Energy cascade utilization heat supply system and method based on high and medium pressure cylinder division

Abstract

The application provides a heat supply system and method based on energy gradient utilization of high-pressure cylinder and medium-pressure cylinder division, which comprises a boiler, a second high-pressure cylinder, a first high-pressure cylinder, a first medium-pressure cylinder, a second medium-pressure cylinder, a low-pressure cylinder and a generator, wherein the boiler, the second high-pressure cylinder, the first high-pressure cylinder, the first medium-pressure cylinder, the second medium-pressure cylinder, the low-pressure cylinder and the generator are sequentially connected; the boiler is used for heating condensate water to generate steam, and the steam is delivered to the first high-pressure cylinder; the boiler is also used for heating cold re-steam discharged from the second high-pressure cylinder to generate hot re-steam, and the hot re-steam is delivered to the first medium-pressure cylinder; and the generator is used for generating electric energy based on the steam. The technical scheme provided by the application divides the high-pressure cylinder and the medium-pressure cylinder into two cylinders, can meet the demand of high-pressure and low-pressure industrial steam supply, and realizes steam energy gradient utilization and energy saving and emission reduction.

Description

Technical Field

[0001] This application relates to the field of energy utilization, and in particular to a heating system and method based on energy cascade utilization of intermediate and high-pressure cylinders. Background Technology

[0002] Renewable energy sources such as wind and solar power are characterized by intermittency and volatility, posing new challenges to the power grid. Combined heat and power (CHP) units, while providing industrial steam, also frequently participate in peak shaving, especially during deep peak shaving. The original design pressure of the industrial steam extraction points cannot meet the industrial steam demand, necessitating a switch to higher extraction pressure points. For example, thermal power units use main steam desuperheating and depressurization under low-load conditions to meet the parameter requirements of high-pressure industrial steam, and hot reheat steam desuperheating and depressurization to meet the parameter requirements of low-pressure industrial steam. These conventional low-load steam source switching methods result in poor unit thermal economy and significantly increased coal consumption. Therefore, it is imperative to comprehensively consider energy-saving and consumption-reducing retrofits for coal-fired power plants, heating system upgrades, and flexibility improvements, achieving a coordinated "three-pronged" approach. Thus, developing a new, efficient, flexible, and energy-efficient CHP technology that can achieve energy cascade utilization and meet the unit's peak shaving needs for large-scale steam supply is urgently needed. Summary of the Invention

[0003] This application provides a heating system and method based on the energy cascade utilization of high-pressure and medium-pressure cylinders, in order to at least solve the technical problems of existing steam-supply cogeneration technology being unable to save energy and reduce emissions, and the poor economic efficiency caused by energy cascade utilization.

[0004] The first aspect of this application proposes an energy cascade utilization heating system based on a high-pressure cylinder and intermediate-pressure cylinder, comprising: a boiler, a second high-pressure cylinder, a first high-pressure cylinder, a first intermediate-pressure cylinder, a second intermediate-pressure cylinder, a low-pressure cylinder, and a generator, wherein the boiler, the second high-pressure cylinder, the first high-pressure cylinder, the first intermediate-pressure cylinder, the second intermediate-pressure cylinder, the low-pressure cylinder, and the generator are connected in sequence;

[0005] The boiler is used to heat condensate to generate steam and deliver the steam to the first high-pressure cylinder; The boiler is also used to heat the cold resteam discharged from the second high-pressure cylinder to generate hot resteam, and to deliver the hot resteam to the first intermediate-pressure cylinder; The second high-pressure cylinder, the first high-pressure cylinder, the first intermediate-pressure cylinder, and the second intermediate-pressure cylinder are all used to provide steam to the user; The generator is used to generate electricity based on steam.

[0006] Preferably, a first connecting pipe is provided between the second high-pressure cylinder and the first high-pressure cylinder; A second connecting pipe is provided between the first intermediate pressure cylinder and the second intermediate pressure cylinder; A third connecting pipe is provided between the second intermediate pressure cylinder and the low pressure cylinder.

[0007] Furthermore, the energy cascade utilization heating system also includes: a high-pressure industrial steam supply header and a medium-pressure industrial steam supply header; The high-pressure industrial steam supply header is connected to the first connecting pipe and the outlet of the second high-pressure cylinder, respectively. The medium-pressure industrial steam supply main pipe is connected to the second connecting pipe and the third connecting pipe, respectively.

[0008] Furthermore, the energy cascade utilization heating system also includes: multiple sealed butterfly valves; The high-pressure industrial steam supply main pipe is connected to the first connecting pipe and the outlet of the second high-pressure cylinder through the sealing butterfly valve. The medium-pressure industrial steam supply main pipe is connected to the second connecting pipe and the third connecting pipe respectively through a sealed butterfly valve; The sealing butterfly valve is installed between the input end of the molten salt heat exchange station and the output end of the second high-pressure cylinder.

