Biomass tar removal device and method based on induction heating mode

Abstract

The invention discloses a biomass tar removal device and method based on an induction heating mode, and relates to the technical field of biomass energy utilization. Comprising a tar removal tank, a synthesis gas inlet, a synthesis gas outlet, a first water vapor inlet, a second water vapor inlet, a first fused salt feeding port, a second fused salt feeding port, an induction heating system, a rotational flow gas inlet system, a fused salt reaction area and a slag discharge pipe, the synthesis gas inlet is positioned in the center of the top of the tar removal tank and is used for conveying synthesis gas to be treated below the liquid level of the molten salt in the molten salt reaction area; the synthesis gas outlet is formed in the lateral upper part of the tank body and is used for outputting the synthesis gas after tar removal; and the fused salt reaction area is arranged in the tar removal tank. The induction heating technology, the fused salt heat storage technology and the catalytic cracking technology are coupled, the'rapid heating-efficient heat storage-catalytic removal 'integrated reaction system is constructed, and the tar removal efficiency and the energy utilization efficiency can be doubly improved.

Description

Technical Field

[0001] This invention belongs to the field of biomass energy utilization technology, specifically, it relates to a biomass tar removal device and method based on induction heating. Background Technology

[0002] Biomass gasification technology is one of the key directions for the efficient utilization of biomass energy, but this technology faces a serious challenge in practical applications due to tar problems. Tar not only clogs pipelines and corrodes equipment, reducing the stability and safety of system operation, but also affects the quality and yield of gas produced.

[0003] Currently, methods for removing biomass tar are mainly divided into two categories: physical purification methods and thermochemical methods.

[0004] Physical purification methods focus on non-chemical separation processes outside the gasifier, directly removing tar through filtration, water washing, and electrostatic collection. While these methods are simple to operate, they have several drawbacks: firstly, tar removal efficiency is limited, making it difficult to meet the demand for high-purity gas production; secondly, the disposal of tar-containing wastewater from water washing and the waste of filter consumables increases operating costs and imposes an environmental burden. More importantly, the chemical energy contained in the tar is not recovered and utilized, resulting in reduced energy efficiency, which contradicts the goal of biomass resource utilization.

[0005] Thermochemical methods aim to break down tar into smaller gas molecules, achieving the cascade utilization of chemical energy through thermal drive or catalysis. These methods are further subdivided into thermal cracking and catalytic cracking. Thermal cracking relies on a high-temperature field of 1000-1300℃ to drive tar cracking; however, the temperature threshold determines efficiency: significant cracking effects are only achieved when the temperature exceeds 1100℃; complete cracking requires temperatures above 1300℃. Excessive temperatures not only place stringent demands on equipment but also require significantly more heat, making thermal cracking uneconomical in practical applications.

[0006] Catalytic cracking reduces the activation energy of cracking through catalysts, enabling more complete conversion of tar at low temperatures (far lower than thermal cracking), and has become the most active research area. However, the "performance-cost" trade-off between different catalyst systems constitutes the core contradiction in technological iteration.

[0007] No effective solutions have yet been proposed to address the problems in the relevant technologies.

[0008] Therefore, in order to solve the above problems, the present invention provides a biomass tar removal device and method based on induction heating. Summary of the Invention

[0009] In order to overcome the above-mentioned technical problems, the purpose of this invention is to provide a biomass tar removal device and method based on induction heating.

[0010] The objective of this invention can be achieved through the following technical solutions: A biomass tar removal device based on induction heating includes a tar removal tank, a syngas inlet, a syngas outlet, a first steam inlet, a second steam inlet, a first molten salt feed port, a second molten salt feed port, an induction heating system, a cyclone air intake system, a molten salt reaction zone, and a slag discharge pipe. The syngas inlet is located at the center of the top of the tar removal tank and is used to transport the syngas to be treated to below the molten salt surface in the molten salt reaction zone. The syngas outlet is located above the side of the tank and is used to output the syngas after tar removal. The molten salt reaction zone is located inside the tar removal tank, which is the space where the syngas comes into contact with the high-temperature molten salt and the tar catalytic cracking reaction occurs. The first steam inlet and the second steam inlet are located at the top of the tar removal tank and above the syngas outlet. Both the first steam inlet and the second steam inlet are connected to a steam jet distributor for introducing steam into the tank to clean the inner wall during maintenance. The first molten salt inlet and the second molten salt inlet are symmetrically arranged on both sides of the tank and located below the synthesis gas outlet, for replenishing molten salt; The induction heating system includes an induction coil spirally wrapped around the outside of the tar removal tank and a magnetic conductive element randomly and uniformly distributed in the molten salt, which is used to heat the magnetic conductive element through electromagnetic induction to maintain the molten salt temperature at 800-1000℃. The swirling air intake system includes four air intake pipes evenly distributed around the circumference of the tar removal tank. Each air intake pipe extends tangentially along the cross-section of the tank to below the molten salt surface, and is used to introduce air into the molten salt layer to form a spiral rising airflow field around the central axis of the tank, generating swirling disturbance. The slag discharge pipe is located at the bottom of the tank and is used for periodic slag discharge.

