Method for optimizing and adjusting deep combustion of tangential boiler of coal-fired power plant

Abstract

The invention relates to a method for optimizing and adjusting deep combustion of a tangential boiler of a coal-fired power plant, which comprises the following steps of: arranging pulverized coal burners at four corners of the lower part in a hearth of the tangential boiler or on a boiler wall, and arranging SOFA air nozzles at four corners of the hearth or on the boiler wall above the pulverized coal burners; sOFA air nozzles at four corners of a hearth or on a furnace wall are divided into two groups, the vertical swing angle of one group of SOFA air nozzles is inclined upwards, the vertical swing angle of the other group of SOFA air nozzles is inclined downwards, and a coal-fired power plant tangential boiler stable load deep combustion optimization and adjustment test is combined, so that the problems of residual smoke rotation at a stable load hearth outlet of the boiler and low smoke emission are effectively solved. The problems that the flue gas temperature deviation of a hearth outlet is large, the reheating steam temperature deviation is large, the low-load reheating steam temperature is low, the desuperheating water amount of a high-load reheater is large, the nitric oxide deviation of a denitration inlet is large, and the steam temperature or the wall temperature is overhigh are caused are solved, and meanwhile the low-nitrogen emission requirement is met.

Description

Technical Field

[0001] This application relates to combustion adjustment or commissioning technology for tangential boilers in coal-fired power plants, specifically to a method for deep combustion optimization and adjustment of tangential boilers in coal-fired power plants. Background Technology

[0002] During pulverized coal combustion, rapid NOx accounts for less than 5%, and thermal NOx is almost non-existent at temperatures below 1300℃. For conventional coal-fired boilers, NOx is mainly generated through fuel-related pathways. From the NOx formation mechanism, it is easy to see that NOx formation is related to the following factors:

[0003] The amount of coal generated depends on the combustion method and conditions, and the amount generated depends on the combustion temperature level.

[0004] Characteristics of coal, such as its nitrogen content, especially the volatile nitrogen content;

[0005] The atmosphere of the flue gas in the reaction zone inside the furnace, namely the content of oxygen, nitrogen, NO and CHi in the flue gas;

[0006] The residence time of fuel and combustion products in the high-temperature zone of the flame and in the furnace.

[0007] After 20 years of low-NOx technology upgrades, the power plant boiler has basically undergone low-NOx combustion technology upgrades and tail-end SCR denitrification technology upgrades, with the concentration of nitrogen oxides in flue gas emissions controlled at 50 mg / Nm³. 3 Within [a certain range]. Significant achievements have been made in environmental pollution control.

[0008] Current low-NOx combustion technology is mainly an air-staged combustion technology, which introduces combustion air into the furnace in separate zones to carry out "oxygen-deficient combustion" and "oxygen-rich burnout," thus avoiding the simultaneous occurrence of excessively high temperatures and large excess air coefficients, thereby reducing NOx formation.

[0009] In the "oxygen-deficient combustion" zone, due to the low oxygen concentration, the combustion rate and temperature of volatiles in the fuel decrease, inhibiting the formation of thermal NOx. Due to incomplete combustion, some intermediate products such as HCN and NH3 reduce some of the generated NOx to N2, thereby inhibiting the emission of fuel-based NOx. Then, the remaining air required for combustion is introduced in the form of SOFA air, i.e., the "oxygen-rich combustion" zone. Although the air volume is large, this stage is a chemical reaction between the remaining unburned coke in the furnace and oxygen in the air at high temperature. The amount of newly generated NOx is very limited. Therefore, the overall NOx emission is significantly reduced.

[0010] Low-NOx combustion technology is an air-staged combustion technology, which involves oxygen-deficient combustion in the furnace combustion zone, resulting in a significant reduction in the concentration of nitrogen oxides generated. At the same time, due to the lack of oxygen in the furnace combustion zone, the pulverized coal is not fully combusted, leading to a significant increase in fly ash combustibles. In order to reduce fly ash combustibles, SOFA air is installed at a certain height above the furnace burner area to allow unburned pulverized coal to be reburned.

