A two-stage built-in dual fluidized bed reactor

Abstract

This invention discloses a two-stage built-in dual fluidized bed reactor for a biomass feedstock chemical chain hydrogen production process. Each built-in dual fluidized bed includes: a gasification chamber, which is a cylindrical structure with a conical surface at the bottom, and an opening on the conical surface for introducing bubbling fluidizing air; a combustion chamber, which is a tubular structure and sleeved within the gasification chamber, with an open bottom located within the conical surface area for introducing vertically upward combustion air; and a return unit, which is located at the top of the reactor, and there are multiple units evenly arranged circumferentially for transporting high-temperature bed material particles from the combustion chamber to an annular gasification zone outside the combustion chamber for mixing with the biomass feedstock in the gasification zone to produce hydrogen; the return unit includes a loosening chamber and a return chamber, with the bottom plate of the loosening chamber inclined toward the return chamber; the two built-in dual fluidized beds are connected in series for introducing the hydrogen-containing syngas produced by the first dual fluidized bed into the combustion chamber of the second dual fluidized bed.

Description

Technical Field

[0001] This invention relates to the field of biomass hydrogen production technology, and in particular to a two-stage built-in dual fluidized bed reactor for producing high-purity hydrogen. Background Technology

[0002] As a highly efficient and clean energy source, hydrogen energy development is timely. Among the various technical routes for producing hydrogen from biomass, the use of fluidized bed reactors for efficient thermal conversion to produce hydrogen-rich gas shows promising prospects.

[0003] Dual fluidized bed reactors are already in use in existing technologies. They have the following advantages: they decouple combustion and gasification, provide indirect heating, and have a high hydrogen production rate; there is only efficient exchange of solids and heat between the combustion chamber and the gasification chamber, which can achieve high heat flux and high throughput with a small volume; and the tar content is lower than that of conventional routes, which facilitates subsequent tar removal.

[0004] Chinese patent application CN109704278A discloses an apparatus and method for producing hydrogen through dual fluidized bed biomass pyrolysis and gasification. The dual fluidized bed includes a fluidized bed pyrolysis furnace and a fluidized bed combustion furnace. The fluidized bed pyrolysis furnace includes a pyrolysis furnace riser, with a pyrolysis furnace cyclone separator connected to its rear end. The upper part of the pyrolysis furnace cyclone separator is connected to a shift reactor, and the lower part is connected to a pyrolysis furnace return valve. Another outlet of the pyrolysis furnace return valve is connected to the fluidized bed combustion furnace, which includes a combustion furnace riser. Another outlet of the pyrolysis furnace return valve is connected to the bottom of the combustion furnace riser. An oxygen-carrying cyclone separator is installed in the middle of the combustion furnace riser, and a CO2 absorbent cyclone separator is installed at the top. This method eliminates the need for pure oxygen as a gasifying agent during the preparation process; the system only requires supplemental air for gasification to meet production needs, resulting in low production costs. Furthermore, since the pyrolysis furnace does not use air for fluidization, the biomass fuel gas has a high content of effective components.

[0005] Existing dual fluidized bed reactors separate the gasification chamber from the combustion chamber, using feed pipes and a return feeder for heat exchange with the bed material. However, heat loss occurs during transport between the two fluidized beds, preventing the already low-calorific-value biomass feedstock from self-heating through the combustion of residual carbon to power the gasification reaction. This necessitates the addition of fuel in the combustion chamber, reducing economic efficiency. Furthermore, during transport to the combustion chamber, the tar adhering to the surface of the low-temperature bed material particles becomes more viscous as the temperature decreases, leading to particle agglomeration and bridging. This can clog the reactor feed pipes, affecting reactor circulation and limiting the plant's operating cycle.

[0006] In addition, since the regeneration of AER bed material (AER technology adds three effects of absorption, enhancement and reform compared to ordinary dual fluidized bed technology) requires a certain amount of time, and the combustion chamber of existing dual fluidized bed devices is mostly a fast fluidized bed, although a high solids conveying rate can be maintained, the bed material regeneration time is relatively short.

[0007] Furthermore, existing dual fluidized beds generally adopt a "single-stage" structure. This one-step process for biomass hydrogen production usually suffers from unstable operation of the equipment and a decrease in hydrogen concentration, which also greatly affects the economics of chemical looping hydrogen production.

[0008] Finally, the existing dual fluidized bed feeders have a small loosening chamber volume and are prone to fluidization dead zones at the corners. In the biomass hydrogen production process, coke particles in the solid particles in the feeder are prone to caking with biomass particles, resulting in coking.

[0009] Therefore, there is an urgent need for a two-stage dual fluidized bed reactor, with each stage employing a built-in heat-exchange dual fluidized bed. This built-in heat-exchange design avoids the use of external feed pipes and prevents the feed pipes and return feeder from being exposed to room temperature, reducing reactor heat loss and improving the economics of the route and the operating cycle of the unit. It also allows sufficient regeneration time for the bed material while maintaining a high solids delivery rate. The two-stage structure effectively improves the stability of the unit's operation, ensures high purity of the produced hydrogen, and effectively solves the coking problem in the return process of existing technologies.

[0010] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0011] The purpose of this invention is to provide a two-stage built-in dual fluidized bed reactor, in which the external dual fluidized bed in each stage is replaced with an internal one, avoiding the exposure of the feed pipe and return feeder to room temperature and reducing reactor heat loss. Simultaneously, this device provides sufficient regeneration time for the bed material while maintaining a high solids delivery rate. The two-stage structure effectively improves the stability of the device operation and ensures that the produced hydrogen has high purity.

[0012] Another objective of this invention is to provide a built-in heat exchange dual fluidized bed reactor that can effectively avoid the fluidization dead zone in the loosening chamber of the return material unit.

