Steam Rankine-organic Rankine combined cycle power generation device

Abstract

The utility model relates to a steam Rankine-organic Rankine combined cycle power generation device which cools positive pressure exhaust steam of a steam turbine in a steam Rankine cycle through an organic working medium in the organic Rankine cycle and recovers latent heat of vaporization of steam in the steam Rankine cycle for organic Rankine cycle power generation. The steam Rankine cycle and the organic Rankine cycle are combined together, meanwhile, an organic heat carrier flue gas waste heat recovery system for internal circulation heat utilization is adopted, the problem of low-temperature corrosion in flue gas waste heat recovery of a power station boiler is solved, and the whole combined cycle power generation device is reasonable in process setting and high in heat utilization efficiency.

Description

Technical Field

[0001] This utility model relates to a steam Rankine-organic Rankine combined cycle power generation device, and more particularly to a combined cycle generator unit that uses a positive pressure condenser, a positive pressure condenser as the ORC heat source, an organic heat carrier as the heat medium, a waste heat recovery unit, and an external air preheater reheating technology, specifically belonging to the technical field of power equipment for thermal power plants. Background Technology

[0002] Zhang Hong's article, "Organic Rankine Cycle Pure Low-Temperature Waste Heat Power Generation Technology with Low-Boiling-Point Working Fluids" (Cement, 2006, No. 8), uses n-pentane as an example to compare the characteristics of conventional steam Rankine cycles and organic Rankine cycles in recovering low and medium enthalpy heat. For low and medium enthalpy heat, the ORC technology has many advantages over the conventional steam Rankine cycle, mainly in its higher efficiency in recovering sensible heat. Because the sensible heat / latent heat ratio is unequal in the cycle, the ORC technology has a larger ratio. Therefore, the ORC technology recovers more heat than the steam cycle.

[0003] Compared to the conventional steam Rankine cycle, ORC has the following advantages:

[0004] (1) Since the boiling point of organic working fluid is lower than that of water, the evaporation pressure is higher at the same temperature. Therefore, the ORC system has higher efficiency in utilizing medium and low temperature heat sources. In practical applications, the same ORC system can be applied to heat sources of different temperatures with only minor modifications.

[0005] (2) Taking n-pentane as an example, n-pentane has a higher density and a lower specific volume than water vapor (see Table 1), which results in smaller pipe sizes in the turbine (especially the height of its last stage blades), exhaust pipes and air-cooled condensers.

[0006] Table 1. Comparison of pressure and density of water vapor and n-pentane

[0007] Temperature / °C Water vapor pressure / kPa <![CDATA[Water vapor density / (kg / m 3 )]]> n-Pentane pressure / kPa <![CDATA[n-Pentane density / (kg / m 3 )]]> 50 12 0.08 160 4.57 100 101 0.60 589 16.49 150 476 2.55 1600 47.77

[0008] (3) Unlike water vapor, n-pentane remains dry throughout the expansion process, which eliminates the possibility of moisture formation and damage to the expander impeller from high-speed small droplets. Therefore, ORC can adapt to partial load operation and large power fluctuations more effectively than steam turbines and does not require a superheater.

[0009] (4) In water-scarce areas, air-cooled condensers are preferred. The air-cooled condensers used in ORC power plants are much smaller and cheaper than those used in steam power plants.

[0010] (5) Compared with water vapor, organic working fluids have a lower sound velocity, which can achieve favorable aerodynamic matching at low blade speeds. The impeller can achieve higher efficiency at 50 Hz and does not require a gearbox.

[0011] (6) The organic working fluid has a high condensation pressure, and the entire system operates at pressure close to or slightly higher than atmospheric pressure, which greatly reduces the leakage of the organic working fluid.

[0012] (7) Organic working fluids have very low freezing points (e.g., n-pentane is below -73°C), allowing them to function normally at lower temperatures. This increases output in cold weather, and the condenser does not require additional antifreeze measures. Furthermore, most components of the ORC system are derived from mature refrigeration components, thus reducing the development difficulty of the ORC system.

