Biomass char powder preparation system and method for entrained flow gasification

Abstract

A biomass charcoal powder preparation system and method for entrained-flow gasification, the system comprises a low-temperature pyrolysis device connected with a drying device, which is used for low-temperature pyrolysis of biomass raw materials, and the temperature of the low-temperature pyrolysis is 220-300 DEG C; a heating furnace connected with the low-temperature pyrolysis device, comprising a furnace body and a combustion tube; the combustion tube is arranged on the furnace body, and the combustion tube is provided with an oil-gas inlet for introducing an oil-gas mixture from the low-temperature pyrolysis device and is used for igniting the oil-gas mixture; the furnace body is provided with a back gas inlet connected with the low-temperature pyrolysis device, a gas outlet and a flue gas distribution ring, the flue gas distribution ring is provided with a plurality of flue gas nozzles, the plurality of flue gas nozzles are arranged in a spiral shape on the flue gas distribution ring, and the combustion tube, the flue gas distribution ring and the gas outlet are sequentially arranged along the transmission path of the gas flow; the spiral-shaped plurality of flue gas distribution rings are used for forming a spiral gas flow collision flow field with the flue gas after combustion of the oil-gas. The system ensures a high carbon yield and effectively utilizes the pyrolysis oil-gas, and reduces the processing difficulty.

Description

Technical Field

[0001] This invention relates to the field of biomass pulverization technology, and in particular to a biomass char powder preparation system and method for fluidized bed gasification. Background Technology

[0002] Biomass, as an important renewable energy source, has attracted widespread attention for its efficient utilization. Using biomass as a raw material, it is converted into syngas through gasification technology, and then methanol can be produced through methanol synthesis. Biomass gasification, as the core technology for methanol production, can be divided into fixed-bed gasification, fluidized-bed gasification, and entrained-flow gasification. Entrained-flow gasification, due to its advantages such as large processing capacity, high efficiency, and good pressure matching, is particularly suitable for large-scale biomass gasification to methanol projects.

[0003] Pyrolysis of biomass in an oxygen-free or oxygen-deficient environment destroys the free cell structure of the biomass. At certain temperatures, this can significantly improve grindability, reduce oxygen content, and increase its calorific value, thereby improving its quality and making it suitable for fluidized bed gasification technology.

[0004] Biomass pyrolysis carbonization is mainly divided into a drying stage, a low-temperature pyrolysis stage (below 300℃), and / or a high-temperature pyrolysis stage (above 300℃).

[0005] Traditional biomass pyrolysis processes for activated carbon production primarily utilize the carbon element in biomass. Therefore, after drying, high-temperature pyrolysis (400-600℃) is chosen for processing. Tar and wood vinegar are condensed and used as byproducts. The pyrolysis gas produced has a high calorific value (>10MJ / Nm³). 3 After purification, the pyrolysis carbon is used as fuel gas as a heat source for the pyrolysis system. The pyrolysis carbon is discharged from the system after cooling and used as a raw material for the preparation of activated carbon.

[0006] Although the above processes are mature, the pyrolysis depth is too deep, and the pyrolysis char yield is extremely low, making them unsuitable for preparing char powder required for biomass fluidized bed gasification.

[0007] Studies have found that the solid products of low-temperature pyrolysis processes with pyrolysis temperatures of 220-300℃ are most suitable. After biomass feedstocks are reacted at this temperature, moisture is removed, oxygen content is reduced by about 60%, and calorific value is significantly increased, achieving the goals of dehydration, quality improvement, and enhanced grindability. Moreover, the yield of pyrolysis char can be increased to over 45%.

[0008] However, this process introduces new problems. Due to the significant reduction in reaction temperature, the composition of both the pyrolysis gas and pyrolysis oil undergoes substantial changes. The CO2 content in the gaseous components exceeds 60%, while the combustible components consist only of CO and trace amounts of H2, resulting in a decrease in calorific value to 4 MJ / Nm³. 3The following are extremely low calorific value fuels, which are not easy to burn stably. Among the liquid phase products, the yield is low and they are mainly composed of phenols, aldehydes, and organic acids with high oxygen content. These components are easily soluble in water. If high-value utilization is desired after condensation, a sophisticated separation process is required, which increases investment and consumption. However, if they are not utilized, an additional wastewater utilization process is required.

[0009] In other words, although the aforementioned low-temperature pyrolysis process has a high carbon yield, the associated pyrolysis oil and pyrolysis gas are difficult to utilize and are difficult to process. Summary of the Invention

[0010] To address the aforementioned problems, this invention provides a biomass char powder preparation system and method for fluidized bed gasification. This system and method can ensure a high char yield while effectively utilizing pyrolysis oil and gas, thus reducing processing difficulty.

