Middle and tail end double-control multi-stage circulating clean type pulverized coal burner

Abstract

The invention discloses a middle-tail end double-control multi-stage circulating clean type pulverized coal burner, aims to solve the problem that pulverized coal in low-load low-temperature flue gas is difficult to burn out, relates to the field of pulverized coal burning equipment, and comprises a fixed ring body, a guide plate, a plasma generator, a sound wave oscillator assembly and an atomizing ring body. A lower-layer blocking hole channel of the fixed ring body reversely blows air to decelerate and control flow; the guide plate gathers flow through a taper angle and is matched with the central flow stabilizing disc to prolong the retention time of pulverized coal; the atomizing ring body injects micro-mist to open up a pulverized coal internal channel; a discharge electrode of the plasma generator generates active particles to realize double ignition; the sound wave oscillator assembly breaks a COair film to promote internal and external circulation. All the components cooperate to upgrade surface combustion of pulverized coal to internal and external synchronous reaction, the low-load burn-off rate exceeds 95%, the NOX emission is reduced by more than 30%, the continuous operation cycle of the equipment is prolonged to more than 6 months, the equipment adapts to a 30%-100% load interval, and no extra energy consumption or pollution exists.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of combustion, in particular to a middle-end double-control multi-stage cycle clean pulverized coal burner. BACKGROUND

[0002] As the core component of energy equipment such as power station boilers and industrial furnaces, the operation performance of the pulverized coal burner directly determines the energy utilization rate and environmental protection level. However, there is an inherent and difficult-to-break core technical bottleneck in the pulverized coal combustion, which is caused by the composite characteristics of "porous particles + double inertness of coke + gas film diffusion limitation" unique to pulverized coal combustion: Although the pulverized coal particles, especially the coarse particles with a particle size of >50 μm, have a large number of pores and can theoretically provide sufficient reaction interfaces, in the traditional combustion process, the CO2 generated by the oxidation of the surface carbon layer will quickly block the pores, so that the efficient reaction condition originally relying on the pores is destroyed, and the originally advantageous structure is changed into a barrier layer that hinders the contact of the internal coke and active substances; At the same time, the internal coke has strong chemical inertness due to the high carbon-carbon bond energy of 347 kJ / mol, and ordinary oxygen is difficult to break through this energy barrier to achieve activation, and a dense carbon oxidation layer similar to a gas film is formed on the surface of the particles, further hindering the diffusion of oxygen and active particles into the interior. The superposition of the above three finally leads to the fact that the combustion reaction is only limited to the surface of the particles, and the internal coke is in an unreacted state for a long time, forming a split state of "combustion only occurs on the surface, and internal coke is difficult to participate".

[0003] This problem is more prominent under low load conditions: when the flue gas temperature drops to 550~700℃, which is lower than the critical ignition temperature of the pulverized coal coke, the surface reaction activity is further reduced at this temperature, and the proportion of internal unburned coke can reach 25%~30%. The traditional technical solutions have not fundamentally solved this core contradiction, whether by increasing the secondary air supply to strengthen mixing, which will actually lower the flue gas temperature and dilute the pulverized coal concentration, aggravating the decline in reaction efficiency, or by adding a heating device to improve the environmental temperature, which not only consumes additional energy, but also cannot activate the internal inert coke, and is also easy to form a local high temperature zone; Even if a simple plasma auxiliary ignition is introduced, the active particles can only act on the surface and cannot reach the internal coke because the problem of active particle penetration has not been solved.

[0004] Finally, the pulverized coal burnout rate under low load conditions is maintained at 65%~75% for a long time, which not only causes serious energy waste, but also causes the unburned pulverized coal to adhere to the equipment wall to form coking, which requires frequent shutdown for cleaning; at the same time, the local high temperature zone formed by the surface concentrated heat release is easy to promote the generation of a large amount of NO x , which is difficult to meet the three requirements of combustion efficiency, environmental protection emission and equipment stability. SUMMARY

[0005] Technical problems solved by the application In view of the deficiencies of the prior art, the present application aims to provide a middle-end double-control multi-stage circulating clean coal powder burner, which solves the problems existing in the prior art.

[0006] Technical solutions To achieve the above-mentioned purpose, the present application provides the following technical solutions: a middle-end double-control multi-stage circulating clean coal powder burner, comprising: A fixed ring body, which is internally provided with an annular cavity, and a plurality of inclined hole channels are axially arranged on the inner edge of the fixed ring body and communicate with the annular cavity; A plasma generator, which comprises a plurality of groups of plasma discharge electrodes uniformly arranged on the inner edge of the fixed ring body in a ring shape; A guide plate, which is arranged on the inner edge of the fixed ring body and located downstream of the plasma discharge electrodes, and the longitudinal section of the guide plate is in a tapered structure for gathering the airflow flowing through the surface of the guide plate towards the shaft center; A sound wave oscillator assembly, which is arranged on the fixed ring body, and the direction of the sound wave emission port forms a non-perpendicular included angle with the surface of the guide plate.

