Type ii absorption heat pump system based on liquid-liquid phase separation, and waste heat recovery apparatus

Abstract

The present invention relates to the technical field of heat exchange. Disclosed are a type II absorption heat pump system based on liquid-liquid phase separation, and a waste heat recovery apparatus. The system comprises an absorber, a cooling member, a phase separator, a pressure reduction member, an evaporator, and a compressor; an absorption liquid outlet of the absorber is connected to a solution inlet of the cooling member; a solution outlet of the cooling member is connected to a solution inlet of the phase separator; an upper solution outlet of the phase separator is connected to the evaporator, and a lower solution outlet of the phase separator is connected to a solution inlet of the absorber; a vapor outlet of the evaporator is connected to a vapor inlet of the absorber; the pressure reduction member is arranged between the phase separator and the evaporator; the compressor is arranged between the evaporator and the absorber and is used for regulating the pressure of vapor entering the absorber; and a working medium pair used in the system is a partially miscible working medium pair. In the system of the present invention, the separation of a refrigerant and an absorbent is realized by means of liquid-liquid phase separation. Compared with "gas-liquid" phase separation, the consumption of a heat source is small, and the coefficient of performance (COP) of the system is significantly increased.

Description

Type II Absorption Heat Pump System and Waste Heat Recovery Device Based on Liquid-Liquid Phase Separation Technical Field

[0001] This invention relates to the field of heat exchange technology, specifically to a second type of absorption heat pump system based on liquid-liquid phase separation and a waste heat recovery device using this system. Background Technology

[0002] An absorption heat pump is a heat energy recovery system that uses thermal energy as its driving energy source. Absorption heat pumps are divided into two types: Type I absorption heat pumps and Type II absorption heat pumps. Type I absorption heat pumps, also known as heat-enhancing heat pumps, use a high-temperature heat source to raise the energy of a low-temperature heat source to an intermediate temperature, thereby improving energy utilization efficiency. Type II absorption heat pumps, also known as temperature-raising heat pumps, utilize the potential difference between a large amount of intermediate waste heat and a low-temperature heat source to produce heat with a smaller heat output but a temperature higher than the intermediate waste heat, thereby improving the quality of some waste heat.

[0003] The existing second-type absorption heat pump mainly consists of a generator, condenser, evaporator, absorber, regenerator, and auxiliary equipment. The working fluid used is either ammonia-water or water-lithium bromide. Taking water-lithium bromide as an example, in the evaporator, the refrigerant water outside the tubes is heated and evaporated into refrigerant vapor by the heat source inside the tubes. It then enters the absorber and is absorbed by the lithium bromide solution from the generator. The heat released during the absorption process heats the water flowing through the heat transfer tubes of the absorber, thus providing the required heat. The dilute solution obtained after absorbing the refrigerant vapor flows out of the absorber, passes through the heat exchanger, and enters the generator. It is heated to boiling by the waste heat medium flowing through the heat transfer tubes, generating refrigerant vapor again. At the same time, it is concentrated into a concentrated solution. The solution pump transports this concentrated solution through the heat exchanger to the absorber to reabsorb refrigerant vapor. The low-pressure refrigerant vapor generated in the generator enters the condenser and is cooled into refrigerant water by the cooling water in the heat transfer tubes. It is then transported to the evaporator by the refrigerant water pump and heated and evaporated again, thus completing the cycle.

[0004] Conventional Type II absorption heat pumps require a large heat source, resulting in a low coefficient of performance (COP), which is theoretically no higher than 0.5, thus limiting their application range. Summary of the Invention

[0005] In view of the above-mentioned deficiencies of the prior art, the present invention provides a second type of absorption heat pump system based on liquid-liquid phase separation, which transforms the traditional gas-liquid phase separation-absorption-desorption cycle into a liquid-liquid phase separation system, thereby reducing the use of heat energy and significantly improving the system performance coefficient. To this end, the present invention also provides a waste heat recovery device for the second type of absorption heat pump system based on liquid-liquid phase separation.

[0006] To solve the above-mentioned technical problems, a first aspect of the present invention provides a second type of absorption heat pump system based on liquid-liquid phase separation, including an absorber, a cooling component, a phase separator, a pressure reducing component, an evaporator, and a compressor;

[0007] The absorbent outlet of the absorber is connected to the solution inlet of the cooling component, the solution outlet of the cooling component is connected to the solution inlet of the phase separator, the upper solution outlet of the phase separator is connected to the evaporator, the lower solution outlet of the phase separator is connected to the solution inlet of the absorber, the vapor outlet of the evaporator is connected to the vapor inlet of the absorber, the pressure reducing component is located between the phase separator and the evaporator, and the compressor is located between the evaporator and the absorber to regulate the vapor pressure entering the absorber. The working fluid pair used in the system is a partially miscible working fluid pair.

[0008] The connection here can be a direct connection, such as the lower solution outlet of the phase separator being directly connected to the solution inlet of the absorber; or it can be an indirect connection, such as when a regenerator is added to the system, the lower solution outlet of the phase separator enters the regenerator and flows into the solution inlet of the absorber through the regenerator outlet.

[0009] In a preferred embodiment, a first solution pump is provided between the absorber and the cooling component, and the absorbent outlet of the absorber is connected to the solution inlet of the cooling component through the first solution pump.

[0010] In a preferred embodiment, the cooling component includes a cooler and / or a regenerator.

[0011] In a preferred embodiment, the cooling component includes a cooler, the absorbent outlet of the absorber is connected to the first solution inlet of the cooler, and the solution outlet of the cooler is connected to a phase separator.

[0012] In a more preferred embodiment, the solution outlet of the evaporator is connected to the second solution inlet of the cooler for cooling the unevaporated solution in the evaporator.

[0013] In a more preferred embodiment, a second solution pump is provided between the evaporator and the cooler, and the solution outlet of the evaporator is connected to the second solution inlet of the cooler through the second solution pump.

