Multi-source waste heat unified evaporator coupled adaptive variable stage heat pump CO2 regeneration heating system

Abstract

This invention discloses a multi-source waste heat unified evaporator coupled with an adaptive variable-stage heat pump CO2 regeneration heating system, including a multi-source waste heat unified evaporator module and an adaptive variable-stage compression unit. The unified evaporator module integrates multi-source distributed waste heat from flue gas, lean liquid, and overhead gas through a parallel architecture, and utilizes independently adjustable electronic expansion valves to balance the superheat of each branch under a unified manifold pressure, achieving efficient waste heat collection. The adaptive variable-stage compression unit is equipped with an inter-stage bypass and series switching mechanism, and the variable-stage controller employs dual-threshold hysteresis logic, adaptively switching between a single-stage high-efficiency mode and a two-stage high-temperature-rise mode based on the temperature difference between the regeneration target temperature and the evaporation temperature. This invention, through deep integration of multi-source waste heat, adaptive variable-stage compression mode, and dual-zone cascade heating on the condenser side, reduces the system's regeneration energy consumption and cooling water consumption, and improves its operational stability over a wide temperature range.

Description

Technical Field

[0001] This invention belongs to the fields of energy, chemical engineering and carbon emission reduction technology, and in particular relates to a multi-source waste heat unified evaporator coupled adaptive variable stage heat pump CO2 regeneration heating system. Background Technology

[0002] Chemical absorption (such as MEA, MDEA, and their mixed amine systems) is one of the more common CO2 capture technologies in coal-fired power plants and chemical plants. This process suffers from high regeneration energy consumption, large cooling water consumption, and insufficient waste heat utilization. CO2 desorption typically requires maintaining a temperature of 110℃–120℃ at the bottom of the desorption tower, and the reboiler heat consumption accounts for more than 60% of the total energy consumption of the capture system. Simultaneously, a large amount of dispersed low-grade waste heat (such as flue gas, lean liquor, and tower top gas) exists within and around the system, making it difficult to utilize directly.

[0003] Existing technologies attempt to recover waste heat using heat pumps, but they mainly suffer from the following problems: First, waste heat sources are scattered. Existing technologies mostly use a single heat source with independent configuration, which results in high equipment investment and difficulty in unified scheduling. Second, heat pumps have poor adaptability. Fixed single-stage or two-stage structures are difficult to handle the large temperature changes in winter and summer, resulting in low efficiency or unstable operation under some conditions. Third, simply connecting multiple evaporators in parallel can easily lead to imbalance in branch flow and liquid carryover in the compressor suction, resulting in insufficient system stability.

[0004] Therefore, there is an urgent need for a system that can efficiently integrate multiple waste heat sources and adapt to operation over a wide temperature range to improve the aforementioned technical problems. Summary of the Invention

[0005] The problem this invention aims to solve is to provide a multi-source waste heat unified evaporator coupled adaptive variable stage heat pump CO2 regeneration heating system. This system unifies the dispersed multi-source waste heat into a single evaporator and, based on a closed-loop control architecture with operating condition feedback, achieves adaptive switching between a single-stage high-efficiency mode and a two-stage high-temperature-rise mode. It adopts a dual-load heating method, simultaneously providing heat for the reboiler and rich liquid preheating, thereby reducing the consumption of regenerated steam and cooling water.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a multi-source waste heat unified evaporator coupled with an adaptive variable-stage heat pump CO2 regeneration heating system, including a multi-source waste heat unified evaporator module and an adaptive variable-stage compression unit. The multi-source waste heat unified evaporation end module includes at least two parallel process waste heat evaporators. Each process waste heat evaporator is used to exchange heat with different process material waste heat sources to absorb low-grade waste heat. Each process waste heat evaporator is connected to an independently adjustable electronic expansion valve. The electronic expansion valve is used to independently adjust the superheat of each branch under a unified manifold pressure and deliver the heat pump working fluid to the adaptive variable stage compression unit in a unified gaseous form. The intake port of the adaptive variable-stage compression unit is connected to the manifold outlet of the multi-source waste heat unified evaporation module, and the exhaust port of the adaptive variable-stage compression unit is connected to the condensation heat release side. The adaptive variable-stage compression unit adopts a single-cycle two-stage compression structure and is equipped with a variable-stage controller. The variable-stage controller adjusts the desorption regeneration target temperature T. target The evaporation temperature T of the multi-source waste heat unified evaporation end module source The temperature difference ΔT between the two stages allows the control system to adaptively switch between a single-stage high-efficiency mode and a two-stage large temperature rise mode.

[0007] Furthermore, the adaptive variable-stage compression unit includes a first-stage heat pump compressor, a second-stage heat pump compressor, and a bypass switching valve group connected in series. The bypass switching valve group includes a series valve and a bypass valve. The series valve is disposed on the pipeline between the outlet of the first-stage heat pump compressor and the inlet of the second-stage heat pump compressor. The bypass valve is disposed on the bypass pipeline between the outlet of the first-stage heat pump compressor and the inlet of the condensing heat release side, and is used to bypass the second-stage heat pump compressor. The variable-stage controller is electrically connected to the actuators of the series valve and the bypass valve, and is used to control the opening and closing of the valve group according to the temperature difference ΔT to switch the compression mode.

