Steam system for starting steam turbine in hot state and extremely hot state

Abstract

The invention relates to the technical field, and discloses a steam system for starting a steam turbine in a hot state and an extremely hot state, the steam system comprises a boiler and a cylinder, and the boiler is connected with the cylinder through a main steam pipeline; the steam system further comprises a surface type heat exchanger, the main steam pipeline is connected with a shell side inlet of the surface type heat exchanger through a first bypass pipeline, and the main steam pipeline is connected with a pipe side inlet of the surface type heat exchanger through a second bypass pipeline. And a shell side outlet of the surface heat exchanger is connected with the main steam pipeline through a steam supply pipeline. According to the invention, the temperature of steam entering the cylinder when the unit is started in a hot state or an extremely hot state can be increased, and the influence on the normal operation of the boiler can be reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steam turbine, in particular to a steam system for hot or extremely hot state start-up of steam turbine. BACKGROUND

[0002] When the steam turbine is started up in hot or extremely hot state, the steam entering the cylinder also needs high temperature because the temperature of the cylinder is high. If the temperature of the steam is low, the cylinder will be partially cooled, which will cause the expansion of the cylinder and the rotor to be inconsistent, and cause problems such as dynamic and static friction and vibration of the unit. Therefore, in general, the temperature of the steam is suggested to be at least 5-10℃ higher than the temperature of the cylinder.

[0003] For the super-high pressure and medium temperature waste power generating unit, the hot state start-up mainly occurs in the condition of stopping the machine but not stopping the furnace. Since the waste is still normally treated, the load of the boiler will be relatively high. Taking the design with common rated parameters of 13.2MPa.a and 445℃ as an example, the pressure in the cylinder is considered as 0.1MPa.a. According to the throttling effect, the temperature of the steam of this parameter will be reduced to about 350℃ after entering the cylinder, and the temperature of the cylinder is about 390℃ when the unit is started up in hot state. It can be seen that the temperature of the steam entering the cylinder is much lower than the temperature of the cylinder, which is not conducive to the smooth start-up of the unit.

[0004] In view of the above technical problems, the current method is to reduce the steam pressure and increase the superheat degree to increase the temperature of the steam entering the cylinder. Taking the cylinder pressure of 0.1MPa.a and the steam temperature of 395℃ as an example, in order to realize this condition, the steam parameters need to be adjusted to 7.48MPa.a and 445℃. However, due to the combustion characteristics of the waste, if the steam parameters at the outlet of the waste furnace are reduced, the emission of polluting gases in the flue gas may exceed the standard, which does not meet the environmental protection requirements. In addition, it will also reduce the load of the boiler and affect the normal treatment of the waste. SUMMARY

[0005] The technical purpose of the present application is to provide a steam system for hot or extremely hot state start-up of steam turbine, which can increase the temperature of the steam entering the cylinder when the unit is started up in hot or extremely hot state, and reduce the influence on the normal operation of the boiler.

[0006] The technical solution adopted by the present application is as follows: A steam system for hot or extremely hot state start-up of steam turbine, the steam system comprising a boiler and a cylinder, the boiler being connected with the cylinder through a main steam pipeline; The steam system further comprises a surface heat exchanger, the main steam pipeline being connected with the shell side inlet of the surface heat exchanger through a first bypass pipeline, the main steam pipeline being connected with the tube side inlet of the surface heat exchanger through a second bypass pipeline, and the shell side outlet of the surface heat exchanger being connected with the main steam pipeline through a steam supply pipeline.

[0007] The above technical measures set the surface heat exchanger, when the steam turbine is started, the steam generated by the boiler is divided into two streams by the first bypass and the second bypass, and enters the shell side and the tube side of the surface heat exchanger respectively, so that the two streams exchange heat in the surface heat exchanger, and convert low-pressure and high-temperature steam, thereby increasing the steam temperature entering the cylinder, meeting the requirements of starting the unit in hot state and extremely hot state, and at the same time, the boiler does not need to be operated at reduced load and reduced parameter, thereby reducing the influence on the normal operation of the boiler.

[0008] Further, the steam system further comprises a first desuperheater, and the main steam pipeline is connected with the first desuperheater through a third bypass pipeline.

