Plasma ignition system and use method thereof

Abstract

The invention belongs to the technical field of combustion equipment, and relates to a plasma ignition system and a using method thereof. The system comprises a plasma generator, a combustor, a power supply system, a carrier working medium system and a cooling water system, an anode and a cathode of the plasma generator are coaxially arranged to form an electric arc cavity and a surrounding cooling water cavity, and the anode is provided with a compressed air inlet and a plasma jet outlet; the plasma combustor is sequentially and coaxially sleeved with a first-stage center cylinder, a second-stage combustion cylinder and an outer wall cylinder from inside to outside, the first-stage center cylinder communicates with the jet flow outlet, and the outer wall cylinder is provided with a pulverized coal inlet; the power supply system supplies power to the generator through the isolation transformer and the rectifier cabinet. The carrier working medium system supplies air to the compressed air inlet; the cooling water system enables demineralized water to circulate in the cooling water cavity. Efficient and stable ignition and low-nitrogen combustion of pulverized coal are achieved, the ignition reliability is remarkably improved, the system service life is remarkably prolonged, and the operation automation level is remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of combustion equipment technology and relates to a plasma ignition system and its usage method. Background Technology

[0002] With the development of modern thermal power generation technology, the requirements for combustion stability and ignition reliability of boilers are becoming increasingly stringent. Traditional boiler ignition generally uses oil or natural gas as starting fuel, which not only results in high operating costs but also poses safety hazards related to fuel storage and pollutant emissions. In recent years, plasma ignition technology, with its advantages of directly igniting pulverized coal, requiring no auxiliary fuel, and being energy-saving and environmentally friendly, has gradually become an important development direction in the field of power plant boiler ignition and stable combustion.

[0003] However, existing plasma ignition systems still face some technical challenges in practical applications. For example, the arc stability and cathode life of the plasma generator need to be improved, the mixing and ignition efficiency of the high-temperature plasma jet and pulverized coal gas flow need further optimization, and there is room for improvement in the overall energy consumption and operating economy of the system. In addition, existing devices are still insufficient in terms of structural integration, cooling effect, and power control reliability, which affects the long-term stable operation and widespread use of the system. Summary of the Invention

[0004] To address the problems in the prior art, this invention provides a plasma ignition system and its usage method, which achieves efficient and stable ignition and low-NOx combustion of pulverized coal, significantly improving ignition reliability, system lifespan, and level of automation.

[0005] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention provides a plasma ignition system, comprising: A plasma generator includes an anode and a cathode arranged coaxially; the anode has a cylindrical structure, the cathode is located at the axial center of the anode, and an arc cavity is formed between the anode and the cathode; the plasma generator also includes a cooling water cavity surrounding the arc cavity; a compressed air inlet communicating with the arc cavity is provided on the cylindrical wall of the anode, and a plasma jet outlet communicating with the arc cavity is provided at one end of the anode; The plasma burner includes a primary central cylinder, a secondary combustion cylinder, and an outer wall cylinder that are coaxially arranged along the direction of pulverized coal gas flow. The inlet of the primary central cylinder is connected to the plasma jet outlet, and the outer wall cylinder is provided with a pulverized coal gas flow inlet, which is connected to the boiler burner interface. The power supply system includes an isolation transformer and a rectifier cabinet; the output terminal of the isolation transformer is connected to the input terminal of the rectifier cabinet, and the DC output terminal of the rectifier cabinet is electrically connected to the cathode and anode of the plasma generator. The carrier working fluid system is connected to the compressed air inlet via an air supply pipeline; The cooling water system includes a demineralized water tank, an inlet pipe, and a return pipe; the inlet end of the inlet pipe is connected to the demineralized water tank, and the outlet end is connected to the inlet of the cooling water chamber; the inlet end of the return pipe is connected to the outlet of the cooling water chamber, and the outlet end is connected to the demineralized water tank.

