Pulverized coal flameless oxygen-enriched burner with stabilizing device

Abstract

The invention discloses a pulverized coal flameless oxygen-enriched burner with a stabilizing device, which comprises a central pulverized coal spray pipe, an oxidant spray pipe and a circulating flue gas spray pipe which are coaxially arranged from inside to outside and are respectively used for conveying pulverized coal airflow, oxidant airflow and circulating flue gas into a combustion chamber, the oxidizing agent airflow is high-temperature high-speed jet flow formed by mixing circulating flue gas and pure oxygen, and stable combustion bluff bodies are arranged at the outlet ends of the center pulverized coal spray pipe and the oxidizing agent spray pipe and used for entraining the circulating flue gas on the outer side to enter a center high-temperature flame area. High-temperature circulating flue gas generated by oxygen-enriched combustion is directly introduced into the hearth and assisted by a high-speed jet mode, flameless combustion is rapidly achieved, the flue gas waste heat utilization efficiency is improved, meanwhile, the problems of energy consumption and cost of flameless combustion high-temperature preheating are solved, and the device has the advantages of being simple in structure, convenient to mount and dismount, easy to maintain and the like, and has wide application prospects. And large-scale industrial application can be realized.

Description

Technical Field

[0001] The invention belongs to the technical field of coal combustion, and in particular relates to a pulverized coal flameless oxygen-enriched burner with a stabilizing device. Background Art

[0002] Oxy-fuel combustion technology is one of the carbon capture technologies with the lowest cost and the highest adaptability. Oxy-fuel combustion technology has two characteristics different from traditional air combustion: 1) The combustion flue gas is not discharged into the atmosphere. After dust removal, purification and condensation, it is circulated into the furnace in a certain proportion. This part of the flue gas is called circulating flue gas, and its main component is high-concentration CO2; 2) The pure oxygen separated by the air separation device and the circulating flue gas mixture are sent to the furnace for combustion instead of air, isolating the participation of N2 in the air. After multiple flue gas cycles, the CO2 concentration continues to increase (the volume concentration can reach 80-90% after condensation). By separating and purifying the high-purity CO2 in the flue gas, large-scale carbon capture can be achieved. Compared with air combustion, the main existing problems of oxygen-enriched combustion are: 1) Compared with N2 in air, CO2 in oxygen-enriched atmosphere has higher specific heat capacity and thermal radiation, which will cause ignition delay, flame temperature and propagation speed decrease, and combustion stability decrease in coal powder combustion; 2) After multiple cycles, the NOx concentration in the flue gas is at a relatively high level, affecting the safety of boiler operation.

[0003] The MILD oxy-fuel combustion technology, which combines the flameless combustion (MILD combustion) technology with good combustion stability and low NOx emission with the oxygen-rich combustion technology, has multiple advantages of high efficiency, cleanness and low carbon. This technology injects the oxidant (composed of pure oxygen and recycled flue gas) into the furnace through high-temperature preheating and high-speed jet flow, and the pulverized coal combustion reaction is diffused throughout the furnace through the strong dilution of the recirculated flue gas in the furnace. In the high-temperature and low-oxygen dilution environment, the combustion process presents a slow chemical reaction state, the peak temperature of the flame in the furnace is reduced, the temperature uniformity is improved, and the generation of NOx is suppressed.

[0004] In industrial applications, the oxidant is usually preheated at high temperature and injected at high speed to achieve flameless combustion. In order to reduce the energy consumption and cost of this process, the burner structure needs to be designed and optimized according to the technical characteristics of flameless combustion. The patent with application number CN202010684144.9 proposes a swirl oxygen-enriched flameless burner. By adding an ejector tube, pure oxygen is used to eject the high-temperature flue gas in the furnace for full mixing, thereby enhancing the suction of high-temperature flue gas in the furnace and improving the flame stability near the burner outlet; the patent with application number CN200910104757.4 designs a flameless combustion heat storage flat flame burner. By setting a porous heat storage body in the burner body, it is beneficial to achieve flameless combustion while ensuring the uniformity of the furnace temperature.