[0009] Furthermore, when high-pressure steam is required, it is determined whether the unit load corresponding to the boiler is less than a preset first load value. If so, the sealing butterfly valve connected to the first connecting pipe is opened, and the sealing butterfly valve connected to the second high-pressure cylinder is closed. High-pressure steam is then provided to the user using the extraction steam from the second high-pressure cylinder and the first high-pressure cylinder. Otherwise, the sealing butterfly valve connected to the second high-pressure cylinder is opened, and the sealing butterfly valve connected to the first connecting pipe is closed. High-pressure steam is then provided to the user using the cold re-extraction steam discharged from the second high-pressure cylinder.

[0010] Furthermore, when medium-pressure steam is required, it is determined whether the unit load corresponding to the boiler is less than the preset second load value. If so, the sealing butterfly valve connected to the second connecting pipe is opened, and the sealing butterfly valve connected to the third connecting pipe is closed, and medium-pressure steam is provided to the user using the extracted steam in the first and second medium-pressure cylinders; otherwise, the sealing butterfly valve connected to the third connecting pipe is opened, and the sealing butterfly valve connected to the second connecting pipe is closed, and medium-pressure steam is provided to the user using the cold re-extraction steam discharged from the second medium-pressure cylinder.

[0011] Furthermore, the energy cascade utilization heating system also includes: a condenser, a condensate pump, and a unit regenerative subsystem; The condenser is connected to the low-pressure cylinder, the condensate pump, and the unit's regenerative subsystem, respectively. The unit's regenerative subsystem is connected to the boiler, the second high-pressure cylinder, the first high-pressure cylinder, the first intermediate-pressure cylinder, the second intermediate-pressure cylinder, the low-pressure cylinder, the condenser, and the condensate pump, respectively.

[0012] The second aspect of this application proposes a method for energy cascade utilization heating based on high-pressure and intermediate-pressure cylinders, including: The boiler heats the condensate to generate steam, and the steam is delivered to the high-pressure cylinder. The high-pressure cylinder performs work to discharge cold reheat steam, and at the same time, the high-pressure cylinder provides high-pressure steam to the user based on the steam. The cold resteam discharged from the high-pressure cylinder is heated by a boiler to generate hot resteam, and the hot resteam is then delivered to the intermediate-pressure cylinder. The intermediate-pressure cylinder provides intermediate-pressure steam to the user based on the heat reheat steam; The high-pressure cylinder includes a second high-pressure cylinder and a first high-pressure cylinder, and the intermediate-pressure cylinder includes a first intermediate-pressure cylinder and a second intermediate-pressure cylinder.

[0013] Preferably, the high-pressure cylinder provides high-pressure steam to the user based on the steam, including: When high-pressure steam is required, it is determined whether the unit load corresponding to the boiler is less than the preset first load value. If so, the sealing butterfly valve connected to the first connecting pipe is opened and the sealing butterfly valve connected to the second high-pressure cylinder is closed, and high-pressure steam is provided to the user using the extraction steam in the second high-pressure cylinder and the first high-pressure cylinder. Otherwise, the sealing butterfly valve connected to the second high-pressure cylinder is opened and the sealing butterfly valve connected to the first connecting pipe is closed, and high-pressure steam is provided to the user using the cold re-extraction steam discharged from the second high-pressure cylinder.

[0014] Furthermore, the intermediate-pressure cylinder provides intermediate-pressure steam to the user based on the hot reheat steam, including: When medium-pressure steam is required, it is determined whether the unit load corresponding to the boiler is less than the preset second load value. If so, the sealing butterfly valve connected to the second connecting pipe is opened and the sealing butterfly valve connected to the third connecting pipe is closed, and medium-pressure steam is provided to the user using the extracted steam in the first and second medium-pressure cylinders. Otherwise, the sealing butterfly valve connected to the third connecting pipe is opened and the sealing butterfly valve connected to the second connecting pipe is closed, and medium-pressure steam is provided to the user using the cold re-extraction steam discharged from the second medium-pressure cylinder.

[0015] The technical solutions provided by the embodiments of this application bring at least the following beneficial effects: This application proposes a heating system and method based on the energy cascade utilization of high-pressure and medium-pressure cylinders. The system includes a boiler, a second high-pressure cylinder, a first high-pressure cylinder, a first medium-pressure cylinder, a second medium-pressure cylinder, a low-pressure cylinder, and a generator. The boiler, second high-pressure cylinder, first high-pressure cylinder, first medium-pressure cylinder, second medium-pressure cylinder, low-pressure cylinder, and generator are connected sequentially. The boiler heats condensate to generate steam and delivers the steam to the first high-pressure cylinder. The boiler also heats cold resteam discharged from the second high-pressure cylinder to generate hot resteam and delivers the hot resteam to the first medium-pressure cylinder. The second high-pressure cylinder, first high-pressure cylinder, first medium-pressure cylinder, and second medium-pressure cylinder all provide steam to users. The generator generates electricity based on the steam. The technical solution proposed in this application divides both the high-pressure and medium-pressure cylinders into two cylinders, enabling the cascade utilization of steam energy and energy conservation and emission reduction while meeting the high-pressure and low-pressure industrial steam supply needs.

