A steam system for starting up a steam turbine in hot and extremely hot states

Abstract

This invention relates to the technical field and discloses a steam system for hot and extremely hot start-up of a steam turbine. The steam system includes a boiler and a cylinder, with the boiler connected to the cylinder via a main steam pipeline. The steam system also includes a surface heat exchanger. The main steam pipeline is connected to the shell-side inlet of the surface heat exchanger via a first bypass pipeline and to the tube-side inlet of the surface heat exchanger via a second bypass pipeline. The shell-side outlet of the surface heat exchanger is connected to the main steam pipeline via a steam supply pipeline. This invention can both increase the steam temperature entering the cylinder during hot or extremely hot start-up of the unit and reduce the impact on normal boiler operation.

Description

Technical Field

[0001] This invention relates to the field of steam turbine technology, and more specifically, to a steam system for starting a steam turbine in hot and extremely hot states. Background Technology

[0002] When a steam turbine is started up in a hot or extremely hot state, the steam entering the cylinder also needs to be at a high temperature due to the high cylinder temperature. If the steam temperature is too low, the cylinder will be locally cooled, causing inconsistent expansion between the cylinder and the rotor, which can lead to problems such as rubbing between moving and stationary parts and vibration of the unit. Therefore, under normal circumstances, it is recommended that the steam temperature be at least 5 to 10°C higher than the cylinder temperature.

[0003] For ultra-high pressure medium-temperature waste-to-energy generator sets, hot start-up mainly occurs under the condition of shutdown without stopping the boiler. Since waste is still being processed normally, the boiler load will be relatively high. Taking a common design with rated parameters of 13.2 MPa.a and 445℃ as an example, and considering the cylinder pressure as 0.1 MPa.a, according to the throttling effect, the temperature of the steam with this parameter will drop to about 350℃ after entering the cylinder. However, the cylinder temperature during hot start-up is about 390℃. It can be seen that the steam temperature entering the cylinder is much lower than the cylinder temperature, which is not conducive to the smooth start-up of the unit.

[0004] To address the aforementioned technical issues, the common approach is to reduce steam pressure and increase superheat to raise the steam temperature entering the cylinder. For example, with a cylinder pressure of 0.1 MPa and a steam temperature of 395°C, the steam parameters would need to be adjusted to 7.48 MPa and 445°C to achieve this condition. However, due to the combustion characteristics of waste, reducing the steam parameters at the waste incinerator outlet may lead to excessive emissions of pollutants in the flue gas, failing to meet environmental protection requirements. Furthermore, it would reduce the boiler load, affecting the normal waste processing operation. Summary of the Invention

[0005] The technical objective of this invention is to address the shortcomings of the prior art by providing a steam system for hot and extremely hot turbine startup that can both increase the steam temperature entering the cylinder during hot or extremely hot turbine startup and reduce the impact on normal boiler operation.

[0006] The technical solution adopted in this invention is as follows:

[0007] A steam system for starting a steam turbine in hot and extremely hot states, the steam system comprising a boiler and a cylinder, wherein the boiler is connected to the cylinder via a main steam pipeline;

[0008] The steam system also includes a surface heat exchanger. The main steam pipeline is connected to the shell-side inlet of the surface heat exchanger via a first bypass pipeline. The main steam pipeline is connected to the tube-side inlet of the surface heat exchanger via a second bypass pipeline. The shell-side outlet of the surface heat exchanger is connected to the main steam pipeline via a steam supply pipeline.

[0009] The above-mentioned technical measures, by setting up a surface heat exchanger, divide the steam generated by the boiler into two streams using the first and second bypasses when the steam turbine starts up. These streams enter the shell side and tube side of the surface heat exchanger respectively, allowing the two steam streams to exchange heat within the surface heat exchanger and convert into low-pressure, high-temperature steam. This increases the steam temperature entering the cylinder, meeting the requirements for hot and extremely hot start-up of the unit. At the same time, it eliminates the need for the boiler to operate at reduced load and parameters, reducing the impact on the normal operation of the boiler.

[0010] Furthermore, the steam system also includes a first-stage desuperheater, and the main steam pipeline is connected to the first-stage desuperheater via a third bypass pipeline.

[0011] The above-mentioned technical measures, by setting up a primary desuperheater and connecting the primary desuperheater to the boiler through a third bypass pipeline, enable the excess steam generated by the boiler to be transported to the primary desuperheater through the main steam pipeline and the third bypass pipeline under the condition of shutdown without stopping the boiler, and the excess steam is discharged after cooling.

[0012] Furthermore, a first regulating valve is provided on the third bypass pipeline.

[0013] The above-mentioned technical measures achieve the regulation of steam flow in the third bypass pipeline by setting a first regulating valve.

[0014] Furthermore, the steam supply pipeline is connected to the first-stage desuperheater via a desuperheating pipeline.

