A tower boiler with low temperature heating surfaces arranged in the furnace and flue gas recirculation

Abstract

The application provides a tower type boiler with low temperature heating surface and flue gas recirculation, and belongs to the tower type boiler field.The upper part of the wall type reheater is sequentially provided with a screen type superheater, a last stage superheater and a last stage reheater from low to high, the outlet is divided into a front tail flue and a rear tail flue, and the front tail flue and the rear tail flue are respectively provided with a low temperature superheater and a low temperature reheater;the outlet of the low temperature superheater and the low temperature reheater in the front tail flue and the rear tail flue is respectively provided with an economizer;and the economizer outlet of the front tail flue and the rear tail flue is respectively provided with a flue gas temperature adjusting baffle.The application adopts a variety of coupled and optimized temperature adjusting modes.The coupled and optimized temperature adjusting mode is a comprehensive use of the above temperature adjusting modes, and two or more than two temperature adjusting modes are used to simultaneously adjust the steam temperature during the operation of the boiler.Compared with the use of a single temperature adjusting mode, the variety of coupled and optimized modes can provide a larger temperature adjusting range and more accurate temperature adjusting.

Description

Technical Field

[0001] This invention relates to a tower boiler with an in-furnace arrangement of low-temperature heating surfaces and flue gas recirculation, belonging to the field of 650℃-class ultra-supercritical single reheat boilers. Background Technology

[0002] In recent years, a large number of 620℃-class ultra-supercritical boilers have been successfully put into operation in my country. Their conventional boiler parameters have main steam / reheat steam temperatures of 605 / 623℃. Increasing these parameters to 650℃-class boilers, with main steam / reheat steam temperatures of 655 / 653℃ or 655 / 673℃, can significantly improve unit efficiency. Compared to conventional boilers, however, they present challenges such as higher steam parameters at high-temperature heating surfaces, greater variation in heat absorption ratios, increased difficulty in heating surface arrangement, delayed steam temperature regulation, poor low-load steam temperature regulation characteristics, and limited load regulation range. Summary of the Invention

[0003] The purpose of this invention is to solve the problems existing in the prior art, and to provide a tower boiler with a low-temperature heating surface and flue gas recirculation arranged inside the furnace.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] A tower boiler with an internal arrangement of low-temperature heating surfaces and flue gas recirculation includes water-cooled walls, wall-type superheaters, wall-type reheaters, screen-type superheaters, final-stage superheaters, final-stage reheaters, low-temperature superheaters, low-temperature reheaters, economizers, flue gas temperature regulating dampers, connecting flues, and flue gas recirculation fans.

[0006] The boiler furnace is entirely composed of water-cooled walls. A wall-type superheater is installed in the upper part of the furnace, close to the inner wall of the water-cooled walls. Above the wall-type superheater is a wall-type reheater. Above the wall-type reheater, from low to high, are a screen-type superheater, a final-stage superheater, and a final-stage reheater. The tail flue at the outlet of the final-stage reheater is divided into a front tail flue and a rear tail flue. Low-temperature superheaters and low-temperature reheaters are installed in both the front and rear tail flues. Economizers are installed at the outlets of the low-temperature superheater and low-temperature reheater in the front and rear flues. Flue gas temperature regulating baffles are installed at the outlets of the economizers in the front and rear flues. The left and right sides of the furnace at the bottom of the boiler are connected to the flue gas recirculation fan through connecting flues. The wall-type superheater, wall-type reheater, screen-type superheater, final stage superheater, final stage reheater, low-temperature superheater, low-temperature reheater and economizer are connected by pipes and headers.

[0007] The present invention discloses a tower boiler with a low-temperature heating surface and flue gas recirculation arranged inside the furnace. The water-cooled wall is covered with a radiant heating surface that is closely attached to the water-cooled wall. The added radiant heating surface is a wall-type radiant heating surface that covers the inner surface of the furnace water-cooled wall and shields the water-cooled wall.

