Industrial heat supply system and method for high-pressure hydrophobic supplementary reheated steam cold section

Abstract

The invention belongs to the technical field of reheat steam cold section industrial heat supply, particularly relates to a system and a method for supplementing reheat steam cold section industrial heat supply through high-pressure hydrophobic water, and aims to solve the problems of insufficient steam supply pressure, complex system transformation, high investment cost and safety risk during low load in the existing reheat steam industrial heat supply technology. According to the scheme, the device comprises a boiler, and the boiler is connected with a main steam pipeline; the reheating cold section pipeline is connected with the boiler; the reheating hot section pipeline is connected with the boiler; according to the invention, high-pressure drain water is utilized to supplement reheat steam cold section industrial heat supply, so that the problem of insufficient steam supply pressure during low load is effectively solved, meanwhile, the system transformation complexity and the investment cost (the investment is reduced by 80-90%) are greatly reduced, the safety and the economy are improved, and the deep peak regulation requirement is met.

Description

Technical Field

[0001] This invention relates to the field of industrial heating technology for reheat steam cold section, and in particular to a system and method for industrial heating in reheat steam cold section supplemented by high-pressure condensate. Background Technology

[0002] As the sector with the highest carbon emissions in China and a key area already included in the carbon market trading, the innovation and application of energy-saving and carbon-reduction technologies in the thermal power industry have become core issues concerning the industry's survival and development. Against this backdrop, combined heat and power (CHP) technology, due to its ability to significantly improve the overall efficiency of primary energy utilization and effectively reduce coal consumption for power generation and carbon emissions per unit of product, is widely recognized as one of the optimal paths for thermal power companies to achieve energy conservation and carbon reduction goals. According to statistics from the China Electricity Council, more than 80% of the currently operating 300MW-class units have been retrofitted to become units with industrial heating or heating supply capabilities. Existing thermal power unit heating technologies are mainly based on steam extraction from different parts of the steam turbine, resulting in the following mainstream modes: High-pressure cylinder exhaust steam for heating: This part of the steam has higher parameters (pressure and temperature) and is mainly used for industrial heating, with a wide range of applications. Since it is part of the turbine's power generation process, its negative impact on the overall power generation coal consumption is relatively small when used for heating. Medium-pressure cylinder exhaust pipe perforation extraction steam heating: This is currently the most widely used heating method, especially suitable for heating and some industrial heating with low parameter requirements. Its technology is relatively mature and easy to modify. Low-pressure cylinder exhaust steam for heating: This part of the steam is the exhaust steam from the last stage of the steam turbine. The parameters are very low and it falls under the category of waste heat utilization. Although its usability is limited, using this part of the heat for heating hardly increases the steam consumption of the steam turbine. It makes the most significant contribution to reducing coal consumption for power generation. In addition, based on the above-mentioned main methods, the industry has also developed a variety of optimization schemes, such as three-stage steam extraction heating, combined steam heating of reheat hot section and reheat cold section, integration of steam heating of different pressure levels through pressure matching device, and extraction of waste heat of working fluid by heat pump. However, these schemes are essentially still combinations and in-depth utilization of the three main steam extraction positions mentioned above, and have not fundamentally solved some core contradictions. With the deepening of my country's energy structure transformation, the installed capacity and power generation share of intermittent new energy sources such as wind power and photovoltaics have continued to rise, posing challenges to the stability of the power grid. This forces thermal power units, as the traditional main power source, to undertake deeper and more frequent peak-shaving tasks. It has become the norm for units to operate under low-load conditions (even below 30% of rated load) for extended periods. This shift in operating mode has brought unprecedented technical challenges to heating systems that heavily rely on steam parameters from specific parts of the turbine, especially industrial heating systems that require stable steam pressure. Existing technologies, particularly when attempting to utilize reheat steam systems for industrial heating, reveal the following prominent problems that urgently need to be addressed: First, the system modification is extensive and complex. Taking the "combined heating of reheat hot section and reheat cold section" scheme as an example, its initial purpose was to broaden the range of steam supply parameters or ensure steam supply capacity under low load. However, this scheme has an inherent pressure defect: under normal operating conditions, the pressure of the reheat hot section steam is already lower than that of the reheat cold section. When the unit is under low load, even the steam pressure of the reheat cold section may not meet the user's requirements, and the even lower-pressure reheat hot section steam is naturally unusable directly. To solve this problem, the intermediate pressure regulating valve (commonly known as the "intermediate valve") must be modified to throttle, artificially increasing the reheat hot section steam pressure. However, the original design function of the intermediate pressure regulating valve is only to meet the starting requirements of the turbine's intermediate pressure cylinder. Its regulating characteristics are only activated at extremely low loads (such as below 30% of rated load). Under high load conditions, the valve is fully open and does not have, nor is it permitted, to perform throttling regulation. Therefore, to achieve stable steam extraction for heating across the entire load range, it is necessary to carry out large-scale adaptive modifications to the actuator, valve core profile, and even the flow passage of the medium-pressure regulating valve, which significantly increases the technical complexity, construction difficulty, and safety risks. The "electrode boiler" solution goes to the other extreme, essentially building a completely independent steam generation system within the power plant. To meet an additional steam demand of, for example, 45 t / h, a massive supporting system is required: including a dedicated 35 MVA step-down transformer, a high-power electrode boiler body, two new 400V power distribution busbars for the plant, two high-flow feedwater pumps, and steam and feedwater connection pipelines throughout the plant area. This kind of transformation not only involves a huge initial investment but also involves multiple disciplines such as civil engineering, electrical engineering, thermal control, and steam and water systems. The scope of the transformation is extremely wide, posing a huge challenge to the power plant's original spatial layout, power distribution system, and operation management. Secondly, the total investment in these projects is prohibitively high, posing a severe challenge to their economic viability. Industry estimates suggest that a 300MW unit using a combined reheat hot and cold section heating scheme, considering costs such as central valve modification, pipeline construction, and control system upgrades, would require a total investment of approximately 12 million RMB. If the aforementioned "electrode boiler" scheme is adopted, the total investment to achieve the same steam supply capacity would rise to approximately 30 million RMB. Such high initial investment directly leads to a prolonged payback period. To meet the industry's basic internal rate of return requirements, investors are often forced to significantly increase steam prices by 80% to 100% on top of the original price. In the current fiercely competitive heating market, this severely weakens the core competitiveness of power plants, causing many technically feasible cogeneration projects to ultimately be shelved due to poor economic viability. Finally, the system safety risks cannot be ignored. For the "combined reheat hot section and reheat cold section heating" scheme, the core risk lies in the need to drill and weld a large-diameter tee on the main reheat hot section pipeline, which operates under high temperature and high pressure (typically exceeding 500℃ and several megapascals). For units of 300MW and above, the diameter of the reheat hot section pipeline usually exceeds DN600, while the diameter of the extraction port is relatively small. This significant size difference leads to abrupt structural changes and complex local stress distribution at the pipeline intersections. This places extremely stringent requirements on the material quality, casting process, welding technology, and subsequent heat treatment processes of the tee castings or forgings. Any minute defect, under long-term high temperature, high pressure, and alternating stress, can develop into cracks, ultimately leading to major safety accidents such as steam leakage or even pipeline rupture. As for electrode boilers, they are special equipment with high voltage and high current. Their design, manufacturing, installation and operation are subject to strict supervision and complicated special equipment use registration procedures. More importantly, their working principle determines that during operation, there is a possibility that water will electrolyze under the action of a strong electric field to produce hydrogen. If the boiler body is not sealed properly or the ventilation design of the plant is unreasonable, hydrogen may accumulate in the confined space. Once it reaches the explosion limit and comes into contact with an open flame or high temperature, it will cause a serious explosion accident, with an extremely high safety risk level. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing reheat steam industrial heating technologies, such as insufficient steam supply pressure at low loads, complex system modifications, high investment costs, and associated safety risks. The invention proposes a system and method for supplementing the cold section of reheat steam with high-pressure condensate.