[0008] Furthermore, the variable-level controller has a preset switching upper limit threshold ΔT. high and switching lower limit threshold ΔT low It employs dual-threshold hysteresis logic for mode switching. When ΔT≥ΔT high At this time, the variable stage controller controls the series valve to open and the bypass valve to close, so that the system switches to a two-stage high temperature rise mode, and the heat pump working fluid is compressed in two stages in sequence; When ΔT≤ΔT low When the variable stage controller controls the series valve to close and the bypass valve to open, the system switches back to single-stage high-efficiency mode, and the heat pump working fluid bypasses the second-stage heat pump compressor. Where, ΔT low <ΔT high This is used to form a hysteresis interval to avoid frequent mode switching.

[0009] Furthermore, the process waste heat source includes any two or three of the following: flue gas, lean process liquor, and desorption tower top gas; the process waste heat evaporator includes any two or three of the following: flue gas waste heat evaporator, lean liquor waste heat evaporator, and tower top gas waste heat evaporator arranged in parallel.

[0010] Furthermore, the process waste heat evaporators are arranged in a distributed manner in physical space. The flue gas waste heat evaporator is coupled to the flue gas emission pipeline to recover flue gas heat; the lean liquor waste heat evaporator is coupled to the lean liquor circulation pipeline to recover lean liquor heat; and the tower top gas waste heat evaporator is coupled to the desorption tower top pipeline to recover gas heat.

[0011] Furthermore, the condensation heat release side adopts a dual-zone tiered heating structure, which includes a first heat exchange zone and a second heat exchange zone. The first heat exchange zone is thermally coupled to the working fluid reboiler, and the latent heat of the compressed high-temperature gaseous heat pump working fluid is used to heat the solution at the bottom of the desorption tower. The second heat exchange zone is thermally coupled to the working fluid-rich liquid heat exchanger and is located downstream of the first condensation zone. It uses the sensible heat of the liquefied heat pump working fluid to heat the rich liquid before it enters the desorption tower.

[0012] Furthermore, the heat pump working fluid is selected from R245fa, R1233zd(E) or a mixed high-temperature working fluid optimized for environmental performance.

[0013] Furthermore, the target temperature T for desorption and regeneration target The equivalent evaporation temperature T at the evaporation end is obtained from a temperature sensor located at the bottom of the desorption tower. source The temperature is obtained from a temperature sensor located at the outlet of the multi-source waste heat unified evaporation module or at the manifold.

[0014] Furthermore, it also includes a CO2 compression unit, which includes a first-stage CO2 compressor, a second-stage CO2 compressor, a first-stage CO2-rich liquid heat exchanger, and a second-stage CO2-rich liquid heat exchanger. The CO2 discharged from the top of the desorption tower enters the first-stage CO2-rich liquid heat exchanger for preliminary cooling and then enters the gas-liquid separator. The gas-liquid separator separates out condensate. The separated CO2 gas enters the second-stage CO2-rich liquid heat exchanger for further cooling. The cooled CO2 then sequentially enters the first-stage CO2 compressor and the second-stage CO2 compressor to output compressed CO2 product.

[0015] Furthermore, it also includes an energy level matching unit, which is connected between the heat pump and the reboiler to ensure that the heat output of the heat pump can match the temperature requirements of the reboiler.

[0016] The advantages and positive effects of this invention are: 1. This invention achieves unified absorption of multi-source waste heat, improving the comprehensive utilization rate of low-grade waste heat. Through the unified evaporation end module of multi-source waste heat, the originally dispersed waste heat from flue gas, lean liquid, and top gas is integrated into the same evaporation end under a unified evaporation pressure, which helps to reduce temperature fluctuations at the evaporation end, reduce the number of independent evaporation loops, and thus simplify the system structure.

[0017] 2. The adaptive variable-stage heat pump of this invention achieves high-efficiency operation under a wide range of operating conditions. Through a single-cycle two-stage compression structure combined with bypass switching and temperature difference criterion control, the system operates in a single-stage high-efficiency mode in summer or under stable conditions, and in a two-stage high-temperature-rise mode in winter or during the start-up phase, thus improving the problem of low efficiency of fixed-stage heat pumps under non-design conditions.

[0018] 3. This invention has high operational stability. The unified evaporator end structure, combined with electronic expansion valves, controls the superheat of each branch, buffering load and temperature fluctuations. The control strategy based on hysteresis logic suppresses frequent switching of the heat pump between single-stage and two-stage modes, which helps to improve the operational stability and reliability of the compressor and the entire system.

