Orc waste heat power generation system and method

Abstract

This invention relates to the field of waste heat power generation technology, providing an ORC waste heat power generation system and method. The system includes a working fluid circulation module, a loss preheating module, a regeneration module, a waste heat recovery module, and a turbine power generation module. The working fluid circulation module drives the liquid working fluid to circulate and condense the working fluid gas after work is performed; the loss preheating module is located on the output side of the working fluid circulation module, utilizing the heat generated by the power electronic equipment and / or the turbine generator to perform primary preheating of the working fluid; the regeneration module utilizes the working fluid gas discharged from the turbine power generation module to perform secondary preheating of the working fluid; the waste heat recovery module uses an external heat source to heat the working fluid into a high-temperature, high-pressure gas to drive the turbine power generation module to perform work and generate electricity. This invention incorporates the heat generated by equipment losses into the waste heat recovery scope, improving the system's waste heat recovery efficiency; the loss preheating module also serves as a cooling structure for the equipment, replacing an independent cooling system, reducing auxiliary energy consumption, and increasing net power generation.

Description

Technical Field

[0001] This invention relates to the field of waste heat power generation technology, and more particularly to ORC waste heat power generation systems and methods. Background Technology

[0002] The Organic Rankine Cycle (ORC) is a waste heat power generation technology that uses an organic working fluid as the circulating fluid. The organic working fluid refers to organic compounds with low boiling points, such as R245fa, R134a, and R601a. ​​These compounds are characterized by their ability to undergo phase change at relatively low temperatures, making them suitable for recovering low-temperature waste heat. The basic principle is to use low-temperature waste heat to heat the organic working fluid, causing it to evaporate into a high-temperature, high-pressure gas. This gas drives a turbine to rotate and perform work, thereby driving a generator to produce electricity. Compared to the traditional steam Rankine cycle, the ORC system can effectively utilize low-grade waste heat resources within the temperature range of 80℃ to 400℃, and is widely used in industrial waste heat recovery, geothermal power generation, solar thermal power generation, and biomass power generation.

[0003] See Figure 1 Existing ORC systems mainly include key components such as working fluid tanks, working fluid pumps, waste heat recovery heat exchangers, turbine generators, and condensers. Figure 1 As shown, a low-temperature, low-pressure liquid working fluid is stored in a working fluid tank. A working fluid pump pressurizes the liquid working fluid and pumps it into the circulation pipeline. The liquid working fluid absorbs energy from external waste heat sources through a single-stage or multi-stage waste heat recovery heat exchanger, and is heated into a high-temperature, high-pressure working fluid gas. This gas drives a turbine to generate electricity. After the turbine performs work, the temperature and pressure of the working fluid gas decrease. The discharged gas is cooled by a condenser and returns to the liquid working fluid, flowing back to the working fluid tank, completing one working cycle. In a typical ORC system, taking R245fa as the working fluid as an example, the working fluid pump outlet pressure is typically between 1.5 MPa and 3.0 MPa, the liquid working fluid temperature is approximately 25°C to 40°C, and after being heated by the waste heat recovery heat exchanger, the working fluid gas temperature can reach 100°C to 180°C. The turbine exhaust temperature is approximately 60°C to 90°C.

[0004] See Figure 2 Based on the above basic solution, there is also an improved solution in the existing technology: such as Figure 2As shown, a regenerator is added before the waste heat recovery heat exchanger. The regenerator is a heat exchange device used to achieve heat exchange within the same circulating system. Its function is to exchange heat between the higher-temperature working fluid gas discharged from the turbine and the lower-temperature liquid working fluid from the working fluid pump, preheating the liquid working fluid and thus recovering residual heat from the turbine exhaust gas, improving the overall waste heat recovery efficiency of the system. With the regenerator, the turbine exhaust temperature can be reduced from approximately 70°C to 90°C to 40°C to 55°C, and the temperature of the liquid working fluid, after preheating by the regenerator, can be increased from 25°C to 40°C to 45°C to 65°C, improving the overall thermal efficiency of the system by 2% to 5%.

[0005] However, regardless of the basic or improved schemes mentioned above, there are still underutilized heat sources during the operation of the ORC system. Specifically, the heat generated by power electronic equipment in the system (including rectifiers, inverters, frequency converters, etc.) during operation due to switching losses, conduction losses, core losses, etc., accounts for approximately 2% to 10% of the system's net power generation. For an ORC system with a net power generation of 100kW, this heat generation is approximately 2kW to 10kW. The heat generated by turbine generators during operation due to copper losses, iron losses, mechanical friction losses, etc., accounts for approximately 2% to 5% of the system's net power generation. For the aforementioned ORC system with a net power generation of 100kW, this is approximately 2kW to 5kW. The combined heat generation from these two sources can reach 4% to 15% of the system's net power generation. This typically requires separate cooling systems (such as fans, radiators, cooling water pumps, etc.) for heat dissipation, resulting in wasted heat energy and increased energy consumption and structural complexity of the auxiliary systems. Summary of the Invention

[0006] The purpose of this invention is to provide an ORC waste heat power generation system and method to solve the technical problem that existing ORC systems fail to fully recover the heat loss generated by power electronic devices and turbine generators during system operation, resulting in insufficient waste heat recovery efficiency.

[0007] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides an ORC waste heat power generation system, comprising: a working fluid circulation module, a loss preheating module, a regeneration module, a waste heat recovery module, and a turbine power generation module. The working fluid circulation module drives the liquid working fluid to circulate within the system and condenses and recovers the working fluid gas after work is performed back into liquid working fluid. The loss preheating module, located on the output side of the working fluid circulation module, is used to perform primary preheating of the liquid working fluid using the loss heat generated during system operation. This loss heat originates from at least one of the loss heat generated by power electronic equipment and the loss heat generated by the turbine generator. The regeneration module, located downstream of the loss preheating module, uses the working fluid gas discharged after work is performed by the turbine power generation module as a heat source to perform secondary preheating of the liquid working fluid after primary preheating. The waste heat recovery module, located between the regeneration module and the turbine power generation module, uses an external waste heat source to heat the working fluid to generate a high-temperature, high-pressure working fluid gas. The turbine power generation module is used to receive the high-temperature and high-pressure working gas to generate electricity. After the working gas is discharged, it releases some heat through the regeneration module and then flows back to the working gas circulation module.

