Pulverized coal boiler bottom zero-leakage dry slag system and coal-fired power generation unit

Abstract

The present invention discloses a dry slag system with zero air leakage at the bottom of a pulverized coal boiler and a coal-fired power generation unit. The dry slag system includes a dry slag discharger, and the dry slag discharger is provided with a circulating air extraction port and a circulating air return port; the circulating air extraction port and the circulating air return port are connected through a circulating air duct, and a circulating cooling fan and a hot air-water heat exchanger are arranged on the circulating air duct. The water path of the hot air-water heat exchanger is communicated with a water pumping source; a first heat exchange space for heat exchange between slag and air is formed inside the dry slag discharger, and a second heat exchange space for heat exchange between hot air and water is formed inside the hot air-water heat exchanger. The first heat exchange space and the second heat exchange space jointly form a circulating heat exchange loop. This system can achieve zero air leakage at the bottom of the pulverized coal boiler, improve the boiler efficiency and combustion stability, and realize the efficient recovery of the waste heat of the slag on the premise of ensuring the dry slag cooling effect.

Description

Technical Field

[0001] The present invention relates to the technical field of boiler slag discharge, and in particular to a dry slag system for achieving zero air leakage at the bottom of a pulverized coal boiler. The present invention also relates to a coal-fired power generation unit provided with the dry slag system. Background Art

[0002] The slag discharge systems of pulverized coal boilers are divided into two types: wet slag discharge and dry slag discharge. Among them: wet slag discharge is a method of directly contacting cooling water with the slag to reduce the slag temperature; dry slag discharge is to suck cooling air into the boiler furnace through the negative pressure of the boiler furnace and contact it with the boiler slag for cooling, so as to achieve the effect of reducing the slag temperature.

[0003] Since the dry slag discharge system is simple and the dry slag contains active CaO with relatively high comprehensive utilization value, the vast majority of pulverized coal boilers in existing coal-fired power generation units adopt the dry slag discharge system. However, the cooling air of the dry slag conveyor will cause air leakage at the bottom of the boiler, which is the main factor of air leakage in the boiler furnace, seriously affecting the combustion characteristics of the boiler (especially the stable combustion characteristics at low loads), and at the same time reducing the boiler efficiency, becoming an important pain point and difficult problem restricting the boiler performance.

[0004] Pulverized coal boilers (especially large-capacity pulverized coal boilers) are characterized by high slag temperature and large slag discharge. There is no effective technical means to solve the problem of zero air leakage at the bottom of the dry slag discharge system for pulverized coal boilers. If the problem of air leakage at the bottom can be fundamentally solved, it is of great significance to the development of flexible and efficient coal-fired power generation units. Summary of the Invention

[0005] The purpose of the present invention is to provide a dry slag system with zero air leakage at the bottom of a pulverized coal boiler to solve the above technical problems.

[0006] Another purpose of the present invention is to provide a coal-fired power generation unit provided with the dry slag system with zero air leakage at the bottom of the pulverized coal boiler.

[0007] To achieve the above object, the present invention provides a dry slag system with zero leakage at the bottom of a pulverized coal boiler, including a dry slag extractor disposed in the boiler. The slag dropping port of the dry slag extractor is located below the boiler slag discharge port at the bottom of the boiler, and the slag discharge port of the dry slag extractor is located above the slag bin. A circulating air extraction port is provided at the top of the dry slag extractor near its slag dropping port, and a circulating air return port is provided at the top of its tail end. The circulating air extraction port and the circulating air return port are connected by a circulating air pipe, and a circulating cooling fan and a hot air - water heat exchanger are provided on the circulating air pipe. The hot air flow path of the hot air - water heat exchanger is connected to the circulating air pipe, and the water path of the hot air - water heat exchanger is connected to a water pumping source. A first heat exchange space for heat exchange between the furnace slag and air is formed inside the dry slag extractor, and the first heat exchange space outputs hot air heated by the furnace slag from the circulating air extraction port. A second heat exchange space for heat exchange between the hot air and water is formed inside the hot air - water heat exchanger, and the second heat exchange space inputs cold air from the circulating air return port to the first heat exchange space. The first heat exchange space and the second heat exchange space jointly form a circulating heat exchange loop.

[0008] Optionally, the circulating cooling fan is located upstream of the hot air - water heat exchanger, and a dust collector is provided upstream of the circulating cooling fan.

[0009] Optionally, the water pumping source is the main engine condensate system, and the inlet water pipe and the outlet water pipe of the hot air - water heat exchanger are both connected to the main engine condensate system.

[0010] Optionally, a condensate booster pump is provided on the inlet water pipe of the hot air - water heat exchanger.