[0014] In a preferred embodiment, the cooling component includes a regenerator, the absorbent outlet of the absorber is connected to the first solution inlet of the regenerator, the first solution outlet of the regenerator is connected to the solution inlet of the phase separator, the lower solution outlet of the phase separator is connected to the second solution inlet of the regenerator, and the second solution outlet of the regenerator is connected to the absorber.

[0015] In a more preferred embodiment, a third solution pump is provided between the phase separator and the regenerator, and the lower solution outlet of the phase separator is connected to the second solution inlet of the regenerator through the third solution pump.

[0016] In another preferred embodiment, the cooling component includes a cooler and a regenerator, the absorbent outlet of the absorber is connected to the first solution inlet of the regenerator, the first solution outlet of the regenerator is connected to the first solution inlet of the cooler, and the solution outlet of the cooler is connected to a phase separator.

[0017] In a preferred embodiment, a third solution pump is provided between the phase separator and the regenerator, and the lower solution outlet of the phase separator is connected to the second solution inlet of the regenerator through the third solution pump.

[0018] In a more preferred embodiment, the solution outlet of the evaporator is connected to the second solution inlet of the cooler for cooling the unevaporated solution in the evaporator.

[0019] In a more preferred embodiment, a second solution pump is provided between the evaporator and the cooler, and the solution outlet of the evaporator is connected to the second solution inlet of the cooler through the second solution pump.

[0020] In a preferred embodiment, the lower solution outlet of the phase separator is connected to the second solution inlet of the regenerator, and the second solution outlet of the regenerator is connected to the absorber.

[0021] In a preferred embodiment, the pressure-reducing component is selected from a throttle valve.

[0022] In a preferred embodiment, the working fluid pair is a binary or ternary partially miscible working fluid pair.

[0023] In a preferred embodiment, the working fluid pair is a working fluid pair having either the highest melting point temperature or the lowest melting point temperature.

[0024] In a preferred embodiment, the highest melting point temperature of the working fluid pair is not lower than 35°C or the lowest melting point temperature is not higher than 35°C.

[0025] In a preferred embodiment, the working fluid pair is selected from any one of water-phenol, water-isobutanol, water-aniline, nitrobenzene-n-hexane, Freon-refrigeration oil, water-ionic liquid, water-triethylamine, n-hexane-diethylene glycol-benzene, ethanol-water-vinyl nitrile, and ether-water-vinyl nitrile.

[0026] In a second aspect, the present invention provides a waste heat recovery device, which includes the above-described second type of absorption heat pump system based on liquid-liquid phase separation, wherein the evaporator is provided with a waste heat medium inlet and a waste heat medium outlet, and the waste heat medium is connected to the waste heat medium inlet through a pipeline.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The present invention is based on a second type of absorption heat pump system with liquid-liquid phase separation. The refrigerant and absorbent are separated by liquid-liquid phase separation. Compared with "gas-liquid" phase separation, the heat source consumption is reduced and the system performance coefficient (COP) is significantly improved.

[0029] (2) The present invention is based on a second type of absorption heat pump system with liquid-liquid phase separation. Compared with conventional second type of absorption heat pump systems, the generator and condenser are non-essential components, which reduces the use of components and lowers the cost of use and installation.

[0030] (3) The present invention is based on a second type of absorption heat pump system with liquid-liquid phase separation. The solution used for evaporation is a solution rich in light phase, rather than a pure light phase solution. The system does not require distillation equipment, which significantly reduces the size of the system equipment and facilitates system equipment integration.

[0031] The following will further explain the concept, specific structure, and technical effects of the present invention in conjunction with the accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Attached Figure Description

[0032] Figure 1 is a schematic diagram of a conventional Type II absorption heat pump system;

[0033] Figure 2 is a schematic diagram of the second type of absorption heat pump system based on liquid-liquid phase separation in Embodiment 1 of the present invention;

[0034] Figure 3 is the equilibrium phase diagram of the working fluid pair used in Embodiment 1 of the present invention;

[0035] Figure 4 is a schematic diagram of the second type of absorption heat pump system based on liquid-liquid phase separation in Embodiment 2 of the present invention.

[0036] Figure 5 is a schematic diagram of the second type of absorption heat pump system based on liquid-liquid phase separation in Embodiment 3 of the present invention.

[0037] Figure 6 is a schematic diagram of the second type of absorption heat pump system based on liquid-liquid phase separation in Embodiment 4 of the present invention.

[0038] Among them, 1-absorber, 2-regenerator, 3-cooler, 4-phase separator, 5-throttle valve, 6-third solution pump, 7-evaporator, 8-compressor, 9-first solution pump, 10-second solution pump; a-generator, b-solution pump, g-refrigerant pump, h-condenser. Detailed Implementation

[0039] To make the technical means, inventive features, objectives, and effects of the invention readily understandable, the invention is further illustrated below with reference to specific figures. However, the invention is not limited to the embodiments described below.

[0040] It should be noted that the structures, proportions, sizes, etc., illustrated in the accompanying drawings of this specification are only used to complement the content disclosed in the specification for those skilled in the art to understand and read, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0041] The second type of absorption heat pump is a heat energy recovery system that uses thermal energy as the driving energy source. It converts the recovered low-temperature heat source into a high-temperature heat source to expand the application range and efficiency of the recovered heat source. A conventional second-type absorption heat pump system is shown in Figure 1, consisting of a generator a, a solution pump b, a throttling valve 5, a regenerator 2, an absorber 1, an evaporator 7, a refrigerant pump g, and a condenser h. The generator a heats the low-boiling-point refrigerant in the working fluid to vaporize. Through the "vapor-liquid" phase equilibrium principle, the refrigerant and absorbent are separated. The separated refrigerant vapor enters the condenser h for condensation and liquefaction, and then enters the evaporator 7 for further heating and vaporization. The vaporized high-pressure refrigerant vapor is absorbed by the absorbent in the absorber 1, releasing absorbed heat and providing a high-temperature heat source to the outside.