[0016] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0017] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a structural diagram of an energy cascade utilization heating system based on a high-pressure cylinder with multiple cylinders, according to an embodiment of this application. Figure 2 This is a detailed schematic diagram of an energy cascade utilization heating system based on a high-pressure cylinder with multiple cylinders according to an embodiment of this application; Figure 3 This is a structural diagram of a heat supply method based on the energy cascade utilization of a high-pressure cylinder according to an embodiment of this application; Figure Labels Boiler 1, Second High Pressure Cylinder 2, First High Pressure Cylinder 3, First Intermediate Pressure Cylinder 4, Second Intermediate Pressure Cylinder 5, Low Pressure Cylinder 6, Generator 7, First Connecting Pipe 8, Second Connecting Pipe 9, Third Connecting Pipe 10, High Pressure Industrial Steam Supply Main Pipe 11, Intermediate Pressure Industrial Steam Supply Main Pipe 12, Sealed Butterfly Valve 13, Condenser 14, Condensate Pump 15, Unit Regenerative Subsystem 16. Detailed Implementation

[0018] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0019] This application proposes a cascaded energy utilization heating system and method based on a high-pressure cylinder divided into intermediate and intermediate pressure cylinders. The system includes a boiler, a second high-pressure cylinder, a first high-pressure cylinder, a first intermediate-pressure cylinder, a second intermediate-pressure cylinder, a low-pressure cylinder, and a generator. The boiler, second high-pressure cylinder, first high-pressure cylinder, first intermediate-pressure cylinder, second intermediate-pressure cylinder, low-pressure cylinder, and generator are connected sequentially. The boiler heats condensate to generate steam and delivers the steam to the first high-pressure cylinder. The boiler also heats cold resteam discharged from the second high-pressure cylinder to generate hot resteam and delivers the hot resteam to the first intermediate-pressure cylinder. The second high-pressure cylinder, first high-pressure cylinder, first intermediate-pressure cylinder, and second intermediate-pressure cylinder all provide steam to users. The generator generates electricity based on the steam. The technical solution proposed in this application divides both the high-pressure and intermediate-pressure cylinders into two cylinders, enabling cascaded utilization of steam energy and energy conservation and emission reduction while meeting the high-pressure and low-pressure industrial steam supply needs.

[0020] The following description, with reference to the accompanying drawings, describes an energy cascade utilization heating system and method based on a high-pressure cylinder with sub-cylinders, according to an embodiment of this application.

[0021] Example 1 Figure 1 This is a structural diagram of an energy cascade utilization heating system based on a high-pressure cylinder with sub-cylinders, according to an embodiment of this application. Figure 1 As shown, the system includes: a boiler 1, a second high-pressure cylinder 2, a first high-pressure cylinder 3, a first intermediate-pressure cylinder 4, a second intermediate-pressure cylinder 5, a low-pressure cylinder 6, and a generator 7, wherein the boiler 1, the second high-pressure cylinder 2, the first high-pressure cylinder 3, the first intermediate-pressure cylinder 4, the second intermediate-pressure cylinder 5, the low-pressure cylinder 6, and the generator 7 are connected in sequence; The boiler 1 is used to heat condensate to generate steam and deliver the steam to the first high-pressure cylinder 3; The boiler 1 is also used to heat the cold resteam discharged from the second high-pressure cylinder 2 to generate hot resteam, and to deliver the hot resteam to the first intermediate-pressure cylinder 4. The second high-pressure cylinder 2, the first high-pressure cylinder 3, the first intermediate-pressure cylinder 4, and the second intermediate-pressure cylinder 5 are all used to provide steam to the user; The generator 7 is used to generate electricity based on steam.

[0022] It should be noted that, Figure 1 The system shown is only a schematic diagram of a heating system based on the energy cascade utilization of intermediate and high-pressure cylinders, and does not limit the structure of the heating system based on the energy cascade utilization of intermediate and high-pressure cylinders of the present invention.

[0023] In the embodiments disclosed herein, such as Figure 2 As shown, a first connecting pipe 8 is provided between the second high-pressure cylinder 2 and the first high-pressure cylinder 3; A second connecting pipe 9 is provided between the first intermediate pressure cylinder 4 and the second intermediate pressure cylinder 5; A third connecting pipe 10 is provided between the second medium-pressure cylinder 5 and the low-pressure cylinder 6.

