A 100MW grade tower type coal-fired boiler with double U-shaped combustion structure and molten salt working medium

Abstract

This invention discloses a 100MW-class tower-type coal-fired boiler with a double-U-shaped combustion structure and molten salt as the working fluid, relating to the field of coal-fired boiler technology. It solves the problems of low maximum thermal power and complex systems in existing molten salt coal-fired boilers. The invention includes a hot salt tank, a cold salt tank, a boiler body, and a salt melter. The boiler body is connected to the hot salt tank, the cold salt tank, and the salt melter, which is also connected to the cold salt tank. The combustion chamber inside the boiler has a double-U-shaped structure, with a molten salt wall above it. Two sets of heat exchangers are installed within the molten salt wall. Molten salt flows from the lower end to the upper end of the molten salt wall and enters the two sets of heat exchangers for heat exchange. Two molten salt wall mixers within the molten salt wall ensure a more uniform temperature distribution of the molten salt entering the wall, improving safety. This invention fully heats the molten salt through multiple heat exchangers, reducing the temperature difference between the flue gas and the heat exchanger wall temperature, ensuring wall temperature safety; and utilizes coal-fired flue gas for salt melting, reducing operating costs.

Description

Technical Field

[0001] This invention relates to the field of coal-fired boiler technology, specifically to a tower-type coal-fired boiler with a molten salt working fluid and a 100MW-class double U-shaped combustion structure. Background Technology

[0002] Existing steam-fired coal-fired boilers cannot achieve complete thermoelectric decoupling, and the steam working fluid undergoes a phase change in the coal-fired boiler, resulting in complex boiler structures. Furthermore, existing molten salt boilers have a maximum thermal power of only 12MW, primarily burning gas, oil, or biomass. Molten salt boilers primarily using coal can achieve a maximum thermal power of 5.8MW, mainly using coil structures; large-scale molten salt boilers have not been researched or reported. Currently, the coupling of molten salt with coal-fired units mostly involves steam heating of the molten salt, but this requires steam to heat the molten salt, which has a low temperature (below 450℃). The steam generation system then releases heat, but the steam parameters are low, with a maximum of only 4MPa, resulting in low power generation. This system has a low electrical conversion efficiency (below 50%), is complex, difficult to control, and has high construction costs. Summary of the Invention

[0003] To address the aforementioned problems of low maximum thermal power and complex systems in existing molten salt coal-fired boilers, this invention proposes a 100MW-class tower-type coal-fired boiler using a double U-shaped combustion structure for molten salt as the working fluid. This invention utilizes several heat exchangers to fully heat the molten salt, reducing the temperature difference between the flue gas and the heat exchanger walls and ensuring wall temperature safety. Two molten salt wall mixers ensure a more uniform temperature distribution of the molten salt entering the molten salt wall, improving safety. Furthermore, the use of coal-fired flue gas for salt dissolution reduces operating costs.

[0004] This invention proposes a tower-type coal-fired boiler with a molten salt working fluid and a double U-shaped combustion structure for 100MW class. Specifically, it includes a hot salt tank, a cold salt tank, a boiler body, and a salt melter. The boiler body is connected to the hot salt tank, the cold salt tank, and the salt melter, respectively. The salt melter is also connected to the cold salt tank.

[0005] The boiler body includes a combustion chamber, a molten salt wall, a primary loop first-stage molten salt heat exchanger, a secondary loop second-stage molten salt heat exchanger, a primary loop second-stage molten salt heat exchanger, and a secondary loop first-stage molten salt heat exchanger. The combustion chamber has a double U-shaped structure with a molten salt wall at the top. Inside the molten salt wall, from bottom to top, are arranged the primary loop first-stage molten salt heat exchanger, the secondary loop second-stage molten salt heat exchanger, the primary loop second-stage molten salt heat exchanger, and the secondary loop first-stage molten salt heat exchanger. The cold salt tank is connected to the lower end of the molten salt wall. The upper end of the molten salt wall is sequentially connected to the primary loop first-stage molten salt heat exchanger, the primary loop second-stage molten salt heat exchanger, and the hot salt tank. The upper end of the molten salt wall is also sequentially connected to the secondary loop first-stage molten salt heat exchanger, the secondary loop second-stage molten salt heat exchanger, and the hot salt tank.

