A two-stage absorption cogeneration system based on different types of power cycles

Abstract

The present invention discloses a two-stage absorption cogeneration system based on different types of power cycles. It utilizes the characteristics of absorption heat pumps and uses the high-temperature heat source to drive the low-temperature waste heat source in a cascade manner. The system includes: a first-stage absorption heat pump, a second-stage absorption heat pump, and a power cycle system. The driving heat source flows through the first generator and the second generator in sequence. The low-temperature waste heat source first transfers heat to the circulating working fluid through the evaporator in the power cycle system, and then enters the second-stage absorption heat pump and the evaporator in the first-stage absorption heat pump in sequence. The working fluid in the power cycle expands and performs work after being heated through three branches, outputting electrical energy. The heat released by the first absorber is used for regional heating. The present invention can utilize waste heat and low-temperature heat in various temperature ranges to achieve large temperature difference heat exchange of waste heat sources, significantly reduce the outlet temperature, thereby improving the utilization rate of waste heat sources, and reducing the consumption of fossil fuels while meeting electricity and heating needs.

Description

Technical Field

[0001] The present invention belongs to the field of energy technology, relates to the fields of absorption heat pump cycle, power cycle and cogeneration, and in particular to a two-stage absorption cogeneration system based on different types of power cycles. Background Art

[0002] Power cycles, such as the organic Rankine cycle, organic flash cycle, Brayton cycle, or Kalina cycle, play a crucial role in waste heat recovery, combined heat and power (CHP), renewable energy generation, and energy storage. Regardless of their application, the evaporator side of the power cycle utilizes very low thermal energy from the heat source, resulting in the outlet temperature of the hot-side fluid being much higher than the inlet temperature of the cold-side fluid.

[0003] Research on power cycles mainly focuses on improving the system cycle form, developing important components, optimizing key parameters, screening working fluids, and changing heat sources. Few studies have taken into account the low utilization rate of heat source thermal energy, and there has never been a good way to solve the problem of excessively high fluid temperature at the heat source outlet. Summary of the Invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a two-stage absorption cogeneration system based on different types of power cycles to further improve the thermal energy utilization rate of low-temperature waste heat sources such as waste heat sources not exceeding 150°C.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A two-stage absorption cogeneration system based on different types of power cycles includes an absorption heat pump circulation system and a power circulation system; the absorption heat pump circulation system includes a first-stage absorption heat pump and a second-stage absorption heat pump; the first-stage absorption heat pump includes a first generator, a first condenser, a first evaporator, a first absorber, and a first solution heat exchanger; the second-stage absorption heat pump includes a second generator, a second condenser, a second evaporator, a second absorber, and a second solution heat exchanger;

[0007] After the power cycle system performs work, the circulating medium is divided into three branches. The first branch flows to the first condenser; the second branch flows through the second absorber and the second condenser in sequence; and the third branch flows to the third evaporator to be heated by the low-temperature waste heat source. The circulating medium in the three branches is combined to perform work and release heat in the power cycle system to generate electricity.

[0008] The low-temperature waste heat source exiting the third evaporator flows through the second evaporator and the first evaporator in sequence and releases heat;

[0009] The driving heat source flows through the first generator and the second generator in sequence and releases heat.

[0010] In one embodiment, the first-stage absorption heat pump and the second-stage absorption heat pump both use lithium bromide solution as the working medium;

[0011] The liquid phase outlet of the first generator is a concentrated lithium bromide solution, which is connected to the hot side inlet of the first solution heat exchanger, and the hot side outlet of the first solution heat exchanger is connected to the liquid phase inlet of the first absorber through a second throttle valve; the gas phase outlet of the first generator is water vapor, which is connected to the hot side inlet of the first condenser, and the hot side outlet of the first condenser is connected to the cold side inlet of the first evaporator through a first throttle valve, and the cold side outlet of the first evaporator is connected to the gas phase inlet of the first absorber; the hot side outlet of the first absorber is a dilute lithium bromide solution, which is connected to the cold side inlet of the first solution heat exchanger through a first booster pump, and the cold side outlet of the first solution heat exchanger is connected to the cold side inlet of the first generator, completing the entire absorption heat pump cycle;

[0012] The liquid phase outlet of the second generator is a concentrated lithium bromide solution, which is connected to the hot side inlet of the second solution heat exchanger, and the hot side outlet of the second solution heat exchanger is connected to the liquid phase inlet of the second absorber through the fourth throttle valve; the gas phase outlet of the second generator is water vapor, which is connected to the hot side inlet of the second condenser, and the hot side outlet of the second condenser is connected to the cold side inlet of the second evaporator through the third throttle valve, and the cold side outlet of the second evaporator is connected to the gas phase inlet of the second absorber; the hot side outlet of the second absorber is a dilute lithium bromide solution, which is connected to the cold side inlet of the second solution heat exchanger through the second booster pump, and the cold side outlet of the second solution heat exchanger is connected to the cold side inlet of the second generator, completing the entire absorption heat pump cycle.

