JPS60162003A - System for recovering waste heat of turbine for driving auxiliary machinery of steam power plant - Google Patents

Abstract

PURPOSE:To greatly enhance the thermal efficiency of a steam powr plant as a whole, by performing the turbine drive (speed control) of auxiliary machinery to save the motive power of the plant, and by recovering the waste latent heat of an auxiliary machinery drive turbine, which would be conventionally abandoned into cooling water. CONSTITUTION:A part of the condensate at the outlet port of a condensate pump 3 is returned to a condensate line (outlet port of a second heater 6) through a boosting pump 28 to recover heat to diminish the quantity of condensate which is sent to heaters 4, 6. As a result, the quantity of bled steam to be consumed to heat the condensate is curtailed so that the quantity of steam for generating electricity can be increased. The thermal efficiency is thus improved. Exhaust gas, which has a temperature of about 140 deg.C and whose pressure is raised through a dust collector 16, an induced draft fan 17 and a pressure-raising fan 18, heats a condensate having a temperature of about 35 deg.C, to about 120 deg.C in a low-level economizer 30. The heat of the exhaust gas is thus recovered into the condensate line. The exhaust gas of about 40 deg.C in a desulfurizer 20 is heated to an anti-white-fuming temperature (about 95 deg.C) by a steam heater 31 and then released into the atmosphere. The waste energy (latent heat in the main) of an induced draft fan drive turbine is thus utilized to heat the exhaust gas.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a recovery system for turbine exhaust heat for driving auxiliary equipment in a steam power plant.

[Background of the invention]

FIGS. 1 and 2 show system configurations according to the prior art.

FIG. 1 shows a normal system configuration in which auxiliary equipment (explained using an induction 7-eye 17 and a booster fan 18 as a representative example) is driven by a motor.

When the auxiliary equipment is driven by a motor, the boiler side (air system, gas system) and turbine side (water supply and condensation system) are completely independent, as shown in FIG.

FIG. 2 shows a typical example of an auxiliary machine in which an induction fan is driven by a condensate turbine.

The exhaust gas of the main turbine 1 exchanges heat with the cooling water in the condenser 2, is cooled and condensed, and is boosted in pressure by the condensate pump 3. ,7.9
The water is heated by the extracted steam and supplied to the deaerator 10.

Feed water degassed in the deaerator 10 by the extracted steam in the extraction line 11 is supplied to the boiler by the feed water pump 12.

On the other hand, in the boiler combustion system, the pressure of the air required for combustion is increased by a pusher 77 (22), preheated by a steam air preheater 23 as needed, and the heat quantity of the exhaust gas is transferred to a regenerative air preheater (1).
5, the heat is collected and supplied to the boiler furnace.

Fuel (coal, oil, gas, etc.) is burned in a boiler furnace, and the heat generates steam, which rotates a turbine and generates electricity.

Even at that stage, the exhaust gas whose temperature has decreased by transferring heat to the feed water and steam through the boiler furnace, superheater, reheater, etc.
The heat is as high as 0.01:', and the amount of heat is used in the regenerative air preheater 15 to heat the combustion air mentioned above.

The outlet gas temperature of the regenerative air preheater 15 is approximately 130 tll.
Although the duct in the gas is removed by the dust collector 16 and the pressure is increased by the induction fan 17 and the pressure booster 18, the temperature is raised again to about 140 t:' and the gas-gas heater 19 will be introduced in

The gas-gas heater 19 is installed to reheat the gas temperature (approximately 45 C) lowered in the desulfurization device (wet type) 20 to a white smoke prevention temperature (approximately 95 C) t for pollution control purposes.

The exhaust gas, from which sulfur oxides are removed in the desulfurization device and heated to a predetermined temperature, is diffused and discharged into the atmosphere through the chimney 21.

The above-mentioned induced fan/17 is connected to the induced fan drive turbine 26.
When driven by the main turbine bleed air (fourth bleed air in this example), the exhaust gas is passed through the turbine exhaust pipe 27.
It is then discharged to the condenser 2.