[0011] Generally, in tangential combustion boilers, the secondary air in the burner area is set to tangential rotation. To eliminate or reduce residual rotation of the flue gas at the furnace outlet and decrease the temperature deviations of the flue gas and steam on both sides of the boiler, the SOFA air is set to anti-tangential rotation. Theoretically, by adjusting the horizontal swing angle of the SOFA air, the rotational momentum of the tangential and anti-tangential air at the furnace outlet can be balanced. However, in reality, sometimes with good luck, the reheat steam temperature deviation can be minimized through adjustments. But as the load changes, the boiler combustion air distribution pattern also changes, making it difficult for operators to balance the tangential and anti-tangential rotational momentum. Therefore, under low-load operating conditions, the reheat steam temperature is still significantly lower than the design value. Moreover, the temperature deviation on both sides of most boilers is excessively large, exceeding 20°C. To reduce the reheat steam temperature deviation, the amount of desuperheating water in the reheater is increased, leading to reduced unit efficiency and increased coal consumption for power generation. Summary of the Invention

[0012] The purpose of this application is to provide a method for optimizing and adjusting deep combustion in a tangential boiler of a coal-fired power plant. This method can solve the problem that the flue gas temperature at the furnace outlet is significantly deviated (a deviation of 100°C is common) due to residual rotation of flue gas at the furnace outlet during stable load operation of the tangential boiler. This results in low reheat steam temperature at low load and large deviation of reheat steam temperature at high load, leading to excessive reheating water volume in the reheater. Consequently, the unit's coal consumption for power generation remains high, and the reheat steam temperature or wall temperature is prone to overheating, seriously affecting the safe operation of the boiler.

[0013] To achieve the above objectives, this application provides the following technical solution:

[0014] This invention provides a method for optimizing deep combustion in a tangentially circular boiler used in a coal-fired power plant. Based on this boiler, the method includes the following specific steps:

[0015] Pulverized coal burners are installed at the four lower corners of the furnace or on the furnace wall of the tangential boiler, and SOFA air nozzles are installed at the four corners of the furnace or on the furnace wall above the pulverized coal burners.

[0016] Divide the SOFA air nozzles at the four corners of the furnace or on the furnace wall into two groups. By adjusting the vertical swing angle of the SOFA air nozzles, tilt one group of SOFA air nozzles upward and the other group of SOFA air nozzles downward.

[0017] Under low-load conditions, the vertical swing angle of the SOFA air nozzle remains unchanged, while the swing angle of the pulverized coal burner nozzle in the pulverized coal burner area tilts upward according to the steam temperature requirement; under high-load conditions, the vertical swing angle of the SOFA air nozzle remains unchanged, while the swing angle of the pulverized coal burner nozzle in the pulverized coal burner area is either horizontal or tilted downward according to the steam temperature requirement.

[0018] When any layer of pulverized coal burners is shut down, the perimeter damper opening is set to 5%-10%; when the pulverized coal burners are in normal operation, the perimeter damper opening is set to a fixed value: under high load, the perimeter damper opening is set to 50-100%; under low load, the perimeter damper opening is set to 5-20%, and the perimeter damper opening is set to the same value for each layer.

[0019] When the tangential boiler of a coal-fired power plant is under high load, the opening of the combustion damper of each burner layer gradually decreases from bottom to top; when the load is low, the opening of the combustion damper is 5-20% for uniform air distribution.

[0020] The operating oxygen content at each load point must be determined through deep combustion optimization and adjustment tests, generally following the rule of high oxygen content at low load and low oxygen content at high load.

