Device and method for degrading biomass tar by microwave-induced stainless steel cone discharge

Abstract

The invention relates to the technical field of biomass energy utilization, in particular to a device and a method for degrading biomass tar by microwave-induced stainless steel cone discharge. The device comprises a protective gas bottle, a quartz reactor, a microwave generator, a temperature sensor, a gas collecting device, a stainless steel cone, a quartz sand layer and a silicon carbide layer. Biomass tar, quartz sand and the like are put into a reactor, and after argon is introduced, a stainless steel cone is radiated by a microwave generator, so that the tip of the stainless steel cone discharges to degrade tar. Stainless steel cone arrays with different numbers and different tip angles are constructed, high-energy plasma is formed by induced discharge under the microwave power of 320-640 W, and the discharge environment is stabilized in cooperation with quartz sand and silicon carbide. The biomass tar can be efficiently degraded, the proportion of H2 and CO in a gas product is increased, and an effective way is provided for clean utilization of biomass energy.

Description

Technical Field

[0001] This invention relates to the field of biomass energy utilization technology, specifically to a device and method for microwave-induced stainless steel cone discharge to degrade biomass tar. Background Technology

[0002] With the continuous growth of global energy demand and the increasing prominence of environmental problems, biomass energy has attracted attention due to its renewable and clean nature. However, the biomass tar (containing polycyclic aromatic hydrocarbons, phenols, aliphatic hydrocarbons, etc.) produced during its gasification process reduces the utilization efficiency of biomass energy, causing system blockage, corrosion, and environmental pollution. Therefore, the efficient degradation of biomass tar is of great significance.

[0003] Currently, biomass tar treatment methods include physical, chemical, and plasma methods. Physical methods only change the phase state of the tar, cannot utilize its energy, and also reduce gasification efficiency and introduce post-processing problems. Chemical methods can completely remove tar, but the high-temperature pyrolysis operation is difficult to achieve, and the catalytic cracking catalyst is prone to deactivation and has poor stability. Although plasma methods are more effective, they face challenges related to equipment lifespan, cost, energy consumption, and scale-up.

[0004] Microwave-induced metal discharge (MIC) technology, as an emerging plasma technology, has made significant progress in recent years. It excites metal electrodes to discharge via microwave radiation, forming high-energy electrons and plasma, effectively degrading complex organic compounds in biomass tar and converting them into high-value-added small-molecule gases (such as H2 and CO). However, this technology still faces challenges, such as insufficient controllability of the discharge process, poor durability of electrode materials, and the need to improve energy utilization efficiency. Furthermore, its large-scale application is also difficult, hindering its widespread application in fields such as biomass energy utilization. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides an apparatus and method for degrading biomass tar using microwave-induced discharge through a stainless steel cone. The apparatus includes a protective gas cylinder, a quartz reactor, a microwave generator, a temperature sensor, a gas collection device, a stainless steel cone, a quartz sand layer, and a silicon carbide layer. This invention utilizes microwave-induced discharge through the stainless steel cone to create a high-energy plasma environment rich in high-energy electrons and active free radicals, which can effectively degrade biomass tar.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: The purpose of this invention is to provide a device for microwave-induced discharge of a stainless steel cone to degrade biomass tar, comprising: A quartz reactor is used to provide a closed space for the degradation of biomass tar. The quartz reactor includes a reaction bottle, an outlet pipe, and an inlet pipe. The inlet pipe is used to introduce protective gas into the reaction bottle, and the outlet pipe is used to detect the degree of degradation of biomass tar.

[0007] Along the height of the reaction flask, from bottom to top, there are a silicon carbide layer, a quartz sand layer, and at least one stainless steel cone. The reaction flask is equipped with a porous partition plate, which is located above the connection between the reaction flask and the gas inlet pipe. The quartz sand layer and the stainless steel cone are located above the porous partition plate, and the silicon carbide layer is located on the inner bottom wall of the reaction flask.

[0008] The outer wall of the quartz reactor is equipped with a microwave generator, which emits microwaves to cause the tip of the stainless steel cone to discharge through microwave radiation, thereby degrading biomass tar.

[0009] In a preferred embodiment of the present invention, the tip angle of the stainless steel cone is 15°~60° or spherical.

[0010] In a preferred embodiment of the present invention, the number of stainless steel cones is 1 to 6, and the arrangement is a vertical linear shape, a vertical circular shape, a planar linear shape, or a planar circular shape.

[0011] In a preferred embodiment of the present invention, the thickness of the quartz sand layer is 15mm~17mm, and the thickness of the silicon carbide layer is 14mm~16mm.

[0012] In a preferred embodiment of the present invention, the inlet of the air inlet pipe is connected to a protective gas cylinder, the outlet of the air outlet is connected to an exhaust device, and a temperature sensor is provided inside the reaction flask, with one end of the temperature sensor extending into the air outlet pipe and the extended end located inside the reaction flask.

[0013] Another object of the present invention is to provide a method for degrading biomass tar using microwave-induced stainless steel cone discharge with the above-described apparatus, comprising the following steps: S1. Silicon carbide is placed on the inner bottom wall of the reaction flask to form a silicon carbide layer, and quartz sand is placed on the porous partition plate of the reaction flask to form a quartz sand layer. Then, a stainless steel cone is inserted into the quartz sand layer; biomass tar is placed on the stainless steel cone.

