A flour milling system and method

Abstract

This invention relates to the field of boiler technology and discloses a pulverizing system and method. The system includes N pulverizing subsystems. Each pulverizing subsystem includes a hot air damper, a waste gas damper, a pulverizing exhaust fan, a waste gas air box, a waste gas recirculation damper, an air duct, and a pulverizing air supply damper. In each pulverizing subsystem, the hot air damper, waste gas exhaust fan, waste gas air box, and waste gas recirculation damper are sequentially connected. The nodes between the hot air damper and the waste gas exhaust fan are connected to the waste gas damper. The air duct in each pulverizing subsystem is connected to the pulverizing air supply damper in one of the other pulverizing subsystems (excluding itself). Wherein, N is a positive integer and N≥2. This invention solves the problems of low stable combustion capability and low combustion efficiency in existing pulverized coal boilers.

Description

Technical Field

[0001] This invention relates to the field of boiler technology, specifically a pulverizing system and method. Background Technology

[0002] There is a rigid demand for energy conservation, emission reduction, and flexible peak-shaving retrofitting of coal-fired power units. The temperature of the primary air-coal mixture has a significant impact on the ignition and burnout of pulverized coal. The higher the temperature of the primary air-coal mixture, the more favorable it is for ignition and burnout, and the more stable the combustion in the boiler furnace. However, due to the safety requirements of the coal mill equipment itself and the explosion-proof requirements of the coal mill, the temperature of the primary air-coal mixture at the outlet of the pulverizing system is limited. Specifically, the upper limit for steel ball mills grinding lean coal is generally 130℃, while the temperature of the primary air-coal mixture in intermediate storage pulverizing systems using exhaust gas is generally 50-60℃. At the same time, the primary air rate of the burner is constrained by the exhaust gas volume of the coal mill, resulting in a lower pulverized coal concentration. Therefore, this greatly restricts the stable combustion capability and combustion efficiency of pulverized coal boilers.

[0003] Currently, coal-fired boiler units use a wide variety of coal types and need to adapt to the high-intensity, flexible peak-shaving requirements of the power grid.

[0004] Therefore, it is necessary to propose a method to effectively increase the pulverized coal feeding temperature and pulverized coal concentration of the intermediate storage type waste gas pulverizing system at low loads, so as to improve the stable combustion capability and combustion efficiency of pulverized coal boilers. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention provides a pulverizing system and method, which solves the problems of low stable combustion capacity and low combustion efficiency of pulverized coal boilers in the prior art.

[0006] The technical solution adopted by the present invention to solve the above problems is:

[0007] A powder-making system includes N powder-making subsystems. Each powder-making subsystem includes a hot air damper, a waste air damper, a powder discharge fan, a waste air box, a waste air recirculation damper, an air duct, and a powder delivery damper. In each powder-making subsystem, the hot air damper, the powder discharge fan, the waste air box, and the waste air recirculation damper are connected sequentially. The nodes between the hot air damper and the powder discharge fan are connected to the waste air damper. The air duct in each powder-making subsystem is connected to the powder delivery damper in another powder-making subsystem (excluding itself). Wherein, N is a positive integer and N≥2.

[0008] As a preferred technical solution, each pulverizing subsystem also includes an air-powder mixer, a pulverizer, a burner primary air nozzle, a pulverizer delivery pipe, a pulverizer delivery damper, an air-powder mixer, a pulverizer delivery pipe, and a burner primary air nozzle connected in sequence, with the pulverizer connected to the air-powder mixer.

[0009] As a preferred technical solution, each pulverizing subsystem also includes a coal mill and a coal powder separator. The coal feeder, coal powder separator, coal mill, and exhaust gas recirculation damper are connected in sequence, and the coal powder separator is connected to the exhaust gas damper.

[0010] As a preferred technical solution, each pulverizing subsystem also includes a pulverizing silo, a coal mill, and a pulverized coal separator. The pulverizer, pulverizing silo, pulverized coal separator, coal mill, and exhaust gas recirculation damper are connected in sequence, and the pulverized coal separator is connected to the exhaust gas damper.

[0011] As a preferred technical solution, it also includes a boiler furnace connected to the primary air nozzle of the burner of each pulverizing subsystem.

