JP2002021508A - Condensate supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the corrosion by sulfuric acid in a low temperature part of a steam generator while minimizing the reduction of power generation efficiency when using fuel containing sulfur. SOLUTION: When combustion gas as a heating fluid contains sulfur oxide, a part of condensate from a condensate pump 40 is supplied to a deaerator 28 by bypassing a preheater 26 of an exhaust gas boiler 14 by a bypass pipe passage 54, and condensate circulates into a heat exchanger inlet pipe passage 46 from a heat exchanger outlet pipe passage 47 through a circulation pipe passage 52 so that an inlet temperature to the preheater 26 for condensation is above a predetermined temperature determined by taking a dew point temperature of sulfur oxide into account.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a condensate supply system for supplying condensate from a condenser to a steam generator in a power generation facility including a steam turbine.

[0002]

2. Description of the Related Art When a fuel containing sulfur, typically light oil, is burned, the combustion gas contains sulfur oxides. The temperature of the combustion gas is reduced to the dew point in the portion having the lowest temperature, that is, the first heat exchanger into which the condensate flows, and so-called sulfuric acid corrosion occurs in this portion. In order to prevent this, in the prior art, when a fuel containing sulfur is used, the inflow of condensate into the heat exchanger, which has the lowest temperature, is shut off.

[0003]

However, in such a configuration, there is a problem that the temperature of the steam generator outlet of the exhaust gas as the heating fluid becomes higher than necessary and the power generation efficiency is lowered. The present invention has a technical problem of solving the problems of the conventional technology. When using a fuel containing sulfur, it is possible to prevent sulfuric acid corrosion in a low-temperature portion of a steam generator and to reduce power generation efficiency. The purpose of the present invention is to provide a condensate supply system that prevents as much as possible.

[0004]

According to the present invention, a condenser for a steam turbine is provided to a steam generator comprising a plurality of heat exchangers arranged in series in the flow direction of a heating fluid. In the condensate supply system, the condensate from the condensate pump outlet is provided at the most downstream in the flow direction of the combustion gas in the steam generator. A heat exchanger inlet line to be introduced into the vessel;
The first stage provided between the first stage heat exchanger and the deaerator
A heat exchanger outlet line for introducing condensate from the stage heat exchanger to the deaerator, and a heat exchanger outlet line provided between the heat exchanger inlet line and the heat exchanger outlet line. A bypass pipe for introducing condensate into the deaerator bypassing the first-stage heat exchanger, and provided between the heat exchanger outlet pipe and the heat exchanger inlet pipe; A circulation line for circulating condensed water from a heat exchanger outlet line to the heat exchanger inlet line, wherein a part of the condensate from the condensate pump when the heating fluid contains sulfur oxide. Is supplied to the deaerator by bypassing the first stage heat exchanger by the bypass line, and is returned from the heat exchanger outlet line to the heat exchanger inlet line via the circulation line. By circulating the water, the inlet temperature of the condensate to the first-stage heat exchanger is determined in consideration of the dew point temperature of the sulfur oxide. And gist condensate supply system was set at a predetermined temperature or higher was.

[0005] The power generation equipment may be a combined power generation equipment including a gas turbine and a steam turbine. In this case, the steam generator generates steam by heat exchange with exhaust gas from the gas turbine as a heating fluid. And the first-stage heat exchanger is a preheater of the exhaust gas boiler. Further, the power generation facility may be a power generation facility including a waste incinerator and a steam turbine.
In this case, the steam generator is an exhaust gas boiler that generates steam by heat exchange with exhaust gas from the waste incinerator as a heating fluid, and the first-stage heat exchanger is a preheater of the exhaust gas boiler. is there.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described with reference to FIGS. First, referring to FIG. 2, as an example of a power generation facility to which the condensate supply system according to the present invention can be applied, a combined power generation facility 10 including a gas turbine and a steam turbine (hereinafter simply referred to as a power generation facility 10).
Is shown in the schematic system diagram of FIG. The power generation equipment 10 includes a gas turbine 12 having a compressor 12a, an expander 12b, and a generator 12c connected in a single shaft, an exhaust gas boiler 14 as a steam generator disposed downstream of the gas turbine 12, and an exhaust gas boiler 14 The steam turbine includes a high-pressure steam turbine 30, a medium-pressure steam turbine 32, and a low-pressure steam turbine 34, which are driven by the steam generated in the above, and a generator 36 connected to the steam turbine. Gas turbine 1
The second generator 12c and the generator 36 of the steam turbines 30, 32, 34 may be the same generator. That is, in the present invention, the gas turbine and the steam turbine may have a single-shaft configuration.