[0024] Furthermore, such as Figure 2 As shown, the energy cascade utilization heating system also includes: a high-pressure industrial steam supply header 11 and a medium-pressure industrial steam supply header 12; The high-pressure industrial steam supply main pipe 11 is connected to the outlet of the first connecting pipe 8 and the outlet of the second high-pressure cylinder 2, respectively. The medium-pressure industrial steam supply main pipe 12 is connected to the second connecting pipe 9 and the third connecting pipe 10, respectively.

[0025] In the embodiments disclosed herein, such as Figure 2 As shown, the energy cascade utilization heating system also includes: multiple sealing butterfly valves 13; The high-pressure industrial steam supply main pipe 11 is connected to the outlet of the first connecting pipe 8 and the outlet of the second high-pressure cylinder 2 through the sealing butterfly valve 13. The medium-pressure industrial steam supply main pipe 12 is connected to the second connecting pipe 9 and the third connecting pipe 10 through a sealing butterfly valve 13.

[0026] When high-pressure steam is required, it is determined whether the unit load corresponding to boiler 1 is less than a preset first load value. If so, the sealing butterfly valve 13 connected to the first connecting pipe 8 is opened, and the sealing butterfly valve 13 connected to the second high-pressure cylinder 2 is closed. High-pressure steam is then provided to the user using the extracted steam from the second high-pressure cylinder 2 and the first high-pressure cylinder 3. Otherwise, the sealing butterfly valve 13 connected to the second high-pressure cylinder 2 is opened, and the sealing butterfly valve 13 connected to the first connecting pipe 8 is closed. High-pressure steam is then provided to the user using the cold re-extraction steam discharged from the second high-pressure cylinder 2.

[0027] When medium-pressure steam is required, it is determined whether the unit load corresponding to boiler 1 is less than the preset second load value. If so, the sealing butterfly valve 13 connected to the second connecting pipe 9 is opened and the sealing butterfly valve 13 connected to the third connecting pipe 10 is closed, and medium-pressure steam is provided to the user using the extraction steam in the first medium-pressure cylinder 4 and the second medium-pressure cylinder 5. Otherwise, the sealing butterfly valve 13 connected to the third connecting pipe 10 is opened and the sealing butterfly valve 13 connected to the second connecting pipe 9 is closed, and medium-pressure steam is provided to the user using the cold re-extraction steam discharged from the second medium-pressure cylinder 5.

[0028] It should be noted that under high unit load conditions, heating is provided by cold reheat steam extraction; after the unit load decreases, cold reheat steam cannot guarantee industrial steam supply parameters. Therefore, the first connecting pipe 8 is used instead of the currently commonly used main steam desuperheating and depressurization heating. The high-pressure steam supply is selected from two steam sources: (1) cold reheat steam, i.e., high-pressure cylinder 2-stage exhaust steam; (2) high-pressure cylinder 1-stage exhaust steam, i.e., the first connecting pipe 3-8. Currently, the heating unit uses main steam desuperheating and depressurization heating under low load conditions, while this paper uses high-pressure cylinder 1-stage exhaust steam heating.

[0029] During operation, condensate enters boiler 1 and is heated into high-temperature and high-pressure steam. It then enters the first high-pressure cylinder 3 of the steam turbine and then the second high-pressure cylinder 2 to perform work. The cold re-steam from the outlet of the second high-pressure cylinder 2 enters boiler 1 for heating to generate hot re-steam. The hot re-steam enters the first intermediate-pressure cylinder 4 and the second intermediate-pressure cylinder 5 to perform work, and then enters the low-pressure cylinder 6 to perform work.

[0030] Meanwhile, the high-pressure cylinder is decomposed into two parts, namely the second high-pressure cylinder 2 and the first high-pressure cylinder 3. After the main steam does work in the first high-pressure cylinder 3, that is, the first high-pressure cylinder section 1, it enters the connecting pipe between the first and second high-pressure cylinder sections, namely the first connecting pipe 8. The first high-pressure cylinder section 1 and the connecting pipe between the first and second high-pressure cylinder sections 1 and 2 can extract steam for heating, of which the second section is the second high-pressure cylinder 2. At the same time, combined with the cold re-extraction steam pipeline in the original power plant, a steam extraction system with dual extraction nodes is formed. The intermediate pressure cylinder is divided into two parts. After the hot reheat steam does work in the first intermediate pressure cylinder 4, it enters the connecting pipe of the first intermediate pressure cylinder 4 and the second intermediate pressure cylinder 5, namely the second connecting pipe 9. The connecting pipe of the first and second intermediate pressure cylinders can extract steam for heating. At the same time, it is combined with the original intermediate pressure cylinder exhaust steam extraction to form a steam extraction system with dual extraction nodes.

