Method for preparing synthesis gas through iron-based oxygen carrier assisted pyrolysis gasification

Abstract

The invention belongs to the technical field of gasification, and discloses a method for preparing synthesis gas through pyrolysis gasification assisted by an iron-based oxygen carrier, the method is applied to a pyrolysis gasification reactor, and the method comprises the following steps: filling a gasification reaction zone with the iron-based oxygen carrier; starting the pyrolysis gasification reactor to enter a fluidized state; the raw materials are introduced into a gasification reaction zone for pyrolysis to generate pyrolysis synthesis gas, after the iron-based oxygen carrier reacts with the pyrolysis synthesis gas to generate a reduction-state oxygen carrier, the reduction-state oxygen carrier is oxidized under the action of fluidizing gas, and the iron-based oxygen carrier recovers lattice oxygen; and discharging the product synthesis gas from the pyrolysis gasification reactor. By utilizing the dual functions of lattice oxygen release and surface catalysis of the iron-based oxygen carrier, water-gas conversion and tar cracking reaction are catalyzed while active oxygen required by gasification is provided, the yield and quality of synthesis gas are synchronously improved, tar generation is remarkably inhibited, and the production cost is reduced. Therefore, the problems of high tar content, low hydrogen-carbon ratio of synthesis gas and high operation cost in the traditional gasification process are effectively solved.

Description

Technical Field

[0001] This invention belongs to the technical field of pyrolysis gasification, and more specifically, relates to a method for producing syngas through pyrolysis gasification assisted by an iron-based oxygen carrier. Background Technology

[0002] Gasification processes commonly suffer from low fuel conversion efficiency, low calorific value of gas components, low hydrogen-to-carbon ratio, and high tar content, limiting the synthesis of downstream high-value chemicals. Tar is one of the main harmful byproducts generated during fuel gasification. It adheres to reactors and catalysts, leading to reactor blockage and catalyst deactivation, affecting the gasification reaction and product quality. Furthermore, it may contain toxic substances, posing hazards to the environment and health, and increasing equipment cleaning and maintenance costs. Therefore, effectively controlling tar formation is a significant challenge in improving fuel gasification efficiency and product quality.

[0003] Oxygen carriers are widely used in chemical looping gasification (CBCG) technology, where they circulate and transfer oxygen and heat between different reactors, enabling the system to operate self-heating and reducing energy consumption. However, due to the complexity and operational difficulties of CBCG serial fluidized bed reaction systems, industrial applications are still some distance away. Traditional fuel gasification technologies suffer from problems such as using inert bed materials (e.g., silica sand) that only act as heat carriers, lacking chemical activity, and having low tar conversion rates. Summary of the Invention

[0004] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a method for producing syngas through iron-based oxygen carrier-assisted pyrolysis gasification. The aim is to utilize the dual functions of lattice oxygen release and surface catalysis of the iron-based oxygen carrier during the gasification process in the pyrolysis gasification reactor. This provides the necessary active oxygen for gasification while simultaneously catalyzing water-gas shift and tar cracking reactions, thereby simultaneously improving syngas yield and quality and significantly inhibiting tar formation. This effectively solves the technical bottlenecks of high tar content, low hydrogen-to-carbon ratio in syngas, and high operating costs in traditional gasification processes.

[0005] To achieve the above objectives, in one aspect of the present invention, a method for producing syngas through iron-based oxygen carrier-assisted pyrolysis gasification is provided, applied to a pyrolysis gasification reactor, the pyrolysis gasification reactor comprising a gasification reaction zone and a fluidizing gas inlet located below the gasification reaction zone, the method comprising the following steps: (1) Fill the gasification reaction zone with an iron-based oxygen carrier to construct an active reaction bed; (2) The pyrolysis gasification reactor is turned on and enters the fluidization state; (3) Fluidizing gas is continuously introduced into the gasification reaction zone to pyrolyze the raw materials to generate pyrolysis synthesis gas. The iron-based oxygen carrier loses lattice oxygen and partially oxidizes the pyrolysis synthesis gas, converting it into a reduced oxygen carrier. Subsequently, the reduced oxygen carrier is oxidized under the action of oxidizing components in the fluidizing gas, and the iron-based oxygen carrier recovers lattice oxygen. The fluidizing gas contains at least one oxygen-containing gas. (4) The gas generated in the gasification reaction zone, which is composed of the pyrolysis synthesis gas and other gases, is discharged from the pyrolysis gasification reactor as synthesis gas; The fluidizing gas in step (2) includes at least one of air, water vapor, and recirculated exhaust gas, and the fluidizing gas in step (3) includes air and water vapor.