[0006] Furthermore, a flue is provided at the upper end of the boiler body, and the flue is connected to the salt ionizer.

[0007] Furthermore, the salt desalting device is equipped with a waste heat flue gas pipe and a salt conveying pipe. One end of the waste heat flue gas pipe is connected to the salt desalting device, and the other end is connected to the combustion chamber. One end of the salt conveying pipe is connected to the salt desalting device, and the other end is connected to the cold salt tank.

[0008] Furthermore, the boiler body is equipped with a primary molten salt wall mixer and a secondary molten salt wall mixer, and the cold salt tank, the primary molten salt wall mixer, and the lower end of the molten salt wall are connected in sequence; the secondary molten salt wall mixer is located on the molten salt wall in the area below the primary molten salt heat exchanger of the primary loop.

[0009] Furthermore, the combustion chamber is equipped with two cold slag hoppers, which are conical in shape.

[0010] Furthermore, the combustion chamber is equipped with several burners.

[0011] The beneficial effects of the 100MW-class tower-type coal-fired boiler with molten salt working fluid and double U-shaped combustion structure described in this invention are as follows:

[0012] (1) The 100MW-class double U-shaped combustion structure tower coal-fired boiler with molten salt working fluid described in this invention fully heats the molten salt through a primary molten salt heat exchanger, a secondary molten salt heat exchanger, a primary secondary molten salt heat exchanger, and a secondary primary molten salt heat exchanger. This arrangement of heat exchangers can reduce the temperature difference between the low-temperature flue gas and the primary molten salt heat exchanger in the secondary loop, and ensure that the temperature difference between the medium- and high-temperature molten salt and the wall temperature is small when the molten salt passes through the secondary molten salt heat exchanger in the secondary loop. At the same time, it can also ensure the safety of the wall temperature of the high-temperature flue gas and the primary molten salt heat exchanger in the primary loop, and reduce the temperature difference when the medium- and high-temperature molten salt passes through the secondary molten salt heat exchanger in the primary loop. Furthermore, the two molten salt wall mixers make the molten salt entering the molten salt wall more uniformly heated and temperature distributed, thus improving safety.

[0013] (2) The 100MW-class double U-shaped combustion structure tower coal-fired boiler with molten salt working fluid described in this invention heats and melts the solid salt in the salt smelter by the flue gas generated by the boiler coal combustion, thereby realizing the waste heat recovery of the flue gas and reducing the operating cost of the device; and the flue gas is led back to the combustion chamber to reduce the flue gas temperature of the U-shaped combustion chamber and ensure that the molten salt does not decompose.

[0014] (3) The 100MW-class double U-shaped combustion structure tower coal-fired boiler with molten salt working fluid described in this invention utilizes the tower coal-fired boiler with molten salt as working fluid. The hot molten salt temperature is high, the heat load of the furnace water-cooled wall is uniformly heated, the heat load distribution of the water-cooled wall is uniform, the molten salt temperature rise is reasonable, and the wall temperature deviation is small. The outlet working fluid is reasonably controlled. Utilizing the tower structure of the coal-fired boiler, the flue gas deviation is small, the molten salt side wall temperature deviation is small, and the start-up, shutdown, and salt removal are convenient. It is not easy for impurities to accumulate and is easy to maintain. Attached Figure Description

[0015] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0016] In the attached diagram:

[0017] Figure 1 This is a schematic diagram of the structure of a 100MW-class tower-type coal-fired boiler with a double U-shaped combustion structure and molten salt working fluid, as described in this invention.

