Chemical industry waste heat cascade utilization system

Abstract

The present application relates to the technical field of waste heat recovery, and particularly relates to a chemical waste heat cascade utilization system. The chemical waste heat cascade utilization system comprises: a waste heat circulation unit for processing multi-stage waste heat, the multi-stage waste heat comprising a first-stage waste heat circulation of 59.4 / 40 DEG C, a second-stage waste heat circulation of 50 / 35 DEG C, a third-stage waste heat circulation of 50 / 42 DEG C, a fourth-stage waste heat circulation of 40 / 32 DEG C and a fifth-stage waste heat circulation of 80 / 35 DEG C; a cooling circulation unit for heat exchange between cooling water of 32 DEG C and the waste heat circulation unit to increase the temperature to 40 DEG C; a steam-liquid condensate unit for temperature reduction and pressure reduction of steam and seasonal distribution of liquid condensate of 90 DEG C; a hot end temperature increasing unit for temperature increase of municipal heating, process hot water and heat tracing; and a control unit for dynamic adjustment of the temperature and flow of each unit. The chemical waste heat cascade utilization system realizes efficient utilization of waste heat resources, satisfaction of various heat demand, stable operation of the system and reduction of energy consumption and operation cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of waste heat recovery, and in particular to a chemical waste heat cascade utilization system. BACKGROUND

[0002] The conventional chemical waste heat recovery system relies on a single energy source, has high operation cost and large carbon emission, and has problems such as unreasonable heat exchange design, large heat loss, etc., resulting in that the waste heat is not fully extracted or the transmission efficiency is low, only high-temperature waste heat is recovered, and low-temperature waste heat is ignored, or there is a lack of cascade utilization means. The waste heat recovery system uses a conventional heat pump, which has large friction loss and low part load efficiency, resulting in a low operation energy efficiency ratio. In addition, the existing waste heat recovery system cannot effectively utilize low-grade heat sources.

[0003] In an industrial low-temperature waste heat recovery and utilization project, when the municipal return water is unstable and the municipal return water is insufficient, the ordinary centrifugal compressor will cause surge shutdown due to the difficulty in frequency conversion of the low-temperature heat source, thereby causing the whole line to stop production.

[0004] In a large-scale heating project (for example, 100 MW), the existing equipment usually uses multiple 10 MW devices in series. If one of the multiple devices is damaged or the circulating water working condition does not meet the requirements, the device cannot operate, and the whole line stops production. SUMMARY

[0005] The technical problem to be solved by the present application is to solve the problems of large heat loss, low operation energy efficiency ratio, and difficulty in effectively utilizing low-grade heat sources in the prior art in the background, and to provide a chemical waste heat cascade utilization system, which realizes efficient recovery and distribution of energy through cooperation of multiple units.

[0006] The technical scheme adopted by the present application to solve the technical problem is: a chemical waste heat cascade utilization system, comprising:

[0007] A waste heat circulation unit for processing multi-stage waste heat, the multi-stage waste heat comprising a first-stage waste heat circulation of 59.4 / 40℃, a second-stage waste heat circulation of 50 / 35℃, a third-stage waste heat circulation of 50 / 42℃, a fourth-stage waste heat circulation of 40 / 32℃, and a fifth-stage waste heat circulation of 80 / 35℃;

[0008] A cooling circulation unit for heating and raising the temperature of 32℃ cooling water to 40℃ through heat exchange with the waste heat circulation unit;

[0009] A steam-liquid condensate unit for temperature and pressure reduction of steam and seasonal distribution of 90℃ liquid condensate;

[0010] A hot end temperature raising unit for raising the temperature of municipal heating, process hot water, and heat tracing;

[0011] A control unit for dynamic adjustment of temperature and flow rate of each unit.

[0012] The waste heat circulation unit classifies and processes waste heat of different temperature ranges to avoid energy waste; the cooling circulation unit uses waste heat to increase the temperature of cooling water, reducing the energy consumption of the cooling tower; the steam- condensate unit realizes flexible scheduling of energy by steam temperature and pressure reduction and seasonal distribution of condensate; the hot end temperature increasing unit meets the high temperature demand of municipal heating, process hot water and heat tracing, improving the overall energy efficiency of the system; the control unit dynamically adjusts the temperature and flow rate to ensure stable operation of the system; the low, medium and high temperature waste heat in the chemical production process is fully recovered, and the energy is matched to different heat users through heat pumps, plate heat exchangers and other equipment, greatly improving the overall energy efficiency.

[0013] According to one embodiment of the present application, the first stage waste heat circulation includes a 59.4℃ water supply pipe, a fourth plate heat exchanger and a 40℃ return water pipe, the water output by the 59.4℃ water supply pipe is heated by the fourth plate heat exchanger to 40℃ and then enters the 40℃ return water pipe, and is combined with 90℃ condensate according to seasonal switching;

[0014] The second stage waste heat circulation is divided into multiple paths, each path including a 50℃ water supply pipe, a second plate heat exchanger, a third plate heat exchanger, a first magnetic suspension centrifugal heat pump, a second magnetic suspension centrifugal heat pump and a 35℃ return water pipe, the water output by the 50℃ water supply pipe is heated by the third plate heat exchanger to 42℃, and then enters the evaporators of the first magnetic suspension centrifugal heat pump and the second magnetic suspension centrifugal heat pump to be cooled to 35℃, and then enters the second plate heat exchanger for heat preservation and then enters the 35℃ return water pipe;

[0015] The third stage waste heat circulation is divided into multiple paths, each path including a 50℃ water supply pipe, a first magnetic suspension centrifugal heat pump, a second magnetic suspension centrifugal heat pump and a 42℃ return water pipe, the 48℃ water output by the 50℃ water supply pipe is cooled to 44.3℃ by the evaporator of the first magnetic suspension centrifugal heat pump, and then cooled to 40℃ by the evaporator of the second magnetic suspension centrifugal heat pump, and then enters the 42℃ return water pipe;

[0016] The fourth stage waste heat circulation is divided into multiple paths, each path including a 40℃ water supply pipe, a first plate heat exchanger and a 32℃ return water pipe, the water output by the 40℃ water supply pipe is heated by the first plate heat exchanger to 32℃, and then enters the 32℃ return water pipe;

[0017] The fifth stage waste heat cycle comprises an 80 DEG C water supply pipe, a first absorption heat pump, a second absorption heat pump, a magnetic suspension centrifugal heat pump one, a magnetic suspension centrifugal heat pump two, a magnetic suspension centrifugal heat pump three, a magnetic suspension centrifugal heat pump four and a 35 DEG C return water pipe one, water output by the 80 DEG C water supply pipe is cooled to 69 DEG C by an evaporator of the first absorption heat pump, then cooled to 58 DEG C by an evaporator of the second absorption heat pump, then sequentially cooled to 42 DEG C by evaporators of the magnetic suspension centrifugal heat pump one, the magnetic suspension centrifugal heat pump two, the magnetic suspension centrifugal heat pump three and the magnetic suspension centrifugal heat pump four, and then enters the 35 DEG C return water pipe one, and the temperature is reduced by 4 DEG C after passing through each magnetic suspension centrifugal heat pump.

[0018] The first stage waste heat cycle recovers waste heat of condensate through a plate heat exchanger and is coupled with a steam condensate system to realize seasonal energy complementation. The second stage waste heat cycle is divided into five paths and is deeply cooled by magnetic suspension centrifugal heat pumps to maximize the extraction of available energy of 50 DEG C hot water. The third stage waste heat cycle adopts two-stage magnetic suspension centrifugal heat pumps to precisely control the return water temperature to 40 DEG C to avoid energy grade waste. The fourth stage waste heat cycle directly exchanges heat through a plate heat exchanger to simplify the low-temperature waste heat recovery process. The fifth stage waste heat cycle is cooled by four-stage absorption and magnetic suspension centrifugal heat pumps to solve the problem of difficult direct utilization of high-temperature waste heat; a wide range of waste heat from 59.4 DEG C to 80 DEG C is covered, different temperature requirements are matched through staged processing, and the waste heat utilization rate is above 85%.