[0013] Chinese patents 201320042189.1 - Steam Rankine-Organic Rankine Combined Cycle Power Generation Device, 201310029372.2 - Steam Rankine-Organic Rankine Combined Cycle Power Generation Device, 201310029366.7 - Breton-Steam Rankine-Organic Rankine Combined Cycle Cogeneration Method and Device, and 201320042188.7 - Breton-Steam Rankine-Organic Rankine Combined Cycle Cogeneration Device, etc., combine the advantages of ORC (Organic Rankine Cycle) and propose a combined cycle power generation device that uses a positive pressure condenser, external circulation makeup water, and a composite phase change heat exchanger to efficiently recover waste heat from flue gas. The positive pressure condenser used in this device has outstanding advantages. This technology effectively avoids the drawbacks of traditional negative pressure condensers, such as air leakage, large size, poor heat transfer, and the need for water jet ejectors. It also avoids the bulky tail impeller and cylinder of the steam turbine, significantly improving safety. Positive pressure condensers are smaller and have higher heat transfer efficiency, and the relative prices of steam turbines and condensers are much lower. However, the technology also has several disadvantages, including complex process setup, the use of distilled water in the makeup water circuit, failure to consider the large makeup water volume during combined heat and power (CHP), and defects in the makeup water treatment process. Furthermore, due to the use of low-temperature flue gas waste heat from organic working fluids during winter and summer temperature changes, the overall performance of the entire unit is affected by various factors, making coordinated operation and optimization difficult.

[0014] However, ORC technology also has its inherent drawbacks: because organic working fluids may be flammable or explosive, when using waste heat from flue gas to organize ORC in the boiler tail flue, it is necessary to consider the resulting explosion protection as well as environmental and work site protection. This is a problem that ORC technology must solve when recovering waste heat from flue gas containing dust and corrosive substances in power plant systems.

[0015] Steam boilers use coal, petroleum, natural gas, etc. as fuel. Because the fuel contains sulfur, sulfur oxides are produced during combustion. These sulfur oxides combine with water vapor to form sulfurous acid or sulfuric acid vapor. If the metal wall temperature of the air preheater located in the tail flue of the steam boiler is lower than the condensation point (acid dew point) of sulfuric acid vapor, liquid sulfuric acid (called acid dew) will form on its surface. Acid dew corrosion and ash blockage caused by excessively low wall temperature often occur. After one to two years of operation, the air preheater will experience acid dew corrosion, and may even perforate and become unusable. This is a global problem that plagues steam boilers.

[0016] Existing power plant boilers use corrosion-resistant low-temperature economizers, warm air blowers-low-temperature economizers, or phase change heat exchangers to recover waste heat from flue gas, achieving certain results, but also having some problems: for example, the hot water produced needs to be disposed of in a reasonable location, is suitable for cogeneration units with a large heat supply, and thermal balance is not easy to achieve.

[0017] An air preheater for recovering waste heat from flue gas, located at the tail flue of a steam boiler, requires space for its air ducts. The air and flue gas in the air preheater need to exchange heat through cross-flow and rotation to effectively avoid heat transfer deviation. The ducts travel a long distance to the boiler burner, resulting in a large air preheater volume. In contrast, an economizer using low-temperature boiler feedwater to recover waste heat from flue gas has a compact, convenient, and space-saving installation of its liquid feedwater pipes. The liquid feedwater, as the heat transfer medium, has a large heat capacity, and the heat transfer coefficient between flue gas and liquid feedwater in the economizer is much greater than that between flue gas and air in the air preheater. Under the same heat exchange conditions, the economizer is much smaller than the air preheater.

[0018] Chinese Patent 202510376090.2 - A steam boiler uses an organic heat carrier as the heat carrier for recovering waste heat from steam boiler flue gas. It utilizes the "low pressure and high temperature" characteristics of organic heat carriers and combines oil-gas heat exchangers with external air preheater regeneration technology to effectively avoid low-temperature corrosion of steam boiler flue gas while achieving safe and efficient internal circulation and recovery of waste heat from flue gas. It is suitable for partial renovation or new construction of industrial steam boilers and power plant boilers. However, it does not fully consider the overall optimization advantages of this technology when applied to combined cycle power generation systems, such as simple operation and adjustment and easy thermal balance organization.

