Stable combustion system and operation method thereof

Abstract

The invention discloses a stable combustion system and an operation method thereof. The stable-combustion combustion system comprises a Venturi tube used for carrying out concentration separation on primary air pulverized coal flowing in so as to divide the primary air pulverized coal into a high-concentration pulverized coal flow and a low-concentration pulverized coal flow; the central pipeline is used for conveying high-concentration pulverized coal flow to the pre-combustion chamber, and the inlet end of the central pipeline is connected with the outlet end of the Venturi tube; the pre-combustion chamber is used for forming a pulverized coal torch based on the high-concentration pulverized coal flow, and the inlet end of the pre-combustion chamber is connected with the outlet end of the central pipeline; and the nozzle pipeline is used for converging a pulverized coal torch generated by the pre-combustion chamber with the low-concentration pulverized coal flow, so that the pulverized coal torch ignites the low-concentration pulverized coal flow. The coal powder which is high in concentration, low in flow rate and under the protection of a strong stable combustion structure is successfully ignited in the pre-combustion chamber by utilizing the extremely small oil amount, so that oil-free stable operation of the boiler under the ultra-low load and remarkable oil saving in the cold state ignition process are realized, and the economical efficiency and the reliability of low-load stable combustion of the pulverized coal boiler are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of boiler combustion technology, and in particular to a stable combustion system and its operation method. Background Technology

[0002] The low-load stable combustion capability and ignition / auxiliary fuel consumption of pulverized coal boilers are key indicators affecting the operational flexibility, economy, and reliability of power plants. Against the backdrop of increasingly urgent energy structure transformation and deep peak-shaving demands, developing combustion technologies capable of stable operation at ultra-low loads with significant fuel savings has become a key research focus for the industry.

[0003] Currently, the mainstream stable combustion technologies mainly include rich-lean separation combustion technology, as well as micro-oil ignition and plasma ignition technologies. The former uses structures such as louvers, elbow centrifugal force, or cyclone separators to create a difference in pulverized coal concentration at the burner inlet to improve local ignition stability; the latter uses oil guns or plasma to ignite a small amount of pulverized coal to form a stable ignition source before igniting the main pulverized coal airflow.

[0004] However, existing burners generally employ passive separation mechanisms such as elbow centrifugal force, louvered grids, or swirl blades. Their concentration-to-lean separation efficiency is easily affected by pulverized coal particle size distribution, moisture content, and primary air velocity fluctuations, resulting in insufficient and significantly fluctuating high-concentration pulverized coal flow, thus impacting stable combustion performance. Furthermore, existing stable combustion burners often rely on high-power micro-oil guns or plasma igniters as auxiliary heat sources, failing to fully realize their actual fuel-saving potential and limiting their economic advantages. Summary of the Invention

[0005] In view of this, the present invention provides a stable combustion system and its operation method to solve the technical problems of low and unstable rich-lean separation efficiency of existing stable combustion technology, which still relies on a high-power auxiliary heat source, resulting in poor fuel saving effect and limited economy.

[0006] Firstly, a stable combustion system is provided, the system comprising: A venturi tube is used to separate the concentration of pulverized primary air into high-concentration and low-concentration pulverized primary air streams. The central pipe is used to deliver a high-concentration pulverized coal stream to the pre-combustion chamber. The inlet end of the central pipe is connected to the outlet end of the Venturi tube. The pre-combustion chamber is used to form a pulverized coal flare based on a high-concentration pulverized coal flow. The inlet end of the pre-combustion chamber is connected to the outlet end of the central pipeline. The nozzle pipe is used to merge the pulverized coal flare generated in the pre-combustion chamber with the low-concentration pulverized coal stream, so that the pulverized coal flare ignites the low-concentration pulverized coal stream.

