Gradient utilization system for chemical waste heat

Abstract

The invention relates to the technical field of waste heat recovery, in particular to a chemical waste heat gradient utilization system. A chemical waste heat gradient utilization system comprises a waste heat circulation unit used for treating multi-stage waste heat, and the multi-stage waste heat comprises a first-stage waste heat circulation at the temperature of 59.4 / 40 DEG C, a second-stage waste heat circulation at the temperature of 50 / 35 DEG C, a third-stage waste heat circulation at the temperature of 50 / 42 DEG C, a fourth-stage waste heat circulation at the temperature of 40 / 32 DEG C and a fifth-stage waste heat circulation at the temperature of 80 / 35 DEG C; the cooling circulation unit is used for carrying out heat exchange on cooling water at 32 DEG C and the waste heat circulation unit and raising the temperature to 40 DEG C; the steam-condensate unit is used for cooling and depressurizing steam and seasonal distribution of 90-DEG C condensate; the heat utilization end heating unit is used for heating municipal heating, process hot water and heat tracing; and the control unit is used for dynamically adjusting the temperature and the flow of each unit. According to the chemical waste heat gradient utilization system, efficient utilization of waste heat resources is achieved, multiple heat utilization requirements are met, stable operation of the system is achieved, and energy consumption and operation cost are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of waste heat recovery, in particular to a chemical waste heat cascade utilization system. Background Art

[0002] Traditional chemical waste heat recovery systems rely on a single energy source, resulting in high operating costs and significant carbon emissions. They also suffer from issues such as irrational heat exchange design and high heat loss, leading to inadequate waste heat extraction or inefficient transfer. They only recover high-temperature waste heat, while neglecting medium- and low-temperature waste heat, or lack a tiered utilization approach. Waste heat recovery systems utilize conventional heat pumps, which suffer from high friction losses and low partial-load efficiency, resulting in low operating energy efficiency. Furthermore, existing waste heat recovery systems struggle to effectively utilize low-grade heat sources.

[0003] In industrial low-temperature waste heat recovery and utilization projects, when the municipal return water is unstable or insufficient, ordinary centrifuges will cause surge shutdown due to the difficulty in frequency conversion of the low-temperature heat source, resulting in the entire line being shut down.

[0004] Existing equipment usually uses multiple 10MW devices in series in large-scale heating projects (such as 100MW). If one device is damaged or the circulating water condition does not meet the requirements, the device will not be able to operate, causing the entire line to stop production. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: in order to solve the problems of large heat loss, low operating energy efficiency ratio and difficulty in effectively utilizing low-grade heat sources in the existing technology in the above-mentioned background technology, a chemical waste heat cascade utilization system is provided to achieve efficient energy recovery and distribution through the collaboration of multiple units.

[0006] The technical solution adopted by the present invention to solve the technical problem is: a chemical waste heat cascade utilization system, comprising: Waste heat circulation unit, used to process multi-stage waste heat, including the first stage waste heat circulation at 59.4 / 40℃, the second stage waste heat circulation at 50 / 35℃, the third stage waste heat circulation at 50 / 42℃, the fourth stage waste heat circulation at 40 / 32℃ and the fifth stage waste heat circulation at 80 / 35℃; The cooling circulation unit is used to heat the 32°C cooling water with the waste heat circulation unit to raise the temperature to 40°C; Steam-condensate unit, used for steam temperature and pressure reduction and seasonal distribution of 90℃ condensate; Hot end heating unit is used for heating municipal heating, process hot water and tracing; Control unit, used for dynamic adjustment of temperature and flow of each unit.

[0007] The waste heat circulation unit classifies and processes waste heat in different temperature ranges to avoid energy waste; the cooling circulation unit uses waste heat to increase the cooling water temperature and reduce the energy consumption of the cooling tower; the steam-condensate unit realizes flexible energy scheduling through steam temperature reduction and pressure reduction and seasonal distribution of condensate; the hot end heating unit meets the high temperature requirements of municipal heating, process hot water and heating, and improves the overall energy efficiency of the system; the control unit dynamically adjusts the temperature and flow to ensure stable operation of the system; it realizes the full gradient recovery of low, medium and high temperature waste heat in the chemical production process, and matches the energy to different heat ends through heat pumps, plate exchangers and other equipment, greatly improving the overall energy efficiency.

[0008] According to one embodiment of the present invention, the first-stage waste heat cycle includes a 59.4°C water supply pipe, a fourth plate heat exchanger, and a 40°C water return pipe. The water output from the 59.4°C water supply pipe is heated to 40°C by the fourth plate heat exchanger and then enters the 40°C water return pipe, where it is combined with the 90°C condensate according to seasonal switching. The second-stage waste heat circulation is divided into multiple paths, each of which includes a 50°C water supply pipe, a second plate heat exchanger, a third plate heat exchanger, a first magnetic levitation centrifugal heat pump, a second magnetic levitation centrifugal heat pump and a 35°C return water pipe. The water output from the 50°C water supply pipe is heated to 42°C by the third plate heat exchanger, and then enters the evaporators of the first magnetic levitation centrifugal heat pump and the second magnetic levitation centrifugal heat pump respectively to cool to 35°C, then enters the second plate heat exchanger for insulation, and then enters the 35°C return water pipe; The third-stage waste heat circulation is divided into multiple paths, each path including a 50°C water supply pipe 1, a first-stage magnetic levitation centrifugal heat pump, a second-stage magnetic levitation centrifugal heat pump, and a 42°C water return pipe. The 48°C water output from the 50°C water supply pipe 1 is cooled to 44.3°C by the evaporator of the first-stage magnetic levitation centrifugal heat pump, and then cooled to 40°C by the evaporator of the second-stage magnetic levitation centrifugal heat pump before entering the 42°C water return pipe. The fourth stage waste heat circulation is divided into multiple paths, each path includes a 40°C water supply pipe, a first plate heat exchanger and a 32°C water return pipe. The water output from the 40°C water supply pipe is heated to 32°C by the first plate heat exchanger and then enters the 32°C water return pipe. The fifth-stage waste heat cycle includes an 80°C water supply pipe, a first absorption heat pump, a second absorption heat pump, a magnetic levitation centrifugal heat pump 1, a magnetic levitation centrifugal heat pump 2, a magnetic levitation centrifugal heat pump 3, a magnetic levitation centrifugal heat pump 4 and a 35°C return water pipe 1. The water output from the 80°C water supply pipe is cooled to 69°C by the evaporator of the first absorption heat pump, and then cooled to 58°C by the evaporator of the second absorption heat pump. Then, it is cooled to 42°C by the evaporators of the magnetic levitation centrifugal heat pump 1, the magnetic levitation centrifugal heat pump 2, the magnetic levitation centrifugal heat pump 3 and the magnetic levitation centrifugal heat pump 4 in sequence before entering the 35°C return water pipe 1, and the temperature is reduced by 4°C each time it passes through a magnetic levitation centrifugal heat pump.

[0009] The first-stage waste heat cycle recovers condensate waste heat through plate exchangers and is coupled with the steam-condensate system to achieve seasonal energy complementarity. The second-stage waste heat cycle is divided into five routes for deep cooling through magnetic levitation centrifugal heat pumps, maximizing the usable energy extraction of 50°C hot water. The third-stage waste heat cycle uses a two-stage magnetic levitation centrifugal heat pump to precisely control the return water temperature to 40°C, avoiding energy waste. The fourth-stage waste heat cycle uses direct heat exchange through plate exchangers, simplifying the low-temperature waste heat recovery process. The fifth-stage waste heat cycle uses four stages of cooling, including absorption and magnetic levitation centrifugal heat pumps, to address the difficulty of directly utilizing high-temperature waste heat. Covering a wide range of waste heat from 59.4°C to 80°C, the waste heat utilization rate exceeds 85% through graded treatment to meet different temperature requirements.

[0010] According to one embodiment of the present invention, each of the second-stage waste heat cycle and the third-stage waste heat cycle is provided with a circulation pump.

[0011] A circulation pump is configured for each branch of the second and third stage waste heat circulation to ensure balanced flow in each branch and avoid local overheating or insufficient flow; improve the hydraulic stability of the system and prevent the decrease in heat exchange efficiency due to uneven flow.

