An absorption-type cogeneration system based on large temperature difference heat exchange

Abstract

The present invention discloses an absorption-type cogeneration system based on large temperature difference heat exchange, which includes two parts: a power cycle system and a two-stage absorption heat exchanger system. The power cycle system is used for power generation, and the two-stage absorption heat exchanger system is used for heat supply. The circulating working fluid expands and does work after being heated in the power cycle system, and outputs electric energy. The district heating network is connected to the absorber and the condenser in the two-stage absorption heat exchanger, and absorbs the released absorption heat and condensation heat to provide hot water to heat users. By utilizing the large temperature difference heat exchange characteristics of the absorption heat exchanger and the high-efficiency power generation ability of the power cycle, the present invention cascades the utilization of low-temperature heat sources, enabling the outlet temperature of the heat source to be lower than the inlet temperature of the cold source, significantly reducing the outlet temperature of the heat source, thereby significantly improving the utilization rate of the heat source energy for power supply and heat supply, and thus reducing the energy consumption and carbon emissions of power generation and heating.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy, and relates to the fields of absorption heat exchangers, power cycles, and cogeneration of heat and power, and particularly relates to an absorption-type cogeneration system based on large-temperature-difference heat exchange. Background Art

[0002] Due to many advantages such as simple structure, high reliability, convenient installation and maintenance, and strong adaptability to the temperature and type of heat sources, power cycles represented by organic Rankine cycle, organic flash cycle, Brayton cycle, or Kalina cycle have been widely studied in the fields of waste heat recovery and cogeneration of heat and power. In the evaporator of the power cycle, the existence of the pinch temperature difference makes it difficult to significantly improve the matching problem of the heat source temperature difference, and further makes the outlet temperature of the hot-side fluid much higher than the inlet temperature of the cold-side fluid. The small temperature drop of the heat source results in most of the heat energy being wasted in vain. How to further utilize this part of heat energy is an urgent problem. Summary of the Invention

[0003] In order to solve the problem of low utilization rate of the above-mentioned heat source, the purpose of the present invention is to provide an absorption-type cogeneration system based on large-temperature-difference heat exchange, so as to reduce the temperature at the outlet of the heat source to the greatest extent and realize the maximum utilization of heat energy.

[0004] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0005] An absorption-type cogeneration system based on large-temperature-difference heat exchange, comprising a power cycle system and a two-stage absorption heat exchanger system; the two-stage absorption heat exchanger system includes a first-stage absorption heat pump, a second-stage absorption heat pump, and a plate heat exchanger; 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, and 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;

[0006] The heat source releases heat in the power cycle system for power generation;

[0007] The heat source after releasing heat flows through the first generator, the second generator, the plate heat exchanger, the second evaporator, and the first evaporator in sequence to further release heat;

[0008] The district heating network is divided into three branches. The first branch passes through the first absorber and the first condenser in sequence, and the end is connected to a third mixer; the second branch passes through the second absorber and the second condenser in sequence, and the end is connected to the third mixer; the third branch is connected to the cold-side inlet of the plate heat exchanger, and the cold-side outlet of the plate heat exchanger is connected to the third mixer; the third mixer supplies heat to heat users.

[0009] 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 heat source is wastewater, flue gas or hot oil, which heats the working fluid of the power cycle system.

[0010] In one embodiment, both the first-stage absorption heat pump and the second-stage absorption heat pump use lithium bromide solution as the working medium; the liquid-phase outlet of the first generator is concentrated lithium bromide solution, which is connected to the hot-side inlet of the first solution heat exchanger. The hot-side outlet of the first solution heat exchanger is connected to the hot-side inlet of the first absorber through the 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. The hot-side outlet of the first condenser is connected to the cold-side inlet of the first evaporator through the first throttle valve. The cold-side outlet of the first evaporator is connected to the hot-side inlet of the first absorber. The hot-side outlet of the first absorber is dilute lithium bromide solution, which is connected to the cold-side inlet of the first solution heat exchanger through the first booster pump. The cold-side outlet of the first solution heat exchanger is connected to the cold-side inlet of the first generator, completing the absorption heat pump cycle.

