Solid fuel chemical looping gasification multistage bed fuel reactor

Abstract

The invention provides a multistage bed fuel reactor for chemical looping gasification of solid fuel, and aims to strengthen mixing, reaction and separation of high-density-difference fuel and oxygen carrier particles. The fuel reactor is composed of a bubbling bed, a central lifting pipe, an oxygen carrier separation area, a cyclone separator and a material returning system. The bubbling bed at the bottom is used as a primary reaction zone and provides longer retention time to promote sufficient gasification of the solid fuel; and a secondary reaction area is formed by the central lifting pipe under the action of high-speed airflow, so that the rapid fluidization reaction of the fuel and the oxygen carrier is realized. And after the mixed particles enter the expanded oxygen carrier separation area, effective separation of the light fuel and the heavy oxygen carrier is realized by reducing the flow rate. The reduced oxygen carrier enters an air reactor for regeneration, and unreacted fuel is subjected to cyclone separation and then returns to the bubbling bed for continuous reaction. The reactor improves the particle circulation efficiency while prolonging the reaction retention time, is beneficial to improving the gasification efficiency and realizing the self-heating operation of the system, and is suitable for fuels such as biomass and coal.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of low-carbon energy utilization, and particularly relates to a solid fuel chemical looping gasification multi-stage bed fuel reactor for intensifying gas-solid flow, particle mixing, reaction and separation. The reactor is suitable for chemical looping gasification of various solid fuels such as biomass, coal and coke, and can realize the intensification of the mixing-reaction-separation process between high-density-difference solid fuels and oxygen carriers. BACKGROUND

[0002] Chemical looping gasification is a high-efficiency energy conversion and carbon capture technology using oxygen carriers as intermediates. It realizes the partial oxidation of solid fuels and the generation of synthesis gas by the circulation of oxygen carriers between the fuel reactor and the air reactor to transfer oxygen elements. Compared with the traditional gasification method, chemical looping gasification can realize the gasification reaction without direct contact between fuel and air, which is conducive to improving the quality of synthesis gas and reducing the energy consumption of carbon dioxide separation, and thus has attracted widespread attention in the field of clean and efficient utilization of solid fuels such as biomass, coal and solid waste.

[0003] In existing chemical looping gasification devices, the fuel reactor usually adopts a fluidized bed structure such as a bubbling bed or a fast fluidized bed. The bubbling bed operates at a relatively low gas velocity, which can provide a long residence time for solid fuel and oxygen carrier particles, and is conducive to the full reaction of the fuel and the improvement of the gasification depth. However, due to the significant density difference between the solid fuel particles and the oxygen carrier particles, the two types of particles are prone to stratification and segregation under low-speed fluidization conditions, making it difficult to form sufficient mixing, thereby limiting the further improvement of the gas-solid heat transfer, mass transfer and reaction efficiency. At the same time, the circulation flow rate of oxygen carrier particles in the bubbling bed is low, making it difficult to realize the self-heating operation of the chemical looping gasification system.

[0004] In contrast, the fast fluidized bed operates at a relatively high gas velocity, which can significantly enhance the contact efficiency between the gas and solid phases and the degree of particle mixing, and increase the circulation flow rate of the oxygen carrier particles. The high circulation flow rate of the oxygen carrier is conducive to the oxygen carrier carrying more reaction heat into the fuel reactor, thereby increasing the gasification reaction intensity and facilitating the system to realize self-heating operation. However, under the condition of high gas velocity fluidization, the residence time of particles in the bed is significantly shortened, and the unreacted fuel particles or coke are easily entrained into the air reactor with the gas flow, causing the fuel to be completely burned in the air reactor and generating carbon dioxide, thereby reducing the synthesis gas yield and weakening the carbon capture advantage of the chemical looping gasification process.

[0005] Therefore, it is difficult to simultaneously meet the multiple requirements of sufficient mixing of high-density-difference fuel particles and oxygen carrier particles, sufficient reaction residence time, and efficient separation of reduced oxygen carrier and unreacted fuel particles in the existing fuel reactor with a single flow pattern. Therefore, it is urgent to propose a new fuel reactor structure design to further optimize the gas-solid contact conditions, improve the reaction efficiency and separation efficiency of fuel and oxygen carrier while ensuring the particle circulation capacity. SUMMARY

[0006] The purpose of the present application is to provide a solid fuel chemical looping gasification multi-stage bed fuel reactor to overcome the problems of insufficient mixing, limited reaction efficiency and difficult separation of light and heavy particles caused by large density difference between solid fuel particles and oxygen carrier particles and significant difference in reaction characteristics in the existing chemical looping gasification fuel reactor.

