Full load peak-shaving boiler and method of operation thereof

Abstract

The full-load peak-shifting boiler and the operation method thereof disclosed by the application relate to the technical field of coal-fired power generation, and comprise a furnace, a vapor-cooling separator and a tail flue, the vapor-cooling separator is connected with the furnace, and the tail flue is connected with the vapor-cooling separator; a superheater screen and a reheater screen are arranged in the furnace, the reheater screen is arranged between the superheater screen and the wall surface of the furnace so as to reduce the radiation heat exchange between the superheater screen and the wall surface of the furnace; the reheater screen and the superheater screen are provided with a radiation heat insulation structure so as to reduce the radiation heat exchange with the wall surface of the furnace; and the furnace is provided with a heat insulation structure. The full-load peak-shifting boiler disclosed by the embodiments of the application can reduce the temperature drop rate of the main steam and the reheated steam, can realize long-period near-zero load operation and rapid start-stop, and can ensure safe operation in the process of fire banking and hot-state re-start or rapid load increase.

Description

Technical Field

[0001] This application relates to the field of coal-fired power generation technology, and more specifically, to a full-load peak-shaving boiler and its operation method. Background Technology

[0002] Circulating fluidized bed boilers utilize the fluidization of solid particles under the influence of gas for combustion. Due to the presence of a large amount of high-temperature bed material, they can provide ignition heat promptly and maintain uniform bed temperature, exhibiting strong combustion stability and outstanding performance under low load conditions.

[0003] Currently, when the boiler stops producing coal and air, the bed temperature slowly decreases due to the cessation of fuel combustion and heat absorption by the furnace heating surfaces. Furthermore, the stagnation of flue gas and material flow significantly reduces the heat transfer coefficient of the heating surface walls. Although the working fluid side continues to produce extremely low-flow steam and drive the turbine, the temperature and pressure of both the main steam and reheat steam show a downward trend due to the gradual decrease in heat transfer. After a certain period of operation, if the bed temperature falls below a certain value, the fuel introduced during restart will fail to ignite successfully, leading to ignition failure and affecting the boiler restart process. If the temperature and pressure of the main steam and reheat steam fall below a certain value, it will seriously affect the operational safety of the turbine unit, causing issues such as water erosion of the last-stage blades and dynamic / static friction.

[0004] In recent years, many scholars have used the characteristics of fire suppression to improve the deep peak-shaving capacity of circulating fluidized bed boilers. However, traditional methods are mostly based on operation, such as standardizing the fire suppression and ignition operation procedures, rationally selecting fuels, and optimizing the control system to maintain the stability of the fire suppression process and achieve near-zero load operation for a longer period of time.

[0005] After the boiler shut-off fire ends, the hot restart rate of the unit is low, causing the bed temperature to continue to drop. If the temperature falls below a certain value, it may lead to difficulty in fuel ignition and increase combustion costs.

[0006] Therefore, how to extend the hot standby time of circulating fluidized bed boilers and improve the hot restart rate to meet the peak shaving needs of the power grid has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] In view of this, the purpose of this application is to disclose a full-load peak-shaving boiler that extends the hot standby time of the circulating fluidized bed boiler and improves the hot restart rate to meet the peak-shaving needs of the power grid.

[0008] Another key aspect of this application is the disclosure of an operating method for the aforementioned full-load peak-shaving boiler.

[0009] To achieve the above objectives, this application provides the following technical solution:

[0010] A full-load peak-shaving boiler includes: a furnace, a steam-cooled separator, and a tail flue, wherein the steam-cooled separator is connected to the furnace and the tail flue is connected to the steam-cooled separator;

[0011] The furnace is equipped with a superheater screen and a reheater screen. The reheater screen is located between the superheater screen and the furnace wall to reduce radiative heat transfer between the superheater screen and the furnace wall. The reheater screen and the superheater screen are equipped with a radiative heat insulation structure to reduce radiative heat transfer with the furnace wall.

[0012] The furnace chamber is equipped with a heat insulation structure.

[0013] Optionally, in the above-mentioned full-load peak-shaving boiler, the angle between the conical inclined furnace wall in the dense phase zone and the vertical direction is in the range of 20°-25°.

[0014] Optionally, in the above-mentioned full-load peak-shaving boiler, the heat insulation structure is a cast-in-place layer disposed in the furnace, and the thickness of the cast-in-place layer is 8cm-13cm.

[0015] Optionally, in the above-mentioned full-load peak-shaving boiler, the casting layer includes a first casting layer and a second casting layer. The first casting layer is disposed in the dense phase region, and the second casting layer is disposed in the dilute phase region of the furnace. The specific heat capacity of the casting material of the first casting layer is greater than that of the casting material of the second casting layer.