[0015] The above-mentioned technical measures, by setting up a desuperheating pipe, allow excess steam discharged from the shell side of the surface heat exchanger to enter the first-stage desuperheater, thus avoiding overpressure in the steam supply pipe.

[0016] Furthermore, a second regulating valve is provided on the cooling pipe.

[0017] The above-mentioned technical measures, by setting a second regulating valve, can regulate the steam flow rate of the desuperheating pipeline and adjust the amount of excess steam discharged according to actual needs.

[0018] Furthermore, the main steam pipeline is sequentially equipped with a third regulating valve, a main steam valve, and a main steam regulating valve;

[0019] The connection point between the steam supply pipeline and the main steam pipeline is located between the third regulating valve and the main steam valve.

[0020] The above-mentioned technical measures achieve the regulation of steam flow in the main steam pipeline by setting a third regulating valve.

[0021] Furthermore, a check valve is installed on the steam supply pipeline.

[0022] The above-mentioned technical measures prevent steam backflow by installing check valves, thus preventing steam in the main steam pipeline from flowing into the desuperheating pipeline through the steam supply pipeline.

[0023] Furthermore, the steam system also includes a condenser, and the tube-side outlet of the surface heat exchanger is connected to a high-pressure condensate tank via a drain pipe, the high-pressure condensate tank being connected to the condenser.

[0024] The above-mentioned technical measures collect water from the tube side of the surface heat exchanger through a high-pressure condensate tank, flash evaporate and cool it before sending it into the condenser, thus achieving resource recovery.

[0025] Furthermore, the first bypass pipeline is equipped with a fourth regulating valve.

[0026] The above-mentioned technical measures achieve the regulation of steam flow in the first bypass pipeline by setting a fourth regulating valve.

[0027] Furthermore, the second bypass pipeline is equipped with a fifth regulating valve.

[0028] The above-mentioned technical measures achieve the regulation of steam flow in the second bypass pipeline by setting a fifth regulating valve.

[0029] One or more technical solutions provided by this invention have at least the following technical effects or advantages:

[0030] This invention utilizes a surface heat exchanger to split the steam generated by the boiler into two streams during turbine startup. These streams enter the shell and tube sides of the surface heat exchanger respectively via a first and second bypass. This allows the two steam streams to exchange heat within the surface heat exchanger, producing low-pressure, high-temperature steam. This increases the steam temperature entering the cylinder, meeting the requirements for hot and extremely hot start-up of the unit. Simultaneously, it eliminates the need for the boiler to operate at reduced load and parameters, minimizing the impact on normal boiler operation. Attached Figure Description

[0031] The accompanying drawings, which are provided to further illustrate embodiments of the invention and constitute a part of this invention, are not intended to limit the scope of the invention.

[0032] Figure 1 This is a schematic diagram of the structure of the present invention;

[0033] 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 condensate tank; 20-fourth regulating valve; 21-fifth regulating valve. Detailed Implementation

[0034] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, where there is no conflict, the embodiments of the present invention and the features thereof can be combined with each other.

[0035] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0036] In the embodiments, the descriptions of first, second, third, fourth, etc., are only used to distinguish different components.

[0037] Reference Figure 1 This embodiment provides a steam system for starting a steam turbine in hot and extremely hot states. The steam system includes a boiler 1 and a cylinder 2. The boiler 1 is connected to the cylinder 2 through a main steam pipe 3. The cylinder 2 refers to the high-pressure cylinder of the steam turbine.

[0038] The steam system also includes a surface heat exchanger 4. The main steam pipeline 3 is connected to the shell-side inlet of the surface heat exchanger 4 through a first bypass pipeline 5. The main steam pipeline 3 is connected to the tube-side inlet of the surface heat exchanger 4 through a second bypass pipeline 6. The shell-side outlet of the surface heat exchanger 4 is connected to the main steam pipeline 3 through a steam supply pipeline 7.

[0039] The first bypass pipe 5 is equipped with a fourth regulating valve 20. The second bypass pipe 6 is equipped with a fifth regulating valve 21.

[0040] The steam system also includes a first-stage desuperheater 8, and the main steam pipeline 3 is connected to the first-stage desuperheater 8 through a third bypass pipeline 9.

[0041] The third bypass pipe 9 is equipped with a first regulating valve 10.

[0042] Steam supply pipeline 7 is connected to the first-stage desuperheater 8 via desuperheating pipeline 11.

[0043] A second regulating valve 12 is provided on the cooling pipe 11.

[0044] The main steam pipeline 3 is sequentially equipped with a third regulating valve 13, a main steam valve 14, and a main steam regulating valve 15.

[0045] The connection point between 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.

[0046] A check valve 16 is installed on the steam supply pipeline 7.

