A coal-fired heat supply unit island operation system, an operation method and a parameter calculation method

Abstract

This invention discloses an islanded operation system, operation method, and parameter calculation method for a coal-fired heating unit. The feedwater pump group outlet is connected to the water-side pipeline of the high-pressure heater group, and the water-side outlet of the high-pressure heater group is connected to the boiler feedwater inlet. The main steam outlet of the boiler is sequentially connected to a high-pressure steam inlet regulating valve, a high-pressure cylinder, a boiler reheater, an intermediate-pressure cylinder, and a low-pressure cylinder. The rotors of the high-pressure cylinder, intermediate-pressure cylinder, and low-pressure cylinder are coaxially connected and connected to the generator rotor. The exhaust port of the low-pressure cylinder is connected to the condenser. A branch of the main steam pipeline of the boiler is connected to the steam-side inlet of the first high-pressure heater in the high-pressure heater group. The boiler reheat steam header is divided into three branches, respectively connected to the steam-side inlet of the third high-pressure heater, the deaerator, and the heating steam header. A branch of the heating steam header is connected to the steam-side inlet of the first low-pressure heater. This system enables islanded operation of the coal-fired heating unit and improves the boiler's heat exchange stability and efficiency.

Description

Technical Field

[0001] This invention belongs to the field of coal-fired power units and relates to an islanded operation system, operation method and parameter calculation method for a coal-fired heating unit. Background Technology

[0002] In 2023, Huaneng Group's Yangliuqing Thermal Power Plant completed its islanded operation test after the modification of its coal-fired units. It became the first coal-fired power plant in China to achieve FCB (Fuel-Controlled Bus) functionality after modification. As the only power source in the second sub-region of the Tianjin power grid, the plant expanded its high- and low-pressure bypass systems for the turbines, enabling rapid load shedding for its coal-fired generating units in islanded operation. This filled a gap in domestic regulations on islanded operation control logic and related operational test procedures for coal-fired generating units, and improved the emergency guarantee capability for critical loads. However, this rudimentary modification and operation method only provides islanded operation for pure condensing power, and has drawbacks such as limited application scenarios and difficulty in widespread application. For example, it is not suitable for units that provide heating (in northern my country, coal-fired heating units are the main source of heat; due to the impact of renewable energy, these coal-fired heating units operate for very short periods during the non-heating season). Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide an islanded operation system, operation method and parameter calculation method for coal-fired heating units, enabling coal-fired heating units to achieve islanded operation and improving the stability and efficiency of boiler operation.

[0004] To achieve the above objectives, the present invention employs the following technical solution: An islanded operation system for a coal-fired heating unit includes a boiler and a generator; and a condensate pump, a low-pressure heater group, a deaerator, a feedwater pump group and a high-pressure heater group connected in series. The outlet of the feedwater pump unit is connected to the water-side pipeline of the high-pressure heater unit, and the water-side outlet of the high-pressure heater unit is connected to the boiler feedwater inlet. The main steam outlet of the boiler is sequentially connected to a high-pressure steam inlet regulating valve, a high-pressure cylinder, a boiler reheater, an intermediate-pressure cylinder, and a low-pressure cylinder. The high-pressure cylinder is connected to the boiler reheater via a cold reheat steam header. The boiler reheater is connected to the intermediate-pressure cylinder via an intermediate-pressure steam inlet regulating valve. The intermediate-pressure cylinder is connected to the low-pressure cylinder via an intermediate-low-pressure connecting pipe. A heating butterfly valve for the intermediate-low-pressure connecting pipe is installed on the intermediate-low-pressure connecting pipe. The rotors of the high-pressure cylinder, intermediate-pressure cylinder, and low-pressure cylinder are coaxially connected and connected to the generator rotor. The exhaust port of the low-pressure cylinder is connected to a condenser. A branch of the boiler's main steam pipeline leads to the No. 1 high-pressure heater's steam inlet regulating valve, which is connected to the No. 1 high-pressure heater's steam side inlet in the high-pressure heater group. The boiler reheat steam header branches into four paths: one path connects to the No. 3 high-pressure heater inlet valve via reheat steam, which is connected to the No. 3 high-pressure heater steam side inlet of the high-pressure heater group; another path connects to the deaerator control valve via reheat steam, which is connected to the deaerator; another path connects to the heating steam supply header control valve via reheat steam, which is connected to the heating steam supply header; and the third path connects to the industrial steam supply header via the hot reheat extraction steam supply valve group.

[0005] A branch of the heating steam supply main pipe leads out to the No. 1 low-pressure heater inlet valve, which is connected to the No. 1 low-pressure heater steam side inlet of the low-pressure heater group.

[0006] Optionally, the heating steam supply main pipe is also connected to a low-pressure cylinder cooling steam regulating valve, and the outlet of the low-pressure cylinder cooling steam regulating valve is connected to the low-pressure cylinder inlet; a branch of the medium-pressure cylinder exhaust pipe is connected to the heating steam supply main pipe through the medium exhaust steam extraction heating valve group; the outlet of the heating steam supply main pipe is also connected to the steam side inlet of the heating network heater, and the drain outlet of the heating network heater is connected to the condensate pump outlet pipe through the drain pump.

[0007] Optionally, the high-pressure cylinder exhaust port and the outlet of the high-pressure bypass desuperheating and pressure reducing device are connected to the cold reheat steam header; the boiler reheat steam header is also connected to the hot reheat extraction steam supply industrial steam valve group.

[0008] Optionally, the high-pressure heater group includes a No. 3 high-pressure heater, a No. 2 high-pressure heater, and a No. 1 high-pressure heater connected in series according to the direction of feedwater flow; the low-pressure heater group includes a No. 4 low-pressure heater, a No. 3 low-pressure heater, a No. 2 low-pressure heater, and a No. 1 low-pressure heater connected in series according to the direction of condensate flow.