[0014] S2. Place the reaction bottle in the microwave generator, and input protective gas into the reaction bottle through the gas inlet pipe to fill the reaction bottle with protective gas. Turn on the microwave generator to irradiate the stainless steel cone in the quartz reactor, so that the tip of the stainless steel cone generates a discharge reaction to degrade biomass tar. Detect the degree of biomass tar degradation reaction through the gas outlet pipe.

[0015] In a preferred embodiment of the present invention, the discharge reaction time is 40 minutes.

[0016] In a preferred embodiment of the present invention, the microwave power of the microwave generator is 320W~640W.

[0017] In a preferred embodiment of the present invention, the protective gas is argon, and the argon gas introduction rate is 290 mL / s to 310 mL / s.

[0018] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention addresses the technical bottleneck of tar degradation during biomass gasification by proposing the aforementioned synergistic catalytic degradation device based on microwave-induced metal discharge. In this device, the microwave generator induces discharge through a stainless steel cone, creating a high-energy plasma environment rich in high-energy electrons and active free radicals, which effectively degrades biomass tar. The quartz sand layer provides a stable and suitable environment for metal discharge, promoting discharge uniformity, optimizing microwave field distribution, and acting as a temperature buffer. The silicon carbide layer absorbs microwave energy, converting it into heat, stabilizing the reaction environment, promoting plasma generation and interaction, and optimizing the electric field distribution. This invention uses a stainless steel cone as the main material. As an excellent conductor, it effectively concentrates the electric field and generates plasma. The chromium oxide (Cr2O3) passivation film on its surface prevents further oxidation and corrosion at the high temperatures generated during discharge and is non-magnetic, solving the problem of poor electrode material durability. Furthermore, by altering the discharge intensity through microwave-induced discharge through the stainless steel cone, the device effectively degrades tar compounds, achieving control over the discharge process and improving energy utilization efficiency.

[0019] 2. The stainless steel cones used in this invention, with tip angles ranging from 15° to 60° and spherical metal materials, can effectively degrade tar compounds by changing the discharge intensity, thereby achieving controllability of the discharge process. Furthermore, this invention, by changing the number and arrangement of different cones, found that the degradation efficiency of tar compounds is highest when the cone angle is 30°, the number is 4, and the arrangement is a planar circle, achieving efficient energy utilization.

[0020] 3. In this invention, the multi-cone array (1 to 6 cones) improves degradation efficiency by expanding the discharge coverage area. When the four cones are arranged in a circular plane, the toluene gas production rate can reach 99.95%. The circular arrangement has a more uniform electric field distribution than the linear arrangement, avoiding "reaction dead zones" and increasing the probability of tar molecules colliding with active species by more than 40%.

[0021] 4. The method provided by this invention, with a power of 480W and a 30° cone, achieves a toluene gas yield of 89.50%, and the combined proportion of H2 and CO in the degradation products exceeds 80%, significantly improving the calorific value of the gaseous fuel. This method overcomes the limitations of traditional physical methods (phase transfer), chemical methods (catalyst deactivation bottleneck), and plasma methods (high equipment cost). It achieves tar degradation without the need for additional catalysts. The main body of the equipment is made of quartz and stainless steel, providing a catalyst-free, highly stable, and clean technological path for biomass gasification tar treatment. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the device for microwave-induced discharge of a stainless steel cone to degrade biomass tar according to the present invention. Explanation of the diagram: 1. Protective gas cylinder; 2. Quartz reactor; 21. Reaction bottle; 22. Gas outlet pipe; 23. Gas inlet pipe; 3. Microwave generator; 4. Temperature sensor; 5. Gas collection device; 6. Toluene; 7. Stainless steel cone; 8. Quartz sand layer; 9. Silicon carbide layer.

[0023] Figure 2 This is a graph showing the toluene degradation yield under different cone tip angles and microwave powers according to the present invention. Figure 2 Figure (a) shows the liquid yield of toluene degradation under different cone tip angles and microwave powers, and Figure (b) shows the gaseous yield of toluene degradation under different cone tip angles and microwave powers.

[0024] Figure 3 This diagram shows the gaseous products of toluene degradation under different cone tip angles and microwave powers according to the present invention. Figure 3 Figure (a) shows the proportion of H2 in the gaseous products, Figure (b) shows the proportion of CO in the gaseous products, Figure (c) shows the proportion of CO2 in the gaseous products, and Figure (d) shows the proportion of CH4 in the gaseous products.

[0025] Figure 4 The total ion chromatograms of the liquid products of Example 12 and Comparative Example 3 of the present invention are shown. Figure 4 Figure (a) shows the total ion chromatogram of the liquid product in Comparative Example 3, and Figure (b) shows the total ion chromatogram of the liquid product in Example 12.

[0026] Figure 5 The graph shows the yield of toluene degradation by microwave-induced discharge of different numbers of stainless steel cones according to the present invention. Figure 5 Figure (a) shows the liquid yield of toluene degradation by discharge with different numbers of stainless steel cones, and Figure (b) shows the gaseous yield of toluene degradation by discharge with different numbers of stainless steel cones.

[0027] Figure 6 This diagram illustrates the component composition of toluene gas products generated by microwave-induced discharge of different numbers of stainless steel cones according to the present invention.

[0028] Figure 7 This is a graph showing the toluene yield of stainless steel cones with different arrangements induced by microwave discharge according to the present invention. Figure 7 Figure (a) shows the liquid yield of toluene by discharge degradation of stainless steel cones with different arrangements, and Figure (b) shows the gas yield of toluene by discharge degradation of stainless steel cones with different arrangements.