[0011] The liquid-phase outlet of the second generator is concentrated lithium bromide solution, which is connected to the hot-side inlet of the second solution heat exchanger. The hot-side outlet of the second solution heat exchanger is connected to the hot-side 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. The hot-side outlet of the second condenser is connected to the cold-side inlet of the second evaporator through the third throttle valve. The cold-side outlet of the second evaporator is connected to the hot-side inlet of the second absorber. The hot-side outlet of the second absorber is dilute lithium bromide solution, which is connected to the cold-side inlet of the second solution heat exchanger through the second booster pump. The cold-side outlet of the second solution heat exchanger is connected to the cold-side inlet of the second generator, completing the absorption heat pump cycle.

[0012] In one embodiment, the first generator consists of a first heat exchanger and a first two-phase separator. The cold-side outlet of the first heat exchanger is connected to the inlet of the first two-phase separator. The cold-side inlet of the first heat exchanger is the cold-side inlet of the first generator, and the hot-side inlet and outlet are the hot-side inlet and outlet of the first generator. The liquid-phase outlet of the first two-phase separator is the liquid-phase outlet of the first generator, and the gas-phase outlet of the first two-phase separator is the gas-phase outlet of the first generator.

[0013] The first absorber consists of a third heat exchanger and a first mixer. Both inlets of the first mixer are the hot-side inlets of the first absorber. The outlet of the first mixer is connected to the hot-side inlet of the third heat exchanger. The hot-side outlet of the third heat exchanger is the hot-side outlet of the first absorber.

[0014] The second generator consists of a second heat exchanger and a second two-phase separator. The cold-side outlet of the second heat exchanger is connected to the inlet of the second two-phase separator. The cold-side inlet of the second heat exchanger is the cold-side inlet of the second generator, the hot-side inlet and outlet are the hot-side inlet and outlet of the second generator. The liquid-phase outlet of the second two-phase separator is the liquid-phase outlet of the second generator, and the gas-phase outlet of the second two-phase separator is the gas-phase outlet of the second generator;

[0015] The second absorber consists of a fourth heat exchanger and a second mixer. Both inlets of the second mixer are the hot-side inlets of the second absorber. The outlet of the second mixer is connected to the hot-side inlet of the fourth heat exchanger. The hot-side outlet of the fourth heat exchanger is the hot-side outlet of the second absorber.

[0016] In one embodiment, the heat source after releasing heat is connected to the hot-side inlet of the first heat exchanger. The hot-side outlet of the first heat exchanger is connected to the hot-side inlet of the second heat exchanger. The hot-side outlet of the second heat exchanger is connected to the hot-side inlet of the plate heat exchanger; the hot-side outlet of the plate heat exchanger is connected to the hot-side inlet of the second evaporator. The hot-side outlet of the second evaporator is connected to the hot-side inlet of the first evaporator. The hot-side outlet of the first evaporator is the heat source outlet.

[0017] In one embodiment, the hot-side outlets of the first condenser and the second condenser are in a saturated liquid state, and the cold-side outlets of the first evaporator and the second evaporator are in a saturated gas state.

[0018] In one embodiment, the parameters of the first-stage absorption heat pump and the second-stage absorption heat pump are different. The parameters include: the concentration of the lithium bromide solution and the high-side and low-side pressures in the absorption heat pump cycle; among them, the concentration of the lithium bromide solution in the second-stage absorption heat pump is lower than that in the first-stage absorption heat pump; the pressure after throttling by the first throttle valve is less than the pressure after throttling by the third throttle valve, and the pressure after throttling by the second throttle valve is less than the pressure after throttling by the fourth throttle valve.

[0019] In one embodiment, each booster pump uses the electric energy generated by the power generation of the power cycle system as the energy source.

[0020] In one embodiment, after the heat source further releases heat through the first evaporator, the temperature of the heat source outlet drops below the temperature of the cold source inlet.

[0021] In one embodiment, the final outlet temperature of the heat source fluid is lower than the return water temperature of the heat user.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. By applying the absorption heat exchanger technology, without wasting the heat energy of the heat source, the outlet temperature of the heat source is significantly reduced, large temperature difference heat transfer is carried out, and the heat energy of the heat source is efficiently converted into electric energy and the heat energy required by heat users, significantly improving the utilization rate of the heat source.

[0024] 2. A two-stage absorption heat exchanger is adopted. Compared with the traditional single-stage absorption heat exchanger, the heat transfer loss in the heat transfer process of the two-stage absorption heat exchanger is significantly reduced. Compared with the multi-stage absorption heat exchanger, the two-stage absorption heat exchanger has better cycle regulation ability.

