Extractive distillation column system and the use thereof in the separation of butenes from C4-hydrocarbon streams

Patent metadata

Field	Value
Publication number	US-11629109-B2
Application number	US-202217808250-A
Country	US
Kind code	B2
Filing date	Jun 22, 2022
Priority date	Jun 25, 2021
Publication date	Apr 18, 2023
Grant date	Apr 18, 2023

Abstract

An extractive distillation column system contains a combination column and a side rectification column. A process can be used for separation of butenes from C4-hydrocarbon streams using the extractive distillation column system.

First claim

The invention claimed is:

1. An extractive distillation column system for separation of butenes from a C4-hydrocarbon stream which contains at least butenes and butanes using a solvent, wherein the extractive distillation column system comprises:
a combination column, and
a side rectification column,
wherein the combination column from top to bottom comprises at least the following different sections:
a top section in which a stream enriched in butanes compared to the C4-hydrocarbon stream is obtained;
a random packing section which comprises at least two random packing beds;
a collection section which comprises at least two liquid collectors;
a regeneration section which comprises at least one further random packing bed; and
a bottom section in which the solvent is obtained;

wherein arranged on the combination column are at least two side evaporator systems, wherein in each evaporator system a liquid phase from one of the at least two liquid collectors of the collection section is at least partially evaporated and subsequently recycled via a respective first inlet or second inlet to the collection section, wherein the first inlet is arranged spatially at least one liquid collector above the second inlet; and
wherein the side rectification column comprises at least two separating trays or at least one random packing or structured packing bed and is supplied with a gaseous phase which is obtained from the collection section of the combination column at a location below the first inlet but above or at a same height as the second inlet.

2. The extractive distillation column system according to claim 1 , wherein the extractive distillation column system further comprises a feed evaporator which at least partially evaporates the C4-hydrocarbon stream before being passed into the combination column.

3. The extractive distillation column system according to claim 2 , wherein the solvent obtained in the bottom section of the combination column is recycled to a third inlet for the solvent.

4. The extractive distillation column system according to claim 3 , wherein the solvent is used for heat integration, wherein heat of the solvent is transferred in a first side evaporator system and a second side evaporator system of the at least two side evaporator systems, and in the feed evaporator.

5. The extractive distillation column system according to claim 1 , wherein arranged at the bottom section of the combination column is a bottoms evaporator which at least partially evaporates liquid obtained in the bottom section to outgas any residues of butenes from the solvent.

6. The extractive distillation column system according to claim 1 , wherein a stream enriched in butenes is withdrawn at a top of the side rectification column.

7. A process for separation of butenes from a C4-hydrocarbon stream containing at least butenes and butanes by extractive distillation in the extractive distillation column system according to claim 1 , the process comprising:
supplying the C4-hydrocarbon stream to a feed evaporator and at least partially evaporating the C4-hydrocarbon stream, and supplying the C4-hydrocarbon stream to the random packing section of the combination column, and supplying the solvent to the combination column at a position at least one random packing bed above the C4-hydrocarbon stream, wherein the C4-hydrocarbon stream and the solvent are brought into contact with one another and predominantly the butenes are transferred from the C4-hydrocarbon stream to the solvent, to obtain a laden solvent;
collecting the laden solvent in a first liquid collector of the at least two liquid collectors of the collection section, passing the laden solvent through a first side evaporator system of the at least two side evaporator systems, wherein the laden solvent is at least partially evaporated therein, and recycling the laden solvent to the collection section via the first inlet;
passing a first liquid phase obtained in a second liquid collector of the at least two liquid collectors of the collection section through a second side evaporator system of the at least two side evaporator systems, wherein the first liquid phase is at least partially evaporated therein, and recycling the first liquid phase via the second inlet to the collection section, and passing the first recycled liquid phase into the regeneration section;
passing a second liquid phase obtained below a last random packing bed of the at least one further random packing bed of the regeneration section, wherein the second liquid phase contains the solvent and residual butenes and/or butanes, through a bottoms evaporator and then into the bottom section, wherein the residual butenes and/or butanes present in the solvent are at least partially outgassed and a resulting solvent is withdrawn as a bottoms stream and recycled to the random packing section; and
providing a gaseous stream containing at least the butenes and residual solvent below the first inlet but above or at the same height as the second inlet from the collection section, and supplying the gaseous stream to the side rectification column, wherein a stream enriched in the butenes is obtained at a top of the side rectification column,
wherein heat of the resulting solvent withdrawn as the bottoms stream is at least partially used for heat integration wherein heat of the resulting solvent is transferred in the first side evaporator system, in the second side evaporator system, and in the feed evaporator.

8. The process according to claim 7 , wherein the solvent is N-methyl-2-pyrrolidone (NMP).

9. The process according to claim 7 , wherein heat for evaporation in the bottoms evaporator is introduced in a heat exchanger by heat transfer with a suitable heat transfer medium.

10. The process according to claim 9 , wherein an employed heating steam undergoes at least partial condensation in the heat exchanger, thus generating a hot condensate at a pressure of 10 to 20 bar absolute, and a temperature of 150° C. to 210° C., which is passed to a condensate container.

11. The process according to claim 10 , wherein a pressure in the condensate container is lower than the pressure in the heat exchanger on a heating steam side, thus causing a portion of the hot condensate to be re-evaporated and obtained as low pressure steam.

12. The process according to claim 11 , wherein the heating steam for the bottoms evaporator is provided using a steam ejector supplied with high pressure or medium pressure steam and the low pressure steam obtained in the condensate container.

13. The process according to claim 7 , wherein the side rectification column comprises a column bottom in which a liquid bottoms stream is obtained, which is passed from the column bottom to the combination column.

14. The process according to claim 7 , wherein the bottoms evaporator is a once-through evaporator.

15. The process according to claim 7 , wherein at least one of the at least two side evaporator systems comprises or consists of a once-through evaporator.

16. The extractive distillation column system according to claim 1 , wherein the at least two liquid collectors of the collection section are chimney trays.

17. The process according to claim 9 , wherein the heat transfer medium is heating steam.

18. The process according to claim 10 , wherein the hot condensate in the heat exchanger is at a pressure of 12 to 17 bar absolute and a temperature of 160° C. to 200° C.

Assignees

• Evonik Operations Gmbh

Inventors

• Lutze Philip
• Peitz Stephan
• Rix Armin Matthias
• Six Tanita Valèrie
• Schröder Moritz
• Paul Niklas

Classifications

• C07C7/08 Primary

  by extractive distillation · CPC title

• B01D3/40 Primary

  Extractive distillation · CPC title

• C07C7/005

  Processes comprising at least two steps in series · CPC title

• B01D3/007

  Energy recuperation; Heat pumps · CPC title

• C07C7/12

  by adsorption, i.e. purification or separation of hydrocarbons with the aid of solids, e.g. with ion-exchangers · CPC title