Black water heat recovery composite system and working method thereof

Abstract

The present application belongs to the technical field of heat recovery, and provides a black water waste heat recovery composite system and a working method thereof. The system comprises a pressure recovery device, an organic Rankine cycle device, an absorption heat pump device, a heat exchange device and a multi-stage flash evaporation device. The 170-184 DEG C, 0.8-1.1 MPa high-pressure steam generated by the black water through a high-pressure flash tank is used as a first heat source, and the pressure energy is recovered by the pressure recovery device to output electric energy. The 120-144 DEG C, 0.2-0.4 MPa low-pressure steam generated by the black water through a low-pressure flash tank is used as a second heat source, and the heat energy is converted into electric energy by the organic Rankine cycle device. The 80-85 DEG C, 47-58 kPa vacuum steam generated by the black water through a vacuum flash tank is used as a third heat source, and the temperature of the industrial water is raised by the absorption heat pump device. The low-grade waste heat discharged by each device is deeply recovered by the three-stage series heat exchange of the heat exchange device, the waste heat is transferred to the industrial water, the high-quality industrial hot water output is raised, and the full-grade cascade utilization of the black water waste heat is realized.

Description

Technical Field

[0001] This invention relates to the field of heat recovery, and more specifically, to a composite system for recovering waste heat from black water in coal gasification processes and its operating method. Background Technology

[0002] In the global energy system's shift towards low-carbon development, coal gasification technology, as a key link in the clean utilization of coal resources, has attracted significant attention regarding its energy efficiency improvement and waste heat recovery. Blackwater, the high-temperature process wastewater generated during coal gasification, contains abundant waste heat resources, and how to efficiently recover and utilize it has become an important issue for improving the overall energy efficiency of the system. Currently, although absorption heat pumps and Organic Rankine Cycle (ORC) technologies have been practically applied in the field of industrial waste heat recovery and have formed standardized solutions for single-stage waste heat utilization, they still face many technical bottlenecks in actual operation. Especially when dealing with blackwater waste heat, which has fluctuating and multi-temperature characteristics, the shortcomings of traditional single-technology solutions, such as insufficient heat source adaptability and low energy conversion efficiency, are more pronounced. Furthermore, the operational stability and energy efficiency maintenance capabilities of existing waste heat recovery systems under varying operating conditions still need breakthroughs, urgently requiring the development of innovative integrated technology solutions.

[0003] Currently, mainstream blackwater waste heat recovery technologies mainly include conventional methods such as flash evaporation, direct heat exchangers, stand-alone heat pumps, or Organic Rankine Cycles (ORC). Flash evaporation, which recovers blackwater heat through reduced-pressure evaporation, boasts advantages such as simple structure and low investment cost, but suffers from limitations in improving heat quality and low recovery efficiency, making it difficult to meet the industrial demand for high-quality heat energy. While direct heat exchangers can achieve basic waste heat recovery, they are less adaptable to changes in blackwater temperature, and their heat exchange efficiency drops significantly in the low-temperature range. Single absorption heat pump technology performs well in improving the utilization rate of low-grade waste heat; however, its coefficient of performance (COP) degrades significantly when treating high-temperature blackwater, and the system has poor operational flexibility. Organic Rankine Cycle systems are applicable to medium- and high-temperature waste heat power generation, but this system has stringent requirements for the stability of heat source parameters and cannot effectively cope with dynamic fluctuations in blackwater flow and temperature. It is worth noting that the energy conversion efficiency of traditional ORC systems drops sharply in the low-temperature waste heat range, resulting in a large amount of usable energy being underutilized. In recent years, the coupling system of absorption heat pumps and ORC has gradually become a research hotspot. However, existing integration schemes mostly adopt mechanical series-parallel structures, failing to fully consider the multi-temperature characteristics and dynamic changes of blackwater waste heat. This simple integration mode leads to a significant reduction in system performance when operating conditions change, and there is a lack of effective collaborative optimization mechanisms between subsystems. More importantly, existing technologies generally lack design for utilizing the temperature gradient of blackwater waste heat, failing to achieve the optimal energy configuration scheme of "temperature matching and tiered utilization," resulting in significant loss of usable energy.