[0042] Specifically: the gas phase outlet at the top of generator a is connected to condenser h; the liquid phase outlet of condenser h is connected to refrigerant pump g; the outlet of refrigerant pump g is connected to evaporator 7; the gas phase outlet of evaporator 7 is connected to absorber 1; the concentrated solution outlet of generator a is connected to the inlet of solution pump b; the outlet of solution pump b is connected to the concentrated solution inlet of regenerator 2; the concentrated solution outlet of regenerator 2 is connected to the concentrated solution inlet of absorber 1; the dilute solution outlet of absorber 1 is connected to the dilute solution inlet of regenerator 2; the dilute solution outlet of regenerator 2 is connected to the inlet of throttle valve 5; and the outlet of throttle valve 5 is connected to the dilute solution inlet of generator a.

[0043] Taking the ammonia-water working fluid pair as an example, the ammonia solution is heated in generator a by a low-temperature heat source. The heated ammonia solution releases ammonia gas and a small amount of water vapor, which is then purified by distillation and enters condenser h where it is condensed into liquid ammonia by cooling water. The liquid ammonia is pressurized by refrigerant pump g and enters evaporator 7, where it is evaporated by low-temperature waste heat to obtain high-pressure ammonia gas. The high-pressure ammonia gas enters absorber 1 and is absorbed by the dilute ammonia solution from generator a. The dilute ammonia solution at the outlet of generator a and the concentrated ammonia solution at the outlet of absorber 1 are heat recovered through regenerator 2. The ammonia concentration at the inlet of generator a is 65%, the generator pressure is 15.5 bar, the finished liquid temperature in generator a is 75°C, and the reflux ratio of the distillation column is 5%. The condensation temperature is 40°C, the evaporation temperature is 75°C, the finished liquid temperature in absorber 1 is 104°C, and the absorption pressure is 37.1 bar. When the heat supply load of absorber 1 is 1000kW, the low-temperature waste heat supply load of evaporator 7 is 1094kW, the low-temperature waste heat supply load of generator a is 1032kW, and the total power consumption of the circulating pump is 18kW. In the above-mentioned second type of absorption heat pump, because the absorption pressure is limited by the refrigerant saturated vapor pressure at the evaporation temperature, the heat source temperature provided by this second type of absorption heat pump is limited. When the low-temperature waste heat temperature is 80℃, its output heat source temperature is not higher than 100℃. The relevant performance parameters are shown in Table 1.

[0044] Table 1

[0045] Therefore, for conventional Type II absorption heat pumps, at least two portions of low-temperature waste heat are required to obtain one unit of high-temperature heat source: one for refrigerant desorption in the generator and the other for refrigerant vaporization in the evaporator, resulting in high heat source consumption. For ammonia-water as the working fluid pair, due to the small difference in boiling points between ammonia and water, the system requires distillation equipment, leading to significant consumption of the driving heat source and cooling water. Furthermore, ammonia has a strong pungent odor, is toxic to humans, and is flammable and explosive. When using water-lithium bromide as the working fluid pair, although the boiling points of water and lithium bromide differ significantly, eliminating the need for distillation equipment, lithium bromide solution is highly corrosive to system equipment, and high-concentration lithium bromide solutions are prone to crystallization and blockage, affecting the stable operation of the heat pump system. In addition, the output temperature of a conventional Type II absorption heat pump system is limited by the phase equilibrium concentration and pressure of the working fluid pair within the absorber; the maximum output temperature is not adjustable, the system temperature rise is small, and its applicability is limited.

[0046] This application changes the existing approach by transforming the existing "gas-liquid" desorption-absorption-"gas-liquid" desorption cycle in the second type of absorption heat pump into a "liquid-liquid" desorption-absorption-"liquid-liquid" desorption cycle. This achieves "liquid-liquid" phase separation without the need for an additional heat source, resulting in lower heat source consumption and a significant improvement in the system performance coefficient, increasing it from 0.5 to 0.8.

[0047] The absorbent mentioned below is a mixed solution obtained after the absorbent absorbs the refrigerant. It can be a completely homogeneous liquid phase or a multiphase system with partial stratification. Taking ammonia-water working fluid pair as an example, ammonia is the refrigerant and water is the absorbent, and the resulting ammonia water is the absorbent.

[0048] This invention provides a second type of absorption heat pump system based on liquid-liquid phase separation, including an absorber, a cooling component, a phase separator, a pressure reducing component, an evaporator, and a compressor. The absorbent outlet of the absorber is connected to the solution inlet of the cooling component, the solution outlet of the cooling component is connected to the solution inlet of the phase separator, the upper solution outlet of the phase separator is connected to the evaporator, the lower solution outlet of the phase separator is connected to the solution inlet of the absorber, the vapor outlet of the evaporator is connected to the vapor inlet of the absorber, the pressure reducing component is disposed between the phase separator and the evaporator, and the compressor is disposed between the evaporator and the absorber to regulate the vapor pressure entering the absorber. The working fluid pair used in the system is a partially miscible working fluid pair.

[0049] An absorber provides a site for the absorbent to absorb refrigerant. In the absorber, the absorbent absorbs refrigerant vapor and releases a large amount of heat for external heating. The absorber described in this application can be a falling film absorber or an absorption tower. The falling film absorber can be a plate-type falling film absorber, a horizontal tube falling film absorber, or a vertical tube falling film absorber. The absorber is not limited to these; any device with similar functionality can be used in this application.

[0050] A cooling component is used to cool the absorbent. This component can be a cooler or a regenerator alone, or both. The cooler only cools the absorbent, while the regenerator, while cooling the absorbent, simultaneously heats the lower layer solution entering the phase separator, reducing heat loss in the system. The cooler can be a shell-and-tube cooler, a plate cooler, or an air-cooled cooler. The regenerator can be a plate heat exchanger or a shell-and-tube heat exchanger. The cooler and regenerator are not limited to these; any device with similar functionality can be used in this application.

