A large-particle biomass microwave gasification system and prepared biochar and its application

Abstract

The present invention belongs to the technical field of renewable energy utilization, and discloses a large-particle biomass microwave gasification system and the prepared biochar and its application. The microwave gasification system includes a microwave gasification device, an oxygen supply device, a nitrogen supply device, a water vapor supply device, a biochar collection device, a tar collection device, a synthesis gas purifier and a synthesis gas collection device. The microwave gasification system of the present invention can effectively achieve the preparation of large-particle biochar. The present invention aims to make full use of the natural properties of biomass raw materials and the high efficiency of microwave heating by combining microwave gasification technology, X-ray computed tomography technology and software reconstruction methods, so as to conduct in-depth research on the pore structure and mineral properties of large-particle biochar, and provide support for optimizing the application of large-particle biochar.

Description

Technical Field

[0001] The present invention relates to the technical field of renewable energy utilization, and in particular to a large-particle biomass microwave gasification system, prepared biochar and its application. Background Art

[0002] Biochar, an emerging carbon material, is widely used in soil improvement, water treatment, and environmental remediation due to its excellent adsorption properties and environmentally friendly properties. Biochar is typically produced by pyrolysis, drying, and gasification of biomass at high temperatures between 600°C and 900°C.

[0003] Traditionally, biomass gasification feedstock is in powder form and requires a finely crushed process, which increases energy consumption and directly raises production costs. However, unlike pulverized coal, biomass materials cannot be economically processed into fine particles, especially fibrous biomass. Consequently, the particle size of biomass feedstock typically used for commercial purposes is relatively large. Large-particle biomass is generally readily available and can be directly sourced from agricultural and forestry waste, reducing the demand for small-particle feedstock and thus improving overall biomass utilization. In some regions, large-particle biomass is relatively easy to collect and transport, reducing costs and resource waste. The gasification process of large-particle biomass can be improved by optimizing reaction conditions such as temperature and pressure, typically resulting in higher gasification yields and gas quality. Larger particles enable optimal airflow and heat exchange during the gasification process, making the pyrolysis and gasification of the biomass more efficient. Therefore, directly using large-particle biomass for gasification can save energy and produce higher-quality biochar and syngas.

[0004] Currently, biochar is primarily produced through electrical heating, which primarily transfers energy through conduction and convection to heat the material. However, this method inevitably creates temperature gradients, leading to external overheating and internal underheating. Because large biomass particles present significant resistance to heat and mass transfer during gasification, conventional electrical heating methods are unable to effectively heat and gasify the interior of such particles. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a large-particle biomass microwave gasification system and the prepared biochar and its application. Microwave heating is essentially a medium heating, which directly provides energy to the sample through ion conduction and dipole rotation, and completes the contactless conversion of electromagnetic energy to thermal energy in the process. Biomass microwave gasification technology uses microwave radiation heating to convert biomass materials into gas fuel with synthesis gas as the main component. Microwave radiation directly acts on the biomass material in the form of electromagnetic waves, causing the internal water and organic molecules to vibrate, thereby rapidly heating up. The conventional use of microwave systems to prepare biochar is a pyrolysis method. The pore structure of the prepared biochar is not well developed, the tar yield is high, and the purity of the synthesis gas is low, which restricts its application efficiency. Traditional microwave fixed-bed gasification is designed for micron-sized biomass particles and has high energy consumption.

[0006] When the present invention performs microwave gasification on biomass raw materials, the particle size of the biomass raw materials can be relaxed to the centimeter level, and there is no need to crush the biomass raw materials into small particles of millimeter level or even micron level, which reduces the energy consumption and cost of crushing. Water vapor is combined with oxygen for microwave gasification. Microwave heating directly penetrates the large-particle biomass through the internal electromagnetic field, causing the internal temperature to rise rapidly, avoiding the heat transfer loss of traditional external heating methods, and the overall thermal efficiency is higher. In addition, oxygen-water vapor as a gasifying agent can promote the redox reaction of carbon, increase the yield of H2 and CO in the synthesis gas, generate more synthesis gas, and combined with the oxygen-water vapor gasification environment, high-temperature microwave pyrolysis can effectively crack tar, and after further removing the tar, the synthesis gas is purer. Microwave gasified biochar is a gasification by-product, which has a developed pore structure, a large specific surface area, and rich surface functional groups, and resource utilization will be solved.

[0007] The large-particle biomass microwave gasification system of the present invention is realized by the following technical solutions:

[0008] The microwave gasification device is used to perform microwave gasification treatment on large-particle biomass raw materials to form large-particle biomass charcoal; the particle size of the large-particle biomass raw materials is centimeter-level, for example, the particle size range of the large-particle biomass raw materials is 1 cm~9.9 cm.

