Amino water solution reabsorption long-distance heat supply system for improving user energy grade

Abstract

The application discloses an ammonia water solution reabsorption long-distance heat supply system for improving user energy grade, which comprises a waste heat source, a heat supply end, a high-pressure generator, a high-pressure absorber, a low-pressure generator, a low-pressure absorber, a high-quality heat supply generator and a high-quality heat supply absorber. The high-pressure generator and the high-pressure absorber are arranged close to the waste heat source and are configured to convert waste heat energy of the waste heat source into solution concentration difference to generate dilute ammonia solution and concentrated ammonia solution. The low-pressure generator and the low-pressure absorber and the high-quality heat supply generator and the high-quality heat supply absorber are arranged close to the heat supply end and are configured to provide different quality heat energy for users. The waste heat source and the heat supply end are connected through a long-distance reabsorption circulation conveying section, and the conveying working medium is dilute ammonia solution, concentrated ammonia solution and mixed concentration ammonia solution. The application can reduce the driving heat source temperature, increase the heat transfer distance, improve the heat supply efficiency and effectively solve the user energy quality.

Description

Technical Field

[0001] This invention relates to the field of long-distance heat transmission system technology, and in particular to a long-distance heat supply system that uses ammonia solution reabsorption to improve the energy quality for users. Background Technology

[0002] 70% of my country's total energy consumption comes from industrial production, and 50% of industrial energy consumption can be converted into industrial waste heat. Currently, my country's industrial waste heat recovery rate is relatively low, at only 30%. The recovery and utilization of industrial waste heat will make a significant contribution to energy conservation and emission reduction. According to temperature range, industrial waste heat can be divided into high-temperature waste heat (>650℃), medium-temperature waste heat (230℃~650℃), and low-temperature waste heat (<230℃). Waste heat resources with temperatures below 200℃ account for 64%, and absorption heat pumps can effectively recover medium and low-temperature waste heat.

[0003] In real-world scenarios, industrial areas generating significant waste heat are often located far from residential areas requiring heating, ranging from tens to hundreds of kilometers apart, necessitating long-distance (generally over 10 kilometers) heat transfer. The performance of traditional hot water sensible heat transfer systems relies heavily on the insulation material and its thickness. Underground trench laying is the primary method for laying heating pipelines in my country. Tests on perlite-insulated heating networks show a temperature drop of 10°C to 20°C per kilometer, resulting in significant energy waste. Using aerogel insulation felt, which offers better insulation, as the insulation material for pipelines, the annual insulation cost reaches as high as 337 yuan per meter. This high cost significantly limits long-distance heat transfer. Developing low-heat-loss heat transfer technologies, expanding the heating radius, and enhancing waste heat utilization are important research directions for energy conservation and emission reduction.

[0004] Therefore, those skilled in the art are dedicated to developing a long-distance heating system that uses ammonia solution reabsorption to improve the energy quality for users, in order to overcome the problems existing in the prior art. Summary of the Invention

[0005] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is:

[0006] 1. The driving heat source temperature of the absorption cycle is relatively high. The driving heat source temperature of the single-stage absorber-generator heat exchanger (GAX) ammonia water cycle is around 150℃, which is insufficient for the utilization of waste heat / solar thermal energy below 150℃.

[0007] 2. The heat source and the heat consumption side are far apart, resulting in significant heat loss during long-distance heat transport.

[0008] 3. The output heat energy level of the absorption long-distance heat transfer system is relatively low, and the maximum heating temperature is 50℃.

[0009] To achieve the above objectives, the present invention provides an ammonia solution reabsorption long-distance heating system for improving the energy quality of users, comprising a waste heat source, a heating end, a high-pressure generator, a high-pressure absorber, a low-pressure generator, a low-pressure absorber, a quality-improving heating generator, and a quality-improving heating absorber. The high-pressure generator and the high-pressure absorber are located near the waste heat source and are configured to convert the waste heat energy of the waste heat source into a solution concentration difference to generate dilute ammonia solution and concentrated ammonia solution. The low-pressure generator and the low-pressure absorber, as well as the quality-improving heating generator and the quality-improving heating absorber, are located near the heating end and are respectively configured to provide users with heat energy of different qualities. The waste heat source and the heating end are connected by a long-distance reabsorption circulation transport section, and the transport working fluid is dilute ammonia solution, concentrated ammonia solution, and a mixed concentration ammonia solution.

[0010] Furthermore, the high-pressure generator is connected to the waste heat source and is configured to absorb the medium-low temperature waste heat from the waste heat source to generate a dilute ammonia solution and a first ammonia vapor, and to deliver the first ammonia vapor to the high-pressure absorber; the low-pressure generator is configured to absorb ambient heat to generate a second ammonia vapor and a second solution, and to deliver the second ammonia vapor to the low-pressure absorber; the quality-improving heating generator is configured to absorb heat from the low-pressure absorber to produce an eighth solution and a third ammonia vapor, and to deliver the third ammonia vapor to the quality-improving heating generator.

