A control system for inhibiting the coking of a heating surface of a coal-fired boiler

Abstract

The application discloses a control system for inhibiting coking of a heating surface of a coal-fired boiler, and the control system comprises a first temperature measuring device for monitoring the flue gas temperature at the inlet of a partition screen superheater, a second temperature measuring device for monitoring the flue gas temperature at the inlet of a final-stage superheater, a third temperature measuring device for monitoring the flue gas temperature at the inlet of a final-stage reheater, and a nano-ceramic material spraying layer arranged on a water cooling wall; wherein, based on the initial temperature data monitored by the first temperature measuring device, the second temperature measuring device and the third temperature measuring device, the area of the nano-ceramic material spraying layer is set so that the water cooling wall has a suitable range of heat absorption, the flue gas temperature at the inlet of the partition screen superheater is T1, the flue gas temperature at the inlet of the final-stage superheater is T2, and the flue gas temperature at the inlet of the final-stage reheater is T3, thereby inhibiting the coking of the heating surface of the coal-fired boiler.

Description

Technical Field

[0001] This invention belongs to the field of coal-fired power plant boiler operation technology, and particularly relates to a control system for suppressing coking on the heating surface of a coal-fired boiler. Background Technology

[0002] Most of the main units of thermal power generation equipment adopt combustion boilers with burners arranged tangentially at the four corners. This type of boiler uses chain ignition and rotary combustion, which can fully mix pulverized coal, oxygen and high-temperature flue gas in the low-pressure zone in the center of the furnace. Therefore, it has the characteristics of strong turbulent mixing and high combustion efficiency, and has a wide range of adaptability to coal type, boiler type, unit capacity and pulverizing system.

[0003] To reduce power generation costs, the four-corner tangential boiler mainly uses lignite and other low-quality coal. When lignite is blended with non-designed low-quality coal for a long time, it will cause coking on the boiler furnace heating surface. Coking on the furnace heating surface will affect the heat exchange effect of the boiler heating surface, resulting in decreased boiler efficiency and increased coal consumption for power generation. Due to the special operating environment of the boiler heating surface, operators have long relied on combustion optimization or changing coal types to make adjustments, which has relatively poor reliability. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the present invention provides a control system for suppressing coking on the heating surface of a coal-fired boiler, so as to solve the problem of coking on the heating surface of existing coal-fired power plant boilers.

[0005] To address the above problems, this invention provides a control system for suppressing coking on the heating surfaces of a coal-fired boiler. The coal-fired boiler includes a furnace and a flue, as well as a water-cooled wall disposed around the outer periphery of the furnace. It also includes a partition screen superheater, a final-stage superheater, and a final-stage reheater sequentially disposed at the top of the furnace along the flue gas flow direction. The control system includes: a first temperature measuring device for monitoring the flue gas temperature at the inlet of the partition screen superheater; a second temperature measuring device for monitoring the flue gas temperature at the inlet of the final-stage superheater; a third temperature measuring device for monitoring the flue gas temperature at the inlet of the final-stage reheater; and a nano-ceramic material coating disposed on the water-cooled wall.

[0006] Based on the initial temperature data monitored by the first, second, and third temperature measuring devices, the area of ​​the nano-ceramic material spray coating is set so that the water-cooled wall has a suitable range of heat absorption, and the flue gas temperature at the inlet of the partition screen superheater is controlled to be T1, the flue gas temperature at the inlet of the final stage superheater is T2, and the flue gas temperature at the inlet of the final stage reheater is T3, thereby suppressing coking on the heating surface of the coal-fired boiler.

[0007] Among them, T1 < 1350℃, T2 < 970℃, and T3 < 850℃.

[0008] Preferably, setting the area of ​​the nano-ceramic material coating based on the initial temperature data monitored by the first temperature measuring device, the second temperature measuring device, and the third temperature measuring device includes:

[0009] S10. Based on the initial temperature data monitored by the first temperature measuring device, the second temperature measuring device and the third temperature measuring device, as well as the temperature data monitored by the coal-fired boiler itself, calculate the heat absorption ratio and heat absorption of each heating surface of the coal-fired boiler.