[0013] To achieve the above objectives, the present invention provides a two-stage built-in dual fluidized bed reactor for a biomass feedstock chemical chain hydrogen production process. Each built-in dual fluidized bed includes: a gasification chamber, which is a cylindrical structure with a conical surface at the bottom, and an opening on the conical surface for introducing bubbling fluidizing air; a combustion chamber, which is a tubular structure and sleeved within the gasification chamber, with an open bottom located within the conical surface area for introducing vertically upward combustion air; and a return unit, which is located at the top of the reactor, and there are multiple units evenly arranged circumferentially for transporting high-temperature bed material particles from the combustion chamber to an annular gasification zone outside the combustion chamber for mixing with the biomass feedstock in the gasification zone to produce hydrogen; the return unit includes a loosening chamber and a return chamber, with the bottom plate of the loosening chamber inclined toward the return chamber; the two built-in dual fluidized beds are connected in series for introducing the hydrogen-containing syngas produced by the first dual fluidized bed into the combustion chamber of the second dual fluidized bed.

[0014] Furthermore, in the above technical solution, each return material unit can be fixed and penetrate through the wall of the combustion chamber; the loosening chamber is located on the side close to the combustion chamber, and its upper part is connected to the cyclone separator through the feed pipe, and the cyclone separator is located in the combustion chamber.

[0015] Furthermore, in the above technical solution, the return chamber is located on the side close to the gasification chamber and is connected to the annular space of the gasification chamber through a feeding pipe.

[0016] Furthermore, in the above technical solution, the loosening chamber receives bed material particles from the combustion chamber and blocks gas; the middle and upper parts of the loosening chamber are separated from the return chamber by a partition; the lower part of the loosening chamber may be provided with a first air distribution chamber; the lower part of the return chamber may be provided with a second air distribution chamber.

[0017] Furthermore, in the above technical solution, both the bottom plate of the loosening chamber and the bottom plate of the return chamber can be provided with air caps or air holes; the first air distribution chamber and the second air distribution chamber are supplied with air through air pipes extending to the outside of the reaction device. The air pipes can be arranged in a cross shape.

[0018] Furthermore, in the above technical solution, the cross-sectional diameter of the loosening chamber can be 1.1 to 1.5 times the cross-sectional diameter of the return chamber.

[0019] Furthermore, in the above technical solution, the feed inlet of biomass raw materials can be located at the bottom of the material layer in the gasification chamber, above the material layer, and / or at the top of the reaction device, and the feeding method can be screw feeding.

[0020] Furthermore, in the above technical solution, the conical surface of the gasification chamber may be provided with an inclined chute structure for extending the residence time of the bed material particles at the bottom and for gas sealing.

[0021] Furthermore, in the above technical solution, the inclined chute structure may specifically include: a first conical surface that extends downward at an angle from the outer wall of the combustion chamber; a second conical surface that extends upward at an angle from the outer wall of the combustion chamber and encloses the first conical surface and the outer wall of the combustion chamber to form a relatively closed structure; and an inclined chute is formed between the second conical surface and the conical surface at the bottom of the gasification chamber.

[0022] Furthermore, in the above technical solution, the sealed structure can be a ventilation cavity for introducing secondary air from outside the reaction device.

[0023] Furthermore, in the above technical solution, inclined upward secondary air holes can be opened on the upper part of the air cavity and the combustion chamber wall. The secondary air works in conjunction with the combustion-supporting air at the bottom of the combustion chamber to extend the residence time of the bed material particles at the bottom.

[0024] Furthermore, in the above technical solution, the pores on the bottom conical surface of the gasification chamber can be configured to have a gradually decreasing diameter from bottom to top.

[0025] Furthermore, in the above technical solution, the bed material particles of the first stage built-in dual fluidized bed can be inert bed material or metal oxide bed material; the bed material particles of the second stage built-in dual fluidized bed can be iron-based oxygen carrier.

[0026] Furthermore, in the above technical solution, the metal oxide bed material can be calcium oxide bed material, which is used to capture carbon dioxide in the gasification chamber to generate calcium carbonate. The calcium carbonate is heated and decomposed into carbon dioxide in the combustion chamber and discharged with the flue gas.

[0027] Furthermore, in the above technical solution, the first and second fluidized beds can be connected by a pipeline. One end of the pipeline is connected to the hydrogen-containing synthesis gas outlet of the first fluidized bed, and the other end is connected to the combustion air inlet of the combustion chamber of the second fluidized bed. A turbocharger can be installed on the pipeline to provide sufficient fluidizing air velocity to the combustion chamber of the second fluidized bed.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1) This invention solves the problem of chemical chain hydrogen production from complex biomass feedstocks by adopting a two-stage built-in dual fluidized bed, and solves the problems of unstable operation and decreased hydrogen concentration in conventional one-step methods, thereby improving the economic efficiency of chemical chain hydrogen production. The two-stage structure is designed with pipelines connected in series. One end of the pipeline is connected to the hydrogen-containing syngas outlet of the first-stage dual fluidized bed, and the other end is connected to the combustion air inlet of the combustion chamber of the second-stage dual fluidized bed. The hydrogen-rich gas generated in the first stage is turbocharged and then enters the second-stage dual fluidized bed reactor through the combustion air inlet and the secondary air inlet of the second stage, which can effectively ensure the fluidization rate of solid particles in the second-stage combustion chamber.

[0030] 2) The present invention uses a “built-in” design for each section of the dual fluidized bed, that is, the combustion chamber is set inside the gasification chamber to form a jacket structure, which can avoid the feed pipe and return device being exposed to room temperature in the prior art (“external” design), effectively reducing the heat loss of the reaction device, improving the economy of the route and the operating cycle of the device;

[0031] 3) Through the “built-in” design of each section of the dual fluidized bed, the present invention can also effectively improve the heat transfer efficiency. The combustion chamber can not only transfer heat through the circulation of hot bed material, but also transfer heat to the gasification zone between the outer wall of the combustion chamber and the gasification chamber cylinder through the heat conduction of the vessel wall.

[0032] 4) The multiple return units of the present invention are evenly arranged in the circumferential direction. When abnormal particle fluidization occurs in different areas of the gasification chamber, resulting in abnormal temperature changes in the area, the drop speed can be controlled by giving the return air volume to the return units at different positions, so as to achieve more uniform and precise control of the gasification zone temperature and thus control the depth of biomass gasification reaction.

