A power plant high-moisture coal yard drying and fine powder utilization system

Abstract

This invention provides a high-moisture coal drying and fine coal powder utilization system for power plants, belonging to the field of power generation technology. It includes a drying unit, with its input connected to a coal feeding unit, its first output connected to a fine coal powder utilization unit, and its second output connected to a coal feeding unit. The coal feeding unit is connected to a hot and cold primary air duct, and a branch pipe of the hot and cold primary air duct is connected to the fine coal powder utilization unit. The output of the coal feeding unit is connected to the furnace, and the output of the fine coal powder utilization unit is connected to the furnace. This system achieves controllable moisture content after coal drying, full utilization of fine coal powder, compatibility with the retrofitting of existing units, increased mill output, recovery of moisture from coal, improved unit flexibility, and increased load change rate.

Description

Technical Field

[0001] This invention relates to the field of power generation technology, specifically to a system for drying and utilizing fine powder from high-moisture coal in power plants. Background Technology

[0002] To improve the fuel adaptability of coal-fired power units and reduce operating costs, some power plants use high-moisture coal types such as lignite as fuel. However, using high-moisture coal as fuel may lead to problems such as insufficient mill output and poor combustion stability. Coal pre-drying is an effective way to reduce coal moisture, increase coal calorific value, increase mill output, and improve combustion stability.

[0003] Currently, the drying of wet coal produces a certain amount of fine coal powder. This fine coal powder has a small particle size and low moisture content, requiring additional processing equipment, which increases equipment costs. With the increasing proportion of wind power and photovoltaic power in recent years, higher demands are placed on the peak-shaving capacity of coal-fired power units. The output adjustment speed of the coal mill in direct-fired pulverizing systems is often slow, becoming one of the bottlenecks in improving unit flexibility. Therefore, we propose a system for drying high-moisture coal in power plants and utilizing the fine coal powder. Summary of the Invention

[0004] The purpose of this invention is to provide a system for drying and utilizing fine powder of high-moisture coal in power plants, in order to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a high-moisture coal drying and fine powder utilization system for power plants, comprising a drying unit, an input end of which is connected to a coal feeding unit, a first output end of which is connected to a fine powder utilization unit, a second output end of which is connected to a coal feeding unit, a coal feeding unit connected to a hot and cold primary air duct, a branch pipe of which is connected to the fine powder utilization unit, an output end of which is connected to a furnace, and an output end of which is connected to the furnace.

[0006] Furthermore, the drying unit includes a coal dryer, the input end of which is connected to the coal feeding unit, the first output end of which is connected to the fine powder utilization unit via a pipeline, and the second output end of which is connected to the coal feeding unit via a coal conveyor belt.

[0007] Furthermore, the coal dryer has a double-layer structure, with one layer being a coal layer and the other a steam layer.

[0008] Furthermore, the coal seam inlet is equipped with a feed screw valve, the coal seam outlet is equipped with a discharge screw valve, the steam layer inlet is equipped with an inlet valve and a drain valve, and the steam layer outlet is equipped with an outlet valve and a drain valve.

[0009] Furthermore, the coal feeding unit includes a coal feeding belt, the output end of which is connected to a weighing belt, and the output end of which is connected to the input end of the coal dryer.

[0010] Furthermore, the fine powder utilization unit includes a fine powder bin one and a fine powder bin two. The input end of the fine powder bin one is connected to the first output end of the dry coal machine through a pipeline. The top of the inner cavity of the fine powder bin one is provided with a bag filter, a back-blowing air port, and a waste gas outlet. The waste gas outlet is connected to an exhaust mechanism. The output end of the fine powder bin one is connected to a conveying mechanism. The output end of the conveying mechanism is connected to the input end of the fine powder bin two. The top of the inner cavity of the fine powder bin two is provided with a bag filter, a back-blowing air port, and a waste gas outlet. The output end of the fine powder bin two is connected to a powder feeder. The output end of the powder feeder is connected to the furnace. The branch pipe of the hot and cold primary air pipeline is connected to the powder feeder.

