Ammonia-doped coal co-combustion direct-current burner and application thereof in corner tangential coal-fired boiler

Abstract

The invention belongs to the technical field of combustion equipment, and particularly relates to an ammonia-doped coal co-combustion direct-current combustor and application thereof in a corner tangential coal-fired boiler, and the ammonia-doped coal co-combustion direct-current combustor comprises a pulverized coal concentrator, an ammonia gas sleeve and a peripheral air sleeve; a pulverized coal concentration and dilution separation assembly is arranged in the pulverized coal concentrator in the airflow flowing direction and used for separating pulverized coal airflow entering the pulverized coal concentrator and outputting concentrated pulverized coal airflow and diluted pulverized coal airflow. The ammonia gas sleeve is arranged outside the pulverized coal concentrator in a sleeving manner, a plurality of ammonia injection holes are formed in the gas outlet end of the ammonia gas sleeve on one side of the pulverized coal concentrator for outputting thick pulverized coal airflow, and the ammonia injection holes are arranged towards the center line of the pulverized coal concentrator; the ammonia gas sleeve is sleeved with the peripheral air sleeve, and the gas outlet end of the peripheral air sleeve is arranged back to the center line of the pulverized coal concentrator. Compared with the prior art, the problems that nitrogen oxide emission is greatly increased and emission exceeds the standard easily due to ammonia and coal blending combustion in a direct-current combustor are solved. According to the scheme, the nitrogen oxide emission amount of the ammonia coal blending combustion power station boiler is greatly reduced.

Description

Technical Field

[0001] This invention belongs to the field of combustion equipment technology, specifically relating to a coal-ammonia co-fired DC burner and its application in a tangential coal-fired boiler. Background Technology

[0002] Coal will remain dominant in my country's energy supply structure for the foreseeable future. To achieve dual carbon targets, a carbon emission control transformation is needed for coal-fired power plant boilers. Research has shown that co-firing coal with zero-carbon combustion (e.g., biomass, ammonia, hydrogen) in power plant boilers can effectively reduce carbon dioxide emissions.

[0003] Ammonia and hydrogen, as fuels, each have their own advantages and disadvantages. Hydrogen combustion produces only water, and its flame spreads quickly, ignites easily, and has a high calorific value, making it suitable for high-speed combustion scenarios. However, hydrogen faces significant transportation challenges: gaseous hydrogen has a low energy density, therefore, for long-distance transportation, it must be stored in liquid form, requiring a low temperature of -253°C and high-pressure containers capable of withstanding 70 MPa, which translates to extremely high transportation costs. Furthermore, hydrogen has a wide flammability range and is colorless and odorless, making leaks difficult to detect, thus posing a major challenge to hydrogen transportation safety.

[0004] Compared to hydrogen, gaseous ammonia has a higher energy density, comparable to coal per kilogram, and can be liquefied, stored, and transported at normal temperature and pressure, resulting in lower costs. Furthermore, my country already has a mature and comprehensive ammonia transportation and supply system, transporting over 200 million tons of ammonia annually. However, ammonia has a very low flame propagation speed of only 0.015 m / s and a high ignition temperature of approximately 650°C, requiring stable combustion in a high-temperature environment, or it can be co-fired with other fuels. Therefore, the high-temperature combustion environment of over 1000°C in power plant boilers is highly suitable for ammonia combustion, and using ammonia-blended coal can be an important means for power plants to reduce carbon emissions.

[0005] Existing domestic and international research indicates that the combustion of coal with ammonia generates a large amount of nitrogen oxides (NOx), with NOx concentrations far exceeding those from pure coal combustion, sometimes by an order of magnitude. Clearly, simply blending coal with ammonia in power plant boilers can easily lead to a surge in NOx emissions, causing serious problems such as exceeding boiler emission standards and increasing flue gas denitrification costs. Our recent research shows that ammonia only oxidizes into NOxes and causes air pollution under high-temperature, oxygen-rich conditions. However, directly injecting ammonia onto the high-temperature flame surface at the rear of the pulverized coal flow can significantly reduce NOx formation. This is because the rear flame surface is an oxygen-deficient, high-temperature combustion environment. Under these conditions, ammonia decomposes into nitrogen and hydrogen. Furthermore, hydrogen has a higher reactivity with oxygen than nitrogen, thus ammonia is burned to produce nitrogen and water instead of NOxes.

