Coarse particle pulverized coal efficient cracking method and plasma nozzle structure

Abstract

The invention provides a coarse particle pulverized coal efficient cracking method and a plasma nozzle structure, and the plasma nozzle structure comprises a plasma and pulverized coal nozzle which is used for spraying coarse pulverized coal to a stepped expansion stage by using ultra-high temperature plasma jet; a high-temperature area is formed in the stepped expansion stage, and is used for crushing the coarse coal powder to form micron-sized porous carbon particles; the stabilizing and transition area is used for stabilizing the flow field and smoothly transiting to the contraction section; in the contraction stage, the movement path of the micron-sized porous carbon particles is increased by utilizing a shear layer formed in an inner cavity, the effective retention time of the micron-sized porous carbon particles at high temperature is prolonged, and sufficient ignition is ensured; by improving the flame stability under the low load, the boiler can operate safely and stably under the lower load, and the capacity of a power plant participating in power grid peak regulation is directly enhanced.

Description

Technical Field

[0001] This invention belongs to the field of clean combustion technology, specifically relating to a method for efficient pyrolysis of coarse-particle coal powder and a plasma nozzle structure. Background Technology

[0002] Plasma ignition and combustion-assisted technology is an important component of clean coal combustion technology, especially for low-rank coals (such as lignite and lean coal) with poor combustion characteristics that require oil-assisted combustion. This technology uses a high-temperature, highly active jet (temperatures can reach 3000~5000℃) generated by a plasma torch to instantly ignite pulverized coal, achieving oil-free boiler start-up and stable combustion, with economic and environmental advantages.

[0003] High-volatile coal powder is theoretically easy to ignite. However, in practical applications, especially for coarsely ground coal powder with high moisture content, the ignition process faces significant challenges: (1) Large particle inertia: Coarse coal powder is difficult to deflect and mix fully with the airflow in the nozzle, and easily passes directly through the high temperature zone without being fully heated.

[0004] (2) Delayed thermal decomposition process: Coarse coal powder requires more time to complete the evaporation of internal moisture and the precipitation of volatiles. Within the limited nozzle length and residence time, only surface pyrolysis often occurs, while the interior remains a "cold core", resulting in incomplete combustion.

[0005] (3) Insufficient thermal decomposition: Traditional nozzles only provide a heating environment and lack an active "crushing" mechanism. Coarse coal powder cannot be effectively broken down, and its specific surface area cannot be significantly increased, which limits the subsequent reaction rate.

[0006] Therefore, existing plasma ignition technology generally has a low ignition rate for coarse pulverized coal, resulting in high ignition energy requirements, unstable combustion, and even the risk of unburned pulverized coal explosion, which limits the economic benefits and reliability of this technology in power plants.

[0007] Currently, the solutions adopted in the existing technology to address the above problems are: (1) Multi-stage sleeve structure, designed with the concept of staged combustion. That is: plasma with a smaller ignition energy ignites part of the pulverized coal in the first stage cylinder, the flame after the first stage cylinder ignites part of the pulverized coal in the second stage cylinder, and so on, igniting the pulverized coal in the third stage cylinder and the nozzle, thereby achieving staged combustion.

[0008] (2) The concentrated-dilute separation nozzle structure mainly revolves around the pulverized coal gas flow itself. Before entering the furnace, a pulverized coal gas flow is separated into two streams with high concentration and low concentration through a special design, and then sent into the furnace through different nozzles.

[0009] However, the existing technology has the following drawbacks: (1) The structure is complex, and the manufacturing and maintenance costs are high; (2) The residence time of pulverized coal is short, making staged combustion difficult to achieve; (3) The flow field distribution is unstable, resulting in incomplete combustion. Summary of the Invention

[0010] The purpose of this invention is to provide a high-efficiency pyrolysis method for coarse-particle coal powder and a plasma nozzle structure, which solves the problem that traditional plasma burners cannot achieve staged combustion function when the operating conditions of the burner matched with the coal mill are significantly different from those of low-speed and medium-speed mills.