[0008] The present invention relates to a tower boiler with a low-temperature heating surface and flue gas recirculation inside the furnace, wherein the positions of the low-temperature superheater and the low-temperature reheater in the front and rear flues can be interchanged.

[0009] This invention discloses a tower boiler with an internal low-temperature heating surface and flue gas recirculation. The tower boiler employs five temperature control methods, namely:

[0010] 1) Swing burner: The boiler burner is located in the middle area of ​​the boiler furnace, and the boiler uses a swing burner;

[0011] 2) Coal-to-water ratio: Controlling the ratio of boiler coal feed rate to boiler water feed rate;

[0012] 3) Flue gas dampers: By adjusting the opening and closing angle of the flue gas temperature regulating dampers on the front and rear flues, the amount of flue gas in the two flues is changed, thereby changing the heat absorption ratio of the low-temperature superheater and the low-temperature reheater, and thus regulating the reheat steam temperature.

[0013] 4) Excess air volume: Change the excess air coefficient;

[0014] 5) Flue gas recirculation: This includes flue gas recirculation fans, flue gas temperature regulating dampers, and connecting flue ducts. The recirculated flue gas is taken from the low-temperature flue gas of the economizer. The flue gas recirculation fans are used to circulate the flue gas to the bottom of the boiler furnace, thereby increasing the amount of flue gas in the boiler and increasing the convective heat transfer and heat absorption of the boiler's low-temperature heating surfaces.

[0015] This invention discloses a tower boiler with an in-furnace arrangement of low-temperature heating surfaces and flue gas recirculation. Five temperature control methods are coupled together for temperature control. The specific steps are as follows: First, the superheater steam temperature is adjusted by prioritizing the coal-water ratio, the reheater steam temperature is adjusted by the oscillating burner, and the reheat steam temperature is adjusted by the tail-end double flue gas temperature control baffle. The excess air coefficient plays a fine-tuning role in the superheater and reheat steam temperatures. Under low load conditions, when the above methods have been exhausted, flue gas recirculation is used to adjust the reheat steam temperature, which can provide a larger temperature control range and higher sensitivity.

[0016] This invention discloses a tower boiler with an in-furnace arrangement of low-temperature heating surfaces and flue gas recirculation. It employs multiple coupled and optimized temperature control methods, including a swing burner, coal-to-water ratio, flue gas recirculation system, flue gas dampers, and excess air volume. These coupled and optimized temperature control methods combine several of these approaches. During boiler operation, two or more of these methods are used to simultaneously regulate the steam temperature. Compared to using a single temperature control method, multiple coupled and optimized methods provide a wider temperature control range and more precise temperature regulation. Attached Figure Description

[0017] Figure 1This is a schematic diagram of the structure of a tower boiler with a low-temperature heating surface and flue gas recirculation inside the furnace, as described in this invention.

[0018] Figure 2 This is a top view of the tower boiler of the present invention, which has a low-temperature heating surface and flue gas recirculation inside the furnace. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to the accompanying drawings: This embodiment is implemented under the premise of the technical solution of the present invention, and detailed implementation methods are given, but the protection scope of the present invention is not limited to the following embodiments.

[0020] Example 1: As Figure 1 As shown, this embodiment involves a tower boiler with an in-furnace arrangement of low-temperature heating surfaces and flue gas recirculation.

[0021] This includes water-cooled walls, wall-mounted superheaters, wall-mounted reheaters, screen-type superheaters, final-stage superheaters, final-stage reheaters, low-temperature superheaters, low-temperature reheaters, economizers, flue gas temperature regulating dampers, connecting flue ducts, and flue gas recirculation fans.

