Novel burner structure for improving utilization rate of unit boiler aiming at east coal

Abstract

The utility model discloses a novel burner structure used for improving the utilization rate of a unit boiler aiming at east coal. A boiler combustion system of the unit boiler comprises a coal pulverizing system and a burner. The combustion system forms a direct-blowing pulverizing system in a direct-blowing manner of a medium-speed coal mill; the combustors are arranged on the boiler in a regular four-corner mode. The combustor is divided into five layers of primary air chambers from bottom to top, and the distances between the adjacent primary air chambers are equal. After the structure of the novel combustor is improved, on the premise that 90% of Zhundong coal is combusted, the on-load capacity of a boiler is improved, the boiler has the capacity of being brought to 350 MW or above for a long time, meanwhile, a hearth has the high hearth anti-slagging capacity, and the safety of a heating surface is guaranteed.

Description

TECHNICAL FIELD

[0001] The utility model relates to a power plant unit boiler technical field especially relates to a kind of novel combustor structure for improving the utilization of unit boiler alignment east coal. BACKGROUND

[0002] East coal has the characteristics of low ash content, high volatile matter and high calorific value, and is an ideal power coal. However, according to element analysis, the content of sodium and potassium ions reaches 7%. From the current situation of domestic power plants independently blending east coal, it is found that it is easy to cause slagging, fouling and over-temperature in the combustion process, and the tail flue is prone to ash accumulation, the preheater is blocked, and the boiler cannot carry the load and is forced to shut down for treatment. Therefore, the use of east coal with lower procurement cost is limited. However, in the long run, the large-scale blending or even full combustion of east coal is the trend.

[0003] In the prior art, ten east pot 350MW unit boilers are used in some self-provided power plants of aluminum plants. Currently, the main fuel for the boilers is east coal. As the load rate is getting higher and higher, it is urgently needed to stably and long-termly burn east coal at high load in the unit boilers. Currently, some boilers are burning east coal, and phenomena such as low load and serious boiler slagging occur during the burning of east coal. The phenomena seriously affect the operation of the boilers.

[0004] Therefore, at the current stage, it is urgently needed to comprehensively reform the combustor of the unit boiler, improve the hourly utilization rate of the unit, and increase the amount of east coal. Under the current coal resource situation, how to increase the amount of blended east coal and ensure the safe, stable, economic and environmentally-friendly operation of the boiler is a very practical problem. Only by optimizing, improving and reforming the existing combustion system equipment and facilities can the stability of the boiler for burning east coal with strong anti-slagging and anti-fouling ability be improved.

[0005] Therefore, based on the above technical problems, the skilled in the art urgently needs to develop a novel combustor structure for improving the utilization of unit boiler for east coal. CONTENT OF THE UTILITY MODEL

[0006] The utility model aims at providing a novel combustor structure for improving the utilization of unit boiler for east coal, which comprehensively considers the effective measures for realizing stable combustion, low nitrogen, effectively reducing the overall temperature level of the furnace and the flue gas temperature at the outlet of the furnace, preventing slagging and high-temperature corrosion, and improving economy under the premise of large-scale burning of east coal.

[0007] In order to achieve the above-mentioned purpose, the utility model provides the following technical scheme:

[0008] The novel combustor structure for improving the utilization of unit boiler for east coal comprises a combustion system of the boiler of the unit boiler, and the combustion system of the boiler comprises a pulverizing system and a combustor.

[0009] The combustion system adopts a direct blowing mode of a medium-speed coal mill to form a direct blowing type coal pulverizing system.

[0010] The burners are arranged in a square shape on the boiler.

[0011] The burners are divided into five layers of primary air chambers from bottom to top, and the spacing between adjacent primary air chambers is equal.

[0012] Further, the spacing between adjacent primary air chambers of the burners is 1700mm.

[0013] The distance between the uppermost primary air chamber and the center of the reduction zone of the boiler is 6950mm.

[0014] The center of the overfire air of the boiler is 14130mm away from the lower edge of the large screen of the boiler.

[0015] Further, the burners of the square shape are arranged in a double tangent circle combustion mode with the imaginary circles at the center of the water-cooled wall of the boiler furnace.