[0009] The oxygen supply device has an output end connected to the input end of the microwave gasification device to provide the required oxygen for the microwave gasification process of the microwave gasification device.

[0010] The nitrogen supply device has an output end connected to the input end of the microwave vaporization device, and provides the required nitrogen protective gas for the microwave vaporization process of the microwave vaporization device.

[0011] The water vapor supply device has an output end connected to the input end of the microwave gasification device, and provides gas power for transporting large-particle biomass raw materials to the reaction area of ​​the microwave gasification device.

[0012] The biomass char collection device has an input end connected to the solid output end of the microwave gasification device and is used to collect large-particle biomass char formed by microwave gasification treatment.

[0013] The tar collecting device has an input end connected to the gas output end of the microwave gasification device, and is used to receive the gas generated by the microwave gasification treatment and pre-treat it to remove the tar therein.

[0014] The synthesis gas purifier, whose input end is connected to the gas output end of the tar collection device, is used to remove impurities and moisture in the gas to form pure synthesis gas.

[0015] The input end of the synthesis gas collecting device is connected to the gas output end of the synthesis gas purifier to collect pure synthesis gas for combustion.

[0016] In some preferred embodiments of the present invention, the microwave vaporization device comprises:

[0017] Microwave gasification furnace.

[0018] The microwave generator is arranged in the microwave gasification furnace and is used to provide microwave action.

[0019] The temperature and power controller is electrically connected to the microwave generator and is used to control the reaction temperature and power of the microwaves provided by the microwave generator.

[0020] The quartz tube is horizontally arranged in the microwave gasification furnace to provide a reaction space for microwave gasification treatment.

[0021] The quartz hanging basket is placed in the quartz tube and is used to place large-particle biomass raw materials.

[0022] A microwave thermocouple is horizontally arranged in the quartz tube and is used for real-time monitoring of the microwave gasification reaction temperature in the microwave gasification furnace.

[0023] In some preferred embodiments of the present invention, a first pressure reducing valve is provided between the output end of the oxygen supply device and the input end of the microwave vaporization device, and the first pressure reducing valve is used to reduce the oxygen pressure.

[0024] A second pressure reducing valve is provided between the nitrogen supply device and the input end of the microwave vaporization device, and the second pressure reducing valve is used to reduce the nitrogen pressure.

[0025] A first mass flow meter is provided between the output end of the oxygen supply device and the input end of the first pressure reducing valve, and the first mass flow meter is used to monitor the oxygen flow rate.

[0026] A second mass flow meter is provided between the output end of the nitrogen supply device and the input end of the second pressure reducing valve, and the second mass flow meter is used to monitor the nitrogen flow rate.

[0027] In some preferred embodiments of the present invention, the water vapor supply device includes a water supply device and a heating tape.

[0028] The output end of the water supply device is connected to the input end of the microwave vaporization device through a delivery pipe to provide water.

[0029] The heating tape is wound around the delivery pipe to heat the water in the delivery pipe, generating steam that acts as a gas force and enters the microwave vaporization device. More preferably, the heating tape can be set to a temperature of 140°C to 160°C to ensure that the water in the delivery pipe is heated to generate steam.

[0030] In some preferred embodiments of the present invention, the tar collection device is a scrubber filled with isopropyl alcohol to remove tar from the reaction gas. More preferably, the tar collection device comprises six scrubbers filled with isopropyl alcohol, the scrubbers being located in an ice-water bath to collect the tar generated by gasification.

[0031] In some preferred embodiments of the present invention, the synthesis gas purifier is a synthesis gas purifier filled with dry silica gel particles.

[0032] The second object of the present invention is to provide a biomass charcoal prepared by microwave gasification treatment using the above-mentioned large-particle biomass microwave gasification system.

[0033] A third object of the present invention is to provide a use of biochar in the preparation of soil improvement materials, pollutant adsorption materials, catalytic cracking tar materials, or environmental remediation materials, wherein the porosity of the large-particle biochar is first obtained; the porosity is matched to the specific application of the large-particle biochar, and the porosity is obtained by the following method:

[0034] X-ray computed tomography technology was used to obtain the microstructure images of the above-mentioned large-particle biochar, forming grayscale images at different angles.

[0035] Avizo software was used to preprocess grayscale images at different angles to improve image clarity and recognizability, and multiple preprocessed images were obtained.

[0036] Avizo software is used to perform recognition and threshold segmentation on multiple pre-processed images to obtain multiple threshold segmented images.

[0037] The three-dimensional reconstructed biochar is obtained by combining multiple threshold segmented images.

[0038] The porosity of the three-dimensional reconstructed biochar was analyzed to obtain the porosity of the large-particle biochar.