[0009] Optionally, the high-pressure cylinder extraction port is connected to the No. 1 high-pressure heater via the high-pressure cylinder and the No. 1 high-pressure heater inlet steam regulating valve; the intermediate-pressure cylinder extraction port is connected to the No. 3 high-pressure heater via the intermediate-pressure cylinder and the No. 3 high-pressure heater inlet steam regulating valve; the low-pressure cylinder extraction port is connected to the No. 1 low-pressure heater via the low-pressure cylinder and the No. 1 low-pressure heater inlet steam regulating valve; and the intermediate-pressure cylinder exhaust port is connected to the deaerator via the intermediate-pressure cylinder and the deaerator inlet steam regulating valve.

[0010] An operation method for the isolated operation system of the coal-fired heating unit includes the following steps: Adjust the high-pressure steam inlet regulating valve and the medium-pressure steam inlet regulating valve to control the generator output power to be equal to the power consumption of the auxiliary equipment of the coal-fired power unit; Close the heating butterfly valve of the medium and low pressure connecting pipe to put the low pressure cylinder in zero output operation mode; Open the low-pressure cylinder cooling steam regulating valve to supply cooling steam to the low-pressure cylinder from the steam in the heating steam supply header; Close the steam inlet regulating valve from the high-pressure cylinder to the No. 1 high-pressure heater, and open the main steam inlet regulating valve to the No. 1 high-pressure heater to introduce the main steam from the boiler outlet into the No. 1 high-pressure heater. Close the steam inlet regulating valve from the intermediate pressure cylinder to the No. 3 high-pressure heater, and open the reheat steam inlet regulating valve to the No. 3 high-pressure heater to introduce boiler reheat steam into the No. 3 high-pressure heater. Close the intermediate pressure cylinder exhaust port and open the intermediate pressure cylinder to deaerator steam inlet regulating valve, then open the reheat steam to deaerator regulating valve to introduce boiler reheat steam into the deaerator. Close the steam inlet regulating valve from the low-pressure cylinder to the No. 1 low-pressure heater, and open the steam inlet regulating valve from the heating steam supply header to the No. 1 low-pressure heater to introduce the steam in the heating steam supply header into the No. 1 low-pressure heater.

[0011] Optionally, during operation, the high-pressure bypass desuperheating and pressure reducing device is activated, and the main steam at the boiler outlet is divided into three paths: the first path enters the high-pressure cylinder through the high-pressure inlet steam regulating valve and is discharged after doing work; the second path is discharged into the cold reheat steam header through the high-pressure bypass desuperheating and pressure reducing device; and the third path enters the No. 1 high-pressure heater through the main steam inlet steam regulating valve.

[0012] Optionally, during operation, the reheat steam to heating steam supply header regulating valve can be opened; the steam sources in the heating steam supply header include: steam from the intermediate pressure cylinder exhaust through the intermediate exhaust steam extraction heating valve group, and steam from the boiler reheat steam through the reheat steam to heating steam supply header regulating valve.

[0013] A method for calculating parameters of an islanded operation system of a coal-fired heating unit includes the following steps: Step 1, Determine boundary constraints: Determine heating parameters, industrial steam supply parameters, and low-pressure cylinder cooling steam flow rate, where heating parameters include heating steam flow rate and heat network condensate temperature; Establish the functional relationship between the steam inlet parameters of each heater in the high-pressure heater group and the low-pressure heater group and the new steam flow rate of the boiler; Step 2, thermal balance calculation of the unit's regenerative system: Set an initial value for the feedwater flow rate at the outlet of the No. 1 high-pressure heater, and make the steam flow rate at the boiler outlet equal to this initial value; obtain the steam inlet parameters of each heater based on the functional relationship in Step 1; Based on the outlet, inlet, and condensate temperatures of the No. 1 low-pressure heater and the enthalpy values ​​of the steam inlet and condensate outlet, calculate the flow rate of regenerative steam entering the No. 1 low-pressure heater and the flow rate of condensate entering the deaerator. Based on the outlet, inlet, and condensate temperatures of the No. 1 high-pressure heater and the enthalpy values ​​of the inlet steam and condensate, calculate the flow rate of regenerative steam entering the No. 1 high-pressure heater. Based on the outlet, inlet, and condensate temperatures of the No. 2 high-pressure heater, as well as the enthalpy values ​​of the steam inlet and condensate, and taking into account the influence of the condensate from the previous stage, the flow rate of regenerative steam entering the No. 2 high-pressure heater is calculated. Based on the outlet, inlet, and condensate temperatures of the No. 3 high-pressure heater, as well as the enthalpy values ​​of the steam inlet and condensate, and considering the influence of the condensate from the previous stage, the flow rate of regenerative steam entering the No. 3 high-pressure heater is calculated. Calculate the regenerative steam flow rate entering the deaerator based on the flow and heat balance of the inlet and outlet water of the deaerator. Step 3, Boiler-Turbine Mass Balance Calculation: Calculate the working steam flow of the high-pressure cylinder and intermediate-pressure cylinder based on the generator power equal to the auxiliary machine power consumption; calculate the boiler reheater outlet steam flow based on the regenerative steam flow, heating steam flow, industrial steam supply flow, and cooling steam flow, and then sum them to obtain the calculated value of the main steam flow at the boiler outlet.

