CN104235870A - Condenser dead steam waste heat recovery and energy saving device and energy saving method - Google Patents

Abstract

Condenser waste steam waste heat recovery energy-saving device, including power plant steam turbine exhaust port is cooled by the power plant cooling system, it is characterized in that the circulating water carrying waste steam heat is sent to the cooling tower through the circulating water pump, and the outlet main pipe of the circulating water pump is connected to the branch A part of the circulating water that will be sent to the cooling tower is led to the inlet of the primary fan and the blower in the middle of the boiler through the circulating water branch, where a small intercooling tower connected with the circulating water is established; the inlet of the primary fan and the blower are set in a small On the upper part of the intercooling tower, the fan runs on the upper part to form a negative pressure. The air enters from the bottom of the small intercooling tower, and after heat exchange with the small intercooling tower, hot air is formed. The fan sends the hot air into the furnace, and part of the waste heat is recovered; The circulating water cooled by the intercooling tower is connected to the water inlet pipe of the condenser, and then sent to the condenser to absorb the waste heat of the exhaust steam in the condenser, thereby completing the entire recovery process of exhaust steam and waste heat.

Description

Energy-saving device and energy-saving method for recovering waste heat from exhausted steam in condenser

technical field

The invention relates to an energy-saving device and an energy-saving method for recovering waste heat from exhaust steam of a condenser, in particular to a condenser cooling circulating water system and a boiler air-smoke system in a thermal power plant.

Background technique

During the power generation process of a thermal power plant, the exhausted steam after the steam turbine has done work is discharged into the condenser to condense and release heat. This part of the condensation heat is brought to the cooling tower by the circulating water and directly discharged to the atmosphere. The discharged heat generally accounts for the total input. More than 15% of the energy has caused a huge waste of energy. How to utilize the waste heat discharged to the atmosphere is a difficult problem for thermal power plants today.

Contents of the invention

The main technical problem to be solved by the present invention is to provide an energy-saving device and an energy-saving method for recovering the exhaust heat of the condenser from the cooling circulating water of the condenser. The system is modified accordingly, and the heat originally to be exhausted to the atmosphere is sent into the furnace through the wind and smoke system, and part of the exhaust heat is recovered, so as to improve the comprehensive thermal efficiency of the power plant and reduce the coal consumption of power generation, and multiple units can share a small cooling tower , on the premise of no increase in cost, the energy-saving effect can be doubled.

In order to solve the above-mentioned problems, the technical solution of the present invention is as follows: the energy-saving device for recovering exhaust steam and waste heat of the condenser, including the steam turbine exhaust port of the power plant is cooled by the circulating cooling water system of the power plant, and the circulating water carrying the exhaust steam and waste heat is sent to the cooling system through the circulating water pump. A branch is connected to the outlet main pipe of the circulating water pump, and a part of the circulating water to be sent to the cooling tower is led to the boiler primary fan and the inlet of the blower through the branch, where a small intercooling tower connected to the circulating water is established ( Heat exchange device); the primary air and secondary air inlets of the boiler are set on the upper part of the small intercooling tower, and the fan runs on the upper part to form a negative pressure. The air enters from the bottom of the small intercooling tower and exchanges heat with the internal fins of the small intercooling tower. The hot air is formed, and the fan sends the hot air into the furnace to recover part of the waste heat of the exhaust steam. The water cooled by the small intercooling tower is connected to the circulating water return jellyfish pipe, thereby completing the entire exhaust steam waste heat recovery process;

The method for realizing energy saving by using the above-mentioned energy-saving device comprises the following steps:

1) During summer operation, part of the circulating water carrying condensation heat is directly sent to the small intercooling tower through the branch automatic hydraulic flow adjustment device, and the primary fan and blower operate to absorb the hot air after heat exchange and send it into the furnace. Realize waste heat recovery; the primary fan and blower cool part of the circulating water to lower the temperature of the circulating water, increase the vacuum of the condenser, and improve the efficiency of the unit;

2) During winter operation, under the premise of ensuring safety, the power plant steam turbine moderately increases the operating back pressure of the power plant steam turbine, thereby increasing the condensation temperature of the exhaust steam of the power plant steam turbine in the condenser to meet the return water temperature of the small intercooling tower. Above 40 ℃, to prevent the small intercooling tower from freezing and cracking. Under the premise of ensuring the safe operation of the unit, the primary fan and blower will absorb the hot air after heat exchange and send it into the furnace to realize waste heat recovery;

3) Using the above-mentioned energy-saving device to recover the waste heat of exhaust steam in the condenser of the thermal power plant and the corresponding energy-saving method, the temperature of the air supply can be increased in summer and winter, and the waste heat can be recovered, which improves the combustion efficiency of the boiler and achieves the purpose of saving energy and reducing consumption. Relatively speaking, in summer, the circulating water temperature can be appropriately reduced, the vacuum of the condenser can be increased, and the thermal efficiency of the steam turbine unit can be improved. Combustion efficiency in winter boilers.

