s),” “include(s),” “having,” “has,” “can,” “contain(s),” and variants thereof, as used herein, are intended to be open-ended transitional phrases, terms, or words that do not preclude the possibility of additional acts or structures. The singular forms “a,” “an” and “the” include plural references unless the context clearly dictates otherwise. The presentdisclosure also contemplates other embodiments “comprising,” “consisting of’ and “consisting essentially of,” the embodiments or elements presented herein, whether explicitly set forth or not.

[0022] The modifiers “about” or “approximately” used in connection with a quantity are inclusive of the stated value and has the meaning dictated by the context (for example, it includes at least the degree of error associated with the measurement of the quantity). These modifiers should also be considered as disclosing the range defined by the absolute values of the two endpoints. For example, the expression “from about 2 to about 4” also discloses the range “from 2 to 4.” The term “about” may refer to plus or minus 10% of the indicated number. For example, “about 10%” may indicate a range of 9% to 11%, and “about 1” may mean from 0.9-1.1. Other meanings of “about” may be apparent from the context, such as rounding off, so, for example “about 1” may also mean from 0.5 to 1.4.

[0023] For the recitation of numeric ranges herein, each intervening number there between with the same degree of precision is contemplated. For example, for the range of 6-9, the numbers 7 and 8 are contemplated in addition to 6 and 9, and for the range 6.0-7.0, the numbers 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, and 7.0 are contemplated. For another example, when a pressure range is described as being between ambient pressure and another pressure, a pressure that is ambient pressure is expressly contemplated.

[0024] Definitions of specific functional groups and chemical terms are described in more detail below. For purposes of this disclosure, the chemical elements are identified in accordance with the Periodic Table of the Elements, CAS version, Handbook of Chemistry and Physics, 104thEd., inside cover, and specific functional groups are defined as described therein.

[0025] As used herein, the term “fluidized bed reactor” means a reactor where fluid is passed through catalyst material at a sufficient speed to suspend the solid catalyst material. Typically, oxygen carrier solids may move in any direction, bounded by the walls of the reactor.

[0026] As used herein, the term “fixed bed reactor” means defined as a reactor where catalyst material is fixed in a packed bed. Fluid is passed through catalyst material, but the fluid does not suspend the catalyst material, as in a fluidized bed reactor.

[0027] As used herein, the term “moving bed reactor” means a reactor where catalytic material flows in a single direction, generally, from top to bottom. The fluid material can flow in the same direction as the catalytic material (co-current movement). The fluid material can flow in an opposite direction as the catalytic material (countercurrent movement).IL Exemplary Materials

[0028] Exemplary reactor systems may process and generate various materials. Exemplary materials may include carbonaceous feedstocks, tail gases, oxygen carrier solids, product gases, and fluidized media. Various aspects of exemplary carbonaceous feedstocks, tail gases, oxygen carrier solids, product gases, and fluidized media are discussed below.A. Exemplary Tail Gases

[0019] Exemplary systems and methods disclosed herein may use and process various tail gases. Exemplary tail gases may be obtained from various sources. For instance, tail gases may be generated by various chemical, petrochemical, mining, metallurgical, ceramic, and / or energy processes. In some instances, exemplary tail gases comprise carbon monoxide (CO), hydrogen (H2), methane (CEL), or mixtures thereof.

[0020] In some instances, exemplary tail gases comprise carbon dioxide (CO2) and at least one of: carbon monoxide (CO), hydrogen (H2), and methane (CH4). When exemplary tail gases comprise carbon dioxide (CO2), carbon dioxide (CO2) is present at no more than 99 volume percent (vol%). In various implementations, exemplary tail gases comprise no more than 99 vol%; no more than 98 vol%; no more than 97 vol%; no more than 96 vol%; no more than 95 vol%; no more than 90 vol%; no more than 85 vol%; no more than 80 vol%; no more than 75 vol%; no more than 70 vol%; no more than 60 vol%; or no more than 50 vol% carbon dioxide (CO2).B. Exemplary Carbonaceous Feedstocks

[0001] Example carbonaceous feedstocks may include various types of natural gases, coals, biomasses, peats, and cokes. Various aspects of exemplary coals and biomasses are discussed below.1. Coals

[0002] Exemplary coals may comprise one or more coal types. Example coal types include anthracite, bituminous, subbituminous, and lignite. Exemplary coals may comprise volatile matter, char, and ash at various amounts.

[0003] In various instances, the coal may comprise volatile matter at an amount of 20 wt% to 50 wt%. In some instances, the coal may comprise volatile matter at an amount of 22 wt% to 48 wt%; 25 wt% to 45 wt%; 28% to 42 wt%; 30 wt% to 40 wt%; 32 wt% to 38 wt%; or 34 wt% to 36 wt%. In some instances, the coal may comprise volatile matter at an amount of no greater than about 50 wt%; no greater than about 48 wt%; no greater than about 45 wt%; no greater than about 42 wt%; no greater than about 40 wt%; no greater than about 38 wt%; no greater than about 35 wt%; no greater than about 32 wt%; no greater than about 30 wt%; no greater than about 28 wt%; no greater than about 25 wt%; or no greater than about 22 wt%. In some instances, the coal may comprise volatile matter at an amount of no less than about 20 wt%; no less than about 22 wt%; no less than about 25 wt%; no less than about 28 wt%; no less than about 30 wt%; no less than about 32 wt%; no less than about 35 wt%; no less than about 38 wt%; no less than about 40 wt%; no less than about 42 wt%; no less than about 45 wt%; or no less than about 48 wt%.

[0004] In various instances, the coal may comprise char at an amount of 20 wt% to 50 wt%. In some instances, the coal may comprise char at an amount of 22 wt% to 48 wt%; 25 wt% to 45 wt%; 28% to 42 wt%; 30 wt% to 40 wt%; 32 wt% to 38 wt%; or 34 wt% to 36 wt%. In some instances, the coal may comprise char at an amount of no greater than about 50 wt%; no greater than about 48 wt%; no greater than about 45 wt%; no greater than about 42 wt%; no greater than about 40 wt%; no greater than about 38 wt%; no greater than about 35 wt%; no greater than about 32 wt%; no greater than about 30 wt%; no greater than about 28 wt%; no greater than about 25 wt%; or no greater than about 22 wt%. In some instances, the coal may comprise char at an amount of no less than about 20 wt%; no less than about 22 wt%; no less than about 25 wt%; no less than about 28 wt%; no less than about 30 wt%; no less than about 32 wt%; no less than about 35 wt%; no less than about 38 wt%; no less than about 40 wt%; no less than about 42 wt%; no less than about 45 wt%; or no less than about 48 wt%.

[0005] In some instances, the coal may comprise ash at an amount of 5 wt% to 15 wt%. In some instances, the coal may comprise ash at an amount of 6 wt% to 14 wt%; 7 wt% to 13 wt%; 8 wt% to 12 wt%; or 9 wt% to 11 wt%. In some instances, the coal may comprise ash at an amount of no greater than about 15 wt%; no greater than about 14 wt%; no greater than about 13 wt%; no greater than about 12 wt%; no greater than about 11 wt; no greater than about 10 wt%; no greater than about 9 wt%; no greater than about 8 wt%; no greater than about 7 wt%; or no greater than about 6 wt%. In some instances, the coal may comprise ash at an amount of no less than about 5wt%; no less than about 6 wt%; no less than about 7 wt%; no less than about 8 wt%; no less than about 9 wt%; no less than about 10 wt%; no less than about 11 wt%; no less than about 12 wt%; no less than about 13 wt%; or no less than about 14 wt%.2. Biomasses

[0006] Exemplary biomasses may comprise at least one type of biomass. Example biomass types include wood-based materials and agricultural waste. Exemplary biomasses may comprise volatile matter, char, and ash at various amounts.

[0007] In various instances, the biomass may comprise volatile matter at an amount of 20 wt% to 80 wt%. In some instances, the biomass may comprise volatile matter at an amount of 25 wt% to 75 wt%; 30 wt% to 70 wt%; 35 wt% to 65 wt%; 40 wt% to 60 wt%; 35 wt% to 55 wt%; or 40 wt% to 50 wt%. In some instances, the biomass may comprise volatile matter at an amount of no greater than about 80 wt%; no greater than about 75 wt%; no greater than about 70 wt%; no greater than about 65 wt%; no greater than about 60 wt%; no greater than about 55 wt%; no greater than about 50 wt%; no greater than about 45 wt%; no greater than about 40 wt%; no greater than about 35 wt%; no greater than about 30 wt%; or no greater than about 25 wt%. In some instances, the biomass may comprise volatile matter at an amount of no less than about 20 wt%; no less than about 25 wt%; no less than about 30 wt%; no less than about 35 wt%; no less than about 40 wt%; no less than about 45 wt%; no less than about 50 wt%; no less than about 55 wt%; no less than about 60 wt%; no less than about 65 wt%; no less than about 70 wt%; or no less than about 75 wt%.