[0018] Figure 2 This is a schematic diagram of the heat exchanger structure of a 100MW-class tower-type coal-fired boiler with a double U-shaped combustion structure and molten salt working fluid, as described in this invention.

[0019] Wherein: 1-Hot salt tank, 2-Cold salt tank, 3-Burner, 4-Salt melter, 5-Waste heat flue gas duct, 6-Salt conveying duct, 7-Combustion chamber, 8-Cold slag hopper, 9-Molten salt wall secondary mixer, 10-Primary loop primary molten salt heat exchanger, 101-Mixer, 102-Primary loop primary molten salt outlet header, 11-Secondary loop secondary molten salt heat exchanger, 111-Secondary loop secondary molten salt inlet header, 112-Secondary loop secondary molten salt outlet header, 12-Primary loop secondary molten salt heat exchanger, 121-Primary loop secondary molten salt inlet header, 122-Primary loop secondary molten salt outlet header, 13-Secondary loop primary molten salt heat exchanger, 131-Secondary loop primary molten salt outlet header, 132-Secondary loop primary molten salt inlet header, 14-Molten salt wall outlet header, 15-Flue, 16-Molten salt wall primary mixer, 17-Molten salt wall, 18-Downstream equipment. Detailed Implementation

[0020] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings:

[0021] Specific implementation method one: See Figures 1-2This embodiment is described in detail. The 100MW-class tower-type coal-fired boiler with a double U-shaped combustion structure and molten salt working fluid described in this embodiment specifically includes a hot salt tank 1, a cold salt tank 2, a boiler body, and a salt melter 4. The boiler body is connected to the hot salt tank 1, the cold salt tank 2, and the salt melter 4, respectively. The salt melter 4 is also connected to the cold salt tank 2. The flue gas generated from coal combustion in the boiler body is passed into the salt melter 4 to heat and melt the solid salt. The molten salt, in its low-temperature liquid state, is then transported to the cold salt tank 2 for storage via a salt conveying pipe 6. The low-temperature molten salt in the cold salt tank 2 is pumped to the boiler body, where it is heated by the flue gas generated from coal combustion. The heated salt, in its high-temperature molten state, is then sent to the hot salt tank 1.

[0022] The boiler body includes a combustion chamber 7, a molten salt wall 17, a primary molten salt heat exchanger 10, a secondary molten salt heat exchanger 11, a primary secondary molten salt heat exchanger 12, and a secondary primary molten salt heat exchanger 13. The combustion chamber 7 has a double U-shaped structure, with the molten salt wall 17 at the upper end. Inside the molten salt wall 17, from bottom to top, are arranged the primary primary molten salt heat exchanger 10, the secondary secondary molten salt heat exchanger 11, the secondary secondary molten salt heat exchanger 12, and the primary primary molten salt heat exchanger 13. The cold salt tank 2 is connected to the lower end of the molten salt wall 17. The upper end of the molten salt wall 17 is connected to the primary primary molten salt heat exchanger 10, the primary secondary molten salt heat exchanger 12, and the hot salt tank 1 in sequence. The upper end of the molten salt wall 17 is also connected to the primary primary molten salt heat exchanger 13, the secondary secondary molten salt heat exchanger 11, and the hot salt tank 1 in sequence. The primary molten salt heat exchanger 10, the primary secondary molten salt heat exchanger 12, the secondary primary molten salt heat exchanger 13, and the secondary secondary molten salt heat exchanger 11 are U-shaped structures, arranged in an oblique horizontal position, with the inlet and outlet positions of the heat exchangers tilted downwards.

