Water vapor-organic working medium combined cycle power generation system

Abstract

The invention relates to a water vapor-organic working medium combined cycle power generation system which comprises a water vapor Rankine cycle and an organic working medium Rankine cycle, saturated steam generated by a boiler forms superheated steam through a superheater and drags a steam turbine generator to generate power, steam exhausted by a steam turbine is condensed in a condenser, and formed condensed water returns to the boiler through a water feeding pump and an economizer. A liquid organic working medium passes through an organic working medium booster pump, an organic working medium heater and a condenser to form organic working medium superheated steam, an organic working medium gas turbine generator set is dragged to generate electricity, and exhaust gas of an organic working medium gas turbine is cooled through the condenser to form the liquid organic working medium. And high-temperature flue gas generated in the fuel combustion or industrial production process is discharged after being cooled by the boiler body, the superheater, the economizer and the organic working medium heater, or is discharged from a chimney through purification equipment and an induced draft fan.

Description

Technical Field

[0001] This invention relates to a steam-organic working fluid combined cycle power generation system, and more particularly to a steam-organic working fluid combined cycle power generation unit that uses a steam Rankine cycle with a positive pressure condenser, the positive pressure condenser serving as the heat source for the superheater in the ORC, and the evaporator in the ORC serving as the boiler flue gas waste heat recovery unit, specifically belonging to the technical field of power plant power equipment. Background Technology

[0002] Chinese patents such as 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, 202510636346.9 - A Steam Rankine-Organic Rankine Combined Cycle Power Generation Device, and 202510636349.2 - A Steam Rankine-Organic Rankine Combined Cycle Power Generation Device Combining the advantages of ORC (Organic Cycle) combined cycle power generation systems, Rankine and other research institutions have proposed a combined cycle power generation process using a positive pressure condenser and external circulation water makeup. This approach overcomes the disadvantages of negative pressure condensers, such as low heat density, vacuum disruption due to gas evolution, large size, poor heat transfer, and the need for water jet ejectors. It eliminates the bulky low-pressure cylinder and impeller at the turbine's tail end, replacing them with a more compact and smaller ORC turbine. The latent heat of vaporization from the turbine exhaust is recovered for ORC power generation, effectively improving the combined cycle power generation efficiency. However, this approach also has certain drawbacks: the composite phase change heat exchanger, hot water circulation system, and thermal oil circulation system used for waste heat recovery from the boiler tail flue gas are relatively complex and inconvenient to install; and a significant temperature difference still exists between the combined positive pressure condenser and the ORC evaporator, resulting in substantial heat loss.

[0003] For the utilization of thermal energy in the medium and low temperature range, ORC has many advantages over the steam Rankine cycle:

[0004] First, the sensible heat / latent heat ratio is not equal in the cycle, and the ratio is greater in ORC technology. That is, in a steam Rankine cycle boiler, water absorbs a larger proportion of heat in the evaporation section and a smaller proportion in the preheating section (economizer); while in an ORC boiler, the low-boiling-point organic working fluid absorbs a larger proportion of heat in the preheating section. Therefore, the ORC system can reduce the final exhaust temperature of the flue gas and recover more heat. In the medium and low temperature range (80-250℃), the output power of the ORC turbine can reach more than twice that of the steam Rankine cycle.

[0005] Secondly, in a steam Rankine cycle, the cold end (condenser) is under vacuum (absolute pressure is typically 0.03–0.05 bar). The specific volume of steam in the condenser is much larger than that of the organic working fluid. To remove non-condensable gases, a water jet ejector or similar device is required to maintain the condenser vacuum. The low-pressure cylinder of the turbine requires a larger flow area, which increases the corresponding equipment cost. In contrast, the ORC turbine and condenser operate under positive pressure. The specific volume of the organic working fluid at the cold end is smaller, the turbine flow area is smaller, and air does not leak in. Therefore, a vacuum maintenance system is not required, and steel consumption is significantly reduced.

[0006] Third, because organic working fluids have lower boiling points than water, their evaporation pressure is higher at the same temperature, resulting in higher efficiency for heat recovery from medium- and low-temperature heat sources using the ORC system. In practical applications, the same ORC system can be applied to heat sources of different temperatures with only minor modifications.

[0007] Fourth, taking n-pentane as an example, its density is greater than that of water vapor and its specific volume is smaller, so the size of the gas turbine (especially the height of its last stage blades), exhaust pipes and condensers is smaller;

[0008] Fifth, unlike steam, the organic working fluid remains dry throughout the expansion process, eliminating the possibility of moisture formation and damage to the expander impeller from high-speed droplets. Therefore, the ORC is more adaptable to variable operating conditions and large power fluctuations compared to the steam Rankine cycle.

[0009] Sixth, in water-scarce regions, the air-cooled condensers used in ORC power plants are much smaller and cheaper than those used in steam Rankine cycle units; due to the low velocity of the organic working fluid, favorable aerodynamic matching can be obtained at low blade speeds, allowing the turbine to achieve high efficiency at 50Hz without the need for a gearbox; the high condensation pressure of the organic working fluid and the positive pressure operation of the entire system greatly reduce the leakage of the organic working fluid; the very low freezing point of the organic working fluid (e.g., n-pentane below -73℃) allows it to operate normally at low temperatures and increase output in cold weather, eliminating the need for additional antifreeze facilities on the condenser.