[0010] S20. Under full boiler load, according to the formula △Q=q×(H T1 -H 1350 Calculate the additional heat absorption ΔQ required for the water-cooled wall; where q is the flue gas flow rate at the inlet of the superheater of the partition screen, and H... T1 H is the flue gas enthalpy value corresponding to the flue gas temperature T1 at the inlet of the superheater of the partition screen. 1350 The enthalpy value of the flue gas at the inlet of the superheater of the partition screen is 1350℃.

[0011] S30. According to the formula: δ=(Q 水冷壁 +△Q) / (T 4 烟气 -T 4 水冷壁 The emissivity δ required for the water-cooled wall to increase heat exchange is calculated using ) / ε; where Q 水冷壁 For the original heat absorption of the water-cooled wall, T 烟气 T represents the flue gas temperature in the main burner area of ​​a coal-fired boiler. 水冷壁 ε is the wall temperature of the water-cooled wall, and ε is the Boltzmann constant.

[0012] S40. Calculate the area of ​​the water-cooled wall that needs to be coated with nano-ceramic material based on the emissivity δ obtained in step S30. Then, spray the nano-ceramic material onto the water-cooled wall according to the calculated area to form the nano-ceramic material coating layer.

[0013] Preferably, 1200℃≤T1<1350℃, 850℃≤T2<970℃, and 750℃≤T3<850℃.

[0014] This invention provides a control system for suppressing coking on the heating surfaces of a coal-fired boiler. Temperature measuring devices are installed at the inlet of the superheater of the partition screen, the inlet of the final superheater, and the inlet of the final reheater. These devices measure the flue gas temperature at each heating surface inlet. Based on the monitored initial temperature data, the area on the water-cooled wall requiring the spraying of nano-ceramic material is calculated. This modifies the water-cooled wall by increasing its surface emissivity, thereby enabling the water-cooled wall to absorb heat within a suitable range, reducing the flue gas temperature at each heating surface inlet, and suppressing coking on the boiler's heating surfaces. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the control system provided in an embodiment of the present invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Examples of these preferred embodiments are illustrated in the drawings. The embodiments of the present invention shown in and described with reference to the drawings are merely exemplary, and the present invention is not limited to these embodiments.

[0017] It should also be noted that, in order to avoid obscuring the invention with unnecessary details, only the structures and / or processing steps closely related to the solution according to the invention are shown in the accompanying drawings, while other details that are not closely related to the invention are omitted.

[0018] Figure 1 This is a schematic diagram of the control system provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the coal-fired boiler includes a furnace 1, a flue 2, and a water-cooled wall 6 disposed on the outer periphery of the furnace. It also includes a partition screen superheater 3, a final stage superheater 4, and a final stage reheater 5 arranged sequentially on the top of the furnace 1 along the flue gas flow direction. The control system includes: a first temperature measuring device 71 for monitoring the flue gas temperature at the inlet of the partition screen superheater 3, a second temperature measuring device 72 for monitoring the flue gas temperature at the inlet of the final stage superheater 4, a third temperature measuring device 73 for monitoring the flue gas temperature at the inlet of the final stage reheater 5, and a nano-ceramic material spray coating disposed on the water-cooled wall.

[0019] Based on the initial temperature data monitored by the first temperature measuring device 71, the second temperature measuring device 72, and the third temperature measuring device 73, the area of ​​the nano-ceramic material coating is set so that the water-cooled wall 6 has a suitable range of heat absorption, and the flue gas temperature at the inlet of the partition screen superheater 3 is controlled to be T1, the flue gas temperature at the inlet of the final stage superheater 4 is controlled to be T2, and the flue gas temperature at the inlet of the final stage reheater 5 is controlled to be T3, thereby suppressing coking on the heating surface of the coal-fired boiler.

[0020] Among them, T1 < 1350℃, T2 < 970℃, and T3 < 850℃.

