Energy-saving starting system and operation method of coal-fired power plant

Abstract

The present application relates to the technical field of thermal power generation, in particular to a coal-fired power plant energy-saving starting system and a running method. The coal-fired power plant energy-saving starting system comprises: an auxiliary bypass steam inlet channel, one end of which is communicated with a boiler body, and the other end of which is communicated with a feed water pump turbine, the feed water pump turbine is installed in cooperation with a feed water pump body, and an outlet end of the feed water pump turbine is communicated on a steam turbine bypass channel; a heat recovery channel, one end of which is communicated with a steam turbine unit, and the other end of which is communicated with a heat recovery heater unit, a low-pressure steam inlet channel is communicated between the heat recovery channel and the auxiliary bypass steam inlet channel, and a neighboring machine auxiliary steam channel is further communicated at a connection position of the low-pressure steam inlet channel and the auxiliary bypass steam inlet channel. The steam turbine unit is driven to operate by the steam with residual heat and the neighboring machine auxiliary steam which are introduced into the auxiliary bypass steam inlet channel, the starting bypass steam of the coal-fired power plant is recycled, the starting energy consumption of the coal-fired power plant is reduced, and the thermal economy of the power plant is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal power generation, and in particular to an energy-saving starting system and an operating method for a coal-fired power plant. Background Art

[0002] With the development of renewable energy, the proportion of electricity generated from renewable sources is increasing. However, the unstable nature of renewable energy generation has adversely impacted the stability of the power grid, placing higher demands on the peak-shaving capabilities of coal-fired power plants. Rapid load changes and start-up and shutdown are effective methods for peak-shaving in coal-fired power plants. However, some units are shut down due to grid peak-shaving needs and restarted within 24 hours. This significantly increases the number of unit starts and stops throughout the year, leading to increased startup energy consumption. During the startup process of conventional thermal power generators, bypass steam is desuperheated and decompressed before being sent to the condenser, resulting in energy losses. Summary of the Invention

[0003] Therefore, the technical problem to be solved by the present invention is to overcome the defect in the prior art that during the startup of a thermal power generator set, the bypass steam passes through the condenser and then returns to the boiler, resulting in energy loss, thereby providing an energy-saving startup system and operation method for a coal-fired power plant.

[0004] In order to solve the above technical problems, the present invention provides an energy-saving startup system for a coal-fired power plant, comprising:

[0005] A boiler body, a steam turbine unit, a condenser, a regenerative heater unit, and a feedwater pump body are connected in a circular manner, wherein a steam turbine steam inlet channel is connected between the boiler body and the steam turbine unit;

[0006] Also includes:

[0007] The turbine bypass channel has one end connected to the boiler body and the other end connected to the condenser.

[0008] An auxiliary bypass steam inlet channel, one end of which is connected to the boiler body and the other end of which is connected to a feedwater pump turbine. The feedwater pump turbine is installed in conjunction with the feedwater pump body, and the outlet end of the feedwater pump turbine is connected to the turbine bypass channel.

[0009] A heat recovery channel is connected to the steam turbine unit at one end and to the heat recovery heater group at the other end. A low-pressure steam inlet channel is connected between the heat recovery channel and the auxiliary bypass steam inlet channel. The connection between the low-pressure steam inlet channel and the auxiliary bypass steam inlet channel is also connected to the adjacent machine auxiliary steam channel.

[0010] Optionally, a first bypass desuperheater is installed on the turbine bypass channel, and a second bypass desuperheater is installed on the auxiliary bypass steam inlet channel.

[0011] The present invention further provides an energy-saving startup method for a coal-fired power plant, which is applied to the energy-saving startup system for a coal-fired power plant described in the present invention. The operation method includes:

[0012] Based on the target steam flow from the boiler body to the auxiliary bypass steam inlet channel, the steam flow entering the turbine bypass, the steam flow of the adjacent machine auxiliary steam, and the steam flow from the auxiliary bypass steam inlet channel to the feedwater pump turbine outlet loss, and obtain an objective function; optimizing the objective function using a target steam flow rate from the boiler body into the auxiliary bypass steam inlet channel to obtain a maximum objective function value;

[0013] The target steam flow rate from the boiler body to the auxiliary bypass steam inlet channel is controlled to be a preset steam flow rate corresponding to the maximum objective function value.