The exhaust gas boiler 14 includes a reheater 16, a superheater 18, and a high-pressure steam generator 2 having a high-pressure steam drum 20a.
0, medium-pressure steam generator 2 having medium-pressure steam drum 22a
2. Low-pressure steam generator 2 having low-pressure steam drum 24a
4. It has a plurality of heat exchangers including a preheater 26. The plurality of heat exchangers 16 to 26 are arranged in series in the exhaust gas boiler 14 from upstream to downstream in the flow direction of the exhaust gas as the heating fluid from the gas turbine 12. In the present embodiment, the pre-heater 26 constitutes a first-stage heat exchanger disposed at the most downstream in the flow direction of the heating fluid in the exhaust gas boiler 14.

A condenser 3 is provided at the outlet of the low-pressure steam turbine 34.
8 is provided, and a condenser pump 40 is provided at an outlet of the condenser 38. The condensate pump 40 is connected to the preheater 26 via a heat exchanger inlet line 46, and the preheater 26 is connected to the deaerator 2 via a heat exchanger outlet line 47.
8 is connected.

Next, the condensate supply system according to this embodiment will be described in more detail with reference to FIG. Between the heat exchanger inlet line 46 and the heat exchanger outlet line 47, the condensate from the condensate pump 40 bypasses the preheater 26 and is connected to the deaerator 2.
8 is provided with a flow path sensor 58 and a flow path sensor 5.
A flow regulating valve 56 for controlling the flow rate of the condensate flowing through the bypass conduit 54 to a predetermined value according to the measurement value of 8 is provided. On the other hand, between the heat exchanger outlet pipe 47 and the heat exchanger inlet pipe 46, the heat exchanger outlet pipe 47 is connected to the heat exchanger inlet pipe 4.
A circulation line 52 for circulating the condensate to 6 is provided,
A circulation pump 60 is provided in the circulation line 52. Also, depending on the operating conditions of the power generation equipment 10, the preheater 2
When the steam pressure or steam temperature (that is, condensate temperature) in the deaerator 28 cannot be maintained at a predetermined value only by the heat exchange in Step 6, the low-pressure steam or low-temperature reheat steam to the low-pressure steam turbine 34 is removed as auxiliary steam. An auxiliary steam pipe 48 for supplying to the gasifier 28 is provided.

Hereinafter, the operation of the present embodiment will be described. The air compressed by the compressor 12a is mixed and burned with fuel from a fuel supply source (not shown) in a combustor 12d of the gas turbine 12 to be a high-temperature, high-pressure combustion gas, which is supplied to an expander 12b. The fuel supply source includes at least a device or equipment capable of supplying a fuel containing a sulfur component, for example, light oil. In the present embodiment, a light oil tank,
A light oil supply source including a light oil heating device, a light oil supply pump, etc.,
And a liquefied natural gas supply source including a liquefied natural gas storage tank, a liquefied natural gas evaporator, and a liquefied natural gas supply pump.

The combustion gas supplied to the expander 12b drives the generator 12c while expanding to approximately atmospheric pressure in the expander 12b, and the exhaust gas is exhausted at a reduced temperature and pressure throughout the expansion process. This exhaust gas is supplied to the exhaust gas boiler 14 as a heating fluid via the duct 13 between the expander 12b and the exhaust gas boiler 14. Exhaust gas boiler 14
The exhaust gas supplied to the heat exchanger gradually lowers the temperature through heat exchange with the heat exchangers 16 to 26 and is discharged into the atmosphere from the chimney.

The condensate condensed by the condensate pump 40 is supplied to the preheater 26 through a heat exchanger inlet line 46,
The temperature rises through heat exchange with the exhaust gas and deaerator 2
8. A part of the condensed water deaerated in the deaerator 28 is boosted to a predetermined pressure by a low-pressure boiler feed pump 42 disposed on the outlet side of the deaerator 28, and is supplied as a low-pressure boiler feed to the low-pressure steam generator 24 Low pressure steam drum 24
a. The remaining part of the condensed water deaerated in the deaerator 28 is pressurized to a predetermined pressure by the high-pressure boiler feedwater pump 44 and supplied to the high-pressure steam drum 20a of the high-pressure steam generator 20 as high-pressure boiler feedwater. In the present embodiment, the intermediate-pressure boiler feedwater supplied to the intermediate-pressure steam generator 22 is extracted from an intermediate stage of the high-pressure boiler feedwater pump 44 and supplied to the intermediate-pressure steam drum 22a. It goes without saying that a medium-pressure boiler feed pump (not shown) may be separately provided.

