Double rankine cycle waste heat utilization regulation method and system with steam turbine as security bottom

Abstract

This invention discloses a dual Rankine cycle waste heat utilization control method and system with a steam turbine as a safety backup. The waste heat of the coal-fired unit provides driving heat energy to the organic Rankine cycle system for waste heat power generation. When the coal-fired unit is operating at full load, the organic Rankine cycle system for waste heat power generation operates at full load based on the waste heat of the coal-fired unit. When the coal-fired unit reduces its load and operates under sliding pressure, and the minimum temperature difference between the heat source temperature and the ambient temperature of the organic Rankine cycle system for waste heat power generation is less than ΔT or the total waste heat is too small, a condensate water path is drawn from the water inlet valve of the deaerator in the coal-fired unit to the waste heat collection device to meet the minimum conditions for safe operation of the organic Rankine cycle system for waste heat power generation. Changing the steam turbine operating conditions adjusts the waste heat resources to provide a safety backup for the safe operation of the organic Rankine cycle system for waste heat power generation. This ensures that the organic Rankine cycle system for waste heat power generation can operate safely and stably under all operating conditions, improving the safety of all systems in the entire power plant.

Description

Technical Field

[0001] This invention belongs to the technical field of power plant boilers and steam turbine systems, specifically relating to a dual Rankine cycle waste heat utilization control method and system with the steam turbine as a safety backup. Background Technology

[0002] In-depth utilization of low-grade waste heat from power plants, including flue gas waste heat, circulating water waste heat, continuous exhaust steam from deaerators, and steam condensate from ash hopper heating, is an effective way to improve energy efficiency in coal-fired power units. Currently, the main technologies for utilizing medium- and low-temperature waste heat include: low-temperature economizers, heat pumps, and organic Rankine cycle (ORC) power generation technology. While low-temperature economizers and heat pumps have achieved good results in power plant energy conservation, they are both forms of heat utilization. Similar to the traditional steam Rankine cycle principle, ORC uses low-boiling-point organic matter instead of water as the circulating working fluid. It can vaporize at lower temperatures, generating high-pressure steam to drive an expander. In the field of medium- and low-temperature thermal energy utilization, it has better cycle performance than steam Rankine. Its simple structure, low maintenance cost, and wide selection of working fluids make it widely used in various medium- and low-temperature thermal energy utilization fields. ORC power generation technology has matured in recent years and is widely used by domestic and foreign companies in industrial waste heat recovery, geothermal energy, and biomass incineration. It is currently the most promising route among medium- and low-temperature waste heat-to-work conversion technologies. Fluctuations in the load of coal-fired power units lead to fluctuations in the quality of waste heat energy. Chinese patent CN118582267A discloses a method and system for recovering waste heat and energy from coal-fired power units based on an organic Rankine cycle. The method involves the coal-fired power unit generating waste heat and energy, with the waste energy carrying the waste heat. The lowest pressure in the waste energy is selected, and pressure loss is calculated to determine the rated pressure for waste heat and energy recovery. The recovered waste heat and energy are used to heat the organic working fluid in the organic Rankine cycle, causing the organic working fluid to expand and perform work. Condensate exchanges heat with the waste energy discharged from the evaporator in the organic Rankine cycle in a heat exchanger. The heat discharged from the evaporator is used to recover the heat-exchanged waste energy to the condenser. This invention combines the organic and inorganic Rankine cycles, utilizing the low boiling point of the organic medium to absorb the waste heat contained in the inorganic working fluid to produce high-quality electricity, thus improving the power plant's ability to supply high-quality electricity. The waste heat is used in stages to heat the circulating water, improving the thermal efficiency of the inorganic Rankine cycle and maximizing waste heat utilization and working fluid recovery. However, the invention does not provide a method for coupling and coordinating the two processes to achieve safer unit operation. How to ensure the safe operation of the ORC (Organic Rankine Cycle) system, with the main steam turbine as the safety net for the waste heat recovery system, and how to coordinately optimize the cycle parameters of the waste heat recovery system and the main steam turbine thermal system, and develop a waste heat collection method suitable for a dual Rankine cycle system of organic Rankine + inorganic Rankine, is of great significance for improving the technology of waste heat energy collection and efficient utilization in coal-fired power units. Summary of the Invention