[0014] Optionally, it also includes:

[0015] Based on the target steam flow from the boiler body into the auxiliary bypass steam inlet channel, the boiler body outlet steam Value, steam flow of the adjacent auxiliary steam, steam flow of the adjacent auxiliary steam Value, steam at the outlet of the feedwater pump turbine The steam flow from the auxiliary bypass steam inlet channel to the outlet of the feedwater pump steam turbine is obtained by taking the power of the feedwater pump steam turbine and the relative internal efficiency of the feedwater pump steam turbine into consideration. loss.

[0016] Optionally, it also includes: obtaining the steam flow of the adjacent machine auxiliary steam based on the power of the feedwater pump turbine, the inlet steam enthalpy of the feedwater pump turbine, the outlet steam enthalpy of the feedwater pump turbine, the relative internal efficiency of the feedwater pump turbine and the target steam flow from the boiler body into the auxiliary bypass steam inlet channel.

[0017] Optionally, the steam flow of the adjacent auxiliary steam generator is updated in real time using the following formula:

[0018]

[0019] Where: D ap P is the steam flow of the adjacent machine auxiliary steam; tp is the power of the feedwater pump turbine; h tpi is the inlet steam enthalpy of the feedwater pump turbine; h tpo is the outlet steam enthalpy of the feedwater pump turbine; η is the relative internal efficiency of the feedwater pump turbine; It is the target steam flow rate from the boiler body into the auxiliary bypass steam inlet channel.

[0020] Optionally, the steam entering from the auxiliary bypass steam inlet channel to the steam at the feedwater pump turbine outlet The loss is expressed as:

[0021]

[0022] Where: I tp The steam from the auxiliary bypass steam inlet channel to the feedwater pump turbine outlet loss;e ms Steam outlet for the boiler value;e ap Steam for the adjacent machine auxiliary steam value;e tpo Steam from the feedwater pump turbine outlet value.

[0023] Optionally, the objective function is expressed by the following formula:

[0024]

[0025] Where: ω1 is the first optimization target weight factor; ω2 is the second optimization target weight factor; ω3 is the third optimization target weight factor; D byp I is the steam flow from the boiler body into the turbine bypass channel; tp，max For I tp The maximum value of I tp，min For I tp The minimum value of .

[0026] Optionally, the constraints of the objective function are:

[0027]

[0028]

[0029] D ap ≥0

[0030] Where: γ1 is the set proportional coefficient; T tpo is the steam temperature at the outlet of the feedwater pump turbine; T min The lower limit of steam temperature at the feedwater pump turbine inlet; is the target steam temperature at the feedwater pump turbine inlet; T ms is the steam temperature at the outlet of the boiler body.

[0031] Optionally, when the steam pressure at the extraction outlet of the steam turbine unit reaches a set pressure value, the auxiliary steam channel of the adjacent unit is closed, the low-pressure steam inlet channel is opened, and the power of the feedwater pump turbine is controlled to be the target power;

[0032] When the steam flow in the auxiliary bypass steam inlet channel is less than a preset flow, the auxiliary bypass steam inlet channel is closed.

[0033] The technical solution of the present invention has the following advantages:

[0034] 1. The energy-saving starting system of a coal-fired power plant provided by the present invention comprises: a boiler body, a steam turbine unit, a condenser, a regenerative heater group, and a feedwater pump body which are connected in a loop, wherein a turbine steam inlet channel is connected between the boiler body and the steam turbine unit; further comprising: a steam turbine bypass channel, one end of which is connected to the boiler body and the other end is connected to the condenser, an auxiliary bypass steam inlet channel, one end of which is connected to the boiler body and the other end is connected to the feedwater pump turbine, the feedwater pump turbine is installed in conjunction with the feedwater pump body, and the outlet end of the feedwater pump turbine is connected to the steam turbine bypass channel; a heat recovery channel, one end of which is connected to the steam turbine unit and the other end is connected to the regenerative heater group, a low-pressure steam inlet channel is connected between the heat recovery channel and the auxiliary bypass steam inlet channel, and an adjacent machine auxiliary steam channel is also connected at the connection between the low-pressure steam inlet channel and the auxiliary bypass steam inlet channel.