[0011] As a preferred embodiment of the present invention, the molten salt is an ionic liquid formed by high-temperature melting of inorganic salts, selected from one or more of alkali metal / alkaline earth metal halides, carbonates, and nitrates. The molten salt has both heat storage characteristics and catalytic cracking function, with a specific heat capacity ≥1.5kJ / (kg・℃) and a melting point ≤500℃.

[0012] As a preferred embodiment of the present invention, the induction coil is attached to the outside of the insulation layer of the tar removal tank, the heating coverage area precisely corresponds to the molten salt reaction zone, and the vertical height of the uppermost coil from the molten salt surface is ≥ cm; the magnetic conductive element is a graphite ball with a diameter of 8-15 mm or a hollow iron ball with a wall thickness of 1-3 mm, and its filling rate is 15%-25% of the molten salt volume; the induction heating system achieves a temperature field uniformity of ±10℃ inside the molten salt through electromagnetic induction effect.

[0013] As a preferred embodiment of the present invention, the ER value of the air introduced by the swirl air intake system is ≤0.20, and the spiral rising airflow field can prolong the residence time of the synthesis gas in the molten salt, thereby increasing the contact area between the synthesis gas and the molten salt by 30%-50%.

[0014] As a preferred embodiment of the present invention, the pipe axes of the first molten salt feeding port and the second molten salt feeding port are at a 45° angle to the horizontal plane, and the discharge port is located 50-100mm above the static liquid surface of the molten salt. Combined with the swirling air intake disturbance, the newly added molten salt is uniformly mixed within 60 seconds, and the temperature fluctuation of the molten salt during the replenishment process is ≤±15℃. The slag discharge pipe is equipped with a double-layer valve, the upper layer is a high-temperature resistant ceramic ball valve with a working temperature ≥1000℃, and the lower layer is a stainless steel ball valve. The slag discharge speed is controlled at 20-50kg / min, and the slag discharge pipe is covered with a heat insulation layer to maintain the molten slag temperature ≥500℃.

[0015] As a preferred embodiment of the present invention, the steam jet distributor is located at the top of the tar removal tank and consists of annular nozzles with diameters of 1 / 3 and 2 / 3 of the tank's inner diameter, respectively. The inner annular nozzle has jet holes with a diameter of 3-5 mm extending radially outward, with the jet angle forming an angle of 30°-45° with the vertical. The outer annular nozzle has jet holes with a diameter of 3-5 mm extending radially inward, with the jet angle forming an angle of 15°-30° with the vertical. The steam jets formed by the two sets of jet holes create a counter-current vortex at the junction of the tank wall and the molten salt surface, covering an area of ​​85%-95% of the total area of ​​the tank's inner wall.

[0016] A method for removing biomass tar using an induction heating biomass tar removal device includes the following steps: S. The syngas after cyclone dust removal is introduced into the molten salt reaction zone below the molten salt liquid level in the tar removal tank through the syngas inlet pipe. S. The molten salt is kept in a liquid state at 800-1000℃ by using an induction heating system, and the swirl air intake system introduces air with an ER value ≤0.20 into the molten salt solution. The molten salt provides a high-temperature environment and plays a catalytic role, promoting the full decomposition of tar in the synthesis gas. S. Regularly replenish molten salt through the first and second molten salt inlets and discharge slag through the slag discharge pipe; during the maintenance process of replacing molten salt, introduce steam into the tank through the first steam inlet, the second steam inlet and the connected steam jet distributor to clean the inner wall of the tank. S. The syngas after deep tar removal enters the next unit through the syngas outlet.

