| 摘要 |
A vacuum/pressure swing adsorption method for extracting a more preferred gas from a feed mixture of the more preferred gas and a less preferred gas, employs an adsorbent bed which, on an equilibrium basis, exhibits a selective adsorption preference for the more preferred gas. The method comprises the steps of: pressurizing the adsorbent bed from a medium pressure to a high pressure with a flow of the feed mixture to enable the adsorbent bed to adsorb the more preferred gas. Void gas is fed from the adsorbent bed during the pressurizing to a first storage tank. A further flow of the void gas is fed into a second storage tank, while bringing the adsorbent bed to a low pressure. At about the low pressure, the more preferred gas is desorbed from the adsorbent bed, while the void gas is fed to the adsorbent bed from the second storage tank. The more preferred gas, which is desorbed, provides a product output. Then the void gas is fed from the first storage tank to pressurize the adsorbent bed to about the intermediate pressure and the process is repeated. When the process is used to produce oxygen, the key is the use of desorption purge at a nearly constant pressure that is selected to produce a steady stream of low purity oxygen (30% to 60%), at a pressure in the range of 60 kPa to 20 kPa using oxygen-selective adsorbents. A further important feature of the invention is the use of an adsorbent that is appropriately oxygen-selective and is based on equilibrium selectivity, instead of rate selectivity.
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