Microwave heating of a material, a reaction apparatus and a method using the same

Abstract

This invention discloses a microwave-heated return feeder, a reaction apparatus using the return feeder, and a method thereof. The microwave-heated return feeder is positioned between the combustion reactor and the gasification reactor in a dual fluidized bed reactor used in biomass hydrogen production, at the upper return feed location. It includes: a return feed chamber connected to the gasification reactor via a feed pipe; and a loosening chamber connected to a cyclone separator at the rear end of the combustion reactor via a feed leg, used to receive the bed material particles after combustion and separation. The upper part of the loosening chamber is separated from the return feed chamber by a partition, and the movement speed of the bed material particles in the loosening chamber decreases rapidly compared to that in the feed leg. A microwave generator is installed at a corresponding position on the outer wall of the loosening chamber. This invention avoids the various uncontrollable problems associated with directly using microwave heating in the reactor cavity, and can more effectively ensure the hydrogen production rate.

Description

Technical Field

[0001] This invention relates to the field of biomass hydrogen production technology, and in particular to a microwave-heated return feeder, a reaction apparatus and method using the return feeder. 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 and microwave moving bed reactors for efficient thermal conversion to produce hydrogen-rich gas shows promising prospects.

[0003] Traditional fluidized bed reactors, where combustion and gasification occur in the same reactor, result in partial combustion of syngas and low yield. Microwave moving bed reactors, on the other hand, have gained popularity in recent years due to the penetrating power of microwaves, their ability to uniformly oscillate polar molecules for heating, and the proven ability of non-thermal microwave effects to accelerate chemical reactions. However, the method of biomass gasification via moving bed under microwave conditions also presents several challenges: 1) When heating a large moving bed cavity with microwaves, the large size of the biomass particles makes it difficult for microwaves to penetrate to the inner layers; 2) Heating a large cavity using a microwave moving bed for biomass gasification consumes a lot of energy; 3) Localized hot spots can easily form in the biomass layer during microwave heating, leading to uneven heating, making it difficult to control the chemical reaction rate and the quality of the syngas.

[0004] Chinese patent application CN113122336A discloses a method and system for producing hydrogen from biomass through thermal conversion. The method involves feeding biomass feedstock into a microwave pyrolysis reactor for reaction, followed by gasification of the resulting material in a gasification reactor to obtain crude syngas and solid residue. The crude syngas is then reacted with a calcium-based adsorbent to produce high-purity hydrogen and carbonated calcium-based adsorbent. The carbonated calcium-based adsorbent is regenerated with the solid residue to obtain regenerated calcium-based adsorbent, which is then recycled back into the gasification reactor. While this method produces hydrogen that meets industrial hydrogen requirements, it necessitates microwave heating of the reactor, which presents the aforementioned problems associated with microwave heating of large moving bed chambers.

[0005] When a fluidized bed reactor employs a dual-fluidized-bed design, a return feeder is required between the two fluidized beds. This return feeder is a non-mechanical valve; the fluidized material is conveyed as a solid under pressure on both sides of the feeder. Many issues can lead to insufficient semi-coke particles in the return feed, preventing adequate heat from combustion. Therefore, ensuring the bed material reaches the design temperature is a design challenge for circulating fluidized-bed reactors. The conventional approach is to introduce an external heat source to maintain gasification, such as adding carbon-containing fuel and secondary air at the burner inlet to promote combustion. However, this results in some waste of carbon-containing materials and an increase in carbon emissions from the reactor.

[0006] Therefore, there is an urgent need for a return feeder for use in dual fluidized bed reactors. By improving the structure of the return feeder and using microwave heating on it, the hydrogen production rate can be guaranteed more effectively.

[0007] 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

[0008] The purpose of this invention is to provide a microwave-heated return feeder and a reaction apparatus and method using the return feeder. By improving the structure of the return feeder and using microwave heating of the bed material particles on the return feeder, various uncontrollable problems caused by directly using microwave heating in the reactor cavity are avoided, and the hydrogen production rate can be guaranteed more effectively.

[0009] To achieve the above objectives, according to a first aspect of the present invention, a microwave-heated return feeder is provided, which is disposed between the combustion reactor and the gasification reactor of a dual fluidized bed reactor used in the biomass hydrogen production process, and located at the upper return feed position, comprising: a return feed chamber, which is connected to the gasification reactor via a feed pipe; a loosening chamber, which is connected to a cyclone separator at the rear end of the combustion reactor via a feed leg, for receiving the bed material particles after combustion and separation; the middle and upper parts of the loosening chamber are separated from the return feed chamber by a partition, and the moving speed of the bed material particles in the loosening chamber is rapidly reduced compared to that in the feed leg; a microwave generator is provided at a corresponding position on the outer wall of the loosening chamber.

[0010] Furthermore, in the above technical solution, the cross-sectional dimension of the loosening chamber can be set to 2 to 4 times the cross-sectional dimension of the material leg; the cross-sectional dimension of the return chamber can be set to 1 to 2 times the cross-sectional dimension of the material leg.