[0051] A phase separator provides a site for liquid-liquid phase separation. The upper layer solution in the phase separator is a solution of the light component, which is also a solution rich in refrigerant, and the refrigerant contains dissolved absorbent; the lower layer solution is a solution of the heavy component, which is also a solution rich in absorbent, and the absorbent contains dissolved refrigerant.

[0052] An evaporator can convert a liquid substance into a gaseous substance. The evaporator in this application can be a column-type flooded evaporator or a falling film evaporator. The evaporator is not limited to these; any device with similar functionality can be used in this application.

[0053] A compressor is a driven fluid machine that raises low-pressure gas to high-pressure gas. It draws in low-temperature, low-pressure gas through an intake pipe, compresses it using a motor, and then discharges high-pressure gas through an exhaust pipe. The compressor in this application can be a Roots compressor, screw compressor, centrifugal compressor, or axial compressor. However, the compressor in this application is not limited to these types; any device with similar functionality can be used in this application.

[0054] The steam generated by the evaporator enters the compressor. After being processed by the compressor, the steam pressure increases, and then it enters the absorber, thereby regulating the heat released during the absorption process.

[0055] By adjusting the compression ratio of the compressor, the pressure of the absorber in the system can be changed, allowing for the provision of a higher-temperature heat source. For waste heat recovery at around 80°C, the system in this application can provide a heat source exceeding 100°C.

[0056] The absorbent flowing out of the absorber is a mixture of absorbent and refrigerant. Because the absorbent releases a lot of heat during the absorption of the refrigerant, the absorbent is at a high temperature. After being cooled by the cooling unit, the absorbent enters the phase separator, where it separates into layers. The solution in the upper layer of the phase separator is depressurized by the pressure reducing unit and then enters the evaporator. The evaporator uses the recovered heat (e.g., 80°C) for heating. The steam generated by the evaporator (around 80°C) enters the absorber, while the solution in the lower layer of the phase separator returns to the absorber. The absorbent absorbs the steam, releasing a large amount of heat and providing a high-temperature (above 80°C) heat source to the outside.

[0057] This application achieves the separation of refrigerant and absorbent through liquid-liquid phase separation, eliminating the need for an additional heat source, reducing heat usage and energy consumption; at the same time, it reduces the installation of some equipment, significantly reducing the overall size of the system equipment and facilitating system integration.

[0058] The cooling components include coolers and / or regenerators.

[0059] In a preferred embodiment, the cooling component includes a cooler, wherein the absorbent outlet of the absorber is connected to the first solution inlet of the cooler, and the solution outlet of the cooler is connected to a phase separator.

[0060] The absorbent liquid flowing out of the absorber is cooled by a cooler. At this time, the absorbent liquid is at a lower temperature. After entering the phase separator, the absorbent liquid will show obvious stratification.

[0061] When a cooler is selected as the cooling component, the absorbent flowing out of the absorber is cooled, causing the refrigerant and absorbent in the absorbent to separate. In this case, there is no need to consider the heat loss that occurs when the cooler is in use. This system is suitable for applications with a large waste heat supply.

[0062] Preferably, the solution outlet of the evaporator is connected to the second solution inlet of the cooler for cooling the unevaporated solution in the evaporator.

[0063] After the solution in the upper layer of the phase separator enters the evaporator, it produces steam. The unevaporated solution returns to the cooler to cool down and then continues to separate phases, which increases the concentration of absorbent in the lower layer of the phase separator. When the relatively high concentration of absorbent enters the absorber, the system can obtain a higher heating temperature under the same absorption pressure.

[0064] In another preferred embodiment, the cooling component includes a regenerator, the absorbent outlet of the absorber is connected to the first solution inlet of the regenerator, the first solution outlet of the regenerator is connected to the solution inlet of the phase separator, the lower solution outlet of the phase separator is connected to the second solution inlet of the regenerator, and the second solution outlet of the regenerator is connected to the absorber.

[0065] The absorbent liquid flowing out of the absorber is cooled by a regenerator to lower its temperature, facilitating subsequent phase separation. Simultaneously, the lower layer of solution from the phase separator returns to the regenerator, which then acts as a heat source. By cooling the absorbent liquid from the absorber and simultaneously heating the lower layer of solution from the phase separator, the regenerator enables heat recovery, reduces heat loss, and ensures the absorber can supply heat at the appropriate temperature.

[0066] In another preferred embodiment, the cooling component includes a regenerator and a cooler. The absorbent outlet of the absorber is connected to the first solution inlet of the regenerator, the first solution outlet of the regenerator is connected to the first solution inlet of the cooler, and the solution outlet of the cooler is connected to a phase separator. The cooling component includes both a regenerator and a cooler. The regenerator is used for heat recovery, and the cooler further reduces the temperature of the absorbent, making it suitable for applications with low maximum melting point temperatures.

[0067] Preferably, the solution outlet of the evaporator is connected to the second solution inlet of the cooler for cooling the unevaporated solution in the evaporator. After the solution in the upper layer of the phase separator enters the evaporator, it generates steam. The unevaporated solution returns to the cooler for cooling and then continues to separate phases, which increases the absorbent concentration in the lower layer of the phase separator. Under the same absorption pressure, the system can obtain a higher heating temperature.

[0068] Preferably, the lower solution outlet of the phase separator is connected to the second solution inlet of the regenerator, and the second solution outlet of the regenerator is connected to the absorber.

[0069] The lower layer solution of the phase separator is fed into the regenerator to exchange heat with the high-temperature absorbent liquid flowing into the regenerator from the absorber, thus ensuring heat reuse and reducing heat loss.

[0070] The pressure reducing component is selected from a throttle valve.