[0011] Furthermore, the exhaust mechanism includes a condenser and an exhaust fan. The input end of the condenser is connected to the exhaust gas outlet of the fine powder silo, and the output end of the condenser is connected to the input end of the exhaust fan.

[0012] Furthermore, the conveying mechanism includes a powder feeder, an air compressor, a refrigerated dryer, and an air storage tank. The input end of the air compressor is connected to an air source, the output end of the air compressor is connected to the input end of the refrigerated dryer, the output end of the refrigerated dryer is connected to the input end of the air storage tank, the output end of the air storage tank is connected to the powder feeder, the powder feeder is installed at the output end of fine powder bin one, and the output end of the powder feeder is connected to the input end of fine powder bin two.

[0013] Furthermore, the coal feeding unit includes a coal bunker, a coal feeder, and a coal mill. The input end of the coal bunker is connected to the second output end of the dry coal machine via a coal conveyor belt. The output end of the coal bunker is connected to the input end of the coal feeder. The output end of the coal feeder is connected to the input end of the coal mill. The output end of the coal mill is connected to the furnace via a pulverized coal outlet pipe. The coal mill is provided with a primary air inlet, and the hot and cold primary air pipes are connected to the coal mill through the primary air inlet.

[0014] Furthermore, the hot and cold primary air duct is equipped with several dampers.

[0015] Compared with the prior art, the present invention has the following technical effects: In this invention, high-moisture coal is dried by a coal dryer, and the dried coal enters the coal bunker via a second coal conveyor belt. It is then fed into a coal mill by a coal feeder, where it is pulverized and fed into the furnace. The evaporated moisture from the drying process, along with fine coal powder, enters a fine powder silo. This fine coal powder is intercepted by a bag filter and stored in the fine powder silo. The filtered water vapor is condensed and the moisture is recovered by a condenser. An exhaust fan removes the remaining water vapor and some leaked air, discharging it into the atmosphere. A powder feeder then feeds the fine coal powder from the fine powder silo into a second fine powder silo. The fine coal powder is intercepted by a bag filter and stored in the second fine powder silo. The conveying air is discharged through the exhaust outlet. The powder feeder then feeds the fine coal powder from the second fine powder silo into the furnace for combustion. This system achieves controllable moisture content after coal drying, full utilization of fine coal powder, compatibility with the retrofitting of existing units, increased coal mill output, ability to recover moisture from coal, improved unit flexibility, and increased load change rate. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a power plant high-moisture coal yard drying and fine powder utilization system according to an embodiment of the present invention.

[0017] In the diagram: 1. Coal feeding belt 1, 2. Weighing belt, 3. Coal dryer, 4. Coal feeding belt 2, 5. Fine powder bin 1, 6. Fine powder bin 2, 7. Powder feeder, 8. Powder feeder, 9. Condenser, 10. Exhaust fan, 11. Air compressor, 12. Refrigerated dryer, 13. Air storage tank, 14. Coal bunker, 15. Coal feeder, 16. Coal mill, 17. Hot and cold primary air duct, 18. Furnace. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present invention.

[0019] In this article, terms such as "left," "right," "up," "down," "front," and "back" are established based on the positional relationships shown in the attached drawings. Depending on the attached drawings, the corresponding positional relationships may also change. Therefore, they should not be interpreted as an absolute limitation on the scope of protection.

[0020] Please see Figure 1This embodiment provides a high-moisture coal yard drying and fine powder utilization system for power plants, including a drying unit. The input end of the drying unit is connected to a coal feeding unit, the first output end of the drying unit is connected to a fine powder utilization unit, the second output end of the drying unit is connected to a coal feeding unit, the coal feeding unit is connected to a hot and cold primary air duct 17, the branch pipe of the hot and cold primary air duct 17 is connected to the fine powder utilization unit, the output end of the coal feeding unit is connected to a furnace 18, and the output end of the fine powder utilization unit is connected to the furnace 18.

