System for producing chilled water by using low-temperature heat of styrene coarse separation tower

Abstract

The utility model discloses a system for producing chilled water by using low-temperature heat of a styrene coarse separation tower, which comprises the styrene coarse separation tower, a hot water heat exchanger, a lithium bromide unit, a chilled water heat exchanger and a dehydrogenation tail gas compressor, a top stream of the styrene coarse separation tower is subjected to heat recovery through a hot water heat exchanger, a hot water outlet of the hot water heat exchanger is connected with a hot water inlet of a lithium bromide unit, a chilled water outlet of the lithium bromide unit is connected with a chilled water heat exchanger, and chilled water cools styrene dehydrogenation tail gas through the chilled water heat exchanger; the chilled water heat exchanger is connected with a dehydrogenation tail gas compressor, and the cooled dehydrogenation tail gas is compressed by the dehydrogenation tail gas compressor. Low-temperature heat at the top of the styrene coarse separation tower is effectively utilized, subsequent air cooling power consumption of a top stream is reduced, normal operation of a lithium bromide unit can be guaranteed, and chilled water generated by the lithium bromide unit is utilized to cool styrene dehydrogenation tail gas.

Description

Technical Field

[0001] This utility model relates to chemical equipment, specifically a system for producing chilled water using a styrene coarse separator at low temperature. Background Technology

[0002] Styrene is a key monomer in synthetic resins, ion exchange resins, and synthetic rubber. Its industrial production mainly employs the ethylbenzene catalytic dehydrogenation method. In this process, ethylbenzene is dehydrogenated under high temperature, negative pressure, and the action of a catalyst to produce styrene and hydrogen gas. Simultaneously, side reactions generate dehydrogenation tail gas containing styrene, unreacted ethylbenzene, and light components. This tail gas requires compression, cooling, and separation to recover valuable aromatic components. However, the styrene in the tail gas is chemically reactive and readily undergoes thermal polymerization at temperatures above 65°C, forming styrene polymers. This can lead to compressor and pipeline blockages, severely impacting the long-term operation of the plant.

[0003] CN107721807A provides an apparatus and method for solving the polymerization blockage problem in the styrene tail gas compressor section. It can solve the problem of polymerization blockage that easily occurs in the styrene tail gas compressor section. However, it requires the addition of equipment such as a compressor inlet cooler, an oil-water separator, and a compressor suction tank. The cooling process is complex and the energy consumption is high.

[0004] In traditional styrene dehydrogenation, the condensate is treated and sent to the styrene coarse separator in the styrene separation section for further gas-liquid separation. The coarse separator initially separates benzene, toluene, ethylbenzene, and other substances contained in the dehydrogenation condensate from styrene. In actual production, the overhead stream from the coarse separator needs to be cooled by an air cooler from 121.5°C to 60.4°C before entering the styrene coarse separator separator tank. The cooling process consumes electrical energy, and the low-temperature heat of this stream is not fully utilized. Utility Model Content

[0005] To overcome the above problems, the purpose of this utility model is to provide a process for producing chilled water using low-temperature heat from a styrene coarse separation tower.

[0006] To achieve the above objectives, the technical solution of this utility model is as follows: a system for producing chilled water using low-temperature heat from a styrene coarse separator, comprising a styrene coarse separator, a hot water heat exchanger, a lithium bromide unit, a chilled water heat exchanger, and a dehydrogenation tail gas compressor. The top stream outlet of the styrene coarse separator is connected to the top stream inlet of the hot water heat exchanger. The top stream of the styrene coarse separator undergoes heat recovery through the hot water heat exchanger. The hot water outlet of the hot water heat exchanger is connected to the hot water inlet of the lithium bromide unit. The chilled water outlet of the lithium bromide unit is connected to the chilled water heat exchanger. The chilled water cools the styrene dehydrogenation tail gas through the chilled water heat exchanger. The chilled water heat exchanger is connected to the dehydrogenation tail gas compressor. The cooled dehydrogenation tail gas is compressed by the dehydrogenation tail gas compressor.

[0007] Preferably, the chilled water outlet of the chilled water heat exchanger is connected to a chilled water return tank, which is connected to the chilled water inlet of the lithium bromide unit via a chilled water pump, and the chilled water after heat exchange with the styrene dehydrogenation tail gas is returned to the lithium bromide unit.