[0033] 5) The present invention fixes the return unit on the wall of the combustion chamber (i.e. inside the reaction device) and penetrates through the wall of the combustion chamber. The feed pipe is directly connected to the annular gasification zone, which avoids the heat loss and blockage problems caused by the feed pipe being exposed to room temperature in the existing return device.

[0034] 6) The return material unit of the present invention designs the cross-sectional diameter of the loosening chamber to be larger than that of the return material chamber, so that the bed material in the loosening chamber is conveyed in a dense phase, which can effectively suppress the backflow of gas and form a material seal; considering that fluidization dead zones are easily formed at the bottom corners of the loosening chamber during dense phase conveying, the problem of coking caused by fluidization dead zones can be effectively solved by setting the bottom plate of the loosening chamber at an incline.

[0035] 7) The cyclone separator of the present invention is also a built-in design, which avoids the cyclone separator being exposed to room temperature and can effectively improve heat exchange efficiency; lighter ash particles are carried out of the reaction device by the airflow and then removed in the tail gas cyclone, so that the reaction device of the present invention does not need to be set with a separate slag discharge port.

[0036] 8) The inclined chute structure adopted at the bottom of the gasification chamber (i.e., the gas production chamber) of this invention broadens the operating range of the reaction device, enabling the reactor to adapt to more complex raw material and process conditions; at the same time, the inclined chute structure can better achieve the material sealing effect by reducing the size of the original particle channel.

[0037] 9) The secondary air distribution configuration of the combustion chamber in this invention allows for a reduction in the bottom combustion air, causing the particles to bubble at the bottom of the combustion chamber. As the bubbling particles fluidize to the vicinity of the secondary air, they are accelerated by the upward-sloping secondary air and rapidly transported to the return unit. Above the secondary air is a rapid fluidized bed. This design increases the residence time of the particles in the high-temperature zone at the bottom, allowing for more effective combustion of the tar on their surface. This provides more heat for gasification, reduces the tar content in the flue gas, facilitates flue gas post-treatment, and improves the economics of the process. When applying the AER process, it also improves the particle regeneration rate, which is more conducive to the capture of carbon dioxide in the gasification chamber, thereby increasing the hydrogen production concentration.

[0038] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, and to make the above and other objects, technical features and advantages of the present invention easier to understand, one or more preferred embodiments are listed below and described in detail with reference to the accompanying drawings. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the dual fluidized bed process when calcium oxide is used as the bed material particles in this invention.

[0040] Figure 2 This is a perspective schematic diagram of the two-stage built-in dual fluidized bed reactor of the present invention.

[0041] Figure 3 This is an internal cross-sectional schematic diagram of the two-stage built-in dual fluidized bed reactor of the present invention (the first embodiment in which both stages adopt dual fluidized beds).

[0042] Figure 4 This is a perspective view of each section of the built-in heat exchange dual fluidized bed of the present invention.

[0043] Figure 5 This is a schematic internal cross-sectional view of the dual fluidized bed reactor with built-in heat exchange in each section of the present invention.

[0044] Figure 6 This is a schematic internal cross-sectional view of the return material unit of the present invention.

[0045] Figure 7 This is a partial schematic diagram of the bottom of each section of the built-in heat exchange dual fluidized bed of the present invention (showing the first embodiment; without secondary air cavity and inclined chute structure).

[0046] Figure 8 This is a partial schematic diagram of the bottom of each section of the built-in heat exchange dual fluidized bed of the present invention (showing the second embodiment; having a secondary air cavity and an inclined chute structure).

[0047] Explanation of key figure labels:

[0048] 100 - First stage built-in heat exchange dual fluidized bed; 101 - First product gas outlet; 102 - Connecting pipeline; 200 - Second stage built-in heat exchange dual fluidized bed; 201 - Second product gas outlet;

[0049] 1-Gasification chamber, 11-Conical surface, 110-Air hole, 2-Combustion chamber, 21-Combustion air inlet, 3-Return material unit, 30-Air pipe, 31-Loosening chamber, 310-First air distribution chamber, 311-Loosening chamber inclined bottom plate, 32-Return material chamber, 320-Second air distribution chamber, 33-Baffle plate, 34-Feeding pipe, 4-Cyclone separator, 40-Inlet, 41-Inlet pipe, 42-Flue gas outlet, 5-Air chamber, 50-Secondary air hole, 51-First conical surface, 52-Second conical surface, 53-Inclined chute. Detailed Implementation

[0050] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0051] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0052] In this document, for ease of description, spatial relative terms such as “below,” “under,” “down,” “above,” “above,” “upper,” etc., are used to describe the relationship of one element or feature to another element or feature in the accompanying drawings. It should be understood that spatial relative terms are intended to encompass different orientations of an object in use or operation, in addition to those depicted in the figures. For example, if an object in the figure is flipped, an element described as “below” or “under” another element or feature would be oriented “above” that element or feature. Thus, the exemplary term “below” can encompass both the downward and upward orientations. An object may also have other orientations (rotated 90 degrees or other orientations), and the spatial relative terms used herein should be interpreted accordingly.

[0053] In this document, the terms "first," "second," etc., are used to distinguish two different elements or parts, and are not used to define specific positions or relative relationships. In other words, in some embodiments, the terms "first," "second," etc., can also be used interchangeably.

[0054] This invention employs a dual fluidized bed process for biomass hydrogen production (see process flow diagram). Figure 1Combining AER technology with conventional dual-fluidized bed technology, this method offers advantages over conventional dual-fluidized bed technology by adding three effects: absorption, enhancement, and reforming. Water vapor, acting as the gasification air, also reforms the tar produced during gasification, reducing the tar content in the product gas. The bed material not only serves as a heat carrier but also performs absorption and enhancement functions. AER bed materials are primarily metal oxides. In the gasification chamber, they absorb carbon dioxide, completing carbon dioxide carbonation and releasing heat. This not only reduces the carbon dioxide content in the product gas, improving its quality, but also provides heat for the gasification reaction, enhancing the biomass gasification process. The carbonized bed material decomposes under heat in the combustion chamber, releasing carbon dioxide. This carbon dioxide is then transported into the flue gas, and the bed material returns to its oxide form, re-capturing carbon dioxide in the gasification chamber.