[0004] Current blackwater waste heat recovery technologies face the following key technical challenges: In integrated waste heat recovery systems, the synergistic optimization of multiple technological approaches is crucial. Taking absorption heat pumps and organic Rankine cycles as examples, they are naturally complementary in terms of applicable temperature ranges and energy efficiency characteristics. However, existing solutions typically apply each technology independently, failing to systematically integrate their synergistic effects, resulting in the overall system performance being unable to overcome the efficiency limitations of a single technology. Existing solutions have failed to construct an optimized matching mechanism of "temperature matching and tiered utilization," ultimately leading to persistently high flue gas temperatures and severe energy waste. Summary of the Invention

[0005] To address the technical bottlenecks of existing blackwater waste heat recovery technologies, such as low thermal energy utilization and serious energy waste, this invention proposes a composite blackwater waste heat recovery system and its working method. By constructing a four-stage energy recovery system of "waste pressure power generation - ORC power generation - heat pump heating - cascade heat exchange", it achieves efficient conversion of blackwater waste heat resources and can simultaneously produce high-quality industrial hot water and clean electricity, effectively solving the shortcomings of traditional single technology routes in terms of energy conversion efficiency and product diversity.

[0006] One aspect of the present invention provides a blackwater waste heat recovery composite system, comprising: The residual pressure recovery device uses high-pressure steam (170-184℃, 0.8-1.1MPa) obtained by high-pressure flash evaporation of black water as the first heat source. It utilizes the expansion of the steam turbine to directly convert the pressure energy of the high-pressure steam into mechanical energy, thereby driving the generator to output electrical energy. The organic Rankine cycle device uses low-pressure steam (120-144°C, 0.2-0.4MPa) obtained by low-pressure flash evaporation of black water as a second heat source to supply the first working medium for circulation in the organic Rankine cycle device, thereby realizing the conversion of the thermal energy of the low-pressure steam into electrical energy. An absorption heat pump unit uses vacuum steam (80-85°C, 47-58 kPa) obtained from black water through vacuum flash evaporation as a third heat source. This steam powers the second working medium, which circulates within the absorption heat pump unit. The process of generation-condensation-evaporation-absorption cycle raises the temperature of the industrial water. A heat exchange device that recovers energy from the first heat source via the residual pressure recovery device, the second heat source via the organic Rankine cycle device, and the third heat source via the absorption heat pump device. After the pressure energy is recovered by the residual pressure recovery device, the first heat source directly heats the first stream of industrial water. The third heat source, after heat exchange by the absorption heat pump device, mixes with the first heat source after heating the first stream of industrial water to form a first mixed heat source, which then heats the second stream of industrial water. The second heat source after heat exchange in the organic Rankine circulation device is mixed with the first mixed heat source after heating the second stream of industrial water to form a second mixed heat source, which then heats the first stream of industrial water.

[0007] Furthermore, another aspect of the present invention provides a method for operating a blackwater waste heat recovery composite system, applied to the aforementioned blackwater waste heat recovery composite system, comprising the following steps: In the residual pressure power generation step, the high-pressure steam at 170~184℃ and 0.8~1.1MPa generated by the high-pressure flash evaporation of black water is used as the first heat source and fed into the residual pressure recovery device. The pressure energy of the high-pressure steam is converted into mechanical energy by the expansion of the steam turbine, thereby driving the generator to output electrical energy. In the ORC power generation step, the low-pressure steam (120~144℃, 0.2~0.4MPa) generated by the low-pressure flash evaporation of black water is used as a second heat source and introduced into the organic Rankine cycle device, so that the first working medium circulates in the organic Rankine cycle device, thereby realizing the conversion of the thermal energy of the low-pressure steam into electrical energy. In the heat pump heating process, vacuum steam (80-85℃, 47-58kPa) generated by the vacuum flash evaporation of black water is used as a third heat source and introduced into an absorption heat pump device. This allows the second working medium to complete a generation-condensation-evaporation-absorption cycle within the absorption heat pump device, thereby increasing the temperature of the industrial water. The cascade heat exchange process recovers low-grade waste heat from the first, second, and third heat sources after energy conversion through a heat exchange device in the following manner: The first heat source after pressure energy recovery directly heats the first stream of industrial water; The third heat source after heat exchange by the absorption heat pump device is mixed with the first heat source after heating the first industrial water to form the first mixed heat source, which is used to heat the second industrial water. The second heat source, after heat exchange in the organic Rankine cycle device, is mixed with the first mixed heat source after heating the second stream of industrial water to form a second mixed heat source, which then heats the first stream of industrial water.

