A system and method for improving steam supply capacity and unit efficiency of a reheat steam turbine

Abstract

The present invention discloses a system and method for improving the steam supply capacity and unit efficiency of a reheat steam turbine, the system comprising a feedwater bypass heat exchange system, a heating system and a feedback control system. The present invention simultaneously adjusts the opening of the medium-pressure cylinder heating extraction steam regulating valve and the cold reheat steam to pressure matcher steam regulating valve, so that the steam pressure and flow rate at the outlet of the steam-water heat exchanger can meet the user's needs at the same time. According to the user's temperature requirements and the heat exchange characteristics of the steam-water heat exchanger, the feedwater flow rate corresponding to the feedwater pump outlet to the steam-water heat exchanger inlet pipe is controlled. Finally, the return water position in the steam-water heat exchanger return pipe is selected according to the temperature measurement value and the corresponding electric valve is opened. A system is provided which has a strong universality and heating steam temperature parameter adjustment capability, and does not require a water spray cooling device, and can be used for heating transformation of in-service units to improve their industrial steam supply capacity and unit efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of steam turbine extraction heating, and in particular relates to a system and method for improving the steam supply capacity and unit efficiency of a reheat steam turbine. Background Art

[0002] In recent years, in order to achieve energy conservation and emission reduction and fully utilize the advantages of cogeneration, more and more reheat condensing units have been transformed into heating units. In some existing heating systems, when the steam temperature parameters required by users are low, the temperature of the heating steam is greatly different from the heating temperature required by users, and it is necessary to use water spray to reduce the temperature of the high-temperature heating steam, resulting in the energy of the high-temperature heating steam not being fully utilized.

[0003] At present, there are also some devices that use the superheat of heating steam to increase the feed water temperature and reduce the heat absorption of unit feed water in the boiler to improve the comprehensive energy utilization efficiency of the power plant. For example, in the Chinese patent with the authorization date of August 31, 2016 and the authorization announcement number of CN205535722U, a device for energy cascade utilization for extraction steam heating system is disclosed. The energy cascade utilization device needs to directly replace part of the heat recovery heater according to the principle of matching the boiler feed water return water and heating extraction steam temperature. If the heating transformation of the in-service unit is carried out, this scheme may cause parameter mismatch, resulting in the overall thermal efficiency of the unit not being optimal or even decreasing. It will also cause the out-of-stock index to be unqualified due to the low feed water temperature during low-load operation, and the universality of the system is limited. Therefore, this device is more suitable for the design of new heating units (the system affected by it needs to be greatly improved and designed), and is not suitable for the heating transformation of in-service units. For example, in the Chinese patent with the authorization date of February 15, 2017 and the authorization announcement number of CN205957140U, a heating system with high thermal utilization rate is disclosed. This heating system utilizes part of the superheat of high-temperature steam by installing a steam cooler to heat the final boiler feed water. The steam cooler of this system only heats the final feed water, and the system is relatively simple, but there are certain limitations on the applicable range and regulation capacity of the heating steam temperature, so a water spray cooling device is still required.

[0004] In summary, for the heating renovation of in-service units, there is currently no system that has universal applicability, strong heating steam temperature parameter adjustment capabilities, and does not require the installation of water spray cooling devices, which can be used to improve industrial steam supply capacity and unit efficiency. Summary of the invention

[0005] The object of the present invention is to provide a system and method with strong applicability and parameter adjustment capability, which can be used to perform heating transformation on an in-service reheat steam turbine unit to improve its industrial steam supply capacity and unit efficiency.

