JPH0835404A - Condensed water recirculation heat recovery device for exhaust gas reburn type combined plant - Google Patents

Abstract

(57) [Summary] (Modified) [Object] An object of the present invention is to provide a heat recovery device on a condensate recirculation system in an exhaust gas reburn type combined plant in which a steam turbine plant and a gas turbine plant are combined,
The purpose of the present invention is to provide a condensate recirculation heat quantity recovery device for an exhaust gas re-combustion combined plant, which has excellent economical efficiency and maintainability, by recovering the condensate recirculation heat quantity that was conventionally discharged to the condenser. . [Structure] In order to recover the condensate recirculation heat quantity on the condensate recirculation system 19 which recirculates the condensed water of the low pressure gas heater 7 of the exhaust gas reburn type combined plant to the condensate system on the inlet side of the low pressure gas heater A heat recovery device 24 is installed to recirculate the condensate recirculation heat amount to the boiler intake air after the heat is recovered to the condenser 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recombustion type combined plant, and more particularly to condensate on a condensate recirculation system for recirculating condensed water passing through a low pressure gas heater to a condenser or a condensate system on the inlet side of a low pressure gas heater. The present invention relates to a condensate recirculation heat quantity recovery device for an exhaust gas reburn type combined plant, which is excellent in economy and maintainability by providing a heat recovery device as means for recovering the recirculation heat quantity.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram of a conventional exhaust gas reburn type combined plant.

A gas turbine (compressor 1, combustor 2, gas turbine 3) for driving a generator 4, a forced draft fan (FDF) 20, an air preheater 21, and steam are provided in a combustion air supply system to a boiler 5. The air preheater 23 is provided.

The boiler exhaust gas system has a high-pressure gas heater 6,
A low-pressure gas heater 7 and a chimney 8 are provided. Further, since the air preheater 21 and the steam air preheater 23 are heat exchangers for intake and exhaust of the boiler, they are also equipment of the boiler exhaust gas system.

The steam turbine side cycle is composed of the following: First, as a steam portion, a boiler 5 for converting feed water into steam, a high-pressure steam turbine 9 driven by steam generated in the boiler 5, and an exhaust steam of the high-pressure steam turbine 9 driven by steam reheated in the boiler 5 A low pressure steam turbine 11 driven by the exhaust steam of the pressure steam turbine 10 and the intermediate pressure steam turbine 10. The generator 12 is driven by these steam turbines. Next, in the cycle of the water supply / condensation system, the condenser 13 for condensing the exhaust steam of the low-pressure steam turbine 11, the condensate pump 14 for discharging the condensate of the condenser 13 to the condensate system, the condensate pump Condensate booster pump 26 for boosting the condensate supplied from 14 and condensate booster pump 2
6, the low-pressure feed water heater 15 that heats the condensate supplied from the low-pressure steam turbine 11 by the extraction steam of the low-pressure steam turbine 11, the low-pressure gas heater 7 that exchanges heat with the boiler exhaust installed in parallel with the low-pressure feed water heater 15, the low-pressure feed water heating The degasser 16 that degass the condensate supplied from the device 15 and the low-pressure gas heater 7 with the extracted steam of the intermediate-pressure steam turbine 10, and the condensate degassed by the deaerator 16 is pressurized to the water supply system. Discharge water pump 1
7 and the high-pressure feed water heater 1 for heating the feed water supplied from the feed water pump 17 by the extraction steam of the high-pressure steam turbine 9.
8 and a high-pressure gas heater 6 for exchanging heat with the boiler exhaust gas installed in parallel with the high-pressure feed water heater 18. Further, in the exhaust gas re-combustion type steam combined plant, the condensate is reduced following the load of the steam turbine, but the amount of recovered heat of the low pressure gas heater 7 for recovering the boiler exhaust heat to the condensate is small as shown in FIG. In particular, since it is difficult to recover all the heat to the condensate in the steam turbine low load region, the condensate recirculation system 19 that recirculates the condensate for the surplus heat amount from the outlet of the low pressure gas heater 7 to the condenser 13. In addition, a low pressure gas heater recirculation system 22 for recirculating the outlet condensed water of the low pressure gas heater 7 to the inlet side is provided.