[0010] Air preheaters are one of the core devices for improving the economic efficiency of power plant boilers. By recovering waste heat from flue gas to preheat combustion air, they achieve energy saving, consumption reduction, enhanced combustion, and improved boiler thermal efficiency. In modern large-scale power plants, air preheaters have become an indispensable standard configuration. The inlet air temperature of traditional power plant boiler air preheaters is typically 20℃~50℃ (ambient temperature or after heating by a warm air blower), and the inlet flue gas temperature is generally 300℃~400℃. The outlet air temperature of the air preheater varies depending on the boiler type, capacity, fuel characteristics, and design parameters. For example, the primary air outlet temperature of a general coal-fired boiler is generally 245℃~300℃, and the secondary air outlet temperature is generally 270℃~320℃. This increases boiler efficiency by approximately 4% (corresponding to a 110℃ temperature rise) to 11% (corresponding to a 280℃ temperature rise), and the theoretical combustion temperature increases by approximately 30℃~40℃ (corresponding to a 110℃ temperature rise).

[0011] Traditional air preheaters located in the tail flue of power plants require a large space for the rotating air ducts leading to and from the air preheater. The air and flue gas in the air preheater need to exchange heat in a cross-flow and rotating manner to effectively avoid heat transfer deviation. The ducts are long and the air preheater is large. In contrast, the low-temperature economizer and its inlet and outlet water pipelines for recovering waste heat from flue gas in the existing technology are compact, convenient to install, and occupy less space. The heat transfer coefficient between flue gas and water in the flue is much larger than that between flue gas and air in the air preheater. For the same amount of waste heat recovery, the economizer is much smaller than the air preheater.

[0012] There is an easily overlooked problem with air preheaters in existing power plants: when air preheaters experience air short circuits due to wear or low-temperature corrosion, it inevitably leads to increased power consumption of blowers and induced draft fans, and also affects the effectiveness of subsequent processes such as dust removal, desulfurization, and denitrification. Over time, the resulting economic losses are not small.

[0013] Compared to the furnace fuel combustion temperature, which is generally above 1400℃, the increase in combustion air temperature does not significantly raise the theoretical combustion temperature of the fuel, nor does it have a major impact on the enhanced combustion of the fuel. For example, most oil and gas boilers currently in use do not use air preheaters, yet they can still ensure complete combustion of the fuel, which serves as an example. On the other hand, using an air preheater to increase the combustion air temperature will inevitably lead to an increase in the amount of thermal NO2 generated in the flue gas.

[0014] During the operation of power plant boilers, scale and oxygen corrosion inevitably accumulate in the boiler drum or steam-water separator, and in the water-cooled wall tubes of the furnace. These two phenomena often reinforce each other, forming a vicious cycle of "scale formation - corrosion - more severe scale formation." Only a three-pronged strategy of "strict deoxygenation + scale prevention + water quality regulation" can fundamentally prevent tube rupture accidents. Furthermore, tube rupture accidents in the furnace water-cooled wall tubes of power plant boilers are classified as catastrophic according to the hazard and severity classification.

[0015] Scale formation in power plant boilers is a complex physicochemical process, with the following main mechanisms: Boiler feedwater contains hardness ions such as calcium and magnesium, as well as dissolved oxygen, which are difficult to completely remove with water treatment equipment. During boiler heating, these ions precipitate due to decreased solubility, chemical reactions, and concentration, forming insoluble solid deposits such as carbonates, sulfates, or silicates. These deposits adhere to the walls of the heated surfaces and gradually accumulate as scale. Even with deoxygenation by a deaerator, a small amount of dissolved oxygen remains and is introduced into the boiler's water circulation system, leading to corrosion of the boiler's metal heated surfaces and the formation of oxides. Poor water quality, malfunctioning water treatment equipment, inadequate management, improper selection of chemicals, and oxides generated from corrosion of the boiler's metal heated surfaces all contribute to exacerbating scaling and under-scale corrosion, creating a vicious cycle that affects the safe and economical operation of the power plant boiler and can even lead to major safety accidents.

[0016] Therefore, how to efficiently recover waste heat from flue gas in power plant boilers, eliminate the defects of air preheaters in existing power plant boilers, effectively reduce the unit's footprint and space, make installation more convenient, effectively reduce boiler exhaust temperature while avoiding low-temperature corrosion of flue heat exchangers, and even eliminate the cumulative effects of scale and oxygen corrosion on the furnace heat exchange surfaces of power plant boilers, so as to achieve high-efficiency, safe and economical operation of combined cycle power generation systems, is worthy of in-depth research by practitioners in the power industry. Summary of the Invention

[0017] The purpose of this invention is to address the problems existing in the above-mentioned technologies by proposing a new steam-organic working fluid combined cycle power generation system. This system recovers the latent heat of vaporization of steam in the steam Rankine cycle for power generation in the low-temperature organic Rankine cycle, while simultaneously achieving efficient recovery and utilization of low-temperature waste heat from boiler flue gas, thereby improving the overall operating thermal efficiency and safety of the combined cycle unit.

[0018] The objective of this invention is achieved through the following measures:

[0019] A steam-organic working fluid combined cycle power generation system, comprising a steam Rankine cycle and an organic working fluid Rankine cycle.