[0011] This invention provides a biomass charcoal powder preparation system for fluidized bed gasification, comprising: The low-temperature pyrolysis unit performs low-temperature pyrolysis on biomass raw materials at a temperature of 220-300℃, generating pyrolytic char and an oil-gas mixture. A heating furnace, connected to a low-temperature pyrolysis device, and including a furnace body and a combustion tube; The combustion tube is installed on the furnace body, and the combustion tube is provided with an oil and gas inlet for introducing the oil and gas mixture from the low-temperature pyrolysis device, and for igniting the oil and gas mixture. The furnace body is provided with a return gas port, a gas outlet and a flue gas distribution ring connected to the low-temperature pyrolysis device. The flue gas distribution ring is provided with multiple flue gas nozzles, which are arranged in a spiral pattern on the flue gas distribution ring. Along the airflow transmission path, the combustion tube, the flue gas distribution ring and the gas outlet are arranged in sequence. Multiple spiral flue gas distribution rings are used to form a spiral airflow collision flow field with the flue gas after oil and gas combustion.

[0012] Furthermore, an oil and gas pressurizing fan is provided between the low-temperature pyrolysis device and the oil and gas inlet of the heating furnace.

[0013] Furthermore, a first pipeline and a second pipeline are connected in parallel between the gas outlet of the heating furnace and the low-temperature pyrolysis device. One end of the first pipeline and the second pipeline are both connected to the gas outlet, the other end of the first pipeline is connected to the low-temperature pyrolysis device, and the other end of the second pipeline is connected between the low-temperature pyrolysis device and the oil and gas pressurizing blower.

[0014] Furthermore, a third pipeline and a fourth pipeline are provided in parallel between the low-temperature pyrolysis device and the return gas port. One end of the third pipeline and the fourth pipeline are connected to the low-temperature pyrolysis device, and the other end is connected to the return gas port. A flow valve for regulating the flow rate of the circulating flue gas is provided on the third pipeline, and a waste heat boiler is provided on the fourth pipeline.

[0015] Furthermore, an ignition device, a first air inlet for charging combustion gas, and a second air inlet for charging oxygen are also formed on the combustion tube. The positions of the ignition device, the first air inlet, the second air inlet, and the oil-gas inlet are arranged so that the combustion gas mixes with oxygen and is ignited to heat excess oxygen, which then combines with the oil-gas mixture.

[0016] Furthermore, the combustion tube includes an inner sleeve and an outer sleeve, the inner sleeve being inserted inside the outer sleeve, the first air inlet and the second air inlet being disposed on the inner sleeve, and the oil-gas inlet being disposed on the outer sleeve. In the direction of conveying the oil-gas mixture, the position of the end opening of the inner sleeve is located between the oil-gas inlet and the end opening of the outer sleeve.

[0017] Furthermore, the plane containing the flue gas distribution ring is perpendicular to the axis of the furnace body, and the flue gas nozzle extends obliquely towards the end of the furnace body. The angle between the axis of the flue gas nozzle and the plane containing the flue gas distribution ring is 30-45°. Looking along a direction perpendicular to the plane containing the flue gas distribution ring, the angle between the radius of the flue gas distribution ring at the point where the flue gas nozzle connects to the flue gas distribution ring and the axis of the flue gas nozzle is 5-8°.

[0018] Furthermore, the pyrolysis carbon collection device includes a mill, a carbon powder cooler, a carbon powder collector, and an inert gas circulating fan. The mill is connected between the low-temperature pyrolysis device and the carbon powder cooler to receive the pyrolysis carbon transferred from the low-temperature pyrolysis device and grind the blocky pyrolysis carbon. The carbon powder cooler is disposed between the mill and the carbon powder collector, and the inert gas circulating fan is disposed between the carbon powder collector and the mill to form a circulating inert gas flow between the mill, the carbon powder cooler, and the carbon powder collector, and to drive the carbon powder flow.

[0019] Furthermore, the carbon powder cooler is a gas-solid heat exchange shell-and-tube heat exchanger.

[0020] This invention also provides a method for preparing biomass charcoal powder for fluidized bed gasification, comprising the following steps: Drying biomass raw materials; The dried biomass raw material is subjected to low-temperature pyrolysis to produce pyrolytic char and an oil-gas mixture. The temperature of the low-temperature pyrolysis is 220-300℃. The pyrolysis char is collected and the oil-gas mixture is processed. In the process of treating oil-gas mixtures, the oil-gas mixture is ignited to generate high-temperature flue gas, and the heat of the high-temperature flue gas is used to perform low-temperature pyrolysis on biomass feedstocks. The circulating flue gas formed after the auxiliary low-temperature pyrolysis is mixed with the high-temperature flue gas to regulate the temperature of the high-temperature flue gas used for the auxiliary low-temperature pyrolysis.

[0021] Furthermore, in the process of collecting pyrolytic carbon, the method includes: The pyrolytic carbon is ground to obtain powdered pyrolytic carbon powder. The pyrolytic carbon powder is driven by an inert gas and cooled accordingly. The cooled pyrolytic carbon powder is captured.