[0035] The boiler's outlet is divided into three branches: the turbine inlet channel supplies steam to the turbine unit, driving it to generate electricity; the turbine bypass channel supplies steam to the condenser, recovering excess high-temperature steam; and the auxiliary bypass channel supplies steam to the feedwater pump turbine, driving the feedwater pump unit to operate, ensuring the most efficient recovery of bypass steam. A heat recovery channel is provided to recover residual heat steam from the turbine unit. By providing a low-pressure steam inlet channel and auxiliary steam from adjacent units, residual heat steam from the turbine unit and steam from adjacent units are channeled into the auxiliary bypass inlet channel to drive the feedwater pump turbine. Simultaneously, feedback is provided to regulate the amount of steam entering the turbine bypass channel and the turbine inlet channel from the boiler, ensuring coordinated operation of bypass steam recovery, main steam pressure control, and feedwater pump speed control. By recycling the startup bypass steam during coal-fired power plant startup, the plant's startup energy consumption is reduced and its thermal efficiency is improved.

[0036] 2. The energy-saving startup method of a coal-fired power plant provided by the present invention comprises: based on the target steam flow rate from the boiler body to the auxiliary bypass steam inlet channel, the steam flow rate entering the turbine bypass, the steam flow rate of the adjacent machine auxiliary steam, and the steam flow rate from the auxiliary bypass steam inlet channel to the steam outlet of the feedwater pump turbine. The objective function is obtained by calculating the loss. The objective function is optimized using the target steam flow rate from the boiler body to the auxiliary bypass steam inlet channel to obtain the maximum objective function value. The target steam flow rate from the boiler body to the auxiliary bypass steam inlet channel is controlled to the preset steam flow rate corresponding to the maximum objective function value. The amount of recovered bypass steam is optimized using the objective function optimization algorithm, ensuring that the bypass steam is recycled and utilized as efficiently as possible, while also maintaining the bypass's ability to control the main steam pressure, and ensuring the coordinated operation of recovering bypass steam, controlling the main steam pressure, and controlling the feedwater pump speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0038] Figure 1 It is a structural schematic diagram of the energy-saving startup system of a coal-fired power plant provided in an embodiment of the present invention.

[0039] Explanation of the accompanying symbols: 1. Boiler body; 2. Turbine steam inlet regulating valve; 3. Turbine bypass valve; 4. First bypass desuperheater; 5. Auxiliary bypass steam inlet regulating valve; 6. Second bypass desuperheater; 7. Steam turbine unit; 8. Adjacent machine auxiliary steam channel; 9. Low-pressure steam inlet regulating valve; 10. Feedwater pump turbine; 11. Condenser; 12. Condensate pump; 13. Regenerative heater unit; 14. Feedwater pump body; 15. Feedwater regulating valve. DETAILED DESCRIPTION

[0040] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0041] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0042] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0043] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0044] Example 1

[0045] like Figure 1 The figure shows an energy-saving startup system for a coal-fired power plant provided by this embodiment, comprising a boiler body 1, a steam turbine unit 7, a condenser 11, a condensate pump 12, a regenerative heater unit 13, a feedwater pump body 14, and a feedwater regulating valve 15, all of which are connected in a circular manner. The outlet of the feedwater regulating valve 15 is connected to the inlet of the boiler body 1. A turbine steam inlet passage is connected between the boiler body 1 and the steam turbine unit 7, and a turbine steam inlet regulating valve 2 is installed on the turbine steam inlet passage.