[0004] The high-pressure condensate replenishment reheat steam cold section industrial heating system and method provided in this application adopt the following technical solution: A system for industrial heating using high-pressure condensate replenishment of reheat steam in the cold section includes a boiler connected to a main steam pipeline; and further includes: Reheat cold section piping, which is connected to the boiler; A reheat hot section pipeline, which is connected to the boiler; A high-pressure bypass steam pipe is connected to the main steam pipe, the reheat cold section pipe, and the reheat hot section pipe. A high-pressure cylinder for a steam turbine, which is connected to the main steam pipeline and the reheat cold section pipeline; The intermediate pressure cylinder of the steam turbine is connected to the high pressure cylinder of the steam turbine and the reheat hot section pipeline.

[0005] Furthermore, a heating pipe is connected to the reheat cold section pipe.

[0006] Furthermore, both the main steam pipe and the high-pressure bypass steam pipe are connected to a drain pipe before the valve.

[0007] Furthermore, multiple drain pipes before the valves are connected to heating water supply branches.

[0008] Furthermore, multiple water supply branches are connected to the same main condensate heating pipe.

[0009] Furthermore, a de-cooling and pressure-reducing station is connected to the main heating pipe with drainage.

[0010] Furthermore, the temperature and pressure reduction are used to modulate the steam supply parameters.

