PROCEDURE FOR CONTROLLING AN ADIABATIC PRESSURE VARIATION ADSORPTION PROCESS WHERE AT LEAST PART OF THE PRODUCT GAS IS RETURNED TO THE PROCESS.

摘要

1,270,296. Separating gases. UNION CARBIDE CORP. 6 May, 1969 [7 May, 1968], No. 23008/69. Heading B1L. [Also in Division G1] In a pressure swing adsorption process for continuously separating feed gas mixture using at least three adsorbent beds by the repeating cycle, steps of sequentially contacting the feed gas mixture with each bed in turn at a first, higher, pressure for selective adsorption of at least one component and discharge of one-component-depleted product gas, desorbing the bed by depressurization to a second, lower, pressure and at least partially repressurizing the desorbed bed by the product gas preparatory to recontacting the bed with the feed gas mixture, the flow rate of the repressurization gas is controlled in linear dependence on the relative adsorption rate so that the repressurization of each bed in turn can be spread uniformly over the adsorption period of the bed then in contact with the feed gas mixture, thereby avoiding rapid pressure fluctuations. Indications of relative adsorption rate may be obtained by measuring the flow rate, temperature, or pressure of the feed gas mixture, or the flow rate of the product gas, or detecting the arrival of the adsorption front at a particular point in the bed. The difference between the repressurization pressure and the feed gas pressure may be measured and the repressurization flow control valve may be automatically adjusted so as to tend to make simultaneous detection of the adsorption front and reduction of the difference between the repressurization pressure and the feed gas pressure to a given limit. The adsorbent material may be a crystalline zeolitic molecular seive, activated carbon, or silica gel. Three bed and four bed processes are described in detail (Figs. 4 to 7, not shown).