[0008] The beneficial technical effects of the black water waste heat recovery composite system and its working method provided in the embodiments of the present invention are as follows: (1) This invention constructs a four-stage energy recovery system consisting of "residual pressure power generation - organic Rankine cycle (ORC) power generation - heat pump heating - cascade heat exchange", realizing the full-grade energy recovery from 1MPa high-pressure steam to 0.07MPa vacuum steam. The system adopts pressure energy-thermal energy synergistic conversion technology, and through multiple conversion devices such as steam turbine, organic working fluid turbine, and absorption heat pump, it converts low-grade thermal energy that is difficult to recover by traditional technology into high-value energy.

[0009] (2) The system achieves efficient conversion of waste heat resources of black water through multi-level coupling and cascade utilization technology, and can simultaneously produce high-quality industrial hot water and clean electricity.

[0010] (3) By integrating multiple heat exchangers into a high-efficiency heat exchange device, the low-grade waste heat (such as steam cooled after doing work and condensation heat release) discharged by the residual pressure recovery device, organic Rankine cycle device and absorption heat pump device is deeply recovered. Through multi-stage series heat exchange design, the waste heat that originally needed to be cooled and discharged is further transferred to industrial water, thereby increasing the production of high-quality industrial hot water. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 This is a schematic diagram of the black water waste heat recovery composite system of the present invention; Figure 2 This is a flowchart of the control strategy of the present invention; Figure 3 This is a distribution diagram of heat loss and heat efficiency of an absorption heat pump system based on the present invention; Figure 4 This is a flow path diagram based on the present invention; Figure 5 This is a carbon dioxide emission distribution diagram based on the components of this invention.

[0012] Reference numerals: 1. High-pressure flash tank; 2. Low-pressure flash tank; 3. Vacuum flash tank; 4. Residual pressure recovery device; 5. Working fluid pump; 6. First evaporator; 7. Expander; 8. First condenser; 9. First heat exchanger; 10. Second heat exchanger; 11. Booster pump; 12. Solution exchanger; 13. Generator; 14. Second condenser; 15. Throttling valve; 16. Second evaporator; 17. Absorber; 18. Throttling valve; 19. Third heat exchanger; 20. Control valve. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0014] Figure 1 This is a schematic diagram of the black water waste heat recovery composite system of the present invention.

[0015] As shown in Figure 1, the blackwater waste heat recovery composite system includes a multi-stage flash evaporation unit, a waste pressure recovery unit 4, an organic Rankine cycle unit, an absorption heat pump unit, and a heat exchange unit; wherein: The multi-stage flash evaporation device includes a high-pressure flash evaporation tank 1, a low-pressure flash evaporation tank 2, and a vacuum flash evaporation tank 3, which are used to flash high-temperature and high-pressure black water into steam at different temperatures and pressures in stages, providing a staged heat source for subsequent energy conversion. The residual pressure recovery device 4 uses the high-pressure steam generated by the high-pressure flash tank 1 as a heat source to realize the conversion of pressure energy into electrical energy; The organic Rankine cycle device includes a working fluid pump 5, a first evaporator 6, an expander 7 and a first condenser 8, which uses the low-pressure steam generated by the low-pressure flash tank 2 as a heat source to realize the conversion of thermal energy into electrical energy. The absorption heat pump device includes a booster pump 11, a solution exchanger 12, a generator 13, a second condenser 14, a throttling valve 15, a second evaporator 16, an absorber 17, and a throttling valve 18. It uses the vacuum steam generated by the vacuum flash tank 3 as a heat source to realize the conversion of low-grade heat energy into industrial hydrothermal energy. The heat exchange device includes a first heat exchanger 9, a second heat exchanger 10, and a third heat exchanger 19, which are used to recover low-grade waste heat discharged from each energy conversion device in stages to increase the output of industrial hot water.