[0011] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a high-efficiency pyrolysis plasma nozzle structure for coarse-particle coal powder, comprising: Plasma and pulverized coal nozzles are used to inject coarse pulverized coal into the stepped expansion stage using ultra-high temperature plasma jets. During the stepped expansion stage, a high-temperature zone is formed to crush coarse coal powder into micron-sized porous carbon particles. The stabilization and transition zone is used to stabilize the flow field and smoothly transition to the contraction section; During the contraction phase, the shear layer formed within the cavity increases the movement path of the micron-sized porous carbon particles, prolongs the effective residence time of the micron-sized porous carbon particles at high temperatures, and ensures complete ignition.

[0012] Preferably, the inner cavity of the stepped expansion stage is a stepped shaft structure, and the diameter of the stepped shaft structure increases sequentially from the plasma and pulverized coal nozzle side to the stable and transition zone side, and the inner cavity diameter of the stepped shaft structure on the side closer to the plasma and pulverized coal nozzle is larger than the diameter of the plasma and pulverized coal nozzle.

[0013] Preferably, the inner cavity of the stabilization and transition zone has a constant diameter structure, and its inner diameter is smaller than that of the plasma and pulverized coal nozzles.

[0014] Preferably, the inner cavity of the contraction stage has a gradually shrinking structure, which decreases in size sequentially from the stabilization and transition zone to the outlet.

[0015] Preferably, the outlet of the contraction stage is connected to a flame outlet to eject the fully ignited supersonic high-temperature jet.

[0016] Secondly, the present invention provides a method for efficient pyrolysis of coarse-particle coal powder, comprising the following steps: Coarse coal powder particles are injected into a stepped expansion stage using an ultra-high temperature plasma jet. The inner cavity of the stepped expansion stage has a high-temperature reflux zone, which is used to apply extreme thermal shock to the coarse coal powder, so that the coarse coal powder is crushed into micron-sized porous carbon particles, forming a gas-solid mixture. The gas-solid mixture formed is smoothly transitioned to the contraction stage through a stabilization and transition zone. The micron-sized porous carbon particles are repeatedly entrained by the vortex generated by the shear layer formed in the inner cavity during the contraction phase, so as to prolong their effective residence time in the high-temperature region and ensure complete ignition. The supersonic high-temperature jet, after being fully ignited, is ejected through the flame outlet.

[0017] Preferably, the inner cavity of the stepped expansion stage is a stepped shaft structure, and the diameter of the stepped shaft structure increases sequentially from the plasma and pulverized coal nozzle side to the stable and transition zone side, and the inner cavity diameter of the stepped shaft structure on the side closer to the plasma and pulverized coal nozzle is larger than the diameter of the plasma and pulverized coal nozzle.

[0018] Preferably, the inner cavity of the stabilization and transition zone has a constant diameter structure, and its inner diameter is smaller than that of the plasma and pulverized coal nozzles.

[0019] Preferably, the inner cavity of the contraction stage has a gradually shrinking structure, which decreases in size sequentially from the stabilization and transition zone to the outlet.

[0020] Preferably, the coarse-particle coal powder R 90 Greater than 30%.

[0021] Compared with the prior art, the beneficial effects of the present invention are: This invention provides a high-efficiency plasma nozzle structure for the pyrolysis of coarse-particle coal powder. Through a combination of stepped expansion, stable transition, and accelerated contraction, it achieves revolutionary optimization of the pyrolysis process of coarse-particle coal powder. Specifically: This fundamentally solves the core problem of incomplete combustion of coarse pulverized coal. The stepped expansion stage utilizes abrupt cross-sections to form a stable high-temperature reflux zone, applying extreme thermal shock to the pulverized coal. This induces the instantaneous evaporation and expansion of internal moisture and volatiles, generating a "micro-explosion" effect. This process in situ pulverizes coarse particles into micron-sized porous carbon particles with a larger specific surface area. This synergistic physicochemical process... R 90 The ignition rate of coarse lignite powder with a content of >30% is increased to nearly 85%, which greatly improves the burnout rate and reduces the heat loss due to incomplete mechanical combustion.