[0039] In some preferred embodiments of the present invention, the preprocessing methods include image screening, image type conversion, volume editing, image denoising and contrast enhancement.

[0040] The identification method is: process according to the following steps: distinguish the pore area and the mineral area by brightness, the area between the pore area and the mineral area is the matrix area, and the pore area of ​​large-particle biochar, the matrix area of ​​large-particle biochar and the mineral area of ​​large-particle biochar are obtained.

[0041] In some preferred embodiments of the present invention, the threshold segmentation method is:

[0042] The pore area of ​​the large-particle biochar is threshold segmented according to a first threshold interval to obtain the pore area of ​​the biochar slice; the first threshold interval is 0~2500.

[0043] The mineral region of the large-particle biochar is segmented according to the second threshold interval to obtain the mineral region of the biochar slice; the second threshold interval is 10,000-30,000.

[0044] The matrix region of the large-particle biochar is segmented according to the third threshold value to obtain the matrix region of the biochar slice; the third threshold value range is 2501~9999.

[0045] The present invention aims to directly utilize large-particle biomass for microwave gasification, and then use Avizo to perform three-dimensional reconstruction of large-particle biochar. This fully utilizes the natural properties of biomass raw materials and the high efficiency of microwave heating to study their pore structure and mineral properties. It has many advantages, such as reducing application costs, improving efficiency, and improving the stability of the gasification process.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] The large-particle biomass microwave gasification system of the present invention includes a microwave gasification device, an oxygen supply device, a nitrogen supply device, a steam supply device, a biochar collection device, a tar collection device, a syngas purifier, and a syngas collection device. The large-particle biomass microwave gasification system of the present invention can directly and efficiently heat large-particle biomass to produce high-quality syngas, low-yield tar, and large-particle biochar with a rich pore structure.

[0048] The present invention proposes a large-particle biomass microwave gasification system and a three-dimensional reconstruction method for biochar. The method combines microwave gasification technology, X-ray computed tomography technology and software reconstruction method, aiming to make full use of the natural properties of biomass raw materials and the high efficiency of microwave heating to obtain large-particle biochar. The large-particle biochar is reconstructed using a three-dimensional method to deeply study the pore structure and mineral properties of the large-particle biochar, providing support for optimizing the application of large-particle biochar.

[0049] The present invention provides a large-particle biomass microwave gasification system and a biochar three-dimensional reconstruction method, comprising a large-particle biomass microwave gasification system, computed tomography technology for identifying large-particle biochar, and an Avizo software reconstruction method for large-particle biochar. The large-particle biomass microwave gasification system is connected to the computed tomography technology for identifying large-particle biochar; the computed tomography technology for identifying large-particle biochar is also connected to the Avizo software reconstruction method for large-particle biochar. By accurately identifying and analyzing the pore structure of large-particle biochar, this provides important basic data for optimizing the preparation and application of biochar, and can improve its effectiveness in environmental governance and wastewater treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a schematic structural diagram of the large-particle biomass microwave gasification system of the present invention.

[0051] Figure 2 Schematic diagram of X-ray computed tomography equipment and detection.

[0052] Figure 3 3D reconstruction image and grayscale slice image of the first biochar, where (a) is the 3D reconstruction image of the first biochar, (b) is the 2D grayscale slice image of the first biochar in the xy direction, and (c) is the 2D grayscale slice image of the first biochar in the xz direction.

[0053] Figure 4 These are the three-dimensional reconstruction image and grayscale slice image of the second biochar, where (a) is the three-dimensional reconstruction image of the first biochar, (b) is the two-dimensional grayscale slice image of the first biochar in the xy direction, and (c) is the two-dimensional grayscale slice image of the first biochar in the xz direction.

[0054] Figure 5 These are the three-dimensional reconstruction image and grayscale slice image of the third biochar, where (a) is the three-dimensional reconstruction image of the first biochar, (b) is the two-dimensional grayscale slice image of the first biochar in the xy direction, and (c) is the two-dimensional grayscale slice image of the first biochar in the xz direction.

[0055] Figure 6 This is the surface porosity diagram of three types of large-particle biochar.

[0056] Figure numerals: 1-oxygen supply device, 2-nitrogen supply device, 3-first pressure reducing valve, 4-second pressure reducing valve, 5-first mass flow meter, 6-second mass flow meter, 7-first triangular valve, 8-injection pump, 9-second triangular valve, 10-heating tape, 11-microwave thermocouple, 12-microwave generator, 13-temperature power controller, 14-quartz tube, 15-quartz hanging basket, 16-large particle size biomass raw material, 17-biomass charcoal collection box, 18-large particle size biomass charcoal, 19-tar collection device, 20-isopropanol, 21-synthesis gas purifier, 22-synthesis gas storage bag, 23-X-ray emitter, 24-sample rotation rack, 25-X-ray detector, 26-computer. DETAILED DESCRIPTION

[0057] The technical solutions in the embodiments of the present invention will be described clearly and completely below.