[0019] According to an embodiment of the present application, each path of the second stage waste heat cycle and the third stage waste heat cycle is provided with a circulating pump.

[0020] A circulating pump is configured for each path of the second stage waste heat cycle and the third stage waste heat cycle to ensure balanced flow of each path, avoid local overheating or insufficient flow, improve hydraulic stability of the system and prevent heat exchange efficiency from being reduced due to uneven flow.

[0021] According to an embodiment of the present application, three temperature sensors and two adjusting valves are arranged on each path of the second stage waste heat cycle, and the circulating pump of each path of the second stage waste heat cycle controls the opening degree of the two adjusting valves by detecting the temperatures of the three temperature sensors to ensure that the return water temperature is stably controlled at 35 DEG C.

[0022] The return water temperature is strictly and stably controlled at 35 DEG C through three-sensor middle value detection and double-valve joint control, the temperature control accuracy is ±0.5 DEG C, and the harsh requirements of the chemical process on the return water temperature are met.

[0023] According to an embodiment of the present application, a flow meter and an adjusting valve are arranged on each path of the third stage waste heat cycle, and the circulating pump of each path of the third stage waste heat cycle controls the opening degree of the adjusting valve by detecting the flow of the flow meter to ensure that the flow of the five paths meets the requirements.

[0024] The second-stage waste heat circulation is provided with a flow meter and an adjusting valve, and the circulating pump of each path of the second-stage waste heat circulation controls the opening degree of the adjusting valve by detecting the flow of the flow meter, so that the flow of the five paths meets the demand.

[0025] The second-stage waste heat circulation is provided with a flow meter and an adjusting valve, and the circulating pump of each path of the second-stage waste heat circulation controls the opening degree of the adjusting valve by detecting the flow of the flow meter, so that the flow of the five paths meets the demand.

[0026] According to one embodiment of the present application, the cooling circulation unit is divided into multiple paths, each path comprising a 32 DEG C cooling water supply pipe, a second plate heat exchanger and a 40 DEG C cooling water return pipe, the cooling water output by the 32 DEG C cooling water supply pipe is heated to 40 DEG C by the second plate heat exchanger and then enters the 40 DEG C cooling water return pipe.

[0027] The 32 DEG C cooling water is heated to 40 DEG C after heat exchange with the waste heat circulation unit, thereby recovering waste heat and reducing the load of the cooling tower; the energy consumption of the cooling water system is reduced by 20%, and direct discharge of low-temperature heat sources is avoided.

[0028] According to one embodiment of the present application, when it is detected that the municipal return water temperature is lower than 35 DEG C or the flow is lower than a set threshold, the second plate heat exchanger is automatically operated to maintain the temperature of the heat source side at above 35 DEG C through the second plate heat exchanger.

[0029] When the return water is unstable, the second plate heat exchanger is automatically switched in to stabilize the low-temperature return water temperature, ensure the circulation balance, energy consumption stability and equipment safety of the factory production water system, and thus ensure normal production.

[0030] According to one embodiment of the present application, the steam- condensate unit comprises a steam inlet pipe, a first absorption heat pump, a second absorption heat pump and a 90 DEG C condensate pipe, the steam output by the steam inlet pipe is cooled to 90 DEG C condensate after passing through a desuperheating and pressure reducing device and entering the generators of the first absorption heat pump and the second absorption heat pump, and the 90 DEG C condensate in the 90 DEG C condensate pipe is connected to the 59.4 DEG C supply pipe of the first-stage waste heat circulation in the heating season and connected to the 40 DEG C return pipe of the first-stage waste heat circulation in the non-heating season.

[0031] The 90 DEG C condensate is connected to the 59.4 DEG C supply pipe in the heating season to supplement the heating heat source, and connected to the 40 DEG C return pipe in the non-heating season to avoid energy waste; the seasonal adaptability of condensate energy is realized, and the energy saving rate is improved by 12% throughout the year.

[0032] According to one embodiment of the application, the municipal heating cycle in the hot end heating unit is divided into multiple paths, one of which includes a 30°C municipal return water pipe, a first plate heat exchanger, a fourth plate heat exchanger, a third plate heat exchanger, a first magnetic suspension centrifugal heat pump, a second magnetic suspension centrifugal heat pump, a two-stage magnetic suspension centrifugal heat pump, a first-stage magnetic suspension centrifugal heat pump, and a 88.2°C municipal water supply pipe. This path is further divided into two branches. The first branch: the water output by the 30°C municipal return water pipe is heated to 38°C by the first plate heat exchanger and the 40°C water supply pipe in the fourth-stage waste heat cycle, and then is heated to 57.4°C by the fourth plate heat exchanger and the 59.4°C water supply pipe in the first-stage waste heat cycle. The second branch: the water output by the 30°C municipal return water pipe is heated to 47°C by the third plate heat exchanger and the 50°C water supply pipe in the second-stage waste heat cycle, and then is sequentially heated to 60.5°C by the condenser of the first magnetic suspension centrifugal heat pump and the second magnetic suspension centrifugal heat pump, mixed with the 57.4°C heating water in the first branch to 59°C, and then is sequentially heated to 86.4°C by the condenser of the two-stage magnetic suspension centrifugal heat pump and the first-stage magnetic suspension centrifugal heat pump, and enters the 88.2°C municipal water supply pipe.

[0033] The first branch and the second branch both include a supercooling cycle unit. The heat exchange water in the supercooling cycle unit is connected in parallel to the economizer in the subsequent magnetic suspension centrifugal heat pump. The heat exchange water in the supercooling cycle unit is different from the heating water that is connected in series to the condenser of the magnetic suspension centrifugal heat pump. This can reduce the amount of municipal return water, ensure stable operation of the system when the amount of municipal return water is small, and avoid shutdown of the magnetic suspension centrifugal heat pump due to insufficient municipal return water.

[0034] Further, the heat exchange water in the supercooling cycle unit comes from 29-31°C municipal return water. The heat exchange water directly comes from 29-31°C municipal return water, and the temperature difference between the heat exchange water and the liquid working medium of the magnetic suspension centrifugal heat pump increases, and the heat that can be carried away per unit time increases. That is, to achieve the required supercooling degree of the working medium, the required amount of heat exchange water can be correspondingly reduced, and the flow rate is also reduced. While ensuring that the supercooling degree of the working medium meets the standard, energy saving and system operation efficiency can be improved. It can also ensure 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 suspension centrifugal heat pump due to insufficient municipal return water.

[0035] The remaining several paths include a 30 DEG C municipal return water pipe, a first plate heat exchanger, a third plate heat exchanger, a first magnetic suspension centrifugal heat pump, a second magnetic suspension centrifugal heat pump, a two-stage magnetic suspension centrifugal heat pump, a one-stage magnetic suspension centrifugal heat pump and a 88.2 DEG C municipal water supply pipe, the water output by the 30 DEG C municipal return water pipe is exchanged with the water output by the 40 DEG C water supply pipe in the fourth-stage waste heat circulation through the first plate heat exchanger to 36.8 DEG C, then is exchanged with the water output by the 50 DEG C water supply pipe in the second-stage waste heat circulation through the third plate heat exchanger to 45.5 DEG C, then enters the condenser of the first magnetic suspension centrifugal heat pump, the second magnetic suspension centrifugal heat pump, the two-stage magnetic suspension centrifugal heat pump and the one-stage magnetic suspension centrifugal heat pump in turn to be heated to 88.7 DEG C, and enters the 88.2 DEG C municipal water supply pipe.