[0011] Optionally, a heat exchange chamber for the hot air to flow through is provided inside the hot air - water heat exchanger, and heat exchange tubes are provided inside the heat exchange chamber. The two ends of the heat exchange tubes are respectively connected to the inlet water pipe and the outlet water pipe.

[0012] Optionally, the heat exchange tubes are in a continuous S - shape.

[0013] Optionally, a first air damper is provided at the circulating air extraction port.

[0014] Optionally, a second air damper is provided at the circulating air return port.

[0015] Optionally, a third air damper is provided on the cooling air pipeline of the dry slag extractor body.

[0016] To achieve the above - mentioned another object, the present invention provides a coal - fired power generation unit, including a boiler, a steam turbine, and a generator. The boiler is provided with the dry slag system with zero leakage at the bottom of the pulverized coal boiler according to any one of the above.

[0017] The dry slag system with zero air leakage at the bottom of the pulverized coal boiler provided by the present invention forms a circulating heat exchange loop by combining the first heat exchange space and the second heat exchange space. During operation, air can continuously circulate between the inside of the dry slag extractor and the circulating air duct. During the circulating flow, the air exchanges heat with the hot furnace slag inside the dry slag extractor, cooling the hot furnace slag, and at the same time heating the cold air into hot air. When the heated air passes through the hot air - water heat exchanger along the circulating air duct, it exchanges heat with the water flowing through the hot air - water heat exchanger. The heated water returns to the pumping water source, and at the same time the hot air is cooled into cold air and returns to the dry slag extractor again for the next round of circulation. Since the air in the dry slag extractor always circulates in a closed state and does not communicate with the outside, and the heat of the furnace slag is transferred to the pumping water source through two different heat exchanges, zero air leakage at the bottom of the pulverized coal boiler can be achieved, improving the boiler efficiency and combustion stability, and realizing the efficient recovery of the waste heat of the furnace slag on the premise of ensuring the dry slag cooling effect.

[0018] The coal - fired power generation unit provided by the present invention is equipped with the above - mentioned dry slag system with zero air leakage at the bottom of the pulverized coal boiler. Since the dry slag system with zero air leakage at the bottom of the pulverized coal boiler has the above - mentioned technical effects, the coal - fired power generation unit equipped with this dry slag system with zero air leakage at the bottom of the pulverized coal boiler should also have corresponding technical effects. Brief Description of the Drawings

[0019] Figure 1 It is a schematic structural diagram of the dry slag system with zero air leakage at the bottom of the pulverized coal boiler provided by the embodiment of the present invention.

[0020] In the figure:

[0021] 1. Boiler slag discharge port; 2. Dry slag extractor; 3. Third air damper; 4. Slag bin; 5. Dust collector; 6. Circulating cooling fan; 7. Hot air - water heat exchanger; 8. First air damper; 9. Second air damper; 10. Condensate booster pump; 11. Boiler Detailed Embodiments

[0022] In order to enable those skilled in the art of the present technology to better understand the solution of the present invention, the present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0023] In this article, terms such as "upper, lower, inner, outer" are established based on the positional relationship shown in the drawings. Depending on the different drawings, the corresponding positional relationship may also change accordingly. Therefore, it cannot be understood as an absolute limitation of the protection scope; moreover, relational terms such as "first" and "second" are only used to distinguish one component with the same name from another, and do not necessarily require or imply any such actual relationship or order between these components.

[0024] Please refer to Figure 1 ,Figure 1 This is a schematic structural diagram of the zero-leakage air-dried slag system at the bottom of a pulverized coal boiler provided by an embodiment of the present invention.

[0025] As shown in the figure, in a specific embodiment, the zero-leakage air-dried slag system at the bottom of the pulverized coal boiler provided by the present invention mainly consists of a dry slag extractor 2, a slag bin 4, a dust collector 5, a circulating cooling fan 6, a hot air-water heat exchanger 7, and other components.

[0026] The front section of the dry slag extractor 2 is in a horizontal state, and its slag dropping port is located below the boiler slag discharge port 1 at the bottom of the boiler 11. The rear section of the dry slag extractor 2 is arranged obliquely upward at a certain angle, such as 30°, 35°, etc. Its slag discharge port is located above the slag bin 4. The dry slag extractor 2 is provided with a circulating air extraction port at the top near its slag dropping port, and the dry slag extractor 2 is provided with a circulating air return port at the top of its tail end.

[0027] To facilitate the switching of the circulating air, the circulating air extraction port is provided with a first damper 8, that is, the circulating cooling air inlet shut-off door, the circulating air return port is provided with a second damper 9, that is, the circulating cooling air outlet shut-off door, and the cooling air pipeline of the dry slag extractor 2 body is provided with a third damper 3, that is, the dry slag machine cooling air shut-off door.