[0011] Furthermore, in the above technical solution, the lower part of the loosening chamber and the lower part of the return chamber are connected. The bottom of the return device can be provided with an air distribution chamber. The lower end of the air distribution chamber is connected to the fluidizing air inlet pipe, and the upper end is provided with an air cap. The fluidizing air blows the bed material particles from the loosening chamber, which have been moved at low speed and heated by microwave, to the gasification reactor at high speed through the return chamber.

[0012] Furthermore, in the above technical solution, the outer wall of the material leg can also be equipped with the same microwave generator as the outer wall of the loosening chamber.

[0013] Furthermore, in the above technical solution, the microwave power of the microwave generator can be adjusted in real time according to the preset temperature of the bed material particles. The power adjustment unit includes: a thermocouple, which is used to measure the temperature of the bed material particles in real time; and a control unit, which receives the temperature data of the bed material particles and compares it with the preset temperature. By controlling the activation of the relay, the working interval time of the magnetron is changed to adjust the microwave power so that the temperature of the bed material particles is consistent with the preset temperature.

[0014] Furthermore, in the above technical solution, the bed material particles can be inert bed material or calcium oxide bed material.

[0015] According to a second aspect of the present invention, the present invention provides a dual fluidized bed reactor using the aforementioned microwave-heated return feeder, further comprising: a gasification reactor that receives biomass feedstock and absorbs heat from the bed material particles of the microwave-heated return feeder, and undergoes a gasification reaction under the action of bottom gasification air to generate hydrogen-rich gas and semi-coke; a lower return feeder that is connected to the lower part of the gasification reactor, wherein the semi-coke and cooled bed material particles form a material seal in the lower return feeder; a combustion reactor that is connected to the lower return feeder for receiving the semi-coke and cooled bed material particles blown from the lower return feeder, and burning the semi-coke particles under the action of combustion air to raise the temperature of the bed material particles; the bed material particles separated by cyclone after combustion are fed into the microwave-heated return feeder.

[0016] Furthermore, in the above technical solution, the lower part of the gasification reactor may be equipped with a hopper and a feeding screw to feed biomass raw materials into the gasification reactor.

[0017] According to a third aspect of the present invention, the present invention provides a dual fluidized bed reaction method using the aforementioned microwave-heated return feeder, comprising the following steps: A. A gasification reactor receives biomass feedstock and absorbs heat from the bed material particles from the microwave-heated return feeder, and a gasification reaction occurs under the action of bottom gasification air to generate hydrogen-rich gas and semi-coke; B. The semi-coke and cooled bed material particles form a material seal in the lower return feeder; C. Under the action of fluidization air, the semi-coke and cooled bed material particles in the lower return feeder are blown to the combustion reactor, where the semi-coke particles are burned and the temperature of the bed material particles is increased under the action of combustion air; the bed material particles separated by cyclone separation after combustion are sent to the microwave-heated return feeder; D. The moving speed of the separated bed material particles in the loosening chamber decreases rapidly compared to that in the feed leg, and the bed material particles microwave-heated at the corresponding position in the loosening chamber enter the gasification reactor to complete the cycle of biomass hydrogen production.

[0018] Furthermore, in the above technical solution, when the bed material particles are inert, the bed material particles only serve as a heat carrier; when the bed material particles are calcium oxide bed material, the carbon dioxide generated in the biomass hydrogen production process in the gasification reactor is captured by the calcium oxide bed material to generate calcium carbonate bed material, which simultaneously supplements the heat supply for the gasification reaction.

[0019] Furthermore, in the above technical solution, the gasification air in step A can be nitrogen or water vapor; when the gasification air is water vapor, the tar produced by gasification can be reformed.

[0020] Furthermore, in the above technical solution, the fluidizing air in step C can be water vapor.

[0021] Furthermore, in the above technical solution, the microwave power of the microwave generator can be adjusted in real time according to the preset temperature of the bed material particles. Specifically, this includes: measuring the temperature of the bed material particles in real time through a thermocouple; the control unit receiving the bed material particle temperature data and comparing it with the preset temperature; and adjusting the microwave power by controlling the activation of the relay and changing the working interval time of the magnetron, so that the temperature of the bed material particles remains consistent with the preset temperature.

[0022] Furthermore, in the above technical solution, the preset temperature can be set to 1200K; the power of the microwave generator can be 500 to 2000W, and a 2450MHz microwave magnetron can be used.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1) The dual fluidized bed reactor and reaction method of the present invention utilize microwaves to heat the small cavity of the upper return feeder (i.e., microwave heated return feeder), which provides more uniform heating and lower energy consumption compared to microwave moving bed gasification technology.

[0025] 2) By using calcium oxide and other bed materials, carbon dioxide can be captured in the gasification reactor to generate calcium carbonate bed material. When the carbon dioxide is not completely removed by heating in the combustion reactor, it can be further heated by microwaves inside the upper return feeder to decompose the calcium carbonate bed material by heating, ensuring that the proportion of calcium oxide particles in the bed material entering the gasification reactor is higher, which can capture more carbon dioxide in the gasification reactor and increase the proportion of hydrogen.