[0017] As a preferred technical solution of the present invention, a multi-field synergistic system is formed in step S, including a high temperature field of 800-1000℃ maintained by the induction heating system, a heat storage-catalytic coupling reaction field formed by molten salt, and a spiral flow field generated by the swirling air intake system; the heat released by the partial oxidation reaction of the synthesis gas and air can reduce the heating power of the induction coil by 20%-30% to save energy consumption.

[0018] As a preferred embodiment of the present invention, the syngas in step S comes from one of a fixed-bed reactor, a fluidized-bed reactor, or a dense-phase transport bed reactor. The initial temperature of the syngas is 750-800℃, the initial tar content is 50-100g / Nm³, and the tar removal rate after treatment by the method is ≥90%.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. In this invention, induction heating, molten salt thermal storage and catalytic cracking technologies are coupled together to construct an integrated reaction system of "rapid heating-efficient thermal storage-catalytic removal", which can achieve a dual improvement in tar removal efficiency and energy utilization efficiency.

[0020] 2. In this invention, the catalytic properties of molten salt can reduce the activation energy of tar cracking and achieve deep cracking of tar molecules. Compared with traditional high-temperature tar removal processes, the reaction temperature can be reduced by more than 200°C. Compared with synthesized transition metal catalysts, molten salt is inexpensive and readily available, and is more suitable for industrial applications from the perspective of performance and economy. On the other hand, molten salt has good heat storage characteristics, and its low heat loss property is conducive to improving the heat preservation effect and reducing operating energy consumption.

[0021] 3. In this invention, induction heating technology is used to directly act on the magnetically conductive element, driving the molten salt to melt rapidly and maintain a constant temperature. Compared with traditional heating, it has high heating efficiency and small temperature fluctuations, and can accurately match the high-temperature requirements of tar cracking. Compared with plasma heating, microwave heating and other technologies, it has the advantages of simple equipment, low cost and convenient maintenance, and also has high heating efficiency, high temperature control accuracy, and is easy to apply in industrial applications.

[0022] 4. The tar removal device and method proposed in this invention are applicable to various biomass gasification furnaces such as fluidized bed, fixed bed, and dense phase transport bed. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a cross-sectional view of the swirl intake system of the present invention; Figure 3 This is a cross-sectional view of the water vapor jet distributor at the top of the tank according to the present invention.

[0025] Figure label: 1. Tar removal tank; 2. Syngas inlet; 3. Syngas outlet; 4. First steam inlet; 5. Second steam inlet; 6. First molten salt feed port; 7. Second molten salt feed port; 8. Induction coil; 9. Gas inlet pipe; 10. Molten salt reaction zone; 11. Magnetic conductive element; 12. Slag discharge pipe; 13. Valve; 14. Annular nozzle; 15. Injection hole. Detailed Implementation

[0026] The invention will now be further described with reference to the accompanying drawings and specific embodiments: Please see Figure 1 , Figure 2 and Figure 3 According to an embodiment of the present invention, a biomass tar removal device based on induction heating includes a tar removal tank 1, a syngas inlet 2, a syngas outlet 3, a first steam inlet 4, a second steam inlet 5, a first molten salt feed port 6, a second molten salt feed port 7, an induction heating system, a cyclone air intake system, a molten salt reaction zone 10, and a slag discharge pipe 12. The tar removal tank 1 is the main supporting structure of the entire device, providing a closed and stable space for the reaction of syngas and molten salt and the installation of various components. At the same time, as a container for high-temperature reaction, it needs to withstand a high-temperature environment of 800-1000℃. Its vertical structure design facilitates the syngas to enter the molten salt liquid below the surface from the top inlet 2, and the purified gas to be discharged from the side upper outlet 3, forming a reasonable material flow path and avoiding gas short circuits. The heat insulation material covering the outer wall can suppress heat loss and ensure the temperature stability of the molten salt reaction zone 10.