[0007] The present application integrates the bubbling bed, the central riser and the oxygen carrier separation zone to build a multi-flow state, multi-reaction intensity collaborative reaction and separation space in the same fuel reactor, realize the full gasification reaction of solid fuel, the efficient transportation of particulate material and the effective separation of fuel particles and oxygen carrier particles, thereby improving the synthesis gas yield and carbon conversion efficiency, and facilitating the system to realize stable heat balance operation.

[0008] The reactor has simple structure and stable operation, and is suitable for the chemical looping gasification process of various solid fuels such as biomass, coal, coke and municipal solid waste, and can also be applied to the mixing, reaction and separation process intensification of other heterogeneous particle systems with high density difference.

[0009] To achieve the above purpose, the present application adopts the following technical solutions.

[0010] A solid fuel chemical looping gasification multi-stage bed fuel reactor comprises a bubbling bed, a central riser, an oxygen carrier separation zone, a cyclone separator and a return system connected thereto; the bubbling bed, the central riser and the oxygen carrier separation zone are arranged and communicated in sequence along the vertical direction.

[0011] The bubbling bed is arranged at the bottom of the fuel reactor and is a primary reaction zone. The bottom is sequentially provided with a gas chamber, a wind distribution plate and a central wind pipe inserted into the interior of the bubbling bed; the oxidized oxygen carrier (Me x O y ) enters the bubbling bed through the oxygen carrier inlet, and the solid fuel is metered by the screw feeder after being stored by the storage device and then enters the bubbling bed through the fuel feeding port; the gas chamber and the central wind pipe pass through the gasification agent and / or the fluidization medium to form a low-speed fluidization state in the bubbling bed, thereby providing a longer particle residence time for the solid fuel and the oxygen carrier particles and promoting the full performance of the solid-solid gasification reaction.

[0012] The bottom inlet of the central riser is inserted into the bubbling bed and located at a predetermined distance above the outlet of the central duct, forming a secondary reaction zone. The high-speed airflow entering the central duct creates a localized low-pressure zone at the inlet of the central riser, which, through pressure difference, carries fuel particles and oxygen carrier particles from the bubbling bed into the central riser. Under the influence of the high-speed airflow, the mixed particles are in a state of rapid fluidization or transport within the central riser, thereby enhancing gas-solid contact and mass transfer processes, and promoting fuel gasification and oxygen carrier reduction reactions.

[0013] The top outlet of the central riser is connected to the oxygen carrier separation zone. After the mixed particles enter the oxygen carrier separation zone, a dilute phase separation zone is formed by reducing the airflow velocity. Utilizing the difference in density and terminal settling velocity between the fuel particles and the oxygen carrier particles, effective separation of light fuel particles and heavy oxygen carrier particles is achieved. The separated reduced oxygen carrier (Me...) x O y-1 The oxygen carrier is transported to the air reactor via the waiting inclined tube for oxidation and regeneration to complete the oxygen carrier cycle; the unreacted fuel particles or coke after separation enter the cyclone separator with the airflow, and after cyclone separation, they are returned to the bubble bed through the return riser and U-shaped valve to continue the reaction; the syngas generated by gasification is discharged from the system through the exhaust core pipe of the cyclone separator.

[0014] The operating temperature of the fuel reactor is maintained between 800°C and 1000°C, and the operating pressure can be atmospheric or pressurized to meet the requirements of different solid fuel chemical looping gasification processes for reaction intensity and system stability; the gasifying agent preferably includes water vapor.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects:

[0016] (1) Flow pattern optimization and reaction-transport synergistic enhancement: This invention integrates the bubbling bed and the central riser in the vertical direction to construct a multi-segment bed synergistic operation structure, which combines the advantages of long particle residence time and sufficient gas-solid contact of the bubbling bed with the characteristics of strong particle transport capacity and high circulation flow rate of the central riser. It effectively overcomes the technical defects of single flow pattern fuel reactors in that it is difficult to balance particle mixing performance, reaction efficiency and circulation volume, and realizes the synergistic enhancement of reaction process and particle transport process.