[0071] The pressure reducing component lowers the solution pressure entering the evaporator from the phase separator, facilitating steam generation and improving the efficiency of subsequent absorption processes.

[0072] This application relates to a second type of absorption heat pump system with liquid-liquid phase separation. The generator is not an essential component. Compared with conventional second type absorption heat pumps, it only needs to consume one unit of low-temperature waste heat, resulting in less heat source consumption. At the same time, it simplifies equipment installation and operation and reduces production costs.

[0073] A binary mixture solution refers to a solution containing two components, such as a mixture of ammonia and water; a ternary mixture solution refers to a solution containing three components, such as a mixture of n-hexane, diethylene glycol, and benzene. A multi-component mixture solution is a mixture containing three or more components.

[0074] For binary, ternary, or multi-component mixed solutions, based on the differences in solubility between the solutions, the solution types can be divided into three categories: completely miscible, partially miscible, and completely immiscible. Completely miscible solutions can dissolve each other in any proportion to form a homogeneous liquid phase, with no interface between the substances. Completely immiscible solutions have substances with significantly different properties that do not dissolve in each other, resulting in a clear interface within the system. Partially miscible solutions fall between completely miscible and completely immiscible solutions; their solubility varies with temperature and they are not always in a completely miscible or completely immiscible state.

[0075] For partially miscible solutions, the concentration of a single component cannot be too high or too low. If the concentration of a single component is too high, such as 99%, the system will remain completely miscible rather than partially miscible due to the low concentration of the other component. In this case, the solubility between the components does not change with temperature. The partially miscible solutions discussed in this application refer to situations where the solubility state between the components can change with temperature, and the conversion to a completely miscible solution due to excessively high or low concentrations of a single component is not within the scope of this application.

[0076] Partially miscible solutions can be further classified into three categories based on the change in solubility with temperature: those with a maximum melting point temperature, those with a minimum melting point temperature, and those with both maximum and minimum melting points. For partially miscible solutions with a maximum melting point temperature, the mutual solubility decreases as temperature decreases; the higher the temperature, the closer the compositions of the conjugate solutions become. Above the maximum melting point temperature, they are completely miscible. Therefore, for solutions with a maximum melting point temperature, the temperature can be lowered below this temperature to achieve coarse separation of binary, ternary, or even multi-component solutions through liquid-liquid separation. For partially miscible solutions with a minimum melting point temperature, the mutual solubility decreases as temperature increases; the lower the temperature, the closer the compositions of the conjugate solutions become. Below the minimum melting point temperature, the liquid phases are completely miscible. Therefore, for binary, ternary, or even multi-component solutions with a minimum melting point temperature, the temperature can be raised above this temperature to achieve liquid-liquid phase separation through liquid-liquid separation.

[0077] The working fluid pairs used in this system are partially miscible. These can be binary, ternary, or multi-component partially miscible pairs. The solubility of the working fluid pairs changes with temperature. For ease of selection, the working fluid pairs used in this system are all those with either the highest or lowest melting point temperature.

[0078] The magnitude and minimum melting point of the working fluid determine the ease of liquid-liquid phase separation. If the maximum melting point of the working fluid is high, more cooling water is needed to lower it below the maximum melting point to achieve liquid-liquid phase separation. Conversely, if the minimum melting point of the working fluid is high, liquid-liquid phase separation is easier, but absorption is more difficult. Therefore, this application selects working fluid pairs with a maximum melting point of not less than 35°C and a minimum melting point of not more than 35°C. Commonly used pairs include water-phenol, water-isobutanol, water-aniline, nitrobenzene-n-hexane, Freon-refrigeration oil, water-ionic liquid, and water-triethylamine. Ternary partially miscible working fluid pairs include n-hexane-diethylene glycol-benzene, ethanol-water-vinyl nitrile, and ether-water-vinyl nitrile.

[0079] This invention relates to a second type of absorption heat pump system based on liquid-liquid phase separation, which can be used in waste heat recovery devices to raise waste heat at a lower temperature to a higher temperature. For example, waste heat at around 80°C can be processed by this system to provide heat at around 105°C.

[0080] The working process of the second type of absorption heat pump system based on liquid-liquid phase separation in this application is as follows:

[0081] Partially miscible binary or multi-component solutions undergo temperature regulation in a cooler and / or regenerator. When the system uses a working fluid pair with a maximum or minimum melting point temperature, the solution temperature is reduced to below the maximum melting point temperature or above the minimum melting point temperature via circulating water. That is, the working fluid pair solution temperature is controlled within the partially miscible temperature range by the cooler and / or regenerator, and then the solution enters the phase separator to achieve stratification. The resulting conjugate solutions are a saturated liquid of absorbent dissolved in refrigerant and a saturated liquid of refrigerant dissolved in absorbent, respectively. The stratified solution rich in refrigerant is depressurized and then transported to the evaporator, where it is heated by a low-temperature heat source to vaporize the refrigerant. The refrigerant vapor enters the absorber. The unevaporated solution in the evaporator and the stratified liquid rich in absorbent discharged from the phase separator enter the absorber to absorb the refrigerant vapor. After the refrigerant is absorbed, it releases high-temperature heat to the outside.

[0082] Example 1

[0083] As shown in Figure 2, a second type of absorption heat pump system based on liquid-liquid phase separation includes an absorber 1, a regenerator 2, a cooler 3, a phase separator 4, a pressure reducing component, a third solution pump 6, an evaporator 7, a compressor 8, and a first solution pump 9. The absorber 1 has an absorbent inlet (solution inlet) at the top and an absorbent outlet at the bottom, with a steam inlet and a heating medium inlet / outlet on its side wall. The regenerator 2 has a first solution inlet, a first solution outlet, a second solution inlet, and a second solution outlet. The cooler 3 has a solution inlet, a solution outlet, a temperature regulating medium inlet, and a temperature regulating medium outlet. The phase separator 4 has a solution inlet, an upper solution outlet (light phase solution outlet) on its side wall, and a lower solution outlet (heavy phase solution outlet) at its bottom. The evaporator 7 has a solution inlet, a steam outlet, a solution outlet, and a heating medium inlet / outlet. The pressure reducing component here is a throttle valve 5.

