Intelligent large-temperature-difference absorption heat exchange unit and heat exchange method

Abstract

The invention relates to the technical field of absorption type heat exchange and heat supply technologies, in particular to an intelligent large-temperature-difference absorption type heat exchange unit and a heat exchange method.The intelligent large-temperature-difference absorption type heat exchange unit comprises an I-type unit, an II-type unit and a control system.The I-type unit and the II-type unit each comprise a heat pump host, a generator, a condenser, an evaporator, an absorber, a heat exchanger and heat exchange liquid; the heat exchange liquid conducts cascade heat exchange in the generator, the condenser, the evaporator, the absorber and the heat exchanger, the heat exchange liquid comprises a lithium bromide solution and refrigerant water, the control system comprises a controller and a standby plate heat exchange module, and the two heat pump main machines are both in communication connection with the controller. The multi-stage evaporation and multi-stage absorption process is adopted, cascade heat exchange can be achieved, and the temperature difference of inlets and outlets of the I-type unit and the II-type unit is increased, so that the outlet temperature of the units is reduced, irreversible heat transfer loss in the units is reduced, and the efficiency of the units is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of absorption heat exchange heating technology, and in particular to an intelligent large temperature difference absorption heat exchange unit and a heat exchange method. Background Art

[0002] Currently, the urban heating area in the northern regions of China amounts to up to 12 billion square meters, of which the urban central heating area is approximately 7.1 billion square meters. In order to improve environmental problems, coal-fired boiler houses have been basically phased out in northern cities, and heating mainly relies on cogeneration central heating, achieving certain results.

[0003] There are still many problems in the existing central heating by cogeneration in some cities: First, the heating heat source is insufficient, mainly due to the rapid increase in the total building volume. In addition, due to the requirements of air environment governance, the construction of urban coal-fired boilers and coal-fired power plants needs to be strictly controlled; Second, the pipeline transportation capacity has become a bottleneck for the development of central heating. The heating radius of the heat source has expanded rapidly, the investment burden of the heat network has increased, and with large-scale urban construction and the increase in plot ratio, the original pipeline network is difficult to meet the requirements. Summary of the Invention

[0004] In order to improve the pipeline transportation capacity of the heat network, reduce heating energy consumption, and improve the efficiency of the unit, the present invention provides an intelligent large temperature difference absorption heat exchange unit and a heat exchange method.

[0005] The intelligent large temperature difference absorption heat exchange unit and heat exchange method provided by the present invention adopt the following technical solutions: An intelligent large temperature difference absorption heat exchange unit, including a Type I unit, a Type II unit, and a control system. The Type I unit and the Type II unit both include a heat pump main unit, a generator, a condenser, an evaporator, an absorber, a heat exchanger, and a heat exchange liquid. The heat exchange liquid performs cascaded heat exchange inside the generator, condenser, evaporator, absorber, and heat exchanger. The heat exchange liquid includes lithium bromide solution and refrigerant water. The control system includes a controller and a spare plate heat exchange module. Both of the heat pump main units are communicatively connected to the controller.

[0006] By adopting the above technical solutions, a multi-stage evaporation and multi-stage absorption process can be used to achieve cascaded heat exchange, increase the temperature difference between the inlet and outlet of the Type I unit and the Type II unit, thereby reducing the outlet temperature of the unit and improving the unit efficiency. When the Type I unit and the Type II unit are installed in a heat exchange station, the Type II unit can simultaneously undertake two heating zones with different pressures and different heating parameters, and automatically distribute the primary network flow through an electric distribution valve according to the real-time demand of the heat load in each zone, simultaneously meeting the heating requirements of the two zones;

[0007] Preferably, the controller includes a primary network heating module and a secondary network heating module. Both the primary network heating module and the secondary network heating module exchange heat through Type I units and Type II units. The supply temperature of the primary water in the primary network heating module is d 1 , d 1 ≤130 °C, and the return temperature of the primary water in the primary network heating module is d 2 , 20 °C ≤ d 2 ≤30 °C.

[0008] By adopting the above technical solution, it is beneficial to reduce the infrastructure investment of the pipe network. By using high-temperature supply at 130 °C and low-temperature return at 30 °C, the temperature difference of the primary network increases significantly. Without changing the pipe diameter, it is convenient to improve the transportation and distribution capacity, so that the temperature of the secondary water can be effectively increased without changing the flow rate of the primary water.