[0016] Further, the two imaginary circles at the center of the water-cooled wall of the boiler furnace are an inner circle and an outer circle.

[0017] The center lines of the burners of the square shape are respectively tangent to the corresponding circles according to process requirements.

[0018] The diameter of the inner circle is 578mm, and the diameter of the outer circle is 1052mm.

[0019] In the above technical solution, the novel burner structure for improving the utilization rate of the boiler of the unit for burning Zhun Dong coal has the following beneficial effects:

[0020] The novel burner structure of the utility model comprehensively considers the premise of burning a large proportion of Zhun Dong coal to realize stable combustion, low nitrogen, effectively reduce the overall temperature level of the furnace and the flue gas temperature at the outlet of the furnace, prevent slagging and high-temperature corrosion, and improve the economic efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments described in the utility model, and other drawings can also be obtained by those skilled in the art according to these drawings.

[0022] Figure 1 The primary air chamber position front view before the transformation of the novel burner structure for improving the utilization rate of the boiler of the unit for burning Zhun Dong coal disclosed in the embodiments of the present application;

[0023] Figure 2The side view of the primary air chamber position before the transformation of the new burner structure for improving the utilization rate of the east coal of the boiler of the unit disclosed by the embodiment of the application is shown in the figure;

[0024] Figure 3 The front view of the primary air chamber position after the transformation of the new burner structure for improving the utilization rate of the east coal of the boiler of the unit disclosed by the embodiment of the application is shown in the figure;

[0025] Figure 4 The side view of the primary air chamber position after the transformation of the new burner structure for improving the utilization rate of the east coal of the boiler of the unit disclosed by the embodiment of the application is shown in the figure;

[0026] Figure 5 The schematic view of the water wall before cutting of the new burner structure for improving the utilization rate of the east coal of the boiler of the unit disclosed by the embodiment of the application is shown in the figure;

[0027] Figure 6 The schematic view of the water wall after cutting of the new burner structure for improving the utilization rate of the east coal of the boiler of the unit disclosed by the embodiment of the application is shown in the figure;

[0028] Figure 7 The schematic view of the double cutting circle of the burner of the new burner structure for improving the utilization rate of the east coal of the boiler of the unit disclosed by the embodiment of the application is shown in the figure.

[0029] Explanation of reference signs:

[0030] 1, water wall; 2, cutting line; 3, burner;

[0031] 401, inner circle; 402, outer circle. DETAILED DESCRIPTION

[0032] In order for those skilled in the art to better understand the technical scheme of the utility model, the utility model will be further described in detail below in combination with the drawings.

[0033] Referring to Figures 1 to 7 shown in the figure;

[0034] The embodiment discloses a new burner structure for improving the utilization rate of the east coal of the boiler of the unit, and the combustion system of the boiler of the unit boiler comprises a pulverizing system and a burner 3.

[0035] The combustion system adopts a direct blowing mode of a medium-speed coal mill to form a direct blowing pulverizing system.

[0036] The burner 3 is arranged in a regular quadrilateral form on the boiler.

[0037] The burner 3 is divided into five layers of primary air chambers from bottom to top, and the spacing between adjacent primary air chambers is equal.

[0038] First, this embodiment further describes the boiler unit. The boiler involved in this embodiment has subcritical parameters and the burners 3 are arranged in a tangential combustion configuration. The boiler uses a medium-speed coal mill direct-fired pulverizing system, with each boiler equipped with 5 medium-speed coal mills, of which 4 are in operation and 1 is on standby. The coal mill model in this embodiment is MPS170HP-II. The ash removal system uses an air-cooled dry steel belt conveyor for continuous ash discharge. The boiler is also equipped with two Lonker air preheaters with a rotor diameter of 11284mm. The heat storage elements, from top to bottom, are 400mm, 1000mm, and the 1000mm cold section heat storage elements are enamel-lined heat transfer elements, while the remaining hot section heat storage elements are made of carbon steel.