[0016] Figure 2 An example of the control steps of this control unit is shown. Specifically, it includes the following steps: S01: Start; S02: System initialization; S03: Data monitoring; S04: Determine the validity of high-pressure steam flow rate Q, high-pressure steam temperature T, and hot water supply temperature Tout. If the data is normal, proceed to step S05; if the data is abnormal, proceed to step S06. S05: Monitor whether the temperature of the first heat source exceeds the specified design range (170~184℃). If it is determined that the temperature of the first heat source exceeds the specified design range, proceed to step S07; otherwise, proceed to step S10. S06: Trigger an alarm signal, maintain the current valve status, and then proceed to step S09; S07: Trigger the over-temperature / low-temperature alarm, suspend the operation of the residual pressure recovery device 4, and then proceed to step S08; S08: Regulating valve 20 is fully open, and all (100%) of the first heat source enters the second heat exchanger 10; S09: Wait for maintenance or data recovery, then return to step S03; S10: Determine if the flow rate Q is above 70%. If it is above 70%, proceed to step S11; otherwise, proceed to step S12. S11: Close the regulating valve 20, and all (100%) of the first heat source enters the residual pressure recovery device 4, proceeding to step S13; S12: When it is determined that the flow rate Q is less than 70%, 20%~30% of the first heat source is diverted and directly enters the second heat exchanger 10, and then proceed to step S13; S13: Hot water supply temperature reaches 98±2℃; S14: Monitor in real time whether the hot water supply temperature is at 98±2℃. If it is not at 98±2℃, proceed to step S15. S15: Dynamically fine-tunes the shunt ratio by ±5% via PLC control.

[0017] In summary, based on the aforementioned blackwater waste heat recovery composite system, the high-pressure steam (high grade), low-pressure steam (medium grade), and vacuum steam (low grade) generated by blackwater flash evaporation are each matched with a dedicated energy conversion module. Through functional grading of "power generation - heat exchange - temperature increase," precise matching of energy grade and application is achieved. High-pressure steam (170~184℃, 0.8~1.1MPa): It preferentially enters the residual pressure recovery device 4, uses its pressure energy to generate electricity, and after doing work, the heat source temperature drops to 110~120℃ and the pressure is 0.15MPa. It then enters the second heat exchanger 10 as a medium-grade heat source to provide high-temperature heating for industrial hot water. The heat source itself cools down to 60~70℃ and the pressure is maintained at 0.15MPa before entering the second evaporator 16 as an auxiliary heat source. Low-pressure steam (120~144℃, 0.2~0.4MPa): directly enters the first evaporator 6 of the organic Rankine cycle, and generates low-grade thermal energy through the phase change of R236EA working fluid. After heat exchange, the heat source temperature drops to 50~60℃, and mixes with the 50~55℃ heat source discharged from the third heat exchanger 19 to form the first mixed heat source, and then enters the first heat exchanger 9 to provide medium-temperature preheating for industrial hot water; Vacuum steam (80~85℃, 47~58kPa): As a driving heat source, it enters the generator 13 of the absorption heat pump, drives the separation of lithium bromide solution, and the temperature of the heat source after releasing heat drops to 60~70℃. It mixes with the 60~70℃ heat source from the second heat exchanger 10 and enters the second evaporator 16 as a low-temperature driving heat source. After releasing all the heat, the first mixed heat source (temperature 55~65℃) enters the third heat exchanger 19 to complete the end waste heat recovery.

[0018] Figure 3 This is a distribution diagram of heat loss and heat efficiency of an absorption heat pump system based on the present invention. Figure 4 This illustrates a flow path diagram based on the present invention. Figure 5 This is a carbon dioxide emission distribution diagram based on the components of this invention.