[0021] Preferably, the tangential boiler of the coal-fired power plant includes a partition screen heating surface, a reheater, a SOFA air burnout zone on the rear wall, SOFA air nozzles in the vertical upward tilt direction, SOFA air nozzles in the vertical horizontal tilt direction, a SOFA air burnout zone on the front wall, SOFA air nozzles in the vertical downward tilt direction, pulverized coal burners in the vertical upward tilt direction, pulverized coal burners in the vertical horizontal tilt direction, a pulverized coal burner zone, pulverized coal burners in the downward tilt direction, and a water-cooled wall; different nozzles and air outlets are set at the four corners of the boiler furnace, the main air box is equipped with 6 layers of enhanced ignition pulverized coal nozzles, perimeter air is arranged around the pulverized coal nozzles, one layer of auxiliary air nozzles is arranged between every two adjacent layers of pulverized coal nozzles, two layers of CCOFA nozzles are provided at the upper part of the main air box, and one layer of UFA nozzles is provided at the lower part of the main air box.

[0022] Preferably, the SOFA air nozzles at the four corners of the furnace or on the furnace wall are vertically arranged in 2-10 layers.

[0023] Preferably, in the SOFA air nozzles at the four corners of the furnace or on the furnace wall, the vertical swing angle of the multi-layer SOFA air nozzles installed at each corner or on each furnace wall is individually and dynamically adjusted relative to the other corners or furnace walls.

[0024] Preferably, in the SOFA air nozzles at the four corners of the furnace or on the furnace wall, the opening of the damper of each layer of SOFA air nozzle installed at the four corners or on the furnace wall is adjusted by single-layer linkage.

[0025] This invention also provides a method for optimizing and adjusting deep combustion in a tangential combustion boiler of a coal-fired power plant. Based on a low-NOx combustion boiler using tangential combustion, the CCOFA damper has two layers at the four corners of the furnace; the lower layer is the secondary combustion air for the F-layer burner.

[0026] The lower-level CCOFA damper opening is set as follows:

[0027] When operating at low load, the opening of the lower CCOFA damper is set to 10% when the uppermost pulverized coal burner is in operation; when the F-layer pulverized coal burner is shut down, the lower CCOFA damper is set to 5-20%.

[0028] When operating under high load, the lower CCOFA damper opening is set to 40% when the F-layer pulverized coal burner is in operation, or as needed; when the F-layer pulverized coal burner is out of operation, the lower CCOFA damper opening is set to 5-20%.

[0029] The upper CCOFA damper opening setting is as follows:

[0030] When operating under low load, the opening of the upper CCOFA damper should be set to 5-20%.

[0031] When operating under high load, the opening of the upper CCOFA damper should be set to 60-100%.

[0032] Preferably, in the low-NOx combustion boiler with tangential combustion, an SOFA air burner is arranged above the main air box, including 5 layers of horizontally swingable separator burnout air SOFA nozzles; together with the perimeter air of the pulverized coal nozzles, each corner of the main burner and SOFA air burner has 25 sets of secondary air baffles, all of which are operated individually by electric actuators. The main burner nozzle adopts a swing structure, which is composed of inner and outer connecting rods forming a swing system, and is driven up and down by a single electric actuator. The SOFA air burner is driven up and down by a single electric actuator. All electric actuators adopt imported angular stroke structures.

[0033] The secondary air chamber of the burner is equipped with three layers of 12 light oil guns, which adopt mechanical atomization. The fuel capacity is designed according to 20% MCR load. The ignition device adopts a high-energy electric spark igniter. The burner adopts a water-cooled jacket structure.

[0034] An auxiliary air nozzle is arranged between every two adjacent layers of pulverized coal nozzles.

[0035] Compared with the prior art, the beneficial effects of the present invention are:

[0036] This invention effectively solves numerous problems in coal-fired power plant units, including residual rotating flue gas at the boiler outlet during stable load, leading to significant deviations in furnace outlet flue gas temperature, reheat steam temperature deviations, low reheat steam temperature at low loads, large reheater desuperheating water consumption at high loads, large deviations in nitrogen oxide emissions at the denitrification inlet, and excessive steam or wall temperatures, while simultaneously meeting low-NOx emission requirements. This method is a practical and effective approach for regulating and balancing steam temperature during stable loads in tangential boilers of coal-fired power plants. Experimental results show that boiler units adjusted using this method reduce coal consumption for power generation by at least 1 g / kWh, demonstrating significant energy savings and warranting widespread application. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the overall internal structure of the coal-fired boiler of the present invention.