[0009] The above technical measures set the first desuperheater, and the first desuperheater is connected with the boiler through the third bypass pipeline, so that in the case of shutdown without stopping the boiler, the excess steam generated by the boiler can be transported to the first desuperheater through the main steam pipeline and the third bypass pipeline, and the excess steam is discharged after being cooled.

[0010] Further, the third bypass pipeline is provided with a first regulating valve.

[0011] The above technical measures set the first regulating valve to adjust the steam flow of the third bypass pipeline.

[0012] Further, the steam supply pipeline is connected with the first desuperheater through a desuperheating pipeline.

[0013] The above technical measures set the desuperheating pipeline, so that the excess steam discharged from the shell side of the surface heat exchanger can enter the first desuperheater, and the overpressure of the steam supply pipeline is avoided.

[0014] Further, the desuperheating pipeline is provided with a second regulating valve.

[0015] The above technical measures set the second regulating valve to adjust the steam flow of the desuperheating pipeline, and the discharge amount of the excess steam can be adjusted according to the actual demand.

[0016] Further, the main steam pipeline is sequentially provided with a third regulating valve, a main steam valve and a main steam regulating valve. The connection position of the steam supply pipeline and the main steam pipeline is located between the third regulating valve and the main steam valve.

[0017] The above technical measures set the third regulating valve to adjust the steam flow of the main steam pipeline.

[0018] Further, the steam supply pipeline is provided with a check valve.

[0019] The above technical measures prevent steam backflow by setting the check valve, and prevent steam in the main steam pipeline from flowing into the desuperheating pipeline through the steam supply pipeline.

[0020] Further, the steam system further comprises a condenser, and a high-pressure drain tank is connected to the pipe side outlet of the surface heat exchanger through a drain pipe, and the high-pressure drain tank is connected to the condenser.

[0021] The above technical measures collect water on the pipe side of the surface heat exchanger through the high-pressure drain tank, flash and cool, and then send to the condenser, so as to realize resource recycling.

[0022] Further, the first bypass pipeline is provided with a fourth regulating valve.

[0023] The above technical measures realize the regulation of the steam flow of the first bypass pipeline by setting the fourth regulating valve.

[0024] Further, the second bypass pipeline is provided with a fifth regulating valve.

[0025] The above technical measures realize the regulation of the steam flow of the second bypass pipeline by setting the fifth regulating valve.

[0026] One or more technical solutions provided by the present application have at least the following technical effects or advantages: The present application sets the surface heat exchanger, when the steam turbine is started, the steam generated by the boiler is divided into two streams by the first bypass and the second bypass, and enters the shell side and the pipe side of the surface heat exchanger respectively, so that the two streams of steam exchange heat in the surface heat exchanger, and convert low-pressure and high-temperature steam, so as to improve the steam temperature entering the cylinder, meet the requirements of the unit in hot state and extremely hot state, and at the same time, the boiler does not need to be operated in load reduction and parameter reduction, so as to reduce the influence on the normal operation of the boiler. BRIEF DESCRIPTION OF DRAWINGS

[0027] The accompanying drawings described herein are used to provide further understanding of the embodiments of the present application, and form a part of the present application, and do not constitute a limitation on the embodiments of the present application; Figure 1 is a structural schematic diagram of the present application; Among them, 1-boiler; 2-cylinder; 3-main steam pipeline; 4-surface heat exchanger; 5-first bypass pipeline; 6-second bypass pipeline; 7-steam supply pipeline; 8-first-stage desuperheater; 9-third bypass pipeline; 10-first regulating valve; 11-desuperheating pipeline; 12-second regulating valve; 13-third regulating valve; 14-main steam valve; 15-main steam regulating valve; 16-check valve; 17-condenser; 18-drain pipe; 19-high-pressure drain tank; 20-fourth regulating valve; 21-fifth regulating valve. DETAILED DESCRIPTION

[0028] In order to enable a more complete understanding of the above-mentioned objects, features and advantages of the present application, the application will be described in further detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other in the case of no conflict.

[0029] In the following description, a large number of specific details are set forth in order to facilitate a thorough understanding of the present application, however, the present application can also be implemented in other manners different from those described herein within the scope of the present application, and therefore, the protective scope of the present application is not limited to the specific embodiments disclosed below.