[0020] The steam Rankine cycle refers to a process where saturated steam 5 generated by boiler body 4 passes through heat exchanger 6 to form superheated steam 13, which is then sent to turbine 14 to drive turbine generator 18 to generate electricity. The exhaust steam from turbine 14 has a pressure higher than atmospheric pressure and condenses in positive pressure condenser 15. The resulting condensate 16 is pumped back to boiler body 4 via feedwater pump 17 and economizer 7. Saturated steam 5 is then generated again on the furnace heating surface of boiler body 4, thus forming a steam Rankine cycle loop.

[0021] The aforementioned Rankine cycle of the organic working fluid refers to the process where liquid organic working fluid 19 is fed through an organic working fluid booster pump 20, an organic working fluid heater 8, and a positive pressure condenser 15 to form superheated organic working fluid steam 21, which then enters an organic working fluid turbine 22 to drive an organic working fluid generator 24 to generate electricity. The organic working fluid discharged from the organic working fluid turbine 22 is cooled by a condenser 23 to form liquid organic working fluid 19, which then enters the organic working fluid booster pump 20, thus forming an organic working fluid Rankine cycle loop.

[0022] Fuel 3 and air supplied by blower 1 are burned in burner 2. The high-temperature flue gas generated by burner 2, or the high-temperature flue gas generated by industrial production process, is cooled by the furnace heating surface of boiler body 4, superheater 6, economizer 7, and organic working fluid heater 8, and the resulting low-temperature flue gas 10 is discharged or transported to purification equipment 9 for dust removal, desulfurization or denitrification, and then discharged from the chimney by induced draft fan.

[0023] A steam-organic working fluid combined cycle power generation system, comprising a steam Rankine cycle and an organic working fluid Rankine cycle.

[0024] The steam Rankine cycle refers to a process where saturated steam 5 generated by the boiler body 4 enters the phase changer 33, and the resulting condensate 34 returns to the boiler body 4 directly or via the circulating water pump 35. The steam generated in the phase changer 33 passes through the superheater 6 to form superheated steam 13, which is then fed into the turbine 14 to drive the turbine generator 18 to generate electricity. The exhaust steam from the turbine 14 has a pressure higher than atmospheric pressure and condenses in the positive pressure condenser 15. The resulting condensate 16 returns to the phase changer 33 via the feedwater pump 17 and the economizer 7. The steam generated by the saturated steam 5 then enters the superheater 6, where the furnace heating surfaces of the boiler body 4 generate saturated steam 5 again, thus forming a steam Rankine cycle loop.

[0025] The aforementioned Rankine cycle of the organic working fluid refers to the process where liquid organic working fluid 19 is fed through an organic working fluid booster pump 20, an organic working fluid heater 8, and a positive pressure condenser 15 to form superheated organic working fluid steam 21, which then enters an organic working fluid turbine 22 to drive an organic working fluid generator 24 to generate electricity. The organic working fluid discharged from the organic working fluid turbine 22 is cooled by a condenser 23 to form liquid organic working fluid 19, which then enters the organic working fluid booster pump 20, thus forming an organic working fluid Rankine cycle loop.

[0026] Fuel 3 and air supplied by blower 1 are burned in burner 2. The high-temperature flue gas generated by burner 2, or the high-temperature flue gas generated by industrial production process, is cooled by the furnace heating surface of boiler body 4, superheater 6, economizer 7, and organic working fluid heater 8, and the resulting low-temperature flue gas 10 is discharged or transported to purification equipment 9 for dust removal, desulfurization or denitrification, and then discharged from the chimney by induced draft fan.

[0027] The steam turbine generator 18 can be combined with the organic working fluid generator 24 into one generator.

[0028] The steam turbine 14 and the organic working fluid turbine 22 can operate coaxially.

[0029] The liquid organic working fluid 19 is a single-component organic working fluid or a mixed working fluid composed of a low-boiling-point organic working fluid and a high-boiling-point organic working fluid, forming an organic Rankine cycle based on the low-boiling-point component. For example, the mixed working fluid of the medium-low temperature organic Rankine cycle in Chinese Patent 201811543685.9.

[0030] The organic working fluid in the organic Rankine cycle includes carbon dioxide, and carbon dioxide is regarded as a special organic working fluid in the present invention.

[0031] When the organic Rankine cycle operates with parameters below subcritical, the organic working fluid heater 8 is an evaporative heat exchange heater. When the organic Rankine cycle operates with supercritical parameters, the organic working fluid heater 8 is a supercritical fluid heater.

[0032] When the organic working fluid is carbon dioxide and operates with supercritical parameters, the condenser 23 is a gaseous carbon dioxide cooler, the organic working fluid booster pump 20 is replaced by a carbon dioxide gas compressor, the organic working fluid evaporator 8 is equivalent to a primary heater, and the positive pressure condenser 15 is a subsequent heater. What comes out of the condenser 23 is gaseous carbon dioxide, rather than in a liquid state.

[0033] A make-up water system supporting the steam Rankine cycle is provided: the raw water 27 forms purified water 29 through the water treatment equipment 28, and then is sent to the deaerator 30 to remove the gas components in the purified water 29, and then is supplemented into the water circulation loop of the steam Rankine cycle through the make-up water pump 31.

[0034] The above make-up water system supporting the steam Rankine cycle is used to supplement the blowdown loss, steam leakage loss, etc. in the steam Rankine cycle.