[0006] The present invention is achieved by adopting the following technical solutions:

[0007] A system for improving the steam supply capacity and unit efficiency of a reheat steam turbine, comprising a steam-water system of a steam turbine unit, a feedwater bypass heat exchange system, a heating system and a feedback control system; wherein the steam-water system of the steam turbine unit comprises a boiler, the outlet of a superheated steam pipeline of the boiler is connected to a steam inlet of a high-pressure cylinder, the exhaust port of the high-pressure cylinder is connected to a reheated steam pipeline inlet of the boiler, the outlet of the reheated steam pipeline of the boiler is connected to a steam inlet of an intermediate-pressure cylinder, the first and second stage steam extraction ports of the high-pressure cylinder are respectively connected to the steam inlets of a first-stage high-pressure heater and a second-stage high-pressure heater, the first and second stage steam extraction ports of the intermediate-pressure cylinder are respectively connected to the steam inlets of a third-stage high-pressure heater and a deaerator, the water inlets and outlets of the deaerator, the feedwater pump, the third-stage high-pressure heater, the second-stage high-pressure heater and the first-stage high-pressure heater are sequentially connected, and the water outlet of the first-stage high-pressure heater is connected to the feedwater pipeline inlet of the boiler;

[0008] The feedwater bypass heat exchange system includes a feedwater pump outlet to a steam-water heat exchanger water inlet pipeline, the feedwater pump outlet to the steam-water heat exchanger water inlet pipeline is led out from the feedwater pump to the third-stage high-pressure heater feedwater pipeline branch, and is connected to the steam-water heat exchanger water inlet, a feedwater bypass to the steam-water heat exchanger water inlet electric valve is installed on the feedwater pump outlet to the steam-water heat exchanger water inlet pipeline, the water outlet of the steam-water heat exchanger is connected to the steam-water heat exchanger return pipeline, the steam-water heat exchanger return pipeline is connected to the first-stage high-pressure heater to boiler feedwater pipeline through the steam-water heat exchanger outlet to the first-stage high-pressure heater outlet electric valve, the steam-water heat exchanger return pipeline is connected to the second-stage high-pressure heater to the first-stage high-pressure heater feedwater pipeline through the steam-water heat exchanger outlet to the second-stage high-pressure heater outlet electric valve, and the steam-water heat exchanger return pipeline is connected to the third-stage high-pressure heater to the second-stage high-pressure heater feedwater pipeline through the steam-water heat exchanger outlet to the third-stage high-pressure heater outlet electric valve;

[0009] The heating system comprises a pressure matcher, the inlet of the pressure matcher is respectively connected with the medium-pressure cylinder heating extraction steam pipeline and the cold reheat steam to pressure matcher steam pipeline, the medium-pressure cylinder heating extraction steam regulating valve is installed on the medium-pressure cylinder heating extraction steam pipeline, the cold reheat steam to pressure matcher steam regulating valve is installed on the cold reheat steam to pressure matcher steam pipeline, the outlet of the pressure matcher is connected with the steam inlet of the steam-water heat exchanger, and the steam outlet of the steam-water heat exchanger is connected with the steam pipeline from the steam-water heat exchanger to the user;

[0010] A first temperature measuring point is installed on the steam pipe from the steam-water heat exchanger to the user, a second temperature measuring point is installed on the feed water pipe from the feed water pump to the third-stage high-pressure heater, and a third temperature measuring point is installed on the return water pipe of the steam-water heat exchanger;

[0011] The feedback control system includes a feedback controller, the inlet of the feedback controller is connected to the first temperature measuring point, the second temperature measuring point and the third temperature measuring point, and the outlet of the feedback controller is connected to the electric valve from the outlet of the steam-water heat exchanger to the first-stage high-pressure heater outlet, the electric valve from the outlet of the steam-water heat exchanger to the second-stage high-pressure heater outlet, the electric valve from the outlet of the steam-water heat exchanger to the third-stage high-pressure heater outlet and the electric valve from the feed water bypass to the steam-water heat exchanger inlet.

[0012] A further improvement of the present invention is that a hole is opened on the cylinder body of the medium-pressure cylinder according to the pressure requirement of the user.