[0030] In the embodiments, the first, second, third, fourth, and the like are merely used for distinguishing different components.

[0031] With reference to Figure 1 The present embodiment provides a steam system for starting a turbine in a hot state or an extremely hot state, which comprises a boiler 1 and a cylinder 2. The boiler 1 is connected to the cylinder 2 through a main steam pipeline 3. The cylinder 2 refers to a high-pressure cylinder of a turbine.

[0032] The steam system further comprises a surface heat exchanger 4. The main steam pipeline 3 is connected to a shell side inlet of the surface heat exchanger 4 through a first bypass pipeline 5. The main steam pipeline 3 is connected to a tube side inlet of the surface heat exchanger 4 through a second bypass pipeline 6. A shell side outlet of the surface heat exchanger 4 is connected to the main steam pipeline 3 through a steam supply pipeline 7.

[0033] The first bypass pipeline 5 is provided with a fourth regulating valve 20. The second bypass pipeline 6 is provided with a fifth regulating valve 21.

[0034] The steam system further comprises a first desuperheater 8. The main steam pipeline 3 is connected to the first desuperheater 8 through a third bypass pipeline 9.

[0035] The third bypass pipeline 9 is provided with a first regulating valve 10.

[0036] The steam supply pipeline 7 is connected to the first desuperheater 8 through a desuperheating pipeline 11.

[0037] The desuperheating pipeline 11 is provided with a second regulating valve 12.

[0038] The main steam pipeline 3 is sequentially provided with a third regulating valve 13, a main steam valve 14, and a main steam regulating valve 15. The connection position of the steam supply pipeline 7 and the main steam pipeline 3 is located between the third regulating valve 13 and the main steam valve 14.

[0039] The steam supply pipeline 7 is provided with a check valve 16.

[0040] The steam system further comprises a condenser 17, and the pipe side outlet of the surface heat exchanger 4 is connected with a high pressure drain tank 19 through a drain pipe 18, and the high pressure drain tank 19 is connected with the condenser 17.

[0041] Taking the steam parameter 13.2 MPa.a, 445℃ at the outlet of the boiler 1 as an example, in the condition of shutdown without stopping the boiler, the second regulating valve 12, the third regulating valve 13, the fourth regulating valve 20, the fifth regulating valve 21, the main steam valve 14 and the main steam regulating valve 15 are closed, and the first regulating valve 10 is fully opened, so that the steam generated by the boiler 1 is all delivered to the first stage desuperheater 8 through the third bypass pipeline 9.

[0042] When the steam turbine is ready to start, the second regulating valve 12 is fully opened, the first regulating valve 10 is gradually closed, and the fourth regulating valve 20 and the fifth regulating valve 21 are gradually opened. The adjusting logic of the fourth regulating valve 20 is to control the steam pressure at the shell side outlet of the surface heat exchanger 4 to be 2.0±0.2 MPa.a, and the adjusting logic of the fifth regulating valve 21 is to control the steam temperature at the shell side outlet of the surface heat exchanger 4 to be 430±5℃. According to the above adjusting logic, the fourth regulating valve 20 and the fifth regulating valve 21 are adjusted, and the first regulating valve 10 is gradually closed until the first regulating valve 10 is fully closed, so that the high superheat steam with the pressure of 2.0 MPa.a and the temperature of 430℃ is obtained, which can be used for hot state or extremely hot state start. The second regulating valve 12 is gradually closed, the main steam valve 14 and the main steam regulating valve 15 are opened, the high superheat steam enters the steam cylinder 2 through the steam supply pipeline 7, and the start of the steam turbine is realized with 3% to 5% load. The fourth regulating valve 20 is adjusted so that the steam pressure at the shell side outlet of the surface heat exchanger 4 is increased by 1 MPa.a, the fifth regulating valve 21 is adjusted so that the steam temperature at the shell side outlet of the surface heat exchanger 4 is kept at 430±5℃, then the second regulating valve 12 is gradually closed, the unit load is increased by 10%, and the adjustment of the fourth regulating valve 20 and the fifth regulating valve 21 and the closing of the second regulating valve 12 are repeated until the steam pressure at the shell side outlet of the surface heat exchanger 4 reaches 8 MPa.a and the unit load reaches about 65% of the rated load. The third regulating valve 13 is gradually opened. Since the resistance of the main steam pipeline 3 is much smaller than that of the first bypass pipeline 5 and the second bypass pipeline 6, a large amount of steam generated by the boiler 1 enters the steam cylinder 2 from the main steam pipeline 3, and since the steam pressure at the outlet of the third regulating valve 13 is higher than that at the shell side outlet of the surface heat exchanger 4, the steam flow entering the steam cylinder 2 is increased, so that the unit load is increased. Under the condition of keeping the unit load increasing rate at 1.5 to 2.0 MW / min, the third regulating valve 13 is gradually opened until the third regulating valve 13 is fully opened, then the second regulating valve 12, the fourth regulating valve 20 and the fifth regulating valve 21 are closed, so that the steam turbine is supplied with steam from the boiler, and the hot state or extremely hot state start is completed. Then, the main steam valve 14 and the main steam regulating valve 15 are adjusted according to the conventional operation, and the unit load is brought to the target load.