[0003] The purpose of this invention is to provide a dual Rankine cycle waste heat recovery and control method with the steam turbine as a safety net, and a waste heat collection and utilization method for coal-fired power generating units with ORC operation as the boundary. This waste heat collection and utilization method, based on the characteristics of waste heat energy and the energy consumption patterns of coal-fired power generating units, uses the main steam turbine as a safety net for the waste heat recovery system to ensure that the waste heat energy meets the ORC operation boundary conditions. It collaboratively optimizes the cycle parameters of the waste heat recovery system and the main steam turbine thermal system, developing an optimal waste heat collection and utilization method for coal-fired power generating units with ORC operation as the boundary. This method can improve the operational economy of the entire ORC-coupled coal-fired power generation system, reduce fossil fuel consumption, reduce carbon emissions, save energy and protect the environment, bringing direct economic benefits to the power plant. Simultaneously, it improves the safety of the ORC system operation, enhances the overall safety of the power plant operation, and reduces the system's accident rate and corresponding maintenance work.

[0004] To achieve the above objectives, in a first aspect, the present invention provides a dual Rankine cycle waste heat utilization and control method with a steam turbine as the safety backup, wherein the waste heat of the coal-fired unit provides driving heat energy to the organic Rankine cycle system for waste heat power generation.

[0005] When the coal-fired power unit is operating at full load, the waste heat power generation organic Rankine cycle system operates at full load based on the waste heat of the coal-fired power unit;

[0006] When the coal-fired power unit is operating at reduced load and in sliding pressure mode, the temperature, pressure, and flow rate of the waste heat of the coal-fired power unit decrease. When the minimum temperature difference between the heat source temperature and the ambient temperature of the waste heat power generation organic Rankine cycle system is less than ΔT or the total waste heat is too small, a condensate water line is drawn from the water inlet valve of the deaerator in the coal-fired power unit to the waste heat collection device to increase the minimum temperature difference between the heat source temperature and the ambient temperature or the total waste heat of the waste heat power generation organic Rankine cycle system, thus meeting the minimum conditions for safe operation of the waste heat power generation organic Rankine cycle system.

[0007] By adjusting the turbine operating conditions of the coal-fired power generation unit to regulate waste heat resources, a safety net for the organic Rankine cycle system of waste heat power generation is provided. Through coordinated control of the dual Rankine cycles, waste heat is fully utilized for power generation when the main unit is at full load. During the unit's sliding pressure and load reduction phase, the parameters of the waste heat carrier (temperature and heat flow) are adjusted by dynamically introducing condensate, solving the problem of organic Rankine cycle operation interruption caused by insufficient waste heat quality under low operating conditions, and expanding the effective operating range of the waste heat power generation system. Active adjustment of turbine operating conditions is used as a benchmark guarantee for waste heat supply, ensuring the stability of waste heat resource parameters and avoiding protection shutdowns triggered by heat source mismatch in the waste heat power generation system due to sudden changes in main cycle parameters. This strengthens the overall system from a thermodynamic coupling perspective. Robustness; By using condensate from the deaerator's water supply system as a regulating medium, the waste heat collection device is supplemented with heat in real time through a working fluid bypass. When the waste heat is insufficient at low loads, the minimum temperature difference (ΔT threshold) between the heat source and the environment can be quickly compensated, ensuring that the organic Rankine cycle working fluid completes an efficient phase change expansion process within the design temperature range. The main generator unit's operating status and the waste heat power generation system's heat source demand are integrated into a closed-loop control logic, achieving an optimal balance between energy-saving power generation and waste heat recovery within a wide load range of the main unit. This reduces the risk of frequent start-ups or inefficient operation caused by heat source fluctuations in traditional waste heat power generation systems.

[0008] Furthermore, the coal-fired unit reduces its load to operate at 30% THA.

[0009] Furthermore, the waste heat carrier includes at least one of the following: continuous exhaust steam from the deaerator, condensate drain from the electrostatic precipitator ash hopper, steam condensate drain from the air preheater soot blowing and warming pipes, steam condensate drain from the low-temperature economizer soot blowing and warming pipes, and steam condensate drain from the denitrification soot blowing and warming pipes.

[0010] Furthermore, ΔT is determined based on the working fluid of the organic Rankine cycle system.