[0012] According to one embodiment of the present invention, three temperature sensors and two regulating valves are provided on each circuit of the second-stage waste heat cycle. The circulation pump on each circuit of the second-stage waste heat cycle controls the opening of the two regulating valves by detecting the temperature of the three temperature sensors on the circuit to ensure that the return water temperature is stable at 35°C.

[0013] Through the detection of the intermediate value of three sensors and the joint control of dual valves, the return water temperature is strictly stabilized at 35°C; the temperature control accuracy reaches ±0.5°C, meeting the stringent requirements of chemical processes for return water temperature.

[0014] According to one embodiment of the present invention, a flow meter and a regulating valve are provided on each circuit of the third-stage waste heat cycle. The circulation pump of each circuit of the third-stage waste heat cycle controls the opening of the regulating valve by detecting the flow rate of the flow meter on the circuit to ensure that the flow rates of the five circuits meet the demand. A flow meter and a regulating valve are provided on each route of the second-stage waste heat cycle. The circulation pump on each route of the second-stage waste heat cycle controls the opening of the regulating valve by detecting the flow of the flow meter on that route to ensure that the flow of the five routes meets the demand.

[0015] The valve opening of each of the second and third-stage waste heat circulation systems is adjusted through flow meter feedback to ensure that the five-way flow is distributed according to the designed ratio, achieving adaptive flow balance, avoiding overload of one line while other lines are idle, and improving system energy efficiency by 15%.

[0016] According to one embodiment of the present invention, the cooling circulation unit is divided into multiple routes, each of which includes a 32°C cooling water supply pipe, a second plate heat exchanger and a 40°C cooling water return pipe. The cooling water output from the 32°C cooling water supply pipe is heat exchanged to 40°C through the second plate heat exchanger and then enters the 40°C cooling water return pipe.

[0017] The 32°C cooling water is heated to 40°C after heat exchange with the waste heat circulation unit, recovering waste heat while reducing the cooling tower load; the energy consumption of the cooling water system is reduced by 20%, and the direct discharge of low-temperature heat sources is avoided.

[0018] According to one embodiment of the present invention, when it is detected that the municipal return water temperature is lower than 35°C or the flow rate is lower than the set threshold, the second plate heat exchanger automatically operates to stably maintain the temperature on the heat source side above 35°C through the second plate heat exchanger.

[0019] When the return water is unstable, the second plate heat exchanger is automatically switched in to stabilize the low-temperature return water temperature, ensuring the circulation balance, energy consumption stability and equipment safety of the factory's production water system, thereby ensuring normal production. The second plate heat exchanger here is a backup plate heat exchanger.

[0020] According to one embodiment of the present invention, the steam-condensate unit includes a steam inlet pipe, a first absorption heat pump, a second absorption heat pump and a 90°C condensate pipe. The steam output from the steam inlet pipe enters the generator of the first absorption heat pump and the second absorption heat pump after passing through a temperature reduction and pressure reduction device to be cooled to 90°C condensate. The 90°C condensate in the 90°C condensate pipe is incorporated into the 59.4°C water supply pipe of the first-stage waste heat cycle in the heating season, and is incorporated into the 40°C return water pipe of the first-stage waste heat cycle in the non-heating season.

[0021] During the heating season, the 90°C condensate is incorporated into the 59.4°C water supply pipe to supplement the heating heat source; during the non-heating season, it is incorporated into the 40°C return pipe to avoid energy waste; this achieves seasonal adaptive utilization of condensate energy, and increases the annual energy saving rate by 12%.

[0022] According to one embodiment of the present invention, the municipal heating cycle in the heat-using end heating unit is divided into multiple paths, one of which includes a 30°C municipal return pipe, a first plate heat exchanger, a fourth plate heat exchanger, a third plate heat exchanger, a first magnetic levitation centrifugal heat pump, a second magnetic levitation centrifugal heat pump, a second magnetic levitation centrifugal heat pump, a first magnetic levitation centrifugal heat pump and an 88.2°C municipal water supply pipe. The path is further divided into two branches. The first branch: the water output from the 30°C municipal return pipe is heat-exchanged to 38°C through the first plate heat exchanger and the water output from the 40°C water supply pipe in the fourth stage waste heat cycle, and then passes through the fourth plate heat exchanger. The heat exchanger exchanges heat with the water output from the 59.4℃ water supply pipe in the first-stage waste heat cycle to 57.4℃; in the second branch, the water output from the 30℃ municipal return pipe exchanges heat with the water output from the 50℃ water supply pipe in the second-stage waste heat cycle to 47℃ through the third plate heat exchanger, then enters the condensers of the first magnetic levitation centrifugal heat pump and the second magnetic levitation centrifugal heat pump in turn to increase the temperature to 60.5℃, mixes with the 57.4℃ heating water in the first branch to 59℃, then enters the condensers of the second magnetic levitation centrifugal heat pump and the first magnetic levitation centrifugal heat pump in turn to increase the temperature to 86.4℃, and enters the 88.2℃ municipal water supply pipe; The first branch and the second branch both include a subcooling circulation unit. The hot water in the subcooling circulation unit is input in parallel into the economizer in the subsequent magnetic levitation centrifugal heat pump. The hot water in the subcooling circulation unit is different from the heating water and enters the condenser of the magnetic levitation centrifugal heat pump in series, which can reduce the use of municipal return water and ensure the stable operation of the system when the municipal return water volume is small, avoiding the shutdown of the magnetic levitation centrifugal heat pump due to insufficient municipal return water.

[0023] Furthermore, the hot water in the subcooling circulation unit comes from 29-31°C municipal return water, and the directly used water comes from 29-31°C municipal return water. By lowering the temperature of the hot water, the heat transfer temperature difference between it and the liquid working medium of the magnetic levitation centrifugal heat pump increases, and the amount of heat that can be taken away per unit time increases. In other words, in order to achieve the required supercooling of the working medium, the required amount of hot water can be reduced accordingly, and the flow rate is also reduced. While ensuring that the supercooling of the working medium meets the standard, energy saving and improvement of system operating efficiency can be achieved. It can also solve the problem of ensuring stable operation of the system when the amount of municipal return water is small, further reduce the amount of municipal return water, and avoid shutdown of the magnetic levitation centrifugal heat pump due to insufficient municipal return water.

[0024] The remaining routes include the 30℃ municipal return pipe, the first plate heat exchanger, the third plate heat exchanger, the first magnetic levitation centrifugal heat pump, the second magnetic levitation centrifugal heat pump, the second magnetic levitation centrifugal heat pump, the first magnetic levitation centrifugal heat pump and the 88.2℃ municipal water supply pipe. The water output from the 30℃ municipal return pipe is heat exchanged with the water output from the 40℃ water supply pipe in the fourth-stage waste heat cycle to 36.8℃ through the first plate heat exchanger, and then heat exchanged with the water output from the 50℃ water supply pipe in the second-stage waste heat cycle to 45.5℃ through the third plate heat exchanger, and then enters the condensers of the first magnetic levitation centrifugal heat pump, the second magnetic levitation centrifugal heat pump, the second magnetic levitation centrifugal heat pump and the first magnetic levitation centrifugal heat pump in turn to increase the temperature to 88.7℃, and then enters the 88.2℃ municipal water supply pipe.

[0025] The system is designed with two branches. The first branch directly exchanges heat with waste heat through plate exchange, quickly raising the water temperature to 57.4°C; the second branch gradually raises the temperature through a magnetic levitation centrifugal heat pump, and finally mixes the water to 88.2°C. Combining the advantages of direct heat exchange and heat pump heating, it reduces power consumption while ensuring efficiency, and the heating water temperature reaches 100% of the standard rate.

[0026] According to one embodiment of the present invention, the first magnetic levitation centrifugal heat pump, the second magnetic levitation centrifugal heat pump, the first-stage magnetic levitation centrifugal heat pump and the second-stage magnetic levitation centrifugal heat pump all adopt magnetic levitation centrifugal heat pumps, which include an evaporator, a condenser and an economizer. The water output from the 30°C municipal return pipe in the second branch is supplied to the economizer of each magnetic levitation centrifugal heat pump, and the economizer of each magnetic levitation centrifugal heat pump in the remaining several branches of the hot end heating unit receives 45.5°C water after heat exchange through the third plate heat exchanger, and the condenser of the latter magnetic levitation centrifugal heat pump receives water mixed after heat exchange between the condenser and economizer of the previous magnetic levitation centrifugal heat pump.