[0016] Optionally, in the above-mentioned full-load peak-shaving boiler, the radiant insulation structure is a third casting layer disposed on the reheater screen and the superheater screen. The third casting layer is disposed at the bottom of the reheater screen and the superheater screen and is located on the rising heating surface of the reheater screen and the superheater screen.

[0017] Optionally, in the above-mentioned full-load peak-shaving boiler, the reheater screen includes at least two, the superheater screen includes at least one, and each of the superheater screens is disposed between at least two of the reheater screens.

[0018] Optionally, in the above-mentioned full-load peak-shaving boiler, the full-load peak-shaving boiler includes a first fuel supply device and a second fuel supply device. The first fuel supply device and the second fuel supply device are respectively connected to the furnace. One of the first fuel supply device and the second fuel supply device provides a first fuel, and the other provides a second fuel. The first fuel is used in the boiler hot restart stage, and the second fuel is used in the boiler normal operation stage.

[0019] An operation method for a full-load peak-shaving boiler, used in the aforementioned full-load peak-shaving boiler, includes the following steps:

[0020] a. Maintain the boiler at normal load before shutting down the fire;

[0021] b. Shut down the primary and secondary air fans and close the coal feeding system, reducing the boiler load to 0-2% of full load;

[0022] c. Press and heat the equipment;

[0023] d. Restart the fire, start the induced draft fan, fluidizing fan, primary air fan and secondary air fan, control the increase rate of primary air volume to the preset rate, supply the first fuel through the first fuel supply device, and supply the second fuel through the second fuel supply device when the bed temperature rises to the preset bed temperature.

[0024] Optionally, in the above-mentioned operation method of the full-load peak-shaving boiler, in the step of maintaining the boiler under normal load before fire suppression, the average bed material particle size in the dense phase zone is less than 200μm, and the bed fluidization velocity is 4m / s-6m / s.

[0025] The bed pressure is 10 kPa-13 kPa under low load and 6 kPa-9 kPa under high load.

[0026] Optionally, in the above-mentioned operation method of the full-load peak-shaving boiler, in the step of re-ignition, in the step of providing the first fuel through the first fuel supply device, when the first fuel is difficult-to-burn coal, the particle size range of the first fuel is 0-3mm, and the median diameter is less than 500μm;

[0027] When the first fuel is flammable coal, the particle size range of the first fuel is 0-5 mm, and the median diameter is 2.5 mm.

[0028] As can be seen from the above scheme, the full-load peak-shaving boiler disclosed in this application has a heat insulation structure in the furnace, which can enhance the heat storage capacity of the furnace and maintain a higher bed temperature under the closed-fire state, thereby reducing the temperature drop rate of the main steam. Adjusting the arrangement of the superheater screen and reheater screen so that the reheater screen is set between the superheater screen and the furnace wall can reduce the radiative heat transfer between the superheater screen and the furnace wall under the closed-fire state, thereby reducing the temperature drop rate of the main steam. The radiative heat insulation structure in the reheater screen and superheater screen can reduce the radiative heat transfer between the superheater screen and reheater screen and the furnace wall under the closed-fire state, reduce the temperature drop rate of the main steam and reheat steam, and can achieve long-cycle near-zero load operation (closed-fire hot standby time ≥2h) and rapid start-up and shutdown (unit load change rate ≥3% Pe / min), and ensure safe operation during closed-fire, hot restart or rapid load increase.

[0029] The operation method of the full-load peak-shaving boiler disclosed in this application has the same technical effect as the full-load peak-shaving boiler, and will not be described again. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the full-load peak-shaving boiler disclosed in the embodiments of this application;

[0032] Figure 2 This is a schematic diagram of the dense phase region of an existing boiler.

[0033] Figure 3 This is a schematic diagram of the structure of the dense phase region disclosed in the embodiments of this application. Figure 1 ;

[0034] Figure 4 This is a top view of the furnace chamber disclosed in an embodiment of this application;

[0035] Figure 5 This is a schematic diagram of the structure of the high-temperature heating surface inside an existing boiler.

[0036] Figure 6 This is a schematic diagram of the third casting layer disclosed in the embodiments of this application;

[0037] Figure 7 This is a schematic diagram of the structure of the dense phase region disclosed in the embodiments of this application. Figure 2 ;

[0038] Figure 8 This is a schematic diagram of the structure of the dense phase region disclosed in the embodiments of this application. Figure 3 ;

[0039] Figure 9 This is a graph showing the angle of the cone segment disclosed in the embodiments of this application as a function of the dimensionless degree of fluidization optimization and the degree of fluidization deterioration.

[0040] Figure 10 This is a graph showing the thickness of the castable refractory disclosed in the embodiments of this application in relation to the compressive strength and heat exchange capacity.