[0039] Secondly, the superheater arrangement of the boiler is as follows: the full-screen superheater is arranged in the upper part of the furnace and adopts a full-radiation structure; the screen-type superheater is arranged at the furnace outlet and adopts a radiation-convection structure; the high-temperature superheater is arranged in the horizontal flue; and the low-temperature superheater is arranged in the tail shaft.

[0040] Based on the above basic overview of the boiler, this embodiment improves the burner 3. First, the coal used in this embodiment is bituminous coal, and the ignition and combustion-supporting oil is #0 diesel. The burners 3 are arranged in a square arrangement with a double tangential combustion method. Each corner burner 3 is divided into upper, middle, and lower groups. Each corner of the middle and lower groups is equipped with an electric actuator to drive the nozzle to swing, for a total of 8 burners in the entire boiler. Except for the burnout air nozzle (upper group), which can swing up and down by 15°, the nozzles of the middle and lower groups can swing up and down by 30°. At the same time, the primary air nozzle and secondary air nozzle at the bottom layer are fixed nozzles and cannot swing. In this embodiment, the burners 3 of the boiler are arranged at the four corners of the furnace water-cooled wall 1. In this embodiment, the burners 3 at the four corners are arranged in a double tangential combustion method with the imaginary circle at the center of the boiler furnace water-cooled wall 1. See also Figure 7 As shown, more preferably, in this embodiment, the two imaginary circles at the center of the boiler furnace water-cooled wall 1 are an inner circle 401 and an outer circle 402, where the inner circle is the primary air tangent circle and the outer circle is the secondary air tangent circle; the center lines of the burners 3 at the four corners are tangent to the corresponding circles according to process requirements; the diameter of the inner circle 401 is 578 mm counterclockwise, and the diameter of the outer circle 402 is 1052 mm counterclockwise. Each corner burner 3 of the boiler water-cooled wall 1 has a total of 14 layers of nozzles, including 5 layers of primary air nozzles, 7 layers of secondary air nozzles, and 2 layers of burnout air nozzles. The primary air nozzles of the boiler are surrounded by perimeter air. Each corner burner 3 is divided into three groups: upper, middle, and lower. The upper group burner 3 is an OFA burner with 2 layers of nozzles, the middle group burner 3 has 5 layers of nozzles, from top to bottom: EE, E, DE, D, DD, and the lower group burner 3 has 7 layers of nozzles, from top to bottom: CC, C, BC, B, AB, A, AA.

[0041] The main technical problems addressed in this embodiment are: significant airflow entrainment near burner nozzle 3, severe burn-out of burner nozzle 3, and severe coking near the nozzle. Significant signs of pulverized coal scouring the water-cooled walls in the main combustion zone, with severe coking on the water-cooled walls. Significant signs of airflow scouring the walls in the OFA burnout air zone, with severe coking on the water-cooled walls near OFA. Poor boiler coal adaptability; after the ash melting point of the coal decreases, severe fouling and coking of the water-cooled walls frequently occur, requiring frequent soot blowing and frequent shutdowns of the ash removal machine after coke loss. Furthermore, severe boiler coking leads to a significant increase in furnace temperature, reheater temperature, and horizontal flue temperature. The pre-cooling steam temperature exceeds 460℃ (rated value 417℃), and the reheater outlet flue gas temperature exceeds 1050℃ (100℃ higher than other units) at unit loads above 330MW, exceeding 100t / h for superheater desuperheating water and exceeding 50t / h for reheater desuperheating water, affecting the safe operation of the boiler. When the boiler becomes severely sludge-covered, it is forced to operate at low loads to remove the sludge, which affects the unit's ability to continuously operate at high loads.

[0042] Preferably, in this embodiment, the spacing between adjacent primary air chambers of the burner 3 is 1700mm; the distance between the uppermost primary air chamber and the center of the boiler reduction zone is 6950mm; and the distance between the center of the boiler burnout air and the lower edge of the boiler screen is 14130mm.