[0019] Therefore, how to rationally recover and utilize the waste heat from power plant boiler flue gas, adopting an organic heat carrier flue gas waste heat recovery system, utilizing the "low pressure, high temperature" characteristics of organic heat carriers, using organic heat carriers as the heat absorption medium of the flue gas oil-gas heat exchanger, and using the high-temperature organic heat carrier exiting the oil-gas heat exchanger as the heat source for the external air preheater, can achieve a compact and convenient arrangement of the flue gas oil-gas heat exchanger at the tail end of the power plant boiler, and achieve a compact and simple arrangement of the external air preheater, thereby reducing the exhaust gas temperature while effectively avoiding low-temperature corrosion of the tail flue gas oil-gas heat exchanger, and solving the problems existing in the current steam Rankine-organic Rankine combined cycle technology, has become a research hotspot in this field. Utility Model Content

[0020] The purpose of this invention is to overcome the shortcomings of the aforementioned technologies and propose a new steam Rankine-organic Rankine combined cycle power generation device that can replace the traditional steam Rankine cycle. It also solves the key problem of safe operation of ORC units by recovering the latent heat of vaporization of the turbine exhaust steam in the steam Rankine cycle for low-temperature organic Rankine cycle power generation and using an organic heat carrier to achieve efficient internal circulation and utilization of low-temperature waste heat from flue gas. This effectively improves the overall thermal efficiency of the combined cycle unit, optimizes operation regulation, and enhances safety.

[0021] The objective of this utility model is achieved through the following measures:

[0022] A steam Rankine-organic Rankine combined cycle power generation unit, comprising a steam Rankine cycle, an organic Rankine cycle, and an organic heat carrier flue gas waste heat recovery system.

[0023] The steam Rankine cycle refers to the process where saturated steam 5 exiting from the furnace heating surface 2 of the boiler body 1 passes through the heat exchanger 6 to form superheated steam 7, which is then sent to the steam turbine 8 to drive the steam turbine generator 9 to generate electricity. The exhaust steam exiting the steam turbine 8 has a pressure higher than atmospheric pressure and is condensed in the positive pressure condenser 10. The condensate 11 formed enters the furnace heating surface 2 of the boiler body 1 via the boiler feed water pump 12 and the economizer 13, where it generates saturated steam 5 again, thus forming a steam Rankine cycle loop.

[0024] The aforementioned organic Rankine cycle refers to a process where liquid organic working fluid 37 is converted into gaseous organic working fluid 33 by organic working fluid circulation pump 32 and positive pressure condenser 10, and then enters gas turbine 34 to drive gas turbine generator set 35 to generate electricity. The organic working fluid discharged from gas turbine 34 is cooled by organic working fluid condenser 36 to form liquid organic working fluid 37, which then enters organic working fluid circulation pump 32, thus forming an organic Rankine cycle loop. The liquid organic working fluid 37 is a single-component organic working fluid, or a mixed solution with a single-component base low-boiling-point component and a high-boiling-point component as absorbent. The liquid organic working fluid 37 includes liquid carbon dioxide.

[0025] The high-temperature flue gas generated by the burner 3 of the boiler body 1 is cooled by the furnace heating surface 2, superheater 6, economizer 13, and oil-gas heat exchanger 19, and then forms low-temperature flue gas 31 after passing through the dust collector 29 and desulfurization facility 30, and is discharged from the chimney through the boiler induced draft fan.

[0026] Air forms hot air 17 through the blower 15 and the air preheater outside the furnace 16, and is transported to the burner 3 of the boiler body 1 as a combustion-supporting substance, and burns with the fuel 4 to form high-temperature flue gas.

[0027] The high-temperature organic heat carrier coming out of the oil-gas heat exchanger 19 enters the air preheater outside the furnace 16 through the high-temperature organic heat carrier pipeline 20 and serves as the heat source of the air preheater outside the furnace 16. The low-temperature organic heat carrier coming out of the air preheater outside the furnace 16 enters the oil-gas separator 21. The gas in the oil-gas separator 21 enters the high-level oil storage tank through the expansion pipe 24. The organic heat carrier liquid separated in the oil-gas separator 21 enters the organic heat carrier circulation pump 18 through the downcomer 22, and after boosting, enters the oil-gas heat exchanger 19. Or the high-temperature organic heat carrier coming out of the oil-gas heat exchanger 19 enters the oil-gas separator 21 through the high-temperature organic heat carrier pipeline 20, and then is transported into the air preheater outside the furnace 16 through the downcomer 22 and the organic heat carrier circulation pump 18 to heat the air transported by the blower 15. The low-temperature organic heat carrier coming out of the air preheater outside the furnace 16 then enters the oil-gas heat exchanger 19, thus forming an organic heat carrier flue gas waste heat recovery system.

[0028] A filter 23 is provided: The organic heat carrier liquid coming out of the oil-gas separator 21 enters the organic heat carrier circulation pump 18 through the filter 23 to remove impurities such as solid particles and carbon deposition in the organic heat carrier.