[0017] (2) Adjustable gas velocity and structure enhance the controllability of heterogeneous particle mixing and reaction: By adjusting the gas flow rate entering the central duct and the gas chamber respectively, and optimizing the design of key structural parameters such as the height-to-diameter ratio of the bubble bed and the central riser pipe and the angle of the cone section below the bubble bed, the hydrodynamic characteristics of each functional area can be matched with the reaction rate of oxygen carrier particles and fuel particles of different properties, thereby achieving effective control of the mixing state, residence time and gas-solid reaction intensity of multi-component heterogeneous particles.

[0018] In particular, the lower part of the bubbling bed adopts a conical structure design, which makes the rising airflow gradually slow down as the cross-sectional area increases. This is conducive to the separation and dispersion of fuel particles and further promotes the full mixing of high-density difference fuel particles and oxygen carrier particles.

[0019] (3) High separation accuracy, which is conducive to reducing carbon loss: The oxygen carrier separation zone set up in this invention operates under dilute phase flow conditions. Based on the difference in density and terminal settling velocity between fuel particles and oxygen carrier particles, it achieves effective separation of light fuel or coke particles from heavy oxygen carrier particles, thereby avoiding the complete oxidation of unreacted fuel particles or coke into the air reactor with the oxygen carrier to generate carbon dioxide. This is conducive to improving the syngas yield and reducing carbon resource loss, while enhancing the stability of the system's self-heating operation.

[0020] (4) Modular structure and strong engineering adaptability: The reactor adopts flange connection between each functional section, which has a high degree of modularity and facilitates the disassembly, inspection and maintenance of the device. At the same time, by adjusting the length of each section and the overall height, the structure can be flexibly expanded or scaled according to the processing scale and operation requirements. It can adapt to the chemical chain gasification process of various solid fuels such as biomass and coal as well as different types of oxygen carriers, and has good engineering application potential.

[0021] (5) Good thermal balance and outstanding environmental benefits: By utilizing the heat of reaction released by the oxygen carrier in the reduction and oxidation cycle, the internal thermal balance of the system is maintained, reducing the external energy input requirement; at the same time, CO2 emissions are reduced through efficient separation, which is in line with the development direction of clean energy technology.

[0022] Furthermore, the present invention can also be adapted to different processing scales and operating conditions by adjusting parameters such as gas flow rate, bed height and material selection; all equivalent transformations or improvements made by those skilled in the art without departing from the technical concept of the present invention should fall within the protection scope of the present invention. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the overall structure of a multi-stage bed fuel reactor for solid fuel chemical looping gasification according to the present invention;

[0025] Figure 2 This is a schematic diagram of the structure of the bubbling bed air distribution plate in the multi-stage bed fuel reactor of the present invention;

[0026] Figure 3 for Figure 1 AA cross-section view.

[0027] In the attached diagram: 1. Central air duct; 2. Air chamber; 3. Air distribution plate; 4. Oxygen carrier inlet; 5. Bubble bed; 6. Central riser; 7. Waiting inclined pipe; 8. Oxygen carrier separation zone; 9. Horizontal pipe; 10. Exhaust core pipe; 11. Cyclone separator; 12. Return material riser; 13. U-valve; 14. Hopper; 15. Screw feeder; 16. Return material port; 17. Fuel inlet; 18. Ceramic fiber insulation layer. Detailed Implementation

[0028] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the specific embodiments of this invention will be described in detail below with reference to the accompanying drawings. It should be noted that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of this invention. Various modifications or substitutions made by those skilled in the art based on the technical solutions of this invention without creative effort should fall within the scope of protection of this invention.

[0029] like Figure 1 As shown in the figure, this embodiment provides a multi-stage bed fuel reactor for solid fuel chemical looping gasification, comprising a bubbling bed 5, a central riser 6, an oxygen carrier separation zone 8, and a cyclone separator 11 arranged sequentially from bottom to top. The reactor body is made of high-temperature resistant material and is externally covered with a ceramic fiber insulation layer 18 to reduce heat loss during the reaction process. The overall height of the reactor can be adjusted according to the processing capacity requirements, for example, from 5 m to 10 m.