[0006] Preferably, the iron-based oxygen carrier is a solid particle with iron oxide as the active component, which is selected from one or more of natural iron ore, iron-containing industrial waste, and artificially synthesized iron-based materials.

[0007] Preferably, the iron-based oxygen carrier is further doped with a metal additive, which is one or more oxides of Co, Cu, Mn, Ca, and Ni, and the mass of the metal additive is 0.5-50% of the mass of the iron-based oxygen carrier.

[0008] Preferably, the particle size of the iron-based oxygen carrier is 0.1-1 mm.

[0009] Preferably, in step (1), the iron-based oxygen carrier and conventional bed material are mixed and then filled into the gasification reaction zone to construct an active reaction bed.

[0010] Preferably, in step (3), the fluidizing gas contains air and water vapor, the air equivalent ratio is 0.2-0.6, the volume percentage of water vapor is 5-60%, and the mass of water vapor corresponding to the mass of fuel at room temperature is 0.5-3.

[0011] Preferably, the raw materials are solid raw materials and liquid raw materials; the solid raw materials include one or more of coal, biomass, municipal solid waste, and solid polymer waste; the liquid raw materials are liquid raw materials containing hydrocarbon elements, including one or more of naphtha, gasoline, kerosene, diesel, heavy oil, methanol, ethanol, tar, industrial organic waste liquid, waste edible oil, and liquid animal fat.

[0012] Preferably, the gasification reaction temperature in the fluidized state is controlled at 600-1100℃.

[0013] Preferably, the operating pressure of the pyrolysis gasification reactor is controlled at 0.1 MPa-6.0 MPa; the apparent gas velocity of the fluidizing gas in the gasification reaction zone is controlled at 0.2-8.0 m / s.

[0014] Preferably, the pyrolysis gasification reactor is a bubbling fluidized bed, a circulating fluidized bed, a spouted bed, or a pressurized fluidized bed.

[0015] In summary, compared with the prior art, the above-described technical solutions conceived by this invention mainly possess the following technical advantages: (1) This invention proposes for the first time a method for producing syngas by pyrolysis gasification assisted by an iron-based oxygen carrier. This method replaces the traditional inert bed material with an iron-based oxygen carrier. In a single gasification reaction zone, a dynamic circulation system with iron-based particles as the core is constructed with fluidized gas of a specific composition. By utilizing the characteristics of releasing lattice oxygen in the oxygen-deficient zone and absorbing gaseous oxygen in the relatively oxygen-rich zone, the active regulation and optimization of oxygen distribution in the fluidized bed is achieved, which significantly improves the reaction rate and bed utilization. More importantly, the dual function of "oxygen supply-catalysis" of the iron-based oxygen carrier is used to achieve the integrated coupling of multi-step reactions: that is, the iron-based carrier is reduced by fuel pyrolysis gas, and then the reduced carrier captures oxygen from water vapor and releases hydrogen in situ. This process not only reduces the tar content through lattice oxygen transfer, but also cleverly utilizes its catalytic properties to enhance the water-gas conversion and tar cracking reaction, thereby significantly improving the hydrogen yield and quality of the syngas product while inhibiting tar formation. In this invention, the fluidizing gas not only serves as a physical medium to maintain the good fluidization state of the bed, but also participates in the core transformation as a key reactant. Depending on its component characteristics (such as air, water vapor, etc.), it plays multiple roles, providing heat of reaction, supplementing the gasifying agent, or providing a hydrogen source. Specifically, the fluidizing gas, on the one hand, flexibly regulates the temperature balance and redox atmosphere within the system through thermochemical reactions with hydrocarbon feedstocks and reduced oxygen carriers; on the other hand, the oxidizing components in the fluidizing gas can participate in the phase transition regeneration process of the iron-based oxygen carrier, promoting the restoration of reduced iron (Fe / FeO) to the highly active Fe3O4 state. This not only avoids the risk of particle agglomeration and defluidization caused by deep reduction and maintains the circulation stability of the carrier, but also induces the generation of additional hydrogen sources through the lattice oxygen transfer mechanism when a hydrogen-containing gasifying agent (such as water vapor) is introduced, achieving synergistic regulation of gasification efficiency, product distribution, and system operational stability. Therefore, by applying iron-based oxygen carriers to pyrolysis gasification reactors with specific structures, this invention can improve syngas yield, effectively suppress tar formation, and improve syngas quality, thereby solving problems such as high tar content, insufficient syngas quality, and high equipment operating costs during fuel gasification.

