Elastic regenerative system of power station boiler under deep peak regulation condition

Abstract

The utility model discloses a kind of elastic regenerative systems of power plant boiler under depth peak shaving condition, including air heater, air preheater, drain expander and low-temperature coal economizer, the heat medium import of air heater is entered for low-quality steam, the heat medium export of air heater is connected with the import of drain expander, the refrigerant import of air heater is entered for air, the refrigerant export of air heater and the air import of air preheater are connected, the air export of air preheater and power plant boiler are connected, the flue gas import of air preheater and the flue gas export of power plant boiler are connected, the heat medium import of low-temperature coal economizer is connected with the flue gas export of air preheater, the heat medium export of low-temperature coal economizer is used for discharging flue gas, the refrigerant import and refrigerant export of low-temperature coal economizer are water import and water export respectively.The present application uses low-quality steam heat source to make air preheater flue gas temperature rise, reduce the risk of air preheater corrosion, and low-temperature coal economizer can recover part of heat of flue gas discharge.

Description

Technical Field

[0001] This utility model relates to an elastic regenerative system for power plant boilers under deep peak-shaving conditions, and belongs to the technical field. Background Technology

[0002] To absorb the increasing power generation from new energy sources, it is necessary to tap the peak-shaving potential of existing coal-fired power units to improve the flexibility of thermal power plant operation systems. However, during deep peak-shaving operations in power plant boilers, the flue gas temperature often drops below 100℃. This excessively low temperature not only prevents low-temperature economizers from operating frequently but also causes severe condensation in the air preheater, increasing the risk of corrosion, leakage, and ash accumulation, significantly impacting the stable and safe operation of the unit. Existing technologies reduce the corrosion risk of air preheaters under deep peak-shaving conditions by installing air heaters in the duct system; however, the existing air heater system's adjustment methods and control strategies have some shortcomings. 1. The steam side of the heater is equipped with a regulating valve. The outlet air temperature of the heater is controlled by adjusting the steam flow. In actual operation, water hammer causes very severe vibration. 2. The method of using a condensate pump to transport the condensate from the heater to the deaerator is mainly used during the winter when the ambient temperature is low. At this time, there is a large temperature difference in heat transfer between the condensate temperature of the heater and the condensate temperature in the deaerator, which causes a decrease in the thermal efficiency of the unit. 3. When the ambient temperature is higher than the boiler's design inlet air temperature, the operation of the air heater will cause the boiler's flue gas temperature to be too high, reducing the boiler's thermal efficiency. Utility Model Content

[0003] The purpose of this invention is to provide a flexible regenerative heating system for power plant boilers under deep peak shaving conditions, so as to improve boiler thermal efficiency and solve the technical problem of low-temperature corrosion of air preheaters caused by excessively low flue gas temperature.

[0004] This utility model adopts the following technical solution: a power plant boiler elastic regenerative system under deep peak shaving conditions, including a warm air heater, an air preheater, a condensate expansion tank, and a low-temperature economizer. The warm air heater's heat medium inlet supplies low-quality steam, and its heat medium outlet is connected to the inlet of the condensate expansion tank. The warm air heater's refrigerant inlet supplies air, and its refrigerant outlet is connected to the air inlet of the air preheater. The air preheater's air outlet is connected to the power plant boiler, and its flue gas inlet is connected to the flue gas outlet of the power plant boiler. The low-temperature economizer's heat medium inlet is connected to the flue gas outlet of the air preheater, and its heat medium outlet is used to discharge flue gas. The low-temperature economizer's refrigerant inlet and outlet are respectively a water inlet and a water outlet.

[0005] A fan is installed between the refrigerant outlet of the heater and the inlet of the air preheater.

[0006] There are two heaters and two fans. The heat medium inlets of the two heaters are connected in parallel to the low-quality steam supply pipeline, and the heat medium outlets of the two heaters are connected in parallel to the inlet of the condensate expansion tank. The two fans are respectively connected to the refrigerant outlet pipelines of the two heaters, and the air outlets of the two fans are connected to the air preheater.

[0007] The bottom of the hydrophobic expansion container is connected to a discharge port, which is connected to a condenser via a pipeline.

[0008] A water seal is installed on the pipeline between the discharge port and the condenser.

[0009] The heat exchange outlet pipe of the heater is equipped with a first electric control valve, and the refrigerant outlet pipe of the heater is equipped with a first temperature sensor. The first temperature sensor and the first electric control valve are connected by a signal.

[0010] The refrigerant outlet pipe of the low-temperature economizer is equipped with a second electric control valve, and the heat medium outlet pipe of the low-temperature economizer is equipped with a second temperature sensor. The second temperature sensor and the second electric control valve are connected by a signal.