[0036] The design is divided into two branches, the first branch directly exchanges heat with waste heat through a plate exchanger to rapidly increase the water temperature to 57.4 DEG C, the second branch is gradually heated by a magnetic suspension centrifugal heat pump, and finally the mixed water is heated to 88.2 DEG C; the advantages of direct heat exchange and heat pump temperature raising are combined to reduce power consumption while ensuring efficiency, and the standard rate of heating water temperature is 100%.

[0037] According to one embodiment of the present application, the first magnetic suspension centrifugal heat pump, the second magnetic suspension centrifugal heat pump, the one-stage magnetic suspension centrifugal heat pump and the two-stage magnetic suspension centrifugal heat pump all adopt magnetic suspension centrifugal heat pumps, the magnetic suspension centrifugal heat pump includes an evaporator, a condenser and an economizer, the water output by the 30 DEG C municipal return water pipe in the second branch supplies the economizer of each magnetic suspension centrifugal heat pump, the economizer of each magnetic suspension centrifugal heat pump in the remaining several paths of the hot end heating unit receives the 45.5 DEG C water after heat exchange through the third plate heat exchanger, and the condenser of the latter magnetic suspension centrifugal heat pump receives the mixed water after heat exchange through the condenser and the economizer of the former magnetic suspension centrifugal heat pump.

[0038] The economizer of each magnetic suspension centrifugal heat pump in the second branch is separately supplied with return water, the low-temperature return water supplied to the economizer can cool the condensed liquid working medium, and can also give the liquid working medium a certain degree of supercooling, thereby reducing gas evaporation in the process of heat exchange with the non-condensable gas through the expansion valve, and improving the heat exchange efficiency. At the same time, if the municipal return water is unstable and the municipal return water quantity is small, directly dividing a part of the return water to separately supply the economizer of the magnetic suspension centrifugal heat pump can reduce the use amount of municipal return water in the system, and maintain the stability of the system. In the remaining several paths of the hot end heating unit, the economizer of each magnetic suspension centrifugal heat pump is not separately supplied with return water, but a part of the heating water of the previous magnetic suspension centrifugal heat pump is divided to the economizer, a part directly passes through the condenser of the magnetic suspension centrifugal heat pump, and a part passes through the economizer, and then the heating water is combined to the next magnetic suspension centrifugal heat pump.

[0039] According to one embodiment of the present application, a main pipe is further included, and the input end and the output end of each magnetic suspension centrifugal heat pump are connected to the main pipe through a connecting branch pipe, a switch valve is arranged on the main pipe corresponding to each magnetic suspension centrifugal heat pump, and a switch valve is also arranged on the connecting branch pipe; when any magnetic suspension centrifugal heat pump fails or the circulating water working condition does not meet the requirements, the switch valve on the connecting branch pipe is automatically closed, the switch valve on the corresponding main pipe is automatically opened, and water flows into the next magnetic suspension centrifugal heat pump through the main pipe; or when the municipal return water is insufficient, the switch valves on the connecting branch pipes of a plurality of magnetic suspension centrifugal heat pumps are closed, the switch valves on the corresponding main pipes are opened, and water flows through the main pipe.

[0040] The magnetic suspension centrifugal heat pump of the present application has a small heating capacity of about 3 MW, and a single set of high power up to 100 MW can be formed by connecting multiple magnetic suspension machines in series and in parallel. The temperature difference between the inlet and outlet of the evaporator side of the magnetic suspension centrifugal heat pump heat pump is small, for example, ΔT is reduced from 5℃ to 1.5℃, which can improve the energy utilization in the circulating water and improve the utilization rate of low-grade heat energy of the magnetic suspension centrifugal heat pump. A single magnetic suspension centrifugal heat pump can be directly removed from the main pipe when it is damaged, or when the municipal return water is insufficient, a plurality of magnetic suspension centrifugal heat pumps can not be used, and the main pipe can be used.

[0041] According to one embodiment of the present application, the process hot water circulation in the heat utilization end temperature rising unit includes a 85℃ process hot water return pipe, a first absorption heat pump, a second absorption heat pump and a 105℃ process hot water supply pipe, the water output by the 85℃ process hot water return pipe is sequentially heated to 95℃ by the absorber of the first absorption heat pump and the second absorption heat pump, and then is sequentially heated to 105℃ by the condenser of the first absorption heat pump and the second absorption heat pump, and then enters the 105℃ process hot water supply pipe.

[0042] The 85℃ process hot water is heated to 105℃ by two-stage absorption heat pump, which meets the high temperature demand of chemical reaction, replaces traditional electric heating or boiler, and reduces the energy consumption of process section by 40%.

[0043] According to one embodiment of the present application, the heat tracing circulation in the heat utilization end temperature rising unit includes a 85℃ heat tracing return pipe, a first magnetic suspension centrifugal heat pump, a second magnetic suspension centrifugal heat pump, a third magnetic suspension centrifugal heat pump, a fourth magnetic suspension centrifugal heat pump and a 90℃ heat tracing supply pipe, the heat tracing hot water output by the 85℃ heat tracing return pipe enters the condenser of the first magnetic suspension centrifugal heat pump, the second magnetic suspension centrifugal heat pump, the third magnetic suspension centrifugal heat pump and the fourth magnetic suspension centrifugal heat pump respectively, and is heated to 90℃, and then enters the 90℃ heat tracing supply pipe.

[0044] The 85℃ heat tracing water is heated to 90℃ by parallel magnetic suspension centrifugal heat pumps, which maintains the anti-freezing requirement of the pipeline, reduces the energy consumption of the heat tracing system by 30%, and controls the temperature more accurately.

[0045] The beneficial effects of the present application are:

[0046] (1) The system can well reduce load and frequency through the magnetic suspension centrifugal heat pump and the control system; the backup plate heat exchanger is set, which can cut into the backup plate heat exchanger when the return water is unstable, can guarantee the low-temperature return water of 35℃, can guarantee the return water requirement of the factory, ensures the cycle balance, energy consumption stability and equipment safety of the water system for factory production, so as to ensure the normal production; the main pipeline is set to timely reduce a part of the temperature rise; the control of supplying low-temperature return water to the economizer of the magnetic suspension centrifugal heat pump is carried out to solve the surge stop of the ordinary centrifugal machine caused by the difficulty of low-temperature heat source frequency conversion in the prior art when the municipal return water is unstable and the municipal return water is less;

[0047] (2) The system is provided with five-stage waste heat circulation, which covers waste heat of different temperature ranges, can fully exploit and utilize various waste heat resources generated in the chemical production process, avoids waste of waste heat, and improves the energy utilization rate; by utilizing the waste heat of different temperatures according to the temperature gradient, the energy is recycled and reused step by step;

[0048] (3) The cooling circulation unit can heat exchange with the waste heat circulation unit to make the cooling water of 32℃ rise to 40℃, which not only can effectively utilize waste heat to increase the temperature of the cooling water, but also can reduce the temperature difference of the cooling water and reduce the energy consumption of the cooling water system; after the cooling water is heated, it can be used in other process links requiring 40℃ hot water, realizes the recycling of the cooling water, reduces the consumption and discharge of the cooling water, and also reduces the operation cost of the cooling water treatment system;

[0049] (4) The steam-liquid unit can flexibly distribute the destination of 90℃ condensate according to seasonal changes: in the heating season, the condensate is merged into the 59.4℃ water supply pipe of the first-stage waste heat circulation to fully utilize its heat for heating; in the non-heating season, the condensate is merged into the 40℃ return water pipe of the first-stage waste heat circulation to avoid waste of heat and ensure stable operation of the system; the unit is also responsible for the temperature and pressure reduction of the steam to ensure the reasonable utilization of the steam in the system, prevent damage to the equipment caused by too high steam pressure or temperature, and improve the safety and reliability of the system:

[0050] (5) The municipal heating circulation in the hot end temperature rising unit is designed with multiple different heat exchange processes, which can gradually raise the municipal return water of 30℃ to 88.2℃ according to different needs to meet the hot water demand of municipal heating; by reasonably configuring the heat exchange equipment and heat exchange process, efficient and stable heating hot water supply is realized, and the heating experience of residents is improved;

[0051] The process hot water recycling absorption heat pump and magnetic suspension centrifugal heat pump and other equipment, the process hot water backwater of 85℃ is gradually warmed to 105℃, meet the demand of high temperature process hot water in chemical production process; this design not only improves the temperature of process hot water, but also reduces the dependence on other energy, reduces the production cost;

[0052] Heat cycle through the magnetic suspension centrifugal heat pump to 85℃ hot water temperature to 90℃, provide heat tracing for pipeline, equipment and other, prevent the medium in low temperature environment condensation or freeze, ensure the smooth progress of chemical production process;

[0053] (6) the control unit can adjust the temperature and flow of each unit, according to the system operation and demand changes, real-time adjustment of the operating parameters of each device, ensure the stable operation of the system and efficient use; in each waste heat circulation path set temperature sensor, flow meter and regulating valve and other equipment, through the detection of temperature and flow, automatic control of regulating valve opening, ensure the stability of backwater temperature and flow;

[0054] (7) each level of waste heat circulation, municipal heating cycle and cooling cycle unit, etc. all adopt the design of multiple circulation, when a road on the device failure or need repair, other road can continue to run, ensure the overall stability of the system, reduce the system downtime caused by local failure; in some key links, such as the second level of waste heat circulation heat pump configuration, etc., by setting multiple magnetic suspension centrifugal heat pump or absorption heat pump, and reasonable distribution of its workload, improve the redundancy and reliability of the equipment, even if part of the device failure, other devices can continue to work, ensure the normal operation of the system;

[0055] (8) by making full use of waste heat resources in chemical production process, reduces the dependence on purchased energy, reduces the energy procurement cost of enterprises; accurate control and regulation function can make each device in the best working condition, avoid the overrunning or inefficient operation of the equipment, so as to reduce the energy consumption and wear of the equipment, prolong the service life of the equipment, further reduce the operation cost and maintenance cost of the system; cooling water recycling reduces the amount of cooling water and discharge, reduces the operation cost of cooling water treatment system, at the same time, also reduces the consumption of water resources, in line with the environmental protection requirements;

[0056] (9) due to the full use of waste heat resources, reduces the consumption of traditional energy such as fossil fuel, thereby reduces the emission of carbon dioxide and other greenhouse gases, has positive significance to environmental protection; the system recycles the waste heat which may be directly discharged into the environment, reduces the heat pollution of waste heat to the environment, improves the cleanliness of energy utilization.

[0057] In summary, the chemical waste heat cascade utilization system realizes efficient utilization of waste heat resources, satisfaction of various heat demand, stable operation of the system, reduction of energy consumption and operation cost, and has significant economic, environmental and social benefits by reasonably configuring the waste heat cycles, cooling cycles, steam- condensate units and heat utilization end temperature raising units, and combining with accurate control and adjustment functions. BRIEF DESCRIPTION OF DRAWINGS

[0058] The application will be further described below in combination with the drawings and examples.

[0059] Figure 1 is a process flow diagram of the chemical waste heat cascade utilization system of the application.

[0060] Figure 2 is a process flow diagram of the first-stage waste heat cycle in the chemical waste heat cascade utilization system of the application.

[0061] Figure 3 is a process flow diagram of the second-stage waste heat cycle in the chemical waste heat cascade utilization system of the application.

[0062] Figure 4 is a process flow diagram of the third-stage waste heat cycle in the chemical waste heat cascade utilization system of the application.

[0063] Figure 5 is a process flow diagram of the fourth-stage waste heat cycle in the chemical waste heat cascade utilization system of the application.

[0064] Figure 6 is a process flow diagram of the fifth-stage waste heat cycle in the chemical waste heat cascade utilization system of the application.

[0065] Figure 7 is a process flow diagram of the cooling cycle unit in the chemical waste heat cascade utilization system of the application.

[0066] Figure 8 is a process flow diagram of the steam-condensate unit in the chemical waste heat cascade utilization system of the application.

[0067] Figure 9 is a process flow diagram of the municipal heating cycle in the chemical waste heat cascade utilization system of the application.

[0068] Figure 10 is a process flow diagram of the process hot water cycle in the chemical waste heat cascade utilization system of the application.

[0069] Figure 11 is a process flow diagram of the heat tracing cycle in the chemical waste heat cascade utilization system of the application.

[0070] Figure 12 is a structural schematic diagram of the magnetic suspension centrifugal heat pump in the chemical waste heat cascade utilization system of the application.

[0071] Figure 13 Figure 1 is a schematic diagram of the connection structure of the main pipeline and the magnetic suspension centrifugal heat pump in the chemical waste heat cascade utilization system of the present application.

[0072] In the figure: 1, first stage waste heat cycle; 101, 59.4℃ water supply pipe; 102, 40℃ return water pipe; 2, second stage waste heat cycle; 201, 50℃ water supply pipe; 202, 35℃ return water pipe; 3, third stage waste heat cycle; 301, 50℃ water supply pipe; 302, 42℃ return water pipe; 4, fourth stage waste heat cycle; 401, 40℃ water supply pipe; 402, 32℃ return water pipe; 5, fifth stage waste heat cycle; 501, 80℃ water supply pipe; 502, 35℃ return water pipe; 6, cooling cycle 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 cycle; 811, 30℃ municipal return water pipe; 812, 88.2℃ municipal water supply pipe; 813, subcooling cycle unit; 82, process hot water cycle; 821, 85℃ process hot water return pipe; 822, 105℃ process hot water supply pipe; 83, heat tracing cycle; 831, 85℃ heat tracing return pipe; 832, 90℃ heat tracing supply pipe; 9, control unit; 10, fourth plate heat exchanger; 11, second plate heat exchanger; 12, third plate heat exchanger; 13, first magnetic suspension centrifugal heat pump; 14, second magnetic suspension centrifugal heat pump; 15, first stage magnetic suspension centrifugal heat pump; 16, second stage magnetic suspension centrifugal heat pump; 17, first plate heat exchanger; 18, first absorption heat pump; 19, second absorption heat pump; 20, magnetic suspension centrifugal heat pump one; 21, magnetic suspension centrifugal heat pump two; 22, magnetic suspension centrifugal heat pump three; 23, magnetic suspension centrifugal heat pump four; 24, circulating pump; 25, temperature and pressure reducing device; 261, circulating water main pipe; 262, heating water main pipe; 271, connection 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

[0073] The present application will now be further described in greater detail in connection with the enclosed drawings. These drawings form a part of this specification and embody therein major or all features of the present application. For a better understanding of the present application, its operating advantages and specific objects attained by its uses, reference should be made to the drawings and descriptive matter in which there are illustrated and described its preferred embodiments.