[0027] Please see Figure 1Syngas inlet 2 is located at the center of the top of tar removal tank 1. It is used to transport the syngas to be treated to below the molten salt surface in the molten salt reaction zone 10. The function of syngas inlet 2 is to transport the syngas to be treated after cyclone dust removal to below the molten salt surface in the molten salt reaction zone 10, ensuring that the syngas directly contacts the high-temperature molten salt. Its design at the center of the tank top allows the syngas to enter the molten salt vertically downwards, avoiding uneven contact caused by bias to one side. At the same time, the deep transport method below the liquid surface can prevent the syngas from being discharged directly from the syngas outlet 3 before fully reacting with the molten salt, ensuring the initial reaction conditions.

[0028] Please see Figure 1 Syngas outlet 3 is located on the upper side of the tank and is used to output the syngas after tar removal. The function of syngas outlet 3 is to output the purified syngas after deep tar removal to the next processing unit. It is the product discharge channel. Its position on the upper side of the tank is designed to be higher than the molten salt liquid level, which can prevent molten salt from being carried out with the gas. At the same time, it forms an upper and lower staggered flow path with syngas inlet 2, which prolongs the residence time of the gas in the tank and ensures that the reaction is complete.

[0029] Please see Figure 1 The molten salt reaction zone 10 is located inside the tar removal tank 1. It is a space where the syngas comes into contact with the high-temperature molten salt and a catalytic cracking reaction of tar occurs. The molten salt reaction zone 10 is the place where the syngas and molten salt can come into full contact and a catalytic cracking reaction of tar occurs. It is a key area for tar removal. It is located inside the tar removal tank 1 and is filled with high-temperature liquid molten salt and magnetic elements 11. The high temperature of 800-1000℃ is maintained by induction heating. The catalytic properties of the molten salt reduce the activation energy of tar cracking, and the spiral flow field enhances mass transfer. The three work together to fully decompose the tar into small molecule gases.

[0030] Please see Figure 1 and Figure 3The first steam inlet 4 and the second steam inlet 5 are located at the top of the tar removal tank 1, above the syngas outlet 3. Both the first steam inlet 4 and the second steam inlet 5 are connected to a steam jet distributor for introducing steam into the tank to clean the inner wall during maintenance. The steam jet distributor is located at the top inside the tar removal tank 1 and consists of annular nozzles 14 with diameters of 1 / 3 and 2 / 3 of the tank's inner diameter, respectively. The inner annular nozzle has spray holes 15 with a diameter of 3-5 mm extending radially outward, with the spray angle forming a 30°-45° angle with the vertical. The outer annular nozzle has spray holes 15 with a diameter of 3-5 mm extending radially inward. The injection orifice 15 has an injection angle of 15°-30° with the vertical. The steam jets formed by the two sets of orifices create a counter-current vortex at the interface between the tank wall and the molten salt surface, covering an area of ​​85%-95% of the total inner wall area of ​​the tank. The combined function of the first steam inlet 4 and the second steam inlet 5 is to introduce steam into the tank during maintenance processes such as molten salt replacement, providing a water source for the steam jet distributor and serving as the input channel for the cleaning medium. Their symmetrical arrangement above the syngas outlet 3 facilitates the uniform connection of the annular nozzles 14 of the steam jet distributor, ensuring that the steam can diffuse downwards from the top, covering all areas of the inner wall of the tank. The dual-inlet design increases the steam supply and accelerates the cleaning process, while preventing cleaning interruptions caused by blockage of a single inlet. The annular nozzle 14 is the core structure of the steam jet distributor, evenly distributing steam to various areas within the tank to create opposing swirling currents, thus cleaning the tank's inner wall. It consists of inner and outer ring nozzles with diameters of 1 / 3 and 2 / 3 of the tank's inner diameter, respectively. The radially outward spray direction of the inner ring nozzle and the radially inward spray direction of the outer ring nozzle create opposing currents at the interface between the tank wall and the molten salt surface, covering 85%-95% of the total inner wall area, effectively removing residual molten salt. To prevent scaling, the nozzle material is resistant to high temperatures from water vapor and is not easily corroded. The spray hole 15 is the water vapor ejection channel, which ejects the water vapor in the annular nozzle 14 at a specific angle and pressure, forming a jet with scouring force that directly acts on the inner wall of the tank. Its 3-5mm diameter design ensures that the water vapor pressure is stable and the flow rate is moderate when it is ejected. It can form sufficient scouring force to remove scale while avoiding excessive pressure that would cause water vapor to splash. The spray angle of the inner ring nozzle is 30°-45° and the outer ring nozzle is 15°-30°, which allows the jet to accurately cover the area of ​​the tank wall from the top to the liquid surface, forming a counter-current swirling flow and improving the uniformity of cleaning.