[0007] Secondly, a method for operating a stable combustion system is provided, the method comprising: In response to the pulverized coal ignition request, the stable combustion system is activated, allowing primary air and pulverized coal to enter the stable combustion system through the inlet pulverized coal pipe; Part of the pulverized coal flow in the inlet pulverized coal pipe enters the Venturi tube for concentration separation, forming a high-concentration pulverized coal flow and a low-concentration pulverized coal flow. High-concentration pulverized coal flows through the central pipeline into the pre-combustion chamber, where it is ignited by the oil flames generated by the micro oil gun and ignition gun to form a pulverized coal torch, which is then transported to the nozzle pipeline. The remaining pulverized coal that did not enter the Venturi tube and the low-concentration pulverized coal that did not enter the central pipeline are transported to the nozzle pipeline through the annular cavity channel; The pulverized coal torch inside the nozzle ignites the low-concentration pulverized coal stream and the remaining pulverized coal.

[0008] The aforementioned stable combustion system and its operation method utilize a minimal amount of oil to successfully ignite high-concentration, low-flow-rate pulverized coal protected by a strong stable combustion structure within the pre-combustion chamber. This forms a small, highly energy-density, and extremely stable flare, achieving staged ignition and stable combustion by igniting a large flame with a small flame. This stable, high-intensity flare generated in the pre-combustion chamber serves as a reliable main ignition source, positioned at the pre-combustion chamber outlet and directly acting on the primary airflow of pulverized coal flowing out of the annular cavity, achieving efficient and reliable ignition. This significantly reduces reliance on traditional ignition oil guns, requiring only a minimal amount of oil to maintain combustion within the pre-combustion chamber itself, and relying on the high-intensity flare generated to ignite the main airflow. Ultimately, this achieves oil-free stable operation of the boiler under ultra-low loads and significant oil savings during cold ignition, fundamentally solving the technical challenges of economic efficiency and reliability in low-load stable combustion of pulverized coal boilers. Attached Figure Description

[0009] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 This is a schematic diagram of the stable combustion system in one embodiment of the present invention.

[0010] in, Figure 1 The correspondence between the reference numerals and component names in the attached drawings is as follows: 100 Stable combustion system; 101 Venturi tube; 102 Central duct; 103 Pre-combustion chamber; 104 Nozzle duct; 105 Inlet powder duct; 106 Elbow; 107 Oil gun combustion air sleeve; 108 Micro oil gun; 109 Ignition gun; 110 First blunt body; 111 Second blunt body; 112 Swirl secondary air duct; 113 Secondary air swirl blade. Detailed Implementation

[0011] 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. It should be understood that the accompanying drawings in the present invention are only for illustrative and descriptive purposes and are not intended to limit the scope of protection of the present invention.

[0012] Furthermore, it should be understood that the schematic drawings are not drawn to scale. The flowcharts used in this invention illustrate operations implemented according to some embodiments of the invention. It should be understood that the operations in the flowcharts may not be implemented in sequence, and steps without logical contextual relationships may be reversed or performed simultaneously. Moreover, those skilled in the art, guided by the content of this invention, may add one or more other operations to the flowcharts, or remove one or more operations from the flowcharts.

[0013] Furthermore, the embodiments described herein are merely some, not all, of the embodiments of the invention. The components of the embodiments of the invention described and illustrated herein can typically be arranged and designed in various different configurations. 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.

[0014] It should be noted that the term "comprising" will be used in the embodiments of the present invention to indicate the presence of a feature subsequently declared, but does not exclude the addition of other features. It should also be noted that similar reference numerals 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.

[0015] The following is a detailed description of this case, in conjunction with the relevant accompanying drawings in the instruction manual.

[0016] Please see Figure 1 This embodiment provides a stable combustion system 100, including: a Venturi tube 101, a central pipe 102, a pre-combustion chamber 103, and a nozzle pipe 104. The Venturi tube 101 is used to separate the incoming primary air pulverized coal into a high-concentration pulverized coal stream and a low-concentration pulverized coal stream; the central pipe 102 is used to deliver the high-concentration pulverized coal stream to the pre-combustion chamber 103, and its inlet end is connected to the outlet end of the Venturi tube 101; the pre-combustion chamber 103 is used to form a pulverized coal flare based on the high-concentration pulverized coal stream, and its inlet end is connected to the outlet end of the central pipe 102; the nozzle pipe 104 is used to merge the pulverized coal flare generated in the pre-combustion chamber 103 with the low-concentration pulverized coal stream, so that the pulverized coal flare ignites the low-concentration pulverized coal stream.