[0035] The water treatment equipment 28 includes ultrafiltration membrane separation desalination, chemical desalination (cation and anion exchange method), etc.

[0036] The deaerator 30 includes thermal deaeration, chemical deaeration, desorption deaeration, electrochemical deaeration or deaeration resin deaeration, etc. Preferably, a normal temperature deaerator is used.

[0037] The furnace heating surface of the boiler body 4 adopts water treatment measures such as adding medicine in the pot, continuous or periodic blowdown, etc. to adjust the water quality in the pot to meet the process and safety requirements.

[0038] The steam-organic working fluid combined cycle power generation system employs dust removal, desulfurization, and denitrification facilities to remove harmful components such as dust, sulfur oxides, and nitrogen oxides from the flue gas generated during fuel combustion.

[0039] The condenser 23 in the Rankine cycle of the organic working fluid is set up according to conventional technology, using water or air as the cooling medium, as shown in the attached figure. Figure 1 As shown, the refrigerant 25 of the condenser 23 is water or air. Preferably, the refrigerant 25 is water, and the cooling water system of the condenser 23 adopts an open-loop circulation process or a closed-loop circulation process. When the condenser 23 adopts a closed-loop circulating water cooling process, the cooling water (i.e., the heat transfer medium 26) that comes out of the organic working fluid condenser 23 with increased temperature is cooled by a cooling tower and then sent back to the organic working fluid condenser 23 by a cooling water pump, thereby forming a closed-loop circulation process of cooling water.

[0040] A regenerator 32 is provided: the organic working fluid discharged from the organic working fluid turbine 22 enters the condenser 23 through the regenerator 32, and the liquid organic working fluid 19 from the condenser 23 enters the organic working fluid heater 8 through the organic working fluid booster pump 20 and the regenerator 32. The regenerator 32 adopts a partitioned heat exchange method.

[0041] The installation of the regenerator 32 helps to increase the inlet temperature of the organic working fluid heater 8, thereby increasing its metal wall temperature. Similar to the function of the warm air blower in the air preheater of a traditional power plant, it reduces the possibility of low-temperature corrosion of the organic working fluid heater 8 from a technical point of view.

[0042] For organic working fluid heaters, where low-temperature corrosion is likely to occur, corrosion-resistant stainless steel pipes and increased heat exchange tube wall thickness can be used as technical measures.

[0043] Equipment not described in this invention, such as backup systems, pipelines, instruments, valves, insulation, bypasses with regulating functions, and automatic control equipment, shall be equipped with known and mature technologies.

[0044] The present invention has the following advantages over the prior art:

[0045] 1. The steam-organic working fluid combined cycle power generation system adopted in this invention differs from existing steam Rankine-organic Rankine combined cycle power generation technology, and also from the Portma cycle power generation technology in a two-fluid cycle. In the Portma cycle, the condenser-evaporator has a large heat transfer temperature difference and significant heat loss. In the Portma cycle, the large amount of heat released when steam condenses in the steam Rankine cycle condenser is used as the heat source for the vaporization of the low-boiling-point organic working fluid in the ORC evaporator (the low-boiling-point organic working fluid needs to absorb a large amount of heat during vaporization). In this disclosure, the condenser in the steam Rankine cycle operates under positive pressure, utilizing the large proportion of heat absorbed by water in the evaporation section of the steam Rankine cycle. For example, given the relatively small heat absorption in the preheating section (economizer), the positive pressure condenser in the steam Rankine cycle is used as the heat source for the superheater of the ORC. The latent heat of vaporization released when the steam in the positive pressure condenser of the steam Rankine cycle is absorbing the heat for ORC power generation. Taking advantage of the high proportion of heat absorption of the low-boiling-point working fluid in the preheating section of the organic Rankine cycle, the preheating section of the ORC, i.e., the evaporation section (operating below subcritical parameters), is used to recover waste heat from boiler flue gas. The output power of the ORC turbine can reach more than twice that of the steam Rankine cycle in the same temperature range. Therefore, this invention improves the Bodema cycle in the dual-fluid cycle, and the integrated system has higher power generation efficiency.

[0046] 2. This invention effectively reduces flue gas temperature by utilizing the low boiling point and high heat absorption of the organic working fluid in the ORC preheating section. It also has a large amount of waste heat recovery. The heat transfer coefficient (gas-liquid heat transfer, phase change heat transfer) of the ORC preheating section is much larger than that of the air preheater (gas-gas heat transfer). As an "indispensable core device" in modern power plant boilers, the air preheater is replaced by a more compact and efficient organic working fluid heater in the flue. The inherent defects of the traditional air preheater in power plant boilers are fundamentally eliminated.

[0047] 3. The system equipment layout is more compact, occupies less space, is easy to install, and is easier to operate and adjust. It is conducive to the safe and economical operation of purification equipment such as dust collectors and desulfurization and denitrification devices, and the water-saving effect of desulfurization devices is obvious.

[0048] 4. Because the exhaust steam of the steam turbine is under positive pressure, its specific volume is much smaller than that of the low-pressure cylinder exhaust steam in traditional negative pressure operation. The volume of the condenser can be greatly reduced. Since the back pressure of the steam turbine in the steam Rankine cycle is positive pressure operation, 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 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.