[0013] In one embodiment, the first generator is composed of a first heat exchanger and a first two-phase separator, the hot side inlet of the first heat exchanger is the hot side inlet of the first generator, connected to the driving heat source, the cold side inlet of the first heat exchanger is the cold side inlet of the first generator, and the cold side outlet is connected to the first two-phase separator, the liquid phase outlet of the first two-phase separator is the liquid phase outlet of the first generator, and the gas phase outlet is the gas phase outlet of the first generator;

[0014] The first absorber is composed of a third heat exchanger and a first mixer, wherein the first inlet of the first mixer is the liquid phase inlet of the first absorber, the second inlet is the gas phase inlet of the first absorber, the outlet of the first mixer is connected to the hot side inlet of the third heat exchanger, and the hot side outlet of the third heat exchanger is the hot side outlet of the first absorber;

[0015] The second generator is composed of a second heat exchanger and a second two-phase separator, the hot side inlet of the second heat exchanger is the hot side inlet of the second generator, connected to the hot side outlet of the first heat exchanger, the cold side inlet of the second heat exchanger is the cold side inlet of the second generator, and the cold side outlet is connected to the second two-phase separator, the liquid phase outlet of the second two-phase separator is the liquid phase outlet of the second generator, and the gas phase outlet is the gas phase outlet of the second generator;

[0016] The second absorber consists of a fourth heat exchanger and a second mixer, the first inlet of the second mixer is the liquid phase inlet of the second absorber, the second inlet is the gas phase inlet of the second absorber, the outlet of the second mixer is connected to the hot side inlet of the fourth heat exchanger, and the hot side outlet of the fourth heat exchanger is the hot side outlet of the second absorber.

[0017] In one embodiment, the first absorber is connected to a district heating network, and the district heating network receives the heat released by the first absorber to provide domestic hot water to heat users.

[0018] In one embodiment, the concentration of the lithium bromide solution in the first-stage absorption heat pump is greater than the concentration of the lithium bromide solution in the second-stage absorption heat pump; the flow rate of the first-stage absorption heat pump is greater than the flow rate of the lithium bromide solution in the second-stage absorption heat pump; the pressure after throttling by the second throttle valve is less than the pressure after throttling by the fourth throttle valve; and the pressure after throttling by the first throttle valve is less than the pressure after throttling by the third throttle valve.

[0019] In one embodiment, the working fluid exiting the first condenser, the second condenser and the third evaporator flows into the third mixer; the third mixer and the third evaporator are both components of the power circulation system; the outlet of the third mixer is connected to the working part of the power circulation system to provide it with high-temperature working fluid.

[0020] In one embodiment, when the temperature of the low-temperature waste heat source is 90-150°C, the third branch flows through the third evaporator; the low-temperature waste heat source heats the circulating working fluid to a saturated gas state or a superheated state in the third evaporator, and the temperature drops to 30°C after leaving the first evaporator.

[0021] In one embodiment, when the temperature of the low-temperature waste heat source is below 90° C., the low-temperature waste heat source directly flows into the second evaporator, and the third branch is omitted.

[0022] In one embodiment, for low-temperature waste heat sources with different flow rates, the flow rate of the power cycle working fluid in the third branch flowing to the third evaporator can be adjusted, or the flow rate of the lithium bromide solution in the absorption heat pump cycle can be adjusted, thereby reducing the final outlet temperature of the waste heat source to a lower level.

[0023] In one embodiment, the power cycle system is an organic Rankine cycle system, an organic flash cycle system, a Brayton cycle system or a Kalina cycle system; the circulating working fluid after doing work releases heat in the third condenser and is taken away by cooling water to provide hot water to heat users.