[0017] In this embodiment, a venturi tube 101 located at the front end of the system performs initial concentration separation on the primary air pulverized coal stream entering the stable combustion system 100, dividing the primary air pulverized coal stream into two streams of high concentration and low concentration, forming a preliminary distribution pattern of concentrated coal in the center and less concentrated coal around the edges. Subsequently, the high-concentration pulverized coal stream enters the central pipe 102 through the outlet of the venturi tube 101, and is then transported to the pre-combustion chamber 103 via the central pipe 102, ensuring that only a high-concentration pulverized coal stream enters the pre-combustion chamber 103. In the pre-combustion chamber 103, a small spark can ignite the high-concentration pulverized coal stream, forming a stable, high-temperature pulverized coal flare. Finally, the high-temperature pulverized coal torch generated in the pre-combustion chamber 103 merges with the low-concentration main pulverized coal flow at the nozzle pipe 104. As a powerful active ignition source, the pulverized coal torch transfers its enormous heat to the low-concentration pulverized coal flow. The high temperature causes the volatiles in the low-concentration pulverized coal to be rapidly released and reach the ignition temperature, thereby achieving efficient and reliable ignition of the low-concentration pulverized coal flow.

[0018] Optionally, the front end of the pre-combustion chamber 103 adopts a gradually expanding section structure to reduce the flow velocity of the pulverized coal airflow and prevent the flame from being blown out due to excessive airflow velocity.

[0019] In one embodiment, the system further includes: an inlet pulverized coal pipe 105 and an elbow 106, wherein the inlet pulverized coal pipe 105 is used to introduce primary air pulverized coal, and a venturi tube 101 is disposed inside the inlet pulverized coal pipe 105; the elbow 106 has its inlet end connected to the outlet end of the inlet pulverized coal pipe 105, and a central pipe 102 is disposed inside the elbow 106.

[0020] In this embodiment, after the primary air pulverized coal enters the burner through the inlet pulverized coal pipe 105, some of the pulverized coal flows through the Venturi tube 101 located inside the inlet pulverized coal pipe 105, where it undergoes preliminary concentration before entering the bend 106, forming a distribution with a concentrated center and a less concentrated periphery. At this time, the high-concentration and low-concentration fluids are not yet physically separated and there is still a possibility of mixing. Since the outlet of the Venturi tube 101 is directly opposite the inlet of the central pipe 102, the central pulverized coal flow with high inertia and high concentration is precisely guided into the central pipe 102 through a preset path; while the remaining pulverized coal, including the low-concentration pulverized coal flow around the Venturi tube 101 and the pulverized coal that did not enter the Venturi tube 101 at all, is blocked outside the central pipe 102.

[0021] By combining the pre-positioned Venturi tube 101 and the sleeve-type elbow 106 separation structure at the burner inlet, a dual mechanism of "Venturi pre-concentration + elbow active diversion" is formed. Compared with the passive separation method that relies solely on fluid inertia or louvers, this mechanism achieves a more precise and controllable concentration-to-lean separation effect, ensuring that the extremely high concentration of pulverized coal enters the pre-combustion chamber 103, laying the foundation for subsequent reliable ignition and high-intensity combustion, while also reserving a high-intensity ignition source for the large amount of low-concentration main pulverized coal in the annular cavity channel for efficient ignition.

[0022] In one embodiment, the outer wall of the central pipe 102 and the inner wall of the elbow 106 form an annular cavity channel, which is used to constrain and guide the flow of low-concentration pulverized coal.