[0014] Optionally, step 4 may also be included: Determine whether the difference between the calculated value of the main steam flow rate at the boiler outlet obtained in step 3 and the initial value of the feedwater flow rate at the outlet of the No. 1 high-pressure heater set in step 2 is zero. If the difference is zero, output the calculation results of each parameter; If the difference is not zero, set the initial value of the feedwater flow rate at the outlet of the No. 1 high-pressure heater to be equal to the calculated value of the main steam flow rate at the boiler outlet obtained in step 3, and repeat steps 2 and 3 until the two are equal.

[0015] Compared with the prior art, the present invention has the following beneficial effects: In islanded mode, this invention employs a low-pressure cylinder zero-output method to minimize power generation and match auxiliary equipment power consumption. Simultaneously, it breaks the limitations of traditional turbine-based staged steam extraction and reheating, utilizing regulating valve groups to directly introduce main steam and reheat steam into the high-pressure heater and deaerator across stages. This not only forcibly increases boiler feedwater temperature under low electrical load, improving boiler hydrodynamic circulation and combustion stability, but also ensures continuity of external heating and industrial steam supply through intermediate-pressure cylinder exhaust and reheat steam branches. Thus, it achieves safe operation of coal-fired heating units with low electrical load and stable thermal load in off-grid conditions. This solves the core problem of unstable boiler operation in coal-fired units under extremely low electrical load (islanded) conditions. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the islanded operation system of the coal-fired heating unit of the present invention.

[0017] Wherein: 1-Boiler; 2-High-pressure cylinder; 3-Medium-pressure cylinder; 4-Low-pressure cylinder; 5-Generator; 6-Condenser; 7-Condensate pump; 8-No. 4 low-pressure heater; 9-No. 3 low-pressure heater; 10-No. 2 low-pressure heater; 11-No. 1 low-pressure heater; 12-Deaerator; 13-Feed water pump group; 14-No. 3 high-pressure heater; 15-No. 2 high-pressure heater; 16-No. 1 high-pressure heater; 17-High-pressure steam inlet regulating valve; 18-Medium-pressure steam inlet regulating valve; 19-High-pressure exhaust check valve; 20-High-pressure bypass desuperheating and pressure reducing device; 21-Medium and low-pressure connecting pipe heating butterfly valve; 22-Medium exhaust steam extraction heating valve group; 23-Low-pressure... 24-Main steam to No. 1 high-pressure heater inlet steam regulating valve; 25-Hot reheat steam to No. 1 high-pressure heater inlet steam regulating valve; 26-Hot reheat extraction steam to industrial steam valve group; 27-High-pressure cylinder to No. 1 high-pressure heater inlet steam regulating valve; 28-Medium-pressure cylinder to No. 3 high-pressure heater inlet steam regulating valve; 29-Low-pressure cylinder to No. 1 low-pressure heater inlet steam regulating valve; 30-Heating steam supply header to No. 1 low-pressure heater inlet steam regulating valve; 31-Heating network heater; 32-Drain pump; 33-Hot reheat steam to heating steam supply header regulating valve; 34-Hot reheat steam to deaerator regulating valve; 35-Medium-pressure cylinder to deaerator inlet steam regulating valve. Detailed Implementation

[0018] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0019] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0020] like Figure 1 As shown, the islanded operation system of the coal-fired heating unit according to the present invention includes a boiler 1.

[0021] The main steam outlet of boiler 1 is connected to the inlet of high-pressure steam inlet regulating valve 17 via a pipeline. The outlet of high-pressure steam inlet regulating valve 17 is directly connected to the steam inlet of high-pressure cylinder 2. The exhaust port of high-pressure cylinder 2 merges with the outlet of high-pressure bypass desuperheating and pressure reducing device 20 and is connected to the cold reheat steam header, which in turn connects to the reheater inlet of boiler 1. The reheated steam pipeline after reheating is connected at its end to the inlet of intermediate-pressure steam inlet regulating valve 18, which is then connected to the steam inlet of intermediate-pressure cylinder 3.

[0022] The exhaust end of the intermediate-pressure cylinder 3 is connected to the inlet of the low-pressure cylinder 4 through a medium-low pressure connecting pipe. A heating butterfly valve 21 for the medium-low pressure connecting pipe is installed on this connecting pipe. The rotors of the high-pressure cylinder 2, intermediate-pressure cylinder 3, and low-pressure cylinder 4 are coaxially connected and are all connected to the rotor of the generator 5.

[0023] The lower part of the exhaust port of low-pressure cylinder 4 is connected to condenser 6, and the bottom outlet of condenser 6 is connected to condensate pump 7 via a pipeline. The outlet pipeline of condensate pump 7 is connected in series with the water-side pipelines of low-pressure heater 8 (No. 4), low-pressure heater 9 (No. 3), low-pressure heater 10 (No. 2), and low-pressure heater 11 (No. 1), and finally connects to the inlet of deaerator 12. The outlet of deaerator 12 is connected to feedwater pump group 13, and the outlet pipeline of feedwater pump group 13 is connected in series with the water-side pipelines of high-pressure heater 14 (No. 3), high-pressure heater 15 (No. 2), and high-pressure heater 16 (No. 1), and finally returns to the feedwater inlet of boiler 1, forming the main steam-water circulation loop.