[0039] Figure 2 This is a schematic diagram of the planar layout and nozzle direction of a pulverized coal burner.

[0040] In the diagram: 1—Heating surface of the partition screen, 2—Reheater, 3—SOFA air burnout area on the rear wall, 4—Upward tilt of the SOFA air nozzle vertical angle, 5—Horizontal tilt of the SOFA air nozzle vertical angle, 6—SOFA air burnout area on the front wall, 7—Downward tilt of the SOFA air nozzle vertical angle, 8—Upward tilt of the pulverized coal burner angle, 9—Horizontal tilt of the pulverized coal burner angle, 10—Pulverized coal burner area, 11—Downward tilt of the pulverized coal burner angle, 12—Water-cooled wall, 13—Coal-fired boiler. Detailed Implementation

[0041] The technical solutions of the embodiments of this application will now be described with reference to the accompanying drawings. It should be noted that similar reference numerals and letters in the following drawings indicate similar items; therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0042] The terms “comprising,” “including,” or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase “comprising one…” does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0043] like Figure 1 As shown, a tangentially circular boiler for a coal-fired power plant includes a partitioned heating surface 1, a reheater 2, a SOFA (Solar Flame Air) burnout zone on the rear wall 3, an upward tilt direction of the SOFA nozzle vertical angle 4, a horizontal tilt direction of the SOFA nozzle vertical angle 5, a SOFA burnout zone on the front wall 6, a downward tilt direction of the SOFA nozzle vertical angle 7, an upward tilt direction of the pulverized coal burner vertical angle 8, a horizontal tilt direction of the pulverized coal burner 9, a pulverized coal burner zone 10, a downward tilt direction of the pulverized coal burner 11, and a water-cooled wall 12. Different nozzles and air inlets are arranged at the four corners of the boiler furnace. The main air box has six layers of enhanced ignition (EI) pulverized coal nozzles, and perimeter air is arranged around the pulverized coal nozzles. One layer of auxiliary air nozzles is arranged between every two adjacent layers of pulverized coal nozzles. Two layers of CCOFA (Close-coupled OFA) nozzles are located at the top of the main air box, and one layer of UFA (Underfire Air) nozzles is located at the bottom of the main air box. Figure 2 This is a plan view of the burner.

[0044] This application provides a method for optimizing deep combustion in a tangential boiler of a coal-fired power plant, including the following specific steps: pulverized coal burners are installed at the four lower corners or furnace walls of the furnace chamber of the tangential boiler, and SOFA air nozzles are installed at the four corners or furnace walls above the pulverized coal burners.

[0045] The SOFA air nozzles at the four corners of the furnace or on the furnace wall are divided into two groups. By adjusting the vertical swing angle of the SOFA air nozzles, one group of SOFA air nozzles is tilted upward and the other group of SOFA air nozzles is tilted downward, thus completing the deep combustion optimization adjustment of the tangential boiler in the coal-fired power plant.

[0046] The SOFA air nozzles at the four corners of the furnace or on the furnace wall are vertically arranged in 2-10 layers.

[0047] Under low-load conditions, the vertical swing angle of the SOFA air nozzle remains unchanged, while the swing angle of the pulverized coal burner nozzle in the pulverized coal burner area tilts upward.

[0048] Under high load conditions, the vertical swing angle of the SOFA air nozzle remains unchanged, while the swing angle of the pulverized coal burner nozzle in the pulverized coal burner area is either horizontal or tilted downwards.

[0049] In the SOFA air nozzles at the four corners of the furnace or on the furnace wall, the vertical swing angle of the multi-layer SOFA air nozzles installed at each corner or on each furnace wall is individually linked and adjusted relative to the other corners or furnace walls. The opening of the damper baffle of each layer of SOFA air nozzle installed at the four corners or on the furnace wall is adjusted by a single layer.