[0024] In one embodiment, according to the changes in heating and power supply demands, the heat released in the first condenser, or the second absorber and the second condenser, or the third evaporator is used to provide domestic hot water, thereby achieving matching and adjustment of heating and power supply demands.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. Applying heat-increasing absorption heat pump technology, with high-temperature water vapor as the driving heat source, and cascading utilization of low-temperature waste heat sources (150°C and below), the outlet temperature of the waste heat source can be reduced to 30°C, greatly improving the utilization rate of the heat source.

[0027] 2. Combining thermal cycle with absorption heat pump technology, a new type of cogeneration coupling system is proposed to efficiently convert the thermal energy of the heat source into electrical energy and the thermal energy required by heat users without wasting heat energy.

[0028] 3. The use of a two-stage absorption heat pump can reduce heat exchange losses during the heat exchange process and has better thermodynamic performance.

[0029] 4. For the absorber in the first-stage absorption heat pump, the heat energy at a lower temperature level released is used for district heating; for the condenser in the first-stage absorption heat pump and the second absorber and condenser, the heat energy at a higher temperature level released is used to generate electricity using an organic Rankine cycle.

[0030] 5. When the demand for heating is large, the heat released by the condenser in the first-stage absorption heat pump, or the second absorber or condenser, or the evaporator of the organic Rankine cycle can be selectively used for heating, so as to achieve flexible matching and adjustment of heating and power supply needs.

[0031] 6. Waste heat sources in different temperature ranges or other low-temperature waste heat sources such as geothermal heat can be utilized. When the temperature is low, the evaporator in the power cycle can be omitted.

[0032] 7. For waste heat sources with different flow rates, the flow rate of the circulating working fluid in the third branch flowing to the power cycle evaporator can be adjusted, or the flow rate of the lithium bromide solution in the absorption heat pump cycle can be adjusted to reduce the final outlet temperature of the waste heat source to the lowest level, thereby achieving flexible control of the system.

[0033] 8. The proposed cogeneration system is applicable to different types of power cycles, such as organic Rankine cycle, organic flash cycle, Brayton cycle or Kalina cycle, which can significantly reduce the final outlet temperature of the heat source and improve the utilization rate of the heat source. Different power cycles can be selected according to the actual project.

[0034] In summary, compared with conventional power cycles, the present invention can greatly improve the heat source utilization rate and thermal energy conversion rate without significantly increasing the cost, thereby bringing more power supply and heating benefits, and is both thermally economical and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural schematic diagram of the present invention. DETAILED DESCRIPTION

[0036] The embodiments of the present invention are described in detail below with reference to the accompanying drawings and examples.

[0037] like Figure 1 As shown, the present invention is a two-stage absorption cogeneration system based on different types of power cycles, mainly comprising an absorption heat pump circulation system and a power circulation system. The absorption heat pump circulation system further comprises a first-stage absorption heat pump and a second-stage absorption heat pump. Absorption heat pumps are also known as heat-increasing heat pumps. In the present invention, the first-stage absorption heat pump mainly comprises a first generator, a first condenser 3, a first evaporator 5, a first absorber, and a first solution heat exchanger 6; the second-stage absorption heat pump mainly comprises a second generator, a second condenser 13, a second evaporator 15, a second absorber, and a second solution heat exchanger 16.

[0038] The circulating working fluid of the power cycle system of the present invention after doing work is divided into three branches. The first branch flows to the first condenser 3; the second branch flows through the second absorber and the second condenser 13 in sequence; according to the temperature range of the low-temperature waste heat source, the third branch flows to the third evaporator 26 and is heated by the low-temperature waste heat source; the circulating working fluids of the three branches converge, do work and release heat in the power cycle system, and generate electricity; the low-temperature waste heat source leaving the third evaporator 26 flows through the second evaporator 15 and the first evaporator 5 in sequence and releases heat; the driving heat source flows through the first generator and the second generator in sequence and releases heat.

[0039] According to the above structure, the present invention combines the absorption heat pump circulation system and the power circulation system, utilizes the characteristics of the absorption heat pump, and drives the heat source to perform cascade utilization of the low-temperature waste heat source. It can utilize waste heat and low-temperature heat in various temperature ranges to achieve large temperature difference heat exchange of the waste heat source, greatly reduce the outlet temperature of the waste heat source, thereby improving the thermal energy utilization rate of the heat source and meeting the power supply and heating needs, realizing efficient and clean use of energy, and effectively solving the problem of low heat source utilization rate.