[0019] like Figure 3 As shown in the figure, the driving capacity and exhaust efficiency of each component in the black water waste heat recovery composite system are compared, and the energy conversion efficiency of each component is displayed in the form of bar charts and line graphs. Figure 3 It can be seen that the optimized temperature matching design of the system effectively reduces the terminal temperature difference, achieving low energy loss (12.13 kW) and high energy efficiency (48.08%). The absorption heat pump unit exhibits superior thermal performance, mainly due to its optimized temperature matching and efficient heat transfer structure. This complements the complementary distribution of energy loss and energy efficiency among the various devices in the system. It achieves both coarse energy release and coarse heat exchange through flash tanks, heat exchangers, and other links, and relies on the efficient energy conversion of core equipment such as residual pressure recovery devices, expanders, and absorption heat pumps to ultimately achieve a low energy loss and high energy efficiency operation pattern under energy cascade utilization.

[0020] Figure 4 This is a Sankey diagram of the energy flow of the black water waste heat recovery composite system of the present invention. It uses streamlines of different colors to show the flow paths and energy transfer relationships of media such as black water, industrial water, and working fluid in the system, and marks the energy values ​​of each part. The diagram illustrates the flow process of the system under steady-state conditions: Black water enters the high-pressure flash tank 1 with a heat of 13.591 kW, and undergoes a three-stage flash evaporation (flash tanks 1, 2, and 3) to achieve a stepped release of heat; the residual pressure recovery device 4 recovers 9.294 kW of heat, outputting 3.027 kW of electricity on one hand and transferring 5.510 kW of waste heat to the second heat exchanger 10 on the other; on the organic Rankine cycle side, the first evaporator 6 receives 1.134 kW of waste heat, which is circulated through the working fluid pump 5, expander 7, and first condenser 8, with expander 7 outputting 0.380 kW of electricity; on the absorption heat pump side, generator 13 is driven by lithium bromide solution, circulating through solution exchanger 12, booster pump 11, absorber 17, etc., and exchanging heat with the condensate in combination with the waste heat of the third heat exchanger 19, finally passing through the second condenser 16. The system achieves the conversion and utilization of heat. The overall system follows the cascade heat utilization logic of "high heat power generation, medium heat heat exchange, and low heat temperature increase". Through the synergy of modules such as black water flash evaporation, residual pressure recovery, organic Rankine cycle, and absorption heat pump, it realizes the efficient transfer and multi-level recovery of heat between media such as electricity, waste heat, working fluid, and solution.

[0021] Figure 5The illustration compares the carbon dioxide emission reduction effects of the main equipment in the blackwater waste heat recovery composite system of this invention, showing the impact of the residual pressure recovery device 4, working fluid pump 5, expander 7, and booster pump 11 on carbon dioxide emissions. Through the coordinated operation of these devices, the system can effectively utilize the waste heat in the blackwater, improve energy efficiency, and reduce carbon dioxide emissions. The system's carbon dioxide emissions exhibit characteristics of "core emission reduction + minor energy consumption emissions + additional emissions from working fluid leakage." The residual pressure recovery device 4 and expander 7, as core carbon emission reduction units, achieve negative emissions of -113371.13 and -14215.27 kg / m³, respectively, contributing the majority of emission reductions by generating electricity from recovered steam energy to replace fossil fuel consumption. The working fluid pump 5 and booster pump 11 generate positive emissions of 421.75 and 45.22 kg / m³ due to indirect energy consumption during operation, but these emissions account for a very small percentage. Additionally, the system must consider the 94500 kg / m³ CO₂eq emissions from working fluid leakage. After comprehensive calculation, the system's total net carbon emissions are -32619.43 kg / m³ CO₂eq. The system maintains a significant net emission reduction effect, demonstrating the low-carbon advantages of cascade energy recovery technology.