[0031] Furthermore, such as Figure 2 As shown, the energy cascade utilization heating system also includes: a condenser 14, a condensate pump 15, and a unit regenerative subsystem 16. The condenser 14 is connected to the low-pressure cylinder 6, the condensate pump 15, and the unit regenerative subsystem 16, respectively. The unit's regenerative subsystem 16 is connected to the boiler 1, the second high-pressure cylinder 2, the first high-pressure cylinder 3, the first intermediate-pressure cylinder 4, the second intermediate-pressure cylinder 5, the low-pressure cylinder 6, the condenser 14, and the condensate pump 15, respectively.

[0032] Among them, such as Figure 2 As shown, the unit's regenerative subsystem 3-16 includes: 3 high-pressure heaters, 1 deaerator, 1 feedwater pump, and 4 low-pressure heaters.

[0033] For example, the calculation results of a conventional 350MW supercritical unit (main steam pressure 24.2MPa, main steam temperature 566℃, hot resteam temperature 566℃, back pressure set at 4.9kPa) under pure condensing conditions are shown in Table 1.

[0034] In the combined heat and power (CHP) process, the high-pressure industrial steam supply parameters are 3 MPa pressure, 250℃ temperature, and 100 t / h extraction rate; the low-pressure industrial steam supply parameters are 0.5 MPa pressure, 200℃ temperature, and 100 t / h extraction rate.

[0035] Calculation results show that at the flow rate corresponding to 100% THA pure condensation, the cold reheat steam pressure is 3.97 MPa, which can be used for heating through cold reheat extraction. However, at the flow rates corresponding to 75% THA and 50% THA, the cold reheat steam pressures are 2.96 MPa and 1.97 MPa, respectively, which are insufficient to meet the heating demand; the exhaust pressures of the first stage of the high-pressure cylinder are 4.60 MPa and 3.08 MPa, respectively, which are higher than the industrial steam supply pressure, and heating can be provided through the exhaust steam of the first stage of the high-pressure cylinder.

[0036] At the flow rate corresponding to 100% THA pure condensate operation, the intermediate-pressure cylinder exhaust pressure is 0.585 MPa, which can be used for heating (the pressure is adjusted via the regulating valve of the intermediate-low pressure cylinder connecting pipe). However, at the flow rates corresponding to 75% THA and 50% THA operation, the intermediate-pressure cylinder exhaust steam pressures are 0.444 MPa and 0.305 MPa respectively, both below 0.5 MPa. Adjusting these pressures via the regulating valve of the intermediate-low pressure cylinder connecting pipe is relatively difficult and insufficient to meet heating demands. The exhaust pressures of the first stage of the intermediate-pressure cylinder are 1.65 MPa and 1.11 MPa respectively, higher than the industrial supply steam pressure, and can be used for heating via the exhaust of the first stage of the intermediate-pressure cylinder.

[0037] Table 1 Main parameters of the unit under pure condensing conditions

[0038] The system performance analysis under high-pressure industrial steam supply conditions is as follows: According to the system proposed in this invention, a high-pressure industrial steam supply condition analysis was conducted. Under 100% THA conditions, cold reheat steam was used for heating; under 75% THA and 50% THA conditions, exhaust steam from the first stage of the high-pressure cylinder was used for heating. The calculation results are summarized in Table 2. As shown in Table 2, under the main steam parameters corresponding to 100% THA operating conditions, when 100 t / h (3 MPa, 250℃) of steam is supplied via cold reheat steam, the unit's coal consumption for power generation is 276.8 g / kWh, and the ratio of power generation to nameplate power is 0.92; under the main steam parameters corresponding to 75% THA operating conditions, when 100 t / h (3 MPa, 250℃) of steam is supplied via exhaust steam from the first stage of the high-pressure cylinder, the unit's coal consumption for power generation is 279.4 g / kWh, and the ratio of power generation to nameplate power is 0.67; under the main steam parameters corresponding to 50% THA operating conditions, when 100 t / h (3 MPa, 250℃) of steam is supplied via exhaust steam from the first stage of the high-pressure cylinder, the unit's coal consumption for power generation is 288.1 g / kWh, and the ratio of power generation to nameplate power is 0.39.

[0039] Table 2. Main parameters of the unit of this invention under high-pressure industrial steam supply conditions.