[0022] Furthermore, in processing the oil-gas mixture, the method includes: The combustion gases and excess oxygen are mixed, and the combustion gases are ignited to heat the oxygen. The heated oxygen is mixed with the oil-gas mixture to ignite the oil-gas mixture.

[0023] In summary, this invention, by employing a heating furnace and the circulating flow of flue gas between the furnace and the low-temperature pyrolysis unit, achieves stable combustion of the low-temperature pyrolysis oil while ensuring a high pyrolysis char yield and enabling system self-heating. Simultaneously, the sequential arrangement of air intakes within the heating furnace ensures efficient combustion of the oil-gas mixture, converting the pyrolysis-produced oil into H2O and CO2. The system also eliminates the generation of difficult-to-treat biomass tar products, solving the problems of difficult tar wastewater treatment and additional investment.

[0024] Furthermore, the system employs a process of pulverizing followed by cooling within the pyrolysis carbon recovery unit, and utilizes a gas-solid cooling method during cooling, which can significantly improve heat exchange efficiency and reduce system consumption and investment.

[0025] 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 in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 The diagram shown is a schematic diagram of a biomass char powder preparation system for fluidized bed gasification provided in an embodiment of the present invention.

[0028] Figure 2 As shown Figure 1 A schematic diagram of the structure of the intermediate heating furnace.

[0029] Figure 3 As shown Figure 2 A schematic diagram of the circulating flue gas distribution ring pipe viewed along the length of the heating furnace. Detailed Implementation

[0030] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. Based on the description of the present invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of the present invention.

[0031] In the description of this invention, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0032] The terms “upper,” “lower,” “left,” “right,” “front,” “back,” “top,” “bottom,” “inner,” and “outer,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship that the product of the invention is usually placed in during use. They are used only for the convenience of description and simplification, and do not indicate or imply that the system or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0033] The terms “first,” “second,” “third,” etc., are used merely to distinguish elements with similar attributes, not to indicate or imply relative importance or a specific order.

[0034] The terms “include,” “comprising,” or any other variation thereof are intended to cover non-exclusive inclusion, which includes not only the elements listed but also other elements not expressly listed.

[0035] To address the aforementioned problems, this invention provides a biomass char powder preparation system and method for fluidized bed gasification. This system and method can ensure a high char yield while effectively utilizing pyrolysis oil and gas, thus reducing processing difficulty.

[0036] like Figures 1 to 3 As shown, the biomass char powder preparation system for fluidized bed gasification provided in this embodiment of the invention includes a feed hopper 11, a drying device 21, a low-temperature pyrolysis device 31, a heating furnace 40, and a pyrolysis char collection device 50. The feed hopper 11 is connected to the drying device 21 to feed the biomass raw materials into the drying device 21. The drying device 21 is connected to the low-temperature pyrolysis device 31 to feed the dried biomass raw materials into the low-temperature pyrolysis device 31 after drying. The low-temperature pyrolysis device 31 performs low-temperature pyrolysis on the biomass raw materials to generate char and pyrolysis oil and gas. The low-temperature pyrolysis temperature can be set to 220-300℃. The heating furnace 40 includes a furnace body 41 (see...). Figure 2 ) and combustion tube 42 (see Figure 2 The combustion tube 42 is equipped with an oil-gas inlet C, which introduces the oil-gas mixture from the low-temperature pyrolysis device 31 and is used to ignite the oil-gas mixture. The furnace body 41 is also equipped with a return gas port D, an outlet gas port E, and a flue gas distribution ring 43, all connected to the low-temperature pyrolysis device 31. Understandably, the return gas port D refers to the gas flowing from the low-temperature pyrolysis device 31 into the combustion furnace, while the outlet gas port E refers to the gas flowing from the combustion furnace into the low-temperature pyrolysis device. The flue gas distribution ring 43 is connected to the return gas port D and is equipped with multiple flue gas nozzles 44 arranged in a spiral pattern to allow the circulating flue gas and the high-temperature flue gas from oil-gas combustion to form a spiral collision flow field and mix. Along the airflow path, the combustion tube 42, the flue gas distribution ring 43, and the outlet gas port E are arranged sequentially. That is, the flue gas flowing out of the combustion tube 42 first passes through the flue gas distribution ring 43 and then exits from the outlet gas port E. The low-temperature pyrolysis device 31 is connected to the pyrolysis char collection device 50. The pyrolysis char is transported to the pyrolysis char collection device 50, which collects the char powder.