[0008] In various instances, the biomass may comprise char at an amount of 10 wt% to 50 wt%. In various instances, the biomass may comprise char at an amount of 15 wt% to 45 wt%; 17 wt% to 43 wt%; 20 wt% to 40 wt%; 22 wt% to 38 wt%; 25 wt% to 35 wt%; 28 wt% to 33 wt%; or 29 wt% to 32 wt%. In various instances, the biomass may comprise char at an amount of no greater than about 50 wt%; no greater than about 45 wt%; no greater than about 40 wt%; no greater than about 35 wt%; no greater than about 30 wt%; no greater than about 25 wt%; no greater than about 20 wt%; or no greater than about 15 wt%. In various instances, the biomass may comprise char at an amount of no less than about 10 wt%; no less than about 15 wt%; no less than about 20 wt%; no less than about 25 wt%; no less than about 30 wt%; no less than about 35 wt%; no less than about 40 wt%; or no less than about 45 wt%.

[0009] In various instances, the biomass may comprise ash at an amount of 0 wt% to 10 wt%. In some instances, the biomass may comprise ash at an amount of 1 wt% to 9 wt%; 2 wt% to 8 wt%; 3 wt% to 7 wt%; or 4 wt% to 6 wt%. In some instances, the biomass may comprise ash at an amount of no greater than about 10 wt%; no greater than about 9 wt%; no greater than about 8 wt%; no greater than about 7 wt%; no greater than about 6 wt%; no greater than about 5 wt%; no greater than about 4 wt%; no greater than about 3 wt%; no greater than about 2 wt%; or no greater than about 1 wt%. In some instances, the biomass may comprise ash at an amount of no less than about 1 wt%; no less than about 2 wt%; no less than about 3 wt%; no less than about 4 wt%; no less than about 5 wt%; no less than about 6 wt%; no less than about 7 wt%; no less than about 8 wt%; or no less than about 9 wt%.C. Exemplary Oxygen Carrier Solids

[0021] Exemplary systems and methods disclosed herein may use various exemplary oxygen carrier solids, also referred to herein as “oxygen carriers.” Exemplary oxygen carrier solids may include one or more active metal oxides and inert material.

[0022] Exemplary oxygen carrier solids may have multiple oxidation states. Accordingly, exemplary active metal oxides may be capable of undergoing multiple cyclic redox reactions. In various instances, exemplary active metal oxides may have multiple oxidation states. Exemplary active metal oxides may include zinc oxide (ZnO), tin (IV) oxide (SnCh), iron (II, III) oxide (FesCU), nickel (II) oxide (NiO), manganese (IV) oxide (MnCh), cobalt (II) oxide (CoO), and chromium (III) oxide (CnCh).

[0023] In various instances, exemplary oxygen carrier solids may comprise an iron (Fe)-based active metal oxide material. In some instances, the Fe-based active metal oxide material comprises iron ore. Exemplary iron ores include haematite and magnetite.

[0024] Exemplary inert materials may include silicon dioxide (SiCh), silicon carbide (SiC), aluminum oxide (AI2O3), magnesium oxide (MgO), calcium oxide (CaO), titanium oxide (TiCh), magnesium aluminum oxide (MgAhCh), zirconium dioxide (ZrCh), yttria-stabilized ZrCh, alumina-silicates, clay supports such as kaolin and bentonite, alumina-zirconia-silica, and combinations thereof. In some instances, exemplary oxygen carrier solids may comprise titanium (IV) oxide (TiCh).

[0025] Exemplary oxygen carrier solids may comprise various amounts of the one or more active metal oxides and inert material. In various instances, the one or more active metal oxides may be present at 5 weight percent (wt%) to 95 wt% of the total weight of the exemplary oxygen carrier solids. In various implementations, the one or more active metal oxides may comprise 10 wt% to 95 wt%; 15 wt% to 95 wt%; 20 wt% to 95 wt%; 25 wt% to 95 wt%; 30 wt% to 95 wt%; 35 wt% to 95 wt%; 40 wt% to 95 wt%; 45 wt% to 95 wt%; 50 wt% to 95 wt%; 55 wt% to 95 wt%; 60 wt% to 95 wt%; 65 wt% to 95 wt%; 70 wt% to 95 wt%; 75 wt% to 95 wt%; 80 wt% to 95 wt%; 85 wt% to 95 wt%; 90 wt% to 95 wt%; 5 wt% to 90 wt%; 5 wt%; to 85 wt%; 10 wt% to 85 wt%; 15 wt% to 85 wt%; 20 wt% to 85 wt%; 20 wt% to 80 wt%; 25 wt% to 80 wt%; 25 wt% to 75 wt%; 30 wt% to 75 wt%; 30 wt% to 70 wt%; 35 wt% to 70 wt%; 35 wt% to 65 wt%; 40 wt% to 65 wt%; 40 wt% to 60 wt%; 45 wt% to 60 wt%; 45 wt% to 55 wt%; or about 50 wt% of the total weight of the exemplary oxygen carrier solids. In various implementations, the one or more active metal oxides may comprise no less than 5 wt%; no less than 15 wt%; no less than 25 wt%; no less than 35 wt%; no less than 45 wt%; no less than 55 wt%; no less than 65 wt%; no less than 75 wt%; or no less than 85 wt% of the total weight of the exemplary oxygen carrier solids. In various implementations, the one or more active metal oxides may comprise no greater than 95 wt%; no greater than 90 wt%; no greater than 80 wt%; no greater than 70 wt%; no greater than 60 wt%; no greater than 50 wt%; no greater than 40 wt%; no greater than 30 wt%; no greater than 20 wt%; or no greater than 10 wt% of the total weight of the exemplary oxygen carrier solids.

[0026] In various implementations, the inert material may comprise 5 wt% to 95 wt% of the total weight of the exemplary oxygen carrier solids. In various implementations, the inert material may comprise 10 wt% to 95 wt%; 15 wt% to 95 wt%; 20 wt% to 95 wt%; 25 wt% to 95 wt%; 30 wt% to 95 wt%; 35 wt% to 95 wt%; 40 wt% to 95 wt%; 45 wt% to 95 wt%; 50 wt% to 95 wt%; 55 wt% to 95 wt%; 60 wt% to 95 wt%; 65 wt% to 95 wt%; 70 wt% to 95 wt%; 75 wt% to 95 wt%;80 wt% to 95 wt%; 85 wt% to 95 wt%; 90 wt% to 95 wt%; 5 wt% to 90 wt%; 5 wt%; to 85 wt%;10 wt% to 85 wt%; 15 wt% to 85 wt%; 20 wt% to 85 wt%; 20 wt% to 80 wt%; 25 wt% to 80 wt%;25 wt% to 75 wt%; 30 wt% to 75 wt%; 30 wt% to 70 wt%; 35 wt% to 70 wt%; 35 wt% to 65 wt%;40 wt% to 65 wt%; 40 wt% to 60 wt%; 45 wt% to 60 wt%; 45 wt% to 55 wt%; or about 50 wt% of the total weight of the exemplary oxygen carrier solids. In various implementations, the inert material may comprise no less than 5 wt%; no less than 15 wt%; no less than 25 wt%; no less than 35 wt%; no less than 45 wt%; no less than 55 wt%; no less than 65 wt%; no less than 75 wt%; orno less than 85 wt% of the total weight of the exemplary oxygen carrier solids. In various implementations, the inert material may comprise no greater than 95 wt%; no greater than 90 wt%; no greater than 80 wt%; no greater than 70 wt%; no greater than 60 wt%; no greater than 50 wt%; no greater than 40 wt%; no greater than 30 wt%; no greater than 20 wt%; or no greater than 10 wt% of the total weight of the exemplary oxygen carrier solids.

[0027] In some instances, exemplary oxygen carrier solids may be oxygen carrier solids at a first oxidation state (“first oxidation state oxygen carrier solids”). Exemplary first oxidation state oxygen carrier solids may comprise iron (III) oxide (Fe2O3). Exemplary first oxidation state carrier solids may further comprise an inert material.

[0028] In some instances, oxygen carrier solids may be oxygen carrier solids at a first lower oxidation state (“first lower oxidation state oxygen carrier solids”). Exemplary first lower oxidation state oxygen carrier solids may comprise iron (II, III) oxide (FesCE) and / or iron (II) oxide (FeO).

[0029] In some instances, oxygen carrier solids may be oxygen carrier solids at a second lower oxidation state (“second lower oxidation state oxygen carrier solids”). Exemplary second lower oxidation state oxygen carrier solids may comprise iron (II) oxide (FeO) and / or iron (Fe).