[0011] Further, the long-distance reabsorption circulation transport section includes a solution separation tank, a solution mixing tank, a quality improvement and heating solution mixing tank, a dilute solution transport pipeline, a mixed solution transport pipeline, and a concentrated solution transport pipeline. The dilute ammonia solution generated by the high-pressure generator is divided into two paths via a heat source-side heat exchanger, a dilute solution transport pump, the dilute solution transport pipeline, and a user-side heat exchanger through a first three-way valve. One path, as the tenth solution, enters the low-pressure absorber through a dilute solution throttling valve to absorb the exothermic heat from the low-temperature, low-pressure ammonia vapor generated by the low-pressure generator absorbing ambient heat, producing a first solution. After exchanging heat with the dilute ammonia solution in the user-side heat exchanger, the first solution enters the solution mixing tank and mixes with the second solution to generate the mixed concentration ammonia solution. The other path, as the fifth solution, enters the quality improvement and heating absorber through a quality improvement and heating dilute solution heat exchanger and a quality improvement and heating dilute solution throttling valve to absorb the third ammonia vapor, producing a seventh solution. The seventh solution, after exchanging heat with the fifth solution in the quality improvement and heating dilute solution heat exchanger, enters the quality improvement and heating solution mixing tank; the mixed... A mixed-concentration ammonia solution, via a mixed-solution delivery pump and pipeline, is separated into a third and a fourth solution by a solution separation tank. The third solution is preheated by a heat exchanger on the heat source side and then enters the high-pressure generator. The fourth solution enters the high-pressure absorber, absorbing the first ammonia vapor from the high-pressure generator and releasing heat to generate the concentrated ammonia solution. The concentrated ammonia solution is pressurized by a concentrated solution delivery pump and then enters the concentrated solution delivery pipeline. It is split into two paths by a second three-way valve. One path, as the eleventh solution, enters the low-pressure generator via a concentrated solution throttling valve to absorb ambient heat and generate the second ammonia vapor and the second solution. The other path, as the sixth solution, enters the upgrading and heating concentrated solution heat exchanger and throttling valve to generate the upgrading and heating generator. The eighth solution exchanges heat with the sixth solution via the upgrading and heating concentrated solution heat exchanger and then enters the upgrading and heating mixing tank to mix with the seventh solution to generate the ninth solution, which flows to the solution mixing tank via the upgrading and heating shut-off valve.

[0012] Further, the system includes a third three-way valve, a fourth three-way valve, a first three-way valve at the heating end, and a second three-way valve at the heating end. The return water from the heating end is divided into two paths by the second three-way valve at the heating end. One path, as the second return water, enters the quality-improving heating absorber and absorbs heat to form the second supply water. The other path, as the first return water, enters the low-pressure absorber through the third three-way valve and then passes through the fourth three-way valve to form the first supply water. The first and second supply waters are combined by the first three-way valve at the heating end to provide heat to the heating end. The other end of the fourth three-way valve, as the third supply water, absorbs heat in the low-pressure absorber and flows to the quality-improving heating absorber to provide heat, forming the third return water. The third return water then flows back to the low-pressure absorber through the other end of the third three-way valve.

[0013] Furthermore, the system's operating modes include a normal heating mode and an upgraded heating mode. The normal heating mode is used when the energy demand temperature at the heating end is not higher than 50°C, and the upgraded heating mode is used when the energy demand temperature is higher than 50°C but lower than 80°C.

[0014] Furthermore, when the system is operating in the normal heating mode, the first three-way valve is operated to allow the dilute ammonia solution to flow, the tenth solution to flow, and the fifth solution to be cut off; the second three-way valve is operated to allow the concentrated ammonia solution to flow, the eleventh solution to flow, and the sixth solution to be cut off; the quality-enhancing heating shut-off valve is closed; the third three-way valve is operated to allow the first return water to flow and the third return water to be cut off; the fourth three-way valve is operated to allow the first supply water to flow and the third supply water to be cut off; the first three-way valve at the heating end is operated to allow the supply water to flow, the first supply water to flow, and the second supply water to be cut off; the second three-way valve at the heating end is operated to allow the return water to flow, the first return water to flow, and the second return water to be cut off.

[0015] Furthermore, when the system operates in the upgraded heating mode, the first three-way valve is operated to allow the dilute ammonia solution, the tenth solution, and the fifth solution to flow; the second three-way valve is operated to allow the concentrated ammonia solution, the eleventh solution, and the sixth solution to flow; the upgraded heating shut-off valve is opened; the third three-way valve is operated to cut off the first return water flow and allow the third return water flow; the fourth three-way valve is operated to cut off the first supply water flow and allow the third supply water flow; the first three-way valve at the heating end is operated to allow the supply water flow, cut off the first supply water flow, and allow the second supply water flow; the second three-way valve at the heating end is operated to allow the return water flow, cut off the first return water flow, and allow the second return water flow.

[0016] Furthermore, the dilute ammonia solution, concentrated ammonia solution, and mixed concentration ammonia solution can be transported with virtually no temperature difference from the environment in the dilute solution transport pipeline, concentrated solution transport pipeline, and mixed solution transport pipeline, respectively.

[0017] Furthermore, the waste heat source is a heat source with a temperature higher than 90°C and lower than 150°C generated by the high-temperature exhaust steam from the boiler after the steam turbine has done work, which is recovered by the circulating water of the condenser and cooling tower of the power plant.

[0018] Furthermore, the heating end is equipped with a hot water storage tank and a fan coil unit. Heat energy with a required temperature of no more than 50°C is directly radiated for heating at the heating end through the fan coil unit, while heat energy with a required temperature of more than 50°C but less than 80°C is stored through the hot water storage tank.

