CN203035350U - Britten-hybrid combined steam rankine cycle power generation device - Google Patents

Abstract

The utility model relates to a Breton-mixed steam Rankine combined cycle power generation device, adopting the exhaust gas of the Breton cycle as the heat source of the mixed steam Rankine cycle system, and the mixed steam Rankine combined cycle is generated by low-pressure steam Device 5 directly combines the steam Rankine cycle at the high-pressure end with the steam Rankine cycle at the low-pressure end, and utilizes all the latent heat of vaporization released during the condensation of exhaust steam from the steam turbine at the high-temperature end steam Rankine cycle for power generation with the steam Rankine cycle at the low-temperature end, effectively reducing the The load of the condenser in the traditional steam Rankine cycle system is more than 20%. Using system optimization technology, the cycle absolute thermal efficiency of the entire system can be increased by more than 5%. The utility model can be used not only for the energy-saving renovation of existing units, but also for the design and construction of newly-built units, and has remarkable economic, social and environmental benefits.

Description

Bretton-Hybrid Steam Rankine Combined Cycle Power Plant

technical field

The invention relates to a Breton-mixed steam Rankine combined cycle power generation device, specifically belonging to the technical field of thermal power plant power devices.

Background technique

Gas-steam combined cycle has a series of advantages such as high thermal efficiency, fast start-up speed, good environmental protection conditions, short installation period, low investment cost, etc., coupled with the rapid development of gas turbine technology in recent years, the single unit power of gas turbine is also increasing continuously, combined cycle The research has attracted the attention and implementation of countries all over the world.

The research on combined cycle power generation technology in foreign countries began in the late 1960s. After decades of development, at present, the gas-steam combined cycle power generation technology in many developed countries such as the United States, the United Kingdom, and Japan has become relatively mature, and its power supply efficiency has reached Reach more than 50%. Such as the US CE company is about 53%; ABB company is 48% ~ 51.9%; Mitsubishi Heavy Industries is 51% ~ 52%. Many companies (such as Texco in the United States, CMI in Belgium, etc.) have relatively mature performance design, system optimization, structure optimization, and manufacturing technology of combined cycle waste heat boilers, and have fully mastered the thermal characteristics and operating characteristics of combined cycle waste heat boilers. . The gas-steam combined cycle and the two-fluid cycle currently under development-the Cheng's cycle of reinjecting steam from the gas turbine and the regenerative cycle of spraying water and evaporating at the outlet of the gas turbine's compressor are just representatives of this technology development, and the former has matured , and achieved huge economic benefits, the latter two are being intensively studied, and Cheng's cycle has already had application examples and formal products.

A thermal power plant that uses water vapor as a working medium is a large-scale factory that converts thermal energy into mechanical energy, and then converts mechanical energy into electrical energy. The cycle applied in power plants is very complicated, but in essence, it is mainly completed by the Rankine cycle composed of boilers, steam turbines, condensers, water pumps and other equipment. The working principle is: the feed water is first pressurized by the feed water pump and then sent Into the boiler, the water in the boiler is heated and vaporized to form high-temperature and high-pressure superheated steam. The superheated steam expands and does work in the steam turbine and becomes low-temperature and low-pressure exhaust steam. Finally, it is discharged into the condenser to condense into condensed water, and the condensed water will be condensed by the water pump again. Water is sent to the boiler for a new cycle. As for the complex cycle used in thermal power plants, it is just a new cycle formed on the basis of the Rankine cycle, in order to improve the thermal efficiency, that is, the regenerative cycle, the reheat cycle, etc. The Rankine cycle has become a modern steam power plant. basic cycle.

Without exception, modern large and medium-sized steam power plants all adopt steam extraction heating feed water reheating cycle and steam reheating cycle technology, thereby increasing the average heating temperature. In addition to significantly improving the thermal efficiency of the cycle, although the steam consumption rate has increased, However, due to the step-by-step extraction of steam, the exhaust rate is reduced, which is beneficial to the improvement of the ratio of actual work to theoretical work, that is, the relative internal efficiency η _oi of the cycle, and at the same time solves the difficulty of the flow capacity limitation of the final stage blades of large-power steam turbines , the condenser volume can also be reduced accordingly. However, when the steam condenses in the condenser, it still releases a large amount of latent heat of vaporization, which requires a large amount of water or air for cooling, which wastes heat, causes thermal pollution, and wastes electricity and water resources. Therefore, how to effectively utilize the large amount of latent heat of vaporization released during the condensation of steam in the condenser is worthy of further study.