[0030] In various instances, exemplary oxygen carrier solids may have a particle size of 100 pm to 3000 pm. In various instances, exemplary oxygen carrier solids have a particle size of 100 pm to 2900 pm; 200 pm to 2800 pm; 300 pm to 2700 pm; 400 pm to 2600 pm; 500 pm to 2500 pm; 600 pm to 2400 pm; 700 pm to 2300 pm; 800 pm to 2200 pm; 900 pm to 2100 pm; 1000 pm to 2000 pm; 1100 pm to 1900 pm; 1200 pm to 1800 pm; 1300 pm to 1700 pm; or 1400 pm to 1600 pm. In various instances, exemplary oxygen carrier solids have a particle size of no greater than 3000 pm; no greater than 2800 pm; no greater than 2500 pm; no greater than 2300 pm; no greater than 2000 pm; no greater than 1800 pm; no greater than 1500 pm; no greater than 1300 pm; no greater than 1200 pm; no greater than 1000 pm; no greater than 800 pm; no greater than 500 pm; no greater than 300 pm; or no greater than 200 pm. In various instances, exemplary oxygen carrier solids have a particle size of no less than 100 pm; no less than 200 pm; no less than 500 pm; no less than 700 pm; no less than 1000 pm; no less than 1200 pm; no less than 1500 pm; no less than 1700 pm; no less than 2000 pm; no less than 2200 pm; no less than 2500 pm; no less than 2700 pm; or no less than 2800 pm.D. Exemplary Product Gases

[0031] Exemplary reactors disclosed herein may generate various exemplary product gases. Exemplary product gases may comprise complete oxidation product gases and / or partial oxidation product gases. Exemplary complete oxidation product gases include carbon dioxide (CO2) and / or steam (H2O). Exemplary partial oxidation product gases include hydrogen (H2), carbon monoxide (CO), and syngas (a mixture H2 and CO).

[0032] Exemplary product gases may comprise carbon dioxide (CO2) at various amounts. In some instances, the product gas comprises at least 90 volume percent (vol%) CO2. In some instances, the product gas comprises at least 91 vol%; at least 92 vol%; at least 93 vol%; at least 94 vol% at least 95 vol%; at least 96 vol%; at least 97 vol%; at least 98 vol %; or at least 99 vol% CO2.

[0033] Exemplary product gases may comprise syngas at various amounts. In various instances, the product gas comprises at least 90 vol% syngas. In some instances, the product gas comprises at least 91 vol%; at least 92 vol%; at least 93 vol%; at least 94 vol% at least 95 vol%; at least 96 vol%; at least 97 vol%; at least 98 vol%; or at least 99 vol% syngas.

[0034] Exemplary product gases may comprise carbon monoxide (CO) and hydrogen (H2) at various relative amounts. In various instances, the product gas may comprise CO and H2 at a CO:H2 ratio of from 0 to 5: 1. In some instances, the product gas may comprise CO and H2 at a CO:H2 ratio of from 0.01: 1 to 4.99: 1; 0.1: 1 to 4.9: 1; from 0.25: 1 to 4.75: 1; from 0.5:1 to 4.5: 1; from 0.75: 1 to 4.25: 1; from 1 : 1 to 4: 1; from 1.25: 1 to 3.75: 1; from 1.5: 1 to 3.5: 1; from 1.75:1 to 3.25:1; from 2:1 to 3: 1; or from 2.25:1 to 2.75: 1. In some instances, the product gas may comprise CO and H2 at a CO:H2 ratio of no greater than 5: 1; no greater than 4.5: 1; no greater than 4: 1; no greater than 3.5 : 1 ; no greater than 3:1; no greater than 2.5: 1; no greater than 2 : 1 ; no greater than 1.5: 1; no greater than 1 : 1; no greater than 0.5: 1; or no greater than 0.1: 1. In some instances, the product gas may comprise CO and H2 at a CO:H2 ratio of no less than 0.01 : 1; no less than 0.1 : 1; no less than 0.5: 1; no less than 1 :1; no less than 1.5: 1; no less than 2: 1; no less than 2.5:1; no less than 3: 1; no less than 3.5: 1; no less than 4: 1; or no less than 4.5: 1.E. Exemplary Fluidized Media

[0035] Exemplary systems and methods disclosed herein may implement various types of fluidized media. The type of fluidized media and / or its specific use may depend on the specificreactor system. Exemplary fluidized media types include sand, quartz, hematite, and / or magnetite. In some instances, exemplary fluidized media may comprise a sand, such as olivine sand.

[0036] In some instances, exemplary fluidized media may in the form of a fixed bed. In other instances, exemplary fluidized media may be present as a free-flowing material that is capable of circulating throughout different units in of a reactor system.

[0037] In some instances, exemplary fluidized media may be inert. In various instances, exemplary fluidized media may possess catalytic activity to enhance the gasification rates and have tar cracking tendency. In some instances, exemplary fluidized media may contain a sacrificial material that may trap impurities, thereby providing in-situ purification of the raw gases. For example, exemplary fluidized media may comprise calcium oxide (CaO). The CaO may react with the sulfur present in the carbonaceous feedstock, thereby generating calcium sulfate (CaSCh), and capturing the sulfur within the fluidized media itself.

[0038] In some instances, the fluidized media may be heat transfer media. Heat transfer media may be any type of fluidized media capable of supplying heat to a reactor system unit. In some instances, exemplary heat transfer media may be in the form of solids, referred to as “heat transfer media solids.” Exemplary heat transfer media may further include non-solids, such as hot gases and hot oils. Exemplary hot gases may include hot flue gas.III. Exemplary Systems

[0039] Various reactor systems may be used to perform exemplary methods and techniques described herein. Exemplary reactor systems may comprise a first reactor and a second reactor. In some instances, the first reactor is a countercurrent reactor, and the second reactor is a co-current reactor. In other instances, the first reactor is a first countercurrent reactor, and the second reactor is a second countercurrent reactor. Various aspects of exemplary reactor systems are discussed below.A. Reactor Systems Comprising a Countercurrent Reactor and a Co-current Reactor

[0040] FIG. 1 schematically depicts an exemplary reactor system comprising a countercurrent reactor and a co-current reactor. As indicated in FIG. 1, the countercurrent reactor and the cocurrent reactor are each a reducer reactor (“reducer 1” and “reducer 2”). As used herein, the term “reducer reactor” means a reactor where oxygen carrier solids are reduced. Broadly, the reactorsystem depicted in FIG. 1 includes the countercurrent reactor (reducer 1), the co-current reactor (reducer 2) in fluid communication with the countercurrent reactor (reducer 1), a combustor reactor in fluid communication with the co-current reactor (reducer 2), and a separation unit (PPS) in fluid communication with the combustor reactor (combustor) and the countercurrent reactor (reducer 1). Also shown in FIG. 1 is a downstream process. Other embodiments may include more or fewer components. Other implementations may include one or more of the units shown in FIG. 1 arranged and operating in parallel (e.g., there may be multiple Reducer 1 reactors all operating in parallel).

[0041] The countercurrent reactor (reducer 1) generates combustion products comprising carbon dioxide (CO2) and / or steam (H2O). As shown, the countercurrent reactor (reducer 1) includes a first solids inlet, a first solids outlet, a tail gas inlet, and a carbon dioxide (CO2) outlet. The countercurrent reactor (reducer 1) is configured as a moving bed reactor.

[0042] The first solids inlet is positioned adjacent a top portion of the countercurrent reactor (reducer 1). The first solids inlet is configured to receive oxygen carrier solids (oxygen carriers) having multiple oxidation states. Exemplary oxygen carrier solids are discussed above. In some instances, the oxygen carrier solids received by the countercurrent reactor may comprise iron (III) oxide (Fe20a) and titanium (IV) oxide (TiCh). In various instances, the oxygen carrier solids received by the countercurrent reactor may have a particle size of 100 pm to 3000 pm.

[0043] The first solids outlet is positioned adjacent a bottom portion of the countercurrent reactor (reducer 1). As shown, oxygen carrier solids are discharged through the first solids outlet which is in fluid communication with the co-current reactor (reducer 2). Typically, the oxygen carrier solids (oxygen carriers) exiting the countercurrent reactor (reducer 1) have been reduced. In some instances, the reduced oxygen carrier solids discharged through the first solids outlet may comprise FesCU and / or FeO.

[0044] The tail gas inlet is positioned adjacent the bottom portion of the countercurrent reactor (reducer 1). Because tail gases enter the countercurrent reactor (reducer 1) near the bottom portion, the oxygen carrier solids move counter currently relative to the tail gases. The tail gas inlet is in fluid communication with a first process element, indicated in FIG. 1 as a downstream process. The tail gas inlet is configured to receive tail gases from the first process element. The downstream process may be any process that generates a tail gas stream. The tail gas inlet is configured to receive tail gases from the downstream process.

[0045] The carbon dioxide (CO2) gas outlet is positioned adjacent the top portion of the countercurrent reactor (reducer 1). The carbon dioxide (CO2) gas outlet is configured to discharge carbon dioxide (CO2) gas generated in the countercurrent reactor (reducer 1) to a second process element. The second process element may be one or more operations or storage units.