[0026] 3) This invention avoids the need to add carbon-containing fuels such as fuel oil and biomass pellets to the combustion reactor. The carbon-containing fuels will only be used as raw materials for the gasification reaction, which reduces carbon emissions and the scale of the flue gas after-treatment device.

[0027] 4) This invention can effectively control microwave power, heat the bed material more precisely and quickly, accurately control the depth of gasification reaction, and save thermal energy.

[0028] 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

[0029] Figure 1 This is a cross-sectional schematic diagram of the microwave heating return device of the present invention.

[0030] Figure 2 This is a schematic diagram of the structure of the dual fluidized bed reactor that utilizes a microwave-heated return feeder according to the present invention.

[0031] Figure 3 This is a schematic diagram of the dual fluidized bed process when calcium oxide is used as the bed material particles in this invention.

[0032] Explanation of key figure labels:

[0033] 1-Microwave heating return feeder, 10-Material leg, 11-Loosening chamber, 110-Baffle, 12-Return chamber, 120-First feeding pipe, 13-Air distribution chamber, 130-Air cap, 14-Fluidizing air inlet pipe;

[0034] 2-Gasification reactor, 21-Hopper, 22-Feeding screw, 23-Second feeding pipe;

[0035] 3-lower return device, 31-third feeding pipe;

[0036] 4- Combustion reactor, 5- Cyclone separator, 6- Microwave generator. Detailed Implementation

[0037] 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.

[0038] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprising" shall be understood to include the stated elements or components without excluding other elements or other components.

[0039] 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.

[0040] 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.

[0041] This invention employs a dual fluidized bed reactor for biomass hydrogen production. The dual fluidized bed reactor offers the following advantages: Traditional routes involve combustion and gasification in the same reactor, resulting in partial combustion of the syngas and low yield. The dual fluidized bed reactor decouples combustion and gasification, using indirect heating, leading to higher hydrogen production. 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 reactors, 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, which facilitates subsequent tar removal treatment. The dual fluidized bed reactor of the present invention includes a gasification reactor and a combustion reactor, with an upper return feeder and a lower return feeder between the two reactors, wherein the upper return feeder is a microwave-heated return feeder.

[0042] Example 1

[0043] like Figure 1As shown, this embodiment provides a microwave-heated return feeder 1, which is installed between the combustion reactor 4 and the gasification reactor 2 of a dual fluidized bed reactor used in the biomass hydrogen production process. (Refer to...) Figure 2 The microwave-heated return feeder 1 specifically includes a loosening chamber 11 and a return chamber 12, wherein the return chamber 12 is connected to the gasification reactor 2 via a first feed pipe 120. The loosening chamber 11 is connected to the cyclone separator 5 (located at the top of the feed leg 10) at the rear end (i.e., downstream position) of the combustion reactor 4 via the feed leg 10. The cyclone separator 5 is used to separate fly ash, flue gas, and bed material particles from the combustion reactor. The loosening chamber 11 is used to receive the bed material particles after combustion and separation, and the loosening chamber 11 is also used to store the bed material particles entering from the feed leg 10. The middle and upper parts of the loosening chamber 11 are separated from the return chamber 12 by a partition 110, and the lower parts of the two are connected. Preferably, but not limitingly, in this embodiment, the cross-sectional dimension of the loosening chamber 11 is 2 to 4 times the cross-sectional dimension of the feed leg 10, that is, much larger than the size of the feed leg 10, and the cross-sectional dimension of the return chamber 12 is 1 to 2 times the cross-sectional dimension of the feed leg. This design rapidly reduces the movement speed of the bed material particles entering from the feed leg within the loosening chamber. This is because, in this embodiment, the microwave generator 6 is positioned at a corresponding location on the outer wall of the loosening chamber 11 (see reference). Figure 2 In conjunction with the aforementioned structural design of the loosening chamber 11, the efficiency and effect of microwave heating are improved. This structural design differs from conventional top return feeders (i.e., the diameters of the loosening chamber and return chamber are usually relatively small, basically the same as the diameter of the material leg, facilitating rapid circulation of the bed material). In this embodiment, the microwave heating return feeder 1 enlarges the volume of the loosening chamber 11, slowing down the movement speed of the bed material particles in the loosening chamber, thus enabling them to be heated rapidly by microwaves. In addition, the increased size of the loosening chamber 11 also increases the quality of the material seal, reducing the possibility of gas backflow from the gasification chamber to the combustion chamber under adverse operating conditions, leading to deflagration and improving the safety of the device. Furthermore, the relatively small volume of the return chamber 12 allows the bed material particles passing through the return chamber 12 to still be transported to the gasification reactor 2 at a relatively fast speed by the fluidizing air.

[0044] Further as Figure 1 As shown, the loosening chamber 11 and the return feeder 12 are equipped with an air distribution chamber 13 at the bottom. The lower end of the air distribution chamber 13 is connected to the fluidizing air inlet pipe 14, and the upper end of the air distribution chamber 13 is equipped with an air cap 130 for distributing the flow rate of the fluidizing air. The fluidizing air blows the bed material particles from the loosening chamber 11, which have been moved at low speed and heated by microwave, to the gasification reactor 2 at high speed through the return feeder 12.