[0022] The boiler furnace is entirely composed of water-cooled walls. A wall-type superheater is installed in the upper part of the furnace, close to the inner wall of the water-cooled walls. Above the wall-type superheater is a wall-type reheater. Above the wall-type reheater, from low to high, are a screen-type superheater, a final-stage superheater, and a final-stage reheater. The tail flue at the outlet of the final-stage reheater is divided into a front tail flue and a rear tail flue. Low-temperature superheaters and low-temperature reheaters are installed in both the front and rear tail flues. Economizers are installed at the outlets of the low-temperature superheater and low-temperature reheater in the front and rear flues. Flue gas temperature regulating baffles are installed at the outlets of the economizers in the front and rear flues. The left and right sides of the furnace at the bottom of the boiler are connected to the flue gas recirculation fan through connecting flues. The wall-type superheater, wall-type reheater, screen-type superheater, final stage superheater, final stage reheater, low-temperature superheater, low-temperature reheater and economizer are connected by pipes and headers.

[0023] The present invention discloses a tower boiler with a low-temperature heating surface and flue gas recirculation arranged inside the furnace. The water-cooled wall is covered with a radiant heating surface that is closely attached to the water-cooled wall. The added radiant heating surface is a wall-type radiant heating surface that covers the inner surface of the furnace water-cooled wall and shields the water-cooled wall.

[0024] The present invention relates to a tower boiler with a low-temperature heating surface and flue gas recirculation inside the furnace, wherein the positions of the low-temperature superheater and the low-temperature reheater in the front and rear flues can be interchanged.

[0025] This invention discloses a tower boiler with an internal low-temperature heating surface and flue gas recirculation. The tower boiler employs five temperature control methods, namely:

[0026] 1) Swing burner: The boiler burner is located in the middle area of ​​the boiler furnace, and the boiler uses a swing burner;

[0027] 2) Coal-to-water ratio: Controlling the ratio of boiler coal feed rate to boiler water feed rate;

[0028] 3) Flue gas dampers: By adjusting the opening and closing angle of the flue gas temperature regulating dampers on the front and rear flues, the amount of flue gas in the two flues is changed, thereby changing the heat absorption ratio of the low-temperature superheater and the low-temperature reheater, and thus regulating the reheat steam temperature.

[0029] 4) Excess air volume: Change the excess air coefficient;

[0030] 5) Flue gas recirculation: This includes flue gas recirculation fans, flue gas temperature regulating dampers, and connecting flue ducts. The recirculated flue gas is taken from the low-temperature flue gas of the economizer. The flue gas recirculation fans are used to circulate the flue gas to the bottom of the boiler furnace, thereby increasing the amount of flue gas in the boiler and increasing the convective heat transfer and heat absorption of the boiler's low-temperature heating surfaces.

[0031] This invention discloses a tower boiler with an in-furnace arrangement of low-temperature heating surfaces and flue gas recirculation. Five temperature control methods are coupled together for temperature control. The specific steps are as follows: First, the coal-water ratio is used to adjust the steam temperature of all superheaters, the oscillating burner is used to adjust the steam temperature of all reheaters, and then the tail-end double flue gas temperature control baffle is used to adjust the reheat steam temperature. The excess air coefficient plays a fine-tuning role in the superheater and reheat steam temperatures. Under low load conditions, when the above methods have been exhausted, flue gas recirculation is used to adjust the reheat steam temperature, which can provide a larger temperature control range and higher sensitivity.

[0032] The added radiant heating surfaces of the superheaters and reheaters are located inside the furnace. These added surfaces are wall-type radiant heating surfaces, covering the inner surface of the furnace water-cooled walls and obstructing them. This reduces the heat absorption of the water-cooled walls while increasing the radiant heat absorption of the superheaters and reheaters, and decreasing the convective heat absorption. This achieves an adjustment of the radiant and convective heat absorption ratio of the water-cooled walls and the superheaters / reheaters.

[0033] Example 2: Figure 1-2 As shown, the tower boiler with low-temperature heating surfaces and flue gas recirculation arranged in the furnace involved in this embodiment has the following specific temperature control method:

[0034] Oscillating burner:

[0035] A swing burner is a type of pulverized coal burner whose nozzle can swing up and down at a certain angle. By swinging the burner up and down, the position of the flame center in the furnace is changed, causing a change in the temperature of the flue gas at the furnace outlet. This, in turn, alters the temperature of the flue gas entering the downstream heating surfaces of the furnace outlet, thereby changing the heat absorption of each heating surface and thus regulating the steam temperature.