[0021] The control system, starting from the source, improves the surface emissivity of the water-cooled wall by spraying and modifying it, thereby increasing the heat absorption of the water-cooled wall without changing the original operation mode, reducing the flue gas temperature of the heating surface of the coal-fired boiler, inhibiting coking on the heating surface, and increasing the proportion of high-alkali coal blending.

[0022] In a preferred embodiment, setting the area of ​​the nano-ceramic material coating based on the initial temperature data monitored by the first temperature measuring device 71, the second temperature measuring device 72, and the third temperature measuring device 73 includes:

[0023] S10. Based on the initial temperature data monitored by the first temperature measuring device 71, the second temperature measuring device 72 and the third temperature measuring device 73, as well as the temperature data monitored by the coal-fired boiler itself, calculate the heat absorption ratio and heat absorption of each heating surface of the coal-fired boiler.

[0024] Specifically, the temperature data monitored by the coal-fired boiler itself includes the flue gas temperature in the main burner area of ​​the coal-fired boiler and the wall temperature of the water-cooled wall 6.

[0025] S20. Under full boiler load, according to the formula △Q=q×(H T1 -H 1350 Calculate the additional heat absorption ΔQ required for the water-cooled wall 6; where q is the flue gas flow rate at the inlet of the partition screen superheater 3, and H... T1 H is the flue gas enthalpy value corresponding to the flue gas temperature T1 at the inlet of the superheater 3 of the partition screen. 1350 This refers to the flue gas enthalpy value corresponding to a flue gas temperature of 1350℃ at the inlet of the superheater 3 of the partition screen.

[0026] S30. According to the formula: δ=(Q 水冷壁 +△Q) / (T 4 烟气 -T 4 水冷壁 The emissivity δ required for the water-cooled wall 6 to be increased when the heat exchange is increased is calculated using ) / ε; where Q 水冷壁 For the original heat absorption of the water-cooled wall, T 烟气 T represents the flue gas temperature in the main burner area of ​​a coal-fired boiler. 水冷壁 Let ε be the wall temperature of the water-cooled wall, and ε be the Boltzmann constant.

[0027] Specifically, the Q 水冷壁The original heat absorption of the water-cooled wall, specifically the heat absorption of the water-cooled wall before the nano-ceramic material was sprayed onto it, can be calculated in step S10. The flue gas temperature T in the main burner area of ​​the coal-fired boiler. 烟气 and the wall temperature T of the water-cooled wall 水冷壁 This refers to the temperature data monitored by the coal-fired boiler itself.

[0028] S40. Calculate the area of ​​the water-cooled wall 6 that needs to be coated with nano-ceramic material based on the emissivity δ obtained in step S30. Then, spray the nano-ceramic material onto the water-cooled wall 6 according to the calculated area to form the nano-ceramic material coating layer.

[0029] Specifically, firstly, based on the initial temperature data monitored by the temperature measuring device and the temperature data monitored by the coal-fired boiler itself, the heat absorption ratio and heat absorption of each heating surface of the coal-fired boiler are calculated. For example, based on the initial temperature data monitored by the temperature measuring device, the heat absorption ratio and heat absorption of the water-cooled wall 6, the partition screen superheater 3, the final superheater 4, and the final reheater 5 are calculated. Secondly, the emissivity δ that the water-cooled wall 6 needs to achieve when increasing the heat exchange is calculated using the above formula. Then, the area of ​​the nano-ceramic material spray coating is calculated using the emissivity δ. In this way, the water-cooled wall 6 is modified by spraying, and the heat absorption of the water-cooled wall 6 is controlled within a suitable range. This ensures that the flue gas temperature at the inlet of the partition screen superheater 3 is less than 1350℃, the flue gas temperature at the inlet of the final superheater 4 is less than 970℃, and the flue gas temperature at the inlet of the final reheater 5 is less than 850℃, forming a three-stage temperature gradient control principle, thereby suppressing coking on the heating surface of the coal-fired boiler. By adopting the three-stage temperature gradient control principle, the heat absorption ratio of each stage of the heating surface is calculated based on temperature data, thereby increasing the heat exchange of the water-cooled wall, reducing the flue gas temperature at the inlet of the partition screen, and thus suppressing the coking phenomenon of each stage of the heating surface.