[0050] When any layer of pulverized coal burners is shut down, the opening of the perimeter damper is set to 5%-10%; when the pulverized coal burners are in normal operation, the opening of the perimeter damper is set to a fixed value: under high load, the opening of the perimeter damper is set to 50-100%; under low load, the opening of the perimeter damper is set to 5-20%, and the opening of the perimeter damper is set the same for each layer.

[0051] When the tangential boiler of a coal-fired power plant is under high load, the opening of the combustion damper of each burner layer gradually decreases from bottom to top; if any burner layer stops operating, the opening of the combustion damper of that layer is closed; under low load, the opening of the combustion damper is 5-20% for uniform air distribution.

[0052] This application provides another method for optimizing and adjusting deep combustion in a tangential combustion boiler of a coal-fired power plant. The CCOFA damper of the low-NOx boiler using tangential combustion has two layers at the four corners of the furnace; the lower layer is the secondary combustion air for the F-layer burners.

[0053] Setting the opening degree of the lower-level CCOFA damper:

[0054] When operating at low load, the opening of the lower CCOFA damper is set to 10% when the uppermost pulverized coal burner is in operation; when the F-layer pulverized coal burner is shut down, the lower CCOFA damper is set to 5-20%.

[0055] When operating under high load, the lower CCOFA damper opening is set to 40% when the F-layer pulverized coal burner is in operation, or as needed; when the F-layer pulverized coal burner is out of operation, the lower CCOFA damper opening is set to 5-20%.

[0056] Setting the opening degree of the upper CCOFA damper:

[0057] When operating under low load, the opening of the upper CCOFA damper should be set to 5-20%.

[0058] When operating under high load, the opening of the upper CCOFA damper should be set to 60-100%.

[0059] In the embodiment shown in the figure, an SOFA air burner is arranged on the upper part of the main air box, including 5 layers of horizontally swingable separator burnout air SOFA nozzles.

[0060] Including the perimeter airflow of the pulverized coal nozzles, each corner main burner and SOFA air burner has 25 sets of secondary air dampers, all operated individually by electric actuators. To meet the needs of boiler steam temperature regulation, the main burner nozzles adopt a swing structure, consisting of an inner and outer connecting rod forming a swing system, driven up and down by a single electric actuator. The SOFA air burners are also driven up and down by a single electric actuator. All of the above electric actuators adopt imported angular stroke structures, characterized by compact structure, simple control, and adaptability to frequent adjustments.

[0061] The burner's secondary air chamber is equipped with three layers of 12 light oil guns, employing mechanical atomization. The fuel capacity is designed for a 20% MCR load, and a high-energy electric spark igniter is used. The burner adopts a water-cooled jacket structure. In traditional boiler systems, to prevent excessive reheat steam temperature deviation, the desuperheating water flow is increased to reduce the reheat steam temperature or the temperature of the heated surface walls. However, due to the uneven temperature field within the furnace, this often leads to excessive desuperheating water consumption and increased coal consumption for power generation.

[0062] An auxiliary air nozzle is arranged between every two adjacent layers of pulverized coal nozzles.

[0063] The flue gas temperature deviation at the furnace outlet is caused by the uneven distribution of the flow field within the furnace. Analysis of flue gas temperature and velocity data from currently operating coal-fired power units reveals that the flue gas velocity at the vertical outlet section of the furnace has a much greater impact on the temperature deviation than the flue gas temperature itself. This suggests that the temperature deviation is an aerodynamic phenomenon. There is a correlation between the flue gas temperature deviation at the furnace outlet and the swirl index. The swirl index represents the ratio of tangential momentum to axial momentum of the combustion product flue gas as it leaves the furnace outlet section (a higher swirl index implies a faster swirl velocity). The swirl index can be reduced through various means, such as decreasing the airflow injection angle, arranging compact burnout air (CCOFA) nozzles and separated burnout air (SOFA) nozzles, applying a certain angle to the SOFA back tangent, and increasing the distance from the burner region to the furnace outlet, thereby weakening the rotation intensity of the airflow entering the upper region of the burner.

[0064] This invention proposes a new method for leveling the deviation of flue gas temperature or steam temperature at the furnace outlet in a tangential combustion mode.