[0006] Preferably, the cathode includes a cathode rod extending axially and a cathode head disposed at the end of the cathode rod; the cathode head extends into the arc cavity, and a discharge gap is formed between its end and the inner wall of the anode.

[0007] Preferably, the plasma burner further includes a first-stage air inlet disposed between the first-stage central cylinder and the second-stage combustion cylinder, and a second-stage air inlet disposed between the second-stage combustion cylinder and the outer wall cylinder; both the first-stage air inlet and the second-stage air inlet are connected to the primary air system of the boiler for introducing staged cooling air.

[0008] Preferably, the carrier working fluid system includes a compressed air tank, a pressure reducing valve, a proportional valve, and a pressure detection unit; the outlet of the compressed air tank is connected to the air supply pipeline in sequence through the pressure reducing valve and the proportional valve; the pressure detection unit is located on the air supply pipeline; the pressure reducing valve, the proportional valve, and the pressure detection unit are all connected to the control unit.

[0009] Preferably, a regulating valve and a water flow switch are sequentially installed along the water flow direction on the inlet pipe; a return water pressure gauge is installed on the return water pipe; and both the inlet water flow switch and the return water pressure gauge are connected to the control unit.

[0010] Preferably, it also includes an image flame monitoring system; the image flame monitoring system includes a flame probe, a cooling air source, and a signal processing unit; the flame probe is fixed to the observation port of the plasma burner by a mounting bracket; the cooling air source is connected to the cooling air channel inlet of the flame probe through a cooling air duct; the video signal output terminal of the flame probe is connected to the signal processing unit; the signal processing unit is connected to the control unit.

[0011] Preferably, the central axis of the flame probe lens forms a preset angle with the outlet axis of the plasma burner, so that the field of view of the flame probe completely covers the outlet area of ​​the plasma burner.

[0012] Preferably, it also includes a wind speed monitoring device; the wind speed monitoring device is installed on the primary air duct that supplies pulverized coal airflow to the plasma burner, and is used to monitor the flow rate of the pulverized coal and air mixture in the duct online; the wind speed monitoring device is connected to the control unit.

[0013] Preferably, the cooling water chamber includes a sleeve coaxially sleeved on the outside of the anode, and an annular cooling channel is formed between the sleeve and the outer wall of the anode; the sleeve is respectively provided with an inlet and an outlet communicating with the annular cooling channel.

[0014] Secondly, the present invention provides a method of using a plasma ignition system, comprising the following steps: The carrier working fluid system is turned on to supply compressed air to the compressed air inlet, and the cooling water system is turned on to allow demineralized water to flow through the cooling water chamber; The power system is started, and a DC voltage is applied to the cathode and anode through the rectifier cabinet to ignite an electric arc between the cathode and anode, thereby generating a high-temperature plasma jet in the arc cavity. The plasma jet is ejected from the plasma jet outlet. The pulverized coal gas flow carried by the primary air is introduced into the plasma burner through the pulverized coal gas flow inlet. The pulverized coal gas flow comes into contact with and is ignited by the high-temperature plasma jet ejected from the plasma jet outlet inside the first-stage central cylinder. The ignited pulverized coal flame mixes with the air introduced in stages within the progressively expanding combustion space formed by the primary central cylinder, the secondary combustion cylinder, and the outer wall cylinder, achieving staged stable combustion. During the boiler ignition or low-load stable combustion phase, the power supply system, carrier working fluid system, and cooling water system are maintained to continuously provide an ignition source. Once the boiler enters normal operation, the power supply system, carrier working fluid system, and cooling water system are shut down in sequence, and the plasma burner is used as a regular burner.