The flow of intake / exhaust of the flue air system of the boiler 5 in the exhaust gas reburn type combined plant of this prior art is as follows.

During the combined operation (gas turbine plant and steam turbine plant operation), the exhaust gas from the gas turbine 3 and F are used as combustion air to the boiler 5.
Supply pushing air from DF20. Since the gas turbine exhaust gas is a high temperature gas, it is combined with the boiler suction air at the outlet of the air preheater 21 and supplied to the boiler 5. Since the outlet gas temperature of the exhaust gas of the boiler 5 is relatively high, the air preheater 21 aims to recover the heat to the boiler intake air, and at the same time, the high pressure gas heater 6 recovers the heat to the feed water. The exhaust gas is condensed by the low-pressure gas heater 7 to recover heat.

On the other hand, when the steam turbine plant is operated independently (the gas turbine plant is stopped and the steam turbine plant is operated), the gas turbine plant is stopped, so that the passing gas amount decreases with respect to the passing air amount of the air preheater 21. However, the exhaust gas of the boiler 5 may be excessively cooled, the outlet gas temperature of the air preheater 21 may be below the water dew point, and the element may be corroded. In order to prevent this, the steam type air preheater 23 aims to recover the heat of the turbine bleed air and the boiler intake air to raise the inlet air temperature of the air preheater 21.

Note that Japanese Patent Application Laid-Open No. 4-209904 and Japanese Patent Application Laid-Open No. 4-234506 are related to the exhaust gas recombustion combined plant.

[0010]

The exhaust gas reburn type combined plant of the prior art has the following problems.

(1) Condensed water decreases following the steam turbine load, but the amount of heat exchanged by the gas heater is small, so the amount of heat that cannot be recovered by the steam turbine plant (excess heat) is Heat is discharged to the condenser by the condensate recirculation system.

(2) In the independent operation of the steam turbine plant, the steam type air preheater is used to recover the heat of the turbine bleed air and the boiler intake air to raise the inlet air temperature of the air preheater, but the turbine bleed air is used. Therefore, the amount of boiler evaporation required to secure the same output increases.

(3) The low temperature gas heater inlet condensate temperature is 35
In order to prevent low temperature corrosion of the low pressure gas heater, the low pressure gas heater recirculation system is required so that the low pressure gas heater outlet condensate is recirculated to the inlet side and the inlet condensate temperature becomes 60 ° C or higher. .

An object of the present invention is to provide a heat recovery device on a condensate recirculation system in an exhaust gas re-combustion type combined plant in which a steam turbine plant and a gas turbine plant are combined, and to recover the heat which was conventionally exhausted to the condenser. An object of the present invention is to provide a condensate recirculation heat quantity recovery device for an exhaust gas reburn type combined plant, which is excellent in economical efficiency and maintainability by collecting the water recirculation heat quantity.

[0015]

The present invention makes it possible to recover the heat of the condensate recirculation heat exhausted to the condenser and solve the problems of the conventional exhaust gas reburn type combined plant. The configuration and means of the present invention are as follows.

(1) When the condensate passing through the low-pressure gas heater is recirculated to the condenser, a heat recovery device is provided on the condensate recirculation system to recover heat to the forced air (boiler intake air) from the FDF. Try.

(2) When the condensate passing through the low-pressure gas heater is recirculated to the condensate system on the inlet side of the low-pressure gas heater, a heat recovery device and, if necessary, a condensate recirculation pump are provided on the condensate recirculation system. Provide heat recovery to the forced air (boiler intake) from the installed FDF.

[0018]

The condensate recirculation heat quantity in the conventional exhaust gas re-combustion combined plant was exhausted to the condenser, but the following effects can be mentioned by the above-mentioned constitution and means.

(1) It is possible to improve the thermal efficiency by utilizing the amount of condensate recirculation heat exhausted to the condenser.

(2) The steam type air preheater for increasing the temperature of the forced air from the FDF can be replaced with the condensate recirculation heat quantity recovery device.

(3) The low pressure gas heater recirculation system for preventing low temperature corrosion of the low pressure gas heater can be replaced with the condensate recirculation system.