[0007] Preferably, the plurality of inclined hole channels comprise lower blocking hole channels and upper spiral wind hole channels; the included angle between the axis of the lower blocking hole channels and the axis of the burner is 15°-20°, and the direction is opposite to the flow direction of the flue gas; the included angle between the axis of the upper spiral wind hole channels and the axis of the burner is 30°-45°, and the upper spiral wind hole channels are distributed in a spiral shape in a ring shape.

[0008] Preferably, the plasma discharge electrodes of the annular low-temperature plasma generator are arranged in the outlet area of the upper spiral wind hole channels.

[0009] Preferably, the adjustable annular guide plate has a cone angle of 75°.

[0010] Preferably, the upper end edge of the guide plate is provided with a center flow stabilizing disc extending horizontally towards the shaft center, and the guide plate and the center flow stabilizing disc jointly form a flow gathering structure with an L-shaped section.

[0011] Preferably, the sound wave emission port of the sound wave oscillator assembly is obliquely directed towards the conical inclined surface of the guide plate, and the included angle between the direction and the normal line of the surface of the guide plate is 30°-60°.

[0012] Preferably, the sound wave oscillator assembly and the plasma discharge electrodes are arranged in a ring shape.

[0013] The active particle groups generated by the plasma discharge electrode and the high-frequency acoustic wave field generated by the acoustic wave oscillator assembly are synergized in the tapered flow channel formed by the adjustable annular guide plate, and the synergies include: the flow gathering effect generated by the guide plate, which increases the collision probability of the coal powder particles and the active particle groups; the mechanical vibration effect generated by the acoustic wave field, which equivalently extends the residence time of the active particle groups and suppresses the coking on the surface of the guide plate.

[0014] (Three) beneficial effects The present application aims to provide a middle-end double-control multi-stage circulating clean coal powder burner, which solves the problem of the split of surface reaction and internal reaction in traditional combustion by the synergistic effect of the atomizing ring body, the acoustic wave oscillator assembly, the guide plate and the plasma generator, and realizes the synchronous reaction of the surface and the interior of the coal powder according to the core characteristics of the coal powder combustion, i.e. "porous particles easy to block, high inertness of coke, and gas film diffusion limitation".

[0015] The guide plate adopts a tapered flow gathering structure, which can direct and concentrate the dispersed coal powder and micro-mist, and the local backflow formed by the center flow stabilizing disc greatly extends the residence time of the coal powder in the reaction zone, creating conditions for sufficient reaction. The micro-mist injected by the atomizing ring body can penetrate into the pores of the coal powder, and the polar molecules thereof are adsorbed on the surface of the carbon-carbon bond of the internal coke to weaken the bond energy, and at the same time, a steam cavity is formed by high temperature to break the barrier structure formed by the blocked pores and open a channel for the active particles to enter the interior of the particles.

[0016] The high-energy electrons generated by the plasma generator dissociate the micro-mist to generate high-concentration OH・and H・: the oxidation activity of OH・is 5 times that of ordinary oxygen, which can quickly break through the surface gas film; H・penetrates into the core of the particle along the channel opened by the micro-mist and activates the originally inert coke. The 15-30 kHz high-frequency acoustic waves emitted by the acoustic wave oscillator periodically destroy the surface CO2 gas film to make it continuously break and recombine, and at the same time, micro-convection is induced in the interior of the particle to realize the continuous supplement of active particles to the reaction zone and the timely discharge of reaction products, forming a stable cycle. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 Figure 1 is a schematic diagram of the whole middle-end double-control multi-stage circulating clean coal powder burner of the present application; Figure 2 Figure 2 is a sectional view of the whole middle-end double-control multi-stage circulating clean coal powder burner of the present application; Figure 3 Figure 3 is an enlarged view of position A in the middle-end double-control multi-stage circulating clean coal powder burner of the present application; Figure 4This is a schematic diagram of a guide plate with 1 / 4 cut off in a mid-to-end dual-control multi-stage circulating clean pulverized coal burner of the present invention; In the figure: 1-fixed ring, 2-guide plate, 3-plasma generator, 4-acoustic oscillator assembly, 5-atomizing ring, 6-fan, 11-annular cavity, 12-multi-layer inclined channel, 121-lower layer obstruction channel, 122-upper layer spiral air channel, 21-central flow stabilizer, 31-plasma discharge electrode, 51-atomizing nozzle. Detailed Implementation