[0022] In summary, the beneficial technical effects of the black water waste heat recovery composite system and working method provided by the embodiments of the present invention are as follows: 1. This invention constructs a four-stage energy recovery system: "residual pressure power generation - Organic Rankine Cycle (ORC) power generation - heat pump heating - cascade heat exchange," achieving full-grade energy recovery from 0.8~1.1MPa high-pressure steam to 47~58kPa vacuum steam. The system employs pressure energy-thermal energy synergistic conversion technology, using multiple conversion devices such as steam turbines, organic working fluid turbines, and absorption heat pumps to convert low-grade thermal energy, which is difficult to recover using traditional technologies, into high-value energy. The system's overall energy utilization rate reaches over 80%.

[0023] 2. Through multi-level coupling and cascade utilization technology, the system achieves efficient conversion of waste heat resources from black water, and can simultaneously produce high-quality industrial hot water and clean electricity. Taking the black water flow rate of 100 kg / h as an example, the system can generate 27,280 kWh of electricity per year to meet the power needs of the factory's auxiliary equipment, while stably outputting 2 tons of industrial hot water at about 98°C per year to meet the heat needs of the production process.

[0024] 3. By integrating multiple heat exchangers into a high-efficiency heat exchange device, the low-grade waste heat discharged from the residual pressure recovery device, organic Rankine cycle device, and absorption heat pump device is deeply recovered. Through multi-stage series heat exchange design, the waste heat that originally needed to be cooled and discharged is further transferred to industrial water, thereby increasing the production of high-quality industrial hot water. At the same time, it realizes the customized production of two industrial hot waters at different temperatures to match the heat demand of different processes.

[0025] 4. The system is equipped with an intelligent control unit and regulating valves, which can dynamically adjust the steam distribution ratio according to the flow rate and temperature of high-pressure steam, ensuring stable industrial hot water temperature. This solves the problem of weak load fluctuation resistance of a single power generation module and improves the system's operational stability under varying operating conditions.

[0026] The organic Rankine cycle unit uses R236EA as the circulating working medium. This medium has zero ozone depletion potential (ODP=0) and low global warming potential, taking into account both thermodynamic performance and environmental protection requirements. It can achieve efficient phase change under low-grade heat sources. The first evaporator adopts an S-vortex flow channel heat exchange structure, which uses strong disturbance effect to increase fluid velocity and solves the problem of scaling on the heat exchange surface caused by trace impurities carried by low-grade steam.

[0027] 5. The absorption heat pump unit uses lithium bromide solution as the working medium and vacuum steam as the driving heat source. It does not require additional high-grade energy and heats ambient temperature industrial cold water to 60°C in three stages. This solves the problem that traditional vacuum steam is difficult to utilize due to its low temperature and requires a large amount of circulating water for cooling, thus improving the utilization rate of low-grade waste heat.

[0028] 6. Through cascaded energy recovery and deep utilization of waste heat, the system significantly reduces the consumption of fossil fuels and achieves remarkable carbon emission reduction. Compared with traditional absorption heat pump systems, the carbon emission reduction effect is significant, improving the environmental performance of industrial waste heat recovery systems.

[0029] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A blackwater waste heat recovery composite system, characterized in that, include: The residual pressure recovery device (4) uses high-pressure steam at 170~184℃ and 0.8~1.1MPa obtained by high-pressure flash evaporation of black water as the first heat source. It uses the expansion of the steam turbine to directly convert the pressure energy of the high-pressure steam into mechanical energy, thereby driving the generator to output electrical energy. The organic Rankine cycle device uses low-pressure steam (120-144°C, 0.2-0.4MPa) obtained by low-pressure flash evaporation of black water as a second heat source to supply the first working medium for circulation in the organic Rankine cycle device, thereby realizing the conversion of the thermal energy of the low-pressure steam into electrical energy. An absorption heat pump device uses vacuum steam at 80~85℃ and 47~58kPa obtained by vacuum flash evaporation of black water as the third heat source, which is used to supply the second working medium to circulate in the absorption heat pump device. The temperature of industrial water is increased through a generation-condensation-evaporation-absorption cycle. as well as A heat exchange device that recovers energy from the first heat source via the residual pressure recovery device (4), the second heat source via the organic Rankine cycle device, and the third heat source via the absorption heat pump device. After the pressure energy is recovered by the residual pressure recovery device (4), the first heat source directly heats the first stream of industrial water. The third heat source, after heat exchange by the absorption heat pump device, mixes with the first heat source after heating the first stream of industrial water to form a first mixed heat source, which then heats the second stream of industrial water. The second heat source after heat exchange in the organic Rankine circulation device is mixed with the first mixed heat source after heating the second stream of industrial water to form a second mixed heat source, which then heats the first stream of industrial water.