[0055] The inventors discovered through research that dual fluidized bed reactors for biomass hydrogen production offer the following advantages: The dual fluidized bed reactor decouples combustion and gasification, providing indirect heating and resulting in a high hydrogen production rate. The hydrogen content in the dry gas exiting the dual fluidized bed reactor can reach over 50%, and combined with in-situ carbon dioxide capture, the hydrogen content can reach 78%. Using a dual fluidized bed reactor, where there is only efficient exchange of solids and heat between the combustion and gasification chambers, high heat flux and high throughput can be achieved with a smaller volume. The tar content in the gas from the dual fluidized bed reactor is 2-10 g / m³. 3 The tar content is lower than that of conventional routes, facilitating subsequent tar removal. The built-in dual fluidized bed reactor of this invention adopts a two-stage structure (see reference). Figure 2 , 3 As shown, the two sections are connected in series via connecting pipes. Each section has a combustion chamber designed as a tube and built into a cylindrical gasification chamber, forming an annular space outside the tubular structure as the gasification zone. This avoids the exposed feed pipes and return feeders caused by the "complete separation of the gasification chamber and combustion chamber" (i.e., external design) in existing technologies, which can greatly reduce heat loss. It can also effectively prevent the tar adhering to the surface of the bed material particles from becoming more viscous as the temperature decreases during the transportation to the combustion chamber, making it easy for particles to clump and bridge. At the same time, the modification of the bottom of the gasification chamber can maintain a high solids conveying rate and provide bed material regeneration time.

[0056] like Figure 2 , 3As shown, this invention provides a two-stage built-in dual fluidized bed reactor, comprising a first-stage built-in heat-exchange dual fluidized bed 100 (with a product gas outlet 101 at the top) and a second-stage built-in heat-exchange dual fluidized bed 200 (with a product gas outlet 201 at the top) connected in series. It is used for chemical chain hydrogen production processes using complex raw materials such as biomass. The biomass feed inlet (not shown in the figure) can be located at the bottom of the material layer, above the material layer, and / or at the top of the reactor in the gasification chamber 1 (feeding at different locations depending on the type and particle density of the raw material). The feeding method can be a spiral feed. The first-stage built-in heat-exchange dual fluidized bed 100 of this invention includes at least a gasification chamber 1, a combustion chamber 2, and a return unit 3. The gasification chamber 1 has a cylindrical structure and a conical surface 11 at the bottom, with openings on the conical surface 11 for introducing bubbling fluidizing air (see reference). Figure 7 Combustion chamber 2 is a tubular structure housed within gasification chamber 1. The bottom of combustion chamber 2 is open and located within the conical region at the bottom of the gasification chamber, used to introduce vertically upward combustion air (see reference). Figure 7 The combustion air inlet 21 is located in the upper part of the reactor. Multiple return units 3 are arranged circumferentially at the top of the reactor. They are used to transport the high-temperature bed material particles from the combustion chamber to the annular gasification zone outside the combustion chamber 2 and mix them with the biomass feedstock in the gasification zone to produce hydrogen. The return unit 3 has a loosening chamber 31 and a return chamber 32. The bottom plate 311 of the loosening chamber is inclined towards the return chamber 32 (see reference). Figure 6 This invention features two internally connected dual fluidized beds connected in series, used to feed the hydrogen-containing syngas produced by the first dual fluidized bed into the combustion chamber of the second dual fluidized bed. By embedding the combustion chamber 2 within the gasification chamber 1, this invention effectively solves the problems of high heat loss and easy clogging of the external feed pipe in dual fluidized bed devices, effectively reducing heat loss and preventing particles from clogging the feed pipe due to cooling. This invention uses a two-stage reactor to solve the problem of chemical looping hydrogen production from complex biomass feedstocks, solving the problems of stable operation and hydrogen concentration decline in conventional one-step methods, and improving the economics of chemical looping hydrogen production. The bed material of the first dual fluidized bed reactor can be inert materials such as olivine and quartz sand, or materials such as calcium oxide particles that can be used for in-situ carbon dioxide capture using AER technology, and other materials. The bed material of the second stage can be an iron-based oxygen carrier. The internal structures of the two reactors are identical; the following description uses the first reactor as an example. Furthermore, the multiple return units of this invention are uniformly arranged circumferentially. When abnormal particle fluidization occurs in different areas of the gasification chamber, leading to abnormal temperature changes, the material drop speed can be controlled by adjusting the return air volume of the return units at different locations. This achieves more uniform and precise temperature control in the gasification zone, thereby controlling the depth of biomass gasification reaction. The inclined bottom plate 311 of the loosening chamber of the return unit 3 effectively avoids the problem of fluidization dead zones at the corners of the loosening chamber.

[0057] Specifically, further reference Figure 4 , Figure 5 The "built-in" structural design of this invention features a jacketed structure for the gasification chamber 1 and the combustion chamber 2. The combustion chamber 2 has a vertically upward-facing combustion air supply at its bottom, while the gasification chamber 1 has a fluidizing air supply via a vertical conical inlet 11 at its bottom (see reference). Figure 7 Combustion air is air, and fluidizing air is water vapor; both can be introduced via air caps. The pore size of the fluidizing air caps gradually decreases from bottom to top (i.e., the fluidization state of the solid particles gradually decreases from bottom to top, acting as a material seal). The ratio of fluidizing air to combustion air is optimized to ensure that air does not diffuse into gasification chamber 1. Combustion chamber 2 contains a rapid fluidized bed, while the area outside combustion chamber 2 (i.e., the bottom of gasification chamber 1) is a bubbling fluidized bed. The combustion chamber 2 walls and the heated bed material provide as much heat as possible to the gasification chamber. Further details are as follows... Figures 4 to 6 As shown, a cyclone separator 4 can be connected to the upper part of the combustion chamber 2 to separate flue gas, fly ash, and hot bed material. Flue gas, fly ash, and hot bed material enter the feed inlet 40. Flue gas and fly ash are discharged through the flue gas outlet 42 at the top of the cyclone separator, while bed material particles enter the loosening chamber 31 of the return unit 3 through the feed pipe 41 at the bottom. The height of the gasification chamber in this invention differs from that of existing biomass dual fluidized beds (such as gussing fluidized beds). The combustion chamber 2 can not only transfer heat through the circulation of hot bed material, but also transfer heat to the gasification zone through heat conduction through the reactor wall, avoiding heat loss caused by the external dual fluidized bed reactor combustion chamber and feed pipe being exposed to room temperature.