A large amount of flue gas is emitted during the production process of power plant boilers, and a lot of heat can be recovered. Although this part of waste heat resources is a huge waste, it is difficult to recycle it. The main reasons are: (1) The quality of waste heat is low, and no effective utilization method has been found; (2) Recovering this part of waste heat is often harmful to boilers. It is risky to make major changes to the original thermal system; (3) The heat balance problem is difficult to organize, and it is difficult to use it directly in the factory. It is often necessary to look for suitable heat users outside, and the heat load of heat users is often There will be fluctuations, thereby limiting the generalizability of the recovery method.

Therefore, how to use the basic laws of thermodynamics of steam Rankine cycle thermal power plants, retain the advantages of power plant technology based on the principle of Rankine cycle, explore new combined cycle theory, and really find a new way to greatly improve the thermal efficiency of steam Rankine cycle power plants , has become a difficult point of research in this field.

Contents of the invention

The purpose of the present invention is to solve the problems existing in the above-mentioned steam Rankine cycle, and propose a new thermal power plant combined cycle process, that is, the Bretton-cascade steam Rankine combined cycle power generation unit, which can retain the traditional steam Rankine At the same time, it can recover the latent heat of vaporization of the traditional steam Rankine cycle condenser greatly, so that the load of the traditional Rankine cycle condenser can be greatly reduced, and the absolute magnitude of the reduction can reach 20%, so that Realize the effective improvement of the thermal efficiency of the entire combined cycle unit, and finally achieve the purpose of saving energy and reducing consumption, and improving the thermal efficiency of the system.

The object of the present invention is achieved by the following measures:

A Bretton-mixed steam Rankine combined cycle power generation device, the device includes a Bretton cycle, a high-pressure end steam Rankine cycle and a low-pressure end steam Rankine cycle, characterized in that:

The air 23 is sent to the combustion equipment 25 through the compressor 24, fully combusted with the incoming fuel 28, and the generated high-temperature flue gas enters the gas turbine 26, drives the gas turbine generator 29 to generate electricity, and completes the gas turbine unit Breton cycle.

The high-temperature flue gas 27 discharged from the gas turbine 26 is used as the heat source of the hybrid steam Rankine cycle system. The high-temperature flue gas 27 passes through the waste heat boiler body 1, the low-pressure superheater 15, the high-pressure superheater 3, and the high-pressure feed water heater along the flue 20 8. The low-pressure feed water heater 11 is discharged after cooling down.

The steam Rankine cycle at the high-pressure end refers to the saturated steam 2 coming out of the waste heat boiler body 1, which forms the high-pressure superheated steam 3-1 through the high-pressure superheater 3, and sends it to the high-pressure steam turbine 4 to drive the generator 19 to generate electricity; the high-pressure steam turbine 4 The exhausted steam 4-1 is directly mixed with the feedwater of the low-pressure end steam Rankine cycle in the low-pressure steam generator 5 to generate saturated steam 5-1, and the formed condensed water 6 is sent to the high-pressure feedwater heater 8 through the high-pressure feedwater pump 7, The waste heat boiler body 1, and the waste heat boiler body 1 generates saturated steam again, thereby forming a steam Rankine cycle at the high pressure end.

The steam Rankine cycle at the low-pressure end refers to that the low-pressure steam generator 5 uses the exhaust steam 4-1 of the steam Rankine cycle at the high-pressure end as a heat source, and directly mixes and heats it with the feed water at the low-pressure end to generate low-pressure saturated steam 5-1 , which is passed through the low-pressure The superheater 15 forms low-pressure superheated steam 16, which is sent to the low-pressure steam turbine 17 to drive the generator 19 to generate electricity; the exhausted steam from the low-pressure steam turbine 17 is condensed into low-pressure end condensate 9 in the low-pressure condenser 18, and the condensate 9 passes through the condensate pump 10, the low-pressure Feedwater heater 11, deaerator 12, low-pressure feedwater pump 13, and secondary low-pressure feedwater heater 14 are sent to low-pressure steam generator 5, which then generates steam 5-1 to form low-pressure end steam Rankine loop loop.

The low-pressure steam generator 5 adopts a positive pressure operation mode, that is, the pressure of exhaust steam from the high-pressure steam turbine 4 is higher than atmospheric pressure.