[0005] In summary, the existing pulverized coal flameless oxygen-enriched combustion devices mostly use methods such as adding ejectors and heat storage bodies to achieve flameless combustion of fuel. However, there are still problems such as complex burner structure and relatively high manufacturing cost, which is not conducive to the industrial application of pulverized coal flameless oxygen-enriched combustion. Summary of the invention

[0006] Purpose of the invention: In order to solve the above problems, the present invention provides a pulverized coal flameless oxygen-enriched burner with a stabilizing device, which can realize the flameless oxygen-enriched combustion of pulverized coal without adding ejectors, heat storage bodies and other devices, and has the characteristics of simple structure, easy installation and low cost.

[0007] Invention content: To achieve the above-mentioned objectives, the present invention provides a pulverized coal flameless oxygen-enriched burner with a stabilizing device, comprising a central pulverized coal nozzle, an oxidant nozzle and a circulating flue gas nozzle coaxially arranged from the inside to the outside, which are respectively used to convey the pulverized coal airflow, the oxidant airflow and the circulating flue gas into the combustion chamber, wherein the pulverized coal airflow is a circulating flue gas jet carrying pulverized coal, and the oxidant airflow is a high-temperature and high-speed jet mixed with circulating flue gas and pure oxygen, and the outlet ends of the central pulverized coal nozzle and the oxidant nozzle are provided with a combustion stabilizing blunt body for entraining the circulating flue gas on the outside into the high-temperature flame zone in the center.

[0008] Specifically, a central pulverized coal nozzle and a circumferential oxidant nozzle are provided inside the combustion stabilizing blunt body, which are connected to the central pulverized coal nozzle and the oxidant nozzle respectively. The outer periphery of the combustion stabilizing blunt body forms an annular stopper which gradually extends outward along the axial direction, thereby drawing more flue gas into the high-temperature flame zone near the burner outlet, fully diluting the oxygen concentration in the oxidant, reducing the peak temperature of the flame, and enhancing the uniformity of temperature distribution.

[0009] Furthermore, the circumferential oxidant nozzles are evenly distributed around the central pulverized coal nozzle, and the jet velocity thereof is preferably 100-120 m / s, and the jet velocity of the central pulverized coal nozzle is preferably 30-40 m / s.

[0010] Specifically, the central pulverized coal nozzle adopts a tapered nozzle structure, which includes an inlet section, a contraction section and an outlet section that are connected in sequence, wherein the diameter ratio of the outlet section to the inlet section is preferably 1 / 4 to 1 / 3.

[0011] Specifically, the oxidant nozzle adopts a tapered cylindrical structure, which includes an inlet section, a contraction section and an outlet section that are connected in sequence, wherein the diameter ratio of the outlet section to the inlet section is preferably 1 / 3 to 1 / 2.

[0012] Specifically, a swirler is provided between the oxidant nozzle and the central pulverized coal nozzle, and comprises a swirl inner ring, guide vanes and a swirl outer ring, wherein the guide vanes are evenly distributed between the swirl inner ring and the swirl outer ring along the circumferential direction.

[0013] Furthermore, the number of the guide blades is preferably 6 to 8, and the inclination angle is preferably 15 to 25°.

[0014] Specifically, the circulating flue gas nozzle adopts a sleeve structure, and its air inlet is arranged on the side of one end of the circulating flue gas nozzle away from the combustion chamber, and the end of the circulating flue gas nozzle close to the combustion chamber is connected with the combustion chamber.

[0015] Specifically, the airflow transported by the central pulverized coal nozzle and the circulating flue gas nozzle is preferably low-temperature circulating flue gas that has undergone dust removal, desulfurization, denitrification and condensation; the airflow transported by the oxidant nozzle is preferably a mixture of high-temperature circulating flue gas at the furnace outlet and pure oxygen; the proportion of circulating flue gas in the central pulverized coal nozzle, oxidant nozzle and circulating flue gas nozzle is 5-10%, 20-30% and 60-75%, respectively.

[0016] Specifically, the ratio of the maximum outer diameter of the combustion stabilizing body to the outlet inner diameter of the circulating flue gas nozzle is preferably 1 / 4 to 1 / 3.