[0013] A method for improving the steam supply capacity and unit efficiency of a reheat steam turbine, based on the above-mentioned system for improving the steam supply capacity and unit efficiency of a reheat steam turbine, comprises the following steps:

[0014] Step 1: When the unit load is high and the intermediate pressure cylinder heating extraction steam can meet the user's pressure requirements, close the cold reheat steam to pressure matching device steam regulating valve, and adjust the opening of the intermediate pressure cylinder heating extraction steam regulating valve to make the outlet steam flow of the steam-water heat exchanger meet the user's requirements; when the unit load is low and the intermediate pressure cylinder heating extraction steam cannot meet the user's pressure requirements, adjust the openings of the intermediate pressure cylinder heating extraction steam regulating valve and the cold reheat steam to pressure matching device steam regulating valve at the same time to make the outlet steam pressure and flow of the steam-water heat exchanger meet the user's requirements at the same time;

[0015] Step 2: setting a target value of the first temperature measuring point in the feedback controller according to the user's temperature requirement, and transmitting the measured values ​​of the first temperature measuring point and the second temperature measuring point to the feedback controller;

[0016] Step 3: According to the heat transfer characteristics of the steam-water heat exchanger and the measured values ​​of the first temperature measuring point and the second temperature measuring point, the feedback controller is used to process the measured values, and the feed water flow corresponding to the feed water pump outlet to the steam-water heat exchanger water inlet pipeline is controlled by controlling the opening of the feed water bypass to the steam-water heat exchanger water inlet electric valve;

[0017] Step 4: Transmit the measured value of the third temperature measuring point to the feedback controller, and select the return position in the return pipe of the steam-water heat exchanger as the first-stage high-pressure heater to the boiler feed water pipe or the second-stage high-pressure heater to the first-stage high-pressure heater feed water pipe or the third-stage high-pressure heater to the second-stage high-pressure heater feed water pipe according to the temperature measurement value. After confirming the position, open the corresponding control valve from the steam-water heat exchanger outlet to the first-stage high-pressure heater outlet electric valve or the steam-water heat exchanger outlet to the second-stage high-pressure heater outlet electric valve or the steam-water heat exchanger outlet to the third-stage high-pressure heater outlet electric valve and close the other two control valves.

[0018] The present invention has at least the following beneficial technical effects:

[0019] The present invention provides a system and method for improving the steam supply capacity and unit efficiency of a reheat steam turbine. First, by simultaneously adjusting the opening of the intermediate pressure cylinder heating extraction steam regulating valve and the cold reheat steam to pressure matching steam regulating valve, the steam pressure and flow rate at the outlet of the steam-water heat exchanger can meet the user's needs at the same time. Then, according to the user's temperature requirements, the target value of the first temperature measuring point is set in the feedback controller, and the measured values ​​of the first temperature measuring point and the second temperature measuring point are transmitted to the feedback controller. Combined with the heat exchange characteristics of the steam-water heat exchanger, the corresponding feed water flow rate from the outlet of the feed water pump to the water inlet pipe of the steam-water heat exchanger is controlled. Finally, the measured value of the third temperature measuring point is transmitted to the feedback controller, and the return water position in the return water pipe of the steam-water heat exchanger is selected according to the temperature measurement value and the corresponding electric valve is opened. Provided is a system with strong universality and heating steam temperature parameter adjustment capability, and no water spray cooling device is required, which can be used for heating transformation of in-service units to improve their industrial steam supply capacity and unit efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of the present invention.

[0021] Description of reference numerals:

[0022] 1. Boiler, 2. High-pressure cylinder, 3. Medium-pressure cylinder, 4. Feedwater pump, 5. Deaerator, 6. Pressure matcher, J1. First-stage high-pressure heater, J2. Second-stage high-pressure heater, J3. Third-stage high-pressure heater, J4. Steam-water heat exchanger, L1. First-stage high-pressure heater to boiler feedwater pipeline, L2. Second-stage high-pressure heater to first-stage high-pressure heater feedwater pipeline, L3. Third-stage high-pressure heater to second-stage high-pressure heater feedwater pipeline, L4. Feedwater pump to third-stage high-pressure heater feedwater pipeline, L5. Cold reheat steam to pressure matcher steam pipeline, L6. Medium-pressure cylinder heat extraction pipeline, L7. Feedwater pump outlet to steam-water heat exchanger inlet pipeline, L 8. The outlet water of the steam-water heat exchanger to the return water pipe at the first-stage high-pressure heater outlet, L9, the steam-water heat exchanger to the user's steam pipe, V1, the outlet water of the steam-water heat exchanger to the electric valve at the first-stage high-pressure heater outlet, V2, the outlet water of the steam-water heat exchanger to the electric valve at the second-stage high-pressure heater outlet, V3, the outlet water of the steam-water heat exchanger to the electric valve at the third-stage high-pressure heater outlet, V4, the feed water bypass to the electric valve at the steam-water heat exchanger inlet, V5, the cold reheat steam to the steam regulating valve of the pressure matcher, V6, the heating extraction regulating valve of the intermediate pressure cylinder, T1, the first temperature measuring point, T2, the second temperature measuring point, T3, the third temperature measuring point, C1, the feedback controller. DETAILED DESCRIPTION

[0023] The present invention is described in detail below with reference to the accompanying drawings.

[0024] See also Figure 1The present invention provides a system for improving the steam supply capacity and unit efficiency of a reheat steam turbine, including a steam-water system of a steam turbine unit, a feedwater bypass heat exchange system, a heating system and a feedback control system.

[0025] Wherein, the steam-water system of the steam turbine unit includes a boiler 1, the outlet of the superheated steam pipeline of the boiler 1 is connected to the steam inlet of the high-pressure cylinder 2, the exhaust port of the high-pressure cylinder 2 is connected to the inlet of the reheated steam pipeline of the boiler 1, the outlet of the reheated steam pipeline of the boiler 1 is connected to the steam inlet of the intermediate-pressure cylinder 3, the first and second stage steam extraction ports of the high-pressure cylinder 2 are respectively connected to the steam inlets of the first-stage high-pressure heater J1 and the second-stage high-pressure heater J2, the first and second stage steam extraction ports of the intermediate-pressure cylinder 3 are respectively connected to the steam inlets of the third-stage high-pressure heater J3 and the deaerator 5, the water inlets and outlets of the deaerator 5, the feed water pump 4, the third-stage high-pressure heater J3, the second-stage high-pressure heater J2 and the first-stage high-pressure heater J1 are connected in sequence, and the water outlet of the first-stage high-pressure heater J1 is connected to the feed water pipeline inlet of the boiler 1.

[0026] The feedwater bypass heat exchange system includes a feedwater pump outlet to a steam-water heat exchanger water inlet pipeline L7, which is led out from the feedwater pump outlet to the steam-water heat exchanger water inlet pipeline L4 of the third-stage high-pressure heater and is connected to the water inlet of the steam-water heat exchanger J4. A feedwater bypass to the steam-water heat exchanger water inlet electric valve V4 is installed on the feedwater pump outlet to the steam-water heat exchanger water inlet pipeline L7, and the water outlet of the steam-water heat exchanger J4 is connected to the steam-water heat exchanger return water pipeline L8. The water pipe L8 is connected to the first-stage high-pressure heater to boiler feed water pipe L1 through the outlet of the steam-water heat exchanger to the first-stage high-pressure heater outlet electric valve V1, the return water pipe L8 of the steam-water heat exchanger is connected to the second-stage high-pressure heater to the first-stage high-pressure heater feed water pipe L2 through the outlet of the steam-water heat exchanger to the second-stage high-pressure heater outlet electric valve V2, and the return water pipe L8 of the steam-water heat exchanger is connected to the third-stage high-pressure heater to the second-stage high-pressure heater feed water pipe L3 through the outlet of the steam-water heat exchanger to the third-stage high-pressure heater outlet electric valve V3.