[0012] A powder-making system according to any one of the claims, characterized in that N = 2.

[0013] A method for making flour, using the aforementioned flour making system, includes two flour making subsystems, namely flour making subsystem A and flour making subsystem B.

[0014] As a preferred technical solution, when the boiler load exceeds the set threshold, and both the pulverizing subsystem A and its corresponding burner primary air nozzles, and the pulverizing subsystem B and its corresponding burner primary air nozzles are operating normally, the hot air damper is closed and the exhaust gas damper is open. The exhaust gas enters the exhaust gas box after passing through the exhaust fan. A small portion of the exhaust gas is regulated by the exhaust gas recirculation damper and then recirculated back to the coal mill. The remaining majority of the exhaust gas is mixed with pulverized coal through the air duct to achieve pulverized coal delivery. When the pulverized coal level in the pulverized coal bin exceeds the set threshold, and both the pulverizing subsystem A and the homogenizing subsystem B are shut down, the hot air damper is opened and the exhaust gas damper is closed.

[0015] As a preferred technical solution, when the boiler load is lower than the set threshold, the pulverizing subsystem B and its corresponding burner primary air nozzles are shut down, and only the pulverizing subsystem A and its corresponding burner primary air nozzles are operated. The hot air damper of the pulverizing subsystem B is opened and the exhaust gas damper is closed. The hot air from the pulverizing subsystem B enters the exhaust gas box after passing through the exhaust fan. At this time, the exhaust gas recirculation damper is closed, and the hot air passes through the air duct and the pulverizing air damper of the pulverizing subsystem A, and then goes to the air-pulverizing mixer to mix with the pulverized coal, thereby realizing hot air pulverizing.

[0016] As a preferred technical solution, when the coal mill of pulverizing subsystem A is running, the hot air damper of pulverizing subsystem A is closed and the exhaust gas damper is opened. The exhaust gas of pulverizing subsystem A enters the exhaust gas box after passing through the exhaust fan. A small portion of the exhaust gas is regulated by the exhaust gas recirculation damper and then recirculated back to the coal mill. The remaining majority of the exhaust gas is sent to the air-coal mixer of pulverizing subsystem B through the air duct, and then sent to the burner through the coal feeding pipeline to burn off the exhaust gas. When pulverizing subsystem A stops operating because the coal level in the coal bin is higher than the set threshold, but the primary air nozzle of the burner corresponding to pulverizing subsystem A is still running, the hot air damper and exhaust gas damper of pulverizing subsystem A are both closed, the exhaust fan is stopped, and no exhaust gas passes through the primary air nozzle of the burner corresponding to pulverizing subsystem B.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] (1) This invention can increase the temperature of the pulverized coal mixture in the pulverized coal feeding pipeline to 140-160°C or even higher when the boiler is under low load, and increase the pulverized coal concentration by reducing the amount of hot air used for pulverized coal feeding, effectively improving the ignition and self-stabilizing combustion capabilities of the burner; it can enable the pulverized coal mixture to ignite and burn stably in advance, and enable the pulverized coal to be heated quickly to ignite and release heat, providing favorable combustion conditions for subsequent pulverized coal, enhancing the coal adaptability of the coal-fired boiler unit, improving the boiler combustion efficiency, and significantly improving the unit's flexibility and peak-shaving capabilities; when the boiler is under high load, the pulverizing system still uses exhaust gas or warm air pulverized coal feeding to meet the normal operation of the boiler; at the same time, it does not affect high load operation, and the modification does not require additional equipment and operating costs. The switching of pulverized coal feeding methods for high and low loads can be achieved simply by arranging the exhaust gas pipelines of the two pulverizers in a cross manner and combining them with the corresponding control logic; the investment cost is relatively small;

[0019] (2) The flexible powder feeding method provided by the present invention is applicable to two or more intermediate storage type waste gas powder making systems. It does not require additional equipment and operating costs. The switching of high and low load powder feeding modes can be achieved simply by arranging the waste gas pipelines of two powder dischargers in a cross manner and combining them with corresponding control logic. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the powder-making subsystem A;

[0021] Figure 2 This is a schematic diagram of the structure of the powder-making subsystem B;

[0022] Figure 3 This is one of the structural schematic diagrams of a pulverizing system according to the present invention (not connected to the boiler furnace);

[0023] Figure 4 This is a second schematic diagram of the structure of a pulverizing system according to the present invention (connected to the boiler furnace).