[0023] In this embodiment, an annular, hollow interlayer chamber is formed between the inner wall of the elbow 106 and the outer wall of the central pipe 102 to confine low-concentration pulverized coal and unseparated pulverized coal, and guide their flow along the annular path. This chamber achieves precise control of the pulverized coal flow stream, physically isolating the high- and low-concentration pulverized coal flows, and effectively preventing the two airflows from remixing within the elbow 106.

[0024] By constructing a dedicated channel for the low-concentration pulverized coal flow inside the elbow 106, the initial concentration results are solidified and enhanced. The two-phase flow of concentrated and diluted coal that might have mixed again is completely separated and introduced into dedicated channels, laying a decisive foundation for subsequent staged ignition.

[0025] In one embodiment, the system further includes: a fuel gun combustion air sleeve 107, a micro fuel gun 108, and an ignition gun 109. The fuel gun combustion air sleeve 107 provides combustion air, and its outlet end is connected to the inlet end of the pre-combustion chamber 103. The micro fuel gun 108 is disposed within the fuel gun combustion air sleeve 107 and is used to spray atomized fuel to provide an oil flame for the pre-combustion chamber 103. The ignition gun 109 is disposed within the fuel gun combustion air sleeve 107 and is used to generate an electric spark to ignite the fuel sprayed from the micro fuel gun 108.

[0026] In this embodiment, the oil gun combustion air sleeve 107 serves as an air supply and cooling channel, providing the necessary oxygen for the combustion of the micro oil gun 108. Its outlet directly leads to the pre-combustion chamber 103, ensuring that the combustion air and flame are precisely delivered to the ignition position to form a high-temperature flame and avoid the generation of black smoke. Simultaneously, the air flowing inside the sleeve cools the micro oil gun 108 and the ignition gun 109, preventing them from being burned by their own high-temperature flames. The micro oil gun 108 atomizes the fuel into extremely fine droplets, greatly increasing the contact area with air, thus enabling rapid and stable ignition and forming a concentrated initial ignition heat source (i.e., an oil flame). The ignition gun 109 generates a high-energy spark, performing the final action of igniting the atomized fuel sprayed from the micro oil gun 108. These three components are integrated within the same sleeve, forming a stable oil flame used to ignite the high-concentration pulverized coal flow passing through the pre-combustion chamber 103, thereby forming a larger-scale pulverized coal flare. This allows a reliable ignition source to be generated with a very small amount of oil, which in turn ignites the entire subsequent combustion chain.

[0027] In one embodiment, the system further includes: combustion-supporting cyclone vanes (not shown in the figure) and a micro-oil gun flame stabilizer (not shown in the figure). The combustion-supporting cyclone vanes are disposed at the outlet of the oil gun combustion air sleeve 107, and are used to rotate the passing combustion air; the micro-oil gun flame stabilizer is disposed around the outlets of the ignition gun 109 and the micro-oil gun 108, and is used to stabilize the oil flame.

[0028] In this embodiment, to ensure that the oil flame, serving as the ignition source, possesses sufficient intensity and resistance to blowout, a combustion air swirl vane is installed at the outlet of the oil gun combustion air sleeve 107, causing the originally directly injected combustion air to form a rotating flow field. The rotating air mixes more vigorously and thoroughly with the atomized oil droplets, greatly improving combustion efficiency and increasing flame temperature. Simultaneously, the micro-oil gun stabilizing hood installed at the flame root creates a low-pressure recirculation zone downstream of the high-speed swirling air and flame. This recirculation zone acts like a magnet, continuously drawing the high-temperature flue gas burning downstream back to the flame root. The returning high-temperature flue gas continuously provides heat to the newly ejected oil mist, effectively creating a perpetual ignition source at the flame root. Furthermore, it firmly holds the flame, preventing it from being blown away or extinguished by the high-speed primary airflow, ensuring extremely stable flame performance.

[0029] The above method transforms an easily extinguished oil flame into a compact, powerful, high-temperature, and extremely stable high-intensity torch.