[0040] For example, the driving heat source of the absorption heat pump of the present invention can be a high-temperature heat source such as high-temperature water vapor, hot water, or combustible gas combustion heat. The high-temperature water vapor generated by the boiler in the chemical plant is generally above 200°C. Therefore, the present invention uses 230°C water vapor generated by the chemical plant as the driving heat source of the absorption heat pump.

[0041] The low-temperature waste heat of the present invention can be waste hot water, industrial flue gas, thermal oil, etc. The present invention uses waste hot water with a temperature below 150°C as the low-temperature heat source.

[0042] Specifically, when the temperature of the low-temperature waste heat source is between 90°C and 150°C, the third branch flows through the third evaporator 26. In the third evaporator 26, the low-temperature waste heat source heats the circulating medium to a saturated gaseous state or a superheated state. The medium then enters the second evaporator 15 and the first evaporator 5 in sequence, ultimately leaving the first evaporator 5 at a temperature of 30°C. When the temperature of the low-temperature waste heat source is below 90°C, it flows directly into the second evaporator 15, eliminating the third branch. Low-temperature waste heat sources below 90°C can also be replaced with geothermal or other low-temperature heat sources.

[0043] In an embodiment of the present invention, different heat engines such as an organic Rankine cycle, an organic flash cycle, a Brayton cycle or a Kalina cycle may be used. The low-temperature waste heat source releases heat in the power cycle system, and the absorption heat pump plays the role of heating the working medium.

[0044] In an embodiment of the present invention, an absorption heat pump system uses lithium bromide solution as the working medium, and the power cycle system utilizes an organic Rankine cycle heat engine, using R245fa, R134a, or other environmentally friendly organic compounds as the working fluid. The absorption heat pump system uses high-temperature steam as the driving heat source and utilizes low-temperature waste heat in a cascaded manner. A portion of the converted heat energy is used for district heating, while another portion is combined with the organic Rankine cycle to generate electricity. The following describes a detailed description of the specific or preferred system architecture.

[0045] 1. First stage absorption heat pump.

[0046] In the present invention, the components of the first-stage absorption heat pump mainly include a first generator, a first condenser 3 , a first evaporator 5 , a first absorber and a first solution heat exchanger 6 .

[0047] like Figure 1As shown, in the first-stage absorption heat pump, a heat source is first driven into the first generator and releases heat, where the dilute lithium bromide solution is heated to form a two-phase mixture of concentrated lithium bromide solution and water vapor. The liquid phase outlet of the first generator is a concentrated lithium bromide solution, which is connected to the hot-side inlet of the first solution heat exchanger 6. The hot-side outlet of the first solution heat exchanger 6 flows through a second throttle valve 7 into the liquid-phase inlet of the first absorber. The vapor phase outlet of the first generator is superheated water vapor, which is connected to the hot-side inlet of the first condenser 3. The hot-side outlet of the first condenser 3 is a saturated liquid and, after passing through a first throttle valve 4, is connected to the cold-side inlet of the first evaporator 5. The cold-side outlet of the first evaporator 5 is a saturated gas and connected to the vapor phase inlet of the first absorber. The hot-side outlet of the first absorber is a dilute lithium bromide solution, which is connected to the cold-side inlet of the first solution heat exchanger 6 through a first booster pump 10. The cold-side outlet of the first solution heat exchanger 6 is connected to the cold-side inlet of the first generator, completing the entire absorption heat pump cycle.

[0048] Furthermore, the first heat exchanger 1 and the first two-phase separator 2 constitute a first generator, the hot side inlet of the first heat exchanger 1 is the hot side inlet of the first generator, and is connected to the driving heat source, the cold side inlet of the first heat exchanger 1 is the cold side inlet of the first generator, and the cold side outlet is connected to the inlet of the first two-phase separator 2, the liquid phase outlet of the first two-phase separator 2 is the liquid phase outlet of the first generator, and the gas phase outlet is the gas phase outlet of the first generator.

[0049] Furthermore, the third heat exchanger 9 and the first mixer 8 constitute a first absorber, the first inlet of the first mixer 8 is the liquid phase inlet of the first absorber, the second inlet is the gas phase inlet of the first absorber, the outlet of the first mixer 8 is connected to the inlet of the third heat exchanger 9, and the hot side outlet of the third heat exchanger 9 is the hot side outlet of the first absorber.

[0050] Furthermore, the first absorber is connected to a district heating network, which receives the heat released by the first absorber and can provide domestic hot water to heat users.

