Adsorptive separation process

Details Adsorptive separation process Adsorptive separation process

1989-05-16

1991-05-14

Spitzer, Robert

Gas separation

Means within gas stream for conducting concentrate to collector

55 62, 55 68, 55 75, B01D 5304

Patent

active

050152726

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to an adsorptive separation process for separating hydrogen and/or helium as high purity product gas, and, more particularly, to an adsorptive separation process for separating and refining gas by a pressure swing process for adsorptive separation.


BACKGROUND ART

The pressure swing adsorption process (hereinafter referred to as PSA process) is widely used as a gas separation and refining process, and is used in a variety of application fields, such as removal of water or carbonic acid gas from air or nitrogen gas, production of hydrogen from steam reforming gas, such as butane, naphtha or methanol, production of hydrogen from coal-based generated gas, such as COG, recovery of hydrogen from gas produced by oil refining, and recovery of helium from natural gas.
With the use of an adsorptive separation apparatus employing a PSA process, the essential factors from the view point of consumers of product gas are high purity and recovery rate of product and a small variation in product flow rate and pressure.
In general, according to the PSA process which separates an unadsorbed component as high purity product, for regeneration of an adsorbent, unadsorbed component gas or product gas is used to purge an easy adsorptive component gas. The most primitive process is to use product gas stored in a tank, as an unadsorbed component gas for this regeneration. In this case, however, since the product gas is used for regeneration, the recovery rate of the product gas significantly decreases, resulting in an increase in the cost of products. In addition, since part of product gas is used at the time that an adsorbent bed purged for regeneration of an adsorbent is repressurized, there arises a problem of causing a variation in flow rate and pressure of product gas to be sent to consumers.
As a solution to this problem, a selective adsorptive separation process is known which is disclosed in, for example, Japanese Patent Publication Nos. 45-20082 and 55-12295. According to the disclosed processes, in principle, four adsorbent beds are provided. High pressure unadsorbed component gas remaining in the first bed whose adsorption step has been completed is used to increase the pressure, by pressure equalization, in the second bed which has already been purged and purified under lower pressure (e.g., atmospheric pressure). Intermediate pressure unadsorbed component gas remaining in the first bed is expanded and then used to purge the third bed under the lowest pressure to thereby prevent loss of precious product gas and improve the recovery rate. High pressure product gas is constantly introduced to increase the pressure in the fourth bed which has been purified from intermediate pressure to high pressure. It is described that the above solves the problem of causing a variation in flow rate and pressure of the product gas.
FIG. 3 illustrates a flow sheet described in the aforementioned Japanese Patent Publication No. 45-20082, and FIG. 4 a time schedule for the process.
Although the notation is partially altered for the ease of comparison with the present invention, the same reference numerals are used for the same elements to facilitate the comparison with the publication. Although the cycle time is changed, it should be properly set depending on the size of adsorbent beds, the type of an adsorbent, the flow rate of each gas, etc. and is substantially the same as the procedure disclosed in the publication.
Four adsorbent beds A, B, C and D are arranged in parallel between a raw gas feed manifold 10 and a feed manifold 11 for product gas or unadsorbed component gas. Automatic valves 1A, 1B, 1C and 1D serve to feed the raw gas from the raw gas feed manifold 10 to the adsorbent beds A, B, C and D, respectively, and automatic valves 2A, 2B, 2C and 2D serve to feed product gas consisting of unadsorbed component gas from the respective adsorbent beds to the product gas feed manifold 11.
Easy adsorptive component gas adsorbed in the individual adsorbent beds is removed and discharged t

REFERENCES:
patent: 3430418 (1969-03-01), Wagner
patent: 3564816 (1971-02-01), Batta
patent: 3636679 (1972-01-01), Batta
patent: 3738087 (1973-06-01), McCombs
patent: 4026680 (1977-05-01), Collins
patent: 4077780 (1978-03-01), Dashi
patent: 4461630 (1984-07-01), Cassidy et al.
patent: 4834780 (1989-05-01), Benkmann
WO89/02309, 3/23/89, Okada et al.

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