Flow-stabilizing waste heat closed type cyclic utilization method, circulating system and application of circulating system

Abstract

According to the waste heat closed type cyclic utilization method with the stable flow, the circulating system and the application of the circulating system, the heated temperature of heating medium water is controlled by adjusting steam condensate, the heated heating medium water enters the hot water buffer tank, when the water level of the hot water buffer tank drops, it is indicated that the loss of the heating medium water in the whole closed cycle is large, and therefore the energy consumption is reduced. Steam condensate is adopted for supplementing water, the pressure of a hot water buffer tank is controlled through nitrogen, the pressure entering a refrigeration station and a process device is kept stable, when the flow of needed chilled water is certain, the temperature of the chilled water entering the process device depends on the circulation amount of whole heat medium water, and pump backflow is adjusted through the temperature. When the temperature of the hot water outlet of the refrigeration station fluctuates, the temperature of the hot water entering the process device is controlled to be stable by adjusting the backflow flow after the pump.

Description

Technical Field

[0001] The present invention belongs to the field of heat recovery, and specifically relates to a waste heat recovery technology combining process hot water with chilled water. Aiming at the situation where chilled water and heat medium water are used simultaneously in chemical plants, a waste heat closed circulation utilization method with a stable flow rate, a circulation system and its application are provided. Background Art

[0002] Chilled water, circulating water and steam are often used in chemical plants. When the temperature of the cooled medium is high, the use of circulating water is prone to scaling and is wasteful. The production of chilled water consumes a lot of electricity. If chilled water, heat medium water and steam condensate are used together, a lot of circulating water and electricity can be saved, and the temperature of the discharged condensate can be reduced, achieving three goals at one stroke.

[0003] The return water of heat medium water can be used as the heat source of lithium bromide refrigeration unit, and after the refrigeration unit is used, it can be returned to the process device as the cold source of the heat exchanger. However, the heat required for heat removal in most devices does not match the heat required for producing chilled water. At the same time, there are different heat losses in different seasons, and the deviation fluctuates within a certain range. In addition, even if it is exactly matched, if there is subsequent optimization, it will break the balance and become a bottleneck. Summary of the invention

[0004] Some condensers in chemical plants can use heat medium water to cool process materials, and some coolers need chilled water for further cooling. Energy saving can be achieved through the combined use of heat medium water, chilled water, and steam condensate. In order to achieve stable operation of the heat medium water return cycle process, the present invention provides a closed-loop waste heat recycling method with a stable flow rate, a circulation system, and its application.

[0005] One of the purposes of the present invention is to provide a closed-loop waste heat utilization method with a stable flow rate, comprising the following steps:

[0006] (1) The heat medium water I after heat exchange in the process unit enters the heat exchanger for heating;

[0007] (2) The heat medium water II heated by the heat exchanger is sent to the hot water buffer tank;

[0008] (3) The hot water buffer tank transports heat medium water III to the refrigeration station;

[0009] (4) The heat medium water IV after being used in the refrigeration station is circulated to the process equipment for recycling;

[0010] Wherein, the heat exchanger uses steam condensate as the heating medium.

[0011] According to the present invention, in step (1):

[0012] After heat exchange in the process device, the temperature of the heat medium water I is 75-95°C, preferably 90-95°C;

[0013] The steam condensate comes from a process unit; and / or,

[0014] The temperature of the steam condensate is 110-115°C.

[0015] According to the present invention, in step (2):

[0016] The temperature of the heat medium water II heated by the heat exchanger is controlled by adjusting the flow rate of the steam condensate;

[0017] After being heated by the heat exchanger, the temperature of the heat medium water II is 90-120°C, preferably 95-115°C;

[0018] The water level in the hot water buffer tank is maintained by using steam condensate. Preferably, the water level in the hot water buffer tank is maintained at 1 / 2 to 2 / 3 of the height from top to bottom of the hot water buffer tank.