[0017] Beneficial effects:

[0018] 1. The present invention adopts a step-by-step sleeve design of a circulating flue gas nozzle, an oxidant nozzle, and a central pulverized coal nozzle, and uses the high-temperature flue gas generated by oxygen-enriched combustion to preheat the pulverized coal particles, promote the ignition of the pulverized coal, and alleviate the problem of delayed ignition of the pulverized coal under high CO2 concentration conditions;

[0019] 2. The present invention adopts the structural design of the central combustion stabilizing blunt body to strengthen the flue gas circulation at the burner outlet, prevent the local flame temperature from being too high and the flame floating distance from being too long, improve the flame stability, and at the same time, the oxygen concentration in the high temperature zone is fully diluted, inhibiting the oxidation process of fuel nitrogen, which is conducive to reducing NOx emissions;

[0020] 3. The present invention utilizes the high-temperature circulating flue gas generated by oxygen-enriched combustion to directly pass into the furnace and is assisted by a high-speed jet to quickly achieve flameless combustion, thereby improving the utilization efficiency of flue gas waste heat and alleviating the energy consumption and cost issues of high-temperature preheating of flameless combustion. It has the characteristics of simple structure, easy installation, easy disassembly, and easy maintenance, which is conducive to large-scale industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the structure of a pulverized coal flameless oxygen-enriched burner in an embodiment of the present invention;

[0022] Figure 2 for Figure 1 AA section view in;

[0023] Figure 3 for Figure 1 BB section diagram in;

[0024] Figure 4 This is a combustion principle diagram of a pulverized coal flameless oxygen-enriched burner in an embodiment of the present invention;

[0025] The figure includes: 1. central pulverized coal nozzle, 2. oxidant nozzle, 3. cyclone, 4. circulating flue gas nozzle, 5. combustion stabilizing blunt body, 51. central pulverized coal nozzle, 52. circumferential oxidant nozzle. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0027] Reference Figure 1 , Figure 3 This embodiment provides a pulverized coal flameless oxygen-enriched burner with a stabilizing device, which mainly includes a central pulverized coal nozzle 1, an oxidant nozzle 2 and a circulating flue gas nozzle 4 coaxially arranged from the inside to the outside. In addition, a combustion stabilizing blunt body 5 is also provided at the outlet end of the central pulverized coal nozzle 1 and the oxidant nozzle 2.

[0028] Specifically, the central pulverized coal nozzle 1 uses part of the circulating flue gas as the primary air to transport pulverized coal into the combustion chamber. It is coaxially arranged inside the oxidant nozzle 2, one end of which is used to receive the pulverized coal airflow, and the other end is connected to the central pulverized coal nozzle 51 inside the combustion stabilizing body 5. Furthermore, the central pulverized coal nozzle 1 adopts a tapered nozzle structure, which includes an inlet section, a contraction section and an outlet section that are connected in sequence. The pulverized coal jet enters from the inlet section, is accelerated in the contraction section, and is quickly ejected from the outlet section. In order to ensure the high-speed injection of the pulverized coal jet, the diameter of the outlet section of the central pulverized coal nozzle 1 is smaller than the diameter of the inlet section, and the ratio of the two is preferably 1 / 4 to 1 / 3.

[0029] Specifically, the oxidant nozzle 2 is used to transport a mixture of high-temperature circulating flue gas and pure oxygen generated by oxygen-enriched combustion into the combustion chamber. It is coaxially arranged inside the circulating flue gas nozzle 4, one end of which is used to receive the oxidant gas flow, and the other end is connected to the circumferential oxidant nozzle 52 inside the flame-stabilizing blunt body 5. Further, the oxidant nozzle 2 is a cylindrical structure, which includes an inlet section, a contraction section and an outlet section that are connected in sequence, wherein the rear part of the inlet section, the contraction section and the outlet section are coaxially arranged inside the circulating flue gas nozzle 4, and the oxidant gas flow enters from the inlet section, is accelerated by the contraction section, and finally ejected from the outlet section. In order to ensure the high-speed injection of the oxidant gas flow, the diameter of the outlet section of the oxidant nozzle 2 is smaller than the diameter of the inlet section, and the ratio of the two is preferably 1 / 3 to 1 / 2.