[0030] In one embodiment, the system further includes a first blunt body 110 and a second blunt body 111. The first blunt body 110 is disposed within the pre-combustion chamber 103 and is used to optimize the concentration distribution of the high-concentration pulverized coal flow. The second blunt body 111 is disposed within the pre-combustion chamber 103 and located downstream of the first blunt body 110, and is used to form a high-temperature flue gas recirculation zone in the flowing high-concentration pulverized coal flow.

[0031] In this embodiment, the annular first blunt body 110 is located at the inlet of the pre-combustion chamber 103. When a high-concentration pulverized coal stream rushes in, its state may not be ideal, for example, the center may be too concentrated or the edges may be uneven. At this time, the first blunt body 110 performs a secondary combing of the pulverized coal stream, making its distribution more uniform and reasonable, laying the foundation for subsequent efficient combustion. After being combed and evenly distributed, the pulverized coal stream and the flame pass through the second blunt body 111 located downstream, creating a high-temperature flue gas recirculation zone behind it. This recirculation zone acts like a magnet, continuously drawing back the high-temperature flue gas generated by downstream combustion, directly heating the newly injected pulverized coal. This constitutes a continuous and stable high-temperature ignition source, effectively anchoring the flame, ensuring that the flame will not be blown out, and ensuring a stable and intense combustion process.

[0032] Optionally, the first blunt body 110 is an annular blunt body, and the second blunt body 111 is a V-shaped blunt body. The front end of the pre-combustion chamber 103 adopts a gradually expanding section structure to reduce the coal powder airflow velocity and prevent the high-speed airflow from extinguishing the flame. A V-shaped blunt body is arranged behind the gradually expanding section, creating a strong high-temperature flue gas recirculation zone downstream of the high-concentration coal powder airflow. This recirculation zone continuously entrains the already combusted high-temperature flue gas and newly injected coal powder within the pre-combustion chamber 103, forming a continuous and stable high-temperature ignition source and combustion heat source, becoming the core of stable combustion in the pre-combustion chamber 103. Furthermore, the annular blunt body also performs secondary sorting of the central concentrated coal powder flow, optimizing its concentration distribution. The swirling secondary air introduced around the central pipe 102 achieves a three-in-one function of "cooling-oxygen replenishment-flame stabilization," thereby directly cooling the central pipe outlet and the wall of the pre-combustion chamber 103, which are susceptible to high-temperature burn-out and coking, significantly improving equipment reliability and replenishing the necessary oxygen for combustion in the pre-combustion chamber 103. Furthermore, its swirling effect enhances airflow mixing, further strengthening the stability of the recirculation zone generated by the V-shaped blunt body and effectively controlling the flame morphology. By integrating flow field control (gradually expanding and reducing velocity), flame stabilization core (V-shaped blunt body recirculation zone), and key auxiliary functions (swirling secondary air), it becomes crucial for the pre-combustion chamber 103 to maintain a high-intensity, ultra-stable small flare under extremely low oil conditions.

[0033] The above methods ensure that high-concentration pulverized coal can be reliably ignited in the pre-combustion chamber 103 with minimal ignition energy, forming an ultra-stable high-temperature flare.

[0034] In one embodiment, the system further includes a swirl secondary air duct 112 and secondary air swirl blades 113. The swirl secondary air duct 112 is coaxially sleeved outside the pre-combustion chamber 103, and its outlet end is connected to the inlet end of the pre-combustion chamber 103. The swirl secondary air duct is used to supply secondary air to the pre-combustion chamber 103. The secondary air swirl blades 113 are disposed at the outlet of the swirl secondary air duct and are used to convert the direct current air in the swirl secondary air duct 112 into swirl air.