[0041] Among them, 100 is the furnace, 110 is the dense phase zone, 120 is the air distribution plate, 121 is the air cap, 130 is the first casting layer, 140 is the second casting layer, 200 is the superheater screen, 300 is the reheater screen, 400 is the steam-cooled separator, 410 is the return valve, 420 is the outlet flue, 500 is the tail flue, 600 is the primary air duct, 700 is the secondary air duct, 800 is the first fuel supply device, and 900 is the second fuel supply device. Detailed Implementation

[0042] The core of this application is to disclose a full-load peak-shaving boiler that extends the hot standby time of the circulating fluidized bed boiler and improves the hot restart rate to meet the peak-shaving needs of the power grid.

[0043] Another key aspect of this application is the disclosure of an operating method for the aforementioned full-load peak-shaving boiler.

[0044] Full-load peak shaving refers to shutting down the boiler coal feeder and all fans in response to the peak shaving demand of the power grid, using the heat stored in the boiler to generate extremely low flow steam to drive the turbine to operate, maintaining a long-term near-zero load (0-2%) operation, that is, in a state of hot standby with reduced fire; when the load needs to be increased, it can quickly increase the load to the specified value within a certain period of time, that is, it has the ability to restart in a hot state.

[0045] Under closed-fire conditions, after the boiler stops coal and reduces airflow, the heat release in the furnace and the amount of circulating ash rapidly decline, and the steam temperature drops significantly over time. To ensure the safe operation of the steam turbine, the main steam temperature is usually required not to fall below the limit value. Once the main steam parameters fall below the safety window, the closed-fire operation is terminated. Therefore, as the closed-fire time increases, the inability of the main steam parameters to meet the safe operation of the steam turbine is the main factor limiting the closed-fire duration. This application is proposed against this background, by increasing the initial furnace temperature and extending the rate of temperature drop of the main steam, thereby extending the closed-fire standby time and achieving full-load peak shaving of the generator unit.

[0046] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0047] like Figure 1 As shown in the figure, this application discloses a full-load peak-shaving boiler, including a furnace 100, a steam-cooled separator 400 and a tail flue 500. The steam-cooled separator 400 is connected to the furnace 100, and the tail flue 500 is connected to the steam-cooled separator 400. It should be noted that the full-load peak-shaving boiler disclosed in this application refers to a circulating fluidized bed boiler.

[0048] The furnace 100 is equipped with a superheater screen 200 and a reheater screen 300, such as Figure 4As shown, the reheater screen 300 is positioned between the superheater screen 200 and the furnace wall 100 to block direct radiative heat transfer between the superheater screen 200 and the furnace wall 100. This reduces radiative heat exchange between the superheater screen 200 and the furnace wall 100 during peak load regulation or shaving, thus decreasing the rate of temperature drop of the main steam. To further reduce the rate of temperature drop of both the main steam and reheat steam, both the reheater screen 300 and the superheater screen 200 are equipped with radiative insulation structures to reduce direct heat transfer to the upper high-temperature heating surface area, reduce heat loss between the superheater screen 200 and the upper water-cooled wall of the furnace 100, and slow down the rate of temperature drop of the main steam.

[0049] To improve the heat storage capacity of the furnace 100 and slow down the rate of main steam descent, the furnace 100 is equipped with a heat insulation structure. This structure allows the boiler to maintain a higher bed temperature during shutdown, reducing the rate of temperature drop and thus extending the shutdown standby time. Furthermore, the higher initial temperature and heat storage capacity of the furnace 100 can increase the temperature during hot restart and shorten the restart time.

[0050] The full-load peak-shaving boiler disclosed in this application has a heat insulation structure in the furnace 100, which enhances the heat storage capacity of the furnace 100, maintains a higher bed temperature under reduced firing conditions, and reduces the temperature drop rate of the main steam. Adjusting the arrangement of the superheater screen 200 and reheater screen 300, with the reheater screen 300 positioned between the superheater screen 200 and the furnace 100 wall, reduces radiative heat transfer between the superheater screen 200 and the furnace 100 wall under reduced firing conditions, thereby reducing the temperature drop rate of the main steam. The radiative heat insulation structure in the reheater screen 300 and superheater screen 200 further reduces radiative heat transfer between them and the furnace 100 wall under reduced firing conditions, lowering the temperature drop rate of both main steam and reheat steam. This allows for long-term near-zero load operation (reheater standby time ≥ 2 hours) and rapid start-up and shutdown (unit load change rate ≥ 3%). Pe / min), and ensure safe operation during compression firing, hot restart, or rapid load increase.

