CN115163221A - Rapid cooling process for gas-steam combined cycle generator set - Google Patents

Abstract

The invention discloses a rapid cooling process for a gas-steam combined cycle generator set, which relates to the technical field of gas-steam combined cycle power generation. In the rapid cooling process of the gas-steam combined cycle generator set of the present invention, while the high disk cools the steam combustion engine, the steam turbine sliding parameter shutdown mode is adopted to reduce its steam parameters, so as to rapidly cool the steam turbine. The temperature drop rate of the metal parts is uniform and controllable, thereby shortening the shutdown cooling time, reducing the maintenance period, and improving the operating utilization rate of the unit; during the 600rpm cooling and rushing process of the gas turbine, the desuperheater in the steam system is activated and the temperature is reduced by decompression. In order to reduce the steam parameters of the flushing steam to the superheated steam temperature under the pressure of 1.4MPa and 1.0MPa successively, there is no need to add a special fast cooling device, which avoids the influence of the reliability of the fast cooling device on the safety of the steam turbine.

Description

A rapid cooling process for gas-steam combined cycle generator set

technical field

The invention relates to the technical field of gas-steam combined cycle power generation, in particular to a rapid cooling process for a gas-steam combined cycle generator set.

Background technique

M701S(DA) type gas-steam combined cycle generator set has a long cooling waiting time after shutdown. Although Mitsubishi's high-disk cooling strategy is used to cool the gas turbine after shutdown, Mitsubishi's cooling strategy is only effective for gas turbines, not for steam turbines. Cooling is ineffective. Because the temperature drop of the gas turbine and the steam turbine is not synchronized, the cooling time of the steam turbine is still very long, which seriously affects the maintenance period of the unit.

In the existing design, as shown in Figure 1, the shutdown cooling process is as follows: first, the gas turbine is reduced to 4.6 MW, and when the metal temperature of the gimbal ring is <430 °C, the generator is disengaged and the gas turbine is stopped. After the gas turbine was stopped for 2 hours, the steam turbine (turbine) was started again by starting the steam, and the gas turbine was cooled by the high plate, and then the gas turbine and steam turbine were stopped to cool down naturally.

SUMMARY OF THE INVENTION

1. The technical problem to be solved by the invention

Aiming at the problems that the temperature of the gas turbine and the steam turbine of the existing steam combined cycle generator set are not synchronized, resulting in a long waiting time for cooling downtime, the present invention proposes a rapid cooling process for the gas-steam combined cycle generator set, which cools the steam gas turbine on a high plate. At the same time, by reducing the steam parameters, the steam turbine is rapidly cooled, thereby shortening the shutdown cooling time, reducing the maintenance period and improving the operating utilization rate of the unit.

2. Technical solutions

In order to achieve the above object, the technical scheme provided by the invention is:

A rapid cooling process for a gas-steam combined cycle generator set. While the high-plate cooling of the steam combustion engine, the steam turbine is used to reduce its steam parameters in a shutdown mode with sliding parameters, so as to rapidly cool the steam turbine. During the cooling process, various metal parts of the steam turbine are used. The temperature drop rate is uniform and controllable, thereby shortening the cooling time of shutdown, reducing the maintenance period and improving the operating utilization rate of the unit.

A further technical solution, the steam turbine cooling specifically includes the following steps:

Step 1. Preliminary cooling: Preliminary cooling is carried out by using sliding parameters to reduce the load. The sliding parameters of the unit are reduced to the minimum load of 4.6MW, the waste heat boiler is depressurized and cooled, and the metal temperature of the steam turbine packing ring drops to 430℃～440℃. Change the time to stop, after the rotor idles stop, immediately put into continuous low-speed cranking for natural cooling for 2 hours;

Step 2. Cooling again: After the low-speed cranking is naturally cooled for 2 hours, the metal temperature of the packing ring of the steam turbine is 410°C to 420°C, and the gas turbine body is cooled immediately by the gas turbine cooling and rushing procedure, and it is cooled to superheat under the pressure of 1.0MPa. shutdown when steam temperature;

Step 3. Deep cooling: connect the compressed air for the instrument through the main steam drain bypass to conduct deep cooling of the steam turbine until the metal temperature of the steam turbine packing ring (the metal temperature of the inner wall of the high-pressure inner cylinder of the steam turbine) drops to 180°C.

In a further technical solution, in step 2, during the cooling and rushing process of the gas turbine at 600 rpm, the desuperheater and the desuperheating pressure reducer in the steam system are activated to reduce the rushing steam parameters to 1.4MPa and 1.0MPa pressures successively. Therefore, there is no need to add a special fast cooling device, which avoids the influence of the reliability of the fast cooling device on the safety of the steam turbine, reduces equipment reinvestment, saves energy, and realizes the rapidity, speed and efficiency of the gas-steam combined cycle generator set. Safe cooling improves the annual utilization rate of the unit and has good economic benefits.

