A steam-hot air coupling system for CFB units

Abstract

This utility model relates to the field of flexible operation retrofitting technology for thermal power generating units, and discloses a steam-hot-air coupling system for CFB units, including a boiler, a steam-hot-air heat exchanger, and a high-pressure cylinder of a steam turbine. A separator is connected to the right side of the boiler. The separator contains a superheated steam system and a reheated steam system. An economizer is located in the lower middle part of the inner side of the separator, and an air preheater is located at the bottom of the inner side of the separator. In this utility model, high-temperature steam is used to heat the primary and secondary hot air at the outlet of the air preheater, increasing the flame temperature inside the furnace and solving the problems of limited inlet flue gas temperature, poor regulation and control, low precision, and limited space in SNCR (Steam-to-Rotation Filter) systems. It also reduces the amount of main steam entering the high-pressure cylinder and reheated steam entering the intermediate-pressure cylinder, increasing the reheated steam temperature and the main steam temperature. Furthermore, it increases the heat load in the water-cooled wall area, reduces the load during the dry-wet state conversion of the unit, and effectively reduces the unit's coal consumption for power generation.

Description

Technical Field

[0001] This utility model relates to the field of flexible operation modification technology for thermal power generating units, and in particular to a steam-hot-air coupling system for CFB units. Background Technology

[0002] In recent years, with the increasing proportion of new energy in the energy structure, thermal power units have been operating at low loads or in a deep peak-shaving manner to meet the demand for new energy consumption. However, due to their unique combustion characteristics, circulating fluidized bed (CFB) units face more complex operating challenges than pulverized coal boilers under low load or deep peak-shaving conditions.

[0003] When a CFB unit operates at low load, the bed temperature drops significantly, which directly leads to a substantial decrease in boiler combustion efficiency. At the same time, the low furnace temperature greatly reduces the efficiency of selective non-catalytic reduction (SNCR) denitrification, making it difficult to meet environmental emission requirements. Furthermore, the boiler unit's stable combustion capability deteriorates under low load, further exacerbating the decline in combustion efficiency. The low main steam temperature and reheat steam temperature are also common problems when CFB units operate at low load. These issues not only affect the operating economy of CFB units but also restrict the full utilization of their peak-shaving capacity, making it difficult to adapt well to the needs of unit flexibility modification and operation. Utility Model Content

[0004] To overcome the above deficiencies, this utility model provides a steam-hot-air coupling system for CFB units, which aims to improve the problem of low SNCR reaction temperature and reduced denitrification efficiency of existing CFB units during operation.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a CFB unit steam-hot-air coupling system, comprising a boiler, a steam-hot-air heat exchanger, and a high-pressure cylinder of a steam turbine, wherein a separator is connected to the right side of the boiler, and a superheated steam system and a reheated steam system are provided inside the separator, an economizer is provided in the lower middle part of the inner side of the separator, an air preheater is provided at the bottom of the inner side of the separator, a first air box is connected to the left side of the boiler, and a second air box is connected to the bottom of the boiler.

[0006] As a further description of the above technical solution:

[0007] The right side of the high-pressure cylinder of the steam turbine is connected to a main steam pipeline, one end of which is connected to a superheated steam system. The bottom end of the high-pressure cylinder of the steam turbine is connected to an extraction steam pipeline, and an isolation valve three is installed on the outside of the extraction steam pipeline. The bottom end of the extraction steam pipeline is connected to a high-pressure heater one, and a high-pressure heater two is installed on the right side of the high-pressure heater one. The top of the high-pressure heater two is connected to an extraction steam pipeline two, and an isolation valve four is installed on the outside of the extraction steam pipeline two. One end of the extraction steam pipeline two is connected to a reheat steam cold section pipeline, and one end of the reheat steam cold section pipeline is connected to the reheat steam system.

[0008] As a further description of the above technical solution:

[0009] The top right side of the steam hot air heat exchanger is connected to the heat exchanger inlet steam extraction pipe. A de-heating and pressure reducing device is installed on the outside of the heat exchanger inlet steam extraction pipe. One end of the heat exchanger inlet steam extraction pipe is connected to the main steam pipe and is equipped with an isolation valve. The top left side of the steam hot air heat exchanger is connected to the hot air pipe, and the other end of the hot air pipe is connected to the air preheater.