[0008] In some embodiments, the working fluid circulation module includes a working fluid storage unit, a working fluid driving unit, and a condensation unit. In some embodiments, the working fluid storage unit is a working fluid tank, the working fluid driving unit is a working fluid pump, and the condensation unit is a condenser. In some embodiments, the loss preheating module includes a power electronic heat exchange unit and a turbine generator heat exchange unit, which are arranged in series along the working fluid flow direction. In some embodiments, the power electronic heat exchange unit is a liquid-cooled heat exchanger covering the outside of a power electronic device, and the turbine generator heat exchange unit is a liquid-cooled jacket covering the turbine generator housing. In some embodiments, the loss preheating module includes only one of the power electronic heat exchange unit or the turbine generator heat exchange unit.

[0009] Secondly, the present invention provides an ORC waste heat power generation method, applied to the aforementioned ORC waste heat power generation system. The method includes: driving a liquid working fluid into a circulation pipeline via a working fluid circulation module; performing primary preheating of the liquid working fluid using loss-induced heat generation via a loss preheating module; sending the liquid working fluid after primary preheating to a regeneration module for secondary preheating; sending the working fluid after secondary preheating to a waste heat recovery module for heating to generate a high-temperature, high-pressure working fluid gas; sending the high-temperature, high-pressure working fluid gas to a turbine power generation module to generate electricity; and returning the working fluid gas after generating electricity to the working fluid circulation module after releasing some heat via the regeneration module to condense into a liquid working fluid, thus completing the system cycle.

[0010] The technical solution of the present invention has the following beneficial effects: 1) By adding a loss preheating module, the heat generated by the loss of power electronic equipment and / or turbine generator is included in the scope of waste heat recovery, thereby improving the overall waste heat recovery efficiency of the system; 2) The loss preheating module also serves as a cooling and heat dissipation structure, integrating cooling and preheating functions, thereby improving the stability and reliability of the system; 3) By removing the independent cooling system, the energy consumption of the auxiliary system is reduced, and the net power generation of the system is increased; 4) The cooling effect of liquid working fluid as a cooling medium is better than that of traditional air cooling or water cooling methods. Attached Figure Description

[0011] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below.

[0012] Figure 1 This is a schematic diagram of the basic ORC waste heat power generation system in the prior art.

[0013] Figure 2 A schematic diagram of the structure of an improved ORC waste heat power generation system with the addition of a regenerator to the existing technology.

[0014] Figure 3 This is a schematic diagram of the ORC waste heat power generation system provided in an embodiment of the present invention.

[0015] Figure 4 This is a schematic flowchart of the ORC waste heat power generation method provided in an embodiment of the present invention.

[0016] 100 working fluid circulation module 110 working fluid storage units 120 working fluid drive unit 130 condensing unit 200 loss preheating module 210 Power Electronic Heat Exchanger Unit 220 Turbine Generator Heat Exchanger Unit 300 regenerative module More than 400 heat recovery modules 500 Turbine Power Generation Module Detailed Implementation

[0017] The following detailed description, in conjunction with specific embodiments and accompanying drawings, clarifies that the described embodiments are only a portion, not all, of the embodiments. All other embodiments obtained by those skilled in the art based on the following embodiments without inventive effort are also within the scope of protection of this invention.

[0018] It should be understood that if the controllers or control circuits involved in the embodiments are conventional control technologies or units for those skilled in the art, such as the control circuits of the controllers, they can be implemented by those skilled in the art using existing technologies.

[0019] The disclosure of the embodiments provides many different implementations or examples for different ways of implementing the present invention. To simplify the disclosure of the present invention, the embodiments describe components and arrangements of specific examples. Of course, these are merely examples and are not intended to limit the present invention. Furthermore, reference numerals and / or reference letters may be repeated in different examples in the embodiments; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various implementations and / or arrangements discussed. Moreover, if examples of various specific processes and materials are provided in the embodiments, those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0020] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0021] See Figure 3 The first embodiment provides an ORC waste heat power generation system, including: a working fluid circulation module 100, a loss preheating module 200, a regeneration module 300, a waste heat recovery module 400, and a turbine power generation module 500.

[0022] The working fluid circulation module 100 is used to drive the liquid working fluid to circulate in the system and to condense and recover the working fluid gas after work into a liquid working fluid. The working fluid circulation refers to the repeated phase change cycle of the organic working fluid in the system from liquid to gas to liquid, completing heat absorption, work, and release during the circulation process. In this embodiment, the circulating working fluid can be selected from low-boiling-point organic compounds such as R245fa, R134a, R601a, and R1233zd(E). Among them, R245fa has a boiling point of 15.3℃ (at atmospheric pressure), a critical temperature of 154℃, and a critical pressure of 3.65MPa, making it suitable for applications with waste heat temperatures ranging from 80℃ to 180℃; R1233zd(E) has a boiling point of 18.3℃, a critical temperature of 166.5℃, and a critical pressure of 3.57MPa, and has a low global warming potential (GWP=1), making it an environmentally friendly alternative working fluid. The selection of working fluid needs to take into account factors such as waste heat source temperature, system pressure level, environmental protection requirements, and economic efficiency.