[0006] To ensure that ammonia can enter the high-temperature, oxygen-deficient region for decomposition immediately upon injection into the furnace through a coal-blended ammonia burner, the pulverized coal gas flow (primary air) can be divided into rich and lean sections through the internal structure of the burner. The rich pulverized coal gas flow has a lower ignition temperature, faster ignition, shorter ignition distance, and more stable combustion. Correspondingly, it requires less combustion air, allowing for faster combustion and heat release to heat the surrounding environment, creating a high-temperature region and establishing an oxygen-deficient atmosphere earlier. Existing technologies, such as CN111895393A, disclose a deep-peak-shaving, center-enriched fuel-enhanced direct-current low-NOx burner. To address the issue that existing burners cannot meet the operational requirements for low-load deep peak shaving, a Venturi concentrator installed within the burner nozzle body concentrates the pulverized coal gas flow entering the burner, forming a rich-lean pulverized coal gas flow with a concentrated center and a lean periphery. The Venturi concentrator also ensures a more uniform gas velocity at the outlet. However, this scheme only achieves the separation of concentrated and dilute coal powder gas flow. Directly adding ammonia gas into the concentrated coal powder gas flow or the dilute coal powder gas flow formed by separation will cause the ammonia gas to burn directly in the excess oxygen and bring about the generation of nitrogen oxides.

[0007] In the prior art, CN119532735A discloses a swirl burner for ammonia-coal co-combustion, comprising a first to a third cylinder; the inner cavity of the first cylinder forms a pulverized coal gas flow channel; an ammonia gas channel is formed between the first and second cylinders; a secondary air channel is formed between the second and third cylinders; the inner cavity of the first cylinder is divided into four sections from front to back, namely a first stabilizing section, a gradually expanding section, a second stabilizing section, and a gradually contracting section, wherein the first and second stabilizing sections are cylindrical, and the gradually expanding and contracting sections are frustum-shaped, with a larger diameter at the front end of the gradually expanding section and a smaller diameter at the front end of the contracting section; a blunt body with a cylindrical front end and a frustum-shaped rear end is provided inside the first cylinder, except that a portion of the rear end of the blunt body is located inside or outside the gradually expanding section, and the rest is located inside the first stabilizing section; swirl blades are connected between the inner wall of the first cylinder and the outer wall of the blunt body; and multiple guide plates are evenly distributed circumferentially at the front end of the second cylinder. However, this design uses a swirl burner, which is unsuitable for tangential combustion boilers. Furthermore, the swirl blades at the outlet of the primary air (pulverized coal flow) channel (first cylinder) completely negate the separation effect of the pulverized coal flow, and some ammonia is mixed into the primary air. This results in excessive oxygen during the initial combustion of pulverized coal, inevitably leading to a large amount of NO production. In addition, water spray holes along the outer edge of the primary air nozzle spray water into the pulverized coal ignition flow, lowering the flame temperature, delaying the rapid oxygen consumption and heat release of the pulverized coal, and weakening the decomposition reaction of ammonia into hydrogen. This causes ammonia from the second cylinder to be injected into the low-temperature flame region of the pulverized coal that has not yet exhausted its oxygen, significantly increasing NO generation and making it difficult to meet the power plant's requirements for high combustion efficiency and low NOx emissions.

[0008] Therefore, there is an urgent need to develop an ammonia-coal co-fired direct-current burner for low nitrogen oxide emissions in tangential coal-fired boilers, in order to solve the problem of excessive emissions caused by a significant increase in nitrogen oxide emissions from ammonia-coal co-fired power plant boilers. Summary of the Invention

[0009] The purpose of this invention is to provide a coal-ammonia co-fired once-through burner and its application in a tangential coal-fired boiler, thereby addressing at least one of the aforementioned problems. This solves the problem of significantly increased nitrogen oxide emissions and resulting emissions exceeding standards in existing once-through burners that use ammonia-coal co-firing. This solution divides the pulverized coal airflow (primary air) into rich and lean sections, directly accelerating and injecting ammonia into the rich pulverized coal combustion zone. This allows the ammonia to decompose and burn in a high-temperature, oxygen-deficient environment, thus significantly reducing nitrogen oxide emissions from ammonia-coal co-fired power plant boiler.