[0027] The heating system includes a pressure matcher 6, the inlet of the pressure matcher 6 is respectively connected to the intermediate pressure cylinder heating extraction steam pipeline L6 and the cold reheat steam to pressure matcher steam pipeline L5, the intermediate pressure cylinder heating extraction steam pipeline L6 is installed with an intermediate pressure cylinder heating extraction steam regulating valve V6, the cold reheat steam to pressure matcher steam pipeline L5 is installed with a cold reheat steam to pressure matcher steam regulating valve V5, the outlet of the pressure matcher 6 is connected to the steam inlet of the steam-water heat exchanger J4, and the steam outlet of the steam-water heat exchanger J4 is connected to the steam pipeline L9 from the steam-water heat exchanger to the user.

[0028] The feedback control system includes a feedback controller C1, the inlet of the feedback controller C1 is connected to the first temperature measuring point T1, the second temperature measuring point T2 and the third temperature measuring point T3, the outlet of the feedback controller C1 is connected to the outlet of the steam-water heat exchanger to the first-stage high-pressure heater outlet electric valve V1, the outlet of the steam-water heat exchanger to the second-stage high-pressure heater outlet electric valve V2, the outlet of the steam-water heat exchanger to the third-stage high-pressure heater outlet electric valve V3 and the feed water bypass to the steam-water heat exchanger inlet electric valve V4.

[0029] In addition, a first temperature measuring point T1 is installed on the steam pipe L9 from the steam-water heat exchanger to the user, a second temperature measuring point T2 is installed on the feed water pipe L4 from the feed water pump to the third-stage high-pressure heater, and a third temperature measuring point T3 is installed on the return water pipe L8 of the steam-water heat exchanger.

[0030] According to the user's pressure requirements, a hole is opened on the intermediate pressure cylinder body to lead out the intermediate pressure cylinder heating extraction steam pipeline L6. The pipeline size is calculated based on the user's flow requirements.

[0031] The present invention provides a method for improving the steam supply capacity and unit efficiency of a reheat steam turbine, comprising the following steps:

[0032] Step 1: When the unit load is high and the intermediate-pressure cylinder heating extraction steam can meet the user's pressure requirements, close the cold reheat steam to pressure matcher steam regulating valve V5, and adjust the opening of the intermediate-pressure cylinder heating extraction steam regulating valve V6 to make the outlet steam flow of the steam-water heat exchanger 6 meet the user's requirements; when the unit load is low and the intermediate-pressure cylinder heating extraction steam cannot meet the user's pressure requirements, adjust the openings of the intermediate-pressure cylinder heating extraction steam regulating valve V6 and the cold reheat steam to pressure matcher steam regulating valve V5 at the same time to make the outlet steam pressure and flow of the steam-water heat exchanger 6 meet the user's requirements at the same time.

[0033] Step 2: According to the user's temperature requirement, a target value of the first temperature measuring point T1 is set in the feedback controller C1, and the measured values ​​of the first temperature measuring point T1 and the second temperature measuring point T2 are transmitted to the feedback controller C1.

[0034] Step 3: Based on the heat transfer characteristics of the steam-water heat exchanger J4 and the measured values ​​of the first temperature measuring point T1 and the second temperature measuring point T2, processing is performed in the feedback controller C1, and the opening of the feed water bypass to the steam-water heat exchanger water inlet electric valve V4 is controlled to control the feed water flow rate corresponding to the feed water pump outlet to the steam-water heat exchanger water inlet pipe L7.

[0035] Step 4: Transmit the measured value of the third temperature measuring point T3 to the feedback controller C1, and select the return position in the steam-water heat exchanger return pipe L8 as the first-stage high-pressure heater to the boiler feed water pipe L1 or the second-stage high-pressure heater to the first-stage high-pressure heater feed water pipe L2 or the third-stage high-pressure heater to the second-stage high-pressure heater feed water pipe L3 according to the temperature measurement value; after confirming the position, open the corresponding control valve from the steam-water heat exchanger outlet to the first-stage high-pressure heater outlet electric valve V1 or the steam-water heat exchanger outlet to the second-stage high-pressure heater outlet electric valve V2 or the steam-water heat exchanger outlet to the third-stage high-pressure heater outlet electric valve V3 and close the other two control valves.