[0011] Furthermore, the heating pipeline is connected to the main heating pipeline for draining water, and the heating pipeline is used to combine qualified steam with the steam extracted from the reheat cold section for supply.

[0012] This invention also proposes a method for using a high-pressure condensate-supplemented reheat steam cold section industrial heating system. The high-pressure condensate-supplemented reheat steam cold section industrial heating system is the aforementioned system, comprising the following steps: S1: The main steam generated by the boiler enters the high-pressure cylinder of the turbine through the main steam pipeline to do work. The exhaust steam from the high-pressure cylinder enters the reheat cold section pipeline and returns to the boiler for reheating to form reheat steam. It then enters the intermediate-pressure cylinder of the turbine through the reheat hot section pipeline to continue doing work. The high-pressure bypass steam pipe is connected to the main steam pipeline, the reheat cold section pipeline and the reheat hot section pipeline. It is used to bypass part of the steam during unit startup or abnormal operating conditions to maintain system balance. S2: Extract high-pressure condensate from the inlet water pipes on the main steam pipe and the high-pressure bypass steam pipe (these condensates are usually high-temperature and high-pressure saturated water or steam containing a large amount of heat energy). Multiple inlet water pipes are connected to the heating branch of the water supply pipe respectively, and the high-pressure condensate is collected into the main condensate heating pipe to form a centralized condensate source. S3: The de-cooling and pressure reducing station installed on the main heating pipe of the condensate drains the high-pressure condensate drains to de-cool and reduce the pressure. By spraying water to cool down and regulating the pressure, the condensate drain parameters (such as temperature and pressure) are made to meet the industrial heating standards (for example, the pressure is reduced to 1-2MPa and the temperature is reduced to 200-300°C) to avoid impact on user equipment. S4: The heating pipeline connected to the reheat cold section pipeline is used to extract part of the reheat cold section steam (usually with higher parameters, suitable for industrial heating). However, the reheat cold section pressure may be insufficient under low load. The treated high-pressure condensate is connected to the heating pipeline through the condensate main heating pipe and mixed with the reheat cold section extracted steam to supplement the steam flow and energy, forming qualified steam. The parameters of the mixed steam are stable and can meet the needs of industrial users, achieving continuous and reliable heating. By controlling the valve opening of the condensate pipe before the control valve and the operation of the desuperheating and pressure reducing station, the amount of high-pressure condensate replenishment can be dynamically adjusted according to the unit load and heating demand to ensure that the reheat cold section heating pressure is always within the allowable range.

[0013] In summary, this application includes at least one of the following beneficial technical effects: 1. This solution uses a shared main pipeline interface for both drainage and heating, which reduces the number of new welds on large-diameter, thick-walled main pipelines and ensures safety; 2. This scheme uses main steam as a supplementary steam source for the industrial steam supply in the cold section of reheat steam, which can meet 30% of the deep peak shaving demand, effectively control the scope of single-unit thermoelectric decoupling retrofit and the total investment, and significantly improve the project's economic efficiency. Compared with the existing scheme, the investment is reduced by nearly 80-90%. 3. This solution uses the newly added total system resistance calculation value and draws on the standard for calculating flow rate using the throttling method. Through the correction factor, it calculates the available flow rate of the system under different loads, which basically meets the actual needs.

[0014] This invention effectively solves the problem of insufficient steam supply pressure at low loads by using high-pressure condensate to supplement the cold section of reheat steam for industrial heating. At the same time, it significantly reduces the complexity of system modification and investment costs (investment decreases by 80-90%), while improving safety and economy and meeting the needs of deep peak shaving. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the high-pressure hydrophobic replenishment reheat steam cold section industrial heating system proposed in this invention.

[0016] Attached reference numerals: 1. Boiler; 2. High-pressure cylinder of steam turbine; 3. Intermediate-pressure cylinder of steam turbine; 4. Main steam pipeline; 5. Reheat cold section pipeline; 6. Reheat hot section pipeline; 7. High-pressure bypass steam pipe; 8. Water supply pipes before each valve; 9. Water supply pipe heating branch; 10. Main condensate heating pipe; 11. Desuperheating and pressure reducing station. Detailed Implementation

[0017] 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.

[0018] Example 1 Reference Figure 1 A system for industrial heating of the cold section of reheat steam supplemented by high-pressure condensate drainage includes a boiler 1, which is connected to a main steam pipe 4; and also includes: Reheat cold section pipe 5 is connected to boiler 1; Reheat hot section pipe 6 is connected to boiler 1; High-pressure bypass steam pipe 7 is connected to main steam pipe 4, reheat cold section pipe 5 and reheat hot section pipe 6. High-pressure cylinder 2 of the steam turbine is connected to the main steam pipeline 4 and the reheat cold section pipeline 5. The intermediate pressure cylinder 3 of the steam turbine is connected to the high pressure cylinder 2 of the steam turbine and the reheat hot section pipeline 6.