[0031] Please see Figure 1The first molten salt feed port 6 and the second molten salt feed port 7 are symmetrically arranged on both sides of the tank and located below the synthesis gas outlet 3. They are used to replenish the molten salt. The pipe axes of the first molten salt feed port 6 and the second molten salt feed port 7 form a 45° angle with the horizontal plane. The discharge port is located 50-100 mm above the static liquid surface of the molten salt. Combined with the swirling air intake disturbance, the newly replenished molten salt is uniformly mixed within 60 seconds. During the replenishment process, the temperature fluctuation of the molten salt is ≤±15℃. The molten salt is an ionic liquid formed by the high-temperature melting of inorganic salts, selected from one or more of alkali metal / alkaline earth metal halides, carbonates, and nitrates. The molten salt has both heat storage characteristics and catalytic cracking function, with a specific heat capacity ≥1.5 kJ. / kg・℃, melting point ≤500℃, the first molten salt feeding port 6 and the second molten salt feeding port 7 regularly replenish the molten salt in the tank to make up for the loss of molten salt during the reaction process (such as being carried out with the slag discharge), and ensure that the amount of molten salt in the molten salt reaction zone 10 is stable. The design of symmetrical arrangement on both sides of the tank and located below the synthesis gas outlet 3, combined with the parameters that the pipeline axis is at a 45° angle to the horizontal plane and the discharge port is located 50-100mm above the static liquid surface of the molten salt, allows the replenished molten salt to fall steadily onto the surface of the molten salt by gravity. Combined with the disturbance of the swirling air intake, it can be quickly mixed and uniformly integrated into the main molten salt within 60 seconds. The temperature fluctuation during the replenishment process is ≤±15℃, avoiding sudden changes in local temperature.

[0032] Please see Figure 1The induction heating system includes an induction coil 8 spirally wound around the outside of the tar removal tank 1 and magnetically conductive elements 11 randomly and uniformly distributed in the molten salt. The induction coil 8 is used to heat the magnetically conductive elements 11 through electromagnetic induction, maintaining the molten salt temperature at 800-1000℃. The induction coil 8 is attached to the outside of the insulation layer of the tar removal tank 1, with the heating coverage area precisely corresponding to the molten salt reaction zone 10, and the uppermost coil being at least 30cm above the molten salt surface. The magnetically conductive elements 11 are graphite spheres with a diameter of 8-15mm or hollow iron spheres with a wall thickness of 1-3mm, and their filling rate is 15%-25% of the molten salt volume. The induction heating system achieves a temperature field uniformity of ±10℃ within the molten salt through electromagnetic induction. The induction coil 8 is the core heating component of the induction heating system, generating Joule heat through electromagnetic induction to heat the magnetically conductive elements 11, thereby maintaining the molten salt temperature within the molten salt reaction zone 10 at 800-1000℃. The design of the insulation layer surrounding the tar removal tank 1 ensures that the heating coverage area precisely corresponds to the molten salt reaction zone 10, allowing heat to be directionally transferred to the molten salt and reducing heat loss to the gas phase zone or the outside. The uppermost coil is ≥30cm above the molten salt surface, further avoiding thermal interference to the gas phase zone and ensuring heating efficiency. The magnetic element 11 is the heat transfer medium of the induction heating system. Under the electromagnetic induction of the induction coil 8, it generates eddy current heat, which is transferred to the molten salt to help maintain the high temperature of the molten salt reaction zone 10. Its irregular and uniform distribution in the molten salt allows heat to be transferred to the molten salt from multiple points, avoiding local overheating or undercooling. Combined with parameters of 8-15mm diameter (graphite spheres) or 1-3mm wall thickness (hollow iron spheres) and 15%-25% filling rate, it ensures high heat transfer efficiency without affecting the fluidity of the molten salt. Ultimately, the internal temperature field uniformity of the molten salt reaches ±10℃, providing a stable environment for tar cracking.

