Primary air ammonia mixing burner of tangential combustion pulverized coal fired boiler

Abstract

The utility model provides a primary air ammonia mixing burner of a tangential combustion pulverized coal fired boiler, and belongs to the technical field of pulverized coal fired boilers. Pure ammonia gas is directly jetted into flames on the fire-flowing side of the pulverized coal through high-speed jet flow, ignition and combustion of ammonia gas are effectively promoted through the preheating effect of high-temperature flue gas in a near-wall area on the ammonia gas jet flow and high-temperature heating in the pulverized coal flames, and the technical problems that the ammonia gas is not prone to ignition and combustion and poor in combustion stability are solved. Finally, the burn-off rate of the ammonia gas is high, and the ammonia escape phenomenon is avoided. Ammonia gas is combusted in pulverized coal flames under the condition of low oxygen concentration, the generation amount of fuel type NOx in the combustion process is restrained, the generation amount of NOx pollutants in the ammonia-doped combustion process of the pulverized coal boiler is reduced, and the technical problem that in the ammonia gas combustion process, the high-concentration fuel type NOx emission concentration potential value exists is solved. The structural design is simple and convenient, the ammonia spray gun does not need to supply combustion air, the complexity of the structure and debugging of equipment is reduced, and the manufacturing cost of the equipment is low.

Description

Technical Field

[0001] This utility model relates to the field of pulverized coal boilers, and in particular to a primary air mixed ammonia burner for tangentially burning pulverized coal boilers. Background Technology

[0002] Due to the extensive use of fossil fuels, energy depletion and climate degradation have become two major challenges facing humanity in the 21st century. To address these threats, countries have successively formulated new energy development strategies and carbon reduction targets.

[0003] The "carbon peak and carbon neutrality" goals proposed by General Secretary Xi Jinping at the 75th UN General Assembly in 2020 have presented my country's power industry with an urgent task of CO2 emission reduction. Achieving these dual carbon goals requires the participation of a wide range of carbon emission reduction technologies, and the application of carbon-free fuels in the combustion field is an important technological means.

[0004] Ammonia, as a mature and inexpensive non-carbon-based zero-carbon hydrogen storage material, can be stored and transported in liquid form at -33℃ / 0.1MPa. It has significant advantages such as high hydrogen content per unit volume, relatively high volumetric energy density, and high safety, which can effectively break through the bottleneck of hydrogen energy development.

[0005] Partially replacing coal with ammonia can be an effective way to reduce carbon emissions at the front end of thermal power units under the "dual carbon" target. Developing efficient and low-polluting combustion technologies for ammonia / coal co-combustion can solve the problem of fossil energy substitution and is one of the effective measures to achieve clean combustion in thermal power units.

[0006] The use of ammonia as a fuel also has some obvious drawbacks, and the comprehensive application of ammonia in combustion equipment still faces huge challenges, requiring in-depth research to overcome these problems.

[0007] Ammonia is a non-flammable fuel. Its high ignition temperature, large ignition energy, slow flame propagation speed, and narrow flammability limit make it difficult to ignite and burn, resulting in poor combustion stability and burnout. Compared to hydrogen and methane, ammonia fuel has significantly lower reactivity, with a maximum laminar flame propagation speed only 1 / 5 that of methane, a narrower flame ignition limit, and a higher ignition temperature.

[0008] Ammonia combustion under lean-fuel, oxygen-rich conditions produces high concentrations of nitrogen oxides (NOx), while combustion under rich-fuel, low-oxygen conditions results in high ammonia slip. As a fuel containing a large proportion of nitrogen, ammonia exhibits a high potential for fuel-type NOx emissions during combustion. Therefore, low NOx emissions have become a key performance indicator for ammonia combustion technology.

[0009] These characteristics limit its application in direct combustion, and currently, ammonia burners on the market have not fully solved the aforementioned technical problems.

[0010] To address the issue of ammonia's poor flammability, a common technical approach is to incorporate more reactive combustible gases, such as natural gas or hydrogen. This method not only requires an additional combustible gas supply system, increasing system complexity and operational control workload, but also necessitates the addition of a separate combustible gas supply system.