[0021] Specifically, the drying unit includes a coal dryer 3. The input end of the coal dryer 3 is connected to the coal feeding unit, the first output end of the coal dryer 3 is connected to the fine powder utilization unit via a pipeline, and the second output end of the coal dryer 3 is connected to the coal feeding unit via a coal conveyor belt 4. The coal dryer 3 has a double-layer structure; coal passes through one layer, called the coal layer, and hot steam passes through the other layer, called the steam layer. The coal layer inlet is equipped with a feed screw valve, and the coal layer outlet is equipped with a discharge screw valve, which controls the entry and exit of coal. The steam layer inlet is equipped with an inlet valve and a drain valve, and the steam layer outlet is equipped with an outlet valve and a drain valve. During operation, hot steam passes through the partition wall between the two layers of the coal dryer 3 to heat the coal and evaporate the moisture in the coal, thereby achieving the purpose of drying the coal.

[0022] Specifically, the coal feeding unit includes a coal feeding belt 1, the output end of which is connected to a weighing belt 2, and the output end of the weighing belt 2 is connected to the input end of the coal dryer 3. Through the cooperation of the coal feeding belt 1 and the weighing belt 2, the required amount of coal is transported from the coal feeding belt 1 to the coal dryer 3.

[0023] Specifically, the fine coal utilization unit includes a fine coal bin 1 (5) and a fine coal bin 2 (6). The input end of fine coal bin 1 (5) is connected to the first output end of the coal dryer 3 via a pipeline. The top of the inner cavity of fine coal bin 1 (5) is equipped with a bag filter, a back-flushing air inlet, and a waste gas outlet. The waste gas outlet is connected to an exhaust mechanism, which is used to recover and discharge the water vapor generated during drying (i.e., waste gas containing coal powder). The output end of fine coal bin 1 (5) is connected to a conveying mechanism, which is used to transport the fine coal powder in fine coal bin 1 (5) to fine coal bin 2 (6). The output end of the conveying mechanism is connected to the input end of fine coal bin 2 (6). The top of the inner cavity of fine coal bin 2 (6) is equipped with a bag filter, a back-flushing air inlet, and a waste gas outlet. The output end of fine coal bin 2 (6) is connected to a coal feeder 8, whose output end is connected to a coal discharge pipe, which is connected to the furnace 18. A branch pipe of the hot and cold primary air pipe 17 is connected to the coal feeder 8. The coal feeder 8 operates according to the amount of fine coal powder in fine coal bin 2 (6) and operational needs. The output end of the pulverizer 8 can also be connected to the burner port separately provided in the furnace 18.

[0024] Specifically, the exhaust system includes a condenser 9 and an exhaust fan 10. The inlet of the condenser 9 is connected to the exhaust outlet of the fine powder hopper 5, and the outlet of the condenser 9 is connected to the inlet of the exhaust fan 10. The condenser 9 is used to condense and recover the water vapor gas filtered by the bag filter, and the exhaust fan 10 is used to draw away the remaining water vapor and some of the leaked air and discharge it into the atmosphere.

[0025] Specifically, the conveying mechanism includes a powder feeder 7, an air compressor 11, a refrigerated dryer 12, and an air storage tank 13. The input end of the air compressor 11 is connected to an air source, and its output end is connected to the input end of the refrigerated dryer 12. The output end of the refrigerated dryer 12 is connected to the input end of the air storage tank 13, and the output end of the air storage tank 13 is connected to the powder feeder 7. The powder feeder 7 is installed at the output end of fine powder bin 5 and is connected to the input end of fine powder bin 6. During operation, the air compressor 11 compresses the gas into compressed gas. The compressed gas enters the refrigerated dryer 12 for drying and purification, and then enters the air storage tank 13 for storage. The compressed air in the air storage tank 13 enters the powder feeder 7, while the fine powder in fine powder bin 5 falls into the powder feeder 7. The compressed air (i.e., exhaust gas) then delivers the fine powder into fine powder bin 6.