[0029] The high-level oil storage tank 25 is connected to the low-level oil storage tank 27 through an overflow pipeline 26 and an oil discharge pipeline.

[0030] A makeup water system supporting the steam Rankine cycle is provided: The boiler makeup water 40 forms primary demineralized water 42 through the water treatment unit 41. After entering the deaerator 43 to remove the gas components in the primary demineralized water 42, it is then supplemented into the water circulation system of the steam Rankine cycle through the makeup water booster pump 44.

[0031] The makeup water system supporting the steam Rankine cycle is used to supplement the gas-water blowdown loss, steam leakage loss, heat supply steam water consumption, etc. in the steam Rankine cycle.

[0032] After being deoxidized, the primary demineralized water 42 meets the usage requirements of the furnace heating surface 2 of the boiler body 1.

[0033] The water treatment unit 41 includes thermal demineralization, chemical demineralization (cation and anion exchange method), or desalination by membrane separation technology, etc.

[0034] The deaerator 43 includes thermal deaeration, chemical deaeration, desorption deaeration, electrochemical deaeration, or deaeration resin deaeration, etc. Preferably, an ambient temperature deaerator is used.

[0035] The furnace heating surface 2 adopts water treatment measures such as adding chemicals inside the boiler and continuous or periodic sewage discharge.

[0036] The fuel 4 of the burner 3 of the boiler body 1 is pulverized coal, biomass fuel, fuel oil or combustible gas.

[0037] The organic heat carrier in the external air preheater 16 exchanges heat with the air indirectly. The heat exchange tubes are plain tubes, finned tubes or spiral groove tubes, etc. Preferably, enhanced heat transfer measures are adopted.

[0038] The organic heat carrier in the oil-gas heat exchanger 19 exchanges heat with the flue gas indirectly, and the heat exchange tubes are made of plain tubes, finned tubes or spiral grooved tubes, etc.

[0039] By controlling the temperature of the organic heat carrier in the oil-gas heat exchanger 19 (for example, above 85°C, with the appropriate temperature determined based on the sulfur content of the fuel), the average temperature of the organic heat carrier entering the oil-gas heat exchanger 19 and the exhaust temperature, i.e., the metal wall temperature, is higher than the acid dew point temperature of the flue gas. This effectively avoids low-temperature corrosion of the oil-gas heat exchanger 19. Under the premise of avoiding condensation, the waste heat of the flue gas is utilized to the maximum extent, enabling the flue gas waste heat recovery device to operate economically and with high thermal efficiency, thereby achieving the goal of energy saving and consumption reduction.

[0040] The high-level oil storage tank 25 is equipped with an exhaust valve, pressure gauge or safety valve, etc.

[0041] The high-level oil storage tank 25 is protected by a nitrogen-sealed system.

[0042] The steam Rankine-organic Rankine combined cycle power generation system employs a denitrification facility to remove nitrogen oxides from the flue gas generated during fuel combustion.

[0043] The organic working fluid condenser 36 is set up according to conventional technology, using water or air as the cooling medium and a closed or open cooling water circulation mode.

[0044] The heat exchange elements of the aforementioned equipment mentioned in this utility model can be tubes, finned tubes, serpentine tubes or spiral grooved tubes, or tubes or other types of hollow cavity heat exchange elements that adopt other heat transfer enhancement measures.

[0045] Equipment and its backup systems, pipelines, instruments, valves, insulation, and bypass facilities with regulating functions not described in this utility model shall be equipped with known and mature technologies.

[0046] Compared with the prior art, the present invention has the following advantages:

[0047] 1. Simple process setup and significant energy-saving effect: The steam Rankine-organic Rankine combined cycle power generation device designed in this utility model is different from the traditional steam Rankine cycle based on the Rankine cycle principle, the organic Rankine cycle system that utilizes flue gas and organic working fluid through a wall-type heat exchange, and the steam Rankine-organic Rankine combined cycle power generation technology. It adopts a positive pressure operation mode for the condenser, using the turbine exhaust steam as the heat source of the organic Rankine cycle. Taking advantage of the higher efficiency of the organic Rankine cycle system in utilizing medium and low temperature heat sources, the condenser in the steam Rankine cycle and the evaporator in the organic Rankine cycle are cleverly combined together, and the latent heat of vaporization of steam is effectively utilized. The organic Rankine cycle process is simple, safe, and efficient. Because the back pressure adopts a positive pressure mode, the exhaust steam at the turbine outlet can ensure a certain degree of superheat. The initial steam pressure of the newly built unit can adopt supercritical or ultra-supercritical pressure, further improving the thermal efficiency of the power generation cycle.