(4) It is possible to reduce the capacity of equipment such as an air preheater and an intake / exhaust duct for recovering heat from the boiler intake air and exhaust air.

From the above, it is possible to provide a condensate recirculation heat quantity recovery device for an exhaust gas reburn type combined plant, which is excellent in economic efficiency and maintainability.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

First, as a first embodiment of the present invention, FIG. 1 is a plant system diagram in which the heat of condensate recirculation of an exhaust gas recombustion combined plant is recovered in a boiler intake air and recirculated to a condenser.

The combustion air supply system for the boiler 5 includes a gas turbine (compressor 1, combustor 2, gas turbine 3) for driving the generator 4, a forced draft fan (FDF) 20, an air preheater 21, and a recuperator. A water recirculation heat recovery device 24 is provided. The boiler exhaust gas system includes a high pressure gas heater 6, a low pressure gas heater 7, and a chimney 8.

The cycle on the steam turbine side is composed of the following. First, as a steam portion, a boiler 5 for converting feed water into steam, a high-pressure steam turbine 9 driven by steam generated in the boiler 5, and an exhaust steam of the high-pressure steam turbine 9 driven by steam reheated in the boiler 5 A low pressure steam turbine 11 driven by the exhaust steam of the pressure steam turbine 10 and the intermediate pressure steam turbine 10. The generator 12 is driven by these steam turbines. Next, in the cycle of the water supply / condensation system, the condenser 13 for condensing the exhaust steam of the low-pressure steam turbine 11, the condensate pump 14 for boosting the condensate of the condenser 13 and discharging it to the condensate system, The condensate booster pump 26 for boosting the condensate supplied from the condensate pump 14 and the condensate supplied from the condensate booster pump 26 are supplied to the low-pressure steam turbine 11
Low-pressure feed water heater 15 that is heated by the extracted steam of B, low-pressure gas heater 7 that exchanges heat with the boiler exhaust installed in parallel to low-pressure feed water heater 15, low-pressure feed water heater 15, and recovery supplied from low-pressure gas heater 7. A deaerator 16 that deaerates water with the extracted steam of the medium-pressure steam turbine 10, a water supply pump 17 that pressurizes the condensate deaerated by the deaerator 16 and discharges it to a water supply system, and a water supply pump 17 High-pressure feed water heater 18 for heating the supplied feed water by extraction steam of high-pressure steam turbine 9, high-pressure gas heater 6 for exchanging heat with boiler exhaust installed in parallel to high-pressure feed water heater 18, and outlet recovery of low-pressure gas heater 7. A low pressure gas heater recirculation system 22 for recirculating water to the inlet side is provided. Further, a condensate recirculation system 19 for recirculating the condensate for the surplus heat quantity from the outlet of the low-pressure gas heater 7 to the condenser 13, and a condensate recirculation heat quantity recovery device 24 on the condensate recirculation system 19.

According to this configuration, the amount of condensate recirculation heat that was conventionally exhausted to the condenser 13 is recovered to the boiler intake air, but the low pressure gas heater 7 and the air preheater 21 are installed near each other. Therefore, as a result, it is considered that there is no particular problem with the piping arrangement between the boiler intake system from the FDF 20 and the condensate recirculation system from the outlet side of the low-pressure gas heater 7. Next, FIG. 2 shows, as a second embodiment of the present invention, a plant system diagram in which the amount of condensate recirculation heat of an exhaust gas recombustion combined plant is recovered in the boiler intake air and recirculated to the outlet condensate of the condensate pump 14. Is.

Conventionally, the condensate pump 14 is used for the condensate recirculation flow rate.
It is necessary to increase the shaft power of the condensate pump 14 to operate, but with this configuration, the condensate pump shaft power can be reduced because the recirculation destination is the condensate at the outlet of the condensate pump 14.

Next, referring to FIG. 3, as Embodiment 3 of the present invention, the amount of condensate recirculation heat of an exhaust gas recombustion combined plant is recovered to the boiler intake air, and the inlet condensate of the low pressure gas heater 7 and the low pressure feed water heater 15 are used. 2 is a system diagram of a plant recirculated to the inlet condensate of the plant.