[0024] The labels and their corresponding names in the attached diagram are as follows: 1. Hot air damper, 2. Exhaust gas damper, 3. Pulverizing fan, 4. Exhaust gas box, 5. Exhaust gas recirculation damper, 6. Air duct, 7. Pulverizing air damper, 8. Air-coal mixer, 9. Pulverizer, 10. Pulverizing silo, 11. Burner primary air nozzle, 12. Pulverizing pipeline, 13. Coal mill, 14. Pulverizing subsystem, A15. Pulverizing subsystem, B16. Pulverized coal separator, 17. Boiler furnace. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0026] Example 1

[0027] like Figures 1 to 4 As shown, the intermediate storage type waste gas pulverizing system of the present invention normally uses waste gas to deliver pulverized coal, and the delivery temperature is generally 50-60°C. If the temperature of the air-coal mixture and the concentration of pulverized coal can be increased, the ignition of the pulverized coal entering the furnace can be advanced, the pulverized coal can be quickly heated to the ignition temperature and release heat, providing favorable combustion conditions for subsequent pulverized coal, enhancing the coal type adaptability of the coal-fired boiler unit, improving the boiler combustion efficiency, and improving the unit's flexibility and peak-shaving capability.

[0028] This invention provides a reliable and effective flexible pulverized coal feeding method applicable to at least two intermediate storage-type waste gas pulverizing systems. It can improve the pulverized coal feeding temperature and primary air pulverized coal concentration when the boiler is operating at low load, while not affecting the normal operation of the boiler at high load.

[0029] The present invention arranges the outlet air ducts 6 of the exhaust air box 4 of the two pulverizing systems in a cross manner to increase the temperature of the air-powder mixture and the coal powder concentration.

[0030] This invention relates to a waste gas feeding system for intermediate storage silos in ball mills.

[0031] Both pulverizing subsystems A14 and B15 include: hot air damper 1, exhaust gas damper 2, pulverized coal exhaust fan 3, exhaust gas air box 4, exhaust gas recirculation damper 5, air duct 6, pulverized coal conveying damper 7, air-coal mixer 8, pulverizer 9, pulverized coal silo 10, burner primary air nozzle 11, pulverized coal conveying pipeline 12, coal mill 13, and pulverized coal separator 16. Figure 1 , Figure 2 As shown.

[0032] like Figure 3 As shown, the present invention optimizes the powder delivery method of two intermediate storage-type powder making systems by cross-arranging the exhaust air box 4 and outlet air duct 6 of the powder discharge fan 3 corresponding to the powder making subsystem A14 and the powder making subsystem B15.

[0033] The process is as follows:

[0034] 1. The hot air damper 1 is used to control the hot air from the dust removal fan 3;

[0035] 2. The exhaust gas damper 2 is used to control the exhaust gas of the powder discharge fan 3;

[0036] 3. The hot air damper 1 and the exhaust air damper 2 can be used to switch the powder supply air source: hot air or exhaust air;

[0037] 4. The exhaust air box 4 and outlet air duct 6 of the exhaust air fan 3 of the powder making subsystem A14 and the powder making subsystem B15 are arranged in a cross manner to realize the flexible use of powder delivery method;

[0038] 5. Under high load, pulverizing subsystems A14 and B15 and their corresponding burner primary air nozzles 11 are operating normally. At this time, the hot air damper 1 is closed and the exhaust gas damper 2 is open. The exhaust gas enters the exhaust gas box 4 after passing through the exhaust fan 3. A small amount of exhaust gas is regulated by the exhaust gas recirculation damper 5 and then circulated back to the coal mill 13. Most of the remaining exhaust gas is mixed with pulverized coal through the air duct 6 to achieve pulverized coal delivery. When the pulverized coal level in the pulverized coal bin is high and pulverizing subsystems A14 and B15 are shut down, the hot air damper 1 is open and the exhaust gas damper 2 is closed. The system adopts the conventional warm air delivery method to achieve pulverized coal delivery.