The exhaust gas from the induced fan-driven turbine can be directly connected to the condenser as described above, or it can be collected as condensed water to the turbine plant through an auxiliary condenser in the middle. The basic system configuration is similar.

In this system (prior art), the exhaust gas of the auxiliary drive turbine (in this example, the induced fan drive turbine) is condensed in the condenser, so the following problems have been identified as issues that need to be solved.

1) Since the exhaust heat amount (latent heat) of the auxiliary drive turbine cannot be recovered in the thermal cycle, the efficiency difference with the main turbine and the thermal efficiency decrease.

2) The improvement in efficiency due to the reduction of throttling loss of dampers etc. by using a turbine drive for the auxiliary fan and controlling the rotation speed, and the reduction of shaft power (internal power) by improving the efficiency of the fan itself, etc., is calculated from the above l) Since the amount of waste is reduced, the amount of overall efficiency improvement is small.

[Purpose of the invention]

The purpose of the present invention is that the conventional auxiliary drive, condensing type turbine discharges its exhaust heat into the cooling water through the condenser, so the efficiency improvement is small and the equipment cost and operating cost are taken into account. By selecting the optimal auxiliary equipment and configuring the heat recovery system, the exhaust latent heat of the auxiliary drive turbine can be effectively used, and the shaft power can be improved by using speed-controlled auxiliary equipment. The object of the present invention is to provide a steam power plant that greatly improves overall thermal efficiency by utilizing the reduction effect.

[Summary of the invention]

Conventionally, turbine-driven auxiliary equipment has been limited to water supply pumps, despite the fact that by controlling the auxiliary equipment at multiple speeds based on the turbine rotation speed, it is possible to significantly reduce the power required. Since the exhaust heat of the condensing turbine for auxiliary equipment, which has lower thermal efficiency than the main turbine, is released into the cooling water through the condenser, there is little improvement in overall thermal efficiency and an increase in equipment costs is taken into consideration. This is due to the low economic evaluation.

The present invention achieves
Focusing on the point that it can improve the efficiency of the heat cycle, as a first step, the boiler exhaust gas calorific value is recovered to the turbine plant side water supply and condensation system, and the exhaust calorific value of the auxiliary drive turbine is transferred to the boiler exhaust gas system, which has become low temperature. By supplying , the temperature of the exhaust gas is maintained at a predetermined level, and the plant inlet and outlet conditions are maintained as a whole, while the thermal efficiency of the steam power plant is significantly improved.

[Embodiments of the invention]

Hereinafter, an embodiment of the present invention will be explained with reference to FIG.

FIG. 3 shows a case where the induction fan 17 is driven by a turbine 26 as a typical example of the auxiliary equipment.

The exhaust gas from the main turbine 1 exchanges heat with cooling water in the condenser 2, is cooled and condensed, and is then pressurized by the condensate pump 3 and heated by heaters 4 and 6.8. Water is supplied to the deaerator 10.

At this time, the low-temperature gas (
In order to raise the temperature of the high temperature gas (approximately 45C) to the white smoke prevention temperature (approximately 95C) for pollution control purposes, the high temperature gas (approximately 140C) at the outlet of the booster fan
In this embodiment, the boiler exhaust gas calorific value, which had been reheated using a regenerative gas-gas heater, is transferred to the low-level economizer 30, which is installed as an alternative heat exchanger, to the condensate pump 3 outlet condenser. Part of the water is passed through the water supply pipe 29 by the boost pump 28, heat is absorbed into the condensate side, and the water is recovered into the condensate system (in this example, the outlet of the second heater 6). With this configuration, the amount of condensate water passed through the heaters 4 and 6 is reduced, and as a result, the amount of extracted air consumed by the first heater 4 and second heater 6 for condensate heating is reduced. The amount of steam used for power generation increases accordingly, improving thermal efficiency.