[0027] In the second branch, each economizer of the magnetic levitation centrifugal heat pump is supplied with a separate return water supply. Supplying low-temperature return water to the economizer cools the condensed liquid working fluid and provides a certain degree of subcooling, reducing evaporation during the subsequent heat exchange between the expansion valve and the non-condensable gases, thereby improving heat exchange efficiency. Furthermore, if the municipal return water volume is unstable or low, directly diverting a portion of the return water to the economizer of the magnetic levitation centrifugal heat pump can reduce the amount of municipal return water in the system and maintain system stability. In the remaining branches of the hot-end heating unit, the economizer of each magnetic levitation centrifugal heat pump is not supplied with a separate return water supply. Instead, a portion of the heating water from the previous magnetic levitation centrifugal heat pump is diverted to the economizer, with some going directly to the condenser of the magnetic levitation centrifugal heat pump and some going to the economizer. The heating water is then combined with the next magnetic levitation centrifugal heat pump.

[0028] According to one embodiment of the present invention, it also includes a main line, and the input and output ends of each magnetic levitation centrifugal heat pump are connected to the main line through a connecting branch pipe. A switch valve is provided on the main line corresponding to each magnetic levitation centrifugal heat pump, and a switch valve is also provided on the connecting branch pipe; when any magnetic levitation centrifugal heat pump fails or the circulating water condition does not meet the requirements, the switch valve on its connecting branch pipe is automatically closed, and the switch valve on the corresponding main line is automatically opened, and water flows through the main line into the next magnetic levitation centrifugal heat pump; or when the municipal return water is insufficient, the switch valves on several magnetic levitation centrifugal connecting branches are closed, and the switch valves on the corresponding main line are opened, and the water flows through the main line.

[0029] The magnetic levitation centrifugal heat pump of this invention has a low heat output of approximately 3MW per unit. By connecting multiple units in series or in parallel, a single unit can generate a high-power output of up to 100MW. The inlet and outlet temperature difference on the evaporator side of the magnetic levitation centrifugal heat pump is reduced, for example, ΔT is reduced from 5°C to 1.5°C. This improves energy utilization in the circulating water and enhances the magnetic levitation centrifugal heat pump's efficiency in utilizing low-grade thermal energy. If a single magnetic levitation centrifugal heat pump becomes damaged, it can be directly routed through the main line. Alternatively, if municipal return water is low, the system can be routed through the main line without requiring multiple stages of magnetic levitation centrifugal heat pumps.

[0030] According to one embodiment of the present invention, the process hot water circulation in the hot end heating unit includes an 85°C process hot water return pipe, a first absorption heat pump, a second absorption heat pump and a 105°C process hot water supply pipe. The water output from the 85°C process hot water return pipe passes through the absorbers of the first absorption heat pump and the second absorption heat pump in sequence to be heated to 95°C, and then passes through the condensers of the first absorption heat pump and the second absorption heat pump in sequence to be heated to 105°C, and then enters the 105°C process hot water supply pipe.

[0031] The 85℃ process hot water is heated to 105℃ in two stages by an absorption heat pump, meeting the high temperature requirements of chemical reactions and replacing traditional electric heating or boilers, reducing energy consumption in the process section by 40%.

[0032] According to one embodiment of the present invention, the heating cycle in the hot end heating unit includes an 85°C heating return pipe, magnetic levitation centrifugal heat pump 1, magnetic levitation centrifugal heat pump 2, magnetic levitation centrifugal heat pump 3, magnetic levitation centrifugal heat pump 4 and a 90°C heating water supply pipe. The heated hot water output from the 85°C heating return pipe enters the condensers of magnetic levitation centrifugal heat pump 1, magnetic levitation centrifugal heat pump 2, magnetic levitation centrifugal heat pump 3, and magnetic levitation centrifugal heat pump 4 respectively to be heated to 90°C and then enters the 90°C heating water supply pipe.

[0033] The 85°C heating water is heated to 90°C through a parallel magnetic levitation centrifugal heat pump to maintain the antifreeze requirements of the pipeline. The energy consumption of the heating system is reduced by 30%, and the temperature control is more precise.

[0034] Beneficial effects of the present invention: (1) This system can effectively reduce load and frequency through the magnetic levitation centrifugal heat pump and control system; a guarantee plate is set up, and the guarantee plate is cut into when the return water is unstable, which can ensure low-temperature return water of 35℃, which can meet the return water requirements of the factory, ensure the circulation balance of the factory production water system, energy consumption stability and equipment safety, thereby ensuring normal production; a main line is set up to timely reduce part of the temperature increase; by supplying low-temperature return water to the economizer of the magnetic levitation centrifugal heat pump separately, it can solve the problem of surge shutdown caused by the difficulty of frequency conversion of low-temperature heat source when the municipal return water is unstable or the municipal return water is small in the existing technology; (2) The system is equipped with a five-stage waste heat cycle, covering waste heat at different temperature ranges. It can fully tap and utilize various waste heat resources generated in the chemical production process, avoid waste heat waste, and improve energy utilization. By utilizing waste heat at different temperatures step by step according to the temperature gradient, energy recovery and reuse can be achieved step by step. (3) The cooling circulation unit can exchange heat between the 32°C cooling water and the waste heat circulation unit to raise its temperature to 40°C. This not only effectively utilizes waste heat to increase the temperature of the cooling water, but also reduces the temperature difference of the cooling water and reduces the energy consumption of the cooling water system. After the cooling water is heated, it can be used in other process links that require 40°C hot water, thus realizing the recycling of cooling water, reducing the consumption and discharge of cooling water, and also reducing the operating cost of the cooling water treatment system. (4) The steam-condensate unit can flexibly allocate the destination of the 90°C condensate according to seasonal changes: in the heating season, the condensate is incorporated into the 59.4°C water supply pipe of the first-stage waste heat cycle to fully utilize its heat for heating; in the non-heating season, the condensate is incorporated into the 40°C return pipe of the first-stage waste heat cycle to avoid heat waste and ensure the stable operation of the system; the unit is also responsible for cooling and depressurizing the steam to ensure the rational use of steam in the system, prevent damage to the equipment due to excessive steam pressure or temperature, and improve the safety and reliability of the system: (5) Multiple different heat exchange processes are designed using the municipal heating cycle in the hot end heating unit, which can gradually heat the municipal return water from 30°C to 88.2°C according to different needs, meeting the hot water demand for municipal heating. By rationally configuring the heat exchange equipment and heat exchange process, an efficient and stable heating hot water supply is achieved, improving the heating experience of residents. The process hot water circulation system utilizes absorption heat pumps and magnetic levitation centrifugal heat pumps to gradually heat the 85°C process hot water return water to 105°C, meeting the high-temperature process hot water demand in chemical production. This design not only increases the temperature of the process hot water, but also reduces dependence on other energy sources, lowering production costs. The heating cycle uses a magnetic levitation centrifugal heat pump to raise the temperature of the heated return water from 85°C to 90°C, providing heating for pipelines and equipment, preventing the medium from condensing or freezing in low-temperature environments, and ensuring the smooth progress of the chemical production process; (6) The control unit can dynamically adjust the temperature and flow of each unit, and adjust the operating parameters of each device in real time according to the system's operating conditions and demand changes to ensure stable operation and efficient utilization of the system; temperature sensors, flow meters, regulating valves and other equipment are set in each waste heat circulation circuit to automatically control the opening of the regulating valve by detecting changes in temperature and flow to ensure the stability of return water temperature and flow; (7) All levels of waste heat circulation, municipal heating circulation and cooling circulation units adopt a multi-circuit design. When equipment on a certain circuit fails or needs maintenance, other circuits can continue to operate, ensuring the overall stability of the system and reducing system downtime caused by local failures. In some key links, such as the heat pump configuration of the second-stage waste heat circulation, multiple magnetic levitation centrifugal heat pumps or absorption heat pumps are set up and their workloads are reasonably distributed, thereby improving the redundancy and reliability of the equipment. Even if some equipment fails, other equipment can continue to work, ensuring the normal operation of the system. (8) By making full use of waste heat resources in the chemical production process, the dependence on purchased energy is reduced, and the energy procurement cost of the enterprise is reduced; the precise control and regulation function can make each equipment operate under the best working conditions, avoid excessive operation or inefficient operation of the equipment, thereby reducing the energy consumption and wear of the equipment, extending the service life of the equipment, and further reducing the operating cost and maintenance cost of the system; the recycling of cooling water reduces the amount of cooling water replenishment and discharge, reduces the operating cost of the cooling water treatment system, and also reduces the consumption of water resources, which meets the requirements of environmental protection; (9) Since the waste heat resources are fully utilized, the consumption of traditional energy such as fossil fuels is reduced, thereby reducing the emission of greenhouse gases such as carbon dioxide, which has positive significance for environmental protection; the system recycles the waste heat that may have been directly discharged into the environment, reducing the thermal pollution of waste heat to the environment and improving the cleanliness of energy utilization.