[0011] Secondly, the present invention also provides a dual Rankine cycle waste heat utilization system with a steam turbine as the safety backup, including a coal-fired unit, a waste heat collection device, and a waste heat power generation organic Rankine cycle system. The waste heat carrier inlet of the waste heat collection device is connected to the waste heat carrier outlet of the coal-fired unit. The outlet of the waste heat collection device is sequentially connected to a pipeline booster pump, the hot-side inlet of the evaporator of the organic Rankine cycle system, the hot-side inlet of the waste heat cascade utilization heat exchanger, and the condenser of the coal-fired unit. The cold side of the waste heat cascade utilization heat exchanger is connected to the outlet of the condensate pump group in the coal-fired unit and the inlet of the No. 1 low-pressure heater.

[0012] Furthermore, the cold-side outlet of the evaporator in the organic Rankine cycle system is sequentially connected to the organic Rankine cycle system turbine, the hot side of the organic Rankine cycle system heat exchanger, the organic Rankine cycle system condenser, and the organic Rankine cycle system booster pump. The outlet of the organic Rankine cycle system booster pump is connected to the cold-side inlet of the organic Rankine cycle system heat exchanger, and the cold-side outlet of the organic Rankine cycle system heat exchanger is connected to the cold-side inlet of the organic Rankine cycle system evaporator.

[0013] Furthermore, temperature and pressure monitoring devices are installed at both the inlet and outlet of the waste heat collection device.

[0014] Furthermore, the condenser of the organic Rankine cycle system is connected to the circulating cooling water system.

[0015] Furthermore, a bypass pipeline is installed at the outlet of the pipeline booster pump to connect to the condenser of the coal-fired unit.

[0016] Furthermore, the temperature difference between the heat source temperature and the ambient temperature of the waste heat power generation organic Rankine cycle system is calculated to obtain the command for controlling the opening of the water supply regulating valve of the waste heat power generation system. When the temperature difference is less than ΔT, it indicates that the temperature of the heat source of the waste heat system is too low. In this case, the opening of the water supply regulating valve of the waste heat power generation system needs to be increased to increase the waste heat supply and ensure the safe operation of the organic Rankine cycle system. When the temperature difference is greater than ΔT, it indicates that the temperature of the heat source of the waste heat system meets the operating requirements of the organic Rankine cycle system. In this case, the opening of the water supply regulating valve of the waste heat power generation system needs to be decreased to reduce the waste heat supply and ensure the safe and economical operation of both the inorganic Rankine cycle power generation system of the large unit and the waste heat utilization organic Rankine cycle power generation system.

[0017] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention achieves close synergistic operation of three major systems: a coal-fired power generation inorganic Rankine cycle system, a waste heat high-efficiency recovery system, and a waste heat power generation organic Rankine cycle system. With the coal-fired power generation inorganic Rankine cycle system as a safety net, it ensures the safe and stable operation of the waste heat power generation organic Rankine cycle system under all operating conditions, thereby improving the safety of all systems in the entire power plant. Through the continuous and efficient power generation of the waste heat power generation inorganic Rankine cycle system, it can bring direct and stable waste heat power generation revenue to the power plant, increasing the power plant's sellable electricity, increasing the power plant's revenue, and improving the economic efficiency of power plant operation. Furthermore, by recovering waste heat for power generation, it also reduces the power plant's carbon emissions. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a dual Rankine cycle waste heat utilization and control method with a steam turbine as the safety backup according to the present invention;

[0019] In the diagram, 1. Boiler; 2. High-pressure cylinder of steam turbine; 3. Intermediate-pressure cylinder of steam turbine; 4. Low-pressure cylinder of steam turbine; 5. Generator; 6. Condenser; 7. High-pressure heater No. 1; 8. High-pressure heater No. 2; 9. High-pressure heater No. 3; 10. Deaerator; 11. Feedwater pump set; 12. Low-pressure heater No. 5; 13. Low-pressure heater No. 6; 14. Low-pressure heater No. 7; 15. Low-pressure heater No. 8; 16. Condensate pump set; 17. Water supply regulating valve of waste heat power generation system; 18. Waste heat collection device; 19. Pipeline booster pump; 20. Evaporator of organic Rankine cycle system; 21. Waste heat cascade utilization heat exchanger; 22. Turbine of organic Rankine cycle system; 23. Generator of organic Rankine cycle system; 24. Heat exchanger of organic Rankine cycle system; 25. Condenser of organic Rankine cycle system; 26. Booster pump of organic Rankine cycle system. Detailed Implementation