[0049] 5. In the steam Rankine cycle, the makeup water system can adapt to the cogeneration needs of the combined cycle power generation system. The deaerator has a high efficiency and reliable deoxygenation effect, avoiding the problems of vacuum destruction and heat transfer deterioration caused by negative pressure gas evolution and gas leakage in the condenser in the traditional process. The makeup water system is set up more reasonably and effectively.

[0050] 6. When this invention employs a combined cycle power generation system of steam and organic working fluid with a phase changer, the internal circulation steam boiler uses a closed-loop purified water circulation process, unlike the open-loop process in traditional power plant boilers which requires continuous water replenishment to compensate for steam and water losses caused by continuous blowdown, turbine leakage, and deaeration. Therefore, there is no scale formation or cumulative oxygen corrosion on the heating surfaces of the internal circulation steam boiler. This avoids the possibility of scale and oxygen corrosion on the water-cooled wall tubes, convective heat exchange surfaces, and steam condensation side heat exchange surfaces of the phase changer. Essentially, it shifts the main area of ​​scale and oxygen corrosion from the harsh high-temperature heat source environment of the internal circulation steam boiler to the external phase changer. The scale and oxygen corrosion transferred to the phase changer can be safely controlled through blowdown, cleaning, feedwater deaeration, and the addition of deaerators to the phase changer, because the phase changer operates in the medium-temperature range below the critical temperature of water. The regulatory risks from national regulatory authorities, as well as the safety risks to users and operators, are greatly reduced. This also generates economic benefits from long-term safe operation of the equipment, and significantly reduces related costs due to convenient maintenance and repair. This ensures the safe, economical, and long-term operation of the power plant boiler and its supporting generator sets. The innovative economizer feedwater and superheater external circulation process means that the heated economizer effluent is no longer sent to the traditional power plant boiler body to generate superheated steam for the turbine generator set. Instead, it enters the phase change heat exchanger and becomes an integral part of the external circulation steam boiler's water circulation loop. The saturated steam generated by the phase change heat exchanger enters the superheater, and the generated superheated steam then drives the turbine generator set to generate electricity. Therefore, this is fundamentally different from the working fluid circulation of traditional power plant boilers. Because the feedwater heated by the economizer reaches or approaches saturation temperature, the heat transfer process of the phase change heat exchanger is more efficient. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of the process flow of a steam-organic working fluid combined cycle power generation system according to the present invention.

[0052] Figure 1In the diagram, 1-Blower, 2-Burner, 3-Fuel, 4-Boiler body, 5-Saturated steam, 6-Superheater, 7-Economizer, 8-Organic working fluid heater, 9-Purification equipment, 10-Low-temperature flue gas, 11-Flue duct, 12-Feed water pipeline, 13-Superheated steam, 14-Steam turbine, 15-Positive pressure condenser, 16-Condensate, 17-Feed water pump, 18-Steam turbine generator, 19-Liquid organic working fluid, 20-Organic working fluid booster pump, 21-Organic working fluid superheated steam, 22-Organic working fluid turbine, 23-Condenser, 24-Organic working fluid generator, 25-Refrigerant, 26-Heating medium, 27-Clean water, 28-Water treatment equipment, 29-Purified water, 30-Deaerator, 31-Make-up water pump, 32-Regenerator.

[0053] Figure 2 This is a schematic diagram of another process flow of the steam-organic working fluid combined cycle power generation system of the present invention.

[0054] Figure 2 In the diagram, 1-Blower, 2-Burner, 3-Fuel, 4-Boiler body, 5-Saturated steam, 6-Superheater, 7-Economizer, 8-Organic working fluid heater, 9-Purification equipment, 10-Low-temperature flue gas, 11-Flue duct, 12-Feed water pipeline, 13-Superheated steam, 14-Steam turbine, 15-Positive pressure condenser, 16-Condensate, 17-Feed water pump, 18-Steam turbine generator, 19-Liquid organic working fluid, 20-Organic working fluid booster pump, 21-Organic working fluid superheated steam, 22-Organic working fluid turbine, 23-Condenser, 24-Organic working fluid generator, 25-Refrigerant, 26-Heating medium, 27-Clean water, 28-Water treatment equipment, 29-Purified water, 30-Deaerator, 31-Make-up water pump, 32-Regenerator, 33-Phase change heat exchanger, 34-Condensate, 35-Circulating water pump.

[0055] Figure 3 This is a schematic diagram of another process flow for a combined cycle power generation system of steam and organic working fluid (supercritical carbon dioxide) according to the present invention.

[0056] Figure 3In the middle, 1-blower, 2-burner, 3-fuel, 4-boiler body, 5-saturated steam, 6-superheater, 7-economizer, 8-1-supercritical carbon dioxide heater, 9-purification equipment, 10-low temperature flue gas, 11-flue, 12-feed water pipeline, 13-superheated steam, 14-steam turbine, 15-positive pressure condenser, 16-condensate, 17-feed water pump, 18-steam turbine generator, 19-1-gaseous carbon dioxide, 20-1-carbon dioxide compressor, 21-1-supercritical carbon dioxide, 22-1-carbon dioxide turbine, 23-1-cooler, 24-1-carbon dioxide generator, 25-refrigerant, 26-heating medium, 27-clean water, 28-water treatment equipment, 29-purified water, 30-deaerator, 31-make-up water pump, 32-regenerator. Detailed Implementation

[0057] The present disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0058] Example 1:

[0059] As attached Figure 1 As shown, a steam-organic working fluid combined cycle power generation system includes a steam Rankine cycle and an organic working fluid Rankine cycle.