[0051] 2. Second stage absorption heat pump.

[0052] In the present invention, the components of the second-stage absorption heat pump mainly include a second generator, a second condenser 13 , a second evaporator 15 , a second absorber and a second solution heat exchanger 16 .

[0053] The driving heat source, which has released some heat in the first-stage absorption heat pump, enters the second generator and releases heat there. Here, the dilute lithium bromide solution is heated to form a two-phase mixture of concentrated lithium bromide solution and water vapor. Similar to the first-stage absorption heat pump, the liquid phase outlet of the second generator is a concentrated lithium bromide solution, which is connected to the hot side inlet of the second solution heat exchanger 16. The hot side outlet of the second solution heat exchanger 16 is connected to the liquid phase inlet of the second absorber through a fourth throttle valve 17. The vapor phase outlet of the second generator is superheated water vapor, which is connected to the hot side inlet of the second condenser 13. The hot side outlet of the second condenser 13 is a saturated liquid and is connected to the cold side inlet of the second evaporator 15 through a third throttle valve 14. The cold side outlet of the second evaporator 15 is a saturated gas and is connected to the vapor phase inlet of the second absorber. The hot side outlet of the second absorber is a dilute lithium bromide solution, which is connected to the cold side inlet of the second solution heat exchanger 16 through a second booster pump 20. The cold side outlet of the second solution heat exchanger 16 is connected to the cold side inlet of the second generator, completing the entire absorption heat pump cycle. That is, the water vapor generated in the second generator flows into the second condenser 13, the third throttle valve 14 and the second evaporator 15 in sequence, and finally flows into the second absorber; the lithium bromide concentrated solution generated in the second generator passes through the second solution heat exchanger 16 and the fourth throttle valve 17, enters the second absorber and absorbs the saturated water vapor from the second evaporator 15. The formed lithium bromide dilute solution is preheated in the second solution heat exchanger 16 and finally returns to the second generator.

[0054] Compared to the first-stage absorption heat pump, the lithium bromide solution in the second-stage absorption heat pump cycle has a lower concentration and flow rate. The throttled pressure is higher, resulting in a higher evaporation temperature. The waste heat source first enters the second evaporator 15 and then the first evaporator 5. Therefore, by setting the relevant parameters of the two absorption heat pump cycles to different values, the waste heat source can be utilized in a cascaded manner, reducing heat exchange losses during the heat exchange process and minimizing the outlet temperature.

[0055] Furthermore, the second heat exchanger 11 and the second two-phase separator 12 constitute a second generator, and the second generator consists of the second heat exchanger 11 and the second two-phase separator 12. The hot side inlet of the second heat exchanger 11 is the hot side inlet of the second generator, which is connected to the hot side outlet of the first heat exchanger 1. The cold side inlet of the second heat exchanger 11 is the cold side inlet of the second generator, and the cold side outlet is connected to the inlet of the second two-phase separator 12. The liquid phase outlet of the second two-phase separator 12 is the liquid phase outlet of the second generator, and the gas phase outlet is the gas phase outlet of the second generator.

[0056] Furthermore, the fourth heat exchanger 19 and the second mixer 18 constitute a second absorber, the first inlet of the second mixer 18 is the liquid phase inlet of the second absorber, the second inlet is the gas phase inlet of the second absorber, the outlet of the second mixer 18 is connected to the inlet of the fourth heat exchanger 19, and the hot side outlet of the fourth heat exchanger 19 is the hot side outlet of the second absorber.

[0057] 3. Power circulation system.