[0020] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0021] Example 1

[0022] A 350MW supercritical coal-fired power unit has long neglected a significant amount of medium- and low-temperature waste heat during daily operation. The current waste heat emissions from the power plant involve direct discharge of waste heat from the deaerator's continuous exhaust steam and the electrostatic precipitator's ash hopper; the working fluid from the furnace heating surface soot blowing and warming steam ducts, air preheater soot blowing and warming steam ducts, low-temperature economizer soot blowing and warming steam ducts, and denitrification soot blowing and warming steam ducts is recycled to the expansion tank, resulting in heat waste; the heating return water is recycled to the condenser, also resulting in heat waste; thus causing substantial waste heat energy loss. To recover the power plant's waste heat resources and improve the plant's operational safety and economy, this invention patents a dual Rankine cycle waste heat utilization and control method with the steam turbine as a safety backup. Based on water quality requirements and long-term on-site statistical data, four types of waste heat were initially selected for recovery and utilization. The waste heat parameters for the coal-fired unit under THA conditions are shown in Table 1. The waste heat parameters for the coal-fired unit under 30% THA conditions are shown in Table 2. The ambient temperature is 25℃, and the critical temperature for the evaporation of the organic working fluid is 95℃.

[0023] Table 1. Four waste heat parameters of coal-fired units under THA operating conditions.

[0024]

[0025] Table 2. Four waste heat parameters for coal-fired power units under 30% THA operating conditions.

[0026]

[0027] Comparing the waste heat parameters in Tables 1 and 2, it can be seen that when the load of the coal-fired unit decreases, the parameters of the waste heat resources emitted by the unit also decrease due to the unit's sliding pressure operation. When the coal-fired unit is in THA (Total Heat Affected) operation, the waste heat carrier in Table 1 is discharged into the waste heat collection device and transported to the organic Rankine cycle system for waste heat power generation through pipeline booster pump 19. The waste heat heats the organic working fluid, and the evaporation of the organic working fluid drives the turbine to generate electricity. At this time, the three major systems—the inorganic Rankine cycle system for coal-fired power generation, the high-efficiency waste heat collection system, and the organic Rankine cycle system for waste heat power generation—are operating normally and stably.

[0028] When the coal-fired unit is operating at 30% THA, the waste heat carrier listed in Table 2 is discharged into the waste heat collection device and then transported to the organic Rankine cycle system for waste heat power generation via pipeline booster pump 19. At this time, because the temperature of the waste heat resource is lower than the critical evaporation temperature of the organic working fluid (95℃) and the waste heat flow rate decreases, the organic working fluid cannot evaporate, causing the organic Rankine cycle system for waste heat power generation to shut down or malfunction, and unable to generate electricity normally. At this point, the water inlet regulating valve 17 of the waste heat power generation system is opened to regulate the temperature and flow rate of the waste heat resource, ensuring that the waste heat temperature is greater than or equal to 95℃, while the evaporation rate of the organic working fluid meets the minimum flow rate required for the normal operation of the organic Rankine cycle system turbine. By closely coordinating the operation of three major systems—the inorganic Rankine cycle system for coal-fired power generation, the efficient waste heat recovery system, and the organic Rankine cycle system for waste heat power generation—with the inorganic Rankine cycle system serving as a safety net, the organic Rankine cycle system for waste heat power generation can operate safely and stably under all operating conditions, thereby improving the safety of all systems in the entire power plant. The continuous and efficient power generation from the inorganic Rankine cycle system provides the power plant with direct and stable waste heat power generation revenue, increasing the power plant's sellable electricity, boosting its profits, and improving the economic efficiency of its operation. Furthermore, recovering waste heat for power generation helps reduce the power plant's carbon emissions.