[0030] The bubbling bed 5 is located at the bottom of the reactor, and its bottom is equipped with a gas chamber 2, an air distribution plate 3, and a central air duct 1. A gasifying agent and / or fluidizing gas are introduced into the gas chamber 2 and the central air duct 1. The gas enters the bubbling bed 5 after passing through the gas chamber 2 and being evenly distributed through the air distribution plate 3, thereby adjusting the apparent gas velocity of the bed and maintaining a stable bubbling fluidization state. The gasifying agent can be water vapor, serving as both the gasification reaction medium and the fluidizing medium.

[0031] In this embodiment, by adjusting the gas flow rate entering the central air duct 1 and the air chamber 2, and by reasonably matching the height-to-diameter ratio of the bubble bed 5 and the central riser 6, as well as the structural angle of the lower cone section of the bubble bed 5, the hydrodynamic characteristics of each functional area are adapted to the reaction rate of oxygen carrier particles and fuel particles of different properties, thereby achieving effective mixing and full gasification reaction of high-density differential particles.

[0032] Oxidized oxygen carrier (Me x O yThe oxygen carrier enters the bubble bed 5 through the oxygen carrier inlet 4 located on one side of the bubble bed 5; the solid fuel is stored in the silo 14 and the feeding rate is controlled by the screw feeder 15. It is fed into the bubble bed 5 through the fuel inlet 17, where it comes into full contact with the oxygen carrier particles and undergoes a gasification reaction.

[0033] The high-speed airflow introduced into the central duct 1 creates a low-pressure zone between its outlet and the inlet of the central riser 6, thereby suctioning the mixed particles within the bubbling bed 5 and carrying fuel and oxygen-carrying particles into the central riser 6. Inside the central riser 6, the mixed particles are in a rapidly fluidized state, further enhancing gas-solid contact and promoting fuel gasification and oxygen-carrying reduction reactions. By adjusting the air velocity in the central duct 1 and its relative position to the central riser 6, the particle transport flow rate and particle circulation volume within the central riser 6 can be controlled.

[0034] The mixed particles output from the central riser 6 enter the oxygen carrier separation zone 8 located above it. The oxygen carrier separation zone 8 reduces the airflow velocity by increasing the flow cross-sectional area, forming a dilute phase separation zone within it. It effectively separates light fuel particles from heavy oxygen carrier particles by utilizing the density difference and terminal settling velocity difference between the fuel particles and the oxygen carrier particles. The separated heavy reduced oxygen carrier (Me...) x O y-1 The oxygen carrier is transported to an air reactor (not shown) via the waiting inclined tube 7 for oxidation and regeneration, thus completing the recycling of the oxygen carrier.

[0035] The unreacted fuel particles or coke after separation enter the cyclone separator 11 with the airflow. After gas-solid separation, they are returned to the bubbling bed 5 through the return riser 12 to continue participating in the gasification reaction. The purified syngas is discharged from the system through the exhaust core pipe 10 at the top of the cyclone separator 11.

[0036] In this embodiment, the operating temperature of the reactor is 800°C to 1000°C, and the operating pressure can be atmospheric pressure or pressurized conditions to ensure the efficient execution of the chemical looping gasification reaction and the stability and safety of the system operation.

[0037] The multi-stage bed fuel reactor described in this invention can be adapted to solid fuel and oxygen carrier systems of different processing scales and properties by adjusting the gas velocity, bed height, and structural parameters. Any reasonable modifications made by those skilled in the art based on the above technical solution should be considered to fall within the protection scope of this invention.

Claims

1. A multi-stage bed fuel reactor for solid fuel chemical looping gasification, characterized in that, include: Bubble bed (5), central lift pipe (6), central air duct (1), oxygen carrier separation zone (8), cyclone separator (11), return riser (12), and U-valve (13); wherein, the bottom of the bubble bed (5) is provided with an air chamber (2), an air distribution plate (3), and a central air duct (1), and the central air duct (1) is inserted into the bubble bed (5) at a predetermined distance; one side of the bubble bed (5) is provided with an oxygen carrier inlet (4), and the other side is provided with a fuel inlet (17) and a return outlet (16); the central lift pipe (8) The bottom inlet of the central lifting pipe (6) is inserted into the bubble bed (5) and located at a predetermined distance above the central air duct (1). The top outlet of the central lifting pipe (6) extends into the oxygen carrier separation zone (8). The oxygen carrier separation zone (8) is provided with a waiting inclined pipe (7) on its lower side, and its top is connected to the cyclone separator (11) through a horizontal pipe (9). The upper part of the cyclone separator (11) is provided with an exhaust core pipe (10), and its lower part is connected to the return material riser (12). The bottom of the return material riser (12) is connected to a U-shaped valve (13).