[0058] The power cycle system uses an organic Rankine cycle heat engine as an example. The organic Rankine cycle uses R245fa, R134a, or other environmentally friendly organic compounds as the working fluid. The organic working fluid exiting the working fluid pump is divided into three branches. The first branch flows to the first condenser 3, where it is heated by the high-temperature steam in the first condenser 3. The second branch flows to the second condenser 13, where it is heated by the high-temperature steam in the second condenser 13. Alternatively, it flows through the second absorber and the second condenser 13 in sequence, where it is heated by the high-temperature steam in the second condenser 13. Alternatively, it absorbs heat released by the second absorber before being heated by the high-temperature steam in the second condenser 13. The third branch flows to the third evaporator 26 of the organic Rankine cycle. The third evaporator 26 is part of the organic Rankine cycle, and the working fluid in the third branch is heated by a low-temperature waste heat source in the third evaporator 26. Finally, the working fluids in the three branches are heated and then converge in the third mixer 21, which is also part of the organic Rankine cycle. The working fluid output by the third mixer 21 flows into the turbine 22, the working part of the power cycle system, in a saturated gaseous or superheated state, providing it with high-temperature working fluid, which expands and produces work, outputting electrical energy. The exhaust gas at the outlet of turbine 22 is connected to the hot side inlet of the third condenser 23. The hot side outlet of the third condenser 23 is in a saturated liquid state. After being pressurized by the working fluid pump 24, it is connected to the inlet of the diverter 25. The organic working fluid releases heat in the third condenser 23 after work, and is carried away by cooling water to provide hot water to heat users. At the diverter 25, the low-temperature waste heat source with different flow rates is divided into the three branches with different flow rates according to the heat matching requirements. Alternatively, the flow rate of the lithium bromide solution in the absorption heat pump cycle can be adjusted to reduce the final outlet temperature of the waste heat source to a lower level.

[0059] Based on the above system, the specific implementation process of the present invention is as follows:

[0060] The present invention uses 230°C water vapor as the driving heat source, sequentially heating the dilute lithium bromide solution in the first-stage and second-stage absorption heat pump generators, with solution flow rates of 16 kg / s and 8 kg / s, respectively. The components and workflow of the second-stage absorption heat pump are identical to those of the first-stage absorption heat pump. Taking the first-stage absorption heat pump as an example, the first heat exchanger 1 and the first two-phase separator 2 form the first generator, while the third heat exchanger 9 and the first mixer 8 form the first absorber. The driving heat source first enters the generator and releases heat, where the dilute lithium bromide solution is heated to form a two-phase mixture of concentrated lithium bromide solution and water vapor. The concentrated lithium bromide solution enters the first solution heat exchanger 6, preheating the dilute lithium bromide solution. After heat exchange, the concentrated lithium bromide solution passes through the throttling action of the second throttle valve 7, reducing its pressure to 3 kPa and flowing into the absorber. The superheated water vapor generated in the generator enters the first condenser 3, transferring heat to the organic working fluid in the organic Rankine cycle. The water vapor condenses into a saturated liquid, then passes through the first throttle valve 4, reducing its pressure to 3 kPa. It then enters the first evaporator 5, where it is evaporated by the waste heat source into a saturated gas before entering the absorber. In the absorber, the concentrated lithium bromide solution absorbs the water vapor and releases a large amount of heat, which is used for district heating. The absorber outlet is the dilute lithium bromide solution, which passes through a booster pump, increasing its pressure to 300 kPa. It then enters the first solution heat exchanger 6 for preheating and returns to the generator, completing the absorption heat pump cycle. In the second-stage absorption heat pump, the pressure after the throttle valve is throttled is 30 kPa.

[0061] In the power cycle system, an organic Rankine cycle heat engine is used as an example, using R245fa as the working fluid. The organic working fluid exiting the working fluid pump is divided into three branches. The first branch flows to the first condenser 3 of the first-stage absorption heat pump. The second branch flows sequentially through the second absorber and second condenser 13. The third branch flows to the third evaporator 26 of the organic Rankine cycle, where it is heated by a low-temperature waste heat source (90-150°C). For heat sources below 90°C, the third branch is negligible. After absorbing heat, the organic working fluid in the three branches is combined through the third mixer 21 and flows into the turbine 22 in a saturated or superheated state, where it expands and generates work, outputting electrical energy. The expanded working fluid is condensed by cooling water in the third condenser 23. When the condensation temperature is high, the cooling water outlet temperature reaches above 50°C, providing hot water to heat users. The condensed organic working fluid is in saturated liquid state. After being pressurized by the working fluid pump 24, it is divided into three branches with different flow rates by the diverter 25 and enters the absorption heat pump system again. The entire cogeneration system cycle is completed.