The steam Rankine cycle at the high-pressure end and the steam Rankine cycle at the low-pressure end are directly combined through the low-pressure steam generator 5, and the latent heat of vaporization released during the condensation of the steam at the high-temperature end steam Rankine cycle is efficiently recovered for use in the steam Rankine cycle at the low-temperature end For power generation, the low-pressure superheater technology adopted absorbs the advantages of the reheat cycle technology, so the thermal efficiency of the entire cycle can be significantly improved. the

The high-temperature flue gas produced by fuel combustion is discharged into the atmosphere after being cooled by the boiler body 1, low-pressure superheater 15, high-pressure superheater 3, high-pressure feedwater heater 8, secondary low-pressure feedwater heater 14, and low-pressure feedwater heater 11; or through the boiler Body 1, high-pressure superheater 3, low-pressure superheater 15, high-pressure feedwater heater 8, secondary low-pressure feedwater heater 14, and low-pressure feedwater heater 11 cool down and discharge into the atmosphere.

When the low-pressure feedwater heater 11 and the flue gas adopt a separate heat exchange method, the low-pressure feedwater heater is a composite phase-change heat exchanger, including an evaporator 11-1, a condenser 11-2, an evaporator 11-1 and The condenser adopts a split or integrated structure; the phase change working medium is water or other suitable substances; the phase change working medium absorbs the heat of the flue gas in the evaporator 11-1 to generate saturated steam, and the saturated steam passes through the condenser 11-2 exchanges heat with the condensate water at the low-pressure end 9 partition wall, after cooling, the condensate is formed, and then the evaporator 11-1 absorbs the heat of the flue gas to generate steam, thereby forming the internal circulation process of the phase change working medium; the phase change working medium adopts Natural circulation or forced circulation; the preferred method is the split arrangement of the evaporator and condenser, that is, the evaporator 11-1 is arranged inside the flue 20, the condenser 11-2 is arranged outside the flue, and the phase change working medium is water. Use natural circulation.

One or more high-pressure feedwater heaters 8, low-pressure steam evaporators 5, low-pressure feedwater heaters 14, low-pressure feedwater heaters 11, high-pressure superheaters 3, and low-pressure superheaters 15 can be respectively arranged in series, in parallel or in combination. Linked connection.

The low-pressure end condenser 18 is set according to conventional technology, and water or air is used as a cooling medium.

The heat exchange elements of the aforementioned equipment mentioned in the present invention can adopt row tubes, finned tubes, serpentine tubes or spiral groove tubes, or tubes with other heat transfer enhancement measures or other types of hollow cavity heat exchange elements.

Control the wall temperature of the heat exchange surface of the evaporator 11-1 of the low-pressure feed water heater 11 to be slightly higher than the acid dew point temperature of the flue gas, or use corrosion-resistant materials to effectively reduce the low-temperature corrosion of the flue gas, which can effectively reduce the exhaust gas temperature and avoid smoke. At the same time as the gas is corroded at low temperature, the waste heat of the flue gas is efficiently recovered.

Equipment not described in the present invention and its backup system, pipelines, instruments, valves, heat preservation, bypass facilities with regulating functions, etc. are matched by well-known mature technologies.

Equipped with safety and control devices matching the system of the present invention, the well-known mature control technology of the existing steam Rankine cycle power plant, Cheng's cycle power plant or gas-steam combined cycle power plant is used for matching, so that the hybrid steam Langine Ken combined cycle power generation device can operate economically, safely and with high thermal efficiency, achieving the purpose of saving energy and reducing consumption.

Compared with the prior art, the present invention has the following advantages:

1. The Bretton-mixed steam Rankine combined cycle power generation device designed by the present invention is different from the traditional Bretton-steam Rankine combined cycle system. The low-pressure steam generator of the steam Rankine cycle at the high-pressure end adopts positive pressure In the operation mode, the exhaust steam of the high-pressure steam turbine is used as the heat source of the steam generator of the low-pressure end steam Rankine cycle, which is directly mixed with the feed water of the low-pressure end steam Rankine cycle to generate low-pressure steam, so that the high-pressure end steam Rankine cycle and the low-pressure end steam The Rankine cycle is ingeniously compounded by the low-pressure steam generator, and the latent heat of vaporization of the steam in the high-pressure end steam Rankine cycle is fully utilized. Compared with the load of the low-pressure end condenser of the unit with the same power generation capacity, the load of the condenser is reduced The absolute value of the absolute amplitude value can reach 20%, and the absolute efficiency value of the entire system cycle can be increased by at least 2%; because the back pressure of the high-pressure end steam Rankine cycle steam turbine is operated in a positive pressure mode, the exhaust steam at the outlet of the high-pressure steam turbine can guarantee a certain degree of superheat , under the condition that the temperature of the superheated steam at the high-pressure end remains unchanged, the thermal efficiency of the cycle can be further increased by more than 2% by appropriately increasing the initial pressure of the steam at the high-pressure end. Using system optimization technology, the absolute magnitude of the efficiency improvement of the combined cycle system can reach more than 5%.