[0051] In some specific embodiments, such as Figure 3 As shown, the angle between the inclined furnace wall of the conical section of the dense phase zone 110 and the vertical direction is preferably between 20° and 25°, that is, the angle α shown in the figure is between 20° and 25°. Here, angle α refers to the angle between the sidewall of the conical section of the dense phase zone 110 and the vertical direction. The existing arrangement of the conical section of the dense phase zone 110 is as follows: Figure 2As shown, the angle b between the conical sidewall of the dense phase zone 110 and the vertical direction ranges from 18° to 20°. This application, while maintaining the total height of the furnace 100, increases the angle between the conical sidewall of the dense phase zone 110 and the vertical direction, thus shrinking the structure of the dense phase zone 110. This means the area of ​​the air distribution plate 120 is reduced by 10%-30%, thereby reducing the effective cross-sectional area of ​​the bottom dense phase zone 110. Under the same primary air volume, this increases the fluidization velocity, resulting in increased local air velocity at the bottom during boiler hot restart. This allows the bed material to be fluidized at low air volumes, preventing local bed collapse and uneven fluidization, and shortening the hot restart time. Simultaneously, increasing the angle between the conical sidewall of the dense phase zone 110 and the vertical direction increases the disturbance of the lower bed material, enhancing gas-solid mixing and heat transfer, which is beneficial for rapid load increase. It should be noted that the angle range between the sidewall of the conical segment of the dense phase region 110 and the vertical direction is a preferred embodiment. In practice, it can be adjusted according to actual needs.

[0052] It should be noted that the derivation of the angle between the sidewall of the conical segment in the dense phase region 110 and the vertical direction is as follows: (e.g.) Figure 7 As shown, the height of the cone section is denoted as h, then the width of the transition section of furnace 100 (B) top The width of the air distribution plate 120 at the bottom of the cone section (B) bot The relationship is:

[0053]

[0054] In the formula, B top D represents the width of the transition section at the top of the conical section of the furnace, in meters; top h represents the depth of the transition section at the top of the conical section of the furnace, in meters; h represents the height of the conical section, in meters.

[0055] The rectangular furnace chamber 100 is narrowed in both width and depth, resulting in the following area for the bottom air distribution plate 120:

[0056]

[0057] When the primary air volume flow rate (V1) under low load is given, the bottom average apparent wind speed u(a) is:

[0058]

[0059] In the formula, V1 represents the primary air flow rate, which is the fluidizing air volume in the furnace, in m³ / s; A bot This indicates the area of ​​the 120mm air distribution panel, in square meters (m²). 2 u(a) is the average apparent wind speed, in m / s.

[0060] As can be seen from the above formula, as the inclination angle of the air distribution plate 120 increases, the average wind speed at the bottom air distribution plate 120 of the furnace 100 gradually increases.

[0061] However, the increase in the aforementioned included angle α also introduces an increase in the static pressure difference of the bed. When phenomena such as tilting, contraction, flow deviation, and bed material slippage occur, more bed material accumulates on one side, resulting in a situation where one side of the bed material is thicker and the other side is thinner. The difference in bed height is defined as ΔH. Figure 8 As shown, if the bed heights on both sides are different, the bed pressure will be different, which will cause the air distribution to be off-center. The pressure difference between the two sides is calculated as follows:

[0062]

[0063] In the formula, ΔPbed,var represents the pressure difference, with units of Pa; ρ bed The density of the bed material is expressed in kg / m³; g represents the acceleration due to gravity, g = 9.81 m / s²; ΔH = Ltana, where L represents the dimension along the inclined direction, in meters. Figure 8 As shown, the maximum value of L is the length of the inclined section of the entire conical segment.

[0064] The pressure drop of the 120 air distribution plate under normal operating conditions is ∆P bed This phenomenon will cause an additional pressure drop on the air distribution plate 120. Define the dimensionless deflection parameter:

[0065]

[0066] The minimum wind speed u(α) at ​​the most unfavorable fluidization point is approximately calculated as follows:

[0067]

[0068] The lower limit of the fluidization velocity for restarting or low-load operation must be several times (multiple of γ) greater than the minimum fluidization velocity, i.e.

[0069]

[0070] Based on the above formula, the upper limit condition for SYMBOL 70 \f "Symbol" \s 14F(a) is:

[0071]

[0072] In the formula, u mf This represents the minimum fluidization velocity, expressed in m / s.

[0073] According to the above formula, the angle between the sidewall of the conical section of the dense phase zone 110 and the vertical direction cannot be increased indefinitely. Increasing this angle increases the area of ​​the air distribution plate 120 and the average wind speed, which is beneficial for establishing a restarted fluidization state. On the other hand, it increases the static pressure difference in the bed, intensifies flow deviation, and decreases the local minimum wind speed. A graph showing how this angle can improve fluidization capacity and reduce the degree of fluidization deterioration is shown below. Figure 9 As shown, an optimal range is selected between improving fluidization capacity and reducing fluidization deterioration. The range of the included angle is 20°-25°. Within this range, the fluidization capacity of the fluidizing air can be improved, while the impact on fluidization deterioration will not be too great.