[0019] The temperature of the hot water in the hot water buffer tank is 90-115°C, preferably 95-110°C;

[0020] Use nitrogen to control the pressure in the hot water buffer tank;

[0021] The pressure in the hot water buffer tank is controlled at 0.3-0.5 MPaG, preferably 0.35-0.45 MPaG.

[0022] According to the present invention, in step (3):

[0023] The pressure of the heat medium water III entering the refrigeration station is controlled at 0.75-0.90 MPaG, preferably 0.8-0.85 MPaG;

[0024] The temperature of the heat medium water III entering the refrigeration station is 85-115°C, preferably 92-110°C;

[0025] When the temperature of the heat medium water III transported by the hot water buffer tank fluctuates, part of the heat medium water III is sent back to the hot water buffer tank for temperature adjustment. The amount of the returned heat medium water III can be adjusted in time according to the temperature of the heat medium water III transported by the hot water buffer tank, so that the temperature of the heat medium water III that finally enters the refrigeration station can be controlled at 85-115°C.

[0026] According to the present invention, in step (4):

[0027] After heat exchange in the refrigeration station, the temperature of the heat medium water IV is 60-80°C, preferably 65-75°C;

[0028] The pressure of the heat medium water IV circulating to the process device is controlled at 0.45-0.65 MPaG, preferably 0.5-0.6 MPaG;

[0029] When the temperature of the heat medium water IV circulating to the process unit fluctuates, the temperature is adjusted by returning part of the heat medium water III to the hot water buffer tank.

[0030] In addition, when the temperature of heat medium water IV fluctuates after heat exchange in the refrigeration station, part of heat medium water III can be sent back to the hot water buffer tank for temperature adjustment by means of an adjusting pump. The amount of heat medium water III sent back can be adjusted in time according to the temperature of heat medium water IV, so that the final temperature of heat medium water IV can be controlled at 60-80°C.

[0031] A second object of the present invention is to provide a waste heat closed circulation system with a stable flow rate, which is used to implement the above-mentioned waste heat closed circulation utilization method with a stable flow rate to utilize the waste heat in the process device in a closed circulation.

[0032] According to the present invention, the system comprises a process device, a heat exchanger, a hot water buffer tank and a refrigeration station connected in sequence by pipelines, and the refrigeration station is connected to the process device by pipelines to form a closed circulation pipeline. The refrigeration station can be a lithium bromide unit in industry.

[0033] According to an embodiment of the present invention, in the waste heat closed circulation system with a stable flow rate:

[0034] A three-way regulating valve is arranged on the heating medium inlet pipeline of the heat exchanger, and the heating medium is steam condensate, preferably steam condensate from a process device;

[0035] The hot water buffer tank side line is provided with a steam condensate inlet and a heat medium water II inlet;

[0036] A nitrogen inlet and a gas discharge outlet are also provided on the top of the hot water buffer tank to adjust the pressure in the hot water buffer tank;

[0037] A heat medium water III outlet is arranged at the bottom of the hot water buffer tank and is connected to the refrigeration station by a pipeline.

[0038] According to an embodiment of the present invention, in the waste heat closed circulation system with a stable flow rate:

[0039] A branch is provided on the heating medium inlet pipeline of the heat exchanger to connect to the steam condensate side line inlet of the hot water buffer tank;

[0040] The steam condensate sideline inlet of the hot water buffer tank is arranged above the water level in the hot water buffer tank, preferably at 1 / 4 to 1 / 2 of the hot water buffer tank from top to bottom;

[0041] The heat medium water II inlet of the hot water buffer tank is arranged above the water level in the hot water buffer tank, preferably arranged at 1 / 4 to 1 / 2 from the top to the bottom of the hot water buffer tank;

[0042] The pipeline of the heat medium water III is also provided with a branch connected to the hot water buffer tank, which is used to return part of the heat medium water III to the hot water buffer tank;

[0043] The temperature of the heat medium water after heat exchange in the heat exchanger is adjusted by adjusting the three-way regulating valve to control the flow rate of the steam condensate, thereby adjusting the temperature of the heat medium water in the hot water buffer tank to a suitable temperature.