[0025] 3. The power consumption of the booster pump in the absorption heat pump cycle is so small that it can be ignored and can be driven by the electric energy output by the turbine in the organic Rankine cycle. The heat source energy can be highly converted without additional electricity or heat, and power supply and heating can bring considerable benefits.

[0026] 4. The absorption heat pump is a closed cycle, which is environmentally friendly and highly reliable. The entire cogeneration system can flexibly match heat sources of different types, flow rates and temperatures.

[0027] 5. Different types of power cycles can be adopted according to the actual project, such as organic Rankine cycle, organic flash cycle, Brayton cycle or Kalina cycle, etc., which can significantly reduce the final outlet temperature of the heat source and improve the utilization rate of the heat source. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic structural diagram of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] The embodiments of the present invention will be specifically described below with reference to the drawings and embodiments.

[0030] As Figure 1 shown, the present invention is an absorption type cogeneration system based on large temperature difference heat transfer, mainly including a power cycle system and a two-stage absorption heat exchanger system. The heat source releases heat in the power cycle system to heat the working fluid of the power cycle system, and the heated working fluid is used for power generation. The two-stage absorption heat exchanger system includes a first-stage absorption heat pump, a second-stage absorption heat pump and a plate heat exchanger 21. The first-stage absorption heat pump includes a first generator, a first condenser 3, a first evaporator 5, a first absorber and a first solution heat exchanger 6, and the second-stage absorption heat pump includes a second generator, a second condenser 13, a second evaporator 15, a second absorber and a second solution heat exchanger 16.

[0031] After the heat source releases heat in the power cycle system, it flows through the first generator, the second generator, the plate heat exchanger 21, the second evaporator 15 and the first evaporator 5 in sequence, further releasing heat.

[0032] The district heating network is divided into three branches. The first branch passes through the first absorber and the first condenser 3 in sequence, and the end is connected to the third mixer 22; the second branch passes through the second absorber and the second condenser 13 in sequence, and the end is connected to the third mixer 22; the third branch is connected to the cold-side inlet of the plate heat exchanger 21 and exchanges heat with the heat source flowing out of the second generator. The cold-side outlet of the plate heat exchanger 21 is connected to the third mixer 22; by using the third mixer 22, heating can be provided to heat users. That is, the three branches indirectly or directly exchange heat with the heat source through a two-stage absorption heat exchanger, and after fully obtaining the heat released by the heat source, heating is provided to heat users.

[0033] In the present invention, the power cycle system can be different heat engines such as an organic Rankine cycle system, an organic flash cycle system, a Brayton cycle system, or a Kalina cycle system; the heat source can be other common waste heat carriers such as wastewater, flue gas, or hot oil.

[0034] In an embodiment of the present invention, taking the organic Rankine cycle heat engine as an example, the power cycle system includes a third evaporator 23, a turbine 24, a third condenser 25, and a circulation pump 26. The heat source first releases heat in the organic Rankine cycle system to heat the working fluid, and the organic Rankine cycle system uses the heated working fluid to generate electricity. Exemplarily, the organic Rankine cycle uses R245fa, R134a, or other environmentally friendly organic substances as the working fluid. The heat source is first connected to the hot-side inlet of the third evaporator 23, and the heat source flowing out of the third evaporator 23 flows through the first generator, the second generator, the plate heat exchanger 21, the second evaporator 15, and the first evaporator 5 in sequence, and the heat source releases heat and the temperature gradually decreases. The cold-side outlet of the third evaporator 23 is connected to the inlet of the turbine 24. The organic working fluid at the inlet of the turbine 24 is in a saturated gaseous state or a superheated state. The organic working fluid expands and does work in the turbine 24 to output electrical energy. The exhaust gas at the outlet of the turbine 24 is connected to the hot-side inlet of the third condenser 25. The cooling water inlet is connected to the cold-side inlet of the third condenser 25. The hot-side outlet of the third condenser 25 is in a saturated liquid state, and the condensation heat is carried away by the cooling water. The hot-side outlet of the third condenser 25 is connected to the cold-side inlet of the third evaporator 23 through the circulation pump 26, and the organic working fluid returns to the initial point and starts the next cycle, which is the circulating working fluid.

[0035] In an embodiment of the present invention, both the first-stage absorption heat pump and the second-stage absorption heat pump use lithium bromide solution as the working medium. Lithium bromide solution is suitable for heating systems, while ammonia water solution is usually used in refrigeration systems. Compared with ammonia water solution, the absorption heat pump cycle using lithium bromide solution has better thermodynamic performance.

