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Oxygen Enrichment of Air: Process Developments and Economic Trends

IP.com Disclosure Number: IPCOM000019383D
Publication Date: 2003-Sep-12

Publishing Venue

The IP.com Prior Art Database

Abstract

Many industrial processes are based on oxidation reactions to produce heat, power, inorganic and organic compounds. Some of these processes take the oxidation reactions to completion, such as the combustion of fuels to yield heat and/or power. Other processes are based on incomplete or partial oxidation. Examples of partial oxidation processes include the formation of ethylene oxide or the formation of synthesis gas (typically a mixture predominantly containing carbon monoxide and hydrogen) from a hydrocarbon feedstock. Atmospheric or ambient air is a logical source of oxygen for industrial use. It can be drawn from the atmosphere into the process using a natural draft or compressed for use in processes operating at above atmospheric pressure. If carbon dioxide, water or pollutants will interfere with the oxidation process or introduce impurities into the final product, the air may be pretreated to remove the problem component(s).

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Oxygen Enrichment of Air: Process Developments and Economic Trends

Introduction

Many industrial processes are based on oxidation reactions to produce heat, power, inorganic and organic compounds. Some of these processes take the oxidation reactions to completion, such as the combustion of fuels to yield heat and/or power. Other processes are based on incomplete or partial oxidation. Examples of partial oxidation processes include the formation of ethylene oxide or the formation of synthesis gas (typically a mixture predominantly containing carbon monoxide and hydrogen) from a hydrocarbon feedstock. Atmospheric or ambient air is a logical source of oxygen for industrial use. It can be drawn from the atmosphere into the process using a natural draft or compressed for use in processes operating at above atmospheric pressure. If carbon dioxide, water or pollutants will interfere with the oxidation process or introduce impurities into the final product, the air may be pretreated to remove the problem component(s).

A drawback to using air as the oxidant for certain processes is its relatively low oxygen concentration, less than 21% by volume on a dry basis. Combustion processes for the production of heat and/or power, by nature, operate at elevated temperatures. When air is used as the oxidant in these processes, a portion of the fuel is consumed in the heating of the required oxygen flow and the inert materials (predominantly nitrogen and argon) contained in the air (1). In furnace operations such as the melting of glass, non-ferrous or ferrous metals, the inert constituents of air may limit the operating temperature and/or consume large quantities of fuel to raise their temperature from ambient to furnace conditions. Recuperative equipment can be added to transfer heat from the furnace exhaust gases to the incoming air stream, thus reducing the fuel consumption but adding considerable capital cost. In the example where hydrocarbon feedstocks are partially oxidized to synthesis gas, the inert materials in air dilute the valuable constituents in the product gas. Downstream processes to remove sulfur containing materials and other byproducts are larger and more energy intensive due to the increased synthesis gas flow attributable to the presence of inert nitrogen and argon (2).

The adverse effects of using air as an oxidant can be eliminated by reducing the amount of inert material in air prior to its use in an oxidation-based process. Methods to increase the oxygen concentration of ambient air include (3):

·        Adsorption processes using molecular sieves or other materials that selectively remove oxygen or nitrogen molecules from a feed air stream.

·        Chemical processes such as absorption/desorption cycles using molten salts.

·        Cryogenic processes that liquefy air and distill it into one or more relatively pure product streams.

·        Ionic transport membrane processes that ionize oxygen molecules contained in an air stream, conduct the oxygen ions thro...