[0018] The following will refer to the appendix in the examples of this invention. Figures 1-4 The technical solutions in the present invention will be clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] This invention provides a technical solution: a mid-to-end dual-control multi-stage circulating clean pulverized coal burner, such as... Figure 1 As shown, it includes a fixed ring 1, a plasma generator 2, a guide plate 3, an acoustic oscillator assembly 4, and an atomizing ring 5. The fixed ring 1 is the basic load-bearing component of the burner, which is integrally cast from a high-temperature resistant alloy. Its annular structure is fixed coaxially with the furnace body. The fixed ring 1 has an annular cavity 11 inside, which serves as the main channel for airflow distribution. Its inner edge has multiple layers of inclined channels 12 along the axial direction, which communicate with the annular cavity 11 to guide the airflow to the combustion zone.

[0020] The multi-layer inclined channel 12 includes a lower layer obstruction channel 121 and an upper layer spiral air channel 122. The lower layer obstruction channel 121 is evenly distributed in the circumferential direction, and its axis makes an angle of 15°-20° with the burner axis. It is also opposite to the flue gas flow direction, that is, the channel outlet faces the flue gas flow direction. Its function is to obstruct the flue gas flow velocity by injecting air in the opposite direction, thereby prolonging the residence time of unburned coal powder in the combustion zone. The upper spiral air duct 122 is distributed in a circumferential spiral, and the angle between its axis and the burner axis is 30°-45°. Its function is to spray spiral airflow into the combustion zone, promote the coal powder and air to form a rotating mixing flow field, and avoid local concentration imbalance.

[0021] A fan 6 is connected to the outside of the fixed ring 1. The fan 6 is connected to the annular cavity 11 through a pipe, providing a stable airflow for the multi-layer inclined channel 12. The air volume can be adapted to different loads by frequency conversion control of the fan.

[0022] The guide plate 2 is made of high-temperature and wear-resistant materials, such as silicon carbide composite ceramics, and is fixed to the inner edge of the fixed ring 1 and located downstream of the plasma discharge electrode 31. The longitudinal section of the guide plate 2 has a tapered structure with a cone angle of 75°. This angle design can achieve the concentration of airflow towards the axis with minimal flow resistance, thereby increasing the coal powder concentration in the axis region by 40% to 50%.

[0023] The upper edge of the guide plate 2 is provided with a central flow stabilizer 21 extending horizontally in the axial direction. The guide plate 2 and the central flow stabilizer 21 together form an L-shaped flow-gathering structure: the central flow stabilizer 21 can block part of the airflow from flowing out directly, forming a local recirculation zone below it, so that the temperature is maintained at 600~650℃. It preheats the unburned coal powder by entraining high-temperature flue gas, making up for the insufficient heat in the low-temperature environment.

[0024] The plasma generator 3 is connected to a high-frequency high-voltage power supply and has a plasma discharge electrode 31 at the front. The plasma discharge electrode 31 is made of tungsten rhenium alloy, with a temperature resistance of >1800℃, and is evenly arranged along the inner edge of the fixed ring 1. It is located in the outlet area of ​​the upper spiral air channel 122, and the distance between the electrode discharge end and the channel outlet is ≤50mm.

[0025] The plasma discharge electrode 31 is connected to a high-frequency, high-voltage power supply with an output frequency of 10-20kHz. This allows for gas discharge between the electrode and the gas flow, generating low-temperature plasma containing active particles such as O· and OH·, with a temperature <500℃. Since the electrode position corresponds to the upper spiral air channel 122, the spiral airflow can uniformly transport the active particles to the coal powder accumulation area, reducing the ignition temperature of the coal powder from 600℃ to 420-450℃, thus achieving low-temperature ignition.

[0026] The acoustic oscillator assembly 4 is uniformly arranged circumferentially along the fixed ring 1 and is staggered from the plasma discharge electrode 31 in the circumferential direction, thereby avoiding interference of acoustic waves with plasma discharge. The acoustic emission port of the acoustic generator 41 is obliquely pointed to the conical inclined surface of the guide plate 2, and the angle between its direction and the normal of the guide plate 2 surface is 30°-60°. This angle design allows the acoustic waves to form a spiral propagation path in the current-gathering region.

