Flash condensate waste heat recycling system and method

Abstract

The invention provides a flash condensate waste heat recycling system and method, and belongs to the technical field of waste heat recycling. According to the system and the method, by means of gas-liquid heat exchange with nitrogen, the temperature of flash evaporation condensate at 125-135 DEG C obtained through flash evaporation of a steam flash evaporation tank is reduced to 70-80 DEG C, and cavitation of an external hot water delivery pump and the liquid impact risk when the condensate is mixed with condensate at the temperature lower than 100 DEG C are avoided; and meanwhile, desalted water is prevented from being used for cooling the flash evaporation condensate, so that the cost is saved. The waste heat of the flash evaporation condensate obtained through flash evaporation of the steam flash evaporation tank is utilized, the temperature of 20-30 DEG C of nitrogen is increased to 70-80 DEG C, the use amount of a steam heater is reduced, energy consumption is reduced, and the use amount of the steam heater is reduced by about 1 ton / hour. The cost recovery period of the system is about half a year, and economic benefits are good.

Description

Technical Field

[0001] The invention belongs to the technical field of waste heat recycling, and relates to a system and method for recycling waste heat of flash condensate. Background Art

[0002] The devolatilization drying system is a system for removing polymer solvents during the synthesis of polycarbonate. It has the advantages of low energy consumption, low pollution and low cost.

[0003] In the devolatilization drying system, after the high-temperature steam with a pressure of 1.0Mpa enters the flash system and flashes out 0.2MPa of steam, the remaining flash condensate still has a temperature of about 130°C. If this part of the flash condensate is directly sent out through the heat pump, it is easy to cause pump cavitation due to the high temperature, affecting the performance of the pump. In addition, if this part of the flash condensate is mixed with other low-temperature condensate, it will cause liquid hammer due to the large temperature difference, causing safety problems.

[0004] In order to prevent the above safety problems, desalted water is usually added to this part of the flash condensate to reduce the temperature to 100°C, and then it is transported to the condensate network to be used as water for other devices. However, this treatment method wastes the heat carried by this part of the flash condensate, resulting in energy waste; at the same time, the use of desalted water also increases the treatment cost. Summary of the invention

[0005] The object of the present invention is to provide a system and method for recycling waste heat of flash condensate, so as to solve the problem of heat waste of flash condensate after flash evaporation treatment.

[0006] To achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present application provides a flash condensate waste heat recycling system, comprising a steam flash tank, a corrugated heat exchanger and a condensate collecting tank which are sequentially connected, and the corrugated heat exchanger is also connected to a nitrogen drying tower.

[0007] Preferably, the corrugated heat exchanger is connected to a liquid inlet pipeline and a liquid outlet pipeline respectively, and the liquid inlet pipeline is connected to the steam flash tank, and the liquid outlet pipeline is connected to the condensate collecting tank.

[0008] Preferably, a condensate flowmeter and a liquid inlet regulating valve are provided on the liquid inlet pipeline, and the liquid inlet regulating valve is located between the condensate flowmeter and the corrugated heat exchanger.

[0009] Preferably, a liquid outlet regulating valve is provided on the liquid outlet pipeline.

[0010] Preferably, a flow regulating valve group is further provided between the steam flash tank and the liquid inlet pipeline.

[0011] Preferably, the steam flash tank is also connected to a steam regulating valve group.

[0012] In a second aspect, the present application provides a method for recycling waste heat of flash condensate, comprising: exchanging heat between a flash condensate at 125-135°C flashed out from a steam flash tank and nitrogen at 20-30°C in a corrugated heat exchanger to obtain a condensate at a temperature of 70-80°C and nitrogen at 70-80°C, and discharging the condensate after heat exchange into a condensate collection tank at a temperature of 80-90°C.

[0013] Preferably, the flow rate of the flash condensate is 15m 3 / h, the flow rate of nitrogen is 50000m 3 / h.