[0058] As described in the background technology, biochar is currently mainly prepared by electric heating pyrolysis method. The biomass gasification raw materials traditionally used are powdered. Microwave gasification technology for large-particle biomass raw materials has many advantages such as reducing costs, improving efficiency, and improving the stability of the gasification process. It can produce large-particle biochar with developed pore structure and high-quality synthesis gas. Traditional analytical methods are unable to fully and accurately describe the microstructure of biochar. In view of this situation, the present invention proposes an innovative technology that combines microwave gasification of large-particle biomass, identification of large-particle biochar by computed tomography technology, and reconstruction by Avizo software, aiming to achieve three-dimensional visualization of the pore structure and minerals of biochar, and provide theoretical support for optimizing the application of biochar.

[0059] Example 1

[0060] This embodiment provides a large-particle biomass microwave gasification system. Figure 1 The large-particle biomass microwave gasification system of this embodiment includes a microwave gasification device, an oxygen supply device 1, a nitrogen supply device 2, a water vapor supply device, a biomass char collection device, a tar collection device 19, a synthesis gas purifier 21 and a synthesis gas collection device.

[0061] The microwave gasification device is used to perform microwave gasification treatment on large-particle biomass raw materials 16 to form large-particle biomass charcoal 18; the microwave gasification device is a microwave gasification furnace, and a microwave generator 12 is provided in the microwave gasification furnace to provide microwave action. The microwave generator 12 is electrically connected to a temperature power controller 13, and the microwave generator 12 is arranged around a quartz tube 14; a quartz tube 14 is horizontally arranged in the microwave gasification furnace to provide a reaction space for microwave gasification treatment; the large-particle biomass raw materials 16 are placed in a quartz hanging basket 15; and then placed in the quartz tube 14.

[0062] The microwave thermocouple 11 , whose detection end is located on the surface of the biomass, is horizontally arranged in the quartz tube 14 .

[0063] When the large-particle biomass raw material 16 is subjected to microwave gasification, the large-particle biomass raw material 16 is first placed in the quartz hanging basket 15 and then placed in the quartz tube 14. The temperature power controller 13 controls the microwave generator 12 to provide the reaction temperature and power required for microwave gasification during the experiment. During the heating period, the microwave gasification reaction temperature in the microwave gasification furnace is monitored in real time by the microwave thermocouple 11. The large-particle biomass raw material 16 is subjected to microwave gasification treatment. During the microwave gasification treatment process, oxygen is only supplied during the microwave gasification reaction, and nitrogen is supplied throughout the process.

[0064] When oxygen is supplied, it enters the microwave vaporization device through the output end of the oxygen supply device 1, providing the required oxygen for the microwave gasification process. Furthermore, a first pressure reducing valve 3 and a first mass flow meter 5 are provided between the output end of the oxygen supply device 1 and the input end of the microwave gasification device. According to experimental requirements, the first pressure reducing valve 3 is used to reduce the pressure of the oxygen entering the first mass flow meter 5. The oxygen flow rate is monitored by the first mass flow meter 5, thereby controlling the oxygen flow rate entering the microwave gasification furnace.

[0065] During nitrogen supply, nitrogen enters the microwave vaporizer through the output end of the nitrogen supply device 2, providing the nitrogen shielding gas required for microwave vaporization. A second pressure-reducing valve 4 and a second mass flowmeter 6 are provided between the nitrogen supply device 2 and the input end of the microwave vaporizer. Based on experimental requirements, the second pressure-reducing valve 4 is used to reduce the pressure of nitrogen entering the second mass flowmeter 6. The second mass flowmeter 6 monitors the nitrogen flow rate, thereby controlling the nitrogen flow rate entering the microwave vaporizer.

[0066] Nitrogen and oxygen merge into a mixed gas path through the first triangular valve 7, and then the mixed gas path is connected to the water vapor supply device, and water is transported to the microwave vaporization device through the delivery pipe. Specifically, the water vapor supply device includes a water supply device and a heating tape 10. The water supply device used in this embodiment is an injection pump 8. The mixed gas path merges with the water flowing out of the injection pump 8 through the second triangular valve 9. The second triangular valve 9 is connected to the delivery pipe. The delivery pipe is wrapped with the heating tape 10. When the microwave vaporization furnace reaches the reaction temperature, the heating tape 10 heating pipeline is turned on. The temperature of the heating tape 10 is set to 150°C, which is used to heat the water in the delivery pipe to form water vapor as aerodynamic force to enter the microwave vaporization device.