[0036] For the first-stage absorption heat pump, the liquid-phase outlet of the first generator is 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 is connected to the hot-side inlet of the first absorber through the 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. The hot-side outlet of the first condenser 3 is in a saturated liquid state and is connected to the cold-side inlet of the first evaporator 5 through the first throttle valve 4. The cold-side outlet of the first evaporator 5 is in a saturated gaseous state and is connected to the hot-side inlet of the first absorber. The hot-side outlet of the first absorber is dilute lithium bromide solution, which is connected to the cold-side inlet of the first solution heat exchanger 6 through the 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 absorption heat pump cycle.

[0037] For the second-stage absorption heat pump, the liquid-phase outlet of the second generator is 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 hot-side inlet of the second absorber through the 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 in a saturated liquid state and is connected to the cold-side inlet of the second evaporator 15 through the third throttle valve 14. The cold-side outlet of the second evaporator 15 is in a saturated gaseous state and is connected to the hot-side inlet of the second absorber. The hot-side outlet of the second absorber is dilute lithium bromide solution, which is connected to the cold-side inlet of the second solution heat exchanger 16 through the 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 absorption heat pump cycle. That is, the heat source that has released part of the heat in the first-stage absorption heat pump enters the second generator. The water vapor generated in the second generator flows through the second condenser 13, the third throttle valve 14, and the second evaporator 15 in sequence, and finally flows into the second absorber. The concentrated lithium bromide 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 dilute lithium bromide solution is preheated in the second solution heat exchanger 16 and finally returns to the second generator.

[0038] Further, in the embodiment of the present invention, the first heat exchanger 1 and the first two-phase separator 2 form the first generator of the first-stage absorption heat pump. The cold-side outlet of the first heat exchanger 1 is connected to the inlet of the first two-phase separator 2. The cold-side inlet of the first heat exchanger 1 is the cold-side inlet of the first generator, and the hot-side inlet and outlet are the hot-side inlet and outlet of the first generator. 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 of the first two-phase separator 2 is the gas-phase outlet of the first generator.

[0039] Further, in the embodiments of the present invention, the third heat exchanger 9 and the first mixer 8 form the first absorber of the first-stage absorption heat pump. The two inlets of the first mixer 8 are the hot-side inlets 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.

[0040] Further, in the embodiments of the present invention, the second heat exchanger 11 and the second two-phase separator 12 form the second generator of the second-stage absorption heat pump. The cold-side outlet of the second heat exchanger 11 is connected to the inlet of the second two-phase separator 12. The cold-side inlet of the second heat exchanger 11 is the cold-side inlet of the second generator, and the hot-side inlet and outlet are the hot-side inlet and outlet of the second generator. 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 of the second two-phase separator 12 is the gas-phase outlet of the second generator.

[0041] Further, in the embodiments of the present invention, the fourth heat exchanger 19 and the second mixer 18 form the second absorber of the second-stage absorption heat pump. The two inlets of the second mixer 18 are the hot-side inlets 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.

[0042] At this time, the heat source after releasing heat is connected to the hot-side inlet of the first heat exchanger 1. The hot-side outlet of the first heat exchanger 1 is connected to the hot-side inlet of the second heat exchanger 11. The hot-side outlet of the second heat exchanger 11 is connected to the hot-side inlet of the plate heat exchanger 21. The hot-side outlet of the plate heat exchanger 21 is connected to the hot-side inlet of the second evaporator 15. The hot-side outlet of the second evaporator 15 is connected to the hot-side inlet of the first evaporator 5, and the hot-side outlet of the first evaporator 5 is the final outlet of the heat source.

[0043] Further, in the embodiments of the present invention, the parameters of the first-stage absorption heat pump and the second-stage absorption heat pump are different. Here, the parameters mainly refer to the concentration of the lithium bromide solution and the high-side and low-side pressures in the absorption heat pump cycle. Compared with the first-stage absorption heat pump, the concentration of the lithium bromide solution in the second-stage absorption heat pump cycle is lower, and the pressure after throttling by the throttle valve is greater. That is, the pressure after throttling by the first throttle valve 4 is less than the pressure after throttling by the third throttle valve 14, and the pressure after throttling by the second throttle valve 7 is less than the pressure after throttling by the fourth throttle valve 17, so that the evaporation temperature is higher and the generation temperature is lower. The heat source passes through the first generator, the second generator and the plate heat exchanger 21, then enters the second evaporator 15 of the second-stage absorption heat pump, and then enters the first evaporator 5 of the first-stage absorption heat pump, and the temperature gradually decreases. The final outlet temperature of the heat source can be reduced below the cold source inlet temperature. Therefore, by setting the relevant parameters of the two absorption heat pump cycles to different values, the heat energy of the heat source can be utilized in a cascaded manner, reducing the heat transfer loss during the heat transfer process and reducing the outlet temperature to the lowest level.