[0035] In summary, the chemical waste heat cascade utilization system achieves efficient utilization of waste heat resources, satisfaction of various heat demands, stable operation of the system, and reduction of energy consumption and operating costs by rationally configuring waste heat cycles, cooling cycles, steam-condensate units and heat-end heating units at various levels, and combining precise control and regulation functions. It has significant economic, environmental and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The present invention will be further described below with reference to the accompanying drawings and examples.

[0037] Figure 1 This is a process flow chart of the chemical waste heat cascade utilization system of the present invention.

[0038] Figure 2 This is a process flow chart of the first-stage waste heat cycle in the chemical waste heat cascade utilization system of the present invention.

[0039] Figure 3 This is a process flow chart of the second stage waste heat cycle in the chemical waste heat cascade utilization system of the present invention.

[0040] Figure 4 It is a process flow chart of the third stage waste heat cycle in the chemical waste heat cascade utilization system of the present invention.

[0041] Figure 5 This is a process flow chart of the fourth-stage waste heat cycle in the chemical waste heat cascade utilization system of the present invention.

[0042] Figure 6 This is a process flow chart of the fifth stage waste heat cycle in the chemical waste heat cascade utilization system of the present invention.

[0043] Figure 7 It is a process flow chart of the cooling circulation unit in the chemical waste heat cascade utilization system of the present invention.

[0044] Figure 8 It is a process flow chart of the steam-condensate unit in the chemical waste heat cascade utilization system of the present invention.

[0045] Figure 9 It is a process flow chart of the municipal heating cycle in the chemical waste heat cascade utilization system of the present invention.

[0046] Figure 10 It is a process flow chart of process hot water circulation in the chemical waste heat cascade utilization system of the present invention.

[0047] Figure 11 It is a process flow chart of the heat tracing cycle in the chemical waste heat cascade utilization system of the present invention.

[0048] Figure 12 It is a structural schematic diagram of a magnetic levitation centrifugal heat pump in the chemical waste heat cascade utilization system of the present invention.

[0049] Figure 13 It is a schematic diagram of the connection structure between the main pipeline and the magnetic levitation centrifugal heat pump in the chemical waste heat cascade utilization system of the present invention.

[0050] In the figure: 1. First stage waste heat cycle; 101, 59.4℃ water supply pipe; 102, 40℃ return pipe; 2. Second stage waste heat cycle; 201, 50℃ water supply pipe; 202, 35℃ return pipe; 3. Third stage waste heat cycle; 301, 50℃ water supply pipe 1; 302, 42℃ return pipe; 4. Fourth stage waste heat cycle; 401, 40℃ water supply pipe; 402, 32℃ return pipe; 5. Fifth stage waste heat cycle; 501, 80℃ water supply pipe; 502, 3 5℃ return pipe 1; 6. Cooling circulation unit; 601, 32℃ cooling water supply pipe; 602, 40℃ cooling water return pipe; 7. Steam-condensate unit; 71, steam inlet pipe; 72, 90℃ condensate pipe; 81, municipal heating circulation; 811, 30℃ municipal return pipe; 812, 88.2℃ municipal supply pipe; 813, subcooling circulation unit; 82, process hot water circulation; 821, 85℃ process hot water return pipe; 822, 105℃ process hot water supply pipe; 83, heating cycle; 831, 85℃ heating return pipe; 832, 90℃ heating supply pipe; 9, control unit; 10, fourth plate heat exchanger; 11, second plate heat exchanger; 12, third plate heat exchanger; 13, first magnetic levitation centrifugal heat pump; 14, second magnetic levitation centrifugal heat pump; 15, first magnetic levitation centrifugal heat pump; 16, second magnetic levitation centrifugal heat pump; 17, first plate heat exchanger; 18, first absorption heat pump; 19, second absorption Retractable heat pump; 20. Magnetic levitation centrifugal heat pump 1; 21. Magnetic levitation centrifugal heat pump 2; 22. Magnetic levitation centrifugal heat pump 3; 23. Magnetic levitation centrifugal heat pump 4; 24. Circulating pump; 25. Temperature and pressure reduction device; 261. Circulating water main; 262. Heating water main; 271. Connecting branch pipe; 272. Bypass pipe; 28. On-off valve; 100. Evaporator; 200. Condenser; 300. Economizer; 400. First-stage compressor; 500. Second-stage compressor. DETAILED DESCRIPTION

[0051] The present invention will now be described in further detail with reference to the accompanying drawings, which are simplified schematic diagrams that illustrate the basic structure of the present invention in a schematic manner.

[0052] like Figures 1 to 11As shown, a chemical waste heat cascade utilization system includes a waste heat circulation unit, a cooling circulation unit 6, a steam-condensate unit 7, a hot end temperature rising unit and a control unit 9, wherein the waste heat circulation unit is used to process multi-stage waste heat, and the multi-stage waste heat includes a first-stage waste heat circulation 1 of 59.4 / 40℃, a second-stage waste heat circulation 2 of 50 / 35℃, a third-stage waste heat circulation 3 of 50 / 42℃, a fourth-stage waste heat circulation 4 of 40 / 32℃ and a fifth-stage waste heat circulation 5 of 80 / 35℃; the cooling circulation unit 6 is used to heat the 32℃ cooling water with the waste heat circulation unit to 40℃; the steam-condensate unit 7 is used for cooling and depressurizing steam and seasonal distribution of 90℃ condensate; the hot end temperature rising unit is used for municipal heating, process hot water and heating; the control unit 9 is used for dynamic adjustment of the temperature and flow of each unit. Figure 1 This is an actual process flow chart. Box A in the figure includes the steam-condensate unit 7, the process hot water circuit 82 and heat tracing circuit 83 in the heat-using end heating unit, and the fifth-stage waste heat circuit 5. Box B in the figure also contains the municipal heating circuit 81, the first-stage waste heat circuit 1, the second-stage waste heat circuit 2, the third-stage waste heat circuit 3, the fourth-stage waste heat circuit 4 of the waste heat circuit unit, and the cooling circuit unit 6. The control unit 9 is capable of independent automatic control and primarily houses equipment such as a programmable control cabinet, a communications network cabinet, an instrument, valve, and power supply cabinet, and a cabinet-type engineering station. Operators at the engineering station control the system's start / stop, monitor and adjust normal operation, and handle abnormal and accident conditions. At least 15% of the analog and digital I / O points are reserved. A visual monitoring platform is installed in the centralized control center. All data is exchanged with the control center's visual monitoring platform via a communications network, establishing an automated control system that serves the energy supply system and features automated group control, energy efficiency accounting, and energy management.

[0053] In order to further clarify the specific structure of each unit or cycle, Figure 1 Disassemble by unit or cycle as follows: like Figure 2 As shown, the first-stage waste heat cycle 1 includes a 59.4°C water supply pipe 101, a fourth plate heat exchanger 10, and a 40°C return pipe 102. The water output from the 59.4°C water supply pipe 101 is heated to 40°C by the fourth plate heat exchanger 10 before entering the 40°C return pipe 102, where it circulates repeatedly. The first-stage waste heat cycle 1 also combines with 90°C condensate on a seasonal basis. Plate heat exchangers offer a compact structure and a large heat transfer area per unit, saving material compared to shell-and-tube heat exchangers. Of course, bellows heat exchangers can also be used, improving heat exchanger efficiency. The use of high-efficiency heat exchangers reduces the amount of cooling water required for production cooling. The first-stage waste heat cycle 1 recovers condensate waste heat and is coupled to the steam system. The compact design of the plate heat exchanger saves 20% of space. Seasonal consolidation of 90°C condensate avoids energy waste.