The condensate temperature at the outlet of the low-level economizer 30 can be adjusted to the condensate system confluence section (in this example, the condensate temperature at the outlet of the second heater 6) by adjusting the flow rate so that the condensate temperature is the same at the outlet downstream of the condensate system (in this example, the condensate temperature at the outlet of the second heater 6). 8, the operating temperature and other conditions of the deaerator 10 side) are maintained approximately the same as in the past.

On the other hand, the boiler combustion system uses a forced fan 22 to increase the pressure of air necessary for combustion, and uses a steam air preheater 2 as necessary.
3 preheats, and then regenerates the heat amount of exhaust gas with air preheater 15
It absorbs heat and is supplied as combustion air into the boiler furnace.

Exhaust gas, which has been reduced to approximately 4000 by heat transfer to feed water and steam in the boiler (furnace, superheater, reheater, etc.), can be used for preheating the combustion air mentioned above by the regenerative air preheater 15. , is the same as the prior art.

After passing through the dust collector 16, the induction fan 17. Boost fan 18
The approximately 140C exhaust gas that has been pressurized is converted into condensate of approximately 35C to approximately 120C by a low-level economizer 30 installed in combination with a steam/gas heater 31 (described later) according to the present invention.
By heating the exhaust gas to a certain temperature (same as the second heater 6 outlet temperature), the amount of heat held in the exhaust gas is recovered to the turbine plant condensate system.

The temperature of the exhaust gas, which has dropped to about 70C due to heat transfer to the condensate system, is further reduced to about 45C by water spraying in the desulfurizer 20, and if it is discharged into the atmosphere as it is, it will become white due to water vapor. Since the smoke will be discharged through the chimney, it will be heated to the white smoke prevention temperature (approximately 95C) using the steam-gas heater 31 installed at the exit of the desulfurization device 20, and then diffused and discharged into the atmosphere through the chimney 21. .

By installing a steam-gas heater 31 in the flue at the outlet of this desulfurization device 20, a low-pressure, low-temperature induced fan-driven turbine 2
By guiding the exhaust gas from No. 6 through the line 27, the energy (mainly latent heat) of this exhaust gas can be effectively utilized for heating the exhaust gas.

Therefore, the exhaust gas of the induced 7-amp drive turbine according to the prior art was discharged into the condenser cooling water, resulting in energy loss, but the above-mentioned low-level economizer 30 and the optimal capacity of the steam-gas heater By combining this and the system, it is possible to recover the heat in the exhaust gas to the turbine plant condensation system, and recover the exhaust latent heat of the induction fan-driven turbine to the smoke inlet exhaust gas side, and the thermal efficiency of the entire plant is r.
i=i L+-+ L FIG. 4 shows a second embodiment of the present invention.

The principle is the same as that shown in Fig. 3, in which the entire amount of heat of the boiler exhaust gas in the low-level economizer 30 is recovered by the four first heaters. It is characterized by a small thermal area.

FIG. 5 shows a third embodiment of the present invention.

The principle is the same as that shown in FIG. 3, but the extracted air from the induction fan-driven turbine 26 (which has a higher pressure than the exhaust gas) is used to heat the steam-gas heater 31 through the line 33, and the exhaust gas is returned to the main turbine for load adjustment. The water is discharged to the water unit 2 or a condenser for an auxiliary turbine installed separately.

FIG. 6 shows a fourth embodiment of the present invention.

The principle is the same as that shown in Fig. 3, but the extracted air (or exhaust air) from the induction fan-driven turbine 26 is guided through a line 33 to the steam-type air preheater 23 for preheating the gay 2 combustion air, and is used as heating steam for the air. It is.

The feature of this system is that in cases where the steam-gas heater 31 exceeds the storage capacity due to the selection of the steam source for the drive turbine 26 or the power of the fan 17, the excess steam can be converted into a steam system. It is intended to be used as heating steam for an air preheater, and in such a case, it is characterized by a large gain in thermal efficiency.

FIG. 7 shows a fifth embodiment of the present invention.