[0019] The beneficial effects of this invention are as follows:

[0020] 1. A single-stage reabsorption heating cycle using ammonia as the working fluid can reduce the driving heat source temperature to 82℃, and a two-stage cycle based on the single-stage reabsorption cycle can reduce the driving heat source temperature to 73℃.

[0021] 2. It increases the heat transmission distance, with a theoretical transmission distance of up to 113km for the reabsorption cycle; it has advantages over hot water systems; the high-pressure generator can utilize waste heat at a lower temperature and release it on the heat-using side, resulting in higher heating efficiency.

[0022] 3. The reabsorption cycle heating temperature can reach 80℃, effectively solving the energy quality problem for users.

[0023] 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

[0024] Figure 1 This is a process flow diagram of the ordinary heating mode of a heat transfer system according to a preferred embodiment of the present invention;

[0025] Figure 2 This is a process flow diagram of the heat transfer system's improved heating mode according to a preferred embodiment of the present invention.

[0026] Among them, 1-high pressure generator, 2-high pressure absorber, 3-low pressure absorber, 4-low pressure generator, 5-quality upgrading and heating absorber, 6-quality upgrading and heating generator, 7-solution separation tank, 8-solution mixing tank, 9-quality upgrading and heating solution mixing tank, 10-dilute solution transfer pump, 11-mixed solution transfer pump, 12-concentrated solution transfer pump, 13-dilute solution transfer pipeline, 14-mixed solution transfer pipeline, 15-concentrated solution transfer pipeline, 16-dilute solution throttling valve, 17-concentrated solution throttling valve, 18-quality upgrading and heating dilute solution throttling valve, 19-quality upgrading and heating concentrated solution throttling valve, 20-heat source side heat exchanger, 21-user side heat exchanger, 22-quality upgrading and heating dilute solution heat exchanger, 23-... - Heat exchanger for upgraded heating concentrated solution, 24-First three-way valve, 25-Second three-way valve, 26-Upgraded heating shut-off valve, 27-Third three-way valve, 28-Fourth three-way valve, 29-Heating end first three-way valve, 30-Heating end second three-way valve, 31-Industrial waste heat source, 32-Heating end, A-Dilute ammonia solution, B-Mixed concentration ammonia solution, C-Concentrated ammonia solution, D-First solution, E-Second solution, F-Third solution, G-Fourth solution, H-Fifth solution, J-Sixth solution, K-Seventh solution, L-Eighth solution, M-Ninth solution, N-Tenth solution, P-Eleventh solution, X-High temperature and high pressure ammonia vapor, Y-Low temperature and low pressure ammonia vapor, Z-Upgraded heating ammonia vapor. Detailed Implementation

[0027] The preferred embodiments of the present invention are described below with reference to the accompanying drawings to make the technical content clearer and easier to understand. The present invention can be embodied in many different forms, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0028] In the accompanying drawings, components with the same structure are indicated by the same numerical designation, and components with similar structures or functions are indicated by similar numerical designations. The dimensions and thicknesses of each component shown in the drawings are arbitrary, and the present invention does not limit the dimensions and thicknesses of each component. To make the illustrations clearer, the thickness of some components has been appropriately exaggerated in the drawings.

[0029] Among various long-distance heat energy transmission technologies, gas-liquid absorption technology can effectively solve the problems of high pump power consumption and high heat loss. This invention uses ammonia water reabsorption circulation, which further reduces the temperature of the high-temperature heat source compared to general absorption circulation, expanding the scope of waste heat utilization. On the user side, the heating temperature can be increased to 80°C according to actual heat demand, effectively solving the problem of energy quality.

[0030] In existing technologies, the driving heat source temperature of absorption cycles is relatively high, with a single-stage GAX ammonia cycle reaching around 150°C. This results in insufficient utilization of waste heat / solar thermal energy below 150°C. Therefore, this invention uses a high-pressure absorber and a low-pressure generator to replace the condenser and evaporator in a typical absorption cycle. The absorption process of the binary solution replaces the evaporation and condensation processes, relying on the concentration difference to drive the heating cycle. The concentration of the concentrated solution in the absorption cycle remains constant at 99.8%. After the cycle is reconstructed, the concentration of the concentrated solution is slightly lower. Under the condition of the same outlet concentrated solution temperature, the pressure on the heat source side is lower, significantly reducing the requirement for the driving heat source temperature. The driving heat source temperature of a single-stage reabsorption heating cycle using ammonia as the working fluid can be reduced to 82°C, and a two-stage cycle based on a single-stage reabsorption cycle can reduce the driving heat source temperature to 73°C.

[0031] To address the issue of significant heat loss during long-distance heat transfer when the heat source and heat-consuming side are far apart, this invention employs a reabsorption cycle. Heat from the heat source is converted into a concentration gradient stored in the solution, and then the solution concentration is converted back into heat at the heat-consuming end. This avoids excessive temperature loss to the environment during transport and eliminates the need for insulation. Ammonia solutions absorb or release heat during concentration changes. In the reabsorption cycle, the heat input at the heat-consuming end is converted into a concentration gradient in the high-pressure generator, and then converted back into heat in the low-pressure absorber to supply the user. This increases the heat transfer distance; theoretically, the reabsorption cycle can reach a distance of 113 km, offering advantages over hot water systems. The high-pressure generator can utilize lower-temperature waste heat and release it at the heat-consuming side, resulting in higher heating efficiency.