[0023] A molten salt wall outlet header 14 is provided at the upper end of the molten salt wall 17. The molten salt wall outlet header 14 is connected to the primary molten salt inlet header 132 of the primary molten salt heat exchanger 10 and the secondary molten salt heat exchanger 13 of the secondary loop through pipelines. The primary molten salt heat exchanger 10 is connected to the primary secondary molten salt inlet header 121 of the primary secondary molten salt heat exchanger 12 through the primary molten salt outlet header 102 and pipelines. The primary secondary molten salt outlet header 122 of the primary secondary molten salt heat exchanger 12 is connected to the hot salt tank 1 through pipelines. The secondary molten salt heat exchanger 13 is connected to the secondary secondary molten salt inlet header 111 of the secondary molten salt heat exchanger 11 through the secondary molten salt outlet header 131 and pipelines. The secondary secondary molten salt outlet header 112 of the secondary molten salt heat exchanger 11 is connected to the hot salt tank 1 through pipelines. A mixer 101 is installed on the primary molten salt heat exchanger 10 of the primary loop to mix and stir the newly entered molten salt so that it is heated evenly.

[0024] The upper end of the boiler body is provided with a flue 15, which is connected to the salter 4 to guide the flue gas into the salter 4.

[0025] The salt dissolving device 4 is equipped with a waste heat flue gas pipe 5 and a salt conveying pipe 6. One end of the waste heat flue gas pipe 5 is connected to the salt dissolving device 4, and the other end is connected to the combustion chamber 7 and the downstream equipment 18 respectively. By reintroducing the flue gas into the combustion chamber 7, the flue gas temperature in the U-shaped combustion chamber 7 is reduced, ensuring that the outlet flue gas temperature is below 1100℃. One end of the salt conveying pipe 6 is connected to the salt dissolving device 4, and the other end is connected to the cold salt tank 2.

[0026] The boiler body is equipped with a primary molten salt wall mixer 16 and a secondary molten salt wall mixer 9. The lower ends of the cold salt tank 2, the primary molten salt wall mixer 16, and the molten salt wall 17 are connected in sequence. The secondary molten salt wall mixer 9 is located on the molten salt wall 17 in the area below the primary molten salt heat exchanger 10 of the primary loop. The primary molten salt wall mixer 16 performs preliminary stirring and mixing on the molten salt before it enters the molten salt wall 17, and the secondary molten salt wall mixer 9 performs a second stirring and mixing on the molten salt inside the molten salt wall 17, making the molten salt entering the molten salt wall more evenly heated and with a more uniform temperature distribution.

[0027] The combustion chamber 7 is equipped with two cold slag hoppers 8, which are conical in shape and have slag discharge ports at the bottom.

[0028] The combustion chamber 7 is made of heat-insulating material, and several burners 3 are installed on the combustion chamber 7.

[0029] Because molten salt is prone to oxidation and pipe blockage when it exceeds its temperature, it significantly impacts boiler safety. Therefore, temperature measuring points must be installed at each outlet of the heating surface to continuously monitor temperature changes. An online wall temperature monitoring system should also be added to constantly monitor the wall temperature and molten salt flow rate changes in each tube section of each heating surface stage. This ensures that the molten salt does not clog and the wall temperature does not exceed 600℃, preventing oxidation, volatilization, and pipe blockage.

[0030] Considering the reliability and safety of production equipment, the mature Solar Salt binary salt (60% NaNO3 + 40% KNO3) is used as the working medium. It has a melting point of 220℃, a decomposition temperature of 617.7℃, and a working temperature of 280℃-560℃, allowing for a wider range of molten salt applications.

[0031] Since the maximum temperature of molten salt does not exceed 560℃, in order to ensure that the molten salt does not decompose at high temperatures, the wall temperature of molten salt wall 17 does not exceed 600℃. In the flue gas inlet area, low-temperature molten salt is used, and the molten salt flow rate is controlled below 3m / s to ensure that the outlet temperature of molten salt wall 17 does not exceed 350℃.

[0032] Multiple sets of inclined U-shaped series heat exchangers are arranged in a horizontal multi-stage manner in the furnace to ensure uniform heat exchange. This arrangement can also accelerate the salt removal speed in emergency conditions. In addition, several inlet and outlet headers are set on one side of the boiler body and are inclined so that salt can be removed in time when the molten salt boiler is shut down.