[0019] In this embodiment, a heating pipeline is connected to the reheat cold section pipeline 5, and a valve-front drain pipe 8 is connected to both the main steam pipeline 4 and the high-pressure bypass steam pipeline 7. Multiple valve-front drain pipes 8 are connected to water supply heating branches 9, and multiple water supply heating branches 9 are connected to the same drain main heating pipe 10. A desuperheating and pressure reducing station 11 is connected to the drain main heating pipe 10. The desuperheating and pressure reducing station 11 is used to modulate the steam supply parameters. The heating pipeline is connected to the drain main heating pipe 10, and the heating pipeline is used to combine qualified steam with the reheat cold section extraction steam for supply.

[0020] This embodiment also proposes a method for using a high-pressure condensate-supplemented reheat steam cold section industrial heating system. The high-pressure condensate-supplemented reheat steam cold section industrial heating system is the one described above, and includes the following steps: S1: The main steam generated by boiler 1 enters the high-pressure cylinder 2 of the turbine through the main steam pipeline 4 to do work. The exhaust steam from the high-pressure cylinder enters the reheat cold section pipeline 5 and returns to boiler 1 for reheating to form reheat steam. It then enters the intermediate-pressure cylinder 3 of the turbine through the reheat hot section pipeline 6 to continue doing work. The high-pressure bypass steam pipe 7 is connected to the main steam pipeline 4, the reheat cold section pipeline 5 and the reheat hot section pipeline 6. It is used to bypass part of the steam during unit startup or abnormal operating conditions to maintain system balance. S2: High-pressure condensate is extracted from the pre-valve water supply pipes 8 on the main steam pipe 4 and the high-pressure bypass steam pipe 7 (these condensates are usually high-temperature and high-pressure saturated water or steam containing a large amount of heat energy). Multiple pre-valve condensate pipes 8 are connected to the water supply heating branch 9 respectively, and the high-pressure condensate is collected into the main condensate heating pipe 10 to form a centralized condensate source. S3: The de-cooling and pressure reducing station 11 installed on the main heating pipe 10 dewatering drains the collected high-pressure drains by de-cooling and pressure reducing. Through water spraying for cooling and pressure regulation, the drain parameters (such as temperature and pressure) meet the industrial heating standards (for example, the pressure is reduced to 1-2 MPa and the temperature is reduced to 200-300°C) to avoid impacting user equipment. S4: The heating pipeline connected to the reheat cold section pipeline 5 is used to extract part of the reheat cold section steam (usually with higher parameters, suitable for industrial heating). However, the reheat cold section pressure may be insufficient under low load. The treated high-pressure condensate is connected to the heating pipeline through the condensate main heating pipeline 10 and mixed with the reheat cold section extracted steam to supplement the steam flow and energy, forming qualified steam. The parameters of the mixed steam are stable and can meet the needs of industrial users, achieving continuous and reliable heating. By controlling the valve opening of the condensate pipeline 8 before the control valve and the operation of the desuperheating and pressure reducing station 11, the amount of high-pressure condensate replenishment can be dynamically adjusted according to the unit load and heating demand to ensure that the reheat cold section heating pressure is always within the allowable range.

[0021] Example 2 The difference between this embodiment and Embodiment 1 is that the high-pressure condensate replenishment reheat steam cold section industrial heating system includes a boiler 1, which is connected to a main steam pipe 4; it also includes: The reheat cold section pipeline 5 is connected to the boiler 1. A steam pressure matching device is connected to the main steam pipeline 4. The low-pressure ejector steam source interface of the steam pressure matching device is connected to the heating extraction steam port of the reheat cold section pipeline 5. The outlet of the steam pressure matching device and the condensate main heating pipeline 10 converge after the desuperheating and pressure reducing station 11 and are connected to the external industrial heating pipeline. Reheat hot section pipe 6 is connected to boiler 1; High-pressure bypass steam pipe 7 is connected to main steam pipe 4, reheat cold section pipe 5 and reheat hot section pipe 6. High-pressure cylinder 2 of the steam turbine is connected to the main steam pipeline 4 and the reheat cold section pipeline 5. The intermediate pressure cylinder 3 of the steam turbine is connected to the high pressure cylinder 2 of the steam turbine and the reheat hot section pipeline 6.