[0062] In summary, the present invention leverages the heat-increasing properties of absorption heat pumps, combining a power cycle system with a two-stage absorption heat pump system. Using higher-temperature water vapor as the driving heat source, this system utilizes low-temperature waste heat sources or other low-temperature heat sources (150°C and below) in a cascaded manner. This reduces the waste heat source outlet temperature to 30°C, significantly improving heat source utilization and efficiently converting heat source energy into electricity and heat required by users without wasting heat energy. The present invention utilizes a two-stage absorption heat pump, which reduces heat exchange losses during the heat exchange process, lowers the waste heat source outlet temperature even further, and offers improved thermodynamic performance. Furthermore, when heating demand is high, heat released by the condenser in the first-stage absorption heat pump, the second absorber or condenser, or the evaporator in the power cycle can be selectively used for heating, enabling flexible matching and adjustment of heating and power supply needs. It can also utilize waste heat sources of different temperature ranges or other low-temperature waste heat sources, such as geothermal heat, and eliminate the evaporator in the power cycle when the heat source temperature is low. At the same time, for waste heat sources with different flow rates, the flow rate of the working fluid in the third branch of the power cycle evaporator can be adjusted, or the flow rate of the lithium bromide solution in the absorption heat pump cycle can be adjusted to minimize the final outlet temperature of the waste heat source, achieving flexible control of the system. In short, compared with conventional power cycles, this invention can significantly improve heat source utilization and thermal energy conversion efficiency without significantly increasing costs, thereby generating greater power and heating benefits, achieving both thermal economics and environmental benefits, and reducing fossil fuel consumption.

Claims

1. A two-stage absorption cogeneration system based on different types of power cycles, characterized in that: The invention comprises an absorption heat pump circulation system and a power circulation system; the absorption heat pump circulation system comprises a first-stage absorption heat pump and a second-stage absorption heat pump; the first-stage absorption heat pump comprises a first generator, a first condenser (3), a first evaporator (5), a first absorber and a first solution heat exchanger (6); the second-stage absorption heat pump comprises a second generator, a second condenser (13), a second evaporator (15), a second absorber and a second solution heat exchanger (16); The circulating medium after the power cycle system performs work is divided into three branches. The first branch flows to the first condenser (3); the second branch flows through the second absorber and the second condenser (13) in sequence; the third branch flows to the third evaporator (26) and is heated by the low-temperature waste heat source; the circulating medium of the three branches is combined, performs work and releases heat in the power cycle system, and generates electricity; The low-temperature waste heat source exiting the third evaporator (26) flows through the second evaporator (15) and the first evaporator (5) in sequence and releases heat; The driving heat source flows through the first generator and the second generator in sequence and releases heat.

2. The two-stage absorption cogeneration system based on different types of power cycles according to claim 1 is characterized in that: The first-stage absorption heat pump and the second-stage absorption heat pump both use lithium bromide solution as the working medium; The liquid phase outlet of the first generator is a concentrated lithium bromide solution, which is connected to the hot side inlet of the first solution heat exchanger (6), and the hot side outlet of the first solution heat exchanger (6) is connected to the liquid phase inlet of the first absorber through a second throttle valve (7); the gas phase outlet of the first generator is water vapor, which is connected to the hot side inlet of the first condenser (3), and the hot side outlet of the first condenser (3) is connected to the cold side inlet of the first evaporator (5) through a first throttle valve (4), and the cold side outlet of the first evaporator (5) is connected to the gas phase inlet of the first absorber; the hot side outlet of the first absorber is a dilute lithium bromide solution, which is connected to the cold side inlet of the first solution heat exchanger (6) through a first booster pump (10), and the cold side outlet of the first solution heat exchanger (6) is connected to the cold side inlet of the first generator, completing the entire absorption heat pump cycle; The liquid phase outlet of the second generator is a concentrated lithium bromide solution, which is connected to the hot side inlet of the second solution heat exchanger (16). The hot side outlet of the second solution heat exchanger (16) is connected to the liquid phase inlet of the second absorber through a fourth throttle valve (17); the gas phase outlet of the second generator is water vapor, which is connected to the hot side inlet of the second condenser (13). The hot side outlet of the second condenser (13) is connected to the cold side inlet of the second evaporator (15) through a third throttle valve (14). The cold side outlet of the second evaporator (15) is connected to the gas phase inlet of the second absorber; the hot side outlet of the second absorber is a dilute lithium bromide solution, which is connected to the cold side inlet of the second solution heat exchanger (16) through a second booster pump (20). The cold side outlet of the second solution heat exchanger (16) is connected to the cold side inlet of the second generator, completing the entire absorption heat pump cycle.