The low-pressure steam generated by the low-pressure steam generator 24 is, for example, a medium-pressure steam turbine 32 and a low-pressure steam turbine 3.
The low-pressure steam turbine 34 is supplied to the low-pressure steam turbine 34 through the connecting pipe 31 between the low-pressure steam turbine 3 and the low-pressure steam turbine 34. The low-pressure steam from the low-pressure steam drum 24 a may be converted into superheated steam before being supplied to the low-pressure steam turbine 34 by a heat exchanger (not shown) provided separately in the exhaust gas boiler 14. The medium-pressure steam generated by the medium-pressure steam generator 22 can be supplied to, for example, the low-temperature reheat steam pipe 15, mixed with the exhaust gas of the high-pressure steam turbine 30, and supplied to the reheater 16. The medium-pressure steam that has become superheated steam in the reheater 16 is passed through the high-temperature reheat steam pipe 17 to the medium-pressure steam turbine 3.
2. The intermediate-pressure steam from the intermediate-pressure steam drum 22a may be converted into superheated steam before being supplied to the low-temperature reheat steam pipe 15 by a heat exchanger (not shown) separately provided in the exhaust gas boiler 14. The high-pressure steam generated by the high-pressure steam generator 20 is supplied from the high-pressure steam drum 20a to the superheater 1
8, and supplied to the high-pressure steam turbine 30.

When a fuel containing sulfur, typically light oil, is burned, the combustion gas contains sulfur oxides. This combustion gas is supplied to the exhaust gas boiler 14 as in this embodiment.
When the temperature of the preheater 26 disposed at the most downstream in the flow direction of the heating fluid in the exhaust gas boiler 14 is low, the temperature of the heating fluid on the outer surface of the preheater 26 decreases to the dew point temperature, and the sulfuric acid corrosion occurs. Occurs. In order to prevent this, in the prior art, a shutoff valve (not shown) is provided in the heat exchanger inlet line 46 and the heat exchanger outlet line 47 connected to the preheater 26, and condensate from the condensate pump 40 is provided. Is supplied directly to the deaerator 28 bypassing the preheater 26. However, such a configuration has a problem that the temperature of the exhaust gas at the outlet of the exhaust gas boiler 14 becomes unnecessarily high, and the power generation efficiency decreases.

On the other hand, if the inlet temperature of the combustion gas to the preheater 26 and the inlet temperature of the condensate to the preheater 26 are determined, the outer surface temperature of the preheater 26 can be obtained from an empirical formula. Therefore, if the outer surface temperature of the preheater 26 is appropriately determined in consideration of the dew point temperature of the combustion gas containing sulfur oxide, the minimum preheater inlet temperature of the condensate required to maintain the temperature can be determined. The bypass flow rate to be circulated through the bypass pipe 26 under certain operating conditions of the power generation facility 10 can be determined in advance by calculation of the heat mass balance based on the above. As already mentioned,
In the present embodiment, a flow sensor 58 is connected to the bypass conduit 56.
And the bypass line 54 according to the measurement value of the flow sensor 58.
A flow control valve 56 for controlling the flow rate of the condensate flowing through the gas to a predetermined value is provided. When the combustion gas as the heating fluid contains sulfur oxide, the flow control valve 56 and the flow rate sensor 58 control the bypass pipe line. The condensate flow rate (bypass flow rate) flowing through the heat exchanger 54 is appropriately determined based on the above calculated value, and the heat exchanger outlet pipe 47 is connected to the heat exchanger inlet pipe 46 via the circulation pipe 52.
By circulating the condensate to the preheater 26
To prevent sulfuric acid corrosion.

As shown in FIG. 1, a temperature sensor 64 is provided in the heat exchanger inlet line 46 on the downstream side of the connection point with the circulation line 52, and based on the measured value of the temperature sensor 64. A controllable flow regulating valve 62 is disposed at the outlet side of the circulation pump 60 in the circulation line 52 so that the inlet temperature of the preheater of the condensate is equal to or higher than the desired temperature determined as described above. May be controlled.

On the other hand, when a fuel that does not contain a sulfur component such as liquefied natural gas is used as the fuel for the gas turbine 12, the above-mentioned sulfuric acid corrosion does not pose a problem, and condensate does not need to bypass the preheater 26. Therefore, the flow regulating valve 56 of the bypass conduit 54 is closed or the minimum flow opening is set. Thus, the power generation facility 10 according to the present embodiment
Thus, appropriate equipment operation can be performed depending on whether the combustion contains sulfur or not.