[0060] The steam Rankine cycle refers to a process where saturated steam 5 generated by the furnace heating surface of the boiler body 4 passes through the heat exchanger 6 to form superheated steam 13, which is then sent to the turbine 14 to drive the turbine generator 18 to generate electricity. The exhaust steam from the turbine 14 has a pressure higher than atmospheric pressure and condenses in the positive pressure condenser 15. The resulting condensate 16 returns to the boiler body 4 via the feedwater pump 17 and economizer 7. The furnace heating surface of the boiler body 4 then generates saturated steam 5 again, thus forming a steam Rankine cycle loop.

[0061] The aforementioned Rankine cycle of the organic working fluid refers to the process where liquid organic working fluid 19 is fed through an organic working fluid booster pump 20, an organic working fluid heater 8, and a positive pressure condenser 15 to form superheated organic working fluid steam 21, which then enters an organic working fluid turbine 22 to drive an organic working fluid generator 24 to generate electricity. The organic working fluid discharged from the organic working fluid turbine 22 is cooled by a condenser 23 to form liquid organic working fluid 19, which then enters the organic working fluid booster pump 20, thus forming an organic working fluid Rankine cycle loop.

[0062] Fuel 3 and air supplied by blower 1 are burned in burner 2. The high-temperature flue gas generated by burner 2, or the high-temperature flue gas generated by industrial production process, is cooled by the furnace heating surface of boiler body 4, superheater 6, economizer 7, and organic working fluid heater 8, and the resulting low-temperature flue gas 10 is discharged or transported to purification equipment 9 for dust removal, desulfurization or denitrification, and then discharged from the chimney by induced draft fan.

[0063] The steam turbine generator 18 and the organic working fluid generator 24 are combined into one generator.

[0064] The steam turbine 14 and the organic working fluid turbine 22 operate coaxially.

[0065] The liquid organic working fluid 19 is a single-component organic working fluid.

[0066] The organic working fluid of the organic Rankine cycle adopts R245fa.

[0067] When the organic Rankine cycle operates with supercritical parameters, the organic working fluid heater 8 is a supercritical fluid heater.

[0068] There is a make-up water system supporting the steam Rankine cycle: fresh water 27 forms purified water 29 through the water treatment equipment 28, and then is sent to the deaerator 30 to remove the gas components in the purified water 29, and then is supplemented into the water circulation loop of the steam Rankine cycle through the make-up water pump 31.

[0069] The above make-up water system supporting the steam Rankine cycle is used to supplement the blowdown loss, steam leakage loss, etc. in the steam Rankine cycle.

[0070] The water treatment equipment 28 adopts a combined process of ultrafiltration membrane separation desalination and chemical desalination (cation and anion exchange method).

[0071] The deaerator 30 adopts a thermal deaerator.

[0072] The furnace heating surface of the boiler body 4 adopts water treatment measures such as adding medicine in the boiler, continuous or periodic blowdown, etc. to adjust the water quality in the boiler to meet the process and safety requirements.

[0073] The steam-organic working fluid combined cycle power generation system adopts dust removal, desulfurization, and denitration facilities to remove harmful components such as dust, sulfur oxides, nitrogen oxides, etc. in the flue gas formed during the fuel combustion process.

[0074] The cooling water system of the condenser 23 in the organic Rankine cycle adopts a closed-loop circulation process, that is, the cooling water (heat medium 26) with an increased temperature coming out of the organic working fluid condenser 23 is cooled by the cooling tower and then sent back to the organic working fluid condenser 23 through the cooling water pump, thus forming a closed-loop circulation process of the cooling water.

[0075] There is a regenerator 32: the organic working fluid discharged from the organic working fluid turbine 22 enters the condenser 23 through the regenerator 32, and the liquid organic working fluid 19 coming out of the condenser 23 enters the organic working fluid heater 8 through the organic working fluid booster pump 20 and the regenerator 32.

[0076] The parts of the organic working fluid evaporator 8 that are prone to low-temperature corrosion adopt corrosion-resistant stainless steel materials, etc.

[0077] Example 2:

[0078] As attached Figure 2 As shown, a steam-organic working fluid combined cycle power generation system includes a steam Rankine cycle and an organic working fluid Rankine cycle.

[0079] The steam Rankine cycle refers to a process where saturated steam 5 generated by the boiler body 4 enters the phase changer 33, and the resulting condensate 34 returns to the boiler body 4 directly or via the circulating water pump 35. The steam generated in the phase changer 33 passes through the superheater 6 to form superheated steam 13, which is then fed into the turbine 14 to drive the turbine generator 18 to generate electricity. The exhaust steam from the turbine 14 has a pressure higher than atmospheric pressure and condenses in the positive pressure condenser 15. The resulting condensate 16 returns to the phase changer 33 via the feedwater pump 17 and the economizer 7. The steam generated by the saturated steam 5 then enters the superheater 6, where the furnace heating surfaces of the boiler body 4 generate saturated steam 5 again, thus forming a steam Rankine cycle loop.