[0011] The beneficial effects of this invention are as follows: Cold air enters the cold side of the air heater as a refrigerant. The cold air absorbs heat from the low-quality steam, which then heats the air and turns into condensate, which flows into the condensate expansion tank. The heated cold air then enters the air preheater and subsequently the power plant boiler system. The flue gas in the boiler system enters the low-temperature economizer, where the feedwater absorbs heat from the flue gas. The increased outlet air temperature of the air preheater leads to an increase in the boiler exhaust temperature. The low-temperature economizer recovers heat from the flue gas, maintaining the boiler exhaust temperature within a set range. This invention utilizes low-quality steam as a heat source to provide heat to the power plant boiler system, increasing the air preheater exhaust temperature and reducing the risk of air preheater corrosion. Furthermore, the low-temperature economizer recovers some of the heat from the exhaust gas, maintaining the exhaust temperature at a suitable level. By adjusting the steam extraction rate on the condensate side of the air heater, the air temperature at the refrigerant outlet of the air heater is changed, thus preventing water hammer vibration and heat transfer temperature differences, and therefore not affecting the system's thermal efficiency.

[0012] In summary, this invention can improve the thermal efficiency of the circulating system, avoid low-temperature corrosion of the air preheater caused by excessively low exhaust gas temperature, expand the range of adjustment flexibility, and improve the economic efficiency of unit operation.

[0013] As a preferred option, installing a water seal between the discharge port and the condenser can eliminate the need for a drain pump, saving equipment and electricity.

[0014] As a preferred embodiment, the piping between the heater and the condensate expansion tank is a steam condensate piping, equipped with a first electrically controlled valve. This valve is interlocked with a first temperature sensor at the refrigerant outlet of the heater, allowing for flexible adjustment of the steam extraction rate. When the outlet air temperature detected by the first temperature sensor is too high, the first electrically controlled valve is adjusted to reduce the steam extraction rate.

[0015] As a preferred option, the second electric control valve at the refrigerant outlet of the low-temperature economizer is interlocked with the second temperature sensor. When the exhaust gas temperature detected by the second temperature sensor is too high, the second electric control valve is adjusted to increase the water supply, thereby maintaining the temperature of the final exhaust gas within the set range. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a power plant boiler elastic regenerative system under deep peak shaving conditions according to an embodiment of this utility model.

[0017] In the diagram: 1-Warm air heater, 1.1-Primary air heater, 1.2-Secondary air heater, 2-Air preheater, 3-Drainage expansion tank, 4-Low temperature economizer, 5-Fan, 5.1-Primary air fan, 5.2-Secondary air fan, 6-Power plant boiler, 7.1-First electric control valve, 7.2-Second electric control valve, 8.1-First temperature sensor, 8.2-Second temperature sensor, 9-Water seal. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0019] like Figure 1 As shown, an embodiment of the flexible regenerative heating system for a power plant boiler under deep peak-shaving conditions according to this utility model includes a heater 1, an air preheater 2, a condensate expansion tank 3, and a low-temperature economizer 4. The heater 1 has a heat transfer medium inlet for low-quality steam, and its heat transfer medium outlet connected to the inlet of the condensate expansion tank 3. The heater 1 has a refrigerant inlet for air, and its refrigerant outlet connected to the air inlet of the air preheater 2. The air outlet of the air preheater 2 is connected to the power plant boiler 6, and its flue gas inlet is connected to the flue gas outlet of the power plant boiler 6. The low-temperature economizer 4 has a heat transfer medium inlet connected to the flue gas outlet of the air preheater 2, and its heat transfer medium outlet is used to discharge flue gas. The refrigerant inlet and outlet of the low-temperature economizer 4 are a water inlet and a water outlet, respectively. A fan 5 is provided between the refrigerant outlet of the heater 1 and the inlet of the air preheater 2.

[0020] In this embodiment, there are two heaters 1 and two fans 5. The heat medium inlets of the two heaters 1 are connected in parallel to the low-quality steam supply pipeline, and the heat medium outlets of the two heaters 1 are connected in parallel to the inlet of the condensate expansion container 3. The two fans 5 are respectively connected to the refrigerant outlet pipelines of the two heaters 1, and the air outlets of the two fans 5 are connected to the air preheater 2. Figure 1 In the middle, the heater and fan located at the top are primary air heater 1.1 and primary air fan 5.1, respectively, and the heater and fan located at the bottom are secondary air heater 1.2 and secondary air fan 5.2, respectively.

[0021] The bottom of the hydrophobic expansion container 3 is connected to a discharge port, which is connected to a condenser via a pipeline. A water seal 9 is installed on the pipeline between the discharge port and the condenser. A first electric control valve 7.1 is installed on the heat medium outlet pipeline of the air heater 1, and a first temperature sensor 8.1 is installed on the refrigerant outlet pipeline of the air heater 1. The first temperature sensor 8.1 is connected to the first electric control valve 7.1 via a signal connection. A second electric control valve 7.2 is installed on the refrigerant outlet pipeline of the low-temperature economizer 4, and a second temperature sensor 8.2 is installed on the heat medium outlet pipeline of the low-temperature economizer 4. The second temperature sensor 8.2 is connected to the second electric control valve 7.2 via a signal connection.