[0043] For other parameters of the unit, the recommended steam parameters for starting and rotating the unit can be selected according to Table 1, as shown below. For other parameters of the unit, the steam parameters for increasing load can be considered by reducing the rated main steam temperature by 10-15°C.

[0044] The steam system in the embodiment mainly applies to ultra-high pressure waste power generation, and is also applicable to other steam turbine scenes with main steam parameters presenting the characteristics of "high pressure and low temperature".

[0045] Although the preferred embodiments of the present application have been described, those skilled in the art who, once aware of the basic inventive concept, can make further changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0046] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application also intends to include these modifications and variations.

Claims

1. A steam system for hot and super-hot state starting of a steam turbine, the steam system comprising a boiler (1) and a cylinder (2), the boiler (1) being connected to the cylinder (2) through a main steam pipe (3); characterized in that: the steam system further comprises a surface heat exchanger (4), the main steam pipe (3) being connected to a shell side inlet of the surface heat exchanger (4) through a first bypass pipe (5), the main steam pipe (3) being connected to a tube side inlet of the surface heat exchanger (4) through a second bypass pipe (6), and a shell side outlet of the surface heat exchanger (4) being connected to the main steam pipe (3) through a steam supply pipe (7).

2. The steam system for hot and super-hot state starting of a steam turbine according to claim 1, characterized in that: the steam system further comprises a first desuperheater (8), the main steam pipe (3) being connected to the first desuperheater (8) through a third bypass pipe (9).

3. The steam system for hot and super-hot state starting of a steam turbine according to claim 2, characterized in that: a first regulating valve (10) is arranged on the third bypass pipe (9).

4. The steam system for hot and super-hot state starting of a steam turbine according to claim 2, characterized in that: the steam supply pipe (7) is connected to the first desuperheater (8) through a desuperheating pipe (11).

5. The steam system for hot and super-hot state starting of a steam turbine according to claim 4, characterized in that: a second regulating valve (12) is arranged on the desuperheating pipe (11).

6. The steam system for hot and super-hot state starting of a steam turbine according to claim 1, characterized in that: a third regulating valve (13), a main steam valve (14) and a main steam regulating valve (15) are arranged on the main steam pipe (3) in sequence; the connection position of the steam supply pipe (7) and the main steam pipe (3) is located between the third regulating valve (13) and the main steam valve (14).

7. The steam system for hot and super-hot state starting of a steam turbine according to claim 1, characterized in that: a check valve (16) is arranged on the steam supply pipe (7).

8. The steam system for hot and super-hot state starting of a steam turbine according to claim 1, characterized in that: the steam system further comprises a condenser (17), a high-pressure drain tank (19) is connected to a tube side outlet of the surface heat exchanger (4) through a drain pipe (18), and the high-pressure drain tank (19) is connected to the condenser (17).

9. The steam system for hot and super-hot state starting of a steam turbine according to claim 1, characterized in that: the first bypass pipe (5) is provided with a fourth regulating valve (20).

10. The steam system for hot and super-hot state starting of a steam turbine according to claim 1, characterized in that: the second bypass pipe (6) is provided with a fifth regulating valve (21).

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