[0033] Please see Figure 1 and Figure 2The swirl air intake system includes four air intake pipes 9 evenly distributed around the circumference of the tar removal tank 1. Each air intake pipe 9 extends tangentially along the cross-section of the tank to below the molten salt surface, used to introduce air into the molten salt layer to form a spiral upward airflow field around the central axis of the tank, generating swirling disturbance. The ER value of the air introduced into the swirl air intake system is ≤0.20 (ER value: air equivalence ratio, which refers to the ratio of the required air volume to the theoretical air volume under complete combustion conditions). The spiral upward airflow field can prolong the residence time of the synthesis gas in the molten salt, making the contact between the synthesis gas and the molten salt more efficient. With a 30%-50% increase in contact area, the air intake pipe 9 is the core channel of the swirling air intake system, which introduces air into the molten salt layer of the molten salt reaction zone 10, forming a spiral upward airflow field. Its design of four pipes evenly distributed along the circumference of the tank and extending tangentially along the cross-section to below the molten salt surface allows air to enter the molten salt tangentially from different directions, pushing the molten salt to form a spiral flow around the central axis of the tank, extending the residence time of the synthesis gas in the molten salt, increasing the contact area by 30%-50%, and at the same time, the air and synthesis gas undergo a partial oxidation reaction, releasing heat to help maintain the temperature of the molten salt.

[0034] Please see Figure 1 The slag discharge pipe 12 is located at the bottom of the tank and is used for periodic slag discharge. The slag discharge pipe 12 is equipped with a double-layer valve 13. The upper layer is a high-temperature resistant ceramic ball valve with a working temperature ≥1000℃, and the lower layer is a stainless steel ball valve. The slag discharge speed is controlled at 20-50 kg / min. The slag discharge pipe 12 is covered with a heat insulation layer to maintain the molten slag temperature ≥500℃. The slag discharge pipe 12 periodically discharges the molten slag in the molten salt reaction zone 10 to ensure the purity of the molten salt and the smooth flow of the equipment. Its design of being located in the middle of the bottom of the tank facilitates the collection and discharge of molten slag under the action of gravity. The double-layer valve group forms a double seal to prevent the leakage of high-temperature molten salt. The heat insulation layer maintains the molten slag temperature ≥500℃ to prevent the molten salt from solidifying and clogging the pipe. The slag discharge speed is stable at 20-50 kg / min and can be adjusted according to the amount of slag.

[0035] A method for removing biomass tar using an induction heating biomass tar removal device includes the following steps: S1. The syngas after cyclone dust removal is introduced into the molten salt reaction zone 10 below the molten salt liquid level in the tar removal tank 1 through the pipeline of syngas inlet 2. S2. The molten salt is kept in a liquid state at 800-1000℃ by using an induction heating system. The swirl air intake system introduces air with an ER value ≤0.20 into the molten salt solution. The molten salt provides a high-temperature environment and plays a catalytic role, promoting the full decomposition of tar in the synthesis gas. S3. Periodically replenish molten salt through the first molten salt feed port 6 and the second molten salt feed port 7, and perform slag discharge operation through the slag discharge pipe 12; during the maintenance process of replacing molten salt, water vapor is introduced into the tank through the first steam inlet 4, the second steam inlet 5 and the connected steam jet distributor to clean the inner wall of the tank. S4. The syngas after deep tar removal enters the next unit through syngas outlet 3.

[0036] Specifically, in step S2, a multi-field synergistic system is formed, including the 800-1000℃ high temperature field maintained by the induction heating system, the heat storage-catalytic coupling reaction field formed by molten salt, and the spiral flow field generated by the swirling air intake system; the heat released by the partial oxidation reaction of the syngas and air can reduce the heating power of the induction coil 8 by 20%-30% to save energy consumption.

[0037] Specifically, the syngas in step S1 comes from one of a fixed-bed reactor, a fluidized-bed reactor, or a dense-phase transport bed reactor. The initial temperature of the syngas is 750-800℃, the initial tar content is 50-100g / Nm³, and the tar removal rate after treatment is ≥90%.