[0009] Preferably, the d 1 ≤60 °C, 20 °C ≤ d 2 ≤30 °C.

[0010] By adopting the above technical solution, when the supply temperature of the primary water fluctuates between 30 °C and 50 °C, even when the temperature of the primary water drops below 60 °C, a smooth transition can still be achieved, and the high-efficiency operation state of the unit can be maintained all the time. The outlet temperature of the primary network remains below 30 °C or 25 °C throughout the heating season.

[0011] Preferably, the spare plate heat exchange module includes inlet valves and outlet valves for the generator, condenser, evaporator, and absorber, and a bypass valve is fixedly connected to the generator.

[0012] By adopting the above technical solution, when the external power supply fails and the equipment stops running, heating cannot be provided at this time. Close the inlet and outlet valves of the generator, open the bypass valve of the generator, close the inlet and outlet valves of the evaporator, for the secondary water, close the inlet valve of the condenser, and close the inlet valve of the absorber, so that all the primary water and secondary water pass through the plate heat exchanger to maintain operation.

[0013] Preferably, baffle plates are fixedly connected between the generator and the condenser and between the evaporator and the absorber.

[0014] By adopting the above technical solution, the baffle plates play a separation role, which is convenient for the generated steam to be absorbed by the condenser and the absorber respectively.

[0015] Preferably, the plate heat exchanger includes a primary side flow channel and a secondary side flow channel. The width of the secondary side flow channel is times that of the primary side flow channel, and the designed flow rate of the secondary side flow channel is 1.2 - 1.5 times that of the primary side flow channel.

[0016] By adopting the above technical solution, the flow rates on the secondary side and the primary side can still reach the turbulent state when they are 1:1. Even if a small amount of secondary water scaling occurs, the heat exchanger still maintains a high heat transfer coefficient, avoiding the influence of the scaling phenomenon on the normal operation of the unit.

[0017] Preferably, the tube row length of the heat exchanger is reduced by 1 / 3, and the tube row height of the heat exchanger is increased by 1 / 3.

[0018] By adopting the above technical solution, the tube row height is increased. Without changing the tube row area, the contact area between the solution and the tubes is increased, enabling the solution to be fully concentrated or absorbed, improving the utilization rate of the solution under the same working conditions, and reducing the circulation volume of the solution.

[0019] A heat exchange method, wherein the refrigerant water includes heat source water and heating water, and the following specific operation steps are included: A. After assembling the Type I unit and the Type II unit, connect them to a conventional heat exchange station, start the Type I unit and the Type II unit for cascade heat exchange, and turn off the Type I unit and the Type II unit after the heat exchange is completed; after the lithium bromide solution and the refrigerant water flow through the generator and the evaporator, the temperature of the heat source water is reduced, and after the lithium bromide solution and the refrigerant water flow through the condenser and the absorber, the temperature of the heating water is increased; B. When the heat pump hosts of the Type I unit and the Type II unit are damaged, start the standby plate heat exchange module.

[0020] By adopting the above technical solution, heating is carried out using the Type I unit and the Type II unit, which can realize the coexistence of a conventional heat exchange station and a large temperature difference heat exchange station. The control system can also control various operations such as in-station regulation of the conventional heat exchange station and hydraulic regulation of the heat network, achieving balanced heating of the entire heat network. It also realizes heat exchange between the primary network and the secondary network, and on the premise of ensuring that the secondary side heating parameters remain unchanged, achieves large temperature difference heating of the primary network with basically no increase in energy consumption, solves the bottleneck of heat network transmission and distribution, and creates conditions for deep recovery of power plant waste heat and long-distance heat transmission.

[0021] Preferably, in step A, the specific operation steps of the cascade heat exchange include that the lithium bromide solution includes a concentrated lithium bromide solution and a dilute lithium bromide solution, and both the concentrated lithium bromide solution and the dilute lithium bromide solution are heat-exchanged through a heat exchanger.

[0022] By adopting the above technical solution, the heat exchange effect is enhanced.

[0023] Preferably, in step B, the specific operation steps of starting the standby plate heat exchange module include that the Type I unit and the Type II unit fail and stop, start the standby plate heat exchange module for valve switching, and only use the water-water plate heat exchanger inside the Type I unit and the Type II unit for heating, and the heating output ≥ 70% of the designed output.

[0024] By adopting the above technical solution, when the external power outage or the failure of the Type-I unit or the Type-II unit causes the main engine to shut down, the heating safety is ensured.