2. The black water waste heat recovery composite system according to claim 1, characterized in that, The organic Rankine cycle device includes a first evaporator (6). The absorption heat pump device includes a generator (13), a second condenser (14), a second evaporator (16), and an absorber (17). The heat exchange device includes a first heat exchanger (9), a second heat exchanger (10), and a third heat exchanger (19). After the pressure energy is recovered by the residual pressure recovery device (4), the first heat source directly enters the second heat exchanger (10) to perform secondary final heating on the first-stage preheated industrial water that has been preheated by the first heat exchanger (9). The third heat source, after heat exchange with the second working medium by the absorption heat pump device, mixes with the first heat source after the first industrial water flowing out from the second heat exchanger (10) has undergone the second stage of final heating to become the first mixed heat source. This mixed heat source serves as the 55~65℃ low-temperature driving heat source for the second evaporator (16). After heat exchange with the second working medium, the mixed heat source enters the third heat exchanger (19) to perform a first-stage preheating of the second industrial water entering the third heat exchanger (19). The second industrial water, after this first-stage preheating, enters the absorber (17) to absorb and release heat for a second-stage reheating. Then, it enters the second condenser (14) to condense and release heat for a third-stage final heating. The second heat source, after heat exchange with the first working medium through the organic Rankine cycle device, mixes with the first mixed heat source flowing out from the third heat exchanger (19) after the second industrial water has undergone primary preheating to become the second mixed heat source, and then enters the first heat exchanger (9) to perform the primary preheating on the first industrial water entering the first heat exchanger (9).

3. The black water waste heat recovery composite system according to claim 2, characterized in that, It also includes a control unit that monitors in real time the flow rate and temperature of the high-pressure steam, which serves as the first heat source, and the outlet temperature of the industrial water.

4. The black water waste heat recovery composite system according to claim 3, characterized in that, The residual pressure recovery device (4) is equipped with a regulating valve (20), and the control unit controls the regulating valve (20) in a manner that can automatically adjust the steam distribution ratio according to the flow rate of the high-pressure steam.

5. The black water waste heat recovery composite system according to claim 4, characterized in that, When the flow rate is greater than 70%, the regulating valve (20) is closed; when the flow rate is less than 70%, the regulating valve (20) is opened and 20-30% of the first heat source is directly introduced into the second heat exchanger (10).

6. The black water waste heat recovery composite system according to claim 4, characterized in that, When the temperature of the first heat source exceeds the specified range, the control unit stops the operation of the residual pressure recovery device (4) and opens the regulating valve (20) to allow all of the first heat source to enter the second heat exchanger (10).

7. The black water waste heat recovery composite system according to claim 1 or 2, characterized in that, It also includes a multi-stage flash evaporation device, which has a high-pressure flash tank (1), a low-pressure flash tank (2) and a vacuum flash tank (3). High-temperature and high-pressure black water enters the high-pressure flash tank (1) to generate high-pressure steam and high-pressure flash liquid. The high-pressure flash liquid is introduced into the low-pressure flash tank (2) for low-pressure flash evaporation to generate low-pressure steam and low-pressure flash liquid. The low-pressure flash liquid is introduced into the vacuum flash tank (3) for vacuum flash evaporation to generate vacuum steam.

8. The black water waste heat recovery composite system according to claim 1 or 2, characterized in that, The organic Rankine cycle device uses R236EA as the first working medium.

9. The black water waste heat recovery composite system according to claim 2, characterized in that, The first evaporator (6) is an S-vortex flow channel evaporator with an internal S-vortex flow channel heat exchange structure.