2. High-efficiency recovery and utilization of flue gas waste heat in the power plant: When the heat exchanger installed in the tail flue adopts a phase-change heat exchanger, the waste heat of the flue gas can be recovered efficiently, and the exhaust gas temperature can be reduced to about 120°C, and the phase-change heat When the corrosion-resistant material is used for the evaporator, the exhaust gas temperature can be reduced even more, reaching about 85°C, which is extremely beneficial to the operation of the desulfurization and denitrification system. Power generation is more in line with the principle of energy cascade utilization.

3. Significantly improved operational safety:

The high-pressure steam turbine in the steam Rankine cycle at the high-pressure end operates under positive pressure, and the outlet steam is superheated steam, so the operating conditions of the steam turbine are optimized; the low-pressure superheater in the steam Rankine cycle at the low-pressure end improves the operating safety due to its lower pressure The inlet steam of the low-pressure steam turbine adopts superheated steam, so that the advantages of the traditional reheat cycle can be fully utilized, and it can effectively solve the design, manufacture and operation problems of the last-stage blade of the steam turbine in the traditional steam Rankine cycle due to wet steam. The vibration of the generator set has been significantly improved compared to before.

4. The scheme of the present invention can be used not only for the design and construction of new power plant systems, but also for the energy-saving transformation of existing Breton-Steam Rankine combined cycle units, which can fully tap the potential of equipment and revitalize existing assets. At the same time, it conforms to the national industrial policy, and the economy and safety of the unit operation are reliably guaranteed, which can effectively improve the thermal efficiency of the system.

Description of drawings

Fig. 1 is a schematic flow chart of a Breton-mixed steam Rankine combined cycle power generation device of the present invention.

In Figure 1: 1-waste heat boiler body, 2-saturated steam, 3-high-pressure superheater, 3-1-high-pressure superheated steam, 4-high-pressure steam turbine, 4-1-exhaust steam from high-pressure steam turbine, 5-low-pressure steam generator, 5-1-Low pressure saturated steam, 6-Condensate water, 7-High pressure feed water pump, 8-High pressure feed water heater, 9-Low pressure condensate water, 10-Condensate water pump, 11-Low pressure feed water heater, 11-1-Evaporator , 11-2-condenser, 12-deaerator, 13-low pressure feed water pump, 14-secondary low pressure feed water heater, 15-low pressure superheater, 16-low pressure superheated steam, 17-low pressure steam turbine, 18-low pressure condenser steamer, 19-generator, 20-flue, 23-air, 24-compressor, 25-combustion equipment, 26-gas turbine, 27-high temperature flue gas, 28-fuel, 29-gas turbine generator.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Example 1:

As shown in Fig. 1, a kind of Breton-mixed steam Rankine combined cycle power generation device, the device includes high pressure end steam Rankine cycle, low pressure end steam Rankine cycle, described high pressure end steam Rankine cycle:

The air 23 is sent to the combustion equipment 25 through the compressor 24, fully combusted with the incoming fuel 28, and the generated high-temperature flue gas enters the gas turbine 26, drives the gas turbine generator 29 to generate electricity, and completes the gas turbine unit Breton cycle.

The high-temperature flue gas 27 discharged from the gas turbine 26 is used as the heat source of the hybrid steam Rankine cycle system. The high-temperature flue gas 27 passes through the waste heat boiler body 1, the low-pressure superheater 15, the high-pressure superheater 3, and the high-pressure feed water heater along the flue 20 8. The secondary low-pressure feed water heater 14 and the low-pressure feed water heater 11 are discharged after cooling down.