[0046] The system also includes a turbine bypass channel, an auxiliary bypass steam inlet channel, and a regenerative heat channel. The turbine bypass channel connects to the boiler body 1 at one end and to the condenser 11 at the other. A turbine bypass regulating valve is installed on the turbine bypass channel. The auxiliary bypass steam inlet channel connects to the boiler body 1 at one end and to the feedwater pump turbine 10 at the other end. The feedwater pump turbine 10 is mounted in conjunction with the feedwater pump body 14. The outlet of the feedwater pump turbine 10 connects to the turbine bypass channel. An auxiliary bypass steam inlet regulating valve 5 is installed on the auxiliary bypass steam inlet channel. The regenerative heat channel connects to the turbine unit 7 at one end and to the regenerative heat unit 13 at the other. A low-pressure steam inlet channel connects the regenerative heat channel and the auxiliary bypass steam inlet channel. The connection between the low-pressure steam inlet channel and the auxiliary bypass steam inlet channel also connects to the adjacent unit's auxiliary steam channel 8. A low-pressure steam inlet regulating valve is installed on the low-pressure steam inlet channel. A first bypass desuperheater 4 is installed downstream of the turbine bypass valve 3 on the turbine bypass channel, and a second bypass desuperheater 6 is installed downstream of the auxiliary bypass steam inlet regulating valve 5 on the auxiliary bypass steam inlet channel.

[0047] The outlet of the boiler body 1 is divided into three branches: the first branch is connected to the inlet of the turbine inlet regulating valve 2, the second branch is connected to the inlet of the turbine bypass valve 3, and the third branch is connected to the inlet of the auxiliary bypass inlet regulating valve 5. The outlet of the turbine inlet regulating valve 2 is connected to the steam inlet of the steam turbine unit 7, the exhaust steam outlet of the steam turbine unit 7 is connected to the exhaust steam inlet of the condenser 11, and the outlet of the turbine bypass valve 3 is connected to the inlet of the first bypass desuperheater 4. The outlet of the first bypass desuperheater 4 merges with the exhaust steam outlet of the feedwater pump turbine 10 and is then connected to the exhaust low-temperature steam inlet of the condenser 11. The condensate outlet of the condenser 11 is connected to the inlet of the condensate pump 12, the outlet of the condensate pump 12 is connected to the feedwater inlet of the regenerative heater group 13, and the steam inlet of the regenerative heater group 13 is connected to the extraction steam outlet of the steam turbine unit 7. The feedwater outlet of the regenerative heater group 13 is connected to the feedwater inlet of the steam-driven feedwater pump, which serves as the feedwater pump body 14. The outlet of the auxiliary bypass steam inlet regulating valve 5 is connected to the inlet of the second bypass desuperheater 6, which in turn merges with two other branches: one branch is the auxiliary steam passage 8 for the adjacent unit, and the other is the extraction steam outlet of the steam turbine group 7, which passes through the low-pressure steam inlet regulating valve 9. These three branches then merge and connect to the steam inlet of the feedwater pump turbine 10. The exhaust steam outlet of the feedwater pump turbine 10 merges with the outlet of the first bypass desuperheater 4. The shaft of the feedwater pump turbine 10 is coaxially connected to the shaft of the steam-driven feedwater pump. The feedwater outlet of the steam-driven feedwater pump is connected to the feedwater inlet of the feedwater regulating valve 15, which in turn is connected to the feedwater inlet of the boiler body 1.

[0048] Example 2

[0049] The present invention further provides an energy-saving startup operation method for a coal-fired power plant, which is applied to the energy-saving startup system for a coal-fired power plant described in Example 1 and is used to control the system operation of the energy-saving startup system for a coal-fired power plant during the startup phase. The operation method includes:

[0050] First, the steam temperature, steam pressure and steam flow rate at the boiler outlet are measured, as well as the steam flow rate consumed by the steam turbine unit during startup. The enthalpy and Measure the steam temperature and steam pressure of the auxiliary steam channel of the adjacent machine, and calculate the enthalpy and pressure of the steam input to the auxiliary steam channel of the adjacent machine through the water vapor physical property function. Value, enthalpy value is mainly used to calculate the energy consumed, The value is mainly used to calculate the generated damage.