[0074] In some specific embodiments, the air distribution plate 120 is provided with an air cap 121. The air cap 121 can be an existing air cap 121 capable of adjusting the resistance coefficient, and its specific structure and working principle will not be described in detail here. The furnace 100 is provided with a primary air duct 600 and a secondary air duct 700. The primary air duct 600 provides primary air, and the secondary air duct 700 provides secondary air.

[0075] In some specific embodiments, the heat insulation structure is a cast-in-place layer disposed in the furnace 100. The thickness of the cast-in-place layer is 8cm-13cm, while the existing cast-in-place layer thickness is typically 5cm. Increasing the thickness of the cast-in-place layer can improve the heat storage capacity of the furnace 100, maintain a higher bed temperature under controlled firing conditions, and reduce the rate of temperature drop. Since the furnace 100 has a higher initial temperature and heat storage capacity, it can increase the temperature during hot restart and shorten the hot restart time. It should be noted that the thickness of the cast-in-place layer is determined as follows:

[0076] The heat storage capacity of the furnace wall per unit area of ​​the castable refractory thickness, assuming the castable refractory is an infinitely extending flat plate, is Q. store for

[0077]

[0078] Q store Energy storage is expressed in J; δ is the thickness of the castable refractory δ, in m; ρ is the density of the castable refractory, in kg / m³. 3 ;c p ∆T represents the heat capacity of the castable, in J / (kg·K); ∆T represents the temperature difference between the two sides of the castable, in K; and A represents the area of ​​the castable, in m². 2 .

[0079] The heat transfer resistance of the castable section is:

[0080]

[0081] In the formula, k represents the thermal conductivity of the castable refractory, with units of W / (m·K);

[0082] The instantaneous heat dissipation during fire suppression is approximately as follows: If the furnace side no longer supplies heat during fire suppression, the heat flux q will decrease over time.

[0083]

[0084] In the formula, A represents the area of ​​the castable refractory, in m². 2 q represents heat flux, with units of W / m 2 R represents the thermal resistance of the castable portion, measured in K / W; T SYMBOL 165 \f "Symbol" \s 14¥， i represents the temperature inside the castable refractory, i.e., inside the furnace chamber 100, in Kelvin (TSYM). BOL 165 \f "Symbol" \s 14¥，0表示 The temperature of the outer surface of the castable refractory, i.e., the outer wall surface of the furnace, is measured in K.

[0085] Assuming the internal temperature of the castable is uniform, then

[0086]

[0087] In the formula, T(t) represents the furnace temperature under any pressing time, and the unit is K.

[0088] The solution obtained from the above formula is as follows:

[0089]

[0090] In the formula, T(0) represents the furnace temperature at the initial test of the fire suppression, in K; t represents the fire suppression time, in s.

[0091] The time constant τ is:

[0092]

[0093] If the lowest acceptable temperature for pressurization is denoted as T min Then, we can solve it from the exponent:

[0094]

[0095] From the above formula, it can be seen that the pressing time t and the castable thickness δ... 2 The relationship is linear.

[0096] The heat transfer flux q of the castable under a unit temperature difference can be expressed as:

[0097]

[0098] The relative heat exchange capacity is:

[0099]

[0100] [P]

[0101] In the formula, U represents the actual heat transfer capacity after the change in the thickness of the castable refractory, and the unit is W / (m). 2 ·K), U ref This indicates the heat transfer capacity under normal operating conditions, expressed in W / (m²). 2 ·K), SYMBOL 100 \f "Symbol" \s 14dref 表示参 The thickness of the castable under normal working conditions, in meters;

[0102] Considering that the actual heat exchange capacity reduction cannot exceed a certain value (such as 5% or 10%), that is, the heat exchange efficiency is η≥90% or 95%, then:

[0103]

[0104]

[0105] As can be seen from the above formula, the thickness δ of the castable refractory cannot be increased indefinitely, otherwise the required heat exchange limit will be exceeded.

[0106] To extend the calcination time, the thickness of the castable needs to be increased, but there are certain limitations to increasing the castable thickness. Based on these two factors, the calcination time extension capacity and heat exchange capacity are plotted as follows: Figure 10 As shown, when the thickness of the casting layer is 8cm-13cm, it can maintain both the boiler's good fire suppression capability and its good heat exchange capability.