[0036] The present invention provides a system for improving the steam supply capacity and unit efficiency of a reheat steam turbine, in which the flow of bypass feed water can be comprehensively adjusted and the position of return water in the return water pipe of the steam-water heat exchanger can be set. Therefore, the system has strong universality and heating steam temperature parameter adjustment capabilities, and there is no need to set up a water spray cooling device. It can be used to carry out heating transformation of in-service units to improve their industrial steam supply capacity and unit efficiency.

Claims

1. A system for improving the steam supply capacity and unit efficiency of a reheat steam turbine, characterized in that: It includes steam-water system of steam turbine unit, feedwater bypass heat exchange system, heating system and feedback control system; among which, The steam-water system of the steam turbine unit comprises a boiler (1), wherein the outlet of the superheated steam pipeline of the boiler (1) is connected to the steam inlet of the high-pressure cylinder (2), the exhaust port of the high-pressure cylinder (2) is connected to the inlet of the reheated steam pipeline of the boiler (1), the outlet of the reheated steam pipeline of the boiler (1) is connected to the steam inlet of the medium-pressure cylinder (3), the first and second stage steam extraction ports of the high-pressure cylinder (2) are respectively connected to the steam inlets of the first-stage high-pressure heater (J1) and the second-stage high-pressure heater (J2), the first and second stage steam extraction ports of the medium-pressure cylinder (3) are respectively connected to the steam inlets of the third-stage high-pressure heater (J3) and the deaerator (5), the water inlets and outlets of the deaerator (5), the feed water pump (4), the third-stage high-pressure heater (J3), the second-stage high-pressure heater (J2) and the first-stage high-pressure heater (J1) are connected in sequence, and the water outlet of the first-stage high-pressure heater (J1) is connected to the feed water pipeline inlet of the boiler (1); The feedwater bypass heat exchange system comprises a water inlet pipe (L7) from the outlet of the feedwater pump to the steam-water heat exchanger, the water inlet pipe (L7) from the outlet of the feedwater pump to the steam-water heat exchanger is led out from the branch of the feedwater pump to the third-stage high-pressure water supply pipe (L4), and is connected to the water inlet of the steam-water heat exchanger (J4), a water bypass to the steam-water heat exchanger water inlet electric valve (V4) is installed on the water inlet pipe (L7) from the outlet of the feedwater pump to the steam-water heat exchanger, the water outlet of the steam-water heat exchanger (J4) is connected to the steam-water heat exchanger return pipe (L8), and the steam-water heat exchanger return pipe (L8) is connected to the steam-water heat exchanger return pipe (L9). The pipeline (L8) is connected to the first-stage high-pressure heater to boiler feed water pipeline (L1) through the outlet of the steam-water heat exchanger to the first-stage high-pressure heater outlet electric valve (V1), the return water pipeline (L8) of the steam-water heat exchanger is connected to the second-stage high-pressure heater to the first-stage high-pressure heater feed water pipeline (L2) through the outlet of the steam-water heat exchanger to the second-stage high-pressure heater outlet electric valve (V2), and the return water pipeline (L8) of the steam-water heat exchanger is connected to the third-stage high-pressure heater to the second-stage high-pressure heater feed water pipeline (L3) through the outlet of the steam-water heat exchanger to the third-stage high-pressure heater outlet electric valve (V3); The heating system comprises a pressure matcher (6), the inlet of the pressure matcher (6) is respectively connected to the medium-pressure cylinder heating extraction steam pipeline (L6) and the cold reheat steam to pressure matcher steam pipeline (L5), the medium-pressure cylinder heating extraction steam pipeline (L6) is equipped with a medium-pressure cylinder heating extraction steam regulating valve (V6), the cold reheat steam to pressure matcher steam pipeline (L5) is equipped with a cold reheat steam to pressure matcher steam regulating valve (V5), the outlet of the pressure matcher (6) is connected to the steam inlet of the steam-water heat exchanger (J4), and the steam outlet of the steam-water heat exchanger (J4) is connected to the steam pipeline (L9) from the steam-water heat exchanger to the user; A first temperature measuring point (T1) is installed on a steam pipe (L9) from a steam-water heat exchanger to a user, a second temperature measuring point (T2) is installed on a feed water pipe (L4) from a feed water pump to a third-stage high-pressure heater, and a third temperature measuring point (T3) is installed on a return water pipe (L8) from the steam-water heat exchanger; The feedback control system comprises a feedback controller (C1), the inlet of the feedback controller (C1) is connected to a first temperature measuring point (T1), a second temperature measuring point (T2) and a third temperature measuring point (T3), and the outlet of the feedback controller (C1) is connected to an electric valve (V1) from the outlet of the steam-water heat exchanger to the outlet of the first-stage high-pressure heater, an electric valve (V2) from the outlet of the steam-water heat exchanger to the outlet of the second-stage high-pressure heater, an electric valve (V3) from the outlet of the steam-water heat exchanger to the outlet of the third-stage high-pressure heater, and an electric valve (V4) from a feed water bypass to an inlet of the steam-water heat exchanger.