[0080] The aforementioned Rankine cycle of the organic working fluid refers to the process where liquid organic working fluid 19 is fed through an organic working fluid booster pump 20, an organic working fluid heater 8, and a positive pressure condenser 15 to form superheated organic working fluid steam 21, which then enters an organic working fluid turbine 22 to drive an organic working fluid generator 24 to generate electricity. The organic working fluid discharged from the organic working fluid turbine 22 is cooled by a condenser 23 to form liquid organic working fluid 19, which then enters the organic working fluid booster pump 20, thus forming an organic working fluid Rankine cycle loop.

[0081] Fuel 3 and air supplied by blower 1 are burned in burner 2. The high-temperature flue gas generated by burner 2, or the high-temperature flue gas generated by industrial production process, is cooled by the furnace heating surface of boiler body 4, superheater 6, economizer 7, and organic working fluid heater 8, and the resulting low-temperature flue gas 10 is discharged or transported to purification equipment 9 for dust removal, desulfurization or denitrification, and then discharged from the chimney by induced draft fan.

[0082] The rest is the same as in Example 1.

[0083] Example 3:

[0084] As attached Figure 3 As shown, a steam-organic working fluid combined cycle power generation system includes a steam Rankine cycle and an organic working fluid Rankine cycle, wherein the organic working fluid is carbon dioxide.

[0085] The steam Rankine cycle refers to that the saturated steam 5 generated by the furnace heating surface of the boiler body 4 forms superheated steam 13 through the superheater 6 and is sent to the steam turbine 14 to drive the steam turbine generator 18 to generate electricity. The exhaust steam from the steam turbine 14 has a pressure higher than the atmospheric pressure and is condensed in the positive-pressure condenser 15. The formed condensate 16 returns to the boiler body 4 through the feed water pump 17 and the economizer 7. The furnace heating surface of the boiler body 4 generates saturated steam 5 again, thus forming a steam Rankine cycle loop.

[0086] The organic working fluid Rankine cycle refers to that gaseous carbon dioxide 19-1 forms supercritical carbon dioxide 21-1 through the carbon dioxide compressor 20-1, the supercritical carbon dioxide heater 8-1, and the positive-pressure condenser 15, enters the carbon dioxide steam turbine 22-1, and drives the carbon dioxide generator 24-1 to generate electricity. The carbon dioxide discharged from the carbon dioxide steam turbine 22-1 is cooled by the cooler 23-1 to form gaseous carbon dioxide 19-1 and then enters the carbon dioxide compressor 20-1 again, thus forming an organic working fluid Rankine cycle loop.

[0087] The fuel 3 and the air sent by the blower 1 burn in the burner 2. The high-temperature flue gas generated by the burner 2, or the high-temperature flue gas generated in the industrial production process, is cooled by the furnace heating surface, the superheater 6, the economizer 7, and the supercritical carbon dioxide heater 8-1 of the boiler body 4, and then the formed low-temperature flue gas 10 is discharged, or is transported to the purification equipment 9 for dust removal, desulfurization, denitrification and other treatments, and then is discharged from the chimney through the induced draft fan.

[0088] The steam turbine generator 18 and the carbon dioxide generator 24-1 are combined into one generator.

[0089] The steam turbine 14 and the carbon dioxide steam turbine 22-1 operate coaxially.

[0090] A makeup water system supporting the steam Rankine cycle is provided: The fresh water 27 forms purified water 29 through the water treatment equipment 28, and then is sent to the deaerator 30 to remove the gas components in the purified water 29, and then is supplemented into the water circulation loop of the steam Rankine cycle through the makeup water pump 31.

[0091] The above makeup water system supporting the steam Rankine cycle is used to supplement the blowdown loss, steam leakage loss, etc. in the steam Rankine cycle.

[0092] The water treatment equipment 28 adopts a combined process of ultrafiltration membrane separation desalination and chemical desalination (cation and anion exchange method).

[0093] The deaerator 30 adopts a thermal deaerator.

[0094] The furnace heating surface of the boiler body 4 adopts water treatment measures such as adding medicine in the pot, continuous or periodic blowdown, etc. to adjust the water quality in the pot to meet the process and safety requirements.

[0095] The steam-organic working fluid combined cycle power generation system employs dust removal, desulfurization, and denitrification facilities to remove harmful components such as dust, sulfur oxides, and nitrogen oxides from the flue gas generated during fuel combustion.

[0096] The cooling water system of the cooler 23-1 in the organic Rankine cycle adopts a closed-loop circulation process. That is, the cooling water (heat medium 26) that comes out of the cooler 23-1 with increased temperature is cooled by the cooling tower and then sent back to the cooler 23-1 by the cooling water pump, thus forming a closed-loop circulation process of cooling water.

[0097] A regenerator 32 is provided: the carbon dioxide discharged from the carbon dioxide turbine 22-1 enters the cooler 23-1 through the regenerator 32, and the gaseous carbon dioxide 19-1 coming out of the cooler 23-1 enters the supercritical carbon dioxide heater 8-1 through the carbon dioxide compressor 20-1 and the regenerator 32.

[0098] In the supercritical carbon dioxide heater 8-1, corrosion-resistant stainless steel materials are used in areas prone to low-temperature corrosion.

[0099] The aforementioned economizer 7, organic working fluid heater 8, or supercritical carbon dioxide heater 8-1 are arranged in the flue 11.

[0100] Equipment not described in this invention, such as backup systems, pipelines, instruments, valves, insulation, and bypasses with regulating functions, shall be equipped with well-known and mature technologies.