[0067] When the microwave gasification furnace reaches the preset reaction temperature, the steam supply device and the oxygen supply device 1 are turned on, and the large-particle biomass raw material 16 is pushed into the reaction zone of the microwave gasification furnace for microwave reaction. The microwave generator 12 is used to heat the large-particle biomass raw material 16, and a rapid gasification reaction is performed to obtain a mixed gas and large-particle biomass charcoal.

[0068] The microwave gasifier is connected to the biochar collection box and the inlet of the tar collection device 19 . The tar collection device 19 is connected to the inlet of the synthesis gas purifier 21 . The synthesis gas purifier 21 is connected to the inlet of the synthesis gas storage bag 22 .

[0069] The large-particle biochar generated by microwave gasification treatment enters the biochar collection device through the solid output end of the microwave gasification device and the input end of the biochar collection device in sequence. The biochar collection device used in the present invention is a biochar collection box 17.

[0070] The mixed gas generated by microwave gasification is sequentially connected through the gas output of the microwave gasification device and the input of the tar collection device 19 and enters the tar collection device 19. Within the tar collection device 19, the mixed gas is cooled with an ice-water mixture and pre-treated by adsorbing liquid tar with isopropyl alcohol 20 to remove tar from the gas, thereby obtaining a first gas. The obtained first gas then passes through the gas output of the tar collection device 19 and the input of the synthesis gas purifier 21 and enters the synthesis gas purifier 21. In the synthesis gas purifier 21, a gas washing bottle filled with silica gel particles is used for adsorption and drying to remove impurities and moisture from the gas, thereby obtaining a pure synthesis gas. The pure synthesis gas then passes through the gas output of the synthesis gas purifier 21 and the input of the synthesis gas collection device and enters the synthesis gas collection device to be collected for subsequent combustion. The synthesis gas collection device used in the present invention is a synthesis gas storage bag 22.

[0071] Through the effective operation of the above system, large-particle biochar 18 with a large specific surface area and good pore structure can be generated, providing a good sample for subsequent image processing.

[0072] Example 2

[0073] This embodiment provides a method for three-dimensional reconstruction of biochar, comprising the following steps:

[0074] Step 1: Use the microwave gasification system of Example 1 to perform microwave gasification treatment on the large-particle biomass raw material 16 to obtain large-particle biomass char 18.

[0075] Step 2: Using X-ray computed tomography technology, obtain the internal structure image of the large-particle biochar 18 to form several grayscale images at different angles, as follows:

[0076] X-ray computed tomography was used to perform high-resolution imaging of large-particle biochar 18 to obtain its microstructural image. Figure 2 As shown, computed tomography (CT) utilizes the principle of X-ray penetration. Large-particle biochar 18 is placed on a sample rotating rack 24. An X-ray emitter 23 and an X-ray detector 25 rotate and scan the large-particle biochar 18. The sample is scanned from multiple angles, and the X-ray detector 25 collects electrical signals. Computer 26 converts these signals into image data at multiple angles. The resulting image data is presented as a grayscale image, with grayscale values ​​related to the material's density, laying the foundation for subsequent image processing.

[0077] Step 3: Use Avizo software to preprocess the grayscale image to obtain a preprocessed image. The preprocessing steps are as follows:

[0078] The acquired computed tomography images need to go through the preprocessing steps of image screening, image type conversion, volume editing, image denoising, and contrast enhancement to improve the clarity and recognizability of the image. Image denoising includes Gaussian filtering and image sharpening.

[0079] Image screening was performed according to the following steps: After importing computed tomography images from different angles into Avizo 2023, batch screening was first performed based on a signal-to-noise ratio of <5, a dynamic range of >2000, and an annular / strip-shaped abnormality covering >5% of the area in artifact detection. The screened images were marked as low-quality images; the remaining images were marked as valid images after the initial screening.

[0080] Subsequently, the pore structure continuity and edge distortion of the low-quality images were manually reviewed, and invalid data images with non-connected pores and abnormal pore size were eliminated to obtain the valid images after the second screening. The valid images after the initial screening and the valid images after the second screening are collectively referred to as qualified images. It should be noted that pore structure continuity refers to the absence of axial faults and edge distortion refers to curvature > 0.5, non-connected pores refer to connectivity of 0, and pore size abnormalities refer to noise < 2 μm or fractures > 1 mm.

[0081] Qualified images are stored according to resolution and completeness. The resolution is divided into 2μm and 5μm, and the completeness is divided into complete and partial.

[0082] During the screening process, the screening parameters and abnormal causes are recorded synchronously to ensure the reliability of 3D reconstruction and porosity analysis.