[0054] like Figure 3 As shown, the second-stage waste heat cycle 2 is divided into five routes (it can also be divided into more or fewer routes as needed), each of which includes a 50°C water supply pipe 201, a second plate heat exchanger 11, a third plate heat exchanger 12, a first magnetic levitation centrifugal heat pump 13, a second magnetic levitation centrifugal heat pump 14 and a 35°C return water pipe 202. The water output from the 50°C water supply pipe 201 is heat exchanged to 42°C by the third plate heat exchanger 12, and then enters the evaporator 100 of the first magnetic levitation centrifugal heat pump 13 and the second magnetic levitation centrifugal heat pump 14 respectively to be cooled to 35°C. After that, it enters the second plate heat exchanger 11 for insulation and then enters the 35°C return water pipe 202, and the cycle repeats. The first and second magnetic levitation centrifugal heat pumps 13 and 14 utilize magnetic levitation centrifugal heat pumps. These utilize advanced magnetic levitation technology, significantly reducing mechanical friction losses and improving unit efficiency. This not only saves electricity and lowers operating costs, but also helps reduce energy consumption and carbon emissions. The second-stage waste heat cycle 2 utilizes five parallel magnetic levitation heat pumps for deep cooling, reducing power consumption per circuit by 40% and maintaining a stable return water temperature of 35°C (±0.5°C).

[0055] like Figure 4 As shown, the third-stage waste heat cycle 3 is divided into five routes, each of which includes a 50°C water supply pipe 301, a first-stage magnetic levitation centrifugal heat pump 15, a second-stage magnetic levitation centrifugal heat pump 16, and a 42°C return pipe 302. The 48°C water output from the 50°C water supply pipe 301 is cooled to 44.3°C by the evaporator 100 of the first-stage magnetic levitation centrifugal heat pump 15. It then cools to 40°C by the evaporator 100 of the second-stage magnetic levitation centrifugal heat pump 16 before entering the 42°C return pipe 302, repeating this cycle. Both the first-stage magnetic levitation centrifugal heat pump 15 and the second-stage magnetic levitation centrifugal heat pump 16 are also magnetic levitation centrifugal heat pumps. Multiple units of each can be installed as needed, preferably 3 to 4. The third-stage waste heat cycle 3 uses two-stage magnetic levitation heat pumps in series to precisely control the final temperature to 40°C, meeting process requirements.

[0056] like Figure 5 As shown, the fourth-stage waste heat cycle 4 is divided into five paths. Each path includes a 40°C water supply pipe 401, a first plate heat exchanger 17, and a 32°C water return pipe 402. The water output from the 40°C water supply pipe 401 is heated to 32°C by the first plate heat exchanger 17 before entering the 32°C water return pipe 402, where it continues this cycle. The fourth-stage waste heat cycle 4 utilizes direct plate heat exchange to recover low-temperature waste heat, simplifying the process and reducing maintenance costs by 30%.

[0057] like Figure 6As shown, the fifth-stage waste heat cycle 5 includes an 80°C water supply pipe 501, a first absorption heat pump 18, a second absorption heat pump 19, a magnetic levitation centrifugal heat pump 1 20, a magnetic levitation centrifugal heat pump 2 21, a magnetic levitation centrifugal heat pump 3 22, a magnetic levitation centrifugal heat pump 4 23, and a 35°C return water pipe 1 502. The water output from the 80°C water supply pipe 501 is cooled to 69°C by the evaporator 100 of the first absorption heat pump 18, and then cooled to 58°C by the evaporator 100 of the second absorption heat pump 19. Then, the water is cooled to 42°C by the evaporators 100 of the magnetic levitation centrifugal heat pump 1 20, the magnetic levitation centrifugal heat pump 2 21, the magnetic levitation centrifugal heat pump 3 22, and the magnetic levitation centrifugal heat pump 4 23 in sequence before entering the 35°C return water pipe 1 502. The water is cooled by 4°C each time it passes through a magnetic levitation centrifugal heat pump. Among them, the first absorption heat pump 18 and the second absorption heat pump 19 use a superconducting thermal core heat pump, a circulation system that utilizes a low-grade heat source to pump heat from a low-temperature heat source to a high-temperature heat source. It is an effective device for recycling low-temperature thermal energy, and has the dual functions of saving energy and protecting the environment. The superconducting thermal core heat pump uses a corrugated plate heat exchanger as disclosed in CN117588900A. By changing the cross-sectional area of ​​the flow channel, the fluid dynamic pressure head continuously changes, producing regular expansion and compression during the flow process, increasing the fluid Reynolds number, and achieving efficient heat exchange. The fifth-stage waste heat cycle 5 uses a superconducting thermal core heat pump and a magnetic levitation centrifugal heat pump for four-stage cooling, achieving a utilization rate of 90% of high-temperature waste heat (80°C), solving a problem that is difficult to handle with traditional technologies.

[0058] A circulating pump 24 is installed in each circuit of the second-stage waste heat cycle 2 and the third-stage waste heat cycle 3. Each circuit of the second-stage waste heat cycle 2 is equipped with three temperature sensors and two regulating valves (not shown in the figure, but conventional commercially available products). The circulating pump 24 in each circuit of the second-stage waste heat cycle 2 controls the opening of the two regulating valves by detecting the temperature of the three temperature sensors on that circuit, specifically taking the middle value of the two temperature values ​​to ensure that the return water temperature remains stable at 35°C. A flow meter and a regulating valve are installed in each circuit of the third-stage waste heat cycle 3. The circulating pump 24 in each circuit of the third-stage waste heat cycle 3 controls the opening of the regulating valve by detecting the flow rate of the flow meter on that circuit to ensure that the flow rate of all five circuits meets the demand. A flow meter and a regulating valve are installed in each circuit of the second-stage waste heat cycle 2. The circulating pump 24 in each circuit of the second-stage waste heat cycle 2 controls the opening of the regulating valve by detecting the flow rate of the flow meter on that circuit to ensure that the flow rate of all five circuits meets the demand. Circulation pump 24 utilizes a horizontal, single-stage, double-suction (single-suction) centrifugal pump. Liquid enters the center of the impeller simultaneously. The high-speed rotation of the impeller expel the liquid under centrifugal force, creating a low-pressure zone at the center. Under atmospheric pressure, the inlet liquid continuously flows toward this low-pressure zone, creating a cycle of entering and then being expelled from the impeller. This horizontal, single-stage, double-suction (single-suction) centrifugal pump boasts a compact structure, aesthetically pleasing appearance, excellent stability, and easy installation. It operates smoothly, and the optimized double-suction impeller minimizes axial force. The impeller has a blade profile with excellent hydraulic performance, and the inner surface of the pump casing and impeller are resistant to cavitation. Multi-sensor feedback and valve control enable adaptive system regulation, resulting in a failure rate of <0.1%.

[0059] like Figure 7 As shown, cooling circulation unit 6 is divided into five circuits. Each circuit includes a 32°C cooling water supply pipe 601, a second plate heat exchanger 11, and a 40°C cooling water return pipe 602. Cooling water from 32°C cooling water supply pipe 601 is heated to 40°C by second plate heat exchanger 11 before entering 40°C cooling water return pipe 602, where it circulates repeatedly. The 32°C cooling water is heated to 40°C by waste heat exchange, reducing the load on the cooling tower and saving approximately 100,000 tons of water annually.

[0060] like Figure 8As shown, the steam-condensate unit 7 comprises a steam inlet pipe 71, a first absorption heat pump 18, a second absorption heat pump 19, and a 90°C condensate pipe 72. Steam (250°C, 1.5 MPa) output from the steam inlet pipe 71 is converted to 173°C, 0.85 MPa steam after passing through the desuperheating and pressure reduction device 25. This steam then enters the generators of the first and second absorption heat pumps 18, 19, where it is cooled to 90°C condensate. The 90°C condensate in the 90°C condensate pipe 72 is fed into the 59.4°C supply pipe 101 of the first-stage waste heat cycle 1 during the heating season and into the 40°C return pipe 102 of the first-stage waste heat cycle 1 during the non-heating season. It should be noted that the condensate must be tested for compliance before being fed into the heat pumps. Only qualified condensate is fed into the heat pumps. The steam drives the heat pumps to generate 90°C condensate, which is distributed seasonally. This improves steam energy utilization by 25% and ensures a condensate quality rate exceeding 95%.