[0019] 4. This invention reduces the consumption of regenerated steam and cooling water. Through the unified absorption of multi-source waste heat and adaptive heat pump upgrading, this invention recovers and upgrades low-grade waste heat that would otherwise be carried away by cooling water, converting it into high-grade heat energy that can be directly used for regeneration heating. Heat balance analysis based on typical design conditions shows that, thanks to the energy efficiency performance of the heat pump unit under corresponding conditions, this invention can theoretically replace a portion of the externally supplied regenerated steam, and is expected to reduce regenerated steam consumption by approximately 20%. Simultaneously, because a large amount of waste heat in the process is absorbed by the evaporator, the system's external heat load is correspondingly reduced, and theoretically, cooling water consumption is expected to be reduced by approximately 30%. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of an embodiment of the present invention.

[0021] Figure 2 This is a schematic diagram of the multi-source waste heat unified evaporation end module structure according to an embodiment of the present invention.

[0022] Figure 3 This is a schematic diagram of the adaptive variable-level compression unit structure and control principle according to an embodiment of the present invention.

[0023] In the picture: 1. Absorption tower; 2. Rich and poor liquid heat exchanger; 3. Desorption tower; 4. Reboiler; 4-1. Steam reboiler; 4-2. Working fluid reboiler; 5. Gas-liquid separator; 6. Multi-source waste heat unified evaporation end module; 6-1. Flue gas waste heat evaporator; 6-2. Lean liquid waste heat evaporator; 6-3. Tower top gas waste heat evaporator; 7. Adaptive variable-stage compression unit; 7-1. First-stage heat pump compressor; 7-2. Second-stage heat pump compressor; 7-3. Variable-stage controller; V1. Series valve; V2. Bypass valve; 8. Flue gas waste heat recovery unit; 8-1. Exhaust fan; 8-2. Flue gas-rich liquid heat exchanger; 9. CO2 compression unit; 9-1. First-stage CO2 compressor; 9-2. Second-stage CO2 compressor; 9-3. First-stage CO2-rich liquid heat exchanger; 9-4. Second-stage CO2-rich liquid heat exchanger; 10. Energy level matching unit; 11. Working fluid-rich liquid heat exchanger. Detailed Implementation

[0024] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0026] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0027] The embodiments of the present invention will be further described below with reference to the accompanying drawings: like Figure 1As shown, this invention provides a multi-source waste heat unified evaporator coupled with an adaptive variable-stage heat pump CO2 regeneration heating system, including an absorption tower 1, a lean-rich liquid heat exchanger 2, a desorption tower 3, a multi-source waste heat unified evaporator module 6, and an adaptive variable-stage compression unit 7. The multi-source waste heat unified evaporator module 6 provides energy to the heat pump by recovering multi-source low-grade waste heat from the process flow, and the adaptive variable-stage compression unit 7 upgrades the recovered heat before supplying it to the regeneration process of the desorption tower 3.

[0028] Among them, such as Figure 2 As shown, the multi-source waste heat unified evaporation end module 6 includes at least two parallel waste heat recovery branches, each of which is coupled to a different process material waste heat source; each process waste heat evaporator is equipped with an independently adjustable electronic expansion valve on the heat pump working fluid inlet pipe.

[0029] Preferably, the waste heat source for the process stream includes any two or three of the following: flue gas, lean process liquor, and desorption tower overhead gas. The corresponding waste heat evaporator includes any two or three of the following: flue gas waste heat evaporator 6-1, lean liquor waste heat evaporator 6-2, and tower overhead gas waste heat evaporator 6-3, all arranged in parallel.

[0030] The process waste heat evaporators are arranged in a distributed manner in physical space. The flue gas waste heat evaporator 6-1 is coupled to the flue gas emission pipeline to recover the heat of the flue gas; the lean liquid waste heat evaporator 6-2 is coupled to the lean liquid circulation pipeline to recover the heat of the lean liquid; and the tower top gas waste heat evaporator 6-3 is coupled to the top pipeline of the desorption tower to recover the heat of the gas.

[0031] The multi-source waste heat unified evaporation end module 6 is configured to collect multiple low-grade waste heat sources that are dispersed through parallel evaporators, independently adjust the superheat of each branch under a unified manifold pressure using electronic expansion valves, and deliver the heat pump working fluid to the adaptive variable stage compression unit in a unified gaseous form.

[0032] Specifically, the multi-source waste heat unified evaporation end module 6 uses the dynamic feedback control of the electronic expansion valve to compensate for the pipeline resistance deviation caused by the spatial distribution differences of waste heat sources in various process flows, so that each branch maintains its own preset superheat under a unified confluence pressure, thereby achieving coordinated and stable recovery of multi-source heat.

[0033] The adaptive variable-stage compression unit 7 has its intake port connected to the confluence outlet of the multi-source waste heat unified evaporation module 6, and its exhaust port connected to the condensation heat release side.

[0034] like Figure 3 As shown, the adaptive variable-stage compression unit 7 is equipped with a variable-stage controller 7-3 and adopts a single-cycle two-stage compression structure, including a first-stage heat pump compressor 7-1, a second-stage heat pump compressor 7-2 connected in series, and a bypass switching valve group for changing the flow path of the heat pump working fluid.

