Separation method and apparatus

Abstract

A method and apparatus for producing an oxygen product in which air is separated in an installation including one or more air separation units having higher and lower pressure columns. An exhaust stream produced from a turboexpander and optionally an impure oxygen stream such as that derivable from higher pressure column bottoms is rectified within an auxiliary column to produce an oxygen containing stream that is introduced into the lower pressure column of each of the air separation units to increase the capacity of such columns. The pressure within the auxiliary column is set by the pressure of the exhaust stream such that a nitrogen-rich vapor stream extracted from the top of the auxiliary column can be used in regenerating adsorbent within a pre-purification unit utilized in connection with the installation.

Description

RELATED APPLICATIONS[0001]This application is a continuation-in-part of U.S. patent application Ser. No. 12 / 634,810, filed Dec. 10, 2009.FIELD OF THE INVENTION[0002]The present invention relates to a method and apparatus for separating air into oxygen and nitrogen-rich fractions. More particularly, the present invention relates to such a method and apparatus in which one or more air separation units having higher and lower pressure columns are connected to an auxiliary column that produces one or more oxygen containing streams that are lean in nitrogen and that are introduced into lower pressure columns to allow the air separation units to operate at a higher capacity and a nitrogen-rich vapor stream that can be used in regenerating adsorbent beds of a pre-purification unit used in purifying the air without further compression.BACKGROUND OF THE INVENTION[0003]Large quantities of high purity oxygen are required for purposes of coal gasification where the resulting synthesis gas will ...

AI Technical Summary

Benefits of technology

The present invention provides a method of separating air using a cryogenic rectification process. The method includes a pre-purification unit to remove higher boiling impurities and an air separation unit with a lower pressure column and an auxiliary column. The method also includes a turboexpander and a bottom region of the auxiliary column that can produce a nitrogen-rich vapor column overhead. The exhaust stream from the air separation unit can be introduced into the auxiliary column to regenerate the adsorbent. The method reduces nitrogen in the lower pressure column and allows for more efficient operation of the air separation unit. The use of an impure oxygen stream and the introduction of a higher pressure nitrogen-rich column overhead can also improve the purity of the oxygen product. The method also includes the use of a liquid air stream and intermediate reflux streams to further improve the purity of the oxygen product.

Problems solved by technology

This saves on the electrical power that would otherwise be consumed in such compression and therefore, the ongoing operational costs of running the process and plant incorporating the process as well as a compressor that is normally used for such purposes.

Images