A system and method for reducing the cooling air volume of a coal mill

Abstract

The present invention discloses a system and method for reducing the cold air volume of a coal mill. The system includes a coal mill, which is connected to a hot primary air duct of the coal mill and an air-powder pipeline at the outlet of the coal mill. A steam heat exchanger is arranged in the hot primary air duct of the coal mill and is connected to a boiler drum. The boiler drum is respectively connected to a steam pipeline and a return water pipeline, and the steam pipeline and the return water pipeline are connected to the air-powder pipeline heat exchanger. A booster pump is installed on the return water pipeline. The method is as follows: the working medium water in the steam heat exchanger absorbs excess heat in the hot primary air duct of the coal mill to become steam and enter the boiler drum, and then enters the air-powder pipeline heat exchanger through the steam pipeline to heat the air-powder mixture passing there. After the steam completes the heat exchange, it becomes water, which is sent back to the boiler drum through the return water pipeline through the booster pump, and then enters the steam heat exchanger for the next round of heat exchange. The present invention reduces the amount of cold air introduced into the coal mill, reduces the primary air rate, improves the economic efficiency of boiler operation, and the system operation is safer.

Description

Technical Field

[0001] The present invention relates to a system and a method, and in particular to a system and a method for reducing the cooling air volume of a coal mill. Background Art

[0002] Coal mill is one of the important auxiliary equipment of coal-fired power plant boilers. As a pulverizing equipment that turns raw coal into qualified coal powder, it plays the role of grinding, conveying and drying coal powder.

[0003] Among them, the drying heat source comes from the hot primary air entering the coal mill. When the temperature of the hot primary air is higher than the temperature required for drying the raw coal inside the coal mill, cold air needs to be mixed in to reduce it to a reasonable temperature before it is sent to the coal mill. At this time, the amount of primary air entering the boiler will increase, and the primary air rate will be increased, causing the combustion of coal powder in the furnace to be delayed and the center of the combustion flame to be higher, which in turn causes the exhaust gas temperature to be higher, reducing the economic efficiency of the boiler operation and increasing the power consumption rate of the primary fan.

[0004] At the same time, the outlet temperature of the coal mill is closely related to the economy and safety of the boiler. Increasing the outlet temperature of the coal mill can effectively reduce the ignition heat. In the prior art, the hot air is often directly blown in to heat the air-powder mixture. However, the reverse blowing of hot air leads to the formation of negative pressure in the air-powder pipe at the outlet of the coal mill. In order to discharge the air-powder mixture normally, auxiliary equipment such as blowers need to be added, resulting in greatly increased investment costs and increased maintenance costs. In addition, the air-powder mixture has many volatile components, and the blowing of hot air brings about an increase in oxygen content and temperature, which can easily cause the highly volatile coal powder to spontaneously combust, posing a high safety hazard. Summary of the invention

[0005] In order to solve the deficiencies of the above-mentioned technology, the present invention provides a system and method for reducing the cooling air volume of a coal mill.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a system for reducing the cold air volume of a coal mill, comprising a coal mill, which also includes a steam heat exchanger, a boiler drum, a steam pipeline, a return water pipeline, an air-powder pipeline heat exchanger and a booster pump;

[0007] The coal mill is connected with the coal mill hot primary air duct and the coal mill outlet air and powder pipeline respectively. The steam heat exchanger is arranged in the coal mill hot primary air duct, and the steam heat exchanger is connected with the boiler drum; the boiler drum is connected with the steam pipeline and the return water pipeline respectively. The steam pipeline is connected with the water inlet of the air and powder pipeline heat exchanger, and the return water pipeline is connected with the water outlet of the air and powder pipeline heat exchanger; the air and powder pipeline heat exchanger is arranged on the coal mill air and powder pipeline, and the booster pump is installed on the return water pipeline;

[0008] The hot primary air duct of the coal mill is also connected to the cold air duct, on which a cold air regulating door is installed, and the hot primary air duct of the coal mill is also connected to the cold air duct.

[0009] Furthermore, a No. 1 stop valve is provided on the steam pipe, and a No. 2 stop valve is provided on the return water pipe, and the No. 2 stop valve is located on the water inlet side of the booster pump.

[0010] Furthermore, a check valve and an electric regulating valve are also provided on the return water pipeline. The check valve is located on the water outlet side of the booster pump, and the electric regulating valve is located on the water outlet side of the check valve.