[0025] In summary, the present invention has the following beneficial technical effects: 1. The present invention includes a Type-I unit and a Type-II unit, both of which adopt a multi-stage evaporation and multi-stage absorption process, which can achieve cascade heat exchange, increase the temperature difference between the inlet and outlet of the Type-I unit and the Type-II unit, thereby reducing the outlet temperature of the unit, reducing the irreversible heat transfer loss inside the unit, improving the unit efficiency. When the Type-I unit and the Type-II unit are installed in the heat exchange station, the Type-II unit can simultaneously undertake two heating zones with different pressures and different heating parameters, and automatically distribute the primary network flow through the electric distribution valve according to the real-time demand of the heat load of each zone, and meet the heating requirements of the two zones at the same time; 2. The Type-I unit and the Type-II unit of the present invention are connected to a conventional heat exchange station, and the conventional heat exchange station and the large temperature difference heat exchange station coexist. Without changing the original pipe network, that is, without changing the diameter of the urban primary pipe network, the conveying capacity of the primary heat network can be greatly improved, and the heat supply on the secondary side can be increased. The control system can also control various operations such as the regulation inside the conventional heat exchange station and the hydraulic regulation of the heat network, realize the balanced heating of the entire heat network, reduce the overall return water of the heat network, take into account the economy of the transformation, and also realize the heat exchange between the primary network and the secondary network. On the premise of ensuring that the heating parameters on the secondary side remain unchanged, the large temperature difference heating of the primary network is realized with basically no increase in energy consumption, solve the bottleneck of heat network transmission and distribution, and create conditions for the deep recovery of power plant waste heat and long-distance heat transmission; 3. The Type-I unit and the Type-II unit of the present invention are connected to a conventional heat exchange station, and the conventional heat exchange station and the large temperature difference heat exchange station coexist. Without changing the original pipe network, that is, without changing the diameter of the urban primary pipe network, the conveying capacity of the primary heat network can be greatly improved, and the heat supply on the secondary side can be increased. The control system can also control various operations such as the regulation inside the conventional heat exchange station and the hydraulic regulation of the heat network, realize the balanced heating of the entire heat network, reduce the overall return water of the heat network, take into account the economy of the transformation, and also realize the heat exchange between the primary network and the secondary network. On the premise of ensuring that the heating parameters on the secondary side remain unchanged, the large temperature difference heating of the primary network is realized with basically no increase in energy consumption, solve the bottleneck of heat network transmission and distribution, and create conditions for the deep recovery of power plant waste heat and long-distance heat transmission. Under the working conditions with a large temperature fluctuation range, the Type-I unit and the Type-II unit can still operate stably. For the central heating system, the supply water temperature and flow of the primary network, and the supply and return water temperature and flow of the secondary water will fluctuate greatly according to the change of the heat load during the entire heating season. The supply water temperature of the primary water has a temperature fluctuation range of 30-50°C. The Type-I unit and the Type-II unit can achieve a smooth transition, so that the outlet temperature of the primary network remains below 30°C or 25°C during the entire heating season. Even when the primary water temperature drops below 60°C, the Type-I unit and the Type-II unit can still operate stably; 4. The present invention is provided with a spare plate heat exchange module. When there is a power outage externally or the main unit shuts down due to a failure of the Type I unit or the Type II unit, it can be switched through internal valves to a mode of only using the internal water-water plate heat exchanger for heating, and the heating output can still reach more than 70% of the designed output, ensuring the heating safety of the Type I unit and the Type II unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic structural diagram of the intelligent large-temperature-difference absorption heat exchange unit according to an embodiment of the present invention; Figure 2 is a heat exchange diagram of primary water and secondary water in the intelligent large-temperature-difference absorption heat exchange unit according to an embodiment of the present invention; Figure 3 is a flowchart of the heat exchange method according to an embodiment of the present invention; Figure 4 is a schematic diagram of the water temperature change in the heat exchange method according to an embodiment of the present invention; Figure 5 is a heat exchange diagram of primary water and secondary water of the heat exchange unit in the background art of the present invention; Figure 6 is a partial model diagram of the Type I unit and the Type II unit in the intelligent large-temperature-difference absorption heat exchange unit according to an embodiment of the present invention.