[0035] Specifically, the bypass switching valve group includes a series valve V1 and a bypass valve V2. The series valve V1 is installed on the pipeline between the outlet of the first-stage heat pump compressor 7-1 and the inlet of the second-stage heat pump compressor 7-2. The bypass valve V2 is installed on the bypass pipeline between the outlet of the first-stage heat pump compressor 7-1 and the inlet of the condensing heat release side, and is used to bypass the second-stage heat pump compressor 7-2. The variable stage controller 7-3 is electrically connected to the actuators of the series valve V1 and the bypass valve V2, and is used to control the opening and closing of the valve group according to the temperature difference ΔT to switch the compression mode.

[0036] The variable stage controller 7-3 monitors the desorption and regeneration target temperature T in real time. target Evaporation temperature T of the unified evaporation end module 6 with multi-source waste heat source The temperature difference ΔT between the two is calculated. The controller has a preset dual-threshold hysteresis switching logic, including a switching upper threshold ΔT. high and lower limit threshold ΔT low This controls the action of the bypass switching valve group, enabling the system to adaptively switch between single-stage high-efficiency mode and two-stage high-temperature-rise mode.

[0037] Preferably, the target temperature for desorption regeneration is T. target The equivalent evaporation temperature T at the evaporation end is obtained from a temperature sensor located at the bottom of desorption tower 3. source The temperature is obtained by a temperature sensor located at the outlet or manifold of the multi-source waste heat unified evaporation module 6.

[0038] To further improve the feasibility and operational stability of the system, the variable-stage controller 7-3 adopts a closed-loop control strategy based on state feedback to achieve real-time monitoring of the system's operating status and smooth mode switching, specifically including: Multivariable dynamic feedback control: based on real-time monitoring of evaporation temperature T source Regeneration target temperature T target Based on sensor data such as suction superheat, the controller synchronously corrects the opening of the bypass switching valve group and the electronic expansion valves of each branch. This linkage adjustment mechanism helps to reduce system pressure and flow fluctuations during mode switching, promoting the continuity of heat pump operation.

[0039] Dual-threshold hysteresis logic control: To address the mode oscillation problem that easily occurs in heat pump systems at the critical temperature point, this invention introduces hysteresis control logic. By setting ΔT... high and ΔT lowTwo differentiated thresholds give the system control inertia during switching. The dual-stage mode is activated only when the temperature difference ΔT continuously rises and exceeds the upper threshold, while single-stage operation resumes only when the temperature difference falls back below the lower threshold. This strategy suppresses frequent switching and oscillations of the actuator near the critical point, ensuring heat exchange stability while extending the service life of the compressor and valve components.

[0040] The specific switching logic is as follows: when ΔT ≥ ΔT high At this time, the control series valve V1 is opened and the bypass valve V2 is closed, so that the system switches to the two-stage high temperature rise mode, and the heat pump working fluid goes through two stages of compression in sequence.

[0041] When ΔT≤ΔT low At this time, the control series valve V1 is closed and the bypass valve V2 is opened, so that the system switches back to single-stage high-efficiency mode, and the heat pump working fluid bypasses the second-stage heat pump compressor 7-2.

[0042] Where, ΔT low <ΔT high By using the hysteresis interval formed by two thresholds, frequent starts and stops or repeated mode switching near the switching point are reduced.

[0043] Preferably, the condensation heat release side adopts a dual-zone cascade heating structure, which includes a first heat exchange zone and a second heat exchange zone. The first heat exchange zone is thermally coupled to the working fluid reboiler 4-2, and uses the latent heat of the compressed high-temperature gaseous heat pump working fluid to heat the solution at the bottom of the desorption tower 3, providing the main regeneration heat.

[0044] The second heat exchange zone is thermally coupled to the working fluid-rich liquid heat exchanger 11 and is located downstream of the first condensation zone. It uses the sensible heat of the liquefied heat pump working fluid to heat the rich liquid before entering the desorption tower 3.

[0045] This tiered heat release structure achieves temperature level matching between the heat pump heat release process and the heat demand of the desorption process, which helps to improve the efficiency of heat energy utilization.

[0046] Preferably, the high-temperature heat pump working fluid is selected from R245fa, R1233zd(E) or a mixed high-temperature working fluid optimized for environmental performance, in order to match the condensation temperature range required by the CO2 regeneration process.

[0047] Those skilled in the art will recognize that the above control strategy can be implemented using PID control, model predictive control (MPC), or other conventional control algorithms applicable to thermal systems, and this invention does not impose any specific limitations on this.

[0048] like Figure 1As shown, the present invention also includes a CO2 compression unit 9, which includes a first-stage CO2 compressor 9-1, a second-stage CO2 compressor 9-2, a first-stage CO2-rich liquid heat exchanger 9-3, and a second-stage CO2-rich liquid heat exchanger 9-4. The CO2 discharged from the top of the desorption tower 3 enters the first-stage CO2-rich liquid heat exchanger 9-3 for preliminary cooling and then enters the gas-liquid separator 5. The gas-liquid separator 5 separates out condensate. The separated CO2 gas enters the second-stage CO2-rich liquid heat exchanger 9-4 for further cooling. The cooled CO2 then enters the first-stage CO2 compressor 9-1 and the second-stage CO2 compressor 9-2 in sequence, and outputs the compressed CO2 product.