[0038] The working principle of a biomass tar removal device based on induction heating is as follows: First, before the device is started, the prepared molten salt and magnetic element 11 are injected into the tar removal tank 1 through the first molten salt feeding port 6 and the second molten salt feeding port 7. The amount of molten salt is controlled to be 2 / 3 of the tank volume to form the molten salt reaction zone 10. Then, the induction coil 8 is started, and the magnetic element 11 is used to generate eddy current heat by electromagnetic induction effect, which quickly heats the molten salt to 800-1000℃ liquid state. The heat preservation layer suppresses heat loss, and the temperature control system ensures that the internal temperature field of the molten salt is uniform to ±10℃, providing a stable high temperature environment for tar cracking. After the molten salt temperature stabilizes, the swirl air intake system introduces air with an ER value ≤ 0.20 into the molten salt layer through four tangentially arranged air intake pipes 9. The tangential air intake forms a spiral upward airflow field around the central axis of the tank, disturbing the molten salt to form a swirl. At the same time, the synthesis gas after cyclone dust removal is transported to below the molten salt liquid surface through the synthesis gas inlet 2 at the center of the tank top and enters the molten salt reaction zone 10. Within the molten salt reaction zone 10, a multi-field synergistic system is formed: the 800-1000℃ high-temperature field maintained by the induction heating system provides energy for tar cracking; the alkali metal active sites of the molten salt play a catalytic role in reducing the activation energy of tar cracking; and the spiral flow field prolongs the residence time of the syngas and increases the contact area by 30%-50%. The three work together to promote the full decomposition of tar into small molecule gases. At the same time, the syngas undergoes a partial oxidation reaction with air, releasing heat, which can reduce the heating power of the induction coil 8 by 20%-30%, thus saving energy. During the reaction, molten salt is periodically replenished through the first molten salt feed port 6 and the second molten salt feed port 7, and molten slag is discharged through the bottom slag discharge pipe 12. When it is necessary to replace the molten salt for maintenance, steam is introduced through the first steam inlet 4 and the second steam inlet 5. The steam forms a counter-current vortex through the spray hole 15 of the annular nozzle 14 to clean the residual molten salt and scale on the tank wall and ensure the cleanliness of the device. Finally, the purified syngas after deep tar removal is discharged from the syngas outlet 3 on the upper side of the tank and enters the next processing unit, completing the entire tar removal process.

[0039] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0040] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A biomass tar removal device based on induction heating, characterized in that: It includes a tar removal tank (1), a syngas inlet (2), a syngas outlet (3), a first steam inlet (4), a second steam inlet (5), a first molten salt feed port (6), a second molten salt feed port (7), an induction heating system, a swirl gas inlet system, a molten salt reaction zone (10), and a slag discharge pipe (12). The syngas inlet (2) is located at the center of the top of the tar removal tank (1) and is used to transport the syngas to be treated to below the molten salt liquid surface in the molten salt reaction zone (10). The syngas outlet (3) is located above the tank body and is used to output the syngas after tar removal; The molten salt reaction zone (10) is located inside the tar removal tank (1), which is the space where the syngas comes into contact with the high-temperature molten salt and the tar catalytic cracking reaction occurs; The first steam inlet (4) and the second steam inlet (5) are located at the top of the tar removal tank (1) and above the syngas outlet (3). The first steam inlet (4) and the second steam inlet (5) are both connected to a steam jet distributor for introducing steam into the tank to clean the inner wall during maintenance. The first molten salt inlet (6) and the second molten salt inlet (7) are symmetrically arranged on both sides of the tank and located below the synthesis gas outlet (3) for replenishing molten salt; The induction heating system includes an induction coil (8) spirally wrapped around the outside of the tar removal tank (1) and a magnetic conductive element (11) randomly and uniformly distributed in the molten salt, which is used to heat the magnetic conductive element (11) by electromagnetic induction and maintain the molten salt temperature at 800-1000℃. The swirling air intake system includes four air intake pipes (9) evenly distributed around the circumference of the tar removal tank (1). Each air intake pipe (9) extends tangentially along the cross-section of the tank to below the molten salt surface, and is used to introduce air into the molten salt layer to form a spiral rising airflow field around the central axis of the tank, generating swirling disturbance. The slag discharge pipe (12) is located at the bottom of the tank and is used for periodic slag discharge.

2. The biomass tar removal device based on induction heating according to claim 1, characterized in that, The molten salt is an ionic liquid formed by high-temperature melting of inorganic salts, selected from one or more of alkali metal / alkaline earth metal halides, carbonates, and nitrates. The molten salt has both heat storage characteristics and catalytic cracking function, with a specific heat capacity ≥1.5kJ / (kg・℃) and a melting point ≤500℃.

