Low-cost Refrigeration in Low-Pressure Gaseous Oxygen Air Separation Cycles
Publication Date: 2003-Sep-12
The IP.com Prior Art Database
The proposed processes described here present a number of methods by which refrigeration may be supplied to an air separation unit (ASU). These methods are applicable to air separation processes that do not contain air streams with a pressure substantially higher than that of the high pressure column. High pressure gas is withdrawn from any available compression source and is partially cooled in the main heat exchanger. The cooled gas is then turboexpanded to a low pressure. Although expander flow may be provided by any available compression source, it is likely that this source will either be the main air compressor or a product compressor. If the main air compressor is used, then the cold low-pressure expander exhaust stream may be directed through the main heat exchanger, mixed with fresh feed air and recycled back to the main air compressor. If a product compressor is used, the cold expander exhaust may be mixed with the appropriate low-pressure product stream before the stream is directed to the cold end of the main heat exchanger or it may be recycled as a separate stream to the product compressor suction. This method allows the entire fresh feed flow of the ASU to be directed to the high pressure column. Flowsheets depicting two possible processes are shown in Figures 1 and 2 with the expander recycle circuits shown in bold lines.