[0022] In this embodiment, a heating pipeline is connected to the reheat cold section pipeline 5, and a valve-front drain pipe 8 is connected to both the main steam pipeline 4 and the high-pressure bypass steam pipeline 7. Multiple valve-front drain pipes 8 are connected to water supply heating branches 9, and multiple water supply heating branches 9 are connected to the same drain main heating pipeline 10. A desuperheating and pressure reducing station 11 is connected to the drain main heating pipeline 10. The desuperheating and pressure reducing station 11 is used to modulate the steam supply parameters. The heating pipeline is connected to the drain main heating pipeline 10, and the heating pipeline is used to combine qualified steam with the reheat cold section extraction steam for supply. Pressure sensors are installed in both the hot and cold section pipe 5 and the heating pipe, while a flow sensor is installed in the heating pipe. Both pressure and flow sensors are connected to the same intelligent control unit. This intelligent control unit receives signals from the pressure sensors in the reheat cold section pipe 5, the flow sensor in the heating pipe, and the pressure sensor. It is configured to dynamically control the opening of three key valves based on the unit load and heating demand. The regulating valve on the drain pipe 8 before the high-pressure drain valve; The main steam enters the regulating valve of the pressure matching unit; The regulating mechanism of the de-cooling and pressure reducing station 11.

[0023] This embodiment also proposes a method for using a high-pressure condensate-supplemented reheat steam cold section industrial heating system. The high-pressure condensate-supplemented reheat steam cold section industrial heating system is the one described above, and includes the following steps: S1: The main steam generated by boiler 1 enters the high-pressure cylinder 2 of the turbine through the main steam pipeline 4 to do work. The exhaust steam from the high-pressure cylinder enters the reheat cold section pipeline 5 and returns to boiler 1 for reheating to form reheat steam. It then enters the intermediate-pressure cylinder 3 of the turbine through the reheat hot section pipeline 6 to continue doing work. The high-pressure bypass steam pipe 7 is connected to the main steam pipeline 4, the reheat cold section pipeline 5 and the reheat hot section pipeline 6. It is used to bypass part of the steam during unit startup or abnormal operating conditions to maintain system balance. S2: High-pressure condensate is extracted from the pre-valve water supply pipes 8 on the main steam pipe 4 and the high-pressure bypass steam pipe 7 (these condensates are usually high-temperature and high-pressure saturated water or steam, containing a large amount of heat energy). Multiple pre-valve condensate pipes 8 are connected to the water supply heating branch 9 respectively, and the high-pressure condensate is collected into the condensate main heating pipe 10 to form a centralized condensate source. The main steam pipe 4 serves as a high-pressure driving steam source, ready to enter the pressure matching device at any time. S3: The de-cooling and pressure reducing station 11 installed on the main heating pipe 10 de-cools and reduces the pressure of the collected high-pressure condensate. By spraying water to cool down and regulate the pressure, the condensate parameters (such as temperature and pressure) meet the industrial heating standards (for example, the pressure is reduced to 1-2 MPa and the temperature is reduced to 200-300°C), so as to avoid impacting the user's equipment. The pressure of the reheat cold section is sufficient to meet the industrial steam supply requirements. At this time, the intelligent control unit mainly relies on the steam extraction of the reheat cold section and supplements a small amount of high-pressure condensate after de-cooling and pressure reducing as needed to balance the system's thermal parameters. The main steam valve of the pressure matcher is closed and not in operation. When the pressure in the reheat cold section drops below the critical value, the intelligent control unit starts the pressure matcher, introducing a small stream of high-pressure main steam into the pressure matcher as power, and drawing in the low-pressure reheat cold section steam to raise its pressure to the qualified level. At the same time, the high-pressure condensate system is put into operation. After desuperheating and depressurization, it mixes and complements the qualified steam from the pressure matcher, ultimately forming a stable and sufficient industrial steam supply. The intelligent control unit monitors the pressure and flow of the externally supplied steam in real time and dynamically adjusts the high-pressure condensate replenishment, the main steam consumption of the pressure matcher, and the desuperheating water volume through algorithms to meet the steam supply demand with the lowest energy cost (especially the consumption of high-quality main steam). S4: The heating pipeline connected to the reheat cold section pipeline 5 is used to extract part of the reheat cold section steam (usually with higher parameters, suitable for industrial heating). However, the reheat cold section pressure may be insufficient under low load. The treated high-pressure condensate is connected to the heating pipeline through the condensate main heating pipe 10 and mixed with the reheat cold section extracted steam to supplement the steam flow and energy, forming qualified steam. The parameters of the mixed steam are stable and can meet the needs of industrial users, achieving continuous and reliable heating. By controlling the valve opening of the condensate pipe 8 before the control valve and the operation of the desuperheating and pressure reducing station 11, the amount of high-pressure condensate replenishment can be dynamically adjusted according to the unit load and heating demand to ensure that the reheat cold section heating pressure is always within the allowable range. By proactively increasing the reheat cold section steam pressure through a pressure matcher, the pain point of insufficient steam supply pressure under extremely low loads is fundamentally solved, which is more proactive than simply supplementing condensate. The intelligent control unit prioritizes the use of lower-pressure reheat cold section steam and high-pressure condensate, and only uses a small amount of high-pressure main steam for pressure matching when necessary. This achieves tiered utilization of steam source quality, minimizes the consumption of high-quality main steam, and improves overall economy. This forms a triple guarantee of "reheat cold section steam extraction + pressure matching enhancement + high-pressure condensate supplementation", which enables the system to adapt to a wider range of unit load changes and heating demand fluctuations, significantly enhancing its flexibility.