[0015] Compared with the prior art, the present invention has the following beneficial effects: By coaxially arranging the anode and cathode to form an arc cavity, the concentration and stability of the arc are ensured, providing a core structural foundation for the efficient generation of high-temperature plasma jets. A cooling water chamber surrounding the arc cavity effectively removes high-temperature heat from the generator's interior through forced circulation cooling, significantly extending the working life of the anode and cathode and ensuring continuous arc stability. Directly connecting the plasma generator's jet outlet to the burner's primary central cylinder inlet enables directional and efficient transfer of ignition energy to the pulverized coal. The burner employs a coaxial structure of the primary central cylinder, secondary combustion cylinder, and outer wall cylinder, providing optimized flow field and spatial conditions for the staged ignition, staged combustion, and flame stability of the pulverized coal gas flow. A power supply system consisting of an isolation transformer and rectifier cabinet ensures electrical safety and stable and reliable DC arc operation. Independent carrier working medium and cooling water systems respectively ensure a stable supply of the plasma forming medium and effective cooling of key components. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of a plasma ignition system according to the present invention.

[0018] The components include: 1. Plasma generator; 2. Plasma burner; 3. Power supply system; 4. Carrier working fluid system; 5. Cooling water system; and 6. Boiler burner. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0021] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0022] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0023] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0024] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" 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; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0025] The present invention will now be described in further detail with reference to the accompanying drawings: The first objective of this invention is to provide a plasma ignition system, such as... Figure 1 As shown, it includes: The plasma generator 1 includes an anode and a cathode arranged coaxially; the anode has a cylindrical structure, the cathode is located at the axial center of the anode, and an arc cavity is formed between the anode and the cathode; the plasma generator 1 also includes a cooling water cavity arranged around the arc cavity; a compressed air inlet communicating with the arc cavity is opened on the cylindrical wall of the anode, and a plasma jet outlet communicating with the arc cavity is provided at one end of the anode; The plasma burner 2 includes a primary central cylinder, a secondary combustion cylinder, and an outer wall cylinder that are coaxially arranged along the direction of pulverized coal airflow. The inlet of the primary central cylinder is connected to the plasma jet outlet, and the outer wall cylinder is provided with a pulverized coal airflow inlet, which is connected to the interface of the boiler burner 6. The power supply system 3 includes an isolation transformer and a rectifier cabinet; the output terminal of the isolation transformer is connected to the input terminal of the rectifier cabinet, and the DC output terminal of the rectifier cabinet is electrically connected to the cathode and anode of the plasma generator 1. The carrier working fluid system 4 is connected to the compressed air inlet via an air supply pipeline; The cooling water system 5 includes a demineralized water tank, an inlet pipe, and a return pipe; the inlet end of the inlet pipe is connected to the demineralized water tank, and the outlet end is connected to the inlet of the cooling water chamber; the inlet end of the return pipe is connected to the outlet of the cooling water chamber, and the outlet end is connected to the demineralized water tank.

[0026] In plasma generator 1, the coaxially arranged cathode and anode form a high-energy electric arc within the arc cavity. Compressed air, as the carrier working fluid, is ionized and heated by the arc, forming a high-temperature, high-speed plasma jet that is ejected from the outlet, providing the energy basis for igniting pulverized coal. The cooling water chamber surrounding the arc cavity effectively removes a large amount of heat from the generator through circulating cooling, ensuring the long-term working life of the anode and cathode, especially the cathode, and the continuous stability of the electric arc. Plasma burner 2 is the key site for pulverized coal ignition and stable combustion. Its unique multi-stage coaxial sleeve structure—a first-stage central cylinder, a second-stage combustion cylinder, and an outer wall cylinder—creates ideal conditions for the ignition and development of the pulverized coal gas flow: the high-temperature plasma jet first mixes intensely with the pulverized coal in the first-stage central cylinder and completes initial ignition. Subsequently, the flame fully mixes with the air introduced from the air inlet in stages within the progressively expanding space, achieving accelerated flame propagation and stable combustion. At the same time, the staged air also cools the burner wall. Power system 3 provides stable and reliable DC power for the excitation and maintenance of the plasma arc. Its combination of isolation transformer and rectifier cabinet ensures electrical safety and stable, continuous current supply. The carrier working fluid system 4 provides compressed air with stable and controllable flow and pressure. It not only forms the plasma medium but also compresses and stabilizes the arc. Cooling water system 5 provides continuous and effective cooling for plasma generator 1. Forced circulation of demineralized water ensures that critical components remain within safe operating temperature ranges, providing a fundamental guarantee for the system's long-term continuous operation.