[0023] The loss preheating module 200 is located on the output side of the working fluid circulation module 100. Loss preheating refers to using the waste heat generated by various devices during system operation due to electromagnetic losses, resistance losses, mechanical friction losses, etc., to preheat the working fluid. In traditional ORC systems, this waste heat is considered waste heat and dissipated into the environment through an independent cooling system. The core concept of this invention is to convert this waste heat into a heat source for preheating the working fluid, thereby achieving cascaded utilization of heat. The loss preheating module 200 is used to preheat the liquid working fluid in the first stage using the loss heat generated during system operation. This loss heat originates from at least one of the loss heat from power electronic equipment and turbine generators. By setting up the loss preheating module 200, the liquid working fluid has already achieved a certain degree of temperature rise before entering the regeneration module 300, which improves subsequent heat exchange efficiency and effectively cools the power electronic equipment and / or turbine generators, avoiding performance degradation or malfunctions caused by overheating.

[0024] The regenerative heat recovery module 300 is located downstream of the loss preheating module 200. Regenerative heat recovery refers to the process within the same thermodynamic cycle system where the higher-temperature working gas discharged after work is used to preheat the lower-temperature liquid working fluid that has not yet entered the main heat exchanger. The regenerative heat recovery module 300 uses the working gas discharged after work is performed by the turbine power generation module 500 as a heat source to perform secondary preheating of the liquid working fluid after primary preheating. Through the regenerative heat recovery module 300, the residual heat in the working gas discharged from the turbine power generation module 500 is recovered and utilized, rather than being completely wasted in the condenser, reducing the cooling load on the condenser and further improving the system's thermal efficiency.

[0025] The waste heat recovery module 400 is located between the regeneration module 300 and the turbine power generation module 500. Waste heat recovery refers to the process of transferring low-grade waste heat generated during industrial production to the organic working fluid through a heat exchange device. External waste heat sources include, but are not limited to, industrial waste gas (such as cement kiln exhaust gas, ceramic kiln exhaust gas, etc., with temperatures typically between 150℃ and 400℃), geothermal hot water (temperatures typically between 80℃ and 180℃), solar thermal collectors (heat sources with temperatures of 100℃ to 300℃ can be obtained through concentrating collectors), and waste heat from internal combustion engine exhaust (exhaust temperatures typically between 200℃ and 600℃). Because the working fluid has already undergone two stages of preheating by the loss preheating module 200 and the regeneration module 300 before entering the waste heat recovery module 400, its temperature has been significantly increased. Therefore, the waste heat recovery module 400 can utilize external waste heat sources more efficiently.

[0026] The turbine power generation module 500 is used to receive high-temperature, high-pressure working gas to generate electricity. Turbine power generation refers to the process where the high-temperature, high-pressure working gas drives the turbine impeller to rotate at high speed, converting thermal and pressure energy into mechanical energy, which is then converted into electrical energy by a generator coaxially connected to the turbine. The turbine power generation module 500 includes a turbine and a generator. The turbine's operating speed is typically between 20,000 rpm and 80,000 rpm, depending on the system power rating and the type of working gas. After the work is done, the temperature and pressure of the working gas decrease. The discharged working gas first enters the regenerative module 300 to release some heat as a heat source for secondary preheating, and then flows back to the working gas circulation module 100.

[0027] In summary, the ORC waste heat power generation system of the first embodiment, by adding a loss preheating module 200 between the working fluid circulation module 100 and the regeneration module 300, converts the heat loss from the originally discarded equipment into a heat source for preheating the working fluid, thus achieving cascade utilization of heat. Compared with the prior art, this embodiment can recover an additional 4% to 15% of the loss heat from the system's net power generation, significantly improving the overall waste heat recovery efficiency of the system.

[0028] The second embodiment further provides a specific implementation of the working fluid circulation module 100 based on the first embodiment. In this embodiment, the working fluid circulation module 100 includes a working fluid storage unit 110, a working fluid driving unit 120, and a condensation unit 130.

[0029] The working fluid storage unit 110 is a working fluid tank. The working fluid tank is a sealed pressure vessel used to store liquid organic working fluids. Its material is typically corrosion-resistant 304 or 316L stainless steel, and it maintains a certain internal pressure to ensure the working fluid remains in a liquid state. For ORC systems with a net power generation capacity of 50kW to 200kW, the working fluid tank capacity is typically between 50L and 500L, and its design pressure should be no less than 1.5 times the system's maximum operating pressure to ensure a safety margin.

[0030] The working fluid drive unit 120 is a working fluid pump. A working fluid pump is a type of pump used to pressurize and transport liquid working fluid to a circulation pipeline. Its working principle is to convert electrical energy into the pressure energy and kinetic energy of the working fluid through mechanical work. The selection of the working fluid pump needs to consider the required flow rate, head, and the physicochemical properties of the working fluid. Common types include centrifugal pumps, plunger pumps, gear pumps, and disc pumps. For small and medium-sized ORC systems (net power generation of 50kW to 200kW), the outlet pressure of the working fluid pump is typically between 1.5MPa and 3.0MPa, the flow rate is typically between 0.5kg / s and 3.0kg / s, and the isentropic efficiency of the pump is generally between 60% and 80%. The working fluid pump is used to pressurize the liquid working fluid in the working fluid tank and output it to the loss preheating module 200.

[0031] The condensing unit 130 is a condenser. The condenser is a heat exchange device used to cool and condense the gaseous working fluid into a liquid state. Its working principle is to absorb the latent heat and sensible heat of the working fluid gas using an external cold source. The condenser type can be either air-cooled or water-cooled. For applications with sufficient cooling water, water-cooled condensers are preferred due to their higher heat exchange efficiency; air-cooled condensers can be used in water-scarce areas. The condenser is located between the exhaust side of the regenerator module 300 and the working fluid tank. The condensing temperature is typically controlled between 25℃ and 40℃, and the corresponding condensing pressure is the saturation pressure of the working fluid at that temperature. For example, the saturation pressure of R245fa at 30℃ is approximately 0.18 MPa. By refining the working fluid circulation module 100 into three independent functional components—the working fluid tank, the working fluid pump, and the condenser—it is beneficial to independently select and optimize each component according to specific application scenarios, improving the system's flexibility and maintainability.