[0049] like Figure 1 As shown, the present invention also includes an energy level matching unit 10, which is connected between the heat pump and the reboiler 4 to ensure that the heat output of the heat pump can match the temperature requirements of the reboiler 4.

[0050] The present invention will now be described in detail with reference to specific embodiments: Example 1: System Overall Layout A gas-fired boiler is equipped with a chemical absorption CO2 capture device, using MEA solution as the absorbent for CO2 absorption and regeneration. The original system mainly consists of an absorption tower 1, a lean-rich liquid heat exchanger 2, a desorption tower 3, a steam reboiler 4-1, and a matching cooling water system. Based on this, the multi-source waste heat unified evaporator coupled with an adaptive variable-stage heat pump system of this invention is deployed.

[0051] In this embodiment, the multiple process material waste heat sources arranged in a distributed manner are specifically configured as follows: Flue gas waste heat evaporator 6-1: Arranged in the flue gas waste heat recovery unit 8, specifically, placed on the flue gas pipeline downstream of the boiler tail flue induced draft fan 8-1, used to recover the sensible heat of medium and low temperature flue gas after heat exchange in the flue gas-rich liquid heat exchanger 8-2.

[0052] Lean liquid waste heat evaporator 6-2: Arranged between the cold lean liquid outlet of lean and rich liquid heat exchanger 2 and the lean liquid inlet of absorption tower 1, it is used to recover the sensible heat of lean liquid.

[0053] Top gas waste heat evaporator 6-3: Located at the CO2 gas outlet at the top of desorption tower 3, it is used to recover the latent heat and sensible heat of the top gas.

[0054] The aforementioned waste heat evaporators are connected in parallel on the heat pump working fluid side via insulated piping. Each evaporator inlet is equipped with an independently adjustable electronic expansion valve, and its inlet is connected to the high-pressure liquid supply main pipe from the condensation heat release side. The outlet of each evaporator is connected to the suction port of the first-stage heat pump compressor 7-1 of the adaptive variable-stage compression unit 7 via a manifold, forming a unified evaporation end.

[0055] The exhaust port of the first-stage heat pump compressor 7-1 is divided into two paths via a three-way pipe. One path is connected to the suction port of the second-stage heat pump compressor 7-2 via a series valve V1, and the other path is connected to the condenser inlet via a bypass valve V2. The exhaust outlet of the second-stage heat pump compressor 7-2 is connected to the condenser inlet.

[0056] The heat release side adopts a dual-zone cascade heating structure. It is thermally coupled to the working fluid reboiler 4-2 and the working fluid-rich liquid heat exchanger 11 in sequence according to the working fluid flow direction. After heat exchange, the high-pressure liquid heat pump working fluid is throttled and depressurized by the electronic expansion valves set at the inlet of each branch, and then enters the flue gas waste heat evaporator 6-1, the lean liquid waste heat evaporator 6-2 and the tower top gas waste heat evaporator 6-3 respectively to complete the evaporation and heat absorption process. After the outlet flow is merged, it enters the suction port of the first-stage heat pump compressor 7-1 to form a closed loop.

[0057] The variable stage controller 7-3 is electrically connected to the temperature sensor at the bottom of the desorption tower 3, the temperature sensor at the outlet of the heat pump working fluid at the unified evaporation end, the temperature and pressure sensors at the outlet of each evaporator, the independent electronic expansion valves of each branch, and the actuators of the series valve V1 and bypass valve V2, so as to realize the comprehensive control of the compression mode and the evaporation branch.

[0058] Example 2: Unified operation and resistance compensation of multi-source waste heat evaporator Under normal boiler operating conditions, the outlet flue gas, after being pressurized by the induced draft fan 8-1, first enters the flue gas-rich liquid heat exchanger 8-2, where the rich liquid is preheated using the sensible heat of the higher-grade flue gas, thereby reducing the flue gas temperature to 85℃. Subsequently, this medium-low temperature flue gas enters the flue gas waste heat evaporator 6-1. Simultaneously, the lean liquid temperature at the outlet of the lean-rich liquid heat exchanger 2 is approximately 75℃, and the CO2 gas temperature at the top of the desorption tower 3 is approximately 90℃.

[0059] During normal operation, the flue gas waste heat evaporator 6-1, lean liquid waste heat evaporator 6-2 and tower top gas waste heat evaporator 6-3 are physically distributed in different locations within the plant area, resulting in differences in the length of the pipeline from each evaporation branch to the compressor suction port.

[0060] The variable-stage controller 7-3 monitors the temperature and pressure signals at the outlet of each evaporator in real time. The system compensates for pressure drop fluctuations caused by differences in physical distance by combining a preset pipeline resistance calculation model with dynamic feedback control of the independent electronic expansion valves in each branch. During operation, the opening of the three electronic expansion valves is adjusted to ensure that each branch maintains a consistent pressure at the uniform junction point, and the superheat at the outlet of each evaporator is controlled within the range of 5℃ to 8℃.