The steam Rankine cycle at the high-pressure end refers to the saturated steam 2 coming out of the waste heat boiler body 1, which forms the high-pressure superheated steam 3-1 through the high-pressure superheater 3, and sends it to the high-pressure steam turbine 4 to drive the generator 19 to generate electricity; the high-pressure steam turbine 4 The exhausted steam 4-1 is directly mixed with the feedwater of the low-pressure end steam Rankine cycle in the low-pressure steam generator 5 to generate saturated steam 5-1, and the formed condensed water 6 is sent to the high-pressure feedwater heater 8 through the high-pressure feedwater pump 7, The waste heat boiler body 1, and the waste heat boiler body 1 generates saturated steam again, thereby forming a steam Rankine cycle at the high pressure end.

The steam Rankine cycle at the low-pressure end refers to that the low-pressure steam generator 5 uses the exhaust steam 4-1 of the steam Rankine cycle at the high-pressure end as a heat source, and directly mixes and heats it with the feed water at the low-pressure end to generate low-pressure saturated steam 5-1 , which is passed through the low-pressure The superheater 15 forms low-pressure superheated steam 16, which is sent to the low-pressure steam turbine 17 to drive the generator 19 to generate electricity; the exhausted steam from the low-pressure steam turbine 17 is condensed into low-pressure end condensate 9 in the low-pressure condenser 18, and the condensate 9 passes through the condensate pump 10, the low-pressure Feedwater heater 11, deaerator 12, low-pressure feedwater pump 13, and secondary low-pressure feedwater heater 14 are sent to low-pressure steam generator 5, which then generates steam 5-1 to form low-pressure end steam Rankine loop loop.

The low-pressure steam generator 5 adopts a positive pressure operation mode, that is, the pressure of exhaust steam from the high-pressure steam turbine 4 is higher than atmospheric pressure.

The low-pressure feed water heater 11 and the flue gas adopt a separate heat exchange method, which is a composite phase-change heat exchanger, including an evaporator 11-1 and a condenser 11-2, and the evaporator 11-1 is arranged in the flue 20 1. The condenser 11-2 is arranged outside the flue 20, the phase change working medium is water, and the natural circulation mode is adopted. The phase-change working medium absorbs the heat of the flue gas in the evaporator 11-1 to generate saturated steam, and the saturated steam passes through the condenser 11-2 to exchange heat with the condensed water 9 at the low-pressure end, and forms a condensate after cooling, which is then sent to the evaporator 11- 1 Absorb the heat of the flue gas to generate steam, thereby forming the internal circulation process of the phase change working medium; the high-temperature flue gas generated by fuel combustion passes through the boiler body 1, the low-pressure superheater 15, the high-pressure superheater 3, the high-pressure feed water heater 8, and the second stage The low-pressure feedwater heater 14, the air preheater 23, and the evaporator 11-1 of the low-pressure feedwater heater 11 cool down and discharge them into the atmosphere; the low-pressure steam generator 5 uses the exhaust steam 4-1 of the high-pressure steam Rankine cycle as a heat source, It is directly mixed with the feed water at the low-pressure end to generate low-pressure saturated steam 5-1, which is formed by the low-pressure superheater 15 to form low-pressure superheated steam 16, which is sent to the low-pressure steam turbine 17 to drive the generator 19 to generate electricity; the exhaust steam from the low-pressure steam turbine 17 is in the low-pressure condenser 18 Condensate into condensate 9 at the low-pressure end, condensate 9 passes through the condensate pump 10, the condenser 11-2 of the low-pressure feedwater heater 11, the deaerator 12, the low-pressure feedwater pump 13, and the secondary low-pressure feedwater heater 14, and then enters the low-pressure steam Generator 5, the low-pressure steam generator 5 generates steam 5-1 again, thereby forming a steam Rankine cycle at the low-pressure end.

One or more high-pressure feedwater heaters 8, low-pressure steam evaporators 5, secondary low-pressure feedwater heaters 14, low-pressure feedwater heaters 11, high-pressure superheaters 3, and low-pressure superheaters 15 can be respectively arranged in series or in parallel. or hybrid connection.

The low-pressure end condenser 18 is set according to conventional technology, and water is used as the cooling medium.

The heat exchange elements of the aforementioned equipment mentioned in the present invention can adopt row tubes, finned tubes, serpentine tubes or spiral groove tubes, or tubes with other heat transfer enhancement measures or other types of hollow cavity heat exchange elements.