[0010] The objective of this invention is achieved through the following technical solution: The first aspect of the present invention discloses a coal-ammonia co-firing DC burner, comprising a pulverized coal concentrator, an ammonia sleeve, and a perimeter air sleeve; The coal powder concentrator is equipped with a coal powder concentration separation component inside along the airflow direction, which is used to separate the coal powder airflow entering the coal powder concentrator and output concentrated coal powder airflow and dilute coal powder airflow respectively. The ammonia sleeve is fitted outside the coal powder concentrator, and the outlet end of the ammonia sleeve has several ammonia injection holes on the side of the coal powder concentrator that outputs concentrated coal powder airflow, and the ammonia injection holes are set towards the jet direction of the coal powder concentrator. The perimeter air sleeve is fitted outside the ammonia sleeve, and the nozzle of the perimeter air sleeve is arranged circumferentially along the nozzle of the pulverized coal thickener, with the perimeter air jet ejected from the perimeter air sleeve pointing outward.

[0011] Preferably, the pulverized coal concentration separation component includes airflow collision bosses and airflow separation baffles arranged sequentially along the airflow direction; The airflow collision protrusion is located near the air inlet of the coal powder thickener, and is located on one side inside the coal powder thickener; the airflow collision protrusion achieves the impact-type separation of coal powder airflow through the inertia difference between coal powder particles and gas. The airflow separation baffle is connected to the outlet end of the pulverized coal thickener, and the airflow separation baffle is located in the middle of the pulverized coal thickener; the airflow separation baffle separates the concentrated pulverized coal airflow and the light pulverized coal airflow formed by the collision of the airflow with the boss.

[0012] Preferably, the slope of the windward side of the airflow collision protrusion is less than the slope of the leeward side.

[0013] Preferably, the airflow separation baffle has an upward-curving section at one end near the airflow collision protrusion, and the upward-curving section curves toward the side of the concentrated coal powder airflow.

[0014] Preferably, the airflow separation baffle has an inclined surface at one end connected to the pulverized coal thickener, and the inclined surface is located on the side of the concentrated pulverized coal airflow.

[0015] Preferably, the normal direction of the ammonia injection hole is set at an angle of 10-15° with the center line of the coal powder thickener.

[0016] Preferably, the normal direction of the spray surface at the outlet end of the perimeter air sleeve is set at a 35-60° angle to the centerline of the pulverized coal thickener.

[0017] Preferably, the air inlet end of the pulverized coal concentrator is provided with a first mounting flange.

[0018] Preferably, the inlet end of the ammonia sleeve is connected to an ammonia hose via a second mounting flange, and the outlet end of the ammonia sleeve has at least 10 ammonia injection holes.

[0019] The second aspect of the present invention discloses the application of a coal-ammonia co-fired direct-current burner as described above in a four-corner tangential coal-fired boiler. The coal-ammonia co-fired direct-current burner is located at the four corners of the furnace of the coal-fired boiler, and the airflow entering the furnace forms a tangential rotating airflow. The light pulverized coal airflow is located outside the rotating airflow flame, the concentrated pulverized coal airflow is located inside the rotating airflow flame, and ammonia is injected into the inner combustion zone of the concentrated pulverized coal flame.

[0020] The working principle of this invention is as follows: The pulverized coal concentration separation component separates the incoming pulverized coal gas flow into concentrated pulverized coal gas flow and dilute pulverized coal gas flow in the pulverized coal thickener. Ammonia gas flow is then sprayed out on the concentrated pulverized coal gas flow side through an ammonia sleeve. This allows the gas flow from the DC burner to undergo tangential combustion, where the concentrated pulverized coal gas flow rapidly consumes the surrounding oxygen. This enables the ammonia gas to be injected into the oxygen-deficient, high-temperature concentrated pulverized coal combustion zone, where most of it decomposes into hydrogen and nitrogen gas, which mix with oxygen and burn in the middle and later stages of combustion in the furnace, significantly reducing the generation of nitrogen oxides.

[0021] Compared with the prior art, the present invention has the following beneficial effects: After the mixed gas flow ejected from the DC burner enters the boiler furnace, the light pulverized coal gas flow is located on the outer side of the entire rotating gas flow (i.e., the back-fire side near the furnace wall), while the concentrated pulverized coal gas flow is located on the inner side of the entire rotating gas flow (i.e., the fire-facing side near the center of the furnace). At the same time, the ammonia jet directly penetrates the flame root and enters the middle and rear region of the combustion flame (concentrated pulverized coal combustion zone), effectively suppressing the direct contact between ammonia and oxygen and significantly reducing the generation of nitrogen oxides.