[0044] In the embodiments of the present invention, the cold source includes the organic working medium on the cold side in the evaporator of the power cycle (taking the organic Rankine cycle as an example) and the hot water supplied to the heat user. Therefore, the cold source inlet is the cold side inlet of the evaporator 23 (at a temperature of about 35°C) and the cold side inlets of the heat exchangers 9, 19 and the plate heat exchanger 21 (at a temperature of 40°C).

[0045] Based on the above system, the specific implementation process of the present invention is as follows:

[0046] The present invention adopts different types of power cycle systems. Taking the organic Rankine cycle heat engine as an example, hot water or flue gas at 130 °C is used as the waste heat heat source to sequentially heat the organic working fluid in the third evaporator 23 of the organic Rankine cycle, the lithium bromide dilute solution in the first generator and the second generator, the hot water in the plate heat exchanger 21, and the liquid and gaseous water in the second evaporator 15 and the first evaporator 5. In the organic Rankine cycle system, R245fa is used as the working fluid. The working fluid is evaporated by the heat source in the third evaporator 23 and flows into the turbine 24 in a saturated gaseous state or superheated state to expand and do work externally, outputting electrical energy. The working fluid after expansion and work is condensed by cooling water in the third condenser 25. The condensed organic working fluid is in a saturated liquid state, and then is pressurized by the third booster pump 26 and flows back to the third evaporator 23, completing the organic Rankine cycle. The heat source after releasing part of the heat in the organic Rankine cycle system enters the two-stage absorption heat exchanger and releases heat at different temperature levels to the first-stage and second-stage absorption heat pumps and the plate heat exchanger 21. The components and working process of the second-stage absorption heat pump are the same as those of the first-stage absorption heat pump. Taking the first-stage absorption heat pump as an example, first, the heat source enters the first generator and releases heat. Here, the lithium bromide dilute solution is heated to form a two-phase mixture of lithium bromide concentrated solution and water vapor. The lithium bromide concentrated solution enters the first solution heat exchanger 6 to preheat the lithium bromide dilute solution from the first absorber. After heat exchange, the lithium bromide concentrated solution undergoes a throttling effect through the second throttle valve 7, and the pressure drops from 14.77 kPa to 2.16 kPa and flows into the first absorber; the superheated water vapor generated in the first generator enters the first condenser 3, transfers heat to the hot water in the district heating network, and the water vapor condenses into a saturated liquid state and then passes through the first throttle valve 4, and the pressure drops to 2.16 kPa, being in the two-phase region. Subsequently, it enters the first evaporator 5 and is evaporated into a saturated gaseous state by the heat source fluid from the second evaporator 15, and finally flows into the first absorber. In the first absorber, the lithium bromide concentrated solution absorbs water vapor to become lithium bromide dilute solution and releases a large amount of heat, and this part of the heat is also used for district heating. The lithium bromide dilute solution at the outlet of the first absorber passes through the first booster pump 10, and the pressure increases to 14.77 kPa, and then enters the first solution heat exchanger 6 to be preheated by the lithium bromide concentrated solution, and then returns to the first generator, completing the entire absorption heat pump cycle. In the second-stage absorption heat pump, the pressure before throttling of the third throttle valve 14 and the fourth throttle valve 17 is 14.75 kPa, and the pressure after throttling is 3.57 kPa. Compared with the first-stage absorption heat pump, the pressure after throttling of the throttle valve in the second-stage absorption heat pump cycle is greater, resulting in a higher evaporation temperature and a lower generation temperature, thereby realizing a cascaded utilization of the heat source energy. The heat source fluid coming out of the first generator releases heat in the second generator and then enters the plate heat exchanger 21 to heat the water in the district heating network. The temperature of the heat source drops significantly and flows into the second evaporator 15 and the first evaporator 5 to further release heat.