[0074] As Figures 1-11As shown, a cascade utilization system for chemical waste heat includes a waste heat circulation unit, a cooling circulation unit 6, a steam-condensate unit 7, a heat-consuming end heating unit, and a control unit 9. The waste heat circulation unit handles multiple stages of waste heat, including a first-stage waste heat circulation 1 at 59.4 / 40℃, a second-stage waste heat circulation 2 at 50 / 35℃, a third-stage waste heat circulation 3 at 50 / 42℃, a fourth-stage waste heat circulation 4 at 40 / 32℃, and a fifth-stage waste heat circulation 5 at 80 / 35℃. The cooling circulation unit 6 exchanges heat between 32℃ cooling water and the waste heat circulation unit to raise the temperature to 40℃. The steam-condensate unit 7 is used for cooling and depressurizing steam and seasonally distributing 90℃ condensate. The heat-consuming end heating unit is used for raising the temperature of municipal heating, process hot water, and heat tracing. The control unit 9 is used for dynamic adjustment of the temperature and flow rate of each unit. Figure 1 This is the actual process flow diagram. Box A in the diagram includes the steam-condensate unit 7, the process hot water circulation 82 and heat tracing circulation 83 in the heat-generating unit, and the fifth-stage waste heat circulation 5. The municipal heating circulation 81, the first-stage waste heat circulation 1, the second-stage waste heat circulation 2, the third-stage waste heat circulation 3, the fourth-stage waste heat circulation 4, and the cooling circulation unit 6 are located in box B. The control unit 9 can independently and automatically control the system, mainly housing programmable control cabinets, communication network cabinets, instrument valve power supply cabinets, and rack-mounted engineering workstations. Operators at the engineering workstations control the system's start / stop, monitor and adjust normal operation, and handle abnormal and accident conditions. At least 15% of analog and digital I / O points are reserved. A visual monitoring platform is set up in the central control center. All data interacts with the central control center's visual monitoring platform through the communication network, establishing an automatic control system that serves the energy supply system, featuring automated group control, energy efficiency calculation, and energy management.

[0075] To further clarify the specific structure of each unit or loop, Figure 1 Decompose by unit or cycle, as follows:

[0076] like Figure 2 As shown, the first-stage waste heat cycle 1 includes a 59.4℃ supply water pipe 101, a fourth plate heat exchanger 10, and a 40℃ return water pipe 102. Water output from the 59.4℃ supply water pipe 101 is heated to 40℃ by the fourth plate heat exchanger 10 before entering the 40℃ return water pipe 102, and this cycle repeats continuously. The first-stage waste heat cycle 1 is also combined with the 90℃ condensate, which is seasonally switched. The plate heat exchanger has a compact structure and a large heat transfer area per unit, saving materials compared to shell-and-tube heat exchangers. Alternatively, a corrugated tube heat exchanger can be used, improving heat exchanger efficiency. The use of high-efficiency heat exchangers saves on the amount of cooling water required for production cooling. The first-stage waste heat cycle 1 recovers waste heat from the condensate and couples it with the steam system. The compact design of the plate heat exchanger saves 20% of space; the seasonal merging of the 90℃ condensate avoids energy waste.

[0077] As shown in Figure 3 , the second-stage waste heat circulation 2 is divided into five paths (it can also be divided into more or fewer paths as needed), each path including a 50℃ water supply pipe 201, a second plate heat exchanger 11, a third plate heat exchanger 12, a first magnetic suspension centrifugal heat pump 13, a second magnetic suspension centrifugal heat pump 14, and a 35℃ return water pipe 202. The water output by the 50℃ water supply pipe 201 is heat-exchanged to 42℃ by the third plate heat exchanger 12, and then enters the evaporators 100 of the first magnetic suspension centrifugal heat pump 13 and the second magnetic suspension centrifugal heat pump 14 to be cooled to 35℃, and then enters the second plate heat exchanger 11 for heat preservation and then enters the 35℃ return water pipe 202, and so on. The first magnetic suspension centrifugal heat pump 13 and the second magnetic suspension centrifugal heat pump 14 are magnetic suspension centrifugal heat pumps, which use advanced magnetic suspension technology to greatly reduce mechanical friction loss and thus improve the operating efficiency of the unit. This not only saves electricity and reduces operating costs, but also helps to reduce energy consumption and carbon emissions. The second-stage waste heat circulation 2 uses five parallel magnetic suspension heat pumps for deep cooling, with a 40% reduction in single-path power consumption and a stable return water temperature of 35℃ (±0.5℃).

[0078] As shown in Figure 4 , the third-stage waste heat circulation 3 is divided into five paths, each path including a 50℃ water supply pipe 301, a first magnetic suspension centrifugal heat pump 15, a second magnetic suspension centrifugal heat pump 16, and a 42℃ return water pipe 302. The 48℃ water output by the 50℃ water supply pipe 301 is cooled to 44.3℃ by the evaporator 100 of the first magnetic suspension centrifugal heat pump 15, and then cooled to 40℃ by the evaporator 100 of the second magnetic suspension centrifugal heat pump 16, and then enters the 42℃ return water pipe 302, and so on. The first magnetic suspension centrifugal heat pump 15 and the second magnetic suspension centrifugal heat pump 16 are also magnetic suspension centrifugal heat pumps, and the first magnetic suspension centrifugal heat pump 15 and the second magnetic suspension centrifugal heat pump 16 are each provided with multiple units as needed, preferably 3-4 units. The third-stage waste heat circulation 3 uses two-stage magnetic suspension heat pumps in series for cooling, and precisely controls the final temperature to 40℃ to match the process requirements.

[0079] As shown in Figure 5 , the fourth-stage waste heat circulation 4 is divided into five paths, each path including a 40℃ water supply pipe 401, a first plate heat exchanger 17, and a 32℃ return water pipe 402. The water output by the 40℃ water supply pipe 401 is heat-exchanged to 32℃ by the first plate heat exchanger 17, and then enters the 32℃ return water pipe 402, and so on. The fourth-stage waste heat circulation 4 uses plate heat exchangers for direct heat exchange to recover low-temperature waste heat, simplifying the process and reducing maintenance costs by 30%.

[0080] As shown in Figure 6As shown, the fifth-stage waste heat circulation 5 includes an 80°C water supply pipe 501, a first absorption heat pump 18, a second absorption heat pump 19, a magnetic suspension centrifugal heat pump one 20, a magnetic suspension centrifugal heat pump two 21, a magnetic suspension centrifugal heat pump three 22, a magnetic suspension centrifugal heat pump four 23, and a 35°C water return pipe one 502. The water output by the 80°C water supply pipe 501 is cooled to 69°C by the evaporator 100 of the first absorption heat pump 18, then cooled to 58°C by the evaporator 100 of the second absorption heat pump 19, and then sequentially cooled to 42°C by the evaporators 100 of the magnetic suspension centrifugal heat pump one 20, the magnetic suspension centrifugal heat pump two 21, the magnetic suspension centrifugal heat pump three 22, and the magnetic suspension centrifugal heat pump four 23, and then enters the 35°C water return pipe one 502, and the temperature is reduced by 4°C after passing through each magnetic suspension centrifugal heat pump. Among them, the first absorption heat pump 18 and the second absorption heat pump 19 are superconducting heat core heat pumps, which are a kind of circulating system that uses low-grade heat sources to pump heat from low-temperature heat sources to high-temperature heat sources, an effective device for recycling low-temperature heat energy, and has the dual effects of energy saving and environmental protection. The superconducting heat core heat pump adopts the wave node plate heat exchanger disclosed in CN117588900A, which changes the cross-sectional area of the flow channel to constantly change the fluid dynamic pressure head, generates regular expansion and compression during the flow process, increases the fluid Reynolds number, and realizes high-efficiency heat exchange. The fifth-stage waste heat circulation 5 uses superconducting heat core heat pumps and magnetic suspension centrifugal heat pumps for four-stage temperature reduction, and the utilization rate of high-temperature waste heat (80°C) reaches 90%, solving the problem that traditional technologies are difficult to handle.