[0016] (2) This invention proposes a method for producing syngas through iron-based oxygen carrier-assisted pyrolysis gasification, realizing in-situ oxidation-reduction micro-circulation of the iron-based oxygen carrier within the gasifier. The iron-based oxygen carrier can be flexibly selected and has a wide range of applications. It consists of solid particles with iron oxide as the active component, selected from one or more of inexpensive and readily available natural iron ore, iron-containing industrial waste that can be recycled, or artificially synthesized iron-based materials with controllable performance. This broad material adaptability significantly reduces process costs and endows the system with strong engineering applicability.

[0017] (3) Preferably, the iron-based oxygen carrier of the present invention is also doped with metal additives, which are one or more of the oxides of Co, Cu, Mn, Ca, and Ni. The mass of the metal additives is 0.5-50% of the mass of the iron-based oxygen carrier, which effectively solves the technical problems of slow reaction kinetics, low tar conversion rate and easy sintering at high temperature that exist in single iron-based carriers. These metal additives form a synergistic effect with iron oxides. On the one hand, by improving the lattice structure, they reduce the lattice oxygen activation energy and significantly improve the oxygen release rate and redox activity of the oxygen carrier (such as Co, Cu, Mn). On the other hand, they introduce strong catalytic sites and structural support components (such as Ni and Ca), which enhance the in-situ tar cracking and anti-carbon deposition performance, while enhancing the mechanical strength and thermal stability of the particles. Thus, while ensuring the production of high-quality syngas, the service life of the active bed is greatly extended.

[0018] (4) In this invention, the iron-based oxygen carrier and quartz sand are mixed and then packed into the gasification reaction zone to construct an active reaction bed. This addresses the technical problems of difficult fluidization quality control and easy agglomeration caused by the magnetic properties and high-temperature softening characteristics of iron oxides. The present invention preferably uses a mixture of quartz sand and iron-based oxygen carrier to construct the active reaction bed. Quartz sand, as an inexpensive and physically stable inert heat carrier, serves two purposes: firstly, it physically separates and dilutes the active iron-based particles, effectively preventing contact sintering between iron particles and preventing bed deadness at reaction temperatures of 600-1100℃; secondly, the excellent heat capacity of quartz sand helps to smooth temperature fluctuations within the reactor, ensuring a stable heat source for biomass pyrolysis. This mixing strategy significantly improves gas-solid fluidization characteristics while ensuring sufficient active sites participate in the redox cycle, achieving the best balance between system operating economy and fluidization stability.

[0019] (5) In the preferred embodiment of this invention, the fluidized gas composition is precisely controlled in step (3) to construct an "air-water vapor" coupled gasification mechanism, thereby achieving a synergistic improvement in syngas quality and deep tar cracking. On the one hand, in the air gasification mode, by controlling the air equivalence ratio (ER) to be 0.2-0.6, the oxygen carrier circulates between FeO and Fe3O4 in a mixed low-valence state, ensuring a continuous supply of lattice oxygen and avoiding the precipitation of metallic iron caused by deep reduction. This allows the lattice oxygen release rate and regeneration rate of the oxygen carrier to reach a dynamic balance, and the microcirculation path completely avoids the low-activity FeO stable region, ensuring the stability of the high-energy-level cycle. In the water vapor gasification mode, the water vapor volume ratio is 5-60% and the water / fuel mass ratio (S / B) is 0.5-3. The oxygen source of the water vapor is used to further oxidize and regenerate FeO in situ into high-valence Fe3O4, forming "Fe The high oxidation potential of Fe3O4 significantly enhances lattice oxygen capacity and reactivity. On the other hand, high-valence Fe3O4 particles directly release lattice oxygen to the tar and coke attached to their surface, and the reaction kinetics are not limited by gas film diffusion, realizing in-situ deep oxidation and catalytic cracking of tar. At the same time, by adjusting the amount of water vapor added, the catalytic properties of iron-based oxygen carriers are used to enhance tar cracking and reforming reactions, converting tar macromolecules into small molecules such as CH4, CO, and H2, significantly reducing tar content.

[0020] (6) High operational flexibility. The gasification reaction temperature is controlled at 600-1100℃, the oxygen carrier replacement ratio is 5%-100%, the gasification medium can be air, water vapor or a mixture of both, and the raw materials include solid raw materials and liquid raw materials. The operating mode can be flexibly adjusted according to actual needs, and it has wide applicability.

[0021] (7) The kinetic enhancement of the gasification process and the high-efficiency energy level matching of downstream processes are achieved. By widening the operating pressure to 0.1-6.0 MPa and controlling the fluidizing gas velocity to 0.2-8.0 m / s, this invention significantly improves the gas phase partial pressure and reaction kinetics by utilizing the high-pressure environment, thereby greatly increasing the unit volume processing capacity. The high-pressure syngas produced can be directly matched with downstream methanol or Fischer-Tropsch synthesis processes, eliminating the expensive intermediate compression stage. On the other hand, the wide range of gas velocity control gives the system extremely high operational flexibility, enhances gas-solid mass and heat transfer, and ensures that a highly efficient and stable fluidizing reaction environment can be maintained under different load and pressure conditions.