[0032] Addressing the issue of low output heat energy levels in existing absorption-type long-distance heat transfer systems, with a maximum heating temperature of only 50°C, this invention supplies the heat released by the low-pressure absorber to the booster generator, further increasing the internal pressure difference of the cycle and achieving a higher temperature level on the heat source side. While the coefficient of performance (COP) of a single-stage cycle has a theoretical upper limit, cascaded cycles reduce the system's COP, effectively improving heat release quality and thus enabling applications in various heating demand scenarios. The reabsorption cycle can achieve a heating temperature of 80°C, effectively solving users' energy quality problems.

[0033] Example

[0034] like Figure 1 , Figure 2 As shown, this embodiment provides a long-distance heating system for ammonia solution reabsorption that improves the energy quality for users. It consists of an industrial waste heat source 31, a heating terminal 32, and a heat transfer circulation system with zero heat loss due to concentration difference reabsorption. The medium- and low-temperature heat source of the industrial waste heat source 31 comes from a power plant. The power plant recovers the high-temperature exhaust steam from the boiler after it has been used by the turbine through the circulating water in the condenser and cooling tower, generating a heat source of 90℃~150℃.

[0035] High-pressure generator 1 is connected to industrial waste heat source 31 and is used to absorb low-temperature waste heat from industrial waste heat source 31 to generate high-temperature dilute ammonia solution A and high-temperature high-pressure ammonia vapor X.

[0036] Solution separation tank 7 is used to separate the mixed concentration ammonia solution B delivered to the heat source side into a third solution F and a fourth solution G. Heat exchanger 20 on the heat source side is used to recover the sensible heat of the dilute ammonia solution A generated by high-pressure generator 1, ensuring no temperature difference between the dilute ammonia solution A and the environment, and simultaneously preheating the third solution F that is about to enter high-pressure generator 1. Dilute solution transfer pump 10 is used to transfer the dilute ammonia solution A generated by high-pressure generator 1 to dilute solution transfer pipeline 13. Concentrated solution transfer pump 12 is used to transfer the concentrated ammonia solution C generated by high-pressure absorber 2 to concentrated solution transfer pipeline 15.

[0037] High-temperature dilute ammonia solution A exits from high-pressure generator 1, exchanges heat with the third solution F from solution separation tank 7 via heat exchanger 20 on the heat source side, and then enters dilute solution delivery pipeline 13 after being pressurized by dilute solution delivery pump 10, where it is transmitted to the environment without temperature difference.

[0038] High-temperature, high-pressure ammonia vapor X enters high-pressure absorber 2 from high-pressure generator 1. Mixed-concentration ammonia solution B is separated into third solution F and fourth solution G via solution separator 7. Third solution F exchanges heat with dilute ammonia solution A in heat source-side heat exchanger 20 to increase its temperature before entering high-pressure generator 1 to absorb industrial waste heat. Fourth solution G enters high-pressure absorber 2, where it absorbs the high-temperature, high-pressure ammonia vapor X from high-pressure generator 1, releasing heat to generate concentrated ammonia solution C. Concentrated ammonia solution C is pressurized by concentrated solution transfer pump 12 and enters concentrated solution transfer pipeline 15 for temperature-free transmission to the environment.

[0039] Dilute ammonia solution A, pressurized by dilute solution transfer pump 10, enters user-side heat exchanger 21 through dilute solution transfer pipeline 13. Dilute ammonia solution A exchanges heat with the first solution D through user-side heat exchanger 21. After being heated, dilute ammonia solution A is divided into tenth solution N and fifth solution H through first three-way valve 24.

[0040] The tenth solution N, after being depressurized by the dilute solution throttling valve 16, enters the low-pressure absorber 3 to absorb low-temperature, low-pressure ammonia vapor Y and release heat, producing the first solution D. The first solution D, after exchanging heat with the dilute ammonia solution A in the user-side heat exchanger 21, enters the solution mixing tank 8 and mixes with the second solution E to generate a mixed concentration ammonia solution B.

[0041] The fifth solution H enters the upgrading and heating dilute solution heat exchanger 22 and exchanges heat with the seventh solution K, then its temperature rises. It then enters the upgrading and heating absorption tank 5 via the upgrading and heating dilute solution throttling valve 18. In the upgrading and heating absorption tank 5, the fifth solution H absorbs the upgrading and heating ammonia vapor Z to produce the seventh solution K, releasing heat which enters the heating end 32. The seventh solution K exits the upgrading and heating absorption tank 5, exchanges heat with the fifth solution H again via the upgrading and heating dilute solution heat exchanger 22, and enters the upgrading and heating solution mixing tank 9 to mix with the eighth solution L to generate the ninth solution M. This ninth solution M then flows back to the solution mixing tank 8 via the upgrading and heating shut-off valve 26.

[0042] A mixed concentration ammonia solution B flows out from the solution mixing tank 8, is pressurized by the mixed solution transfer pump 11, and enters the solution separation tank 7 through the mixed solution transfer pipeline 14, where it is transferred to the environment without temperature difference.

[0043] The concentrated ammonia solution C, pressurized by the concentrated solution transfer pump 12, enters the second three-way valve 25 through the concentrated solution transfer pipeline 15. The concentrated ammonia solution C is then divided into the sixth solution J and the eleventh solution P by the second three-way valve 25.