[0045] Further as Figure 2As shown, in this embodiment, in addition to setting the microwave generator 6 on the upper return feeder, the same microwave generator can also be set on the outer wall of the feed leg 10, which can further improve the microwave heating effect on the bed material particles. The bed material particles in this embodiment can be inert bed materials (such as olivine, quartz sand, etc.) or calcium oxide bed materials. Setting the microwave generator 6 on the upper return feeder and the feed leg avoids using microwave heating on the outer wall of the large gasification reactor cavity, and does not directly heat the biomass raw materials. This effectively solves the problem that when microwaves directly heat a large moving bed cavity, the microwaves are easily absorbed by the outer biomass layer during the penetration process due to the large volume of the biomass particles in the cavity, and cannot be transmitted to the inner layer of the biomass particles. At the same time, it greatly reduces microwave energy consumption. Specifically, the loosening chamber 11 and the feed leg 10 are made of stainless steel, and corresponding microwave transmission windows (made of porous microwave-transparent ceramic) are set on the side walls. Each window is equipped with a microwave generator 6, and the power of a single microwave generator is 500-2000W. Depending on the volume of the return feeder, several microwave generators are installed at different heights on the outer walls of the loosening chamber 11 and the material leg 10, preferably 6 to 14. Since microwave heating requires control of the microwave power, in this embodiment, the microwave power is adjusted in real-time according to the preset temperature of the bed material particles via a power adjustment unit (not shown in the figure) to ensure that the particle temperature entering the gasification chamber is around 1200K. The power adjustment unit includes a thermocouple and a control unit. The thermocouple is used to measure the bed material particle temperature in real time; the control unit receives the bed material particle temperature data and compares it with the preset temperature (i.e., 1200K). By controlling the activation of the relay, the microwave power is adjusted by changing the working interval time of the microwave magnetron, so that the bed material particle temperature remains consistent with the preset temperature.

[0046] Example 2

[0047] like Figure 2As shown, this embodiment provides a dual fluidized bed reactor, including the microwave-heated return feeder 1 described in Embodiment 1. It also includes a gasification reactor 2, a lower return feeder 3, and a combustion reactor 4. This embodiment addresses the problems of insufficient penetration depth, high energy consumption, and uneven radiation in microwave moving beds when heating large moving bed cavities. The dual fluidized bed device of this embodiment overcomes the technical problems of poor return feed and insufficient particle circulation leading to insufficient heat supply to the gasification chamber. By placing the microwave generator at the upper return feeder (i.e., the microwave-heated return feeder 1), and combining the advantages of the gasification reactor 2 and the combustion reactor 4 through the structural design of Embodiment 1, microwaves are used to heat the small cavity, providing clean, rapid, and precise heating of the high-throughput bed material particles in the return chamber of the microwave-heated return feeder 1. The heated bed material particles then enter the gasification reactor 2 to provide heat for the biomass gasification reaction. The bed material particles can be inert materials such as olivine and quartz sand, or materials that can capture carbon dioxide in situ using AER technology, such as calcium oxide particles, and other easily absorbing microwave materials. When calcium oxide granules are used as the bed material, three effects are added: absorption, enhancement, and reforming. Specifically, water vapor, while acting as the gasification air, is also responsible for reforming the tar produced during gasification to reduce the tar content in the product gas. The bed material, heated by the microwave-heated return feeder 1 and then entering the gasification reactor 2, not only acts as a heat carrier but also undertakes the tasks of absorption and enhancement: the AER bed material (e.g., calcium oxide) can absorb carbon dioxide in the gasification reactor 2 to complete carbonation and release heat, which not only reduces the carbon dioxide content in the product gas and improves its quality but also provides some heat for the gasification reaction, supplementing the heating of the heated bed material carrier and enhancing the biomass gasification process. After the gasification reaction, the bed material becomes carbonized bed material, which is transported to the combustion reactor 4 through the lower return feeder 3. In the combustion reactor, it is heated and decomposed to release carbon dioxide. In this way, the carbon dioxide is transported into the flue gas, and the bed material can continue to return to the oxide form (i.e., regenerate calcium oxide bed material). After being microwave heated by the upper return feeder (i.e., microwave heated return feeder 1), it enters the gasification reactor 2 to recapture carbon dioxide, thus completing the cycle of biomass hydrogen production of the present invention.