[0084] The absorbent outlet at the bottom of absorber 1 is connected to the inlet of the first solution pump 9, and the outlet of the first solution pump 9 is connected to the first solution inlet of regenerator 2; the absorbent inlet at the top of absorber 1 is connected to the second solution outlet of regenerator 2; the first solution outlet of regenerator 2 is connected to the solution inlet of cooler 3, and the second solution inlet of regenerator 2 is connected to the outlet of third solution pump 6; the solution outlet of cooler 3 is connected to the solution inlet of phase separator 4, the heavy phase solution outlet at the bottom of phase separator 4 is connected to the inlet of third solution pump 6, and the light phase solution outlet on the side wall of phase separator 4 is connected to the inlet of throttle valve 5; the outlet of throttle valve 5 is connected to the solution inlet of evaporator 7, the solution outlet of evaporator 7 is connected to the inlet of third solution pump 6, the steam outlet of evaporator 7 is connected to the inlet of compressor 8, and the outlet of compressor 8 is connected to the steam inlet of absorber 1.

[0085] In this embodiment, water-phenol is used as the working fluid pair. The water-phenol solution has a maximum melting point temperature, and its equilibrium phase diagram is shown in Figure 3. The maximum melting point temperature of the water-phenol solution is 65.9℃. That is, when the temperature of the binary mixed solution is higher than 65.9℃, water and phenol are completely miscible, and the solution cannot be separated without stratification. However, when the temperature is lower than 65.9℃, the solution stratifies and forms an upper aqueous phase solution, in which the phenol concentration is w1 as shown in the figure. A lower phenol-rich phase solution is formed, in which the phenol concentration is w2 as shown in the figure. The aqueous phase solution obtained from the stratification is used as the circulating coolant of the system, and the phenol-rich phase solution obtained from the stratification by the phase separator is used as the circulating absorbent of the system.

[0086] This embodiment uses the example of producing steam at a temperature greater than 100°C from waste heat at 80°C to illustrate the system's working process.

[0087] The outlet solution temperature of absorber 1 is 105℃, the absorption pressure is 1.20 bar (absolute pressure, the same below), and the water concentration is 50% (mass concentration, the same below). The high-temperature solution at 105℃ is cooled to 60℃ after passing through regenerator 2, and then enters cooler 3 where it is cooled to 40℃ by circulating water. The binary mixed solution at 40℃ enters phase separator 4 for settling and stratification. The resulting upper aqueous phase solution has a water content of 84.6%; the lower phenol-rich phase solution has a water content of 24.4%. The upper aqueous phase solution in phase separator 4 is depressurized to 0.38 bar through throttling valve 5, and then enters evaporator 7 where it is heated to 75℃ by a low-temperature heat source at 80℃, and then partially evaporates, yielding steam. The water content is 89.2%, the pressure is 0.38 bar, and the steam is pressurized to 1.20 bar by compressor 8 before entering absorber 1. The unevaporated solution in evaporator 7 has a water content of 81.6% and a temperature of 75°C. This solution mixes with the lower layer of phenol-rich solution (40°C, water content 24.4%) from phase separator 4, and after being pressurized by third solution pump 6, it enters regenerator 2, where it is heated to 100°C by the high-temperature solution. It then enters absorber 1 and absorbs 89.2% water vapor from compressor 8. The final liquid concentration in absorber 1 is 50%, the pressure is 1.2 bar, and the absorbent temperature is 105°C. Absorber 1 can provide 100°C steam externally. When the heat load of absorber 1 is 1000 kW, the low-temperature waste heat heat supply load of evaporator 7 is 1089 kW, and the total power consumption of compressor 8 and pumps is 99 kW. By adjusting the compression ratio of compressor 8 and changing the pressure of system absorber 1, a heat source above 100°C can be provided externally.

[0088] Table 2 shows a comparison of the relevant performance of the system in Example 1 with that of a conventional Type II absorption heat pump.

[0089] Table 2

[0090] This embodiment uses water-phenol as the working fluid pair, with a maximum melting point of 65.9℃. Therefore, solution stratification and coarse separation can be achieved through circulating water cooling. Compared to traditional type II absorption heat pumps, the separation process of the refrigerant and absorbent in this embodiment does not require heat consumption, and the system does not require driving heat input. The system performance coefficient (COP = total heat supply / (total heat consumption + total power consumption)) can reach over 0.8. Furthermore, the absorber pressure can be adjusted by the compressor, allowing the system to provide heat source temperatures of 100℃ or even higher.

[0091] Example 2

[0092] The difference from Example 1 is that the second type of absorption heat pump system based on liquid-liquid phase separation in this example does not include a cooler.

[0093] As shown in Figure 4, a second type of absorption heat pump system based on liquid-liquid phase separation includes an absorber 1, a regenerator 2, a phase separator 4, a throttling valve 5, a third solution pump 6, an evaporator 7, a compressor 8, and a first solution pump 9. The absorber 1 has an absorbent inlet at the top, an absorbent outlet at the bottom, a steam inlet on the side wall, and inlets and outlets for the heating medium. The regenerator 2 has a first solution inlet, a first solution outlet, a second solution inlet, and a second solution outlet. The phase separator 4 has a solution inlet, a light phase solution outlet on the side wall, and a heavy phase solution outlet at the bottom. The evaporator 7 has a solution inlet, a steam outlet, a solution outlet, and inlets and outlets for the heating medium. The absorbent outlet at the bottom of absorber 1 is connected to the inlet of the first solution pump 9, and the outlet of the first solution pump 9 is connected to the first solution inlet of regenerator 2; the absorbent inlet at the top of absorber 1 is connected to the second solution outlet of regenerator 2; the first solution outlet of regenerator 2 is connected to the solution inlet of phase separator 4, and the second solution inlet of regenerator 2 is connected to the outlet of third solution pump 6; the heavy phase solution outlet at the bottom of phase separator 4 is connected to the inlet of third solution pump 6, and the light phase solution outlet on the side wall of phase separator 4 is connected to the inlet of throttle valve 5; the outlet of throttle valve 5 is connected to the solution inlet of evaporator 7, the solution outlet of evaporator 7 is connected to the inlet of third solution pump 6, the steam outlet of evaporator 7 is connected to the inlet of compressor 8, and the outlet of compressor 8 is connected to the steam inlet of absorber 1.