[0024] Several key bypass and extraction steam connection branches are set on the high-pressure and reheat steam sides. A branch is led out from the main steam pipeline of boiler 1, connecting the main steam to the inlet steam regulating valve 24 of the No. 1 high-pressure heater. The outlet of the inlet steam regulating valve 24 of the No. 1 high-pressure heater is connected to the steam-side inlet of the No. 1 high-pressure heater 16. At the same time, the extraction steam port of the high-pressure cylinder 2 is also connected to the No. 1 high-pressure heater 16 through the inlet steam regulating valve 27 of the high-pressure cylinder to the No. 1 high-pressure heater. On the reheat steam header at the outlet of boiler 1, four branches are branched out: the first branch connects to the hot reheat extraction steam supply industrial steam valve group 26, which is used for external industrial heating interface; the second branch connects to the inlet steam regulating valve 25 of the No. 3 high-pressure heater, whose outlet is connected to the steam-side inlet of the No. 3 high-pressure heater 14; the third branch connects to the deaerator regulating valve 34, which is connected to the deaerator 12; and the fourth branch connects to the heating steam supply header regulating valve 33, which is connected to the heating steam supply header. In addition, the intermediate pressure cylinder 3 is also equipped with a steam extraction pipeline, which is connected to the No. 3 high pressure heater 14 through the intermediate pressure cylinder to the No. 3 high pressure heater inlet steam regulating valve 28, and to the deaerator 12 through the intermediate pressure cylinder to the deaerator inlet steam regulating valve 35.

[0025] A branch line is led out from the exhaust pipe of the intermediate-pressure cylinder 3 and connected to the heating steam supply main pipe through the intermediate exhaust steam extraction heating valve group 22. The heating steam supply main pipe has three outlet connection branches: one is connected to the steam side inlet of the heating network heater 31, and the condensate outlet of the heating network heater 31 is connected to the main condensate pipe of the condensate pump 7 outlet through the condensate pump 32; the second is connected to the heating steam supply main pipe to the steam inlet regulating valve 30 of the first low-pressure heater, and then connected to the steam side inlet of the first low-pressure heater 11, and the steam inlet regulating valve 29 from the low-pressure cylinder to the first low-pressure heater is closed; the third is connected to the cooling steam regulating valve 23 of the low-pressure cylinder, the outlet of which leads directly to the low-pressure cylinder 4, and is used to provide a source of cooling steam when the steam inlet of the low-pressure cylinder is cut off during islanded operation.

[0026] During normal operation, the main steam generated by boiler 1 sequentially enters high-pressure cylinder 2, intermediate-pressure cylinder 3, and low-pressure cylinder 4 to perform work, jointly driving generator 5 to generate electricity. The exhaust steam from low-pressure cylinder 4 enters condenser 5 for condensation, is then pressurized by condensate pump 6, and sequentially enters low-pressure heater 8 (number four), low-pressure heater group 9 (number three), low-pressure heater 10 (number two), and low-pressure heater 11 (number one). It then enters deaerator 12 for heating, and after being pressurized by feedwater pump 13, sequentially enters high-pressure heater 14 (number three), high-pressure heater 15 (number two), and high-pressure heater 16 (number one) for further heating before returning to boiler 1 to complete the thermal cycle. Hot re-extraction steam is supplied to the industrial steam valve group 26 for regulation, and an equal amount of demineralized water is added to condenser 5. The heating butterfly valve 21 of the medium- and low-pressure connecting pipe and the steam extraction valve group 22 of the medium-pressure cylinder 3 and the steam inlet of the low-pressure cylinder 4 are involved in the regulation. Steam is extracted from the medium- and low-pressure connecting pipes at the exhaust of the medium-pressure cylinder 3 and the steam inlet of the low-pressure cylinder 4 to supply heating. The steam enters the heating network heater 31 to release heat, and the condensate is returned to the outlet of the condensate pump 7 via the condensate pump 32. At this time, the low-pressure cylinder cooling steam regulating valve 23, the high-pressure bypass desuperheating and pressure reducing device 20, and the reheat steam to heating steam supply main pipe regulating valve 33 are opened according to the operation needs. The strategy is to open them to participate in regulation during deep peak shaving and close them during other periods. In addition, the following valves are normally open: high-pressure cylinder to No. 1 high-pressure heater inlet steam regulating valve 27, intermediate-pressure cylinder to No. 3 high-pressure heater inlet steam regulating valve 28, low-pressure cylinder to No. 1 low-pressure heater inlet steam regulating valve 29, intermediate-pressure cylinder to deaerator inlet steam regulating valve 35; main steam to No. 1 high-pressure heater inlet steam regulating valve 24, reheat steam to No. 3 high-pressure heater inlet steam regulating valve 25, heating steam supply main pipe to No. 1 low-pressure heater inlet steam regulating valve 30, reheat steam to deaerator regulating valve 34.

[0027] In islanded operation mode, the output power of generator 5 of the coal-fired power unit is the same as the power consumption of all auxiliary equipment of the coal-fired power unit. That is, the coal-fired power unit neither supplies power to the grid nor disconnects power from the grid. The process of switching the coal-fired power unit from normal operation mode to islanded operation mode is described below.