[0061] When the boiler load changes, the temperature and flow rate of waste heat sources such as flue gas, lean liquor, and tower top gas fluctuate accordingly, and the evaporation load of each evaporation branch also changes accordingly. The variable stage controller monitors the temperature and pressure signals at the outlet of each evaporator in real time. When a deviation in superheat is detected in a certain branch, the working fluid flow rate of that branch is corrected by adjusting the opening of the corresponding electronic expansion valve. At the same time, the opening of the electronic expansion valves of the other branches is adjusted in a coordinated manner to maintain the overall evaporation pressure and superheat level at the evaporation end within a stable range.

[0062] Through the above control methods, the unified evaporation end of the multi-source waste heat can maintain a stable operating state even under load fluctuations, providing good suction conditions for the compression unit. Those skilled in the art will understand that the waste heat sources are not limited to the three specific media mentioned above. Depending on the available waste heat distribution in the actual process, the type, location, and quantity of waste heat sources can be adaptively increased or decreased, all based on the unified convergence and independent adjustment logic described in this invention, and falling within the essential technical scope of this invention.

[0063] Example 3: Adaptive switching threshold determination and efficient operation of single-stage compression in summer To improve the safety and energy efficiency of system operation, in this embodiment, the dual threshold parameters preset inside the variable stage controller 7-3 are set as follows: upper threshold ΔT high Set to 65℃, lower limit threshold ΔT low Set to 55℃.

[0064] Under typical summer operating conditions, due to the high ambient temperature, the temperature of multiple waste heat sources increases accordingly, resulting in a uniform evaporation end equivalent evaporation temperature T. source Approximately 68℃. The target regeneration temperature T for desorption tower 3 is... target The temperature is 120℃, and the real-time temperature difference ΔT is approximately 52℃.

[0065] The variable-stage controller 7-3 monitors sensor data in real time and determines whether the current ΔT ≤ ΔT. low (55℃) meets the conditions for high-efficiency single-stage operation. The variable-stage controller 7-3 then issues a command to close the series valve V1 and open the bypass valve V2, putting the system into single-stage compression mode. At this time, only the first-stage heat pump compressor 7-1 operates, and the heat pump working fluid, after compression, directly enters the condensation and heat release side. Under the operating parameters set in this embodiment, the system can achieve a heating demand of 120℃ with relatively low power consumption, demonstrating the energy efficiency advantage of single-stage mode under high evaporation temperature conditions.

[0066] Example 4: Hysteresis Logic Control and Two-Stage High Temperature Rise Operation in Winter In winter or during startup, the temperature of the waste heat source in the process flow decreases due to the low ambient temperature. At this time, the equivalent evaporation temperature T at the unified evaporation end... sourceThe temperature drops to approximately 50°C. The target regeneration temperature T for desorption tower 3 is... target The temperature remains at 120°C, and the real-time temperature difference ΔT of the system increases to approximately 70°C.

[0067] When the system is in operation, the variable stage controller 7-3 detects that ΔT ≥ ΔT. high (65℃) It was determined that the single-stage compression could not meet the high-level condensation requirements within the safe pressure ratio range, so the two-stage high temperature rise mode switching program was initiated. The variable stage controller 7-3 issued a linkage command: open the series valve V1, close the bypass valve V2, and simultaneously start the second-stage heat pump compressor 7-2, so that the heat pump working fluid enters the condenser after passing through two stages of compression.

[0068] In the two-stage compression mode, the outlet temperature of the first-stage heat pump compressor 7-1 is about 95℃~100℃. After interstage pressure balancing or cooling, it enters the second-stage heat pump compressor 7-2, and the final exhaust temperature can reach 125℃~135℃, which meets the demand of the desorption tower 3 for high-grade heat source in winter or during start-up.

[0069] As the ambient temperature rises or the load decreases, the temperature at the uniform evaporator gradually increases, and ΔT gradually decreases. When ΔT ≤ ΔT low At this time, the variable stage controller 7-3 issues a switching command again, so that the system can smoothly switch back from two-stage mode to single-stage mode, reducing the impact of frequent switching on the equipment.

[0070] In this embodiment, the dual-threshold hysteresis control logic executed by the variable-stage controller 7-3 constitutes the control inertia of the system: Mode hold: When the temperature difference fluctuates between 55℃ and 65℃, the system maintains the current operating mode without switching, suppressing frequent start-stop and mode oscillation of the actuator near the critical temperature difference point.

[0071] Extended lifespan: The system only executes valve linkage and compressor start-up / stop actions when the temperature difference actually exceeds the upper threshold (65℃) or falls below the lower threshold (55℃). This strategy reduces compressor mechanical fatigue and solenoid valve opening and closing losses, helps ensure the stability of continuous heat supply in the CO2 regeneration process, and extends the overall system lifespan.

[0072] Example 5: Dual-zone cascade heating process and energy-saving effect Under the above operating mode, the system's heat release side adopts a dual-zone cascade heating structure consisting of a working fluid reboiler 4-2 and a working fluid-rich liquid heat exchanger 11. Taking the stable operation under the dual-stage high temperature rise mode as an example, the specific heat exchange process is as follows: First heat exchange zone (high-temperature phase change heating): High-temperature and high-pressure gaseous working fluid from the second-stage heat pump compressor 7-2 enters the working fluid reboiler 4-2. In this zone, the working fluid heats the lean liquid at the bottom of the desorption tower 3 through the latent heat of phase change, maintaining it at a regeneration temperature of 110°C to 120°C.