[0107] In some specific embodiments, the casting layer includes a first casting layer 130 and a second casting layer 140. The first casting layer 130 is disposed in the dense phase region 110, and the second casting layer 140 is disposed in the dilute phase region of the furnace 100. The specific heat capacity of the casting material of the first casting layer is greater than that of the casting material of the second casting layer. Preferably, the specific heat capacity of the casting material of the first casting layer is greater than >2kJ / kg / K; and / or, the thermal conductivity of the casting material of the first casting layer 130 is <1.5w / m / K. That is, the first casting layer uses a material with high specific heat and low thermal conductivity to enhance the heat storage capacity of the dense phase region 110. Under normal boiler load, it can store a large amount of heat, improve the heat storage capacity of the bottom of the furnace 100, thereby enabling the boiler to maintain a high initial bed temperature under closed-fire conditions. Due to its low thermal conductivity, it can prolong the closed-fire time and improve the hot restart rate. The second casting layer is preferably made of conventional casting material with low thermal conductivity, typically ranging from 0.3 W / m / K to 1.5 W / m / K. Specifically, the casting material for the first casting layer 130 can be magnesia-alumina refractories, some high-alumina (high Al2O3 content) refractory castables, or composite castables (composite ceramic / oxide-based composite materials); the casting material for the second casting layer 140 can be lightweight mullite castables, high-alumina refractory insulating castables, high-alumina (mullite) refractory castables, etc. It should be noted that the above types of casting materials are only examples and not limitations; the specific type can be determined according to actual needs.

[0108] In some specific embodiments, the radiant insulation structure is a third cast-in-place layer disposed on the reheater screen 300 and the superheater screen 200. Specifically, the third cast-in-place layer is disposed at the bottom of the reheater screen 300 and the superheater screen 200, and is located on the rising heating surface of the reheater screen 300 and the superheater screen 200. The area of ​​the third cast-in-place layer is preferably 10%-30% of the area of ​​the rising heating surface of the reheater screen 300 and the superheater screen 200, preferably 30%. It should be noted that the existing superheater screen 200 and reheater screen 300 are provided with a cast-in-place layer at the elbow position. This cast-in-place layer plays a role in preventing local overheating and preventing flue gas abrasion. In the full-load peak-shaving boiler disclosed in the embodiments of this application, the third cast-in-place layer is located on the rising heating surface, which refers to the pipe section located above the elbow. Figure 5 and Figure 6 As shown, Figure 6 Taking the reheater screen 300 as an example, the area of ​​the third casting layer is approximately 30% of the area of ​​the rising heating surface of the reheater screen 300. Figure 5This is a schematic diagram of the high-temperature heating surface within the existing furnace 100. It should be noted that the area of ​​the third casting layer is preferably 10%-30% of the area of ​​the rising heating surface of the reheater screen 300 and superheater screen 200. This third casting layer area ensures normal heat exchange of the high-temperature heating surface while reducing radiative heat exchange with the furnace 100 during the heat suppression process, thus reducing the rate of temperature decrease of the main steam and reheat steam. The material of the third casting layer can refer to the material of the second casting layer, and will not be elaborated here.

[0109] In some specific embodiments, at least two reheater panels 300 are included, and at least one superheater panel 200 is included, with each superheater panel 200 disposed between at least two reheater panels 300. Specifically, as shown... Figure 4 As shown in the diagram, the heat exchangers located at the top and bottom are both reheater screens 300, and at least one heat exchanger between two reheater screens 300 is a superheater screen 200. Alternatively, the reheater screen 300 can consist of only one at the top and bottom, with the remaining heat exchangers being superheater screens 200. In this arrangement, two walls of the reheater screen 300 directly face the furnace wall 100, and the superheater screens 200 are positioned between the reheater screens 300, with one wall directly facing the furnace wall 100. When there are multiple superheater screens 200 and multiple reheater screens 300, the reheater screens 300 can be connected in series or in parallel, and the superheater screens 200 can be connected in series or in parallel.

[0110] In some other specific embodiments, the reheater screen 300 can be arranged around the superheater screen 200, that is, the reheater screen 300 is close to the water-cooled walls around the furnace 100, and the superheater screen 200 is arranged close to the center. The superheater screen 200 is isolated from the wall of the furnace 100 in the radiative heat transfer path through the reheater screen 300, so as to reduce the radiative heat transfer between the superheater screen 200 and the wall of the furnace 100.