[0040] Table 3 summarizes the main performance indicators of the unit under the high-pressure cylinder stage 1 exhaust steam heating scheme and the conventional main steam desuperheating and pressure-reducing heating scheme of this invention. As can be seen from the table, under the main steam parameters corresponding to a pure condensing 75% THA condition, the coal consumption for power generation under the high-pressure cylinder stage 1 exhaust steam heating scheme of this invention is 279.4 g / kWh, while the coal consumption for power generation under the conventional main steam heating scheme is 287.3 g / kWh, representing a reduction of 7.9 g / kWh. Under the main steam parameters corresponding to a pure condensing 50% THA condition, the coal consumption for power generation under the high-pressure cylinder stage 1 exhaust steam heating scheme of this invention is 288.1 g / kWh, while the coal consumption for power generation under the conventional main steam heating scheme is 302.4 g / kWh, representing a reduction of 14.3 g / kWh. Through calculation and comparison, it can be concluded that the heating scheme proposed in this invention has significant coal-saving benefits.

[0041] Table 3 Comparison of the high-pressure cylinder stage 1 exhaust steam heating scheme in this invention with the conventional main steam heating scheme.

[0042] The system performance analysis under low-pressure industrial steam supply conditions is as follows: Based on the system proposed in this invention, calculations and analyses were performed for low-pressure heating conditions. Under 100% THA conditions, heating was provided by exhaust steam from the intermediate-pressure cylinder; under 75% THA and 50% THA conditions, heating was provided by exhaust steam from the first stage of the intermediate-pressure cylinder. The calculation results are summarized in Table 4. As shown in Table 4, under the main steam parameters corresponding to 100% THA operating conditions, when the steam supply through the second stage of the intermediate pressure cylinder is 100 t / h (0.5 MPa, 200℃), the unit's coal consumption for power generation is 270.6 g / kWh; under the main steam parameters corresponding to 75% THA operating conditions, when the steam supply through the first stage of the intermediate pressure cylinder is 100 t / h (0.5 MPa, 200℃), the unit's coal consumption for power generation is 276.0 g / kWh; and under the main steam parameters corresponding to 50% THA operating conditions, when the steam supply through the first stage of the intermediate pressure cylinder is 100 t / h (0.5 MPa, 200℃), the unit's coal consumption for power generation is 278.7 g / kWh.

[0043] Table 4. Main parameters of the system of the present invention under low-pressure industrial steam supply conditions.

[0044] Table 5 summarizes the main performance indicators of the unit under the medium-pressure cylinder stage 1 exhaust steam heating scheme and the conventional hot reheat steam desuperheating and pressure-reducing heating scheme of this invention. As can be seen from the table, under the main steam parameters corresponding to the 75% THA pure condensing condition, the coal consumption for power generation under the medium-pressure cylinder stage 1 exhaust steam heating scheme of this invention is 276.0 g / kWh, while the coal consumption for power generation under the conventional hot reheat steam heating scheme is 279.7 g / kWh, representing a reduction of 3.7 g / kWh in coal consumption. Under the main steam parameters corresponding to the 50% THA pure condensing condition, the coal consumption for power generation under the medium-pressure cylinder stage 1 exhaust steam heating scheme of this invention is 278.7 g / kWh, while the coal consumption for power generation under the conventional main steam heating scheme is 288.2 g / kWh, representing a reduction of 9.5 g / kWh in coal consumption. Through calculation and comparison, it can be concluded that the heating scheme proposed in this invention has significant coal-saving benefits.

[0045] Table 5 Comparison of the exhaust steam heating scheme of the intermediate pressure cylinder stage 1 in this invention with the conventional main steam heating scheme.

[0046] In summary, the energy cascade utilization heating system based on the high-pressure cylinder and intermediate-pressure cylinder proposed in this embodiment has the following advantages: (1) Under low load conditions, compared with the main steam de-cooling and de-pressure heating, this scheme can realize energy cascade utilization, energy saving and emission reduction. For a conventional 350MW ultra-supercritical unit, under the condition of high pressure steam supply, under the main steam parameters corresponding to the pure condensing 50% THA condition, the power generation coal consumption of the high-pressure cylinder 1-stage exhaust steam heating scheme proposed in this invention is reduced by 14.3 g / kWh; under the condition of high and low pressure steam supply, under the main steam parameters corresponding to the pure condensing 50% THA condition, the power generation coal consumption of the intermediate-pressure cylinder 1-stage exhaust steam heating scheme proposed in this invention is reduced by 9.5 g / kWh. (2) Compared with the limitation of the limited steam extraction capacity of the traditional regenerative system 1 extraction, this invention drills holes in the connecting pipe between the high-pressure cylinder 1-stage and 2-stage to extract steam, and the extraction capacity is significantly increased, which can meet the demand of 100t / h for high-pressure industrial steam supply extraction. In this invention system, there are two-stage extraction steam sources: cold reheat steam and high-pressure cylinder section 1 exhaust steam. The heating steam source can be flexibly switched according to the unit's electrical load. (3) Compared with the limitation of the limited extraction steam volume of the traditional regenerative system, this invention extracts steam by drilling holes in the connecting pipe between the first and second sections of the intermediate-pressure cylinder, which significantly increases the extraction steam volume and can meet the demand of 100t / h for low-pressure industrial steam supply. In this invention heating system, there are two-stage extraction steam sources: intermediate-pressure cylinder exhaust steam and intermediate-pressure cylinder section 1 exhaust steam. The heating steam source can be flexibly switched according to the unit's electrical load.