Control the wall temperature of the heat exchange surface of the evaporator 11-1 of the low-pressure feed water heater 11 to be slightly higher than the acid dew point temperature of the flue gas, or use corrosion-resistant materials to effectively reduce the low-temperature corrosion of the flue gas, which can effectively reduce the exhaust gas temperature and avoid smoke. At the same time as the gas is corroded at low temperature, the waste heat of the flue gas is efficiently recovered.

Equipment not described in the present invention and its backup systems, pipelines, instruments, valves, heat preservation, bypasses with regulating functions, safety protection devices, etc. are matched by well-known mature technologies.

Equipped with a safety and control device matching the system of the present invention, it is matched with the well-known mature control technology of the existing steam Rankine cycle power plant, Cheng's cycle power plant or gas-steam combined cycle power plant, so that the cascade steam The Rankine combined cycle power generation unit can operate economically, safely and with high thermal efficiency, achieving the purpose of saving energy and reducing consumption.

Although the present invention has been disclosed above with preferred embodiments, they are not intended to limit the present invention, and any skilled person can make various changes or modifications without departing from the spirit and scope of the present invention. Belong to the protection scope of the present invention. Therefore, the protection scope of the present invention should be defined by the claims of the present application.

Claims (9)

1. A Breton-mixed steam Rankine combined cycle power plant, the device comprises a high-pressure end steam Rankine cycle and a low-pressure end organic Rankine cycle system, characterized in that: The air (23) is sent into the combustion equipment (25) through the compressor (24), fully combusted with the incoming fuel (28), and the generated high-temperature flue gas enters the gas turbine (26), which drives the gas turbine generator (29) to generate electricity, and completes Gas turbine unit Britton cycle; The high-temperature flue gas (27) discharged from the gas turbine (26) is used as the heat source of the hybrid steam Rankine cycle system, and the high-temperature flue gas (27) cools down along the auxiliary heating surface of the waste heat boiler body (1) and the flue (20). rear discharge; The steam Rankine cycle at the high-pressure end refers to the saturated steam (2) coming out of the waste heat boiler body (1), forming high-pressure superheated steam (3-1) through the high-pressure superheater (3), and sending it into the high-pressure steam turbine (4 ) drives the generator (19) to generate electricity; the exhaust steam from the high-pressure steam turbine (4) passes through the low-pressure steam generator (5) to form condensed water (6), and the condensed water (6) is sent to the waste heat boiler body through the high-pressure feed water pump (7) (1), the waste heat boiler body (1) regenerates saturated steam, thus forming a steam Rankine cycle at the high pressure end; Described low-pressure side steam Rankine cycle refers to the saturated steam (5-1) that comes out by low-pressure steam evaporator (5), forms low-pressure superheated steam (16) through low-pressure superheater (15), sends into low-pressure steam turbine ( 17) Drive the generator (19) to generate electricity; the exhausted steam from the low-pressure steam turbine (17) is condensed in the condenser (18) into condensed water (9) at the low-pressure end, and sent to the low-pressure steam evaporator through the low-pressure feed water pump (13), It is directly mixed with the exhaust steam (4-1) of the high-pressure steam turbine (4) to generate saturated steam (5-1), thereby forming a steam Rankine cycle loop at the low-pressure end; The low-pressure steam generator (5) adopts a positive pressure operation mode, that is, the pressure of the exhaust steam (4-1) discharged from the high-pressure steam turbine (4) is higher than atmospheric pressure; The steam Rankine cycle at the high-pressure end and the steam Rankine cycle at the low-pressure end are directly combined through the low-pressure steam generator (5), and the latent heat of vaporization released when the steam of the steam Rankine cycle at the high-temperature end is condensed is recovered and used for the steam Rankine cycle at the low-temperature end. cycle power generation. 