[0022] (8) It possesses excellent engineering adaptability and industrial scale-up potential, overcoming the equipment limitations of traditional technologies. The method of this invention is widely applicable to various mainstream configurations such as bubbling fluidized beds, circulating fluidized beds, spouted beds, and pressurized fluidized beds. It can flexibly select the optimal reactor form according to fuel characteristics (such as recalcitrant solids) and production scale (such as high throughput requirements). This method does not rely on complex dual-bed circulation structures, which greatly reduces system complexity and construction costs, and facilitates rapid upgrading and large-scale commercialization based on existing mature fluidized bed industrial devices.

[0023] In summary, the method of this invention achieves synergistic enhancement of multiphase reactions. The iron-based oxygen carrier not only undergoes solid-solid reactions with coke to improve fuel conversion efficiency, but also undergoes gas-solid reactions with syngas (such as water-gas shift reaction). Simultaneously, it converts large tar molecules into small molecule gases through catalytic tar cracking and reforming reactions, achieving multiple objectives of tar suppression, syngas quality improvement, and increased hydrogen production. Attached Figure Description

[0024] Figure 1 This is a schematic diagram illustrating the principle of producing syngas in a pyrolysis gasification reactor using the method of the present invention.

[0025] Figure 2 This is a fluidized bed reactor as shown in an embodiment of the present invention.

[0026] Figure 3 The values ​​represent the average concentration of each component of the syngas and the total gas yield under different processes shown in the embodiments of the present invention.

[0027] Figure 4 The figures represent the gas yields of each component of syngas, the H2 / CO ratio, and the fuel conversion efficiency under different processes shown in the embodiments of the present invention.

[0028] Figure 5 This is a comparison of tar content under quartz sand and oxygen-carrier-assisted gasification as shown in the embodiments of the present invention; wherein, Figure 5 The bottle on the right contains tar produced by quartz sand-assisted gasification. Figure 5 The bottle on the right contains tar under oxygen-carrier-assisted vaporization.

[0029] Figure 6 The oxygen carrier XRD results of this invention are shown in the images: fresh oxygen carrier (a), oxygen carrier in water vapor operation mode (b), and oxygen carrier in air operation mode (c). Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0031] To achieve the above objectives, this invention provides a method for producing syngas through iron-based oxygen carrier-assisted pyrolysis gasification. In this method, iron-based oxygen carrier particles are introduced into the pyrolysis gasification reactor to partially or completely replace the inert bed material during the gasification process. Under the assistance of the gasification medium and the iron-based oxygen carrier, the fuel undergoes a gasification reaction to produce gasification products. In the fluidized bed gasification process, an active iron-based oxygen carrier replaces the inert bed material in the traditional feedstock gasification process. Through the lattice oxygen transfer and valence state cycle of the iron-based oxygen carrier, the coupling of biomass gasification, tar cracking, and water splitting for hydrogen production is achieved.

[0032] Specifically, the present invention provides a method for producing syngas through iron-based oxygen carrier-assisted pyrolysis gasification, applied to a pyrolysis gasification reactor. The pyrolysis gasification reactor includes a gasification reaction zone and a fluidizing gas inlet located below the gasification reaction zone. The method includes the following steps: (1) Fill the pyrolysis gasification reactor with an iron-based oxygen carrier as an active bed material to construct an active reaction bed with lattice oxygen transfer capability. (2) Start the pyrolysis gasification reactor to enter the fluidization state; (3) such as Figure 1 As shown, a fluidizing gas containing at least one oxygen-containing gas is continuously introduced to feed the raw material into the gasification reaction zone of the pyrolysis gasification reactor, causing the raw material to undergo pyrolysis to generate pyrolysis syngas. The iron-based oxygen carrier loses its lattice oxygen, partially oxidizes the pyrolysis syngas, and converts it into a reduced oxygen carrier. Subsequently, the reduced oxygen carrier is oxidized under the action of oxidizing components in the fluidizing gas, and the iron-based oxygen carrier recovers its lattice oxygen. (4) The pyrolysis syngas generated in the gasification reaction zone and other gases generated in the reaction are discharged from the pyrolysis gasification reactor as syngas. Here, when the fluidizing gas contains water vapor, hydrogen is generated in situ by cracking water molecules while the reduced oxygen carrier is being oxidized and regenerated.