[0039] 6. At lower loads, when the pulverizing subsystem B15 and its corresponding burner primary air nozzle 11 are shut down, and only the pulverizing subsystem A14 and its corresponding burner primary air nozzle 11 are operating:

[0040] With the hot air damper 1 of the pulverizing subsystem B15 open and the exhaust gas damper 2 closed, the hot air from the pulverizing subsystem B15 enters the exhaust gas box 4 after passing through the exhaust fan 3. At this time, the exhaust gas recirculation damper 5 is closed. The hot air passes through the air duct 6 and the pulverizing air supply damper 7 of the pulverizing subsystem A14, and then goes to the air-coal mixer 8 to mix with the pulverized coal, thus realizing hot air pulverizing. This can increase the temperature of the combustion air-coal mixture in the corresponding pulverizing pipeline 12 to 140-160℃ or even higher. In addition, the amount of hot air for pulverizing can be reduced accordingly according to the low-load stable combustion requirements to increase the pulverized coal concentration in the pulverized coal airflow, thereby further improving the ignition ability and combustion stability of the pulverized coal airflow.

[0041] When the coal mill in pulverizing subsystem A14 is running, the hot air damper 1 of pulverizing subsystem A14 is closed and the exhaust gas damper 2 is opened. The exhaust gas of pulverizing subsystem A14 enters the exhaust gas box 4 after passing through the exhaust fan 3. A small amount of exhaust gas is regulated by the exhaust gas recirculation damper 5 and then circulated back to the coal mill 13. The majority of the remaining exhaust gas is sent to the air-coal mixer 8 of pulverizing subsystem B15 through the air duct 6, and then sent to the burner 11 through the coal delivery pipe 12 to burn off the exhaust gas. When pulverizing subsystem A14 is shut down due to high coal level in the coal silo, but its corresponding burner primary air nozzle 11 is still running, the hot air damper 1 and exhaust gas damper 2 of pulverizing subsystem A14 are both closed, the exhaust fan 3 is stopped, and no exhaust gas passes through the primary air nozzle 11 of the burner corresponding to pulverizing subsystem B15. It is treated as a burner primary air nozzle that is normally shut down.

[0042] 7. At lower loads, when the pulverizing subsystem A14 and its corresponding burner primary air nozzle 11 are shut down, and only the pulverizing subsystem B15 and its corresponding burner primary air nozzle 11 are running, the operating mode described in the previous section can be referred to.

[0043] 8. Exhaust air or hot air enters the air-powder mixer 8 through the powder supply damper 7; the powder supply damper 7 is used to regulate the airflow of exhaust air or hot air.

[0044] 9. The pulverized coal that comes out of the coal mill 13 and is separated by the pulverized coal separator 16 and stored in the pulverized coal silo 10 is fed into the air-pulverized coal mixer 8 by the pulverizer 9; the pulverizer 9 is used to control the pulverized coal feeding rate.

[0045] 10. The air-coal mixture from the outlet of the air-coal mixer 8 is sent to the primary air nozzle 11 of the burner via the coal feeding pipe 12 and enters the boiler furnace 17 for combustion.

[0046] This invention optimizes the powder delivery method of two intermediate storage-type powder making systems by cross-arranging the exhaust air box 4 and outlet air duct 6 of the corresponding exhaust fan 3 of powder making subsystem A14 and powder making subsystem B15 to achieve flexible powder delivery.

[0047] At low load, the exhaust gas from the pulverizing system in operation can be directed to the pulverizing air damper 7 of another pulverizing system that is out of operation. The exhaust gas is then sent from the primary air nozzle 11 of the corresponding out-of-operation burner into the boiler furnace 17 for combustion. At the same time, the hot air at the inlet of the exhaust fan 3 of the out-of-operation pulverizing system is opened. After passing through the exhaust fan 3, the hot air is directed to the coal powder bin 10 of the pulverizing system in operation and mixed with the coal powder to achieve hot air delivery to the primary air nozzle 11 of the operating burner and into the boiler furnace 17 for combustion.