[0048] Further as Figure 2As shown, specifically, the microwave-heated return feeder 1 is located at the upper return feeder position. When the bed material in the combustion reactor 4 is heated, it is separated by the cyclone separator 5 and enters the microwave-heated return feeder 1. In the microwave-heated return feeder, it is further heated to a higher temperature so that the bed material particles entering the gasification reactor 1 can reach the temperature required for the gasification reaction. The reasons for choosing the upper return feeder as the location for high-throughput microwave heating of bed material in this invention are as follows: 1) In the dual fluidized bed reactor, the particle movement speed in the return feeder is the lowest, most particles are not fluidized, and the movement pattern is consistent with the particle flow pattern in the moving bed. Microwave heating is performed here, and the particles have sufficient residence time to be heated; 2) The particle composition in the upper return feeder is relatively uniform, consisting entirely of bed material particles, and there is no risk of combustion explosion caused by microwave heating. The particle composition transported from the gasification reactor 2 to the combustion reactor 4 via the lower return feeder 3 is complex, including semi-coke particles, bed material particles, ash particles, and fine bed material powder generated due to bed material abrasion. These particles have large differences in particle size and density, and varying residence times, and microwave heating may lead to combustion explosion. The particles entering the upper return feeder are calcined in the combustion reactor 4 and separated in the cyclone separator 5, leaving only bed material with relatively uniform composition and particle size, which facilitates heating; 3) In civilian industrial applications, microwave magnetrons mainly use 915MHz and 2450MHz. The 915MHz magnetron has high power, longer microwave wavelength, and deeper penetration, but is more expensive; the 2450MHz magnetron has lower power, shorter wavelength, and shallower microwave penetration, but is cheaper. The more economical 2450MHz microwave magnetron can be used to heat the small cavity of the return feeder, which can effectively save equipment and operating costs; When technically modifying existing circulating fluidized bed and dual fluidized bed devices, only the structural design of the return feeder (the structural design involved in Example 1) needs to be modified, and the main body of the gasification reactor and combustion reactor does not need to be changed, saving technical modification costs.

[0049] Further as Figure 2As shown, the gasification reactor 2 receives biomass feedstock and absorbs heat from the bed material particles from the microwave-heated return feeder 1. Under the action of the bottom gasification air, a gasification reaction occurs, generating hydrogen-rich gas and semi-coke. Specifically, biomass enters the gasification reactor 2, which is filled with hot bed material, through the feeding screw 22 from the hopper 21. The bottom gasification air can be nitrogen or steam. The product gas (i.e., hydrogen-rich gas) generated after the gasification reaction is discharged from the top of the gasification reactor 2. The lower return feeder 3 is connected to the bottom of the gasification reactor 2. The semi-coke and cooled bed material particles form a material seal in the lower return feeder 3. When the bed material particles are inert bed material, the inert bed material is only a heat carrier in the gasification reactor 2 and does not undergo chemical reaction; when the bed material particles are calcium oxide bed material, the bed material particles become calcium carbonate bed material after the gasification reaction. Combustion reactor 4 is connected to the lower return feeder 3 and is used to receive semi-coke and cooled bed material particles blown from the lower return feeder 3. Under the action of combustion air, the semi-coke particles are burned, and the temperature of the bed material particles is increased. The burned particles are then separated into bed material particles by a cyclone separator and sent to microwave-heated return feeder 1. Specifically, combustion air is passed through combustion reactor 4, see [link to details]. Figure 2 Combustion air can be provided by combustion air and secondary combustion air located at the bottom of combustion reactor 4. Carbon-containing semi-coke particles are ignited in the air, raising the temperature of the bed material particles in the combustion reactor. The ash particles remaining after the semi-coke is completely burned, the unburned semi-coke particles, the bed material, and the fine powder generated by bed material abrasion are carried by the flue gas to cyclone separator 5. Due to the large difference in density and particle size between other particles and bed material particles, they are discharged from the top of cyclone separator 5 along with the flue gas, while the bed material particles are discharged from the bottom of cyclone separator 5 and fall into the material leg 10, forming a material seal. The bed material particles are further heated by microwaves in the loosening chamber of microwave-heated return feeder 1 and the corresponding positions of the material leg 10 to reach the preset temperature. The hot bed material particles in the return chamber are transported to gasification reactor 2 by the fluidizing air at the bottom of the microwave-heated return feeder to heat the gasification reaction, thus forming the circulation of bed material in the dual fluidized bed system.

[0050] Example 3

[0051] like Figure 2 As shown, this embodiment provides a dual fluidized bed reaction method corresponding to Embodiment 2, including the following steps:

[0052] In step S101, the gasification reactor 2 receives biomass feedstock and absorbs heat from the bed material particles of the microwave-heated return feeder 1. Under the action of the bottom gasification air, a gasification reaction occurs, generating hydrogen-rich gas and semi-coke. The hydrogen-rich gas is discharged from the top of the gasification reactor 2 as the product gas. Preferably, but not limitingly, the gasification air can be nitrogen or steam; when the gasification air is steam, the steam can also reform the tar produced by gasification.

[0053] In step S102, the semi-coke generated by the gasification reaction in step S101 and the cooled bed material particles form a material seal in the lower return feeder 3. The particles are transported to the combustion reactor 4 by the lower return feeder under the action of the fluidizing air.

[0054] In step S103, under the action of fluidizing air, the semi-coke and cooled bed material particles in the lower return feeder 3 are blown to the combustion reactor, where the semi-coke particles are burned and the temperature of the bed material particles is increased under the action of combustion air (i.e., combustion air). The burned particles (including ash particles remaining after the semi-coke is burned out, unburned semi-coke particles, bed material, and fine powder generated by bed material abrasion, etc.) are separated by cyclone separation and sent to the microwave-heated return feeder 1. Preferably, but not limitingly, the fluidizing air of the lower return feeder 3 can be steam (the same as the fluidizing air of the microwave-heated return feeder 1).