[0111] In some specific embodiments, the outlet flue 420 of the steam-cooled separator 400 is composed of a membrane water-cooled wall, which has a fourth casting layer. The membrane water-cooled wall includes multiple parallel pipes and connectors disposed between adjacent pipes; and / or, the wall cladding of the tail flue 500 is provided with a fifth casting layer. The casting materials for the fourth and fifth casting layers can be lightweight mullite castable, high-alumina refractory insulating castable, high-alumina (mullite) refractory castable, etc. It should be noted that the structure and working principle of the steam-cooled separator 400 can refer to existing steam-cooled separators, and this application does not improve the structure of the steam-cooled separator 400. In the steam-cooled separator 400, superheated steam absorbs heat. The fourth casting layer enables the superheated steam to absorb heat from the outlet flue gas of the steam-cooled separator 400 during unit shutdown, thereby increasing the temperature of the superheated steam. The fifth casting layer can reduce heat loss from the tail flue by 500 mm and extend the boiler's standby time.

[0112] In some specific embodiments, a cold ash collector is also included. The cold ash collector is connected to the return valve 410 of the steam-cooled separator 400 and is used to store a portion of the circulating ash. When the boiler needs to rapidly reduce its load, some of the circulating ash can be stored in the cold ash collector to reduce the heat transfer within the furnace by decreasing the ash concentration. When it needs to rapidly increase its load, the circulating ash in the cold ash collector can be returned to the furnace 100, quickly re-establishing circulation within the furnace 100, thus shortening the hot restart time. The specific structure and working principle of the cold ash collector can be found in existing cold ash collectors and will not be elaborated here.

[0113] In some specific embodiments, such as Figure 1 As shown, the full-load peak-shaving boiler includes a first fuel supply device 800 and a second fuel supply device 900. Both devices are connected to the furnace 100. One device provides the first fuel, and the other provides the second fuel. Specifically, the first fuel includes lignite, biomass, etc., and the second fuel includes anthracite, some bituminous coal, coal gangue, washed middlings coal, coal slime, etc. The first and second fuels have different combustion activities. Fuel activity here refers to its ignition and burnout characteristics during combustion, judged by the dry ash-free volatile matter content and ignition temperature. The first fuel has a higher volatile matter content and a lower ignition temperature, making it easy to burn. Preferably, the first fuel has a volatile matter content of not less than 40% and an ignition temperature of not more than 250°C. The second fuel has a lower volatile matter content and a higher ignition temperature, enabling continuous combustion. Specifically, the second fuel has a volatile matter content of not more than 20%-30% and an ignition temperature of not less than 300-350°C. The first fuel is used during the boiler's hot restart phase, and the second fuel is used during the boiler's normal operation phase. Different fuel supply devices can be used according to the boiler's operating status to shorten the boiler's hot restart time.

[0114] The full-load peak-shaving boiler disclosed in this application can achieve a furnace temperature of >920°C through the above measures, thereby increasing the initial temperature of the bed.

[0115] Furthermore, this application also discloses an operation method for a full-load peak-shaving boiler, used for the above-mentioned purposes, including the following steps:

[0116] Step S1: Maintain the boiler at normal load before shutting down the fire;

[0117] The average bed material particle size in the dense phase zone 110 is less than 200μm, and the bed fluidization velocity is 4m / s-6m / s; the bed pressure is 10kpa-13kPa at low load and 6kpa-9kPa at high load. Here, low load refers to 30%-50% below the full load of the boiler, and high load refers to 70%-50% above the full load of the boiler.

[0118] Step S2: Shut down the primary and secondary air fans and close the coal feeding system, reducing the boiler load to 0-2% of full load;

[0119] When the boiler receives the fire suppression command, the primary and secondary air fans are shut down and the coal feeding system is closed, and the boiler load is gradually reduced to 0-2% of the full load.

[0120] Step S3: Preheat the furnace;

[0121] Step S4: Restart the fire;

[0122] Start the induced draft fan, fluidizing fan, primary air fan, and secondary air fan, controlling the primary air volume increase rate to a preset speed. Provide the first fuel through the first fuel supply device 800. The first fuel can be either difficult-to-burn or easy-to-burn coal. The particle size range of the difficult-to-burn coal is 0-3mm, preferably 0-1mm, with a median diameter less than 500μm; the particle size range of the easy-to-burn coal is 0-5mm, with a median diameter of approximately 2.5mm. When the bed temperature reaches the preset temperature, use fuel with conventional particle size, and the existing coal feeder can be used, i.e., the second fuel supply device 900 can be employed. It should be noted that the preset temperature here is not specifically limited and can be determined based on the type of fuel.

[0123] The full-load peak-shaving boiler disclosed in this application, by optimizing the bed material particle size, can achieve stable fluidization under low airflow conditions during the initial stage of hot restart while maintaining a constant total bed material volume, thus avoiding local bed collapse. Reducing the bed material particle size improves the gas-solid mixing characteristics of the dense phase zone 110, increasing gas-solid contact efficiency and promoting heat transfer, thereby shortening the hot restart time. The feed particle size range is dynamically adjusted according to the volatile matter, ignition characteristics, and crushing performance of different coal types. For high-volatile coals, a larger particle size can be retained; for low-volatile coals, the particle size is appropriately refined. The selection of particle size mainly aims to ensure the combustion activity of the fuel, ensuring ignition and rapid temperature rise during restart, and can accommodate different fuel characteristics, making it more applicable.