[0047] The district heating network described in the present invention is divided into three branches. The first branch successively passes through the first absorber and the first condenser 3 in the first-stage absorption heat pump. The second branch successively passes through the second absorber and the second condenser 13 in the second-stage absorption heat pump. The third branch is connected to the cold-side inlet of the plate heat exchanger 21 and exchanges heat with the heat source flowing out of the second generator. The three branches indirectly or directly exchange heat with the heat source through a two-stage absorption heat exchanger. After fully obtaining the heat released by the heat source, heat is supplied to heat users. The electric energy generated in the organic Rankine cycle can be used to drive the booster pump and supply power. Therefore, the two-stage absorption heat exchange system of the present invention is applicable to heat source scenarios of different types, flow rates, and temperatures due to the large temperature difference heat exchange characteristics of the two-stage absorption heat exchange system. For example, in this embodiment, the final outlet temperature of the heat source fluid can be reduced to 24°C, which is lower than the return water temperature (40°C) of the heat user, and the supply water temperature of the heat user is 50°C, realizing large temperature difference heat exchange of the heat source.

[0048] In more embodiments of the present invention, the heat source types include hot water, flue gas, steam, heat transfer oil, etc.; the flow rate of the heat source varies within the range of 10 kg / s - 60 kg / s; the heat source temperature range is 100°C - 150°C; the heat source scenario refers to different systems such as waste heat recovery, combined heat and power, renewable energy power generation, and energy storage, etc. As long as it involves the evaporator absorbing the heat of the heat fluid, this system can be applied.

[0049] In summary, the present invention utilizes the large temperature difference heat exchange characteristics of the absorption heat exchanger, combines different types of power cycle systems with the two-stage absorption heat exchanger system, and cascades the thermal energy of low-temperature heat sources. It can reduce the outlet temperature of the heat source below the inlet temperature of the cold source, significantly improve the utilization rate of the heat source, and efficiently convert the heat source energy into electric energy and the heat energy required by heat users without wasting thermal energy. By using a two-stage absorption heat exchanger, compared with the traditional single-stage absorption heat exchanger, the heat exchange loss during the heat exchange process of the two-stage absorption heat exchanger is greatly reduced. Compared with the multi-stage absorption heat exchanger, the two-stage absorption heat exchanger has better cycle regulation ability. The absorption heat pump cycle therein is a closed cycle, which is environmentally friendly and highly reliable. The entire combined heat and power system can flexibly match heat sources of different types, flow rates, and temperatures, and is also applicable to different heat engines such as the organic Rankine cycle, organic flash cycle, Brayton cycle, or Kalina cycle, etc., greatly improving the utilization rate of the heat source. In addition, power supply and heating can bring considerable benefits.

Claims

1. An absorption-type combined heat and power generation system based on large temperature difference heat exchange, characterized in that, It includes a power cycle system and a two-stage absorption heat exchanger system; the two-stage absorption heat exchanger system includes a first-stage absorption heat pump, a second-stage absorption heat pump and a plate heat exchanger (21); the first-stage absorption heat pump includes a first generator, a first condenser (3), a first evaporator (5), a first absorber and a first solution heat exchanger (6), and the second-stage absorption heat pump includes a second generator, a second condenser (13), a second evaporator (15), a second absorber and a second solution heat exchanger (16); The heat source releases heat in the power cycle system to generate electricity; The heat source after releasing heat flows through the first generator, the second generator, the plate heat exchanger (21), the second evaporator (15) and the first evaporator (5) in sequence to further release heat; The district heating network is divided into three branches. The first branch passes through the first absorber and the first condenser (3) in sequence, and the end is connected to a third mixer (22); the second branch passes through the second absorber and the second condenser (13) in sequence, and the end is connected to the third mixer (22); the third branch is connected to the cold-side inlet of the plate heat exchanger (21), and the cold-side outlet of the plate heat exchanger (21) is connected to the third mixer (22); the third mixer (22) supplies heat to heat users.

2. The absorption-type combined heat and power generation system based on large temperature difference heat exchange 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 heat source is wastewater, flue gas or hot oil, which heats the working fluid of the power cycle system.