[0008] Preferably, a second valve is installed on the pipeline connecting the lithium bromide unit and the chilled water heat exchanger, and a third valve is installed on the pipeline connecting the chilled water heat exchanger and the chilled water return tank.

[0009] Preferably, the chilled water heat exchanger is connected to the styrene dehydrogenation tail gas.

[0010] Preferably, the hot water outlet of the lithium bromide unit is connected to the hot water inlet of the hot water heat exchanger via a hot water return pump.

[0011] Preferably, an additional hot water pipeline is added to the pipeline connecting the lithium bromide unit and the hot water return pump. This hot water enters the hot water heat exchanger as hot water makeup water.

[0012] Preferably, the top flow outlet of the hot water heat exchanger is connected to an air cooler, and the air cooler is connected to the liquid separator of the styrene coarse separator.

[0013] Preferably, the styrene crude separator liquid separator tank is connected to the styrene crude separator via a styrene crude separator reflux pump, and a first valve is installed on the pipeline connecting the styrene crude separator liquid separator tank and the styrene crude separator reflux pump.

[0014] Preferably, the styrene coarse separator is connected to the absorption tower.

[0015] Preferably, the dehydrogenation tail gas compressor is connected to the liquid separator.

[0016] The beneficial effects of this utility model are as follows:

[0017] This system effectively utilizes the low-temperature heat from the top of the styrene coarse fractionation tower, reducing the subsequent air-cooling power consumption of the top stream and ensuring the normal operation of the lithium bromide unit. It also utilizes the chilled water generated by the lithium bromide unit to cool the styrene dehydrogenation tail gas. The hot water heat exchanger and the lithium bromide unit recover and utilize the low-temperature heat from the top stream of the styrene coarse fractionation tower. The top stream of the styrene coarse fractionation tower undergoes heat recovery through the hot water heat exchanger, further reducing the temperature of the top stream and decreasing the power consumption for subsequent cooling. The heated hot water provides a heat source for the lithium bromide unit, allowing it to operate normally. Simultaneously, before the styrene dehydrogenation tail gas enters the dehydrogenation tail gas compressor, the chilled water generated by the lithium bromide unit cools the styrene dehydrogenation tail gas through a chilled water heat exchanger, reducing the temperature from 40°C to approximately 20°C. This significantly reduces the gaseous styrene content in the compressor inlet dehydrogenation tail gas and also lowers the compressor outlet temperature, reducing the risk of polymer generation in the dehydrogenation tail gas treatment system. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a system for producing chilled water using a styrene coarse separator according to the present invention.

[0019] In the diagram: 1. Styrene coarse separator, 2. Styrene coarse separator top stream, 3. Hot water heat exchanger, 4. Lithium bromide unit, 5. Chilled water, 6. Chilled water heat exchanger, 7. Chilled water reflux tank, 8. Chilled water pump, 9. Hot water reflux pump, 10. Air cooler, 11. Styrene coarse separator liquid separator, 12. Styrene coarse separator reflux pump, 13. Dehydrogenation tail gas compressor, 14. Styrene dehydrogenation tail gas, 15. Make-up hot water, 16. Absorber, 17. Liquid separator, 18. First valve, 19. Second valve, 20. Third valve. Detailed Implementation

[0020] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0021] See Figure 1 See Figure 1A system for producing chilled water using low-temperature heat from a styrene coarse separator includes a styrene coarse separator 1, a hot water heat exchanger 3, a lithium bromide unit 4, a chilled water heat exchanger 6, and a dehydrogenation tail gas compressor 13. The top stream outlet of the styrene coarse separator 1 is connected to the top stream inlet of the hot water heat exchanger 3. The top stream 2 of the styrene coarse separator 1 undergoes heat recovery through the hot water heat exchanger 3. The hot water outlet of the hot water heat exchanger 3 is connected to the hot water inlet of the lithium bromide unit 4. The chilled water outlet of the lithium bromide unit 4 is connected to the chilled water heat exchanger 6. The chilled water 5 cools the styrene dehydrogenation tail gas 14 through the chilled water heat exchanger 6. The chilled water heat exchanger 6 is connected to the dehydrogenation tail gas compressor 13. The cooled dehydrogenation tail gas is compressed by the dehydrogenation tail gas compressor 13.

