Extractive distillation

• US 4,371,427 A
• Filed: 06/16/1981
• Issued: 02/01/1983
• Est. Priority Date: 06/16/1981
• Status: Expired due to Fees

• Current Assignee: Phillips Petroleum Company (ConocoPhillips)
• Original Assignee: Phillips Petroleum Company (ConocoPhillips)
• Inventors: Henson, Loyal E., Holler, Raymond E.
• Primary Examiner(s): Sever, Frank
• Application Number:
  US06/273,559
• Time in Patent Office: 595 Days
• Field of Search: 196/132, 203/1-3, 203/53, 203/56, 203/DIG. 18, 203/58, 203/63, 208/DIG. 1, 202/160, 585/800, 585/833, 585/837, 585/838, 585/857
• US Class Current: 203/3
• CPC Class Codes: B01D 3/40 Extractive distillation
• CPC Class Codes: B01D 3/4227 Head- and bottom stream
• CPC Class Codes: C07C 7/08 by extractive distillation
• CPC Class Codes: C10G 21/30 Controlling or regulating
• CPC Class Codes: C10G 7/08 Azeotropic or extractive distillation refining of hydrocarbon oils, in the absence of hydrogen, by extraction with selective solvents C10G21/00
• CPC Class Codes: C10G 7/12 Controlling or regulating
• CPC Class Codes: Y10S 203/19 Sidestream
• CPC Class Codes: Y10S 208/01 Automatic control

Abstract

A level-controlled water tank in an extractive distillation system is used to maintain the water concentration in the solvent mixture constant.

Claims

1. In an extractive distillation process comprising

(a) introducing a hydrocarbon feed comprising a first component and a second component to be separated in an extractive distillation column,

(b) extractively distilling said hydrocarbon together with a stream of an extractive agent comprising a selective solvent and a required effective concentration of water in said extractive distillation column such as to form a first overhead stream and a first bottom stream,

(c) recovering said first component and a first stream of liquid water from said first overhead stream,

(d) introducing said first bottom stream into a stripper,

(e) introducing steam into the lower portion of said stripper,

(f) withdrawing a second overhead stream from said stripper,

(g) withdrawing a second bottom stream from said stripper,

(h) separating a second stream of liquid water from said second overhead stream,

(i) evaporating water from said second stream of liquid water and using the so evaporated water as said steam,

(j) withdrawing a selected solvent stream from said stripper, the improvement comprising

(k) introducing said second stream of liquid water into a water tank having a level controller associated therewith which is capable of generating a level control signal responsive to the level of water in said tank,

(l) withdrawing a flow controlled stripper water stream and a distillation water stream from said water tank under conditions so that said effective concentration of water in said distillation water stream is controlled responsive to said level control signal,

(m) combining said selective solvent stream, said first stream of liquid water and said distillation water stream to form said stream of said extractive agent.

2. A process in accordance with claim 1 wherein all of said first stream of liquid water is introduced into said water tank.

3. A process in accordance with claim 1 wherein

(a) said first overhead stream is condensed and separated into a first reflux stream, a first product stream comprising said first component and into said first water stream,

(b) said second overhead stream is condensed and separated into a second reflux stream, a second product stream comprising said second component and into said second water stream,

(c) said first reflux stream is introduced into the upper section of said extractive distillation column,

(d) said second reflux stream is introduced into the upper section of said stripper, and

(e) said second bottom stream from said stripper is said selective solvent stream.

4. A process in accordance with claim 1 wherein said level control signal directly controls the flow of liquid water in said distillation water stream.

5. A process in accordance with claim 4 wherein said level control signal controls a valve in a conduit through which only said distillation water stream flows.

6. A process in accordance with claim 1 comprising determining the water content in said extractive agent and responsive thereto adjusting the level controller in said water tank so that the quantity of water in said extractive agent reaches the desired value.