[0035] In this embodiment, after the high-concentration pulverized coal flow in the pre-combustion chamber 103 is ignited, a large amount of oxygen is required to maintain intense combustion and form a high-intensity flare. Secondary air, serving as the primary oxygen source, is supplied to the interior through a swirling secondary air duct 112 connected to the pre-combustion chamber 103. This duct is a coaxial annular air duct surrounding the pre-combustion chamber 103, where the direct current air is converted into swirling air by the secondary air swirling blades 113 at the outlet. This swirling air works synergistically with the second blunt body 111 to effectively expand and stabilize the high-temperature flue gas recirculation zone behind the blunt body, thereby enhancing the anchoring effect on the flame. Simultaneously, the flowing secondary air continuously cools the walls of the pre-combustion chamber 103 and the central duct outlet during transport, preventing coking and burn-out, significantly improving equipment reliability and service life.

[0036] In this way, controllable secondary air with a specific flow field is delivered, simultaneously achieving the three functions of flame stabilization, oxygen replenishment and cooling, thereby ensuring that the pre-combustion chamber 103 can generate and maintain a stable, high-temperature pulverized coal flare under extremely low oil conditions.

[0037] In one embodiment, the nozzle pipe 104 is disposed inside the boiler furnace wall, and the inlet end of the nozzle pipe 104 is connected to the outlet end of the elbow 106.

[0038] In this embodiment, the nozzle pipe 104, as the final component of the burner, is the last link in the flame injection into the furnace, and it penetrates and is embedded in the boiler furnace wall. Figure 1 Within the area indicated by the dashed line, and with the inlet connected to the outlet of elbow 106, the two pulverized coal streams separated by elbow 106—the high-temperature pulverized coal flare formed by being transported by the central pipe 102 and ignited in the pre-combustion chamber 103, and the low-concentration main pulverized coal stream transported by the annular cavity channel—are simultaneously transported to the nozzle pipe 104. The high-temperature pulverized coal flare, acting as a powerful active ignition source, transfers a large amount of heat to the low-concentration pulverized coal stream, causing its volatiles to rapidly precipitate and reach their ignition point. At this point, within the nozzle pipe 104, under sufficient heat and optimized mixing conditions, even with a low concentration of main pulverized coal, reliable and efficient ignition can still be achieved, ultimately forming a fully stable combustion state within the boiler furnace. Thus, the main fuel of the entire boiler is successfully ignited with minimal energy cost (a trace amount of fuel oil).

[0039] Optionally, the length of the nozzle pipe 104 is consistent with the thickness of the boiler furnace wall, and its outlet end face is flush with the inner wall surface of the furnace wall. This structure ensures that the nozzle pipe 104 can pass through the entire boiler furnace wall seamlessly, ensuring the stability and sealing of the installation, preventing air or powder leakage, and ensuring that the flame fully expands only after leaving the nozzle and entering the spacious furnace space, rather than spreading prematurely inside the nozzle, thus protecting the equipment. At the same time, this structure effectively prevents the nozzle metal material from being directly exposed to high-temperature flame radiation, avoiding nozzle burn-out, deformation, or coking due to overheating.

[0040] In one embodiment, the system further includes a flame detection component (not shown) for detecting the combustion state of a low-concentration pulverized coal stream.

[0041] In this embodiment, the flame detection probe of the flame detection component is inserted obliquely from the wall of the pre-combustion chamber 103, so that its detection range can fully cover the oil gun ignition area and the mainstream pulverized coal combustion area, thereby accurately monitoring the ignition process and the steady-state combustion state of the low-concentration main pulverized coal flow.

[0042] The stable combustion system 100 provided in this application successfully ignites high-concentration, low-flow-rate pulverized coal protected by a strong stable combustion structure within the pre-combustion chamber 103 using a minimal amount of oil, forming a small, highly energy-density, and extremely stable flare. This achieves staged ignition and stable combustion by igniting a large flame with a small flame. The stable, high-intensity flare generated by the pre-combustion chamber 103 serves as a reliable main ignition source, positioned at the outlet of the pre-combustion chamber 103, directly acting on the primary air and main pulverized coal airflow flowing out of the annular cavity, achieving efficient and reliable ignition. This significantly reduces reliance on traditional ignition oil guns, requiring only a minimal amount of oil to maintain combustion within the pre-combustion chamber 103 itself, and relying on the high-intensity flare generated to ignite the main airflow. Ultimately, this achieves oil-free stable operation of the boiler under ultra-low loads and significant oil savings during cold ignition, fundamentally solving the technical challenges of economic efficiency and reliability in low-load stable combustion of pulverized coal boilers.