[0027] For example, the cathode includes an axially extending cathode rod and a cathode head disposed at the end of the cathode rod; the cathode head extends into the arc cavity, and a discharge gap is formed between its end and the inner wall of the anode.

[0028] The cathode rod, serving as the structural support and conductive path, is responsible for stably transmitting electrical energy to the working end and ensuring the overall axial positioning accuracy and mechanical stability of the cathode. The cathode head, as the direct discharge actuator, extends into the arc cavity and precisely maintains the configuration of the discharge gap with the inner wall of the anode. This allows the arc to be effectively constrained and guided, forming a high-energy-density plasma arc root within a predetermined narrow space. This not only improves the initial ignition reliability of the arc but also significantly enhances the temperature and velocity of the plasma jet through concentrated energy release, thereby greatly optimizing its ability and efficiency in igniting pulverized coal.

[0029] For example, the plasma burner 2 further includes a first-stage air inlet disposed between the first-stage central cylinder and the second-stage combustion cylinder, and a second-stage air inlet disposed between the second-stage combustion cylinder and the outer wall cylinder; both the first-stage air inlet and the second-stage air inlet are connected to the primary air system of the boiler for introducing staged cooling air.

[0030] The first-stage air inlet is located downstream of the first-stage central cylinder. The cooling air introduced through it serves as the first-stage supplementary air, primarily regulating the initial flame ignited by the plasma jet. On one hand, it provides the necessary initial oxygen for the continued combustion and expansion of the flame, preventing combustion interruption or incomplete combustion due to uneven mixing within the central cylinder. On the other hand, this airflow, either adhering to the wall or swirling in, cools the high-temperature wall surface in the central cylinder outlet area, preventing it from burning off. Simultaneously, it optimizes the flame shape through flow field organization, allowing it to smoothly transition into the larger secondary combustion cylinder space. The second-stage air inlet is located between the secondary combustion cylinder and the outer wall cylinder, introducing a larger volume of air. Its main function is to achieve complete combustion and final flame stabilization. It provides sufficient oxygen for the later-stage burnout of pulverized coal particles, ensuring combustion efficiency. Simultaneously, this airflow further mixes with the main flame, effectively suppressing the formation of nitrogen oxides in the flame core area through dilution and cooling effects, resulting in significant low-NOx emission reduction. Furthermore, it also forms an effective gas film cooling on the inner surface of the outer wall cylinder, providing comprehensive protection for the burner's structure.

[0031] For example, the carrier working fluid system 4 includes a compressed air tank, a pressure reducing valve, a proportional valve, and a pressure detection unit; the outlet of the compressed air tank is connected to the air supply pipeline in sequence through the pressure reducing valve and the proportional valve; the pressure detection unit is located on the air supply pipeline; the pressure reducing valve, the proportional valve, and the pressure detection unit are all connected to the control unit.

[0032] The compressed air storage tank, serving as a gas source reserve unit, acts as a buffer and stabilizer, smoothing out potential fluctuations in the upstream gas source and providing a continuous and stable initial gas supply to the system. The pressure reducing valve performs primary pressure regulation on the high-pressure gas output from the storage tank, reducing it to the operating pressure range required by plasma generator 1, a fundamental element ensuring the safe operation of the system. The proportional valve, as a core regulating component, can precisely and continuously dynamically control the air flow according to the control unit's instructions, thereby achieving fine-tuning of plasma power and morphology based on coal characteristics, load changes, and other operating conditions. The pressure detection unit installed on the gas supply pipeline monitors the gas pressure at the operating point in real time and feeds it back to the control unit. The control unit processes the pressure feedback signal and integrates other system parameters to form a closed-loop control logic, dynamically adjusting the opening of the pressure reducing valve and the proportional valve to ensure a highly stable and precise match between the gas supply pressure and flow rate.