The investment and use of the exhaust steam waste heat recovery energy-saving device of the condenser can replace the primary air heater, secondary air heater and other devices under the premise of improving the efficiency of the unit, saving investment costs.

For two units, a small intercooling tower can be shared to save construction cost. the

The energy-saving device for waste heat recovery of exhaust steam can be installed independently, that is, an independent heat exchange device is installed in the condenser to absorb the waste heat of exhaust steam in the condenser, and the circulating water pump will send the water carrying waste heat of exhaust steam to the small cooling tower for heat exchange , the water after heat exchange enters the condenser to absorb the exhaust heat of the condenser, forming a complete cycle.

Description of drawings

Figure 1 is a schematic diagram of the implementation of the exhaust steam waste heat recovery system of the condenser.

Figure 2 is a schematic diagram of the separate layout of the circulating water system of the exhaust steam waste heat recovery device system of the condenser.

In Figure 1, 1 is the low-pressure cylinder, 2 is the condenser, 3 is the circulating water pump, 4 is the outlet main pipe of the circulating water pump, 5 is the cooling tower, 6 is the water inlet pipe of the condenser, 7 is the automatic hydraulic flow adjustment device, 8 is Small cooling tower, 9 is a fan, 10 is a blower, and 11 is a boiler.

In Figure 2, 1 is the low-pressure cylinder, 2 is the condenser, 3 is the circulating water pump, 4 is the outlet main pipe of the circulating water pump, 5 is the cooling tower, 6 is the water inlet pipe of the condenser, 7 is the automatic hydraulic flow adjustment device, 8 is Circulating water pump, 9 is a small cooling tower, 10 is a blower fan, 11 is a primary fan, and 12 is a boiler.

Detailed ways

The circulating water of the small cooling tower is connected to the circulating water of the cooling tower. As shown in Figure 1, the exhausted steam discharged from the low-pressure cylinder 1 is cooled by the circulating water and condenses into a liquid. A vacuum environment is established in the condenser 2, and the circulating water pump 3 will carry The water with exhausted steam and waste heat is sent to the circulating water outlet main pipe 4, and a part of the circulating water outlet main pipe 4 is sent to the cooling tower 5, and a part is sent to the small cooling tower 8 through the automatic hydraulic flow adjustment device 7; it is cooled by the cooling tower 5 The final circulating water is sent to the condenser 2 to continue circulating cooling to keep the condenser vacuum; the circulating water sent to the small cooling tower 8 is cooled by the small cooling tower 8 and then sent to the condenser inlet pipe 6, once The air duct of the fan 9 and the inlet of the air supply fan 10 are set on the upper part of the small cooling tower 8, and the primary fan 9 and the air supply fan 10 run in the inlet air duct to form a negative pressure, and the ambient air is sucked in from the bottom intercooling pipe, thereby realizing cooling The purpose of circulating water to increase the inlet air temperature is to send it into the furnace through the action of the fan, so as to realize the improvement of the operation efficiency of the thermal power plant.

The circulating water of the small cooling tower is arranged separately. As shown in Figure 2, the heat exchange device is arranged on the upper part of the condenser 2 to absorb the waste heat of exhausted steam discharged from the low-pressure cylinder 1. After being adjusted by the automatic hydraulic flow adjustment device 7, it is sent to The small cooling tower 9 is pressurized by the circulating water pump 8 to form the entire waste steam waste heat recovery cycle, and the rest of the waste heat is cooled by the original circulating water cooling system.

The energy-saving effect of adopting the exhaust steam waste heat recovery energy-saving device of the condenser is as follows. Taking a 300MW condensing unit as an example, the annual utilization hours of the unit are 5012 hours (the Electric Regulatory Commission in 2013 the national regional unified adjustment of conventional coal-fired generating units of 6000 kilowatts and the average utilization hours of power generation equipment in power plants above), and the total air volume of primary air and secondary air is calculated with an air intake of 1200 t/h:

1) After adopting the technical transformation of the present invention, for the indirect cooling system (indirect cooling tower) and the direct air cooling system (air cooling island), the primary air and secondary air inlet air temperature can generally be increased by 20°C in summer, and the cooling method of the small cooling tower It belongs to forced air cooling, which increases the heat dissipation area. It can reduce the circulating water temperature and increase the vacuum of the condenser during summer operation. The benefits brought by it can basically be offset by the extension resistance brought by the small cooling tower. Generally, it can be used in winter. The air temperature at the inlet of primary air and secondary air can be increased by 40°C. Generally, the air temperature at the inlet of primary air and secondary air can be increased by 30°C in spring and autumn; in summer, for the wet cooling tower system, the temperature difference between circulating water and ambient temperature is 8- 15 degrees Celsius, the temperature difference is small, and the recoverable heat is less. It can be decided whether to stop operation according to the actual situation. The recovery effect in autumn and winter is not much different from that of the indirect cooling system and the direct air cooling system;