2. The device according to claim 1, characterized in that: Equipped with high-pressure feed water heater (8): The saturated steam (2) from the waste heat boiler body (1) passes through the high-pressure superheater (3) to form high-pressure superheated steam (3-1), and sends it to the high-pressure steam turbine (4) to drive the generator (19) to generate electricity; the high-pressure steam turbine (4 ) exhaust steam (4-1) passes through the low-pressure steam generator (5) to form condensed water (6), and the condensed water (6) is sent to the high-pressure feed water heater (8) and waste heat boiler body through the high-pressure feed water pump (7) (1), the waste heat boiler body (1) generates saturated steam again, thus forming a steam Rankine cycle at the high pressure end. 3. The device according to claim 1, characterized in that: A deaerator (12) is provided: The saturated steam (5-1) produced by the low-pressure steam evaporator (5) passes through the low-pressure superheater (15) to form low-pressure superheated steam (16), which is sent to the low-pressure steam turbine (17) to drive the generator (19) to generate electricity; the low-pressure steam turbine (17) exhausted steam is condensed into low-pressure end condensate (9) in condenser (18), and low-pressure end condensate (9) passes through condensate pump (10), deaerator (12), low-pressure feed water pump (13) ), sent to the low-pressure steam evaporator (5), and directly mixed with the exhaust steam (4-1) of the high-pressure steam turbine to generate saturated steam (5-1), thereby forming a steam Rankine cycle at the low-pressure end. 4. The device according to claim 3, characterized in that: Equipped with a low-pressure feed water heater (11): The saturated steam (5-1) produced by the low-pressure steam evaporator (5) passes through the low-pressure superheater (15) to form low-pressure superheated steam (16), which is sent to the low-pressure steam turbine (17) to drive the generator (19) to generate electricity; the low-pressure steam turbine The exhausted steam from (17) is condensed in the condenser (18) into condensate (9) at the low-pressure end, and the condensate (9) at the low-pressure end passes through the condensate pump (10), the low-pressure feed water heater (11), and the deaerator ( 12). The low-pressure feed water pump (13) is sent to the low-pressure steam evaporator (5), and is directly mixed with the exhaust steam (4-1) of the high-pressure steam turbine to generate saturated steam (5-1), thereby forming the rankine steam at the low-pressure end. loop loop. 5. The device according to claim 3, characterized in that: Equipped with a secondary low-pressure feed water heater (14): The saturated steam (5-1) produced by the low-pressure steam evaporator (5) passes through the low-pressure superheater (15) to form low-pressure superheated steam (16), which is sent to the low-pressure steam turbine (17) to drive the generator (19) to generate electricity; the low-pressure steam turbine (17) exhausted steam is condensed into low-pressure end condensate (9) in condenser (18), and low-pressure end condensate (9) passes through condensate pump (10), deaerator (12), low-pressure feed water pump (13) ), the secondary low-pressure feed water heater (14), which is sent to the low-pressure steam evaporator (5), and is directly mixed with the exhaust steam (4-1) of the high-pressure steam turbine to generate saturated steam (5-1), thereby forming low-pressure end steam Rankine cycle. 6. Device according to one of claims 3 to 5, characterized in that: The saturated steam (5-1) produced by the low-pressure steam evaporator (5) passes through the low-pressure superheater (15) to form low-pressure superheated steam (16), which is sent to the low-pressure steam turbine (17) to drive the generator (19) to generate electricity; the low-pressure steam turbine The exhausted steam from (17) is condensed in the condenser (18) into condensate (9) at the low-pressure end, and the condensate (9) at the low-pressure end passes through the condensate pump (10), the low-pressure feed water heater (11), and the deaerator ( 12), the low-pressure feed water pump (13), and the secondary low-pressure feed water heater (14), are sent to the low-pressure steam evaporator (5), and are directly mixed with the exhaust steam (4-1) of the high-pressure steam turbine to generate saturated steam (5- 1), thus forming a steam Rankine cycle loop at the low pressure end. 7. The device according to claim 4, characterized in that: The low-pressure feed water heater (11) adopts a partition or separate heat exchange method with flue gas. 8. The device according to claim 7, characterized in that: The low-pressure feed water heater (11) and the flue gas adopt a separate heat exchange method, including an evaporator (11-1) and a condenser (11-2); the evaporator (11-1) is arranged on the flue gas side, Through the phase-change working medium and flue gas partition heat exchange, the phase-change working medium absorbs heat to generate steam, and the steam passes through the condenser (11-2) to exchange heat with the low-pressure end steam Rankine cycle feed water partition wall, and forms condensate after cooling Then the evaporator (11-1) absorbs the heat of the flue gas to generate steam, thereby forming the internal circulation process of the phase change working substance. 9. The device according to claim 2 or 5, characterized in that: The high-pressure superheater (3), low-pressure superheater (15), high-pressure feedwater heater (8), secondary low-pressure feedwater heater (14), low-pressure feedwater heater (11), and low-pressure steam evaporator (5) One or more can be set and connected in series, parallel or hybrid.