[0029] Figure 8This diagram shows the component proportions of toluene gas products generated by microwave-induced discharge degradation of stainless steel cones with different arrangements according to the present invention. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0032] This invention provides a device for microwave-induced discharge of a stainless steel cone to degrade biomass tar, such as... Figure 1 As shown, a quartz reactor 2 provides a sealed space for the degradation of biomass tar. The quartz reactor 2 includes a reaction bottle 21, an outlet pipe 22, and an inlet pipe 23. The inlet pipe 23 is used to introduce protective gas into the reaction bottle 21, and the outlet pipe 22 is used to detect the degree of biomass tar degradation. Along the height of the reaction bottle 21, from bottom to top, there are sequentially arranged a silicon carbide layer 9, a quartz sand layer 8, and at least one stainless steel cone 7. A porous partition plate is provided inside the reaction bottle 21, located above the connection between the reaction bottle 21 and the inlet pipe 23. The quartz sand layer 8 and the stainless steel cone 7 are located above the porous partition plate, and the silicon carbide layer 9 is located on the inner bottom wall of the reaction bottle 21. A microwave generator 3 is provided on the outer wall of the quartz reactor 2. The microwave generator 3 is used to emit microwaves, which cause the tip of the stainless steel cone 7 to discharge, thus degrading the biomass tar.

[0033] It should be noted that the microwave-induced discharge of the stainless steel cone in this invention requires an air medium, namely argon gas. The discharge mechanism is as follows: in the microwave field, a localized strong electric field is formed at the tip of the stainless steel cone. Electrons inside the cone "escape" from the surface. The microwave electric field is alternating, and the free electrons gain kinetic energy. These high-energy electrons collide violently with surrounding argon gas molecules, forming new electrons and positive ions. These new electrons and ions then gain high kinetic energy again and collide, resulting in an even higher density of electrons and ions, forming plasma. At this point, a corona discharge or bright sparks can be observed at the tip of the cone.

[0034] In the quartz reactor 2, both the outlet pipe 22 and the inlet pipe 23 are connected to the reaction bottle 21. The connection is made with a double-beveled frosted surface to ensure the airtightness of the internal space of the reactor during the reaction. The reaction bottle 21 is divided into upper and lower parts, which are separated by a thin quartz plate. The center of the plate has 25 small holes with a diameter of 0.5 mm that are connected to each other to ensure gas communication within the reaction area and to maintain a consistent pressure inside the bottle.

[0035] The inlet of the air inlet pipe 23 is connected to a protective gas cylinder 1, and the outlet of the air outlet pipe 22 is connected to an exhaust device 5. A temperature sensor 4 is installed inside the reaction bottle 21, with one end of the temperature sensor 4 extending into the air outlet pipe 22 and the extended end located inside the reaction bottle 21.

[0036] The microwave generator 3 has a rated power of 800W / 2450MHz and provides stepless, non-pulsed continuous microwave power output. Its internal structure is T-shaped, with a Φ40mm insert quartz tube at the top, a Φ3mm insert quartz tube on one side for atmosphere introduction and material support, and a double-quartz glass plate sealing the other side as a viewing port. The entire unit is insulated using multi-specification low-εγ loss ceramic fiber material from the outside in, resulting in lightweight construction and a heat dissipation rate of approximately 0.226W / m·k, significantly reducing energy loss. Thermocouple temperature measurement is used for direct contact testing of the material temperature. The temperature measurement range is between 0℃ and 1000℃.

[0037] It should be noted that toluene-6 was chosen as a model compound to replace biomass tar in this study for the following reasons: First, biomass tar is an extremely complex mixture with nearly two hundred compounds detected, making direct research susceptible to interference from component interactions and hindering the focus on core issues. Second, toluene constitutes a high proportion of biomass tar, and its chemical structure and physical properties are typical, effectively reflecting the degradation characteristics of the main components of tar. Third, using a model compound can eliminate interference from complex components, simplify the research system, and facilitate in-depth investigation of the degradation mechanism and influencing factors of key components of tar caused by microwave-induced discharge.

[0038] The protective gas is argon, and the argon introduction rate is 290 mL / s to 310 mL / s. The reasons are as follows: First, it has stable chemical properties: Argon is an inert gas and does not readily react with metals or other substances, maintaining a pure reaction environment. Second, it prevents oxidation interference: It eliminates air, water vapor, and oxygen, avoiding oxidation of the metal during discharge and ensuring the accuracy of the microwave-metal interaction. Third, it has high ionization efficiency: Argon has a low ionization potential and easily ionizes into plasma in a microwave field, enhancing microwave-metal coupling and promoting the discharge process. Fourth, it has minimal spectral interference: Argon has simple spectral characteristics and does not interfere with the metal discharge spectrum, facilitating the analysis of microscopic processes such as electronic transitions.

[0039] The quartz sand layer 8 provides a stable and suitable environment for metal discharge. Its functions are as follows: First, chemical stability: its main component is silicon dioxide, which is resistant to localized high temperatures, protecting the reactor from damage. Second, promoting discharge uniformity: as a discharge medium, it makes microwave-induced metal discharge more uniform and stable, facilitating observation and research. Third, optimizing microwave field distribution: by absorbing and scattering microwaves, it homogenizes the microwave field within the system, enhances the coupling between the metal and microwaves, improves the metal's absorption efficiency of microwave energy, and lowers the discharge threshold. Fourth, temperature buffering: by utilizing heat capacity to absorb and store heat, it maintains the temperature stability of the reaction system, avoids drastic local temperature fluctuations, and ensures that the metal discharge behavior and reaction products are less affected by temperature.