[0048] 2. Lower equipment investment and significantly reduced operating costs:

[0049] (1) It eliminates the unavoidable air and water leakage phenomena of traditional condenser negative pressure operation technology, and does not require the installation of deaerators, ejectors and low-pressure heaters in the steam Rankine loop, thus avoiding the steam and water loss caused by the operation of traditional deaerators and ejectors; the external circulation water supply system has high deoxygenation efficiency and good effect, and the process flow selection is flexible.

[0050] (2) Because the specific volume of the exhaust steam of the steam turbine is much smaller than that of the traditional condenser, the volume of the condenser can be greatly reduced. Because the back pressure of the steam turbine in the steam Rankine cycle is positive pressure, the exhaust steam at the turbine outlet can ensure a certain degree of superheat. This overcomes the design, operation and safety problems caused by wet steam in the last stage blades of the steam turbine in the traditional Rankine cycle unit. After the removal of the tail blades and impellers at the low pressure end of the steam turbine, the entire steam turbine generator set is compact and safe. The vibration of the steam turbine generator set is significantly improved compared to before. This fundamentally eliminates the design, manufacturing and operation problems caused by wet steam in the last stage blades of the steam turbine in the traditional steam Rankine cycle. The operating conditions of the steam turbine are optimized. Therefore, the relative price of the steam turbine and condenser equipment is greatly reduced.

[0051] 3. Operational safety is significantly improved:

[0052] Compared to traditional organic Rankine combined cycle power generation technology, the organic Rankine cycle unit directly uses the positive pressure exhaust steam from the turbine in the steam Rankine cycle as its heat source, which is then piped to a safe location with reliable protection measures. The organic Rankine cycle process is simple to set up and can effectively avoid many problems caused by leakage of organic working fluid and direct interaction with the steam Rankine cycle system. The safety of the organic Rankine cycle system is reliably guaranteed, further eliminating safety hazards for its industrial application.

[0053] 4. The organic heat carrier deep recovery and internal circulation heat utilization system for flue gas waste heat fully utilizes the "low pressure and high temperature" characteristics of organic heat carriers. The waste heat recovery system with organic heat carriers as the heat medium has been maturely applied in industry. The equipment layout is simple, the operation and adjustment are convenient, and it is less affected by external factors. The exhaust temperature can be reduced to about 110℃ (depending on the acid dew point of the flue gas). By bypassing the organic heat carrier flue gas waste heat recovery system, the low-temperature corrosion at the end of the oil-gas heat exchanger can be avoided, which is conducive to the safe operation of dust collectors (such as bag dust collectors). The water-saving effect of desulfurization facilities is obvious.

[0054] 5. The water makeup system is designed to meet the cogeneration needs of the combined cycle power generation system. The deaerator has a high efficiency and reliable deoxygenation effect, avoiding problems such as oxygen leakage due to negative pressure in the condenser and poor deoxygenation effect caused by condensate dilution of oxygen concentration in the traditional process. The water makeup system is designed to be more reasonable and effective.

[0055] 6. The system's linkage and circulation adjustment is simpler, safer, and more efficient than existing technologies, and facilitates thermal equilibrium organization.

[0056] 7. The installation and layout of system equipment have been significantly optimized. Attached Figure Description

[0057] Figure 1 This is a schematic diagram of the structure of the steam Rankine-organic Rankine combined cycle power generation device of this utility model.

[0058] Figure 1 In this diagram, 1-boiler body, 2-furnace heating surface, 3-burner, 4-fuel, 5-saturated steam, 6-superheater, 7-superheated steam, 8-steam turbine, 9-steam turbine generator, 10-positive pressure condenser, 11-condensate, 12-boiler feedwater pump, 13-economizer, 14-boiler feedwater, 15-blower, 16-external air preheater, 17-hot air, 18-organic heat carrier circulating pump, 19-oil-gas heat exchanger, 20-high temperature organic heat carrier pipeline, 21-oil-gas separator, 22-downcomer, 23-filter, 24-expansion pipe. 25-High-level oil storage tank, 26-Overflow pipeline, 27-Low-level oil storage tank, 28-Flue duct, 29-Dust collector, 30-Desulfurization facility, 31-Low-temperature flue gas, 32-Organic working fluid circulation pump, 33-Gaseous organic working fluid, 34-Gas turbine, 35-Gas turbine generator, 36-Organic working fluid condenser, 37-Liquid organic working fluid, 38-Cooling water inlet, 39-Cooling water outlet, 40-Boiler feedwater, 41-Water treatment unit, 42-Primary demineralized water, 43-Deaerator, 44-Make-up water booster pump, 45-Make-up water pipeline, 46-Heating steam. Detailed Implementation