[0024] Experimental Example Based on a 300MW steam turbine unit of a certain company's Dongfang Turbine, designed to extract 50t / h of reheat cold section steam to meet the needs of industrial users, while requiring deep peak shaving to 30% of rated operating conditions, this invention provides a detailed description of the system and method for industrial heating in the reheat steam cold section using high-pressure condensate replenishment: 1. Technical preparation Based on the original design of the reheat cold section supply pipeline for industrial extraction steam, and using the recommended superheated steam velocity of 40 m / s, the design flow rate and pipe diameter of the reheat cold section, as well as the mass flow rate under different loads, are calculated as shown in Table 1 below: Table 1 Design Flow Rate of Reheating and Cooling Section Extraction Pipeline It can be seen that under the above design parameters, the unit can meet the 50t / h steam supply of the reheat steam cooling section under 75%-100% normal operating conditions. Below 75%, supplementary steam supply is required. Under deep peak shaving conditions, the steam supply is only 21t / h, and the maximum required supplementary steam supply is about 30t / h. 2. Design of High-Pressure Drainage Supplementation Industrial Steam Supply System (1) Based on the requirement of 30t / h of supplementary steam supply per unit to achieve thermal-electric decoupling, the following three supplementary steam source schemes are designed according to the existing system: Option 1: Use the first-stage extraction steam as a supplementary steam source. The parameters of the first-stage extraction steam (based on the heat balance diagram of the performance test conditions after the overhaul of the 300MW unit A) are: 150MW load pressure 3.08Mpa, temperature 382℃, flow rate 26.62t / h. Using the first-stage extraction steam as a supplementary steam source satisfies the pressure and temperature requirements, but the extraction steam flow rate will affect the reheater flow rate and cause it to decrease synchronously. When the reheater flow rate decreases by more than 8% of the design flow rate of 376t / h under the 150MW operating condition (approximately 30t / h), it will affect the safe operation of the boiler reheater tube wall and cannot meet the extraction steam volume required for heating. Option 2: Use reheat hot section extraction steam as a supplementary steam source. The reheat hot section extraction steam parameters (based on the heat balance diagram of the performance test conditions after the 300MW unit A overhaul) are: 150MW load pressure 1.60Mpa, temperature 537℃, flow rate 357t / h. The 120MW load pressure drops to 1.3Mpa, which is too low. In order to reduce the impact of extraction steam on the turbine shaft thrust, the intermediate pressure combined steam valve needs to be modified. The modification cost is about 12 million yuan for two units (budgeted by Dongfang Turbine Plant). On the one hand, the investment is too large, and on the other hand, due to the replacement of many main equipment and the long manufacturing cycle, it cannot meet the emergency needs. Option 3: Superheated steam extraction is used as a supplementary steam source. The original soot blowing steam interface at the outlet of the rear superheater can meet the lateral balance of the tube screen and reduce the impact of flow imbalance on the tube screen after the extraction point. At a load of 150MW, the pressure is 9MPa and the temperature is 420℃. The extracted steam is de-cooled by superheater desuperheating water. After depressurization, it basically meets the supplementary steam source flow requirement of 30t / h. Extracting superheated steam will have a certain impact on the unit's economy. Option 4: Superheated steam extraction is used as a supplementary steam source. Steam is drawn from the drain pipe interface of the main steam system on the turbine side, which can meet the lateral balance of the tube panel and reduce the impact of flow imbalance on the tube panel after the extraction point. There are four drain points on site: including the drain point of the main steam header, the drain points of the pipelines before the left and right main steam valves, and the drain point before the high-pressure bypass valve. The valves are DN50 and the pipelines are Φ76×10. The calculated steam flow rate can meet the requirement of 30t / h, and the maximum can reach 50t / h. (2) Analysis of available steam capacity for the project As can be seen from the above scheme, the supplementary steam needs to pass through manual shut-off valves, pipe elbows, electric shut-off valves, electric pressure reducing valves, water spray expansion tanks, medium-pressure elbows, medium-pressure pipes, and the resistance of extension pipes from the main steam pipeline to the high-pressure auxiliary steam header to participate in the heating supplementary steam volume. The resistance above is calculated based on a design flow velocity of 40m / s, and the formula is as follows: ; in For system resistance, For local resistance, Where g is the friction loss, v is the gravitational constant, and v is the steam velocity, the total resistance of the system is calculated to be approximately 0.2-0.3 MPa after considering different layout configurations. This