[0033] In this operating mode, the fluidizing gas flexibly controls the temperature balance and redox atmosphere within the system through thermochemical reactions with hydrocarbon feedstocks and reduced oxygen carriers. The fluidizing gas contains air, and the molecular oxygen in the fluidizing gas replenishes the lattice oxygen lost by the oxygen carrier. The post-reaction phase mainly consists of a mixture of low-valence states of FeO and Fe3O4, forming Fe... The FeO+Fe3O4 cycle involves the fluidizing gas containing water vapor. The oxidizing components in the fluidizing gas can replenish the lattice oxygen lost by the oxygen carrier using molecular oxygen, and can also participate in the phase transition regeneration process of the iron-based oxygen carrier, promoting the reduction of iron (Fe / FeO) to the highly active Fe3O4 state, thus restoring the lattice oxygen of the iron-based oxygen carrier and achieving regeneration cycle. At the same time, when the fluidizing gas contains water vapor, this process is accompanied by the release of hydrogen.

[0034] More specifically, the characteristics of this method or system are: a: The iron-based oxygen carrier acts as a heat source for gasification during the reaction, utilizing the heat released during the oxidation of the oxygen carrier to maintain the temperature field required for the gasification reaction. By leveraging the exothermic properties of the iron-based oxygen carrier during oxidation (regeneration), a portion of the chemical energy can be converted into heat energy to supply the gasification reaction in situ, significantly reducing the external energy load. Under optimized processes, a self-heating reaction can be achieved without an external heat source (such as electric heating), realizing the cascade utilization of energy. When the chemical heat is insufficient to maintain the system's set reaction temperature, heat is supplemented by an external auxiliary heating device, which can be one of electric heating, combustion heating, or solar heating.

[0035] b: The iron-based oxygen support acts as an in-situ catalyst during the reaction, that is, it uses the active sites on the reduced iron-based surface to reduce the activation energy of bond breaking of tar macromolecules.

[0036] c: Regeneration of iron-based oxygen carrier coupled with hydrogen production, i.e. hydrogen production is achieved through the reaction pathway Fe / FeO+H2O→Fe3O4+H2.

[0037] d: In the cycle described in step (3), Fe3O4 particles directly release lattice oxygen to the tar and coke attached to their surface. The reaction kinetics are not limited by gas film diffusion, thus realizing in-situ deep oxidation and pyrolysis.

[0038] e: The microcirculation reconstruction process realizes the coupling of gasification and chemical chain hydrogen production. Unlike the traditional gasification process where water vapor only participates in the water-gas shift reaction (CO + H2O → CO2 + H2) as a gasifying agent, in step S3 of this method, water vapor participates in the phase change regeneration process of the iron-based oxygen carrier. Through the oxidation of iron, water molecules are directly cracked to generate an additional hydrogen source, which significantly improves the H2 / CO ratio of the syngas.

[0039] In some implementations, the amount of iron-based oxygen carrier is determined based on its active oxygen supply to prevent excessive oxygen supply from over-oxidizing the syngas and causing a decline in syngas quality.

[0040] In some embodiments, the iron-based oxygen support is a solid particle with iron oxide as the active component. Its source is flexible; it can be synthesized artificially or selected from one or more of natural iron ore and iron-containing industrial waste. Specifically, the iron-based oxygen support includes simple iron oxides (such as Fe2O3, Fe3O4), supported composite materials (such as Fe2O3 / Al2O3, Fe2O3 / ZrO2), spinel-type (such as NiFe2O4), and perovskite-type (such as Ca2Fe2O5, La). 0.8 Sr 0.2 Systems such as FeO3.

[0041] In some embodiments, the iron-based oxygen carrier is further doped with a metal additive, which is one or more of the oxides of Co, Cu, Mn, Ca, and Ni, and the mass of the metal additive is 0.5-50% of the mass of the iron-based oxygen carrier.

[0042] In some embodiments, the particle size of the iron-based oxygen carrier is 0.1-1 mm, which enables the oxygen carrier to achieve good fluidization during the gasification process.

[0043] In some embodiments, in step (1), the iron-based oxygen carrier and conventional bed material, such as quartz sand, are mixed and packed into the gasification reaction zone to construct an active reaction bed. Quartz sand physically separates the oxygen carrier particles in the pyrolysis gasification reactor to prevent high-temperature sintering and agglomeration; it also acts as a thermal buffer to make the reaction temperature more uniform; and simultaneously, it optimizes reaction control by diluting the active components and prevents excessive oxidation of the syngas by diluting the oxygen release density. Typically, the iron-based oxygen carrier particle replacement ratio is 5%-100%.