[0040] The silicon carbide layer 9 plays the following roles in this invention: First, it absorbs microwave energy and generates high temperatures: it has excellent microwave absorption performance, converting microwave energy into heat energy, forming a local high-temperature region around it, reducing the metal discharge threshold, and improving the efficiency of microwave-induced metal discharge. Second, it stabilizes the reaction environment: its chemical properties are stable, allowing it to act as a catalyst carrier, loading catalysts that promote discharge; it can also act as a reaction medium, reacting with oxides on the metal surface, affecting the metal surface state and electronic structure, and indirectly regulating discharge behavior. Third, it promotes plasma generation and action: after absorbing microwaves, plasma is easily generated on the surface, and its high-energy particles collide with the metal to excite it, promoting electron emission, while improving the electric field distribution, enhancing microwave-metal coupling, and maintaining continuous discharge. Fourth, it optimizes the electric field distribution: its dielectric properties can change the propagation of the microwave field, making the electric field around the metal more concentrated or uniform, enhancing the electric field strength on the metal surface, which is beneficial for electron emission and discharge.

[0041] The stainless steel cone 7 has a tip angle of 15°~60° or is spherical. The stainless steel cone is a discharge material manufactured using additive manufacturing technology. In specific embodiments, the cone tip angles are 15°, 30°, 45°, 60°, and spherical metal materials. Each cone consists of two parts: an upper cone and a lower cylinder. The mass of each cone or sphere is (1g ± 0.05g). To reduce the potential impact of edge defects on the results, the lower end of all cones is hemispherical, and the connection between the conical and cylindrical parts of the stainless steel cone is also an arc-shaped connection. Additive manufacturing technology ensures consistency among all cones in each type, reducing systematic errors.

[0042] The microwave generator 3 has a microwave power of 320W to 640W. By setting different power gradients, the relationship between microwave energy input and the discharge effect of the stainless steel cone can be systematically investigated, and the discharge threshold, plasma generation efficiency, and stability under different powers can be verified. For example, low power (320W) can test the discharge initiation conditions, while high power (640W) can analyze the discharge characteristics under extreme energy inputs. This power range covers the energy requirements of small-scale laboratory experiments and also provides data support for subsequent pilot-scale or industrial applications, meeting the requirements of controllable energy input in biomass tar treatment.

[0043] The number of stainless steel cones 7 is 1 to 6, arranged in any of the following configurations: vertical linear, vertical circular, planar linear, and planar circular. A single cone has a limited discharge area and cannot cover the entire reactor. Increasing the number of cones expands the discharge coverage area, creating a synergistic plasma superposition effect, achieving a toluene gas yield of 99.95%. A circular arrangement results in a more uniform electric field distribution, avoiding "reaction dead zones." The circular structure optimizes the electric field coverage area and intensity distribution, increasing the probability of collisions between tar molecules and reactive species. Vertical arrangements act on gaseous tar, while planar arrangements can directly act on solid tar, resolving the time difference between discharge timing and tar sublimation, thus improving reaction controllability.

[0044] The temperature sensor 4 is a thermocouple.

[0045] The following specific examples will provide further explanation.

[0046] Example 1 A method for degrading toluene using microwave-induced discharge of a stainless steel cone includes the following steps: S1. Place 50g of silicon carbide in the lower part of the reaction flask 21 of the quartz reactor 2 in the microwave-induced stainless steel conical discharge device for toluene degradation to form a silicon carbide layer 9. Place 50g of quartz sand in the upper part of the reaction flask 21 of the quartz reactor 2 in the microwave-induced stainless steel conical discharge device for toluene degradation to form a quartz sand layer 8. Insert a stainless steel cone 7 with a tip angle of 15° into the quartz sand. Add 1.15mL of toluene 6 evenly to the reaction flask 21.

[0047] S2. Place reaction flask 21 into microwave generator 3. The inlet pipe 23 enters through the side passage of microwave generator 3 and connects to reaction flask 21. The outlet pipe 22 enters through the top passage of microwave generator 3 and connects to reaction flask 21. Twist the pipe several times to ensure a tight connection. Insert thermocouple 4 into reaction flask 21 through the top passage, ensuring it does not contact any material, and measure the ambient temperature during the reaction. Close the microwave generator 3 door and connect argon cylinder 1 and exhaust device 5 to ensure the reactor is airtight. Turn on the argon gas switch and introduce gas at a rate of 300 mL / s for 10 minutes to ensure the reaction proceeds under an argon atmosphere.

[0048] S3. Turn off the argon gas switch, turn on microwave generator 3, set the microwave power to 320W, and perform radiation for 40 minutes to ensure that the toluene degradation reaction is complete. Record the data.

[0049] S4. After the reaction is complete, turn off the microwave generator 3. After the microwave generator 3 has cooled down, open the box door, remove the thermocouple 4, and after the reactor has cooled down, take out the recorded data and calculate the gas and liquid yields, and characterize and analyze the pyrolysis products.

[0050] Example 2 The difference from Example 1 is that this example uses a stainless steel cone with a tip angle of 30°.

[0051] Example 3 The difference from Example 1 is that this example uses a stainless steel cone with a tip angle of 45°.

[0052] Example 4 The difference from Example 1 is that this example uses a stainless steel cone with a tip angle of 60°.

[0053] Example 5 The difference from Example 1 is that this example uses spherical stainless steel.

[0054] Example 6 The difference from Example 1 is that the microwave power used in this example is 400W.