Having described the preferred embodiment of the invention,
It is obvious to those skilled in the art that the present invention is not limited to this, and various changes and modifications are possible. In the above-described embodiment, the power generation facility 10 is a combined power generation facility including the gas turbine 12 and the steam turbines 30, 32, and 34.
The present invention may be another type of power generation equipment, for example, a power generation equipment including a waste incinerator for burning waste and a steam turbine using a combustion gas generated in the incinerator as a heat source. In such incinerators for waste treatment, the components of the waste to be burned are not constant, and may contain sulfur depending on the type. In these cases,
The invention can be applied particularly advantageously.

In the above-described embodiment, the preheater 26 of the exhaust gas boiler 14 has been described as an example of the first stage heat exchanger. However, the first stage heat exchanger of the present invention generally includes a preheater, a economizer, It may be referred to by the name of economizer, condensate preheater, etc., all of which can be included in the scope of the present invention. In short, the first-stage heat exchanger is a heat exchanger that is arranged at the most downstream in the flow direction of the heating fluid in the steam generator and has the lowest temperature.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a preferred embodiment of a condensate supply system of the present invention.

FIG. 2 is a system diagram showing an example of a power plant to which the condensate supply system of the present invention is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Power generation equipment 12 ... Gas turbine 14 ... Exhaust gas boiler 26 ... Preheater 40 ... Condenser pump 46 ... Heat exchanger inlet pipe 47 ... Heat exchanger outlet pipe 52 ... Circulation pipe 54 ... Bypass pipe 56 ... Bypass pipe Road flow regulating valve 60: Circulation pump

Claims (5)

[Claims] Condensation of the steam turbine to the steam generator of a power generation facility including a steam turbine and a steam generator in which a plurality of heat exchangers are sequentially arranged in series in a flow direction of a heating fluid. In the condensate supply system, the condensate is supplied from a condensate pump by a condensate pump, and the condensate from the condensate pump outlet is disposed in the steam generator at the first stage located at the most downstream in the flow direction of the heating fluid. A heat exchanger inlet line to be introduced into the exchanger; and a first heat exchanger provided between the first stage heat exchanger and the deaerator.
A heat exchanger outlet line for introducing condensate from the stage heat exchanger to the deaerator; and a heat exchanger outlet line provided between the heat exchanger inlet line and the heat exchanger outlet line. A bypass line for introducing condensate to the deaerator, bypassing the first-stage heat exchanger, and provided between the heat exchanger outlet line and the heat exchanger inlet line; A circulation line for circulating condensed water from a heat exchanger outlet line to the heat exchanger inlet line, wherein when the heating fluid contains sulfur oxide, a part of the condensate from the condensate pump Is supplied to the deaerator by bypassing the first stage heat exchanger by the bypass line, and is returned from the heat exchanger outlet line to the heat exchanger inlet line via the circulation line. By circulating water, the inlet temperature of the condensate to the first-stage heat exchanger is determined in consideration of the dew point temperature of the sulfur oxide. Boss was condensate supply system was set at a predetermined temperature or higher. 2. A flow rate sensor, and a flow regulating valve for controlling a flow rate of condensate flowing through the bypass line to a predetermined value in accordance with a measurement value of the flow rate sensor, are provided in the bypass line. The condensate flow to be circulated through the bypass pipe is calculated in advance from the heat mass balance with respect to the operating conditions of the power generation equipment, and the flow control valve is opened so that the measured value of the flow sensor matches the calculation result. The condensate supply system according to claim 1, wherein the degree is controlled. 3. A circulation pump for circulating condensate from the heat exchanger outlet line to the heat exchanger inlet line in the circulation line, and a flow regulating valve provided at an outlet of the circulation pump. Is provided, a temperature sensor is disposed downstream of a connection portion with the circulation pipeline in the heat exchanger inlet pipeline,
3. The temperature of the inlet of the condensate to the first-stage heat exchanger based on a measurement value of the temperature sensor is set to be equal to or higher than a predetermined temperature determined in consideration of a dew point temperature of the sulfur oxide.
3. The condensate supply system according to 1. 4. The power generation facility is a combined power generation facility including a gas turbine and a steam turbine, and the steam generator includes:
An exhaust gas boiler that generates steam by heat exchange with exhaust gas from the gas turbine as a heating fluid, and wherein the first-stage heat exchanger is a preheater of the exhaust gas boiler. Condensate supply system as described. 5. The power generation facility comprising a waste incinerator and a steam turbine, wherein the steam generator generates steam by heat exchange with exhaust gas from the waste incinerator as a heating fluid. 4. The condensate supply system according to claim 1, wherein the first-stage heat exchanger is a pre-heater of the exhaust gas boiler. 5.