[0058] Further as Figure 6 As shown, the specific structure of the return material unit 3 of the present invention is as follows: Each return material unit 3 is fixed and penetrates the wall of the combustion chamber 2; the loosening chamber 31 is located near the combustion chamber 2, and its upper part is connected to the cyclone separator 4 through the feed pipe 41, and the cyclone separator 4 is located inside the combustion chamber 2. The return material chamber 32 is located near the gasification chamber 1, and is connected to the annular space of the gasification chamber 1 through the feed pipe 34. The loosening chamber 31 receives the bed material particles from the combustion chamber 2 and blocks the gas. The middle and upper parts of the loosening chamber 31 are separated from the return material chamber 32 by the partition plate 33. The lower part of the loosening chamber is provided with a first air distribution chamber 310; the lower part of the return material chamber 32 is provided with a second air distribution chamber. The bottom plate of the loosening chamber 31 and the bottom plate of the return material chamber 32 are both provided with air caps or air holes (not shown in the figure). The first air distribution chamber 310 and the second air distribution chamber 320 are supplied with gas through the air pipe 30 extending to the outside of the reaction device. By introducing external air into the first air distribution chamber 310 and the second air distribution chamber 320, bubbles are formed in the lower part of the loosening chamber and the return chamber, and the bed material particles are transported to the feeding pipe 34 and then flow into the gasification chamber 1. Preferably, but not limitingly, the air pipes 30 are arranged in a cross shape (see reference). Figure 2 This makes the circumferential air distribution more uniform.

[0059] The inventors discovered through research that existing return feed devices typically have relatively small loosening and return chambers, with diameters matching those of the feed leg section. This facilitates rapid circulation of the bed material, which is generally transported in a dilute phase within the loosening chamber of the return feeder. This existing return feeder is used for air gasification of biomass in circulating fluidized bed reactors. Because the hydrogen concentration in the syngas produced by air gasification is low, it can effectively transport the bed material and prevent cross-contamination. However, dual fluidized bed reactors used for biomass hydrogen production produce higher hydrogen concentrations (50% VOL-78% VOL). Existing return feeders are not ideal in suppressing gas backflow during dilute phase transport of the bed material, and during dense phase transport, fluidization dead zones form at the bottom corners of the loosening chamber 11. This leads to poor return feed due to cooling blockage of the bed material and coke particles, affecting the stable operation of the reactor. Therefore, through the improvement of the return feeder unit in this invention, the bed material in the loosening chamber 31 of the return feeder unit 3 is arranged in a dense phase to form a material seal. Furthermore, this invention designs the cross-sectional diameter of the loosening chamber 31 to be 1.1 to 1.5 times the cross-sectional diameter of the return chamber 32, and the bottom plate 311 of the loosening chamber is inclined, which effectively solves the problems in the prior art. In addition, the return unit 3 is entirely mounted on the wall of the combustion chamber 2 (i.e., inside the reaction device), avoiding the heat loss and blockage problems caused by the feed pipe being exposed to room temperature in existing return devices (see [link to specific bed material particle orientation]). Figure 6 (The dashed arrow in the middle indicates the direction).

[0060] Further as Figure 4-6 As shown, the cyclone separator 4 of the present invention can be configured in multiple ways, preferably the same number as the return material unit 3, and arranged in a circumferential manner. This can more effectively separate fly ash, flue gas and bed material particles, and avoid the temperature of the bed material particles from dropping, thereby improving heat exchange efficiency.

[0061] Further as Figure 8 As shown above, in the aforementioned Figure 7 Based on the first embodiment of the gasification chamber bottom, an inclined chute structure (i.e., the second embodiment of the gasification chamber bottom) can be provided at the conical surface 11 of the gasification chamber 1 to prolong the residence time of the bed material particles at the bottom and for gas sealing. The inclined chute structure specifically includes a first conical surface 51 and a second conical surface 52. The first conical surface 51 extends downwards at an angle from the outer wall of the combustion chamber 2; the second conical surface 52 extends upwards at an angle from the outer wall of the combustion chamber and forms a relatively sealed structure with the first conical surface 51 and the outer wall of the combustion chamber 2. Thus, an inclined chute 53 is formed between the second conical surface 52 and the conical surface 11 at the bottom of the gasification chamber 1. This sealed structure is a wind chamber 5 for introducing secondary air from outside the reaction device. Preferably, but not limitingly, inclined upward secondary air holes 50 are provided on the upper part of the wind chamber 5 and the wall of the combustion chamber 2. The secondary air cooperates with the combustion air at the bottom of the combustion chamber 2 to prolong the residence time of the bed material particles at the bottom.

[0062] The inclined chute 53 effectively reduces the diameter of the particle running channel, allowing the bed material to maintain a gas seal even under high-speed circulation. This design broadens the operating range of the reactor, enabling it to adapt to more complex raw material and process conditions. Simultaneously, the first conical surface 51 and the second conical surface 52 can be used for secondary air distribution in the combustion chamber 2. With secondary air present, the bottom combustion air can be appropriately reduced, causing the particles to bubble at the bottom of the combustion chamber 2. As the bubbling fluidizes to the vicinity of the secondary air, the particles are accelerated by the upward-sloping secondary air and rapidly transported to the return unit 3. Above the secondary air is a rapid fluidized bed. This design increases the residence time of the particles in the high-temperature zone at the bottom, allowing for more effective combustion of the tar on their surface, providing more heat for gasification, reducing the tar content in the flue gas, facilitating flue gas post-treatment, and improving the process's economics. When applying the AER process, it also improves the particle regeneration rate, further facilitating carbon dioxide capture in the gasification chamber, thereby increasing the hydrogen production concentration.

