Energy-efficient polypropylene production by reducing the power consumption of the heat dissipation system.

Abstract

Embodiments disclosed herein relate to the production of polypropylene. At least one olefin monomer stream (10, 12) is supplied to a polymerization zone (2). A recirculating gas stream (31) is drawn from there, compressed to a compressor (4), cooled in a first heat exchanger (5), separated in a phase separator (6), flushed in a pressure regulator (7), supplied to a second heat exchanger (8), and recycled to the polymerization zone (2) (83).

Claims

1. A process for producing polypropylene, At least one olefin monomer stream (10, 12) is supplied to the polymerization zone (2) where the olefin monomers are reacted to generate a polymerization product stream (11), The recirculated gas flow (31) from the gas-phase polymerization zone (2) is supplied to the compressor (4) to form a compressed recirculated gas flow (32), The compressed recirculating gas flow (32) is supplied to the first heat exchanger (5) to form a cooled compressed recirculating gas flow (33) containing liquefied recirculating gas and optionally a vapor phase, The cooled compressed recirculating gas flow (33) is supplied to the phase separator (6) to form a liquefied recirculating gas flow (34) and a vapor phase flow (35), The steam phase flow (35) is supplied to the high-temperature side of the second heat exchanger (8), The liquefied recirculating gas flow (34) is supplied to the pressure regulator (7) to form a flash recirculating gas flow (36), The flash recirculation gas flow (36) is supplied to the low-temperature side of the second heat exchanger (8), The outlet steam flow (86) and outlet liquid flow (82) are recovered from the high-temperature side of the second heat exchanger (8), To recover the outlet steam flow (87) and at least one outlet liquid flow from the low-temperature side of the second heat exchanger (8), A process comprising supplying the recycled outlet liquid flow (83) from the low-temperature side of the second heat exchanger (8) to the polymerization zone (2).

2. The process according to claim 1, further comprising drawing out part (81) or all of the flow from the outlet steam flow (86) from the high-temperature side of the second heat exchanger (8).

3. The process according to claim 1 or 2, further comprising drawing a portion (84) from the at least one outlet liquid flow from the low-temperature side of the second heat exchanger (8).

4. Adding the outlet liquid flow (82) from the high-temperature side of the second heat exchanger (8), or a portion thereof, to the phase separator (6), and / or the liquefied recirculation gas flow (34), and / or the flash recirculation gas flow (36), and / or the recycled outlet liquid flow (83), and / or The process according to any one of claims 1 to 3, further comprising adding the outlet steam flow (87) from the low-temperature side of the second heat exchanger (8), or a portion thereof, to the recycle outlet liquid flow (83).

5. The process according to any one of claims 1 to 4, further comprising adding the recycle outlet steam flow (86) from the high-temperature side of the second heat exchanger (8) to the recycle outlet liquid flow (83).

6. To draw a portion (38) from the liquid outlet on the low-temperature side of the first heat exchanger (5) and / or from the cooled compressed recirculated gas flow (33), and / or The process according to any one of claims 1 to 5, further comprising drawing a portion (39) from the liquid outlet of the phase separator (6) and / or from the liquefied recirculation gas flow (34).

7. The process according to any one of claims 1 to 6, further comprising reducing the pressure of the cooled compressed recirculating gas flow (33) via a pressure control valve located between the first heat exchanger (5) and the phase separator (6), or via a pressure control valve included in the phase separator (6).

8. The process according to any one of claims 1 to 7, wherein the first heat exchanger (5) is a horizontal shell-and-tube exchanger.

9. The process according to any one of claims 1 to 8, wherein the second heat exchanger (8) is a two-pass U-bundle kettle type heat exchanger.

10. The recycling outlet liquid flow (83) from the low-temperature side of the second heat exchanger (8) is supplied to the gas-phase polymerization zone (2). The process according to any one of claims 1 to 9, comprising introducing the recycle outlet liquid flow (83) to the bottom and / or top of the reactor in the gas-phase polymerization zone (2).

11. A system (1) for producing polypropylene, A polymerization zone (2) is configured to convert at least one olefin monomer stream (10, 12) into polypropylene and generate a polymerization product stream (11). A compressor (4) is configured to form a compressed recirculating gas flow (32) from the recirculating gas flow (31) generated from the polymerization zone (2). A first heat exchanger (5) is configured to form a cooled compressed recirculating gas flow (33) from the compressed recirculating gas flow (32) that includes liquefied recirculating gas and optionally a vapor phase. A phase separator (6) is configured to form a liquefied recirculating gas flow (34) and a vapor phase flow (35) from the cooled compressed recirculating gas flow (33). A pressure regulator (7) configured to form a flash recirculation gas flow (36) from the liquefied recirculation gas flow (34), A second heat exchanger (8) having a high-temperature side configured to receive the steam phase flow (35) and a low-temperature side configured to receive the flash recirculation gas flow (36), The second heat exchanger (8) Outlet steam flow (86) and outlet liquid flow (82) are formed from the high-temperature side of the second heat exchanger. A second heat exchanger (8) is configured to form an outlet steam flow (87) and at least one outlet liquid flow from the low-temperature side of the second heat exchanger. A system (1) comprising a flow line for supplying the recycled outlet liquid flow (83) from the low-temperature side of the second heat exchanger (8) to the polymerization zone (2).

12. A flow line for drawing out part (81) or all of the flow from the outlet steam flow (86) from the high-temperature side of the second heat exchanger (8), and / or The system according to claim 11, further comprising a flow line for drawing a portion (84) from the at least one outlet liquid flow from the low-temperature side of the second heat exchanger (8).

13. The system according to claim 11 or 12, wherein the polymerization zone (2) has a cascade configuration in which a first reactor (21) and a second reactor (22) are placed in series.

14. The system according to any one of claims 11 to 13, further comprising an expansion valve located between the first heat exchanger (5) and the phase separator (6), or included in the phase separator (6).

15. The second heat exchanger (8) is provided with a flow line for adding the outlet liquid flow (82), or a portion thereof, from the high-temperature side to the phase separator (6) and / or the liquefied recirculation gas flow (34), The system according to any one of claims 11 to 14, wherein the second heat exchanger (8) is physically located above the phase separation container (6), so that the outlet liquid flow (82) from the high-temperature side of the second heat exchanger flows by gravity.

Images