[0094] In this embodiment, water-triethylamine, which has a minimum melting point temperature, is used as the working fluid pair in the second-type absorption compression heat pump system. The minimum melting point temperature of water-triethylamine is 18.5℃, meaning that when the binary mixed solution is below 18.5℃, water and triethylamine are completely miscible and the solution does not separate into layers; when the temperature is above 18.5℃, the solution separates into layers, forming an upper water-rich phase solution and a lower triethylamine-rich phase solution. In this embodiment, the upper water-rich phase solution in the phase separator 4 is used as the system refrigerant, and the lower triethylamine-rich solution in the phase separator 4 is used as the absorbent.

[0095] This embodiment uses the production of steam at temperatures above 100°C from waste heat at 80°C as an example to illustrate the system's operation. The outlet solution temperature of absorber 1 is 105°C. This high-temperature solution is cooled to 70°C after passing through regenerator 2. At this temperature, which is higher than the minimum melting point of water-triethylamine, the solution can directly enter phase separator 4 without further cooling. The resulting upper aqueous phase solution is depressurized by throttling valve 5 and then enters evaporator 7. Heated by low-temperature waste heat, some of the water in the solution vaporizes. The resulting steam is pressurized by compressor 8 and then enters absorber 1. The unevaporated triethylamine solution in evaporator 7 mixes with the lower triethylamine-rich solution in phase separator 4, and after being pressurized by third solution pump 6, it enters regenerator 2. It then enters absorber 1 and absorbs the steam compressed by compressor 8. Absorber 1 can provide 100°C steam externally.

[0096] In this embodiment, the absorber is a horizontal tube falling film absorber; the compressor is a Roots compressor; the regenerator is a shell and tube heat exchanger; and the evaporator is a falling film evaporator.

[0097] In this embodiment, water-triethylamine is used as the working fluid pair. The solution has a minimum melting point temperature of 18.5°C. The temperature of the absorbent after passing through the regenerator is higher than the melting point temperature of water-triethylamine. Therefore, the solution can achieve liquid-liquid separation without further cooling, reducing the consumption of circulating water.

[0098] Example 3

[0099] The difference from Example 1 is that the unevaporated solution in the evaporator is returned to the cooler for cooling and phase separation.

[0100] As shown in Figure 5, a second type of absorption heat pump system based on liquid-liquid phase separation includes an absorber 1, a regenerator 2, a cooler 3, a phase separator 4, a throttling valve 5, a third solution pump 6, an evaporator 7, a compressor 8, a first solution pump 9, and a second solution pump 10. The absorber 1 has an absorbent inlet at the top, an absorbent outlet at the bottom, a steam inlet on the side wall, and inlets and outlets for the heating medium. The regenerator 2 has a first solution inlet, a first solution outlet, a second solution inlet, and a second solution outlet. The cooler 3 has a solution inlet, a solution outlet, a temperature regulating medium inlet, and a temperature regulating medium outlet. The phase separator 4 has a solution inlet, a light phase solution outlet on the side wall, and a heavy phase solution outlet at the bottom. The evaporator 7 has a solution inlet, a steam outlet, a solution outlet, and inlets and outlets for the heating medium.

[0101] The absorbent outlet at the bottom of absorber 1 is connected to the inlet of the first solution pump 9, and the outlet of the first solution pump 9 is connected to the first solution inlet of regenerator 2; the absorbent inlet at the top of absorber 1 is connected to the second solution outlet of regenerator 2; the first solution outlet of regenerator 2 is connected to the solution inlet of cooler 3, and the second solution inlet of regenerator 2 is connected to the outlet of the third solution pump 6; the solution outlet of cooler 3 is connected to the solution inlet of phase separator 4, the heavy phase solution outlet at the bottom of phase separator 4 is connected to the inlet of the third solution pump 6, and the light phase solution outlet on the side wall of phase separator 4 is connected to the inlet of throttle valve 5; the outlet of throttle valve 5 is connected to the solution inlet of evaporator 7, the solution outlet of evaporator 7 is connected to the inlet of second solution pump 10, and the outlet of second solution pump 10 is connected to the solution inlet of cooler 3; the steam outlet of evaporator 7 is connected to the inlet of compressor 8, and the outlet of compressor 8 is connected to the steam inlet of absorber 1.

[0102] In this embodiment, water-isobutanol is used as the working fluid pair, and the water-isobutanol solution has the highest melting point temperature. In this embodiment, the absorber is a vertical tube falling film absorber; the compressor is a centrifugal compressor; the regenerator is a plate heat exchanger; the cooler is a plate cooler; and the evaporator is a kettle evaporator.

[0103] The working method of this embodiment is similar to that of Embodiment 1, and will not be repeated here. The difference from Embodiment 1 is that the unevaporated solution in the evaporator 7 is returned to the cooler 3 by the second solution pump 10 for cooling and phase separation.