[0061] like Figure 9 As shown, the municipal heating cycle 81 in the hot end heating unit is divided into five routes, one of which includes a 30°C municipal return water pipe 811, a first plate heat exchanger 17, a fourth plate heat exchanger 10, a third plate heat exchanger 12, a first magnetic levitation centrifugal heat pump 13, a second magnetic levitation centrifugal heat pump 14, a second magnetic levitation centrifugal heat pump 16, a first magnetic levitation centrifugal heat pump 15 and an 88.2°C municipal water supply pipe 812. The route is further divided into two branches. The first branch: the water output from the 30°C municipal return water pipe 811 is heat-exchanged to 38°C through the first plate heat exchanger 17 and the water output from the 40°C water supply pipe 401 in the fourth stage waste heat cycle 4, and then heat-exchanged to 57.4°C through the fourth plate heat exchanger 10 and the water output from the 59.4°C water supply pipe 101 in the first stage waste heat cycle 1; the second branch: the water output from the 30°C municipal return water pipe 811 is heat-exchanged to 57.4°C through the third plate heat exchanger 17. The heat exchanger 12 exchanges heat with the water output from the 50℃ water supply pipe 201 in the second-stage waste heat cycle 2 to 47℃, then enters the condenser 200 of the first magnetic levitation centrifugal heat pump 13 to increase its temperature to 53.9℃, then enters the condenser 200 of the second magnetic levitation centrifugal heat pump 14 to increase its temperature to 60.5℃, mixes with the 57.4℃ heating water in the first branch to 59℃, and then enters the condenser 200 of the first-stage magnetic levitation centrifugal heat pump 15 in turn to increase its temperature to 86.4℃, and enters the 88.2℃ municipal water supply pipe 812; among them, the second-stage magnetic levitation centrifugal heat pump 16 has three units, and the condensers 200 passing through the three units are respectively heated to 63.9℃, 68.7℃ and 74.9℃, and the first-stage magnetic levitation centrifugal heat pump 15 has two units, and the condensers 200 passing through the two units are respectively heated to 80.8℃ and 86.4℃.

[0062] Both the first branch and the second branch include a subcooling circulation unit 813. The hot water in the subcooling circulation unit 813 is input in parallel into the economizer 300 in the subsequent magnetic levitation centrifugal heat pump. The hot water in the subcooling circulation unit 813 is different from the heating water and is connected in series into the condenser 200 of the magnetic levitation centrifugal heat pump, which can reduce the use of municipal return water and ensure the stable operation of the system when the municipal return water volume is small, thereby avoiding the shutdown of the magnetic levitation centrifugal heat pump due to insufficient municipal return water.

[0063] Furthermore, the hot water in the supercooling circulation unit 813 comes from the 29-31°C municipal return water. The 29-31°C municipal return water is directly used. By lowering the temperature of the hot water, the heat transfer temperature difference between it and the liquid working medium of the magnetic levitation centrifugal heat pump increases, and the amount of heat that can be removed per unit time increases. In other words, in order to achieve the required supercooling of the working medium, the required amount of hot water can be reduced accordingly, and the flow rate is also reduced. While ensuring that the supercooling of the working medium meets the standard, energy saving and improvement of system operating efficiency can be achieved. It can also solve the problem of ensuring stable operation of the system when the amount of municipal return water is small, further reduce the amount of municipal return water, and avoid the shutdown of the magnetic levitation centrifugal heat pump due to insufficient municipal return water.

[0064] The remaining four routes include the 30°C municipal return water pipe 811, the first plate heat exchanger 17, the third plate heat exchanger 12, the first magnetic levitation centrifugal heat pump 13, the second magnetic levitation centrifugal heat pump 14, the second magnetic levitation centrifugal heat pump 16, the first magnetic levitation centrifugal heat pump 15 and the 88.2°C municipal water supply pipe 812. The water output from the 30°C municipal return water pipe 811 is heat exchanged with the water output from the 40°C water supply pipe 401 in the fourth-stage waste heat cycle 4 to 36.8°C through the first plate heat exchanger 17, and then heat exchanged with the water output from the 50°C water supply pipe 201 in the second-stage waste heat cycle 2 to 45.5°C through the third plate heat exchanger 12. The water then enters the condenser 200 of the first magnetic levitation centrifugal heat pump 13, the second magnetic levitation centrifugal heat pump 14, the second magnetic levitation centrifugal heat pump 16 and the first magnetic levitation centrifugal heat pump 15 in sequence to be heated to 88.7°C and enters the 88.2°C municipal water supply pipe 812. The municipal heating cycle adopts 81 dual-branch design, and the plate heat exchanger and magnetic levitation centrifugal heat pump mix water, which optimizes the heating path, reduces power consumption, and improves the output water temperature compliance rate.

[0065] like Figure 10As shown, the process hot water circuit 82 in the hot-end heating unit includes an 85°C process hot water return pipe 821, a first absorption heat pump 18, a second absorption heat pump 19, and a 105°C process hot water supply pipe 822. The water output from the 85°C process hot water return pipe 821 passes through the absorbers of the first and second absorption heat pumps 18 and 19, raising its temperature to 95°C. It then passes through the condensers 200 of the first and second absorption heat pumps 18 and 19, raising its temperature to 105°C, before entering the 105°C process hot water supply pipe 822, repeating this cycle. The process hot water circuit 82 uses absorption heat pumps for two-stage heating, replacing electrical heating, reducing carbon emissions from the process section by 50%.

[0066] like Figure 11 As shown, heating circuit 83 in the hot-end heating unit includes an 85°C heating return pipe 831, magnetic levitation centrifugal heat pumps 1 20, 21, 3, 22, and 4 23, and a 90°C heating water supply pipe 832. The heated water output from 85°C heating return pipe 831 enters condensers 200 of magnetic levitation centrifugal heat pumps 1 20, 21, 3, 22, and 4 23, where it is heated to 90°C before entering 90°C heating water supply pipe 832. Heating circuit 83 utilizes parallel magnetic levitation centrifugal heat pumps for heating, reducing antifreeze energy consumption by 30% and ensuring temperature fluctuations of less than 1°C.

[0067] The first magnetic levitation centrifugal heat pump 13, the second magnetic levitation centrifugal heat pump 14, the first magnetic levitation centrifugal heat pump 15 and the second magnetic levitation centrifugal heat pump 16 all adopt magnetic levitation centrifugal heat pumps. Figure 12 The magnetic levitation centrifugal heat pump includes an evaporator 100, a condenser 200 and an economizer 300. The water output from the 30°C municipal return pipe 811 in the second branch is supplied to the economizer 300 of each magnetic levitation centrifugal heat pump. The economizer 300 of each magnetic levitation centrifugal heat pump in the remaining several routes of the hot end heating unit receives 45.5°C water after heat exchange through the third plate heat exchanger 12, and the condenser 200 of the subsequent magnetic levitation centrifugal heat pump receives the mixed water after heat exchange between the condenser 200 and economizer 300 of the previous magnetic levitation centrifugal heat pump.

[0068] The liquid working medium enters the evaporator 100 from the inlet for heat exchange inside the evaporator 100, and then becomes a gaseous working medium and flows out from the outlet of the evaporator 100; the gaseous working medium first flows upward and passes through the first-stage compressor 400 and the second-stage compressor 500 for compression, and then flows downward into the condenser 200, and heats the heating water flowing into the condenser 200; after the heating water enters the condenser 200, the gaseous working medium exchanges heat with it, and after the gaseous working medium is cooled and becomes liquid, it enters the economizer 300, and the heated heating water flows out for heating. Since the temperature of the liquid working medium entering the economizer 300 is still relatively high, in order to avoid heat waste, some low-temperature heating water inside the condenser 200 will enter the economizer 300. The low-temperature heating water entering the economizer 300 performs heat exchange on the liquid working medium flowing through the economizer 300, and the liquid working medium is further cooled. This part of the low-temperature heating water is heated and then heated up, and the liquid working medium is cooled a second time in the economizer 300. At the same time, the low-temperature heating water can be heated, avoiding wasting the heat of the liquid working medium and reused for heating.