[0055] Example 7 The difference from Example 1 is that this example uses a stainless steel cone with a tip angle of 30° and a microwave power of 400W.

[0056] Example 8 The difference from Example 1 is that this example uses a stainless steel cone with a tip angle of 45° and a microwave power of 400W.

[0057] Example 9 The difference from Example 26 is that this example uses a stainless steel cone with a tip angle of 60° and a microwave power of 400W.

[0058] Example 10 The difference from Example 1 is that this example uses spherical stainless steel and has a microwave power of 400W.

[0059] Example 11 The difference from Example 1 is that the microwave power used in this example is 480W.

[0060] Example 12 The difference from Example 1 is that this example uses a stainless steel cone with a tip angle of 30° and a microwave power of 480W.

[0061] Example 13 The difference from Example 1 is that this example uses a stainless steel cone with a tip angle of 45° and a microwave power of 480W.

[0062] Example 14 The difference from Example 1 is that this example uses a stainless steel cone with a tip angle of 60° and a microwave power of 480W.

[0063] Example 15 The difference from Example 1 is that this example uses spherical stainless steel and has a microwave power of 480W.

[0064] Example 16 The difference from Example 1 is that the microwave power used in this example is 560W.

[0065] Example 17 The difference from Example 1 is that this example uses a stainless steel cone with a tip angle of 30° and a microwave power of 560W.

[0066] Example 18 The difference from Example 1 is that this example uses a stainless steel cone with a tip angle of 45° and a microwave power of 560W.

[0067] Example 19 The difference from Example 1 is that this example uses a stainless steel cone with a tip angle of 60° and a microwave power of 560W.

[0068] Example 20 The difference from Example 1 is that this example uses spherical stainless steel and has a microwave power of 560W.

[0069] Example 21 The difference from Example 1 is that the microwave power used in this example is 640W.

[0070] Example 22 The difference from Example 1 is that this example uses a stainless steel cone with a tip angle of 30° and a microwave power of 640W.

[0071] Example 23 The difference from Example 1 is that this example uses a stainless steel cone with a tip angle of 45° and a microwave power of 640W.

[0072] Example 24 The difference from Example 1 is that this example uses a stainless steel cone with a tip angle of 60° and a microwave power of 640W.

[0073] Example 25 The difference from Example 1 is that this example uses spherical stainless steel and has a microwave power of 640W.

[0074] Comparative Example 1 The difference from Example 1 is that this example does not use a stainless steel cone.

[0075] Comparative Example 2 The difference from Example 1 is that this example does not use a stainless steel cone and the microwave power is 400W.

[0076] Comparative Example 3 The difference from Example 1 is that this example does not use a stainless steel cone and the microwave power is 480W.

[0077] Comparative Example 4 The difference from Example 1 is that this example does not use a stainless steel cone and the microwave power is 560W.

[0078] Comparative Example 5 The difference from Example 1 is that this example does not use a stainless steel cone and the microwave power is 640W.

[0079] Toluene degradation tests were conducted on Examples 1 to 25 and Comparative Examples 1 to 5.

[0080] Figure 2 This is a graph showing the toluene degradation yield under different cone tip angles and microwave powers according to the present invention. Figure 2 Figure (a) shows the liquid yield of toluene degradation under different cone tip angles and microwave powers, and Figure (b) shows the gaseous yield of toluene degradation under different cone tip angles and microwave powers. Figure 2It is evident that the gaseous and liquid yields of toluene degradation exhibit a significant negative correlation with power. Without the stainless steel cone, increasing the microwave power from 320W to 640W resulted in a 25.68% decrease in liquid yield. This is because the higher power leads to a higher system temperature (up to 850℃), resulting in a more abundant activation energy (>150kJ / mol) for toluene molecules. Consequently, the breaking efficiency of their C-C and CH bonds is enhanced, leading to superior degradation efficiency. At a fixed power, the cone tip angle significantly affects the toluene degradation effect: a smaller angle (e.g., 15°) results in a larger radius of curvature gradient and a concentrated electric field at the tip, which lowers the argon ionization threshold and promotes plasma formation. This high-energy plasma environment is rich in high-energy electrons (energy >10eV) and reactive free radicals such as ·OH and ·O, which enhance the toluene degradation efficiency by increasing molecular collision energy and the concentration of reactive species. For example, at 400W, the gas yield of the 15° cone group increased by 54.86% compared to the 60° group. This is due to the energy focusing characteristics caused by the tip effect. As the cone tip angle decreases, the non-uniformity of surface charge distribution intensifies, leading to an order-of-magnitude increase in local electric field strength, thus achieving effective ionization of argon gas even at lower power. The generated plasma gradually degrades toluene molecules into smaller molecule products (such as CO and H2) through collision excitation and ionization dissociation, ultimately resulting in a significant increase in gas yield. However, when the microwave power exceeds 400W, the degradation efficiency of the 15° cone decreases non-linearly, with a 27.30% decrease in gas yield at 640W. This is because the high-density plasma (electron density > 10¹⁸ m⁻¹) formed at the tip under high power... -3 The plasma forms an electromagnetic shielding layer. On one hand, it absorbs the incident microwave energy through inverse bremsstrahlung, reducing the effective power density on the metal surface. On the other hand, it hinders the escape of high-energy electrons and active free radicals, reducing the probability of toluene molecule collisions and forming a "reaction blind zone." Comparing the degradation performance of cones with different angles, the 30° stainless steel cone exhibits the best wide power adaptability, achieving a gas yield of 89.50% at 480W. At low power, it can form an effective electric field enhancement through the tip effect; at high power, the plasma region expands, avoiding a strong shielding effect, while also being superior to the weak ionization state. At 640W, the gas yield of the 30° cone is higher than that of the 15° and 60° cones, respectively, proving that it can still maintain a large volume of active reaction region at high power. This balanced characteristic of "energy focusing-region expansion" allows the 30° cone to improve the overall degradation efficiency by expanding the plasma coverage area while avoiding the shielding effect. The geometric configuration of the 30° cone achieves the optimal balance between tip electric field strength, plasma volume, and shielding effect threshold, making it an ideal choice for microwave-induced discharge degradation of toluene.