3. The two-stage absorption cogeneration system based on different types of power cycles according to claim 2, characterized in that: The first generator is composed of a first heat exchanger (1) and a first two-phase separator (2), the hot side inlet of the first heat exchanger (1) is the hot side inlet of the first generator, connected to the driving heat source, the cold side inlet of the first heat exchanger (1) is the cold side inlet of the first generator, and the cold side outlet is connected to the first two-phase separator (2), the liquid phase outlet of the first two-phase separator (2) is the liquid phase outlet of the first generator, and the gas phase outlet is the gas phase outlet of the first generator; The first absorber is composed of a third heat exchanger (9) and a first mixer (8), the first inlet of the first mixer (8) is the liquid phase inlet of the first absorber, the second inlet is the gas phase inlet of the first absorber, the outlet of the first mixer (8) is connected to the hot side inlet of the third heat exchanger (9), and the hot side outlet of the third heat exchanger (9) is the hot side outlet of the first absorber; The second generator is composed of a second heat exchanger (11) and a second two-phase separator (12), the hot side inlet of the second heat exchanger (11) is the hot side inlet of the second generator, connected to the hot side outlet of the first heat exchanger (1), the cold side inlet of the second heat exchanger (11) is the cold side inlet of the second generator, and the cold side outlet is connected to the second two-phase separator (12), the liquid phase outlet of the second two-phase separator (12) is the liquid phase outlet of the second generator, and the gas phase outlet is the gas phase outlet of the second generator; The second absorber is composed of a fourth heat exchanger (19) and a second mixer (18), the first inlet of the second mixer (18) is the liquid phase inlet of the second absorber, the second inlet is the gas phase inlet of the second absorber, the outlet of the second mixer (18) is connected to the hot side inlet of the fourth heat exchanger (19), and the hot side outlet of the fourth heat exchanger (19) is the hot side outlet of the second absorber.

4. The two-stage absorption cogeneration system based on different types of power cycles according to claim 2, characterized in that: The concentration of the lithium bromide solution in the first-stage absorption heat pump is greater than the concentration of the lithium bromide solution in the second-stage absorption heat pump; the flow rate of the first-stage absorption heat pump is greater than the flow rate of the lithium bromide solution in the second-stage absorption heat pump; the pressure after throttling by the second throttle valve (7) is less than the pressure after throttling by the fourth throttle valve (17); and the pressure after throttling by the first throttle valve (4) is less than the pressure after throttling by the third throttle valve (14).

5. The two-stage absorption cogeneration system based on different types of power cycles according to claim 1 is characterized in that: The first absorber is connected to a district heating network, and the district heating network receives the heat released by the first absorber and provides domestic hot water to heat users.

6. The two-stage absorption cogeneration system based on different types of power cycles according to claim 1, characterized in that: The working fluid exiting the first condenser (3), the second condenser (13) and the third evaporator (26) is fed into the third mixer (21); the third mixer (21) and the third evaporator (26) are both components of the power circulation system; the outlet of the third mixer (21) is connected to the working part of the power circulation system to provide it with high-temperature working fluid.

7. The two-stage absorption cogeneration system based on different types of power cycles according to claim 1, characterized in that: When the temperature of the low-temperature waste heat source is 90-150°C, the third branch flows through the third evaporator (26); the low-temperature waste heat source heats the power cycle working medium to a saturated gas state or a superheated state in the third evaporator (26), and the temperature drops to 30°C after leaving the first evaporator (5); when the temperature of the low-temperature waste heat source is below 90°C, the low-temperature waste heat source directly flows into the second evaporator (15), and the third branch is omitted.

8. The two-stage absorption cogeneration system based on different types of power cycles according to claim 1, characterized in that: For low-temperature waste heat sources with different flow rates, the flow rate of the circulating working medium in the third branch flowing to the third evaporator (26) is adjusted, or the flow rate of the lithium bromide solution in the absorption heat pump cycle is adjusted, so as to reduce the final outlet temperature of the waste heat source to a lower level.

9. The two-stage absorption cogeneration system based on different types of power cycles according to claim 1, characterized in that: The power cycle system is an organic Rankine cycle system, an organic flash cycle system, a Brayton cycle system or a Kalina cycle system; the circulating working fluid after doing work releases heat in the third condenser (23) and is taken away by cooling water to provide hot water to heat users.

10. The two-stage absorption cogeneration system based on different types of power cycles according to claim 1, characterized in that: According to the changes in heating and power supply demands, the heat released in the first condenser (3), or the second absorber and the second condenser (13), or the third evaporator (26) is used to provide domestic hot water, thereby achieving matching and adjustment of heating and power supply demands.

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