[0030] In the preferred embodiment, the flue gas temperature at the inlet of the partition screen superheater 3 is controlled to be 1200℃≤T1<1350℃ by spraying nano-ceramic material onto the water-cooled wall 6, the flue gas temperature at the inlet of the final stage superheater 4 is 850℃≤T2<970℃, and the flue gas temperature at the inlet of the final stage reheater 5 is 750℃≤T3<850℃.

[0031] Example 1

[0032] This implementation example provides a method for suppressing coking on the heating surface of a coal-fired boiler using the control system described above. The main implementation steps are as follows:

[0033] The study focuses on a 660MW ultra-supercritical tangential boiler.

[0034] (1) Installation of flue gas temperature measuring devices. Temperature measuring devices were installed at the inlet of the superheater of the partition screen, the inlet of the final superheater, and the inlet of the final reheater. That is, three flue gas temperature measuring points were added to the existing temperature measuring points of the coal-fired boiler. Before the nano-ceramic material spray coating was installed, the flue gas temperature at the inlet of the partition screen superheater was measured to be 1420℃, the flue gas temperature at the inlet of the final superheater was 1080℃, and the flue gas temperature at the inlet of the final reheater was 970℃ after the boiler was in operation.

[0035] (2) Calculation of heat absorption and heat absorption ratio of each stage of heating surface. The unit's DCS operating data was collected. Based on the water pressure, working fluid temperature, and temperature data monitored by the coal-fired boiler itself, the enthalpy values ​​of the steam and water at the inlet and outlet of each heating surface at this state point were obtained. Using the heat balance equation on the working fluid side, the heat absorption and heat absorption ratio of each heating surface were calculated. According to the calculation results, under full load, the heat absorption ratio of the water-cooled wall was approximately 46%, the heat absorption ratio of the partition superheater was approximately 7.1%, the heat absorption ratio of the final stage superheater was approximately 5.5%, and the heat absorption ratio of the final stage reheater was approximately 7.5%.

[0036] (3) Calculate the spraying area of ​​the water-cooled wall and modify the water-cooled wall coating. According to the three-stage temperature gradient control principle, that is, according to steps S20 to S40 above, calculate the emissivity that the water-cooled wall needs to achieve when increasing the heat exchange using the above formula, and then calculate the spraying area of ​​the nano-ceramic material to be sprayed on the water-cooled wall using the emissivity. It is proposed to increase the heat absorption ratio of the water-cooled wall area to 48%. The calculation results determine that the area to be sprayed is 1330m². 2 The area is then calculated, and the water-cooled wall is sprayed to form the nano-ceramic material coating. Specifically, the lower elevation of the water-cooled wall spraying at the production site is 35.087m (the elevation of the burner nozzle in layer D), and the upper elevation of the water-cooled wall spraying is 53.88m (2m above the upper elevation of the burnout air). The actual spraying height is calculated as 53.88 - 35.087 = 18.79m. The furnace adopts a square cross-section with furnace dimensions of 20402.3mm × 20072.3mm. A 7-meter wide area is sprayed on each side of each wall. The temperature in the middle is slightly lower, so the 6-meter area in the middle is temporarily not considered for spraying. Therefore, the spraying area S = 18.79 × 14 × 4 × 1.305 = 1373m². 2 The combined area of ​​the primary and secondary air nozzles and the burnout air nozzles is approximately 40m². 2 The actual sprayed area of ​​the water-cooled wall tube is 1373-40=1333m² 2 In the calculation of the sprayed area S above, the parameter 1.305 is an empirical parameter.

[0037] (4) After spraying, the system is put into operation. The flue gas temperature in the superheater area of ​​the partition screen is controlled below 1350℃, the flue gas temperature at the superheater inlet is controlled below 970℃, and the flue gas temperature at the reheat gas inlet is controlled below 850℃. The heat absorption ratio of the water-cooled wall area is increased to 48%, and the phenomenon of coking on the boiler heating surface is controlled.