[0081] Figure 3 This diagram shows the gaseous products of toluene degradation under different cone tip angles and microwave powers according to the present invention. Figure 3Figure (a) shows the proportion of H2 in the gaseous products, (b) shows the proportion of CO in the gaseous products, (c) shows the proportion of CO2 in the gaseous products, and (d) shows the proportion of CH4 in the gaseous products. Figure 3 It can be seen that the main gaseous products of toluene degradation are H2, CO, CO2, and CH4, and their volume fractions are synergistically controlled by microwave power and cone angle, as follows: Figure 3 As shown in (a), the proportion of H2 increases significantly with increasing power, reaching 48.89% in the 15° cone group at 640W. The high-power-driven high-temperature environment (local temperature >1000℃) promotes the breaking and recombination of toluene CH bonds (413kJ / mol), and the small-angle cone (such as 15°) accelerates molecular dissociation and dehydrogenation due to the strong electric field focusing, resulting in the highest H2 proportion at 480W and 560W for the same power. Figure 3 Figure (b) shows that the CO volume fraction is greatly affected by the cone angle and less affected by the power. At 640W, the CO content of the 60° cone is 47.86%, and remains high across all power levels. Due to the weak electric field and insufficient active species in the large-angle cone, toluene is incompletely oxidized (C7H8→CO). Furthermore, the argon atmosphere limits deep oxidation, making CO the main oxygen-containing product. Figure 3 As shown in (c), the volume fraction of CO2 decreases with increasing power. At low power, the CO bond with low bond energy (358 kJ / mol) is broken preferentially to form an oxygen-rich environment, resulting in more CO2 production. At high power, the breaking of C-C bonds intensifies, the amount of free carbon increases, the reaction shifts to carbon chain breaking, and CO2 decreases. Figure 3 As shown in (d), the volume fraction of CH4 gradually increases with increasing power. At high power, CO and CO2 consume oxygen atoms, and free H combines with C to form CH4. The small-angle cone exhibits a lower CH4 fraction due to the high-energy environment promoting CH4 fragmentation compared to the large-angle cone. This is because of the high-energy environment in the strong electric field region (temperature > 1200℃, electron density > 10¹⁸ m³). -3 This promotes further cleavage of CH4 molecules (CH bond breaking energy 439 kJ / mol), inhibiting their accumulation; the weak ionization environment of the large-angle cone (electron density <10¹⁷ m²) -3 It is more suitable for the stable existence of CH4, and its energy dispersion characteristics avoid deep cracking reactions.

[0082] Since Example 12 (microwave power 480W, stainless steel cone with a tip angle of 30°) had the highest gas yield, the liquid collected in Example 12 was selected for gas chromatography-mass spectrometry detection, while Comparative Example 3 (microwave power 480W, no stainless steel cone) was used as a control group.

[0083] Table 1 shows the main components and contents of the liquid products of Example 12 and Comparative Example 3 in this invention. Figure 4 The total ion chromatograms of the liquid products of Example 12 and Comparative Example 3 of the present invention are shown. Figure 4 Figure (a) shows the total ion current chromatogram of the liquid product in Comparative Example 3, and Figure (b) shows the total ion current chromatogram of the liquid product in Example 12. Figure 4 As shown in Table 1, qualitative analysis of the reaction products by gas chromatography-mass spectrometry (GC-MS) revealed high residual amounts of toluene in both the liquid and gas phases. This is attributed to the mismatch between the plasma electric field region (approximately 1-2 mm in diameter) formed by the single stainless steel cone and the reactor size (50 mL volume)—toluene molecules that did not enter the high-energy reaction zone escaped directly with the carrier gas, leading to their enrichment in the gas collection device. The product distribution characteristics showed that the gas phase components were mainly fragmented intermediates of methyl (-CH3) and phenyl (-C6H5) molecules and their recombined products. This phenomenon is directly related to the bond energy differences in toluene molecules: the C1-C7 single bond energy connecting the benzene ring and the methyl group is 346 kJ / mol, significantly lower than the C-C bond (500 kJ / mol) and CH bond (460 kJ / mol) within the benzene ring, and also lower than the CH bond energy in the methyl group (413 kJ / mol). According to the principles of chemical reaction kinetics, energy input preferentially acts on the site with the lowest bond energy. Therefore, in a plasma environment, the toluene molecule first undergoes the breakage of the C-C single bond between the methyl and benzene rings, generating phenyl radicals (·C6H5) and methyl radicals (·CH3). These reactive intermediates exhibit two competing pathways in the reaction system: a deep degradation pathway, occurring in regions with strong electric fields (electric field strength > 10). 5 V / m), high-energy electron collisions (kinetic energy > 10 eV) promote further fragmentation of phenyl and methyl groups, generating small molecule products such as CO and H2; Recombination pathway: when free radicals diffuse to the low-energy environment outside the plasma region, due to the lack of continuous energy input, they generate toluene (·C6H5+·CH3→C7H8) and biphenyl (·C6H5+·C6H5→C7H8) through random recombination reactions. 12 H 10 ) and methylbiphenyl (·C6H5+·CH3+·C6H5→C 13 H 12 Polycyclic aromatic hydrocarbons (PAHs) and other polycyclic aromatic hydrocarbons (PAHs) were detected as the recombined products in Table 1. The amount of unreacted toluene residue was negatively correlated with the cone electric field coverage efficiency. When the tip angle was 30°, the plasma region expanded to a diameter of 2 mm to 3 mm, and the amount of toluene residue decreased by 23.7% compared with the 15° cone. This indicates that optimizing the cone geometry parameters can effectively improve the coverage of the reaction region and suppress the ineffective recombination of intermediates.