[0081] The circulation pump 24 is arranged on each path of the second waste heat circulation 2 and the third waste heat circulation 3. Three temperature sensors and two regulating valves (not shown in the figure, existing conventional products on the market) are arranged on each path of the second waste heat circulation 2, and the circulation pump 24 on each path of the second waste heat circulation 2 controls the opening degree of the two regulating valves by detecting the temperature of the three temperature sensors on the path, specifically, taking the middle value of the two temperature values, so as to ensure that the return water temperature is stable at 35℃. A flow meter and a regulating valve are arranged on each path of the third waste heat circulation 3, and the circulation pump 24 on each path of the third waste heat circulation 3 controls the opening degree of the regulating valve by detecting the flow of the flow meter on the path, so as to ensure that the flow of the five paths meets the demand; a flow meter and a regulating valve are arranged on each path of the second waste heat circulation 2, and the circulation pump 24 on each path of the second waste heat circulation 2 controls the opening degree of the regulating valve by detecting the flow of the flow meter on the path, so as to ensure that the flow of the five paths meets the demand. The circulation pump 24 adopts a horizontal single-stage double (single) suction centrifugal pump, the inlet liquid enters the center area of the impeller at the same time, the high-speed rotating impeller is driven by the centrifugal force to throw out the liquid, the center of the impeller forms a low pressure area, the inlet liquid continuously flows to the low pressure area under the action of atmospheric pressure, that is, the circulation process of being thrown out after entering the center of the impeller. The horizontal single-stage double (single) suction centrifugal pump has compact structure, beautiful appearance, good stability and is convenient to install; the double suction impeller runs stably, the axial force is reduced to the minimum, the blade type has excellent hydraulic performance, the inner surface of the centrifugal pump shell and the surface of the impeller have anti-cavitation performance. Multi-sensor feedback and valve joint control, system adaptive adjustment, fault rate <0.1%.

[0082] As shown in Figure 7 The cooling circulation unit 6 is divided into five paths, each path includes a 32℃ cooling water supply pipe 601, a second plate heat exchanger 11 and a 40℃ cooling water return pipe 602, the cooling water output by the 32℃ cooling water supply pipe 601 is heated to 40℃ by the second plate heat exchanger 11 and then enters the 40℃ cooling water return pipe 602, and the above process is repeated. The 32℃ cooling water is heated to 40℃ by waste heat exchange, which reduces the load of the cooling tower and saves about 100,000 tons of water per year.

[0083] As shown in Figure 8As shown, the steam-condensate unit 7 includes 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 (250°C, 1.5MPa) output from the steam inlet pipe 71 is converted into 173°C, 0.85MPa steam after passing through a desuperheating and pressure reducing device 25. This steam then enters the generators of the first and second absorption heat pumps 18 and is cooled to 90°C condensate. The 90°C condensate in the 90°C condensate pipe 72 is connected to the 59.4°C supply water pipe 101 of the first-stage waste heat cycle 1 during the heating season, and to the 40°C return water 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 quality before connection; only qualified condensate can be connected. After the steam drives the heat pump, it generates 90°C condensate, which is distributed seasonally, increasing the steam energy utilization rate by 25% and achieving a condensate qualification rate of over 95%.

[0084] like Figure 9 As shown, the municipal heating cycle 81 in the hot-end heating unit is divided into five circuits. One circuit includes a 30℃ 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℃ municipal supply water pipe 812. This circuit is further divided into two branches. In the first branch, the water output from the 30℃ municipal return water pipe 811 is heated to 38℃ by the first plate heat exchanger 17 and the water output from the 40℃ supply water pipe 401 in the fourth stage waste heat cycle 4. Then, it is heated to 57.4℃ by the fourth plate heat exchanger 10 and the water output from the 59.4℃ supply water pipe 101 in the first stage waste heat cycle 1. In the second branch, the water output from the 30℃ municipal return water pipe 811 is heated to 38℃ by the third plate heat exchanger 17 and the fourth plate heat exchanger 10. 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 be heated to 53.9℃, then enters the condenser 200 of the second magnetic levitation centrifugal heat pump 14 to be heated 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 to be heated to 86.4℃, and then enters the 88.2℃ municipal water supply pipe 812; wherein, the second-stage magnetic levitation centrifugal heat pump 16 has 3 sets of units, and the condensers 200 of the 3 sets of units are heated to 63.9℃, 68.7℃ and 74.9℃ respectively, and the first-stage magnetic levitation centrifugal heat pump 15 has 2 sets of units, and the condensers 200 of the 2 sets of units are heated to 80.8℃ and 86.4℃ respectively.

[0085] The subcooling cycle unit 813 in the first branch and the second branch includes heat exchange water which is connected in parallel to the economizer 300 of the subsequent magnetic suspension centrifugal heat pump. The heat exchange water in the subcooling cycle unit 813 is different from the heating water which is connected in series to the condenser 200 of the magnetic suspension centrifugal heat pump. The use of municipal return water can be reduced, the stable operation of the system can be ensured when the municipal return water is small, and the shutdown of the magnetic suspension centrifugal heat pump caused by insufficient municipal return water can be avoided.

[0086] Further, the heat exchange water in the subcooling cycle unit 813 comes from the municipal return water at 29-31℃. The heat exchange water directly comes from the municipal return water at 29-31℃, and the heat exchange water temperature is reduced. The heat transfer temperature difference between the heat exchange water and the liquid working medium of the magnetic suspension centrifugal heat pump is increased, and the heat carried away per unit time is increased. That is, to achieve the required subcooling degree of the working medium, the required amount of heat exchange water can be correspondingly reduced, and the flow rate is also reduced. While ensuring that the subcooling degree of the working medium meets the standard, energy saving and system operation efficiency can be improved. The stable operation of the system can be ensured when the municipal return water is small, the use of municipal return water can be further reduced, and the shutdown of the magnetic suspension centrifugal heat pump caused by insufficient municipal return water can be avoided.

[0087] The remaining four paths include a 30℃ municipal return water pipe 811, a first plate heat exchanger 17, a third plate heat exchanger 12, a first magnetic suspension centrifugal heat pump 13, a second magnetic suspension centrifugal heat pump 14, a two-stage magnetic suspension centrifugal heat pump 16, a one-stage magnetic suspension centrifugal heat pump 15, and a 88.2℃ municipal water supply pipe 812. The water output by the 30℃ municipal return water pipe 811 is exchanged with the water output by the 40℃ water supply pipe 401 in the fourth-stage waste heat cycle 4 through the first plate heat exchanger 17 to 36.8℃, and then exchanged with the water output by the 50℃ water supply pipe 201 in the second-stage waste heat cycle 2 through the third plate heat exchanger 12 to 45.5℃, and then sequentially enters the condenser 200 of the first magnetic suspension centrifugal heat pump 13, the second magnetic suspension centrifugal heat pump 14, the two-stage magnetic suspension centrifugal heat pump 16, and the one-stage magnetic suspension centrifugal heat pump 15 to be heated to 88.7℃, and then enters the 88.2℃ municipal water supply pipe 812. The municipal heating cycle 81 is designed with double branches, the plate heat exchanger and the magnetic suspension centrifugal heat pump are mixed, the heating path is optimized, the power consumption is reduced, and the standard rate of output water temperature is improved.

[0088] As Figure 10As shown, the process hot water circulation 82 in the hot end temperature raising unit includes the 85°C process hot water return pipe 821, the first absorption heat pump 18, the second absorption heat pump 19, and the 105°C process hot water supply pipe 822. The water output by the 85°C process hot water return pipe 821 is sequentially raised in temperature by the absorber of the first absorption heat pump 18 and the absorber of the second absorption heat pump 19 to 95°C, and then sequentially raised in temperature by the condenser 200 of the first absorption heat pump 18 and the condenser 200 of the second absorption heat pump 19 to 105°C, and enters the 105°C process hot water supply pipe 822, to be circulated in this way. The process hot water circulation 82 uses two-stage temperature raising by absorption heat pumps, replacing electric heating, and the carbon emission of the process section is reduced by 50%.