[0051] Then calculate the thermodynamic parameters of the steam after the feedwater pump turbine. According to the target value of the steam flow entering the auxiliary bypass steam inlet regulating valve, the valve characteristic curve function can be used to calculate the valve pressure after the auxiliary bypass steam inlet regulating valve. According to the target value of the inlet steam temperature of the feedwater pump turbine, the outlet steam temperature and pressure of the feedwater pump turbine are calculated using the operating characteristic function of the feedwater pump turbine. The inlet steam enthalpy of the feedwater pump turbine and the outlet steam enthalpy of the feedwater pump turbine are calculated using the water vapor physical property function. After obtaining the inlet and outlet steam enthalpy values ​​of the feedwater pump steam turbine, the steam flow consumed by the feedwater pump steam turbine can be obtained through the power and relative internal efficiency of the feedwater pump steam turbine. Since the inlet steam of the feedwater pump steam turbine consists of two parts, one part is the steam entering the auxiliary bypass steam inlet regulating valve, and the other part is the steam in the auxiliary steam channel of the adjacent machine. When the steam flow target value entering the auxiliary bypass steam inlet regulating valve is known, the steam flow in the auxiliary steam channel of the adjacent machine can be calculated. Value, steam of the auxiliary steam channel of the adjacent machine Value and steam at the outlet of the feedwater pump turbine The auxiliary steam inlet regulating valve and feedwater pump turbine can be calculated by damage.

[0052] The optimization algorithm can be used to obtain the target value of steam flow entering the auxiliary bypass steam inlet regulating valve and the target value of steam temperature at the inlet of the feedwater pump turbine. There are three optimization goals: one is to use the bypass steam of the steam turbine unit as much as possible; the second is to reduce the amount of steam used in the auxiliary steam channel of the adjacent unit; and the third is to reduce the flow of steam into the auxiliary bypass steam inlet regulating valve and the feedwater pump turbine. loss.

[0053] Based on the target steam flow from the boiler body to the auxiliary bypass steam inlet channel, the steam flow entering the turbine bypass, the steam flow of the adjacent machine auxiliary steam, and the steam flow from the auxiliary bypass steam inlet channel to the feedwater pump turbine outlet loss, and obtain the objective function; optimize the objective function using the target steam flow rate entering from the boiler body to the auxiliary bypass steam inlet channel to obtain the maximum objective function value; control the target steam flow rate entering from the boiler body to the auxiliary bypass steam inlet channel to be the preset steam flow rate corresponding to the maximum objective function value.

[0054] Based on the target steam flow from the boiler body into the auxiliary bypass steam inlet channel, the boiler body outlet steam Value, steam flow of the adjacent auxiliary steam, steam flow of the adjacent auxiliary steam Value, steam at the outlet of the feedwater pump turbine The steam flow from the auxiliary bypass steam inlet channel to the outlet of the feedwater pump steam turbine is obtained by taking the power of the feedwater pump steam turbine and the relative internal efficiency of the feedwater pump steam turbine into consideration. loss.

[0055] The steam flow rate of the adjacent machine auxiliary steam is obtained based on the power of the feedwater pump turbine, the inlet steam enthalpy of the feedwater pump turbine, the outlet steam enthalpy of the feedwater pump turbine, the relative internal efficiency of the feedwater pump turbine and the target steam flow rate entering the auxiliary bypass steam inlet channel from the boiler body.

[0056] The steam flow of the adjacent auxiliary steam generator is updated in real time using the following formula:

[0057]

[0058] In formula (1): D ap P is the steam flow of the adjacent machine auxiliary steam; tp is the power of the feedwater pump turbine; h tpi is the inlet steam enthalpy of the feedwater pump turbine; h tpo is the outlet steam enthalpy of the feedwater pump turbine; η is the relative internal efficiency of the feedwater pump turbine; It is the target steam flow rate from the boiler body into the auxiliary bypass steam inlet channel.

[0059] Steam from the auxiliary bypass steam inlet channel to the feedwater pump turbine outlet The loss is expressed as:

[0060]

[0061] In formula (2): I tp The steam from the auxiliary bypass steam inlet channel to the feedwater pump turbine outlet loss;e ms Steam outlet for the boiler value;e ap Steam for the adjacent machine auxiliary steam value;e tpo Steam from the feedwater pump turbine outlet value.

