Process for purifying raw-material gases by fractionation

Patent metadata

Field	Value
Publication number	US-9938147-B2
Application number	US-201314891986-A
Country	US
Kind code	B2
Filing date	May 22, 2013
Priority date	May 22, 2013
Publication date	Apr 10, 2018
Grant date	Apr 10, 2018

Abstract

The present invention relates to a process for purifying raw-material gases by fractionation. In particular, the present invention relates to a process for cleansing chlorine gas of bromine.

First claim

The invention claimed is:

1. A process for cleansing a raw material having a content of contaminants by fractionation, with which a raw material is split up into a stream of gas with a high purity and a stream of gas with a low purity, the contaminants having a higher boiling-point than the raw material, and at least one of the contaminants being an explosive substance, comprising:
I. evaporating the raw material in a first evaporator to yield a raw-material gas, or making available a raw-material gas from a supply source,
II. introducing the raw-material gas into a wash column in which a washing liquid for diminishing the content of contaminants trickles towards said gas,
III. removing and partially condensing the raw-material gas purified in this way at the head of the wash column to form a condensate that is returned as washing liquid to the head of the wash column, and drawing off remaining raw-material gas from the wash column, the remaining raw-material gas having a lower content of contaminants than the raw-material gas yielded or made available in step I,
IV. removing the washing liquid as a stream of liquid at the bottom of the wash column, the washing liquid having a higher content of contaminants than the washing liquid used in step II,
V. introducing the washing liquid removed from the bottom of the wash column into the top of a second evaporator comprising a shell and horizontal tubes, wherein the washing liquid removed from the bottom of the wash column is introduced into the shell side of the second evaporator, enters a tube bundle in the second evaporator, and completely evaporates before reaching the bottom of the second evaporator to generate a vapour,
VI. guiding the vapour and not yet evaporated washing liquid in co-current flow in the second evaporator, and
VII. removing the vapour from the second evaporator as a stream of gas that exhibits a higher content of contaminants than the raw-material gas yielded or made available in step I.

2. The process of claim 1 , comprising evaporating the raw material completely to yield the raw-material gas.

3. The process of claim 1 , comprising introducing the washing liquid removed from the bottom of the wash column into the top of a second evaporator comprising a shell and horizontal tubes and redirecting the vapour by a baffle before it is drawn off as a stream of gas so that the vapour flows through the second evaporator on the other side of said baffle and the stream of gas is in step VII withdrawn through an outlet at the top of the second evaporator.

4. The process of claim 3 , wherein the baffle is arranged in the bundle of tubes of the second evaporator in such a way that the vapour after redirection on its way to the outlet at the top of the second evaporator once again flows through the tube bundle and thereby is superheated before being removed from the second evaporator as a stream of gas in step VII.

5. The process of claim 1 , comprising introducing the washing liquid removed from the bottom of the wash column into the top of a second evaporator comprising a shell and horizontal tubes and wherein the washing liquid removed from the bottom of the wash column impinges on a plate after entering the shell side of the second evaporator and is thereby spread over the tube bundle of the second evaporator.

6. The process of claim 5 , wherein the plate is perforated.

7. The process of claim 1 , wherein the raw material is chlorine and the contaminants are bromine and NCl 3 .

8. The process of claim 1 , comprising routing the raw-material gas, prior to entering the wash column, through one side of a recuperator in which it is cooled, and conducting and superheating the purified stream of gas remaining after condensation on another side of the recuperator.

9. The process of claim 8 , wherein the wash column is arranged above the second evaporator, the process comprising:
(i) conducting the raw-material gas from the first evaporator only partly into the wash column and into the recuperator,
(ii) directly mixing a residual portion of the raw-material gas with the stream of gas of low purity from the second evaporator,
(iii) guiding the washing liquid removed from the bottom of the wash column through a connecting line from the bottom of the column to the second evaporator, and
(iv) compensating for loss of pressure of the stream of gas of low purity by a liquid-filled vertical section of the connecting line between column bottom and second evaporator.

10. The process of claim 1 , comprising only partially evaporating the raw material in the first evaporator, routing the evaporated portion of the raw material into the wash column, and routing the washing liquid trickling towards the raw material in the column into the first evaporator and from there, together with the non-evaporated portion of the raw material, the washing liquid arrives at the second evaporator.

Assignees

• Covestro Deutschland Ag

Inventors

• Soppe Alfred
• Bittner Juergen
• Leidig Thorsten
• Steffens Friedhelm
• Werner Knud
• Runowski Thomas

Classifications

• C01B7/075

  of liquid chlorine · CPC title

• C01B7/0743 Primary

  of gaseous or dissolved chlorine · CPC title