[0010] As a further description of the above technical solution:

[0011] The bottom left side of the steam hot air heat exchanger is connected to a hot air pipe, and the other end of the hot air pipe is connected to a wind box and a wind box. The bottom right side of the steam hot air heat exchanger is connected to a heat exchanger outlet steam pipe. A check valve is installed on the outside of the heat exchanger outlet steam pipe, and an isolation valve is installed on the right side of the check valve. One end of the heat exchanger outlet steam pipe is connected to an extraction steam pipe.

[0012] As a further description of the above technical solution:

[0013] The right side of the second high-pressure heater is connected to a connecting pipe, and the left end of the connecting pipe passes through the first high-pressure heater and is connected to the economizer.

[0014] This utility model has the following beneficial effects:

[0015] 1. In this utility model, high-temperature steam is used to heat the hot primary air and hot secondary air at the outlet of the air preheater, which increases the air temperature of the primary air and secondary air of the CFB unit, increases the bed temperature at the bottom of the furnace and the furnace temperature, reduces the carbon content of the slag and the carbon content of the fly ash, and thus improves the boiler combustion efficiency.

[0016] 2. In this utility model, the furnace temperature rises under low load, which effectively solves the key problem of low denitrification efficiency caused by low SNCR reaction temperature under low load. It helps to remove ammonium bisulfate from the heat storage element of the air preheater online and regulate the unit load. At the same time, the CFB unit significantly increases the main steam temperature and reheat steam temperature under low load conditions, effectively reducing the unit's coal consumption for power supply.

[0017] 3. In this utility model, while the CFB unit is operating under low load conditions, it can increase the feedwater temperature at the economizer outlet, thereby further increasing the heat load of the water-cooled wall area and reducing the load of the unit's dry-wet state conversion. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a steam-hot air coupling system for a CFB unit proposed in this utility model.

[0019] Legend:

[0020] 1. Boiler; 2. Separator; 3. Superheated steam system; 4. Reheated steam system; 5. Economizer; 6. Air preheater; 7. Wind box one; 8. Wind box two; 9. Isolation valve one; 10. Desuperheating and pressure reducing device; 11. Steam-hot air heat exchanger; 12. Check valve; 13. Isolation valve two; 14. High-pressure heater one; 15. High-pressure heater two; 16. Isolation valve three; 17. Isolation valve four; 18. High-pressure cylinder of steam turbine; 19. Main steam pipeline; 20. Steam extraction pipeline at the inlet of heat exchanger; 21. Reheat steam cold section pipeline; 22. Extraction steam pipeline one; 23. Steam pipeline at the outlet of heat exchanger; 24. Extraction steam pipeline two; 25. Hot air pipeline one; 26. Hot air pipeline two; 27. Connecting pipe. Detailed Implementation

[0021] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0022] Reference Figure 1 The present invention provides an embodiment of a CFB unit steam-hot-air coupling system, comprising a boiler 1, a steam-hot-air heat exchanger 11, and a high-pressure cylinder 18 of a steam turbine. A separator 2 is connected to the right side of the boiler 1. The separator 2 is equipped with a superheated steam system 3 and a reheated steam system 4. An economizer 5 is provided in the lower middle part of the inner side of the separator 2. An air preheater 6 is provided at the bottom of the inner side of the separator 2. A wind box 7 is connected to the left side of the boiler 1, and a wind box 8 is connected to the bottom of the boiler 1.