[0011] Furthermore, the air-powder pipeline heat exchanger is a shell-and-tube heat exchanger, which is sleeved on the air-powder pipeline at the outlet of the coal mill.

[0012] A method for reducing the cooling air volume of a coal mill system, the method comprising:

[0013] The working medium water in the steam heat exchanger absorbs the excess heat of the hot air entering the hot primary air duct of the coal mill. The working medium water is heated and evaporates into steam and enters the boiler drum, and then enters the air-powder pipe heat exchanger through the steam pipe to heat the air-powder mixture flowing out of the air-powder pipe at the coal mill outlet. After completing the heat exchange, the steam turns into water and is sent back to the boiler drum through the return water pipe through the booster pump, and then enters the steam heat exchanger for the next round of heat exchange.

[0014] Furthermore, the water quantity adjustment process of the working water in the steam heat exchanger is:

[0015] When the load of the coal mill is high, the water pumping capacity of the booster pump is increased, and the amount of working water returning from the air-powder pipeline heat exchanger to the steam heat exchanger increases, thereby absorbing more heat from the hot primary air duct of the coal mill;

[0016] When the load of the coal mill is low, the pumping volume of the booster pump is reduced, and the amount of working water returning from the air-powder pipeline heat exchanger to the steam heat exchanger is reduced, thereby absorbing less heat from the hot primary air duct of the coal mill;

[0017] In the above-mentioned process of regulating the amount of working water, since it is inconvenient to maintain the total hot air volume entering the hot primary air duct of the coal mill, the booster pump is coordinated with the coal mill hot air regulating door according to the specific working requirements of the coal mill to reasonably regulate the amount of working water in the reflux steam heat exchanger.

[0018] The present invention discloses a system and method for reducing the cold air volume of a coal mill. The system uses working medium water as a heat carrier to transfer the excess heat in the hot primary air duct at the coal mill inlet to the air-powder mixture at the coal mill outlet, thereby reducing the cold air volume of the coal mill, thereby reducing the primary air rate and the power consumption rate of the primary fan; the coal powder can be ignited in advance after entering the boiler, reducing the center height of the flame in the furnace, thereby reducing the exhaust temperature and improving the economy of the boiler. In addition, a heat exchanger is used to heat the outlet air-powder mixture in a heat exchange manner, which solves the problem of increased investment cost and increased safety hazards caused by the traditional hot air direct blowing of the air-powder mixture. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the system composition of the present invention.

[0020] In the figure: 1. Coal mill; 2. Coal mill hot primary air duct; 3. Coal mill outlet air and powder duct; 4. Steam heat exchanger; 5. Boiler drum; 6. Steam pipe; 7. Return water pipe; 8. Air and powder duct heat exchanger; 9. Booster pump; 10. Cold air regulating door; 11. Cold air duct; 12. Hot air regulating door; 13. No. 1 stop valve; 14. No. 2 stop valve; 15. Check valve; 16. Electric regulating valve. DETAILED DESCRIPTION

[0021] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0022] like Figure 1 A system for reducing the cooling air volume of a coal mill is shown, comprising a coal mill 1, which also includes a steam heat exchanger 4, a boiler drum 5, a steam pipe 6, a return water pipe 7, an air-powder pipe heat exchanger 8 and a booster pump 9;

[0023] The coal mill 1 is connected to the coal mill hot primary air duct 2 and the coal mill outlet air and powder pipeline 3, wherein the steam heat exchanger 4 is arranged in the coal mill hot primary air duct 2, so that the working medium water in the steam heat exchanger 4 absorbs the excess heat of the hot primary air, and the steam heat exchanger 4 is connected to the drum 5, and the drum 5 is used to separate steam and water and purify steam; the drum 5 is respectively connected to the steam pipeline 6 and the return water pipeline 7, the steam pipeline 6 is connected to the water inlet of the air and powder pipeline heat exchanger 8, and the air and powder pipeline The air-powder pipe heat exchanger 8 is arranged on the coal mill air-powder pipe 3, so that the steam enters the air-powder pipe heat exchanger 8 through the steam pipe 6 to heat the air-powder mixture at the outlet; at the same time, the return water pipe 7 is connected to the water outlet of the air-powder pipe heat exchanger 8, so that the steam becomes water after heat exchange, and continues to flow back from the return water pipe 7 to the boiler drum 5, and then enters the steam heat exchanger 4 for the next round of heat exchange; and a booster pump 9 is installed on the return water pipe 7 to pump water into the boiler drum 5 and adjust the water volume;