[0084] Table 1. Main components and contents of the liquid products of Example 12 and Comparative Example 3. Example 26 The difference from Example 12 is that this example uses two stainless steel cones with a tip angle of 30°, arranged in a regular polygonal manner.

[0085] Example 27 The difference from Example 12 is that this example uses three stainless steel cones with a tip angle of 30°, arranged in a regular polygonal manner.

[0086] Example 28 The difference from Example 12 is that this example uses four stainless steel cones with a tip angle of 30°, arranged in a regular polygonal manner.

[0087] Example 29 The difference from Example 12 is that this example uses five stainless steel cones with a tip angle of 30°, arranged in a regular polygonal manner.

[0088] Example 30 The difference from Example 12 is that this example uses six stainless steel cones with a tip angle of 30°, arranged in a regular polygonal manner.

[0089] The degradation rate of toluene was tested in Examples 12, 26 to 30.

[0090] Figure 5 The graph shows the yield of toluene degradation by microwave-induced discharge of different numbers of stainless steel cones according to the present invention. Figure 5 Figure (a) shows the liquid yield of toluene degradation by different numbers of stainless steel cone discharges, and Figure (b) shows the gaseous yield of toluene degradation by different numbers of stainless steel cone discharges. Figure 5 It can be seen that as the number of stainless steel cones increases, the gas yield of toluene degradation first increases and then decreases, with the optimal effect achieved with 4 cones: the gas yield reaches 99.92% (the liquid yield is only 0.08%), which is 11.64% higher than that of a single cone. When the number of cones is ≤4, increasing the number of cones creates a larger electrical grid, allowing more toluene vapor to pass through and degrade; toluene is a liquid at room temperature, and the heat required for toluene vaporization is small, so the timing of toluene vaporization coincides more closely with the discharge of stainless steel cones. When the number of cones exceeds 4 (e.g., 6), the gas yield slightly decreases to 99.66%, only 0.26% lower than that with 4 cones. This is not because more cones have a smaller impact, but rather because in the reactor of this invention, 4 cones are already optimal—at this point, each cone occupies a reasonable amount of space under a specific power, with minimal mutual influence and full utilization of the reactor space, which is the threshold for the number of cones in this system.

[0091] Figure 6 This diagram shows the component composition of toluene gaseous products from microwave-induced discharge using different numbers of stainless steel cones. Figure 6 It can be seen that the group with the highest H2 content was the group without stainless steel cones participating in the reaction, accounting for 39%. The H2 content is mainly related to the grid strength during the reaction, which is more related to the tip angle of the stainless steel cones. Under the same microwave power, more stainless steel cones disperse the energy supplied by the microwave, reducing the grid strength formed by each stainless steel cone. However, the control group without stainless steel cones had the highest H2 content, probably because there was no oxygen source in the entire reaction system, so the CO and CO2 contents were destined to be low, while the relative contents of H2 and CH4 were relatively high. Since there was no oxygen element in the entire system, the oxygen element came from the residual air in various devices. Although air was purged from each reactor, it was difficult to ensure complete removal of air. At the same time, the surface smoothness of the stainless steel cones was limited, so these rough surfaces could allow some air to remain in the reactor. Therefore, the relative contents of CO and CO2 increased with the increase of the number of stainless steel cones.

[0092] Next, the four stainless steel cones were arranged in different ways. Four stainless steel cones were chosen because they represent the threshold of the entire reaction system for the stainless steel cones, maximizing the degradation of toluene. The different arrangements included linear, circular, linear, and circular configurations.

[0093] Example 31 The difference from Example 28 is that the arrangement of the four stainless steel cones with a tip angle of 30° in this example is a vertical line type.

[0094] Example 32 The difference from Example 28 is that the arrangement of the four stainless steel cones with a tip angle of 30° in this example is a planar line.

[0095] Example 33 The difference from Example 28 is that the arrangement of the four stainless steel cones with a tip angle of 30° in this example is a planar circle.

[0096] The toluene degradation rate was tested for Examples 28, 31-33. In Example 28, the stainless steel cones were arranged in a vertical circular shape.

[0097] Figure 7 This is a graph showing the toluene yield of stainless steel cones with different arrangements induced by microwave discharge according to the present invention. Figure 7 Figure (a) shows the liquid yield of toluene degradation by stainless steel cone discharge with different arrangements, and Figure (b) shows the gaseous yield of toluene degradation by stainless steel cone discharge with different arrangements. Figure 7It was found that when stainless steel cones with different microwave-induced discharges degrade toluene, the circular arrangement was more effective than the linear arrangement: in the vertical arrangement, the liquid yield of the circular arrangement was 0.08%, a decrease of 75% compared to the linear arrangement; in the planar arrangement, the liquid yield of the circular arrangement was 0.05%, a decrease of 85.71% compared to the linear arrangement. This indicates that the circular arrangement forms a larger and stronger electrical grid, and because toluene has a lower boiling point (110.6℃) and latent heat of vaporization (360.7kJ / kg), it is more likely to become ionized, allowing more toluene to participate in the reaction and be completely degraded, thus reducing liquid products. It should be noted that the liquid yield was extremely low when four cones participated in the reaction, a result that was verified by repeated testing.