[0027] Description of reference numerals: 1, generator; 2, condenser; 3, evaporator; 4, absorber; 5, heat exchanger; 6, liquid baffle. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] The following further describes the present invention in detail Figures 1-6 in conjunction with the accompanying drawings.

[0029] An embodiment of the present invention discloses an intelligent large-temperature-difference absorption heat exchange unit.

[0030] Referring to Figure 1, including Type I units, Type II units and a control system. The Type I units and Type II units can be disassembled into modules or directly be a whole, suitable for different occasions. Both the Type I units and Type II units include heat pump hosts, a generator 1, a condenser 2, an evaporator 3, an absorber 4, a heat exchanger 5 and a heat transfer fluid. The intelligent large temperature difference absorption heat exchange unit is applied to the heat exchange station of a centralized heating network, replacing the traditional plate heat exchanger to achieve efficient heat exchange between primary water and secondary water. The Type I units and Type II units are respectively used for floor heating and radiator heating. The heat transfer fluid conducts cascade heat exchange inside the generator 1, the condenser 2, the evaporator 3, the absorber 4 and the heat exchanger 5. The heat exchanger 5 adopts a plate heat exchanger. The lithium bromide concentrated solution and the lithium bromide dilute solution are inside the heat exchanger 5, and the heat is mutually matched to achieve a greater heat exchange effect, thus facilitating the step-by-step reduction of the temperature of the heat source water and finally reducing it to a temperature lower than that of the secondary water. The heating water is gradually heated and finally reaches the required heating temperature. The absorption heat exchange process of two-stage evaporation / absorption and multi-pass cross-flow dripping is adopted to further reduce the irreversible heat transfer loss inside the unit. The heat transfer fluid includes lithium bromide solution and refrigerant water. The lithium bromide solution undergoes pure physical changes and has no chemical changes, and the circulation process is safe. The control system includes a controller and a standby plate heat exchange module. Both heat pump hosts are communicatively connected to the controller; The lithium bromide dilute solution is heated and concentrated by a high-temperature heat source in the generator 1 to generate water vapor and lithium bromide concentrated solution. At the same time, the temperature of the heat source decreases. The water vapor enters the condenser 2, and the lithium bromide concentrated solution enters the absorber 4; After the water vapor generated by the generator 1 enters the condenser 2, due to the relatively low temperature of the external circulating water, the water vapor condenses into refrigerant water, releasing heat to the external circulating water, and the temperature of the circulating water increases. The refrigerant water enters the evaporator 3; After the refrigerant water enters the evaporator 3, due to the pressure reduction, its boiling point drops below the temperature of the external circulating water. At this time, the refrigerant water evaporates and absorbs heat, and the generated water vapor enters the absorber 4; at the same time, the external circulating water releases heat and the temperature decreases, producing a refrigeration effect; In the absorber 4, the concentrated solution absorbs the water vapor and dilutes it into a dilute solution. This process is an exothermic process. The external circulating water is heated, and the generated dilute solution enters the generator 1 again to carry out the next cycle; Two-stage evaporation / absorption means that the generator 1 and the evaporator 3 reduce the temperature of the heat source circulating water, while the condenser 2 and the absorber 4 increase the temperature of the heating circulating water.

[0031] Refer to Figure 1 、 Figure 2 、 Figure 5 , the controller includes a primary network heating module and a secondary network heating module. Both the primary network heating module and the secondary network heating module conduct heat exchange through the Type I units and Type II units. The supply temperature of the primary water of the primary network heating module is d 1 ,d 1≤130 °C, the return temperature of the primary water of the primary network heating module is d 2 , 20 °C ≤ d 2 ≤ 30 °C; Compared with direct heat exchange of traditional plate heat exchangers, Type I and Type II units make full use of the work capacity brought by the grade difference between the high-temperature heat source of the primary water and the low-temperature secondary water to drive the lithium bromide unit to produce a refrigeration effect. Without affecting the heating parameters of the secondary network, the return temperature of the primary water is greatly reduced, making it much lower than the return temperature of the secondary water, thereby increasing the temperature difference between the supply and return water of the primary water and the transmission and distribution capacity of the primary heat network. On the premise that the supply and return water parameters of the secondary network are the same, compared with the conventional cycle (refer to Figure 5 ), the temperature difference between the inlet and outlet of the primary water increases significantly, and the return temperature of the primary network can be reduced to about 20 °C (refer to Figure 2 ), that is, the return temperature of the primary network is greatly reduced, creating conditions for the efficient and in-depth recovery of power plant waste heat. As a result, the temperature difference between the supply and return water of the primary network can be greatly increased, the transmission and distribution capacity of the existing heat network can be increased by 80%, the expansion investment of the existing pipe network can be avoided, funds can be saved, the water volume transported by the primary pipe network can be reduced, thereby improving the hydraulic regulation environment of the pipe network, making the pipe network distribution easier to regulate, especially beneficial to improving the heat exchange effect at the end, beneficial to reducing the pipe diameter of the newly built large-scale heat network, eliminating the heat preservation measures of the return water pipe network, and greatly reducing the investment in the newly built pipe network.