[0032] The third embodiment, based on the first embodiment, further provides a specific implementation of the loss preheating module 200. In this embodiment, the loss preheating module 200 includes both a power electronic heat exchange unit 210 and a turbine generator heat exchange unit 220, which are connected in series along the working fluid flow direction.

[0033] The power electronic heat exchange unit 210 is used to heat the liquid working fluid using the heat generated during the operation of the power electronic equipment. The power electronic equipment refers to electronic devices used for power conversion, regulation, and control in the ORC system, including but not limited to rectifiers, inverters, frequency converters, and power regulators. During operation, these devices generate significant heat due to switching losses, conduction losses, and core losses, with the power loss accounting for approximately 2% to 10% of the system's net power generation. The operating temperature of the power electronic equipment is typically between 40°C and 100°C, with the junction temperature of the IGBT module generally not exceeding 125°C to 150°C. In this embodiment, the power electronic heat exchange unit 210 is a liquid-cooled heat exchanger encased outside the power electronic equipment, employing a microchannel heat exchange structure made of aluminum alloy or copper alloy. The heat exchange area is designed based on the heat generation of the power electronic equipment and the working fluid flow rate. When the liquid working fluid flows through the power electronic heat exchange unit 210, it absorbs the heat generated by the power electronic equipment, increasing the working fluid temperature and simultaneously cooling the power electronic equipment.

[0034] The turbine generator heat exchange unit 220 is used to reheat the liquid working fluid after primary heating by utilizing the heat generated during turbine generator operation. The turbine generator refers to an integrated module consisting of a turbine and a generator. During operation, the generator generates heat due to copper losses, iron losses, and mechanical friction losses, with the power loss being approximately 2% to 5% of the system's net power generation. The generator casing temperature is typically between 60°C and 120°C. In this embodiment, the turbine generator heat exchange unit 220 is a liquid-cooled jacket covering the turbine generator casing. The liquid-cooled jacket is made of heat-resistant and thermally conductive copper alloy or stainless steel, with a wall thickness typically between 1.0mm and 2.5mm, tightly fitting the generator casing surface to ensure effective heat exchange. When the liquid working fluid, after primary heating, flows through the turbine generator heat exchange unit 220, it further absorbs the heat generated by the turbine generator, further increasing the working fluid temperature and simultaneously cooling the turbine generator.

[0035] Since the power electronics heat exchange unit 210 and the turbine generator heat exchange unit 220 respectively undertake the cooling and heat dissipation functions of the power electronics equipment and the turbine generator, the system in this embodiment no longer requires separate cooling systems for the power electronics equipment and the turbine generator. This design simplifies the system structure, eliminates the auxiliary energy consumption of independent cooling systems, and increases the net power generation of the system.

[0036] The following example illustrates the working fluid temperature and pressure parameters for each pipeline section in the third embodiment. This example uses R245fa as the circulating working fluid, with waste heat source being cement kiln exhaust gas (heat source temperature approximately 200°C), and the system's net power generation is approximately 100kW.

[0037] Table 1 shows the working fluid parameters for each pipeline section in this example.

[0038] As shown in Table 1, the temperature of the liquid working fluid at the working fluid pump outlet is approximately 28°C to 32°C. After being heated by the power electronic heat exchange unit 210, the temperature rises by approximately 5°C to 6°C. Then, after being heated by the turbine generator heat exchange unit 220, the temperature rises again by approximately 5°C to 7°C. The combined preheating from these two stages increases the working fluid temperature by approximately 10°C to 13°C. Subsequently, the working fluid is further heated to 55°C to 75°C by the heat recovery module 300, and finally heated to a superheated gaseous state of 130°C to 165°C in the waste heat recovery module 400 before entering the turbine generator module 500 to generate electricity.

[0039] The following example illustrates another operating condition. This example uses R1233zd(E) as the working fluid, with the waste heat source being the exhaust heat from the internal combustion engine (heat source temperature approximately 300℃), and the system's net power generation is approximately 150kW.

[0040] Table 2 shows the working fluid parameters for each pipeline section in this example.

[0041] As can be seen from Table 2, when a higher temperature external waste heat source is used, the system's working pressure and temperature range are correspondingly increased. However, the working principle and beneficial effects of the loss preheating module 200 are the same as those in working condition example 1. Both can raise the working fluid temperature by about 10°C to 15°C, thus achieving effective recovery of heat generated by equipment losses.

[0042] In this embodiment, the waste heat recovery module 400 can employ a plate heat exchanger or a shell-and-tube heat exchanger. Plate heat exchangers have the advantages of high heat exchange efficiency, compact structure, and small footprint, making them suitable for applications with low working fluid flow and low pressure. Shell-and-tube heat exchangers have the advantages of high pressure resistance and wide applicability, making them suitable for applications with high working fluid flow and high pressure. The heat recovery module 300 can also employ a plate heat exchanger or a shell-and-tube heat exchanger. Its heat exchange area is designed based on the temperature difference between the turbine exhaust temperature and the working fluid pump outlet temperature. Typically, the logarithmic mean temperature difference should be no less than 5°C to 10°C to ensure effective heat exchange.

[0043] The fourth embodiment, based on the first embodiment, further provides an implementation in which the loss preheating module 200 contains only a single heat exchange unit.

[0044] In one embodiment, the loss preheating module 200 includes only the power electronic heat exchange unit 210 and does not include the turbine generator heat exchange unit. The liquid working fluid output from the working fluid pump only flows through the power electronic heat exchange unit 210 for primary preheating, raising the working fluid temperature by approximately 3°C to 6°C, and then sequentially enters the heat recovery module 300 and the waste heat recovery module 400. Since the loss preheating module 200 in this embodiment does not perform working fluid heat exchange on the turbine generator, the turbine generator needs to have an independent cooling system to meet its heat dissipation requirements. This embodiment is suitable for applications where the turbine generator's heat loss is relatively small, or where there are special requirements for cooling temperature that make working fluid cooling unsuitable.