[0044] The third object of the present invention is to provide a method for utilizing the waste heat closed cycle with a stable flow rate or a waste heat closed cycle system with a stable flow rate, and to apply the waste heat combination between a chemical plant and a refrigeration station.

[0045] The waste heat closed circulation system with stable flow rate adopted by the present invention can achieve:

[0046] 1) The temperature of the heat medium water entering the process device is required to be controlled between 65 and 75°C;

[0047] 2) The return temperature of the heat medium water entering the refrigeration station is required to be controlled between 92 and 110°C;

[0048] 3) The pressure entering the process device is required to be 0.5-0.6MPaG, and the pressure entering the refrigeration station is controlled at 0.8-0.85MPaG;

[0049] 4) The heat medium water is in a closed cycle, and the device is replenished with water when it is "running, bubbling, dripping, or leaking";

[0050] 5)Stable pressure.

[0051] like Figure 1 The process flow, the heat medium water I from the process device is heated by the steam condensate produced by the device through a heat exchanger, and the target temperature of the heating depends on the heat required by the refrigeration station that produces chilled water. The present invention uses a three-way regulating valve to adjust the steam condensate to control the heating temperature of the heat medium water in the heat exchanger. The heated heat medium water enters the hot water buffer tank. When the water level of the hot water buffer tank drops, it means that the heat medium water loss of the entire closed-loop circulation is large. Steam condensate is used for water replenishment, and nitrogen is used to control the pressure of the hot water buffer tank to maintain the pressure entering the refrigeration station and the process device stable. When the flow rate of chilled water required by the process device is constant, the temperature entering the process device depends on the circulation volume of the entire heat medium water. The temperature of the heat medium water entering the refrigeration station is adjusted by pump reflux. When the temperature of the heat medium water at the outlet of the hot water buffer tank fluctuates, the heat medium water reflux flow is controlled by adjusting the pump to achieve effective control of the heat medium water temperature, thereby controlling the temperature of the hot water entering the process device to be stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1Schematic diagram of the waste heat closed circulation system used in the embodiment of the present invention. In the figure, 1-process device, 2-heat exchanger, 3-hot water buffer tank, 4-lithium bromide unit, 5-heat medium water I delivery pipeline, 6-heat medium water II delivery pipeline, 7-heat medium water III delivery pipeline, 8-heat medium water IV delivery pipeline, 9-steam condensate generating device, 10-three-way regulating valve, 11-exhaust gas collection tank, 12-nitrogen storage tank, 13-steam condensate external storage tank, 14-heat medium water delivery pump. DETAILED DESCRIPTION

[0053] The present invention provides a closed-loop waste heat utilization method with a stable flow rate, comprising the following steps:

[0054] (1) The heat medium water I after heat exchange in the process unit enters the heat exchanger for heating;

[0055] (2) The heat medium water II heated by the heat exchanger is sent to the hot water buffer tank;

[0056] (3) The hot water buffer tank transports heat medium water III to the refrigeration station;

[0057] (4) The heat medium water IV after being used in the refrigeration station is circulated to the process equipment for recycling;

[0058] Wherein, the heat exchanger uses steam condensate as the heating medium.

[0059] According to the present invention, in step (1):

[0060] After heat exchange in the process device, the temperature of the heat medium water I is 75-95°C, preferably 90-95°C;

[0061] The steam condensate comes from a process unit;

[0062] Preferably, the temperature of the steam condensate is 110-115°C.

[0063] According to the present invention, in step (2):

[0064] The temperature of the heat medium water II heated by the heat exchanger is controlled by adjusting the flow rate of the steam condensate;

[0065] After being heated by the heat exchanger, the temperature of the heat medium water II is 90-120°C, preferably 95-115°C;

[0066] The water level in the hot water buffer tank is maintained by using steam condensate. Preferably, the water level in the hot water buffer tank is maintained at 1 / 2 to 2 / 3 of the height from top to bottom of the hot water buffer tank.