[0063] The structure of the second-stage built-in heat exchange dual fluidized bed 200 of this invention is the same as that of the first-stage built-in heat exchange dual fluidized bed 100, and will not be described in detail here. The only difference is the bed material particles; the second stage uses an iron-based oxygen carrier. The first-stage dual fluidized bed 100 and the second-stage dual fluidized bed 200 are connected by a pipeline 102. One end of the pipeline is connected to the hydrogen-containing synthesis gas outlet (i.e., the first product gas outlet 101) of the first-stage dual fluidized bed, and the other end is connected to the combustion air inlet of the combustion chamber of the second-stage dual fluidized bed 200. Preferably, but not limitingly, a turbocharger (not shown in the figure) is provided on the connecting pipeline 102 to provide sufficient fluidizing air velocity to the combustion chamber of the second-stage dual fluidized bed 200.

[0064] The following describes the application of this invention. Figure 3 The biomass-to-hydrogen process of the two-stage reaction unit shown is described in detail below (in conjunction with references). Figure 6 and Figure 7 ):

[0065] 1) Biomass enters the gasification chamber 1 (i.e., gasification chamber) of the first stage double fluidized bed filled with hot bed material through the feeding screw from the hopper. Together with the bed material, it is in a bubbling fluidized state in the gasification chamber 1, absorbs the heat of the bed material, and undergoes a gasification reaction with water vapor to produce hydrogen-rich gas and semi-coke. The semi-coke particles and cooled bed material particles move downward, while the gas moves upward, achieving preliminary gas-solid separation here.

[0066] 2) Hydrogen-rich gas is discharged from outlet 101 of the first-stage dual-fluidized bed gasification chamber 1, and the semi-coke and cooling bed material are subjected to cone-shaped water vapor (i.e., Figure 7The loosened fluidizing air enters the bottom of the combustion chamber and is rapidly fluidized under the action of the combustion air (air). Here, the water vapor at the bottom of the vaporization chamber acts as a barrier to hydrogen-rich gas and air and as a fluidizing agent for particles.

[0067] 3) In the combustion chamber 2 of the first-stage dual fluidized bed, carbonaceous semi-coke particles are ignited in the air, raising the temperature of the bed material particles in the combustion chamber; the ash particles remaining after the semi-coke is completely burned, the incompletely burned semi-coke particles, the bed material, and the fine powder generated by bed material abrasion enter the cyclone separator 4 from the feed inlet 40 (reference). Figure 6 Since the density and particle size of other particles and bed material particles differ greatly, they are discharged from the flue gas outlet 42 at the top of the cyclone separator along with the flue gas, while the bed material is discharged from the bottom of the cyclone separator 4 and enters the loosening chamber 31 of the return material unit 3 through the feed pipe 41.

[0068] 4) The hot bed material particles form a material seal in the loosening chamber 31 of the return unit. The syngas generated in the gasification chamber 1 is blocked in the return chamber 32 of the return unit 3, while the flue gas is blocked in the loosening chamber 31 by the material seal. The particles are transported to the gasification chamber 1 by the return air of the return unit. During the falling process, the rising syngas and fluidized gas are heated and mixed, which promotes the further removal of syngas tar and improves the quality of hydrogen-rich syngas. The hot bed material particles continue to fall and mix with the biomass particles to provide heat for the gasification reaction. In this way, the bed material is circulated in the dual fluidized bed system.

[0069] 5) The hydrogen-rich gas generated by the first-stage built-in dual fluidized bed is pressurized by the compressor and then enters the second-stage dual fluidized bed reactor through the combustion air inlet and secondary air inlet. It reacts with the iron-based oxygen carrier (Fe3O4) entering the second-stage combustion chamber, reducing it to elemental Fe or FeO. The syngas is oxidized into flue gas, releasing a large amount of heat in the process. The particles are in a bubbling fluidized state at the bottom of the second-stage combustion chamber, and then undergo rapid fluidization under the action of secondary air. The generated low-valent iron-based oxygen carrier or elemental iron enters the cyclone separator, while the flue gas is discharged from the top. The low-valent iron-based oxygen carrier or elemental iron falls into the return unit below the cyclone and is then transported by the return air (water vapor) to the second-stage dual fluidized bed gasification chamber (i.e., the gasification chamber). The high-temperature low-valent iron-based oxygen carrier or elemental iron particles react with the water vapor introduced from the bottom conical surface of the gasification chamber to produce high-purity hydrogen and iron-based oxygen carrier (Fe3O4). The high-purity hydrogen is discharged from the top of the gasification chamber for further purification. The cooled iron-based oxygen carrier (Fe3O4) is loosened by the water vapor on the conical surface and enters the bottom of the second-stage combustion chamber to continue to be reduced, thus completing the cycle regeneration of the oxygen carrier.

[0070] Example 1

[0071] The ambient temperature biomass feedstock in the hopper is fed into the gasification chamber of the first-stage dual fluidized bed reactor via a screw feeder. The feedstock falls into the dense phase zone of the fluidized bed under gravity, mixing with the thermally inert bed material at 1200K. It is then bubbling and fluidized at the bottom of the fluidized bed under the influence of 600K fluidizing air. The fluidizing gas is water vapor. The biomass pellets, when heated, produce a mixture of hydrogen-rich gases including hydrogen, carbon monoxide, carbon dioxide, and low-carbon hydrocarbons, as well as liquids such as tar, and solid particles such as semi-coke and ash. If the gasification gas is water vapor, the tar will undergo a reforming gasification reaction with the water vapor, decomposing into low-carbon hydrocarbon gases, which are discharged as product gas along with the hydrogen-rich gas. The hydrogen yield in the dry product gas can reach 55%. The cooled bed material particles, as well as semi-coke particles and ash particles, are loosened by the water vapor on the cone surface and enter the bottom of the combustion chamber. Under the action of the combustion air, they are rapidly fluidized. Some of the semi-coke particles come into contact with the fast-flowing 600K combustion air in the combustion chamber, and combustion releases a large amount of heat, which heats the cooled bed material particles. The flue gas produced by combustion carries the bed material particles, incompletely burned semi-coke particles, and ash particles into the cyclone separator. Because the actual density of the bed material particles differs significantly from that of other particles, the bed material particles can be separated from the flue gas and other particles relatively thoroughly. The flue gas and other particles are discharged from the top of the cyclone separator, while the bed material particles are discharged from the bottom of the cyclone separator and fall into the return unit. The particles gradually accumulate to form a material seal. The 1200K hot bed material particles are fluidized by the loosening air (water vapor) of the return unit and are carried by the return air (water vapor) into the gasification chamber. Under the action of gravity, they fall into the dilute phase zone of the fluidized bed. First, the rising syngas and the fluidized gas mixture are heated to promote further removal of tar from the syngas. Then, the biomass particles falling into the dense phase zone of the gasification chamber are heated. In this way, the bed material completes the circulation in the first stage of the dual fluidized bed reactor without participating in any reaction, only serving as a heat carrier.