[0045] In another embodiment, the loss preheating module 200 includes only the turbine generator heat exchange unit 220, excluding the power electronics heat exchange unit. The liquid working fluid output from the working fluid pump flows only through the turbine generator heat exchange unit 220 for primary preheating, raising the working fluid temperature by approximately 4°C to 7°C, before sequentially entering the heat recovery module 300 and the waste heat recovery module 400. Since the loss preheating module 200 in this embodiment does not perform working fluid heat exchange on the power electronic equipment, the power electronic equipment needs an independent cooling system to meet its heat dissipation requirements. This embodiment is suitable for applications where the heat loss of power electronic equipment is relatively small, or where the operating environment temperature requirements are strict.

[0046] The advantages of the fourth embodiment are: while retaining the preheating function, it provides a more flexible system configuration scheme, which enables the system to selectively recover the heat generated by the loss of one of the devices according to the specific equipment loss characteristics and cooling requirements, thereby achieving a balance between improving waste heat recovery efficiency and ensuring equipment operation reliability.

[0047] See Figure 4 The fifth embodiment further provides an ORC waste heat power generation method based on the first to fourth embodiments. This embodiment uses the system structure of the third embodiment as an example, and describes the method based on operating condition example one (R245fa working fluid, 100kW net power generation). The method includes the following steps: Step S100: The liquid working fluid is driven into the circulation pipeline by the working fluid circulation module. Specifically, the working fluid pump pressurizes the liquid R245fa working fluid stored in the working fluid tank to 2.2MPa to 2.5MPa and then outputs it to the circulation pipeline. At this time, the working fluid temperature is approximately 28℃ to 32℃. The input power of the working fluid pump is approximately 3% to 5% of the net power generation of the system, i.e., approximately 3kW to 5kW. The purpose of this step is to provide the driving force for the working fluid to circulate in the system, ensuring that the working fluid enters the subsequent heat exchange stage at a flow rate of approximately 1.5kg / s to 2.0kg / s.

[0048] Step S200: The liquid working fluid is preheated using the heat generated during system operation via a loss preheating module. This first-stage preheating includes sequential primary heating and secondary heating. Primary heating utilizes the heat generated by the power electronics equipment (approximately 2kW to 10kW) through a power electronics heat exchange unit to heat the liquid working fluid, raising its temperature from approximately 28°C to 32°C to approximately 33°C to 38°C. Secondary heating utilizes the heat generated by the turbine generator (approximately 2kW to 5kW) through a turbine generator heat exchange unit to heat the liquid working fluid after primary heating, raising its temperature from approximately 33°C to 38°C to approximately 38°C to 45°C. As the liquid working fluid flows through the power electronics heat exchange unit and the turbine generator heat exchange unit, it simultaneously acts as a cooling medium to cool the corresponding equipment, controlling the operating temperature of the power electronics equipment between 60°C and 80°C, and controlling the turbine generator casing temperature between 65°C and 90°C. The beneficial effect of this step is that it transforms the heat generated by the waste of the originally abandoned equipment into a heat source for preheating the working fluid, while simplifying the equipment's cooling system.

[0049] Step S300: The liquid working fluid, after primary preheating, is fed into the regenerative module. Secondary preheating is performed using the working fluid gas (temperature approximately 65°C to 85°C) discharged from the turbine power generation module after it has performed work. After this step, the temperature of the liquid working fluid increases from approximately 38°C to 45°C to approximately 55°C to 75°C, while the turbine exhaust temperature correspondingly decreases from 65°C to 85°C to 38°C to 50°C. The principle behind this step is that the working fluid gas discharged from the turbine power generation module still has a relatively high temperature, which is transferred to the liquid working fluid through the regenerative module, thus both increasing the temperature of the liquid working fluid and reducing the cooling load on the condenser.

[0050] Step S400: The working fluid, after two stages of preheating, is fed into the waste heat recovery module, where it is heated by an external waste heat source (in this example, 200°C cement kiln exhaust gas) to generate a high-temperature, high-pressure working fluid gas. The working fluid is heated from a liquid or two-phase state of approximately 55°C to 75°C to a superheated gaseous state of 130°C to 165°C, with a pressure of approximately 1.8 MPa to 2.0 MPa. Because the working fluid has undergone the aforementioned two stages of preheating, its temperature upon entering the waste heat recovery module is significantly increased, allowing the module to utilize the external heat source more efficiently.

[0051] Step S500: The high-temperature, high-pressure working gas is fed into the turbine power generation module to generate electricity. The high-temperature, high-pressure working gas drives the turbine impeller to rotate at high speed, with the turbine speed being approximately 30,000 rpm to 50,000 rpm, converting thermal and pressure energy into mechanical energy to drive the generator to produce electrical energy. The isentropic efficiency of the turbine is typically between 70% and 85%, and the generator efficiency is typically between 90% and 97%. After the work is done, the temperature of the working gas decreases to 65°C to 85°C, and the pressure decreases to 0.15 MPa to 0.25 MPa.

[0052] Step S600: After the work is done, the working gas discharged is partially heated by the regenerator module and then returned to the working gas circulation module to condense into a liquid working gas, entering the next cycle. The working gas after the work is done first enters the regenerator module, transferring some heat to the liquid working gas in step S300. The gas temperature decreases from 65℃ to 85℃ to 38℃ to 50℃, then enters the condenser to condense into a liquid working gas at 25℃ to 35℃, and then returns to the working gas tank. At this point, the working gas completes one full cycle.

[0053] It should be noted that when the system structure of the fourth embodiment is adopted, the first-level preheating in step S200 only includes one heating, which corresponds to heating the liquid working fluid by utilizing the heat loss of the power electronic equipment or the heat loss of the turbine generator.