[0033] For example, a regulating valve and a water flow switch are sequentially installed along the water flow direction on the inlet pipe; a return water pressure gauge is installed on the return water pipe; both the inlet water flow switch and the return water pressure gauge are connected to the control unit.

[0034] The regulating valve on the inlet water pipe is responsible for setting the basic flow rate of the cooling water and adjusting it manually / automatically. Downstream, a flow switch serves as a critical safety monitoring point, detecting the actual inlet water flow rate in real time and transmitting the flow status signal (usually on / off or an analog signal) to the control unit. If the detected flow rate is lower than a preset safety threshold, indicating insufficient cooling, the control unit can immediately trigger an alarm or even interlock shutdown, effectively preventing the generator from being damaged by overheating. The return water pressure gauge on the return water pipe monitors the outlet pressure of the cooling water after it flows through the complex internal flow channels of the generator. Its reading is fed back to the control unit, indirectly reflecting whether there are any abnormalities in the cooling water system, such as pipe blockage, valve failure, or system leakage, as abnormal changes in return water pressure are often early signs of these problems. By integrating these key parameters (flow rate and pressure) into the control unit, the system achieves continuous online monitoring and intelligent logic judgment of the cooling conditions. Once parameters exceed limits, protective measures can be taken in a timely manner, greatly improving the automation level and inherent safety of the system operation.

[0035] For example, the system of the present invention also includes an image flame monitoring system; the image flame monitoring system includes a flame probe, a cooling air source and a signal processing unit; the flame probe is fixed to the observation hole position of the plasma burner 2 by a mounting bracket; the cooling air source is connected to the cooling air channel inlet of the flame probe through a cooling air duct; the video signal output terminal of the flame probe is connected to the signal processing unit; the signal processing unit is connected to the control unit.

[0036] The flame probe is fixed to the observation port of the plasma burner 2 via a mounting bracket. Its internal camera element directly captures the flame image of the burner outlet area. To prevent damage to the probe's optical components from high temperatures, ash accumulation, and flame radiation inside the burner, a specially designed cooling air source continuously supplies clean cooling air to the probe's cooling air channel through pipelines. This airflow forms a positive air curtain in front of the lens, effectively cooling the probe body and blowing away any dust that may adhere to the lens surface, ensuring clear and stable imaging. The raw video signal acquired by the probe is transmitted to the signal processing unit, which performs real-time image analysis, such as identifying flame morphology, brightness, and stability, and quantifying them into interpretable combustion state signals. Finally, the signal processing unit transmits the processing results to the control unit, enabling the control system to automatically make logical judgments based on the real-time flame state (such as whether it is ignited and whether the flame is stable). This can be used to trigger advanced control functions such as successful ignition confirmation, low-load stable combustion auxiliary adjustment, or fire extinguishing protection interlock, thereby upgrading traditional experience-based operation relying on manual observation to precise and reliable automated monitoring, greatly improving the intelligence level and operational safety of the entire ignition system.

[0037] The flame probe's lens center axis forms a predetermined angle with the outlet axis of the plasma burner 2, ensuring that the flame probe's field of view completely covers the outlet area of ​​the plasma burner 2. Simultaneously, this design effectively avoids direct contact with the core region of the flame, which has extremely high temperature and particle concentration, ejected from the burner. This significantly reduces the risk of thermal shock and contamination to the lens caused by high-temperature flame radiation and potentially splashing molten ash, thereby improving the probe's durability and operational reliability.

[0038] For example, the system of the present invention also includes a wind speed monitoring device; the wind speed monitoring device is installed on the primary air duct that supplies coal powder airflow to the plasma burner 2, and is used to monitor the flow rate of the coal powder and air mixture in the duct online; the wind speed monitoring device is connected to the control unit.