[0029] like Figure 1As shown, the present invention provides a system capable of implementing the above method, comprising a boiler 1, a high-pressure cylinder 2 of a steam turbine, an intermediate-pressure cylinder 3 of a steam turbine, a low-pressure cylinder 4 of a steam turbine, a generator 5, a condenser 6, a No. 1 high-pressure heater 7, a No. 2 high-pressure heater 8, a No. 3 high-pressure heater 9, a deaerator 10, a feedwater pump set 11, a No. 5 low-pressure heater 12, a No. 6 low-pressure heater 13, a No. 7 low-pressure heater 14, a No. 8 low-pressure heater 15, a condensate pump set 16, a waste heat power generation system water supply regulating valve 17, a waste heat collection device 18, a pipeline booster pump 19, an organic Rankine cycle system evaporator 20, a waste heat cascade utilization heat exchanger 21, an organic Rankine cycle system turbine 22, an organic Rankine cycle system generator 23, an organic Rankine cycle system heat exchanger 24, an organic Rankine cycle system condenser 25, and an organic Rankine cycle system booster pump 26. Among them, the boiler 1, the high-pressure cylinder of the steam turbine 2, the intermediate-pressure cylinder of the steam turbine 3, the low-pressure cylinder of the steam turbine 4, the generator 5, the condenser 6, the No. 1 high-pressure heater 7, the No. 2 high-pressure heater 8, the No. 3 high-pressure heater 9, the deaerator 10, the feedwater pump set 11, the No. 5 low-pressure heater 12, the No. 6 low-pressure heater 13, the No. 7 low-pressure heater 14, the No. 8 low-pressure heater 15, and the condensate pump set 16 are connected according to the existing coal-fired unit structure. A pipeline connecting the waste heat collection device 18 is installed on the pipeline from the No. 5 low-pressure heater 12 to the deaerator 10. A waste heat power generation system water supply regulating valve 17 is installed on the pipeline from the No. 5 low-pressure heater 12 to the waste heat collection device 18. The outlet of the waste heat collection device 18 is sequentially connected to the pipeline booster pump 19, the hot-side inlet of the organic Rankine cycle evaporator 20, the hot-side inlet of the waste heat cascade utilization heat exchanger 21, and the condenser 6. The cold side of the waste heat cascade utilization heat exchanger 21 is connected to the outlet of the condensate pump group 16 and the No. 7... The inlet of the low-pressure heater 14; the cold-side outlet of the organic Rankine cycle evaporator 20 is sequentially connected to the organic Rankine cycle turbine 22, the hot side of the organic Rankine cycle heat exchanger 24, the organic Rankine cycle condenser 25, and the organic Rankine cycle booster pump 26. The outlet of the organic Rankine cycle booster pump 26 is connected to the cold-side inlet of the organic Rankine cycle heat exchanger 24, and the cold-side outlet of the organic Rankine cycle heat exchanger 24 is connected to the cold-side inlet of the organic Rankine cycle evaporator 20.

[0030] Temperature and pressure monitoring devices are installed at both the inlet and outlet of the waste heat collection device 18 to monitor the operating condition of the waste heat collection device 18 in real time.

[0031] The organic Rankine cycle system condenser 25 is connected to the circulating cooling water system, and the working fluid is condensed through the circulating cooling water.

[0032] Example 2: The system described in this application includes an inorganic Rankine cycle system for coal-fired power generation, a high-efficiency waste heat recovery system, and an organic Rankine cycle system for waste heat power generation. The inorganic Rankine cycle system is a conventional coal-fired power unit. During daily operation, coal-fired power units directly discharge a significant amount of waste heat and waste materials, such as: continuous exhaust steam from the deaerator, condensate drain from the electrostatic precipitator ash hopper, steam condensate drain from the air preheater soot blowing and warming pipes, steam condensate drain from the low-temperature economizer soot blowing and warming pipes, and steam condensate drain from the denitrification soot blowing and warming pipes. The waste heat recovery system is used to recover these discharged waste heat and waste materials. Generally, the lowest pressure among all waste materials, considering a certain pressure loss, is selected as the rated pressure of the waste heat recovery system. All waste heat and waste materials are collected in the waste heat recovery device. If the waste material is steam, it can be introduced from the bottom of the recovery device and cooled down by the waste material in the recovery device. If the steam content in the waste material is high, the medium in the recovery device can be divided into steam and water for recycling. If the waste material is water... The water can be depressurized through a throttling valve and then fed into the recovery device. The method of recovery and utilization of the flash steam generated during the throttling and depressurization process can be determined according to the amount of flash steam. If there is very little flash steam, water can be recovered from the top of the recovery device by spraying. If there is a lot of flash steam, the medium in the recovery device can be divided into two parts, steam and water, for recovery and utilization. When the mass ratio of steam is less than 1%, the impact of steam bubbles on heat exchange can be ignored considering the investment. The organic Rankine cycle system utilizes the low boiling point of the organic working fluid to absorb the low-temperature waste heat in the recovery device and evaporate it, thereby driving the expander to do work and generate electricity, directly bringing electricity revenue to the power plant. The heat discharged from the evaporator can be deeply and cascaded through the heat exchanger to heat the condensate, further improving the cycle thermal efficiency. Finally, the residual mass is recovered to the condenser. The waste heat and residual mass are utilized and recovered to the extreme, reducing the consumption of fossil energy, saving energy and protecting the environment, and improving efficiency.