[0054] The ORC waste heat power generation method provided in the fifth embodiment achieves full recovery and cascade utilization of heat at each stage during system operation through a multi-stage heating process of loss preheating, reheating, and waste heat recovery, which significantly improves the overall waste heat recovery efficiency and power generation efficiency of the system.

[0055] In practical engineering applications, the ORC waste heat power generation system of this invention also needs to consider the following factors during design: Regarding pipeline design, the pipe diameter for each section should be designed based on the working fluid flow rate and velocity. For liquid working fluid pipelines (i.e., the pipeline between the working fluid pump outlet and the waste heat recovery module inlet), the working fluid velocity is typically controlled between 1.0 m / s and 3.0 m / s. For R245fa working fluid with a flow rate of 1.5 kg / s to 2.0 kg / s, the corresponding pipe diameter is typically DN25 to DN40. For gaseous working fluid pipelines (i.e., the pipeline between the waste heat recovery module outlet and the turbine inlet, and between the turbine exhaust port and the regenerative module), due to the lower density of the gaseous working fluid, the flow velocity is typically controlled between 10 m / s and 30 m / s, and the corresponding pipe diameter is typically DN50 to DN100. 304 stainless steel or 316L stainless steel is preferred for pipeline materials to ensure corrosion resistance and compatibility with organic working fluids.

[0056] Regarding the system control strategy, the ORC system of this invention typically employs a PLC or DCS control system for automated control. Key control parameters include: the working fluid pump speed or frequency (adjusted via a frequency converter to regulate working fluid flow), the opening of the flow control valve on the heat source side of the waste heat recovery module, the cooling water flow or fan speed of the condenser, and the turbine inlet guide vane opening. During system operation, the control system monitors the working fluid temperature and pressure of each pipeline section in real time and automatically adjusts the working fluid pump speed and the operating parameters of each heat exchanger based on changes in the temperature and flow of the external waste heat source to maintain the system operating at its optimal point. Specifically, when fluctuations occur in the temperature or flow of the external waste heat source, the control system should be able to adjust the working fluid flow in a timely manner to prevent droplet entrainment at the turbine inlet and ensure safe and stable system operation.

[0057] Regarding safety protection measures, the system should be equipped with safety valves at the following critical locations: the working fluid pump outlet, the waste heat recovery module outlet, and the top of the working fluid tank. The opening pressure of the safety valves should be set to 1.1 to 1.15 times the system design pressure. In addition, the system should be equipped with an emergency shutdown function, which can automatically cut off the heat source and stop the working fluid pump when abnormal increases in waste heat source temperature, abnormal working fluid pump outlet pressure, or abnormal turbine speed are detected. Temperature sensors should be installed on the power electronic equipment and turbine generator; when the equipment temperature exceeds a set threshold, the control system should increase the working fluid flow rate or issue an alarm signal.

[0058] Regarding the determination of the working fluid charge, the total working fluid charge of the system should consider the following factors: the internal volume of each heat exchanger and pipeline, the storage capacity of the working fluid tank (usually 30% to 50% of the total system working fluid mass), and a make-up margin. For a system with a net power generation of 100kW, when using R245fa working fluid, the total working fluid charge is usually between 50kg and 200kg, depending on the system's pipeline length, heat exchanger volume, and working fluid tank size. A certain liquid level should be maintained in the working fluid tank, usually not less than 20% of the tank height, to ensure that the working fluid pump can always draw in liquid working fluid normally and avoid gas leakage.

[0059] To more intuitively illustrate the technical effects of the present invention, a performance comparison between the ORC system of the present invention and the prior art is given below. Taking the operating condition example one (R245fa working fluid, 200℃ heat source, 100kW net power generation) as the benchmark, the system performance of the three schemes is compared.

[0060] Table 3 compares the system performance of the three schemes.

[0061] As shown in Table 3, compared to the basic ORC system, the proposed solution increases the net power generation by approximately 10kW. Part of this increase comes from the recovery of heat generated by losses, which raises the coke value of the working fluid entering the turbine, thus increasing the turbine's output power. Another part comes from the auxiliary energy savings achieved by removing the independent cooling system. The combined effect of these two factors results in an overall system thermal efficiency improvement of approximately 8% to 12%.

[0062] Further explanation regarding the selection of working fluids: different organic working fluids have different thermophysical properties and are suitable for different waste heat temperature ranges. Table 4 lists the main thermophysical parameters of several common organic working fluids.

[0063] Table 4 compares the thermophysical parameters of common organic working fluids.

[0064] As shown in Table 4, for applications with waste heat temperatures ranging from 80℃ to 200℃, R245fa and R1233zd(E) are suitable working fluid choices. R1233zd(E) has a GWP value of only 1, far lower than R245fa's 1030, making it an environmentally friendly working fluid with better application prospects under increasingly stringent environmental regulations. For applications with lower waste heat temperatures (60℃ to 120℃), low-boiling-point working fluids such as R134a or R1234ze(E) can be selected. The choice of working fluid directly affects the system's operating pressure, flow rate, heat exchanger area, and turbine design parameters; therefore, a comprehensive evaluation and selection should be made based on the specific waste heat source conditions and system design requirements.

[0065] Regarding the installation method of the loss preheating module, the power electronics heat exchange unit 210 is typically installed as follows: a liquid-cooled plate or microchannel heat exchanger is installed on the cabinet or distribution box of the power electronic equipment. The working fluid is connected to the main circulation pipeline through inlet and outlet joints. The liquid-cooled plate has serpentine or parallel working fluid channels inside, and the working fluid absorbs the heat generated by the power electronic devices when flowing in the channels. For IGBT modules with large heat generation, a direct contact liquid-cooled plate can be used to ensure that the thermal resistance is less than 0.1℃ / W. The turbine generator heat exchange unit 220 is typically installed as follows: a liquid-cooled sleeve is wrapped or covered around the turbine generator casing. The sleeve and the generator casing are tightly fitted with thermally conductive adhesive or fastening clamps. The working fluid is connected to the main circulation pipeline through the inlet and outlet of the sleeve. The number of turns and the diameter of the sleeve are designed according to the heat generation of the generator and the size of the casing, and copper or stainless steel tubes with an outer diameter of 8mm to 16mm are typically used.