[0098] Figure 8 This diagram illustrates the component composition of toluene gas products generated by microwave-induced discharge degradation of stainless steel cones with different arrangements, as described in this invention. Figure 8 It is known that the main components of the gaseous products are H2, CO, CO2, and CH4. Since all four groups involve four stainless steel cones in the reaction, it can be understood that the oxygen source is the same, so the combined proportion of CO and CO2 does not change significantly, remaining around 60% in all four groups. Furthermore, the circular arrangement creates a more complex reaction environment than the linear arrangement, with a high-intensity electrical grid appearing in various corners of the reaction environment, increasing the likelihood of H2 generation. Therefore, H2 accounts for a higher proportion in the circular arrangement group, reaching 39% of the total gas in the planar circular arrangement of stainless steel cones degrading toluene. Simultaneously, the higher grid intensity also causes the chemical bonds within free methyl groups to break, thus reducing the probability of CH4 generation and resulting in a lower relative CH4 content, which only accounts for 4% of the total gas in the planar circular arrangement of stainless steel cones degrading toluene.

[0099] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of this invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended scope of protection is intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of this invention.

[0100] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of protection of this invention and its equivalents, this invention also intends to include these modifications and variations.

Claims

1. A device for microwave-induced discharge of a stainless steel cone to degrade biomass tar, characterized in that, include: A quartz reactor (2) is used to provide a closed space for the biomass tar degradation reaction. The quartz reactor (2) includes a reaction bottle (21), an outlet pipe (22) and an inlet pipe (23). The inlet pipe (23) is used to input protective gas into the reaction bottle (21), and the outlet pipe (22) is used to detect the degree of biomass tar degradation reaction. Along the height direction of the reaction bottle (21), from bottom to top, there are a silicon carbide layer (9), a quartz sand layer (8) and at least one stainless steel cone (7). The reaction bottle (21) is provided with a porous partition plate, which is located above the connection end of the reaction bottle (21) and the gas inlet pipe (23). The quartz sand layer (8) and the stainless steel cone (7) are located above the porous partition plate, and the silicon carbide layer (9) is located on the inner bottom wall of the reaction bottle (21). The outer wall of the quartz reactor (2) is equipped with a microwave generator (3), which is used to emit microwaves. The tip of the stainless steel cone (7) is discharged by microwave radiation, thus degrading biomass tar.

2. The apparatus for microwave-induced discharge degradation of biomass tar using a stainless steel cone as described in claim 1, characterized in that, The tip angle of the stainless steel cone (7) is 15°~60° or spherical.

3. The apparatus for microwave-induced discharge degradation of biomass tar using a stainless steel cone as described in claim 1, characterized in that, The number of stainless steel cones (7) is 1 to 6, and the arrangement is linear, circular, linear or circular.

4. The apparatus for microwave-induced discharge degradation of biomass tar using a stainless steel cone as described in claim 1, characterized in that, The thickness of the quartz sand layer (8) is 15mm~17mm, and the thickness of the silicon carbide layer (9) is 14mm~16mm.

5. The apparatus for microwave-induced discharge degradation of biomass tar using a stainless steel cone as described in claim 1, characterized in that, The inlet of the inlet pipe (23) is connected to a protective gas cylinder (1), and the outlet of the outlet pipe (22) is connected to an exhaust device (5). A temperature sensor (4) is installed inside the reaction bottle (21). One end of the temperature sensor (4) extends into the outlet pipe (22) and the extended end is located inside the reaction bottle (21).

6. A method for degrading biomass tar using microwave-induced discharge of a stainless steel cone, characterized in that, Performed using the apparatus according to any one of claims 1 to 5, comprising the following steps: Silicon carbide is placed on the inner bottom wall of the reaction vessel (21) to form a silicon carbide layer (9), and quartz sand is placed on the porous spacer plate of the reaction vessel (21) to form a quartz sand layer (8). Then, a stainless steel cone (7) is inserted into the quartz sand layer (8); biomass tar is placed on the stainless steel cone (7). The reaction bottle (21) is placed in the microwave generator (3), and protective gas is introduced into the reaction bottle (21) through the gas inlet pipe (23) to fill the reaction bottle (21) with protective gas. The microwave generator (3) is turned on to irradiate the stainless steel cone (7) in the quartz reactor (2) so that the tip of the stainless steel cone (7) generates a discharge reaction to degrade biomass tar. The degree of biomass tar degradation reaction is detected through the gas outlet pipe (22).

7. The method for degrading biomass tar using microwave-induced stainless steel cone discharge according to claim 6, characterized in that, The discharge reaction time is 40 minutes.

8. The apparatus for microwave-induced stainless steel cone discharge degradation of biomass tar according to claim 6, characterized in that, The microwave power of the microwave generator (3) is 320W~640W.

9. The apparatus for microwave-induced discharge degradation of biomass tar using a stainless steel cone according to claim 6, characterized in that, The protective gas is argon, and the argon gas introduction rate is 290 mL / s to 310 mL / s.

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