[0022] The ammonia sleeve is directly positioned on the outside of the pulverized coal thickener. This arrangement offers two advantages: firstly, the low-temperature ammonia flow passing through the outside of the thickener cools the nozzle; secondly, the high-temperature nozzle also heats the ammonia, preheating it and increasing its decomposition reaction rate when injected into the high-temperature combustion zone of the concentrated pulverized coal stream. Furthermore, by installing the ammonia sleeve and injection holes near the burner nozzle and the concentrated pulverized coal stream outlet, ammonia can be directly and rapidly injected into the concentrated pulverized coal combustion zone. Combined with the flammability and oxygen-deficient atmosphere of concentrated pulverized coal, this allows more ammonia to enter the high-temperature, oxygen-deficient environment for cracking and combustion, thereby significantly reducing nitrogen oxide emissions from ammonia-coal co-firing power plant boiler.

[0023] The perimeter air sleeve provides cooling air to the burner nozzle, protecting it from high-temperature erosion when the DC burner is shut down. In addition, the cooling air jet leaves the perimeter air nozzle at a certain angle away from the centerline, ensuring that ammonia does not mix with it and react to produce nitrogen oxides. Attached Figure Description

[0024] Figure 1 A cross-sectional schematic diagram of a coal-ammonia co-firing DC burner; Figure 2 A side view schematic diagram of a coal-ammonia co-firing DC burner; Figure 3 A schematic cross-sectional view of the combustion field inside a four-cornered tangent-circle coal-fired boiler; In the diagram: 1-First mounting flange; 2-Pulverized coal concentrator; 3-Burner nozzle; 4-Airflow separation baffle; 5-Ammonia sleeve; 6-Perimeter air sleeve; 7-Second mounting flange; 8-Ammonia hose; 9-Ammonia injection hole. Detailed Implementation

[0025] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0026] Example 1 A coal-ammonia co-fired DC burner, such as Figure 1 , 2 As shown, it includes a pulverized coal concentrator 2, an ammonia sleeve 5, and a perimeter ventilation sleeve 6; The coal powder concentrator 2 is equipped with a coal powder concentration separation component inside along the airflow direction, which is used to separate the coal powder airflow entering the coal powder concentrator 2 and output concentrated coal powder airflow and dilute coal powder airflow respectively. The ammonia sleeve 5 is sleeved on the outside of the coal powder concentrator 2, and the outlet end of the ammonia sleeve 5 has several ammonia injection holes 9 on the side where the coal powder concentrator 2 outputs concentrated coal powder airflow. The ammonia injection holes 9 are set towards the jet direction of the coal powder concentrator 2. The perimeter air sleeve 6 is sleeved outside the ammonia sleeve 5. The nozzle of the perimeter air sleeve 6 is arranged around the nozzle of the entire coal powder thickener 2, and the jet direction is set outward (the angle with the jet direction of the light coal powder gas is not less than 35°).

[0027] The airflow organization within a four-corner tangential coal-fired boiler equipped with the aforementioned once-through burner is as follows: Figure 3 As shown, this specifically reflects the arrangement of the burners in the furnace of the coal-fired boiler and the connection position of the direct-current burner for coal-ammonia co-firing as described above; The coal-ammonia co-fired DC burner is located at the four corners of the furnace of the coal-fired boiler, and the airflow entering the furnace forms a tangential rotating airflow; wherein, the light pulverized coal airflow is located on the outside of the rotating airflow flame, the concentrated pulverized coal airflow is located on the inside of the rotating airflow flame, and ammonia is injected into the inner combustion zone of the concentrated pulverized coal flame.

[0028] More specifically, in this embodiment: To address the issue of significantly increased nitrogen oxide emissions from ammonia-coal co-fired power plant boilers, leading to emissions exceeding standards, this invention provides a low-nitrogen-oxide-emission ammonia-coal co-fired direct-flow burner for tangential coal-fired boilers. In this burner, the pulverized coal gas flow (primary air) is divided into rich and lean sections by a pulverized coal concentrator 2. Ammonia gas is directly accelerated and injected into the stable, high-temperature combustion zone of the rich pulverized coal through small holes in the ammonia sleeve 5. This allows the ammonia gas to decompose and burn in a high-temperature, oxygen-deficient environment, thereby significantly reducing nitrogen oxide emissions from ammonia-coal co-fired power plant boiler.