10. The black water waste heat recovery composite system according to claim 1 or 2, characterized in that, The absorption heat pump device uses lithium bromide solution as the second working medium.

11. A method for operating a blackwater waste heat recovery composite system, characterized in that, The black water waste heat recovery composite system applied to any one of claims 1 to 10 includes the following steps: In the residual pressure power generation step, the high-pressure steam at 170~184℃ and 0.8~1.1MPa generated by the high-pressure flash evaporation of black water is used as the first heat source and fed into the residual pressure recovery device. The pressure energy of the high-pressure steam is converted into mechanical energy by the expansion of the steam turbine, thereby driving the generator to output electrical energy. In the ORC power generation step, the low-pressure steam (120~144℃, 0.2~0.4MPa) generated by the low-pressure flash evaporation of black water is used as a second heat source and introduced into the organic Rankine cycle device, so that the first working medium circulates in the organic Rankine cycle device, thereby realizing the conversion of the thermal energy of the low-pressure steam into electrical energy. In the heat pump heating process, vacuum steam at 80~85℃ and 47~58kPa generated by vacuum flash evaporation of black water is used as the third heat source and fed into the absorption heat pump device, so that the second working medium completes the generation-condensation-evaporation-absorption cycle in the absorption heat pump device, thereby increasing the temperature of industrial water. as well as The cascade heat exchange process recovers low-grade waste heat from the first, second, and third heat sources after energy conversion through a heat exchange device in the following manner: The first heat source after pressure energy recovery directly heats the first stream of industrial water; The third heat source after heat exchange by the absorption heat pump device is mixed with the first heat source after heating the first industrial water to form the first mixed heat source, which is used to heat the second industrial water. The second heat source, after heat exchange in the organic Rankine cycle device, is mixed with the first mixed heat source after heating the second stream of industrial water to form a second mixed heat source, which then heats the first stream of industrial water.

12. The working method of the black water waste heat recovery composite system according to claim 11, characterized in that, In the aforementioned cascade heat exchange steps, the parameters of each heat source, the heat exchange parameters of the industrial water, and the operating parameters of the device are as follows: High-pressure steam at 170~184℃ and 0.8~1.1MPa, after being processed by the residual pressure recovery device (4), has its temperature reduced to 110~120℃ and its pressure reduced to 0.15MPa. It then enters the second heat exchanger (10) to perform secondary final heating on the first-stage preheated industrial water from the first heat exchanger (9), raising the temperature of the first-stage industrial water to 98℃. At the same time, the first heat source is cooled to 60~70℃ and its pressure is maintained at 0.15MPa. Low-pressure steam at 120~144℃ and 0.2~0.4MPa enters the first evaporator (6) of the organic Rankine cycle device to exchange heat with the first working medium. After heat exchange, its temperature drops to 50~60℃ and it mixes with the first mixed heat source at 50~55℃ discharged from the third heat exchanger (19) to become the second mixed heat source. Steam at 80~85℃ and 47~58kPa Vacuum steam enters the generator (13) of the absorption heat pump device to exchange heat with the second working medium. After heat exchange, the temperature drops to 60~70℃ and mixes with the first heat source (60~70℃) from the second heat exchanger (10) to become the first mixed heat source. The first mixed heat source enters the second evaporator (16) to release heat and then drops to 55~65℃. It then enters the third heat exchanger (19) to preheat the second industrial water (25~30℃) to 40℃. At the same time, the first mixed heat source cools down to 50℃. ~55℃; The first stream of industrial water with an initial temperature of 25℃ enters the first heat exchanger (9) to exchange heat with the second mixed heat source, and the temperature is raised to 45~50℃. Then it enters the second heat exchanger (10) to exchange heat with the first heat source with a temperature of 110~120℃, and the temperature is raised to 98℃. The second stream of industrial water with an initial temperature of 25~30℃ is preheated to 40℃ by the third heat exchanger (19), and then enters the absorber (17) to absorb and release heat to raise the temperature to 56℃. Then it enters the second condenser (14) to condense and release heat, and finally maintains a stable output of 60℃.

Images