[0065] First, assuming the flue gas temperature or steam temperature on side A is significantly higher than that on side B (at least 10°C higher), adjust the vertical swing angle of SOFA air burners at corners 1 and 4 to near the maximum upward tilt position, and adjust the vertical swing angle of SOFA air burners at corners 2 and 3 to near the minimum downward tilt position; conversely, if the flue gas temperature or steam temperature on side A is significantly lower than that on side B (at least 10°C lower), adjust the vertical swing angle of SOFA air burners at corners 1 and 4 to near the maximum downward tilt position, and adjust the vertical swing angle of SOFA air burners at corners 2 and 3 to near the minimum upward tilt position.

[0066] The power plant boiler features tangential burners arranged at corners 1, 2, 3, and 4, forming an imaginary tangential circle of a certain diameter. Generally, the primary air (a few boilers use a reverse tangential design for primary air) and secondary air in the burner area adopt a tangential design (e.g., ...). Figure 2 As shown), it rotates counterclockwise; the four corner burners of the boiler are driven by electric actuators located at their respective corners, and the connecting rods at each corner simultaneously drive the multi-layer combustion, which can swing up and down in the vertical direction to adjust the position of the flame center.

[0067] SOFA air burners are installed at a certain height on the topmost burner, typically with 2-10 layers of SOFA air. The SOFA air at the four corners of the boiler can be manually adjusted horizontally to set the SOFA air to tangential or reverse tangential, thereby adjusting the deviation of flue gas temperature and steam temperature on both sides of the boiler. The SOFA air at the four corners of the boiler can also be driven by connecting rods through electric actuators at each corner. Each connecting rod at each corner simultaneously drives the multi-layer SOFA air burners to swing up and down vertically to adjust the flame center, thereby adjusting the superheated steam temperature and reheat steam temperature.

[0068] Theoretically, as long as a tangential combustion boiler achieves equilibrium between the tangential and counter-tangential rotating air momentum, the residual rotating flue gas at the furnace outlet is almost zero, and the temperature deviation of the flue gas and steam on both sides of the boiler is zero. However, in reality, residual rotating flue gas always exists at the furnace outlet, and temperature deviations on both sides, as well as steam temperature deviations, always exist. Sometimes side A is higher than side B, and sometimes side B is higher than side A. This is because boiler combustion is a dynamic equilibrium process with many interfering factors. Additionally, there are errors in the burner installation angle. Therefore, generally, the flue gas temperature on side A at the furnace outlet is always higher than side B. In some boilers, the temperature deviation on both sides can reach as high as 100℃, and the steam temperature deviation exceeds 20℃. This leads to problems such as excessive reheater desuperheating water, excessive steam temperature at the final reheater outlet, excessive reheater or superheater tube wall temperature, excessively low reheat steam temperature at low loads, and excessive steam temperature deviation.

[0069] In response to the above problems, during the boiler combustion depth optimization and adjustment test, a set of effective methods were explored that can completely solve the above problems.

[0070] To address the issue of excessively low reheat steam temperature under low load, a vertical sway angle offset setting for the SOFA airflow is adopted. Combined with appropriate operating oxygen levels and a reasonable air distribution method, the low-load reheat steam temperature can be raised to the design value.

[0071] Due to the significant reduction in coal consumption at low loads, the furnace volumetric heat load also decreases, leading to a lower furnace temperature. While tilting the burner upwards can raise the flame center position, simply tilting the burner upwards often fails to raise the reheat steam temperature. This is because the low-NOx combustion technology results in oxygen-deficient combustion in the burner area, aiming to reduce the concentration of nitrogen oxides generated in the furnace. The pulverized coal entering the furnace is not completely burned, releasing only a portion of the heat. To ensure complete combustion and release of residual heat, SOFA (Solar Air Fabric) air is installed at a certain height above the burner to supplement sufficient air, promoting complete combustion of the pulverized coal.