[0023] The right side of the high-pressure cylinder 18 of the steam turbine is connected to the main steam pipe 19. One end of the main steam pipe 19 is connected to the superheated steam system 3. The bottom end of the high-pressure cylinder 18 of the steam turbine is connected to the extraction steam pipe 1 22. An isolation valve 3 16 is installed on the outside of the extraction steam pipe 1 22. The bottom end of the extraction steam pipe 1 22 is connected to the high-pressure heater 1 14. The right side of the high-pressure heater 1 14 is connected to the high-pressure heater 2 15. The top of the high-pressure heater 2 15 is connected to the extraction steam pipe 2 24. An isolation valve 4 17 is installed on the outside of the extraction steam pipe 2 24. One end of the extraction steam pipe 2 24 is connected to the reheat steam cold section pipe 21. One end of the reheat steam cold section pipe 21 is connected to the reheat steam system 4. The right side of the high-pressure heater 2 15 is connected to the connecting pipe 27. The left end of the connecting pipe 27 passes through the high-pressure heater 1 14 and is connected to the economizer 5.

[0024] Specifically, during normal operation, boiler 1 utilizes superheated steam or hot-section reheat steam from the CFB unit. This steam undergoes precise conditioning treatment via desuperheating and pressure reduction device 10 to ensure ideal temperature and pressure. The conditioned steam is then introduced to the outlet of air preheater 6 to efficiently heat the primary and secondary air. During this process, the steam, after sufficient heat exchange via steam-hot-air heat exchanger 11, is rationally allocated to the unit's high-pressure heater system, deaerator, or other related thermal systems based on its specific steam parameters. By utilizing this high-temperature steam to further heat the primary and secondary air at the outlet of air preheater 6, the air temperature of the CFB unit's primary and secondary air can be significantly increased. The direct effect of this heating method is to increase the bed temperature at the bottom of the furnace and the overall furnace temperature, thereby effectively reducing the carbon content in the slag and fly ash, and significantly improving the overall combustion efficiency of boiler 1.

[0025] Reference Figure 1The top right side of the steam hot air heat exchanger 11 is connected to the heat exchanger inlet steam extraction pipe 20, which plays a crucial role in transporting high-temperature, high-pressure steam into the heat exchanger. A de-icing and pressure-reducing device 10 is installed on the outside of the heat exchanger inlet steam extraction pipe 20. This device can precisely and in real-time regulate the temperature and pressure of the steam entering the steam hot air heat exchanger 11 according to its operating conditions, ensuring that the steam parameters meet the requirements for safe and stable operation of the heat exchanger and preventing damage to the heat exchanger due to excessively high or low steam parameters. One end of the heat exchanger inlet steam extraction pipe 20 is connected to the main steam pipe 19 and is equipped with an isolation valve 9. The top left side of the steam hot air heat exchanger 11 is connected to a hot air pipe 26, through which hot air... The other end of pipe 26 is connected to air preheater 6. The main steam pipe 19 transports the high-temperature and high-pressure main steam generated by boiler 1, providing a stable steam source for the heat exchanger. The bottom left side of the steam hot air heat exchanger 11 is connected to hot air pipe 25. The other end of hot air pipe 25 is connected to wind box 7 and wind box 8 respectively. The bottom right side of the steam hot air heat exchanger 11 is connected to heat exchanger outlet steam pipe 23. A check valve 12 is installed on the outside of heat exchanger outlet steam pipe 23. An isolation valve 23 is installed on the right side of check valve 12. This valve can cut off the steam flow between heat exchanger inlet steam extraction pipe 20 and main steam pipe 19 when needed. One end of heat exchanger outlet steam pipe 23 is connected to extraction pipe 22.

[0026] Specifically, by heating the primary and secondary air through the superheated steam system 3 or reheat steam, the flow rate of main steam entering the high-pressure cylinder 18 of the turbine is effectively reduced. At the same time, the amount of reheat steam entering the intermediate-pressure cylinder is also significantly reduced. This operating strategy not only improves the temperature level of reheat steam and main steam under low-load conditions, but also further optimizes the thermal performance of the unit, thereby significantly reducing the coal consumption of the unit during power supply, and achieving improved energy utilization efficiency and reduced operating costs.