[0032] For a centralized heating system, the supply temperature and flow rate of the primary water, and the supply and return water temperature and flow rate of the secondary water will fluctuate greatly according to the change of the heat load during the entire heating season. Especially for the supply temperature of the primary water, the temperature fluctuation range is 30 - 50 °C, d 1 ≤ 60 °C, 20 °C ≤ d 2 ≤ 30 °C, that is, to ensure stable operation of the unit under extreme conditions, and when the working conditions change, a smooth transition can be achieved, and the high-efficiency operation state of Type I and Type II units can always be maintained. The outlet temperature of the primary network remains below 30 °C or 25 °C during the entire heating season. Even when the temperature of the primary water drops below 60 °C, the large-temperature-difference absorption heat exchange unit can still operate stably.

[0033] The standby plate heat exchange module includes the inlet and outlet valves of the generator 1, condenser 2, evaporator 3, and absorber 4. The generator 1 is fixedly connected with a bypass valve. When the external power-off equipment stops operating and heating cannot be provided at this time, when the main engines of Type I and Type II units fail, the following valves can be adjusted to continue heating. Close the inlet and outlet valves of the generator 1, open the bypass valve of the generator 1, close the inlet and outlet valves of the evaporator 3, for the secondary water, close the inlet valve of the condenser 2, close the inlet valve of the absorber 4, and let the primary water and secondary water all pass through the plate heat exchanger 5 to maintain operation.

[0034] A liquid baffle plate 6 is fixedly connected between the generator 1 and the condenser 2 and between the evaporator 3 and the absorber 4. The liquid baffle plate 6 serves to separate the steam generated by the generator 1 and the evaporator 3, which are respectively absorbed by the condenser 2 and the absorber 4.

[0035] The plate heat exchanger includes a primary side flow channel and a secondary side flow channel. The width of the secondary side flow channel is twice that of the primary side flow channel, and the designed flow rate of the secondary side flow channel is 1.2 - 1.5 times that of the primary side flow channel. The most common thing in heat supply of the heat exchange station is the scaling on the secondary side of the plate heat exchanger. Generally, the maintainer has to clean the plate heat exchanger once a year. The plate heat exchanger of the Type I unit and the Type II unit is an important process. The width of the secondary side flow channel of the plate heat exchanger is twice that of the primary side flow channel, and the designed flow rate of the secondary side is 1.2 - 1.5 times that of the primary side. Therefore, when the Type I unit and the Type II unit are operating normally, as long as the flow rates of the secondary side and the primary side are at 1:1 and still can reach the turbulent state, even if there is a small amount of water scaling on the secondary side, the heat exchanger 5 can still maintain a high heat transfer coefficient, avoiding affecting the normal operation of the Type I unit and the Type II unit.

[0036] Refer to Figure 6 , the tube row length of the heat exchanger 5 is reduced by 1 / 3, and the tube row height of the heat exchanger 5 is increased by 1 / 3. The models of the Type I unit and the Type II unit are 1MW - 10MV. The tube row lengths in all heat exchangers 5 are reduced by 1 / 3 compared with the tube row lengths of the heat exchangers installed originally. Compared with the heat exchangers installed originally, the total heat transfer area of the heat exchanger 5 remains unchanged. Furthermore, the number of tube rows increases, so that the tube row height in the heat exchanger 5 is increased by 1 / 3 compared with the tube row height of the heat exchangers installed originally. All the heat exchangers installed originally adopt various conventional models of plate heat exchangers of Hongda.