[0062] The objective function is expressed by the following formula:

[0063]

[0064] In formula (3), ω1 is the first optimization target weight factor; ω2 is the second optimization target weight factor; ω3 is the third optimization target weight factor; D byp I is the steam flow from the boiler body into the turbine bypass channel; tp，max For I tpThe maximum value of I tp，min For I tp The minimum value of .

[0065] There are constraints in the optimization process. The constraints of the objective function are: the steam flow entering the turbine bypass valve cannot be too small to ensure the pressure control effect of the turbine bypass valve; the inlet steam temperature of the feedwater pump turbine cannot be too low to ensure the operating efficiency of the feedwater pump turbine; because the steam entering the auxiliary bypass steam inlet regulating valve must pass through the cooling effect of the second bypass desuperheater, the inlet steam temperature of the feedwater pump turbine must be lower than the outlet main steam temperature of the boiler body. The mathematical expression of the constraint conditions is:

[0066]

[0067]

[0068] D ap ≥0 (6)

[0069] In formula (4), γ1 is a set proportional coefficient, which is 0.8 in this embodiment.

[0070] In formula (5): T tpo is the steam temperature at the outlet of the feedwater pump turbine; T min is the lower limit of the steam temperature at the feedwater pump turbine inlet, which is 280°C in this embodiment; is the target steam temperature at the feedwater pump turbine inlet; T ms is the steam temperature at the outlet of the boiler body.

[0071] After obtaining the target steam flow rate entering the auxiliary bypass steam inlet regulating valve and the target steam temperature at the feedwater pump turbine inlet, PID feedback control is used to adjust the auxiliary bypass steam inlet regulating valve to ensure that the steam flow rate entering the auxiliary bypass steam inlet regulating valve is equal to the target steam flow rate. The second bypass desuperheater is adjusted to ensure that the steam temperature at the feedwater pump turbine inlet is equal to the target steam temperature. The turbine bypass valve and the first bypass desuperheater are adjusted to control the boiler outlet steam pressure and the steam temperature entering the condenser to their respective target values. During unit startup, if the steam pressure at the extraction outlet of the steam turbine unit reaches 0.8 MPa, the auxiliary steam passage of the adjacent unit is not used, and the power of the feedwater pump turbine is controlled by adjusting the low-pressure steam inlet regulating valve. If the valve signal of the auxiliary bypass steam inlet regulating valve is less than 5%, the auxiliary bypass steam inlet regulating valve is closed.

[0072] During the startup process of the unit, bypass steam is used to drive the feedwater pump turbine, which reduces the energy loss during the startup process and improves the thermal economy of the unit. The formulation of the control strategy ensures the coordinated operation of recovering bypass steam, controlling the main steam pressure and controlling the feedwater pump speed. By recycling the startup bypass steam of the coal-fired power plant, the startup energy consumption of the coal-fired power plant is reduced and the thermal economy of the power plant is improved.