[0067] The temperature of the hot water in the hot water buffer tank is 90-115°C, preferably 95-110°C;

[0068] Use nitrogen to control the pressure in the hot water buffer tank;

[0069] The pressure in the hot water buffer tank is controlled at 0.3-0.5 MPaG, preferably 0.35-0.45 MPaG.

[0070] According to the present invention, in step (3):

[0071] The pressure of the heat medium water III entering the refrigeration station is controlled at 0.75-0.90 MPaG, preferably 0.8-0.85 MPaG;

[0072] The temperature of the heat medium water III entering the refrigeration station is 85-115°C, preferably 92-110°C.

[0073] According to the present invention, in step (4):

[0074] After heat exchange in the refrigeration station, the temperature of the heat medium water IV is 60-80°C, preferably 65-75°C;

[0075] The pressure of the heat medium water IV circulating to the process device is controlled at 0.45-0.65 MPaG, preferably 0.5-0.6 MPaG.

[0076] When the temperature of heat medium water III or heat medium water IV fluctuates, the temperature is adjusted by returning part of heat medium water III to the hot water buffer tank.

[0077] The present invention also provides a waste heat closed circulation system with a stable flow rate, which is used to implement the above-mentioned waste heat closed circulation utilization method with a stable flow rate to utilize the waste heat in the process device in a closed circulation.

[0078] According to the present invention, the system comprises a process device, a heat exchanger, a hot water buffer tank and a refrigeration station connected in sequence by pipelines, and the refrigeration station is connected to the process device by pipelines to form a closed circulation pipeline. In the embodiment of the present invention, the refrigeration station adopts a lithium bromide unit.

[0079] According to an embodiment of the present invention, in the waste heat closed circulation system with a stable flow rate:

[0080] A three-way regulating valve is arranged on the heating medium inlet pipeline of the heat exchanger, and the heating medium is steam condensate, preferably steam condensate from a process device;

[0081] The hot water buffer tank side line is provided with a steam condensate inlet and a heat medium water II inlet;

[0082] A nitrogen inlet and a gas discharge outlet are also provided on the top of the hot water buffer tank to adjust the pressure in the hot water buffer tank;

[0083] A heat medium water III outlet is arranged at the bottom of the hot water buffer tank and is connected to the refrigeration station by a pipeline.

[0084] According to an embodiment of the present invention, in the waste heat closed circulation system with a stable flow rate:

[0085] A branch is provided on the heating medium inlet pipeline of the heat exchanger to connect to the steam condensate side line inlet of the hot water buffer tank;

[0086] The steam condensate sideline inlet of the hot water buffer tank is arranged above the water level in the hot water buffer tank, preferably at 1 / 4 to 1 / 2 of the hot water buffer tank from top to bottom;

[0087] The heat medium water II inlet of the hot water buffer tank is arranged above the water level in the hot water buffer tank, preferably arranged at 1 / 4 to 1 / 2 from the top to the bottom of the hot water buffer tank;

[0088] A branch is also arranged on the pipeline of the heat medium water III to be connected to the hot water buffer tank.

[0089] According to an embodiment of the present invention, in the waste heat closed circulation system with a stable flow rate:

[0090] A temperature controller is provided on the outlet pipeline of the heat medium water II of the heat exchanger and is electrically connected to the three-way regulating valve at the inlet of the heating medium of the heat exchanger;

[0091] A flow valve is arranged on the pipeline where the steam condensate enters the steam condensate inlet of the hot water buffer tank, and a liquid level controller is arranged on the hot water buffer tank and is electrically connected to the flow valve;

[0092] A flow valve is respectively arranged on the nitrogen inlet pipeline and the gas discharge outlet pipeline at the top of the hot water buffer tank, and a pressure controller is arranged on the top of the hot water buffer tank, which is electrically connected to the flow valves on the nitrogen inlet pipeline and the gas discharge outlet pipeline;

[0093] A flow valve is also provided on the pipeline connecting the heat medium water III to the hot water buffer tank, and a temperature controller is provided on the pipeline connecting the refrigeration station to the process device, which is electrically connected to the flow valve on the pipeline of the heat medium water III returning to the hot water buffer tank.