[0037] In this embodiment, when preparing biomass charcoal powder, the biomass raw material can first be fed into the drying device 21 through the feed hopper 11 to remove moisture. The dehydrated biomass raw material is then fed into the low-temperature pyrolysis device 31 for low-temperature pyrolysis. Since the low-temperature pyrolysis temperature is 220-300℃, there will be a high pyrolysis charcoal yield. During the low-temperature pyrolysis process, an oil-gas mixture mainly composed of phenols, aldehydes, and organic acids with high oxygen content will be generated. The aforementioned oil-gas mixture will enter the combustion tube 42 through the oil-gas inlet C on the combustion tube 42 and be ignited to generate high-temperature flue gas. This high-temperature flue gas will return to the low-temperature pyrolysis device 31 through the outlet E. Since the temperature of this high-temperature flue gas is high, it can provide heat to the low-temperature pyrolysis device 31. After the flue gas passes through the low-temperature pyrolysis device 31, the temperature will decrease, and it will flow back to the heating furnace 40 through the flue gas distribution ring 43 connected to the return gas port D. Because the temperature of the recirculated flue gas is low, while the temperature of the newly generated high-temperature flue gas from the oil-gas mixture is high, the recirculated flue gas mixes with the newly generated high-temperature flue gas in the heating furnace 40 to regulate the temperature of the flue gas entering the low-temperature pyrolysis device 31, ensuring a stable temperature within the device. In this invention, multiple flue gas nozzles 44 are provided on the flue gas distribution ring 43, and these nozzles are spiral-shaped. The recirculated flue gas and the high-temperature flue gas from oil-gas combustion can form a spiral airflow collision field, accelerating airflow mixing and achieving a rapid, stable, and uniform temperature reduction. This ensures that the high-temperature flue gas can be used for the pyrolysis process within the low-temperature pyrolysis device 31. In other words, through the above system setup, a high carbon yield can be guaranteed while effectively utilizing the pyrolysis oil and gas, reducing processing difficulty. The pyrolysis carbon formed from the low-temperature pyrolysis device 31 can enter the pyrolysis carbon collection device 50 for carbon powder collection.

[0038] More specifically, in this embodiment, the biomass raw material can be agricultural and forestry solid waste, including but not limited to various straws, bamboo, garden pruning waste, and other biomass resources.

[0039] When the biomass material enters the feed hopper 11, it can be crushed first so that the maximum length of the biomass material is less than 5cm, so as to facilitate subsequent pyrolysis.

[0040] Furthermore, a star feeder 12 and a first screw feeder 13 are connected in sequence between the feed hopper 11 and the low-temperature pyrolysis device 31, so that the biomass raw materials in the feed hopper 11 can enter the drying device 21 more quickly.

[0041] The drying device 21 can be a drying rotary kiln.

[0042] A second screw feeder 14 is also provided between the drying device 21 and the low-temperature pyrolysis device 31 to facilitate the dried biomass raw materials to enter the low-temperature pyrolysis device 31 more quickly.

[0043] Furthermore, in order to make fuller use of the heat of the oil-gas mixture, a flue gas conveying pipe 311 is provided between the low-temperature pyrolysis device 31 and the drying device 21, so that part of the circulating flue gas from the low-temperature pyrolysis device 31 enters the heating furnace 40 to mix with the newly generated high-temperature flue gas, and the other part enters the drying device 21 to dry the biomass raw materials using the heat in the circulating flue gas.

[0044] In order to prevent the circulating flue gas from entering the drying device 21 and affecting the biomass raw materials, in this embodiment, a denitrification reactor 15 is also provided on the flue gas conveying pipe 311.

[0045] An oil and gas pressurizing fan 32 is also installed between the low-temperature pyrolysis device 31 and the oil and gas inlet C of the heating furnace 40 to pressurize the oil and gas mixture. After passing through the oil and gas pressurizing fan 32, the pressure of the oil and gas mixture pyrolyzed in the low-temperature pyrolysis device 31 can be increased to 15-20 kPa.

[0046] Furthermore, a first pipe 312 and a second pipe 313 are connected in parallel between the gas outlet E of the heating furnace 40 and the low-temperature pyrolysis device 31. One end of the first pipe 312 and the second pipe 313 are both connected to the gas outlet E, and the other end of the first pipe 312 is connected to the low-temperature pyrolysis device 31 to transfer high-temperature flue gas into the low-temperature pyrolysis device 31, providing a heat source for the low-temperature pyrolysis of biomass raw materials. The other end of the second pipe 313 is connected between the low-temperature pyrolysis device 31 and the oil-gas pressurizing blower 32, preferably at the outlet of the oil-gas mixture in the low-temperature pyrolysis device 31. By introducing high-temperature flue gas into the channel through which the oil-gas mixture flows, the condensation of the oil-gas mixture in the pipe between the low-temperature pyrolysis device 31 and the oil-gas inlet C of the heating furnace 40 can be prevented.

[0047] Furthermore, a flue gas circulation fan 33 is installed in the pipeline between the low-temperature pyrolysis device 31 and the return gas port D of the heating furnace 40. The flue gas circulation fan 33 allows for the regulation of the flow rate of the circulating flue gas entering the heating furnace 40, thereby facilitating the adjustment of the temperature of the circulating flue gas flowing out of the outlet E of the heating furnace 40.