[0104] This embodiment increases the absorbent concentration in the lower layer solution of the phase separator by returning the unevaporated solution in the evaporator to the cooler for cooling and further phase separation. When the high-concentration absorbent enters the absorber, the system can achieve a higher heating temperature under the same absorption pressure. Furthermore, because the unevaporated solution in the evaporator returns to the cooler instead of entering the absorber together with the heavy phase solution from the phase separator, the absorbent circulation volume is reduced, significantly decreasing the area of ​​the regenerator and the power consumption of the first and second solution pumps.

[0105] Example 4

[0106] The difference from Example 1 is that this example does not have a regenerator.

[0107] As shown in Figure 6, a second type of absorption heat pump system based on liquid-liquid phase separation includes an absorber 1, a cooler 3, a phase separator 4, a throttling valve 5, a third solution pump 6, an evaporator 7, a compressor 8, and a first solution pump 9. The absorbent outlet at the bottom of the absorber 1 is connected to the inlet of the first solution pump 9, and the outlet of the first solution pump 9 is connected to the solution inlet of the cooler 3; the solution inlet of the absorber 1 is connected to the outlet of the third solution pump 6; the solution outlet of the cooler 3 is connected to the solution inlet of the phase separator 4; the heavy phase solution outlet at the bottom of the phase separator 4 is connected to the inlet of the third solution pump 6; the light phase solution outlet on the side wall of the phase separator 4 is connected to the inlet of the throttling valve 5; the outlet of the throttling valve 5 is connected to the solution inlet of the evaporator 7; the solution outlet of the evaporator 7 is connected to the inlet of the third solution pump 6; the steam outlet of the evaporator 7 is connected to the inlet of the compressor 8; and the outlet of the compressor 8 is connected to the steam inlet of the absorber 1.

[0108] In this embodiment, the working fluid is water-aniline, and the water-aniline solution has the highest melting point temperature. The absorber is a vertical tube falling film absorber; the compressor is a centrifugal compressor; the cooler is a plate cooler; and the evaporator is a kettle evaporator.

[0109] The working method of this embodiment is similar to that of Embodiment 1, and will not be repeated here. Compared with Embodiment 1, this embodiment does not contain a regenerator, which facilitates system integration and skid mounting, and is suitable for applications with a large waste heat supply.

[0110] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A second order absorption heat pump system based on liquid-liquid phase separation, characterized in that, The system comprises an absorber, a cooling component, a phase separator, a pressure reducing component, an evaporator and a compressor; the absorption liquid outlet of the absorber is connected to the solution inlet of the cooling component, the solution outlet of the cooling component is connected to the solution inlet of the phase separator, the upper layer solution outlet of the phase separator is connected to the evaporator, the lower layer solution outlet of the phase separator is connected to the solution inlet of the absorber, the steam outlet of the evaporator is connected to the steam inlet of the absorber, the pressure reducing component is arranged between the phase separator and the evaporator, and the compressor is arranged between the evaporator and the absorber to regulate the steam pressure entering the absorber; and the working medium pair used in the system is a partially miscible working medium pair. The cooling component comprises a cooler, the absorption liquid outlet of the absorber is connected to the first solution inlet of the cooler, and the solution outlet of the cooler is connected to the phase separator. The solution outlet of the evaporator is connected to the second solution inlet of the cooler to cool the non-evaporated solution in the evaporator.

2. The second class liquid-liquid phase separation based absorption heat pump system according to claim 1, wherein, The cooling component further comprises a regenerator, the absorption liquid outlet of the absorber is connected to the first solution inlet of the regenerator, the first solution outlet of the regenerator is connected to the first solution inlet of the cooler, and the solution outlet of the cooler is connected to the phase separator.

3. The second class liquid-liquid phase separation based absorption heat pump system according to claim 1 or 2, characterized in that, A first solution pump is arranged between the absorber and the cooling component, and the absorption liquid outlet of the absorber is connected to the solution inlet of the cooling component through the first solution pump.

4. The second class liquid-liquid phase separation based absorption heat pump system according to claim 1 or 2, characterized in that, A second solution pump is arranged between the evaporator and the cooler, and the solution outlet of the evaporator is connected to the second solution inlet of the cooler through the second solution pump.

5. The liquid-liquid phase separation based second order absorption heat pump system according to claim 2, wherein, A third solution pump is arranged between the phase separator and the regenerator, and the lower layer solution outlet of the phase separator is connected to the second solution inlet of the regenerator through the third solution pump.

6. The liquid-liquid phase separation based second order absorption heat pump system according to claim 2, wherein, The lower layer solution outlet of the phase separator is connected to the second solution inlet of the regenerator, and the second solution outlet of the regenerator is connected to the absorber.

7. The liquid-liquid phase separation based second order absorption heat pump system according to claim 1 or 2, characterized in that, The pressure reducing component is selected from a throttle valve.

8. The liquid-liquid phase separation based second order absorption heat pump system according to claim 1 or 2, characterized in that, The working medium pair is a binary or ternary partially miscible working medium pair.

9. The liquid-liquid phase separation based second order absorption heat pump system according to claim 8, characterized in that, The working medium pair is a working medium pair with the highest consolute temperature or a working medium pair with the lowest consolute temperature.

10. The liquid-liquid phase separation based second order absorption heat pump system according to claim 9, characterized in that, The working medium pair has a consolute temperature not lower than 35℃ or a consolute temperature not higher than 35℃.

11. The liquid-liquid phase separation based second order absorption heat pump system according to claim 10, characterized in that, The working medium pair is selected from any one of water-phenol, water-isobutanol, water-aniline, nitrobenzene-n-hexane, freon-refrigerant oil, water-ionic liquid, water-triethylamine, n-hexane-diethylene glycol-benzene, ethanol-water-vinyl cyanide, ether-water-vinyl cyanide.

12. A waste heat recovery device comprising a second class absorption heat pump system based on liquid-liquid phase separation according to any one of claims 1 to 11, characterized in that, The evaporator is provided with a waste heat medium inlet and a waste heat medium outlet, and the waste heat medium is connected to the waste heat medium inlet through a pipeline.

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