[0073] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for energy-saving startup of a coal-fired power plant, characterized in that: The energy-saving startup system for coal-fired power plants includes: A boiler body (1), a steam turbine unit (7), a condenser (11), a regenerative heater unit (13), and a feedwater pump body (14) are cyclically connected, wherein a steam turbine steam inlet passage is connected between the boiler body (1) and the steam turbine unit (7); Also includes: a turbine bypass channel, one end of which is in communication with the boiler body (1) and the other end of which is in communication with the condenser (11); An auxiliary bypass steam inlet channel, one end of which is connected to the boiler body (1), and the other end of which is connected to a feedwater pump turbine (10), the feedwater pump turbine (10) being mounted in conjunction with the feedwater pump body (14), and the outlet end of the feedwater pump turbine (10) being connected to the turbine bypass channel; A heat recovery channel, one end of which is in communication with the steam turbine unit (7) and the other end of which is in communication with the heat recovery heater unit (13); a low-pressure steam inlet channel is in communication between the heat recovery channel and the auxiliary bypass steam inlet channel; and an adjacent machine auxiliary steam channel (8) is also in communication at the connection between the low-pressure steam inlet channel and the auxiliary bypass steam inlet channel; The operating method includes the following steps: obtaining an objective function based on a target steam flow rate entering the auxiliary bypass steam inlet passage from the boiler body, a steam flow rate entering the turbine bypass, a steam flow rate of auxiliary steam from an adjacent unit, and a steam exergy loss from steam entering the auxiliary bypass steam inlet passage to an outlet of a feedwater pump turbine; optimizing the objective function using the target steam flow rate entering the auxiliary bypass steam inlet passage from the boiler body to obtain a maximum objective function value; Controlling the target steam flow rate from the boiler body to the auxiliary bypass steam inlet channel to be a preset steam flow rate corresponding to the maximum objective function value; When the steam pressure at the extraction outlet of the steam turbine unit reaches the set pressure value, the auxiliary steam channel of the adjacent unit is closed, the low-pressure steam inlet channel is opened, and the power of the feedwater pump turbine is controlled to be the target power; when the steam flow in the auxiliary bypass steam inlet channel is less than the preset flow, the auxiliary bypass steam inlet channel is closed; Also includes: Based on the target steam flow rate from the boiler body to the auxiliary bypass steam inlet passage, the steam exergy value at the boiler body outlet, the steam flow rate of the adjacent turbine auxiliary steam, the steam exergy value of the adjacent turbine auxiliary steam, the steam exergy value at the feedwater pump turbine outlet, the power of the feedwater pump turbine, and the relative internal efficiency of the feedwater pump turbine, the steam exergy loss from the steam entering the auxiliary bypass steam inlet passage to the feedwater pump turbine outlet is obtained; The method further includes: obtaining the steam flow rate of the auxiliary steam of the adjacent machine based on the power of the feedwater pump steam turbine, the inlet steam enthalpy of the feedwater pump steam turbine, the outlet steam enthalpy of the feedwater pump steam turbine, the relative internal efficiency of the feedwater pump steam turbine, and the target steam flow rate entering the auxiliary bypass steam inlet passage from the boiler body; The steam flow of the adjacent auxiliary steam generator is updated in real time using the following formula: Where: D ap P is the steam flow of the adjacent machine auxiliary steam; tp is the power of the feedwater pump turbine; h tpi is the inlet steam enthalpy of the feedwater pump turbine; h tpo is the outlet steam enthalpy of the feedwater pump turbine; η is the relative internal efficiency of the feedwater pump turbine; is the target steam flow rate from the boiler body into the auxiliary bypass steam inlet channel; The steam exergy loss from the steam entering the auxiliary bypass steam inlet channel to the outlet of the feedwater pump turbine is expressed as: Where: I tp e is the steam exergy loss from the steam entering the auxiliary bypass steam inlet channel to the outlet of the feedwater pump turbine; ms is the steam exergy value at the outlet of the boiler; e ap is the steam exergy value of the adjacent machine auxiliary steam; e tpo is the steam exergy value at the outlet of the feedwater pump turbine; The objective function is expressed by the following formula: Where: ω1 is the first optimization target weight factor; ω2 is the second optimization target weight factor; ω3 is the third optimization target weight factor; D byp I is the steam flow rate from the boiler body into the turbine bypass channel; tp,max For I tp The maximum value of I tp,min For I tp The minimum value of .

2. The energy-saving startup method for a coal-fired power plant according to claim 1, characterized in that: A first bypass desuperheater (4) is installed on the turbine bypass channel, and a second bypass desuperheater (6) is installed on the auxiliary bypass steam inlet channel.

3. The energy-saving startup method for a coal-fired power plant according to claim 1, characterized in that: The constraints of the objective function are: Where: γ1 is the set proportional coefficient; T min The lower limit of steam temperature at the feedwater pump turbine inlet; is the target steam temperature at the feedwater pump turbine inlet; T ms is the steam temperature at the outlet of the boiler body.

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