[0046] The co-current reactor in FIG. 1 (reducer 2) generates syngas and reduced oxygen carrier solids. Because the oxygen carrier solids entering the co-current reactor were reduced to a lower oxidation state, their reduction power is lower and, accordingly, a higher selectivity of the oxygen carrier particle towards the partial oxidation product is achieved.

[0047] In some instances, the co-current reactor (reducer 2) is positioned vertically below the countercurrent reactor (reducer 1). In some instances, the co-current reactor (reducer 2) is positioned vertically even with the countercurrent reactor (reducer 1).

[0048] Broadly, the co-current reactor (reducer 2) includes a second solids inlet, a second solids outlet, a carbonaceous feedstock inlet, a steam inlet, and a syngas outlet. The co-current reactor (reducer 2) is configured as a moving bed reactor.

[0049] The second solids inlet is positioned adjacent a top portion of the co-current reactor (reducer 2). The second solids inlet is in fluid communication with the first solids outlet and receives reduced oxygen carrier solids from the countercurrent reactor (reducer 1).

[0050] The second solids outlet is positioned adjacent a bottom portion of the co-current reactor. The second solids outlet is configured to discharge reduced oxygen carrier solids reduced in the co-current reactor (reducer 2).

[0051] The carbonaceous feedstock inlet is positioned adjacent the top portion of the cocurrent reactor (reducer 2). Because the carbonaceous feedstock is provided near the top portion, the carbonaceous feedstock and the oxygen carrier solids move co-currently through the bed in the co-current reactor (reducer 2).

[0052] The carbonaceous feedstock inlet is in communication with a carbonaceous feedstock source, not shown in FIG. 1. The carbonaceous feedstock inlet is configured to receive carbonaceous feedstock from the carbonaceous feedstock source. The carbonaceous feedstock source may be any suitable source of carbonaceous feedstock. In some instances, the carbonaceous feedstock source may be a biomass source, such as an agricultural waste pit.

[0053] A steam inlet is positioned adjacent the top portion of the co-current reactor. Because the steam inlet is positioned near the top portion of the co-current reactor, the steam moves co-currently with the oxygen carrier solids through the bed in the co-current reactor. The steam inlet is in fluid communication with a steam source, not shown in FIG. 1.

[0054] The syngas outlet is positioned adjacent the bottom portion of the co-current reactor and is configured to discharge syngas generated within the co-current reactor. In some instances, the syngas generated within the co-current reactor may comprise carbon monoxide (CO) and hydrogen (H2) at a CO:H2 ratio of 0 to 5 : 1. As shown, in some instances, the syngas outlet may be in fluid communication with the same process element that provided the tail gases to the countercurrent reactor. In other instances, the syngas outlet may be in fluid communication with a different process or unit than the process element that provided the tail gases to the countercurrent reactor (not shown).

[0055] In some implementations, the co-current reactor (reducer 2) may also receive tail gas from the downstream process. In those implementations, the co-current reactor (reducer 2) further comprises a second tail gas inlet, where the second tail gas inlet is in fluid communication with the downstream process.

[0056] The combustor reactor in FIG. 1 regenerates the reduced oxygen carrier solids received from the co-current reactor. In some instances, the regenerated oxygen carrier solids may comprise Fe20s and TiCh. Broadly, the combustor reactor includes a third solids inlet, an air inlet, and a third solids outlet.

[0057] The third solids inlet is in fluid communication with the second solids outlet of the cocurrent reactor.

[0058] The air inlet is in fluid communication with an air source. Air received at the air inlet regenerates the oxygen carrier solids by oxidation. Air provided to the combustor reactor comprises nitrogen (N2), oxygen (O2) and argon (Ar). In some implementations, air provided to the combustor reactor may be pure oxygen (O2).

[0059] The third solids outlet is in fluid communication with a riser, not shown in FIG. 1. The third solids outlet is configured to discharge the regenerated oxygen carrier solids through the riser to a separation unit (PPS).

[0060] The separation unit (PPS) in FIG. 1 separates regenerated oxygen carrier solids from depleted air. Broadly, the separation unit (PPS) comprises a fourth solids inlet, an air outlet, and a fourth solids outlet.

[0061] The fourth solids inlet is positioned adjacent a top portion of the separation unit (PPS) and is in fluid communication with the riser.

[0062] The air outlet is positioned adjacent the top portion of the separation unit (PPS) and is configured to discharge depleted air.

[0063] The fourth solids outlet is positioned adjacent a bottom portion of the separation unit (PPS) and is in fluid communication with the first solids inlet. The fourth solids outlet is configured to provide regenerated oxygen carrier solids to the countercurrent reactor (reducer 1).B. Reactor Systems Comprising a First Countercurrent Reactor and a Second Countercurrent Reactor

[0064] FIG. 2 schematically depicts a reactor system comprising a first countercurrent reactor and a second countercurrent reactor. As indicated in FIG. 2, the first countercurrent reactor is a reducer reactor (“reducer”), and the second countercurrent reactor is an oxidizer reactor (“oxidizer”). As used herein, the term “oxidizer reactor” means a reactor where oxygen carrier solids are oxidized. Broadly, the reactor system in FIG. 2 includes the first countercurrent reactor (reducer), the second countercurrent reactor (oxidizer) in fluid communication with the first countercurrent reactor (reducer), a combustor reactor (combustor) in fluid communication with the second countercurrent reactor (oxidizer), and a separation unit (PPS) in fluid communication with the combustor reactor (combustor) and the first countercurrent reactor (reducer). Also shown in FIG. 2 is a steel mill. Other embodiments may include more or fewer components. Other implementations may include one or more of the units shown in FIG. 2 arranged and operating in parallel.

[0065] The first countercurrent reactor (reducer) in FIG. 2 generates combustion products comprising carbon dioxide (CO2) and / or steam (H2O). As shown, the first countercurrent reactor (reducer) includes a first solids inlet, a first solids outlet, a carbonaceous feedstock inlet, a tail gas inlet, and a carbon dioxide (CO2) outlet. The first countercurrent reactor (reducer) is configured as a moving bed reactor.

[0066] The first solids inlet is positioned adjacent a top portion of the first countercurrent reactor (reducer). The first solids inlet is configured to receive oxygen carrier solids (oxygen carriers) having multiple oxidation states. In some instances, the oxygen carrier solids received by the first countercurrent reactor (reducer) may comprise Fe2O3 and TiCh.

[0067] The first solids outlet is positioned adjacent a bottom portion of the first countercurrent reactor (reducer). As shown, oxygen carrier solids are discharged through the first solids outlet which is in fluid communication with the second countercurrent reactor (oxidizer). Typically, the oxygen carrier solids (oxygen carriers) exiting the first countercurrent reactor (reducer) have been reduced. In some instances, the oxygen carrier solids discharged through the first solids outlet may comprise FesC and / or FeO.

[0068] The carbonaceous feedstock inlet is positioned adjacent the top portion of the first countercurrent reactor (reducer).

[0069] The carbonaceous feedstock inlet is in communication with a carbonaceous feedstock source, not shown in FIG. 2. The carbonaceous feedstock inlet is configured to receive carbonaceous feedstock from the carbonaceous feedstock source. The carbonaceous feedstock source may be any suitable source of carbonaceous feedstock. In some instances, the carbonaceous feedstock source may be a biomass source, such as an agricultural waste pit.

[0070] The tail gas inlet is positioned adjacent the bottom portion of the first countercurrent reactor (reducer). Because tail gases enter the first countercurrent reactor (reducer) near the bottom portion, the oxygen carrier solids move counter currently relative to the tail gases.

[0071] The tail gas inlet is in fluid communication with a first process element. The first process element may be one or more operations or storage units. As shown, the first process element is a streel production process element, indicated in FIG. 2 as a “steel mill.” The steel production process element receives and processes natural gas to generate steel materials and discharge various tail gases. The tail gas inlet is configured to receive tail gases generated and discharged from the streel production process element.

[0072] The carbon dioxide (CO2) gas outlet is positioned adjacent the top portion of the first countercurrent reactor (reducer). The carbon dioxide (CO2) gas outlet is configured to discharge carbon dioxide (CO2) gas generated in the first countercurrent reactor (reducer 1) to a second process element. The second process element may be one or more operations or storage units.

[0073] The second countercurrent reactor in FIG. 2 (oxidizer) generates syngas and oxidizes the oxygen carrier solids received from the first countercurrent reactor (reducer).

[0074] In some instances, the second countercurrent reactor (oxidizer) is positioned vertically below the first countercurrent reactor (reducer). In some instances, the second countercurrent reactor (oxidizer) is positioned vertically even with the first countercurrent reactor (reducer).

[0075] Broadly, the second countercurrent reactor (oxidizer) includes a second solids inlet, a second solids outlet, a gas inlet, and a syngas outlet. The second countercurrent reactor (oxidizer) is configured as a moving bed reactor.

[0076] The second solids inlet is positioned adjacent a top portion of the second countercurrent reactor (oxidizer). The second solids inlet is in fluid communication with the first solids outlet and receives reduced oxygen carrier solids from the first countercurrent reactor (reducer).