[0022] The supersonic jet formed in the contraction section possesses both high rigidity and strong penetrating power, effectively resisting complex airflow interference within the furnace. This provides an extremely stable, high-intensity fire core for the furnace's stable combustion zone, thus completely solving the problems of flameout and deflagration that easily occur in traditional burners when burning low-quality coal or operating at low loads. This significantly enhances the boiler's operational safety and adaptability across a wide load range. Furthermore, this design overcomes the challenges of high-moisture, difficult-to-crack lignite. Its efficient thermal shock and particle refinement mechanism are also applicable to processing other difficult-to-burn coal types such as lean coal, anthracite, and even biomass pellets, greatly expanding the range of fuel sources and operational flexibility for power plants.

[0023] At the same time, by improving flame stability under low load, the boiler can operate safely and stably under even lower loads, which directly enhances the power plant's ability to participate in grid peak shaving and brings considerable economic and environmental benefits.

[0024] Furthermore, through a stepped expansion-contraction geometric structure, the thermodynamic and hydrodynamic processes of the gas-solid two-phase flow are precisely controlled, ensuring that the pulverized coal forms a strong and stable combustion zone and flow field state within the cavity; by utilizing the ultra-strong thermal shock, the pulverized coal can instantly generate a "micro-explosion" effect, thereby obtaining finer micron-sized pulverized coal particles. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the process involved in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure involved in an embodiment of the present invention; The stages are: 1. Plasma and pulverized coal nozzle; 2. Stepped expansion stage; 3. Stabilization and transition zone; 4. Contraction stage; 5. Flame outlet. Detailed Implementation

[0026] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0027] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0028] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0029] As used in this application specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if detected [the described condition or event]" may be interpreted, depending on the context, as meaning "once determined," "in response to determination," "once detected [the described condition or event]," or "in response to detection [the described condition or event]."

[0030] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0031] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0032] Example 1 This embodiment provides a high-efficiency pyrolysis plasma nozzle structure for coarse-particle coal powder, comprising: Plasma and pulverized coal nozzles are used to inject coarse pulverized coal into the stepped expansion stage using ultra-high temperature plasma jets. During the stepped expansion stage, a high-temperature zone is formed to crush coarse coal powder into micron-sized porous carbon particles. The stabilization and transition zone is used to stabilize the flow field and smoothly transition to the contraction section; During the contraction phase, the shear layer formed within the cavity increases the movement path of the micron-sized porous carbon particles, prolongs the effective residence time of the micron-sized porous carbon particles at high temperatures, and ensures complete ignition.

[0033] Example 2 This embodiment provides a high-efficiency pyrolysis plasma nozzle structure for coarse-particle pulverized coal, comprising a plasma and pulverized coal nozzle 1, a stepped expansion stage 2, a stabilization and transition zone 3, a contraction stage 4, and a flame outlet 5, wherein: The plasma and pulverized coal nozzle are sequentially connected to the stepped expansion stage, the stable and transition zone, the contraction stage, and the flame outlet.

[0034] The inner cavity of the stepped expansion stage has a stepped shaft structure, and the diameter of the stepped shaft structure increases sequentially from the plasma and pulverized coal nozzle side to the stable and transition zone side.

[0035] The inner diameter of the stable and transition zone is smaller than the inner diameter of the plasma and pulverized coal nozzles.

[0036] The inner cavity of the contraction phase has a gradually shrinking structure, which decreases in size sequentially from the stable and transition zone to the flame outlet side.

[0037] The plasma and pulverized coal nozzle is used to utilize the ultra-high temperature plasma jet from the self-plasma generator to propagate coarse pulverized coal ( R 90 Spraying is carried out when the concentration is >30%.

[0038] The stepped expansion stage is the primary reaction zone, i.e., the pyrolysis chamber. Abrupt cross-sectional changes are used to anchor and stabilize the reflux zone, preventing it from oscillating and ensuring the formation of the high-temperature zone. Here, coarse coal powder undergoes extreme thermal shock, causing internal moisture and volatiles to evaporate and expand instantaneously, producing a "micro-explosion" effect that pulverizes it into micron-sized porous carbon particles.

[0039] The stabilization and transition zone is the narrowest part of the channel, which plays a role in stabilizing the flow field of the entire section and smoothly transitioning to the contraction section.