[0037] The implementation principle of the intelligent large temperature difference absorption type heat exchange unit in the embodiment is as follows: The Type I unit and the Type II unit mainly utilize the hygroscopic property of the lithium bromide solution and the property of water having a low boiling point under vacuum conditions. 1. Generator 1: The dilute lithium bromide solution is heated and concentrated in the generator 1 by a high-temperature heat source, generating water vapor and concentrated lithium bromide solution. At the same time, the temperature of the heat source decreases. The water vapor enters the condenser 2, and the concentrated lithium bromide solution enters the absorber 4. 2. Condenser 2: After the water vapor generated by the generator 1 enters the condenser 2, due to the relatively low temperature of the external circulating water, the water vapor condenses into refrigerant water, releasing heat to the external circulating water, and the temperature of the circulating water rises. The refrigerant water enters the evaporator 3. 3. Evaporator 3: After the refrigerant water enters the evaporator 3, due to the pressure reduction, its boiling point drops below the temperature of the external circulating water. At this time, the refrigerant water evaporates and absorbs heat, and the generated water vapor enters the absorber 4; at the same time, the external circulating water releases heat and the temperature decreases, producing a refrigeration effect. 4. Absorber 4: In the absorber 4, the concentrated lithium bromide solution absorbs water vapor and is diluted into a dilute lithium bromide solution. This process is an exothermic process, and the external circulating water is heated. The resulting dilute solution re-enters the generator 1 for the next cycle.

[0038] An embodiment of the present invention discloses a heat exchange method.

[0039] Refer to Figure 1 、 Figure 3 , including the following specific operation steps: A. After assembling the Type I unit and the Type II unit, connect them to a conventional heat exchange station. The conventional heat exchange station and the large temperature difference heat exchange station coexist. Without changing the original pipe network, the control system can also control various operations such as in-station regulation of the conventional heat exchange station and hydraulic regulation of the heat network, achieving balanced heating of the entire heat network, reducing the overall heat network return water, and taking into account the economy of the transformation; The Type I unit and the Type II unit can be assembled according to the generator 1 module, condenser 2 module, evaporator 3 module, and absorber 4 module, and are used for heat exchange stations with small site or transportation conditions, high installation position height, or being scattered. For heat exchange stations with large sites and sufficient primary heat, the Type I unit and the Type II unit can be directly used without installation, and the integral Type I unit and Type II unit are directly adopted. Start the Type I unit and the Type II unit for cascade heat exchange, and close the Type I unit and the Type II unit after the heat exchange ends; after the lithium bromide solution and the refrigerant water flow through the generator 1 and the evaporator 3, the temperature of the heat source water is reduced, and after the lithium bromide solution and the refrigerant water flow through the condenser 2 and the absorber 4, the temperature of the heating water is increased; B. When the heat pump main engines of the Type I unit and the Type II unit are damaged, start the standby plate heat exchange module.

[0040] Refer to Figure 1 、 Figure 3 , in step A, the specific operation steps of the cascade heat exchange include: the lithium bromide solution includes a concentrated lithium bromide solution and a dilute lithium bromide solution, and both the concentrated lithium bromide solution and the dilute lithium bromide solution are heat exchanged through the heat exchanger 5.

[0041] Refer to Figure 1 、 Figure 3 , in step B, the specific operation steps of starting the standby plate heat exchange module include: the Type I unit and the Type II unit stop operating due to faults. The heat exchange modules of the Type I unit and the Type II unit are mainly composed of a heat pump main engine and a water-water plate heat exchanger. When the main engine stops due to external power failure or unit faults, start the standby plate heat exchange module for valve switching, and only use the water-water plate heat exchanger inside the Type I unit and the Type II unit for heating. The heating output ≥ 70% of the design output, that is, the heating output can still reach more than 70% of the design output, ensuring heating safety.

[0042] The implementation principle of a heat exchange method in an embodiment of the present invention is as follows: Compared with the direct heat exchange of traditional plate heat exchangers, the large temperature difference absorption heat exchange unit makes full use of the work capacity brought by the grade difference between the high-temperature heat source of the primary water and the low-temperature secondary water, drives the lithium bromide unit to produce a refrigeration effect, and without affecting the heating parameters of the secondary network, significantly reduces the return water temperature of the primary water, making it much lower than the return water temperature of the secondary water, thereby increasing the supply and return water temperature difference of the primary water and the transmission and distribution capacity of the primary heat network; In the heat power station, type I units and type II units are used to replace the conventional water-water plate heat exchangers, significantly reducing the return water temperature of the primary network, thereby significantly improving the transmission capacity of the primary heat network without changing the diameter of the urban primary pipe network, increasing the heat supply on the secondary side, and creating conditions for recovering the waste heat of the power plant; In the thermal power plant, a newly developed waste heat recovery unit with an absorption heat pump as the core is set up to recover the waste heat of the exhaust steam of the air-cooled island or the circulating water of the cooling tower, and the return water of the primary network is heated in a stepped manner, which can increase the heating capacity of the thermal power plant by more than 30%, increase the transmission capacity of the primary heat network by about 75%, and reduce the heating energy consumption by about 40%.