2. The solid fuel chemical looping gasification multi-stage bed fuel reactor according to claim 1, characterized in that, Fresh fuel is stored in a silo (14) and conveyed by a screw feeder (15) into the bubbling bed (5) through a fuel inlet (17); the bubbling bed (5) has a cylindrical-conical structure with a conical section at the bottom and an angle of 30° to 60°, and a cylindrical section at the top, with the two sections connected by a flange.

3. The fuel reactor according to claim 1, characterized in that, The inlet gas of the gas chamber (2) and the central air duct (1) is a gasifying agent and / or a fluidizing medium, the gasifying agent including water vapor; the fluidizing gas velocity at the bottom air distribution plate (3) of the bubble bed (5) is greater than the critical fluidizing velocity of the oxygen carrier particles used, and is 1 to 3 times the critical fluidizing velocity.

4. The fuel reactor according to claim 1, characterized in that, The central lift pipe (6) is located at the center of the bed and runs through the bubbling bed (5) and the oxygen carrier separation zone (8); a low-pressure zone is formed between the outlet of the central air duct (1) and the inlet of the central lift pipe (6) under the action of high-speed airflow, so that the particles in the bubbling bed (5) are drawn into the central lift pipe (6), thereby improving the conveying flow rate and particle circulation flow rate of the mixed particles; the operating air velocity of the central air duct (1) is greater than 10 times the critical fluidization velocity of the oxygen carrier particles.

5. The fuel reactor according to claim 1, characterized in that, By adjusting the air velocity of the central air duct (1) and the distance between the central air duct (1) and the central lift pipe (6), the particle conveying flow rate in the central lift pipe (6) is controlled, thereby regulating the particle residence time and circulation flow rate in the bubble bed (5); by adjusting the air velocity flowing into the central air duct (1) and the air chamber (2), and adjusting at least one of the geometric dimensions of the height-to-diameter ratio of the bubble bed (5) and the central lift pipe (6) or the angle of the cone section below the bubble bed (5), the hydrodynamic characteristics of each functional area are matched with the reaction rate of the oxygen carrier and fuel particles used.

6. The fuel reactor according to claim 1, characterized in that, The oxygen carrier separation zone (8) and the outlet of the central riser pipe (6) form an annular structure, and the fuel particles and oxygen carrier particles are separated into light and heavy particles based on the density difference; the fuel is biomass, coal or municipal solid waste, and the fuel particle size is 0.1 mm to 5 mm; the oxygen carrier is different types of oxygen carriers such as iron-based, copper-based, nickel-based or carrier-supported, and the particle size is 0.1 mm to 1 mm.

7. The fuel reactor according to claim 1, characterized in that, The oxygen carrier waiting inclined tube (7) is connected to the air reactor, which is an independent unit. The oxygen carrier after oxidation and regeneration enters the bubbling bed (5) from the air reactor outlet through the oxygen carrier inlet (4). The bubbling bed (5), the central riser (6), the oxygen carrier separation zone (8) and the cyclone separator (11) are connected by flanges, and sealing gaskets are set at the flange connections to ensure airtightness and facilitate disassembly and maintenance. The flange connections of each section are telescopic structures with adjustable lengths so that the overall height of the fuel reactor can be adjusted according to the processing capacity requirements.

8. The fuel reactor according to claim 1, characterized in that, The cyclone separator (11) is used to perform gas-solid separation of syngas, separate unreacted fuel particles, and send them back to the bubbling bed (5) through the return riser (12) for continued reaction.

9. The fuel reactor according to claim 1, characterized in that, The fuel reactor operates at a temperature of 800°C to 1000°C and at an atmospheric or pressurized pressure.

10. The fuel reactor according to claim 1, characterized in that, The main body of the bubble bed (5), the central lift pipe (6), the oxygen carrier separation zone (8) and the cyclone separator (11) is covered with a ceramic fiber insulation layer (18) to reduce heat loss during the reaction and separation process.

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