[0048] To better adjust the temperature of the circulating flue gas flowing out of the outlet E of the heating furnace 40, a third pipe 314 and a fourth pipe 315 are connected in parallel between the low-temperature pyrolysis device 31 and the return gas outlet D, preferably the flue gas circulation fan 33. That is, one end of the third pipe 314 and the fourth pipe 315 are connected to the low-temperature pyrolysis device 31, and the other end is connected to the flue gas circulation fan 33. A flow valve 34 is formed on the third pipe 314 to regulate the flow rate of the circulating flue gas, and a waste heat boiler 35 is installed on the fourth pipe 315 to utilize or exchange the heat of the circulating flue gas. By adjusting the opening of the flow valve 34 on the third pipe 314 and the flow rate of the circulating flue gas introduced into the waste heat boiler 35, heat exchange of the circulating flue gas can be completed within the waste heat boiler 35, the temperature of the circulating flue gas can be adjusted, and subsequently the temperature of the circulating flue gas passing through the flue gas circulation fan 33 can be adjusted.

[0049] That is, part of the circulating flue gas flowing out of the low-temperature pyrolysis device 31 will flow into the drying device 21 to assist in the drying of biomass raw materials; the other part will flow into the heating furnace 40 after temperature adjustment through the third pipeline 314 and the fourth pipeline 315.

[0050] In this embodiment, the circulating flue gas exiting the low-temperature pyrolysis device 31 can reach 330-380℃, the drying temperature of the drying device 21 is below 150℃, the moisture content of the dried biomass raw material is controlled below 3%, and the temperature of the dried biomass raw material is 110-120℃. The outlet temperature of the drying device 21 reaches 100-140℃. Through the regulation of the circulating flue gas via the first pipeline 312 and the second pipeline 313, the temperature of the flue gas entering the heating furnace 40 is made 300-400℃.

[0051] Please continue to refer to Figures 1 to 3 In this embodiment, the combustion tube 42 is further provided with an ignition device (not shown), a first air inlet A for introducing combustion gas (such as natural gas), and a second air inlet B for introducing oxygen. Along the airflow path, the first air inlet A and the second air inlet B are positioned before the oil and gas inlet C, so that the combustion gas mixes with oxygen and is ignited to heat excess oxygen. The excess oxygen combines with the oil and gas mixture and ignites the oil and gas mixture.

[0052] When the oil-gas mixture enters the combustion tube 42, combustion gas is first injected through the first air inlet A, and excess oxygen is injected through the second air inlet B. The combustion gas and oxygen mix within the combustion tube 42, and the ignition device ignites the mixture. During combustion, some oxygen is consumed, generating significant heat that heats the remaining oxygen. The temperature of the heated oxygen is higher than the ignition point of the oil-gas mixture. When the oil-gas mixture fed from the low-temperature pyrolysis unit 31 encounters the heated oxygen, the mixture ignites, generating high-temperature flue gas.

[0053] The combustion tube 42 includes an inner sleeve 421 and an outer sleeve 422, with the inner sleeve 421 passing through the outer sleeve 422. A first air inlet A and a second air inlet B are located on the inner sleeve 421, and an oil / gas inlet C is located on the outer sleeve 422. In the direction of oil / gas mixture transport, the end opening of the inner sleeve 421 is positioned between the oil / gas inlet C and the end opening of the outer sleeve 422. That is, since the end of the inner sleeve 421 is located inside the outer sleeve 422, the oil / gas mixture will flow a certain distance between the inner and outer sleeves after entering the outer sleeve 422 before contacting the oxygen flowing out from the end opening of the inner sleeve 421.

[0054] The exhaust port E and the combustion pipe 42 are respectively located at both ends of the furnace body 41. At the end where the exhaust port E is located, the end of the furnace body 41 is tapered, that is, at this end of the furnace body 41, the diameter of the furnace body 41 gradually shortens from the end facing the combustion pipe 42 to the end away from the combustion pipe 42. Through the above arrangement, the mixing of the high-temperature flue gas generated in the combustion pipe 42 with the circulating flue gas flowing in from the return port D can be further accelerated.

[0055] Further, please refer to Figure 2 In this embodiment, the plane containing the flue gas distribution ring 43 is perpendicular to the axis of the furnace body 41. The flue gas nozzle 44 is inclined towards the end of the furnace body 41 (i.e., Figure 2 (The lower part of the middle) extends. The angle between the axis of the flue gas nozzle 44 and the plane of the flue gas distribution ring 43 (e.g., the angle between the axis of the flue gas nozzle 44 and the plane of the flue gas distribution ring 43) Figure 2 The α angle in the equation is 30-45°.