[0011] Another type of patent in the field of ammonia combustion addresses the problem by decomposing ammonia into hydrogen and nitrogen through a catalytic decomposition reaction. The hydrogen formed by the catalytic decomposition has good combustion characteristics. However, the additional ammonia catalytic decomposer complicates the burner's structure, increases its space requirements, and limits its ease of use. Utility Model Content

[0012] The purpose of this invention is to solve the technical problems faced by current ammonia-blended combustion technology in pulverized coal boilers (ammonia is non-flammable, and NOx emission concentration is high). It proposes "a tangentially circular combustion pulverized coal boiler primary air ammonia-blended burner," which directly utilizes ammonia as fuel to achieve coupled combustion of pulverized coal and ammonia within the boiler furnace. This results in a stable combustion state, high ammonia burnout rate, and effective control of NOx emission concentration during combustion. To achieve the above objectives, the technical solution adopted by this invention is as follows:

[0013] A tangentially circularly burning pulverized coal boiler primary air mixed ammonia burner, comprising a pulverized coal burner, an ammonia injection gun, a secondary air box, pulverized coal burner nozzles and secondary air nozzles, wherein four sets of pulverized coal burners are respectively arranged at the four corners of the pulverized coal boiler furnace, the ammonia injection guns are arranged on the furnace wall of the pulverized coal boiler, secondary air boxes are arranged on both sides of the pulverized coal burner, pulverized coal burner nozzles are arranged at the outlet of the pulverized coal burner, and secondary air nozzles are arranged at the outlet of the secondary air box;

[0014] Primary air is injected into the furnace of the pulverized coal boiler through the nozzle of the pulverized coal burner, forming a primary air jet. The primary air consists of primary air and pulverized coal particles.

[0015] The ammonia jet ejected from the ammonia spray gun is injected into the furnace of the pulverized coal boiler, where the ammonia jet mixes with the primary air jet.

[0016] Secondary air is supplied into the secondary air box to aid combustion. The secondary air is injected into the furnace of the pulverized coal boiler through the secondary air nozzle, forming a secondary air jet. In the high-temperature environment of the pulverized coal boiler furnace, the pulverized coal reacts with the oxygen provided by the primary air and the secondary air to form a flame jet. The flame jets at the four corners interact with each other to form a tangential flame in the pulverized coal boiler furnace.

[0017] This utility model relates to a tangentially circular pulverized coal boiler primary air mixed ammonia burner, wherein the nozzle jet velocity of the ammonia spray gun is 50-80m / s.

[0018] This utility model relates to a primary air-ammonia mixed burner for a tangentially circular pulverized coal boiler, wherein the primary air jet and the secondary air jet have parallel jet directions.

[0019] This utility model relates to a tangentially circular pulverized coal boiler primary air mixed ammonia burner, wherein the vertical distance between the outlet jet boundaries of the pulverized coal burner nozzle and the secondary air nozzle is 200mm-300mm.

[0020] This utility model relates to a tangentially circular combustion pulverized coal boiler primary air mixed ammonia burner, wherein the ammonia spray gun is arranged on the furnace wall of the pulverized coal boiler and on the flame-facing side of the pulverized coal burner corresponding to the flame.

[0021] This utility model discloses a tangentially circular combustion pulverized coal boiler primary air mixed ammonia burner, wherein the cross-section of the pulverized coal boiler furnace is a rectangle that is close to a square.

[0022] This utility model relates to a primary air mixed ammonia burner for a tangentially circular pulverized coal boiler, wherein the primary air accounts for 18%-25% of the total air supply in the furnace of the pulverized coal boiler, and the primary air velocity is 22m / s-28m / s.

[0023] This utility model relates to a primary air mixed ammonia burner for a tangentially circular pulverized coal boiler, wherein the temperature of the secondary air is 300℃-350℃ and the wind speed of the secondary air at the outlet of the secondary air nozzle is 40m / s-50m / s.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The ammonia burner injects pure ammonia gas directly into the flame of the pulverized coal jet via a high-speed jet. The preheating effect of the high-temperature flue gas near the wall and the high-temperature heating within the pulverized coal flame effectively promote the ignition and combustion of ammonia, solving the technical problems of ammonia's difficulty in ignition and combustion and its poor combustion stability. Ultimately, the ammonia has a high burnout rate and no ammonia escape.

[0026] (2) Ammonia combustion in a pulverized coal flame at a lower oxygen concentration suppresses the formation of fuel-type NOx during combustion, thus reducing the amount of nitrogen oxides (NOx) generated during ammonia-blended combustion in pulverized coal boilers. The boiler's NOx emissions are no higher than those under pure coal-fired operation conditions. This solves the technical challenge of high potential concentrations of fuel-type NOx emissions during ammonia combustion.