[0027] The high-frequency sound waves emitted by the acoustic oscillator assembly 4 at 15~30kHz and 120~150dB can first extend the residence time of active particles in the combustion zone through mechanical vibration, increasing it from 100~150μs to 250~300μs; secondly, it can enhance the collision and mixing of active particles and coal powder particles; and finally, it can drive the surface of the guide plate 2 to generate micro-amplitude vibration of 5~10μm, which can suppress the adhesion and coking of coal powder.

[0028] The atomizing ring 5 is made of stainless steel and is fitted inside the fixed ring 1, located upstream of the acoustic oscillator assembly 4 along the flue gas flow direction. Its position design ensures that the micro-mist can be pre-mixed with the airflow and coal powder before entering the plasma interaction zone. Multiple atomizing nozzles 51 are arranged circumferentially on the inner edge of the atomizing ring 5, and the outlet direction of the atomizing nozzles 51 faces the front end face of the guide plate 2, so that the micro-mist can be effectively collected by the guide plate 2 with the airflow.

[0029] The atomizing nozzle 51 has an orifice diameter of 0.5-2 mm, and its axis forms an angle of 15°-30° with the radial direction of the fixed ring 1. It can atomize external steam source, 80-100℃ saturated steam, into micro-droplets of 5-10 μm, with the micro-mist injection volume being 0.5%-2% of the secondary air volume. The micro-mist dissociates into H・ and OH・ free radicals in the high-energy plasma field, which synergistically enhance the oxidation of coal powder with the plasma's own active particles, while achieving uniform distribution across the entire cross-section through acoustic oscillation.

[0030] The working principle is specifically divided into the following stages: 1. Flue gas hindrance: When the flue gas containing unburned coal powder in the main combustion zone flows toward the outlet, it first flows through the lower hindrance channel 121 at the bottom of the fixed ring 1. The reverse jet of air in this channel not only directly reduces the flue gas velocity, but also prevents the coal powder from being lost too quickly, which would make it difficult for the subsequent micro-mist to fully contact the coal powder.

[0031] 2. Airflow Guiding and Concentration: Subsequently, the decelerated flue gas enters the area of ​​guide plate 2. Guide plate 2 adopts a 75° tapered structure, which can directionally concentrate the dispersed coal powder towards the axis, forming a high-concentration reaction zone. At the same time, the central stabilizing plate 21 at the upper end of guide plate 2 forms a local recirculation zone, which entrains the already combusted high-temperature flue gas to preheat the coal powder, extending its residence time in the reaction zone. This design not only precisely adapts to the characteristic that coal powder needs sufficient concentration and time to fully react, but also, because recirculation preheating does not require additional energy consumption, the activity of coal powder, which originally required a separate heating device to improve, can be enhanced simply through the waste heat of the flue gas, indirectly reducing the system's energy consumption.

[0032] Under the convergence effect of the guide plate 2, the flue gas comes into full contact with the micro-mist injected by the atomizing ring 5: the micro-mist particles utilize the porous characteristics of pulverized coal to penetrate into the particle core along the pores, forming a micro-mist channel that connects the inside and outside; at the same time, the polar molecules of the micro-mist adsorb onto the carbon-carbon bond surface of the internal coke, weakening its binding force, and forming a steam chamber with high temperature, breaking the barrier state of pores blocked by CO2 in traditional combustion. This process not only opens up a path for active particles to enter the interior, but also, due to the weakening of carbon bonds, greatly reduces the difficulty for subsequent active particles to overcome the inertia of the internal coke. The internal reaction that originally required strong energy input to activate is more easily started after this pretreatment.

[0033] 3. Plasma Ignition: Next, a high-concentration mist-powder-gas mixture flows to the plasma discharge electrode 31 region of the plasma generator 3. The low-temperature plasma generated by the plasma discharge electrode 31 dissociates the surface micro-mist to generate highly active OH・, whose oxidizing power is far stronger than ordinary oxygen, and can quickly break through the carbon layer on the surface of coal powder under low-temperature conditions. On the other hand, the high-energy particles of the plasma act on the micro-mist in the internal steam chamber to generate tiny H・. These H・ penetrate deep into the particle core along the micro-mist channels, activating the originally inert internal coke, achieving simultaneous surface and internal ignition. This dual ignition design not only solves the problem of difficult ignition at low temperatures, but also unexpectedly avoids the local high temperature caused by traditional single surface ignition. Due to the simultaneous internal and external heat release, the previously common local high temperature zone of >1500℃ is greatly reduced, indirectly reducing NO. x The amount generated.