[0028] The low-pressure cylinder of the steam turbine is in zero-output operation mode. The heating butterfly valve 21 of the intermediate-low pressure connecting pipe is closed, and the low-pressure cylinder cooling steam regulating valve 23 participates in regulation, with heating steam providing cooling steam to the low-pressure cylinder. The high-pressure inlet steam regulating valve 17 and the intermediate-pressure inlet steam regulating valve 18 participate in regulation, controlling the output power of the steam turbine generator 5 to equal the power consumption of all auxiliary machines of the coal-fired power unit. The high-pressure cylinder to No. 1 high-pressure heater inlet steam regulating valve 27, the intermediate-pressure cylinder to No. 3 high-pressure heater inlet steam regulating valve 28, the low-pressure cylinder to No. 1 low-pressure heater inlet steam regulating valve 29, and the intermediate-pressure cylinder to deaerator inlet steam regulating valve 35 are closed. The main steam to No. 1 high-pressure heater inlet steam regulating valve 24, the reheat steam to No. 3 high-pressure heater inlet steam regulating valve 25, the heating steam supply main pipe to No. 1 low-pressure heater inlet steam regulating valve 30, the reheat steam to deaerator regulating valve 34, the high-pressure bypass desuperheating and pressure reducing device 20, and the reheat steam to heating steam supply main pipe regulating valve 33 are open and participate in regulation. The main steam from boiler 1 outlet is divided into three paths: one path enters the high-pressure cylinder 2 through the high-pressure inlet steam regulating valve 17 and then enters the cold reheat steam header; another path enters the cold reheat steam header through the high-pressure bypass desuperheating and pressure reducing device 20; and the third path enters the No. 1 high-pressure heater through the main steam inlet steam regulating valve 24. The cold reheat steam from the header enters the boiler reheater and absorbs heat, then is divided into five paths: one path enters the intermediate-pressure cylinder 3 through the intermediate-pressure inlet steam regulating valve 18 and then exits through valve group 22 into the heating steam header; another path supplies industrial steam externally through the hot reheat extraction steam valve group 26; another path supplies the No. 3 high-pressure heater through the reheat steam inlet steam regulating valve 25; another path supplies the No. 3 high-pressure heater through the reheat steam inlet steam regulating valve 25; another path supplies the deaerator through the deaerator regulating valve 34; and the third path supplies the heating steam header through the heating steam supply header regulating valve 33. The heating steam header is supplied by the steam inlet and outlet of the intermediate pressure cylinder 3. The outlet is divided into three paths: one path goes through the heating steam header to the No. 1 low-pressure heater steam inlet regulating valve 30 and enters the No. 1 low-pressure heater; another path goes into the heating network heater 31 to release heat; the condensate is returned to the outlet of the condensate pump 7 via the condensate pump 32; and the third path goes through the low-pressure cylinder cooling steam regulating valve 23 and enters the low-pressure cylinder 4.

[0029] In the isolated operation mode, each parameter is controlled according to the method provided by this invention. The parameter operation control calculation process is as follows: Step 1: Define the boundary constraints.

[0030] For coal-fired heating units, the heating parameters must be clearly defined. The heating parameters are: heating steam flow rate. Q cn (t / h), condensate temperature of the heating network t ss (°C); If it also supplies steam for industrial use, the parameter is the steam supply flow rate. Q gq (t / h).

[0031] The steam turbine adopts a zero-output operation mode for low-pressure cylinder 4, and the cooling steam flow rate of low-pressure cylinder 4 is... Qlq (t / h).

[0032] For heaters in a regenerative system, such as high-pressure heater 16 (No. 1), high-pressure heater 15 (No. 2), high-pressure heater 14 (No. 3), and low-pressure heater 11 (No. 1), their heat exchange performance is characterized by the heat exchange terminal difference. The upper terminal difference is defined as the difference between the saturation temperature corresponding to the heater inlet steam pressure and the heater outlet water temperature; the lower terminal difference is defined as the difference between the heater condensate temperature and the heater inlet water temperature. For operating units, the heater terminal difference is mainly affected by the inlet steam parameters.

[0033] The extraction parameters (pressure, temperature) of each stage of the steam turbine regenerative system can be considered to be positively correlated with the boiler load. Based on the statistical analysis of the operating data of the coal-fired heating unit, it can be concluded that the No. 1 high-pressure heater 16 ( p 1h , t 1h ), No. 2 high-pressure heater 15 ( p 2h , t 2h ), No. 3 high-pressure heater 14 ( p 3h , t 3h ), No. 1 low-pressure heater 11 ( p 5h , t 5h The steam inlet parameters and the new steam flow rate of boiler 1 Q b The correlation characteristics are shown in the following formula ①: ( p 1h , t 1h )= f 1 ( Q b ) ( p 2h , t 2h )= f 1 ( Q b ) ( p 3h , t 3h )= f 1 ( Q b ) ( p 4h , t 4h )= f 1 (Q b ) ( p 5h , t 5h )= f 1 ( Q b ) Step 2: Calculation of thermal balance of the unit's regenerative system.

[0034] 1) Assign an initial value to the feedwater flow rate at outlet 16 of the No. 1 high-pressure heater. Q gs0 .

[0035] 2) Steam flow rate at boiler 1 outlet Q b Equal to the feedwater flow rate of boiler 1: Q b = Q gs0 .

[0036] 3) Based on formula ①, the steam inlet parameters of No. 1 high-pressure heater 16, No. 2 high-pressure heater 15, No. 3 high-pressure heater 14, deaerator 12, and No. 1 low-pressure heater 11 are obtained.

[0037] 4) Based on the thermodynamic performance of each high-pressure heater and low-pressure heater, as well as the steam inlet parameters, the upper and lower end differences of each heater are obtained.

[0038] 5) Calculate the thermal balance of the No. 1 low-pressure heater 11 on the condensate side. Q njs × C p ×( t 5o - t 5i )= Q 5c ×( h ( p 5h , t 5h )- h ( p 5h , t 5ss )) Q njs = Q 5c + Q lq + Q gq + Qcn In the formula, Q njs The condensate flow rate entering deaerator 12 is expressed in t / h. t 5o , t 5i , t 5ss The outlet, inlet, and condensate temperatures of the No. 1 low-pressure heater 11 are respectively, in °C. Q 5c The regenerative steam flow rate entering the No. 1 low-pressure heater 11 is t / h; Q lq The cooling steam flow rate for low-pressure cylinder 4 is t / h. C p is the specific heat capacity of water at constant pressure, kJ / kg·K; h ( p 5h , t 5h ), h ( p 5h , t 5ss The values ​​are the steam enthalpy and condensate enthalpy of the No. 1 low-pressure heater 11, respectively, in kJ / kg. In summary, by solving the two equations above, we obtain... Q 5c and Q njs .