[0033] The specific working process of the 100MW-class tower-type coal-fired boiler with molten salt working fluid and double U-shaped combustion structure described in this invention is as follows:

[0034] Flue gas flow: The flue gas generated by coal combustion in the burners 3 on both sides passes through the U-shaped combustion chamber 7 and enters the molten salt wall 17. After heat exchange in the primary loop first-stage molten salt heat exchanger 10, the secondary loop second-stage molten salt heat exchanger 11, the primary loop second-stage molten salt heat exchanger 12, and the secondary loop first-stage molten salt heat exchanger 13, it enters the flue duct 15. Through the flue duct 15, it enters the salt scavenger 4 and uses the waste heat of the flue gas at 350℃ to desalinate the salt. The last part of the flue gas enters the downstream equipment, and the other part of the tail waste heat flue gas at 180-200℃ enters the combustion chamber 7 from both sides through pipelines.

[0035] Molten salt process: Molten salt drawn from cold salt tank 2 enters the interior of molten salt wall 17 above combustion chamber 7, enters the secondary annular mixer 9 of molten salt wall through molten salt wall 17, and then enters the molten salt wall outlet header 14 at the top of boiler body through the upper molten salt wall 17. Then it splits into two paths: one part of the molten salt enters the primary molten salt heat exchanger 10 of the primary loop through a pipeline, and the other part of the molten salt enters the primary molten salt heat exchanger 13 of the secondary loop through a pipeline.

[0036] Primary loop molten salt process: A portion of the molten salt enters the primary loop first-stage molten salt heat exchanger 10 through several pipes, passes through the heating surface of the primary loop first-stage molten salt heat exchanger 10, enters the primary loop first-stage molten salt outlet header 102, then enters the primary loop second-stage molten salt inlet header 121 through the primary loop second-stage molten salt heat exchanger 12, is heated by the primary loop second-stage molten salt heat exchanger 12, exchanges heat with the flue gas, enters the primary loop second-stage molten salt outlet header 122, and finally enters the hot salt tank 1 for heat storage.

[0037] Secondary loop molten salt process: Another portion of the molten salt in the molten salt wall outlet header 14 enters the secondary loop primary molten salt inlet header 132, is heated by heat exchange in the secondary loop primary molten salt heat exchanger 13, enters the secondary loop primary molten salt outlet header 131, then enters the secondary loop secondary molten salt inlet header 111, is heated by the secondary loop secondary molten salt heat exchanger 11, exchanges heat with the flue gas, enters the secondary loop secondary molten salt outlet header 112, and finally flows into the hot salt tank 1 for heat storage.

[0038] In summary, the 100MW-class tower-type coal-fired boiler with a double U-shaped combustion structure and molten salt working fluid described in this invention fully heats the molten salt through a primary molten salt heat exchanger 10, a secondary molten salt heat exchanger 11, a secondary molten salt heat exchanger 12, and a primary molten salt heat exchanger 13. This arrangement of heat exchangers reduces the temperature difference between the low-temperature flue gas and the primary molten salt heat exchanger 13, while ensuring a small temperature difference between the medium- and high-temperature molten salt and the wall temperature when passing through the secondary molten salt heat exchanger 11. Simultaneously, it ensures the safety of the wall temperature between the high-temperature flue gas and the primary molten salt heat exchanger 10, and reduces the temperature difference when the medium- and high-temperature molten salt passes through the secondary molten salt heat exchanger 12. Furthermore, the two molten salt wall mixers ensure more uniform heating and temperature distribution of the molten salt entering the molten salt wall, improving efficiency and performance. High safety; the 100MW-class double U-shaped combustion structure tower-type coal-fired boiler with molten salt working fluid described in this invention heats and melts the solid salt in the salter 4 through the flue gas generated by the boiler coal combustion, realizing the waste heat recovery of the flue gas and reducing the operating cost of the device; and the flue gas is led back into the combustion chamber 7 to reduce the flue gas temperature of the U-shaped combustion chamber 7, ensuring that the molten salt does not decompose; the 100MW-class double U-shaped combustion structure tower-type coal-fired boiler with molten salt working fluid described in this invention utilizes a tower-type coal-fired boiler with molten salt as the working fluid, the hot molten salt temperature is high, the heat load of the furnace water-cooled wall is uniformly heated, the heat load distribution of the water-cooled wall is uniform, the molten salt temperature rise is reasonable, and the wall temperature deviation is small, and the outlet working fluid is reasonably controlled; the tower structure of the coal-fired boiler results in small flue gas deviation, small molten salt side wall temperature deviation control, convenient start-up and shutdown of salt removal, less accumulation of impurities, and easy maintenance.