[0044] The eleventh solution P enters the low-pressure generator 4 through the concentrated solution throttling valve 17. In the low-pressure generator 4, the eleventh solution P absorbs heat from the environment, generating the second solution E and low-temperature, low-pressure ammonia vapor Y. The low-temperature, low-pressure ammonia vapor Y enters the low-pressure absorber 3 and is absorbed and releases heat by the tenth solution N. The second solution E and the first solution D are mixed in the solution mixing tank 8 to generate a mixed-concentration ammonia solution B.

[0045] The sixth solution J enters the heat exchanger 23 for concentrated solution in the upgrading and heating process, where it exchanges heat with the eighth solution L and is heated. It then enters the upgrading and heating generator 6 via the throttling valve 19. In the generator 6, the sixth solution J absorbs heat from the low-pressure absorber 3, generating the eighth solution L and high-temperature upgrading and heating ammonia vapor Z. The eighth solution L exchanges heat with the sixth solution J again via the heat exchanger 23 and enters the mixing tank 9 for upgrading and heating, where it mixes with the seventh solution K to generate the ninth solution M. The upgrading and heating ammonia vapor Z enters the absorber 5, where it is absorbed by the fifth solution H, releasing heat and generating the seventh solution K.

[0046] Q HPG Q is the heat absorbed by the high-voltage generator 1 from the industrial waste heat source 31. HPA Q is the heat released into the environment by the high-pressure absorber 2. LPG This is the heat absorbed by the low-pressure generator 4 from the environment. Q LPA It is the heat released by the low-pressure generator 3 to the heating end 32.

[0047] Return water RW is the return water from the heating end 32. The first return water RW1 flows to the low-pressure absorber 3 via the second three-way valve 30 at the heating end. The second return water RW2 flows to the upgrading heat absorption unit 5 via the second three-way valve 30 at the heating end. The third return water RW3 flows back to the low-pressure absorber 3 to absorb absorbed heat after absorbing heat in the upgrading heat generator 6. Supply water SW is the water supplied to the heating end 32. The first supply water SW1 flows to the first three-way valve 29 at the heating end via the low-pressure absorber 3. The second supply water SW2 flows to the first three-way valve 29 at the heating end via the upgrading heat absorption unit 5. The third supply water SW3 flows to the upgrading heat absorption unit 5 to provide heat after absorbing absorbed heat in the low-pressure absorber 3.

[0048] The heating end 32 is located far from the industrial waste heat source 31. The heating end 32 is equipped with a hot water storage tank and fan coil units. Heat energy at 40℃~50℃ is directly used for radiant heating at the heating end 32 via the fan coil units. Heat energy at 50℃~80℃ can be stored in the hot water storage tank, which helps to smooth out peak and off-peak temperatures and improve energy efficiency. High-pressure generator 1 and high-pressure absorber 2 are located on the side of the industrial waste heat source 31, converting waste heat energy into a concentration difference to produce dilute and concentrated ammonia solutions. Low-pressure generator 4 and low-pressure absorber 3, along with the quality-improving heating generator 6 and quality-improving heating absorber 5, are located on the side of the heating end 32, providing users with heat energy of different qualities. A long-distance transmission section connects the industrial waste heat source 31 and the heating end 32, using dilute ammonia solution A, concentrated ammonia solution C, and a mixed concentration ammonia solution B as the working fluid, ensuring temperature-free transmission with the environment.

[0049] This embodiment includes two operating modes: normal heating mode and upgraded heating mode. Normal heating mode is used when the energy demand temperature at the heating end 32 is not higher than 50℃, and upgraded heating mode is used when the energy demand temperature is higher than 50℃ but lower than 80℃.

[0050] The first operating mode of the embodiment is the normal heating mode, such as... Figure 1 As shown. In this heating mode, at the connection of the first three-way valve 24: dilute ammonia solution A is open, the tenth solution N is open, and the fifth solution H is closed. At the connection of the second three-way valve 25: concentrated ammonia solution C is open, the eleventh solution P is open, and the sixth solution J is closed. The quality-upgrading heating shut-off valve 26 is closed. At the connection of the third three-way valve 27: the first return water RW1 is open, and the third return water RW3 is closed. At the connection of the fourth three-way valve 28: the first supply water SW1 is open, and the third supply water SW3 is closed. At the connection of the first three-way valve 29 at the heating end: supply water SW is open, the first supply water SW1 is open, and the second supply water SW2 is closed. At the connection of the second three-way valve 30 at the heating end: return water RW is open, the first return water RW1 is open, and the second return water RW2 is closed. After passing through the user-side heat exchanger 21, dilute ammonia solution A goes through the first three-way valve 24 to the dilute solution throttling valve 16. Concentrated ammonia solution C goes through the second three-way valve 25 to the concentrated solution throttling valve 17. The return water RW passes through the second three-way valve 30 at the heating end to become the first return water RW1. The first return water RW1 enters the low-pressure absorber 3 through the third three-way valve 27 to absorb heat, and then becomes the first supply water SW1 through the fourth three-way valve 28. The first supply water SW1 becomes the supply water SW through the first three-way valve 29 at the heating end, which is used for heating the residence.