[0039] 6) Calculate the thermodynamic balance of the No. 1 high-pressure heater. Q gs0 × C p ×( t 1o - t 1i )= Q 1c ×( h ( p 1h , t 1h )- h ( p 1h , t 1ss )) In the formula, t 1o ,t 1i , t 1ss The outlet, inlet, and condensate temperatures of the No. 1 high-pressure heater 16 are respectively, in °C; Q 1c The regenerative steam flow rate, t / h, entering the No. 1 high-pressure heater 16 is drawn from the main steam at the outlet of boiler 1.

[0040] h ( p 1h , t 1h ), h ( p 1h , t 1ss The values ​​are the steam enthalpy and condensate enthalpy of the No. 1 high-pressure heater, respectively, in kJ / kg.

[0041] 7) Calculate the thermal balance of high-pressure heater 15. Q gs0 × C p ×( t 2o - t 2i )= Q 2c ×( h ( p 2h , t 2h )- h ( p 2h , t 2ss ))+ Q 1c ×( h ( p 1h , t 1ss )- h ( p 2h , t 2ss )) In the formula, t 2o , t 2i , t 2ss The outlet, inlet, and condensate temperatures of the No. 2 high-pressure heater 15 are respectively, in °C; where, t 2o= t 1i .

[0042] Q 2c The regenerative steam flow rate, t / h, entering the No. 2 high-pressure heater 15 is drawn from the cold resteamer at the inlet of boiler 1.

[0043] h ( p 2h , t 2h ), h ( p 2h , t 2ss The values ​​are the steam enthalpy and condensate enthalpy of the No. 2 high-pressure heater, respectively, in kJ / kg.

[0044] 8) Calculate the thermal balance of high-pressure heater 14 (No. 3). Q gs0 × C p ×( t 3o - t 3i )= Q 3c ×( h ( p 3h , t 3h )- h ( p 3h , t 3ss ))+( Q 1c + Q 2c )×( h ( p 2h , t 2ss )- h ( p 3h , t 3ss )) In the formula, t 3o , t 3i , t 3ss The outlet, inlet, and condensate temperatures of the No. 3 high-pressure heater 14 are respectively, in °C; among which, t 3o =t 2i .

[0045] Q 3c The regenerative steam flow rate, t / h, entering the No. 3 high-pressure heater 14 is drawn from the reheat steam generator outlet at the boiler 1 outlet.

[0046] h ( p 3h , t 3h ), h ( p 3h , t 3ss The values ​​are the steam enthalpy and condensate enthalpy of the No. 3 high-pressure heater 14, respectively, in kJ / kg.

[0047] 9) Calculate the thermal balance of deaerator 12 Q gs0 × C p × t 3i = Q njs × C p × t 5o +( Q 1c + Q 2c + Q 3c )× h ( p 3h , t 3ss )+ Q 3c × h ( p 4h , t 4h ) In the formula, Q 4c The regenerative steam flow rate (t / h) entering the deaerator 12 is drawn from the reheat steam outlet at the boiler inlet or the exhaust port of the intermediate pressure cylinder 3.

[0048] h ( p 4h , t 4h () is the enthalpy of the steam entering the deaerator 12, kJ / kg.

[0049] Step 3: Boiler-turbine mass balance calculation.

[0050] 1) Based on the islanded operation mode, the power of generator 5 is equal to the power consumption of the unit's auxiliary equipment. Combining this with the known working characteristics of the steam turbine, calculate the steam flow rate of the main steam from boiler 1 entering the high-pressure cylinder 2 to perform work. Q gg And the steam flow rate of reheat steam from boiler 1 entering intermediate pressure cylinder 3 to perform work. Q zg The unit is t / h.

[0051] 2) Low-pressure cylinder 4 is in zero-output operation mode. Determine the cooling steam flow rate of low-pressure cylinder 4. Q lq .

[0052] 3) The cooling steam of the low-pressure cylinder 4 and the regenerating steam of the No. 1 low-pressure heater 11 are both drawn from the heating steam header.

[0053] 4) Calculate the steam flow rate at the boiler reheater outlet. Q rh Q rh = Q 3c + Q gq + Q 4c + Q cn + Q 5c + Q lq 5) Calculate the main steam flow rate at boiler outlet 1. Q ms Q ms =Q rh + Q 1c + Q 2c Step 4: Iterative Calculation For a given coal-fired power generating unit, the main steam flow rate at boiler 1 outlet is... Q ms It equals the water supply flow rate at outlet 16 of high-pressure heater No. 1.

[0054] 1) Determine the result obtained in step 3 Q ms -Q gs0 = 0? 2) If so, the calculation is considered complete, and the calculation results of each parameter are generated to guide the operation of the unit.

[0055] 3) If not, then let Q ms =Q gs0 Then perform steps 1, 2, and 3 to obtain a new result. Q ms .

[0056] 4) Execute step 1) until the two are equal.

[0057] This embodiment focuses on the goal of achieving islanded operation of coal-fired heating units. It proposes an innovative idea for reconstructing the steam-water thermal system for islanded operation by providing steam bypass and cross-stage regeneration. Combining the turbine high-pressure bypass system, the hot re-extraction system, and the low-pressure cylinder zero-output system, during system operation, the work capacity is reduced by partially cutting off high-pressure cylinder 2 and intermediate-pressure cylinder 3, and completely cutting off low-pressure cylinder 4. The hot re-extraction system supplies industrial steam and heating steam. Through the reconstruction of the steam flow system, the steam inlet of high-pressure cylinder 2, intermediate-pressure cylinder 3, and heating steam are used for No. 1 high-pressure heater 16, No. 3 high-pressure heater 14, and No. 1 low-pressure heater 11, respectively, to improve the effect of the regeneration system and the inlet water temperature of boiler 1, thereby improving the heat exchange stability and effect of boiler 1.