[0055] In step S104, the separated bed material particles move at a significantly slower speed in the loosening chamber of the microwave-heated return feeder 1 compared to their movement in the material leg. Since the cross-sectional dimensions of the loosening chamber are much larger than those of the material leg, this reduced speed allows for bed material storage and more effective material sealing. Furthermore, microwave heating at this location effectively ensures the heating effect. The return chamber, with a cross-sectional dimension similar to the material leg, experiences a rapid increase in bed material movement speed under the influence of bottom fluidizing air, ensuring smooth return of the bed material and a high particle circulation rate. The microwave-heated bed material particles then enter the gasification reactor 2, completing the biomass hydrogen production cycle.

[0056] Furthermore, when inert bed material is used, the bed material in gasification reactor 1 only serves as a heat carrier and does not participate in any chemical reaction; when calcium oxide bed material is used, refer to... Figure 3 The process shown involves carbon dioxide produced during the biomass hydrogen production process in the gasification reactor being captured by calcium oxide bed material to generate calcium carbonate bed material. Since this reaction is exothermic, it can simultaneously supplement the heat supplied to the gasification reaction.

[0057] Furthermore, temperature control of the microwave-heated return feeder 1 used in this embodiment is necessary. This is because the quantity of semi-coke particles entering the combustion reactor 4 through the return feeder 3 is not stable, resulting in varying temperatures of the bed material heated by combustion in the combustion reactor 4 at different times. Therefore, it is necessary to adjust the microwave power according to the bed material temperature. When the bed material temperature is higher than the set temperature, microwave heating stops; when the bed material temperature is lower than the set temperature, microwave heating is applied appropriately to avoid unnecessary energy consumption. Simultaneously, in the AER process, the carbonation of the bed material is an exothermic reaction, and the temperature in the gasification reactor 2 cannot be too high, otherwise the efficiency of in-situ carbon dioxide capture by the bed material will decrease. Therefore, when the bed material temperature is too high, microwave heating is stopped to prevent further temperature increases, which would affect capture efficiency and reduce the quality of the product gas. Therefore, in this embodiment, the microwave power of the microwave generator used in the microwave heating return material unit 1 can be adjusted in real time according to the preset temperature of the bed material particles. The preset temperature is set to approximately 1200K. The real-time adjustment method specifically includes: measuring the bed material particle temperature in real time using thermocouples; the control unit receiving the bed material particle temperature data and comparing it with the preset temperature, and adjusting the microwave power by controlling the activation of the relay and changing the working interval time of the magnetron, so that the bed material particle temperature remains consistent with the preset temperature. Specifically, the real-time temperature of the bed material can be measured using thermocouples in the loosening chamber of the microwave heating return material unit 1, and the online data can be transmitted to the processor; the processor receives the temperature data and connects to the microwave generator, controlling the microwave power through instructions; by judging the relationship between the current temperature data and the set temperature, if it is higher than the set temperature, a negative feedback signal is output to reduce the microwave power; if it is lower than the set temperature, a positive feedback signal is output to increase the microwave power.

[0058] The dual fluidized bed reactor and reaction method of this invention utilize microwaves to heat the small cavity of the upper return feeder (i.e., microwave-heated return feeder). Compared with microwave moving bed gasification technology, the heating is more uniform and the energy consumption is lower. By using bed materials such as calcium oxide, carbon dioxide can be captured in the gasification reactor to generate calcium carbonate bed material. When carbon dioxide removal is incomplete in the combustion reactor, it can be further heated by microwaves inside the upper return feeder, causing the calcium carbonate bed material to decompose thermally. This ensures that the proportion of calcium oxide particles in the bed material entering the gasification reactor is higher, which can capture more carbon dioxide in the gasification reactor and increase the proportion of hydrogen. This invention avoids the additional addition of carbon-containing fuels such as fuel oil and biomass pellets to the combustion reactor. Carbon-containing fuels will only be used as raw materials for the gasification reaction, reducing carbon emissions and the scale of flue gas after-treatment devices. This invention can effectively control microwave power, more accurately and quickly heat the bed material, accurately control the depth of the gasification reaction, and save thermal energy.

