Flow regulated pressure swing adsorption system

Abstract

Pressure swing adsorption (PSA) separation of a gas mixture is performed in an apparatus with a plurality of adsorbent beds. The invention provides rotary multiport distributor valves to control the timing sequence of the PSA cycle steps between the beds, with flow controls cooperating with the rotary distributor valves to control the volume rates of gas flows to and from the adsorbent beds in blowdown, purge, equalization and repressurization steps.

Description

TECHNICAL FIELDThe invention relates to separations conducted by pressure swing adsorption (PSA). The present invention provides simplified controls, with enhanced flexibility of control adjustment through flow regulation under changing operating conditions.BACKGROUND ARTGas separation by pressure swing adsorption is achieved by coordinated pressure cycling and flow reversals over adsorbent beds which preferentially adsorb a more readily adsorbed component relative to a less readily adsorbed component of the mixture. The total pressure is elevated to a higher pressure during intervals of flow in a first direction through the adsorbent bed, and is reduced to a lower pressure during intervals of flow in the reverse direction. As the cycle is repeated, the less readily adsorbed or "light" component is concentrated in the first direction, while the more readily adsorbed or "heavy" component is concentrated in the reverse direction.The conventional process for gas separation by pressure ...

AI Technical Summary

Benefits of technology

The present invention achieves pressurization and depressurization steps primarily by gas exchanges between the adsorbent beds. Steps entailing exchange of gas enriched in the second component between adsorbent beds will be described as light reflux steps. A predetermined logical sequence of ...

Problems solved by technology

With a greater number of beds, multiple pressure equalization steps can be achieved, although the valve logic and controls are then greatly complicated.

For large industrial PSA systems, mechanical immobilization of the adsorbent beds has not been practicable.

However, a rotary adsorbent bed assembly may be impracticable for large PSA units, owing to the weight of the rotating assembly.

Also, when separating gas components which are highly inflammable or toxic, the rotary adsorbent bed assembly would need to be completely enclosed in a containment shroud to capture any leakage from large diameter rotary seals.

However, these prior art devices have limited utility except in small scale applications, owing to their lack of control flexibility.

Since valve timing logic and port orifice sizing of the multiport valves are fixed rigidly in these prior art inventions, there is no provision for flow control to provide operational adjustment under changing feed conditions or during intervals of reduced product demand, or for performance optimization.

This inflexibility of control is most limiting for those of the cited prior art inventions which use multiport valves to exchange gas between a pair of beds, and across a pressure difference between that pair of beds.

Once the internal orifice apertures of the rotary valves and piping connections have been fixed, the prior art PSA cycle using multiport valves could only operat...

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