2) With the energy-saving device mentioned above, for the indirect cooling system (indirect cooling tower) and the direct air cooling system (air cooling island), about 24000 MJ of exhaust heat of the condenser can be recovered by the primary air and secondary air every hour in summer, In the first quarter of summer (evenly distributed to the four seasons according to the annual utilization hours), about 30,072,000 MJ of waste steam waste heat of the condenser can be recovered, which is equivalent to saving 1,026 tons of standard coal; the condenser can be recovered by primary air and secondary air every hour in spring and autumn The exhaust steam waste heat is about 36000 MJ, and the exhaust steam waste heat of the condenser can be recovered about 90216000 MJ in spring and autumn, which is equivalent to saving 3079 tons of standard coal; the exhaust steam waste heat of the condenser can be recovered every hour in winter. About 60,144,000 MJ of waste steam waste heat can be recovered from the condenser, which is equivalent to saving 2,052 tons of standard coal, and a total of 6,157 tons of standard coal can be saved per 300,000 units per year; if it is a wet cooling tower system, the waste heat recovery effect in summer is relatively poor. For the northern part of China, such as Xinjiang, where the winter is long, and most of the units that use indirect air-cooling and direct air-cooling systems due to lack of water, the energy-saving effect is better;

3) For the energy-saving device mentioned above, if the two units share a small cooling tower, the energy-saving effect and energy-saving benefits will be doubled without increasing the cost;

4) The above-mentioned energy-saving device can reduce the installation and use of primary air heaters and secondary air heaters.

As mentioned above, the small intercooling tower only needs to have corresponding indirect cooling tube bundles in its layout, and its layout can be in various forms, such as directly leading the circulating water pipe to the fan inlet, and arranging the circulating water heat exchange tube bundle in the corresponding The inlet of the fan plays the role of replacing the heater, and it can also be a small intercooling tower with only bottom heat exchange fins.

In summary, the present invention can bring huge economic and environmental benefits to the enterprise.

Claims (5)

1. Condenser exhaust heat recovery energy-saving device, including the direct connection between the condenser exhaust heat recovery device and the cooling cycle water branch and the independent setting of the condenser exhaust heat recovery device; for the condenser exhaust The waste heat recovery device is directly connected with the cooling circulating water branch, including the steam turbine exhaust port of the power plant for cooling through the cooling system of the power plant. Connect a branch, and the circulating water to be sent to the cooling tower will pass through the circulating water branch, through the automatic hydraulic flow adjustment device, to the boiler primary fan and the air inlet of the blower, where a small intercooling tower connected to the circulating water will be established; The primary fan and blower inlet are set on the upper part of the small intercooling tower. The fan runs on the upper part to form a negative pressure. The air enters from the bottom of the small intercooling tower. After exchanging heat with the intercooling tower, hot air is formed. Part of exhaust steam waste heat; the circulating water cooled by the small inter-cooling tower is connected to the condenser inlet pipe, and then sent to the condenser to absorb the condensation heat of exhaust steam in the condenser, thereby completing the entire exhaust steam waste heat recovery process; For the exhaust steam waste heat recovery device of the condenser, the independent setting includes setting the heat exchange device in the condenser to absorb the waste heat of the exhaust steam in the condenser, and the circulating water that absorbs the waste heat is sent to the small room cooler The tower, after exchanging heat with the air, returns to the condenser to continue the heat exchange. The circulating water pump provides power for the whole cycle. After exchanging heat with the small cooling tower, the hot air is sent to the boiler through the primary fan and the secondary fan, thereby Complete the exhaust steam waste heat recovery process of the entire condenser. 2. The energy-saving device for recovering exhausted steam and waste heat of the condenser as claimed in claim 1, characterized in that: a circulating water flow regulating hydraulic butterfly valve is installed on the branch of the small cooling tower to adjust the flow of the small cooling tower. 3. The energy-saving device for recovering exhausted steam waste heat of the condenser as claimed in claim 1, characterized in that: the small cooling tower has two forms, one is that the direct circulating water branch leads to the fan inlet, and directly connects the primary fan, A heat exchanger with a corresponding heat exchange tube bundle is established at the inlet of the blower to exchange heat with the air; one is to establish a heat exchange tube bundle at the bottom, that is, a small indirect cooling tower, and the primary air and secondary air inlets are set on the upper part of the circular tube bundle. Draw out the hot air after heat exchange. 4. The energy-saving device for recovering exhaust steam and waste heat of the condenser according to claim 1, wherein two or more units can share a small intercooling tower. 5. Utilize the energy-saving method of condenser exhaust steam waste heat recovery energy-saving device as claimed in claim 1, it is characterized in that comprising the following steps: 1) During spring, autumn and summer operation, adjust the flow of circulating water by adjusting the hydraulic butterfly valve, so that the temperature of the return water after circulating through the small cooling tower is close to the return water temperature of the circulating water of the cooling tower. The device can be shut down when the temperature is similar to the return water temperature of the circulating water of the cooling tower; 2) During winter operation, on the premise of ensuring the safe operation of the unit, appropriately increase the pressure of the exhaust back pressure of the steam turbine in the power plant to increase the temperature of the circulating water, adjust the hydraulic butterfly valve to adjust the flow of circulating water, and prevent the intercooling tower from freezing. At this time, the air temperature at the inlet of the fan is relatively increased.