[0056] Please continue to refer to Figure 2 and Figure 3 Looking along a direction perpendicular to the plane containing the flue gas distribution ring 43, the angle between the radius of the flue gas distribution ring 43 (where the flue gas nozzle 44 connects to the flue gas distribution ring 43) and the axis of the flue gas nozzle 44 (i.e., ...) on the plane containing the flue gas distribution ring 43. Figure 3 The β angle in the figure is 5-8°.

[0057] Please continue to refer to Figure 1A sealed inert conveyor 36 is also provided between the low-temperature pyrolysis device 31 and the pyrolysis carbon collection device 50 to transport the pyrolysis carbon in the low-temperature pyrolysis device 31 to the pyrolysis carbon collection device 50. This sealed inert conveyor 36 is self-sealed and completes the transport under an inert gas atmosphere. This inert gas can be N2 or CO2, etc., to prevent the high-temperature pyrolysis carbon from burning.

[0058] The pyrolysis char collection device 50 includes a mill 51, a char powder cooler 52, a char powder collector 53, and an inert gas circulating fan 54. The mill 51 is connected between the low-temperature pyrolysis unit 31 and the char powder cooler 52 to receive the pyrolysis char transferred from the low-temperature pyrolysis unit 31, grind the lumpy pyrolysis char, and then transfer the ground pyrolysis char to the char powder cooler 52. The mill 51 grinds the lumpy pyrolysis char to a particle size <100μm. The ground pyrolysis char can be air-classified to send char powder of suitable particle size into the char powder cooler 52. The char powder collector 53 is connected to the char powder cooler 52 to collect the cooled char powder. The inert gas circulating fan 54 is connected between the char powder collector 53 and the mill 51 to form a circulating inert gas flow between the mill 51, the char powder cooler 52, and the char powder collector 53, promoting the flow of char powder.

[0059] Furthermore, in this embodiment, the carbon powder cooler 52 can be a gas-solid heat exchange shell-and-tube heat exchanger, where the circulating air containing carbon powder flows through the tube side, while the cooling medium, such as water, flows through the shell side. This arrangement minimizes carbon powder deposition and, moreover, the pyrolytic carbon, encased in the inert airflow, is in a turbulent state, further breaking down the laminar thermal resistance between the gas and the heat exchange tubes inside the carbon powder cooler 52, thus improving heat exchange efficiency. In this embodiment, the carbon powder cooler 52 can lower the temperature of the carbon powder to below 40°C before it enters the carbon powder trap.

[0060] The carbon powder collector 53 can be a bag filter to capture the pyrolysis carbon powder and use it as a feedstock for the subsequent gasification stage.

[0061] Understandably, all parts of the pyrolysis char collection device 50 operate in an inert gas atmosphere to prevent the pyrolysis char from burning.

[0062] Please continue to refer to Figure 1 The system also includes an exhaust gas treatment device 60, which is connected to the drying device 21 to receive the exhaust gas flowing out of the drying device 21. The exhaust gas treatment device 60 includes a cyclone separator 61, a water-washing dust collector 62, a wet electrostatic precipitator 63, and an exhaust fan 64. The cyclone separator 61, the water-washing dust collector 62, the wet electrostatic precipitator 63, and the exhaust fan 64 are arranged sequentially.

[0063] Cyclone separator 61 can separate solids and liquids in the discharged waste gas; water washing dust removal tower 62 and wet electrostatic precipitator 63 can recover solid particles and dust. Vent fan 64 can discharge the treated waste gas.

[0064] The exhaust gas treatment device 60 can treat the exhaust gas flowing out of the dryer. In this embodiment, the exhaust gas flowing out of the dryer may include the exhaust gas generated during the drying of biomass raw materials, as well as the flue gas flowing from the low-temperature pyrolysis device 31 into the dryer.

[0065] In this embodiment, by setting up a heating furnace 40 and circulating flue gas between the heating furnace 40 and the low-temperature pyrolysis device 31, stable combustion of the low-temperature pyrolysis oil can be achieved, ensuring a high pyrolysis char yield and enabling the system to self-heat. Simultaneously, the sequential arrangement of the air intakes within the heating furnace 40 enables efficient combustion of the oil-gas mixture, allowing the oil produced by pyrolysis to be converted into H2O and CO2. The system no longer produces difficult-to-treat biomass tar products, solving the problems of difficult tar wastewater treatment and additional investment.

[0066] Furthermore, the system employs a process of pulverizing followed by cooling within the pyrolysis carbon recovery unit, and utilizes a gas-solid cooling method during cooling, which can significantly improve heat exchange efficiency and reduce system consumption and investment.

[0067] The present invention also provides a method for preparing biomass char powder for fluidized bed gasification, the method comprising the following steps: S1: Drying the biomass raw materials.

[0068] In this embodiment, biomass raw materials refer to agricultural and forestry solid waste, including but not limited to various straws, bamboo, and garden pruning waste. Before drying, the biomass raw materials can be crushed into particles with a maximum size of less than 5 cm. After drying, the moisture content of the biomass raw materials is controlled below 3%, and the material temperature after drying is 110-120℃.