[0101] Although the present invention has been disclosed above with reference to preferred embodiments, these are not intended to limit the invention. Any person skilled in the art can make various changes or modifications without departing from the spirit and scope of this disclosure, and these changes also fall within the protection scope of the present invention. Therefore, the protection scope of the present invention should be defined by the claims of this application.

Claims

1. A steam-organic working fluid combined cycle power generation system, characterized in that: The steam-organic working fluid combined cycle power generation system includes a steam Rankine cycle and an organic working fluid Rankine cycle. The steam Rankine cycle refers to a process where saturated steam generated by the boiler body passes through a heat exchanger to form superheated steam, which is then fed into a steam turbine to drive a steam turbine generator to produce electricity. The exhaust steam from the turbine condenses in a positive pressure condenser to form condensate, which is then pumped back to the boiler body via a feedwater pump and an economizer. The boiler body absorbs heat from the high-temperature flue gas to generate saturated steam again, thus forming a steam Rankine cycle loop. The aforementioned Rankine cycle of organic working fluid refers to a process where liquid organic working fluid enters an organic working fluid turbine via an organic working fluid booster pump, an organic working fluid heater, and a positive pressure condenser, driving an organic working fluid generator to produce electricity. The gaseous organic working fluid discharged from the organic working fluid turbine is cooled by a condenser to form liquid organic working fluid, which then enters the organic working fluid booster pump, thus forming an organic working fluid Rankine cycle loop. Fuel and air supplied by the blower are burned in the burner. The high-temperature flue gas generated by the burner, or the high-temperature flue gas generated by the industrial production process, is cooled by the boiler body, superheater, economizer, and organic working fluid heater, and the resulting low-temperature flue gas is discharged. Alternatively, it can be transported to purification equipment for treatment and then discharged from the chimney by the induced draft fan.

2. The steam-organic working fluid combined cycle power generation system according to claim 1, characterized in that: The fuel may be in one or more of the following states: gaseous, liquid, or solid.

3. The steam-organic working fluid combined cycle power generation system according to claim 1, characterized in that: A water supply system is provided: clean water is treated by water treatment equipment to form purified water, which is then sent to a deaerator to remove gas components from the purified water, and then pumped into the water circulation loop of the steam Rankine cycle.

4. The steam-organic working fluid combined cycle power generation system according to claim 1, characterized in that: The organic working medium in the Rankine cycle is a single-component organic working medium or a mixture of low-boiling-point and high-boiling-point organic working medium.

5. The steam-organic working fluid combined cycle power generation system according to claim 4, characterized in that: The organic working medium in the Rankine cycle is carbon dioxide.

6. The steam-organic working fluid combined cycle power generation system according to claim 1, characterized in that: A regenerator is provided: the organic working fluid discharged from the organic working fluid turbine enters the condenser through the regenerator, and the liquid organic working fluid coming out of the condenser enters the organic working fluid heater through the organic working fluid booster pump and the regenerator.

7. A steam-organic working fluid combined cycle power generation system, characterized in that: The steam-organic working fluid combined cycle power generation system includes a steam Rankine cycle and an organic working fluid Rankine cycle. The steam Rankine cycle refers to a process where saturated steam generated by the boiler body condenses in a phase changer, returning directly or via a circulating water pump to the boiler body. Steam generated in the phase changer then becomes superheated steam, which is fed into a turbine to drive a generator. The turbine exhaust condenses in a positive pressure condenser, returning to the phase changer via a feedwater pump and economizer. The steam heated by the saturated steam then enters the superheater, where the boiler body absorbs heat from the high-temperature flue gas to generate saturated steam again, thus forming a steam Rankine cycle loop. The aforementioned Rankine cycle of organic working fluid refers to a process in which liquid organic working fluid enters an organic working fluid turbine via an organic working fluid booster pump, an organic working fluid heater, and a positive pressure condenser, driving an organic working fluid generator to generate electricity. The organic working fluid discharged from the organic working fluid turbine is cooled by a condenser to form liquid organic working fluid, which then enters the organic working fluid booster pump, thus forming an organic working fluid Rankine cycle loop. Fuel and air supplied by the blower are burned in the burner. The high-temperature flue gas generated by the burner, or the high-temperature flue gas generated by the industrial production process, is cooled by the boiler body, superheater, economizer, and organic working fluid heater, and the resulting low-temperature flue gas is discharged. Alternatively, it can be transported to purification equipment for treatment and then discharged from the chimney by the induced draft fan.

8. The steam-organic working fluid combined cycle power generation system according to claim 7, characterized in that: A regenerator is provided: the organic working fluid discharged from the organic working fluid turbine enters the condenser through the regenerator, and the liquid organic working fluid coming out of the condenser enters the organic working fluid heater through the organic working fluid booster pump and the regenerator.

9. The steam-organic working fluid combined cycle power generation system according to claim 7, characterized in that: A water supply system is provided: clean water is treated by water treatment equipment to form purified water, which is then sent to a deaerator to remove gas components from the purified water, and then pumped into the water circulation loop of the steam Rankine cycle.

10. The steam-organic working fluid combined cycle power generation system according to claim 7, characterized in that: The organic working medium in the Rankine cycle is a single-component organic working medium or a mixture of low-boiling-point and high-boiling-point organic working medium.

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