[0040] The contraction stage is the secondary reaction zone. Its smooth contraction angle, equivalent to the taper section of a Laval nozzle, accelerates the airflow to supersonic speeds, forming a jet with powerful penetrating force. Simultaneously, a shear layer forms between the high-speed core airflow and the wall boundary layer, creating a significant velocity gradient. Micron-sized particles are repeatedly entrained by vortices within this shear layer, greatly increasing the movement path of the pulverized coal and thus extending its effective residence time at high temperatures, ensuring complete combustion.

[0041] In this embodiment, the nozzle structure of current mainstream plasma burners is simple, and their flow field design either fails to effectively extend the residence time of pulverized coal or fails to promote the combustion of coarse particles. Their design intention is to "heat" rather than process "pulverized coal". However, the high-efficiency pyrolysis plasma nozzle for coarse pulverized coal of this application has the following effects: (1) It solves the problem of incomplete and insufficient combustion of coarse coal powder particles. The coarse coal powder particles ( R 90The ignition rate (>30%) was increased to nearly 85%; since the pulverized coal has already undergone refinement and full combustion in the nozzle, it can be fully combusted more quickly after entering the furnace, which improves the burnout rate of pulverized coal and reduces the heat loss from incomplete mechanical combustion.

[0042] (2) It solves the problems of flameout and deflagration in traditional burners. The supersonic, high-rigidity jet from the nozzle can effectively resist airflow interference inside the furnace, providing a stable and powerful high-temperature fire core for stable combustion in the furnace. It greatly enhances the flame stability when under low load or burning low-quality coal.

[0043] (3) This design overcomes the difficulties of coarse-grained, high-moisture lignite. It can also efficiently process other difficult-to-burn coal types (such as lean coal and anthracite) or biomass pellets, broadening the range and flexibility of fuel sources for power plants.

[0044] (4) It solves the problem of unstable combustion in power plants at low loads. The high-intensity and high-stability pyrometallurgical energy enables the boiler to operate safely and stably at even lower loads, enhancing the flexibility of power grid peak shaving.

[0045] Example 3 This embodiment provides a method for high-efficiency pyrolysis of coarse-particle coal powder, including the following steps: Coarse coal powder particles are injected into a stepped expansion stage using an ultra-high temperature plasma jet. The inner cavity of the stepped expansion stage has a high-temperature reflux zone, which is used to apply extreme thermal shock to the coarse coal powder, so that the coarse coal powder is crushed into micron-sized porous carbon particles, forming a gas-solid mixture. The gas-solid mixture formed is smoothly transitioned to the contraction stage through a stabilization and transition zone. The micron-sized porous carbon particles are repeatedly entrained by the vortex generated by the shear layer formed in the inner cavity during the contraction phase, so as to prolong their effective residence time in the high-temperature region and ensure complete ignition. The supersonic high-temperature jet, after being fully ignited, is ejected through the flame outlet.

[0046] In this embodiment, an extreme thermal shock is first applied to coarse coal powder using a stable high-temperature reflux zone formed during a stepped expansion stage. This induces the instantaneous evaporation and expansion of internal moisture and volatiles, generating a "micro-explosion" effect. This process pulverizes the originally difficult-to-ignite coarse particles in situ into micron-sized porous carbon particles with a larger specific surface area. This synergistic physicochemical process fundamentally solves the problem of incomplete combustion of coarse coal powder. R 90The ignition rate of coarse-grained lignite powder (>30%) is significantly increased from less than 50% under traditional technology to nearly 85%, significantly improving the burnout rate and reducing heat loss from incomplete mechanical combustion. Subsequently, a stable transition zone ensures a smooth transition of the gas-solid mixture flow field, effectively preventing flame interruption or backfire. During the critical contraction phase, the formed supersonic jet and its generated shear layer vortex repeatedly entrain the refined micron-sized carbon particles, greatly extending the effective residence time of the particles in the high-temperature region and ensuring full ignition. At the same time, the formed supersonic high-rigidity jet effectively resists airflow interference inside the furnace, providing an extremely stable high-intensity fire core for the stable combustion zone of the furnace. This completely solves the problems of flameout and deflagration that easily occur in traditional burners when burning low-quality coal or operating at low loads, significantly enhancing the safety and load adaptability of boiler operation. In addition, this efficient pyrolysis method not only overcomes the combustion difficulties of high-moisture lignite, but is also applicable to the processing of difficult-to-burn fuels such as lean coal, anthracite and biomass pellets, greatly expanding the range of fuel choices and operational flexibility of power plants. Its improved low-load stable combustion capability further enhances the power plant's ability to participate in grid peak shaving, bringing considerable economic benefits and environmental value.