[0077] The second solids outlet is positioned adjacent a bottom portion of the second countercurrent reactor. The second solids outlet is configured to discharge oxygen carrier solids oxidized in the second countercurrent reactor (oxidizer).

[0078] The gas inlet is positioned adjacent the bottom portion of the second countercurrent reactor and is configured to provide a gaseous stream of steam and / or CO2. Because the gas inlet is positioned near the bottom portion of the second countercurrent reactor, the gaseous stream moves counter-currently with the oxygen carrier solids through the bed in the second countercurrent reactor. The gas inlet is in fluid communication with a gas source, not shown in FIG. 2.

[0079] The syngas outlet is positioned adjacent the top portion of the second countercurrent reactor and is configured to discharge syngas generated within the second countercurrent reactor. In some instances, the syngas generated within the second countercurrent reactor may comprise carbon monoxide (CO) and hydrogen (H2) at a CO:H2 ratio of 0 to 5: 1. As shown, in some instances, the syngas outlet may be in fluid communication with the same process element that provided the tail gases to the first countercurrent reactor. In some instances, the syngas outlet may be in fluid communication with a different process element (not shown).

[0080] The combustor reactor in FIG. 2 regenerates the oxygen carrier solids received from the second countercurrent reactor. In some instances, the regenerated oxygen carrier solids may comprise Fe2C>3 and TiCh. Broadly, the combustor reactor includes a third solids inlet, an air inlet, and a third solids outlet.

[0081] The third solids inlet is in fluid communication with the second solids outlet of the second countercurrent reactor.

[0082] The air inlet is in fluid communication with an air source. Air received at the air inlet regenerates the oxygen carrier solids by oxidation. Air provided to the combustor reactorcomprises nitrogen (N2), oxygen (O2) and argon (Ar). In some implementations, air provided to the combustor reactor may be pure oxygen (O2).

[0083] The third solids outlet is in fluid communication with a riser. The third solids outlet is configured to discharge the regenerated oxygen carrier solids through the riser to a separation unit (PPS).

[0084] The separation unit (PPS) in FIG. 2 separates regenerated oxygen carrier solids from depleted air. Broadly, the separation unit (PPS) comprises a fourth solids inlet, an air outlet, and a fourth solids outlet.

[0085] The fourth solids inlet is positioned adjacent a top portion of the separation unit (PPS) and is in fluid communication with the riser.

[0086] The air outlet is positioned adjacent the top portion of the separation unit (PPS) and is configured to discharge depleted air.

[0087] The fourth solids outlet is positioned adjacent a bottom portion of the separation unit (PPS) and is in fluid communication with the first solids inlet. The fourth solids outlet is configured to provide regenerated oxygen carrier solids to the first countercurrent reactor (reducer) through the first solids inlet.IV. Exemplary Methods of Operation

[0088] Exemplary methods of operating a reactor system may comprise various operations. Broadly, exemplary methods may include receiving oxygen carrier solids and tail gases, generating lower oxidation state oxygen carrier solids, collecting a first gas stream, providing a carbonaceous feedstock and a gaseous stream, and collecting a second gas stream. The first gas stream may comprise at least 90 volume percent (vol%) carbon dioxide (CO2). The second gas stream may comprise carbon monoxide (CO) and hydrogen (H2). Exemplary systems described above may be used to implement one or more of the methods described below. Other embodiments may include more or fewer operations than those discussed below.A. Methods of Operating Reactor Systems Comprising a Countercurrent Reactor and a Co-current Reactor

[0089] An example method may comprise operating a rector system comprising a countercurrent reactor and a co-current reactor. The countercurrent reactor and the co-currentreactor may each be a reducer reactor. In various instances, the reactor system depicted in FIG. 1 may be used to implement the example method.

[0090] The example method may comprise receiving first oxidation state oxygen carrier solids at a first solids inlet of the countercurrent reactor. The first oxidation state oxygen carrier solids may be oxygen carrier solids having multiple oxidation states. The oxygen carrier solids having multiple oxidation states may comprise oxygen carrier solids at a first oxidation state (“first oxidation state oxygen carrier solids ”) In various instances, the first oxidation state oxygen carrier solids may comprise iron (III) oxide (Fe2Os).

[0091] The example method may further comprise receiving tail gases at a tail gas inlet of the countercurrent reactor. In various instances, the tail gases may be provided such that the tail gases flow in a countercurrent fashion relative to the first oxidation state oxygen carrier solids.

[0092] Upon receiving the tail gases at the tail gas inlet of the countercurrent reactor, the first oxidation state oxygen carrier solids may be reduced, thereby generating first lower oxidation state oxygen carrier solids. In various instances, the first lower oxidation state oxygen carrier solids may comprise iron (II, III) oxide (FeaC ) and / or iron (II) oxide (FeO). In various instances, the tail gases may comprise at least one of: carbon monoxide (CO), carbon dioxide (CO2), hydrogen (H2), and methane (CFU). Exemplary tail gases are described above.

[0093] In various instances, the example method may further comprise operating the countercurrent reactor at a temperature of 300 °C to 1400 °C. In various instances, an example method may comprise operating the countercurrent reactor at a temperature of 350 °C to 1390 °C; 400 °C to 1370 °C; 450 °C to 1350 °C; 500 °C to 1330 °C; 550 °C to 1310 °C; 600 °C to 1300 °C; 650 °C to 1250 °C; 700 °C to 1200 °C; 750 °C to 1150 °C; 800 °C to 1100 °C; 850 °C to 1050 °C; 900 °C to 1000 °C; or 925 °C to 975 °C. In various instances, the example method may further comprise operating the countercurrent reactor at a temperature of no greater than 1400 °C; no greater than 1300 °C; no greater than 1200 °C; no greater than 1100 °C; no greater than 1000 °C; no greater than 900 °C; no greater than 800 °C; no greater than 700 °C; no greater than 600 °C; no greater than 500 °C; or no greater than 400 °C. In various instances, the example method may comprise operating the countercurrent reactor at a temperature of no less than 300 °C; no less than 400 °C; no less than 500 °C; no less than 600 °C; no less than 700 °C; no less than 800 °C; no less than 900 °C; no less than 1000 °C; no less than 1100 °C; no less than 1200 °C; or no less than 1300

[0094] In various instances, the example method may further comprise operating the countercurrent reactor at a pressure of 0 MPa to 5 MPa. In some instances, the example method may comprise operating the countercurrent reactor at a pressure of 0.1 MPa to 4.9 MPa; 0.25 MPa to 4.5 MPa; 0.5 MPa to 4 MPa; 0.75 MPa to 3.5 MPa; 1 MPa to 3 MPa; 1.25 MPa to 2.5 MPa; or 1.5 MPa to 2 MPa. In some instances, the example method may comprise operating the countercurrent reactor at a pressure of no greater than 5 MPa; no greater than 4 MPa; no greater than 3 MPa; no greater than 2 MPa; no greater than 1 MPa; no greater than 0.5 MPa; or no greater than 0.25 MPa. In some instances, an example method may comprise operating the countercurrent reactor at a pressure of no less than 0.1 MPa; no less than 1 MPa; no less than 2 MPa; no less than 3 MPa; no less than 4 MPa; or no less than 4.5 MPa.

[0095] The example method may further comprise collecting a first gas stream. The first gas stream may be collected from an outlet of the countercurrent reactor. In various instances, the first gas stream may comprise at least 90 volume percent (vol%) carbon dioxide (CO2).

[0096] The example method may further comprise providing the first lower oxidation state oxygen carrier solids from the countercurrent reactor to the co-current reactor. The first lower oxidation state oxygen carrier solids may be provided to the co-current reactor through a second solids inlet of the co-current reactor.

[0097] The example method may further comprise providing a carbonaceous feedstock and steam to the co-current reactor. In various instances, the carbonaceous feedstock, steam, and first lower oxidation state oxygen carrier solids may be provided in co-current flow. Exemplary carbonaceous feedstocks are described above. In some instances, the carbonaceous feedstock may comprise biomass.

[0098] In various instances, the steam may be provided to the co-current reactor at an amount that is 1 percent by weight (wt%) to 10 wt% of an amount of carbon in the carbonaceous feedstock. In some instances, the steam may be provided to the co-current reactor an amount that is 0.5 wt% to 9.5 wt%; 1 wt% to 9 wt%; 1.5 wt% to 8.5 wt%; 2 wt% to 8 wt%; 2.5 wt% to 7.5 wt%; 3 wt% to 7 w%; 3.5 wt% to 6.5 wt%; or 4 wt% to 6 wt% of an amount of carbon in the carbonaceous feedstock. In some instances, the steam may be provided to the co-current reactor an amount that is no greater than 10 wt%; no greater than 9 wt%; no greater than 8 wt%; no greater than 7 wt%; no greater than 6 wt%; no greater than 5 wt%; no greater than 4 wt%; no greater than 3 wt%; or no greater than 2 wt% of an amount of carbon in the carbonaceous feedstock. In some instances,the steam may be provided to the co-current reactor an amount that is no greater than 10 wt%; no greater than 9 wt%; no greater than 8 wt%; no greater than 7 wt%; no greater than 6 wt%; no greater than 5 wt%; no greater than 4 wt%; no greater than 3 wt%; or no greater than 2 wt% of an amount of carbon in the carbonaceous feedstock. In some instances, the steam may be provided to the co-current reactor an amount that is no less than 1 wt%; no less than 2 wt%; no less than 3 wt%; no less than 4 wt%; no less than 5 wt%; no less than 6 wt%; no less than 7 wt%; no less than 8 wt%; or no less than 9 wt% of an amount of carbon in the carbonaceous feedstock.