[0043] This embodiment provides a method for operating a stable combustion system, the method comprising: S10: In response to the pulverized coal ignition request, start the stable combustion system so that the primary air and pulverized coal enter the stable combustion system through the inlet pulverized coal pipe; S20: Part of the pulverized coal flow in the inlet pulverized coal pipe enters the Venturi tube for concentration separation, forming a high-concentration pulverized coal flow and a low-concentration pulverized coal flow. S30: High-concentration pulverized coal flows through the central pipeline into the pre-combustion chamber, where it is ignited by the oil flame generated by the micro oil gun and ignition gun to form a pulverized coal torch, which is then transported to the nozzle pipeline. S40: The remaining pulverized coal that did not enter the Venturi tube and the low-concentration pulverized coal that did not enter the central pipeline are transported to the nozzle pipeline through the annular cavity channel. S50: The pulverized coal torch inside the nozzle pipe ignites the low-concentration pulverized coal stream and the remaining pulverized coal.

[0044] In this embodiment, when the boiler starts up or requires stable combustion at low load, the boiler control system issues an ignition command, and the stable combustion system starts working after receiving the command. A pre-positioned Venturi tube and a sleeve-type elbow separation structure are integrated at the system inlet. The primary air pulverized coal flow first flows through the Venturi tube located in the straight pipe section of the inlet elbow of the burner, utilizing its throttling and acceleration effect to concentrate the pulverized coal towards the center, forming an initial concentration distribution that is concentrated at the center and thin at the edges. Subsequently, under the action of inertial force, the high-concentration pulverized coal flow ejected from the Venturi tube is precisely guided into the central pipe, while the remaining primary air pulverized coal between the Venturi tube and the inlet pulverized coal pipe is diverted to the annular cavity channel between the central pipe and the outer elbow. The high-concentration pulverized coal flow in the central pipe enters the pre-combustion chamber. The front end of the pre-combustion chamber adopts a gradually expanding section structure to reduce the flow velocity and prevent the flame from being blown out. An annular first blunt body inside the pre-combustion chamber further streamlines the pulverized coal flow, forming a more optimized concentration distribution. In the horizontal section, the flame ignited by the oil gun in the pre-combustion chamber impacts the V-shaped second blunt body, creating a strong high-temperature flue gas recirculation zone behind it, entraining high-temperature flue gas and light pulverized coal in the pre-combustion chamber. Under the combined action of the triple stabilization mechanism of low-speed airflow, strong recirculation, and swirling secondary air, a high-intensity, self-sustaining stable flare is rapidly formed. The swirling secondary air simultaneously cools the central pipe outlet and the pre-combustion chamber wall, preventing burn-off and coking. Finally, the high-temperature stable flare at the pre-combustion chamber outlet directly acts on the low-concentration main pulverized coal airflow flowing out of the annular cavity channel, achieving reliable ignition at the nozzle pipe with sufficient heat and optimized spatial positioning, enabling the burner to achieve stable combustion across the entire cross-section with only an initial trace amount of fuel oil under ultra-low load.

[0045] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A stable combustion combustion system characterized by, The system comprises: a Venturi tube for performing concentration separation on the primary air pulverized coal flowing in, so as to divide the primary air pulverized coal into a high-concentration pulverized coal flow and a low-concentration pulverized coal flow; a central pipe for conveying the high-concentration pulverized coal flow to a precombustion chamber, an inlet end of the central pipe being connected with an outlet end of the Venturi tube; a precombustion chamber for forming a pulverized coal torch based on the high-concentration pulverized coal flow, an inlet end of the precombustion chamber being connected with an outlet end of the central pipe; a nozzle pipe for combining the pulverized coal torch generated by the precombustion chamber with the low-concentration pulverized coal flow, so that the pulverized coal torch ignites the low-concentration pulverized coal flow.