[0069] S2: The dried biomass feedstock is subjected to low-temperature pyrolysis to produce pyrolytic char and an oil-gas mixture. The temperature of this low-temperature pyrolysis is 220-300℃. After this step, the pyrolytic char is processed according to step S3, and the oil-gas mixture is processed according to step S4.

[0070] In this embodiment, the biomass feedstock will undergo a pyrolysis reaction in the low-temperature pyrolysis device 31, producing pyrolysis char (50-55%, dry basis), pyrolysis oil (15-20%, dry basis), pyrolysis water (20-25%, dry basis), and pyrolysis gas (5-17%). Understandably, the pyrolysis oil and pyrolysis gas exiting the low-temperature pyrolysis device 31 will be at approximately 200-220°C; therefore, the pyrolysis oil and pyrolysis gas will exit the low-temperature pyrolysis device 31 in the form of an oil-gas mixture.

[0071] S3: Recover pyrolytic carbon.

[0072] In this embodiment, the following steps may be included in the pyrolysis carbon recovery process: S31: Grind the pyrolytic char to make it into pyrolytic char powder.

[0073] In this embodiment, the particle size of the ground pyrolytic carbon powder can be less than 100 μm.

[0074] S32: The pyrolytic carbon powder is driven to flow by inert gas and cooled.

[0075] In this embodiment, a gas-heat exchange method can be used to cool the pyrolytic carbon powder. The flow of inert gas not only drives the flow of the pyrolytic carbon powder but also filters its particle size.

[0076] After cooling, the temperature of the pyrolytic carbon powder is below 40°C.

[0077] S33: Capture the cooled charcoal powder.

[0078] It should be noted that during the entire pyrolytic carbon recovery process, inert gas can be used to circulate the airflow, thereby driving the movement of the pyrolytic carbon powder.

[0079] S4: Ignite the fuel gas mixture to generate high-temperature flue gas, and use the heat of the high-temperature flue gas to perform low-temperature pyrolysis on the biomass feedstock; form a spiral collision flow field, mix the circulating flue gas formed after the auxiliary low-temperature pyrolysis with the high-temperature flue gas in the spiral collision flow field, so as to regulate the temperature of the high-temperature flue gas used for the auxiliary low-temperature pyrolysis.

[0080] More specifically, the method includes the following steps when performing step S4: S41: Mix the combustion gases with excess oxygen and ignite the combustion gases to heat the oxygen.

[0081] In this embodiment, the combustion gas can be gaseous diesel, liquefied petroleum gas (LPG), or natural gas. The excess oxygen refers to the presence of a large amount of oxygen in the mixture of combustion gas and oxygen even after combustion; the purpose of combustion is to heat the oxygen. The flow rate of the combustion gas can be 3%-5% of the oxygen flow rate. The temperature of the heated oxygen is 400-430°C.

[0082] S42: Mix heated oxygen with the oil-gas mixture to ignite the oil-gas mixture.

[0083] In this embodiment, since the temperature of oxygen after heating is 400-430°C, the oil-gas mixture can be ignited even if its temperature is relatively low. After combustion, the temperature of the flue gas produced reaches 1000-1300°C.

[0084] In this embodiment, the method further includes using the heat of the high-temperature flue gas to heat the oil-gas mixture to prevent condensation.

[0085] Furthermore, the method also includes using the heat from the circulating flue gas after auxiliary low-temperature pyrolysis to dry the biomass feedstock.

[0086] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A biomass charcoal powder preparation system for fluidized bed gasification, characterized in that: include: The low-temperature pyrolysis unit performs low-temperature pyrolysis on biomass raw materials at a temperature of 220-300℃, generating pyrolytic char and an oil-gas mixture. A heating furnace, connected to a low-temperature pyrolysis device, and including a furnace body and a combustion tube; The combustion tube is installed on the furnace body, and the combustion tube is provided with an oil and gas inlet for introducing the oil and gas mixture from the low-temperature pyrolysis device, and for igniting the oil and gas mixture. The furnace body is provided with a return gas port, a gas outlet and a flue gas distribution ring connected to the low-temperature pyrolysis device. The flue gas distribution ring is provided with multiple flue gas nozzles, which are arranged in a spiral pattern on the flue gas distribution ring. Along the airflow transmission path, the combustion tube, the flue gas distribution ring and the gas outlet are arranged in sequence. The spiral-shaped multiple flue gas distribution rings are used to form a spiral airflow collision flow field with the flue gas after oil and gas combustion.

2. The biomass charcoal powder preparation system for fluidized bed gasification according to claim 1, characterized in that: An oil and gas pressurizing fan is installed between the low-temperature pyrolysis device and the oil and gas inlet of the heating furnace.