[0072] To increase the reheat steam temperature at low loads, operators tried increasing the SOFA (Solar Air Flow) airflow and tilting the SOFA burner vertically upwards. However, contrary to expectations, the reheat steam temperature only increased by a few degrees before dropping again. Why? It turns out that when retrofitting burners using low-NOx combustion technology, the distance between the burner area and the SOFA airflow is often designed to be too large to further reduce NOx emissions. While this is beneficial for reducing NOx emissions, it doesn't pose a problem at high loads. However, when the boiler is running at low loads, the number of burners in the furnace burner area decreases, the furnace temperature drops, and the volumetric heat load decreases. Consequently, the ignition in the boiler burner area weakens. Combined with oxygen-deficient combustion in the burner area, the pulverized coal ignition becomes even weaker. Therefore, tilting the burner upwards is correct, but because the distance between the burner area and the SOFA airflow is large, the heat from the flue gas at low loads is insufficient to allow the pulverized coal to reach the SOFA airflow area for complete combustion. Therefore, combustion in the boiler is unstable at low loads, let alone increasing the reheat steam temperature.

[0073] Under this operating condition, the SOFA air is set with a vertical sway angle offset, which can shorten the effective distance H between the burner area and the SOFA air for pulverized coal re-burning, and maintain the continuous stability of pulverized coal combustion. Therefore, when unburned pulverized coal reaches the SOFA air area, it continues to re-burn under sufficient oxygen conditions, releasing heat and raising the reheat steam temperature to the design value.

[0074] Since 2016, we have conducted low-load reheat steam temperature improvement and reheat steam temperature deviation combustion depth optimization and adjustment tests in power plants across the country. By adopting the SOFA wind vertical direction swing angle offset setting, we have solved the above-mentioned problems of low boiler reheat steam temperature and large reheat steam temperature deviation, and significantly reduced coal consumption for power supply.

[0075] According to an embodiment of this application, the power plant's deep combustion optimization operation control curves are shown in the table below:

[0076] Boiler oxygen content and secondary air distribution mode operation control curves

[0077]

[0078] Perimeter damper operation control curve

[0079]

[0080] As can be seen from the table above, the method of this application is applied to the stable load steam temperature regulation and steam temperature leveling of tangential boilers in coal-fired power plants. The test results show that the boiler unit adjusted by this method reduces the coal consumption for power supply by at least 1g / kWh, and the energy-saving effect is very significant.

[0081] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for optimizing and adjusting deep combustion in a tangential boiler of a coal-fired power plant, characterized in that, Based on a tangential boiler in a coal-fired power plant, the specific steps include: Pulverized coal burners are installed at the four lower corners of the furnace or on the furnace wall of the tangential boiler, and SOFA air nozzles are installed at the four corners of the furnace or on the furnace wall above the pulverized coal burners. Divide the SOFA air nozzles at the four corners of the furnace or on the furnace wall into two groups. By adjusting the vertical swing angle of the SOFA air nozzles, tilt one group of SOFA air nozzles upward and the other group of SOFA air nozzles downward. Under low-load conditions, the vertical swing angle of the SOFA air nozzle remains unchanged, while the swing angle of the pulverized coal burner nozzle in the pulverized coal burner area tilts upward according to the steam temperature requirement; under high-load conditions, the vertical swing angle of the SOFA air nozzle remains unchanged, while the swing angle of the pulverized coal burner nozzle in the pulverized coal burner area is either horizontal or tilted downward according to the steam temperature requirement. When any layer of pulverized coal burners is shut down, the perimeter damper opening is set to 5%-10%; when the pulverized coal burners are in normal operation, the perimeter damper opening is set to a fixed value: under high load, the perimeter damper opening is set to 50-100%; under low load, the perimeter damper opening is set to 5-20%, and the perimeter damper opening is set to the same value for each layer. When the tangential boiler of a coal-fired power plant is under high load, the opening of the combustion damper of each burner layer gradually decreases from bottom to top; when the load is low, the opening of the combustion damper is 5-20% for uniform air distribution. The operating oxygen content at each load point must be determined through deep combustion optimization and adjustment tests, generally following the rule of high oxygen content at low load and low oxygen content at high load.