[0094] In the waste heat closed circulation system with stable flow provided by the present invention, the flow of steam condensate in the heat exchanger is controlled by a three-way regulating valve to control the temperature of the heat medium water II after heat exchange in the heat exchanger, the liquid level in the hot water buffer tank is maintained by pumping in steam condensate for water replenishment, and the pressure of the hot water buffer tank is controlled by releasing exhaust gas and filling in nitrogen. When the hot water entering the refrigeration station fluctuates, part of the heat medium water is returned to the hot water buffer tank by adjusting the pump to adjust the temperature and thus control the temperature of the heat medium water after use in the refrigeration station.

[0095] The process device used in the present invention can be a system in the prior art that requires cooling operation of the system, such as a propylene oxide production device, including a high-pressure circulating methanol pre-cooler, a propylene preheater, a propylene glycol tower condenser, etc.

[0096] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall within the scope of protection of the present invention.

[0097] Example 1

[0098] Combine the following Figure 1 The waste heat closed circulation system with a stable flow rate and the waste heat closed circulation utilization method with a stable flow rate provided in Example 1 are described.

[0099] like Figure 1 As shown, the waste heat closed circulation system with a stable flow rate adopted in Example 1 comprises a process device (1), a heat exchanger (2), a hot water buffer tank (3) and a lithium bromide unit (4) connected in sequence by pipelines, and the lithium bromide unit (4) is connected to the process device (1) by pipelines to form a closed circulation pipeline. A three-way regulating valve (10) is arranged on the heating medium inlet pipeline of the heat exchanger (2), a steam condensate inlet and a heat medium water II inlet are arranged on the side line of the hot water buffer tank (3), and a nitrogen inlet and a gas discharge outlet are also arranged on the top of the hot water buffer tank (3) for adjusting the pressure in the hot water buffer tank (3); a heat medium water III outlet is arranged at the bottom of the hot water buffer tank (3), and is connected to the lithium bromide unit (4) by pipelines. A branch is arranged on the heating medium inlet pipeline of the heat exchanger (2) to be connected to the steam condensate side line inlet of the hot water buffer tank (3). A branch is also arranged on the pipeline of the heat medium water III to be connected to the hot water buffer tank (3). The steam condensate side line inlet of the hot water buffer tank (3) is arranged at 1 / 2 of the hot water buffer tank (3) from top to bottom; and the heat medium water II inlet of the hot water buffer tank (3) is arranged at 1 / 4 of the hot water buffer tank (3) from top to bottom.

[0100] use Figure 1 The waste heat closed circulation system is described in detail by taking the process unit (1) using a propylene oxide production unit as an example, including:

[0101] (1) After heat exchange in the process device, the heat medium water I enters the heat exchanger for heating. After heat exchange in the process device, the temperature of the heat medium water I is 95°C.

[0102] (2) The heat medium water II heated by the heat exchanger is sent to the hot water buffer tank. The heat exchanger uses steam condensate from the process device as the heating medium. The temperature of the steam condensate is 113°C. The flow of the steam condensate is adjusted by a three-way regulating valve so that the temperature of the heat medium water II heated by the heat exchanger is 100°C. The temperature of the heat medium water in the hot water buffer tank is 100°C. The water level in the hot water buffer tank is maintained at 2 / 3 of the hot water buffer tank from top to bottom; nitrogen is used to control the pressure in the hot water buffer tank at 0.4MPaG. When the water level in the hot water buffer tank drops, steam condensate is used to replenish water.

[0103] (3) The hot water buffer tank transports heat medium water III to the lithium bromide unit; the temperature of the heat medium water III entering the lithium bromide unit is 100°C and the pressure is 0.8MPaG.

[0104] (4) The heat medium water IV after being utilized by the lithium bromide unit is circulated to the process unit for recycling; after heat exchange by the lithium bromide unit, the temperature of the heat medium water IV is 70°C and the pressure is 0.6MPaG.