[0059] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0060] Example 1:

[0061] like Figure 1 As shown, a steam Rankine-organic Rankine combined cycle power generation unit is disclosed. The system includes a steam Rankine cycle, an organic Rankine cycle, and an organic heat carrier flue gas waste heat recovery system.

[0062] The steam Rankine cycle refers to the process where saturated steam 5 exiting the furnace heating surface 2 of the boiler body 1 passes through the heat exchanger 6 to form superheated steam 7, which is then sent to the steam turbine 8 to drive the steam turbine generator 9 to generate electricity. The exhaust steam exiting the steam turbine 8 has a pressure higher than atmospheric pressure and is condensed in the positive pressure condenser 10. The resulting condensate 11 enters the furnace heating surface 2 of the boiler body 1 via the boiler feed water pump 12 and the economizer 13, where it generates saturated steam 5 again. The steam extracted from the steam turbine is used as heating steam 46 and supplied externally through the heating pipeline to achieve combined heat and power, thus forming a steam Rankine cycle loop.

[0063] The organic Rankine cycle refers to the process where liquid organic working fluid 37 is converted into gaseous organic working fluid 33 by organic working fluid circulation pump 32 and positive pressure condenser 10, and then enters gas turbine 34 to drive gas turbine generator set 35 to generate electricity. The organic working fluid discharged from gas turbine 34 is cooled by organic working fluid condenser 36 to form liquid organic working fluid 37, which then enters organic working fluid circulation pump 32, thus forming an organic Rankine cycle loop. Organic working fluid condenser 36 is cooled by cooling water, using a conventional open or closed circulation system of circulating cooling water. Cooling water inlet 38 with a lower temperature enters organic working fluid condenser 36 to liquefy the exhaust gas of gas turbine 34, and the resulting cooling water outlet 39 with a higher temperature is discharged.

[0064] The high-temperature flue gas generated by the burner 3 of the boiler body 1 is cooled by the furnace heating surface 2, superheater 6, economizer 13, and oil-gas heat exchanger 19, and then forms low-temperature flue gas 31 by the dust collector 29 and desulfurization facility 30, which is then discharged from the chimney by the boiler induced draft fan.

[0065] Air is blown by blower 15 and external air preheater 16 to form hot air 17, which is then delivered to burner 3 of boiler body 1 as a combustion aid, where it burns with fuel 4 to form high-temperature flue gas.

[0066] The high-temperature organic heat carrier coming out of the oil-gas heat exchanger 19 enters the air preheater 16 outside the furnace through the high-temperature organic heat carrier pipeline 20 and serves as the heat source of the air preheater 16 outside the furnace. The low-temperature organic heat carrier coming out of the air preheater 16 outside the furnace enters the oil-gas separator 21. The gas in the oil-gas separator 21 enters the high-level oil storage tank through the expansion pipe 24. The organic heat carrier liquid separated in the oil-gas separator 21 enters the oil-gas heat exchanger 19 after being boosted by the organic heat carrier circulation pump 18. Or the high-temperature organic heat carrier coming out of the oil-gas heat exchanger 19 enters the oil-gas separator 21 through the high-temperature organic heat carrier pipeline 20, and then is transported by the organic heat carrier circulation pump 18 into the air preheater 16 outside the furnace to heat the air sent by the blower 15. The low-temperature organic heat carrier coming out of the air preheater 16 outside the furnace then enters the oil-gas heat exchanger 19, thus forming an organic heat carrier flue gas waste heat recovery system.

[0067] A filter 23 is provided: The organic heat carrier liquid coming out of the oil-gas separator 21 enters the organic heat carrier circulation pump 18 through the filter 23 to remove impurities such as solid particles and carbon deposition in the organic heat carrier.

[0068] The high-level oil storage tank 25 is connected to the low-level oil storage tank 27 through an overflow pipeline 26 and an oil discharge pipeline.