[0044] In some embodiments, the fluidizing gas contains at least water vapor to prevent oxygen carrier sintering and agglomeration caused by deep reduction. The oxidation effect of water vapor on the microcirculation regeneration end ensures that even in areas with extremely strong local reducing atmosphere, the oxygen carrier can quickly recover from the metallic Fe or FeO state to the Fe3O4 state, thereby avoiding particle agglomeration and bed defluidization caused by metallic iron precipitation.

[0045] In some embodiments, at least one oxygen-containing gas is included, such as air, water vapor, or CO2. The fluidizing gas includes air, with an air equivalent ratio (ER) of 0.2-0.6. Preferably, the fluidizing gas includes air and water vapor, with an air equivalent ratio (ER) of 0.2-0.6 and water vapor accounting for 5-60% of the volume; and the water vapor corresponds to a mass ratio of 0.5-3 of water to fuel at room temperature to maintain the stability of the high-energy-level cycle. Within this range, the lattice oxygen release rate and regeneration rate of the oxygen carrier reach a dynamic equilibrium, and the microcirculation path completely avoids the low-activity FeO stability region. Simultaneously, by adjusting the amount of water vapor added, the lattice oxygen capacity advantage of high-valence Fe3O4 and the catalytic properties of the iron-based oxygen carrier are utilized to enhance the oxidation and catalytic cracking of tar.

[0046] In some embodiments, the raw materials are solid and liquid. Solid raw materials include one or more of coal, biomass, municipal solid waste, and solid polymer waste. Under the combined action of high temperature and fluidized medium, these materials produce syngas, tar, coke, and other substances. These products are further transformed under the action of an oxygen carrier. The oxygen carrier undergoes a solid-solid reaction with coke, improving fuel conversion efficiency, and a gas-solid reaction with syngas, such as reacting with CO through a water-gas shift reaction to produce H2. In addition, the oxygen carrier catalyzes tar cracking and reforming reactions, breaking the C-C and CH bonds of large tar molecules into smaller molecules such as CH4, CO, and H2, effectively inhibiting tar production. Liquid raw materials refer to liquid substances rich in hydrocarbons, including but not limited to: hydrocarbon compounds such as naphtha, gasoline, kerosene, diesel, and heavy oil; alcohol compounds such as methanol and ethanol; and complex mixtures such as tar, industrial organic waste liquid, waste cooking oil, and animal fat.

[0047] In some implementations, the gasification reaction temperature in the fluidized state is controlled at 600-1100°C.

[0048] In some implementations, the operating pressure of the pyrolysis gasification reactor is controlled at 0.1 MPa-6.0 MPa; the apparent gas velocity of the fluidizing gas in the gasification reaction zone is controlled at 0.2-8.0 m / s.

[0049] In some embodiments, the pyrolysis gasification reactor is a bubbling fluidized bed, a circulating fluidized bed, a sputtering bed, or a pressurized fluidized bed.

[0050] In some implementations, the fluidized bed reactor operates in a single-bed mode. The single-bed mode includes a single-bed intermittent switching mode and a mixed mode. The single-bed intermittent switching mode refers to alternating the introduction of either air or steam within the same fluidized bed's gasification reaction zone, achieving a cycle of gasification and regeneration by switching the type of gas introduced (gasifying agent / steam). The single-bed mixed mode refers to simultaneously gasifying air and steam within the same fluidized bed's gasification reaction zone, achieving in-situ regeneration of the oxygen carrier.

[0051] In this invention, the H2 / CO ratio of the syngas products obtained by the method of this invention is 0.5-3.5.

[0052] The technical solution provided by the present invention will be described in detail below with reference to specific embodiments.

[0053] Specific embodiment: Biomass oxygen carrier-assisted gasification to produce syngas.

[0054] Using natural hematite as the iron-based oxygen carrier raw material, the specific preparation steps are as follows: The raw materials were dried in a drying oven at 80℃ for 6 hours. The samples were then removed, cooled to room temperature, crushed, and sieved to a size of 150-350 micrometers. To improve the mechanical strength of the oxygen carrier and remove sulfur-containing components, the iron-based oxygen carrier was calcined in a muffle furnace at 1000℃ for 10 hours under air. Its chemical composition was determined by XRF and is shown in Table 1. To ensure similar fluidization rates, the particle size of both the oxygen carrier and the quartz sand was 0.15-0.35 mm in the experiment.

[0055] Table 1: Analysis of Main Chemical Components of Hematite

[0056] The biomass raw material used was paulownia wood chips with a particle size of 3-6 mm. Elemental and industrial analyses are shown in Table 2.