[0051] The driving heat source for the high-pressure generator 1 comes from the power plant. When the power plant supplies energy to the system, it recovers the high-temperature exhaust steam from the boiler after it has done work on the turbine through the circulating water of the condenser and cooling tower, generating a heat source of 90℃~150℃. The heat source provides heat to the high-pressure generator 1 through the circulating water, generating a high-temperature dilute ammonia solution A and a high-temperature, high-pressure ammonia vapor X. The high-pressure absorber 2 absorbs the high-temperature, high-pressure ammonia vapor X to produce a concentrated ammonia solution C. The high-temperature dilute ammonia solution A is reheated by the third solution F from the solution separator 7 through the heat exchanger 20 on the heat source side, and most of the sensible heat is recovered. The dilute ammonia solution A, which has a small temperature difference with the environment, is pressurized by the dilute solution transfer pump 10 and enters the long-distance dilute solution transfer pipeline 13. The concentrated ammonia solution C is cooled by cooling water, and its outlet temperature has a small temperature difference with the environment, so it does not need to be reheated. It is then pressurized by the concentrated solution transfer pump 12 and enters the long-distance concentrated solution transfer pipeline 15. Ammonia solution B, with no temperature difference from the environment, is transported to the heat source side via mixed solution transfer pump 11 and mixed solution transfer pipeline 14. It is then separated into a third solution F and a fourth solution G by solution separator 7, which enter high-pressure generator 1 and high-pressure absorber 2 respectively. The fourth solution G enters high-pressure absorber 2 without reheating, absorbing high-temperature, high-pressure ammonia vapor X to generate concentrated ammonia solution C. The third solution F enters high-pressure generator 1, exchanging heat with high-temperature dilute ammonia solution A in heat exchanger 20 on the heat source side to raise its inlet temperature. In high-pressure generator 1, it absorbs waste heat from the power plant, reaching saturation and generating high-temperature, high-pressure ammonia vapor X and high-temperature dilute ammonia solution A.

[0052] The pipeline transports dilute ammonia solution A generated by high-pressure generator 1 and concentrated ammonia solution C generated by high-pressure absorber 2 from one side of industrial waste heat source 31 to the heating end 32. Meanwhile, mixed-concentration ammonia water B generated by solution mixing tank 8 is transported from the heating end 32 to industrial waste heat source 31. Compared to general hot water sensible heat transport systems, the ammonia solution reabsorption long-distance transport system has a smaller pipe diameter and lower pipe material costs. Since heat energy is stored in the form of concentration difference, there is no need to add insulation material to the outside of the pipeline, resulting in better economic efficiency in long-distance transport scenarios. The working fluid is an ammonia solution, resulting in relatively low pump consumption, only about 1 / 50th or even less of the heat released on the user side. The critical transport distance is very high, reaching tens to hundreds of kilometers.

[0053] Dilute ammonia solution A, delivered to the user side via dilute solution delivery pipeline 13, exchanges heat with the first solution D from the low-pressure absorber 3 via user-side heat exchanger 21 to increase its temperature. It then enters the low-pressure absorber 3 after being depressurized via dilute solution throttling valve 16, absorbing low-temperature, low-pressure ammonia vapor Y from the low-pressure generator 4, generating high-temperature first solution D and releasing absorbed heat. This absorbed heat heats the return water RW at the heating end 32, forming the supply water SW to meet the user's heating needs. The high-temperature first solution D exchanges heat with dilute ammonia solution A via user-side heat exchanger 21, recovering the outlet sensible heat, and then mixes with the second solution E in the solution mixing tank 8 to generate a mixed concentration ammonia solution B. Concentrated ammonia solution C, delivered to the user side via concentrated solution delivery pipeline 15, enters the low-pressure generator 4 after being depressurized via concentrated solution throttling valve 17, absorbing heat from the environment to generate low-temperature, low-pressure ammonia vapor Y. The heat energy stored in the concentration difference is released in the low-pressure absorber 3 to supply heating to the user. The water supply temperature can reach 50℃, and the energy density can reach 100~200kJ / kg.

[0054] The second operating mode of the embodiment is the quality-enhancing heating mode, such as... Figure 2 As shown. In this heating mode, at the connection of the first three-way valve 24: dilute ammonia solution A is open, the tenth solution N is open, and the fifth solution H is open. At the connection of the second three-way valve 25: concentrated ammonia solution C is open, the eleventh solution P is open, and the sixth solution J is open. The quality-upgrading heating shut-off valve 26 is open. At the connection of the third three-way valve 27: the first return water RW1 is closed, and the third return water RW3 is open. At the connection of the fourth three-way valve 28: the first supply water SW1 is closed, and the third supply water SW3 is open. At the connection of the first three-way valve 29 at the heating end: supply water SW is open, the first supply water SW1 is closed, and the second supply water SW2 is open. At the connection of the second three-way valve 30 at the heating end: return water RW is open, the first return water RW1 is closed, and the second return water RW2 is open. Dilute ammonia solution A, after passing through the user-side heat exchanger 21, is divided into two streams, the tenth solution N and the fifth solution H, via the first three-way valve 24. The tenth solution N leads to the dilute solution throttling valve 16, and the fifth solution H leads to the quality-enhancing heating dilute solution heat exchanger 22. Concentrated ammonia solution C is divided into two streams, the eleventh solution P and the sixth solution J, via the second three-way valve 25. The eleventh solution P leads to the concentrated solution throttling valve 17. The sixth solution J leads to the quality-enhancing heating concentrated solution heat exchanger 23. The ninth solution M leads unidirectionally to the solution mixing tank 8. Return water RW becomes the second return water RW2 via the second three-way valve 30 at the heating end. The second return water RW2 enters the quality-enhancing heating absorber 5 to absorb heat and becomes the second supply water SW2. The second supply water SW2 becomes the supply water SW via the first three-way valve 29 at the heating end, providing heating for the residence. The heat generated by the low-pressure absorber 3 is supplied to the quality-improving heat generator 6 via the fourth three-way valve 28 to produce the third water supply SW3. After passing through the quality-improving heat generator 6, the third return water RW3 is generated and enters the low-pressure absorber 3 to absorb heat via the third three-way valve 27.