[0069] A make-up water system supporting the steam Rankine cycle is provided: The boiler make-up water 40 forms primary demineralized water 42 through the water treatment unit 41. After entering the deaerator 43 to remove the gas components in the primary demineralized water 42, it is then supplemented into the outlet pipeline of the boiler feed pump 12 through the make-up water booster pump 44 and the make-up water pipeline 45, or is supplemented into the inlet pipeline of the boiler feed pump 12 through the make-up water booster pump 44.

[0070] The make-up water system supporting the steam Rankine cycle is used to supplement the gas-water blowdown loss, steam leakage loss, heat supply steam water consumption, etc. in the steam Rankine cycle.

[0071] After being deoxidized, the primary demineralized water 42 meets the usage requirements of the furnace heating surface 2 of the boiler body 1.

[0072] The water treatment unit 41 includes thermal demineralization, chemical demineralization (cation and anion exchange method), or desalination by membrane separation technology, etc.

[0073] The deaerator 43 includes thermal deaeration, chemical deaeration, desorption deaeration, electrochemistry deaeration, or deaeration resin deaeration, etc. Preferably, a normal temperature deaerator is adopted.

[0074] The furnace heating surface 2 adopts water treatment measures such as adding medicine in the boiler, continuous or periodic blowdown, etc.

[0075] The fuel 4 of the burner 3 of the boiler body 1 adopts pulverized coal, biomass fuel, fuel oil, combustible gas, etc.

[0076] The economizer 13 and the oil-gas heat exchanger 19 are arranged in the flue 28.

[0077] The superheater 6 is arranged in the flue 28 or partially arranged in the boiler furnace.

[0078] The organic heat carrier in the external air preheater 16 exchanges heat with the air indirectly. The heat exchange tubes are plain tubes, finned tubes or spiral groove tubes, etc. Preferably, enhanced heat transfer measures are adopted.

[0079] The organic heat carrier in the oil-gas heat exchanger 19 exchanges heat with the flue gas indirectly, and the heat exchange tubes are made of plain tubes, finned tubes or spiral grooved tubes, etc.

[0080] By controlling the temperature of the organic heat carrier in the oil-gas heat exchanger 19 (for example, above 85°C, with the appropriate temperature determined based on the sulfur content of the fuel), the average temperature of the organic heat carrier entering the oil-gas heat exchanger 19 and the exhaust temperature, i.e., the metal wall temperature, is higher than the acid dew point temperature of the flue gas. This effectively avoids low-temperature corrosion of the oil-gas heat exchanger 19. Under the premise of avoiding condensation, the waste heat of the flue gas is utilized to the maximum extent, enabling the flue gas waste heat recovery device to operate economically and with high thermal efficiency, thereby achieving the goal of energy saving and consumption reduction.

[0081] The high-level oil storage tank 25 is equipped with an exhaust valve, a pressure gauge, a safety valve, etc.

[0082] The high-level oil storage tank 25 is protected by a nitrogen-sealed system.

[0083] The steam Rankine-organic Rankine combined cycle power generation system employs a denitrification facility to remove nitrogen oxides from the flue gas generated during fuel combustion.

[0084] The organic working fluid condenser 36 is set up according to conventional technology, using water or air as the cooling medium and a closed or open cooling water circulation mode.

[0085] The heat exchange elements of the aforementioned equipment mentioned in this utility model can be tubes, finned tubes, serpentine tubes or spiral grooved tubes, or tubes or other types of hollow cavity heat exchange elements that adopt other heat transfer enhancement measures.

[0086] Equipment and its backup systems, pipelines, instruments, valves, insulation, and bypass facilities with regulating functions not described in this utility model shall be equipped with known and mature technologies.

[0087] Although the present invention has been disclosed above with reference to preferred embodiments, these are not intended to limit the present invention. Any person skilled in the art can make various changes or modifications without departing from the spirit and scope of the present invention, and these changes and modifications also fall within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the claims of this application.