[0036] Coal-to-water ratio:

[0037] The coal-water ratio refers to the amount of steam produced per kilogram of coal burned in a boiler, representing the ratio of coal feed to boiler feedwater. Regulating steam temperature through the coal-water ratio essentially means matching the heat input from the fuel with the heat output from the steam, i.e., controlling the coal-water ratio. For supercritical once-through boilers, the fuel and feedwater quantities directly affect the temperature of the working fluid in the steam-water pipelines. Furthermore, changes in the enthalpy of the working fluid at all cross-sections of the boiler outlet and the steam-water pipelines are correlated. When the coal-water ratio changes, it correspondingly causes a shift in the steam-water interface. Therefore, the first effect is a change in steam temperature at the beginning of the superheater section in the evaporation zone, which in turn causes a change in the superheater outlet steam temperature.

[0038] Smoke baffle:

[0039] Flue gas temperature regulation involves placing the heated surface requiring temperature control in one of two parallel flues and installing a regulating damper in that flue. By changing the opening of the damper, the resistance of the flue is increased or decreased, thereby altering the distribution ratio of flue gas in the two flues and thus changing the amount of heat released by the flue gas in the two flues, achieving the purpose of regulating steam temperature.

[0040] Excess air volume:

[0041] The excess air coefficient, also known as the "excess air quantity" or "excess air factor," is the ratio of the actual amount of air supplied for fuel combustion to the theoretical amount of air. It is an important parameter reflecting the fuel-air ratio. In various furnaces or combustion chambers, to ensure complete combustion, the actual amount of air supplied must always exceed the theoretical amount (this excess is called "excess air"), meaning the excess air coefficient must be greater than 1. Changing the excess air coefficient alters the total flue gas volume of the boiler, thereby changing the heat transfer efficiency of the convective heating surfaces and regulating the steam temperature.

[0042] Flue gas recirculation:

[0043] The flue gas recirculation system mainly consists of a flue gas recirculation fan, a flue gas recirculation duct, and corresponding accessories such as dampers. The recirculated flue gas is taken from the low-temperature flue gas at the economizer or preheater outlet and circulated to the bottom of the boiler furnace by the recirculation fan. This increases the amount of flue gas in the boiler, increases the convective heat transfer and heat absorption of the boiler's low-temperature heating surfaces, and plays a role in regulating the steam temperature.

[0044] Various temperature control methods are coupled: Firstly, the coal-to-water ratio is used to regulate the superheater steam temperature, and the oscillating burner is used to regulate the reheater steam temperature. However, in actual operation, the oscillating burner's actuator is prone to jamming, often fixing at a certain angle, thus limiting its adjustment sensitivity. Therefore, the tail-end double flue damper is used to regulate the reheat steam temperature. The excess air coefficient plays a fine-tuning role in the superheater and reheat steam temperatures; however, a large excess air coefficient negatively impacts boiler efficiency, so it is only used as an auxiliary fine-tuning tool.

[0045] Under low load conditions, when all the above methods have been exhausted, using flue gas recirculation to regulate reheat steam temperature can provide a larger temperature regulation range and higher sensitivity.

[0046] The superheater temperature control method uses a combination of coal-to-water ratio and water spray. The coal-to-water ratio adjustment regulates the steam temperature by altering the ratio of input fuel and working fluid. Water spray involves installing desuperheaters on the superheater pipes, injecting lower-temperature water to regulate the temperature of the high-temperature superheated steam. The reheater temperature control method uses a tail-end temperature control baffle combined with an excess air coefficient, assisted by a swing burner. The tail-end temperature control baffle divides the boiler's tail flue into two sections, housing a low-temperature superheater and a low-temperature reheater respectively. Baffles are installed at the outlets of both flues; adjusting the baffle opening changes the flue gas volume in both flues, thus altering the heat absorption ratio of the superheater and reheater, and regulating the reheat steam temperature. The excess air coefficient adjustment involves measuring and changing the oxygen content in the boiler flue gas, thereby altering the total flue gas volume and regulating the heat absorption of the reheater, ultimately regulating the reheat steam temperature.