[0058] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0059] In the above embodiments of this application, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0060] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. The device embodiments described above are merely illustrative; for example, the division of units can be a logical functional division, and in actual implementation, there may be other division methods. For instance, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual coupling, direct coupling, or communication connection may be through some interfaces; the indirect coupling or communication connection between units or modules may be electrical or other forms.

[0061] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0062] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

[0063] It should be understood that the above description is for illustrative purposes and not for limitation. Many embodiments and applications beyond the provided examples will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of this patent should not be determined by reference to the above description, but rather by reference to the foregoing claims and the full scope of their equivalents. For purposes of completeness, all articles and references, including patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the foregoing claims is not intended as a waiver of that subject matter, nor should it be construed as an indication that the applicant has not considered that subject matter as part of the disclosed inventive subject matter.

Claims

1. An islanded operation system for a coal-fired heating unit, characterized in that, It includes a boiler (1) and a generator (5); and a condensate pump (7), a low-pressure heater group, a deaerator (12), a feed water pump group (13) and a high-pressure heater group connected in series. The outlet of the water pump group (13) is connected to the water-side pipeline of the high-pressure heater group, and the water-side outlet of the high-pressure heater group is connected to the water inlet of the boiler (1). The main steam outlet of the boiler (1) is connected in sequence to a high-pressure steam inlet regulating valve (17), a high-pressure cylinder (2), a boiler reheater, a medium-pressure cylinder (3), and a low-pressure cylinder (4). The high-pressure cylinder (2) is connected to the boiler reheater through a cold reheat steam header. The boiler reheater is connected to the medium-pressure cylinder (3) through a medium-pressure steam inlet regulating valve (18). The medium-pressure cylinder (3) is connected to the low-pressure cylinder (4) through a medium-low pressure connecting pipe. A medium-low pressure connecting pipe heating butterfly valve (21) is installed on the medium-low pressure connecting pipe. The rotors of the high-pressure cylinder (2), the medium-pressure cylinder (3), and the low-pressure cylinder (4) are coaxially connected and connected to the rotor of the generator (5). The exhaust port of the low-pressure cylinder (4) is connected to a condenser (6). The main steam pipeline of the boiler (1) leads out a branch through the main steam to the steam inlet regulating valve (24) of the No. 1 high-pressure heater, which is connected to the steam side inlet of the No. 1 high-pressure heater (16) in the high-pressure heater group; The boiler (1) reheat steam main pipe branches out into four paths: one path leads to the No. 3 high-pressure heater inlet regulating valve (25) via reheat steam and is connected to the No. 3 high-pressure heater (14) steam side inlet in the high-pressure heater group; another path leads to the deaerator regulating valve (34) via reheat steam and is connected to the deaerator (12); another path leads to the heating steam supply main pipe regulating valve (33) via reheat steam and is connected to the heating steam supply main pipe; and the third path leads to the industrial steam supply main pipe via the hot reheat extraction steam supply industrial steam valve group (26). A branch of the heating steam supply main pipe leads out to the No. 1 low-pressure heater inlet valve (30) and is connected to the No. 1 low-pressure heater (11) steam side inlet of the low-pressure heater group.

2. The islanded operation system for a coal-fired heating unit according to claim 1, characterized in that, The heating steam supply main pipe is also connected to the low-pressure cylinder cooling steam regulating valve (23), and the outlet of the low-pressure cylinder cooling steam regulating valve (23) is connected to the inlet of the low-pressure cylinder (4); the exhaust pipe of the medium-pressure cylinder (3) leads out a branch and is connected to the heating steam supply main pipe through the medium exhaust steam extraction heating valve group (22); the outlet of the heating steam supply main pipe is also connected to the steam side inlet of the heat network heater (31), and the drain outlet of the heat network heater (31) is connected to the outlet pipe of the condensate pump (7) through the drain pump (32).

3. The islanded operation system for a coal-fired heating unit according to claim 1, characterized in that, The exhaust port of the high-pressure cylinder (2) is connected to the outlet of the high-pressure bypass de-heating and pressure reducing device (20) and then connected to the cold reheat steam header; the reheat steam header of the boiler (1) is also connected to the hot reheat extraction steam supply industrial steam valve group (26).

4. The islanded operation system for a coal-fired heating unit according to claim 1, characterized in that, The high-pressure heater group includes a No. 3 high-pressure heater (14), a No. 2 high-pressure heater (15), and a No. 1 high-pressure heater (16) connected in series according to the direction of water flow; the low-pressure heater group includes a No. 4 low-pressure heater (8), a No. 3 low-pressure heater (9), a No. 2 low-pressure heater (10), and a No. 1 low-pressure heater (11) connected in series according to the direction of condensate flow.

5. The islanded operation system for a coal-fired heating unit according to claim 4, characterized in that, The steam extraction port of the high-pressure cylinder (2) is connected to the No. 1 high-pressure heater (16) via the high-pressure cylinder to the No. 1 high-pressure heater inlet steam regulating valve (27); the steam extraction port of the intermediate-pressure cylinder (3) is connected to the No. 3 high-pressure heater (14) via the intermediate-pressure cylinder to the No. 3 high-pressure heater inlet steam regulating valve (28); the steam extraction port of the low-pressure cylinder (4) is connected to the No. 1 low-pressure heater (11) via the low-pressure cylinder to the No. 1 low-pressure heater inlet steam regulating valve (29); the steam exhaust port of the intermediate-pressure cylinder (3) is connected to the deaerator (12) via the intermediate-pressure cylinder to the deaerator inlet steam regulating valve (35).