[0105] Example 2

[0106] This embodiment specifically describes the specific implementation process of waste heat recycling by adjusting the reflux flow rate by adjusting the pump when the outlet temperature of the lithium bromide unit fluctuates. The specific operation is as follows:

[0107] use Figure 1 The waste heat closed circulation system is described in detail by taking the process unit (1) using a propylene oxide production unit as an example, including:

[0108] (1) After heat exchange in the process device, the heat medium water I enters the heat exchanger for heating. After heat exchange in the process device, the temperature of the heat medium water I is 95°C.

[0109] (2) The heat medium water II heated by the heat exchanger is sent to the hot water buffer tank. The heat exchanger uses steam condensate as the heating medium. The temperature of the steam condensate is 113°C. The flow of steam condensate is adjusted by a three-way regulating valve so that the temperature of the heat medium water II heated by the heat exchanger is 100°C. The temperature of the heat medium water in the hot water buffer tank is 100°C. The water level in the hot water buffer tank is maintained at 2 / 3 of the hot water buffer tank from top to bottom; nitrogen is used to control the pressure in the hot water buffer tank at 0.35MPaG. When the water level in the hot water buffer tank decreases, steam condensate is used to replenish water.

[0110] (3) The hot water buffer tank transports heat medium water III to the lithium bromide unit. In the waste heat closed circulation method, the temperature of heat medium water III is 95°C and the pressure is 0.85MPaG.

[0111] (4) The temperature of the heat medium water IV after being used by the lithium bromide unit is 80°C and the pressure is 0.6MPaG. Since the heat medium water temperature required by the process unit is 75°C, part of the heat medium water III (about 10%) is refluxed to the hot water buffer tank through the regulating pump, and the heat medium water III (100°C) is transported to the lithium bromide unit after the temperature is adjusted in the hot water buffer tank. The temperature of the heat medium water IV after being used by the lithium bromide unit is 75°C and transported to the process unit for recycling.

[0112] Comparative Example 1

[0113] Taking the steam condensate heat energy recovery integrated device disclosed in patent CN 216845195 U as an example, it is compared with the waste heat closed cycle utilization method and circulation system with a stable flow rate provided by the present invention.

[0114] Patent CN 216845195 U recovers condensate heat energy through lithium bromide unit and reduces the temperature of discharged condensate, but due to large temperature fluctuations, the process device cannot directly reuse the cooled condensate. The present invention can control the temperature of hot water entering the process device to be stable by adjusting the reflux flow after the pump, while recovering the energy of heat medium water and reducing the temperature of discharged condensate.

Claims

1. A closed-loop waste heat utilization method with a stable flow rate, The following steps are involved: (1) The heat medium water I after heat exchange in the process unit enters the heat exchanger for heating; (2) The heat medium water II heated by the heat exchanger is sent to the hot water buffer tank; (3) The hot water buffer tank transports heat medium water III to the refrigeration station; (4) The heat medium water IV after being used in the refrigeration station is circulated to the process equipment for recycling; Wherein, the heat exchanger uses steam condensate as the heating medium.

2. The method according to claim 1, It is characterized in that In the step (1): After heat exchange in the process device, the temperature of the heat medium water I is 75-95°C, preferably 90-95°C; and / or, The steam condensate comes from a process unit; and / or, The temperature of the steam condensate is 110-115°C.

3. The method according to claim 1, It is characterized in that In the step (2): Controlling the temperature of the heat medium water II heated by the heat exchanger by adjusting the flow rate of the steam condensate; and / or, After being heated by the heat exchanger, the temperature of the heat medium water II is 90 to 120°C, preferably 95 to 115°C; and / or, The water level in the hot water buffer tank is maintained by using steam condensate. Preferably, the water level in the hot water buffer tank is maintained at 1 / 2 to 2 / 3 of the height of the hot water buffer tank from top to bottom; and / or, The temperature of the hot water in the hot water buffer tank is 90 to 115° C., preferably 95 to 110° C.; and / or, Using nitrogen to control the pressure in the hot water buffer tank; and / or, The pressure in the hot water buffer tank is controlled at 0.3-0.5 MPaG, preferably 0.35-0.45 MPaG.