[0027] (3) The structure is simple and the ammonia spray gun does not require the supply of combustion air, which reduces the complexity of the equipment structure and debugging, and the equipment cost is low. It can be used for boiler renovation projects and new unit design. Attached Figure Description

[0028] Figure 1This is a plan view of a primary air mixed ammonia burner for a tangentially circular pulverized coal boiler according to this utility model.

[0029] Figure 2 This is an elevation view of a primary air mixed ammonia burner for a tangentially circular pulverized coal boiler according to this utility model.

[0030] Figure 3 This is a structural diagram of a typical pulverized coal boiler.

[0031] The attached diagram is labeled as follows: 1 is the furnace of a pulverized coal boiler; 2 is the pulverized coal burner; 3 is the tangential flame; 4 is the ammonia spray gun; 5 is the ammonia jet; 6 is the secondary air box; 7 is the pulverized coal burner nozzle; 8 is the secondary air nozzle; 9 is the primary air jet; 10 is the secondary air jet; 11 is the primary air ignition point; 12 is the pulverized coal flame; 13 is the ammonia mixing point; and 14 is the secondary air mixing point. Detailed Implementation

[0032] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0033] Example 1

[0034] like Figure 1-3 As shown, this embodiment relates to a tangentially circular pulverized coal boiler primary air mixed ammonia burner, including a pulverized coal burner, an ammonia spray gun, a secondary air box, a pulverized coal burner nozzle and a secondary air nozzle. Four sets of pulverized coal burners are respectively set at the four corners of the pulverized coal boiler furnace. The ammonia spray gun is arranged on the wall of the pulverized coal boiler furnace (1) and on the fire-facing side of the flame corresponding to the pulverized coal burner. Secondary air boxes are set on both sides of the pulverized coal burner. A pulverized coal burner nozzle is set at the outlet of the pulverized coal burner. A secondary air nozzle is set at the outlet of the secondary air box.

[0035] Primary air is injected into the furnace of the pulverized coal boiler through the nozzle of the pulverized coal burner, forming a primary air jet (9). The primary air consists of primary air and pulverized coal particles.

[0036] Ammonia jets ejected from ammonia spray guns are injected into the furnace of pulverized coal boilers, where they mix with primary air jets and then burn.

[0037] Secondary air is supplied into the secondary air box to aid combustion. The secondary air is injected into the furnace of the pulverized coal boiler through the secondary air nozzle, forming a secondary air jet. In the high-temperature environment of the pulverized coal boiler furnace, the pulverized coal reacts with the oxygen provided by the primary air and the secondary air to form a flame jet. The flame jets at the four corners interact with each other to form a tangential flame in the pulverized coal boiler furnace.

[0038] Preferably, the nozzle jet velocity of the ammonia spray gun is 50-80 m / s.

[0039] Preferably, the primary air jet and the secondary air jet are parallel in direction.

[0040] Preferably, the vertical distance between the outlet jet boundaries of the pulverized coal burner nozzle and the secondary air nozzle is 200mm-300mm.

[0041] Preferably, the ammonia spray gun is arranged on the furnace wall of the pulverized coal boiler and on the flame-facing side of the pulverized coal burner. The distance between the ammonia spray gun and the pulverized coal burner is required; the injection point of the ammonia jet and the pulverized coal flame is the ammonia mixing point. The arrangement of the ammonia spray gun and the pulverized coal burner must achieve the above objectives.

[0042] Preferably, the cross-section of the pulverized coal boiler furnace is a rectangle that is close to a square, and the aspect ratio of the rectangular cross-section must be within a certain range. This is because a flow field with tangentially rounded flames at the four corners needs to be formed inside the furnace, and the cross-section must be close to a square in order to ensure that the flow field inside the furnace is uniform.

[0043] Preferably, the primary air accounts for 18%-25% of the total air supply in the pulverized coal boiler furnace, and the primary air velocity is 22m / s-28m / s.

[0044] Preferably, the temperature of the secondary air is 300℃-350℃, the wind speed of the secondary air at the outlet of the secondary air nozzle is 40m / s-50m / s, and the secondary air is hot air heated by the air preheater.