[0066] Regarding the system's scope of application, the ORC waste heat power generation system of this invention is applicable to various waste heat source scenarios, including but not limited to: waste heat recovery from industrial kilns such as cement, ceramics, and glass; waste heat recovery from exhaust gases of internal combustion engines, gas turbines, and diesel generator sets; geothermal power generation; solar thermal power generation; biomass combustion power generation; and waste heat recovery from process industries such as steel and chemicals. For all the above application scenarios, the working principle of the loss preheating module 200 is the same, enabling it to incorporate the heat loss from power electronic equipment and / or turbine generators into the waste heat recovery scope, thereby improving the overall thermal efficiency of the system. In different application scenarios, it is only necessary to select a suitable working fluid and adjust the heat exchange area of ​​each heat exchanger and the system operating pressure according to the temperature, flow rate, and other parameters of the external waste heat source.

[0067] Regarding the system startup and shutdown procedures, during startup, the condenser's cooling water pump or fan should be started first to bring the condenser to normal operating condition. Then, the working fluid pump should be started at a low speed to allow the working fluid to begin circulating in the system. Subsequently, an external waste heat source should be gradually introduced, and the working fluid pump speed should be gradually increased according to the superheat of the working fluid at the turbine inlet until the system reaches stable operating conditions. During startup, the loss preheating module 200 plays a particularly significant role because, in the initial startup phase, before the external waste heat source is fully engaged, the power electronic equipment and turbine generator begin to generate loss heat. The loss preheating module 200 can effectively preheat the working fluid at this stage, accelerating the system's progress to a stable operating state. During shutdown, the external waste heat source should be cut off first to allow the turbine inlet working fluid temperature to gradually decrease. When the turbine output power drops below the set threshold, the turbine should be stopped and the working fluid pump speed reduced. Finally, the working fluid pump and condenser cooling system should be stopped.

[0068] Regarding system maintenance and repair, the ORC system of this invention should be checked regularly during normal operation, including: whether the working fluid charge is sufficient (by observing the working fluid tank level gauge), whether the heat exchange efficiency of each heat exchanger has decreased (by monitoring temperature differences in each pipeline section), the operating status of the working fluid pump (including vibration, noise, and sealing), the sealing of pipeline joints, and the accuracy of control system sensors. For the loss preheating module 200, special attention should be paid to the sealing of the interfaces between the power electronic heat exchange unit 210 and the turbine generator heat exchange unit 220 and the main circulation pipeline, as well as the fit between the heat exchange unit and the equipment casing. It is recommended to conduct a comprehensive inspection every 1000 to 2000 hours of operation and a quality test of the working fluid every 3000 to 5000 hours to confirm whether its chemical stability and thermophysical properties have changed.

[0069] Regarding pressure drop control on the working fluid side, the preheating module 200, while preheating the working fluid, generates some flow resistance, leading to a decrease in working fluid pressure. During design, the total pressure drop of the preheating module 200 should be controlled within 5% of the total system pressure difference. Specifically, for systems with operating pressures between 2.0 MPa and 2.5 MPa, the pressure drop of the preheating module 200 should not exceed 0.1 MPa to 0.15 MPa. To reduce pressure drop, measures such as increasing the working fluid flow cross-sectional area of ​​the heat exchange unit, optimizing the working fluid flow channel design, or adopting a parallel multi-channel structure can be used. Reasonable pressure drop control ensures that the working fluid maintains sufficient pressure when entering the waste heat recovery module 400, thereby guaranteeing the stability of the turbine inlet working fluid parameters.

[0070] The following is a specific application scenario example to further illustrate the implementation conditions of this invention. The exhaust gas temperature of a rotary kiln in a cement plant is approximately 250℃, and the exhaust gas flow rate is approximately 5000 Nm³. 3The system can provide approximately 500kW of waste heat power per hour. The ORC waste heat power generation system of this invention uses R245fa as the circulating working fluid. The system design parameters are as follows: working fluid pump outlet pressure 2.5MPa, working fluid flow rate 2.0kg / s, a three-stage series shell-and-tube heat exchanger (preheating section + evaporation section + superheating section) for waste heat recovery, a radial turbine with a design speed of 35000rpm and an isentropic efficiency of approximately 80%. The loss preheating module adopts the dual heat exchange unit series scheme of the third embodiment. The power electronic equipment loss heat generation is approximately 8kW (using an IGBT module inverter, operating temperature approximately 85℃), and the turbine generator loss heat generation is approximately 4kW (permanent magnet synchronous generator, casing temperature approximately 95℃). Calculations show that the net power generation of this system is approximately 90kW, which is an increase of approximately 9kW compared to the traditional scheme without a loss preheating module, representing an increase of approximately 11%. The plant operates for approximately 7,500 hours per year, which can increase annual power generation by about 67,500 kWh. Based on an industrial electricity price of 0.7 yuan / kWh, this translates to an annual increase in revenue of about 47,000 yuan.

[0071] Another application example is waste heat recovery from the exhaust of marine diesel generator sets. The exhaust temperature of a certain marine diesel generator set is approximately 350℃, and the exhaust flow rate is approximately 2000 Nm³. 3 The system provides approximately 300kW of waste heat power per hour. Using the ORC system of this invention, R1233zd(E) is selected as the circulating working fluid (due to its low GWP value, meeting the environmental requirements of the International Maritime Organization). The system design parameters are as follows: working fluid pump outlet pressure 3.0MPa, working fluid flow rate 1.8kg / s, and turbine inlet working fluid temperature approximately 190℃. The loss preheating module also adopts a dual heat exchange unit series scheme, which can raise the working fluid temperature by 13℃ to 16℃. In marine applications, another significant advantage of the loss preheating module is that, given the limited space in ship engine rooms, removing independent power electronics equipment and generator cooling systems can significantly reduce the system's footprint and weight, which is of great importance for marine applications.