A further technical solution is to start the desuperheater first to reduce the temperature of the rushing steam to the superheated steam temperature under the pressure of 1.4MPa at a temperature drop rate of 0.5～1℃/min, and the superheated steam temperature is 245℃; The pressure reducer reduces the steam parameters to the superheated steam temperature under the pressure of 1.0MPa at a depressurization rate of 0.05～0.1MPa/min and a cooling rate of 0.2～0.5℃/min, and the superheated steam temperature is 230℃, so as to fully Using the principle of stopping the steam turbine with sliding parameters, by reducing the pressure, the required superheated steam at a lower temperature can be obtained, so that the temperature drop rate of each metal part of the steam turbine is uniform and controllable during the cooling process, and the life loss of the steam turbine is not increased. The cooling speed of the unit is greatly reduced, the waiting time for unit maintenance is greatly reduced, and the maintenance period is shortened.

In a further technical solution, in step 3, the cooling rate is 3°C to 4°C/h.

3. Beneficial effects

Adopting the technical scheme provided by the present invention, compared with the prior art, has the following beneficial effects:

(1) In the rapid cooling process of the gas-steam combined cycle generator set of the present invention, the steam turbine is cooled by the high plate, and its steam parameters are reduced by using the steam turbine sliding parameter shutdown mode, so as to rapidly cool the steam turbine, thereby shortening the Stop cooling time, reduce maintenance period, and improve unit operating utilization; make the temperature drop rate of each metal part of the steam turbine uniform and controllable during the cooling process, do not increase the life loss of the steam turbine, speed up the cooling speed of the unit, and greatly reduce the unit The waiting time for maintenance is shortened, and the maintenance period is shortened;

(2) In the rapid cooling process of the gas-steam combined cycle generator set of the present invention, the desuperheater in the steam system is first started to reduce the temperature of the impulsive steam to the superheated steam temperature under the pressure of 1.4MPa; The desuperheating and pressure reducing device is used to reduce the parameters of the impulsive steam to the superheated steam temperature under the pressure of 1.0MPa, so as to obtain the required superheated steam at a lower temperature by reducing the pressure;

(3) The rapid cooling process of the gas-steam combined cycle generator set of the present invention does not require additional special rapid cooling device, avoids the influence of the reliability of the rapid cooling device on the safety of the steam turbine, reduces equipment reinvestment, and saves energy. The rapid and safe cooling of the gas-steam combined cycle generating unit is realized, the annual utilization rate of the unit is improved, and the utility model has good economic benefits.

Description of drawings

Fig. 1 is an existing gas turbine high disk cooling process flow diagram;

FIG. 2 is a flow chart of the rapid cooling process of the gas-steam combined cycle generator set of the present invention.

Detailed ways

In order to further understand the content of the present invention, the present invention is described in detail with reference to the accompanying drawings.

Example 1

A rapid cooling process for a gas-steam combined cycle generator set in this embodiment, as shown in FIG. 2 , is used to cool the steam turbine at the same time as the high disk, and use the steam turbine slip parameter shutdown mode to reduce its steam parameters, so as to quickly cool the steam turbine. During the cooling and cooling process, the temperature drop rate of each metal part of the steam turbine is uniform and controllable, thereby shortening the shutdown cooling time, reducing the maintenance period, and improving the operating utilization rate of the unit.

The steam turbine cooling specifically includes the following steps:

Step 1. Preliminary cooling: Preliminary cooling is carried out by using sliding parameters to reduce the load. The sliding parameters of the unit are reduced to the minimum load of 4.6MW, the waste heat boiler is depressurized and cooled, and the metal temperature of the steam turbine packing ring drops to 430℃～440℃. Change the time to stop, after the rotor idles stop, immediately put into continuous low-speed cranking for natural cooling for 2 hours;

Step 2. Cooling again: After the low-speed cranking is naturally cooled for 2 hours, the metal temperature of the packing ring of the steam turbine is 410°C to 420°C, and the gas turbine body is cooled immediately by the gas turbine cooling and rushing procedure, and it is cooled to superheat under the pressure of 1.0MPa. shutdown when steam temperature;

Step 3. Deep cooling: connect the compressed air for the instrument through the main steam drain bypass to deeply cool the steam turbine. The metal temperature of the inner wall of the inner cylinder) drops to 180 °C.

In this embodiment, compared with the natural cooling time of the metal temperature of the packing ring of the existing steam turbine from 430°C to 180°C is 60 hours, it only takes 25 hours after the fast cooling technology of the present invention is adopted, which is 35 hours earlier than the natural cooling time. Hour.