[0028] The circulating air extraction port and the circulating air return port are connected by a circulating air pipe. The circulating air pipe is provided with a circulating cooling fan 6 and a hot air-water heat exchanger 7. The hot air flow path of the hot air-water heat exchanger 7 is connected to the circulating air pipe, and the water path of the hot air-water heat exchanger 7 is connected to the water pumping source.

[0029] In this embodiment, the water pumping source is the main engine condensate water source. In other embodiments, it can also be other water sources such as the heat network circulating water of a heat supply unit.

[0030] In this embodiment, the water pumping source is the main engine condensate water system. The inlet water pipe and the outlet water pipe of the hot air-water heat exchanger 7 are both connected to the main engine condensate water system, and the inlet water pipe of the hot air-water heat exchanger 7 is provided with a condensate booster pump 10.

[0031] The circulating cooling fan 6 is located upstream of the hot air-water heat exchanger 7. Considering that the extracted hot air will be mixed with dust, a dust collector 5 is provided upstream of the circulating cooling fan 6.

[0032] The hot air-water heat exchanger 7 is an indirect heat exchanger with air and water as the medium. Its internal is provided with a heat exchange cavity for the flowing of heating air. The inside of the heat exchange cavity is provided with heat exchange tubes. The heat exchange tubes are in a continuous S shape, and both ends of the heat exchange tubes are respectively connected to the inlet water pipe and the outlet water pipe.

[0033] Inside the dry slag extractor 2, a first heat exchange space for heat exchange between slag and air is formed. The first heat exchange space outputs hot air heated by the slag from the circulating air extraction opening. Inside the hot air - water heat exchanger 7, a second heat exchange space for heat exchange between hot air and water is formed. The second heat exchange space inputs cold air from the circulating air return opening to the first heat exchange space. The first heat exchange space and the second heat exchange space jointly form a circulating heat exchange loop.

[0034] During operation, the cooling process of the slag is as follows: Boiler slag enters the dry slag extractor 2 from the boiler slag discharge opening 1. The hot air after cooling the dry slag is sent into the circulation by using the circulating cooling fan 6. The slag undergoes sufficient cooling and heat exchange during the process of passing through the conveyor belt of the dry slag extractor 2 and then enters the slag bunker 4.

[0035] The process of waste heat recovery is as follows: A part of the water volume is extracted from the main engine condensate system and enters the hot air - water heat exchanger 7 through the condensate booster pump 10. The heat exchange balance of the hot air - water heat exchanger 7 is maintained by controlling the condensate volume.

[0036] In this system, a first air damper 8 and a second air damper 9 are provided on the circulating air duct, enabling flexible switching with the original dry slag cooling system. When the circulating air system is turned on, the third air damper 3 of the dry slag extractor 2 is closed to ensure zero air leakage at the bottom of the boiler 11 during the operation of the dry slag system.

[0037] Under normal operating conditions, the third air damper 3 is closed, and the dry slag extractor 2 cools and enters the closed - loop mode. The circulating cooling air system is turned on. The cooling air first directly contacts and exchanges heat with the slag, that is, "slag - air" heat exchange; the hot air after heat exchange first passes through the dust collector 5, then enters the hot air - water heat exchanger 7 through the circulating cooling fan 6, and indirectly exchanges heat with the condensate, that is, "air - water" heat exchange; the hot air is cooled by the condensate and becomes cold air, then enters the dry slag extractor 2 again to continue cooling the slag, forming a cycle.

[0038] When the circulating air system needs to be repaired and maintained, the first air damper 8 and the second air damper 9 of the circulating air system are closed, and the third air damper 3 of the dry slag extractor 2 is opened. The cooling of the dry slag extractor 2 switches from the closed - loop mode to the open - loop mode.

[0039] The above - mentioned embodiments are only the preferred solutions of the present invention, and are not specifically limited thereto. On this basis, targeted adjustments can be made according to actual needs to obtain different implementation manners. For example, in order to improve the heat exchange efficiency, two groups of hot air - water heat exchangers 7 are provided and connected to different water sources, etc. Since there are many possible implementation manners, they will not be listed one by one here.

[0040] In the zero-leakage air-dried slag system at the bottom of the pulverized coal boiler, the air in the dry slag extractor 2 is always circulated in a closed state without being connected to the outside, and the heat of the slag is transferred to the pumping water source through two different heat exchanges. Compared with the traditional dry slag system with a bottom air leakage rate of usually 1.5% - 2%, the bottom air leakage rate of this system can reach 0%, thus significantly improving the boiler efficiency and combustion stability, and realizing the efficient recovery of the slag waste heat on the premise of ensuring the dry slag cooling effect.