is less than 5% relative to the pressure difference between the main steam pipeline and the high-pressure auxiliary steam header under different operating conditions. The approximate flow rate variation calculated using throttling theory is shown in Table 2 below. Table 2 Analysis of System Flow and Resistance Changes (3) Actual construction technical solution Superheated steam is extracted from four condensate drain points in the main steam system as a supplementary steam source. On-site inspection revealed that all four condensate drain points are Φ76×10 high-temperature alloy pipes, and the distance between the four condensate drain points is within 5 meters. The arrangement is relatively concentrated, which facilitates the layout of the extraction steam pipes. Based on flow calculations, under deep-load conditions and a flow velocity of 60 m / s, a minimum flow rate of 55 t / h can be extracted, which basically meets the requirements. The main equipment includes four manually operated DN50 high-pressure shut-off valves at drainage points, one DN500 high-pressure desuperheating and pressure reducing device, one electric steam pressure regulating valve and one desuperheating water regulating valve, one electric desuperheating water isolation valve and one electric main steam isolation valve before the main steam valve, as well as 12Cr1MoV high-temperature alloy steel pipeline (Φ168×22, primary pipeline before the desuperheating and pressure reducing device) and 20g medium-pressure medium-temperature pipeline (Φ219×...). 6.5, secondary pipeline after desuperheater and pressure reducer), 20g desuperheating water pipeline (Φ50×6.5, main pipeline before high-pressure bypass desuperheating water valve to desuperheating water isolation valve before desuperheating water valve of this project) several, the total project cost shall not exceed RMB 2.5 million, the total construction period is about 45 days, the desuperheating and pressure reducing outlet is sent to the nearest point of the high-pressure auxiliary steam pipe and the high-pressure auxiliary steam pipe auxiliary steam pipe, and the original high-pressure auxiliary steam pipe is used to supplement the insufficient steam supply of the high-pressure auxiliary steam pipe of this machine, so that the thermoelectric decoupling requirements of the design steam supply can be met under the condition of 30%-100% working condition; The actual cost of equipment procurement and construction labor in this project is calculated to be 1.5 million yuan. 3. Key issues to consider in system design (1) After the high-pressure and high-temperature drainage pipeline is led out, the junction box system should be given priority to avoid drainage in the upstream section when the main pipe is connected, which poses a certain safety risk. (2) After the high-pressure and high-temperature main pipe collects steam, it leads it to the desuperheating and pressure reducing station. Sufficient pipe length should be considered to meet the stress release of the pipe. 4. System security and economic analysis (1) Economic benefits After the industrial heating system achieves thermoelectric decoupling, it can supply an additional 30t / h of steam. Based on 4 hours of deep peak shaving per day and 300 days of steam supply per year, the annual increase in steam supply is 4×300×30=36,000 tons. Based on a price of 200 yuan / ton for external heating and steam supply, the additional annual revenue from supplementary steam supply is 3.6 × 200 = 7.2 million yuan; According to DL / T904-2015 "Calculation Method of Technical and Economic Indicators of Thermal Power Plants"; ; Where G is the heat supply, H is the steam enthalpy (taken as 3300 kJ / kg based on design value), and η l For boiler efficiency (based on a design value of 92%, η) l Pipeline efficiency (typically taken as a constant of 99%); Based on the above formula, the coal consumption for steam supply is 123.78 kg / ton. With a steam supply of 36,000 tons, the additional standard coal consumption is 4,456 tons. Based on the current standard coal price of 700 yuan / ton, the additional coal cost is 3.1192 million yuan. Calculate the annual net income = additional annual revenue from supplementary steam - additional coal cost = 720 - 311.92 = 408.08 million yuan; With an annual return of 4.0808 million yuan and an investment of 1.5 million yuan, the project payback period is calculated to be 4.41 months, resulting in an excellent rate of return. (2) Social benefits When a single unit achieves a power generation load rate of 100-30%, the unit's heating capacity reaches the design value, increasing peak-shaving capacity by (75%-30%)×300=1350MW compared to before the upgrade. The annual increase in renewable energy consumption is 4×300×1350=162000MWh. The total electricity consumption for the whole society is reduced by 48,600 tons of standard coal, resulting in a reduction of 126,360 tons of carbon dioxide emissions. In Option 3, the steam pipe for soot blowing on the boiler side can achieve a similar effect, but the interface is located on the 60m platform of the boiler. Using this option requires the pipe to be laid down along the boiler steel frame, which is difficult to construct and poses a high risk to personnel. This is the direct reason why this option was not adopted in this project.

