JPS60138213A - Composite cycle waste heat recovery power generating plant - Google Patents

Abstract

PURPOSE:To increase an amount of waste heat recovered, by a method wherein a high pressure feed water heater is heated by means of high-temperature high-pressure steam bled from the high pressure stage of a steam turbine, and drain produced therein is fed to a waste heat recovery boiler for evaporation to charge it to the high-pressure stage of the steam turbine. CONSTITUTION:A waste heat recovery boiler 7 of a titled plant is constituted such that a high-pressure steam heating pipe 10, a high-pressure boiler water heating pipe 11, a high-pressure feed water preheating pipe 12, a low-pressure steam heating pipe 13, a low-pressure boiler water heating pipe 14 and a low-pressure feed water preheating pipe 15 are aligned, in order named, from the inlet side, and steam, generated in low-pressure and high-pressure steam drums 17 and 26, is charged to the middle-pressure stage and the high-pressure of a steam turbine 18. In which case, a high-pressure feed water heater 101 is located in a piping 100 running between a high-pressure feed water pump 26 and the high-pressure steam drum 26, and feed water is heated by means of steam bled at A from the high-pressure stage of the steam turbine 18 which serves as a heat source. Drain 102 produced therein is evaporated in a heating pipe 104, and the generated steam is charged to the high pressure side of the steam turbine 18 through a gas liquid separator 105.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a combined cycle waste heat recovery type power plant, and more particularly to a power plant that generates electricity by recovering waste heat from a gas turbine that discharges clean exhaust gas.

[Background of the invention]

Figure 1 shows a typical example of a gas turbine combined cycle power plant using the waste heat recovery method. In FIG. 1, combustion air 1 is supplied to a compressor 2, and the compressed air is supplied to a combustor 3, where it is used to burn fuel 4. Next, the combustion gas is given to a gas turbine 5 to do work, and is discharged as exhaust gas 6 from a chimney (not shown) via a waste heat recovery boiler 7. 29 indicates a generator.

The waste heat recovery boiler 7 is provided with a power generation system that utilizes waste heat contained in the exhaust gas 6 from the gas turbine 5. A well-known waste heat recovery system is the multi-stage pressure Rankine cycle. In this system, steam is generated in the waste heat recovery boiler 7 at a pressure corresponding to the temperature of the exhaust gas gradually decreasing from the inlet side to the outlet side, and the generated steam is input into a turbine stage corresponding to the pressure. This is to drive the motor efficiently. In general, in the case of gas turbines, a two-stage high and low pressure type is considered to be the economical limit. In the example shown in FIG. 1, there are also two stages, one on the high pressure side and one on the low pressure side.

In other words, the systems include a power generation system (hereinafter referred to as high temperature side system) 8 that uses waste heat in the high temperature range in the waste heat recovery boiler 7, and a power generation system (hereinafter referred to as the high temperature side system) that uses waste heat in the low temperature range (
The low-temperature side system) 9 below. In other words, the exergy (defined as mechanical effective work) is high in the high temperature range, and the exergy is low in the low temperature range, so they are converted into useful energy accordingly.

Inside the waste heat recovery boiler 7, from the inlet side to the outlet side (
(from the high temperature range to the low temperature range of the exhaust gas 6) high pressure steam heating pipe 10, high pressure boiler water heating pipe 11, high pressure feed water preheating pipe 12, low pressure steam heating pipe 13, low pressure boiler water heating pipe 14,
Low pressure water supply preheating pipes 15 are arranged in sequence. Note that the low-pressure feed water preheating pipe 15 plays the same role as the low-pressure feed water heater 16 described later, and is unnecessary when using the low-pressure feed water heater t6. may be piped to the low pressure steam drum 17.

Now, the exhaust gas discharged from the steam turbine 18 is transferred to the condenser 1
9, the water is condensed through a condensate pump 20, and then sent to a deaerator 21 through a condensate pump 20.
sent to. The condensate water is heated and deaerated by the air extracted from the middle stage of the steam turbine 18 in the deaerator 21 and sent to the low pressure feed water heater 16 via the low pressure feed water pump 22 . Here, water is supplied to the low pressure steam drum 17 after being preheated by the low pressure feed water heater 16 or by the low pressure feed water preheating pipe 15 as described above. The boiler water in the low pressure steam drum 17 is forcedly circulated and heated by the low pressure boiler water heating pipe 14 via the can water circulation pump 23 .