The principle is the same as that shown in Fig. 3, but as a driving steam source for the induced fan drive turbine 26, not only the extracted air from the main turbine 1 but also white can auxiliary steam, auxiliary steam from other units, and in-house boiler generated steam 34 are auxiliary. The steam is introduced from the steam header 35 to the induction fan driven turbine 26 via a turbine drive auxiliary steam pipe 36.

The feature of this embodiment is that the main turbine 1
It is possible to start the induction fan 17 even when there is no bleed air, and it is used in combination with each method of the present invention.

FIG. 8 shows a sixth embodiment of the present invention.

The principle is the same as in Fig. 3, but the drain of the heat exchanger (in this example, the steam-gas heater 31 is shown) is connected to the drain pump 3.
The pressure is increased at step 7, and the heater of the turbine plant side heat cycle (in this example, the first heater 4 is shown) or the condenser 2
It is to be collected. The heat exchanger may be a steam air preheater 23.

The feature of this method is that the condensate drain of the heat exchanger is approximately IQOt.
The purpose is to improve the thermal efficiency by recovering the energy in the cycle when the temperature is around 100.

FIG. 9 shows a seventh embodiment of the present invention.

The principle is the same as that in FIG. 3, but a case is shown in which multiple types of target auxiliary machines are driven by a turbine.

In this example, the induction fan 17 and the booster 7amp 18 are connected to the turbine 2.
The case is shown in which it is driven by 6 and 29, but
The target auxiliary equipment is other auxiliary equipment (for example, push-in 77n 22
) are basically the same.

The feature of this method is that multiple types of auxiliary equipment are driven by turbines, and the effect of the present invention can be maximized.In actual machines, this method will be adopted subject to the optimal combination. Become.

FIG. 1O shows an eighth embodiment of the present invention.

The principle is the same as in FIG. 9, but the auxiliary drive turbine 26.
29 shows a case where there are multiple types of exhaust heat recovery destinations.

In this example, a case is shown in which the steam-gas heater 31 and the steam air preheater 23 are used as recovery destinations, but the recovery destination may also be a heater in a turbine plant or the like.

FIG. 11 shows a ninth embodiment of the present invention.

W, the principle is the same as in Fig. 1O, but the auxiliary drive turbine 2
6.39 When there is insufficient capacity to recover heat from the exhaust gas,
That is, when the amount of exhaust heat from the auxiliary drive turbine is larger than the amount of heat recovery, the equivalent amount of excess heat is recovered to the heater 4, condenser 2, etc. through the spillover pipe 42.

Depending on the configuration and operation of the system in which each of the application examples shown in Figs. Due to the effect of reducing shaft power (in-house power) by converting the auxiliary equipment to turbine drive (speed control) and the heat recovery effect of the exhaust latent heat of the auxiliary equipment drive turbine, the thermal efficiency of the entire plant has been greatly improved (0.5~ o, 7s) improve.

The gain from this improvement in thermal efficiency is equivalent to 200 to 300 million yen per year.

〔Effect of the invention〕

According to the present invention, there are the following effects.

Due to the effect of reducing shaft power (in-house power) by converting the auxiliary equipment to turbine drive (speed control) and the heat recovery effect of exhaust latent heat of the auxiliary equipment drive turbine, which was conventionally released into the cooling water,
The thermal efficiency of the entire plant is greatly improved (0.5-0.7%).

The gain in fuel cost savings due to this improvement in thermal efficiency is approximately 2 to 20% per year.
The amount is equivalent to 300 million yen.

[Brief explanation of the drawing]

Claims (1)

[Scope of Claims] 1. In a steam power plant where the auxiliary equipment of the steam power plant is driven by a steam turbine and the speed is controlled, a low-level economizer installed on the desulfurization equipment inlet side of the D2 exhaust gas flue is used to reduce high temperature. This is an auxiliary drive turbine exhaust heat recovery system for steam power plants, which is characterized by recovering boiler exhaust gas heat to the turbine side heat cycle. λ The auxiliary drive turbine of a steam power plant according to claim 1, wherein the exhaust heat amount of the auxiliary drive turbine is recovered by a steam air preheater provided in the combustion air system of the boiler. Exhaust heat recovery system.