[0043] The above are all preferred embodiments of the present invention, and the protection scope of the present invention is not limited accordingly. Therefore, all equivalent changes made according to the structure, shape, and principle of the present invention shall be covered within the protection scope of the present invention.

Claims

1. Intelligent large temperature difference absorption heat exchange unit, characterized by: The invention comprises a type I unit, a type II unit and a control system. The type I unit and the type II unit both comprise a heat pump host, a generator (1), a condenser (2), an evaporator (3), an absorber (4), a heat exchanger (5) and a heat exchange fluid. The heat exchange fluid performs stepwise heat exchange inside the generator (1), the condenser (2), the evaporator (3), the absorber (4) and the heat exchanger (5). The heat exchange fluid comprises a lithium bromide solution and refrigerant water. The control system comprises a controller and a standby board heat exchange module. Both the heat pump hosts are communicatively connected to the controller.

2. The intelligent large temperature difference absorption heat exchange unit according to claim 1 is characterized in that: The controller includes a primary network heating module and a secondary network heating module. The primary network heating module and the secondary network heating module both exchange heat through type I units and type II units. The primary water supply temperature of the primary network heating module is d1, d1≤130°C, and the primary water return temperature of the primary network heating module is d2, 20°C≤d2≤30°C.

3. The intelligent large temperature difference absorption heat exchange unit according to claim 2 is characterized in that: The d1≤60℃, 20℃≤d2≤30℃.

4. The intelligent large temperature difference absorption heat exchange unit according to claim 2 is characterized in that: The standby plate heat exchange module comprises a generator (1), a condenser (2), an evaporator (3), and a water inlet valve and a water outlet valve of an absorber (4); the generator (1) is fixedly connected to a bypass valve.

5. The intelligent large temperature difference absorption heat exchange unit according to claim 4 is characterized in that: A liquid baffle (6) is fixedly connected between the generator (1) and the condenser (2) and between the evaporator (3) and the absorber (4).

6. The intelligent large temperature difference absorption heat exchange unit according to claim 5 is characterized in that: The plate exchanger comprises a primary flow channel and a secondary flow channel, the width of the secondary flow channel is twice the width of the primary flow channel, and the design flow rate of the secondary flow channel is 1.2-1.5 times the design flow rate of the primary flow channel.

7. The intelligent large temperature difference absorption heat exchange unit according to claim 6 is characterized in that: The length of the tube row of the heat exchanger (5) is reduced by 1 / 3, and the height of the tube row of the heat exchanger (5) is increased by 1 / 3.

8. A heat exchange method, characterized in that: The intelligent large temperature difference absorption heat exchanger unit according to claim 7 is used for heat exchange, wherein the refrigerant water includes heat source water and heating water, and the specific operation steps are as follows: A. After assembling type I and type II units, connect them to the conventional heat exchange station, start type I and type II units for cascade heat exchange, and shut down type I and type II units after the heat exchange is completed; After the lithium bromide solution and the refrigerant water flow through the generator (1) and the evaporator (3), the temperature of the heat source water is reduced; after the lithium bromide solution and the refrigerant water flow through the condenser (2) and the absorber (4), the temperature of the heating water is increased; B. When the heat pump host of the Type I unit or Type II unit is damaged, the standby board heat exchange module is started.

9. The heat exchange method according to claim 8, characterized in that: In step A, the specific operation steps of the cascade heat exchange include: The lithium bromide solution comprises a concentrated lithium bromide solution and a dilute lithium bromide solution, and both the concentrated lithium bromide solution and the dilute lithium bromide solution are heat exchanged through a heat exchanger (5).

10. The heat exchange method according to claim 9, characterized in that: In step B, the specific operation steps of starting the standby plate heat exchange module include: When the Type I and Type II units fail and shut down, the standby plate heat exchange module is started to switch the valve, and only the water-to-water plate heat exchanger inside the Type I and Type II units is used for heating, and the heating output is ≥ 70% of the design output.

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