[0057] Table 2: Elemental and Industrial Analysis of Paulownia Wood Chips

[0058] During the experiment, the static bed height-to-diameter ratio was maintained at 1. Quartz sand was used as the inert bed material. Air and steam were used as fluidizing gases, with the air equivalent ratio maintained at 0.2. The biomass feed rate was fixed at 2 g / min.

[0059] The specific steps are as follows: Before heating, add 50g of oxygen carrier and 150g of quartz sand, and mix the oxygen carrier and quartz sand bed material and pile it on the air distribution plate; heat the fluidized bed reactor to 850℃ at a heating rate of 10℃ / min, while simultaneously introducing air from the bottom to fluidize the bed material, and using the oxygen in the air to fully oxidize the oxygen carrier; when the target temperature is reached, switch the atmosphere to a fluidized gas mixture of air and steam. After the fluidized gas stabilizes, turn on the biomass feeding device to introduce biomass into the reactor reaction zone for biomass gasification; the biomass pyrolyzes at high temperature to produce syngas, tar, and coke. Under the oxygen supply and catalytic action of the iron-based oxygen carrier, the coke is further gasified, and the syngas produces higher levels of H2 through reactions such as water-gas shift reaction, while the tar is cracked into smaller molecules; the filtered syngas is connected to a flue gas analyzer to detect the concentrations of gases such as CO, O2, H2, and CH4. The fluidized bed reactor is as follows: Figure 2 As shown.

[0060] To investigate the effect of oxygen carrier on biomass gasification, the effects of air gasification, steam gasification, and oxygen carrier-assisted gasification (with and without steam) were compared at 850℃. The results are as follows: Figures 3-4 As shown, without the addition of water vapor, compared with pure air gasification, the addition of an oxygen carrier slightly increases the carbon conversion rate from 0.78 to 0.79, indicating that the oxygen source provided by the oxygen carrier promotes the conversion of coke. However, due to the limited solid-solid reaction, the improvement in carbon conversion rate is limited. Due to the presence of the oxygen carrier, the hydrogen yield increased from 0.146 m³ / s. 3 / kg increased to 0.222 m 3 / kg, the H2 / CO ratio increased from 0.53 to 0.86, indicating that the oxygen carrier has a significant regulatory effect on syngas. When both water vapor and oxygen carrier are added simultaneously, the carbon conversion rate further increases to 0.86. CO2 and H2 yields increase significantly, with the H2 yield increasing to 0.414 m³ / kg. 3 / kg, this is because, under the condition of steam introduction, the iron-based oxygen carrier can strongly catalyze the water-gas shift reaction (CO + H2O → CO2 + H2). Since the amount of CH4 produced is relatively small, the change is not significant. Furthermore, due to the decrease in CO yield, the H2 / CO ratio is as high as 2.19 during steam-oxygen carrier-assisted gasification, significantly higher than the 0.53 of air oxidation. The various indicators are shown in Table 3.

[0061] Table 3: Indicators for Different Processes

[0062] To investigate the effect of oxygen carrier on tar removal, isopropanol was used to collect tar from syngas. (See figure.) Figure 5 The results show the collection outcomes of quartz sand and oxygen-assisted gasification, respectively. It can be seen that... Figure 5The color in the bottle on the right is much lighter, indicating that the tar content in the syngas from oxygen-carrier-assisted gasification is significantly reduced, demonstrating the catalytic effect of oxygen-carrier-assisted gasification on tar cracking in this invention.

[0063] Furthermore, to verify the "microcirculation" mechanism proposed in this invention, X-ray diffraction (XRD) phase analysis was performed on the fresh oxygen carrier, the oxygen carrier after air vaporization, and the oxygen carrier after water vaporization in this embodiment. The results are as follows: Figure 6 As shown, under conventional air vaporization mode, the XRD pattern of the oxygen support after reaction showed obvious FeO characteristic diffraction peaks, which coexisted with Fe3O4 peaks. This confirms that under a simple air atmosphere, the regeneration process of the oxygen support is thermodynamically or kinetically limited, and cannot be completely restored to the highest oxidation state; the microcirculation is forced to operate in the Fe... The low-energy mixed phase region of FeO + Fe3O4 leads to the failure of some active sites on the oxygen support. After introducing water vapor coupling, the XRD pattern changed significantly: the characteristic peaks of FeO completely disappeared, and the pattern showed a high-purity spinel phase (Fe3O4). This result strongly confirms the key role of water vapor as an oxidant. The reaction FeO + H2O → Fe3O4 + H2 successfully eliminated the low-valence FeO accumulated in the cycle, forcibly raising the regeneration endpoint of the oxygen support to Fe3O4, which has high lattice oxygen transfer activity. The above-mentioned phase evolution law confirms that the method of this invention not only achieves efficient regeneration of the oxygen support but also achieves optimal reconstruction of the microcirculation path through atmosphere control, thereby ensuring a continuous supply of highly active lattice oxygen and the chemical loop hydrogen production function during the gasification process.