[0039] This device is directly installed on the primary air duct that transports pulverized coal gas, enabling real-time online monitoring of the flow velocity of the pulverized coal and air mixture within the duct. On one hand, a suitable air velocity is a prerequisite for ensuring sufficient mixing of pulverized coal with the plasma jet in the burner, stable ignition, and complete combustion. Excessive air velocity may extinguish the flame, while insufficient air velocity may cause pulverized coal deposition or uneven mixing, affecting ignition success rate and combustion efficiency. On the other hand, the continuous air velocity signal is transmitted to the control unit, allowing the control system to compare the real-time air velocity with preset safe and optimized operating ranges. Based on this, the control unit can implement feedforward or feedback control, such as adjusting the pulverized coal feed rate or the primary air damper opening, to dynamically maintain the optimal gas-solid two-phase flow velocity, thereby actively optimizing ignition conditions. Simultaneously, the air velocity data also serves as an important safety interlock parameter. When an abnormal air velocity is detected (such as a sudden drop in air velocity due to fan failure) that may endanger combustion stability or duct safety, the control unit can promptly issue an alarm or activate protection procedures.

[0040] For example, the cooling water chamber includes a sleeve coaxially sleeved on the outside of the anode, and an annular cooling channel is formed between the sleeve and the outer wall of the anode; the sleeve is respectively provided with the water inlet and the water outlet communicating with the annular cooling channel.

[0041] This invention tightly fits a sleeve coaxially with the anode onto the outside of the anode, creating a ring-shaped cooling channel that surrounds the entire working area of ​​the anode between the inner wall of the sleeve and the outer wall of the anode. This coaxial ring structure ensures that the cooling medium (demineralized water) enters from the inlet at one end of the sleeve and evenly wraps around and flows across the entire outer circumference of the anode cylinder, achieving 360-degree, large-area contact cooling of the anode and significantly improving heat exchange efficiency. As the cooling water flows through this ring channel, it continuously and stably absorbs the large amount of Joule heat generated by the high-energy electric arc and some of the arc radiation heat, effectively suppressing the rise in the anode's working temperature and preventing material ablation, deformation, or performance degradation due to overheating. The cooled water, having absorbed heat, is finally discharged from the outlet at the other end of the sleeve, completing one cooling cycle.

[0042] A second objective of this invention is to provide a method of using a plasma ignition system, comprising the following steps: S1. When starting up the boiler or when low-load stable combustion is required, first conduct pre-operation checks and preparations. After confirming that all equipment is in normal condition, start the carrier working fluid system 4 to supply compressed air to the compressed air inlet of the plasma generator 1. The supply pressure and flow rate of the compressed air should be preset and stabilized according to the design values. At the same time, start the cooling water system 5 so that the demineralized water flows through the cooling water chamber surrounding the arc cavity at the design flow rate, ensuring effective cooling protection for the key components of the generator before the arc is ignited.

[0043] S2. After completing the preparations in S1, start the power system 3. Apply DC voltage to the cathode and anode of the plasma generator 1 by controlling the rectifier cabinet. Under the influence of compressed air and the electric field, a high-intensity electric arc is ignited between the cathode and anode. The arc is violently disturbed, compressed, and heated by the compressed air within the narrow arc cavity, thereby ionizing and heating the flowing compressed air to extremely high temperatures, forming a high-temperature, high-speed plasma jet. This jet is ejected with extremely high kinetic energy from the plasma jet outlet at the front end of the plasma generator 1 and enters the first-stage central cylinder of the plasma burner 2, which is directly connected to it.