[0029] The DC burner is specifically: It includes a pulverized coal concentrator 2 and its internal pulverized coal concentration-degradation separation components, a burner nozzle 3, an ammonia sleeve 5, a perimeter air sleeve 6, etc., wherein the ammonia sleeve 5 is fitted outside the pulverized coal concentrator 2 and the perimeter air sleeve 6 is fitted outside the ammonia sleeve 5.

[0030] The coal pulverizer 2 is equipped with an airflow collision boss for inertial separation of coal pulverizer and an airflow separation baffle 4 for separating the concentrated and dilute phases of coal pulverizer. The uniformly delivered coal pulverizer airflow (primary air) is divided into two streams of concentrated and dilute airflow through the flow guiding structure of the airflow collision boss and the airflow separation baffle 4, and then sprayed out separately from the burner nozzle 3. The flow rates of the concentrated coal pulverizer airflow and the dilute coal pulverizer airflow are equal, and after leaving the burner nozzle 3, they are sent into the boiler furnace for combustion in the form of primary air jet in the direction of a set imaginary tangential circle.

[0031] The airflow collision protrusion is set at the inlet end of the pulverized coal thickener 2 and is located on one side wall of the light pulverized coal airflow; its cross section along the axial direction of the pulverized coal thickener 2 is trapezoidal, and the slope of the windward side (the side facing the pulverized coal airflow) is less than the slope of the leeward side (the side away from the pulverized coal airflow); thus, the inertial difference between pulverized coal and airflow can be used to separate the concentrated pulverized coal airflow and the light pulverized coal airflow through impact separation.

[0032] The airflow separation baffle 4 is connected to the middle of the outlet (burner nozzle 3) of the pulverized coal thickener 2 to divide the burner nozzle 3 into two independent nozzles that spray concentrated pulverized coal airflow and dilute pulverized coal airflow respectively. The airflow separation baffle 4 has an upward-curved section at the end near the air inlet of the pulverized coal thickener 2, which curves towards the concentrated pulverized coal airflow side; the airflow separation baffle 4 has a slope at the end located at the burner nozzle 3, and this slope is located on the side of the concentrated pulverized coal airflow.

[0033] The inlet of the pulverized coal concentrator 2 is provided with a first mounting flange 1 that connects to the primary air duct. The first mounting flange 1 of the burner is specifically used to connect to the primary air duct of the coal mill.

[0034] The outer shell of the pulverized coal concentrator 2 is equipped with an ammonia sleeve 5 for conveying ammonia gas. The normal direction of the outlet section (injection surface) of the ammonia sleeve 5 is oriented towards the center line of the ammonia sleeve 5 or the center line of the burner, and the angle between the normal direction and the center line of the ammonia sleeve 5 or the center line of the burner is 10-15°.

[0035] On the outlet section (injection surface) of the ammonia sleeve 5, ten or more small circular holes are uniformly opened as ammonia injection holes 9 on the side from which the concentrated coal powder gas flow is ejected. Obviously, the surface normal direction of these ammonia injection holes 9 is consistent with the surface normal direction of the outlet section of the ammonia sleeve 5. Thus, the axis of these ammonia injection holes 9 forms an angle of 10-15° with the surface normal of the cross-section of the ammonia sleeve 5.

[0036] An inlet connection pipe and a second mounting flange 7 are arranged on the ammonia sleeve 5 at the flange position near the burner (away from the boiler end) outside the pulverized coal concentrator 2. The second mounting flange 7 is connected to the flange of the ammonia hose 8 that supplies ammonia. The ammonia hose 8 is preferably a metal hose and is used to transport ammonia to the ammonia sleeve 5.

[0037] The ammonia sleeve 5 is further provided with a perimeter air sleeve 6, which is used to provide cooling air to the burner nozzle 3, while preventing the flame of combustion in the boiler from burning against the wall, thus reducing the coking and corrosion of the furnace water-cooled wall.

[0038] The nozzle cross-section (injection surface) of the perimeter air sleeve 6 is positioned with its normal direction facing away from the centerline of the perimeter air sleeve 6 or the centerline of the burner, and the angle between this normal direction and the centerline of the perimeter air sleeve or the transverse centerline of the burner is 35-60°. This prevents direct contact between the perimeter air and the ammonia gas flow during the use of this direct-flow burner, while also protecting the burner nozzle 3. The inlet of the perimeter air sleeve 6 is connected to the interior of the secondary air box.