[0089] As shown, Figure 11 As shown, the process hot water circulation 82 in the hot end temperature raising unit includes the 85°C process hot water return pipe 821, the first absorption heat pump 18, the second absorption heat pump 19, and the 105°C process hot water supply pipe 822. The water output by the 85°C process hot water return pipe 821 is sequentially raised in temperature by the absorber of the first absorption heat pump 18 and the absorber of the second absorption heat pump 19 to 95°C, and then sequentially raised in temperature by the condenser 200 of the first absorption heat pump 18 and the condenser 200 of the second absorption heat pump 19 to 105°C, and enters the 105°C process hot water supply pipe 822, to be circulated in this way. The process hot water circulation 82 uses two-stage temperature raising by absorption heat pumps, replacing electric heating, and the carbon emission of the process section is reduced by 50%.

[0090] The first magnetic suspension centrifugal heat pump 13, the second magnetic suspension centrifugal heat pump 14, the first-stage magnetic suspension centrifugal heat pump 15, and the second-stage magnetic suspension centrifugal heat pump 16 all adopt magnetic suspension centrifugal heat pumps, as shown in Figure 12 The magnetic suspension centrifugal heat pump includes an evaporator 100, a condenser 200, and an economizer 300. The water output by the 30°C municipal return water pipe 811 in the second branch is supplied to the economizer 300 of each magnetic suspension centrifugal heat pump. The economizer 300 of each magnetic suspension centrifugal heat pump in the remaining several branches of the hot end temperature raising unit receives the water that has been heat-exchanged by the third plate heat exchanger 12 to 45.5°C, and the condenser 200 of a later magnetic suspension centrifugal heat pump receives the water that has been heat-exchanged by the condenser 200 and the economizer 300 of a previous magnetic suspension centrifugal heat pump and then mixed.

[0091] The liquid working medium enters the evaporator 100 from the inlet of the evaporator 100, exchanges heat inside the evaporator 100, and becomes gaseous working medium and flows out from the outlet of the evaporator 100; the gaseous working medium flows upwards through the primary compressor 400 and the secondary compressor 500 for compression, and then flows downwards 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 the heating water, the gaseous working medium is cooled to become liquid working medium and enters the economizer 300, and the heating water is heated and flows out for heating. Since the temperature of the liquid working medium entering the economizer 300 is still relatively high, in order to avoid waste of heat, part of the low-temperature heating water in the condenser 200 enters the economizer 300, the low-temperature heating water in the economizer 300 exchanges heat with the liquid working medium flowing through the economizer 300, the liquid working medium is further cooled, and the low-temperature heating water is heated and heated in the economizer 300, avoiding waste of heat of the liquid working medium, and the heating water is used for heating again.

[0092] As Figure 13 , the input end and the output end of the condenser 200 of the adjacent series magnetic suspension centrifugal heat pump are connected through the connecting branch pipe 271, and the condenser 200 is connected with the heating water main pipe 262, the connecting branch pipe 271 is connected with the heating water main pipe 262 through the bypass pipe 272, the connecting branch pipe 271 is provided with a switch valve 28, and the heating water main pipe 262 is also provided with a switch valve 28. Similarly, the input end and the output end of the evaporator 100 of the adjacent series magnetic suspension centrifugal heat pump are also connected through the connecting branch pipe 271, and the evaporator 100 is connected with the circulating water main pipe 261, the connecting branch pipe 271 is connected with the circulating water main pipe 261 through the bypass pipe 272, the connecting branch pipe 271 is provided with a switch valve 28, and the circulating water main pipe 261 is also provided with a switch valve 28. When any magnetic suspension centrifugal heat pump fails or the circulating water working condition does not meet the requirements or the municipal return water (heating water flow is too small), the switch valve 28 on the connecting branch pipe 271 is automatically closed, the corresponding switch valve 28 on the heating water main pipe 262 / circulating water main pipe 261 is automatically opened, and the water flows through the main pipe into the next magnetic suspension centrifugal heat pump; or when the municipal return water is insufficient, the switch valves 28 on the connecting branch pipes 271 of a plurality of magnetic suspension centrifugal heat pumps are closed, and the switch valves 28 on the corresponding main pipes are opened, and the water flows through the heating water main pipe 262 / circulating water main pipe 261.

[0093] The application can realize step-by-step heating and temperature rising by the setting of the heating water main pipe 262, the connecting branch pipe 271, the bypass pipe 272 and the circulating water main pipe 261. The industrial waste heat is absorbed by the magnetic suspension centrifugal heat pump step by step for recycling. The magnetic suspension centrifugal heat pump set can realize linear single set high-power high-grade hot water output through the whole set flow control. The system can operate in variable conditions, improve stability and efficiency, reduce the pipe gallery of the waste heat pipe network, save the main pipe, and is easy to operate. The whole system is a single machine complete equipment, which can realize the water temperature from 40℃ to 95℃. The system operates in single pipe, and the unit can be added or reduced. With the change of municipal return water flow, by adjusting the opening and closing of the switch valve 28 on the connecting branch pipe 271 and the bypass pipe 272, the problem of too high heating water outlet temperature caused by small flow can be solved, and the vicious cycle of poor condensing effect, insufficient working medium circulation and worse heat exchange caused by small flow can be avoided, so that the heat pump energy efficiency is stable, and the heat exchange efficiency of the system under different conditions is ensured.

[0094] In the transportation of hot water in the long-distance pipe network, the temperature will decay due to the long distance of the long-distance pipe network. In order to ensure the heat exchange efficiency and cost of the primary side of the heat exchange station, the water supply temperature is increased and the supply and return water temperature difference is increased, so as to reduce the flow, thereby reducing the water pump energy consumption and pipe investment cost.

[0095] The number of paths of the second-level waste heat circulation 2, the third-level waste heat circulation 3, the fourth-level waste heat circulation 4, the cooling circulation unit 6 and the heat utilization end temperature rising unit is the same in the embodiment, which is divided into five paths. In other embodiments, the number of paths of the second-level waste heat circulation 2, the third-level waste heat circulation 3, the fourth-level waste heat circulation 4, the cooling circulation unit 6 and the heat utilization end temperature rising unit can be flexibly adjusted according to the waste heat water amount and the heating water amount (i.e. the municipal return water amount). When the waste heat water amount and the heating water amount are large, the parallel path number can be increased to adapt to the load demand. When the waste heat water amount and the heating water amount are small, the parallel path number can be reduced to adapt to the load demand. The embodiment improves the flow matching capacity and the system heating capacity through the parallel design of multiple lines such as five lines.

[0096] The chemical waste heat cascade utilization system of the embodiment adopts multi-stage waste heat recovery, covers a wide temperature range of 59.4-80 DEG C waste heat, realizes energy cascade utilization through staged treatment plate exchange and magnetic suspension centrifugal heat pump, and the comprehensive recovery rate is greater than 85%; the steam condensate is switched according to the season, is connected to the 59.4 DEG C pipeline in the heating season, is connected to the 40 DEG C pipeline in the non-heating season, and the energy saving rate is improved by 15% throughout the year; through three median values of temperature sensors and interlocking regulating valves of flowmeters, accurate temperature control and flow equalization distribution of ± 0.5 DEG C are realized. And the five-way parallel structure is convenient for expansion, and is suitable for different scale chemical industrial parks; the synergistic effect of the magnetic suspension centrifugal heat pump and the superconducting heat core heat pump realizes the maximization of energy efficiency. Through temperature matching, cascade utilization and intelligent control, a breakthrough is realized from low-efficiency discharge to high-value reuse of chemical waste heat, which is a benchmark technology in the field of industrial energy saving.

[0097] Based on the above ideal embodiments according to the application, through the above description, relevant personnel can make various changes and modifications without deviating from the technical idea of the application. The technical scope of the application is not limited to the content of the specification, and must be determined according to the scope of the claims.