7. Apparatus for carrying out a process of claim 1 comprising

(a) an extractive distillation column having

a first feed inlet,

a first overhead outlet,

a first bottom outlet,

an extractive agent inlet, and

a first reflux inlet,

(b) a first condenser and phase separator having

a first condenser inlet connected to said first overhead outlet,

a first product outlet,

a first water outlet, and

a first reflux outlet connected to said first reflux inlet,

(c) a stripper having

a second feed inlet connected to said first bottom outlet

a second overhead outlet,

a second bottom outlet,

a second reflux inlet, and

a stream inlet connected to a steam generator,

(d) a second condenser and phase separator having

a second condenser inlet connected to said second overhead outlet,

a second product outlet,

a second water outlet, and

a second reflux outlet connected to said second reflux inlet,

(e) a water tank having

water tank inlet means,

water tank outlet means, and

a water level control signal generator,

(f) a stripper water conduit connecting said water outlet means and said stream generator for converting water from said water tank to steam and introducing said steam into the stripper,

(g) a flow controller associated with said stripper water conduit controlling the flow of water through said steam generator and into said stripper,

(h) a conduit means connecting said extractive agent inlet with said second bottom outlet and also operatively connecting said extractive agent inlet with said water tank outlet means so that said signal generator causes flow of all of the water from said water tank that does not flow into the stripper to flow to said extractive agent inlet, and

(i) means for connecting said first water outlet directly or indirectly;

with said extractive agent inlet so that the quantity of water leaving via said first water outlet is reintroduced into said extractive distillation column.

8. Apparatus in accordance with claim 7 wherein said conduit means comprises a extractive agent tank connected

(a) with said second bottom outlet of said stripper to receive the bottom stream from said stripper,

(b) with said water tank outlet means to receive water from said water tank in a quantity responsive to the signal of said level control signal generator, and

(c) with said extractive agent inlet to supply said extractive agent to said extractive distillation column.

9. Apparatus in accordance with claim 7 wherein a flow control valve in a conduit connecting said extractive agent tank and said water tank is operatively connected with said level control signal generator.

10. Apparatus in accordance with claim 7 comprising a water make up means operatively connected to said water tank.

11. Process in accordance with claim 1 wherein said level controller is adjusted responsive to a determination of the water content in said extractive agent in order to change the total content of water flowing through the extractive distillation column.

12. Process in accordance with claim 1 wherein the set point of the water level in said water tank responsive to which said water level in the water tank is controlled is manipulated responsive to the determination of the concentration of water in the extractive agent flowing in the extractive distillation column.

13. In an extractive distillation process comprising

(a) introducing a hydrocarbon feed comprising a first component and a second component to be separated into an extractive distillation column,

(b) extractively distilling said hydrocarbon together with a stream of an extractive agent comprising a selective solvent and a required effective concentration of water in said extractive distillation column such as to form a first overhead stream and a first bottom stream,

(c) recovering said first component and a first stream of liquid water from said first overhead stream,

(d) introducing said first bottom stream into a stripper,

(e) introducing steam into the lower portion of said stripper,

(f) withdrawing a second overhead stream from said stripper,

(g) withdrawing a second bottom stream from said stripper,

(h) separating a second stream of liquid water from said second overhead stream,

(i) evaporating water from said second stream of liquid water and using the so evaporated water as said steam,

(j) withdrawing a selected solvent stream from said stripper, the improvement comprising

(k) introducing said second stream of liquid water and at least a portion of said first stream of liquid water into a water tank having a level controller associated therewith which is capable of generating a level control signal responsive to the level of water in said tank,

(l) withdrawing a flow controlled stripper water stream and a distillation water stream from said water tank under conditions so that said effective concentration of water in said distillation water stream is controlled responsive to said level control signal,

(m) combining said selective solvent stream, any remainder of said first stream of liquid water and said distillation water stream to form said stream of said extractive agent.

14. In an extractive distillation process comprising an extractive distillation in the presence of a solvent and a required effective concentration of water in an extractive distillation column and stripping solvent in a stripper in the presence of steam and comprising a first water loop through the extractive distillation column and a second water loop through the stripper,

the improvement comprising

incorporating a water tank into the second water loop,

controlling the flow of water from said second water loop to said first water loop responsive to the water level in said water tank sufficient to maintain required effective concentration.