[0039] In the above, the cavity cross-section of the DC burner is rectangular, and correspondingly, the axial cross-section of the first mounting flange 1 of the DC burner is rectangular, the axial cross-section of the ammonia sleeve 5 is rectangular, and the axial cross-section of the perimeter air sleeve 6 is rectangular; in addition, the axial cross-section of the second mounting flange 7 is circular.

[0040] Example 2 According to an embodiment of the present invention, a low-NOx emission ammonia-coal co-fired once-through burner for a tangential coal-fired boiler includes a pulverized coal concentrator 2 and a burner nozzle 3 for primary air conveying, an ammonia sleeve 5 for ammonia conveying and an ammonia injection hole 9 on the end face of the sleeve, and a perimeter air sleeve 6 as an air cooling device. Figure 1 , Figure 2 As shown.

[0041] The coal pulverizer 2 is equipped with a coal pulverizer concentration separation component, which includes an airflow collision boss and an airflow separation baffle 4. The coal pulverizer concentration separation component divides the coal pulverizer airflow into two parts: a concentrated coal pulverizer airflow and a dilute coal pulverizer airflow. The burner nozzle 3 consists of a concentrated coal pulverizer airflow nozzle for ejecting the concentrated coal pulverizer airflow and a dilute coal pulverizer airflow nozzle for ejecting the dilute coal pulverizer airflow. They send the two separated coal pulverizer airflows into the furnace and provide the oxygen used for pyrolysis and volatilization in the initial stage of combustion.

[0042] The ammonia injection device includes an ammonia sleeve 5, ammonia injection holes 9, and an ammonia hose 8. The ammonia sleeve 5 is located outside the pulverized coal concentrator 2, and its outlet has 10 or more ammonia injection holes 9 on the side of the concentrated pulverized coal gas flow nozzle. The number of ammonia injection holes is evenly distributed and arranged around the upper and lower edges and side walls of the concentrated pulverized coal gas flow nozzle to inject ammonia gas at high speed onto the flame surface of the concentrated pulverized coal gas flow combustion zone. The ammonia hose 8 is used to supply ammonia gas to the ammonia sleeve 5, and it is connected to the ammonia sleeve 5 via a second mounting flange 7 and corresponding connecting pipes.

[0043] The cooling of the burner nozzle 3 comes from the perimeter air located outside the burner nozzle 3, which is specifically delivered through the perimeter air sleeve 6. The inlet of the perimeter air sleeve 6 is connected to the secondary air box and is arranged outside the ammonia sleeve 5, thereby sending the perimeter air to the area around the burner nozzle 3 and injecting it into the furnace.

[0044] The specific working process and benefits of this invention are as follows: like Figure 1 , Figure 2 As shown, the pulverized coal concentrator 2 included in the DC burner is equipped with a gas flow collision protrusion and a gas flow separation baffle 4 that utilizes inertia to achieve gas-solid two-phase flow separation.

[0045] When the pulverized coal airflow (primary air) passes the airflow collision boss located near the inlet, it is located on the lower side of the DC burner channel (the lower side here refers to...). Figure 1 Taking the direction shown as an example, it is described as follows: Figure 2 The coal powder airflow (corresponding to the left side) will directly collide with the airflow collision protrusion, causing the airflow to turn upward and guide the flow. Then it can bypass the airflow collision protrusion and flow downward into the side of the light coal powder airflow of the burner nozzle 3. The pulverized coal particles in the airflow have much greater inertia than the airflow itself. Therefore, after impact, these particles, especially larger ones, will rebound and separate from the airflow. This rebound will further cause the pulverized coal particles to enter the upper part of the DC burner (here, "upper part" refers to...). Figure 1 The upper side of the middle Figure 2 In the pulverized coal airflow on the right side of the burner nozzle 3, the concentration of pulverized coal in the upper side (the side with the concentrated pulverized coal airflow) is increased, forming a more concentrated pulverized coal airflow. At the same time, in the airflow flowing into the lower side, some pulverized coal has rebounded and separated into the airflow on the upper side of the channel, so the pulverized coal airflow on the lower side is a less concentrated pulverized coal airflow.