3. The biomass tar removal device based on induction heating according to claim 1, characterized in that, The induction coil (8) is attached to the outside of the insulation layer of the tar removal tank (1), and the heating coverage area corresponds precisely to the molten salt reaction zone (10). The uppermost coil is ≥30cm above the molten salt surface. The magnetic element (11) is a graphite ball with a diameter of 8-15mm or a hollow iron ball with a wall thickness of 1-3mm. Its filling rate is 15%-25% of the molten salt volume. The induction heating system makes the temperature field inside the molten salt uniform to ±10℃ through electromagnetic induction effect.

4. The biomass tar removal device based on induction heating according to claim 1, characterized in that, The ER value of the air introduced by the swirl air intake system is ≤0.20, and the spiral rising airflow field can prolong the residence time of the synthesis gas in the molten salt, thereby increasing the contact area between the synthesis gas and the molten salt by 30%-50%.

5. The biomass tar removal device based on induction heating according to claim 1, characterized in that, The pipe axis of the first molten salt feeding port (6) and the second molten salt feeding port (7) is at a 45° angle to the horizontal plane. The discharge port is located 50-100 mm above the static liquid surface of the molten salt. Combined with the swirling air intake disturbance, the newly added molten salt is uniformly mixed within 60 seconds. The temperature fluctuation of the molten salt during the replenishment process is ≤±15℃. The slag discharge pipe (12) is equipped with a double-layer valve (13). The upper layer is a high-temperature resistant ceramic ball valve with a working temperature ≥1000℃, and the lower layer is a stainless steel ball valve. The slag discharge speed is controlled at 20-50 kg / min. The slag discharge pipe (12) is covered with a heat insulation layer to maintain the molten slag temperature ≥500℃.

6. The biomass tar removal device based on induction heating according to claim 1, characterized in that, The steam jet distributor is located at the top of the tar removal tank (1) and consists of annular nozzles (14) with diameters of 1 / 3 and 2 / 3 of the inner diameter of the removal tank, respectively. The inner annular nozzle has a jet hole (15) with a diameter of 3-5 mm opened radially outward, and the jet angle is 30°-45° with the vertical. The outer annular nozzle has a jet hole (15) with a diameter of 3-5 mm opened radially inward, and the jet angle is 15°-30° with the vertical. The steam jet formed by the two sets of nozzles forms an opposing vortex at the junction of the tank wall and the molten salt surface, and the coverage area accounts for 85%-95% of the total area of ​​the inner wall of the tank.

7. A method for removing biomass tar using the apparatus described in any one of claims 1-6, characterized in that, Includes the following steps: S1. The syngas after cyclone dust removal is introduced into the molten salt liquid below the surface of the tar removal tank (1) through the pipeline of syngas inlet (2) and enters the molten salt reaction zone (10). S2. The molten salt is kept in a liquid state at 800-1000℃ by using an induction heating system. The swirl air intake system introduces air with an ER value ≤0.20 into the molten salt solution. The molten salt provides a high-temperature environment and plays a catalytic role, promoting the full decomposition of tar in the synthesis gas. S3. Periodically replenish molten salt through the first molten salt feed port (6) and the second molten salt feed port (7), and perform slag discharge operation through the slag discharge pipe (12); during the maintenance process of replacing molten salt, steam is introduced into the tank through the first steam inlet (4), the second steam inlet (5) and the connected steam jet distributor to clean the inner wall of the tank. S4. The syngas after deep tar removal enters the next unit through the syngas outlet (3).

8. The method for removing biomass tar according to claim 7, characterized in that, In step S2, a multi-field synergistic system is formed, including the high temperature field of 800-1000℃ maintained by the induction heating system, the heat storage-catalytic coupling reaction field formed by molten salt, and the spiral flow field generated by the swirling air intake system; the heat released by the partial oxidation reaction of the syngas and air can reduce the heating power of the induction coil (8) by 20%-30% to save energy consumption.

9. The method for removing biomass tar according to claim 7, characterized in that, The syngas in step S1 comes from one of a fixed-bed reactor, a fluidized-bed reactor, or a dense-phase transport bed reactor. The initial temperature of the syngas is 750-800℃, and the initial tar content is 50-100g / Nm³. After treatment by the method, the tar removal rate is ≥90%.

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