[0083] The qualified images obtained through the image screening step are converted into 16-bit explicit images through image type conversion. The images are then sheared to remove the air portion scanned by the computed tomography device, retaining only the desired biochar region, resulting in a sheared image. The sheared image is then volume-edited to obtain cylindrical large-particle biochar 18. Image denoising and contrast enhancement are then performed to improve image clarity and recognizability, resulting in multiple preprocessed images. These preprocessing steps ensure the accuracy of subsequent threshold segmentation, facilitating the precise identification of the pores, matrix, and minerals of the biochar.

[0084] Step 4: Use Avizo software to perform recognition and threshold segmentation on the multiple pre-processed images to obtain multiple threshold segmented images, and combine the multiple threshold segmented images to obtain a three-dimensional reconstructed biochar.

[0085] Recognition and threshold segmentation are processed in the following steps:

[0086] In the first step, the area with lower brightness value of the biochar slice is determined to be the pore area of ​​the large-particle biochar, the first threshold interval is selected, and then threshold segmentation is performed to obtain the pore area of ​​the biochar slice; the first threshold interval is 0~2500.

[0087] In the second step, the area with higher brightness of the biochar slice is determined to be the mineral area of ​​large-particle biochar, and the second threshold interval is selected, and then threshold segmentation is performed to obtain the mineral area of ​​the biochar slice; the second threshold interval is 10,000~30,000.

[0088] In the third step, the area between the pores and the minerals is the matrix area of ​​the large-particle biochar. The third threshold interval is selected, and then threshold segmentation is performed to obtain the matrix area of ​​the biochar slice. The third threshold interval is 2501~9999.

[0089] The combination steps are: combining the pore area of ​​the biochar slice, the mineral area of ​​the biochar slice and the matrix area of ​​the biochar slice in multiple threshold segmented images through the regional summation mathematical operation algorithm in the Avizo2023 software to obtain a three-dimensional reconstructed biochar.

[0090] After three-dimensional reconstruction, the obtained three-dimensional reconstructed biochar was subjected to the layer analysis algorithm in the Avizo2023 software to calculate the proportion of pores in each plane layer, and the surface porosity results were obtained. Based on the surface porosity results, the porosity of the prepared large-particle biochar 18 was analyzed.

[0091] Example 3

[0092] Large-particle biomass charcoal 18 was prepared using the large-particle biomass microwave gasification system of Example 1. The specific preparation steps are as follows:

[0093] The large-particle biomass used in this embodiment is large-particle paulownia biomass with a diameter of 2 cm. During the experiment, it is necessary to avoid the knots of the paulownia.

[0094] Before the gasification experiment, a certain amount of large-particle Paulownia biomass was weighed and placed in the quartz hanging basket 15. Then, they were placed on the left side of the quartz tube 14. After checking the airtightness of the device, the gas supply valve of the nitrogen supply device 2 was opened and the second mass flow meter 6 was used to measure the gas at 100 mL min. -1 The impurity gas is discharged at a flow rate of 100 mL / min for 30 minutes. The microwave generator 12 and the temperature power controller 13 are configured. The vaporization temperature is set to the predetermined temperature of 800°C and the power is set to 600 W on the temperature power controller 13 of the microwave vaporization furnace. After reaching the predetermined temperature, the first mass flow meter 5 is used to flow at 100 mL / min. -1 The flow rate of oxygen supply device 1 is controlled. Then the quartz hanging basket 15 is pushed into the center of the quartz tube 14. The gasification reaction lasts for 25 minutes. After the reaction is completed, the quartz hanging basket 15 is pulled to the left side of the quartz tube 14. Turn off the temperature power controller 13 and the supply of oxygen supply device 1. When the quartz tube is cooled to room temperature, a large-particle size biochar 18 sample is obtained, which is recorded as the first biochar. The obtained first biochar is pushed into the biochar collection box 17 and collected for the subsequent biochar three-dimensional reconstruction step.

[0095] Example 4

[0096] Large-particle biomass charcoal 18 was prepared using the large-particle biomass microwave gasification system of Example 1. The specific preparation steps are as follows:

[0097] The large-particle biomass used in this example is large-particle oak biomass with a diameter of 2 cm. During the experiment, it is necessary to avoid the knots of the oak.