[0046] Located at an appropriate distance downstream of the airflow collision protrusion, airflow separation baffles 4 are arranged symmetrically on the upper and lower axes of the pulverized coal thickener 2. These baffles further separate the concentrated and diluted pulverized coal airflows at the burner nozzle 3, forming two primary airflows of concentrated and diluted pulverized coal airflows, which are then delivered to the burner nozzle 3 of the direct-flow burner. Therefore, the burner nozzle 3 can actually be considered to consist of two nozzles, i.e., in... Figure 2 The image shows the concentrated pulverized coal gas flow nozzle on the right and the light pulverized coal gas flow outlet on the left.

[0047] The two primary air streams, one rich and one lean, formed by the pulverized coal gas flow, are further injected into the boiler furnace from burner nozzles 3. Since identical direct-flow burners are installed at the four corners of the boiler furnace, the injected rich and lean primary air streams further form a rotating airflow within the furnace, thus creating a rotating fire ring during combustion. Figure 3 As shown in the figure. At the same time, it can also be concluded from the figure that the configuration of the burner nozzle 3 is as follows: the light primary air (light pulverized coal airflow) is on the outside of the entire rotating airflow, that is, on the backfire side near the wall; the rich primary air (rich pulverized coal airflow) is on the inside of the entire rotating airflow, that is, on the fire-facing side near the center of the furnace.

[0048] The ammonia sleeve 5 is directly arranged around the outside of the pulverized coal concentrator 2. This arrangement has two advantages: First, the low-temperature ammonia gas flow passing through the outside of the cavity of this direct-flow burner can cool the burner nozzle 3; second, the high-temperature burner nozzle 3 can heat the ammonia gas, preheating it and improving the degree of decomposition reaction in the high-temperature zone of the concentrated pulverized coal combustion gas. The ammonia injection port consists of more than 10 evenly distributed circular holes at the end of the ammonia sleeve 5, located at the outer edge of the concentrated pulverized coal gas injection port. Because the pyrolysis and combustion of the primary air injected into the furnace quickly depletes the oxygen in the primary air, the high-speed ammonia gas flow from the injection port will penetrate the flame root and enter the middle and rear regions of the combustion flame, allowing the ammonia gas to be injected into the concentrated pulverized coal combustion zone (e.g.,...). Figure 3 (As shown). At this location, due to the high concentration of pulverized coal, the oxygen in the gas flow has been almost completely consumed at the flame root. Therefore, the area near the flame face is an oxygen-deficient high-temperature environment. As ammonia gas injected onto the flame face here will mostly decompose into hydrogen and nitrogen gas, instead of being converted into nitrogen oxides. Subsequently, the hydrogen gas generated by decomposition will mix with oxygen and burn in the middle and later stages of the furnace, realizing the conversion of ammonia combustion into hydrogen combustion, which greatly reduces the formation of nitrogen oxides.

[0049] The perimeter air sleeve 6 provides cooling air to the burner nozzle 3. When the DC burner is shut down, it can protect the burner nozzle 3 from high-temperature erosion. The cooling air jet leaves the perimeter air nozzle at a certain angle, which can ensure that ammonia will not mix with it and react to produce nitrogen oxides.

[0050] In summary, this invention aims to reduce carbon emissions from coal-fired power plants and simultaneously address the issue of significantly increased nitrogen oxide emissions from coal-fired ammonia-blended burners. It proposes a coal-fired ammonia-blended direct-fired burner for use in tangentially round coal-fired boilers, effectively controlling nitrogen oxide emissions. This direct-fired burner mainly comprises a pulverized coal concentrator 2 and its internal pulverized coal concentration / lean separation component, an ammonia sleeve 5, a perimeter air sleeve 6, and burner nozzles 3. The pulverized coal concentrator 2 and its internal pulverized coal concentration / lean separation component separate the primary air pulverized coal flow into rich and lean portions. The ammonia sleeve 5 delivers ammonia and injects it at high speed into the rear combustion zone of the high-temperature, oxygen-deficient rich pulverized coal flow flame within the furnace, causing most of the ammonia to decompose into hydrogen at high temperature, significantly reducing the generation of nitrogen oxides from the direct combustion of ammonia in excess oxygen. The perimeter air sleeve 6 injects a small amount of cooling air to protect the burner nozzles 3 from high-temperature erosion.