6. An operation method for an islanded operation system of a coal-fired heating unit according to any one of claims 1-5, characterized in that, Includes the following processes: Adjust the high-pressure steam inlet regulating valve (17) and the medium-pressure steam inlet regulating valve (18) to control the output power of the generator (5) to be equal to the power consumption of the auxiliary equipment of the coal-fired power unit; Close the heating butterfly valve (21) of the medium and low pressure connecting pipe to put the low pressure cylinder (4) into zero output operation mode; Open the low-pressure cylinder cooling steam regulating valve (23) to supply cooling steam to the low-pressure cylinder (4) from the steam in the heating steam supply header; Close the steam inlet regulating valve (27) from the high-pressure cylinder to the No. 1 high-pressure heater, open the steam inlet regulating valve (24) from the main steam to the No. 1 high-pressure heater, and introduce the main steam from the boiler (1) outlet into the No. 1 high-pressure heater (16). Close the steam inlet regulating valve (28) from the intermediate pressure cylinder to the No. 3 high pressure heater, open the reheat steam inlet regulating valve (25) to the No. 3 high pressure heater, and introduce the reheat steam from the boiler (1) into the No. 3 high pressure heater (14). Close the steam outlet of the intermediate pressure cylinder (3) and the steam inlet regulating valve (35) of the intermediate pressure cylinder to the deaerator. Open the reheat steam to the deaerator regulating valve (34) and introduce the reheat steam of the boiler (1) into the deaerator (12). Close the steam inlet regulating valve (29) from the low-pressure cylinder to the No. 1 low-pressure heater, and open the steam inlet regulating valve (30) from the heating steam supply header to the No. 1 low-pressure heater to introduce the steam in the heating steam supply header into the No. 1 low-pressure heater (11).

7. The operating method according to claim 6, characterized in that, During operation, the high-pressure bypass desuperheating and pressure reducing device (20) is activated, and the main steam at the boiler (1) outlet is divided into three paths: the first path enters the high-pressure cylinder (2) through the high-pressure inlet steam regulating valve (17) and is discharged after doing work; the second path is discharged into the cold reheat steam header through the high-pressure bypass desuperheating and pressure reducing device (20); and the third path enters the No. 1 high-pressure heater (16) through the main steam to the No. 1 high-pressure heater inlet steam regulating valve (24).

8. The operating method according to claim 6, characterized in that, During operation, the reheat steam to heating steam supply main pipe regulating valve (33) is opened; the steam sources in the heating steam supply main pipe include: the steam discharged from the intermediate pressure cylinder (3) through the intermediate exhaust steam extraction heating valve group (22), and the steam discharged from the boiler (1) through the reheat steam to heating steam supply main pipe regulating valve (33).

9. A method for calculating parameters of an islanded operation system of a coal-fired heating unit based on any one of claims 1-5, characterized in that, Includes the following processes: Step 1, determine boundary constraints: determine heating parameters, industrial steam supply parameters and cooling steam flow of low-pressure cylinder (4), wherein heating parameters include heating steam flow and heat network condensate temperature; establish the functional relationship between the steam inlet parameters of each heater in the high-pressure heater group and the low-pressure heater group and the new steam flow of boiler (1); Step 2, thermal balance calculation of the unit's regenerative system: set the initial value of the feedwater flow rate at the outlet of the No. 1 high-pressure heater (16), and make the steam flow rate at the outlet of the boiler (1) equal to the initial value; obtain the steam inlet parameters of each heater according to the functional relationship in Step 1; Based on the outlet, inlet, and condensate temperatures of the No. 1 low-pressure heater (11) and the enthalpy values ​​of the steam inlet and condensate outlet, calculate the flow rate of the regenerated steam entering the No. 1 low-pressure heater (11) and the flow rate of the condensate entering the deaerator (12). Based on the outlet, inlet, and condensate temperatures of the No. 1 high-pressure heater (16) and the enthalpy values ​​of the inlet steam and condensate, calculate the flow rate of regenerative steam entering the No. 1 high-pressure heater (16). Based on the outlet, inlet, and condensate temperatures of the No. 2 high-pressure heater (15) and the enthalpy values ​​of the steam inlet and condensate, and combined with the influence of the condensate from the previous stage, the flow rate of regenerative steam entering the No. 2 high-pressure heater (15) is calculated. Based on the outlet, inlet, and condensate temperatures of the No. 3 high-pressure heater (14) and the enthalpy values ​​of the steam inlet and condensate, and combined with the influence of the condensate in the previous stage, the flow rate of regenerative steam entering the No. 3 high-pressure heater (14) is calculated. Based on the flow balance and heat balance of the inlet and outlet water of the deaerator (12), the flow rate of regenerated steam entering the deaerator (12) is calculated. Step 3, Boiler-Turbine Mass Balance Calculation: Calculate the working steam flow of the high-pressure cylinder (2) and the intermediate-pressure cylinder (3) based on the power of the generator (5) being equal to the power consumption of the auxiliary machine; calculate the boiler reheater outlet steam flow based on the regenerative steam flow, heating steam flow, industrial steam supply flow and cooling steam flow, and then sum them to obtain the calculated value of the main steam flow at the boiler (1) outlet.

10. The parameter calculation method according to claim 9, characterized in that, It also includes step 4: Determine whether the difference between the calculated value of the main steam flow rate at the boiler outlet (1) obtained in step 3 and the initial value of the feedwater flow rate at the outlet of the No. 1 high-pressure heater (16) set in step 2 is zero; If the difference is zero, output the calculation results of each parameter; If the difference is not zero, then set the initial value of the feedwater flow rate at the outlet of the No. 1 high-pressure heater (16) to be equal to the calculated value of the main steam flow rate at the outlet of the boiler (1) obtained in step 3, and repeat steps 2 and 3 until the two are equal.

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