[0072] The above description is merely a specific embodiment of the present invention and does not limit the patent scope of the present invention. Equivalent substitutions or changes made by those skilled in the art based on the technical solutions of the present invention regarding the specific types, materials, parameters, etc., of each module, unit, or component, as well as adjustments to the working fluid temperature and pressure parameters of each pipeline section, should all fall within the protection scope of the present invention. Similarly, any equivalent structural or process transformations made using the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are also included within the patent protection scope of the present invention.

Claims

1. An ORC waste heat power generation system, characterized in that, include: Working fluid circulation module, loss preheating module, regeneration module, waste heat recovery module and turbine power generation module; The working fluid circulation module is used to drive the liquid working fluid to circulate in the system and to condense and recover the working fluid gas after it has done work back into liquid working fluid; The loss preheating module is located on the output side of the working fluid circulation module and is used to preheat the liquid working fluid in the first stage by utilizing the loss heat generated during the operation of the system; the loss heat comes from at least one of the loss heat of power electronic equipment and the loss heat of turbine generator. The regenerative module is located downstream of the loss preheating module and is used to use the working gas discharged after the turbine power generation module does work as a heat source to perform secondary preheating on the liquid working gas after primary preheating. The waste heat recovery module is located between the heat recovery module and the turbine power generation module, and is used to heat the working fluid using an external waste heat source to generate a high-temperature and high-pressure working fluid gas. The turbine power generation module is used to receive the high-temperature and high-pressure working gas to generate electricity; after the working gas is discharged, it releases some heat through the regeneration module and then flows back to the working gas circulation module.

2. The ORC waste heat power generation system according to claim 1, characterized in that, The working fluid circulation module includes a working fluid storage unit, a working fluid driving unit, and a condensation unit; The working fluid storage unit is used to store liquid working fluid; The working fluid driving unit is used to pressurize and output the liquid working fluid in the working fluid storage unit to the loss preheating module; The condensation unit is located between the exhaust side of the regenerative module and the working fluid storage unit, and is used to condense the working fluid gas into a liquid working fluid and return it to the working fluid storage unit.

3. The ORC waste heat power generation system according to claim 2, characterized in that, The working fluid storage unit is a working fluid tank; the working fluid driving unit is a working fluid pump; and the condensation unit is a condenser.

4. The ORC waste heat power generation system according to claim 1, characterized in that, The loss preheating module includes a power electronic heat exchange unit and a turbine generator heat exchange unit, which are connected in series along the working fluid flow direction. The power electronic heat exchange unit is used to heat the liquid working fluid once by utilizing the heat loss generated during the operation of the power electronic equipment. The turbine generator heat exchange unit is used to reheat the liquid working fluid that has been heated once by utilizing the heat loss generated during the operation of the turbine generator.

5. The ORC waste heat power generation system according to claim 4, characterized in that, The power electronics heat exchange unit is a liquid-cooled heat exchanger covering the outside of the power electronics equipment; and / or, the turbine generator heat exchange unit is a liquid-cooled jacket covering the turbine generator housing.

6. The ORC waste heat power generation system according to claim 4, characterized in that, The power electronics heat exchange unit also serves as the cooling and heat dissipation structure for the power electronics equipment, and the turbine generator heat exchange unit also serves as the cooling and heat dissipation structure for the turbine generator. The system no longer has separate cooling systems for the power electronics equipment and the turbine generator.

7. The ORC waste heat power generation system according to claim 1, characterized in that, The waste heat recovery module includes a single or multiple plate heat exchanger or shell-and-tube heat exchanger connected in series; and / or, the heat recovery module includes a single or multiple plate heat exchanger or shell-and-tube heat exchanger connected in series.

8. The ORC waste heat power generation system according to claim 1, characterized in that, The loss preheating module includes only one of the power electronic heat exchange unit or the turbine generator heat exchange unit. When the loss preheating module only includes the power electronic heat exchange unit, the turbine generator is equipped with an independent cooling system; When the loss preheating module only includes the turbine generator heat exchange unit, the power electronic equipment is equipped with an independent cooling system.

9. The ORC waste heat power generation method, characterized in that, The method, applied to the ORC waste heat power generation system according to any one of claims 1 to 8, comprises: The liquid working fluid is driven into the circulation pipeline by the working fluid circulation module; The liquid working fluid is preheated in the first stage by utilizing the heat generated during system operation through the loss preheating module, wherein the heat generated during loss originates from power electronic equipment and / or turbine generator; The liquid working fluid, after primary preheating, is sent to the regenerative module, and the working fluid gas discharged after the turbine power generation module does work is used as a heat source for secondary preheating. The working fluid, after being preheated in two stages, is sent to the waste heat recovery module, where it is heated by an external waste heat source to generate a high-temperature, high-pressure working fluid gas. The high-temperature and high-pressure working gas is sent into the turbine power generation module to generate electricity. After the working gas is discharged after doing work, it releases some heat through the heat recovery module and then flows back to the working gas circulation module to condense into liquid working gas, thus completing the system cycle.

10. The ORC waste heat power generation method according to claim 9, characterized in that, The primary preheating includes a first heating and a second heating performed sequentially. The first heating uses the heat generated by the power electronic equipment losses to heat the liquid working fluid through a power electronic heat exchange unit. The second heating uses the heat generated by the turbine generator losses to heat the liquid working fluid after the first heating through a turbine generator heat exchange unit. As the liquid working fluid flows through the power electronic heat exchange unit and the turbine generator heat exchange unit, it also acts as a cooling medium to cool and dissipate heat from the corresponding equipment.

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