[0051] The burner of this invention has a simple structure and can effectively organize the pulverized coal airflow into two streams, one rich and one lean, before entering the furnace. Furthermore, the ammonia jet enters the high-temperature, oxygen-deficient flame region within the rich pulverized coal airflow, where it is decomposed into hydrogen to a high degree. This effectively controls oxide emissions when pulverized coal is co-fired with a high proportion of ammonia. Therefore, this invention can provide technical support for reducing carbon emissions from coal-fired boilers.

[0052] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A coal-ammonia mixed combustion once-through burner, characterized by comprising: The coal powder concentrator (2), the ammonia sleeve (5) and the perimeter wind sleeve (6) are included. The coal powder concentrator (2) is internally provided with a coal powder concentration and dilution separation assembly along the airflow flow direction, which is used for separating the coal powder airflow entering the coal powder concentrator (2) and respectively outputting the concentrated coal powder airflow and the dilute coal powder airflow. The ammonia sleeve (5) is externally sleeved on the coal powder concentrator (2), and a plurality of ammonia injection holes (9) are formed in the gas outlet end of the ammonia sleeve (5) on the side of the coal powder concentrator (2) outputting the concentrated coal powder airflow, and the ammonia injection holes (9) are arranged towards the jet direction of the coal powder concentrator (2). The perimeter wind sleeve (6) is externally sleeved on the ammonia sleeve (5), the nozzle of the perimeter wind sleeve (6) is arranged in the circumferential direction of the nozzle of the coal powder concentrator (2), and the jet direction of the perimeter wind sleeve (6) is externally arranged.

2. The coal-ammonia mixed combustion once-through combustor according to claim 1, wherein The coal powder concentration and dilution separation assembly comprises, in sequence along the airflow flow direction, an airflow collision boss and an airflow separation baffle (4). The airflow collision boss is arranged close to the gas inlet end of the coal powder concentrator (2), and the airflow collision boss is arranged on one side in the interior of the coal powder concentrator (2); the airflow collision boss realizes the impingement separation of the coal powder airflow through the inertia difference between the coal powder particles and the gas. The airflow separation baffle (4) is connected to the gas outlet end of the coal powder concentrator (2), and the airflow separation baffle (4) is arranged in the middle part in the interior of the coal powder concentrator (2); the airflow separation baffle (4) separates the concentrated coal powder airflow and the dilute coal powder airflow formed by the airflow collision boss.

3. The coal-ammonia mixed combustion once-through combustor according to claim 2, characterized by The slope of the windward face of the airflow collision boss is smaller than the slope of the leeward face.

4. The coal-ammonia mixed combustion direct-flow burner according to claim 2, wherein The airflow separation baffle (4) is provided with an upturned section at one end close to the airflow collision boss, and the upturned section is upturned towards the side of the concentrated coal powder airflow.

5. The coal-ammonia mixed combustion direct-flow burner according to claim 2, wherein The airflow separation baffle (4) is provided with a slope at one end connected to the coal powder concentrator (2), and the slope is arranged on the side of the concentrated coal powder airflow.

6. The coal-ammonia mixed combustion direct-flow burner according to claim 1, wherein The injection face normal direction of the ammonia injection hole (9) is arranged at an angle of 10-15° with the center line of the coal powder concentrator (2).

7. The coal-ammonia mixed combustion direct-flow burner according to claim 1, wherein The injection face normal direction of the gas outlet end of the perimeter wind sleeve (6) is arranged at an angle of 35-60° with the center line of the coal powder concentrator (2).

8. The coal-ammonia mixed combustion direct-flow burner according to claim 1, wherein The gas inlet end of the coal powder concentrator (2) is provided with a first mounting flange (1).

9. The coal-ammonia mixed combustion direct-flow burner according to claim 1, wherein The gas inlet end of the ammonia sleeve (5) is connected to the ammonia gas hose (8) through a second mounting flange (7), and the gas outlet end of the ammonia sleeve (5) is provided with at least 10 ammonia injection holes (9).

10. The use of the coal-ammonia mixed combustion direct-flow burner according to any one of claims 1 to 9 in a tangentially-fired coal-fired boiler, characterized in that, The coal-ammonia mixed combustion direct-flow burner is arranged at the four corners of the furnace of the coal-fired boiler, and the airflow entering the furnace forms a rotating airflow in the form of a tangent circle; wherein the dilute coal powder airflow is located on the outside of the rotating airflow flame, the concentrated coal powder airflow is located on the inside of the rotating airflow flame, and the ammonia gas is injected into the inside combustion zone of the concentrated coal powder flame.

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