[0026] Specifically, during the operation of the fine powder utilization unit, the water vapor generated during drying (i.e., exhaust gas carrying powder) will contain fine coal powder. This powder-laden water vapor enters the interior of fine powder silo 15. The fine coal powder in the water vapor is intercepted by the bag filter in fine powder silo 15, and then either injected with back-flushing air through the back-flushing port or shaken down to the lower part of fine powder silo 15 for storage. The gas filtered by the bag filter flows into condenser 9 from the exhaust gas outlet. Condenser 9 condenses and recovers the water vapor gas. Exhaust fan 10 removes the remaining water vapor and some leaked air, discharging it into the atmosphere. The fine powder in fine powder silo 15 falls into the powder feeder 7, and compressed air sends the fine powder into fine powder silo 26. The powder is intercepted by the bag filter in fine powder silo 26, and then either injected with back-flushing air through the back-flushing port or shaken down to the lower part of fine powder silo 26 for storage. The compressed gas filtered by the bag filter is discharged from the exhaust gas outlet. The branch pipe of the hot and cold primary air duct 17 provides primary air gas to the pulverizer 8. The fine coal powder in the fine powder bin 2 6 falls into the pulverizer 8. The primary air carries the pulverizer 8 into the pulverizer outlet pipe, where it merges with the pulverizer 16 carried by the primary air, and finally they are sent into the furnace 18 for combustion.

[0027] Specifically, the coal feeding unit includes a coal bunker 14, a coal feeder 15, and a coal mill 16. The input end of the coal bunker 14 is connected to the second output end of the coal feeder 15 via a second coal conveyor belt 4. The output end of the coal bunker 14 is connected to the input end of the coal feeder 15 via a coal drop pipe. The output end of the coal feeder 15 is connected to the input end of the coal mill 16 via a coal drop pipe. The output end of the coal mill 16 is connected to the furnace 18 via a pulverized coal discharge pipe. A primary air inlet is provided on the coal mill 16, and a hot and cold primary air duct 17 is connected to the coal mill 16 through the primary air inlet. A baffle or valve for controlling coal drop is provided at the output end of the coal bunker 14. Several dampers are provided on the hot and cold primary air duct 17 to control the airflow of the primary air. Several dampers form a damper group.

[0028] Specifically, during operation, the dried coal is transported from the second output end of the coal dryer 3 to the coal bunker 14 via the second coal conveyor belt 4. The coal stored in the coal bunker 14 falls onto the coal feeder 15, which weighs and transports the coal to the coal mill 16. The coal mill 16 crushes and grinds the coal into pulverized coal. The hot and cold primary air pipe 17 introduces primary air into the coal mill 16 through the primary air inlet. The primary air carries the pulverized coal into the pulverized coal outlet pipe, where it merges with the pulverized coal fed by the primary air feeder 8 and is finally sent into the furnace 18 for combustion.

[0029] Specifically, coal conveyor belt 1 and coal conveyor belt 2 can be the same belt, that is, the dried coal is sent back to the same belt. When the coal dryer 3 is not running, it does not affect the original equipment from sending undried coal to the boiler.

[0030] Specifically, during installation, the coal conveyor belt 1, weighing belt 2, coal dryer 3, fine powder bin 5, condenser 9, exhaust fan 10, powder feeder 7, air compressor 11, refrigerated dryer 12, and air storage tank 13 are arranged on the coal yard side, while the coal bunker 14, coal feeder 15, coal mill 16, fine powder bin 2 6, powder feeder 8, furnace 18, and hot and cold primary air ducts 17 are arranged on the unit side.