[0030] Furthermore, a swirler 3 is provided in the inlet section of the oxidant nozzle 2 to promote the full mixing of oxygen and high-temperature circulating flue gas and adjust the airflow stability. Specifically, the swirler 3 includes a swirling inner ring, guide vanes and a swirling outer ring, wherein the swirling outer ring cooperates with the inner wall of the oxidant nozzle 2, and the swirling inner ring cooperates with the outer wall of the central pulverized coal nozzle 1; the guide vanes are evenly distributed between the swirling inner ring and the swirling outer ring along the circumferential direction, the number of the vanes is preferably 6 to 8, and the inclination angle is preferably 15 to 25 degrees.

[0031] Furthermore, the interior of the flame stabilizing body 5 is provided with a central pulverized coal nozzle 51 and a peripheral oxidant nozzle 52, both of which can adopt a tapered structural design to further increase the inlet velocity of the pulverized coal jet and the oxidant jet, enhance the flue gas recirculation in the furnace caused by the high-speed jet, and thus promote the flameless combustion of the pulverized coal. Figure 2 The number of the circumferential oxidant nozzles 52 is 6, which are evenly distributed around the central pulverized coal nozzle 51, and the jet velocity is preferably 100-120 m / s, and the jet velocity of the central pulverized coal nozzle 51 is preferably 30-40 m / s.

[0032] Specifically, the circulating flue gas nozzle 4 is used to transport part of the circulating flue gas into the combustion chamber. The circulating flue gas nozzle 4 adopts a sleeve structure, and the oxidant nozzle 2 is coaxially arranged inside. Furthermore, the air inlet of the circulating flue gas nozzle 4 is arranged on the side of the end away from the combustion chamber (which is also the side of the furnace) to facilitate the transportation of the circulating flue gas pipeline. At the same time, the end of the circulating flue gas nozzle 4 close to the combustion chamber is directly connected with the combustion chamber. In order to achieve high-speed injection, the central pulverized coal nozzle 1 and the oxidant nozzle 2 need to adopt a tapered structural design, and in order to promote the reflux of the burner outlet and stabilize the flame combustion, the outlet end of the circulating flue gas nozzle 4 can be directly connected with the combustion chamber.

[0033] It should be noted that the flue gas circulation temperature at different positions in oxygen-enriched combustion is different. It can be divided into two types of circulating flue gas, one of which is the high-temperature circulating flue gas directly discharged from the furnace, and the other is the low-temperature circulating flue gas generated during dust removal, desulfurization and denitrification, and condensation. Among them, the oxidant nozzle 2 uses a mixture of pure oxygen and high-temperature circulating flue gas, and is supplemented by a high-speed jet, which is conducive to quickly achieving a flameless combustion state of pulverized coal, effectively saving the preheating cost. The central pulverized coal nozzle 1 and the circulating flue gas nozzle 4 can use low-temperature circulating flue gas, and the oxidant nozzle 2 is coaxially arranged with the central pulverized coal nozzle 1, thereby using the high-temperature circulating flue gas in the oxidant nozzle 2 to preheat the pulverized coal jet, which is conducive to shortening the preheating time of pulverized coal particles and promoting ignition of pulverized coal. Specifically, the circulating flue gas in the central pulverized coal nozzle 1, the oxidant nozzle 2 and the circulating flue gas nozzle 4 account for 5-10%, 20-30% and 60-75% respectively.

[0034] Specifically, the outer periphery of the combustion stabilizing body 5 forms an annular stopper that gradually extends outward in the axial direction, thereby entraining more circulating flue gas from the outside into the high-temperature flame zone near the burner outlet, fully diluting the oxygen concentration in the oxidant, reducing the peak temperature of the flame, and enhancing the uniformity of temperature distribution. Figure 4 When the airflow in the circulating flue gas nozzle 4 enters the combustion chamber, due to the obstruction of the bluff body, a strong recirculation zone will be formed behind the bluff body, and a large amount of circulating flue gas will be sucked to the vicinity of the burner outlet. At this time, the coal powder particles are in a strong turbulent mixing and low oxygen dilution environment. The homogeneous reduction of NO by the coke-CO2 gasification reaction and the heterogeneous reduction of NO by the coke particles are both beneficial to reducing the generation of NOx. In order to ensure the flow stability of the circulating flue gas nozzle 4 and the suction effect of the combustion stabilizing bluff body 5, the ratio of the maximum outer diameter of the combustion stabilizing bluff body 5 to the outlet inner diameter of the circulating flue gas nozzle 4 is preferably 1 / 4 to 1 / 3. Furthermore, the combustion stabilizing bluff body 5 and the central coal powder nozzle 1 and the oxidant nozzle 2 can be separately processed and manufactured and assembled together, which is convenient for loading and unloading and replacement, while reducing production costs.