[0033] In summary, this invention achieves its goals by closely coordinating the operation of three major systems: a coal-fired power generation inorganic Rankine cycle system, a waste heat high-efficiency recovery system, and a waste heat power generation organic Rankine cycle system. With the coal-fired power generation inorganic Rankine cycle system serving as a safety net, the invention ensures the safe and stable operation of the waste heat power generation organic Rankine cycle system under all operating conditions, thereby improving the overall safety of the power plant. Furthermore, the continuous and efficient power generation of the waste heat power generation inorganic Rankine cycle system provides the power plant with direct and stable waste heat power generation revenue, increasing the power plant's sellable electricity, boosting its profits, and improving the economic efficiency of its operation. Finally, the recovery of waste heat for power generation also reduces the power plant's carbon emissions.

[0034] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for regulating waste heat utilization in a dual Rankine cycle system with a steam turbine as a safety backup, characterized in that, Based on a dual Rankine cycle waste heat utilization system with a steam turbine as the safety backup, the system includes a coal-fired unit, a waste heat collection device (18), and a waste heat power generation organic Rankine cycle system. The waste heat carrier inlet of the waste heat collection device (18) is connected to the waste heat carrier outlet of the coal-fired unit. The outlet of the waste heat collection device (18) is sequentially connected to the pipeline booster pump (19), the hot-side inlet of the organic Rankine cycle system evaporator (20), the hot-side inlet of the waste heat cascade utilization heat exchanger (21), and the condenser (6) of the coal-fired unit. The cold side of the waste heat cascade utilization heat exchanger (21) is connected to the outlet of the condensate pump group (16) in the coal-fired unit and the inlet of the No. 7 low-pressure heater (14). The cold-side outlet of the organic Rankine cycle system evaporator (20) is sequentially connected to the organic Rankine cycle system turbine (22), the hot side of the organic Rankine cycle system heat exchanger (24), and the... The organic Rankine cycle system includes a condenser (25) and a booster pump (26). The outlet of the booster pump (26) is connected to the cold-side inlet of the heat exchanger (24) and the cold-side outlet of the heat exchanger (24) is connected to the cold-side inlet of the evaporator (20). Temperature and pressure monitoring devices are installed at both the inlet and outlet of the waste heat collection device (18). The condenser (25) is connected to the circulating cooling water system. A bypass pipe is installed at the outlet of the booster pump (19) to connect to the condenser (6) of the coal-fired unit. The temperature difference between the heat source temperature and the ambient temperature of the waste heat power generation organic Rankine cycle system is calculated to obtain the command to control the opening of the water supply regulating valve (17) of the waste heat power generation system. The waste heat of the coal-fired unit provides driving heat energy to the waste heat power generation organic Rankine cycle system. When the coal-fired power unit is operating at full load, the waste heat power generation organic Rankine cycle system operates at full load based on the waste heat of the coal-fired power unit; When the coal-fired unit reduces its load, the temperature, pressure and flow rate of the waste heat of the coal-fired generator set decrease, and the temperature difference between the heat source temperature and the ambient temperature of the waste heat power generation organic Rankine cycle system is less than ΔT or the total heat of the waste heat is too small, a high-temperature condensate is led out from the water inlet valve of the deaerator (10) in the coal-fired generator set to the waste heat collection device (18). A waste heat power generation system water inlet regulating valve (17) is installed on the pipeline from the high-temperature condensate to the waste heat collection device (18) to meet the minimum conditions for safe operation of the waste heat power generation organic Rankine cycle system. By adjusting the turbine operating conditions of coal-fired power generation units, waste heat resources are utilized to ensure the safe operation of the organic Rankine cycle system for waste heat power generation; the load of coal-fired units is reduced to operate at 30% THA.

2. The dual Rankine cycle waste heat utilization and control method with steam turbine as the safety backup as described in claim 1, characterized in that, Waste heat carriers include at least one of the following: continuous exhaust steam from deaerator, condensate drain from electrostatic precipitator ash hopper, steam condensate drain from air preheater soot blowing and warming pipes, steam condensate drain from low-temperature economizer soot blowing and warming pipes, and steam condensate drain from denitrification soot blowing and warming pipes.

3. The dual Rankine cycle waste heat utilization and control method with a steam turbine as the safety backup, as described in claim 1, is characterized in that... ΔT is determined based on the working fluid of the organic Rankine cycle system.

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