[0099] Upon providing the carbonaceous feedstock and steam to the co-current reactor, the first lower oxidation state oxygen carrier solids may be reduced, thereby generating second lower oxidation state oxygen carrier solids. Exemplary second lower oxidation state oxygen carrier solids may comprise iron (II) oxide (FeO) and / or iron (Fe).

[0100] In various instances, the example method may further comprise operating the cocurrent reactor at a temperature of 300 °C to 1400 °C. In various instances, an example method may comprise operating the co-current reactor at a temperature of 350 °C to 1390 °C; 400 °C to 1370 °C; 450 °C to 1350 °C; 500 °C to 1330 °C; 550 °C to 1310 °C; 600 °C to 1300 °C; 650 °C to 1250 °C; 700 °C to 1200 °C; 750 °C to 1150 °C; 800 °C to 1100 °C; 850 °C to 1050 °C; 900 °C to 1000 °C; or 925 °C to 975 °C. In various instances, the example method may further comprise operating the co-current reactor at a temperature of no greater than 1400 °C; no greater than 1300 °C; no greater than 1200 °C; no greater than 1100 °C; no greater than 1000 °C; no greater than 900 °C; no greater than 800 °C; no greater than 700 °C; no greater than 600 °C; no greater than 500 °C; or no greater than 400 °C. In various instances, the example method may comprise operating the co-current reactor at a temperature of no less than 300 °C; no less than 400 °C; no less than 500 °C; no less than 600 °C; no less than 700 °C; no less than 800 °C; no less than 900 °C; no less than 1000 °C; no less than 1100 °C; no less than 1200 °C; or no less than 1300 °C.

[0101] In various instances, the example method may further comprise operating the cocurrent reactor at a pressure of 0 MPa to 5 MPa. In some instances, the example method may comprise operating the co-current reactor at a pressure of 0.1 MPa to 4.9 MPa; 0.25 MPa to 4.5 MPa; 0.5 MPa to 4 MPa; 0.75 MPa to 3.5 MPa; 1 MPa to 3 MPa; 1.25 MPa to 2.5 MPa; or 1.5 MPa to 2 MPa. In some instances, the example method may further comprise operating the cocurrent reactor at a pressure of no greater than 5 MPa; no greater than 4 MPa; no greater than 3 MPa; no greater than 2 MPa; no greater than 1 MPa; no greater than 0.5 MPa; or no greater than0.25 MPa. In some instances, an example method may further comprise operating the co-current reactor at a pressure of no less than 0.1 MPa; no less than 1 MPa; no less than 2 MPa; no less than 3 MPa; no less than 4 MPa; or no less than 4.5 MPa.

[0102] The example method may further comprise collecting a second gas stream from an outlet of the co-current reactor. The second gas stream may comprise carbon monoxide (CO) and hydrogen (H2) at various amounts. In various instances, the second gas stream may comprise carbon monoxide (CO) and hydrogen (H2) at a CO:H2 ratio of 0 to 5 : 1.

[0103] In some instances, the example method may further comprise providing tail gas to the co-current reactor. The tail gas may be provided to the co-current reactor such that the tail gas flows co-currently with the oxygen carrier solids. In some instances, the tail gas may be provided to a bottom portion of the co-current reactor

[0104] The example method may further comprise providing the second lower oxidation state oxygen carrier solids to a combustor. The second lower oxidation state oxygen carrier solids may be provided to the combustor through a solids inlet of the combustor.

[0105] The example method may further comprise providing air to the combustor. Upon providing air to the combustor, the second lower oxidation state oxygen carrier solids may be oxidized, thereby regenerating the first oxidation state oxygen carrier solids, and generating depleted air.

[0106] In various instances, the example method may further comprise operating the combustor reactor at a temperature of 300 °C to 1400 °C. In various instances, an example method may comprise operating the combustor reactor at a temperature of 350 °C to 1390 °C; 400 °C to 1370 °C; 450 °C to 1350 °C; 500 °C to 1330 °C; 550 °C to 1310 °C; 600 °C to 1300 °C; 650 °C to 1250 °C; 700 °C to 1200 °C; 750 °C to 1150 °C; 800 °C to 1100 °C; 850 °C to 1050 °C; 900 °C to 1000 °C; or 925 °C to 975 °C. In various instances, the example method may further comprise operating the combustor reactor at a temperature of no greater than 1400 °C; no greater than 1300 °C; no greater than 1200 °C; no greater than 1100 °C; no greater than 1000 °C; no greater than 900 °C; no greater than 800 °C; no greater than 700 °C; no greater than 600 °C; no greater than 500 °C; or no greater than 400 °C. In various instances, the example method may further comprise operating the combustor reactor at a temperature of no less than 300 °C; no less than 400 °C; no less than 500 °C; no less than 600 °C; no less than 700 °C; no less than 800 °C; no less than 900 °C; no less than 1000 °C; no less than 1100 °C; no less than 1200 °C; or no less than 1300 °C.

[0107] The example method may further comprise providing the first oxidation state oxygen carrier solids and the depleted air to a separation unit. In various instances, providing the first oxidation state oxygen carrier solids to the separation unit may comprise pneumatically transferring the first oxidation state oxygen carrier solids and the depleted air through a riser.

[0108] The example method may further comprise collecting depleted air from the separation unit. In various instances, collecting depleted air from the separation unit may comprise discharging depleted air through an air outlet.

[0109] The example method may further comprise providing the first oxidation state oxygen carrier solids to the countercurrent reactor. The first oxidation state oxygen carrier solids may be provided to the to the countercurrent reactor through the first solids inlet of the countercurrent reactor.B. Methods of Operating Reactor Systems Comprising a First Countercurrent Reactor and a Second Countercurrent Reactor

[0110] An alternative example method may comprise operating a reactor system comprising a first countercurrent reactor and a second countercurrent reactor. The first countercurrent reactor may be a reducer reactor and the second countercurrent reactor may be an oxidizer reactor. In various instances, the reactor system depicted in FIG. 2 may be used to implement the alternative example method.[0U1] The alternative example method may comprise the same or similar operations and conditions as the example method described above, with the exception of a few key differences.

[0112] In contrast with the example method described above, the alternative example method may comprise providing the carbonaceous feedstock to the first countercurrent reactor. Moreover, the carbonaceous feedback may be provided to the first countercurrent reactor such that the carbonaceous feedstock flows in a countercurrent fashion relative to the tail gases.

[0113] Moreover, in contrast with the example method described above, the alternative example method further comprises providing a gaseous stream comprising steam and / or CO2 to the second countercurrent reactor such that the first lower oxidation state oxygen carrier solids may be provided in countercurrent flow relative to the gaseous stream.

[0114] Additionally, in contrast with the example method described above, upon providing the first lower oxidation state oxygen carrier solids and the gaseous stream comprising steam and / orCO2 to the second countercurrent reactor, the first lower oxidation state oxygen carrier solids may be oxidized.V. Experimental Examples

[0115] Various data were computationally generated, and the results are described below.Process Simulations

[0116] Simulations were carried out using the ASPEN Plus V10 simulation software. The ASPEN model, depicted in FIG. 3, was prepared for reactor operation at temperatures of 800 °C to 1000 °C and atmospheric pressure. In FIG. 4, a countercurrent reactor (reducer 1) was simulated where the waste gas predominantly comprising CO, FE, CO2 and H2O from the steel mill was introduced at the bottom and flows countercurrent with oxygen carrier solids. Simulated countercurrent reactor (reducer 1) achieved a high purity of over 95 vol%, thus indicating that CO2 suitable for sequestration can be obtained. Additionally, FIG. 4 illustrates that while the purity of CO2 remained constant, the conversion of the oxygen carrier solids was about 20-30 wt%. This indicates that the CO2 purity remains constant regardless of the conversion of the oxygen carrier solids.