3. The absorption-type combined heat and power generation system based on large temperature difference heat exchange according to claim 1, characterized in that, Both the first-stage absorption heat pump and the second-stage absorption heat pump use lithium bromide solution as the working medium; the liquid-phase outlet of the first generator is 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 hot-side 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), the cold-side outlet of the first evaporator (5) is connected to the hot-side inlet of the first absorber, the hot-side outlet of the first absorber is 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 to complete the absorption heat pump cycle; The liquid phase outlet of the second generator is 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 hot side inlet of the second absorber through the 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 the third throttle valve (14). The cold side outlet of the second evaporator (15) is connected to the hot side inlet of the second absorber. The hot side outlet of the second absorber is dilute lithium bromide solution, which is connected to the cold side inlet of the second solution heat exchanger (16) through the 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, thus completing the absorption heat pump cycle.

4. The absorption-type combined heat and power generation system based on large temperature difference heat exchange according to claim 3, characterized in that, The first generator consists of a first heat exchanger (1) and a first two-phase separator (2). The cold side outlet of the first heat exchanger (1) is connected to the inlet of the first two-phase separator (2). The cold side inlet of the first heat exchanger (1) is the cold side inlet of the first generator, and the hot side inlet and outlet are the hot side inlet and outlet of the first generator. 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 of the first two-phase separator (2) is the gas phase outlet of the first generator. The first absorber consists of a third heat exchanger (9) and a first mixer (8). Both inlets of the first mixer (8) are the hot side inlets of the first absorber. The outlet of the first mixer (8) is connected to the hot side inlet of the third heat exchanger (9). The hot side outlet of the third heat exchanger (9) is the hot side outlet of the first absorber. The second generator consists of a second heat exchanger (11) and a second two-phase separator (12). The cold side outlet of the second heat exchanger (11) is connected to the inlet of the second two-phase separator (12). The cold side inlet of the second heat exchanger (11) is the cold side inlet of the second generator, and the hot side inlet and outlet are the hot side inlet and outlet of the second generator. 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 of the second two-phase separator (12) is the gas phase outlet of the second generator. The second absorber consists of a fourth heat exchanger (19) and a second mixer (18). Both inlets of the second mixer (18) are the hot side inlets of the second absorber. The outlet of the second mixer (18) is connected to the hot side inlet of the fourth heat exchanger (19). The hot side outlet of the fourth heat exchanger (19) is the hot side outlet of the second absorber.

5. The absorption-type combined heat and power generation system based on large temperature difference heat exchange according to claim 4, characterized in that, The heat source after releasing heat is connected to the hot side inlet of the first heat exchanger (1). The hot side outlet of the first heat exchanger (1) is connected to the hot side inlet of the second heat exchanger (11). The hot side outlet of the second heat exchanger (11) is connected to the hot side inlet of the plate heat exchanger (21); the hot side outlet of the plate heat exchanger (21) is connected to the hot side inlet of the second evaporator (15). The hot side outlet of the second evaporator (15) is connected to the hot side inlet of the first evaporator (5). The hot side outlet of the first evaporator (5) is the heat source outlet.

6. The absorption-type combined heat and power generation system based on large temperature difference heat exchange according to claim 3 or 4 or 5, characterized in that, The hot-side outlets of the first condenser (3) and the second condenser (13) are in a saturated liquid state, and the cold-side outlets of the first evaporator (5) and the second evaporator (15) are in a saturated gaseous state.

7. The absorption-type combined heat and power generation system based on large temperature difference heat exchange according to claim 3 or 4 or 5, characterized in that, The parameters of the first-stage absorption heat pump and the second-stage absorption heat pump are different. The parameters include: the concentration of the lithium bromide solution and the high-side and low-side pressures in the absorption heat pump cycle; among them, the concentration of the lithium bromide solution in the second-stage absorption heat pump is lower than that in the first-stage absorption heat pump; the pressure after throttling by the first throttle valve (4) is less than the pressure after throttling by the third throttle valve (14), and the pressure after throttling by the second throttle valve (7) is less than the pressure after throttling by the fourth throttle valve (17).

8. The absorption-type combined heat and power generation system based on large temperature difference heat exchange according to claim 3 or 4 or 5, characterized in that, Each booster pump uses the electric energy generated by the power generation of the power cycle system as the energy source.

9. The absorption-type combined heat and power generation system based on large temperature difference heat exchange according to claim 1, characterized in that, After further releasing heat through the first evaporator (5), the temperature at the heat source outlet drops below the temperature at the cold source inlet.

10. The absorption-type combined heat and power generation system based on large temperature difference heat exchange according to claim 1, characterized in that, The final outlet temperature of the heat source fluid is lower than the return water temperature of the heat user.

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