[0045] Example 2

[0046] like Figure 1-3 As shown, this embodiment relates to a tangentially circular pulverized coal boiler primary air mixed ammonia burner, and the plan layout diagram is shown below. Figure 1 This is a plan view of the main burner area of ​​a pulverized coal boiler corresponding to a conventional tangential combustion method. The boiler furnace 1 serves as the main space for fuel combustion, where the fuel is burned and heat is released by the combustion system. The inner boundary wall of the boiler furnace 1 absorbs the heat released by the flame within the furnace through radiation and convection.

[0047] Four pulverized coal burners 2 are respectively installed at the four corners of the pulverized coal boiler furnace 1. The function of the pulverized coal burners 2 is to organize the flow field of pulverized coal airflow (primary air) and combustion air (secondary air) and inject it into the boiler furnace 1. Under suitable combustion conditions, pulverized coal and combustion air undergo combustion reaction to form a flame. The flame jets of the pulverized coal burners 2 at the four corners interact with each other, forming a tangential flame 3 in the shape of a four-corner tangential circle in the furnace.

[0048] The tangential combustion method involves each group of burners forming a unified tangential rotating flame within the furnace. This tangential flame combustion pattern results in intense fuel mixing in the later stages, which is beneficial for complete fuel combustion. A certain distance needs to be maintained between the ammonia injection lance and the pulverized coal burner to ensure that the ammonia is injected directly into the ammonia mixing point 13 after the pulverized coal flame ignites, thus facilitating the coupled combustion of ammonia and pulverized coal.

[0049] Ammonia jet 4 is positioned on the wall of the pulverized coal boiler furnace 1, on the flame-facing side of the pulverized coal burner 2. Pure ammonia gas ejected from the ammonia jet 4 forms an ammonia jet 5, which is injected into the pulverized coal boiler furnace 1 at high speed. After mixing with the primary air jet 9, the ammonia burns under high temperature and in the presence of oxygen. The ammonia jet 4 needs to be designed with an appropriate jet velocity to ensure the rigidity of the ammonia jet 5, prevent it from being affected by the airflow near the furnace wall, and achieve a thorough and rapid mixing effect with the pulverized coal flame 12. Typically, the jet velocity at the nozzle of the ammonia jet 4 is 50-80 m / s, depending on the ammonia flow rate. Before mixing into the pulverized coal flame 12, the ammonia jet 5 entrains the high-temperature flue gas near the furnace wall, which preheats the ammonia.

[0050] See facade layout plan Figure 2 Combustion air (secondary air) is supplied into the secondary air box 6 and injected into the boiler furnace through the secondary air nozzle 8, forming a secondary air jet 10. Primary air consists of primary air carrying pulverized coal particles and is injected into the boiler furnace through the pulverized coal burner nozzle 7, forming a primary air jet 9. The primary air jet 9 and the secondary air jet 10 are parallel in direction.

[0051] The primary air jet 9 entrains nearby high-temperature flue gas in the furnace and absorbs the radiant heat of the flame in the furnace. After the pulverized coal particles are heated to the ignition temperature, they burn to produce pulverized coal flame 12. The location where the primary air jet 9 burns is the primary air ignition point 11.

[0052] The primary air ignition point 11 needs to be ensured. The temperature of the primary air (pulverized coal) during injection is determined by the coal quality, and is generally in the range of 70℃-100℃. After the pulverized coal is injected into the furnace, its temperature rises after absorbing heat. It takes a certain delay time for the pulverized coal to start burning. The pulverized coal starts to ignite when its temperature reaches the ignition conditions. Therefore, the primary air ignition point 11 must be a certain distance away from the pulverized coal burner nozzle 7.

[0053] Ammonia jet 5 is injected into the pulverized coal flame 12, at the ammonia mixing point 13. Under the high-temperature heating effect of the pulverized coal flame 12, the ammonia burns in a high-temperature environment, and the high temperature inside the pulverized coal flame effectively promotes the ignition and combustion of the ammonia. When ammonia is injected into the already ignited pulverized coal flame, it is heated by the flame and burns together with the pulverized coal. The ammonia is injected into the ammonia mixing point 13, which is located after the primary air ignition point 11. The ammonia mixing point 13 is located inside the already ignited pulverized coal flame 12, where the ammonia is heated by the flame and then burns.

[0054] During the initial combustion stage of pulverized coal particles and ammonia, the oxygen in the combustion air of the pulverized coal flame 12 is rapidly consumed. Combustion under low oxygen concentration conditions can effectively control the NOx concentration generated by ammonia combustion. Fuel-type NOx is generated by the oxidation reaction of oxygen and nitrogen contained in the fuel. The oxygen concentration at which the reaction occurs is an important factor affecting the amount of fuel-type NOx generated; lower fuel-type NOx is more easily obtained under low oxygen concentration conditions.