[0025] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A system for industrial heating of reheat steam cold section supplemented by high-pressure condensate, comprising a boiler (1), characterized in that: The boiler (1) is connected to a main steam pipe (4); it also includes: Reheat cold section pipe (5), which is connected to boiler (1); Reheat hot section pipe (6), which is connected to boiler (1); High-pressure bypass steam pipe (7), which is connected to main steam pipe (4), reheat cold section pipe (5) and reheat hot section pipe (6); Steam turbine high-pressure cylinder (2), which is connected to the main steam pipeline (4) and the reheat cold section pipeline (5); The intermediate pressure cylinder (3) of the steam turbine is connected to the high pressure cylinder (2) of the steam turbine and the reheat hot section pipeline (6).

2. The system for industrial heating in the cold section of reheat steam replenishment under high pressure condensate as described in claim 1, characterized in that: A heating pipe is connected to the reheat cold section pipe (5).

3. The system for industrial heating in the cold section of reheat steam replenishment under high pressure condensate as described in claim 2, characterized in that: Both the main steam pipe (4) and the high-pressure bypass steam pipe (7) are connected to a drain pipe (8) before the valve.

4. The system for industrial heating in the cold section of reheat steam replenishment under high pressure condensate as described in claim 3, characterized in that: Multiple drain pipes (8) before the valves are connected to heating water supply branches (9).

5. The system for industrial heating in the cold section of reheat steam replenishment under high pressure condensate as described in claim 4, characterized in that: Multiple water supply heating branches (9) are connected to the same main drain heating pipe (10).

6. The system for industrial heating of the cold section of high-pressure condensate-supplemented reheat steam according to claim 5, characterized in that: A de-cooling and pressure-reducing station (11) is connected to the main heating pipe (10) with drainage.

7. The system for industrial heating in the cold section of reheat steam replenishment under high pressure condensate as described in claim 6, characterized in that: The de-temperature and de-pressure function (11) is used to modulate the steam supply parameters.

8. The system for industrial heating in the cold section of reheat steam replenishment under high pressure condensate as described in claim 7, characterized in that: The heating pipeline is connected to the main heating pipeline (10) for draining water. The heating pipeline is used to supply qualified steam and the steam extracted from the reheat cold section.

9. A method of using a high-pressure condensate-supplemented reheat steam cold section industrial heating system, wherein the high-pressure condensate-supplemented reheat steam cold section industrial heating system is as described in any one of claims 1-8, characterized in that: Includes the following steps: S1: The main steam generated by the boiler (1) enters the high-pressure cylinder (2) of the turbine through the main steam pipeline (4) to do work. The exhaust steam from the high-pressure cylinder enters the reheat cold section pipeline (5) and returns to the boiler (1) for reheating to form reheat steam. It enters the intermediate-pressure cylinder (3) of the turbine through the reheat hot section pipeline (6) to continue doing work. The high-pressure bypass steam pipe (7) is connected to the main steam pipeline (4), the reheat cold section pipeline (5) and the reheat hot section pipeline (6) to bypass some steam and maintain system balance during unit startup or abnormal operating conditions. S2: High-pressure condensate is extracted from the pre-valve water supply pipe (8) on the main steam pipe (4) and the high-pressure bypass steam pipe (7). Multiple pre-valve condensate pipes (8) are connected to the water supply pipe heating branch (9) respectively, and the high-pressure condensate is collected into the condensate main heating pipe (10) to form a centralized condensate source. S3: The de-cooling and pressure reducing station (11) set on the main heating pipe (10) de-cools and reduces the pressure of the collected high-pressure condensate. By spraying water to cool down and regulate the pressure, the condensate parameters meet the industrial heating standards and avoid impacting the user's equipment. S4: The heating pipeline connected to the reheat cold section pipeline (5) is used to extract part of the reheat cold section steam. The treated high-pressure condensate is connected to the heating pipeline through the condensate main heating pipe (10) and mixed with the reheat cold section steam to supplement the steam flow and energy, forming qualified steam. The parameters of the mixed steam are stable, meeting the needs of industrial users and realizing continuous and reliable heating. By controlling the valve opening of the condensate pipe (8) before the control valve and the operation of the de-heating and pressure reducing station (11), the amount of high-pressure condensate replenishment is dynamically adjusted according to the unit load and heating demand to ensure that the heating pressure of the reheat cold section is always within the allowable range.

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