[0047] The above description is merely a preferred embodiment of the present invention. These specific embodiments are different implementations based on the overall concept of the present invention, and the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A tower boiler with a low-temperature heating surface and flue gas recirculation inside the furnace, characterized in that, The boiler includes a water-cooled wall (1), a wall-type superheater (2), a wall-type reheater (3), a screen-type superheater (4), a final-stage superheater (5), a final-stage reheater (6), a low-temperature superheater (7), a low-temperature reheater (8), an economizer (9), a flue gas temperature regulating baffle (10), a connecting flue (11), and a flue gas recirculation fan (12). The boiler furnace is entirely composed of water-cooled walls (1). A wall-type superheater (2) is installed at the upper part of the furnace close to the inner wall of the water-cooled wall (1). The wall-type superheater (2) is a wall-type radiant heating surface covering the inner surface of the water-cooled wall (1) and shielding the water-cooled wall (1). A wall-type reheater (3) is installed above the wall-type superheater (2). The wall-type reheater (3) is a wall-type radiant heating surface covering the inner surface of the water-cooled wall (1) and shielding the water-cooled wall (1). The upper part is arranged in sequence from low to high as a screen-type superheater (4), a final stage superheater (5) and a final stage reheater (6); the tail flue at the outlet of the final stage reheater (6) is divided into front and rear tail flues, each of which is equipped with a low temperature superheater (7), a low temperature reheater (8) and an economizer (9) at the outlet. The outlet of the economizer (9) is equipped with a flue gas temperature regulating baffle (10); the bottom of the boiler furnace is connected to the left and right sides of the furnace by a connecting flue (11) to the flue gas recirculation fan (12); each heating surface and the economizer are connected by pipes and headers.

2. The tower boiler with low-temperature heating surfaces and flue gas recirculation arranged inside the furnace as described in claim 1, characterized in that, The positions of the low-temperature superheater (7) and low-temperature reheater (8) in the front and rear flues can be interchanged.

3. The tower boiler with low-temperature heating surfaces and flue gas recirculation arranged inside the furnace as described in claim 1, characterized in that, Tower boilers employ five methods for temperature control: 1) Swing burner: The boiler burner is located in the middle area of ​​the boiler furnace, and the boiler uses a swing burner; 2) Coal-to-water ratio: Controlling the ratio of boiler coal feed rate to boiler water feed rate; 3) Flue gas damper: The opening and closing angle of the flue gas temperature regulating damper (10) on the front and rear flue gas ducts is adjusted to change the amount of flue gas in the two flue gas ducts, thereby changing the heat absorption ratio of the low temperature superheater (7) and the low temperature reheater (8) to achieve the regulation of reheat steam temperature. 4) Excess air volume: Change the excess air coefficient; 5) Flue gas recirculation: including flue gas recirculation fan (12), flue gas temperature regulating baffle (10) and connecting flue (11). The recirculated flue gas is taken from the low-temperature flue gas of the economizer (9). The flue gas is circulated to the bottom of the boiler furnace by the flue gas recirculation fan (12) to increase the amount of flue gas in the boiler and increase the convective heat transfer and heat absorption of the low-temperature heating surface of the boiler.

4. The tower boiler with low-temperature heating surfaces and flue gas recirculation arranged inside the furnace as described in claim 3, characterized in that, Five temperature control methods are coupled to control the temperature. The specific steps are as follows: First, the coal-water ratio is used to adjust the superheater steam temperature, the oscillating burner is used to adjust the reheater steam temperature, and then the tail-end double flue gas temperature control baffle (10) is used to adjust the reheat steam temperature. The excess air coefficient plays a fine-tuning role on the superheater and reheat steam temperatures. Under low load conditions, when all the above methods are exhausted, flue gas recirculation is used to adjust the reheat steam temperature, which can provide a larger temperature control range and higher sensitivity.

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