[0059] Example 4

[0060] This embodiment is a specific example of the reaction method in Example 3: (See reference...) Figure 2 The ambient temperature biomass feedstock in hopper 21 is fed into the gasification reactor 2 of the dual fluidized bed reactor of this invention via screw feeder 22. The feedstock falls into the dense phase zone of the fluidized bed under gravity and mixes with the hot inert bed material at 1200K. It is then bubbling and fluidized in the lower part of the fluidized bed under the influence of 600K gasification air. The gasification gas can be nitrogen or water vapor. The biomass pellets are heated to produce a mixture of hydrogen-rich gas, carbon monoxide, carbon dioxide, and low-carbon hydrocarbons, as well as liquids such as tar and solid particles such as semi-coke particles and ash particles. When the gasification gas is water vapor, the tar will also 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 the semi-coke particles and ash particles, enter the lower return feeder 3, gradually accumulating to form a material seal, preventing the gas in the gasification reactor 2 from entering the combustion reactor 4. Solid particles at the bottom of the material seal are transported to the combustion reactor by 600K fluidizing air (which can be nitrogen or steam) from the return feeder. Some of the semi-coke particles come into contact with the faster-flowing 600K combustion air in the combustion reactor 4, releasing a large amount of heat. This heat-cooled bed material particles, along with the flue gas from combustion, carry the bed material particles, incompletely burned semi-coke particles, and ash particles into the cyclone separator 5. Because the actual density of the bed material particles differs significantly from other particles, the bed material particles can be separated relatively thoroughly from the flue gas and other particles. The flue gas and other particles are discharged from the top of the cyclone separator 5, while the bed material particles are discharged from the bottom of the cyclone separator 5 and fall into the microwave-heated return feeder 1 through the hopper 10, gradually accumulating in the loosening chamber 11 to form a material seal. The loosening chamber of the microwave-heated return feeder has a large volume, so the particles move very slowly there. Except for the fluidized bottom, the rest of the bed material exists as a moving bed. The microwave generator power is set to 1×10⁻⁶. 5 W / m 3 Then, the bed material temperature is adjusted according to the thermocouple temperature. The bed material particles are heated by microwaves while moving slowly, reaching about 1200K. The 1200K bed material particles are transported by the fluidizing air (which can be nitrogen or water vapor) of the microwave-heated return feeder 1 from the return chamber 12 into the gasification reactor 2. Under the action of gravity, they fall into the dense phase zone of the fluidized bed, heating the biomass particles falling into the gasification reactor. In this way, the bed material completes the circulation in the dual fluidized bed reactor, without participating in any reaction, only serving as a heat carrier.

[0061] Example 5

[0062] This embodiment is another specific example of the reaction method in Example 3 (the bed material in this embodiment combines AER technology and uses calcium oxide bed material, which has a different effect than the inert bed material in Example 4): Reference Figure 2The ambient temperature biomass feedstock in hopper 21 is fed into the gasification reactor 2 of the dual fluidized bed reactor via screw feeder 22. The feedstock falls into the dense phase zone of the fluidized bed under gravity, mixing with calcium oxide bed material at 1200K. It is then bubbly fluidized at the bottom of the fluidized bed by 600K steam vaporization air. The biomass particles, when heated, 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 particles. Carbon dioxide combines with the calcium oxide bed material to form calcium carbonate bed material, releasing a certain amount of heat. This heat not only captures carbon dioxide from the gas but also replenishes the energy for the gasification reaction. Tar undergoes a reforming gasification reaction with steam, 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 particles and ash particles, enter the lower return feeder 3, gradually accumulating to form a material seal, preventing gas from the gasification reactor 2 from entering the combustion reactor 4. The solid particles at the bottom of the material seal are transported to the combustion reactor 4 by the 600K fluidizing air (which can be nitrogen or steam) from the lower return feeder 3. Some of the semi-coke particles come into contact with the faster-flowing 600K combustion air in the combustion reactor 4, burning and releasing a large amount of heat. This heats the cooled calcium carbonate bed particles, and some of the calcium carbonate bed is heated, removing carbon dioxide and regenerating calcium oxide bed particles, thus completing the task of "transporting" carbon dioxide from the product gas to the flue gas. The flue gas generated by combustion carries the bed particles, incompletely burned semi-coke particles, and ash particles into the cyclone separator 5. Because the actual density of calcium oxide and calcium carbonate bed materials differs significantly from that of other particles, the bed material particles can be separated relatively thoroughly from flue gas and other particles. Flue gas and other particles are discharged from the top of the cyclone separator 5, while the bed material particles are discharged from the bottom of the cyclone separator 5 and fall into the microwave-heated return feeder 1 via the material leg 10, gradually accumulating to form a material seal. The loosening chamber 11 of the microwave-heated return feeder 1 has a large volume, so the particles move very slowly there. Except for the bottom, where fluidization occurs, the rest of the bed material exists as a moving bed. The microwave generator power is set to 1×10⁻⁶. 5 W / m 3 Then, the bed material temperature is adjusted according to the thermocouple temperature. The bed material particles are heated by microwaves while moving slowly. The calcium carbonate bed material that is not converted in the combustion reactor 4 absorbs heat and removes carbon dioxide in the microwave-heated return feeder 1 to generate calcium oxide bed material. The calcium oxide bed material is heated to about 1200K. The bed material particles are transported by the fluidizing air (which can be nitrogen or water vapor) in the microwave-heated return feeder 1 and enter the gasification reactor 2. Under the action of gravity, they fall into the dense phase zone of the fluidized bed to heat the biomass particles falling into the gasification reactor 2 and capture carbon dioxide to complete carbonation. In this way, the bed material completes the circulation in the dual fluidized bed reactor, serving as a carrier of heat and carbon dioxide.