[0055] The fifth solution H, whose temperature is increased by the user-side heat exchanger 21, exchanges heat with the seventh solution K from the heat-enhancing absorber 5 via the heat-enhancing dilute solution heat exchanger 22, further increasing its temperature. After its pressure is reduced by the heat-enhancing dilute solution throttling valve 18, it enters the heat-enhancing absorber 5, where it absorbs high-temperature heat-enhancing ammonia vapor Z from the heat-enhancing generator 6, producing the seventh solution K and releasing high-grade heat. This high-grade heat energy increases the temperature of the residential return water RW, forming the supply water SW for residential heating. It can also be stored in a hot water storage tank, improving energy efficiency and shaving off peak flows. The high-temperature seventh solution K generated by the heat-enhancing absorber 5 exchanges heat with the fifth solution H via the heat-enhancing dilute solution heat exchanger 22, and then mixes with the eighth solution L in the heat-enhancing solution mixing tank 9 to generate the ninth solution M.

[0056] Concentrated ammonia solution C, delivered to the user side via concentrated solution delivery pipeline 15, becomes the sixth solution J via the second three-way valve 25. It exchanges heat with the eighth solution L generated by the upgrading and heating generator 6 to raise its temperature. The pressure is then reduced by the concentrated solution throttling valve 19 before entering the upgrading and heating generator 6 again. The sixth solution J absorbs the heat from the upgrading and heating generator 6, generating the eighth solution L and high-temperature upgrading and heating ammonia vapor Z. The eighth solution L exchanges heat with the sixth solution J via the upgrading and heating concentrated solution heat exchanger 23, recovering sensible heat, and then reacts with the seventh solution K in the upgrading and heating solution mixing tank 9 to generate the ninth solution M. The high-temperature upgrading and heating ammonia vapor Z enters the upgrading and heating absorber 5 and is absorbed by the fifth solution H to generate the seventh solution K, releasing high-grade heat energy to form the water supply SW. To further improve the quality of heat use, the absorption temperature needs to be increased in the reabsorption cycle. Based on the original cycle, the heat generated by the low-pressure absorber 3 is used as a heat source to construct the upgrading and heating section, which can generate heat energy of 50℃~80℃.

[0057] 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 long-distance heating system for reabsorption of ammonia solution to improve the energy quality for users, characterized in that, The system includes a waste heat source, a heating terminal, a high-pressure generator, a high-pressure absorber, a low-pressure generator, a low-pressure absorber, a quality-enhancing heating generator, and a quality-enhancing heating absorber. The high-pressure generator and high-pressure absorber are located near the waste heat source and configured to convert the waste heat energy into a solution concentration difference to produce dilute and concentrated ammonia solutions. The low-pressure generator and low-pressure absorber, as well as the quality-enhancing heating generator and quality-enhancing heating absorber, are located near the heating terminal and configured to provide users with heat energy of different qualities. The terminals are connected by a long-distance reabsorption circulation transport section, and the transport working fluid is dilute ammonia solution, concentrated ammonia solution, and a mixed concentration ammonia solution. The high-pressure generator is connected to the waste heat source and is configured to absorb the medium- and low-temperature waste heat from the waste heat source to generate dilute ammonia solution and first ammonia vapor, and transport the first ammonia vapor to the high-pressure absorber. The low-pressure generator is configured to absorb ambient heat to generate second ammonia vapor and second solution, and transport the second ammonia vapor to the low-pressure absorber. The quality-improving heating generator is configured to absorb heat from the low-pressure absorber. The heat from the generator produces an eighth solution and a third ammonia vapor, and the third ammonia vapor is transported to the upgrading and heating generator. The long-distance reabsorption circulation transport section includes a solution separation tank, a solution mixing tank, an upgrading and heating solution mixing tank, a dilute solution transport pipeline, a mixed solution transport pipeline, and a concentrated solution transport pipeline. The dilute ammonia solution generated by the high-pressure generator is divided into two paths via a heat source-side heat exchanger, a dilute solution transport pump, the dilute solution transport pipeline, and a user-side heat exchanger. One path, as the tenth solution, enters the low-pressure absorber through a dilute solution throttling valve to absorb the ammonia vapor from the heat source. The low-pressure generator absorbs ambient heat to generate low-temperature, low-pressure ammonia vapor, which releases heat to produce a first solution. The first solution exchanges heat with the dilute ammonia solution in the user-side heat exchanger and then enters the solution mixing tank to mix with the second solution to generate the mixed concentration ammonia solution. Another path leads to the fifth solution, which passes through the upgrading and heating dilute solution heat exchanger and the upgrading and heating dilute solution throttling valve to enter the upgrading and heating absorber to absorb the third ammonia vapor and generate a seventh solution. The seventh solution exchanges heat with the fifth solution in the upgrading and heating dilute solution heat exchanger and then enters the upgrading and heating solution mixing tank.The mixed concentration ammonia solution, delivered to the heat source side via a mixed solution delivery pump and pipeline, is separated into a third solution and a fourth solution through a solution separation tank. The third solution is preheated by a heat exchanger on the heat source side before entering the high-pressure generator. The fourth solution enters the high-pressure absorber, absorbing the first ammonia vapor from the high-pressure generator and releasing heat to generate the concentrated ammonia solution. The concentrated ammonia solution is pressurized by a concentrated solution delivery pump and enters the concentrated solution delivery pipeline. It is then split into two paths via a second three-way valve. One path, acting as the eleventh solution, enters the low-pressure generator via a concentrated solution throttling valve to absorb ambient heat and generate the second ammonia vapor and the second solution. The other path, acting as the sixth solution, enters the upgrading and heating generator via a upgrading and heating concentrated solution heat exchanger and throttling valve. The eighth solution exchanges heat with the sixth solution via the upgrading and heating concentrated solution heat exchanger and then enters the upgrading and heating mixing tank, where it mixes with the seventh solution to generate the ninth solution. This ninth solution then flows to the solution mixing tank via an upgrading and heating shut-off valve.