[0047] The steam system also includes a condenser 17. The tube-side outlet of the surface heat exchanger 4 is connected to a high-pressure condensate tank 19 via a drain pipe 18. The high-pressure condensate tank 19 is connected to the condenser 17.

[0048] Taking the boiler 1 outlet steam parameters of 13.2 MPa and 445℃ as an example, in the case 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. All the steam generated by the boiler 1 is transported to the first-stage desuperheater 8 through the third bypass pipeline 9.

[0049] When the steam turbine is ready to start, fully open the second regulating valve 12, gradually close the first regulating valve 10, and simultaneously gradually open the fourth regulating valve 20 and the fifth regulating valve 21. The regulating 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 2.0 ± 0.2 MPa.a; the regulating 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 430 ± 5℃. Adjust the fourth regulating valve 20 and the fifth regulating valve 21 according to the above regulating logic, while closing the first regulating valve 10 until the first regulating valve 10 is completely closed. This will produce high superheated steam of 2.0 MPa.a and 430℃, which can be used for hot and extremely hot start-up. Gradually close the second regulating valve 12, open the main steam valve 14 and the main steam regulating valve 15, allowing high-superheated steam to enter the turbine cylinder 2 through the steam supply pipeline 7 to start the turbine and operate at 3%–5% load; adjust the fourth regulating valve 20 to increase the steam pressure at the shell-side outlet of the surface heat exchanger 4 by 1 MPa.a, adjust the fifth regulating valve 21 to maintain the steam temperature at the shell-side outlet of the surface heat exchanger at 430±5℃, then continue to close the second regulating valve 12 to increase the unit load by 10%, repeating the adjustment of the fourth regulating valve 20 and the fifth regulating valve 21 and the closing of the second regulating valve 12 until the steam pressure at the shell-side outlet of the surface heat exchanger reaches 8 MPa.a and the unit load reaches approximately 65% ​​of the rated load; gradually open the third regulating valve 13, as the main steam… The resistance of pipe 3 is much smaller than that of the first bypass pipe 5 and the second bypass pipe 6. A large amount of steam generated by boiler 1 will enter the turbine cylinder 2 from the main steam pipe 3. At the same time, since the steam pressure at the outlet of the third regulating valve 13 is higher than the steam pressure at the shell-side outlet of the surface heat exchanger 4, the steam flow rate entering the cylinder 2 increases, causing the unit load to rise. While maintaining the unit load increase rate of 1.5 to 2.0 MW / min, the third regulating valve 13 is opened further until it is fully open. Then, the second regulating valve 12, the fourth regulating valve 20, and the fifth regulating valve 21 are closed, so that all the steam entering the turbine comes from the boiler, thus completing the hot or extremely hot start-up. Subsequently, the main steam valve 14 and the main steam regulating valve 15 are adjusted according to conventional operation to bring the unit to the target load.

[0050] For units with other parameters, the recommended steam parameters for startup can be selected according to Table 1, as shown below:

[0051] For units with other parameters, the steam parameters for load increase can be considered by reducing the rated main steam temperature by 10℃ to 15℃.

[0052] The steam system in this embodiment is mainly used for ultra-high pressure waste-to-energy power generation, but it is also applicable to other steam turbine scenarios where the main steam parameters exhibit the characteristics of "high pressure and low temperature".

[0053] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0054] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A steam system for starting a steam turbine in hot and extremely hot states, the steam system comprising a boiler (1) and a cylinder (2), wherein the boiler (1) is connected to the cylinder (2) via a main steam pipe (3); Its features are: The steam system also includes a surface heat exchanger (4), the main steam pipe (3) is connected to the shell-side inlet of the surface heat exchanger (4) through a first bypass pipe (5), the main steam pipe (3) is connected to the tube-side inlet of the surface heat exchanger (4) through a second bypass pipe (6), and the shell-side outlet of the surface heat exchanger (4) is connected to the main steam pipe (3) through a steam supply pipe (7). The steam system also includes a first-stage desuperheater (8), and the main steam pipeline (3) is connected to the first-stage desuperheater (8) through a third bypass pipeline (9); The third bypass pipe (9) is equipped with a first regulating valve (10); The steam supply pipeline (7) is connected to the first-stage desuperheater (8) via the desuperheating pipeline (11); The de-heating pipe (11) is equipped with a second regulating valve (12); The main steam pipeline (3) is provided with a third regulating valve (13), a main steam valve (14) and a main steam regulating valve (15) in sequence. The connection point between 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); The steam supply pipeline (7) is equipped with a check valve (16); The steam system also includes a condenser (17), and the tube-side outlet of the surface heat exchanger (4) is connected to a high-pressure condensate tank (19) via a drain pipe (18), and the high-pressure condensate tank (19) is connected to the condenser (17). A fourth regulating valve (20) is provided on the first bypass pipe (5); The second bypass pipe (6) is equipped with a fifth regulating valve (21).

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