[0034] 4. Acoustic wave enhancement and spiral wind circulation: The acoustic wave oscillator component 4 located below the atomizing ring 5 first emits high-frequency acoustic waves. In response to the situation where CO2 gas film is easily formed during coal powder combustion, the compression and sparsity waves of the acoustic waves continuously impact the surface gas film, causing it to break and recombine continuously, ensuring that fresh active particles are replenished to the surface. At the same time, the acoustic waves induce micro-convection inside the particles, promoting the migration of internal reaction products to the surface, reacting with surface active particles, and also pumping excess active particles from the surface into the interior, forming a cycle of active particle replenishment and product discharge.

[0035] Subsequently, the upper spiral air duct 122 of the fixed ring 1 injects spiral airflow, directly driving unburned coal powder back into the high-concentration reaction zone of the guide plate 2, repeating the entire process of micro-mist penetration, plasma activation, and acoustic enhancement. This cyclic design not only allows unburned coal powder that might have escaped with the flue gas to undergo secondary treatment, significantly improving the overall burnout rate, but also further optimizes the flow field in the combustion zone. The spiral airflow can break through local airflow dead zones, preventing local coking caused by coal powder accumulation, while making the contact between active particles and coal powder more uniform. The mixing effect that originally required adjusting the secondary air ratio can now be achieved with the help of the spiral airflow, indirectly reducing the complexity of airflow control and allowing the system to operate stably within the 30%~100% load range.

[0036] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A mid-to-end dual-control multi-stage circulating clean pulverized coal burner, characterized in that, include: A fixed ring (1) has an annular cavity (11) inside, and a multi-layered inclined channel (12) communicating with the annular cavity (11) is axially opened on its inner edge. The plasma generator (3) includes multiple sets of plasma discharge electrodes (31) uniformly arranged in a circumferential direction on the inner edge of the fixed ring (1). The guide plate (2) is located on the inner edge of the fixed ring (1) and downstream of the plasma discharge electrode (31). The longitudinal section of the guide plate (2) is tapered, which is used to concentrate the airflow flowing over its surface toward the axis. The acoustic oscillator assembly (4) is disposed on the fixed ring (1), and the direction of the acoustic emission port forms a non-perpendicular angle with the surface of the guide plate (2). The atomizing ring (5) is fitted inside the fixed ring (1) and located upstream of the acoustic oscillator assembly (4) along the flue gas flow direction. Multiple atomizing nozzles (51) are arranged circumferentially on the inner edge of the atomizing ring (5). The outlet direction of the atomizing nozzles (51) faces the front end face of the guide plate (2) and is used to inject micro-mist into the airflow.

2. The mid-to-end dual-control multi-stage circulating clean pulverized coal burner according to claim 1, characterized in that, The multi-layer inclined channel (12) includes a lower layer obstruction channel (121) and an upper layer spiral air channel (122); the axis of the lower layer obstruction channel (121) is at an angle of 15°-20° with the axis of the burner and is opposite to the direction of flue gas flow; the axis of the upper layer spiral air channel (122) is at an angle of 30°-45° with the axis of the burner and is distributed in a circumferential spiral.

3. A mid-to-end dual-control multi-stage circulating clean pulverized coal burner according to claim 2, characterized in that, The plasma discharge electrode (31) of the plasma generator (3) is correspondingly arranged in the outlet area of ​​the upper spiral air channel (122).

4. The mid-to-end dual-control multi-stage circulating clean pulverized coal burner according to claim 1, characterized in that, The cone angle of the guide plate (2) is 75°.

5. A mid-to-end dual-control multi-stage circulating clean pulverized coal burner according to claim 4, characterized in that, The upper edge of the guide plate (2) is provided with a central flow stabilizing disk (21) extending horizontally in the axial direction. The guide plate (2) and the central flow stabilizing disk (21) together form an L-shaped cross-section flow-gathering structure.

6. A mid-to-end dual-control multi-stage circulating clean pulverized coal burner according to claim 1, characterized in that, The acoustic oscillator assembly (4) has its acoustic emission port pointing obliquely toward the conical inclined surface of the guide plate (2), and the angle between its direction and the normal of the guide plate (2) is 30°-60°.

7. A mid-to-end dual-control multi-stage circulating clean pulverized coal burner according to claim 1, characterized in that, The acoustic oscillator assembly (4) and the plasma discharge electrode (3) are arranged offset in the circumferential direction.

8. A mid-to-end dual-control multi-stage circulating clean pulverized coal burner according to claim 1, characterized in that, A fan (6) is connected to the outside of the fixed ring (1), and the fan (6) is connected to the annular cavity (11) through a pipe.

9. A mid-to-end dual-control multi-stage circulating clean pulverized coal burner according to claim 1, characterized in that, The aperture of the atomizing nozzle (51) is 0.5-2mm, and the angle between its axis and the radial direction of the fixed ring (1) is 15°-30°.

Images