[0031] Specifically, this system also has the function of improving the unit's load change rate, and the specific implementation method is as follows: During stable operation, dried coal continuously enters the pulverizer 16 for pulverization and is then fed into the furnace 18 for combustion. The exhaust gas carrying the pulverized coal enters two fine coal bins. The fine coal powder in fine coal bin 2 6 continuously enters the feeder 8, is carried away by the primary air, and merges with the feed gas from the pulverizer 16 carried by the primary air before being fed into the furnace 18 for combustion. At this time, the coal feed rate is the same as the coal input rate into the furnace 18, and the fine coal bin level (i.e., the storage height of the fine coal powder in the fine coal bin) remains stable.

[0032] When the unit rapidly reduces load, the feeder 8 is quickly shut down, and its air supply is cut off. The amount of coal supplied by the fine pulverized coal decreases rapidly until it reaches zero. The feeder 15, dry coal mill 3, and coal mill 16 slowly reduce their loads. After the fine powder bin level rises to load rebalancing, the feeder 8 resumes feeding pulverized coal, and then the fine powder bin level stabilizes at the new position. The rapid load reduction capability provided by the fine powder bin depends on the proportion of pulverized coal carried by the exhaust gas to the amount of coal fed by the feeder 15.

[0033] When the unit rapidly increases its load, the feeder 8 increases its pulverized coal supply and corresponding air volume, resulting in a rapid increase in the amount of pulverized coal fed into the furnace 18. This causes the fine powder bin level to drop, and the amount of coal fed into the furnace to increase rapidly. The feeder 15, dry coal mill 3, and coal mill 16 then slowly increase their loads. The fine powder bin level decreases until the load is rebalanced, after which the feeder 8 reduces its pulverized coal supply (to its original rate), and the pulverized coal bin level stabilizes at its new position.

[0034] The positions of the two fine powder bins are adjusted by adjusting the pneumatic conveying volume between the two bins.

[0035] Specifically, after the high-moisture coal is dried by the coal dryer 3, the dried coal enters the coal bunker 14 via the second coal conveyor belt 4, and then is fed into the coal mill 16 via the coal feeder 15. After being pulverized by the coal mill 16, it is sent into the furnace 18. The water vapor evaporated from the drying process will be mixed with fine coal powder and enter the fine powder silo 5. The fine coal powder is intercepted by the bag filter and stored in the fine powder silo 5. The filtered water vapor gas is condensed and the moisture is recovered by the condenser 9. The exhaust fan 10 draws away the remaining water vapor and some of the leaked air. The fine coal powder in the fine coal powder bin 1 5 is discharged into the atmosphere. The fine coal powder is then sent from the fine coal powder bin 2 6 to the fine coal powder bin 3 6. After being intercepted by the bag filter, the fine coal powder is stored in the fine coal powder bin 2 6. The conveying air is discharged through the exhaust gas outlet. The fine coal powder in the fine coal powder bin 2 6 is sent into the furnace 18 for combustion. This system realizes controllable moisture content after coal drying, full utilization of fine coal powder, compatibility with the renovation of existing units, improved output of coal mill 16, ability to recover moisture from coal, improved unit flexibility, and increased load change rate.

[0036] The above embodiments merely illustrate the basic principles and characteristics of the present invention, but are not limited to the above implementation schemes. It should be understood that those skilled in the art can make various changes and modifications to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A system for drying and utilizing fine powder from high-moisture coal in a power plant, characterized in that, The system includes a drying unit, an input end of which is connected to a coal feeding unit, a first output end of which is connected to a fine powder utilization unit, a second output end of which is connected to a coal feeding unit, a coal feeding unit connected to a hot and cold primary air duct (17), a branch pipe of the hot and cold primary air duct (17) connected to the fine powder utilization unit, an output end of which is connected to a furnace (18), and an output end of the fine powder utilization unit connected to the furnace (18).

