Gas separation system and enriched gas production method

Abstract

In a gas separation system, a retentate gas discharge port of a first unit U1 and a gas inlet port of a second unit U2 are connected by a retentate gas discharge line. A permeate gas discharge port of U1 and a gas inlet port of a third unit U3 are connected by a permeate gas discharge line. A feed gas mixture supply line is connected to a gas inlet port of U1. A permeate gas discharge port of U2 and the feed gas mixture supply line are connected by a permeate gas return line. A retentate gas discharge port of U3 and the feed gas mixture supply line are connected by a retentate gas return line. At least in operation, the gas permeability of U2 is higher than that of U3, and the gas selectivity of U3 is higher than that of U2.

Description

TECHNICAL FIELD[0001]The present invention relates to a gas separation system that separates a gas mixture by using a plurality of gas separation membrane units, and an enriched gas production method using this gas separation system.BACKGROUND ART[0002]The membrane separation method, which employs the difference in gas permeability with respect to a membrane, is known as a method for separating a gas mixture including at least two different gas species into the respective gases. With this method, at least either a highly-pure high-permeability gas or a highly-pure low-permeability gas, which are the target gases, can be obtained by recovering the permeate gas and / or the retentate gas. The permeability—which is the volume of permeation, through a membrane, of each gas included in the gas mixture per unit membrane area, per unit time, per unit partial pressure difference—can be expressed as P′ (unit: ×10−5 cm3 (STP) / cm2·sec·cmHg). The gas selectivity of the membrane can be expressed a...

AI Technical Summary

Benefits of technology

[0026]With the present invention, it is possible to reduce the membrane area in the entire system—e.g., reduce the number of membrane modules—and thus reduce initial cost, while maintaining a high target-gas recovery rate. Thus, the gas separation system of the invention is economically effective.

Problems solved by technology

In this case, however, the permeability is low, and thus, it is necessary to increase the membrane area or increase operation pressure.

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