[0064] The above examples demonstrate the effectiveness of the oxygen carrier-assisted gasification device and method of this invention, significantly improving fuel conversion efficiency, syngas yield, and H2 / CO ratio. Furthermore, it also shows potential in addressing the critical challenge of in-situ tar removal in biomass gasification. This invention provides crucial technical support for the high-value utilization of biomass.

[0065] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for producing syngas through iron-based oxygen carrier-assisted pyrolysis and gasification, characterized in that, The method, applied to a pyrolysis gasification reactor comprising a gasification reaction zone and a fluidizing gas inlet located below the gasification reaction zone, includes the following steps: (1) Fill the gasification reaction zone with an iron-based oxygen carrier to construct an active reaction bed; (2) Start the pyrolysis gasification reactor to enter the fluidization state; (3) Fluidizing gas is continuously introduced to introduce the raw material into the gasification reaction zone, causing the raw material to undergo pyrolysis to generate pyrolysis synthesis gas. The iron-based oxygen carrier loses lattice oxygen and partially oxidizes the pyrolysis synthesis gas, converting it into a reduced oxygen carrier. The reduced oxygen carrier is oxidized under the action of oxidizing components in the fluidizing gas, and the iron-based oxygen carrier recovers lattice oxygen. The fluidizing gas contains at least one oxygen-containing gas. (4) The pyrolysis synthesis gas generated in the gasification reaction zone and other gases generated by the reaction are discharged from the pyrolysis gasification reactor as synthesis gas.

2. The method for producing syngas by iron-based oxygen carrier-assisted pyrolysis and gasification according to claim 1, characterized in that, The iron-based oxygen carrier is a solid particle with iron oxide as the active component, which is selected from one or more of natural iron ore, iron-containing industrial waste, and artificially synthesized iron-based materials.

3. The method for producing syngas by iron-based oxygen carrier-assisted pyrolysis and gasification according to claim 2, characterized in that, The iron-based oxygen carrier is further doped with a metal additive, which is one or more of the oxides of Co, Cu, Mn, Ca, and Ni, and the mass of the metal additive is 0.5-50% of the mass of the iron-based oxygen carrier.

4. The method for producing syngas by iron-based oxygen carrier-assisted pyrolysis gasification according to claim 1, characterized in that, The particle size of the iron-based oxygen carrier is 0.1-1 mm.

5. The method for producing syngas by iron-based oxygen carrier-assisted pyrolysis gasification according to any one of claims 1-4, characterized in that, In step (1), the iron-based oxygen carrier and conventional bed material are mixed and then filled into the gasification reaction zone to construct an active reaction bed.

6. The method for producing syngas by iron-based oxygen carrier-assisted pyrolysis and gasification according to claim 1, characterized in that, In step (3), the fluidizing gas contains air and water vapor, the air equivalent ratio is 0.2-0.6, the water vapor volume ratio is 5-60%, and the water vapor corresponds to the mass ratio of water at room temperature to the mass of fuel is 0.5-3.

7. The method for producing syngas by iron-based oxygen carrier-assisted pyrolysis and gasification according to claim 1, characterized in that, The raw materials are solid raw materials and liquid raw materials; the solid raw materials include one or more of coal, biomass, municipal solid waste, and solid polymer waste; the liquid raw materials are liquid raw materials containing carbon and hydrogen elements, including one or more of naphtha, gasoline, kerosene, diesel, heavy oil, methanol, ethanol, tar, industrial organic waste liquid, waste edible oil, and liquid animal fat.

8. The method for producing syngas by iron-based oxygen carrier-assisted pyrolysis and gasification according to claim 1, characterized in that, The gasification reaction temperature in the fluidized state is controlled at 600-1100℃.

9. The method for producing syngas by iron-based oxygen carrier-assisted pyrolysis and gasification according to claim 1, characterized in that, The operating pressure of the pyrolysis gasification reactor is controlled between 0.1 MPa and 6.0 MPa; the apparent gas velocity of the fluidizing gas in the gasification reaction zone is controlled between 0.2 and 8.0 m / s.

10. The method for producing syngas by iron-based oxygen carrier-assisted pyrolysis and gasification according to claim 1, characterized in that, The pyrolysis gasification reactor is a bubbling fluidized bed, a circulating fluidized bed, a jet-driven bed, or a pressurized fluidized bed.

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