The low-pressure steam generated in the low-pressure steam drum 17 is heated by the low-pressure steam heating pipe 13 and then introduced into the middle stage of the steam turbine 18 through the pipe 24. On the other hand, the boiler water in the low-pressure steam drum 17 is sent to the high-pressure water preheating pipe 12 via the high-pressure water pump 25, heated, and then supplied to the high-pressure steam drum 26. Boiler water in the high-pressure steam drum 26 is sent to the high-pressure boiler water heating pipe 11 by a canned water circulation pump 27 and is forcedly circulated and heated.

The high-pressure steam generated in the high-pressure steam drum 26 is heated by the high-pressure steam heating pipe 1O, and then introduced into the high-pressure stage of the steam turbine 18 to perform a predetermined work.

The work is converted into electric power by the generator 28 and output.

In a power generation plant using the gas turbine waste heat recovery method as described above, when recovering the sensible heat of clean exhaust gas (natural gas, etc.), the gas outlet temperature in the waste heat recovery boiler 7 is lower than that of dirty gas (heavy oil, etc.). There are no restrictions. Although this is advantageous in terms of waste heat recovery, even if the boiler feed water temperature is increased by installing the low pressure feed water heater 16 or the low pressure feed water preheating pipe 15 as in the conventional method, the amount of recovered heat does not increase, and it is necessary to install the low pressure feed water heater 16 or the low pressure feed water preheating pipe 15. Otherwise, cycle efficiency will not increase. For this reason, even if the gas is clean, increasing the amount of recovered heat (that is, lowering the outlet gas temperature of the waste heat recovery boiler 7) does not necessarily lead to an increase in the power generation output.

[Purpose of the invention]

Therefore, an object of the present invention is to provide a power generation plant that can increase the amount of waste heat recovered from the exhaust gas of a gas turbine using clean gas and increase the power generation output.

[Summary of the invention] Unlike a boiler that burns fuel to produce steam, such as in thermal power generation, a waste heat recovery power plant uses exhaust gas from a gas turbine with a predetermined sensible heat as a heat source to power the waste heat recovery boiler. It consists of a cycle that depends on the temperature drop along the flow path of the exhaust gas.

To this end, we introduced the concept of exergy (mechanical effective work) when converting thermal energy possessed by waste heat into mechanical work, and focused on the fact that exergy is higher in areas with higher temperatures than in areas with lower temperatures. The high temperature (high pressure) of the waste heat recovery power generation plant consists of a two-stage Rankine cycle, high and low.
It can be seen that the amount of steam generated in the side system can be increased.

Therefore, the present invention extracts high-temperature, high-pressure steam from a predetermined extraction point in the high-pressure stage of a steam turbine, and heats the feed water from the low-pressure steam drum to the high-pressure steam drum using a high-pressure feed water heater that uses this turbine extracted air as a heating source. The condensate generated in the high-pressure feed water heater is sent to a heating pipe installed in a predetermined temperature range in the waste heat recovery boiler to vaporize it, and the superheated steam is sent to the turbine at a higher pressure than the extraction point. It is characterized by the fact that the piping is arranged so that it is fed into the paragraph.

[Embodiments of the invention]

Embodiments of the power plant according to the present invention will be described below with reference to the drawings.

FIG. 2 shows an embodiment according to the present invention. In FIG. 2, parts that overlap with those in FIG. 1 are designated by the same reference numerals, and explanations thereof will be omitted. In FIG. 2, there is a high-pressure water heater i in the middle of the piping 100 from the high-pressure water pump 25 to the high-pressure steam drum
01 is provided. This high-pressure feed water heater toi heats the water to be fed to the high-pressure steam drum 26 using the heat possessed by turbine steam extracted from a predetermined extraction point A in the high-pressure stage of the steam turbine 18 as a heat source. High pressure water heater! Drain 102 generated in 01 is sent to a heating pipe 104 via a drain transfer pump 103, vaporized, and sent to a gas-liquid separator 105. The reason why the gas-liquid separator 105 is provided here is to prevent moisture-containing steam from entering the steam turbine +8. The steam exiting the gas-liquid separator 105 is transferred to the extraction point BK piping tO, which is on the higher pressure side than the previous extraction point A.
It is input through S. On the other hand, the drain 106 generated in the gas-liquid separator TO5 passes through the pipe 107 to the high-pressure feed water heater +
It is combined with the drain 102 from 01 and circulated by the drain transfer pump 103.