[0047] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application 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 this application, and should all be included within the protection scope of this application.

Claims

1. A high-efficiency plasma nozzle structure for coarse-particle coal pyrolysis, characterized in that, include: Plasma and pulverized coal nozzles are used to inject coarse pulverized coal into the stepped expansion stage using ultra-high temperature plasma jets. During the stepped expansion stage, a high-temperature zone is formed to crush coarse coal powder into micron-sized porous carbon particles. The stabilization and transition zone is used to stabilize the flow field and smoothly transition to the contraction section; During the contraction phase, the shear layer formed within the cavity increases the movement path of the micron-sized porous carbon particles, prolongs the effective residence time of the micron-sized porous carbon particles at high temperatures, and ensures complete ignition.

2. The high-efficiency pyrolysis plasma nozzle structure for coarse-particle coal powder according to claim 1, characterized in that, The inner cavity of the stepped expansion stage is a stepped shaft structure. The diameter of the stepped shaft structure increases sequentially from the plasma and pulverized coal nozzle side to the stable and transition zone side. The inner cavity diameter of the stepped shaft structure on the side closer to the plasma and pulverized coal nozzle is larger than the diameter of the plasma and pulverized coal nozzle.

3. The high-efficiency pyrolysis plasma nozzle structure for coarse-particle coal powder according to claim 2, characterized in that, The inner cavity of the stable and transition zone has a constant diameter structure, and its inner diameter is smaller than that of the plasma and pulverized coal nozzles.

4. The high-efficiency pyrolysis plasma nozzle structure for coarse-particle coal powder according to claim 1, characterized in that, The inner cavity of the contraction stage has a gradually shrinking structure, which decreases in size sequentially from the stable and transition zone to the outlet.

5. The high-efficiency pyrolysis plasma nozzle structure for coarse-particle coal powder according to claim 1, characterized in that, The outlet of the contraction phase is connected to a flame outlet to eject the fully ignited supersonic high-temperature jet.

6. A method for high-efficiency pyrolysis of coarse-particle coal powder, characterized in that, Includes the following steps: Coarse coal powder particles are injected into a stepped expansion stage using an ultra-high temperature plasma jet. The inner cavity of the stepped expansion stage has a high-temperature reflux zone, which is used to apply extreme thermal shock to the coarse coal powder, so that the coarse coal powder is crushed into micron-sized porous carbon particles, forming a gas-solid mixture. The gas-solid mixture formed is smoothly transitioned to the contraction stage through a stabilization and transition zone. The micron-sized porous carbon particles are repeatedly entrained by the vortex generated by the shear layer formed in the inner cavity during the contraction phase, so as to prolong their effective residence time in the high-temperature region and ensure complete ignition. The supersonic high-temperature jet, after being fully ignited, is ejected through the flame outlet.

7. The method for high-efficiency pyrolysis of coarse-particle coal powder according to claim 6, characterized in that, The inner cavity of the stepped expansion stage is a stepped shaft structure. The diameter of the stepped shaft structure increases sequentially from the plasma and pulverized coal nozzle side to the stable and transition zone side. The inner cavity diameter of the stepped shaft structure on the side closer to the plasma and pulverized coal nozzle is larger than the diameter of the plasma and pulverized coal nozzle.

8. The method for high-efficiency pyrolysis of coarse-particle coal powder according to claim 7, characterized in that, The inner cavity of the stable and transition zone has a constant diameter structure, and its inner diameter is smaller than that of the plasma and pulverized coal nozzles.

9. The method for high-efficiency pyrolysis of coarse-particle coal powder according to claim 6, characterized in that, The inner cavity of the contraction stage has a gradually shrinking structure, which decreases in size sequentially from the stable and transition zone to the outlet.

10. The method for high-efficiency pyrolysis of coarse-particle coal powder according to claim 6, characterized in that, The coarse-particle coal powder R 90 Greater than 30%.

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