[0027] Working principle: When boiler 1 is in operation, the superheated steam or hot section reheat steam from the CFB unit is conditioned by the desuperheating and pressure reducing device 10 to heat the hot primary and secondary air at the outlet of the air preheater 6. At this time, the steam after heat exchange in the steam-hot air heat exchanger 11 will enter the unit's high-pressure heater system, deaerator, or other thermal systems according to the steam parameters. The high-temperature steam heats the hot primary and secondary air at the outlet of the air preheater 6, which can increase the air temperature of the CFB unit's primary and secondary air, increase the bed temperature at the bottom of the furnace and the furnace temperature, and reduce the carbon content of the slag. The reduction of carbon content in fly ash improves the combustion efficiency of boiler 1; the increase in furnace temperature under low load effectively solves the key problem of low denitrification efficiency caused by low SNCR reaction temperature under low load, which helps to remove ammonium bisulfate from the heat storage element of air preheater 6 online and regulate the unit load. At the same time, the use of superheated steam system 3 or reheat hot section steam to heat the primary air and secondary air reduces the amount of main steam entering the high-pressure cylinder 18 of the turbine and the amount of reheat steam entering the intermediate-pressure cylinder, thereby increasing the reheat steam temperature and main steam temperature under low load and reducing the unit's coal consumption for power supply.

[0028] Finally, it should be noted that the above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A CFB unit steam hot air coupling system, comprising a boiler (1), a steam hot air heat exchanger (11) and a steam turbine high pressure cylinder (18), characterized in that: The boiler (1) is connected to a separator (2) on the right side. The separator (2) is equipped with a superheated steam system (3) and a reheated steam system (4). An economizer (5) is provided in the lower middle part of the inner side of the separator (2). An air preheater (6) is provided at the bottom of the inner side of the separator (2). The boiler (1) is connected to a first wind box (7) on the left side. The boiler (1) is connected to a second wind box (8) at the bottom.

2. The CFB unit steam hot air coupling system according to claim 1, characterized in that: The right side of the high-pressure cylinder (18) of the steam turbine is connected to the main steam pipe (19), one end of the main steam pipe (19) is connected to the superheated steam system (3), the bottom end of the high-pressure cylinder (18) of the steam turbine is connected to the extraction steam pipe one (22), the outer side of the extraction steam pipe one (22) is provided with the isolation valve three (16), the bottom end of the extraction steam pipe one (22) is connected to the high-pressure heater one (14), the right side of the high-pressure heater one (14) is provided with the high-pressure heater two (15), the top of the high-pressure heater two (15) is connected to the extraction steam pipe two (24), the outer side of the extraction steam pipe two (24) is provided with the isolation valve four (17), one end of the extraction steam pipe two (24) is connected to the reheat steam cold section pipe (21), one end of the reheat steam cold section pipe (21) is connected to the reheat steam system (4).

3. The CFB unit steam hot air coupling system according to claim 1, characterized in that: The top right side of the steam hot air heat exchanger (11) is connected to the heat exchanger inlet steam extraction pipe (20), and a de-heating and pressure reducing device (10) is provided on the outside of the heat exchanger inlet steam extraction pipe (20). One end of the heat exchanger inlet steam extraction pipe (20) is connected to the main steam pipe (19) and is equipped with an isolation valve (9). The top left side of the steam hot air heat exchanger (11) is connected to the hot air pipe (26), and the other end of the hot air pipe (26) is connected to the air preheater (6).

4. The CFB unit steam hot air coupling system according to claim 3, characterized in that: The bottom left side of the steam hot air heat exchanger (11) is connected to a hot air pipe (25), and the other end of the hot air pipe (25) is connected to a wind box (7) and a wind box (8) respectively. The bottom right side of the steam hot air heat exchanger (11) is connected to a heat exchanger outlet steam pipe (23), and a check valve (12) is provided on the outside of the heat exchanger outlet steam pipe (23). An isolation valve (13) is provided on the right side of the check valve (12). One end of the heat exchanger outlet steam pipe (23) is connected to an extraction steam pipe (22).

5. The CFB unit steam hot air coupling system according to claim 2, characterized in that: The right side of the second high-pressure heater (15) is connected to a connecting pipe (27), and the left end of the connecting pipe (27) passes through the first high-pressure heater (14) and is connected to the economizer (5).

Images