[0041] Moreover, the present invention transfers the heat of the slag to the air (i.e., "slag-air" heat exchange), and then uses the indirect heat exchange method of "air-water" to heat the main engine condensate (i.e., "air-water" heat exchange). While improving the waste heat utilization efficiency, it has the characteristics of high reliability, low investment, and flexible layout.

[0042] In addition to the above zero-leakage air-dried slag system at the bottom of the pulverized coal boiler, the present invention provides a coal-fired power generation unit, which is provided with a boiler 11, a steam turbine, and a generator, and the boiler 11 is provided with the zero-leakage air-dried slag system at the bottom of the pulverized coal boiler described above. For the remaining structures of the coal-fired power generation unit, please refer to the prior art and will not be elaborated herein.

[0043] The above has introduced in detail the zero-leakage air-dried slag system at the bottom of the pulverized coal boiler and the coal-fired power generation unit provided by the present invention. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the core idea of the present invention. It should be pointed out that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and modifications can still be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A pulverized coal boiler bottom zero-leakage dry slag system, comprising a dry slag discharger (2) arranged on a boiler (11), wherein a slag discharge port of the dry slag discharger (2) is located below a boiler slag discharge port (1) at the bottom of the boiler (11), and a slag discharge port of the dry slag discharger (2) is located above a slag bin (4), characterized in that: The dry slag discharger (2) is provided with a circulating air exhaust port at the top near the slag discharge port thereof, and the dry slag discharger (2) is provided with a circulating air return port at the top of its tail end; the circulating air exhaust port is connected to the circulating air return port via a circulating air duct, and the circulating air duct is provided with a circulating cooling fan (6) and a hot air-water heat exchanger (7); the hot air flow path of the hot air-water heat exchanger (7) is connected to the circulating air duct, and the water path of the hot air-water heat exchanger (7) is connected to a pumping water source; a first heat exchange space is formed inside the dry slag discharger (2) for heat exchange between slag and air, and the first heat exchange space outputs hot air heated by the slag from the circulating air exhaust port; a second heat exchange space is formed inside the hot air-water heat exchanger (7) for heat exchange between hot air and water, and the second The heat exchange space inputs cold air from the circulating air return air port to the first heat exchange space; the first heat exchange space and the second heat exchange space can be combined to form a closed circulating heat exchange loop to transfer the heat of the slag to the pumping water source through two heat exchanges; the circulating air exhaust port is provided with a first damper (8), the circulating air return air port is provided with a second damper (9), and the cooling air duct of the dry slag discharger body is provided with a third damper (3); under normal operating conditions, the third damper (3) is closed, the dry slag discharger (2) is cooled to enter a closed circulation mode, and the circulating cooling air system is turned on; when the circulating air system needs to be overhauled and maintained, the first damper (8) and the second damper (9) of the circulating air system are closed, the third damper (3) of the dry slag discharger (2) is turned on, and the cooling of the dry slag discharger (2) is switched from a closed mode to an open mode.

2. The zero-leakage air drying slag system for pulverized coal boiler bottom according to claim 1 is characterized in that: The circulating cooling fan (6) is located upstream of the hot air-water heat exchanger (7), and a dust collector (5) is provided upstream of the circulating cooling fan (6).

3. The zero-leakage air drying slag system for pulverized coal boiler bottom according to claim 1 is characterized in that: The pumping water source is the main engine condensate water system, and the water inlet pipe and the water outlet pipe of the hot air-water heat exchanger (7) are both connected to the main engine condensate water system.

4. The zero-leakage air drying slag system for pulverized coal boiler bottom according to claim 3 is characterized in that: The water inlet pipeline of the hot air-water heat exchanger (7) is provided with a condensate booster pump (10).

5. The zero-leakage air drying slag system for pulverized coal boiler bottom according to claim 4 is characterized in that: The hot air-water heat exchanger (7) is provided with a heat exchange cavity for hot air to flow through, and a heat exchange tube is provided inside the heat exchange cavity, and both ends of the heat exchange tube are respectively connected to a water inlet pipeline and a water outlet pipeline.

6. The zero-leakage air drying slag system for pulverized coal boiler bottom according to claim 5 is characterized in that: The heat exchange tube is in a continuous S shape.

7. A coal-fired power generation unit, comprising a boiler (11), a steam turbine and a generator, characterized in that: The boiler (11) is provided with a pulverized coal boiler bottom zero-leakage air drying slag system according to any one of claims 1 to 6.

Images