2. A system for improving the steam supply capacity and unit efficiency of a reheat steam turbine according to claim 1, characterized in that: Holes are drilled on the medium pressure cylinder body according to the user's pressure requirements.

3. A method for improving the steam supply capacity and unit efficiency of a reheat steam turbine, characterized in that: The method is based on a system for improving the steam supply capacity and unit efficiency of a reheat steam turbine as described in claim 1 or 2, and comprises the following operating steps: Step 1: When the unit load is high and the intermediate pressure cylinder heating extraction steam can meet the user's pressure requirements, close the cold reheat steam to pressure matching device steam regulating valve (V5), and adjust the opening of the intermediate pressure cylinder heating extraction steam regulating valve (V6) so that the outlet steam flow of the steam-water heat exchanger (6) meets the user's requirements; when the unit load is low and the intermediate pressure cylinder heating extraction steam cannot meet the user's pressure requirements, adjust the openings of the intermediate pressure cylinder heating extraction steam regulating valve (V6) and the cold reheat steam to pressure matching device steam regulating valve (V5) at the same time so that the outlet steam pressure and flow of the steam-water heat exchanger (6) meet the user's requirements at the same time; Step 2: setting a target value of the first temperature measuring point (T1) in the feedback controller (C1) according to the temperature requirement of the user, and transmitting the measured values ​​of the first temperature measuring point (T1) and the second temperature measuring point (T2) to the feedback controller (C1); Step 3: Based on the heat exchange characteristics of the steam-water heat exchanger (J4) and the measured values ​​of the first temperature measuring point (T1) and the second temperature measuring point (T2), the feedback controller (C1) processes the measured values ​​and controls the opening of the feedwater bypass to the steam-water heat exchanger water inlet electric valve (V4) to control the corresponding feedwater flow from the feedwater pump outlet to the steam-water heat exchanger water inlet pipeline (L7); Step 4: The measured value of the third temperature measuring point (T3) is transmitted to the feedback controller (C1), and the return water position in the steam-water heat exchanger return water pipe (L8) is selected as the first-stage high-pressure heater to the boiler feed water pipe (L1) or the second-stage high-pressure heater to the first-stage high-pressure heater feed water pipe (L2) or the third-stage high-pressure heater to the second-stage high-pressure heater feed water pipe (L3) according to the temperature measurement value. After confirming the position, the corresponding control valve is opened, the steam-water heat exchanger outlet to the first-stage high-pressure heater outlet electric valve (V1) or the steam-water heat exchanger outlet to the second-stage high-pressure heater outlet electric valve (V2) or the steam-water heat exchanger outlet to the third-stage high-pressure heater outlet electric valve (V3) and the other two control valves are closed.

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