[0069] like Figure 13 The input and output ends of the condensers 200 of the adjacent series-connected magnetic levitation centrifugal heat pumps are connected via a connecting branch pipe 271. The condensers 200 also include a heating water main pipe 262. The main pipe of the condenser 200 is connected to the heating water main pipe 262. The connecting branch pipe 271 is connected to the heating water main pipe 262 via a bypass pipe 272. The connecting branch pipe 271 is provided with an on-off valve 28. The heating water main pipe 262 is also provided with an on-off valve 28. Similarly, the input and output ends of the evaporators 100 of the adjacent series-connected magnetic levitation centrifugal heat pumps are also connected via a connecting branch pipe 271. The evaporators 100 also include a circulating water main pipe 261. The main pipe of the evaporator 100 is connected to the circulating water main pipe 261. The connecting branch pipe 271 is connected to the circulating water main pipe 261 via a bypass pipe 272. The connecting branch pipe 271 is provided with an on-off valve 28. The circulating water main pipe 261 is also provided with an on-off valve 28. When any magnetic levitation centrifugal heat pump fails or the circulating water condition does not meet the requirements or the municipal return water occurs (the heating water flow is too small), the switch valve 28 on its connecting branch pipe 271 is automatically closed, and the switch valve 28 on the corresponding heating water main pipe 262 / circulating water main pipe 261 is automatically opened, and the water flows through the main pipe to enter the next magnetic levitation centrifugal heat pump; or when the municipal return water is insufficient, the switch valves 28 on several magnetic levitation centrifugal connecting branch pipes 271 are closed, and the switch valves 28 on the corresponding main pipe are opened, and the water flows through the heating water main pipe 262 / circulating water main pipe 261.

[0070] The present invention provides a magnetic levitation centrifugal heat pump that can achieve step-by-step heating and temperature increase through the arrangement of the heating water main 262, the connecting branch pipe 271, the bypass pipe 272, and the circulating water main 261. Industrial waste heat is absorbed and reused step by step by the magnetic levitation centrifugal heat pump. The complete set of magnetic levitation centrifugal heat pumps can achieve linear single-set high-power and high-quality hot water output through a complete set of flow control. The system can operate under variable working conditions, improve stability and efficiency, reduce the pipe corridor of the waste heat pipe network, save the main pipe, operate simply, and achieve unmanned operation through unified centralized control. The entire system is a single-machine complete set of equipment that can increase the water temperature from 40°C to 95°C. The system operates on a single pipe, and units can be added or reduced one by one. As the municipal return water flow changes, by adjusting the switch of the switch valve 28 on the connecting branch pipe 271 and the bypass pipe 272, the problem of excessively high outlet temperature of the heating water caused by small flow can be solved. At the same time, the vicious cycle of poor condensation effect, insufficient working fluid circulation and worse heat exchange caused by small flow can be avoided, thereby ensuring the stable energy efficiency of the heat pump and the heat exchange efficiency of the system under different working conditions.

[0071] During the transportation of hot water in long-distance pipelines, the temperature will decay due to the long distance. In order to ensure the heat exchange efficiency and cost on the primary side of the heat exchange station, the supply water temperature will be increased while the supply and return water temperature difference will be widened, thereby reducing the flow rate, thereby reducing the energy consumption of the water pump and the pipeline investment cost.

[0072] The number of circuits for the second-stage waste heat circulation 2, the third-stage waste heat circulation 3, the fourth-stage waste heat circulation 4, the cooling circulation unit 6, and the heat-using end heating unit is the same. In this embodiment, they are divided into five circuits. In other embodiments, the number of circuits for the second-stage waste heat circulation 2, the third-stage waste heat circulation 3, the fourth-stage waste heat circulation 4, the cooling circulation unit 6, and the heat-using end heating unit can be flexibly adjusted based on the amount of waste hot water and heating water (i.e., municipal return water). When the amount of waste hot water and heating water is large, the number of parallel circuits can be increased to adapt to the load demand. When the amount of waste hot water and heating water is small, the number of parallel circuits can be reduced to adapt to the load demand. This embodiment improves the flow matching capability and the system heating capacity by designing multiple circuits, such as five circuits, in parallel.

[0073] The chemical waste heat cascade utilization system of this embodiment adopts multi-stage waste heat recovery, covering a wide temperature range of 59.4℃ to 80℃. It realizes energy cascade utilization through graded plate exchange and magnetic levitation centrifugal heat pump, with a comprehensive recovery rate of >85%; the steam condensate switches the path according to the season, and is incorporated into the 59.4℃ pipeline in the heating season and the 40℃ pipeline in the non-heating season, which increases the energy saving rate by 15% throughout the year; through the temperature sensor taking the median of three values ​​and the flow meter interlocking the regulating valve, accurate temperature control of ±0.5℃ and balanced flow distribution are achieved. The five-way parallel structure is easy to expand and adapt to chemical parks of different sizes; the synergistic effect of the magnetic levitation centrifugal heat pump and the superconducting thermal core heat pump maximizes energy efficiency. Through temperature matching, cascade utilization, and intelligent regulation, a breakthrough has been achieved from inefficient discharge to high-value reuse of chemical waste heat, which is a benchmark technology in the field of industrial energy conservation.

[0074] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A chemical waste heat cascade utilization system, characterized in that: include: A waste heat circulation unit for processing multi-stage waste heat, wherein the multi-stage waste heat includes a first-stage waste heat circulation (1) at 59.4 / 40°C, a second-stage waste heat circulation (2) at 50 / 35°C, a third-stage waste heat circulation (3) at 50 / 42°C, a fourth-stage waste heat circulation (4) at 40 / 32°C, and a fifth-stage waste heat circulation (5) at 80 / 35°C; The cooling circulation unit (6) is used to heat the cooling water at 32°C with the waste heat circulation unit to raise the temperature to 40°C; Steam-condensate unit (7), used for cooling and depressurizing steam and seasonal distribution of 90°C condensate; Hot end heating unit is used for heating municipal heating, process hot water and tracing heating; The control unit (9) is used for dynamically adjusting the temperature and flow of each unit.

2. The chemical waste heat cascade utilization system according to claim 1, characterized in that: The first-stage waste heat cycle (1) includes a 59.4°C water supply pipe (101), a fourth plate heat exchanger (10) and a 40°C water return pipe (102). The water output from the 59.4°C water supply pipe (101) is heated to 40°C by the fourth plate heat exchanger (10) and then enters the 40°C water return pipe (102) and is combined with the 90°C condensate according to seasonal switching. The second-stage waste heat cycle (2) is divided into multiple paths, each path including a 50°C water supply pipe (201), a second plate heat exchanger (11), a third plate heat exchanger (12), a first magnetic levitation centrifugal heat pump (13), a second magnetic levitation centrifugal heat pump (14) and a 35°C return water pipe (202). The water output from the 50°C water supply pipe (201) is heated to 42°C by the third plate heat exchanger (12), enters the evaporator (100) of the first magnetic levitation centrifugal heat pump (13) and the second magnetic levitation centrifugal heat pump (14), is cooled to 35°C, enters the second plate heat exchanger (11), is kept warm, and then enters the 35°C return water pipe (202). The third-stage waste heat cycle (3) is divided into multiple paths, each path including a 50°C water supply pipe (301), a first-stage magnetic levitation centrifugal heat pump (15), a second-stage magnetic levitation centrifugal heat pump (16) and a 42°C water return pipe (302). The 48°C water output from the 50°C water supply pipe (301) is cooled to 44.3°C by the evaporator (100) of the first-stage magnetic levitation centrifugal heat pump (15), and then cooled to 40°C by the evaporator (100) of the second-stage magnetic levitation centrifugal heat pump (16) before entering the 42°C water return pipe (302). The fourth stage waste heat cycle (4) is divided into multiple paths, each path including a 40°C water supply pipe (401), a first plate heat exchanger (17) and a 32°C water return pipe (402). The water output from the 40°C water supply pipe (401) is heated to 32°C by the first plate heat exchanger (17) and then enters the 32°C water return pipe (402). The fifth stage waste heat cycle (5) includes an 80°C water supply pipe (501), a first absorption heat pump (18), a second absorption heat pump (19), a magnetic levitation centrifugal heat pump 1 (20), a magnetic levitation centrifugal heat pump 2 (21), a magnetic levitation centrifugal heat pump 3 (22), a magnetic levitation centrifugal heat pump 4 (23) and a 35°C return water pipe 1 (502). The water output from the 80°C water supply pipe (501) passes through the evaporator ( 100) is cooled to 69°C, and then cooled to 58°C by the evaporator (100) of the second absorption heat pump (19), and then cooled to 42°C by the evaporators (100) of the magnetic levitation centrifugal heat pump 1 (20), magnetic levitation centrifugal heat pump 2 (21), magnetic levitation centrifugal heat pump 3 (22), and magnetic levitation centrifugal heat pump 4 (23) in sequence, and then enters the 35°C return pipe 1 (502), and the temperature is reduced by 4°C each time it passes through a magnetic levitation centrifugal heat pump.