[0044] S3. The pulverized coal gas flow carried by the primary air is introduced into the burner through the pulverized coal gas flow inlet on the outer wall of the plasma burner 2. The pulverized coal gas flow flows in the annular channel between the outer wall and the secondary combustion chamber, and meets the high-temperature plasma jet ejected from the primary central chamber at the front end, resulting in intense mixing and heat exchange. Under the high temperature of thousands of degrees and the abundant active particles (ions and electrons) of the plasma jet, the pulverized coal particles are rapidly heated, volatiles are released, and decomposition occurs, completing the initial ignition in the primary central chamber and forming the initial flame core.

[0045] S4. The initial flame then enters a larger space comprised of two secondary combustion chambers. During this process, cooling air (also serving as supplementary combustion air) introduced from the first-stage air inlet mixes with the flame, providing initial oxygen for the continued development of the flame and further combustion of pulverized coal volatiles, while also cooling the outlet area of ​​the first-stage central chamber. The flame continues to develop, entering the maximum combustion space defined by the outer wall chamber, and a larger flow of staged cooling air is introduced from the second-stage air inlet. This air mixes thoroughly with the flame, providing sufficient oxygen for the complete combustion of pulverized coal and coke, ensuring combustion efficiency. Simultaneously, the staged combustion effectively suppresses the formation of nitrogen oxides and forms a cooling protective film on the inner wall of the outer wall chamber. The flame achieves dynamic equilibrium with the staged air within the progressively expanding space, forming a stable and bright flare, which is then injected into the boiler furnace through the burner outlet.

[0046] S5. During boiler ignition or low-load stable combustion, the power supply system 3, carrier working fluid system 4, and cooling water system 5 must be continuously maintained. The plasma jet, as a stable high-intensity ignition source and auxiliary heat source, continuously provides energy support for the pulverized coal flame, ensuring successful ignition and maintaining stable combustion under low-load conditions, thus avoiding the high costs and pollution associated with operating large oil guns.

[0047] S6. Once the boiler combustion gradually intensifies, the main burner is put into operation, and the boiler enters a stable and normal operating state, the plasma ignition system can be phased out in an orderly manner.

[0048] First, power system 3 is shut off, extinguishing the arc between the cathode and anode, causing the plasma jet to disappear. Then, carrier working fluid system 4 is shut off, stopping the supply of compressed air. Finally, after confirming that the internal temperature of plasma generator 1 has sufficiently decreased, cooling water system 5 is shut off, stopping cooling water circulation. At this point, the plasma ignition system has completely ceased operation.

[0049] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A plasma ignition system, characterized in that, include: A plasma generator (1) includes an anode and a cathode arranged coaxially; the anode is a cylindrical structure, the cathode is located at the axial center of the anode, and an arc cavity is formed between the anode and the cathode; the plasma generator (1) also includes a cooling water cavity arranged around the arc cavity; a compressed air inlet communicating with the arc cavity is provided on the cylindrical wall of the anode, and a plasma jet outlet communicating with the arc cavity is provided at one end of the anode; The plasma burner (2) includes a primary central cylinder, a secondary combustion cylinder and an outer wall cylinder that are coaxially arranged along the direction of pulverized coal flow; the inlet of the primary central cylinder is connected to the plasma jet outlet, and the outer wall cylinder is provided with a pulverized coal flow inlet, which is connected to the interface of the boiler burner (6). The power supply system (3) includes an isolation transformer and a rectifier cabinet; the output terminal of the isolation transformer is connected to the input terminal of the rectifier cabinet, and the DC output terminal of the rectifier cabinet is electrically connected to the cathode and anode of the plasma generator (1); The carrier working fluid system (4) is connected to the compressed air inlet via an air supply pipeline; The cooling water system (5) includes a demineralized water tank, an inlet pipe, and a return pipe; the inlet end of the inlet pipe is connected to the demineralized water tank, and the outlet end is connected to the inlet of the cooling water chamber; the inlet end of the return pipe is connected to the outlet of the cooling water chamber, and the outlet end is connected to the demineralized water tank.