4. The method according to claim 1, It is characterized in that In the step (3): The pressure of the heat medium water III entering the refrigeration station is controlled at 0.75-0.90 MPaG, preferably 0.8-0.85 MPaG; and / or, The temperature of the heat medium water III entering the refrigeration station is 85-115°C, preferably 92-110°C; and / or, When the temperature of the heat medium water III delivered by the hot water buffer tank fluctuates, the temperature is adjusted by returning part of the heat medium water III to the hot water buffer tank.

5. The method according to claim 1, It is characterized in that In the step (4): After heat exchange in the refrigeration station, the temperature of the heat medium water IV is 60-80°C, preferably 65-75°C; and / or, The pressure of the heat medium water IV circulating to the process device is controlled at 0.45-0.65 MPaG, preferably 0.5-0.6 MPaG; When the temperature of the heat medium water IV circulating to the process unit fluctuates, the temperature is adjusted by returning part of the heat medium water III to the hot water buffer tank.

6. A waste heat closed circulation system with a stable flow rate, used for implementing the waste heat closed circulation utilization method with a stable flow rate as described in any one of claims 1 to 5 to utilize the waste heat in a process device in a closed circulation.

7. The system according to claim 6, It is characterized in that The device comprises a process device, a heat exchanger, a hot water buffer tank and a refrigeration station which are sequentially connected by pipelines. The refrigeration station is connected to the process device by pipelines to form a closed circulation pipeline.

8. The system according to claim 7, It is characterized in that A three-way regulating valve is arranged on the heating medium inlet pipeline of the heat exchanger, and the heating medium is steam condensate, preferably steam condensate from a process device; and / or, The hot water buffer tank side line is provided with a steam condensate inlet and a heat medium water II inlet; and / or, The top of the hot water buffer tank is also provided with a nitrogen inlet and a gas discharge outlet for adjusting the pressure in the hot water buffer tank; and / or, A heat medium water III outlet is arranged at the bottom of the hot water buffer tank and is connected to the refrigeration station by a pipeline.

9. The system according to claim 8, It is characterized in that A branch is arranged on the heating medium inlet pipeline of the heat exchanger to connect to the steam condensate side line inlet of the hot water buffer tank; and / or, The steam condensate sideline inlet of the hot water buffer tank is arranged above the water level in the hot water buffer tank, preferably at 1 / 4 to 1 / 2 of the hot water buffer tank from top to bottom; and / or, The heat medium water II inlet of the hot water buffer tank is arranged above the water level in the hot water buffer tank, preferably arranged at 1 / 4 to 1 / 2 from top to bottom of the hot water buffer tank; and / or, A branch is also arranged on the pipeline of the heat medium water III to be connected to the hot water buffer tank.

10. The system according to claim 9, It is characterized in that A temperature controller is arranged on the outlet pipeline of the heat medium water II of the heat exchanger and is electrically connected to the three-way regulating valve at the inlet of the heating medium of the heat exchanger; and / or, A flow valve is arranged on the pipeline where the steam condensate enters the steam condensate inlet of the hot water buffer tank, and a liquid level controller is arranged on the hot water buffer tank and is electrically connected to the flow valve; and / or, A flow valve is respectively arranged on the nitrogen inlet pipeline and the gas discharge outlet pipeline at the top of the hot water buffer tank, and a pressure controller is arranged on the top of the hot water buffer tank, which is electrically connected to the flow valves on the nitrogen inlet pipeline and the gas discharge outlet pipeline; and / or, A flow valve is also provided on the branch line connecting the heat medium water III to the hot water buffer tank, and a temperature controller is provided on the pipeline connecting the refrigeration station to the process device, which is electrically connected to the flow valve on the branch line of the heat medium water III returning to the hot water buffer tank.

11. A method for closed-loop recycling of waste heat with a stable flow rate as described in any one of claims 1 to 5 or a closed-loop recycling system for waste heat with a stable flow rate as described in any one of claims 6 to 10, and its application in the waste heat combination between a chemical plant and a refrigeration station.

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