[0022] Hot water heat exchanger 3 and lithium bromide unit 4 recover and utilize the low-temperature heat from the overhead stream 2 of the styrene coarse fractionation tower. The hot water heat exchanger 3 recovers heat from the overhead stream 2, further reducing its temperature and minimizing the power consumption for subsequent cooling. The heated hot water then passes through the lithium bromide unit 4, providing a heat source for its operation. Simultaneously, before the styrene dehydrogenation tail gas 14 enters the dehydrogenation tail gas compressor 13, chilled water 5 produced by the lithium bromide unit 4 cools the styrene dehydrogenation tail gas 14 via a chilled water heat exchanger 6, reducing its temperature from 40°C to approximately 20°C. This significantly reduces the gaseous styrene content in the compressor inlet dehydrogenation tail gas and also lowers the compressor outlet temperature, reducing the risk of polymer generation in the dehydrogenation tail gas treatment system.

[0023] In this embodiment, the lithium bromide unit 4 is an existing structure. The lithium bromide unit 4 is a device that utilizes absorption refrigeration technology. Its working principle is that lithium bromide solution acts as the absorbent and water as the refrigerant. Under high vacuum, water evaporates and absorbs heat, cooling the cold water in the water pipes to produce chilled water, thus achieving the purpose of refrigeration. The evaporated refrigerant water vapor is absorbed by the lithium bromide solution, diluting the solution; this process occurs in the absorber. Then, by using hot water heated through heat exchange as a heat source, the water in the solution is separated, concentrating the solution; this process takes place in the generator. The vapor in the generator condenses into water in the condenser and is then sent to the evaporator for further evaporation.

[0024] The chilled water outlet of the chilled water heat exchanger 6 is connected to the chilled water return tank 7. The chilled water return tank 7 is connected to the chilled water inlet of the lithium bromide unit 4 through the chilled water pump 8. The chilled water after heat exchange with the styrene dehydrogenation tail gas 14 is returned to the lithium bromide unit 4 to realize chilled water circulation.

[0025] A second valve 19 is installed on the pipeline connecting the lithium bromide unit 4 and the chilled water heat exchanger 6, and a third valve 20 is installed on the pipeline connecting the chilled water heat exchanger 6 and the chilled water return tank 7. The cooling temperature of the styrene dehydrogenation tail gas 14 in the chilled water heat exchanger 6 is observed, and the valve opening is adjusted accordingly to regulate the chilled water flow rate, so that the styrene dehydrogenation tail gas 14 drops to approximately 20°C.

[0026] The chilled water heat exchanger 6 is connected to the styrene dehydrogenation tail gas 14, and the chilled water generated by the lithium bromide unit 4 is used to cool the styrene dehydrogenation tail gas 14.

[0027] The hot water outlet of the lithium bromide unit 4 is connected to the hot water inlet of the hot water heat exchanger 3 via the hot water return pump 9 to achieve hot water circulation.

[0028] Since hot water is used as the power source, hot water loss will occur during the operation of the lithium bromide unit 4. To address this, an additional hot water pipeline is added to the pipeline connecting the lithium bromide unit 4 and the hot water return pump 9. This hot water enters the hot water heat exchanger 3 as hot water replenishment to ensure the normal operation of the lithium bromide unit 4.

[0029] The top flow outlet of the hot water heat exchanger 3 is connected to the air cooler 10, and the air cooler 10 is connected to the styrene coarse separator separator tank 11.

[0030] The styrene crude separator liquid separator tank 11 is connected to the styrene crude separator 1 via the styrene crude separator reflux pump 12, and a first valve 18 is installed on the pipeline connecting the styrene crude separator liquid separator tank 11 and the styrene crude separator reflux pump 12.

[0031] The styrene coarse separator separator 11 is connected to the absorption tower 16.

[0032] The separation effect of the top stream 2 of the styrene coarse separator directly affects the purity and yield of the styrene product. The air cooler 10 further cools the top stream, condensing the high-temperature gas phase into a liquid phase. Then, the gas-liquid mixture is separated in the styrene coarse separator separator tank 11. The gas phase enters the absorption tower 16 for further processing and is captured and recovered by the absorbent. The liquid phase is returned to the styrene coarse separator 1 through the styrene coarse separator reflux pump 12.

[0033] The dehydrogenated tail gas compressor 13 is connected to the liquid separator 17. The compressed styrene tail gas enters the liquid separator 17 for further separation of the residual liquid.