[0047] Example 2 Figure 3 The flowchart below shows a method for energy cascade utilization heating based on a high-pressure cylinder with multiple cylinders according to an embodiment of this application. Figure 3 As shown, the method includes: Step 1: The boiler heats the condensate to generate steam, and the steam is delivered to the high-pressure cylinder. The high-pressure cylinder performs work to discharge cold reheat steam, and at the same time, the high-pressure cylinder provides high-pressure steam to the user based on the steam. Step 2: Use a boiler to heat the cold resteam discharged from the high-pressure cylinder to generate hot resteam, and then send the hot resteam to the intermediate-pressure cylinder; Step 3: The intermediate-pressure cylinder provides intermediate-pressure steam to the user based on the hot reheat steam; The high-pressure cylinder includes a second high-pressure cylinder and a first high-pressure cylinder, and the intermediate-pressure cylinder includes a first intermediate-pressure cylinder and a second intermediate-pressure cylinder.

[0048] In this embodiment of the disclosure, the high-pressure cylinder provides high-pressure steam to the user based on the steam, including: When high-pressure steam is required, it is determined whether the unit load in the thermal power plant subsystem is less than a preset first load value. If so, the sealing butterfly valve connected to the first connecting pipe is opened, and the sealing butterfly valve connected to the second high-pressure cylinder is closed. High-pressure steam is then provided to the user using the extraction steam from the second high-pressure cylinder and the first high-pressure cylinder. Otherwise, the sealing butterfly valve connected to the second high-pressure cylinder is opened, and the sealing butterfly valve connected to the first connecting pipe is closed. Steam is then provided to the user using the cold re-extraction steam discharged from the second high-pressure cylinder.

[0049] In this embodiment of the disclosure, the intermediate-pressure cylinder provides intermediate-pressure steam to the user based on the hot reheat steam, including: When medium-pressure steam is required, it is determined whether the unit load in the thermal power plant subsystem is less than the preset second load value. If so, the sealing butterfly valve connected to the second connecting pipe is opened, and the sealing butterfly valve connected to the third connecting pipe is closed. Medium-pressure steam is provided to the user using the extracted steam in the first and second medium-pressure cylinders. Otherwise, the sealing butterfly valve connected to the third connecting pipe is opened, and the sealing butterfly valve connected to the second connecting pipe is closed. Medium-pressure steam is provided to the user using the cold re-extraction steam discharged from the second medium-pressure cylinder.

[0050] In summary, the energy cascade utilization heating method based on high-pressure and medium-pressure cylinders proposed in this embodiment divides both the high-pressure and medium-pressure cylinders into two cylinders, which can achieve cascade utilization of steam energy and energy saving and emission reduction while meeting the steam supply needs of high-pressure and low-pressure industries.

[0051] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0052] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing custom logic functions or processes, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of this application pertain.

[0053] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A cascaded energy utilization heating system based on a high-pressure, medium-pressure cylinder, characterized in that, include: The boiler, the second high-pressure cylinder, the first high-pressure cylinder, the first intermediate-pressure cylinder, the second intermediate-pressure cylinder, the low-pressure cylinder, and the generator are connected in sequence. The boiler is used to heat condensate to generate steam and deliver the steam to the first high-pressure cylinder; The boiler is also used to heat the cold resteam discharged from the second high-pressure cylinder to generate hot resteam, and to deliver the hot resteam to the first intermediate-pressure cylinder; The second high-pressure cylinder, the first high-pressure cylinder, the first intermediate-pressure cylinder, and the second intermediate-pressure cylinder are all used to provide steam to the user; The generator is used to generate electrical energy based on steam; The system includes a first connecting pipe between the second high-pressure cylinder and the first high-pressure cylinder; a second connecting pipe between the first medium-pressure cylinder and the second medium-pressure cylinder; and a third connecting pipe between the second medium-pressure cylinder and the low-pressure cylinder. The energy cascade heating system also includes a high-pressure industrial steam supply header and a medium-pressure industrial steam supply header. The high-pressure industrial steam supply header is connected to both the first connecting pipe and the outlet of the second high-pressure cylinder. The medium-pressure industrial steam supply header is connected to both the second connecting pipe and the third connecting pipe.

