Method for concentrating aqueous lye and apparatus suitable therefor

Patent metadata

Field	Value
Publication number	US-9849400-B2
Application number	US-201214233842-A
Country	US
Kind code	B2
Filing date	Jun 27, 2012
Priority date	Jul 21, 2011
Publication date	Dec 26, 2017
Grant date	Dec 26, 2017

Abstract

Method of concentrating aqueous alkali and apparatus suitable for this purpose. A very energy-saving method of concentrating aqueous alkali originating, for example, from a chloralkali electrolysis plant and an apparatus suitable for this purpose are described. The method/the apparatus utilizes heat of reaction from the formation of 1,2-dichloroethane and includes multistage concentration of the aqueous alkali, where at least part of the heat required for concentrating the aqueous alkali originates from the plant for preparing 1,2-dichloroethane and at least a further part of the heat required for concentrating the aqueous alkali originates from at least one of the higher stages of the plant for concentrating the aqueous alkali and is used for partial heating of the first stage. The apparatus can be used for retrofitting existing integrated plants made up of a DCE plant and chloralkali electrolysis or in the erection of new plants.

First claim

The invention claimed is:

1. A method for concentrating dilute aqueous alkali comprising utilizing heat of reaction from the formation of 1,2-dichloroethane, wherein the dilute aqueous alkali is concentrated in a plurality of stages, at least part of heat required for concentrating the dilute aqueous alkali originates from a plant for preparing 1,2-dichloroethane, and at least a further part of heat required for concentrating the dilute aqueous alkali originates from at least one higher stage of the plant for concentrating the aqueous alkali and is used for partial heating of a first stage of the plurality of stages, the method comprising the following steps:
producing a first aqueous alkali concentrate from a dilute aqueous alkali in a first concentration unit to which heat is supplied only by waste heat from one or more further concentration units,
further concentrating the first aqueous alkali concentrate to give a second aqueous alkali concentrate in a second concentration unit to which heat is supplied,
supplying at least part of the heat supplied to the second concentration unit in the form of heat originating from the plant for preparing 1,2-dichloroethane, and
supplying at least a part of the heat supplied to the first concentration unit in the form of heat originating from the second concentration unit, and
supplying heat to a heating unit located between the first and second concentration units to supply heat to the first alkali concentrate, at least part of the heat supplied to the heating unit being heat originating from at least one of: the plant for preparing 1,2-dichloroethane, the second concentration unit, and/or from a plant for concentrating aqueous alkali associated with a plant for chloralkali electrolysis,
wherein the first and second concentration units each comprise a plate heat exchanger and a phase separator.

2. The method of claim 1 , wherein the dilute aqueous alkali originates from a chloralkali electrolysis plant.

3. The method of claim 1 , wherein the heating unit for the first aqueous alkali concentrate comprises from one to three heat exchangers connected in series.

4. The method of claim 1 , wherein the method further comprises operating in three stages, comprising the following steps:
concentrating the second aqueous alkali concentrate to give a third aqueous alkali concentrate in a third concentration unit to which heat is supplied,
providing at least part of the heat supplied to the second and third concentration units in the form of heat originating from the plant for preparing 1,2-dichloroethane, and
providing at least part of the heat supplied to the first concentration unit in the form of heat originating from the second and third concentration units.

5. The method of claim 1 , wherein the first concentration unit comprises one or more heat exchangers or evaporators connected in series, where at least 50% of the heat supplied to the first concentration unit originates from downstream concentration unit(s) and the heat is recovered therefrom by the use of heat exchangers, and/or from recompressed steam obtained in the operation of the downstream concentration unit(s).

6. The method of claim 1 , wherein the second concentration unit comprises at least one falling film evaporator, where at least 50% of heat supplied to the second concentration unit is obtained from a 1,2-dichloroethane circulation stream originating from the plant for preparing 1,2-dichloroethane.