[0034] Working Principle: In this system, the overhead stream 2 of the styrene coarse separator recovers heat through the hot water heat exchanger 3, is further cooled by the air cooler 10, and then the gas-liquid two-phase mixture is separated by the styrene coarse separator separator 11. It is then returned to the styrene coarse separator 1 by the styrene coarse separator reflux pump 12. This fully utilizes the low-temperature heat of the overhead stream of the coarse styrene tower, reducing the subsequent air cooling power consumption of the overhead stream. The hot water heated in the hot water heat exchanger 3 provides a heat source for the lithium bromide unit 4. The utilized hot water is then circulated back into the hot water heat exchanger 3 by the hot water reflux pump 9. Then, the chilled water produced by the lithium bromide unit 4 cools the styrene dehydrogenation tail gas 14 through the chilled water heat exchanger 6, reducing its temperature from 40℃ to approximately 20℃. This significantly reduces the gaseous styrene content in the compressor inlet dehydrogenation tail gas and also lowers the compressor outlet temperature, reducing the risk of polymer generation in the dehydrogenation tail gas treatment system. The chilled water that has exchanged heat with the styrene dehydrogenation tail gas 14 is returned to the lithium bromide unit 4 via the chilled water return tank 7 and the chilled water pump 8 to achieve chilled water circulation.

[0035] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A system for producing chilled water using low temperature heat from a crude styrene splitter column, characterized by: The system includes a styrene coarse separation tower, a hot water heat exchanger, a lithium bromide unit, a chilled water heat exchanger, and a dehydrogenation tail gas compressor. The top stream outlet of the styrene coarse separation tower is connected to the top stream inlet of the hot water heat exchanger. The top stream of the styrene coarse separation tower undergoes heat recovery through the hot water heat exchanger. The hot water outlet of the hot water heat exchanger is connected to the hot water inlet of the lithium bromide unit. The chilled water outlet of the lithium bromide unit is connected to the chilled water heat exchanger. The chilled water cools the styrene dehydrogenation tail gas through the chilled water heat exchanger. The chilled water heat exchanger is connected to the dehydrogenation tail gas compressor, and the cooled dehydrogenation tail gas is compressed by the dehydrogenation tail gas compressor.

2. The system for producing chilled water using low temperature heat of a crude fraction column of styrene according to claim 1, characterized by: The chilled water outlet of the chilled water heat exchanger is connected to the chilled water return tank, which is connected to the chilled water inlet of the lithium bromide unit via a chilled water pump. The chilled water after heat exchange with the styrene dehydrogenation tail gas flows back to the lithium bromide unit.

3. The system for producing chilled water using low temperature heat of a crude fraction column of styrene according to claim 2, characterized by: A second valve is installed on the pipeline connecting the lithium bromide unit and the chilled water heat exchanger, and a third valve is installed on the pipeline connecting the chilled water heat exchanger and the chilled water return tank.

4. The system for producing chilled water using low temperature heat of a styrene crude column according to claim 1, wherein: The chilled water heat exchanger is connected to the styrene dehydrogenation tail gas.

5. The system for producing chilled water using low temperature heat of a styrene crude column according to claim 1, wherein: The hot water outlet of the lithium bromide unit is connected to the hot water inlet of the hot water heat exchanger via a hot water return pump.

6. The system for producing chilled water at low temperature using a styrene crude column according to claim 5, characterized in that: An additional hot water pipeline is added to the pipeline connecting the lithium bromide unit and the hot water return pump. This hot water enters the hot water heat exchanger as hot water makeup water.

7. The system for producing chilled water at low temperature using a styrene crude column according to claim 1, wherein: The top flow outlet of the hot water heat exchanger is connected to an air cooler, which is connected to the liquid separator of the styrene coarse separator.

8. The system for producing chilled water at low temperature using a styrene crude column according to claim 7, characterized in that: The styrene coarse separator liquid separator tank is connected to the styrene coarse separator via a styrene coarse separator reflux pump, and a first valve is installed on the pipeline connecting the styrene coarse separator liquid separator tank and the styrene coarse separator reflux pump.

9. The system for producing chilled water at low temperature using a styrene crude column according to claim 7, wherein: The styrene coarse separator's liquid separator is connected to the absorption tower.

10. The system for producing chilled water at low temperature using a styrene crude column according to claim 1, wherein: The dehydrogenated tail gas compressor is connected to the separator.

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