2. The power plant high-moisture coal yard drying and fine powder utilization system according to claim 1, characterized in that, The drying unit includes a coal dryer (3), the input end of which is connected to the coal feeding unit, the first output end of which is connected to the fine powder utilization unit through a pipeline, and the second output end of which is connected to the coal feeding unit through a coal conveyor belt (4).

3. The power plant high-moisture coal yard drying and fine powder utilization system according to claim 2, characterized in that, The coal dryer (3) has a double-layer structure, with one layer being a coal layer and the other a steam layer.

4. The power plant high-moisture coal yard drying and fine powder utilization system according to claim 3, characterized in that, The coal seam is equipped with a feed screw valve at its inlet and a discharge screw valve at its outlet. The steam layer is equipped with an inlet valve and a drain valve at its inlet and an outlet valve and a drain valve at its outlet.

5. The power plant high-moisture coal yard drying and fine powder utilization system according to claim 2, characterized in that, The coal feeding unit includes a coal feeding belt (1), the output end of which is connected to a weighing belt (2), and the output end of the weighing belt (2) is connected to the input end of the dry coal machine (3).

6. The power plant high-moisture coal yard drying and fine powder utilization system according to claim 2, characterized in that, The fine powder utilization unit includes a fine powder bin one (5) and a fine powder bin two (6). The input end of the fine powder bin one (5) is connected to the first output end of the dry coal machine (3) through a pipe. The top of the inner cavity of the fine powder bin one (5) is provided with a bag filter, a back-blowing air port and a waste gas outlet. The waste gas outlet is connected to an exhaust mechanism. The output end of the fine powder bin one (5) is connected to a conveying mechanism. The output end of the conveying mechanism is connected to the input end of the fine powder bin two (6). The top of the inner cavity of the fine powder bin two (6) is provided with a bag filter, a back-blowing air port and a waste gas outlet. The output end of the fine powder bin two (6) is connected to a powder feeder (8). The output end of the powder feeder (8) is connected to the furnace (18). The branch pipe of the hot and cold primary air pipe (17) is connected to the powder feeder (8).

7. The power plant high-moisture coal yard drying and fine powder utilization system according to claim 6, characterized in that, The exhaust mechanism includes a condenser (9) and an exhaust fan (10). The input end of the condenser (9) is connected to the exhaust gas outlet of the fine powder bin (5), and the output end of the condenser (9) is connected to the input end of the exhaust fan (10).

8. The power plant high-moisture coal yard drying and fine powder utilization system according to claim 6, characterized in that, The conveying mechanism includes a powder feeder (7), an air compressor (11), a refrigerated dryer (12), and an air tank (13). The input end of the air compressor (11) is connected to an air source. The output end of the air compressor (11) is connected to the input end of the refrigerated dryer (12). The output end of the refrigerated dryer (12) is connected to the input end of the air tank (13). The output end of the air tank (13) is connected to the powder feeder (7). The powder feeder (7) is installed at the output end of the fine powder bin one (5). The output end of the powder feeder (7) is connected to the input end of the fine powder bin two (6).

9. The power plant high-moisture coal yard drying and fine powder utilization system according to claim 1, characterized in that, The coal feeding unit includes a coal bunker (14), a coal feeder (15), and a coal mill (16). The input end of the coal bunker (14) is connected to the second output end of the dry coal machine (3) via a second coal conveyor belt (4). The output end of the coal bunker (14) is connected to the input end of the coal feeder (15). The output end of the coal feeder (15) is connected to the input end of the coal mill (16). The output end of the coal mill (16) is connected to the furnace (18) via a powder discharge pipe. The coal mill (16) is provided with a primary air inlet. The hot and cold primary air pipe (17) is connected to the coal mill (16) via the primary air inlet.

10. The power plant high-moisture coal yard drying and fine powder utilization system according to claim 1, characterized in that, The hot and cold primary air duct (17) is equipped with several dampers.

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