[0073] Second heat exchange zone (sensible heat recovery preheating): The condensed liquid heat pump working fluid enters the downstream working fluid-rich liquid heat exchanger 11. This zone utilizes the sensible heat of the working fluid to raise the temperature of the process rich liquid before it enters the desorption tower 3 from 50°C to 80°C–85°C. Through this sensible heat recovery, not only is the enthalpy of the working fluid before entering the throttling valve reduced, but the heating load required by the reboiler 4 is also directly reduced.

[0074] Based on heat balance analysis and experimental verification under typical design conditions, thanks to the unified integrated recovery of multi-source waste heat and the efficient upgrading of low-grade heat energy by the adaptive heat pump, the energy saving and consumption reduction effects of this system are as follows: Regenerated steam savings: Compared to traditional processes without integrated heat pumps, this system replaces a large amount of purchased steam with high-grade heat energy produced by the heat pump, which is expected to reduce regenerated steam consumption by about 20%.

[0075] Reduced cooling water consumption: Because a large amount of waste heat from the flue gas, lean liquor, and overhead gas is recovered and utilized at the evaporation end, the heat load that the system previously needed to discharge to the environment via external cooling water is reduced. Based on theoretical calculations, the system's cooling water consumption is expected to be reduced by approximately 30%.

[0076] This embodiment achieves deep coupling and precise matching between the heat pump heat release process and the heat demand of the CO2 desorption process through a dual-zone cascade heat release structure.

[0077] The advantages and positive effects of this invention are: 1. This invention achieves unified absorption of multi-source waste heat, improving the comprehensive utilization rate of low-grade waste heat. Through the unified evaporation end module of multi-source waste heat, the originally dispersed waste heat from flue gas, lean liquid, and top gas is integrated into the same evaporation end under a unified evaporation pressure, which helps to reduce temperature fluctuations at the evaporation end, reduce the number of independent evaporation loops, and thus simplify the system structure.

[0078] 2. The adaptive variable-stage heat pump of this invention achieves high-efficiency operation under a wide range of operating conditions. Through a single-cycle two-stage compression structure combined with bypass switching and temperature difference criterion control, the system operates in a single-stage high-efficiency mode in summer or under stable conditions, and in a two-stage high-temperature-rise mode in winter or during the start-up phase, thus improving the problem of low efficiency of fixed-stage heat pumps under non-design conditions.

[0079] 3. This invention has high operational stability. The unified evaporator end structure, combined with electronic expansion valves, controls the superheat of each branch, buffering load and temperature fluctuations. The control strategy based on hysteresis logic suppresses frequent switching of the heat pump between single-stage and two-stage modes, which helps to improve the operational stability and reliability of the compressor and the entire system.

[0080] 4. This invention reduces the consumption of regenerated steam and cooling water. Through the unified absorption of multi-source waste heat and adaptive heat pump upgrading, this invention recovers and upgrades low-grade waste heat that would otherwise be carried away by cooling water, converting it into high-grade heat energy that can be directly used for regeneration heating. Heat balance analysis based on typical design conditions shows that, thanks to the energy efficiency performance of the heat pump unit under corresponding conditions, this invention can theoretically replace a portion of the externally supplied regenerated steam, and is expected to reduce regenerated steam consumption by approximately 20%. Simultaneously, because a large amount of waste heat in the process is absorbed by the evaporator, the system's external heat load is correspondingly reduced, and theoretically, cooling water consumption is expected to be reduced by approximately 30%.

[0081] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A multi-source waste heat unified evaporator coupled with an adaptive variable-stage heat pump CO2 regeneration heating system, characterized in that: Includes a multi-source waste heat unified evaporation end module and an adaptive variable-stage compression unit. The multi-source waste heat unified evaporation end module includes at least two parallel process waste heat evaporators. Each process waste heat evaporator is used to exchange heat with different process material waste heat sources to absorb low-grade waste heat. Each process waste heat evaporator is connected to an independently adjustable electronic expansion valve. The electronic expansion valve is used to independently adjust the superheat of each branch under a unified manifold pressure and deliver the heat pump working fluid to the adaptive variable stage compression unit in a unified gaseous form. The intake port of the adaptive variable-stage compression unit is connected to the manifold outlet of the multi-source waste heat unified evaporation module, and the exhaust port of the adaptive variable-stage compression unit is connected to the condensation heat release side. The adaptive variable-stage compression unit adopts a single-cycle two-stage compression structure and is equipped with a variable-stage controller. The variable-stage controller adjusts the desorption regeneration target temperature T. target The evaporation temperature T of the multi-source waste heat unified evaporation end module source The temperature difference ΔT between the two stages allows the control system to adaptively switch between a single-stage high-efficiency mode and a two-stage large temperature rise mode.