[0014] The present invention has the following beneficial effects: (1) By exchanging gas-liquid heat with nitrogen, the temperature of the flash condensate at 125-135°C flashed out of the steam flash tank is reduced to 70-80°C, thus avoiding the risk of cavitation of the external hot water pump and liquid hammer when mixing with the condensate at a temperature below 100°C. At the same time, it also avoids the use of desalted water to cool the flash condensate, thus saving costs.

[0015] (2) The waste heat of the flash condensate flashed out of the steam flash tank is used to raise the temperature of nitrogen at 20-30°C to 70-80°C, reducing the use of steam heaters and saving energy. The use of steam heaters is reduced by about 1 ton / hour.

[0016] (3) The cost recovery period of this system is about half a year, with good economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of the structure of a flash condensate waste heat recycling system provided in an embodiment of the present application; Symbols represent: 1-steam flash tank, 2-corrugated heat exchanger, 3-condensate collection tank, 4-nitrogen drying tower, 5-liquid inlet pipeline, 6-liquid outlet pipeline, 7-condensate flow meter, 8-liquid inlet regulating valve, 9-liquid outlet regulating valve, 10-flow regulating valve group, 11-steam regulating valve group. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is further explained and illustrated by means of specific embodiments below.

[0019] Example 1 The embodiment of the present application provides a flash condensate waste heat recycling system, which includes a steam flash tank 1, a corrugated heat exchanger 2 and a condensate collecting tank 3 which are connected in sequence, and the corrugated heat exchanger 2 is also connected to a nitrogen drying tower 4. Figure 1 shown.

[0020] The steam flash tank 1 is a component for flashing high-temperature steam in the devolatilization drying system, and is connected to the corrugated heat exchanger 2 and the steam regulating valve group 11 respectively. The high-temperature steam flashes in the steam flash tank 1 using its high-temperature heat to flash out flash condensate and steam, wherein the steam is discharged under the regulation of the steam regulating valve group 11. The flash condensate still has a temperature of 125-135°C. In the embodiment of the present application, this part of the flash condensate is transported to the corrugated heat exchanger 2.

[0021] The corrugated heat exchanger 2 is a component for realizing gas-liquid heat exchange between the flash condensate and nitrogen. Specifically, the corrugated heat exchanger 2 is connected to the liquid inlet pipeline 5 and the liquid outlet pipeline 6, respectively, and the liquid inlet pipeline 5 is connected to the steam flash tank 1, and the liquid outlet pipeline 6 is connected to the condensate collecting tank 3. Therefore, the flash condensate flashed out of the steam flash tank 1 enters the corrugated heat exchanger 2 through the liquid inlet pipeline 5, and after heat exchange with nitrogen, it is discharged into the condensate collecting tank 3 through the liquid outlet pipeline 6.

[0022] In order to control the flow rate and feeding time of the flash condensate entering the corrugated heat exchanger 2, a condensate flowmeter 7 and a liquid inlet regulating valve 8 are provided on the liquid inlet pipeline 5, and the liquid inlet regulating valve 8 is located between the condensate flowmeter 7 and the corrugated heat exchanger 2. Similarly, in order to control the start and stop of the condensate after heat exchange in the corrugated heat exchanger 2 flowing to the condensate collecting tank 3, a liquid outlet regulating valve 9 is provided on the liquid outlet pipeline 6. Further, in order to control the flow rate of the flash condensate flashed out of the steam flash tank 1 entering the liquid inlet pipeline 5, a flow regulating valve group 10 is also provided between the steam flash tank 1 and the liquid inlet pipeline 5.

[0023] The nitrogen drying tower 4 is a component for drying nitrogen. The dried nitrogen is introduced into the corrugated heat exchanger 2 to exchange heat with the flash condensate to increase the temperature of the nitrogen.

[0024] Example 2 An embodiment of the present application provides a method for recycling waste heat of flash condensate, which comprises: exchanging heat between a flash condensate at 125-135°C flashed out from a steam flash tank and nitrogen at 20-30°C in a corrugated heat exchanger to obtain a condensate at a temperature of 70-80°C and nitrogen at 70-80°C, and discharging the condensate after heat exchange into a condensate collection tank at a temperature of 80-90°C.