3. The biomass charcoal powder preparation system for fluidized bed gasification according to claim 2, characterized in that: A first pipeline and a second pipeline are connected in parallel between the gas outlet of the heating furnace and the low-temperature pyrolysis device. One end of the first pipeline and the second pipeline are connected to the gas outlet, the other end of the first pipeline is connected to the low-temperature pyrolysis device, and the other end of the second pipeline is connected between the low-temperature pyrolysis device and the oil and gas pressurizing blower.

4. The biomass charcoal powder preparation system for fluidized bed gasification according to claim 1, characterized in that: A third pipeline and a fourth pipeline are connected in parallel between the low-temperature pyrolysis device and the return gas port. One end of the third pipeline and the fourth pipeline are connected to the low-temperature pyrolysis device, and the other end is connected to the return gas port. A flow valve for regulating the flow rate of the circulating flue gas is installed on the third pipeline, and a waste heat boiler is installed on the fourth pipeline.

5. The biomass charcoal powder preparation system for fluidized bed gasification according to claim 1, characterized in that: An ignition device, a first air inlet for introducing combustion gas, and a second air inlet for introducing oxygen are also formed on the combustion tube. The positions of the ignition device, the first air inlet, the second air inlet, and the oil-gas inlet are arranged so that the combustion gas mixes with oxygen and is ignited to heat excess oxygen, which then combines with the oil-gas mixture.

6. The biomass charcoal powder preparation system for fluidized bed gasification according to claim 5, characterized in that: The combustion tube includes an inner sleeve and an outer sleeve. The inner sleeve passes through the outer sleeve. The first air inlet and the second air inlet are disposed on the inner sleeve. The oil and gas inlet is disposed on the outer sleeve. In the direction of conveying the oil and gas mixture, the end opening of the inner sleeve is located between the oil and gas inlet and the end opening of the outer sleeve.

7. The biomass charcoal powder preparation system for fluidized bed gasification according to claim 1, characterized in that: The plane containing the flue gas distribution ring is perpendicular to the axis of the furnace body. The flue gas nozzle extends at an angle towards the end of the furnace body. The angle between the axis of the flue gas nozzle and the plane containing the flue gas distribution ring is 30-45°. Looking along a direction perpendicular to the plane containing the flue gas distribution ring, the angle between the radius of the flue gas distribution ring at the point where the flue gas nozzle connects to the flue gas distribution ring and the axis of the flue gas nozzle is 5-8°.

8. The biomass charcoal powder preparation system for fluidized bed gasification according to claim 1, characterized in that: The biomass charcoal preparation system for fluidized bed gasification includes a pyrolysis charcoal collection device, which comprises a mill, a charcoal cooler, a charcoal collector, and an inert gas circulating fan. The mill is connected between the low-temperature pyrolysis device and the charcoal cooler to receive the pyrolysis charcoal transferred from the low-temperature pyrolysis device and to grind the lumpy pyrolysis charcoal. The charcoal cooler is located between the mill and the charcoal collector, and the inert gas circulating fan is located between the charcoal collector and the mill to form a circulating inert gas flow between the mill, the charcoal cooler, and the charcoal collector, and to drive the charcoal flow.

9. The biomass charcoal powder preparation system for fluidized bed gasification according to claim 8, characterized in that: The carbon powder cooler is a gas-solid heat exchange shell-and-tube heat exchanger.

10. A method for preparing biomass charcoal powder for fluidized bed gasification, characterized in that: Includes the following steps: Drying biomass raw materials; The dried biomass raw material is subjected to low-temperature pyrolysis to produce pyrolytic char and an oil-gas mixture. The temperature of the low-temperature pyrolysis is 220-300℃. The pyrolysis char is collected and the oil-gas mixture is processed. During the processing of oil-gas mixtures, the oil-gas mixture is ignited to generate high-temperature flue gas, and the heat of the high-temperature flue gas is used to perform low-temperature pyrolysis on the biomass feedstock; a spiral airflow collision flow field is formed, and the circulating flue gas formed after the auxiliary low-temperature pyrolysis is mixed with the high-temperature flue gas in the spiral airflow collision flow field to regulate the temperature of the high-temperature flue gas used for the auxiliary low-temperature pyrolysis.

11. The method for preparing biomass charcoal powder for fluidized bed gasification according to claim 10, characterized in that: The method for collecting pyrolytic carbon includes: The pyrolytic carbon is ground to obtain powdered pyrolytic carbon powder. The pyrolytic carbon powder is driven by an inert gas and cooled accordingly. The cooled pyrolytic carbon powder is captured.

12. The method for preparing biomass charcoal powder for fluidized bed gasification according to claim 10, characterized in that: When processing an oil-gas mixture, the method includes: The combustion gases and excess oxygen are mixed, and the combustion gases are ignited to heat the oxygen. The heated oxygen is mixed with the oil-gas mixture to ignite the oil-gas mixture.

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