Gas separation – Means within gas stream for conducting concentrate to collector
Patent
1987-05-06
1988-10-04
Spitzer, Robert
Gas separation
Means within gas stream for conducting concentrate to collector
55 58, 55 62, 55 68, B01D 5304
Patent
active
047753943
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a National phase application corresponding to PCT/JP86/0045 filed Sept. 11, 1986 and based, in turn, upon a Japanese application 60-200900 filed Sept. 11, 1985.
The present invention relates to a Pressure Swing Adsorption (PSA) process for the separation and recovery of high purity gas from mixed gas or a gas mixture by the use of adsorbent and by a subsequent gas washing followed by desorption.
BACKGROUND OF THE INVENTION
The Japanese unexamined Patent Publication No. 173116/84 and other literatures already describe processes for separation and purification of a product gas by the Pressure Swing Adsorption method, starting with gas mixtures containing carbon dioxide, methane or other gas components which can be adsorbed relatively easily. The separation and purification processes of carbon dioxide, methane or the like by the PSA method, generally use more than one adsorption tower in which, individually, the pressurization/adsorption step, the washing step, and the desorption step are repeated, and which altogether are operated in combination. After adsorption is completed in a tower, a part of the gas desorbed in another adsorption tower is sent to the adsorption tower to flush the interior, and then, the gas is desorbed at a reduced pressure, a part of which is continuously recovered as product, while the balance is used for flushing of another adsorption tower.
In the conventional process, a large-size unit had to be used to obtain the product gas at high purities, for example, 99% or more and preferably 99.5% or more, because the desired product gas was easily contaminated with other gas components. In order to recover the desired gas component at high purity, it was necessary to flush the interior of the adsorption tower with the same desired gas of relatively high purity for a considerable time, thus flushing the voids with such high purity gas as well as purifying the gas adsorbed on the adsorbent through consequential rise of partial pressure of the desired gas component. This operation resulted in a reduced separation/purification capacity per unit adsorbent. Therefore, the size of the unit had to be increased in order to maintain the capacity, and this fact has posed a problem in the industrial application of the process.
OBJECT OF THE INVENTION
To overcome that described disadvantage an object of the present invention is to enable recovery of a high purity gas with a compact unit.
SUMMARY OF THE INVENTION
In a Pressure Swing Adsorption process for separation and recovery of high purity gas, i.e. in the separation of a desired gas component, from mixed gas by adsorption of the desired gas component by the use of adsorbent and by the subsequent gas flushing followed by desorption, the present invention achieves this object by the division of the desorption step into initial, middle, and final stages and by recovery of the gas desorbed at the middle stage as product gas and at the initial and final stage as gas for a flushing step.
For many years, we have diligently studied the separation and purification of various gas mixtures by the PSA method. Surprisingly we have found that there exist concentration distributions in the purity of the gas desorbed at a reduced pressure.
The process of the present invention is carried out in an adsorption tower filed with an adsorbent wherein the following steps are repeated in succession. pressurized by the introduction of mixed gas, and more mixed gas is introduced and passed through the adsorption tower to enable the desired gas component to be adsorbed. unwanted gas components in the voids of the adsorbent are flushed away by the introduction of a part of the desired gas component previously desorbed having a relatively high concentration. the adsorbent is desorbed at a reduced pressure, and the gas desorbed at the middle stage is recovered as product gas, while the gases desorbed at the initial and final stages are used for flushing.
Although more than one adsorption tower is usually use
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Aono Tadayoshi
Kurimoto Makoto
Uno Masaru
Yamano Matsuki
Dubno Herbert
Nippon Steel Corporation
Seitetsu Kagaku Co., Ltd.
Spitzer Robert
Sumitomo Chemical Company Limited
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