2. The ammonia solution reabsorption long-distance heating system for improving user energy quality as described in claim 1, characterized in that, The system includes a third three-way valve, a fourth three-way valve, a first three-way valve at the heating end, and a second three-way valve at the heating end. The return water from the heating end is divided into two paths by the second three-way valve at the heating end. One path, as the second return water, enters the heat-improving absorption unit and absorbs heat to form the second supply water. The other path, as the first return water, enters the low-pressure absorption unit through the third three-way valve and then passes through the fourth three-way valve to form the first supply water. The first and second supply waters are combined by the first three-way valve at the heating end to provide heat to the heating end. The other end of the fourth three-way valve, as the third supply water, absorbs heat in the low-pressure absorption unit and flows to the heat-improving absorption unit to provide heat, forming the third return water. The third return water then flows back to the low-pressure absorption unit through the other end of the third three-way valve.

3. The ammonia solution reabsorption long-distance heating system for improving user energy quality as described in claim 2, characterized in that, The system operates in two modes: a normal heating mode and an upgraded heating mode. The normal heating mode is used when the energy demand temperature at the heating end is not higher than 50°C, and the upgraded heating mode is used when the energy demand temperature is higher than 50°C but lower than 80°C.

4. The ammonia solution reabsorption long-distance heating system for improving user energy quality as described in claim 3, characterized in that, When the system is operating in the normal heating mode, the first three-way valve is operated to allow the dilute ammonia solution to flow, the tenth solution to flow, and the fifth solution to be cut off. The second three-way valve is operated to allow the concentrated ammonia solution to flow, the eleventh solution to flow, and the sixth solution to be cut off. The heat supply shut-off valve is closed; the third three-way valve is operated to allow the first return water to flow and the third return water to stop flowing; the fourth three-way valve is operated to allow the first supply water to flow and the third supply water to stop flowing; the first three-way valve at the heating end is operated to allow the supply water to flow, the first supply water to flow, and the second supply water to stop flowing. The second three-way valve at the heating end is operated to allow the return water to flow, the first return water to flow, and the second return water to be cut off.

5. The ammonia solution reabsorption long-distance heating system for improving user energy quality as described in claim 3, characterized in that, When the system is operating in the quality improvement and heating mode, the first three-way valve is operated to allow the dilute ammonia solution, the tenth solution, and the fifth solution to flow; The second three-way valve is operated to allow the concentrated ammonia solution to flow, the eleventh solution to flow, and the sixth solution to flow; The heating supply shut-off valve is opened; the third three-way valve is operated to cut off the first return water flow and allow the third return water flow; the fourth three-way valve is operated to cut off the first supply water flow and allow the third supply water flow; the first three-way valve at the heating end is operated to allow the supply water flow, cut off the first supply water flow, and allow the second supply water flow; the second three-way valve at the heating end is operated to allow the return water flow, cut off the first return water flow, and allow the second return water flow.

6. The ammonia solution reabsorption long-distance heating system for improving user energy quality as described in claim 1, characterized in that, The dilute ammonia solution, concentrated ammonia solution, and mixed concentration ammonia solution are respectively transported in the dilute solution transport pipeline, concentrated solution transport pipeline, and mixed solution transport pipeline with essentially no temperature difference from the environment.

7. The ammonia solution reabsorption long-distance heating system for improving user energy quality as described in claim 1, characterized in that, The waste heat source is a heat source with a temperature higher than 90°C and lower than 150°C generated by the high-temperature exhaust steam from the boiler after the steam turbine has done work, which is recovered by the circulating water of the condenser and cooling tower of the power plant.

8. The ammonia solution reabsorption long-distance heating system for improving user energy quality as described in claim 1, characterized in that, The heating end is equipped with a hot water storage tank and a fan coil unit. Heat energy with a required temperature of no more than 50°C is directly radiated for heating at the heating end through the fan coil unit. Heat energy with a required temperature of more than 50°C but less than 80°C is stored in the hot water storage tank.

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