2. The method for optimizing and adjusting deep combustion in a tangential boiler of a coal-fired power plant according to claim 1, characterized in that, The tangential boiler of the coal-fired power plant includes a partition screen heating surface, a reheater, a SOFA air burnout zone on the rear wall, SOFA air nozzles in the vertical upward tilt direction, SOFA air nozzles in the vertical horizontal tilt direction, a SOFA air burnout zone on the front wall, SOFA air nozzles in the vertical downward tilt direction, pulverized coal burners in the vertical upward tilt direction, pulverized coal burners in the vertical horizontal tilt direction, a pulverized coal burner area, pulverized coal burners in the downward tilt direction, and a water-cooled wall. Different nozzles and air outlets are set at the four corners of the boiler furnace. The main air box has 6 layers of enhanced ignition pulverized coal nozzles. Perimeter air is arranged around the pulverized coal nozzles. One layer of auxiliary air nozzles is arranged between every two adjacent layers of pulverized coal nozzles. Two layers of CCOFA nozzles are set at the top of the main air box, and one layer of UFA nozzles is set at the bottom of the main air box.

3. The method for optimizing and adjusting deep combustion in a tangential boiler of a coal-fired power plant according to claim 1, characterized in that, The SOFA air nozzles at the four corners of the furnace or on the furnace wall are vertically arranged in 2-10 layers.

4. The method for optimizing and adjusting deep combustion in a tangential boiler of a coal-fired power plant according to claim 1, characterized in that, In the SOFA air nozzles at the four corners of the furnace or on the furnace wall, the multi-layer SOFA air nozzles installed at each corner or on each furnace wall have their vertical swing angles adjusted independently relative to the other corners or furnace walls.

5. The method for optimizing and adjusting deep combustion in a tangential boiler of a coal-fired power plant according to claim 1, characterized in that, In the SOFA air nozzles at the four corners of the furnace or on the furnace wall, the opening of the damper of each layer of SOFA air nozzle installed at the four corners or on the furnace wall is adjusted by single-layer linkage.

6. A method for optimizing and adjusting deep combustion in a tangential boiler of a coal-fired power plant, characterized in that, In low-NOx combustion boilers based on tangential combustion, the CCOFA dampers have two layers at the four corners of the furnace; the lower layer provides secondary combustion air for the F-layer burners. The lower-level CCOFA damper opening is set as follows: When operating at low load, the opening of the lower CCOFA damper is set to 10% when the uppermost pulverized coal burner is in operation; when the F-layer pulverized coal burner is shut down, the lower CCOFA damper is set to 5-20%. When operating under high load, the lower CCOFA damper opening is set to 40% when the F-layer pulverized coal burner is in operation, or as needed; when the F-layer pulverized coal burner is out of operation, the lower CCOFA damper opening is set to 5-20%. The upper CCOFA damper opening setting is as follows: When operating under low load, the opening of the upper CCOFA damper should be set to 5-20%. When operating under high load, the opening of the upper CCOFA damper should be set to 60-100%.

7. The method for optimizing and adjusting deep combustion in a tangential boiler of a coal-fired power plant according to claim 6, characterized in that, In a low-NOx combustion boiler with tangential combustion, SOFA air burners are arranged above the main air box, including 5 layers of horizontally swingable separator burnout air SOFA nozzles; together with the perimeter air of the pulverized coal nozzles, each corner of the main burner and SOFA air burner has 25 sets of secondary air baffles, all of which are operated individually by electric actuators. The main burner nozzles adopt a swing structure, which is composed of inner and outer connecting rods to form a swing system, which is driven up and down by a single electric actuator. The SOFA air burners are driven up and down by a single electric actuator. All electric actuators adopt imported angular stroke structures. The secondary air chamber of the burner is equipped with three layers of 12 light oil guns, which adopt mechanical atomization. The fuel capacity is designed according to 20% MCR load. The ignition device adopts a high-energy electric spark igniter. The burner adopts a water-cooled jacket structure. An auxiliary air nozzle is arranged between every two adjacent layers of pulverized coal nozzles.

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