In this way, the water supplied to the high-pressure steam drum 26 is heated in the high-pressure feed water heater 101 using the heat retained in the turbine bleed air. On the other hand, the drain 102 of the high-pressure feed water heater 101 is vaporized by the heating pipe 104 in the waste heat recovery boiler 7 to produce high-temperature and high-pressure steam, and after separating the gas and liquid (usually through which superheated steam passes), the high-pressure stage is heated. By introducing it to the extraction point B, the amount of steam generated in the high pressure side system 9 can be increased,
Therefore, it becomes possible to effectively convert the energy in the high temperature range within the waste heat recovery boiler 7 into mechanical energy.

FIG. 3 shows heat flow diagrams in the waste heat recovery boiler of the conventional case X (broken line) and the present invention Y (solid line). Here, Ti is the inlet exhaust gas temperature of the waste heat recovery boiler, TO is the outlet exhaust gas temperature in the conventional case, TO/ is the outlet exhaust gas temperature in the case of the present invention,
Tn represents the inlet steam temperature of the high-pressure steam drum, TL represents the exit steam temperature of the low-pressure steam drum, and Tr represents the reheated steam temperature by the heating tube 104, respectively. As can be seen from Fig. 3, the slope of the temperature drop line . Further, straight lines X and Y indicate the temperature drop of the waste heat recovery boiler as the heating side, whereas straight line 2 indicates the temperature drop line of the steam drum or the like as the heated side. The part 21 in this straight line z shows a steep decline in the conventional case (broken line), but does not decline according to the present invention (solid line), which indicates that the amount of recovered exergy is large. It shows.

In the above embodiments, the case of a power generation plant that recovers waste heat from gas turbine exhaust gas has been described, but it goes without saying that it is also possible to apply the present invention to a regeneration reheat cycle in a general thermal power plant or the like.

〔Effect of the invention〕

As described above, according to the present invention, high-temperature and high-pressure steam is extracted from a predetermined extraction point in the high-pressure stage of a steam turbine, and the high-pressure feed water heater uses this turbine extracted air as a heating source to supply water from the low-pressure steam drum to the high-pressure steam drum. On the other hand, condensate generated in the high-pressure feedwater heater is vaporized by a heating pipe installed in the waste heat recovery boiler to produce superheated high-pressure steam and injected into the turbine stage whose pressure is higher than the extraction point. By doing so, it is possible to increase the generation steam cover of the power generation system on the high temperature side, thereby increasing the power generation output.

[Brief explanation of drawings]

Fig. 1 is a system diagram of a conventional gas turbine combined cycle waste heat recovery plant, Fig. 2 is a system diagram showing an embodiment of a power generation plant according to the present invention, and Fig. 3 is a state of waste heat recovery in the case of the present invention and the conventional case. FIG. 1... Combustion air, 2... Compressor, 3...
- Combustor, 4... Fuel, 5... Gas turbine, 6... Exhaust gas, 7... Waste heat recovery boiler, 8... High temperature side system, 9... Low temperature side system, 10. ...High pressure steam heating tube, 17...
Low pressure steam drum, I8...Steam turbine, 19...
Condenser, 25... High pressure feed water pump, 26... High pressure steam drum, 28... Generator, 101... High pressure feed water heater, 102... Drain, 104... Heating tube, 108・
...Piping, A...Bleed point, B...High pressure side bleed point, TO...Temperature of exhaust gas at outlet of waste heat recovery boiler (conventional) T
o'...Exhaust gas temperature at the outlet of the waste heat recovery boiler (this invention)
Agent Tatsuyuki Unuma (and 1 other person)

Claims (1)

[Scope of Claims] A high-temperature side waste heat recovery power generation system in which high-pressure generated steam from a high-pressure steam drum is heated through a high-temperature region in a waste heat recovery boiler and then supplied to a high-pressure stage of a steam turbine; The exhaust gas of the steam turbine is condensed, and from the condensate, generated steam having a relatively lower pressure than the high-pressure generated steam is generated from a low-pressure steam drum, and the low-pressure generated steam is passed through a low-temperature area in the waste heat recovery boiler. a low-temperature side waste heat recovery power generation system configured to heat the water and then supply it to the low-pressure stage of the steam turbine, and to supply boiler water in the low-pressure steam drum to the high-pressure steam drum. In a power generation plant, a high-pressure feed water heater that heats feed water from the low-pressure steam drum to the high-pressure steam drum using high-pressure steam extracted from a predetermined bleed point in the high-pressure stage of the steam turbine as a heat source;
A heating pipe is installed in a predetermined temperature range in the waste heat recovery boiler to heat and vaporize the condensate generated in the high-pressure feed water heater, and A combined cycle waste heat recovery power generation plant characterized by comprising: a piping system for supplying a paragraph;