[0098] Before the gasification experiment, a certain amount of large-particle oak biomass was weighed and placed in the quartz hanging basket 15. Then, they were placed on the left side of the quartz tube 14. After checking the airtightness of the device, the gas supply valve of the nitrogen supply device 2 was opened and the second mass flow meter 6 was used to measure the gas at 100 mL min. -1 The impurity gas is discharged at a flow rate of 100 mL / min for 30 minutes. The microwave generator 12 and the temperature power controller 13 are configured. The vaporization temperature is set to the predetermined temperature of 800°C and the power is set to 600 W on the temperature power controller 13 of the microwave vaporization furnace. After reaching the predetermined temperature, the first mass flow meter 5 is used to flow at 100 mL / min. -1The flow rate of oxygen supply device 1 is controlled. Then the quartz hanging basket 15 is pushed into the center of the quartz tube 14. The gasification reaction lasts for 25 minutes. After the reaction is completed, the quartz hanging basket 15 is pulled to the left side of the quartz tube 14. Turn off the temperature power controller 13 and the supply of oxygen supply device 1. When the quartz tube is cooled to room temperature, a large-particle size biochar 18 sample is obtained, which is recorded as the second biochar. The obtained second biochar is pushed into the biochar collection box 17 and collected for the subsequent biochar three-dimensional reconstruction step.

[0099] Example 5

[0100] Large-particle biomass charcoal 18 was prepared using the large-particle biomass microwave gasification system of Example 1. The specific preparation steps are as follows:

[0101] The large-particle biomass used in this embodiment is large-particle pine biomass with a diameter of 2 cm. During the experiment, it is necessary to avoid the knot positions of the pine wood.

[0102] Before the gasification experiment, a certain amount of large-particle pine biomass was weighed and placed in the quartz hanging basket 15. Then, they were placed on the left side of the quartz tube 14. After checking the airtightness of the device, the gas supply valve of the nitrogen supply device 2 was opened and the second mass flow meter 6 was used to measure the gas at 100 mL min. -1 The impurity gas is discharged at a flow rate of 100 mL / min for 30 minutes. The microwave generator 12 and the temperature power controller 13 are configured. The vaporization temperature is set to the predetermined temperature of 800°C and the power is set to 600 W on the temperature power controller 13 of the microwave vaporization furnace. After reaching the predetermined temperature, the first mass flow meter 5 is used to flow at 100 mL / min. -1 The flow rate of oxygen supply device 1 is controlled. Then the quartz hanging basket 15 is pushed into the center of the quartz tube 14. The gasification reaction lasts for 25 minutes. After the reaction is completed, the quartz hanging basket 15 is pulled to the left side of the quartz tube 14. Turn off the temperature power controller 13 and the supply of oxygen supply device 1. When the quartz tube is cooled to room temperature, a large-particle size biochar 18 sample is obtained, which is recorded as the third biochar. The obtained third biochar is pushed into the biochar collection box 17 and collected for the subsequent biochar three-dimensional reconstruction step.

[0103] The large-particle biochar prepared in Examples 3 to 5 was subjected to the three-dimensional reconstruction of the biochar according to the method of Example 2. Figures 3 to 5 As shown in the figure, the three-dimensional reconstruction and grayscale slice of three different large-particle biochars are shown. The mineral area is red, the pore area is blue, and the matrix area is yellow. Then, the porosity analysis of the biochar is carried out. The layer analysis algorithm in the Avizo2023 software is used to calculate the proportion of pores in each layer plane, and the porosity results of each layer are obtained, as shown in the figure. Figure 6As shown in Figure 3, the third biochar has the highest porosity, while the second biochar has the lowest. This third biochar could be used for further research in soil improvement, pollutant adsorption, catalytic tar cracking, and environmental remediation, with potential applications in industrial production.

[0104] In summary, the present invention combines biomass microwave gasification, computed tomography (CT) technology, and image processing methods to form an innovative biochar research method. The present method for producing biochar can be applied to a variety of fields, including environmental governance, wastewater treatment, and soil improvement. The present invention uses CT and image processing techniques to accurately identify and analyze the pore structure and mineral distribution of biochar. This invention can promote the advancement of biochar research and provide new ideas for subsequent technological development.

[0105] Obviously, the above embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