2. The plasma ignition system according to claim 1, characterized in that, The cathode includes an axially extending cathode rod and a cathode head disposed at the end of the cathode rod; the cathode head extends into the arc cavity, and a discharge gap is formed between its end and the inner wall of the anode.

3. The plasma ignition system according to claim 1, characterized in that, The plasma burner (2) further includes a first-stage air inlet disposed between the first-stage central cylinder and the second-stage combustion cylinder, and a second-stage air inlet disposed between the second-stage combustion cylinder and the outer wall cylinder; both the first-stage air inlet and the second-stage air inlet are connected to the primary air system of the boiler for introducing staged cooling air.

4. The plasma ignition system according to claim 1, characterized in that, The carrier working medium system (4) includes a compressed air tank, a pressure reducing valve, a proportional valve and a pressure detection unit; the outlet of the compressed air tank is connected to the air supply pipeline in sequence through the pressure reducing valve and the proportional valve; the pressure detection unit is located on the air supply pipeline; the pressure reducing valve, the proportional valve and the pressure detection unit are all connected to the control unit.

5. A plasma ignition system according to claim 1, characterized in that, A regulating valve and a water flow switch are sequentially installed along the water flow direction on the inlet pipe; a return water pressure gauge is installed on the return water pipe; both the inlet water flow switch and the return water pressure gauge are connected to the control unit.

6. A plasma ignition system according to claim 1, characterized in that, It also includes an image flame monitoring system; the image flame monitoring system includes a flame probe, a cooling air source and a signal processing unit; the flame probe is fixed to the observation hole of the plasma burner (2) by a mounting bracket; the cooling air source is connected to the cooling air channel inlet of the flame probe through a cooling air duct; the video signal output terminal of the flame probe is connected to the signal processing unit; the signal processing unit and the control unit are connected.

7. A plasma ignition system according to claim 6, characterized in that, The central axis of the flame probe lens forms a preset angle with the outlet axis of the plasma burner (2), so that the field of view of the flame probe completely covers the outlet area of ​​the plasma burner (2).

8. A plasma ignition system according to claim 1, characterized in that, It also includes a wind speed monitoring device; the wind speed monitoring device is installed on the primary air duct that supplies coal powder airflow to the plasma burner (2) and is used to monitor the flow rate of the coal powder and air mixture in the duct online; the wind speed monitoring device is connected to the control unit.

9. A plasma ignition system according to claim 1, characterized in that, The cooling water chamber includes a sleeve coaxially sleeved on the outside of the anode, and an annular cooling channel is formed between the sleeve and the outer wall of the anode; the sleeve is respectively provided with an inlet and an outlet that communicate with the annular cooling channel.

10. A method of using a plasma ignition system according to any one of claims 1 to 9, characterized in that, Includes the following steps: Turn on the carrier working fluid system (4) to supply compressed air to the compressed air inlet, and turn on the cooling water system (5) to allow demineralized water to flow through the cooling water chamber; Start the power system (3), apply DC voltage to the cathode and anode through the rectifier cabinet, ignite the electric arc between the cathode and anode, thereby generating a high-temperature plasma jet in the arc cavity, and the plasma jet is ejected from the plasma jet outlet; The coal powder gas flow carried by the primary air is introduced into the plasma burner (2) through the coal powder gas flow inlet. The coal powder gas flow comes into contact with and is ignited by the high-temperature plasma jet ejected from the plasma jet outlet in the first-stage central cylinder. The ignited pulverized coal flame mixes with the air introduced in stages within the progressively expanding combustion space formed by the primary central cylinder, the secondary combustion cylinder, and the outer wall cylinder, achieving staged stable combustion. During the boiler ignition or low-load stable combustion stage, the power supply system (3), carrier working fluid system (4) and cooling water system (5) are maintained to continuously provide ignition source; when the boiler enters normal operation, the power supply system (3), carrier working fluid system (4) and cooling water system (5) are shut down in sequence, and the plasma burner (2) is used as a regular burner.

Images