Patent ID: 8690990

Claim:
A pre-purification method of feed air for cryogenic air separation; wherein feed air is purified in succession with plural adsorption columns, and an adsorption step and a regenerating step are performed for the columns alternatively by switching the steps so that at least one of the columns is constantly treated in the adsorption step, the method including the following steps (a) to (e): (a) an adsorption step wherein a compressed feed air is supplied in an adsorption column, wherein a moisture adsorbent which adsorbs water included in feed air and a carbon dioxide adsorbent which adsorbs carbon dioxide included in feed air are filled in layers in this order from the side where the feed air is introduced in the column, to remove at least water and carbon dioxide from the feed air; (b) a decompression step wherein pressure in the adsorption column is reduced to atmospheric pressure after the adsorption step is terminated; (c) a heating step wherein the moisture adsorbent and the carbon dioxide adsorbent in the adsorption column, which has decompressed to the atmospheric pressure, are heated and regenerated; (d) a cooling step wherein the moisture adsorbent and the carbon dioxide adsorbent are cooled at a temperature, wherein an adsorption operation is performable, by introducing a purge gas which does not comprise water and carbon dioxide and is not heated; and (e) a pressurization step wherein the cooled moisture adsorbent and the cooled carbon dioxide adsorbent are pressurized by purified air; wherein the heating step (c) includes a total heating step and a partial heating step, which are performed in parallel, wherein the total heating step is a step wherein a heated purge gas, which does not comprise water and carbon dioxide, is supplied to the discharged side of a purified air of the adsorption column to heat the moisture adsorbent and the carbon dioxide adsorbent, and the partial heating step is a step wherein heated raw air is supplied between a layer of the moisture adsorbent and a layer of the carbon dioxide adsorbent to heat the moisture adsorbent; and wherein a temperature of the purge gas which is supplied to perform the total heating step in the step (c) is 100 to 250° C.