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A pulverized coal flameless oxygen-enriched burner with a stabilizing device, characterized in that: It includes a central pulverized coal nozzle, an oxidant nozzle and a circulating flue gas nozzle which are coaxially arranged from the inside to the outside, and are respectively used to convey the pulverized coal airflow, the oxidant airflow and the circulating flue gas into the combustion chamber, wherein the pulverized coal airflow is a circulating flue gas jet carrying pulverized coal, and the oxidant airflow is a high-temperature and high-speed jet mixed with circulating flue gas and pure oxygen. The outlet ends of the central pulverized coal nozzle and the oxidant nozzle are provided with a combustion stabilizing blunt body, which is used to draw the circulating flue gas on the outside into the high-temperature flame zone in the center.

2. The pulverized coal flameless oxygen-enriched burner according to claim 1, characterized in that: The interior of the combustion stabilizing body is provided with a central coal powder nozzle and a circumferential oxidant nozzle, which are respectively connected with the central coal powder nozzle and the oxidant nozzle. The outer periphery of the combustion stabilizing body forms an annular stopper which gradually extends outward along the axial direction.

3. The pulverized coal flameless oxygen-enriched burner according to claim 2, characterized in that: The circumferential oxidant nozzles are evenly distributed around the central pulverized coal nozzle, and the jet velocity thereof is 100-120 m / s. The jet velocity of the central pulverized coal nozzle is 30-40 m / s.

4. The pulverized coal flameless oxygen-enriched burner according to claim 1, characterized in that: The central pulverized coal nozzle adopts a tapered nozzle structure, which includes an inlet section, a contraction section and an outlet section which are connected in sequence, wherein the diameter ratio of the outlet section to the inlet section is 1 / 4 to 1 / 3.

5. The pulverized coal flameless oxygen-enriched burner according to claim 1, characterized in that: The oxidant nozzle adopts a tapered cylindrical structure, which includes an inlet section, a contraction section and an outlet section which are connected in sequence, wherein the diameter ratio of the outlet section to the inlet section is 1 / 3 to 1 / 2.

6. The pulverized coal flameless oxygen-enriched burner according to claim 1, characterized in that: A swirler is arranged between the oxidant nozzle and the central pulverized coal nozzle, and comprises a swirling inner ring, guide vanes and a swirling outer ring, wherein the guide vanes are evenly distributed between the swirling inner ring and the swirling outer ring along the circumferential direction.

7. The pulverized coal flameless oxygen-enriched burner according to claim 6, characterized in that: The number of the guide blades is 6 to 8, and the inclination angle is 15 to 25 degrees.

8. The pulverized coal flameless oxygen-enriched burner according to claim 1, characterized in that: The circulating flue gas nozzle adopts a sleeve structure, and its air inlet is arranged on the side of one end of the circulating flue gas nozzle away from the combustion chamber. The end of the circulating flue gas nozzle close to the combustion chamber is connected with the combustion chamber.

9. The pulverized coal flameless oxygen-enriched burner according to claim 1, characterized in that: The airflow transported by the central pulverized coal nozzle and the circulating flue gas nozzle is low-temperature circulating flue gas, and the airflow transported by the oxidant nozzle is a mixture of high-temperature circulating flue gas and pure oxygen. The circulating flue gas accounts for 5-10%, 20-30% and 60-75% in the central pulverized coal nozzle, the oxidant nozzle and the circulating flue gas nozzle, respectively.

10. The pulverized coal flameless oxygen-enriched burner according to claim 1, characterized in that: The ratio of the maximum outer diameter of the combustion stabilizing body to the inner diameter of the outlet of the circulating flue gas nozzle is 1 / 4 to 1 / 3.

Images