[0048] This invention can raise the temperature of the pulverized coal mixture in the pulverized coal feeding pipeline to 140-160°C or even higher when the boiler is under low load. Furthermore, by reducing the amount of hot air used for feeding, the pulverized coal concentration is increased, allowing the air-coal mixture to ignite and burn stably earlier. This enables the pulverized coal to be heated rapidly to ignition and release heat, providing favorable combustion conditions for subsequent pulverized coal. This enhances the coal adaptability of the coal-fired boiler unit, improves boiler combustion efficiency, and significantly improves the unit's flexibility and peak-shaving capabilities. When the boiler is under high load, the pulverizing system still uses exhaust gas or warm air for feeding, ensuring normal boiler operation.

[0049] The flexible powder feeding method provided by this invention is applicable to two or more intermediate storage-type waste gas powder making systems. It does not require additional equipment or operating costs. The switching between high and low load powder feeding modes can be achieved simply by arranging the waste gas pipelines of two powder dischargers in a cross manner and combining them with corresponding control logic.

[0050] Example 2

[0051] like Figures 1 to 4 As shown, as a further optimization of Embodiment 1, this embodiment also includes the following technical features based on Embodiment 1:

[0052] Figure 4 This is a specific system design scheme of the present invention:

[0053] The boiler pulverizing system of a certain project adopts a waste gas feeding system using intermediate storage bins for ball mills, with 4 mills per boiler. The fuel is bituminous coal, and the designed outlet air temperature of the mills is 90℃. In actual operation, fly ash is relatively high, and the minimum non-combustion load is ~50% BMCR. In order to further reduce fly ash and improve the unit's flexibility and peak-shaving capability, it is considered to cross-modify the waste gas pipelines at outlet A14 of the A exhaust gas box pulverizing subsystem and outlet B15 of the B exhaust gas box pulverizing subsystem. At low loads, it is recommended to adopt an operation mode in which the A mill and its corresponding burner nozzle pulverizing subsystem A14 are shut down, and the B mill and its corresponding burner nozzle pulverizing subsystem B15 are operated. The exhaust gas from the B mill pulverizing subsystem B15 can be led to the A pulverizing subsystem A14 in front of the A pulverizing air damper, and the exhaust gas is sent into the furnace for combustion from the burner nozzle corresponding to the A pulverizing subsystem A14. At the same time, the hot air at the inlet of the A pulverizer pulverizing subsystem A14 is opened, and after passing through the pulverizer, it is led to the B pulverizing subsystem B15 to mix with the pulverized coal to achieve hot air pulverizing, and then sent into the boiler furnace 17 for combustion from the primary air nozzle 11 of the burner corresponding to the B pulverizing subsystem B15.

[0054] This invention can raise the temperature of the pulverized coal mixture for combustion to 140-160°C or even higher, and reduce the amount of hot air used for pulverized coal feeding, thereby increasing the pulverized coal concentration in the airflow to the optimal concentration required for ignition, effectively improving the burner's ignition and self-stabilizing combustion capabilities; at the same time, it does not affect high-load operation, and the modification does not require additional equipment or operating costs. The switching of pulverized coal feeding modes for high and low loads can be achieved simply by cross-arranging the exhaust gas pipelines of two pulverizers and combining them with corresponding control logic; the investment cost is relatively small.

[0055] This invention can advance the ignition of pulverized coal entering the furnace by increasing the temperature of the air-coal mixture and the concentration of pulverized coal, and can rapidly heat the pulverized coal to ignite and release heat, providing favorable combustion conditions for subsequent pulverized coal. This can enhance the coal type adaptability of coal-fired boiler units, reduce fly ash, and improve the unit's flexibility and peak-shaving capabilities.

[0056] As described above, the present invention can be implemented well.