[0063] 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 microwave-heated return feeder, characterized in that, Located between the combustion reactor and the gasification reactor of a dual fluidized bed reactor used in the biomass hydrogen production process, and situated at the top return feed location, it includes: The return chamber is connected to the gasification reactor via a feed pipe; The loosening chamber, which is connected to the cyclone separator at the rear end of the combustion reactor via a feed leg, is used to receive the bed material particles after combustion and separation; the middle and upper parts of the loosening chamber are separated from the return chamber by a partition, and the moving speed of the bed material particles in the loosening chamber is rapidly reduced compared to that in the feed leg; a microwave generator is provided at a corresponding position on the outer wall of the loosening chamber.

2. The microwave heating return device according to claim 1, characterized in that, The cross-sectional dimension of the loosening chamber is 2 to 4 times the cross-sectional dimension of the material leg; the cross-sectional dimension of the return chamber is 1 to 2 times the cross-sectional dimension of the material leg.

3. The microwave heating return device according to claim 2, characterized in that, The lower part of the loosening chamber is connected to the lower part of the return chamber. The bottom of the return device is provided with an air distribution chamber. The lower end of the air distribution chamber is connected to the fluidizing air inlet pipe, and the upper end is provided with an air cap. The fluidizing air blows the bed material particles that have been moved at low speed and microwave heated from the loosening chamber to the gasification reactor at high speed through the return chamber.

4. The microwave heating return device according to claim 1, characterized in that, The microwave generator is provided on the outer wall of the material leg.

5. The microwave heating return device according to claim 4, characterized in that, The microwave power of the microwave generator is adjusted in real time according to the preset temperature of the bed material particles. The power adjustment unit includes: Thermocouples are used to measure the temperature of the bed material particles in real time; The control unit receives the temperature data of the bed material particles and compares it with a preset temperature. By controlling the activation of the relay, it changes the working interval time of the magnetron to adjust the microwave power so that the temperature of the bed material particles is consistent with the preset temperature.

6. The microwave heating return device according to claim 1, characterized in that, The bed material particles are inert bed material or calcium oxide bed material.

7. A reaction apparatus using a microwave-heated return feeder as described in any one of claims 1 to 6, characterized in that, Also includes: The gasification reactor receives biomass feedstock and absorbs heat from the bed material particles of the microwave-heated return feeder. Under the action of bottom gasification air, a gasification reaction occurs to generate hydrogen-rich gas and semi-coke. A bottom feeder is connected to the lower part of the gasification reactor, in which the semi-coke and the cooled bed material particles form a material seal; The combustion reactor, which is connected to the lower return feeder, is used to receive the semi-coke and cooled bed material particles blown from the lower return feeder, and burns the semi-coke particles under the action of combustion air to raise the temperature of the bed material particles; the bed material particles separated by cyclone after combustion are sent to the microwave heating return feeder.

8. The reaction apparatus according to claim 7, characterized in that, The lower part of the gasification reactor is equipped with a hopper and a feeding screw for feeding the biomass raw materials into the gasification reactor.

9. A reaction method using the reaction apparatus as described in any one of claims 7 to 8, characterized in that, Includes the following steps: A. The gasification reactor receives biomass raw materials and absorbs heat from the bed material particles of the microwave-heated return feeder. Under the action of the bottom gasification air, a gasification reaction occurs to generate hydrogen-rich gas and semi-coke. B. The semi-coke and the cooled bed material particles form a material seal in the lower return feeder; C. Under the action of fluidizing air, the semi-coke and cooled bed material particles in the lower return feeder are blown to the combustion reactor, where the semi-coke particles are burned and the temperature of the bed material particles is increased under the action of combustion-supporting air; the bed material particles separated by cyclone after combustion are sent to the microwave heating return feeder. D. The moving speed of the separated bed material particles in the loosening chamber decreases rapidly compared to that in the feed leg. After being microwave-heated at the corresponding position in the loosening chamber, the bed material particles enter the gasification reactor to complete the cycle of biomass hydrogen production.

10. The reaction method according to claim 9, characterized in that, When the bed material particles are inert, they only serve as a heat carrier; when the bed material particles are calcium oxide, the carbon dioxide produced during the biomass hydrogen production process in the gasification reactor is captured by the calcium oxide bed material to generate calcium carbonate, which simultaneously supplies heat for the gasification reaction.

11. The reaction method according to claim 9, characterized in that, The gasification air in step A is nitrogen or water vapor; when the gasification air is water vapor, the tar produced by gasification is reformed.

12. The reaction method according to claim 9, characterized in that, The fluidizing air in step C is water vapor.

13. The reaction method according to claim 9, characterized in that, The microwave power of the microwave generator is adjusted in real time according to the preset temperature of the bed material particles, specifically including: The temperature of the bed material particles is measured in real time using thermocouples; The control unit receives the temperature data of the bed material particles and compares it with the preset temperature. By controlling the activation of the relay, the working interval time of the magnetron is changed to adjust the microwave power so that the temperature of the bed material particles is consistent with the preset temperature.

14. The reaction method according to claim 13, characterized in that, The preset temperature is 1200K; the power of the microwave generator is 500 to 2000W, and a 2450MHz microwave magnetron is used.

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