2. The energy cascade utilization heating system as described in claim 1, characterized in that, The energy cascade utilization heating system also includes: multiple sealed butterfly valves; The high-pressure industrial steam supply main pipe is connected to the first connecting pipe and the outlet of the second high-pressure cylinder through the sealing butterfly valve. The medium-pressure industrial steam supply main pipe is connected to the second connecting pipe and the third connecting pipe respectively through a sealed butterfly valve; The sealing butterfly valve is installed between the input end of the high-pressure industrial steam supply header and the output end of the second high-pressure cylinder.

3. The energy cascade utilization heating system as described in claim 2, characterized in that, When high-pressure steam is required, it is determined whether the unit load corresponding to the boiler is less than the preset first load value. If so, the sealing butterfly valve connected to the first connecting pipe is opened and the sealing butterfly valve connected to the second high-pressure cylinder is closed, and high-pressure steam is provided to the user using the extraction steam in the second high-pressure cylinder and the first high-pressure cylinder. Otherwise, the sealing butterfly valve connected to the second high-pressure cylinder is opened and the sealing butterfly valve connected to the first connecting pipe is closed, and high-pressure steam is provided to the user using the cold re-extraction steam discharged from the second high-pressure cylinder.

4. The energy cascade utilization heating system as described in claim 3, characterized in that, When medium-pressure steam is required, it is determined whether the unit load corresponding to the boiler is less than the preset second load value. If so, the sealing butterfly valve connected to the second connecting pipe is opened and the sealing butterfly valve connected to the third connecting pipe is closed, and medium-pressure steam is provided to the user using the extracted steam in the first and second medium-pressure cylinders. Otherwise, the sealing butterfly valve connected to the third connecting pipe is opened and the sealing butterfly valve connected to the second connecting pipe is closed, and medium-pressure steam is provided to the user using the cold re-extraction steam discharged from the second medium-pressure cylinder.

5. The energy cascade utilization heating system as described in claim 4, characterized in that, The energy cascade utilization heating system also includes: a condenser, a condensate pump, and a unit regenerative subsystem; The condenser is connected to the low-pressure cylinder, the condensate pump, and the unit's regenerative subsystem, respectively. The unit's regenerative subsystem is connected to the boiler, the second high-pressure cylinder, the first high-pressure cylinder, the first intermediate-pressure cylinder, the second intermediate-pressure cylinder, the low-pressure cylinder, the condenser, and the condensate pump, respectively.

6. A method for energy cascade utilization heating based on a high- and medium-pressure cylinder sub-cylinder in an energy cascade utilization heating system according to any one of claims 1-5, characterized in that, The method includes: The boiler heats the condensate to generate steam, and the steam is delivered to the high-pressure cylinder. The high-pressure cylinder performs work to discharge cold reheat steam, and at the same time, the high-pressure cylinder provides high-pressure steam to the user based on the steam. The cold resteam discharged from the high-pressure cylinder is heated by a boiler to generate hot resteam, and the hot resteam is then delivered to the intermediate-pressure cylinder. The intermediate-pressure cylinder provides intermediate-pressure steam to the user based on the heat reheat steam; The high-pressure cylinder includes a second high-pressure cylinder and a first high-pressure cylinder, and the intermediate-pressure cylinder includes a first intermediate-pressure cylinder and a second intermediate-pressure cylinder.

7. The energy cascade utilization heating method as described in claim 6, characterized in that, The high-pressure cylinder provides high-pressure steam to the user based on the steam, including: When high-pressure steam is required, it is determined whether the unit load corresponding to the boiler is less than the preset first load value. If so, the sealing butterfly valve connected to the first connecting pipe is opened and the sealing butterfly valve connected to the second high-pressure cylinder is closed, and high-pressure steam is provided to the user using the extraction steam in the second high-pressure cylinder and the first high-pressure cylinder. Otherwise, the sealing butterfly valve connected to the second high-pressure cylinder is opened and the sealing butterfly valve connected to the first connecting pipe is closed, and high-pressure steam is provided to the user using the cold re-extraction steam discharged from the second high-pressure cylinder.

8. The method as described in claim 7, characterized in that, The intermediate-pressure cylinder provides intermediate-pressure steam to the user based on the hot reheat steam, including: When medium-pressure steam is required, it is determined whether the unit load corresponding to the boiler is less than the preset second load value. If so, the sealing butterfly valve connected to the second connecting pipe is opened and the sealing butterfly valve connected to the third connecting pipe is closed, and medium-pressure steam is provided to the user using the extracted steam in the first and second medium-pressure cylinders. Otherwise, the sealing butterfly valve connected to the third connecting pipe is opened and the sealing butterfly valve connected to the second connecting pipe is closed, and medium-pressure steam is provided to the user using the cold re-extraction steam discharged from the second medium-pressure cylinder.

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