[0124] It should be noted that the various embodiments in this specification mainly describe the differences from other embodiments, and the same or similar parts between the various embodiments can be referred to each other.

[0125] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0126] In the description of this specification, it should be noted that, unless otherwise explicitly specified and limited, the technical terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or a single connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the meaning of the above technical terms in this application based on the specific circumstances.

[0127] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0128] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand the core ideas of this application. It should be noted that those skilled in the art can make several improvements and modifications to this application without departing from the principles of this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

Claims

1. A full-load peak-shaving boiler, characterized in that, include: The furnace (100), the steam-cooled separator (400), and the tail flue (500) are connected to the furnace (100) and the tail flue (500). The furnace (100) is provided with a superheater screen (200) and a reheater screen (300). The reheater screen (300) is disposed between the superheater screen (200) and the wall of the furnace (100) to reduce radiative heat transfer between the superheater screen (200) and the wall of the furnace (100). The reheater screen (300) and the superheater screen (200) are provided with a radiation insulation structure to reduce radiation heat exchange with the wall of the furnace (100); The furnace chamber (100) is equipped with a heat insulation structure.

2. The full-load peak-shaving boiler as described in claim 1, characterized in that, The angle between the conical inclined wall of the dense phase zone (110) of the furnace (100) and the vertical direction is in the range of 20°-25°.

3. The full-load peak-shaving boiler as described in claim 1, characterized in that, The heat insulation structure is a casting layer disposed in the furnace (100), and the thickness of the casting layer is 8cm-13cm.

4. The full-load peak-shaving boiler as described in claim 3, characterized in that, The casting layer includes a first casting layer and a second casting layer. The first casting layer (130) is disposed in the dense phase region (110) of the furnace (100), and the second casting layer (140) is disposed in the dilute phase region of the furnace (100). The specific heat capacity of the casting material of the first casting layer is greater than that of the casting material of the second casting layer.

5. The full-load peak-shaving boiler as described in claim 4, characterized in that, The radiative heat insulation structure is a third casting layer disposed on the reheater screen (300) and the superheater screen (200). The third casting layer is disposed at the bottom of the reheater screen (300) and the superheater screen (200) and is located on the rising heat-receiving surface of the reheater screen (300) and the superheater screen (200).

6. The full-load peak-shaving boiler as described in claim 1, characterized in that, The reheater panel (300) includes at least two, the superheater panel (200) includes at least one, and each of the superheater panels (200) is disposed between at least two of the reheater panels (300).

7. The full-load peak-shaving boiler as described in any one of claims 1-6, characterized in that, The full-load peak-shaving boiler includes a first fuel supply device (800) and a second fuel supply device (900). The first fuel supply device (800) and the second fuel supply device (900) are respectively connected to the furnace (100). One of the first fuel supply device (800) and the second fuel supply device (900) provides a first fuel and the other provides a second fuel. The first fuel is used in the boiler hot restart stage and the second fuel is used in the boiler normal operation stage.

8. A method for operating a full-load peak-shaving boiler, characterized in that, For use in the full-load peak-shaving boiler as described in claim 7, the steps include: a. Maintain the boiler at normal load before shutting down the fire; b. Shut down the primary and secondary air fans and close the coal feeding system, reducing the boiler load to 0-2% of full load; c. Pressurize and heat up; d. Restart the fire, start the induced draft fan, fluidizing fan, primary air fan and secondary air fan, control the increase rate of primary air volume to the preset speed, supply the first fuel through the first fuel supply device (800), and supply the second fuel through the second fuel supply device (900) when the bed temperature rises to the preset bed temperature.

9. The operation method of the full-load peak-shaving boiler as described in claim 8, characterized in that, In the step of maintaining the boiler under normal load before the fire is suppressed, the average bed material particle size of the dense phase zone (110) of the furnace (100) is less than 200μm, and the bed fluidization velocity is 4m / s-6m / s. The bed pressure is 10 kPa-13 kPa under low load and 6 kPa-9 kPa under high load.

10. The operation method of the full-load peak-shaving boiler as described in claim 8, characterized in that, In the step of reigniting the fire, in the step of providing the first fuel through the first fuel supply device (800), when the first fuel is difficult-to-burn coal, the particle size range of the first fuel is 0-3mm, and the median diameter is less than 500μm; When the first fuel is flammable coal, the particle size range of the first fuel is 0-5 mm, and the median diameter is 2.5 mm.

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