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Integration of Argon Producing VPSA Systems with Cryogenic Distillation Systems

IP.com Disclosure Number: IPCOM000171530D
Publication Date: 2008-Jun-13
Document File: 5 page(s) / 59K

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Integration of Argon Producing VPSA Systems with Cryogenic Distillation Systems

Abstract

A method to integrate argon vacuum/pressure swing adsorption (Ar VPSA) systems with cryogenic air separation plants is described. The method is directed towards Ar VPSA systems in which a VPSA system is used to remove both nitrogen and oxygen from crude argon to produce substantially pure argon. The method allows a portion of the vent gas from the VPSA to be recycled to the cryogenic distillation system.

Introduction

An argon pressure/vacuum swing adsorption system (Ar VPSA) is an adsorption system that is used to purify argon. A VPSA system might comprise a stream which is fed to the system (feed stream) and two streams which are removed from the system (a product stream and a vent stream). The feed pressure might be superatmospheric, or less common, atmospheric, or subatmospheric.  The vent (or desorption) pressure might be superatmospheric, atmospheric, or subatmospheric. The feed to an Ar VPSA system might comprise crude argon with an oxygen concentration of about 2% to 20%, a nitrogen concentration of about 0% to 2%, and balance argon. The product from the VPSA system might be a purified argon stream with trace amounts (ppm levels or less) of oxygen and nitrogen. The vent stream comprises the material in the feed stream that is not recovered as product.

In the prior art, Ar VPSA systems are described which are integrated with cryogenic distillation plants. For example, US 5,730,003 describes a VPSA system that is integrated with a cryogenic distillation column. Due to the rather low recovery that is typical of the VPSA, at least a portion of the vent gas from the VPSA must be recycled back to the cryogenic distillation column. Several embodiments are given in which the vent gas is recycled to the following locations of the cryogenic distillation plants:

1)       Crude argon column.

2)       Low pressure distillation column.

3)       Inlet to main air compressor.

Additionally, various features of VPSA system are described in the prior art, including cycle steps (US 6,527,831), various types of adsorbents (see for example US 5,730,003), and methods to integrate VPSA systems with cryogenic distillation systems (US 20070209508A1). Prior art system also describe VPSA systems that provide both oxygen and nitrogen removal within the VPSA system. For example, a VPSA system might comprise a layer of carbon molecular sieve (CMS) adsorbent that has a kinetic selectivity for oxygen and a layer of zeolite that has selectivity for nitrogen. With the combination of both adsorbents, the VPSA system is capable of removing both nitrogen and oxygen from the feed argon (see

US

5,730,003 for more details).

The prior art does not describe adequate methods to integrate an Ar VPSA  with nitrogen removal based on cryogenic distillation columns. For example,...