2. The stable flame combustion system of claim 1, wherein, The system further comprises: an inlet powder pipe for introducing the primary air pulverized coal, the Venturi tube being arranged in the inlet powder pipe; an elbow, an inlet end of the elbow being connected with an outlet end of the inlet powder pipe, the central pipe being arranged in the elbow.

3. The stable combustion system according to claim 2, wherein an outer wall of the central pipe and an inner wall of the elbow enclose a ring cavity channel, the ring cavity channel being used for restraining and guiding the flow of the low-concentration pulverized coal flow.

4. The stable flame combustion system of claim 1, wherein The system further comprises: an oil gun combustion-supporting air sleeve pipe for providing combustion-supporting air, an outlet end of the oil gun combustion-supporting air sleeve pipe being connected with the inlet end of the precombustion chamber; a micro oil gun arranged in the oil gun combustion-supporting air sleeve pipe, the micro oil gun being used for spraying atomized fuel oil to provide an oil flame for the precombustion chamber; an ignition gun arranged in the oil gun combustion-supporting air sleeve pipe, the ignition gun being used for generating an electric spark to ignite the fuel oil sprayed by the micro oil gun.

5. The stable flame combustion system of claim 4, wherein, The system further comprises: combustion-supporting cyclone swirling vane blades arranged at an outlet of the oil gun combustion-supporting air sleeve pipe, the combustion-supporting cyclone swirling vane blades being used for making the combustion-supporting air passing through rotate; a micro oil gun stable combustion cover arranged at the periphery of the outlet of the ignition gun and the micro oil gun, the micro oil gun stable combustion cover being used for stabilizing the oil flame.

6. The stable flame combustion system of claim 1, wherein, The system further comprises: a first bluff body arranged in the precombustion chamber, the first bluff body being used for optimizing the concentration distribution of the high-concentration pulverized coal flow; a second bluff body arranged in the precombustion chamber and located downstream of the first bluff body, the second bluff body being used for forming a high-temperature flue gas backflow area in the high-concentration pulverized coal flow flowing therethrough.

7. The stable flame combustion system of claim 1, wherein The system further comprises: a swirling secondary air pipe coaxially sleeved outside the precombustion chamber, an outlet end of the swirling secondary air pipe being connected with the inlet end of the precombustion chamber, the swirling secondary air pipe being used for conveying secondary air to the precombustion chamber; secondary air swirling vane blades arranged at an outlet of the swirling secondary air sleeve pipe, the secondary air swirling vane blades being used for converting straight-flow air in the swirling secondary air pipe into swirling air.

8. The stable combustion system according to claim 1, wherein the nozzle pipe is arranged in a boiler wall, and an inlet end of the nozzle pipe is connected with an outlet end of the elbow.

9. The stable flame combustion system of claim 1, wherein, The system further comprises: a flame detection assembly for detecting the combustion state of the low-concentration pulverized coal flow.

10. A method of operating a stable combustion system according to any one of claims 1 to 9, characterized in that The method comprises: in response to a pulverized coal ignition request, starting the stable combustion system, so that the primary air pulverized coal enters the stable combustion system through the inlet powder pipe; part of the pulverized coal flow in the inlet powder pipe enters the Venturi tube to perform concentration separation, forming a high-concentration pulverized coal flow and a low-concentration pulverized coal flow; The high-concentration coal powder flows through the central pipe into the pre-combustion chamber, and the oil flame generated by the micro-oil gun and the ignition gun ignites the coal powder torch, which is then transported to the nozzle pipe; The remaining coal powder that does not enter the Venturi tube and the low-concentration coal powder that does not enter the central pipe flow through the ring cavity channel to the nozzle pipe; The coal powder torch in the nozzle pipe ignites the low-concentration coal powder flow and the remaining coal powder.

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