[0117] The objective of the simulated co-current reactor (reducer 2) was to produce high- purity syngas from carbonaceous feedstock. As shown in FIG. 5, the syngas purity and the conversion of the oxygen carrier solids vary depending on the type of carbonaceous feedstock. In this case, the carbonaceous feedstock was com cob biomass. About 20-30 wt% of the converted / reduced oxygen carrier solids were fed into the simulated co-current reactor (reducer 2) from the simulated countercurrent reactor (reducer 1) along with the com cob biomass in a cocurrent manner. In the simulated co-current reactor (reducer 2), the oxygen carrier solids underwent further reduction to approximately 35-40 wt%, resulting in the production of high- purity syngas with a purity level of 90-95 vol%. However, adding biomass beyond a certain limit introduced more oxygen into the system, leading to the formation of CO2 and consequently reducing the syngas purity.Bench-Scale Experiments

[0118] Experimental Setup. Experiments were conducted using a moving bed reactor which was be modified for co-current and countercurrent operations. The reactor housed eight type-K thermocouples and an equal number of sampling ports spaced 10 cm apart. The ports were positioned 180° opposite the thermocouple ports. The reactor's external surface was equipped with clamshell heaters, allowing for an operating temperature range of 700 °C to 1050 °C with a setpoint tolerance of + / -5 °C. A lock-hopper at the upper section of the unit was used to introduce oxygen carrier solids, and a quartz window above the heated zone ensured that the reaction zone remained filled during operation. To regulate solids velocity, a screw feeder was connected to a direct current (DC) motor, which maintains a linear relationship between voltage and flow rate, located at the bottom of the moving bed.

[0119] Experimental Results. As shown in FIG. 6, greater than 90 vol% purity CO2 gas was generated from the example countercurrent reactor (reducer 1), where simulated waste gases are introduced in the moving bed reactor. As shown in FIG. 7, 80-90 vol% purity syngas was generated from the example co-current reactor (reducer 2). These bench-scale experimental results agree with the simulations performed, thereby proving the feasibility of such a system.Exemplary Embodiments

[0010] For reasons of completeness, various aspects of the technology are set out in the following numbered embodiments:Embodiment 1. A reactor system, comprising: a countercurrent reactor comprising: a first solids inlet adjacent atop portion of the countercurrent reactor, the first solids inlet configured to receive oxygen carrier solids having multiple oxidation states; a first solids outlet adjacent a bottom portion of the countercurrent reactor; a tail gas inlet adjacent the bottom portion of the countercurrent reactor, the tail gas inlet being in fluid communication with a first process element; and a carbon dioxide (CO2) gas outlet adjacent the top portion of the countercurrent reactor; a co-current reactor comprising:a second solids inlet adjacent a top portion of the co-current reactor, the second solids inlet being in fluid communication with the first solids outlet; a second solids outlet adjacent a bottom portion of the co-current reactor; a carbonaceous feedstock inlet adjacent the top portion of the co-current reactor, the carbonaceous feedstock inlet being in communication with a carbonaceous feedstock source; a steam inlet adjacent the top portion of the co-current reactor, the steam inlet being in fluid communication with a steam source; and a syngas outlet adjacent the bottom portion of the co-current reactor, the syngas outlet being in fluid communication with a second process element; a combustor reactor comprising: a third solids inlet in fluid communication with the second solids outlet; an air inlet in fluid communication with an air source; and a third solids outlet in fluid communication with a riser; and a separation unit configured to separate solids from depleted air, the separation unit comprising: a fourth solids inlet in fluid communication with the riser; an air outlet; and a fourth solids outlet in fluid communication with the first solids inlet.Embodiment 2. The reactor system according to embodiment 1, wherein the oxygen carrier solids comprise iron (Fe).Embodiment 3. The reactor system according to embodiment 1 or 2, wherein the oxygen carrier solids comprise iron (III) oxide (Fe2O3) and titanium (IV) oxide (TiCh).Embodiment 4. The reactor system according to any one of embodiments 1-3, wherein the oxygen carrier solids further comprise an inert support material.Embodiment 5. The reactor system according to any one of embodiments 1-4, wherein the oxygen carrier solids have a particle size of 100 pm to 3000 pm.Embodiment 6. The reactor system according to any one of embodiments 1-5, wherein the second process element is the same as the first process element.Embodiment 7. The reactor system according to any one of embodiments 1-6, wherein the co-current reactor further comprises a second tail gas inlet adjacent the top portion of the co-current reactor, wherein the second tail gas inlet is in fluid communication with the first process element.Embodiment 8. A method for operating a reactor system comprising a countercurrent reactor and a co-current reactor, the method comprising: receiving first oxidation state oxygen carrier solids at a first solids inlet of the countercurrent reactor, the first oxidation state oxygen carrier solids being oxygen carrier solids at a first oxidation state and having multiple oxidation states; receiving tail gases at a tail gas inlet of the countercurrent reactor whereby the first oxidation state oxygen carrier solids in the countercurrent reactor are reduced to generate first lower oxidation state oxygen carrier solids, the tail gases comprising at least one of: carbon monoxide (CO), carbon dioxide (CO2), hydrogen (H2), and methane (CH4); the tail gases being provided such that the tail gases flow in a countercurrent fashion relative to the first oxidation state oxygen carrier solids; collecting a first gas stream from an outlet of the countercurrent reactor, the first gas stream comprising at least 90 volume percent (vol%) carbon dioxide (CO2); providing the first lower oxidation state oxygen carrier solids from the countercurrent reactor to a second solids inlet of the co-current reactor; providing a carbonaceous feedstock and steam to the co-current reactor such that the carbonaceous feedstock, steam, and first lower oxidation state oxygen carrier solids are in cocurrent flow, whereupon the first lower oxidation state oxygen carrier solids are reduced, thereby generating second lower oxidation state oxygen carrier solids; collecting a second gas stream from an outlet of the co-current reactor, the second gas stream comprising carbon monoxide (CO) and hydrogen (H2); providing the second lower oxidation state oxygen carrier solids to a solids inlet of a combustor;providing air to the combustor, whereupon the second lower oxidation state oxygen carrier solids are oxidized, thereby regenerating the first oxidation state oxygen carrier solids, and generating depleted air; providing the first oxidation state oxygen carrier solids and the depleted air to a separation unit; collecting depleted air from the separation unit; and providing the first oxidation state oxygen carrier solids to the countercurrent reactor.Embodiment 9. The method according to embodiment 8, wherein the first oxidation state oxygen carrier solids comprise iron (III) oxide (Fe20.3).Embodiment 10. The method according to embodiment 8 or 9, wherein the first lower oxidation state oxygen carrier solids comprise iron (II, III) oxide (FesCh) and / or iron (II) oxide (FeO).Embodiment 11. The method according to any one of embodiments 8-10, wherein the carbonaceous feedstock comprises biomass.Embodiment 12. The method according to any one of embodiments 8-11, wherein the steam is provided to the co-current reactor at an amount that is 1 percent by weight (wt%) to 10 wt% of an amount of carbon in the carbonaceous feedstock.Embodiment 13. The method according to any one of embodiments 8-12, wherein the steam is provided to the co-current reactor at an amount that is 4 wt% to 6 wt% of the amount of carbon in the carbonaceous feedstock.Embodiment 14. The method according to any one of embodiments 8-13, further comprising operating the countercurrent reactor at a temperature of 300 °C to 1400 °C and a pressure of 0 MPa to 5 MPa.Embodiment 15. The method according to any one of embodiments 8-14, further comprising operating the co-current reactor at a temperature of 300 °C to 1400 °C and a pressure of 0 MPa to 5 MPa.Embodiment 16. The method according to any one of embodiments 8-15, wherein providing the first oxidation state oxygen carrier solids to the separation unit comprises pneumatically transferring the first oxidation state oxygen carrier solids and the depleted air to the separation unit through a riser.Embodiment 17. A reactor system, comprising: a first countercurrent reactor comprising: a first solids inlet adjacent a top portion of the first countercurrent reactor, the first solids inlet configured to receive oxygen carrier solids; a first solids outlet adjacent a bottom portion of the first countercurrent reactor; a tail gas inlet adjacent the bottom portion of the first countercurrent reactor, the tail gas inlet being in fluid communication with a first process element; a carbonaceous feedstock inlet adjacent the top portion of the first countercurrent reactor, the carbonaceous feedstock inlet being in fluid communication with a carbonaceous feedstock source; and a carbon dioxide (CCh) gas outlet adjacent the top portion of the first countercurrent reactor; a second countercurrent reactor comprising: a second solids inlet adjacent a top portion of the second countercurrent reactor, the second solids inlet being in fluid communication with the first solids outlet; a second solids outlet adjacent a bottom portion of the second countercurrent reactor; a gas inlet adjacent the bottom portion of the second countercurrent reactor, the gas inlet being in fluid communication with a gas source configured to provide a gaseous stream comprising steam and / or carbon dioxide (CCh); and a syngas outlet adjacent the top portion of the second countercurrent reactor, the syngas outlet being in fluid communication with a second process element;a combustor reactor comprising: a third solids inlet in fluid communication with the second solids outlet; an air inlet in fluid communication with an air source; and a third solids outlet in fluid communication with a riser; and a separation unit configured to separate solids from depleted air, the separation unit comprising: a fourth solids inlet in fluid communication with the riser; an air outlet; and a fourth solids outlet in fluid communication with the first solids inlet.Embodiment 18. The reactor system according to embodiment 17, wherein the oxygen carrier solids comprise iron ore.Embodiment 19. The reactor system according to embodiment 17 or 18, wherein the first countercurrent reactor is further configured to react the oxygen carrier solids with carbonaceous feedstock from the carbonaceous feedstock source, thereby generating lower oxidation state oxygen carrier solids; wherein the first solids outlet is configured to provide the lower oxidation state oxygen carrier solids to the second solids inlet.Embodiment 20. The reactor system according to any one of embodiments 17-19, wherein the syngas outlet is configured to provide a gas stream to the second process element, the gas stream comprising carbon monoxide (CO) and hydrogen (H2) at a CO:H2 ratio of 0 to 5:1.