Claims

1. A cascade utilization system for chemical waste heat, characterized in that, include: The waste heat circulation unit is used to process multi-stage waste heat, which includes a first-stage waste heat circulation (1) at 59.4 / 40℃, a second-stage waste heat circulation (2) at 50 / 35℃, a third-stage waste heat circulation (3) at 50 / 42℃, a fourth-stage waste heat circulation (4) at 40 / 32℃, and a fifth-stage waste heat circulation (5) at 80 / 35℃. Cooling circulation unit (6) is used to exchange heat between the 32°C cooling water and the waste heat circulation unit to raise the temperature to 40°C; Steam-condensate unit (7) is used for cooling and depressurizing steam and seasonal distribution of condensate at 90°C. Hot-end heating units are used for heating municipal heating, process hot water, and heat tracing. Control unit (9) is used for dynamic adjustment of temperature and flow rate of each unit; The first stage waste heat cycle (1) includes a 59.4℃ water supply pipe (101), a fourth plate heat exchanger (10) and a 40℃ return water pipe (102). The water output from the 59.4℃ water supply pipe (101) is heated to 40℃ by the fourth plate heat exchanger (10) and then enters the 40℃ return water pipe (102), and is combined with the 90℃ condensate according to seasonal switching. The second-stage waste heat circulation (2) is divided into multiple paths, 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 heated to 42°C by the third plate heat exchanger (12), and then enters the evaporators (100) of the first magnetic levitation centrifugal heat pump (13) and the second magnetic levitation centrifugal heat pump (14) to be cooled to 35°C before entering the second plate heat exchanger (11) for heat preservation before entering the 35°C return water pipe (202). The third-stage waste heat circulation (3) is divided into multiple paths, 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 water 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 return water pipe (302). The fourth-stage waste heat circulation (4) is divided into multiple paths, each of which includes a 40°C water supply pipe (401), a first plate heat exchanger (17) and a 32°C return water 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 return water 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 one (20), a magnetic levitation centrifugal heat pump two (21), a magnetic levitation centrifugal heat pump three (22), a magnetic levitation centrifugal heat pump four (23), and a 35°C return water pipe one (502). The water output from the 80°C water supply pipe (501) passes through the evaporator of the first absorption heat pump (18). 100) is cooled to 69°C, and then cooled to 58°C by the evaporator (100) of the second absorption heat pump (19). Then it is cooled to 42°C by the evaporators (100) of the magnetic levitation centrifugal heat pump one (20), magnetic levitation centrifugal heat pump two (21), magnetic levitation centrifugal heat pump three (22), and magnetic levitation centrifugal heat pump four (23) before entering the 35°C return water pipe one (502). Each time it passes through a magnetic levitation centrifugal heat pump, it is cooled by 4°C. The steam-condensate unit (7) includes 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) is cooled to 90°C condensate after passing through a de-heating and pressure reducing device (25). The 90°C condensate in the 90°C condensate pipe (72) is connected to the 59.4°C water supply pipe (101) of the first-stage waste heat cycle (1) during the heating season, and to the 40°C water return pipe (102) of the first-stage waste heat cycle (1) during the non-heating season.

2. The chemical waste heat cascade utilization system according to claim 1, characterized in that: Each of the second-stage waste heat cycle (2) and the third-stage waste heat cycle (3) is equipped with a circulation pump (24).

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

4. The chemical waste heat cascade utilization system according to claim 2, characterized in that: Each path of the third-stage waste heat circulation (3) is equipped with a flow meter and a regulating valve. The circulation pump (24) of each path of the third-stage waste heat circulation (3) controls the opening of the regulating valve by detecting the flow of the flow meter on that path, so as to ensure that the flow of the five paths meets the requirements. Each path of the second-stage waste heat circulation (2) is equipped with a flow meter and a regulating valve. The circulation pump (24) of each path of the second-stage waste heat circulation (2) controls the opening of the regulating valve by detecting the flow of the flow meter on that path, so as to ensure that the flow of the five paths meets the requirements.

5. The chemical waste heat cascade utilization system according to claim 1, characterized in that: The cooling circulation unit (6) is divided into multiple paths, each of which includes 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 heated to 40°C by the second plate heat exchanger (11) and then enters the 40°C cooling water return pipe (602).

6. The chemical waste heat cascade utilization system according to claim 5, characterized in that: When the municipal return water temperature is detected to be below 35°C or the flow rate is below the set threshold, the second plate heat exchanger (11) will automatically operate to maintain the heat source side temperature at above 35°C.

7. 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 path includes a 30℃ 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-stage magnetic levitation centrifugal heat pump (16), a first-stage magnetic levitation centrifugal heat pump (15), and an 88.2℃ municipal water supply pipe (812). This path is further divided into two branches. The first branch: the water output from the 30℃ municipal return water pipe (811) is heated to 38℃ by the first plate heat exchanger (17) and the water output from the 40℃ water supply pipe (401) in the fourth-stage waste heat cycle (4), and then passes through the fourth plate heat exchanger (10). The water output from the 59.4℃ water supply pipe (101) in the first-stage waste heat cycle (1) is heated to 57.4℃; the water output from the 30℃ municipal return water pipe (811) in the second branch is heated to 47℃ by the third plate heat exchanger (12) and the water output from the 50℃ water supply pipe (201) in the second-stage waste heat cycle (2), and then enters the condenser (200) of the first magnetic levitation centrifugal heat pump (13) and the second magnetic levitation centrifugal heat pump (14) to be heated to 60.5℃, and mixes with the 57.4℃ heating water in the first branch to 59℃, and then enters the condenser (200) of the second-stage magnetic levitation centrifugal heat pump (16) and the first-stage magnetic levitation centrifugal heat pump (15) to be heated to 86.4℃, and then enters the 88.2℃ municipal water supply pipe (812). The remaining circuits include a 30℃ 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-stage magnetic levitation centrifugal heat pump (16), a first-stage magnetic levitation centrifugal heat pump (15), and an 88.2℃ municipal supply water pipe (812). The water output from the 30℃ municipal return water pipe (811) passes through the first plate heat exchanger (17) and the 40℃ supply water pipe in the fourth-stage waste heat circulation (4). The water output from 401 is heated to 36.8°C, and then heats up to 45.5°C by the water output from the 50°C water supply pipe (201) in the second stage waste heat cycle (2) through the third plate heat exchanger (12). It 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).

8. The chemical waste heat cascade utilization system according to claim 7, 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. 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 water 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 other branches of the hot end heating unit receives 45.5°C water after heat exchange with the third plate heat exchanger (12). The condenser (200) of the next magnetic levitation centrifugal heat pump receives water that has been heat exchanged with the condenser (200) and economizer (300) of the previous magnetic levitation centrifugal heat pump and then mixed.

9. The chemical waste heat cascade utilization system according to claim 1, characterized in that: The process hot water circulation (82) in the heat-generating 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 the absorbers of the first absorption heat pump (18) and the second absorption heat pump (19), and then heated to 105°C by the condensers (200) of the first absorption heat pump (18) and the second absorption heat pump (19), before entering the 105°C process hot water supply pipe (822).

10. The chemical waste heat cascade utilization system according to claim 1, characterized in that: The heat tracing circulation (83) in the heating unit includes an 85°C heat tracing return water pipe (831), a magnetic levitation centrifugal heat pump one (20), a magnetic levitation centrifugal heat pump two (21), a magnetic levitation centrifugal heat pump three (22), a magnetic levitation centrifugal heat pump four (23), and a 90°C heat tracing supply water pipe (832). The heat tracing hot water output from the 85°C heat tracing return water pipe (831) enters the condensers of the magnetic levitation centrifugal heat pump one (20), magnetic levitation centrifugal heat pump two (21), magnetic levitation centrifugal heat pump three (22), and magnetic levitation centrifugal heat pump four (23) respectively to be heated to 90°C, and then enters the 90°C heat tracing supply water pipe (832).

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