[0024] For the air-powder pipe heat exchanger 8, a shell-and-tube heat exchanger is used, which is mounted on the coal mill outlet air-powder pipe 3. Thus, the outlet air-powder mixture is heated by heat exchange without direct contact with the air-powder mixture. Under the premise of not affecting the normal discharge of the air-powder mixture, spontaneous combustion is avoided, thereby greatly improving safety.

[0025] At the same time, the hot primary air duct 2 is also connected to the cold air duct 11, and a cold air regulating door 10 is installed on the cold air duct 11, and a hot air regulating door 12 is installed on the hot primary air duct 2 of the coal mill. The setting and installation of the cold air regulating door 10 and the hot air regulating door 12 are all existing technologies.

[0026] In addition, stop valves are installed on the steam pipe 6 and the return pipe 7 to facilitate the closure of the pipeline when the coal mill 1 stops running. At this time, the booster pump 9 is stopped and the valves on the steam pipe 6 and the return pipe 7 are closed to isolate the system; that is: a No. 1 stop valve 13 is provided on the steam pipe 6, and a No. 2 stop valve 14 is provided on the return pipe 7. Both the No. 1 stop valve and the No. 2 stop valve can adopt drain valves to prevent steam leakage to the greatest extent. At the same time, the No. 2 stop valve 14 is installed on the water inlet side of the booster pump 9.

[0027] Furthermore, a check valve 15 and an electric regulating valve 16 are also provided on the return water pipe 7. The check valve 15 is located on the outlet side of the booster pump 9 to prevent water flow from flowing back and improve safety; the electric regulating valve 16 is located on the outlet side of the check valve 15 to cooperate with the booster pump 9 to regulate the return water volume.

[0028] The specific working method of the system for reducing the cooling air volume of the coal mill disclosed in the present invention is as follows:

[0029] The working medium water in the steam heat exchanger 4 absorbs the excess heat of the hot air entering the hot primary air duct 2 of the coal mill. The working medium water is heated and evaporated into steam and enters the boiler drum 5. Then it enters the air-powder pipe heat exchanger 8 through the steam pipe 6, and heats the air-powder mixture flowing out of the air-powder pipe 3 at the coal mill outlet. After completing the heat exchange, the steam becomes water and is sent back to the boiler drum 5 through the return water pipe 7 via the booster pump 9, and then enters the steam heat exchanger 4 for the next round of heat exchange.

[0030] The water volume regulation process of the working water in the steam heat exchanger 4 is as follows:

[0031] When the load of the coal mill 1 is high, the water pumping capacity of the booster pump 9 is increased, and the amount of working water refluxed from the air-powder pipeline heat exchanger 8 to the steam heat exchanger 4 increases, thereby absorbing more heat from the coal mill hot primary air duct 2;

[0032] When the load of the coal mill 1 is low, the pumping amount of the booster pump 9 is reduced, and the amount of working water flowing back from the air-powder pipeline heat exchanger 8 to the steam heat exchanger 4 is reduced, thereby absorbing less heat from the coal mill hot primary air duct 2;

[0033] In the above-mentioned process of regulating the amount of working water, since the total amount of hot air entering the hot primary air duct 2 of the coal mill is inconvenient to maintain, according to the specific working requirements of the coal mill 1, the booster pump 9 is coordinated with the coal mill hot air regulating door 12 to reasonably regulate the amount of working water in the reflux steam heat exchanger 4.

[0034] The system and method for reducing the cooling air volume of a coal mill disclosed in the present invention can realize the transfer of excess heat in the hot primary air from the hot primary air duct to the air-powder duct at the coal mill outlet through the working medium water for the coal mill that needs to be mixed with cold air, without the need to mix with cold air, thereby achieving the purpose of reducing the cooling air volume of the coal mill; thereby reducing the primary air rate and the power consumption rate of the primary fan; the reduction in the primary air rate allows the coal powder to ignite in advance after entering the boiler, and can also reduce the center height of the flame in the furnace, reduce the exhaust gas temperature, and significantly improve the economy of the boiler operation; at the same time, the air-powder mixture at the outlet is heated by indirect heating, abandoning the traditional direct contact heating method of hot air, and no auxiliary equipment such as an external blower is required, thereby reducing investment cost and maintenance cost, and at the same time, greatly reducing the occurrence of spontaneous combustion of coal powder, ensuring the safety of system operation.