[0120] It is understood that the foregoing detailed description and accompanying examples are merely illustrative and are not to be taken as limitations upon the scope of the disclosure. Various changes and modifications to the disclosed embodiments will be apparent to those skilled in the art. Such changes and modifications, including without limitation those relating to the chemical structures, substituents, derivatives, intermediates, syntheses, compositions, formulations, pH and temperature adjustments, separation, recovery, or methods of use, may be made without departing from the spirit and scope of the disclosure.

Claims

CLAIMS1. A reactor system, comprising: a countercurrent reactor comprising: a first solids inlet adjacent a top portion of the countercurrent reactor, the first solids inlet configured to receive oxygen carrier solids having multiple oxidation states; a first solids outlet adjacent a bottom portion of the countercurrent reactor; a tail gas inlet adjacent the bottom portion of the countercurrent reactor, the tail gas inlet being in fluid communication with a first process element; and a carbon dioxide (CO2) gas outlet adjacent the top portion of the countercurrent reactor; a co-current reactor comprising: a second solids inlet adjacent a top portion of the co-current reactor, the second solids inlet being in fluid communication with the first solids outlet; a second solids outlet adjacent a bottom portion of the co-current reactor; a carbonaceous feedstock inlet adjacent the top portion of the co-current reactor, the carbonaceous feedstock inlet being in communication with a carbonaceous feedstock source; a steam inlet adjacent the top portion of the co-current reactor, the steam inlet being in fluid communication with a steam source; and a syngas outlet adjacent the bottom portion of the co-current reactor, the syngas outlet being in fluid communication with a second process element; a combustor reactor comprising: a third solids inlet in fluid communication with the second solids outlet; an air inlet in fluid communication with an air source; and a third solids outlet in fluid communication with a riser; and a separation unit configured to separate solids from depleted air, the separation unit comprising: a fourth solids inlet in fluid communication with the riser; an air outlet; and a fourth solids outlet in fluid communication with the first solids inlet.

2. The reactor system according to claim 1, wherein the oxygen carrier solids comprise iron (Fe).

3. The reactor system according to claim 2, wherein the oxygen carrier solids comprise iron (III) oxide (Fe2O3) and titanium (IV) oxide (TiCh).

4. The reactor system according to claim 2, wherein the oxygen carrier solids further comprise an inert support material.

5. The reactor system according to claim 2, wherein the oxygen carrier solids have a particle size of 100 pm to 3000 pm.

6. The reactor system according to claim 1, wherein the second process element is the same as the first process element.

7. The reactor system according to claim 1, wherein the co-current reactor further comprises a second tail gas inlet adjacent the top portion of the co-current reactor, wherein the second tail gas inlet is in fluid communication with the first process element.

8. A method for operating a reactor system comprising a countercurrent reactor and a cocurrent reactor, the method comprising: receiving first oxidation state oxygen carrier solids at a first solids inlet of the countercurrent reactor, the first oxidation state oxygen carrier solids being oxygen carrier solids at a first oxidation state and having multiple oxidation states; receiving tail gases at a tail gas inlet of the countercurrent reactor whereby the first oxidation state oxygen carrier solids in the countercurrent reactor are reduced to generate first lower oxidation state oxygen carrier solids, the tail gases comprising at least one of: carbon monoxide (CO), carbon dioxide (CO2), hydrogen (H2), and methane (CH4); the tail gases being provided such that the tail gases flow in a countercurrent fashion relative to the first oxidation state oxygen carrier solids;collecting a first gas stream from an outlet of the countercurrent reactor, the first gas stream comprising at least 90 volume percent (vol%) carbon dioxide (CO2); providing the first lower oxidation state oxygen carrier solids from the countercurrent reactor to a second solids inlet of the co-current reactor; providing a carbonaceous feedstock and steam to the co-current reactor such that the carbonaceous feedstock, steam, and first lower oxidation state oxygen carrier solids are in cocurrent flow, whereupon the first lower oxidation state oxygen carrier solids are reduced, thereby generating second lower oxidation state oxygen carrier solids; collecting a second gas stream from an outlet of the co-current reactor, the second gas stream comprising carbon monoxide (CO) and hydrogen (H2); providing the second lower oxidation state oxygen carrier solids to a solids inlet of a combustor; providing air to the combustor, whereupon the second lower oxidation state oxygen carrier solids are oxidized, thereby regenerating the first oxidation state oxygen carrier solids, and generating depleted air; providing the first oxidation state oxygen carrier solids and the depleted air to a separation unit; collecting depleted air from the separation unit; and providing the first oxidation state oxygen carrier solids to the countercurrent reactor.

9. The method according to claim 8, wherein the first oxidation state oxygen carrier solids comprise iron (III) oxide (Fe2O3).

10. The method according to claim 8, wherein the first lower oxidation state oxygen carrier solids comprise iron (II, III) oxide (FeaCh) and / or iron (II) oxide (FeO).

11. The method according to claim 8, wherein the carbonaceous feedstock comprises biomass.

12. The method according to claim 8, wherein the steam is provided to the co-current reactor at an amount that is 1 percent by weight (wt%) to 10 wt% of an amount of carbon in the carbonaceous feedstock.

13. The method according to claim 12, wherein the steam is provided to the co-current reactor at an amount that is 4 wt% to 6 wt% of the amount of carbon in the carbonaceous feedstock.

14. The method according to claim 8, further comprising operating the countercurrent reactor at a temperature of 300 °C to 1400 °C and a pressure of 0 MPa to 5 MPa.

15. The method according to claim 8, further comprising operating the co-current reactor at a temperature of 300 °C to 1400 °C and a pressure of 0 MPa to 5 MPa.

16. The method according to claim 8, wherein providing the first oxidation state oxygen carrier solids to the separation unit comprises pneumatically transferring the first oxidation state oxygen carrier solids and the depleted air to the separation unit through a riser.

17. A reactor system, comprising: a first countercurrent reactor comprising: a first solids inlet adjacent a top portion of the first countercurrent reactor, the first solids inlet configured to receive oxygen carrier solids; a first solids outlet adjacent a bottom portion of the first countercurrent reactor; a tail gas inlet adjacent the bottom portion of the first countercurrent reactor, the tail gas inlet being in fluid communication with a first process element; a carbonaceous feedstock inlet adjacent the top portion of the first countercurrent reactor, the carbonaceous feedstock inlet being in fluid communication with a carbonaceous feedstock source; and a carbon dioxide (CO2) gas outlet adjacent the top portion of the first countercurrent reactor; a second countercurrent reactor comprising: a second solids inlet adjacent a top portion of the second countercurrent reactor, the second solids inlet being in fluid communication with the first solids outlet; a second solids outlet adjacent a bottom portion of the second countercurrent reactor;a gas inlet adjacent the bottom portion of the second countercurrent reactor, the gas inlet being in fluid communication with a gas source configured to provide a gaseous stream comprising steam and / or carbon dioxide (CO2); and a syngas outlet adjacent the top portion of the second countercurrent reactor, the syngas outlet being in fluid communication with a second process element; a combustor reactor comprising: a third solids inlet in fluid communication with the second solids outlet; an air inlet in fluid communication with an air source; and a third solids outlet in fluid communication with a riser; and a separation unit configured to separate solids from depleted air, the separation unit comprising: a fourth solids inlet in fluid communication with the riser; an air outlet; and a fourth solids outlet in fluid communication with the first solids inlet.

18. The reactor system according to claim 17, wherein the oxygen carrier solids comprise iron ore.

19. The reactor system according to claim 17, wherein the first countercurrent reactor is further configured to react the oxygen carrier solids with carbonaceous feedstock from the carbonaceous feedstock source, thereby generating lower oxidation state oxygen carrier solids; wherein the first solids outlet is configured to provide the lower oxidation state oxygen carrier solids to the second solids inlet.

20. The reactor system according to claim 17, wherein the syngas outlet is configured to provide a gas stream to the second process element, the gas stream comprising carbon monoxide (CO) and hydrogen (H2) at a CO:H2 ratio of 0 to 5 : 1.

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