[0022] In this embodiment, under the deep peak-shaving condition, the power plant boiler's elastic regenerative system operates by first introducing cold air into the primary air heater and secondary air heater to absorb heat from the low-quality steam. Once the air heater outlet temperature reaches the set value, the air passes through the primary and secondary air fans and then enters the air preheater. After that, it enters the burner of the power plant boiler system. The flue gas in the power plant boiler system enters the air preheater, where it heats the air before entering the low-temperature economizer, where it transfers heat to the feedwater.

[0023] On the hot side of the heater: low-quality steam heats the air, turning it into condensate which flows into the condensate drain tank. The condensate in the drain tank is then discharged into the condenser. The piping between the heater and the condensate drain tank is a steam condensate drain line, equipped with a first electrically controlled valve. This valve is interlocked with a first temperature sensor at the refrigerant outlet of the heater, allowing for flexible adjustment of the steam extraction rate. When the outlet air temperature detected by the first temperature sensor is too high, the first electrically controlled valve is adjusted to reduce the steam flow.

[0024] Cold side of the low-temperature economizer: The air passing through the air preheater is heated by the air heater, increasing the temperature of the air entering the boiler system. This leads to an increase in the temperature of the flue gas at the outlet, resulting in exhaust heat loss. Therefore, an increase in the outlet air temperature of the air preheater means an increase in boiler exhaust heat loss. However, this loss can be recovered by the low-temperature economizer. The second electric control valve at the refrigerant outlet of the low-temperature economizer is interlocked with the second temperature sensor to maintain the final exhaust gas temperature within the set range. When the exhaust gas temperature detected by the second temperature sensor is too high, the second electric control valve is adjusted to increase the feedwater flow.

[0025] The following is a specific application example: The sixth-stage extraction steam from the turbine of a 2×350MW supercritical steam turbine generator unit is used as the low-quality steam as the heat transfer medium for the air heaters. The pressure is 0.2MPa, and the temperature is 260℃. The primary air volume of the primary air heater is 290310 kg / h, and the secondary air volume of the secondary air heater is 362434 kg / h. The ambient temperature is set to -15℃, the lowest winter temperature in Jiangsu Province. The refrigerant outlet temperature of both the primary and secondary air heaters is set to 35℃. The extraction steam volume of the sixth-stage extraction is indirectly adjusted by regulating the condensate flow rate to ensure the air heater temperature reaches the set value of 35℃. The air heater consumes 26t / h of steam. The exhaust gas temperature at the outlet of the low-temperature economizer is set to 110℃. The exhaust gas temperature is kept constant by adjusting the feedwater flow rate of the low-temperature economizer.

[0026] The embodiments and descriptions above are merely illustrative of the principles of this utility model. Various changes and modifications may be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of this utility model as claimed.

Claims

1. A flexible regenerative heating system for a power plant boiler under deep peak-shaving conditions, characterized in that: It includes a warm air heater, an air preheater, a condensate expansion tank, and a low-temperature economizer. The warm air heater's heat medium inlet supplies low-quality steam, and its heat medium outlet is connected to the inlet of the condensate expansion tank. The warm air heater's refrigerant inlet supplies air, and its refrigerant outlet is connected to the air inlet of the air preheater. The air preheater's air outlet is connected to the power plant boiler, and its flue gas inlet is connected to the flue gas outlet of the power plant boiler. The low-temperature economizer's heat medium inlet is connected to the flue gas outlet of the air preheater, and its heat medium outlet is used to discharge flue gas. The low-temperature economizer's refrigerant inlet and outlet are a water inlet and a water outlet, respectively.

2. The power plant boiler elastic regenerative heating system under deep peak shaving conditions according to claim 1, characterized in that: A fan is installed between the refrigerant outlet of the heater and the inlet of the air preheater.

3. The power plant boiler elastic regenerative heating system under deep peak shaving conditions according to claim 2, characterized in that: There are two heaters and two fans. The heat medium inlets of the two heaters are connected in parallel to the low-quality steam supply pipeline, and the heat medium outlets of the two heaters are connected in parallel to the inlet of the condensate expansion tank. The two fans are respectively connected to the refrigerant outlet pipelines of the two heaters, and the air outlets of the two fans are connected to the air preheater.

4. The power plant boiler elastic regenerative heating system under deep peak shaving conditions according to claim 1, characterized in that: The bottom of the hydrophobic expansion container is connected to a discharge port, which is connected to a condenser via a pipeline.

5. The power plant boiler elastic regenerative heating system under deep peak shaving conditions according to claim 4, characterized in that: A water seal is installed on the pipeline between the discharge port and the condenser.

6. The power plant boiler elastic regenerative system under deep peak-shaving conditions according to claim 1, characterized in that: The heat exchange outlet pipe of the heater is equipped with a first electric control valve, and the refrigerant outlet pipe of the heater is equipped with a first temperature sensor. The first temperature sensor and the first electric control valve are connected by a signal.

7. The power plant boiler elastic regenerative system under deep peak-shaving conditions according to claim 1, characterized in that: The refrigerant outlet pipe of the low-temperature economizer is equipped with a second electric control valve, and the heat medium outlet pipe of the low-temperature economizer is equipped with a second temperature sensor. The second temperature sensor and the second electric control valve are connected by a signal.

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