Calculated on the basis of saving 35 hours for each shutdown and maintenance, the additional power generation is 150,000 kWh/hour, and the electricity price is 0.38 yuan/kWh (outsourced electricity price). The annual additional power generation benefits are:

35 hours × 150,000 degrees / hour × 0.38 yuan / degree = 1.995 million yuan

That is: the annual economic benefit is 1.995 million yuan.

Example 2

A rapid cooling process for a gas-steam combined cycle generator set in this embodiment, the basic structure is the same as that of Embodiment 1, and the difference and improvement are: as shown in FIG. By starting the desuperheater and desuperheater and decompressor in the steam system to reduce the parameters of the rushing steam to the superheated steam temperature under the pressure of 1.4MPa and 1.0MPa successively, there is no need to add a special fast cooling device and avoid fast cooling. The reliability of the device affects the safety of the steam turbine, reduces equipment reinvestment, saves energy, realizes the rapid and safe cooling of the gas-steam combined cycle generator set, improves the annual utilization rate of the unit, and has good economic benefits.

In this embodiment, during the cooling and rushing process of the gas turbine at 600 rpm, the desuperheater is first started to reduce the temperature of the rushing steam to 245°C at a temperature drop rate of 0.5-1°C/min (this temperature is the superheated steam under the pressure of 1.4MPa). Restart the desuperheater and reducer to reduce the steam parameters to 1.0MPa and 230°C (the temperature is 1.0MPa) at a depressurization rate of 0.05-0.1MPa/min and a cooling rate of 0.2-0.5℃/min. The temperature of superheated steam under pressure), so as to make full use of the principle of steam turbine sliding parameter shutdown, to obtain the required superheated steam at a lower temperature by reducing the pressure, so that the temperature drop rate of each metal part of the steam turbine during the cooling process is uniform, Controllable, does not increase the life loss of the steam turbine, accelerates the cooling speed of the unit, greatly reduces the waiting time for the unit maintenance, and shortens the maintenance period.

The present invention and its embodiments have been described above schematically, and the description is not restrictive, and what is shown in the accompanying drawings is only one of the embodiments of the present invention, and the actual structure is not limited thereto. Therefore, if those of ordinary skill in the art are inspired by it, without departing from the purpose of the present invention, any structural modes and embodiments similar to this technical solution are designed without creativity, which shall belong to the protection scope of the present invention. .

Claims (5)

1. A quick cooling process of a gas-steam combined cycle generator set is characterized in that: and simultaneously cooling the steam turbine by adopting a high-disk cooling steam turbine, and reducing the steam parameters of the steam turbine by adopting a steam turbine sliding parameter shutdown mode so as to rapidly cool the steam turbine.

2. The rapid cooling process of the gas-steam combined cycle generator set according to claim 1, characterized in that: the steam turbine cooling specifically comprises the following steps:

step one, primary cooling: adopting a slip parameter load reduction to carry out primary cooling, reducing the slip parameter load of the unit to the lowest load of 4.6MW, reducing the pressure and the temperature of the waste heat boiler, stopping the machine when the metal temperature of a packing ring of the steam turbine is reduced to 430-440 ℃ and is basically unchanged, and immediately putting a continuous low-speed barring gear for natural cooling for 2 hours after the rotor stops idling;

step two, cooling again: naturally cooling the low-speed jigger for 2 hours, then controlling the metal temperature of a packing ring of the steam turbine to be between 410 and 420 ℃, immediately cooling a gas turbine body by adopting a gas turbine cooling and impulsing program, and stopping when the gas turbine body is cooled to the temperature of superheated steam under the pressure of 1.0 MPa;

step three, deep cooling: and (3) connecting compressed air for the instrument to the main steam drainage bypass to deeply cool the steam turbine until the metal temperature of the packing ring of the steam turbine is reduced to 180 ℃.

3. The rapid cooling process of the gas-steam combined cycle generator set according to claim 2, characterized in that: in the second step, in the cooling and rushing process of the gas turbine at 600rpm, the rushing steam parameters are reduced to the temperature of the superheated steam under the pressure of 1.0MPa by starting a desuperheater pressure reducer in the steam system.

4. The rapid cooling process of the gas-steam combined cycle generator set according to claim 3, characterized in that: firstly, starting a desuperheater to reduce the temperature of the rushing steam to the temperature of the superheated steam under the pressure of 1.4MPa at the temperature reduction speed of 0.5-1 ℃/min, wherein the temperature of the superheated steam is 245 ℃; then starting the temperature and pressure reducing device to reduce the temperature of the flush steam to the temperature of the superheated steam under the pressure of 1.0MPa at the pressure reducing speed of 0.05-0.1 MPa/min and the temperature reducing speed of 0.2-0.5 ℃/min, wherein the temperature of the superheated steam is 230 ℃.

5. The rapid cooling process of the gas-steam combined cycle generator set according to claim 2, characterized in that: in the third step, the cooling speed is 3-4 ℃/h.

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