[0055] The secondary air jet 10 diffuses within the furnace and eventually mixes with the pulverized coal flame 12 at the secondary air mixing point 14. This replenishes the amount of air needed for the unburned pulverized coal particles and ammonia to burn completely inside the pulverized coal flame 12, ultimately achieving a higher fuel (pulverized coal particles, ammonia) burnout rate.

[0056] After the primary or secondary air jet leaves the nozzle, it enters the furnace. Due to the exchange of momentum with the flue gas in the surrounding environment and the entrainment, the boundary of the jet diffuses outward and has a small jet diffusion angle.

[0057] There is a certain distance between the primary air nozzle and the secondary air nozzle structure. After diffusion, the primary and secondary air jets intersect at their boundaries, and the intersection point is defined as the secondary air mixing point 14. The secondary air mixing point 14 should be located at an appropriate position after the primary air ignition point 11.

[0058] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection of this utility model is defined by the appended claims and their equivalents.

Claims

1. A tangentially circular pulverized coal boiler primary air mixed with ammonia burner, characterized in that: The tangentially circular pulverized coal boiler primary air mixed ammonia burner includes: pulverized coal burner (2), ammonia spray gun (4), secondary air box (6), pulverized coal burner nozzle (7) and secondary air nozzle (8). The four sets of pulverized coal burners (2) are respectively set at the four corners of the pulverized coal boiler furnace (1). The ammonia spray gun (4) is arranged on the wall of the pulverized coal boiler furnace (1). The secondary air box (6) is set on both sides of the pulverized coal burner (2). The pulverized coal burner nozzle (7) is set at the outlet of the pulverized coal burner (2). The secondary air nozzle (8) is set at the outlet of the secondary air box (6). Primary air is injected into the furnace (1) of the pulverized coal boiler through the nozzle (7) of the pulverized coal burner, forming a primary air jet (9). The primary air consists of primary air and pulverized coal particles. The ammonia jet (5) ejected from the ammonia spray gun (4) is injected into the furnace (1) of the pulverized coal boiler, and the ammonia jet (5) is mixed with the primary air jet (9); Secondary air combustion air is supplied into the secondary air box (6). The secondary air is injected into the furnace (1) of the pulverized coal boiler through the secondary air nozzle (8), forming a secondary air jet (10). In the high-temperature environment inside the furnace (1) of the pulverized coal boiler, the pulverized coal reacts with the oxygen provided by the primary air and the secondary air to form a flame jet. The flame jets at the four corners interact with each other to form a tangential flame (3) in the furnace (1) of the pulverized coal boiler.

2. The tangentially circular pulverized coal boiler primary air mixed ammonia burner according to claim 1, characterized in that: The nozzle jet velocity of the ammonia spray gun (4) is 50-80 m / s.

3. The tangentially circular pulverized coal boiler primary air mixed ammonia burner according to claim 1, characterized in that: The primary wind jet (9) and the secondary wind jet (10) are parallel in direction.

4. The tangentially circular pulverized coal boiler primary air mixed ammonia burner according to claim 1, characterized in that: The vertical distance between the outlet jet boundaries of the pulverized coal burner nozzle (7) and the secondary air nozzle (8) is 200mm-300mm.

5. The tangentially circular pulverized coal boiler primary air mixed ammonia burner according to claim 1, characterized in that: The ammonia spray gun (4) is arranged on the wall of the pulverized coal boiler furnace (1) and on the flame-facing side of the pulverized coal burner (2).

6. The primary air ammonia-mixed burner for a tangentially circular pulverized coal boiler according to claim 1, characterized in that: The cross-section of the furnace (1) of the pulverized coal boiler is a rectangle that is close to a square.

7. The primary air mixed ammonia burner for a tangentially circular pulverized coal boiler according to claim 1, characterized in that: The primary air accounts for 18%-25% of the total air supply in the furnace (1) of the pulverized coal boiler, and the primary air velocity is 22m / s-28m / s.

8. The tangentially circular pulverized coal boiler primary air mixed ammonia burner according to claim 1, characterized in that: The temperature of the secondary air is 300℃-350℃, and the wind speed at the outlet of the secondary air nozzle is 40m / s-50m / s.

Images