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Quench MAC Air prior to or Inside a DCAC Disclosure Number: IPCOM000132289D
Publication Date: 2005-Dec-06
Document File: 3 page(s) / 26K

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The Prior Art Database

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Quench MAC Air prior to or Inside a DCAC

It is well known to cool hot air from a MAC (main air compressor) inside a DCAC (direct contact aftercooler) of an Air Separation unit (ASU). Typically the DCAC is a packed column in which rising air is cooled to a close approach to the temperature of downflowing CW (cooling water). Usually the DCAC contains random or structured packing to increase the surface area for heat and mass transfer between the air and cooling water.

The minimum diameter of the DCAC is determined by an approach to the floodpoint of the packing. This flood point depends on the characteristics of the packing, the CW flow and the flow, pressure and temperature of the air stream entering the packing. The minimum CW flow is easily calculated for any defined MAC discharge conditions and specified maximum temperature rise of the CW. The packing will be closest to flood at the bottom of the packed section as the air temperature in the packing will be highest at that location (resulting in the highest volumetric flowrate). The higher the temperature of the inlet air, the larger the DCAC diameter must be to avoid flooding, both because the air volumetric flow increases and because the required CW flow increases, due to the higher air cooling duty required.

A MAC can be designed with a reduced number of intercoolers, or even with no intercoolers. This might be done to reduce the capital cost of the MAC at the expense of an increase in MAC power consumption. A second downside is that the MAC discharge temperature would be much higher than for a more normally intercooled MAC. If this very hot air is routed direct to the D...