Claims

1. A steam Rankine-organic Rankine combined cycle power generation device, characterized in that, The steam Rankine-organic Rankine combined cycle power generation system includes a steam Rankine cycle, an organic Rankine cycle, and an organic heat carrier flue gas waste heat recovery system. The steam Rankine cycle refers to the process where saturated steam (5) from the furnace heating surface (2) of the boiler body (1) passes through the heat exchanger (6) to form superheated steam (7), which is then sent to the steam turbine (8) to drive the steam turbine generator (9) to generate electricity. The exhaust steam from the steam turbine (8) has a pressure higher than atmospheric pressure and is condensed in the positive pressure condenser (10). The condensate (11) formed is then pumped through the boiler feed water pump (12) and the economizer (13) into the furnace heating surface (2) of the boiler body (1) to generate saturated steam (5) again, thus forming a steam Rankine cycle loop. The organic Rankine cycle refers to the process where liquid organic working fluid (37) is transformed into gaseous organic working fluid (33) through organic working fluid circulation pump (32) and positive pressure condenser (10), and then enters gas turbine (34) to drive gas turbine generator set (35) to generate electricity. The organic working fluid discharged from gas turbine (34) is cooled by organic working fluid condenser (36) to form liquid organic working fluid (37), and then enters organic working fluid circulation pump (32) to form organic Rankine cycle loop. The high-temperature flue gas generated by the burner (3) of the boiler body (1) is cooled by the furnace heating surface (2), superheater (6), economizer (13), and oil-gas heat exchanger (19), and then forms low-temperature flue gas (31) through the dust collector (29) and desulfurization facility (30), and is discharged from the chimney by the boiler induced draft fan. Air is blown by a blower (15) and an external air preheater (16) to form hot air (17), which is then delivered to the burner (3) of the boiler body (1) as a combustion aid to burn fuel (4) and form high-temperature flue gas. The high-temperature organic heat carrier from the oil-gas heat exchanger (19) enters the external air preheater (16) via the high-temperature organic heat carrier pipeline (20). The low-temperature organic heat carrier from the external air preheater (16) enters the oil-gas separator (21). The gas in the oil-gas separator (21) enters the high-level oil storage tank (25) via the expansion pipe (24). The organic heat carrier liquid separated in the oil-gas separator (21) enters the organic heat carrier circulation pump (18) via the downcomer (22), and after being pressurized, it enters the... The oil-gas heat exchanger (19), or the high-temperature organic heat carrier from the oil-gas heat exchanger (19), enters the oil-gas separator (21) through the high-temperature organic heat carrier pipeline (20), and then is transported to the external air preheater (16) through the downcomer (22) and the organic heat carrier circulation pump (18) to heat the air delivered by the blower (15). The low-temperature organic heat carrier from the external air preheater (16) then enters the oil-gas heat exchanger (19), thus forming an organic heat carrier flue gas waste heat recovery system.

2. The steam Rankine-organic Rankine combined cycle power generation unit according to claim 1, characterized in that: The liquid organic working medium (37) is a single-component organic working medium, or a mixed solution with a single-component base, a low-boiling-point component, and a high-boiling-point component as the absorbent.

3. The steam Rankine-organic Rankine combined cycle power generation unit according to claim 2, characterized in that: The liquid organic working medium (37) includes liquid carbon dioxide.

4. The steam Rankine-organic Rankine combined cycle power generation unit according to claim 1, characterized in that: A makeup water system is provided: the boiler makeup water (40) of the makeup water system is processed by the water treatment unit (41) to form primary demineralized water (42), which enters the deaerator (43) and is then fed into the steam Rankine cycle water circulation system by the makeup water booster pump (44).

5. The steam Rankine-organic Rankine combined cycle power generation unit according to claim 4, characterized in that: The water treatment unit (41) includes thermal desalination, chemical desalination or membrane separation technology desalination.

6. The steam Rankine-organic Rankine combined cycle power generation unit according to claim 4, characterized in that: The deaerator (43) includes thermal deaeration, chemical deaeration, desorption deaeration, electrochemical deaeration, or deaeration resin deaeration.

7. The steam Rankine-organic Rankine combined cycle power generation unit according to claim 1, characterized in that: A filter (23) is provided: the organic heat carrier liquid coming out of the oil-gas separator (21) enters the organic heat carrier circulation pump (18) through the filter (23).

8. The steam Rankine-organic Rankine combined cycle power generation unit according to claim 1, characterized in that: The fuel (4) of the burner (3) is pulverized coal, biomass fuel, fuel oil or combustible gas.

9. The steam Rankine-organic Rankine combined cycle power generation unit according to claim 1, characterized in that: The high-level oil storage tank (25) is protected by a nitrogen-sealed system.

10. The steam Rankine-organic Rankine combined cycle power generation unit according to claim 1, characterized in that: The high-level oil storage tank (25) is equipped with an exhaust valve, a pressure gauge and a safety valve.

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