[0035] The above implementation modes are not limitations of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the scope of the technical solution of the present invention also belong to the protection scope of the present invention.

Claims

1. A system for reducing the amount of cooling air in a coal mill, comprising a coal mill (1), characterized in that: It also includes a steam heat exchanger (4), a boiler drum (5), a steam pipeline (6), a return water pipeline (7), an air-powder pipeline heat exchanger (8) and a booster pump (9); The coal mill (1) is respectively connected to the coal mill hot primary air duct (2) and the coal mill outlet air and powder pipeline (3); the steam heat exchanger (4) is arranged in the coal mill hot primary air duct (2), and the steam heat exchanger (4) is connected to the boiler drum (5); the boiler drum (5) is respectively connected to the steam pipeline (6) and the return water pipeline (7); the steam pipeline (6) is connected to the water inlet of the air and powder pipeline heat exchanger (8), and the return water pipeline (7) is connected to the water outlet of the air and powder pipeline heat exchanger (8); the air and powder pipeline heat exchanger (8) is arranged on the coal mill air and powder pipeline (3), and the booster pump (9) is installed on the return water pipeline (7); The coal mill hot primary air duct (2) is also connected to a cold air duct (11), a cold air regulating door (10) is installed on the cold air duct (11), and a hot air regulating door (12) is installed on the coal mill hot primary air duct (2).

2. The system for reducing the cooling air volume of a coal mill according to claim 1, characterized in that: The steam pipe (6) is provided with a first stop valve (13), the return water pipe (7) is provided with a second stop valve (14), and the second stop valve (14) is located at the water inlet side of the booster pump (9).

3. The system for reducing the cooling air volume of a coal mill according to claim 2, characterized in that: The return water pipeline (7) is also provided with a check valve (15) and an electric regulating valve (16); the check valve (15) is located on the water outlet side of the booster pump (9), and the electric regulating valve (16) is located on the water outlet side of the check valve (15).

4. The system for reducing the cooling air volume of a coal mill according to claim 3, characterized in that: The air-powder pipeline heat exchanger (8) is a shell-and-tube heat exchanger, which is sleeved on the air-powder pipeline (3) at the outlet of the coal mill.

5. The working method of the system for reducing the cooling air volume of a coal mill according to any one of claims 1 to 4, characterized in that: The working method is: The working medium water in the steam heat exchanger (4) absorbs excess heat of the hot air entering the hot primary air duct (2) of the coal mill. The working medium water is heated and evaporates into steam and enters the boiler drum (5). It then enters the air-powder pipe heat exchanger (8) through the steam pipe (6) to heat the air-powder mixture flowing out of the coal mill outlet air-powder pipe (3). After the steam completes the heat exchange, it turns into water and is sent back to the boiler drum (5) through the return water pipe (7) via the booster pump (9). It then enters the steam heat exchanger (4) for the next round of heat exchange.

6. The working method of the system for reducing the cooling air volume of a coal mill according to claim 5, characterized in that: The process of regulating the amount of working water in the steam heat exchanger (4) is as follows: When the load of the coal mill (1) is high, the water pumping rate of the booster pump (9) is increased, and the amount of working water flowing back from the air-powder pipeline heat exchanger (8) to the steam heat exchanger (4) increases, thereby absorbing more heat from the coal mill hot primary air duct (2); When the load of the coal mill (1) is low, the water pumping rate of the booster pump (9) is reduced, and the amount of working water returning from the air-powder pipeline heat exchanger (8) to the steam heat exchanger (4) is reduced, thereby absorbing less heat from the coal mill hot primary air duct (2); In the above-mentioned process of regulating the amount of working water, since the total amount of hot air entering the hot primary air duct (2) of the coal mill is inconvenient to maintain, the booster pump (9) is coordinated with the coal mill hot air regulating door (12) according to the specific working requirements of the coal mill (1) to reasonably regulate the amount of working water in the reflux steam heat exchanger (4).

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