[0057] All features disclosed in all embodiments of this specification, or steps in all methods or processes implied in the disclosure, may be combined and / or extended or replaced in any way, except for mutually exclusive features and / or steps.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Based on the technical essence of the present invention, any simple modifications, equivalent substitutions, and improvements made to the above embodiments within the spirit and principles of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for making flour, characterized in that, A powder making system is used, which includes two powder making subsystems, namely powder making subsystem A (14) and powder making subsystem B (15). Each powder making subsystem includes a hot air damper (1), a waste gas damper (2), a powder discharge fan (3), a waste gas air box (4), a waste gas recirculation damper (5), an air duct (6), and a powder delivery damper (7). In each powder making subsystem, the hot air damper (1), the powder discharge fan (3), the waste gas air box (4), and the waste gas recirculation damper (5) are connected in sequence. The node between the hot air damper (1) and the powder discharge fan (3) is connected to the waste gas damper (2). The air duct (6) in each powder making subsystem is connected to the powder delivery damper (7) in the other powder making subsystem. Each pulverizing subsystem also includes an air-powder mixer (8), a pulverizer (9), a pulverizer silo (10), a burner primary air nozzle (11), a pulverizer pipeline (12), a coal mill (13), a pulverizer (16), a pulverizer damper (7), an air-powder mixer (8), a pulverizer pipeline (12), and a burner primary air nozzle (11) connected in sequence. The pulverizer (9) is connected to the air-powder mixer (8). The pulverizer (9), the pulverizer silo (10), the pulverizer (16), the coal mill (13), and the exhaust gas recirculation damper (5) are connected in sequence. The pulverizer (16) is connected to the exhaust gas damper (2). When the coal mill (13) of the pulverizing subsystem A (14) is running, the hot air damper (1) of the pulverizing subsystem A (14) is closed and the exhaust gas damper (2) is opened. The exhaust gas of the pulverizing subsystem A (14) enters the exhaust gas box (4) after passing through the exhaust fan (3). A small part of the exhaust gas is circulated back to the coal mill (13) after being regulated by the exhaust gas recirculation damper (5). The remaining majority of the exhaust gas is sent to the air-coal mixer (8) of the pulverizing subsystem B (15) through the air duct (6), and then fed into the coal mill. Pipeline (12) sends the exhaust gas to the burner primary air nozzle (11) to burn off the exhaust gas; when the pulverizing subsystem A (14) stops operating because the powder level in the powder bin (10) is higher than the set threshold, but the burner primary air nozzle (11) corresponding to the pulverizing subsystem A (14) is still running, the hot air damper (1) and exhaust gas damper (2) of the pulverizing subsystem A (14) are closed, the exhaust fan (3) stops operating, and no exhaust gas passes through the burner primary air nozzle (11) corresponding to the pulverizing subsystem B (15).

2. The powder-making method according to claim 1, characterized in that, It also includes the boiler furnace (17) connected to the primary air nozzle (11) of the burner of each pulverizing subsystem.

3. The powder preparation method according to claim 1, characterized in that, When the boiler load is higher than the set threshold, and the pulverizing subsystem A (14) and its corresponding burner primary air nozzle (11), and the pulverizing subsystem B (15) and its corresponding burner primary air nozzle (11) are all operating normally, the hot air damper (1) is closed and the exhaust gas damper (2) is opened. The exhaust gas enters the exhaust gas box (4) after passing through the exhaust fan (3). A small part of the exhaust gas is regulated by the exhaust gas recirculation damper (5) and then circulated back to the coal mill (13). The remaining exhaust gas is mixed with coal powder through the air duct (6) to achieve powder delivery. When the powder level in the powder bin (10) is higher than the set threshold, and the pulverizing subsystem A (14) and the pulverizing subsystem B (15) are shut down, the hot air damper (1) is opened and the exhaust gas damper (2) is closed.

4. The powder-making method according to claim 1, characterized in that, When the boiler load is lower than the set threshold, the pulverizing subsystem B (15) and its corresponding burner primary air nozzle (11) are shut down. Only the pulverizing subsystem A (14) and its corresponding burner primary air nozzle (11) are operated. The hot air damper (1) of the pulverizing subsystem B (15) is opened and the exhaust gas damper (2) is closed. The hot air of the pulverizing subsystem B (15) enters the exhaust gas box (4) after passing through the exhaust fan (3). At this time, the exhaust gas recirculation damper (5) is closed. The hot air passes through the air duct (6) and the pulverizing air damper (7) of the pulverizing subsystem A (14) before going to the air-pulverizing mixer (8) to mix with the pulverized coal, thus realizing hot air pulverizing.

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