[0025] Specifically, the flash condensate at 125-135°C flashed out from the steam flash tank 1 is transported to the corrugated heat exchanger 2 through the flow regulating valve group 10 and the liquid inlet pipeline 5. At the same time, the nitrogen dried in the nitrogen drying tower 4 on the adjacent floor and position is introduced into the corrugated heat exchanger 2. In the corrugated heat exchanger 2, the flash condensate at 125-135°C is heat exchanged with the nitrogen at 20-30°C to obtain a condensate at a temperature of 70-80°C and nitrogen at 70-80°C, thereby realizing the secondary utilization of the flash condensate, recovering energy, and increasing the temperature of the nitrogen. In the embodiment of the present application, the flow rate of the flash condensate is 15m 3 / h, the flow rate of nitrogen is 50000m 3 / h.

[0026] By utilizing the height difference of the floors, the cooled condensate enters the condensate collection tank 3 through the liquid outlet pipeline 6. Since the temperature of the condensate after heat exchange is reduced to 70-80°C, cavitation of the external hot water pump is avoided; at the same time, when it is mixed with the condensate below 100°C in the condensate collection tank 3, it will not cause pipeline vibration, and thus will not generate the risk of liquid hammer, thereby improving safety. In addition, through heat exchange with nitrogen, the use of desalted water to cool the flash condensate is avoided, saving costs.

[0027] The nitrogen heated to 70-80℃ is transported to the steam heater through the nitrogen delivery fan, so that the nitrogen is heated to about 135℃ by the steam heater and then used directly. Since the steam heater heats the nitrogen at 70-80℃ to about 135℃ instead of heating the nitrogen at 20-30℃ to about 135℃, the use of the steam heater can be greatly reduced, saving energy consumption, and the use of the steam heater is reduced by about 1 ton / hour.

[0028] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A flash condensate waste heat recycling system, characterized in that: It comprises a steam flash tank (1), a corrugated heat exchanger (2) and a condensate collecting tank (3) which are connected in sequence, and the corrugated heat exchanger (2) is also connected to a nitrogen drying tower (4).

2. The flash condensate waste heat recycling system according to claim 1, characterized in that: The corrugated heat exchanger (2) is respectively connected to a liquid inlet pipeline (5) and a liquid outlet pipeline (6), and the liquid inlet pipeline (5) is connected to the steam flash tank (1), and the liquid outlet pipeline (6) is connected to the condensate collection tank (3).

3. The flash condensate waste heat recycling system according to claim 2, characterized in that: The liquid inlet pipeline (5) is provided with a condensate flow meter (7) and a liquid inlet regulating valve (8), and the liquid inlet regulating valve (8) is located between the condensate flow meter (7) and the corrugated heat exchanger (2).

4. The flash condensate waste heat recycling system according to claim 2, characterized in that: The liquid outlet pipeline (6) is provided with a liquid outlet regulating valve (9).

5. The flash condensate waste heat recycling system according to claim 2, characterized in that: A flow regulating valve group (10) is also provided between the steam flash tank (1) and the liquid inlet pipeline (5).

6. The flash condensate waste heat recycling system according to claim 1, characterized in that: The steam flash tank (1) is also connected to a steam regulating valve group (11).

7. A method for recycling waste heat of flash condensate, characterized in that: include: The flash condensate at 125-135°C flashed out from the steam flash tank exchanges heat with nitrogen at 20-30°C in a corrugated heat exchanger to obtain condensate at a temperature of 70-80°C and nitrogen at 70-80°C. The condensate after heat exchange is discharged into a condensate collection tank at a temperature of 80-90°C.

8. The flash condensate waste heat recycling method according to claim 7, characterized in that: The flow rate of the flash condensate is 15m 3 / h, the flow rate of nitrogen is 50000m 3 / h.

Images