7. The method of claim 4 , wherein the third concentration unit comprises at least one of a heat exchange or evaporator, where at least 50% of heat supplied to the third concentration unit is obtained from 1,2-dichloroethane vapor originating from the plant for preparing 1,2-dichloroethane.

8. The method of claim 7 , wherein the vapor is condensed in the third concentration unit forming condensed 1,2-dichloroethane, a part of the condensed 1,2-dichloroethane from the third concentration unit is branched off for heating the second concentration unit and is combined with a 1,2-dichloroethane circulation stream coming directly from the plant for providing 1,2-dichloroethane.

9. An apparatus for concentrating aqueous alkali associated with a plant for preparing 1,2-dichloroethane, by the method of claim 1 , comprising:
a first concentration unit for concentrating dilute aqueous alkali and for producing a first aqueous alkali concentrate, the first concentration unit being heated only by waste heat from one or more further concentration units;
a second concentration unit to which the first aqueous alkali concentrate is fed, for further concentrating the first aqueous alkali concentrate and producing a second aqueous alkali concentrate, the second concentration unit heated at least partially by heat originating from the plant for preparing 1,2-dichloroethane;
a heating unit for heating the first aqueous alkali concentrate, the heating unit located between the first and second concentration units; and
a hot feed line coupled at an open end to a hot stream originating from at least one of the plant for preparing 1,2-dichloroethane, the second concentration unit, and/or from a plant for concentrating aqueous alkali associated with a plant for chloralkali electrolysis, and coupled at a second end with the heating unit, for supplying heat to the heating unit,
wherein the first and second concentration units each comprise a plate heat exchanger and a phase separator.

10. The apparatus of claim 9 , wherein the heating unit comprises three heat exchangers connected in series, a first heating unit heat exchanger heated by heat originating from the plant for preparing 1,2-dichloroethane, a second heating unit heat exchanger heated by heat originating from the second concentration unit, and a third heating unit heat exchanger heated by heat originating from the plant for concentrating aqueous alkali associated with the plant for chloralkali electrolysis.

11. The apparatus of claim 9 , wherein the apparatus is retrofitted into an existing integrated plant comprising the plant for preparing 1,2-dichloroethane and the chloralkali electrolysis plant.

12. The apparatus of claim 9 , further comprising:
a third concentration unit to which the second aqueous alkali concentrate is fed for concentrating the second aqueous alkali concentrate, to which heat is supplied at least in part in the form of heat originating from the plant for preparing 1,2-dichloroethane, and optionally
the heating unit is formed by a heat exchanger unit coupled to the third concentration unit for recovering heat from the third concentration unit, the heat exchanger unit connected to the second concentration unit such that heat recovered by the heat exchanger unit is utilized for preheating the first aqueous alkali concentrate upstream of the second concentration unit.

13. The apparatus of claim 10 , wherein the heat originating from the plant for preparing 1,2-dichloroethane is heat from a condensate of a 1,2-dichloroethane vapor obtained in a heat exchanger of the second concentration unit.

14. The apparatus of claim 12 , wherein the first concentration unit is heated by steam from a steam compression unit which compresses steam originating from the second concentration unit and optionally from further concentration units.

15. The apparatus of claim 10 , wherein the heating unit, the first concentration unit, and the second concentration unit are spatially separated from one another.

16. An apparatus for concentrating aqueous alkali comprising:
a first concentration unit for concentrating dilute aqueous alkali and for producing a first aqueous

Assignees

• Benje Michael
• Petersen Sven
• Kleiber Michael
• Thyssenkrupp Uhde Gmbh
• Vinnolit Gmbh & Co Kg

Inventors

• Benje Michael
• Petersen Sven
• Kleiber Michael

Classifications

• B01D1/0058 Primary

  Use of waste energy from other processes or sources, e.g. combustion gas (for water treatment C02F1/16) · CPC title

• B01D1/26

  Multiple-effect evaporating · CPC title

• B01D1/065

  by film evaporating · CPC title

• Y02P20/129

  Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines · CPC title

• C07C17/02

  to unsaturated hydrocarbons · CPC title