[0039] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the invention. They can also be reasonable combinations of the features described in the above embodiments. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A tower-type coal-fired boiler with a molten salt working fluid and a 100MW-class double U-shaped combustion structure, characterized in that: It includes a hot salt tank (1), a cold salt tank (2), a boiler body and a salt melter (4). The boiler body is connected to the hot salt tank (1), the cold salt tank (2) and the salt melter (4) respectively. The salt melter (4) is also connected to the cold salt tank (2). The boiler body includes a combustion chamber (7), a molten salt wall (17), a primary molten salt heat exchanger (10), a secondary molten salt heat exchanger (11), a primary secondary molten salt heat exchanger (12), and a secondary primary molten salt heat exchanger (13). The combustion chamber (7) has a double U-shaped structure with a molten salt wall (17) at the top. Inside the molten salt wall (17), from bottom to top, are arranged the primary primary molten salt heat exchanger (10) and the secondary secondary molten salt heat exchanger (11). The primary loop secondary molten salt heat exchanger (12) and the secondary loop primary molten salt heat exchanger (13) are connected; the lower end of the cold salt tank (2) and the molten salt wall (17) are connected; the upper end of the molten salt wall (17) is connected in sequence to the primary loop primary molten salt heat exchanger (10), the primary loop secondary molten salt heat exchanger (12) and the hot salt tank (1); the upper end of the molten salt wall (17) is also connected in sequence to the secondary loop primary molten salt heat exchanger (13), the secondary loop secondary molten salt heat exchanger (11) and the hot salt tank (1); The upper end of the boiler body is provided with a flue (15), which is connected to the salt ionizer (4).

2. The tower-type coal-fired boiler with molten salt working fluid and a 100MW-class double U-shaped combustion structure according to claim 1, characterized in that: The salt dissolving device (4) is equipped with a waste heat flue gas pipe (5) and a salt conveying pipe (6). One end of the waste heat flue gas pipe (5) is connected to the salt dissolving device (4), and the other end is connected to the combustion chamber (7). One end of the salt conveying pipe (6) is connected to the salt dissolving device (4), and the other end is connected to the cold salt tank (2).

3. The tower-type coal-fired boiler with molten salt working fluid and a 100MW-class double U-shaped combustion structure according to claim 1, characterized in that: The boiler body is provided with a primary molten salt wall mixer (16) and a secondary molten salt wall mixer (9). The lower ends of the cold salt tank (2), the primary molten salt wall mixer (16) and the molten salt wall (17) are connected in sequence. The secondary molten salt wall mixer (9) is located on the molten salt wall (17) in the area below the primary molten salt heat exchanger (10) of the primary circuit.

4. The tower-type coal-fired boiler with molten salt working fluid and a 100MW-class double U-shaped combustion structure according to claim 1, characterized in that: The combustion chamber (7) is provided with two cold slag hoppers (8), which are conical in shape.

5. The tower-type coal-fired boiler with molten salt working fluid and a 100MW-class double U-shaped combustion structure according to claim 1, characterized in that: The combustion chamber (7) is equipped with several burners (3).

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