2. The multi-source waste heat unified evaporator coupled adaptive variable stage heat pump CO2 regeneration heating system according to claim 1, characterized in that: The adaptive variable-stage compression unit includes a first-stage heat pump compressor, a second-stage heat pump compressor, and a bypass switching valve group connected in series. The bypass switching valve group includes a series valve and a bypass valve. The series valve is installed on the pipeline between the outlet of the first-stage heat pump compressor and the inlet of the second-stage heat pump compressor. The bypass valve is installed on the bypass pipeline between the outlet of the first-stage heat pump compressor and the inlet of the condensing heat release side, and is used to bypass the second-stage heat pump compressor. The variable-stage controller is electrically connected to the actuators of the series valve and the bypass valve, and is used to control the opening and closing of the valve group according to the temperature difference ΔT to switch the compression mode.

3. The multi-source waste heat unified evaporator coupled adaptive variable stage heat pump CO2 regeneration heating system according to claim 2, characterized in that: The variable controller has a preset switching upper limit threshold ΔT. high and switching lower limit threshold ΔT low It employs dual-threshold hysteresis logic for mode switching. When ΔT≥ΔT high At this time, the variable stage controller controls the series valve to open and the bypass valve to close, so that the system switches to a two-stage high temperature rise mode, and the heat pump working fluid is compressed in two stages in sequence; When ΔT≤ΔT low When the variable stage controller controls the series valve to close and the bypass valve to open, the system switches back to single-stage high-efficiency mode, and the heat pump working fluid bypasses the second-stage heat pump compressor. Where, ΔT low <ΔT high This is used to form a hysteresis interval to avoid frequent mode switching.

4. The multi-source waste heat unified evaporator coupled adaptive variable-stage heat pump CO2 regeneration heating system according to any one of claims 1 to 3, characterized in that: The process waste heat source includes any two or three of the following: flue gas, lean process liquor, and desorption tower top gas; the process waste heat evaporator includes any two or three of the following: flue gas waste heat evaporator, lean liquor waste heat evaporator, and tower top gas waste heat evaporator arranged in parallel.

5. The multi-source waste heat unified evaporator coupled adaptive variable stage heat pump CO2 regeneration heating system according to claim 4, characterized in that: The process waste heat evaporators are arranged in a distributed manner in physical space. The flue gas waste heat evaporator is coupled to the flue gas emission pipeline to recover the heat of the flue gas; the lean liquor waste heat evaporator is coupled to the lean liquor circulation pipeline to recover the heat of the lean liquor; and the tower top gas waste heat evaporator is coupled to the desorption tower top pipeline to recover the heat of the gas.

6. The multi-source waste heat unified evaporator coupled adaptive variable-stage heat pump CO2 regeneration heating system according to any one of claims 1 to 3, characterized in that: The condensation heat release side adopts a dual-zone tiered heating structure, which includes a first heat exchange zone and a second heat exchange zone. The first heat exchange zone is thermally coupled to the working fluid reboiler, and the latent heat of the compressed high-temperature gaseous heat pump working fluid is used to heat the solution at the bottom of the desorption tower. The second heat exchange zone is thermally coupled to the working fluid-rich liquid heat exchanger and is located downstream of the first condensation zone. It uses the sensible heat of the liquefied heat pump working fluid to heat the rich liquid before it enters the desorption tower.

7. The multi-source waste heat unified evaporator coupled adaptive variable-stage heat pump CO2 regeneration heating system according to any one of claims 1 to 3, characterized in that: The heat pump working fluid is selected from R245fa, R1233zd(E) or a mixed high-temperature working fluid optimized for environmental performance.

8. The multi-source waste heat unified evaporator coupled adaptive variable-stage heat pump CO2 regeneration heating system according to any one of claims 1 to 3, characterized in that: The target temperature for desorption regeneration T target The equivalent evaporation temperature T at the evaporation end is obtained from a temperature sensor located at the bottom of the desorption tower. source The temperature is obtained from a temperature sensor located at the outlet of the multi-source waste heat unified evaporation module or at the manifold.

9. The multi-source waste heat unified evaporator coupled adaptive variable-stage heat pump CO2 regeneration heating system according to any one of claims 1 to 3, characterized in that: It also includes a CO2 compression unit, which includes a first-stage CO2 compressor, a second-stage CO2 compressor, a first-stage CO2-rich liquid heat exchanger, and a second-stage CO2-rich liquid heat exchanger. The CO2 discharged from the top of the desorption tower enters the first-stage CO2-rich liquid heat exchanger for preliminary cooling and then enters the gas-liquid separator. The gas-liquid separator separates out condensate. The separated CO2 gas enters the second-stage CO2-rich liquid heat exchanger for further cooling. The cooled CO2 then enters the first-stage CO2 compressor and the second-stage CO2 compressor in sequence to output compressed CO2 product.

10. The multi-source waste heat unified evaporator coupled adaptive variable-stage heat pump CO2 regeneration heating system according to any one of claims 1 to 3, characterized in that: It also includes an energy level matching unit, which is connected between the heat pump and the reboiler to ensure that the heat output of the heat pump can match the temperature requirements of the reboiler.

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