[0072] The hydrogen-rich gas generated in the first-stage dual fluidized bed reactor is pressurized by a compressor and then enters the second-stage dual fluidized bed reactor through the second-stage combustion air inlet and secondary air inlet. There, it reacts with the iron-based oxygen carrier (Fe3O4) entering the second-stage combustion chamber, reducing it to elemental Fe or FeO. The syngas is oxidized into flue gas, releasing a large amount of heat in the process. The particles are in a bubbling fluidized state at the bottom of the second-stage combustion chamber at a bed temperature of 1123 K. Subsequently, under the action of secondary air, they undergo rapid fluidization. The generated low-valent iron-based oxygen carrier or elemental iron enters the cyclone separator, while the high-temperature flue gas is discharged from the top. The low-valent iron-based oxygen carrier or elemental iron falls into the return unit below the cyclone and is then transported by the return air (water vapor) to the second-stage dual fluidized bed gasification chamber. The high-temperature low-valent iron-based oxygen carrier or elemental iron particles react with the water vapor introduced from the bottom conical surface of the gasification chamber to produce 91%-99% high-purity hydrogen and iron-based oxygen carrier (Fe3O4). The cooled iron-based oxygen carrier (Fe3O4) is loosened by the water vapor on the conical surface and enters the bottom of the second-stage combustion chamber to continue to be reduced. In this way, the oxygen carrier is regenerated. The high-purity hydrogen is discharged from the top of the gasification chamber for further purification.

[0073] Example 2

[0074] When incorporating AER technology, the role of the first-stage bed material differs from that in Example 1. The ambient-temperature biomass feedstock in the hopper is fed into the gasification chamber of the first-stage dual fluidized bed reactor via a screw feeder. The feedstock falls into the dense phase zone of the fluidized bed under gravity, mixing with hot calcium oxide bed material at 1200K. It is then bubbly fluidized at the bottom of the fluidized bed by 600K fluidizing air. The fluidizing gas is water vapor. The biomass pellets, upon heating, produce a mixture of hydrogen, carbon monoxide, carbon dioxide, and low-carbon hydrocarbons (hydrogen-rich gas), liquids such as tar, and solid particles such as semi-coke and ash. Carbon dioxide combines with the calcium oxide bed material to form calcium carbonate bed material, releasing a certain amount of heat. This heat captures carbon dioxide from the gas while supplying some energy for the gasification reaction. Tar undergoes a reforming gasification reaction with water vapor, decomposing into low-carbon hydrocarbon gases, which are discharged as product gas along with the hydrogen-rich gas. Thus, the hydrogen content in the dry product gas can reach 78%. Cooled calcium carbonate bed particles, along with semi-coke and ash particles, are loosened by water vapor from the conical surface and enter the bottom of the combustion chamber. Under the action of combustion air, they rapidly fluidize. Some semi-coke particles come into contact with the fast-flowing 600K combustion air in the combustion chamber, burning and releasing a large amount of heat. This heats the cooled calcium carbonate bed particles, causing them to lose carbon dioxide and regenerate calcium oxide bed particles, thus completing the task of "transporting" carbon dioxide from the product gas to the flue gas. The flue gas produced by combustion carries the bed particles, incompletely burned semi-coke particles, and ash particles into the cyclone separator. Because the actual density of the bed material particles differs significantly from that of other particles, the bed material particles can be separated from the flue gas and other particles relatively thoroughly. The flue gas and other particles are discharged from the top of the cyclone separator, while the bed material particles are discharged from the bottom of the cyclone separator and fall into the return unit. The particles gradually accumulate to form a material seal. The 1200K hot bed material particles are fluidized by the loosening air (water vapor) of the return unit and are carried by the return air (water vapor) into the gasification chamber. Under the action of gravity, they fall into the dilute phase zone of the fluidized bed. First, the rising syngas and the fluidized gas mixture are heated to promote further removal of tar from the syngas. Then, the biomass particles falling into the dense phase zone of the gasification chamber are heated to further capture carbon dioxide and complete carbonation. In this way, the bed material completes the circulation in the first stage of the dual fluidized bed reactor, serving as a carrier of heat and carbon dioxide.

[0075] The hydrogen-rich gas, which is purer and has less tar than that produced in Example 1, generated by the first-stage dual fluidized bed is pressurized by a compressor and then enters the second-stage dual fluidized bed reactor through the combustion air inlet and secondary air inlet. There, it reacts with the iron-based oxygen carrier (Fe3O4) entering the second-stage combustion chamber, reducing it to elemental Fe or FeO. The syngas is oxidized into flue gas, releasing a large amount of heat in the process. The particles are in a bubbling fluidized state at the bottom of the second-stage combustion chamber at a bed temperature of 1123 K, and then undergo rapid fluidization under the action of secondary air. The resulting low-valent iron-based oxygen carrier or elemental iron enters the cyclone separator. High-temperature flue gas is discharged from the top, while low-valent iron-based oxygen carriers or elemental iron fall into the return unit below the cyclone. They are then transported by the return air (water vapor) to the second-stage dual fluidized bed gasification chamber. The high-temperature low-valent iron-based oxygen carriers or elemental iron particles react with the water vapor introduced from the bottom conical surface of the gasification chamber to produce 91%-99% high-purity hydrogen and iron-based oxygen carrier (Fe3O4). The cooled iron-based oxygen carrier (Fe3O4) is loosened by the water vapor on the conical surface and enters the bottom of the second-stage combustion chamber to continue to be reduced. This completes the cycle and regeneration of the oxygen carrier. The high-purity hydrogen is discharged from the top of the gasification chamber for further purification.