3. The chemical waste heat cascade utilization system according to claim 2, characterized in that: Each of the second-stage waste heat cycle (2) and the third-stage waste heat cycle (3) is provided with a circulation pump (24).

4. The chemical waste heat cascade utilization system according to claim 3, characterized in that: Each path of the second-stage waste heat cycle (2) is provided with three temperature sensors and two regulating valves. The circulation pump (24) of each path of the second-stage waste heat cycle (2) controls the opening of the two regulating valves by detecting the temperature of the three temperature sensors on the path, so as to ensure that the return water temperature is stabilized at 35°C.

5. The chemical waste heat cascade utilization system according to claim 3, characterized in that: Each path of the third-stage waste heat cycle (3) is provided with a flow meter and a regulating valve. The circulation pump (24) of each path on the third-stage waste heat cycle (3) controls the opening of the regulating valve by detecting the flow rate of the flow meter on the path, so as to ensure that the flow rates of the five paths meet the demand; A flow meter and a regulating valve are provided on each route of the second-stage waste heat cycle (2). The circulation pump (24) on each route of the second-stage waste heat cycle (2) controls the opening of the regulating valve by detecting the flow rate of the flow meter on the route, so as to ensure that the flow rates of the five routes meet the demand.

6. The chemical waste heat cascade utilization system according to claim 2, characterized in that: The cooling circulation unit (6) is divided into multiple paths, each path including a 32°C cooling water supply pipe (601), a second plate heat exchanger (11) and a 40°C cooling water return pipe (602). The cooling water output from the 32°C cooling water supply pipe (601) is heat-exchanged to 40°C by the second plate heat exchanger (11) and then enters the 40°C cooling water return pipe (602).

7. The chemical waste heat cascade utilization system according to claim 6, characterized in that: When it is detected that the municipal return water temperature is lower than 35°C or the flow rate is lower than the set threshold, the second plate heat exchanger (11) automatically operates to stably maintain the temperature on the heat source side above 35°C through the second plate heat exchanger (11).

8. The chemical waste heat cascade utilization system according to claim 1, characterized in that: The steam-condensate unit (7) comprises a steam inlet pipe (71), a first absorption heat pump (18), a second absorption heat pump (19) and a 90°C condensate pipe (72). The steam output from the steam inlet pipe (71) passes through a temperature reduction and pressure reduction device (25) and enters the generators of the first absorption heat pump (18) and the second absorption heat pump (19) to be cooled to 90°C condensate. The 90°C condensate in the 90°C condensate pipe (72) is incorporated into the 59.4°C water supply pipe (101) of the first stage waste heat cycle (1) during the heating season and is incorporated into the 40°C return water pipe (102) of the first stage waste heat cycle (1) during the non-heating season.

9. The chemical waste heat cascade utilization system according to claim 1, characterized in that: The municipal heating cycle (81) in the heat-using end heating unit is divided into multiple paths, one of which includes a 30°C municipal return water pipe (811), a first plate heat exchanger (17), a fourth plate heat exchanger (10), a third plate heat exchanger (12), a first magnetic levitation centrifugal heat pump (13), a second magnetic levitation centrifugal heat pump (14), a second magnetic levitation centrifugal heat pump (16), a first magnetic levitation centrifugal heat pump (15) and an 88.2°C municipal water supply pipe (812). The path is further divided into two branches. The first branch: the water output from the 30°C municipal return water pipe (811) is heat-exchanged to 38°C through the first plate heat exchanger (17) and the water output from the 40°C water supply pipe (401) in the fourth stage waste heat cycle (4), and then passes through the fourth plate heat exchanger (10 ) is heat exchanged with the water output from the 59.4℃ water supply pipe (101) in the first-stage waste heat cycle (1) to 57.4℃; the second branch: the water output from the 30℃ municipal return water pipe (811) is heat exchanged with the water output from the 50℃ water supply pipe (201) in the second-stage waste heat cycle (2) to 47℃ through the third plate heat exchanger (12), and then enters the condenser (200) of the first magnetic levitation centrifugal heat pump (13) and the second magnetic levitation centrifugal heat pump (14) in sequence to increase the temperature to 60.5℃, and is mixed with the 57.4℃ heating water in the first branch to 59℃, and then enters the condenser (200) of the second magnetic levitation centrifugal heat pump (16) and the first magnetic levitation centrifugal heat pump (15) in sequence to increase the temperature to 86.4℃, and enters the 88.2℃ municipal water supply pipe (812); The remaining several routes include a 30°C municipal return water pipe (811), a first plate heat exchanger (17), a third plate heat exchanger (12), a first magnetic levitation centrifugal heat pump (13), a second magnetic levitation centrifugal heat pump (14), a second magnetic levitation centrifugal heat pump (16), a first magnetic levitation centrifugal heat pump (15) and an 88.2°C municipal water supply pipe (812). The water output from the 30°C municipal return water pipe (811) passes through the first plate heat exchanger (17) and the 40°C water supply pipe ( The water output from the second stage waste heat cycle (2) is heated to 36.8°C by heat exchange, and then passes through the third plate heat exchanger (12) and the water output from the 50°C water supply pipe (201) in the second stage waste heat cycle (2) to 45.5°C, and then enters the condenser (200) of the first magnetic levitation centrifugal heat pump (13), the second magnetic levitation centrifugal heat pump (14), the second stage magnetic levitation centrifugal heat pump (16) and the first stage magnetic levitation centrifugal heat pump (15) in sequence to be heated to 88.7°C, and then enters the 88.2°C municipal water supply pipe (812).

10. The chemical waste heat cascade utilization system according to claim 9, characterized in that: The first magnetic levitation centrifugal heat pump (13), the second magnetic levitation centrifugal heat pump (14), the first-stage magnetic levitation centrifugal heat pump (15) and the second-stage magnetic levitation centrifugal heat pump (16) all adopt magnetic levitation centrifugal heat pumps, and the magnetic levitation centrifugal heat pumps include an evaporator (100), a condenser (200) and an economizer (300). The water output from the 30°C municipal return water pipe (811) in the second branch is supplied to the economizer (300) of each magnetic levitation centrifugal heat pump, and the economizer (300) of each magnetic levitation centrifugal heat pump in the remaining several branches of the hot end heating unit receives 45.5°C water after heat exchange through the third plate heat exchanger (12), and the condenser (200) of the next magnetic levitation centrifugal heat pump receives the mixed water after heat exchange through the condenser (200) and economizer (300) of the previous magnetic levitation centrifugal heat pump.

11. The chemical waste heat cascade utilization system according to claim 1, characterized in that: The process hot water circulation (82) in the heat-end heating unit includes an 85°C process hot water return pipe (821), a first absorption heat pump (18), a second absorption heat pump (19) and a 105°C process hot water supply pipe (822). The water output from the 85°C process hot water return pipe (821) is heated to 95°C by passing through the absorbers of the first absorption heat pump (18) and the second absorption heat pump (19) in sequence, and then is heated to 105°C by passing through the condensers (200) of the first absorption heat pump (18) and the second absorption heat pump (19) in sequence, and then enters the 105°C process hot water supply pipe (822).

12. The chemical waste heat cascade utilization system according to claim 1, characterized in that: The heating cycle (83) in the heat-using end heating unit includes an 85°C heating return pipe (831), a magnetic levitation centrifugal heat pump 1 (20), a magnetic levitation centrifugal heat pump 2 (21), a magnetic levitation centrifugal heat pump 3 (22), a magnetic levitation centrifugal heat pump 4 (23) and a 90°C heating water supply pipe (832). The heating hot water output from the 85°C heating return pipe (831) enters the condensers of the magnetic levitation centrifugal heat pump 1 (20), the magnetic levitation centrifugal heat pump 2 (21), the magnetic levitation centrifugal heat pump 3 (22) and the magnetic levitation centrifugal heat pump 4 (23) respectively to be heated to 90°C and then enters the 90°C heating water supply pipe (832).

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