According to this configuration, the amount of condensate recirculation heat that has been conventionally exhausted to the condenser 13 is intended to be recovered in the boiler intake air. However, the low pressure gas heater for low temperature corrosion prevention of the low pressure gas heater 7 is used. Instead of the recirculation system, a condensate recirculation pump is installed in the condensate recirculation system, and a part of the condensate recirculation flow rate is heated to the boiler intake air so that the condensate temperature at the inlet of the low-pressure gas heater 7 becomes 60 ° C or higher. Before the recovery, it is branched and recirculated to the inlet side condensate of the low pressure gas heater 7. At the same time, the remaining condensate recirculation flow rate is recovered to the boiler intake air and then recirculated to the inlet side of the low pressure feed water heater 15. is there.

[0032]

As described above, the first embodiment of the present invention is described.
According to the above, a heat quantity recovery device was installed in the condensate recirculation system of the exhaust gas re-combustion combined plant to improve the thermal efficiency of the plant by utilizing the heat quantity of condensate recirculation exhausted to the conventional condenser. It becomes possible. Also, FD
Since it is not necessary to install a steam type air preheater for increasing the temperature of the forced air from F, it is possible to increase the generator output for the same boiler evaporation amount during the steam turbine single operation.
Furthermore, the capacity of the equipment such as the air preheater and the intake / exhaust duct for recovering the heat of the boiler intake air and exhaust gas can be reduced.

The second embodiment also has the same effect as that of the first embodiment, and since the condensate recirculation system is recirculated to the condensate pump outlet, the condensate pump shaft power can be reduced.

The third embodiment has the same effect as that of the first embodiment, and the low temperature corrosion of the low pressure gas heater can be prevented by the condensate recirculation system.

[Brief description of drawings]

FIG. 1 is a plant system diagram showing Example 1 of an exhaust gas re-combustion combined plant according to the present invention.

FIG. 2 is a plant system diagram showing a second embodiment of an exhaust gas re-combustion combined plant according to the present invention.

FIG. 3 is a plant system diagram showing Example 3 of an exhaust gas re-combustion combined plant according to the present invention.

FIG. 4 is a system diagram of a conventional exhaust gas reburn type combined plant.

FIG. 5 is a characteristic diagram of a low-pressure gas heater exchange heat quantity of a conventional exhaust gas reburn type combined plant.

[Explanation of symbols]

1 ... Compressor, 2 ... Combustor, 3 ... Gas turbine, 4, 12
... Generator, 5 ... Boiler, 6 ... High pressure gas heater, 7 ... Low pressure gas heater, 8 ... Chimney, 9 ... High pressure steam turbine, 10 ...
Medium-pressure steam turbine, 11 ... Low-pressure steam turbine, 13 ... Condenser, 14 ... Condensate pump, 15 ... Low-pressure feed water heater, 16
… Deaerator, 17… Water pump, 18… High-pressure water heater,
19 ... Condensate recirculation system, 20 ... Push-in fan (FD
F), 21 ... Air preheater, 22 ... Low pressure gas heater recirculation system, 23 ... Steam type air preheater, 24 ... Condensate recirculation heat recovery device, 25 ... Condensate recirculation pump, 26 ... Condensate booster pump.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mikio Okada 3-2-1, Sachimachi, Hitachi City, Ibaraki Prefecture Hitachi Engineering Co., Ltd. (72) Inventor Tetsuzo Kuribayashi 2-3-2, Sachimachi, Hitachi City, Ibaraki Prefecture No. 1 within Hitachi Engineering Co., Ltd.

Claims (1)

[Claims] 1. A low-pressure gas heater that uses both the exhaust gas of a gas turbine and the atmosphere as boiler combustion air, and recovers the exhaust heat of the boiler into condensate, and the condensate passing through the low-pressure gas heater is a condenser or a low-pressure gas heater inlet. In the exhaust gas reburn type combined plant that has a condensate recirculation system that recirculates to the condensate system on the other side, a heat recovery device is installed on the condensate recirculation system as a means to recover the condensate recirculation heat quantity. Condensed water recirculation heat recovery device for an exhaust gas reburn type combined plant.