[0038] In summary, this invention provides a control system for suppressing coking on the heating surfaces of a coal-fired boiler. Temperature measuring devices are installed at the inlet of the superheater of the partition screen, the inlet of the final superheater, and the inlet of the final reheater. These devices measure the flue gas temperature at each heating surface inlet. Based on the monitored initial temperature data, the area on the water-cooled wall requiring the application of nano-ceramic material is calculated. This modifies the water-cooled wall by spraying, increasing its surface emissivity and enabling it to absorb heat within a suitable range. This reduces the flue gas temperature at each heating surface inlet, thereby suppressing coking on the boiler's heating surfaces.

[0039] The above description is only a specific embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A control system for suppressing coking on the heating surface of a coal-fired boiler, the coal-fired boiler comprising a furnace (1) and a flue (2) and a water-cooled wall (6) disposed on the outer periphery of the furnace, and further comprising a partition screen superheater (3), a final-stage superheater (4) and a final-stage reheater (5) sequentially disposed on the top of the furnace (1) along the flue gas flow direction; characterized in that, The control system includes: a first temperature measuring device (71) for monitoring the flue gas temperature at the inlet of the partition screen superheater (3), a second temperature measuring device (72) for monitoring the flue gas temperature at the inlet of the final stage superheater (4), a third temperature measuring device (73) for monitoring the flue gas temperature at the inlet of the final stage reheater (5), and a nano-ceramic material spray coating disposed on the water-cooled wall. Based on the initial temperature data monitored by the first temperature measuring device (71), the second temperature measuring device (72), and the third temperature measuring device (73), the heat absorption ratio and heat absorption of each heating surface of the coal-fired boiler are calculated. Under full load of the boiler, according to the formula △Q=q×(H T1 -H 1350 ) Calculate the additional heat absorption ΔQ required for the water-cooled wall (6), according to the formula: δ=(Q 水冷壁 +△Q) / (T 4 烟气 -T 4 水冷壁 The emissivity δ that the water-cooled wall (6) needs to reach when increasing the heat exchange is calculated by ) / ε. Then, based on the emissivity δ, the area that the water-cooled wall (6) needs to be coated with nano-ceramic material is calculated. The nano-ceramic material is sprayed on the water-cooled wall (6) according to the calculated area to form the nano-ceramic material coating layer. This makes the water-cooled wall (6) have a suitable range of heat absorption, and controls the flue gas temperature at the inlet of the partition screen superheater (3) to be T1, the flue gas temperature at the inlet of the last stage superheater (4) to be T2, and the flue gas temperature at the inlet of the last stage reheater (5) to be T3, thereby suppressing coking on the heating surface of the coal-fired boiler. Among them, T1 < 1350℃, T2 < 970℃, and T3 < 850℃; Where q is the flue gas flow rate at the inlet of the partition screen superheater (3), and H T1 H is the flue gas enthalpy value corresponding to the flue gas temperature T1 at the inlet of the superheater (3) of the partition screen. 1350 Q is the flue gas enthalpy value corresponding to a flue gas temperature of 1350℃ at the inlet of the superheater (3) of the partition screen; 水冷壁 For the original heat absorption of the water-cooled wall, T 烟气 T represents the flue gas temperature in the main burner area of ​​a coal-fired boiler. 水冷壁 Let ε be the wall temperature of the water-cooled wall, and ε be the Boltzmann constant.

2. The control system according to claim 1, characterized in that, The calculation of the heat absorption ratio and heat absorption of each heating surface of the coal-fired boiler includes the initial temperature data and the temperature data monitored by the coal-fired boiler itself, wherein the temperature data monitored by the coal-fired boiler itself includes the flue gas temperature in the main burner area of ​​the coal-fired boiler and the wall temperature of the water-cooled wall.

3. The control system according to claim 1 or 2, characterized in that, 1200℃≤T1<1350℃, 850℃≤T2<970℃, 750℃≤T3<850℃.

Images