Claims

1. A large-particle biomass microwave gasification system, characterized in that: include: A microwave gasification device is used for performing microwave gasification treatment on large-particle biomass raw materials (16) to form large-particle biomass charcoal (18); the particle size of the large-particle biomass raw materials (16) is in the centimeter order; an oxygen supply device (1), the output end of which is connected to the input end of the microwave vaporization device, and provides the oxygen required for the microwave vaporization process of the microwave vaporization device; a nitrogen supply device (2), the output end of which is connected to the input end of the microwave vaporization device, and provides the required nitrogen protective gas for the microwave vaporization process of the microwave vaporization device; A water vapor supply device, the output end of which is connected to the input end of the microwave gasification device, provides aerodynamic force for transporting the large-particle biomass raw material (16) to the reaction area of ​​the microwave gasification device; the water vapor supply device includes a water supply device and a heating belt (10); the output end of the water supply device is connected to the input end of the microwave gasification device through a delivery pipe to provide water; the heating belt (10) is wound around the delivery pipe to heat the water in the delivery pipe, so that the water forms water vapor as aerodynamic force and enters the microwave gasification device; a biochar collecting device, the input end of which is connected to the solid output end of the microwave gasification device, and is used to collect large-particle biochar formed by microwave gasification treatment; a tar collecting device (19), the input end of which is in communication with the gas output end of the microwave gasification device, for receiving the gas generated by the microwave gasification process and pre-treating the gas to remove the tar therein; a synthesis gas purifier (21), the input end of which is connected to the gas output end of the tar collection device (19), for removing impurities and moisture from the gas to form pure synthesis gas; a synthesis gas collecting device, the input end of which is connected to the gas output end of the synthesis gas purifier (21) to collect pure synthesis gas for combustion; The microwave gasification device comprises: microwave gasification furnace; A microwave generator (12) is provided in the microwave gasification furnace and is used to provide microwave action; a temperature power controller (13), electrically connected to the microwave generator (12), and used to control the reaction temperature and power of the microwaves provided by the microwave generator (12); A quartz tube (14) is horizontally arranged in the microwave gasification furnace to provide a reaction space for microwave gasification treatment; A quartz hanging basket (15) is placed in the quartz tube (14) and is used to place large-particle biomass raw materials (16); A microwave thermocouple (11) is horizontally arranged in the quartz tube (14) and is used for real-time monitoring of the microwave gasification reaction temperature in the microwave gasification furnace.

2. The large-particle biomass microwave gasification system according to claim 1, characterized in that: A first pressure reducing valve (3) is provided between the output end of the oxygen supply device (1) and the input end of the microwave vaporization device, and the first pressure reducing valve (3) is used to reduce the oxygen pressure; A second pressure reducing valve (4) is provided between the nitrogen supply device (2) and the input end of the microwave vaporization device, and the second pressure reducing valve (4) is used to reduce the nitrogen pressure; A first mass flow meter (5) is provided between the output end of the oxygen supply device (1) and the input end of the first pressure reducing valve (3), and the first mass flow meter (5) is used to monitor the oxygen flow rate; A second mass flow meter (6) is provided between the output end of the nitrogen supply device (2) and the input end of the second pressure reducing valve (4), and the second mass flow meter (6) is used to monitor the nitrogen flow rate.

3. The large-particle biomass microwave gasification system according to claim 1, characterized in that: The tar collecting device (19) is a gas washing device containing isopropyl alcohol (20) to remove tar from the reaction gas.

4. The large-particle biomass microwave gasification system according to claim 1, characterized in that: The synthesis gas purifier (21) is a synthesis gas purifier filled with dry silica gel particles.

5. A biochar, characterized in that: The biomass is prepared by microwave gasification treatment using the large-particle biomass microwave gasification system according to any one of claims 1 to 4.

6. A use of biochar in the preparation of soil improvement materials, pollutant adsorption materials, catalytic cracking tar materials or environmental remediation materials, characterized in that: First, the porosity of the large-particle biochar is obtained; the porosity is matched to the specific application of the large-particle biochar, and the porosity is obtained by the following method: Using X-ray computed tomography technology, obtaining a microstructure image of the biochar according to claim 5 to form grayscale images at different angles; Avizo software was used to preprocess grayscale images at different angles to improve image clarity and recognizability, and multiple preprocessed images were obtained; Use Avizo software to perform recognition and threshold segmentation on multiple pre-processed images to obtain multiple threshold segmented images; Combining multiple threshold segmented images to obtain three-dimensional reconstructed biochar; The porosity of the three-dimensional reconstructed biochar was analyzed to obtain the porosity of the large-particle biochar.

7. The use of biochar as claimed in claim 6 in preparing soil improvement materials, pollutant adsorption materials, catalytic cracking tar materials or environmental remediation materials, characterized in that: Preprocessing includes image screening, image type conversion, volume editing, image denoising, and contrast enhancement; The identification method is: process according to the following steps: distinguish the pore area and the mineral area by brightness, the area between the pore area and the mineral area is the matrix area, and the pore area of ​​large-particle biochar, the matrix area of ​​large-particle biochar and the mineral area of ​​large-particle biochar are obtained.

8. The use of biochar as claimed in claim 6 in preparing soil improvement materials, pollutant adsorption materials, catalytic cracking tar materials or environmental remediation materials, characterized in that: The threshold segmentation method is: The pore area of ​​the large-size biochar is segmented according to the first threshold interval to obtain the pore area of ​​the biochar slice; the first threshold interval is 0~2500; Performing threshold segmentation on the mineral region of the large-particle biochar according to the second threshold interval to obtain the mineral region of the biochar slice; The second threshold range is 10000~30000; Performing threshold segmentation on the matrix region of the large-particle biochar according to the third threshold value to obtain the matrix region of the biochar slice; The third threshold range is 2501~9999.

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