[0043] First, in this embodiment, the burner 3 is divided into five primary air chambers (A, B, C, D, and E) from bottom to top. See first... Figure 1 and Figure 2 As shown, Figure 1 and Figure 2 This describes the layout of boiler burner 3 before modification. See also... Figure 3 and Figure 4 As shown, Figure 3 and Figure 4 This is the arrangement of the boiler burner 3 after modification. In this embodiment, the secondary air chambers DE and EE are moved down by 1600mm, and the original DD air chamber is eliminated. After the relocation, the spacing between the five primary air chambers after the modification is 1700mm. The distance between the center of the top layer (i.e., layer E) and the center of SOFA (separated burnout air) is 6950mm, and the distance between the center of SOFA and the lower edge of the large screen is 14130mm. Subsequently, the flow area of ​​the primary and secondary air is redesigned according to the actual coal type in operation, and the tangential circle of the primary air is readjusted.

[0044] See Figure 5 and Figure 6 As shown, during the renovation, the water-cooled wall tubes between the CC layer and DD layer near the corner area were cut off (cut according to cutting line 2 in the figure), and the whole structure was moved down by 1600mm (the bend tube with the coke hole was moved down together). 15 straight tubes were used to connect the corners, and the space after the upper burner 3 was moved down was sealed with a new tube screen.

[0045] In the above technical solution, the novel burner structure provided by this utility model for improving the utilization rate of coal supplied to the boiler unit has the following beneficial effects:

[0046] The novel burner structure of this utility model comprehensively considers effective measures to achieve stable combustion, low nitrogen content, and effectively reduce the overall furnace temperature and furnace outlet flue gas temperature, prevent slagging and high-temperature corrosion, and improve economic efficiency under the premise of burning a large proportion of Zhundong coal.

[0047] The modified burner structure of this utility model improves the boiler's load-carrying capacity while using 90% Zhundong coal, enabling it to operate at 350MW or higher for extended periods. Simultaneously, it enhances the furnace's anti-slagging capabilities, ensuring the safety of the heating surfaces. This achieves a 350MW load operating coal mill with "4 units and 1 standby".

[0048] This new type of boiler further reduces NOx emission concentration to 180 mg / Nm³ across the entire load range. 3 (Standard conditions, dry basis, 6% O2) below; after the modification, the boiler output remains unchanged, the superheated steam temperature reaches the original design value of 541℃, and the superheated steam desuperheating water volume is within the design range.

[0049] In addition, the flue gas temperature deviation at the furnace outlet is less than 50℃, and the CO concentration emission concentration is less than 200ppm. The modified boiler is safe, economical and operable, and the combustion system can meet the requirements of the current coal types, further reducing the proportion of kaolin blending, and does not cause slagging or high-temperature corrosion of the water-cooled walls.

[0050] The modified boiler reduces the number of times soot is blown from the furnace and heating surfaces.

[0051] The foregoing description only illustrates certain exemplary embodiments of the present invention. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A new type of burner structure for improving the utilization rate of coal from the east of the unit boiler. The combustion system of the unit boiler includes a pulverizing system and a burner (3); The combustion system adopts a direct-fired pulverizing method using a medium-speed coal mill; Its features are: The burners (3) are arranged in a square pattern on the boiler; The burner (3) is divided into five primary air chambers from bottom to top, and the distance between adjacent primary air chambers is equal.

2. The novel burner structure for improving the utilization rate of coal from the east of the boiler in a power unit, as described in claim 1, is characterized in that... The distance between adjacent primary air chambers of the burner (3) is 1700 mm; The distance between the uppermost primary air chamber and the center of the boiler reduction zone is 6950 mm; The center of the boiler burnout air is 14130mm from the bottom edge of the boiler screen.

3. The novel burner structure for improving the utilization rate of coal from the east of the boiler in a power unit, as described in claim 1 or 2, is characterized in that... The burners (3) at the four corners are arranged in a double-tangential combustion manner with the imaginary circle at the center of the boiler furnace water-cooled wall (1).

4. The novel burner structure for improving the utilization rate of coal from the east of the boiler in a unit, as described in claim 3, is characterized in that... The two imaginary circles at the center of the boiler furnace water-cooled wall (1) are the inner circle (401) and the outer circle (402), respectively; The center lines of the burners (3) at the four corners are tangent to the corresponding circles according to the process requirements; The inner circle (401) has a diameter of 578 mm, and the outer circle (402) has a diameter of 1052 mm.

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