[0076] The foregoing description of specific exemplary embodiments of the present invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. Any simple modifications, equivalent changes, and alterations made to the foregoing exemplary embodiments should fall within the scope of protection of the present invention.

Claims

1. A two-stage built-in dual fluidized bed reactor, characterized in that, The application relates to a biomass raw material chemical chain hydrogen production process, and each section is provided with a double fluidized bed. A gasification chamber is provided with a conical surface at the bottom, and a hole is formed in the conical surface for the passage of bubbling fluidization air. A combustion chamber is provided with a tubular structure and is sleeved in the gasification chamber, the bottom of the combustion chamber is in an open state and is arranged in the conical surface area for the passage of vertical upward combustion-supporting air. A plurality of return units are arranged in the upper part of the reaction device and are uniformly arranged in the circumferential direction, and are used for carrying high-temperature bed material particles from the combustion chamber to the annular gasification area outside the combustion chamber and mixing with the biomass raw material in the gasification area to produce hydrogen; the return unit is provided with a loosening chamber and a return chamber, and the bottom plate of the loosening chamber is arranged to be inclined towards the return chamber. The two sections of the double fluidized bed are connected in series, and the hydrogen-containing synthesis gas produced by the first section of the double fluidized bed is introduced into the combustion chamber of the second section of the double fluidized bed.

2. The two-stage, built-in dual fluidized bed reaction apparatus according to claim 1, wherein Each return unit is fixed and penetrates the wall surface of the combustion chamber; the loosening chamber is arranged close to one side of the combustion chamber, and the upper part is communicated with a cyclone separator through a feeding pipe; the cyclone separator is arranged in the combustion chamber.

3. The two-stage, built-in dual fluidized bed reaction apparatus according to claim 2, wherein The return chamber is arranged close to one side of the gasification chamber and is communicated with the annular space of the gasification chamber through a feeding pipe.

4. The two-stage, built-in dual fluidized bed reaction apparatus according to claim 3, wherein The loosening chamber receives bed material particles from the combustion chamber and blocks gas, and the middle and upper parts of the loosening chamber are separated from the return chamber through a partition plate; the lower part of the loosening chamber is provided with a first air distribution cavity; and the lower part of the return chamber is provided with a second air distribution cavity.

5. The two-stage, built-in dual fluidized bed reaction apparatus according to claim 4, wherein Air caps or air holes are arranged on the bottom plates of the loosening chamber and the return chamber; the first air distribution cavity and the second air distribution cavity are supplied with air through air pipes extending to the outside of the reaction device.

6. The two-stage, built-in double fluidized bed reaction apparatus according to claim 5, wherein The air pipes are arranged in a cross shape.

7. The two-stage, built-in dual fluidized bed reaction apparatus according to claim 1, wherein The cross-sectional dimension of the loosening chamber is 1.1 to 1.5 times that of the return chamber.

8. The two-stage, built-in double fluidized bed reaction apparatus according to claim 1, wherein The feeding port of the biomass raw material is arranged at the bottom of the material layer of the gasification chamber, above the material layer and / or at the top of the reaction device, and the feeding mode is screw feeding.

9. The two-stage, built-in dual fluidized bed reaction apparatus according to claim 1, wherein The conical surface of the gasification chamber is provided with a chute structure for prolonging the residence time of bed material particles at the bottom and for gas sealing.

10. The two-stage, built-in dual fluidized bed reaction apparatus according to claim 9, wherein The chute structure specifically comprises: A first conical surface extends downwardly and obliquely from the outer wall surface of the combustion chamber; A second conical surface extends upwardly and obliquely from the outer wall surface of the combustion chamber and forms a relatively closed structure together with the first conical surface and the outer wall surface of the combustion chamber; and the second conical surface and the conical surface of the bottom of the gasification chamber form a chute.

11. The two-stage, built-in dual fluidized bed reaction apparatus according to claim 10, wherein The closed structure is an air cavity for the passage of secondary air from the outside of the reaction device.

12. The two-stage, built-in dual fluidized bed reaction apparatus according to claim 11, wherein An upwardly inclined secondary air hole is formed in the upper part of the air cavity and the wall surface of the combustion chamber, and the secondary air is combined with the combustion-supporting air at the bottom of the combustion chamber to prolong the residence time of bed material particles at the bottom.

13. The two-stage, built-in dual fluidized bed reaction apparatus according to claim 1, wherein The air holes on the conical surface of the bottom of the gasification chamber gradually decrease in size from bottom to top.

14. The two-stage, built-in double fluidized bed reaction apparatus according to claim 1, wherein The bed material particles of the first section of the double fluidized bed are inert bed material or metal oxide bed material; and the bed material particles of the second section of the double fluidized bed are iron-based oxygen carriers.

15. The two-stage, built-in dual fluidized bed reaction apparatus according to claim 14, wherein The metal oxide bed material is calcium oxide bed material, which is used for capturing carbon dioxide in the gasification chamber to generate calcium carbonate, and the calcium carbonate is decomposed by heat in the combustion chamber to generate carbon dioxide and is discharged with flue gas.

16. The two-stage, built-in double fluidized bed reaction apparatus according to claim 1, wherein The first-stage double fluidized bed and the second-stage double fluidized bed are connected by a pipeline, one end of which is connected to the hydrogen-containing synthesis gas outlet of the first-stage double fluidized bed, and the other end is connected to the combustion-supporting air inlet of the combustion chamber of the second-stage double fluidized bed.

17. The two-stage, built-in double fluidized bed reaction apparatus according to claim 16, wherein A turbocharger is arranged on the pipeline to provide sufficient fluidizing air speed for the combustion chamber of the second-stage double fluidized bed.

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